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1

Probing polar molecules with high harmonic spectroscopy.  

PubMed

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

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

2012-12-01

2

Inducing elliptically polarized high-order harmonics from aligned molecules with linearly polarized femtosecond pulses  

SciTech Connect

A recent paper reported elliptically polarized high-order harmonics from aligned N{sub 2} using a linearly polarized driving field [X. Zhou et al., Phys. Rev. Lett. 102, 073902 (2009)]. This observation cannot be explained in the standard treatment of the Lewenstein model and has been ascribed to many-electron effects or the influence of the Coulomb force on the continuum electron. We show that nonvanishing ellipticity naturally appears within the Lewenstein model when using a multicenter stationary-phase method for treating the dynamics of the continuum electron. The reason for this is the appearance of additional contributions, which can be interpreted as quantum orbits in which the active electron is ionized at one atomic center within the molecule and recombines at another. The associated exchange harmonics are responsible for the nonvanishing ellipticity and result from a correlation between the ionization site and the recombination site in high-order harmonic generation.

Etches, Adam; Madsen, Christian Bruun; Madsen, Lars Bojer [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

2010-01-15

3

High-order elliptically polarized harmonic generation in extended molecules with ultrashort intense bichromatic circularly polarized laser pulses  

SciTech Connect

Numerical solutions of the time-dependent Schroedinger equation (TDSE) for a two-dimensional H{sub 2}{sup +} molecule excited by a bichromatic ultrashort intense circularly polarized laser pulse with frequencies {omega}{sub 0} and 2{omega}{sub 0} and relative carrier envelope phase {phi} are used to explore the generation of high-order elliptically polarized harmonics as a function of internuclear distance R. Optimal values of {phi} and R for efficient and maximum molecular high-order harmonic generation (MHOHG) are determined from a classical model of collision with neighboring ions and confirmed from the TDSE nonperturbative simulations. Maximum elliptically polarized harmonic energies of I{sub p}+13.5U{sub p} are found, where I{sub p} is the ionization potential and U{sub p}=I{sub 0}/4m{sub e{omega}0}{sup 2} is the ponderomotive energy at intensity I{sub 0} and frequency {omega}{sub 0}. The polarization properties of MHOHG, phase difference {delta}, ellipticity {epsilon}, and orientation angle {phi} are presented as well. The high efficiency of the proposed MHOHG scheme should be useful for production of elliptically polarized attosecond extreme ultraviolet pulses.

Yuan, Kai-Jun; Bandrauk, Andre D. [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

2010-06-15

4

High-order elliptically polarized harmonic generation in extended molecules with ultrashort intense bichromatic circularly polarized laser pulses  

NASA Astrophysics Data System (ADS)

Numerical solutions of the time-dependent Schrödinger equation (TDSE) for a two-dimensional H2+ molecule excited by a bichromatic ultrashort intense circularly polarized laser pulse with frequencies ?0 and 2?0 and relative carrier envelope phase ? are used to explore the generation of high-order elliptically polarized harmonics as a function of internuclear distance R. Optimal values of ? and R for efficient and maximum molecular high-order harmonic generation (MHOHG) are determined from a classical model of collision with neighboring ions and confirmed from the TDSE nonperturbative simulations. Maximum elliptically polarized harmonic energies of Ip+13.5Up are found, where Ip is the ionization potential and Up=I0/4me?02 is the ponderomotive energy at intensity I0 and frequency ?0. The polarization properties of MHOHG, phase difference ?, ellipticity ?, and orientation angle ? are presented as well. The high efficiency of the proposed MHOHG scheme should be useful for production of elliptically polarized attosecond extreme ultraviolet pulses.

Yuan, Kai-Jun; Bandrauk, André D.

2010-06-01

5

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

PubMed

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

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

2014-06-16

6

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

PubMed Central

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

Beausang, John F.; Shroder, Deborah Y.; Nelson, Philip C.; Goldman, Yale E.

2013-01-01

7

Electron interactions with polar molecules  

SciTech Connect

A description is given of a number of the features of discrete and continuous spectra of electrons interacting with polar molecules. Attention is focused on the extent to which theoretical predictions concerning cross sections, resonances, and bound states are strongly influenced by the various approximations that are so ubiquitous in the treatment of such problems. Similarly, threshold scattering and photodetachment processes are examined for the case of weakly bound dipole states whose higher members overlap the continuum.

Garrett, W.R.

1981-01-01

8

Nuclear polarization of hydrogen molecules from recombination of polarized atoms.  

PubMed

The nuclear polarization of H(2) molecules formed by recombination of polarized H atoms on a Cu surface was measured as a function of external magnetic field and of temperature of the surface. The proton polarization of the molecules was determined by scattering of a longitudinally polarized 203-MeV proton beam in the Indiana University Cyclotron Facility storage ring. The nuclear polarization of the molecules, relative to the polarization of the atoms before recombination, increased from near zero in a weak magnetic field to 0.42 +/- 0.02 in a 0.66 T field. A simple model of the relaxation accounts quantitatively for the observations. PMID:11461611

Wise, T; Haeberli, W; Lorentz, B; Quin, P A; Rathmann, F; Schwartz, B; Walker, T G; Wellinghausen, A; Balewski, J T; Doskow, J; Meyer, H O; Pollock, R E; Przewoski, B; Rinckel, T; Saha, S K; Pancella, P V

2001-07-23

9

Polarization spectroscopy of single fluorescent molecules  

SciTech Connect

Polarization spectroscopy of single fluorescent molecules is used to probe their rotational dynamics. When a molecule is immobilized on a dry surface, its in-plane dipole orientation is precisely determined by utilizing its transition dipole moment. An angular offset between the absorption and the emission dipoles was detected from a single fluorophore revealing its binding geometry to the surface. In an aqueous environment, DNA-tethered fluorophores display dynamics that are well-described by a hindered rotational diffusion model. A detailed description of the model is given, including calculations to estimate depolarization effects resulting from the high numerical aperture objective used to collect fluorescence photons. Protein-conjugated fluorophores display very distinct dynamics with continuous evolution of the rotational profile, possibly reflecting fluctuations in the polypeptide chain. When protein-conjugated fluorophores are allowed to freely diffuse in solution, it is possible to determine the fluorescence polarization anisotropy of each molecule that traverses the laser beam. The anisotropy values could, in principle, be used to identify conformational states of single molecules without the potential artifacts associated with surface immobilization.

Ha, T.; Weiss, S. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States); Laurence, T.A.; Chemla, D.S. [Lawrence Berkeley National Lab., CA (United States). Material Sciences Div.] [Lawrence Berkeley National Lab., CA (United States). Material Sciences Div.; [Univ. of California, Berkeley, CA (United States). Physics Dept.

1999-08-19

10

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

11

Optical production of ultracold polar molecules  

NASA Astrophysics Data System (ADS)

We present recent work resulting in the production of ultracold, polar RbCs molecules in their absolute vibronic ground state. The production process consists of several steps: photoassociation of laser-cooled atoms; radiative stabilization of the resulting molecules; identification of the resulting population distribution; and laser-stimulated stale transfer lo the vibrational ground state. We discuss the properties of the resulting sample of of X1?+(? = 0) molecules, with a view to the future directions of these experiments.

Demille, D.; Sage, J. M.; Sainis, S.; Bergeman, T.

2006-11-01

12

Controlling polar molecules in optical lattices  

SciTech Connect

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

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

2006-04-15

13

Decelerating polar molecules using traveling microwave lattices  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

14

Tunable Superfluidity and Quantum Magnetism with Ultracold Polar Molecules.  

National Technical Information Service (NTIS)

By selecting two dressed rotational states of ultracold polar molecules in an optical lattice, we obtain a highly tunable generalization of the t-J model, which we refer to as the t-J-V-W model. In addition to XXZ spin exchange, the model features density...

A. V. Gorshkov E. Demler G. Chen J. Ye S. R. Manmana

2011-01-01

15

Asymmetric scattering of polarized photons and electrons by chiral molecules  

NASA Astrophysics Data System (ADS)

We review the recent theoretical activity connected with the problem of the scattering of polarized particles, photons or electrons and positrons, by chiral molecules. It is shown that the asymmetry of the total ionization cross-sections (?+-?-)/(?++?-) for slow, v~?, longitudinally polarized charged particles appears in the order ?2 from the degree of molecule geometrical asymmetry even in neglect of the exchange interaction and the spin-orbit interaction inside a molecule (Pospelov, 1993). It contradicts to the common believe that the asymmetry in the scattering of polarized positrons is suppressed by a factor ?4 (Zel'dovich and Saakyan, 1980). In the case of the electron scattering the exchange interaction combined with the specifics of electron state inside chiral molecule leads to the further Z2-enhancement of the effect (Hegstrom, 1982). This specifics, the helicity density of the molecular electron, manifests also in the high-frequency asymptotics of the scattering of circularly polarized light (Khriplovich and Pospelov, 1992). The matrix element determining this asymptotics practically coincides, up to an overall factor, with that of the weak interaction responsible for the P-odd energy difference of right- and left-handed molecules.

Pospelov, M. E.

1996-07-01

16

Dipolar collisions of polar molecules in the quantum regime.  

PubMed

Ultracold polar molecules offer the possibility of exploring quantum gases with interparticle interactions that are strong, long-range and spatially anisotropic. This is in stark contrast to the much studied dilute gases of ultracold atoms, which have isotropic and extremely short-range (or 'contact') interactions. Furthermore, the large electric dipole moment of polar molecules can be tuned using an external electric field; this has a range of applications such as the control of ultracold chemical reactions, the design of a platform for quantum information processing and the realization of novel quantum many-body systems. Despite intense experimental efforts aimed at observing the influence of dipoles on ultracold molecules, only recently have sufficiently high densities been achieved. Here we report the experimental observation of dipolar collisions in an ultracold molecular gas prepared close to quantum degeneracy. For modest values of an applied electric field, we observe a pronounced increase in the loss rate of fermionic potassium-rubidium molecules due to ultracold chemical reactions. We find that the loss rate has a steep power-law dependence on the induced electric dipole moment, and we show that this dependence can be understood in a relatively simple model based on quantum threshold laws for the scattering of fermionic polar molecules. In addition, we directly observe the spatial anisotropy of the dipolar interaction through measurements of the thermodynamics of the dipolar gas. These results demonstrate how the long-range dipolar interaction can be used for electric-field control of chemical reaction rates in an ultracold gas of polar molecules. Furthermore, the large loss rates in an applied electric field suggest that creating a long-lived ensemble of ultracold polar molecules may require confinement in a two-dimensional trap geometry to suppress the influence of the attractive, 'head-to-tail', dipolar interactions. PMID:20428166

Ni, K-K; Ospelkaus, S; Wang, D; Quéméner, G; Neyenhuis, B; de Miranda, M H G; Bohn, J L; Ye, J; Jin, D S

2010-04-29

17

Single Molecule Dynamics Studied by Polarization Modulation  

SciTech Connect

We observed and made unambiguous distinctions between abrupt photophysical events of single molecules: a rotational jump of a single dipole, a transition to a dark state (reversible and irreversible photobleaching), and a spectral jump. The study was performed in the far field by modulating the excitation polarization and monitoring the fluorescence in time. This technique also allowed us to measure the in-plane dipole orientation of stationary single molecular dipoles with subdegree accuracy and to resolve desorption and readsorption of fluorophores from and onto a glass surface. In one case, clear evidence was obtained for rapid rotation of the dipole after a desorption process. {copyright} {ital 1996 The American Physical Society.}

Ha, T.; Enderle, T.; Chemla, S. [Physics Department, University of California at Berkeley, Berkeley, California 94720 (United States)] [Physics Department, University of California at Berkeley, Berkeley, California 94720 (United States); [Molecular Design Institute, Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Selvin, R. [Life Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)] [Life Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Weiss, S. [Molecular Design Institute, Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)] [Molecular Design Institute, Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States)

1996-11-01

18

Multichannel quantum defect theory for polar molecules  

NASA Astrophysics Data System (ADS)

Our work is devoted to developing a general approach for nonpenetrating Rydberg states of polar molecules. We propose a method to estimate the accuracy of calculation of their wave functions and quantum defects. Basing on this method we estimate the accuracy of Born-Oppenheimer (BO) and inverse Born-Oppenheimer (IBO) approximations for these states. This estimation enables us to determine the space and energy regions where BO and IBO approximations are valid. It depends on the interplay between l coupling (due to dipole potential of the core) and l uncoupling (due to rotation the core). Next we consider the intermediate region where both BO and IBO are not valid. For this intermediate region we propose a modification of Fano's multichannel quantum defect theory to match BO and IBO wave functions and show that it gives more reliable results. They are demonstrated on the example of SO molecule.

Elfimov, Sergei V.; Dorofeev, Dmitrii L.; Zon, Boris A.

2014-02-01

19

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

20

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.

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

2009-01-01

21

Nonlocal state swapping of polar molecules in bilayers  

SciTech Connect

The observation of significant dipolar effects in gases of ultracold polar molecules typically demands a strong external electric field to polarize the molecules. We show that, even in the absence of a significant polarization, dipolar effects may play a crucial role in the physics of polar molecules in bilayers, provided that the molecules in each layer are initially prepared in a different rotational state. Then, interlayer dipolar interactions result in a nonlocal swap of the rotational state between molecules in different layers, even for weak applied electric fields. The interlayer scattering due to the dipole-dipole interaction leads to a nontrivial dependence of the swapping rate on density, temperature, interlayer spacing, and population imbalance. For reactive molecules such as KRb, chemical recombination immediately follows a nonlocal swap and dominates the losses even for temperatures well above quantum degeneracy, and hence could be observed under current experimental conditions.

Pikovski, A.; Santos, L. [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, D-30169 Hannover (Germany); Klawunn, M.; Recati, A. [Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (INO-CNR) BEC Center and Dipartimento di Fisica, Universita di Trento, I-38123 Povo (Italy)

2011-12-15

22

Topological px+ipy superfluid phase of fermionic polar molecules  

NASA Astrophysics Data System (ADS)

We discuss the topological px+ipy 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 V0(r) that has an attractive dipole-dipole 1/r3 tail, which provides p-wave superfluid pairing at fairly high temperatures. We calculate the amplitude of elastic p-wave scattering in the potential V0(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 Tc can be varied within a few orders of magnitude by modifying the short-range part of the potential V0(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 ~109 cm-2. This leads to Tc of up to a few tens of nanokelvins and makes it realistic to obtain the topological px+ipy phase in experiments with ultracold polar molecules.

Levinsen, J.; Cooper, N. R.; Shlyapnikov, G. V.

2011-07-01

23

On the Probability of Intermolecular Energy Transfer in Polar Molecules.  

National Technical Information Service (NTIS)

An expression is developed for the probability of intermolecular energy transfer P in polar molecules for particular orientations on the basis of the Lennard-Jones-dipole-quadrupole interaction energy. The temperature dependence of P is briefly discussed....

H. K. Shin

1968-01-01

24

Spin waves and dielectric softening of polar molecule condensates.  

PubMed

We consider an oblate Bose-Einstein condensate of heteronuclear polar molecules in a weak applied electric field. This system supports a rich quasiparticle spectrum that plays a critical role in determining its bulk dielectric properties. In particular, in sufficiently weak fields the system undergoes a polarization wave rotonization, leading to the development of textured electronic structure and a dielectric instability that is characteristic of the onset of a negative static dielectric function. PMID:24745433

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

2014-04-01

25

Influence of polarity on filling polymer molecules into carbon nanotubes  

Microsoft Academic Search

Using molecular dynamics (MD) simulation, we studied the influence of polarity of polymer chains and modified single-walled nanotubes (SWNTs) on filling polymer chains into SWNTs. The center of mass (COM) distance and the interaction energy between the polymer molecules and SWNTs, as well as non-bond energy (including van der Waals energy and electrostatics energy) differences (?E) between initial structure and

Nuannuan Jing; Qingzhong Xue; Jianpeng Li; Sheng Wang; Cuicui Ling

2011-01-01

26

Preparation of polarized molecules using coherent infrared multicolor ladder excitation.  

PubMed

A density matrix treatment is presented for a general process of preparing polarized molecules through their coherent interaction with two or more infrared photons of different frequencies, each tuned to cause a transition between real levels. This process, which might be called infrared stimulated Raman adiabatic passage, allows complete population transfer to selected rotational-vibrational levels and controls the direction of the rotational angular momentum vector J of the molecule with the possibility of preparing higher moments of the J spatial distribution. HCl molecules in a supersonic molecular beam are considered as a candidate system. Theory predicts that under collision-free conditions two infrared laser pulses of microsecond duration and milliwatt power are able to achieve complete population transfer and alignment of HCl (v=2, J=2, and M=0) for mutually parallel excitation and HCl (v=2, J=2, and M=+/-1) for mutually perpendicular excitation. Orientation of the HCl (v=2, J=2, and M=+/-2) can also be achieved using two circularly polarized pulses of the same helicity. For simplicity, our treatment ignores nuclear spin depolarization, which would be the case for molecules such as (12)C(16)O and (12)C(16)OO(2). Polarized molecules in higher vibrational levels can be prepared using additional infrared pulses. PMID:20423176

Mukherjee, Nandini; Zare, Richard N

2010-04-21

27

Model Independence in Two Dimensions and Polarized Cold Dipolar Molecules  

SciTech Connect

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

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

2011-06-24

28

Three-dimensional optical polarization tomography of single molecules  

NASA Astrophysics Data System (ADS)

We apply the concept of tomography to polarization-sensitive optical microscopy of single fluorophores to determine the three-dimensional orientation of molecular absorption dipoles with isotropic sensitivity. Wide-field microscopy provides the opportunity to monitor simultaneously three-dimensional rotation and two-dimensional translation of many molecules in parallel. For orientation determination the molecules are illuminated from different directions of incidence with linearly polarized light. In each exposure the excitation along a particular projection of the absorption dipole on the electric field leads to a distinct fluorescence intensity. Five exposures are sufficient to determine the full orientation of the fluorophores. To demonstrate the potential of the method we determine the orientation and position of individual immobilized lipid membrane markers. The shot-noise-limited isotropic angular resolution is 2°. For time-resolved studies the bandwidth can be expanded up to 200 Hz.

Prummer, Michael; Sick, Beate; Hecht, Bert; Wild, Urs P.

2003-06-01

29

Spectromicroscopy Study of the Organic Molecules Utilizing Polarized Radiation  

SciTech Connect

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

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

2004-05-12

30

Tuning stamp surface energy for soft lithography of polar molecules to fabricate bioactive small-molecule microarrays.  

PubMed

Soft-lithography-based techniques are widely used to fabricate microarrays. Here, the use of microcontact insertion printing is described, a soft-lithography method specifically developed for patterning at the dilute scales necessary for highly selective biorecognition. By carefully tuning the polar surface energy of polymeric stamps, problems associated with patterning hydrophilic tether molecules inserted into hydrophilic host self-assembled monolayers (SAMs) are surmounted. Both prefunctionalized tethers and on-chip functionalization of SAMs patterned by microcontact insertion printing enable the fabrication of small-molecule microarrays. Substrates patterned with the neurotransmitter precursor 5-hydroxytryptophan selectively capture a number of different types of membrane-associated receptor proteins, which are native binding partners evolved to recognize free serotonin. These advances provide new avenues for chemically patterning small molecules and fabricating small molecule microarrays with highly specific molecular recognition capabilities. PMID:21538866

Vaish, Amit; Shuster, Mitchell J; Cheunkar, Sarawut; Weiss, Paul S; Andrews, Anne M

2011-05-23

31

Tunable superfluidity and quantum magnetism with ultracold polar molecules.  

PubMed

By selecting two dressed rotational states of ultracold polar molecules in an optical lattice, we obtain a highly tunable generalization of the t-J model, which we refer to as the t-J-V-W model. In addition to XXZ spin exchange, the model features density-density interactions and density-spin interactions; all interactions are dipolar. We show that full control of all interaction parameters in both magnitude and sign can be achieved independently of each other and of the tunneling. As a first step towards demonstrating the potential of the system, we apply the density matrix renormalization group method to obtain the 1D phase diagram of the simplest experimentally realizable case. Specifically, we show that the tunability and the long-range nature of the interactions in the t-J-V-W model enable enhanced superfluidity. Finally, we show that Bloch oscillations in a tilted lattice can be used to probe the phase diagram experimentally. PMID:22026682

Gorshkov, Alexey V; Manmana, Salvatore R; Chen, Gang; Ye, Jun; Demler, Eugene; Lukin, Mikhail D; Rey, Ana Maria

2011-09-01

32

Formation of ultracold polar molecules in a single quantum state  

SciTech Connect

We compute the formation rate of a polar molecule, LiH, into the lowest triplet electronic state, a {sup 3{Sigma}+}, via population of the intermediate excited electronic state, b {sup 3{Pi}}, followed by radiative decay. We find large formation rates into the single rovibrational bound state (v=0,J=0) of the a {sup 3{Sigma}+}, which can be explained by the unusually large overlap of its wave function with those of the two upper-most bound levels of the b {sup 3{Pi}}. With conservative parameters, we estimate that over 10{sup 4} molecules/s could be produced in the single rovibrational level of the a {sup 3{Sigma}+} state. We also discuss scattering properties of LiH triplet molecules and their relevance to ultracold chemical reactions.

Cote, Robin; Juarros, Elizabeth [Physics Department, University of Connecticut, 2152 Hillside Rd., Storrs, Connecticut 06269-3046 (United States); Kirby, Kate [ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States); American Physical Society, One Physics Ellipse, College Park, MD 20740 (United States)

2010-06-15

33

Dissociation of Highly Excited Molecules  

NASA Astrophysics Data System (ADS)

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

Hatano, Yoshihiko

1997-10-01

34

High intensity polarized electron sources  

SciTech Connect

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

Sinclair, C.K.

1980-10-01

35

Fermi liquid of two-dimensional polar molecules  

NASA Astrophysics Data System (ADS)

We study Fermi-liquid properties of a weakly interacting two-dimensional 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/r3 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 kFr*, where kF is the Fermi momentum and r*=md2/?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 kFr* and argue that many-body corrections to the ground-state energy can be identified in experiments with ultracold molecules, as 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.

Lu, Zhen-Kai; Shlyapnikov, G. V.

2012-02-01

36

Symmetry Protected Topological Phases in Polar Molecule Spin Ladder Systems  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

37

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

PubMed

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

Sagawa, Naoya; Shikata, Toshiyuki

2014-06-11

38

High frequency dynamic nuclear polarization.  

PubMed

During the three decades 1980-2010, 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 = 1/2 species (13)C or (15)N. The difficulty is still greater when quadrupolar nuclei, such as (17)O or (27)Al, 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 150-660 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

2013-09-17

39

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 mechanisms—the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in ?w and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.

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

2009-01-01

40

Dynamic nuclear polarization at high magnetic fields.  

PubMed

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 (microw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (gamma(e)gamma(l)), being approximately 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 (> or =5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms-the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in microw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments. PMID:18266416

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

2008-02-01

41

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

PubMed

A layer-by-layer growth model is presented for the theoretical investigation of growth-induced polarity formation in solid solutions H(1-X)G(X) of polar (H) and nonpolar (G) molecules (X: molar fraction of G molecules in the solid, 0molecules and to an exchange of H and G molecules, while previously attached layers are kept frozen. The model is analyzed by means of a Markov mean-field description and Monte Carlo simulations. In solid solutions, polarity results from a combined effect of orientational selectivity by H and G molecules with respect to the alignment of the dipoles of H molecules and miscibility between the two components. Even though both native structures (H,G) may be centrosymmetric, polarity can arise just from the admixture of G molecules in the H crystal upon growth. An overview of possible phenomena is given by random selection of molecular interaction energies within an assumed but realistic energy range. The analytical approach describes sufficiently basic phenomena and is in good agreement with simulations. High probabilities for significant vectorial alignment of H molecules are found for low (X< or =0.2) and high (X> or =0.8) fractions of G molecules, respectively, as well as for ordered HG compounds (X=0.5). PMID:15836085

Wüst, Thomas; Hulliger, Jürg

2005-02-22

42

Electrically dressed ultra-long-range polar Rydberg molecules  

NASA Astrophysics Data System (ADS)

We investigate the impact of an electric field on the structure of ultra-long-range polar diatomic rubidium Rydberg molecules. Both the s-wave and p-wave interactions of the Rydberg electron and the neutral ground-state atom are taken into account. In the presence of the electric field the angular degree of freedom between the electric field and the internuclear axis acquires vibrational character and we encounter two-dimensional oscillatory adiabatic potential energy surfaces with an antiparallel equilibrium configuration. The electric field allows shifting of the corresponding potential wells in such a manner that the importance of the p-wave interaction can be controlled and the individual wells are energetically lowered at different rates. As a consequence the equilibrium configuration and corresponding energetically lowest well move to larger internuclear distances for increasing field strength. For strong fields the admixture of nonpolar molecular Rydberg states leads to the possibility of exciting the large angular momentum polar states via two-photon processes from the ground state of the atom. The resulting properties of the electric dipole moment and the vibrational spectra are analyzed with varying field strength.

Kurz, Markus; Schmelcher, Peter

2013-08-01

43

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

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

44

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

45

Implementation of quantum logic gates using polar molecules in pendular states  

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

46

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

47

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

48

Fluorescence Polarization Screening for Allosteric Small Molecule Ligands of the Cholecystokinin Receptor  

PubMed Central

Abstract The success in screening for drug candidates is highly dependent on the power of the strategy implemented. In this work, we report and characterize a novel fluorescent benzodiazepine antagonist of the type 1 cholecystokinin receptor (3-(3-(7-fluoro-1-(2-isopropyl(4-methoxyphenyl)amino)-2-oxoethyl)-2,4-dioxo-5-phenyl-2,3,4,5-tetrahydro-1H-benzo[b][1,4]-diazepin-3-yl)ureido)benzoic acid) that can be used as a receptor ligand in a fluorescence polarization assay, which is ideally suited for the identification of small molecule allosteric modulators of this physiologically important receptor. By binding directly to the small molecule-docking region within the helical bundle of this receptor, this indicator can be displaced by many small molecule candidate drugs, even those that might not affect the binding of an orthosteric cholecystokinin-like peptide ligand. The biological, pharmacological, and fluorescence properties of this reagent are described, and proof-of-concept is provided in a fluorescence polarization assay utilizing this fluorescent benzodiazepine ligand.

Harikumar, Kaleeckal G.; Cawston, Erin E.

2011-01-01

49

Beam dynamics in a storage ring for neutral (polar) molecules  

SciTech Connect

The force from a non-uniform electric field on the electric dipole moment of a molecule may be used to circulate and focus molecules in a storage ring. The nature of the forces from multipole electrodes for bending and focusing are described for strong-field-seeking and for weak-field-seeking molecules. Fringe-field forces are analyzed. Examples of storage ring designs are presented; these include long straight sections and provide bunching and acceleration.

Lambertson, Glen R.

2003-05-01

50

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

51

Spin-polarized transport through single-molecule magnet Mn6 complexes.  

PubMed

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 Mn(III) 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. PMID:23599124

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

2013-06-01

52

Universalities in ultracold reactions of alkali-metal polar molecules  

SciTech Connect

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

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

2011-12-15

53

One-photon-assisted formation of ultracold polar molecules  

SciTech Connect

Alkali-metal hydride molecules have large dipole moments in their ground electronic states. We explore the possibility of forming such molecules from a mixture of the ultracold atomic gases, employing a one-photon stimulated radiative association process. Using accurate molecular potential-energy curves and dipole moments, we have calculated the rate coefficients for populating each of the vibrational levels of the X {sup 1}{sigma}{sup +} states of LiH and NaH. We have found that significant molecule formation rates into the upper vibrational levels can be realized with laser intensities and atomic densities that are easily attainable experimentally. We examine the spontaneous emission cascade which takes place from these upper vibrational levels on a time scale of milliseconds, and calculate the resulting rotational populations in v=0. We show that photon emission in the cascade process does not contribute to trap loss and that a large population of molecules in v=0 can be achieved.

Juarros, Elizabeth; Pellegrini, Philippe; Cote, Robin [Physics Department, University of Connecticut, 2152 Hillside Road, Storrs, Connecticut 06269-3046 (United States); Kirby, Kate [ITAMP, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

2006-04-15

54

Excitonic Polarization and Polarization Scattering in a Highly Excited Semiconductor  

Microsoft Academic Search

Interaction between free carriers and excitons in a highly excited semiconductor is considered in terms of the polarization on the part of excitons caused by the elecric field due to the free carriers. When the distribution of excitons is uniform, one may have the chance of getting an orderly coupling between carriers and excitons which we call ``excitonic polaron''. On

Eizo Otsuka

1975-01-01

55

Giant enhancement of photodissociation of polar diatomic molecules in electric fields.  

PubMed

We explore the photodissociation of polar diatomic molecules in static electric fields in the rotationally cold regime using the example of the LiCs molecule. A giant enhancement of the differential cross section is found for laboratory electric field strengths, and analyzed with varying rovibrational bound states, continuum energies as well as field strengths. PMID:21796279

González-Férez, R; Schmelcher, P

2011-11-14

56

High current polarized proton sources  

SciTech Connect

Polarized proton sources are now being used more frequently on linacs. In pulsed operation up to 10 mA of /rvec H//sup +/ and 0.4 mA of /rvec H//sup /minus// have been produced. The present status of these sources, and developments to reach even higher intensities, are reviewed. 39 refs., 1 tab.

Alessi, J.G.

1988-01-01

57

Changepoint Analysis for Single-Molecule Polarized Total Internal Reflection Fluorescence Microscopy Experiments  

PubMed Central

The experimental study of individual macromolecules has opened a door to determining the details of their mechanochemical operation. Motor enzymes such as the myosin family have been particularly attractive targets for such study, in part because some of them are highly processive and their “product” is spatial motion. But single-molecule resolution comes with its own costs and limitations. Often, the observations rest on single fluorescent dye molecules, which emit a limited number of photons before photobleaching and are subject to complex internal dynamics. Thus, it is important to develop methods that extract the maximum useful information from a finite set of detected photons. We have extended an experimental technique, multiple polarization illumination in total internal reflection fluorescence microscopy (polTIRF), to record the arrival time and polarization state of each individual detected photon. We also extended an analysis technique, previously applied to FRET experiments, that optimally determines times of changes in photon emission rates. Combining these improvements allows us to identify the structural dynamics of a molecular motor (myosin V) with unprecedented detail and temporal resolution.

Beausang, John F.; Goldman, Yale E.; Nelson, Philip C.

2011-01-01

58

Collisional dynamics of ultracold polar molecules in an electrostatic field.  

NASA Astrophysics Data System (ADS)

We have calculated cross sections and rate constants between two OH molecules in an electrostatic field at temperatures below 1K, focusing on molecules in their weak- electric seeking- field states. These molecules interact primarily via long- range dipole- dipole forces, and the interplay of this interaction with the Stark interaction defines the properties of their collisional dynamics. We have analyzed the dominant role of long-range potentials in determining the basic features of rate constans. At an electrostatic field up to several tens of thousands of V/cm the inelastic rate constant is large and comparable with the elastic one, which implies that evaporative cooling in an electrostatic trap is unlikely to succeed. The strong dipole- dipole couplings between channels with different partial waves restrict the interaction to their long- range contribution only, which implies an extremely weak dependence on the short- range potential for weak- seeking field states. This circumstance will greatly simplify the theoretical analysis of cold collision data. It also implies the existence of a new set of long- range bound states for two OH molecules. This work is sponsored by the National Science Foundation.

Avdeenkov, Alexandr V.; Bohn, John L.

2002-05-01

59

Transport of small polar molecules across nonporous polymeric membranes  

Microsoft Academic Search

A molecule within the nonporous polymeric membrane moves in response to the local driving force and has no memory of how it entered the membrane or how the local gradients were generated. This means that a properly formulated model of transport within the membrane should be equally applicable to dialysis, pervaporation or vapour permeation. The phenomenological approach of irreversible thermodynamics

A. A. Ghoreyshi; F. A. Farhadpour; M. Soltanieh; M. Abdelghani

2003-01-01

60

Alignment and orientation of diatomic molecules induced by polarized electron impact  

NASA Astrophysics Data System (ADS)

We report measurements of linear and circular fluorescence polarizations for molecular transitions in H2, D2, and N2 induced by spin-polarized electron impact. Circular polarizations resulting from some Fulcher-? transitions in H2 and D2 are found to be significant, while the null results from nitrogen's second positive system are consistent with an earlier measurement by the Münster group. We compare this nitrogen data to that from our previous study of nitrogen's first negative system. Emphasis is placed on understanding the mechanisms that cause the values of circular polarization from N2 to be relatively small compared to those observed from H2 and D2 molecules.

Maseberg, J. W.; Gay, T. J.

2010-02-01

61

High Energy Polarization - Historical Remarks  

NASA Technical Reports Server (NTRS)

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

Weisskopf, Martin C.

2008-01-01

62

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

63

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

64

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

SciTech Connect

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

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

2011-02-15

65

Coupling between tilt and polar orders in liquid crystal phases formed from achiral bent shaped molecules  

NASA Astrophysics Data System (ADS)

A phenomenological description is given of the mesophases which may arise below a liquid formed from achiral molecules possessing a transverse dipole, as the result of a coupling between their tilt and polar orders. Six stable mesophases are found. Two of them have a cholesteric biaxial structure. The others display antiferroelectric or ferrielectric, incommensurately modulated, structures with in-plane or out-of-plane spontaneous polarization. The in-plane polarized structures become unstable under application of a longitudinal electric field. Other field-induced effects are discussed.

Tolédano, Pierre; Martins, Odair G.; Figueiredo Neto, Antonio M.

2000-10-01

66

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

NASA Astrophysics Data System (ADS)

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

Dale, Glenn Lamar

67

High power coherent polarization locked laser diode.  

PubMed

We have coherently combined a broad area laser diode array to obtain high power single-lobed output by using coherent polarization locking. The single-lobed coherent beam is achieved by spatially combining four diode emitters using walk-off crystals and waveplates while their phases are passively locked via polarization discrimination. While our previous work focused on coherent polarization locking of diode in Gaussian beams, we demonstrate in this paper, the feasibility of the same polarization discrimination for locking multimode beams from broad area diode lasers. The resonator is designed to mitigate the loss from smile effect by using retro-reflection feedback in the cavity. In a 980 nm diode array, we produced 7.2 W coherent output with M2 of 1.5x11.5. The brightness of the diode is improved by more than an order of magnitude. PMID:21560783

Purnawirman; Phua, P B

2011-03-14

68

Van der Waals Interaction Potential between Polar Molecules. Pair Potential and (Nonadditive) Triple Potential  

Microsoft Academic Search

A unified treatment, based on the method of the fluctuating reaction field, is presented for the van der Waals potential between polar molecules. Only dipolar interactions exclusive of retardation effects are considered. The general formulation is given in terms of frequency-dependent molecular susceptibilities and holds for any finite temperature. It is shown that, under certain restrictive conditions, the generalized potential

Bruno Linder

1964-01-01

69

Photoelectron angular distributions from polar molecules probed by intense femtosecond lasers  

SciTech Connect

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

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

2010-10-15

70

Strong-field ionization of polar molecules: Stark-shift-corrected strong-field approximation  

SciTech Connect

We extend the molecular strong-field approximation for ionization, in the tunneling limit, to include systematically the linear and quadratic static Stark shifts of the ionizing molecular orbital. This approach, simple to implement, is capable of describing the essential physics of the process of strong-field ionization of oriented polar molecules by circularly polarized laser pulses. The modification of the molecular orbitals in strong fields is also discussed and in cases of extreme polarization of inner electrons a simple model is devised. We find very good agreement between the results from our model and those obtained in the recent experiment on ionizaton of oriented carbonyl sulphide and benzonitrile molecules [L. Holmegaard et al., Nature Phys. 6, 428 (2010)].

Dimitrovski, D.; Martiny, C. P. J.; Madsen, L. B. [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C (Denmark)

2010-11-15

71

Novel high-sensitivity fluorescence polarization reader  

NASA Astrophysics Data System (ADS)

We have developed a new fluorescence polarization (FP) reader suitable for high-throughput screening (HST) and ultra-HTS whose assay-performance and sample-throughput are both considerably improved over present state-of-the-art instrumentation. The SymmetryTM reader possesses a number of features that differ from conventional HTS FP readers. These include: laser-based excitation, liquid crystal polarization optics that rapidly and accurately measure polarization states; and CCD detectors to capture emission from multiple wells. We show that the performance in assays relevant to the drug discovery process, such as G- protein coupled receptor-based assays, is significantly enhanced due to a dramatic improvement in precision. Furthermore, the CCD-detection system used can substantially improve sample throughput compared to sequential readers while maintaining high performance.

Hoyt, Clifford C.; Levenson, Richard M.; Banks, Peter

2001-05-01

72

The nano-gap and the emitting molecule: Control of polarization and spectral shape  

NASA Astrophysics Data System (ADS)

The realization of single-molecule surface-enhanced Raman scattering (SERS) from molecules positioned within nano-gaps between metallic nanopraticles has opened up exciting opportunities for studying plasmonic fields and their effects on quantum emitters. We recently showed that constructs made of pairs of nanoparticles with an individual molecules bridging their gap can be systematically formed and studied [1]. By changing the size of the particles, we were able to tune the position of the plasmon resonance spectrum, so that the overlap with different parts of the molecular Raman spectrum changed, leading to significant modulation of its shape. More intricate control over molecular properties can be achieved if a third particle is added to the contstruct. It was found that by breaking the dimer symmetry, a third particle can couple strongly to the emitted Raman field and modulate its polarization in a wavelength-dependent fashion [2]. This surprising experimental result was backed up by a series of Generalized Mie calculations, showing the effect of the distance of the third particle, its size and position [3]. Interestingly, the refractive index of the surrounding medium serves as another control parameter that allows changing the coupling between the particles and modulating the polarization of emitted light. [4pt] [1] Dadosh T, et al. (2009) Plasmonic Control of the Shape of the Raman Spectrum of a Single Molecule in a Silver Nanoparticle Dimer. Acs Nano 3:1988-1994. [0pt] [2] Shegai T, et al. (2008) Managing light polarization via plasmon-molecule interactions within an asymmetric metal nanoparticle trimer. Proc Natl Acad Sci USA 105:16448-16453. [0pt] [3] Li ZP, Shegai T, Haran G, Xu HX (2009) Multiple-Particle Nanoantennas for Enormous Enhancement and Polarization Control of Light Emission. Acs Nano 3:637-642.

Haran, Gilad

2010-03-01

73

Polarized electrons from high-gradient guns  

SciTech Connect

To take advantage of the lower emittance associated with extraction fields >> 10 MV/m, a number of technological hurdles must be overcome before photocathodes appropriate for generating polarized electrons can be utilized in high-gradient guns. Both rf guns and very fast ultra-high gradient ({ge} 1 GV/m) diode guns are anticipated. The known problems--some of which may be more than just technical--are delineated, and the present status of relevant research is reviewed.

Clendenin, J.E.; Mulhollan, G.A.

1998-09-01

74

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

PubMed

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

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

2014-08-14

75

Dimers, Effective Interactions, and Pauli Blocking Effects in a Bilayer of Cold Fermionic Polar Molecules  

NASA Astrophysics Data System (ADS)

We consider a bilayer setup with two parallel planes of cold fermionic polar molecules when the dipole moments are oriented perpendicular to the planes. The binding energy of two-body states with one polar molecule in each layer is determined and compared to various analytic approximation schemes in both coordinate- and momentum-space. The effective interaction of two bound dimers is obtained by integrating out the internal dimer bound state wave function and its robustness under analytical approximations is studied. Furthermore, we consider the effect of the background of other fermions on the dimer state through Pauli blocking, and discuss implications for the zero-temperature many-body phase diagram of this experimentally realizable system.

Zinner, N. T.; Armstrong, J. R.; Volosniev, A. G.; Fedorov, D. V.; Jensen, A. S.

2012-10-01

76

Two-dimensional scattering and bound states of polar molecules in bilayers  

SciTech Connect

Low-energy two-dimensional scattering is particularly sensitive to the existence and the properties of weakly bound states. We show that interaction potentials V(r) with the vanishing zero-momentum Born approximation {integral}dr rV(r)=0 leads to an anomalously weak bound state that crucially modifies the two-dimensional scattering properties. This anomalous case is especially relevant in the context of polar molecules in bilayer arrangements.

Klawunn, Michael [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany); INO-CNR BEC Center and Dipartimento di Fisica, Universita di Trento, I-38123 Povo (Italy); Pikovski, Alexander; Santos, Luis [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)

2010-10-15

77

Higher excited states of aromatic hydrocarbons. III. Assigning the in-plane polarized transitions of low-symmetry molecules: chrysene and E-stilbene  

Microsoft Academic Search

The polarization of the UV and near VUV bands of chrysene and E-stilbene have been measured up to 70000 cm?1. The high natural polarization of the synchrotron radiation was used in combination with matrix-isolation to perform photoselection experiments. The limits of the of photoselection technique in connection with low symmetry molecules are discussed. Comparison with existing data for the low

Murthy S. Gudipati; Michael Maus; Johannes Daverkausen; Georg Hohlneicher

1995-01-01

78

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

79

Dynamic Core Polarization in Strong-Field Ionization of CO Molecules  

NASA Astrophysics Data System (ADS)

The orientation-dependent strong-field ionization of CO molecules is investigated using the fully propagated three-dimensional time-dependent Hartree-Fock theory. The full ionization results are in good agreement with recent experiments. The comparisons between the full method and the single active orbital method show that although the core electrons are generally more tightly bound and contribute little to the total ionization yields, their dynamics cannot be ignored, which effectively modifies the behavior of electrons in the highest occupied molecular orbital. By incorporating it into the single active orbital method, we identify that the dynamic core polarization plays an important role in the strong-field tunneling ionization of CO molecules, which is helpful for the future development of the tunneling ionization theory of molecules beyond the single active electron approximation.

Zhang, Bin; Yuan, Jianmin; Zhao, Zengxiu

2013-10-01

80

Dynamic core polarization in strong-field ionization of CO molecules.  

PubMed

The orientation-dependent strong-field ionization of CO molecules is investigated using the fully propagated three-dimensional time-dependent Hartree-Fock theory. The full ionization results are in good agreement with recent experiments. The comparisons between the full method and the single active orbital method show that although the core electrons are generally more tightly bound and contribute little to the total ionization yields, their dynamics cannot be ignored, which effectively modifies the behavior of electrons in the highest occupied molecular orbital. By incorporating it into the single active orbital method, we identify that the dynamic core polarization plays an important role in the strong-field tunneling ionization of CO molecules, which is helpful for the future development of the tunneling ionization theory of molecules beyond the single active electron approximation. PMID:24182261

Zhang, Bin; Yuan, Jianmin; Zhao, Zengxiu

2013-10-18

81

Magnetic surface states in high polarization materials  

NASA Astrophysics Data System (ADS)

Surfaces are often different materials, and typically have a different electronic structure from the bulk and since the dawn of surface science, surface-localized electronic states, surface states, have been extensively studied and investigated with growing accuracy. Of particular importance to spintronics are magnetic surface states. Interfaces will play a very important role in many spintronics devices, yet the interface properties are often ignored, poorly understood or badly characterized. For many nominally half metal materials, materials that in some ground state calculations exhibit 100% spin polarization, the magnetic surface states may significantly reduce the effective spin polarization. We review the magnetic surface states of several well known and often highly touted high spin polarized materials such as NiMnSb, Fe3O4, CoS2 and CrO2. Finally, we summarize surface state measurements of magnetoelectric antiferromagnets Cr2O3, which has electrically controllable net surface spins, a major complication to the study of CrO2 by photoemission.

Wu, Ning; Dowben, Peter A.

2011-09-01

82

Polarization converters in highly birefringent microfibers.  

PubMed

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

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

2014-02-10

83

Doppler-free laser polarization and optical-optical double resonance polarization labeling spectroscopies of a large molecule: Naphthalene  

NASA Astrophysics Data System (ADS)

Doppler-free laser polarization (DFLP) spectroscopy is successfully applied to a large polyatomic molecule, naphthalene. Rotationally resolved spectra of the 33(b2g)01 vibronic band of the A~ 1B1u<--X~ 1Ag electronic transition of gas phase naphthalene at room temperature have been measured with the technique of DFLP spectroscopy. The typical width of the observed spectral lines was 15 MHz, and the absolute wave numbers were measured with an accuracy of better than +/-0.0002 cm-1. In order to assign the dense and complicated parts of the spectra, the technique of Doppler-free optical-optical double resonance polarization labeling spectroscopy was used. Both V-type and ?-type double resonances were observed, and these signals were found to be very useful for the unambiguous assignment of the complicated lines of DFLP spectrum. Three rotational constants A, B, and C, three symmetric-top quartic centrifugal distortion constants ?J, ?JK, and ?K, and two asymmetric-top distortion constants ?J and ?K were determined by a least-squares fitting of 4632 spectral lines in the range J=4-154 and Ka=0-40 with a standard deviation of 0.0002 cm-1. No appreciable perturbation was observed.

Kabir, M. H.; Kasahara, S.; Demtröder, W.; Tatamitani, Y.; Doi, A.; Katô, Hajime; Baba, Masaaki

2003-08-01

84

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

85

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2000-04-01

87

Molecular frame photoemission in multiphoton ionization of small molecules induced by linearly and circularly polarized light  

NASA Astrophysics Data System (ADS)

We report results for one-color multiphoton dissociative ionization (MPDI) of NO2 induced by linearly (P) and circularly (k, ê) polarized femtosecond (fs) pulses centered at 400 nm. The experiments were performed by combining the use of 1 kHz femtosecond laser sources (SLIC, Saclay) and the electron-ion vector correlation method. The recoil frame photoelectron angular distributions (RFPADs), derived from the analysis of the (Ve, VNO+) velocity vector correlation, are analyzed using a new formalism. It generalizes the expression of the MFPADs for one-photon photoionization of linear molecules, and models the reaction as n-1 bound-to-bound transitions and ionization induced by the nth photon. The polar and azimuthal angle dependences of the RFPAD are characterized. We illustrate the discussion by the RFPADs measured for a MPDI process induced by five-photon absorption.

Lucchese, R. R.; Elkharrat, C.; Picard, Y.; Billaud, P.; Dowek, D.

2009-11-01

88

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

NASA Astrophysics Data System (ADS)

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 Mclean

89

Controlling Magnetic Feshbach Resonances in Polar Open-Shell Molecules with Nonresonant Light  

NASA Astrophysics Data System (ADS)

Magnetically tunable Feshbach resonances for polar paramagnetic ground-state diatomics are too narrow to allow for magnetoassociation starting from trapped, ultracold atoms. We show that nonresonant light can be used to engineer the Feshbach resonances in their position and width. For nonresonant field intensities of the order of 109 W/cm2, we find the width to be increased by 3 orders of magnitude, reaching a few Gauss. This opens the way for producing ultracold molecules with sizable electric and magnetic dipole moments and thus for many-body quantum simulations with such particles.

Tomza, Micha?; González-Férez, Rosario; Koch, Christiane P.; Moszynski, Robert

2014-03-01

90

Long-range scattering resonances in strong-field-seeking states of polar molecules  

SciTech Connect

We present first steps toward understanding the ultracold scattering properties of polar molecules in strong electric field-seeking states. We have found that the elastic cross section displays a quasiregular set of potential resonances as a function of the electric field, which potentially offers intimate details about the intermolecular interaction. We illustrate these resonances in a 'toy' model composed of pure dipoles, and in more physically realistic systems. To analyze these resonances, we use a simple WKB approximation to the eigenphase, which proves both reasonably accurate and meaningful. A general treatment of the Stark effect and dipolar interactions is also presented.

Ticknor, Christopher; Bohn, John L. [JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440 (United States)

2005-09-15

91

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

SciTech Connect

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

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

2008-10-10

92

Controlling magnetic Feshbach resonances in polar open-shell molecules with nonresonant light.  

PubMed

Magnetically tunable Feshbach resonances for polar paramagnetic ground-state diatomics are too narrow to allow for magnetoassociation starting from trapped, ultracold atoms. We show that nonresonant light can be used to engineer the Feshbach resonances in their position and width. For nonresonant field intensities of the order of 10(9) W/cm(2), we find the width to be increased by 3 orders of magnitude, reaching a few Gauss. This opens the way for producing ultracold molecules with sizable electric and magnetic dipole moments and thus for many-body quantum simulations with such particles. PMID:24702365

Tomza, Micha?; González-Férez, Rosario; Koch, Christiane P; Moszynski, Robert

2014-03-21

93

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.

2013-01-01

94

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

NASA Astrophysics Data System (ADS)

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

Omiste, Juan J.; González-Férez, Rosario

2013-12-01

95

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

96

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

SciTech Connect

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

2011-11-15

97

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

98

Solid phases and pairing in a mixture of polar molecules and atoms  

SciTech Connect

We consider a mixture of hard-core bosonic polar molecules, interacting via repulsive dipole-dipole interaction, and one atomic bosonic species. The mixture is confined on a two-dimensional square lattice and, at low enough temperatures, can be described by the two-component Bose-Hubbard model. The latter displays an extremely rich phase diagram including solid, superfluid, and supersolid phases. Here, we mainly focus on the checkerboard molecular solid, stabilized by the long-range dipolar interaction, and study how the presence of atoms affects its robustness both at zero and finite temperatures. We find that, due to atom-molecule interactions, solid phases can be stabilized at both (much) lower strengths of dipolar interaction and higher temperatures, than when no atoms are present. As a byproduct, atoms also order in a solid phase with the same melting temperatures as for molecules. Finally, we find that for large enough interaction between atoms and molecules, a paired supersolid phase can be stabilized.

Capogrosso-Sansone, B. [Institute for Theoretical Atomic, Molecular, and Optical Physics, Harvard-Smithsonian Center of Astrophysics, Cambridge, Massachusetts 02138 (United States)

2011-05-15

99

On the choice of a reference state for one-step perturbation calculations between polar and nonpolar molecules in a polar environment.  

PubMed

One-step perturbation is an efficient method to estimate free energy differences in molecular dynamics (MD) simulations, but its accuracy depends critically on the choice of an appropriate, possibly unphysical, reference state that optimizes the sampling of the physical end states. In particular, the perturbation from a polar moiety to a nonpolar one and vice versa in a polar environment such as water poses a challenge which is of importance when estimating free energy differences that involve entropy changes and the hydrophobic effect. In this work, we systematically study the performance of the one-step perturbation method in the calculation of the free enthalpy difference between a polar water solute and a nonpolar "water" solute molecule solvated in a box of 999 polar water molecules. Both these polar and nonpolar physical reference states fail to predict the free enthalpy difference as obtained by thermodynamic integration, but the result is worse using the nonpolar physical reference state, because both a properly sized cavity and a favorable orientation of the polar solute in a polar environment are rarely, if ever, sampled in a simulation of the nonpolar solute in such an environment. Use of nonphysical soft-core reference states helps to sample properly sized cavities, and post-MD simulation rotational and translational sampling of the solute to be perturbed leads to much improved free enthalpy estimates from one-step perturbation. PMID:23081811

Lin, Zhixiong; van Gunsteren, Wilfred F

2013-02-15

100

Single molecule and single quantum dot photodynamics by polarization-rotating modulation microscopy  

NASA Astrophysics Data System (ADS)

We present our recent study of polarization modulating fluorescence imaging microscopy on single CdSe colloidal quantum dots (QDs) and quantum rods (QRs) adsorbed on silica glass substrates at room temperatures. Simple optical setup is introduced to provide detection of emission profiles projected on to the sample plane as well as detection of rotating excitation polarization effect. While most studies so far in structural changes in biological or amorphous systems rely on extrinsic fluorophores with linear transition dipoles, those with twofold degenerate dipoles are noteworthy due to the intrinsic advantage for 3D orientation information. Performance of modulations is also evaluated in combination with tetramethylrodamine moieties as typical linear emitters. CdSe QDs with aspect ratio of 1.3 actually reveal plane-polarized emission at room temperature and, based on maximum-likelihood analysis, are exceptionally highly oriented on silica glass substrates.

Tani, Toshiro; Sakai, Hiroshi; Usukura, Eiji; Suzuki, Tetsu; Oda, Masaru

101

Surface impact ionization of polar-molecule clusters through pickup of alkali atoms  

NASA Astrophysics Data System (ADS)

The observation that clusters of neutral H2O () or SO2 (ref. 5) molecules, on impact with essentially any solid surface, can decay efficiently into positively and negatively charged fragments has defied explanation, not least because the kinetic energy per molecule can be much smaller than the molecular ionization potentials. Here we present a microscopic model of the charging mechanism, based on a mass analysis of charged SO2 cluster fragments, which appears to be applicable to polar-molecule clusters more generally. Our mass spectra reveal that all positively charged fragments carry an alkali ion (sodium, potassium or caesium), whereas the negative fragments are simply (SO2)n-. The yields of both charged species are comparable, and can be enhanced significantly by pre-treating the sample surface with additional alkali atoms. The key to charge separation in the clusters therefore appears to be the pickup of a neutral (but readily ionized) adatom during impact, followed by delocalization of the adatom's valence electron within the cluster and the subsequent collision-induced fragmentation of the cluster into charged pieces. This process could be of practical use in, for example, charge-pair generation and surface analysis; it may also be relevant to atmospheric ionization processes.

Gebhardt, C. R.; Schröder, H.; Kompa, K.-L.

1999-08-01

102

Evidence for Extremely High Dust Polarization Efficiency in NGC 3184  

Microsoft Academic Search

Recent studies have found the Type II-plateau supernova (SN) 1999gi to be highly polarized (pmax=5.8%, where pmax is the highest degree of polarization measured in the optical bandpass) and minimally reddened [E(B-V)=0.21+\\/-0.09 mag]. From multiple lines of evidence, including the convincing fit of a ``Serkowski'' interstellar polarization (ISP) curve to the continuum polarization shape, we conclude that the bulk of

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

2002-01-01

103

Infrared spectroscopy of conjugated organic molecules under high pressure  

Microsoft Academic Search

Conjugated organic molecules are important components in solid-state optoelectronic devices and laser dyes. Changes in the conformations of these molecules affect the optical emission wavelengths. In order to probe the conformation of conjugated molecules, infrared (IR) spectroscopy was performed on organic solids under high hydrostatic pressures. We investigated polyphenyl molecules, such as biphenyl, p-terphenyl, and p-quaterphenyl. It was shown that

Kirill Khamidovich Zhuravlev

2004-01-01

104

Induced and Form Birefringence in High-Frequency Polarization Gratings  

NASA Astrophysics Data System (ADS)

High-frequency phase polarization gratings are fabricated holographically in dichromated gelatin dyed with malachite green. It is observed that the intensity of the -1 diffracted beam is a sinusoidal function of the incident polarization angle. In addition, we analyze the dependence of the diffracted order polarization on grating frequency. It is evident from our results that form birefringence becomes significant when the grating period is smaller than the illumination wavelength, thus modifying the optically induced birefringence. Then, in polarization hologram reconstruction, it is not possible to obtain the polarization distribution at the recording step for high-frequency objects.

Martinez-Ponce, Geminiano; Solano, Cristina

2001-08-01

105

Ion momentum analysis of double ionization of stretched molecules by circularly polarized laser pulses  

NASA Astrophysics Data System (ADS)

Using classical ensemble method, we study double ionization (DI) of stretched molecules driven by circularly polarized laser pulses. Classical DI trajectories show that DI is dominated by nonsequential double ionization (NSDI). We find that as R increases, the ion sum-momentum distribution translates from a single-band structure to a three-band structure, and its projection in the direction parallel to the molecular axis changes from a single central peak, to a central-peak with two side shoulders, then to a double-peak. From the ion sum-momentum distributions, the dominant ionization mechanism is identified that translates from collision excitation with subsequent field-ionization (CESI) to collision ionization (CI) as R increases.

Tong, Aihong

2014-02-01

106

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

NASA Astrophysics Data System (ADS)

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

?urík, R.; Šulc, M.

2010-09-01

107

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

PubMed Central

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

Alsharaeh, Edreese H.

2011-01-01

108

Photoinduced electric currents in ring-shaped molecules by circularly polarized laser pulses  

SciTech Connect

We have theoretically demonstrated that circularly polarized laser pulses induce electric currents and magnetic moments in ring-shaped molecules Na{sub 10} and benzene. The time-dependent adiabatic local density approximation is employed for this purpose, solving the time-dependent Kohn-Sham equation in real space and real time. It has been found that the electric currents are induced efficiently and persist continuously even after the laser pulses were switched off provided the frequency of the applied laser pulse is in tune with the excitation energy of the electronic excited state with the dipole strength for each molecular system. The electric currents are definitely revealed to be a second-order nonlinear optical response to the magnitude of the electric field. The magnetic dipole moments inevitably accompany the ring currents, so that the molecules are magnetized. The production of the electric currents and the magnetic moments in the present procedure is found to be much more efficient than that utilizing static magnetic fields.

Nobusada, Katsuyuki; Yabana, Kazuhiro [Department of Theoretical Studies, Institute for Molecular Science, Okazaki 444-8585 (Japan); Center for Computational Sciences and Institute of Physics, University of Tsukuba, Tsukuba 305-8571 (Japan)

2007-03-15

109

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

110

High energy physics with polarized proton beams  

Microsoft Academic Search

A brief review of the polarization program at the Argonne ZGS is given. Elastic and inelastic proton-proton interactions are discussed including such topics as total cross sections and analyzing power. (AIP)

R. C. Fernow; A. D. Krisch

1981-01-01

111

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

NASA Astrophysics Data System (ADS)

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

Ma, Xiao

112

Orbital geometry determined by orthogonal high-order harmonic polarization components  

SciTech Connect

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

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

2010-04-15

113

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 (M² < 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

114

A comparison of the properties of highly polarized QSOs versus low-polarization QSOs  

NASA Technical Reports Server (NTRS)

An optical linear-polarization survey testing the relationships between polarization and other properties of QSOs is presented. Polarimetric observations of 239 QSOs have been made. Data from the literature are used to analyze the relationships between polarization and radio, optical, and X-ray properties. The highly polarized QSOs are generally compact radio sources, are associated with radio properties such as low-frequency variability and superluminal motion, exhibit large-amplitude rapid photometric variability, have steep nonthermal optical continua, and may show excess X-ray emission. No relationship is seen between polarization and redshift, optical luminosity, or the equivalent width of emission lines. The results are discussed in the context of both isotropic and anisotropic (beaming) models. While the associations between the optical and radio properties of highly polarized QSOs provide strong motivation for the anisotropic model, the lack of associations with redshift, optical luminosity, and emission-line strength is inconsistent with this model. It is concluded that the highly polarized QSOs are probably fundamentally different in their physical properties from low-polarization QSOs.

Moore, R. L.; Stockman, H. S.

1984-01-01

115

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

116

Odor sensor with water membrane using surface polarity controlling method and analysis of responses to partial structures of odor molecules  

Microsoft Academic Search

A novel odor sensing system which imitates the process of reception of odorants in biological olfactory system had been developed, utilizing surface polarity controlling method as a transducer of the sensor. In biological system, odorants are received by a large number of receptors, which recognize not whole structures but partial structures of molecules. The present sensor responded partial structures of

Ryosuke Izumi; Kenshi Hayashi; Kiyoshi Toko

2004-01-01

117

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

118

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

119

Dip-Pen Nanolithography of High Melting-Temperature Molecules  

PubMed Central

Direct nanopatterning of a number of high melting-temperature molecules have been systematically investigated by Dip-Pen Nanolithography (DPN). By tuning DPN experimental conditions, all of the high melting-temperature molecules transported smoothly from the AFM tip to the surface at room temperature without tip pre-heating. Water meniscus formation between the tip and substrate is found to play a critical role in patterning high melting-temperature molecules. These results show that heating an AFM probe to a temperature above the ink's melting temperature is not a prerequisite for ink delivery, which extends the current “ink-substrate” combinations, available to DPN users.

Huang, Ling; Chang, Yu-Hsu; Kakkassery, Joseph J.; Mirkin, Chad A.

2008-01-01

120

Elliptical polarization of Saturn Kilometric Radiation observed from high latitudes  

NASA Astrophysics Data System (ADS)

The high-inclination orbits of the Cassini spacecraft from autumn 2006 until spring 2007 allowed the Cassini/RPWS (Radio and Plasma Wave Science) instrument to observe Saturn Kilometric Radiation (SKR) from latitudes up to 60° for the first time. This has revealed a surprising new property of SKR: above ˜30° in observational latitude, a significant amount of SKR is strongly elliptically polarized, in marked contrast to previous observations from low latitudes, which showed only circular polarization. There are transitional latitudes where the elliptical polarization occurs in “patches” in the time-frequency spectrograms next to regions of still completely circularly polarized SKR. From ˜45° to 60° in northern latitude, it is found that most of the SKR is elliptically polarized throughout its entire frequency range with an average degree of ˜0.7 in linear polarization. We demonstrate the ellipticity of SKR by using the concept of “apparent polarization” in case of two-antenna measurements, but also show three-antenna measurements from which the polarization can be unambiguously determined. Possible reasons for the variation of SKR polarization with the observer's latitude will be discussed.

Fischer, G.; Cecconi, B.; Lamy, L.; Ye, S.-Y.; Taubenschuss, U.; Macher, W.; Zarka, P.; Kurth, W. S.; Gurnett, D. A.

2009-08-01

121

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

122

High value of ferroelectric polarization in BFO nanorods  

NASA Astrophysics Data System (ADS)

Significantly high value of polarization is obtained in multiferroic Bismuth Ferrite (BFO) in form of nanorods protruding out. These were developed on porous Anodised Alumina (AAO) templates using wet chemical technique. Diameters of nanorods vary in the range from 10-100 nm. The high value of polarization is attributed to the nanostructure. There is no leakage current in P-E loop observed at various fields and frequencies.

Bandyopadhyay, S. K.; Dutta, Nabanita; Rana, Subhasis; Sen, Pintu; Himanshu, A. K.; Chakraborty, P. K.

2014-04-01

123

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

124

Cold polar molecules in two-dimensional traps: Tailoring interactions with external fields for novel quantum phases  

SciTech Connect

We discuss techniques to engineer effective long-range interactions between polar molecules using external static electric and microwave fields. We consider a setup where molecules are trapped in a two-dimensional pancake geometry by a far-off-resonance optical trap, which ensures the stability of the dipolar collisions. We detail how to modify the shape and the strength of the long-range part of interaction potentials, which can be utilized to realize interesting quantum phases in the context of cold molecular gases.

Micheli, A.; Pupillo, G.; Buechler, H. P.; Zoller, P. [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria) and Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020, Innsbruck (Austria)

2007-10-15

125

Implementation of van der Waals Density Functional Approach to the Spin-Polarized System: Interaction Potential between Oxygen Molecules  

NASA Astrophysics Data System (ADS)

We propose a practical approach to spin-polarized systems within the van der Waals density functional (vdW-DF). The method was applied to a gas phase oxygen molecule and a parallel (H-type) pair of oxygen molecules. It was found that vdW-DF improves the equilibrium distance and binding energy. In particular, one type of vdW-DF can describe such systems reasonably well. The van der Waals interaction has been confirmed to have an energy comparable to the magnetic one, while emerging at a distance rather longer than the latter.

Obata, Masao; Nakamura, Makoto; Hamada, Ikutaro; Oda, Tatsuki

2013-09-01

126

Circularly polarized attosecond pulses from molecular high-order harmonic generation by ultrashort intense bichromatic circularly and linearly polarized laser pulses  

NASA Astrophysics Data System (ADS)

We describe the generation of high-order elliptically and circularly polarized harmonic spectra in an aligned H+2 molecule ion by a combination of two-colour ultrashort intense laser fields from numerical solutions of the corresponding time-dependent Schrödinger equation (TDSE). In intense bichromatic circularly and linearly or circularly polarized laser pulses with intensity I0 and angular frequencies ?0 and 2?0, it is found that maximum molecular high-order harmonic generation (MHOHG) energies are functions of the molecular internuclear distance. Based on a classical model of laser-induced electron collisions with neighbouring ions, the optimal values of the pulse relative carrier envelope phase phi, the molecular internuclear distance R and the angle thetav of molecular alignment to the laser polarization axis are obtained for efficiently producing MHOHG spectra with the maximum harmonic energy Ip + 13.5Up, where Ip is the ionization potential of the molecule and Up = I0/4me?20 is the ponderomotive energy of the continuum electron at intensity I0 and frequency ?0 of the laser pulse. The results have been confirmed from corresponding TDSE nonperturbative numerical simulations. The polarization property of the generated harmonics is also presented. The mechanism of MHOHG is further characterized with a Gabor time frequency analysis. It is confirmed that a single collision trajectory of the continuum electron with neighbouring ions dominates in the MHOHG processes. The high efficiency of the proposed MHOHG scheme provides a possible source for production of elliptically and/or circularly polarized attosecond extreme ultraviolet pulses. Circularly polarized attosecond pulses can also be generated by using intense ultrashort circularly polarized laser pulses in combination with static electric fields of comparable intensity for H+2 at equilibrium. A time frequency analysis also confirms the role of single recollisions as the dominant mechanism of the generation of circularly polarized harmonics.

Yuan, Kai-Jun; Bandrauk, André D.

2012-04-01

127

Molecules in intense xuv pulses: Beyond the dipole approximation in linearly and circularly polarized fields  

SciTech Connect

The ionization dynamics of H{sub 2}{sup +} in an intense xuv laser pulse is studied beyond the dipole approximation in fields of linear and circular polarization. Our theoretical work shows distinct signatures of new ionization mechanisms and subsequent dynamics. Both low- and high-energy electrons emerge from the interaction to yield a characteristic and universal multilobe structure in the angular distributions which is uniquely linked to the initial molecular orientation. Each lobe is associated with its own characteristic electron dynamics. The emission spectra reveal processes that can be associated with single-center scattering, but show also clear evidence of two-center interference dynamics that can be explained by a simple two-center interference-diffraction model capturing the symmetry differences between 1{sigma}{sub g} and 1{sigma}{sub u} initial states.

Foerre, M.; Selstoe, S.; Hansen, J. P. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Kjeldsen, T. K.; Madsen, L. B. [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus (Denmark)

2007-09-15

128

Determination of molecular multipole moments and potential function parameters of non-polar molecules from far infra-red spectra  

Microsoft Academic Search

The quadrupole, Theta, and hexadecapole, Phi, moments of N2 and O2, and the octupole, Omega, and hexadecapole moments of CF4 and SiH4 are obtained from far infra-red collision-induced absorption in the gas phase at low densities where bimolecular collisions predominate. An accurate theory for evaluating Theta and Phi for non-polar diatomic molecules is presented here ; the theory for evaluating

George Birnbaum; E. Richard Cohen

1976-01-01

129

Electron Transfer from Highly Excited Atoms to Molecules  

Microsoft Academic Search

It is theoretically shown that the rate constant for reaction of electron transfer from highly excited atoms A** to polyatomic molecules B, A**+B-->A++B-, (1) at thermal velocities is equal to that of non-dissociative thermal electron capture by the molecules B, e+B-->B-, (2) based on the assumption that the negative ion formed in reaction (1) is the same species as that

Michio Matsuzawa

1972-01-01

130

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

131

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

132

Polymerization of biological molecules under high magnetic fields  

Microsoft Academic Search

The polymerization process of fibrin, one of the diamagnetic molecules in blood plasma, is carried out in a static high magnetic field up to 8 T. SEM images of the polymerized samples show a clear magnetic field effect, i.e. alignment of fibers along the field. Magnetic birefringence using pulsed high magnetic fields is also investigated.

A. Yamagishi; T. Takeuchi; M. Date; T. Higashi

1989-01-01

133

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.

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

2013-01-01

134

Polarizing agents and mechanisms for high-field dynamic nuclear polarization of frozen dielectric solids.  

PubMed

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-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 high-field 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 <20K, 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

2011-09-01

135

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.

Hu, Kan-Nian

2011-01-01

136

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 substrate’s 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.

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

2012-01-01

137

Propagation of coherent polarized light in turbid highly scattering medium.  

PubMed

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

Doronin, Alexander; Macdonald, Callum; Meglinski, Igor

2014-02-01

138

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

139

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

PubMed

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

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

2013-01-01

140

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

PubMed Central

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

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

2013-01-01

141

Focusing and trapping of DNA molecules by head-on ac electrokinetic streaming through join asymmetric polarization  

PubMed Central

In this work, invoking join asymmetric ac polarization using double half-quadrupole electrodes in a symmetric arrangement, we demonstrate a head-on ac electro-osmotic streaming capable of focusing and trapping DNA molecules efficiently. This is manifested by the observation that picomolar DNA molecules can be trapped into a large crosslike spot with at least an order of magnitude concentration enhancement within just half a minute. We identify that the phenomenon is a combined result of the formation of two prefocused DNA jets flowing toward each other, dipole-induced attraction between focused DNA molecules, and dielectrophoretic trap on the spot. With an additional horizontal pumping, we observe that the trap can transform into a peculiar pitchfork streaming capable of continuous collection and long-distance transport of concentrated DNA molecules. We also show that the same electrode design can be used to direct assembly of submicrometer particles. This newly designed microfluidic platform not only has potentials in enhancing detection sensitivity and facilitating functional assembly for on-chip analysis but also provides an added advantage of transporting target molecules in a focused and continuous manner.

Du, Jung-Rong; Wei, Hsien-Hung

2010-01-01

142

Polar Worker Adaptability to Antarctic High Altitudes.  

National Technical Information Service (NTIS)

The examinations were carried out during the 27th Soviet Antarctic expedition. Baseline data were collected before the departure of the test subjects to the Antarctic Region. Prior to their ascent to the high mountain area they were divided into two group...

A. A. Aydaraliyev A. L. Maksimov T. B. Chernook

1988-01-01

143

Possibilities with pulsed polarized high density slow positrons  

NASA Astrophysics Data System (ADS)

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

Mills, A. P., Jr.

2014-04-01

144

High throughput single molecule detection for monitoring biochemical reactions  

PubMed Central

The design, performance and application of a novel optical system for high throughput single molecule detection (SMD) configured in a continuous flow format using microfluidics is reported. The system consisted of a microfabricated polymer-based multi-channel fluidic network situated within the optical path of a laser source (?ex = 660 nm) with photon transduction accomplished using an electron-multiplying charge coupled device (EMCCD) operated in a frame transfer mode that allowed tracking single molecules as they passed through a large field-of-view (FoV) illumination zone. The microfluidic device consisted of 30 microchannels possessing dimensions of 30 ?m (width) × 20 ?m (depth) with a 25 mm pitch. Individual molecules were electrokinetically driven through the fluidic network and excited within the wide-field illumination area with the resulting fluorescence collected via an objective and imaged onto the EMCCD camera. The detection system demonstrated sufficient sensitivity to detect single DNA molecules labeled with a fluorescent tag (AlexaFluor 660) identified through their characteristic emission wavelength and the burst of photons produced during their transit through the excitation volume. In its present configuration and fluidic architecture, the sample processing throughput was ?4.02 × 105 molecules s?1, but could be increased dramatically through the use of narrower channels and a smaller pitch. The system was further evaluated using a single molecule-based fluorescence quenching assay for measuring the population differences between duplexed and single-stranded DNA molecules as a function of temperature for determining the duplex melting temperature, Tm.

Okagbare, Paul I.; Soper, Steven A.

2009-01-01

145

Manipulating ultracold polar molecules with microwave radiation: The influence of hyperfine structure  

SciTech Connect

We calculate the microwave spectra of ultracold {sup 40}K{sup 87}Rb alkali-metal dimers, including hyperfine interactions and in the presence of electric and magnetic fields. We show that microwave transitions may be used to transfer molecules between different hyperfine states, but only because of the presence of nuclear quadrupole interactions. Hyperfine splittings may also complicate the use of ultracold molecules for quantum computing. The spectrum of molecules oriented in electric fields may be simplified dramatically by applying a simultaneous magnetic field.

Aldegunde, J.; Hutson, Jeremy M. [Department of Chemistry, Durham University, South Road, Durham DH1 3LE (United Kingdom); Ran Hong [Department of Chemistry, Durham University, South Road, Durham DH1 3LE (United Kingdom); Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

2009-10-15

146

Infrared spectroscopy of conjugated organic molecules under high pressure  

NASA Astrophysics Data System (ADS)

Conjugated organic molecules are important components in solid-state optoelectronic devices and laser dyes. Changes in the conformations of these molecules affect the optical emission wavelengths. In order to probe the conformation of conjugated molecules, infrared (IR) spectroscopy was performed on organic solids under high hydrostatic pressures. We investigated polyphenyl molecules, such as biphenyl, p-terphenyl, and p-quaterphenyl. It was shown that polyphenyl molecules experience a phase transition in which molecules change their conformation from a twisted to a planar structure. This transition manifests itself in dramatic changes in the IR spectra. Beyond a critical pressure, specific IR-active modes abruptly become IR-inactive. IR spectra have been obtained with a Bomem DA8 Fourier-Transform IR spectrometer in the 500--5000 cm-1 spectral range. Those spectra clearly showed that when the pressure increases above the critical value some IR-peaks completely disappear from the spectrum. The critical pressure was found to range from 0.2 GPa for biphenyl to 0.9 GPa for p-quaterphenyl molecule. Numerical analysis of conjugated molecules has been done using ab initio calculations. Using the local density approximation, calculations of molecular structure, vibrational frequencies, and IR intensities were performed. The results of these numerical simulations confirmed the experimental observations and allowed us to resolve a controversy about the p-terphenyl structure in the twisted conformation. They also demonstrated that high-pressure IR spectroscopy can be a very sensitive tool in probing molecular structure. In order to investigate the effect of pressure, as dimensions approach the nano-scale, IR spectroscopy was performed on nm-thick organic films. The special technique called surface-enhanced infrared absorption spectroscopy (SEIRA) has been applied to the investigation of a thin film (30 nm) of p-nitrothiophenol under high pressure. The phenomenon of absorption enhancement in the presence of thin metal film has been used to obtain the absorption spectra of thin layer of p-nitrothiophenol.

Zhuravlev, Kirill Khamidovich

147

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

Microsoft Academic Search

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

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

2007-01-01

148

Polarized expression of major histocompatibility complex class I molecules in human endometrial and endocervical epithelial cells.  

PubMed

The localization of major histocompatibility complex (MHC) class I molecules in human endometrial and endocervical epithelial cells was studied with an immunogold technique on ultrathin cryosections. At the cell surface, MHC class I molecules are delivered solely to the basolateral plasma membrane in human epithelia. Therefore, only the basolateral domain of epithelial cells is capable of presenting antigen to MHC class I-restricted cytotoxic T cells. PMID:1748151

Van Eijkeren, M A; Peters, P J; Geuze, H J

1991-12-01

149

The complex susceptibility of liquid water as a two-potential system of reorienting polar molecules  

NASA Astrophysics Data System (ADS)

The theory, elaborated in previous works is applid to the calculation of liquid water wideband (0 < ?/cm -1 < 1000) dielectric spectra. These comprise the Debye relaxation region at the centimeter/millimeter wavelengths and the two-humped absorption coefficient frequency dependence in the far infrared (FIR) region. It is supposed that a major part of the H 2O molecules, called [L]-particles or [L]-molecules, are bonded by relatively strong H-bonds; [L]-molecules perform librations of relatively small amplitude ? (? is about 20°). The remaining molecules, called [R]-molecules, have more rotational/translational mobility. A new microscopic molecular confined rotator/double well potential model of liquid water is developed. The contributions of [L]- and [R]-molecules to the complex permittivity ? are found on the basis of the confined rotator (CR) and the double well potential (DWP) models, with rectangular and cos 2? intermolecular potential profiles, respectively. It is shown that the CR/DWP model gives a good description of the Debye relaxation and a qualitative description of the FIR dielectric spectra of water.

Gaiduk, Vladimir I.; Gaiduk, Vladimir V.; McConnell, James

1995-02-01

150

Preparation of highly polarized nuclei: Observation and control of time-dependent polarization transfer from H{sup 35}Cl molecular rotation to {sup 35}Cl nuclear spin  

SciTech Connect

We demonstrate time-dependent polarization transfer from molecular rotation to nuclear spin. The H{sup 35}Cl (v=2,J=1,M=1) state is excited with a 1.7 {mu}m laser pulse, and then dissociated with a delayed 235 nm laser pulse to produce {sup 35}Cl atoms. Time-dependent polarizations of both H{sup 35}Cl (v=2,J=1) molecules and {sup 35}Cl({sup 2}P{sub 3/2}) atoms, which vary due to hyperfine quantum beating, are measured. The {sup 35}Cl nuclear spin is highly polarized ({approx_equal}1.1) at a pump-probe delay of 145 ns. Densities surpassing 10{sup 14} cm{sup -3} are achieved. The technique is applicable to many atoms not amenable to optical pumping.

Sofikitis, Dimitris; Rakitzis, T. Peter [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, 71110 Heraklion-Crete (Greece); Department of Physics, University of Crete, P.O. 2208, 71003 Voutes-Heraklion (Greece); Rubio-Lago, Luis [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, 71110 Heraklion-Crete (Greece); Martin, Marion R.; Brown, Davida J. Ankeny; Bartlett, Nathaniel C.-M.; Zare, Richard N. [Department of Chemistry, Stanford University, Stanford, California 94305-5080 (United States)

2007-07-15

151

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.

Xu, Yanji; Weiss, Louis M.

2011-01-01

152

High Harmonic Spectroscopy of the Cooper Minimum in Molecules  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

153

Polarization synthesized optical transversal filter employing high birefringence fiber gratings  

Microsoft Academic Search

Polarization synthesizing is introduced into a Bragg grating based optical fiber transversal filter to realize incoherent operation. High birefringence fiber Bragg gratings are used to produce an optical transversal filter with tunable microwave frequency response and large free spectral range immune to optical coherent noise

W. Zhang; J. A. R. Williams; I. Bennion

2001-01-01

154

Spectropolarimetry of the unusual high-polarization quasar OI 287  

SciTech Connect

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

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

1988-08-01

155

Studies of ultra-low energy electron-molecule collisions using very-high-n Rydberg atoms  

Microsoft Academic Search

Potassium atoms in selected high-lying np Rydberg states (80 ⤠n ⤠400) are being used as a tool to examine electron-polar molecule collisions at ultra-low energies (â¼80 μeV - 1 meV). This energy regime has not been investigated previously and is of interest because the corresponding electron de Broglie wavelength is large, â¼1300 - 330 â«, and because the

M. T. Frey; X. Ling; K. A. Smith; F. B. Dunning

1993-01-01

156

The Spreading of Oils on Water Part I. Ionized Molecules Having Only One Polar Group  

Microsoft Academic Search

The spreading phenomena on water of drops of mineral oils containing a wide variety of organic acids and amines having but one polar group have been studied under conditions where dissociation at the oil-water interface could most readily occur. Particular emphasis is placed on the homologous series as an aid in separating the variables involved. Various phenomena of edge diffusion

W. A. Zisman

1941-01-01

157

Radiative polarization in high-energy storage rings  

SciTech Connect

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

Mane, S.R.

1989-03-01

158

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

SciTech Connect

In collaboration with the Max-Planck-Institut (MPI) fuer Kernphysik in Heidelberg and the University of Marburg we presently design and construct a high intensity polarized atomic beam source. It is intended to deliver 1*10{sup 17} atoms/sec in one hyperfine state into a storage cell for FILTEX. FILTEX is an abbreviation for FILTer EXperiment aiming to polarize storage ring beams. The structure and the vacuum chambers of this source are completed and installed at the Heidelberg Test Storage Ring (TSR). Vacuum pumps, gauges etc. are mounted and partly connected to a logical operation system. When atomic beam nozzle and skimmer geometries and distances as well as the nozzle temperature are optimized, the final geometrical arrangement or our new hybrid sixpole magnets will be decided and the whole source should be completed by the end of 1989.

Schiemenz, P. (University of Munchen, Am Coulombwall 1, D-8046 Garching, Germany (DE))

1989-05-05

159

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

NASA Astrophysics Data System (ADS)

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

Schiemenz, P.

1989-05-01

160

Collective phenomena in a quasi-two-dimensional system of fermionic polar molecules: Band renormalization and excitons  

SciTech Connect

We theoretically analyze a quasi-two-dimensional system of fermionic polar molecules trapped in a harmonic transverse confining potential. The renormalized energy bands are calculated by solving the Hartree-Fock equation numerically for various trap and dipolar interaction strengths. The intersubband excitations of the system are studied in the conserving time-dependent Hartree-Fock (TDHF) approximation from the perspective of lattice modulation spectroscopy experiments. We find that the excitation spectrum consists of both intersubband particle-hole excitation continua and antibound excitons whose antibinding behavior is associated to the anisotropic nature of dipolar interactions. The excitonic modes are shown to capture the majority of the spectral weight. We evaluate the intersubband transition rates in order to investigate the nature of the excitonic modes and find that they are antibound states formed from particle-hole excitations arising from several subbands. We discuss the sum rules in the context of lattice modulation spectroscopy experiments and utilize them to check the consistency of the obtained results. Our results indicate that the excitonic effects persist for interaction strengths and temperatures accessible in the current experiments with polar molecules.

Babadi, Mehrtash; Demler, Eugene [Physics Department, Harvard University, Cambridge, Massachusetts 02138 (United States)

2011-09-15

161

Zeeman atomic absorption spectrometry using high frequency modulated light polarization  

NASA Astrophysics Data System (ADS)

This paper reports the novel use of Zeeman atomic absorption spectrometry using high frequency modulated light polarization (ZAAS-HFM), its theoretical basis and experimental validation. Due to the high frequency modulation of the analytical and reference signals, the temporal background correction error is reduced below 10 -5 absorbance units. In addition, the use of ZAAS-HFM enables the operator to increase the apparatus transmittance and therefore to reduce the detection limits and to broaden the dynamic range of the analytical curves.

Sholupov, S. E.; Ganeyev, A. A.

1995-09-01

162

High-throughput single-molecule optofluidic analysis  

PubMed Central

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

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

2011-01-01

163

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

PubMed Central

Two luminescent terbium(III) complexes have been prepared from chiral ligands containing 2-hydroxyisophthalamide (IAM) antenna chromophores and their non-polarized and circularly-polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/TbIII complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in TbIII complexes that display both large luminescence quantum yield (?) values and strong circularly polarized luminescence (CPL) activities. Both TbIII complexes are highly emissive, with ? values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H2O and D2O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H2O molecule directly bound to the TbIII ion and a complex with no water molecules in the inner coordination sphere. Both cyLI-Tb and dpenLI-Tb display increased CPL activity compared to previously reported TbIII complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI-Tb, and multiple emissive species in the case of dpenLI-Tb.

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

2010-01-01

164

Quantitative polarized Raman spectroscopy in highly turbid bone tissue  

PubMed Central

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

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

2010-01-01

165

Magnetically-induced ferroelectric polarization in a molecule-based quantum magnet  

NASA Astrophysics Data System (ADS)

Ferroelectricity coupled to antiferromagnetic (AFM) order has been observed in the organic S=1/2 chain compound CDC (CuCl2 2(CH3)2SO). For magnetic fields along the orthorhombic c-axis, AFM order occurs below TN = 0.93 K and H ˜ 4 T. A spin-flop transition above Hsf = 0.35 T leads to a magnetically ordered state that breaks inversion symmetry along the b-axis for 0.35 T < H < 4 T. Measurements of the pyroelectric effect and the dielectric constant along b indicate ferroelectricity occurring in this same region of HT phase space with the spin polarization closely tracking the magnetic order parameter. The ferroelectric polarization is observed without electrically poling the material, and polarization switching can be observed by consecutive field sweeps in the same direction. While the magnetically-induced ferroelectricity in CDC is far from practical temperatures and fields, it nevertheless demonstrates that this phenomena can occur in a whole new class of compounds.

Zapf, Vivien; Fabris, Frederik; Kenzelmann, Michel; Balakirev, Fedor; Chen, Ying; Broholm, Colin

2008-03-01

166

Polarized distribution of carcinoembryonic antigen is associated with a tight junction molecule in human colorectal adenocarcinoma.  

PubMed

This study we presents a novel anti-occludin monoclonal antibody that can be used for formalin-fixed, paraffin-embedded tissue sections. The relationships between aberrant localization of carcinoembryonic antigen (CEA) and abnormalities of tight junctions were studied in human colorectal cancers by this antibody. Abnormalities in the cell surface expression of CEA have been shown to be characteristic of human colorectal cancer cells. Cancer cells that participated in the formation of glandular structures expressed occludin at the apical cell border and CEA was expressed more apically than occludin. Where cancer cells showed solid nests without glandular structures, occludin was completely lost and CEA was demonstrated in a diffuse pattern throughout the cells. These findings suggest that the polarized apical expression of CEA in neoplastic glandular structures depends on the expression of occludin and the fence function of tight junctions. During tumour progression, loss of occludin may lead to the loss of membrane polarity and the non-polarized expression of CEA. The antibody described provides a powerful tool for the study of tight junctions in surgically resected human tissue. PMID:12237880

Tobioka, Hirotoshi; Isomura, Hiroshi; Kokai, Yasuo; Sawada, Norimasa

2002-10-01

167

Radio properties of the highly polarized, quiescent quasar OI 287  

SciTech Connect

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

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

1988-05-01

168

Radio properties of the highly polarized, quiescent quasar OI 287  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

169

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

170

Highly parallelized detection of single fluorescent molecules: simulation and experiment  

NASA Astrophysics Data System (ADS)

We are developing an ultrasensitive, fluorescence-based detection system in highly parallel microchannels. Multichannel microfluidic devices have been fabricated by direct femtosecond laser machining of fused silica substrates. We approach single-molecule detection sensitivity by introducing dilute aqueous solutions (˜ pM) of fluorescently labeled molecules into the microchannels. In a custom-built, wide-field microscope, a line-generating red diode laser provides narrow epi-illumination across a 500 ?m field of view. Fluorescence is detected with an electron-multiplying CCD camera allowing readout rates of several kHz. Rapid initial assessment is performed through digital filtering derived from simulations based on experimental parameters. Good agreement has been shown between simulation and experimental data. Fluorescence correlation spectroscopy then provides more detailed analysis of each separate channel. Following optimization, microfluidic devices could easily be mass-produced in low-cost polymers using imprint lithography.

Canfield, Brian K.; King, Jason K.; Robinson, William N.; Hofmeister, William H.; Davis, Lloyd M.

2011-10-01

171

High-Resolution, Single-Molecule Measurements of Biomolecular Motion  

PubMed Central

Many biologically important macromolecules undergo motions that are essential to their function. Biophysical techniques can now resolve the motions of single molecules down to the nanometer scale or even below, providing new insights into the mechanisms that drive molecular movements. This review outlines the principal approaches that have been used for high-resolution measurements of single-molecule motion, including centroid tracking, fluorescence resonance energy transfer, magnetic tweezers, atomic force microscopy, and optical traps. For each technique, the principles of operation are outlined, the capabilities and typical applications are examined, and various practical issues for implementation are considered. Extensions to these methods are also discussed, with an eye toward future application to outstanding biological problems.

Greenleaf, William J.; Woodside, Michael T.; Block, Steven M.

2007-01-01

172

Fusion with highly spin polarized HD and D2  

NASA Astrophysics Data System (ADS)

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

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

1993-12-01

173

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

PubMed

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

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

2011-07-26

174

Orientation of jet-cooled polar molecules with an intense single-cycle THz pulse  

NASA Astrophysics Data System (ADS)

We report the direct observation of the orientation of jet-cooled molecules induced by a THz pulse. The intense THz field (˜30 kV/cm) creates a superposition between the rotational ground state (J =0) and the excited state (J =1) of HBr molecules. The rotational dynamics is probed by Coulomb explosion imaging of the fragment ions produced by a near-infrared femtosecond laser pulse. Comparing with the simulations based on a time-dependent Schrödinger equation, the rotational wave packets are completely reconstructed, which reveal that ˜7×10-4 of the ground-state population is transferred to the J =1 state at an initial temperature of 8 K, achieving a degree of orientation of ˜0.017.

Kitano, Kenta; Ishii, Nobuhisa; Kanda, Natsuki; Matsumoto, Yoshiyuki; Kanai, Teruto; Kuwata-Gonokami, Makoto; Itatani, Jiro

2013-12-01

175

Studies of parity and time reversal violations in heavy polar molecules  

NASA Astrophysics Data System (ADS)

Investigation of phenomena involving parity (P) and time reversal (T) symmetry violations is of fundamental importance in physics. A few experiments to search for the P,T-odd effects have been performed on TlF and YbF molecules and considerable progress for PbO and PbF molecules is on the way. For the interpretation of the measured experimental data, it is necessary to calculate a few molecular properties which cannot be measured experimentally. These molecular properties establish some connection between the measured data and well studied fundamental constants. Very accurate and reliable calculations of these properties usually require accurate accounting for both relativistic and correlation effects in heavy-atom systems. In this review, we discuss the P, T-odd interaction constants W d and W s. The interaction constant W d arises from the interaction of electron electric dipole moment (EDM) d e with the molecular electric field, and the constant W s arises due to the electron-nucleus scalar-pseudoscalar (S-PS) interaction. The knowledge of W d is essential to put a reliable limit on the electron EDM d e , where as the knowledge of W s is necessary to get the information about the electron-nucleus (S-PS) coupling constant k s , and to test the Standard Model (SM) of particle physics. Presently available theoretical results of W d and W s for the ground states of YbF and BaF molecules are also presented.

Nayak, Malaya K.

2010-06-01

176

Studies of parity and time reversal violations in heavy polar molecules  

NASA Astrophysics Data System (ADS)

Investigation of phenomena involving parity (P) and time reversal (T) symmetry violations is of fundamental importance in physics. A few experiments to search for the P,T-odd effects have been performed on TlF and YbF molecules and considerable progress for PbO and PbF molecules is on the way. For the interpretation of the measured experimental data, it is necessary to calculate a few molecular properties which cannot be measured experimentally. These molecular properties establish some connection between the measured data and well studied fundamental constants. Very accurate and reliable calculations of these properties usually require accurate accounting for both relativistic and correlation effects in heavy-atom systems. In this review, we discuss the P, T-odd interaction constants W d and W s. The interaction constant W d arises from the interaction of electron electric dipole moment (EDM) d e with the molecular electric field, and the constant W s arises due to the electron-nucleus scalar-pseudoscalar (S-PS) interaction. The knowledge of W d is essential to put a reliable limit on the electron EDM d e , where as the knowledge of W s is necessary to get the information about the electron-nucleus (S-PS) coupling constant k s , and to test the Standard Model (SM) of particle physics. Presently available theoretical results of W d and W s for the ground states of YbF and BaF molecules are also presented.

Nayak, Malaya K.

177

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

PubMed

Hydrogen produced from the photocatalytic splitting of water is one of the reliable alternatives to replace the polluting fossil and the radioactive nuclear fuels. Here, we provide unequivocal evidence for the existence of blue- and red-shifting O-H covalent bonds within a single water molecule adsorbed on the MgO surface as a result of asymmetric displacement polarizabilities. The adsorbed H-O-H on MgO gives rise to one weaker H-O bond, while the other O-H covalent bond from the same adsorbed water molecule compensates this effect with a stronger bond. The weaker bond (nearest to the surface), the interlayer tunneling electrons and the silver substrate are shown to be the causes for the smallest dissociative activation energy on the MgO monolayer. The origin that is responsible to initiate the splitting mechanism is proven to be due to the changes in the polarizability of an adsorbed water molecule, which are further supported by the temperature-dependent static dielectric constant measurements for water below the first-order electronic-phase transition temperature. PMID:21776515

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

2011-09-01

178

A high-resolution micro-circular-polarization-analyzer array for real-time active circular polarization imaging  

Microsoft Academic Search

In this paper, a high-resolution micro-circular-polarization-analyzer (MCPA) array is presented and characterized. MCPAs for extracting right-handed and left-handed circularly polarized components of incident light are implemented by fabricating polymerizable-liquid-crystal (PLC) micro-retarders with perpendicular fast axes on top of a 45° laminated linear polarizing film. With sulfonic-dye-1 (SD1) as the PLC photoalignment material, an MCPA feature size as small as 5\\/Ltm

Xiaojin Zhao; A. Bermak; F. Boussaid; Lishuang Yao; V. G. Chigrinov

2009-01-01

179

High-sensitivity single molecule fluorescence detection using scanning single-molecule counting  

NASA Astrophysics Data System (ADS)

A new, simple technique for single molecule fluorescence detection has been developed and detection limit of less than 100 aM fluorophores has been demonstrated. The technique, similarly to Fluorescence Correlation Spectroscopy (FCS) and other related techniques, uses confocal optics, but differs in that it detects individual molecules crossing the inside of a scanning confocal volume without using statistical techniques as applied in FCS or similar methods. The scanning speed of the confocal volume is higher than the Brownian motion speed of the molecules. Thus, the time evolution of the light intensity data reflects the confocal volume intensity profile, which clearly shows the crossing of single molecules. The estimated total scanning volume enables the concentration or the density of molecules to be obtained. In addition, information related to the rotational and translational diffusion of the molecule was obtained for the purpose of identifying different molecules. It was shown that utilizing the plural characteristic properties of molecules passing through a confocal volume makes possible the discrimination of different molecules. The proposed technique is based on the simple principle of counting molecules one by one using a scanning confocal volume, and is hereafter referred to as Scanning Single-Molecule Counting (SSMC).

Yamaguchi, Mitsushiro; Tanabe, Tetsuya; Nakata, Hidetaka; Hanashi, Takuya; Nishikawa, Kazutaka; Hori, Kunio; Kondo, Seiji

2014-02-01

180

High-fidelity linear optical quantum computing with polarization encoding  

SciTech Connect

We show that the KLM scheme [Knill, Laflamme, and Milburn, Nature 409, 46 (2001)] can be implemented using polarization encoding, thus reducing the number of path modes required by half. One of the main advantages of this new implementation is that it naturally incorporates a loss detection mechanism that makes the probability of a gate introducing a non-detected error, when non-ideal detectors are considered, dependent only on the detector dark-count rate and independent of its efficiency. Since very low dark-count rate detectors are currently available, a high-fidelity gate (probability of error of order 10{sup -6} conditional on the gate being successful) can be implemented using polarization encoding. The detector efficiency determines the overall success probability of the gate but does not affect its fidelity. This can be applied to the efficient construction of optical cluster states with very high fidelity for quantum computing.

Spedalieri, Federico M. [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 126-347, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States); Lee, Hwang [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 126-347, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States); Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Dowling, Jonathan P. [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 126-347, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States); Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Institute for Quantum Studies, Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States)

2006-01-15

181

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

Microsoft Academic Search

We describe a novel scanning optical microscope based on a polarization-modulated nulling ellipsometry. The new microscope employs a combination of scanning mirror and sample translation and thus enables high-throughput label-free detection of biomolecular microarrays with more than 10 000 protein or small-molecule targets. For illustration, we show the image of a 2760-spot protein microarray on a functionalized glass slide obtained

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

2008-01-01

182

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

183

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

PubMed

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

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

2013-04-01

184

Intermolecular vibrational coherence in bacteriochlorophyll a with clustered polar solvent molecules.  

PubMed

We show that resonant impulsive excitation of the Qy absorption band of bacteriochlorophyll a (BChl) launches a rapidly damped (gamma < 200 fs) ground-state coherent wave-packet motion that arises from intermolecular modes with clustered solvent molecules. Femtosecond pump-probe, dynamic-absorption signals were obtained at room temperature with BChl solutions in pyridine, acetone, and 1-propanol. The vibrational coherence observed in the 0-800-fs regime is modeled in the time domain by two (or three, in the case of 1-propanol) modulation components with asymmetric, inhomogeneously broadened line shapes and frequencies in the 100-200-cm(-1) range. The mean frequency of the vibrational coherence exhibits at least a quadratic dependence on the dipole moment of the solvent molecules and a y-intercept in the 100-cm(-1) regime. This trend is modeled by an expression for the natural frequency of a "6-12" potential composed of attractive terms from van der Waals forces and a repulsive term from the exchange (Pauli exclusion) force. The model suggests that comparable contributions to the potential are provided by the dipole-dipole and London dispersion interactions. These results support the hypothesis that the low-frequency vibrational modes in the 100-cm(-1) regime that are coupled to the light-driven charge-separation reactions in the reaction center from purple bacteria are derived from intermolecular vibrational modes between the chromophores and the surrounding protein medium. PMID:17034248

Shelly, Katherine R; Golovich, Elizabeth C; Beck, Warren F

2006-10-19

185

New highly polar semiconductor ferroelectrics for solar energy conversion devices  

NASA Astrophysics Data System (ADS)

Solar energy is a promising long-term solution for future energy requirements; however, current solar energy conversion devices are plagued by low efficiency. The use of ferroelectric ABO3 perovskite oxides is one approach for boosting conversion efficiency. Ferroelectric oxides possess spontaneous polarization and have been shown to produce a bulk photovoltaic effect, in which charged carriers, specifically electrons and holes, separate to prevent recombination. Once separated, the high-energy electrons are available for electrical work or for the catalytic splitting of water into hydrogen and oxygen. Currently, most solid oxide ferroelectrics have a band gap of at least 3 eV, absorbing primarily in the ultra-violet (UV) region. Since UV light comprises only 8% of the solar spectrum, new materials with a decreased band gap and large polarization would be highly desirable. We use first-principles density functional theory (DFT) calculations to investigate the ground state structures of PbTiO3 solid solutions containing Ni, Pd and Pt. We predict that these proposed materials will display a decreased band gap when compared to PbTiO3, while maintaining or enhancing polarization. They are promising candidates for use as semi-conducting ferroelectric substrates for solar conversion devices.

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

2009-03-01

186

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

PubMed

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

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

2007-05-01

187

Stellar and 0ther high-temperature molecules.  

PubMed

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

Weltner, W

1967-01-13

188

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

189

High bandwidth single polarization fiber with elliptical central air hole  

Microsoft Academic Search

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

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

2005-01-01

190

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

191

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.

2009-01-01

192

High gal. lat. stars interstellar polarization (Berdyugin+, 2014)  

NASA Astrophysics Data System (ADS)

Polarization data for 2400 stars measured with the DiPol-1 and DiPol-2 CCD polarimeters at the 60cm KVA remote-controled telescope at La Palma (Canary Islands, Spain) are presented. For each star the star number (either from HD or BD catalogs), galactic coordinates (l, b), measured polarization (in percents), error of polarization, polarization angle (in degrees), error of polarization angle, and the parallax (in mas) are given. (1 data file).

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

2013-11-01

193

Diamagnetic Orientation of Polymerized Molecules under High Magnetic Field  

Microsoft Academic Search

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

Akio Yamagishi; Tetsuya Takeuchi; Terumasa Higashi; Muneyuki Date

1989-01-01

194

High sensitivity optical microscope for single molecule spectroscopy studies  

NASA Astrophysics Data System (ADS)

We describe the setup and apply two algorithms for fast imaging in a sample raster scanning two photon microscope. Imaging can be performed at a rate of 1-100 lines per second with a closed loop piezo actuator, and the detection is performed via avalanche photodiodes. This allows to investigate single molecule emission with 50 ms time resolution. In a slow scanning algorithm we have implemented fluorescence fluctuation analysis by computing the photon counting histogram (PCH) on each pixel of the image. In a fast-scan acquistion method the image acquistion rate is 5 lines per second on a large field of view and high resolution(50 nm scanning step, 100×100 ?m2 field of view) and ?100 lines per second on smaller field of views with optically limited resolution (200 nm scanning step, 20×20 ?m2 field of view). This figure, which is lower than the typical value for normal confocal scanning imaging (?500 lines per second), allows nevertheless to perform imaging studies of extended samples in reasonable times for intracellular kinetics and interactions. With this setup and by means of the PCH analysis we are able to discriminate between local concentration and molecular brightness on extended samples also at the level of the single molecule.

Malengo, Gabriele; Milani, Roberto; Cannone, Fabio; Krol, Silke; Diaspro, Alberto; Chirico, Giuseppe

2004-08-01

195

Self-assembly of disc-like molecules on polar surfaces  

NASA Astrophysics Data System (ADS)

Solution-processable solar cells provide the potential to reduce the cost and increase the availability of solar electricity. Long-range molecular order in active media of solution-processable solar cells is essential for charge transfer, and self-assembly provides a simple and efficient process to achieve molecular order on a large scale. Obtaining spontaneous alignment of charge-transfer media that maximizes light-to-electricity conversion while minimizing energy waste is essential long-range molecular order development. Molecular order decreases the potential of hole and electron pair recombination and provides a direct path for the electron to reach the electrode and produce energy. Graphene quantum dots (GQD) are ideal for solution-processable solar cells due to the abundance of carbon and a large absorption cross-section in the visible light range. Hexabenzocoronene tri-acid (HBCTA) is a smaller system that has ideal properties for preliminary investigation of molecular order. In this study, we investigate the assembly of HBCTA and different GQDs on water and mica substrates with Langmuir techniques and atomic force microscopy (AFM). GQD of varying size and functionality, and HBCTA were observed to have isothermal compression behavior involving gas, liquid, and condensed phase transitions. We further characterized these molecular behaviors at particular pressures by Langmuir deposition to mica substrates. AFM imagining reveals monolayer assemblies of "face-on" orientation for larger quantum dots and "edge-on" orientation for smaller quantum dots. These assembly features are attributed to the numbers of carboxylic acid groups in the GQDs and their geometrical arrangement. HBCTA shows a concentration and pressure-dependent arrangement of molecules.

Hamilton, Irma P.

196

A method to polarize stored antiprotons to a high degree.  

PubMed

Polarized antiprotons can be produced in a storage ring by spin-dependent interaction in a purely electron-polarized hydrogen gas target. The polarizing process is based on spin transfer from the polarized electrons of the target atoms to the orbiting antiprotons. After spin filtering for about two beam lifetimes at energies T approximately equal 40-170 MeV using a dedicated large acceptance ring, the antiproton beam polarization would reach P=0.2-0.4. Polarized antiprotons would open new and unique research opportunities for spin-physics experiments in p(-) p interactions. PMID:15698088

Rathmann, F; Lenisa, P; Steffens, E; Contalbrigo, M; Dalpiaz, P F; Kacharava, A; Lehrach, A; Lorentz, B; Maier, R; Prasuhn, D; Ströher, H

2005-01-14

197

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

PubMed

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

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

2014-03-01

198

The use of electric multipole lenses for bending and focusing polar molecules, with application to the design of a rotational-state separator  

Microsoft Academic Search

The dipole interaction (Stark effect) of a polar molecule allows one to use an inhomogeneous electric field to bend and focus a neutral beam in a transport line. The dependence of the optics on the Stark potential energy is discussed and we describe the type of multipole-field lenses that are needed. The special features that differ from charged particle optics

Juris G Kalnins

2003-01-01

199

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.

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

2009-01-01

200

A recognition algorithm for high voltage transmission lines at horizontal polarization millimeter-wave radar  

Microsoft Academic Search

In this paper, the radar phenomenology of high voltage transmission line (HVTL) is studied for examining the feasibility of recognizing HVTL using the horizontal polarization millimeter-wave radar system. For this purpose, horizontal polarization RCS and high resolution range profile (HRRP) of some HVTL are calculated at 34 GHz. Based on the observed behavior, a horizontal polarization recognition algorithm that makes

Xizhang Wei; Rui Zhang; Bin Deng

2008-01-01

201

Polarization Measurements in High-Energy Deuteron Photodisintegration  

SciTech Connect

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

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

2001-04-01

202

Amplification without inversion and high refractive index in heterogeneous molecules  

NASA Astrophysics Data System (ADS)

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

Budriga, O.

2014-10-01

203

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

NSDL National Science Digital Library

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

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

2006-06-27

204

Main Results and Perspectives of Investigation of Polarization Effects Using High Energy Accelerators.  

National Technical Information Service (NTIS)

Results of polarization investigations into high energy physics are set forth. Polarization phenomena in binary reactions (elastic hadron-hadron scattering, reactions of charge and hypercharge exchange) as well as in inclusive reactions (proton and meson ...

S. B. Nurushev

1983-01-01

205

Relativistic polarized beams for experiments on the polarized proton target at the Laboratory of High Energies  

Microsoft Academic Search

This paper gives a short review on neutron beams and a beam line to the Polarized Proton Target operating at the LHE accelerator\\u000a facility at present. A proposal and simulation results on complementary providing the setup with charged beams including polarized\\u000a protons are also presented.

P. Rukoyatkin

2001-01-01

206

An all-dielectric broadband high-transmission efficiency circular polarizer  

NASA Astrophysics Data System (ADS)

We investigated numerically an all-dielectric semiconductor-based circular polarizer consisting of silicon helix on glass substrate. Only three turns of the dielectric helix structure provides extremely high polarization suppression ratio above 2,300:1 with almost 100% transmission. Transmission efficiency greater than 85% for one circularly polarized light is maintained for incident angles as high as 300. The influence of the various helix lattice parameters on the polarization gap and the circular dichroism is also presented.

Chadha, Arvinder S.; Zhao, Deyin; Zhou, Weidong

2014-02-01

207

NCTM of liquids at high temperatures using polarization techniques  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

208

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

Microsoft Academic Search

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

W. Weltner Jr.

1980-01-01

209

Dipole polarizability of alkali-metal (Na, K, Rb)-alkaline-earth-metal (Ca, Sr) polar molecules: Prospects for alignment  

NASA Astrophysics Data System (ADS)

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

Gopakumar, Geetha; Abe, Minori; Hada, Masahiko; Kajita, Masatoshi

2014-06-01

210

Dipole polarizability of alkali-metal (Na, K, Rb)-alkaline-earth-metal (Ca, Sr) polar molecules: Prospects for alignment.  

PubMed

Electronic open-shell ground-state properties of selected alkali-metal-alkaline-earth-metal polar molecules are investigated. We determine potential energy curves of the (2)?(+) ground state at the coupled-cluster singles and doubles with partial triples (CCSD(T)) level of electron correlation. Calculated spectroscopic constants for the isotopes ((23)Na, (39)K, (85)Rb)-((40)Ca, (88)Sr) are compared with available theoretical and experimental results. The variation of the permanent dipole moment (PDM), average dipole polarizability, and polarizability anisotropy with internuclear distance is determined using finite-field perturbation theory at the CCSD(T) level. Owing to moderate PDM (KCa: 1.67 D, RbCa: 1.75 D, KSr: 1.27 D, RbSr: 1.41 D) and large polarizability anisotropy (KCa: 566 a.u., RbCa: 604 a.u., KSr: 574 a.u., RbSr: 615 a.u.), KCa, RbCa, KSr, and RbSr are potential candidates for alignment and orientation in combined intense laser and external static electric fields. PMID:24929384

Gopakumar, Geetha; Abe, Minori; Hada, Masahiko; Kajita, Masatoshi

2014-06-14

211

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

SciTech Connect

We propose to use pure phase filter in combination with high NA lens axicon to achieve high efficient longitudinally polarized beam with a subwavelength spot size and large depth of focus using hyper geometric Gaussian beam. Using this system, the spot size is reduced to 0.392 {lambda} and the depth of focus is increased to 7 {lambda}. The efficiency of such system is found to be 87%. This high efficient longitudinally polarized beam generated by hyper geometric Gaussian beam is useful for most of the near-field optics applications.

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

2011-10-20

212

Anti-Hyperon polarization in high energy pp collisions withpolarized beams  

SciTech Connect

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

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

2007-11-20

213

High efficiency two-dimensional grating reflectors with angularly tunable polarization efficiency  

NASA Astrophysics Data System (ADS)

We report on two-dimensional high-contrast subwavelength gratings with a polarization efficiency that is tunable in the angular spectrum. Due to the high index contrast it is possible to realize highly efficient reflectors with nearly angular independent reflection for light with transverse-electric polarization. Simultaneously, for transverse-magnetic polarized light the minimum and maximum reflectance can be tuned to a defined angle of incidence. Configurations with minimized and maximized polarization efficiencies at incidence angles of 0° and 45° are exemplified for a design wavelength of 1550 nm. For the case of minimum polarization efficiency we present the experimental results for a non-monolithic and a monolithic realization.

Kroker, Stefanie; Käsebier, Thomas; Steiner, Stefan; Kley, Ernst-Bernhard; Tünnermann, Andreas

2013-04-01

214

A Simple High Performance Beamline for Small Molecule Chemical Crystallography  

SciTech Connect

An innovative beamline for small molecule chemical crystallography has been built at the Advanced Light Source. The system permits the study of crystals as small as 10{mu}m x 10{mu}m x 10{mu}m. The beamline produces a 7-17 keV x-ray beam focused to a 280{mu}m x 90{mu}m spot. A channel-cut Si<111> monochromator and a toroidal mirror are inside the synchrotron shield wall only 7m from the bending magnet source point. The monochromator is cooled with a small Joule-Thomson refrigerator to produce a very small beam motion with different heat loads. The experimental hutch contains a vertically mounted sample goniometer and a CCD detector. An on-axis visual alignment camera allows the small crystals to be accurately centered within the x-ray beam. Examples of the crystal structures solved with this system are given. The beamline is also used for high-pressure powder diffraction experiments using a diamond anvil cell that is mounted on a stage system that can be quickly installed and removed.

Thompson, A.C.; Padmore, H.A.; Celestre, R.S.; Clark, S.M.; Domning, E.E.; Franck, K.D.; Morrison, G.Y. [Lawrence Berkeley Laboratory (United States); Oliver, A.G. [Chemistry Dept., University of California at Berkeley (United States); Teat, S.J. [Daresbury Laboratory (United Kingdom)

2004-05-12

215

High Frequency Electron Paramagnetic Resonance Studies of Single Molecule Magnets  

NASA Astrophysics Data System (ADS)

Single crystal samples of different single-molecule magnets (SMMs) were studied by High Frequency Electron Paramagnetic Resonance (HFEPR) in order to characterize their magnetic properties. Multiple studies have been conducted to determine the spin Hamiltonian parameters for different systems, including various Mn and Ni based SMMs. The use of single crystals allows studies in multiple orientations: when the sample's easy axis of magnetization is aligned parallel (perpendicular) to the external field, the axial (transverse) anisotropy parameters can be determined. Variable temperature studies allow the determination of the sign of the axial anisotropy parameters, as well as the energy difference between the ground state and excited states. Multiple orientation studies in a Zn system that is lightly doped with Ni allow determination of the anisotropy parameters for a single Ni^+2 ion. These results can then be compared to those for the tetranuclear nickel complex consisting of 4 Ni^+2 ions, enabling an explanation for the fast magnetic quantum tunneling in this system. Finally, analysis of absorption peak linewidths enables characterization of the disorder in SMMs. All of these studies have contributed to a better understanding of the magnetic quantum tunneling behavior in these materials.

Datta, Saiti

2005-11-01

216

A Simple High Performance Beamline for Small Molecule Chemical Crystallography  

NASA Astrophysics Data System (ADS)

An innovative beamline for small molecule chemical crystallography has been built at the Advanced Light Source. The system permits the study of crystals as small as 10?m × 10?m × 10?m. The beamline produces a 7-17 keV x-ray beam focused to a 280?m × 90?m spot. A channel-cut Si<111> monochromator and a toroidal mirror are inside the synchrotron shield wall only 7m from the bending magnet source point. The monochromator is cooled with a small Joule-Thomson refrigerator to produce a very small beam motion with different heat loads. The experimental hutch contains a vertically mounted sample goniometer and a CCD detector. An on-axis visual alignment camera allows the small crystals to be accurately centered within the x-ray beam. Examples of the crystal structures solved with this system are given. The beamline is also used for high-pressure powder diffraction experiments using a diamond anvil cell that is mounted on a stage system that can be quickly installed and removed.

Thompson, A. C.; Padmore, H. A.; Oliver, A. G.; Teat, S. J.; Celestre, R. S.; Clark, S. M.; Domning, E. E.; Franck, K. D.; Morrison, G. Y.

2004-05-01

217

Studies of ultra-low energy electron-molecule collisions using very-high-n Rydberg atoms  

SciTech Connect

Potassium atoms in selected high-lying np Rydberg states (80 {<=} n {<=} 400) are being used as a tool to examine electron-polar molecule collisions at ultra-low energies ({approximately}80 {mu}eV - 1 meV). This energy regime has not been investigated previously and is of interest because the corresponding electron de Broglie wavelength is large, {approximately}1300 - 330 {Angstrom}, and because the collision time is comparable to the period of molecular rotation. A variety of target molecules has been studied, including simple rotors such as HF, and more complex species such as NH{sub 3}, CH{sub 3}I, CH{sub 2}Br{sub 2} and C{sub 6}H{sub 5}NO{sub 2}. These targets encompass a range of dipole moments and rotational behavior, but analysis of the data shows that in each case the cross section {sigma}({epsilon}) for rotationally-inelastic electron-polar molecule scattering varies approximately as 1/{epsilon} where {epsilon} is the electron energy. Such threshold behavior is not predicted by the Born approximation and possible reasons for this discrepancy will be discussed. In the case of NH{sub 3}, the data show that near-resonant energy transfer associated with transitions between different inversion levels is an important process leading to collisional state changing.

Frey, M.T.; Ling, X.; Smith, K.A.; Dunning, F.B.

1993-05-01

218

Experimental evidence of Brillouin-induced polarization wheeling in highly birefringent optical fibers.  

PubMed

We study the influence of Stimulated Brillouin Scattering on the polarization stabilization of a light beam propagating in a highly-birefringent optical fiber. In particular, due to a saturation effect, we find that the output polarization lies on a ring when the polarization is represented onto the Poincaré sphere. PMID:19654665

Fatome, Julien; Pitois, Stéphane; Millot, Guy

2009-07-20

219

POLARIZED ION SOURCES FOR HIGH ENERGY ACCELERATORS AND COLLIDERS  

SciTech Connect

The recent progress in polarized ion source development is reviewed. In dc operation a 1.0 mA polarized H{sup -} ion current is now available from the Optically-Pumped Polarized Ion Source (OPPIS). In pulsed operation a 10 mA polarized H{sup -} ion current was demonstrated at the TRIUMF pulsed OPPIS test bench and a 3.5 mA peak current was obtained from an Atomic Beam Source (ABS) at the INR Moscow test bench. The possibilities for future improvements with both techniques are discussed. A new OPPIS for RHIC spin physics is described. The OPPIS reliably delivered polarized beam for the polarized run at RHIC. The results obtained with a new pulsed ABS injector for the IUCF Cooler Ring are also discussed.

ZELENSKI,A.N.

2000-10-16

220

POLARIZED ION SOURCES FOR HIGH ENERGY ACCELERATORS AND COLLIDERS  

SciTech Connect

The recent progress in polarized ion source development is reviewed. In dc operation a 1.0 mA polarized H{sup -} ion current is now available from the Optically-Pumped Polarized Ion Source (OPPIS) . In pulsed operation a 10 mA polarized H{sup -} ion current was demonstrated at the TRIUMF pulsed OPPIS test bench and a 3.5 mA peak current was obtained from an Atomic Beam Source (ABS) at the INR Moscow test bench. The possibilities for future improvements with both techniques are discussed. A new OPPIS for RHIC spin physics is described. The OPPIS reliably delivered polarized beam for the polarized run at RHIC. The results obtained with a new pulsed ABS injector for the IUCF Cooler Ring are also discussed.

ZELENSKI,A.N.

2000-10-16

221

Polarized ion sources for high-energy accelerators and colliders  

NASA Astrophysics Data System (ADS)

The recent progress in polarized ion source development is reviewed. In dc operation a 1.0 mA polarized H- ion current is now available from the Optically-Pumped Polarized Ion Source (OPPIS). In pulsed operation a 10 mA polarized H- ion current was demonstrated at the TRIUMF pulsed OPPIS test bench and a 2.5 mA peak current was obtained from an Atomic Beam Source (ABS) at the INR Moscow test bench. The possibilities for future improvements with both techniques are discussed. A new OPPIS for RHIC spin physics is described. The OPPIS reliably delivered polarized beam for the polarized run at RHIC. The results obtained with a new pulsed ABS injector for the IUCF Cooler Ring are also discussed. .

Zelenski, A. N.

2001-06-01

222

Polarization measurements in high-energy deuteron photodisintegration.  

PubMed

We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime. PMID:11290086

Wijesooriya, K; Afanasev, A; Amarian, M; Aniol, K; Becher, S; Benslama, K; Bimbot, L; Bosted, P; Brash, E; Calarco, J; Chai, Z; Chang, C C; Chang, T; Chen, J P; Choi, S; Chudakov, E; Churchwell, S; Crovelli, D; Dieterich, S; Dumalski, S; Dutta, D; Epstein, M; Fissum, K; Fox, B; Frullani, S; Gao, H; Gao, J; Garibaldi, F; Gayou, O; Gilman, R; Glamazdin, S; Glashausser, C; Gomez, J; Gorbenko, V; Hansen, O; Holt, R J; Hovdebo, J; Huber, G M; de Jager, C W; Jiang, X; Jones, C; Jones, M K; Kelly, J; Kinney, E; Kooijman, E; Kumbartzki, G; Kuss, M; LeRose, J; Liang, M; Lindgren, R; Liyanage, N; Malov, S; Margaziotis, D J; Markowitz, P; McCormick, K; Meekins, D; Meziani, Z E; Michaels, R; Mitchell, J; Morand, L; Perdrisat, C F; Pomatsalyuk, R; Punjabi, V; Ransome, R D; Roche, R; Rvachev, M; Saha, A; Sarty, A; Schulte, E C; Simon, D; Strauch, S; Suleiman, R; Todor, L; Ulmer, P E; Urciuoli, G M; Wojtsekhowski, B; Xiong, F; Xu, W

2001-04-01

223

Multielectron effects in high harmonic generation in N2 and benzene: Simulation using a non-adiabatic quantum molecular dynamics approach for laser-molecule interactions  

NASA Astrophysics Data System (ADS)

A mixed quantum-classical approach is introduced which allows the dynamical response of molecules driven far from equilibrium to be modeled. This method is applied 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 are possible. The approach is applied to the study of high harmonic generation in N2 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 N2 an enhancement of the cut-off harmonics is observed whenever the laser polarization is aligned perpendicular to the molecular axis. This enhancement is attributed to the symmetry properties of the Kohn-Sham orbital that responds predominantly to the pulse. In benzene we predict that a suppression in the cut-off harmonics occurs whenever the laser polarization is aligned parallel to the molecular plane. We attribute this suppression to the symmetry-induced response of the highest-occupied molecular orbital.

Dundas, Daniel

2012-05-01

224

Polarization Transfer in Proton Compton Scattering at High Momentum Transfer  

Microsoft Academic Search

Compton scattering from the proton was investigated at s = 6.9 GeV² and t = -4.0 TeV² via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in excellent agreement with a prediction based on a reaction mechanism in which the photon interacts with a single quark

D. J. Hamilton; Vahe Mamyan

2004-01-01

225

High-Resolution Waveguide THz Spectroscopy of Biological Molecules?  

PubMed Central

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

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

2008-01-01

226

The infrared polarizations of high-redshift radio galaxies  

NASA Astrophysics Data System (ADS)

This thesis reports the K-band polarizations of a representative sample of nine radio galaxies: seven 3C objects at 0.7 < z < 1.3, and two other distinctive sources. Careful consideration is given to the accurate measurement and `debiasing' of faint polarizations, with recommendations for the function of polarimetric software. 3C 22 and 3C 41 both have 3% polarization perpendicular to their radio structures, consistent with suggestions that they may be obscured quasars. 3C 54 is polarized at 6%, parallel to its radio structure. 3C 65 and 3C 356 are faint: the noisy measurements give no firm evidence for polarization. MRC 0156-252 at z~2 is found to be unpolarized in K. 3C 114 has a complex structure of four bright knots, one offset from the radio structure and three along the axis. There is strong evidence for polarization in the source as a whole (12%) and the brightest knot (5%). 3C 441 lies in a rich field; one of its companions appears to be 18% polarized. The identification of the knot containing the active nucleus has been disputed, and is discussed. LBDS 53W091 was controversially reported to have a 40% H-band polarization. No firm evidence is found for non-zero K-band polarization in 53W091, though there is some evidence for its companion being polarized. The object is discussed in the context of other radio-weak galaxies. Simple spectral and spatial models for polarization in radio galaxies are discussed and used to interpret the measurements. The important cosmological question of the fraction of K-band light arising in radio galaxy nuclei is considered: in particular, the contribution of scattered nuclear light to the total K-band emission is estimated to be of order 7% in 3C 22 and 3C 41, 26% in 3C 114, and tentatively 25% or more in 3C 356.

Leyshon, Gareth

1999-10-01

227

Polarized laser-induced photofragmentation studies of JKM-selected CH 3 I molecules: retention of orientation in optical and DC electric fields  

Microsoft Academic Search

The technique of linearly polarized laser-induced photofragmentation for the measurement of the degree of orientation of rotationally state-selected symmetric top molecules [Phys. Rev. Lett.59, 2951 (1987)] has been used to study the retention of molecular orientation in optical frequency AC and homogeneous DC electric fields. For CH3I beams, state-selected by the electrostatic hexapole focuser in several specific low-J parent states,

S. R. Gandhi; R. B. Bernstein

1988-01-01

228

Theoretical studies on the anisotropy of the first hyperpolarizabilities of one- and two-dimensional charge-transfer molecules: role of solvent polarity  

Microsoft Academic Search

The effects of solvent polarity on the geometry and static first hyperpolarizability of one- and two-dimensional charge transfer molecules based on para-nitroaniline (PNA) and 1,3-diamino-4,6-dinitrobenzene (DADB) were studied using a polarizable continuum model (PCM) at the B3LYP\\/6-31+G(d,p) level of theory. The inclusion of solvent does not change the geometry significantly, but produces a change in the calculated results of the

Hai-Peng Li; Kui Han; Gang Tang; Ming-Xue Li; Xiao-Peng Shen; Zhi-Min Huang

2009-01-01

229

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

PubMed Central

We investigated the polarization dependence of the near-band-edge photoluminescence in ZnO strain-free nanowires grown by vapor phase technique. The emission is polarized perpendicular to the nanowire axis with a large polarization ratio (as high as 0.84 at 4.2 K and 0.63 at 300 K). The observed polarization ratio is explained in terms of selection rules for excitonic transitions derived from the k·p 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.

2011-01-01

230

Polarization Transfer in Proton Compton Scattering at High Momentum Transfer  

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

231

High Resolution Vacuum Ultraviolet Spectroscopy of Small Molecules.  

National Technical Information Service (NTIS)

A 6.65 metre vacuum spectrograph operated at a wavelength resolution of 0.0006 nm has been used to study the spectroscopy of rare gas molecules relevant to the development of intense vacuum ultraviolet radiation sources and lasers, and photoabsorption and...

W. H. Parkinson D. E. Freeman K. Yoshino

1980-01-01

232

Broadening and Shifting of the Methanol 119 m Gain Line of Linear and Circular Polarization by Collision with Chiral Molecules.  

National Technical Information Service (NTIS)

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 ...

G. J.S. Bakos

2000-01-01

233

Real Time Magnetic Imaging by Spin-Polarized Low Energy Electron Microscopy with Highly Spin-Polarized and High Brightness Electron Gun  

Microsoft Academic Search

We developed a spin-polarized low energy electron microscopy (SPLEEM) with a highly polarized and high brightness spin electron gun in the present study. Magnetic structures of Co\\/W(110) were observed with an acquisition time of 0.02 s with a field of view of 6 mum. We carried out a dynamic observation of magnetic structures with the SPLEEM during the growth of

Masahiko Suzuki; Michihiro Hashimoto; Tsuneo Yasue; Takanori Koshikawa; Yasuhide Nakagawa; Taro Konomi; Atsushi Mano; Naoto Yamamoto; Makoto Kuwahara; Masahiro Yamamoto; Shoji Okumi; Tsutomu Nakanishi; Xiuguang Jin; Toru Ujihara; Yoshikazu Takeda; Teruo Kohashi; Takashi Ohshima; Takashi Saka; Toshihiro Kato; Hiromichi Horinaka

2010-01-01

234

An original circularly polarized backfire antenna with high gain  

Microsoft Academic Search

In this paper, a circularly polarized backfire antenna with an original structure and excellent properties is presented. It\\u000a is designed on the basis of “Equivalent Reflector Method” proposed by the author.

Song Ximing

1986-01-01

235

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

236

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

Microsoft Academic Search

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

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

2012-01-01

237

Proton polarization at room temperature  

SciTech Connect

We have polarized protons in naphthalene doped with pentacene at higher temperature ({ge}77 K) and lower magnetic field ({approximately}3 kG) than those for ordinary polarized proton targets. Pentacene molecules have been excited with a laser beam. Protons in naphthalene have been polarized dynamically on the intermediate state of pentacene. We obtain about 13{percent} polarization at liquid nitrogen temperature in about 3kG with a N{sub 2}-laser of about 150 mW. It has been found to be also possible to obtain high polarization at room temperature. {copyright} {ital 1995 American Institute of Physics.}

Daigo, M. [Premedical Course, Wakayama Medical College, Wakayama 649-63 (Japan); Hirota, N. [Department of Chemistry, Kyoto University, Kyoto 606 (Japan); Iinuma, M.; Masaike, A.; Shake, I. [Department of Physics, Kyoto University, Kyoto 606 (Japan); Shimizu, H.M. [National Laboratory for High Energy Physics (KEK), Ibaraki-ken 305 (Japan); Takahashi, Y.; Takizawa, R. [Department of Physics, Kyoto University, Kyoto 606 (Japan); Terazima, M. [Department of Chemistry, Kyoto University, Kyoto 606 (Japan); Yabuzaki, T. [Department of Physics, Kyoto University, Kyoto 606 (Japan)

1995-09-01

238

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, Grégory; Delmotte, Franck; Sebban, Stéphane; Lüning, Jan; Zeitoun, Philippe

2011-02-28

239

High resolution inner-shell photoabsorption measurements of simple molecules  

SciTech Connect

Inner-shell adsorption spectra of CO, {sup 13}C{sup 18}O, NO, O{sub 2}, CO{sub 2}, N{sub 2}O, C{sub 2}H{sub 2}, C{sub 2}D{sub 2}, C{sub 2}H{sub 4}, C{sub 2}D{sub 4}, C{sub 2}H{sub 6}, C{sub 2}D{sub 6}, measured with unprecedent energy resolution and signal to noise ratio at the Dragon soft x-ray beamline, are reported. These spectra reveal many new features in core excited valence and Rydberg states. Detailed vibrational structures are observed in these spectra, providing valuable information on the geometrical and vibrational properties of the core excited molecules. In addition, C1s and N1s core hole lifetimes are found to be {similar to}120 meV and {similar to}135 meV in these molecules with little dependence on their bonding environments. The results are discussed briefly in terms of the equivalent core model, multi-electron exctiations, exchange interactions, and the geometry of the excited molecules.

Ma, Y.; Chen, C.T.; Meigs, G. (AT T Bell Laboratories, Murray Hill, NJ (United States)); Randall, K. (Fritz-Haber Institute, Berlin (Germany)); Sette, F. (AT T Bell Laboratories, Murray Hill, NJ (United States))

1990-12-06

240

High-resolution K -shell photoabsorption measurements of simple molecules  

SciTech Connect

{ital K}-shell photoabsorption spectra of CO, {sup 13}C{sup 18}O, NO, O{sub 2}, CO{sub 2}, N{sub 2}O, C{sub 2}H{sub 2}, C{sub 2}D{sub 2}, C{sub 2}H{sub 4}, C{sub 2}D{sub 4}, C{sub 2}H{sub 6}, C{sub 2}D{sub 6} measured with unprecedented energy resolution and signal-to-noise ratio are presented. These spectra reveal many new features in core-excited valence and Rydberg states. Detailed vibrational structures are observed in these spectra, providing valuable information on the geometrical and vibrational properties of the core-excited molecules. In addition, C 1{ital s} and N 1{ital s} core-hole lifetimes are found to be {similar to}120 and {similar to}135 meV in these molecules with little dependence on their bonding environments. These results and the tentative peak assignments are discussed briefly in terms of the equivalent core model, multielectron excitations, exchange interactions, and the geometry of the excited molecules.

Ma, Y.; Chen, C.T.; Meigs, G. (AT T Bell Laboratories, Murray Hill, NJ (USA)); Randall, K. (Fritz-Haber Institute, Berlin, Germany (DE)); Sette, F. (AT T Bell Laboratories, Murray Hill, NJ (USA))

1991-08-01

241

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

242

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

PubMed Central

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

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

2011-01-01

243

Evaluation of Chromatographic Methods for Drug Products Containing Polar and Non-Polar Molecules Using Reversed Phase, Hydrophilic Interaction, and Ion Exchange Chromatography  

Microsoft Academic Search

In recent years the pharmaceutical industry has developed an increasing variety of complex double or triple combination drug therapies. Method development for these combination drug products is particularly challenging when the analytes have significantly different polarities, often requiring multiple chromatographic methods for each active component. An alternative to the commonly used practice of developing multiple reversed phase chromatographic methods for

Lance A. Rogers; Karen E. Crews; Susan G. Long; Kristin M. Patterson; John E. McCune

2009-01-01

244

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

245

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

SciTech Connect

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

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

2008-03-31

246

Real time, high resolution studies of protein adsorption and structure at the solid liquid interface using dual polarization interferometry  

NASA Astrophysics Data System (ADS)

A novel method for the analysis of thin biological films, called dual polarization interferometry (DPI), is described. This high resolution (<1 Å), laboratory-based technique allows the thickness and refractive index (density) of biological molecules adsorbing or reacting at the solid-liquid interface to be measured in real time (up to 10 measurements per second). Results from the adsorption of bovine serum albumin (BSA) on to a silicon oxynitride chip surface are presented to demonstrate how time dependent molecular behaviour can be examined using DPI. Mechanistic and structural information relating to the adsorption process is obtained as a function of the solution pH.

Freeman, Neville J.; Peel, Louise L.; Swann, Marcus J.; Cross, Graham H.; Reeves, Andrew; Brand, Stuart; Lu, Jian R.

2004-07-01

247

Polarization effects in a highly birefringent nonlinear photonic crystal fiber with two-zero dispersion wavelengths.  

PubMed

A theoretical and experimental study is presented on polarized pulsed propagation from a highly birefringent nonlinear photonic crystal fiber with two-zero dispersion wavelengths. Experimental observations show that the input polarization state can maintain its linearity and that the fiber birefringence creates different spectral properties dependent on the input polarization orientation. The most extensive spectra are obtained for a coupling polarization angles aligned with the fast and slow axis, which is created by the high-order dispersion and Kerr nonlinearity. PMID:19030095

Chick, Brendan J; Chon, James W M; Gu, Min

2008-11-24

248

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

NASA Astrophysics Data System (ADS)

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

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

2004-08-01

249

Circular polarization with crossed-planar undulators in high gain FELs.  

SciTech Connect

We propose a crossed undulator configuration for a high-gain free-electron laser to allow versatile polarization control. This configuration consists of a long (saturation length) planar undulator, a dispersive section, and a short (a few gain lengths) planar undulator oriented perpendicular to the first one. In the first undulator, a radiation component linearly polarized in the x-direction is amplified to saturation. In the second undulator, the x-polarized component propagates freely, while a new component, polarized in the y-direction, is generated and reaches saturation in a few gain lengths. By adjusting the strength of the dispersive section, the relative phase of two radiation components can be adjusted to obtain a suitable polarization for the total radiation field, including the circular polarization. The operating principle of the high-gain crossed undulator, which is quite different from that of the crossed undulator for spontaneous radiation, is illustrated in terms of 1-D FEL theory.

Kim, K.-J.

1999-08-31

250

Experimental study of polarization properties of highly birefringent photonic crystal fibers.  

PubMed

We analyze experimentally the polarization properties of highly nonlinear small-core photonic crystal fibers (PCFs) with no intentional birefringence. The properties of recently emerged polarization maintaining PANDA PCFs are also investigated. The wavelength and temperature dependence of phase and group delay of these fibers are examined in the telecommunications wavelength range. Compared to a standard PANDA fiber, the polarization characteristics and temperature dependence are found to be qualitatively different for both types of fibers. PMID:19488234

Ritari, Tuomo; Ludvigsen, H; Wegmuller, M; Legré, M; Gisin, N; Folkenberg, J; Nielsen, M

2004-11-29

251

New highly polar semiconductor ferroelectrics for solar energy conversion devices  

Microsoft Academic Search

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

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

2009-01-01

252

Density matrix for polarization of high-spin particles  

Microsoft Academic Search

The Bouchiat-Michel formula for the polarization of spin-(1\\/2 particles is extended to higher-spin cases. Explicit formulas for massive spin-1 and spin-(3\\/2 particles are given and discussed in connection with density matrices.

S. Y. Choi; Taeyeon Lee; H. S. Song

1989-01-01

253

Density matrix for polarization of high-spin particles  

Microsoft Academic Search

The Bouchiat-Michel formula for the polarization of spin-1\\/2 particles is extended to higher-spin cases. Explicit formulas for massive spin-1 and spin-3\\/2 particles are given and discussed in connection with density matrices.

S. Y. Choi; Taeyeon Lee; H. S. Song

1989-01-01

254

Polarization: A must for fusion  

NASA Astrophysics Data System (ADS)

The complete polarization of DT fuel would increase the fusion reactivity by 50% in magnetic as well as in inertial confinements. The persistence of polarization in a fusion process could be tested, using a terawatt laser hitting a polarized HD target. The polarized deuterons heated in the plasma induced by the laser can fuse producing a 3He and a neutron in the final state. The angular distribution of the emitted neutrons and the change in the corresponding total Cross Section (CS) can sign the polarization persistence. The polarization of solid H2, D2 or T2 Hydrogen isotopes is very difficult. However, it has been possible to polarize HD, a hetero-molecular form of Hydrogen, by static polarization, at very low temperature and very high field. The radioactivity of DT molecules forbids there high polarization by the static method, therefore one has to develop the Dynamic Nuclear Polarization (DNP) by RF transitions. The DNP of HD has been investigated in the past. The magnetic properties of HD and DT molecules are very similar, it is therefore expected that any polarization result obtained with HD could be extrapolated to DT.

Didelez, J.-P.; Deutsch, C.

2013-11-01

255

Ionization and vibronic transitions during slow collisions of highly excited atoms with molecules  

Microsoft Academic Search

Inelastic transitions and ionization occurring during the collision of highly excited Rydberg atoms A(double asterisk) and diatomic molecules X2 are investigated on the basis of information on the adiabatic and vibronic terms of the A(double asterisk)-X2 quasi-molecule, obtained by an asymptotic method. It is shown that, in the case of slow collisions with vibrationally nonexcited molecules, the principal channel of

G. V. Golubkov; G. K. Ivanov

1990-01-01

256

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

257

Proposal for a pulsed optically pumped polarized H- ion source for high energy accelerators  

NASA Astrophysics Data System (ADS)

The acceleration of polarized protons in multi-GeV machines is a great challenge for accelerator physicists. An essential part of such development is the primary source of polarized H- ions. Recent studies at TRIUMF and INR, Moscow, showed that pulsed Optically Pumped Polarized Ion Source (OPPIS) could produce up to 1.2 mA H- ion beam with polarization in excess of 80% within 1.5 ? mm-mrad normalized emittance. This current is ten times higher than the best currently available from atomic beam sources. The pulsed OPPIS is quite inexpensive in comparison with atomic beam source, and is ideally suited for high energy accelerator applications.

Zelenski, A. N.; Levy, C. D. P.; Schmor, P. W.; van Oers, W. T. H.; Dutto, G.; Mori, Y.

1993-12-01

258

Highly mobile vortex structures inside polar twin boundaries in SrTiO3  

NASA Astrophysics Data System (ADS)

We present computer simulations of previously unknown polarization singularities (vortexes) inside polar SrTiO3 twin boundaries. Usually polarity in twin walls is ferri-electric, whereas vortex excitations lead to true ferroelectricity on a very local scale. As a result, in-plane electric fields can selectively stabilize one of the vortex polarization states and enhance the ability of the walls to move. This behavior can explain the well-known and uniquely high, mobility of twin boundaries in SrTiO3. For nanoscale ferroelectric memory devices, we envisage a precisely controllable device, where a desired domain wall pattern is manipulated by shifting the vortex position electrically.

Zykova-Timan, Tatyana; Salje, Ekhard K. H.

2014-02-01

259

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

260

Cosmic Microwave Background Polarization Detector with High Efficiency, Broad Bandwidth, and Highly Symmetric Coupling to Transition Edge Sensor Bolometers  

Microsoft Academic Search

We describe a prototype detector system designed for precise measurements of Cosmic Microwave Background polarization. The\\u000a design combines a quasi-optical polarization modulator, a metal feedhorn, a superconducting planar microwave circuit, and\\u000a a pair of transition-edge sensor (TES) bolometers operating at <100 mK. The circular feedhorn produces highly symmetric beams\\u000a with very low cross-polarization. The planar circuit preserves symmetry in coupling

T. Stevenson; D. Benford; C. Bennett; N. Cao; D. Chuss; K. Denis; W. Hsieh; A. Kogut; S. Moseley; J. Panek; G. Schneider; D. Travers; K. U-Yen; G. Voellmer; E. Wollack

2008-01-01

261

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

SciTech Connect

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

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

2007-01-15

262

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

263

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

NASA Astrophysics Data System (ADS)

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

Simonsen, S. I.; Sørngård, S. A.; Førre, M.; Hansen, J. P.

2014-03-01

264

Relativistic polarized neutrons at the Laboratory of High Energy Physics, JINR.  

National Technical Information Service (NTIS)

Using slowly extracted polarized deuterons, available at the accelerator facility of the Laboratory of High Energy Physics, JINR, polarized quasi-monochromatic neutrons with momenta from 1.1 to 4.5 GeV/c have been generated. Depending on momentum, from 10...

A. Kirillov L. Komolov A. Kovalenko E. Matyushevskij A. Nomofilov

1996-01-01

265

Ultra-high-Q TE\\/TM dual-polarized photonic crystal nanocavities  

Microsoft Academic Search

We demonstrate photonic crystal nanobeam cavities that support both TE- and TM-polarized modes, each with a Quality factor greater than one million and a mode volume on the order of the cubic wavelength. We show that these orthogonally polarized modes have a tunable frequency separation and a high nonlinear spatial overlap. We expect these cavities to have a variety of

Yinan Zhang; Murray W. McCutcheon; Ian B. Burgess; Marko Loncar

2009-01-01

266

Single-stranded DNA binding protein-assisted fluorescence polarization aptamer assay for detection of small molecules.  

PubMed

Here, we describe a new fluorescence polarization aptamer assay (FPAA) strategy which is based on the use of the single-stranded DNA binding (SSB) protein from Escherichia coli as a strong FP signal enhancer tool. This approach relied on the unique ability of the SSB protein to bind the nucleic acid aptamer in its free state but not in its target-bound folded one. Such a feature was exploited by using the antiadenosine (Ade)-DNA aptamer (Apt-A) as a model functional nucleic acid. Two fluorophores (fluorescein and Texas Red) were introduced into different sites of Apt-A to design a dozen fluorescent tracers. In the absence of the Ade target, the binding of the labeled aptamers to SSB governed a very high fluorescence anisotropy increase (in the 0.130-0.200 range) as the consequence of (i) the large global diffusion difference between the free and SSB-bound tracers and (ii) the restricted movement of the dye in the SSB-bound state. When the analyte was introduced into the reaction system, the formation of the folded tertiary structure of the Ade-Apt-A complex triggered the release of the labeled nucleic acids from the protein, leading to a strong decrease in the fluorescence anisotropy. The key factors involved in the fluorescence anisotropy change were considered through the development of a competitive displacement model, and the optimal tracer candidate was selected for the Ade assay under buffer and realistic (diluted human serum) conditions. The SSB-assisted principle was found to operate also with another aptamer system, i.e., the antiargininamide DNA aptamer, and a different biosensing configuration, i.e., the sandwich-like design, suggesting the broad usefulness of the present approach. This sensing platform allowed generation of a fluorescence anisotropy signal for aptamer probes which did not operate under the direct format and greatly improved the assay response relative to that of the most previously reported small target FPAA. PMID:22793528

Zhu, Zhenyu; Ravelet, Corinne; Perrier, Sandrine; Guieu, Valérie; Fiore, Emmanuelle; Peyrin, Eric

2012-08-21

267

Maintenance of neuronal polarity.  

PubMed

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

Szu-Yu Ho, Tammy; Rasband, Matthew N

2011-06-01

268

Release of a model molecule from highly concentrated fluorinated reverse emulsions  

Microsoft Academic Search

Highly concentrated reverse emulsions have been used to study the diffusion of a model molecule entrapped in these gel-emulsions. The influence of several parameters on the release of coumarin from fluorinated gel-emulsions has been investigated, and a computational method has been elaborated to determine the numerical value of the diffusion coefficients. The amount of probe molecule released depends on the

S. Rocca; S. Muller; M. J. Stébé

1999-01-01

269

Calculations of Low Energy Electron-Impact Excitation Cross Sections of Diatomic Molecules by the Close-Coupling R-Matrix and Polarized-Orbital Methods  

Microsoft Academic Search

Low energy electron-impact excitation cross sections of diatomic molecules are calculated by the close-coupling, R-matrix, and polarized-orbital methods. The standard close-coupling procedure is generalized to the excitation of the a('1)(PI)(,g) state of N(,2) in the energy range 12.5-50.0 eV. The target wave functions are calculated by the molecular self-consistent-field method using 10 s-type and 6 p-type Gaussian orbitals as basis

Thomas Kennedy Holley

1982-01-01

270

A model for molecules with twisted intramolecular charge transfer characteristics: solvent polarity effect on the nonradiative rates of dyes in a series of water—ethanol mixed solvents  

NASA Astrophysics Data System (ADS)

The model of Grabowski et al. has been modified and used to account for the absence of a fluorescence band from the twisted form of molecules with torsional mechanisms. We have measured the ground and excited state spectroscopic properties of rhodamine B dissolved in a series of water—ethanol mixed solvents, and used the data to test the model. We also applied our model to 8-anilino-1-naphthalenesulfonate (ANS) in the same solvent system, using previously published decay and quantum yield data. The results show that the variation of the nonradiative rates may be attributed to changes in solvent polarity for both systems.

Chang, Tzyh-Lee; Cheung, Herbert C.

1990-10-01

271

Long-range interaction effects in a formation of dipole-bound anions induced by collisions of Rydberg atoms with polar molecules  

NASA Astrophysics Data System (ADS)

We report results of theoretical studies of dipole-bound anion formation reactions in collisions of polar molecules CH3NO2,CH3CN, and C3H4O3 with Rydberg atoms Cs(ns),Xe(nf), and Rb(nl) (l = 0, 3, and n - 1). It is shown that the inclusion of the long-range interaction effects into the calculations of the Rydberg-covalent-ionic coupling terms is crucial for a reliable quantitative description of such processes. A particular attention is paid to the comparison of the results obtained with the calculations performed using previous models and with the experiment.

Lebedev, V. S.; Narits, A. A.

2013-09-01

272

Piezoelectric cryptand-coated quartz crystal liquid chromatographic detector for cations\\/anions and polar organic molecules in solutions  

Microsoft Academic Search

A reusable and sensitive multifunctional piezoelectric quartz crystal liquid chromatographic detector was developed for the detection of cations, anions and organic molecules in solutions. The quartz crystal coated with dioctadecanoyl-cryptand-22 could adsorb cations or anions depending on whether the cryptand was protonated or not. The cryptand molecule which can be protonated in an acid solution with pH <6.0 can absorb

Chyow-San Chiou; Jeng-Shong Shih

1999-01-01

273

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

274

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

275

Efficient production of polar molecular Bose-Einstein condensates via an all-optical R-type atom-molecule adiabatic passage  

NASA Astrophysics Data System (ADS)

We propose a scheme of 'R-type' photoassociative adiabatic passage (PAP) to create polar molecular condensates from two different species of ultracold atoms. Due to the presence of a quasi-coherent population trapping state in the scheme, it is possible to associate atoms into molecules with a low-power photoassociation (PA) laser. One remarkable advantage of our scheme is that a tunable atom-molecule coupling strength can be achieved by using a time-dependent PA field, which exhibits larger flexibility than using a tunable magnetic field. In addition, our results show that the PA intensity required in the 'R-type' PAP could be greatly reduced compared to that in a conventional '?-type' one.

Qian, Jing; Zhou, Lu; Zhang, Keye; Zhang, Weiping

2010-03-01

276

All-fiber single polarized Yb-doped fiber laser with a high extinction ratio  

NASA Astrophysics Data System (ADS)

We present an all-fiber design for a single polarization Yb-doped fiber laser with all-fiber connections spliced. Single polarization with a high extinction ratio was achieved by the design of a laser cavity consisting of a fiber Bragg grating inscribed on a single-polarization fiber as a high reflective mirror and a piece of end-cleaved single-polarization fiber as an output coupler. The fiber laser operates at 1063.25 nm with an output power of 1.7 W, an optical signal- to-noise ratio of 70 dB and a narrow bandwidth of 54 pm. The laser output has a polarization extinction ratio of 700:1 or 28 dB, and a very stable power output.

Xue, Dong; El-Damak, Angie R.; Gu, Xijia

2010-03-01

277

New materials research for high spin polarized current  

NASA Astrophysics Data System (ADS)

The author reports here a thorough investigation of structural and magnetic properties of Co2FeAl0.5Si0.5 Heusler alloy films, and the tunnel magnetoresistance effect for junctions with Co2FeAl0.5Si0.5 electrodes, spin injection into GaAs semiconductor from Co2FeAl0.5Si0.5, and spin filtering phenomena for junctions with CoFe2O4 ferrite barrier. It was observed that tunnel magnetoresistance ratio up to 832%(386%) at 9 K (room temperature), which corresponds to the tunnel spin polarization of 0.90 (0.81) for the junctions using Co2FeAl0.5Si0.5 Heusler electrodes by optimizing the fabrication condition. It was also found that the tunnel magnetoresistance ratio are almost the same between the junctions with Co2FeAl0.5Si0.5 Heusler electrodes on Cr buffered (1 0 0) and (1 1 0) MgO substrates, which indicates that tunnel spin polarization of Co2FeAl0.5Si0.5 for these two direction are almost the same. The next part of this paper is a spin filtering effect using a Co ferrite. The spin filtering effect was observed through a thin Co-ferrite barrier. The inverse type tunnel magnetoresistance ratio of -124% measured at 10 K was obtained. The inverse type magnetoresistance suggests the negative spin polarization of Co-ferrite barrier. The magnetoresistance ratio of -124% corresponds to the spin polarization of -0.77 by the Co-ferrite barrier. The last part is devoted to the spin injection from Co2FeAl0.5Si0.5 into GaAs. The spin injection signal was clearly obtained by three terminal Hanle measurement. The spin relaxation time was estimated to be 380 ps measured at 5 K.

Tezuka, Nobuki

2012-10-01

278

High Field Gradient Polarized Electron Gun for Ilc  

NASA Astrophysics Data System (ADS)

A 200-keV gun has been developed for generation of bunch charge of ? 3.2 nC, bunch length of ? 2 ns multi-bunch polarized electron beam that is required for International Linear Collider. In this paper, the beam simulations using General Particle Tracer (GPT) code for such space-charge dominated regions, and a fabrication method of electrode for higher electric field (? 3 MV/m) at the photocathode surface by using a titanium anode and a molybdenum cathode are described.

Yamamoto, M.; Yamamoto, N.; Nakanishi, T.; Okumi, S.; Kuwahara, M.; Yasui, K.; Morino, T.; Sakai, R.; Tamagaki, K.; Furuta, F.; Kuriki, M.; Matsumoto, H.; Yoshioka, M.

2007-04-01

279

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

PubMed Central

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

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

1998-01-01

280

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

281

High Resolution Measures of Polarization and Color of Selected Lunar Areas.  

National Technical Information Service (NTIS)

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...

J. S. Hall L. A. Riley

1972-01-01

282

Radiation forces of a highly focused radially polarized beam on spherical particles  

SciTech Connect

A radially polarized beam focused by a high-numerical-aperture (NA) objective has a strong longitudinal and nonpropagating electric field in the focal region, which implies that it is suitable for axial optical trapping. In this paper, we use the vectorial diffraction integral to represent the field distribution of the radially polarized beam focused by a high-NA objective and then employ the T-matrix method to compute the radiation forces on spherical particles. Effects of different parameters, such as the size of the sphere, the inner radius of the radially polarized beam, and the NA of the objective, on the radiation forces are presented.

Yan Shaohui [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Yao Baoli [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119 (China)

2007-11-15

283

Preparation and Alignment of Highly Vibrationally Excited Molecules by CARP - Chirped Adiabatic Raman Passage  

NASA Astrophysics Data System (ADS)

3-D time-dependent Schroedinger equation simulations of Raman excitation of Cl2 molecule are used to demonstrate the feasibility of efficient high vibrational excitation (v > 20) using short (ps) chirped frequency laser pulses at intensities below the ionization threshold (I = 2*10**13 W/cm2). Considerable laser alignment of higly excited vibrational level is obtained as a result of many successive CARP transitions. A novel scheme of dissociating nonaligned molecules (large Mj states) is shown to lead to predicable and controllable post-pulse alignment recurrences, thus offering a new tool for the study of dynamics and reactivity of highly aligned excited nonpolar molecules. We report preliminary experiments.

Légaré, François; Chelkowski, Szczepan; Bandrauk, André D.

2001-05-01

284

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.

Upadhyaya, Kalpana; Gude, Venkatesh; Mohiuddin, Golam

2013-01-01

285

Chemisorption of Hydrogen Molecules on Carbon Nanotubes under High Pressure  

Microsoft Academic Search

Based on first principles calculations, we propose a mechanism for the dissociative chemisorption of H2 on carbon nanotubes. The breaking of the H-H bond is concerted with the formation of two C-H bonds on two adjacent carbon nanotubes in solid phase, facilitated by the application of high pressure which shortens the interstitial distance between nanotubes. The process is reversible upon

Siu-Pang Chan; Gang Chen; X. G. Gong; Zhi-Feng Liu

2001-01-01

286

Using metallic noncontact atomic force microscope tips for imaging insulators and polar molecules: tip characterization and imaging mechanisms.  

PubMed

We demonstrate that using metallic tips for noncontact atomic force microscopy (NC-AFM) imaging at relatively large (>0.5 nm) tip-surface separations provides a reliable method for studying molecules on insulating surfaces with chemical resolution and greatly reduces the complexity of interpreting experimental data. The experimental NC-AFM imaging and theoretical simulations were carried out for the NiO(001) surface as well as adsorbed CO and Co-Salen molecules using Cr-coated Si tips. The experimental results and density functional theory calculations confirm that metallic tips possess a permanent electric dipole moment with its positive end oriented toward the sample. By analyzing the experimental data, we could directly determine the dipole moment of the Cr-coated tip. A model representing the metallic tip as a point dipole is described and shown to produce NC-AFM images of individual CO molecules adsorbed onto NiO(001) in good quantitative agreement with experimental results. Finally, we discuss methods for characterizing the structure of metal-coated tips and the application of these tips to imaging dipoles of large adsorbed molecules. PMID:24787716

Gao, David Zhe; Grenz, Josef; Watkins, Matthew Benjamin; Federici Canova, Filippo; Schwarz, Alexander; Wiesendanger, Roland; Shluger, Alexander L

2014-05-27

287

Neuronal Polarity and the Kinesin Superfamily Proteins  

NSDL National Science Digital Library

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

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

2007-02-06

288

HIGH-ENTROPY POLAR REGIONS AROUND THE FIRST PROTOSTARS  

SciTech Connect

We report on simulations of the formation of the first stars in the universe, where we identify regions of hot atomic gas (f{sub H{sub 2}}< 10{sup -6}) at densities above 10{sup -14} g cm{sup -3}, heated to temperatures ranging between 3000 and 8000 K. Within this temperature range atomic hydrogen is unable to cool effectively. We describe the kinetic and thermal characteristics of these regions and investigate their origin. We find that these regions, while small in total mass fraction of the cloud, may be dynamically important over the accretion timescale for the central clump in the cloud, particularly as a chemical, rather than a radiative, mechanism for clearing the polar regions of the accretion disk of material and terminating accretion along these directions. These inherently three-dimensional effects stress the need for multi-dimensional calculations of protostellar accretion for reliable predictions of the masses of the very first stars.

Turk, Matthew J.; Norman, Michael L. [Center for Astrophysics and Space Science, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424 (United States); Abel, Tom [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

2010-12-20

289

Theoretical studies of high-power laser ionization of molecules in the tunneling region  

SciTech Connect

In this paper, we extend our previous works on the generalization of Keldysh's theory to the photoionization processes of molecules. In particular, we include the Franck-Condon factors into our photoionization rate formulas which are based on the use of the molecular orbital theory to describe the electronic degrees of freedom. The inclusion of Franck-Condon factors leads to the proper treatment of the molecular vibrational degrees of freedom. All of our formulas consist of the preexponential and exponential factors, and have explicit laser frequency dependence in the same manner as the original atomic Keldysh theory. The latter fact facilitates the exploration of the laser frequency dependence of the photoionization rate, which is more advantageous than the popular Ammosov-Delone-Krainov formulas. As a result, our analytical expressions turn out to be quite instructive to deduce physical meanings of the photoionization processes of molecules. As an illustrative example, we have applied our formulas to the photoionization process of H{sub 2} molecules and found that our formulas reproduce the numerical results reported in the literature quite well. Without the Franck-Condon factors, our formulas cannot fit the numerical results well, which implies the importance of including properly the Franck-Condon factors for the tunneling photoionization processes of molecules. The results also indicate that the exponential factors which depend on the nuclear equilibrium state play a key role in determining the photoionization rates of the spatially aligned molecules. Comparing the Condon and non-Condon approximations shows that the Condon approximation is usually appropriate for the case of the laser polarization perpendicular to the molecular axis, while it is not necessarily true for the parallel case. Our theoretical results are also applied to analyze the experimental data of Urbain et al. [Phys. Rev. Lett. 92, 163004 (2004)] for the photoionization process of H{sub 2} molecules.

Mishima, K.; Nagaya, K.; Lin, S.H. [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 10764, Taiwan (China); Hayashi, M. [Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan (China)

2004-12-01

290

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

PubMed

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 (1)H 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 (5-10 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; Paëpe, 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

2008-08-01

291

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 (5–10 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.

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

2008-01-01

292

Polarization and Piezoelectric Properties of High Performance Bismuth Sodium Titanate Single Crystals Grown by High-Oxygen-Pressure Flux Method  

NASA Astrophysics Data System (ADS)

(Bi0.5Na0.5)TiO3 (BNT) single crystals were grown by flux method at a high oxygen pressure (PO2) of 1 MPa, and their polarization and piezoelectric properties were investigated. BNT single crystals exhibited a saturated polarization hysteresis with remanent polarizations (Pr) of 31 ?C/cm2 along [100]c, 44 ?C/cm2 along [110]c and 54 ?C/cm2 along [111]c. These results show that spontaneous polarization of BNT is approximately 55 ?C/cm2 or larger. Strain measurements of rhombohedral BNT crystals suggest that the polarization reversal along [111]c is achieved by non-180° Ps rotation whereas that along [100]c is accomplished by 180° Ps switching.

Suzuki, Muneyasu; Morishita, Akifumi; Kitanaka, Yuuki; Noguchi, Yuji; Miyayama, Masaru

2010-09-01

293

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

PubMed

We investigated the mobility of the polar localized serine chemoreceptor, Tsr, labeled by the fluorescent protein Venus in the inner membrane of live Escherichia coli cells at observation rates up to 1000 Hz. A fraction (7%) of all Tsr molecules shows free diffusion over the entire cell surface with an average diffusion coefficient of 0.40 ± 0.01 ?m(2) s(-1). The remaining molecules were found to be ultimately confined in compartments of size 290 ± 15 nm and showed restricted diffusion at an inner barrier found at 170 ± 10 nm. At the shortest length-scales (<170 nm), all Tsr molecules diffuse equally. Disruption of the cytoskeleton and rounding of the cells resulted in an increase in the mobile fraction of Tsr molecules and a fragmenting of the previously polar cluster of Tsr consistent with a curvature-based mechanism of Tsr cluster maintenance. PMID:24411246

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

2014-01-01

294

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

295

High laser-induced damage threshold polarizer-coatings for 1054 nm  

NASA Astrophysics Data System (ADS)

Polarizer coatings developed for the OMEGA laser are performing well without sustaining any significant damage. Similar polarizers developed for the National Ignition Facility have exceptionally high damage thresholds when tested with a 1-ns pulse at 1054 nm. Polarizers for OMEGA were originally developed using Ta2O5/SiO2 multilayers. All final polarizers before the frequency conversion cell were made using this method. A new coating was developed for a polarizing beamsplitter with more stringent optical and laser-damage requirements. The new coating used a HfO2/SIO2 system with the hafnia formed by reactive evaporation from a hafnium metal melt. The new process provided better film control, lower defect counts, better stress control, and higher damage thresholds. Beamsplitter coatings made from both processes were installed in the OMEGA laser. After 1.5 years of operation the Ta2O5/SiO2 beamsplitters are developing signs of damage on OMEGA while the HfO2/SiO2 coatings show no damage. The HfO2/SiO2 process was also used to develop polarizer coatings for the NIF. Damage- threshold results from 1-on-1 testing will be presented for both types of polarizers. Experimental results show that the coating damage threshold is not strongly dependent on deposition parameters, allowing use of these parameters to control film stress. The damage thresholds are higher for s- polarized incident light, and different damage morphologies for the two polarizations have been observed. A base layer of scandium oxide that allows the coating to be safely stripped does not affect the polarizer damage threshold.

Smith, Douglas J.; Anzellotti, J. F.; Papernov, Semyon; Chrzan, Z. Roman

1997-05-01

296

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.

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

2013-01-01

297

Intermolecular Potentials and Width of Pressure-Broadened Spectral Lines. III. The Rotational Lines of Diatomic Molecules Perturbed by Linear Molecules with High Moment of Inertia  

Microsoft Academic Search

Expressions of the differential cross section for diatomic molecules perturbed by linear molecules with high moment of inertia have been derived using a simplified version of the Anderson theory of line shape. The corresponding validity conditions have been presented. The connection with a ``classical description'' of the rotational degrees of freedom of the perturber has been shown. The cases of

M. Giraud; D. Robert; L. Galatry

1972-01-01

298

High-density localization of active molecules using Structured Sparse Model and Bayesian Information Criterion  

NASA Astrophysics Data System (ADS)

Localization-based super-resolution microscopy (or called localization microscopy) rely on repeated imaging and localization of active molecules, and the spatial resolution enhancement of localization microscopy is built upon the sacrifice of its temporal resolution. Developing algorithms for high-density localization of active molecules is a promising approach to increase the speed of localization microscopy. Here we present a new algorithm called SSM_BIC for such purpose. The SSM_BIC combines the advantages of the Structured Sparse Model (SSM) and the Bayesian Information Criterion (BIC). Through simulation and experimental studies, we evaluate systematically the performance between the SSM_BIC and the conventional Sparse algorithm in high-density localization of active molecules. We show that the SSM_BIC is superior in processing single molecule images with weak signal embedded in strong background.

Quan, Tingwei; Zhu, Hongyu; Liu, Xiaomao; Liu, Yongfeng; Ding, Jiuping; Zeng, Shaoqun; Huang, Zhen-Li

2011-08-01

299

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

300

High-performance N-polar GaN enhancement-mode device technology  

NASA Astrophysics Data System (ADS)

In this paper, we report the recent progress in the high-frequency performance of enhancement-mode devices in the novel N-polar GaN technology and provide a pathway for further scaling. The intrinsic advantages of electron confinement, polarization doping of the back-barrier and the absence of a source barrier in N-polar GaN technology were leveraged with polarization engineering with a top barrier for enhancement mode operation and advanced self-aligned source/drain technology for low parasitic access resistances. The scalability of the device structures are explored in terms of short-channel effects and high-frequency performance. Low-field electron mobility in vertically scaled channel was also investigated providing insights on the scattering mechanism.

Singisetti, Uttam; Hoi Wong, Man; Mishra, Umesh K.

2013-07-01

301

High-resolution laser spectroscopy of the potassium–argon molecule: The B 2? + state  

Microsoft Academic Search

The absorption spectrum of the KAr molecule has been observed with high resolution between 13032 and 13077cm?1 using tunable laser diodes as light sources, a supersonic beam for production of the molecules, and laser-induced fluorescence for detection. In addition, optical–optical double resonance (OODR) experiments have been performed to simplify the spectrum and to get rotational assignment. Altogether, 670 lines due

Markus Braune; Hamid Valipour; Dieter Zimmermann

2006-01-01

302

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

303

Time Resolved Spectroscopy of High Field Polars (FUSE 00)  

NASA Technical Reports Server (NTRS)

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

Barrett, Paul

2004-01-01

304

Adjustable compensation of polarization mode dispersion using a high-birefringence nonlinearly chirped fiber Bragg grating  

Microsoft Academic Search

We demonstrate an adjustable polarization-mode-dispersion (PMD) compensator. The device uses a nonlinearly chirped fiber Bragg grating written into a high-birefringence photosensitive fiber. By mechanically stretching the grating, the device generates a time delay between different polarizations that is adjustable from 100 to 320 ps and is tunable over 2.3 nm. We demonstrate tunable PMD compensation of a 10-Gb\\/s signal that

S. Lee; R. Khosravani; J. Peng; V. Grubsky; D. S. Starodubov; A. E. Willner; J. Feinberg

1999-01-01

305

Ultra-high-Q TE\\/TM dual-polarized photonic crystal nanocavities  

Microsoft Academic Search

We demonstrate photonic crystal nanobeam cavities that support both TE- and\\u000aTM-polarized modes, each with a Quality factor greater than one million and a\\u000amode volume on the order of the cubic wavelength. We show that these\\u000aorthogonally polarized modes have a tunable frequency separation and a high\\u000anonlinear spatial overlap. We expect these cavities to have a variety of

Yinan Zhang; Murray W. McCutcheon; Ian B. Burgess; Marko Loncar

2009-01-01

306

Ultra-high-Q TE/TM dual-polarized photonic crystal nanocavities.  

PubMed

We demonstrate photonic crystal nanobeam cavities that support both TE- and TM-polarized modes, each with a Q factor greater than one million and a mode volume on the order of the cubic wavelength. We show that these orthogonally polarized modes have a tunable frequency separation and a high nonlinear spatial overlap. We expect these cavities to have a variety of applications in resonance-enhanced nonlinear optics. PMID:19724535

Zhang, Yinan; McCutcheon, Murray W; Burgess, Ian B; Loncar, Marko

2009-09-01

307

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

308

Dynamic Lateral Polarization in CdZnTe Under High Flux X-Ray Irradiation  

Microsoft Academic Search

The dynamic lateral polarization and charge steering effect was studied in 2D pixilated CdZnTe monolithic detector arrays designed for high flux X-ray imaging applications. While these detectors have shown the ability to work at 15 times 106 counts s-1 mm-2 and higher count-rates in pulse mode, we observed some detectors that exhibited a dynamic lateral polarization and charge steering effect

Stephen A. Soldner; Derek S. Bale; Csaba Szeles

2007-01-01

309

Generation of circularly polarized high-order harmonics by two-color coplanar field mixing  

NASA Astrophysics Data System (ADS)

An efficient method is investigated for the generation of circularly polarized high-order harmonics by a bichromatic laser field whose two components with frequencies ? and 2? are circularly polarized in the same plane, but rotate in opposite directions. The generation of intense harmonics by such a driving-field configuration was already confirmed by a previous experiment. With the help of both a semiclassical three-step model as well as a saddle-point analysis, the mechanism of harmonic generation in this case is elucidated and the plateau structure of the harmonic response and their cutoffs are established. The sensitivity of the harmonic yield and the polarization of the harmonics to imperfect circular polarization of the driving fields are investigated. Optimization of both the cutoff frequency and the harmonic efficiency with respect to the intensity ratio of the two components of the driving field is discussed. The electron trajectories responsible for the emission of particular harmonics are identified. Unlike the case of a linearly polarized driving field, they have a nonzero start velocity. By comparison with the driving-field configuration where the two components rotate in the same direction, the mechanism of the intense harmonic emission is further clarified. Depending on the (unknown) saturation intensity for the bichromatic field with counter-rotating polarizations, this scheme might be of practical interest not only because of the circular polarization of the produced harmonics, but also because of their production efficiency.

Miloševi?, Dejan B.; Becker, Wilhelm; Kopold, Richard

2000-06-01

310

Salmonella enterica Invasion of Polarized Epithelial Cells Is a Highly Cooperative Effort.  

PubMed

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

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

2014-06-01

311

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

SciTech Connect

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

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

2007-03-28

312

High throughput method to quantify anterior-posterior polarity of T-cells and epithelial cells.  

PubMed

The virologic synapse (VS), which is formed between a virus-infected and uninfected cell, plays a central role in the transmission of certain viruses, such as HIV and HTLV-1. During VS formation, HTLV-1-infected T-cells polarize cellular and viral proteins toward the uninfected T-cell. This polarization resembles anterior-posterior cell polarity induced by immunological synapse (IS) formation, which is more extensively characterized than VS formation and occurs when a T-cell interacts with an antigen-presenting cell. One measure of cell polarity induced by both IS or VS formation is the repositioning of the microtubule organizing center (MTOC) relative to the contact point with the interacting cell. Here we describe an automated, high throughput system to score repositioning of the MTOC and thereby cell polarity establishment. The method rapidly and accurately calculates the angle between the MTOC and the IS for thousands of cells. We also show that the system can be adapted to score anterior-posterior polarity establishment of epithelial cells. This general approach represents a significant advancement over manual cell polarity scoring, which is subject to experimenter bias and requires more time and effort to evaluate large numbers of cells. PMID:22355445

Irvin-Wilson, Charletha V; Newberg, Justin Y; Kong, Kathleen; Javier, Ronald T; Marriott, Susan J

2011-12-01

313

High Throughput Method to Quantify Anterior-Posterior Polarity of T-Cells and Epithelial Cells  

PubMed Central

The virologic synapse (VS), which is formed between a virus-infected and uninfected cell, plays a central role in the transmission of certain viruses, such as HIV and HTLV-1. During VS formation, HTLV-1-infected T-cells polarize cellular and viral proteins toward the uninfected T-cell. This polarization resembles anterior-posterior cell polarity induced by immunological synapse (IS) formation, which is more extensively characterized than VS formation and occurs when a T-cell interacts with an antigen-presenting cell. One measure of cell polarity induced by both IS or VS formation is the repositioning of the microtubule organizing center (MTOC) relative to the contact point with the interacting cell. Here we describe an automated, high throughput system to score repositioning of the MTOC and thereby cell polarity establishment. The method rapidly and accurately calculates the angle between the MTOC and the IS for thousands of cells. We also show that the system can be adapted to score anterior-posterior polarity establishment of epithelial cells. This general approach represents a significant advancement over manual cell polarity scoring, which is subject to experimenter bias and requires more time and effort to evaluate large numbers of cells.

Irvin-Wilson, Charletha V.; Newberg, Justin Y.; Kong, Kathleen; Javier, Ronald T.; Marriott, Susan J.

2011-01-01

314

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

SciTech Connect

The glass development laser (GDL), has been operating at the Laboratory for Laser Energetics since 1978. This Nd:phosphate glass system produces high peak power optical radiation at lambda = 1054 nm or lambda = 351 nm for use in studying the interaction physics of intense laser beams with matter. The amplifier staging incorporates the propagation of linearly and circularly polarized light in rod amplifiers which vary in diameter from 16 mm to 90 mm. Numerous quartz or mica quarter waveplates and Brewster angle dielectric thin film polarizers are required to limit accumulated phase retardation between amplification stages and to accommodate interstage Pockels' cell isolation switches. We have recently replaced most of the waveplate-dielectric polarizer combinations in GDL with liquid crystal polarizers. Comprised of 11 ..mu..m thick cholesteric fluids sandwiched between optical quality glass plates, liquid crystal polarizers provide excellent polarization properties, low insertion loss, angular insensitivity, and laser damage resistance at lambda = 1054 nm. The design, fabrication, and performance of left-handed and right-handed circular polarizers will be discussed.

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

1985-03-01

315

High dielectric constant and frozen macroscopic polarization in dense nanocrystalline BaTi O3 ceramics  

NASA Astrophysics Data System (ADS)

Theoretical models for small ferroelectric particles predict a progressive decrease of the Curie temperature, spontaneous lattice strain, and polarization until the critical size corresponding to transition to the cubic phase and disappearance of ferroelectricity is reached. In contrast, the behavior of nanocrystalline BaTiO3 ceramics with a grain size of ?30nm is dominated by extrinsic effects related to the grain boundaries which mask the expected downscaling of properties. While the noncubic crystal structure, the high dielectric constant (?1600) and the variation of permittivity with temperature suggest a ferroelectric behavior, very slim, and nearly linear polarization hysteresis loops are observed. Evidence for the existence of a ferroelectric domain structure with domains extending over several grains and of polarization switching at local scale is given by piezoresponse force microscopy. The suppression of macroscopic ferroelectric hysteresis and switching originates from a frozen domain structure stable under an external field owing to the effects exerted by the grain boundaries, such as the clamping of the domain walls and the hindrance of polarization switching. Furthermore, the depolarization field originated by the low-permittivity nonferroelectric grain boundaries can cause a significant reduction of polarization. If the grain size is small enough, the ceramic is expected to undergo a “phase transition” to a polar phase with nonswitchable polarization. The BaTiO3 ceramics with grain size of 30nm investigated in the present study are deemed to be close to this transition.

Buscaglia, Maria Teresa; Viviani, Massimo; Buscaglia, Vincenzo; Mitoseriu, Liliana; Testino, Andrea; Nanni, Paolo; Zhao, Zhe; Nygren, Mats; Harnagea, Catalin; Piazza, Daniele; Galassi, Carmen

2006-02-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

317

Polarization properties of dye-based random lasers  

NASA Astrophysics Data System (ADS)

We present the first systematic study on the emission polarization of coherent random lasing (RL). Employing a single-shot spectro-polarimeter the complete polarization state and the degree of polarization could be recovered for individual RL modes. It turned out that the polarization of RL modes is strongly dependent on the pump polarization, which can be explained with the dipolar nature of the dye molecules. Furthermore, by using a highly viscous solvent for the laser-dye and a linear pump polarization, it was possible to force all random-lasing modes into just the same linear polarization.

Knitter, Sebastian; Kues, Michael; Fallnich, Carsten

2013-03-01

318

Electron delocalization by polar molecules: Interaction of Na atoms with solid ammonia films studied with MIES and density functional theory  

NASA Astrophysics Data System (ADS)

The interaction of Na and NH3 on tungsten was studied with metastable impact electron spectroscopy under UHV conditions. NH3(Na) films were grown at 90(+/-10) K on tungsten substrates and exposed to Na(NH3). No Na-induced reaction involving NH3 takes place. At small Na exposures a Na-induced shift of the NH3 spectral features is seen, in parallel with a decrease of the surface work function. At larger exposures three 3sNa-related spectral structures are seen, two of them at energetic positions different from that found for Na on metals or semiconductors. The main additional peak is attributed to delocalized Na species. A small additional feature is attributed to simultaneous ionization and excitation of partially ammoniated Na2 species. The results are compared with density functional theory calculations which suggest that the 3sNa emission at small exposures appears to originate mainly from delocalized 3sNa electrons; they are located far from the Na species and become stabilized by solvent molecules. When depositing NH3 molecules onto Na films, metalliclike Na patches and delocalized Na species coexist. The delocalization of 3sNa is seen up to T=130 K where the NH3 species desorb.

Borodin, A.; Höfft, O.; Kempter, V.; Ferro, Y.; Allouche, A.

2004-08-01

319

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

320

High performance and compact polarization beam splitter based on silicon-on-insulator subwavelength grating coupler  

NASA Astrophysics Data System (ADS)

A high coupling efficiency silicon grating which serves both as a high extinction ratio polarization beam splitter and a vertical coupler for silicon photonic circuits at the wavelength of 1550nm is presented. The design is based on the Bragg diffraction condition and the phase matching equation by using the rigorous coupled wave analysis (RCWA). For TE-polarized light, the computing coupling efficiency is as high as 69%, and the extinction ratio can reach - 20dB. The efficiency of TM-polarized wave is better than 53% and the extinction ratio is approximately -11dB. The device has compact structure, high TE to TM extinction ratio, low excess loss and wide operation bandwidth. Moreover, the simple fabrication method involves only single etch step and good compatibility with complementary metal oxide semiconductor (CMOS) technology.

Yang, Junbo; Shao, Zhengzheng; Zhou, Kuo; Xu, Suzhi; Xu, Jia

2013-12-01

321

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

NASA Astrophysics Data System (ADS)

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; Mirizzi, Alessandro; Roncadelli, Marco

2010-05-01

322

Optical fiber polarizer based on highly birefringent single-mode fiber.  

PubMed

An in-line fiber polarizer is proposed and demonstrated. The attenuation of a single-mode fiber experiencing an axial periodic perturbation shows peaks at certain wavelengths, resulting from the power coupling between the guided mode and the cladding modes. When the fiber has significant linear birefringence, each of these peaks is split into two peaks. The fiber thus exhibits polarization-selective attenuation characteristics. An example of such a polarizer is demonstrated based on a highly birefringent fiber with a beat length of 1.3 mm. A 25-dB polarization extinction ratio is obtained, with an attenuation of 1.3 dB at an operating wavelength of 1177 nm. PMID:19859160

Wang, A; Arya, V; Nasta, M H; Murphy, K A; Claus, R O

1995-02-01

323

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

324

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

325

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

326

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

327

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

NASA Astrophysics Data System (ADS)

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

Kita, Takashi; Suwa, Masaya; Kaizu, Toshiyuki; Harada, Yukihiro

2014-06-01

328

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

PubMed Central

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

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

2012-01-01

329

Highly birefringent terahertz polarization maintaining plastic photonic crystal fibers.  

PubMed

Guided-wave propagation of sub-ps terahertz (THz) pulses in a highly birefringent plastic photonic crystal fiber was studied by using a THz time domain spectroscopy technique. The plastic photonic crystal fiber was fabricated by using high density polyethylene tubes and solid filaments. The fabricated THz plastic photonic crystal fibers exhibit an extremely large birefringence of ~ 2.1 x 10(-2), which is almost one order of magnitude larger than that of previously reported photonic crystal fibers. PMID:18521127

Cho, M; Kim, J; Park, H; Han, Y; Moon, K; Jung, E; Han, H

2008-01-01

330

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

PubMed

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

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

2013-01-01

331

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

332

High-speed endless optical polarization stabilization using calibrated waveplates and field-programmable gate array-based digital controller.  

PubMed

A truly endless polarization stabilization experiment with a tracking speed of 15 krad/s is presented. The high-speed polarization tracking is realized by using calibrated lithium niobate linear retardation waveplates as the polarization transformers combined with a very fast digital controller running on a field-programmable gate array (FPGA). PMID:19581991

Hidayat, Ariya; Koch, Benjamin; Zhang, Hongbin; Mirvoda, Vitali; Lichtinger, Manfred; Sandel, David; Noé, Reinhold

2008-11-10

333

Single molecule magnets: High frequency electron paramagnetic resonance study of two isomeric forms of an Mn12 molecule  

NASA Astrophysics Data System (ADS)

Different crystallographic forms of the single molecule magnet [Mn12O12(O2CR)16(H2O)4] (complex 1) with a given R substituent have been isolated. The two different isomeric forms of the p-methylbenzoate complex crystallize as [Mn12O12(O2CC6H4-p-Me)16(H2O)4].(HO2CC6H4-p-Me) (complex 2) and [Mn12O12(O2CC6H4-p-Me)16(H2O)4].3H2O (complex 3). In complex 2, one MnIII ion has an abnormal Jahn-Teller distortion axis oriented at an oxide ion, and thus 2 and 3 are Jahn-Teller isomers. This reduces the symmetry of the core of complex 2 compared with that of complex 3. Complex 2 likely has a larger tunneling matrix element and this explains why this complex shows an out-of-phase ac peak (?M'') in the signal in the 2-3 K region, whereas complex 3 has its ?M'' peak in the 4-7 K range, i.e., the rate of tunneling of magnetization is greater in complex 2 than complex 3. High frequency electron paramagnetic resonance (HFEPR) experiments were performed on both isomers. Computed simulations of the experimental HFEPR data yield spin Hamiltonian parameters for both complexes.

Aubin, S. M. J.; Sun, Z.; Rumberger, E. M.; Hendrickson, D. N.; Christou, G.

2002-05-01

334

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

Microsoft Academic Search

Purpose  To assess the effect of sugar molecules on solution viscosity at high protein concentrations.\\u000a \\u000a \\u000a \\u000a Methods  A 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

335

High-Harmonic Probing of Electronic Coherence in Dynamically Aligned Molecules  

NASA Astrophysics Data System (ADS)

We introduce and demonstrate a new approach to measuring coherent electron wave packets using high-harmonic spectroscopy. By preparing a molecule in a coherent superposition of electronic states, we show that electronic coherence opens previously unobserved high-harmonic-generation channels that connect distinct but coherently related electronic states. Performing the measurements in dynamically aligned nitric oxide molecules we observe the complex temporal evolution of the electronic coherence under coupling to nuclear motion. Choosing a weakly allowed transition to prepare the wave packet, we demonstrate an unprecedented sensitivity that arises from optical interference between coherent and incoherent pathways. This mechanism converts a 0.1% excitation fraction into a ˜20% signal modulation.

Kraus, P. M.; Zhang, S. B.; Gijsbertsen, A.; Lucchese, R. R.; Rohringer, N.; Wörner, H. J.

2013-12-01

336

A novel small molecule target in human airway smooth muscle for potential treatment of obstructive lung diseases: a staged high-throughput biophysical screening  

PubMed Central

Background A newly identified mechanism of smooth muscle relaxation is the interaction between the small heat shock protein 20 (HSP20) and 14-3-3 proteins. Focusing upon this class of interactions, we describe here a novel drug target screening approach for treating airflow obstruction in asthma. Methods Using a high-throughput fluorescence polarization (FP) assay, we screened a library of compounds that could act as small molecule modulators of HSP20 signals. We then applied two quantitative, cell-based biophysical methods to assess the functional efficacy of these molecules and rank-ordered their abilities to relax isolated human airway smooth muscle (ASM). Scaling up to the level of an intact tissue, we confirmed in a concentration-responsive manner the potency of the cell-based hit compounds. Results Among 58,019 compound tested, 268 compounds caused 20% or more reduction of the polarized emission in the FP assay. A small subset of these primary screen hits, belonging to two scaffolds, caused relaxation of isolated ASM cell in vitro and attenuated active force development of intact tissue ex vivo. Conclusions This staged biophysical screening paradigm provides proof-of-principle for high-throughput and cost-effective discovery of new small molecule therapeutic agents for obstructive lung diseases.

2011-01-01

337

Understanding the participation of quadricyclane as nucleophile in polar [2sigma + 2sigma + 2pi] cycloadditions toward electrophilic pi molecules.  

PubMed

The formal [2sigma + 2sigma + 2pi] cycloaddition of quadricyclane, 1, with dimethyl azodicarboxylate, 2, in water has been studied using DFT methods at the B3LYP/6-31G** and MPWB1K/6-31G** levels. In the gas phase, the reaction of 1 with 2 has a two-stage mechanism with a large polar character and an activation barrier of 23.2 kcal/mol. Inclusion of water through a combined discrete-continuum model changes the mechanism to a two-step model where the first nucleophilic attack of 1 to 2 is the rate-limiting step with an activation barrier of 14.7 kcal/mol. Analysis of the electronic structure of the transition state structures points out the large zwitterionic character of these species. A DFT analysis of the global electrophilicity and nucleophilicity of the reagents provides a sound explanation about the participation of 1 as a nucleophile in these cycloadditions. This behavior is reinforced by a further study of the reaction of 1 with 1,1-dicyanoethylene. PMID:18942791

Domingo, Luis R; Saéz, José A; Zaragozá, Ramón J; Arnó, Manuel

2008-11-21

338

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(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

339

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

340

Prospects of Pulsar Timing at High Frequencies Including Polarization Measurements  

Microsoft Academic Search

We have been exploring the possibility of high frequency pulsar timing with the Effelsberg radio telescope. We describe briefly the instrumentation for such a project and discuss its advantages in comparison to low frequency timing. Successful observations of some millisecond pulsars at 4.85 GHz as well as the results from an ongoing timing experiment at 1.4 GHz give further confidence

M. Kramer; O. Doroshenko; K. M. Xilouris

1999-01-01

341

Characterization of a Low Pressure, High Capacity ^129Xe Flow-Through Polarizer  

NASA Astrophysics Data System (ADS)

Hyperpolarized ^129Xe produced via spin-exchange optical pumping continues to be an interesting physical system to study and is useful in many NMR and MRI applications. The generation of large quantities of highly polarized ^129Xe is complicated by xenon's large cross section for spin destruction of the alkali-metal electron. This problem has been addressed in recent years by the development of flow-through xenon polarizers, which operate with a gas mixture that is lean in xenon flowing continuously through the optical pumping cell. We describe here our own flow-through xenon polarizer that is based on the University of New Hampshire design: it operates at low pressure, employs counterpropagating laser beam and gas flow, and has a long narrow optical pumping region. In our version, the systems for heating and Rb vapor generation have been simplified. We examine both the output ^129Xe polarization by NMR and the in situ ^85Rb polarization by optically detected EPR as a function of position in the meter-long cell. Under near-optimal conditions with 28 W of frequency-narrowed laser light, we achieve ^129Xe polarizations >30% with a flow of 5 bar.cm^3/min of natural xenon. We compare our results with a numerical model.

Saam, Brian; Schrank, Geoffry; Ma, Zayd; Schoeck, Allison

2009-05-01

342

PolarBase: A Database of High-Resolution Spectropolarimetric Stellar Observations  

NASA Astrophysics Data System (ADS)

PolarBase is an evolving database that contains all stellar data collected with the ESPaDOnS and NARVAL high-resolution spectropolarimeters, in their reduced form, as soon as they become public. As of early 2014, observations of 2000 stellar objects throughout the Hertzsprung-Russell diagram are available. Intensity spectra are available for all targets, and the majority of the observations also include simultaneous spectra in circular or linear polarization, with the majority of the polarimetric measurements being performed only in circularly polarized light (Stokes V). Observations are associated with a cross-correlation pseudoline profile in all available Stokes parameters, greatly increasing the detectability of weak polarized signatures. Stokes V signatures are detected for more than 300 stars of all masses and evolutionary stages, and linear polarization is detected in 35 targets. The detection rate in Stokes V is found to be anticorrelated with the stellar effective temperature. This unique set of Zeeman detections offers the first opportunity to run homogeneous magnetometry studies throughout the H-R diagram. The Web interface of PolarBase is available at http://polarbase.irap.omp.eu.

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

2014-05-01

343

Polarized Electrons for Polarized Positrons  

NASA Astrophysics Data System (ADS)

Recently, the nuclear and high-energy physics communities have shown a growing interest in the availability of high current, highly spin-polarized positron beams. The Polarized Electrons for Polarized Positrons (PEPPo) experiment at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) aims to measure the transfer of polarization from a low energy 10 MeV highly spin polarized electron beam to positrons. A sufficiently energetic polarized photon or lepton may generate, via bremsstrahlung and pair creation processes within a target foil, electron-positron pairs that will carry a fraction of the initial polarization. This approach has been successfully tested using polarized photons created with a multi-GeV unpolarized electron beam, resulting in positrons with polarization of 80%. Although pair creation yield is reduced at lower energy, recent advances in high current milliampere spin-polarized electron sources at Jefferson Lab offer the perspective of creating polarized positrons using a low energy electron beam. A successful demonstration of this technique would provide an alternative scheme to produce low energy polarized positrons, as well as useful information to optimize the design of a polarized positron source using sub-GeV electron beam. An overview and status of the PEPPo experiment will be presented, along with some of the motivations in the context of the Jefferson Lab nuclear physics program.

Fanchini, Erica

2012-03-01

344

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

345

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

346

Polarization-independent and high-diffraction-efficiency Fresnel lenses based on blue phase liquid crystals.  

PubMed

A polarization-independent and high-diffraction-efficiency Fresnel lens is developed based on blue phase liquid crystals (BPLCs). The optically isotropic characteristic of BPLCs is used to produce a polarization-independent Fresnel lens. The small optical phase shift of BPLCs that is induced by the Kerr effect is sufficient for the BPLC Fresnel lens to have high theoretical and experimental diffraction efficiencies of 41% and ?34%, respectively. An electrically erasable memory effect in the focusing diffraction at an electric field E>4.44?V/?m is observed. The electro-optical properties of the BPLC Fresnel lens are analyzed and discussed. PMID:21326436

Lin, Chi-Huang; Wang, Yu-Yin; Hsieh, Cheng-Wei

2011-02-15

347

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

348

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

NASA Astrophysics Data System (ADS)

BACH, a soft x-ray beamline for polarization-dependent experiments at the Italian synchrotron radiation facility ELETTRA, was recently completed and characterized. Its performance, in terms of energy resolution, flux and polarization, is presented. Based on two APPLE II undulators, BACH covers the energy range between 35 and 1600 eV with the control of the light polarization. The monochromator is equipped with four gratings and allows one to work either in a high resolution or in a high flux mode. After the monochromator, the beamline is split into two branches with different refocusing properties. One is optimized to exploit the performance of the soft x-ray spectrometer (ComIXS) available at the beamline. Resolving powers between 12000 at 90 eV photon energy and 6600 near 867 eV were achieved using the high-resolution gratings and the smallest available slit width (10 ?m). For the high-brilliance grating, which works between 290 and 1600 eV, resolving powers between 7000 at 400 eV and 2200 at 867 eV were obtained. The flux in the experimental chamber, measured with the high-resolution gratings for linearly polarized light at the best achievable resolution, ranges between 4×1011 photons/s at 125 eV and 2×1010 photons/s between 900 and 1250 eV. In circularly polarized mode the flux is two times larger for energies up to 380 eV. A gain of nearly one order of magnitude is obtained for the high-brilliance grating, in accordance with theoretical predictions. Flux beyond 1.3×1011 photons/s was measured up to 1300 eV, and thus over nearly the complete energy range covered by this high-brilliance grating, with a maximum of 1.6×1011 photons/s between 800 and 1100 eV. First results from polarization measurements confirm a polarization above 99.7% for both linearly and circularly polarized modes at low energies. Circular dichroism experiments indicate a circular polarization beyond 90% at the Fe L2/L3 edge near 720 eV.

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

2004-01-01

349

A fixed-charge model for alcohol polarization in the condensed phase, and its role in small molecule hydration.  

PubMed

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

Fennell, Christopher J; Wymer, Karisa L; Mobley, David L

2014-06-19

350

Unitary Superfluidity Of Polarized Fermionic Gases In Highly Elongated Traps  

NASA Astrophysics Data System (ADS)

Recent groundbreaking experiments on resonantly interacting fermionic superfluids encountered qualitative and quantitative discrepancies which seem to be a function of the confining geometry. Despite long familiarity with BCS (Bardeen-Cooper-Schrieffer) superfluids in a wide range of physical systems such as nuclear matter, QCD, Astrophysics and Condensed Matter, these observations have defied theoretical explanation. Mindful of quantum rigidity and motivated by this impasse, we study the solution space for 3-dimensional fully self-consistent mean field formulation. Relying on numerical algorithms specifically developed for this purpose, we study realistic systems with up to 10^5 atoms. We find that for a large enough sample in a cigar-shaped trap, there are typically three types of solutions which are almost degenerate and have the ff. properties: (i) There is a solution very similar to the local density approximation (LDA) which is consistently the lowest in energy. (ii) However one of the other two solutions, connected by a smooth transition, and which are more consistent with experiment at high aspect ratio, supports a state very similar to the long sought FFLO (Fulde Ferrel Larkin Ovchinnikov) state. We submit that these solutions are relevant false vacua because, given high energy barriers and near degeneracy of the obtained solutions, the actual states observed in an experiment could be a strong function of the experimental procedure. Darpa OLE grant, ARO Grant no. W911NF-07-1-0464, Welch foundation (C-1669, C-1681) and NSF.

Baksmaty, L.; Lu, H.; Bolech, C.; Pu, H.

2010-03-01

351

High-resolution spectroscopy and dynamics of multiphoton processes in atoms and molecules  

Microsoft Academic Search

This report summarizes research on resonantly enhanced multiphoton absorption dissociation, and ionization processes in atoms and molecules. Multiphoton processes are studied using from one to three independently tunable visible and\\/or UV laser beams in order to establish both the underlying physics and the high degree of selectivity of multiphoton processes. Measurements are made to probe both the formation of excited

P. M. Dehmer; J. L. Dehmer

1985-01-01

352

Polarization holographic high-density optical data storage in bacteriorhodopsin film.  

PubMed

Optical films containing the genetic variant bacteriorhodopsin BR-D96N were experimentally studied in view of their properties as media for holographic storage. Different polarization recording schemes were tested and compared. The influence of the polarization states of the recording and readout waves on the retrieved diffractive image's intensity and its signal-to-noise ratio were analyzed. The experimental results showed that, compared with the other tested polarization relations during holographic recording, the discrimination between the polarization states of diffracted and scattered light is optimized with orthogonal circular polarization of the recording beams, and thus a high signal-to-noise ratio and a high diffraction efficiency are obtained. Using a He-Ne laser (633 nm, 3 mW) for recording and readout, a spatial light modulator as a data input element, and a 2D-CCD sensor for data capture in a Fourier transform holographic setup, a storage density of 2 x 10(8) bits/cm2 was obtained on a 60 x 42 microm2 area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density. PMID:16353805

Yao, Baoli; Ren, Zhiwei; Menke, Neimule; Wang, Yingli; Zheng, Yuan; Lei, Ming; Chen, Guofu; Hampp, Norbert

2005-12-01

353

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; Kjær, Helle Astrid; Vallelonga, Paul; Azuma, Nobuhiko; Takata, Morimasa

2014-05-01

354

Nonsequential double ionization of molecules  

SciTech Connect

Double ionization of diatomic molecules by short linearly polarized laser pulses is analyzed. We consider the final stage of the ionization process, that is the decay of a highly excited two electron molecule, which is formed after rescattering. The saddles of the effective adiabatic potential energy close to which simultaneous escape of electrons takes place are identified. Numerical simulations of the ionization of molecules show that the process can be dominated by either sequential or nonsequential events. In order to increase the ratio of nonsequential to sequential ionizations very short laser pulses should be applied.

Prauzner-Bechcicki, Jakub S.; Sacha, Krzysztof; Zakrzewski, Jakub [Instytut Fizyki imienia Mariana Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, PL-30-059 Cracow (Poland); Eckhardt, Bruno [Fachbereich Physik, Philipps-Universitaet Marburg, D-35032 Marburg (Germany)

2005-03-01

355

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

PubMed Central

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

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

2011-01-01

356

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

357

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

358

High-Contrast NIR Polarization Imaging of MWC480  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

359

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

PubMed

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

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

2010-01-24

360

High-throughput single-molecule fluorescence spectroscopy using parallel detection  

PubMed Central

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

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

2011-01-01

361

Analytic description of highly excited vibrational-rotational states of diatomic molecules: II. Application to the hydrogen chloride molecule  

SciTech Connect

Processing of the precise experimental data on transition frequencies and energy levels in the ground electronic state of the H{sup 35}Cl molecule was carried out on the basis of the asymptotically correct perturbation series analytically constructed to describe the discrete vibrational-rotational spectrum of a diatomic molecule. The perturbation series was shown to converge rapidly up to the dissociation energy E{sub D}, whereas the conventional Dunham series has a distinct limit of applicability equal to 0.39E{sub D}. 12 refs., 2 figs.

Burenin, A.V.; Ryabikin, M.Y. [Institute of Applied Physics, Novgorod (Russian Federation)

1995-08-01

362

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

363

High gain linear polarization microstrip antenna with four element electromagnetically coupled patch  

Microsoft Academic Search

A high gain linear polarization antenna with four element electromagnetically coupled patch is presented in this paper. This antenna may be used to limited scan phased array. Two-layer patch is employed to broad impedance band and feeding network with exponential taper line transformer and coax to microstrip transition power divider is employed. Single element of electromagnetically coupled patch compared with

Cui WeiDong

2009-01-01

364

Bright, rapid, highly polarized radio spikes from the M dwarf AD Leonis  

Microsoft Academic Search

A rapid sequence of highly polarized spikes was observed during the gradual rise of a longer lasting event in an Arecibo Observatory study of a radio burst at 1400 MHz from the main sequence radio star AD Leo. The maximum flux density of the spikes was 130 mJy, and they had rise times of less than about 200 msec. The

K. R. Lang; J. Bookbinder; L. Golub; M. M. Davis

1983-01-01

365

A high power gain switched diode laser oscillator and amplifier for the CEBAF polarized electron injector  

SciTech Connect

The photocathode in the polarized electron source at Jefferson Lab is illuminated with pulsed laser light from a gain switched diode laser and diode optical amplifier. Laser pulse repetition rates up to 2,000 MHz, optical pulsewidths between 31 and 123 ps, and average power > 100 mW are demonstrated. The laser system is highly reliable and completely remotely controlled.

Poelker, M.; Hansknecht, J.

1996-12-31

366

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

367

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...

368

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

Microsoft Academic Search

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

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

2005-01-01

369

Permanent porous materials from discrete organic molecules-towards ultra-high surface areas.  

PubMed

In recent years, the development of porous materials derived from discrete organic molecules made a substantial progress towards high-surface-area materials with distinct properties. One major advantage in comparison to existing, well-established porous polymers is their solubility, making such compounds potential valuable precursors for "processing porosity". One important parameter of porous compounds is their specific surface area. The possibilities to reach ultra-high-surface-area materials from this new type of porous compounds are critically discussed. PMID:22806828

Mastalerz, Michael

2012-08-13

370

Reactive oxygen species as glucose signaling molecules in mesangial cells cultured under high glucose  

Microsoft Academic Search

Reactive oxygen species as glucose signaling molecules in mesangial cells cultured under high glucose.BackgroundOxidative stress is one of the important mediators of vascular complications in diabetes including nephropathy. High glucose (HG) generates reactive oxygen species (ROS) as a result of glucose auto-oxidation, metabolism, and formation of advanced glycosylation end products. The concept of ROS-induced tissue injury has recently been revised

Hunjoo Ha; Hi Bahl Lee

2000-01-01

371

A high-rate detection system to study parity violation with polarized epithermal neutrons at LANSCE  

SciTech Connect

We describe an apparatus for studies of parity violation in neutron-nucleus scattering. This experiment requires longitudinally polarized neutrons from the Los Alamos Neutron Scattering Center over the energy-range from 1 to 1000 eV, the ability to reverse the neutron spin without otherwise affecting the apparatus, the ability to detect neutrons at rates up to 500 MHz, and an appropriate data acquisition system. We will discuss the neutron polarizer, fast neutron spin reverser, detector for transmitted neutrons, and high rate data acquisition system.

Knudson, J.N.; Bowman, J.D. [Los Alamos National Lab., NM (United States); Crawford, B.E. [Duke Univ., Durham, NC (United States)]|[Triangle Universities Nuclear Laboratory, Durham, NC (United States)

1995-07-01

372

High-order harmonic generation from graphene: Strong attosecond pulses with arbitrary polarization  

NASA Astrophysics Data System (ADS)

We explore high-order harmonic generation (HHG) from a graphene sheet exposed to intense femtosecond laser pulses based on the Lewenstein model. It is demonstrated that the HHG cutoff frequency increases with graphene size up to the classical limit for distant diatomic systems. In contrast to two-center systems, the cutoff frequency remains constant with increasing power of the harmonics as the graphene diameter extends beyond maximal electron excursion. It is shown that the extended nature of the graphene sheet allows for strong HHG signals at maximum cutoff for linearly as well as circularly polarized laser pulses, the latter opening for generation of strong circularly polarized attosecond pulses.

Sørngård, Stian Astad; Simonsen, Sigrid Ina; Hansen, Jan Petter

2013-05-01

373

Prospect for observation of polarization in electron-deuteron elastic scattering at high momentum transfer  

SciTech Connect

A measurement of the charge and quadrupole form factors of the deuteron would address the most fundamental questions in nuclear physics: validity of perturbative QCD at relatively low momentum transfer, effect of isoscalar meson-exchange currents, and the deuteron structure at short range. Polarization methods will be required in order to provide the separation of these form factors. We propose that the high current of electrons in a storage ring be employed in order to scatter electrons from a gaseous, tensor-polarized, deuterium target.

Holt, R.J.; Green, M.C.; Young, L.; Kowalczyk, R.S.; Geesaman, D.F.; Zeidman, B.; Goodman, L.S.; Napolitano, J.

1985-01-01

374

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

NASA Astrophysics Data System (ADS)

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

Yang, Yiming; Peng, Xingyue; Yu, Dong

2014-05-01

375

Femtosecond laser pumped by high-brightness coherent polarization locked diodes  

NASA Astrophysics Data System (ADS)

We demonstrate, for the first time to our knowledge, the use of a coherent polarization locked diode as the high-brightness pump source for a femtosecond laser. Four diode emitters are coherently locked to produce more than 5Wlinearly polarized, narrow linewidth, and single-lobed pump beam. This gives >10× brightness improvement over the conventional diode array. The diode beam is then used to pump a Yb:KYW laser to obtain 2W output with 57% slope efficiency in cw laser operation. By using a saturable absorber mirror, we achieved cw mode-locking operation with a 177fs pulse width at an average power of 0.55W.

Purnawirman, Purnawirman; Phua, P. B.

2011-08-01

376

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

377

Circularly polarized high-efficiency cholesteric liquid crystal lasers with a tunable nematic phase retarder.  

PubMed

A high efficiency dye-doped cholesteric liquid crystal (CLC) is demonstrated by optimizing the dye concentration and using an electrically tunable nematic liquid crystal (NLC) phase retarder. The state of polarization of laser emission in CLC lasers, contrary to our expectations, due to the refractive index mismatch at the boundaries is not exactly circular. A double-cell structure including a CLC laser and an adjustable NLC phase retarder with a mirror reflector on one of the inner surfaces not only purifies the polarization state of the laser output but also improves the laser efficiency by 6.7X, over the single-direction dye-doped CLC laser. PMID:20389514

Shirvani-Mahdavi, Hamidreza; Mohajerani, Ezeddin; Wu, Shin-Tson

2010-03-01

378

Polarization coupling in a highly birefringent photonic crystal fiber by torsional acoustic wave.  

PubMed

We demonstrate and analyze the acousto-optic coupling between two optical polarization modes of the LP(01) mode propagating in a highly birefringent photonic crystal fiber. The coupling is realized based on wavelength selective acousto-optic coupling by traveling torsional acoustic wave in an all-fiber tunable polarization filter configuration. The dispersion properties of the torsional acoustic wave in the photonic crystal fiber and the influence of axial non-uniformity in the modal birefringence on the filter transmission are discussed in detail. PMID:18542561

Lee, Kwang Jo; Hong, Kee Suk; Park, Hyun Chul; Kim, Byoung Yoon

2008-03-31

379

Multi-polarization fringe projection imaging for high dynamic range objects.  

PubMed

Traditional fringe-projection three-dimensional (3D) imaging techniques struggle to estimate the shape of high dynamic range (HDR) objects where detected fringes are of limited visibility. Moreover, saturated regions of specular reflections can completely block any fringe patterns, leading to lost depth information. We propose a multi-polarization fringe projection (MPFP) imaging technique that eliminates saturated points and enhances the fringe contrast by selecting the proper polarized channel measurements. The developed technique can be easily extended to include measurements captured under different exposure times to obtain more accurate shape rendering for very HDR objects. PMID:24787887

Salahieh, Basel; Chen, Zhenyue; Rodriguez, Jeffrey J; Liang, Rongguang

2014-04-21

380

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

DOEpatents

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

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

2000-01-01

381

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

SciTech Connect

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.

Dolph, P.A. M; Averett, T; Kelleher, A; Mooney, K E; Nelyubin, V; Tobias, W A; Wojsekhowski, B

2011-12-01

382

Highly selective uptake and release of charged molecules by pH-responsive polydopamine microcapsules.  

PubMed

A systematic study of the permeation of small molecules through Pdop microcapsules is reported. The zwitterionic Pdop microcapsules are prepared by oxidative polymerization of dopamine on polystyrene microspheres followed by core removal with THF. Rhodamine 6G, methyl orange and alizarin red are chosen as differently charged probing dyes. The loading amount is affected by pH and dye concentration. Highly selective and unidirectional uptake and release of charged molecules through Pdop microcapsules can be achieved by controlling pH value: at low pH, the Pdop particles incorporate cationic dye (rhodamine 6G); at high pH, they incorporate anionic dyes (methyl orange and alizarin red). In each case, the uptake is highly selective. PMID:21721126

Liu, Qinze; Yu, Bo; Ye, Weichun; Zhou, Feng

2011-09-01

383

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

NASA Astrophysics Data System (ADS)

Here we present high spatial resolution (<1'') observations of molecular emission in Orion-KL conducted using the Combined Array for Research in Millimeter-wave Astronomy. This work was motivated by recent millimeter continuum imaging studies of this region conducted at a similarly high spatial resolution, which revealed that the bulk of the emission arises from numerous compact sources, rather than the larger-scale extended structures typically associated with the Orion Hot Core and Compact Ridge. Given that the spatial extent of molecular emission greatly affects the determination of molecular abundances, it is important to determine the true spatial scale for complex molecules in this region. Additionally, it has recently been suggested that the relative spatial distributions of complex molecules in a source might give insight into the chemical mechanisms that drive complex chemistry in star-forming regions. In order to begin to address these issues, this study seeks to determine the spatial distributions of ethyl cyanide [C2H5CN], dimethyl ether [(CH3)2O], methyl formate [HCOOCH3], formic acid [HCOOH], acetone [(CH3)2CO], SiO, methanol [CH3OH], and methyl cyanide [CH3CN] in Orion-KL at ? = 3 mm. We find that for all observed molecules, the molecular emission arises from multiple components of the cloud that include a range of spatial scales and physical conditions. Here, we present the results of these observations and discuss the implications for studies of complex molecules in star-forming regions.

Widicus Weaver, Susanna L.; Friedel, Douglas N.

2012-08-01

384

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

PubMed

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

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

2010-09-01

385

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

NASA Astrophysics Data System (ADS)

A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous-Tertiary mass extinction event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest Cretaceous dinosaur taxa could reproduce in polar region and were probably year-round residents of high latitudes. Palaeobotanical data suggest that these polar dinosaurs lived in a temperate climate (mean annual temperature about 10°C), 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, Géraldine; Alekseev, Pavel

2009-04-01

386

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

PubMed

A latest Cretaceous (68 to 65 million years ago) vertebrate microfossil assemblage discovered at Kakanaut in northeastern Russia reveals that dinosaurs were still highly diversified in Arctic regions just before the Cretaceous-Tertiary mass extinction event. Dinosaur eggshell fragments, belonging to hadrosaurids and non-avian theropods, indicate that at least several latest Cretaceous dinosaur taxa could reproduce in polar region and were probably year-round residents of high latitudes. Palaeobotanical data suggest that these polar dinosaurs lived in a temperate climate (mean annual temperature about 10 degrees C), 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. PMID:19089398

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

2009-04-01

387

A high throughput screening assay system for the identification of small molecule inhibitors of gsp.  

PubMed

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

388

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.

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

389

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

Microsoft Academic Search

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

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

390

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

PubMed

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

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

2014-02-01

391

High resolution spatiotemporal characterization of electric field polarization for indoor wireless environments  

Microsoft Academic Search

The effects of the electric field polarization on the received power are investigated based on high resolution measurements of the indoor wireless channel. The results presented here were obtained using a channel sounding testbed, which was specially designed to study the radio propagation in the 5-6 GHz frequency band with high resolution in terms of angle-of-arrival (AOA) and time-of-arrival (TOA).

Luis Enrique Gurrieri; Chris C. Squires; S. Noghanian; Tricia J. Willink

2006-01-01

392

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

393

NSOM/QD-based fluorescence-topographic image fusion directly reveals nano-spatial peak-valley polarities of CD69 and CD71 activation molecules on cell-membrane fluctuations during T-cell activation  

PubMed Central

Nano-spatial distribution of cell surface molecules on cell membrane fluctuations during T-cell activation has not been reported. In this study, we innovated application of near-field scanning optical microscopy (NSOM)/quantum dots (QD)-based nanotechnology through three-dimensional image fusion algorithm to merge the simultaneously-obtained dual-color fluorescence information and three-dimensional topography. This novel imaging system made it possible to visualize nano-spatial distribution and organization of early-activation molecules CD69 and late-activation molecules CD71 on cell-membrane fluctuations during T-cell activation. Interestingly, most CD69 molecules were clustered to form 250–500 nm nano-domains polarizing predominantly in the peak of the cell-membrane fluctuations. In contrast, although CD71 molecules were also clustered as 250–500 nm nano-domains, they polarized dominantly in the valley of the cell-membrane fluctuations. The peak-valley polarities of CD69 nano-domains and CD71 nano-domains implied their different functions. CD69 nano-domains polarizing on membrane-peak fluctuations might serve as transient platforms driving TCR/CD3-induced signaling and activation, whereas CD71 nano-domains distributing in the membrane-valley fluctuations appeared to facilitate iron uptake for increased metabolisms in T-cell activation. Importantly, this NSOM/QD-based fluorescence-topographic image fusion provides a powerful tool to visualize nano-spatial distribution of cell-surface molecules on cell-membrane fluctuations and enable better understanding of distribution-function relationship.

Zhong, Liyun; Zhang, Zhun; Lu, Xiaoxu; Huang, Dan; Chen, Crystal Y.; Wang, Richard; Chen, Zheng W.

2011-01-01

394

Collisional properties of cold spin-polarized nitrogen gas: Theory, experiment, and prospects as a sympathetic coolant for trapped atoms and molecules  

SciTech Connect

We report a combined experimental and theoretical study of collision-induced dipolar relaxation in a cold spin-polarized gas of atomic nitrogen (N). We use buffer gas cooling to create trapped samples of {sup 14}N and {sup 15}N atoms with densities (5{+-}2)x10{sup 12} cm{sup -3} and measure their magnetic relaxation rates at milli-Kelvin temperatures. These measurements, together with rigorous quantum scattering calculations based on accurate ab initio interaction potentials for the {sup 7}{Sigma}{sub u}{sup +} electronic state of N{sub 2} demonstrate that dipolar relaxation in N+N collisions occurs at a slow rate of {approx}10{sup -13} cm{sup 3}/s over a wide range of temperatures (1 mK to 1 K) and magnetic fields (10 mT to 2 T). The calculated dipolar relaxation rates are insensitive to small variations of the interaction potential and to the magnitude of the spin-exchange interaction, enabling the accurate calibration of the measured N atom density. We find consistency between the calculated and experimentally determined rates. Our results suggest that N atoms are promising candidates for future experiments on sympathetic cooling of molecules.

Tscherbul, T. V.; Dalgarno, A. [Harvard-Massachusetts Institute of Technology Center for Ultracold Atoms, Cambridge, Massachusetts 02138 (United States); Institute for Theoretical Atomic, Molecular, and Optical Physics, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Klos, J. [Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742 (United States); Zygelman, B. [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, Nevada 89154 (United States); Pavlovic, Z. [Institute for Theoretical Atomic, Molecular, and Optical Physics, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Hummon, M. T.; Lu, H.-I.; Tsikata, E.; Doyle, J. M. [Harvard-Massachusetts Institute of Technology Center for Ultracold Atoms, Cambridge, Massachusetts 02138 (United States); Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)

2010-10-15

395

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

396

A study on high NA and evanescent imaging with polarized illumination  

NASA Astrophysics Data System (ADS)

Simulation techniques are developed for high NA polarized microscopy with Babinet's principle, partial coherence and vector diffraction for non-periodic geometries. A mathematical model for the Babinet approach is developed and interpreted. Simulation results of the Babinet's principle approach are compared with those of Rigorous Coupled Wave Theory (RCWT) for periodic structures to investigate the accuracy of this approach and its limitations. A microscope system using a special solid immersion lens (SIL) is introduced to image Blu-Ray (BD) optical disc samples without removing the protective cover layer. Aberration caused by the cover layer is minimized with a truncated SIL. Sub-surface imaging simulation is achieved by RCWT, partial coherence, vector diffraction and Babinet's Principle. Simulated results are compared with experimental images and atomic force microscopy (AFM) measurement. A technique for obtaining native and induced using a significant amount of evanescent energy is described for a solid immersion lens (SIL) microscope. Characteristics of native and induced polarization images for different object structures and materials are studied in detail. Experiments are conducted with a NA = 1.48 at lambda = 550nm microscope. Near-field images are simulated and analyzed with an RCWT approach. Contrast curve versus object spatial frequency calculations are compared with experimental measurements. Dependencies of contrast versus source polarization angles and air gap for native and induced polarization image profiles are evaluated. By using the relationship between induced polarization and topographical structure, an induced polarization image of an alternating phase shift mask (PSM) is converted into a topographical image, which shows very good agreement with AFM measurement. Images of other material structures include a dielectric grating, chrome-on-glass grating, silicon CPU structure, BD-R and BD-ROM.

Yang, Seung-Hune

397

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.

Justesen, Sune; Harndahl, Mikkel; Lamberth, Kasper; Nielsen, Lise-Lotte B; Buus, S?ren

2009-01-01

398

High sensitivity molecule detection by plasmonic nanoantennas with selective binding at electromagnetic hotspots  

NASA Astrophysics Data System (ADS)

We report a highly sensitive biomolecule detection by plasmonic nanoantenna arrays with selective binding at the optical hotspots. The plasmonic nanoantennas consist of two separated Au nanorods with a thin Ti disk placed in between. By using selective surface modification chemistry, controlled binding occurs only in the gaps between the plasmonic nanoantennas, which ensures a high detection sensitivity. Both optical characterization using a dark field microscope and the FDTD simulation show that after the streptavidin binding, the signal increases with decreasing gap size. Compared to a single nanorod, the signal obtained per bound molecule in the nanoantennas increases by a factor of six, which is promising with respect to the future detection of single molecules.

Zhang, Nan; Liu, Yan Jun; Yang, Jing; Su, Xiaodi; Deng, Jie; Chum, Chan Choy; Hong, Minghui; Teng, Jinghua

2014-01-01

399

High sensitivity molecule detection by plasmonic nanoantennas with selective binding at electromagnetic hotspots.  

PubMed

We report a highly sensitive biomolecule detection by plasmonic nanoantenna arrays with selective binding at the optical hotspots. The plasmonic nanoantennas consist of two separated Au nanorods with a thin Ti disk placed in between. By using selective surface modification chemistry, controlled binding occurs only in the gaps between the plasmonic nanoantennas, which ensures a high detection sensitivity. Both optical characterization using a dark field microscope and the FDTD simulation show that after the streptavidin binding, the signal increases with decreasing gap size. Compared to a single nanorod, the signal obtained per bound molecule in the nanoantennas increases by a factor of six, which is promising with respect to the future detection of single molecules. PMID:24311121

Zhang, Nan; Liu, Yan Jun; Yang, Jing; Su, Xiaodi; Deng, Jie; Chum, Chan Choy; Hong, Minghui; Teng, Jinghua

2014-01-16

400

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

401

Resonancelike enhancement in high-order above-threshold ionization of molecules  

NASA Astrophysics Data System (ADS)

Rresonancelike enhancement of groups of adjacent peaks in the photoelectron spectrum of high-order above-threshold ionization has been well documented for noble-gas atoms subjected to intense infrared laser pulses. However, its physical origin is still under debate. In this Rapid Communication, we investigate experimentally and theoretically high-order above-threshold ionization of diatomic nitrogen and oxygen molecules in order to shed more light on the underlying mechanism. The resonancelike enhancement is experimentally observed for N2 but is absent for O2 molecules. A simulation on the basis of S-matrix theory and the strong-field approximation reproduces the experimental observations. This implies that the resonancelike enhancement can be attributed to the channel-closing effect. The specific molecular structure plays a decisive role for the presence or absence of this enhancement in molecular systems.

Quan, Wei; Lai, XuanYang; Chen, YongJu; Wang, ChuanLiang; Hu, ZiLong; Liu, XiaoJun; Hao, XiaoLei; Chen, Jing; Hasovi?, Elvedin; Busuladži?, Mustafa; Becker, Wilhelm; Miloševi?, Dejan B.

2013-08-01

402

Bright, rapid, highly polarized radio spikes from the M dwarf AD Leonis  

NASA Astrophysics Data System (ADS)

A rapid sequence of highly polarized spikes was observed during the gradual rise of a longer lasting event in an Arecibo Observatory study of a radio burst at 1400 MHz from the main sequence radio star AD Leo. The maximum flux density of the spikes was 130 mJy, and they had rise times of less than about 200 msec. The rise times provide an upper limit to the linear size of the emitter of 6 billion cm, and an area of less than 0.03 of the star's surface area is inferred, for a spike brightness temperature of more than about 10 to the 13th K. The high brightness temperatures and high degrees of circular polarization are explained in terms of electron-cyclotron maser emission at the second harmonic of the gyrofrequency, in longitudinal magnetic fields of about 250 G.

Lang, K. R.; Bookbinder, J.; Golub, L.; Davis, M. M.

1983-09-01

403

The high-pressure segmented quadrupole collision cell (HP-SQCC) as an ion molecule reactor.  

PubMed

A high-pressure 20-segment quadrupole collision cell (HP-SQCC), which replaces a collision cell in a modified triple-quadrupole mass spectrometer is investigated in this work as an ion-molecule reactor with an inherent heat source. The highest working pressure achievable is 20 mTorr. The 20 quadrupole segments permit superimposition of linear axial electric field over the conventional quadrupole field in the radial direction. The axial and radial fields are employed to control ion temperature. Heat is transferred to the reactants through ion frictional heating. The HP-SQCC utilizes a combination of several physicochemical phenomena and an attempt is made to examine a range of ion-molecule reactions. Due to a sufficiently large number of reactive collisions, the reactor is used to promote sequential exothermic ion-molecule reactions. To characterize the performance of the HP-SQCC, the various ion-molecule reactions between the fragment ions of ferrocene (Cp(2)Fe), cobaltocene (Cp(2)Co) and nitrogen, oxygen, water and carbon monoxide are investigated. PMID:15907710

Guo, Yuzhu; Siu, K W Michael; Baranov, Vladimir I

2005-06-01

404

High-field dynamic nuclear polarization with high-spin transition metal ions.  

PubMed

We report the dynamic nuclear polarization of (1)H spins in magic-angle-spinning spectra recorded at 5 T and 84 K via the solid effect using Mn(2+) and Gd(3+) complexes as polarizing agents. We show that the magnitude of the enhancements can be directly related to the effective line width of the central (m(S) = -1/2 ? +1/2) EPR transition. Using a Gd(3+) complex with a narrow central transition EPR line width of 29 MHz, we observed a maximum enhancement of ?13, which is comparable to previous results on the narrow-line-width trityl radical. PMID:21446700

Corzilius, Björn; Smith, Albert A; Barnes, Alexander B; Luchinat, Claudio; Bertini, Ivano; Griffin, Robert G

2011-04-20

405

High Field Dynamic Nuclear Polarization with High-Spin Transition Metal Ions  

PubMed Central

We report the dynamic nuclear polarization of 1H spins in magic angle spinning spectra recorded at 5 T and 84K via the solid effect using Mn2+ and Gd3+ complexes as polarizing agents. We show that the magnitude of the enhancements can be directly related to the effective linewidth of the central (MS = ?1/2 ?+1/2) EPR transition. Using a Gd3+ complex with a narrow central transition EPR linewidth of 29 MHz, a maximum enhancement of ~13 is observed, which is comparable to previous results on the narrow linewidth trityl radical.

Corzilius, Bjorn; Smith, Albert A.; Barnes, Alexander B.; Luchinat, Claudio; Bertini, Ivano; Griffin, Robert G.

2011-01-01

406

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

PubMed

An accurate ab initio quantum chemistry study at level of quadratic configuration interaction method of the electronic ground state of the KCN molecule is presented. A fitting of the results to an analytical series expansion was performed to obtain a global potential energy surface suitable for the study of the associated vibrational dynamics. Additionally, classical Poincare? surfaces of section for different energies and quantum eigenstates were calculated, showing the highly nonlinear behavior of this system. PMID:24320323

Párraga, H; Arranz, F J; Benito, R M; Borondo, F

2013-11-21

407

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

Microsoft Academic Search

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

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

1996-01-01

408

Transient enhancement of high-order harmonic generation in expanding molecules  

SciTech Connect

High-order harmonic generation (HHG) is limited by the probability of recombination of the returning electron with the parent ion. We show here that the internuclear distance of simplest diatomic molecules, determining differently delocalized initial electronic states, can be used to enhance the HHG conversion efficiency exceeding the atomic one. We propose an experiment based on a double-pulse pump-drive scheme where a strong transient enhancement of the HHG yield is predicted.

Pfeifer, T.; Walter, D.; Gerber, G.; Emelin, M.Yu.; Ryabikin, M.Yu.; Chernobrovtseva, M.D.; Sergeev, A.M. [Physikalisches Institut, Universitaet Wuerzburg, Am Hubland, D-97074 Wuerzburg (Germany); Institute of Applied Physics, Russian Academy of Sciences, ul. Ul'yanova 46, Nizhni Novgorod, 603950 (Russian Federation)

2004-07-01

409

Modulation by high glucose of adhesion molecule expression in cultured endothelial cells  

Microsoft Academic Search

Summary  We evaluated the influence of high ambient glucose on cellular expression of adhesion molecules, known to mediate endothelial interaction of leucocytes and monocytes. Paired cultures of individual isolates of human umbilical vein endothelial cells (HUVECs) were studied by fluorescence activated cell sorter analysis after exposure to 30 vs 5 mmol\\/l glucose. Incubation of HUVECs for 24 h in 30 mmol\\/l

S. M. Baumgartner-Parzer; L. Wagner; M. Pettermann; A. Gessl; W. Waldhiiusl

1995-01-01

410

A high resolution time-of-flight mass spectrometer for the detection of ultracold molecules  

Microsoft Academic Search

We have realized a high-resolution time-of-flight mass spectrometer combined with a magneto-optical trap. The spectrometer enables excellent optical access to the trapped atomic cloud using specifically devised acceleration and deflection electrodes. The ions are extracted along a laser beam axis and deflected onto an off axis detector. The setup is applied to detect atoms and molecules photoassociated from ultracold atoms.

Stephan D. Kraft; Jochen Mikosch; Peter Staanum; Johannes Deiglmayr; Joerg Lange; Andrea Fioretti; Roland Wester; Matthias Weidemueller

2005-01-01

411

A high-resolution time-of-flight mass spectrometer for the detection of ultracold molecules  

Microsoft Academic Search

We have realized a high-resolution time-of-flight mass spectrometer combined with a magneto-optical trap. The spectrometer\\u000a enables excellent optical access to the trapped atomic cloud using specifically devised acceleration and deflection electrodes.\\u000a The ions are extracted along a laser beam axis and deflected onto an off-axis detector. The setup is applied to detect atoms\\u000a and molecules photoassociated from ultracold atoms. The

Stephan D. Kraft; Jochen Mikosch; Peter Staanum; Johannes Deiglmayr; Joerg Lange; Andrea Fioretti; Roland Wester; M. Weidemüller

2007-01-01

412

High resolution studies of heacy NO(y) molecules in atmospheric spectra  

NASA Technical Reports Server (NTRS)

New line parameters for two heavy odd nitrogen molecules HNO3 in the nu(sub 5)/2nu(sub 9) region, and ClONO2 in the nu(sub 4) region are incorporated in the analysis of high resolution i.r. atmospheric spectra. The line parameters are tested and renormalized vs laboratory spectra, and then applied to retrievals from balloon-borne and ground-based solar absorption spectra.

Goldman, A.; Rinsland, C. P.; Murcray, F. J.; Blatherwick, R. D.; Murcray, D. G.

1994-01-01