Science.gov

Sample records for highly polar molecules

  1. Interplay of Polarization Geometry and Rotational Dynamics in High-Order Harmonic Generation from Coherently Rotating Linear Molecules

    SciTech Connect

    Faisal, F. H. M.; Abdurrouf, A.

    2008-03-28

    Recent reports on intense-field pump-probe experiments for high-order harmonic generation (HHG) from coherently rotating linear molecules have revealed remarkable characteristic effects of the simultaneous variation of the polarization geometry and the time delay on the high-order harmonic signals. We analyze the effects and give a unified theoretical account of the experimental observations. Furthermore, characteristic behavior at critical polarization angles are found that can help to identify the molecular orbital symmetry in connection with the problem of molecular imaging from the HHG data.

  2. quantum mechanics finite dimensional systems Ammonia (NH3) is a highly polar molecule, with dipole moment p = 4.7 10-30 C m. Ammonia

    E-print Network

    quantum mechanics finite dimensional systems Ammonia Ammonia (NH3) is a highly polar molecule, with dipole moment p = 4.7 × 10-30 C · m. Ammonia undergoes quantum oscillations between the two phases of up of the rotating molecule is preserved. Let us consider the ammonia molecule in the presence of an electric field

  3. Formation of Ultracold Polar Molecules

    NASA Astrophysics Data System (ADS)

    Taylor-Juarros, E.; Côté, R.; Kirby, K.

    2002-05-01

    A variety of experimental techniques have been employed to create a number of ultracold molecules, including CaH, Na_2, K_2, Cs_2, Rb2 and CO. Novel effects are predicted to occur in samples of ultracold polar molecules.(L. Santos et al.), Phys. Rev. Lett. 85, 1791 (2000). We present calculations of the formation rate of ultracold hydrides (LiH, NaH, KH, RbH, and CsH), using the most accurate molecular potentials and dipole moments available. We show that these polar molecules can be produced in selected vibrational and rotational states by stimulated radiative association in a mixture of ultracold hydrogen and alkali metal atoms. We study the properties of these atomic mixtures as well as those of the hydrides, and explore the effect of shape resonances on the formation rates. [2ex] *Supported by NSF

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

    E-print Network

    Son, Sang-Kil; Telnov, Dmitry A.; Chu, Shih-I

    2010-10-18

    PHYSICAL REVIEW A 82, 043829 (2010) Probing the origin of elliptical high-order harmonic generation from aligned molecules in linearly polarized laser fields Sang-Kil Son (#1;#1;#1;),1,* Dmitry A. Telnov,2,† and Shih-I Chu (#1;#1;#1;)1,3,‡ 1...(t) is the wave function propagated in time. The function dy(t) is zero for this alignment. The vector quantity d(t) can be 1050-2947/2010/82(4)/043829(4) 043829-1 ©2010 The American Physical Society SANG-KIL SON, DMITRY A. TELNOV, AND SHIH-I CHU PHYSICAL REVIEW A...

  5. Rydberg atom mediated polar molecule interactions

    NASA Astrophysics Data System (ADS)

    Sadeghpour, Hossein

    2012-06-01

    Manipulating Rydberg interactions in ultracold ensemble is currently in vogue due to the long-range nature of forces and large dipole moments. Interactions between ultracold Rydberg and ground state atoms lead for formation of exotic classes of Rydberg molecules with peculiar properties. A particular class of such homonuclear molecules was recently observed to exhibit linear Stark shifts, pointing to significant permanent electric dipole moments. The symmetry-breaking in these molecules is explained. Rydberg atom mediated coupling with polar molecules leads to formation of ultralong range polyatomic molecules, which can be employed to dramatically enhance the range of controlled interaction between polar molecules, to coherently control molecular orientation, and to individually address polar molecules in optical lattices. A number of scenarios are described.

  6. Production and Trapping of Ultracold Polar Molecules

    SciTech Connect

    David, DeMille

    2015-04-21

    We report a set of experiments aimed at the production and trapping of ultracold polar molecules. We begin with samples of laser-cooled and trapped Rb and Cs atoms, and bind them together to form polar RbCs molecules. The binding is accomplished via photoassociation, which uses a laser to catalyze the sticking process. We report results from investigation of a new pathway for photoassociation that can produce molecules in their absolute ground state of vibrational and rotational motion. We also report preliminary observations of collisions between these ground-state molecules and co-trapped atoms.

  7. Trapping polar molecules in an ac trap

    SciTech Connect

    Bethlem, Hendrick L.; Veldhoven, Jacqueline van; Schnell, Melanie; Meijer, Gerard

    2006-12-15

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

  8. Trapping cold polar molecules on chips

    NASA Astrophysics Data System (ADS)

    Bigelow, N. P.; Vigil, D.; Tscherneck, M.; Kleinert, J.; Haimberger, C.

    2007-06-01

    We summarize recent progress in the production of cold polar molecules emphasizing the photoassociation of laser cooled and trapped atoms in a magneto-optical trap. We then describe one approach to trapping these molecules via interaction with their electric dipole moments. Our studies focus on the case of a simple electrode geometry that can be realized using photolithography on the surface of a silicon chip, enabling the realization of a “molecule chip.”

  9. Spinor Bose-Einstein condensates of rotating polar molecules

    NASA Astrophysics Data System (ADS)

    Deng, Y.; Yi, S.

    2015-09-01

    We propose a scheme to realize a pseudospin-1 /2 model of the 1? (v =0 ) bialkali polar molecules with the spin states corresponding to two sublevels of the first excited rotational level. We show that the effective dipole-dipole interaction between two spin-1 /2 molecules couples the rotational and orbital angular momenta and is highly tunable via a microwave field. We also investigate the ground-state properties of a spin-1 /2 molecular condensate. A variety of nontrivial quantum phases, including the doubly quantized vortex states, are discovered. Our scheme can also be used to create spin-1 model of polar molecules. Thus we show that the ultracold gases of bialkali polar molecules provide a unique platform for studying the spinor condensates of rotating molecules.

  10. Strong-field approximation for ionization of a diatomic molecule by a strong laser field. III. High-order above-threshold ionization by an elliptically polarized field

    SciTech Connect

    Busuladzic, M.; Gazibegovic-Busuladzic, A.; Milosevic, D. B.

    2009-07-15

    We investigate high-order above-threshold ionization (HATI) of diatomic molecules having different symmetries by an elliptically polarized laser field using the modified molecular strong-field approximation. The yields of high-energy electrons contributing to the plateau region of the photoelectron spectra strongly depend on the employed ellipticity. This is more pronounced if the major axis of the polarization ellipse is parallel or perpendicular to the molecular axis and at the end of the high-energy plateau. For the O{sub 2} molecule (characterized by {pi}{sub g} symmetry) the maximum yield is observed for some value of the ellipticity {epsilon} different from zero. On the other hand, in the same circumstances, the N{sub 2} molecule ({sigma}{sub g}) behaves as an atom, i.e., the yield is maximum for {epsilon}=0. These characteristics of the photoelectron spectra remain valid in a wide region of the molecular orientations and laser peak intensities. The symmetry properties of the molecular HATI spectra are considered in detail: by changing the molecular orientation one or other type of the symmetry emerges or disappears. Presenting differential ionization spectra in the ionized electron energy-emission angle plane we have observed similar interference effects as in the HATI spectra governed by a linearly polarized field.

  11. Controlling Polar Molecules in Optical Lattices

    E-print Network

    S. Kotochigova; E. Tiesinga

    2006-02-01

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

  12. Lithium as a refrigerant for polar molecules

    NASA Astrophysics Data System (ADS)

    Kaushik, A.; Tokunaga, S. K.; Hendricks, R. J.; Hinds, E. A.; Tarbutt, M. R.

    2013-03-01

    Gases of ultracold polar molecules offer exciting new possibilities in many areas, including precision measurements, simulations of many-body quantum systems, and quantum information processing. We aim to cool polar molecules by sympathetic cooling with ultracold atoms inside a suitable trap. This poster presents our work on the production and transportation of a dense ultracold cloud of lithium for use as a refrigerant in sympathetic cooling. Up to 1010 lithium atoms are loaded from a Zeeman slower into a magneto-optical trap. Using a moving magnetic trap the atoms are transported to a separate chamber where they will later be co-trapped with molecules. We present the design of our setup and our recent results on transport. We also explore the possibility of electrically polarizing the lithium so that dipole-dipole interactions become important in the gas.

  13. Optical Production of Ultracold Polar Molecules

    SciTech Connect

    Sage, Jeremy M.; Sainis, Sunil; DeMille, David; Bergeman, Thomas

    2005-05-27

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

  14. Direct absorption imaging of ultracold polar molecules

    SciTech Connect

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

    2010-06-15

    We demonstrate a scheme for direct absorption imaging of an ultracold ground-state polar molecular gas near quantum degeneracy. Imaging molecules without closed optical cycling transitions is challenging. Our technique relies on photon-shot-noise-limited absorption imaging on a strong but open bound-bound molecular transition. We present a systematic characterization of this imaging technique. Using this technique combined with time-of-flight expansion, we demonstrate the capability to determine momentum and spatial distributions for the molecular gas. With its capability of imaging molecules in arbitrary external fields, we anticipate that this technique will find many applications in the study of molecular quantum gases.

  15. Dynamics of reactive ultracold alkali polar molecules

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  16. Dipolar collisions of polar molecules in the quantum regime

    E-print Network

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

    2010-01-16

    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 dilute gases of ultracold atoms, which have isotropic and extremely short-range, or "contact", interactions. The large electric dipole moment of polar molecules can be tuned with an external electric field; this provides unique opportunities such as control of ultracold chemical reactions, quantum information processing, and the realization of novel quantum many-body systems. In spite of 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 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 dramatic increase in the loss rate of fermionic KRb molecules due to ultrcold 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 with a relatively simple model based on quantum threshold laws for scattering of fermionic polar molecules. We directly observe the spatial anisotropy of the dipolar interaction as manifested in 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 polar molecule gas. 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 dipolar interactions.

  17. Aspects of Quantum Computing with Polar Paramagnetic Molecules

    NASA Astrophysics Data System (ADS)

    Karra, Mallikarjun; Friedrich, Bretislav

    2015-05-01

    Since the original proposal by DeMille, arrays of optically trapped ultracold polar molecules have been considered among the most promising prototype platforms for the implementation of a quantum computer. The qubit of a molecular array is realized by a single dipolar molecule entangled via its dipole-dipole interaction with the rest of the array's molecules. A superimposed inhomogeneous electric field precludes the quenching of the body-fixed dipole moments by rotation and a time dependent external field controls the qubits to perform gate operations. Much like our previous work in which we considered the simplest cases of a polar 1 ? and a symmetric top molecule, here we consider a X2?3 / 2 polar molecule (exemplified by the OH radical) which, by virtue of its nonzero electronic spin and orbital angular momenta, is, in addition, paramagnetic. We demonstrate entanglement tuning by evaluating the concurrence (and the requisite frequencies needed for gate operations) between two such molecules in the presence of varying electric and magnetic fields. Finally, we discuss the conditions required for achieving qubit addressability (transition frequency difference, ?? , as compared with the concomitant Stark and Zeeman broadening) and high fidelity. International Max Planck Research School - Functional Interfaces in Physics and Chemistry.

  18. Multichannel quantum defect theory for polar molecules

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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.

  19. Towards a low entropy gas of fermionic polar molecules

    NASA Astrophysics Data System (ADS)

    Gadway, Bryce; Moses, Steven; Yan, Bo; Covey, Jacob; Jin, Deborah; Ye, Jun

    2013-05-01

    In recent years, ultracold gases of polar molecules have garnered much attention, owing in part to their prospects for emulating condensed matter systems with long-range interactions. To enable the observation of long-range dipolar interactions, which has so far been precluded by insufficient molecular densities, we aim to create a high-filling-fraction sample of ground state polar KRb molecules in a three-dimensional optical lattice. This can be accomplished by disposing an initial Bose-Fermi lattice mixture towards the formation of preformed pairs - one boson and one fermion per lattice site - via control over the interspecies interactions, followed by efficient conversion to deeply bound ground state molecules. To characterize the entropy in our system, we shall study two-body losses due to reactive collisions occurring in molecular rotational-state mixtures.

  20. Toroidal nanotraps for cold polar molecules

    SciTech Connect

    Salhi, Marouane; Passian, Ali; Siopsis, George

    2015-09-14

    Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface-enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength, and polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasistatic limit within the first-order perturbation of the scalar electric potential. The possibility of extending the single nanoring trapping properties to two-dimensional arrays of nanorings is suggested by obtaining the field distribution of nanoring dimers and trimers.

  1. Toroidal nanotraps for cold polar molecules

    NASA Astrophysics Data System (ADS)

    Salhi, Marouane; Passian, Ali; Siopsis, George

    2015-09-01

    Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface-enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength, and polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasistatic limit within the first-order perturbation of the scalar electric potential. The possibility of extending the single nanoring trapping properties to two-dimensional arrays of nanorings is suggested by obtaining the field distribution of nanoring dimers and trimers.

  2. Toroidal nanotraps for cold polar molecules

    DOE PAGESBeta

    Salhi, Marouane; Passian, Ali; Siopsis, George

    2015-09-14

    Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface-enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength, andmore »polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasistatic limit within the first-order perturbation of the scalar electric potential. The possibility of extending the single nanoring trapping properties to two-dimensional arrays of nanorings is suggested by obtaining the field distribution of nanoring dimers and trimers.« less

  3. Transport of polar molecules by an alternating-gradient guide

    SciTech Connect

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

    2009-10-15

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

  4. COMMUNICATIONS Relationship between bipolar moments and molecule-frame polarization

    E-print Network

    COMMUNICATIONS Relationship between bipolar moments and molecule-frame polarization parameters quantum mechanical significance. In particular, it is shown that the coherent contribution a set of reduced parameters s2 , 2 , 2 , and 2) selected to isolate dynamically distinct, coherent

  5. Cooling polar NaCs molecules in an electrostatic trap

    NASA Astrophysics Data System (ADS)

    Haruza, Marek; Jayaseelan, Maitreyi; Bigelow, Nicholas P.

    2015-05-01

    We present our scheme for creating an ultracold and dense sample of polar NaCs molecules. The molecules are photoassociated from laser cooled atoms and held in an electrostatic trap in their vibrational ground state and the lowest trappable rotational states. The trap depth dependance on the rotational quantum numbers can be exploited to cool the motion of the molecules by optical pumping between rotational levels.

  6. Quantum phase gate and controlled entanglement with polar molecules

    SciTech Connect

    Charron, Eric; Keller, Arne; Atabek, Osman; Milman, Perola

    2007-03-15

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

  7. A model for positron binding to polar molecules

    E-print Network

    Gribakin, G F

    2015-01-01

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

  8. Evanescent-Wave Mirror for Ultracold Diatomic Polar Molecules

    NASA Astrophysics Data System (ADS)

    Kallush, S.; Segev, B.; Côté, R.

    2005-10-01

    We describe the interaction of an ultracold diatomic polar molecule with an evanescent-wave mirror. Several features of this system are explored, such as the coupling between internal rovibrational states of the molecule and the laser field. Numerical simulations show quantum reflection and state selection under attainable physical conditions. Such molecular optics components will facilitate the manipulation and trapping of ultracold molecules, and might serve in future applications in several fields, e.g., as devices to filter and select a state for ultracold chemistry, to measure extremely low temperatures of molecules, or to manipulate states for quantum information processing.

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

    NASA Astrophysics Data System (ADS)

    Qi, Ran; Tan, Shina

    2014-05-01

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

  10. Electron Capture and Scaling Anomaly in Polar Molecules

    E-print Network

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

    2007-03-13

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

  11. Interactions between Rydberg atoms and ultracold polar molecules

    NASA Astrophysics Data System (ADS)

    Jayaseelan, Maitreyi; Haruza, Marek; Bigelow, Nicholas P.

    2015-05-01

    We investigate dipolar interactions arising in a hybrid system containing both ultracold polar molecules and atomic Rydberg states. Ultracold NaCs molecules are produced by photoassociation from laser cooled mixtures of sodium and cesium atoms and detected through resonant multi-photon ionization (REMPI). Rydberg atoms with large dipole moments are excited in the atomic cloud using a multi-photon process and detected via field-ionization. We look for evidence of the interactions in the observed spectra.

  12. Polarization forces in water deduced from single molecule data

    E-print Network

    Eugene V. Tsiper

    2004-07-08

    Intermolecular polarization interactions in water are determined using a minimal atomic multipole model constructed with distributed polarizabilities. Hydrogen bonding and other properties of water-water interactions are reproduced to fine detail by only three multipoles $\\mu_H$, $\\mu_O$, and $\\theta_O$ and two polarizabilities $\\alpha_O$ and $\\alpha_H$, which characterize a single water molecule and are deduced from single molecule data.

  13. Universal Matchgate Quantum Computing With Cold Polar Molecules

    NASA Astrophysics Data System (ADS)

    Herrera, Felipe

    2015-03-01

    Polar molecules in optical lattices are attractive for quantum simulation and computation due to the ability to implement a variety of spin-lattice models using static, microwave and optical fields to engineer the long-range dipolar interaction between molecular qubits. Quantum simulation of spin models requires global control over the molecular ensemble, while quantum computation requires control of individual molecules with sub-wavelength resolution. In this talk, we describe the implementation of a matchgate quantum processor with an ensemble of polar molecules in an optical lattice. The scheme uses few-body qubit encoding and sequential control of two-body dipolar interactions over small plaquetes on a square lattice to perform universal quantum computing without single-site addressing. Effective spin-spin interactions with matchgate symmetry between open-shell polar molecules (e.g., SrF, OH) are driven by two infrared control pulses in the absence of static electric fields. The resulting matchgates are robust with respect to realistic imperfections in the driving fields and lattice trapping. Applications of the architecture for the simulation of interacting fermions in quantum chemistry are discussed, considering an imperfect lattice filling.

  14. Model Independence in Two Dimensions and Polarized Cold Dipolar Molecules

    SciTech Connect

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

    2011-06-24

    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.

  15. Three-dimensional optical polarization tomography of single molecules

    NASA Astrophysics Data System (ADS)

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

    2003-06-01

    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.

  16. Measuring dipolar spin exchanges in ultracold polar KRb molecules

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    By encoding spin in rotational states, we have observed spin exchanges of ultracold polar KRb molecules that are confined in a deep three dimensional optical lattice [Yan et al., Nature 501, 521 (2013)]. The interactions manifest as a density dependent decay of the spin coherence of the system, which is probed via Ramsey spectroscopy. In addition to decaying, there are oscillations in the contrast, with frequency components that are consistent with the dipolar interaction energies. By adding additional pulses, we can suppress pairwise dipolar interactions. We have studied these spin exchanges for two different pairs of rotational states, which differ by a factor of two in interaction strength, and find the decay and oscillations to be roughly twice as fast in the case of stronger interactions. This work lays the foundation for future studies of quantum magnetism with polar molecules in optical lattices. We acknowledge funding from NIST, NSF, DOE, AFOSR-MURI, DARPA, and the NDSEG Graduate Fellowship.

  17. Ferroelectric quantum phase transition with cold polar molecules

    NASA Astrophysics Data System (ADS)

    Klinsmann, Markus; Peter, David; Büchler, Hans Peter

    2015-08-01

    We analyze a system of polar molecules in a one-dimensional optical lattice. By controlling the internal structure of the polar molecules with static electric and microwave fields, we demonstrate the appearance of a quantum phase transition into a ferroelectric phase via spontaneous breaking of a U(1) symmetry. The phase diagram is first analyzed within mean-field theory, while in a second step the results are verified by a mapping onto the Bose-Hubbard model for hard-core bosons. The latter is studied within the well-established bosonization procedure. We find that the ferroelectric phase is characterized by (quasi) long-range order for the electric dipole moments.

  18. Dipole-interaction-mediated laser cooling of polar molecules to ultracold temperatures.

    PubMed

    Huber, S D; Büchler, H P

    2012-05-11

    We present a method to design a finite decay rate for excited rotational states in polar molecules. The setup is based on a hybrid system of polar molecules with atoms driven into a Rydberg state. The atoms and molecules are coupled via the strong dipolar exchange interaction between two rotation levels of the polar molecule and two Rydberg states. Such a controllable decay rate opens the way to optically pump the hyperfine levels of polar molecules and it enables the application of conventional laser cooling techniques for cooling polar molecules into quantum degeneracy. PMID:23003035

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

    E-print Network

    Jin, Deborah

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

  20. Formation of ultracold polar molecules in a single quantum state

    SciTech Connect

    Cote, Robin; Juarros, Elizabeth; Kirby, Kate

    2010-06-15

    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.

  1. Fermi liquid of two-dimensional polar molecules

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

  2. Formation of ultracold polar molecules via Raman excitation

    NASA Astrophysics Data System (ADS)

    Taylor-Juarros, E.; Côté, R.; Kirby, K.

    2004-11-01

    Alkali hydride molecules are very polar, exhibiting large ground-state dipole moments. As ultracold sources of alkali atoms, as well as hydrogen, have been created in the laboratory, we explore theoretically the feasibility of forming such molecules from a mixture of the ultracold atomic gases, employing a two-photon stimulated radiative association process — Raman excitation. Using accurate molecular potential energy curves and dipole transition moments, we have calculated the rate coefficients for populating all the vibrational levels of the X^1?+ state of LiH via the excited A^1?+ state. We have found that significant molecule formation rates can be realized with laser intensities and atomic densities that are attainable experimentally. Because of the large X state dipole moment, rapid cascade occurs down the ladder of vibrational levels to v=0. The calculated recoil momentum imparted to the molecule is small, and thus negligible trap loss results from the cascade process. This allows for the build-up of a large population of v=0 trapped molecules.

  3. Toroidal nano-traps for cold polar molecules

    E-print Network

    Salhi, Marouane; Siopsis, George

    2015-01-01

    Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength and polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasi-static limit within the first-order perturbation of the scalar elect...

  4. Tunable disorder in a crystal of cold polar molecules

    SciTech Connect

    Herrera, Felipe; Krems, Roman V.; Litinskaya, Marina

    2010-09-15

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

  5. Doublon dynamics and polar molecule production in an optical lattice

    E-print Network

    Covey, Jacob P; Garttner, Martin; Safavi-Naini, Arghavan; Miecnikowski, Matthew T; Fu, Zhengkun; Schachenmayer, Johannes; Julienne, Paul S; Rey, Ana Maria; Jin, Deborah S; Ye, Jun

    2015-01-01

    Ultracold polar molecules provide an excellent platform to study quantum many-body spin dynamics, which has become accessible in the recently realized low entropy quantum gas of polar molecules in an optical lattice. To obtain a detailed understanding for the molecular formation process in the lattice, we prepare a density distribution where lattice sites are either empty or occupied by a doublon composed of a bosonic atom interacting with a fermionic atom. By letting this disordered, out-of-equilibrium system evolve from a well-defined initial condition, we observe clear effects on pairing that arise from inter-species interactions, a higher partial wave Feshbach resonance, and excited Bloch-band population. When only the lighter fermions are allowed to tunnel in the three-dimensional (3D) lattice, the system dynamics can be well described by theory. However, in a regime where both fermions and bosons can tunnel, we encounter correlated dynamics that is beyond the current capability of numerical simulations....

  6. Astrocyte polarization and wound healing in culture: studying cell adhesion molecules.

    PubMed

    Peng, H; Carbonetto, S

    2012-01-01

    Astrocytes are highly polarized cells. This is manifest not only during development and in the adult brain, but also following injury. In response to a wound, astrocytes extend processes that participate in formation of a glial scar, which walls off lesions in the brain or spinal cord. Similarly, astrocytes in culture polarize dramatically and extend processes towards a scrape wound. This simple assay has allowed much progress in understanding the cellular events and molecular pathways in astrocyte polarization (1). Cell adhesion is essential for the early response to the wound, both with respect to process extension and cell polarization. This is evident in the involvement of members of the integrin family of cell adhesion molecules at the leading edge of the wounded astrocyte. Understanding the cellular and molecular bases of these events is likely relevant to astrocyte function during development (radial glia) as well as in wound healing. PMID:22144308

  7. Dynamic nuclear polarization at high magnetic fields

    PubMed Central

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

    2009-01-01

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

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

    PubMed

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

    2015-11-01

    Ultracold polar molecules, with their long-range electric dipolar interactions, offer a unique platform for studying correlated quantum many-body phenomena. However, realizing a highly degenerate quantum gas of molecules with a low entropy per particle is challenging. We report the synthesis of a low-entropy quantum gas of potassium-rubidium molecules (KRb) in a three-dimensional optical lattice. We simultaneously load into the optical lattice a Mott insulator of bosonic Rb atoms and a single-band insulator of fermionic K atoms. Then, using magnetoassociation and optical state transfer, we efficiently produce ground-state molecules in the lattice at those sites that contain one Rb and one K atom. The achieved filling fraction of 25% should enable future studies of transport and entanglement propagation in a many-body system with long-range dipolar interactions. PMID:26542566

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Ultracold polar molecules, with their long-range electric dipolar interactions, offer a unique platform for studying correlated quantum many-body phenomena. However, realizing a highly degenerate quantum gas of molecules with a low entropy per particle is challenging. We report the synthesis of a low-entropy quantum gas of potassium-rubidium molecules (KRb) in a three-dimensional optical lattice. We simultaneously load into the optical lattice a Mott insulator of bosonic Rb atoms and a single-band insulator of fermionic K atoms. Then, using magnetoassociation and optical state transfer, we efficiently produce ground-state molecules in the lattice at those sites that contain one Rb and one K atom. The achieved filling fraction of 25% should enable future studies of transport and entanglement propagation in a many-body system with long-range dipolar interactions.

  10. High Intensity Polarized Electron Sources

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

    During the 1990s, at numerous facilities world wide, extensive R&D devoted to constructing reliable GaAs photoguns helped ensure successful accelerator-based nuclear and high-energy physics programs using spin polarized electron beams. Today, polarized electron source technology is considered mature, with most GaAs photoguns meeting accelerator and experiment beam specifications in a relatively trouble-free manner. Proposals for new collider facilities however, require electron beams with parameters beyond today's state-of-the-art and serve to renew interest in conducting polarized electron source R&D. And at CEBAF/Jefferson Lab, there is an immediate pressing need to prepare for new experiments that require considerably more beam current than before. One experiment in particular—Q-weak, a parity violation experiment that will look for physics beyond the Standard Model—requires 180 uA average current at polarization >80% for a duration of one year, with run-averaged helicity correlated current asymmetry less than 0.1 ppm. Neighboring halls will continue taking beam during Q-weak, pushing the total average beam current from the gun beyond 300 uA. This workshop contribution describes R&D at Jefferson Lab, dedicated toward extending the operating current of polarized electron sources to meet the requirements of high current experiments at CEBAF and to better appreciate the technological challenges of new accelerators, particularly high average current machines like eRHIC that require at least 25 mA at high polarization.

  11. High Intensity Polarized Electron Gun

    SciTech Connect

    Redwine, Robert P.

    2012-07-31

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

  12. A microwave trap for sympathetic cooling of polar molecules

    NASA Astrophysics Data System (ADS)

    Dunseith, Devin; Truppe, Stefan; Hendricks, Richard; Sauer, Ben; Hinds, Edward; Tarbutt, Michael

    2015-03-01

    We have been developing techniques to cool molecules into the microkelvin regime. One method is to use sympathetic cooling, using ultracold atoms as a refrigerant to cool molecules. Previous work has suggested that atoms and molecules can be trapped in the antinode of a Fabry­-Pérot microwave cavity. We couple microwave power into this cavity from a rectangular waveguide via a small hole in one mirror. We have developed an analytical model that helps us understand this coupling, and gives us an idea of how the size of the hole affects the cavity's coupling and finesse. We carried out finite-­difference time­-domain simulations and performed experiments on a prototype cavity to verify this model. We have now designed and built this trap for operation under ultra­high vacuum, with the ability to cool the mirrors to 77 K and couple in up to 2 kW of microwave power. This will allow us to trap molecules with a moderate dipole moment at temperatures of hundreds of millikelvin, as well as atoms at a few millikelvin. We will present our work in creating and understanding the microwave trap, as well as our first results demonstrating trapping of lithium atoms in the microwave trap. The authors would like to thank EPSRC for supporting this work.

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

    SciTech Connect

    Bomble, Laeetitia; Pellegrini, Philippe; Ghesquiere, Pierre; Desouter-Lecomte, Michele

    2010-12-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

    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.

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

    SciTech Connect

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

    2011-07-15

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

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

    PubMed

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

    2014-06-21

    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

  17. Uptake of neutral polar vapor molecules by charged clusters//particles: Enhancement due to dipole-charge interaction

    E-print Network

    Yu, Fangqun

    Uptake of neutral polar vapor molecules by charged clusters//particles: Enhancement due to dipole that the enhanced uptake of neutral polar molecules by the charged clusters as a result of dipole-charge interaction: Nadykto, A. B., and F. Yu, Uptake of neutral polar vapor molecules by charged clusters

  18. arXiv:0811.4618v1[physics.atom-ph]27Nov2008 Ultracold polar molecules near quantum degeneracy

    E-print Network

    Kotochigova, Svetlana

    , Temple University, Philadelphia, PA 19122-6082, USA 3 Joint Quantum Institute, NIST and University energy. This requirement can be fulfilled only with an ultracold, high-density gas of polar molecules

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

    SciTech Connect

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

    2014-10-15

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

  20. Single photon detector with high polarization sensitivity

    PubMed Central

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

    2015-01-01

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

  1. High harmonic generation spectra of aligned benzene in circular polarized laser field

    E-print Network

    Moiseyev, Nimrod

    High harmonic generation spectra of aligned benzene in circular polarized laser field Petra Zda-order harmonic generation in benzene, aligned in the polarization plane of circular polarized laser field-induced dynamics of the model benzene molecule at the laser wavelength of 800 nm is dominated by a single long

  2. Dipole-dipole interaction-induced spin-orbit coupling of polar molecules in optical lattices

    NASA Astrophysics Data System (ADS)

    Wall, M. L.; Syzranov, S. V.; Rey, A. M.

    2014-05-01

    Long-range dipole-dipole interactions between polar molecules in an optical lattice enable rotational excitations to move through the lattice even when the molecules themselves cannot, as has been directly observed in recent experiments [Yan et al., Nature 501, 521-525 (2013)]. We study the dynamics of rotational excitations in a 2D lattice of (bosonic or fermionic) polar molecules in the presence of electric dipole-dipole interactions which exchange rotational ``spin'' angular momentum projection with orbital angular momentum, forming a cold molecule analog of the Einstein-de Haas effect. In particular, we present analytic results for the statics and dynamics of a dilute gas of rotational excitations in a unit-filed lattice. Prospects for observing such processes in near-term polar molecule experiments are discussed.

  3. Single Molecule Raman Spectroscopy Under High Pressure

    NASA Astrophysics Data System (ADS)

    Fu, Yuanxi; Dlott, Dana

    2014-06-01

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

  4. Accelerating Polarized Protons to High Energy

    NASA Astrophysics Data System (ADS)

    Bai, M.; Ahrens, L.; Alekseev, I. G.; Alessi, J.; Beebe-Wang, J.; Blaskiewicz, M.; Bravar, A.; Brennan, J. M.; Bruno, D.; Bunce, G.; Butler, J.; Cameron, P.; Connolly, R.; Delong, J.; D'Ottavio, T.; Drees, A.; Fischer, W.; Ganetis, G.; Gardner, C.; Glenn, J.; Hayes, T.; Hseuh, H.-C.; Huang, H.; Ingrassia, P.; Laster, J.; Lee, R.; Luccio, A.; Luo, Y.; MacKay, W. W.; Makdisi, Y.; Marr, G.; Marusic, A.; McIntyre, G.; Michnoff, R.; Montag, C.; Morris, J.; Nicoletti, A.; Oddo, P.; Oerter, B.; Piacentino, J.; Pilat, F.; Ptitsyn, V.; Roser, T.; Satogata, T.; Smith, K.; Svirida, D. N.; Tepikian, S.; Trbojevic, D.; Tsoupas, N.; Tuozzolo, J.; Wilinski, M.; Zaltsman, A.; Zelenski, A.; Zeno, K.; Zhang, S. Y.

    2007-06-01

    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.

  5. Accelerating Polarized Protons to High Energy

    SciTech Connect

    Bai, M.; Ahrens, L.; Alekseev, I. G.; Alessi, J.; Beebe-Wang, J.; Blaskiewicz, M.; Bravar, A.; Brennan, J. M.; Bruno, D.; Bunce, G.; Butler, J.; Cameron, P.; Connolly, R.; Delong, J.; D'Ottavio, T.; Drees, A.; Fischer, W.; Ganetis, G.; Gardner, C.; Glenn, J.

    2007-06-13

    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.

  6. ACCELERATING POLARIZED PROTONS TO HIGH ENERGY.

    SciTech Connect

    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

    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.

  7. Dynamic nuclear polarization of amorphous and crystalline small molecules

    E-print Network

    Ong, Ta-Chung

    2014-01-01

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

  8. Controllable binding of polar molecules and metastability of one-dimensional gases with attractive dipole forces.

    PubMed

    Byrd, Jason N; Montgomery, John A; Côté, Robin

    2012-08-24

    We explore one-dimensional samples of ultracold polar molecules with attractive dipole-dipole interactions and show the existence of a repulsive barrier caused by a strong quadrupole interaction between molecules. This barrier can stabilize a gas of ultracold KRb molecules and even lead to long-range wells supporting bound states between the molecules. The properties of these wells can be controlled by external electric fields, allowing the formation of long polymerlike chains of KRb and studies of quantum phase transitions by varying the effective interaction between molecules. We discuss the generalization of those results to other systems. PMID:23002744

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    SciTech Connect

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

    2011-12-15

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

  11. Mitigation of charged impurity effects in graphene field-effect transistors with polar organic molecules (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Worley, Barrett C.; Kim, Seohee; Akinwande, Deji; Rossky, Peter J.; Dodabalapur, Ananth

    2015-09-01

    Recent developments in monolayer graphene production allow its use as the active layer in field-effect transistor technology. Favorable electrical characteristics of monolayer graphene include high mobility, operating frequency, and good stability. These characteristics are governed by such key transport physical phenomena as electron-hole transport symmetry, Dirac point voltage, and charged impurity effects. Doping of graphene occurs during device fabrication, and is largely due to charged impurities located at or near the graphene/substrate interface. These impurities cause scattering of charge carriers, which lowers mobility. Such scattering is detrimental to graphene transistor performance, but our group has shown that coating with fluoropolymer thin films or exposure to polar organic vapors can restore favorable electrical characteristics to monolayer graphene. By partially neutralizing charged impurities and defects, we can improve the mobility by approximately a factor of 2, change the Dirac voltage by fairly large amounts, and reduce the residual carrier density significantly. We hypothesize that this phenomena results from screening of charged impurities by the polar molecules. To better understand such screening interactions, we performed computational chemistry experiments to observe interactions between polar organic molecules and monolayer graphene. The molecules interacted more strongly with defective graphene than with pristine graphene, and the electronic environment of graphene was altered. These computational observations correlate well with our experimental results to support our hypothesis that polar molecules can act to screen charged impurities on or near monolayer graphene. Such screening favorably mitigates charge scattering, improving graphene transistor performance.

  12. Charge-induced spin polarization in non-magnetic organic molecule Alq$_{3}$

    E-print Network

    Tarafder, Kartick; Oppeneer, Peter

    2010-01-01

    Electrical injection in organic semiconductors is a key prerequisite for the realization of organic spintronics. Using density-functional theory calculations we report the effect of electron transfer into the organic molecule Alq$_3$. Our first-principles simulations show that electron injection spontaneously spin-polarizes non-magnetic Alq$_3$ with a magnetic moment linearly increasing with induced charge. An asymmetry of the Al--N bond lengths leads to an asymmetric distribution of injected charge over the molecule. The spin-polarization arises from a filling of dominantly the nitrogen $p_z$ orbitals in the molecule's LUMO together with ferromagnetic coupling of the spins on the quinoline rings.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  14. Effect of dipole polarizability on positron binding by strongly polar molecules

    NASA Astrophysics Data System (ADS)

    Gribakin, G. F.; Swann, A. R.

    2015-11-01

    A model for positron binding to polar molecules is considered by combining the dipole potential outside the molecule with a strongly repulsive core of a given radius. Using existing experimental data on binding energies leads to unphysically small core radii for all of the molecules studied. This suggests that electron-positron correlations neglected in the simple model play a large role in determining the binding energy. We account for these by including the polarization potential via perturbation theory and non-perturbatively. The perturbative model makes reliable predictions of binding energies for a range of polar organic molecules and hydrogen cyanide. The model also agrees with the linear dependence of the binding energies on the polarizability inferred from the experimental data (Danielson et al 2009 J. Phys. B: At. Mol. Opt. Phys. 42 235203). The effective core radii, however, remain unphysically small for most molecules. Treating molecular polarization non-perturbatively leads to physically meaningful core radii for all of the molecules studied and enables even more accurate predictions of binding energies to be made for nearly all of the molecules considered.

  15. Surface-induced heating of cold polar molecules

    E-print Network

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

    2009-12-14

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

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

    E-print Network

    Tomza, Micha?

    2013-01-01

    The properties of the electronic ground state of the polar and paramagnetic chromium--closed-shell-atom molecules have been investigated. State-of-the-art \\textit{ab initio} techniques have been applied to compute the potential energy curves for the chromium--alkaline-earth-metal-atom, CrX (X = Be, Mg, Ca, Sr, Ba), and chromium--ytterbium, CrYb, molecules in the Born-Oppenheimer approximation for the $X^7\\Sigma^+$ high-spin electronic ground state. The spin restricted open-shell coupled cluster method restricted to single, double, and noniterative triple excitations, RCCSD(T), was employed and the scalar relativistic effects within Douglas-Kroll-Hess Hamiltonian or energy-consistent pseudopotentials were included. The permanent electric dipole moments and static electric dipole polarizabilities were computed. The leading long-range coefficients describing the dispersion interaction between atoms at large interatomic distances, $C_6$, are also reported. Molecules under investigation are an example of species p...

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

    NASA Astrophysics Data System (ADS)

    Julienne, Paul; Hanna, Thomas; Idziaszek, Zbigniew

    2011-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  19. Nano-doped weakly polar versus highly polar liquid crystal

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  20. ACCELERATION OF POLARIZED PROTONS TO HIGH ENERGY.

    SciTech Connect

    ROSER,T.

    1999-03-29

    High energy polarized beam collisions will open up the unique physics opportunities of studying spin effects in hard processes. However, the acceleration of polarized beams in circular accelerators is complicated by the numerous depolarizing spin resonances. Using a partial Siberian Snake and a rf dipole that ensure stable adiabatic spin motion during acceleration has made it possible to accelerate polarized protons to 25 GeV at the Brookhaven AGS. Full Siberian Snakes and polarimeters are being developed for RHIC to make the acceleration of polarized protons to 250 GeV possible. A similar scheme is being studied for the 800 GeV HERA proton accelerator.

  1. Simple quantum model of ultracold polar molecule collisions

    SciTech Connect

    Idziaszek, Zbigniew; Quemener, Goulven; Bohn, John L.; Julienne, Paul S.

    2010-08-15

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

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

    SciTech Connect

    Dimitrovski, Darko; Abu-samha, Mahmoud; Madsen, Lars Bojer; Filsinger, Frank; Meijer, Gerard; Kuepper, Jochen; Holmegaard, Lotte; Kalhoej, Line; Nielsen, Jens H.; Stapelfeldt, Henrik

    2011-02-15

    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.

  3. Supersolid Phase with Cold Polar Molecules on a Triangular Lattice

    SciTech Connect

    Pollet, L.; Picon, J. D.; Buechler, H. P.; Troyer, M.

    2010-03-26

    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.

  4. Polarization properties of light scattered off solutions of chiral molecules in non-forward direction

    NASA Astrophysics Data System (ADS)

    Vidal, Xavier; Fernandez-Corbaton, Ivan; Barbara, Alex F.; Molina-Terriza, Gabriel

    2015-11-01

    Measuring the optical activity from an ensemble of chiral molecules is a common tool to know their stereo-structure. These measurements are done in the same propagation direction of the probe beam of light, because that is the direction where most signal is emitted. We provide experimental and theoretical evidence that, even though other interesting information may be gathered when collecting light emitted in other directions, for most molecules, the phenomenon of optical activity is only present in the forward scattering direction. The fundamental reason behind this is that forward scattered light preserves the circular polarization states due to the cylindrical symmetry of the system, an essential requirement for optical activity. An important exemption happens in dual molecules, i.e., molecules which present the same response to electric and magnetic fields. We present a series of experiments measuring the optical activity and the scattering of chiral solutions in the forward and perpendicular directions. We experimentally show that these molecules present optical activity and preservation of circular polarization in the forward direction, while the polarization pattern in non-forward directions is much more complex and, in particular, does not preserve the circular polarization. Finally, we show that when probing the particle with different wavelengths, the scattering in non-forward directions presents some interesting structural features which are hidden in the forward measurements.

  5. Solvent tuned single molecule dual emission in protic solvents: effect of polarity and H-bonding.

    PubMed

    Chevreux, S; Allain, C; Wilbraham, L; Nakatani, K; Jacques, P; Ciofini, I; Lemercier, G

    2015-12-22

    has recently been proposed as a promising new molecule displaying solvent-tuned dual emission, highlighting an original and newly-described charge transfer model. The study of the photophysical behaviour of this molecule was extended to include protic solvents. The effects of polarity and hydrogen bonding lead to an even more evident dual emission associated with a large multi-emission band in some solvents like methanol, highlighting as a promising candidate for white light emission. PMID:26411633

  6. Bilayer superfluidity of fermionic polar molecules: Many-body effects

    SciTech Connect

    Baranov, M. A.; Micheli, A.; Ronen, S.; Zoller, P.

    2011-04-15

    We study the BCS superfluid transition in a single-component fermionic gas of dipolar particles loaded in a tight bilayer trap, with the electric dipole moments polarized perpendicular to the layers. Based on the detailed analysis of the interlayer scattering, we calculate the critical temperature of the interlayer superfluid pairing transition when the layer separation is both smaller (dilute regime) and on the order or larger (dense regime) than the mean interparticle separation in each layer. Our calculations go beyond the standard BCS approach and include the many-body contributions resulting in the mass renormalization, as well as additional contributions to the pairing interaction. We find that the many-body effects have a pronounced effect on the critical temperature and can either decrease (in the very dilute limit) or increase (in the dense and moderately dilute limits) the transition temperature as compared to the BCS approach.

  7. Spin polarization and spin separation realized in the double-helical molecules

    NASA Astrophysics Data System (ADS)

    Wu, Hai-Na; Zhu, Yu-Lian; Sun, Xue; Gong, Wei-Jiang

    2015-11-01

    We investigate the electron transport through one double-helical molecule with four terminals, by considering one terminal to be the source and others to be the drains. It is found that notable spin polarizations simultaneously occur during the processes of intra-chain electron tunneling and inter-chain electron reflection. More importantly, in these two processes, the spin polarizations always show similar strengths and opposite directions. Based on these results, we consider that the spin polarization and spin separation can be co-realized in this system.

  8. HIGH ENERGY POLARIZATION OF BLAZARS: DETECTION PROSPECTS

    SciTech Connect

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

    2015-01-01

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

  9. High Energy Polarization of Blazars: Detection Prospects

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  10. d-wave superfluidity in optical lattices of ultracold polar molecules

    SciTech Connect

    Kuns, Kevin A.; Gorshkov, Alexey V.; Rey, Ana Maria

    2011-12-15

    Recent work on ultracold polar molecules, governed by a generalization of the t-J Hamiltonian, suggests that molecules may be better suited than atoms for studying d-wave superfluidity due to stronger interactions and larger tunability of the system. We compute the phase diagram for polar molecules in a checkerboard lattice consisting of weakly coupled square plaquettes. In the simplest experimentally realizable case where there is only tunneling and an XX-type spin-spin interaction, we identify the parameter regime where d-wave superfluidity occurs. We also find that the inclusion of a density-density interaction destroys the superfluid phase and that the inclusion of a spin-density or an Ising-type spin-spin interaction can enhance the superfluid phase. We also propose schemes for experimentally realizing the perturbative calculations exhibiting enhanced d-wave superfluidity.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  12. Radiative transitions between Rydberg states of polar diatomic molecule. Part I: Linearly polarized light

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    With the help of a simple semi-analytical procedure the dipole matrix elements for Rydberg electron-rotational transitions in the SO molecule are calculated with account for dipole moment of rotating core. It results in non-zero matrix elements even for some transitions which are forbidden in conventional models of molecular Rydberg states.

  13. HIGH LUMINOSITY POLARIZED PROTON COLLISIONS AT RHIC.

    SciTech Connect

    ROSER,T.

    2001-03-26

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

  14. Switching mechanism in polar columnar mesophases made of bent-core molecules

    E-print Network

    Ewa Gorecka; Natasa Vaupotic; Damian Pociecha; Mojca Cepic; Josef Mieczkowski

    2004-09-14

    The behavior of polar columnar phases made of bent shaped molecules (B_1Rev and B_1RevTilted) was studied under applied electric field. There are two competing mechanisms of switching in polar B_1RevTilted columnar phase: the collective rotation around the long molecular axis and the collective rotation around the tilt cone. Respectively monostable and bistable optical switching is observed for antiferroelectric B_1RevTilted phase. The main factor discriminating the type of the switching is a width of the column cross-section.

  15. Controlling spin-polarized electron transport through a molecule: The role of molecular conformation

    NASA Astrophysics Data System (ADS)

    Senapati, L.; Pati, R.; Erwin, S. C.

    2007-07-01

    We investigate theoretically the spin-polarized electron transport through a complex organic molecule coupled to magnetic contacts. Our focus is on how low-energy deformations of the molecule affect the current-voltage characteristics and the magnetotransport of this molecular-scale device. We find that fairly modest deformations, costing only a few tens of meVs, can substantially change the tunneling current—by factors of 2 or more. Such deformations have still larger impact on the magnetoresistance, with small changes in molecular conformation even leading to changes in the sign of the magnetoresistance.

  16. Cold polar molecules in 2D traps: Tailoring interactions with external fields for novel quantum phases

    E-print Network

    A. Micheli; G. Pupillo; H. P. Büchler; P. Zoller

    2007-03-04

    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.

  17. Enzymatic cleavage and mass amplification strategy for small molecule detection using aptamer-based fluorescence polarization biosensor.

    PubMed

    Kang, Liping; Yang, Bin; Zhang, Xiaobing; Cui, Liang; Meng, Hongmin; Mei, Lei; Wu, Cuichen; Ren, Songlei; Tan, Weihong

    2015-06-16

    Fluorescence polarization (FP) assays incorporated with fluorophore-labeled aptamers have attracted great interest in recent years. However, detecting small molecules through the use of FP assays still remains a challenge because small-molecule binding only results in negligible changes in the molecular weight of the fluorophore-labeled aptamer. To address this issue, we herein report a fluorescence polarization (FP) aptamer assay that incorporates a novel signal amplification strategy for highly sensitive detection of small molecules. In the absence of adenosine, our model target, free FAM-labeled aptamer can be digested by nuclease, resulting in the release of FAM-labeled nucleotide segments from the dT-biotin/streptavidin complex with weak background signal. However, in the presence of target, the FAM-labeled aptamer-target complex protects the FAM-labeled aptamer from nuclease cleavage, allowing streptavidin to act as a molar mass amplifier. The resulting increase in molecular mass and FP intensity of the aptamer-target complex provides improved sensitivity for concentration measurement. The probe could detect adenosine from 0.5 ?M to 1000 ?M, with a detection limit of 500 nM, showing that the sensitivity of the probe is superior to aptamer-based FP approaches previously reported for adenosine. Importantly, FP could resist environmental interferences, making it useful for complex biological samples without any tedious sample pretreatments. Our results demonstrate that this dual-amplified, aptamer-based strategy can be used to design fluorescence polarization probes for rapid, sensitive, and selective measurement of small molecules in complicated biological environment. PMID:26002482

  18. A new series of amphiphilic molecules forming stable z-type (polar) Langmuir-Blodgett films

    SciTech Connect

    Popovitz-Biro, R.; Hill, K.; Shavit, E.; Hung, D.J.; Lahav, M.; Leiserowitz, L.; Sagiv, J. ); Hsiung, H.; Meredith, G.R.; Vanherzeele, H. )

    1990-03-28

    A new series of amphiphilic molecules bearing two amide groups along the hydrocarbon chain form head-to-tail Z-type (polar) multilayers by the Langmuir-Blodgett (LB) technique, in contrast with the common amphiphiles that tend to deposit in the head-to-head, tail-to-tail Y-type fashion. Molecules with one amide group along the chain form Y-type or Z-type structures, depending on the location of the amide along the chain. p-Nitroaniline or merocyanine groups could be aligned in a polar sense, by attaching them covalently to such amphiphiles, to yield multilayers displaying second-harmonic generation (SHG). These films were characterized by ellipsometric, X-ray diffraction, IR, UV, and SHG measurements. The Z-type deposition correlates with the observed low water contact angles of the films, indicating formation of porous structures in which water may penetrate.

  19. Shaping interactions between polar molecules with far-off-resonant light

    SciTech Connect

    Lemeshko, Mikhail

    2011-05-15

    We show that dressing polar molecules with a far-off-resonant optical field leads to new types of intermolecular potentials, which undergo a crossover from the inverse power to oscillating behavior depending on the intermolecular distance, and whose parameters can be tuned by varying the laser intensity and wavelength. We present analytic expressions for the potential energy surfaces, thereby providing direct access to the parameters of an optical field required to design intermolecular interactions experimentally.

  20. Field-free orientation of diatomic molecule via the linearly polarized resonant pulses

    NASA Astrophysics Data System (ADS)

    Li, Su-Yu; Guo, Fu-Ming; Wang, Jun; Yang, Yu-Jun; Jin, Ming-Xing

    2015-10-01

    We propose a scheme to coherently control the field-free orientation of NO molecule whose rotational temperature is above 0 K. It is found that the maximum molecular orientation is affected by two factors: one is the sum of the population of M = 0 rotational states and the other is their distribution, however, their distribution plays a much more significant role in molecular orientation than the sum of their population. By adopting a series of linearly polarized pulses resonant with the rotational states, the distribution of M = 0 rotational states is well rearranged. Though the number of pulses used is small, a relatively high orientation degree can be obtained. This scheme provides a promising approach to the achievement of a good orientation effect. Project supported by the National Basic Research Program of China (Grant No. 2013CB922200), the National Natural Science Foundation of China (Grant Nos. 11034003, 11474129, 11274141, and 11304116), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20130061110021), and the Graduate Innovation Fund of Jilin University (Grant No. 2015091).

  1. Raising the metal–insulator transition temperature of VO2 thin films by surface adsorption of organic polar molecules

    NASA Astrophysics Data System (ADS)

    Shioya, Hiroki; Shoji, Yoshiaki; Seiki, Noriya; Nakano, Masaki; Fukushima, Takanori; Iwasa, Yoshihiro

    2015-12-01

    We report a molecular adsorption effect on the first-order metal–insulator transition of vanadium dioxide (VO2) thin films. The phase transition temperature is shifted higher by the adsorption of particular polar and rigid tripodal molecules on the film surfaces. The shift becomes larger with increasing dipole moment magnitude, which ranges from 0 to 20 D. The orientation of polar molecules aligned on the surface is most likely responsible for the higher shift of the transition temperature. Coating the surfaces with polar molecules, as demonstrated in this work, might provide a unique way of controlling the phase transition of materials.

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

    SciTech Connect

    Odzak, S.; Milosevic, D. B.

    2010-08-15

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

  3. Molecules in high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Tomassetti, Matteo; Porciani, Cristiano; Romano-Diaz, Emilio; Ludlow, Aaron; Dekel, Avishai

    2015-08-01

    One of the biggest challenges in simulations of galaxy formation is properly modelling the means by which gas is converted into stars. The standard way to address the problem is to adopt a Schmidt-like law, often coupled to conditions of the local gas properties. However, there is a growing body of evidence that the local star formation rate correlates more tightly with the density of molecular hydrogen than with that of the total gas density. Motivated by this we have developed a sub-grid model for the non-equilibrium abundance of molecular hydrogen that accounts for the unresolved cloud structure by combining observational and numerical results on the properties of the turbulent interstellar medium. Using this model we studied the impact of molecule-regulated star formation on a Milky Way-sized galaxy at z=2. When compared to the standard prescription for star formation, our galaxy was considerably more gas-rich and formed fewer stars when star formation was linked directly to the H2 abundance, resulting in 30 per cent fewer luminous satellites. Molecular regulated star formation therefore acts as an effective non-ejective feedback mechanism that prevents gas from being converted into stars within small, metal-poor dark-matter haloes where the H2 formation timescales are long. We have now built a suite of templates of high-redshift galaxies with different stellar masses and metallicities and wish to present how these different properties affect H2 and star formation.

  4. Anti-Lambda Polarization in High Energy pp Collisions withPolarized Beams

    SciTech Connect

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

    2005-11-06

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

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

    E-print Network

    Kotochigova, Svetlana

    Kotochigova1 , Eite Tiesinga2 , and Paul S. Julienne2 1 Department of Physics, Temple University, Philadelphia for optical trapping of the molecules. I. INTRODUCTION The recent successful creation of a high phase

  6. Strongly Correlated 2D Quantum Phases with Cold Polar Molecules: Controlling the Shape of the Interaction Potential

    SciTech Connect

    Buechler, H. P.; Micheli, A.; Pupillo, G.; Zoller, P.; Demler, E.; Lukin, M.; Prokof'ev, N.

    2007-02-09

    We discuss techniques to tune and shape the long-range part of the interaction potentials in quantum gases of bosonic polar molecules by dressing rotational excitations with static and microwave fields. This provides a novel tool towards engineering strongly correlated quantum phases in combination with low-dimensional trapping geometries. As an illustration, we discuss the 2D superfluid-crystal quantum phase transition for polar molecules interacting via an electric-field-induced dipole-dipole potential.

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

    E-print Network

    Romain Guérout; Mireille Aymar; Olivier Dulieu

    2010-07-12

    In this study, we investigate the structure of the polar alkali-Strontium diatomic molecules as possible candidates for the realization of samples of new species of ultracold polar molecules. Using a quantum chemistry approach based on Effective Core Potentials and Core Polarization Potentials, we model these systems as effective three valence electron systems, allowing for calculation of electronic properties with Full Configuration Interaction. The potential curve and the permanent dipole moment of the $^2\\Sigma^+$ ground state are determined as functions of the internuclear distances for LiSr, NaSr, KSr, RbSr, and CsSr molecules. These molecules are found to exhibit a significant permanent dipole moment, though smaller than those of the alkali-Rb molecules.

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

    PubMed Central

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

    2012-01-01

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

  9. Polarization effects on the electric properties of urea and thiourea molecules in solid phase.

    PubMed

    Santos, O L; Fonseca, T L; Sabino, J R; Georg, H C; Castro, M A

    2015-12-21

    We present theoretical results for the dipole moment, linear polarizability, and first hyperpolarizability of the urea and thiourea molecules in solid phase. The in-crystal electric properties were determined by applying a supermolecule approach in combination with an iterative electrostatic scheme, in which the surrounding molecules are represented by point charges. It is found for both urea and thiourea molecules that the influence of the polarization effects is mild for the linear polarizability, but it is marked for the dipole moment and first hyperpolarizability. The replacement of oxygen atoms by sulfur atoms increases, in general, the electric responses. Our second-order Møller-Plesset perturbation theory based iterative scheme predicts for the in-crystal dipole moment of urea and thiourea the values of 7.54 and 9.19 D which are, respectively, increased by 61% and 58%, in comparison with the corresponding isolated values. The result for urea is in agreement with the available experimental result of 6.56 D. In addition, we present an estimate of macroscopic quantities considering explicit unit cells of urea and thiourea crystals including environment polarization effects. These supermolecule calculations take into account partially the exchange and dispersion effects. The results illustrate the role played by the electrostatic interactions on the static second-order nonlinear susceptibility of the urea crystal. PMID:26696062

  10. Multielectron signatures in the polarization of high-order harmonic radiation

    SciTech Connect

    Zhao Zengxiu; Yuan Jianmin; Brabec, Thomas

    2007-09-15

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

  11. Polarization converters in highly birefringent microfibers.

    PubMed

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

    2014-02-10

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

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

    SciTech Connect

    Tsentalovich, E.

    2009-08-04

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

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

    SciTech Connect

    Goodson, Boyd M.

    1999-12-01

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

  14. The effect of permanent dipole moment on the polar molecule cavity quantum electrodynamics

    E-print Network

    Jing-Yun Zhao; Li-Guo Qin; Xun-Ming Cai; Qiang Lin; Zhong-Yang Wang

    2015-11-02

    A dressed-state perturbation theory beyond the rotating waveapproxi-mation (RWA) is presented to investigate the interaction between a two level electronic transition of the polar molecules and a quantized cavity field. Analytical expressions can be explicitly derived for both the ground- and excited-state-energy spectrums and wave functions of the system, where the contribution of permanent dipole moments (PDM) and the counter-rotating wave term (CRT) can be shown separately. The validity of these explicit results is discussed by comparing with the direct numerical simulation. Comparing to CRT coupling, PDM results in the coupling of more dressed states and the energy shift proportional to the square of the normalized permanent dipole difference, and a greater Bloch-Siegert shift could be produced in giant dipole molecule cavity QED. In addition, our method could also be extended to the solution of two-level atom Rabi model Hamiltonian beyond the RWA.

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

    PubMed Central

    2013-01-01

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

  16. Achieving ground-state polar molecular condensates by chainwise atom-molecule adiabatic passage

    SciTech Connect

    Qian Jing; Zhang Weiping; Ling, Hong Y.

    2010-01-15

    We generalize the idea of chainwise stimulated Raman adiabatic passage (STIRAP) [Kuznetsova et al., Phys. Rev. A 78, 021402(R) (2008)] to a photoassociation-based chainwise atom-molecule system, with the goal of directly converting two-species atomic Bose-Einstein condensates (BEC) into a ground polar molecular BEC. We pay particular attention to the intermediate Raman laser fields, a control knob inaccessible to the usual three-level model. We find that an appropriate exploration of both the intermediate laser fields and the stability property of the atom-molecule STIRAP can greatly reduce the power demand on the photoassociation laser, a key concern for STIRAPs starting from free atoms due to the small Franck-Condon factor in the free-bound transition.

  17. Electron scattering cross section calculations for polar molecules over a broad energy range.

    PubMed

    Sanz, A G; Fuss, M C; Blanco, F; Mašín, Zden?k; Gorfinkiel, Jimena D; Carelli, F; Sebastianelli, F; Gianturco, F A; García, G

    2014-01-01

    We report computational integral and differential cross sections for electron scattering by two different polar molecules, HCN and pyrimidine, over a broad energy range. We employ, for low energies, either the single-centre expansion (ePOLYSCAT) or the R-matrix method, while for the higher energies we select a corrected form of the independent-atom representation (IAM-SCAR). We provide complete sets of integral electron scattering cross sections from low energies up to 10,000 eV. Our present calculated data agree well with prior experimental results. PMID:23434441

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

    SciTech Connect

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

    2008-10-10

    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.

  19. Molecules with a High Electron Affinity

    NASA Astrophysics Data System (ADS)

    Sidorov, Lev N.

    1982-04-01

    Experimental values of the electron affinity of inorganic compounds reported between 1975 and 1980 are systematically examined. The following methods of measuring electron affinity are briefly reviewed: photo-extraction and photo-electron spectroscopy, electron impact, ion-molecule reactions, ionisation by alkali metal atoms, ion-molecule equilibria, and methods based on measuring the frequency for intramolecular charge transfer in the absorption spectra of complexes and on calculations using a thermochemical cycle. Classes of compounds having an electron affinity greater than that of halogen atoms are identified by analysing published data. 166 references.

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

    NASA Astrophysics Data System (ADS)

    Stwalley, W. C.

    2004-11-01

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

  1. An ultracold high-density sample of rovibronic ground-state molecules in an optical lattice

    NASA Astrophysics Data System (ADS)

    Danzl, Johann G.; Mark, Manfred J.; Haller, Elmar; Gustavsson, Mattias; Hart, Russell; Aldegunde, Jesus; Hutson, Jeremy M.; Nägerl, Hanns-Christoph

    2010-04-01

    Control over all internal and external degrees of freedom of molecules at the level of single quantum states will enable a series of fundamental studies in physics and chemistry. In particular, samples of ground-state molecules at ultralow temperatures and high number densities will facilitate new quantum-gas studies and future applications in quantum information science. However, high phase-space densities for molecular samples are not readily attainable because efficient cooling techniques such as laser cooling are lacking. Here we produce an ultracold and dense sample of molecules in a single hyperfine level of the rovibronic ground state with each molecule individually trapped in the motional ground state of an optical lattice well. Starting from a zero-temperature atomic Mott-insulator state with optimized double-site occupancy, weakly bound dimer molecules are efficiently associated on a Feshbach resonance and subsequently transferred to the rovibronic ground state by a stimulated four-photon process with >50% efficiency. The molecules are trapped in the lattice and have a lifetime of 8s. Our results present a crucial step towards Bose-Einstein condensation of ground-state molecules and, when suitably generalized to polar heteronuclear molecules, the realization of dipolar quantum-gas phases in optical lattices.

  2. Spin-polarization inversion at small organic molecule/Fe4N interfaces: A first-principles study

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Mi, Wenbo

    2015-09-01

    We report the first-principles calculations on the electronic structure and simulation of the spin-polarized scan tunneling microscopy graphic of the small organic molecules (benzene, thiophene, and cyclopentadienyl)/Fe4N interfaces. It is found that the plane of benzene and thiophene keeps parallel to Fe4N surface, while that of cyclopentadienyl does not. For all the systems, the organic molecules bind strongly with Fe4N. Due to the hybridization between molecule pz orbitals and d orbitals of Fe, i.e., Zener interaction, all the three systems realize the spin-polarization inversion, whereas the spatial spin-polarization inversion distribution shows different intensities influenced by the competition between the spin polarization of C pz and Fe d states.

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

    SciTech Connect

    Guerout, R.; Aymar, M.; Dulieu, O.

    2010-10-15

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

  4. Cold ion-polar-molecule reactions studied with a combined Stark-velocity-filter-ion-trap apparatus

    NASA Astrophysics Data System (ADS)

    Okada, Kunihiro; Suganuma, Takuya; Furukawa, Takahiro; Takayanagi, Toshinobu; Wada, Michiharu; Schuessler, Hans A.

    2013-04-01

    We have developed a combined Stark-velocity-filter-ion-trap apparatus for the purpose of reaction-rate measurements between cold trapped ions and slow polar molecules under ultrahigh vacuum conditions. The prerequisite steps such as the characterization of velocity-selected polar molecules (PM), namely ND3, H2CO, and CH3CN, were performed using time-of-flight (TOF) measurements. We confirmed the generation of slow ND3, H2CO, and CH3CN molecules having thermal energies of a few Kelvin. Additionally, the number densities of the slow velocity-filtered polar molecules were determined to be in the range of n=104 to 106 cm-3 by calibrating the TOF signals. In a first experiment, the Stark velocity filter was connected to a cryogenic linear Paul trap and reaction-rate measurements between laser-cooled Ca+ Coulomb crystals and velocity-selected polar molecules were carried out. The observed reaction rates are of the order of 10-5 s-1, which are much slower than typical reaction rates of molecular ion-polar-molecule reactions at low temperatures. The present results confirm that reaction-rate measurements between velocity-selected polar molecules and sympathetically cooled molecular ions cooled by a laser-cooled Ca+ Coulomb crystal can be performed. Next we measured the reaction rates between sympathetically cooled nonfluorescent stored ion molecules namely N2H+ ions and velocity-selected CH3CN molecules at the average reaction energy of about 3 K. The measured reaction rate of 2.0(2)×10-3 s-1 is much faster than those of the Ca++PM reactions. This is strong evidence that the velocity-selected polar molecules undergo reactive collisions. We also confirmed that the present reaction-rate constant of CH3CN+N2H+ ? CH3CNH++N2 is consistent with the estimated values from the room temperature results and the trajectory-scaling formula of Su In the future, the present velocity-filter combined cryogenic trap apparatus will enable us to perform systematic measurements of cold ion-polar-molecule reactions, which are important problems from a fundamental viewpoint and also contribute to astrochemistry.

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

    E-print Network

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

    2011-10-06

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

  6. High Performance Circularly Polarized Microstrip Antenna

    NASA Technical Reports Server (NTRS)

    Bondyopadhyay, Probir K. (Inventor)

    1997-01-01

    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.

  7. Nonchiral polar smectic liquid crystals formed by bent-core molecules: weak coupling regime

    NASA Astrophysics Data System (ADS)

    Kranjc, Tomaz

    2002-12-01

    The structure and dynamic properties of achiral polar smectic liquid crystals formed by bow shaped molecules is considered and described by two two-dimensional order parameters, \\vec P and \\vec ?. The first, polarization order parameter, gives the average projection of the arrow vectors on the smectic layer planes. The second, tilt order parameter, gives the average magnitude and direction of the tilt. To study the possible liquid crystal structures and their properties, a discrete phenomenological model taking into account the competing interactions between the nearest-neighbor smectic layers is used. The free energy of the system is expressed as a sum over smectic layers with terms modeling the appropriate intralayer and interlayer interactions and written only in terms of the arrow and the string order parameters. The free energy is then minimized in order to obtain stable structures and deduce their optical properties. There exist solutions for the case of strong coupling between the polarization and the tilt order parameters arising from attractive intralayer van der Waals and from steric interactions. In this contribution, we focus our attention to the case of weak coupling between the two order parameters and investigate possible structures and related optical properties of the system.

  8. Spectroscopy, reaction, and photodissociation in highly vibrationally excited molecules

    SciTech Connect

    Not Available

    1991-01-01

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

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

    PubMed Central

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Ma, Xiao

    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.

  11. Highly Parallel Translation of DNA Sequences into Small Molecules

    PubMed Central

    Weisinger, Rebecca M.; Wrenn, S. Jarrett; Harbury, Pehr B.

    2012-01-01

    A large body of in vitro evolution work establishes the utility of biopolymer libraries comprising 1010 to 1015 distinct molecules for the discovery of nanomolar-affinity ligands to proteins.[1], [2], [3], [4], [5] Small-molecule libraries of comparable complexity will likely provide nanomolar-affinity small-molecule ligands.[6], [7] Unlike biopolymers, small molecules can offer the advantages of cell permeability, low immunogenicity, metabolic stability, rapid diffusion and inexpensive mass production. It is thought that such desirable in vivo behavior is correlated with the physical properties of small molecules, specifically a limited number of hydrogen bond donors and acceptors, a defined range of hydrophobicity, and most importantly, molecular weights less than 500 Daltons.[8] Creating a collection of 1010 to 1015 small molecules that meet these criteria requires the use of hundreds to thousands of diversity elements per step in a combinatorial synthesis of three to five steps. With this goal in mind, we have reported a set of mesofluidic devices that enable DNA-programmed combinatorial chemistry in a highly parallel 384-well plate format. Here, we demonstrate that these devices can translate DNA genes encoding 384 diversity elements per coding position into corresponding small-molecule gene products. This robust and efficient procedure yields small molecule-DNA conjugates suitable for in vitro evolution experiments. PMID:22479303

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

    PubMed Central

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

    2014-01-01

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

  13. High-sensitivity and high-spatial-resolution imaging of self-assembled monolayer on platinum using radially polarized beam excited second-harmonic-generation microscopy

    NASA Astrophysics Data System (ADS)

    Hashimoto, Mamoru; Niioka, Hirohiko; Ashida, Koichiro; Yoshiki, Keisuke; Araki, Tsutomu

    2015-11-01

    High-sensitivity, high-spatial-resolution imaging of organic monolayers on platinum with second harmonic generation (SHG) microscopy using radially polarized beam excitation is investigated. A tightly focused, radially polarized beam forms a longitudinal electric field at the focus. The longitudinal field is enhanced at a metal surface and increases the intensity of SHG from the molecules on the metal surface. The SHG signal from a self-assembled monolayer (SAM) on a platinum surface excited by a radially polarized beam is approximately 3.7 times higher than that obtained with a linearly polarized beam. Improved spatial resolution is also demonstrated using a SAM patterned by electron beam lithography.

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

    ERIC Educational Resources Information Center

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

    2000-01-01

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

  15. Electron transport through molecules: Gate-induced polarization and potential shift San-Huang Ke,1,2

    E-print Network

    Baranger, Harold U.

    the basis of a future molecular electronics technology.1,2 To control the transport and to realize singleElectron transport through molecules: Gate-induced polarization and potential shift San-Huang Ke,1 for electron transport. For a general view, we study several systems: 1 atomic chains of C or Al sandwiched

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

    PubMed

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

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  18. Stark-potential evaporative cooling of polar molecules in a novel optical-access opened electrostatic trap

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Wang, Zhen-Xia; Wang, Qin; Li, Xing-Jia; Liu, Jian-Ping; Yin, Jian-Ping

    2015-11-01

    We propose a novel optical-access opened electrostatic trap to study the Stark-potential evaporative cooling of polar molecules by using two charged disk electrodes with a central hole of radius r0 =1.5 mm, and derive a set of new analytical equations to calculate the spatial distributions of the electrostatic field in the above charged-disk layout. Afterwards, we calculate the electric-field distributions of our electrostatic trap and the Stark potential for cold ND3 molecules, and analyze the dependences of both the electric field and the Stark potential on the geometric parameters of our charged-disk scheme, and find an optimal condition to form a desirable trap with the same trap depth in the x, y, and z directions. Also, we propose a desirable scheme to realize an efficient loading of cold polar molecules in the weak-field-seeking states, and investigate the dependences of the loading efficiency on both the initial forward velocity of the incident molecular beam and the loading time by Monte Carlo simulations. Our study shows that the maximal loading efficiency of our trap scheme can reach about 95%, and the corresponding temperature of the trapped cold molecules is about 28.8 mK. Finally, we study the Stark-potential evaporative cooling for cold polar molecules in our trap by the Monte Carlo method, and find that our simulated evaporative cooling results are consistent with our developed analytical model based on trapping-potential evaporative cooling.

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

    E-print Network

    Amir Levinson; David Eichler

    2004-02-19

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

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

    SciTech Connect

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

    2010-03-01

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

  1. Probing non polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH+)?

    PubMed Central

    Agúndez, M.; Cernicharo, J.; de Vicente, P.; Marcelino, N.; Roueff, E.; Fuente, A.; Gerin, M.; Guélin, M.; Albo, C.; Barcia, A.; Barbas, L.; Bolaño, R.; Colomer, F.; Diez, M. C.; Gallego, J. D.; Gómez-González, J.; López-Fernández, I.; López-Fernández, J. A.; López-Pérez, J. A.; Malo, I.; Serna, J. M.; Tercero, F.

    2015-01-01

    Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds through the detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through the J = 5 – 4 and J = 10 – 9 rotational transitions using the 40m radiotelescope of Yebes and the IRAM 30m telescope. We derive beam averaged column densities for NCCNH+ of (8.6 ± 4.4) × 1010 cm?2 in TMC-1 and (3.9 ± 1.8) × 1010 cm?2 in L483, which translate to fairly low fractional abundances relative to H2, in the range (1-10) × 10?12. The chemistry of protonated molecules in dark clouds is discussed, and it is found that, in general terms, the abundance ratio between the protonated and non protonated forms of a molecule increases with increasing proton affinity. Our chemical model predicts an abundance ratio NCCNH+/NCCN of ~ 10?4, which implies that the abundance of cyanogen in dark clouds could be as high as (1-10) × 10?8 relative to H2, i.e., comparable to that of other abundant nitriles such as HCN, HNC, and HC3N. PMID:26543239

  2. Ionization and high-order harmonic generation in aligned benzene by a short intense circularly polarized laser pulse

    E-print Network

    Moiseyev, Nimrod

    Ionization and high-order harmonic generation in aligned benzene by a short intense circularly and high-order harmonic generation by benzene aligned in the polarization plane of a short circularly pulses 4 . Recently, other types of HHG processes have been dis- covered in molecules. The planar benzene

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

    SciTech Connect

    Hansen, Jonas L.; Holmegaard, Lotte; Kalhoej, Line; Kragh, Sofie Louise; Stapelfeldt, Henrik; Filsinger, Frank; Meijer, Gerard; Kuepper, Jochen; Dimitrovski, Darko; Abu-samha, Mahmoud; Martiny, Christian Per Juul; Madsen, Lars Bojer

    2011-02-15

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

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

    PubMed Central

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

    2012-01-01

    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. PMID:22548234

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

    PubMed Central

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

    2013-01-01

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

  6. Dangling OH Vibrations of Water Molecules in Aqueous Solutions of Aprotic Polar Compounds Observed in the Near-Infrared Regime.

    PubMed

    Sagawa, Naoya; Shikata, Toshiyuki

    2015-06-25

    Near-infrared (NIR) absorption spectrum measurements over a frequency range from 4000 to 12000 cm(-1) were employed to investigate the effects of the presence of solute compounds to vibrational modes of water molecules in aqueous solutions of some aprotic hydroneutral polar compounds with large dipole moments, such as nitro compounds and nitriles. The obtained NIR spectra for the aqueous solutions were decomposed into three components: free water, solute, and water molecules affected by the presence of solutes. Newly determined NIR spectra of affected water molecules were well-described with at least four absorption modes observed at 7040, 6850, 6450, and 5640 cm(-1) for both the nitro compounds and nitriles. The highest frequency mode at 7040 cm(-1) possessing the strongest intensity was assigned to the first stretching overtone of affected water hydroxy (O-H) groups, which are nonhydrogen bonded to other water molecules and dangling. The second highest frequency mode at 6850 cm(-1) was assigned to the first stretching overtone of affected water O-H groups hydrated to other (free) water molecules. The third mode at 6400 cm(-1) was attributed to a combination mode of the fundamental stretching of O-H and the first overtone of the O-H bending mode of the affected water molecules. The lowest frequency mode at 5640 cm(-1) was assigned to the combination mode of the fundamental O-H stretching mode, the fundamental O-H bending mode, and the hindered rotational (libration) mode of the affected water molecules. Because absorption intensities of the third and lowest frequency modes for water molecules affected by the solutes depended on the sizes of alkyl groups of polar solutes, these two modes possibly result from the contribution of hydrophobic hydration effects. PMID:25996246

  7. Hybrid calculation of electron--polar-molecule scattering: Integrated andmomentum-transfer cross sections for LiF

    SciTech Connect

    Siegel, J.; Dehmer, J.L.; Dill, D.

    1981-02-01

    We describe in detail a hybrid method for calculation of electron--polar-molecule scattering in which (1) low-l S-matrix elements are calculated in the body frame using a potential which incorporates a realistic representation of the molecular core; (2) intermediate-l elements are calculated in the body frame using an exact method with a point-dipole potential; and (3) high-l elements are calculated in the laboratory frame using the first Born approximation with a point-dipole potential. By taking into account the dominant interactions of each l range when choosing the coordinate frame, potential, and calculational method, this hybrid framework achieves an exceptionally high level of efficiency and economy of calculation without sacrifice of accuracy. Using this method, we have calculated integrated and momentum-transfer cross sections for e-LiF scattering from 1 to 20 eV (differential cross sections have been reported elsewhere). The integrated cross section is dominated (>99%) by the j=0..-->..j'=1 rotational transition, whereas the momentum-transfer cross section is composed of comparable contributions from transitions to final j'=0 through 3, owing to its deemphasis of small-angle scattering. Eigenphase sums show no sign of resonant activity in this energy range.

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

    SciTech Connect

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

    2011-04-15

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

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

    SciTech Connect

    Micheli, A.; Pupillo, G.; Buechler, H. P.; Zoller, P.

    2007-10-15

    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.

  10. VOLUME 75, NUMBER 11 P H Y S I C A L R E V I E W L E T T E R S 11 SEPTEMBER 1995 Orientation of Amphiphilic Molecules on Polar Substrates

    E-print Network

    Marrucci, Lorenzo

    of Amphiphilic Molecules on Polar Substrates X. Zhuang, D. Wilk, L. Marrucci, and Y. R. Shen Department to calculate the orientations of amphiphilic molecules on various polar substrates. The calculated orientations

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

    SciTech Connect

    Sukiasyan, Suren; Ivanov, Misha Yu.; Patchkovskii, Serguei; Smirnova, Olga; Brabec, Thomas

    2010-10-15

    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.

  12. Polarized neutron reflectometry in high magnetic fields

    SciTech Connect

    Fritzsche, H.

    2005-11-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  14. Probing non-polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH+)

    NASA Astrophysics Data System (ADS)

    Agúndez, M.; Cernicharo, J.; de Vicente, P.; Marcelino, N.; Roueff, E.; Fuente, A.; Gerin, M.; Guélin, M.; Albo, C.; Barcia, A.; Barbas, L.; Bolaño, R.; Colomer, F.; Diez, M. C.; Gallego, J. D.; Gómez-González, J.; López-Fernández, I.; López-Fernández, J. A.; López-Pérez, J. A.; Malo, I.; Serna, J. M.; Tercero, F.

    2015-07-01

    Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds by detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through the J = 5-4 and J = 10-9 rotational transitions using the 40 m radiotelescope of Yebes and the IRAM 30 m telescope. We derive beam-averaged column densities for NCCNH+ of (8.6 ± 4.4) × 1010 cm-2 in TMC-1 and (3.9 ± 1.8) × 1010 cm-2 in L483, which translate into fairly low fractional abundances relative to H2, in the range (1-10) × 10-12. The chemistry of protonated molecules in dark clouds is discussed, and it is found that, in general terms, the abundance ratio between the protonated and non-protonated forms of a molecule increases with increasing proton affinity. Our chemical model predicts an abundance ratio NCCNH+/NCCN of ~10-4, which implies that the abundance of cyanogen in dark clouds could be as high as (1-10) × 10-8 relative to H2, i.e., comparable to that of other abundant nitriles such as HCN, HNC, and HC3N. Based on observations carried out with the IRAM 30 m Telescope and the Yebes 40 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). The 40 m radiotelescope at Yebes Observatory is operated by the Spanish National Geographic Institute (IGN, Ministerio de Fomento).

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

    DOEpatents

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

    2014-07-15

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

  16. Toward a 2-D magneto-optical trap for polar molecules

    NASA Astrophysics Data System (ADS)

    Hummon, Matthew; Stuhl, Benjamin; Yeo, Mark; Collopy, Alejandra; Ye, Jun

    2012-06-01

    The additional structure that arises from the rotational degree of freedom in diatomic molecules makes difficult the adaptation of a traditional atomic magneto-optical trap (MOT) for use with molecules. We describe progress toward development of a 2-D MOT for laser cooled yttrium monoxide molecules based on a resonant LC baseball coil geometry.

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

    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

    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

  19. Spin angular momentum and tunable polarization in high-harmonic generation

    NASA Astrophysics Data System (ADS)

    Fleischer, Avner; Kfir, Ofer; Diskin, Tzvi; Sidorenko, Pavel; Cohen, Oren

    2014-07-01

    The roles of energy, momentum and orbital angular momentum conservation in high-harmonic generation were studied in the past. Here, we explore the role of spin angular momentum in high-harmonic generation by experimentally generating high harmonics of bichromatic elliptically polarized pump beams that interact with isotropic media. We explain qualitatively many observed intricate selection rules with a model that includes spin conservation in the conversion of many pump photons into a single photon. However, we also observe unequivocal deviations from this model, indicating that emission of an elliptically polarized high-energy photon is accompanied by an additional excitation (radiative or electronic). The presented results are also important for applications, because our system exhibits full control over the polarization of the harmonics, from circular through elliptical to linear polarization, without compromising the efficiency of the process. This work paves the way for a broad range of applications with high-harmonic generation, including ultrafast circular dichroism of molecules and magnetic materials.

  20. Structural polarization-rocking filters in highly birefringent microfibers.

    PubMed

    Jin, Wa; Xuan, Haifeng; Jin, Wei

    2014-06-15

    We report the first fabrication, to our knowledge, of polarization-rocking filters in highly birefringent elliptical microfibers. A rocking filter was made by periodically heating/twisting a microfiber with an ellipticity of ?0.7 and a diameter of ?2.8???m along its major axis. Strong input polarization suppression of ?20??dB was achieved at a resonant wavelength of ?1556.4??nm with a device length of ?3??mm. PMID:24978486

  1. Highly directional fluorescence emission from dye molecules embedded in a dielectric layer adjacent to a silver film

    NASA Astrophysics Data System (ADS)

    Luan, L.; Sievert, P. R.; Mu, W.; Hong, Z.; Ketterson, J. B.

    2008-07-01

    We report measurements on the angular radiation patterns from dye molecules embedded in a polymethyl methacrylate thin film spin-coated on a thin silver film. We systematically studied the influence of the thickness of the silver films and the thickness of the dielectric layers on the radiation pattern. We present the detailed radiation patterns over a large angular range showing highly polarized fluorescence emission coupled into the surface plasmon modes or waveguide modes. We also studied the influence of the polarization of the excitation beam on the radiation patterns. The experimental data are compared with numerical simulations using an asymptotic approach based on the Lorentz reciprocity theorem.

  2. High Brightness and high polarization electron source using transmission photocathode

    SciTech Connect

    Yamamoto, Naoto; Jin Xiuguang; Ujihara, Toru; Takeda, Yoshikazu; Mano, Atsushi; Nakagawa, Yasuhide; Nakanishi, Tsutomu; Okumi, Shoji; Yamamoto, Masahiro; Konomi, Taro; Ohshima, Takashi; Saka, Takashi; Kato, Toshihiro; Horinaka, Hiromichi; Yasue, Tsuneo; Koshikawa, Takanori

    2009-08-04

    A transmission photocathode was fabricated based on GaAs-GaAsP strained superlattice layers on a GaP substrate and a 20 kV-gun was built to generate the polarized electron beams with the diameter of a few micro-meter. As the results, the reduced brightness of 1.3x10{sup 7} A/cm{sup 2}/sr and the polarization of 90% were achieved.

  3. Fusion with highly spin polarized HD and D sub 2

    SciTech Connect

    Honig, A. . Dept. of Physics); Kremens, R.; Skupsky, S. . Lab. for Laser Energetics)

    1991-05-05

    During the course of this grant, we succeeded in overcoming essentially all of the obstacles on the route to carrying out ICF shots with polarized deuteron fuel in plastic target shells. ICF with polarized deuterons is expected to answer the question of survival of polarization in the high temperature plasma prior to fusion, as well as to give quantitative information on anisotropic particle emissions and possible suppression of particular fusion reactions. The techniques previously developed for high D polarization in large solid HD samples have been adapted to polystyrene target shells which are cooled conductively via very thin metal wire supports. An independent NMR experiment on a normal-D{sub 2}-filled glass target shell with 2 {mu}m copper-coated spider silk supports affirmed the thermal conduction adequacy by registering very low sample temperatures in the presence of the generation of considerable D{sub 2} conversion heat. In a permeation experiment employing very pure ortho-D{sub 2}, it was demonstrated that hydrogens diffuse into polystyrene shells at room temperature without molecular dissociation, a requirement for preservation of the composition of our HD samples used for polarization. An advanced version of the permeation apparatus was designed and constructed which permits preparation of target shells loaded with very high density HD or D{sub 2} fuels. That system includes provision for cryocondensation and cold-transfer either to the dilution refrigerator for polarization or to the OMEGA fusion chamber for ICF experiments with denser unpolarized fuel targets than were heretofore realizable in plastic target shells. a major effort resulted in improvements of cold-transfer inter-apparatus mating procedures which minimize the temperature rise of the target shells over that of the helium reservoir temperature. High D polarization in solid pure 0-D{sub 2} was shown to be retained into the liquid state after rapid melting.

  4. High Resolution Studies of Electron Attachment to Molecules

    SciTech Connect

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

    2009-05-02

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

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

    NASA Astrophysics Data System (ADS)

    Mineo, Hirobumi; Fujimura, Yuichi

    2015-06-01

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

  6. Intrinsic instrumental polarization and high-precision pulsar timing

    NASA Astrophysics Data System (ADS)

    Foster, G.; Karastergiou, A.; Paulin, R.; Carozzi, T. D.; Johnston, S.; van Straten, W.

    2015-10-01

    Radio telescopes are used to accurately measure the time of arrival (ToA) of radio pulses in pulsar timing experiments that target mostly millisecond pulsars (MSPs) due to their high rotational stability. This allows for detailed study of MSPs and forms the basis of experiments to detect gravitational waves. Apart from intrinsic and propagation effects, such as pulse-to-pulse jitter and dispersion variations in the interstellar medium, timing precision is limited in part by the following: polarization purity of the telescope's orthogonally polarized receptors, the signal-to-noise ratio of the pulsar profile, and the polarization fidelity of the system. Using simulations, we present how fundamental limitations in recovering the true polarization reduce the precision of ToA measurements. Any real system will respond differently to each source observed depending on the unique pulsar polarization profile. Using the profiles of known MSPs, we quantify the limits of observing system specifications that yield satisfactory ToA measurements, and we place a practical design limit beyond which improvement of the system results in diminishing returns. Our aim is to justify limits for the front-end polarization characteristics of next-generation radio telescopes, leading to the Square Kilometre Array.

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

    E-print Network

    Lee, Youngbok

    2013-03-13

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

  8. High contrast single molecule tracking in the pericellular coat

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  9. Biogeography of photoautotrophs in the high polar biome

    PubMed Central

    Pointing, Stephen B.; Burkhard Büdel; Convey, Peter; Gillman, Len N.; Körner, Christian; Leuzinger, Sebastian; Vincent, Warwick F.

    2015-01-01

    The global latitudinal gradient in biodiversity weakens in the high polar biome and so an alternative explanation for distribution of Arctic and Antarctic photoautotrophs is required. Here we identify how temporal, microclimate and evolutionary drivers of biogeography are important, rather than the macroclimate features that drive plant diversity patterns elsewhere. High polar ecosystems are biologically unique, with a more central role for bryophytes, lichens and microbial photoautotrophs over that of vascular plants. Constraints on vascular plants arise mainly due to stature and ontogenetic barriers. Conversely non-vascular plant and microbial photoautotroph distribution is correlated with favorable microclimates and the capacity for poikilohydric dormancy. Contemporary distribution also depends on evolutionary history, with adaptive and dispersal traits as well as legacy influencing biogeography. We highlight the relevance of these findings to predicting future impacts on diversity of polar photoautotrophs and to the current status of plants in Arctic and Antarctic conservation policy frameworks. PMID:26442009

  10. Biogeography of photoautotrophs in the high polar biome.

    PubMed

    Pointing, Stephen B; Burkhard Büdel; Convey, Peter; Gillman, Len N; Körner, Christian; Leuzinger, Sebastian; Vincent, Warwick F

    2015-01-01

    The global latitudinal gradient in biodiversity weakens in the high polar biome and so an alternative explanation for distribution of Arctic and Antarctic photoautotrophs is required. Here we identify how temporal, microclimate and evolutionary drivers of biogeography are important, rather than the macroclimate features that drive plant diversity patterns elsewhere. High polar ecosystems are biologically unique, with a more central role for bryophytes, lichens and microbial photoautotrophs over that of vascular plants. Constraints on vascular plants arise mainly due to stature and ontogenetic barriers. Conversely non-vascular plant and microbial photoautotroph distribution is correlated with favorable microclimates and the capacity for poikilohydric dormancy. Contemporary distribution also depends on evolutionary history, with adaptive and dispersal traits as well as legacy influencing biogeography. We highlight the relevance of these findings to predicting future impacts on diversity of polar photoautotrophs and to the current status of plants in Arctic and Antarctic conservation policy frameworks. PMID:26442009

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

    E-print Network

    Dundas, Daniel

    2012-01-01

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

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

    SciTech Connect

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

    2010-03-15

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

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

    NASA Astrophysics Data System (ADS)

    Debolt, Stephen Edward

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

  14. Circularly Polarized Luminescence by Visible-Light Absorption in a Chiral O-BODIPY Dye: Unprecedented Design of CPL Organic Molecules from Achiral Chromophores

    PubMed Central

    2015-01-01

    Circularly polarized luminescence (CPL) in simple (small, nonaggregated, nonpolymeric) O-BODIPYs (R)-1 and (S)-1 by irradiation with visible light is first detected as proof of the ability of a new structural design to achieve CPL from inherently achiral monochromophore systems in simple organic molecules. The measured level of CPL (|glum|) in solution falls into the usual range of that obtained from other simple organic molecules (10–5–10–2 range), but the latter having more complex architectures since axially chiral chromophores or multichromophore systems are usually required. The new design is based on chirally perturbing the acting achiral chromophore by orthogonally tethering a single axially chiral 1,1?-binaphtyl moiety to it. The latter does not participate as a chromophore in the light-absorption/emission phenomenon. This simple design opens up new perspectives for the future development of new small-sized CPL organic dyes (e.g., those based on other highly luminescent achiral chromophores and/or chirally perturbing moieties), as well as for the improvement of the CPL properties of the organic molecules spanning their use in photonic applications. PMID:24524257

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

    PubMed Central

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

    2015-01-01

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

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

    ERIC Educational Resources Information Center

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

    2012-01-01

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

  17. Quantitative polarized Raman spectroscopy in highly turbid bone tissue

    PubMed Central

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

    2010-01-01

    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. PMID:20615030

  18. Status of high polarization DC high voltage Gallium Arsenide photoelectron guns

    SciTech Connect

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

    2008-01-01

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

  19. Applications of highly spin-polarized xenon in NMR

    SciTech Connect

    Long, H.W.

    1993-09-01

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

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

    E-print Network

    Hu, Kan-Nian

    2006-01-01

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

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

    E-print Network

    Tianrui Xu; Roman V. Krems

    2015-05-05

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

  2. High performance photovoltaic applications using solution-processed small molecules.

    PubMed

    Chen, Yongsheng; Wan, Xiangjian; Long, Guankui

    2013-11-19

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

  3. Polarization conversion from highly conducting, asymmetric trapezoidal gratings.

    PubMed

    Depine, Ricardo A; Inchaussandague, Marina E

    2003-07-01

    The differences in the curves of the zeroth-order cross-polarization reflection coeffients (p --> s and s --> p) versus angle of incidence have remarkable potential for application in scatterometry because, if the differences are larger than the measurement error, they could contribute to a reliable nondestructive technique for detecting asymmetries in grating profiles. The cross-polarization efficiencies of highly conducting metallic gratings with asymmetric trapezoidal profiles are investigated theoretically by means of a rigorous electromagnetic code. The results show that the differences between p --> s and s --> p conversion tend to be undetectable for highly conducting materials, a fact that limits, in principle, the application of this potential detection technique. PMID:12868808

  4. High-fidelity linear optical quantum computing with polarization encoding

    SciTech Connect

    Spedalieri, Federico M.; Lee, Hwang; Dowling, Jonathan P.

    2006-01-15

    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.

  5. Identification of Small-Molecule Inhibitors of the HuR/RNA Interaction Using a Fluorescence Polarization Screening Assay Followed by NMR Validation

    PubMed Central

    Wang, Zhonghua; Bhattacharya, Akash; Ivanov, Dmitri N.

    2015-01-01

    The human antigen R (HuR) stabilizes many mRNAs of proto-oncogene, transcription factors, cytokines and growth factors by recognizing AU-rich elements (AREs) presented in their 3’ or 5’ untranslated region (UTR). Multiple lines of experimental evidence suggest that this process plays a key role in cancer development. Thus, destabilizing HuR/RNA interaction by small molecules presents an opportunity for cancer treatment/prevention. Here we present an integrated approach to identify inhibitors of HuR/RNA interaction using a combination of fluorescence-based and NMR-based high throughput screening (HTS). The HTS assay with fluorescence polarization readout and Z’-score of 0.8 was used to perform a screen of the NCI diversity set V library in a 384 well plate format. An NMR-based assay with saturation transfer difference (STD) detection was used for hits validation. Protein NMR spectroscopy was used to demonstrate that some hit compounds disrupt formation of HuR oligomer, whereas others block RNA binding. Thus, our integrated high throughput approach provides a new avenue for identification of small molecules targeting HuR/RNA interaction. PMID:26390015

  6. Efficient polarization gating of high-order harmonic generation by polarization-shaped ultrashort pulses

    E-print Network

    Silberberg, Yaron

    an alternative method based on polarization pulse shaping techniques. This method is shown to be significantly a result of the very limited method of generating the polarization gated pulse. By using polarization-shaped obtainable from commercially available systems. Polarization shaped pulses, i.e., ultrashort pulses whose

  7. High transmittance silicon terahertz polarizer using wafer bonding technology

    NASA Astrophysics Data System (ADS)

    Yu, Ting-Yang; Tsai, Hsin-Cheng; Wang, Shiang-Yu; Luo, Chih-Wei; Chen, Kuan-Neng

    2015-08-01

    Due to the difficulties faced in fabricating robust Terahertz (THz) optical components with low Fresnel reflection loss, the need to increase the efficiency of THz system with reduced cost is still considered as one of the most essential tasks. In this report, a new low cost THz polarizer with robust structure is proposed and demonstrated. This new THz wire grid polarizer was based on an anti-reflection (AR) layer fabricated with low temperature metal bonding and deep reactive ion etching (DRIE). After patterning Cu wire gratings and the corresponding In/Sn solder ring on the individual silicon wafers, the inner gratings were sealed by wafer-level Cu to In/Sn guard ring bonding, providing the protection against humidity oxidation and corrosion. With the low eutectic melting point of In/Sn solder, wafers could be bonded face to face below 150°C. Two anti-reflection layers on both outward surfaces were fabricated by DRIE. With the mixing of empty holes and silicon, the effective refractive index was designed to be the square root of the silicon refractive index. The central frequency of the anti-reflection layers was designed between 0.5THz to 2THz with an approximate bandwidth of 0.5THz. The samples were measured with a commercial free-standing wire grid polarizer by a THz time domain spectroscopy (THz-TDS) from 0.2THz to 2.2THz. The power transmittance is close to 100% at central frequency. Extinction ratio of the polarizer is between 20dB to 40dB depending on the frequency. The advantages of this new polarizer include high transmittance, robust structure and low cost with no precision optical alignment required.

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2014-01-29

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

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

    PubMed

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

    2014-10-17

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

  11. High-precision spectroscopy of ultracold molecules in an optical lattice

    E-print Network

    Zelevinsky, Tanya

    High-precision spectroscopy of ultracold molecules in an optical lattice B. H. McGuyer1 , M. Mc Abstract. The study of ultracold molecules tightly trapped in an optical lattice can expand the frontier Molecules, Photoassociation, Photodissociation, Optical Lattice, Molecular Clock. Email: tz

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

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

    PubMed

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

    2010-06-01

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

  14. Evidence for accretion disks in highly polarized quasars

    NASA Technical Reports Server (NTRS)

    Smith, Paul S.; Elston, Richard; Berriman, Graham; Allen, Richard G.; Balonek, Thomas J.

    1988-01-01

    The results of a search for thermal components in 11 highly polarized quasars (HPQs) using UVBRI polarimetry and photometry are reported. The 2000-2500 A luminosities of the thermal components are calculated and the estimated luminosities of the broad-line region (BLR) are given in the same wavelength for comparison. The observed optical continua are modeled as a combination of polarized synchrotron emission, unpolarized emission from the BLR, and an unpolarized flat spectral component that may be optically thick thermal emission from an accretion disk. Evidence for thermal emission components is found in three HPQs: PKS 0420-014, B2 1156+295, and 3C 454.3, with marginal evidence in another two, PKS 1510-089 and PKS 2345-167.

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

    E-print Network

    Nadgorny, Boris

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

  16. High Efficacy Green LEDs by Polarization Controlled MOVPE

    SciTech Connect

    Wetzel, Christian

    2013-03-31

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

  17. High thermopower of mechanically stretched single-molecule junctions

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  19. High thermopower of mechanically stretched single-molecule junctions

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    PubMed

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

    2015-08-01

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

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

    SciTech Connect

    Jiang, X.; Benmokhtar, F.; Glashauser, C.; McCormick, K.; Ransome, R. D.; Arrington, J.; Holt, R. J.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Camsonne, A.

    2007-05-04

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

  2. Spin rotation of polarized beams in high energy storage ring

    E-print Network

    V. G. Baryshevsky

    2006-03-23

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  4. PVDF shock sensors: applications to polar materials and high explosives.

    PubMed

    Bauer, F

    2000-01-01

    Ferroelectric polymers (PVDF) with well-defined and precisely known electrical properties are now routinely available from commercial sources. Electrical processing with the Bauer cyclic poling method can produce individual films with well-defined remanent polarization up to 9 /spl mu/C/cm/sup 2/. These polymers provide an unusual opportunity to study the structure and physical properties of materials subjected to shock loading. The behavior of PVDF has been studied over a wide range of pressures using high-pressure shock loading and has yielded well-behaved, reproducible data up to 25 GPa in inert materials. The application of PVDF gauges for recording shock waves induced in polar materials such as Kel-F, PMMA, or in reactive materials is hampered by observations of anomalous responses due to shock-induced polarization or an electrical charge released inside a shock-compressed explosive. A solution using an appropriate electrical shielding has been identified and applied to PVDF for shock measurement studies of Kel-F, and for Hugoniot measurements of high explosives (PH). Furthermore, shock pressure profiles obtained with in situ PVDF gauges in porous HE (Formex) in a detonation regime have been achieved. Typical results of shock pressure profile versus time show a fast superpressure of a few nanoseconds followed by a pressure release down to a plateau level and then by a pressure decay. More accurate measurements are reported with electrically improved PVDF gauges as well as with 0.25 mm/sup 2/ active area PVDF gauges. PMID:18238691

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

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

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

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

    SciTech Connect

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

    2014-10-06

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

  7. Anti-Hyperon polarization in high energy pp collisions withpolarized beams

    SciTech Connect

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

    2007-11-20

    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.

  8. NCTM of liquids at high temperatures using polarization techniques

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  9. Submillimeterwave Spectroscopy of Highly Astrophysical Interest Molecule: Hydroxyacetonitrile

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  10. Chiral molecular films as electron polarizers and polarization modulators

    E-print Network

    Medina, Ernesto; Ratner, Mark; Mujica, Vladimiro

    2012-01-01

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

  11. Chiral molecular films as electron polarizers and polarization modulators

    E-print Network

    Ernesto Medina; Floralba López; Mark Ratner; Vladimiro Mujica

    2012-02-16

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

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

    E-print Network

    Byer, Robert L.

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

  13. Topical Developments in High-Field Dynamic Nuclear Polarization

    PubMed Central

    Kiesewetter, Matthew K.; Frantz, Derik K.; Walish, Joseph J.; Ravera, Enrico; Luchinat, Claudio; Swager, Timothy M.; Griffin, Robert G.

    2015-01-01

    We report our recent efforts directed at improving high-field DNP experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from ? = 25 to 82 that demonstrate the impact of molecular structure on performance. We directly polarized low-gamma nuclei including 13C, 2H, and 17O using trityl via the cross effect. We discuss a variety of sample preparation techniques for DNP with emphasis on the benefit of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700 MHz / 460 GHz DNP system that improves microwave delivery and increases enhancements up to 50%. PMID:25977588

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

    SciTech Connect

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

    1993-12-01

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

  15. High-resolution subsurface microscopy of CMOS integrated circuits using radially polarized light.

    PubMed

    Rutkauskas, M; Farrell, C; Dorrer, C; Marshall, K L; Lundquist, T R; Vedagarbha, P; Reid, D T

    2015-12-01

    Under high numerical aperture (NA) conditions, a linearly polarized plane wave focuses to a spot that is extended along the E-field vector, but radially polarized light is predicted to form a circular spot whose diameter equals the narrower dimension obtained with linear polarization. This effect provides an opportunity for improved resolution in high-NA microscopy, and here we present a performance study of subsurface two-photon optical-beam-induced current solid-immersion-lens microscopy of a complementary metal-oxide semiconductor integrated circuit, showing a resolution improvement by using radially polarized illumination. By comparing images of the same structural features we show that radial polarization achieves a resolution of 126 nm, while linear polarization achieves resolutions of 122 and 165 nm, depending on the E-field orientation. These results are consistent with the theoretically expected behavior and are supported by high-resolution images which show superior feature definition using radial polarization. PMID:26625036

  16. POLARIZED ION SOURCES FOR HIGH ENERGY ACCELERATORS AND COLLIDERS

    SciTech Connect

    ZELENSKI,A.N.

    2000-10-16

    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.

  17. POLARIZED ION SOURCES FOR HIGH ENERGY ACCELERATORS AND COLLIDERS

    SciTech Connect

    ZELENSKI,A.N.

    2000-10-16

    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.

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

    SciTech Connect

    Not Available

    1991-12-31

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

  19. Extracting an electron's angle of return from shifted interference patterns in macroscopic high-order-harmonic spectra of diatomic molecules

    NASA Astrophysics Data System (ADS)

    Das, T.; Augstein, B. B.; Figueira de Morisson Faria, C.; Chipperfield, L. E.; Hoffmann, D. J.; Marangos, J. P.

    2015-08-01

    We investigate high-order-harmonic spectra from aligned diatomic molecules in intense driving fields whose components have orthogonal polarizations. We focus on how the driving-field ellipticity influences structural interference patterns in a macroscopic medium. In a previous publication [Phys. Rev. A 88, 023404 (2013), 10.1103/PhysRevA.88.023404] we have shown that the nonvanishing ellipticity introduces an effective dynamic shift in the angle for which the two-center interference maxima and minima occur, with regard to the existing condition for linearly polarized fields. In this work we show through simulation that it is still possible to observe this shift in harmonic spectra that have undergone macroscopic propagation, and discuss the parameter range for doing so. These features are investigated for H2 in a bichromatic field composed of two orthogonally polarized waves. The shift is visible both in the near- and in the far-field regime, so that, in principle, it can be observed in experiments.

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

    E-print Network

    Rocca, Jorge J.

    Generation and application of a high-average- power polarized soft-x-ray laser beam B. R. Benware- top soft-x-ray laser. The radiation emitted by a high-average-power discharge-pumped tabletop Ne The development of compact table- top sources of high-power polarized soft-x-ray radiation can be expected to have

  1. THE ACCURACY OF PRESENT MODELS OF THE HIGH ALTITUDE POLAR MAGNETOSPHERE

    E-print Network

    Russell, Christopher T.

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

  2. The infrared polarizations of high-redshift radio galaxies

    NASA Astrophysics Data System (ADS)

    Leyshon, Gareth

    1999-10-01

    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.

  3. The infrared polarizations of high-redshift radio galaxies

    E-print Network

    Gareth Leyshon

    1999-10-29

    This thesis reports the K-band polarizations of a representative sample of nine radio galaxies: seven 3C objects at 0.7 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.

  4. Ultracold high-density samples of rovibronic ground-state molecules in an optical lattice

    NASA Astrophysics Data System (ADS)

    Danzl, Johann Georg

    2011-03-01

    Ultracold molecules controlled at the level of single quantum states with respect to all internal and external degrees of freedom will enable a series of fundamental studies in physics and chemistry, ranging from novel quantum gas experiments and cold controlled chemistry to quantum information and quantum simulation. Ultracold molecules trapped in an optical lattice at high density and prepared in their lowest internal quantum state are an ideal starting point for these studies. We create ultracold and dense samples of molecules in a single hyperfine sublevel of the rovibronic ground state while each molecule is individually trapped in the motional ground state of an optical lattice well [1,2]. Starting from an atomic Mott-insulator state with optimized double-site occupancy, weakly bound Cs dimer molecules are efficiently formed on a Feshbach resonance and subsequently transferred to the rovibronic ground state by a stimulated 4-photon process with the Stimulated Raman Adiabatic Passage (STIRAP) technique. The molecules are trapped in the lattice with a lifetime of 8 s. We aim at producing Bose-Einstein condensates of ground-state molecules by adiabatically removing the lattice. Our results, when suitably generalized to heteronuclear molecules, present an important step towards the realization of dipolar quantum-gas phases in optical lattices. I will report on recent progress in Innsbruck on the formation of RbCs ground state molecules.

  5. Superior adsorption of pharmaceutical molecules by highly porous BN nanosheets.

    PubMed

    Liu, Dan; Lei, Weiwei; Qin, Si; Klika, Karel D; Chen, Ying

    2016-01-01

    Highly porous boron nitride nanosheets (BNNSs) were tested as a re-usable adsorbent for the removal of pharmaceuticals from aqueous solution. The BNNSs exhibit both unprecedentedly high adsorption capacities and excellent recyclability while maintaining their high adsorption capacity by a simple regeneration process. These advantages render BNNSs a promising material for water remediation applications. PMID:26618906

  6. High resolution laser spectroscopy of cesium and rubidium molecules with optically induced coherence 

    E-print Network

    Chen, Hui

    2006-10-30

    with high resolution single mode laser spectroscopy. The derived electronic and rotational vibrational constants were used in the backward Raman amplification experiment of Rb diatomic molecule. Both experimental results and theoretical calculation confirms...

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

    E-print Network

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

    2009-12-31

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

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

    PubMed

    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

    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

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

    PubMed Central

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

    2014-01-01

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

  11. Unique High-Resolution Stratospheric Observations of Polar Mesospheric Clouds

    NASA Astrophysics Data System (ADS)

    Miller, A.; Araujo, D.; Chapman, D.; Didier, J.; Fritts, D. C.; Jones, G.; Kjellstrand, B.; Limon, M.; Lizancos, A.; Luu, T. V.; Macioce, T.; Tucker, G.; Vinokurov, J.

    2014-12-01

    We present a unique data set consisting of high-resolution optical images of Polar Mesospheric Clouds (PMCs), observed serendipitously from a stratospheric balloon platform in January of 2013. Complex morphological structures in the PMC brightness distribution provide observable consequences of the deposition of energy and momentum by atmospheric gravity waves in the mesosphere and lower thermosphere. This data set represents the highest resolution set of optical images of this phenomenon to date, and therefore provides a unique window into the poorly understood instability and turbulent dynamics on the smallest scales (between roughly a meter and a few km). Through this analysis, morphological features identified in individual images will be compared with those predicted in numerical models in order to identify key dynamical features present in the data on these small scales. Multiple spatially-overlapping sequential images will be analyzed together in order to extract cloud velocities and to measure timescales for feature permanence. These image compilations will also be used to place the observed small-scale features in a broader context by using multiple images to re-construct larger features, as well as to compare to features simultaneously observed on much larger scales by the CIPS instrument flying on the AIM satellite.

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

    SciTech Connect

    Hamilton, D.J.; Annand, J.R.M.; Mamyan, V.H.; Aniol, K.A.; Margaziotis, D.J.; Bertin, P.Y.; Camsonne, A.; Laveissiere, G.; Bosted, P.; Paschke, K.; Calarco, J.R.; Chang, G.C.; Horn, T.; Savvinov, N.; Chang, T.-H.; Danagoulian, A.; Nathan, A.M.; Roedelbronn, M.; Chen, J.-P.

    2005-06-24

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

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

    NASA Technical Reports Server (NTRS)

    Lister, M.; Smith, P.

    2000-01-01

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

  14. Highly circularly polarized electroluminescence from a chiral europium complex.

    PubMed

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

    2015-03-11

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

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

    E-print Network

    Hergenrother, Paul J.

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-11-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    SciTech Connect

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

    2007-01-15

    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.

  20. Highly stable polarization independent Mach-Zehnder interferometer.

    PubMed

    Mi?uda, Michal; Doláková, Ester; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Fiurášek, Jaromír; Ježek, Miroslav

    2014-08-01

    We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27×40 cm offers individually accessible paths and shows phase deviation less than 0.4° during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3° or 7 nm for 1.5 h without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually. PMID:25173242

  1. Highly stable polarization independent Mach-Zehnder interferometer

    SciTech Connect

    Mi?uda, Michal Doláková, Ester; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Fiurášek, Jaromír; Ježek, Miroslav

    2014-08-15

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

  2. Benchmarking Ground-State Geometries and Vertical Excitation Energies of a Selection of P-Type Semiconducting Molecules with Different Polarity.

    PubMed

    Brückner, Charlotte; Engels, Bernd

    2015-12-24

    A benchmark of TD-DFT, wave function-based and semiempiric methods was performed for the geometries and excitation energies of diverse molecular organic semiconductors with varying polarity. Geometries were benchmarked by means of RMSD (root-mean-square deviation) values and MAE (maximum absolute error) values of geometric parameters specific for the electronic structure of the respective molecule. MS-CASPT2 calculations were used to benchmark excitation energies with respect to a confidence interval around the values obtained with CASPT2. The effect of spin-component scaling (SCS) on several wave function-based methods was thoroughly evaluated. PMID:26625100

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

    SciTech Connect

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

    2011-06-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  5. Bombardment of gas molecules on single graphene layer at high temperature

    SciTech Connect

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

    2014-12-09

    Graphite is widely used as a material for rocket-nozzle inserts due to its excellent thermo-physical properties as well as low density. During the operation of rockets, the surface of the graphite nozzle is subjected to very high heat fluxes and the undesirable erosion of the surface occurs due to the bombardment of gas molecules with high kinetic energy, which causes a significant reduction of nozzle performance. However, the understanding and quantification of such bombardment is not satisfactory due to its complexity: The bond breaking-forming happens simultaneously for the carbon atoms of graphene, some gas molecules penetrate through the surface, some of them are reflected from the surface, etc. In the present study, we perform extensive molecular dynamics (MD) simulations to examine the bombardment phenomena in high temperature environment (several thousand Kelvin). Advanced from the previous studies that have focused on the bombardment by light molecules (e.g., H{sub 2}), we will concentrate on the impact by realistic molecules (e.g., CO{sub 2} and H{sub 2}O). LAMMPS is employed for the MD simulations with NVE ensemble and AIREBO potential for graphene. The molecular understanding of the interaction between graphene and highly energetic gas molecules will enable us to design an efficient thermo-mechanical protection system.

  6. Fusion with highly spin polarized HD and D sub 2

    SciTech Connect

    Honig, A.

    1992-06-29

    This report discusses the following topics relating to inertial confinement with spin polarized hydrogen targets: low temperature implementation of mating a target to omega; dilution-refrigerator cold-entry and retrieval system; target shell tensile strength characterization at low temperatures; and proton and deuteron spin-lattice relaxation measurements in HD in the millikelvin temperature range. (LSP)

  7. Comparison of the polarization properties in the retinas of different rodents using high resolution polarization sensitive OCT

    NASA Astrophysics Data System (ADS)

    Fialová, Stanislava; Augustin, Marco; Plasenzotti, Roberto; Rauscher, Sabine; Gröger, Marion; Pircher, Michael; Hitzenberger, Christoph K.; Baumann, Bernhard

    2015-07-01

    Animal models play an important role for understanding the pathophysiology of glaucoma and age-related macular degeneration. With these models, longitudinal studies can be performed and therefore there is need for non-invasive evaluation of disease progress. For that purpose optical coherence tomography (OCT) can be used. Since tissues with different polarization properties are important in these diseases, polarization sensitive OCT (PS-OCT) could be a valuable tool in preclinical research. In this work a high resolution PS-OCT (HR-PS-OCT) system was used in-vivo for rodent retinal imaging. A super luminescent diode with a bandwidth of 100 nm was used as a light source that yielded an axial resolution of 5.1 ?m in air (3.8 ?m in tissue). The A-scan rate was 83 kHz, a whole 3D dataset was acquired in a few seconds (1536x1024x200 pixels in 3.5 s) which reduced motion artifacts. Rats (Sprague-Dawley, Long-Evans and Brown Norway) as well as mice (C57BL/6) were imaged. High resolution reflectivity images showed all retinal layers in all animals. From acquired data also phase retardation, fast axis orientation and degree of polarization uniformity (DOPU) images were calculated. On phase retardation images sclera was identified as birefringent and retinal pigment epithelium (RPE) and choroid as depolarizing tissues. Our results demonstrate the suitability of the system for high speed/resolution imaging in follow up studies on rodents.

  8. Single high-order round-trip feedback effects in orthogonally polarized dual frequency laser

    NASA Astrophysics Data System (ADS)

    Zeng, Z.; Zhang, S.; Tan, Y.; Zhang, P.; Li, Y.

    2012-05-01

    We present the effects of single high-order round-trip feedback in orthogonally polarized dual frequency laser. The high quality intensity fringes of two orthogonally polarized lights are obtained, which are cosine-like. The fringe frequency of a single high-order round-trip feedback is five times that of the conventional optical feedback. Even higher frequencies are possible with this setup. Particularly, there is a phase difference between two orthogonal polarized lights in single high-order round-trip feedback and the phase difference is determined by the feedback order, the length of the external cavity, and the frequency difference of the two orthogonal polarized lights. A theoretical analysis based on a compound cavity model of a dual frequency laser agrees well with the experimental results. These results provide a potential application in precision measurement with both directional discrimination and high optical resolution.

  9. High-resolution electrohydrodynamic jet printing of small-molecule organic light-emitting diodes.

    PubMed

    Kim, Kukjoo; Kim, Gyeomuk; Lee, Bo Ram; Ji, Sangyoon; Kim, So-Yun; An, Byeong Wan; Song, Myoung Hoon; Park, Jang-Ung

    2015-08-28

    The development of alternative organic light-emitting diode (OLED) fabrication technologies for high-definition and low-cost displays is an important research topic as conventional fine metal mask-assisted vacuum evaporation has reached its limit to reduce pixel sizes and manufacturing costs. Here, we report an electrohydrodynamic jet (e-jet) printing method to fabricate small-molecule OLED pixels with high resolution (pixel width of 5 ?m), which significantly exceeds the resolutions of conventional inkjet or commercial OLED display pixels. In addition, we print small-molecule emitting materials which provide a significant advantage in terms of device efficiency and lifetime compared to those with polymers. PMID:26214140

  10. Non-collinear generation of angularly isolated circularly polarized high harmonics

    NASA Astrophysics Data System (ADS)

    Hickstein, Daniel D.; Dollar, Franklin J.; Grychtol, Patrik; Ellis, Jennifer L.; Knut, Ronny; Hernández-García, Carlos; Zusin, Dmitriy; Gentry, Christian; Shaw, Justin M.; Fan, Tingting; Dorney, Kevin M.; Becker, Andreas; Jaro?-Becker, Agnieszka; Kapteyn, Henry C.; Murnane, Margaret M.; Durfee, Charles G.

    2015-11-01

    We generate angularly isolated beams of circularly polarized extreme ultraviolet light through the first implementation of non-collinear high harmonic generation with circularly polarized driving lasers. This non-collinear technique offers numerous advantages over previous methods, including the generation of higher photon energies, the separation of the harmonics from the pump beam, the production of both left and right circularly polarized harmonics at the same wavelength and the capability of separating the harmonics without using a spectrometer. To confirm the circular polarization of the beams and to demonstrate the practicality of this new light source, we measure the magnetic circular dichroism of a 20?nm iron film. Furthermore, we explain the mechanisms of non-collinear high harmonic generation using analytical descriptions in both the photon and wave models. Advanced numerical simulations indicate that this non-collinear mixing enables the generation of isolated attosecond pulses with circular polarization.

  11. Can ferroelectric polarization explain the high performance of hybrid halide perovskite solar cells?

    PubMed

    Sherkar, Tejas S; Jan Anton Koster, L

    2016-01-01

    The power conversion efficiency of photovoltaic cells based on the use of hybrid halide perovskites, CH3NH3PbX3 (X = Cl, Br, I), now exceeds 20%. Recently, it was suggested that this high performance originates from the presence of ferroelectricity in the perovskite, which is hypothesized to lower charge recombination in the device. Here, we investigate and quantify the influence of mesoscale ferroelectric polarization on the device performance of perovskite solar cells. We implement a 3D drift diffusion model to describe the solar cell operation. To account for the mesoscale ferroelectricity, we incorporate domains defined by polarization strength, P, in 3D space, forming different polarization landscapes or microstructures. Study of microstructures with highly-ordered polarized domains shows that charge transport and recombination in the solar cell depends significantly on the polarization landscape viz. the orientation of domain boundaries and the size of domains. In the case of the microstructure with random correlated polarization, a realistic scenario, we find indication of the existence of channels for efficient charge transport in the device which leads to lowering of charge recombination, as evidenced by the high fill factor (FF). However, the high open-circuit voltage (VOC), which is typical of high performance perovskite solar cells, is unlikely to be explained by the presence of ferroelectric polarization in the perovskite. PMID:26612111

  12. High-Throughput Universal DNA Curtain Arrays for Single-Molecule Fluorescence Imaging

    PubMed Central

    Gallardo, Ignacio F.; Pasupathy, Praveenkumar; Brown, Maxwell; Manhart, Carol M.; Neikirk, Dean P.; Alani, Eric; Finkelstein, Ilya J.

    2015-01-01

    Single-molecule studies of protein–DNA interactions have shed critical insights into the molecular mechanisms of nearly every aspect of DNA metabolism. The development of DNA curtains—a method for organizing arrays of DNA molecules on a fluid lipid bilayer—has greatly facilitated these studies by increasing the number of reactions that can be observed in a single experiment. However, the utility of DNA curtains is limited by the challenges associated with depositing nanometer-scale lipid diffusion barriers onto quartz microscope slides. Here, we describe a UV lithography-based method for large-scale fabrication of chromium (Cr) features and organization of DNA molecules at these features for high-throughput single-molecule studies. We demonstrate this approach by assembling 792 independent DNA arrays (containing >900 000 DNA molecules) within a single microfluidic flowcell. As a first proof of principle, we track the diffusion of Mlh1-Mlh3—a heterodimeric complex that participates in DNA mismatch repair and meiotic recombination. To further highlight the utility of this approach, we demonstrate a two-lane flowcell that facilitates concurrent experiments on different DNA substrates. Our technique greatly reduces the challenges associated with assembling DNA curtains and paves the way for the rapid acquisition of large statistical data sets from individual single-molecule experiments. PMID:26325477

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    SciTech Connect

    Wong, M. C. H.; Brichta, J.-P.; Bhardwaj, V. R.

    2010-06-15

    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.

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

    SciTech Connect

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

    2005-12-01

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

  16. Polarization-Independent and High-Efficiency Dielectric Metasurfaces Spanning 600-800 nm Wavelengths

    E-print Network

    Li, Qi-Tong; Wang, Bo; Gan, Fengyuan; Chen, Jianjun; Chu, Weiguo; Xiao, Yun-Feng; Gong, Qihuang; Li, Yan

    2015-01-01

    Artificial metasurfaces are capable of completely manipulating the phase, amplitude, and polarization of light with high spatial resolutions. The emerging design based on high-index and low-loss dielectrics has led to the realization of novel metasurfaces with high transmissions, but these devices usually operate at the limited bandwidth, and are sensitive to the incident polarization. Here, for the first time we report experimentally the polarization-independent and high-efficiency dielectric metasurfaces spanning the visible wavelengths about 200 nm, which are of importance for novel flat optical devices operating over a broad spectrum. The diffraction efficiencies of the gradient metasurfaces consisting of the multi-fold symmetric nano-crystalline silicon nanopillars are up to 93% at 670 nm, and exceed 75% at the wavelengths from 600 to 800 nm for the two orthogonally polarized incidences. These dielectric metasurfaces hold great potential to replace prisms, lenses and other conventional optical elements.

  17. Experimental study of high speed polarization-coding quantum key distribution with sifted-key

    E-print Network

    .mink@nist.gov Abstract: We present a quantitative study of various limitations on quantum cryptographic systems operatingExperimental study of high speed polarization- coding quantum key distribution with sifted.5570) Quantum detectors ___________________________________________________________________________ References

  18. Tackling the bottleneck in bacterial signal transduction research: high-throughput identification of signal molecules.

    PubMed

    Krell, Tino

    2015-05-01

    Signal transduction processes are typically initiated by the interaction of signal molecules with sensor domains. The current lack of information on the signal molecules that feed into regulatory circuits forms a major bottleneck that hampers the understanding of regulatory processes. McKellar et?al. report a high-throughput approach for the identification of signal molecules, which is based on thermal shift assays of recombinant sensor domains in the absence and presence of compounds from commercially available ligand collections. Initial binding studies with the sensor domain of the PctA chemoreceptor of Pseudomonas aeruginosa showed a close match between thermal shift assay results and microcalorimetric studies reported previously. Using thermal shift assays the authors then identify signals that bind to three chemoreceptors of the kiwifruit pathogen P. syringae pv. Actinidiae?NZ-V13. Microcalorimetric binding studies and chemotaxis assays have validated the relevance of these ligands. The power of this technique lies in the combination of a high-throughput analytical tool with commercially available compound collections. The approach reported is universal since it can be employed to identify signal molecules to any type of sensor domain. There is no doubt that this technique will facilitate the identification of many signal molecules in future years. PMID:25708679

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

    PubMed Central

    Khanal, Ashok

    2014-01-01

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

  20. The search for novel highly polar betainic optical materials

    NASA Astrophysics Data System (ADS)

    Neilands, Ojars; Utinans, Maris

    2003-08-01

    Mentioned betaines comprise in molecule directly connected electron donor anion moiety and electron acceptor cation A novel class of active nonlinear optical (NL) materials -- strongly dipolar intramolecular salts (betaines) are offered. The betaines are principally different from the commonly used push-pull dipolar molecules. A donor moiety is directly bonded to heterocyclic N-onium cation moiety within the same molecule. The anion is five-member ?-dicarbonyl compound, usually indan-1,3-dione. Calculations show that electric dipole moment is changed considerably at photo-induced intramolecular electron transfer from HOMO to LUMO, the difference between dipole moment values in the ground and excited states being unusual large. The HOMO is strongly localized on the anion moiety while the LUMO -- on the heterocyclic N-onium cation moiety. The hyperpolarizabilities are remarkable. Betaines are easy to synthesize and fine-tuning of their NLO properties is possible. Preparing of betaine solution in polymer matrices (host-guest systems) and formation of films is found to be the best method for examining the NLO properties. Obtained films are subjected to corona poling before measuring the change of surface potential. Due to strong photo oxidation it is necessary to exclude contact with air or avoid light while processing betaines films.

  1. An increasing number of synthetic compounds have been shown to facilitate ion and polar molecule transport across

    E-print Network

    Smith, Bradley D.

    amino acid sequences to transport peptides and proteins across cellular membranes. Addresses Department Science Ltd. All rights reserved. Published online 18 October 2002 Abbreviations PC phosphatidylcholine PE naturally occurring channel-forming proteins or carrier molecules. The resultant compounds may utilize

  2. High-resolution electrohydrodynamic jet printing of small-molecule organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kim, Kukjoo; Kim, Gyeomuk; Lee, Bo Ram; Ji, Sangyoon; Kim, So-Yun; An, Byeong Wan; Song, Myoung Hoon; Park, Jang-Ung

    2015-08-01

    The development of alternative organic light-emitting diode (OLED) fabrication technologies for high-definition and low-cost displays is an important research topic as conventional fine metal mask-assisted vacuum evaporation has reached its limit to reduce pixel sizes and manufacturing costs. Here, we report an electrohydrodynamic jet (e-jet) printing method to fabricate small-molecule OLED pixels with high resolution (pixel width of 5 ?m), which significantly exceeds the resolutions of conventional inkjet or commercial OLED display pixels. In addition, we print small-molecule emitting materials which provide a significant advantage in terms of device efficiency and lifetime compared to those with polymers.The development of alternative organic light-emitting diode (OLED) fabrication technologies for high-definition and low-cost displays is an important research topic as conventional fine metal mask-assisted vacuum evaporation has reached its limit to reduce pixel sizes and manufacturing costs. Here, we report an electrohydrodynamic jet (e-jet) printing method to fabricate small-molecule OLED pixels with high resolution (pixel width of 5 ?m), which significantly exceeds the resolutions of conventional inkjet or commercial OLED display pixels. In addition, we print small-molecule emitting materials which provide a significant advantage in terms of device efficiency and lifetime compared to those with polymers. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03034j

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

    E-print Network

    Michalet, Xavier

    -spot excitation, fast multi-pixel detection, algorithms to handle many channels and suitable software to processUltra high-throughput single molecule spectroscopy with a 1024 pixel SPAD Ryan A. Colyera on silicon spatial light modulator (LCOS-SLM) and a novel standard CMOS 1024 pixel SPAD array, opening

  4. Dielectric metasurfaces for complete control of phase and polarization with subwavelength spatial resolution and high transmission.

    PubMed

    Arbabi, Amir; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

    2015-11-01

    Metasurfaces are planar structures that locally modify the polarization, phase and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurface have been realized, but with either low transmission efficiencies or limited control over polarization and phase. Here, we show a metasurface platform based on high-contrast dielectric elliptical nanoposts that provides complete control of polarization and phase with subwavelength spatial resolution and an experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase plates, wave plates, polarizers, beamsplitters, as well as polarization-switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform. PMID:26322944

  5. Dielectric metasurfaces for complete control of phase and polarization with subwavelength spatial resolution and high transmission

    NASA Astrophysics Data System (ADS)

    Arbabi, Amir; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

    2015-11-01

    Metasurfaces are planar structures that locally modify the polarization, phase and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurface have been realized, but with either low transmission efficiencies or limited control over polarization and phase. Here, we show a metasurface platform based on high-contrast dielectric elliptical nanoposts that provides complete control of polarization and phase with subwavelength spatial resolution and an experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase plates, wave plates, polarizers, beamsplitters, as well as polarization-switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform.

  6. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

    PubMed

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J; Mancuso, Christopher A; Hogle, Craig W; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L; Dorney, Kevin M; Chen, Cong; Shpyrko, Oleg G; Fullerton, Eric E; Cohen, Oren; Oppeneer, Peter M; Miloševi?, Dejan B; Becker, Andreas; Jaro?-Becker, Agnieszka A; Popmintchev, Tenio; Murnane, Margaret M; Kapteyn, Henry C

    2015-11-17

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform. PMID:26534992

  7. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism

    PubMed Central

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D.; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J.; Mancuso, Christopher A.; Hogle, Craig W.; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L.; Dorney, Kevin M.; Chen, Cong; Shpyrko, Oleg G.; Fullerton, Eric E.; Cohen, Oren; Oppeneer, Peter M.; Miloševi?, Dejan B.; Becker, Andreas; Jaro?-Becker, Agnieszka A.; Popmintchev, Tenio; Murnane, Margaret M.; Kapteyn, Henry C.

    2015-01-01

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform. PMID:26534992

  8. Gamma-ray polarization of the synchrotron self-compton process from a highly relativistic jet

    SciTech Connect

    Chang, Zhe; Lin, Hai-Nan

    2014-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    PubMed Central

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

    2009-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  12. Droplet-based microfluidic systems for high-throughput single DNA molecule isothermal amplification and analysis.

    PubMed

    Mazutis, Linas; Araghi, Ali Fallah; Miller, Oliver J; Baret, Jean-Christophe; Frenz, Lucas; Janoshazi, Agnes; Taly, Valérie; Miller, Benjamin J; Hutchison, J Brian; Link, Darren; Griffiths, Andrew D; Ryckelynck, Michael

    2009-06-15

    We have developed a method for high-throughput isothermal amplification of single DNA molecules in a droplet-based microfluidic system. DNA amplification in droplets was analyzed using an intercalating fluorochrome, allowing fast and accurate "digital" quantification of the template DNA based on the Poisson distribution of DNA molecules in droplets. The clonal amplified DNA in each 2 pL droplet was further analyzed by measuring the enzymatic activity of the encoded proteins after fusion with a 15 pL droplet containing an in vitro translation system. PMID:19518143

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Scheffler, Silvia; Strauß, Denis; Sauer, Markus

    2007-07-01

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

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

    PubMed Central

    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.

    2008-01-01

    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. PMID:19194532

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

    PubMed

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

    2010-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Hu, Changkui; Liu, Deming

    2008-11-01

    In this study, we propose a high-performance polarizer with Aluminum wire-grid structure that an antireflection layer (AR) is deposited between the metal wires and the transparent substrate. The polarization properties of the polarizer are analyzed in detail using rigorous coupled wave analysis (RCWA). The theoretical research shows that aluminum wire-grid polarizer has high transmission coefficient and extinction ratio in near infrared, as well as uniform performance with wide variations in the angle of incidence. For the fiber communication window of 1550nm, the transmittance and the extinction ratio are 95.4% and 35.3dB, respectively. Furthermore, a layer of Al203 forms rapidly on the aluminum wires even in high vacuum, the effect of the metal oxide layers on the polarization properties is modeled and analyzed. The results have shown that the polarizer with oxide layers coating on the wires still provides high performance. These features with their small form factor make it has potential for use in many integrated optical applications.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

    Gerchikov, L. G.; Kuz'michev, V. V.; Mamaev, Yu. A.; Vasiliev, D. A.; Yashin, Yu. P.; Aulenbacher, K.; Clendenin, J. E.; Maruyama, T.; Mikhrin, V. S.; Ustinov, V. M.; Vasiliev, A. P.; Zhukov, A. E.; Roberts, J. S.

    2008-02-06

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

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

    SciTech Connect

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

    2007-11-28

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

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

    SciTech Connect

    Li, Lifei; Jin, Chenjie; Qi, Mei; Chen, Xiaoming; Ren, Zhaoyu E-mail: rzy@nwu.edu.cn; Zheng, Xinliang E-mail: rzy@nwu.edu.cn; Bai, Jintao; Sun, Zhipei

    2014-12-01

    We demonstrate a Q-switched radially polarized all-solid-state laser by transferring a graphene film directly onto an output coupler. The laser generates Q-switched radially polarized beam (QRPB) with a pulse width of 192?ns and 2.7?W average output power. The corresponding single pulse energy is up to 16.2??J with a high repetition rate of 167?kHz. The M{sup 2} factor and the polarization purity are ?2.1 and 96%, respectively. Our QRPB source is a simple and low-cost source for a variety of applications, such as industrial material processing, optical trapping, and microscopy.

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

    SciTech Connect

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

    2011-03-28

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

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

    SciTech Connect

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

    2007-06-25

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

  4. Polarization measurement of dielectronic recombination transitions in highly charged krypton ions

    NASA Astrophysics Data System (ADS)

    Shah, Chintan; Jörg, Holger; Bernitt, Sven; Dobrodey, Stepan; Steinbrügge, René; Beilmann, Christian; Amaro, Pedro; Hu, Zhimin; Weber, Sebastian; Fritzsche, Stephan; Surzhykov, Andrey; Crespo López-Urrutia, José R.; Tashenov, Stanislav

    2015-10-01

    We report linear polarization measurements of x rays emitted due to dielectronic recombination into highly charged krypton ions. The ions in the He-like through O-like charge states were populated in an electron-beam ion trap with the electron-beam energy adjusted to recombination resonances in order to produce K ? x rays. The x rays were detected with a newly developed Compton polarimeter using a beryllium scattering target and 12 silicon x-ray detector diodes sampling the azimuthal distribution of the scattered x rays. The extracted degrees of linear polarization of several dielectronic recombination transitions agree with results of relativistic distorted-wave calculations. We also demonstrate a high sensitivity of the polarization to the Breit interaction, which is remarkable for a medium-Z element like krypton. The experimental results can be used for polarization diagnostics of hot astrophysical and laboratory fusion plasmas.

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

    PubMed

    Yano, Yuichiro; Goka, Shigeyoshi

    2014-12-01

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

  6. Experimental Detection of Branching at a Conical Intersection in a Highly Fluorescent Molecule.

    PubMed

    Brazard, Johanna; Bizimana, Laurie A; Gellen, Tobias; Carbery, William P; Turner, Daniel B

    2016-01-01

    Conical intersections are molecular configurations at which adiabatic potential-energy surfaces touch. They are predicted to be ubiquitous, yet condensed-phase experiments have focused on the few systems with clear spectroscopic signatures of negligible fluorescence, high photoactivity, or femtosecond electronic kinetics. Although rare, these signatures have become diagnostic for conical intersections. Here we detect a coherent surface-crossing event nearly two picoseconds after optical excitation in a highly fluorescent molecule that has no photoactivity and nanosecond electronic kinetics. Time-frequency analysis of high-sensitivity measurements acquired using sub-8 fs pulses reveals phase shifts of the signal due to branching of the wavepacket through a conical intersection. The time-frequency analysis methodology demonstrated here on a model compound will enable studies of conical intersections in molecules that do not exhibit their diagnostic signatures. Improving the ability to detect conical intersections will enrich the understanding of their mechanistic role in molecular photochemistry. PMID:26647278

  7. Optical attosecond mapping by polarization selective detection

    SciTech Connect

    Kitzler, Markus; Xie Xinhua; Scrinzi, Armin; Baltuska, Andrius

    2007-07-15

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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1985-12-01

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

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

    SciTech Connect

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

    2007-02-01

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

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

    PubMed Central

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

    2014-01-01

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

  13. High-precision measurement of polarized-. sigma. /sup -/ beta decay

    SciTech Connect

    Hsueh, S.Y.; Mueller, D.; Tang, J.; Winston, R.; Zapalac, G.; Swallow, E.C.; Berge, J.P.; Brenner, A.E.; Cooper, P.S.; Grafstroem, P.; and others

    1988-10-01

    We report the results of a polarized-..sigma../sup -/ beta-decay experiment carried out in the Fermilab Proton Center charged-hyperon beam. These results are based on 49 671 observed ..sigma../sup -/..-->..ne/sup -/nu-bar decays. The ..sigma../sup -/ beam had a nominal momentum of 250 GeV/c and was produced by 400-GeV/c protons im- pinging on a Cu target. At a production angle of 2.5 mrad, the polarization was (23.6 +- 4.3)%. The decay asymmetries of the electron (..cap alpha../sub e/ = -0.519 +- 0.104), neutron (..cap alpha../sub n/ = +0.509 +- 0.102), and antineutrino (..cap alpha../sub ..nu../ = -0.230 +- 0.061) were measured and used to establish sign and approximate magnitude of the axial-vector-to-vector form-factor ratio g/sub 1//f/sub 1/. The form-factor ratios chemically bondg/sub 1//f/sub 1/chemically bond and f/sub 2//f/sub 1/ were determined most sensitively from the neutron and electron center-of-mass spectra, respectively. We obtain chemically bondg/sub 1//f/sub 1/-0.237g/sub 2//f/sub 1/chemically bond = 0.327 +- 0.007 +- 0.019 and f/sub 2/(0)/f/sub 1/(0) = -0.96 +- 0.97 +- 0.13, where the stated errors are statistical and systematic, respectively. A general fit that includes the asymmetries and makes the conventional assumption g/sub 2/ = 0 gives the final value g/sub 1/(0)/f/sub 1/(0) = -0.328 +- 0.019. The data are also compatible with positive values for g/sub 2//f/sub 1/ combined with corresponding reduced values for chemically bondg/sub 1//f/sub 1/chemically bond. .AE

  14. Electrode fabrication for high-speed polarization mode converter

    NASA Astrophysics Data System (ADS)

    Meng, X.; Zhang, S.; Chen, C.; Poirier, M.; Shepherd, F. R.; Das, S. R.

    2004-05-01

    As part of the development of a traveling wave polarization converter (TWPC), a technique for producing ``T-electrodes'' adjacent to the ridge sidewalls and air bridges has been developed. To maximize the conversion efficiency, the rf electrodes on the etched floor are required to be very close to the ridge sidewalls. In the fabrication of the electrode, patterned seed layer stripes were first put on the etched floor on both sides of the waveguide by a metal lift-off process. Onto this seed layer, the T-electrode was electroplated through a patterned thick photoresist. After resist removal, the unwanted seed layer was stripped off by chemical etch back. Through this multistep process, the electrodes were constructed successfully with the desired proximity to the ridge waveguide. For easy chip assembly, the bond pads were designed to be on the same side of the device. Two long and wide metal air bridges over the ridge waveguide were made to connect the electrode on one side to the bond pads on the other side of the ridge. It was found that the air bridges were easily damaged in the bonding process prior to lap and polish because of the particular device structure, i.e., air bridges being the highest point of the wafer and only a small number of air bridges on the wafer. To protect the air bridge a patterned photoresist layer was applied before the wafer was bonded to a carrier. .

  15. Identification of small molecules with type I interferon inducing properties by high-throughput screening.

    PubMed

    Martínez-Gil, Luis; Ayllon, Juan; Ortigoza, Mila Brum; García-Sastre, Adolfo; Shaw, Megan L; Palese, Peter

    2012-01-01

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

  16. Selecting, Acquiring, and Using Small Molecule Libraries for High-Throughput Screening

    PubMed Central

    Dandapani, Sivaraman; Rosse, Gerard; Southall, Noel; Salvino, Joseph M.; Thomas, Craig J.

    2015-01-01

    The selection, acquisition and use of high quality small molecule libraries for screening is an essential aspect of drug discovery and chemical biology programs. Screening libraries continue to evolve as researchers gain a greater appreciation of the suitability of small molecules for specific biological targets, processes and environments. The decisions surrounding the make-up of any given small molecule library is informed by a multitude of variables and opinions vary on best-practices. The fitness of any collection relies upon upfront filtering to avoiding problematic compounds, assess appropriate physicochemical properties, install the ideal level of structural uniqueness and determine the desired extent of molecular complexity. These criteria are under constant evaluation and revision as academic and industrial organizations seek out collections that yield ever improving results from their screening portfolios. Practical questions including cost, compound management, screening sophistication and assay objective also play a significant role in the choice of library composition. This overview attempts to offer advice to all organizations engaged in small molecule screening based upon current best practices and theoretical considerations in library selection and acquisition.

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

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    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

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

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    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.

  20. Ultra-high tunable liquid crystal-plasmonic photonic crystal fiber polarization filter.

    PubMed

    Hameed, Mohamed Farhat O; Heikal, A M; Younis, B M; Abdelrazzak, Maher; Obayya, S S A

    2015-03-23

    A novel ultra-high tunable photonic crystal fiber (PCF) polarization filter is proposed and analyzed using finite element method. The suggested design has a central hole infiltrated with a nematic liquid crystal (NLC) that offers high tunability with temperature and external electric field. Moreover, the PCF is selectively filled with metal wires into cladding air holes. Results show that the resonance losses and wavelengths are different in x and y polarized directions depending on the rotation angle ? of the NLC. The reported filter of compact device length 0.5 mm can achieve 600 dB / cm resonance losses at ? = 90° for x-polarized mode at communication wavelength of 1300 mm with low losses of 0.00751 dB / cm for y-polarized mode. However, resonance losses of 157.71 dB / cm at ? = 0° can be achieved for y-polarized mode at the same wavelength with low losses of 0.092 dB / cm for x-polarized mode. PMID:25837045

  1. Electron-beam-deposited distributed polarization rotator for high-power laser applications.

    PubMed

    Oliver, J B; Kessler, T J; Smith, C; Taylor, B; Gruschow, V; Hettrick, J; Charles, B

    2014-10-01

    Electron-beam deposition of silica and alumina is used to fabricate distributed polarization rotators suitable for smoothing the intensity of large-aperture, high-peak-power lasers. Low-modulation, low-loss transmittance with a high 351-nm laser-damage threshold is achieved. PMID:25321966

  2. Generating Polarized High-Brightness Muon Beams With High-Energy Gammas

    SciTech Connect

    Yakimenko, Vitaly

    2009-01-22

    Hadron colliders are impractical at very high energies as effective interaction energy is a fraction of the energies of the beams and luminosity must rise as energy squared. Further, the prevailing gluon-gluon background radiation makes it difficult to sort out events. e{sup +}e{sup -} colliders, on other hand, are constrained at TeV energies by beamstrahlung radiation and also by cost as long linacs are required to avoid synchrotron radiation in the rings. A muon collider will have the same advantages in energy reach as an e{sup +}e{sup -} collider, but without prohibitive beamstrahlung- and synchrotron- radiation. Generation of the high-brightness polarized muon ({mu}{sup -}{mu}{sup +}) beams through gamma conversion into pairs in the nuclei field is considered in this paper. The dominant effect in the interaction of the high-energy photons with the solid target will be the production of electron-positron pairs. The low-phase space of the resulting muon beams adequately compensates for the small probability of generating a {mu}{sup -}{mu}{sup +} pair.

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

    DOEpatents

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

    2010-03-02

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

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

    NASA Technical Reports Server (NTRS)

    Byer, R. L.

    1982-01-01

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

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

    PubMed

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

    2015-03-23

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

  6. PolarBase: A Database of High-Resolution Spectropolarimetric Stellar Observations

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

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

    E-print Network

    Collins, Gary S.

    Modeling and Simulation of Microwave Heating Microwave heating is very popular in warming up foods quickly and efficiently. In microwave heating, the time-varying electric field polarizes the molecules items under microwave heating. The microwave heating phenomenon is modeled by the finite element method

  8. Single-molecule detection technologies in miniaturized high-throughput screening: fluorescence intensity distribution analysis.

    PubMed

    Haupts, Ulrich; Rüdiger, Martin; Ashman, Stephen; Turconi, Sandra; Bingham, Ryan; Wharton, Charlotte; Hutchinson, Jonathan; Carey, Charlotte; Moore, Keith J; Pope, Andrew J

    2003-02-01

    Single-molecule detection technologies are becoming a powerful readout format to support ultra-high-throughput screening. These methods are based on the analysis of fluorescence intensity fluctuations detected from a small confocal volume element. The fluctuating signal contains information about the mass and brightness of the different species in a mixture. The authors demonstrate a number of applications of fluorescence intensity distribution analysis (FIDA), which discriminates molecules by their specific brightness. Examples for assays based on brightness changes induced by quenching/dequenching of fluorescence, fluorescence energy transfer, and multiple-binding stoichiometry are given for important drug targets such as kinases and proteases. FIDA also provides a powerful method to extract correct biological data in the presence of compound fluorescence. PMID:12854995

  9. Macroscopic Measurement of Resonant Magnetization Tunneling in High-Spin Molecules

    NASA Astrophysics Data System (ADS)

    Friedman, Jonathan R.; Sarachik, M. P.; Tejada, J.; Maciejewski, J.; Ziolo, R.

    1996-03-01

    We report the observation of steps in the hysteresis loop of a macroscopic sample of oriented crystals of Mn_12O_12(CH_3COO)_16(H_2O)_4, a high-spin (S=10) molecule. The steps occur at regular intervals of magnetic field, every 0.46 T. The magnetic relaxation rate increases substantially when the field is tuned to a step. We interpret these effects as manifestations of thermally assisted, field-tuned resonant tunneling between quantum spin states. A simple model is presented that accounts for the observations and yields good quantitative agreement with measured values of the anisotropy barrier. We attribute the observation of quantum-mechanical phenomena on a macroscopic scale to tunneling in a large (Avogadro's) number of magnetically identical molecules.

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

    PubMed

    Horváth, Gábor; Hegedüs, Ramón; Barta, András; Farkas, Alexandra; Åkesson, Susanne

    2011-10-01

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

  11. Phagemid Encoded Small Molecules for High Throughput Screening of Chemical Libraries

    E-print Network

    Yin, Jun

    Sfp phosphopante- theinyl transferase6a was used to covalently link the small molecules to a specific molecules. Sfp showed the anticipated impressive substrate promiscuity with small molecule entities attached

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

    PubMed Central

    2015-01-01

    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

  13. Time and Space Resolved High Harmonic Imaging of Electron Tunnelling from Molecules

    NASA Astrophysics Data System (ADS)

    Smirnova, O.

    2009-05-01

    High harmonic generation in intense laser fields carries the promise of combining sub-Angstrom spatial and attosecond temporal resolution of electronic structures and dynamics in molecules, see e.g. [1-3]. High harmonic emission occurs when an electron detached from a molecule by an intense laser field recombines with the parent ion [4]. Similar to Young's double-slit experiment, recombination to several ``lobes'' of the same molecular orbital can produce interference minima and maxima in harmonic intensities [1]. These minima (maxima) carry structural information -- they occur when the de-Broglie wavelength of the recombining electron matches distances between the centers. We demonstrate both theoretically and experimentally that amplitude minima (maxima) in the harmonic spectra can also have dynamical origin, reflecting multi-electron dynamics in the molecule. We use high harmonic spectra to record this dynamics and reconstruct the position of the hole left in the molecule after ionization. Experimental data are consistent with the hole starting in different places as the ionization dynamics changes from tunnelling to the multi-photon regime. Importantly, hole localization and subsequent attosecond dynamics are induced even in the tunnelling limit. Thus, even ``static'' tunnelling induced by a tip of a tunnelling microscope will generate similar attosecond dynamics in a sample. We anticipate that our approach will become standard in disentangling spatial and temporal information from high harmonic spectra of molecules.[4pt] In collaboration with Serguei Patchkovskii, National Research Council, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada; Yann Mairesse, NRC Canada and CELIA, Universit'e Bordeaux I, UMR 5107 (CNRS, Bordeaux 1, CEA), 351 Cours de la Lib'eration, 33405 Talence Cedex, France; Nirit Dudovich, NRC Canada and Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel; David Villeneuve, Paul Corkum, NRC Canada; and Misha Yu. Ivanov, NRC Canada and Imperial College of Science, Technology and Medicine, London SW7 2BW, United Kingdom. [4pt] [1] Lein, M., et al. Phys. Rev. Lett. 88, 183903 (2002).[0pt] [2] Itatani, J. et al. Nature 432, 834 (2004).[0pt] [3] Baker, S. et al Science 312, 424 (2006).[0pt] [4] Corkum, P. B.Phys. Rev. Lett. 71, 1994 (1993).

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

    SciTech Connect

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

    2014-10-20

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

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

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

    PubMed

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

    2010-03-01

    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

  17. A fluorescence-based high throughput assay for the determination of small molecule–human serum albumin protein binding

    PubMed Central

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

    2014-01-01

    Herein, we describe the development of a fluorescence-based high throughput assay to determine the small molecule binding towards human serum albumin (HSA). This innovative competition assay is based on the use of a novel fluorescent small molecule Red Mega 500 with unique spectroscopic and binding properties. The commercially available probe displays a large fluorescence intensity difference between the protein-bound and protein-unbound state. The competition of small molecules for HSA binding in the presence of probe resulted in low fluorescence intensities. The assay was evaluated with the LOPAC small molecule library of 1280 compounds identifying known high protein binders. The small molecule competition of HSA–Red Mega 500 binding was saturable at higher compound concentrations and exhibited IC50 values between 3–24 ?M. The compound affinity towards HSA was confirmed by isothermal titration calorimetry indicating that the new protein binding assay is a valid high throughput assay to determine plasma protein binding. PMID:24390461

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

    E-print Network

    Matthew L. Lister; Paul S. Smith

    2000-03-21

    A significant fraction of compact radio-loud quasars display most of the characteristics of relativistically beamed, high-optical polarization blazars, yet are weakly polarized in the optical regime. We have used the VLBA at 22 and 43 GHz to look for differences in the parsec-scale magnetic field structures of 18 high- and low-optically polarized, compact radio-loud quasars (HPQs and LPRQs, respectively). We find a strong correlation between the polarization level of the unresolved parsec-scale radio core at 43 GHz and overall optical polarization of the source, which suggests a common (possibly co-spatial) origin for the emission at these two wavelengths. The magnetic fields of the polarized 43 GHz radio cores are aligned roughly transverse to the jet axis. Similar orientations are seen in the optical, suggesting that the polarized flux at both wavelengths is due to one or more strong transverse shocks located very close to the base of the jet. In LPRQs, these shocks appear to be weak near the core, and gradually increase in strength down the jet. The LPRQs in our sample tend to have less luminous radio cores than the HPQs, and jet components with magnetic fields predominantly parallel to the flow. The components in HPQ jets, on the other hand, tend to have transverse alignments. These differences cannot be accounted for by a simple model in which HPQs and LPRQs are the same type of object, seen at different angles to the line of sight. A more likely scenario is that LPRQs represent a quiescent phase of blazar activity, in which the inner jet flow does not undergo strong shocks.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    Context. The vacuum-UV (VUV) absorption cross sections of most molecular solids present in interstellar ice mantles with the exception of H2O, NH3, and CO2 have not been reported yet. Models of ice photoprocessing depend on the VUV absorption cross section of the ice to estimate the penetration depth and radiation dose, and in the past, gas phase cross section values were used as an approximation. Aims: We aim to estimate the VUV absorption cross section of molecular ice components. Methods: Pure ices composed of CO, H2O, CH3OH, NH3, or H2S were deposited at 8 K. The column density of the ice samples was measured in situ by infrared spectroscopy in transmittance. VUV spectra of the ice samples were collected in the 120-160 nm (10.33-7.74 eV) range using a commercial microwave-discharged hydrogen flow lamp. Results: We provide VUV absorption cross sections of the reported molecular ices. Our results agree with those previously reported for H2O and NH3 ices. Vacuum-UV absorption cross section of CH3OH, CO, and H2S in solid phase are reported for the first time. H2S presents the highest absorption in the 120-160 nm range. Conclusions: Our method allows fast and readily available VUV spectroscopy of ices without the need to use a synchrotron beamline. We found that the ice absorption cross sections can be very different from the gas-phase values, and therefore, our data will significantly improve models that simulate the VUV photoprocessing and photodesorption of ice mantles. Photodesorption rates of pure ices, expressed in molecules per absorbed photon, can be derived from our data. Data can be found at http://ghosst.osug.fr/

  20. Pressure-induced penetration of guest molecules in high-silica zeolites: the case of mordenite.

    PubMed

    Arletti, R; Leardini, L; Vezzalini, G; Quartieri, S; Gigli, L; Santoro, M; Haines, J; Rouquette, J; Konczewicz, L

    2015-10-01

    A synthetic high-silica mordenite (HS-MOR) has been compressed in both non-penetrating (silicone oil, s.o.) and penetrating [methanol?:?ethanol?:?water (16?:?3?:?1) (m.e.w.), water?:?ethanol (3?:?1) (w.e.), and ethylene glycol (e.gl.)] pressure transmitting media (PTM). In situ high-pressure (HP) synchrotron X-ray powder diffraction (XRPD) experiments allowed the unit cell parameters to be followed up to 1.6, 1.8, 8.4, and 6.7 GPa in s.o., w.e., m.e.w., and e.gl., respectively. Moreover, e.gl. was also used as a PTM in in situ HP Raman and ex situ IR experiments. The structural refinement of HS-MOR compressed in e.gl. at 0.1 GPa - the lowest investigated pressure - revealed the presence of 3.5 ethylene glycol molecules per unit cell. The infrared spectrum of the recovered sample, after compression to 1 GPa, is consistent with the insertion of ethylene glycol molecules in the pores. XRPD and Raman spectroscopy experiments performed under pressure indicated the insertion of a small number of guest molecules. Ethylene glycol is partially retained inside mordenite upon pressure release. A symmetry lowering was observed in s.o. above 0.8 GPa, while above 1.6 GPa the patterns indicated a rapid loss of long range order. From ambient pressure (Pamb) to 1.6 GPa, a high cell volume contraction (?V = -9.5%) was determined. The patterns collected with penetrating PTM suggested the penetration of guest molecules into the porous host matrix, starting from a very low P regime. The entrapment of PTM molecules inside micropores contributes to the stiffening of the structure and, as a consequence, to the decrease of the compressibility with respect to that measured in s.o. From the structural point of view, HS-MOR reacts to compression and to the penetration of different guest species with appropriate framework deformations. Interestingly, ethylene glycol is partially retained inside mordenite upon pressure release, which is of importance for potential application of this composite material. PMID:26325490

  1. Solution-processed new porphyrin-based small molecules as electron donors for highly efficient organic photovoltaics.

    PubMed

    Chen, Song; Xiao, Liangang; Zhu, Xunjin; Peng, Xiaobing; Wong, Wai-Kwok; Wong, Wai-Yeung

    2015-10-01

    A series of unsymmetrical ?-conjugated small molecules have been constructed from meso-alkyl substituted porphyrins as the central unit and 3-ethylrhodanine as the terminal group. Using PC71BM as an acceptor, and these small molecules as electron donors in solution-processed bulk-heterojunction solar cells, a high power conversion efficiency of 6.49% has been achieved. PMID:26248887

  2. Spin Torque Oscillators with Highly Spin-Polarized Heusler Alloy

    NASA Astrophysics Data System (ADS)

    Seki, Takeshi; Yamamoto, Tatsuya; Takanashi, Koki

    2015-03-01

    An intriguing spin torque device is the spin torque oscillator (STO). An important issue for STOs from the viewpoint of practical use is to enhance the rf output power (Pout). Since Pout is roughly proportional to the square of the magnetoresistance (MR) ratio, a ferromagnetic material showing a large MR effect is a candidate for high-performance STO. In this study, we have developed high-power all-metal STOs with a full Heusler Co2Fe0.4Mn0.6Si (CFMS) showing a large MR effect. The present STOs consist of current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) stacks of CFMS |Ag |CFMS. A pillar-shaped STO showed clear auto-oscillation. The large Pout of 23.7 nW was obtained owing to its out-of-plane magnetization precession. Simultaneously, the oscillation linewidth showed the minimum value of 10 MHz. On the other hand, a point-contact-type STO showed auto-oscillation even at zero external magnetic field, and the oscillation mode was drastically changed as the bias current was increased. The large Pout for both STOs indicates the CPP-GMR devices with CFMS layers are promising for high performance STO.

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    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 2×108 bits/cm2 was obtained on a 60×42 µm2 area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density.

  4. On-bead antibody-small molecule conjugation using high-capacity magnetic beads.

    PubMed

    Nath, Nidhi; Godat, Becky; Benink, Hélène; Urh, Marjeta

    2015-11-01

    Antibodies labeled with small molecules such as fluorophore, biotin or drugs play an important role in various areas of biological research, drug discovery and diagnostics. However, the majority of current methods for labeling antibodies is solution-based and has several limitations including the need for purified antibodies at high concentrations and multiple buffer exchange steps. In this study, a method (on-bead conjugation) is described that addresses these limitations by combining antibody purification and conjugation in a single workflow. This method uses high capacity-magnetic Protein A or Protein G beads to capture antibodies directly from cell media followed by conjugation with small molecules and elution of conjugated antibodies from the beads. High-capacity magnetic antibody capture beads are key to this method and were developed by combining porous and hydrophilic cellulose beads with oriented immobilization of Protein A and Protein G using HaloTag technology. With a variety of fluorophores it is shown that the on-bead conjugation method is compatible with both thiol- and amine-based chemistry. This method enables simple and rapid processing of multiple samples in parallel with high-efficiency antibody recovery. It is further shown that recovered antibodies are functional and compatible with downstream applications. PMID:26316179

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  6. High-resolution spatiotemporal analysis of receptor dynamics by single-molecule fluorescence microscopy.

    PubMed

    Sungkaworn, Titiwat; Rieken, Finn; Lohse, Martin J; Calebiro, Davide

    2014-01-01

    Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., kinetics, coexistence of different states and populations, transient interactions), which are typically hidden in ensemble measurements, such as those obtained with standard biochemical or microscopy methods. Thus, dynamic events, such as receptor-receptor interactions, can be followed in real time in a living cell with high spatiotemporal resolution. This protocol describes a method based on labeling with small and bright organic fluorophores and total internal reflection fluorescence (TIRF) microscopy to directly visualize single receptors on the surface of living cells. This approach allows one to precisely localize receptors, measure the size of receptor complexes, and capture dynamic events such as transient receptor-receptor interactions. The protocol provides a detailed description of how to perform a single-molecule experiment, including sample preparation, image acquisition and image analysis. As an example, the application of this method to analyze two G-protein-coupled receptors, i.e., ?2-adrenergic and ?-aminobutyric acid type B (GABAB) receptor, is reported. The protocol can be adapted to other membrane proteins and different cell models, transfection methods and labeling strategies. PMID:25145374

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

    SciTech Connect

    Dragan Isailovic

    2005-12-17

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

  8. Unitary Superfluidity Of Polarized Fermionic Gases In Highly Elongated Traps

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

    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.

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

    SciTech Connect

    Assary, R. S.; Curtiss, L. A.

    2012-02-01

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

  10. Non perturbative approach for a polar and polarizable linear molecule in an inhomogeneous electric field: Application to molecular beam deviation experiments

    NASA Astrophysics Data System (ADS)

    Benichou, E.; Allouche, A. R.; Antoine, R.; Aubert-Frecon, M.; Bourgoin, M.; Broyer, M.; Dugourd, Ph.; Hadinger, G.; Rayane, D.

    A non perturbative approach is used to solve the problem of a rigid linear molecule with both a permanent dipole moment and a static dipole polarizability, in a static electric field. Eigenenergies are obtained and compared to perturbative low field and high field approximations. Analytical expressions for the orientation parameters and for the gradient of the energy are given. This non perturbative approach is applied to the simulation of beam deviation experiments in strong electric field. Results of simulations are given for inhomogeneous alkali dimers. For LiNa, the simulations are compared to experimental data. For LiK, deviation profiles have been simulated in order to prepare future experiments on this molecule.

  11. High-order polarization mode crosstalk effect: a calibration scheme of white light-based optical coherence domain polarimetry

    NASA Astrophysics Data System (ADS)

    Wu, Bing; Yang, Jun; Zhang, Jianzhong; Liang, Shuai; Yu, Zhangjun; Yuan, Yonggui; Peng, Feng; Zhou, Ai; Zhang, Yu; Yuan, Libo

    2015-09-01

    We propose a calibration scheme of the white light interferometer based optical coherence domain polarimetry (OCDP), which could be used to measure the ultra-weak polarization mode crosstalk (PMC) or the ultra-high polarization extinction ratio (PER) of different polarization optical devices. The calibration depends on the first and second order PMC effect of different polarization devices in series. The first and second PMCs between 0 and -90dB, established by five pieces of polarization maintaining fiber (PMF) and a Y-waveguide, is used to prove its feasibility.

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  13. Possibilitiesfor a high intensity polarized slow positron sourceusing 13N A. P. Mills. Jr.

    E-print Network

    Mills, Allen P.

    Ps and of Psz,correlationeffectson the negative work function emission of high density positrons from a solid and 58Co,all of which suffer somewhat from difficult preparation requirements associatedwith a nuclear be suitable for an intense polarized source. The thick target yield of 13Nfor a given power is almost constant

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

    E-print Network

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

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

    E-print Network

    Greiner, Jochen

    High spectral and time resolution observations of the eclipsing polar RX J0719.2+6557 G. H Abstract. We present phase­resolved spectral and multicolor CCD­ photometric observations of the eclipsing. The light curves and eclipse profiles provide additional information about the system geometry. 1

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

    SciTech Connect

    Andrew Puckett

    2010-02-01

    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.

  17. X-Ray Polarization from High-mass X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Kallman, T.; Dorodnitsyn, A.; Blondin, J.

    2015-12-01

    X-ray astronomy allows study of objects that may be associated with compact objects, i.e., neutron stars or black holes, and also may contain strong magnetic fields. Such objects are categorically nonspherical, and likely noncircular when projected on the sky. Polarization allows study of such geometric effects, and X-ray polarimetry is likely to become feasible for a significant number of sources in the future. Potential targets for future X-ray polarization observations are the high-mass X-ray binaries (HMXBs), which consist of a compact object in orbit with an early-type star. In this paper we show that X-ray polarization from HMXBs has a distinct signature that depends on the source inclination and orbital phase. The presence of the X-ray source displaced from the star creates linear polarization even if the primary wind is spherically symmetric whenever the system is viewed away from conjunction. Direct X-rays dilute this polarization whenever the X-ray source is not eclipsed; at mid-eclipse the net polarization is expected to be small or zero if the wind is circularly symmetric around the line of centers. Resonance line scattering increases the scattering fraction, often by large factors, over the energy band spanned by resonance lines. Real winds are not expected to be spherically symmetric, or circularly symmetric around the line of centers, owing to the combined effects of the compact object gravity and ionization on the wind hydrodynamics. A sample calculation shows that this creates polarization fractions ranging up to tens of percent at mid-eclipse.

  18. Hyperon Polarization and Single Spin Left-Right Asymmetry in Inclusive Production Processes at High Energies

    SciTech Connect

    Zuo-tang, L.; Boros, C.; Boros, C.

    1997-11-01

    It is shown that the polarization of hyperons observed in high energy collisions using unpolarized hadron beams and unpolarized nucleon or nuclear targets is closely related to the left-right asymmetries observed in single spin inclusive hadron production processes. The relationship is most obvious for the production of the hyperons which have only one common valence quark with the projectile. Examples of this kind are given. Further implications of the existence of large polarization for a hyperon which has two valence quarks in common with the projectile and their consequences are discussed. A comparison with the available data is made. Further tests are suggested. {copyright} {ital 1997} {ital The American Physical Society}

  19. Hyperon polarization and single spin left-right asymmetry in inclusive production processes at high energies

    E-print Network

    Liang Zuo-tang; C. Boros

    1997-11-25

    It is shown that the polarization of hyperons observed in high energy collisions using unpolarized hadron beams and unpolarized nucleon or nuclear targets is closely related to the left-right asymmetries observed in single spin inclusive hadron production processes. The relationship is most obvious for the production of the hyperons which have only one common valence quark with the projectile. Examples of this kind are given. Further implications of the existence of large polarization for hyperon which has two valence quarks in common with the projectile and their consequences are discussed. A comparison with the available data is made. Further tests are suggested.

  20. Polarized high pressure {sup 3}H-vectore target at MAMI

    SciTech Connect

    Rohe, Daniela; Becker, J.; Bermuth, J.; Deninger, A.; Ebert, M.; Grossmann, T.; Lauer, L.; Otten, E. W.; Rohe, D.; Surkau, R.; Bartsch, P.; Baumann, D.; Boehm, R.; Caprano, T.; Clawiter, N.; Derber, S.; Ding, M.; Distler, M.; Ebbes, A.; Ewald, I.

    1998-01-20

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

  1. Highly Polarized Raman Scattering Anisotropy in Single GaN Nanowires

    SciTech Connect

    Sutter, E.; Schäfer-Nolte, E.O.; Stoica, T.; Gotschke, T.; Limbach, F.; Sutter, P.; Calarco, R.

    2010-03-01

    Single GaN nanowires and larger GaN ensembles are investigated by Raman spectroscopy. Spectra of nanowire ensembles prove the high crystal quality and are in agreement with selection rules for the wurtzite structure. Single nanowires are studied with a spatial resolution of the order of 400 nm for different polarization directions of the incident laser beam relative to the nanowire axis. In the single wire spectrum, only the A{sub 1}(TO) was observed and the Raman intensity was suppressed for perpendicular polarization. These results confirm that Raman scattering in isolated GaN nanowires is governed by size effects.

  2. Development of high-performance alkali-hybrid polarized 3He targets for electron scattering

    NASA Astrophysics Data System (ADS)

    Singh, Jaideep T.; Dolph, P. A. M.; Tobias, W. A.; Averett, T. D.; Kelleher, A.; Mooney, K. E.; Nelyubin, V. V.; Wang, Yunxiao; Zheng, Yuan; Cates, G. D.

    2015-05-01

    Background: Polarized 3He targets have been used as effective polarized neutron targets for electron scattering experiments for over twenty years. Over the last ten years, the effective luminosity of polarized 3He targets based on spin-exchange optical pumping has increased by over an order of magnitude. This has come about because of improvements in commercially-available lasers and an improved understanding of the physics behind the polarization process. Purpose: We present the development of high-performance polarized 3He targets for use in electron scattering experiments. Improvements in the performance of polarized 3He targets, target properties, and operating parameters are documented. Methods: We utilize the technique of alkali-hybrid spin-exchange optical pumping to polarize the 3He targets. Spectrally narrowed diode lasers used for the optical pumping greatly improved the performance. A simulation of the alkali-hybrid spin-exchange optical pumping process was developed to provide guidance in the design of the targets. Data was collected during the characterization of 24 separate glass target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. Results: From the data obtained we made determinations of the so-called X -factors that quantify a temperature-dependent and as-yet poorly understood spin-relaxation mechanism that limits the maximum achievable 3He polarization to well under 100%. The presence of the X -factor spin-relaxation mechanism was clearly evident in our data. Good agreement between the simulation and the actual target performance was obtained by including details such as off-resonant optical pumping. Included in our results is a measurement of the K -3He spin-exchange rate coefficient kseK=(7.46 ±0.62 ) ×10-20cm3/s over the temperature range 503 K to 563 K. Conclusions: In order to achieve high performance under the operating conditions described in this paper, the K to Rb alkali vapor density ratio should be about 5 ±2 and the line width of the optical pumping lasers should be no more than 0.3 nm. Our measurements of the X -factors under these conditions seem to indicate the 3He polarization is limited to ?90 %. The simulation results, now benchmarked against experimental data, are useful for the design of future targets. Further work is required to better understand the temperature dependence of the X -factor spin-relaxation mechanism and the limitations of our optical pumping simulation.

  3. High Resolution Continuous Flow Analysis System for Polar Ice Cores

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

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

    E-print Network

    Barnes, Alexander B. (Alexander Benjamin)

    2011-01-01

    Dynamic Nuclear Polarization (DNP) has exploded in popularity over the last few years, finally realizing its potential to overcome the detrimental lack of sensitivity that has plagued performing NMR experiments. Applied ...

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

    PubMed Central

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

    2013-01-01

    Polarized light microscopy provides unique opportunities for analyzing the molecular order in man-made and natural materials, including biological structures inside living cells, tissues, and whole organisms. 20 years ago, the LC-PolScope was introduced as a modern version of the traditional polarizing microscope enhanced by liquid crystal devices for the control of polarization, and by electronic imaging and digital image processing for fast and comprehensive image acquisition and analysis. The LCPolScope is commonly used for birefringence imaging, analyzing the spatial and temporal variations of the differential phase delay in ordered and transparent materials. Here we describe an alternative use of the LC-PolScope for imaging the polarization dependent transmittance of dichroic materials. We explain the minor changes needed to convert the instrument between the two imaging modes, discuss the relationship between the quantities measured with either instrument, and touch on the physical connection between refractive index, birefringence, transmittance, diattenuation, and dichroism. PMID:24273640

  6. High Resolution UV Emission Spectroscopy of Molecules Excited by Electron Impact

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  7. Pump-probe study of atoms and small molecules with laser driven high order harmonics

    NASA Astrophysics Data System (ADS)

    Cao, Wei

    A commercially available modern laser can emit over 1015 photons within a time window of a few tens of femtoseconds (10-15second), which can be focused into a spot size of about 10 mum, resulting in a peak intensity above 1014W/cm2. This paves the way for table-top strong field physics studies such as above threshold ionization (ATI), non-sequential double ionization (NSDI), high order harmonic generation (HHG), etc.. Among these strong laser-matter interactions, high order harmonic generation, which combines many photons of the fundamental laser field into a single photon, offers a unique way to generate light sources in the vacuum ultraviolet (VUV) or extreme ultraviolet (EUV) region. High order harmonic photons are emitted within a short time window from a few tens of femtoseconds down to a few hundreds of attoseconds (10 -18second). This highly coherent nature of HHG allows it to be synchronized with an infrared (IR) laser pulse, and the pump-probe technique can be adopted to study ultrafast dynamic processes in a quantum system. The major work of this thesis is to develop a table-top VUV(EUV) light source based on HHG, and use it to study dynamic processes in atoms and small molecules with the VUV(EUV)-pump IR-probe method. A Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) apparatus is used for momentum imaging of the interaction products. Two types of high harmonic pump pulses are generated and applied for pump-probe studies. The first one consists of several harmonics forming a short attosecond pulse train (APT) in the EUV regime (around 40 eV). We demonstrate that, (1) the auto-ionization process triggered by the EUV in cation carbon-monoxide and oxygen molecules can be modified by scanning the EUV-IR delay, (2) the phase information of quantum trajectories in bifurcated high harmonics can be extracted by performing an EUV-IR cross-correlation experiment, thus disclosing the macroscopic quantum control in HHG. The second type of high harmonic source implemented in this work is a single harmonic in the VUV regime (around 15 eV) filtered out from a monochromator. Experiments on D2 molecules have been conducted using the 9th or the 11th harmonic as the pump pulse. Novel dissociative ionization pathways via highly excited states of D 2 have been revealed, thus suggesting potential applications for time-resolved studies and control of photochemistry processes.

  8. High-intracavity-power thin-disk laser for the alignment of molecules.

    PubMed

    Deppe, Bastian; Huber, Günter; Kränkel, Christian; Küpper, Jochen

    2015-11-01

    We propose a novel approach for strong alignment of gas-phase molecules for experiments at arbitrary repetition rates. A high-intracavity-power continuous-wave laser will provide the necessary ac electric field of 1010-1011 W/cm2. We demonstrate thin-disk lasers based on Yb:YAG and Yb:Lu2O3 in a linear high-finesse resonator providing intracavity power levels in excess of 100 kW at pump power levels on the order of 50 W. The multi-longitudinal-mode operation of this laser avoids spatial-hole burning even in a linear standing-wave resonator. The system will be scaled up as in-vacuum system to allow for the generation of fields of 1011 W/cm2. This system will be directly applicable for experiments at modern X-ray light sources, such as synchrotrons or free-electron lasers, which operate at various very high repetition rates. This would allow to record molecular movies through temporally resolved diffractive imaging of fixed-in-space molecules, as well as the spectroscopic investigation of combined X-ray-NIR strong-field effects of atomic and molecular systems. PMID:26561120

  9. High-intracavity-power thin-disk laser for the alignment of molecules

    E-print Network

    Deppe, Bastian; Kränkel, Christian; Küpper, Jochen

    2015-01-01

    We propose a novel approach for strong alignment of gas-phase molecules for experiments at arbitrary repetition rates. A high-intracavity-power continuous-wave laser will provide the necessary ac electric field of $\\!10^{10}$- $10^{11}~\\text{W}/\\text{cm}^2$. We demonstrate thin-disk lasers based on Yb:YAG and Yb:Lu$_2$O$_3$ in a linear high-finesse resonator providing intracavity power levels in excess of 100~kW at pump power levels on the order of 50~W. The multi-longitudinal-mode operation of this laser avoids spatial-hole burning even in a linear standing-wave resonator. The system will be scaled up as in-vacuum system to allow for the generation of fields of $10^{11}~\\text{W}/\\text{cm}^2$. This system will be directly applicable for experiments at modern X-ray light sources, such as synchrotrons or free-electron lasers, which operate at various very high repetition rates. This would allow to record molecular movies through temporally resolved diffractive imaging of fixed-in-space molecules, as well as the...

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

    DOE PAGESBeta

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

    2015-02-17

    Single-molecule fluorescence microscopy is a powerful approach to observe biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual, labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Then, making use ofmore »short-distance energy-transfer mechanisms, the fluorescence from only those proteins bound to their substrate are selectively activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 (IFI16) with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease (pVIc-AVP) on DNA in the presence of a background of hundreds of nM Cy5 fluorophore.« less

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

    SciTech Connect

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

    2015-02-17

    Single-molecule fluorescence microscopy is a powerful approach to observe biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual, labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Then, making use of short-distance energy-transfer mechanisms, the fluorescence from only those proteins bound to their substrate are selectively activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 (IFI16) with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease (pVIc-AVP) on DNA in the presence of a background of hundreds of nM Cy5 fluorophore.

  12. Compartmentalized microchannel array for high-throughput analysis of single cell polarized growth and dynamics

    SciTech Connect

    Geng, Tao; Bredeweg, Erin L.; Szymanski, Craig J.; Liu, Bingwen; Baker, Scott E.; Orr, Galya; Evans, James E.; Kelly, Ryan T.

    2015-11-04

    Interrogating polarized growth is technologically challenging due to extensive cellular branching and uncontrollable environmental conditions in conventional assays. Here we present a robust and high-performance microfluidic system that enables observations of polarized growth with enhanced temporal and spatial control over prolonged periods. The system has built-in tunability and versatility to accommodate a variety of science applications requiring precisely controlled environments. Using the model filamentous fungus, Neurospora crassa, this microfluidic system enabled direct visualization and analysis of cellular heterogeneity in a clonal fungal cell population, nuclear distribution and dynamics at the subhyphal level, and quantitative dynamics of gene expression with single hyphal compartment resolution in response to carbon source starvation and exchange experiments. Although the microfluidic device is demonstrated on filamentous fungi, our technology is immediately extensible to a wide array of other biosystems that exhibit similar polarized cell growth with applications ranging from bioenergy production to human health.

  13. Compartmentalized microchannel array for high-throughput analysis of single cell polarized growth and dynamics.

    PubMed

    Geng, Tao; Bredeweg, Erin L; Szymanski, Craig J; Liu, Bingwen; Baker, Scott E; Orr, Galya; Evans, James E; Kelly, Ryan T

    2015-01-01

    Interrogating polarized growth is technologically challenging due to extensive cellular branching and uncontrollable environmental conditions in conventional assays. Here we present a robust and high-performance microfluidic system that enables observations of polarized growth with enhanced temporal and spatial control over prolonged periods. The system has built-in tunability and versatility to accommodate a variety of scientific applications requiring precisely controlled environments. Using the model filamentous fungus, Neurospora crassa, our microfluidic system enabled direct visualization and analysis of cellular heterogeneity in a clonal fungal cell population, nuclear distribution and dynamics at the subhyphal level, and quantitative dynamics of gene expression with single hyphal compartment resolution in response to carbon source starvation and exchange. Although the microfluidic device is demonstrated on filamentous fungi, the technology is immediately extensible to a wide array of other biosystems that exhibit similar polarized cell growth, with applications ranging from bioenergy production to human health. PMID:26530004

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

    E-print Network

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

    2011-09-15

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

  15. High spin polarization in CoFeMnGe equiatomic quaternary Heusler alloy

    SciTech Connect

    Bainsla, Lakhan; Suresh, K. G.; Nigam, A. K.; Manivel Raja, M.; Varaprasad, B. S. D. Ch. S.; Takahashi, Y. K.; Hono, K.

    2014-11-28

    We report the structure, magnetic property, and spin polarization of CoFeMnGe equiatomic quaternary Heusler alloy. The alloy was found to crystallize in the cubic Heusler structure (prototype LiMgPdSn) with considerable amount of DO{sub 3} disorder. Thermal analysis result indicated the Curie temperature is about 750?K without any other phase transformation up to melting temperature. The magnetization value was close to that predicted by the Slater-Pauling curve. Current spin polarization of P?=?0.70?±?0.01 was deduced using point contact andreev reflection measurements. The temperature dependence of electrical resistivity has been fitted in the temperature range of 5–300?K in order to check for the half metallic behavior. Considering the high spin polarization and Curie temperature, this material appears to be promising for spintronic applications.

  16. Compartmentalized microchannel array for high-throughput analysis of single cell polarized growth and dynamics

    PubMed Central

    Geng, Tao; Bredeweg, Erin L.; Szymanski, Craig J.; Liu, Bingwen; Baker, Scott E.; Orr, Galya; Evans, James E.; Kelly, Ryan T.

    2015-01-01

    Interrogating polarized growth is technologically challenging due to extensive cellular branching and uncontrollable environmental conditions in conventional assays. Here we present a robust and high-performance microfluidic system that enables observations of polarized growth with enhanced temporal and spatial control over prolonged periods. The system has built-in tunability and versatility to accommodate a variety of scientific applications requiring precisely controlled environments. Using the model filamentous fungus, Neurospora crassa, our microfluidic system enabled direct visualization and analysis of cellular heterogeneity in a clonal fungal cell population, nuclear distribution and dynamics at the subhyphal level, and quantitative dynamics of gene expression with single hyphal compartment resolution in response to carbon source starvation and exchange. Although the microfluidic device is demonstrated on filamentous fungi, the technology is immediately extensible to a wide array of other biosystems that exhibit similar polarized cell growth, with applications ranging from bioenergy production to human health. PMID:26530004

  17. High-Contrast NIR Polarization Imaging of MWC480

    NASA Technical Reports Server (NTRS)

    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

    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.

  18. X-ray Polarization from High Mass X-ray Binaries

    E-print Network

    Kallman, T; Blondin, J

    2015-01-01

    X-ray astronomy allows study of objects which may be associated with compact objects, i.e. neutron stars or black holes, and also may contain strong magnetic fields. Such objects are categorically non-spherical, and likely non-circular when projected on the sky. Polarization allows study of such geoemetric effects, and X-ray polarimetry is likely to become feasible for a significant number of sources in the future. A class of potential targets for future X-ray polarization observations is the high mass X-ray binaries (HMXBs), which consist of a compact object in orbit with an early type star. In this paper ws show that X-ray polarization from HMXBs has a distinct signature which depends on the source inclination and orbital phase. The presence of the X-ray source displaced from the star creates linear polarization even if the primary wind is spherically symmetric whenever the system is viewed away from conjunction. Direct X-rays dilute this polarization whenever the X-ray source is not eclipsed; at mid-eclips...

  19. PolarBase: a data base of high resolution spectropolarimetric stellar observations

    E-print Network

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

    2014-01-01

    PolarBase is an evolving data base that contains all stellar data collected with the ESPaDOnS and NARVAL high-resolution spectropolarimeters, in their reduced form, as soon as they become public. As of early 2014, observations of 2,000 stellar objects throughout the Hertzsprung-Russell diagram are available. Intensity spectra are available for all targets, and the majority of the observations also include simultaneous spectra in circular or linear polarization, with the majority of the polarimetric measurements being performed only in circularly polarized light (Stokes V). Observations are associated with a cross-correlation pseudo-line profile in all available Stokes parameters, greatly increasing the detectability of weak polarized signatures. Stokes V signatures are detected for more than 300 stars of all masses and evolutionary stages, and linear polarization is detected in 35 targets. The detection rate in Stokes V is found to be anti-correlated with the stellar effective temperature. This unique set of ...

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

    DOEpatents

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

    2000-01-01

    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.

  1. High-order harmonic generation from polyatomic molecules including nuclear motion and a nuclear modes analysis

    SciTech Connect

    Madsen, C. B.; Abu-samha, M.; Madsen, L. B.

    2010-04-15

    We present a generic approach for treating the effect of nuclear motion in high-order harmonic generation from polyatomic molecules. Our procedure relies on a separation of nuclear and electron dynamics where we account for the electronic part using the Lewenstein model and nuclear motion enters as a nuclear correlation function. We express the nuclear correlation function in terms of Franck-Condon factors, which allows us to decompose nuclear motion into modes and identify the modes that are dominant in the high-order harmonic generation process. We show results for the isotopes CH{sub 4} and CD{sub 4} and thereby provide direct theoretical support for a recent experiment [S. Baker et al., Science 312, 424 (2006)] that uses high-order harmonic generation to probe the ultrafast structural nuclear rearrangement of ionized methane.

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

    PubMed

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

    2014-10-17

    Nitrogen-rich graphene sheets were successfully achieved via facile thermal condensation of glucose and dicyandiamide at different temperatures during which dicyandiamide acts both as nitrogen source and sacrifice template. Devoid of surfactants or poisonous organic solvents, this small-molecule synthetic approach is a simple and cost-effective way to obtain nitrogen-rich graphene sheets (NRGS) with high specific surface area and large pore volume. Shown to be a promising anode material, the NRGS displayed high reversible capacity, excellent rate capability, and superior cycle performance. The superior lithium-storage performance is ascribed to the unique features of NRGS, including a large quantity of defects due to the high nitrogen doping level, favorable lithium ion transportation channels by virtue of the large surface area, and ultrahigh pore volume, as well as the crumpled two-dimensional structure. PMID:25258306

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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.

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

    PubMed

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

    2009-04-01

    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

  5. Organizing polarized delivery of exosomes at synapses.

    PubMed

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

    2015-04-01

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

  6. Fullerene-free small molecule organic solar cells with a high open circuit voltage of 1.15 V.

    PubMed

    Ni, Wang; Li, Miaomiao; Kan, Bin; Liu, Feng; Wan, Xiangjian; Zhang, Qian; Zhang, Hongtao; Russell, Thomas P; Chen, Yongsheng

    2016-01-11

    A new small molecule named DTBTF with thiobarbituric acid as a terminal group was designed and synthesized as an acceptor for organic photovoltaic applications. DTBTF exhibits strong absorption in the visible region, and a relatively high lying LUMO energy level (-3.62 eV). All-small-molecule organic solar cells based on DR3TSBDT:DTBTF blend films show a considerable PCE of 3.84% with a high Voc of 1.15 V. PMID:26538446

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

    E-print Network

    Chu, Shih-I

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

  8. Descent from the polar mesosphere and anomalously high stratopause observed in 8 years of water vapor and

    E-print Network

    Limpasuvan, Varavut

    from the polar mesosphere and anomalously high stratopause observed in 8 years of water vaporClick Here for Full Article Descent from the polar mesosphere and anomalously high stratopause observed in 8 years of water vapor and temperature satellite observations by the Odin Sub

  9. Diffusion of Dye Molecules in High Concentration Dye/Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Walhout, Peter K.; Ediger, M. D.

    1998-03-01

    We introduce a novel technique for studying the translational diffusion of small molecules present in high concentration (1-10 wt. %) in a polymer matrix. Diffusion in this concentration regime is relevant to the dye sublimation color printing process but is virtually unexplored at temperatures close to T_g. A 1-10 ?m thin film of the dye/polymer melt is solvent cast directly onto a Ronchi ruling glass substrate. A periodic concentration profile is generated upon irradiation with an intense laser pulse which photobleaches a small fraction of the dye molecules. The subsequent time-dependent transmission of a weak probe beam reveals the diffusive dynamics associated with the smoothing of the concentration profile. The use of high-density rulings allows measurements of translational diffusion coefficients as small as 10-12 cm^2/sec. We report results on the concentration and temperature-dependent diffusion of an indol-pyrazol dye in a poly(vinyl butyral) thin film.

  10. A model for energy transfer in collisions of atoms with highly excited molecules.

    PubMed

    Houston, Paul L; Conte, Riccardo; Bowman, Joel M

    2015-05-21

    A model for energy transfer in the collision between an atom and a highly excited target molecule has been developed on the basis of classical mechanics and turning point analysis. The predictions of the model have been tested against the results of trajectory calculations for collisions of five different target molecules with argon or helium under a variety of temperatures, collision energies, and initial rotational levels. The model predicts selected moments of the joint probability distribution, P(Jf,?E) with an R(2) ? 0.90. The calculation is efficient, in most cases taking less than one CPU-hour. The model provides several insights into the energy transfer process. The joint probability distribution is strongly dependent on rotational energy transfer and conservation laws and less dependent on vibrational energy transfer. There are two mechanisms for rotational excitation, one due to motion normal to the intermolecular potential and one due to motion tangential to it and perpendicular to the line of centers. Energy transfer is found to depend strongly on the intermolecular potential and only weakly on the intramolecular potential. Highly efficient collisions are a natural consequence of the energy transfer and arise due to collisions at "sweet spots" in the space of impact parameter and molecular orientation. PMID:25907301

  11. Conjugated Polymer-Small Molecule Alloy Leads to High Efficient Ternary Organic Solar Cells.

    PubMed

    Zhang, Jianqi; Zhang, Yajie; Fang, Jin; Lu, Kun; Wang, Zaiyu; Ma, Wei; Wei, Zhixiang

    2015-07-01

    Ternary organic solar cells are promising candidates for bulk heterojunction solar cells; however, improving the power conversion efficiency (PCE) is quite challenging because the ternary system is complicated on phase separation behavior. In this study, a ternary organic solar cell (OSC) with two donors, including one polymer (PTB7-Th), one small molecule (p-DTS(FBTTH2)2), and one acceptor (PC71BM), is fabricated. We propose the two donors in the ternary blend forms an alloy. A notable averaged PCE of 10.5% for ternary OSC is obtained due to the improvement of the fill factor (FF) and the short-circuit current density (J(sc)), and the open-circuit voltage (V(oc)) does not pin to the smaller V(oc) of the corresponding binary blends. A highly ordered face-on orientation of polymer molecules is obtained due to the formation of an alloy structure, which facilitates the enhancement of charge separation and transport and the reduction of charge recombination. This work indicates that a high crystallinity and the face-on orientation of polymers could be obtained by forming alloy with two miscible donors, thus paving a way to largely enhance the PCE of OSCs by using the ternary blend strategy. PMID:26052738

  12. Gas Separation Membranes Derived from High-Performance Immiscible Polymer Blends Compatibilized with Small Molecules.

    PubMed

    Panapitiya, Nimanka P; Wijenayake, Sumudu N; Nguyen, Do D; Huang, Yu; Musselman, Inga H; Balkus, Kenneth J; Ferraris, John P

    2015-08-26

    An immiscible polymer blend comprised of high-performance copolyimide 6FDA-DAM:DABA(3:2) (6FDD) and polybenzimidazole (PBI) was compatibilized using 2-methylimidazole (2-MI), a commercially available small molecule. Membranes were fabricated from blends of 6FDD:PBI (50:50) with and without 2-MI for H2/CO2 separations. The membranes demonstrated a matrix-droplet type microstructure as evident with scanning electron microscopy (SEM) imaging where 6FDD is the dispersed phase and PBI is the continuous phase. In addition, membranes with 2-MI demonstrated a uniform microstructure as observed by smaller and more uniformly dispersed 6FDD domains in contrast to 6FDD:PBI (50:50) blend membranes without 2-MI. This compatibilization effect of 2-MI was attributed to interfacial localization of 2-MI that lowers the interfacial energy similar to a surfactant. Upon the incorporation of 2-MI, the H2/CO2 selectivity improved remarkably, compared to the pure blend, and surpassed the Robeson's upper bound. To our knowledge, this is the first report of the use of a small molecule to compatibilize a high-performance immiscible polymer blend. This approach could afford a novel class of membranes in which immiscible polymer blends can be compatibilized in an economical and convenient fashion. PMID:26259013

  13. Solution-Processable Organic Molecule for High-Performance Organic Solar Cells with Low Acceptor Content.

    PubMed

    Wang, Kun; Guo, Bing; Xu, Zhuo; Guo, Xia; Zhang, Maojie; Li, Yongfang

    2015-11-11

    A new planar D2-A-D1-A-D2 structured organic molecule with bithienyl benzodithiophene (BDT) as central donor unit D1 and fluorine-substituted benzothiadiazole (BTF) as acceptor unit and alkyl-dithiophene as end group and donor unit D2, BDT-BTF, was designed and synthesized for the application as donor material in organic solar cells (OSCs). BDT-BTF shows a broad absorption in visible region, suitable highest occupied molecular orbital energy level of -5.20 eV, and high hole mobility of 1.07 × 10(-2) cm(2)/(V s), benefitted from its high coplanarity and strong crystallinity. The OSCs based on BDT-BTF as donor (D) and PC71BM as acceptor (A) at a D/A weight ratio of 3:1 without any extra treatment exhibit high photovoltaic performance with Voc of 0.85 V, Jsc of 10.48 mA/cm(2), FF of 0.66, and PCE of 5.88%. The morphological study by transmission electron microscopy reveals that the blend of BDT-BTF and PC71BM (3:1, w/w) possesses an appropriate interpenetrating D/A network for the exciton separation and charge carrier transport, which agrees well with the good device performance. The optimized D/A weight ratio of 3:1 is the lowest acceptor content in the active layer reported so far for the high-performance OSCs, and the organic molecules with the molecular structure like BDT-BTF could be promising high-performance donor materials in solution-processable OSCs. PMID:26492421

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  17. Topological Defect Structure and Annihilation in High-Polarization Freely Suspended Films

    NASA Astrophysics Data System (ADS)

    Zhu, Chenhui; Pattanaporkratana, Apichart; Maclennan, Joseph; Clark, Noel

    2007-03-01

    The texture of freely suspended liquid crystal SmC* films of a high polarization material C7 [4-(3-methyl-2-chloropentanoyloxy)-4'-heptyloxybiphenyl] is studied using polarized light microscopy. In particular, we focus on c-director defects with topological strength --1 found in the chessboard texture. Due to the competition between the elastic energy and the electrostatic energy of polarization splay, the c-director field near the defect core consists of four domains with homogenous orientation of the c-director inside each domain. The boundaries between domains are sharp and the c-director orientation jumps by 90 degrees at each boundary. We will present experimental and theoretical studies of the structure of these polarization-stabilized discontinuities. We will also present studies of the annihilation dynamics of +1 and --1 pairs of defects on this high-P material film and compare them to those on low-P material films. [1] E. Demikhov, Europhys. Lett. 25 (4), 259 (1994). [2] E. Demikhov and H. Stegemeyer, Liq. Cry. 18, 37 (1995). [3] Ch. Bahr and G. Heppke, Phys. Chem. 91, 925 (1987). [4] D. R. Link, N. Chattham, J.E. Maclennan, and N.A. Clark, Phys. Rev. E 71, 021704 (2005). This work is supported by NSF MRSEC Grant DMR0213918.

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

    SciTech Connect

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

    2006-02-27

    The GaAsP/GaAs strained superlattice photocathode structure has proven to be a significant advance for polarized electron sources operating with high peak currents per microbunch and relatively low duty factor. This is the characteristic type of operation for SLAC and is also planned for the ILC. This superlattice structure was studied at SLAC [1], and an optimum variation was chosen for the final stage of E-158, a high-energy parity violating experiment at SLAC. Following E-158, the polarized source was maintained on standby with the cathode being re-cesiated about once a week while a thermionic gun, which is installed in parallel with the polarized gun, supplied the linac electron beams. However, in the summer of 2005, while the thermionic gun was disabled, the polarized electron source was again used to provide electron beams for the linac. The performance of the photocathode 24 months after its only activation is described and factors making this possible are discussed.

  19. Analysis of polyatomic molecules using high resolution coherent two-dimensional spectroscopy: Application to nitrogen dioxide.

    PubMed

    Chen, Peter C; Mitchell, Kamilah

    2008-11-21

    The peak-sorting capabilities of high resolution coherent two-dimensional (2D) spectroscopy provide a new way of dealing with severe rotational congestion. This paper describes the application of this technique to the polyatomic molecule, NO(2). NO(2) is a primary component of photochemical smog and has a notoriously complex and congested spectrum that extends from the infrared to the ultraviolet regions. This spectrum is infamous for having an unusually high density of peaks and very few regular patterns. However, the coherent 2D spectrum of NO(2) shows a network consisting of numerous X-shaped patterns that mark the locations of vibronic origins. This paper describes how peak sorting leads to the formation of such patterns and how peak coupling can be used to conduct a rotational analysis of congested areas in the visible spectrum of NO(2). PMID:19026054

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

    SciTech Connect

    Myong, R. S.

    2014-05-15

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

  1. Highly precise quantification of protein molecules per cell during stress and starvation responses in Bacillus subtilis.

    PubMed

    Maa?, Sandra; Wachlin, Gerhild; Bernhardt, Jörg; Eymann, Christine; Fromion, Vincent; Riedel, Katharina; Becher, Dörte; Hecker, Michael

    2014-09-01

    Systems biology based on high quality absolute quantification data, which are mandatory for the simulation of biological processes, successively becomes important for life sciences. We provide protein concentrations on the level of molecules per cell for more than 700 cytosolic proteins of the Gram-positive model bacterium Bacillus subtilis during adaptation to changing growth conditions. As glucose starvation and heat stress are typical challenges in B. subtilis' natural environment and induce both, specific and general stress and starvation proteins, these conditions were selected as models for starvation and stress responses. Analyzing samples from numerous time points along the bacterial growth curve yielded reliable and physiologically relevant data suitable for modeling of cellular regulation under altered growth conditions. The analysis of the adaptational processes based on protein molecules per cell revealed stress-specific modulation of general adaptive responses in terms of protein amount and proteome composition. Furthermore, analysis of protein repartition during glucose starvation showed that biomass seems to be redistributed from proteins involved in amino acid biosynthesis to enzymes of the central carbon metabolism. In contrast, during heat stress most resources of the cell, namely those from amino acid synthetic pathways, are used to increase the amount of chaperones and proteases. Analysis of dynamical aspects of protein synthesis during heat stress adaptation revealed, that these proteins make up almost 30% of the protein mass accumulated during early phases of this stress. PMID:24878497

  2. Highly Precise Quantification of Protein Molecules per Cell During Stress and Starvation Responses in Bacillus subtilis *

    PubMed Central

    Maa?, Sandra; Wachlin, Gerhild; Bernhardt, Jörg; Eymann, Christine; Fromion, Vincent; Riedel, Katharina; Becher, Dörte; Hecker, Michael

    2014-01-01

    Systems biology based on high quality absolute quantification data, which are mandatory for the simulation of biological processes, successively becomes important for life sciences. We provide protein concentrations on the level of molecules per cell for more than 700 cytosolic proteins of the Gram-positive model bacterium Bacillus subtilis during adaptation to changing growth conditions. As glucose starvation and heat stress are typical challenges in B. subtilis' natural environment and induce both, specific and general stress and starvation proteins, these conditions were selected as models for starvation and stress responses. Analyzing samples from numerous time points along the bacterial growth curve yielded reliable and physiologically relevant data suitable for modeling of cellular regulation under altered growth conditions. The analysis of the adaptational processes based on protein molecules per cell revealed stress-specific modulation of general adaptive responses in terms of protein amount and proteome composition. Furthermore, analysis of protein repartition during glucose starvation showed that biomass seems to be redistributed from proteins involved in amino acid biosynthesis to enzymes of the central carbon metabolism. In contrast, during heat stress most resources of the cell, namely those from amino acid synthetic pathways, are used to increase the amount of chaperones and proteases. Analysis of dynamical aspects of protein synthesis during heat stress adaptation revealed, that these proteins make up almost 30% of the protein mass accumulated during early phases of this stress. PMID:24878497

  3. High Mobility Group Box Protein 1 (HMGB1): The Prototypical Endogenous Danger Molecule

    PubMed Central

    Yang, Huan; Wang, Haichao; Chavan, Sangeeta S; Andersson, Ulf

    2015-01-01

    High mobility group box protein 1 (HMGB1) is an evolutionary ancient nuclear protein that exerts divergent biological tasks inside and outside of cells. The functions of HMGB1 depend on location, binding partners and redox states of the molecule. In the nucleus, HMGB1 organizes DNA and nucleosomes and regulates gene transcription. Upon cell activation or injury, nuclear HMGB1 can translocate to the cytoplasm, where it is involved in inflammasome activation and pyroptosis, as well as regulation of the autophagy/apoptosis balance. When actively secreted or passively released into the extracellular milieu, HMGB1 has cytokine, chemokine, neuroimmune and metabolic activities. Thus, HMGB1 plays multiple roles in the pathogenesis of inflammatory diseases and mediates immune responses that range from inflammation and bacterial killing to tissue repair. HMGB1 has been associated with divergent clinical conditions such as sepsis, rheumatoid arthritis and atherosclerosis. HMGB1 initiates and perpetuates immune responses during infectious and sterile inflammation, as the archetypical alarmin and damage-associated molecular pattern (DAMP) molecule. We here describe advances in the understanding of HMGB1 biology with focus on recent findings of its mission as a DAMP in danger sensing and as a therapeutic target in inflammatory diseases. PMID:26605648

  4. Angle-Resolved High-Order Above-Threshold Ionization of a Molecule: Sensitive Tool for Molecular Characterization

    SciTech Connect

    Busuladzic, M.; Gazibegovic-Busuladzic, A.; Milosevic, D. B.; Becker, W.

    2008-05-23

    The strong-field approximation for ionization of diatomic molecules by an intense laser field is generalized to include rescattering of the ionized electron off the various centers of its molecular parent ion. The resulting spectrum and its interference structure strongly depend on the symmetry of the ground state molecular orbital. For N{sub 2}, if the laser polarization is perpendicular to the molecular axis, we observe a distinct minimum in the emission spectrum, which survives focal averaging and allows determination of, e.g., the internuclear separation. In contrast, for O{sub 2}, rescattering is absent in the same situation.

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

    NASA Astrophysics Data System (ADS)

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

    1996-07-01

    A novel scheme for high-capacity optical transmission is studied. The proposed system is based on a multilevel modulation technique that uses solitons. The basic idea relies on the property of solitons that the evolution of the state of polarization during propagation can be represented with a good degree of approximation with a rigid rotation of the Poincare sphere. Therefore, besides the rigid rotation that can be compensated for at the receiver, the state of polarization of the signal can be used to carry information. Here the limits of the rigid rotation that are due to polarization mode dispersion and amplified spontaneous emission noise are envisaged. Results show how this scheme permits the transmission-distance limit to be overcome for single-channel intensity-modulated direct-detection soliton systems. As an example we show how a 2.5-Gsymbol / s system with 24 polarization levels leads to a total capacity of 10 Gbits / s over distances up to 3000 km in links encompassing standard dispersion fibers.

  6. High-speed polarization sensitive optical coherence tomography for retinal diagnostics

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  7. Broadband polarization independent nanophotonic coupler for silicon waveguides with ultra-high efficiency.

    PubMed

    Cheben, Pavel; Schmid, Jens H; Wang, Shurui; Xu, Dan-Xia; Vachon, Martin; Janz, Siegfried; Lapointe, Jean; Painchaud, Yves; Picard, Marie-Josée

    2015-08-24

    Coupling of light to and from integrated optical circuits has been recognized as a major practical challenge since the early years of photonics. The coupling is particularly difficult for high index contrast waveguides such as silicon-on-insulator, since the cross-sectional area of silicon wire waveguides is more than two orders of magnitude smaller than that of a standard single-mode fiber. Here, we experimentally demonstrate unprecedented control over the light coupling between the optical fiber and silicon chip by constructing the nanophotonic coupler with ultra-high coupling efficiency simultaneously for both transverse electric and transverse magnetic polarizations. We specifically demonstrate a subwavelength refractive index engineered nanostructure to mitigate loss and wavelength resonances by suppressing diffraction effects, enabling a coupling efficiency over 92% (0.32 dB) and polarization independent operation for a broad spectral range exceeding 100 nm. PMID:26368222

  8. Clicked Isoreticular Metal-Organic Frameworks and Their High Performance in the Selective Capture and Separation of Large Organic Molecules.

    PubMed

    Li, Pei-Zhou; Wang, Xiao-Jun; Tan, Si Yu; Ang, Chung Yen; Chen, Hongzhong; Liu, Jia; Zou, Ruqiang; Zhao, Yanli

    2015-10-19

    Three highly porous metal-organic frameworks (MOFs) with a uniform rht-type topological network but hierarchical pores were successfully constructed by the assembly of triazole-containing dendritic hexacarboxylate ligands with Zn(II) ions. These transparent MOF crystals present gradually increasing pore sizes upon extension of the length of the organic backbone, as clearly identified by structural analysis and gas-adsorption experiments. The inherent accessibility of the pores to large molecules endows these materials with unique properties for the uptake of large guest molecules. The visible selective adsorption of dye molecules makes these MOFs highly promising porous materials for pore-size-dependent large-molecule capture and separation. PMID:26316365

  9. Impact ionization in N-polar AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Killat, N. E-mail: Martin.Kuball@bristol.ac.uk; Uren, M. J.; Kuball, M. E-mail: Martin.Kuball@bristol.ac.uk; Keller, S.; Kolluri, S.; Mishra, U. K.

    2014-08-11

    The existence of impact ionization as one of the open questions for GaN device reliability was studied in N-polar AlGaN/GaN high electron mobility transistors. Electroluminescence (EL) imaging and spectroscopy from underneath the device gate contact revealed the presence of hot electrons in excess of the GaN bandgap energy even at moderate on-state bias conditions, enabling impact ionization with hole currents up to several hundreds of pA/mm. The detection of high energy luminescence from hot electrons demonstrates that EL analysis is a highly sensitive tool to study degradation mechanisms in GaN devices.

  10. Separations method for polar molecules

    DOEpatents

    Thoma, Steven G.; Bonhomme, Francois R.

    2004-07-27

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

  11. Label free, highly sensitive and selective recognition of small molecule using gold surface confined aptamers

    NASA Astrophysics Data System (ADS)

    Liu, Li; Liang, Zhiqiang; Li, Yongjun

    2012-08-01

    A highly sensitive and selective small molecule detection platform has been developed using aptamers immobilized on electrode surface. In our system, two aptamers were used - one of which is for ATP recognition and the other is for signal produce. We designed two probes L1 (containing ATP aptamer and a part of hemin aptamer) and L2 (containing the complementary strand of ATP aptamer and the rest of hemin aptamer) and immobilized L1 on electrode surface. L2 was used to hybridize to L1 and form L1-L2 duplex which brought the two parts of hemin aptamer into close proximity. Then hemin can be captured by this duplex and detected by electrochemical methods. When we introduced ATP into the system, the ATP binding destroyed the duplex and L2 diffused into the solution. As a result, hemin cannot be captured to bring electrochemical signal.

  12. High-resolution filtering for improved small molecule identification via GC/MS.

    PubMed

    Kwiecien, Nicholas W; Bailey, Derek J; Rush, Matthew J P; Cole, Jason S; Ulbrich, Arne; Hebert, Alexander S; Westphall, Michael S; Coon, Joshua J

    2015-08-18

    Gas chromatography/mass spectrometry (GC/MS) has long been considered one of the premiere analytical tools for small molecule analysis. Recently, a number of GC/MS systems equipped with high-resolution mass analyzers have been introduced. These systems provide analysts with a new dimension of information, accurate mass measurement to the third or fourth decimal place; however, existing data processing tools do not capitalize on this information. Beyond that, GC/MS spectral reference libraries, which have been curated over the last several decades, contain almost exclusively unit resolution MS spectra making integration of accurate mass data dubious. Here we present an informatic approach, called high-resolution filtering (HRF), which bridges this gap. During HRF, high-resolution mass spectra are assigned putative identifications through traditional spectral matching at unit resolution. Once candidate identities have been assigned, all unique combinations of atoms from these candidate precursors are generated and matched to m/z peaks using narrow mass tolerances. The total amount of measured signal that is annotated is used as a metric of plausibility for the presumed identification. Here we demonstrate that the HRF approach is both feasible and highly specific toward correct identifications. PMID:26192401

  13. Origin of high- and low-conductance traces in alkanediisothiocyanate single-molecule contacts

    NASA Astrophysics Data System (ADS)

    Luzhbin, D. A.; Kaun, C.-C.

    2010-01-01

    Zero-bias transport properties of alkanediisothiocyanate [-SCN-(CH2)n-NCS-,n=4,6,8] molecules anchored to various quasi-one-dimensional Au(111) electrodes are studied by an ab initio method within a standard two-probe methodology based on the density-functional theory and the nonequilibrium Green’s functions formalism. We have shown that the high-/low-conductance traces observed in STM break-junction experiments on this molecular species can be clearly related to the difference in the electronic structures between the molecular contacts with different geometric configurations of the near-interface planes of the electrodes. The difference in transport properties of alkanediisothiocyanate single-molecule junctions can be understood in terms of the distribution of the surface states, emerging in the energy gap of the alkanes due to the electrode environment. A general feature of the high-conductance junctions is a number of closely located surface states around the Fermi energy, well coupled to the scattering states of the junctions. These well-coupled states broaden the transmission peaks responsible for conductance, increasing their amplitudes at the Fermi energy, while the sparser distribution of the surface states gives sharper peaks with smaller amplitudes at the Fermi energy, naturally representing the low-conductance junctions. The effects of changing the end groups, junction distance, and electrode cross-section are also investigated and analyzed in terms of changes in the electronic structure of the molecular junctions. A comparison with the available experimental data is also provided.

  14. Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments

    SciTech Connect

    Gregory A. Mulhollan

    2010-11-16

    Specific activation recipes for bulk, 100 nm thick MBE grown and high polarization III-V photocathode material have been developed which mitigate the effects of exposure to background gasses. Lifetime data using four representative gasses were acquired for bulk GaAs, 100 nm unstrained GaAs and strained superlattice GaAs/GaAsP, all activated both with Cs and then Cs and Li (bi-alkali). Each photoemitter showed marked resilience improvement when activated using the bi-alkali recipe compared to the standard single alkali recipe. A dual alkali activation system at SLAC was constructed, baked and commissioned with the purpose of performing spin-polarization measurements on electrons emitted from the bi-alkali activated surfaces. An end station at SSRL was configured with the required sources for energy resolved photoemission measurements on the bi-alkali activated and CO2 dosed surfaces. The bi-alkali recipes were successfully implemented at SLAC/SSRL. Measurements at SLAC of the photoelectron spin-polarization from the modified activation surface showed no sign of a change in value compared to the standard activated material, i.e., no ill effects. Analysis of photoemission data indicates that the addition of Li to the activation layer results in a multi-layer structure. The presence of Li in the activation layer also acts as an inhibitor to CO2 absorption, hence better lifetimes in worse vacuum were achieved. The bi-alkali activation has been tested on O2 activated GaAs for comparison with NF3 activated surfaces. Comparable resilience to CO2 exposure was achieved for the O2 activated surface. An RF PECVD amorphous silicon growth system was modified to allow high temperature heat cleaning of GaAs substrates prior to film deposition. Growth versus thickness data were collected. Very thin amorphous silicon germanium layers were optimized to exhibit good behavior as an electron emitter. Growth of the amorphous silicon germanium films on the above substrates was fine tuned with respect to time and power to moderate plasma damage to the photo-generating layer. Auger electron spectroscopy was used to analyze the composition and thickness of the emitter layers. AFM studies showed conformal growth on the GaAs substrates. Measurements at SLAC on the photoemitted electrons from high polarization substrates coated with amorphous silicon germanium indicated an ~10% relative drop in spin-polarization at the wavelength corresponding to the maximum spin-polarization when compared to the uncoated material,

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

    SciTech Connect

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

    1989-02-13

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

  16. Multi-instrument, high-resolution imaging of polar cap patch transportation

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    Transionospheric radio signals in the high-latitude polar cap are susceptible to degradation when encountering sharp electron density gradients associated with discrete plasma structures, or patches. Multi-instrument measurements of polar cap patches are examined during a geomagnetic storm interval on 22 January 2012. For the first time, we monitor the transportation of patches with high spatial and temporal resolution across the polar cap for 1-2 h using a combination of GPS total electron content (TEC), all-sky airglow imagers (ASIs), and Super Dual Auroral Radar Network (SuperDARN) HF radar backscatter. Simultaneous measurements from these data sets allow for continuous tracking of patch location, horizontal extent, and velocity despite adverse observational conditions for the primary technique (e.g., sunlit regions in the ASI data). Spatial collocation between patch-like features in relatively coarse but global GPS TEC measurements and those mapped by high-resolution ASI data was very good, indicating that GPS TEC can be applied to track patches continuously as they are transported across the polar cap. In contrast to previous observations of cigar-shaped patches formed under weakly disturbed conditions, the relatively narrow dawn-dusk extent of patches in the present interval (500-800 km) suggests association with a longitudinally confined plasma source region, such as storm-enhanced density (SED) plume. SuperDARN observations show that the backscatter power enhancements corresponded to the optical patches, and for the first time we demonstrate that the motion of the optical patches was consistent with background plasma convection velocities.

  17. Gas phase Boudouard disproportionation reaction between highly vibrationally excited CO molecules

    NASA Astrophysics Data System (ADS)

    Essenhigh, Katherine; Utkin, Yurii; Bernard, Chad; Adamovich, Igor; Rich, William

    2006-10-01

    The gas-phase Boudouard disproportionation reaction (1) between highly vibrationally excited CO molecules in nonequilibrium optically excited plasma has been studied in this work. CO(v) + CO(w) -> CO2 +C The experiments were conducted in a mixture of Ar and CO at different CO partial pressures. The cw CO laser beam (14 Watt) was used to create an optically pumped plasma in a small glass reactor. The vibrational distribution function (VDF) of CO was measured in the plasma region using the fourier transform infrared emission spectroscopy. Carbon dioxide production rate was determined from the absorption of CO2 asymmetric stretch. Small amounts of helium was added to the mixture to alter the VDFs and change the of CO2 production rate. The activation energy Ea ˜11eV was inferred by using the transition state theory to fit the experimental data. This activation energy is very close to the CO dissociation energy of 11.09eV. Such a high activation energy suggests that both colliding particles have to be in very highly excited vibrational states for the reaction (1) to occur. The total rate constant KB for the reaction (1) was found to be 6.10-17 cm^3/sec.

  18. TEMPO-Oxidized Nanofibrillated Cellulose as a High Density Carrier for Bioactive Molecules.

    PubMed

    Weishaupt, Ramon; Siqueira, Gilberto; Schubert, Mark; Tingaut, Philippe; Maniura-Weber, Katharina; Zimmermann, Tanja; Thöny-Meyer, Linda; Faccio, Greta; Ihssen, Julian

    2015-11-01

    Controlled and efficient immobilization of specific biomolecules is a key technology to introduce new, favorable functions to materials suitable for biomedical applications. Here, we describe an innovative and efficient, two-step methodology for the stable immobilization of various biomolecules, including small peptides and enzymes onto TEMPO oxidized nanofibrillated cellulose (TO-NFC). The introduction of carboxylate groups to NFC by TEMPO oxidation provided a high surface density of negative charges able to drive the adsorption of biomolecules and take part in covalent cross-linking reactions with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDAC) and glutaraldehyde (Ga) chemistry. Up to 0.27 ?mol of different biomolecules per mg of TO-NFC could be reversibly immobilized by electrostatic interaction. An additional chemical cross-linking step prevented desorption of more than 80% of these molecules. Using the cysteine-protease papain as model, a highly active papain-TO-NFC conjugate was achieved. Once papain was immobilized, 40% of the initial enzymatic activity was retained, with an increase in kcat from 213 to >700 s(-1) for the covalently immobilized enzymes. The methodology presented in this work expands the range of application for TO-NFC in the biomedical field by enabling well-defined hybrid biomaterials with a high density of functionalization. PMID:26413931

  19. High Throughput Screen Identifies Small Molecule Inhibitors Specific for Mycobacterium tuberculosis Phosphoserine Phosphatase*

    PubMed Central

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

    2014-01-01

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

  20. Polarization dependence of the strain sensitivity of fiber Bragg gratings inscribed in highly birefringent optical fibers

    NASA Astrophysics Data System (ADS)

    Singh, Paul; Jülich, Florian; Roths, Johannes

    2012-04-01

    It can be expected that the range of applications for FBG-based strain and temperature sensors would expand if the accuracy of this sensor technique was improved. In this study, polarization effects of FBG sensors, which contribute significantly to the measurement uncertainty of this technique, were investigated. Therefore, FBGs were inscribed into highly birefringent optical fibers. These sensor elements were attached to a specimen with defined orientations of the fiber's slow and fast axes with regard the specimen's surface. We observed a change of the fiber's birefringence in the order of 5 10-5 as a consequence of the gluing process, that was employed to attach the fiber onto the specimen. The strain sensitivities were determined for each polarization mode and for different fiber orientations using a highly accurate strain calibration facility. It was found that in all experiments the strain sensitivity for the slow axis was significantly higher (about 0.8%) than for the fast axis. The strain sensitivity also depends on the orientation of the fiber's birefringent axes with regard to the surface of the specimen. Although the investigations were performed with FBGs inscribed into birefringent fibers, the findings are still of importance for understanding the polarization-dependant accuracy limits of FBGs in standard single-mode fibers.

  1. Polarization sensitive detection of 100 GHz radiation by high mobility field-effect transistors

    NASA Astrophysics Data System (ADS)

    Sakowicz, M.; ?usakowski, J.; Karpierz, K.; Grynberg, M.; Knap, W.; Gwarek, W.

    2008-07-01

    Detection of 100 GHz electromagnetic radiation by a GaAs/AlGaAs high electron mobility field-effect transistor was investigated at 300 K as a function of the angle ? between the direction of linear polarization of the radiation and the symmetry axis of the transistor. The angular dependence of the detected signal was found to be A0 cos2(? -?0)+C with A0, ?0, and C dependent on the electrical polarization of the transistor gate. This dependence is interpreted as due to excitation of two crossed phase-shifted oscillators. A response of the transistor chip (including bonding wires and the substrate) to 100 GHz radiation was numerically simulated. Results of calculations confirmed experimentally observed dependencies and showed that the two oscillators result from an interplay of 100 GHz currents defined by the transistor impedance together with bonding wires and substrate related modes.

  2. High Performance Polarized Electron Photocathodes Based on InGaAlAs/AlGaAs Superlattices

    SciTech Connect

    Mamaev, Yu.

    2004-12-10

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

  3. High-order harmonic generation by a bichromatic elliptically polarized field: conservation of angular momentum

    NASA Astrophysics Data System (ADS)

    Miloševi?, D. B.

    2015-09-01

    We present a theory of high-order harmonic generation by a bichromatic elliptically polarized laser field which consists of two coplanar components having the frequencies r? and s? (r and s are integers) and is defined in the xy plane. Laser and harmonic fields are decomposed in the components having opposite helicities. Using the conservation laws for energy and projection of the total angular momentum of atom and laser and harmonic photons on the z axis we have derived a general selection rule. This rule reduces to the known result in the case of bicircular field which consists of two counter-rotating circularly polarized fields. We apply our results to explain recent experiment by Fleischer et al 2014 (Nature Photonics 8 543).

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

    E-print Network

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

    2010-01-01

    We present the design and operation of a fiber-based cryogenic confocal microscope. It is designed as a compact cold-finger that fits inside the bore of a superconducting magnet, and which is a modular unit that can be easily swapped between use in a dilution refrigerator and other cryostats. We aimed at application in quantum optical experiments with electron spins in semiconductors and the design has been optimized for driving with, and detection of optical fields with well-defined polarizations. This was implemented with optical access via a polarization maintaining fiber together with Voigt geometry at the cold finger, which circumvents Faraday rotations in the optical components in high magnetic fields. Our unit is versatile for use in experiments that measure photoluminescence, reflection, or transmission, as we demonstrate with a quantum optical experiment with an ensemble of donor-bound electrons in a thin GaAs film.

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

    E-print Network

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

    2010-10-09

    We present the design and operation of a fiber-based cryogenic confocal microscope. It is designed as a compact cold-finger that fits inside the bore of a superconducting magnet, and which is a modular unit that can be easily swapped between use in a dilution refrigerator and other cryostats. We aimed at application in quantum optical experiments with electron spins in semiconductors and the design has been optimized for driving with, and detection of optical fields with well-defined polarizations. This was implemented with optical access via a polarization maintaining fiber together with Voigt geometry at the cold finger, which circumvents Faraday rotations in the optical components in high magnetic fields. Our unit is versatile for use in experiments that measure photoluminescence, reflection, or transmission, as we demonstrate with a quantum optical experiment with an ensemble of donor-bound electrons in a thin GaAs film.

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

    PubMed Central

    Götzinger, Erich; Pircher, Michael; Hitzenberger, Christoph K.

    2010-01-01

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

  7. Dynamic Two-Center Interference in High-Order Harmonic Generation from Molecules with Attosecond Nuclear Motion

    E-print Network

    Lein, Manfred

    Dynamic Two-Center Interference in High-Order Harmonic Generation from Molecules with Attosecond in high-harmonic generation from H2, in which the attosecond nuclear motion of H 2 initiated at ionization. To enable this measurement we utilize a recently developed technique for probing the attosecond nuclear

  8. Steps in the hysteresis loops of a high-spin molecule Jonathan R. Friedman and M. P. Sarachik

    E-print Network

    Friedman, Jonathan R.

    Steps in the hysteresis loops of a high-spin molecule Jonathan R. Friedman and M. P. Sarachik Corporation, Webster, New York 14580 We report the first observation of steps in the hysteresis loop of a high of 3 K, hysteresis is observed3,5 and slow exponential relaxation of the magneti- zation has been found

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

    PubMed

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

    2014-06-01

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

  10. High-power near-infrared linearly-polarized supercontinuum generation in a polarization-maintaining Yb-doped fiber amplifier.

    PubMed

    Zhang, Bin; Jin, Aijun; Ma, Pengfei; Chen, Shengping; Hou, Jing

    2015-11-01

    We report an all-fiber linearly-polarized (LP) supercontinuum (SC) source with high average power generated in a polarization-maintaining (PM) master-oscillation power-amplifier (MOPA). The experimental configuration comprises an LP picosecond pulsed laser and three PM Yd-doped fiber amplifiers (YDFA). The output has the average power of 124.8 W with the spectrum covering from 850 to 1900 nm. The measured polarization extinction ratio (PER) of the whole SC source is about 85% which verifies the SC an LP source. This work is, to our best knowledge, the highest output average power of an LP SC source that ever reported. The influence of PM fiber splicing method on the LP SC property is investigated by splicing the PM fibers with slow axis parallel or perpendicularly aligned, and also an LP SC with low output power is demonstrated. PMID:26561136

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

    PubMed Central

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

    2011-01-01

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

  12. A Manual Small Molecule Screen Approaching High-throughput Using Zebrafish Embryos

    PubMed Central

    Poureetezadi, Shahram Jevin; Donahue, Eric K.; Wingert, Rebecca A.

    2014-01-01

    Zebrafish have become a widely used model organism to investigate the mechanisms that underlie developmental biology and to study human disease pathology due to their considerable degree of genetic conservation with humans. Chemical genetics entails testing the effect that small molecules have on a biological process and is becoming a popular translational research method to identify therapeutic compounds. Zebrafish are specifically appealing to use for chemical genetics because of their ability to produce large clutches of transparent embryos, which are externally fertilized. Furthermore, zebrafish embryos can be easily drug treated by the simple addition of a compound to the embryo media. Using whole-mount in situ hybridization (WISH), mRNA expression can be clearly visualized within zebrafish embryos. Together, using chemical genetics and WISH, the zebrafish becomes a potent whole organism context in which to determine the cellular and physiological effects of small molecules. Innovative advances have been made in technologies that utilize machine-based screening procedures, however for many labs such options are not accessible or remain cost-prohibitive. The protocol described here explains how to execute a manual high-throughput chemical genetic screen that requires basic resources and can be accomplished by a single individual or small team in an efficient period of time. Thus, this protocol provides a feasible strategy that can be implemented by research groups to perform chemical genetics in zebrafish, which can be useful for gaining fundamental insights into developmental processes, disease mechanisms, and to identify novel compounds and signaling pathways that have medically relevant applications. PMID:25407322

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

    PubMed

    Blomberg, Margareta R A; Siegbahn, Per E M

    2015-03-01

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

  14. ATP molecule ATP molecule

    E-print Network

    ATP molecule 9 ATP molecule 8 Autumn 2003 · Vol. 1 No. 2 · inSiDE inSiDE · Vol. 1 No. 2 · Autumn with adenosine 5`-triphosphate (ATP). ATP is the most important energy carrier in cellular metabolism, and each human being produces its own weight in ATP every day. The ATP molecule is shown in Figure 1, where

  15. Gas-phase Boudouard disproportionation reaction between highly vibrationally excited CO molecules

    NASA Astrophysics Data System (ADS)

    Essenhigh, Katherine A.; Utkin, Yurii G.; Bernard, Chad; Adamovich, Igor V.; William Rich, J.

    2006-11-01

    The gas-phase Boudouard disproportionation reaction between two highly vibrationally excited CO molecules in the ground electronic state has been studied in optically pumped CO. The gas temperature and the CO vibrational level populations in the reaction region, as well as the CO 2 concentration in the reaction products have been measured using FTIR emission and absorption spectroscopy. The results demonstrate that CO 2 formation in the optically pumped reactor is controlled by the high CO vibrational level populations, rather than by CO partial pressure or by flow temperature. The disproportionation reaction rate constant has been determined from the measured CO 2 and CO concentrations using the perfectly stirred reactor (PSR) approximation. The reaction activation energy, 11.6 ± 0.3 eV (close to the CO dissociation energy of 11.09 eV), was evaluated using the statistical transition state theory, by comparing the dependence of the measured CO 2 concentration and of the calculated reaction rate constant on helium partial pressure. The disproportionation reaction rate constant measured at the present conditions is kf = (9 ± 4) × 10 -18 cm 3/s. The reaction rate constants obtained from the experimental measurements and from the transition state theory are in good agreement.

  16. A Novel High-Throughput Screening Assay for Discovery of Molecules That Increase Cellular Tetrahydrobiopterin

    PubMed Central

    LI, LI; DU, YUHONG; CHEN, WEI; FU, HAIAN; HARRISON, DAVID G.

    2015-01-01

    Tetrahydrobiopterin (BH4) is an essential cofactor for the nitric oxide (NO) synthases and the aromatic amino acid hydroxylases. Insufficient BH4 has been implicated in various cardiovascular and neurological disorders. GTP cyclohydrolase 1 (GTPCH-1) is the rate-limiting enzyme for de novo biosynthesis of BH4. The authors have recently shown that the interaction of GTPCH-1 with GTP cyclohydrolase feedback regulatory protein (GFRP) inhibits endothelial GTPCH-1 enzyme activity, BH4 levels, and NO production. They propose that agents that disrupt the GTPCH-1/GFRP interaction can increase cellular GTPCH-1 activity, BH4 levels, and NO production. They developed and optimized a novel time-resolved fluorescence resonance energy transfer (TR-FRET) assay to monitor the interaction of GTPCH-1 and GFRP. This assay is highly sensitive and stable and has a signal-to-background ratio (S/B) greater than 12 and a Z? factor greater than 0.8. This assay was used in an ultra-high-throughput screening (uHTS) format to screen the Library of Pharmacologically Active Compounds. Using independent protein–protein interaction and cellular activity assays, the authors identified compounds that disrupt GTPCH-1/GFRP binding and increase endothelial cell biopterin levels. Thus, this TR-FRET assay could be applied in future uHTS of additional libraries to search for molecules that increase GTPCH-1 activity and BH4 levels. PMID:21693765

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

    PubMed Central

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

    2014-01-01

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

  18. High-quality source of fiber-coupled polarization-entangled photons at 1.56 [mu]m

    E-print Network

    Stelmakh, Veronika

    2012-01-01

    This thesis describes the development of a high-quality source of single-mode fibercoupled polarization-entangled photon pairs based on a collinear spontaneous parametric down-conversion process in a bidirectionally pumped ...

  19. Characterizing polarized illumination in high numerical aperture optical lithography with phase shifting masks

    NASA Astrophysics Data System (ADS)

    McIntyre, Gregory Russell

    The primary objective of this dissertation is to develop the phase shifting mask (PSM) as a precision instrument to characterize effects in optical lithography related to the use of polarized partially coherent illumination. The intent is to provide an in-situ characterization technique to add to the lithographer's tool-kit to help enable the stable and repeatable mass production of integrated circuits with feature sizes approaching 1/6th the wavelength of light being used. A series of complex-valued mathematical functions have been derived from basic principles and recent advances in photomask fabrication technology have enabled their implementation with four-phase mask making. When located in the object plane of an imaging system, these test functions serve to engineer a wavefiront that interacts with one particular optical effect, creating a measurable signal in the image plane. In most cases, these test patterns leverage proximity effects to create a central image intensity and are theoretically the most sensitive to the desired effect. Five novel classes of test patterns have been developed for in-situ characterization. The first two classes, The Linear Phase Grating (LPG) and Linear Phase Ring (LPR), both serve to characterize illumination angular distribution and uniformity by creating signals dependent on illumination angular frequency. The third class consists of the Radial Phase Grating (RPG) and Proximity Effect Polarization Analyzers (PEPA), which each create a polarization-dependent signal by taking advantage of the image reversal of one polarization component at high numerical aperture (NA). PSM Polarimetry employs a series of these patterns to form a complete polarization characterization of any arbitrary illumination scheme. The fourth and fifth classes employ sub-resolution interferometric reference probes to coherently interact with proximity effect spillover from a surrounding pattern. They measure the effective phase and transmission of the shifted regions of an alternating PSM and projection lens birefringence, respectively. A secondary objective of this dissertation has been to leverage some of these functions to extend the application of pattern matching software to rapidly identify areas in a circuit design layout that may be vulnerable to polarization and high-NA effects. Additionally, polarization aberrations have been investigated, as they may become important with hyper-NA imaging systems. Three multi-phase test reticles have been developed for this thesis and have pushed the limits of photomask fabrication. Coupled with a variety of experimental and simulation studies at 193nm wavelength, they have validated the scientific principles of the PSM monitors and have offered unique insight into implementation issues such as electromagnetic (EM) effects and mask making tolerances. Although all five classes are novel theoretical concepts, it is believed that PSM Polarimetry is commercially viable. Despite a 70% loss of sensitivity due to mask making limitations and a 20% loss due to EM effects, it can likely still monitor polarization to within 2%. Experimental results are comparable to the only other known technique, which requires special equipment. Taken collectively, the five novel classes of PSM monitors offer the lithographer an independent tool-kit to ensure proper tool operation. They also provide circuit designers an understanding of the impact of imaging on layouts. Although they have been developed for optical lithography, their principles are relevant to any image-forming optical system and are likely to find applications in other fields of optics or acoustics.

  20. STM study of C60F18 high dipole moment molecules on Au(111)

    NASA Astrophysics Data System (ADS)

    Bairagi, K.; Bellec, A.; Chumakov, R. G.; Menshikov, K. A.; Lagoute, J.; Chacon, C.; Girard, Y.; Rousset, S.; Repain, V.; Lebedev, A. M.; Sukhanov, L. P.; Svechnikov, N. Yu.; Stankevich, V. G.

    2015-11-01

    Scanning tunneling microscopy and spectroscopy studies of C60F18 molecules deposited on Au(111) are reported and compared to C60 molecules both at liquid helium temperature and room temperature (RT). Whereas adsorption and electronic properties of C60F18 single molecules were studied at low temperature (LT), self-assemblies were investigated at RT. In both cases, the fluorine atoms of the C60F18 molecules are pointed towards the surface. Individual C60F18 molecules on Au(111) have a HOMO-LUMO gap of 2.9 eV. The self-assembled islands exhibit a close-packed hexagonal lattice with amorphous borders. The comparison with C60 molecules clearly demonstrates the influence of the C60F18 electric dipole moment (EDM) on the electronic properties of single molecules and on the thermodynamics of self-assembled islands. Besides, the apparent height value of a separate molecule increases in a self-assembly environment as a result of a depolarization phenomenon.

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

    SciTech Connect

    Goodman, T. P.; Felici, F.; Udintsev, V. S.

    2009-11-26

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

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

    SciTech Connect

    Herkenhoff, K.E.; Murray, B.C. )

    1990-08-30

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

  3. On stochastic spatial patterns and neuronal polarity

    NASA Astrophysics Data System (ADS)

    Menchón, Silvia A.; Wio, Horacio S.

    2014-08-01

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

  4. Net Ecosystem Production of Polar Desert and Wetland Landscapes in the Rapidly Changing Canadian High Arctic

    NASA Astrophysics Data System (ADS)

    Emmerton, C. A.; St Louis, V. L.; Humphreys, E.; Barker, J. D.; Gamon, J. A.; Pastorello, G.

    2014-12-01

    A rapidly warming and wetting Arctic climate is changing the net ecosystem production (NEP) of northern landscapes and subsequent exchange of carbon dioxide (CO2) with the atmosphere. Assessments of northern terrestrial NEP have focused mostly on the rich peatland landscapes of the low Arctic, with far fewer studies from expansive, but sparse, high Arctic polar landscapes. Consequently, how these ecosystems may respond to a warming and wetting climate is still a key gap in our understanding of global carbon feedbacks. We used multi-season eddy covariance measurements to quantify growing season (June to September) NEP on contrasting polar desert and meadow wetland landscapes near Lake Hazen on northern Ellesmere Island (81ºN), in Canada's high Arctic. We also used variation in contemporary NEP and weather to improve our understanding of potential future carbon cycling in a warmer and wetter high Arctic climate. During a typical growing season, we found that a dry polar desert landscape accumulated only 6.6±1.2 g C m-2 similar to other high Arctic sites and consistent with cold, barren soils with weak plant growth. Desert NEP coincided strongest with landscape moisture, rather than heating, with increased NEP occurring during drier conditions when soil heterotrophic rates were lowest. With a nearly constant but varying supply of water, the productive meadow wetland accumulated 13 times more carbon (86.1±16.9 g C m-2) than the desert during the growing season. NEP at the wetland was similar to comparable landscapes much further south, owing to continuous 24-hour daylight and typically clear-skies surrounding Lake Hazen. Wetland soils showed a consistent strong burst of CO2 to the atmosphere each spring (min. NEP: -2.5 µmol CO2 s-1 m-2) and a well-defined peak in July productivity (3.9-4.4 µmol CO2 s-1 m-2). Wetland NEP associated positively and strongly with both landscape heating and moisture, suggesting that autotrophic limitations other than water or heat controlled ultimate carbon accumulation on the wetland landscape. Because polar desert landscapes comprise the majority of land area in the high Arctic, changes in moisture, rather than heating, will likely continue to strongly affect future net carbon accumulation, at least until plant cover and soil quality changes substantially.

  5. Micro injector sample delivery system for charged molecules

    DOEpatents

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

    1999-11-09

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

  6. Polarization developments

    SciTech Connect

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist.

  7. Two-dimensional array of cold-electron bolometers for high-sensitivity polarization measurements

    NASA Astrophysics Data System (ADS)

    Kuzmin, L. S.

    2012-01-01

    A new concept of a two-dimensional array of cold-electron bolometers with distributed dipole antennas in the focal plane for high-sensitivity polarization measurements is proposed. The concept gives a unique combination of high polarization resolution due to a large uniforms array of cold-electron bolometers and optimal matching with junction field effect transistor (JFET) amplifiers because of flexibility in direct-current connections. The noise characteristics are improved due to arriving-signal power distribution among numerous cold-electron bolometers and an increase in their response. This should lead to a significant increase in the sensitivity and dynamic range compared with competing alternative bolometer technologies. The reliability of the twodimensional array significantly increases due to a series-parallel connection of a large number of cold-electron bolometers. High polarization resolution should be ensured due to uniform covering of a substrate by a two-dimensional array over a large area and the absence of the beam compression to small lumped elements. The fundamental sensitivity limit of the cold-electron bolometer array is smaller than photon noise which is considered to be the ultimate level restricted by the background radiation. Estimates of noise of bolometers with the JFET reading system show the possibility of realizing the ultimate sensitivity below the photon-noise level 5 ?10-17 W/Hz1/2 at a frequency of 350 GHz for an optical load with a power of 5 pW. These parameters correspond to the requirements to the receiving system of a BOOMERanG balloon telescope.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  9. Phase modulation in polarization beating quasi-phase-matching of high-order-harmonic generation

    NASA Astrophysics Data System (ADS)

    Diskin, Tzvi; Kfir, Ofer; Fleischer, Avner; Cohen, Oren

    2015-09-01

    Polarization beating quasi-phase-matching (PB QPM) in high-harmonic generation (HHG) is currently understood as a purely-intensity-modulation quasi-phase-matching (QPM) technique. In PB QPM, the driver ellipticity oscillates during propagation, modulating the HHG conversion efficiency since the single-atom HHG yield decreases rapidly with increasing ellipticity of the driving laser. We show that PB QPM is in fact based on both intensity and phase modulations. Unfortunately, in PB QPM the intensity and phase contributions oppose each other, resulting in significant reduction in the QPM efficiency.

  10. High Performance Error Correction for Quantum Key Distribution using Polar Codes

    E-print Network

    Paul Jouguet; Sébastien Kunz-Jacques

    2013-07-29

    We study the use of polar codes for both discrete and continuous variables Quantum Key Distribution (QKD). Although very large blocks must be used to obtain the efficiency required by quantum key distribution, and especially continuous variables quantum key distribution, their implementation on generic x86 CPUs is practical. Thanks to recursive decoding, they exhibit excellent decoding speed, much higher than large, irregular Low Density Parity Check (LDPC) codes implemented on similar hardware, and competitive with implementations of the same codes on high-end Graphic Processing Units (GPUs).

  11. Threshold resummation for polarized high-pT hadron production at COMPASS

    NASA Astrophysics Data System (ADS)

    Uebler, Claudia; Schäfer, Andreas; Vogelsang, Werner

    2015-11-01

    We study the cross section for the photoproduction process ? N ?h X where the incident photon and nucleon are longitudinally polarized and a hadron h is observed at high transverse momentum. Specifically, we address the "direct" part of the cross section, for which the photon interacts in a pointlike way. For this contribution we perform an all-order resummation of logarithmic threshold corrections generated by soft or collinear gluon emission to next-to-leading logarithmic accuracy. We present phenomenological results relevant for the COMPASS experiment and compare to recent COMPASS data.

  12. Polarization observables in dp backward elastic scattering at high and intermediate energies

    E-print Network

    M. Tanifuji; S. Ishikawa; Y. Iseri

    1997-01-28

    The tensor analyzing power $T_{20}$ and the polarization transfer coefficients $\\kappa_0 (= 3/2 K_y^y)$ and $K_{xz}^y$ are investigated for dp backward elastic scattering by the invariant-amplitude method. Discrepancies between the conventional calculations and the experimental data on $T_{20}$ and $\\kappa_0$ at high and intermediate energies are mostly dissolved by including imaginary parts in the amplitudes. The quantity $K_{xz}^y$ is shown to be useful in criticizing nuclear force assumptions.

  13. High spin-polarization in ultrathin Co2MnSi/CoPd multilayers

    NASA Astrophysics Data System (ADS)

    Galanakis, I.

    2015-03-01

    Half-metallic Co2MnSi finds a broad spectrum of applications in spintronic devices either in the form of thin films or as spacer in multilayers. Using state-of-the-art ab-initio electronic structure calculations we exploit the electronic and magnetic properties of ultrathin Co2MnSi/CoPd multilayers. We show that these heterostructures combine high values of spin-polarization at the Co2MnSi spacer with the perpendicular magnetic anisotropy of binary compounds such as CoPd. Thus they could find application in spintronic/magnetoelectronic devices.

  14. High-quality fiber-optic polarization entanglement distribution at 1.3 microm telecom wavelength.

    PubMed

    Zhong, Tian; Hu, Xiaolong; Wong, Franco N C; Berggren, Karl K; Roberts, Tony D; Battle, Philip

    2010-05-01

    We demonstrate high-quality distribution of 1.3 microm polarization-entangled photons generated from a fiber-coupled periodically poled KTiOPO(4) waveguide over 200 m fiber-optic cables. Time-multiplexed measurements with a 19% efficient superconducting nanowire single-photon detector at the remote location show a detected flux of 5.8 pairs/s at a pump power of 25 microW and an average two-photon quantum-interference visibility of 97.7% without subtraction of accidentals. PMID:20436580

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

    NASA Astrophysics Data System (ADS)

    Alexander, Neil Brooks

    1992-01-01

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

  16. Discovering Molecules That Regulate Efferocytosis Using Primary Human Macrophages and High Content Imaging

    PubMed Central

    Santulli-Marotto, Sandra; Gervais, Alexis; Fisher, Jamie; Strake, Brandy; Ogden, Carol Anne; Riveley, Chelsea; Giles-Komar, Jill

    2015-01-01

    Defective clearance of apoptotic cells can result in sustained inflammation and subsequent autoimmunity. Macrophages, the “professional phagocyte” of the body, are responsible for efficient, non-phlogistic, apoptotic cell clearance. Controlling phagocytosis of apoptotic cells by macrophages is an attractive therapeutic opportunity to ameliorate inflammation. Using high content imaging, we have developed a system for evaluating the effects of antibody treatment on apoptotic cell uptake in primary human macrophages by comparing the Phagocytic Index (PI) for each antibody. Herein we demonstrate the feasibility of evaluating a panel of antibodies of unknown specificities obtained by immunization of mice with primary human macrophages and show that they can be distinguished based on individual PI measurements. In this study ~50% of antibodies obtained enhance phagocytosis of apoptotic cells while approximately 5% of the antibodies in the panel exhibit some inhibition. Though the specificities of the majority of antibodies are unknown, two of the antibodies that improved apoptotic cell uptake recognize recombinant MerTK; a receptor known to function in this capacity in vivo. The agonistic impact of these antibodies on efferocytosis could be demonstrated without addition of either of the MerTK ligands, Gas6 or ProS. These results validate applying the mechanism of this fundamental biological process as a means for identification of modulators that could potentially serve as therapeutics. This strategy for interrogating macrophages to discover molecules regulating apoptotic cell uptake is not limited by access to purified protein thereby increasing the possibility of finding novel apoptotic cell uptake pathways. PMID:26674639

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

    SciTech Connect

    Chu, P.M.Y.

    1991-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  19. HIGH-TIME-RESOLUTION MEASUREMENTS OF THE POLARIZATION OF THE CRAB PULSAR AT 1.38 GHz

    SciTech Connect

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

    2015-01-20

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

  20. Role of Multi-Electron Effects in the Asymmetry of Strong-Field Ionization and Fragmentation of Polar Molecules: The Methyl Halide Series.

    PubMed

    Walt, Samuel G; Bhargava Ram, N; von Conta, Aaron; Tolstikhin, Oleg I; Madsen, Lars Bojer; Jensen, Frank; Wörner, Hans Jakob

    2015-12-10

    We report angle- and momentum-resolved measurements of the dissociative ionization and Coulomb explosion of methyl halides (CH3F, CH3Cl, CH3Br, and CH3I) in intense phase-controlled two-color laser fields. At moderate laser intensities, we find that the emission asymmetry of low-energy CH3(+) fragments from the CH3(+) + X(+) (X = F, Cl, Br, or I) channel reflects the asymmetry of the highest occupied molecular orbital of the neutral molecule with important contributions from the Stark effect. This asymmetry is correctly predicted by the weak-field asymptotic theory, provided that the Stark effect on the ionization potentials is calculated using a nonperturbative multielectron approach. In the case of high laser intensities, we observe a reversal of the emission asymmetries for high-energy CH3(+) fragments, originating from the dissociation of CH3X(q+) with q ? 2. We propose ionization to electronically excited states to be at the origin of the reversed asymmetries. We also report the measurements of the emission asymmetry of H3(+), which is found to be identical to that of the low-energy CH3(+) fragments measured at moderate laser intensities. All observed fragmentation channels are assigned with the help of CCSD(T) calculations. Our results provide a benchmark for theories of strong-field processes and demonstrate the importance of multielectron effects in new aspects of the molecular response to intense laser fields. PMID:26565126

  1. Corrosion-resistant iridium-platinum anode material for high polarization application in corrosive acids

    SciTech Connect

    Farmer, J.; Summers, L.; Lewis, P.

    1993-09-08

    The present invention relates to highly corrosion resistant components for use in an electrochemical cell. Specifically, these components are resistant to corrosion under very extreme conditions such as exposure to aqua regia in the presence of a constant current density of 100mA/m{sup 2}. The components are comprised of an iridium-platinum alloy that comprises less than 30% iridium. In a preferred embodiment of the present invention, the iridium-platinum alloy comprises 15-20% iridium. In another preferred embodiment of the present invention, the iridium-platinum alloy is deposited on the surface of an electrochemical cell component by magnetron sputtering. The present invention also relates to a method for conducting an electrochemical reaction in the presence of highly corrosive acids under a high degree of polarization wherein the electrochemical cell comprises a component, preferably the anode, containing an iridium-platinum alloy that comprises less than 30% iridium.

  2. Discovery of small molecule inhibitors of xyloglucan endotransglucosylase (XET) activity by high-throughput screening.

    PubMed

    Chormova, Dimitra; Franková, Lenka; Defries, Andrew; Cutler, Sean R; Fry, Stephen C

    2015-09-01

    Small molecules (xenobiotics) that inhibit cell-wall-localised enzymes are valuable for elucidating the enzymes' biological roles. We applied a high-throughput fluorescent dot-blot screen to search for inhibitors of Petroselinum xyloglucan endotransglucosylase (XET) activity in vitro. Of 4216 xenobiotics tested, with cellulose-bound xyloglucan as donor-substrate, 18 inhibited XET activity and 18 promoted it (especially anthraquinones and flavonoids). No compounds promoted XET in quantitative assays with (cellulose-free) soluble xyloglucan as substrate, suggesting that promotion was dependent on enzyme-cellulose interactions. With cellulose-free xyloglucan as substrate, we found 22 XET-inhibitors - especially compounds that generate singlet oxygen ((1)O2) e.g., riboflavin (IC50 29 ?M), retinoic acid, eosin (IC50 27 ?M) and erythrosin (IC50 36 ?M). The riboflavin effect was light-dependent, supporting (1)O2 involvement. Other inhibitors included tannins, sulphydryl reagents and triphenylmethanes. Some inhibitors (vulpinic acid and brilliant blue G) were relatively specific to XET, affecting only two or three, respectively, of nine other wall-enzyme activities tested; others [e.g. (-)-epigallocatechin gallate and riboflavin] were non-specific. In vivo, out of eight XET-inhibitors bioassayed, erythrosin (1 ?M) inhibited cell expansion in Rosa and Zea cell-suspension cultures, and 40 ?M mycophenolic acid and (-)-epigallocatechin gallate inhibited Zea culture growth. Our work showcases a general high-throughput strategy for discovering wall-enzyme inhibitors, some being plant growth inhibitors potentially valuable as physiological tools or herbicide leads. PMID:26093490

  3. Discovery of small molecule inhibitors of xyloglucan endotransglucosylase (XET) activity by high-throughput screening

    PubMed Central

    Chormova, Dimitra; Franková, Lenka; Defries, Andrew; Cutler, Sean R.; Fry, Stephen C.

    2015-01-01

    Small molecules (xenobiotics) that inhibit cell-wall-localised enzymes are valuable for elucidating the enzymes’ biological roles. We applied a high-throughput fluorescent dot-blot screen to search for inhibitors of Petroselinum xyloglucan endotransglucosylase (XET) activity in vitro. Of 4216 xenobiotics tested, with cellulose-bound xyloglucan as donor-substrate, 18 inhibited XET activity and 18 promoted it (especially anthraquinones and flavonoids). No compounds promoted XET in quantitative assays with (cellulose-free) soluble xyloglucan as substrate, suggesting that promotion was dependent on enzyme–cellulose interactions. With cellulose-free xyloglucan as substrate, we found 22 XET-inhibitors – especially compounds that generate singlet oxygen (1O2) e.g., riboflavin (IC50 29 ?M), retinoic acid, eosin (IC50 27 ?M) and erythrosin (IC50 36 ?M). The riboflavin effect was light-dependent, supporting 1O2 involvement. Other inhibitors included tannins, sulphydryl reagents and triphenylmethanes. Some inhibitors (vulpinic acid and brilliant blue G) were relatively specific to XET, affecting only two or three, respectively, of nine other wall-enzyme activities tested; others [e.g. (?)-epigallocatechin gallate and riboflavin] were non-specific. In vivo, out of eight XET-inhibitors bioassayed, erythrosin (1 ?M) inhibited cell expansion in Rosa and Zea cell-suspension cultures, and 40 ?M mycophenolic acid and (?)-epigallocatechin gallate inhibited Zea culture growth. Our work showcases a general high-throughput strategy for discovering wall-enzyme inhibitors, some being plant growth inhibitors potentially valuable as physiological tools or herbicide leads. PMID:26093490

  4. c 2013 by Jacob Thomas Stewart. All rights reserved. HIGH-RESOLUTION INFRARED SPECTROSCOPY OF LARGE MOLECULES AND

    E-print Network

    McCall, Benjamin J.

    , which represents the first high-resolution study of the bending modes of water dimer. Two perpendicular in the water dimer complex. Excitation of the donor bending mode was found to have little effect OF LARGE MOLECULES AND WATER CLUSTERS USING QUANTUM CASCADE LASERS BY JACOB THOMAS STEWART DISSERTATION

  5. Label-Free Screening Small-Molecule Compound Libraries for Protein-Ligands Using a High-Throughput Optical Scanning

    E-print Network

    Zhu, Xiangdong

    targets, we can acquire an end-point image of the microarray in 90 minutes with pixel resolution of 20 m: microarrays, high-throughput, label-free detection, in situ detection, oblique-incidence reflectivity a functionalized solid surface. In addition, detection of protein binding to small- molecule microarrays

  6. Introducing Bond-Line Organic Structures in High School Biology: An Activity that Incorporates Pleasant-Smelling Molecules

    ERIC Educational Resources Information Center

    Rios, Andro C.; French, Gerald

    2011-01-01

    Chemical education occurs in settings other than just the chemistry classroom. High school biology courses are frequently where students are introduced to organic molecules and their importance to cellular chemistry. However, structural representations are often intimidating because students have not been introduced to the language. As part of a…

  7. PREFACE: Workshop on Sources of Polarized Leptons and High Brightness Electron Beams

    NASA Astrophysics Data System (ADS)

    Hillert, Wolfgang; Aulenbacher, Kurt

    2011-04-01

    This volume contains the proceedings of the International Workshop on Sources of Polarized Leptons and High Brightness Electron Beams (PESP2010). The workshop was hosted by the University of Bonn from 21-24 September 2010. PESP2010 has been conducted as satellite workshop preceding the International SPIN Physics Symposium (SPIN2010). In view of the expanding and challenging field of the production of high brightness lepton beams, the selection of workshop topics was extended to cover the demands of modern accelerator developments and applications. As novel light sources such as FELs and ERLs place new requirements on the properties of unpolarized beams in terms of brightness and intensity, the generation of DC and pulsed beams was included as a major topic in the scientific program. In keeping with tradition, polarized beams formed another key topic. The discussion was however extended to the generation of polarized positron beams, as e.g. required for future linear colliders. Besides the presentation of recent developments in these fields and status reports from laboratories worldwide, additional emphasis was put on the applications of polarized electron beams. PESP2010 was attended by 61 registered participants from all over the world. The scientific program comprised 30 talks in plenary sessions and 7 posters. An overview of the scientific results presented at PESP2010 was given in a summary talk at the SPIN2010 symposium. In total 24 contributions to the proceedings were submitted and reviewed by members of the scientific advisory committee before publication in this volume. Many people contributed to the success of the workshop. Among them are members of the Local Organizing Committee as well as the scientific and technical staff of the Physics Institute and the in-house accelerator facility ELSA, who patiently and efficiently took care of the numerous organizational aspects related to the event. The environment they created was highly conducive to a productive working atmosphere and fruitful discussions. The dedication of all who contributed is gratefully acknowledged. We would like to extend our warmest thanks to all of them. Bonn, May 10, 2011 Wolfgang Hillert and Kurt AulenbacherEditors Conference photograph Conference poster

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

    E-print Network

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

    2011-04-22

    -electron nonperturbative investigation of HHG processes of homonuclear (N2 and F2) and heteronuclear (CO, BF, and HF) molecules in intense ultrashort laser pulses with the emphasis on the role of multiple molecular orbitals (MOs). The results reveal intriguing...

  9. Thermodynamics of long supercoiled molecules: insights from highly efficient Monte Carlo simulations.

    PubMed

    Lepage, Thibaut; Képès, François; Junier, Ivan

    2015-07-01

    Supercoiled DNA polymer models for which the torsional energy depends on the total twist of molecules (Tw) are a priori well suited for thermodynamic analysis of long molecules. So far, nevertheless, the exact determination of Tw in these models has been based on a computation of the writhe of the molecules (Wr) by exploiting the conservation of the linking number, Lk=Tw+Wr, which reflects topological constraints coming from the helical nature of DNA. Because Wr is equal to the number of times the main axis of a DNA molecule winds around itself, current Monte Carlo algorithms have a quadratic time complexity, O(L(2)), with respect to the contour length (L) of the molecules. Here, we present an efficient method to compute Tw exactly, leading in principle to algorithms with a linear complexity, which in practice is O(L(1.2)). Specifically, we use a discrete wormlike chain that includes the explicit double-helix structure of DNA and where the linking number is conserved by continuously preventing the generation of twist between any two consecutive cylinders of the discretized chain. As an application, we show that long (up to 21 kbp) linear molecules stretched by mechanical forces akin to magnetic tweezers contain, in the buckling regime, multiple and branched plectonemes that often coexist with curls and helices, and whose length and number are in good agreement with experiments. By attaching the ends of the molecules to a reservoir of twists with which these can exchange helix turns, we also show how to compute the torques in these models. As an example, we report values that are in good agreement with experiments and that concern the longest molecules that have been studied so far (16 kbp). PMID:26153710

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

    PubMed

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

    2015-02-01

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

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

    SciTech Connect

    Jourdain, E.; Roques, J. P.; Chauvin, M.; Clark, D. J.

    2012-12-10

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

  12. Cathode performance during two beam operation of the high current high polarization electron gun for eRHIC

    SciTech Connect

    Rahman, O.; Ben-Zvi, I.; Degen, C.; Gassner, D. M.; Lambiase, R.; Meng, W.; Pikin, A.; Rao, T.; Sheehy, B.; Skaritka, J.; Wang, E.; Pietz, J.; Ackeret, M.; Yeckel, C.; Miller, R.; Dobrin, E.; Thompson, K.

    2015-05-03

    Two electron beams from two activated bulk GaAs photocathodes were successfully combined during the recent beam test of the High Current High Polarization Electron gun for eRHIC. The beam test took place in Stangenes Industries in Palo Alto, CA, where the cathodes were placed in diagonally opposite locations inside the high voltage shroud. No significant cross talking between the cathodes was found for the pertinent vacuum and low average current operation, which is very promising towards combining multiple beams for higher average current. This paper describes the cathode preparation, transport and cathode performance in the gun for the combining test, including the QE and lifetimes of the photocathodes at various steps of the experiment.

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

    PubMed Central

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

    2013-01-01

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

  14. High spin polarization and spin splitting in equiatomic quaternary CoFeCrAl Heusler alloy

    NASA Astrophysics Data System (ADS)

    Bainsla, Lakhan; Mallick, A. I.; Coelho, A. A.; Nigam, A. K.; Varaprasad, B. S. D. Ch. S.; Takahashi, Y. K.; Alam, Aftab; Suresh, K. G.; Hono, K.

    2015-11-01

    In this paper, we investigate CoFeCrAl alloy by means of ab-initio electronic structure calculations and various experimental techniques. The alloy is found to exist in the B2-type cubic Heusler structure, which is very similar to Y-type (or LiMgPdSn prototype) structure with space group F-43m (#216). Saturation magnetization (MS) of about 2 ?B/f.u. is observed at 8 K under ambient pressure, which is in good agreement with the Slater-Pauling rule. MS values are found to be independent of pressure, which is a prerequisite for half-metals. The ab-initio electronic structure calculations predict half-metallicity for the alloy with a spin slitting energy of 0.31 eV. Importantly, this system shows a high current spin polarization value of 0.67±0.02, as deduced from the point contact Andreev reflection measurements. Linear dependence of electrical resistivity with temperature indicates the possibility of reasonably high spin polarization at elevated temperatures (~150 K) as well. All these suggest that CoFeCrAl is a promising material for the spintronic devices.

  15. Highly polarized polymer light-emitting diodes utilizing friction-transferred poly(9,9-dioctylfluorene) thin films

    NASA Astrophysics Data System (ADS)

    Misaki, Masahiro; Ueda, Yasukiyo; Nagamatsu, Shuichi; Chikamatsu, Masayuki; Yoshida, Yuji; Tanigaki, Nobutaka; Yase, Kiyoshi

    2005-12-01

    Polarized polymer light-emitting diodes (PLEDs) have been constructed utilizing friction-transferred poly(9,9-dioctylfluorene) (PFO) thin films. The friction transfer technique allows oriented PFO to be deposited directly onto an indium tin oxide anode without an alignment layer such as polyimide. Polarized absorption and photoluminescence spectra revealed that the polymer backbones are highly aligned in the friction direction. We fabricated PLEDs consisting of friction-transferred PFO as an emissive layer, vacuum-deposited bathocuproine as an electron transport and hole-blocking layer, and a vacuum-deposited LiF /Al cathode. Highly polarized blue emission with an integrated polarization ratio of 31 and a luminance of up to 300cd/m2 was observed from the PLEDs.

  16. High-resolution single-molecule characterization of the enzymatic states in Escherichia coli F1-ATPase.

    PubMed

    Bilyard, Thomas; Nakanishi-Matsui, Mayumi; Steel, Bradley C; Pilizota, Teuta; Nord, Ashley L; Hosokawa, Hiroyuki; Futai, Masamitsu; Berry, Richard M

    2013-02-01

    The rotary motor F(1)-ATPase from the thermophilic Bacillus PS3 (TF(1)) is one of the best-studied of all molecular machines. F(1)-ATPase is the part of the enzyme F(1)F(O)-ATP synthase that is responsible for generating most of the ATP in living cells. Single-molecule experiments have provided a detailed understanding of how ATP hydrolysis and synthesis are coupled to internal rotation within the motor. In this work, we present evidence that mesophilic F(1)-ATPase from Escherichia coli (EF(1)) is governed by the same mechanism as TF(1) under laboratory conditions. Using optical microscopy to measure rotation of a variety of marker particles attached to the ?-subunit of single surface-bound EF(1) molecules, we characterized the ATP-binding, catalytic and inhibited states of EF(1). We also show that the ATP-binding and catalytic states are separated by 35±3°. At room temperature, chemical processes occur faster in EF(1) than in TF(1), and we present a methodology to compensate for artefacts that occur when the enzymatic rates are comparable to the experimental temporal resolution. Furthermore, we show that the molecule-to-molecule variation observed at high ATP concentration in our single-molecule assays can be accounted for by variation in the orientation of the rotating markers. PMID:23267177

  17. Exploring Rotation-Vibration Coupling in Highly Fluxional Molecules Using Surface Hopping Diffusion Monte Carlo

    NASA Astrophysics Data System (ADS)

    Petit, Andrew S.; McCoy, Anne B.

    2012-06-01

    Diffusion Monte Carlo (DMC) has widely been shown to be a powerful technique for studying ro-vibrational states of highly fluxional molecules and clusters. An extension of DMC to multiple potential energy surfaces (PESs) based on the Tully surface hopping approach has previously been developed by our group. Here, we report an application of this approach to the calculation of rotationally excited states of systems with pronounced rotation-vibration coupling and large-amplitude, zero-point vibrational motion. More specifically, for a chosen value of J, each walker in the DMC ensemble is expanded in a symmetric top basis. The expansion coefficients are updated each time-step based on the action of the rigid-rotor asymmetric top Hamiltonian. This Hamiltonian is constructed using the inverse moment of inertia tensor evaluated in the Eckart frame at the walker's position in configuration space. Each walker is then localized onto a single, K-dependent effective PES, and the effective potential energy associated with the walker's position on that surface determines the evolution of its weight in the DMC ensemble. Preliminary results of the application of this methodology to model systems such as H_3^+ and H_2D^+ will be discussed as well as its prospect for accurately evaluating ro-vibrational states of systems like CH_5^+. Finally, a comparison of this technique with our previously developed fixed-node DMC approach for the evaluation of ro-vibrational energies and wave functions will be presented. J. C. Tully, J. Chem. Phys. 93, 1061 (1990). A.B. McCoy, Chem. Phys. Lett. 321, 71 (2000). A. S. Petit, B. A. Wellen, and A. B. McCoy, J. Chem. Phys. 136, 074101 (2012).

  18. High-resolution soft x-ray photoionization studies of selected molecules

    SciTech Connect

    Hudson, E.A.

    1993-08-01

    Near-edge soft x-ray photoionization spectra were measured for CO, SF{sub 6}, H{sub 2}S, and D{sub 2}S in the gas phase, using the Free University of Berlin plane-grating SX-700-II monochromator at the synchrotron radiation source BESSY. Photoionization spectra of carbon monoxide were measured near the carbon and oxygen K edges. Vibrational spacings and bond lengths are derived for several resonances. Results are consistent with equivalent-core model and indicate the different influences of the carbon and oxygen Is core holes. Corresponding spectra of H{sub 2}CO and D{sub 2}CO were also measured. Assignment of complex vibrational structure in valence-shell and Rydberg resonances is facilitated by comparison of spectra for the two isotopic species. Geometric and vibrational parameters are derived for several carbon 1s core-excited states. Isotopic shifts are observed in the energies and linewidths of some core-excited states. Sulfur hexafluoride photoionization spectra, measured near the sulfur L{sub 2,3} edges, show several series of weak, narrow Rydberg resonances. High resolution and good counting statistics allow a complete assignment of these states. Lineshapes of the broad inner-well resonances are analyzed to establish the magnitudes of vibrational and lifetime broadening in these states. Spectra of the H{sub 2}S and D{sub 2}S molecules were also measured near the sulfur L{sub 2,3} edges. Besides lower-energy transitions to inner-well states, a complex manifold of overlapping Rydberg resonances is observed. The rich fine structure of these states arises mainly from removal of orbital degeneracies in molecular field. Additional structure due to vibrational excitations in the final state is identified by comparison of the spectra for the two isotopic species.

  19. Retrieving the ionization dynamics of high-energy photoelectrons in elliptically polarized laser fields

    NASA Astrophysics Data System (ADS)

    Yu, Jizhou; Sun, Xufei; Shao, Yun; Li, Min; Gong, Qihuang; Liu, Yunquan

    2015-10-01

    Using a three-dimensional semiclassical model that incorporates tunneling and Coulomb field effect, we investigate photoelectron angular distributions from single ionization of atoms in intense elliptically polarized laser fields. We have studied the photoelectron angular distributions of the first and second recollisions by tracing the respective tunnel-ionized electron trajectories. Through studying the instant of ionization and recollision with respect to the laser phase, the relative contributions of the first recollision and second recollision on two-dimensional photoelectron angular distributions have been analyzed, respectively. We find that the relative contribution of the later recollision increases with the ellipticity. The electron recollision favors the later recollision trajectory at larger field ellipticity and the later recollision trajectory contributes dominantly to the yield of the high-energy photoelectrons. We have analyzed the dependence of high-energy photoelectrons on the initial momentum and the ionization phase with respect to the laser field.

  20. Exploring the Standard Model with the High Luminosity, Polarized Electron-Ion Collider

    SciTech Connect

    Milner, Richard G.

    2009-08-04

    The Standard Model is only a few decades old and has been successfully confirmed by experiment, particularly at the high energy frontier. This will continue with renewed vigor at the LHC. However, many important elements of the Standard Model remain poorly understood. In particular, the exploration of the strong interaction theory Quantum Chromodynamics is in its infancy. How does the spin-1/2 of the proton arise from the fundamental quark and gluon constituents? Can we understand the new QCD world of virtual quarks and gluons in the nucleon? Using precision measurements can we test the limits of the Standard Model and look for new physics? To address these and other important questions, physicists have developed a concept for a new type of accelerator, namely a high luminosity, polarized electron-ion collider. Here the scientific motivation is summarized and the accelerator concepts are outlined.

  1. The development of high-performance alkali-hybrid polarized He3 targets for electron scattering

    DOE PAGESBeta

    Singh, Jaideep T.; Dolph, Peter A.M.; Tobias, William Al; Averett, Todd D.; Kelleher, Aiden; Mooney, K. E.; Nelyubin, Vladimir V.; Wang, Yunxiao; Zheng, Yuan; Cates, Gordon D.

    2015-05-01

    We present the development of high-performance polarized ³He targets for use in electron scattering experiments that utilize the technique of alkali-hybrid spin-exchange optical pumping. We include data obtained during the characterization of 24 separate target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. The results presented here document dramatic improvement in the performance of polarized ³He targets, as well as the target properties and operating parameters that made those improvements possible. Included in our measurements were determinations of the so-called X-factors that quantify a temperature-dependent and as-yet poorlymore »understood spin-relaxation mechanism that limits the maximum achievable ³He polarization to well under 100%. The presence of this spin-relaxation mechanism was clearly evident in our data. We also present results from a simulation of the alkali-hydrid spin-exchange optical pumping process that was developed to provide guidance in the design of these targets. Good agreement with actual performance was obtained by including details such as off-resonant optical pumping. Now benchmarked against experimental data, the simulation is useful for the design of future targets. Included in our results is a measurement of the K- ³He spin-exchange rate coefficient $k^\\mathrm{K}_\\mathrm{se} = \\left ( 7.46 \\pm 0.62 \\right )\\!\\times\\!10^{-20}\\ \\mathrm{cm^3/s}$ over the temperature range 503 K to 563 K.« less

  2. High-resolution polarization sensitive OCT for ocular imaging in rodents

    NASA Astrophysics Data System (ADS)

    Fialová, Stanislava; Rauscher, Sabine; Gröger, Marion; Pircher, Michael; Hitzenberger, Christoph K.; Baumann, Bernhard

    2015-03-01

    A new high-resolution polarization sensitive optical coherence tomography system was developed for imaging rodent retina. Various light-tissue interactions such as birefringence and depolarization can change the polarization state of light. In the eye, there are several tissues that have these properties, for example retinal pigment epithelium (depolarization) and sclera (birefringence). These layers play key roles in diseases like age-related macular degeneration or glaucoma. Animal models are an important component for understanding disease pathogenesis. The gold standard for the evaluation of preclinical experiments is histology, which is an invasive and terminal procedure. Since OCT is non-invasive, it has the potential to be an alternative to histology with the benefit of long-term study of the disease progression in the same animal. In this study, a superluminescent diode with spectrum width 100 nm and mean wavelength 840 nm is used as a light source in order to enable high axial resolution. Spectrometers are custom built to enable high imaging speed that allows acquiring 3D data sets with 1024x200x1536 voxels in 3.44 s. From the acquired data, images displaying phase retardation induced by birefringence and orientation of birefringent axis were calculated. In first measurements, we were able to identify the RPE-choroid complex (depolarization effect) and the sclera (strong birefringence) in the retina of Long-Evans and Sprague-Dawley rats. Our preliminary results demonstrate the feasibility of the system for high speed/resolution imaging of the rodent retina. This is useful for longitudinal studies of disease models of retinal disease in rats and mice

  3. 5kW High peak power, 0.2 mJ high pulse energy, linearly-polarized pulsed laser from a single all-fiber oscillator

    NASA Astrophysics Data System (ADS)

    Shi, Chen; Huang, Long; Wang, Xiaolin; Zhou, Pu

    2015-12-01

    We report a high peak power ytterbium-doped fiber laser that emitted linearly-polarized laser at 1064 nm. An intracavity polarization-maintaining (PM) acousto-optic modulator (AOM) was used as a Q-switch to generate pulsed laser output. The whole system was constructed with all-fiber structure. The power of the polarized laser reached 4.21 W and a polarization purity of greater than 97.6% under the repetition rate of 20 kHz. The pulse width was 37 ns, which implied a 5 kW peak power and 0.2 mJ pulse energy. It is the highest peak power output from a linearly-polarized, Q-switched fiber laser oscillator to the best of our knowledge.

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

    SciTech Connect

    Jiang, X.; Arrington, J.; Benmokhtar, F.; Camsonne, A.; Chen, J. P.; Holt, R. J.; Qattan, I. A.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Physics; Rutgers Univ.; Univ. Blaise Pascal; Thomas Jefferson National Accelerator Facility

    2007-05-01

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

  5. Adsorption and binding of capping molecules for highly luminescent CdSenanocrystals - DFT simulation studies

    NASA Astrophysics Data System (ADS)

    Chou, Hung-Lung; Tseng, Chih-Hsiang; Pillai, K. Chandrasekara; Hwang, Bing-Joe; Chen, Liang-Yih

    2010-12-01

    During CdSenanocrystalgrowth, loss of surface capping molecules occurs leading to a decrease of photoluminescence (PL) quantum yield. In general, aliphatic capping molecules are applied to passivate the surface of CdSenanocrystals to modulate the optical properties of the CdSe. In this work, two kinds of alkylamine (n-butylamine (n-BA) and n-hexylamine (n-HA)) and oleic acid (OA) were used to modify the surfaces of the CdSenanocrystals. From the PL spectra and quantum yield analyses, we observed that the PL emission peak positions of the modified CdSenanocrystals have blue shifted for all three capping molecules. However, the PL quantum yield of the CdSenanocrystals increased after introduction of the alkylamine molecules, but decreased with oleic acid. The detailed mechanism was not clear until now. In this study, a density function theory (DFT) simulation was employed to demonstrate binding energy and charge analyses of CdSe with n-BA, n-HA and OA. By comparing the binding energy of the bare CdSenanocrystals to that of the CdSe with the capping molecules, it was shown that n-BA and n-HA as capping molecules help to increase the charge on Se and decrease it on cadmium of the CdSe.During CdSenanocrystalgrowth, loss of surface capping molecules occurs leading to a decrease of photoluminescence (PL) quantum yield. In general, aliphatic capping molecules are applied to passivate the surface of CdSenanocrystals to modulate the optical properties of the CdSe. In this work, two kinds of alkylamine (n-butylamine (n-BA) and n-hexylamine (n-HA)) and oleic acid (OA) were used to modify the surfaces of the CdSenanocrystals. From the PL spectra and quantum yield analyses, we observed that the PL emission peak positions of the modified CdSenanocrystals have blue shifted for all three capping molecules. However, the PL quantum yield of the CdSenanocrystals increased after introduction of the alkylamine molecules, but decreased with oleic acid. The detailed mechanism was not clear until now. In this study, a density function theory (DFT) simulation was employed to demonstrate binding energy and charge analyses of CdSe with n-BA, n-HA and OA. By comparing the binding energy of the bare CdSenanocrystals to that of the CdSe with the capping molecules, it was shown that n-BA and n-HA as capping molecules help to increase the charge on Se and decrease it on cadmium of the CdSe. Electronic supplementary information (ESI) available: Figure S1. See DOI: 10.1039/c0nr00569j

  6. Study of Spectroscopic Properties of Diatomic Molecules Based on High Orders of the Operator Perturbation Theory

    NASA Astrophysics Data System (ADS)

    Bekhtereva, E. S.; Litvinovskaya, A. G.; Konov, I. A.; Gromova, O. V.; Chertavskikh, Yu. V.; Tse, Yang Fang; Ulenikov, O. N.

    2015-08-01

    The form of the effective Hamiltonian of a quantum system with allowance for corrections of arbitrary order for solving arbitrary quantum-mechanical problems with perturbation operator depending not only on the same coordinates as the operator of the zero approximation, but also on an arbitrary set of other coordinates whose derivative operators may not commute with each other, is retrieved based on the operator perturbation theory (the recurrence formulas for corrections of any arbitrary order of the operator perturbation theory are presented in the paper in the most general form). The general results obtained allow the special features of the effective operators of any polyatomic molecule to be investigated. As a first step, an arbitrary diatomic molecule is investigated. Isotopic relations among different spectroscopic parameters are derived for the parent molecule and its various isotopic modifications.

  7. Parallel and series FED microstrip array with high efficiency and low cross polarization

    NASA Technical Reports Server (NTRS)

    Huang, John (inventor)

    1995-01-01

    A microstrip array antenna for vertically polarized fan beam (approximately 2 deg x 50 deg) for C-band SAR applications with a physical area of 1.7 m by 0.17 m comprises two rows of patch elements and employs a parallel feed to left- and right-half sections of the rows. Each section is divided into two segments that are fed in parallel with the elements in each segment fed in series through matched transmission lines for high efficiency. The inboard section has half the number of patch elements of the outboard section, and the outboard sections, which have tapered distribution with identical transmission line sections, terminated with half wavelength long open-circuit stubs so that the remaining energy is reflected and radiated in phase. The elements of the two inboard segments of the two left- and right-half sections are provided with tapered transmission lines from element to element for uniform power distribution over the central third of the entire array antenna. The two rows of array elements are excited at opposite patch feed locations with opposite (180 deg difference) phases for reduced cross-polarization.

  8. Fermi level tuning of highly spin-polarized complex Heusler alloys via materials genome

    NASA Astrophysics Data System (ADS)

    Pandey, Sudip; Quetz, Abdiel; Aryal, Anil; Fralaide, Michael; Samanta, Tapas; Munira, Kamran; Butler, William; Dubenko, Igor; Mazumdar, Dipanjan; Stadler, Shane; Ali, Naushad

    2015-03-01

    Heusler alloys are the largest family of half-metals (100% spin polarized at the Fermi level) and most promising for spintronic device applications. Many half-metallic full-Huesler alloys are predicted from ab-initio calculations, but may or may not be experimentally realizable. Here, we present a novel strategy to utilize these predicted materials to tune the Fermi level of well-known, highly spin-polarized Heusler alloys. We start with the test sample of [Co2MnSi]1-x[Co2CrGe]x, and, by controlling the ratio of these materials, we were able to shift the Fermi level of Co2MnSi. Experimentally, we study the structural and magnetic properties of such Heusler alloys by room temperature X-ray diffraction (XRD) and taking magnetization measurements; It was found that these complex combinations of materials are single phase even though some components (Co2CrGe for example) might not be stable in bulk form alone. This work was supported by the Office of Basic Energy Sciences, Material Science Division of the U.S. Department of Energy (DOE Grant No. DE-FG02-06ER46291 and DE-FG02-13ER46946).

  9. DEM Extraction from High-Resolution Stereoscopic Worldview 1 & 2 Imagery of Polar Outlet Glaciers

    NASA Astrophysics Data System (ADS)

    Porter, C. C.; Morin, P. J.; Howat, I. M.; Niebuhr, S.; Smith, B. E.

    2011-12-01

    There are few reliable digital elevation models (DEMs) in polar regions and most are of low resolution (on the order of 100's of meters to km) or of poor quality. Polar environments are changing rapidly and accurate DEMs are critical for correcting imagery, measuring glacier thickness changes and modeling ice flow and surface melt water drainage. Using in-track stereoscopic images from Worldview-1 and Worldview-2, we derived high-resolution DEMs for outlet glaciers and other areas of interest in Antarctica and the Arctic. We used ERDAS Imagine's LPS eATE (enhanced automated terrain extraction) algorithm to derive a dense point cloud of matches. The resulting point cloud is comparable in density to that obtained by LiDAR flown at 10,000 feet. Preliminary comparisons of our results to ground control points collected by field teams and airborne and satellite laser altimeters show 0.5 - 10 meter vertical error over glaciers and 2 - 10 meter error over ice-free terrain. The error is primarily due to approximations in the sensor model and is consistent across the DEM. Our results indicate that refinements in the sensor model and point matching algorithm will improve accuracy. Given the increasing interest in glacier change detection around the globe, DEMs extracted from frequent satellite stereo pairs can be used to monitor and quantify changes in both movement and volume.

  10. High image quality 3D displays with polarizer glasses based on active retarder technology

    NASA Astrophysics Data System (ADS)

    Jung, Sung-min; Lee, Young-bok; Park, Hyung-ju; Park, Jin-woo; Lee, Dong-hoon; Jeong, Woo-nam; Kim, Jeong-hyun; Chung, In-Jae

    2011-03-01

    In this study, we proposed methods to reduce a black-white (BW) 3D crosstalk and gray-to-gray (GtoG) 3D crosstalk in active retarder 3D (AR3D) technology. To obtain the BW 3D crosstalk to 2.5% without backlight scanning, we first optimized the switching time of AR panel. Then, the BW 3D crosstalk of 1.0% was achieved by scanning the backlight synchronized with the liquid crystal display (LCD) panel and AR panel. Finally, with the over-driving method for various condition of gray-to-gray transition, the average GtoG 3D crosstalk was obtained to be under 1.8% showing clear 3D images. With these concepts of reducing the 3D crosstalk in AR3D technology, we developed AR3D monitor having 23 inches in diagonal with full HD resolution. The luminance of our prototype is 73 nits at 3D mode through polarizer glasses and 300 nits at 2D mode for bare eyes, showing that 24% light efficiency in 3D mode. In conclusion, our prototype shows clear 3D image with full HD resolution and high luminance even though it employs polarizer glasses.

  11. Performances of a Compact, High-Power WB Source with Circular Polarization

    NASA Astrophysics Data System (ADS)

    Delmote, P.; Pinguet, S.; Bieth, F.

    This paper presents the design and the performances of an embedded high-power microwave (HPM) wideband source, developed and built at the French-German Research Institute of Saint-Louis. The system was intended for dual use, homeland security, and military applications. It is powered by a 400 kV compact Marx generator with specificities in coaxial design and low energy. The slow monopolar signal from the Marx is sharpened using a pulse-forming stage, made of a switching module pressurized with nitrogen, followed by a monopulse-to-monocycle converter. The duration and rise times of this signal could be adjusted by varying the pressure and space between electrodes. Repetitive operations were performed up to 100 Hz during 10 s without a gas flow. Two kinds of antennas can be connected to the source. The first one is a TEM horn, with an optional dielectric lens, that radiates a vertically polarized UWB short pulse. The second one is a nine-turn helix, working in Kraus monopolar axial mode and radiating a circularly polarized wideband signal along the main axis. A dedicated conical reflector increases its directivity and bandwidth. The whole source is designed to be embedded inside an aluminum trailer, powered by batteries and remote controlled through an optical fiber.

  12. Optically controlled microwave phase shifter based on nonlinear polarization rotation in a highly nonlinear fiber.

    PubMed

    Li, Wei; Sun, Wen Hui; Wang, Wen Ting; Zhu, Ning Hua

    2014-06-01

    This Letter reports an optically controlled microwave phase shifter with an ultra-wideband working bandwidth and a full 360° phase shifting range based on nonlinear polarization rotation (NPR) in a highly nonlinear fiber (HNLF). A continuous wave probe light is modulated by a polarization modulator (PolM) that is driven by a microwave signal to be phase shifted. The optical carrier and the first-order sidebands of the probe light experience different phase shifts due to the NPR induced by the control light in the HNLF. An optical bandpass filter is used to realize single-sideband modulation of the probe light by removing one of the first-order sidebands, as well as to reject the control light. After detecting by a photodetector, the phase of the recovered microwave signal is continuously tunable by adjusting the power of the control light. The proposed approach is theoretically analyzed and experimentally verified. A full 360° tunable phase shift is realized over an ultra-wideband frequency range from 8 to 38 GHz when the power of the control light is tuned from 0 to 570 mW. PMID:24876035

  13. Polarization control in high power microwaves from a rectangular cross section gyrotron

    SciTech Connect

    Hochman, J.M.; Gilgenbach, R.M.; Jaynes, R.J.; Rintamaki, J.I.; Lau, Y.Y.; Spencer, T.A.

    1997-12-31

    The authors summarize the results of experiments on a gyrotron utilizing rectangular-cross-section (RCS) interaction cavities. Current issues under investigation include polarization control as a function of magnetic field, power versus pulselength of microwave emission, and mode competition. The electron beam driver producing an annular beam is the Michigan Electron Long Beam Accelerator (MELBA). The annular e-beam is spun up into an axis-encircling beam by passing it through a magnetic cusp prior to entering the RCS interaction cavity. Initial experimental results show a high degree of polarization [P(TE{sub 10})/P(TE{sub 01}) = 30 or 1/30] as a function of cavity fields. Megawatt microwave output shifts from the fundamental mode, which dominates the next order mode by an order of magnitude, to the next order mode as the field is raised from 1.4 to 1.7 kGauss. Frequency measurements using microstrip bandpass filters and a superheterodyne mixer support this result as well as MAGIC simulations. MAGIC code simulations using various magnetic fields will be presented as well as results utilizing the E-gun code.

  14. High-priority lunar landing sites for in situ and sample return studies of polar volatiles

    NASA Astrophysics Data System (ADS)

    Lemelin, Myriam; Blair, David M.; Roberts, Carolyn E.; Runyon, Kirby D.; Nowka, Daniela; Kring, David A.

    2014-10-01

    Our understanding of the Moon has advanced greatly over the last several decades thanks to analyses of Apollo samples and lunar meteorites, and recent lunar orbital missions. Notably, it is now thought that the lunar poles may be much more enriched in H2O and other volatile chemical species than the equatorial regions sampled during the Apollo missions. The equatorial regions sampled, themselves, contain more H2O than previously thought. A new lunar mission to a polar region is therefore of great interest; it could provide a measure of the sources and processes that deliver volatiles while also evaluating the potential in situ resource utilization value they may have for human exploration. In this study, we determine the optimal sites for studying lunar volatiles by conducting a quantitative GIS-based spatial analysis of multiple relevant datasets. The datasets include the locations of permanently shadowed regions, thermal analyses of the lunar surface, and hydrogen abundances. We provide maps of the lunar surface showing areas of high scientific interest, including five regions near the lunar north pole and seven regions near the lunar south pole that have the highest scientific potential according to rational search criteria. At two of these sites-a region we call the “Intercrater Polar Highlands” (IPH) near the north pole, and Amundsen crater near the south pole-we provide a more detailed assessment of landing sites, sample locations, and exploration strategies best suited for future human or robotic exploration missions.

  15. High sensitivity fluorescent single particle and single molecule detection apparatus and method

    DOEpatents

    Mathies, Richard A. (Contra Costa County, CA); Peck, Konan (Contra Costa County, CA); Stryer, Lubert (Santa Clara County, CA)

    1990-01-01

    Apparatus is described for ultrasensitive detection of single fluorescent particles down to the single fluorescent molecule limit in a fluid or on a substrate comprising means for illuminating a predetermined volume of the fluid or area of the substrate whereby to emit light including background light from the fluid and burst of photons from particles residing in the area. The photon burst is detected in real time to generate output representative signal. The signal is received and the burst of energy from the fluorescent particles is distinguished from the background energy to provide an indication of the number, location or concentration of the particles or molecules.

  16. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs

    E-print Network

    Chung, Il-Sug

    2015-01-01

    A theoretical study of differences in broadband high-index-contrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating thicknesses and smaller grating periods than the TE HCG reflectors. This difference is found to originate from the different boundary conditions met for the electric field of each polarization. Due to this difference, the TM HCG reflectors have much shorter evanescent extension of HCG modes into low-refractive-index media surrounding the HCG. This enables to achieve a very short effective cavity length for VCSELs, which is essential for ultrahigh speed VCSELs and MEMS-tunable VCSELs. The obtained understandings on polarization dependences will be able to serve as important design guidelines for various HCG-based devices.

  17. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs.

    PubMed

    Chung, Il-Sug

    2015-06-29

    A theoretical study of differences in broadband high-index-contrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating thicknesses and smaller grating periods than the TE HCG reflectors. This difference is found to originate from the different boundary conditions met for the electric field of each polarization. Due to this difference, the TM HCG reflectors have much shorter evanescent extension of HCG modes into low-refractive-index media surrounding the HCG. This enables to achieve a very short effective cavity length for VC-SELs, which is essential for ultrahigh speed VCSELs and MEMS-tunable VCSELs. The obtained understandings on polarization dependences will be able to serve as important design guidelines for various HCG-based devices. PMID:26191685

  18. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs

    NASA Astrophysics Data System (ADS)

    Chung, Il-Sug

    2015-06-01

    A theoretical study of differences in broadband high-index-contrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating thicknesses and smaller grating periods than the TE HCG reflectors. This difference is found to originate from the different boundary conditions met for the electric field of each polarization. Due to this difference, the TM HCG reflectors have much shorter evanescent extension of HCG modes into low-refractive-index media surrounding the HCG. This enables to achieve a very short effective cavity length for VCSELs, which is essential for ultrahigh speed VCSELs and MEMS-tunable VCSELs. The obtained understandings on polarization dependences will be able to serve as important design guidelines for various HCG-based devices.

  19. Towards high-frequency operation of polarization oscillations in spin vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Höpfner, Henning; Gerhardt, Nils C.; Hofmann, Martin R.; Pusch, Tobias; Michalzik, Rainer

    2015-09-01

    Compared to purely charge based devices, spintronic lasers offer promising perspectives for new superior device concepts. Especially vertical-cavity surface-emitting lasers with spin-polarization (spin-VCSELs) feature ultrafast spin and polarization dynamics. Oscillations in the circular polarization degree can be generated using pulsed spin-injection. The oscillations evolve due to the carrier-spin-photon system that is coupled for the linear modes in the VCSEL's cavity via the birefringence. The polarization oscillations are independent of the conventional relaxation oscillations and have the potential to exceed frequencies of 100 GHz. The oscillations are switchable and can be the basis for ultrafast directly modulated spin-VCSELs for, e.g., communication purposes. The polarization oscillation frequency is mainly determined by the birefringence. We show a method to tune the birefringence and thus the polarization oscillation frequency by adding mechanical strain to the substrate in the vicinity of the laser. We achieved first experimental results for high-frequency operation using 850 nm oxide-confined single-mode VCSELs. The results are compared with simulations using the spin-flip-model for high birefringence values.

  20. Hepatitis C viral infection is associated with activated cytolytic natural killer cells expressing high levels of T cell immunoglobulin- and mucin-domain-containing molecule-3.

    PubMed

    Golden-Mason, Lucy; Waasdorp Hurtado, Christine E; Cheng, Linling; Rosen, Hugo R

    2015-05-01

    T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) is an inhibitory receptor implicated in T cell exhaustion characteristic of chronic viral infection. Limited data exist on NK cell Tim-3 expression and functional consequences. In chronic hepatitis C virus (HCV)-infected subjects, we found increased Tim-3 on NKs, which was associated with an activated phenotype. The high level of Tim-3 was not reversed by successful IFN-alpha-based antiviral therapy. Tim-3(high) NK cells up-regulated TRAIL in response to IFN-alpha to a greater extent and demonstrated greater lymphokine-activated killing activity, viral control, and degranulation but similar cytokine production than their Tim-3(low) counterparts. Our results suggest that Tim-3 on NKs is associated with activation of this innate lymphocyte population that is polarized towards cytotoxicity in chronic HCV. These findings reveal roles for Tim-3 in the regulation of NKs that might represent targets for treatment of chronic viral infections. PMID:25797693

  1. Measurements of single DNA molecule packaging dynamics in bacteriophage ? reveal high forces, high motor processivity, and capsid transformations

    PubMed Central

    Fuller, Derek N.; Raymer, Dorian M.; Rickgauer, John Peter; Robertson, Rae M.; Catalano, Carlos E.; Anderson, Dwight L.; Grimes, Shelley; Smith, Douglas E.

    2012-01-01

    Molecular motors drive genome packaging into preformed procapsids in many dsDNA viruses. Here, we present optical tweezers measurements of single DNA molecule packaging in bacteriophage ?. DNA-gpA-gpNu1 complexes were assembled with recombinant gpA and gpNu1 proteins and tethered to microspheres, and procapsids were attached to separate microspheres. DNA binding and initiation of packaging were observed within a few seconds of bringing these microspheres into proximity in the presence of ATP. The motor was observed to generate greater than 50 picoNewtons (pN) of force, in the same range as observed with bacteriophage ?29, suggesting that high force generation is a common property of viral packaging motors. However, at low capsid filling the packaging rate averaged ~600 bp/s, which is 3.5-fold higher than ?29, and the motor processivity was also 3-fold higher, with less than one slip per genome length translocated. The packaging rate slowed significantly with increasing capsid filling, indicating a buildup of internal force reaching 14 pN at 86% packaging, in good agreement with the force driving DNA ejection measured in osmotic pressure experiments and calculated theoretically. Taken together, these experiments show that the internal force that builds during packaging is largely available to drive subsequent DNA ejection. In addition, we observed an 80 bp/s dip in the average packaging rate at 30% packaging, suggesting that procapsid expansion occurs at this point following the buildup of an average of 4 pN of internal force. In experiments with a DNA construct longer than the wild-type genome, a sudden acceleration in packaging rate was observed above 90% packaging in many cases, and greater than 100% of the genome length was translocated, suggesting that internal force can rupture the immature procapsid. PMID:17919653

  2. Highly Accurate Classification of Watson-Crick Basepairs on Termini of Single DNA Molecules

    PubMed Central

    Winters-Hilt, Stephen; Vercoutere, Wenonah; DeGuzman, Veronica S.; Deamer, David; Akeson, Mark; Haussler, David

    2003-01-01

    We introduce a computational method for classification of individual DNA molecules measured by an ?-hemolysin channel detector. We show classification with better than 99% accuracy for DNA hairpin molecules that differ only in their terminal Watson-Crick basepairs. Signal classification was done in silico to establish performance metrics (i.e., where train and test data were of known type, via single-species data files). It was then performed in solution to assay real mixtures of DNA hairpins. Hidden Markov Models (HMMs) were used with Expectation/Maximization for denoising and for associating a feature vector with the ionic current blockade of the DNA molecule. Support Vector Machines (SVMs) were used as discriminators, and were the focus of off-line training. A multiclass SVM architecture was designed to place less discriminatory load on weaker discriminators, and novel SVM kernels were used to boost discrimination strength. The tuning on HMMs and SVMs enabled biophysical analysis of the captured molecule states and state transitions; structure revealed in the biophysical analysis was used for better feature selection. PMID:12547778

  3. High flux polarized gamma rays production: first measurements with a four-mirror cavity at the ATF

    E-print Network

    Delerue, Nicolas; Chaikovska, Iryna; Chiche, R; Cizeron, R; Cohen, M; Colin, J; Cornebise, P; Jehanno, D; Labaye, F; Lacroix, M; Marie, R; Peinaud, Y; Soskov, V; Variola, A; Zomer, F; Cormier, E; Flaminio, R; Pinard, L; Araki, S; Funahashi, S; Honda, Y; Omori, T; Shimizu, H; Terunuma, T; Urakawa, J; Akagi, T; Miyoshi, S; Nagata, S; Takahashi, T

    2011-01-01

    The next generation of e+/e- colliders will require a very intense flux of gamma rays to allow high current polarized positrons to be produced. This can be achieved by converting polarized high energy photons in polarized pairs into a target. In that context, an optical system consisting of a laser and a four-mirror passive Fabry-Perot cavity has recently been installed at the Accelerator Test Facility (ATF) at KEK to produce a high flux of polarized gamma rays by inverse Compton scattering. In this contribution, we describe the experimental system and present preliminary results. An ultra-stable four-mirror non planar geometry has been implemented to ensure the polarization of the gamma rays produced. A fiber amplifier is used to inject about 10W in the high finesse cavity with a gain of 1000. A digital feedback system is used to keep the cavity at the length required for the optimal power enhancement. Preliminary measurements show that a flux of about $4\\times10^6 \\gamma$/s with an average energy of about 2...

  4. Polarized internal target apparatus

    DOEpatents

    Holt, R.J.

    1984-10-10

    A polarized internal target apparatus with a polarized gas target of improved polarization and density (achieved by mixing target gas atoms with a small amount of alkali metal gas atoms, and passing a high intensity polarized light source into the mixture to cause the alkali metal gas atoms to become polarized which interact in spin exchange collisions with target gas atoms yielding polarized target gas atoms) is described.

  5. Online polar two phase countercurrent chromatography×high performance liquid chromatography for preparative isolation of polar polyphenols from tea extract in a single step.

    PubMed

    Chen, Wei-Bin; Li, Shu-Qi; Chen, Long-Jiang; Fang, Mei-Juan; Chen, Quan-Cheng; Wu, Zhen; Wu, Yun-Long; Qiu, Ying-Kun

    2015-08-01

    Herein, we report an on-line two-dimensional system constructed by counter-current chromatography (CCC) coupling with preparative high-performance liquid chromatography (prep-HPLC) for the separation and purification of polar natural products. The CCC was used as the first dimensional isolation column, where an environmental friendly polar two-phase solvent system of isopropanol and 16% sodium chloride aqueous solution (1:1.2, v/v) was introduced for low toxicity and favorable resolution. In addition, by applying the stop-and-go flow technique, effluents pre-fractionated by CCC was further purified by a preparative column packed with octadecyl silane (ODS) as the second dimension. The interface between the two dimensions was comprised of a 6-port switching valve and an electronically controlled 2-position 10-port switching valve connected with two equivalent holding columns. To be highlighted here, this rationally designed interface for the purpose of smooth desalination, absorption and desorption, successfully solved the solvent compatibility problem between the two dimensional separation systems. The present integrated system was successfully applied in a one-step preparative separation and identification of 10 pure compounds from the water extracts of Tieguanyin tea (Chinese oolong tea). In short, all the results demonstrated that the on-line 2D CCC×LC method is an efficient and green approach for harvesting polar targets in a single step, which showed great promise in drug discovery. PMID:26114653

  6. Relation between Pressure Balance Structures and Polar Plumes from Ulysses High Latitude Observations

    NASA Technical Reports Server (NTRS)

    Yamauchi, Yohei; Suess, Steven T.; Sakurai, Takashi

    2002-01-01

    Ulysses observations have shown that pressure balance structures (PBSs) are a common feature in high-latitude, fast solar wind near solar minimum. Previous studies of Ulysses/SWOOPS plasma data suggest these PBSs may be remnants of coronal polar plumes. Here we find support for this suggestion in an analysis of PBS magnetic structure. We used Ulysses magnetometer data and applied a minimum variance analysis to magnetic discontinuities in PBSs. We found that PBSs preferentially contain tangential discontinuities, as opposed to rotational discontinuities and to non-PBS regions in the solar wind. This suggests that PBSs contain structures like current sheets or plasmoids that may be associated with network activity at the base of plumes.

  7. Relation Between Pressure Balance Structures and Polar Plumes from Ulysses High Latitude Observations

    NASA Technical Reports Server (NTRS)

    Yamauchi, Y.; Suess, Steven T.; Sakurai, T.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Ulysses observations have shown that pressure balance structures (PBSs) are a common feature in high-latitude, fast solar wind near solar minimum. Previous studies of Ulysses/SWOOPS plasma data suggest these PBSs may be remnants of coronal polar plumes. Here we find support for this suggestion in an analysis of PBS magnetic structure. We used Ulysses magnetometer data and applied a minimum variance analysis to discontinuities. We found that PBSs preferentially contain tangential discontinuities, as opposed to rotational discontinuities and to non-PBS regions in the solar wind. This suggests that PBSs contain structures like current sheets or plasmoids that may be associated with network activity at the base of plumes.

  8. Intrinsic polarization of the high energy W-boson structure functions

    SciTech Connect

    Ralston, J.P.; Olness, F.

    1986-01-01

    Several new issues are presented that are to be incorporated into a consistent treatment of high-energy transverse effective-W boson structure functions. The issues included the numerical importance of the proper choice of scale, and the q/sup 2/ evolution of the boson structure functions in an Altarelli-Parisi framework. We investigate a novel effect of the V-A coupling which produces a sizable intrinsic polarization of the W distributions. A preliminary estimate yields a left- to right-helicity structure function ratio W/sub L///sup +/W/sub R//sup +/ approx. = 1 - 21/(1 - x) + 21/(1 - x)/sup 2/. For x greater than or equal to 0.06, there are two lift-handed W/sup +/'s for every right-handed one in an unpolarized proton. 11 refs., 2 figs.

  9. Complete dipole strength distributions in 208Pb from high-resolution polarized proton scattering at 0°

    NASA Astrophysics Data System (ADS)

    von Neumann-Cosel, Peter

    2012-02-01

    Small-angle polarized proton scattering including 0° at incident energies of a few 100 MeV/nucleon is established as a new spectrospcopic tool for the study of E1 and M1 strength distributions. Experiments of this type have been realized recently at RCNP, Osaka, Japan with high energy resolution of the order 25 - 30 keV (FWHM). Using 208Pb as an example, the physics potential of such data is discussed. It includes information on the properties of the Pygmy Dipole Resonance but also on complete E1 and M1 strength distributions and thus the gamma strength function. The E1 polarizability can be extracted with a precision of about 4% providing important experimental constraints on the neutron skin thickness in 208Pb.

  10. Temporal and spectral studies of high-order harmonics generated by polarization-modulated infrared fields

    SciTech Connect

    Sola, I. J.; Zaier, A.; Cormier, E.; Mevel, E.; Constant, E.; Lopez-Martens, R.; Johnsson, P.; Varju, K.; Mauritsson, J.; L'Huillier, A.; Strelkov, V.

    2006-07-15

    The temporal confinement of high harmonic generation (HHG) via modulation of the polarization of the fundamental pulse is studied in both temporal and spectral domains. In the temporal domain, a collinear cross-correlation setup using a 40 fs IR pump for the HHG and a 9 fs IR pulse to probe the generated emission is used to measure the XUV pulse duration. The observed temporal confinement is found to be consistent with theoretical predictions. An increased confinement is observed when a 9 fs pulse is used to generate the harmonics. An important spectral broadening, including a continuum background, is also measured. Theoretical calculations show that with 10 fs driving pulses, either one or two main attosecond pulses are created depending on the value of the carrier envelope phase.

  11. Large-field high-speed polarization sensitive spectral domain OCT and its applications in ophthalmology

    PubMed Central

    Zotter, Stefan; Pircher, Michael; Torzicky, Teresa; Baumann, Bernhard; Yoshida, Hirofumi; Hirose, Futoshi; Roberts, Philipp; Ritter, Markus; Schütze, Christopher; Götzinger, Erich; Trasischker, Wolfgang; Vass, Clemens; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

    2012-01-01

    We present a novel spectral domain polarization sensitive OCT system (PS-OCT) that operates at an A-scan rate of 70 kHz and supports scan angles of up to 40° × 40°. The high-speed imaging allows the acquisition of up to 1024 × 250 A-scans per 3D scan, which, together with the large field of view, considerably increases the informative value of the images. To demonstrate the excellent performance of the new PS-OCT system, we imaged several healthy volunteers and patients with various diseases such as glaucoma, AMD, Stargardt’s disease, and albinism. The results are compared with clinically established methods such as scanning laser polarimetry and autofluorescence. PMID:23162711

  12. High-speed polarization multiplexed optical scanner for three-dimensional scanning applications

    NASA Astrophysics Data System (ADS)

    Khan, Sajjad A.; Riza, Nabeel A.

    2004-01-01

    A versatile high speed 3-D scanner design is proposed and demonstrated for optical beamforming applications such as free-space laser communications, 3-D displays, scanning 3-D optical microscopy, data retrieval, and vision applications. The scanner consists of fast digital-analog control polarization-based optical beamforming cells resulting in complete three-dimensional beamforming programmability. Features include low electrical power consumption and large aperture beamforming optics, digital repeatability, and time multiplexed accurate analog beamforming. Analog frequency and amplitude control of the nematic liquid crystal beamformer cells allows continuous fine scan programmability over a 0.66 mrad horizontal-deflection, 0.75 mrad vertical deflection, and an infinity to 1.84 m focal length longitudinal scan, all at 1310nm. For the first time is demonstrated a coarse angular deflection of an 8-point linear 1-D scan at 1550 nm with a 35 microsecond random-access time.

  13. Electroweak supersymmetric effects on high energy unpolarized and polarized single top quark production at CERN LHC

    SciTech Connect

    Beccaria, M.; Renard, F.M.; Verzegnassi, C.

    2005-02-01

    We consider various processes of single top production at LHC in the theoretical framework of the MSSM and examine the role of the supersymmetric electroweak one-loop corrections in a special moderately light SUSY scenario, in an initial parton-pair c.m. high energy range where a logarithmic asymptotic expansion of Sudakov type can be used. We show that the electroweak virtual effects are systematically large, definitely beyond the relative 10% size, particularly for a final tH{sup -} pair where a special enhancement is present. We show then in a qualitative way the kind of precision tests of the model that would be obtainable from accurate measurements of the energy distributions of the various cross sections and of the top polarization asymmetries.

  14. High diffraction efficiency polarization gratings recorded by biphotonic holography in an azobenzene liquid crystalline polyester

    SciTech Connect

    Sanchez, C.; Alcala, R.; Hvilsted, S.; Ramanujam, P. S.

    2001-06-18

    High diffraction efficiencies have been achieved with polarization gratings recorded in thin films of an azobenzene side-chain liquid crystalline polyester by means of biphotonic processes. Efficiency values up to 30% have been reached after an induction period of 300 s and subsequent evolution with the sample in darkness. These values are at least two orders of magnitude higher than those previously reported for biphotonic recording. The gratings can be erased with unpolarized blue light and partial recovery of the diffraction efficiency has been observed after the erasure process when the sample is kept in darkness. Red light illumination of the erased film increases the recovered efficiency value and the recovery rate. {copyright} 2001 American Institute of Physics.

  15. Circular polarization effects in ion acceleration from high intensity, short pulse laser interactions

    NASA Astrophysics Data System (ADS)

    Dollar, F.; Zulick, C.; Bulanov, S. S.; Chvykov, V.; Kalintchenko, G.; Matsuoka, T.; McGuffey, C.; Thomas, A. G. R.; Willingale, L.; Yanovsky, V.; Maksimchuk, A.; Krushelnick, K.; Petrov, G.; Davis, J.

    2011-10-01

    Experiments were performed to investigate ion acceleration effects from circular polarization from thin targets, using a high contrast, ultra-short laser pulse from the HERCULES laser facility at the Univ. of Michigan. Experiments were performed with 50 TW, 35 fs pulses at an intensity of >1021Wcm-2 on Si3N4 and Mylar targets of 30 nm to 1 ?m thickness with contrast <10-13 . Protons with maximum energy 18 MeV and Carbon ions with energies of up to 10 MeV per nucleon were measured. Particle-in-cell simulations demonstrating the acceleration mechanism will be presented as well. Supported by NSF Physics Frontier Center FOCUS (Grant PHY-0114336), Defense Threat Reduction Agency, and Naval Research Laboratory. We acknowledge the OSIRIS consortium for the use of OSIRIS.

  16. Polarized nuclear target based on parahydrogen induced polarization

    SciTech Connect

    D. Budker, M.P. Ledbetter, S. Appelt, L.S. Bouchard, B. Wojtsekhowski

    2012-12-01

    We discuss a novel concept of a polarized nuclear target for accelerator fixed-target scattering experiments, which is based on parahydrogen induced polarization (PHIP). One may be able to reach a 33% free-proton polarization in the ethane molecule. The potential advantages of such a target include operation at zero magnetic field, fast ({approx}100 HZ) polarization oscillation (akin to polarization reversal), and operation with large intensity of an electron beam.

  17. Meteors do not break exogenous organic molecules into high yields of diatomics

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter; Schaller, Emily L.; Laux, Christophe O.; Wilson, Michael A.; Schmidt, Greg; Rairden, Rick L.

    2004-01-01

    Meteoroids that dominate the Earth's extraterrestrial mass influx (50-300 microm size range) may have contributed a unique blend of exogenous organic molecules at the time of the origin of life. Such meteoroids are so large that most of their mass is ablated in the Earth's atmosphere. In the process, organic molecules are decomposed and chemically altered to molecules differently from those delivered to the Earth's surface by smaller (<50 microm) micrometeorites and larger (>10 cm) meteorites. The question addressed here is whether the organic matter in these meteoroids is fully decomposed into atoms or diatomic compounds during ablation. If not, then the ablation products made available for prebiotic organic chemistry, and perhaps early biology, might have retained some memory of their astrophysical nature. To test this hypothesis we searched for CN emission in meteor spectra in an airborne experiment during the 2001 Leonid meteor storm. We found that the meteor's light-emitting air plasma, which included products of meteor ablation, contained less than 1 CN molecule for every 30 meteoric iron atoms. This contrasts sharply with the nitrogen/iron ratio of 1:1.2 in the solid matter of comet 1P/Halley. Unless the nitrogen content or the abundance of complex organic matter in the Leonid parent body, comet 55P/Tempel-Tuttle, differs from that in comet 1P/Halley, it appears that very little of that organic nitrogen decomposes into CN molecules during meteor ablation in the rarefied flow conditions that characterize the atmospheric entry of meteoroids approximately 50 microm-10 cm in size. We propose that the organics of such meteoroids survive instead as larger compounds.

  18. Astronomical sources of circularly polarized light and the origin of homochirality.

    PubMed

    Bailey, J

    2001-01-01

    Possible astronomical sources of ultraviolet circularly polarized light (UVCPL) which might be responsible for enantiomeric selection in interstellar organic molecules are considered, Synchrotron radiation from magnetic neutron stars has been suggested as a possible source of UVCPL. However, synchrotron radiation in these situations is not predicted to be strongly circularly polarized. Very few such sources show optical synchrotron radiation and in the few that do circular polarization has not been observed. Magnetic white dwarfs and white dwarf binaries (Polars) can be highly circularly polarized but any effect on molecular clouds and star formation regions must rely on rare chance encounters. Recent observations show that substantial levels of circular polarization are present in reflection nebulae in star formation regions. This mechanism produces polarized light exactly when and where it is needed in regions where star formation is occurring and organic molecules are known to be present. PMID:11296520

  19. Automatic analyzer for highly polar carboxylic acids based on fluorescence derivatization-liquid chromatography.

    PubMed

    Todoroki, Kenichiro; Nakano, Tatsuki; Ishii, Yasuhiro; Goto, Kanoko; Tomita, Ryoko; Fujioka, Toshihiro; Min, Jun Zhe; Inoue, Koichi; Toyo'oka, Toshimasa

    2015-03-01

    A sensitive, versatile, and reproducible automatic analyzer for highly polar carboxylic acids based on a fluorescence derivatization-liquid chromatography (LC) method was developed. In this method, carboxylic acids were automatically and fluorescently derivatized with 4-(N,N-dimethylaminosulfonyl)-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ) in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride by adopting a pretreatment program installed in an LC autosampler. All of the DBD-PZ-carboxylic acid derivatives were separated on the ODS column within 30 min by gradient elution. The peak of DBD-PZ did not interfere with the separation and the quantification of all the acids with the exception of lactic acid. From the LC-MS/MS analysis, we confirmed that lactic acid was converted to an oxytriazinyl derivative, which was further modified with a dimethoxy triazine group of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). We detected this oxytriazinyl derivative to quantify lactic acid. The detection limits (signal-to-noise ratio = 3) for the examined acids ranged from 0.19 to 1.1 µm, which correspond to 95-550 fmol per injection. The intra- and inter-day precisions of typical, highly polar carboxylic acids were all <9.0%. The developed method was successfully applied to the comprehensive analysis of carboxylic acids in various samples, which included fruit juices, red wine and media from cultured tumor cells. PMID:25082081

  20. A comparative study of annealing of waxy, normal and high-amylose maize starches: the role of amylose molecules.

    PubMed

    Wang, Shujun; Wang, Jinrong; Yu, Jinglin; Wang, Shuo

    2014-12-01

    The effect of annealing on starch structure and functionality of three maize starches (waxy, normal and high-amylose) was investigated, with the aim of understanding the role of amylose molecules during starch annealing. Amylose content, granular morphology and crystallinity of maize starches were little affected by annealing treatment. Annealing treatment did not alter the swelling power of waxy maize starch, but reduced the swelling power of normal and high-amylose maize starches. The thermal transition temperatures were increased, and the temperature range was decreased, but the enthalpy change was not affected greatly. The pasting viscosities of normal and waxy maize starches were decreased significantly, with the pasting temperature being little affected. The in vitro digestibility of three maize starches was not affected significantly by annealing treatment. Our results demonstrated that amylose molecules play an important role in the structural reorganization of starch granules during annealing treatment. PMID:24996342