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1

Inertial effects in anomalous dielectric relaxation of symmetrical top molecules.  

PubMed

The linear dielectric response of an assembly of noninteracting symmetrical top molecules (each of which is free to rotate in space) is evaluated in the context of fractional dynamics. The infinite hierarchy of differential-recurrence relations for the relaxation functions appropriate to the dielectric response is derived by using the underlying inertial fractional Klein-Kramers equation. On solving this hierarchy in terms of matrix continued fractions (as in the normal rotational diffusion), the complex dynamic susceptibility is obtained and is calculated for typical values of the model parameters. For the limiting case of spherical top molecules, the solution is obtained in terms of an ordinary continued fraction. It is shown that the model can reproduce nonexponential anomalous dielectric relaxation behavior at low frequencies (omegatau

Titov, Sergey V; Kalmykov, Yuri P; Coffey, William T

2004-03-01

2

Torsionally inelastic collisions between a near-symmetric top molecule and a structureless atom  

Microsoft Academic Search

The close-coupling formulation is presented for collisions of a structureless atom with a near-symmetric top exhibiting internal rotation, such as methanol. The molecule is approximated as a symmetric top whose internal rotation axis coincides with the symmetry axis. The K doubling arising from the asymmetry is taken into account only to first order. Both rotational and torsional inelasticity are considered,

Stephen L. Davis

1991-01-01

3

Pressure Broadening of Symmetric-Top Molecules in the Millimeter-Wavelength Region  

Microsoft Academic Search

Self-broadened and foreign-gas-broadened widths of a number of millimeter lines of the symmetric-top molecules CH3F and CHF3 have been measured and compared with values calculated by Anderson's and Murphy and Boggs' theories of pressure broadening. The lines studied are the J = 2 ? 3, K = 0, 1, 2 lines of CH3F, and the J = 6 ? 7,

George Birnbaum; E. R. Cohen; J. R. Rusk

1968-01-01

4

Rovibrational Interaction and Vibrational Constants of the Symmetric Top Molecule 14NF3  

PubMed Central

Several accurate experimental values of the ?C and ?B rotation-vibration interaction parameters and ?i, xij, and gij vibrational constants have been extracted from the most recent high-resolution Fourier transform infrared, millimeter wave, and centimeter wave investigations in the spectra of the oblate symmetric top molecule 14NF3. The band-centres used are those of the four fundamental, the overtones, the combination, and hot bands identified in the region between 400?cm?1 and 2000?cm?1. Comparison of our constants with the ones measured previously, by infrared spectroscopy at low resolution, reveals orders of magnitude higher accuracy of the new values. The agreement between our values and those determined by ab initio calculations employing the TZ2Pf basis is excellent.

2013-01-01

5

Theory of oriented symmetric-top molecule beams: Precession, degree of orientation, and photofragmentation of rotationally state-selected molecules  

SciTech Connect

A theoretical study of the properties of rotationally state-selected symmetric top molecules has been carried out. Quantum mechanical and classical calculations are presented for the orientational probability density function P/sub J/KM( rho), characterizing the molecular precessional motion for various rotational states Vertical BarJKM> in terms of the degree of orientation rho (equivalentmu-circumflexxE) of the dipole moment ..mu.. in a (weak) electric field E. For all J>0, the breadths of the quantum mechanical distributions P/sub J/KM( rho) are significantly greater than those of the classically calculated ones P/sub cl/( rho). Their first moments, i.e., < rho>equivalentKM/(J/sup 2/+J), are, of course, identical. P( rho) is, in principle, directly observable through measurements of polarized laser-induced photofragmentation of oriented molecule beams. Expressions are derived to analyze experimentally observable angular distributions of photofragments. It is shown that I/sub J/KM/I/sub J/K = 2P/sub J/KM( rho), where I/sub J/KM and I/sub J/K are the photofragment intensities from oriented (JKM) and unoriented (JK) state-selected beams, respectively.

Choi, S.E.; Bernstein, R.B.

1986-07-01

6

Rotational excitation of symmetric top molecules by collisions with atoms. II - Infinite order sudden approximation  

NASA Technical Reports Server (NTRS)

The infinite order sudden (IOS) approximation is extended to rotational excitation of symmetric tops by collisions with atoms. After development of a formalism for 'primitive' or 'one-ended' tops, proper parity-adapted linear combinations describing real rotors are considered and modifications needed for asymmetric rigid rotors are noted. The generalized spectroscopic relaxation cross sections are discussed. IOS calculations for NH3-He and H2CO-He are performed and compared with more accurate calculations, and the IOS approximation is found to provide a reasonably accurate description.

Green, S.

1979-01-01

7

Ejs Symmetric Top Model  

NSDL National Science Digital Library

The Ejs Symmetric Top model displays the motion of a top, in both the space frame and body frame, with no net toque applied. The top has an initial angular speed in the x, y, and z directions. The moments of inertia in each direction, and the initial angular positions and angular speeds can be changed via textboxes. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Symmetric Top model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_rigid_bodies_symmetric.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for rigid body dynamics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

8

Spectra of Some Symmetric-Top Molecules in the One-to Four-Millimeter Wave Region  

Microsoft Academic Search

Rotational transitions of several symmetric-top molecules have been measured in the 1 to 4 mm wave region. The molecular rotational constants for the most abundant isotopic species are: B0=8545.877 Mc\\/sec, DJ=2.960 kc\\/sec, DJK=162.9 kc\\/sec, for CH3CCH; B0=10 348.862 Mc\\/sec, DJ=11.3 kc\\/sec, DJK=—18.06 kc\\/sec, for CF3H; B0=4 594.262 Mc\\/sec, DJ=1.020 kc\\/sec, DJK=1.284 kc\\/sec, for OPF3; B0=7208.049 Mc\\/sec, DJ=7.556 kc\\/sec, DJK=—12.45 kc\\/sec,

Charles A. Burrus; Walter Gordy

1957-01-01

9

Quantum effects in the capture of charged particles by dipolar polarizable symmetric top molecules. II. Interplay between electrostatic and gyroscopic interactions  

NASA Astrophysics Data System (ADS)

Within the general axially nonadiabatic channel approach described in Paper I of this series [M. Auzinsh, E. I. Dashevskaya, I. Litvin, E. E. Nikitin, and J. Troe, J. Chem. Phys. 139, 084311 (2013)], the present article analyzes the simultaneous manifestation of electrostatic and gyroscopic interactions in the quantum capture of dipolar polarizable symmetric top molecules by ions. As a demonstration, the rate coefficients for capture of CH3D and CD3H by H+, D+, and H3+ are calculated.

Auzinsh, M.; Dashevskaya, E. I.; Litvin, I.; Nikitin, E. E.; Troe, J.

2013-10-01

10

Quantum effects in the capture of charged particles by dipolar polarizable symmetric top molecules. II. Interplay between electrostatic and gyroscopic interactions.  

PubMed

Within the general axially nonadiabatic channel approach described in Paper I of this series [M. Auzinsh, E. I. Dashevskaya, I. Litvin, E. E. Nikitin, and J. Troe, J. Chem. Phys. 139, 084311 (2013)], the present article analyzes the simultaneous manifestation of electrostatic and gyroscopic interactions in the quantum capture of dipolar polarizable symmetric top molecules by ions. As a demonstration, the rate coefficients for capture of CH3D and CD3H by H(+), D(+), and H3(+) are calculated. PMID:24116627

Auzinsh, M; Dashevskaya, E I; Litvin, I; Nikitin, E E; Troe, J

2013-10-14

11

Extended rotational diffusion and orientational relaxation of symmetric top molecules in a strong dc electric field: second-rank orientational correlation functions.  

PubMed

Second-rank orientational correlation functions (pertaining to Kerr effect relaxation and Raman scattering) are obtained using the extended rotational diffusion (J-diffusion) model of symmetric top polar molecules in a strong constant external field. It is shown that the shape of the molecule noticeably affects all second-rank correlation functions and relaxation times in the rare collision limit. In the opposite limit of frequent collisions, the quantities of interest are shown to be shape independent as a consequence of vanishingly small inertial effects. An interpolation formula for the orientation relaxation times in the intermediate regime between the rare and frequent collision limits is also given. PMID:15267345

Titov, S V; Dejardin, P M; Kalmykov, Yu P

2004-03-01

12

Rotational Spectra of Symmetric Top Molecules in Ground and Different Vibrational Excited States, and Phenomenon of Resonance - Applying in CF3CCH  

PubMed Central

This paper deals with review of exploration of resonance in symmetric top molecules in different vibrational excited states, vt = n (n =1, 2, 3, 4). Calculations for CF3CCH shows that resonance take place at k=x??+(A-B)-2A?A?-(A-B) and k=x??+(A-B)-2A?A?-(A-B) for v10 = 2 and v10 = 3 respectively. In order to account for splitting about 3 MHz for the ? 2 series in v10 = 4 is necessary to introduce the element ? J,k, ?|f24| J,k + 2, ? ? 4? in fitting program.

Motamedi, Masoud

2007-01-01

13

A new treatment of the v4 = 2 excited state of the symmetric top molecule PF3 around 693 cm?1  

NASA Astrophysics Data System (ADS)

All experimental data of the 2?40 parallel and 2?4-2 perpendicular components of the pyramidal molecule PF3 have been refined using five equivalent D-, Q-, QD-, L-, LD-reduction forms of the effective rovibrational Hamiltonian recently developed for the vt(E) = 2 vibrational state of a C3v symmetric top molecule. The v4 = 2 excited level of the PF3 molecule has been treated with models taking into account ?- and k-intravibrational resonances. The body of data comprised 1171 IR lines of the 2?40 component, 249 energies of the v4 = 2?2 substate deduced from the 2?4-2-?4-1 hot band and 5 reported MW data. The standard deviations of the fits are practically similar for the reductions applied and close to the quality of measurements. The unitary equivalence of the tested relations between the derived parameters was satisfactorily fulfilled.

Najib, Hamid

2013-07-01

14

Rotational excitation of symmetric top molecules by collisions with atoms: Close coupling, coupled states, and effective potential calculations for NH3-He  

NASA Technical Reports Server (NTRS)

The formalism for describing rotational excitation in collisions between symmetric top rigid rotors and spherical atoms is presented both within the accurate quantum close coupling framework and also the coupled states approximation of McGuire and Kouri and the effective potential approximation of Rabitz. Calculations are reported for thermal energy NH3-He collisions, treating NH3 as a rigid rotor and employing a uniform electron gas (Gordon-Kim) approximation for the intermolecular potential. Coupled states are found to be in nearly quantitative agreement with close coupling results while the effective potential method is found to be at least qualitatively correct. Modifications necessary to treat the inversion motion in NH3 are discussed.

Green, S.

1976-01-01

15

Effective correlation-free reduced Hamiltonian for the ?t( E), ?n( A1) Coriolis-interacting states of C3 v symmetric-top molecules  

NASA Astrophysics Data System (ADS)

The effective correlation-free vibrational-rotational Hamiltonian for the Coriolis-interacting ?t( E) and ?n( A1) states in C3 v molecules has been derived. The Hamiltonian includes the terms describing the x- y Coriolis interaction up to the fourth-order, and several useful reduction schemes for the Hamiltonian are suggested.

St?íteská, Lucie Nová; Sarka, Kamil; Urban, Št?pán

2009-07-01

16

Ab initio ro-vibrational Hamiltonian in irreducible tensor formalism: a method for computing energy levels from potential energy surfaces for symmetric-top molecules  

Microsoft Academic Search

A theoretical approach to study ro-vibrational molecular states from a full nuclear Hamiltonian expressed in terms of normal-mode irreducible tensor operators is presented for the first time. Each term of the Hamiltonian expansion can thus be cast in the tensor form in a systematic way using the formalism of ladder operators. Pyramidal XY3 molecules appear to be good candidates to

M. Rey; A. V. Nikitin; Vl. G. Tyuterev

2010-01-01

17

Resonances in the heavy symmetrical top with vibrating pivot  

NASA Astrophysics Data System (ADS)

In this work we consider a heavy symmetrical top whose pivot is subjected to small-amplitude, high-frequency vibrations in the vertical direction. For analytical simplicity we confine ourselves to positions of the top close to the vertical. We first apply the slow-fast separation method originally devised by Kapitza and Landau for analysing the vibrational stabilization of an inverted pendulum. This analysis yields the slow precession frequency but we see that the equations become undefined at a particular value of the vibration frequency. This breakdown is seen to correspond to a resonance and we use Euler's equations to write down the solution at the resonance. For vibration in the horizontal direction there is a resonance at more or less the same frequency as before but the dynamics at the resonance is different from the former case.

Bhattacharjee, S.

2013-02-01

18

CMISTARK: Python package for the Stark-effect calculation and symmetry classification of linear, symmetric and asymmetric top wavefunctions in dc electric fields  

NASA Astrophysics Data System (ADS)

The Controlled Molecule Imaging group (CMI) at the Center for Free Electron Laser Science (CFEL) has developed the CMISTARK software to calculate, view, and analyze the energy levels of adiabatic Stark energy curves of linear, symmetric top and asymmetric top molecules. The program exploits the symmetry of the Hamiltonian to generate fully labeled adiabatic Stark energy curves.

Chang, Yuan-Pin; Filsinger, Frank; Sartakov, Boris G.; Küpper, Jochen

2014-01-01

19

Strain-Induced Formation of Fourfold Symmetric SiGe Quantum Dot Molecules  

NASA Astrophysics Data System (ADS)

The strain field distribution at the surface of a multilayer structure with disklike SiGe nanomounds formed by heteroepitaxy is exploited to arrange the symmetric quantum dot molecules typically consisting of four elongated quantum dots ordered along the [010] and [100] directions. The morphological transition from fourfold quantum dot molecules to continuous fortresslike quantum rings with an increasing amount of deposited Ge is revealed. We examine key mechanisms underlying the formation of lateral quantum dot molecules by using scanning tunneling microscopy and numerical calculations of the strain energy distribution on the top of disklike SiGe nanomounds. Experimental data are well described by a simple thermodynamic model based on the accurate evaluation of the strain dependent part of the surface chemical potential. The spatial arrangement of quantum dots inside molecules is attributed to the effect of elastic property anisotropy.

Zinovyev, V. A.; Dvurechenskii, A. V.; Kuchinskaya, P. A.; Armbrister, V. A.

2013-12-01

20

Modulated structures in nematic monolayers formed by symmetric molecules.  

PubMed

An analysis based on symmetry yields a general form for the deformation elastic energy of a nematic monolayer, formed by achiral symmetric molecules, deposited on a solid substrate. Lifshitz-invariant-like terms in the energy, which originate from the substrate field, can induce a modulated-tilt state if the anchoring energy is sufficiently low. A way to enhance the symmetry breaking is to apply a destabilizing magnetic or electric field that serves to lower the anchoring energy. In the case of an initial state with homeotropic alignment, the phase diagram displays a cusp-shaped tilt-modulated state intervening between two uniform tilt states. PMID:15783361

Lelidis, I; Barbero, G

2005-02-01

21

Multipulse Three-Dimensional Alignment of Asymmetric Top Molecules  

NASA Astrophysics Data System (ADS)

We show, by computation and experiment, that a sequence of nonresonant and impulsive laser pulses with different ellipticities can effectively align asymmetric top molecules in three dimensions under field-free conditions. By solving the Schrödinger equation for the evolution of the rotational wave packet, we show that the 3D alignment of 3,5 difluoroiodobenzene molecules improves with each successive pulse. Experimentally, a sequence of three pulses is used to demonstrate these results, which extend the multipulse schemes used for 1D alignment to full 3D control of rotational motion.

Ren, Xiaoming; Makhija, Varun; Kumarappan, Vinod

2014-05-01

22

Building 2D crystals from 5-fold-symmetric molecules.  

PubMed

Concepts of close packing in monolayers of 5-fold-symmetric buckybowls are discussed. When the symmetry of lattice and molecular building blocks are incompatible, new strategies evolve. Corannulene forms a hexagonal lattice on Cu(111) by tilting away from the C(5) symmetry and aligning one hexagonal ring parallel to the surface. The chiral 5-fold-substituted chloro and methyl derivatives do not show this tilt and maintain the 5-fold symmetry as adsorbates. Consequently, a nonperfect tiling is observed. Their lattices are quasi-hexagonal: one in an antiparallel fashion with almost pm symmetry and the other with azimuthal and positional disorder on the hexagonal grid. Our results are in remarkable agreement with computational and mechanical modeling experiments of close packing of hard pentagonal discs in macroscopic two-dimensional systems and prove the validity of such modeling strategies. PMID:19236092

Bauert, Tobias; Merz, Leo; Bandera, Davide; Parschau, Manfred; Siegel, Jay S; Ernst, Karl-Heinz

2009-03-18

23

Test of the Wigner method for the photodissociation of symmetric triatomic molecules  

Microsoft Academic Search

The validity of the semiclassical Wigner method for photodissociation of symmetric triatomic molecules is studied. The photodissociation of H2O in the first absorption band using an abinitio potential energy surface and a collinear model for CO2 are considered. In both cases comparison is made with exact quantum mechanical calculations. The overall agreement with the exact results is reasonable, and the

N. E. Henriksen; V. Engel; R. Schinke

1987-01-01

24

Analysis and fit of the Fourier-transform microwave spectrum of the two-top molecule N-methylacetamide  

NASA Astrophysics Data System (ADS)

The jet-cooled Fourier-transform microwave spectrum of N-methylacetamide (CH 3?NH?C(?O)?CH 3), a molecule containing two methyl tops with relatively low barriers to internal rotation, has been recorded and fit to nearly experimental uncertainty. Measurements were carried out between 10 and 26 GHz, with the nitrogen quadrupole splittings resolved for many transitions. The permutation-inversion group for this molecule is G18 (not isomorphic to any point group), with irreducible representations A1, A2, E1, E2, E3, and E4. One of these symmetry species and the usual three asymmetric rotor quantum numbers JKaKc were assigned to each torsion-rotation level involved in the observed transitions. F values were assigned to hyperfine components, where F= J+ IN. Transitions involving levels of A1 and A2 species could be fit to an asymmetric rotor Hamiltonian. The other transitions were first fit separately for each symmetry species using a Pickett-like effective rotational Hamiltonian. Constants from these fits show a number of additive properties which can be correlated with sums and differences of effects involving the two tops. A final global fit to 48 molecular parameters for 839 hyperfine components of 216 torsion-rotation transitions involving 152 torsion-rotation levels was carried out using a newly written two-top computer program, giving a root-mean-square deviation of observed-minus-calculated residuals of 4 kHz. This program was written in the principal axis system of the molecule and uses a free-rotor basis set for each top, a symmetric-top basis set for the rotational functions, and a single-step diagonalization procedure. Such an approach requires quite long computation times, but it is much less prone to subtle programming errors (a consideration felt to be important since checking the new program against precise fits of low-barrier two-top molecules in the literature was not possible). The two internal rotation angles in this molecule correspond to the Ramachandran angles ? and ? often defined to describe polypeptide folding. Barriers to internal rotation about these two angles were found to be 73 and 79 cm -1, respectively. Top-top coupling in both the kinetic and potential energy part of the Hamiltonian is relatively small in this molecule.

Ohashi, N.; Hougen, J. T.; Suenram, R. D.; Lovas, F. J.; Kawashima, Y.; Fujitake, M.; Pyka, J.

2004-09-01

25

Symmetry breaking puzzles in inner-shell photoionization of symmetric linear molecules  

NASA Astrophysics Data System (ADS)

Core-level photoionization of small molecules, followed by Auger decay, generally leads to molecular fragmentation. Modern momentum imaging (COLTRIMS) techniques, combined with coincident measurement of all charged particles produced by a single photoabsorption event, allow one to reconstruct photo- and Auger electron angular distributions in the body frame, which are generally far richer than conventionally measured laboratory-frame angular distributions. In this talk, I will discuss two cases where such measurements on symmetric linear target molecules have revealed interesting symmetry paradoxes. The first case involves K-shell ionization of molecular nitrogen where experimental measurements raise familiar questions about whether the photoprocess creates a localized hole at one of two equivalent, but spatially well-separated sites or rather a delocalized hole, smeared over the equivalent sites, preserving the symmetry of the molecule. The second example involves carbon 1s ejection from the symmetric CO2 molecule and the origin of observed asymmetry in the molecular-frame photoelectron angular distributions. In both cases, theoretical calculations assist in interpreting the experimental findings.

Rescigno, Thomas

2010-03-01

26

Collisional deexcitation of optically allowed excited atoms by axially symmetric molecules.  

PubMed

The deexcitation process of an atom in an optically allowed excited state by a collision with an axially symmetric molecule is considered. In order to make a precise comparison with experimental data that have recently been obtained, we extend previous work for a Penning ionization process [T. Watanabe and K. Katsuura, J. Chem. Phys. 47, 800 (1967)]. Using the straight-line trajectory impact parameter method, the probability of deexcitation in the incident atom is described by a discrete-continuum excitation transfer mechanism. The effects of the ionization yield eta in molecular target and of the molecular anisotropic property of the optical transition dipole are considered. The cross-section formula sigma is presented by a similar formula for Penning ionization of the atomic target by introducing a stereo factor C(lambda) as sigma = C(lambda)[e(4)mu(2)mu(E, perpendicular)/(4piepsilon(0))(2) (2)hv](2/5). Here, v is the relative velocity of the colliding system and lambda is given by the ratio lambda =(mu(E||)/mu(E perpendicular)), where mu, mu(E perpendicular), mu(E||) are the transition dipole moments of an excited atom, A-->A(*), those of a molecule at energy E for the perpendicular component and the parallel component with respect to molecular axis. Applications to He(*)(2(1)P)+H(2) (or D(2)), Ne(*)[2p(5)((2)P(1/2))3 s (1)P(1)]+ H(2) (or D(2)) systems and systems of the same projectiles on C(6)H(6), (or C(6)D(6)) molecules are made. The results for hydrogen molecules are compared with the experimental data. PMID:15549869

Watanabe, Tsutomu; Stener, Mauro

2004-11-22

27

Single molecule diffusion and the solution of the spherically symmetric residence time equation.  

PubMed

The residence time of a single dye molecule diffusing within a laser spot is propotional to the total number of photons emitted by it. With this application in mind, we solve the spherically symmetric "residence time equation" (RTE) to obtain the solution for the Laplace transform of the mean residence time (MRT) within a d-dimensional ball, as a function of the initial location of the particle and the observation time. The solutions for initial conditions of potential experimental interest, starting in the center, on the surface or uniformly within the ball, are explicitly presented. Special cases for dimensions 1, 2, and 3 are obtained, which can be Laplace inverted analytically for d = 1 and 3. In addition, the analytic short- and long-time asymptotic behaviors of the MRT are derived and compared with the exact solutions for d = 1, 2, and 3. As a demonstration of the simplification afforded by the RTE, the Appendix obtains the residence time distribution by solving the Feynman-Kac equation, from which the MRT is obtained by differentiation. Single-molecule diffusion experiments could be devised to test the results for the MRT presented in this work. PMID:21306174

Agmon, Noam

2011-06-16

28

Laser-field-free orientation of state-selected asymmetric top molecules  

NASA Astrophysics Data System (ADS)

With combined electrostatic and shaped laser fields with a slow turn on and rapid turn off, laser-field-free orientation of asymmetric top iodobenzene molecules with higher degrees of orientation has been achieved. In order to further increase the degrees of orientation, state-selected molecules are used as a sample. It is confirmed that higher degrees of orientation are maintained in the laser-field-free condition for 5-10 ps, which is long enough to study femtosecond-attosecond dynamics in molecules, after the rapid turn off of the laser pulse. The observation of the slow dephasing time of 5-10 ps ensures future prospects in molecular orientation techniques. This accomplishment means not only that a unique molecular sample has become available in various applications but also that the present technique can be used as a spectroscopic technique to investigate ultrafast rotational dynamics of molecules.

Mun, Je Hoi; Takei, Daisuke; Minemoto, Shinichirou; Sakai, Hirofumi

2014-05-01

29

Submillimeter Stark Spectroscopy of Symmetric Top Molecules Methyl-Fluoride and Carbon - Deuterium - Fluoride  

Microsoft Academic Search

This thesis deals with a study of the Stark effect in Methyl Fluoride using the 964 313.00 MHz line and in deuterated Methyl Fluoride using the 894 414.20 MHz line of the HCN laser. For CH(,3)F we identify the multiplet transition as J(,K) = 19(,K) (<---) 18(,K) in the ground vibrational state. We have seen seven families with K =

Gubbi Ramarao Sudhakaran

1982-01-01

30

Analysis of the Microwave Spectrum of the Three-Top Molecule Trimethoxylmethane  

NASA Astrophysics Data System (ADS)

Although many investigations about the spectrum of molecules displaying internal rotation of one or two methyl tops have been reported, there are much fewer results about the spectrum of molecules with three methyl tops. In this paper, we will deal with the microwave spectrum of trimethoxylmethane, HC(OCH_3)_3, a molecule displaying three conformers of quite different symmetry which all exhibit internal rotation of their three methyl tops. In a first step, a theoretical approach dedicated to the calculation of the rotation-torsion energy levels of a molecule with three inequivalent tops was developed. The model is based on a DVR approach; it accounts accurately for the rotation-torsion Coriolis couplings due to the torsion of each methyl top and leads to matrices which are smaller than those arising with the usual free internal rotation functions. The theoretical approach shows that internal rotation of the three tops leads to 27 tunneling sublevels, including 13 doubly degenerate ones. The statistical weights of the sublevels are 2^4, 2^5, and 2^6. The microwave spectrum of trimethoxylmethane has been recorded from to 10 to 19 GHz with the molecular beam Fourier transform spectrometer of the University of Bologna. The spectra of the TMM1, TMM2, and TMM3 conformers with C_1, C_3, and C_s symmetry, respectively, have been observed. The theoretical model has been applied to the lowest lying TMM1 conformer since it is the only one with three inequivalent methyl tops. The parameters describing the rotational energy and the rotation-torsion Coriolis couplings were obtained from the geometry of the conformer and those corresponding to height of the barriers hindering the internal rotations were retrieved through ab initio calculations. Calculated tunneling patterns were compared to experimental ones. As far as the number of tunneling components is concerned, there is a qualitative agreement between experiment and theory. However, the present calculation seems to underestimate the various tunneling splittings and this probably due to the fact that the barrier heights obtained through ab initio calculations are too high. Light and Ba?i?, J. Chem. Phys. 87 (1987) 4008.

Coudert, L. H.; Feng, G.; Caminati, W.

2013-06-01

31

Collision-induced absorption in mixtures of symmetrical linear and tetrahedral molecules - Methane-nitrogen  

NASA Technical Reports Server (NTRS)

The far infrared absorption of a CH4-N2 mixture was measured at 297, 195, and 162 K from 30 to 650/cm. The spectral invariants gamma1 and alpha1, proportional, respectively, to the zeroth and first spectral moments, due to bimolecular collisions between CH4 and N2 were obtained from these data and compared with theoretical values. The theory for collision-induced dipoles between a tetrahedral and a diatomic or symmetrical linear molecule includes contributions not previously considered. Whereas the theoretical values of gamma1 are only somewhat greater than experiment at all temperatures, the theoretical values of alpha1 are significantly lower than the experimental values. From the theoretical spectral moments for the various induced dipole components, the parameters of the BC shape were computed, and theoretical spectra were constructed. Good agreement was obtained at the lower frequencies, but with increasing frequencies the theoretical spectra were increasingly less intense than the experimental spectra. Although the accuracy of the theoretical results may suffer from the lack of a reliable potential function, it does not appear that this high frequency discrepancy can be removed by any conceivable modification in the potential.

Birnbaum, G.; Borysow, A.; Buechele, A.

1993-01-01

32

Charge symmetric dissociation of doubly ionized N2 and CO molecules  

NASA Astrophysics Data System (ADS)

We report a comparative study of the features in dissociative double ionization by high energy electron impact of N2 and CO molecules. The ratio of cross-section of charge symmetric dissociative ionization to non-dissociative ionization (CSD-to-ND ratio) and the kinetic energy release (KER) spectra of dissociation are experimentally measured and carefully corrected for various ion transmission losses and detector inefficiencies. Given that the double ionization cross sections of these iso-electronic diatomics are very similar, the large difference in the CSD-to-ND ratios must be attributable to the differences in the evolution dynamics of the dications. To understand these differences, potential energy curves (PECs) of dications have been computed using multi-reference configuration interaction method. The Franck-Condon factors and tunneling life times of vibrational levels of dications have also been computed. While the KER spectrum of N_2^{++} can be readily explained by considering dissociation via repulsive states and tunneling of meta-stable states, indirect dissociation processes such as predissociation and autoionization have to be taken into account to understand the major features of the KER spectrum of CO++. Direct and indirect processes identified on the basis of the PECs and experimental KER spectra also provide insights into the differences in the CSD-to-ND ratios.

Pandey, A.; Bapat, B.; Shamasundar, K. R.

2014-01-01

33

Tops  

NSDL National Science Digital Library

In this activity, learners discover that some things only stand up while they are spinning. To explore this phenomenon, learners build tops from household items such as CD's, paper plates, cups, and craft sticks. Learners will discover that the weight and radius of each top plays a role in the amount of momentum it has to spin. The launcher is also used to demonstrate one of the simple machines of physics: the wheel. Basic tools (e.g. drill) and plaster are required.

Workshop, Watsonville E.

2011-01-01

34

Mesophase formation in a system of top-shaped hard molecules: Density functional theory and Monte Carlo simulation  

Microsoft Academic Search

We present the phase diagram of a system of mesogenic top-shaped molecules based on the Parsons-Lee density functional theory and Monte Carlo simulation. The molecules are modeled as a hard spherocylinder with a hard sphere embedded in its center. The stability of five different phases is studied, namely, isotropic, nematic, smectic A, smectic C, and columnar phases. The positionally ordered

Daniel de las Heras; Szabolcs Varga; Franz J. Vesely

2011-01-01

35

Extension of the Measurement, Assignment, and Fit in the Ground State of the Two-Top Molecule Methyl Acetate  

NASA Astrophysics Data System (ADS)

New spectroscopic data were recorded for the two-top molecule methyl acetate with a chirped-pulse Fourier transform microwave spectrometer at room temperature and a jet cooled sub-millimeterwave spectrometer. More than 650 new lines with J up to 35 and K up to 15 were assigned. In total, approximately 1500 lines were fitted with 34 parameters using the program BELGI-C_s-2tops to a standard deviation close to the measurement error. More precise determinations of the top-top interaction and the J, K dependent parameters as well as the influence of the total rotation on the top-top interaction were carried out. The extension of the ground state spectrum of methyl acetate is a necessary step before searching for the first torsional excited transition in both torsional modes in the room temperature spectrum.

Nguyen, H. V. L.; Kleiner, I.; Shipman, S.; Kobayashi, K.

2013-06-01

36

Gs-HSQC-NOESY versus gs-NOESY-HSQC experiments: signal attenuation due to diffusion; application to symmetrical molecules.  

PubMed

Gradient-selected (gs) HSQC-NOESY type experiments are often applied in order to obtain NOE cross peaks in symmetrical molecules or in complex organic molecules, e.g. carbohydrates. Since the coherence-selecting gradients in these pulse sequences are separated by several delays, including the mixing time, the gs-HSQC-NOESY spectra exhibit severe signal attenuation due to diffusion effects. The respective NOE information unaffected by diffusion effects can be obtained by X-half-filtered gs-NOESY-HSQC spectra. In this paper, an X-half-filtered version of the gs-NOESY-HSQC experiment is presented and the NOE cross peak integrals of its spectra are compared with those of a standard gs-HSQC-NOESY experiment. With phenanthrene as an example of symmetrical molecules, it is shown that the relative signal attenuation of gs-HSQC-NOESY cross peaks versus gs-NOESY-HSQC cross peaks is caused by diffusion effects and follows the Stejskal-Tanner equation. In contrast, the X-half-filtered gs-NOESY-HSQC experiment provides NOE cross peaks with reasonable signal-to-noise ratios even for long-range interactions in the presence of quadrupolar relaxation. This is demonstrated by the spectra of lithium dimethylcuprate. PMID:14971015

Gschwind, Ruth M; Xie, Xiulan; Rajamohanan, Pattuparambil R

2004-03-01

37

Extension of the measurement, assignment, and fit of the rotational spectrum of the two-top molecule methyl acetate  

NASA Astrophysics Data System (ADS)

New and previous spectroscopic data were recorded for the two-top molecule methyl acetate using five spectrometers in four different labs: a room temperature chirped-pulse Fourier transform microwave (FTMW) spectrometer in the frequency range from 8.7 to 26.5 GHz, two molecular beam FTMW spectrometers (2-40 GHz), a free jet absorption Stark-modulated spectrometer (60-78 GHz), and a room temperature millimeter-wave spectrometer (44-68 GHz). Approximately 800 new lines with J up to 40 and K up to 16 were assigned. In total, 1603 lines were fitted with 34 parameters using an internal rotation Hamiltonian in the Rho Axis Method (RAM) and the program BELGI-Cs-2tops to standard deviations close to the experimental uncertainties. More precise determinations of the top-top interaction and the J, K dependent parameters were carried out.

Nguyen, Ha Vinh Lam; Kleiner, Isabelle; Shipman, Steven T.; Mae, Yoshiaki; Hirose, Kazue; Hatanaka, Shota; Kobayashi, Kaori

2014-05-01

38

Anomalous Spectral and Yield Features of Auger Emission from Symmetric Molecules  

Microsoft Academic Search

Proton-induced sulfur LMM and carbon KLL Auger yields from SF6, CF4, and CCl4 gaseous targets are found to be substantially reduced from the corresponding yields observed using H2S, SO2, and CH4. Speculations about the observed dependence on chemical species include inelastic scattering of the Auger electron during its transit out of the molecule and double Auger emission to the continuum.

Dennis L. Matthews; Forrest Hopkins

1978-01-01

39

ATIRS package: A program suite for the rovibrational analysis of infrared spectra of asymmetric top molecules  

NASA Astrophysics Data System (ADS)

Nowadays high-resolution infrared spectra can be recorded quite easily and therefore it has become important to assist the rovibrational analysis, especially the assignment step, that is still fraught with many problems in the presence of perturbation effects. In this article we provide a description of ATIRS, a complete software suite developed for assisting in the rotational investigation of vibrational bands of asymmetric top molecules. This package uses the Pickett's CALPGM suite for fitting transitions and predicting line positions and is composed by three stand-alone applications: (1) Visual Loomis-Wood for the assignment of spectral lines based on Loomis-Wood type diagrams; (2) Visual CALPGM, a new graphical interface to Pickett's programs SPFIT and SPCAT; (3) Visual Spectra Simulator for the simulation of spectra. The graphical interface to the CALPGM suite is developed for asymmetric rotors. The main feature of this application is to avoid the use of the parameter codes that are here replaced employing the well known parameter names or symbols. Highlighting the regular transition sequences, Visual Loomis-Wood assists in the assignment of the spectral lines. It visualizes the description of a transition and the assignment can be simply done by mouse-clicking on the diagram; moreover its display mode feature lets to check the experimental spectrum in which all the assigned lines together with their description are reported. Visual Spectra Simulator provides a simple and functionally application that, using the calculated frequencies and intensities given by SPCAT, simulates the high-resolution infrared spectrum and compare it to the experimental one. ATIRS, freely available to the spectroscopic community, is designed to be easy to use and presents a standard graphical interface; being based on the CALPGM package it can handle forbidden transitions and perturbations among many states.

Tasinato, N.; Pietropolli Charmet, A.; Stoppa, P.

2007-06-01

40

The origin of transverse anisotropy in axially symmetric single molecule magnets.  

PubMed

Single-crystal high-frequency electron paramagnetic resonance spectroscopy has been employed on a truly axial single molecule magnet of formula [Mn(12)O(12)(tBu-CH(2)CO(2))16(CH(3)OH)4].CH(3)OH to investigate the origin of the transverse magnetic anisotropy, a crucial parameter that rules the quantum tunneling of the magnetization. The crystal structure, including the absolute structure of the crystal used for EPR experiments, has been fully determined and found to belong to I4 tetragonal space group. The angular dependence of the resonance fields in the crystallographic ab plane shows the presence of high-order tetragonal anisotropy and strong dependence on the MS sublevels with the second-highest-field transition being angular independent. This was rationalized including competing fourth- and sixth-order transverse parameters in a giant spin Hamiltonian which describes the magnetic anisotropy in the ground S = 10 spin state of the cluster. To establish the origin of these anisotropy terms, the experimental results have been further analyzed using a simplified multispin Hamiltonian which takes into account the exchange interactions and the single ion magnetic anisotropy of the Mn(III) centers. It has been possible to establish magnetostructural correlations with spin Hamiltonian parameters up to the sixth order. Transverse anisotropy in axial single molecule magnets was found to originate from the multispin nature of the system and from the breakdown of the strong exchange approximation. The tilting of the single-ion easy axes of magnetization with respect to the 4-fold molecular axis of the cluster plays the major role in determining the transverse anisotropy. Counterintuitively, the projections of the single ion easy axes on the ab plane correspond to hard axes of magnetization. PMID:17685613

Barra, Anne-Laure; Caneschi, Andrea; Cornia, Andrea; Gatteschi, Dante; Gorini, Lapo; Heiniger, Leo-Philipp; Sessoli, Roberta; Sorace, Lorenzo

2007-09-01

41

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

SciTech Connect

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

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

2011-02-15

42

Mesophase formation in a system of top-shaped hard molecules: density functional theory and Monte Carlo simulation.  

PubMed

We present the phase diagram of a system of mesogenic top-shaped molecules based on the Parsons-Lee density functional theory and Monte Carlo simulation. The molecules are modeled as a hard spherocylinder with a hard sphere embedded in its center. The stability of five different phases is studied, namely, isotropic, nematic, smectic A, smectic C, and columnar phases. The positionally ordered phases are investigated only for the case of parallel alignment. It is found that the central spherical unit destabilizes the nematic with respect to the isotropic phase, while increasing the length of the cylinder has the opposite effect. Also, the central hard sphere has a strong destabilizing effect on the smectic A phase, due the inefficient packing of the molecules into layers. For large hard sphere units the smectic A phase is completely replaced by a smectic C structure. The columnar phase is first stabilized with increasing diameter of the central unit, but for very large hard sphere units it becomes less stable again. The density functional results are in good agreement with the simulations. PMID:21663376

de las Heras, Daniel; Varga, Szabolcs; Vesely, Franz J

2011-06-01

43

Mesophase formation in a system of top-shaped hard molecules: Density functional theory and Monte Carlo simulation  

NASA Astrophysics Data System (ADS)

We present the phase diagram of a system of mesogenic top-shaped molecules based on the Parsons-Lee density functional theory and Monte Carlo simulation. The molecules are modeled as a hard spherocylinder with a hard sphere embedded in its center. The stability of five different phases is studied, namely, isotropic, nematic, smectic A, smectic C, and columnar phases. The positionally ordered phases are investigated only for the case of parallel alignment. It is found that the central spherical unit destabilizes the nematic with respect to the isotropic phase, while increasing the length of the cylinder has the opposite effect. Also, the central hard sphere has a strong destabilizing effect on the smectic A phase, due the inefficient packing of the molecules into layers. For large hard sphere units the smectic A phase is completely replaced by a smectic C structure. The columnar phase is first stabilized with increasing diameter of the central unit, but for very large hard sphere units it becomes less stable again. The density functional results are in good agreement with the simulations.

de Las Heras, Daniel; Varga, Szabolcs; Vesely, Franz J.

2011-06-01

44

Excited-state relaxation processes of DPA-DSB: Investigation of the reason for high fluorescence quantum yield of symmetric D-?-D molecule  

NASA Astrophysics Data System (ADS)

The temporal evolution of excited states of a symmetric D-?-D structure two-photon absorption material, 1,4-di(4'- N, N-diphenylaminostyryl) benzene (DPA-DSB), was investigated by femtosecond transient absorption spectrum and solvent polarity dependent fluorescence properties. The results suggested that the structure of DPA-DSB did not change much during the intramolecular charge-transfer (ICT) process, which could be the reason for good radiative ability of the ICT state. The major non-radiative deactive channel may be a large structure-changed process, which was formed more slowly than the radiative ICT state. Symmetric charge-transfer in this D-?-D structure molecule could make the non-radiative structure-changed process slow and ineffective, which should be the reason for the high fluorescence quantum yield.

He, Xing; Liu, Yuqiang; Du, Xin; Yang, Yanqiang; Xu, Bin; Tian, Wenjing; Ma, Yuguang

2011-01-01

45

A new graphical version of STROTAB: The analysis and fitting of singlet triplet spectra of asymmetric top molecules in the prolate or oblate limits  

NASA Astrophysics Data System (ADS)

The original version of STROTAB has been modified to run under Microsoft Windows using the C++ programming language. The new version takes full advantage of the Microsoft Foundation Classes available within the Microsoft Visual C++ Version 6 development environment. Specifically, windows can be created that edit the input file, summarize the results of the least-squares fit, display the calculated and observed spectra, display whole or partial sections of the calculated spectra as a stick or Gaussian de-convoluted spectrum. A listing of the rotational quantum numbers in the cases (a) and (b) limits for each of the displayed lines is provided. A branch annotating routine provides a quick visual guide to the assignment of the spectrum. A new eigenvalue sorting method has been added as an option that complements the existing method based on the eigenvector coefficients. The new sorting method has eliminated some difficulties that may arise using the existing "Least Ambiguous Method". The program has been extended to handle near-oblate asymmetric tops using a type III r representation. New version summaryTitle of program: STROTAB Version number: 2 Catalogue identifier:ADCA_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADCA_v2_0 Program obtainable from:CPC Program Library, Queen's University of Belfast, N. Ireland Reference in CPC to previous version: 93 (1996) 241-264 Catalog identifier of previous version: ADCA Authors of previous version: R.H. Judge, E.D. Womeldorf, R.A. Morris, D.E. Shimp, D.J. Clouthier, D.L. Joo, D.C. Moule Does the new version supersede the original program: Yes Computers for which the program is designed and others on which it has been tested: Pentium Xenon, Pentium Pro and Later Operating systems or monitors under which program has been tested: Windows 98, Windows 2000, Windows XP Programming language used in the new version: ANSI C, C++, Microsoft Foundation Class (MFC) No. of lines in distributed program, including test data, etc.:11 913 No. of bytes in distributed program, including test data, etc.: 2 816 652 Memory required to execute with typical data: 7 Meg No of bits in a word: 16 No of processors used: 1 Has the code been vectorized or parallelized?: No No. of bytes in distributed program, including test data, etc.: ˜3.2 MB (compressed) Distribution format: zip file Additional keywords:near oblate top, bootstrap eigenvalue sorting, graphical environment, band contour Nature of physical problem: The least-squares/band contour fitting of the singlet-triplet spectra of asymmetric tops of orthorhombic symmetry using a basis set appropriate to the symmetric top limit (prolate or oblate) of the molecule in either Hund's case (a) or case (b) coupling situations. Method of solution: The calculation of the eigenvectors and eigenvalues remains unchanged from the earlier version. An option to sort the eigenvalues of the current J by fitting them to regular progressions formed from earlier J values (bootstrap method) can be used as an option in place of the existing method based on eigenvector coefficients. Reasons for the new version: The earlier version can only handle oblate tops by diagonalizing using the prolate limit. This has turned out to be unacceptable. An improved method of sorting eigenvalues under certain conditions is also needed. A graphical interface has been added to ease the use of the program. Summary of revisions: The Hamiltonian can now be constructed in a limit appropriate the representation for of the molecule. Sorting by an alternate method is now offered. Numerous graphical features have been added. Restrictions on complexity of the problem: The rotational quantum number restrictions are J?255 and K (or P) ?127. The allowed transition frequency minus the band origin frequency must be in the range of ±10 000 cm -1. Up to five decimal places may be reported. The number of observed lines is limited by the dynamic memory and the amount of disk space available. Only molecules of symmetry D 2h, D 2 and C 2v can be accommodated in this version. Only constant

Kodet, John; Judge, Richard H.

2007-05-01

46

Trinitrotoluene explosive lights up ultrahigh Raman scattering of nonresonant molecule on a top-closed silver nanotube array.  

PubMed

The highest Raman enhancement factors are obtained in a double resonance: molecular electronic resonance and plasmon resonance with a "hot spot" in surface-enhanced Raman scattering (SERS). However, for most molecules of interest the double resonance is not realized with the excitation frequencies normally used in Raman. The latter may limit the practical applications of SERS for trace analysis. Here, we report that Raman-inactive trinitrotoluene (TNT) lights up the ultrahigh Raman scattering of off-resonated p-aminobenzenethiol (PABT) through the formation of charge-transfer TNT-PABT complex on the top-closed flexible silver nanotube array. Raman hot spots can spontaneously form in a reversible way by the self-approaching of flexible nanotubes driven through the capillary force of solvent evaporation. Meanwhile, the PABT-TNT-PABT bridges between self-approaching silver nanotubes possibly form by the specific complexing and zwitterion interactions, and the resultant chromophores can absorb the visible light that matches with the incident laser and the localized surface plasmon of a silver nanotube array. The multiple spectral resonances lead to the huge enhancement of Raman signals of PABT molecules due to the presence of ultratrace TNT. The enhancement effect is repeatedly renewable by the reconstruction of molecular bridges and can selectively detect TNT with a limit of 1.5 × 10(-17) M. The results in this report provide the simple and supersensitive approach to the detection of TNT explosives and the possibility of building a robust Raman-based assay platform. PMID:21853974

Zhou, Haibo; Zhang, Zhongping; Jiang, Changlong; Guan, Guijian; Zhang, Kui; Mei, Qingsong; Liu, Renyong; Wang, Suhua

2011-09-15

47

Effects on calculated half-widths and shifts from the line coupling for asymmetric-top molecules.  

PubMed

The refinement of the Robert-Bonamy formalism by considering the line coupling for linear molecules developed in our previous studies [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013); 140, 104304 (2014)] have been extended to asymmetric-top molecules. For H2O immersed in N2 bath, the line coupling selection rules applicable for the pure rotational band to determine whether two specified lines are coupled or not are established. Meanwhile, because the coupling strengths are determined by relative importance of off-diagonal matrix elements versus diagonal elements of the operator -iS1 - S2, quantitative tools are developed with which one is able to remove weakly coupled lines from consideration. By applying these tools, we have found that within reasonable tolerances, most of the H2O lines in the pure rotational band are not coupled. This reflects the fact that differences of energy levels of the H2O states are pretty large. But, there are several dozen strongly coupled lines and they can be categorized into different groups such that the line couplings occur only within the same groups. In practice, to identify those strongly coupled lines and to confine them into sub-linespaces are crucial steps in considering the line coupling. We have calculated half-widths and shifts for some groups, including the line coupling. Based on these calculations, one can conclude that for most of the H2O lines, it is unnecessary to consider the line coupling. However, for several dozens of lines, effects on the calculated half-widths from the line coupling are small, but remain noticeable and reductions of calculated half-widths due to including the line coupling could reach to 5%. Meanwhile, effects on the calculated shifts are very significant and variations of calculated shifts could be as large as 25%. PMID:24985632

Ma, Q; Boulet, C; Tipping, R H

2014-06-28

48

Asymmetric-top molecules containing one methyl-like internal rotor: Methods and codes for fitting and predicting spectra  

NASA Astrophysics Data System (ADS)

This paper is a review of various effective Hamiltonians, methods and codes dealing with asymmetric-top molecules containing one internal rotor with C3v (or close to C3v) symmetry. It aims at helping high-resolution spectroscopists to find the most appropriate method(s) and code(s) to assign and fit their internal rotor spectra. The topics included are: description of some of the available effective Hamiltonians, methods (PAM, Principal Axis Method, RAM, Rho-Axis Method and IAM, Internal-Axis Method) and codes to deal with internal rotor spectra (JB95, ERHAM, XIAM, SPFIT/SPCAT/IAMCALC and BELGI). The methods are also classified by the way they are dealing with the set of torsional states associated with the internal rotation large amplitude motion: globally or locally. Examples are given of internal rotors treated by each of those codes with root-mean-square deviations, Jmax, torsional bath levels involved, and parameters obtained to allow the reader to choose the appropriate method for his study. More details are given for the RAM method used in BELGI, with series of examples. Some user-manual-like hints for running the fits are also given.

Kleiner, I.

2010-03-01

49

Hierarchical chiral expression from the nano- to mesoscale in synthetic supramolecular helical fibers of a nonamphiphilic C3-symmetrical ?-functional molecule.  

PubMed

The controlled preparation of chiral structures is a contemporary challenge for supramolecular science because of the interesting properties that can arise from the resulting materials, and here we show that a synthetic nonamphiphilic C(3) compound containing ?-functional tetrathiafulvalene units can form this kind of object. We describe the synthesis, characterization, and self-assembly properties in solution and in the solid state of the enantiopure materials. Circular dichroism (CD) measurements show optical activity resulting from the presence of twisted stacks of preferential helicity and also reveal the critical importance of fiber nucleation in their formation. Molecular mechanics (MM) and molecular dynamics (MD) simulations combined with CD theoretical calculations demonstrate that the (S) enantiomer provides the (M) helix, which is more stable than the (P) helix for this enantiomer. This relationship is for the first time established in this family of C(3) symmetric compounds. In addition, we show that introduction of the "wrong" enantiomer in a stack decreases the helical reversal barrier in a nonlinear manner, which very probably accounts for the absence of a "majority rules" effect. Mesoscopic chiral fibers, which show inverted helicity, i.e. (P) for the (S) enantiomer and (M) for the (R) one, have been obtained upon reprecipitation from dioxane and analyzed by optical and electronic microscopy. The fibers obtained with the racemic mixture present, as a remarkable feature, opposite homochiral domains within the same fiber, separated by points of helical reversal. Their formation can be explained through an "oscillating" crystallization mechanism. Although C(3) symmetric disk-shaped molecules containing a central benzene core substituted in the 1,3,5 positions with 3,3'-diamido-2,2'-bipyridine based wedges have shown peculiar self-assembly properties for amphiphilic derivatives, the present result shows the benefits of reducing the nonfunctional part of the molecule, in our case with short chiral isopentyl chains. The research reported herein represents an important step toward the preparation of functional mesostructures with controlled helical architectures. PMID:21517038

Danila, Ion; Riobé, François; Piron, Flavia; Puigmartí-Luis, Josep; Wallis, John D; Linares, Mathieu; Ågren, Hans; Beljonne, David; Amabilino, David B; Avarvari, Narcis

2011-06-01

50

Using fixed-node diffusion Monte Carlo to investigate the effects of rotation-vibration coupling in highly fluxional asymmetric top molecules: application to H2D+.  

PubMed

A fixed-node diffusion Monte Carlo approach for obtaining the energies and wave functions of the rotationally excited states of asymmetric top molecules that undergo large amplitude, zero-point vibrational motions is reported. The nodal surfaces required to introduce rotational excitation into the diffusion Monte Carlo calculations are obtained from the roots of the asymmetric top rigid rotor wave functions calculated using the system's zero-point, vibrationally averaged rotational constants. Using H(2)D(+) as a model system, the overall accuracy of the methodology is tested by comparing to the results of converged variational calculations. The ability of the fixed-node diffusion Monte Carlo approach to provide insights into the nature and strength of the rotation-vibration coupling present in the rotationally excited states of highly fluxional asymmetric tops is discussed. Finally, the sensitivity of the methodology to the details of its implementation, such as the choice of embedding scheme, is explored. PMID:23343266

Petit, Andrew S; Wellen, Bethany A; McCoy, Anne B

2013-01-21

51

Enhanced ionization of the non-symmetric HeH+ molecule driven by intense ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

We study enhanced single and double ionizations and enhanced single and double excitations in the nonsymmetric two-electron diatomic molecular ion HeH+ in an intense ultrashort laser pulse linearly polarized along the internuclear axis (z axis). We solve a three-dimensional time-dependent Schrödinger equation, TDSE, via correlated two-electron ab initio calculations within the fixed-nuclei approximation. A complex scaling method is used for calculation of both single and double ionizations. These nonperturbative processes increase with large internuclear distance R and reach a maximum at some critical distance Rc and decrease by further increase of R. This enhanced ionization (EI) at Rc is accompanied by enhanced single and double excitation processes. Furthermore, EI is stronger when the permanent dipole moment of the molecule and the electric field at the peak of the laser pulse are antiparallel than when they are parallel. We predict analytically the Rc at which the enhancement of all these molecular processes happens in HeH+ from a simple quasistatic model and investigate the effect of Carrier Envelope Phase on these nonlinear nonperturbative processes.

Dehghanian, E.; Bandrauk, A. D.; Lagmago Kamta, G.

2013-08-01

52

Enhanced ionization of the non-symmetric HeH{sup +} molecule driven by intense ultrashort laser pulses  

SciTech Connect

We study enhanced single and double ionizations and enhanced single and double excitations in the nonsymmetric two-electron diatomic molecular ion HeH{sup +} in an intense ultrashort laser pulse linearly polarized along the internuclear axis (z axis). We solve a three-dimensional time-dependent Schrödinger equation, TDSE, via correlated two-electron ab initio calculations within the fixed-nuclei approximation. A complex scaling method is used for calculation of both single and double ionizations. These nonperturbative processes increase with large internuclear distance R and reach a maximum at some critical distance R{sub c} and decrease by further increase of R. This enhanced ionization (EI) at R{sub c} is accompanied by enhanced single and double excitation processes. Furthermore, EI is stronger when the permanent dipole moment of the molecule and the electric field at the peak of the laser pulse are antiparallel than when they are parallel. We predict analytically the R{sub c} at which the enhancement of all these molecular processes happens in HeH{sup +} from a simple quasistatic model and investigate the effect of Carrier Envelope Phase on these nonlinear nonperturbative processes.

Dehghanian, E. [Department of Chemistry, University of Sistan and Baluchestan, Zahedan 98155-987 (Iran, Islamic Republic of)] [Department of Chemistry, University of Sistan and Baluchestan, Zahedan 98155-987 (Iran, Islamic Republic of); Bandrauk, A. D. [Département de Chimie, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1 (Canada)] [Département de Chimie, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1 (Canada); Lagmago Kamta, G. [Cancer Research Institute, Hopital C. LeMoyne, Greenfield Park, Québec J4V 2H1 (Canada)] [Cancer Research Institute, Hopital C. LeMoyne, Greenfield Park, Québec J4V 2H1 (Canada)

2013-08-28

53

Relationship between shifts of spectral lines and the dipole moment of perturbing-gas molecules  

Microsoft Academic Search

A submillimeter spectrometer was used to study the dependence of the frequency-shift parameter of the transition s(1,0)-a(0,0) of the N-(14)H3 molecule on the dipole moment of perturbing-gas molecules at a frequency of 572.5 GHz. The perturbing molecules studied were the symmetric-top molecules PH3 and NH3, the linear molecules N2O and OCS, and the asymmetric-top molecules C6H5Cl and C3H7ON. A linear

S. P. Belov; A. F. Krupnov; A. A. Melnikov; V. A. Skvortsov; M. Iu. Tretiakov

1985-01-01

54

On-Top ?-Stacking of Quasiplanar Molecules in Hole-Transporting Materials: Inducing Anisotropic Carrier Mobility in Amorphous Films.  

PubMed

Dimers of partially oxygen-bridged triarylamines were designed and synthesized as hole-transporting materials. X-ray structural analyses revealed that these compounds form on-top ?-stacking aggregates in the crystalline state. TRMC measurements showed that high levels of anisotropic charge transport were induced in the direction of the ?-stacking. Surprisingly, even in vacuum-deposited amorphous films, these compounds retained some of the face-on ?-stacking, thus facilitating an out-of-plane carrier mobility. PMID:24764307

Wakamiya, Atsushi; Nishimura, Hidetaka; Fukushima, Tatsuya; Suzuki, Furitsu; Saeki, Akinori; Seki, Shu; Osaka, Itaru; Sasamori, Takahiro; Murata, Michihisa; Murata, Yasujiro; Kaji, Hironori

2014-06-01

55

Interaction of rotationally aligned and of oriented molecules in gas phase and at surfaces  

Microsoft Academic Search

Recent developments concerning the generation of molecular beams containing oriented\\/aligned molecules will be reviewed and applications of such tools to the study of elementary processes occurring both in homogeneous and heterogeneous phases will be presented. First we will discuss the case of symmetric top molecules oriented by hexapoles. Here the molecular polarization is obtained by the use of an external

L. Vattuone; L. Savio; F. Pirani; D. Cappelletti; M. Okada; M. Rocca

2010-01-01

56

Synthesis, ?-Face-Selective Aggregation, and ?-Face Chiral Recognition of Configurationally Stable C3 -Symmetric Propeller-Chiral Molecules with a ?-Core.  

PubMed

The C3 -symmetric propeller-chiral compounds (P,P,P)-1 and (M,M,M)-1 with planar ?-cores perpendicular to the C3 -axis were synthesized in optically pure states. (P,P,P)-1 possesses two distinguishable propeller-chiral ?-faces with rims of different heights named the (P/L)-face and (P/H)-face. Each face is configurationally stable because of the rigid structure of the helicenes contained in the ?-core. (P,P,P)-1 formed dimeric aggregates in organic solutions as indicated by the results of (1) H?NMR, CD, and UV/Vis spectroscopy and vapor pressure osmometry analyses. The (P/L)/(P/L) interactions were observed in the solid state by single-crystal X-ray analysis, and they were also predominant over the (P/H)/(P/H) and (P/L)/(P/H) interactions in solution, as indicated by the results of (1) H and 2D NMR spectroscopy analyses. The dimerization constant was obtained for a racemic mixture, which showed that the heterochiral (P,P,P)-1/(M,M,M)-1 interactions were much weaker than the homochiral (P,P,P)-1/(P,P,P)-1 interactions. The results indicated that the propeller-chiral (P/L)-face interacts with the (P/L)-face more strongly than with the (P/H)-face, (M/L)-face, and (M/H)-face. The study showed the ?-face-selective aggregation and ?-face chiral recognition of the configurationally stable propeller-chiral molecules. PMID:24737294

Saito, Nozomi; Terakawa, Ryo; Yamaguchi, Masahiko

2014-05-01

57

The microwave spectrum of a two-top peptide mimetic: The N-acetyl alanine methyl ester molecule  

NASA Astrophysics Data System (ADS)

The rotational spectrum of N-acetyl alanine methyl ester, a derivative of the biomimetic, N-acetyl alanine N'-methyl amide or alanine dipeptide, has been measured using a mini Fourier transform spectrometer between 9 and 25 GHz as part of a project undertaken to determine the conformational structures of various peptide mimetics from the torsion-rotation parameters of low-barrier methyl tops. Torsion-rotation splittings from two of the three methyl tops capping the acetyl end of the -NH-C(=O)- and the methoxy end of -C(=O)-O- groups account for most of the observed lines. In addition to the AA state, two E states have been assigned and include an AE state having a torsional barrier of 396.45(7) cm-1 (methoxy rotor) and an EA state having a barrier of 64.96(4) cm-1 (acetyl rotor). The observed torsional barriers and rotational constants of alanine dipeptide and its methyl ester are compared with predictions from Møller-Plesset second-order perturbation theory (MP2) and density functional theory (DFT) in an effort to explore systematic errors at the two levels of theory. After accounting for zero-point energy differences, the torsional barriers at the MP2/cc-pVTZ level are in excellent agreement with experiment for the acetyl and methoxy groups while DFT predictions range from 8% to 80% too high or low. DFT is found to consistently overestimate the overall molecular size while MP2 methods give structures that are undersized. Structural discrepancies of similar magnitude are evident in previous DFT results of crystalline peptides.

Plusquellic, David F.; Kleiner, Isabelle; Demaison, Jean; Suenram, Richard D.; Lavrich, Richard J.; Lovas, Frank J.; Fraser, Gerald T.; Ilyushin, Vadim V.

2006-09-01

58

Symmetric textures  

SciTech Connect

The Wolfenstein parametrization is extended to the quark masses in the deep ultraviolet, and an algorithm to derive symmetric textures which are compatible with existing data is developed. It is found that there are only five such textures.

Ramond, P. (Florida Univ., Gainesville, FL (United States). Dept. of Physics)

1993-01-01

59

Symmetric textures  

SciTech Connect

The Wolfenstein parametrization is extended to the quark masses in the deep ultraviolet, and an algorithm to derive symmetric textures which are compatible with existing data is developed. It is found that there are only five such textures.

Ramond, P. [Florida Univ., Gainesville, FL (United States). Dept. of Physics

1993-04-01

60

Quantum theory and collisional propensity rules for rotationally inelastic collisions between polyatomic molecules (NH3 and CO2) and an uncorrugated surface  

Microsoft Academic Search

We present the general quantum theory of collisions of a symmetric top molecule with an uncorrugated surface. The similarities between the description of collisions of a molecule with a structureless atom and a flat surface allow us to exploit earlier gas-phase results. We then derive several collisional propensity rules: (1) In experiments in which both inversion states in the initial

Gregory C. Corey; Millard H. Alexander

1988-01-01

61

Two C3 -Symmetric Dy3 (III) Complexes with Triple Di-?-methoxo-?-phenoxo Bridges, Magnetic Ground State, and Single-Molecule Magnetic Behavior.  

PubMed

Two series of isostructural C3 -symmetric Ln3 complexes Ln3 ?[BPh4 ] and Ln3 ?0.33[Ln(NO3 )6 ] (in which Ln(III) =Gd and Dy) have been prepared from an amino-bis(phenol) ligand. X-ray studies reveal that Ln(III) ions are connected by one ?2 -phenoxo and two ?3 -methoxo bridges, thus leading to a hexagonal bipyramidal Ln3 O5 bridging core in which Ln(III) ions exhibit a biaugmented trigonal-prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self-consistent field (CASSCF) calculations indicate that the magnetic coupling between the Dy(III) ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest Dy?O distance, the local magnetic moments are oriented almost perpendicular to the Dy3 plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the Dy(III) ions are separated by approximately 150 and 177?cm(-1) , for Dy3 ?[BPh4 ] and Dy3 ?0.33[Dy(NO3 )6 ], respectively. As expected for these large energy gaps, Dy3 ?[BPh4 ] and Dy3 ?0.33[Dy(NO3 )6 ] exhibit, under zero direct-current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied Hdc field of 1000?Oe, Dy3 ?[BPh4 ] exhibits two thermally activated processes with Ueff values of 34.7 and 19.5?cm(-1) , whereas Dy3 ?0.33[Dy(NO3 )6 ] shows only one activated process with Ueff =19.5?cm(-1) . PMID:24890335

Hänninen, Mikko M; Mota, Antonio J; Aravena, Daniel; Ruiz, Eliseo; Sillanpää, Reijo; Camón, Agustín; Evangelisti, Marco; Colacio, Enrique

2014-07-01

62

Two dimensional symmetric correlation functions of the hat S operator and two dimensional Fourier transforms: Considering the line coupling for P and R lines of linear molecules  

NASA Astrophysics Data System (ADS)

The refinement of the Robert-Bonamy (RB) formalism by considering the line coupling for isotropic Raman Q lines of linear molecules developed in our previous study [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] has been extended to infrared P and R lines. In these calculations, the main task is to derive diagonal and off-diagonal matrix elements of the Liouville operator iS1 - S2 introduced in the formalism. When one considers the line coupling for isotropic Raman Q lines where their initial and final rotational quantum numbers are identical, the derivations of off-diagonal elements do not require extra correlation functions of the hat S operator and their Fourier transforms except for those used in deriving diagonal elements. In contrast, the derivations for infrared P and R lines become more difficult because they require a lot of new correlation functions and their Fourier transforms. By introducing two dimensional correlation functions labeled by two tensor ranks and making variable changes to become even functions, the derivations only require the latters' two dimensional Fourier transforms evaluated at two modulation frequencies characterizing the averaged energy gap and the frequency detuning between the two coupled transitions. With the coordinate representation, it is easy to accurately derive these two dimensional correlation functions. Meanwhile, by using the sampling theory one is able to effectively evaluate their two dimensional Fourier transforms. Thus, the obstacles in considering the line coupling for P and R lines have been overcome. Numerical calculations have been carried out for the half-widths of both the isotropic Raman Q lines and the infrared P and R lines of C2H2 broadened by N2. In comparison with values derived from the RB formalism, new calculated values are significantly reduced and become closer to measurements.

Ma, Q.; Boulet, C.; Tipping, R. H.

2014-03-01

63

Two dimensional symmetric correlation functions of the ? operator and two dimensional Fourier transforms: considering the line coupling for P and R lines of linear molecules.  

PubMed

The refinement of the Robert-Bonamy (RB) formalism by considering the line coupling for isotropic Raman Q lines of linear molecules developed in our previous study [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] has been extended to infrared P and R lines. In these calculations, the main task is to derive diagonal and off-diagonal matrix elements of the Liouville operator iS1 - S2 introduced in the formalism. When one considers the line coupling for isotropic Raman Q lines where their initial and final rotational quantum numbers are identical, the derivations of off-diagonal elements do not require extra correlation functions of the ? operator and their Fourier transforms except for those used in deriving diagonal elements. In contrast, the derivations for infrared P and R lines become more difficult because they require a lot of new correlation functions and their Fourier transforms. By introducing two dimensional correlation functions labeled by two tensor ranks and making variable changes to become even functions, the derivations only require the latters' two dimensional Fourier transforms evaluated at two modulation frequencies characterizing the averaged energy gap and the frequency detuning between the two coupled transitions. With the coordinate representation, it is easy to accurately derive these two dimensional correlation functions. Meanwhile, by using the sampling theory one is able to effectively evaluate their two dimensional Fourier transforms. Thus, the obstacles in considering the line coupling for P and R lines have been overcome. Numerical calculations have been carried out for the half-widths of both the isotropic Raman Q lines and the infrared P and R lines of C2H2 broadened by N2. In comparison with values derived from the RB formalism, new calculated values are significantly reduced and become closer to measurements. PMID:24628166

Ma, Q; Boulet, C; Tipping, R H

2014-03-14

64

Rigid rotators. [deriving the time-independent energy states associated with rotational motions of the molecule  

NASA Technical Reports Server (NTRS)

The two-particle, steady-state Schroedinger equation is transformed to center of mass and internuclear distance vector coordinates, leading to the free particle wave equation for the kinetic energy motion of the molecule and a decoupled wave equation for a single particle of reduced mass moving in a spherical potential field. The latter describes the vibrational and rotational energy modes of the diatomic molecule. For fixed internuclear distance, this becomes the equation of rigid rotator motion. The classical partition function for the rotator is derived and compared with the quantum expression. Molecular symmetry effects are developed from the generalized Pauli principle that the steady-state wave function of any system of fundamental particles must be antisymmetric. Nuclear spin and spin quantum functions are introduced and ortho- and para-states of rotators, along with their degeneracies, are defined. Effects of nuclear spin on entropy are deduced. Next, rigid polyatomic rotators are considered and the partition function for this case is derived. The patterns of rotational energy levels for nonlinear molecules are discussed for the spherical symmetric top, for the prolate symmetric top, for the oblate symmetric top, and for the asymmetric top. Finally, the equilibrium energy and specific heat of rigid rotators are derived.

1976-01-01

65

Ejs Lagrange Top Model  

NSDL National Science Digital Library

The Ejs Lagrange Top model displays the motion of a heavy symmetric top under the effect of gravity. The top has an initial angular speed that provides the precessional, nutational, and rotational speeds. The ratio of Lz to Lâ can be set via slider and the initial angular position and angular speeds can be changed via textboxes. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Lagrange Top model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_rigid_bodies_Lagrange.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for rigid body dynamics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

66

Architectural Tops  

ERIC Educational Resources Information Center

The development of the skyscraper is an American story that combines architectural history, economic power, and technological achievement. Each city in the United States can be identified by the profile of its buildings. The design of the tops of skyscrapers was the inspiration for the students in the author's high-school ceramic class to develop…

Mahoney, Ellen

2010-01-01

67

a Fitting Program for Molecules with Two Equivalent Tops and C_{2V} Point-Group Symmetry at Equilibrium: Application to Existing Microwave, Millimeter, and Sub-Millimeter Wave Measurements of Acetone  

NASA Astrophysics Data System (ADS)

We will present a new theoretical tool, a program called PAM-C2v-2tops, for analysis of the high-resolution torsion-rotation spectra of molecules with two equivalent methyl rotors and C_{2V} symmetry at equilibrium. The new tool belongs to the broad class of effective Hamiltonians, is based on Longuet-Higgins' group theoretical ideas and uses G_{36} permutation-inversion group-theoretical considerations, the principal axis method and a two-step diagonalization procedure. The program was used to carry out a weighted least-squares fit of 1720 microwave, millimeter-wave, and sub-millimeter-wave line frequencies of acetone [(CH_3)_2CO] that are available in the literature. The weighted root-mean-square deviation of 0.93 obtained for a joint fit of the microwave lines belonging to the ground, the lower torsional fundamental, and the higher torsional fundamental states of acetone represents significant progress in comparison with previous fitting attempts, especially for the excited torsional states.

Ilyushin, Vadim V.; Hougen, Jon T.

2013-06-01

68

A fitting program for molecules with two equivalent methyl tops and C2v point-group symmetry at equilibrium: Application to existing microwave, millimeter, and sub-millimeter wave measurements of acetone  

NASA Astrophysics Data System (ADS)

A program, called PAM_C2v_2tops, for fitting the high-resolution torsion–rotation spectra of molecules with two equivalent methyl rotors and C2v symmetry at equilibrium is described and applied to the spectrum of acetone [(CH3)2CO]. The G36 permutation–inversion group-theoretical considerations used in the design of the program are presented followed by a description of the structure of the program, which uses the principal axis method and a two-step diagonalization procedure. The program was used to carry out a weighted least-squares fit of 1720 microwave, millimeter-wave, and sub-millimeter-wave line frequencies of acetone that are available in the literature. The weighted standard deviation of 0.94 obtained here for a joint fit of rotational lines belonging to the ground, the lower torsional fundamental, and the higher torsional fundamental states of acetone represents significant progress in comparison with previous fitting attempts, especially for the excited torsional states.

Ilyushin, Vadim V.; Hougen, Jon. T.

2013-07-01

69

Photovoltaic response of symmetric sandwich polymer cells with identical electrodes  

NASA Astrophysics Data System (ADS)

The photovoltaic response of symmetric sandwich polymer cells based on poly[5-(2'-ethylhexyloxy)-2-methoxy-1,4-phenylene vinylene] (MEH-PPV) and MEH-PPV:fullerene blends has been investigated. Identical, semitransparent gold, silver, aluminum, and calcium are used as top and bottom electrodes. Most of the nominally symmetric sandwich cells exhibit pronounced photovoltaic (PV) response. The PV parameters are strongly dependent on the direction of illumination, the active layer thickness, and the evaporation rate of top electrode. Open-circuit voltage as high as 0.7 V has been measured in silver/MEH-PPV/silver cells. The addition of fullerene leads to reduced open-circuit voltage and higher short-circuit current. The photovoltaic response observed in these nominally symmetric sandwich cells is attributed to their different top and bottom electrode interfaces.

Alem, Salima; Gao, Jun; Wantz, Guillaume

2009-08-01

70

Creating a Symmetrical Design  

NSDL National Science Digital Library

This unit teaches students the meaning of symmetry by having them manipulate a variety of objects. Using this knowledge, they will create a symmetrical design and write an informative paragraph about the quilt design and the importance of symmetry.

Service, National S.

2009-04-24

71

Noncommutative spherically symmetric spaces  

SciTech Connect

We examine some noncommutative spherically symmetric spaces in three space dimensions. A generalization of Snyder's noncommutative (Euclidean) space allows the inclusion of the generator of dilations into the defining algebra of the coordinate and rotation operators. We then construct a spherically symmetric noncommutative Laplacian on this space having the correct limiting spectrum. This is presented via a creation and annihilation operator realization of the algebra, which may lend itself to a truncation of the Hilbert space.

Murray, Sean; Govaerts, Jan [Centre for Cosmology, Particle Physics and Phenomenology, Universite catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve (Belgium); Centre for Cosmology, Particle Physics and Phenomenology, Universite catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve (Belgium) and International Chair in Mathematical Physics and Applications, University of Abomey-Calavi, 072 B. P. 50, Cotonou (Benin)

2011-01-15

72

Depolarization ratio of Rayleigh scattered radiation by molecules.  

PubMed

The depolarization ratios of Rayleigh scattered radiation by molecules has been used to measure the ratio of anisotropic polarizability to isotropic (average) polarizability in the laboratory. The authors have calculated the depolarization ratio for N2, CH3Cl, and H2O from the first principles. It is shown that the depolarization ratio derived from input polarizabilities differs by a factor of about 4 for 1Sigma diatom N2, by a factor of about 2.9 for symmetric top CH3Cl, and by a factor of about 5 for asymmetric top H2O. These large discrepancies arise because in deriving the ratio of anisotropic polarizability to isotropic (average) polarizability from the measured depolarization ratio, the constraints imposed by the conservation of angular momentum have been completely ignored. PMID:17228953

Sharma, Ramesh D; Burtt, Kelly D

2007-01-14

73

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

Microsoft Academic Search

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

S. R. Gandhi; R. B. Bernstein

1988-01-01

74

Symmetrized curve-straightening  

Microsoft Academic Search

The ‘traditional’ curve-straightening flow is based on one of the standard Sobolev inner products and it is known to break certain symmetries of reflection. The purpose of this paper is to show that there are alternative Riemannian structures on the space of curves that yield flows that preserve symmetries. This feature comes at a price. In one symmetrizing metric the

Anders Linnér

2003-01-01

75

Yangian symmetric correlators  

NASA Astrophysics Data System (ADS)

Similarity transformations and eigenvalue relations of monodromy operators composed of Jordan-Schwinger type L matrices are considered and used to define Yangian symmetric correlators of n-dimensional theories. Explicit expressions are obtained and relations are formulated. In this way basic notions of the Quantum inverse scattering method provide a convenient formulation for high symmetry and integrability not only in lower dimensions.

Chicherin, D.; Kirschner, R.

2013-12-01

76

Multistrip multigap symmetric RPC  

NASA Astrophysics Data System (ADS)

The characteristics of a symmetric multigap resistive plate chamber with multistrip readout electrode, recently developed by us, continued to be investigated. Studies of the time resolution, efficiency, average charge and dark rate as a function of applied voltage and the influence of the angle of incidence of the detected particle on these observables have been performed. Different type of discriminators have been tested.

Petrovici, M.; Herrmann, N.; Hildenbrand, K. D.; Augustinski, G.; Ciobanu, M.; Cruceru, I.; Duma, M.; Hartmann, O.; Koczon, P.; Kress, T.; Marquardt, M.; Moisa, D.; Petri?, M.; Schroeder, C.; Simion, V.; Stoicea, G.; Weinert, J.

2003-08-01

77

Multistrip multigap symmetric RPC  

Microsoft Academic Search

The characteristics of a symmetric multigap resistive plate chamber with multistrip readout electrode, recently developed by us, continued to be investigated. Studies of the time resolution, efficiency, average charge and dark rate as a function of applied voltage and the influence of the angle of incidence of the detected particle on these observables have been performed. Different type of discriminators

M. Petrovici; N. Herrmann; K. D. Hildenbrand; G. Augustinski; M. Ciobanu; I. Cruceru; M. Duma; O. Hartmann; P. Koczon; T. Kress; M. Marquardt; D. Moisa; M. Petris; C. Schroeder; V. Simion; G. Stoicea; J. Weinert

2003-01-01

78

Geometry and bonding in the ground and lowest triplet state of D6h symmetric crenellated edged C 6[3m(m-1)+1]H 6(2m-1) ( m = 2, … , 6) graphene hydrocarbon molecules  

NASA Astrophysics Data System (ADS)

Ab initio plane wave all valence electron based DFT calculations were used to explore the dichotomy of perimeter vs. interior in the electronic and geometric structure of the D6h singlet ground state and D2h lowest triplet state of planar graphene hydrocarbon molecules with crenellated (arm chair) edges and the general formula C 6[3m(m-1)+1] H 6(2m-1) where m = 2, … , 6. The largest molecule C 546H 66 was 4.78 nm across and contained 2250 valence electrons. These molecules are nominally "fully benzenoid hydrocarbons". However with increasing size, the core of central atoms abandoned any fully benzenoid geometry they had in small systems and organized into single layer graphite (graphene) structure. The perimeter atoms of the crenellation adopted a conjugated geometry with unequal bonds and between core and perimeter there were some C 6 rings retaining remnants of aromatic sextet-type properties. Compared to a zigzag edge the crenellated edge conferred stability in all the systems studied as measured by the singlet homo-lumo level gap BG 0 and the singlet-lowest triplet energy gap ? EST. For the largest crenellated system ( m = 6) BG 0 and ? EST were approximately 0.7 eV, larger in value than for similarly sized hexagonal graphenes with zigzag edges. Triplet states were identified for all the molecules in the series and in the case of the m = 2 molecule hexabenzocoronene C 42H 18, two conformations with D2h symmetry were identified and compared to features on the triplet state potential energy surface of benzene.

Philpott, Michael R.; Kawazoe, Yoshiyuki

2009-03-01

79

Symmetric modular torsatron  

DOEpatents

A fusion reactor device is provided in which the magnetic fields for plasma confinement in a toroidal configuration is produced by a plurality of symmetrical modular coils arranged to form a symmetric modular torsatron referred to as a symmotron. Each of the identical modular coils is helically deformed and comprise one field period of the torsatron. Helical segments of each coil are connected by means of toroidally directed windbacks which may also provide part of the vertical field required for positioning the plasma. The stray fields of the windback segments may be compensated by toroidal coils. A variety of magnetic confinement flux surface configurations may be produced by proper modulation of the winding pitch of the helical segments of the coils, as in a conventional torsatron, winding the helix on a noncircular cross section and varying the poloidal and radial location of the windbacks and the compensating toroidal ring coils.

Rome, J.A.; Harris, J.H.

1984-01-01

80

Self-Assembling Dessert Toppings  

NSDL National Science Digital Library

This is an activity (located on page 3 of the PDF) about self-assembly, the ability of molecules to assemble themselves according to certain rules. Learners will use food-grade components to create delicious dessert topping-filled gel capsules, macroscale relatives of the capsules nanoscientists make in a lab to carry medicine to targeted cells of the body. Relates to linked video, DragonflyTV Nano: Self-Assembly.

Twin Cities Public Television, Inc.

2008-01-01

81

Top physics at CDF  

SciTech Connect

Precision studies of top quark properties are a primary goal of the Run II physics program at the Fermilab Tevatron. Marking the first stages of this program, the CDF collaboration presents recent results on top pair production cross section, single top physics and top mass, using between 109 and 200 pb{sup -1} of Run II data.

Julia Thom

2004-06-24

82

Tevatron top physics  

SciTech Connect

A summary of the most recent results on top quark physics obtained at Fermilab's Tevatron proton-antiproton collider, operating at a centre of mass energy of 1.96 TeV, is presented. Measurements of the top pair and single top quark production cross sections, the investigation of top quark decay properties, the precision measurement of the top quark mass as well as searches for physics beyond the standard model are discussed.

Wagner-Kuhr, Jeannine; /Karlsruhe U.

2009-04-01

83

Stereoisomers of compounds with symmetric constitutions.  

PubMed

Chiral organic compounds with unsymmetric constitutions can lead to N(r) = 2(n) stereoisomers. By contrast, if a chiral compound has a symmetric constitution, then the number of stereoisomers is reduced. In this publication, we wish to present an algorithm to calculate the number of stereoisomers of chiral organic compounds of the latter type (e. g. sugar acids). The first step is the development of two different functions for unbranched compounds where the number of repeating units is even or uneven. Other stereogenic units like double bonds, chiral axes or planes are not discussed. The results are then checked against the actual isomers. The next step leads to a unified equation to predict the precise number of stereoisomers that can exist. Thus, the relationship between chirality and symmetry is shown in detail. Additionally, the algorithm is applied to some drug molecules with symmetric constitutions. PMID:16281306

Siebert, Carsten D; Tampe, Niels

2005-11-01

84

Symmetrical peripheral gangrene.  

PubMed Central

Two cases of symmetrical peripheral gangrene associated with intracardiac lesions are described. One had a secondary deposit from a uterine leiomyosarcoma in the wall of the right ventricle, the other had a free ball thrombus in the right atrium; there were no valvular lesions in either case. The published reports of this type of gangrene indicate that it may result from (1) va sospastic conditions, (2) small vessel obstruction, or (3) conditions producing a very low cardiac output. The two patients reported are unusual examples of the last. Images

McGouran, R C; Emmerson, G A

1977-01-01

85

Modifications to Axially Symmetric Simulations Using New DSMC (2007) Algorithms  

NASA Technical Reports Server (NTRS)

Several modifications aimed at improving physical accuracy are proposed for solving axially symmetric problems building on the DSMC (2007) algorithms introduced by Bird. Originally developed to solve nonequilibrium, rarefied flows, the DSMC method is now regularly used to solve complex problems over a wide range of Knudsen numbers. These new algorithms include features such as nearest neighbor collisions excluding the previous collision partners, separate collision and sampling cells, automatically adaptive variable time steps, a modified no-time counter procedure for collisions, and discontinuous and event-driven physical processes. Axially symmetric solutions require radial weighting for the simulated molecules since the molecules near the axis represent fewer real molecules than those farther away from the axis due to the difference in volume of the cells. In the present methodology, these radial weighting factors are continuous, linear functions that vary with the radial position of each simulated molecule. It is shown that how one defines the number of tentative collisions greatly influences the mean collision time near the axis. The method by which the grid is treated for axially symmetric problems also plays an important role near the axis, especially for scalar pressure. A new method to treat how the molecules are traced through the grid is proposed to alleviate the decrease in scalar pressure at the axis near the surface. Also, a modification to the duplication buffer is proposed to vary the duplicated molecular velocities while retaining the molecular kinetic energy and axially symmetric nature of the problem.

Liechty, Derek S.

2008-01-01

86

Symmetrization for redundant channels  

NASA Technical Reports Server (NTRS)

A plurality of redundant channels in a system each contain a global image of all the configuration data bases in each of the channels in the system. Each global image is updated periodically from each of the other channels via cross channel data links. The global images of the local configuration data bases in each channel are separately symmetrized using a voting process to generate a system signal configuration data base which is not written into by any other routine and is available for indicating the status of the system within each channel. Equalization may be imposed on a suspect signal and a number of chances for that signal to heal itself are provided before excluding it from future votes. Reconfiguration is accomplished upon detecting a channel which is deemed invalid. A reset function is provided which permits an externally generated reset signal to permit a previously excluded channel to be reincluded within the system. The updating of global images and/or the symmetrization process may be accomplished at substantially the same time within a synchronized time frame common to all channels.

Tulplue, Bhalchandra R. (Inventor); Collins, Robert E. (Inventor)

1988-01-01

87

Technical Operations Support (TOPS).  

National Technical Information Service (NTIS)

The Technical Operations Support (TOPS) program was established to assess existing and future Air Force systems requirements and identify materials and processes needs to met these requirements. TOPS was implemented to develop draft research and developme...

R. Cochoy

2000-01-01

88

Spherical Tippe Tops  

ERIC Educational Resources Information Center

A tippe top (see Fig. 1) is usually constructed as a truncated sphere with a cylindrical peg on top, as indicated in Fig. 2(a). When spun rapidly on a horizontal surface, a tippe top spins about a vertical axis while rotating slowly about a horizontal axis until the peg touches the surface. At that point, weight is transferred to the peg, the…

Cross, Rod

2013-01-01

89

Spherical Tippe Tops  

NASA Astrophysics Data System (ADS)

A tippe top (see Fig. 1) is usually constructed as a truncated sphere with a cylindrical peg on top, as indicated in Fig. 2(a). When spun rapidly on a horizontal surface, a tippe top spins about a vertical axis while rotating slowly about a horizontal axis until the peg touches the surface. At that point, weight is transferred to the peg, the truncated sphere rises off the surface, and the top spins on the peg until it is upright. A feature of a tippe top is that its center of mass, labeled G in Fig. 2, is below the geometric center of the sphere, C, when the top is at rest. That is where it will return if the top is tilted sideways and released since that is the stable equilibrium position. The fact that a tippe top turns upside down when it spins is therefore astonishing. The behavior of a tippe top is quite unlike that of a regular top since the spin axis remains closely vertical the whole time. The center of mass of a regular top can also rise, but the spin axis tilts upward as the top rises and enters a ``sleeping'' position.

Cross, Rod

2013-03-01

90

Tinkering with Tops  

NSDL National Science Digital Library

In this activity, learners explore the history, design and motion of spinning tops. Learners work in teams of "engineers" to design and build their own tops out of everyday items. Their challenge is to design a spinning top that can spin for at least 10 seconds within a circle 30 cm in diameter.

Ieee

2014-05-22

91

CDF top physics  

SciTech Connect

The authors present the latest results about top physics obtained by the CDF experiment at the Fermilab Tevatron collider. The data sample used for these analysis (about 110 pb{sup {minus}1}) represents almost the entire statistics collected by CDF during four years (1992--95) of data taking. This large data size has allowed detailed studies of top production and decay properties. The results discussed here include the determination of the top quark mass, the measurement of the production cross section, the study of the kinematics of the top events and a look at top decays.

Tartarelli, G.F. [I.N.F.N., Milano (Italy). Sezione di Milano; CDF Collaboration

1996-05-01

92

Top quark physics  

SciTech Connect

While the top quark was discovered in 1995 at the Fermilab Tevatron, a decade later they still have very little information about the top. As the heaviest particle yet discovered, the top quark is interesting in and of itself, but some speculate that it may play a special role in physics beyond the Standard Model. With Run 2 of the Tevatron well underway, they have the opportunity to study top quark properties with much better sensitivity, and to test whether top quarks behave as predicted by current theories. This article focuses on the basics of top quark physics at the Tevatron, highlighting only a sample of the many recent measurements, as new results are being released monthly, and constantly changing the landscape of our knowledge of top.

Erbacher, Robin D.; /UC, Davis

2005-10-01

93

Conformally symmetric traversable wormholes  

SciTech Connect

Exact solutions of traversable wormholes are found under the assumption of spherical symmetry and the existence of a nonstatic conformal symmetry, which presents a more systematic approach in searching for exact wormhole solutions. In this work, a wide variety of solutions are deduced by considering choices for the form function, a specific linear equation of state relating the energy density and the pressure anisotropy, and various phantom wormhole geometries are explored. A large class of solutions impose that the spatial distribution of the exotic matter is restricted to the throat neighborhood, with a cutoff of the stress-energy tensor at a finite junction interface, although asymptotically flat exact solutions are also found. Using the 'volume integral quantifier', it is found that the conformally symmetric phantom wormhole geometries may, in principle, be constructed by infinitesimally small amounts of averaged null energy condition violating matter. Considering the tidal acceleration traversability conditions for the phantom wormhole geometry, specific wormhole dimensions and the traversal velocity are also deduced.

Boehmer, Christian G.; Harko, Tiberiu; Lobo, Francisco S. N. [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 2EG (United Kingdom); Department of Physics and Center for Theoretical and Computational Physics, University of Hong Kong, Pok Fu Lam Road, Hong Kong (China); Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 2EG, United Kingdom and Centro de Astronomia e Astrofisica da Universidade de Lisboa, Campo Grande, Ed. C8 1749-016 Lisbon (Portugal)

2007-10-15

94

Top Physics at CDF  

SciTech Connect

We present the recent results of top-quark physics using up to 6 fb{sup -1} of p{bar p} collisions at a center of mass energy of {radical}s = 1.96 TeV analyzed by the CDF collaboration. Thanks to this large data sample, precision top quark measurements are now a reality at the Tevatron. Further, several new physics signals could appear in this large dataset. We will present the latest measurements of top quark intrinsic properties as well as direct searches for new physics in the top sector.

Moon, Chang-Seong

2011-06-01

95

Top quark measurements  

SciTech Connect

Ten years after its discovery at the Tevatron collider, we still know little about the top quark. Its large mass suggests it may play a key role in the mechanism of Electroweak Symmetry Breaking (EWSB), or open a window of sensitivity to new physics related to EWSB and preferentially coupled to it. To determine whether this is the case, precision measurements of top quark properties are necessary. The high statistics samples being collected by the Tevatron experiments during Run II start to incisively probe the top quark sector. This report summarizes the experimental status of the top quark, focusing in particular on the recent measurements from the Tevatron Run II.

Juste, A.; /Fermilab

2005-11-01

96

Nonstandard top substructure  

NASA Astrophysics Data System (ADS)

The top quark, being the heaviest particle of the Standard Model (SM), is a prime candidate of where physics beyond the SM (BSM) might currently hide before our eyes. There are many natural extensions of the SM that rely on top compositeness, and the top quark could follow the paradigm of revealing a substructure when it is probed at high enough momentum transfers. Observing high pT top final states naturally drives us toward boosted hadronic analyses that can be tackled efficiently with jet substructure techniques. In this paper we analyze the prospects of constraining exemplary nonstandard QCD top interactions in this kinematical regime. We correctly include QCD modifications to additional gluon emission off the boosted top quark and keep track of the modified top tagging efficiencies. We conclude that nonstandard top QCD interactions can be formidably constrained at the LHC 14 TeV. Experimental systematic uncertainties are a major obstacle of the described measurement. Unless significantly improved for the 14 TeV run, they will saturate the direct sensitivity to nonresonant BSM top physics at luminosities of around 100/fb.

Englert, Christoph; Gonçalves, Dorival; Spannowsky, Michael

2014-04-01

97

HUBBLE'S TOP TEN GRAVITATIONAL LENSES  

NASA Technical Reports Server (NTRS)

The NASA Hubble Space Telescope serendipitous survey of the sky has uncovered exotic patterns, rings, arcs and crosses that are all optical mirages produced by a gravitational lens, nature's equivalent of having giant magnifying glass in space. Shown are the top 10 lens candidates uncovered in the deepest 100 Hubble fields. Hubble's sensitivity and high resolution allow it to see faint and distant lenses that cannot be detected with ground-based telescopes whose images are blurred by Earth's atmosphere. [Top Left] - HST 01248+0351 is a lensed pair on either side of the edge-on disk lensing galaxy. [Top Center] - HST 01247+0352 is another pair of bluer lensed source images around the red spherical elliptical lensing galaxy. Two much fainter images can be seen near the detection limit which might make this a quadruple system. [Top Right] - HST 15433+5352 is a very good lens candidate with a bluer lensed source in the form of an extended arc about the redder elliptical lensing galaxy. [Middle Far Left] - HST 16302+8230 could be an 'Einstein ring' and the most intriguing lens candidate. It has been nicknamed the 'the London Underground' since it resembles that logo. [Middle Near Left] - HST 14176+5226 is the first, and brightest lens system discovered in 1995 with the Hubble telescope. This lens candidate has now been confirmed spectroscopically using large ground-based telescopes. The elliptical lensing galaxy is located 7 billion light-years away, and the lensed quasar is about 11 billion light-years distant. [Middle Near Right] - HST 12531-2914 is the second quadruple lens candidate discovered with Hubble. It is similar to the first, but appears smaller and fainter. [Middle Far Right] - HST 14164+5215 is a pair of bluish lensed images symmetrically placed around a brighter, redder galaxy. [Bottom Left] - HST 16309+8230 is an edge-on disk-like galaxy (blue arc) which has been significantly distorted by the redder lensing elliptical galaxy. [Bottom Center] - HST 12368+6212 is a blue arc in the Hubble Deep Field (HDF). [Bottom Right] - HST 18078+4600 is a blue arc caused by the gravitational potential of a small group of 4 galaxies. Credit: Kavan Ratnatunga (Carnegie Mellon Univ.) and NASA

2002-01-01

98

Theory of x-ray diffraction from laser-aligned molecules.  

SciTech Connect

We present the theory of x-ray diffraction from an ensemble of symmetric-top molecules aligned by an intense optical laser pulse at finite rotational temperature. Using QED, the x-ray/molecule interaction is treated as an electronically elastic one-photon scattering process. In the practically important case that the x-ray pulse is quasi-monochromatic and its coherence time is much shorter than the time scale of molecular rotational dynamics in the laser field, there is a simple connection between the rotational wave-packet dynamics and the diffraction pattern obtained. Our theory thus opens up a new perspective for quantum molecular imaging using x-ray radiation.

Ho, P. J.; Santra, R. (Chemical Sciences and Engineering Division)

2010-06-01

99

Single-Electron Tunneling Behavior of Organic-Molecule-Based Electronic Device  

NASA Astrophysics Data System (ADS)

We fabricated electronic devices utilizing chemically synthesized organic molecules and Au nanoparticles and studied their electrical transport properties at low temperature. The Au/Ti electrodes separated by 10-60 nm were fabricated by electron-beam lithography and double-angle shadow evaporation. A self-assembled monolayer (SAM) of the organic molecules was formed on top of the electrodes, which was then bridged with Au nanoparticles trapped by electrostatic trapping. All the devices with SAM exhibited symmetric but nonlinear current-voltage characteristics along with the periodic gate modulation curves at low temperature. Our experimental data suggested that Coulomb blockade of single-electron tunneling is a dominant transport mechanism in our devices.

So, Hye-Mi; Park, Jong-Wan; Won, Do-Jae; Yun, Wan Soo; Kang, Yongku; Lee, Changjin; Kim, Ju-Jin; Kim, Jinhee

2004-09-01

100

Top Quark Physics  

SciTech Connect

We give an overview of the physics of the Top quark, from the experimental discovery to the studies of its properties. We review some of the work done on the Electroweak and Flavor Changing couplings associated with the Top quark in the Standard Model and beyond. We will focus on the specific contribution of phycisits working in Mexico and Mexican physicists working abroad.

Larios, F. [Departmento de Fisica Aplicada, CINVESTAV-Merida, AP 73 Cordemex, 97310 Merida, Yucatan (Mexico)

2006-09-25

101

Top search at CDF  

SciTech Connect

We review top quark searches carried out at CDF with data collected during the 1988--1989 Collider Run. The latest analyses give a lower limit on the top quark mass of 91 GeV/c{sup 2} at the 95% confidence level, assuming Standard Model decays. 8 refs., 6 figs., 1 tab.

Contreras, M. (Chicago Univ., IL (United States))

1991-10-01

102

Training Top 125  

ERIC Educational Resources Information Center

The best learning and development organizations support business initiatives tactically "and" help drive strategic change. Verizon did just that, earning it the No. 1 spot for the first time on the Training Top 125. Verizon and the other 2012 Top 125 winners continued to invest in training, collectively dedicating a mean of 4.52 percent of their…

Training, 2012

2012-01-01

103

Top-Level Structures  

ERIC Educational Resources Information Center

In this article, the author discusses top-level structure, a form of text structure that would help students improve their reading comprehension. There are four main organizational patterns, or top-level structures, that occur mostly in factual texts: compare/contrast, cause/effect, problem/ solution, and list-like. Authors often use signaling…

Bolton, Faye

2007-01-01

104

Infrared absorption of explosive molecule vapors  

Microsoft Academic Search

Infrared absorption spectra have been obtained for the high explosive molecules TNT, RDX, and PETN in the vapor phase. Integrated band strengths were measured for the symmetric and antisymmetric -NO2 vibrations in each of these molecules. Ab initio calculations of vibrational frequencies and intensities were carried out for comparison with the experimental data. Previous measurements of the heats of vaporization

James Janni; Brian D Gilbert; R. W Field; Jeffrey I Steinfeld

1997-01-01

105

Polyatomic molecule vibrations  

NASA Technical Reports Server (NTRS)

Polyatomic molecule vibrations are analyzed as harmonic vibrations along normal coordinates. The energy eigenvalues are found for linear and nonlinear symmetric triatomic molecules for valence bond models of the potential function with arbitrary coupling coefficients; such models can usually be fitted to observed energy levels with reasonably good accuracy. Approximate normal coordinates for the H2O molecule are discussed. Degenerate vibrational modes such as occur in CO2 are analyzed and expressions for Fermi resonance between close-lying states of the same symmetry are developed. The bending modes of linear triatomic molecules are expressed in terms of Laguerre polynomials in cylindrical coordinates as well as in terms of Hermite polynomials in Cartesian coordinates. The effects of large-amplitude bending such as occur in the C3 molecule are analyzed, along with anharmonic effects, which split the usually degenerate bending mode energy levels. Finally, the vibrational frequencies, degeneracies, and symmetry properties of XY3, X2Y2, and XY4 type molecules are discussed.

1976-01-01

106

Experimental Support for the Evolution of Symmetric Protein Architecture from a Simple Peptide Motif  

SciTech Connect

The majority of protein architectures exhibit elements of structural symmetry, and 'gene duplication and fusion' is the evolutionary mechanism generally hypothesized to be responsible for their emergence from simple peptide motifs. Despite the central importance of the gene duplication and fusion hypothesis, experimental support for a plausible evolutionary pathway for a specific protein architecture has yet to be effectively demonstrated. To address this question, a unique 'top-down symmetric deconstruction' strategy was utilized to successfully identify a simple peptide motif capable of recapitulating, via gene duplication and fusion processes, a symmetric protein architecture (the threefold symmetric {beta}-trefoil fold). The folding properties of intermediary forms in this deconstruction agree precisely with a previously proposed 'conserved architecture' model for symmetric protein evolution. Furthermore, a route through foldable sequence-space between the simple peptide motif and extant protein fold is demonstrated. These results provide compelling experimental support for a plausible evolutionary pathway of symmetric protein architecture via gene duplication and fusion processes.

J Lee; M Blaber

2011-12-31

107

Molecule Shapes  

NSDL National Science Digital Library

Explore molecule shapes by building molecules in 3D! How does molecule shape change with different numbers of bonds and electron pairs? Find out by adding single, double or triple bonds and lone pairs to the central atom. Then, compare the model to real molecules!

Simulations, Phet I.; Moore, Emily; Olson, Jonathan; Lancaster, Kelly; Chamberlain, Julia; Perkins, Kathy

2011-10-10

108

Mighty Molecules  

NSDL National Science Digital Library

In this activity, learners use marshmallows and gum drops to construct seven models of molecules. Learners classify (solid, liquid or gas) and draw diagrams of the molecules. Learners can also create a table showing the chemical formula for each molecule and identify a common use for each chemical. Use this activity to introduce learners to molecules, compounds, and bonds.

Little, Carlyn; Lahart, David; Meyers, Ted; Weisblat, Brooks

1997-01-01

109

Top Quark Properties  

SciTech Connect

Since its discovery in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron collider, the top quark has undergone intensive studies. Besides the Tevatron experiments, with the start of the LHC in 2010 a top quark factory started its operation. It is now possible to measure top quark properties simultaneously at four different experiments, namely ATLAS and CMS at LHC and CDF and D0 at Tevatron. Having collected thousands of top quarks each, several top quark properties have been measured precisely, while others are being measured for the first time. In this article, recent measurements of top quark properties from ATLAS, CDF, CMS and D0 are presented, using up to 5.4 fb{sup -1} of integrated luminosity at the Tevatron and 1.1 fb{sup -1} at the LHC. In particular, measurements of the top quark mass, mass difference, foward backward charge asymmetry, t{bar t} spin correlations, the ratio of branching fractions, W helicity, anomalous couplings, color flow and the search for flavor changing neutral currents are discussed.

Peters, Yvonne

2011-12-01

110

Using charge asymmetries to measure single-top-quark production at the CERN LHC  

SciTech Connect

Electroweak production of single top quarks is still an unverified prediction of the standard model, potentially sensitive to new physics. Two of the single-top-quark production channels have significant charge asymmetries at the LHC, while the much larger background from tt is nearly charge symmetric. This can be used to reduce systematic uncertainties and make precision measurements of single-top-quark production.

Bowen, Matthew T. [Department of Physics, P.O. Box 351560, University of Washington, Seattle, Washington 98195 (United States)

2006-05-01

111

Top quark mass measurements  

SciTech Connect

The top quark, with its extraordinarily large mass (nearly that of a gold atom), plays a significant role in the phenomenology of EWSB in the Standard Model. In particular, the top quark mass when combined with the W mass constrains the mass of the as yet unobserved Higgs boson. Thus, a precise determination of the mass of the top quark is a principal goal of the CDF and D0 experiments. With the data collected thus far in Runs 1 and 2 of the Tevatron, CDF and D0 have measured the top quark mass in both the lepton+jets and dilepton decay channels using a variety of complementary experimental techniques. The author presents an overview of the most recent of the measurements.

Hill, Christopher S.; /UC, Santa Barbara

2004-12-01

112

Top physics: CDF results  

SciTech Connect

The top quark plays an important role in the grand scheme of particle physics, and is also interesting on its own merits. We present recent results from CDF on top-quark physics based on 100-200 pb{sup -1} of p{bar p} collision data. We have measured the t{bar t} cross section in different decay modes using several different techniques, and are beginning our studies of top-quark properties. New analyses for this conference include a measurement of {sigma}{sub t{bar t}} in the lepton-plus-jets channel using a neural net to distinguish signal and background events, and measurements of top-quark branching fractions.

K. Bloom

2004-06-23

113

Top quark physics: Overview  

SciTech Connect

In this presentation I will primarily focus on top quark physics but I will include a discussion of the W-boson mass and the possibility of discovering a light Higgs boson via associated production at the Tevatron.

Parke, S.

1998-01-01

114

Noncommutative Symmetric Functions Vi: Free Quasi-Symmetric Functions and Related Algebras  

Microsoft Academic Search

This article is devoted to the study of several algebras which are related to symmetric functions, and which admit linear bases labelled by various combinatorial objects: per- mutations (free quasi-symmetric functions), standard Young tableaux (free symmetric functions) and packed integer matrices (matrix quasi-symmetric functions). Free quasi- symmetric functions provide a kind of noncommutative Frobenius characteristic for a certain category of

Gérard Duchamp; Florent Hivert; Jean-yves Thibon

2002-01-01

115

Top spin and experimental tests  

SciTech Connect

The authors examine pair mass dependence near threshold as a means to measure the spin of the top quark in hadron collisions, and they discuss the possibility that a top quark signal could be hidden among the top events.

Berger, E. L.; Tait, T. M. P.

2000-03-21

116

Symmetrizations for clustering directed graphs  

Microsoft Academic Search

Graph clustering has generally concerned itself with clustering undirected graphs; however the graphs from a number of important domains are essentially directed, e.g. networks of web pages, research papers and Twitter users. This paper investigates various ways of symmetrizing a directed graph into an undirected graph so that previous work on clustering undirected graphs may subsequently be leveraged. Recent work

Venu Satuluri; Srinivasan Parthasarathy

2011-01-01

117

Symmetrized Bregman Divergences and Metrics  

Microsoft Academic Search

While JB divergences are non-negative, symmetric, and zero only when x = y, they are not squares of metrics in general. We show that square root of JB divergences give a metric only when the associated convex functions have a certain conditional positive definiteness (CPD) structure. Using results from harmonic analysis of infinitely divisible distributions (6), we show that the

Arindam Banerjee; Daniel Boley; Sreangsu Acharyya

118

DEC OSF\\/1 Symmetric Multiprocessing  

Microsoft Academic Search

The primary goal for an operating system in a symmetric multiprocessing (SMP) implementation is to convert the additional computing power provided to the system, as processors are added, into improved system performance without compromising system quality. The DEC OSF\\/1 version 3.0 operating system uses a number of techniques to achieve this goal. The techniques include algorithmic enhancements to improve parallelism

Jeffrey M. Denham; Paula Long; James A. Woodward

119

Simulation of Symmetrical Induction Machinery  

Microsoft Academic Search

The effectiveness of an analog computer in studying the performance of induction machinery is demonstrated with computer results which show the dynamic behavior of 2-phase and 3-phase machines during balanced and unbalanced operation. The computer simulation for these various modes of operation is conveniently obtained from the equations which describe the symmetrical induction machine in an arbitrary reference frame. Of

P. C. Krause; C. H. Thomas

1965-01-01

120

On Symmetrical Multilevel Diversity Coding  

Microsoft Academic Search

Symmetrical multilevel diversity coding with independent data streams has been studied by Roche et al. (1992), and the admissible coding rate region was determined for the case of three levels. In particular, it was shown that coding by superposition is optimal, which means that optimality can be achieved by very simple coding. However, it is very difficult to generalize their

Raymond W. Yeung; Zhen Zhang

1999-01-01

121

Spreads and the symmetric topos  

Microsoft Academic Search

We introduce a new intrinsic notion of spread for toposes and geometric morphisms, and use it to give a “topological” characterization of Lawvere distributions on a topos. In the process, we relate spreads to zero-dimensional locales, and establish two new pure\\/spread factorizations for geometric morphisms. Our results are then applied to the study of the symmetric topos as a generalized

M. Bunge; J. Funk

1996-01-01

122

Molecule nanoweaver  

DOEpatents

A method, apparatus, and system for constructing uniform macroscopic films with tailored geometric assemblies of molecules on the nanometer scale. The method, apparatus, and system include providing starting molecules of selected character, applying one or more force fields to the molecules to cause them to order and condense with NMR spectra and images being used to monitor progress in creating the desired geometrical assembly and functionality of molecules that comprise the films.

Gerald, II; Rex E. (Brookfield, IL); Klingler, Robert J. (Glenview, IL); Rathke, Jerome W. (Homer Glen, IL); Diaz, Rocio (Chicago, IL); Vukovic, Lela (Westchester, IL)

2009-03-10

123

Top-ophilia  

SciTech Connect

Almost from the moment in June 1977 when the discovery of the Upsilon resonance revealed the existence of what we now call the bottom quark, physicists began searching for its partner. Through the years, as we established the electric charge and weak isospin of the b-quark, and detected the virtual influence of its mate, it became clear that the top quark must exist. Exactly at what mass, we couldn't say, but we knew just how top events would look. We also knew that top events would be rare--if the Tevatron could make them at all--and that picking out the events would pose a real challenge for the experimenters and their detectors.

Quigg, Chris; /Fermilab

2008-01-01

124

Kernel mucking in top  

SciTech Connect

For many years, the popular program top has aided system administrations in examination of process resource usage on their machines. Yet few are familiar with the techniques involved in obtaining this information. Most of what is displayed by top is available only in the dark recesses of kernel memory. Extracting this information requires familiarity not only with how bytes are read from the kernel, but also what data needs to be read. The wide variety of systems and variants of the Unix operating system in today`s marketplace makes writing such a program very challenging. This paper explores the tremendous diversity in kernel information across the many platforms and the solutions employed by top to achieve and maintain ease of portability in the presence of such divergent systems.

LeFebvre, W.

1994-08-01

125

Tight focusing of axially symmetric polarized vortex beams  

NASA Astrophysics Data System (ADS)

Tight focusing of axially symmetric polarized vortex beams is studied numerically based on vector diffraction theory. The mathematical expressions for the focused fields are derived. Simulation results show that the focused fields and phase distributions at focus are largely influenced by both the polarization order and topological charge of the incident beams. Moreover, focal spots with flat-topped or tightly-focused patterns can be flexibly achieved by carefully choosing the polarization order and the topological charge, which confirms the potential of such beams in wide applications, such as optical tweezers, laser printing, lithography, and material processing.

Zhou, Zhe-Hai; Guo, Yang-Kuan; Zhu, Lian-Qing

2014-04-01

126

Schwarz Methods: To Symmetrize or not to Symmetrize  

NASA Technical Reports Server (NTRS)

A preconditioning theory for Schwarz methods is presented. The theory establishes sufficient conditions for multiplicative and additive Schwarz algorithms to yield self-adjoint positive definite preconditioners. It allows for the analysis and use of non-variational and non-convergent linear methods as preconditioners for conjugate gradient methods, and it is applied to domain decomposition and multigrid. This paper illustrates why symmetrizing may be a bad idea for linear methods. Numerical examples are presented for a test problem.

Holst, Michael; Vandewalle, Stefan

1996-01-01

127

Observations of large biologically important interstellar and cometary molecules  

NASA Astrophysics Data System (ADS)

There has been much interest in recent years in astronomical searches for large biologically-important molecules which possess known millimeter wavelength transitions. Biologically-important species include amino acids, possible precursors to amino acids, and other biologically interesting molecules. This thesis continued the search for large biomolecules towards hot molecular cores (HMCs) associated with ultracompact (HC) HII regions and comets. First, we followed up the detection of acetic acid (CH3COOH) towards Sgr B2(N-LMH) by performing a survey of transitions with large line strengths toward several hot core regions. There has been great interest in searching a variety of star forming regions for interstellar acetic acid because it shares common structural elements with glycine (NH2CH2 COOH), the simplest amino acid, and because it is an isomer to both methyl formate (HCOOCH3) and glycolaldehyde (CH2OHCHO). In our survey we detected two new sources of acetic acid and placed constraints on the detectability of acetic acid elsewhere with current generation radio telescopes. Second, in order to study the physical conditions that lead to the formation of large biomolecules toward HMCs, we observed the hot core regions W51 e1 and e2 using the symmetric top species methyl cyanide (CH3CN). Symmetric tops have properties that make them ideal probes of hot molecular cores. Thus, we obtained better measurements of the physical conditions present in these regions and a better understanding of the chemistry that forms large molecular species. Third, using multiply degenerate transitions in both the 3 mm and 1 mm wavelength regions, we conducted the most extensive survey for the elusive biomolecule urea [(NH2)2CO] toward the high mass hot molecular core sources, Sgr B2(N-LMH) and W51 e2. As a result, our spectral line data support the first detection of interstellar urea toward Sgr B2(N-LMH). Finally, we discuss the observational results of an extensive survey for biologically interesting molecules toward Comet Hale-Bopp (1995 O1). To date, no large biomolecule has ever been reported toward a comet with an array. The importance of detecting large biomolecules in comets is that in doing so will tie together the chemistry in HMCs with cometary chemistry.

Remijan, Anthony John

128

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

National Technical Information Service (NTIS)

Evidence of circular dichroism has been observed in the spectral properties of a gas of left-right symmetric molecules. This dichroism comes about as the result of collisions of the symmetric molecules with left-right asymmetric molecules introduced as a ...

G. J.S. Bakos

2000-01-01

129

Top quark physics: Future measurements  

SciTech Connect

The authors discuss the study of the top quark at future experiments and machines. Top`s large mass makes it a unique probe of physics at the natural electroweak scale. They emphasize measurements of the top quark`s mass, width, and couplings, as well as searches for rare or nonstandard decays, and discuss the complementary roles played by hadron and lepton colliders.

Frey, R. [Univ. of Oregon, Eugene, OR (United States). Dept. of Physics; Vejcik, S. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Physics; Berger, E.L. [Argonne National Lab., IL (United States)] [and others

1997-04-04

130

Nonlocal \\cal{PT} -symmetric potentials  

NASA Astrophysics Data System (ADS)

The factorization approach for complex Hamiltonians has been used to obtain the exactly solvable nonlocal variant of \\cal {PT} -symmetric local potentials. The formalism is used to obtain exact eigenvalues and eigenfunctions of the nonlocal \\cal {PT} -symmetric Scarf potential.

Roy, B.; Roychoudhury, R.

2007-07-01

131

Observational Tests of Baryon Symmetric Cosmology.  

National Technical Information Service (NTIS)

Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiat...

F. W. Stecker

1982-01-01

132

Top Quark Physics  

Microsoft Academic Search

In this contribution I review the physics of top quarks at a future Linear Collider. Main emphasis is put on the process e+ e- --> t bar t close to threshold. Different physical observables, their sensitivity to the basic parameters and their theoretical prediction are discussed. Recent higher order calculations are shown to have a considerable impact on a precise

Thomas Teubner

1999-01-01

133

The Top Ten Lists.  

ERIC Educational Resources Information Center

Presents several tables of "top ten" data related to educational facilities, including districts with the largest enrollments, states with the most teachers, number of school buildings in large cities, expenditures for public K-12 schools, states with the highest and lowest per-pupil expenditures, and states with the highest average teacher…

American School & University, 2003

2003-01-01

134

Bregman sided and symmetrized centroids  

Microsoft Academic Search

We generalize the notions of centroids and barycenters to the broad class of information-theoretic distortion measures called Bregman divergences. Because Bregman divergences are typically asymmetric, we consider both the left-sided and right-sided centroids and the symmetrized centroids, and prove that all three are unique. We give closed-form solutions for the sided centroids that are generalized means, and design a provably

Frank Nielsen; Richard Nock

2008-01-01

135

Symmetric informationally complete quantum measurements  

Microsoft Academic Search

We consider the existence in arbitrary finite dimensions d of a positive operator valued measure (POVM) comprised of d2 rank-one operators all of whose operator inner products are equal. Such a set is called a “symmetric, informationally complete” POVM (SIC–POVM) and is equivalent to a set of d2 equiangular lines in Cd. SIC–POVMs are relevant for quantum state tomography, quantum

Joseph M. Renes; Robin Blume-Kohout; A. J. Scott; Carlton M. Caves

2004-01-01

136

Top Quark Physics at CDF  

NASA Astrophysics Data System (ADS)

The existence of the top quark, discovered by CDF and DØ in 1995, has been re-established in the burgeoning dataset being collected in Run 2 of the Tevatron at Fermilab. Results from CDF on the top quark production cross section and top quark mass are consistent with the Standard Model expectations. The well-characterized top data samples will make it possible in the future to probe further for new physics in the top quark sector.

Nielsen, Jason

2005-04-01

137

Spherically symmetric quantum geometry: Hamiltonian constraint  

Microsoft Academic Search

Variables adapted to the quantum dynamics of spherically symmetric models are introduced, which further simplify the spherically symmetric volume operator and allow an explicit computation of all matrix elements of the Euclidean and Lorentzian Hamiltonian constraints. The construction fits completely into the general scheme available in loop quantum gravity for the quantization of the full theory as well as symmetric

Martin Bojowald; Rafal Swiderski

2006-01-01

138

A Hopf laboratory for symmetric functions  

Microsoft Academic Search

An analysis of symmetric function theory is given from the perspective of the underlying Hopf and bi-algebraic structures. These are presented explicitly in terms of standard symmetric function operations. Particular attention is focused on Laplace pairing, Sweedler cohomology for 1- and 2-cochains and twisted products (Rota cliffordizations) induced by branching operators in the symmetric function context. The latter are shown

Bertfried Fauser; P. D. Jarvis

2004-01-01

139

RIEMANNIAN AND FINSLER STRUCTURES OF SYMMETRIC CONES  

Microsoft Academic Search

The theory of domains of positivity or symmetric cones is closely tied to that of Euclidean Jordan algebras and plays an important role in various branches of analysis and geometry. The goal of this paper is to provide a self-contained description of Riemannian and Finsler geometries of symmetric cones and their applications. 1. Symmetric cones and Euclidean Jordan algebras An

YONGDO LIM

140

Symmetric functions and P-recursiveness  

Microsoft Academic Search

Many enumeration problems, such as that of counting nonnegative integer matrices with given row and column sums, have solutions which can be expressed as coefficients of symmetric functions. We show here how useful formulas can be obtained from these symmetric function generating functions. In some cases, the symmetric functions yield reasonably simple explicit formulas or generating functions for the coefficients.

Ira M. Gessel

1990-01-01

141

Single Molecules  

NSDL National Science Digital Library

A new molecular science journal, Single Molecules, from Wiley Interscience, "will provide researchers with a broad overview of current methods and techniques, recent applications and shortcomings of present techniques in the field of single molecules." With temporary free access, the journal's latest issue contains a few full-text articles, with more articles being regularly added. This journal is currently calling for papers.

142

The leaking liner top  

SciTech Connect

An imperfect cement seal at the top of a liner will allow gas from below to leak into the drilling annulus above a production liner. Conversely, with a pressure differential toward the formation, fluid can be lost from the annuli during drilling or during stimulation for production. Since perfect liner cementation is an elusive target, this paper will discuss briefly the cause and effect of the leaking liner top and list the options available for solving the associated problems. This paper was written to address the problems encountered in the drilling and completion of deep high pressure gas wells; however, much of the information can be applied to wells drilled and completed under less rigorous conditions.

Agnew, J.W.; Klein, R.S.

1984-04-01

143

Modeling Symmetric Macromolecular Structures in Rosetta3  

PubMed Central

Symmetric protein assemblies play important roles in many biochemical processes. However, the large size of such systems is challenging for traditional structure modeling methods. This paper describes the implementation of a general framework for modeling arbitrary symmetric systems in Rosetta3. We describe the various types of symmetries relevant to the study of protein structure that may be modeled using Rosetta's symmetric framework. We then describe how this symmetric framework is efficiently implemented within Rosetta, which restricts the conformational search space by sampling only symmetric degrees of freedom, and explicitly simulates only a subset of the interacting monomers. Finally, we describe structure prediction and design applications that utilize the Rosetta3 symmetric modeling capabilities, and provide a guide to running simulations on symmetric systems.

DiMaio, Frank; Leaver-Fay, Andrew; Bradley, Phil; Baker, David; Andre, Ingemar

2011-01-01

144

Cloud top entrainment instability and cloud top distributions  

NASA Technical Reports Server (NTRS)

Classical cloud-top entrainment instability condition formulation is discussed. A saturation point diagram is used to investigate the details of mixing in cases where the cloud-top entrainment instability criterion is satisfied.

Boers, Reinout; Spinhirne, James D.

1990-01-01

145

An optimized TOPS+ comparison method for enhanced TOPS models  

PubMed Central

Background Although methods based on highly abstract descriptions of protein structures, such as VAST and TOPS, can perform very fast protein structure comparison, the results can lack a high degree of biological significance. Previously we have discussed the basic mechanisms of our novel method for structure comparison based on our TOPS+ model (Topological descriptions of Protein Structures Enhanced with Ligand Information). In this paper we show how these results can be significantly improved using parameter optimization, and we call the resulting optimised TOPS+ method as advanced TOPS+ comparison method i.e. advTOPS+. Results We have developed a TOPS+ string model as an improvement to the TOPS [1-3] graph model by considering loops as secondary structure elements (SSEs) in addition to helices and strands, representing ligands as first class objects, and describing interactions between SSEs, and SSEs and ligands, by incoming and outgoing arcs, annotating SSEs with the interaction direction and type. Benchmarking results of an all-against-all pairwise comparison using a large dataset of 2,620 non-redundant structures from the PDB40 dataset [4] demonstrate the biological significance, in terms of SCOP classification at the superfamily level, of our TOPS+ comparison method. Conclusions Our advanced TOPS+ comparison shows better performance on the PDB40 dataset [4] compared to our basic TOPS+ method, giving 90% accuracy for SCOP alpha+beta; a 6% increase in accuracy compared to the TOPS and basic TOPS+ methods. It also outperforms the TOPS, basic TOPS+ and SSAP comparison methods on the Chew-Kedem dataset [5], achieving 98% accuracy. Software Availability The TOPS+ comparison server is available at http://balabio.dcs.gla.ac.uk/mallika/WebTOPS/.

2010-01-01

146

PT-symmetric Talbot effects.  

PubMed

We show that complex PT-symmetric photonic lattices can lead to a new class of self-imaging Talbot effects. For this to occur, we find that the input field pattern has to respect specific periodicities dictated by the symmetries of the system. While at the spontaneous PT-symmetry breaking point the image revivals occur at Talbot lengths governed by the characteristics of the passive lattice, at the exact phase it depends on the gain and loss parameter, thus allowing one to control the imaging process. PMID:22861852

Ramezani, Hamidreza; Christodoulides, D N; Kovanis, V; Vitebskiy, I; Kottos, Tsampikos

2012-07-20

147

Integrability properties of symmetric-space fields reduced from axially symmetric Einstein and Yang-Mills equations  

SciTech Connect

A gauge-covariant symmetric-space formulation and integrability properties are given for symmetric-space fields reduced from the stationary axially symmetric Einstein equation and static axially symmetric self-dual Yang-Mills equations.

Chau, L.; Chou, K.; Hou, B.; Song, X.

1986-09-15

148

Interstellar molecules  

NASA Astrophysics Data System (ADS)

Some 70 different molecular species have so far been detected variously in diffuse interstellar clouds, dense interstellar clouds, and circumstellar shells. Only simple (diatomic and triatomic) species exist in diffuse clouds because of the penetration of destructive UV radiations, whereas more complex (polyatomic) molecules survive in dense clouds as a result of the shielding against this UV radiation provided by dust grains. A current list of interstellar molecules is given together with a few other molecular species that have so far been detected only in circumstellar shells. Also listed are those interstellar species that contain rare isotopes of several elements. The gas phase ion chemistry is outlined via which the observed molecules are synthesized, and the process by which enrichment of the rare isotopes occurs in some interstellar molecules is described.

Smith, D.

1987-09-01

149

Mobius Molecules  

ERIC Educational Resources Information Center

Discusses formation of chemical molecules via Mobius strip intermediates, and concludes that many special physics-chemical properties of the fully closed circular form (1) of polyoma DNA are explainable by this topological feature. (CC)

Eckert, J. M.

1973-01-01

150

Modeling Molecules  

NASA Technical Reports Server (NTRS)

The molecule modeling method known as Multibody Order (N) Dynamics, or MBO(N)D, was developed by Moldyn, Inc. at Goddard Space Flight Center through funding provided by the SBIR program. The software can model the dynamics of molecules through technology which stimulates low-frequency molecular motions and properties, such as movements among a molecule's constituent parts. With MBO(N)D, a molecule is substructured into a set of interconnected rigid and flexible bodies. These bodies replace the computation burden of mapping individual atoms. Moldyn's technology cuts computation time while increasing accuracy. The MBO(N)D technology is available as Insight II 97.0 from Molecular Simulations, Inc. Currently the technology is used to account for forces on spacecraft parts and to perform molecular analyses for pharmaceutical purposes. It permits the solution of molecular dynamics problems on a moderate workstation, as opposed to on a supercomputer.

2000-01-01

151

Top physics results at CDF  

SciTech Connect

The most recent results on top quark physics at CDF are reported. Measurements of cross-section and mass are presented, and the status of single top quark production searches are discussed. The results obtained from probing various top quark properties are also presented.

Vickey, Trevor; /Illinois U., Urbana

2005-05-01

152

Top quark physics: Future Measurements  

SciTech Connect

We discuss the study of the top quark at future experiments and machines. Top's large mass makes it a unique probe of physics at the natural electroweak scale. We emphasize measurements of the top quark's mass, width, and couplings, as well as searches for rare or nonstandard decays, and discuss the complementary roles played by hadron and lepton colliders.

Frey, Raymond; Gerdes, David; Jaros, John; Vejcik, Steve; Berger, Edmond L.; Chivukula, R. Sekhar; Cuypers, Frank; Drell, Persis S.; Fero, Michael; Hadley, Nicholas; Han, Tao; Heinson, Ann P.; Knuteson, Bruce; Larios, Francisco; Miettinen, Hannu; Orr, Lynne H.; Peskin, Michael E.; Rizzo, Thomas; Sarid, Uri; Schmidt, Carl; Stelzer, Tim; Sullivan, Zack

1996-12-31

153

Top 50 Financial Websites  

NSDL National Science Digital Library

In order to help their users navigate around the World Wide Web, Money.com has ranked the top 50 financial sites found on the Internet. A wide list of types of sites is posted in a column on the left side of the screen, including the broad categories of Portals, Investing, and Saving and Spending. Two or three of the best sites are pithily described, and visitors are encouraged to vote for their favorite financial sites. This superlative list will help users quickly find the best financial sites for their needs.

154

Top quark mass measurements  

SciTech Connect

Preliminary results on the measurement of the top quark mass at the Tevatron Collider are presented. In the dilepton decay channel, the CDF Collaboration measures m{sub t} = 175.0{sub -16.9}{sup +17.4}(stat.){+-}8.4(syst.) GeV/c{sup 2}, using a sample of {approx} 126 pb{sup -1} of proton-antiproton collision data at {radical}s = 1.96 TeV (Run II). In the lepton plus jets channel, the CDF Collaboration measures 177.5{sub -9.4}{sup +12.7}(stat.) {+-} 7.1(syst.) GeV/c{sup 2}, using a sample of {approx} 102 pb{sup -1} at {radical}s = 1.96 TeV. The D0 Collaboration has newly applied a likelihood technique to improve the analysis of {approx} 125 pb{sup -1} of proton-antiproton collisions at {radical}s = 1.8 TeV (Run I), with the result: m{sub t} = 180.1 {+-} 3.6(stat.) {+-}3.9(syst.) GeV/c{sup 2}. The latter is combined with all the measurements based on the data collected in Run I to yield the most recent and comprehensive experimental determination of the top quark mass: m{sub t} = 178.0 {+-} 2.7(stat.) {+-} 3.3(syst.) GeV/c{sup 2}.

L. Cerrito

2004-07-16

155

Top quark physics at CDF  

SciTech Connect

We present the recent results of top-quark physics using up to 6 fb{sup -1} of p{bar p} collisions analyzed by the CDF collaboration. The large number of top quark events analyzed, of the order of several thousands, allows stringent checks of the standard model predictions. Also, the top quark is widely believed to be a window to new physics. We present the latest measurements of top quark intrinsic properties as well as direct searches for new physics in the top sector.

Potamianos, Karolos

2011-12-01

156

The search for the top quark  

SciTech Connect

This paper discusses the following topics: top search in the near future, general remarks, top search at HERA, searching for the top quarks at the Z/sup 0/ machines, finding the top at Lep II, top search in UA2, top search in UA1, and top search at CDF. 58 refs., 38 figs.

Barbaro-Galtieri, A.

1989-03-01

157

Symmetrical mixtures in external fields.  

PubMed

We have studied the behavior of symmetrical binary mixtures of Lennard-Jones particles in contact with strongly adsorbing walls using Monte Carlo simulation methods in the grand canonical and semi-grand canonical ensembles. Two types of the surface potential have been applied. The first depends on the distance from the surface only, while the second involves periodic modulations in the directions parallel to the wall. In the latter case, it has been assumed that the solid substrate is a fcc crystal with the surface being the (100) face. We have considered the systems in which the surface potential is strong enough to induce the layer-by-layer adsorption at low temperatures and discussed the interplay between the demixing transition and the structure of thin films for several systems characterized by different parameters describing the interactions in the system. PMID:23822318

Materniak, S; Patrykiejew, A

2013-07-01

158

Top-Higgs and top-pion phenomenology in the top triangle moose model  

SciTech Connect

We discuss the deconstructed version of a topcolor-assisted technicolor model wherein the mechanism of top quark mass generation is separated from the rest of electroweak symmetry breaking. The minimal deconstructed version of this scenario is a ''triangle moose'' model, where the top quark gets its mass from coupling to a top-Higgs field, while the gauge boson masses are generated from a Higgsless sector. The spectrum of the model includes scalar (top-Higgs) and pseudoscalar (top-pion) states. In this paper, we study the properties of these particles, discuss their production mechanisms and decay modes, and suggest how best to search for them at the LHC.

Chivukula, R. Sekhar; Simmons, Elizabeth H.; Coleppa, Baradhwaj; Logan, Heather E.; Martin, Adam [Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States); Ottawa-Carleton Institute for Physics, Carleton University, Ottawa, Ontario K1S 5B6 (Canada); Theoretical Physics Department, Fermilab, Batavia, Illinois 60510 (United States)

2011-03-01

159

Biological Molecules  

NSDL National Science Digital Library

Paul Anderson describes the four major biological molecules found in living things. He begins with a brief discussion of polymerization. Dehydration synthesis is used to connect monomers into polymers and hydrolysis breaks them down again. The major characteristics of nucleic acids are described as well as there directionality from 3' to 5' end.

Anderson, Paul

2013-03-12

160

On H?-control for symmetric systems  

Microsoft Academic Search

Results regarding H? control for symmetric systems are introduced. It is shown that in order to find the compensator, only one nonlinear matrix equation has to be solved, instead of two Riccati equations as in the general case. A numerically robust algorithm for the solution of the equation introduced is presented. The compensator obtained is also shown to be symmetric.

L. Fortuna; G. Muscato; G. Nunnari

1992-01-01

161

Continuity and Separation in Symmetric Topologies  

ERIC Educational Resources Information Center

In this note, it is shown that in a symmetric topological space, the pairs of sets separated by the topology determine the topology itself. It is then shown that when the codomain is symmetric, functions which separate only those pairs of sets that are already separated are continuous, generalizing a result found by M. Lynch.

Harris, J.; Lynch, M.

2007-01-01

162

Symmetric drawings of triconnected planar graphs  

Microsoft Academic Search

Symmetry is one of the most important aesthetic criteria in graph drawing because it reveals structure in the graph. To draw graphs symmetrically, we need two steps. The first step is to find appropriate automorphisms. The second step is to draw the graph to display the automorphisms. Our aim in this paper is to construct maximally symmetric straight-line drawings of

Seok-Hee Hong; Brendan D. McKay; Peter Eades

2002-01-01

163

On the Symmetric Space ?-MODEL Kinematics  

NASA Astrophysics Data System (ADS)

The solvable Lie algebra parametrization of the symmetric spaces is discussed. Based on the solvable Lie algebra gauge two equivalent formulations of the symmetric space sigma model are studied. Their correspondence is established by inspecting the normalization conditions and deriving the field transformation laws.

Yilmaz, Nejat T.

164

Angular Motion of Spinning Almost Symmetric Missiles.  

National Technical Information Service (NTIS)

An almost symmetric missile is a missile whose zero-spin pitch and yaw frequencies are 'nearly' equal. The angular motion of a spinning almost symmetric missile can be described by five rotating modal vectors. Two of these vectors vanish when the frequenc...

C. H. Murphy

1978-01-01

165

Symmetric Distributed Source Coding using LDPC Code  

Microsoft Academic Search

Distributed source coding is a promising enabling technology for sensor network applications. Symmetric distributed source coding can achieve the entire Slepian-Wolf rate region and offer sensor network applications a wide range of options to compress and transmit data. In this paper, we design a new symmetric distributed coding scheme that realize the benefits of both simplified code construction and bit

Baochun Bai; Yang Yang; Pierre Boulanger; Janelle J. Harms

2008-01-01

166

Top physics results from CDF  

SciTech Connect

The top quark is by far the most massive fundamental particle observed so far, and the study of its properties is interesting for several reasons ranging from its possible special role in electroweak symmetry breaking to its sensitivity to physics beyond the Standard Model. They present recent top physics results from CDF based on 160-320 pb{sup -1} of p{bar p} collision data at {radical}s = 1.96 TeV. The t{bar t} cross section and the top mass have been measured in different decay channels and using different methods. they have searched for evidence of single top production, setting upper limits on its production rate. Other results shown in this conference include studies of the polarization of W bosons from top decays, a search for charged Higgs decaying from top, and a search for additional heavy t' quarks.

Gomez, Gervasio; /Cantabria Inst. of Phys.

2005-05-01

167

PT-symmetric laser absorber  

NASA Astrophysics Data System (ADS)

In a recent work, Y. D. Chong [Phys. Rev. Lett.0031-900710.1103/PhysRevLett.105.053901 105, 053901 (2010)] proposed the idea of a coherent perfect absorber (CPA) as the time-reversed counterpart of a laser, in which a purely incoming radiation pattern is completely absorbed by a lossy medium. The optical medium that realizes CPA is obtained by reversing the gain with absorption, and thus it generally differs from the lasing medium. Here it is shown that a laser with an optical medium that satisfies the parity-time (PT) symmetry condition ?(-r)=?*(r) for the dielectric constant behaves simultaneously as a laser oscillator (i.e., it can emit outgoing coherent waves) and as a CPA (i.e., it can fully absorb incoming coherent waves with appropriate amplitudes and phases). Such a device can thus be referred to as a PT-symmetric CPA laser. The general amplification or absorption features of the PT CPA laser below lasing threshold driven by two fields are determined.

Longhi, Stefano

2010-09-01

168

A Thermodynamic Model of Phosphorus Distribution Ratio between CaO-SiO2-MgO-FeO-Fe2O3-MnO-Al2O3-P2O5 Slags and Molten Steel during a Top-Bottom Combined Blown Converter Steelmaking Process Based on the Ion and Molecule Coexistence Theory  

NASA Astrophysics Data System (ADS)

A thermodynamic model for calculating the phosphorus distribution ratio between top-bottom combined blown converter steelmaking slags and molten steel has been developed by coupling with a developed thermodynamic model for calculating mass action concentrations of structural units in the slags, i.e., CaO-SiO2-MgO-FeO-Fe2O3-MnO-Al2O3-P2O5 slags, based on the ion and molecule coexistence theory (IMCT). Not only the total phosphorus distribution ratio but also the respective phosphorus distribution ratio among four basic oxides as components, i.e., CaO, MgO, FeO, and MnO, in the slags and molten steel can be predicted theoretically by the developed IMCT phosphorus distribution ratio prediction model after knowing the oxygen activity of molten steel at the slag-metal interface or the Fe t O activity in the slags and the related mass action concentrations of structural units or ion couples in the slags. The calculated mass action concentrations of structural units or ion couples in the slags equilibrated or reacted with molten steel show that the calculated equilibrium mole numbers or mass action concentrations of structural units or ion couples, rather than the mass percentage of components, can present the reaction ability of the components in the slags. The predicted total phosphorus distribution ratio by the developed IMCT model shows a reliable agreement with the measured phosphorus distribution ratio by using the calculated mass action concentrations of iron oxides as presentation of slag oxidation ability. Meanwhile, the developed thermodynamic model for calculating the phosphorus distribution ratio can determine quantitatively the respective dephosphorization contribution ratio of Fe t O, CaO + Fe t O, MgO + Fe t O, and MnO + Fe t O in the slags. A significant difference of dephosphorization ability among Fe t O, CaO + Fe t O, MgO + Fe t O, and MnO + Fe t O has been found as approximately 0.0 pct, 99.996 pct, 0.0 pct, and 0.0 pct during a combined blown converter steelmaking process, respectively. There is a great gradient of oxygen activity of molten steel at the slag-metal interface and in a metal bath when carbon content in a metal bath is larger than 0.036 pct. The phosphorus in molten steel beneath the slag-metal interface can be extracted effectively by the comprehensive effect of CaO and Fe t O in slags to form 3CaO·P2O5 and 4CaO·P2O5 until the carbon content is less than 0.036 pct during a top-bottom combined blown steelmaking process.

Yang, Xue-Min; Duan, Jian-Ping; Shi, Cheng-Bin; Zhang, Meng; Zhang, Yong-Liang; Wang, Jian-Chang

2011-08-01

169

Top-Down Mass Spectrometry: Recent Developments, Applications and Perspectives  

PubMed Central

Top-down mass spectrometry is an emerging approach for the analysis of intact proteins. The term was coined as a contrast with the better-established, bottom-up strategy for analysis of peptide fragments derived from digestion, either enzymatically or chemically, of intact proteins. Although the term top-down originates from proteomics, it can also be applied to mass spectrometric analysis of intact large biomolecules that are constituents of protein assemblies or complexes. Traditionally, mass spectrometry has usually started with intact molecules, and in this regard, top-down approaches reflect the spirit of mass spectrometry. This article provides an overview of the methodologies in top-down mass spectrometry and then reviews applications covering protein posttranslational modifications, protein biophysics, DNAs/RNAs, and protein assemblies. Finally, challenges and future directions are discussed.

Cui, Weidong; Rohrs, Henry W.; Gross, Michael L.

2012-01-01

170

Nonresonant Absorption in Symmetric-Top Gases: Dependence of Relaxation Frequency on Temperature  

Microsoft Academic Search

The nonresonant absorption spectra of CHF3, CH3F, and CClF3 were obtained in the gaseous state at various temperatures in the range 230° to 360°K. In all cases the maximum value of the dielectric loss per unit pressure varies as T—2, in accordance with the Debye equation. The variation of relaxation frequency (line width) with pressure and temperature is represented by

A. A. Maryott; A. Estin; G. Birnbaum

1960-01-01

171

Polarized charginos (and top quarks) in scalar top quark decays  

NASA Astrophysics Data System (ADS)

Current searches for direct production of scalar top quarks, or stops, in supersymmetry focus on their decays into bW+?˜0 by way of t?˜0 and b?˜+. While the polarization of the top quark depends on the stop mixing, the chargino turns out to be fully polarized when the bottom Yukawa coupling can be neglected relative to the top Yukawa coupling. We compute the energy and angular spectra of the charged lepton in the chargino channel, which could serve as the spin analyzer of the chargino. In addition, we demonstrate the top polarization could have a significant impact on the selection efficiencies in direct stop samples at the LHC, while the effect from the chargino polarization is less pronounced. Two observables in the laboratory frame, the opening angle between the charged lepton and the b quark and the energy of the b quark, are also proposed to optimize searches in the chargino channel versus the top channel.

Low, Ian

2013-11-01

172

Moving Molecules!  

NSDL National Science Digital Library

In this activity about molecular diffusion (located on page 2 of the PDF), learners will make predictions and move molecules of iodine through a seemingly solid plastic sandwich bag. The process of diffusion will be visually indicated by a color change when the iodine reacts with starch inside the bag. Information in the resource explains how this activity relates to nanoparticles and research. Related to linked video, DragonflyTV Nano: Nanosilver.

Twin Cities Public Television, Inc.

2008-01-01

173

Symmetric Monotone Venn Diagrams with Seven Curves  

NASA Astrophysics Data System (ADS)

An n-Venn diagram consists of n curves drawn in the plane in such a way that each of the 2 n possible intersections of the interiors and exteriors of the curves forms a connected non-empty region. A k-region in a diagram is a region that is in the interior of precisely k curves. A n-Venn diagram is symmetric if it has a point of rotation about which rotations of the plane by 2?/n radians leaves the diagram fixed; it is polar symmetric if it is symmetric and its stereographic projection about the infinite outer face is isomorphic to the projection about the innermost face. A Venn diagram is monotone if every k-region is adjacent to both some (k - 1)-region (if k > 0) and also to some k + 1 region (if k < n). A Venn diagram is simple if at most two curves intersect at any point. We prove that the "Grünbaum" encoding uniquely identifies monotone simple symmetric n-Venn diagrams and describe an algorithm that produces an exhaustive list of all of the monotone simple symmetric n-Venn diagrams. There are exactly 23 simple monotone symmetric 7-Venn diagrams, of which 6 are polar symmetric.

Cao, Tao; Mamakani, Khalegh; Ruskey, Frank

174

Top results from the Tevatron  

SciTech Connect

This paper summarizes the latest measurements of the properties of the top quark as determined by the CDF and D0 collaborations during the first run of the Fermilab Tevatron p{bar p} collider (1992-1996). Prospects for future measurements of the top quark at the upgraded Tevatron collider are also presented.

E. Barberis

2002-01-18

175

The EAS-TOP calorimeter  

NASA Astrophysics Data System (ADS)

The muon-hadron detector of EAS-TOP is a 270 sq m calorimeter constructed inside the air shower array on the top of the underground Gran Sasso Laboratory (Italy). The general layout of the detector and the performances of the active part (streamer and proportional chambers) are presented.

Aglietta, M.; Alessandro, B.; Arneodo, F.; Bergamasco, L.; Campos Fauth, A.; Castagnoli, C.; Castellina, A.; Cattadori, C.; Chiavassa, A.; Cini, G.

1992-10-01

176

Supersymmetric harmonic maps into symmetric spaces  

NASA Astrophysics Data System (ADS)

We study supersymmetric harmonic maps from the point of view of integrable systems. We show that the superharmonic maps from R into a symmetric space are solutions of an integrable system and that we have a Weierstrass-type representation in terms of holomorphic potentials (as well as of meromorphic potentials). At the end of the paper we show that superprimitive maps from R into a 4-symmetric space give us, by restriction to R2, solutions of the second elliptic system associated with the previous 4-symmetric space.

Khemar, Idrisse

2007-07-01

177

Status of the top quark: Top production cross section and top properties  

SciTech Connect

This report describes the latest cross section and property measurements associated with the top quark at the Tevatron Run II. The largest data sample used is 760 pb{sup -1} of integrated luminosity. Due to its large mass, the top quark might be involved in the process of electroweak symmetry breaking, making it a useful probe for signs of new physics.

Boisvert, V.; /Rochester U.

2006-08-01

178

Nonlocality and entanglement for symmetric states  

NASA Astrophysics Data System (ADS)

In this paper, building on some recent progress combined with numerical techniques, we shed some light on how the nonlocality of symmetric states is related to their entanglement properties and on their potential usefulness in quantum information processing. We use semidefinite programming techniques to devise a device-independent classification of three 4-qubit states into two classes inequivalent under local unitaries and permutation of systems. We study nonlocal properties when the number of parties grows large for two important classes of symmetric states: W states and GHZ states, showing that they behave differently under the inequalities we consider. We also discuss the monogamy arising from the nonlocal correlations of symmetric states. We show that although monogamy in a strict sense is not guaranteed for all symmetric states, strict monogamy is achievable for all Dicke states when the number of parties goes to infinity.

Wang, Zizhu; Markham, Damian

2013-01-01

179

Postpartum Peripheral Symmetrical Gangrene: A Case Report  

PubMed Central

Background Symmetrical peripheral gangrene is usually associated with underlying medical problems and it is seldom seen in pregnancy. Sepsis though common in a setting of delivery by unskilled midwife is rarely accompanied by symmetrical gangrene. Case Presentation We report a case of symmetrical peripheral gangrene which occurred in the winter, triggered possibly by sepsis and a single dose of ergot. A high index of suspicion, early diagnosis and intervention with appropriate measures will result in favorable outcome in such cases. Conclusion Although postpartum period is of high risk for sepsis and use of ergot alkaloids is common in labor but occurrence of peripheral symmetrical gangrene is rare. A high index of suspicion for the diagnosis and timely intervention will prevent irreparable damage and loss of limb.

Sharma, Lipi; Mehta, Sumita; Rajaram, Shalini; Aggarwal, Rachna; Gupta, Sanjay; Goel, Neerja

2012-01-01

180

Symmetric Space ?-MODEL Dynamics:. Current Formalism  

NASA Astrophysics Data System (ADS)

After explicitly constructing the symmetric space sigma model Lagrangian in terms of the coset scalars of the solvable Lie algebra gauge in the current formalism, we derive the field equations of the theory.

Yilmaz, Nejat T.

181

PT-Symmetric Quantum Field Theory  

SciTech Connect

In 1998 it was discovered that the requirement that a Hamiltonian be Dirac Hermitian (H = H{sup {dagger}}) can be weakened and generalized to the requirement that a Hamiltonian be PT symmetric ([H,PT] = 0); that is, invariant under combined space reflection and time reversal. Weakening the constraint of Hermiticity allows one to consider new kinds of physically acceptable Hamiltonians and, in effect, it amounts to extending quantum mechanics from the real (Hermitian) domain into the complex domain. Much work has been done on the analysis of various PT-symmetric quantum-mechanical models. However, only very little analysis has been done on PT-symmetric quantum-field-theoretic models. Here, we describe some of what has been done in the context of PT-symmetric quantum field theory and describe some possible fundamental applications.

Bender, Carl M. [Physics Department, Washington University, St. Louis, MO 63130 (United States)

2011-09-22

182

Multiple symmetric lipomatosis: a diagnostic dilemma.  

PubMed

Introduction. Multiple symmetric lipomatosis, or Madelung's disease, is a rare condition which is characterized with large symmetrical accumulation of noncapsulated fat tissue in upper arms, neck, and shoulder areas. The disease etiology is unknown, with the highest incidence in the Mediterranean region. Case Presentation. Here, we present the case of Madelung's disease with symmetric fat distribution throughout the neck and history of alcoholism. The patient was treated from several diseases associated with alcoholism and hospitalized several times, but the diagnosis of Madelung's disease was omitted. The thyroid gland disease was excluded, while enlargement of the neck adipose tissue was attributed to obesity. Conclusions. This study points out possible diagnostic mistakes when a physician is not aware of a differentiation diagnosis of symmetrically enlarged neck masses, especially in geographic regions with high incidence of this disease. PMID:23983713

Mimica, Mladen; Pravdic, Danijel; Nakas-Icindic, Emina; Karin, Maja; Babic, Emil; Tomic, Monika; Bevanda, Milenko

2013-01-01

183

Symmetric splitting of very light systems  

Microsoft Academic Search

Inclusive and coincidence measurements have been performed to study symmetric products from the reactions 74-186 MeV 12C+40Ca, 141 MeV 9Be+40Ca, and 153 MeV 6Li+40Ca. The binary decay of the composite system has been verified. Energy spectra, angular distributions, and fragment correlations are presented. The total kinetic energies for the symmetric products from these very light composite systems are compared to

K. Grotowski; Z. Majka; R. Planeta; M. Szczodrak; Y. Chan; G. Guarino; L. G. Moretto; D. J. Morrissey; L. G. Sobotka; R. G. Stokstad; I. Tserruya; S. Wald; G. J. Wozniak

1984-01-01

184

Complex symmetric matrices with strongly stable iterates  

NASA Technical Reports Server (NTRS)

Complex-valued symmetric matrices are studied. A simple expression for the spectral norm of such matrices is obtained, by utilizing a unitarily congruent invariant form. A sharp criterion is provided for identifying those symmetric matrices whose spectral norm is not exceeding one: such strongly stable matrices are usually sought in connection with convergent difference approximations to partial differential equations. As an example, the derived criterion is applied to conclude the strong stability of a Lax-Wendroff scheme.

Tadmor, E.

1985-01-01

185

Symmetric informationally complete measurements of arbitrary rank  

Microsoft Academic Search

There has been much interest in so-called SIC-POVMs, i.e., rank 1 symmetric informationally complete positive operator valued\\u000a measures. In this paper we discuss the larger class of POVMs that are symmetric and informationally complete, but not necessarily\\u000a rank 1. This class of POVMs is of some independent interest. In particular it includes a POVM that is closely related to the

D. M. Appleby

2007-01-01

186

Parameter Estimates for Symmetric Stable Distributions  

Microsoft Academic Search

Building on results of an earlier article [6], estimators are suggested for the scale parameter and characteristic exponent of symmetric stable distributions, and Monte Carlo studies of these estimators are reported. The powers of various goodness-of-fit tests of a Gaussian null hypothesis against non-Gaussian stable alternatives are also investigated. Finally, a test of the stability property of symmetric stable variables

Eugene F. Fama; Richard Roll

1971-01-01

187

Light top squark in precision top quark sample  

NASA Astrophysics Data System (ADS)

The uncertainty of tt ¯ production cross section measurement at LHC is at a few percent level which still allows the stop pair production t ˜t ˜* with identical final states 2b +?+nj+notation="updiagonalstrike">ET. In this paper, we attempt to use the existing measurement of W-polarization in top quark decay to improve the distinction between stop and top quark states. We apply the ATLAS ?2 method of W-polarization measurement in semileptonic tt ¯ final state to semileptonic stop pair samples and study its prediction. We find that the faked top events from stop mostly contribute to the left-handed polarized W due to the reconstruction. The benchmark point with maximal contribution to top events only changes FL by 1%. After comparing with the current experiments, we conclude that the current measurement of W-polarization in t decay cannot exclude the light stop scenario.

Li, Xue-Qian; Si, Zong-Guo; Wang, Kai; Wang, Liucheng; Zhang, Liangliang; Zhu, Guohuai

2014-04-01

188

Training Top 10 Hall of Fame  

ERIC Educational Resources Information Center

Microsoft Corporation and SCC Soft Computer are the newest inductees into the Training Top 10 Hall of Fame, joining the ranks of the 11 companies named to the hall since its inception in 2008 (Wyeth Pharmaceuticals subsequently was acquired by Pfizer Inc. in 2009). These 11 companies held Top 10 spots in the Training Top 50, Top 100, and now Top

Training, 2012

2012-01-01

189

Trajectory correction propulsion for TOPS  

NASA Technical Reports Server (NTRS)

A blowdown-pressurized hydrazine propulsion system was selected to provide trajectory correction impulse for outer planet flyby spacecraft as the result of cost/mass/reliability tradeoff analyses. Present hydrazine component and system technology and component designs were evaluated for application to the Thermoelectric Outer Planet Spacecraft (TOPS); while general hydrazine technology was adequate, component design changes were deemed necessary for TOPS-type missions. A prototype hydrazine propulsion system was fabricated and fired nine times for a total of 1600 s to demonstrate the operation and performance of the TOPS propulsion configuration. A flight-weight trajectory correction propulsion subsystem (TCPS) was designed for the TOPS based on actual and estimated advanced components.

Long, H. R.; Bjorklund, R. A.

1972-01-01

190

Progress in top quark physics  

SciTech Connect

Experimental measurements of the properties of the top quark have improved and will continue to improve significantly, with the excellent operation of the CDF and D0 experiments and the Tevatron p{bar p} collider at the Fermi National Accelerator Laboratory. All of the final state experimental signatures from top quark production and decay are being analyzed to test if this most massive quark is sensitive to new physics beyond the standard model. So far, observations are consistent with the standard model. New techniques have dramatically improved the precision of the top quark mass measurement to 1.7% and set the stage for a sub-1% measurement by 2008. This improved knowledge of the top quark mass sharpens the standard model prediction for the mass of the undiscovered Higgs boson, with implications for Higgs studies at the future LHC and ILC.

Thomson, Evelyn J.; /Pennsylvania U.

2006-02-01

191

Top BSM at D0  

SciTech Connect

The D0 experiment has searched for phenomena beyond the standard model in top quark events. The methods and results of four analyses covering various possible deviations from the standard model behavior are discussed.

Wicke, Daniel; /Wuppertal U.

2008-07-01

192

Top 10 Products of 2011  

ERIC Educational Resources Information Center

In 2011, American School & University (AS&U) showcased some of the hottest products in the industry. This article presents the top ten most requested products as determined by readers. The top one on the list is the Bulb crusher which can cut recycling costs by 50%, can hold 1,350 4-foot lamps in a single 55-gallon drum, can crush a 4-foot lamp in…

American School & University, 2011

2011-01-01

193

Modeling transport through single-molecule junctions  

Microsoft Academic Search

Non-equilibrium Green's functions (NEGF) formalism combined with extended Hckel (EHT) and charging model are used to study\\u000a electrical conduction through single-molecule junctions. The analyzed molecular complex is composed of the asymmetric 1,4-Bis((2?-para-mercaptophenyl)-ethinyl)-2-acetyl-amino-5-nitrobenzene molecule symmetrically coupled to two gold electrodes. Owing to this\\u000a model, the accurate values of the current flowing through such junctions can be obtained by utilizing basic fundamentals

Kamil Walczak; Sergey Edward Lyshevski

2005-01-01

194

Infrared absorption of explosive molecule vapors  

NASA Astrophysics Data System (ADS)

Infrared absorption spectra have been obtained for the high explosive molecules TNT, RDX, and PETN in the vapor phase. Integrated band strengths were measured for the symmetric and antisymmetric -NO 2 vibrations in each of these molecules. Ab initio calculations of vibrational frequencies and intensities were carried out for comparison with the experimental data. Previous measurements of the heats of vaporization of these materials were checked using the temperature dependence of infrared band intensities. Measurements were also carried out on ammonium nitrate; in this case, only the decomposition products NH 3, HNO 3, and N 2O were observed in the vapor phase in equilibrium with the solid.

Janni, James; Gilbert, Brian D.; Field, R. W.; Steinfeld, Jeffrey I.

1997-08-01

195

The symmetric and asymmetric thiophene-fused benzocarborane: structures and first hyperpolarizabilities.  

PubMed

The unusual properties of thiophene-fused benzocarborane have attracted a lot of interest in recent years due to their wide applications in photonics and optoelectronics. In the present work, nine molecules [M, N] (M, N are labeled as the number of thiophene rings on the left and right part, respectively) on the basis of thiophene-fused benzocarborane were considered. The first hyperpolarizability (? tot) values of three synthesized symmetric molecules [1, 1], [2, 2], [3, 3] (M=N, Chem. Eur. J 2012. 18, 11251-11257) and six asymmetric molecules [1, 2], [1, 3], [1, 4], [1, 5], [2, 3], [2, 4] (M?N) were investigated, ? tot values of symmetric molecules show the order: 39 of [1, 1]< 800 of [2, 2]< 903 au of [3, 3], which indicate that ? tot value increases with increasing the number of thiophene ring for symmetric molecules. The other order of ? tot values can be observed: 39 of [1, 1]< 800 of [1, 2]< 3553 of [1, 3]< 7998 of [1, 4]< 13049 au of [1, 5] and 66 of [2, 2]< 3240 of [2, 3]< 8029 au of [2, 4]. Interestingly, when sum of M and N is constant, larger difference between M and N is, larger ? tot value is: 800 au of [2, 2]< 3553 au of [1, 3]; 3240 au of [2, 3] < 7998 au of [1, 4]; 903 au of [3, 3]< 8029 au of [2, 4]< 13049 au of [1, 5]. Significantly, [1, 5] with six thiophene rings has the largest ? tot value (13049 au) which is greatly larger than 903 au of [3, 3] with six thiophene rings. Furthermore, the natural bond orbital (NBO) charge populations, the nucleus-independent chemical shift (NICS), the bond length alternation (BLA) of the nine molecules and crucial transition were studied in our work. We hope that the present work will be beneficial for future theoretical and experimental studies on the electro-optical properties of thiophene-fused benzocarborane molecules. PMID:23793718

Li, Yong; Wu, Heng-Qing; Xu, Hong-Liang; Sun, Shi-Ling; Su, Zhong-Min

2013-09-01

196

Symmetric Kv1.5 Blockers Discovered by Focused Screening  

PubMed Central

Guided by computational methods, a set of 1920 compounds were selected from the AstraZeneca corporate collection and screened for Kv1.5 activity. To facilitate rapid generation of structure–activity relationships, special attention was given to selecting subsets of structurally similar molecules by using a maximum common substructure similarity-based procedure. The focused screen hit rate was relatively high (12%). More importantly, a structural series featured by the symmetric 1,2-diphenylethane-1,2-diamine substructure was identified as potent Kv.1.5 blockers. The property profile for the series is shown to meet stringent lead-optimization criteria, providing a springboard for the development of a new and safe treatment for atrial fibrillation.

2012-01-01

197

Molecular theory for self assembling mixtures of patchy colloids and colloids with spherically symmetric attractions: The single patch case  

NASA Astrophysics Data System (ADS)

In this work we develop a new theory to model self assembling mixtures of single patch colloids and colloids with spherically symmetric attractions. In the development of the theory we restrict the interactions such that there are short ranged attractions between patchy and spherically symmetric colloids, but patchy colloids do not attract patchy colloids and spherically symmetric colloids do not attract spherically symmetric colloids. This results in the temperature, density, and composition dependent reversible self assembly of the mixture into colloidal star molecules. This type of mixture has been recently synthesized by grafting of complimentary single stranded DNA [L. Feng, R. Dreyfus, R. Sha, N. C. Seeman, and P. M. Chaikin, Adv. Mater. 25(20), 2779-2783 (2013)]. As a quantitative test of the theory, we perform new monte carlo simulations to study the self assembly of these mixtures; theory and simulation are found to be in excellent agreement.

Marshall, Bennett D.; Chapman, Walter G.

2013-09-01

198

Asymmetric Flow in Symmetric Branched Structures  

NASA Astrophysics Data System (ADS)

We investigate the fluid flow through a cascade of bifurcations by direct simulation of the 2D Navier-Stokes equations. We show that, for a fully symmetric tree with n generations ( n>=3\\), the flow distribution becomes significantly heterogeneous at an increased Reynolds number. We develop a binary tree model and find that the distribution of flow at the outlet branches can be described by a self-affine landscape, with a self-affine exponent ? = 0.9 for the human lung. We suggest that the asymmetric flow occurring in symmetric branched structures may be important both for the morphogenesis of the bronchial tree, and for its functioning during inspiration.

Andrade, J. S., Jr.; Alencar, A. M.; Almeida, M. P.; Mendes Filho, J.; Buldyrev, S. V.; Zapperi, S.; Stanley, H. E.; Suki, B.

1998-07-01

199

Symmetric splitting of very light systems  

SciTech Connect

Inclusive and coincidence measurements have been performed to study symmetric products from the reactions 74--186 MeV /sup 12/C+ /sup 40/Ca, 141 MeV /sup 9/Be+ /sup 40/Ca, and 153 MeV /sup 6/Li+ /sup 40/Ca. The binary decay of the composite system has been verified. Energy spectra, angular distributions, and fragment correlations are presented. The total kinetic energies for the symmetric products from these very light composite systems are compared to liquid drop model calculations and fission systematics.

Grotowski, K.; Majka, Z.; Planeta, R.; Szczodrak, M.; Chan, Y.; Guarino, G.; Moretto, L.G.; Morrissey, D.J.; Sobotka, L.G.; Stokstad, R.G.; Tserruya, I.; Wald, S.; Wozniak, G.J.

1984-10-01

200

Symmetric integrator for nonintegrable Hamiltonian relativistic systems  

NASA Astrophysics Data System (ADS)

By combining a standard symmetric, symplectic integrator with a new step size controller, we provide an integration scheme that is symmetric, reversible and conserves the values of the constants of motion. This new scheme is appropriate for long-term numerical integrations of geodesic orbits in spacetime backgrounds, whose corresponding Hamiltonian system is nonintegrable, and, in general, for any nonintegrable Hamiltonian system whose kinetic part depends on the position variables. We show by numerical examples that the new integrator is faster and more accurate (i) than the standard symplectic integration schemes with or without standard adaptive step size controllers and (ii) than an adaptive step Runge-Kutta scheme.

Seyrich, Jonathan; Lukes-Gerakopoulos, Georgios

2012-12-01

201

Quantum Secret Sharing Using Symmetric W State  

NASA Astrophysics Data System (ADS)

Quantum secret sharing (QSS) is an important branch of quantum cryptography, but the existing literature contains no mention of a QSS scheme that applies in the symmetric W states. Here, we demonstrate a multipartite QSS protocol that is encoded into these quantum states with unitary operation pairs. This paper proposes a new method of constructing a QSS protocol for the symmetric W state. This scheme is more efficient than other existing QSS schemes because our proposed protocol uses only a single photon measurement and XOR to recover the secret KEY of Alice.

Liu, Lin-Lin; Tsai, Chia-Wei; Hwang, Tzonelih

2012-07-01

202

Observational tests of Baryon symmetric cosmology  

NASA Technical Reports Server (NTRS)

Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of pi(0)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the amma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurement of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed.

Stecker, F. W.

1982-01-01

203

All-optical symmetric ternary logic gate  

NASA Astrophysics Data System (ADS)

Symmetric ternary number (radix=3) has three logical states (1¯, 0, 1). It is very much useful in carry free arithmetical operation. Beside this, the logical operation using this type of number system is also effective in high speed computation and communication in multi-valued logic. In this literature all-optical circuits for three basic symmetrical ternary logical operations (inversion, MIN and MAX) are proposed and described. Numerical simulation verifies the theoretical model. In this present scheme the different ternary logical states are represented by different polarized state of light. Terahertz optical asymmetric demultiplexer (TOAD) based interferometric switch has been used categorically in this manuscript.

Chattopadhyay, Tanay

2010-09-01

204

The Axially Symmetric One-Monopole  

SciTech Connect

We present new classical generalized one-monopole solution of the SU(2) Yang-Mills-Higgs theory with the Higgs field in the adjoint representation. We show that this solution with theta-winding number m = 1 and phi-winding number n = 1 is an axially symmetric generalization of the 't Hooft-Polyakov one-monopole. We construct this axially symmetric one-monopole solution by generalizing the large distance asymptotic solutions of the 't Hooft-Polyakov one-monopole to the Jacobi elliptic functions and solving the second order equations of motion numerically when the Higgs potential is vanishing. This solution is a non-BPS solution.

Wong, K.-M.; Teh, Rosy [School of Physics, Universiti Sains Malaysia, 11800 USM Penang (Malaysia)

2009-07-07

205

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

SciTech Connect

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

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

2000-06-21

206

Consider topped crude for FCC  

SciTech Connect

A case study is presented that illustrates the mechanics for evaluating use of topped crude to load the FCC for more profit. Declining product demands combined with high crude costs has shut down many refineries and left others operting well below design capacity. The study illustrates the step-by-step requirements to debottleneck an existing Kellogg Orthoflow Model B FCC to process topped crude mixed with gas oils. This study was limited to the catalytic converter defined as the reactor, regenerator, air blower, and wet gas compressor. The scope was to examine the ability to process topped crude and to consider modernizing the FCC to employ riser cracking and complete CO combustion regeneration.

Louder, K.E.; Juno, E.J.; Kulapaditharom, L.

1985-09-01

207

Observation of the Top Quark  

NASA Astrophysics Data System (ADS)

The D0 Collaboration reports on a search for the standard model top quark in pp¯ collisions at s = 1.8 TeV at the Fermilab Tevatron with an integrated luminosity of approximately 50 pb-1. We have searched for tt¯ production in the dilepton and single-lepton decay channels with and without tagging of b-quark jets. We observed 17 events with an expected background of 3.8+/-0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2×10-6 (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measured its mass to be 199+19-21 (stat) +/-22 (syst) GeV/c2 and its production cross section to be 6.4+/-2.2 pb.

Abachi, S.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adam, I.; Adams, D. L.; Adams, M.; Ahn, S.; Aihara, H.; Alitti, J.; Álvarez, G.; Alves, G. A.; Amidi, E.; Amos, N.; Anderson, E. W.; Aronson, S. H.; Astur, R.; Avery, R. E.; Baden, A.; Balamurali, V.; Balderston, J.; Baldin, B.; Bantly, J.; Bartlett, J. F.; Bazizi, K.; Bendich, J.; Beri, S. B.; Bertram, I.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Bhattacharjee, M.; Bischoff, A.; Biswas, N.; Blazey, G.; Blessing, S.; Boehnlein, A.; Bojko, N. I.; Borcherding, F.; Borders, J.; Boswell, C.; Brandt, A.; Brock, R.; Bross, A.; Buchholz, D.; Burtovoi, V. S.; Butler, J. M.; Casey, D.; Castilla-Valdez, H.; Chakraborty, D.; Chang, S.-M.; Chekulaev, S. V.; Chen, L.-P.; Chen, W.; Chevalier, L.; Chopra, S.; Choudhary, B. C.; Christenson, J. H.; Chung, M.; Claes, D.; Clark, A. R.; Cobau, W. G.; Cochran, J.; Cooper, W. E.; Cretsinger, C.; Cullen-Vidal, D.; Cummings, M.; Cutts, D.; Dahl, O. I.; de, K.; Demarteau, M.; Demina, R.; Denisenko, K.; Denisenko, N.; Denisov, D.; Denisov, S. P.; Dharmaratna, W.; Diehl, H. T.; Diesburg, M.; di Loreto, G.; Dixon, R.; Draper, P.; Drinkard, J.; Ducros, Y.; Dugad, S. R.; Durston-Johnson, S.; Edmunds, D.; Efimov, A. O.; Ellison, J.; Elvira, V. D.; Engelmann, R.; Eno, S.; Eppley, G.; Ermolov, P.; Eroshin, O. V.; Evdokimov, V. N.; Fahey, S.; Fahland, T.; Fatyga, M.; Fatyga, M. K.; Featherly, J.; Feher, S.; Fein, D.; Ferbel, T.; Finocchiaro, G.; Fisk, H. E.; Fisyak, Yu.; Flattum, E.; Forden, G. E.; Fortner, M.; Frame, K. C.; Franzini, P.; Fredriksen, S.; Fuess, S.; Galjaev, A. N.; Gallas, E.; Gao, C. S.; Gao, S.; Geld, T. L.; Genik, R. J., II; Genser, K.; Gerber, C. E.; Gibbard, B.; Glaubman, M.; Glebov, V.; Glenn, S.; Glicenstein, J. F.; Gobbi, B.; Goforth, M.; Goldschmidt, A.; Gomez, B.; Goncharov, P. I.; Gordon, H.; Goss, L. T.; Graf, N.; Grannis, P. D.; Green, D. R.; Green, J.; Greenlee, H.; Griffin, G.; Grossman, N.; Grudberg, P.; Grünendahl, S.; Guida, J. A.; Guida, J. M.; Guryn, W.; Gurzhiev, S. N.; Gutnikov, Y. E.; Hadley, N. J.; Haggerty, H.; Hagopian, S.; Hagopian, V.; Hahn, K. S.; Hall, R. E.; Hansen, S.; Hatcher, R.; Hauptman, J. M.; Hedin, D.; Heinson, A. P.; Heintz, U.; Hernandez-Montoya, R.; Heuring, T.; Hirosky, R.; Hobbs, J. D.; Hoeneisen, B.; Hoftun, J. S.; Hsieh, F.; Hu, Ting; Hu, Tong; Huehn, T.; Igarashi, S.; Ito, A. S.; James, E.; Jaques, J.; Jerger, S. A.; Jiang, J. Z.-Y.; Joffe-Minor, T.; Johari, H.; Johns, K.; Johnson, M.; Johnstad, H.; Jonckheere, A.; Jöstlein, H.; Jun, S. Y.; Jung, C. K.; Kahn, S.; Kang, J. S.; Kehoe, R.; Kelly, M.; Kernan, A.; Kerth, L.; Kim, C. L.; Kim, S. K.; Klatchko, A.; Klima, B.; Klochkov, B. I.; Klopfenstein, C.; Klyukhin, V. I.; Kochetkov, V. I.; Kohli, J. M.; Koltick, D.; Kostritskiy, A. V.; Kotcher, J.; Kourlas, J.; Kozelov, A. V.; Kozlovski, E. A.; Krishnaswamy, M. R.; Krzywdzinski, S.; Kunori, S.; Lami, S.; Landsberg, G.; Lanou, R. E.; Lebrat, J.-F.; Lee-Franzini, J.; Leflat, A.; Li, H.; Li, J.; Li, Y. K.; Li-Demarteau, Q. Z.; Lima, J. G.; Lincoln, D.; Linn, S. L.; Linnemann, J.; Lipton, R.; Liu, Y. C.; Lobkowicz, F.; Loken, S. C.; Lökös, S.; Lueking, L.; Lyon, A. L.; Maciel, A. K.; Madaras, R. J.; Madden, R.; Mandrichenko, I. V.; Mangeot, Ph.; Mani, S.; Mansoulié, B.; Mao, H. S.; Margulies, S.; Markeloff, R.; Markosky, L.; Marshall, T.; Martin, M. I.; Marx, M.; May, B.; Mayorov, A. A.; McCarthy, R.; McKibben, T.; McKinley, J.; Melanson, H. L.; de Mello Neto, J. R.; Merritt, K. W.; Miettinen, H.; Milder, A.; Milner, C.; Mincer, A.; de Miranda, J. M.; Mishra, C. S.; Mohammadi-Baarmand, M.; Mokhov, N.; Mondal, N. K.; Montgomery, H. E.; Mooney, P.; Mudan, M.; Murphy, C.; Murphy, C. T.; Nang, F.; Narain, M.; Narasimham, V. S.; Narayanan, A.; Neal, H. A.; Negret, J. P.; Neis, E.; Nemethy, P.; Neši?, D.; Norman, D.; Oesch, L.; Oguri, V.; Oltman, E.; Oshima, N.; Owen, D.; Padley, P.; Pang, M.; Para, A.; Park, C. H.; Park, Y. M.; Partridge, R.; Parua, N.; Paterno, M.; Perkins, J.; Peryshkin, A.; Peters, M.; Piekarz, H.; Pischalnikov, Y.; Pluquet, A.; Podstavkov, V. M.; Pope, B. G.; Prosper, H. B.; Protopopescu, S.; Pušelji?, D.; Qian, J.; Quintas, P. Z.; Raja, R.; Rajagopalan, S.; Ramirez, O.; Rao, M. V.; Rapidis, P. A.; Rasmussen, L.; Read, A. L.; Reucroft, S.; Rijssenbeek, M.; Rockwell, T.; Roe, N. A.; Roldan, J. M.; Rubinov, P.; Ruchti, R.; Rusin, S.; Rutherfoord, J.; Santoro, A.; Sawyer, L.; Schamberger, R. D.; Schellman, H.; Schmid, D.; Sculli, J.; Shabalina, E.; Shaffer, C.; Shankar, H. C.; Shivpuri, R. K.; Shupe, M.; Singh, J. B.; Sirotenko, V.; Smart, W.; Smith, A.; Smith, R. P.; Snihur, R.; Snow, G. R.; Snyder, S.; Solomon, J.; Sood, P. M.; Sosebee, M.; Souza, M.; Spadafora, A. L.; Stephens, R. W.; Stevenson, M. L.; Stewart, D.; Stocker, F.; Stoianova, D. A.

1995-04-01

208

Interactions Between a Symmetrical Minor Groove Binding Compound and DNA Oligonucleotides: H and F NMR Studies  

Microsoft Academic Search

High-resolution NMR techniques (proton and F) have been used to study the interactions between several DNA oligonucleotides with varying length of AT base pairs and the synthetic pyrrole-containing compound (P1-F4S-P1), which has properties similar to the DNA minor groove binding drug distamycin A When this two-fold symmetrical DNA binding molecule is added to the self-complementary DNA oligomers, the resulting complex

Andrew H.-J. Wang; Sylvain Cottens; Peter B. Dervan; James P. Yesinowski; Gijs A. van der Marel; Jacques H. van Boom

1989-01-01

209

High resolution laser spectroscopy of selected molecules in the gas phase  

NASA Astrophysics Data System (ADS)

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

Forthomme, Damien

210

Smectic assemblies in C3-symmetric hexa-alkylated liquid crystals: transformation from smectogen to discogen via hydrogen bonding.  

PubMed

In this paper, we report a C3-symmetric liquid crystal (LC) with sixfold alkyl peripheries exhibiting an unusual smectic E-like organization in the LC state. Based on conformational considerations, the smectic assembly is attributed to the formation of an endo-type Y conformer of asymmetric triazolyl and benzylic groups that cannot be accessed in other C3-symmetric molecules exclusively showing columnar assemblies. The Y conformers form a two-dimensional oblique lattice in the aromatic layers of the ordered smectic phase. In addition, the Y-shaped molecule in the smectic phases can change into a circular shape by the 1?:?1 hydrogen-bonding interaction with a gallic acid derivative, which leads to a hexagonal columnar LC phase. The triazole-based LC design concept proves the smectic LC assembly in the C3-symmetric system, and provides the supramolecular manipulation of LC morphologies. PMID:24975589

Park, Soyoung; Ryu, Mi-Hee; Shin, Tae Joo; Cho, Byoung-Ki

2014-08-21

211

Top Quark Spin Correlations - Theory  

SciTech Connect

The top quark decay width (G{sub F}m{sub t}{sup 3} {approx} 1 GeV) is much larger than the QCD hadronization scale ({Lambda}{sub QCD} {approx} 0.1 GeV) and much larger than the spin decorrelation scale ({Lambda}{sub QCD}{sup 2}/m{sub t} {approx} 0.1 MeV). Therefore, spin correlations in top quark pair production are reflected in angular correlations of the decay products, see [1] and [2].

Parke, Stephen J.; /Fermilab

2012-02-01

212

Fragmentation of Small Molecules by Photo-Double Ionization  

Microsoft Academic Search

Molecular structure, formation, breakup pathways and recombination formed the subject of many theoretical and experimental studies. Among molecular species like H2, CO, N2, O2 recently great attention has been paid to the dynamics of the fragmentations and rearrangements of C2H2 molecule. Nature's smallest stable hydrocarbon, the symmetric linear acetylene molecule, C2H2, is an important polyatomic system for the study of

Timur Osipov

2008-01-01

213

Efficient One-Step Synthesis of C3Symmetrical Benzenoid Compounds Mediated by SOCl2\\/EtOH  

Microsoft Academic Search

An efficient one-step synthesis of branched functionalized benzenoid compounds from aryl methyl ketones mediated by SOCl2\\/EtOH is described; some novel C3-symmetrical molecules were prepared with satisfactory yields. The method enjoys short reaction time and simple operation, and avoids use of organometallic reagents.

Sanhu Zhao; Lina Kang; Haixia Ge; Feifei Yang; Chenlu Wang; Chang Li; Qiang Wang; Minggen Zhao

2012-01-01

214

An Efficient One-Step Synthesis of C3-symmetrical Benzenoid Compounds Mediated by SOCl2 \\/ EtOH  

Microsoft Academic Search

An efficient one-step synthesis of branched functionalized benzenoid compounds from aryl methyl ketones mediated by SOCl2 \\/ EtOH is described; some novel C3-symmetrical molecules were prepared with satisfied yields. The method enjoys the short reaction time, simple operation and avoidance of using organometallic reagents.

Sanhu Zhao; Lina Kang; Haixia Ge; Feifei Yang; Chenlu Wang; Chang Li; Qiang Wang; Minggen Zhao

2012-01-01

215

Complex PT-symmetric nonlinear Schrödinger equation and Burgers equation.  

PubMed

The complex -symmetric nonlinear wave models have drawn much attention in recent years since the complex -symmetric extensions of the Korteweg-de Vries (KdV) equation were presented in 2007. In this review, we focus on the study of the complex -symmetric nonlinear Schrödinger equation and Burgers equation. First of all, we briefly introduce the basic property of complex symmetry. We then report on exact solutions of one- and two-dimensional nonlinear Schrödinger equations (known as the Gross-Pitaevskii equation in Bose-Einstein condensates) with several complex -symmetric potentials. Finally, some complex -symmetric extension principles are used to generate some complex -symmetric nonlinear wave equations starting from both -symmetric (e.g. the KdV equation) and non- -symmetric (e.g. the Burgers equation) nonlinear wave equations. In particular, we discuss exact solutions of some representative ones of the complex -symmetric Burgers equation in detail. PMID:23509385

Yan, Zhenya

2013-04-28

216

Gate-all-around Si-nanowire CMOS inverter logic fabricated using top-down approach  

Microsoft Academic Search

We present, for the first time, the monolithic integration of Gate-Ail-Around (GAA) Si-nanowire FETs into CMOS logic using top-down approach. The drive currents for N-and P-MOS transistors are matched using different number of channels for each to obtain symmetric pull-up and pull-down characteristics. Sharp ON-OFF transitions with high voltage gains (up to -45) are obtained which are best reported among

K. D. Buddharaju; N. Singh; S. C. Rustagi; Selin H. G. Teo; L. Y. Wong; L. J. Tang; C. H. Tung; G. Q. Lo; N. Balasubramanian; D. L. Kwong

2007-01-01

217

Analytic solution of flat-top Gaussian and Laguerre-Gaussian laser field components.  

PubMed

We generalized the nonparaxial field components of Laguerre-Gaussian and flattened Gaussian beams obtained using the angular spectrum method to include symmetric radial and angular expansions and simplified them using an approximate evaluation of the integral equations for the field components. These field components possess series expressions in orders of a natural expansion parameter, which clarifies the physical interpretation of the series expansion. A connection between Laguerre-Gaussian and flat-top Gaussian profiles is obtained. PMID:20967101

Cerjan, Alexander; Cerjan, Charles

2010-10-15

218

Generation arbitrary permutation symmetric state with projection  

Microsoft Academic Search

We proposed a scheme to generate arbitrary permutation symmetric multi-partite state. The system contains N equally single quantum particles (We use atoms for these particles) which may interact with single photon to generate entanglement between them. This entanglement can be obtained by the transition from three-level lambda atom's exited state to different low levels and emitting corresponding polarized photon, or

Fangwen Sun; Chee Wei Wong

2008-01-01

219

Rounding in Symmetric Matrices and Undirected Graphs  

Microsoft Academic Search

We consider the problem of rounding the entries of a matrix without distorting the row, column, and grand totals. This problem arises in controlling statistical disclosure, in data analysis, and elsewhere. There are algorithms in the literature which produce roundings that are “tight” in the sense of distorting the totals very little. We concentrate on the case of symmetric matrices.

Pavol Hell; David G. Kirkpatrick; Brenda Li

1996-01-01

220

Resonances for Symmetric Two-Barrier Potentials  

ERIC Educational Resources Information Center

We describe a method for the accurate calculation of bound-state and resonance energies for one-dimensional potentials. We calculate the shape resonances for symmetric two-barrier potentials and compare them with those coming from the Siegert approximation, the complex scaling method and the box-stabilization method. A comparison of the…

Fernandez, Francisco M.

2011-01-01

221

Unidirectional nonlinear PT-symmetric optical structures  

SciTech Connect

We show that nonlinear optical structures involving a balanced gain-loss profile can act as unidirectional optical valves. This is made possible by exploiting the interplay between the fundamental symmetries of parity (P) and time (T), with optical nonlinear effects. This unidirectional dynamics is specifically demonstrated for the case of an integrable PT-symmetric nonlinear system.

Ramezani, Hamidreza [Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States); Kottos, Tsampikos [Department of Physics, Wesleyan University, Middletown, Connecticut 06459 (United States); Max-Planck-Institute for Dynamics and Self-Organization, D-37073 Goettingen (Germany); El-Ganainy, Ramy; Christodoulides, Demetrios N. [College of Optics and Photonics-CREOL, University of Central Florida, Orlando, Florida 32816 (United States)

2010-10-15

222

Iris Recognition Using Circular Symmetric Filters  

Microsoft Academic Search

This paper proposes a new method for personal identification based on iris recognition. The method consists of three major components: image preprocessing, feature extraction and classifier design. A bank of circular symmetric filters is used to capture local iris characteristics to form a fixed length feature vector. In iris matching, an efficient approach called nearest feature line (NFL) is used.

Li Ma; Yunhong Wang; Tieniu Tan

2002-01-01

223

Projective normality of complete symmetric varieties  

Microsoft Academic Search

We prove that in characteristic zero the multiplication of sections of dominant line bundles on a complete symmetric variety $X=\\\\bar{G\\/H}$ is a surjective map. As a consequence the cone defined by a complete linear system over $X$, or over a closed $G$ stable subvariety of $X$ is normal. This gives an affirmative answer to a question raised by Faltings. A

Rocco Chirivi; Andrea Maffei

2002-01-01

224

Stability Analysis of a Symmetrical Induction Machine  

Microsoft Academic Search

A stability study of an induction machine is performed by applying the root-locus criterion to the equations which describe the behavior of the machine during small displacements about a steady-state operating point. This investigation reveals that a symmetrical induction machine may become unstable at low speeds (low frequencies) even though balanced, constant amplitude, sinusoidal voltages are applied to the stator

ROBERT H. NELSON; THOMAS A. LIPO; PAUL C. KRAUSE

1969-01-01

225

The Low Pressure Plane Symmetric Discharge  

Microsoft Academic Search

It is shown that the low pressure plane symmetric plasma equation, using the collision-free model of Tonks and Langmuir, can be solved analytically. Simple expressions are obtained for the mean velocity and the mean square velocity of the ions, and for the wall potential with respect to the plasma. The conditions for the formation of a stable plasma-sheath boundary are

E. R. Harrison; W. B. Thompson

1959-01-01

226

Bruhat Order in Full Symmetric Toda System  

NASA Astrophysics Data System (ADS)

In this paper we discuss some geometrical and topological properties of the full symmetric Toda system. We show by a direct inspection that the phase transition diagram for the full symmetric Toda system in dimensions n = 3, 4 coincides with the Hasse diagram of the Bruhat order of symmetric groups S 3 and S 4. The method we use is based on the existence of a vast collection of invariant subvarieties of the Toda flow in orthogonal groups. We show how one can extend it to the case of general n. The resulting theorem identifies the set of singular points of dim = n Toda flow with the elements of the permutation group S n , so that points will be connected by a trajectory, if and only if the corresponding elements are Bruhat comparable. We also show that the dimension of the submanifolds, spanned by the trajectories connecting two singular points, is equal to the length of the corresponding segment in the Hasse diagram. This is equivalent to the fact that the full symmetric Toda system is in fact a Morse-Smale system.

Chernyakov, Yu. B.; Sharygin, G. I.; Sorin, A. S.

2014-08-01

227

A Concrete Security Treatment of Symmetric Encryption  

Microsoft Academic Search

We study notions and schemes for symmetric (ie. private key) encryption in a concrete security framework. We give four different notions of security against chosen plaintext attack and analyze the concrete complexity of reductions among them, providing both upper and lower bounds, and obtaining tight relations. In this way we classify notions (even though polynomially reducible to each other) as

Mihir Bellare; Anand Desai; E. Jokipii; Phillip Rogaway

1997-01-01

228

The deuterium puzzle in the symmetric universe  

NASA Technical Reports Server (NTRS)

An attempt was made to use deuterium abundance in the symmetric universe to prove that no nucleosynthesis takes place during annihilation and therefore neutrons were loss before nucleosynthesis. Data cover nucleosynthesis during the radiative era, cross section estimates, maximum abundance of He-4 at the end of nucleosynthesis area, and loss rate.

Leroy, B.; Nicolle, J. P.; Schatzman, E.

1973-01-01

229

Models of helically symmetric binary systems  

NASA Astrophysics Data System (ADS)

Results from helically symmetric scalar-field models and first results from a convergent helically symmetric binary neutron-star code are reported here; these are models stationary in the rotating frame of a source with constant angular velocity ?. In the scalar-field models and the neutron-star code, helical symmetry leads to a system of mixed elliptic hyperbolic character. The scalar-field models involve nonlinear terms of the form ?3, (??)2 and ?squ? that mimic nonlinear terms of the Einstein equation. Convergence is strikingly different for different signs of each nonlinear term; it is typically insensitive to the iterative method used, and it improves with an outer boundary in the near zone. In the neutron-star code, one has no control on the sign of the source, and convergence has been achieved only for an outer boundary less than ~1 wavelength from the source or for a code that imposes helical symmetry only inside a near zone of that size. The inaccuracy of helically symmetric solutions with appropriate boundary conditions should be comparable to the inaccuracy of a waveless formalism that neglects gravitational waves, and the (near zone) solutions we obtain for waveless and helically symmetric BNS codes with the same boundary conditions nearly coincide.

Yoshida, Shin'ichirou; Bromley, Benjamin C.; Read, Jocelyn S.; Uryu, Koji; Friedman, John L.

2006-08-01

230

Phenomenology of quark-lepton symmetric models.  

National Technical Information Service (NTIS)

Quark-lepton symmetric models are a new class of gauge theories which unify the quarks and leptons. In these models the gauge group of the standard model is extended to include a color group for the leptons, and consequently the quarks and leptons can the...

R. Foot H. Lew Volkas

1991-01-01

231

Top Mass Measurements at the Tevatron  

SciTech Connect

We present the latest measurements of the top quark mass from the Tevatron. The different top decay channels and measurement techniques used for these results are also described. The world average of the top quark mass based on some of these new results combined with previous results is m{sub top} = 172.6 {+-} 1.4 GeV.

Wang, M.H.L.S.; /Fermilab

2009-04-01

232

Resolution by unassisted Top3 points to template switch recombination intermediates during DNA replication.  

PubMed

The evolutionarily conserved Sgs1/Top3/Rmi1 (STR) complex plays vital roles in DNA replication and repair. One crucial activity of the complex is dissolution of toxic X-shaped recombination intermediates that accumulate during replication of damaged DNA. However, despite several years of study the nature of these X-shaped molecules remains debated. Here we use genetic approaches and two-dimensional gel electrophoresis of genomic DNA to show that Top3, unassisted by Sgs1 and Rmi1, has modest capacities to provide resistance to MMS and to resolve recombination-dependent X-shaped molecules. The X-shaped molecules have structural properties consistent with hemicatenane-related template switch recombination intermediates (Rec-Xs) but not Holliday junction (HJ) intermediates. Consistent with these findings, we demonstrate that purified Top3 can resolve a synthetic Rec-X but not a synthetic double HJ in vitro. We also find that unassisted Top3 does not affect crossing over during double strand break repair, which is known to involve double HJ intermediates, confirming that unassisted Top3 activities are restricted to substrates that are distinct from HJs. These data help illuminate the nature of the X-shaped molecules that accumulate during replication of damaged DNA templates, and also clarify the roles played by Top3 and the STR complex as a whole during the resolution of replication-associated recombination intermediates. PMID:24100144

Glineburg, M Rebecca; Chavez, Alejandro; Agrawal, Vishesh; Brill, Steven J; Johnson, F Brad

2013-11-15

233

Boron-enriched star-shaped molecule via cycloaddition reaction.  

PubMed

The facile synthesis of a thermally stable carborane appended symmetrical star-shaped molecule having six bulky o-carborane clusters on the periphery, thereby containing sixty boron atoms was accomplished via a cobalt-catalyzed [2+2+2] cycloaddition reaction. PMID:19587935

Prasanna Dash, Barada; Satapathy, Rashmirekha; Maguire, John A; Hosmane, Narayan S

2009-06-14

234

Kowalevski top in quantum mechanics  

SciTech Connect

The quantum mechanical Kowalevski top is studied by the direct diagonalization of the Hamiltonian. The spectra show different behaviors depending on the region divided by the bifurcation sets of the classical invariant tori. Some of these spectra are nearly degenerate due to the multiplicity of the invariant tori. The Kowalevski top has several symmetries and symmetry quantum numbers can be assigned to the eigenstates. We have also carried out the semiclassical quantization of the Kowalevski top by the EBK formulation. It is found that the semiclassical spectra are close to the exact values, thus the eigenstates can be also labeled by the integer quantum numbers. The symmetries of the system are shown to have close relations with the semiclassical quantum numbers and the near-degeneracy of the spectra. -- Highlights: •Quantum spectra of the Kowalevski top are calculated. •Semiclassical quantization is carried out by the EBK formulation. •Quantum states are labeled by the semiclassical integer quantum numbers. •Multiplicity of the classical torus makes the spectra nearly degenerate. •Symmetries, quantum numbers and near-degenerate spectra are closely related.

Matsuyama, A., E-mail: spamatu@ipc.shizuoka.ac.jp

2013-09-15

235

Conservation: Top predators and biodiversity  

Microsoft Academic Search

The charisma of top vertebrate predators is often used by conservationists as a lever for financial support, to raise environmental awareness and in planning protected areas - a strategy that has been criticized. Here we use information collected from five raptor species that differ widely in their diet and habitat associations to show that sites occupied by these predators are

Fabrizio Sergio; Ian Newton; Luigi Marchesi

2005-01-01

236

Single Top at the Tevatron.  

National Technical Information Service (NTIS)

The authors review the status of the search for the electroweak production of single top quarks by the CDF and D0 collaborations at the Fermilab Tevatron proton-antiproton collider using Run II data. With a dataset of approximately 160 pb(sup -1) for CDF ...

A. Taffard

2005-01-01

237

Ejs Torque Free Top Model  

NSDL National Science Digital Library

The Ejs Torque Free Top model displays the motion of a top, in both the space frame and body frame, with no net toque applied. The top has an initial angular speed in the x, y, and z directions. The moments of inertia in each direction, and the initial angular positions and angular speeds can be changed via textboxes. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Torque Free Top model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_rigid_bodies_free.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for rigid body dynamics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-18

238

Top Jets at the LHC  

SciTech Connect

We investigatethe reconstruction of high pT hadronically-decaying top quarksat the Large Hadron Collider. One of the main challenges in identifying energetictop quarks is that the decay products become increasingly collimated. This reducesthe efficacy of conventional reconstruction methods that exploit the topology of thetop quark decay chain. We focus on the cases where the decay products of the topquark are reconstructed as a single jet, a"top-jet." The most basic"top-tag" methodbased on jet mass measurement is considered in detail. To analyze the feasibility ofthe top-tagging method, both theoretical and experimental aspects of the large QCDjet background contribution are examined. Based on a factorization approach, wederive a simple analytic approximation for the shape of the QCD jet mass spectrum.We observe very good agreement with the Monte Carlo simulation. We consider high pT tt bar production in the Standard Model as an example, and show that our theoretical QCD jet mass distributions can efficiently characterize the background via sideband analyses. We show that with 25 fb-1 of data, our approach allows us to resolve top-jets with pT _> 1 TeV, from the QCD background, and about 1.5 TeV top-jets with 100 fb-1, without relying on b-tagging. To further improve the significancewe consider jet shapes (recently analyzed in 0807.0234 [hep-ph]), which resolve thesubstructure of energy flow inside cone jets. A method of measuring the top quarkpolarization by using the transverse momentum of the bottom quark is also presented.The main advantages of our approach are: (i) the mass distributions are driven byfirst principle calculations, instead of relying solely on Monte Carlo simulation; (ii) for high pT jets (pT _> 1 TeV), IR-safe jet shape variables are robust against detectorresolution effects. Our analysis can be applied to other boosted massive particlessuch as the electroweak gauge bosons and the Higgs.

Almeida, L.G.; Lee, S.J.; Perez, G.; Sung, I.; Virzi, J.

2008-10-06

239

Controlling polar molecules in optical lattices  

SciTech Connect

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

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

2006-04-15

240

Cold collisions of complex polyatomic molecules  

NASA Astrophysics Data System (ADS)

We introduce a method for classical trajectory calculations to simulate collisions between atoms and large rigid asymmetric-top molecules. We investigate the formation of molecule-helium complexes in buffer-gas cooling experiments at a temperature of 6.5 K for molecules as large as naphthalene. Our calculations show that the mean lifetime of the naphthalene-helium quasi-bound collision complex is not long enough for the formation of stable clusters under the experimental conditions. Our results suggest that it may be possible to improve the efficiency of the production of cold molecules in buffer-gas cooling experiments by increasing the density of helium. In addition, we find that the shape of molecules is important for the collision dynamics when the vibrational motion of molecules is frozen. For some molecules, it is even more crucial than the number of accessible degrees of freedom. This indicates that by selecting molecules with suitable shape for buffer-gas cooling, it may be possible to cool molecules with a very large number of degrees of freedom.

Li, Zhiying; Heller, Eric J.

2012-02-01

241

Top quark production at the Tevatron  

SciTech Connect

The Fermilab Tevatron has, until recently, been the only accelerator with sufficient energy to produce top quarks. The CDF and D0 experiments have collected large samples of top quarks. We report on recent top quark production measurements of the single top and t{bar t} production cross sections, as well as studies of the t{bar t} invariant mass distribution and a search for highly boosted top quarks.

Varnes, Erich W.; /Arizona U.

2010-09-01

242

Top Quark Production at the Tevatron Collider  

SciTech Connect

Top quark physics has been a rich testing ground for the standard model since the top quark discovery in 1995. The large mass of top quark suggests that it could play a special role in searches for new phenomena. In this paper I provide an overview of recent top quark production cross section measurements from both CDF and D0 collaborations and also some new physics searches done in the top quark sector.

Li, Liang; /UC, Riverside

2011-07-01

243

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

NASA Astrophysics Data System (ADS)

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

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

2003-08-01

244

Symmetric Key Structural Residues in Symmetric Proteins with Beta-Trefoil Fold  

PubMed Central

To understand how symmetric structures of many proteins are formed from asymmetric sequences, the proteins with two repeated beta-trefoil domains in Plant Cytotoxin B-chain family and all presently known beta-trefoil proteins are analyzed by structure-based multi-sequence alignments. The results show that all these proteins have similar key structural residues that are distributed symmetrically in their structures. These symmetric key structural residues are further analyzed in terms of inter-residues interaction numbers and B-factors. It is found that they can be distinguished from other residues and have significant propensities for structural framework. This indicates that these key structural residues may conduct the formation of symmetric structures although the sequences are asymmetric.

Huang, Yanzhao; Xiao, Yi

2010-01-01

245

Bifurcations of symmetrical caustics: the creation-annihilation of two symmetric butterflies  

NASA Astrophysics Data System (ADS)

The problem of the bifurcations of symmetrical singularities is attacked in the case of the most simple symmetry. We show that the Lagrangian singularities invariant through the mirror symmetry may undergo two types of bifurcations involving butterflies. In both cases, a pair of symmetric butterflies is created or disappears. In addition, we give a concrete application of our results in the domain of geometrical optics.

Joets, A.; Ribotta, R.

2000-05-01

246

Ionization in symmetric and nearly symmetric low energy ion–surface collisions  

Microsoft Academic Search

Multiply charged ions are emitted following bombardment of Al(100) and Si(111) by low energy Si+ and P+ ions. The ion formation is attributed to inner-shell electron promotion during a hard collision between symmetric or nearly symmetric atomic species, followed by Auger decay outside the surface. The relative yield of triply charged Si ions for Si+?Si(111) is much smaller than that

X. Chen; Z. Sroubek; J. A. Yarmoff

2007-01-01

247

Formation of continuous platinum layer on top of an organic monolayer by electrochemical deposition followed by electroless deposition  

Microsoft Academic Search

A metal–molecule–metal sandwich structure is constructed to wire the molecule to external circuits. A continuous mono-atomic thick metallic layer of platinum is formed on top of a 1,4-benzenedimethanethiol (BDMT) self-assembled monolayer (SAM) on a Au(111) substrate through electrochemical deposition followed by electroless deposition (ELD). At first, about 1\\/3 monolayer of Pt is formed on top of the BDMT SAM by

Deyu Qu; Kohei Uosaki

2011-01-01

248

Conformal Operators from Spinor Fields - I: Symmetric Tensor Case.  

National Technical Information Service (NTIS)

The full system of conformal symmetric traceless tensor operators with minimal twist constructed from generalized free massless spinor fields is given. A series of symmetric tensor operators with higher twist and the simplest antisymmetric tensor operator...

V. K. Dobrev A. C. Ganchev O. I. Yordanov

1981-01-01

249

Thermoelectric Outer Planets Spacecraft (TOPS)  

NASA Technical Reports Server (NTRS)

The research and advanced development work is reported on a ballistic-mode, outer planet spacecraft using radioisotope thermoelectric generator (RTG) power. The Thermoelectric Outer Planet Spacecraft (TOPS) project was established to provide the advanced systems technology that would allow the realistic estimates of performance, cost, reliability, and scheduling that are required for an actual flight mission. A system design of the complete RTG-powered outer planet spacecraft was made; major technical innovations of certain hardware elements were designed, developed, and tested; and reliability and quality assurance concepts were developed for long-life requirements. At the conclusion of its active phase, the TOPS Project reached its principal objectives: a development and experience base was established for project definition, and for estimating cost, performance, and reliability; an understanding of system and subsystem capabilities for successful outer planets missions was achieved. The system design answered long-life requirements with massive redundancy, controlled by on-board analysis of spacecraft performance data.

1973-01-01

250

Single top at the Tevatron  

SciTech Connect

The authors review the status of the search for the electroweak production of single top quarks by the CDF and D0 collaborations at the Fermilab Tevatron proton-antiproton collider using Run II data. With a dataset of approximately 160 pb{sup -1} for CDF and 230 pb{sup -1} for D0, neither experiment finds evidence for single top production and sets 95% C.L. upper limits on the production cross-sections. The CDF limits are 10.1 pb for the t channel, 13.6 pb for the s channel and 17.8 pb for the combined production cross-sections of s and t channel. The D0 limits are 5.0 pb for the t channel, 6.4 pb for the s-channel production cross-sections. Both experiments investigate the prospect for a 3{sigma} evidence and a 5{sigma} discovery.

Taffard, Anyes; /Illinois U., Urbana

2005-11-01

251

Attitude propulsion technology for TOPS  

NASA Technical Reports Server (NTRS)

The thermoelectric outer planet spacecraft (TOPS) attitude propulsion subsystem (APS) effort is discussed. It includes the tradeoff rationale that went into the selection of an anhydrous hydrazine baseline system, followed by a discussion of the 0.22 N thruster and its integration into a portable, self-contained propulsion module that was designed, developed, and man rated to support the TOPS single-axis attitude control tests. The results of a cold-start feasibility demonstration with a modified thruster are presented. A description of three types of 0.44 thrusters that were procured for in-house evaluation is included along with the results of the test program. This is followed by a description of the APS feed system components, their evaluations, and a discussion of an evaluation of elastomeric material for valve seat seals. A list of new technology items which will be of value for application to future systems of this type is included.

Moynihan, P. I.

1972-01-01

252

Cloud Top Scanning radiometer (CTS)  

NASA Technical Reports Server (NTRS)

A scanning radiometer to be used for measuring cloud radiances in each of three spectral regions is described. Significant features incorporated in the Cloud Top Scanner design are: (1) flexibility and growth potential through use of easily replaceable modular detectors and filters; (2) full aperture, multilevel inflight calibration; (3) inherent channel registration through employment of a single shared field stop; and (4) radiometric sensitivity margin in a compact optical design through use of Honeywell developed (Hg,Cd)Te detectors and preamplifiers.

1978-01-01

253

Top quark results at CDF  

SciTech Connect

We present the latest results on the top quark obtained by the CDF experiment using a data sample of about 110 {ital pb}{sup -1} collected at the Fermilab Tevatron collider. We briefly describe the candidate events selection and then discuss the production cross section determination and the mass measurement. The study of two new decay channels (all hadronic and ``tau dilepton``) is also reported.

Leone, S. [Istituto Nazionale di Fisica Nucleare, Pisa (Italy); CDF Collaboration

1996-08-01

254

Multiscale technicolor and top production  

Microsoft Academic Search

Pair-production of heavy top quarks at the Tevatron Collider is significantly enhanced by the color-octet technipion, etaT, occuring in multiscale models of walking technicolor. We discuss ttrates for mt = 170 GeV and MetaT = 400-500GeV Multiscale models also have color-octet technirho states in the mass range 200-600 GeV that appear as resonances in dijet production and technipion pair-production.

Estia Eichten

1994-01-01

255

Top mass measurement at CDF  

SciTech Connect

We present the measurement of the top quark mass using L = 110 pb{sup -1} data sample of p{ovr p} collisions at {radical}s = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). We show the results for the different channels and discuss with some emphasis the determination of the systematic uncertainties. 7 refs., 10 figs., 5 tabs.

Rolli, S. [Istituto Nazionale di Fisica Nucleare, Pavia (Italy)]|[Lawrence Berkeley Lab., CA (United States); CDF Collaboration

1996-06-01

256

Observation of the Top Quark  

Microsoft Academic Search

he D0 Collaboration reports on a search for the standard model top quark in pp? collisions at ?s = 1.8 TeV at the Fermilab Tevatron with an integrated luminosity of approximately 50 pb^{-1}. We have searched for tt? production in the dilepton and single-lepton decay channels with and without tagging of b-quark jets. We observed 17 events with an expected

S. Abachi

1995-01-01

257

Parity-time-symmetric plasmonic metamaterials  

NASA Astrophysics Data System (ADS)

We theoretically investigate the optical properties of parity-time (PT)-symmetric three-dimensional metamaterials composed of strongly coupled planar plasmonic waveguides. By tuning the loss-gain balance, we show how the initially isotropic material becomes both asymmetric and unidirectional. Investigation of the band structure near the material's exceptional point reveals several interesting optical properties, including double negative refraction, Bloch power oscillations, unidirectional invisibility, and reflection and transmission coefficients that are simultaneously equal to or greater than unity. The highly tunable optical dispersion of PT-symmetric metamaterials provides a foundation for designing an unconventional class of three-dimensional bulk synthetic media, with applications ranging from lossless subdiffraction-limited optical lenses to nonreciprocal nanophotonic devices.

Alaeian, Hadiseh; Dionne, Jennifer A.

2014-03-01

258

Binary switching in a 'symmetric' potential landscape  

PubMed Central

A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a ‘symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a ‘symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature.

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-01-01

259

Binary switching in a 'symmetric' potential landscape.  

PubMed

A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a 'symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a 'symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature. PMID:24154561

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-01-01

260

Observational tests of baryon symmetric cosmology  

NASA Technical Reports Server (NTRS)

Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of Pi(O)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the gamma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurements of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed. Previously announced in STAR as N83-10996

Stecker, F. W.

1983-01-01

261

High energy concentration by symmetric shock focusing  

NASA Astrophysics Data System (ADS)

High-energy concentrations in gas are achieved experimentally in a specially constructed shock tube facility at KTH Mechanics. The high-energy concentration is manifested by a formation of a hot, light-emitting gas core. Experimental, numerical and theoretical investigations show that the shape of the imploding shock is of pivotal importance for the final energy concentration. Cylindrical shocks are unstable. Symmetric polygonal shocks are shown to be dynamically stable and are produced by various methods, e.g. thin wing profiles placed radially in the test section. Such symmetric polygonal shocks are able to produce extremely high energy levels at the focal point. Spectral data from 60 nanosecond short intervals of 8 microsecond light pulse give temperatures in the range of 6,000 K.

Apazidis, N.; Kjellander, M.; Tillmark, N.

2013-07-01

262

PT-symmetric representations of fermionic algebras  

SciTech Connect

A recent paper by Jones-Smith and Mathur, Phys. Rev. A 82, 042101 (2010) extends PT-symmetric quantum mechanics from bosonic systems (systems for which T{sup 2}=1) to fermionic systems (systems for which T{sup 2}=-1). The current paper shows how the formalism developed by Jones-Smith and Mathur can be used to construct PT-symmetric matrix representations for operator algebras of the form {eta}{sup 2}=0, {eta}{sup 2}=0, {eta}{eta}+{eta}{eta}={alpha}1, where {eta}={eta}{sup PT}=PT{eta}T{sup -1}P{sup -1}. It is easy to construct matrix representations for the Grassmann algebra ({alpha}=0). However, one can only construct matrix representations for the fermionic operator algebra ({alpha}{ne}0) if {alpha}=-1; a matrix representation does not exist for the conventional value {alpha}=1.

Bender, Carl M. [Physics Department, Washington University, St. Louis, Missouri 63130 (United States); Klevansky, S. P. [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 19, D-69120 Heidelberg (Germany)

2011-08-15

263

Observation of the top quark  

SciTech Connect

The D0 collaboration reports on a search for the Standard Model top quark in p{bar p} collisions at {radical}s = 1.8 TeV at the Femlilab Tevatron, with an integrated luminosity of approximately 50 pb{sup {minus}1}. We have searched for t{bar t} production in the dilepton and single-lepton decay channels, with and without tagging of b quark jets. We observe 17 events with an expected background of 3.8 {plus_minus} 0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2 {delta} 10{sup {minus}6} (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 199{sub {minus}21}{sup +19} (stat.) {plus_minus}22 (syst.) GeV/c{sup 2} and its production cross section to be 6.4 {plus_minus} 2.2 pb.

Thompson, J. [Maryland Univ., College Park, MD (United States); D0 Collaboration

1995-05-01

264

Observation of the top quark  

SciTech Connect

The D0 collaboration reports on a search for the Standard Model top quark in p{bar p} collisions at {radical}s = 1.8 TeV at the Fermilab Tevatron, with an integrated luminosity of approximately 50 pb{sup {minus}1}. We have searched for t{bar t} production in the dilepton and single lepton decay channels, with and without tagging of b quark jets. We observe 17 events with an expected background of 3.8 {plus_minus} 0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2 {times} 10{sup {minus}6} (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measure its mass to be 199{sub {minus}21}{sup +19} (stat.) {plus_minus}22 (syst.) GeV/c{sup 2} and its production cross section to be 6.4 {plus_minus} 2.2 pb.

Klima, B.; D0 Collaboration

1995-05-01

265

Compactly Supported Orthogonal Symmetric Scaling Functions  

Microsoft Academic Search

Daubechies (1988, Comm. Pure Appl. Math.41, 909–996) showed that, except for the Haar function, there exist no compactly supported orthogonal symmetric scaling functions for the dilation q = 2. Nevertheless, such scaling functions do exist for dilations q>2 (as evidenced by Chui and Lian's construction (1995, Appl. Comput. Harmon. Anal.2, 68–84) for q = 3); these functions are the main

Eugene Belogay; Yang Wang

1999-01-01

266

Symmetrically reduced Galileon equations and solutions  

NASA Astrophysics Data System (ADS)

The maximally complicated arbitrary-dimensional “maximal” Galileon field equations simplify dramatically for symmetric configurations. Thus, spherical symmetry reduces the equations from the D- to the two-dimensional (Monge-Ampere) equation, axial symmetry to its cubic extension, etc. We can then obtain explicit solutions, such as spherical or axial waves, and relate them to the (known) general, but highly implicit, lower-D solutions.

Deser, S.; Franklin, J.

2012-08-01

267

NONCOMMUTATIVE SYMMETRIC FUNCTIONS II: TRANSFORMATIONS OF ALPHABETS  

Microsoft Academic Search

Noncommutative analogues of classical operations on symmetric functions are investigated,and applied to the description of idempotents and nilpotents in descent algebras.Its is shown that any sequence of Lie idempotents (one in each descent algebra) givesrise to a complete set of indecomposable orthogonal idempotents of each descent algebra,and various deformations of the classical sequences of Lie idempotents are obtained. Inparticular, we

D. Krob; B. Leclerc; Y. Thibon

1997-01-01

268

Symmetrical Core Improves Micro-Fluxgate Sensors  

Microsoft Academic Search

Microfluxgate sensor with flat coil and double-sided symmetrical core has significantlyimproved parameters over the original asymmetric single-sided core design. The magneticcircuit of the new sensor is more closed and so the core is deeper saturated. The sensorhysteresis was decreased from 30 T to 2.5 T (for full range). Noise level was decreasedfrom 242 nT to 27 nT rms (0.1 mHz

A. Tipek; M. Ishida; S. Kawahito

269

Symmetrical core improves micro-fluxgate sensors  

Microsoft Academic Search

New micro-fluxgate sensor with flat excitation and sensing coils and double-sided symmetrical core has significantly improved parameters over the original asymmetric single-sided core design. The main advantage of the new design is that the demagnetization with respect to the excitation field is much lower than demagnetization with respect to the external measured field. The magnetic circuit of the new sensor

P. Ripka; S. O. Choi; A. Tipek; S. Kawahito; M. Ishida

2001-01-01

270

Scattering from a PT symmetric standing wave  

NASA Astrophysics Data System (ADS)

We study the Kapitza-Dirac diffraction of a free beam particle in the presence of a PT symmetric standing wave. We discuss that the momentum and total probability are not conserved in the non-Hermitian scattering process. We show that the average momentum gain/loss does not vanish over a period even if the non-Hermitian optical potential changes periodically in time. We give the resonance conditions at which large momentum transfer is produced.

Yuce, C.

2012-09-01

271

[Surgical reduction in benign symmetrical lipomatosis].  

PubMed

We report on a 50-year-old female patient suffering from benign symmetric lipomatosis of her upper arms, shoulders, neck, back, abdomen, and thighs. Concomitantly, we found hypertension, hyperuricemia, and hypertriglyceridemia. Since the patient complained of occasional pain in her upper arms and shoulders induced by work or pressure and suffered psychically from her deformity, we decided to reduce the fatty tissue of the upper arms surgically--with good cosmetic and functional results. PMID:2264376

Pfannschmidt, N; Jäger, K

1990-09-01

272

Static axially symmetric solutions in Nordtvedt's theory  

NASA Astrophysics Data System (ADS)

Static axially symmetric solutions in vacuum are obtained in the general scalar-tensor theory proposed by Nordtvedt. The solutions are asymptotically flat and under certain conditions give very large red shift. The asymptotic behavior and singularity are studied and a comparison is made with a corresponding solution with spherical symmetry. It is also observed that with a conformal transformation the Nordtvedt metric appears to reduce to the Brans-Dicke one.

Chatterjee, S.

1983-11-01

273

Active tokamak limiters; symmetrizing the edge plasma  

SciTech Connect

The surface layers of tokamak plasmas are strongly unstable to low frequency oscillations. The limiter, by imposing a non-axisymmetric state in the plasma scrape-off layer, may be the source of the free energy driving the instabilities. An active, two-faced sandwich limiter is proposed to symmetrize the scrape-off layer, thereby minimizing the mismatch between the inner and outer tokamak states.

Motley, R.W.

1981-02-01

274

High energy density dielectrics for symmetric Blumleins  

Microsoft Academic Search

Multilayer, tape cast ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (>106 J\\/m3) and physical size reduction. In particular, symmetric Blumleins are desired with the following properties: High voltage hold off (⩾300 kV); High, nondispersive permittivity: ≈100 to 900; Ability to be fabricated into various shapes and sizes;

W. Huebner; S. C. Zhang

2000-01-01

275

Cuspidality of symmetric powers with applications  

Microsoft Academic Search

The purpose of this paper is to prove that the symmetric fourth\\u000apower of a cusp form on ${\\\\rm GL}(2)$, whose existence was proved\\u000aearlier by the first author, is cuspidal unless the corresponding\\u000aautomorphic representation is of dihedral, tetrahedral, or octahedral\\u000atype. As a consequence, we prove a number of results toward the\\u000aRamanujan-Petersson and Sato-Tate conjectures. In particular,

Henry H. Kim; Freydoon Shahidi

2002-01-01

276

Highly symmetric travelling waves in pipe flow  

Microsoft Academic Search

The recent theoretical discovery of finite-amplitude travelling waves in pipe flow has re-ignited interest in the transitional phenomena that Osborne Reynolds studied 125 years ago. Despite all being unstable, these waves are providing fresh insight into the flow dynamics. Here we describe two new classes of highly-symmetric travelling waves (possessing rotational, shift-&-reflect and mirror symmetries) and report a new family

Chris C. T. Pringle; Yohann Duguet; Rich R. Kerswell

2009-01-01

277

Binding in Charged Spherically Symmetric Objects  

Microsoft Academic Search

We consider the subject of self-binding in static, spherically symmetric objects consisting of a charged fluid. We have shown\\u000a previously that in the case of a perfect fluid, only the localized part of the mass contributes to gravitational self-binding\\u000a of such objects and that in the limiting case of objects comprised purely of electromagnetic mass, there is no gravitational\\u000a binding.

Matthew Corne; Arkady Kheyfets; Jennifer Piasio; Chad Voegele

2011-01-01

278

Optical isolation via -symmetric nonlinear Fano resonances.  

PubMed

We show that Fano resonances created by two -symmetric nonlinear micro-resonators coupled to a waveguide, have line-shape and resonance position that depends on the direction of the incident light. We utilize these features in order to induce asymmetric transport, up to 47 dBs, in the optical C-window. Our theoretical proposal requires low input power and does not compromise the power or frequency characteristics of the output signal. PMID:24787845

Nazari, F; Bender, N; Ramezani, H; Moravvej-Farshi, M K; Christodoulides, D N; Kottos, T

2014-04-21

279

Cold collisions of complex polyatomic molecules  

NASA Astrophysics Data System (ADS)

We introduce a method for classical trajectory calculations to simulate collisions between atoms and large rigid asymmetric-top molecules. Using this method, we investigate the formation of molecule-helium complexes in buffer-gas cooling experiments at the temperature of 6.5 K for molecules as large as naphthalene. Our calculations show that the mean lifetime of the quasi-bound collision complex is not long enough for the formation of stable clusters under the experimental conditions. Our results suggest that it may be possible to improve the efficiency of the production of cold molecules in buffer-gas cooling experiments by increasing the density of helium. In addition, we find that the shape of molecules is important for the collision dynamics where molecular vibrational motions are frozen. For some molecules, it is even more crucial than the number of accessible degrees of freedom. This indicates that by selecting molecules with suitable shape for buffer-gas cooling, one could cool molecules with a very large number of degrees of freedom.

Li, Zhiying; Heller, Eric

2012-02-01

280

Quantum chemistry of confined systems: structure and vibronic spectra of a confined hydrogen molecule  

Microsoft Academic Search

Structure and spectral properties of the hydrogen molecule confined in a spherically symmetric harmonic oscillator potential were studied using the configuration interaction method. Increased strength of the confining potential exerts significant influence on the geometry of the molecule as well as on the vibronic transitions between the electronic ground and lowest excited singlet states. With increasing confinement strength the bond

Geerd H. F Diercksen; Mariusz Klobukowski

2001-01-01

281

Top condensation as a motivated explanation of the top forward-backward asymmetry  

NASA Astrophysics Data System (ADS)

Models of top condensation can provide both a compelling solution to the hierarchy problem as well as an explanation of why the top-quark mass is large. The spectrum of such models, in particular topcolor-assisted technicolor, includes top-pions, top-rhos and the top-Higgs, all of which can easily have large top-charm or top-up couplings. Large top-up couplings in particular would lead to a top forward-backward asymmetry through t-channel exchange, easily consistent with the Tevatron measurements. Intriguingly, there is destructive interference between the top-mesons and the standard model which conspire to make the overall top pair production rate consistent with the standard model. The rate for same-sign top production is also small due to destructive interference between the neutral top-pion and the top-Higgs. Flavor physics is under control because new physics is mostly confined to the top quark. In this way, top condensation can explain the asymmetry and be consistent with all experimental bounds. There are many additional signatures of topcolor with large tu mixing, such as top(s) + jet(s) events, in which a top and a jet reconstruct a resonance mass, which make these models easily testable at the LHC.

Cui, Yanou; Han, Zhenyu; Schwartz, Matthew D.

2011-07-01

282

Symmetric multilayer megampere X-pinch  

NASA Astrophysics Data System (ADS)

Raising the power of X-ray emission from an X-pinch by increasing the pinch current to the megampere level requires the corresponding increase in the initial linear mass of the load. This can be achieved by increasing either the number of wires or their diameter. In both cases, special measures should be undertaken to prevent the formation of a complicated configuration with an uncontrolled spatial structure in the region of wire crossing, because such a structure breaks the symmetry of the neck formed in the crossing region, destabilizes plasma formation, and degrades X-ray generation. To improve the symmetry of the wire crossing region, X-pinch configurations with a regular multilayer arrangement of wires in this region were proposed and implemented. The results of experiments with various symmetric X-pinch configurations on the COBRA facility at currents of ˜1MA are presented. It is shown that an X-pinch with a symmetric crossing region consisting of several layers of wires made of different materials can be successfully used in megampere facilities. The most efficient combinations of wires in symmetric multilayer X-pinches are found in which only one hot spot forms and that are characterized by a high and stable soft X-ray yield.

Shelkovenko, T. A.; Pikuz, S. A.; McBride, R. D.; Knapp, P. F.; Wilhelm, G.; Sinars, D. B.; Hammer, D. A.; Orlov, N. Yu.

2010-01-01

283

Chirally symmetric but confining dense, cold matter  

SciTech Connect

The folklore tradition about the QCD phase diagram is that at the chiral restoration phase transition at finite density hadrons are deconfined and there appears the quark matter. We address this question within the only known exactly solvable confining and chirally symmetric model. It is postulated within this model that there exists linear Coulomb-like confining interaction. The chiral symmetry breaking and the quark Green function are obtained from the Schwinger-Dyson (gap) equation while the color-singlet meson spectrum results from the Bethe-Salpeter equation. We solve this model at T=0 and finite chemical potential {mu} and obtain a clear chiral restoration phase transition at the critical value {mu}{sub cr}. Below this value the spectrum is similar to the previously obtained one at {mu}=0. At {mu}>{mu}{sub cr} the quarks are still confined and the physical spectrum consists of bound states which are arranged into a complete set of exact chiral multiplets. This explicitly demonstrates that a chirally symmetric matter consisting of confined but chirally symmetric hadrons at finite chemical potential is also possible in QCD. If so, there must be nontrivial implications for astrophysics.

Glozman, L. Ya.; Wagenbrunn, R. F. [Institute for Physics, Theoretical Physics Branch, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria)

2008-03-01

284

Technologies for nanofluidic systems: top-down vs. bottom-up - a review  

Microsoft Academic Search

This paper gives an overview of the most commonly used techniques for nanostructuring and nanochannel fabrication employed in nanofluidics. They are divided into two large categories: top-down and bottom-up methods. Top-down methods are based on patterning on large scale while reducing the lateral dimensions to the nanoscale. Bottom-up methods arrange atoms and molecules in nanostructures. Here, we review the advantages

D. Mijatovic; J. C. T. Eijkel; A. van den Berg

2005-01-01

285

Elliptical symmetric distribution based maximal margin classification for hyperspectral imagery  

Microsoft Academic Search

It has been verified that hyperspectral data is statistically characterized by elliptical symmetric distribution. Accordingly, we introduce the ellipsoidal discriminant boundaries and present an elliptical symmetric distribution based maximal margin (ESD-MM) classifier for hypespectral classification. In this method, the characteristic of elliptical symmetric distribution (ESD) of hyperspectral data is combined with the maximal margin rule. This strategy enables the ESD-MM

Lin He; Zhuliang Yu; Zhenghui Gu; Yuanqing Li

2011-01-01

286

Symmetrical perturbation analysis of complex two-dimensional photonic crystals  

Microsoft Academic Search

We study complex photonic crystals with unit cells that include different dielectric cylinders. A symmetrical perturbation approach is developed here which predicts how the band spectrum of the complex structures evolves from the most symmetrical prophase. As a specific example, we apply this symmetrical approach to the analysis of square lattices with alternating layers of dielectric cylinders perpendicular to one

N. Malkova; S. Kim; V. Gopalan

2002-01-01

287

Radionuclides and carrier molecules for therapy  

NASA Astrophysics Data System (ADS)

Although radionuclide therapy has been around for a long time, this modality of cancer treatment has been limited mainly to the use of [TOP"/>]-phosphate and [TOP"/>]-sodium iodide. The last few years, however, have seen an increased interest in this area due to new developments of radionuclides and carrier molecules that may provide selective targeting of tumour sites. The potential of this technique can be further realized if the radionuclide is carefully selected to match both the localization of the carrier molecule and tumour morphology. This paper briefly reviews radionuclides in current use and potential candidates for targeted therapy. Decay characteristics, production methods and relevant chemical properties are discussed.

Zweit, Jamal

1996-10-01

288

Formation of molecular bundles from self-assembly of symmetrical poly(oxyalkylene)-diamido acids.  

PubMed

Sodium salts of poly(oxypropylene)-trimellitic amido acid (POP-amido acid), prepared from the reaction of POP-diamines and trimellitic anhydride, were found to self-assemble into orderly molecular bundles. The POP-amido acid has a symmetrical structure consisting of a hydrophobic POP middle block (2000 g/mol) and four symmetrical carboxyl end groups. By dissolving in water and evaporating on a polyether sulfone film, the POP-amido acid molecules self-assembled into a unique array with average dimensions of 7-13 nm in width, 2-5 nm in height, and 20-50 nm in length, observed by atomic force microscope. Varied morphologies were also observed when varying the pH, solvents, evaporating rate, concentration, and substrate surface. Unlike the common surfactants of single head-to-tail structure and the naturally occurring phospholipids of one head and two tails, the synthesized POP derivative is a symmetrical structure of four hydrophilic heads and one long hydrophobic block. Through the complementary noncovalent bonding forces, the molecules tend to align into molecular bundles or loops as the primary structure. The formation of different morphologies is controlled by the intermolecular forces including hydrogen bonding, aromatic pi-pi stacking, ionic charge, and hydrophobic interaction, in a concerted manner. PMID:16852689

Wang, Chi-He Stephen; Tsai, Wei-Cheng; Wei, Kuan-Liang; Lin, Jiang-Jen

2005-07-21

289

Liquid crystals of disc-like molecules  

Microsoft Academic Search

Thermotropic mesomorphism has been observed in pure compounds consisting of simple disc-like molecules, viz., benzene-hexa-n-alkanoates. Thermodynamic, optical and x-ray studies indicate that the mesophase is a highly ordered lamellar type of liquid\\u000a crystal. Based on the x-ray data, a structure is proposed in which the discs are stacked one on top of the other in columns\\u000a that constitute a hexagonal

S. Chandrasekhar; B K Sadashiva; K A Suresh

1977-01-01

290

Water Molecule Residence Times  

NSDL National Science Digital Library

How long will a molecule of Water stay in a particular reservoir? What is the average time a molecule of Water will stay in an ocean? What is the average time a molecule of water will stay in a river? A lake? As groundwater? A glacier? How long will a water vapor molecule stay suspended in the atmosphere? Why is the residence ...

Science, Sill -.

2010-11-16

291

Physics of Molecules  

NASA Astrophysics Data System (ADS)

Many varieties of molecule have been detected in the Milky Way and in other galaxies. The processes by which these molecules are formed and destroyed are now broadly understood (see INTERSTELLAR CHEMISTRY). These molecules are important components of galaxies in two ways. Firstly, radiation emitted by molecules enables us to trace the presence of diffuse gas, to infer its physical properties and ...

Williams, D.; Murdin, P.

2000-11-01

292

Evidence for production of single top quarks  

Microsoft Academic Search

We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p pmacr collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top-quark partner that is always produced from strong-coupling processes. Top quarks were first observed

V. M. Abazov; B. Abbott; M. Abolins; B. S. Acharya; M. Adams; T. Adams; E. Aguilo; S. H. Ahn; M. Ahsan; G. D. Alexeev; G. Alkhazov; A. Alton; G. Alverson; G. A. Alves; M. Anastasoaie; L. S. Ancu; T. Andeen; S. Anderson; M. S. Anzelc; M. Aoki; Y. Arnoud; M. Arov; M. Arthaud; A. Askew; B. Åsman; A. C. S. Assis Jesus; O. Atramentov; C. Avila; C. Ay; F. Badaud; A. Baden; L. Bagby; B. Baldin; D. V. Bandurin; P. Banerjee; S. Banerjee; E. Barberis; A.-F. Barfuss; P. Bargassa; P. Baringer; J. F. Bartlett; U. Bassler; D. Bauer; S. Beale; A. Bean; M. Begalli; M. Begel; C. Belanger-Champagne; L. Bellantoni; A. Bellavance; J. A. Benitez; S. B. Beri; G. Bernardi; R. Bernhard; I. Bertram; M. Besançon; R. Beuselinck; V. A. Bezzubov; P. C. Bhat; V. Bhatnagar; C. Biscarat; G. Blazey; F. Blekman; S. Blessing; D. Bloch; K. Bloom; A. Boehnlein; D. Boline; T. A. Bolton; E. E. Boos; G. Borissov; T. Bose; A. Brandt; R. Brock; G. Brooijmans; A. Bross; D. Brown; N. J. Buchanan; D. Buchholz; M. Buehler; V. Buescher; V. Bunichev; S. Burdin; S. Burke; T. H. Burnett; C. P. Buszello; J. M. Butler; P. Calfayan; S. Calvet; J. Cammin; W. Carvalho; B. C. K. Casey; H. Castilla-Valdez; S. Chakrabarti; D. Chakraborty; K. M. Chan; A. Chandra; F. Chevallier; E. Cheu; D. K. Cho; S. Choi; B. Choudhary; L. Christofek; T. Christoudias; S. Cihangir; D. Claes; Y. Coadou; M. Corcoran; W. E. Cooper; M.-C. Cousinou; F. Couderc; S. Crépé-Renaudin; D. Cutts; M. Cwiok; H. da Motta; A. Das; G. Davies; K. de; S. J. de Jong; E. de La Cruz-Burelo; C. de Oliveira Martins; J. D. Degenhardt; F. Déliot; M. Demarteau; R. Demina; D. Denisov; S. P. Denisov; S. Desai; H. T. Diehl; M. Diesburg; A. Dominguez; H. Dong; L. V. Dudko; L. Duflot; S. R. Dugad; D. Duggan; A. Duperrin; J. Dyer; A. Dyshkant; M. Eads; D. Edmunds; J. Ellison; V. D. Elvira; Y. Enari; S. Eno; P. Ermolov; H. Evans; A. Evdokimov; V. N. Evdokimov; A. V. Ferapontov; T. Ferbel; F. Fiedler; F. Filthaut; W. Fisher; H. E. Fisk; M. Fortner; H. Fox; S. Fu; S. Fuess; T. Gadfort; C. F. Galea; E. Gallas; C. Garcia; A. Garcia-Bellido; V. Gavrilov; P. D. Grannis; W. Geist; D. Gelé; C. E. Gerber; Y. Gershtein; D. Gillberg; G. Ginther; N. Gollub; B. Gómez; A. Goussiou; H. Greenlee; Z. D. Greenwood; E. M. Gregores; G. Grenier; Ph. Gris; J.-F. Grivaz; A. Grohsjean; S. Grünendahl; M. W. Grünewald; F. Guo; J. Guo; G. Gutierrez; P. Gutierrez; A. Haas; N. J. Hadley; P. Haefner; S. Hagopian; J. Haley; I. Hall; R. E. Hall; L. Han; K. Harder; A. Harel; R. Harrington; J. M. Hauptman; R. Hauser; J. Hays; T. Hebbeker; D. Hedin; J. G. Hegeman; J. M. Heinmiller; A. P. Heinson; U. Heintz; C. Hensel; K. Herner; G. Hesketh; M. D. Hildreth; R. Hirosky; J. D. Hobbs; B. Hoeneisen; H. Hoeth; M. Hohlfeld; S. J. Hong; S. Hossain; P. Houben; Y. Hu; Z. Hubacek; V. Hynek; I. Iashvili; R. Illingworth; A. S. Ito; S. Jabeen; M. Jaffré; S. Jain; K. Jakobs; C. Jarvis; R. Jesik; K. Johns; C. Johnson; M. Johnson; A. Jonckheere; P. Jonsson; A. Juste; E. Kajfasz; A. M. Kalinin; J. M. Kalk; S. Kappler; D. Karmanov; P. A. Kasper; I. Katsanos; D. Kau; V. Kaushik; R. Kehoe; S. Kermiche; N. Khalatyan; A. Khanov; A. Kharchilava; Y. M. Kharzheev; D. Khatidze; T. J. Kim; M. H. Kirby; M. Kirsch; B. Klima; J. M. Kohli; J.-P. Konrath; V. M. Korablev; A. V. Kozelov; J. Kraus; D. Krop; T. Kuhl; A. Kumar; A. Kupco; T. Kurca; J. Kvita; F. Lacroix; D. Lam; S. Lammers; G. Landsberg; P. Lebrun; W. M. Lee; A. Leflat; J. Lellouch; J. Leveque; J. Li; L. Li; Q. Z. Li; S. M. Lietti; J. G. R. Lima; D. Lincoln; J. Linnemann; V. V. Lipaev; R. Lipton; Y. Liu; Z. Liu; A. Lobodenko; M. Lokajicek; P. Love; H. J. Lubatti; R. Luna; A. L. Lyon; A. K. A. Maciel; D. Mackin; R. J. Madaras; P. Mättig; C. Magass; A. Magerkurth; P. K. Mal; H. B. Malbouisson; S. Malik; V. L. Malyshev; H. S. Mao; Y. Maravin; B. Martin; R. McCarthy; A. Melnitchouk; L. Mendoza; P. G. Mercadante; M. Merkin; K. W. Merritt; A. Meyer; J. Meyer; T. Millet; J. Mitrevski; J. Molina; R. K. Mommsen; N. K. Mondal; R. W. Moore; T. Moulik; G. S. Muanza; M. Mulders; M. Mulhearn; O. Mundal; L. Mundim; E. Nagy; M. Naimuddin; M. Narain; N. A. Naumann; H. A. Neal; J. P. Negret; P. Neustroev; H. Nilsen; H. Nogima; S. F. Novaes; T. Nunnemann; V. O'Dell; D. C. O'Neil; G. Obrant; C. Ochando; D. Onoprienko; N. Oshima; N. Osman; J. Osta; R. Otec; G. J. Otero Y Garzón; M. Owen; P. Padley; M. Pangilinan; N. Parashar; S.-J. Park; S. K. Park; J. Parsons; R. Partridge; N. Parua; A. Patwa; G. Pawloski; B. Penning; M. Perfilov; K. Peters; Y. Peters; P. Pétroff; M. Petteni; R. Piegaia; J. Piper; M.-A. Pleier; P. L. M. Podesta-Lerma; V. M. Podstavkov; Y. Pogorelov; M.-E. Pol; P. Polozov; B. G. Pope; A. V. Popov; C. Potter; W. L. Prado da Silva; H. B. Prosper; S. Protopopescu; J. Qian; A. Quadt; B. Quinn; A. Rakitine; M. S. Rangel; K. Ranjan; P. N. Ratoff; P. Renkel; S. Reucroft; P. Rich; J. Rieger

2008-01-01

293

Heavy flavour physics from top to bottom  

SciTech Connect

We review the status of heavy flavour physics at the Fermilab Tevatron collider by summarizing recent top quark and B physics results from CDF and D0. In particular we discuss the measurement of the top quark mass and top production cross section as well as B meson lifetimes and time dependent B{bar B} mixing results. An outlook of perspectives for top and B physics in Run II starting in 1999 is also given. 38 refs., 23 figs., 8 tabs.

Paulini, M. [Lawrence Berkeley National Lab., CA (United States); CDF and D0 Collaborations

1997-01-01

294

Heavy flavour physics from top to bottom  

SciTech Connect

We review the status of heavy flavour physics at the Fermilab Tevatron collider by summarizing recent top quark and B physics results from CDF and D0. In particular we discuss the measurement of the top quark mass and top production cross section as well as B meson lifetimes and time dependent B{anti B} mixing results. An outlook of perspectives for top and B physics in Run II starting in 1999 is also given.

Paulini, M. [Lawrence Berkeley National Lab., CA (United States); CDF and D0 Collaboration

1998-02-01

295

Cloud-top parameters - A hail indicator  

NASA Technical Reports Server (NTRS)

Airborne photographic observations of four hail-producing storms are discussed. With the exception of one storm producing a tornadic event, the overshooting tops were nearly steady-state. The tops were consistently high and wide, reaching maximum heights within about 5 minutes of the initiation of hail. Measured updraft velocities in the turrets composing the overshooting top were 25 m/sec. The dimensions of the overshooting tops were sufficiently large to permit satellite observation.

Pearl, E. W.; Shenk, W. E.; Skillman, W.

1975-01-01

296

Spinning a pseudorotating molecular top by means of a circularly polarized infrared laser pulse: Quantum simulations for 114CdH 2  

NASA Astrophysics Data System (ADS)

A circularly polarized infrared (IR) laser pulse which propagates along the axis of a pre-aligned linear polyatomic molecule may excite unidirectional pseudorotations corresponding to excitation of the molecular bend and rotation of the bent molecule around that axis. This preparation and spinning a molecular top is, in part, analogous to the generation of unidirectional electron circulation in molecules by means of circularly polarized ultraviolet (UV) laser pulses [I. Barth, J. Manz, Angew. Chem. 118 (2006) 3028; Angew. Chem., Int. Ed. 45 (2006) 2962], allowing to apply similar methods for the laser driven wavepacket dynamics. It is demonstrated here by means of quantum simulations of the laser driven wavefunction ?(t) of the model system 114CdH(X1?g+), where ?(t) is expanded in terms of vibrational eigenfunctions ?vl which are labeled by quantum numbers v,l=(vs=0,vbl,va=0) for the vibrations ( v) including the symmetric stretch ( s), bend ( b), antisymmetric stretch ( a), and for the pseudorotation ( l). The corresponding vibrational and pseudorotational eigenenergies and matrix elements for the model 114CdH are adapted as approximations from accurate values which have been determined previously, for simulations of high resolution IR spectra. These dipole matrix elements and related selection or propensity rules imply dominant ladder climbing vbl=00?11?22?⋯ or 00?1-1?2-2?⋯, i.e., sequential populations of the states with increasing quantum numbers for the bends and pseudorotations vbl, where l=+vb or l=-vb depending on the right (+) or left (-) circular polarization of the IR laser pulse, respectively.

Barth, Ingo; Manz, Jörn; Sebald, Peter

2008-05-01

297

Observation of a single proton transfer fluorescence in a biaxially symmetric dihydroxy diflavonol  

NASA Astrophysics Data System (ADS)

The proton transfer (PT) emission of the diflavonol molecule 2,8-diphenyl-3,7-dihydroxy-4H,6H-pyrano[3,2-g]-chromene-4,6-dione (D3HF) is reported for the first time. The D3HF molecule possesses a chemical structure almost equivalent to two 3-hydroxyflavone molecules symmetrically condensed on one-benzene ring. Thus, D3HF contains two five-membered intramolecular hydrogen bonds (IMHB), and it may undergo double-PT. The discovery via experiments of the D3HF PT emission conforms to the theoretical finding, by using time-dependent (TD) density functional theory (DFT) (with the B3LYP hybrid functional), of a stable single PT tautomer either in the first excited electronic state (S 1) or in the ground electronic state. In the S 1 state, once the first single PT process occurs, the second one is hindered.

Falkovskaia, Elena; Pivovarenko, Vasyl G.; del Valle, Juan Carlos

2002-02-01

298

D0 findings on the top quark.  

National Technical Information Service (NTIS)

Recent results on top quark physics with the D0 experiment in pp collisions at (radical)s = 1.8 TeV are reported. The direct measurement of the top quark mass uses single lepton and dilepton events, giving the result m(sub top) = 172.1 (+-) 7.1 GeV/c(sup ...

B. Klima

1998-01-01

299

In Praise of Top-Down Leadership  

ERIC Educational Resources Information Center

In the ongoing debate of the efficacy of top-down versus bottom-up strategies to improve school districts, top-down is clearly losing. Many district leaders are reluctant to champion improvement for fear of being labeled with the epithet "top-down leader," the unkindest cut of all. In this article, the author presents the change processes in three…

Dufour, Richard

2007-01-01

300

Top-down cellular pyramids  

SciTech Connect

A cellular pyramid is an exponentially tapering stack of arrays of processors ('cells'), where each cell is connected to its neighbors ('siblings') on its own level, to a 'parent' on the level above, and to its 'children' on the level below. It is shown that in some situations, if information flows top-down only, from fathers to sons, then a cellular pyramid may be no faster than a one-level cellular array; but it may be possible to use simpler cells in the pyramid case.

Wu, A.Y.; Rosenfeld, A.

1982-07-01

301

MHD Integrated Topping Cycle Project  

SciTech Connect

This eighteenth quarterly technical progress report of the MHD Integrated Topping cycle Project presents the accomplishments during the period November 1, 1991 to January 31, 1992. The precombustor is fully assembled. Manufacturing of all slagging stage components has been completed. All cooling panels were welded in place and the panel/shell gap was filled with RTV. Final combustor assembly is in progress. The low pressure cooling subsystem (LPCS) was delivered to the CDIF. Second stage brazing issues were resolved. The construction of the two anode power cabinets was completed.

Not Available

1992-07-01

302

Top quark physics at CDF  

SciTech Connect

We present preliminary results on top quark physics recently obtained by the CDF collaboration. The data sample consists of 110 {ital pb}{sup -1} of {ital p{anti p}} collisions at {radical}{ital s} = 1.8 TeV, collected with the Collider Detector at Fermilab during the period 1992 - 1995. We report on the {ital t{anti t}} production cross section and on the top quark mass. The measurements are made in three topologies, corresponding to the decay modes of the {ital Wb} pairs in the final state: lepton + multi-jets, dilepton and all hadronic final state. The analysis performed on the single lepton sample yields the most accurate measurements, due to the good acceptance and the favorable signal to noise ratio obtained after applying some b-tagging techniques. In this channel we measure: {sigma}{sub {ital t{anti t}}} = 6.8{sup +2.3}{sub -1.8} pb M{sub {ital t}} = 175.6 {+-} 5.7 ({ital stat}) {+-} 7.1 ({ital syst.}) {ital GeV/c{sup 2}} Combining the cross sections measured with the lepton + multi-jet and dilepton data we obtain: {sigma}{sub {ital t{anti t}}} = 7.5{sup +1.9}{sub -1.6} {ital pb} A preliminary investigation of the production mechanism of the {ital t{anti t}} system is shown and compared to Standard Model expectations.

Caner, A. [European Organization for Nuclear Research, Geneva (Switzerland). PPE Div.; CDF Collaboration

1996-08-01

303

MHD Integrated Topping Cycle Project  

SciTech Connect

The overall objective of the project is to design and construct prototypical hardware for an integrated MHD topping cycle, and conduct long duration proof-of-concept tests of integrated system at the US DOE Component Development and Integration Facility in Butte, Montana. The results of the long duration tests will augment the existing engineering design data base on MHD power train reliability, availability, maintainability, and performance, and will serve as a basis for scaling up the topping cycle design to the next level of development, an early commercial scale power plant retrofit. The components of the MHD power train to be designed, fabricated, and tested include: A slagging coal combustor with a rated capacity of 50 MW thermal input, capable of operation with an Eastern (Illinois {number sign}6) or Western (Montana Rosebud) coal, a segmented supersonic nozzle, a supersonic MHD channel capable of generating at least 1.5 MW of electrical power, a segmented supersonic diffuser section to interface the channel with existing facility quench and exhaust systems, a complete set of current control circuits for local diagonal current control along the channel, and a set of current consolidation circuits to interface the channel with the existing facility inverter.

Not Available

1992-01-01

304

Exploring Rotation-Vibration Coupling in Highly Fluxional Molecules Using Surface Hopping Diffusion Monte Carlo  

NASA Astrophysics Data System (ADS)

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).

Petit, Andrew S.; McCoy, Anne B.

2012-06-01

305

Expanding symmetric multiprocessor capability through gang scheduling  

SciTech Connect

Symmetric Multiprocessor (SMP) systems normally provide both space- sharing and time-sharing to insure high system utilization and good responsiveness. However the prevailing lack of concurrent scheduling for parallel programs precludes SMP use in addressing many large-scale problems. Tightly synchronized communications are impractical and normal time-sharing reduces the benefit of cache memory. Evidence gathered at Lawrence Livermore National Laboratory (LLNL) indicates that gang scheduling can increase the capability of SMP systems and parallel program performance without adverse impact upon system utilization or responsiveness.

Jette, M.A.

1998-03-01

306

Bilateral symmetric stress fractures in a toddler.  

PubMed

Stress fractures are a common injury among adolescent athletes and military recruits. The increase in child participation in organized sport activities has contributed to the inclusion of the skeletally immature age group among those who may suffer from this problem. Bilateral simultaneous symmetric tibial stress fractures that are infrequent in older children are even more rare in toddlers. This entity may cause a diagnostic problem as it must be differentiated from infectious disease, acute trauma or even from the result of a battered child. PMID:11269816

Keret, D; Segev, E; Hayek, S; Lokiec, F; Wientroub, S

2001-01-01

307

Polarization aberrations. 1. Rotationally symmetric optical systems.  

PubMed

The polarization in isotropic radially symmetric lens and mirror systems in the paraxial approximation is examined. Polarized aberrations are variations in the phase, amplitude, and polarization state of the electromagnetic field across the exit pupil. Some are dependent on the incident polarization state and some are not. Expressions through fourth order for phase, amplitude, linear diattenuation, and linear retardance aberrations are derived in terms of the chief and marginal ray angles of incidence and the Taylor series expansion coefficients of the Fresnel equations for reflection and transmission at uncoated and thin-film-coated interfaces. Applications to polarization ray tracing are discussed. PMID:20935891

McGuire, J P; Chipman, R A

1994-08-01

308

Design of spherical symmetric gradient index lenses  

NASA Astrophysics Data System (ADS)

Spherical symmetric refractive index distributions also known as Gradient Index lenses such as the Maxwell-Fish-Eye (MFE), the Luneburg or the Eaton lenses have always played an important role in Optics. The recent development of the technique called Transformation Optics has renewed the interest in these gradient index lenses. For instance, Perfect Imaging within the Wave Optics framework has recently been proved using the MFE distribution. We review here the design problem of these lenses, classify them in two groups (Luneburg moveable-limits and fixed-limits type), and establish a new design techniques for each type of problem.

Miñano, Juan C.; Grabovi?ki?, Dejan; Benítez, Pablo; González, Juan C.; Santamaría, Asunción

2012-10-01

309

Scattering in PT-symmetric quantum mechanics  

SciTech Connect

A general formalism is worked out for the description of one-dimensional scattering in non-hermitian quantum mechanics and constraints on transmission and reflection coefficients are derived in the cases of P, T or PT invariance of the Hamiltonian. Applications to some solvable PT-symmetric potentials are shown in detail. Our main original results concern the association of reflectionless potentials with asymptotic exact PT symmetry and the peculiarities of separable kernels of non-local potentials in connection with Hermiticity, T invariance and PT invariance.

Cannata, Francesco [Istituto Nazionale di Fisica Nucleare, Sezione di Bologna and Dipartimento di Fisica dell' Universita, Via Irnerio 46, I 40126 Bologna (Italy)]. E-mail: Francesco.Cannata@bo.infn.it; Dedonder, Jean-Pierre [GMPIB Universite Paris 7 - Denis-Diderot, 2 Place Jussieu, F-75251, Paris Cedex 05 (France)]. E-mail: dedonder@paris7.jussieu.fr; Ventura, Alberto [Ente Nuove Tecnologie, Energia e Ambiente, Bologna and Istituto Nazionale di Fisica Nucleare, Sezione di Bologna (Italy)]. E-mail: Alberto.Ventura@bologna.enea.it

2007-02-15

310

Complex extensions of semisimple symmetric spaces  

Microsoft Academic Search

Let G\\/H be a pseudo-Riemannian semisimple symmetric space. The tangent bundle T(G\\/H) contains a maximal G-invariant neighbourhood ? of the zero section where the adapted-complex structure exists. Such ? is endowed with a canonical\\u000a G-invariant pseudo-Kähler metric of the same signature as the metric on G\\/H. We use the polar map to define a G-invariant pseudo-Kähler metric on distinguished G-invariant

Laura Geatti

2006-01-01

311

Projective normality of complete symmetric varieties  

Microsoft Academic Search

We prove that in characteristic zero the multiplication of\\u000asections of line bundles generated by global sections on a\\u000acomplete symmetric variety X=\\\\overline{G\\/H}\\u000ais a surjective map.\\u000aAs a consequence, the cone defined by a complete linear system\\u000aover $X$ or over a closed $G$ -stable subvariety of $X$ is normal.\\u000aThis gives an affirmative answer to a question raised

Andrea Maffei

2004-01-01

312

Time-symmetric quantum theory of smoothing.  

PubMed

Smoothing is an estimation technique that takes into account both past and future observations and can be more accurate than filtering alone. In this Letter, a quantum theory of smoothing is constructed using a time-symmetric formalism, thereby generalizing prior work on classical and quantum filtering, retrodiction, and smoothing. The proposed theory solves the important problem of optimally estimating classical Markov processes coupled to a quantum system under continuous measurements, and is thus expected to find major applications in future quantum sensing systems, such as gravitational wave detectors and atomic magnetometers. PMID:19659059

Tsang, Mankei

2009-06-26

313

Hoop conjecture in spherically symmetric spacetimes  

SciTech Connect

We give general sufficient conditions for the existence of trapped surfaces due to concentration of matter in spherically symmetric initial data sets satisfying the dominant energy condition. These results are novel in that they apply and are meaningful for arbitrary spacelike slices, that is, they do not require any auxiliary assumptions such as maximality, time symmetry, or special extrinsic foliations, and most importantly they can easily be generalized to the nonspherical case once an existence theory for a modified version of the Jang equation is developed. Moreover, our methods also yield positivity and monotonicity properties of the Misner-Sharp energy.

Khuri, Marcus A. [Department of Mathematics, Stony Brook University, Stony Brook, New York 11794 (United States)

2009-12-15

314

Benchmarking an even better top tagger algorithm  

NASA Astrophysics Data System (ADS)

Top taggers are established analysis tools used to reconstruct boosted hadronically decaying top quarks, for example, in searches for heavy resonances. We first present a dedicated study of signal efficiency versus background rejection, allowing for an improved choice of working points. Next, we determine to what degree our mass drop selection can be improved by systematically including angular correlations between subjets or N-subjettiness. Finally, we extend the reach of the top tagger to transverse momenta below the top mass. This momentum range will be crucial in searches for the associated production of a Higgs boson with top quarks.

Anders, Christoph; Bernaciak, Catherine; Kasieczka, Gregor; Plehn, Tilman; Schell, Torben

2014-04-01

315

Measurements of top quark properties at CDF  

SciTech Connect

The top quark with its mass of about 172 GeV/c{sup 2} is the most massive fundamental particle observed by experiment. In this talk they highlight the most recent measurements of several top quark properties performed with the CDF detector based on data samples corresponding to integrated luminosities up to 1 fb{sup -1}. These results include a search for top quark pair production via new massive resonances, measurements of the helicity of the W boson from top-quark decay, and a direct limit on the lifetime of the top quark.

Kraan, Aafke C.; /Pennsylvania U.

2006-11-01

316

Matrix isolation ESR spectroscopy and magnetic anisotropy of D{sub 3h} symmetric septet trinitrenes  

SciTech Connect

The fine-structure (FS) parameters D of a series of D{sub 3h} symmetric septet trinitrenes were analyzed theoretically using density functional theory (DFT) calculations and compared with the experimental D values derived from ESR spectra. ESR studies show that D{sub 3h} symmetric septet 1,3,5-trichloro-2,4,6-trinitrenobenzene with D=-0.0957 cm{sup -1} and E= 0 cm{sup -1} is the major paramagnetic product of the photolysis of 1,3,5-triazido-2,4,6-trichlorobenzene in solid argon matrices at 15 K. Trinitrenes of this type display in the powder X-band ESR spectra intense Z{sub 1}-transition at very low magnetic fields, the position of which allows one to precisely calculate the parameter D of such molecules. Thus, our revision of the FS parameters of well-known 1,3,5-tricyano-2,4,6-trinitrenobenzene [E. Wasserman, K. Schueller, and W. A. Yager, Chem. Phys. Lett. 2, 259 (1968)] shows that this trinitrene has Double-Vertical-Line D Double-Vertical-Line = 0.092 cm{sup -1} and E= 0 cm{sup -1}. DFT calculations reveal that, unlike C{sub 2v} symmetric septet trinitrenes, D{sub 3h} symmetric trinitrenes have the same orientations of the spin-spin coupling tensor D-caret{sub SS} and the spin-orbit coupling tensor D-caret{sub SOC} and, as a result, have negative signs for both the D{sub SS} and D{sub SOC} values. The negative magnetic anisotropy of septet 2,4,6-trinitrenobenzenes is considerably strengthened on introduction of heavy atoms in the molecules, owing to an increase in contributions of various excitation states to the D{sub SOC} term.

Misochko, Eugenii Ya.; Akimov, Alexander V.; Masitov, Artem A.; Korchagin, Denis V.; Aldoshin, Sergei M.; Chapyshev, Sergei V. [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region 142432 (Russian Federation)

2013-05-28

317

Three-Dimensional Solutions for Contact Area in Laminated Composite Pinned Joints with Symmetric and Non-Symmetric Stacking Sequences  

NASA Astrophysics Data System (ADS)

The aim of this study is computing and evaluating the behavior of the laminated composite plate at the contact area in single lap, mechanically fastened joints. The analyses involve three dimensional finite element models performed by ABAQUS 6.4-PR11 code to evaluate the stress distribution in contact surface, separation angle, the magnitude and location of maximum radial stress. Results are determined for composite laminates with different layer configurations and attempts are made to validate the models with previous works. For cross ply and angle ply configurations only symmetric stacking sequences are used while for quasi-isotropic laminate both symmetric and non-symmetric models are generated. In cross-ply laminate symmetric separation about bearing plane could be found while in quasi-isotropic and angle-ply laminates non-symmetric separation occurs. Also, the separation angle is less than 90° in symmetric laminates and greater than 90° in some plies of non-symmetric laminates.

Javadi, H.; Rajabi, I.; Yavari, V.; Kadivar, M. H.

318

The Top American Research Universities 2001  

NSDL National Science Digital Library

An updated version of The Top American Research Universities has been released from Florida-based research organization, The Center, which creates this report annually. (The first edition of the Top American Research Universities was included in the July 28, 2000 Scout Report.) Institutions considered "top" are those that have federal research expenditures as reported to NSF of at least $20 million and that fall within the top 25 on at least one of The Center's nine measures (total research expenditures, federal research expenditures, endowment assets, annual giving, faculty members in the National Academies, faculty awards, doctoral degrees, postdoctoral appointees, and entering freshmen SAT scores). This year, the study has been expanded to include national rankings and to include institutions ranked in the top 26-50 (in addition to those ranked in top 25). The data are available in .pdf or spreadsheet (.xls) format. Interestingly, the top ten are all private universities.

2001-01-01

319

Partial symmetrization of the photosynthetic reaction center  

SciTech Connect

The bacterial photosynthetic reaction center (RC) is a pigmented intrinsic membrane protein that performs the primary charge separation event of photosynthesis, thereby converting light to chemical energy. The RC pigments are bound primarily by two homologous peptides, the L and M subunits, each containing five transmembrane helices. These {alpha} helices and pigments are arranged in an approximate C{sub 2} symmetry and form two possible electron transfer pathways. Only one of these pathways is actually used. In an attempt to identify nonhomologous residues that are responsible for functional differences between the two branches, homologous helical regions that interact extensively with the pigments were genetically symmetrized (that is, exchanged). For example, replacement of the fourth transmembrane helix (D helix) in the M subunit with the homologous helix from the L subunit yields photosynthetically inactive RCs lacking a critical photoactive pigment. Photosynthetic revertants have been isolated in which single amino acid substitutions (intragenic suppressors) compensate for this partial symmetrization. 20 refs., 3 figs., 1 tab.

Robles, S.J.; Youvan, D.C. (Massachusetts Institute of Technology, Cambridge (USA)); Breton, J. (CEN Saclay, Gif-sur-Yvette (France))

1990-06-15

320

Magnetic control of a meta-molecule.  

PubMed

Metamaterials offer the prospect of new science and applications. They have been designed by shaping or changing the material of the individual meta-molecules to achieve properties not naturally attainable. Composite meta-molecules incorporating a magnetic component offer new opportunities. In this work we report on the interaction between a non-magnetic split ring resonator (SRR) and a thin film of yttrium iron garnet (YIG). Strong hybridized resonances are observed. While the SRR is characterized by a magnetic and electric resonance, in practice, it is found that the YIG couples strongly to this symmetric (electric) mode of the SRR. It is also demonstrated that the anti-crossing region provides fertile ground for the creation of elementary excitations such as backward volume magnetostatic waves. PMID:23389127

Stenning, Gavin B G; Bowden, Graham J; Maple, Lewis C; Gregory, Simon A; Sposito, Alberto; Eason, Robert W; Zheludev, Nikolay I; de Groot, Peter A J

2013-01-28

321

Decay Structure for Symmetric Hyperbolic Systems with Non-Symmetric Relaxation and its Application  

NASA Astrophysics Data System (ADS)

This paper is concerned with the decay structure for linear symmetric hyperbolic systems with relaxation. When the relaxation matrix is symmetric, the dissipative structure of the systems is completely characterized by the Kawashima-Shizuta stability condition formulated in Umeda et al. (Jpn J Appl Math 1:435-457, 1984) and Shizuta and Kawashima (Hokkaido Math J 14:249-275, 1985) and we obtain the asymptotic stability result together with the explicit time-decay rate under that stability condition. However, some physical models which satisfy the stability condition have non-symmetric relaxation term (for example, the Timoshenko system and the Euler-Maxwell system). Moreover, it had been already known that the dissipative structure of such systems is weaker than the standard type and is of the regularity-loss type (see Duan in J Hyperbolic Differ Equ 8:375-413, 2011; Ide et al. in Math Models Meth Appl Sci 18:647-667, 2008; Ide and Kawashima in Math Models Meth Appl Sci 18:1001-1025, 2008; Ueda et al. in SIAM J Math Anal 2012; Ueda and Kawashima in Methods Appl Anal 2012). Therefore our purpose in this paper is to formulate a new structural condition which includes the Kawashima-Shizuta condition, and to analyze the weak dissipative structure for general systems with non-symmetric relaxation.

Ueda, Yoshihiro; Duan, Renjun; Kawashima, Shuichi

2012-07-01

322

Acute oral toxicity evaluation of symmetrically branched glycerol trimer in ddY mice.  

PubMed

Lipophilic-hydrophilic balance is a quite important determinant of pharmacokinetic properties of pharmaceuticals. Thus it is a key step to successfully manage lipophilic-hydrophilic balance in drug design. We have designed unique modular molecules, symmetrically branched oligoglycerols (BGL) as an alternative means to endow hydrophobic molecules with much hydrophilicity. We have succeeded in improving the water-solubility of several hydrophobic medicinal small molecules and thermal stability of artificial protein by covalent conjugation to BGL. We have also demonstrated that a representative BGL, symmetrically branched glycerol trimer (BGL003) does not exhibit significant cytotoxicity against human hepatocarcinoma HepG2 cells. However, there have been no reports suggesting whether BGL could be used in safety in vivo. Therefore, evaluation of acute oral toxicity of BGL003 in healthy mice was conducted. Here we demonstrate that an oral administration of BGL003 did not exhibit acute lethal toxicity up to 3,000 mg/kg. Body weight, food intake, blood glucose levels and weights of tissues were not affected by a short-term repetitive administration of increasing doses of BGL003. Biochemical indications related to hepatic disorders and tissue damage were unchanged, either. A single administration study revealed that 50% lethal dose of BGL003 should be more than 2,000 mg/kg. BGL003 will be safe and suitable approach to improve hydrophilicity of hydrophobic compounds. PMID:23208440

Miyamoto, Licht; Watanabe, Masashi; Tomida, Yosuke; Kono, Mai; Fujii, Shoko; Matsushita, Tsuyoshi; Hattori, Hatsuhiko; Ishizawa, Keisuke; Nemoto, Hisao; Tsuchiya, Koichiro

2012-01-01

323

MHD Integrated Topping Cycle Project  

SciTech Connect

This seventeenth quarterly technical progress report of the MHD Integrated Topping Cycle Project presents the accomplishments during the period August 1, 1991 to October 31, 1991. Manufacturing of the prototypical combustor pressure shell has been completed including leak, proof, and assembly fit checking. Manufacturing of forty-five cooling panels was also completed including leak, proof, and flow testing. All precombustor internal components (combustion can baffle and swirl box) were received and checked, and integration of the components was initiated. A decision was made regarding the primary and backup designs for the 1A4 channel. The assembly of the channel related prototypical hardware continued. The cathode wall electrical wiring is now complete. The mechanical design of the diffuser has been completed.

Not Available

1992-07-01

324

Collision-induced absorption in a highly symmetric molecule - SF6  

Microsoft Academic Search

The far-infrared absorption spectra of gaseous (298 K) and liquid (273 K, 233 K) SF6 obtained by Rosenberg and Birnbaum [1] are analysed in terms of recent theoretical developments. Analysis of the band shape in the gas and liquid phases indicates that hexadecapole-induced absorption accounts only for the low frequency portion of the collision-induced band. The major part of the

George Birnbaum; Herbert Sutter

1981-01-01

325

Nucleic acid molecule  

US Patent & Trademark Office Database

The invention relates to an isolated nucleic acid molecule encoding a polypeptide capable of producing a triterpenoid hydrocarbon. The invention also relates to the encoded polypeptide, a vector comprising the nucleic acid molecule, a recombinant non-human organism comprising the nucleic acid molecule, and to methods of producing a triterpenoid hydrocarbon or an intermediate of biofuel using the nucleic acid molecule, polypeptide or recombinant organism.

2011-10-11

326

Patterns of energy levels and spectra for polyatomic molecules  

SciTech Connect

Laser spectroscopy has revealed a remarkable intricacy in the rotational, vibrational, and electronic energy levels for polyatomic molecules. The infrared spectra of SF/sub 6/, CF/sub 4/, and related molecules contain several levels of structure on top of structure which resembles a fractal in some ways. The purpose of this article will be to exhibit some of this structure and introduce the simplest theoretical interpretations of it which are presently available.

Harter, W.G.

1983-01-01

327

Symmetric instability in the Gulf Stream  

NASA Astrophysics Data System (ADS)

Analyses of wintertime surveys of the Gulf Stream (GS) conducted as part of the CLIvar MOde water Dynamic Experiment (CLIMODE) reveal that water with negative potential vorticity (PV) is commonly found within the surface boundary layer (SBL) of the current. The lowest values of PV are found within the North Wall of the GS on the isopycnal layer occupied by Eighteen Degree Water, suggesting that processes within the GS may contribute to the formation of this low-PV water mass. In spite of large heat loss, the generation of negative PV was primarily attributable to cross-front advection of dense water over light by Ekman flow driven by winds with a down-front component. Beneath a critical depth, the SBL was stably stratified yet the PV remained negative due to the strong baroclinicity of the current, suggesting that the flow was symmetrically unstable. A large eddy simulation configured with forcing and flow parameters based on the observations confirms that the observed structure of the SBL is consistent with the dynamics of symmetric instability (SI) forced by wind and surface cooling. The simulation shows that both strong turbulence and vertical gradients in density, momentum, and tracers coexist in the SBL of symmetrically unstable fronts. SI is a shear instability that draws its energy from geostrophic flows. A parameterization for the rate of kinetic energy (KE) extraction by SI applied to the observations suggests that SI could result in a net dissipation of 33 mW m-2 and 1 mW m-2 for surveys with strong and weak fronts, respectively. The surveys also showed signs of baroclinic instability (BCI) in the SBL, namely thermally direct vertical circulations that advect biomass and PV. The vertical circulation was inferred using the omega equation and used to estimate the rate of release of available potential energy (APE) by BCI. The rate of APE release was found to be comparable in magnitude to the net dissipation associated with SI. This result points to an energy pathway where the GS's reservoir of APE is drained by BCI, converted to KE, and then dissipated by SI and its secondary instabilities. Similar dynamics are likely to be found at other strong fronts forced by winds and/or cooling and could play an important role in the energy balance of the ocean circulation.

Thomas, Leif N.; Taylor, John R.; Ferrari, Raffaele; Joyce, Terrence M.

2013-07-01

328

Symmetric Resonance Charge Exchange Cross Section Based on Impact Parameter Treatment  

NASA Technical Reports Server (NTRS)

Using a two-state impact parameter approximation, a calculation has been carried out to obtain symmetric resonance charge transfer cross sections between nine ions and their parent atoms or molecules. Calculation is based on a two-dimensional numerical integration. The method is mostly suited for hydrogenic and some closed shell atoms. Good agreement has been obtained with the results of laboratory measurements for the ion-atom pairs H+-H, He+-He, and Ar+-Ar. Several approximations in a similar published calculation have been eliminated.

Omidvar, Kazem; Murphy, Kendrah; Atlas, Robert (Technical Monitor)

2002-01-01

329

Eigenvalue similarity rules for symmetric cross-ply laminated plates  

NASA Technical Reports Server (NTRS)

Symmetric cross-ply laminated plates are analyzed by employing a previously presented affine stretching process, some material constant definitions from Tsai (1964), and by gneralizing existing similarity rules. As examples, similarity rules are employed to find the frequency spectrum of a cross-ply symmetric plate from the corresponding isotropic solution, and a similarity solution is presented for the vibration of an axially loaded, simply supported cross-ply symmetric plate. Buckling similarity rules are also presented.

Brunelle, E. J.

1984-01-01

330

On the Method of N-Body Hyperspherical Basis Symmetrization  

Microsoft Academic Search

Parentage Scheme of Summarization (PSS) to the N-body symmetrized basis construction necessary for the description of the structural characteristics and decay reactions of the hypernuclear and nuclear systems with arbitrary amount of particles is introduced. Proposed method allows to construct N-particle symmetrized hyperspherical functions on the bases of N-particle hyperspherical functions symmetrized with respect to N–1-particles by the use of

Lia Leon Margolin

2012-01-01

331

Entanglement equivalence of N-qubit symmetric states  

NASA Astrophysics Data System (ADS)

We study the interconversion of multipartite symmetric N-qubit states under stochastic local operations and classical communication (SLOCC). We demonstrate that if two symmetric states can be connected with a nonsymmetric invertible local operation (ILO), then they belong necessarily to the separable, W, or Greenberger-Horne-Zeilinger (GHZ) entanglement class, establishing a practical method of discriminating subsets of entanglement classes. Furthermore, we prove that there always exists a symmetric ILO connecting any pair of symmetric N-qubit states equivalent under SLOCC, simplifying the requirements for experimental implementations of local interconversion of those states.

Mathonet, P.; Krins, S.; Godefroid, M.; Lamata, L.; Solano, E.; Bastin, T.

2010-05-01

332

Covariant approach for perturbations of rotationally symmetric spacetimes  

SciTech Connect

We present a covariant decomposition of Einstein's field equations which is particularly suitable for perturbations of spherically symmetric - and general locally rotationally symmetric - spacetimes. Based upon the utility of the 1+3 covariant approach to perturbation theory in cosmology, the semi-tetrad, 1+1+2 approach presented here should be useful for analyzing perturbations of a variety of systems in a covariant and gauge-invariant manner. Such applications range from stellar objects to cosmological models such as the spherically symmetric Lemaitre-Tolman-Bondi solutions or the class of locally rotationally symmetric Bianchi models.

Clarkson, Chris [Cosmology and Gravity Group, Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa)

2007-11-15

333

Concrete Representation and Separability Criteria for Symmetric Quantum State  

NASA Astrophysics Data System (ADS)

Using the typical generators of the special unitary groups S U(2), the concrete representation of symmetric quantum state is established, then the relations satisfied by those coefficients in the representation are presented. Based on the representation of density matrix, the PPT criterion and CCNR criterion are proved to be equivalent on judging the separability of symmetric quantum states. Moreover, it is showed that the matrix ? ? of symmetric quantum state only has five efficient entries, thus the calculation of ?? ? ? is simplified. Finally, the quantitative expressions of real symmetric quantum state under the ?? ? ? separability criterion are obtained.

Li, Chang'e.; Tao, Yuanhong; Zhang, Jun; Li, Linsong; Nan, Hua

2014-05-01

334

D0 findings on the top quark  

SciTech Connect

Recent results on top quark physics with the D0 experiment in pp collisions at {radical}s = 1.8 TeV are reported. The direct measurement of the top quark mass uses single lepton and dilepton events, giving the result m{sub top} = 172.1 {+-} 7.1 GeV/c{sup 2} . The measurement of the t{anti t} production cross section includes analyses from 9 top decay channels: dilepton, electron and neutrino, single leptons with and without b tagging, and all-jets (t{anti t} {r_arrow} b jets). The authors measured the t{anti t} production cross section to be 5.9 {+-} 1.7 pb at m{sub top} = 172.1 GeV/c{sup 2}. Preliminary results on a search for charged Higgs production in top events are presented.

Klima, B.

1998-06-01

335

Flat foliations of spherically symmetric geometries  

NASA Astrophysics Data System (ADS)

We examine the solution of the constraints in spherically symmetric general relativity when spacetime has a flat spatial hypersurface. It is demonstrated explicitly that, given one flat slice, a foliation by flat slices can be consistently evolved. We show that when the sources are finite these slices do not admit singularities and we provide an explicit bound on the maximum value assumed by the extrinsic curvature. If the dominant energy condition is satisfied, the projection of the extrinsic curvature orthogonal to the radial direction possesses a definite sign. We provide both necessary and sufficient conditions for the formation of apparent horizons in this gauge which are qualitatively identical to those established earlier for extrinsic time foliations of spacetime, [J. Guven and N. Ó Murchadha, Phys. Rev. D 56 7658 (1997); 56, 7666 (1997)], which suggests that these conditions possess a gauge invariant validity.

Guven, Jemal; Murchadha, Niall Ó.

1999-11-01

336

Symmetrical Taylor impact of glass bars  

NASA Astrophysics Data System (ADS)

Brar and Bless pioneered the use of plate impact upon bars as a technique for investigating the 1D stress loading of glass but limited their studies to relatively modest stresses (1). We wish to extend this technique by applying VISAR and embedded stress gauge measurements to a symmetrical version of the test in which two rods impact one upon the other. Previous work in the laboratory has characterised the glass types (soda-lime and borosilicate)(2). These experiments identify the failure mechanisms from high-speed photography and the stress and particle velocity histories are interpreted in the light of these results. The differences in response of the glasses and the relation of the fracture to the failure wave in uniaxial strain are discussed.

Murray, N. H.; Bourne, N. K.; Field, J. E.; Rosenberg, Z.

1998-07-01

337

Pseudo-Z symmetric space-times  

NASA Astrophysics Data System (ADS)

In this paper, we investigate Pseudo-Z symmetric space-time manifolds. First, we deal with elementary properties showing that the associated form Ak is closed: in the case the Ricci tensor results to be Weyl compatible. This notion was recently introduced by one of the present authors. The consequences of the Weyl compatibility on the magnetic part of the Weyl tensor are pointed out. This determines the Petrov types of such space times. Finally, we investigate some interesting properties of (PZS)4 space-time; in particular, we take into consideration perfect fluid and scalar field space-time, and interesting properties are pointed out, including the Petrov classification. In the case of scalar field space-time, it is shown that the scalar field satisfies a generalized eikonal equation. Further, it is shown that the integral curves of the gradient field are geodesics. A classical method to find a general integral is presented.

Mantica, Carlo Alberto; Suh, Young Jin

2014-04-01

338

Invisibility in {PT}-symmetric complex crystals  

NASA Astrophysics Data System (ADS)

Bragg scattering in sinusoidal {PT}-symmetric complex crystals of finite thickness is theoretically investigated by the derivation of exact analytical expressions for reflection and transmission coefficients in terms of modified Bessel functions of first kind. The analytical results indicate that unidirectional invisibility, recently predicted for such crystals by coupled-mode theory (Z Lin et al 2011 Phys. Rev. Lett. http://dx.doi.org/10.1103/PhysRevLett.106.213901), breaks down for crystals containing a large number of unit cells. In particular, for a given modulation depth in a shallow sinusoidal potential, three regimes are encountered as the crystal thickness is increased. At short lengths the crystal is reflectionless and invisible when probed from one side (unidirectional invisibility), whereas at intermediate lengths the crystal remains reflectionless but not invisible; for longer crystals both unidirectional reflectionless and invisibility properties are broken.

Longhi, Stefano

2011-12-01

339

a New Symmetric Expression of Weyl Ordering  

NASA Astrophysics Data System (ADS)

For the creation operator a† and the annihilation operator a of a harmonic oscillator, we consider Weyl ordering expression of (a†a)n and obtain a new symmetric expression of Weyl ordering w.r.t. a†a?N and aa†=N+1 where N is the number operator. Moreover, we interpret intertwining formulas of various orderings in view of the difference theory. Then we find that the noncommutative parameter corresponds to the increment of the difference operator w.r.t. variable N. Therefore, quantum (noncommutative) calculations of harmonic oscillators are done by classical (commutative) ones of the number operator by using the difference theory. As a by-product, nontrivial relations including the Stirling number of the first kind are also obtained.

Fujii, Kazuyuki; Suzuki, Tatsuo

340

VACUUM calculation in azimuthally symmetric geometry  

SciTech Connect

A robustly accurate and effective method is presented to solve Laplace`s equation in general azimuthally symmetric geometry for the magnetic scalar potential in the region surrounding a plasma discharge which may or may not contain external conducting shells. These shells can be topologically toroidal or spherical, and may have toroidal gaps in them. The solution is incorporated into the various MHD stability codes either through the volume integrated perturbed magnetic energy in the vacuum region or through the continuity requirements for the normal component of the perturbed magnetic field and the total perturbed pressure across the unperturbed plasma-vacuum boundary. The method is based upon using Green`s second identity and the method of collocation. As useful byproducts, the eddy currents and the simulation of Mirnov loop measurements are calculated.

Chance, M.S.

1996-11-01

341

A natural symmetrization for the plummer potential  

NASA Astrophysics Data System (ADS)

We propose a symmetrized form of the softened gravitational potential which is a natural extension of the Plummer potential. The gravitational potential at the position of particle i( xi, yi, zi), induced by particle j at ( xj, yj, zj), is given by: ?ij=-{Gmj}/{|rij2+?i2+?j2|}, where G is the gravitational constant, mj is the mass of particle j, rij = ?( xi - xj) 2 + ( yi - yj) 2 + ( zi - zj) 2? 1/2 and ?i and ?j are the gravitational softening lengths of particles i and j, respectively. This form is formally an extension of the Newtonian potential to five dimensions. The derivative of this equation in the x, y, and z directions correspond to the gravitational accelerations in these directions and they are always symmetric between two particles. When one applies this potential to a group of particles with different softening lengths, as in the case with a tree code, an averaged gravitational softening length for the group can be used. We find that the most suitable averaged softening length for a group of particles is =?jNmj?j2/M, where M=?jNmj and N are the mass and number of all particles in the group, respectively. The leading error related to the softening length is O?j?rj? ?j2/rij3, where ?rj is the distance between particle j and the center of mass of the group and ??j2=?j2-. Using this averaged gravitational softening length with the tree method, one can use a single tree to evaluate the gravitational forces for a system of particles with a wide variety of gravitational softening lengths. Consequently, this will reduce the calculation cost of the gravitational force for such a system with different softenings without the need for complicated forms of softening. We present the result of simple numerical tests. We found that our modification of the Plummer potential works well.

Saitoh, Takayuki R.; Makino, Junichiro

2012-02-01

342

Top Health Issues for LGBT Populations Information and Resource Kit.  

National Technical Information Service (NTIS)

Contents: Preface; Helpful Terms for Prevention Specialists and Healthcare Providers; A Discussion about Gender Identity; Top Health Issues for Lesbians; Top Health Issues for Gay Men; Top Health Issues for Bisexual Men and Women; Top Health Issues for Tr...

A. Camacho

2012-01-01

343

Top quark measurements at the Tevatron  

SciTech Connect

The authors present top physics results from the CDF and D0 collaborations. The data were collected at the Fermilab Tevatron over the years 1992--1995 and correspond to approximately 110 pb{sup {minus}1} of p{anti p} collisions. Both experiments present determination of the t{anti t} production cross section using a variety of top decay channels, and refined measurements of the top mass.

Kestenbaum, D.S.; CDF Collaboration; D0 Collaboration

1997-01-01

344

Top quark mass and production from CDF  

SciTech Connect

We present the latest results about the top quark obtained by the CDF experiment using a data sample of about 110 pb{sup -1} collected at the Fermilab Tevatron collider. We briefly describe the production cross section determination and the top mass measurement. Finally we review the search for the top quark in rare decay channels and the first direct calculation of the CKM matrix element V{sub tb}.

Leone, S. [Istituto Nazionale di Fisica Nucleare, Pisa (Italy); CDF Collaboration

1997-09-01

345

Top quark properties at the Tevatron  

SciTech Connect

Recent preliminary results on top quark properties from the CDF and D0 collaborations at the Fermilab Tevatron are described. These analyses include: measurements of the ratio B(t {yields} Wb)/B(t {yields} Wq) and of B(t {yields} {tau}vq), search for anomalous kinematics, studies on the helicity of W bosons originating from top quark decays, spin correlations between top quark pairs, and searches for t{bar t} resonance production in models beyond the standard model.

Garcia-Bellido, Aran; /Washington U., Seattle

2004-11-01

346

Si-nanowire CMOS inverter logic fabricated using gate-all-around (GAA) devices and top-down approach  

Microsoft Academic Search

We present the monolithic integration of gate-all-around (GAA) Si-nanowire FETs into CMOS logic using top-down approach. Inverters are chosen as the test vehicles for demonstration. Empirically optimized designs show sharp ON–OFF transitions with high voltage-gains (e.g., ?VOUT\\/?VIN up to ?45) and symmetric pull-up and pull-down characteristics. The matching of the drive currents of n- and p-MOSFETs is achieved using different

K. D. Buddharaju; N. Singh; S. C. Rustagi; Selin H. G. Teo; G. Q. Lo; N. Balasubramanian; D. L. Kwong

2008-01-01

347

Monte Carlo simulations for top pair and single top production at the Tevatron  

SciTech Connect

Monte Carlo (MC) simulations are indispensable tools for top quark physics, both at the current Tevatron collider and the upcoming Large Hadron Collider. In this paper we review how the Tevatron experiments CDF and D0 utilize MC simulations for top quark analyses. We describe the standard MC generators used to simulate top quark pair and single top quark production, followed by a discussion of methods to extract systematic uncertainties of top physics results related to the MC generator choice. The paper also shows the special MC requirements for some example top properties measurements at the Tevatron.

Husemann, U.; /DESY

2008-06-01

348

Top 5 Hidden Hazards in the Home  

MedlinePLUS

... Safety Education Centers OnSafety Blog Neighborhood Safety Network Home / Safety Education / Neighborhood Safety Network / Posters En Español Top 5 Hidden Home Hazards Magnets, recalled products, ...

349

Observations of severe turbulence near thunderstorm tops  

NASA Technical Reports Server (NTRS)

Data derived from the flight tapes of two airliners that experienced severe turbulence near thunderstorm tops are used to produce quantitative descriptions of the turbulence and its environment. The likely turbulence-producing processes include a three-dimensional turbulent wake in the lee of a squall line and an updraft in the top of a thunderstorm. Results suggest that current procedures for using surface and airborne weather radar for routing aircraft near thunderstorm tops should be reexamined. Also, although useful rules for safe flight near thunderstorm tops already exist, there is evidence that they are not universally applied.

Pantley, K. C.; Lester, Peter F.

1990-01-01

350

Observations of Severe Turbulence near Thunderstorm Tops.  

NASA Astrophysics Data System (ADS)

Data derived from the flight tapes of two airliners that experienced severe turbulence near thunderstorm tops are used to produce quantitative descriptions of the turbulence and its environment. The likely turbulence-producing processes include a three-dimensional turbulent wake in the lee of a squall line and an updraft in the top of a thunderstorm. Results suggest that current procedures for using surface and airborne weather radar for routing aircraft near thunderstorm tops should be reexamined. Also, although useful rules for safe flight near thunderstorm tops already exist, there is evidence that they are not universally applied.

Pantley, K. C.; Lester, Peter F.

1990-11-01

351

The emergence of top-down proteomics in clinical research.  

PubMed

Proteomic technology has advanced steadily since the development of 'soft-ionization' techniques for mass-spectrometry-based molecular identification more than two decades ago. Now, the large-scale analysis of proteins (proteomics) is a mainstay of biological research and clinical translation, with researchers seeking molecular diagnostics, as well as protein-based markers for personalized medicine. Proteomic strategies using the protease trypsin (known as bottom-up proteomics) were the first to be developed and optimized and form the dominant approach at present. However, researchers are now beginning to understand the limitations of bottom-up techniques, namely the inability to characterize and quantify intact protein molecules from a complex mixture of digested peptides. To overcome these limitations, several laboratories are taking a whole-protein-based approach, in which intact protein molecules are the analytical targets for characterization and quantification. We discuss these top-down techniques and how they have been applied to clinical research and are likely to be applied in the near future. Given the recent improvements in mass-spectrometry-based proteomics and stronger cooperation between researchers, clinicians and statisticians, both peptide-based (bottom-up) strategies and whole-protein-based (top-down) strategies are set to complement each other and help researchers and clinicians better understand and detect complex disease phenotypes. PMID:23806018

Savaryn, John P; Catherman, Adam D; Thomas, Paul M; Abecassis, Michael M; Kelleher, Neil L

2013-01-01

352

The emergence of top-down proteomics in clinical research  

PubMed Central

Proteomic technology has advanced steadily since the development of 'soft-ionization' techniques for mass-spectrometry-based molecular identification more than two decades ago. Now, the large-scale analysis of proteins (proteomics) is a mainstay of biological research and clinical translation, with researchers seeking molecular diagnostics, as well as protein-based markers for personalized medicine. Proteomic strategies using the protease trypsin (known as bottom-up proteomics) were the first to be developed and optimized and form the dominant approach at present. However, researchers are now beginning to understand the limitations of bottom-up techniques, namely the inability to characterize and quantify intact protein molecules from a complex mixture of digested peptides. To overcome these limitations, several laboratories are taking a whole-protein-based approach, in which intact protein molecules are the analytical targets for characterization and quantification. We discuss these top-down techniques and how they have been applied to clinical research and are likely to be applied in the near future. Given the recent improvements in mass-spectrometry-based proteomics and stronger cooperation between researchers, clinicians and statisticians, both peptide-based (bottom-up) strategies and whole-protein-based (top-down) strategies are set to complement each other and help researchers and clinicians better understand and detect complex disease phenotypes.

2013-01-01

353

MHD Integrated Topping Cycle Project  

SciTech Connect

This fourteenth quarterly technical progress report of the MHD Integrated Topping Cycle Project presents the accomplishments during the period November 1, 1990 to January 31, 1991. Testing of the High Pressure Cooling Subsystem electrical isolator was completed. The PEEK material successfully passed the high temperature, high pressure duration tests (50 hours). The Combustion Subsystem drawings were CADAM released. The procurement process is in progress. An equipment specification and RFP were prepared for the new Low Pressure Cooling System (LPCS) and released for quotation. Work has been conducted on confirmation tests leading to final gas-side designs and studies to assist in channel fabrication.The final cathode gas-side design and the proposed gas-side designs of the anode and sidewall are presented. Anode confirmation tests and related analyses of anode wear mechanisms used in the selection of the proposed anode design are presented. Sidewall confirmation tests, which were used to select the proposed gas-side design, were conducted. The design for the full scale CDIF system was completed. A test program was initiated to investigate the practicality of using Avco current controls for current consolidation in the power takeoff (PTO) regions and to determine the cause of past current consolidation failures. Another important activity was the installation of 1A4-style coupons in the 1A1 channel. A description of the coupons and their location with 1A1 channel is presented herein.

Not Available

1992-02-01

354

Table-top EUV reflectometer  

NASA Astrophysics Data System (ADS)

A novel compact EUV-reflectometer recently developed is presented. The designconcept relies on a flexible approach, thus this reflectometer can be set up as a compact table-top tool for a specified task as well as a full all-purpose reflectometer. As an EUV-source an electron-based microfocus EUV-tube is used. This EUV source is debris-free and provides a typical output of 30?W at 13.5 nm. The reflectometer benefits from the very good long-time stability and spatial stability of this tube. Reflectivity measurements from grazing incidence to nearly normal incidence as well as transmission studies can be realized in the same setup at a typical precision of measurements of 0.5%. A precise computer-controlled positioning unit allows to vary and scan all important parameters online, allowing for example complex surface scans and angle variations. The concept of the reflectometer is discussed and recent results are presented. This device can be purchased from the Laser Zentrum Hannover e.V.

Hinze, U.; Chichkov, B.

2006-04-01

355

The TOP-IMPLART project  

NASA Astrophysics Data System (ADS)

A new proton therapy center is planned to be built in Rome, Italy. The project, named TOP-IMPLART, is developed by three institutions, ENEA (Agenzia Nazionale per le Nuove tecnologie, l'Energia e lo Sviluppo Economico Sostenibile - Italian national agency for new technologies, energy and sustainable economic development), ISS (Istituto Superiore di Sanità, Italian National Institute of Health) and IFO-IRE (Istituto Fisioterapico Ospedaliero - Istituto Regina Elena, Regina Elena, National Cancer Institute in Rome). The project is centered on a medium-energy proton accelerator designed as a sequence of linear accelerators. Two phases of construction are foreseen: the first (funded by the Italian Regione Lazio for 11 M€ spread over four years) with a maximum energy of 150 MeV and the second one up to 230 MeV. The segment up to 150 MeV is under construction and will be tested at the ENEA Research Center in Frascati before the transfer to IFO that is the clinical user. The basic concepts of the design are described here.

Ronsivalle, C.; Carpanese, M.; Marino, C.; Messina, G.; Picardi, L.; Sandri, S.; Basile, E.; Caccia, B.; Castelluccio, D. M.; Cisbani, E.; Frullani, S.; Ghio, F.; Macellari, V.; Benassi, M.; D'Andrea, M.; Strigari, L.

2011-07-01

356

Structural tailoring effects on the magnetic behavior of symmetric and asymmetric cubane-type Ni complexes.  

PubMed

Using two kinds of carboxylate ligands with small but significant differences in steric size, symmetric and asymmetric Fe(II) and Ni(II) cubanes have been synthesized in a controlled fashion. Fast sweeping pulsed field measurements showed magnetization hysteresis loops for two cubane-type molecular complexes, [Ni4(?-OMe)4(O2CAr(4F-Ph))4(HOMe)8] and [Ni4(?-OMe)4(O2CAr(Tol))4(HOMe)6], thus suggesting single-molecule magnet behavior. To differentiate the magnetic properties between the symmetric and asymmetric cubanes, detailed electron paramagnetic resonance (EPR) measurements were performed. From the EPR data, taken at various frequencies and temperatures, zero-field splitting parameters D, E, and other higher-order parameters for both cubane samples were extracted. Compared to the symmetric Ni-cubane, the asymmetric one shows an increase in the D and E values by about 20%, thereby suggesting structural engineering effects on the magnetic properties. By using the magnetic parameters determined by EPR, a static magnetization curve at 2?K and a temperature dependence of the magnetic susceptibility were simulated. A good agreement between theoretical and experimental data confirms the validity of the values obtained from EPR measurements. PMID:23509044

Ponomaryov, Alexey N; Kim, Namseok; Hwang, Jaewon; Nojiri, Hiroyuki; van Tol, Johan; Ozarowski, Andrew; Park, Jena; Jang, Zeehoon; Suh, Byoungjin; Yoon, Sungho; Choi, Kwang-Yong

2013-06-01

357

7. DETAIL OF TOP CHORD/END POST CONNECTION. THE TOPS OF ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. DETAIL OF TOP CHORD/END POST CONNECTION. THE TOPS OF BOTH MEMBERS ARE COVERED WITH SOLID PLATES. - Montgomery County Bridge No. 221, Metz Road spanning Towamencin Creek, Skippack, Montgomery County, PA

358

Measuring top-quark polarization in top-pair + missing-energy events.  

PubMed

The polarization of a top quark can be sensitive to new physics beyond the standard model. Since the charged lepton from top-quark decay is maximally correlated with the top-quark spin, it is common to measure the polarization from the distribution in the angle between the charged lepton and the top-quark directions. We propose a novel method based on the charged lepton energy fraction and illustrate the method with a detailed simulation of top-quark pairs produced in supersymmetric top squark pair production. We show that the lepton energy ratio distribution that we define is very sensitive to the top-quark polarization but insensitive to the precise measurement of the top-quark energy. PMID:23102297

Berger, Edmond L; Cao, Qing-Hong; Yu, Jiang-Hao; Zhang, Hao

2012-10-12

359

The volume operator in spherically symmetric quantum geometry  

Microsoft Academic Search

The spherically symmetric volume operator is discussed and all its eigenstates and eigenvalues are computed. Even though the operator is more complicated than its homogeneous analogue, the spectra are related in the sense that the larger spherically symmetric volume spectrum adds fine structure to the homogeneous spectrum. The formulae of this paper complete the derivation of an explicit calculus for

Martin Bojowald; Rafal Swiderski

2004-01-01

360

Matrix-valued symmetric templates for interpolatory surface subdivisions  

Microsoft Academic Search

The objective of this paper is to introduce a general procedure for deriving interpolatory surface subdivision schemes with “symmetric subdivision templates” (SSTs) for regular vertices. While the precise definition of “symmetry” will be clarified in the paper, the property of SSTs is instrumental to facilitate application of the standard procedure for finding symmetric weights for taking weighted averages to accommodate

Charles K. Chui; Qingtang Jiangy

2005-01-01

361

Symmetric Pin Diversion Detection using a Partial Defect Detector (PDET)  

Microsoft Academic Search

Since the signature from the Partial Defect Detector (PDET) is principally dependent on the geometric layout of the guide tube locations, the capability of the technique in detecting symmetric diversion of pins needs to be determined. The Monte Carlo simulation study consisted of cases where pins were removed in a symmetric manner and the resulting signatures were examined. In addition

S Sitaraman; Y S Ham

2009-01-01

362

Symmetrical analysis of complex two-dimensional hexagonal photonic crystals  

Microsoft Academic Search

We study complex hexagonal photonic crystals with unit cells that include different dielectric cylinders. A general symmetrical perturbation approach for a hexagonal lattice with up to three basis rods is presented that systematically develops other structural derivatives including comblike structures. We show how the band spectrum of these complex structures evolves from the most symmetrical prophase. The results are in

N. Malkova; S. Kim; T. Dilazaro; V. Gopalan

2003-01-01

363

Symmetric Circuits and the Concept of Logical Potential  

Microsoft Academic Search

Symmetric circuits with more than one output can traditionally be reduced by shifting down if the outputs have certain properties. It is shown here that any nontrivial symmetric circuit can be shifted down using the method described. The reduction is made logical and simple to understand by means of the concept of logical potential, in which the circuit is diagrammed,

Norman R. Bell

1967-01-01

364

USING FLOOR TOPPINGS TO CONTROL FLANKING TRANSMISSION  

Microsoft Academic Search

The change in flanking sound insulation due to adding a floor topping is shown to be different for paths where energy propagates perpendicular to the joists, compared to those where energy propagates parallel to the joists. This paper summarises results presented elsewhere (1,2). Floor vibration mappings reveal that a topping will change not only the power injected but also the

T. R. T. Nightingale; R. E. Halliwell; J. D. Quirt

365

Physics of the top quark at CDF  

SciTech Connect

Measurements of Top quark properties with the CDF detector are reported. The production cross section and mass provide a consistent picture of the Top quark as described by the Standard Model. Initial studies of other properties such as estimates of branching ratios are also reported.

Vejcik, S.; CDF Collaboration

1997-07-01

366

Measurement of the Top Quark Mass  

Microsoft Academic Search

We present a measurement of the top quark mass using a sample of tt¯ decays into an electron or a muon, a neutrino, and four jets. The data were collected in pp¯ collisions at s = 1.8 TeV with the Collider Detector at Fermilab and correspond to an integrated luminosity of 109 pb-1. We measure the top quark mass to

Steven R. Blusk; for the CDF; M. G. Albrow; A. Amadon; S. R. Amendolia; D. Amidei; J. Antos; S. Aota; G. Apollinari; T. Arisawa; T. Asakawa; W. Ashmanskas; M. Atac; P. Azzi-Bacchetta; N. Bacchetta; S. Bagdasarov; M. W. Bailey; P. de Barbaro; A. Barbaro-Galtieri; V. E. Barnes; B. A. Barnett; M. Barone; G. Bauer; T. Baumann; F. Bedeschi; S. Behrends; S. Belforte; G. Bellettini; J. Bellinger; D. Benjamin; J. Bensinger; A. Beretvas; J. P. Berge; J. Berryhill; S. Bertolucci; S. Bettelli; B. Bevensee; A. Bhatti; K. Biery; C. Bigongiari; M. Binkley; D. Bisello; R. E. Blair; C. Blocker; A. Bodek; W. Bokhari; G. Bolla; Y. Bonushkin; D. Bortoletto; J. Boudreau; L. Breccia; C. Bromberg; N. Bruner; R. Brunetti; E. Buckley-Geer; H. S. Budd; K. Burkett; G. Busetto; A. Byon-Wagner; K. L. Byrum; M. Campbell; A. Caner; W. Carithers; D. Carlsmith; J. Cassada; A. Castro; D. Cauz; A. Cerri; P. S. Chang; H. Y. Chao; J. Chapman; M.-T. Cheng; M. Chertok; G. Chiarelli; C. N. Chiou; F. Chlebana; L. Christofek; M. L. Chu; S. Cihangir; A. G. Clark; M. Cobal; E. Cocca; M. Contreras; J. Conway; J. Cooper; M. Cordelli; D. Costanzo; C. Couyoumtzelis; D. Cronin-Hennessy; R. Culbertson; D. Dagenhart; T. Daniels; F. Dejongh; S. dell'Agnello; M. dell'Orso; R. Demina; L. Demortier; M. Deninno; P. F. Derwent; T. Devlin; J. R. Dittmann; S. Donati; J. Done; T. Dorigo; N. Eddy; K. Einsweiler; J. E. Elias; R. Ely; E. Engels; W. Erdmann; D. Errede; S. Errede; Q. Fan; R. G. Feild; Z. Feng; C. Ferretti; I. Fiori; B. Flaugher; G. W. Foster; M. Franklin; J. Freeman; J. Friedman; H. Frisch; Y. Fukui; S. Gadomski; S. Galeotti; M. Gallinaro; O. Ganel; M. Garcia-Sciveres; A. F. Garfinkel; C. Gay; S. Geer; D. W. Gerdes; P. Giannetti; N. Giokaris; P. Giromini; G. Giusti; M. Gold; A. Gordon; A. T. Goshaw; Y. Gotra; K. Goulianos; H. Grassmann; L. Groer; C. Grosso-Pilcher; G. Guillian; J. Guimaraes da Costa; R. S. Guo; C. Haber; E. Hafen; S. R. Hahn; T. Handa; R. Handler; F. Happacher; K. Hara; A. D. Hardman; R. M. Harris; F. Hartmann; J. Hauser; E. Hayashi; J. Heinrich; W. Hao; B. Hinrichsen; K. D. Hoffman; M. Hohlmann; C. Holck; R. Hollebeek; L. Holloway; Z. Huang; B. T. Huffman; R. Hughes; J. Huston; J. Huth; H. Ikeda; M. Incagli; J. Incandela; G. Introzzi; J. Iwai; Y. Iwata; E. James; H. Jensen; U. Joshi; E. Kajfasz; H. Kambara; T. Kamon; T. Kaneko; K. Karr; H. Kasha; Y. Kato; T. A. Keaffaber; K. Kelley; R. D. Kennedy; R. Kephart; D. Kestenbaum; D. Khazins; T. Kikuchi; B. J. Kim; H. S. Kim; S. H. Kim; Y. K. Kim; L. Kirsch; S. Klimenko; D. Knoblauch; P. Koehn; A. Köngeter; K. Kondo; J. Konigsberg; K. Kordas; A. Korytov; E. Kovacs; W. Kowald; J. Kroll; M. Kruse; S. E. Kuhlmann; E. Kuns; K. Kurino; T. Kuwabara; A. T. Laasanen; S. Lami; S. Lammel; J. I. Lamoureux; M. Lancaster; M. Lanzoni; G. Latino; T. Lecompte; S. Leone; J. D. Lewis; P. Limon; M. Lindgren; T. M. Liss; J. B. Liu; Y. C. Liu; N. Lockyer; O. Long; C. Loomis; M. Loreti; D. Lucchesi; P. Lukens; S. Lusin; J. Lys; K. Maeshima; P. Maksimovic; M. Mangano; M. Mariotti; J. P. Marriner; A. Martin; J. A. Matthews; P. Mazzanti; P. McIntyre; P. Melese; M. Menguzzato; A. Menzione; E. Meschi; S. Metzler; C. Miao; T. Miao; G. Michail; R. Miller; H. Minato; S. Miscetti; M. Mishina; S. Miyashita; N. Moggi; E. Moore; Y. Morita; A. Mukherjee; T. Muller; P. Murat; S. Murgia; H. Nakada; I. Nakano; C. Nelson; D. Neuberger; C. Newman-Holmes; C.-Y. P. Ngan; L. Nodulman; A. Nomerotski; S. H. Oh; T. Ohmoto; T. Ohsugi; R. Oishi; M. Okabe; T. Okusawa; J. Olsen; C. Pagliarone; R. Paoletti; V. Papadimitriou; S. P. Pappas; N. Parashar; A. Parri; J. Patrick; G. Pauletta; M. Paulini; A. Perazzo; L. Pescara; M. D. Peters; T. J. Phillips; G. Piacentino; M. Pillai; K. T. Pitts; R. Plunkett; L. Pondrom; J. Proudfoot; F. Ptohos; G. Punzi; K. Ragan; D. Reher; M. Reischl; A. Ribon; F. Rimondi; L. Ristori; W. J. Robertson; T. Rodrigo; S. Rolli; L. Rosenson; R. Roser; T. Saab; W. K. Sakumoto; D. Saltzberg; A. Sansoni; L. Santi; H. Sato; P. Schlabach; E. E. Schmidt; M. P. Schmidt; A. Scott; A. Scribano; S. Segler; S. Seidel; Y. Seiya; F. Semeria; T. Shah; M. D. Shapiro; N. M. Shaw; P. F. Shepard; T. Shibayama; M. Shimojima; M. Shochet; J. Siegrist; A. Sill; P. Sinervo; P. Singh; K. Sliwa; C. Smith; F. D. Snider; J. Spalding; T. Speer; P. Sphicas; F. Spinella; M. Spiropulu; L. Spiegel; L. Stanco; J. Steele; A. Stefanini; R. Ströhmer; J. Strologas; F. Strumia; D. Stuart; K. Sumorok; J. Suzuki; T. Suzuki; T. Takahashi; T. Takano; R. Takashima; K. Takikawa; M. Tanaka; B. Tannenbaum; F. Tartarelli; W. Taylor; M. Tecchio; P. K. Teng; Y. Teramoto; K. Terashi; S. Tether; D. Theriot; T. L. Thomas; R. Thurman-Keup; M. Timko; P. Tipton; A. Titov; S. Tkaczyk; D. Toback; K. Tollefson; A. Tollestrup; H. Toyoda; W. Trischuk; J. F. de Troconiz; S. Truitt; J. Tseng; N. Turini; T. Uchida; F. Ukegawa; J. Valls; S. C. van den Brink; S. Vejcik

1998-01-01

367

Race to Top Draws out New Suitors  

ERIC Educational Resources Information Center

The list of 61 finalists for the latest Race to the Top competition shows that the U.S. Department of Education was successful in enticing high-scoring applications from districts in rural America and in states that had not shared in the Race to the Top bounty before. But whether the ultimate winners, which will be announced this month, will be…

McNeil, Michele

2012-01-01

368

Pinch Experiments in a Table Top Generator  

SciTech Connect

The design and construction of a table top multipurpose capacitor bank of hundred of Joules and hundred of kiloAmperes conceived to be used in small scale Z-pinch experiments is reported. A recent result on a Z-pinch gas embedded discharge using hollow conical electrodes done in a similar table top generator is also presented.

Pavez, Cristian; Moreno, Jose; Soto, Leopoldo [Center for Research and Applications in Plasma Physics and Pulsed Power, P4 (Chile); Comision Chilena de Energia Nuclear (Chile); Tarifeno, Ariel [Center for Research and Applications in Plasma Physics and Pulsed Power, P4 (Chile); Universidad de Concepcion (Chile)

2009-01-21

369

Top 12 Web Resources for 2012  

ERIC Educational Resources Information Center

In this article, the authors describe some of the top websites recommended by colleagues for the Association of California School Administrators. The Top 12 for 2012 are: (1) Facebook (facebook.com); (2) Twitter (twitter.com); (3) Tungle (tungle.me); (4) FCMAT (fcmat.org); (5) YouSendIt (yousendit.com); (6) Slideshare (slideshare.net); (7) QR…

Gonzales, Lisa; Vodicka, Devin

2012-01-01

370

Quark and lepton masses from top loops  

Microsoft Academic Search

Assuming that the leptons and quarks other than top are massless at tree level, we show that their masses may be induced by loops involving the top quark. As a result, the generic features of the fermion mass spectrum arise from combinations of loop factors. Explicitly, we construct a renormalizable model involving a few new particles, which leads to 1-loop

Bogdan A. Dobrescu; Patrick J. Fox

2008-01-01

371

Top Quark Pair Production at the Tevatron  

SciTech Connect

The measurement of the top quark pair production crosssection inproton-antiproton collisions at 1.96 TeV is a test ofquantumchromodynamics and could potentially be sensitive to newphysics beyondthe standard model. I report on the latest t-tbarcross section resultsfrom the CDF and DZero experiments in various finalstate topologies whicharise from decays of top quark pairs.

Nielsen, Jason

2005-05-17

372

Top-Ten IT Issues, 2008  

ERIC Educational Resources Information Center

EDUCAUSE presents the top-ten IT-related issues in terms of strategic importance to the higher education institution, as revealed by the ninth annual EDUCAUSE Current Issues Survey. This year, "Security" moves back to the top of the list. (Contains 20 notes.)

Allison, Debra H.; DeBlois, Peter B.

2008-01-01

373

49 CFR 236.779 - Plate, top.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Plate, top. 236.779 Section 236.779 Transportation...AND APPLIANCES Definitions § 236.779 Plate, top. A metal plate secured to a locking bracket to prevent the cross locking from...

2010-10-01

374

49 CFR 236.779 - Plate, top.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Plate, top. 236.779 Section 236.779 Transportation...AND APPLIANCES Definitions § 236.779 Plate, top. A metal plate secured to a locking bracket to prevent the cross locking from...

2013-10-01

375

49 CFR 236.779 - Plate, top.  

Code of Federal Regulations, 2010 CFR

... 2009-10-01 2009-10-01 false Plate, top. 236.779 Section 236.779 Transportation...AND APPLIANCES Definitions § 236.779 Plate, top. A metal plate secured to a locking bracket to prevent the cross locking from...

2009-10-01

376

Cell adhesion molecules and their relation to (cancer) cell stemness.  

PubMed

Despite decades of search for anticancer drugs targeting solid tumors, this group of diseases remains largely incurable, especially if in advanced, metastatic stage. In this review, we draw comparison between reprogramming and carcinogenesis, as well as between stem cells (SCs) and cancer stem cells (CSCs), focusing on changing garniture of adhesion molecules. Furthermore, we elaborate on the role of adhesion molecules in the regulation of (cancer) SCs division (symmetric or asymmetric), and in evolving interactions between CSCs and extracellular matrix. Among other aspects, we analyze the role and changes of expression of key adhesion molecules as cancer progresses and metastases develop. Here, the role of cadherins, integrins, as well as selected transcription factors like Twist and Snail is highlighted, not only in the regulation of epithelial-to-mesenchymal transition but also in the avoidance of anoikis. Finally, we briefly discuss recent developments and new strategies targeting CSCs, which focus on adhesion molecules or targeting tumor vasculature. PMID:24531939

Farahani, Ensieh; Patra, Hirak K; Jangamreddy, Jaganmohan R; Rashedi, Iran; Kawalec, Marta; Rao Pariti, Rama K; Batakis, Petros; Wiechec, Emilia

2014-04-01

377

Bicriterion seriation methods for skew-symmetric matrices.  

PubMed

The decomposition of an asymmetric proximity matrix into its symmetric and skew-symmetric components is a well-known principle in combinatorial data analysis. The seriation of the skew-symmetric component can emphasize information corresponding to the sign or absolute magnitude of the matrix elements, and the choice of objective criterion can have a profound impact on the ordering. In this research note, we propose a bicriterion approach for seriation of a skew-symmetric matrix incorporating both sign and magnitude information. Two numerical demonstrations reveal that the bicriterion procedure is an effective alternative to direct seriation of the skew-symmetric matrix, facilitating favourable trade-offs among sign and magnitude information. PMID:16293204

Brusco, Michael J; Stahl, Stephanie

2005-11-01

378

Top Mass Measurements at the Tevatron  

SciTech Connect

First observed in 1995, the top quark is the third-generation up-type quark of the standard model of particle physics (SM). The CDF and D0 collaborations have analyzed many t{bar t} events produced by the Tevatron collider, studying many properties of the top quark. Among these, the mass of the top quark is a fundamental parameter of the SM, since its value constrains the mass of the yet to be observed Higgs boson. The analyzed events were used to measure the mass of the top quark m{sub t} {approx_equal} 173.2 GeV/c{sup 2} with an uncertainty of less than 1 GeV/c{sup 2}. We report on the latest top mass measurements at the Tevatron, using up to 6 fb{sup -1} of data for each experiment.

Potamianos, Karolos; /Purdue U.

2012-01-01

379

Thermionic topping of electric power plants  

NASA Technical Reports Server (NTRS)

The most likely use of thermionic conversion is in the form of a topping cycle combined with a steam-turbogenerator plant. A specific reference system is chosen in which the thermionic topping cycle occurs in thermionic heat exchangers referred to as large, modular thermionic units to which heat is transferred from a separate heat source and which reject their heat to a conventional steam turboelectric system. Results of analysis show that the performance and cost criteria for practical thermionic topping of large electric power plants are well within the reach of demonstrated and foreseeable converter capabilities. Thermionic topping has many significant advantages over unconventional cycles proposed for topping applications, including level of demonstrated and projected performance and lifetime, development time, and design simplicity.

Britt, E. J.; Fitzpatrick, G. O.; Rasor, N. S.

1975-01-01

380

Protein Identification Using Top-Down  

SciTech Connect

In the last two years, due to advances in protein separation and mass spectrometry, top-down mass spectrometry moved from analyzing single proteins to analyzing complex samples and identifying hundreds and even thousands of proteins. However, computational tools for database search of top-down spectra against protein databases are still in infancy. We describe MS-Align+, a fast algorithm for top-down protein identification based on spectral alignment that enables searches for unexpected post-translational modifications (PTMs). We also propose a method for evaluating statistical significance of top-down protein identifications and further benchmark MS-Align+ along with PIITA, ProSightPTM and SEQUEST, which were previously used for top-down MS/MS database searches. We demonstrate that MS-Align+ and PIITA significantly increase the number of identified proteins as compared to ProSightPTM and SEQUEST.

Liu, Xiaowen; Sirotkin, Yakov; Shen, Yufeng; Anderson, Gordon A.; Tsai, Yi-Hsuan S.; Ting, Ying S.; Goodlett, David R.; Smith, Richard D.; Bafna, Vineet; Pevzner, Pavel A.

2012-06-01

381

Nanophotonics and Single Molecules  

Microsoft Academic Search

Single emitting molecules are currently providing a new window into nanoscale systems ranging from biology to materials science.\\u000a The amount of information that can be extracted from each single molecule depends upon the specific photophysical properties\\u000a of the fluorophore and how these properties are affected by the nearby environment. For this reason, it is necessary to develop\\u000a single-molecule emitters with

W. E. Moerner; P. James Schuck; David P. Fromm; Anika Kinkhabwala; Samuel J. Lord; Stefanie Y. Nishimura; Katherine A. Willets; Arvind Sundaramurthy; Gordon Kino; Meng He; Zhikuan Lu; Robert J. Twieg

382

Droplet epitaxial growth of highly symmetric quantum dots emitting at telecommunication wavelengths on InP(111)A  

NASA Astrophysics Data System (ADS)

We demonstrate the formation of InAs quantum dots (QDs) on InAlAs/InP(111)A by means of droplet epitaxy. The C3v symmetry of the (111)A substrate enabled us to realize highly symmetric QDs that are free from lateral elongations. The QDs exhibit a disk-like truncated shape with an atomically flat top surface. Photoluminescence signals show broad-band spectra at telecommunication wavelengths of 1.3 and 1.5 ?m. Strong luminescence signals are retained up to room temperature. Thus, our QDs are potentially useful for realizing an entangled photon-pair source that is compatible with current telecommunication fiber networks.

Ha, Neul; Liu, Xiangming; Mano, Takaaki; Kuroda, Takashi; Mitsuishi, Kazutaka; Castellano, Andrea; Sanguinetti, Stefano; Noda, Takeshi; Sakuma, Yoshiki; Sakoda, Kazuaki

2014-04-01

383

Bootstrap current in quasi-symmetric stellarators  

NASA Astrophysics Data System (ADS)

This work examines bootstrap current in quasi-symmetric stellarators with a focus on the Quasi- Poloidal Stellarator (QPS). In the design of QPS, a code was used to predict the bootstrap current based on a calculation in an asymptotically collisionless limit. This calculation is believed to be a good approximation of the bootstrap current for low density, high electron temperature (n ˜3x10^19 m-3, Te˜1 keV, Ti˜0.2 keV), ECH heated plasmas in QPS but is expected to be much higher than the actual bootstrap current for more collisional (n ˜8x10^19 m-3, Te˜0.4 keV, Ti˜0.4 keV), ICH heated plasmas in QPS. Recently, a fluid moments approach has been developed to self-consistently calculate viscosities and neoclassical transport coefficients which can be used to calculate the bootstrap current (in addition to neoclassical flows) for arbitrary collisionality and arbitrary magnetic geometry [1]. The predictions from the asymptotic collisionless formula agree qualitatively with the bootstrap current predicted by the fluid moments calculation for the low density, ECH plasmas in QPS. For the high density, ICH heated plasmas, the shape of the predicted profiles are similar but the asymptotic collisionless formula predicts a magnitude of current 4 ˜5 times larger than the prediction from the fluid moments code. Bootstrap currents in NCSX and HSX plasmas are also calculated. [1] D. A. Spong, Phys. Plasmas 12, 056114 (2005).

Ware, A. S.; Spong, D. A.

2005-10-01

384

Monolithic symmetric ion trap for quantum simulation  

NASA Astrophysics Data System (ADS)

We describe the novel design of a monolithic two-level ion trap that combines the flexibility and scalability of VLSI silicon microfabrication with the superior trapping characteristics of multi-level traps. Electrostatic simulations demonstrate that the trap has a deep trapping potential (1 eV for Yb+ ion) and radially symmetric RF confinement field. The trap has an angled through-chip slot which allows backside ion loading and through laser access while avoiding surface light scattering and dielectric charging. The geometrical trap features and dimensions are optimized for investigating ion chains with equal ion spacing. Control potentials have been derived to produce linear equally-spaced ion chains of up to 50 ions that can be used to perform simulations of quantum magnets. The potentials are optimized to give ion separations of 5 to 10 microns, micromotion compensation, and constant motional mode axes and frequencies along the chain. The trap is in fabrication at Georgia Tech using techniques similar to those developed for the planar ion traps.

Shaikh, Fayaz; Slusher, Richart

2011-06-01

385

Plane symmetric relativistic fluids with Taub geometry  

NASA Astrophysics Data System (ADS)

We investigate the problem of generating perfect fluid models by performing a conformal transformation on a non-conformally flat but conformally Ricci-flat (vacuum) seed metric such as the Taub (Ann. Math. 53, 472 (1951)) spacetime. The Taub metric is a static plane symmetric matter-free solution of the Einstein field equations possessing three Killing vectors. It turns out that, assuming a conformal factor depending on the temporal coordinate and one space variable, the resultant metrics are necessarily static. We are able to solve completely the field equations and obtain the geometric and dynamical variables explicitly. A study of the elementary properties required of realistic fluids is made and it is found that the fluid constructed displays necessary qualitative features desirable in realistic cosmological distributions. In particular the energy density and pressure profiles are positive definite and the adiabatic sound-speed index is found to be causal (subluminal) in a region excluding the central axis. Importantly, the weak, strong and dominant energy conditions are all satisfied. It is not possible to obtain a barotropic equation of state in this model.

Hansraj, Sudan

2013-10-01

386

Microtearing Simulations in the Madison Symmetric Torus  

NASA Astrophysics Data System (ADS)

Recent studies of improved confinement discharges in reversed field pinch (RFP) plasmas have revealed the need for greater understanding of the role that microinstabilities may be playing in these devices. In this work, the gyrokinetic codes GYRO and GENE are used to investigate the characteristics of these instabilities in an RFP-type equilibrium. Microtearing is found to have large growth rates across a range of scales for the parameter regime of the Madison Symmetric Torus and may be especially relevant to high-beta PPCD discharges, where large scale tearing mode activity is suppressed and microturbulence is believed to play a greater role in transport. Important features of the mode, such as critical values for beta and electron temperature gradient, are studied for a number of geometric parameters, including flux surface radius and RFP ?. The dependence on collisionality, which plays an important role in this instability, is explored using a Lorentz operator. We find that the RFP microtearing mode is unstable across a range of collisional frequency, and parameter scans show different responses at low versus moderate/high collisionality, possible evidence for different physical drive mechanisms. The source of these drives is explored and compared with existing theory.

Carmody, Daniel; Pueschel, M. J.; Terry, P. W.

2012-10-01

387

On Spherically Symmetric Minimally Coupled Brane Worlds  

NASA Astrophysics Data System (ADS)

For a static, spherically symmetric brane in the framework of the RS2 concept, we study the conditions under which the 4D tensor E?v, arising from the 5D Weyl tensor, vanishes on the brane. Gravity on the brane is then decoupled from the bulk geometry, it is the so-called minimally coupled brane world (MCBW). Assuming E?v =0 in the whole bulk, we try to solve the 5D Einstein equations GAB + ?5gAB =0 and obtain an overdetermined set of equations for functions of the radial coordinate. Some special solutions are found, among which are the well-known ``black string'' solution with the Schwarzschild metric on the brane and its generalizations with Schwarzschild-(A)dS on-brane metrics. It is concluded that a MCBW can be embedded, in general, in a bulk where E?v is not identically zero but only vanishes on the brane. We also present some previous results on the general properties of scalar fields on the brane and give an example of a wormhole supported by a scalar field in a MCBW.

Bronnikov, K. A.; Fadeev, S. B.; Michtchenko, A. V.

2004-07-01

388

Mitotoxicity in distal symmetrical sensory peripheral neuropathies.  

PubMed

Chronic distal symmetrical sensory peripheral neuropathy is a common neurological complication of cancer chemotherapy, HIV treatment and diabetes. Although aetiology-specific differences in presentation are evident, the clinical signs and symptoms of these neuropathies are clearly similar. Data from animal models of neuropathic pain suggest that the similarities have a common cause: mitochondrial dysfunction in primary afferent sensory neurons. Mitochondrial dysfunction is caused by mitotoxic effects of cancer chemotherapeutic drugs of several chemical classes, HIV-associated viral proteins, and nucleoside reverse transcriptase inhibitor treatment, as well as the (possibly both direct and indirect) effects of excess glucose. The mitochondrial injury results in a chronic neuronal energy deficit, which gives rise to spontaneous nerve impulses and a compartmental neuronal degeneration that is first apparent in the terminal receptor arbor-that is, intraepidermal nerve fibres-of cutaneous afferent neurons. Preliminary data suggest that drugs that prevent mitochondrial injury or improve mitochondrial function could be useful in the treatment of these conditions. PMID:24840972

Bennett, Gary J; Doyle, Timothy; Salvemini, Daniela

2014-06-01

389

Drift waves in helically symmetric stellarators  

NASA Astrophysics Data System (ADS)

The local linear stability of electron drift waves and ion temperature gradient modes (ITG) is investigated in a quasihelically symmetric (QHS) stellarator and a conventional asymmetric (Mirror) stellarator. While the eigenfunctions have a similar shape in both magnetic geometries, they are slightly more localized along the field line in the QHS case. The most unstable electron drift modes are strongly localized at the symmetry points (where stellarator symmetry is present) and in the regions where normal curvature is bad and magnitude of the local magnetic shear and magnetic field is minimum. Modes are found more affected by the normal curvature than by the geodesic curvature. The threshold of stability of the ITG modes in terms of ?i is found to be 2/3 in this fluid model consistent with the smallest threshold for toroidal geometry with adiabatic electrons. Optimization to favorable drift wave stability has small field line curvature, short connection lengths, the proper combination of geodesic curvature and local magnetic shear, large values of local magnetic shear and the compression of flux surfaces in the bad curvature region. In most of these studies, a simplified adiabatic electrons response is used. Progress on a more rigorous treatment of the electrons will be reported that accounts for toroidally and helically trapped particles and landau resonances in stellarator geometry.

Rafiq, Tariq

2005-10-01

390

Drift waves in helically symmetric stellarators  

NASA Astrophysics Data System (ADS)

The local linear stability of electron drift waves and ion temperature gradient modes (ITG) is investigated in a quasihelically symmetric (QHS) stellarator and a conventional asymmetric (Mirror) stellarator. The geometric details of the different equilibria are emphasized. Eigenvalue equations for the models are derived using the ballooning mode formalism and solved numerically using a standard shooting technique in a fully three-dimensional stellarator configuration. While the eigenfunctions have a similar shape in both magnetic geometries, they are slightly more localized along the field line in the QHS case. The most unstable electron drift modes are strongly localized at the symmetry points (where stellarator symmetry is present) and in the regions where normal curvature is unfavorable and magnitude of the local magnetic shear and magnetic field is minimum. The presence of a large positive local magnetic shear in the bad curvature region is found to be destabilizing. Electron drift modes are found to be more affected by the normal curvature than by the geodesic curvature. The threshold of stability of the ITG modes in terms of ?i is found to be 2/3 in this fluid model consistent with the smallest threshold for toroidal geometry with adiabatic electrons. Optimization to favorable drift wave stability has small field line curvature, short connection lengths, the proper combination of geodesic curvature and local magnetic shear, large values of local magnetic shear, and the compression of flux surfaces in the unfavorable curvature region.

Rafiq, T.; Hegna, C. C.

2005-11-01

391

Coherent perfect absorption in one-dimensional photonic crystal with a PT-symmetric defect  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate a one-dimensional photonic crystal defect mode coherent perfect absorber (CPA) or antilasing, which is based on the PT-synthetic material defect. It is found that the CPA can be excited by two coherent monochromatic waves which are located at the frequency range of the defect mode (near the top of the transmission peak in the gap) incident with the same amplitude from both sides. Moreover, we found that the CPA frequency possesses the property of flexible controllability. This property can easily be realized by modulating the variation in thickness of the defect layer and the symmetrical incidence angle of the two coherent beams. Therefore, the photonic crystal defect mode CPA proposed here shows much more flexibility in operation frequency compared with the results in the literature (Chong Y. D. et al., Phys. Rev. Lett., 105 (2010) 053901; Wan W. et al., Science, 331 (2011) 889).

Zhang, Zheng-Ren; Li, Hong-Qiang; Chen, Hong; Hu, Chun-Lian; Zhou, Ping

2014-02-01

392

Photon polarization in the b ? s? processes in the left-right symmetric model  

NASA Astrophysics Data System (ADS)

The circular-polarization of the photon in the radiative B decays is dominantly left-handed in the Standard Model (SM), but the right-handed polarization may be enhanced in some new physics models with right-handed currents, such as the Left-Right Symmetric Model (LRSM). In this article, we investigate how large this wrong polarization could be within the allowed parameter space of the LRSM. We show that in the LRSM, the right-handed polarization of the photon in the b ? s? processes could be largely enhanced by the W L - W R mixing contributions because of the helicity flip on the internal top quark line of the penguin diagrams and the enhancement by the CKM factor . We discuss the sensitivity of the proposed methods to determine the b ? s? photon polarization to the LRSM as well as their complementary role compared to the direct search of right-handed charged gauge bosons at LHC.

Yu, Fu-Sheng; Kou, Emi; Lü, Cai-Dian

2013-12-01

393

Symmetrical positive-negative annular phase object for optical nonlinearity characterization  

NASA Astrophysics Data System (ADS)

A novel symmetrical positive-negative annular phase object (PNA-PO) is proposed in the 4f coherent imaging system and a third-order nonlinear refraction of the material is measured. By decomposing the normalized incident field passing through the PNA-PO into three top-hat beams with various radii and phase delays, and by using some applicable approximations, analytical solution of the phase contrast signal ?T is revealed. Furthermore, variations of the analytical solution and numerical simulation of ?T as a function of the on-axis nonlinear phase shift ?0 are shown. CS2 as a standard sample is performed using a PNA-PO to illustrate the feasibility and predominance of our system.

Nie, Zhongquan; Li, Zhongguo; Zhang, Xueru; Ao, Guanghong; Shi, Guang; Wang, Yuxiao; Song, Yinglin

2014-01-01

394

Limits on the strength of a left-right-symmetric electroweak interaction  

SciTech Connect

We have investigated the constraints imposed on left-right-symmetric theories of weak and electromagnetic interactions by the K/sub L/-K/sub S/ mass difference, including the additional restrictions on the top-quark mass and mixing angles coming from the K/sub L/..--> mu../sup +/..mu../sup -/ decay rate, and emphasizing the sensitivity of the results to various model-dependent assumptions. In the manifestly left-right-symmetric electroweak theory it was found that values for m/sub R/, the mass of the charged right-handed boson W/sub R/, as low as 220 GeV/c/sup 2/ (the original estimate of Beg, Budny, Mohapatra, and Sirlin) cannot be ruled out. However, for a large class of plausible models the lower bound on the mass of W/sub R/ was found to be considerably higher, but still within the range that experiments now in progress will be able to explore. The lower bound on m/sub R/ was also found to be quite sensitive to the value assumed for the top-quark mass and to the model-dependent values of the hadronic matrix elements of the quark operators, as well as to certain model-dependent assumptions regarding the dispersive part of the K/sub L/..--> mu../sup +/..mu../sup -/ amplitude. We present the lower bound on m/sub R/ for a wide range of the relevant parameters, which includes two specific models: the MIT bag model and the vacuum-insertion approximation.

Hwang, M.; Oakes, R.J.

1984-01-01

395

Electric top drives gain wide industry acceptance  

SciTech Connect

Since its introduction, the top drive drilling system has gained acceptance as a productive and safe method for drilling oil and gas wells. Originally, the system was used mostly for offshore and higher cost land drilling, and it had to be installed as a permanent installation because of its enormous weight and size. Essentially, a top drive replaces the kelly and rotary table as the means of rotating drillpipe on oil, gas and geothermal rigs and is considered to be 15% to 40% more efficient than a kelly drive. Top drive systems allow the operator to drill and maintain directional orientation for triple stands and provide tripping efficiency because of the ability to ream and circulate with triple stands, to reduce the risk of stuck pipe or lost wells, and to improve well control and pipe handling safety. The paper describes electric top drives with DC motors, top drives with AC motors, top drives with permanent magnet motors, and top drives with permanent magnet brushless synchronous motors.

Riahi, M.L.

1998-05-01

396

THE TOP QUARK, QCD, AND NEW PHYSICS.  

SciTech Connect

The role of the top quark in completing the Standard Model quark sector is reviewed, along with a discussion of production, decay, and theoretical restrictions on the top quark properties. Particular attention is paid to the top quark as a laboratory for perturbative QCD. As examples of the relevance of QCD corrections in the top quark sector, the calculation of e{sup +}e{sup -} + t{bar t} at next-to-leading-order QCD using the phase space slicing algorithm and the implications of a precision measurement of the top quark mass are discussed in detail. The associated production of a t{bar t} pair and a Higgs boson in either e{sup +}e{sup -} or hadronic collisions is presented at next-to-leading-order QCD and its importance for a measurement of the top quark Yulrawa coupling emphasized. Implications of the heavy top quark mass for model builders are briefly examined, with the minimal supersymmetric Standard Model and topcolor discussed as specific examples.

DAWSON,S.

2002-06-01

397

Decelerating Neutral Dipolar Molecules  

Microsoft Academic Search

It is experimentally demonstrated that a beam of neutral dipolar molecules can be efficiently decelerated with a time-varying electric field. A pulsed beam of neutral metastable CO molecules is slowed down from 225 m\\/s ( Ekin = 59 cm-1) to 98 m\\/s ( Ekin = 11 cm-1) upon passage through an array of 63 synchronously pulsed electric field stages.

Hendrick L. Bethlem; Giel Berden; Gerard Meijer

1999-01-01

398

Porous organic molecules  

NASA Astrophysics Data System (ADS)

Most synthetic materials that show molecular-scale porosity consist of one-, two- or three-dimensional networks. Porous metal-organic frameworks in particular have attracted a lot of recent attention. By contrast, discrete molecules tend to pack efficiently in the solid state, leaving as little empty space as possible, which leads to non-porous materials. This Perspective discusses recent developments with discrete organic molecules that are porous in the solid state. Such molecules, which may be either crystalline or amorphous, can be categorized as either intrinsically porous (containing permanent covalent cavities) or extrinsically porous (inefficiently packed). We focus on the possible advantages of organic molecules over inorganic or hybrid systems in terms of molecular solubility, choice of components and functionalities, and structural mobility and responsiveness in non-covalent extended solids. We also highlight the potential for 'undiscovered' porous systems among the large number of cage-like organic molecules that are already known.

Holst, James R.; Trewin, Abbie; Cooper, Andrew I.

2010-11-01

399

Top quark properties from the Tevatron  

SciTech Connect

This report describes latest measurements and studies of top quark properties from the Tevatron in Run II with an integrated luminosity of up to 750 pb{sup -1}. Due to its large mass of about 172 GeV/c{sup 2}, the top quark provides a unique environment for tests of the Standard Model and is believed to yield sensitivity to new physics beyond the Standard Model. With data samples of close to 1 fb{sup -1} the CDF and D0 collaborations at the Tevatron enter a new area of precision top quark measurements.

Klute, Markus; /MIT, LNS

2006-05-01

400

Top Quark Production at the Tevatron  

SciTech Connect

The top quark is the most recently discovered of the standard model quarks, and because of its very large mass, studies of the top quark and its interactions are important both as tests of the standard model and searches for new phenomena. In this document, recent results of analyses of top quark production, via both the electroweak and strong interactions, from the CDF and D0 experiments are presented. The results included here utilize a dataset corresponding to up to 6 fb{sup -1} of integrated luminosity, slightly more than half of the dataset recorded by each experiment before the Tevatron was shutdown in September 2011.

Mietlicki, David J.

2011-12-01

401

Top quark mass measurement at the Tevatron  

SciTech Connect

The authors report on the latest experimental measurements of the top quark mass by the CDF and D0 Collaborations at the Fermilab Tevatron. They present a new top mass measurement using the t{bar t} events collected by the D0 Collaboration in Run I between 1994 and 1996. This result is combined with previous measurements to yield a new world top mass average. They also describe several preliminary results using up to 193 pb{sup -1} of t{bar t} events produced in {bar p}p collisions at {radical}s = 1.96 TeV during the Run II of the Tevatron.

Guimaraes da Costa, Joao; /Harvard U.

2004-12-01

402

Single top quark production at D0  

SciTech Connect

We present first evidence for the production of single top quarks at the Fermilab Tevatron p{bar p} collider. Using a 0.9 fb{sup -1} dataset, we apply a multivariate analysis to separate signal from background and measure cross section for single top quark production. We use the cross section measurement to directly determine the CKM matrix element that describes the Wtb coupling. We also present results of W0 and charged Higgs searches with the same final states as standard model single top quark production.

Jabeen, S.; /Boston U.

2008-07-01

403

Single Top Production at the Tevatron  

SciTech Connect

We present recent results of single top quark production in the lepton plus jet final state, performed by the CDF and D0 collaborations based on 7.5 and 5.4 fb{sup -1} of p{bar p} collision data collected at {radical}s = 1.96 TeV from the Fermilab Tevatron collider. Multivariate techniques are used to separate the single top signal from the backgrounds. Both collaborations present measurements of the single top quark cross section and the CKM matrix element |V{sub tb}|. A search for anomalous Wtb coupling from D0 is also presented.

Wu, Zhenbin; /Baylor U.

2012-05-01

404

The stability of laminar symmetric separated wakes  

NASA Astrophysics Data System (ADS)

Time-dependent computations of the two-dimensional incompressible uniform-velocity laminar flow past a normal flat plate (of unit half-width) in a channel are presented. Attention is restricted to cases in which the well-known anti-symmetric (von Kármán-type) vortex shedding is suppressed by the imposition of a symmetry plane on the downstream plate centreline. With a further symmetry plane at the channel's upper boundary, the only two governing parameters in the problem are the channel half-width, H, and the Reynolds number, Re (based on the body half-width and the upstream velocity, U). The former is restricted to the range 3 {?} H {?} 30 and the interest lies in determining the nature of the initial instability which occurs in the separated wake as Re is gradually increased. It is found that for sufficiently large H and at a critical Re, a long-time-scale global (supercritical) instability is initiated, which in its saturated (limit) state takes the form of ‘lumps’ of vorticity being periodically shed from the tail end of the separated bubble. Stability calculations of corresponding mean flow profiles (typical of those found in the separated wake) are undertaken by examining the impulse response of particular profiles via appropriate solution of the Orr Sommerfeld equation. The results of this analysis extend those available from related published work and are consistent with the behaviour found from the numerical computations. Taken together, all the results suggest that this type of global instability may be generic to many kinds of separated wakes and, indeed, may provide the fundamental explanation for the very low-frequency oscillations often noticed in fully turbulent wake bubbles.

Castro, Ian P.

2005-06-01

405

Creation of Functional Micro/Nano Systems through Top-down and Bottom-up Approaches  

PubMed Central

Mimicking nature’s approach in creating devices with similar functional complexity is one of the ultimate goals of scientists and engineers. The remarkable elegance of these naturally evolved structures originates from bottom-up self-assembly processes. The seamless integration of top-down fabrication and bottom-up synthesis is the challenge for achieving intricate artificial systems. In this paper, technologies necessary for guided bottom-up assembly such as molecular manipulation, molecular binding, and the self assembling of molecules will be reviewed. In addition, the current progress of synthesizing mechanical devices through top-down and bottom-up approaches will be discussed.

Wong, Tak-Sing; Brough, Branden; Ho, Chih-Ming

2009-01-01

406

CD molecules 2005: human cell differentiation molecules.  

PubMed

The immune system works through leukocytes interacting with each other, with other cells, with tissue matrices, with infectious agents, and with other antigens. These interactions are mediated by cell-surface glycoproteins and glycolipids. Antibodies against these leukocyte molecules have provided powerful tools for analysis of their structure, function, and distribution. Antibodies have been used widely in hematology, immunology, and pathology, and in research, diagnosis, and therapy. The associated CD nomenclature is commonly used when referring to leukocyte surface molecules and antibodies against them. It provides an essential classification for diagnostic and therapeutic purposes. The most recent (8th) Workshop and Conference on Human Leukocyte Differentiation Antigens (HLDA), held in Adelaide, Australia, in December 2004, allocated 95 new CD designations and made radical changes to its aims and future operational strategy in order to maintain its relevance to modern human biology and clinical practice. PMID:16020511

Zola, Heddy; Swart, Bernadette; Nicholson, Ian; Aasted, Bent; Bensussan, Armand; Boumsell, Laurence; Buckley, Chris; Clark, Georgina; Drbal, Karel; Engel, Pablo; Hart, Derek; Horejsí, Václav; Isacke, Clare; Macardle, Peter; Malavasi, Fabio; Mason, David; Olive, Daniel; Saalmueller, Armin; Schlossman, Stuart F; Schwartz-Albiez, Reinhard; Simmons, Paul; Tedder, Thomas F; Uguccioni, Mariagrazia; Warren, Hilary

2005-11-01

407

The Top 10 Issues Impacting School Administrators.  

ERIC Educational Resources Information Center

Discusses the top challenges commonly confronted nationwide by school districts districts, facilities, and business. Challenges include construction and repair, enrollment, funding, security and safety, technology, maintenance, staff training and retention, and unfunded mandates. (GR)

Kennedy, Mike

2001-01-01

408

Best of "Earth As Art" -- Top Five  

NASA Video Gallery

Counting down the Top Five Earth As Art images, as voted on by the public. Landsat has been collecting data of the Earth's surface since 1972. Some of the images are visually striking, and they hav...

409

Top and higgs physics at the Tevatron  

SciTech Connect

We present a summary of our experimental understanding of the top quark and discuss the significant improvements expected in Run II at the Fermilab Tevatron Collider. We also discuss prospects for a Higgs boson discovery at the Tevatron.

Pierre Savard

2002-12-23

410

Top partner probes of extended Higgs sectors  

NASA Astrophysics Data System (ADS)

Natural theories of the weak scale often include fermionic partners of the top quark. If the electroweak symmetry breaking sector contains scalars beyond a single Higgs doublet, then top partners can have sizable branching ratios to these extended Higgs sector states. In fact, top partner decays may provide the most promising discovery mode for such scalars, especially given the large backgrounds to direct and associated production. In this paper, we present a search strategy for top partner decays to a charged Higgs boson and a bottom quark, focusing on the case where the charged Higgs dominantly decays to third-generation quarks to yield a multi- b final state. We also discuss ways to extend this search to exotic neutral scalars decaying to bottom quark pairs.

Kearney, John; Pierce, Aaron; Thaler, Jesse

2013-08-01

411

Exotic top partners and Little Higgs  

NASA Astrophysics Data System (ADS)

Little Higgs models often give rise to top partners beyond the minimal ones necessary for the cancellation of quadratic divergences. We review how this occurs and discuss the phenomenology of these exotic states. We emphasize the possible importance of new pseudo-Nambu-Goldstone bosons in top partner decays. Indeed, cascade decays of exotic top partners may be the best way to discover these new bosons. We illustrate these points with a new Little Higgs construction based on an SO(10)/SO(5)2 coset structure, which fills a gap in the model building literature. These observations motivate new search strategies for top partners at the LHC, including for final states with b-jets and a large multiplicity of electroweak bosons.

Kearney, John; Pierce, Aaron; Thaler, Jesse

2013-10-01

412

A first top partner hunter's guide  

NASA Astrophysics Data System (ADS)

We provide a systematic effective lagrangian description of the phenomenology of the lightest top-partners in composite Higgs models. Our construction is based on symmetry, on selection rules and on plausible dynamical assumptions. The structure of the resulting simplified models depends on the quantum numbers of the lightest top partner and of the operators involved in the generation of the top Yukawa. In all cases the phenomenology is conveniently described by a small number of parameters, and the results of experimental searches are readily interpreted as a test of naturalness. We recast presently available experimental bounds on heavy fermions into bounds on top partners: LHC has already stepped well inside the natural region of parameter space.

De Simone, Andrea; Matsedonskyi, Oleksii; Rattazzi, Riccardo; Wulzer, Andrea

2013-04-01

413

Top quark production dynamics in QCD.  

National Technical Information Service (NTIS)

A calculation of the total cross section for top quark production in hadron-hadron collisions is presented based on an all-orders perturbative resummation of initial-state gluon radiative contributions to the basic quantum chromodynamics subprocesses. Pri...

E. L. Berger H. Contopanagos

1995-01-01

414

Total cross section for top quark production.  

National Technical Information Service (NTIS)

We summarize our calculation of the total cross section for top quark production at hadron colliders within the context of perturbative quantum chromodynamics, including resummation of the effects of initial-state soft gluon radiation to all orders in the...

E. L. Berger H. Contopanagos

1996-01-01

415

Remotely operated Top Loading Filter Housing. Summary.  

National Technical Information Service (NTIS)

A new fuel reprocessing facility is in design and construction at the Idaho Chemical Processing Plant (ICPP) located at the Idaho National Engineering Laboratory (INEL). This facility will use a new Top Loading Filter Housing (TLFH) design for remote High...

M. J. Ross J. A. Carter

1989-01-01

416

Dark decay of the top quark  

NASA Astrophysics Data System (ADS)

We suggest top quark decays as a venue to search for light dark force carriers. The top quark is the heaviest particle in the standard model whose decays are relatively poorly measured, allowing sufficient room for exotic decay modes from new physics. A very light (GeV scale) dark gauge boson (Z') is a recently highlighted hypothetical particle that can address some astrophysical anomalies as well as the 3.6? deviation in the muon g-2 measurement. We present and study a possible scenario that top quark decays as t?bW+Z's. This is the same as the dominant top quark decay (t?bW) accompanied by one or multiple dark force carriers. The Z' can be easily boosted, and it can decay into highly collimated leptons (lepton-jet) with large branching ratio. We discuss the implications for the Large Hadron Collider experiments including the analysis based on the lepton-jets.

Kong, Kyoungchul; Lee, Hye-Sung; Park, Myeonghun

2014-04-01

417

Nonfactorizable effects in top quark production  

NASA Astrophysics Data System (ADS)

The production of top-antitop pairs at the Fermilab Tevatron shows a forward-backward asymmetry in which the top quark tends to follow the proton direction, while the antitop tends to follow the antiproton direction. The effect grows with increasing effective mass mtt¯ of the top-antitop pair, and with increasing rapidity difference between the top and antitop. The observed effect is about 3 times as large as predicted by next-to-leading-order QCD, but with the same sign. An estimate of nonfactorizable effects based on a QCD string picture finds they are negligible, but that small distortions of the mt spectrum are possible. Tests for such effects, both at and above the level of this estimate, are suggested.

Rosner, Jonathan L.

2012-07-01

418

Top Ten Technology Breakthroughs for Schools.  

ERIC Educational Resources Information Center

Contributors discuss the top ten technologies that allow for thinking in new and innovative ways about the concept of "school": virtual learning; wireless networking; collaboration tools; digital video; Application Service Providers; handheld devices; optical networking; videoconferencing; XML; and simulations. (AEF)

Bateman, Bill; Crystal, Jerry; Davidson, Hall; Holzberg, Carol S.; McIntire, Todd; McLester, Susan; Ohler, Jason; Rose, Ray; Shields, Jean; Warlick, David

2001-01-01

419

Synthesis of a new class of carborane-containing star-shaped molecules via silicon tetrachloride promoted cyclotrimerization reactions.  

PubMed

Symmetrical star-shaped molecules with carborane clusters on the periphery have been synthesized in good yields via silicon tetrachloride mediated cyclotrimerization reactions of 9-benzyl derivatives of carboranes with acetyl group substitution on the benzene ring. Facile functionalization of these symmetrical core structures with 1-iodoheptane and trivinylchlorosilane produce compounds which could be used as liquid crystalline substances and precursors for synthesis of higher order carbosilane dendrons. PMID:18465864

Dash, Barada Prasanna; Satapathy, Rashmirekha; Maguire, John A; Hosmane, Narayan S

2008-06-01

420

HLA-G molecule.  

PubMed

Human leukocyte antigen-G (HLA-G) is a non-classical HLA class I molecule, which was first discovered in 1987 by Geraghty and colleagues. While classical HLA class I molecules are expressed on all nucleated cells, the expression of the HLA-G molecule is highly tissue-restricted, such as to placental trophoblast cells. HLA-G binds inhibitory receptors such as leukocyte immunoglobulin-like receptors B1 (LILRB1/ILT2/CD85j) and LILRB2 (ILT4/CD85d), which are widely expressed on immune cells, to suppress a broad range of immune responses. Thus, the expression of HLA-G in placenta protects the fetus from the maternal immune system. On the other hand, emerging studies have shown the relevance of the HLA-G molecule in pathologic conditions, such as transplantation rejection, autoimmunity, and cancer. HLA-G has other unique characteristics, in contrast with classical HLA molecules, including the existence of various forms of HLA-G: several splice variants, subunit-deficient conformations, homodimers, and their combinations have been found. In this review, we highlight the molecular basis for the tolerogenic ability of the HLA-G molecule, especially by LILR recognition of various forms of HLA-G. We also discuss the potential clinical applications of HLA-G molecules. PMID:19860681

Kamishikiryo, Jun; Maenaka, Katsumi

2009-01-01

421

The Molecule Pages database  

PubMed Central

The UCSD-Nature Signaling Gateway Molecule Pages (http://www.signaling-gateway.org/molecule) provides essential information on more than 3800 mammalian proteins involved in cellular signaling. The Molecule Pages contain expert-authored and peer-reviewed information based on the published literature, complemented by regularly updated information derived from public data source references and sequence analysis. The expert-authored data includes both a full-text review about the molecule, with citations, and highly structured data for bioinformatics interrogation, including information on protein interactions and states, transitions between states and protein function. The expert-authored pages are anonymously peer reviewed by the Nature Publishing Group. The Molecule Pages data is present in an object-relational database format and is freely accessible to the authors, the reviewers and the public from a web browser that serves as a presentation layer. The Molecule Pages are supported by several applications that along with the database and the interfaces form a multi-tier architecture. The Molecule Pages and the Signaling Gateway are routinely accessed by a very large research community.

Saunders, Brian; Lyon, Stephen; Day, Matthew; Riley, Brenda; Chenette, Emily; Subramaniam, Shankar

2008-01-01

422

The Isotopic Anatomies of Molecules and Minerals  

NASA Astrophysics Data System (ADS)

Most natural compounds are composed of diverse isotopologues that differ in the number and/or symmetrically unique atomic locations of isotopic substitutions. Little of this isotopic diversity is observed by conventional methods of stable isotope geochemistry, which generally measure concentrations of rare isotopes without constraining differences in isotopic composition between different atomic sites or nonrandom probabilities of multiple isotopic substitutions in the same molecule. Recent advances in analytical instrumentation and methodology have created a set of geochemical tools—geothermometers, biosynthetic signatures, forensic fingerprints—based on these position-specific isotope effects and multiply substituted isotopologues. This progress suggests we are entering a period in which many new geochemical tools of this type will be created. This review describes the principles, background, analytical methods, existing applied tools, and likely future progress of this emerging field.

Eiler, John M.

2013-05-01

423

Top-down proteomics in health and disease: challenges and opportunities.  

PubMed

Proteomics is essential for deciphering how molecules interact as a system and for understanding the functions of cellular systems in human disease; however, the unique characteristics of the human proteome, which include a high dynamic range of protein expression and extreme complexity due to a plethora of PTMs and sequence variations, make such analyses challenging. An emerging "top-down" MS-based proteomics approach, which provides a "bird's eye" view of all proteoforms, has unique advantages for the assessment of PTMs and sequence variations. Recently, a number of studies have showcased the potential of top-down proteomics for the unraveling of disease mechanisms and discovery of new biomarkers. Nevertheless, the top-down approach still faces significant challenges in terms of protein solubility, separation, and the detection of large intact proteins, as well as underdeveloped data analysis tools. Consequently, new technological developments are urgently needed to advance the field of top-down proteomics. Herein, we intend to provide an overview of the recent applications of top-down proteomics in biomedical research. Moreover, we will outline the challenges and opportunities facing top-down proteomics strategies aimed at understanding and diagnosing human diseases. PMID:24723472

Gregorich, Zachery R; Ge, Ying

2014-05-01

424

New physics effects in Top quark interactions  

SciTech Connect

The Top quark stands out as the heaviest elementary particle known today and it is expected to be sensitive to the mechanism that breaks the electroweak symmetry. In particular, the study of its couplings to the electroweak gauge bosons is important as it a way to test different models beyond the SM. We review the status of Top quark couplings with the W and Z bosons, as well as FCNC couplings.

Larios, F. [Departamento de Fisica Aplicada, CINVESTAV-Merida, A.P. 73, 97310 Merida, Yucatan (Mexico); Perez, M. A. [Departamento de Fisica, CINVESTAV, A.P. 14-740, 07000, Mexico D.F. (Mexico); Martinez, R. [Departamento de Fisica, Universidad Nacional, Apartado aereo 14490, Bogota (Colombia)

2007-06-19

425

Tools for top physics at CDF  

SciTech Connect

The authors describe here the different tools used for top physics analysis in the CDF Collaboration. In particular, they discuss how the jet energy scale, lepton identification, b tagging algorithms and the neural networks help to improve the signal to background ratio of the top sample in some cases and to reduce the dominant uncertainties in other. Results using each one of these tools are also presented.

Palencia, E.; /Fermilab

2008-07-01

426

TopOwl night vision improvements  

Microsoft Academic Search

TopOwl® is an original concept of binocular Helmet Mounted Sight and Display system (HMSD) for helicopters, where two Image Intensifier Tubes (IIT) are integrated on the headgear and optically coupled to the clear visor placed in front of the pilot's eyes. Thales recently developed a new version of its TopOwl®'s Display Module with the objective to have an HMSD capable

Olivier Lemoine; Jean Claude Ebert; Frédéric Saviot; Marie Charbonneau; Bruno Coumert

2008-01-01

427

Jet substructures of boosted polarized top quarks  

NASA Astrophysics Data System (ADS)

We study jet substructures of a boosted polarized top quark, which undergoes the semileptonic decay t?b??, in the perturbative QCD framework. The jet mass distribution (energy profile) is factorized into the convolution of a hard top-quark decay kernel with the bottom-quark jet function (jet energy function). Computing the hard kernel to the leading order in QCD and inputting the latter functions from the resummation formalism, we observe that the jet mass distribution is not sensitive to the helicity of the top quark, but the energy profile is: energy is accumulated faster within a left-hand top jet than within a right-hand one, a feature related to the V-A structure of weak interaction. It is pointed out that the energy profile is a simple and useful jet observable for helicity discrimination of a boosted top quark, which helps identification of physics beyond the standard model at the Large Hadron Collider. The extension of our analysis to other jet substructures, including those associated with a hadronically decaying polarized top quark, is proposed.

Kitadono, Yoshio; Li, Hsiang-nan

2014-06-01

428

Systems of Differential Equations with Skew-Symmetric, Orthogonal Matrices  

ERIC Educational Resources Information Center

The solution of a system of linear, inhomogeneous differential equations is discussed. The particular class considered is where the coefficient matrix is skew-symmetric and orthogonal, and where the forcing terms are sinusoidal. More general matrices are also considered.

Glaister, P.

2008-01-01

429

Relation between sliding and migration of symmetrical tilt grain boundaries.  

National Technical Information Service (NTIS)

We demonstrate that, based on their unique geometry, the migration of all symmetrical and certain asymmetrical tilt grain boundaries is necessarily accompanied by sliding parallel to the interface. By contrast, for all other types of grain boundaries no c...

D. Wolf S. R. Phillpot J. A. Jaszczak J. M. Rickman S. Yip

1991-01-01

430

Symmetric Pin Diversion Detection using a Partial Defect Detector (PDET)  

SciTech Connect

Since the signature from the Partial Defect Detector (PDET) is principally dependent on the geometric layout of the guide tube locations, the capability of the technique in detecting symmetric diversion of pins needs to be determined. The Monte Carlo simulation study consisted of cases where pins were removed in a symmetric manner and the resulting signatures were examined. In addition to the normalized gamma-to-neutron ratios, the neutron and gamma signatures normalized to their maximum values, were also examined. Examination of the shape of the three curves as well as of the peak-to-valley differences in excess of the maximum expected in intact assemblies, indicated pin diversion. A set of simulations with various symmetric patterns of diversion were examined. The results from these studies indicated that symmetric diversions as low as twelve percent could be detected by this methodology.

Sitaraman, S; Ham, Y S

2009-06-01

431

Quantization of Td- and Oh-symmetric Skyrmions  

NASA Astrophysics Data System (ADS)

The geometrical construction of rational maps using a cubic grid has led to many new Skyrmion solutions, with baryon numbers up to 108. Energy spectra of some of the new Skyrmions are calculated here by semiclassical quantization. Quantization of the B=20 Td-symmetric Skyrmion, which is one of the newly found Skyrmions, is considered, and this leads to the development of a new approach to solving Finkelstein-Rubinstein constraints. Matrix equations are simplified by introducing a Cartesian version of angular momentum basis states, and the computations are easier. The quantum states of all Td-symmetric Skyrmions, constructed from the cubic grid, are classified into three classes, depending on the contribution of vertex points of the cubic grid to the rational maps. The analysis is extended to the larger symmetry group Oh. Quantum states of Oh-symmetric Skyrmions, constructed from the cubic grid, form a subset of the Td-symmetric quantum states.

Lau, P. H. C.; Manton, N. S.

2014-06-01

432

Non-symmetric localized fold of a floating sheet  

NASA Astrophysics Data System (ADS)

An elastic sheet lying on the surface of a liquid, if axially compressed, shows a transition from a smooth sinusoidal pattern to a well-localized fold. This wrinkle-to-fold transition is a manifestation of a localized buckling. The symmetric and antisymmetric shapes of the fold have recently been described by Diamant and Witten (2011), who found two exact solutions of the nonlinear equilibrium equations. In this Note, we show that these solutions can be generalized to a continuous family of solutions, which yields non-symmetric shapes of the fold. We prove that non-symmetric solutions also describe the shape of a soft strip withdrawn from a liquid bath, a physical problem that allows us to easily observe portions of non-symmetric profiles.

Rivetti, Marco

2013-03-01

433

Bianisotropic Negative-Index Metamaterial Embedded in a Symmetric Medium.  

National Technical Information Service (NTIS)

In order to more clearly observe the bianisotropic effects due to fabrication-induced structural asymmetries in negative-index metamaterials based on a fishnet structure, it is necessary to measure the optical properties with symmetric substrate and super...

K. M. Dani P. C. Upadhya S. R. Brueck Z. Ku

2009-01-01

434

A parallel algorithm for the non-symmetric eigenvalue problem  

SciTech Connect

This paper describes a parallel algorithm for computing the eigenvalues and eigenvectors of a non-symmetric matrix. The algorithm is based on a divide-and-conquer procedure and uses an iterative refinement technique.

Dongarra, J.; Sidani, M. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science Oak Ridge National Lab., TN (United States))

1991-12-01

435

Geometry optimization of axially symmetric ion traps  

NASA Astrophysics Data System (ADS)

This paper presents numerical optimization of geometries of axially symmetric ion traps for mass analyzers. Four geometries have been taken up for investigation: one is the well known cylindrical ion trap (CIT) and three others are new geometries. Two of these newer geometries have a step in the region of the midplane of the cylindrical ring electrode (SRIT) and the third geometry has a step in its endcap electrodes (SEIT). The optimization has been carried out around different objective functions composed of the desired weights of higher order multipoles. The Nelder-Mead simplex method has been used to optimize trap geometries. The multipoles included in the computations are quadrupole, octopole, dodecapole, hexadecapole, ikosipole and tetraikosipole having weights A2, A4, A6, A8, A10 and A12, respectively. Poincaré sections have been used to understand dynamics of ions in the traps investigated. For the CIT, it has been shown that by changing the aspect ratio of the trap the harmful effects of negative dodecapole superposition can be eliminated, although this results in a large positive A4/A2 ratio. Improved performance of the optimized CIT is suggested by the ion dynamics as seen in Poincaré sections close to the stability boundary. With respect to the SRIT, two variants have been investigated. In the first geometry, A4/A2 and A6/A2 have been optimized and in the second A4/A2, A6/A2 and A8/A2 have been optimized; in both cases, these ratios have been kept close to their values reported for stretched hyperboloid geometry Paul traps. In doing this, however, it was seen that the weights of still higher order multipoles not included in the objective function, A10/A2 and A12/A2, are high; additionally, A10/A2 has a negative sign. In spite of this, for both these configurations, the Poincaré sections predict good performance. In the case of the SEIT, a geometry was obtained for which A4/A2 and A6/A2 are close to their values in the stretched geometry Paul trap and the higher even multipoles (A8/A2, A10/A2 and A12/A2) are all positive and small in magnitude. The Poincaré sections predict good performance for this configuration too. Finally, direct numerical simulations of coupled nonlinear axial/radial dynamics also predict good performance for the SEIT, which seems to be the most promising among the geometries studied here.

Tallapragada, Pavan K.; Mohanty, Atanu K.; Chatterjee, Anindya; Menon, Ae G.

2007-06-01

436

Remitting seronegative symmetrical synovitis pitting oedema after BCG instillation  

Microsoft Academic Search

Remitting seronegative symmetrical synovitis pitting oedema (RS3PE) is a distinct form of seronegative rheumatoid arthritis like polyarthritis. It is characterized by late onset symmetrical joint involvement and pitting oedema of hands and feet (JAMA 254(19):2763–2767, [1]). Polyarthritis secondary to intravesical Bacillus Calmette Guerin (BCG) therapy has been reported (Clin Rheumatol 21:536–537, [2]). To our knowledge, about 0.5% of patients receiving

Soumaya El Mahou; Luciana Popa; Arnaud Constantin; Alain Cantagrel; Achour Aberrane; Benedicte Jamard; Bernard Mazieres; Michel Laroche

2006-01-01

437

APPROXIMATION OF CONVEX BODIES BY AXIALLY SYMMETRIC BODIES  

Microsoft Academic Search

Let C be an arbitrary planar convex body. We prove that C contains an axially symmetric convex body of area at least 2 3jCj. Also approx- imation by some specic axially symmetric bodies is considered. In particular, we can inscribe a rhombus of area at least 1 2jCj in C, and we can circumscribe a homothetic rhombus of area at

MAREK LASSAK

438

Synchronized PWM control of symmetrical six-phase drives  

Microsoft Academic Search

In order to avoid asynchronism of standard schemes of space-vector modulation, new method of synchronized pulsewidth modulation (PWM) has been applied for scalar control of symmetrical six-phase (dual three-phase) induction motor drives fed by two three-phase inverters. Basic schemes of synchronized continuous and discontinuous PWM, and also its combinations, disseminated for control of symmetrical dual three-phase systems, have been analyzed.

V. Oleschuk; G. Griva; F. Profumo; A. Tenconi

2007-01-01

439

Products of correlated symmetric matrices and q Catalan numbers  

Microsoft Academic Search

.  ?The well known convergence of the spectrum of large random symmetric matrices, due to Wigner, holds for products of correlated\\u000a symmetric matrices with general entries. The limiting moments coincide with weighted enumeration of permutations, or of rooted\\u000a trees. When the correlations are Markovian, the limiting first moments are closely related to Carlitz-Riordan q-Catalan numbers. As a consequence, these moments asymptotically

Christian Mazza; Didier Piau

2002-01-01

440

The Lie algebraic significance of symmetric informationally complete measurements  

Microsoft Academic Search

Examples of symmetric informationally complete positive operator-valued measures (SIC-POVMs) have been constructed in every dimension ?67. However, it remains an open question whether they exist in all finite dimensions. A SIC-POVM is usually thought of as a highly symmetric structure in quantum state space. However, its elements can equally well be regarded as a basis for the Lie algebra gl(d,C).

D. M. Appleby; Steven T. Flammia; Christopher A. Fuchs

2011-01-01

441

Reducing symmetric polarization aberrations in a lens by annealing  

NASA Astrophysics Data System (ADS)

Radially symmetric retardance was found in antireflection coated, molded aspheric glass lenses by measurement with a Mueller matrix imaging polarimeter. The source of the unexpected polarization aberration is traced to a remarkably symmetric radial stress birefringence in the glass believed to arise during fire-polishing of the surfaces. While annealing the lenses relieves much of the stress birefringence, reducing the retardance of the lenses by a factor of five, the lenses remained unusable.

Wolfe, J.; Chipman, R. A.

2004-07-01

442

Gas Molecules Simulation  

NSDL National Science Digital Library

This applet simulates kinetic theory of gases. The volume, temperature of a plate at the bottom, and force of gravity are adjustable. A histogram displays relative velocities of different temperatures of molecules. A description and source code are also included.

Falstad, Paul

2004-07-13

443

Testing for Life's Molecules  

NSDL National Science Digital Library

In this activity, learners conduct tests for proteins, glucose, and starch. At the beginning of the activity, learners choose three items to test: one known to be ânever alive," one known to be âonce was alive,â and one mystery item. In addition, each station includes a positive control. By the end of the experiment, learners should be familiar with some of the major organic molecules and should recognize that living things, and substances derived from them, are made of organic molecules. Use this activity to bring in topics surrounding nutrition, health, and digestion--since our bodies are made up of organic molecules, we need each of these molecules as nutrients in our food.

Salter, Irene

2012-09-28

444

Of Molecules and Models.  

ERIC Educational Resources Information Center

Presents an activity in which models help students visualize both the DNA process and transcription. After constructing DNA, RNA messenger, and RNA transfer molecules; students model cells, protein synthesis, codons, and RNA movement. (MDH)

Brinner, Bonnie

1992-01-01

445

Top Quark Properties in Little Higgs Models  

SciTech Connect

Identifying the mechanism which breaks electroweak symmetry and generates fermion masses is one of the main physics goals for both the LHC and the ILC. Studies of the top quark have the potential to illuminate this issue; since it is the heaviest of the Standard Model (SM) fermions, the top is expected to couple strongly to the symmetry-breaking sector. Consequently, the structure of that sector can have significant, potentially observable effects on the properties of the top. for example, it is well known that the vector and axial t{bar t}Z form factors receive large corrections (of order 5-10%) in certain models of dynamical electroweak symmetry breaking [1]. At future colliders such as the LHC and the ILC, we will be able to pursue a program of precision top physics, similar to the program studying the Z at LEP and SLC. In this manuscript, they study the corrections to the top quark properties in ''Little Higgs'' models of electroweak symmetry breaking [2], and compare the expected deviations from the SM predictions with expected sensitivities of experiments at the LHC and the ILC. In the Little Higgs models, electroweak symmetry is driven by the radiative effects from the top sector, including the SM-like top and its heavy counterpart, a TeV-scale ''heavy top'' T. Probing this structure experimentally is quite difficult. While the LHC should be able to discover the T quark, its potential for studying its couplings is limited [3,4]. Direct production of the T will likely be beyond the kinematic reach of the ILC. However, we will show below that the corrections to the gauge couplings of the SM top, induced by its mixing with the T, will be observable at the ILC throughout the parameter range consistent with naturalness. Measuring these corrections will provide a unique window on the top sector of the Little Higgs. Many Little Higgs models have been proposed in the literature. We will consider two examples in this study, the ''Littlest Higgs'' model [5], and its variation incorporating T parity [6].

Berger, C.F.; /SLAC; Perelstein, M.; /Cornell U., CIHEP; Petriello, F.; /Wisconsin U., Madison

2005-12-08

446

Synthesis of single-molecule nanocars.  

PubMed

The drive to miniaturize devices has led to a variety of molecular machines inspired by macroscopic counterparts such as molecular motors, switches, shuttles, turnstiles, barrows, elevators, and nanovehicles. Such nanomachines are designed for controlled mechanical motion and the transport of nanocargo. As researchers miniaturize devices, they can consider two complementary approaches: (1) the "top-down" approach, which reduces the size of macroscopic objects to reach an equivalent microscopic entity using photolithography and related techniques and (2) the "bottom-up" approach, which builds functional microscopic or nanoscopic entities from molecular building blocks. The top-down approach, extensively used by the semiconductor industry, is nearing its scaling limits. On the other hand, the bottom-up approach takes advantage of the self-assembly of smaller molecules into larger networks by exploiting typically weak molecular interactions. But self-assembly alone will not permit complex assembly. Using nanomachines, we hope to eventually consider complex, enzyme-like directed assembly. With that ultimate goal, we are currently exploring the control of nanomachines that would provide a basis for the future bottom-up construction of complex systems. This Account describes the synthesis of a class of molecular machines that resemble macroscopic vehicles. We designed these so-called nanocars for study at the single-molecule level by scanning probe microscopy (SPM). The vehicles have a chassis connected to wheel-terminated axles and convert energy inputs such as heat, electric fields, or light into controlled motion on a surface, ultimately leading to transport of nanocargo. At first, we used C(60) fullerenes as wheels, which allowed the demonstration of a directional rolling mechanism of a nanocar on a gold surface by STM. However, because of the low solubility of the fullerene nanocars and the incompatibility of fullerenes with photochemical processes, we developed new p-carborane- and ruthenium-based wheels with greater solubility in organic solvents. Although fullerene wheels must be attached in the final synthetic step, p-carborane- and ruthenium-based wheels do not inhibit organometallic coupling reactions, which allows a more convergent synthesis of molecular machines. We also prepared functional nanotrucks for the transport of atoms and molecules, as well as self-assembling nanocars and nanotrains. Although engineering challenges such as movement over long distance and non-atomically flat surfaces remain, the greatest current research challenge is imaging. The detailed study of nanocars requires complementary single molecule imaging techniques such as STM, AFM, TEM, or single-molecule fluorescence microscopy. Further developments in engineering and synthesis could lead to enzyme-like manipulation and assembly of atoms and small molecules in nonbiological environments. PMID:19245268

Vives, Guillaume; Tour, James M

2009-03-17

447

Production and decay of heavy top quarks  

SciTech Connect

Experimental evidence indicates that the top quark exists and has a mass between 50 and 200 GeV/c{sup 2}. The decays of a top quark with a mass in this range are studied with emphasis placed on the mass region near the threshold for production of real W bosons. Topics discussed are: (1) possible enhancement of strange quark production when M{sub W} + m{sub s} < m{sub t} < M{sub W} + m{sub b}; (2) exclusive decays of T mesons to B and B{asterisk} mesons using the non-relativistic quark model; (3) polarization of intermediate W's in top quark decay as a source of information on the top quark mass. The production of heavy top quarks in an e{sup +}e{sup {minus}} collider with a center-of-mass energy of 2 TeV is studied. The effective-boson approximation for photons, Z{sup 0}'s and W's is reviewed and an analogous approximation for interfaces between photons and Z{sup 0}'s is developed. The cross sections for top quark pair production from photon-photon, photon-Z{sup 0}, Z{sup 0}Z{sup 0}, and W{sup +}W{sup {minus}} fusion are calculated using the effective-boson approximation. Production of top quarks along with anti-bottom quarks via {gamma}W{sup +} and Z{sup 0}W{sup +} fusion is studied. An exact calculation of {gamma}e{sup +} {yields} {bar {nu}}t{bar b} is made and compared with the effective-W approximation. 31 refs., 46 figs.

Kauffman, R.P.

1989-08-01

448

Facile synthesis of symmetrical bis(benzhydryl)ethers using p-toluenesulfonyl chloride under solvent-free conditions  

PubMed Central

Background The benzhydryl ether moiety is widely distributed in nature and constitutes a key structural motif in numerous molecules of significant biological potential and of prospective clinical uses. Solvent-free and cost-effective facile synthesis of symmetrical bis(benzhydryl)ethers is, thus, much desirable. Results A simple and efficient method for the facile synthesis of symmetrical bis(benzhydryl)ethers directly from the corresponding benzhydrols has been developed using a catalytic amount of p-toluenesulfonyl chloride (5 mol%) at an oil bath temperature of 110°C under solvent-free conditions. Conclusions Operational simplicity, low reagent loading, high product yields, short reaction time, and solvent-free conditions are the notable advantages of the present method.

2013-01-01

449

Entanglement classes of permutation-symmetric qudit states: Symmetric operations suffice  

NASA Astrophysics Data System (ADS)

We analyze entanglement classes for permutation-symmetric states for n qudits (i.e., d-level systems), with respect to local unitary operations (LU equivalence) and stochastic local operations and classical communication (SLOCC equivalence). In both cases, we show that the search can be restricted to operations where the same local operation acts on all qudits, and we provide an explicit construction for it. Stabilizers of states in the form of one-particle operations preserving permutation symmetry are shown to provide a coarse-grained classification of entanglement classes. We prove that the Jordan form of such one-particle operators is a SLOCC invariant. We find, as representatives of those classes, a discrete set of entangled states that generalize the Greenberger-Horne-Zeilinger and W states for the many-particle qudit case. In the latter case, we introduce the excitation state as a natural generalization of the W state for d>2.

Migda?, Piotr; Rodriguez-Laguna, Javier; Lewenstein, Maciej

2013-07-01

450

Molecular vibrations of methane molecules in the structure I clathrate hydrate from ab initio molecular dynamics simulation  

NASA Astrophysics Data System (ADS)

Vibrational frequencies of guest molecules in clathrate hydrates reflect the molecular environment and dynamical behavior of molecules. A detailed understanding of the mechanism for the vibrational frequency changes of the guest molecules in the clathrate hydrate cages is still incomplete. In this study, molecular vibrations of methane molecules in a structure I clathrate hydrate are calculated from ab initio molecular dynamics simulation. The vibrational spectra of methane are computed by Fourier transform of autocorrelation functions, which reveal distinct separation of each vibrational mode. Calculated symmetric and asymmetric stretching vibrational frequencies of methane molecules are lower in the large cages than in the small cages (8 and 16 cm-1 for symmetric and asymmetric stretching, respectively). These changes are closely linked with the C-H bond length. The vibrational frequencies for the bending and rocking vibrational modes nearly overlap in each of the cages.

Hiratsuka, Masaki; Ohmura, Ryo; Sum, Amadeu K.; Yasuoka, Kenji

2012-01-01

451

Molecular vibrations of methane molecules in the structure I clathrate hydrate from ab initio molecular dynamics simulation.  

PubMed

Vibrational frequencies of guest molecules in clathrate hydrates reflect the molecular environment and dynamical behavior of molecules. A detailed understanding of the mechanism for the vibrational frequency changes of the guest molecules in the clathrate hydrate cages is still incomplete. In this study, molecular vibrations of methane molecules in a structure I clathrate hydrate are calculated from ab initio molecular dynamics simulation. The vibrational spectra of methane are computed by Fourier transform of autocorrelation functions, which reveal distinct separation of each vibrational mode. Calculated symmetric and asymmetric stretching vibrational frequencies of methane molecules are lower in the large cages than in the small cages (8 and 16 cm(-1) for symmetric and asymmetric stretching, respectively). These changes are closely linked with the C-H bond length. The vibrational frequencies for the bending and rocking vibrational modes nearly overlap in each of the cages. PMID:22299892

Hiratsuka, Masaki; Ohmura, Ryo; Sum, Amadeu K; Yasuoka, Kenji

2012-01-28

452

Adhesion molecules and transplantation.  

PubMed Central

OBJECTIVE: Accessory adhesion molecules are thought to influence the first interaction between host leukocytes and graft vascular endothelial cells. Their role in transplantation is reviewed. SUMMARY: Adhesion molecules have been divided into three major families: the selectins, the integrins, and the immunoglobulin superfamily. Selectins are small proteins that mediate the first contact between stimulated endothelial cells and leukocytes. Integrins interact with cytoskeletal components of cells, presumably coordinating extracellular stimuli with cytoskeleton dependent actions, such as motility, shape change, and phagocytic responses. Members of the immunoglobulin superfamily are structurally homologous, although they do not necessarily share similar functions. They are involved in T-cell proliferation and intracellular events. METHODS: Various groups of investigators have studied the influence and expression of adhesion molecules following transplantation. The authors of this article have reviewed and summarized the available literature. RESULTS: Many different adhesion molecules are up-regulated during the rejection event. Treatment of transplant recipients with monoclonal antibodies against accessory molecules, such as leukocyte function associated antigen 1 (LFA-1) and intercellular adhesion molecule 1 (ICAM-1), has resulted in either a prolongation of transplant survival or the induction of tolerance in some models. Other interventions are under study. CONCLUSION: By mediating the initial leukocyte/endothelial cell interactions, adhesion molecules may play an important role in graft rejection, mediation of infiltration into the graft, and dissemination of the antigenic message to the lymphoid tissues of the host. Future studies will have to deal not only with conceptualizing their function and mechanisms of action, but also with manipulating their interrelationships to the benefit of the graft recipient.

Heemann, U W; Tullius, S G; Azuma, H; Kupiec-Weglinsky, J; Tilney, N L

1994-01-01

453

Top quark and neutrino composite Higgs bosons  

NASA Astrophysics Data System (ADS)

In the context of top-quark condensation models, the top quark alone is too light to saturate the correct value of the electroweak scale by its condensate. Within the seesaw scenario the neutrinos can have their Dirac masses large enough so that their condensates can provide a significant contribution to the value of the electroweak scale. We address the question of a phenomenological feasibility of the top-quark and neutrino condensation conspiracy against the electroweak symmetry. It is mandatory to reproduce the masses of electroweak gauge bosons, the top-quark mass and the recently observed scalar mass of 125 GeV and to satisfy the upper limits on absolute value of active neutrino masses. To accomplish that we design a reasonably simplified effective model with two composite Higgs doublets. Additionally, we work with a general number N of right-handed neutrino flavor triplets participating on the seesaw mechanism. There are no experimental constraints limiting this number. The upper limit is set by the model itself. Provided that the condensation scale is of order 1017-18 GeV and the number of right-handed neutrinos is , the model predicts masses of additional Higgs bosons below 250 GeV and a suppression of the top-quark Yukawa coupling to the 125 GeV particle at the ˜60 % level of the Standard model value.

Smetana, Adam

2013-08-01

454

Top Stars: An Opportunity for Educators  

NASA Astrophysics Data System (ADS)

Think you're a Top Star? Want to find out what it takes? Learn about NASA's Top Stars contest and how you can participate. Throughout its lifetime, the Hubble Space Telescope has inspired and promoted education. The final Hubble servicing mission in May of this year and the celebration of Hubble's 20th anniversary in 2010 are key mission milestones, and both enrich activities for the 2009 International Year of Astronomy. U.S. formal (K-12 and college) and informal educators are invited to submit their best examples of using NASA's Hubble Space Telescope for science, technology, engineering or mathematics education. Those selected as Top Stars will receive national recognition and awards. Participants will learn about the contest, the recognition and awards, and how to register and save their entries on the Top Stars Web site. Educators are allowed and encouraged to revise, improve and re-submit their entries up to the final deadline of January 2, 2010. The contest is open to individuals and teams of up to four people who are U.S. citizens and are at least 21 years old. NASA and Institute for Global Environmental Strategies (IGES) employees or their contractors are not eligible. IGES is conducting Top Stars with NASA funding and in cooperation with the Space Telescope Science Institute.

Kinnison, S. M. P.

2010-08-01

455

Top-down causation and social structures  

PubMed Central

Top-down causation has been implicit in many sociological accounts of social structure and its influence on social events, but the social sciences have struggled to provide a coherent account of top-down causation itself. This paper summarizes a critical realist view of causation and emergence, shows how it supports a plausible account of top-down causation and then applies this account to the social world. The argument is illustrated by an examination of the concept of a norm circle, a kind of social entity that, it is argued, is causally responsible for the influence of normative social institutions. Nevertheless, social entities are structured rather differently from ordinary material ones, with the result that the compositional level structure of reality implicit in the concept of top-down causation has some limitations in the social world. The paper closes by considering what might be involved in examining how top-down causation can be shown to be at work in the social domain.

Elder-Vass, Dave

2012-01-01

456

Protein Identification Using Top-Down Spectra*  

PubMed Central

In the last two years, because of advances in protein separation and mass spectrometry, top-down mass spectrometry moved from analyzing single proteins to analyzing complex samples and identifying hundreds and even thousands of proteins. However, computational tools for database search of top-down spectra against protein databases are still in their infancy. We describe MS-Align+, a fast algorithm for top-down protein identification based on spectral alignment that enables searches for unexpected post-translational modifications. We also propose a method for evaluating statistical significance of top-down protein identifications and further benchmark various software tools on two top-down data sets from Saccharomyces cerevisiae and Salmonella typhimurium. We demonstrate that MS-Align+ significantly increases the number of identified spectra as compared with MASCOT and OMSSA on both data sets. Although MS-Align+ and ProSightPC have similar performance on the Salmonella typhimurium data set, MS-Align+ outperforms ProSightPC on the (more complex) Saccharomyces cerevisiae data set.

Liu, Xiaowen; Sirotkin, Yakov; Shen, Yufeng; Anderson, Gordon; Tsai, Yihsuan S.; Ting, Ying S.; Goodlett, David R.; Smith, Richard D.; Bafna, Vineet; Pevzner, Pavel A.

2012-01-01

457

Protein identification using top-down.  

PubMed

In the last two years, because of advances in protein separation and mass spectrometry, top-down mass spectrometry moved from analyzing single proteins to analyzing complex samples and identifying hundreds and even thousands of proteins. However, computational tools for database search of top-down spectra against protein databases are still in their infancy. We describe MS-Align+, a fast algorithm for top-down protein identification based on spectral alignment that enables searches for unexpected post-translational modifications. We also propose a method for evaluating statistical significance of top-down protein identifications and further benchmark various software tools on two top-down data sets from Saccharomyces cerevisiae and Salmonella typhimurium. We demonstrate that MS-Align+ significantly increases the number of identified spectra as compared with MASCOT and OMSSA on both data sets. Although MS-Align+ and ProSightPC have similar performance on the Salmonella typhimurium data set, MS-Align+ outperforms ProSightPC on the (more complex) Saccharomyces cerevisiae data set. PMID:22027200

Liu, Xiaowen; Sirotkin, Yakov; Shen, Yufeng; Anderson, Gordon; Tsai, Yihsuan S; Ting, Ying S; Goodlett, David R; Smith, Richard D; Bafna, Vineet; Pevzner, Pavel A

2012-06-01

458

A study of the interaction between HIV-1 protease and C 2-symmetric inhibitors by computational methods.  

PubMed

The human immunodeficiency virus type 1 protease (HIV-1 PR) is a major target for the design of anti-AIDS (acquired immune deficiency syndrome) drugs. Some C 2-symmetric inhibitors have been designed for the C 2-symmetric binding pocket of HIV-1PR. The crystallographic structures reveal that the binding modes are not C 2-symmetric for C 2- symmetric inhibitors binding to PR. In this work, four molecular dynamics (MD) simulations were performed to investigate the binding modes between four C 2-symmetric inhibitors (6 AD, 6AG, 6FD and 6FG) and PR, as well as the stabilities of these inhibitors in the binding pocket. Analysis of the hydrophobic surface of the binding pocket shows that it is necessary to add a polar group to the P1 (benzyl) and P2 (phenyl) groups of the inhibitor 6AD. Analysis of the hydrogen bonds formed between inhibitors and residues (Asp25/Asp25', Ile50/Ile50') indicates that the steric structures of the inhibitors are not suitable for the binding pocket. The two increased polar groups of trifluoromethyl and formamido meet the needs of the binding pocket for polar molecules. The inhibitor with both these groups (6FG) has stronger stability than the other three inhibitors, which have only one (6AG and 6FD) or none (6AD) of these groups. The ranking of binding free energies calculated by molecular mechanics-generalized born surface area (MM-GBSA) method agrees well with the experimental data. It is expected that this study will provide theoretical guidance for the design of anti-AIDS drugs targeting HIV-1PR. PMID:25024011

Shi, Shuhua; Hu, Guodong; Zhang, Xiumei; Wang, Jihua

2014-08-01

459

Experimental Study of Top Heat Mode Thermosyphon  

NASA Astrophysics Data System (ADS)

The purpose of this study is to develop the top heat mode thermosyphon that is very attractive means, for example, to accumulate directly the summer solar energy into the underground soil for the winter season. In this case, it can exclude the complex piping and mechanical pump to circulate the hot water absorbed the solar energy through the piping system buried in the soil layer. The several ideas concerning the top heat thermosyphon had been proposed, however, there were few reports on the definite experiments. The authors have carried out the experimental study of the top heat mode thermosyphon, with a simple lifting pipe, which could draw the working liquid from the under condenser to the upper evaporator section. The improvement of the main construction parts such as evaporator, lifting pipe, liquid reservoir trap and vapour nozzle have been performed in the present experiment in order to obtain the optimum operation range.

Hirashima, Masao; Kimura, Kenichiro; Utsumi, Yoichi; Kimura, Kenichi; Negishi, Kanji

460

Polarized view of the top asymmetry  

SciTech Connect

Recent experimental results from the CDF collaboration which study the top forward-backward asymmetry have strengthened the case that new physics is playing a role in tt production. Here, we propose a set of measurements, built from the charged lepton kinematics in semileptonic and fully leptonic tt events, designed to further probe the underlying causes of this asymmetry both at the Tevatron and at the LHC. Using a set of conservative reference models, we find that measurements of the charged lepton asymmetry, top polarization, and tt spin correlation can establish the existence of new physics and distinguish between competing models both at the Tevatron and the LHC. At the Tevatron, discrimination between models is possible at the 3{sigma} level. At the LHC, we demonstrate that a top forward-backward asymmetry can be established at > or approx. 3{sigma} in the first {approx}5 fb{sup -1} of data and show how competing explanations can be further disentangled.

Krohn, David [Department of Physics, Harvard University, Cambridge, Massachusetts, 02138 (United States); Liu Tao [Department of Physics, University of California, Santa Barbara, California, 93106 (United States); Shelton, Jessie [Department of Physics, Yale University, New Haven, Connecticut, 06511 (United States); Wang, Lian-Tao [Department of Physics, Enrico Fermi Institute, and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois, 60637 (United States)

2011-10-01

461

Four top production and electroweak symmetry breaking  

SciTech Connect

Recent results of the top-quark search by CDF and D0 at the Tevatron showed the existence of the sixth quark--the top quark. The measured mass was 176 {+-} 8 {+-} 10 GeV from CDF and 199{sub {minus}21}{sup +19} {+-} 22 GeV from D0. The standard model (SM) that was proposed more than 20 years ago is confirmed to a solid ground as all the ingredients were found, except for electroweak symmetry breaking (EWSB). The understanding of EWSB is necessary to explain all fermion and gauge boson masses on a fundamental level. The authors propose the study of four-top, t{bar t}t{bar t}, production at hadronic supercolliders as a probe to electroweak symmetry breaking.

Cheung, K.

1995-07-01

462

Top differential cross section measurements (Tevatron)  

SciTech Connect

Differential cross sections in the top quark sector measured at the Fermilab Tevatron collider are presented. CDF used 2.7 fb{sup -1} of data and measured the differential cross section as a function of the invariant mass of the t{bar t} system. The measurement shows good agreement with the standard model and furthermore is used to derive limits on the ratio {kappa}/M{sub Pl} for gravitons which decay to top quarks in the Randall-Sundrum model. D0 used 1.0 fb{sup -1} of data to measure the differential cross section as a function of the transverse momentum of the top-quark. The measurement shows a good agreement to the next-to-leading order perturbative QCD prediction and various other standard model predictions.

Jung, Andreas W.

2012-01-01

463

IO-Top-k: Index-access Optimized Top-k Query Processing  

Microsoft Academic Search

Top-k query processing is an important building block for ranked retrieval, with applications ranging from text and data integration to distributed aggregation of network logs and sensor data. Top-k queries operate on index lists for a query's elementary conditions and aggregate scores for result candidates. One of the best implementation methods in this setting is the family of threshold algorithms,

Holger Bast; Debapriyo Majumdar; Ralf Schenkel; Martin Theobald; Gerhard Weikum

2006-01-01

464

Top-down vortices developed in a cylindrical annulus cooled on the top.  

PubMed

In this paper we study the generation of top-down vortices by thermoconvective mechanisms in a cylindrical annulus nonhomogeneously cooled on the top. Assuming axisymmetry we study the structure of the vortices, characterized by a spiral downward motion, similar to that observed in tornadoes generated in supercell storms. PMID:23944599

Navarro, M C; Herrero, H

2013-07-01

465

Top-down vortices developed in a cylindrical annulus cooled on the top  

NASA Astrophysics Data System (ADS)

In this paper we study the generation of top-down vortices by thermoconvective mechanisms in a cylindrical annulus nonhomogeneously cooled on the top. Assuming axisymmetry we study the structure of the vortices, characterized by a spiral downward motion, similar to that observed in tornadoes generated in supercell storms.

Navarro, M. C.; Herrero, H.

2013-07-01

466

Synthetic symmetrization in the crystallization and structure determination of CelA from Thermotoga maritima  

PubMed Central

Protein crystallization continues to be a major bottleneck in X-ray crystallography. Previous studies suggest that symmetric proteins, such as homodimers, might crystallize more readily than monomeric proteins or asymmetric complexes. Proteins that are naturally monomeric can be made homodimeric artificially. Our approach is to create homodimeric proteins by introducing single cysteines into the protein of interest, which are then oxidized to form a disulfide bond between the two monomers. By introducing the single cysteine at different sequence positions, one can produce a variety of synthetically dimerized versions of a protein, with each construct expected to exhibit its own crystallization behavior. In earlier work, we demonstrated the potential utility of the approach using T4 lysozyme as a model system. Here we report the successful application of the method to Thermotoga maritima CelA, a thermophilic endoglucanase enzyme with low sequence identity to proteins with structures previously reported in the Protein Data Bank. This protein had resisted crystallization in its natural monomeric form, despite a broad survey of crystallization conditions. The synthetic dimerization of the CelA mutant D188C yielded well-diffracting crystals with molecules in a packing arrangement that would not have occurred with native, monomeric CelA. A 2.4 Å crystal structure was determined by single anomalous dispersion using a seleno-methionine derivatized protein. The results support the notion that synthetic symmetrization can be a useful approach for enlarging the search space for crystallizing monomeric proteins or asymmetric complexes.

Forse, G Jason; Ram, Nina; Banatao, D Rey; Cascio, Duilio; Sawaya, Michael R; Klock, Heath E; Lesley, Scott A; Yeates, Todd O

2011-01-01

467

A measurement of the top quark's charge  

SciTech Connect

The top quark was discovered in 1995 at the Fermilab National Accelerator Laboratory (Fermilab). One way to confirm if the observed top quark is really the top quark posited in the Standard Model (SM) is to measure its electric charge. In the Standard Model the top quark is the isospin partner of the bottom quark and is expected to have a charge of +2/3. However, an alternative 'exotic' model has been proposed with a fourth generation exotic quark that has the same characteristics, such as mass, as our observed top but with a charge of -4/3. This thesis presents the first CDF measurement of the top quark's charge via its decay products, a W boson and a bottom quark, using {approx} 1 fb{sup -1} of data. The data were collected by the CDF detector from proton anti-proton (p{bar p}) collisions at {radical}s = 1.96 TeV at Fermilab. We classify events depending on the charges of the bottom quark and associated W boson and count the number of events which appear 'SM-like' or 'exotic-like' with a SM-like event decaying as t {yields} W{sup +}b and an exotic event as t {yields} W{sup -}b. We find the p-value under the Standard Model hypothesis to be 0:35 which is consistent with the Standard Model. We exclude the exotic quark hypothesis at an 81% confidence level, for which we have chosen a priori that the probability of incorrectly rejecting the SM would be 1%. The calculated Bayes Factor (BF) is 2 x Ln(BF)=8.54 which is interpreted as the data strongly favors the Standard Model over the exotic quark hypothesis.

Unalan, Zeynep Gunay; /Michigan State U.

2007-11-01

468

A measurement of the top quark's charge  

NASA Astrophysics Data System (ADS)

The top quark was discovered in 1995 at the Fermilab National Accelerator Laboratory (Fermilab). One way to confirm if the observed top quark is really the top quark posited in the Standard Model (SM) is to measure its electric charge. In the Standard Model the top quark is the isospin partner of the bottom quark and is expected to have a charge of +2/3. However, an alternative "exotic" model has been proposed with a fourth generation exotic quark that has the same characteristics, such as mass, as our observed top but with a charge of -4/3. This thesis presents the first CDF measurement of the top quark's charge via its decay products, a W boson and a bottom quark, using ? 1fb-1 of data. The data were collected by the CDF detector from proton anti-proton (pp¯) collisions at s = 1.96 TeV at Fermilab. We classify events depending on the charges of the bottom quark and associated W boson and count the number of events which appear "SM-like" or "exotic-like" with a SM-like event decaying as t ? W+b and an exotic event as t ? W--b. We find the p-value under the Standard Model hypothesis to be 0.35 which is consistent with the Standard Model. We exclude the exotic quark hypothesis at an 81% confidence level, for which we have chosen a priori that the probability of incorrectly rejecting the SM would be 1%. The calculated Bayes Factor (BF) is 2xLn(BF)=8.54 which is interpreted as the data strongly favors the Standard Model over the exotic quark hypothesis.

Unalan, Zeynep

469

An Antibody Molecule  

NSDL National Science Digital Library

An antibody molecule. (A) Schematic drawing of a typical antibody molecule. As indicated, this protein is Y-shaped and has two identical binding sites for its antigen, one on either arm of the 3Y.2 The protein is composed of four polypeptide chains (two identical heavy chains and two identical and smaller light chains) held together by disulfide bonds. Each chain is made up of several different domains, here shaded either blue or gray. The antigen-binding site is formed where a heavy chain variable domain (VH) and a light chain variable domain (VL) come close together. These are the domains that differ most in their sequence and structure in different antibodies. (B) Ribbon drawing of a light chain showing the parts of the VL domain most closely involved in binding to the antigen in red; these contribute half of the fingerlike loops that fold around each of the antigen molecules in (A).

BEGIN:VCARD VERSION:2.1 FN:Martin Raff N:Raff;Martin REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Julian Lewis N:Lewis;Julian REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Alexander Johnson N:Johnson;Alexander REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Dennis Bray N:Bray;Dennis REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Bruce Alberts N:Alberts;Bruce REV:2005-04-15 END:VCARD; BEGIN:VCARD VERSION:2.1 FN:Keith Roberts N:Roberts;Keith REV:2005-04-15 END:VCARD

1998-07-01

470<