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Full-Text Articles in Physics

Columnar Molecular Aggregation In The Aqueous Solutions Of Disodium Cromoglycate, Dena Mae Agra-Kooijman, Gautam Singh, Alexander Lorenz, Peter J. Collings, Heinz- S. Kitzerow, Satyendra Kumar Jun 2014

Columnar Molecular Aggregation In The Aqueous Solutions Of Disodium Cromoglycate, Dena Mae Agra-Kooijman, Gautam Singh, Alexander Lorenz, Peter J. Collings, Heinz- S. Kitzerow, Satyendra Kumar

Physics Publications

Stack, chimneylike, and threadlike assemblies have previously been proposed for the structure of disodium cromoglycate (DSCG) aggregates in aqueous solutions. The results of the synchrotron x-ray scattering investigations reported here reveal the formation of simple columnar assemblies with π-π stacking at a separation of 3.4 A between the DSCG molecules. Lateral separation between the assemblies is concentration ˚ and temperature dependent, varying from 35 to 42 A in the orientationally ordered nematic ( ˚ N) phase and from 27 to 32 A in the columnar or middle ( ˚ M) phase having long range lateral positional order. The assemblies’ length depends on concentration and ...


Origin Of Weak Layer Contraction In De Vries Smectic Liquid Crystals, Dena Mae Agra-Kooijman, Hyungguen Yoon, Sonal Dey, Satyendra Kumar Mar 2014

Origin Of Weak Layer Contraction In De Vries Smectic Liquid Crystals, Dena Mae Agra-Kooijman, Hyungguen Yoon, Sonal Dey, Satyendra Kumar

Physics Publications

Structural investigations of the de Vries smectic-A (SmA) and smectic-C (SmC) phases of four mesogens containing a trisiloxane end segment reveal a linear molecular conformation in the SmA phase and a bent conformation resembling a hockey stick in the SmC phase. The siloxane and the hydrocarbon parts of the molecule tilt at different angles relative to the smectic layer normal and are oriented along different directions. For the compounds investigated, the shape of orientational distribution function (ODF) is found to be sugarloaf shaped and not the widely expected volcano like with positive orientational order parameters: P2 = 0.53–0.78 ...


Origin Of Weak Layer Contraction In De Vries Smectics Liquid Crystals, Dena Mae Agra-Kooijman, Hyungguen Yoon, Sonal Dey, Satyendra Kumar Mar 2014

Origin Of Weak Layer Contraction In De Vries Smectics Liquid Crystals, Dena Mae Agra-Kooijman, Hyungguen Yoon, Sonal Dey, Satyendra Kumar

Physics Publications

Structural investigations of the de Vries smectic-A (SmA) and smectic-C (SmC) phases of four mesogens containing a trisiloxane end segment reveal a linear molecular conformation in the SmA phase and a bent conformation resembling a hockey stick in the SmC phase. The siloxane and the hydrocarbon parts of the molecule tilt at different angles relative to the smectic layer normal and are oriented along different directions. For the compounds investigated, the shape of orientational distribution function (ODF) is found to be sugarloaf shaped and not the widely expected volcano like with positive orientational order ...


Bilayers In Nanoparticle-Doped Polar Mesogens, Alexander Lorenz, Dena Mae Agra-Kooijman, Natalie Zimmermann, Heinz-S. Kitzerow, Dean R. Evans Dec 2013

Bilayers In Nanoparticle-Doped Polar Mesogens, Alexander Lorenz, Dena Mae Agra-Kooijman, Natalie Zimmermann, Heinz-S. Kitzerow, Dean R. Evans

Physics Publications

Structures of the mesophases of five members of the 4-n-alkyl-4′-cyanobiphenyl homologous series (4-n-butyl-4′-cyanobiphenyl to 4-n-octyl-4′-cyanobiphenyl) doped with milled BaTiO3 nanoparticles were investigated by x-ray scattering. Clear solutions of each of the 4-n-alkyl-4′-cyanobiphenyls were first prepared in n-heptane and then doped with an n-heptane/nanoparticle dispersion, which led to gelation. The nanogels were found to be one-dimensional, multilayered, smectic nanostructures in each case. Surprisingly, a characteristic layer spacing of 4.5 nm was observed in all five homologues. Synchrotron x-ray scattering study of the multilayer structures of doped 4-n-pentyl-4′-cyanobiphenyl and 4-n-octyl-4′-cyanobiphenyl revealed nine orders ...


Multichannel Parametrization Of Antikaon-Nucleon Scattering Amplitudes And Extraction Of Resonance Parameters, Hongyu Zhang, John Tulpan, Manoj Shrestha, D. Mark Manley Sep 2013

Multichannel Parametrization Of Antikaon-Nucleon Scattering Amplitudes And Extraction Of Resonance Parameters, Hongyu Zhang, John Tulpan, Manoj Shrestha, D. Mark Manley

Physics Publications

We present results of a new multichannel partial-wave analysis for K¯¯¯N scattering in the center-of-mass (c.m.) energy range from 1480 to 2100 MeV. Resonance parameters were extracted by fitting partial-wave amplitudes from all considered channels using a multichannel parametrization that is consistent with S-matrix unitarity. The resonance parameters are generally in good agreement with predictions of the Koniuk-Isgur quark model.


Partial-Wave Analysis Of Kn Scattering Reactions, Hongyu Zhang, John Tulpan, Manoj Shrestha, D. Mark Manley Sep 2013

Partial-Wave Analysis Of Kn Scattering Reactions, Hongyu Zhang, John Tulpan, Manoj Shrestha, D. Mark Manley

Physics Publications

We investigate the two-body reactions K¯¯¯N→K¯¯¯N, K¯¯¯N→πΛ, and K¯¯¯N→πΣ via single-energy partial-wave analyses in the center-of-mass (c.m.) energy range 1480 to 2100 MeV. The partial-wave amplitudes for these reactions thus extracted were constrained by a multichannel energy-dependent model satisfying unitarity of the partial-wave Smatrix. We obtain excellent predictions of differential cross sections, polarizations, polarized cross sections, and cross sections for these reactions from a global energy-dependent solution.


X-Ray Scattering Of A Nematic Liquid Crystal Nano-Dispersion With Negative Dielectric Anisotropy, A. Lorenz, N. Zimmermann, Satyendra Kumar, S. R. Evans, G. Cook, M. F. Martinez, H. S. Kitzerow Jan 2013

X-Ray Scattering Of A Nematic Liquid Crystal Nano-Dispersion With Negative Dielectric Anisotropy, A. Lorenz, N. Zimmermann, Satyendra Kumar, S. R. Evans, G. Cook, M. F. Martinez, H. S. Kitzerow

Physics Publications

A nematic liquid crystal (LC) mixture was doped with harvested ferroelectric BaTiO3 nanoparticles and investigated with wide- and small-angle x-ray scattering upon heating from the nematic to the isotropic phase. At moderate temperatures, colloidal crystallites were observed. LC test cells with homeotropic anchoring were placed in the x-ray beam and the realignment of the LC director was investigated upon applying an electric field.


Soft Elasticity In Main Chain Liquid Crystal Elastomers, S. Dey, D. M. Agra-Kooijman, W. Ren, P. J. Mcmullan, A. C. Griffin, Satyendra Kumar Jan 2013

Soft Elasticity In Main Chain Liquid Crystal Elastomers, S. Dey, D. M. Agra-Kooijman, W. Ren, P. J. Mcmullan, A. C. Griffin, Satyendra Kumar

Physics Publications

Main chain liquid crystal elastomers exhibit several interesting phenomena, such as three different regimes of elastic response, unconventional stress-strain relationship in one of these regimes, and the shape memory effect. Investigations are beginning to reveal relationships between their macroscopic behavior and the nature of domain structure, microscopic smectic phase structure, relaxation mechanism, and sample history. These aspects of liquid crystal elastomers are briefly reviewed followed by a summary of the results of recent elastic and high-resolution X-ray diffraction studies of the shape memory effect and the dynamics of the formation of the smectic-C chevron-like layer structure. A possible route to ...


Doping The Nematic Liquid Crystal 5cb With Milled Batio3 Nanoparticles, Alexander Lorenz, Natalie Zimmerman, Satyendra Kumar, Dean R. Evans, Gary Cook, Hienz-S. Kitzerow Nov 2012

Doping The Nematic Liquid Crystal 5cb With Milled Batio3 Nanoparticles, Alexander Lorenz, Natalie Zimmerman, Satyendra Kumar, Dean R. Evans, Gary Cook, Hienz-S. Kitzerow

Physics Publications

The simple nematic mesogen 5CB was doped with milled BaTiO3 nanoparticles and was investigated with x-ray scattering. Doping with BaTiO3 nanoparticles of 9 nm in diameter led to the formation of crystallites. These crystallites precipitated and formed a waxlike nanodispersion of 5CB and nanoparticles, which led to intense x-ray scattering signals characteristic of a multilayer structure. Surprisingly, the multilayers possess unusual interlayer spacing, which cannot be explained by simple smectic order of the calamitic molecules.


Multichannel Parametrization Of Pi N Scattering Amplitudes And Extraction Of Resonance Parameters, Manoj Shrestha, D. Mark Manley Nov 2012

Multichannel Parametrization Of Pi N Scattering Amplitudes And Extraction Of Resonance Parameters, Manoj Shrestha, D. Mark Manley

Physics Publications

We present results of a new multichannel partial-wave analysis for πN scattering in the c.m. energy range 1080 to 2100 MeV. This work explicitly includes ηN and KΛ channels and the single pion photoproduction channel. Resonance parameters were extracted by fitting partial-wave amplitudes from all considered channels using a multichannel parametrization that is consistent with S-matrix unitarity. The resonance parameters so obtained are compared to predictions of quark models.


Partial-Wave Analysis Of The Pi- + Proton Goes To Eta Meson + Neutron And Pi- + Proton Goes To Neutral Kaon + Lambda Reactions, Manoj Shrestha, D. Mark Manley Oct 2012

Partial-Wave Analysis Of The Pi- + Proton Goes To Eta Meson + Neutron And Pi- + Proton Goes To Neutral Kaon + Lambda Reactions, Manoj Shrestha, D. Mark Manley

Physics Publications

We investigate the hadronic reactions πN→ηN and πN→KΛ via single-energy partial-wave analyses in the c.m. energy range 1080 to 2100 MeV. Our results for the KΛ channel are consistent with prior works; however, for the ηNchannel our results differ significantly from previous energy-dependent partial-wave analyses that violate the S-matrix unitarity. We present results of ηN and KΛ partial-wave amplitudes constrained by a unitary energy-dependent model. We obtain excellent predictions of integrated cross sections for the two reactions from a global energy-dependent solution. Our results imply that the region just above S11(1535) has a major contribution from ...


Homeotropically Aligning Phase Separated Columnar Structures For Fabrication Of Flexible Electrooptical Devices, Bharat R. Acharya, Hyunchul Choi, Mohan Srinivasarao, Satyendra Kumar Nov 2011

Homeotropically Aligning Phase Separated Columnar Structures For Fabrication Of Flexible Electrooptical Devices, Bharat R. Acharya, Hyunchul Choi, Mohan Srinivasarao, Satyendra Kumar

Physics Publications

A method of achieving homeotropic alignment of liquid crystals(LCs) by ultraviolet light induced phase separation of LC from its mixture with photo-curable pre-polymer is reported. Vertical polymer columns and micro-fibrils developed during the phase separation promote homeotropic alignment of the LC director (i.e., alignment perpendicular to the LC-substrate interface), suitable for devices based on LCs possessing negative dielectricanisotropy. These vertical structures extend between two substrates and permit the fabrication of highly flexible electro-optical devices with high contrast coupled with fast response times. This simple single-step technique eliminates the need for the traditional polymer alignment layer pre-deposited on substrates.


Homeotropically Aligning Phase Separated Columnar Structures For Fabrication Of Flexible Electrooptical Devices, Bharat R. Acharya, Hyunchul Choi, Mohan Srinivasarao, Satyendra Kumar Nov 2011

Homeotropically Aligning Phase Separated Columnar Structures For Fabrication Of Flexible Electrooptical Devices, Bharat R. Acharya, Hyunchul Choi, Mohan Srinivasarao, Satyendra Kumar

Physics Publications

A method of achieving homeotropic alignment of liquid crystals (LCs) by ultraviolet light induced phase separation of LC from its mixture with photo-curable pre-polymer is reported. Vertical polymer columns and micro-fibrils developed during the phase separation promote homeotropic alignment of the LC director (i.e., alignment perpendicular to the LC-substrate interface), suitable for devices based on LCs possessing negative dielectric anisotropy. These vertical structures extend between two substrates and permit the fabrication of highly flexible electro-optical devices with high contrast coupled with fast response times. This simple single-step technique eliminates the need for the traditional polymer alignment layer pre-deposited on ...


Direct Observation Of Diffuse Cone Behavior In De Vries Smectic-A And -C Phases Of Organosiloxane Mesogens, Hyungguen Yoon, Dena M. Agra-Kooijman, Khurshid Ayub, Robert P. Lemieux, Satyendra Kumar Feb 2011

Direct Observation Of Diffuse Cone Behavior In De Vries Smectic-A And -C Phases Of Organosiloxane Mesogens, Hyungguen Yoon, Dena M. Agra-Kooijman, Khurshid Ayub, Robert P. Lemieux, Satyendra Kumar

Physics Publications

Simultaneous and direct x-ray measurements of the smectic layer spacing, molecular tilt, and orientational order in the de Vries smectic A (SmA) and C (SmC) phases of two organosiloxane mesogens reveal that (i) the SmC (tilt) order parameter exponent beta = 0.26 +/- 0.01 for 2nd order SmA-SmC transition-in excellent agreement with the tricritical behavior, (ii) the siloxane and hydrocarbon parts of the molecules are segregated and oriented parallel to the director with very different degree of orientational order, and (iii) thermal evolution of the effective molecular length is different in the two phases.


Comment On "Raman Scattering Study Of Phase Biaxiality In A Thermotropic Bent-Core Nematic Liquid Crystal'' Reply, Bharat R. Acharya, Hyunchul Choi, Mohan Srinivasarao, Satyendra Kumar Feb 2011

Comment On "Raman Scattering Study Of Phase Biaxiality In A Thermotropic Bent-Core Nematic Liquid Crystal'' Reply, Bharat R. Acharya, Hyunchul Choi, Mohan Srinivasarao, Satyendra Kumar

Physics Publications

No abstract provided.


Park Et Al. Reply, M. S. Park, B.-J. Yoon, J. O. Park, Satyendra Kumar, M. Srinivasarao Jan 2011

Park Et Al. Reply, M. S. Park, B.-J. Yoon, J. O. Park, Satyendra Kumar, M. Srinivasarao

Physics Publications

No abstract provided.


Homogeneous And Homeotropic Alignment Of Bent-Core Uniaxial And Biaxial Nematic Liquid Crystals, Hyungguen Yoon, Shin-Woong Kang, Matthias Lehmann, Jung Ok Park, Mohan Srinivasarao, Satyendra Kumar Jan 2011

Homogeneous And Homeotropic Alignment Of Bent-Core Uniaxial And Biaxial Nematic Liquid Crystals, Hyungguen Yoon, Shin-Woong Kang, Matthias Lehmann, Jung Ok Park, Mohan Srinivasarao, Satyendra Kumar

Physics Publications

The effect of well-established homeotropically and homogeneously aligning polyimides, developed for calamitic liquid crystals, on the alignment of the nematic phases of bent-core mesogens was investigated using polarizing optical microscopy and conoscopy. Two polyimides, the homogeneously aligning SE7792 and the homeotropically aligning S659, were used to align three bent-core mesogens. Two of the mesogens, with an azo group in one of their arms, are found to align in a manner similar to the calamitic mesogens, while a fluorenone core based mesogen counter-intuitively aligns homogeneously on S659 coated surface and homeotropically on SE7792. Attractive interactions between unidirectionally oriented polyimide side-chains and ...


Raman Scattering Study Of Phase Biaxiality In A Thermotropic Bent-Core Nematic Liquid Crystal, Min Sang Park, Beom-Kin Yoon, Jung Ok Park, Veena Prasad, Satyendra Kumar, Mohan Srinivasarao Jul 2010

Raman Scattering Study Of Phase Biaxiality In A Thermotropic Bent-Core Nematic Liquid Crystal, Min Sang Park, Beom-Kin Yoon, Jung Ok Park, Veena Prasad, Satyendra Kumar, Mohan Srinivasarao

Physics Publications

Polarized Raman spectroscopy was used to investigate the development of orientational order and the degree of phase biaxiality in a bent-core mesogenic system. The values of the uniaxial order parameters ⟨P200⟩ and ⟨P400⟩, and biaxial order parameters ⟨P220⟩, ⟨P420⟩, and ⟨P440⟩, and their evolution with temperature were determined. The temperature dependence of almost all order parameters reveals a second order transition from the uniaxial to biaxial nematic phase with ⟨P220⟩ increasing to ∼0.22 before a first order transition to the smectic-C phase, upon cooling.


Nematic Biaxiality In A Bent-Core Material, Hyungguen Yoon, Shin-Woong Kang, Ronald Y. Dong, Alberto Marini, Kattera A. Suresh, Mohan Srinivasarao, Satyendra Kumar May 2010

Nematic Biaxiality In A Bent-Core Material, Hyungguen Yoon, Shin-Woong Kang, Ronald Y. Dong, Alberto Marini, Kattera A. Suresh, Mohan Srinivasarao, Satyendra Kumar

Physics Publications

The results of a recent investigation of the nematic biaxiality in a bent-core mesogen (A131) are in apparent disagreement with earlier claims. Samples of mesogen A131 used in the two studies were investigated with polarized optical microscopy, conoscopy, carbon-13 NMR, and crossover frequency measurements. The results demonstrate that textural changes associated with the growth of biaxial nematic order appear at similar to 149 degrees C. The Maltese cross observed in the conoscopic figure gradually splits into two isogyres at lower temperatures indicating phase biaxiality. Presence of the uniaxial to biaxial nematic phase transition is further confirmed by temperature trends of ...


Concentration, Temperature, And Ph Dependence Of Sunset-Yellow Aggregates In Aqueous Solutions: An X-Ray Investigation, Leela Joshi, Shin-Woong Kang, Dena Mae Agra-Kooijman, Satyendra Kumar Oct 2009

Concentration, Temperature, And Ph Dependence Of Sunset-Yellow Aggregates In Aqueous Solutions: An X-Ray Investigation, Leela Joshi, Shin-Woong Kang, Dena Mae Agra-Kooijman, Satyendra Kumar

Physics Publications

The dye sunset yellow (SY) forms columnar aggregates via π−π stacking in aqueous solutions. These aggregates develop orientational and translational order at elevated concentrations to exhibit the nematic (N) and columnar (C) mesophases. Positional-order correlation lengths of the aggregates in the directions parallel and perpendicular to the stacking direction were measured as functions of temperature, concentration, and ionic content of solutions with synchrotron x-ray scattering in magnetically aligned samples. Average length of aggregates (i.e., the number of SY molecules in an aggregate) grows monotonically with concentration while their effective transverse separation decreases. The scission energy, E, determined from ...


Concentration, Temperature, And Ph Dependence Of Sunset-Yellow Aggregates In Aqueous Solutions: An X-Ray Investigation, Leela Joshi, Shin-Woong Kang, Dena Mae Agra-Kooijman, Satyendra Kumar Oct 2009

Concentration, Temperature, And Ph Dependence Of Sunset-Yellow Aggregates In Aqueous Solutions: An X-Ray Investigation, Leela Joshi, Shin-Woong Kang, Dena Mae Agra-Kooijman, Satyendra Kumar

Physics Publications

The dye sunset yellow (SY) forms columnar aggregates via π-π stacking in aqueous solutions. These aggregates develop orientational and translational order at elevated concentrations to exhibit the nematic (N) and columnar (C) mesophases. Positional-order correlation lengths of the aggregates in the directions parallel and perpendicular to the stacking direction were measured as functions of temperature, concentration, and ionic content of solutions with synchrotron x-ray scattering in magnetically aligned samples. Average length of aggregates (i.e., the number of SY molecules in an aggregate) grows monotonically with concentration while their effective transverse separation decreases. The scission energy, E, determined from ...


Measurement Of The Slope Parameter Α For The Η→3Π0 Decay With The Crystal Ball Detector At The Mainz Microtron (Mami-C), S. Prakhov, B. M.K. Nefkens, P. Aguar-Bartolomé, L. K. Akasoy, J. R.M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, H. Berghäuser, B. Boillat., A. Braghien, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, R. F.B. Codling, E. J. Downie, P. Drexler, L. V. Fil'kov, D. I. Glazier, R. Gregor, E. Heid, D. Hornidge, O. Jahn, T. C. Jude, V. L. Kashevarov, J. D. Kellie, R. Kondratiev, M. Korolija, M. Kotulla, A. Koulbardis, D. Krambrich, S. Kruglov, B. Krusche, M. Lang, V. Lisin, K. Livingston, I. J.D. Macgregor, Y. Maghrbi, D. Mark Manley, M. Martinez, J. C. Mcgeorge, E. F. Mcnicoll, D. Mekterovic, V. Metag, S. Micanovic, A. Nikolaev, R. Novotny, M. Ostrick, R. B. Otte, P. Pedroni, F. Pheron, A. Polonski, J. Robinson, G. Rosner, M. Rost, T. Rostomyan, S. Schumann, M. H. Sikora, D. I. Sober, A. Starostin, I. M. Suarez, I. Supek, C. M. Tarbert, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, I. Zamboni, F. Zehr Mar 2009

Measurement Of The Slope Parameter Α For The Η→3Π0 Decay With The Crystal Ball Detector At The Mainz Microtron (Mami-C), S. Prakhov, B. M.K. Nefkens, P. Aguar-Bartolomé, L. K. Akasoy, J. R.M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, H. Berghäuser, B. Boillat., A. Braghien, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, R. F.B. Codling, E. J. Downie, P. Drexler, L. V. Fil'kov, D. I. Glazier, R. Gregor, E. Heid, D. Hornidge, O. Jahn, T. C. Jude, V. L. Kashevarov, J. D. Kellie, R. Kondratiev, M. Korolija, M. Kotulla, A. Koulbardis, D. Krambrich, S. Kruglov, B. Krusche, M. Lang, V. Lisin, K. Livingston, I. J.D. Macgregor, Y. Maghrbi, D. Mark Manley, M. Martinez, J. C. Mcgeorge, E. F. Mcnicoll, D. Mekterovic, V. Metag, S. Micanovic, A. Nikolaev, R. Novotny, M. Ostrick, R. B. Otte, P. Pedroni, F. Pheron, A. Polonski, J. Robinson, G. Rosner, M. Rost, T. Rostomyan, S. Schumann, M. H. Sikora, D. I. Sober, A. Starostin, I. M. Suarez, I. Supek, C. M. Tarbert, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, I. Zamboni, F. Zehr

Physics Publications

The dynamics of the η→3π0 decay have been studied with the Crystal Ball multiphoton spectrometer and the TAPS calorimeter. Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz microtron MAMI-C and tagged by the Glasgow photon spectrometer were used for η-meson production. The analysis of 3×106 γp→ηp→3π0p→6γp events yields the value α=−0.032±0.003 for the η→3π0 slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The π0π0invariant-mass spectrum was investigated for the occurrence of a cusplike ...


Measurement Of The Total Cross Section Of The Reaction K−P→Σ0Γ Between 514 And 750 Mev/C, T. D.S. Stanislaus, V. V. Abaev, D. Allen, C. E. Allgower, J. Alyea, M. A. Bates, V. S. Bekrenev, W. J. Briscoe, R. V. Cadman, J. Comfort, R. Corliss, K. Craig, A. Gibson, R. Greene, D. P. Grosnick, D. Isenhower, T. E. Kasprzyk, N. Knecht, D. D. Koetke, N. G. Kozlenko, S. P. Kruglov, A. A. Kulbardis, G. Lolos, I. V. Lopatin, D. Mark Manley, R. Manweiler, A. Marus˘Ić, S. Mcdonald, J. Olmsted, Z. Papandreou, D. C. Peaslee, N. Phaisangittisakul, J. W. Price, A. F. Ramirez, M. Sadler, S. Schlobohm, A. Shafi, H. Spinka, H. M. Staudenmaier, I. I. Strakovsky, I. Supek, J. Thoms, S. Wolf Jan 2009

Measurement Of The Total Cross Section Of The Reaction K−P→Σ0Γ Between 514 And 750 Mev/C, T. D.S. Stanislaus, V. V. Abaev, D. Allen, C. E. Allgower, J. Alyea, M. A. Bates, V. S. Bekrenev, W. J. Briscoe, R. V. Cadman, J. Comfort, R. Corliss, K. Craig, A. Gibson, R. Greene, D. P. Grosnick, D. Isenhower, T. E. Kasprzyk, N. Knecht, D. D. Koetke, N. G. Kozlenko, S. P. Kruglov, A. A. Kulbardis, G. Lolos, I. V. Lopatin, D. Mark Manley, R. Manweiler, A. Marus˘Ić, S. Mcdonald, J. Olmsted, Z. Papandreou, D. C. Peaslee, N. Phaisangittisakul, J. W. Price, A. F. Ramirez, M. Sadler, S. Schlobohm, A. Shafi, H. Spinka, H. M. Staudenmaier, I. I. Strakovsky, I. Supek, J. Thoms, S. Wolf

Physics Publications

We report the first measurements of the total cross section of the reaction K−p→Σ0γ at eight beam momenta from 514 to 750 MeV/c. The data were obtained at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory using the Crystal Ball detector consisting of 672 NaI crystals. All charged particles were vetoed by a barrel of plastic scintillators, resulting in a study of only the neutral decays of the Σ0. The prompt photon and the photons from the decay products of Σ0 were detected for each reconstructed event; the neutron was also detected ...


Spatiotemporal Patterns In A Langmuir Monolayer Due To Driven Molecular Precession, Satyendra Kumar, R. K. Gupta, K. A. Suresh, L. M. Lopatina, R. L. B. Selinger, Jonathan V. Selinger Oct 2008

Spatiotemporal Patterns In A Langmuir Monolayer Due To Driven Molecular Precession, Satyendra Kumar, R. K. Gupta, K. A. Suresh, L. M. Lopatina, R. L. B. Selinger, Jonathan V. Selinger

Physics Publications

Langmuir monolayers of chiral liquid crystals on the surface of water exhibit orientational waves with complex spatiotemporal patterns. These patterns arise from a collective precession of the mesogenic molecules, driven by the evaporation of water through the monolayer. We investigate the behavior of these orientational waves around topological defects in the molecular orientation. Through Brewster angle microscopy, we find that the waves form a reversing spiral pattern, which rotates about the central vortex. With increasing relative humidity, the rotation slows and then stops. We model the system theoretically, and show that predicted patterns are in good agreement with the experiments.


Landau-De Gennes Theory Of Biaxial Nematics Reexamined, David W. Allender, Lech Longa Jul 2008

Landau-De Gennes Theory Of Biaxial Nematics Reexamined, David W. Allender, Lech Longa

Physics Publications

Recent experiments report that the long-looked-for thermotropic biaxial nematic phase has been finally detected in some thermotropic liquid crystalline systems. Inspired by these experimental observations, we concentrate on some elementary theoretical issues concerned with the classical sixth-order Landau-de Gennes free energy expansion in terms of the symmetric and traceless tensor order parameter Q(alpha beta). In particular, we fully explore the stability of the biaxial nematic phase giving analytical solutions for all distinct classes of the phase diagrams that theory allows. This includes diagrams with triple, critical, and tricritical points and with multiple (reentrant) biaxial and uniaxial phase transitions. A ...


Measurement Of The Invariant-Mass Spectrum For The Two Photons From The Η→Π0Γγ Decay, S. N. Prakhov, B. M.K. Nefkens, C. E. Allgower, V. Bekrenev, W. J. Briscoe, J. Comfort, K. Craig, D. Grosnick, D. Isenhower, N. Knecht, D. Koetke, A. Koulbardis, N. Kozlenko, S. Kruglov, G. Lolos, I. Lopatin, D. Mark Manley, R. Manweiler, A. Marus˘Ić, S. Mcdonald, J. Olmsted, Z. Papandreou, D. Peaslee, N. Phaisangittisakul, J. W. Price, A. F. Ramirez, M. Sadler, A. Shafi, H. Spinka, T. D.S. Stanislaus, A. Starostin, H. M. Staudenmaier, I. Supek Jul 2008

Measurement Of The Invariant-Mass Spectrum For The Two Photons From The Η→Π0Γγ Decay, S. N. Prakhov, B. M.K. Nefkens, C. E. Allgower, V. Bekrenev, W. J. Briscoe, J. Comfort, K. Craig, D. Grosnick, D. Isenhower, N. Knecht, D. Koetke, A. Koulbardis, N. Kozlenko, S. Kruglov, G. Lolos, I. Lopatin, D. Mark Manley, R. Manweiler, A. Marus˘Ić, S. Mcdonald, J. Olmsted, Z. Papandreou, D. Peaslee, N. Phaisangittisakul, J. W. Price, A. F. Ramirez, M. Sadler, A. Shafi, H. Spinka, T. D.S. Stanislaus, A. Starostin, H. M. Staudenmaier, I. Supek

Physics Publications

New results on the rare, doubly radiative decay η→π0γγ have been obtained from a revised analysis of the Crystal Ball experiment performed at the AGS. The analysis yields the first information on the dependence of the decay width, Γ(η→π0γγ), on the two-photon invariant mass squared, m2(γγ). A re-evaluation of the branching ratio is also made, BR(η→π0γγ)=(2.21±0.24stat±0.47syst)×10−4; it implies that the decay width is Γ(η→π0γγ)=0.285±0.031stat±0.061syst eV ...


Incoherent Neutral Pion Photoproduction On C[Superscript]12, C. M. Tarbert, D. P. Watts, P. Aguar, J. Ahrens, J. R. Annand, H. J. Arends, R. Beck, V. Bekrenev, B. Boillat., A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, R. Codling, E. J. Downie, K. Föhl, D. I. Glazier, P. Grabmayr, R. Gregor, E. Heidari, D. Hornidge, O. Jahn, V. L. Kashevarov, A. Knezevic, R. Kondratiev, M. Korolija, M. Kotulla, D. Krambrich, B. Krusche, M. Lang, V. Lisin, K. Livingston, S. Lugert, I. J.D. Macgregor, D. Mark Manley, M. F. Martinez, J. C. Mcgeorge, D. Mekterovic, V. Metag, B. M.K. Nefkens, A. Nikolaev, R. Novotny, R. O. Owens, P. Pedroni, A. Polonski, S. N. Prakhov, J. W. Price, G. Rosner, M. Rost, T. Rostomyan, S. Schadmand, S. Schumann, D. Sober, A. Starostin, I. Supek, A. Thomas, M. Unverzagt, Th. Walcher, F. Zehr Apr 2008

Incoherent Neutral Pion Photoproduction On C[Superscript]12, C. M. Tarbert, D. P. Watts, P. Aguar, J. Ahrens, J. R. Annand, H. J. Arends, R. Beck, V. Bekrenev, B. Boillat., A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, R. Codling, E. J. Downie, K. Föhl, D. I. Glazier, P. Grabmayr, R. Gregor, E. Heidari, D. Hornidge, O. Jahn, V. L. Kashevarov, A. Knezevic, R. Kondratiev, M. Korolija, M. Kotulla, D. Krambrich, B. Krusche, M. Lang, V. Lisin, K. Livingston, S. Lugert, I. J.D. Macgregor, D. Mark Manley, M. F. Martinez, J. C. Mcgeorge, D. Mekterovic, V. Metag, B. M.K. Nefkens, A. Nikolaev, R. Novotny, R. O. Owens, P. Pedroni, A. Polonski, S. N. Prakhov, J. W. Price, G. Rosner, M. Rost, T. Rostomyan, S. Schadmand, S. Schumann, D. Sober, A. Starostin, I. Supek, A. Thomas, M. Unverzagt, Th. Walcher, F. Zehr

Physics Publications

We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The C12(γ,π0)12C*4.4  MeV reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a π0 spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation ...


Dynamics Of Molecular Exchange Between Aligning Adsorbed Film Of Liquid Crystal And The Bulk, Rui Guo, Yuriy Reznikov, Kostyantyn Slyusarenko, Satyendra Kumar Mar 2008

Dynamics Of Molecular Exchange Between Aligning Adsorbed Film Of Liquid Crystal And The Bulk, Rui Guo, Yuriy Reznikov, Kostyantyn Slyusarenko, Satyendra Kumar

Physics Publications

The liquid crystal (LC) originally filled in thin cells is replaced by a different LC having a drastically different pretilt angle. The mechanism of desorption/adsorption of LC molecules from/on the adsorbed LC film at the substrate changes the composition of the adsorbed layer and thus the pretilt angle. The time dependence of molecular pretilt angle at solid surfaces of homogeneously aligned LC cells is measured. The characteristic molecular exchange time depends on the coefficients of desorption of the first LC. The results presented here provide an important insight into the molecular exchange between solid surface and bulk fluid ...


Model-Independent Resonance Parameter Extraction From The Trace Of K And T Matrices, S. Ceci, B. Zauner, Mark Manley Jan 2008

Model-Independent Resonance Parameter Extraction From The Trace Of K And T Matrices, S. Ceci, B. Zauner, Mark Manley

Physics Publications

A model-independent method for the determination of resonance parameters as K-matrix pole parameters from a T matrix is presented. The method is based on eliminating the dependence on the choice of channel basis by analyzing the trace of the K and Tmatrices in the coupled-channel formalism, rather than individual matrix elements of the multichannel scattering matrix.


Measurement Of The K−P→Σ0Π0 Reaction Between 514 And 750 Mev/C, R. W. Manweiler, R. V. Cadman, H. Spinka, V. V. Abaev, D. Allen, C. E. Allgower, J. Alyea, M. A. Bates, V. S. Bekrenev, W. J. Briscoe, M. Clajus, J. Comfort, R. Corliss, K. Craig, A. Gibson, R. Greene, D. P. Grosnick, D. Isenhower, T. E. Kasprzyk, N. Knecht, D. D. Koetke, N. G. Kozlenko, S. P. Kruglov, A. A. Kulbardis, G. Lolos, I. V. Lopatin, D. Mark Manley, A. Marus˘Ić, S. Mcdonald, J. Olmsted, Z. Papandreou, D. C. Peaslee, N. Phaisangittisakul, A. F. Ramirez, M. Sadler, A. Shafi, T. D.S. Stanislaus, H. M. Staudenmaier, I. I. Strakovsky, I. Supek, J. Thoms, W. B. Tippens, S. Wolf Jan 2008

Measurement Of The K−P→Σ0Π0 Reaction Between 514 And 750 Mev/C, R. W. Manweiler, R. V. Cadman, H. Spinka, V. V. Abaev, D. Allen, C. E. Allgower, J. Alyea, M. A. Bates, V. S. Bekrenev, W. J. Briscoe, M. Clajus, J. Comfort, R. Corliss, K. Craig, A. Gibson, R. Greene, D. P. Grosnick, D. Isenhower, T. E. Kasprzyk, N. Knecht, D. D. Koetke, N. G. Kozlenko, S. P. Kruglov, A. A. Kulbardis, G. Lolos, I. V. Lopatin, D. Mark Manley, A. Marus˘Ić, S. Mcdonald, J. Olmsted, Z. Papandreou, D. C. Peaslee, N. Phaisangittisakul, A. F. Ramirez, M. Sadler, A. Shafi, T. D.S. Stanislaus, H. M. Staudenmaier, I. I. Strakovsky, I. Supek, J. Thoms, W. B. Tippens, S. Wolf

Physics Publications

The reaction K−p→Σ0π0→ neutrals was studied with the Crystal Ball detector at the BNL Alternating Gradient Synchrotron for beam momenta between 514 and 750 MeV/c. The photons from Σ0 and π0 decays were detected, as well as the neutron in a small fraction of the events. The differential cross section and the Σ0 polarization are reported at eight momenta and nearly the full angular range. Total cross sections are derived from Legendre polynomial fits to the data. The measurements presented are of considerably higher precision than previous results.