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Sample records for chiral nematic phases

  1. Detecting, visualizing, and measuring gold nanoparticle chirality using helical pitch measurements in nematic liquid crystal phases.

    Science.gov (United States)

    Sharma, Anshul; Mori, Taizo; Lee, Huey-Charn; Worden, Matthew; Bidwell, Eric; Hegmann, Torsten

    2014-12-23

    Chirality at the nanoscale, or more precisely, the chirality or chiroptical effects of chiral ligand-capped metal nanoparticles (NPs) is an intriguing and rapidly evolving field in nanomaterial research with promising applications in catalysis, metamaterials, and chiral sensing. The aim of this work was to seek out a system that not only allows the detection and understanding of NP chirality but also permits visualization of the extent of chirality transfer to a surrounding medium. The nematic liquid crystal phase is an ideal candidate, displaying characteristic defect texture changes upon doping with chiral additives. To test this, we synthesized chiral cholesterol-capped gold NPs and prepared well-dispersed mixtures in two nematic liquid crystal hosts. Induced circular dichroism spectropolarimetry and polarized light optical microscopy revealed that all three gold NPs induce chiral nematic phases, and that those synthesized in the presence of a chiral bias (disulfide) are more powerful chiral inducers than those where the NP was formed in the absence of a chiral bias (prepared by conjugation of a chiral silane to preformed NPs). Helical pitch data here visually show a clear dependence on the NP size and the number of chiral ligands bound to the NP surface, thereby supporting earlier experimental and theoretical data that smaller metal NPs made in the presence of a chiral bias are stronger chiral inducers.

  2. Low symmetry tetrahedral nematic liquid crystal phases: Ambidextrous chirality and ambidextrous helicity.

    Science.gov (United States)

    Pleiner, Harald; Brand, Helmut R

    2014-02-01

    We discuss the symmetry properties as well as the dynamic behavior of various non-polar nematic liquid crystal phases with tetrahedral order. We concentrate on systems that show biaxial nematic order coexisting with octupolar (tetrahedral) order. Non-polar examples are phases with D2 and S4 symmetries, which can be characterized as biaxial nematics lacking inversion symmetry. It is this combination that allows for new features in the statics and dynamics of these phases. The D2-symmetric phase is chiral, even for achiral molecules, and shows ambidextrous chirality in all three preferred directions. The achiral S4-symmetric phase allows for ambidextrous helicity, similar to the higher-symmetric D2d-symmetric phase. Such phases are candidates for nematic phases made from banana-shaped molecules.

  3. The helical phase of chiral nematic liquid crystals as the Bianchi VII(0) group manifold

    CERN Document Server

    Gibbons, G W

    2011-01-01

    We show that the optical structure of the helical phase of a chiral nematic is naturally associated with the Bianchi VII(0) group manifold. The Joets-Ribotta metric governing propagation of the extraordinary rays is invariant under the simply transitive action of the universal cover of the three dimensional Euclidean group of two dimensions. Thus extraordinary light rays are geodesics of a left-invariant metric on this Bianchi type VII(0) group. We are able to solve by separation of variables both the wave equation and the Hamilton-Jacobi equation for this metric. The former reduces to Mathieu's equation and the later to the quadrantal pendulum equation. We further discuss Maxwell's equations for uniaxial optical materials where the configuration is invariant under a group action. The material is not assumed to be impedance matched, thus going beyond the usual scope of transformation optics. We show that for a chiral nematic in its helical phase Maxwell's equations reduce to a generalised Mathieu equation. Ou...

  4. Electric-field-induced transport of microspheres in the isotropic and chiral nematic phase of liquid crystals

    Science.gov (United States)

    Oh, Jiyoung; Gleeson, Helen F.; Dierking, Ingo

    2017-02-01

    The application of an electric field to microspheres suspended in a liquid crystal causes particle translation in a plane perpendicular to the applied field direction. Depending on applied electric field amplitude and frequency, a wealth of different motion modes may be observed above a threshold, which can lead to linear, circular, or random particle trajectories. We present the stability diagram for these different translational modes of particles suspended in the isotropic and the chiral nematic phase of a liquid crystal and investigate the angular velocity, circular diameter, and linear velocity as a function of electric field amplitude and frequency. In the isotropic phase a narrow field amplitude-frequency regime is observed to exhibit circular particle motion whose angular velocity increases with applied electric field amplitude but is independent of applied frequency. The diameter of the circular trajectory decreases with field amplitude as well as frequency. In the cholesteric phase linear as well as circular particle motion is observed. The former exhibits an increasing velocity with field amplitude, while decreasing with frequency. For the latter, the angular velocity exhibits an increase with field amplitude and frequency. The rotational sense of the particles on a circular trajectory in the chiral nematic phase is independent of the helicity of the liquid crystalline structure, as is demonstrated by employing a cholesteric twist inversion compound.

  5. Modulated nematic structures induced by chirality and steric polarization

    Science.gov (United States)

    Longa, Lech; PajÄ k, Grzegorz

    2016-04-01

    What kind of one-dimensional modulated nematic structures (ODMNS) can form nonchiral and chiral bent-core and dimeric materials? Here, using the Landau-de Gennes theory of nematics, extended to account for molecular steric polarization, we study a possibility of formation of ODMNS, both in nonchiral and intrinsically chiral liquid crystalline materials. Besides nematic and cholesteric phases, we find four bulk ODMNS for nonchiral materials, two of which, to the best of our knowledge, have not been reported so far. These two structures are longitudinal (NLP) and transverse (NTP) periodic waves where the polarization field being periodic in one dimension stays parallel and perpendicular, respectively, to the wave vector. The other two phases are the twist-bend nematic phase (NTB) and the splay-bend nematic phase (NSB), but their fine structure appears more complex than that considered so far. The presence of molecular chirality converts nonchiral NTP and NSB into new NTB phases. Surprisingly, the nonchiral NLP phase can stay stable even in the presence of intrinsic chirality.

  6. Tuning the iridescence of chiral nematic cellulose nanocrystals and mesoporous silica films by substrate variation.

    Science.gov (United States)

    Nguyen, Thanh-Dinh; Hamad, Wadood Y; MacLachlan, Mark J

    2013-12-14

    We have discovered that the self-assembly of cellulose nanocrystals (CNCs) into chiral nematic phases varies significantly with the substrate and evaporation rate. These variables allow the reflectance peak of iridescent chiral nematic films of CNCs and mesoporous silica templated from CNCs to be tuned over a wide range of wavelengths.

  7. The development of chiral nematic mesoporous materials.

    Science.gov (United States)

    Kelly, Joel A; Giese, Michael; Shopsowitz, Kevin E; Hamad, Wadood Y; MacLachlan, Mark J

    2014-04-15

    Cellulose nanocrystals (CNCs) are obtained from the sulfuric acid-catalyzed hydrolysis of bulk cellulose. The nanocrystals have diameters of ~5-15 nm and lengths of ~100-300 nm (depending on the cellulose source and hydrolysis conditions). This lightweight material has mostly been investigated to reinforce composites and polymers because it has remarkable strength that rivals carbon nanotubes. But CNCs have an additional, less explored property: they organize into a chiral nematic (historically referred to as cholesteric) liquid crystal in water. When dried into a thin solid film, the CNCs retain the helicoidal chiral nematic order and assemble into a layered structure where the CNCs have aligned orientation within each layer, and their orientation rotates through the stack with a characteristic pitch (repeating distance). The cholesteric ordering can act as a 1-D photonic structure, selectively reflecting circularly polarized light that has a wavelength nearly matching the pitch. During CNC self-assembly, it is possible to add sol-gel precursors, such as Si(OMe)4, that undergo hydrolysis and condensation as the solvent evaporates, leading to a chiral nematic silica/CNC composite material. Calcination of the material in air destroys the cellulose template, leaving a high surface area mesoporous silica film that has pore diameters of ~3-10 nm. Importantly, the silica is brilliantly iridescent because the pores in its interior replicate the chiral nematic structure. These films may be useful as optical filters, reflectors, and membranes. In this Account, we describe our recent research into mesoporous films with chiral nematic order. Taking advantage of the chiral nematic order and nanoscale of the CNC templates, new functional materials can be prepared. For example, heating the silica/CNC composites under an inert atmosphere followed by removal of the silica leaves highly ordered, mesoporous carbon films that can be used as supercapacitor electrodes. The composition

  8. Observation of blue phase in chiral nematic liquid crystal and its stabilization by silica nanoparticles

    Science.gov (United States)

    Singh, Arshdeep; Malik, Praveen; Jayoti, Divya

    2016-01-01

    In the present work, we report the blue phase (BP) in a binary mixture of cholesteryl nonanoate (CN) and N-(4-ethoxybenzylidene)-4-butylaniline (EBBA). The mixture exhibits BP over a temperature range of 2.3 K at optimum composition (50:50) of liquid crystals (LCs). The effect of silica nanoparticles (SNPs) doping on thermal stability of BPs has also been demonstrated and nearly 6 K wide BP temperature range was achieved at 0.5 wt.% of SNPs. A porous type texture was also observed during the BP formation process in the doped samples.

  9. Right-handed double-helix ultrashort DNA yields chiral nematic phases with both right- and left-handed director twist.

    Science.gov (United States)

    Zanchetta, Giuliano; Giavazzi, Fabio; Nakata, Michi; Buscaglia, Marco; Cerbino, Roberto; Clark, Noel A; Bellini, Tommaso

    2010-10-12

    Concentrated solutions of duplex-forming DNA oligomers organize into various mesophases among which is the nematic (N(∗)), which exhibits a macroscopic chiral helical precession of molecular orientation because of the chirality of the DNA molecule. Using a quantitative analysis of the transmission spectra in polarized optical microscopy, we have determined the handedness and pitch of this chiral nematic helix for a large number of sequences ranging from 8 to 20 bases. The B-DNA molecule exhibits a right-handed molecular double-helix structure that, for long molecules, always yields N(∗) phases with left-handed pitch in the μm range. We report here that ultrashort oligomeric duplexes show an extremely diverse behavior, with both left- and right-handed N(∗) helices and pitches ranging from macroscopic down to 0.3 μm. The behavior depends on the length and the sequence of the oligomers, and on the nature of the end-to-end interactions between helices. In particular, the N(∗) handedness strongly correlates with the oligomer length and concentration. Right-handed phases are found only for oligomers shorter than 14 base pairs, and for the sequences having the transition to the N(∗) phase at concentration larger than 620 mg/mL. Our findings indicate that in short DNA, the intermolecular double-helical interactions switch the preferred liquid crystal handedness when the columns of stacked duplexes are forced at high concentrations to separations comparable to the DNA double-helix pitch, a regime still to be theoretically described.

  10. Tuning the helical twisting power of nematic liquid crystals induced by chiral 1,2-propanediol derivatives using varied substituents

    Institute of Scientific and Technical Information of China (English)

    Hai Quan Zhang; An Lei Qin

    2012-01-01

    In this study,a novel series of chiral 1,2-propanediol derivatives with different electron-donating and electron-withdrawing groups were synthesized and characterized by FT-IR and 1H NMR.The helical twisting properties of all the chiral dopants were investigated by doping the chiral dopants into a nematic liquid crystal host (SLC- 1717).The results indicate that the donor-acceptor electron effect have a prominent influence on helical twisting property of the chiral nematic phase induced by the chiral dopants.Introducing electron-withdrawing groups into the terminal ends of chiral 1,2-propanediol can decrease the absolute values of the helical twisting power.In addition,the helix inversion temperatures of the induced chiral nematic phase are variational with the change of terminal groups.

  11. Nematic twist cell: Strong chirality induced at the surfaces

    Science.gov (United States)

    Lin, Tzu-Chieh; Nemitz, Ian R.; Pendery, Joel S.; Schubert, Christopher P. J.; Lemieux, Robert P.; Rosenblatt, Charles

    2013-04-01

    A nematic twist cell having a thickness gradient was filled with a mixture containing a configurationally achiral liquid crystal (LC) and chiral dopant. A chiral-based linear electrooptic effect was observed on application of an ac electric field. This "electroclinic effect" varied monotonically with d, changing sign at d =d0 where the chiral dopant exactly compensated the imposed twist. The results indicate that a significant chiral electrooptic effect always exists near the surfaces of a twist cell containing molecules that can be conformationally deracemized. Additionally, this approach can be used to measure the helical twisting power (HTP) of a chiral dopant in a liquid crystal.

  12. Modulational instability of nematic phase

    Indian Academy of Sciences (India)

    T Mithun; K Porsezian

    2014-02-01

    We numerically observe the effect of homogeneous magnetic field on the modulationally stable case of polar phase in = 2 spinor Bose–Einstein condensates (BECs). Also we investigate the modulational instability of uniaxial and biaxial (BN) states of polar phase. Our observations show that the magnetic field triggers the modulational instability and demonstrate that irrespective of the magnetic field effect the uniaxial and biaxial nematic phases show modulational instability.

  13. Sensing and tuning microfiber chirality with nematic chirogyral effect

    Science.gov (United States)

    Čopar, Simon; Seč, David; Aguirre, Luis E.; Almeida, Pedro L.; Dazza, Mallory; Ravnik, Miha; Godinho, Maria H.; Pieranski, Pawel; Žumer, Slobodan

    2016-03-01

    Microfibers with their elongated shape and translation symmetry can act as important components in various soft materials, notably for their mechanics on the microscopic level. Here we demonstrate the mechanical response of a micro-object to imposed chirality, in this case, the tilt of disclination rings in an achiral nematic medium caused by the chiral surface anchoring on an immersed microfiber. This coupling between chirality and mechanical response, used to demonstrate sensing of chirality of electrospun cellulose microfibers, is revealed in the optical micrographs due to anisotropy in the elastic response of the host medium. We provide an analytical explanation of the chirogyral effect supported with numerical simulations and perform an experiment to test the effect of the cell confinement and fiber size. We controllably twist the microfibers and demonstrate the response of the nematic medium. More generally the demonstrated study provides means for experimental discrimination of surface properties and allows mechanical control over the shape of disclination rings.

  14. Vitrified chiral-nematic liquid crystalline films for selective reflection and circular polarization

    Energy Technology Data Exchange (ETDEWEB)

    Katsis, D.; Chen, P.H.M.; Mastrangelo, J.C.; Chen, S.H. [Univ. of Rochester, NY (United States); Blanton, T.N. [Eastman Kodak Co., Rochester, NY (United States)

    1999-06-01

    Nematic and left-handed chiral-nematic liquid crystals comprising methoxybiphenylbenzoate and (S)-(-)-1-phenylethylamine pendants to a cyclohexane core were synthesized and characterized. Although pristine samples were found to be polycrystalline, thermal quenching following heating to and annealing at elevated temperatures permitted the molecular orders characteristic of liquid crystalline mesomorphism to be frozen in the glassy state. Left at room temperature for 6 months, the vitrified liquid crystalline films showed no evidence of recrystallization. An orientational order parameter of 0.65 was determined with linear dichroism of a vitrified nematic film doped with Exalite 428 at a mole fraction of 0.0025. Birefringence dispersion of a blank vitrified nematic film was determined using a phase-difference method complemented by Abbe refractometry. A series of vitrified chiral-nematic films were prepared to demonstrate selective reflection and circular polarization with a spectral region tunable from blue to the infrared region by varying the chemical composition. The experimentally measured circular polarization spectra were found to agree with the Good-Karali theory in which all four system parameters were determined a priori: optical birefringence, average refractive index, selective reflection wavelength, and film thickness.

  15. Characterization of a chiral nematic mesoporous organosilica using NMR

    Science.gov (United States)

    Manning, Alan; Shopsowitz, Kevin; Giese, Michael; MacLachlan, Mark; Dong, Ronald; Michal, Carl

    2012-10-01

    Using templation with nanocrystalline cellulose, a mesoporous organosilica film with a chiral nematic pore structure has recently been developed. [1] We have used a variety of Nuclear Magnetic Resonance (NMR) techniques to characterize the pore structure. The pore size distribution has been found by analyzing the freezing point depression of absorbed water via NMR cryoporometry. The effective longitudinal and transverse pore diameters for diffusing water were investigated with Pulsed-Field Gradient (PFG) NMR and compared to a 1-D connected-pore model. Preliminary data on testing imposed chiral ordering in absorbed liquid crystals is also presented. [4pt] [1] K.E. Shopsowitz et al. JACS 134(2), 867 (2012)

  16. Localised polymer networks in chiral nematic liquid crystals for high speed photonic switching

    Science.gov (United States)

    Tartan, Chloe C.; Salter, Patrick S.; Booth, Martin J.; Morris, Stephen M.; Elston, Steve J.

    2016-05-01

    Self-assembled periodic structures based upon chiral liquid crystalline materials have significant potential in the field of photonics ranging from fast-switching optoelectronic devices to low-threshold lasers. The flexoelectro-optic effect, which is observed in chiral nematic liquid crystals (LCs) when an electric field is applied perpendicular to the helical axis, has significant potential as it exhibits analogue switching in 10-100 μs. However, the major technological barrier that prohibits the commercial realisation of this electro-optic effect is the requirement of a uniform, in-plane alignment of the helix axis between glass substrates. Here, it is shown that periodic polymer structures engineered in the nematic phase of a chiral nematic LC device using direct laser writing can result in the spontaneous formation of the necessary uniform lying helix (ULH) state. Specifically, two-photon polymerization is used in conjunction with a spatial light modulator so as to correct for aberrations introduced by the bounding glass substrates enabling the polymer structures to be fabricated directly into the device. The ULH state appears to be stable in the absence of an externally applied electric field, and the optimum contrast between the bright and dark states is obtained using polymer structures that have periodicities of the order of the device thickness.

  17. Elastic interactions between topological defects in chiral nematic shells

    Science.gov (United States)

    Darmon, Alexandre; Dauchot, Olivier; Lopez-Leon, Teresa; Benzaquen, Michael

    2016-12-01

    We present a self-consistent and robust theoretical model to investigate elastic interactions between topological defects in liquid crystal shells. Accounting for the nonconcentric nature of the shell in a simple manner, we are able to successfully and accurately explain and predict the positions of the defects, most relevant in the context of colloidal self-assembly. We calibrate and test our model on existing experimental data and extend it to all observed defects configurations in chiral nematic shells. We perform experiments to check further and confirm the validity of the present model. Moreover, we are able to obtain quantitative estimates of the energies of +1 or +3 /2 disclination lines in cholesterics, whose intricate nature was only reported recently [A. Darmon, et al. Proc. Natl. Acad. Sci. USA 113, 9469 (2016), 10.1073/pnas.1525059113].

  18. Hidden topological constellations and polyvalent charges in chiral nematic droplets

    Science.gov (United States)

    Posnjak, Gregor; Čopar, Simon; Muševič, Igor

    2017-02-01

    Topology has an increasingly important role in the physics of condensed matter, quantum systems, material science, photonics and biology, with spectacular realizations of topological concepts in liquid crystals. Here we report on long-lived hidden topological states in thermally quenched, chiral nematic droplets, formed from string-like, triangular and polyhedral constellations of monovalent and polyvalent singular point defects. These topological defects are regularly packed into a spherical liquid volume and stabilized by the elastic energy barrier due to the helical structure and confinement of the liquid crystal in the micro-sphere. We observe, for the first time, topological three-dimensional point defects of the quantized hedgehog charge q=-2, -3. These higher-charge defects act as ideal polyvalent artificial atoms, binding the defects into polyhedral constellations representing topological molecules.

  19. Hidden topological constellations and polyvalent charges in chiral nematic droplets

    Science.gov (United States)

    Posnjak, Gregor; Čopar, Simon; Muševič, Igor

    2017-01-01

    Topology has an increasingly important role in the physics of condensed matter, quantum systems, material science, photonics and biology, with spectacular realizations of topological concepts in liquid crystals. Here we report on long-lived hidden topological states in thermally quenched, chiral nematic droplets, formed from string-like, triangular and polyhedral constellations of monovalent and polyvalent singular point defects. These topological defects are regularly packed into a spherical liquid volume and stabilized by the elastic energy barrier due to the helical structure and confinement of the liquid crystal in the micro-sphere. We observe, for the first time, topological three-dimensional point defects of the quantized hedgehog charge q=−2, −3. These higher-charge defects act as ideal polyvalent artificial atoms, binding the defects into polyhedral constellations representing topological molecules. PMID:28220770

  20. Modeling Textural Processes during Self-Assembly of Plant-Based Chiral-Nematic Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Yogesh K. Murugesan

    2010-12-01

    Full Text Available Biological liquid crystalline polymers are found in cellulosic, chitin, and DNA based natural materials. Chiral nematic liquid crystalline orientational order is observed frozen-in in the solid state in plant cell walls and is known as a liquid crystal analogue characterized by a helicoidal plywood architecture. The emergence of the plywood architecture by directed chiral nematic liquid crystalline self assembly has been postulated as the mechanism that leads to optimal cellulose fibril organization. In natural systems, tissue growth and development takes place in the presence of inclusions and secondary phases leaving behind characteristic defects and textures, which provide a unique testing ground for the validity of the liquid crystal self-assembly postulate. In this work, a mathematical model, based on the Landau-de Gennes theory of liquid crystals, is used to simulate defect textures arising in the domain of self assembly, due to presence of secondary phases representing plant cells, lumens and pit canals. It is shown that the obtained defect patterns observed in some plant cell walls are those expected from a truly liquid crystalline phase. The analysis reveals the nature and magnitude of the viscoelastic material parameters that lead to observed patterns in plant-based helicoids through directed self-assembly. In addition, the results provide new guidance to develop biomimetic plywoods for structural and functional applications.

  1. Odd-parity superconductors with two-component order parameters: Nematic and chiral, full gap, and Majorana node

    Science.gov (United States)

    Venderbos, Jörn W. F.; Kozii, Vladyslav; Fu, Liang

    2016-11-01

    Motivated by the recent experiment indicating that superconductivity in the doped topological insulator CuxBi2Se3 has an odd-parity pairing symmetry with rotational symmetry breaking, we study the general class of odd-parity superconductors with two-component order parameters in trigonal and hexagonal crystal systems. In the presence of strong spin-orbit interaction, we find two possible superconducting phases below Tc, a time-reversal-breaking (i.e., chiral) phase and an anisotropic (i.e., nematic) phase, and determine their relative energetics from the gap function in momentum space. The nematic superconductor generally has a full quasiparticle gap, whereas the chiral superconductor with a three-dimensional (3D) Fermi surface has point nodes with lifted spin degeneracy, resulting in itinerant Majorana fermions in the bulk and topological Majorana arcs on the surface.

  2. Electrolyte effects on the chiral induction and on its temperature dependence in a chiral nematic lyotropic liquid crystal.

    Science.gov (United States)

    Dawin, Ute C; Osipov, Mikhail A; Giesselmann, Frank

    2010-08-19

    We present a study on the effect of added CsCl and of temperature variation on the chiral induction in a chiral nematic lyotropic liquid crystal (LC) composed of the surfactant cesium perfluorooctanoate (CsPFO), water, and the chiral dopant d-Leucine (d-Leu). The chiral induction was measured as the helical pitch P. The role of the additives CsCl and d-Leu on the phase behavior is investigated and discussed. The thermal stabilization effect of CsCl is shown to lead to an apparent salt effect on the pitch when the pitch is compared at a constant temperature. This apparent effect is removed by comparing the pitch measured for different salt concentrations at a temperature relative to the phase-transition temperatures; thus, the real salt effect on the pitch is described. High salt concentrations are shown to increase the pitch, that is, hinder the chiral induction. The effect is discussed in terms of a decreased solubilization of the amphiphilic chiral solute d-Leu in the micelles due to the salt-induced screening of the surfactant head groups and the consequential denser packing of the surfactants. The temperature variation of the pitch is investigated for all CsCl concentrations and is found to be essentially independent of the salt concentration. The temperature variation is analyzed and discussed in the context of a theoretical model taking into account specific properties of lyotropic liquid crystals. A hyperbolic decrease of the pitch is found with increasing temperature, which is known, from thermotropic liquid crystals, to stem from pretransitional critical fluctuations close to the lamellar phase. However, the experimental data confirmed the theoretical prediction that, at high temperature, that is, far away from the transition into the lamellar phase, the pitch is characterized by a linear temperature dependence which is determined by a combination of steric and dispersion chiral interactions. The parameters of the theoretical expression for the pitch have

  3. Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Derek G. Gray

    2015-11-01

    Full Text Available Cellulosic liquid crystalline solutions and suspensions form chiral nematic phases that show a rich variety of optical textures in the liquid crystalline state. These ordered structures may be preserved in solid films prepared by evaporation of solvent or suspending medium. Film formation from aqueous suspensions of cellulose nanocrystals (CNC was investigated by polarized light microscopy, optical profilometry and atomic force microscopy (AFM. An attempt is made to interpret qualitatively the observed textures in terms of the orientation of the cellulose nanocrystals in the suspensions and films, and the changes in orientation caused by the evaporative process. Mass transfer within the evaporating droplet resulted in the formation of raised rings whose magnitude depended on the degree of pinning of the receding contact line. AFM of dry films at short length scales showed a radial orientation of the CNC at the free surface of the film, along with a radial height variation with a period of approximately P/2, ascribed to the anisotropic shrinkage of the chiral nematic structure.

  4. Chiral nematic stained glass: controlling the optical properties of nanocrystalline cellulose-templated materials.

    Science.gov (United States)

    Kelly, Joel A; Shopsowitz, Kevin E; Ahn, Jun Myun; Hamad, Wadood Y; MacLachlan, Mark J

    2012-12-18

    Chiral nematic mesoporous materials decorated with metal nanoparticles have been prepared using the templated self-assembly of nanocrystalline cellulose (NCC). By adding small quantities of ionic compounds to aqueous dispersions of NCC and tetramethoxysilane (TMOS), the helical pitch of the chiral nematic structure could be manipulated in a manner complementary to the ratio of NCC/TMOS previously demonstrated by our group. We have studied the transformation of these ion-loaded composites into high surface area mesoporous silica and carbon films decorated with metal nanoparticles through calcination and carbonization, respectively. This general and straightforward approach to prepare chiral nematic metal nanoparticle assemblies may be useful in a variety of applications, particularly for their chiral optical properties.

  5. Vortexlike topological defects in nematic colloids: chiral colloidal dimers and 2D crystals.

    Science.gov (United States)

    Tkalec, U; Ravnik, M; Zumer, S; Musevic, I

    2009-09-18

    We show that chiral ordering of the underlying complex fluid strongly influences defect formation and colloidal interactions. Nonsingular defect loops with a topological charge -2 are observed, with a cross section identical to hyperbolic vortices in magnetic systems. These loops are binding spontaneously formed pairs of colloidal particles and dimers, which are chiral objects. Chiral dimer-dimer interaction weakly depends on the chirality of dimers and leads to the assembly of 2D nematic colloidal crystals of pure or "mixed" chirality, intercalated with a lattice of nonsingular vortexlike defects.

  6. Phase diagrams of charged colloidal rods: Can a uniaxial charge distribution break chiral symmetry?

    Science.gov (United States)

    Drwenski, Tara; Dussi, Simone; Hermes, Michiel; Dijkstra, Marjolein; van Roij, René

    2016-03-07

    We construct phase diagrams for charged rodlike colloids within the second-virial approximation as a function of rod concentration, salt concentration, and colloidal charge. Besides the expected isotropic-nematic transition, we also find parameter regimes with a coexistence between a nematic and a second, more highly aligned nematic phase including an isotropic-nematic-nematic triple point and a nematic-nematic critical point, which can all be explained in terms of the twisting effect. We compute the Frank elastic constants to see if the twist elastic constant can become negative, which would indicate the possibility of a cholesteric phase spontaneously forming. Although the twisting effect reduces the twist elastic constant, we find that it always remains positive. In addition, we find that for finite aspect-ratio rods the twist elastic constant is also always positive, such that there is no evidence of chiral symmetry breaking due to a uniaxial charge distribution.

  7. Holographic RG flows with nematic IR phases

    CERN Document Server

    Cremonini, Sera; Rong, Junchen; Sun, Kai

    2014-01-01

    We construct zero-temperature geometries that interpolate between a Lifshitz fixed point in the UV and an IR phase that breaks spatial rotations but preserves translations. We work with a simple holographic model describing two massive gauge fields coupled to gravity and a neutral scalar. Our construction can be used to describe RG flows in non-relativistic, strongly coupled quantum systems with nematic order in the IR. In particular, when the dynamical critical exponent of the UV fixed point is z=2 and the IR scaling exponents are chosen appropriately, our model realizes holographically the scaling properties of the bosonic modes of the quadratic band crossing model.

  8. Temperature-tunable lasing in negative dielectric chiral nematic liquid crystal

    Science.gov (United States)

    Wu, Ri-Na; Wu, Jie; Wu, Xiao-Jiao; Dai, Qin

    2015-05-01

    In this work, negative dielectric nematic liquid crystal SLC12V620-400, chiral dopant S811, and laser dye DCM are used to prepare dye-doped chiral nematic liquid crystal laser sample. In order to investigate temperature-tunable lasing in negative dielectric chiral nematic liquid crystal, we measure the transmission and lasing spectrum of this sample. The photonic band gap (PBG) is observed to red shift with its width reducing from 71.2 nm to 40.2 nm, and its short-wavelength band edge moves 55.3 nm while the long-wavelength band edge only moves 24.9 nm. The wavelength of output laser is found to red shift from 614.4 nm at 20 °C to 662.8 nm at 67 °C, which is very different from the previous experimental phenomena. The refractive indices, parallel and perpendicular to the director in chiral nematic liquid crystal have different dependencies on temperature. The experiment shows that the pitch of this chiral nematic liquid crystal increases with the increase of temperature. The decrease in the PBG width, different shifts of band edges, and the red shift of laser wavelength are the results of refractive indices change and pitch thermal elongation. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Outstanding Young Scholars Growth Plans of Colleges and Universities in Liaoning Province, China (Grant No. LJQ2013022), the Science and Technology Research of Liaoning Province, China (Grant No. L2010465), the Open Funds of Liaoning Province Key Laboratory of Laser and Optical Information of Shenyang Ligong University, China.

  9. Topological Insulators and Nematic Phases from Spontaneous Symmetry Breaking in

    Energy Technology Data Exchange (ETDEWEB)

    Sun, K.

    2010-05-26

    We investigate the stability of a quadratic band-crossing point (QBCP) in 2D fermionic systems. At the non-interacting level, we show that a QBCP exists and is topologically stable for a Berry flux {-+}2{pi}, if the point symmetry group has either fourfold or sixfold rotational symmetries. This putative topologically stable free-fermion QBCP is marginally unstable to arbitrarily weak shortrange repulsive interactions. We consider both spinless and spin-1/2 fermions. Four possible ordered states result: a quantum anomalous Hall phase, a quantum spin Hall phase, a nematic phase, and a nematic-spin-nematic phase.

  10. Towards the biaxial nematic phase via specific intermolecular interactions

    CERN Document Server

    Omnes, L

    2001-01-01

    The work described in this thesis has been focussed on the search of an elusive liquid crystal phase, known as the biaxial nematic phase. Indeed, despite nearly thirty years of intense research, no-one has been able to characterise unambiguously a biaxial nematic phase in a low-molar-mass thermotropic system. Our research is based on the concept of molecular biaxiality as distinct from shape biaxiality. Thus, we are seeking to design palladium complexes where specific intermolecular interactions could exist. Therefore, a few original synthetic strategies were developed to tackle the challenge of discovering the biaxial nematic phase

  11. Twist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane: A dielectric, 2H NMR, and calorimetric study

    Science.gov (United States)

    Robles-Hernández, Beatriz; Sebastián, Nerea; de la Fuente, M. Rosario; López, David O.; Diez-Berart, Sergio; Salud, Josep; Ros, M. Blanca; Dunmur, David A.; Luckhurst, Geoffrey R.; Timimi, Bakir A.

    2015-12-01

    The nature of the nematic-nematic phase transition in the liquid crystal dimer 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB) has been investigated using techniques of calorimetry, dynamic dielectric response measurements, and 2H NMR spectroscopy. The experimental results for CB9CB show that, like the shorter homologue CB7CB, the studied material exhibits a normal nematic phase, which on cooling undergoes a transition to the twist-bend nematic phase (NTB), a uniaxial nematic phase, promoted by the average bent molecular shape, in which the director tilts and precesses describing a conical helix. Modulated differential scanning calorimetry has been used to analyze the nature of the NTB-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and 2H magnetic resonance studies have revealed information on the structural characteristics of the recently discovered twist-bend nematic phase. Analysis of the dynamic dielectric response in both nematic phases has provided an estimate of the conical angle of the heliconical structure for the NTB phase. Capacitance measurements of the electric-field realignment of the director in initially planar aligned cells have yielded values for the splay and bend elastic constants in the high temperature nematic phase. The bend elastic constant is small and decreases with decreasing temperature as the twist-bend phase is approached. This behavior is expected theoretically and has been observed in materials that form the twist-bend nematic phase. 2H NMR measurements characterize the chiral helical twist identified in the twist-bend nematic phase and also allow the determination of the temperature dependence of the conical angle and the orientational order parameter with respect to the director.

  12. Fluctuational shift of nematic-isotropic phase transition temperature

    Science.gov (United States)

    Kats, E. I.

    2017-02-01

    In this work we discuss a macroscopic counterpart to the microscopic mechanism of the straightening dimer mesogens conformations, proposed recently by S.M. Saliti, M.G.Tamba, S.N. Sprunt, C.Welch, G.H.Mehl, A. Jakli, J.T. Gleeson (Phys. Rev. Lett. 116, 217801 (2016)) to explain their experimental observation of the unprecedentedly large shift of the nematic-isotropic transition temperature. Our interpretation is based on singular longitudinal fluctuations of the nematic order parameter. Since these fluctuations are governed by the Goldstone director fluctuations they exist only in the nematic state. External magnetic field suppresses the singular longitudinal fluctuations of the order parameter (similarly as it is the case for the transverse director fluctuations, although with a different scaling over the magnetic field). The reduction of the fluctuations changes the equilibrium value of the modulus of the order parameter in the nematic state. Therefore it leads to additional (with respect to the mean field contribution) fluctuational shift of the nematic-isotropic transition temperature. Our mechanism works for any nematic liquid crystals, however the magnitude of the fluctuational shift increases with decrease of the Frank elastic moduli. Since some of these moduli supposed to be anomalously small for so-called bent-core or dimer nematic liquid crystals, just these liquid crystals are promising candidates for the observation of the predicted fluctuational shift of the phase transition temperature.

  13. Flexoelectro-optic properties of chiral nematic liquid crystals in the uniform standing helix configuration.

    Science.gov (United States)

    Castles, F; Morris, S M; Coles, H J

    2009-09-01

    The flexoelectro-optic effect describes the rotation of the optic axis of a short-pitch chiral nematic liquid crystal under the application of an electric field. We investigate the effect in the uniform standing helix, or "Grandjean" configuration. An in-plane electric field is applied. The director profile is determined numerically using a static one-dimensional continuum model with strong surface anchoring. The Berreman method is used to solve for plane-wave solutions to Maxwell's equations, and predict the optical properties of the resulting structure in general cases. By using a chiral nematic with short pitch between crossed polarizers an optical switch may be generated. With no applied field the configuration is nontransmissive at normal incidence, but becomes transmissive with an applied field. For this case, numerical results using the Berreman method are supplemented with an analytic theory and found to be in good agreement. The transmitted intensity as a function of tilt, the contrast ratio, and the tilt required for full intensity modulation are presented. The angular dependence of the transmission is calculated and the isocontrast curves are plotted. For typical material and cell parameters a switching speed of 0.017 ms and contrast ratio of 1500:1 at normal incidence are predicted, at a switch-on tilt of 41.5 degrees. Experimental verification of the analytic and numerical models is provided.

  14. Induced smectic phases in phase diagrams of binary nematic liquid crystal mixtures.

    Science.gov (United States)

    Huang, Tsang-Min; McCreary, Kathleen; Garg, Shila; Kyu, Thein

    2011-03-28

    To elucidate induced smectic A and smectic B phases in binary nematic liquid crystal mixtures, a generalized thermodynamic model has been developed in the framework of a combined Flory-Huggins free energy for isotropic mixing, Maier-Saupe free energy for orientational ordering, McMillan free energy for smectic ordering, Chandrasekhar-Clark free energy for hexagonal ordering, and phase field free energy for crystal solidification. Although nematic constituents have no smectic phase, the complexation between these constituent liquid crystal molecules in their mixture resulted in a more stable ordered phase such as smectic A or B phases. Various phase transitions of crystal-smectic, smectic-nematic, and nematic-isotropic phases have been determined by minimizing the above combined free energies with respect to each order parameter of these mesophases. By changing the strengths of anisotropic interaction and hexagonal interaction parameters, the present model captures the induced smectic A or smectic B phases of the binary nematic mixtures. Of particular importance is the fact that the calculated phase diagrams show remarkable agreement with the experimental phase diagrams of binary nematic liquid crystal mixtures involving induced smectic A or induced smectic B phase.

  15. Transparent nematic phase in a liquid-crystal-based microemulsion.

    Science.gov (United States)

    Yamamoto, J; Tanaka, H

    2001-01-18

    Complex fluids are usually produced by mixing together several distinct components, the interactions between which can give rise to unusual optical and rheological properties of the system as a whole. For example, the properties of microemulsions (composed of water, oil and surfactants) are determined by the microscopic structural organization of the fluid that occurs owing to phase separation of the component elements. Here we investigate the effect of introducing an additional organizing factor into such a fluid system, by replacing the oil component of a conventional water-in-oil microemulsion with an intrinsically anisotropic fluid--a nematic liquid crystal. As with the conventional case, the fluid phase-separates into an emulsion of water microdroplets (stabilized by the surfactant as inverse micelles) dispersed in the 'oil' phase. But the properties are further influenced by a significant directional coupling between the liquid-crystal molecules and the surfactant tails that emerge (essentially radially) from the micelles. The result is a modified bulk-liquid crystal that is an ordered nematic at the mesoscopic level, but which does not exhibit the strong light scattering generally associated with bulk nematic order: the bulk material here is essentially isotropic and thus transparent.

  16. Matched elastic constants for a perfect helical planar state and a fast switching time in chiral nematic liquid crystals.

    Science.gov (United States)

    Yu, Meina; Zhou, Xiaochen; Jiang, Jinghua; Yang, Huai; Yang, Deng-Ke

    2016-05-11

    Chiral nematic liquid crystals possess a self-assembled helical structure and exhibit unique selective reflection in visible and infrared light regions. Their optical properties can be electrically tuned. The tuning involves the unwinding and restoring of the helical structure. We carried out an experimental study on the mechanism of the restoration of the helical structure. We constructed chiral nematic liquid crystals with variable elastic constants by doping bent-dimers and studied their impact on the restoration. With matched twist and bend elastic constants, the helical structure can be restored dramatically fast from the field-induced homeotropic state. Furthermore, defects can be eliminated to produce a perfect planar state which exhibits high selective reflection.

  17. Neutrino Oscillation Induced by Chiral Phase Transition

    Institute of Scientific and Technical Information of China (English)

    MU Cheng-Fu; SUN Gao-Feng; ZHUANG Peng-Fei

    2009-01-01

    Electric charge neutrality provides a relationship between chiral dynamics and neutrino propagation in compact stars.Due to the sudden drop of the electron density at the first-order chiral phase transition,the oscillation for low energy neutrinos is significant and can be regarded as a signature of chiral symmetry restoration in the core of compact stars.

  18. Berry Phase of Light under Bragg Reflection by Chiral Liquid-Crystal Media

    Science.gov (United States)

    Barboza, Raouf; Bortolozzo, Umberto; Clerc, Marcel G.; Residori, Stefania

    2016-07-01

    A Berry phase is revealed for circularly polarized light when it is Bragg reflected by a chiral liquid-crystal medium of the same handedness. By using a chiral nematic layer we demonstrate that if the input plane of the layer is rotated with respect to a fixed reference frame, a geometric phase effect occurs for the circularly polarized light reflected by the periodic helical structure of the medium. Theory and numerical simulations are supported by an experimental observation, disclosing novel applications in the field of optical manipulation and fundamental optical phenomena.

  19. Berry phase of light Bragg-reflected by chiral liquid crystal media

    CERN Document Server

    Barboza, Raouf; Residori, Stefania; Clerc, Marcel G

    2016-01-01

    Berry phase is revealed for circularly polarized light when it is Bragg-reflected by a chiral liquid crystal medium of the same handedness. By using a chiral nematic layer we demonstrate that if the input plane of the layer is rotated with respect to a fixed reference frame, then, a geometric phase effect occurs for the circularly polarized light reflected by the periodic helical structure of the medium. Theory and numerical simulations are supported by an experimental observation, disclosing novel applications in the field of optical manipulation and fundamental optical phenomena.

  20. Phase separation and disorder in doped nematic elastomers

    KAUST Repository

    Köpf, M. H.

    2013-10-01

    We formulate and analyse a model describing the combined effect of mechanical deformation, dynamics of the nematic order parameter, and concentration inhomogeneities in an elastomeric mixture of a mesogenic and an isotropic component. The uniform nematic state may exhibit a long-wave instability corresponding to nematic-isotropic demixing. Numerical simulations starting from either a perfectly ordered nematic state or a quenched isotropic state show that coupling between the mesogen concentration and the nematic order parameter influences the shape and orientation of the domains formed during the demixing process. © EDP Sciences/ Società Italiana di Fisica/ Springer-Verlag 2013.

  1. Asymmetric dynamic phase holographic grating in nematic liquid crystal

    Science.gov (United States)

    Ren, Chang-Yu; Shi, Hong-Xin; Ai, Yan-Bao; Yin, Xiang-Bao; Wang, Feng; Ding, Hong-Wei

    2016-09-01

    A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal (NLC) was presented. An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating. The diffraction efficiency we achieved is more than 40%, exceeding the theoretical limit for symmetric profile gratings. Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC. Finally, physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented, based on the photo-refractive-like (PR-like) effect. Project supported by the Science and Technology Programs of the Educational Committee of Heilongjiang Province, China (Grant No. 12541730) and the National Natural Science Foundation of China (Grant No. 61405057).

  2. Insights on some chiral smectic phases

    Indian Academy of Sciences (India)

    B Pansu

    2003-08-01

    Combining layered positional order as smectic order and chirality can generate complex architectures since twist parallel to the layers is not allowed. This paper will review some new experimental results on different phases resulting from the competition between smectic positional order and twist orientational order. It concerns the TGBA and the NL*, that is the liquid line phase as well as the SmQ phase. Chiral effects in the isotropic phase will also be discussed.

  3. Oscillatory motion of sheared nanorods beyond the nematic phase.

    Science.gov (United States)

    Strehober, David A; Engel, Harald; Klapp, Sabine H L

    2013-07-01

    We study the role of the control parameter triggering nematic order (temperature or concentration) on the dynamical behavior of a system of nanorods under shear. Our study is based on a set of mesoscopic equations of motion for the components of the tensorial orientational order parameter. We investigate these equations via a systematic bifurcation analysis based on a numerical continuation technique, focusing on spatially homogeneous states. Exploring a wide range of parameters we find, unexpectedly, that states with oscillatory motion can exist even under conditions where the equilibrium system is isotropic. These oscillatory states are characterized by a wagging motion of the paranematic director, and they occur if the tumbling parameter is sufficiently small. We also present full nonequilibrium phase diagrams in the plane spanned by the concentration and the shear rate.

  4. Chromonic nematic phase and scalar order parameter of indanthrone derivative with ionic additives

    OpenAIRE

    Boiko O.P.; Vasyuta R.M.; Semenyshyn O.M.; Nastishin Yu.A.; Nazarenko V.G.

    2008-01-01

    We investigate influence of different ionic additives on the phase behaviour and scalar order parameter of lyotropic chromonic nematic liquid crystals formed by the molecules representing derivatives of indanthrone. KI, (NH4)2SO4 and NaCl salts increase biphasic nematic region on the temperature-concentration phase diagram, whereas the scalar orientational order parameter is hardly sensitive to their presence. We suggest that these changes are attributed to increase in the ag-gregate length a...

  5. Elasticity of Spider dragline Silks Viewed as Nematics: Yielding Induced by Isotropic-Nematic Phase Transition

    CERN Document Server

    Cui, Lin-ying; Liu, Fei

    2008-01-01

    Spider dragline silk is an intriguing biomaterial of practical use, and it has long been suggested to be a liquid crystalline material. We model the dragline silk as nematics by using continuum liquid crystal theory. The overall stress-strain curve and the yield point can be evaluated quantitatively and agree with experiment data well. Additionally, our model can account for the drop of stress in wet spider dragline, i.e. in supercontracted dragline silk.

  6. Chiral Liquid Crystals: Structures, Phases, Effects

    Directory of Open Access Journals (Sweden)

    Ingo Dierking

    2014-06-01

    Full Text Available The introduction of chirality, i.e., the lack of mirror symmetry, has a profound effect on liquid crystals, not only on the molecular scale but also on the supermolecular scale and phase. I review these effects, which are related to the formation of supermolecular helicity, the occurrence of novel thermodynamic phases, as well as electro-optic effects which can only be observed in chiral liquid crystalline materials. In particular, I will discuss the formation of helical superstructures in cholesteric, Twist Grain Boundary and ferroelectric phases. As examples for the occurrence of novel phases the Blue Phases and Twist Grain Boundary phases are introduced. Chirality related effects are demonstrated through the occurrence of ferroelectricity in both thermotropic as well as lyotropic liquid crystals. Lack of mirror symmetry is also discussed briefly for some biopolymers such as cellulose and DNA, together with its influence on liquid crystalline behavior.

  7. The elusive thermotropic biaxial nematic phase in rigid bent-core molecules

    Indian Academy of Sciences (India)

    Bharat R Acharya; Andrew Primak; Theo J Dingemans; Edward T Samulski; Satyendra Kumar

    2003-08-01

    The biaxial nematic liquid crystalline phase was predicted several decades ago. Several vigorous attempts to find it in various systems resulted in mis-identifications. The results of X-ray diffraction and optical texture studies of the phases exhibited by rigid bent-core molecules derived from 2,5-bis-(-hydroxyphenyl)-1,3,4-oxadiazole reveal that the biaxial nematic phase is formed by three compounds of this type. X-ray diffraction studies reveal that the nematic phase of these compounds has the achiral symmetry D2h, in which the overall long axes of the molecules are oriented parallel to each other to define the major axis of the biaxial phase. The apex of the bent-cores defines the minor axis of this phase along which the planes containing the bent-cores of neighboring molecules are oriented parallel to each other.

  8. Chiral-induced self-assembly sphere phase liquid crystal with fast switching time

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Ji-Liang; Ni, Shui-Bin; Ping Chen, Chao; Lu, Jian-Gang, E-mail: lujg@sjtu.edu.cn; Su, Yikai [National Engineering Lab for TFT-LCD Materials and Technologies, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Wu, Dong-Qing [College of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Song, Xiao-Long; Chen, Chao-Yuan [The Jiangsu Hecheng Display Technology Co., Ltd., Nanjing 211300 (China); Shieh, Han-Ping D. [National Engineering Lab for TFT-LCD Materials and Technologies, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Department of Photonics and Display Institute, National Chiao Tung University, Hsinchu 300, Taiwan (China)

    2014-03-03

    A fluid self-assembly sphere phase (SP) of liquid crystal induced by chiral dopant is observed in a narrow temperature range between isotropic and blue phase or between isotropic and chiral nematic phase. The SP consists of three-dimensional twist spheres (3-DTSs) and disclinations among 3-DTSs. The temperature range of the SP has been broadened to more than 85 °C by stabilizing the disclinations with amorphous polymer chains. The electro-optical switching time of the polymer-stabilized SP is demonstrated in sub-millisecond with a low switching electric field of 4.4 V μm{sup −1}, which is of promising applications in displays, 3-D tunable photonic crystals, and phase modulators.

  9. Lattice Boltzmann Simulation of 3D Nematic Liquid Crystal near Phase Transition

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; TAO Rui-Bao

    2002-01-01

    Phase transition between nematic and isotropic liquid crystal is a very weak first order phase transition.We avoid to use the normal Landau-de Gennes's free energy that reduces a strong first order transition, and set up adata base of free energy calculated by means of Tao-Sheng Lin's extended molecular field theory that can explain theexperiments of the equilibrium properties of nematic liquid crystal very well. Then we use the free energy method oflattice Boltzmann developed by Oxford group to study the phase decomposition, pattern formation in the flow of theliquid crystal near transition temperature.

  10. Chirality effects on 2D phase transitions

    DEFF Research Database (Denmark)

    Scalas, E.; Brezesinski, G.; Möhwald, H.

    1996-01-01

    -nearest neighbours (NNN) and an NNN-distorted lattice is observed. At 5 degrees C, the transition pressure is 15 mN m(-1), whereas at 20 degrees C it is 18 mN m(-1). Chirality destroys this transition: the pure enantiomer always exhibits an oblique lattice with tilted molecules, and the azimuths of tilt...... and distortion continuously vary from a direction close to NN to a direction close to NNN. The nature of the phase transition and the influence of chirality on it are discussed within the framework of Landau's theory of phase transitions....

  11. Magnetic properties in the inhomogeneous chiral phase

    CERN Document Server

    Yoshiike, Ryo; Tatsumi, Toshitaka

    2016-01-01

    We investigate the magnetic properties of quark matter in the inhomogeneous chiral phase, where both scalar and pseudoscalar condensates spatially modulate. The energy spectrum of the lowest Landau level becomes asymmetric about zero in the external magnetic field, and gives rise to the remarkably magnetic properties: quark matter has a spontaneous magnetization, while the magnetic susceptibility does not diverge on the critical point.

  12. Dynamics of the chiral phase transition

    CERN Document Server

    van Hees, H; Meistrenko, A; Greiner, C

    2013-01-01

    The intention of this study is the search for signatures of the chiral phase transition in heavy-ion collisions. To investigate the impact of fluctuations, e.g., of the baryon number, at the transition or at a critical point, the linear sigma model is treated in a dynamical (3+1)-dimensional numerical simulation. Chiral fields are approximated as classical mean fields, and quarks are described as quasi particles in a Vlasov equation. Additional dynamics is implemented by quark-quark and quark-sigma-field interactions. For a consistent description of field-particle interactions, a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.

  13. Compression induced phase transition of nematic brush: A mean-field theory study

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Jiuzhou [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Xinghua, E-mail: zhangxh@bjtu.edu.cn [School of Science, Beijing Jiaotong University, Beijing 100044 (China); Yan, Dadong, E-mail: yandd@bnu.edu.cn [Department of Physics, Beijing Normal University, Beijing 100875 (China)

    2015-11-28

    Responsive behavior of polymer brush to the external compression is one of the most important characters for its application. For the flexible polymer brush, in the case of low grafting density, which is widely studied by the Gaussian chain model based theory, the compression leads to a uniform deformation of the chain. However, in the case of high grafting density, the brush becomes anisotropic and the nematic phase will be formed. The normal compression tends to destroy the nematic order, which leads to a complex responsive behaviors. Under weak compression, chains in the nematic brush are buckled, and the bending energy and Onsager interaction give rise to the elasticity. Under deep compression, the responsive behaviors of the nematic polymer brush depend on the chain rigidity. For the compressed rigid polymer brush, the chains incline to re-orientate randomly to maximize the orientational entropy and its nematic order is destroyed. For the compressed flexible polymer brush, the chains incline to fold back to keep the nematic order. A buckling-folding transition takes place during the compressing process. For the compressed semiflexible brush, the chains are collectively tilted to a certain direction, which leads to the breaking of the rotational symmetry in the lateral plane. These responsive behaviors of nematic brush relate to the properties of highly frustrated worm-like chain, which is hard to be studied by the traditional self-consistent field theory due to the difficulty to solve the modified diffusion equation. To overcome this difficulty, a single chain in mean-field theory incorporating Monte Carlo simulation and mean-field theory for the worm-like chain model is developed in present work. This method shows high performance for entire region of chain rigidity in the confined condition.

  14. A Simple Free Energy for the Isotropic-Nematic Phase Transition of Rods

    Directory of Open Access Journals (Sweden)

    Remco Tuinier

    2016-01-01

    Full Text Available A free energy expression is proposed that describes the isotropic-nematic binodal concentrations of hard rods. A simple analytical form for this free energy was yet only available using a Gaussian trial function for the orientation distribution function (ODF, leading, however, to a significant deviation of the predicted binodals. The new free energy proposed here is based upon a rationalized correction to the orientational and packing entropies when using the Gaussian ODF. In combination with Parsons-Lee theory or scaled particle theory, it enables describing the isotropic-nematic phase coexistence concentrations of rods accurately using the simple Gaussian ODF for a wide range of aspect ratios.

  15. The isotropic-nematic phase transition of tangent hard-sphere chain fluids—Pure components

    NARCIS (Netherlands)

    Van Westen, T.; Oyarzun, B.; Vlugt, T.J.H.; Gross, J.

    2013-01-01

    An extension of Onsager's second virial theory is developed to describe the isotropic-nematic phase transition of tangent hard-sphere chain fluids. Flexibility is introduced by the rod-coil model. The effect of chain-flexibility on the second virial coefficient is described using an accurate, analyt

  16. Chiral phase transition in QED3 at finite temperature

    Science.gov (United States)

    Yin, Pei-Lin; Xiao, Hai-Xiao; Wei, Wei; Feng, Hong-Tao; Zong, Hong-Shi

    2016-12-01

    In the framework of Dyson-Schwinger equations, we employ two kinds of criteria (one kind is the chiral condensate, the other kind is thermodynamic quantities, such as the pressure, the entropy, and the specific heat) to investigate the nature of chiral phase transitions in QED3 for different fermion flavors. It is found that the chiral phase transitions in QED3 for different fermion flavors are all typical second-order phase transitions; the critical temperature and order of the chiral phase transition obtained from the chiral condensate and susceptibility are the same with that obtained by the thermodynamic quantities, which means that they are equivalent in describing the chiral phase transition; the critical temperature decreases as the number of fermion flavors increases and there is a boundary that separates the Tc-Nf plane into chiral symmetry breaking and restoration regions.

  17. Two-Particle Cluster Theory for Biaxial Nematic Phase Based on a Recently Proposed Interaction Potential

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Dong; ZHANG Yan-Jun; SUN Zong-Li

    2006-01-01

    @@ Two-particle cluster theory is applied to study the biaxial nematic phase formed by biaxial molecules interacting with a simplified model proposed by Sonnet et al. [Phys. Rev. E 67 (2003) 061701]. For the temperature dependences of the internal energy per particle and of the order parameters, the two-particle theory yields an improved result compared with mean field theory. Concerning the phase diagram, the two-particle theory gives the numerical result in qualitative agreement with the mean field theory.

  18. Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules.

    Science.gov (United States)

    Lehmann, Matthias; Seltmann, Jens

    2009-12-04

    A series of V-shaped, shape-persistent thiadiazole nematogens, based on an oligo(phenylene ethynylene) scaffold with ester groups connected via alkyloxy spacers, was efficiently prepared by a two-step procedure. Phase engineering results in an optimum of the mesophase range and low melting temperature when the nematogens are desymmetrised with a butoxy and a heptyloxy spacer. The mesophases are enantiotropic and over the whole temperature range nematic. For the optimised mesogen structure, optical investigations by conoscopy monitored a uniaxial nematic phase upon cooling from the isotropic phase to room temperature (ΔT = 150° C). X-ray studies on magnetic-field-aligned samples of this mesogen family revealed a general pattern, indicating the alignment of two molecular axes along individual directors in the magnetic field. These observations may be rationalised with larger assemblies of V-shaped molecules isotropically distributed around the direction of the magnetic field.

  19. Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules

    Directory of Open Access Journals (Sweden)

    Matthias Lehmann

    2009-12-01

    Full Text Available A series of V-shaped, shape-persistent thiadiazole nematogens, based on an oligo(phenylene ethynylene scaffold with ester groups connected via alkyloxy spacers, was efficiently prepared by a two-step procedure. Phase engineering results in an optimum of the mesophase range and low melting temperature when the nematogens are desymmetrised with a butoxy and a heptyloxy spacer. The mesophases are enantiotropic and over the whole temperature range nematic. For the optimised mesogen structure, optical investigations by conoscopy monitored a uniaxial nematic phase upon cooling from the isotropic phase to room temperature (ΔT = 150 °C. X-ray studies on magnetic-field-aligned samples of this mesogen family revealed a general pattern, indicating the alignment of two molecular axes along individual directors in the magnetic field. These observations may be rationalised with larger assemblies of V-shaped molecules isotropically distributed around the direction of the magnetic field.

  20. Chiral phase transition from string theory.

    Science.gov (United States)

    Parnachev, Andrei; Sahakyan, David A

    2006-09-15

    The low energy dynamics of a certain D-brane configuration in string theory is described at weak t'Hooft coupling by a nonlocal version of the Nambu-Jona-Lasinio model. We study this system at finite temperature and strong t'Hooft coupling, using the string theory dual. We show that for sufficiently low temperatures chiral symmetry is broken, while for temperatures larger then the critical value, it gets restored. We compute the latent heat and observe that the phase transition is of the first order.

  1. Simultaneous Chiral SeparationUsing a Combinatorial Molecular Imprinting Phase

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Molecular imprinting chiral stationary phase against Cbz-L-Serine (Cbz-L-Ser) and Cbz-L-Alaine (Cbz-L-Ala) were prepared utilizing acrylamide + 2-vinylpyridine as combined basic functional monomers.Cross-selectivity was used to obtain simultaneous chiral separations of Cbz-DL-Ser and Cbz-DL-Ala by connecting two columns packed with Cbz-L-Ser and Cbz-L-Ala imprinted chiral stationary phase, respectively.

  2. Order parameter and its critical exponent for some binary mixtures showing induced nematic phase

    Science.gov (United States)

    Sarkar, Sudipta Kumar; Das, Malay Kumar

    2016-09-01

    Refractive index measurements as a function of temperature have been performed for an induced nematic binary system by means of thin prism technique. The temperature dependence of the birefringence (Δn) has been assessed from the measured refractive index data. A direct extrapolation method has been employed to determine the orientational order parameter for the investigated mixtures and the order parameter so obtained has also been compared with the mean field values. The Haller type fitting expression results in a relatively lower value of the order parameter critical exponent (β) compared to the theoretically predicted values. Therefore, a four-parameter power law expression, consistent with the mean field theory as well as the first-order character of the nematic-isotropic (N-I) phase transition have been used to explore the critical behavior of the order parameter near the N-I transition.

  3. One-dimensional frustrated plaquette compass model: Nematic phase and spontaneous multimerization

    Science.gov (United States)

    Brzezicki, Wojciech; Oleś, Andrzej M.

    2016-06-01

    We introduce a one-dimensional (1D) pseudospin model on a ladder where the Ising interactions along the legs and along the rungs alternate between XiXi +1 and ZiZi +1 for even/odd bond (rung). We include also the next-nearest-neighbor Ising interactions on plaquettes' diagonals that alternate in such a way that a model where only leg interactions are switched on is equivalent to the one when only the diagonal ones are present. Thus in the absence of rung interactions the model can interpolate between two 1D compass models. The model possesses local symmetries which are the parities within each 2 ×2 cell (plaquette) of the ladder. We find that for different values of the interaction it can realize ground states that differ by the patterns formed by these local parities. By exact diagonalization we derive detailed phase diagrams for small systems of L =4 , 6, and 8 plaquettes, and use next L =12 to identify generic phases that appear in larger systems as well. Among them we find a nematic phase with macroscopic degeneracy when the leg and diagonal interactions are equal and the rung interactions are larger than a critical value. By performing a perturbative expansion around this phase we find indeed a very complex competition around the nematic phase which has to do with releasing frustration in this range of parameters. The nematic phase is similar to the one found in the two-dimensional compass model. For particular parameters the low-energy sector of the present plaquette model reduces to a 1D compass model with spins S =1 which suggests that it realizes peculiar crossovers within the class of compass models. Finally, we show that the model can realize phases with broken translation invariance which can be either dimerized, trimerized, etc., or completely disordered and highly entangled in a well identified window of the phase diagram.

  4. Optical Anisotropy and Four Possible Orientations of a Nematic Liquid Crystal on the Same Film of a Photochromic Chiral Smectic Polymer

    Science.gov (United States)

    Blinov, Lev M.; Barberi, Riccardo; Kozlovsky, Mikhail V.; Lazarev, Vladimir V.; de Santo, Maria P.

    Spin coated films of a chiral comb-like liquid crystalline copolymer containing azobenzene chromophores in its side chains are optically isotropic in their twisted smectic-like glassy state. In contact with a nematic liquid crystal (5CB, E7, MBBA) they provide a degenerate planar orientation. When irradiated by unpolarized UV light, they orient the same nematics homeotropically. Treated with linearly polarized UV light they orient nematics homogeneously with the director along the electric vector of the exciting light. After a combined irradiation first with unpolarized UV light and then with linearly polarized visible light, the films again provide a homogeneous liquid crystal orientation, this time with the director perpendicular to the visible light electric vector. The phenomena observed are related to the light induced optical anisotropy. Two main processes are responsible for the anisotropy (1) a UV light depletion of trans-isomers of the azobenzene chromophores from the chosen direction and (2) a reorientation of the chromophores by polarized visible light.

  5. Periodic structures induced by director reorientation in the lyotropic nematic phase of disodium cromoglycate-water

    Science.gov (United States)

    Hui, Y. W.; Kuzma, M. R.; San Miguel, M.; Labes, M. M.

    1985-07-01

    A nonequilibrium periodic structure is induced by a magnetic field H applied to an aligned lyotropic uniaxial nematic phase of disodium cromoglycate-water. A series of parallel lines perpendicular to H represents boundaries between 180° out-of-phase regions of director reorientation. The distance between the lines decreases with increasing H. The line spacing is also directly proportional to thickness of the sample (in a limited range of thickness), and a secondary periodicity, consisting of nodes in these lines, is observed in thicker samples. An extension of a theoretical model by Guyon et al. is used to qualitatively interpret the abovementioned dependencies.

  6. Charge fluctuations in chiral models and the QCD phase transition

    CERN Document Server

    Skokov, V; Karsch, F; Redlich, K

    2011-01-01

    We consider the Polyakov loop-extended two flavor chiral quark--meson model and discuss critical phenomena related with the spontaneous breaking of the chiral symmetry. The model is explored beyond the mean-field approximation in the framework of the functional renormalisation group. We discuss properties of the net-quark number density fluctuations as well as their higher cumulants. We show that with the increasing net-quark number density, the higher order cumulants exhibit a strong sensitivity to the chiral crossover transition. We discuss their role as probes of the chiral phase transition in heavy-ion collisions at RHIC and LHC.

  7. Chiral phases of fundamental and adjoint quarks

    Energy Technology Data Exchange (ETDEWEB)

    Natale, A. A. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC 09210-170, Santo André, SP (Brazil); Instituto de Física Teórica - UNESP Rua Dr. Bento T. Ferraz, 271, Bl.II - 01140-070, São Paulo, SP (Brazil)

    2016-01-22

    We consider a QCD chiral symmetry breaking model where the gap equation contains an effective confining propagator and a dressed gluon propagator with a dynamically generated mass. This model is able to explain the ratios between the chiral transition and deconfinement temperatures in the case of fundamental and adjoint quarks. It also predicts the recovery of the chiral symmetry for a large number of quarks (n{sub f} ≈ 11 – 13) in agreement with lattice data.

  8. Dissipative particle dynamics study of translational diffusion of rigid-chain rodlike polymer in nematic phase

    Science.gov (United States)

    Zhao, Tongyang; Wang, Xiaogong

    2013-09-01

    In this study, dissipative particle dynamics (DPD) method was employed to investigate the translational diffusion of rodlike polymer in its nematic phase. The polymer chain was modeled by a rigid rod composed of consecutive DPD particles and solvent was represented by independent DPD particles. To fully understand the translational motion of the rods in the anisotropic phase, four diffusion coefficients, D_{||}u, D_ bot u, D_{||}n, D_ bot n were obtained from the DPD simulation. By definition, D_{||}n and D_ bot n denote the diffusion coefficients parallel and perpendicular to the nematic director, while D_{||}u and D_ bot u denote the diffusion coefficients parallel and perpendicular to the long axis of a rigid rod u. In the simulation, the velocity auto-correlation functions were used to calculate the corresponding diffusion coefficients from the simulated velocity of the rods. Simulation results show that the variation of orientational order caused by concentration and temperature changes has substantial influences on D_{||}u and D_ bot u. In the nematic phase, the changes of concentration and temperature will result in a change of local environment of rods, which directly influence D_{||}u and D_ bot u. Both D_{||}n and D_ bot n can be represented as averages of D_{||}u and D_ bot u, and the weighted factors are functions of the orientational order parameter S2. The effect of concentration and temperature on D_{||}n and D_ bot n demonstrated by the DPD simulation can be rationally interpreted by considering their influences on D_{||}u, D_ bot u and the order parameter S2.

  9. Kinetic attractor phase diagrams of active nematic suspensions: the dilute regime.

    Science.gov (United States)

    Forest, M Gregory; Wang, Qi; Zhou, Ruhai

    2015-08-28

    Large-scale simulations by the authors of the kinetic-hydrodynamic equations for active polar nematics revealed a variety of spatio-temporal attractors, including steady and unsteady, banded (1d) and cellular (2d) spatial patterns. These particle scale activation-induced attractors arise at dilute nanorod volume fractions where the passive equilibrium phase is isotropic, whereas all previous model simulations have focused on the semi-dilute, nematic equilibrium regime and mostly on low-moment orientation tensor and polarity vector models. Here we extend our previous results to complete attractor phase diagrams for active nematics, with and without an explicit polar potential, to map out novel spatial and dynamic transitions, and to identify some new attractors, over the parameter space of dilute nanorod volume fraction and nanorod activation strength. The particle-scale activation parameter corresponds experimentally to a tunable force dipole strength (so-called pushers with propulsion from the rod tail) generated by active rod macromolecules, e.g., catalysis with the solvent phase, ATP-induced propulsion, or light-activated propulsion. The simulations allow 2d spatial variations in all flow and orientational variables and full spherical orientational degrees of freedom; the attractors correspond to numerical integration of a coupled system of 125 nonlinear PDEs in 2d plus time. The phase diagrams with and without the polar interaction potential are remarkably similar, implying that polar interactions among the rodlike particles are not essential to long-range spatial and temporal correlations in flow, polarity, and nematic order. As a general rule, above a threshold, low volume fractions induce 1d banded patterns, whereas higher yet still dilute volume fractions yield 2d patterns. Again as a general rule, varying activation strength at fixed volume fraction induces novel dynamic transitions. First, stationary patterns saturate the instability of the isotropic

  10. Peak of Chiral Susceptibility and Chiral Phase Transition in QED3

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yu-Qing; YANG Yong-Hong

    2011-01-01

    A general expression for the scalar susceptibility in QEDs is given. We adopt the Dyson-Schwinger equation for the fermion propagator to solve xc within a range of the number of fermion flavors, N, in chiral symmetry breaking phase. We show that the scalar susceptibility has a peak and the corresponding N is less than the critical number of fermion flavors for chiral symmetry.%@@ A general expression for the scalar susceptibility in QED3 is given.We adopt the Dyson-Schwinger equation for the fermion propagator to solve Xc within a range of the number of fermion flavors, N, in chiral symmetry breaking phase.We show that the scalar susceptibility has a peak and the corresponding N is less than thecritical number of fermion flavors for chiral symmetry.

  11. KN Phase Shifts in Chiral SU(3) Quark Model

    Institute of Scientific and Technical Information of China (English)

    HUANGFei; ZHANGZong-Ye; YUYou-Wen

    2004-01-01

    The isospin I = 0 and I = 1 kaon-nucleon S and P partial waves phase shifts have been studied in the chiral SU(3) quark model by solving a resonating group method equation. When the parameters of the chiral fields are taken in a reasonable region, the numerical results of S-wave are in good agreement with the experimental data, and the P-wave phase shifts can also be explained qualitatively by the calculation of only central force considered.

  12. Chiral Floquet Phases of Many-Body Localized Bosons

    Science.gov (United States)

    Po, Hoi Chun; Fidkowski, Lukasz; Morimoto, Takahiro; Potter, Andrew C.; Vishwanath, Ashvin

    2016-10-01

    We construct and classify chiral topological phases in driven (Floquet) systems of strongly interacting bosons, with finite-dimensional site Hilbert spaces, in two spatial dimensions. The construction proceeds by introducing exactly soluble models with chiral edges, which in the presence of many-body localization (MBL) in the bulk are argued to lead to stable chiral phases. These chiral phases do not require any symmetry and in fact owe their existence to the absence of energy conservation in driven systems. Surprisingly, we show that they are classified by a quantized many-body index, which is well defined for any MBL Floquet system. The value of this index, which is always the logarithm of a positive rational number, can be interpreted as the entropy per Floquet cycle pumped along the edge, formalizing the notion of quantum-information flow. We explicitly compute this index for specific models and show that the nontrivial topology leads to edge thermalization, which provides an interesting link between bulk topology and chaos at the edge. We also discuss chiral Floquet phases in interacting fermionic systems and their relation to chiral bosonic phases.

  13. On SU(3) effective models and chiral phase-transition

    CERN Document Server

    Tawfik, Abdel Nasser

    2015-01-01

    The sensitivity of Polyakov Nambu-Jona-Lasinio (PNJL) model as an effective theory of quark dynamics to chiral symmetry has been utilized in studying the QCD phase-diagram. Also, Poyakov linear sigma-model (PLSM), in which information about the confining glue sector of the theory was included through Polyakov-loop potential. Furthermore, from quasi-particle model (QPM), the gluonic sector of QPM is integrated to LSM in order to reproduce recent lattice calculations. We review PLSM, QLSM, PNJL and HRG with respect to their descriptions for the chiral phase-transition. We analyse chiral order-parameter M(T), normalized net-strange condensate Delta_{q,s}(T) and chiral phase-diagram and compare the results with lattice QCD. We conclude that PLSM works perfectly in reproducing M(T) and Delta_{q,s}(T). HRG model reproduces Delta_{q,s}(T), while PNJL and QLSM seem to fail. These differences are present in QCD chiral phase-diagram. PLSM chiral boundary is located in upper band of lattice QCD calculations and agree we...

  14. Characteristics of the chiral phase transition in nonlocal quark models

    CERN Document Server

    Dumm, D G

    2004-01-01

    The characteristics of the chiral phase transition are analyzed within the framework of chiral quark models with nonlocal interactions in the mean field approximation (MFA). In the chiral limit, we show that there is a region of low values of the chemical potential in which the transition is a second order one. In that region, it is possible to perform a Landau expansion and determine the critical exponents which, as expected, turn out to be the MFA ones. Our analysis also allows to obtain semi-analytical expressions for the transition curve and the location of the tricritical point. For the case of finite current quark masses, we study the behavior of various thermodynamical and chiral response functions across the phase transition.

  15. How tetraquarks can generate a second chiral phase transition

    CERN Document Server

    Pisarski, Robert D

    2016-01-01

    We consider how tetraquarks can affect the chiral phase transition in theories like QCD, with light quarks coupled to three colors. For two flavors the tetraquark field is an isosinglet, and its effect is minimal. For three flavors, however, the tetraquark field transforms in the same representation of the chiral symmetry group as the usual chiral order parameter, and so for very light quarks there may be two chiral phase transitions, which are both of first order. In QCD, results from the lattice indicate that any transition from the tetraquark condensate is a smooth crossover. In the plane of temperature and quark chemical potential, though, a crossover line for the tetraquark condensate is naturally related to the transition line for color superconductivity. For four flavors we suggest that a triquark field, antisymmetric in both flavor and color, combine to form hexaquarks.

  16. Unified molecular field theory of nematic, smectic-A, and smectic-C phases.

    Science.gov (United States)

    Pająk, G; Osipov, M A

    2013-07-01

    A unified mean-field molecular theory of nematic (N(U)), smectic A (SmA), and smectic C (SmC) liquid crystal phases, composed of uniaxial nonpolar molecules, is developed taking into account the variation of all orientational and translational order parameters in these phases. Numerical results, obtained by direct global minimization of the free energy, are presented in the form of three typical phase diagrams of different topology. Temperature variation of the relevant order parameters in different sequences of phases is analyzed for various cross sections of the phase diagrams. The present model enables one to reproduce all possible sequences of phase transitions between the given phases including isotropic (Iso)-N(U)-SmA-SmC, Iso-N(U)-SmC, Iso-SmA-SmC, and Iso-SmC. The properties of the NAC point, where the N(U), SmA, and SmC structures coexist, are considered in detail and the shape of the phase diagram in the vicinity of the NAC point is compared with existing experimental data.

  17. On SU(3 Effective Models and Chiral Phase Transition

    Directory of Open Access Journals (Sweden)

    Abdel Nasser Tawfik

    2015-01-01

    Full Text Available Sensitivity of Polyakov Nambu-Jona-Lasinio (PNJL model and Polyakov linear sigma-model (PLSM has been utilized in studying QCD phase-diagram. From quasi-particle model (QPM a gluonic sector is integrated into LSM. The hadron resonance gas (HRG model is used in calculating the thermal and dense dependence of quark-antiquark condensate. We review these four models with respect to their descriptions for the chiral phase transition. We analyze the chiral order parameter, normalized net-strange condensate, and chiral phase-diagram and compare the results with recent lattice calculations. We find that PLSM chiral boundary is located in upper band of the lattice QCD calculations and agree well with the freeze-out results deduced from various high-energy experiments and thermal models. Also, we find that the chiral temperature calculated from HRG is larger than that from PLSM. This is also larger than the freeze-out temperatures calculated in lattice QCD and deduced from experiments and thermal models. The corresponding temperature and chemical potential are very similar to that of PLSM. Although the results from PNJL and QLSM keep the same behavior, their chiral temperature is higher than that of PLSM and HRG. This might be interpreted due the very heavy quark masses implemented in both models.

  18. Activated kinetics of the Crystalline to Nematic (K-N) and Nematic to Isotropic (N-I) phase transitions of Pentylcyanobiphenyl (5CB) liquid crystal

    Science.gov (United States)

    Sharma, Dipti

    2011-04-01

    Activated kinetics of the crystalline to Nematic (K-N) and the Nematic to Isotropic (N-I) phase transitions of the Pentylcyanobiphenyl (5CB) liquid crystal are discussed here. A kinetic comparison of the same types of transitions of other family member with higher number of carbon atoms i.e. Octylcyanobiphenyl (8CB) are also made to see the difference between the kinetic behavior of the above two transitions of the liquid crystals. Experiments were performed using high resolution calorimetric technique for heating and cooling runs. Two different scans i.e. Temperature scans and Rate scans were performed for 5CB and 8CB from 280 to 333 K at various rates to get the detailed behavior of the transitions. As a result, Double activation was observed for 5CB for two heating rate regimes whereas 8CB indicated single activation only. The 5CB has smaller enthalpy and entropy of the transitions and needs larger activation than 8CB. This kinetic change can be explained in terms of the length scale and mobility of the liquid crystal molecules.

  19. Entropic screening preserves non-equilibrium nature of nematic phase while enthalpic screening destroys it

    Energy Technology Data Exchange (ETDEWEB)

    Dan, K.; Roy, M.; Datta, A. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Saltlake, Kolkata 700064, West Bengal (India)

    2016-02-14

    The present manuscript describes the role of entropic and enthalpic forces mediated by organic non-polar (hexane) and polar (methanol) solvents on the bulk and microscopic phase transition of a well known nematic liquid crystalline material MBBA (N-(4-methoxybenzylidene)-4-butylaniline) through Differential Scanning calorimetry (DSC), UV-Visible (UV–Vis), and Fourier Transform Infrared (FTIR) spectroscopy. DSC study indicates continuous linear decreases in both nematic-isotropic (N-I) phase transition temperature and enthalpy of MBBA in presence of hexane while both these parameters show a saturation after an initial decay in methanol. These distinct transitional behaviours were explained in terms of the “depletion force” model for entropic screening in hexane and “screening-self-screening” model for methanol. Heating rate dependent DSC studies find that non-Arrhenius behaviour, characteristic of pristine MBBA and a manifestation of non-equilibrium nature [Dan et al., J. Chem. Phys. 143, 094501 (2015)], is preserved in presence of entropic screening in the hexane solution, while it changes to Arrhenius behaviour (signifying equilibrium behaviour) in presence of enthalpic screening in methanol solution. FTIR spectra show similar dependence on the solvent induced screening in the intensities of the imine (—C = N) stretch and the out-of-plane distortion vibrations of the benzene rings of MBBA with hexane and methanol as in DSC, further establishing our entropic and enthalpic screening models. UV–Vis spectra of the electronic transitions in MBBA as a function of temperature also exhibit different dependences of intensities on the solvent induced screening, and an exponential decrease is observed in presence of hexane while methanol completely changes the nature of interaction to follow a linear dependence.

  20. The Phase Transition of Nematic Liquid Crystal Cells Bounded by Surfactant-Laden Interfaces

    Institute of Scientific and Technical Information of China (English)

    ZENG Ming-Ying; CUI Wei; TAN Xiao-Qin; WU Chen-Xu

    2011-01-01

    @@ Taking into account the surface-coupling strength effect, we discuss the phase transitions of a finite thickness cell bounded by surfactant-laden interfaces in a magnetic field perpendicular to the substrate and it is compared with that of a semi-infinite system.It is found that the larger the thickness, the closer the three-dimensional phase transition surfacc of the finite system to that of the semi-infinite one.The simulation also shows that when a magnetic field is applied to a nematic semi-infinite sample, an orientational phase transition first takes place close to the interface and thcn extends to the inner space as the temperature increases.%Taking into account the surface-coupling strength effect, we discuss the phase transitions of a finite thickness cell bounded by surfactant-laden interfaces in a magnetic field perpendicular to the substrate and it is compared with that of a semi-infinite system. It is found that the larger the thickness, the closer the three-dimensional phase transition surface of the finite system to that of the semi-infinite one. The simulation also shows that when a magnetic field is applied to a nernatic semi-infinite sample, an orientational phase transition first takes place close to the interface and then extends to the inner space as the temperature increases.

  1. Chiral Paramagnetic Skyrmion-like Phase in MnSi

    NARCIS (Netherlands)

    Pappas, C.; Lelièvre-Berna, E.; Falus, P.; Bentley, P.M.; Moskvin, E.; Grigoriev, S.; Fouquet, P.; Farago, B.

    2009-01-01

    We present a comprehensive study of chiral fluctuations in the reference helimagnet MnSi by polarized neutron scattering and neutron spin echo spectroscopy, which reveals the existence of a completely left-handed and dynamically disordered phase. This phase may be identified as a spontaneous Skyrmio

  2. Chiral phase transition in QED$_3$ at finite temperature

    CERN Document Server

    Wei, Wei; Zong, Hong-Shi

    2016-01-01

    Chiral phase transition in (2+1)-dimensional quantum electrodynamics (QED$_3$) at finite temperature is investigated in the framework of truncated Dyson-Schwinger equations (DSEs). We go beyond the widely used instantaneous approximation and adopt a method that retains the full frequency dependence of the fermion self-energy. We also take further step to include the effects of wave-function renormalizations and introduce a minimal dressing of the bare vertex. Finally, with the more complete solutions of the truncated DSEs, we revisit the study of chiral phase transition in finite-temperature QED$_3$.

  3. Enantiomeric Separation of Four Chiral Compounds Using Immobilized Cellulose 3, 5-Dimethylphenylcarbamate as Chiral Stationary Phase

    Institute of Scientific and Technical Information of China (English)

    Yong Fei MING; Liang ZHAO; Hong Li ZHANG; Yan Ping SHI; Yong Min LI; Li Ren CHEN

    2006-01-01

    A new chiral stationary phase of 3, 5-dimethylphenylcarbamates of cellulose,chemically bonded to 3-aminopropylsilica gel at the 6-positions of the glucose units, was prepared.The solvent versatility of the CSP was investigated for the enantioselective separation of four pairs of enantiomers using THF and chloroform as non-standard mobile phase eluent in HPLC. The influence of temperature on the resolution was investigated.

  4. Isotropic-nematic phase equilibria of hard-sphere chain fluids-Pure components and binary mixtures.

    Science.gov (United States)

    Oyarzún, Bernardo; van Westen, Thijs; Vlugt, Thijs J H

    2015-02-14

    The isotropic-nematic phase equilibria of linear hard-sphere chains and binary mixtures of them are obtained from Monte Carlo simulations. In addition, the infinite dilution solubility of hard spheres in the coexisting isotropic and nematic phases is determined. Phase equilibria calculations are performed in an expanded formulation of the Gibbs ensemble. This method allows us to carry out an extensive simulation study on the phase equilibria of pure linear chains with a length of 7 to 20 beads (7-mer to 20-mer), and binary mixtures of an 8-mer with a 14-, a 16-, and a 19-mer. The effect of molecular flexibility on the isotropic-nematic phase equilibria is assessed on the 8-mer+19-mer mixture by allowing one and two fully flexible beads at the end of the longest molecule. Results for binary mixtures are compared with the theoretical predictions of van Westen et al. [J. Chem. Phys. 140, 034504 (2014)]. Excellent agreement between theory and simulations is observed. The infinite dilution solubility of hard spheres in the hard-sphere fluids is obtained by the Widom test-particle insertion method. As in our previous work, on pure linear hard-sphere chains [B. Oyarzún, T. van Westen, and T. J. H. Vlugt, J. Chem. Phys. 138, 204905 (2013)], a linear relationship between relative infinite dilution solubility (relative to that of hard spheres in a hard-sphere fluid) and packing fraction is found. It is observed that binary mixtures greatly increase the solubility difference between coexisting isotropic and nematic phases compared to pure components.

  5. Enantioseparation of Racemic Naproxen Esters on Cellulose Tris (4-methylbenzoate) Chiral Stationary Phase

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Several kinds of racemic naproxen ester were successfully separated on CTMB chiral stationary phase with hexane-ethanol (98:2, vol./vol.) as the mobile phase. The influence of mobile phase composition and structure of racemic naproxen ester on chiral separation was studied and the chiral recognition mechanism of CTMB was discussed.

  6. Enantioseparation of Racemic Naproxen Esters on Cellulose Tris(4—methylbenzoate) Chiral Stationary Phase

    Institute of Scientific and Technical Information of China (English)

    BaoHaiSHAO; XiuZhuXU; 等

    2002-01-01

    Several kinds of racemic naproxen ester were successfully separated on CTMB chiral stationary phase with hexane-ethanol(98:2,vol./vol.) as the mobile phase. The influence of mobile phase composition and structure of racemic naproxen ester on chiral separation was studied and the chiral recognition mechanism of CTMB was discussed.

  7. Kinetic pathways of the nematic-isotropic phase transition as studied by confocal microscopy on rod-like viruses

    Energy Technology Data Exchange (ETDEWEB)

    Lettinga, M Paul [IFF, Institut Weiche Materie, Forschungszentrum Juelich, D-52425 Juelich (Germany); Kang, Kyongok [IFF, Institut Weiche Materie, Forschungszentrum Juelich, D-52425 Juelich (Germany); Imhof, Arnout [Soft Condensed Matter, Debye Institute, Utrecht University, Princetonplein 5, 3584 CC Utrecht (Netherlands); Derks, Didi [Soft Condensed Matter, Debye Institute, Utrecht University, Princetonplein 5, 3584 CC Utrecht (Netherlands); Dhont, Jan K G [IFF, Institut Weiche Materie, Forschungszentrum Juelich, D-52425 Juelich (Germany)

    2005-11-16

    We investigate the kinetics of phase separation for a mixture of rod-like viruses (fd) and polymer (dextran), which effectively constitutes a system of attractive rods. This dispersion is quenched from a flow-induced fully nematic state into the region where the nematic and the isotropic phase coexist. We show experimental evidence that the kinetic pathway depends on the overall concentration. When the quench is made at high concentrations, the system is meta-stable and we observe typical nucleation-and-growth. For quenches at low concentration the system is unstable and the system undergoes a spinodal decomposition. At intermediate concentrations we see the transition between both demixing processes, where we locate the spinodal point.

  8. Phases of (Asymptotically) Safe Chiral Theories with(out) Scalars

    CERN Document Server

    Molgaard, Esben

    2016-01-01

    We unveil the dynamics of four dimensional chiral gauge-Yukawa theories featuring several scalar degrees of freedom transforming according to distinct representations of the underlying gauge group. We consider generalized Georgi-Glashow and Bars-Yankielowicz theories. We determine, to the maximum known order in perturbation theory, the phase diagram of these theories and further disentangle their ultraviolet asymptotic nature according to whether they are asymptotically free or safe. We therefore extend the number of theories that are known to be fundamental in the Wilsonian sense to the case of chiral gauge theories with scalars.

  9. Mass transfer mechanism in chiral reversed phase liquid chromatography.

    Science.gov (United States)

    Gritti, Fabrice; Guiochon, Georges

    2014-03-01

    The mechanism of mass transfer in chiral chromatography was investigated using an experimental protocol already applied in RPLC and HILIC chromatography. The different contributions to the reduced height equivalent to a theoretical plate (HETP) include the longitudinal diffusion HETP term, the solid-liquid mass transfer resistance HETP term, the short-range eddy dispersion HETP term, and the long-range eddy dispersion HETP term. Their accurate measurement permits the determination of the adsorption rate constant kads of trans-stilbene enantiomers on a column packed with Lux 5 μm Cellulose-1 particles. The experimental results demonstrate that the number of adsorption-desorption steps per unit time of chiral compounds on polysaccharide-based chiral stationary phases is four orders of magnitude smaller than that of achiral compounds.

  10. Geometric phase and o-mode blue shift in a chiral anisotropic medium inside a Fabry-P\\'erot cavity

    CERN Document Server

    Timofeev, I V; Sutormin, V S; Myslivets, S A; Arkhipkin, V G; Vetrov, S Ya; Lee, W; Zyryanov, V Ya

    2015-01-01

    Anomalous spectral shift of transmission peaks is observed in a Fabry--P\\'erot cavity filled with a chiral anisotropic medium. The effective refractive index value resides out of the interval between the ordinary and the extraordinary refractive indices. The spectral shift is explained by contribution of a geometric phase. The problem is solved analytically using the approximate Jones matrix method, numerically using the accurate Berreman method and geometrically using the generalized Mauguin--Poincar\\'e rolling cone method. The $o$-mode blue shift is measured for a 4-methoxybenzylidene-4'-$n$-butylaniline twisted--nematic layer inside the Fabry--P\\'erot cavity. The twist is electrically induced due to the homeoplanar--twisted configuration transition in an ionic-surfactant-doped liquid crystal layer. Experimental evidence confirms the validity of the theoretical model.

  11. Geometric phase and o-mode blueshift in a chiral anisotropic medium inside a Fabry-Pérot cavity.

    Science.gov (United States)

    Timofeev, Ivan V; Gunyakov, Vladimir A; Sutormin, Vitaly S; Myslivets, Sergey A; Arkhipkin, Vasily G; Vetrov, Stepan Ya; Lee, Wei; Zyryanov, Victor Ya

    2015-11-01

    Anomalous spectral shift of transmission peaks is observed in a Fabry-Pérot cavity filled with a chiral anisotropic medium. The effective refractive index value resides out of the interval between the ordinary and the extraordinary refractive indices. The spectral shift is explained by contribution of a geometric phase. The problem is solved analytically using the approximate Jones matrix method, numerically using the accurate Berreman method, and geometrically using the generalized Mauguin-Poincaré rolling cone method. The o-mode blueshift is measured for a 4-methoxybenzylidene-4'-n-butylaniline twisted-nematic layer inside the Fabry-Pérot cavity. The twist is electrically induced due to the homeoplanar-twisted configuration transition in an ionic-surfactant-doped liquid crystal layer. Experimental evidence confirms the validity of the theoretical model.

  12. The effect of the chiral chemical potential on the chiral phase transition in the NJL model with different regularization schemes

    CERN Document Server

    Yu, Lang; Huang, Mei

    2015-01-01

    We study the chiral phase transition in the presence of the chiral chemical potential $\\mu_5$ using the two-flavor Nambu--Jona-Lasinio model. In particular, we analyze the reason why one can obtain two opposite behaviors of the chiral critical temperature as a function of $\\mu_5$ in the framework of different regularization schemes. We compare the modifications of the chiral condensate and the critical temperature due to $\\mu_5$ in different regularization schemes, analytically and numerically. Finally, we find that, for the conventional hard-cutoff regularization scheme, the increasing dependence of the critical temperature on the chiral chemical potential is an artifact, which is caused by the fact that it does not include complete contribution from the thermal fluctuations. When the thermal contribution is fully taken into account, the chiral critical temperature should decrease with $\\mu_5$.

  13. Dynamic aspect of the chiral phase transition in the mode coupling theory

    CERN Document Server

    Ohnishi, K; Ohta, K

    2005-01-01

    We analyze the dynamic aspect of the chiral phase transition. We apply the mode coupling theory to the linear sigma model and derive the kinetic equation for the chiral phase transition. We challenge Hohenberg and Halperin's classification scheme of dynamic critical phenomena in which the dynamic universality class of the chiral phase transition has been identified with that of the antiferromagnet. We point out a crucial difference between the chiral dynamics and the antiferromagnet system. We also calculate the dynamic critical exponent for the chiral phase transition. Our result is $z=1-\\eta/2\\cong 0.98$ which is contrasted with $z=d/2=1.5$ of the antiferromagnet.

  14. Chiral Phase Transition at Finite Isospin Density in Linear Sigma Model

    Institute of Scientific and Technical Information of China (English)

    SHU Song; LI Jia-Rong

    2005-01-01

    Using the linear sigma model, we have introduced the pion isospin chemical potential. The chiral phase transition is studied at finite temperatures and finite isospin densities. We have studied the μ - T phase diagram for the chiral phase transition and found the transition cannot happen below a certain low temperature because of the BoseEinstein condensation in this system. Above that temperature, the chiral phase transition is studied by the isotherms of pressure versus density. We indicate that the transition, in the chiral limit, is a first-order transition from a low-density phase to a high-density phase like a gas-liquid phase transition.

  15. Disorienting the Chiral Condensate at the QCD Phase Transition

    CERN Document Server

    Rajagopal, K

    1997-01-01

    I sketch how long wavelength modes of the pion field can be amplified during the QCD phase transition. If nature had been kinder, and had made the pion mass significantly less than the critical temperature for the transition, then this phenomenon would have characterized the transition in thermal equilibrium. Instead, these long wavelength oscillations of the orientation of the chiral condensate can only arise out of equilibrium. There is a simple non-equilibrium mechanism, plausibly operational during heavy ion collisions, which naturally amplifies these oscillations. The characteristic signature of this phenomenon is large fluctuations in the ratio of the number of neutral pions to the total number of pions in regions of momentum space, that is in phase space in a detector. Detection in a heavy ion collision would imply an out of equilbrium chiral transition.

  16. On the Chiral Phase Transition in the Linear Sigma Model

    CERN Document Server

    Phat, T H; Hoa, L V; Phat, Tran Huu; Anh, Nguyen Tuan; Hoa, Le Viet

    2004-01-01

    The Cornwall-Jackiw-Tomboulis (CJT) effective action for composite operators at finite temperature is used to investigate the chiral phase transition within the framework of the linear sigma model as the low-energy effective model of quantum chromodynamics (QCD). A new renormalization prescription for the CJT effective action in the Hartree-Fock (HF) approximation is proposed. A numerical study, which incorporates both thermal and quantum effect, shows that in this approximation the phase transition is of first order. However, taking into account the higher-loop diagrams contribution the order of phase transition is unchanged.

  17. [Enantioseparation behavior of chiral stationary phases AD, AS and OD].

    Science.gov (United States)

    Li, Liqun; Fan, Jun; Zhang, Jing; Chen, Xiaodong; Wang, Tai; He, Jianfeng; Zhang, Weiguang

    2016-01-01

    Over the past decades, HPLC enantioseparation with chiral stationary phases (CSPs) has been widely applied in chiral analysis and preparation of new pharmaceuticals, pesticides, food, etc. Herein, enantioseparation of 20 chiral compounds have been carried out on three polysaccharide-based CSPs (EnantioPak AD, AS and OD) with normal phases by HPLC, separately. The influences of skeletal structure and the kinds of derivative groups on separation behaviors of these CSPs have been studied in detail. As results indicated, except for compound 13, the other compounds were baseline separated on EnantioPak AD, with most of resolution over 2. 0; in addition, better separation for acidic or basic compounds was achieved through adding acidic/basic additives into the mobile phase of hexane-alcohol. For four aromatic alcohols (compounds 13-16), their retention in the EnantioPak AD column showed a weakening tendency with increase of carbon number in side chain group, and the reverse trend of their resolution was observed. Furthermore, EnantioPak AD showed much better separation performance for eight compounds (13-20) than the others. In short, these results have provided some references for further investigation of separation behavior and applications of polysaccharide-based CSPs.

  18. Extraction of Phenylalanine Phase Systems Containing Enantiomers by Aqueous Two Combinatorial Chiral Selector

    Institute of Scientific and Technical Information of China (English)

    陈晓青; 刘莉; 焦飞鹏; 王珍

    2012-01-01

    In order to obtain a better enantioselectivity of phenylalanine enantiomers and establish the optimal chiral ex- traction conditions, the distribution behavior was investigated in aqueous two-phase systems which were composed of polyethylene glycol and ammonium sulfate containing combinatorial chiral selector: β-cyclodextrin and HP-β-cyclodextrin. The influence of the molar concentration ratio of combinatorial chiral selectors, the total molar concentration of combinatorial chiral selectors, pH value, buffer type and its concentration were thoroughly studied, respectively. The results show that the enantioselectivity reaches 1.53 under the optimal chiral extraction conditions This extraction is a potential economical and effective way for chiral resolution.

  19. Biaxial nematic liquid crystals theory, simulation and experiment

    CERN Document Server

    Luckhurst, Geoffrey R

    2015-01-01

    Liquid Crystals are a state of matter that have properties between those of conventional liquid and those of a solid crystal. Thermotropic liquid crystals react to changes in temperature or, in some cases, pressure. The reaction of lyotropic liquid crystals, which are used in the manufacture of soaps and detergents, depends on the type of solvent they are mixed with. Since the accidental discovery of the chiral nematic (ordered) phase in 1888 many liquid crystal phases have been found, sometimes by chance and sometimes by design. The existence of one such phase was predicted by Freiser in 197

  20. The QCD phase transition with physical-mass, chiral quarks

    CERN Document Server

    Bhattacharya, Tanmoy; Christ, Norman H; Ding, H -T; Gupta, Rajan; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; McGlynn, Greg; Mukherjee, Swagato; Murphy, David; Petreczky, P; Schroeder, Chris; Soltz, R A; Vranas, P M; Yin, Hantao

    2014-01-01

    We report on the first lattice calculation of the QCD phase transition using chiral fermions at physical values of the quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm$)^3$ and (11 fm$)^3$ and temperatures between 139 and 196 MeV . Each temperature was calculated using a single lattice spacing corresponding to a temporal Euclidean extent of $N_t=8$. The disconnected chiral susceptibility, $\\chi_{\\rm disc}$ shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability in the region of the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD ``phase transition'' is not first order but a continuous cross-over for $m_\\pi=135$ MeV. The peak location determines a pseudo-critical temperature $T_c = 155(1)(8)$ MeV. Chiral $SU(2)_L\\times SU(2)_R$ symmetry is fully restored above 164 MeV, but anomalous $U(1)_A$ symmetry breaking is non-zero above $T...

  1. QCD phase transition with chiral quarks and physical quark masses.

    Science.gov (United States)

    Bhattacharya, Tanmoy; Buchoff, Michael I; Christ, Norman H; Ding, H-T; Gupta, Rajan; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; McGlynn, Greg; Mukherjee, Swagato; Murphy, David; Petreczky, P; Renfrew, Dwight; Schroeder, Chris; Soltz, R A; Vranas, P M; Yin, Hantao

    2014-08-22

    We report on the first lattice calculation of the QCD phase transition using chiral fermions with physical quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm)(3) and (11 fm)(3) and temperatures between 139 and 196 MeV. Each temperature is calculated at a single lattice spacing corresponding to a temporal Euclidean extent of N(t) = 8. The disconnected chiral susceptibility, χ(disc) shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability near the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD "phase transition" is not first order but a continuous crossover for m(π) = 135 MeV. The peak location determines a pseudocritical temperature T(c) = 155(1)(8) MeV, in agreement with earlier staggered fermion results. However, the peak height is 50% greater than that suggested by previous staggered results. Chiral SU(2)(L) × SU(2)(R) symmetry is fully restored above 164 MeV, but anomalous U(1)(A) symmetry breaking is nonzero above T(c) and vanishes as T is increased to 196 MeV.

  2. Tuning the birefringence of the nematic phase in suspensions of colloidal gibbsite platelets

    NARCIS (Netherlands)

    Verhoeff, A.A.; Brand, R.P.; Lekkerkerker, H.N.W.

    2011-01-01

    We consider the birefringence patterns of nematic liquid crystals of gibbsite platelets at interfaces and in an aligning magnetic field. In solvents with a refractive index close to the particle refractive index, the intrinsic birefringence of the platelets dominates, resulting in positive birefring

  3. New chiral reverse phase HPLC method for enantioselective analysis of ketorolac using chiral AGP column

    Institute of Scientific and Technical Information of China (English)

    Sunil K. Dubey; Jangala Hemanth; Chiranjeevi Venkatesh K.; R.N. Saha; S. Pasha

    2012-01-01

    A simple, specific, precise, sensitive and rapid reverse phase-HPLC method was developed for determination of ketorolac enantiomers, a potent nonnarcotic analgesic in pharmaceutical formulations. The method was developed on a chiral AGP column. Mobile phase was 0.1 M sodium phosphate buffer (pH 4.5): lsopropanol (98:2, v/v), at a flow rate of 1 mL/min with run time of 15 min. Ultraviolet detection was made at 322 nm. The linearity range was 0.02 10 μg/mL for each of the enantiomers. The mobile phase composition was systematically studied to find the optimum chromatographic conditions. Validation of the method under the conditions selected showed that it was selective and precise and that the detector response was linear function of ketorolac.

  4. Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field.

    Science.gov (United States)

    Matsuyama, Akihiko

    2014-11-14

    We present a mean field theory to describe phase behaviors in mixtures of a polymer and a cholesteric liquid crystal under an external magnetic or electric field. Taking into account a chiral coupling between a polymer and a liquid crystal under the external field, we examine twist-untwist phase transitions and phase separations in the mixtures. It is found that a cholesteric-nematic phase transition can be induced by not only the external field but also concentration and temperature. Depending on the strength of the external field, we predict cholesteric-paranematic (Ch+pN), nematic-paranematic (N+pN), cholesteric-nematic (Ch+N) phase separations, etc., on the temperature-concentration plane. We also discuss mixtures of a non-chiral nematic liquid crystal and a chiral dopant.

  5. Synthesis of novel chiral stationary phases for high-performance liquid chromatography

    Institute of Scientific and Technical Information of China (English)

    Xu Lin Tan; Shi Cong Hou; Qing Hua Bian; Min Wang

    2007-01-01

    Three novel chiral selectors 4a-c were synthesized from (S)-amino acids and (R)- 1-phenyl-2-(4-methylphenyl)ethylamine. 4a-c were connected to 3-aminopropylsilanized silica gel to be used as the chiral stationary phase for HPLC. Five amino acid derivatives and two pyrethroid insecticides were fairly resolved on these three new chiral stationary phases under normal phase condition.

  6. Separation of piracetam derivatives on polysaccharide-based chiral stationary phases.

    Science.gov (United States)

    Kažoka, H; Koliškina, O; Veinberg, G; Vorona, M

    2013-03-15

    High-performance liquid chromatography was used for the enantiomeric separation of two chiral piracetam derivatives. The suitability of six commercially available polysaccharide-based chiral stationary phases (CSPs) under normal phase mode for direct enantioseparation has been investigated. The influence of the CSPs as well the nature and content of an alcoholic modifier in the mobile phase on separation and elution order was studied. It was established that CSP Lux Amylose-2 shows high chiral recognition ability towards 4-phenylsubstituted piracetam derivatives.

  7. Electromagnetic chirality-induced negative refraction with the same amplitude and anti-phase of the two chirality coefficients

    Institute of Scientific and Technical Information of China (English)

    Zhao Shun-Cai; Liu Zheng-Dong; Zheng Jun; Li Gen

    2011-01-01

    This paper suggests a scheme of electromagnetic chirality-induced negative refraction utilizing magneto-electric cross coupling in a four-level atomic system. The negative refraction can be achieved with the two chirality coefficients having the same amplitude but the opposite phase, without requiring the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency.

  8. A liquid crystalline chirality balance for vapours

    Science.gov (United States)

    Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-Ichi

    2014-04-01

    Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of ‘zig’ and ‘zag.’ We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of ‘zig’ and ‘zag’ depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based ‘chirality balance’ offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs).

  9. Glucose, cellobiose, lactose and raffinose used as chiral stationary phases in HPLC

    Institute of Scientific and Technical Information of China (English)

    Jian Yu Wang; Feng Zhao; Mei Zhang; Ya Peng; Li Ming Yuan

    2008-01-01

    This paper presents the enantioseparation using glucose,cellobiose,lactose and raffinose as chiral selector bonded to silica gel via an arm in HPLC.Surprisingly,they also possess high enantioseparation selectivity,may be used in normal-phase and reversedphase mode.and there is a big chiral discriminating complementary.This work indicates that oligosacchafides could soon become very attractive as a new class of chiral stationary phase for HPLC.

  10. Synthesis and characterization of mesoporous silica modified with chiral auxiliaries for their potential application as chiral stationary phase.

    Science.gov (United States)

    Mayani, Vishal J; Abdi, S H R; Kureshy, R I; Khan, N H; Agrawal, Santosh; Jasra, R V

    2008-05-16

    Novel chiral stationary phase (CSP) based on chiral aminoalcohol immobilized on ordered mesoporous silica SBA-15 1a and standard silica 1b and their copper complexes 1a' and 1b', respectively, was synthesized as potential material for chiral ligand exchange chromatography (CLEC). Microanalysis, inductively coupled plasma spectroscopy (ICP), thermo-gravimetric analysis (TGA), cross polarized magic angle spinning (CP-MAS) (13)C NMR, Powder X-ray diffraction (PXRD), FTIR, N(2) adsorption isotherm, scanning electron microscopy (SEM), transmitted electron microscope (TEM) and solid reflectance UV-vis spectroscopy were used to characterize these materials. All the chiral stationary phases thus synthesized were used for the separation of different racemic compounds such as mandelic acid, 2,2'-dihydroxy-1,1'-binaphthalene BINOL) and diethyl tartrate by simple medium-pressure column chromatography. Successful enantio-separation of racemic mandelic acid was achieved with all the stationary phases but 1a and 1b gave slightly better resolution than their copper complexes 1a' and 1b'. Remarkably these materials are stable under the given experimental conditions and can be used repeatedly for several cycles of enantioresolution. It was observed that the porosity and surface area of the stationary phase play an important role in the chiral separation.

  11. A decoupled energy stable scheme for a hydrodynamic phase-field model of mixtures of nematic liquid crystals and viscous fluids

    Science.gov (United States)

    Zhao, Jia; Yang, Xiaofeng; Shen, Jie; Wang, Qi

    2016-01-01

    We develop a linear, first-order, decoupled, energy-stable scheme for a binary hydrodynamic phase field model of mixtures of nematic liquid crystals and viscous fluids that satisfies an energy dissipation law. We show that the semi-discrete scheme in time satisfies an analogous, semi-discrete energy-dissipation law for any time-step and is therefore unconditionally stable. We then discretize the spatial operators in the scheme by a finite-difference method and implement the fully discrete scheme in a simplified version using CUDA on GPUs in 3 dimensions in space and time. Two numerical examples for rupture of nematic liquid crystal filaments immersed in a viscous fluid matrix are given, illustrating the effectiveness of this new scheme in resolving complex interfacial phenomena in free surface flows of nematic liquid crystals.

  12. Chirality-dependent vapor-phase epitaxial growth and termination of single-wall carbon nanotubes.

    Science.gov (United States)

    Liu, Bilu; Liu, Jia; Tu, Xiaomin; Zhang, Jialu; Zheng, Ming; Zhou, Chongwu

    2013-09-11

    Structurally uniform and chirality-pure single-wall carbon nanotubes are highly desired for both fundamental study and many of their technological applications, such as electronics, optoelectronics, and biomedical imaging. Considerable efforts have been invested in the synthesis of nanotubes with defined chiralities by tuning the growth recipes but the approach has only limited success. Recently, we have shown that chirality-pure short nanotubes can be used as seeds for vapor-phase epitaxial cloning growth, opening up a new route toward chirality-controlled carbon nanotube synthesis. Nevertheless, the yield of vapor-phase epitaxial growth is rather limited at the present stage, due in large part to the lack of mechanistic understanding of the process. Here we report chirality-dependent growth kinetics and termination mechanism for the vapor-phase epitaxial growth of seven single-chirality nanotubes of (9, 1), (6, 5), (8, 3), (7, 6), (10, 2), (6, 6), and (7, 7), covering near zigzag, medium chiral angle, and near armchair semiconductors, as well as armchair metallic nanotubes. Our results reveal that the growth rates of nanotubes increase with their chiral angles while the active lifetimes of the growth hold opposite trend. Consequently, the chirality distribution of a nanotube ensemble is jointly determined by both growth rates and lifetimes. These results correlate nanotube structures and properties with their growth behaviors and deepen our understanding of chirality-controlled growth of nanotubes.

  13. Finite-Temperature Phase Structure in the Chiral σ-ω Model with Dilatons

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-Bing ZHANG Xiao-Bing; LI Xue-Qian; NING Ping-Zhi

    2000-01-01

    We investigate the finite-temperature phase structure in a scaled chiral model which includes the dilaton (glueball) field. It is shown that hot nuclear matter undergoes a discontinuous transition in the mean field of scalar mesons as well as the Lee-Wick abnormal transition. The corresponding behavior of the gluon condensate during the chiral phase transition is also studied.

  14. Topological String in Quantum-Chromodynamical Chiral Phase Transitions

    Institute of Scientific and Technical Information of China (English)

    LI Yun-De

    2005-01-01

    @@ It is pointed out that if in heavy ion collision processes, the quark-gluon plasma SU(2) chiral phase transition really takes place and the phase transition is a second order. Then the topological string, i.e., the π string, will be formed. The main effect of this phenomenon is that there will be a number of pions produced by decay of the π string in the final state. The pions from the decay of the π string lead to the same effect of decreasing the Hanbury-Brown-Twiss peak in two-pion spectra which is just as that of the long-lived hadronic resonances.At relativistic heavy-ion collision and large hadron collision energies, it is expected that the factors are about α~ 0.7 - 0.9 and α~ 0.6 - 0.85, respectively.

  15. 信息动态%Preparation of Polysaccharide Derivatives-based Composite Chiral Stationary Phases and Their Chiral Recognition

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Two coated-type composite chiral stationary phases (CSPs) were prepared based on cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) and amylose tris (3,5-dimethylphenylcarbamate)(ADMPC) by coating the corresponding derivatives onto 3-aminopropyl silica gel separately and then mixing or by coating the mixed derivatives onto silica gel. The CSPs containing only CDMPC or ADMPC were also prepared for comparison. The mixing method does not significantly influence the enantioselectivities. The composite CSPs generally show chiral recognition abilities intermediate between those of the two individual phases, while some racemates were poorer and at the same time one was better resolved on the composite CSPs.

  16. Phase transition from focal conic to cubic smectic blue phase in partially fluorinated cyano-phenyl alkyl benzoate ester doped with ultrahigh twisting power chiral dopant

    CERN Document Server

    Nayek, Prasenjit; Li, Guoqiang

    2015-01-01

    Blue phase liquid crystal (BPLC) has important applications in adaptive lenses and phase modulators due to its polarization-independent property. During our efforts for development of the new materials, we found a novel phenomenology of phase transition, from focal conic smectic to smectic blue phase in a partially fluorinated cyanophenyl alkyl benzoate ester based nematic liquid crystal (LCM-5773) doped by ultra-high twisting power [H.T.P~160 um^-1] chiral dopant (R5011/3 wt%). Polarized optical microscopy (POM) investigations revealed focal conic and fan-shaped textures typical for columnar mesophases. These focal conic domains (FCDs) are squeezed under electric field and finally at a critical electric field they undergo a dark state. When the electric field is withdrawn, the FCDs are regrown in a one dimensional array with smaller domain size. Interestingly, we have observed the domain size of the FCDs can grow several times by decreasing the cooling rate (0.02 degrees(C)/min.) ten times without any change...

  17. Enantioseparation of Timolol on a Novel β-Cyclodextrin Derivative Chiral Stationary Phase in HPLC.

    Science.gov (United States)

    Zhou, Jie; Sun, Fang; Du, Qiuzheng; Zhao, Suzhen; Pei, Wenjuan

    2016-01-01

    A novel chiral stationary phase was prepared by bonding a novel β-cyclodextrin derivative on silica gel, and it was used for the separation of timolol in high efficiency liquid phase. In the reverse mode, the factors such as the proportion of chiral additives, flow rate, column temperature, repeatability and stability were investigated. The optimum chromatographic conditions are as follows: column temperature was 25°C, flow rate was 0.6 mL min(-1) and mobile phase was methanol-25 mM KH2PO4 (80/20, v/v). The chiral column has good reproducibility (Rs = 4.49, 4.51 and 4.40, respectively) and a certain degree of stability (Rs = 4.49, 3.01 and 0.72, respectively). This chiral stationary phase presented good chiral recognition performance toward timolol with good resolution (Rs = 4.49).

  18. Flexoelectric coefficient measurements in the nematic liquid crystal phase of 5CB

    Directory of Open Access Journals (Sweden)

    F. Castles

    2012-06-01

    Full Text Available We report measurements of the bulk flexoelectric coefficient (e1 − e3 of 5CB (4-Cyano-4′-pentylbiphenyl, in the temperature range 20–34 °C, with a relative combined standard uncertainty of 2 %. The chiral flexoelectro-optic method was used with 1 wt % high-twisting-power chiral additive. At 25 °C, (e1 − e3 = 7.10 pC/m with a combined standard uncertainty of 0.14 pC/m.

  19. Alternating twist structures formed by electroconvection in the nematic phase of an achiral bent-core molecule.

    Science.gov (United States)

    Tanaka, Shingo; Dhara, Surajit; Sadashiva, B K; Shimbo, Yoshio; Takanishi, Yoichi; Araoka, Fumito; Ishikawa, Ken; Takezoe, Hideo

    2008-04-01

    We report an unusual electroconvection in the nematic phase of a bent-core liquid crystal. In a voltage-frequency diagram, two frequency regions exhibiting prewavy stripe patterns were found, as reported by Wiant We found that these stripes never show extinction dark when cells were rotated under crossed polarizers. Based on the color interchange in between neighboring stripes by the rotation of the cells or an analyzer, twisted molecular orientation is suggested; i.e., the directors are alternately twisted from the top to the bottom surfaces with a pretilt angle in adjacent stripes, which is an analogue of the twisted (splayed) structure observed in surface-stabilized ferroelectric liquid crystal cells. The transmittance spectra calculated using the 4x4 matrix method from the model structure are consistent with the experimental observation.

  20. The effect of quasispherical and chainlike solutes on the nematic to isotropic phase transition in liquid crystals

    Science.gov (United States)

    Oweimreen, G. A.; Martire, D. E.

    1980-02-01

    The effects of solute molecular structure (size, shape and flexibility) and solvent molecular structure (length-to-breadth ratio and end-chain flexibility) on nematic phase stability in dilute binary mixtures of nonmesomorphic solutes and nematogenic solvents are examined through experiment and theory. Addition of the perturbing solute to the liquid-crystalline solvent leads to depression of the nematic-isotropic (NI) transition temperature and formation of a two-phase region. Directly determined moduli of the slopes, βn and βi, of the nematic and isotropic phase boundary lines in the reduced NI transition temperature (T*) vs solute mole fraction (x2) diagrams are reported for quasispherical and chainlike solutes with two nematogenic solvents. The systems studied are the quasispheres Et4C (tetraethylmethane) and R4Sn (R = CH3, C2H5, n-C3H7 and n-C4H9) and the chains n-C8H18 through n-C14H30, mixed with p-methoxybenzylidine-p'-n-butylaniline (MBBA) and p-n-pentyl-p'-cyanobiphenyl (5CB). Also reported are indirectly determined β∞n and β∞i values (limit as x2→0), using a novel approach combining differential scanning calorimetry (for the pure solvent contribution) and gas-liquid chromatography (for the solution contribution), for Et4C and n-C5H12 through n-C11H24, with MBBA, 5CB, p-azoxyanisole (PAA), and p,p'-di-n-hexyloxyazoxybenzene (DHAB). For the systems in common, the average difference between the directly and indirectly determined β values is approximately 10% and, qualitatively consistent with lattice model predictions, the comparison suggests slight curvature of the phase boundary lines. The experimental β values, as a function of increasing solute size, are found to double (roughly) for the quasispheres and increase only slightly for the chains, reflecting the concurrent behavior of the solution contribution to β. The thermodynamic results for the quasispherical solutes are compared in some detail with predicted values from statistical

  1. Dispersive Stabilization of Liquid Crystal-in-Water with Acrylamide Copolymer/Surfactant Mixture: Nematic Curvilinear Aligned Phase Composite Film.

    Science.gov (United States)

    Park; Lee

    1999-11-01

    The effect of nonionic surfactant, (H(OCH(2)-CH(2))(8)-OC(6)H(4)-C(9)H(19)), on the dispersion stabilization of liquid crystal (LC)-in-water with acrylamide copolymer containing the related nonylphenyl groups was studied. It was observed that the addition of nonionic surfactant increases the stability of LC dispersions and improves the electrooptical properties of the nematic curvilinear aligned phase (NCAP) composite film. On the basis of the surface tension, reduced viscosity, cloud point, and coalescence time measurements, it was proposed that formation of an integrated structure induced by interactions between hydrophobic groups in the polymer chains is probably important to fabrication of a polymer composite film made of LC and polymer matrix. Copyright 1999 Academic Press.

  2. Metal Complexes:Novel Chiral Dopants with High Helical Twisting Power in Liquid Crystals

    Institute of Scientific and Technical Information of China (English)

    Manfred; Braun; R.Fleischer; A.Hahn; M.Engelmann; S.Schlecht

    2007-01-01

    1 Introduction A particularly efficient and elegant route to chiral mesophases is based on the addition of small amounts of an enantiomerically pure dopant to a nematic phase so that the latter is converted into a cholesteric phase(See Fig.1).Fig.1 A nematic phase is converted into a cholesteric phase Fig.2 Bis-chelated imine-alkoxy-titanium complexes2 ExperimetalBis-chelated imine-alkoxy-titanium complexes like 1 and 2 (Fig.2) have been synthesizedstarting from triphenyl-substituted aminoethanols, T...

  3. Preparation and evaluation of novel chiral stationary phases based on quinine derivatives comprising crown ether moieties.

    Science.gov (United States)

    Wang, Dongqiang; Zhao, Jianchao; Wu, Haixia; Wu, Haibo; Cai, Jianfeng; Ke, Yanxiong; Liang, Xinmiao

    2015-01-01

    The C9-position of quinine was modified by meta- or para-substituted benzo-18-crown-6, and immobilized on 3-mercaptopropyl-modified silica gel through the radical thiol-ene addition reaction. These two chiral stationary phases were evaluated by chiral acids, amino acids, and chiral primary amines. The crown ether moiety on the quinine anion exchanger provided a ligand-exchange site for primary amino groups, which played an important role in the retention and enantioselectivity for chiral compounds containing primary amine groups. These two stationary phases showed good selectivity for some amino acids. The complex interaction between crown ether and protonated primary amino group was investigated by the addition of inorganic salts such as LiCl, NH4Cl, NaCl, and KCl to the mobile phase. The resolution results showed that the simultaneous interactions between two function moieties (quinine and crown ether) and amino acids were important for the chiral separation.

  4. ({alpha},{eta}) phase diagrams in tilted chiral smectics

    Energy Technology Data Exchange (ETDEWEB)

    Rjili, M., E-mail: medrjili@yahoo.fr [Laboratoire de Physique de la Matiere Molle et de la Modelisation Electromagnetique, Faculte des Sciences de Tunis, Universite Tunis El Manar, 2092 El Manar Tunis (Tunisia); Marcerou, J.P., E-mail: marcerou@crpp-bordeaux.cnrs.fr [Centre de Recherches Paul Pascal, 115, Av. Albert-Schweitzer, 33600 Pessac (France); Gharbi, A.; Othman, T. [Laboratoire de Physique de la Matiere Molle et de la Modelisation Electromagnetique, Faculte des Sciences de Tunis, Universite Tunis El Manar, 2092 El Manar Tunis (Tunisia)

    2013-02-01

    The polymorphism of tilted chiral smectics liquid crystals is incredibly rich and encompasses many subphases such as SmC{sub A}{sup Low-Asterisk }; SmC{sub Fi1}{sup Low-Asterisk }; SmC{sub Fi2}{sup Low-Asterisk }; SmC{sup Low-Asterisk }; SmC{sub {alpha}}{sup Low-Asterisk }. The continuum theory established by Marcerou (2010) is used to derive an expression for the free energy density of those subphases. The minimization of this free energy is obtained through a combination of analytical and numerical methods. It leads to a phase diagram built in the ({alpha},{eta}) plane where {alpha} is local angular parameter and {eta} describes the variation of the temperature. From this graphical representation, many experimentally observed phase sequences of ferroelectric liquid crystals can be explained, even them including subphases which were recently observed like the SmC{sub 5}{sup Low-Asterisk} and the SmC{sub 6}{sup Low-Asterisk} ones. However, it should be emphasized that the details of predicted phase diagram are strongly dependent on the compound studied.

  5. Enantioseparation of Novel Chiral Tetrahedral Clusters on an Amylose Tris-(3,5-dimethylphenylcarbamate) Chiral Stationary Phase by Normal Phase HPLC

    Institute of Scientific and Technical Information of China (English)

    LI,Wen-Zhi(李文智); WANG,Xia(王霞); ZHANG,Wei-Qiang(张伟强); CHEN Li-Ren(陈立仁); LI,Yong-Min(李永民); MA,Chun-Lin(马春林); YIN,Yuan-Qi(殷元骐)

    2004-01-01

    Amylose tris(3,5-dimethylphenylcarbamate) (ADMPC) coated on a kind of small particle silica gel was prepared. On this ADMPC chiral stationary phase (CSP), the direct enantiomeric separation of six novel chiral transition metal tetrahedral clusters has firstly been achieved using n-hexane as the mobile phase containing various alcohols as modifiers. The effect of mobile phase modifiers and the structural variation of the solutes on their retention factors (k′) and resolutions (Rs) were investigated. The result suggests that not only the structure and concentration of alcohol in mobile phase, but also the structural differences in racemates can have a pronounced effect on enantiomeric separation. ADMPC-CSP is a suitable CSP for the optical resolution of chiral tetrahedral cluster by HPLC.

  6. Liquid Crystal Phases of Molecular Bananas: Polarity and Chirality as Broken Symmetries

    Science.gov (United States)

    Clark, Noel

    2006-03-01

    The study of the interplay of chirality and polarity has been a particularly rich theme of soft matter science since Meyer's seminal discovery that tilted smectics of chiral molecules are macroscopically polar. This event, and the subsequent realization of polar domains and high-speed electro-optic switching in chiral smectics, engaged the liquid crystal community in a worldwide pursuit of novel smectics for applications, featured by the synthesis of more than 50,000 new liquid crystal compounds, and by a consequent broad diversification of the palette of liquid crystal phases and possibilities for supermolecular ordering. A current important activity in this scenario is the study of polar order in synthetically achiral molecules, for example, in molecular bananas, which, as their shape suggests, might be expected to organize in a polar way. Indeed they do, but beyond this, almost everything learned about them has been surprising, including their persistent tendency to exhibit chirality as a spontaneously broken symmetry. I will discuss some of these new phases and phenomena, including the discovery of fluid conglomerates (Pasteur's experiment in a fluid), triclinic fluid order, chiral twist grain boundary phases of achiral molecules, chirality flipping and field-induced deracemization, ferroelectric and antiferroelectric phases with supermolecular- scale polarization modulation, and chiral thermotropic sponge phases.

  7. Colloidal spirals in nematic liquid crystals.

    Science.gov (United States)

    Senyuk, Bohdan; Pandey, Manoj B; Liu, Qingkun; Tasinkevych, Mykola; Smalyukh, Ivan I

    2015-12-07

    One of the central experimental efforts in nematic colloids research aims to explore how the interplay between the geometry of particles along with the accompanying nematic director deformations and defects around them can provide a means of guiding particle self-assembly and controlling the structure of particle-induced defects. In this work, we design, fabricate, and disperse low-symmetry colloidal particles with shapes of spirals, double spirals, and triple spirals in a nematic fluid. These spiral-shaped particles, which are controlled by varying their surface functionalization to provide tangential or perpendicular boundary conditions of the nematic molecular alignment, are found inducing director distortions and defect configurations with non-chiral or chiral symmetry. Colloidal particles also exhibit both stable and metastable multiple orientational states in the nematic host, with a large number of director configurations featuring both singular and solitonic nonsingular topological defects accompanying them, which can result in unusual forms of colloidal self-assembly. Our findings directly demonstrate how the symmetry of particle-generated director configurations can be further lowered, or not, as compared to the low point group symmetry of solid micro-inclusions, depending on the nature of induced defects while satisfying topological constraints. We show that achiral colloidal particles can cause chiral symmetry breaking of elastic distortions, which is driven by complex three-dimensional winding of induced topological line defects and solitons.

  8. Directing the phase behavior of polyelectrolyte complexes using chiral patterned peptides

    Science.gov (United States)

    Pacalin, Naomi M.; Leon, Lorraine; Tirrell, Matthew

    2016-10-01

    Polyelectrolyte complexes (PECs) have a broad range of promising applications as soft materials due to their self-assembly and diversity of structure and chemical composition. Peptide polymer PECs are highly biocompatible and biodegradable, making them particularly useful for encapsulation of food additives and flavors, micellar drug delivery, medical and underwater adhesives, fetal membrane patches, and scaffolds for cell growth in tissue engineering. While parameters affecting PEC formation and stability in regards to charge effects are well researched, little is known about the effects of van der Waals interactions, hydrogen bonding, and secondary structure in these materials. Peptide chirality provides a unique opportunity to manipulate PEC phase to modulate the amount of solid-like (precipitate) or liquid-like (coacervate) character by influencing hydrogen bonding interactions among peptide chains. In previous work, we showed that chiral peptides form solid complexes, while complexes with even one racemic peptide were fluid. This raised the interesting question of how long a homochiral sequence must be to result in solid phase formation. In this work, we designed chiral patterned peptides of polyglutamic acid and polylysine ranging from 50 to 90% L-chiral residues with increasing numbers of sequential L-chiral residues before a chirality change. These polymers were mixed together to form PECs. We observed that 8 or more sequential L-chiral residues are necessary to achieve both the appearance of a precipitate phase and sustained β-sheets in the complex, as determined by optical imaging and FTIR Spectroscopy. Less homochiral content results in formation of a coacervate phase. Thus, we show that chiral sequence can be used to control the phase transition of PECs. Understanding how to manipulate PEC phase using chiral sequence as presented here may enable tuning of the material properties to achieve the desired mechanical strength for coatings and polymer

  9. Influence of boson mass on chiral phase transition in QED3

    Science.gov (United States)

    Feng, Hong-tao; Wang, Xiu-Zhen; Yu, Xin-hua; Zong, Hong-shi

    2016-08-01

    Based on the truncated Dyson-Schwinger equations for the fermion propagator with N fermion flavors at zero temperature, the chiral phase transition of quantum electrodynamics in 2 +1 dimensions (QED3 ) with boson mass—which is obtained via the Anderson-Higgs mechanism—is investigated. In the chiral limit, we find that the critical behavior of QED3 with a massless boson is different from that with a massive boson: the chiral phase transition in the presence of a nonzero boson mass reveals the typical second-order phase transition, at either the critical boson mass or a critical number of fermion flavors, while for a vanishing boson mass it exhibits a higher than second-order phase transition at the critical number of fermion flavors. Furthermore, it is shown that the system undergoes a crossover behavior from a small number of fermion flavors or boson mass to its larger one beyond the chiral limit.

  10. Detection of Zak phases and topological invariants in a chiral photonic quantum walk

    CERN Document Server

    Cardano, F; Dauphin, A; Maffei, M; Piccirillo, B; de Lisio, C; De Filippis, G; Cataudella, V; Santamato, E; Marrucci, L; Lewenstein, M; Massignan, P

    2016-01-01

    Topological insulators are fascinating states of matter exhibiting protected edge states and robust quantized features in their bulk. Here, we propose and validate experimentally a method to detect topological properties in the bulk of one-dimensional chiral systems. We first introduce the mean chiral displacement, and we show that it rapidly approaches a multiple of the Zak phase in the long time limit. Then we measure the Zak phase in a photonic quantum walk, by direct observation of the mean chiral displacement in its bulk. Next, we measure the Zak phase in an alternative, inequivalent timeframe, and combine the two windings to characterize the full phase diagram of this Floquet system. Finally, we prove the robustness of the measure by introducing dynamical disorder in the system. This detection method is extremely general, as it can be applied to all one-dimensional platforms simulating static or Floquet chiral systems.

  11. O(N) universality and the chiral phase transition in QCD

    CERN Document Server

    Karsch, Frithjof

    2010-01-01

    We discuss universal scaling properties of (2+1)-flavor QCD in the vicinity of the chiral phase transition at vanishing as well as non-vanishing light quark chemical potential (mu_l). We provide evidence for O(N) scaling of the chiral order parameter in (2+1)-flavor QCD and show that the scaling analysis of its derivative with respect to the light quark chemical potential provides a unique approach to the determination of the curvature of the chiral phase transition line in the vicinity of mu_l/T=0.

  12. High-performance liquid chromatographic separations of stereoisomers of chiral basic agrochemicals with polysaccharide-based chiral columns and polar organic mobile phases.

    Science.gov (United States)

    Matarashvili, Iza; Shvangiradze, Iamze; Chankvetadze, Lali; Sidamonidze, Shota; Takaishvili, Nino; Farkas, Tivadar; Chankvetadze, Bezhan

    2015-12-01

    The separation of the stereoisomers of 23 chiral basic agrochemicals was studied on six different polysaccharide-based chiral columns in high-performance liquid chromatography with various polar organic mobile phases. Along with the successful separation of analyte stereoisomers, emphasis was placed on the effect of the chiral selector and mobile phase composition on the elution order of stereoisomers. The interesting phenomenon of reversal of enantiomer/stereoisomer elution order function of the polysaccharide backbone (cellulose or amylose), type of derivative (carbamate or benzoate), nature, and position of the substituent(s) in the phenylcarbamate moiety (methyl or chloro) and the nature of the mobile phase was observed. For several of the analytes containing two chiral centers all four stereoisomers were resolved with at least one chiral selector/mobile phase combination.

  13. Generalized Liquid Crystals: Giant Fluctuations and the Vestigial Chiral Order of I , O , and T Matter

    Science.gov (United States)

    Liu, Ke; Nissinen, Jaakko; Slager, Robert-Jan; Wu, Kai; Zaanen, Jan

    2016-10-01

    The physics of nematic liquid crystals has been the subject of intensive research since the late 19th century. However, the focus of this pursuit has been centered around uniaxial and biaxial nematics associated with constituents bearing a D∞ h or D2 h symmetry, respectively. In view of general symmetries, however, these are singularly special since nematic order can in principle involve any point-group symmetry. Given the progress in tailoring nanoparticles with particular shapes and interactions, this vast family of "generalized nematics" might become accessible in the laboratory. Little is known because the order parameter theories associated with the highly symmetric point groups are remarkably complicated, involving tensor order parameters of high rank. Here, we show that the generic features of the statistical physics of such systems can be studied in a highly flexible and efficient fashion using a mathematical tool borrowed from high-energy physics: discrete non-Abelian gauge theory. Explicitly, we construct a family of lattice gauge models encapsulating nematic ordering of general three-dimensional point-group symmetries. We find that the most symmetrical generalized nematics are subjected to thermal fluctuations of unprecedented severity. As a result, novel forms of fluctuation phenomena become possible. In particular, we demonstrate that a vestigial phase carrying no more than chiral order becomes ubiquitous departing from high point-group symmetry chiral building blocks, such as I , O , and T symmetric matter.

  14. Reexamination of the mean-field phase diagram of biaxial nematic liquid crystals: Insights from Monte Carlo studies

    Science.gov (United States)

    Kamala Latha, B.; Jose, Regina; Murthy, K. P. N.; Sastry, V. S. S.

    2015-07-01

    Investigations of the phase diagram of biaxial liquid-crystal systems through analyses of general Hamiltonian models within the simplifications of mean-field theory (MFT), as well as by computer simulations based on microscopic models, are directed toward an appreciation of the role of the underlying molecular-level interactions to facilitate its spontaneous condensation into a nematic phase with biaxial symmetry. Continuing experimental challenges in realizing such a system unambiguously, despite encouraging predictions from MFT, for example, are requiring more versatile simulational methodologies capable of providing insights into possible hindering barriers within the system, typically gleaned through its free-energy dependences on relevant observables as the system is driven through the transitions. The recent paper from this group [Kamala Latha et al., Phys. Rev. E 89, 050501(R) (2014), 10.1103/PhysRevE.89.050501], summarizing the outcome of detailed Monte Carlo simulations carried out employing an entropic sampling technique, suggested a qualitative modification of the MFT phase diagram as the Hamiltonian is asymptotically driven toward the so-called partly repulsive regions. It was argued that the degree of (cross) coupling between the uniaxial and biaxial tensor components of neighboring molecules plays a crucial role in facilitating a ready condensation of the biaxial phase, suggesting that this could be a plausible factor in explaining the experimental difficulties. In this paper, we elaborate this point further, providing additional evidence from curious variations of free-energy profiles with respect to the relevant orientational order parameters, at different temperatures bracketing the phase transitions.

  15. Structure of chiral phase transitions at finite temperature in abelian gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Fukazawa, Kenji [Kure National College of Technology, Kure (Japan); Inagaki, Tomohiro [Information Media Center, Hiroshima Univ., Hiroshima (Japan); Mukaigawa, Seiji [Department of Electrical and Electronic Engineering, Faculty of Engineering, Iwate Univ., Iwate (Japan); Muta, Taizo [Department of Physics, Hiroshima Univ., Hiroshima (Japan)

    2001-06-01

    The mechanism of chiral symmetry breaking is investigated in strong-coupling Abelian gauge theories at finite temperature. The Schwinger-Dyson equation in the Landau gauge is employed in the real time formalism and is solved numerically within the framework of the instantaneous exchange approximation, including the effect of the thermal mass for the photon propagator. It is found that the chiral symmetry is broken below the critical temperature T for sufficiently large coupling {alpha}. The chiral phase transition is found to be of second order, and the phase diagram in the T-{alpha} plane is obtained. It is investigated how the structure of the chiral phase transition is affected by the thermal mass in the photon propagator. (author)

  16. Structure of chiral phase transitions at finite temperature in Abelian gauge theories

    CERN Document Server

    Fukazawa, K; Mukaigawa, S; Muta, T; Fukazawa, Kenji; Inagaki, Tomohiro; Mukaigawa, Seiji; Muta, Taizo

    1999-01-01

    The mechanism of the chiral symmetry breaking is investigated in the strong-coupling Abelian gauge theories at finite temperature. The Schwinger-Dyson equation in Landau gauge is employed in the real time formalism and is solved numerically within the framework of the instantaneous exchange approximation including the effect of the hard thermal loop for the photon propagator. It is found that the chiral symmetry is broken below the critical temperature T for sufficiently large coupling. The chiral phase transition is found to be of the 2nd order and the phase diagram on the $T-\\alpha$ plane is obtained. It is investigated how the structure of the chiral phase transition is affected by the hard thermal loops in the photon propagator.

  17. Description and Evaluation of Chiral Interactive Sites on Bonded Cyclodextrin Stationary Phases for Liquid Chromatography

    Science.gov (United States)

    Beesley, Thomas E.

    Development of chiral separations has been essential to the drug discovery and development process. The solubility requirements for a number of methods and/or the mobile phase requirements for application of certain detection systems have opened up many opportunities for cyclodextrin-based CSPs for liquid chromatography. Even though a few chiral stationary phases cover a wide area of enantioselectivity, they do not meet the entire needs of the industry. Cyclodextrin phases offer some unique mechanisms and opportunities to resolve chiral separation problems especially in the aqueous reversed-phase and non-aqueous polar organic modes. This chapter addresses the need to understand the chiral stationary phase structure, the mechanisms at work, and the role mobile phase composition plays in driving those mechanisms to produce enantioselectivity. In addition, the development of certain derivatives has played an essential part in expanding that basic role for certain chiral separations. What these derivatives contribute in concert with the basic structure is a critical part of the understanding to the effective use of these phases. During this study it was determined that the role of steric hindrance has been vastly underestimated, both to the extent that it has occurred and to its effectiveness for obtaining enantioselectivity. References to the entire 20-year history of the cyclodextrin phase development and application literature up to this current date have been reviewed and incorporated.

  18. Planar anchoring strength and pitch measurements in achiral and chiral chromonic liquid crystals using 90-degree twist cells

    Science.gov (United States)

    McGinn, Christine K.; Laderman, Laura I.; Zimmermann, Natalie; Kitzerow, Heinz-S.; Collings, Peter J.

    2013-12-01

    Chromonic liquid crystals are formed by molecules that spontaneously assemble into anisotropic structures in water. The ordering unit is therefore a molecular assembly instead of a molecule as in thermotropic liquid crystals. Although it has been known for a long time that certain dyes, drugs, and nucleic acids form chromonic liquid crystals, only recently has enough knowledge been gained on how to control their alignment so that studies of their fundamental liquid crystal properties can be performed. In this article, a simple method for producing planar alignment of the nematic phase in chromonic liquid crystals is described, and this in turn is used to create twisted nematic structures of both achiral and chiral chromonic liquid crystals. The optics of 90-degree twist cells allows the anchoring strength to be measured in achiral systems, which for this alignment technique is quite weak, about 3×10-7 J/m2 for both disodium cromoglycate and Sunset Yellow FCF. The addition of a chiral amino acid to the system causes the chiral nematic phase to form, and similar optical measurements in 90-degree twist cells produce a measurement of the intrinsic pitch of the chiral nematic phase. From these measurements, the helical twisting power for L-alanine is found to be (1.1±0.4)×10-2 μm-1 wt%-1 for 15 wt% disodium cromoglycate.

  19. Nanocellulose 3, 5-Dimethylphenylcarbamate Derivative Coated Chiral Stationary Phase: Preparation and Enantioseparation Performance.

    Science.gov (United States)

    Zhang, Xiaoli; Wang, Litao; Dong, Shuqing; Zhang, Xia; Wu, Qi; Zhao, Liang; Shi, Yanping

    2016-05-01

    Nanocrystalline cellulose (NCC) with high surface area and high ordered crystalline structure was prepared from microcrystalline cellulose (MCC) under the hydrolysis of sodium hypochlorite. NCC was further reacted with 3,5-dimethylphenyl isocyanate to obtain the nanocellulose derivative, and then coated successfully on the surface of silica gel to a prepared NCC-coated chiral stationary phase (CSP) as a new kind of chiral separation material. Similarly, MCC derivative-coated CSP was also prepared as contrast. The chiral separation performance of NCC-based CSP was evaluated and compared with MCC-based CSP by high-performance liquid chromatography. Moreover, the effects of the alcohol modifiers, mobile phase additives, and flow rates on chiral separations were investigated in detail. The results showed that 10 chiral compounds were separated on NCC-based CSP with better peak shape and higher column efficiency than MCC-based CSP, which confirmed that NCC-based CSP was a promising packing material for the resolution of chiral compounds.Chirality 28:376-381, 2016. © 2016 Wiley Periodicals, Inc.

  20. Preparation of Two New Diasteromeric Chiral Stationary Phases Based on (+-(18-Crown-6-2,3,11,12-tetracarboxylic Acid and (R- or (S-1-(1-Naphthylethylamine and Chiral Tethering Group Effect on the Chiral Recognition

    Directory of Open Access Journals (Sweden)

    Rajalingam Agneeswari

    2016-08-01

    Full Text Available Two new diastereomeric chiral stationary phases (CSPs based on (+-(18-crown-6-2,3,11,12-tetracarboxylic acid as a chiral tethering group and a Π-basic chiral unit such as (R-1-(1-naphthylethylamine (CSP 1 or (S-1-(1-naphthylethylamine (CSP 2 were prepared. The two CSPs were applied to the enantiomeric separation of N-(3,5-dinitrobenzoyl-1-phenylalkylamines and N-(3,5-dinitrobenzoyl-α-amino acid derivatives using 20% isopropyl alcohol in hexane as a normal mobile phase. To elucidate the effect of the two chiral units on the chiral recognition, the chiral recognition abilities of the two CSPs were compared with each other and with that of a CSP (CSP 3 based on (R-1-(1-naphthylethylamine. From the chromatographic chiral recognition results, (R-1-(1-naphthylethylamine and (+−(18-crown-6-2,3,11,12-tetracarboxylic acid constituting CSP 1 were concluded to show a cooperative (“matched” effect on the chiral recognition while (S-1-(1-naphthylethylamine and (+-(18-crown-6-2,3,11,12-tetracarboxylic acid constituting CSP 2 were concluded to show an uncooperative (“mismatched” effect on the chiral recognition. From these results, it was concluded that (+-(18-crown-6-2,3,11,12-tetracarboxylic acid can be successfully used as a chiral tethering group for the preparation of new CSPs.

  1. Preparation of Two New Diasteromeric Chiral Stationary Phases Based on (+)-(18-Crown-6)-2,3,11,12-tetracarboxylic Acid and (R)- or (S)-1-(1-Naphthyl)ethylamine and Chiral Tethering Group Effect on the Chiral Recognition.

    Science.gov (United States)

    Agneeswari, Rajalingam; Sung, Ji Yeong; Jo, Eun Sol; Jeon, Hee Young; Tamilavan, Vellaiappillai; Hyun, Myung Ho

    2016-08-12

    Two new diastereomeric chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as a chiral tethering group and a Π-basic chiral unit such as (R)-1-(1-naphthyl)ethylamine (CSP 1) or (S)-1-(1-naphthyl)ethylamine (CSP 2) were prepared. The two CSPs were applied to the enantiomeric separation of N-(3,5-dinitrobenzoyl)-1-phenylalkylamines and N-(3,5-dinitrobenzoyl)-α-amino acid derivatives using 20% isopropyl alcohol in hexane as a normal mobile phase. To elucidate the effect of the two chiral units on the chiral recognition, the chiral recognition abilities of the two CSPs were compared with each other and with that of a CSP (CSP 3) based on (R)-1-(1-naphthyl)ethylamine. From the chromatographic chiral recognition results, (R)-1-(1-naphthyl)ethylamine and (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid constituting CSP 1 were concluded to show a cooperative ("matched") effect on the chiral recognition while (S)-1-(1-naphthyl)ethylamine and (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid constituting CSP 2 were concluded to show an uncooperative ("mismatched") effect on the chiral recognition. From these results, it was concluded that (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid can be successfully used as a chiral tethering group for the preparation of new CSPs.

  2. Chiral phase transition in charge ordered 1T-TiSe2.

    Science.gov (United States)

    Castellan, John-Paul; Rosenkranz, Stephan; Osborn, Ray; Li, Qing'an; Gray, K E; Luo, X; Welp, U; Karapetrov, Goran; Ruff, J P C; van Wezel, Jasper

    2013-05-10

    It was recently discovered that the low-temperature, charge-ordered phase of 1T-TiSe(2) has a chiral character. This unexpected chirality in a system described by a scalar order parameter could be explained in a model where the emergence of relative phase shifts between three charge density wave components breaks the inversion symmetry of the lattice. Here, we present experimental evidence for the sequence of phase transitions predicted by that theory, going from disorder to nonchiral and finally to chiral charge order. Employing x-ray diffraction, specific heat, and electrical transport measurements, we find that a novel phase transition occurs ~7 K below the main charge ordering transition in TiSe(2), in agreement with the predicted hierarchy of charge-ordered phases.

  3. Phase structure of the massive chiral Gross-Neveu model from Hartree-Fock

    CERN Document Server

    Boehmer, Christian; Kraus, Sebastian; Thies, Michael

    2008-01-01

    The phase diagram of the massive chiral Gross-Neveu model (the massive Nambu-Jona-Lasinio model in 1+1 dimensions) is constructed. In the large N limit, the Hartree-Fock approach can be used. We find numerically a chiral crystal phase separated from a massive Fermi gas phase by a 1st order transition. Using perturbation theory, we also construct the critical sheet where the homogeneous phase becomes unstable in a 2nd order transition. A tricritical curve is located. The phase diagram is mapped out as a function of fermion mass, chemical potential and temperature and compared with the one of the discrete chiral Gross-Neveu model. As a by-product, we illustrate the crystal structure of matter at zero temperature for various densities and fermion masses.

  4. Amplification of Quantum Meson Modes in the Late Time of the Chiral Phase Transition

    CERN Document Server

    Watanabe, K

    2007-01-01

    We investigate the time evolution of the quantum meson modes in the late time of chiral phase transition. In particular, it is shown that there exists a possible solution to the equation of motion for the quantum meson modes, which reveals a parametric resonance and/or resonance through forced oscillation induced by the small oscillation of the chiral condensate. After that, we demonstrate the unstable regions for the quantum meson modes in both the cases of a uniform and spatially expanding system.

  5. Optimize the modulation response of twisted-nematic liquid crystal displays as pure phase spatial light modulators

    Science.gov (United States)

    Ma, Baiheng; Peng, Fei; Kang, Mingwu; Zhou, Jiawu

    2014-11-01

    Twisted-nematic liquid crystal displays (TN-LCD) are widely used in numerous research fields of optics working as spatial light modulators. Approaches to obtaining desired intensity or phase modulation by TN-LCD have been extensively studied based on the knowledge of TN-LCD's internal structure parameters, e.g., the orientation of LC molecules at the surfaces, the twist angle, the thickness of the LC layer, and the birefringence of the material. Generally TN-LCD placed between two linear polarizers (P) produces coupled intensity and phase modulation. To obtain the commonly used pure phase modulation, quarter wave plates (QWP) are often used in front of and/or behind the LCD. In this paper, we present a method to optimize the optical modulation properties of the TN-LCD to obtain pure phase modulation in the configuration of P-QWP-LCD-QWP-P each with proper orientation. Firstly an improved method for determining the Jones matrix of the TN-LCD without knowing its internal parameters is presented, which is based on the macroscopical Jones matrix descriptions for TN-LCD, linear polarizer and QWP. Only three sets of intensity measurements are needed for the complete determination of the TN-LCD's Jones matrix for a single wavelength. Then Jones matrix calculations are carried out to determine the orientations of the polarizers and QWPs for pure phase modulation response. In addition, we prove that the phase modulation depth (PMD) of the TN-LCD can be further increased provided that the mean intensity transmission is decreased to a lower level, which is very useful when the TN-LCD is used as a phase modulator and the ratio between the intensities of the desired diffracted order relative to the other diffracted orders is required higher. Experimental results coincide well with the optical modulation properties of the TN-LCD predicted by our determined Jones matrix. In contrast to the traditional method which requires knowledge of the TN-LCD's internal structure parameters

  6. The Influence of Disorder on Thermotropic Nematic Liquid Crystals Phase Behavior

    Directory of Open Access Journals (Sweden)

    Samo Kralj

    2009-09-01

    Full Text Available We review the theoretical research on the influence of disorder on structure and phase behavior of condensed matter system exhibiting continuous symmetry breaking focusing on liquid crystal phase transitions. We discuss the main properties of liquid crystals as adequate systems in which several open questions with respect to the impact of disorder on universal phase and structural behavior could be explored. Main advantages of liquid crystalline materials and different experimental realizations of random field-type disorder imposed on liquid crystal phases are described.

  7. Effects of gauge boson mass on chiral and deconfinement phase transitions in QED$_{3}$

    CERN Document Server

    Yin, Pei-Lin; Feng, Hong-Tao; Zong, Hong-Shi

    2016-01-01

    Based on the experimental observation that there is a coexisting region between the antiferromagnetic (AF) and $\\textit{d}$-wave superconducting ($\\textit{d}$SC) phases, the influences of gauge boson mass $m_{a}$ on chiral symmetry restoration and deconfinement phase transitions in QED$_{3}$ are investigated simultaneously within a unified framework, i.e., Dyson-Schwinger equations. The results show that the chiral symmetry restoration phase transition in the presence of the gauge boson mass $m_{a}$ is a typical second-order phase transition; the chiral symmetry restoration and deconfinement phase transitions are coincident; the critical number of fermion flavors $N^{c}_{f}$ decreases as the gauge boson mass $m_{a}$ increases and there exists a boundary that separates the $N^{c}_{f}$-$m_{a}$ plane into chiral symmetry breaking/confinement region for ($N_{f}^{c}$, $m_{a}$) below the boundary and chiral symmetry restoration/deconfinement region for ($N_{f}^{c}$, $m_{a}$) above it.

  8. The chicken or the egg; or Who ordered the chiral phase transition?

    CERN Document Server

    Kogan, I I; Tekin, B; Kogan, Ian I.; Kovner, Alex; Tekin, Bayram

    2001-01-01

    We draw an analogy between the deconfining transition in the 2+1 dimensional Georgi-Glashow model and the chiral phase transition in 3+1 dimensional QCD. Based on the detailed analysis of the former (hep-th/0010201) we suggest that the chiral symmetry restoration in QCD at high temperature is driven by the thermal ensemble of baryons and antibaryons. The chiral symmetry is restored when roughly half of the volume is occupied by the baryons. Surprisingly enough, even though baryons are rather heavy, a crude estimate for the critical temperature gives $T_c=180$ Mev. In this scenario the binding of the instantons is not the cause but rather a consequence of the chiral symmetry restoration.

  9. Multi critical point structure for chiral phase transition induce by charge neutrality and vector interaction

    CERN Document Server

    Zhang, Zhao

    2010-01-01

    The combined effect of the repulsive vector interaction and the positive electric chemical potential on the chiral phase transition is investigated by considering neutral color superconductivity. Under the charge-neutrality constraint, the chiral condensate, diquark condensate and quark number densities are obtained in two-plus-one-flavor Nambu-Jona-Lasinio model with the so called Kobayashi-Maskawa-'t Hooft term. We demonstrate that multiple chiral critical-point structures always exist in the Nambu-Jona-Lasinio model within the self-consistent mean-field approximation, and that the number of chiral critical points can vary from zero to four, which is dependent on the magnitudes of vector interaction and the diquark coupling.

  10. Chiral phase transition of $N_f$=2+1 QCD with the HISQ action

    CERN Document Server

    Ding, H -T; Karsch, F; Maezawa, Y; Mukherjee, Swagato; Petreczky, P

    2013-01-01

    We present studies of universal properties of the chiral phase transition in $N_f$=2+1 QCD based on the simulations using Highly Improved Staggered fermions on lattices with temporal extent $N_\\tau$=6. We analyze the quark mass and volume dependence of the chiral condensates and chiral susceptibilities in QCD with two degenerate light quarks and a strange quark. The strange quark mass is chosen to be fixed to its physical value ($m^{phy}_s$) and five values of light quark masses ($m_l$) that are varied in the interval 1/20$\\gtrsim m_l/m^{phy}_s \\gtrsim$1/80. Here various quark masses correspond to pseudo Goldstone pion masses ranging from about 160 MeV to about 80 MeV. The O(N) scaling of chiral observables and the influence of universal scaling on physical observables in the region of physical quark mass values are also discussed.

  11. Separation of chiral primary amino compounds by forming a sandwiched complex in reversed-phase high performance liquid chromatography.

    Science.gov (United States)

    Zhang, Chen; Huang, Wei X; Chen, Zhi; Rustum, Abu M

    2010-07-23

    Separation of chiral primary amino compounds was efficiently achieved under reversed-phase high performance liquid chromatography (RP-HPLC) conditions using a mixture of non-chiral crown ether (18-crown-6) and dimethyl-beta-cyclodextrin (DM-beta-CD) in the mobile phase. Under these conditions, the amino group of the chiral compound was protonated in a low pH mobile phase, and then interacted with 18-crown-6 and DM-beta-CD to form a sandwiched complex [18-crown-6+amine+CD]. Enantiomers of the compound in the sandwiched complex were separated with good enantioselectivity. Formation of the sandwiched complex among the chiral compound and additives in the mobile phase is a key step of the chiral separation. Four different chiral amino compounds namely, 1-aminoindan (AI), 1,2,3,4-tetrahydro-1-naphthylamine (THNA), tyrosine (Tyr), and phenylalanine (Phe), were selected to demonstrate the separation using the sandwiched complex mechanism in RP-HPLC.

  12. Chiral anion exchangers applied to capillary electrochromatography enantioseparation of oppositely charged chiral analytes: investigation of stationary and mobile phase parameters.

    Science.gov (United States)

    Lämmerhofer, M; Tobler, E; Lindner, W

    2000-07-28

    Weak anion-exchange (WAX) type chiral stationary phases (CSPs) based on tert.-butyl carbamoyl quinine as chiral selector (SO) and different types of silica particles (porous and non-porous) as chromatographic support are evaluated in packed capillary electrochromatography (CEC). Their ability to resolve the enantiomers of negatively charged chiral analytes, e.g., N-derivatized amino acids, in the anion-exchange mode and their electrochromatographic characteristics are described in dependence of several mobile phase parameters (pH, buffer type and concentration, organic modifier type and concentration) and other experimental variables (electric field strength, capillary temperature). The inherent "zwitterionic" surface character of such silica-based WAX type CSPs (positively charged SO and negatively charged residual silanols) allows the reversal of the electroosmotic flow (EOF) towards the anode at pH values below the isoelectric point (pI) of the modified surface, whereas a cathodic EOF results at pH values above the pI. Since for negatively charged analytes also an electrophoretic transport increment has to be considered, which can be either in or against the EOF direction, several distinct modes of elution have been observed under different stationary phase and mobile phase conditions: (i) co-electrophoretic elution of the negatively charged solutes with the anodic EOF in the negative polarity mode, (ii) counter-electrophoretic elution with the cathodic EOF in the positive polarity mode, and (iii) electrophoretically dominated elution in the negative polarity mode with a cathodic EOF directed to the injection end of the capillary. Useful enantioseparations of chiral acids have been obtained with all three modes. Enantioselectivity values as high as under pressure-driven conditions and theoretical plate numbers up to 120000 per meter could be achieved under electrically driven conditions. A repeatability study yielded RSD values below 2% for retention times and

  13. Nematicity in charge and orbital ordered structure: a new description of phase transitions in La0.33Ca0.67MnO3

    Science.gov (United States)

    Tao, Jing; Yin, W. G.; Zhu, Y.; Sun, K.

    2014-03-01

    Doped manganites have a well-known unidirectional superlattice modulation at low temperatures, although the origin of the modulation is still under debate. The phase transition of the modulation in this compound has been characterized by the superlattice reflections and the transition temperature was determined when the modulation becomes long-range. Here we report a new description of the phase transition in La0.33Ca0.67MnO3 from the aspect of symmetry by measuring anisotropy based on transmission electron microscopy results. Instead of one phase transition, we found that the electronic structures undergo smectic, nematic and isotropic behaviors upon warming. Comparing to previous characterizations of the phase transition in La0.33Ca0.67MnO3, this symmetry measurement enables a better unification between electronic structure and other properties such as the crystal lattice variation. Moreover, we directly observed the creation of dislocation pairs in the smectic phase, which is consistent with the dislocation-proliferation mechanism predicted by the nematicity theory in correlated systems. The defect observations also suggest the charge and orbital ordering nature of the modulation in La0.33Ca0.67MnO3.

  14. PHOTOINDUCED HOLOGRAPHIC PHASE GRATINGS BURIED IN AZOBENZENE SIDE-CHAIN POLYMER FILMS WITH A CHIRAL GROUP

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    An optically active polymer (PM1) containing azobenzene moieties with a chiral group (s-2-methyl-butyl) was synthesized by homopolymerization of monomer, 4-[2-(methacryloyloxy)ethyloxy]-4'-(s-2-methyl-1-butyloxycarbonyl)azobenzene, using the free radical polymerization method. The polymer dissolved in tetrahydrofuran (THF) could be easily processed into high optical quality films. The optical anisotropy of the polymer films was investigated by polarizing optical microscopy (POM). The experimental results showed that irradiation with a circularly polarized beam could align the orientation of the molecules in the polymer films. Moreover, the holographic phase gratings of photo-induced polymer films were detected by atomic force microscopy (AFM) and POM. In comparison with polymer containing no chiral group, it was found from the preliminary measurement of the photo-induced holographic phase gratings that PM1 containing a chiral group could form holographic phase gratings buried in the films.

  15. The Chirality Of Life: From Phase Transitions To Astrobiology

    CERN Document Server

    Gleiser, Marcelo

    2008-01-01

    The search for life elsewhere in the universe is a pivotal question in modern science. However, to address whether life is common in the universe we must first understand the likelihood of abiogenesis by studying the origin of life on Earth. A key missing piece is the origin of biomolecular homochirality: permeating almost every life-form on Earth is the presence of exclusively levorotary amino acids and dextrorotary sugars. In this work we discuss recent results suggesting that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events in a mechanism referred to as punctuated chirality. Applying these arguments to other potentially life-bearing platforms has significant implications for the search for extraterrestrial life: we predict that a statistically representative sampling of extraterrestrial stereochemistry will be racemic on average.

  16. Recent progress in understanding deconfinement and chiral restoration phase transitions

    CERN Document Server

    Shuryak, Edward

    2016-01-01

    Paradigme shift in gauge topology, from instantons to their constituents -- instanton-dyons -- has recently lead to very significant advances. Like instantons, they have fermionic zero modes, and their collectivization at sufficiently high density explains the chiral symmetry breaking. Unlike instantons, these objects have electric and magnetic charges. Their back reaction on the mean value of the Polyakov line (holonomy) allows to explain the deconfinement transition. The talk summarizes recent works on the dyon ensemble, done in the mean field approximation (MFA), and also by direct numerical statistical simulation. Introduction of non-trivial quark periodicity conditions leads to drastic changes in both deconfinement and chiral transitions. In particulaly, in the so called Z(N_c)-QCD model the former gets much stronger, while the latter does not seem to occur at all.

  17. Spontaneous magnetization of quark matter in the inhomogeneous chiral phase

    CERN Document Server

    Yoshiike, Ryo; Tatsumi, Tositaka

    2015-01-01

    Considering the density wave of scalar and pseudoscalar condensates, we study the response of quark matter to a weak external magnetic field. In an external magnetic field, the energy spectrum of the lowest Landau level becomes asymmetric about zero, which is closely related to chiral anomaly, and gives rise to the spontaneous magnetization. This mechanism may be one of candidates for the origin of the strong magnetic field in pulsars and/or magnetars.

  18. Spontaneous magnetization of quark matter in the inhomogeneous chiral phase

    Directory of Open Access Journals (Sweden)

    R. Yoshiike

    2015-12-01

    Full Text Available Considering the density wave of scalar and pseudoscalar condensates, we study the response of quark matter to a weak external magnetic field. In an external magnetic field, the energy spectrum of the lowest Landau level becomes asymmetric about zero, which is closely related to chiral anomaly, and gives rise to the spontaneous magnetization. This mechanism may be one of candidates for the origin of the strong magnetic field in pulsars and/or magnetars.

  19. Preparation of novel chiral stationary phase based on click chemistry for ligand exchange chromatography

    Institute of Scientific and Technical Information of China (English)

    Chun Mei Fu; Hong Yu Shi; Guang Sheng Qian; Zhang Wan Li

    2009-01-01

    Click chemistry was applied to immobilize L-proline derivative onto azide-modified silica gel to give a novel chiral stationary phase (denoted as click-CSP) for ligand exchange chromatography. The developed protocol combines the benefits of operational simplicity, exceptionally mild conditions and high surface loadings. The enantioselectivity α of some DE-amino acids on the click-CSP were found to be in the range from 1.13 to 3.46. The chromatographic resolutions of some DL-amino acids and the stability study firmly illustrate the potential of click chemistry for preparation chiral stationary phase for ligand exchange chromatography.

  20. Enantioseparation of Six Antihistamines with Immobilized Cellulose Chiral Stationary Phase by HPLC

    Science.gov (United States)

    Zhou, Jie; Luo, Pei; Chen, Shanshan; Meng, Lingchang; Sun, Chong; Du, Qiuzheng; Sun, Fang

    2016-01-01

    A stereoselective high performance liquid chromatography method has been developed for the chiral separation of the enantiomers of six antihistamines, doxylamine, carbinoxamine, dioxopromethazine, oxomemazine, cetirizine and hydroxyzine. The effects of mobile phase additive, column temperature and flow rate on the retention time and resolution were studied. Enantiomeric separation of cetirizine, doxylamine and hydroxyzine were achieved on cellulose tris-(3,5-dichlorophenylcarbamate) immobilized on silica gel chiral stationary phase known as Chiralpak IC (RS = 3.74, RS = 1.85 and RS = 1.74, respectively). PMID:26657408

  1. Enantioseparation of Six Antihistamines with Immobilized Cellulose Chiral Stationary Phase by HPLC.

    Science.gov (United States)

    Zhou, Jie; Luo, Pei; Chen, Shanshan; Meng, Lingchang; Sun, Chong; Du, Qiuzheng; Sun, Fang

    2016-04-01

    A stereoselective high performance liquid chromatography method has been developed for the chiral separation of the enantiomers of six antihistamines, doxylamine, carbinoxamine, dioxopromethazine, oxomemazine, cetirizine and hydroxyzine. The effects of mobile phase additive, column temperature and flow rate on the retention time and resolution were studied. Enantiomeric separation of cetirizine, doxylamine and hydroxyzine were achieved on cellulose tris-(3,5-dichlorophenylcarbamate) immobilized on silica gel chiral stationary phase known as Chiralpak IC (RS = 3.74, RS = 1.85 and RS = 1.74, respectively).

  2. T-\\mu phase diagram of the chiral quark model from a large flavor number expansion

    CERN Document Server

    Jakovác, A; Szép, Z; Szépfalusy, P; Szep, Zs.

    2004-01-01

    The chiral phase boundary of strong matter is determined in the T-\\mu plane from the chiral quark model, applying a non-perturbatively renormalised treatment, involving chains of pion-bubbles and 1-loop fermion contributions. In the absence of explicit symmetry breaking the second order portion of the phase boundary and the location of the tricritical point (TCP) are determined analytically. Sensitivity of the results to the renormalisation scale is carefully investigated. The softening of the sigma-pole near the second order transitions is confirmed.

  3. Nanocellulose Derivative/Silica Hybrid Core-Shell Chiral Stationary Phase: Preparation and Enantioseparation Performance

    Directory of Open Access Journals (Sweden)

    Xiaoli Zhang

    2016-05-01

    Full Text Available Core-shell silica microspheres with a nanocellulose derivative in the hybrid shell were successfully prepared as a chiral stationary phase by a layer-by-layer self-assembly method. The hybrid shell assembled on the silica core was formed using a surfactant as template by the copolymerization reaction of tetraethyl orthosilicate and the nanocellulose derivative bearing triethoxysilyl and 3,5-dimethylphenyl groups. The resulting nanocellulose hybrid core-shell chiral packing materials (CPMs were characterized and packed into columns, and their enantioseparation performance was evaluated by high performance liquid chromatography. The results showed that CPMs exhibited uniform surface morphology and core-shell structures. Various types of chiral compounds were efficiently separated under normal and reversed phase mode. Moreover, chloroform and tetrahydrofuran as mobile phase additives could obviously improve the resolution during the chiral separation processes. CPMs still have good chiral separation property when eluted with solvent systems with a high content of tetrahydrofuran and chloroform, which proved the high solvent resistance of this new material.

  4. Universal mean-field phase diagram for biaxial nematics obtained from a minimax principle.

    Science.gov (United States)

    Bisi, Fulvio; Virga, Epifanio G; Gartland, Eugene C; De Matteis, Giovanni; Sonnet, André M; Durand, Georges E

    2006-05-01

    We study a class of quadratic Hamiltonians which describe both fully attractive and partly repulsive molecular interactions, characteristic of biaxial liquid crystal molecules. To treat the partly repulsive interactions we establish a minimax principle for the associated mean-field free energy. We show that the phase diagram described by Sonnet [Phys. Rev. E 67, 061701 (2003)] is universal. Our predictions are in good agreement with the recent observations on both V-shaped and tetrapodal molecules.

  5. Effect of Single-walled Carbon Nanotubes on Cellulose Phenylcarbamate Chiral Stationary Phases

    Institute of Scientific and Technical Information of China (English)

    CHANG Yin-xia; REN Chao-xing; RUAN Qiong; YUAN Li-ming

    2007-01-01

    Single-walled carbon nanotubes(SWNTs) have a high adsorption ability and nanoscale interactions. Cellulose trisphenylcarbamates possess high enantioseparation ability in high-performance liquid chromatography(HPLC). Single-walled carbon nanotubes mixed with cellulose trisphenylcarbamate are coated on the silica gel as chiral stationary phases and higher enantioseparation factors are obtained. After a single-walled carbon nanotube is linked to the 6-position of cellulose 2,3-bisphenylcarbamate, its enantioseparation resolution increases compared to that of the cellulose trisphenylcarbamate. It is the first time that SWNTs have been applied to enantioseparation. The results indicate that the single-walled carbon nanotubes are good promoters of chiral recognition. This method can be used to improve the enantioseparation efficiency of the polysaccharide chiral stationary phases.

  6. Chiral phase transition of QCD with N f = 2 + 1 flavors from holography

    Science.gov (United States)

    Li, Danning; Huang, Mei

    2017-02-01

    Chiral phase transition for three-flavor N f = 2 + 1 QCD with m u = m d ≠ m s is investigated in a modified soft-wall holographic QCD model. Solving temperature dependent chiral condensates from equations of motion of the modified soft-wall model, we extract the quark mass dependence of the order of chiral phase transition in the case of N f = 2 + 1, and the result is in agreement with the "Columbia Plot", which is summarized from lattice simulations and other non-perturbative methods. First order phase transition is observed around the three flavor chiral limit m u/ d = 0, m s = 0, while at sufficient large quark masses it turns to be a crossover phase transition. The first order and crossover regions are separated by a second order phase transition line. The second order line is divided into two parts by the m u/ d = m s line, and the m s dependence of the transition temperature in these two parts are totally contrast, which might indicate that the two parts are governed by different universality classes.

  7. Polyakov SU(3) extended linear $\\sigma$-model: Sixteen mesonic states in chiral phase-structure

    CERN Document Server

    Tawfik, Abdel Nasser

    2014-01-01

    The derivative of the grand potential in mean field approximation, non-strange and strange condensates and deconfinement phase-transition in thermal and dense hadronic medium are verified in extended SU(3) linear sigma-model (eLSM). In determining the chiral phase-transition, the chiral condensates sigma_x and sigma_y are analysed. The chiral mesonic phase-structures in temperature- and density-dependence are taken as free parameters to be fitted. These parameters are classified corresponding to scalar meson nonets; (pseudo)-scalar and (axial)-vector. For deconfinement phase-transition, effective Polyakov loop-potentials phi and phi^* are utilized. We investigated the in-medium effects on the masses of sixteen mesonic states states. The results are presented for two different forms for the effective Polyakov loop-potential and compared with other models with and without anomalous terms. The Polyakov loop potential in LSM has considerable effects on the chiral phase-transition in meson masses so that the resto...

  8. Thermodynamic studies of induced antiferroelectric phases in chiral and racemic systems

    Science.gov (United States)

    Filipowicz, M.; Kula, P.; Czuprynski, Krzysztof

    2004-09-01

    Bi- and multicomponent mixtures consisted of two groups of synclinic chiral esters: first one with a partially fluorinated terminal chain and the second one with hydrogenated terminal chain have been used for investigations. For some systems the induction of the anticlinic smectic CA* phase was observed. Enthalpies of the phase transitions for the systems with induced smectic CA phase upon compositions and specific heat were measured by DSC method.

  9. Spin nematic and orthogonal nematic states in S=1 non-Heisenberg magnet

    Energy Technology Data Exchange (ETDEWEB)

    Fridman, Yu.A., E-mail: frid@tnu.crimea.edu [V.I. Vernadsky Taurida national university, Academician Vernadsky ave., 4, 95007 Simferopol (Ukraine); Kosmachev, O.A. [V.I. Vernadsky Taurida national university, Academician Vernadsky ave., 4, 95007 Simferopol (Ukraine); Klevets, Ph.N. [V.I. Vernadsky Taurida national university, Academician Vernadsky ave., 4, 95007 Simferopol (Ukraine); Institut fuer Physik, Universitaet Augsburg, Universitaetsstrasse 1, 86159 Augsburg (Germany)

    2013-01-15

    Phases of S=1 non-Heisenberg magnet at various relationships between the exchange integrals are studied in the mean-field limit at zero temperature. It is shown that four phases can be realized in the system under consideration: the ferromagnetic, antiferromagnetic, nematic, and the orthogonal nematic states. The phase diagram is constructed. It is shown that the phase transitions between the ferromagnetic phase and the orthogonal nematic phase and between the antiferromagnetic phase and the orthogonal nematic phase are the degenerated first-order transitions. For the first time the spectra of elementary excitations in all phases are obtained within the mean-field limit. - Highlights: Black-Right-Pointing-Pointer We investigated phases of S=1 non-Heisenberg magnet. Black-Right-Pointing-Pointer Found four phases: ferromagnetic, antiferromagnetic, nematic, and orthogonal nematic. Black-Right-Pointing-Pointer The phase diagram is determined. Black-Right-Pointing-Pointer The spectra of elementary excitations are obtained in all phases for the first time.

  10. Spontaneous Magnetization of Quark Matter in Inhomogeneous Chiral Phase

    CERN Document Server

    Yoshiike, Ryo; Tatsumi, Toshitaka

    2015-01-01

    Considering the density wave of scalar and pseudoscalar condensates, we study the response of quark matter to a weak external magnetic field. In an external magnetic field, the energy spectrum of the lowest Landau level becomes asymmetric about zero, which is closely related to chiral anomaly. This spectral asymmetry gives rise to spontaneous magnetization. This mechanism may be one of candidates for the origin of the strong magnetic field in magnetars. Furthermore, using the generalized Ginzburg-Landau(gGL) expansion, we show that magnetic susceptibility exhibits a peculiar feature

  11. Time evolution of chiral phase transition at finite temperature and density in the linear sigma model

    Energy Technology Data Exchange (ETDEWEB)

    Sato, K.; Koide, Tomoi; Maruyama, Masahiro [Tohoku Univ., Faculty of Science, Sendai, Miyagi (Japan)

    1999-08-01

    There are various approaches to nonequilibrium system. We use the projection operator method investigated by F. Shibata and N. Hashitsume on the linear sigma model at finite temperature and density. We derive a differential equation of the time evolution for the order parameter and pion number density in chiral phase transition. (author)

  12. OPTICAL PHASE CONJUGATION RESPONSE OF PHOTOINDUCED POLYMER FILMS CONTAINING AZOBENZENE MOIETIES WITH CHIRAL GROUP

    Institute of Scientific and Technical Information of China (English)

    Ze-da Xu; Yong Zhang; Xing-he Fan; Xin-hua Wan; Qi-feng Zhou

    2002-01-01

    An optically active monomer containing azobenzene moieties with chiral group (s-2-methyl-butyl), 4-[2-(methacryloyloxy)ethyloxy]-4'-(s-2-methyl-1-butyloxycarbonyl) azobenzene (M1) was synthesized. Polymer (PM1) possessing optical phase conjugated response was obtained by homopolymerization of the optically active monomer (M1) using free radical polymerization. The polymer was very soluble in common solvents and good optical quality films could be easily fabricated by spin coating. The optical phase conjugated responses of the polymer PM1 were measured by degenerate four-wave mixing (DFWM). In comparison with polymer containing no chiral group, it was found from the preliminary measurement of photoisomeric change that optical phase conjugated response of the PM1 in the long-range order hexagonal symmetry microstructure could be easily controlled by choosing the appropriate polarization direction of the irradiating beams (514.5 nm) and the irradiating number, presumably due to the chiral group in the PM1 molecular structure. For the case of the polymer investigated here, a chiral group side chain was introduced to increase optical phase conjugated response intensity with different polarization directions of the irradiating beams, which aims originally at searching for a new photoactive material.

  13. Magnetic fluctuations and correlations in MnSi: Evidence for a chiral skyrmion spin liquid phase

    NARCIS (Netherlands)

    Pappas, C.; Lelièvre-Berna, E.; Bentley, P.; Falus, P.; Fouquet, P.; Farago, B.

    2011-01-01

    We present a comprehensive analysis of high-resolution neutron scattering data involving neutron spin echo spectroscopy and spherical polarimetry, which confirm the first-order nature of the helical transition in MnSi. The experiments reveal the existence of a totally chiral dynamic phase in a very

  14. COVALENTLY BONDING CHIRAL POLYURETHANE ON AMINATED SILICA GEL: A NEW STRATEGY TO PREPARE CHIRAL STATIONARY PHASE FOR HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

    Institute of Scientific and Technical Information of China (English)

    Shao-hua Huang; Zheng-wu Bai; Chuan-qi Yin; Shi-rong Li

    2006-01-01

    Two polyurethanes of different molecular weights were prepared by the copolymerization of phenyl diisocyanate and diisopropyl tartrate. The polyurethanes having terminal isocyanate groups were reacted with 3-aminopropyl silica gel to afford two chiral stationary phases. The (M-)n of the two polyurethanes were 4057 g/mol and 6442 g/mol. The polyurethanes and the corresponding chiral stationary phases were characterized by FT-IR, 1H NMR and elemental analysis. The loading capacities of the polyurethanes on silica gel were 0.68 mmol units/g and 0.61 mmol units/g, respectively. The separation performance and the influence of additives, triethylamine and trichloroacetic acid, on the separation of chiral compounds were investigated by HPLC. The chiral stationary phase prepared from polyurethane with (M-)n of 4057 g/mol demonstrated better enantioseparation capability than that with (M-)n of 6442 g/mol. Additionally, it was found that the addition of triethylamine and trichloroacetic acid in the mobile phases significantly improved the enantioseparation for these two chiral stationary phases.

  15. Silica-based polypeptide-monolithic stationary phase for hydrophilic chromatography and chiral separation.

    Science.gov (United States)

    Zhao, Licong; Yang, Limin; Wang, Qiuquan

    2016-05-13

    Glutathione (GSH)-, somatostatin acetate (ST)- and ovomucoid (OV)-functionalized silica-monolithic stationary phases were designed and synthesized for HILIC and chiral separation using capillary electrochromatography (CEC). GSH, ST and OV were covalently incorporated into the silica skeleton via the epoxy ring-opening reaction between their amino groups and the glycidyl moiety in γ-glycidoxypropyltrimethoxysilane (GPTMS) together with polycondensation and copolymerization of tetramethyloxysilane and GPTMS. Not only could the direction and electroosmotic flow magnitude on the prepared GSH-, ST- and OV-silica hybrid monolithic stationary phases be controlled by the pH of the mobile phase, but also a typical HILIC behavior was observed so that the nucleotides and HPLC peptide standard mixture could be baseline separated using an aqueous mobile phase without any acetonitrile during CEC. Moreover, the prepared monolithic columns had a chiral separation ability to separate dl-amino acids. The OV-silica hybrid monolithic column was most effective in chiral separation and could separate dl-glutamic acid (Glu) (the resolution R=1.07), dl-tyrosine (Tyr) (1.57) and dl-histidine (His) (1.06). Importantly, the chiral separation ability of the GSH-silica hybrid monolithic column could be remarkably enhanced when using gold nanoparticles (AuNPs) to fabricate an AuNP-mediated GSH-AuNP-GSH-silica hybrid monolithic column. The R of dl-Glu, dl-Tyr and dl-His reached 1.19, 1.60 and 2.03. This monolithic column was thus applied to separate drug enantiomers, and quantitative separation of all four R/S drug enantiomers were achieved with R ranging from 4.36 to 5.64. These peptide- and protein-silica monolithic stationary phases with typical HILIC separation behavior and chiral separation ability implied their promise for the analysis of not only the future metabolic studies, but also drug enantiomers recognition.

  16. The chiral phase transition in a random matrix model with molecular correlations

    CERN Document Server

    Wettig, T; Weidenmüller, H A; Wettig, Tilo

    1995-01-01

    The chiral phase transition of QCD is analyzed in a model combining random matrix elements of the Dirac operator with specially chosen non-random ones. The special form of the latter is motivated by the assumption that the fermionic quasi-zero modes associated with instanton and anti-instanton configurations determine the chiral properties of QCD. Our results show that the degree of correlation between these modes plays the decisive role. To reduce the value of the chiral condensate by more than a factor of 2 about 95 percent of the instantons and anti-instantons must form so-called molecules. This conclusion agrees with numerical results of the Stony Brook group.

  17. Chiral phase transition and Schwinger mechanism in a pure electric field

    CERN Document Server

    Cao, Gaoqing

    2016-01-01

    We systematically study the chiral symmetry breaking and restoration in the presence of a pure electric field in the Nambu--Jona-Lasinio (NJL) model at finite temperature and baryon chemical potential. In addition, we also study the effect of the chiral phase transition on the charged pair production due to the Schwinger mechanism. For these purposes, a general formalism for parallel electric and magnetic fields is developed at finite temperature and chemical potential for the first time. In the pure electric field limit $B\\rightarrow0$, we compute the order parameter, the transverse-to-longitudinal ratio of the Goldstone mode velocities, and the Schwinger pair production rate as functions of the electric field. The inverse catalysis effect of the electric field to chiral symmetry breaking is recovered. And the Goldstone mode is find to disperse anisotropically such that the transverse velocity is always smaller than the longitudinal one, especially at nonzero temperature and baryon chemical potential. As exp...

  18. Chiral Phase Transition in the Soft-Wall Model of AdS/QCD

    CERN Document Server

    Chelabi, Kaddour; Huang, Mei; Li, Danning; Wu, Yue-Liang

    2015-01-01

    We investigate the chiral phase transition in the soft-wall model of AdS/QCD at zero chemical potential for two-flavor and three-flavor cases, respectively. We show that there is no spontaneous chiral symmetry breaking in the original soft-wall model. After detailed analysis, we find that in order to realize chiral symmetry breaking and restoration, both profiles for the scalar potential and the dilaton field are essential. The scalar potential determines the possible solution structure of the chiral condensate, except the mass term, it takes another quartic term for the two-flavor case, and for the three-flavor case, one has to take into account an extra cubic term due to the t'Hooft determinant interaction. The profile of the dilaton field reflects the gluodynamics, which is negative at a certain ultraviolet scale and approaches positive quadratic behavior at far infrared region. With this set-up, the spontaneous chiral symmetry breaking in the vacuum and its restoration at finite temperature can be realize...

  19. The Optical Resolution of Chiral Tetrahedrone-type Clusters Contai- ning SCoFeM (M=Mo or W) Using High Performance Liquid Chromatography Chiral Stationary Phase

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Amylose tris (phenylcarbamate) chiral stationary phase (ATPC-CSP) was prepared and used for optical resolution of clusters 1 and 2. n-Hexane/2-propanol ( 99/1; v/v) were found to be the most suitable mobile phase on ATPC-CSP.

  20. Vortex beam generation and other advanced optics experiments reproduced with a twisted-nematic liquid-crystal display with limited phase modulation

    Science.gov (United States)

    Cofré, Aaron; García-Martínez, Pascuala; Vargas, Asticio; Moreno, Ignacio

    2017-01-01

    In this work we propose the use of twisted-nematic liquid-crystal spatial light modulators (TN-LC-SLM) as a useful tool for training students in the manipulation of light beams with phase-only masks. In particular, we focus the work on the realization of phase-only gratings and phase-only spiral phases for the generation of vortex beams, beams carrying orbital angular momentum (OAM). Despite the extensive activity in this field, its experimental implementation for educational purposes is limited because it requires the use of very expensive high-resolution liquid-crystal on silicon (LCOS) SLMs. Here, we show that a low-cost experimental implementation can be done with older TNLC technology. However, these devices, intended for display applications, exhibit rather limited optical phase modulation properties in comparison with modern LCOS devices, such as a very low range of phase modulation and a general coupled intensity modulation. However, we show that a precise characterization of their retardance parameters permits their operation in useful modulation configurations. As examples, we include one continuous phase-only configuration useful for reproducing the optimal triplicator phase grating, and a binary π-phase modulation. We include experiments with the realization of different phase diffraction gratings, and their combination with spiral phase patterns and lens functions to generate a variety of vortex beams.

  1. Thermodynamic phases and mesonic fluctuations in a chiral nucleon-meson model

    CERN Document Server

    Drews, Matthias; Klein, Bertram; Weise, Wolfram

    2013-01-01

    Studies of the QCD phase diagram must properly include nucleonic degrees of freedom and their thermodynamics in the range of baryon chemical potentials characteristic of nuclear matter. A useful framework for incorporating relevant nuclear physics constraints in this context is a chiral nucleon-meson effective Lagrangian. In the present paper, such a chiral nucleon-meson model is extended with systematic inclusion of mesonic fluctuations using the functional renormalization group approach. The resulting description of the nuclear liquid-gas phase transition shows a remarkable agreement with three-loop calculations based on in-medium chiral effective field theory. No signs of a chiral first-order phase transition and its critical endpoint are found in the region of applicability of the model, at least up to twice the density of normal nuclear matter and at temperatures T<100 MeV. Fluctuations close to the critical point of the first-order liquid-gas transition are also examined with a detailed study of the ...

  2. Synthesis of novel glucose-based polymers and their applications as chiral stationary phases for high performance liquid chromatography

    Institute of Scientific and Technical Information of China (English)

    Tomoyuki IKAI; Takayuki YAMADA

    2016-01-01

    Two novel polymers containing glucose units as the main-chain that only differ in terms of their regioregularity were synthesized to evaluate their chiral recognition abilities as chiral stationary phases( CSPs) for high performance liquid chromatography( HPLC). The regioregular polymer( poly-5)shows clear resolution ability for the racemate of cobalt(Ⅲ)acetylacetonate( Co( acac)3 ),whereas the corresponding regioirregular polymer(poly-3)does not show any chiral recognition for Co(acac)3. The regioregular polymer main-chain seems to play an important role not only in providing an efficient interaction with the racemate but also in expressing the chiral recognition ability as a CSP for HPLC.

  3. Possible surface nematic order in iron pnictides

    Science.gov (United States)

    Song, Kok Wee; Koshelev, Alexei

    Nematic fluctuations play important role in the physics of the iron-based superconductors. Indications for weak precursor nematic transition has been found in the compound BaAs2-xPxFe2 [1 ]. However, high-resolution specific-heat measurements did not reveal any bulk transition [2 ]. To resolve this controversy, we consider the possibility of the surface nematic transition preceding the bulk transition. We consider the simplest model of two interacting quasi-two-dimensional electronic bands and explore the free-surface effects on the nematic order. We found that three-dimensional effects suppress the bulk nematic order and therefore this order is enhanced near the surface. [1 ]Kasahara, S., et al. ''Electronic nematicity above the structural and superconducting transition in Ba(As1-xPxFe)2.'' Nature 486.7403 (2012): 382-385. [2 ]Luo, X., et al. ''Antiferromagnetic and nematic phase transitions in Ba(As1-xPxFe)2 studied by ac microcalorimetry and SQUID magnetometry.'' Physical Review B 91.9 (2015): 094512. This work was supported by the Center for Emergent Superconductivity, an Energy FrontierResearch Center funded by the US DOE, Office of Science, under Award No. DEAC0298CH1088.

  4. Spontaneous thermal expansion of nematic elastomers

    OpenAIRE

    Tajbakhsh, A. R.; Terentjev, E.M.

    2001-01-01

    We study the monodomain (single-crystal) nematic elastomer materials, all side-chain siloxane polymers with the same mesogenic groups and crosslinking density, but differing in the type of crosslinking. Increasing the proportion of long di-functional segments of main-chain nematic polymer, acting as network crosslinking, results in dramatic changes in the uniaxial equilibrium thermal expansion on cooling from isotropic phase. At higher concentration of main chains their behaviour dominates th...

  5. Novel chiral stationary phases based on peptoid combining a quinine/quinidine moiety through a C9-position carbamate group.

    Science.gov (United States)

    Wu, Haibo; Wang, Dongqiang; Song, Guangjun; Ke, Yanxiong; Liang, Xinmiao

    2014-04-01

    By connecting a quinine or quinidine moiety to the peptoid chain through the C9-position carbamate group, we synthesized two new chiral selectors. After immobilizing them onto 3-mercaptopropyl-modified silica gel, two novel chiral stationary phases were prepared. With neutral, acid, and basic chiral compounds as analytes, we evaluated these two stationary phases and compared their chromatographic performance with chiral columns based on quinine tert-butyl carbamate and the previous peptoid. From the resolution of neutral and basic analytes under normal-phase mode, it was found that the new stationary phases exhibited much better enantioselectivity than the quinine tert-butyl carbamate column; the peptoid moiety played an important role in enantiorecognition, which controlled the elution orders of enantiomers; the assisting role of the cinchona alkaloid moieties was observed in some separations. Under acid polar organic phase mode, it was proved that cinchona alkaloid moieties introduced excellent enantiorecognitions for chiral acid compounds; in some separations, the peptoid moiety affected enantioseparations as well. Overall, chiral moieties with specific enantioselectivity were demonstrated to improve the performance of peptoid chiral stationary phase efficiently.

  6. Zwitterionic chiral stationary phases based on cinchona and chiral sulfonic acids for the direct stereoselective separation of amino acids and other amphoteric compounds.

    Science.gov (United States)

    Zhang, Tong; Holder, Emilie; Franco, Pilar; Lindner, Wolfgang

    2014-06-01

    An extensive series of free amino acids and analogs were directly resolved into enantiomers (and stereoisomers where appropriate) by HPLC on zwitterionic chiral stationary phases (Chiralpak ZWIX(+) and Chiralpak ZWIX(-)). The interaction and chiral recognition mechanisms were based on the synergistic double ion-paring process between the analyte and the chiral selectors. The chiral separation and elution order were found to be predictable for primary α-amino acids with apolar aliphatic side chains. A systematic investigation was undertaken to gain an insight into the influence of the structural features on the enantiorecognition. The presence of polar and/or aromatic groups in the analyte structure is believed to tune the double ion-paring equilibrium by the involvement of the secondary interaction forces such as hydrogen bonding, Van der Waals forces and π-π stacking in concert with steric parameters. The ZWIX chiral columns were able to separate enantiomers and stereoisomers of various amphoteric compounds with no need for precolumn derivatization. Column switching between ZWIX(+) and ZWIX(-) is believed to be an instrumental tool to reverse or control the enantiomers elution order, due to the complementarity of the applied chiral selectors.

  7. Phase diagram of 4D field theories with chiral anomaly from holography

    CERN Document Server

    Ammon, Martin; Macedo, Rodrigo P

    2016-01-01

    Within gauge/gravity duality, we study the class of four dimensional CFTs with chiral anomaly described by Einstein-Maxwell-Chern-Simons theory in five dimensions. In particular we determine the phase diagram at finite temperature, chemical potential and magnetic field. At high temperatures the solution is given by an electrically and magnetically charged AdS Reissner-Nordstroem black brane. For sufficiently large Chern-Simons coupling and at sufficiently low temperatures and small magnetic fields, we find a new phase with helical order, breaking translational invariance spontaneously. For the Chern-Simons couplings studied, the phase transition is second order with mean field exponents. Since the entropy density vanishes in the limit of zero temperature we are confident that this is the true ground state which is the holographic version of a chiral magnetic spiral.

  8. Generalized Ginzburg–Landau approach to inhomogeneous phases in nonlocal chiral quark models

    Energy Technology Data Exchange (ETDEWEB)

    Carlomagno, J.P. [IFLP, CONICET – Dpto. de Física, FCE, Universidad Nacional de La Plata, C.C. 67, 1900 La Plata (Argentina); CONICET, Rivadavia 1917, 1033 Buenos Aires (Argentina); Gómez Dumm, D., E-mail: dumm@fisica.unlp.edu.ar [IFLP, CONICET – Dpto. de Física, FCE, Universidad Nacional de La Plata, C.C. 67, 1900 La Plata (Argentina); CONICET, Rivadavia 1917, 1033 Buenos Aires (Argentina); Scoccola, N.N. [CONICET, Rivadavia 1917, 1033 Buenos Aires (Argentina); Physics Department, Comisión Nacional de Energía Atómica, Av. Libertador 8250, 1429 Buenos Aires (Argentina); Universidad Favaloro, Solís 453, 1078 Buenos Aires (Argentina)

    2015-05-18

    We analyze the presence of inhomogeneous phases in the QCD phase diagram within the framework of nonlocal chiral quark models. We concentrate in particular in the positions of the tricritical (TCP) and Lifshitz (LP) points, which are studied in a general context using a generalized Ginzburg–Landau approach. We find that for all the phenomenologically acceptable model parametrizations considered the TCP is located at a higher temperature and a lower chemical potential in comparison with the LP. Consequently, these models seem to favor a scenario in which the onset of the first order transition between homogeneous phases is not covered by an inhomogeneous, energetically favored phase.

  9. Chiral symmetry breaking by spatial confinement in tactoidal droplets of lyotropic chromonic liquid crystals.

    Science.gov (United States)

    Tortora, Luana; Lavrentovich, Oleg D

    2011-03-29

    In many colloidal systems, an orientationally ordered nematic (N) phase emerges from the isotropic (I) melt in the form of spindle-like birefringent tactoids. In cases studied so far, the tactoids always reveal a mirror-symmetric nonchiral structure, sometimes even when the building units are chiral. We report on chiral symmetry breaking in the nematic tactoids formed in molecularly nonchiral polymer-crowded aqueous solutions of low-molecular weight disodium cromoglycate. The parity is broken by twisted packing of self-assembled molecular aggregates within the tactoids as manifested by the observed optical activity. Fluorescent confocal microscopy reveals that the chiral N tactoids are located at the boundaries of cells. We explain the chirality induction as a replacement of energetically costly splay packing of the aggregates within the curved bipolar tactoidal shape with twisted packing. The effect represents a simple pathway of macroscopic chirality induction in an organic system with no molecular chirality, as the only requirements are orientational order and curved shape of confinement.

  10. Chiral symmetry breaking by spatial confinement in tactoidal droplets of lyotropic chromonic liquid crystals

    Science.gov (United States)

    Tortora, Luana; Lavrentovich, Oleg D.

    2011-01-01

    In many colloidal systems, an orientationally ordered nematic (N) phase emerges from the isotropic (I) melt in the form of spindle-like birefringent tactoids. In cases studied so far, the tactoids always reveal a mirror-symmetric nonchiral structure, sometimes even when the building units are chiral. We report on chiral symmetry breaking in the nematic tactoids formed in molecularly nonchiral polymer-crowded aqueous solutions of low-molecular weight disodium cromoglycate. The parity is broken by twisted packing of self-assembled molecular aggregates within the tactoids as manifested by the observed optical activity. Fluorescent confocal microscopy reveals that the chiral N tactoids are located at the boundaries of cells. We explain the chirality induction as a replacement of energetically costly splay packing of the aggregates within the curved bipolar tactoidal shape with twisted packing. The effect represents a simple pathway of macroscopic chirality induction in an organic system with no molecular chirality, as the only requirements are orientational order and curved shape of confinement. PMID:21402929

  11. Chiral phase transition in a planar four-Fermi model in a tilted magnetic field

    CERN Document Server

    Ramos, Rudnei O

    2013-01-01

    We study a planar four-Fermi Gross-Neveu model in the presence of a tilted magnetic field, with components parallel and perpendicular to the system's plane. We determine how this combination of magnetic field components, when applied simultaneously, affects the phase diagram of the model. It is shown that each component of the magnetic field causes a competing effect on the chiral symmetry in these fermionic systems. While the perpendicular component of the magnetic field tends to make the chiral symmetry breaking to become stronger, the effect of the parallel component of the field in these planar systems is to weaken the chiral symmetry. We show that this competing effect, when combined also with temperature and chemical potential, can lead to a rich phase diagram, with the emergence of multiple critical points and reentrant phase transitions. We also study how the presence of these multiple critical points and reentrant phases can manifest in the quantum Hall effect. Our results provide a possible way to p...

  12. Chiral assembly of weakly curled hard rods: Effect of steric chirality and polarity

    Energy Technology Data Exchange (ETDEWEB)

    Wensink, H. H., E-mail: wensink@lps.u-psud.fr; Morales-Anda, L. [Laboratoire de Physique des Solides–UMR 8502, Université Paris-Sud & CNRS, 91405 Orsay (France)

    2015-10-14

    We theoretically investigate the pitch of lyotropic cholesteric phases composed of slender rods with steric chirality transmitted via a weak helical deformation of the backbone. In this limit, the model is amenable to analytical treatment within Onsager theory and a closed expression for the pitch versus concentration and helical shape can be derived. Within the same framework, we also briefly review the possibility of alternative types of chiral order, such as twist-bend or screw-like nematic phases, finding that cholesteric order dominates for weakly helical distortions. While long-ranged or “soft” chiral forces usually lead to a pitch decreasing linearly with concentration, steric chirality leads to a much steeper decrease of quadratic nature. This reveals a subtle link between the range of chiral intermolecular interaction and the pitch sensitivity with concentration. A much richer dependence on the thermodynamic state is revealed for polar helices where parallel and anti-parallel pair alignments along the local director are no longer equivalent. It is found that weak temperature variations may lead to dramatic changes in the pitch, despite the lyotropic nature of the assembly.

  13. Unusual dileptions at RHIC a field theoretic approach based on a non-equilibrium chiral phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, F. [Los Alamos National Labs., NM (United States)

    1997-09-22

    This paper contains viewgraphs on unusual dileptons at Brookhaven RHIC. A field theory approach is used based on a non-equilibrium chiral phase transformation utilizing the schroedinger and Heisenberg picture.

  14. Simultaneous Chiral Symmetry Restoration and Deconfinement Consequences for the QCD Phase Diagram

    Science.gov (United States)

    Klähn, Thomas; Fischer, Tobias; Hempel, Matthias

    2017-02-01

    For studies of quark matter in astrophysical scenarios, the thermodynamic bag model is commonly employed. Although successful, it does not account for dynamical chiral symmetry breaking and repulsions due to the vector interaction which is crucial to explain recent observations of massive, two solar mass neutron stars. In Klähn & Fischer we developed the novel vBag quark matter model which takes these effects into account. This article extends vBag to finite temperatures and isospin asymmetry. Another particular feature of vBag is the determination of the deconfinement bag constant {B}{dc} from a given hadronic equation of state in order to ensure that chiral and deconfinement transitions coincide. We discuss consequences of this novel approach for the phase transition construction, the phase diagram, and implications for protoneutron stars.

  15. The $N_f= 2$ chiral phase transition from imaginary chemical potential with Wilson Fermions

    CERN Document Server

    Philipsen, Owe

    2015-01-01

    The order of the thermal transition in the chiral limit of QCD with two dynamical flavours of quarks is a long-standing issue. Still, it is not definitely known whether the transition is of first or second order in the continuum limit. Which of the two scenarios is realized has important implications for the QCD phase diagram and the existence of a critical endpoint at finite densities. Settling this issue by simulating at successively decreased pion mass was not conclusive yet. Recently, an alternative approach was proposed, extrapolating the first order phase transition found at imaginary chemical potential to zero chemical potential with known exponents, which are induced by the Roberge-Weiss symmetry. For staggered fermions on $N_t=4$ lattices, this results in a first order transition in the chiral limit. Here we report of $N_t=4$ simulations with Wilson fermions, where the first order region is found to be large.

  16. Simultaneous chiral symmetry restoration and deconfinement - Consequences for the QCD phase diagram

    CERN Document Server

    Klahn, Thomas; Hempel, Matthias

    2016-01-01

    For studies of quark matter in astrophysical scenarios the thermodynamic bag model (tdBag) is commonly employed. Although successful, it does not account for dynamical chiral symmetry breaking (D$\\chi$SB) and repulsions due to the vector interaction which is crucial to explain recent observations of massive, two solar mass neutron stars. In Kl\\"ahn & Fischer (2015) we developed the novel vBag quark matter model which takes these effects into account. This article extends vBag to finite temperatures and isospin asymmetry. Another particular feature of vBag is the determination of the deconfinement bag constant $B_{\\rm dc}$ from a given hadronic equation of state (EoS) in order to ensure that chiral and deconfinement transitions coincide. We discuss consequences of this novel approach for the phase transition construction and the phase diagram.

  17. Floquet topological phase transitions and chiral edge states in a kagome lattice

    Energy Technology Data Exchange (ETDEWEB)

    He, Chaocheng; Zhang, Zhiyong, E-mail: zyzhang@nju.edu.cn

    2014-09-05

    The Floquet topological phases and chiral edge states in a kagome lattice under a circularly-polarized driving field are studied. In the off-resonant case, the system exhibits the similar character as the kagome lattice model with staggered magnetic fluxes, but the total band width is damped in oscillation. In the on-resonant case, the degeneracy splitting at the Γ point does not always result in a gap. The positions of the other two gaps are influenced by the flat band. With the field intensity increased, these two gaps undergo closing-then-reopening processes, accompanied with the changing of the winding numbers. - Highlights: • A kagome lattice under a circularly-polarized driving field is studied. • The band structures and chiral edge states are studied via exact Floquet method. • Various modifications of the Floquet band structure are found. • Floquet topological phase transitions appear in both off- and on-resonant cases.

  18. Comparative Optical Separation of Racemic Ibuprofen by Using Chiral Stationary Phase

    Institute of Scientific and Technical Information of China (English)

    Dalkeun; PARK; Joong; Kee; LEE; 等

    2002-01-01

    Ibprofen is widely used as a non-steroidal anti-inflammatory drug and poduced as racemic mixture.Its pharmacological activity resides only is S-(+)-enantiomer,and R-(-)-enantiomer is not only inactive but also has many side effects.Thus it is necessary to separate Renantiomer from racemic ibuprofen.We studied optical separation of racemic Ibuprofen with chiral high performance liquid chromatography(HPLC).,Out of three different chiral stationary phases,which were selected on the basis of structure and availability,two were found to be effective.There was optimum eluent composition for each stationary phase for good resolution in optical separation.Resolution decreased with increase of eluent flow rate,but effect of injection volume on resolution was insignificant at high eluent flow rate.

  19. Chiral HPLC analysis of milnacipran and its FMOC-derivative on cellulose-based stationary phases.

    Science.gov (United States)

    Patti, Angela; Pedotti, Sonia; Sanfilippo, Claudia

    2008-02-01

    The HPLC enantioseparation of the last generation antidepressive drug milnacipran (+/-)-1 was investigated on different cellulose-based chiral stationary phases (CSPs). On carbamate-type columns, Chiralcel OD and OD-H (+/-)-1 could be separated with alpha value about 1.20 but the resolution was quite low because of the tailing of the peaks. Direct determination of (+/-)-1 with high selectivity and resolution was obtained on Chiralcel OJ in normal phase mode elution. Precolumn derivatization of milnacipran with Fmoc-Cl gave compound (+/-)-2 which was enantioseparated on all the investigated CSPs and allowed enhanced UV or fluorimetric detection. The Chiralpak IB, that could be considered the immobilized version of Chiralcel OD-H, was found completely ineffective in the chiral recognition of (+/-)-1 and moderately efficient in the separation of (+/-)-2.

  20. The chiral phase transition in two-flavor QCD from imaginary chemical potential

    CERN Document Server

    Bonati, Claudio; D'Elia, Massimo; Philipsen, Owe; Sanfilippo, Francesco

    2014-01-01

    We investigate the order of the finite temperature chiral symmetry restoration transition for QCD with two massless fermions, by using a novel method, based on simulating imaginary values of the quark chemical potential $\\mu=i\\mu_i,\\mu_i\\in\\mathbb{R}$. Our method exploits the fact that, for low enough quark mass $m$ and large enough chemical potential $\\mu_i$, the chiral transition is decidedly first order, then turning into crossover at a critical mass $m_c(\\mu)$. It is thus possible to determine the critical line in the $m - \\mu^2$ plane, which can be safely extrapolated to the chiral limit by taking advantage of the known tricritical indices governing its shape. We test this method with standard staggered fermions and the result of our simulations is that $m_c(\\mu=0)$ is positive, so that the phase transition at zero density is definitely first order in the chiral limit, on our coarse $N_t=4$ lattices with $a\\simeq 0.3\\,\\mathrm{fm}$.

  1. Copolymerization preparation of cationic cyclodextrin chiral stationary phases for drug enantioseparation in chromatography

    OpenAIRE

    sprotocols

    2015-01-01

    Authors: Ren-Qi Wang, Teng-Teng Ong, Ke Huang, Weihua Tang & Siu-Choon Ng ### Abstract We described a facile and effective protocol wherein radical copolymerization is employed to covalently bond cationic β-cyclodextrin (β-CD) onto silica particles with extended linkage, resulting in a chiral stationary phase (IMPCSP) that can be used for the enantioseparation of racemic drugs in both high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). Start...

  2. Novel local symmetries and chiral-symmetry-broken phases in S = 1/2 triangular-lattice Heisenberg model

    Science.gov (United States)

    Baskaran, G.

    1989-01-01

    Using a nonmean-field approach the triangular-lattice S = 1/2 Heisenberg antiferromagnet with nearest- and next-nearest-neighbor couplings is shown undergo an Ising-type phase transition into a chiral-symmetry-broken phase (Kalmeyer-Laughlin-like state) at small T. Removal of next-nearest-neighbor coupling introduces a local Z2 symmetry, thereby suppressing any finite-T chiral order.

  3. Polarized photoluminescence from nematic and chiral- nematic liquid crystalline films

    Science.gov (United States)

    Conger, Brooke Morgan

    Polarization control is key to optoelectronics in terms of the processing and display of optical information. In principle, photonic or electronic excitation of anisotropic films should result in polarized light emission. Because of spontaneous molecular self-assembly, liquid crystals are ideal for the exploration of polarized luminescence. Although most studies on polarized luminescence have been based on liquid crystalline fluid films, solid films are preferred in view of morphological stability. Therefore, the theme of my thesis is the study of polarized luminescence from various fluorescent liquid crystal systems. From the fundamental perspective, a theory modeling the process of polarized photoluminescence was validated using fluorophore doped fluid liquid crystal films. To provide the morphological stability crucial to practical application, polarized fluorescence using vitrifiable and polymeric liquid crystals functionalized with fluorescent moieties was investigated. In addition, liquid crystalline π- conjugated polymers were synthesized and characterized as a new class of optical polymers. The effect of the emission source on achievable polarization from pyrene and carbazole systems was also elucidated. The main observations are as follows: (1) The observed degrees of polarization for all fluorescent liquid crystal systems were found to agree with the theories governing polarized fluorescence. (2) Low molar mass vitrifiable and polymeric liquid crystalline cyanoterphenyl and cyanotolane derivatives were found to yield moderate polarized fluorescence. Monomer emission was established as the decay pathway for the precursors and cyclohexane and polymethacrylate derivatives. (3) Ordered solid films from thiophene and p-phenylene π-conjugated polymers were found to induce significant degrees of polarized fluorescence. (4) Emission from glass-forming pyrenyl derivatives exhibited excimer emission in dilute solution and neat film, whereas in solid hosts it was from monomers. Carbazolyl derivatives exhibited mostly monomer emission in all media. Polarized emission results indicate the ease of pyrenyl alignment presumably because of the favorable regiochemistry and conformational flexibility.

  4. Phenomena at the QCD phase transition in nonequilibrium chiral fluid dynamics (NχFD)

    Energy Technology Data Exchange (ETDEWEB)

    Nahrgang, Marlene [Duke University, Department of Physics, Durham, NC (United States); Herold, Christoph [Suranaree University of Technology, School of Physics, Nakhon Ratchasima (Thailand)

    2016-08-15

    Heavy-ion collisions performed in the beam energy range accessible by the NICA collider facility are expected to produce systems of extreme net-baryon densities and can thus reach yet unexplored regions of the QCD phase diagram. Here, one expects the phase transition between the plasma of deconfined quarks and gluons and the hadronic matter to be of first order. A discovery of the first-order phase transition would as well prove the existence of the QCD critical point, a landmark in the phase diagram. In order to understand possible signals of the first-order phase transition in heavy-ion collision experiments it is very important to develop dynamical models of the phase transition. Here, we discuss the opportunities of studying dynamical effects at the QCD first-order phase transition within our model of nonequilibrium chiral fluid dynamics. (orig.)

  5. Resolution of α-cyclohexyl-mandelic acid enantiomers by two-phase (O/W) recognition chiral extraction

    Institute of Scientific and Technical Information of China (English)

    TANG; KeWen; ZHANG; GuoLi; HUANG; KeLong; LI; Yuanjian; YI; JianMin

    2007-01-01

    This paper presents a new chiral separation technology: two-phase (O/W) recognition chiral extraction. Distribution behavior of α-cyclohexyl-mandelic acid enantiomers was studied in the extraction system with D(L)-isobutyl tartrate in 1,2-dichloroethane organic phase and β-CD derivatives in aqueous phase, and the influence of the kind and concentration of extractant and pH on extraction performance was investigated. The experimental results indicate that two-phase (O/W) recognition chiral extraction is of strong chiral separation ability. HP-β-CD, HE-β-CD and Me-β-CD have higher recognition ability for S-CHMA than that for R-CHMA, among which HP-β-CD has the strongest ability; whereas, D-isobutyl tartrate has reversed recognition ability for them. In the extraction system containing HP-β-CD and D-isobutyl tartrate, e.e.% of S-CHMA in aqueous phase reached 27.6% by one stage extraction, and the distribution ratio for R-CHMA(kR) and for S-CHMA(kS) and separation factor (α) are 2.44, 0.89 and 2.49, respectively. Meanwhile, pH and concentration of extractant have great effects on chiral separation ability. Two-phase (O/W) recognition chiral extraction has great significance for preparative separation of racemic compounds.

  6. Chiral stationary phases based on chitosan bis(methylphenylcarbamate)-(isobutyrylamide) for high-performance liquid chromatography.

    Science.gov (United States)

    Tang, Sheng; Bin, Qin; Chen, Wei; Bai, Zheng-Wu; Huang, Shao-Hua

    2016-04-01

    A series of chitosan bis(methylphenylcarbamate)-(isobutyrylamide) derivatives were synthesized by carbamylating chitosan isobutyrylamide with different methylphenyl isocyanates. Then the prepared chitosan derivatives were coated onto 3-aminopropyl silica particles, resulting in a series of new chiral stationary phases (CSPs) for high-performance liquid chromatography. It was observed that the chiral recognition abilities of these coated-type CSPs depended very much on the substituents on the phenyl moieties of the chitosan derivatives, the eluent composition, as well as the structure of racemates. As a typical example, the eluent tolerance of the prepared CSP with the best enantioseparation ability was investigated in detail, and the results revealed that the CSP exhibited extraordinary solvent tolerance and could still work without significant loss in enantioseparation capability after being flushed with chloroform (100%), ethyl acetate (100%) and even THF/n-hexane (70/30, v/v), while the traditional coated-type CSPs based on the cellulose and amylose derivatives, such as cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) and amylose tris(3,5-dimethylphenylcarbamate) (ADMPC), might be dissolved or highly swollen in these eluents. Therefore, the application of the resultant CSPs could address the problem of the dissolution and high swelling of traditional coated-type CSPs in some unusual eluents, broadening the possibility of eluent choice. In addition, a comparison of the prepared CSPs with the well known CDMPC- and ADMPC- based CSPs concerning the chiral recognition ability was also made. Separation performances achieved on the as-prepared CSPs in different eluents were found to be even superior to CDMPC- and ADMPC-based CSPs for the tested chiral compounds. In summary, we could safely draw the conclusion that the CSPs derived from chitosan isobutyrylamide derivatives were capable of excellent chiral recognition ability, and meanwhile possessed satisfactory

  7. Oriented circular dichroism analysis of chiral surface-anchored metal-organic frameworks grown by liquid-phase epitaxy and upon loading with chiral guest compounds

    KAUST Repository

    Gu, Zhigang

    2014-06-17

    Oriented circular dichroism (OCD) is explored and successfully applied to investigate chiral surface-anchored metal-organic frameworks (SURMOFs) based on camphoric acid (D- and Lcam) with the composition [Cu2(Dcam) 2x(Lcam)2-2x(dabco)]n (dabco=1,4-diazabicyclo- [2.2.2]-octane). The three-dimensional chiral SURMOFs with high-quality orientation were grown on quartz glass plates by using a layer-by-layer liquid-phase epitaxy method. The growth orientation, as determined by X-ray diffraction (XRD), could be switched between the [001] and [110] direction by using either OH- or COOH-terminated substrates. These SURMOFs were characterized by using OCD, which confirmed the ratio as well as the orientation of the enantiomeric linker molecules. Theoretical computations demonstrate that the OCD band intensities of the enantiopure [Cu2(Dcam)2(dabco)] n grown in different orientations are a direct result of the anisotropic nature of the chiral SURMOFs. Finally, the enantiopure [Cu 2(Dcam)2(dabco)]n and [Cu2(Lcam) 2(dabco)]n SURMOFs were loaded with the two chiral forms of ethyl lactate [(+)-ethyl-D-lactate and (-)-ethyl-L-lactate)]. An enantioselective enrichment of >60 % was observed by OCD when the chiral host scaffold was loaded from the racemic mixture. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Quark matter in a parallel electric and magnetic field background: Chiral phase transition and equilibration of chiral density

    Science.gov (United States)

    Ruggieri, M.; Peng, G. X.

    2016-05-01

    In this article, we study spontaneous chiral symmetry breaking for quark matter in the background of static and homogeneous parallel electric field E and magnetic field B . We use a Nambu-Jona-Lasinio model with a local kernel interaction to compute the relevant quantities to describe chiral symmetry breaking at a finite temperature for a wide range of E and B . We study the effect of this background on the inverse catalysis of chiral symmetry breaking for E and B of the same order of magnitude. We then focus on the effect of the equilibration of chiral density n5 , produced dynamically by an axial anomaly on the critical temperature. The equilibration of n5 , a consequence of chirality-flipping processes in the thermal bath, allows for the introduction of the chiral chemical potential μ5, which is computed self-consistently as a function of the temperature and field strength by coupling the number equation to the gap equation and solving the two within an expansion in E /T2 , B /T2 , and μ52/T2 . We find that even if chirality is produced and equilibrates within a relaxation time τM , it does not change drastically the thermodynamics, with particular reference to the inverse catalysis induced by the external fields, as long as the average μ5 at equilibrium is not too large.

  9. Scaling behavior of chiral phase transition in two-flavor QCD with improved Wilson quarks at finite density

    CERN Document Server

    Ejiri, S; Aoki, S; Kanaya, K; Ohno, H; Saito, H; Hatsuda, T; Maezawa, Y; Umeda, T

    2010-01-01

    We study scaling behavior of a chiral order parameter performing a simulation of two-flavor QCD with improved Wilson quarks. It has been shown that the scaling behavior of the chiral order parameter defined by a Ward-Takahashi identity agrees with the scaling function of the three-dimensional O(4) spin model at zero chemical potential. We extend the scaling study to finite density QCD. Calculating derivatives of the chiral order parameter with respect to the chemical potential in two-flavor QCD, the scaling property of chiral phase transition is discussed in the low density region. We moreover calculate the curvature of the phase boundary of the chirl phase transition in the temperature and chemical potential plane assuming the O(4) scaling relation.

  10. Fine structure of point defects and soliton decay in nematic liquid crystals

    OpenAIRE

    Penzenstadler, E.; Trebin, H. -R.

    1989-01-01

    On the basis of Landau-de Gennes-theory it is demonstrated that point defects in nematic liquid crystals may have a biaxial nonsingular core. From this result a critical diameter is derived for linear topological solitons in nematics. Solitons of smaller diameter can relax to the uniform nematic state without energy barrier via an intermediate biaxial phase.

  11. Chiral separation of cathinone and amphetamine derivatives by HPLC/UV using sulfated ß-cyclodextrin as chiral mobile phase additive.

    Science.gov (United States)

    Taschwer, Magdalena; Seidl, Yvonne; Mohr, Stefan; Schmid, Martin G

    2014-08-01

    In the last years the identification of new legal and illegal highs has become a huge challenge for the police and prosecution authorities. In an analytical context, only a few analytical methods are available to identify these new substances. Moreover, many of these recreational drugs are chiral and it is supposed that the enantiomers differ in their pharmacological potency. Since nonenantioselective synthesis is easier and cheaper, they are mainly sold as racemic mixtures. The goal of this research work was to develop an inexpensive method for the chiral separation of cathinones and amphetamines. This should help to discover if the substances are sold as racemic mixtures and give further information about their quality as well as their origin. Chiral separation of a set of 6 amphetamine and 25 cathinone derivatives, mainly purchased from various Internet shops, is presented. A LiChrospher 100 RP-18e, 250 x 4 mm, 5 µm served as the stationary phase. The chiral mobile phase consisted of methanol, water, and sulfated ß-cyclodextrin. Measurements were performed under isocratic conditions in reversed phase mode using UV detection. Four model compounds of the two substance classes were used to optimize the mobile phase. Under final conditions (methanol:water 2.5:97.5 + 2% sulfated ß-cyclodextrin) enantiomers of amphetamine and five derivatives were baseline separated within 23 min. In all, 17 cathinones were completely or partially chirally separated. However, as only 3 of 25 cathinones were baseline resolved, the application of this method is limited for cathinone analogs. Additionally, the results were compared with an RP-8e column.

  12. Pulse and quench induced dynamical phase transition in a chiral multiferroic spin chain

    Science.gov (United States)

    Azimi, M.; Sekania, M.; Mishra, S. K.; Chotorlishvili, L.; Toklikishvili, Z.; Berakdar, J.

    2016-08-01

    Quantum dynamics of magnetic order in a chiral multiferroic chain is studied. We consider two different scenarios: ultrashort terahertz excitations or a sudden electric field quench. Performing analytical and numerical exact diagonalization calculations, we trace the pulse induced spin dynamics and extract quantities that are relevant to quantum information processing. In particular, we analyze the dynamics of the system chirality, the von Neumann entropy, and the pairwise and many-body entanglement. If the characteristic frequencies of the generated states are noncommensurate, then a partial loss of pair concurrence occurs. Increasing the system size, this effect becomes even more pronounced. Many-particle entanglement and chirality are robust and persist in the incommensurate phase. To analyze the dynamical quantum transitions for the quenched and pulsed dynamics we combined the Weierstrass factorization technique for entire functions and the Lanczos exact diagonalization method. For a small system we obtained analytical results including the rate function of the Loschmidt echo. Exact numerical calculations for a system up to 40 spins confirm phase transition. Quench-induced dynamical transitions have been extensively studied recently. Here we show that related dynamical transitions can be achieved and controlled by appropriate electric field pulses.

  13. Asymmetric cyclopropanation of chalcones using chiral phase-transfer catalysts

    OpenAIRE

    2013-01-01

    The first phase-transfer catalyzed cyclopropanation reaction of chalcones using bromomalonates as the nucleophiles in a Michael Initiated Ring Closing reaction (MIRC) was developed. Key to success was the use of a free OH-containing cinchona alkaloid ammonium salt catalyst and carefully optimized liquid/liquid reaction conditions. The reaction performed well for electron neutral and electron deficient chalcones giving the products in yields up to 98% and with enantiomeric ratios up to 91:9.

  14. Frustrated smectic liquid crystalline phases in lactic acid derivatives

    Science.gov (United States)

    Glogarová, M.; Novotná, V.

    2016-08-01

    We have prepared and studied a series of compounds with different types of molecular core and lactate unit in the chiral terminal chain. We draw a survey and comparison of their mesomorphic properties with respect to the occurrence of twist grain boundary (TGB) phases. The materials exhibit extremely wide TGBA phase more than 60K broad, unique TGBA-TGBC-SmC*-SmCA* phase sequence and unique re-entrant TGBA phase below the SmA phase. TGB phases have been induced in binary mixtures of molecules with different molecular shape and chirality (chiral lactic acid derivative and non-chiral hockey-stick mesogen). Unique effect is observed for compounds with TGBA phase, where the applied electric field transforms the planar texture into the homeotropic one, homogeneously dark in crossed polarizers. The process is analogy of the Frederiks transition so far known only for nematics. This effect, changing the bright state to the dark one, is promising for applications.

  15. New studies on molecular chirality in the gas phase: enantiomer differentiation and determination of enantiomeric excess.

    Science.gov (United States)

    Patterson, David; Schnell, Melanie

    2014-06-21

    Chirality plays a fundamental role in the activity of biological molecules and broad classes of chemical reactions. The chemistry of life is built almost exclusively on left-handed amino acids and right-handed sugars, a phenomenon known as "homochirality of life". Furthermore, most drugs developed in the last decade are of specified chirality. Thus, fast and reliable methods that can differentiate molecules of different handedness, determine the enantiomeric excess of even molecular mixtures, and allow for an unambiguous determination of molecular handedness are of great interest, in particular with respect to complex mixtures. In this perspective article, we discuss the recent developments, with an emphasis on modern spectroscopic methods using gas-phase samples, such as photoelectron circular dichroism, Coulomb explosion imaging, and microwave three-wave mixing.

  16. The effect of the Polyakov loop on the chiral phase transition

    Directory of Open Access Journals (Sweden)

    Szép Zs.

    2011-04-01

    Full Text Available The Polyakov loop is included in the S U(2L × S U(2R chiral quark-meson model by considering the propagation of the constituent quarks, coupled to the (σ, π meson multiplet, on the homogeneous background of a temporal gauge field, diagonal in color space. The model is solved at finite temperature and quark baryon chemical potential both in the chiral limit and for the physical value of the pion mass by using an expansion in the number of flavors Nf. Keeping the fermion propagator at its tree-level, a resummation on the pion propagator is constructed which resums infinitely many orders in 1/Nf, where O(1/Nf represents the order at which the fermions start to contribute in the pion propagator. The influence of the Polyakov loop on the tricritical or the critical point in the µq – T phase diagram is studied for various forms of the Polyakov loop potential.

  17. Quark Matter in a Parallel Electric and Magnetic Field Background: Equilibrated Chiral Density Effect on Chiral Phase Transition

    CERN Document Server

    Ruggieri, M

    2016-01-01

    In this article we study spontaneous chiral symmetry breaking for quark matter in the background of an electric-magnetic flux tube with static, homogeneous and parallel electric field $\\bm E$ and magnetic field $\\bm B$. We use a Nambu-Jona-Lasinio model with a local kernel interaction to compute the relevant quantities to describe chiral symmetry breaking at finite temperature for a wide range of $E$ and $B$. We study the effect of the flux tube background on inverse catalysis of chiral symmetry breaking for $E$ and $B$ of the same order of magnitude. We then focus on the effect of equilibration of chiral density, $n_5$, produced dynamically by axial anomaly on the critical temperature. The equilibration of $n_5$, a consequence of chirality flipping processes in the thermal bath, allows for the introduction of the chiral chemical potential, $\\mu_5$, which is computed self-consistently as a function of temperature and field strength by coupling the number equation to the gap equation. We find that even if chir...

  18. Synthesis of chiral dopants based on carbohydrates.

    Science.gov (United States)

    Tsuruta, Toru; Koyama, Tetsuo; Yasutake, Mikio; Hatano, Ken; Matsuoka, Koji

    2014-07-01

    Chiral dopants based on carbohydrates for nematic liquid crystals were synthesized from D-glucose, and their helical twisting power (HTP) values were evaluated. The chiral dopants induced helices in the host nematic liquid crystals. An acetyl derivative having an ether-type glycosidic linkage between carbohydrate and a mesogenic moiety showed the highest HTP value of 10.4 μm(-1), while an acetyl derivative having an anomeric ester-type linkage did not show any HTP. It was surprising that this molecule had no HTP despite the presence of chirality in the molecule. A relationship between HTP and specific rotation was not observed in this study.

  19. The $N_f=2 chiral phase transition from imaginary chemical potential with Wilson Fermions

    CERN Document Server

    Cuteri, Francesca; Philipsen, Owe; Pinke, Christopher

    2015-01-01

    The finite temperature chiral and deconfinement phase transitions at zero density for light and heavy quarks, respectively, have analytic continuations to imaginary chemical potential. At some critical imaginary chemical potential, they meet the Roberge-Weiss transition between adjacent $Z3$ sectors. For light and heavy quarks, where the chiral and deconfinement transitions are first order, the transition lines meet in a triple point. For intermediate masses chiral or deconfinement transitions are crossover and the Roberge-Weiss transition ends in a second order point. At the boundary between these regimes the junction is a tricritical point, as shown in studies with $N_f=2,3$ flavors of staggered and Wilson quarks on $N_\\tau=4$ lattices. Employing finite size scaling we investigate the nature of this point as a function of quark mass for $N_f=2$ flavors of Wilson fermions with a temporal lattice extent of $N_\\tau=6$. In particular we are interested in the change of the location of tricritical points compared...

  20. Floquet engineering of Haldane Chern insulators and chiral bosonic phase transitions

    Science.gov (United States)

    Plekhanov, Kirill; Roux, Guillaume; Le Hur, Karyn

    2017-01-01

    The realization of synthetic gauge fields has attracted a lot of attention recently in relation to periodically driven systems and the Floquet theory. In ultracold atom systems in optical lattices and photonic networks, this allows one to simulate exotic phases of matter such as quantum Hall phases, anomalous quantum Hall phases, and analogs of topological insulators. In this paper, we apply the Floquet theory to engineer anisotropic Haldane models on the honeycomb lattice and two-leg ladder systems. We show that these anisotropic Haldane models still possess a topologically nontrivial band structure associated with chiral edge modes. Focusing on (interacting) boson systems in s -wave bands of the lattice, we show how to engineer through the Floquet theory, a quantum phase transition (QPT) between a uniform superfluid and a Bose-Einstein condensate analog of Fulde-Ferrell-Larkin-Ovchinnikov states, where bosons condense at nonzero wave vectors. We perform a Ginzburg-Landau analysis of the QPT on the graphene lattice, and compute observables such as chiral currents and the momentum distribution. The results are supported by exact diagonalization calculations and compared with those of the isotropic situation. The validity of high-frequency expansion in the Floquet theory is also tested using time-dependent simulations for various parameters of the model. Last, we show that the anisotropic choice for the effective vector potential allows a bosonization approach in equivalent ladder (strip) geometries.

  1. Phase transitions and ordering structures of a model of a chiral helimagnet in three dimensions

    Science.gov (United States)

    Nishikawa, Yoshihiko; Hukushima, Koji

    2016-08-01

    Phase transitions in a classical Heisenberg spin model of a chiral helimagnet with the Dzyaloshinskii-Moriya interaction in three dimensions are numerically studied. By using the event-chain Monte Carlo algorithm recently developed for particle and continuous spin systems, we perform equilibrium Monte Carlo simulations for large systems up to about 106 spins. Without magnetic fields, the system undergoes a continuous phase transition with critical exponents of the three-dimensional XY model, and a uniaxial periodic helical structure emerges in the low-temperature region. In the presence of a magnetic field perpendicular to the axis of the helical structure, it is found that there exists a critical point on the temperature and magnetic-field phase diagram and that above the critical point the system exhibits a phase transition with strong divergence of the specific heat and the uniform magnetic susceptibility.

  2. Chiral separation of novel diazenes on a polysaccharide-based stationary phase in the reversed-phase mode.

    Science.gov (United States)

    Vojtylová, Terézia; Hamplová, Věra; Galewski, Zbigniew; Korbecka, Izabela; Sýkora, David

    2017-01-31

    Chiral high-performance liquid chromatography separation of two recently synthesized liquid crystalline materials C1 and C2 was studied in the reversed-phase mode. Both materials have an azo-moiety and one chiral centre in their molecular structures. They were available in racemic and pure S forms. For the enantiomeric separations, a Chiralpak AY-RH stationary phase based on amylose tris(5-chloro-2-methylphenylcarbamate) coated on 5 μm silica was used. The compounds were analyzed in both of their possible forms, the more thermodynamically stable E form and the labile Z form. The conditions and time scale of the UV-induced E to Z transition were briefly evaluated. Under the optimized conditions, we were able to baseline separate S and R enantiomers of both of the studied materials not only in their E forms but also in their Z forms. In comparison to the separation in the normal-phase mode, which we have reported recently, the resolution in the reversed-phase mode is significantly better. Interestingly, peak reversal was noticed for the S and R enantiomers when the separation was carried out with E versus Z forms of both compounds. This article is protected by copyright. All rights reserved.

  3. Progress in vacuum susceptibilities and their applications to the chiral phase transition of QCD

    CERN Document Server

    Cui, Zhu-Fang; Shi, Yuan-Mei; Wang, Yong-Long; Zong, Hong-Shi

    2015-01-01

    The QCD vacuum condensates and various vacuum susceptibilities are all important parameters which characterize the nonperturbative properties of the QCD vacuum. In the QCD sum rules external field formula, various QCD vacuum susceptibilities play important roles in determining the properties of hadrons. In this paper, we review the recent progress in studies of vacuum susceptibilities together with their applications to the chiral phase transition of QCD. The results of the tensor, the vector, the axial-vector, the scalar, and the pseudo-scalar vacuum susceptibilities are shown in detail in the framework of Dyson-Schwinger equations.

  4. Progress in vacuum susceptibilities and their applications to the chiral phase transition of QCD

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Zhu-Fang, E-mail: phycui@nju.edu.cn [Department of Physics, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing, 100190 (China); Hou, Feng-Yao [Institute of Theoretical Physics, CAS, Beijing 100190 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing, 100190 (China); Shi, Yuan-Mei [Department of Physics, Nanjing University, Nanjing 210093 (China); Department of Physics and Electronic Engineering, Nanjing Xiaozhuang University, Nanjing 211171 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing, 100190 (China); Wang, Yong-Long [Department of Physics, Nanjing University, Nanjing 210093 (China); Department of Physics, School of Science, Linyi University, Linyi 276005 (China); Zong, Hong-Shi, E-mail: zonghs@nju.edu.cn [Department of Physics, Nanjing University, Nanjing 210093 (China); Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing 210093 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, CAS, Beijing, 100190 (China)

    2015-07-15

    The QCD vacuum condensates and various vacuum susceptibilities are all important parameters which characterize the nonperturbative properties of the QCD vacuum. In the QCD sum rules external field formula, various QCD vacuum susceptibilities play important roles in determining the properties of hadrons. In this paper, we review the recent progress in studies of vacuum susceptibilities together with their applications to the chiral phase transition of QCD. The results of the tensor, the vector, the axial–vector, the scalar, and the pseudo-scalar vacuum susceptibilities are shown in detail in the framework of Dyson–Schwinger equations.

  5. Fractal butterflies of chiral fermions in bilayer graphene: Phase transitions and emergent properties

    Science.gov (United States)

    Ghazaryan, Areg; Chakraborty, Tapash

    2015-12-01

    We have studied the influence of electron-electron interaction on the fractal butterfly spectrum of Dirac fermions in biased bilayer graphene in the fractional quantum Hall effect (FQHE) regime. We demonstrate that the butterfly spectrum exhibits remarkable phase transitions between the FQHE gap and the butterfly gap for chiral electrons in bilayer graphene, when the periodic potential strength or the bias voltage is varied. We also find that, in addition to those phase transitions, by varying the bias voltage one can effectively control the periodic potential strength experienced by the electrons. The electron-electron interaction causes the butterfly spectrum to exhibit new gaps inside the Bloch sub-bands not found in the single-particle case. We expect that both the observed phase transition and other new features in the butterfly spectrum of interacting Dirac fermions will be of great interest to researchers from diverse fields.

  6. HPLC Enantioseparation of Phenylcarbamic Acid Derivatives by Using Macrocyclic Chiral Stationary Phases

    Directory of Open Access Journals (Sweden)

    Hroboňová Katarína

    2016-06-01

    Full Text Available The HPLC by using chiral stationary phases based on macrocyclic antibiotics, dimethylphenyl carbamate cyklofructan 7 and β-cyclodextrin in terms of polar-organic separation mode (mobile phase methanol/acetonitrile/acetic acid/triethylamine were used for enantioseparation of alkoxy derivatives of phenylcarbamic acid. The effect of the analyte structures on the efficiency of enantioseparation was investigated. The most suitable stationary phase was teicoplanin aglycone, where the separations of the enantiomers were obtained (the resolution value from 0.65 to 2.90, depending on the structure of the analyte. Significant effect on the resolution of the enantiomers has position of alkoxy substituent in the hydrophobic part of the molecule. The enantiorecognition was achieved for 3-alkoxysubstituted derivatives.

  7. Chiral superconductors.

    Science.gov (United States)

    Kallin, Catherine; Berlinsky, John

    2016-05-01

    Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.

  8. Influence of Mobile Phase Composition on the Enantioseparation of Methoxyl Flavanones with Self-prepared CDMPC Column and Chiral Recognition Mechanism

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The influence of different alcohol modifiers in mobile phase on the chiral separation of 4`-methoxyl flavanone, 5-methoxyl flavanone and 6-methoxyl flavanone on cellulose tris (3, 5-dimethylphenylcarbamate) (CDMPC) column was studied and the chiral recognition mechanism was discussed. Using hexane-tert-butanol (1.31 mol L-1) as the mobile phase, those three methoxyl flavanones were excellently separated on CDMPC chiral column.

  9. [Separation mechanism of chiral stationary phase based on quinine and crown ether for the direct stereoselective separation of amino acids].

    Science.gov (United States)

    Wu, Haixia; Wang, Dongqiang; Zhao, Jianchao; Ke, Yanxiong; Liang, Xinmiao

    2016-01-01

    A novel chiral stationary phase combining quinine and crown ether (QN-CR CSP) was developed to separate amino acid enantiomers. This CSP showed good enantioselectivity for some amino acids. Since the synergistic effect of ion exchange and complexation in chiral recognition of amino acids, a new adsorption isotherm was built. Using the method of frontal analysis by characteristic point (FACP), the adsorption isotherms of tryptophan (Trp) under different mobile phase conditions were determined and fitted the proposed adsorption isotherm model well. With the increase of the competition between metal cationic and amino to crown ether, the equilibrium constant of complexing adsorption was found increased. The chiral separation ability was decreased. The adsorption isotherm improved the understanding of the retention behavior of amino acids on QN-CR CSP, which was also benefit to optimize the structure of the stationary phase.

  10. Molecular engineering of discotic nematic liquid crystals

    Indian Academy of Sciences (India)

    Sandeep Kumar

    2003-08-01

    Connecting two columnar phase forming discotic mesogens via a short rigid spacer leads to the formation of a -conjugated discotic dimer showing discotic nematic (D) phase. Attaching branched-alkyl chains directly to the core in hexaalkynylbenzene resulted in the stabilisation of D phase at ambient temperature. Pentalkynylbenzene derivatives possessing a combination of normal-and branched-alkoxy chains display a very broad D phase which is stable well below and above the room temperature.

  11. A resolution approach of racemic phenylalanine with aqueous two-phase systems of chiral tropine ionic liquids.

    Science.gov (United States)

    Wu, Haoran; Yao, Shun; Qian, Guofei; Yao, Tian; Song, Hang

    2015-10-30

    Aqueous two-phase systems (ATPS) based on tropine type chiral ionic liquids and inorganic salt solution were designed and prepared for the enantiomeric separation of racemic phenylalanine. The phase behavior of IL-based ATPS was comprehensive investigated, and phase equilibrium data were correlated by Merchuk equation. Various factors were also systematically investigated for their influence on separation efficiency. Under the appropriate conditions (0.13g/g [C8Tropine]pro, 35mg/g Cu(Ac)2, 20mg/g d,l-phenylalanine, 0.51g/g H2O and 0.30g/g K2HPO4), the enantiomeric excess value of phenylalanine in solid phase (mainly containing l-enantiomer) was 65%. Finally, the interaction mechanism was studied via 1D and 2D NMR. The results indicate that d-enantiomer of phenylalanine interacts more strongly with chiral ILs and Cu(2+) based on the chiral ion-pairs space coordination mechanism, which makes it tend to remain in the top IL-rich phase. By contrast, l-enantiomer is transferred into the solid phase. Above chiral ionic liquids aqueous two-phase systems have demonstrated obvious resolution to racemic phenylalanine and could be promising alterative resolution approach for racemic amino acids in aqueous circumstance.

  12. Chiral-phase high-performance liquid chromatography of rotenoid racemates

    Science.gov (United States)

    Abidi, S.L.

    1987-01-01

    The high-performance liquid chromatograhic (HPLC) behavior of parent rotenoids (type I) and the hydroxyl-analogues (type II) on three different chiral stationary phases (CSPs) was studied. Separations of optical isomers were achieved in various degrees depending largely upon the rotenoidal structures and the CSP types employed. Enantiomers of all but elliptone compounds were separable on β-cyclodextrin-bonded silica (CDS). Without exception, the 12a-hydroxyrotenoid antipodes were resolved on Pirkle's phenylglycine-bonded silica (PGS) despite unsuccessful attenmpts to resolve the type I rotenoidal racemates. Conversely, optical resolution of the latter rotenoids was accomplished by using a helical polytriphenylmethylacrylate-coated silica (TPS) column and the observed separation factors (α values) ranged from 1.14 to 1.90. The results from HPLC of type II rotenoids on TPS (α = 1.00–1.63) suggested that variations in E-ring structures had profound influence on the resolution outcome. Conjugated double bonds on the E-ring and the desisopropylation of the five-membered E-ring ot type II rotenoids appeared to be important structural features for chiral recognition involving the TPS substrate. In both reversed-phase (CDS) and normal-pahse (PGS and TPS) HPLC modes, the less polar enantiomers were the 6aβ,12aβ-rotenoids as observed in most cases, though this relationship was reversed in the cases of deguelin and hydroxyelliptone probably due to conformational effects of rotenoidal ring systems.

  13. Development and Validation of a Reversed-Phase Chiral HPLC Method to Determine the Chiral Purity of Bulk Batches of (S)-Enantiomer in Afoxolaner.

    Science.gov (United States)

    Kumar, Satish; Rustum, Abu; Padivitage, Nilusha

    2016-10-13

    Afoxolaner is a new antiparasitic molecule from the isoxazoline family that acts on insect acarine γ-aminobutyric acid and glutamate receptors. Afoxolaner is a racemic mixture, which has a chiral center at the isoxazoline ring. A reversed-phase chiral HPLC method has been developed to determine the chiral purity of bulk batches of (S)-enantiomer in afoxolaner for the first time. This method can also be used to verify that afoxolaner is a racemic mixture, which was demonstrated by specific rotation. ChromSword, an artificial intelligence method development tool, was used for initial method development. The column selected for the final method was CHIRALPAK AD-RH (150 × 4.6 mm, 5 μm particle size), maintained at 45°C, and isocratic elution using water-isopropanol-acetonitrile (40 + 50 + 10, v/v/v) as the mobile phase with a detection wavelength of 312 nm. The run time for the method was 11 min. The resolution and selectivity factors of the two enantiomers were 2.3 and 1.24, respectively. LOQ and LOD of the method were 1.6 and 0.8 μg/mL, respectively. This method was appropriately validated according to International Conference on Harmonization guidelines for its intended use.

  14. Theory of solvation in polar nematics

    CERN Document Server

    Kapko, V; Kapko, Vitaly; Matyushov, Dmitry V.

    2005-01-01

    We develop a linear response theory of solvation of ionic and dipolar solutes in anisotropic, axially symmetric polar solvents. The theory is applied to solvation in polar nematic liquid crystals. The formal theory constructs the solvation response function from projections of the solvent dipolar susceptibility on rotational invariants. These projections are obtained from Monte Carlo simulations of a fluid of dipolar spherocylinders which can exist both in the isotropic and nematic phase. Based on the properties of the solvent susceptibility from simulations and the formal solution, we have obtained a formula for the solvation free energy which incorporates experimentally available properties of nematics and the length of correlation between the dipoles in the liquid crystal. Illustrative calculations are presented for the Stokes shift and Stokes shift correlation function of coumarin-153 in 4-n-pentyl-4'-cyanobiphenyl (5CB) and 4,4-n-heptyl-cyanopiphenyl (7CB) solvents as a function of temperature in both th...

  15. Preparation and Evaluation of a Novel Cellulose Tris(N-3,5-dimethylphenylcarbamate) Chiral Stationary Phase

    Institute of Scientific and Technical Information of China (English)

    GE,Jin; ZHAO,Liang; SHI,Yan-Ping

    2008-01-01

    A novel cellulose tris(N-3,5-dimethylphenylcarbamate) (CDMPC) chiral stationary phase (CSP) was prepared by coating CDMPC on TiO2/SiO2, which was prepared by coating titania nanoparticles on silica through a self-assemble technique. At first, 2-hydroxyl-phenyl acetonitrile and α-phenylethanol were separated on this new CSP to evaluate the chiral separation ability. Then, two pesticides, matalaxyl and diclofop-methyl were separated.The influence of the mobile phase composition on the enantioselectivity was discussed, and the repeatability and stability of the CSP were studied too.

  16. Preparation of new hybrid organic/inorganic polymeric chiral stationary phases for ligand-exchange chromatography

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Three new hybrid organic/inorganic polymeric ligand-exchange chiral stationary phases were developed by radical chain transfer reaction and surface grafting on silica gel, and successfully used for the enantioseparations of DL-amino acids and DL-hydroxyl acids. The resolutions were achieved by using water containing 2.0 × 10-4 mol/L of CuAc2 as a mobile phase, column temperature of 40 ℃, flow rate of 1.0 mL/min and detection at UV 254 mn. The elution order of D-isomer before L-isomer was observed for all DL-amino acids resolved except DL-Pro.

  17. Consequences of simultaneous chiral symmetry breaking and deconfinement for the isospin symmetric phase diagram

    Science.gov (United States)

    Fischer, Tobias; Klähn, Thomas; Hempel, Matthias

    2016-08-01

    The thermodynamic bag model (tdBag) has been applied widely to model quark matter properties in both heavy-ion and astrophysics communities. Several fundamental physics aspects are missing in tdBag, e.g., dynamical chiral symmetry breaking (D χ SB) and repulsions due to the vector interaction are both included explicitly in the novel vBag quark matter model of Klähn and Fischer (Astrophys. J. 810, 134 (2015)). An important feature of vBag is the simultaneous D χ SB and deconfinement, where the latter links vBag to a given hadronic model for the construction of the phase transition. In this article we discuss the extension to finite temperatures and the resulting phase diagram for the isospin symmetric medium.

  18. Kagome Chiral Spin Liquid as a Gauged U (1 ) Symmetry Protected Topological Phase

    Science.gov (United States)

    He, Yin-Chen; Bhattacharjee, Subhro; Pollmann, Frank; Moessner, R.

    2015-12-01

    While the existence of a chiral spin liquid (CSL) on a class of spin-1 /2 kagome antiferromagnets is by now well established numerically, a controlled theoretical path from the lattice model leading to a low-energy topological field theory is still lacking. This we provide via an explicit construction starting from reformulating a microscopic model for a CSL as a lattice gauge theory and deriving the low-energy form of its continuum limit. A crucial ingredient is the realization that the bosonic spinons of the gauge theory exhibit a U (1 ) symmetry protected topological (SPT) phase, which upon promoting its U (1 ) global symmetry to a local gauge structure ("gauging"), yields the CSL. We suggest that such an explicit lattice-based construction involving gauging of a SPT phase can be applied more generally to understand topological spin liquids.

  19. Consequences of simultaneous chiral symmetry breaking and deconfinement for the isospin symmetric phase diagram

    CERN Document Server

    Fischer, Tobias; Hempel, Matthias

    2016-01-01

    The thermodynamic bag model (tdBag) has been applied widely to model quark matter properties in both heavy-ion and astrophysics communities. Several fundamental physics aspects are missing in tdBag, e.g., dynamical chiral symmetry breaking (D$\\chi$SB) and repulsions due to the vector interaction are both included explicitly in the novel vBag quark matter model of Kl\\"ahn and Fischer (2015) (Astrophys. J. 810, 134 (2015)). An important feature of vBag is the simultaneous D$\\chi$SB and deconfinement, where the latter links vBag to a given hadronic model for the construction of the phase transition. In this article we discuss the extension to finite temperatures and the resulting phase diagram for the isospin symmetric medium.

  20. Low-Energy Kπ Phase Shifts in Chiral SU(3) Quark Model

    Institute of Scientific and Technical Information of China (English)

    HUANG Fei; ZHANG Zong-Ye; YU You-Wen

    2005-01-01

    The low-energy region kaon-pion S- and P-wave phase shifts with isospin I = 1/2 and I = 3/2 are dynamically studied in the chiral SU(3) quark model by solving a resonating group method equation. The model parameters are taken to be the values fitted by the energies of the baryon ground states and the kaon-nucleon elastic scattering phase shifts of different partial waves. As a preliminary study the s-channel q(-q) annihilation interactions are not included since they only act in the very short range and are subsequently assumed to be unimportant in the low-energy domain. The numerical results are in qualitative agreement with the experimental data.

  1. Consequences of simultaneous chiral symmetry breaking and deconfinement for the isospin symmetric phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Tobias; Klaehn, Thomas [University of Wroclaw, Institute of Theoretical Physics, Wroclaw (Poland); Hempel, Matthias [University of Basel, Department of Physics, Basel (Switzerland)

    2016-08-15

    The thermodynamic bag model (tdBag) has been applied widely to model quark matter properties in both heavy-ion and astrophysics communities. Several fundamental physics aspects are missing in tdBag, e.g., dynamical chiral symmetry breaking (D χ SB) and repulsions due to the vector interaction are both included explicitly in the novel vBag quark matter model of Klaehn and Fischer (Astrophys. J. 810, 134 (2015)). An important feature of vBag is the simultaneous D χ SB and deconfinement, where the latter links vBag to a given hadronic model for the construction of the phase transition. In this article we discuss the extension to finite temperatures and the resulting phase diagram for the isospin symmetric medium. (orig.)

  2. Kagome Chiral Spin Liquid as a Gauged U(1) Symmetry Protected Topological Phase.

    Science.gov (United States)

    He, Yin-Chen; Bhattacharjee, Subhro; Pollmann, Frank; Moessner, R

    2015-12-31

    While the existence of a chiral spin liquid (CSL) on a class of spin-1/2 kagome antiferromagnets is by now well established numerically, a controlled theoretical path from the lattice model leading to a low-energy topological field theory is still lacking. This we provide via an explicit construction starting from reformulating a microscopic model for a CSL as a lattice gauge theory and deriving the low-energy form of its continuum limit. A crucial ingredient is the realization that the bosonic spinons of the gauge theory exhibit a U(1) symmetry protected topological (SPT) phase, which upon promoting its U(1) global symmetry to a local gauge structure ("gauging"), yields the CSL. We suggest that such an explicit lattice-based construction involving gauging of a SPT phase can be applied more generally to understand topological spin liquids.

  3. Topological electromagnetic responses of bosonic quantum Hall, topological insulator, and chiral semimetal phases in all dimensions

    Science.gov (United States)

    Lapa, Matthew F.; Jian, Chao-Ming; Ye, Peng; Hughes, Taylor L.

    2017-01-01

    We calculate the topological part of the electromagnetic response of bosonic integer quantum Hall (BIQH) phases in odd (space-time) dimensions, and bosonic topological insulator (BTI) and bosonic chiral semimetal (BCSM) phases in even dimensions. To do this, we use the nonlinear sigma model (NLSM) description of bosonic symmetry-protected topological (SPT) phases, and the method of gauged Wess-Zumino (WZ) actions. We find the surprising result that for BIQH states in dimension 2 m -1 (m =1 ,2 ,⋯ ), the bulk response to an electromagnetic field Aμ is characterized by a Chern-Simons term for Aμ with a level quantized in integer multiples of m ! (factorial). We also show that BTI states (which have an extra Z2 symmetry) can exhibit a Z2-breaking quantum Hall effect on their boundaries, with this boundary quantum Hall effect described by a Chern-Simons term at level m/! 2 . We show that the factor of m ! can be understood by requiring gauge invariance of the exponential of the Chern-Simons term on a general Euclidean manifold, and we also use this argument to characterize the electromagnetic and gravitational responses of fermionic SPT phases with U(1 ) symmetry in all odd dimensions. We then use our gauged boundary actions for the BIQH and BTI states to (i) construct a bosonic analog of a chiral semimetal (BCSM) in even dimensions, (ii) show that the boundary of the BTI state exhibits a bosonic analog of the parity anomaly of Dirac fermions in odd dimensions, and (iii) study anomaly inflow at domain walls on the boundary of BTI states. In a series of Appendixes we derive important formulas and additional results. In particular, in Appendix A we use the connection between equivariant cohomology and gauged WZ actions to give a mathematical interpretation of the actions for the BIQH and BTI boundaries constructed in this paper.

  4. Vacuum Polarization and Dynamical Chiral Symmetry Breaking: Phase Diagram of QED with Four-Fermion Contact Interaction

    CERN Document Server

    Akram, F; Gutierrez-Guerrero, L X; Masud, B; Rodriguez-Quintero, J; Calcaneo-Roldan, C; Tejeda-Yeomans, M E

    2012-01-01

    We study chiral symmetry breaking for fundamental charged fermions coupled electromagnetically to photons with the inclusion of four-fermion contact self-interaction term. We employ multiplicatively renormalizable models for the photon dressing function and the electron-photon vertex which minimally ensures mass anomalous dimension = 1. Vacuum polarization screens the interaction strength. Consequently, the pattern of dynamical mass generation for fermions is characterized by a critical number of massless fermion flavors above which chiral symmetry is restored. This effect is in diametrical opposition to the existence of criticality for the minimum interaction strength necessary to break chiral symmetry dynamically. The presence of virtual fermions dictates the nature of phase transition. Miransky scaling laws for the electromagnetic interaction strength and the four-fermion coupling, observed for quenched QED, are replaced by a mean-field power law behavior corresponding to a second order phase transition. T...

  5. Topology in the SU(Nf) chiral symmetry restored phase of unquenched QCD and axion cosmology

    CERN Document Server

    Azcoiti, Vicente

    2016-01-01

    We investigate the topological properties of unquenched QCD on the basis of numerical results of simulations at fixed topological charge, recently reported by Borsanyi et al., and analytical predictions of the dilute instanton gas approximation. We demonstrate that the mean value of the chiral condensate at fixed topological charge is, in both cases, inconsistent with the analytical prediction of the large volume expansion around the saddle point, and argue that the most plausible explanation for the failure of the saddle point expansion is a vacuum energy density theta-independent at high temperatures, but surprisingly not too high (T\\sim 2T_c), a result which would imply a vanishing topological susceptibility, and the absence of all physical effects of the U(1) axial anomaly at these temperatures. We also show that under a general assumption concerning the high temperature phase of QCD, where the SU(Nf)_A symmetry is restored, the analytical prediction for the chiral condensate at fixed topological charge i...

  6. Topology in the S U (Nf) chiral symmetry restored phase of unquenched QCD and axion cosmology

    Science.gov (United States)

    Azcoiti, Vicente

    2016-11-01

    We investigate the topological properties of unquenched QCD on the basis of numerical results of simulations at fixed topological charge, recently reported by Borsanyi et al. We demonstrate that their results for the mean value of the chiral condensate at fixed topological charge are inconsistent with the analytical prediction of the large-volume expansion around the saddle point, and argue that the most plausible explanation for the failure of the saddle-point expansion is a vacuum energy density that is θ -independent at high temperatures, but surprisingly not too high (T ˜2 Tc), a result which would imply a vanishing topological susceptibility and the absence of all physical effects of the U (1 ) axial anomaly at these temperatures. We also show that under a general assumption concerning the high-temperature phase of QCD, where the S U (Nf)A symmetry is restored, the analytical prediction for the chiral condensate at fixed topological charge is in very good agreement with the numerical results of Borsanyi et al., all effects of the axial anomaly should disappear, the topological susceptibility and all the θ derivatives of the vacuum energy density vanish, and the theory becomes θ independent at any T >Tc in the infinite-volume limit.

  7. Nematic quantum critical point without magnetism in FeSe1-xSx superconductors

    Science.gov (United States)

    Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

    2016-07-01

    In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near ≈0.17, the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.

  8. Nematic quantum critical point without magnetism in FeSe1-xSx superconductors.

    Science.gov (United States)

    Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

    2016-07-19

    In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near [Formula: see text], the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.

  9. Improved Procedure for Preparation of Covalently Bonded Cellulose Tris-phenylcarbamate Chiral Stationary Phases

    Institute of Scientific and Technical Information of China (English)

    秦峰; 陈小明; 刘月启; 邹汉法; 王俊德

    2005-01-01

    The classical method for preparation of covalently boned cellulose derivative chiral stationary phases (CSP) with diisocyanate as spacer was improved. Diisocyanate was firstly allowed to react with 3-aminopropyltriethoxysilane, and the resulting product was then applied as the spacer reagent to immobilize cellulose derivatives onto silica gel. Influences of the amount and the length of the spacer on the optical resolution ability of the CSP were investigated. Comparing improved procedure to classical diisocyanate method, the cross-linking between the glucose units of the cellulose derivatives was avoided to the most extent. With the improved procedure, regio-nonselective ways could be adooted to prepare covalently bonded CSP, which showed an advantage for the rapid preparation.

  10. Effects of Tsallis distribution on parametric resonance in chiral phase transitions

    CERN Document Server

    Ishihara, Masamichi

    2016-01-01

    The parametric resonance was studied in chiral phase transitions when the momentum distribution is described by a Tsallis distribution. A Tsallis distribution has two parameters, the temperature $T$ and the entropic index $q$. The amplification was estimated in two cases: 1) expansionless case and 2) one dimensional expansion case. In an expansionless case, the temperature $T$ is constant, and the amplified modes as a function of $T$ were calculated for various $q$. In one dimensional expansion case, the temperature $T$ decreases as a function of the proper time, and the amplification as a function of the transverse momentum was calculated for various $q$. In the expansionless case, the following facts were found: 1) the larger the value $q$ is, the softer the amplified modes are for the first and second resonance bands, 2) the amplified mode of the first resonance band decreases and vanishes, as the temperature $T$ increases, and 3) the amplified mode of the second resonance band decreases and approaches to ...

  11. Chiral conducting polymers.

    Science.gov (United States)

    Kane-Maguire, Leon A P; Wallace, Gordon G

    2010-07-01

    This critical review describes the preparation and properties of a relatively new class of chiral macromolecules, namely chiral conducting polymers. It focuses in particular on examples based on polypyrrole, polythiophene and polyaniline. They possess remarkable properties, combining not only chirality with electrical conductivity but also the ability to undergo facile redox and pH switching. These unique properties have opened up a range of exciting new potential applications, including as chiral sensors, as novel stationary phases for chiral separations, and as chiral electrodes for electrochemical asymmetric synthesis (153 references).

  12. Enantioselective and diastereoselective separation of synthetic pyrethroid insecticides on a novel chiral stationary phase by high-performance liquid chromatography.

    Science.gov (United States)

    Tan, Xulin; Hou, Shicong; Wang, Min

    2007-07-01

    A novel chiral packing material for high-performance liquid chromatography (HPLC) was prepared by connecting (R)-1-phenyl-2-(4-methylphenyl) ethylamine (PTE) amide derivative of (S)-isoleucine to aminopropyl silica gel through 2-amino-3,5-dinitro-1-carboxamido-benzene unit. This chiral stationary phase was applied to the enantioselective and diastereoselective separation of five pyrethroid insecticides by HPLC under normal phase condition. To achieve satisfactory baseline separation an optimization of the variables of mobile phase composition was required. The two enantiomers of fenpropathrin and four stereoisomers of fenvalerate were baseline separated using hexane-1,2-dichloroethane-2-propanol as mobile phase. The results show that the enantioselectivity of CSP is better than Pirkle type 1-A column for these compounds. Only partial separations for the cypermethrin and cyfluthrin stereoisomers were observed. Seven peaks and eight peaks were observed for cypermethrin and cyfluthrin, respectively. The elution orders were assigned by using different stereoisomer-enriched products.

  13. Quinine-Based Zwitterionic Chiral Stationary Phase as a Complementary Tool for Peptide Analysis: Mobile Phase Effects on Enantio- and Stereoselectivity of Underivatized Oligopeptides.

    Science.gov (United States)

    Ianni, Federica; Sardella, Roccaldo; Carotti, Andrea; Natalini, Benedetto; Lindner, Wolfgang; Lämmerhofer, Michael

    2016-01-01

    Peptide stereoisomer analysis is of importance for quality control of therapeutic peptides, the analysis of stereochemical integrity of bioactive peptides in food, and the elucidation of the stereochemistry of peptides from a natural chiral pool which often contains one or more D-amino acid residues. In this work, a series of model peptide stereoisomers (enantiomers and diastereomers) were analyzed on a zwitterionic ion-exchanger chiral stationary phase (Chiralpak ZWIX(+) 5 µm), in order to investigate the retention and separation performance for such compounds on this chiral stationary phase and elucidate its utility for this purpose. The goal of the study focused on 1) investigations of the effects of the sample matrix used to dissolve the peptide samples; 2) optimization of the mobile phase (enabling deriving information on factors of relevance for retention and separation); and 3) derivation of structure-selectivity relationships. It turned out that small di- and tripeptides can be well resolved under optimized conditions, typically with resolutions larger than 1.5. The optimized mobile phase often consisted of methanol-tetrahydrofuran-water (49:49:2; v/v/v) with 25 mM formic acid and 12.5 mM diethylamine. This work proposes some guidance on which mobile phases can be most efficiently used for peptide stereoisomer separations on Chiralpak ZWIX. Chirality 28:5-16, 2016. © 2015 Wiley Periodicals, Inc.

  14. Scaling properties of the chiral phase transition in the low density region of two-flavor QCD with improved Wilson fermions

    CERN Document Server

    Umeda, T; Kanaya, K; Maezawa, Y; Nakagawa, Y; Ohno, H; Saito, H; Yoshida, S

    2013-01-01

    We study scaling behavior of a chiral order parameter in the low density region, performing a simulation of two-flavor QCD with improved Wilson quarks. The scaling behavior of the chiral order parameter defined by a Ward-Takahashi identity agrees with the scaling function of the three-dimensional O(4) spin model at zero chemical potential. We extend the scaling study to finite density QCD. Applying the reweighting method and calculating derivatives of the chiral order parameter with respect to the chemical potential, the scaling properties of the chiral phase transition are discussed in the low density region. We moreover calculate the curvature of the phase boundary of the chiral phase transition in the temperature and chemical potential plane assuming the O(4) scaling relation.

  15. Adsorption phenomena and anchoring energy in nematic liquid crystals

    CERN Document Server

    Barbero, Giovanni

    2005-01-01

    Despite the large quantity of phenomenological information concerning the bulk properties of nematic phase liquid crystals, little is understood about the origin of the surface energy, particularly the surface, interfacial, and anchoring properties of liquid crystals that affect the performance of liquid crystal devices. Self-contained and unique, Adsorption Phenomena and Anchoring Energy in Nematic Liquid Crystals provides an account of new and established results spanning three decades of research into the problems of anchoring energy and adsorption phenomena in liquid crystals.The book contains a detailed discussion of the origin and possible sources of anchoring energy in nematic liquid crystals, emphasizing the dielectric contribution to the anchoring energy in particular. Beginning with fundamental surface and anchoring properties of liquid crystals and the definition of the nematic phase, the authors explain how selective ion adsorption, dielectric energy density, thickness dependence, and bias voltage...

  16. Spontaneous Planar Chiral Symmetry Breaking in Cells

    Science.gov (United States)

    Hadidjojo, Jeremy; Lubensky, David

    Recent progress in animal development has highlighted the central role played by planar cell polarity (PCP) in epithelial tissue morphogenesis. Through PCP, cells have the ability to collectively polarize in the plane of the epithelium by localizing morphogenetic proteins along a certain axis. This allows direction-dependent modulation of tissue mechanical properties that can translate into the formation of complex, non-rotationally invariant shapes. Recent experimental observations[1] show that cells, in addition to being planar-polarized, can also spontaneously develop planar chirality, perhaps in the effort of making yet more complex shapes that are reflection non-invariant. In this talk we will present our work in characterizing general mechanisms that can lead to spontaneous chiral symmetry breaking in cells. We decompose interfacial concentration of polarity proteins in a hexagonal cell packing into irreducible representations. We find that in the case of polar concentration distributions, a chiral state can only be reached from a secondary instability after the cells are polarized. However in the case of nematic distributions, we show that a finite-amplitude (subcritical, or ``first-order'') nematic transition can send the system from disorder directly to a chiral state. In addition, we find that perturbing the system by stretching the hexagonal packing enables direct (supercritical, or ``second-order'') chiral transition in the nematic case. Finally, we do a Landau expansion to study competition between stretch-induced chirality and the tendency towards a non-chiral state in packings that have retained the full 6-fold symmetry.

  17. Relevance of saddle-splay elasticity in complex nematic geometries.

    Science.gov (United States)

    Kos, Žiga; Ravnik, Miha

    2016-01-28

    We demonstrate the relevance of saddle-splay elasticity in nematic liquid crystalline fluids in the context of complex surface anchoring conditions and the complex geometrical confinement. Specifically, nematic cells with patterns of surface anchoring and colloidal knots are shown as examples where saddle-splay free energy contribution can have a notable role which originates from nonhomogeneous surface anchoring and the varying surface curvature. Patterned nematic cells are shown to exhibit various (meta)stable configurations of nematic field, with relative (meta)stability depending on the saddle-splay. We show that for high enough values of saddle-splay elastic constant K24 a previously unstable conformation can be stabilised, more generally indicating that the saddle-splay can reverse or change the (meta)stability of various nematic structures affecting their phase diagrams. Furthermore, we investigate saddle-splay elasticity in the geometry of highly curved boundaries - the colloidal particle knots in nematic - where the local curvature of the particles induces complex spatial variations of the saddle-splay contributions. Finally, a nematic order parameter tensor based saddle-splay invariant is shown, which allows for the direct calculation of saddle-splay free energy from the Q-tensor, a possibility very relevant for multiple mesoscopic modelling approaches, such as Landau-de Gennes free energy modelling.

  18. Dynamic Behavior of Clobazam on High-Performance Liquid Chromatography Chiral Stationary Phases.

    Science.gov (United States)

    Sabia, Rocchina; De Martino, Michela; Cavazzini, Alberto; Villani, Claudio

    2016-01-01

    Clobazam, a 1,5-benzodiazepin-2,4-dione, is a chiral molecule because its ground state conformation features a nonplanar seven-membered ring lacking reflection symmetry elements. The two conformational enantiomers of clobazam interconvert at room temperature by a simple ring-flipping process. Variable temperature HPLC on the Pirkle type (R)-N-(3,5-dinitronenzoyl)phenylglycine and (R,R)-Whelk-O1 chiral stationary phases (CSPs) allowed us to separate for the first time the conformational enantiomers of clobazam and to observe peak coalescence-decoalescence phenomena due to concomitant separation and interconversion processes occurring on the same time scale. Clobazam showed temperature dependent dynamic high-performance liquid chromatography (HPLC) profiles with interconversion plateaus on the two CSPs indicative of on-column enantiomer interconversion. (enantiomerization) in the column temperature range between Tcol = 10°C and Tcol = 30°C, whereas on-column interconversion was absent at temperature close to or lower than Tcol = 5°C. Computer simulation of exchange-deformed HPLC profiles using a program based on the stochastic model yielded the apparent rate constants for the on-column enantiomerization and the corresponding free energy activation barriers. At Tcol = 20°C the averaged enantiomerization barriers, ΔG(‡), for clobazam were found in the range 21.08-21.53 kcal mol(-1) on the two CSPs. The experimental dynamic chromatograms and the corresponding interconversion barriers reported in this article are consistent with the literature data measured by DNMR at higher temperatures and in different solvents.

  19. Tailoring the interfaces between nematic liquid crystal emulsions and aqueous phases via layer-by-layer assembly.

    Science.gov (United States)

    Tjipto, Elvira; Cadwell, Katie D; Quinn, John F; Johnston, Angus P R; Abbott, Nicholas L; Caruso, Frank

    2006-10-01

    We report the assembly of polyelectrolyte multilayer (PEM) films at the interfaces of thermotropic liquid crystal (LC) droplets dispersed in an aqueous phase. Exposure of PEM-coated droplets to surfactant slowed the bipolar-to-radial ordering transition of the LCs by 2 orders of magnitude relative to naked droplets. This shows that PEMs can be used to influence the interactions of analytes with the LC cores of the droplets, allowing tuning of the LC emulsion sensing properties.

  20. Elastic Properties of Nematic Liquid Crystals Formed by Living and Migrating Cells

    CERN Document Server

    Kemkemer, R; Kaufmann, D; Gruler, H; Kemkemer, Ralf; Kling, Dieter; Kaufmann, Dieter; Gruler, Hans

    1998-01-01

    In culture migrating and interacting amoeboid cells can form nematic liquid crystal phases. A polar nematic liquid crystal is formed if the interaction has a polar symmetry. One type of white blood cells (granulocytes) form clusters where the cells are oriented towards the center. The core of such an orientational defect (disclination) is either a granulocyte forced to be in an isotropic state or another cell type like a monocyte. An apolar nematic liquid crystal is formed if the interaction has an apolar symmetry. Different cell types like human melanocytes (=pigment cells of the skin), human fibroblasts (=connective tissue cells), human osteoblasts (=bone cells), human adipocytes (= fat cells) etc., form an apolar nematic liquid crystal. The orientational elastic energy is derived and the orientational defects (disclination) of nematic liquid crystals are investigated. The existence of half-numbered disclinations show that the nematic phase has an apolar symmetry. The density- and order parameter dependence...

  1. Enantioseparation Using Cellulose Tris(3,5-dimethylphenylcarbamate as Chiral Stationary Phase for HPLC: Influence of Molecular Weight of Cellulose

    Directory of Open Access Journals (Sweden)

    Yuji Okada

    2016-11-01

    Full Text Available The cellulose oligomers with different degrees of polymerization (DP, 7, 11, 18, 24, 26, 40 and 52, were prepared by hydrolysis of microcrystalline cellulose with phosphoric acid. These oligomers including the starting microcrystalline cellulose (DP 124 were converted to tris(3,5-dimethylphenylcarbamate (CDMPC derivatives by the reaction with an excess of 3,5-dimethylphenyl isocyanate to be used as the chiral stationary phase (CSP in high-performance liquid chromatography (HPLC. The structures of the CDMPC derivatives were investigated by infrared spectroscopy (IR, 1H-NMR, circular dichroism (CD and size exclusion chromatography (SEC, and the DPs of the derivatives estimated by SEC agreed with those estimated by 1H-NMR. After coating the derivatives on silica gel, their chiral recognition abilities were evaluated using eight racemates under a normal phase condition with a hexane-2-propanol (99/1 mixture as an eluent. The chiral recognition abilities of 7- and 11-mers, particularly the former, were lower than those of the higher oligomers from DP 18 to 52, which had rather similar abilities to that of 124-mer, although the abilities depended on the racemates. DP 18 seems to be sufficient for CDMPC to exhibit chiral recognition similar to that of the CDMPC with larger DPs.

  2. The phase boundary for the chiral transition in (2+1)-flavor QCD at small values of the chemical potential

    CERN Document Server

    Karsch, F; Miao, C; Mukherjee, S; Petreczky, P; Schmidt, C; Soeldner, W; Unger, W

    2010-01-01

    We determine the chiral phase transition line in (2+1)-flavor QCD for small values of the light quark chemical potential. We show that for small values of the chemical potential the curvature of the phase transition line can be deduced from an analysis of scaling properties of the chiral condensate and its susceptibilities. To do so we extend earlier studies of the magnetic equation of state in (2+1)-flavor QCD to finer lattice spacings, aT=1/8. We use these universal scaling properties of the chiral order parameter to extract the curvature of the transition line at two values of the cut-off, aT=1/4 and 1/8. We find that cut-off effects are small for the curvature parameter and determine the transition line in the chiral limit to leading order in the light quark chemical potential. We obtain Tc(\\mu_q)/Tc(0) = 1 - 0.059(2)(4) (\\mu_q/T)^2 +O(\\mu_q^4).

  3. High performance liquid chromatographic separation of eight drugs collected in Chinese Pharmacopoeia 2010 on amylose ramification chiral stationary phase

    Directory of Open Access Journals (Sweden)

    Yan Wang

    2012-10-01

    Full Text Available The enantiomers separation of eight pharmaceutical racemates collected in Chinese Pharmacopoeia 2010 (Ch.P2010, including nitrendipine, felodipine, omeprazole, praziquantel, sulpiride, clenbuterol hydrochloride, verapamil hydrochloride and chlorphenamine maleate, was performed on chiral stationary phase of amylose ramification by high performance liquid chromatography (HPLC on Chiralpak AD-H column and Chiralpak AS-H column with the mobile phase consisted of isopropanol and n-hexane. The detection wavelength and the flow rate were set at 254 nm and 0.7 mL/min, respectively. The effects of proportion of organic additives, alcohol displacer and temperature on the separation were investigated. The results indicated that eight chiral drugs were separated on chiral stationary phase of amylase ramification in normal phase chromatographic system. The chromatographic retention and resolution of enantiomers were adjusted by factors, including the changes of the concentration of alcohol displacer in mobile phase, organic alkaline modifier and column temperature. It was shown that the resolution was improved with reducing concentration of alcohol displacer. When the concentration of organic alkaline modifier was 0.2%, the resolution and the peak shape were fairly good. Most racemates mentioned above had the best resolution at column temperature of 25 °C. The best temperature should be kept unchanged in the process of separation so as to obtain stable separation results.

  4. Mathematical Studies and Simulations of Nematic Liquid Crystal Polymers and Nanocomposites

    Science.gov (United States)

    2010-01-01

    been spun into high strength fibers and then manufactured into special airbags that cushioned the successful landing of NASA’s highly publicized...shaped, boomerang-shaped or banana shaped.76 Recall that in a nematic phase the molecules tend to align along the director n. A biax- ial nematic phase

  5. Magnetic anisotropy and the phase diagram of chiral MnSb2O6

    Science.gov (United States)

    Werner, J.; Koo, C.; Klingeler, R.; Vasiliev, A. N.; Ovchenkov, Y. A.; Polovkova, A. S.; Raganyan, G. V.; Zvereva, E. A.

    2016-09-01

    The magnetic phase diagram and low-energy magnon excitations of structurally and magnetically chiral MnSb2O6 are reported. The specific heat and the static magnetization are investigated in magnetic fields up to 9 and 30 T, respectively, while the dynamic magnetic properties are probed by X-band as well as tunable high-frequency electron spin-resonance spectroscopy. Below TN=11.5 K, we observe antiferromagnetic resonance modes which imply small but finite planar anisotropy showing up in a zero-field splitting of 20 GHz. The data are well described by means of an easy-plane two-sublattice model with the anisotropy field BA=0.02 T. The exchange field BE=13 T is obtained from the saturation field derived from the pulsed-field magnetization. A crucial role of the small anisotropy for the spin structure is reflected by competing antiferromagnetic phases appearing, at T =2 K, in small magnetic fields at BC 1 ≈0.5 T and BC 2=0.9 T. We discuss the results in terms of spin reorientation and of small magnetic fields favoring helical spin structure over the cycloidal ground state which, at B =0 , is stabilized by the planar anisotropy. Above TN, short-range magnetic correlations up to ≳60 K and magnetic entropy changes well above TN reflect the frustrated triangular arrangement of Mn2 + ions in MnSb2O6 .

  6. Phase diagram and two-particle structure of the $Z_3$-chiral Potts model

    CERN Document Server

    Von Gehlen, G

    1992-01-01

    We calculate the low-lying part of the spectrum of the $Z_3$-symmetrical chiral Potts quantum chain in its self-dual and integrable versions, using numerical diagonalisation of the hamiltonian for $N \\leq 12$ sites and extrapolation $N \\ra \\infty$. From the sequences of levels crossing we show that the massive phases have oscillatory correlation functions. We calculate the wave vector scaling exponent. In the high-temperature massive phase the pattern of the low-lying levels can be explained assuming the existence of two particles, with $Z_3$-charge $Q\\!=\\!1$ and $Q\\!=\\!2$, and their scattering states. In the superintegrable case the $Q\\!=\\!2$-particle has twice the mass of the $Q\\!=\\!1$-particle. Exponential convergence in $N$ is observed for the single particle gaps, while power convergence is seen for the scattering levels. In the high temperature limit of the self-dual model the parity violation in the particle dispersion relation is equivalent to the presence of a macroscopic momentum $P_m = \\pm \\vph/3$,...

  7. Comparison of the performance of chiral stationary phase for separation of fluoxetine enantiomers

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jie; YANG Yi-wen; WEI Feng; WU Ping-dong

    2007-01-01

    Separation of fluoxetine enantiomers on five chiral stationary phases (chiralcel OD-H, chiralcel OJ-H, chiralpak AD-H, cyclobond I 2000 DM and kromasil CHI-TBB) was investigated. The optimal mobile phase compositions of fluoxetine separation on each column were hexane/isopropanol/diethyl amine (98/2/0.2, v/v/v), hexane/isopropanol/diethyl amine (99/1/0.1,v/v/v), hexane/isopropanol/diethyl amine (98/2/0.2, v/v/v), methanol/0.2% triethylamine acetic acid (TEAA) (25/75, v/v; pH 3.8)and hexane/isopropanol/diethyl amine (98/2/0.2, v/v/v), respectively. Experimental results demonstrated that baseline separation (RS>1.5) of fluoxetine enantiomers was obtained on chiralcel OD-H, chiralpak AD-H, and cyclobond I 2000 DM while the best separation was obtained on the last one. The eluate orders of fluoxetine enantiomers on the columns were determined. The first eluate by chiralcel OJ-H and kromasil CHI-TBB is the S-enantiomer, while by chiralpak AD-H and cyclobond I 2000 DM is the R-enantiomer.

  8. Application of cyanuric chloride-based six new chiral derivatizing reagents having amino acids and amino acid amides as chiral auxiliaries for enantioresolution of proteinogenic amino acids by reversed-phase high-performance liquid chromatography.

    Science.gov (United States)

    Bhushan, Ravi; Dixit, Shuchi

    2012-04-01

    Six dichloro-s-triazine (DCT) reagents having L-Leu, D-Phg, L-Val, L-Met, L-Ala and L-Met-NH(2) as chiral auxiliaries in cyanuric chloride were introduced for enantioseparation of 13 proteinogenic amino acids. Four other DCTs and six monochloro-s-triazine (MCT) reagents having amino acid amides as chiral auxiliaries were also synthesized. These 16 chiral derivatizing reagents (CDRs) were used for synthesis of diastereomers of all the 13 analytes using microwave irradiation, which were resolved by reversed-phase high-performance liquid chromatography (RP-HPLC) using C18 column and gradient eluting mixture of aqueous TFA and acetonitrile with UV detection at 230 nm. It required only 60-90 s for derivatization using microwave irradiation. Better resolution and lower retention times were observed for the diastereomers prepared with CDRs having amino acids as chiral auxiliaries as compared to counterparts prepared with reagents having amino acid amides as chiral auxiliaries. As the best resolution of all the 13 analytes was observed for their diastereomers prepared using the DCT reagent having L-Leu as chiral auxiliary, this CDR was further employed for derivatization of Lys, Tyr, His and Arg followed by RP-HPLC analysis of resulting diastereomers. The results are discussed in light of acid and amide groups of chiral auxiliaries constituting CDRs, electronegativities of the atoms of achiral moieties constituting CDRs and hydrophobicities of side chains of amino acids constituting CDRs and analytes.

  9. A liquid crystalline chirality balance for vapours

    OpenAIRE

    Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-Ichi

    2014-01-01

    Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a t...

  10. Mirror Symmetry Breaking by Chirality Synchronisation in Liquids and Liquid Crystals of Achiral Molecules.

    Science.gov (United States)

    Tschierske, Carsten; Ungar, Goran

    2016-01-04

    Spontaneous mirror symmetry breaking is an efficient way to obtain homogeneously chiral agents, pharmaceutical ingredients and materials. It is also in the focus of the discussion around the emergence of uniform chirality in biological systems. Tremendous progress has been made by symmetry breaking during crystallisation from supercooled melts or supersaturates solutions and by self-assembly on solid surfaces and in other highly ordered structures. However, recent observations of spontaneous mirror symmetry breaking in liquids and liquid crystals indicate that it is not limited to the well-ordered solid state. Herein, progress in the understanding of a new dynamic mode of symmetry breaking, based on chirality synchronisation of transiently chiral molecules in isotropic liquids and in bicontinuous cubic, columnar, smectic and nematic liquid crystalline phases is discussed. This process leads to spontaneous deracemisation in the liquid state under thermodynamic control, giving rise to long-term stable symmetry-broken fluids, even at high temperatures. These fluids form conglomerates that are capable of extraordinary strong chirality amplification, eventually leading to homochirality and providing a new view on the discussion of emergence of uniform chirality in prebiotic systems.

  11. Enantiomer Separation of α-Dimethyl Dicarboxylate Biphenyl and Related Biphenyl Compounds by Normal Phase HPLC on Polysaccharide Based Chiral Stationary Phases

    Institute of Scientific and Technical Information of China (English)

    LIU,Yue-Qi(刘月启); HAN,Xiao-Qian(韩小茜); Qi,Bang-Feng(齐邦峰); LIU,Chun-Hui(柳春辉); LI,Yong-Min(李永民); CHEN,Li-Ren(陈立仁)

    2002-01-01

    Cellulose tris(4-methylphenylcarbamate), amylose tris(3,5-dimethylpphenylcarbamate) and amylose tris (phenylcarbamate)were prepared by the method reported by Okamoto and were coated onto an aminopropylated mesoporous spherical silica gel. These final products were used as chiral stationary phases of high performance liquid chromatography for the eighteen structurally related biphenyl conmpounds. The resolution was made using normal-phase methodology with a mobile phase consisting of n-hexane-alcohol (ethanol, 1-propanol, 2-propanol or 1-butanol). The effects of various aliphatic alcohols in the mobile phase were studied. The structural features of the solutes that influence their k'were discussed. A dominant effect of trifluoroaetic acid on chiral separation of aacidicdic solutes was noted.

  12. Enantiomeric separation of volatile organics by gas chromatography for the in situ analysis of extraterrestrial materials: kinetics and thermodynamics investigation of various chiral stationary phases.

    Science.gov (United States)

    Freissinet, C; Buch, A; Szopa, C; Sternberg, R

    2013-09-01

    The performances of several commercial chiral capillary columns have been evaluated with the aim of determining the one most suitable for enantiomeric separation in a gas chromatograph onboard a space probe. We compared the GC-MS response of three capillary columns coated with different chiral stationary phases (CSP) using volatile chiral organic molecules which are potential markers of a prebiotic organic chemistry. The three different chiral capillary columns are Chirasil-Val, with an amino acid derivative CSP, ChiralDex-β-PM, with a CSP composed of dissolved permethylated β-cyclodextrins in polysiloxane, and Chirasil-Dex, with a CSP made of modified cyclodextrins chemically bonded to the polysiloxane backbone. Both kinetics and thermodynamics studies have been carried out to evaluate the chiral recognition potential in these different types of columns. The thermodynamic parameters also allow a better understanding of the driving forces affecting the retention and separation of the enantiomers. The Chirasil-Dex-CSP displays the best characteristics for an optimal resolution of the chiral compounds, without preliminary derivatization. This CSP had been chosen to be the only chiral column in the Sample Analysis at Mars (SAM) experiment onboard the current Mars Science Laboratory (MSL) mission, and is also part of the Mars Organic Molecules Analyzer (MOMA) gas chromatograph onboard the next Martian mission ExoMars. The use of this column could also be extended to all space missions aimed at studying chirality in space.

  13. Enantiomeric Excess Determination for Monosaccharides Using Chiral Transmission to Cold Gas-Phase Tryptophan in Ultraviolet Photodissociation

    Science.gov (United States)

    Fujihara, Akimasa; Maeda, Naoto; Doan, Thuc N.; Hayakawa, Shigeo

    2017-02-01

    Chiral transmission between monosaccharides and amino acids via photodissociation in the gas phase was examined using a tandem mass spectrometer fitted with an electrospray ionization source and a cold ion trap in order to investigate the origin of the homochirality of biomolecules in molecular clouds. Ultraviolet photodissociation mass spectra of cold gas-phase noncovalent complexes of the monosaccharide enantiomers glucose (Glc) and galactose (Gal) with protonated l-tryptophan H+( l-Trp) were obtained by photoexcitation of the indole ring of l-Trp. l-Trp dissociated via Cα-Cβ bond cleavage when noncovalently complexed with d-Glc; however, no dissociation of l-Trp occurred in the homochiral H+( l-Trp)( l-Glc) noncovalent complex, where the energy absorbed by l-Trp was released through the evaporation of l-Glc. This enantioselective photodissociation of Trp was due to the transmission of chirality from Glc to Trp via photodissociation in the gas-phase noncovalent complexes, and was applied to the quantitative chiral analysis of monosaccharides. The enantiomeric excess of monosaccharides in solution could be determined by measuring the relative abundance of the two product ions in a single photodissociation mass spectrum of the cold gas-phase noncovalent complex with H+( l-Trp), and by referring to the linear relationships derived in this work.

  14. Nematic films at chemically structured surfaces

    Science.gov (United States)

    Silvestre, N. M.; Telo da Gama, M. M.; Tasinkevych, M.

    2017-02-01

    We investigate theoretically the morphology of a thin nematic film adsorbed at flat substrate patterned by stripes with alternating aligning properties, normal and tangential respectively. We construct a simple ‘exactly-solvable’ effective interfacial model where the liquid crystal distortions are accounted for via an effective interface potential. We find that chemically patterned substrates can strongly deform the nematic-air interface. The amplitude of this substrate-induced undulations increases with decreasing average film thickness and with increasing surface pattern pitch. We find a regime where the interfacial deformation may be described in terms of a material-independent universal scaling function. Surprisingly, the predictions of the effective interfacial model agree semi-quantitatively with the results of the numerical solution of a full model based on the Landau-de Gennes theory coupled to a square-gradient phase field free energy functional for a two phase system.

  15. Recent development of oligosaccharides chiral stationary phases and their applications in chromatography%寡糖手性固定相研究进展

    Institute of Scientific and Technical Information of China (English)

    赵峰; 袁黎明; 熊汝琴

    2015-01-01

    In this paper ,The development of the Oligosaccharide chiral stationary phase for the HPLC chiral stationa‐ry phase is reviewed ,the study found that these sugars as the hplc chiral stationary phase is effect better ,more promis‐ing ,and the prospect of the chiral stationary phase is reviewed .%介绍了葡萄糖、纤维二塘、棉子糖、乳糖等用来作为高效液相色谱手性固定相的研究进展,研究发现这几种糖类作为高效液相色谱的手性固定相拆分效果比较好,比较有前途。同时展望了高效液相色谱手性固定相的发展前景。

  16. Helicity-selective phase-matching and quasi-phase matching of circularly polarized high-order harmonics: towards chiral attosecond pulses

    Science.gov (United States)

    Kfir, Ofer; Grychtol, Patrik; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Fleischer, Avner; Bordo, Eliyahu; Fan, Tingting; Popmintchev, Dimitar; Popmintchev, Tenio; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

    2016-06-01

    Phase matching of circularly polarized high-order harmonics driven by counter-rotating bi-chromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here we propose a new perspective on phase matching of circularly polarized high harmonics. We derive an extended phase matching condition by requiring a new propagation matching condition between the classical vectorial bi-chromatic laser pump and harmonics fields. This allows us to include the influence of the laser pulse envelopes on phase matching. We find that the helicity dependent phase matching facilitates generation of high harmonics beams with a high degree of chirality. Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization. Moreover, while the degree of circularity of the most intense pulse approaches unity, all other pulses exhibit reduced circularity. This feature suggests the possibility of using a train of attosecond pulses as an isolated attosecond probe for chiral-sensitive experiments.

  17. Separation mechanism of chiral impurities, ephedrine and pseudoephedrine, found in amphetamine-type substances using achiral modifiers in the gas phase.

    Science.gov (United States)

    Holness, Howard K; Jamal, Adeel; Mebel, Alexander; Almirall, José R

    2012-11-01

    A new mechanism is proposed that describes the gas-phase separation of chiral molecules found in amphetamine-type substances (ATS) by the use of high-resolution ion mobility spectrometry (IMS). Straight-chain achiral alcohols of increasing carbon chain length, from methanol to n-octanol, are used as drift gas modifiers in IMS to highlight the mechanism proposed for gas-phase separations of these chiral molecules. The results suggest the possibility of using these achiral modifiers to separate the chiral molecules (R,S) and (S,R)-ephedrine and (S,S) and (R,R)-pseudoephedrine which contain an internal hydroxyl group at the first chiral center and an amino group at the other chiral center. Ionization was achieved with an electrospray source, the ions were introduced into an IMS with a resolving power of 80, and the resulting ion clusters were characterized with a coupled quadrupole mass spectrometer detector. A complementary computational study conducted at the density functional B3LYP/6-31g level of theory for the electronic structure of the analyte-modifier clusters was also performed, and showed either "bridged" or "independent" binding. The combined experimental and simulation data support the proposed mechanism for gas-phase chiral separations using achiral modifiers in the gas phase, thus enhancing the potential to conduct fast chiral separations with relative ease and efficiency.

  18. Phase diagram of hot QCD in an external magnetic field: possible splitting of deconfinement and chiral transitions

    CERN Document Server

    Mizher, A J; Fraga, E S

    2010-01-01

    The structure of the phase diagram for strong interactions becomes richer in the presence of a magnetic background, which enters as a new control parameter for the thermodynamics. Motivated by the relevance of this physical setting for current and future high-energy heavy ion collision experiments and for the cosmological QCD transitions, we use the linear sigma model coupled to quarks and to Polyakov loops as an effective theory to investigate how the chiral and the deconfining transitions are affected, and present a general picture for the temperature--magnetic field phase diagram. We compute and discuss each contribution to the effective potential for the approximate order parameters, and uncover new phenomena such as the paramagnetically-induced breaking of global $\\mathbb{Z}_3$ symmetry, and possible splitting of deconfinement and chiral transitions in a strong magnetic field.

  19. Fractal nematic colloids

    Science.gov (United States)

    Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.

    2017-01-01

    Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter.

  20. Fractal nematic colloids

    Science.gov (United States)

    Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.

    2017-01-01

    Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter. PMID:28117325

  1. Dielectrophoretic manipulation of the mixture of isotropic and nematic liquid

    Science.gov (United States)

    Kim, Soo-Dong; Lee, Bomi; Kang, Shin-Woong; Song, Jang-Kun

    2015-08-01

    In various applications involving liquid crystals, the manipulation of the nanoscale molecular assembly and microscale director alignment is highly useful. Here we show that a nematic-isotropic mixture, a unique bi-liquid system, has potential for the fabrication of microstructures having an ordered phase within a disordered phase, or vice versa. The volume expansion and shrinkage, migration, splitting, mergence and elongation of one phase within the other are easily accomplished via thermal treatment and dielectrophoretic manipulation. This is particularly achievable when one phase is suspended in the middle. In that case, a highly biased ordered-phase preference of surfaces, that is, the nematic-philic nature of a polyimide layer and the nematic-phobic nature of a self-assembled monolayer of chlorosilane derivatives, is used. Further, by combining this approach with photopolymerization, the patterned microstructure is solidified as a patterned polymer film having both isotropic and anisotropic molecular arrangements simultaneously, or as a template with a morphological variation.

  2. Molecular model for chirality phenomena.

    Science.gov (United States)

    Latinwo, Folarin; Stillinger, Frank H; Debenedetti, Pablo G

    2016-10-21

    Chirality is a hallmark feature for molecular recognition in biology and chemical physics. We present a three-dimensional continuum model for studying chirality phenomena in condensed phases using molecular simulations. Our model system is based upon a simple four-site molecule and incorporates non-trivial kinetic behavior, including the ability to switch chirality or racemize, as well as thermodynamics arising from an energetic preference for specific chiral interactions. In particular, we introduce a chiral renormalization parameter that can locally favor either homochiral or heterochiral configurations. Using this model, we explore a range of chirality-specific phenomena, including the kinetics of chiral inversion, the mechanism of spontaneous chiral symmetry breaking in the liquid, chirally driven liquid-liquid phase separation, and chiral crystal structures.

  3. Long-range nematic order and anomalous fluctuations in suspensions of swimming filamentous bacteria

    Science.gov (United States)

    Nishiguchi, Daiki; Nagai, Ken H.; Chaté, Hugues; Sano, Masaki

    2017-02-01

    We study the collective dynamics of elongated swimmers in a very thin fluid layer by devising long filamentous nontumbling bacteria. The strong confinement induces weak nematic alignment upon collision, which, for large enough density of cells, gives rise to global nematic order. This homogeneous but fluctuating phase, observed on the largest experimentally accessible scale of millimeters, exhibits the properties predicted by standard models for flocking, such as the Vicsek-style model of polar particles with nematic alignment: true long-range nematic order and nontrivial giant number fluctuations.

  4. Long-range nematic order and anomalous fluctuations in suspensions of swimming filamentous bacteria

    CERN Document Server

    Nishiguchi, Daiki; Chaté, Hugues; Sano, Masaki

    2016-01-01

    We study the collective dynamics of long, filamentous, non-tumbling bacteria swimming in a very thin fluid layer. The strong confinement induces nematic alignment upon collision, which, for large enough density of cells, gives rise to global nematic order. We show that this homogeneous but fluctuating phase, observed on the largest experimentally-accessible scale of millimeters, exhibits the same properties as the Vicsek-style model of polar particles with nematic alignment: true long-range nematic order and non-trivial giant number fluctuations

  5. Direct enantioseparation of underivatized aliphatic 3-hydroxyalkanoic acids with a quinine-based zwitterionic chiral stationary phase.

    Science.gov (United States)

    Ianni, Federica; Pataj, Zoltán; Gross, Harald; Sardella, Roccaldo; Natalini, Benedetto; Lindner, Wolfgang; Lämmerhofer, Michael

    2014-10-10

    While aliphatic 2-hydroxyalkanoic acids have been more or less successfully enantioseparated with various chiral stationary phases by HPLC and GC, analogous applications on underivatized aliphatic 3-hydroxyalkanoic acids are completely absent in the scientific literature. With the aim of closing this gap, the enantioseparation of 3-hydroxybutyric acid, 3-hydroxydecanoic acid and 3-hydroxymyristic acid has been performed with two ion-exchange type chiral stationary phases (CSPs): one containing the anion-exchange type tert-butyl carbamoyl quinine chiral selector motif (Chiralpak QN-AX), and the other carrying the new zwitterionic variant based on trans-(S,S)-2-aminocyclohexanesulfonic acid-derivatized quinine carbamate (Chiralpak ZWIX(+)) as the chiral selector and enantiodiscriminating element, respectively. The zwitterionic enantiorecognition material provided better results in terms of enantioselectivity and resolution compared to the anion-exchanger CSP at reduced retention times due to the intramolecular counterion effect imposed by the sulfonic acid moiety and its competition with the 3-hydroxyalkanoic acid analyte for ionic interaction at the quininium-anion exchanger site. It is thus recommended as the CSP of first choice for enantioseparations of the class of aliphatic 3-hydroxyalkanoic acids. With use of polar organic eluent composed of ACN/MeOH/AcOH - 95/5/0.05 (v/v/v), a good compromise in terms of analysis time and enantioresolution quality was accomplished. The major experimental variables have been investigated for optimization of the resolution and allowed to derive information on the enantiorecognition mechanism. Corresponding Chiralpak ZWIX(-), based on pseudo-enantiomeric selector derived from quinidine and trans-(R,R)-2-aminocyclohexanesulfonic acid with opposite configurations provided reversed enantiomer elution orders. It has further to be stressed that these separations can be obtained with mass spectrometry compatible mobile phases.

  6. Preparation and evaluation of a chiral stationary phase covalently bound with a chiral pseudo-18-crown-6 ether having a phenolic hydroxy group for enantiomer separation of amino compounds.

    Science.gov (United States)

    Yongzhu, Jin; Hirose, Keiji; Nakamura, Takashi; Nishioka, Ryota; Ueshige, Tetsuro; Tobe, Yoshito

    2006-10-06

    In order to develop a chiral stationary phase (CSP), which has even higher separation ability than the corresponding commercially available crown ether based CSP (OA-8000 having a pseudo-18-crown-6 ether with an OMe group as a selector), chemically bonded type CSP having a phenolic OH group on a crown ring was developed. Normal mobile phases with or without acid additive can be used with this OH type CSP in contrast to the conventional OMe type CSP which has a neutral chiral selector. Enantiomers of 25 out of 27 amino compounds, including 20 amino acids, 5 amino alcohols, and 2 lipophilic amines, were efficiently separated on a column with this CSP. Nine amino compounds out of 27 were separated with better separation factors than the corresponding OMe type CSP. It is noteworthy that the chromatography on this CSP exhibited excellent enantiomer-separations for amines and amino alcohols when triethyl amine was used as an additive in the mobile phase. Comparison of enantiomer separation ability on this OH type of CSP and on the OMe type of CSP and correlation between the enantioselectivity in chiral chromatography and that of the corresponding model compounds in solution imply that the chiral separation arose from chiral recognition in host guest interactions.

  7. Anomalous dimension, chiral phase transition and inverse magnetic catalysis in soft-wall AdS/QCD

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Zhen, E-mail: fangzhen@itp.ac.cn [Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Science, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing (China)

    2016-07-10

    A modified soft-wall AdS/QCD model with a z-dependent bulk scalar mass is proposed. We argue for the necessity of a modified bulk scalar mass from the quark mass anomalous dimension and carefully constrain the form of bulk mass by the corresponding UV and IR asymptotics. After fixing the form of bulk scalar mass, we calculate the mass spectra of (axial-)vector and pseudoscalar mesons, which have a good agreement with the experimental data. The behavior of chiral phase transition is also investigated, and the results are consistent with the standard scenario and lattice simulations. Finally, the issue of chiral magnetic effects is addressed. We find that the inverse magnetic catalysis emerges naturally from the modified soft-wall model, which is consistent with the recent lattice simulations.

  8. Structural and dynamical properties of the chiral smectic C phase of ferroelectric liquid crystals showing high spontaneous polarizations

    Energy Technology Data Exchange (ETDEWEB)

    Hemine, J. [Laboratoire de Physique de la Matiere Condensee, Universite Hassan II, F.S.T. Mohammedia BP 146 (Morocco)]. E-mail: hemine1@yahoo.fr; Daoudi, A. [Laboratoire de Thermophysique de la Matiere, Universite du Littoral-Cote d' Opale, 145, Avenue Maurice Schumann, 59 140 Dunkerque, France. (France); Legrand, C. [Laboratoire d' Etude des Materiaux et des Composants pour l' Electronique, EA 2601, Universite du Littoral-Cote d' Opale BP 717, Calais (France); Isaert, N. [Laboratoire de Dynamique et Structures des Materiaux Moleculaires, URA No 801, Universite de Lille 1, 59655 Villeneuve d' Ascq (France); El kaaouachi, A. [Laboratoire de Physique de la Matiere Condensee, Faculte des Sciences Ibnou Zohr, BP 28/S 80000, Agadir (Morocco); Nguyen, H.T. [Centre de Recherche Paul Pascal, Universite de Bordeaux 1, 33600 Pessac (France)

    2007-10-01

    Electro-optical and dielectric investigations of a ferroelectric liquid crystal (FLC) exhibiting the chiral smectic C phase (SmC*) have been carried out as a function of temperature. These experimental studies have been applied to a new FLC having high spontaneous polarization and relaxation frequency. The Goldstone relaxation mode was studied from the dielectric response of FLC cells without DC bias voltage. The rotational viscosity corresponding to molecular motion in the SmC* phase was also determined from both electro-optical and dielectric measurements. An Arrhenius-type behaviour of the rotational viscosity was obtained and the corresponding activation energies were evaluated.

  9. Chiral symmetry breaking, color superconductivity and quark matter phase diagram: a variational approach 12.38.Gc

    CERN Document Server

    Mishra, H

    2001-01-01

    We discuss in this note simultaneous existence of chiral symmetry breaking and color superconductivity at finite temperature and density in a Nambu-Jona-Lasinio type model. The methodology involves an explicit construction of a variational ground state and minimisation of the thermodynamic potential. There exist nontrivial solutions to the gap equations at finite densities with both quark-antiquark as well as diquark condensates for the 'ground' state. However, such a phase is thermodynamically unstable with the pressure being negative in this region. We also compute the equation of state, and obtain the structure of the phase diagram in the model.

  10. Synthesis of fluorescent label, DBD-beta-proline, and the resolution efficiency for chiral amines by reversed-phase chromatography.

    Science.gov (United States)

    Min, Jun Zhe; Toyo'oka, Toshimasa; Kato, Masaru; Fukushima, Takeshi

    2005-01-01

    DBD-d(and l)-beta-proline, new fluorescent chiral derivatization reagents, were synthesized from the reaction of 4-(N,N-dimethylaminosulfonyl)-7- fl uoro-2,1,3-benzoxadiazole (DBD-F) with beta-proline. The racemic mixture synthesized was separated by a chiral stationary phase (CSP) column, Chiralpak AD-H, with n-hexane-EtOH-TFA-diethylamine (70:30:0.1:0.1) as the mobile phase. The dl-forms were decided according to the results obtained from a circular dichroism (CD) detector after separation by the CSP column. The fractionated enantiomers reacted with chiral amine to produce a couple of diastereomers. The labeling proceeded in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and pyridine as the activation reagents. The reaction conditions were mild and no racemization occurred during the diastereomer formation. The resulting diastereomers fluoresced at around 570 nm (excitation at around 460 nm). Good linearity of the calibration curves was obtained in the range 1-75 pmol and the detection limits on chromatogram were less than 1 pmol. The separability of the diastereomers was compared with the diastereomers derived from DBD-d(or l)-proline. The resolution values (Rs) obtained from the diastereomers of three chiral amines with DBD-d(or l)-beta-proline were higher than those derived from DBD-d(or l)-proline, e.g. dl-phenylalanine methylester (dl-PAME), 2.23 vs 1.37; (R)(S)-1-phenylethylamine [(R)(S)-PEA], 2.09 vs 1.13; and (R)(S)-1-(1-naphthyl)ethylamines [(R)(S)-NEA], 5.19 vs 1.23. The results suggest that the position of COOH group on pyrrolidine moiety in the structures is one of the important factors for the efficient separation of a couple of the diastereomers.

  11. Common screening approaches for efficient analytical method development in LC and SFC on columns packed with immobilized polysaccharide-derived chiral stationary phases.

    Science.gov (United States)

    Franco, Pilar; Zhang, Tong

    2013-01-01

    Owing to their remarkable enantioselectivity, versatility, and stability, immobilized polysaccharide-based chiral stationary phases (CSPs) have been successfully integrated into the tool box of many research and industry groups for the separation of enantiomers or stereoisomers by liquid and supercritical fluid chromatography. Due to the structurally diverse range of compounds available, efficient method development for chiral separations utilizing such CSPs is a challenging subject. In this chapter, we will discuss simplified screening protocols and straightforward approaches to achieve chiral separations in HPLC and SFC using the column series CHIRALPAK™ IA, IB, IC, and ID in reasonable time frame and with limited experimental work and a high success rate.

  12. Microwave modulation characteristics of twisted liquid crystals with chiral dopant

    Directory of Open Access Journals (Sweden)

    Rui Yuan

    2017-01-01

    Full Text Available Adding a chiral dopant in twisted nematic (TN liquid crystal cell can stabilize the orientation of liquid crystal molecules, particularly in high TN (HTN or super TN (STN liquid crystal cells. The difference in pitches in liquid crystal is induced by the chiral dopant, and these different pitches affect the orientation of liquid crystal director under an external applied voltage and influence the characteristics of microwave modulation. To illustrate this point, the microwave phase shift per unit length (MPSL versus voltage is calculated on the basis of the elastic theory of liquid crystal and the finite-difference iterative method. Enhancing the pitch induced by the chiral dopant in liquid crystal increases the MPSLs, but the stability of the twisted structures is decreased. Thus, appropriate pitches of 100d, 4d, and 2d can be applied in TN, HTN, and STN cells with cell gap d to enhance the characteristics of microwave modulation and stabilize the structures in twisted cell. This method can improve the characteristics of liquid crystal microwave modulators such that the operating voltage and the size of such phase shifters can be decreased.

  13. Phenomenological dynamics: From Navier–Stokes to chiral granular gases

    Indian Academy of Sciences (India)

    T C Lubensky

    2005-05-01

    This paper reviews the derivation of equations for slow dynamical processes in a variety of systems, including rotating rigid rotors, crystalline solids, isotropic and nematic elastomers, gels in an isotropic fluid background, and nematic liquid crystals. It presents a recent derivation of the Leslie–Ericksen equations for the dynamics of nematic liquid crystals that clarifies the nature of the nonhydrodynamic modes in these equations. As a final example of the phenomenological approach to slow dynamical processes, it discusses the dynamics of a driven nonequilibrium system: a two-dimensional gas of chiral `rattlebacks' on a vibrating substrate.

  14. Preparation and application of methylcalix[4]resorcinarene-bonded silica particles as chiral stationary phase in high-performance liquid chromatography.

    Science.gov (United States)

    Tan, Huey Min; Soh, Shu Fang; Zhao, Jia; Yong, E L; Gong, Yinhan

    2011-01-01

    Two new types of methylcalix[4]resorcinarene-bonded stationary phases, (3-(C-methylcalix[4]resorcinarene)-2-hydroxypropoxy)-propylsilyl-appended silica particles (MCR-HPS) and bromoacetate-substituted MCR-HPS particles (BAMCR-HPS), have been synthesized and used as chiral stationary phases for high-performance liquid chromatography (HPLC) for the first time. The synthetic stationary phases are characterized by means of elemental analysis and Fourier-transform infrared spectroscopy. The chromatographic behavior of MCR-HPS and BAMCR-HPS was studied with several disubstituted benzenes and some chiral drug compounds under both normal phase and reversed-phase conditions. The results show that MCR-HPS has excellent selectivity for the separation of aromatic positional isomers and BAMCR-HPS exhibits excellent performance for separation of enantiomers of chiral compounds.

  15. Chiral phase transition of $N_f$=2+1 and 3 QCD at vanishing baryon chemical potential

    CERN Document Server

    Ding, Heng-Tong

    2015-01-01

    We present updated results on chiral phase structure in (2+1)-flavor ($N_f$=2+1) and 3-flavor ($N_f=3$) QCD based on the simulations using Highly Improved Staggered Quarks on lattices with temporal extent $N_\\tau$ =6 at vanishing baryon chemical potential. In $N_f$=2+1 QCD we have performed simulations with a strange quark fixed to its physical value and two degenerate light quarks whose values are adjusted to have 5 values of Goldstone pion masses in the region of 160 - 80 MeV in the continuum limit. The universal scaling behavior of chiral condensates as well as chiral susceptibilities is discussed and the tri-critical point is suggested to be located below the physical point, i.e. at smaller than physical strange quark mass. In $N_f$=3 QCD simulations with 6 different masses of 3 degenerate quarks corresponding to the Goldstone pion masses in the region of 230 - 80 MeV have also been performed. Our results suggest that the QCD transition with these values of quark masses is of crossover type and an upper b...

  16. Simultaneous achiral-chiral analysis of pharmaceutical compounds using two-dimensional reversed phase liquid chromatography-supercritical fluid chromatography.

    Science.gov (United States)

    Venkatramani, C J; Al-Sayah, Mohammad; Li, Guannan; Goel, Meenakshi; Girotti, James; Zang, Lisa; Wigman, Larry; Yehl, Peter; Chetwyn, Nik

    2016-02-01

    A new interface was designed to enable the coupling of reversed phase liquid chromatography (RPLC) and supercritical fluid chromatography (SFC). This online two-dimensional chromatographic system utilizing RPLC in the first dimension and SFC in the second was developed to achieve simultaneous achiral and chiral analysis of pharmaceutical compounds. The interface consists of an eight-port, dual-position switching valve with small volume C-18 trapping columns. The peaks of interest eluting from the first RPLC dimension column were effectively focused as sharp concentration pulses on small volume C-18 trapping column/s and then injected onto the second dimension SFC column. The first dimension RPLC separation provides the achiral purity result, and the second dimension SFC separation provides the chiral purity result (enantiomeric excess). The results are quantitative enabling simultaneous achiral, chiral analysis of compounds. The interface design and proof of concept demonstration are presented. Additionally, comparative studies to conventional SFC and case studies of the applications of 2D LC-SFC in pharmaceutical analysis is presented.

  17. Enantioseparation of Citalopram by RP-HPLC, Using Sulfobutyl Ether-β-Cyclodextrin as a Chiral Mobile Phase Additive.

    Science.gov (United States)

    Peng, Yangfeng; He, Quan Sophia; Cai, Jiang

    2016-01-01

    Enantiomeric separation of citalopram (CIT) was developed using a reversed phase HPLC (RP-HPLC) with sulfobutylether-β-cyclodextrin (SBE-β-CD) as a chiral mobile phase additive. The effects of the pH value of aqueous buffer, concentration of chiral additive, composition of mobile phase, and column temperature on the enantioseparation of CIT were investigated on the Hedera ODS-2 C18 column (250 mm × 4.6 mm × 5.0 um). A satisfactory resolution was achieved at 25°C using a mobile phase consisting of a mixture of aqueous buffer (pH of 2.5, 5 mM sodium dihydrogen phosphate, and 12 mM SBE-β-CD), methanol, and acetonitrile with a volumetric ratio of 21 : 3 : 1 and flow rate of 1.0 mL/min. This analytical method was evaluated by examining the precision (lower than 3.0%), linearity (regression coefficients close to 1), limit of detection (0.070 µg/mL for (R)-CIT and 0.076 µg/mL for (S)-CIT), and limit of quantitation (0.235 µg/mL for (R)-CIT and 0.254 µg/mL for (S)-CIT).

  18. Enantioseparation of Citalopram by RP-HPLC, Using Sulfobutyl Ether-β-Cyclodextrin as a Chiral Mobile Phase Additive

    Directory of Open Access Journals (Sweden)

    Yangfeng Peng

    2016-01-01

    Full Text Available Enantiomeric separation of citalopram (CIT was developed using a reversed phase HPLC (RP-HPLC with sulfobutylether-β-cyclodextrin (SBE-β-CD as a chiral mobile phase additive. The effects of the pH value of aqueous buffer, concentration of chiral additive, composition of mobile phase, and column temperature on the enantioseparation of CIT were investigated on the Hedera ODS-2 C18 column (250 mm × 4.6 mm × 5.0 um. A satisfactory resolution was achieved at 25°C using a mobile phase consisting of a mixture of aqueous buffer (pH of 2.5, 5 mM sodium dihydrogen phosphate, and 12 mM SBE-β-CD, methanol, and acetonitrile with a volumetric ratio of 21 : 3 : 1 and flow rate of 1.0 mL/min. This analytical method was evaluated by examining the precision (lower than 3.0%, linearity (regression coefficients close to 1, limit of detection (0.070 µg/mL for (R-CIT and 0.076 µg/mL for (S-CIT, and limit of quantitation (0.235 µg/mL for (R-CIT and 0.254 µg/mL for (S-CIT.

  19. Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities

    Energy Technology Data Exchange (ETDEWEB)

    Mustonen, K.; Laiho, P.; Kaskela, A.; Zhu, Z.; Reynaud, O.; Houbenov, N.; Tian, Y.; Jiang, H.; Kauppinen, E. I., E-mail: esko.kauppinen@aalto.fi [Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto (Finland); Susi, T. [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria); Nasibulin, A. G. [Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto (Finland); Skolkovo Institute of Science and Technology, Nobel str. 3, 143026 (Russian Federation); Saint-Petersburg State Polytechnical University, 29 Polytechniheskaya st., St. Petersburg, 195251 (Russian Federation)

    2015-07-06

    We present a floating catalyst synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3–4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67% to 80%. Limiting the nanotube gas phase number concentration to ∼10{sup 5 }cm{sup −3} prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80% of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ω/□ at 90% transparency for 550 nm light.

  20. Diastereomeric resolution directed towards chirality determination focussing on gas-phase energetics of coordinated sodium dissociation

    Science.gov (United States)

    Kanie, Osamu; Shioiri, Yuki; Ogata, Koji; Uchida, Waka; Daikoku, Shusaku; Suzuki, Katsuhiko; Nakamura, Shinichiro; Ito, Yukishige

    2016-01-01

    Defining chiral centres is addressed by introducing a pair of chiral auxiliary groups. Ions of diastereomeric pairs of molecules could be distinguished utilising energy-resolved mass spectrometry, and the applicability of the method to a series of compounds carrying amine, carboxylic acid, alcohol, and all the amino acids was verified. The method was further strengthened by distinguishing diastereomeric ions that did not undergo fragmentation. Mass spectrometric evaluation of the dissociation process of adducted sodium cations from the diastereomeric precursors agreed with the theoretical calculations, indicating the potential usefulness of the method for the determination of absolute configurations. PMID:27040078

  1. Nematic Ordering of Rigid Rods in a Gravitational Field

    CERN Document Server

    Baulin, V A; Baulin, Vladimir A.; Khokhlov, Alexei R.

    1999-01-01

    The isotropic-to-nematic transition in an athermal solution of long rigid rods subject to a gravitational (or centrifugal) field is theoretically considered in the Onsager approximation. The new feature emerging in the presence of gravity is a concentration gradient which coupled with the nematic ordering. For rodlike molecules this effect becomes noticeable at centrifugal acceleration g ~ 10^3--10^4 m/s^2, while for biological rodlike objects, such as tobacco mosaic virus, TMV, the effect is important even for normal gravitational acceleration conditions. Rods are concentrated near the bottom of the vessel which sometimes leads to gravity induced nematic ordering. The concentration range corresponding to phase separation increases with increasing g. In the region of phase separation the local rod concentration, as well as the order parameter, follow a step function with height.

  2. Quenched disorder and spin-glass correlations in XY nematics

    Energy Technology Data Exchange (ETDEWEB)

    Petridis, L; Terentjev, E M [Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE (United Kingdom)

    2006-08-04

    We present a theoretical study of the equilibrium ordering in a 3D XY nematic system with quenched random disorder. Within this model, treated with the replica trick and Gaussian variational method, the correlation length is obtained as a function of the local nematic order parameter Q and the effective disorder strength {gamma}. These results, {xi} {approx} Q{sup 2}e{sup 1/Q{sup 2}} and {xi} {approx} (1/{gamma}) e{sup -{gamma}}, clarify what happens in the limiting cases of diminishing Q and {gamma}, that is near a phase transition of a pure system. In particular, it is found that quenched disorder is irrelevant as Q {yields} 0 and hence does not change the character of the continuous XY nematic-isotropic phase transition. We discuss how these results compare with experiments and simulations.

  3. Asymmetric fluorination of α-branched cyclohexanones enabled by a combination of chiral anion phase-transfer catalysis and enamine catalysis using protected amino acids.

    Science.gov (United States)

    Yang, Xiaoyu; Phipps, Robert J; Toste, F Dean

    2014-04-09

    We report a study involving the successful merger of two separate chiral catalytic cycles: a chiral anion phase-transfer catalysis cycle to activate Selectfluor and an enamine activation cycle, using a protected amino acid as organocatalyst. We have demonstrated the viability of this approach with the direct asymmetric fluorination of α-substituted cyclohexanones to generate quaternary fluorine-containing stereocenters. With these two chiral catalytic cycles operating together in a matched sense, high enantioselectivites can be achieved, and we envisage that this dual catalysis method has the potential to be more broadly applicable, given the breadth of enamine catalysis. It also represents a rare example of chiral enamine catalysis operating successfully on α-branched ketones, substrates commonly inert to this activation mode.

  4. Chiral recognition of N-phthaloyl, N-tetrachlorophthaloyl, and N-naphthaloyl α-amino acids and their esters on polysaccharide-derived chiral stationary phases.

    Science.gov (United States)

    Kim, Byoung-Hyoun; Lee, Sang Uck; Moon, Dong Cheul

    2012-12-01

    Enantiomeric separations of N-phthaloyl (N-PHT), N-tetrachlorophthaloyl (N-TCPHT), and N-naphthaloyl (N-NPHT) α-amino acids and their esters were examined on several kinds of polysaccharide-derived chiral stationary phases (CSPs). Resolution capability of CSPs was greater Chiralcel OF than the others for N-PHT and N-NPHT α-amino acids and their esters. In N-TCPHT α-amino acids and their esters, good enantioselectivities showed Chiralcel OG for N-TCPHT α-amino acids, Chiralpak AD for N-TCPHT α-amino acid methyl esters, and Chiralcel OD for N-TCPHT α-amino acid ethyl esters, respectively. From the results of liquid chromatography and computational chemistry, it is concluded that l-form is preferred and more retained with electrostatic interaction in case of interaction between N-PHT α-amino acid derivatives and Chiralcel OF, N-TCPHT α-amino acid derivatives and Chiralcel OD, and N-NPHT α-amino acid derivatives and Chiracel OF. On the other hand, d-form is preferred and more retained with van der Waals interaction in case of interaction between N-TCPHT α-amino acid ester derivatives and Chiralcel OG and Chiralpak AD.

  5. The synthesis and characterization of novel brush-type chiral stationary phase based on terpenoid selector for resolution of chiral drugs

    OpenAIRE

    Wang Dao-Cai; Luo Jia; Yao Shun; Song Hang

    2016-01-01

    In the light of the chiral resolution mechanism and structures of brush-type CSP, a new chiral selector 4′-carboxyl-1′-ursolic methyl ester-3β-yl-benzoate has been prepared. Then the terpenoid chiral selector was covalently linked to 3-aminopropyl silica gel. Its structure identification data are provided by 1H NMR, MS and elementary analysis. The enantiodiscriminating capability of the brush-type CSP was evaluated by static adsorption experiment with methyl mandelate, aniline derivative of m...

  6. Direct high-performance liquid chromatography enantioseparation of terazosin on an immobilised polysaccharide-based chiral stationary phase under polar organic and reversed-phase conditions.

    Science.gov (United States)

    Ferretti, Rosella; Gallinella, Bruno; La Torre, Francesco; Zanitti, Leo; Turchetto, Luciana; Mosca, Antonina; Cirilli, Roberto

    2009-07-10

    High-performance liquid chromatography (HPLC) enantioseparation of terazosin (TER) was accomplished on the immobilised-type Chiralpak IC chiral stationary phase (CSP) under both polar organic and reversed-phase modes. A simple analytical method was validated using a mixture of methanol-water-DEA 95:5:0.1 (v/v/v) as a mobile phase. Under reversed-phase conditions good linearities were obtained over the concentration range 8.76-26.28 microg mL(-1) for both enantiomers. The limits of detection and quantification were 10 and 30 ng mL(-1), respectively. The intra- and inter-day assay precision was less than 1.66% (RSD%). The optimised conditions also allowed to resolve chiral and achiral impurities from the enantiomers of TER. The proposed HPLC method supports pharmacological studies on the biological effects of the both forms of TER and analytical investigations of potential drug formulations based on a single enantiomer. At the semipreparative scale, 5.3 mg of racemic sample were resolved with elution times less than 12 min using a mobile phase consisting of methanol-DEA 100:0.1 (v/v) and both enantiomers were isolated with a purity of > or = 99% enantiomeric excess (ee). The absolute configuration of TER enantiomers was assigned by comparison of the measured specific rotations with those reported in the literature.

  7. Synthesis and chromatographic evaluation of new polymeric chiral stationary phases based on three (1S,2S)-(-)-1,2-diphenylethylenediamine derivatives in HPLC and SFC.

    Science.gov (United States)

    Payagala, Tharanga; Wanigasekara, Eranda; Armstrong, Daniel W

    2011-03-01

    Three new polymeric chiral stationary phases were synthesized based on (1S,2S)-1,2-bis(2,4,6-trimethylphenyl)ethylenediamine, (1S,2S)-1,2-bis(2-chlorophenyl)ethylenediamine, and (1S,2S)-1,2-di-1-naphthylethylenediamine via a simple free-radical-initiated polymerization in solution. These monomers are structurally related to (1S,2S)-1,2-diphenylethylenediamine which is the chiral monomer used for the commercial P-CAP-DP polymeric chiral stationary phase (CSP). The performance of these three new chiral stationary phases were evaluated in normal phase high-performance liquid chromatography (HPLC) and supercritical fluid chromatography and the results were compared with those of the P-CAP-DP column. All three new phases showed enantioselectivity for a large number of racemates with a variety of functional groups, including amines, amides, alcohols, amino acids, esters, imines, thiols, and sulfoxides. In normal phase, 68 compounds were separated with 28 baseline separations (Rs ≥ 1.5) and in SFC, 65 compounds were separated with 24 baseline separations. In total 72 out of 100 racemates were separated by these CSPs with 37 baseline separations. Complimentary separation capabilities were observed for many analytes. The new polymeric CSPs showed similar or better enantioselectivities compared with the commercial column in both HPLC and SFC. However, faster separations were achieved on the new stationary phases. Also, it was shown that these polymeric stationary phases have good sample loading capacities while maintaining enantioselectivity.

  8. Impact of the nature and composition of the mobile phase on the mass transfer mechanism in chiral reversed phase liquid chromatography. Application to the minimization of the solvent cost in chiral separations.

    Science.gov (United States)

    Gritti, Fabrice; Guiochon, Georges

    2014-01-31

    The mechanism of mass transfer was studied on a cellulose-based chiral stationary phase (CSP, Lux Cellulose-1) using aqueous mixtures of acetonitrile (50/50-90/10, v/v) or methanol (90/10 and 100/0, v/v) as the mobile phase. An experimental protocol validated in RPLC and HILIC chromatography and recently extended to chiral RPLC was applied. The five mass-transfer contributions (longitudinal diffusion, short-range and long-range eddy dispersion, solid-liquid mass transfer resistances due to finite intra-particle diffusivity and slow adsorption-desorption) to the reduced height equivalent to a theoretical plate (HETP) were measured. The experimental results show that the adsorption rate constants kads of trans-stilbene enantiomers onto the CSP are three times larger with acetonitrile than with methanol as the organic modifier. This is correlated to the decrease of enantioselectivity from 1.4 (in methanol) to only 1.1 (in acetonitrile). The amount of solvent needed to achieve a separation factor of exactly 2.0 was determined. This showed that analysis cost could be reduced seven times by selecting pure methanol as the eluent for a 5cm long column rather than an acetonitrile-water mixture for a longer (20-45cm) column.

  9. Intertwined nematic orders in a frustrated ferromagnet

    Science.gov (United States)

    Iqbal, Yasir; Ghosh, Pratyay; Narayanan, Rajesh; Kumar, Brijesh; Reuther, Johannes; Thomale, Ronny

    2016-12-01

    We investigate the quantum phases of the frustrated spin-1/2 J1-J2-J3 Heisenberg model on the square lattice with ferromagnetic J1 and antiferromagnetic J2 and J3 interactions. Using the pseudofermion functional renormalization group technique, we find an intermediate paramagnetic phase located between classically ordered ferromagnetic, stripy antiferromagnetic, and incommensurate spiral phases. We observe that quantum fluctuations lead to significant shifts of the spiral pitch angles compared to the classical limit. By computing the response of the system with respect to various spin rotation and lattice symmetry-breaking perturbations, we identify a complex interplay between different nematic spin states in the paramagnetic phase. While retaining time-reversal invariance, these phases either break spin-rotation symmetry, lattice-rotation symmetry, or a combination of both. We therefore propose the J1-J2-J3 Heisenberg model on the square lattice as a paradigmatic example where different intimately connected types of nematic orders emerge in the same model.

  10. Applications of chiral symmetry

    CERN Document Server

    Pisarski, R D

    1995-01-01

    I discuss several topics in the applications of chiral symmetry at nonzero temperature, including: where the rho goes, disoriented chiral condensates, and the phase diagram for QCD with 2+1 flavors. (Based upon talks presented at the "Workshop on Finite Temperature QCD", Wuhan, P.R.C., April, 1994.)

  11. Investigation on enantiomeric separations of fluorenylmethoxycarbonyl amino acids and peptides by high-performance liquid chromatography using native cyclodextrins as chiral stationary phases.

    Science.gov (United States)

    Tang, Y; Zukowski, J; Armstrong, D W

    1996-09-06

    A systematic study was carried out to investigate enantiomeric separations of fluorenylmethoxycarbonyl (FMOC) amino acids and their peptides. Twenty amino acids were derivatized by 9-fluorenylmethyl chloroformate (FMOC-Cl) and its analogues, FMOC-glycyl-Cl and FMOC-beta-alanyl-Cl. All derivatives were chromatographed on native beta- and gamma-cyclodextrin columns using acetonitrile as the main mobile phase component. The results indicated that glycyl and beta-alanyl groups between FMOC and amino acid moieties enhanced chiral selectivities of amino acid derivatives. The addition of modifiers, triethylamine, acetic acid and methanol, into the mobile phase caused alterations in retention, enantiorecognition and elution order. The structures of amino acids and the type of chiral stationary phase employed exhibited significant impacts on chiral resolutions. It is also found that the number and position of glycyl moieties affect the retentions and enantioselectivities of FMOC derivatized glycyl containing peptides.

  12. Mandelic acid chiral separation utilizing a two-phase partitioning bioreactor built by polysulfone microspheres and immobilized enzymes.

    Science.gov (United States)

    Wang, Xinyu; Cui, Yanjun; Chen, Xia; Zhu, Hao; Zhu, Weiwei; Li, Yanfeng

    2015-03-01

    A novel two-phase partitioning bioreactor (TPPB) modified by polysulfone (PSF) microspheres and immobilized enzyme (novozym-435) was formed, and the resulting TPPB was applied into mandelic acid chiral separation. The PSF microspheres containing n-hexanol (named PSF/hexanol microspheres) was prepared by using the phase inversion method, which was used as the organic phase. Meanwhile, the immobilized enzyme novozym-435 was used as a biocatalyst. The water phase was composed of the phosphate buffer solution (PBS). (R, S)-Methyl mandelate was selected as the substrate to study enzymatic properties. Different reaction factors have been researched, such as pH, reaction time, temperature and the quantity of biocatalyst and PSF/hexanol microspheres added in. Finally, (S)-mandelic acid was obtained with an 80 % optical purity after 24 h in the two-phase partitioning bioreactor. The enantiomeric excess (eep) values were very low in the water phase, in which the highest eep value was only 46 %. The eep of the two-phase partitioning bioreactor had been enhanced more obviously than that catalyzed in the water phase.

  13. The $N_f=2$ QCD chiral phase transition with Wilson fermions at zero and imaginary chemical potential

    CERN Document Server

    Philipsen, Owe

    2016-01-01

    The order of the thermal phase transition in the chiral limit of Quantum Chromodynamics (QCD) with two dynamical flavors of quarks is a long-standing issue and still not known in the continuum limit. Whether the transition is first or second order has important implications for the QCD phase diagram and the existence of a critical endpoint at finite densities. We follow a recently proposed approach to explicitly determine the region of first order chiral transitions at imaginary chemical potential, where it is large enough to be simulated, and extrapolate it to zero chemical potential with known critical exponents. Using unimproved Wilson fermions on coarse $N_t=4$ lattices, the first order region turns out to be so large that no extrapolation is necessary. The critical pion mass $m_\\pi^c\\approx 560$ MeV is by nearly a factor 10 larger than the corresponding one using staggered fermions. Our results are in line with investigations of three-flavour QCD using improved Wilson fermions and indicate that the syste...

  14. Thin film phase and local chirality of surface-bound MOP4 nanofibers

    DEFF Research Database (Denmark)

    Balzer, Frank; Röthel, Christian; Rubahn, Horst-Günter

    2016-01-01

    Vacuum deposition of the methoxy-functionalized p-quaterphenylene MOP4 on muscovite mica at elevated temperatures led to the formation of several ten micrometer long nanofibers. As shown by X-ray diffraction and polarized optical microscopy, the fibers are formed by lying molecules which grow epi...... by atomic force microscopy (AFM). The fibers represent chiral organization into single-handed aggregates of both handednesses, which is not affected by aging. On a global level, the sample remained achiral....

  15. High efficiency, narrow particle size distribution, sub-2 μm based macrocyclic glycopeptide chiral stationary phases in HPLC and SFC.

    Science.gov (United States)

    Barhate, Chandan L; Wahab, M Farooq; Breitbach, Zachary S; Bell, David S; Armstrong, Daniel W

    2015-10-22

    State of the art chiral chromatography still employs 3-5 μm bonded or immobilized chiral selectors in 10-25 cm columns. With the availability of 1.9 μm narrow particle size distribution (NPSD) silica, it is now possible to make ever shorter, high efficiency columns practical for sub-minute chiral separations. Three macrocyclic glycopeptides (teicoplanin, teicoplanin aglycone, and vancomycin) were bonded onto 1.9 μm NPSD particles. Such packed columns had ∼80% lower backpressure as compared to polydisperse (PD) 1.7 μm silica materials when using the same mobile phase. The decreased backpressure allowed for diminution of frictional heating and allowed for the use of the 1.9 μm NPSD particle based columns at high flow rates. The 1.9 μm NPSD particle based columns showed up to 190,000 plates m(-1) for chiral molecules and 210,000 plates m(-1) for achiral probes. Representative enantiomeric separations are shown for wide classes of compounds, including different types of amino acids, β-blockers, and pharmaceutically important heterocyclic compounds such as oxazolidinones. Applications in three liquid chromatography modes, namely, reversed phase, polar organic mode and normal phase chiral separations were shown with resolution values ranging from 1.5 to 5.7. Additionally, the same columns were used with supercritical fluid chromatography (SFC) for ultrafast separations.

  16. The CGC enantiomer separation of 2-arylcarboxylic acid esters by using β-cyclodextrin derivatives as chiral stationary phases.

    Science.gov (United States)

    Shi, Xueyan; Liu, Feipeng; Mao, Jianyou

    2016-03-17

    Chiral 2-arylcarboxylic acid esters are important intermediates in preparation of enantioenriched 2-arylpropionic acids type Non-steroidal anti-inflammatory drugs (NSAIDs). Enantiomer separation of 2-arylcarboxylic acid esters is crucial for evaluation of the asymmetric synthesis efficiency and the enantiomer excess of chiral 2-arylcarboxylic acid derivatives. The capillary gas chromatography (CGC) enantiomer separation of 17 pairs of 2-arylcarboxylic acid esters enantiomers was conducted by using seven different β-cyclodextrin derivatives (CDs) as chiral stationary phases. It was found that for the 7 pairs of 2-phenylpropionates enantiomers, CDs with both alkyl and acyl substituents especially 2,6-di-O-pentyl-3-O-butyryl-β-cyclodextrin exhibited better enantiomer separation abilities than the other CDs examined. For the 7 pairs of 2-(4-substituted phenyl)propionates enantiomers, 2,3,6-tri-O-methyl-β-cyclodextrin possessed better enantiomer separation abilities than the other CDs. Among the 3 pairs of 2-phenylbutyrates enantiomers examined, only methyl 2-phenylbutyrate enantiomers could be separated by three CDs among the 7 CDs tested, while enantiomers of ethyl 2-phenylbutyrate and isopropyl 2-phenylbutyrate couldn't be separated by any of the 7 CDs tested. Besides the structures of CDs, the structures of 2-arylcarboxylic acid esters including different ester moieties, substituents of phenyl, and different carboxylic acids moieties in 2-arylcarboxylic acid esters also affected the enantiomer separation results greatly. The CGC enantiomer separation results of 2-arylcarboxylic acid esters on different CDs are useful for solving the enantiomer separation problem of 2-arylcarboxylic acid esters.

  17. Anchoring-Induced Texture & Shear Banding of Nematic Polymers in Shear Cells

    Science.gov (United States)

    2007-10-01

    varying orientation tensor ellipsoid at several locations between the plates. The Doi- Hess kinetic theory is developed to study the dynamics of LCP...profile is evident in one of the snapshots, a phenomenon seen by Sebastian Heidenreich in related studies and in full kinetic flow-nematic simulations of...kinetic phase diagram for nematic polymers, Rheol. Acta., 43 (2004), 17–37. [20] M.G. Forest, Q. Wang and R. Zhou, The flow-phase diagram of Doi- Hess

  18. Magnetic-Field-Induced Weak Order in Nematic Liquid Crystals Formed by Biaxial Molecules

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Dong; ZHANG De-Xian; SUN Yu-Bao

    2000-01-01

    Nematic liquid crystal system of interacting biaxial particles via dispersion forces is studied. The molecular orienting potential form in a magnetic field is given for the first time. Weakly ordered isotropic phase is treated in the two-particle cluster approximation. Taking account of the molecular biaxiality, it is found that the ratio of the lowest supercooling temperature T* to the nematic-isotropic phase transition temperature TC approaches the observed value, and the validity of the mean field theory is clarified.

  19. High resolution of racemic phenylalanine with dication imidazolium-based chiral ionic liquids in a solid-liquid two-phase system.

    Science.gov (United States)

    Huang, Xiaoxia; Wu, Haoran; Wang, Zhixia; Luo, Yingjie; Song, Hang

    2017-01-06

    A novel solid-liquid two-phase system was developed for the chiral separation of racemic phenylalanine with new dication imidazolium-based chiral ionic liquids. Preliminary experiments showed distinct enantioselectivity in amino acid extraction with the novel solid-liquid two-phase system, more L-enantiomer of amino acid cooperatively interacted with ionic liquids and copper ions to be the solid phase. Various factors, including the alkyl chain length of cations of ionic liquids, the amount of copper acetate, the ratio of n(ILs)/n(Cu(2+)), the amount of water and racemic phenylalanine, the resolution time together with the resolution temperature, were systematically investigated for their influence on resolution efficiency. The results showed that, under a certain condition, the enantiomeric excess value and the yield of phenylalanine in liquid phase (mainly containing D-enantiomer) were 67.8% and 96.5%, the enantiomeric excess value and the yield of phenylalanine in solid phase (mainly containing L-enantiomer) were 99.2% and 85.2%. Finally, 2D NMR technology, infrared spectroscopy and molecular simulation method were used to study the interaction mechanism. The results indicated that L-enantiomer of phenylalanine interacts more strongly with chiral ILs and Cu(2+). The novel system has characteristics of free-organic solvent, simple operation, fast separation process and very high resolution efficiency for racemic phenylalanine. This work could provide a new and alternative resolution approach for other chiral separations.

  20. Photoswitching of helical twisting power by chiral photochromic diarylethene dopants

    Science.gov (United States)

    Yamaguchi, Tadatsugu; Irie, Masahiro

    2002-12-01

    Two kinds of chiral diarylethene derivatives were synthesized and used as dopants for photoresponsive liquid crystals. Both derivatives underwent thermally irreversible and fatigue resistant photochromic reactions and exhibited reversible circular diochroism (CD) spectral changes. Large photostimulated pitch chances of chiral nematic K-15 liquid crystals were observed by the addition of the derivatives as dopants. The relation between the optical rotation and the twisting power force was discussed.

  1. Chiral Separation of Novel a-Aminophosphonates Containing a Benzothiazole Moiety by Liquid Chromatography Using an Amylose Stationary Phase

    Institute of Scientific and Technical Information of China (English)

    LU Ping; ZHANG Yu-Ping; SONG Bao-An; YANG Song; BHADURY Shankar Pinaki; HU De-Yu; XUE Wei; CHEN Zhuo; JIN Lin-Hong

    2008-01-01

    The present report describes a chiral HPLC method for the enantiomeric separation of a-aminophosphonate derivatives using two new coated and immobilized amylose-based chiral stationary phases (CSP,Chiralpak IA and Chiralpak AD-H).The chromatographic parameters such as retention factor (k),separation factor (a),and resolution (Rs) of the solutes were investigated on these two CSPs.Reasonably good baseline separation for these compounds was achieved using Chiralpak IA column.The influences of temperature,content of ethanol modifier and the structure of analyte were also studied.THF,EtOAc and CH2Cl2 were used as ehients on analytical and semi-preparative columns.Highly enriched enantiomers with purities of up to 96.4%--100% (ee) and yields of 90.2%--95.5% were obtained,respectively.The proposed methods were found to be suitable and accurate for rapid separation and semi-preparation of enantiomeric a-aminophosphonate derivatives available.

  2. Field-driven dynamics of nematic microcapillaries

    Science.gov (United States)

    Khayyatzadeh, Pouya; Fu, Fred; Abukhdeir, Nasser Mohieddin

    2015-12-01

    Polymer-dispersed liquid-crystal (PDLC) composites long have been a focus of study for their unique electro-optical properties which have resulted in various applications such as switchable (transparent or translucent) windows. These composites are manufactured using desirable "bottom-up" techniques, such as phase separation of a liquid-crystal-polymer mixture, which enable production of PDLC films at very large scales. LC domains within PDLCs are typically spheroidal, as opposed to rectangular for an LCD panel, and thus exhibit substantially different behavior in the presence of an external field. The fundamental difference between spheroidal and rectangular nematic domains is that the former results in the presence of nanoscale orientational defects in LC order while the latter does not. Progress in the development and optimization of PDLC electro-optical properties has progressed at a relatively slow pace due to this increased complexity. In this work, continuum simulations are performed in order to capture the complex formation and electric field-driven switching dynamics of approximations of PDLC domains. Using a simplified elliptic cylinder (microcapillary) geometry as an approximation of spheroidal PDLC domains, the effects of geometry (aspect ratio), surface anchoring, and external field strength are studied through the use of the Landau-de Gennes model of the nematic LC phase.

  3. One-Pot Click Access to a Cyclodextrin Dimer-Based Novel Aggregation Induced Emission Sensor and Monomer-Based Chiral Stationary Phase

    Directory of Open Access Journals (Sweden)

    Xiaoli Li

    2016-11-01

    Full Text Available A ‘two birds, one stone’ strategy was developed via a one-pot click reaction to simultaneously prepare a novel cyclodextrin (CD dimer based aggregation induced emission (AIE sensor (AIE-DCD and a monomer based chiral stationary phase (CSP-MCD for chiral high performance liquid chromatography (CHPLC. AIE-DCD was found to afford satisfactory AIE response for specific detection of Zn2+ with a detection limit of 50 nM. CSP-MCD exhibits excellent enantioseparation ability toward dansyl amino acids, where the resolution of dansyl amino leucine reaches 5.43.

  4. Monte-Carlo approach to particle-field interactions and the kinetics of the chiral phase transition

    CERN Document Server

    Greiner, Carsten; van Hees, Hendrik; Meistrenko, Alex

    2015-01-01

    The kinetics of the chiral phase transition is studied within a linear quark-meson-$\\sigma$ model, using a Monte-Carlo approach to semiclassical particle-field dynamics. The meson fields are described on the mean-field level and quarks and antiquarks as ensembles of test particles. Collisions between quarks and antiquarks as well as the $q\\overline{q}$ annihilation to $\\sigma$ mesons and the decay of $\\sigma$ mesons is treated, using the corresponding transition-matrix elements from the underlying quantum field theory, obeying strictly the rule of detailed balance and energy-momentum conservation. The approach allows to study fluctuations without making ad hoc assumptions concerning the statistical nature of the random process as necessary in Langevin-Fokker-Planck frameworks.

  5. Transient Splitting of Conoscopic Isogyres of a Uniaxial Nematic

    Science.gov (United States)

    Kim, Young-Ki; Senuk, Bohdan; Tortora, Luana; Sprunt, Samuel; Lehmann, Matthias; Lavrentovich, Oleg D.

    2012-02-01

    The phase identification is often based on conoscopic observations of homeotropic cells: A uniaxial nematic produces a pattern with crossed isogyres, while the biaxial nematic shows a split of isogyres. We demonstrate that the splitting of isogyres occurs even when the material remains in the uniaxial nematic phase. In particular, in the bent core material J35, splitting of isogyres is caused by change of the temperature. The effect is transient and the isogyres return to a uniaxial (crossed) configuration after a certain time that depends on sample thickness, temperature, and rate of temperature change; the time varies from a few seconds to tens of hours. The transient splitting is caused by the temperature-induced material flow that triggers a (uniaxial) director tilt in the cell. The flows and the director tilt are demonstrated by the CARS microscopy and fluorescent confocal polarizing microscopy (FCPM). This transient effect is general and can be observed even in E7 and 5CB. The effect should be considered in textural identifications of potential biaxial nematic materials.

  6. Stabilization of the chiral phase of the SU (6 m ) Heisenberg model on the honeycomb lattice with m particles per site for m larger than 1

    Science.gov (United States)

    Dufour, Jérôme; Mila, Frédéric

    2016-09-01

    We show that, when N is a multiple of 6 (N =6 m , where m is an integer), the SU (N) Heisenberg model on the honeycomb lattice with m particles per site has a clear tendency toward chiral order as soon as m ≥2 . This conclusion has been reached by a systematic variational Monte Carlo investigation of Gutzwiller projected wave functions as a function of m between the case of one particle per site (m =1 ), for which the ground state has recently been shown to be in a plaquette singlet state, and the m →∞ limit, where a mean-field approach has established that the ground state has chiral order. This demonstrates that the chiral phase can indeed be stabilized for not too large values of m , opening the way to its experimental realizations in other lattices.

  7. Evaluation of the chiral recognition properties as well as the column performance of four chiral stationary phases based on cellulose (3,5-dimethylphenylcarbamate) by parallel HPLC and SFC.

    Science.gov (United States)

    Nelander, Hanna; Andersson, Shalini; Ohlén, Kristina

    2011-12-30

    The performance of four commercially available cellulose tris(3,5-dimethylphenylcarbamate) based chiral stationary phases (CSPs) was evaluated with parallel high performance liquid chromatography (HPLC) and super critical fluid chromatography (SFC). Retention, enantioselectivity, resolution and efficiency were compared for a set of neutral, basic and acidic compounds having different physico-chemical properties by using different mobile phase conditions. Although the chiral selector is the same in all the four CSPs, a large difference in the ability to retain and resolve enantiomers was observed under the same chromatographic conditions. We believe that this is mainly due to differences in the silica matrix and immobilization techniques used by the different vendors. An extended study of metoprolol and structure analogues gave a deeper understanding of the accessibility of the chiral discriminating interactions and its impact on the resolution of the racemic compounds on the four CSPs studied. Also, a clear difference in enantioselectivity is observed between SFC and LC mode, hydrogen bonding was found to play an important role in the differential binding of the enantiomers to the CSPs.

  8. Topological phase transitions and chiral inelastic transport induced by the squeezing of light

    Science.gov (United States)

    Peano, Vittorio; Houde, Martin; Brendel, Christian; Marquardt, Florian; Clerk, Aashish A.

    2016-01-01

    There is enormous interest in engineering topological photonic systems. Despite intense activity, most works on topological photonic states (and more generally bosonic states) amount in the end to replicating a well-known fermionic single-particle Hamiltonian. Here we show how the squeezing of light can lead to the formation of qualitatively new kinds of topological states. Such states are characterized by non-trivial Chern numbers, and exhibit protected edge modes, which give rise to chiral elastic and inelastic photon transport. These topological bosonic states are not equivalent to their fermionic (topological superconductor) counterparts and, in addition, cannot be mapped by a local transformation onto topological states found in particle-conserving models. They thus represent a new type of topological system. We study this physics in detail in the case of a kagome lattice model, and discuss possible realizations using nonlinear photonic crystals or superconducting circuits. PMID:26931620

  9. Separation of mandelic acid and its derivatives with new immobilized cellulose chiral stationary phase

    Institute of Scientific and Technical Information of China (English)

    Jie ZHOU; Qian LIU; Guang-jun FU; Zhen-zhong ZHANG

    2013-01-01

    A new liquid chromatographic method has been developed for the chiral separation of the enantiomers of mandelic acid and their derivatives 2-chloromandelic acid,4-hydroxymandelic acid,4-methoxymandelic acid,and 3,4,5-trismethoxymandelic acid.The enantiomers were separated by a CHIRALPAK(R) IC (250 mm×4.6 mm,5 μm).Mandelic acid,4-methoxymandelic acid,and 3,4,5-trismethoxymandelic acid were baseline resolved (resolution factor (Rs)=2.21,Rs=2.14,and Rs=3.70,respectively).In contrast,the enantioselectivities between CHIRALPAK(R) IC and 2-chloromandelic acid and 4-hydroxymandelic acid investigated were low.By comparing the chromatographs of mandelic acid enantiomers and mandelic acid spiked with (R)-mandelic acid,it was determined that the first effluent was (R)-mandelic acid.

  10. Topological Electromagnetic Responses of Bosonic Quantum Hall, Topological Insulator, and Chiral Semi-Metal phases in All Dimensions

    CERN Document Server

    Lapa, Matthew F; Ye, Peng; Hughes, Taylor L

    2016-01-01

    We calculate the topological part of the electromagnetic response of Bosonic Integer Quantum Hall (BIQH) phases in odd (spacetime) dimensions, and Bosonic Topological Insulator (BTI) and Bosonic chiral semi-metal (BCSM) phases in even dimensions. To do this we use the Nonlinear Sigma Model (NLSM) description of bosonic symmetry-protected topological (SPT) phases, and the method of gauged Wess-Zumino (WZ) actions. We find the surprising result that for BIQH states in dimension $2m-1$ ($m=1,2,\\dots$), the bulk response to an electromagnetic field $A_{\\mu}$ is characterized by a Chern-Simons term for $A_{\\mu}$ with a level quantized in integer multiples of $m!$ (factorial). We also show that BTI states (which have an extra $\\mathbb{Z}_2$ symmetry) can exhibit a $\\mathbb{Z}_2$ breaking Quantum Hall effect on their boundaries, with this boundary Quantum Hall effect described by a Chern-Simons term at level $\\frac{m!}{2}$. We show that the factor of $m!$ can be understood by requiring gauge invariance of the expone...

  11. Normal and polar-organic-phase high-performance liquid chromatographic enantioresolution of omeprazole, rabeprazole, lansoprazole and pantoprazole using monochloro-methylated cellulose-based chiral stationary phase and determination of dexrabeprazole.

    Science.gov (United States)

    Dixit, Shuchi; Dubey, Rituraj; Bhushan, Ravi

    2014-01-01

    Enantioresolution of four anti-ulcer drugs (chiral sulfoxides), namely, omeprazole, rabeprazole, lansoprazole and pantoprazole, was carried out by high-performance liquid chromatography using a polysaccharide-based chiral stationary phase consisting of monochloromethylated cellulose (Lux cellulose-2) under normal and polar-organic-phase conditions with ultraviolet detection at 285 nm. The method was validated for linearity, accuracy, precision, robustness and limit of detection. The optimized enantioresolution method was compared for both the elution modes. The optimized method was further utilized to check the enantiomeric purity of dexrabeprazole.

  12. Ordering Quantum Dot Clusters via Nematic Liquid Crystal Defects

    Science.gov (United States)

    Rodarte, Andrea; Pandolfi, R.; Hirst, L. S.; Ghosh, S.

    2012-11-01

    Nematic liquid crystal (LC) materials can be used to create ordered clusters of CdSe/ZnS core/shell quantum dots (QDs) from a homogeneous isotropic dispersion. At the phase transition, the ordered domains of nematic LC expel the majority of dispersed QDs into the isotropic domains. The final LC phase produces a series of QD clusters that are situated at the defect points of the liquid crystal texture. Lower concentrations of QDs are organized in a network throughout the LC matrix that originates from the LC phase transition. Inside the QD clusters the inter-particle distance enables efficient energy transfer from high energy dots to lower energy dots. Because the QD clusters form at defect sites, the location of the clusters can be preselected by seeding the LC cell with defect nucleation points.

  13. Droplet Breakup of the Nematic Liquid Crystal MBBA

    CERN Document Server

    Nachman, Benjamin

    2012-01-01

    Droplet breakup is a well studied phenomena in Newtonian fluids. One property of this behavior is that, independent of initial conditions, the minimum radius exhibits power law scaling with the time left to breakup tau. Because they have additional structure and shear dependent viscosity, liquid crystals pose an interesting complication to such studies. Here, we investigate the breakup of a synthetic nematic liquid crystal known as MBBA. We determine the phase of the solution by using a cross polarizer setup in situ with the liquid bridge breakup apparatus. Consistent with previous studies of scaling behavior in viscous-inertial fluid breakup, when MBBA is in the isotropic phase, the minimum radius decreases as tau^{1.03 \\pm 0.04}. In the nematic phase however, we observe very different thinning behavior. Our measurements of the thinning profile are consistent with two interpretations. In the first interpretation, the breakup is universal and consists of two different regimes. The first regime is characterize...

  14. Enantioseparation of Racemic Flurbiprofen by Aqueous Two-Phase Extraction With Binary Chiral Selectors of L-dioctyl Tartrate and L-tryptophan.

    Science.gov (United States)

    Chen, Zhi; Zhang, Wei; Wang, Liping; Fan, Huajun; Wan, Qiang; Wu, Xuehao; Tang, Xunyou; Tang, James Z

    2015-09-01

    A novel method for chiral separation of flurbiprofen enantiomers was developed using aqueous two-phase extraction (ATPE) coupled with biphasic recognition chiral extraction (BRCE). An aqueous two-phase system (ATPS) was used as an extracting solvent which was composed of ethanol (35.0% w/w) and ammonium sulfate (18.0% w/w). The chiral selectors in ATPS for BRCE consideration were L-dioctyl tartrate and L-tryptophan, which were screened from amino acids, β-cyclodextrin derivatives, and L-tartrate esters. Factors such as the amounts of L-dioctyl tartrate and L-tryptophan, pH, flurbiprofen concentration, and the operation temperature were investigated in terms of chiral separation of flurbiprofen enantiomers. The optimum conditions were as follows: L-dioctyl tartrate, 80 mg; L-tryptophan, 40 mg; pH, 4.0; flurbiprofen concentration, 0.10 mmol/L; and temperature, 25 °C. The maximum separation factor α for flurbiprofen enantiomers could reach 2.34. The mechanism of chiral separation of flurbiprofen enantiomers is discussed and studied. The results showed that synergistic extraction has been established by L-dioctyl tartrate and L-tryptophan, which enantioselectively recognized R- and S-enantiomers in top and bottom phases, respectively. Compared to conventional liquid-liquid extraction, ATPE coupled with BRCE possessed higher separation efficiency and enantioselectivity without the use of any other organic solvents. The proposed method is a potential and powerful alternative to conventional extraction for separation of various enantiomers.

  15. Enantioselective determination of protein amino acids in fertilizers by liquid chromatography-tandem mass spectrometry on chiral teicoplanin stationary phase.

    Science.gov (United States)

    Taujenis, Lukas; Olšauskaitė, Vilma; Padarauskas, Audrius

    2014-11-19

    High-performance liquid chromatography on a glycopeptide antibiotic teicoplanin-based chiral stationary phase coupled with tandem mass spectrometry was developed for fast and reliable enantioseparation and determination of protein amino acids in hydrolyzed fertilizer samples. The effect of the mobile phase parameters (type and content of organic modifier and pH) and the column temperature on the enantioselectivity was investigated. Under optimized conditions, the majority (15 of 19) of d/l-amino acid pairs were resolved with a resolution factor (Rs) higher than 1.5 with a run time of 15 min. A triple quadrupole tandem mass spectrometer operating in multiple reaction monitoring mode with an electrospray ionization (ESI) ion source was employed for detection. The method was validated in terms of linearity, limits of detection, limits of quantitation, precision, and accuracy. Linear responses were obtained with determination coefficients higher than 0.998 for all analytes, and limits of detection were from 0.04 to 0.24 μg/mL. Sample spike/recovery experiments gave recovery values ranging from 73% for d-threonine to 116% for L-tryptophan. Relative standard deviations for inter- and intraday precision experiments were lower than 21.7%. The developed method was successfully applied for determination of the free amino acid enantiomers in five commercially available hydrolyzed protein fertilizer samples.

  16. The effect of acidic and basic additives on the enantioseparation of basic drugs using polysaccharide-based chiral stationary phases.

    Science.gov (United States)

    Ye, Yun K; Stringham, Rodger W

    2006-08-01

    The enantioseparation of nine commercially available basic drugs was achieved on polysaccharide-based chiral stationary phases with the acidic additive ethanesulfonic acid and the basic additive butylamine. Seven different commercially available CSPs were used for the study (AD, AS, OD, OJ, OG, OB, and OC). Mobile phase additives have been proven to be essential in obtaining satisfactory enantio-resolution in terms of both efficiency and selectivity. Significantly improved selectivities were obtained for the basic probe drugs with the acidic additive, ethanesulfonic acid, rather than the basic additive, butylamine. This is best seen with Chiralpak AS CSP. No enantioseparation for the nine drugs was observed when butylamine was used as an additive; however, satisfactory enantioseparation for the nine drugs was achieved using ethanesulfonic acid. Higher column efficiencies were observed with the acidic additive, especially when isopropanol was used as a modifier. Higher sensitivity was also achieved with ethanesulfonic acid because of the significantly lower background at the UV detection wavelength. The acidic additive was demonstrated to be superior to the basic additive for the enantioseparation of basic drugs using seven different polysaccharide-based CSPs. These results are counterintuitive to the common "rule of thumb" in enantioseparation that states acidic additives work best for acidic analytes and basic additives work best for basic analytes. The beneficial effects of acidic additive in enantioseparations observed in this study could significantly improve the applicability of polysaccharide-based CSPs for the enantioseparation of basic analytes.

  17. SU(3) Polyakov Linear $\\sigma$-Model in Magnetic Field: Thermodynamics, Higher-Order Moments, Chiral Phase Structure and Meson Masses

    CERN Document Server

    Tawfik, Abdel Nasser

    2015-01-01

    Effects of external magnetic field on various properties of the quantum chromodynamics under extreme conditions of temperature and density have been analysed. To this end, we use SU(3) Polyakov linear sigma-model and assume that the external magnetic field eB adds some restrictions to the quarks energy due to the existence of free charges in the plasma phase. In doing this, we apply the Landau theory of quantization. This requires an additional temperature to drive the system through the chiral phase-transition. Accordingly, the dependence of the critical temperature of chiral and confinement phase-transitions on the magnetic field is characterized. Based on this, we have studied the thermal evolution of thermodynamic quantities and the first four higher-order moment of particle multiplicity. Having all these calculations, we have studied the effects of magnetic field on chiral phase-transition. We found that both critical temperature T_c and critical chemical potential increase with increasing the magnetic f...

  18. Applications of chiral symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Pisarski, R.D.

    1995-03-01

    The author discusses several topics in the applications of chiral symmetry at nonzero temperature. First, where does the rho go? The answer: up. The restoration of chiral symmetry at a temperature T{sub {chi}} implies that the {rho} and a{sub 1} vector mesons are degenerate in mass. In a gauged linear sigma model the {rho} mass increases with temperature, m{sub {rho}}(T{sub {chi}}) > m{sub {rho}}(0). The author conjectures that at T{sub {chi}} the thermal {rho} - a{sub 1}, peak is relatively high, at about {approximately}1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The {omega} meson also increases in mass, nearly degenerate with the {rho}, but its width grows dramatically with temperature, increasing to at least {approximately}100 MeV by T{sub {chi}}. The author also stresses how utterly remarkable the principle of vector meson dominance is, when viewed from the modern perspective of the renormalization group. Secondly, he discusses the possible appearance of disoriented chiral condensates from {open_quotes}quenched{close_quotes} heavy ion collisions. It appears difficult to obtain large domains of disoriented chiral condensates in the standard two flavor model. This leads to the last topic, which is the phase diagram for QCD with three flavors, and its proximity to the chiral critical point. QCD may be very near this chiral critical point, and one might thereby generated large domains of disoriented chiral condensates.

  19. Transitions through critical temperatures in nematic liquid crystals

    KAUST Repository

    Majumdar, Apala

    2013-08-06

    We obtain estimates for critical nematic liquid crystal (LC) temperatures under the action of a slowly varying temperature-dependent control variable. We show that biaxiality has a negligible effect within our model and that these delay estimates are well described by a purely uniaxial model. The static theory predicts two critical temperatures: the supercooling temperature below which the isotropic phase loses stability and the superheating temperature above which the ordered nematic states do not exist. In contrast to the static problem, the isotropic phase exhibits a memory effect below the supercooling temperature in the dynamic framework. This delayed loss of stability is independent of the rate of change of temperature and depends purely on the initial value of the temperature. We also show how our results can be used to improve estimates for LC material constants. © 2013 American Physical Society.

  20. Dynamical numerical model for nematic order reconstruction

    Science.gov (United States)

    Lombardo, G.; Ayeb, H.; Barberi, R.

    2008-05-01

    In highly frustrated calamitic nematic liquid crystals, a strong elastic distortion can be confined on a few nanometers. The classical elastic theory fails to describe such systems and a more complete description based on the tensor order parameter Q is required. A finite element method is used to implement the Q dynamics by a variational principle and it is shown that a uniaxial nematic configuration can evolve passing through transient biaxial states. This solution, which connects two competing uniaxial nematic textures, is known as “nematic order reconstruction.”

  1. Liquid chromatography with mass spectrometry enantioseparation of pomalidomide on cyclodextrin-bonded chiral stationary phases and the elucidation of the chiral recognition mechanisms by NMR spectroscopy and molecular modeling.

    Science.gov (United States)

    Szabó, Zoltán-István; Szőcs, Levente; Horváth, Péter; Komjáti, Balázs; Nagy, József; Jánoska, Ádám; Muntean, Daniela-Lucia; Noszál, Béla; Tóth, Gergő

    2016-08-01

    A sensitive and validated liquid chromatography with mass spectrometry method was developed for the enantioseparation of the racemic mixture of pomalidomide, a novel, second-generation immunomodulatory drug, using β-cyclodextrin-bonded stationary phases. Four cyclodextrin columns (β-, hydroxypropyl-β-, carboxymethyl-β-, and sulfobutyl-β-cyclodextrin) were screened and the effects of eluent composition, flow rate, temperature, and organic modifier on enantioseparation were studied. Optimized parameters, offering baseline separation (resolution = 2.70 ± 0.02) were the following: β-cyclodextrin stationary phase, thermostatted at 15°C, and mobile phase consisting of methanol/0.1% acetic acid 10:90 v/v, delivered with 0.8 mL/min flow rate. For the optimized parameter at multiple reaction monitoring mode 274.1-201.0 transition with 20 eV collision energy and 100 V fragmentor voltage the limit of detection and limit of quantitation were 0.75 and 2.00 ng/mL, respectively. Since enantiopure standards were not available, elution order was determined upon comparison of the circular dichroism signals of the separated pomalidomide enantiomers with that of enantiopure thalidomide. The mechanisms underlying the chiral discrimination between the enantiomers were also investigated. Pomalidomide-β-cyclodextrin inclusion complex was characterized using nuclear magnetic resonance spectroscopy and molecular modeling. The thermodynamic aspects of chiral separation were also studied.

  2. Chiral separation of neonicotinoid insecticides by polysaccharide-type stationary phases using high-performance liquid chromatography and supercritical fluid chromatography.

    Science.gov (United States)

    Zhang, Cheng; Jin, Lixia; Zhou, Shanshan; Zhang, Yifan; Feng, Shuoli; Zhou, Qinyan

    2011-03-01

    The enantiomeric separations of three neonicotinoid insecticides (identified as compounds 1, 2, and 3) were performed on three polysaccharide-type chiral columns, that is, Chiralcel OD-H, Chiralpak AD-H, and Chiralpak IB, by high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). Effects of the modifier percentage and column temperature on chiral recognitions of chiral stationary phases were also studied. Both 1 and 2 could be resolved on all three columns selected, with the highest R(s) values obtained on Chiralpak AD-H and Chiralcel OD-H, respectively. However, satisfactory separation of the four stereoisomers of 3 was only achieved on Chiralcel OD-H. Considering the effects of ethanol on the values of k, α, and R(s), we concluded that hydrogen bonding, π-π, and/or dipole-dipole interactions might be all responsible for the chiral separation. In comparison to HPLC, a shorter run time was achieved for 1 and 2 by SFC. However, 3 could not be stereoselectively resolved using SFC. On the basis of the calculated thermodynamic parameters, we found that the separation processes of enantiomers of 1 and 2 were entropy controlled and enthalpy controlled, respectively.

  3. Finite-volume effects on phase transition in the Polyakov-loop extended Nambu-Jona-Lasinio model with a chiral chemical potential

    CERN Document Server

    Pan, Zan; Chang, Chao-Hsi; Zong, Hong-Shi

    2016-01-01

    To investigate finite-volume effects on the chiral symmetry restoration and the deconfinement transition and some impacts of possible global topological background for a quantum chromodynamics (QCD) system with $N_f=2$ (two quark flavors), we apply the Polyakov-loop extended Nambu-Jona-Lasinio model by introducing a chiral chemical potential $\\mu_5$ artificially. The final numerical results indicate that the introduced chiral chemical potential does not change the critical exponents but shifts the location of critical end point (CEP) significantly; the ratios for the chiral chemical potentials and temperatures at CEP, $\\mu_c/\\mu_{5c}$ and $T_c/T_{5c}$, are significantly affected by the system size $R$. The behavior is that $T_c$ increases slowly with $\\mu_5$ when $R$ is large and $T_c$ decreases first and then increases with $\\mu_5$ when $R$ is small. It is also found that for a fixed $\\mu_5$, there is a $R_{\\text{min}}$, where the critical end point vanishes, and the whole phase diagram becomes a crossover w...

  4. L—PROLINE—FUNCTIONALIZED POLYSTYRENE WITH 1—METHYLDECYLENE SPACER AS A CHIRAL STATIONARY PHASE FOR LIGAND—EXCHANGE CHROMATOGRAPHIC RESOLUTION OF AMINO ACID RECEMATES

    Institute of Scientific and Technical Information of China (English)

    MaJianbiao; ChenLi; 等

    1995-01-01

    The L-proline-functionalized polystyrene with 1-methyldecylene spacer was synthesized from 2% divinylbenzene-crosslinked polystyrene gel via 10-bromo-1-methyldecyl polystyrene intermediate.After complexed with copper(Ⅱ) ion,the polymer with L-proline ligand was used as the chiral stationary phase (CSP) for ligand exchange chromatography of amino acid racemates.The results showed that the CSP possessed powerful enantioselectivity and all racemates of the fifteen tried amino acids were completely separated.

  5. Chiral phase transitions in quantum chromodynamics at finite temperature: Hard-thermal-loop resummed Dyson–Schwinger equation in the real time formalism

    Indian Academy of Sciences (India)

    Hisao Nakkagawa; Hiroshi Yokota; Koji Yoshida; Yuko Fueki

    2003-05-01

    Chiral phase transition in thermal QCD is studied by using the Dyson–Schwinger (DS) equation in the real time hard thermal loop approximation. Our results on the critical temperature and the critical coupling are significantly different from those in the preceding analyses in the ladder DS equation, showing the importance of properly taking into account the essential thermal effects, namely the Landau damping and the unstable nature of thermal quasiparticles.

  6. Enantiomeric separation of tolperisone and eperisone by reversed-phase HPLC with cellulose tris(3-chloro-4-methylphenylcarbamate)-coated chiral column.

    Science.gov (United States)

    Owada, Yuri; Takahashi, Mizuho; Iwasa, Sumiko; Ichiba, Hideaki; Sadamoto, Kiyomi; Fukushima, Takeshi

    2014-01-01

    Enantiomeric separations of centrally acting muscle relaxants, that is, tolperisone (TOL) and eperisone (EP), that are marketed as racemates were investigated by reversed-phase high-performance liquid chromatography (HPLC) on a polysaccharide-based chiral column. Both TOL and EP are basic drugs because they contain a tertiary amino group and have similar chemical structures with the exception of the p-methylphenyl and p-ethylphenyl groups in TOL and EP, respectively. A reversed-phase chiral column, that is, a Chiralcel OZ-RH column, which bears cellulose tris(3-chloro-4-methylphenylcarbamate) as the chiral moiety, was effective for the enantiomeric separation of TOL and EP enantiomers. The separation factor and resolution values obtained for TOL were 1.22 and 1.66, respectively, and those for EP were 1.21 and 2.24, respectively, using a 20 mm ammonium acetate in H2 O (pH 8.0 and 7.0, respectively)-CH3 CN (70:30) mobile phase. Using the proposed HPLC conditions, it was found that (R)-TOL eluted faster than (S)-TOL, as revealed by the optical rotation and circular dichroism spectroscopy. In contrast, EP was easily racemized under the experimental conditions, and hence, the elution order was not determined.

  7. Preparation and characterization of silica monolith modified with bovine serum albumin-gold nanoparticles conjugates and its use as chiral stationary phases for capillary electrochromatography.

    Science.gov (United States)

    Lu, Junyu; Ye, Fanggui; Zhang, Aizhu; Wei, Zong; Peng, Yan; Zhao, Shulin

    2011-08-01

    This paper describes the development of silica monolith modified with bovine serum albumin-gold nanoparticles (BSA-GNPs) conjugates as chiral stationary phases for capillary electrochromatography (CEC). The bare monolithic silica column was prepared by a sol-gel process and has been modified chemically with 3-mercaptopropyltrimethoxysilane to provide thiol groups, followed by immobilization of gold nanoparticles via the formation of an Au-S bond and modification with BSA as the chiral selector via the nitrogen lone pair of electrons. It has been demonstrated that the monolithic chiral stationary phases can be used for the enantioseparation of a number of phenylthiocarbamyl amino acids (PTC-D/L-AAs) by CEC. Ten pairs of tested amino acids enantiomers were successfully resolved within 18 min under optimized conditions, and the resolution values were in the range of 1.486-2.083. With PTC-D/L-tryptophan used as the probe solute, the influences of applied voltage, organic modifier and buffer pH in mobile phase on apparent retention factor, enantioselectivity and resolution factor were also investigated.

  8. Analysis of stereochemistry and biosynthesis of epicatechin in tea plants by chiral phase high performance liquid chromatography.

    Science.gov (United States)

    Qian, Yumei; Zhao, Xianqian; Zhao, Lei; Cui, Lilan; Liu, Li; Jiang, Xiaolan; Liu, Yajun; Gao, Liping; Xia, Tao

    2015-12-01

    Tea (Camellia sinensis) is rich in flavan-3-ols (catechins), especially epicatechin (EC), which is the predominant extension unit of polymeric proanthocyanidins (PAs). However, studies assessing EC's stereochemistry are scarce. Here, a high performance liquid chromatography column using amylose tris-(3, 5-dimethylphenylcarbamate) immobilized on silica-gel as chiral stationary phases (CSPs) was applied to explore its stereochemistry and biosynthetic pathway in tea plants. The results revealed (-)-epicatechin [(-)-EC] was the predominant di-hyroxy-non-galloylated-catechins, while (+)-epicatechin [(+)-EC] was not detected. Interestingly, (-)-EC was the only product obtained from cyanidin using the partially purified native C. sinensis anthocyanidin reductase (CsANR) in the presence of reduction nicotinamide adenine dinucleotide phosphate (NADPH); meanwhile, (+)-EC was the main product using recombinant CsANR in the same conditions. In addition, (-)-EC could be obtained from (+)-catechin [(+)-C] using recombinant CsANR, which displayed C3-epimerase activity in the presence of oxidation nicotinamide adenine dinucleotide phosphate (NADP(+)). But the partially purified native CsANR did not possess this function. Finally, (-)-EC could result from the de-gallate acid reaction of epicatechin gallate (ECG) catalyzed by a novel partially purified native galloylated catechins hydrolase (GCH) from tea leaves. In summary, (-)-EC is likely the product of native protein from the tea plants, and (+)-EC is only produced in a reaction catalyzed by recombinant CsANR in vitro.

  9. High enantioselective Novozym 435-catalyzed esterification of (R,S)-flurbiprofen monitored with a chiral stationary phase.

    Science.gov (United States)

    Siódmiak, Tomasz; Mangelings, Debby; Vander Heyden, Yvan; Ziegler-Borowska, Marta; Marszałł, Michał Piotr

    2015-03-01

    Lipases form Candida rugosa and Candida antarctica were tested for their application in the enzymatic kinetic resolution of (R,S)-flurbiprofen by enantioselective esterification. Successful chromatographic separation with well-resolved peaks of (R)- and (S)-flurbiprofen and their esters was achieved in one run on chiral stationary phases by high-performance liquid chromatography (HPLC). In this study screening of enzymes was performed, and Novozym 435 was selected as an optimal catalyst for obtaining products with high enantiopurity. Additionally, the influence of organic solvents (dichloromethane, dichloroethane, dichloropropane, and methyl tert-butyl ether), primary alcohols (methanol, ethanol, n-propanol, and n-butanol), reaction time, and temperature on the enantiomeric ratio and conversion was tested. The high values of enantiomeric ratio (E in the range of 51.3-90.5) of the esterification of (R,S)-flurbiprofen were obtained for all tested alcohols using Novozym 435, which have a great significance in the field of biotechnological synthesis of drugs. The optimal temperature range for the performed reactions was from 37 to 45 °C. As a result of the optimization, (R)-flurbiprofen methyl ester was obtained with a high optical purity, eep = 96.3 %, after 96 h of incubation. The enantiomeric ratio of the reaction was E = 90.5 and conversion was C = 35.7 %.

  10. Exact thermodynamics and phase diagram of integrable t-J model with chiral interaction

    Science.gov (United States)

    Tavares, T. S.; Ribeiro, G. A. P.

    2016-09-01

    We study the phase diagram and finite temperature properties of an integrable generalization of the one-dimensional super-symmetric t-J model containing interactions explicitly breaking parity-time reversal (PT) symmetries. To this purpose, we apply the quantum transfer matrix method which results in a finite set of non-linear integral equations. We obtain numerical solutions to these equations leading to results for thermodynamic quantities as a function of temperature, magnetic field, particle density and staggering parameter. Studying the maxima lines of entropy at low but non zero temperature reveals the phase diagram of the model. There are ten different phases which we may classify in terms of the qualitative behaviour of auxiliary functions, closely related to the dressed energy functions.

  11. Creation and manipulation of topological states in chiral nematic microspheres

    NARCIS (Netherlands)

    Orlova, T.; Asshoff, S.J.; Yamaguchi, T.; Katsonis, N.H.; Brasselet, E.

    2015-01-01

    Topology is a universal concept that is encountered in daily life and is known to determine many static and dynamical properties of matter. Taming and controlling the topology of materials therefore constitutes a contemporary interdisciplinary challenge. Building on the controllable spatial properti

  12. Sensing surface morphology of biofibers by decorating spider silk and cellulosic filaments with nematic microdroplets.

    Science.gov (United States)

    Aguirre, Luis E; de Oliveira, Alexandre; Seč, David; Čopar, Simon; Almeida, Pedro L; Ravnik, Miha; Godinho, Maria Helena; Žumer, Slobodan

    2016-02-02

    Probing the surface morphology of microthin fibers such as naturally occurring biofibers is essential for understanding their structural properties, biological function, and mechanical performance. The state-of-the-art methods for studying the surfaces of biofibers are atomic force microscopy imaging and scanning electron microscopy, which well characterize surface geometry of the fibers but provide little information on the local interaction potential of the fibers with the surrounding material. In contrast, complex nematic fluids respond very well to external fields and change their optical properties upon such stimuli. Here we demonstrate that liquid crystal droplets deposited on microthin biofibers--including spider silk and cellulosic fibers--reveal characteristics of the fibers' surface, performing as simple but sensitive surface sensors. By combining experiments and numerical modeling, different types of fibers are identified through the fiber-to-nematic droplet interactions, including perpendicular and axial or helicoidal planar molecular alignment. Spider silks align nematic molecules parallel to fibers or perpendicular to them, whereas cellulose aligns the molecules unidirectionally or helicoidally along the fibers, indicating notably different surface interactions. The nematic droplets as sensors thus directly reveal chirality of cellulosic fibers. Different fiber entanglements can be identified by depositing droplets exactly at the fiber crossings. More generally, the presented method can be used as a simple but powerful approach for probing the surface properties of small-size bioobjects, opening a route to their precise characterization.

  13. Sensing surface morphology of biofibers by decorating spider silk and cellulosic filaments with nematic microdroplets

    Science.gov (United States)

    Aguirre, Luis E.; de Oliveira, Alexandre; Seč, David; Čopar, Simon; Almeida, Pedro L.; Ravnik, Miha; Godinho, Maria Helena; Žumer, Slobodan

    2016-01-01

    Probing the surface morphology of microthin fibers such as naturally occurring biofibers is essential for understanding their structural properties, biological function, and mechanical performance. The state-of-the-art methods for studying the surfaces of biofibers are atomic force microscopy imaging and scanning electron microscopy, which well characterize surface geometry of the fibers but provide little information on the local interaction potential of the fibers with the surrounding material. In contrast, complex nematic fluids respond very well to external fields and change their optical properties upon such stimuli. Here we demonstrate that liquid crystal droplets deposited on microthin biofibers—including spider silk and cellulosic fibers—reveal characteristics of the fibers’ surface, performing as simple but sensitive surface sensors. By combining experiments and numerical modeling, different types of fibers are identified through the fiber-to-nematic droplet interactions, including perpendicular and axial or helicoidal planar molecular alignment. Spider silks align nematic molecules parallel to fibers or perpendicular to them, whereas cellulose aligns the molecules unidirectionally or helicoidally along the fibers, indicating notably different surface interactions. The nematic droplets as sensors thus directly reveal chirality of cellulosic fibers. Different fiber entanglements can be identified by depositing droplets exactly at the fiber crossings. More generally, the presented method can be used as a simple but powerful approach for probing the surface properties of small-size bioobjects, opening a route to their precise characterization. PMID:26768844

  14. SU(N) Schwinger bosons and nematic phases in the bilinear-biquadratic S=1 triangular lattice antiferromagnet with third-nearest neighbor interactions

    Science.gov (United States)

    Pires, A. S. T.

    2017-01-01

    I present in details the SU(N) Schwinger boson formalism, also known as flavor wave theory, that has been used several times in the literature. I use the method to study the ferroquadrupolar phase of a quantum biquadratic Heisenberg model with spin S=1 on the triangular lattice with third-nearest-neighbor interactions. Results for the phase diagram at zero temperature and the static and dynamical quadrupolar structure factors are presented. In principle, the results could be applied to NiGa2S4.

  15. Chiral photochemistry

    CERN Document Server

    Inoue, Yoshihisa

    2004-01-01

    Direct Asymmetric Photochemistry with Circularly Polarized Light, H. RauCoherent Laser Control of the Handedness of Chiral Molecules, P. Brumer and M. ShapiroMagnetochiral Anisotropy in Asymmetric Photochemistry, G.L.J.A.RikkenEnantiodifferentiating Photosensitized Reactions, Y. InoueDiastereodifferentiating Photoreactions, N. Hoffmann and J.-P. PeteChirality in Photochromism, Y. Yokoyama and M. SaitoChiral Photochemistry with Transition Metal Complexes, S. Sakaki and T. HamadaTemplate-Induced Enantioselective Photochemical Reactions in S

  16. Pirkle-type chiral stationary phase on core-shell and fully porous particles: Are superficially porous particles always the better choice toward ultrafast high-performance enantioseparations?

    Science.gov (United States)

    Ismail, Omar H; Pasti, Luisa; Ciogli, Alessia; Villani, Claudio; Kocergin, Jelena; Anderson, Scott; Gasparrini, Francesco; Cavazzini, Alberto; Catani, Martina

    2016-09-30

    Pirkle-type Whelk-O1 chiral stationary phase (CSP) was prepared on 2.6μm superficially porous particles (SPPs). The chromatographic behavior of columns packed with this new CSP was compared with that of columns packed respectively with 1.8 and 2.5μm Whelk-O1 fully porous particles (FPPs). In the comparison, both thermodynamic and kinetic aspects were considered. Contrary to initial expectations, chiral columns packed with 2.6μm SPPs were quasi-comparable to those packed with 2.5μm FPPs, apparently due to larger contributions to band broadening from both eddy dispersion and, especially for the second eluted enantiomer, adsorption-desorption kinetics. These findings raise the question if SPPs, in spite of the undeniable advantages of their morphology to speed up mass transfer, are always the best choice for high-efficient ultrafast chiral separations. The last part of the work focuses on the use of short columns (10mm long) and very high flow rates to realize the separation of the enantiomers of trans-stilbene oxide (TSO) in normal phase mode in less than 1s.

  17. Water-Soluble Phosphine-Protected Au₁₁ Clusters: Synthesis, Electronic Structure, and Chiral Phase Transfer in a Synergistic Fashion.

    Science.gov (United States)

    Yao, Hiroshi; Iwatsu, Mana

    2016-04-05

    Synthesis of atomically precise, water-soluble phosphine-protected gold clusters is still currently limited probably due to a stability issue. We here present the synthesis, magic-number isolation, and exploration of the electronic structures as well as the asymmetric conversion of triphenylphosphine monosulfonate (TPPS)-protected gold clusters. Electrospray ionization mass spectrometry and elemental analysis result in the primary formation of Au11(TPPS)9Cl undecagold cluster compound. Magnetic circular dichroism (MCD) spectroscopy clarifies that extremely weak transitions are present in the low-energy region unresolved in the UV-vis absorption, which can be due to the Faraday B-terms based on the magnetically allowed transitions in the cluster. Asymmetric conversion without changing the nuclearity is remarkable by the chiral phase transfer in a synergistic fashion, which yields a rather small anisotropy factor (g-factor) of at most (2.5-7.0) × 10(-5). Quantum chemical calculations for model undecagold cluster compounds are then used to evaluate the optical and chiroptical responses induced by the chiral phase transfer. On this basis, we find that the Au core distortion is ignorable, and the chiral ion-pairing causes a slight increase in the CD response of the Au11 cluster.

  18. On the strength of the $U_A(1)$ anomaly at the chiral phase transition in $N_f=2$ QCD

    CERN Document Server

    Brandt, Bastian B; Meyer, Harvey B; Philipsen, Owe; Robaina, Daniel; Wittig, Hartmut

    2016-01-01

    We study the thermal transition of QCD with two degenerate light flavours by lattice simulations using $O(a)$-improved Wilson quarks. Temperature scans are performed at a fixed value of $N_t = (aT)^{-1}=16$, where $a$ is the lattice spacing and $T$ the temperature, at three fixed zero-temperature pion masses between 200 MeV and 540 MeV. In this range we find that the transition is consistent with a broad crossover. As a probe of the restoration of chiral symmetry, we study the static screening spectrum. We observe a degeneracy between the transverse isovector vector and axial-vector channels starting from the transition temperature. Particularly striking is the strong reduction of the splitting between isovector scalar and pseudoscalar screening masses around the chiral phase transition by at least a factor of three compared to its value at zero temperature. In fact, the splitting is consistent with zero within our uncertainties. This disfavours a chiral phase transition in the $O(4)$ universality class.

  19. Probing the shear viscosity of an active nematic film

    Science.gov (United States)

    Guillamat, Pau; Ignés-Mullol, Jordi; Shankar, Suraj; Marchetti, M. Cristina; Sagués, Francesc

    2016-12-01

    In vitro reconstituted active systems, such as the adenosine triphosphate (ATP)-driven microtubule bundle suspension developed by the Dogic group [T. Sanchez, D. T. Chen, S. J. DeCamp, M. Heymann, and Z. Dogic, Nature (London) 491, 431 (2012), 10.1038/nature11591], provide a fertile testing ground for elucidating the phenomenology of active liquid crystalline states. Controlling such novel phases of matter crucially depends on our knowledge of their material and physical properties. In this Rapid Communication, we show that the shear viscosity of an active nematic film can be probed by varying its hydrodynamic coupling to a bounding oil layer. Using the motion of disclinations as intrinsic tracers of the flow field and a hydrodynamic model, we obtain an estimate for the shear viscosity of the nematic film. Knowing this now provides us with an additional handle for robust and precision tunable control of the emergent dynamics of active fluids.

  20. An In Vitro Nematic Model for Proliferating Cell Cultures

    CERN Document Server

    Pai, Sunil; Green, Morgaine; Cordeiro, Christine; Cabral, Elise; Chen, Bertha; Baer, Thomas

    2016-01-01

    Confluent populations of elongated cells give rise to ordered patterns seen in nematic phase liquid crystals. We correlate cell elongation and intercellular distance with intercellular alignment using an amorphous spin glass model. We compare in vitro time-lapse imaging with Monte Carlo simulation results by framing a novel hard ellipses model in terms of Boltzmann statistics. Furthermore, we find a statistically distinct alignment energy at quasi-steady state among fibroblasts, smooth muscle cells, and pluripotent cell populations when cultured in vitro. These findings have important implications in both non-invasive clinical screening of the stem cell differentiation process and in relating shape parameters to coupling in active crystal systems such as nematic cell monolayers.

  1. Anisotropic Elastic Properties of Muscle-like Nematic Elastomers

    Science.gov (United States)

    Ratna, Banahalii; Thomseniii, Donald L.; Shenoy, Devanand; Srinivasan, Amritha; Keller, Patrick

    2001-03-01

    De Gennes suggested in 1997 that the liquid crystal elastomers are an excellent framework to mimic muscular action. We have prepared anisotropic freestanding films of nematic elastomers from laterally attached side-chain polymers that show muscle-like mechanical properties. The orientational order of the liquid crystal side groups imposes a conformational anisotropy in the polymer backbone. When the order parameter drops at the nematic-isotropic phase transition, there is a concomitant loss of order in the backbone which results in a contraction of the film in the direction of the director orientation. Dynamic mechanical data along directions parallel and perpendicular to the optic axis, show anisotropic stress-strain behavior. The film exhibits soft elasticity when strained in the perpendicular direction when the liquid crystal mesogens reorient without appreciable stress build up. Thermostrictive studies in the parallel direction show 40constriction at the nematic-isotropic phase transition. Isometric studies show that the elastic energy stored is purely entropic in origin and the elastomer acts like a spring with unusually large spring constant at the NI transition. The maximum stress measured is 300kPa. A strain rate of 5s-1 is estimated from shear relaxation studies.

  2. Chiral gap effect in curved space

    CERN Document Server

    Flachi, Antonino

    2014-01-01

    We discuss a new type of QCD phenomenon induced in curved space. In the QCD vacuum a mass gap of Dirac fermions is attributed to the spontaneous breaking of chiral symmetry. If the curvature is positive large, the chiral condensate melts but a chiral invariant mass gap can still remain, which we name the chiral gap effect in curved space. This leads to decoupling of quark deconfinement which implies a view of black holes surrounded by a first-order QCD phase transition.

  3. SU(3) Polyakov linear-σ model in magnetic fields: Thermodynamics, higher-order moments, chiral phase structure, and meson masses

    Science.gov (United States)

    Tawfik, Abdel Nasser; Magdy, Niseem

    2015-01-01

    Effects of an external magnetic field on various properties of quantum chromodynamics (QCD) matter under extreme conditions of temperature and density (chemical potential) have been analyzed. To this end, we use SU(3) Polyakov linear-σ model and assume that the external magnetic field (e B ) adds some restrictions to the quarks' energy due to the existence of free charges in the plasma phase. In doing this, we apply the Landau theory of quantization, which assumes that the cyclotron orbits of charged particles in a magnetic field should be quantized. This requires an additional temperature to drive the system through the chiral phase transition. Accordingly, the dependence of the critical temperature of chiral and confinement phase transitions on the magnetic field is characterized. Based on this, we have studied the thermal evolution of thermodynamic quantities (energy density and trace anomaly) and the first four higher-order moment of particle multiplicity. Having all these calculations, we have studied the effects of the magnetic field on the chiral phase transition. We found that both critical temperature Tc and critical chemical potential increase with increasing magnetic field, e B . Last but not least, the magnetic effects of the thermal evolution of four scalar and four pseudoscalar meson states are studied. We concluded that the meson masses decrease as the temperature increases up to Tc. Then, the vacuum effect becomes dominant and rapidly increases with the temperature T . At low T , the scalar meson masses normalized to the lowest Matsubara frequency rapidly decrease as T increases. Then, starting from Tc, we find that the thermal dependence almost vanishes. Furthermore, the meson masses increase with increasing magnetic field. This gives a characteristic phase diagram of T vs external magnetic field e B . At high T , we find that the masses of almost all meson states become temperature independent. It is worthwhile to highlight that the various meson

  4. Solid-phase microextraction and chiral HPLC analysis of ibuprofen in urine.

    Science.gov (United States)

    de Oliveira, Anderson Rodrigo Moraes; Cesarino, Evandro José; Bonato, Pierina Sueli

    2005-04-25

    A simple and rapid solid-phase microextraction method was developed for the enantioselective analysis of ibuprofen in urine. The sampling was made with a polydimethylsiloxane-divinylbenzene coated fiber immersed in the liquid sample. After desorptioning from the fiber, ibuprofen enantiomers were analyzed by HPLC using a Chiralpak AD-RH column and UV detection. The mobile phase was made of methanol-pH 3.0 phosphoric acid solution (75:25, v/v), at a flow rate of 0.45 mL/min. The mean recoveries of SPME were 19.8 and 19.1% for (-)-R-ibuprofen and (+)-(S)-ibuprofen, respectively. The method was linear at the range of 0.25-25 microg/mL. Within-day and between-day assay precision and accuracy were below 15% for both ibuprofen enantiomers at concentrations of 0.75, 7.5 and 20 microg/mL. The method was tested with urine quality control samples and human urine fractions after administration of 200 mg rac-ibuprofen.

  5. Report on twisted nematic and supertwisted nematic device characterization program

    Science.gov (United States)

    1995-01-01

    In this study we measured the optical characteristics of normally white twisted nematic (NWTN) and super twisted nematic (STN ) cells. Though no dynamic computer model was available, the static observations were compared with computer simulated behavior. The measurements were taken as a function of both viewing angle and applied voltage and included in the static case not only luminance but also contrast ratio and chromaticity . We employed the computer model Twist Cell Optics, developed at Kent State in conjunction with this study, and whose optical modeling foundation, Iike the ViDEOS program, is the 4 x 4 matrix method of Berreman. In order to resolve discrepancies between the experimental and modeled data the optical parameters of the individual cell components, where not known, were determined using refractometry, profilometry, and various forms of ellipsometry. The resulting agreement between experiment and model is quite good due primarily to a better understanding of the structure and optics of dichroic sheet polarizers. A description of the model and test cells employed are given in section 2. Section 3 contains the experimental data gathered and section 4 gives examples of the fit between model and experiment. Also included with this report are a pair of papers which resulted from the research and which detail the polarizer properties and some of the cell characterization methods.

  6. Temperature-induced inversion of elution order in the chromatographic enantioseparation of 1,1'-bi-2-naphthol on an immobilized polysaccharide-based chiral stationary phase.

    Science.gov (United States)

    Yao, Bixia; Zhan, Fengping; Yu, Guangyan; Chen, Zhifen; Fan, Wenjing; Zeng, Xiongping; Zeng, Qingle; Weng, Wen

    2009-07-10

    In this work, the enantioseparations of 1,1'-bi-2-naphthol (BINOL) and its three derivatives were performed on an immobilized polysaccharide-based chiral stationary phase, Chiralpak IA, under normal-phase mode. The effects of the content of polar modifier in the mobile phase and the column temperature on the retention and enantioseparation were investigated in detail. Temperature-induced inversion of elution order for BINOL was observed directly when n-hexane/2-propanol (92/8, v/v) was used as mobile phase. The isoenantioselective temperature (T(iso)) was calculated to be 31.4 degrees C. When n-hexane/2-propanol/THF (93/2/5, v/v/v) was used as mobile phase, the T(iso) value decreased to -8.2 degrees C. Entropically driven enantioseparation which had practical application was obtained successfully (separation factor being 1.189 and 1.332 at 25 degrees C and 50 degrees C, respectively). The corresponding thermodynamic parameters for other three binaphthyl compounds were compared with that for BINOL. Some inferences about chiral recognition mechanism were stressed.

  7. Observation of dynamical precursors of the isotropic-nematic transition by computer simulation

    NARCIS (Netherlands)

    Allen, M.P.; Frenkel, D.

    1987-01-01

    We present the results of the first molecular-dynamics simulations of a molecular liquid, namely a system of prolate hard ellipsoids of revolution, near the isotropic-nematic liquid-crystal phase transition. Collective rotational motion in the isotropic phase slows down on approach to the transition

  8. Light-Directed Dynamic Chirality Inversion in Functional Self-Organized Helical Superstructures.

    Science.gov (United States)

    Bisoyi, Hari Krishna; Li, Quan

    2016-02-24

    Helical superstructures are widely observed in nature, in synthetic polymers, and in supramolecular assemblies. Controlling the chirality (the handedness) of dynamic helical superstructures of molecular and macromolecular systems by external stimuli is a challenging task, but is of great fundamental significance with appealing morphology-dependent applications. Light-driven chirality inversion in self-organized helical superstructures (i.e. cholesteric, chiral nematic liquid crystals) is currently in the limelight because inversion of the handedness alters the chirality of the circularly polarized light that they selectively reflect, which has wide potential for application. Here we discuss the recent developments toward inversion of the handedness of cholesteric liquid crystals enabled by photoisomerizable chiral molecular switches or motors. Different classes of chiral photoresponsive dopants (guests) capable of conferring light-driven reversible chirality inversion of helical superstructures fabricated from different nematic hosts are discussed. Rational molecular designs of chiral molecular switches toward endowing handedness inversion to the induced helical superstructures of cholesteric liquid crystals are highlighted. This Review is concluded by throwing light on the challenges and opportunities in this emerging frontier, and it is expected to provide useful guidelines toward the development of self-organized soft materials with stimuli-directed chirality inversion capability and multifunctional host-guest systems.

  9. Dispersive shock waves in nematic liquid crystals

    Science.gov (United States)

    Smyth, Noel F.

    2016-10-01

    The propagation of coherent light with an initial step intensity profile in a nematic liquid crystal is studied using modulation theory. The propagation of light in a nematic liquid crystal is governed by a coupled system consisting of a nonlinear Schrödinger equation for the light beam and an elliptic equation for the medium response. In general, the intensity step breaks up into a dispersive shock wave, or undular bore, and an expansion fan. In the experimental parameter regime for which the nematic response is highly nonlocal, this nematic bore is found to differ substantially from the standard defocusing nonlinear Schrödinger equation structure due to the effect of the nonlocality of the nematic medium. It is found that the undular bore is of Korteweg-de Vries equation-type, consisting of bright waves, rather than of nonlinear Schrödinger equation-type, consisting of dark waves. In addition, ahead of this Korteweg-de Vries bore there can be a uniform wavetrain with a short front which brings the solution down to the initial level ahead. It is found that this uniform wavetrain does not exist if the initial jump is below a critical value. Analytical solutions for the various parts of the nematic bore are found, with emphasis on the role of the nonlocality of the nematic medium in shaping this structure. Excellent agreement between full numerical solutions of the governing nematicon equations and these analytical solutions is found.

  10. Modulated liquid-crystal phases induced by polarity: Twist-bend, splay-bend, and blue phases

    Science.gov (United States)

    Selinger, Jonathan; Shamid, Shaikh; Allender, David

    2014-03-01

    Nematic liquid crystals exhibit flexoelectric couplings between polar order and gradients in the director field. When the couplings become strong enough, the uniform nematic phase can become unstable to the formation of a modulated polar phase. The question is then: What is the structure of the modulated polar phase? Classic work by Meyer and further studies by Dozov predicted two possible structures, known as twist-bend and splay-bend. One of these predictions, the twist-bend phase, has recently been identified in experiments on bent-core liquid crystals. Here, we investigate modulated polar phases through a combination of Landau theory and lattice simulations. We find a range of possibilities, including the twist-bend and splay-bend phases as well as polar blue phases, with 2D or 3D modulations of the director field and the polar order. We compare these polar blue phases with chiral blue phases, and discuss opportunities for observing them experimentally. Supported by NSF DMR-1106014.

  11. Theory of nonlocal soliton interaction in nematic liquid crystals

    DEFF Research Database (Denmark)

    Rasmussen, Per Dalgaard; Bang, Ole; Krolikowski, Wieslaw

    2005-01-01

    We investigate interactions between spatial nonlocal bright solitons in nematic liquid crystals using an analytical “effective particle” approach as well as direct numerical simulations. The model predicts attraction of out-of-phase solitons and the existence of their stable bound state....... This nontrivial property is solely due to the nonlocal nature of the nonlinear response of the liquid crystals. We further predict and verify numerically the critical outwards angle and degree of nonlocality which determine the transition between attraction and repulsion of out-of-phase solitons....

  12. Electro-osmosis in nematic liquid crystals

    Science.gov (United States)

    Tovkach, O. M.; Calderer, M. Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J.

    2016-07-01

    We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities.

  13. Quantum control of spin-nematic squeezing in a dipolar spin-1 condensate

    Science.gov (United States)

    Huang, Yixiao; Xiong, Heng-Na; Yang, Yang; Hu, Zheng-Da; Xi, Zhengjun

    2017-01-01

    Versatile controllability of interactions and magnetic field in ultracold atomic gases ha now reached an era where spin mixing dynamics and spin-nematic squeezing can be studied. Recent experiments have realized spin-nematic squeezed vacuum and dynamic stabilization following a quench through a quantum phase transition. Here we propose a scheme for storage of maximal spin-nematic squeezing, with its squeezing angle maintained in a fixed direction, in a dipolar spin-1 condensate by applying a microwave pulse at a time that maximal squeezing occurs. The dynamic stabilization of the system is achieved by manipulating the external periodic microwave pulses. The stability diagram for the range of pulse periods and phase shifts that stabilize the dynamics is numerical simulated and agrees with a stability analysis. Moreover, the stability range coincides well with the spin-nematic vacuum squeezed region which indicates that the spin-nematic squeezed vacuum will never disappear as long as the spin dynamics are stabilized. PMID:28233786

  14. Orbital-dependent Fermi surface shrinking as a fingerprint of nematicity in FeSe

    Science.gov (United States)

    Fanfarillo, Laura; Mansart, Joseph; Toulemonde, Pierre; Cercellier, Hervé; Le Fèvre, Patrick; Bertran, François; Valenzuela, Belen; Benfatto, Lara; Brouet, Véronique

    2016-10-01

    A large anisotropy in the electronic properties across a structural transition in several correlated systems has been identified as the key manifestation of electronic nematic order, breaking rotational symmetry. In this context, FeSe is attracting tremendous interest, since electronic nematicity develops over a wide range of temperatures, allowing accurate experimental investigation. Here we combine angle-resolved photoemission spectroscopy and theoretical calculations based on a realistic multiorbital model to unveil the microscopic mechanism responsible for the evolution of the electronic structure of FeSe across the nematic transition. We show that the self-energy corrections due to the exchange of spin fluctuations between hole and electron pockets are responsible for an orbital-dependent shrinking of the Fermi surface that affects mainly the x z /y z parts of the Fermi surface. This result is consistent with our experimental observation of the Fermi surface in the high-temperature tetragonal phase, which includes the x y electron sheet that was not clearly resolved before. In the low-temperature nematic phase, we experimentally confirm the appearance of a large (˜50 meV) x z /y z splitting. It can be well reproduced in our model by assuming a moderate splitting between spin fluctuations along the x and y crystallographic directions. Our mechanism shows how the full entanglement between orbital and spin degrees of freedom can make a spin-driven nematic transition equivalent to an effective orbital order.

  15. Molecular field theory for nematic liquid crystal film with finite layers

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhi-Dong; Li Jing; Wei Huai-Peng

    2005-01-01

    The nematic liquid crystal film composed of n molecular layers is studied based upon a spatially anisotropic pair potential, which reproduces approximately the elastic free energy density. On condition that the system has perfect nematic order, as in the Lebwohl-Lasher model, the director in the film is isotropic. The effect of the temperature is investigated by means of molecular field theory. Some new results are obtained. Firstly, symmetry breaking takes place when taking account of the temperature, and the state with the director along the normal of the film has the lowest free energy. Secondly, the N-I phase transition temperature increases as an effect of finite sizes instead of decreasing as in the Lebwohl-Lasher model. Thirdly, the nematic order is induced in the layers near the surface in the isotropic phase.

  16. Quarkyonic Chiral Spirals

    CERN Document Server

    Kojo, Toru; McLerran, Larry; Pisarski, Robert D

    2009-01-01

    We consider the formation of chiral density waves in Quarkyonic matter, which is a phase where cold, dense quarks experience confining forces. We model confinement following Gribov and Zwanziger, taking the gluon propagator, in Coulomb gauge and momentum space, as 1/(p^2)^2. We assume that the number of colors, N, is large, and that the quark chemical potential, mu, is much larger than renormalization mass scale, Lambda_QCD. To leading order in 1/N and Lambda_QCD, a gauge theory with Nf flavors of massless quarks in 3+1 dimensions naturally reduces to a gauge theory in 1+1 dimensions, with an enlarged flavor symmetry of SU(2Nf). Through an anomalous chiral rotation, in two dimensions a Fermi sea of massless quarks maps directly onto the corresponding theory in vacuum. A chiral condensate forms locally, and varies with the spatial position, z, as . Following Schon and Thies, we term this two dimensional pion condensate a (Quarkyonic) chiral spiral. Massive quarks also exhibit chiral spirals, with the magnitude...

  17. Theory of Electron Nematic Order in LaOFeAs

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Chen

    2010-04-06

    We study a spin S quantum Heisenberg model on the Fe lattice of the rare-earth oxypnictide superconductors. Using both large S and large N methods, we show that this model exhibits a sequence of two phase transitions: from a high temperature symmetric phase to a narrow region of intermediate 'nematic' phase, and then to a low temperature spin ordered phase. Identifying phases by their broken symmetries, these phases correspond precisely to the sequence of structural (tetragonal to monoclinic) and magnetic transitions that have been recently revealed in neutron scattering studies of LaOFeAs. The structural transition can thus be identified with the existence of incipient ('fluctuating') magnetic order.

  18. Ferromagnetic nanoparticles suspensions in twisted nematic

    Science.gov (United States)

    Cîrtoaje, Cristina; Petrescu, Emil; Stan, Cristina; Creangă, Dorina

    2016-05-01

    Ferromagnetic nanoparticles insertions in nematic liquid crystals (NLC) in twisted configuration are studied and a theoretical model is proposed to explain the results. Experimental observation revealed that nanoparticles tend to overcrowd in long strings parallel to the rubbing direction of the alignment substrate of the LC cell. Their behavior under external field was studied and their interaction with their nematic host is described using elastic continuum theory.

  19. Isotopic chirality

    Energy Technology Data Exchange (ETDEWEB)

    Floss, H.G. [Univ. of Washington, Seattle, WA (United States)

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  20. X-ray and Raman scattering study of orientational order in nematic and heliconical nematic liquid crystals

    Science.gov (United States)

    Singh, Gautam; Fu, Jinxin; Agra-Kooijman, Dena M.; Song, Jang-Kun; Vengatesan, M. R.; Srinivasarao, Mohan; Fisch, Michael R.; Kumar, Satyendra

    2016-12-01

    The temperature dependence of the orientational order parameters cos β ) > and cos β ) > in the nematic (N ) and twist-bend nematic (Ntb) phases of the liquid crystal dimer CB7CB have been measured using x-ray and polarized Raman scattering. The cos β ) > obtained from both techniques are the same, while cos β ) > , determined by Raman scattering is, as expected, systematically larger than its x-ray value. Both order parameters increase in the N phase with decreasing temperature, drop across the N -Ntb transition, and continue to decrease. In the Ntb phase, the x-ray value of cos β ) > eventually becomes negative, providing a direct and independent confirmation of a conical molecular orientational distribution. The heliconical tilt angle α, determined from orientational distribution functions in the Ntb phase, increases to ˜24∘ at ˜15 K below the transition. In the Ntb phase, α (T ) ∝(T*-T)λ , with λ =0.19 ±0.03 . The transition supercools by 1.7 K, consistent with its weakly first-order nature. The value of λ is close to 0.25 indicating close proximity to a tricritical point.

  1. Exploring chiral separation of 3-carboxamido-5-aryl isoxazole derivatives by supercritical fluid chromatography on amylose and cellulose tris dimethyl- and chloromethyl phenylcarbamate polysaccharide based stationary phases.

    Science.gov (United States)

    Zehani, Yasmine; Lemaire, Lucas; Ghinet, Alina; Millet, Régis; Chavatte, Philippe; Vaccher, Claude; Lipka, Emmanuelle

    2016-10-07

    Four polysaccharide based chiral stationary phases were chosen, two chlorinated: Lux™ Amylose-2 (tris-5-chloro-2-methylphenylcarbamate of amylose) and Lux™ Cellulose-2 (tris-3-chloro-4-methylphenylcarbamate of cellulose) and two methylated: Chiralpak(®) AD-H (tris-3,5-dimethylphenylcarbamate of amylose) and Chiralcel(®) OD-H (tris-3,5-dimethylphenylcarbamate of cellulose) to separate four 3-carboxamido-5-aryl isoxazole derivatives by supercritical fluid chromatography. The effect of chiral stationary phase, co-solvent nature (MeOH, EtOH, 2-PrOH and ACN) and percentage (10-20%), temperature (20-45°C) and chemical structure of the compounds on retention, resolution and elution order were thoroughly studied. In addition, thermodynamic parameters were determined from the linear portion of the Van't Hoff plots. For all the derivatives, the Lux™ Cellulose-2 and Chiralpak(®) AD-H provided excellent resolutions (Rs=9.78) in short run time (under 6min). The preparation of about 10mg of each of the eight enantiomers was achieved successfully on a Chiralpak(®) AD-H with various percentages of ethanol as a co-solvent. Lastly, the enantiomeric purity of each of the eight individual enantiomer generated was determined and found higher than 98%.

  2. Development and Validation of a Normal Phase Chiral HPLC Method for Analysis of Afoxolaner Using a Chiralpak® AD-3 Column.

    Science.gov (United States)

    Zhuang, Jinyou; Kumar, Satish; Rustum, Abu

    2016-11-01

    Afoxolaner is a new antiparasitic molecule from the isoxazoline family that acts on the insect acarine gamma-aminobutyric acid and glutamate receptors. Isoxazoline family of compounds has been employed as active pharmaceutical ingredient in drug products prescribed for control of fleas and ticks in dogs. Afoxolaner with a chiral center at isoxazoline ring exists as a racemic mixture. A normal phase chiral high performance liquid chromatography analytical method has been developed to verify that afoxolaner is a racemic mixture as demonstrated by specific rotation, as well as to determine enantiomeric purity of single enantiomer samples. A Chiralpak(®) AD-3 column (150 × 4.6 mm I.D.) maintained at 35°C was used in the method. Analytes were analyzed with an isocratic elution using n-Hexane/IPA/MeOH (89:10:1, v/v/v) as the mobile phase with a detection wavelength of 312 nm. Desired separation of the two enantiomers was achieved in <10 minutes with resolution and selectivity factors of 5.0 and 1.54, respectively. The analytical method was appropriately validated according to ICH guidelines for its intended use. ® All marks are the property of their respective owners.

  3. Laser beam propagation in nematic liquid crystals at the temperature close to the nematicisotropic critical point.

    Science.gov (United States)

    Chen, Yu-Jen; Lin, Yu-Sung; Jiang, I-Min; Tsai, Ming-Shan

    2008-03-17

    This study investigates the optical nonlinearity of beam propagation in homogeneously aligned nematic liquid crystal (NLC) cells at a temperature close to the nematic-isotropic temperature (TNI). The undulate propagation mode with convergent and divergent loops appearing alternately is reported and the thermally enhanced optical reorientation nonlinearity at the focus is described. The optically induced phase transition exists along the pump beam direction. With the application of the conscopic technique, the arrangements of LC at the focus are proposed in this study. Results of this study demonstrate that the evolution of the LC configuration was affected by the pump beam based on the analysis of conoscopic patterns.

  4. Fluctuations and topological transitions of quantum Hall stripes: Nematics as anisotropic hexatics

    Science.gov (United States)

    Ettouhami, A. M.; Doiron, C. B.; Côté, R.

    2007-10-01

    We study fluctuations and topological melting transitions of quantum Hall stripes near half filling of intermediate Landau levels. Taking the stripe state to be an anisotropic Wigner crystal (AWC) allows us to identify the quantum Hall nematic state conjectured in previous studies of the two-dimensional (2D) electron gas as an anisotropic hexatic. The transition temperature from the AWC to the quantum Hall nematic state is explicitly calculated, and a tentative phase diagram for the 2D electron gas near half filling is suggested.

  5. Effective Field Theory of Fractional Quantized Hall Nematics

    Energy Technology Data Exchange (ETDEWEB)

    Mulligan, Michael; /MIT, LNS; Nayak, Chetan; /Station Q, UCSB; Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC

    2012-06-06

    We present a Landau-Ginzburg theory for a fractional quantized Hall nematic state and the transition to it from an isotropic fractional quantum Hall state. This justifies Lifshitz-Chern-Simons theory - which is shown to be its dual - on a more microscopic basis and enables us to compute a ground state wave function in the symmetry-broken phase. In such a state of matter, the Hall resistance remains quantized while the longitudinal DC resistivity due to thermally-excited quasiparticles is anisotropic. We interpret recent experiments at Landau level filling factor {nu} = 7/3 in terms of our theory.

  6. An Extended Chiral SU(3) Quark Model

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zong-Ye; YU You-Wen; WANG Ping; DAI Lian-Rong

    2003-01-01

    The chiral SU(3) quark model is extended by including the vector meson exchanges to describe the short range interactions. The phase shifts of NN scattering are studied in this model. Compared with the results of the chiral SU(3) quark model in which only the pseudo-scalar and scalar chiralfields are considered, the phase shifts of 1 So wave are obviously improved.

  7. Chiral separation of six tetralone derivative enantiomers using immobilized cellulose chiral stationary phase%纤维素键合手性固定相拆分6种萘满酮衍生物对映体

    Institute of Scientific and Technical Information of China (English)

    赵允凤; 宋佳新; 孙嘉仪; 袁晓薇; 郭兴杰

    2014-01-01

    A high performance liquid chromatographic method( HPLC)was developed for the chiral separation of six α-aryl tetralone derivatives using a Chiralpak IC column. The factors influencing the chiral separation including the type and concentration of organic modifier,col-umn temperature and flow rate were investigated. The results showed that high enantiomeric separation can be obtained with isopropanol as modifier for the six compounds. The thermody-namic study indicated that the enantioseparation was enthalpically driven and showed that low column temperature was beneficial to separation. Complete separation of compound Ⅰ was achieved with a binary solvent mixture of n-hexane-isopropanol(90 : 10,v / v)as the recom-mended mobile phase. The compounds Ⅱ,Ⅲ and Ⅳ were separated with the mobile phase of the mixture of n-hexane-isopropanol(99 :1,v / v)and the compound Ⅴ was separated with the mixture of n-hexane-isopropanol(85 :15,v / v). The compound Ⅵ was separated with the mix-ture of n-hexane-isopropanol(80 :20,v / v). The column temperature was 25 ℃ ,and the flow rate was 1. 0 mL / min. The six tetralone derivative enantiomers were separated on a chiral sta-tionary phase of Chiralpak IC by HPLC. The column has high enantiomeric selectivity to the six tetralone derivative enantiomers.%使用 Chiralpak IC(纤维素-三(3,5-二氯苯基氨基甲酸酯)共价键合硅胶)手性柱,建立了采用手性固定相高效液相色谱拆分6种α-芳基萘满酮类衍生物对映体的方法。考察了流动相中有机改性剂的种类和比例、柱温和流速对对映体分离的影响。结果显示6种化合物在异丙醇为改性剂的条件下均可获得较高的对映体分离度。热力学研究表明6种化合物对映体的手性拆分过程均受焓驱动影响,且低温有利于对映体分离。最终推荐分离化合物Ⅰ对映体的流动相是正己烷-异丙醇(90:10,v / v);分离化合物Ⅱ、Ⅲ、Ⅳ对映体

  8. Evidence of Broken Reciprocity in Chiral Liquid Crystals

    Science.gov (United States)

    Moreira, Michele; Venkataraman, Nithya; Taheri, Bahman; Palffy-Muhoray, Peter

    2008-03-01

    Reciprocity in light scattering is predicated on bounded scattering media with symmetric and linear permittivity, conductivity and permeability. Due to their anisotropy and chirality, cholesteric liquid crystal form periodic dielectric structures. If the periodicity is comparable to the wavelength of light, these phases are self-assembled photonic band gap structures. There appear in the permittivity odd powers of the wave vector resulting from nonlocality and broken inversion symmetry. Evidence of non-reciprocity has been found in optically active crystals by Bennett [1] and in stacks of cholesteric and nematic liquid crystal cells by Takezoe [2]. We present experimental data showing broken reciprocity in transmittance and reflectance in cholesteric cells with different pitches having overlapping but distinct reflection bands. We explain our results in terms of simple analytic descriptions of material properties and propagating modes. [1] P.J. Bennett, S. Dhanjal, Yu. P. Svirko and N. I. Zheludev, Opt. Lett. 21, 1955 (1996) [2] J. Hwang; M.H. Song; B. Park; S. Nishimura; T. Toyooka; J.W. Wu; Y. Takanishi; K. Ishikawa; H. Takezoe, Nat. Mat. 4, 383 (2005).

  9. Chiral thermodynamics of nuclear matter

    Energy Technology Data Exchange (ETDEWEB)

    Fiorilla, Salvatore

    2012-10-23

    The equation of state of nuclear matter is calculated at finite temperature in the framework of in-medium chiral perturbation theory up to three-loop order. The dependence of its thermodynamic properties on the isospin-asymmetry is investigated. The chiral quark condensate is evaluated for symmetric nuclear matter. Its behaviour as a function of density and temperature sets important nuclear physics constraints for the QCD phase diagram.

  10. Novel Lifshitz point for chiral transition in the magnetic field

    Directory of Open Access Journals (Sweden)

    Toshitaka Tatsumi

    2015-04-01

    Full Text Available Based on the generalized Ginzburg–Landau theory, chiral phase transition is discussed in the presence of magnetic field. Considering the chiral density wave we show that chiral anomaly gives rise to an inhomogeneous chiral phase for nonzero quark-number chemical potential. Novel Lifshitz point appears on the vanishing chemical potential line, which may be directly explored by the lattice QCD simulation.

  11. [[Chiral separation of five arylpropionic acid drugs and determination of their enantiomers in pharmaceutical preparations by reversed-phase high performance liquid chromatography with cellulose-tris-(4-methylbenzoate) stationary phase

    Science.gov (United States)

    Luo, An; Wan, Qiang; Fan, Huajun; Chen, Zhi; Wu, Xuehao; Huang, Xiaowen; Zang, Linquan

    2014-09-01

    Chromatographic behaviors for enantiomeric separation of arylpropionic acid drugs were systematically developed by reversed phase-high performance liquid chromatography (RP-HPLC) using cellulose-tris-(4-methylbenzoate) (CTMB) as chiral stationary phase (CSP). The effects of the composition of the mobile phase, additives and temperature on chiral separation of flurbiprofen, pranoprofen, naproxen, ibuprofen and loxoprofen were further investigated. The enantiomers had been successfully separated on CSP of CTMB by the mobile phase of methanol-0.1% (v/v) formic acid except naproxen by acetonitrile-0.1% (v/v) formic acid at 25 °C. The mechanisms of the racemic resolution for the above mentioned five drugs are discussed thermodynamically and structurally. The resolutions between respective enantiomers for arylpropionic acid drugs on CTMB had significant differences due to their chromatographic behaviors. The order of resolutions ranked pranoprofen, loxoprofen, flurbiprofen, ibuprofen and naproxen. The method established has been successfully applied to the determination of the enantiomers of the five drugs in commercial preparations under the optimized conditions. It proved that the method is simple, reliable and accurate.

  12. Liquid chromatographic-electrospray mass spectrometric determination (LC-ESI-MS) of phase II metabolites of flobufen in rat liver microsomes-Chiral discrimination.

    Science.gov (United States)

    Babú, Yogeeta N; Nemec, Michal; Solich, Petr; Wsól, Vladimír

    2008-04-15

    Glucuronidation of the non-steroidal anti-inflammatory chiral drug flobufen and its major metabolite M17203 has been implicated as an important mechanism of flobufen elimination. To characterize flobufen metabolism by O-glucuronidation, new liquid chromatographic method (LC) coupled with ESI-MS was developed to detect the conjugates of flobufen and its metabolites formed in vitro in rat liver microsomes. Discovery DSC-18 LT cartridge columns were utilized for solid phase extraction (SPE) and Discovery C18 column (150 mm x 2.1 mm, 5 microm particle size) was used for LC separation. Chiral inversion of flobufen and its metabolites enantiomers was checked by special 1-allyl-(5R,8S,10R)-terguride column (150 mm x 4.6 mm). O-Glucuronidation of the S-enantiomer displayed a typical Michaelis-Menten kinetics, whereas the R-enantiomer exhibited a substrate inhibition type of kinetics. The study of glucuronidation of M17203 led to kinetics with sigmoidal characteristics.

  13. Chiral Nanoscience and Nanotechnology

    OpenAIRE

    Dibyendu S. Bag; T.C. Shami; K.U. Bhasker Rao

    2008-01-01

    The paper reviews nanoscale science and technology of chiral molecules/macromolecules-under twosubtopics-chiral nanotechnology and nano-chiral technology. Chiral nanotechnology discusses thenanotechnology, where molecular chirality plays a role in the properties of materials, including molecularswitches, molecular motors, and other molecular devices; chiral supramolecules and self-assembled nanotubesand their functions are also highlighted. Nano-chiral technology  describes the nanoscale appr...

  14. Proposed chiral texture of the magnetic moments of unit-cell loop currents in the pseudogap phase of cuprate superconductors.

    Science.gov (United States)

    Pershoguba, Sergey S; Kechedzhi, Kostyantyn; Yakovenko, Victor M

    2013-07-26

    We propose a novel chiral order parameter to explain the unusual polar Kerr effect in underdoped cuprates. It is based on the loop-current model by Varma, which is characterized by the in-plane anapole moment N and exhibits the magnetoelectric effect. We propose a helical structure where the vector N(n) in the layer n is twisted by the angle π/2 relative to N(n-1), thus breaking inversion symmetry. We show that coupling between magnetoelectric terms in the neighboring layers for this structure produces optical gyrotropy, which results in circular dichroism and the polar Kerr effect.

  15. Chiral Cyclobutane β-Amino Acid-Based Amphiphiles: Influence of Cis/Trans Stereochemistry on Condensed Phase and Monolayer Structure.

    Science.gov (United States)

    Sorrenti, Alessandro; Illa, Ona; Ortuño, Rosa M; Pons, Ramon

    2016-07-12

    New diastereomeric nonionic amphiphiles, cis- and trans-1, based on an optically pure cyclobutane β-amino ester moiety have been investigated to gain insight into the influence exerted by cis/trans stereochemistry and stereochemical constraints on the physicochemical behavior, molecular organization, and morphology of their Langmuir monolayers and dry solid states. All these features are relevant to the rational design of functional materials. trans-1 showed a higher thermal stability than cis-1. For the latter, a higher fluidity of its monolayers was observed when compared with the films formed by trans-1 whose BAM images revealed the formation of condensed phase domains with a dendritic shape, which are chiral, and all of them feature the same chiral sign. Although the formation of LC phase domains was not observed by BAM for cis-1, compact dendritic crystals floating on a fluid subphase were observed beyond the collapse, which are attributable to multilayered 3D structures. These differences can be explained by the formation of hydrogen bonds between the amide groups of consecutive molecules allowing the formation of extended chains for trans-1 giving ordered arrangements. However, for cis-1, this alignment coexists with another one that allows the simultaneous formation of two hydrogen bonds between the amide and the ester groups of adjacent molecules. In addition, the propensity to form intramolecular hydrogen bonds must be considered to justify the formation of different patterns of hydrogen bonding and, consequently, the formation of less ordered phases. Those characteristics are congruent also with the results obtained from SAXS-WAXS experiments which suggest a more bent configuration for cis-1 than for trans-1.

  16. Chiral Relaxation Time at the Chiral Crossover of Quantum Chromodynamics

    CERN Document Server

    Ruggieri, M; Chernodub, M

    2016-01-01

    We study microscopic processes responsible for chirality flips in the thermal bath of Quantum Chromodynamics at finite temperature and zero baryon chemical potential. We focus on the temperature range where the crossover from chirally broken phase to quark-gluon plasma takes place, namely $T \\simeq (150, 200)$ MeV. The processes we consider are quark-quark scatterings mediated by collective excitations with the quantum number of pions and $\\sigma$-meson, hence we refer to these processes simply as \\sugg{to} one-pion (one-$\\sigma$) exchange\\sugg{s}. We use a Nambu-Jona-Lasinio model to compute equilibrium properties of the thermal bath, as well as the relevant scattering kernel to be used in the collision integral to estimate the chiral relaxation time $\\tau$. We find $\\tau\\simeq 0.1 \\div 1$ fm/c around the chiral crossover.

  17. Dynamic structure of active nematic shells

    Science.gov (United States)

    Zhang, Rui; Zhou, Ye; Rahimi, Mohammad; de Pablo, Juan J.

    2016-11-01

    When a thin film of active, nematic microtubules and kinesin motor clusters is confined on the surface of a vesicle, four +1/2 topological defects oscillate in a periodic manner between tetrahedral and planar arrangements. Here a theoretical description of nematics, coupled to the relevant hydrodynamic equations, is presented here to explain the dynamics of active nematic shells. In extensile microtubule systems, the defects repel each other due to elasticity, and their collective motion leads to closed trajectories along the edges of a cube. That motion is accompanied by oscillations of their velocities, and the emergence and annihilation of vortices. When the activity increases, the system enters a chaotic regime. In contrast, for contractile systems, which are representative of some bacterial suspensions, a hitherto unknown static structure is predicted, where pairs of defects attract each other and flows arise spontaneously.

  18. Janus Nematic Colloids with Designable Valence

    Directory of Open Access Journals (Sweden)

    Simon Čopar

    2014-05-01

    Full Text Available Generalized Janus nematic colloids based on various morphologies of particle surface patches imposing homeotropic and planar surface anchoring are demonstrated. By using mesoscopic numerical modeling, multiple types of Janus particles are explored, demonstrating a variety of novel complex colloidal structures. We also show binding of Janus particles to a fixed Janus post in the nematic cell, which acts as a seed and a micro-anchor for the colloidal structure. Janus colloidal structures reveal diverse topological defect configurations, which are effectively combinations of surface boojum and bulk defects. Topological analysis is applied to defects, importantly showing that topological charge is not a well determined topological invariant in such patchy nematic Janus colloids. Finally, this work demonstrates colloidal structures with designable valence, which could allow for targeted and valence-conditioned self-assembly at micro- and nano-scale.

  19. Transverse vibration of nematic elastomer Timoshenko beams

    Science.gov (United States)

    Zhao, Dong; Liu, Ying; Liu, Chuang

    2017-01-01

    Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.

  20. Nematic antiferromagnetic states in bulk FeSe

    Science.gov (United States)

    Liu, Kai; Lu, Zhong-Yi; Xiang, Tao

    2016-05-01

    The existence of nematic order, which breaks the lattice rotational symmetry with nonequivalent a and b axes in iron-based superconductors, is a well-established experimental fact. An antiferromagnetic (AFM) transition is accompanying this order, observed in nearly all parent compounds, except bulk FeSe. The absence of the AFM order in FeSe casts doubt on the magnetic mechanism of iron-based superconductivity, since the nematic order is believed to be driven by the same interaction that is responsible for the superconducting pairing in these materials. Here we show, through systematic first-principles electronic structure calculations, that the ground state of FeSe is in fact strongly AFM correlated but without developing a magnetic long-range order. Actually, there are a series of staggered n -mer AFM states with corresponding energies below that of the single stripe AFM state, which is the ground state for the parent compounds of most iron-based superconductors. Here, the staggered n -mer (n any integer >1 ) means a set of n adjacent parallel spins on a line along the b axis with antiparallel spins between n -mers along both a and b axes. Moreover, different n -mers can antiparallelly mix with each other to coexist. Among all the states, we find that the lowest energy states formed by the staggered dimer, staggered trimer, and their random antiparallel aligned spin states along the b axis are quasidegenerate. The thermal average of these states does not show any magnetic long-range order, but it does possess a hidden one-dimensional AFM order along the a axis, which can be detected by elastic neutron scattering measurements. Our finding gives a natural account for the absence of long-range magnetic order and suggests that the nematicity is driven predominantly by spin fluctuations even in bulk FeSe, providing a unified description on the phase diagram of iron-based superconductors.

  1. On Chiral Space Groups and Chiral Molecules

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations). For a chiral molecule, which must crystallize in a chiral space group, the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant.

  2. On Chiral Space Groups and Chiral Molecules

    Institute of Scientific and Technical Information of China (English)

    NgSeikWng; HUSheng-Zhi

    2003-01-01

    This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations).For a chiral molecule,which must crystallize in a chiral space group,the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant.

  3. Smectic phase in suspensions of gapped DNA duplexes

    Science.gov (United States)

    Salamonczyk, Miroslaw; Zhang, Jing; Portale, Giuseppe; Zhu, Chenhui; Kentzinger, Emmanuel; Gleeson, James T.; Jakli, Antal; de Michele, Cristiano; Dhont, Jan K. G.; Sprunt, Samuel; Stiakakis, Emmanuel

    2016-11-01

    Smectic ordering in aqueous solutions of monodisperse stiff double-stranded DNA fragments is known not to occur, despite the fact that these systems exhibit both chiral nematic and columnar mesophases. Here, we show, unambiguously, that a smectic-A type of phase is formed by increasing the DNA's flexibility through the introduction of an unpaired single-stranded DNA spacer in the middle of each duplex. This is unusual for a lyotropic system, where flexibility typically destabilizes the smectic phase. We also report on simulations suggesting that the gapped duplexes (resembling chain-sticks) attain a folded conformation in the smectic layers, and argue that this layer structure, which we designate as smectic-fA phase, is thermodynamically stabilized by both entropic and energetic contributions to the system's free energy. Our results demonstrate that DNA as a building block offers an exquisitely tunable means to engineer a potentially rich assortment of lyotropic liquid crystals.

  4. Direct and inverted nematic dispersions for soft matter photonics.

    Science.gov (United States)

    Muševič, I; Skarabot, M; Humar, M

    2011-07-20

    General properties and recent developments in the field of nematic colloids and emulsions are discussed. The origin and nature of pair colloidal interactions in the nematic colloids are explained and an overview of the stable colloidal 2D crystalline structures and superstructures discovered so far is given. The nature and role of topological defects in the nematic colloids is discussed, with an emphasis on recently discovered entangled colloidal structures. Applications of inverted nematic emulsions and binding force mechanisms in nematic colloids for soft matter photonic devices are discussed.

  5. A chiral study of the $a_0(980)$ resonance and $\\pi\\eta$ scattering phase shifts in light of a recent lattice simulation

    CERN Document Server

    Guo, Zhi-Hui; Meißner, Ulf-G; Oller, J A; Rusetsky, A

    2016-01-01

    We investigate the $a_0(980)$ resonance within chiral effective field theory through a three-coupled-channel analysis, namely $\\pi\\eta$, $K\\bar{K}$ and $\\pi\\eta'$. A global fit to recent lattice finite-volume energy levels from $\\pi\\eta$ scattering and relevant experimental data on a $\\pi\\eta$ event distribution and the $\\gamma\\gamma\\to\\pi\\eta$ cross section is performed. Both the leading and next-to-leading order analyses lead to quite similar and successful descriptions of the finite-volume energy levels and the experimental data. However, these two different analyses yield different $\\pi\\eta$ scattering phase shifts after taking the physical masses for the $\\pi, K, \\eta$ and $\\eta'$ mesons. The inelasticities, the pole positions in the complex energy plane and their residues are calculated both for unphysical and physical meson masses.

  6. A new chiral derivatizing agent for the HPLC separation of α-amino acids on a standard reverse-phase column.

    Science.gov (United States)

    Kotthaus, A F; Altenbach, H-J

    2011-02-01

    A new chiral derivatizing agent for α-amino acids is described which leads to diastereomers that can be separated by reverse-phase HPLC with direct detection by a diode array detector. The main advantage of the presented procedure is the fact that an excess of the derivatizing reagent can be employed as the product exhibits an absorption maximum at 360 nm, while the reagent has its absorption maximum at 260 nm. Therefore, it is possible to suppress the reagent signal by a detection wavelength of 400 nm leading to an easy and general method for the enantioseparation of a mixture of DL-amino acids and the determination of the enantiomeric purity of α-amino acid as exemplified by 16 different α-amino acids.

  7. Sorption and selective chromatographic properties of isomer-selective composite sorbent based on a eutectic mixture of nematic liquid crystals and perbenzoylated β-cyclodextrin

    Science.gov (United States)

    Onuchak, L. A.; Kapralova, T. S.; Kuraeva, Yu. G.; Belousova, Z. P.; Stepanova, R. F.

    2015-12-01

    Mesomorphic, sorption, and selective properties of a three-component sorbent based on a mixture of nematic ( N) liquid crystals of 4-methoxy-4'-ethoxyazoxybenzene (MEAB) and 4,4'-diethoxyazoxybenzene (azoxyphenetol, AOP) of an eutectic composition and heptakis-(2,3,6-tri- O-benzoyl)-β-cyclodextrin (Bz-β-CD) are studied. For 30 organic compounds of different classes with linear and cyclic molecular structures, including optical isomers of limonene, pinene, camphene, and butanediol-2,3, thermodynamic functions are determined for their gas-phase sorption using a three-component MEAB-AOP-Bz-β- CD sorbent (62: 28: 10 wt %). It is found that the investigated sorbent possesses high structural selectivity (αp/m = 1.128-1.059, 100-130°C, N) and moderate enantioselectivity (1.07-1.02) within a broad temperature range (95-170°C) including both mesomorphic and isotropic phases of the sorbent. It is shown that the enantioselectivity of the sorbent is apparent under conditions of both increasing retention when a chiral Bz-β-CD additive is introduced into the MEAB-AOP system (limonenes, pinenes, camphenes) and decreasing retention (butanediols-2,3).

  8. Effects from inhomogeneities in the chiral transition

    CERN Document Server

    Taketani, B G; Taketani, Bruno G.; Fraga, Eduardo S.

    2006-01-01

    We consider an approximation procedure to evaluate the finite-temperature one-loop fermionic density in the presence of a chiral background field which systematically incorporates effects from inhomogeneities in the chiral field through a derivative expansion. We apply the method to the case of a simple low-energy effective chiral model which is commonly used in the study of the chiral phase transition, the linear sigma-model coupled to quarks. The modifications in the effective potential and their consequences for the bubble nucleation process are discussed.

  9. Asymmetric synthesis using chiral-encoded metal

    Science.gov (United States)

    Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2016-08-01

    The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity.

  10. Enantioselective recognition at mesoporous chiral metal surfaces

    Science.gov (United States)

    Wattanakit, Chularat; Côme, Yémima Bon Saint; Lapeyre, Veronique; Bopp, Philippe A.; Heim, Matthias; Yadnum, Sudarat; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2014-02-01

    Chirality is widespread in natural systems, and artificial reproduction of chiral recognition is a major scientific challenge, especially owing to various potential applications ranging from catalysis to sensing and separation science. In this context, molecular imprinting is a well-known approach for generating materials with enantioselective properties, and it has been successfully employed using polymers. However, it is particularly difficult to synthesize chiral metal matrices by this method. Here we report the fabrication of a chirally imprinted mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and chiral template molecules. The porous platinum retains a chiral character after removal of the template molecules. A matrix obtained in this way exhibits a large active surface area due to its mesoporosity, and also shows a significant discrimination between two enantiomers, when they are probed using such materials as electrodes.

  11. Nematic world crystal model of gravity explaining absence of torsion in spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Kleinert, H.; Zaanen, J

    2004-04-26

    We attribute the gravitational interaction between sources of curvature to the world being a crystal which has undergone a quantum phase transition to a nematic phase by a condensation of dislocations. The model explains why spacetime has no observable torsion and predicts the existence of curvature sources in the form of world sheets, albeit with different high-energy properties than those of string models.

  12. Meson Effects on the Chiral Condensate at Finite Density

    Institute of Scientific and Technical Information of China (English)

    HUANG Mei; ZHUANG Peng-Fei; ZHAO Wei-Qin

    2002-01-01

    Meson corrections on the chiral condensate up to next-to-leading order in a 1/Nc expansion at finite densityare investigated in the NJL model with explicit chiral symmetry breaking. Compared with mean-field results, the chiralphase transition is still of the first order while the properties near the critical density for chiral phase transition are foundto change significantly.

  13. Chiral spiral induced by a strong magnetic field

    Directory of Open Access Journals (Sweden)

    Abuki Hiroaki

    2016-01-01

    Full Text Available We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it brings a “continent” of chiral spiral in the phase diagram, by which the chiral tricritical point is totally washed out. This is the case no matter how small the intensity of magnetic field is. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However, the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.

  14. Nematic Cells for Digital Light Deflection

    Science.gov (United States)

    Pishnyak, Oleg; Golovin, Andrii; Laventovich, Oleg; Kreminska, Liubov; Winker, Bruce; Pouch, John; Miranda, Felix

    2008-01-01

    Smectic A (SmA) materials can be used in non-mechanical, digital beam deflectors (DBDs) as fillers for passive birefringent prisms based on decoupled pairs of electrically controlled, liquid crystalline polarization rotators, like twisted nematic (TN) cells and passive deflectors. DBDs are used in free-space laser communications, optical fiber communications, optical switches, scanners, and in-situ wavefront correction.

  15. Hydrodynamic correlation functions in nematic liquid crystals

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Carle, D.; Laidlaw, W.G.

    1976-01-01

    The result, recently discovered by Forster, that the strength factors of the nonpropagating modes in certain hydrodynamic correlation functions in nematic liquid crystals are not fully determined by the hydrodynamic matrix is reconsidered. Using time reversal and space inversion symmetry one finds t

  16. Stegosaurus chirality

    OpenAIRE

    Cameron, R.P.; Cameron, J. A.; Barnett, S. M.

    2016-01-01

    We explain that Stegosaurus exhibited exterior chirality and observe that the largest plate in particular of USNM 4394, USNM 4714, DMNS 2818 and NHMUK R36730 appears to have tilted to the right rather than to the left in each case. Several instances in which Stegosaurus specimens have been confused with their distinct, hypothetical mirror-image forms are highlighted. We believe our findings to be consistent with the hypothesis that Stegosaurus's plates acted primarily as display structures. A...

  17. Effect of the water content on the retention and enantioselectivity of albendazole and fenbendazole sulfoxides using amylose-based chiral stationary phases in organic-aqueous conditions.

    Science.gov (United States)

    Materazzo, Sabrina; Carradori, Simone; Ferretti, Rosella; Gallinella, Bruno; Secci, Daniela; Cirilli, Roberto

    2014-01-31

    Four commercially available immobilized amylose-derived CSPs (Chiralpak IA-3, Chiralpak ID-3, Chiralpak IE-3 and Chiralpak IF-3) were used in the HPLC analysis of the chiral sulfoxides albendazole (ABZ-SO) and fenbendazole (FBZ-SO) and their in vivo sulfide precursor (ABZ and FBZ) and sulfone metabolite (ABZ-SO2 and FBZ-SO2) under organic-aqueous mode. U-shape retention maps, established by varying the water content in the acetonitrile- and ethanol-water mobile phases, were indicative of two retention mechanisms operating on the same CSP. The dual retention behavior of polysaccharide-based CSPs was exploited to design greener enantioselective and chemoselective separations in a short time frame. The enantiomers of ABZ-SO and FBZ-SO were baseline resolved with water-rich mobile phases (with the main component usually being 50-65% water in acetonitrile) on the IF-3 CSP and ethanol-water 100:5 mixture on the IA-3 and IE-3 CSPs. A simultaneous separation of ABZ (or FBZ), enantiomers of the corresponding sulfoxide and sulfone was achieved on the IA-3 using ethanol-water 100:60 (acetonitrile-water 100:100 for FBZ) as a mobile phase.

  18. A validated chiral LC method for enantiomeric separation of nebivolol stereoisomers in bulk drugs and dosage forms on amylose-based stationary phase.

    Science.gov (United States)

    Visweswara Rao, Karri; Padmaja Reddy, Kesareddy; Haldar, Pranab

    2014-10-01

    A novel and reproducible isocratic normal phase liquid chromatographic method was developed for the quantitative determination of 10 stereoisomers of Nebivolol in pharmaceutical bulk drugs and dosage forms. The method was developed using an amylose-based chiral stationary phase, Chiralpak AD-3 (250 × 4.6 mm, 3 μm) column with mobile phase containing n-hexane-ethanol-isopropanol-diethanolamine in the ratio 42:45:13:0.1 (v/v/v/v). The eluted compounds were monitored at 280 nm. Ten stereoisomers of Nebivolol were well separated with resolution >2.0 for all pair of components. The developed method was validated as per International Conference on Harmonization (ICH) guidelines with respect to specificity, linearity (R(2) value >0.999), limit of detection, limit of quantification, accuracy (recovery range 95.8-103.2%), precision (relative standard deviation, RSD, <2.5%) and robustness. Nebivolol sample solutions were found to be stable when characterized over a period of 48 h. Forced degradation studies were also performed to demonstrate the stability-indicating power of the developed HPLC method. The method was found to be rugged and robust.

  19. Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates

    Directory of Open Access Journals (Sweden)

    Tomoya Hayata

    2015-05-01

    Full Text Available We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.

  20. Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates

    Energy Technology Data Exchange (ETDEWEB)

    Hayata, Tomoya, E-mail: hayata@riken.jp [Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan); Yamamoto, Arata [Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan)

    2015-05-11

    We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.

  1. Chiral mobile phase in ligand-exchange chromatography of amino acids: exploring the copper(II) salt anion effect with a computational approach.

    Science.gov (United States)

    Sardella, Roccaldo; Macchiarulo, Antonio; Carotti, Andrea; Ianni, Federica; Rubiño, Maria Eugenia García; Natalini, Benedetto

    2012-12-21

    With the use of a chiral ligand-exchange chromatography (CLEC) system operating with the O-benzyl-(S)-serine [(S)-OBS] [1,2] as the chiral mobile phase (CMP) additive to the eluent, the effect of the copper(II) anion type on retention (k) and separation (α) factors was evaluated, by rationally changing the following experimental conditions: salt concentration and temperature. The CLEC-CMP analysis was carried out on ten amino acidic racemates and with nine different cupric salts. While the group of analytes comprised both aliphatic (leucine, isoleucine, nor-leucine, proline, valine, nor-valine, and α-methyl-valine) and aromatic (1-aminoindan-1,5-dicarboxylic acid, phenylglycine, and tyrosine) species, representative organic (formate, methanesulfonate, and trifluoroacetate) and inorganic (bromide, chloride, fluoride, nitrate, perchlorate, and sulfate) Cu(II) salts were selected as the metal source into the eluent. This route of investigation was pursued with the aim of identifying analogies among the employed Cu(II) salts, by observing the variation profile of the selected chromatographic parameters, upon a change of the above experimental conditions. All the data were collected and analyzed through a statistical approach (PCA and k-means clustering) that revealed the presence of two behavioral classes of cupric salts, sharing the same variation profile for k and α values. Interestingly, this clustering can be explained in terms of ESP (electrostatic surface potential) balance (ESP(bal)) values, obtained by an ab initio calculation operated on the cupric salts. The results of this appraisal could aid the rational choice of the most suitable eluent system, to succeed in the enantioseparation of difficult-to-resolve compounds, along with the eventual scale-up to a semi-preparative level.

  2. Molecular theory of nematic liquid crystals viewed as effect of collective excitation in ferromagnetic systems

    Institute of Scientific and Technical Information of China (English)

    Liu Jian-Jun; Shen Man; Liu Xiao-Jing; Yang Guo-Chen

    2006-01-01

    We develop a microscopic theory of the nematic phase with consideration of the effect of the collective excitation on properties of nematic liquid crystals. The model is based on the Heisenberg's exchange model of the ferromagnetic materials. Since the orientation of the molecular long axis and the angular momentum of the molecule rotating around its long axis have the same direction, operators can be introduced to research the nematic liquid crystals. Using the lattice model and the Holstein-Primakoff transformation, the Hamiltonian of the system can be obtained, which has the same form as that of the ferromagnetic substance. The relation between the order parameter and reduced temperature can be gotten. It is in good agreement with the experimental results in the low temperature region, the accordance is better than that of the molecular field theory and the computer simulation. In high temperature region close to the transition point, by considering the effect of the higher-order terms in the Hamiltonian, theoretical prediction is in better agreement with the experiment. That indicates the many-body effect is important to nematic liquid crystals.

  3. Influence of heavy hadronic states on the QCD phase diagram and on the freeze-out within a hadronic chiral model; Einfluss schwerer hadronischer Zustaende auf das QCD-Phasendiagramm und die Ausfrierbedingungen in einem hadronischen chiralen Modell

    Energy Technology Data Exchange (ETDEWEB)

    Zeeb, G.

    2006-07-01

    In this thesis the thermodynamical properties of strongly interacting hadronic matter and the microscopic in-medium properties of hadrons are investigated at high temperatures and high baryonic densities within a chiral flavor-SU(3) model. The applied model is a generalized {sigma}-{omega} model in mean-field approximation with baryons and mesons as effective degrees of freedom. It is built on spontaneously broken chiral symmetry and scale invariance. The phase transition behavior is systematically analyzed and is thus shown to depend significantly on the couplings of additional heavier hadronic degrees of freedom. A phase diagram in qualitative agreement with current lattice QCD (lQCD) calculations can result from an according coupling of the lowest lying baryonic decuplet to the model. Alternatively, the coupling of a heavy baryonic test-resonance is investigated, which effectively represents the spectrum of the heavy hadronic states. For a certain range of parameters one can even obtain a phase diagram in quantitative agreement with the lQCD calculations and, simultaneously, a successful description of the ground state properties of nuclear matter. It is shown that (within the model assumptions) the phase transition region is experimentally accessible for the CBM experiment at the upcoming FAIR facility at GSI Darmstadt. The chiral model is further applied to particle yield ratios measured in heavy-ion collisions from AGS, SPS and RHIC. For these investigations parameter sets with strongly differing phase diagrams due to different couplings of the baryon decuplet are used and in addition an ideal hadron gas. At the lower and mid collision energies the chiral parameter sets show an improved description as compared to the ideal hadron gas, especially for parameter sets with phase diagrams similar to the lQCD predictions. The interaction within the chiral model leads to in-medium modifications of the chemical potentials and the hadron masses. Therefore the

  4. Chirally symmetric but confined hadrons at finite density

    CERN Document Server

    Glozman, L Ya

    2008-01-01

    At a critical finite chemical potential and low temperature QCD undergoes the chiral restoration phase transition. The folklore tradition is that simultaneously hadrons are deconfined and there appears the quark matter. We demonstrate that it is possible to have confined but chirally symmetric hadrons at a finite chemical potential and hence beyond the chiral restoration point at a finite chemical potential and low temperature there could exist a chirally symmetric matter consisting of chirally symmetric but confined hadrons. If it does happen in QCD, then the QCD phase diagram should be reconsidered with obvious implications for heavy ion programs and astrophysics.

  5. Volume phase transitions of cholesteric liquid crystalline gels

    Energy Technology Data Exchange (ETDEWEB)

    Matsuyama, Akihiko, E-mail: matuyama@bio.kyutech.ac.jp [Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502 (Japan)

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  6. Conventional Chiralpak ID vs. capillary Chiralpak ID-3 amylose tris-(3-chlorophenylcarbamate)-based chiral stationary phase columns for the enantioselective HPLC separation of pharmaceutical racemates.

    Science.gov (United States)

    Ahmed, Marwa; Gwairgi, Marina; Ghanem, Ashraf

    2014-11-01

    A comparative enantioselective analysis using immobilized amylose tris-(3-chlorophenylcarbamate) as chiral stationary phase in conventional high-performance liquid chromatography (HPLC) with Chiralpak ID (4.6 mm ID × 250 mm, 5 µm silica gel) and micro-HPLC with Chiralpak ID-3 (0.30 mm ID × 150 mm, 3 µm silica gel) was conducted. Pharmaceutical racemates of 12 pharmacological classes, namely, α- and β-blockers, anti-inflammatory drugs, antifungal drugs, dopamine antagonists, norepinephrine-dopamine reuptake inhibitors, catecholamines, sedative hypnotics, diuretics, antihistaminics, anticancer drugs, and antiarrhythmic drugs were screened under normal phase conditions. The effect of an organic modifier on the analyte retentions and enantiomer recognition was investigated. Baseline separation was achieved for 1-acenaphthenol, carprofen, celiprolol, cizolirtine carbinol, miconazole, tebuconazole, 4-hydroxy-3-methoxymandelic acid, 1-indanol, 1-(2-chlorophenyl)ethanol, 1-phenyl-2-propanol, flavanone, 6-hydroxyflavanone, 4-bromogluthethimide, and pentobarbital on the 4.6 mm ID packed with a 5 µm silica column using conventional HPLC. Nonetheless, baseline separation was achieved for aminoglutethimide, naftopidil, and thalidomide on the 0.3 mm ID packed with a 3 µm silica capillary column.

  7. High-performance liquid chromatographic enantioseparation of cyclic β-aminohydroxamic acids on zwitterionic chiral stationary phases based on Cinchona alkaloids

    Energy Technology Data Exchange (ETDEWEB)

    Lajkó, Gyula [Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7 (Hungary); Institute of Pharmaceutical Chemistry, University of Szeged, H-6720 Szeged, Eötvös u. 6 (Hungary); Orosz, Tímea [Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7 (Hungary); Grecsó, Nóra [Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7 (Hungary); Institute of Pharmaceutical Chemistry, University of Szeged, H-6720 Szeged, Eötvös u. 6 (Hungary); Fekete, Beáta; Palkó, Márta; Fülöp, Ferenc [Institute of Pharmaceutical Chemistry, University of Szeged, H-6720 Szeged, Eötvös u. 6 (Hungary); Lindner, Wolfgang [Department of Analytical Chemistry, University of Vienna, Währingerstrasse 38, A-1090 Vienna (Austria); Péter, Antal [Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7 (Hungary); Ilisz, István, E-mail: ilisz@chem.u-szeged.hu [Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Szeged, Dóm tér 7 (Hungary)

    2016-05-19

    Cyclic β-aminohydroxamic acid enantiomer pairs were stereoselectively separated by high-performance liquid chromatography on the recently developed Cinchona alkaloid-based zwitterionic chiral stationary phases Chiralpak ZWIX(+)™, ZWIX(−)™, ZWIX(+A) and ZWIX(−A). The results of variation of the applied chromatographic conditions, such as the bulk solvent composition, the concentrations and ratio of the acid and base additives, the presence of water as mobile phase additive and the counter-ion concentration furnished a better understanding of the retention mechanism. A thermodynamic study in the temperature range 5–50 °C revealed enthalpy-controlled enantiodiscrimination in all cases. The structure–selectivity relationships clearly indicated the importance of the strereochemistry of the functional groups. From an enantiorecognition aspect, the diexo position of the functional groups always proved more favorable than the diendo position. The elution sequence was determined in all cases and was found to reversed when ZWIX(+)™ was changed to ZWIX(−)™ or ZWIX(+A) to ZWIX(−A). - Highlights: • Zwitterionic columns were applied for the enantioseparation of cyclic β-aminohydroxamic acids. • Enthalpy controlled enantiodiscriminations were observed. • Enantiorecognition depended on the stereochemistry of the functional group.

  8. Enantioseparation of pyroglutamide derivatives on polysaccharide based chiral stationary phases by high-performance liquid chromatography and supercritical fluid chromatography: a comparative study.

    Science.gov (United States)

    Baudelet, Davy; Schifano-Faux, Nadège; Ghinet, Alina; Dezitter, Xavier; Barbotin, Florent; Gautret, Philippe; Rigo, Benoit; Chavatte, Philippe; Millet, Régis; Furman, Christophe; Vaccher, Claude; Lipka, Emmanuelle

    2014-10-10

    Analytical enantioseparation of three pyroglutamide derivatives with pharmacological activity against the purinergic receptor P2X7, was run in both high-performance liquid chromatography and supercritical fluid chromatography. Four polysaccharide based chiral stationary phases, namely amylose and cellulose tris (3,5-dimethylphenylcarbamate), amylose tris ((S)-α-methylbenzylcarbamate) and cellulose tris (4-methylbenzoate) with various mobile phases consisted of either heptane/alcohol (ethanol and 2-propanol) or carbon dioxide/alcohol (methanol or ethanol) mixtures, were investigated. After analytical screenings, the best conditions were transposed, for compound 1, to semi-preparative scale. Each approach was fully validated to meet the International Conference on Harmonisation requirements and compared. Whereas the limits of detection and quantification were near six-fold better in HPLC than in SFC (respectively 0.20 and 0.66 μM versus 1.11 and 3.53 μM for one of the enantiomers), in terms of low solvent consumption (7.2 mL of EtOH versus 3.2 mL of EtOH plus 28.8 mL of toxic and inflammable heptane per injection in SFC and HPLC, respectively), time effective cost (9 min versus 40 min per injection in SFC and HPLC, respectively) and yields (98% versus 71% in SFC and HPLC, respectively), the latter method proved its ecological superiority.

  9. Chiral nuclear thermodynamics

    CERN Document Server

    Fiorilla, Salvatore; Weise, Wolfram

    2011-01-01

    We calculate the equation of state of nuclear matter for arbitrary isospin-asymmetry up to three loop order in the free energy density in the framework of in-medium chiral perturbation theory. In our approach 1\\pi- and 2\\pi-exchange dynamics with the inclusion of the \\Delta-isobar excitation as an explicit degree of freedom, corresponding to the long- and intermediate-range correlations, are treated explicitly. Few contact terms fixed to reproduce selected known properties of nuclear matter encode the short-distance physics. Two-body as well as three-body forces are systematically included. We find a critical temperature of about 15 MeV for symmetric nuclear matter. We investigate the dependence of the liquid-gas first-order phase transition on isospin-asymmetry. In the same chiral framework we calculate the chiral condensate of isospin-symmetric nuclear matter at finite temperatures. The contribution of the \\Delta-isobar excitation is essential for stabilizing the condensate. As a result, we find no indicati...

  10. 手性固定相AD、AS和OD的拆分性能%Enantioseparation behavior of chiral stationary phases AD,AS and OD

    Institute of Scientific and Technical Information of China (English)

    李丽群; 范军; 张晶; 陈晓东; 王泰; 贺建峰; 章伟光

    2016-01-01

    手性固定相-高效液相色谱法在手性药物、手性农药等的分离分析中应用广泛。本文采用3种多糖衍生物的手性固定相(即 EnantioPak AD、AS和 OD)对20种手性化合物开展手性分离研究,进而探讨样品分子结构、多糖骨架和衍生基团对手性分离的影响。结果表明,除化合物13外,其余化合物在 EnantioPak AD 上均实现基线分离,分离度多在2.0以上,在正己烷-醇流动相中加入酸碱添加剂可改善和优化酸性或碱性化合物的分离效果;芳香醇(化合物13~16)随着侧链碳数增加在色谱柱上的保留减弱,其分离度呈现增加的趋势;对比8种化合物在3种手性固定相上的分离结果可知,EnantioPak AD 表现出更优的分离性能。这为深入研究和了解多糖手性固定相、拓展其手性分离应用提供了参考。%Over the past decades, HPLC enantioseparation with chiral stationary phases (CSPs)has been widely applied in chiral analysis and preparation of new pharmaceuticals, pesticides,food,etc. Herein,enantioseparation of 20 chiral compounds have been carried out on three polysaccharide-based CSPs(EnantioPak AD,AS and OD)with normal phases by HPLC,separately. The influences of skeletal structure and the kinds of derivative groups on separation behaviors of these CSPs have been studied in detail. As results indicated ,except for compound 13,the other compounds were baseline separated on EnantioPak AD,with most of resolution over 2. 0;in addition,better separation for acidic or basic compounds was achieved through adding acidic/basic additives into the mobile phase of hexane-alcohol. For four aromat-ic alcohols( compounds 13-16),their retention in the EnantioPak AD column showed a weake-ning tendency with increase of carbon number in side chain group,and the reverse trend of their resolution was observed. Furthermore,EnantioPak AD showed much better separation performance for eight compounds(13-20)than

  11. Instability of a Biaxial Nematic Liquid Crystal Formed by Homeotropic Anchoring on Surface Grooves

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Dong; XUAN Li

    2011-01-01

    A method used to treat the elastic distortion of a uniaxial nematic liquid crystal induced by homogeneous anchoring on the surface grooves is generalized to biaxial nematic liquid crystals under the homeotropic anchoring condition.Employing some approximations for the elastic constants,we obtain an additional term in the elastic energy per unit area which depends on the angle between the minor director at infinity and the direction of the grooves,with a period of π/2.This leads to instability on the surface grooves so that two states with crossed minor directors are energetically indistinguishable.Our theoretical study explains why the homeotropic alignment method developed for uniaxial liquid crystals loses efficacy for biaxial nematics.In most liquid crystal devices,the liquid crystals are sandwiched between two substrates coated with alignment layers.In the absence of externally applied fields,the orientation of the liquid crystal in the cell is determined by the anchoring condition of the alignment layer.[1-3] One usually distinguishes three main types of liquid crystalline director alignment near solid walls:homeotropic,homogeneous (or planar) and tilted orientations.Here we study the first of these and consider the biaxial nematic phase,which was observed in lyotropic systems as early as 1980[4] and has been confirmed by deuterium NMR spectroscopy.%A method used to treat the elastic distortion of a uniaxial nematic liquid crystal induced by homogeneous anchoring on the surface grooves is generalized to biaxial nematic liquid crystals under the homeotropic anchoring condition. Employing some approximations for the elastic constants, we obtain an additional term in the elastic energy per unit area which depends on the angle between the minor director at infinity and the direction of the grooves, with a period of π/2. This leads to instability on the surface grooves so that two states with crossed minor directors are energetically indistinguishable. Our

  12. Non-covalent modification of reduced graphene oxide by a chiral liquid crystalline surfactant

    Science.gov (United States)

    Lin, Pengcheng; Cong, Yuehua; Sun, Cong; Zhang, Baoyan

    2016-01-01

    In order to effectively disperse reduced graphene oxide (RGO) in functional materials and take full advantage of its exceptional physical and chemical properties, a novel and effective approach for non-covalent modification of RGO by a chiral liquid crystalline surfactant (CLCS) consisting of chiral mesogenic units, nematic mesogenic units with carboxyl groups and non-mesogenic units with a polycyclic conjugated structure is firstly established. The polycyclic conjugated structure can anchor onto the RGO surface via π-π interactions, the chiral mesogenic units possess affinity for chiral materials by joining the helical matrix of chiral material and the carboxyl groups in nematic mesogenic units are supposed to form coordination bonds with nano zinc oxide (ZnO) to fabricate functional nano hybrids. The transmittances of CLCS-RGO hybrids exhibit S-shaped nonlinear increase with the increase of wavelength, but the total transmittances from 220 nm to 800 nm show a linear decreasing trend with the increase of RGO content in the CLCS-RGO hybrid. Due to the superior thermal properties of RGO and the interactions between RGO and CLCS, the dispersed RGO can improve the glass transition and increase the thermal stability and decomposition activation energy of CLCS. The intercalation of RGO can decrease the thermochromism temperature and improve the pitch uniformity of CLCS. Furthermore, CLCS can promote the dispersion of RGO in chiral nematic liquid crystals (CNLCs), and the CNLC-RGO-CLCS hybrids present decreased driving voltage and accelerated electro-optical response. The CLCS non-covalently modified RGO can strengthen the photocatalytic degradation of ZnO by suppressing the aggregation of ZnO and RGO.In order to effectively disperse reduced graphene oxide (RGO) in functional materials and take full advantage of its exceptional physical and chemical properties, a novel and effective approach for non-covalent modification of RGO by a chiral liquid crystalline surfactant

  13. Interplay of nematic and magnetic orders in FeSe under pressure

    Science.gov (United States)

    Scherer, Daniel D.; Jacko, A. C.; Friedrich, Christoph; Şaşıoǧlu, Ersoy; Blügel, Stefan; Valentí, Roser; Andersen, Brian M.

    2017-03-01

    We offer an explanation for the recently observed pressure-induced magnetic state in the iron-chalcogenide FeSe based on ab initio estimates for the pressure evolution of the most important Coulomb interaction parameters. We find that an increase of pressure leads to an overall decrease mostly in the nearest-neighbor Coulomb repulsion, which in turn leads to a reduction of the nematic order and the generation of magnetic stripe order. We treat the concomitant effects of band renormalization and the induced interplay of nematic and magnetic order in a self-consistent way and determine the generic topology of the temperature-pressure phase diagram and find qualitative agreement with the experimentally determined phase diagram.

  14. Pseudo-molecular approach for the elastic constants of nematic liquid crystals interacting via anisotropic dispersion forces

    Energy Technology Data Exchange (ETDEWEB)

    Simonário, P.S., E-mail: simonario@gmail.com [Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo, 5790, 87020-900 Maringá, Paraná (Brazil); Freire, F.C.M.; Evangelista, L.R. [Departamento de Física, Universidade Estadual de Maringá, Avenida Colombo, 5790, 87020-900 Maringá, Paraná (Brazil); Teixeira-Souza, R.T. [Universidade Tecnológica Federal do Paraná – Câmpus Apucarana, Rua Marcílio Dias, 635, 86812-460 Apucarana, Paraná (Brazil)

    2014-01-17

    The bulk and the surface-like elastic constants of a nematic liquid crystal are calculated for an ensemble of particles interacting via anisotropic dispersion forces using the pseudo-molecular method. The geometrical anisotropy of the molecules is also taken into account in the calculations by choosing a molecular volume of ellipsoidal shape. Analytical expressions for the elastic constants are obtained as a function of the eccentricity in the molecular volume shape. The method allows one to explore the dependence on the molecular orientation with respect to the intermolecular vector by analyzing the magnitude and the behaviour of macroscopic elastic parameters defining the nematic phase.

  15. Photonic crystals, light manipulation, and imaging in complex nematic structures

    Science.gov (United States)

    Ravnik, Miha; Å timulak, Mitja; Mur, Urban; Čančula, Miha; Čopar, Simon; Žumer, Slobodan

    2016-03-01

    Three selected approaches for manipulation of light by complex nematic colloidal and non-colloidal structures are presented using different own custom developed theoretical and modelling approaches. Photonic crystals bands of distorted cholesteric liquid crystal helix and of nematic colloidal opals are presented, also revealing distinct photonic modes and density of states. Light propagation along half-integer nematic disclinations is shown with changes in the light polarization of various winding numbers. As third, simulated light transmission polarization micrographs of nematic torons are shown, offering a new insight into the complex structure characterization. Finally, this work is a contribution towards using complex soft matter in optics and photonics for advanced light manipulation.

  16. Nematic order by elastic interactions and cellular rigidity sensing

    Science.gov (United States)

    Friedrich, B. M.; Safran, S. A.

    2011-01-01

    We predict spontaneous nematic order in an ensemble of active force generators with elastic interactions as a minimal model for early nematic alignment of short stress fibers in non-motile, adhered cells. Mean-field theory is formally equivalent to Maier-Saupe theory for a nematic liquid. However, the elastic interactions are long-ranged (and thus depend on cell shape and matrix elasticity) and originate in cell activity. Depending on the density of force generators, we find two regimes of cellular rigidity sensing for which orientational, nematic order of stress fibers depends on matrix rigidity either in a step-like manner or with a maximum at an optimal rigidity.

  17. Phenomenological Theory of Isotropic-Genesis Nematic Elastomers

    Science.gov (United States)

    Lu, Bing-Sui; Ye, Fangfu; Xing, Xiangjun; Goldbart, Paul M.

    2012-06-01

    We consider the impact of the elastomer network on the nematic structure and fluctuations in isotropic-genesis nematic elastomers, via a phenomenological model that underscores the role of network compliance. The model contains a network-mediated nonlocal interaction as well as a new kind of random field that reflects the memory of the nematic order present at network formation and also encodes local anisotropy due to localized nematogenic polymers. This model enables us to predict regimes of short-ranged oscillatory spatial correlations (thermal and glassy) in the nematic alignment.

  18. Chiral Nanoscience and Nanotechnology

    Directory of Open Access Journals (Sweden)

    Dibyendu S. Bag

    2008-09-01

    Full Text Available The paper reviews nanoscale science and technology of chiral molecules/macromolecules-under twosubtopics-chiral nanotechnology and nano-chiral technology. Chiral nanotechnology discusses thenanotechnology, where molecular chirality plays a role in the properties of materials, including molecularswitches, molecular motors, and other molecular devices; chiral supramolecules and self-assembled nanotubesand their functions are also highlighted. Nano-chiral technology  describes the nanoscale approaches to chiraltechnology such as asymmetric synthesis and catalysis, chiral separation and detection, and enantiomericanalysis. Chiral sensors have also been included. The state-of-the-art chiral research at DMSRDE,Kanpur isalso presented.Defence Science Journal, 2008, 58(5, pp.626-635, DOI:http://dx.doi.org/10.14429/dsj.58.1685

  19. Hard Spherocylinders of Two Different Lengths as a Model System of a Nematic Liquid Crystal on an Anisotropic Substrate

    Science.gov (United States)

    Koda, Tomonori; Hyodo, Yosuke; Momoi, Yuichi; Kwak, Musun; Kang, Dongwoo; Choi, Youngseok; Nishioka, Akihiro; Haba, Osamu; Yonetake, Koichiro

    2016-02-01

    In this article, we describe the effects of an anisotropic substrate on the alignment of a nematic liquid crystal. We examine how the substrate affects the alignment of a nematic liquid crystal by Monte Carlo simulation. The liquid crystal on a substrate was described by the phase separation of liquid crystal molecules and substrate molecules, both of which were modeled by hard particles. We used hard rods to represent both the liquid crystal and the substrate. The length of the hard rods representing the substrate was adjusted to represent the degree of substrate anisotropy. The results show that the nematic alignment could either be reinforced or weakened, depending on the length of the substrate rods. Mean field theory is used to analyze the simulation results. We confirmed that the distance over which the substrate affects the bulk liquid crystal is about 3 nm for the present hard-rod-based model.

  20. Impact of diffusion limited aggregates of impurities on nematic ordering

    Science.gov (United States)

    Harkai, S.; Ambrožič, M.; Kralj, S.

    2017-02-01

    We study the impact of random bond-type disorder on two-dimensional (2D) orientational ordering of nematic liquid crystal (LC) configurations. The lattice Lebwohl-Lasher pseudospin model is used to model orientational ordering perturbed by frozen-in rod-like impurities of concentration p exhibiting the isotropic orientational probability distribution. The impurities are either (i) randomly spatially distributed or (ii) form diffusion limited aggregation (DLA)-type patterns characterized by the fractal dimensions df, where we consider cases df ∼ 1.7 and df ∼ 1.9. The degree of orientational ordering is quantified in terms of the orientational pair correlation function G(r) . Simulations reveal that the DLA pattern imposed disorder has a significantly weaker impact for a given concentration of impurities. Furthermore, if samples are quenched from the isotropic LC phase, then the fractal dimension is relatively strongly imprinted on quantitative characteristics of G(r) .

  1. Comparative Optical Separation of Racemic Ibuprofen by Using Chiral Stationary Phase%运用手性固定相研究外消旋布洛芬的光学分离

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Ibuprofen is widely used as a non-steroidal anti-inflammatory drug and produced as racemic mixture. Its pharmacological activity resides only in S-(+)-enantiomer, and R-(-)-enantiomer is not only inactive but also has many side effects. Thus it is necessary to separate Renanfiomer from racemic ibuprofen. We studied optical separation of racemic Ibuprofen with chiral high performance liquid chromatography (HPLC). Out of three different chiral stationary phases, which were selected on the basis of structure and availability, two were found to be effective. There was optimum eluent composition for each stationary phase for good resolution in optical separation. Resolution decreased with increase of eluent flow rate, but effect of injection volume on resolution was insignificant at high eluent flow rate.

  2. Thermal diode made by nematic liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Djair, E-mail: djfmelo@gmail.com [Instituto de Física, Universidade Federal de Alagoas, Av. Lourival Melo Mota, s/n, 57072-900 Maceió, AL (Brazil); Fernandes, Ivna [Instituto de Física, Universidade Federal de Alagoas, Av. Lourival Melo Mota, s/n, 57072-900 Maceió, AL (Brazil); Moraes, Fernando [Departamento de Física, CCEN, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900, João Pessoa, PB (Brazil); Departamento de Física, Universidade Federal Rural de Pernambuco, 52171-900 Recife, PE (Brazil); Fumeron, Sébastien [Institut Jean Lamour, Université de Lorraine, BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre les Nancy (France); Pereira, Erms [Escola Politécnica de Pernambuco, Universidade de Pernambuco, Rua Benfíca, 455, Madalena, 50720-001 Recife, PE (Brazil)

    2016-09-07

    This work investigates how a thermal diode can be designed from a nematic liquid crystal confined inside a cylindrical capillary. In the case of homeotropic anchoring, a defect structure called escaped radial disclination arises. The asymmetry of such structure causes thermal rectification rates up to 3.5% at room temperature, comparable to thermal diodes made from carbon nanotubes. Sensitivity of the system with respect to the heat power supply, the geometry of the capillary tube and the molecular anchoring angle is also discussed. - Highlights: • An escaped radial disclination as a thermal diode made by a nematic liquid crystal. • Rectifying effects comparable to those caused by carbon and boron nitride nanotubes. • Thermal rectification increasing with radius and decreasing with height of the tube. • Asymmetric BCs cause rectification from the spatial asymmetry produced by the escape. • Symmetric BCs provide rectifications smaller than those yields by asymmetric BCs.

  3. Electrically controlled dispersion in a nematic cell

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza, Carlos I. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-360, 04510 Mexico, D.F. (Mexico)]. E-mail: cmendoza@iim.unam.mx; Olivares, J.A. [Centro de Investigacion en Polimeros, COMEX, Blvd. M. Avila Camacho 138, PH1 y 2, Lomas de Chapultepec 11560, Mexico, D.F. (Mexico); Reyes, J.A. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 20-364, 01000 Mexico, D.F. (Mexico)

    2007-01-01

    In this work, we show theoretically how the trajectories of a propagating optical beam traveling in a planar-homeotropic hybrid nematic crystal cell depend on the wavelength of the optical beam. We apply a uniform electric field perpendicular to the cell to modify these trajectories. The influence of both, the electric field intensity and the refraction index dependence on the wavelength, give rise to an electrically tuned dispersion that may be useful for practical applications.

  4. On Some Elastic Instabilities in Biaxial Nematics

    OpenAIRE

    Sukumaran, Sreejith; G. Ranganath

    1997-01-01

    Within the framework of the continuum elastic theory of biaxial nematic liquid crystals, we have addressed ourselves to the structure, stability and energetics of some singular and non–singular topological defects, and certain director configurations. We find that certain non–singular hybrid disclinations could be energetically favourable relative to certain half–strength disclinations. The interaction between singular hybrids depends strongly on the biaxial elastic anisotropy. We suggest pos...

  5. a Study of Molecular Order and Motion in Nematic Liquid Crystal Mixtures.

    Science.gov (United States)

    Goetz, Jon Michael

    Materials which flow like fluids, but possess anisotropic properties like molecular crystals, are called 'liquid crystals'. Studies of liquid crystals contribute to our understanding of how molecular orientation influences macroscopic properties. This thesis presents experimental and theoretical investigations of molecular order and dynamics in nematic liquid crystal systems. First, deuterium nuclear magnetic resonance is used to determine the degree of orientational order of both components of a liquid crystal mixture simultaneously. The temperature dependence of the four order parameters is interpreted using a newly developed mean field theory of nematic binary mixtures composed of biaxial molecules. Next, mean field theory is applied to predict the phase behavior of arbitrarily shaped nematogens. For single component liquid crystals, the four order parameters needed to quantify orientational order of biaxial molecules in a biaxial nematic phase are calculated as a function of temperature for both rod-like and plate-like liquid crystals. For binary mixtures, temperature-concentration phase diagrams for a variety of molecular shapes are calculated. These theoretical predictions suggest that binary mixtures of highly asymmetric molecules with opposite shape anisotrophies may display stable biaxial nematic phases. Last, deuterium nuclear magnetic spin relaxation rates are measured as a function of temperature to investigate the molecular motion of a liquid crystal and a liquid crystal binary mixture. These experimental results are interpreted using an anisotropic viscosity model of molecular reorientation. The temperature dependence of the correlation times for the molecular motions is examined and discussed. It is demonstrated that mixing probe molecules into a liquid crystal has a profound effect on the molecular motion of the liquid crystal.

  6. 用液晶与聚合物混合材料的各向异性相分离制备快速响应液晶盒%Fast Switching Nematic Liquid Crystal Cell Fabricated by Anisotropic Phase-separation From a Liquid Crystal and Polymer Composite Material

    Institute of Scientific and Technical Information of China (English)

    王庆兵

    2004-01-01

    展示一种新型含有超薄液晶层( 小于1 μm) 的快速响应液晶盒, 总的响应时间( τon+τoff) 可以达到1.3 ms.这种液晶器件可以通过对一种液晶和聚合物混合材料的各向异性相分离制备获得. 偏光显微镜和扫描电子显微镜的观测结果确认了一种液晶/聚合物的双层膜机构的形成. 实验结果表明液晶层的厚度可以简单地通过改变液晶在混合材料中的含量来精确调节.这种制备方法可以用来制作含有超薄液晶层的快速显示液晶器件用于视频显示方面的应用.%It is demonstrated that a nematic liquid crystal (LC) cell containing a very thin (《1 μm) LC film can perform very fast switching, with a total response time as fast as 1.3 ms. Such type of LC devices can be prepared by a photo-induced anisotropic phase-separation from a nematic LC and polymer composite material. The formation of the LC/polymer bi-layer structure in the cell after the anisotropic phase-separation was confirmed by employing polarized light microscope and scanning electron microscope. It is also found that LC layer thickness can be fine tuned by adjusting the LC concentration in the composite mixture. Such a technique can be used to fabricate LC devices containing very thin LC film and performing fast switching for TV and Video applications where fast response time is required.

  7. Chiral spiral induced by a strong magnetic field

    CERN Document Server

    Abuki, H

    2016-01-01

    We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it totally washes the tricritical point out of the phase diagram, bringing the continent for the chiral spiral. This is the case no matter how small is the intensity of the magnetic field. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.

  8. Comparison of polarimetry and crown ether-based HPLC chiral stationary phase method to determine (L)-amino acid optical purity.

    Science.gov (United States)

    Lee, Mee Sung; Khan, F Nawaz; Shin, Sung Chul; Jeong, Euh Duck; Kim, Hae Gyeong; Kim, Mi Jin; Cho, Yoon Jae; Cha, Jae-Young; Hyun, Myung Ho; Jin, Jong Sung

    2012-11-15

    Although various pharmacopoeias provide titration methods to assay (L)-amino acid content, none of these methods distinguish between (L)- and (D)-amino acids and do not consider the presence of enantiomeric impurities. Consequently, these methods are limited in scope to describe the relationship between content and specific rotation, [α]. In this study, the US Pharmacopoeia method was compared with the crown ether-based high performance liquid chromatographic (HPLC) chiral stationary phase (CSP) method to determine (L)-amino acid content and specific rotation. The (L)-amino acid content specified by the US Pharmacopoeia method was not consistent with the specific rotation in the presence of enantiomeric impurities, whereas the HPLC-CSP method was very effective for determining the (L)-amino acid content and the optical purity. The other advantage is that the HPLC-CSP method requires amino acid samples of quite low concentration (as low as 1 μg/mL), whereas the pharmacopoeia method requires higher concentrations (20-110 mg/mL).

  9. Development of a Validated LC Method for Separation of Process-Related Impurities Including the R-Enantiomer of S-Pramipexole on Polysaccharide Chiral Stationary Phases.

    Science.gov (United States)

    Ramisetti, Nageswara Rao; Kuntamukkala, Ramakrishna; Arnipalli, Manikanta Swamy

    2015-07-01

    Despite the availability of a few methods for individual separation of S-pramipexole from its process-related impurities, no common liquid chromatography (LC) method is reported so far in the literature. The present article describes the development of a single-run LC method for simultaneous determination of S-pramipexole and its enantiomeric and process-related impurities on a Chiralpak AD-H (150 x 4.6 mm, 5μm) column using n-hexane/ethanol/n-butylamine (75:25:0.1 v/v/v) as a mobile phase in an isocratic mode of elution at a flow rate of 1.2 ml/min at 30°C. The chromatographic eluents were monitored at a wavelength of 260 nm using a photodiode array detector. Excellent enantioseparation with good resolutions (Rs ≥ 2.88) and peak shapes (As ≤ 1.21) for all analytes was achieved. The proposed method was validated according to International Conference Harmonization (ICH) guidelines in terms of accuracy, precision, sensitivity, and linearity. Limits of quantification of impurities (0.25-0.55 μg/ml) indicate the highest sensitivity achievable by the proposed method. The method has an advantage of selectivity and suitability for routine determination of not only chiral impurity but also all possible related substances in active pharmaceutical ingredients of S-pramipexole.

  10. Chiral Thirring–Wess model

    Energy Technology Data Exchange (ETDEWEB)

    Rahaman, Anisur, E-mail: anisur.rahman@saha.ac.in

    2015-10-15

    The vector type of interaction of the Thirring–Wess model was replaced by the chiral type and a new model was presented which was termed as chiral Thirring–Wess model in Rahaman (2015). The model was studied there with a Faddeevian class of regularization. Few ambiguity parameters were allowed there with the apprehension that unitarity might be threatened like the chiral generation of the Schwinger model. In the present work it has been shown that no counter term containing the regularization ambiguity is needed for this model to be physically sensible. So the chiral Thirring–Wess model is studied here without the presence of any ambiguity parameter and it has been found that the model not only remains exactly solvable but also does not lose the unitarity like the chiral generation of the Schwinger model. The phase space structure and the theoretical spectrum of this new model have been determined in the present scenario. The theoretical spectrum is found to contain a massive boson with ambiguity free mass and a massless boson.

  11. A charge transfer complex nematic liquid crystalline gel with high electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Bhargavi, R.; Nair, Geetha G., E-mail: geeraj88@gmail.com, E-mail: skpras@gmail.com; Krishna Prasad, S., E-mail: geeraj88@gmail.com, E-mail: skpras@gmail.com [Centre for Nano and Soft Matter Sciences, Jalahalli, Bangalore 560013 (India); Majumdar, R.; Bag, Braja G. [Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore (W) 721 102 (India)

    2014-10-21

    We describe the rheological, dielectric and elastic properties of a nematic liquid crystal gel created using an anthrylidene derivative of arjunolic acid, a chiral triterpenoid, obtained from the extracts of the wood of Terminalia arjuna. In this novel gel, having the electron-donor and acceptor components as minority constituents, the gelation and strengthening of charge-transfer complex (CTC) formation are seen to be occurring concomitantly. In addition to being mechanically strong with a large storage modulus, the gel with the maximized CTC exhibits Frank bend elastic constant values that approach nanonewton levels. The highlight of the study is the observation of 4–5 orders of magnitude increase in electrical conductivity for this gel, a value that is higher than even in the CT complexes of 2-d ordered columnar structures. A further important advantage of the present system over the columnar complex is that the high conductivity is seen for ac probing also, and owing to the nematic nature can be switched between its anisotropic limits. Some of these features are ascribed to a specific molecular packing architecture, which reduces the trapping of the charge carriers.

  12. Shear viscosity at the Ising-nematic quantum critical point in two dimensional metals

    CERN Document Server

    Patel, Aavishkar A; Sachdev, Subir

    2016-01-01

    In a strongly interacting quantum liquid without quasiparticles, general scaling arguments imply that the dimensionless ratio $(k_B /\\hbar)\\, \\eta/s$, where $\\eta$ is the shear viscosity and $s$ is the entropy density, is a universal number. We compute the shear viscosity of the Ising-nematic critical point of metals in spatial dimension $d=2$ by an expansion below $d=5/2$. The anisotropy associated with directions parallel and normal to the Fermi surface leads to a violation of the scaling expectations: $\\eta$ scales in the same manner as a chiral conductivity, and the ratio $\\eta/s$ diverges as $T^{-2/z}$, where $z$ is the dynamic critical exponent for fermionic excitations dispersing normal to the Fermi surface.

  13. Chiral mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Plum, Eric, E-mail: erp@orc.soton.ac.uk [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Zheludev, Nikolay I., E-mail: niz@orc.soton.ac.uk [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637378 (Singapore)

    2015-06-01

    Mirrors are used in telescopes, microscopes, photo cameras, lasers, satellite dishes, and everywhere else, where redirection of electromagnetic radiation is required making them arguably the most important optical component. While conventional isotropic mirrors will reflect linear polarizations without change, the handedness of circularly polarized waves is reversed upon reflection. Here, we demonstrate a type of mirror reflecting one circular polarization without changing its handedness, while absorbing the other. The polarization-preserving mirror consists of a planar metasurface with a subwavelength pattern that cannot be superimposed with its mirror image without being lifted out of its plane, and a conventional mirror spaced by a fraction of the wavelength from the metasurface. Such mirrors enable circularly polarized lasers and Fabry-Pérot cavities with enhanced tunability, gyroscopic applications, polarization-sensitive detectors of electromagnetic waves, and can be used to enhance spectroscopies of chiral media.

  14. Molecular chirality at surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, Karl-Heinz [Empa, Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf (Switzerland); Organic Chemistry Institute, University Zurich, 8057 Zuerich (Switzerland)

    2012-11-15

    With the adsorption of larger molecules being increasingly tackled by surface scientists, the aspect of chirality often plays a role. This paper gives a topical review of molecular chirality at surfaces and gives a phenomenological overview of different aspects of adsorption and self-assembly of chiral and prochiral molecules and the principles of mirror-symmetry breaking at a surface. After a brief introduction into the history of molecular chirality and the important role it played for understanding the spatial structure of molecules, definitions of chirality are presented. Topics treated here are principle ways to create single chiral adsorbates, chiral ensembles, and monolayers by achiral molecules, adsorption of intrinsically chiral molecules at achiral and chiral surfaces, long-range symmetry breaking in two-dimensional (2D) crystals due to additional chiral bias, chiral restructuring of solid surfaces under the influence of chiral molecules, switching the handedness of adsorbates, and chirality at the liquid/air interface. An outlook onto further potential research directions and recommendations for further reading, including nonsurface-related sources of chiral topics completes this paper. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Dynamic wetting model for the isotropic-to-nematic transition over a flat substrate.

    Science.gov (United States)

    Rey, Alejandro D; Herrera-Valencia, E E

    2014-03-14

    Phase ordering over solid substrates is a ubiquitous and important soft material transformation process whose description incorporates wetting, anchoring and phase transition kinetics. In this paper the kinetics of the isotropic-to-nematic isothermal phase transition over a flat solid surface in a growing spherical drop is analyzed based on the Landau-de Gennes Q-tensor order parameter equations. The model, based on a previously derived interface force balance and a newly derived contact line force balance, is shown to be consistent with the generic model of conservative interface and contact line motions. The advancing dynamic contact angle equation is extracted from kinematic compatibility between the moving isotropic-nematic interface and contact line. A tractable surface phase transition kinetic model obtained by focusing on the dominant phase transition and wetting driving forces yields: (i) the constant advancing dynamic contact angle θ, and (ii) the contact line speed as a function of undercooling ΔT. It is shown that as undercooling increases, the surface phase transition mode approaches the bulk phase transition mode, such that θ approaches π. The elastic and wetting parameters that control the phase transformation process are identified and experiments for their determination are defined. These dynamic wetting and surface phase transition results significantly expand existing characterization methods of LC-substrate interfaces based on static phase transition droplet methods.

  16. Colloidal Surfaces with Boundaries, Apex Boojums, and Nested Elastic Self-Assembly of Nematic Colloids

    Science.gov (United States)

    Park, Sungoh; Liu, Qingkun; Smalyukh, Ivan I.

    2016-12-01

    Self-assembly of colloidal particles is poised to become a powerful composite material fabrication technique, but remains challenged by a limited control over the ensuing structures. We develop a new breed of nematic colloids that are physical analogs of a mathematical surface with boundary, interacting with the molecular alignment field without inducing defects when flat. However, made from a thin nanofoil, they can be shaped to prompt formation of self-compensating defects that drive preprogramed elastic interactions mediated by the nematic host. To show this, we wrap the nanofoil on all triangular side faces of a pyramid, except its square base. The ensuing pyramidal cones induce point defects with fractional hedgehog charges of opposite signs, spontaneously align with respect to the far-field director to form elastic dipoles and nested assemblies with tunable spacing. Nanofoils shaped into octahedrons interact as elastic quadrupoles. Our findings may drive realization of low-symmetry colloidal phases.

  17. Nematic-field-driven positioning of particles in liquid crystal droplets.

    Science.gov (United States)

    Whitmer, Jonathan K; Wang, Xiaoguang; Mondiot, Frederic; Miller, Daniel S; Abbott, Nicholas L; de Pablo, Juan J

    2013-11-27

    Common nematic oils, such as 5CB, experience planar anchoring at aqueous interfaces. When these oils are emulsified, this anchoring preference and the resulting topological constraints lead to the formation of droplets that exhibit one or two point defects within the nematic phase. Here, we explore the interactions of adsorbed particles at the aqueous interface through a combination of experiments and coarse-grained modeling, and demonstrate that surface-active particles, driven by elastic forces in the droplet, readily localize to these defect regions in a programmable manner. When droplets include two nanoparticles, these preferentially segregate to the two poles, thereby forming highly regular dipolar structures that could serve for hierarchical assembly of functional structures. Addition of sufficient concentrations of surfactant changes the interior morphology of the droplet, but pins defects to the interface, resulting in aggregation of the two particles.

  18. Director tumbling of nematic wormlike micelles under shear: time-resolved rheo-NMR experiments

    Energy Technology Data Exchange (ETDEWEB)

    Sinyavsky, N. [Dept. of Physics, Baltic State Academy, Kaliningrad (Russian Federation); Quijada-Garrido, I. [Inst. de Ciencia y Tecnologia de Polimeros, Consejo Superior de Investigaciones Cientificas, Madrid (Spain); Schmidt, C. [Dept. Chemie, Univ. Paderborn (Germany)

    2007-07-01

    Nematic liquid crystals show a complex flow behavior due to the coupling between orientation and flow. Some materials show a stable director orientation in steady shear flow (flow aligning), while for others no stable director orientation exists (tumbling). Director tumbling gives rise to oscillations of shear and normal stresses in rheological experiments and can be detected by optical methods, for example by microscopy or birefringence measurements. We have used deuterium NMR spectroscopy to observe shear-induced director orientations. In the lyotropic system cetylpyridinium chloride/hexanol/brine, which forms a nematic phase of wormlike micelles, time-resolved observations of the director orientation by means of deuterium NMR spectroscopy of D{sub 2}O have been possible for the first time. The time-dependence of the director orientations in both shear start-up and flow-reversal experiments will be presented. (orig.)

  19. ARTICLES: Orientation in Nematic Liquid Crystals Doped with Orange Dyes and Effect of Carbon Nanoparticles

    Science.gov (United States)

    Alicilar, Ahmet; Akkurt, Fatih; Kaya, Nihan

    2010-06-01

    Some properties of nematic liquid crystal E7 doped with two disperse orange dyes used together and effect of addition of carbon nanoparticles (single walled carbon nanotube or fullerene C60) on them were studied. Two dyes (disperse orange 11 and 13) having high solubility and order parameter were used as co-dopants. A notable increase in order parameter was obtained comparing to that of liquid crystal doped with single dye. When carbon nanoparticles were used as dopant, a decrease in order parameter was observed at low temperatures while it increased at high temperatures. When applied voltage changed, the order parameter abruptly increased in its threshold value and saturated in higher voltages as expected. An appreciable change in textures was not observed with addition of dopants. This addition gave rise to an increase in nematic-isotropic phase transition temperatures compared with that of pure liquid crystal.

  20. Nematic-Field Driven Positioning of Particles in Liquid Crystal Droplets

    Science.gov (United States)

    Whitmer, Jonathan K.; Wang, Xiaoguang; Mondiot, Frederic; Miller, Daniel S.; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-01-01

    Common nematic oils, such as 5CB, experience planar anchoring at aqueous interfaces. When these oils are emulsified, this anchoring preference and the resulting topological constraints lead to formation of droplets that exhibit one or two point defects within the nematic phase. Here, we explore the interactions of adsorbed particles at the aqueous interface through a combination of experiments and coarse-grained modeling, and demonstrate that surface-active particles, driven by elastic forces in the droplet, readily localize to these defect regions in a programmable manner. When droplets include two nanoparticles, these preferentially segregate to the two poles, thereby forming highly regular dipolar structures that could serve for hierarchical assembly of functional structures. Addition of sufficient concentrations of surfactant changes the interior morphology of the droplet, but pins defects to the interface, resulting in aggregation of the two particles. PMID:24329470

  1. Chiral resolution of derivatized amino acids using uniformly sized molecularly imprinted polymers in hydro-organic mobile phases.

    Science.gov (United States)

    Haginaka, Jun; Kagawa, Chino

    2004-04-01

    Uniformly sized molecularly imprinted polymers (MIPs) for Boc-L-Trp were prepared using ethylene glycol dimethacrylate (EDMA) as the cross-linker, and methacylic acid (MAA) and/or 4-vinylpyridine (4-VPY) as the functional monomers or without use of a functional monomer. The MIPs prepared were evaluated using acetonitrile or a mixture of phosphate buffer and acetonitrile as the mobile phase. The Boc-L-Trp-imprinted EDMA polymers can recognize Boc-L-Trp by its molecular shape, and can thus afford the enantioseparation of Boc-Trp. Besides the molecular shape recognition, the hydrophobic interactions with the polymer backbones as well as the hydrogen-bonding interactions of Boc-L-Trp with carboxyl and pyridyl groups in the polymers should work for the retention and recognition of Boc-L-Trp on the imprinted MAA- co-EDMA and 4-VPY- co-EDMA polymers, respectively, in the hydro-organic mobile phase. The hydrogen-bonding interactions seem to become dominant when only acetonitrile is used as the mobile phase. The Boc-L-Trp-imprinted 4-VPY- co-EDMA polymers gave the highest retentivity and enantioselectivity for Boc-Trp among the MIPs prepared. However, the simultaneous use of MAA and 4-VPY was not effective for the enantioseparation of Boc-Trp in a hydro-organic mobile phase. Furthermore, the baseline separation of Boc-Trp enantiomers was attained within 10 min on the Boc-L-Trp-imprinted 4-VPY- co-EDMA polymers under the optimized HPLC conditions.

  2. Anion effect on the binary and ternary phase diagrams of chiral medetomidine salts and conglomerate crystal formation.

    Science.gov (United States)

    Choobdari, Ebrahim; Fakhraian, Hossein; Peyrovi, Mohammad Hassan

    2014-03-01

    The binary phase diagrams of hydrogen halides salts of medetomidine (Med.HX, X:Br,I) and hydrogen oxalate salt of medetomidine (Med.Ox) were determined based on thermogravimetric/differential thermal analysis (TGA/DTA) and their crystal structure behavior was confirmed by comparison of the X-ray diffractometry and FT-IR spectroscopy of the racemate and pure enantiomer. All hydrogen halide salts presented racemic compound behavior. Heat of fusion of halides salt of (rac)-medetomidine decreased with ionic radius increase. Eutectic points for Med.HCl (previously reported), Med.HBr, and Med.HI rest were unchanged approximately. The solubility of different enantiomeric mixtures of Med.HBr and Med.HI were measured at 10, 20, and 30°C in 2-propanol showing a solubility increase with ionic radius. A binary phase diagram of Med.Ox shows a racemic conglomerate behavior. The solubility of enantiomeric mixtures of Med.Ox were measured at 10, 20, 30, and 40°C. The ternary phase diagram of Med.Ox in ethanol conforms to a conglomerate crystal forming system, favoring its enantiomeric purification by preferential crystallization.

  3. Nuclear chiral dynamics and thermodynamics

    Science.gov (United States)

    Holt, Jeremy W.; Kaiser, Norbert; Weise, Wolfram

    2013-11-01

    This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic description of both isospin-symmetric nuclear matter and neutron matter, with emphasis on the isospin-dependence determined by the underlying chiral NN interaction. The importance of three-body forces is emphasized, and the role of explicit Δ(1232)-isobar degrees of freedom is investigated in detail. Nuclear chiral thermodynamics is developed and a calculation of the nuclear phase diagram is performed. This includes a successful description of the first-order phase transition from a nuclear Fermi liquid to an interacting Fermi gas and the coexistence of these phases below a critical temperature Tc. Density functional methods for finite nuclei based on this approach are also discussed. Effective interactions, their density dependence and connections to Landau Fermi liquid theory are outlined. Finally, the density and temperature dependences of the chiral (quark) condensate are investigated.

  4. 新型键合纤维素手性固定相的制备及其拆分性能评价%Preparation of a new immobilized cellulose-based chiral stationary phase and its enantioseparation behaviors

    Institute of Scientific and Technical Information of China (English)

    涂鸿盛; 范军; 谭艺; 林纯; 华江颖; 章伟光

    2014-01-01

    The immobilized polysaccharide-based chiral stationary phase has attracted consid-erable attention over the past decades due to its high chemical stability,good solvent resist-ance,great enantioseparation ability,etc. In this study,a new immobilized cellulose chiral sta-tionary phase(denoted as ImCel)was prepared through the Staudinger reaction of 6-azido-6-deoxy-cellulose-3,5-dichlorophenylcarbamate and aminopropyl silica gel. The enantioseparation performance of the Imcellfor 20 pairs of chiral analytes and the effect of non-standard solvents have been investigated by high performance liquid chromatography. Baseline separations of 17 pairs of enantiomers were achieved on the ImCel. The separation ability of the Imcellin the nor-mal mode was much better than in reversed mode. In addition,the Imcellshowed good chemi-cal stability in the non-standard mobile phase due to the covalent bonds between the cellulose chiral selectors and silica support. Moreover,it exhibited complementarity with another immo-bilized-cellulose chiral stationary phase containing 3,5-dimethylphenylcarbamate groups for the separation of a series of 9-fluorenylmethyloxycarbonyl ( fmoc )-derived amino acids. The reversal of enantiomer elution order induced by the difference of the substituents in chiral sta-tionary phase was observed under the same chromatographic conditions. In brief,a new immo-bilized cellulose chiral stationary phase with high stability and good separation performance was developed in this work.%键合型多糖手性固定相因具有化学稳定性高和溶剂耐受性好的特点而受到研究者的极大关注。采用施陶丁格( Staudinger)反应将6-叠氮-6-脱氧纤维素-3,5-二氯苯基氨基甲酸酯键合到氨丙基硅胶上得到一种新的键合型手性固定相( ImCel),研究了其手性分离性能,并探讨了非常规流动相(如氯仿、四氢呋喃等)的影响。结果表明,在20对手性化合物中,17对在合适的流动

  5. The importance of screening solid-state phases of a racemic modification of a chiral drug: thermodynamic and structural characterization of solid-state phases of etiracetam.

    Science.gov (United States)

    Herman, Christelle; Vermylen, Valérie; Norberg, Bernadette; Wouters, Johan; Leyssens, Tom

    2013-08-01

    In this contribution different solid-state forms of the racemic compound (RS)-2-(2-oxo-pyrrolidin-1yl)-butyramide are studied from a structural and thermal point of view. Three different solid-state phases were identified, including two polymorphs and one hydrate phase. Comparison is made with the structure of the (S)-enantiomer, for which only one solid-state phase is known. The basic structural motif found in both polymorphs of the racemic compound is similar, but the basic motif observed for the hydrate differs. These synthons could in principle be used in future polymorph prediction studies to screen for possible alternative forms of the enantiopure compound. Based on the structure of the hydrate, further efforts should therefore be made in order to identify a hydrate structure of the enantiopure compound. Studying the different phases of a racemic compound can therefore help to guide polymorphic screening of an enantiopure compound.

  6. Chiral THz metamaterial with tunable optical activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jiangfeng [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; O' Hara, John [Los Alamos National Laboratory; Chowdhury, Roy [Los Alamos National Laboratory; Zhao, Rongkuo [IOWA STATE UNIV; Soukoullis, Costas M [IOWA STATE UNIV

    2010-01-01

    Optical activity in chiral metamaterials is demonstrated in simulation and shows actively tunable giant polarization rotation at THz frequencies. Electric current distributions show that pure chirality is achieved by our bi-Iayer chiral metamaterial design. The chirality can be optically controlled by illumination with near-infrared light. Optical activity, occurring in chiral materials such as DNA, sugar and many other bio-molecules, is a phenomenon of great importance to many areas of science including molecular biology, analytical chemistry, optoelectronics and display applications. This phenomenon is well understood at an effective medium level as a magnetic/electric moment excited by the electric/magnetic field of the incident electromagnetic (EM) wave. Usually, natural chiral materials exhibit very weak optical activity e.g. a gyrotropic quartz crystal. The optical activity of chiral metamaterials, however, can be five orders of magnitude stronger. Chiral metamaterials are made of sub-wavelength resonators lacking symmetry planes. The asymmetry allows magnetic moments to be excited by the electric field of the incident EM wave and vice versa. Recently, chiral metamaterials have been demonstrated and lead to prospects in giant optical activity, circular dichroism, negative refraction and reversing the Casmir force. These fascinating optical properties require strong chirality, which may be designed through the microscopic structure of chiral metamaterials. However, these metamaterials have a fixed response function, defined by the geometric structuring, which limits their ability to manipulate EM waves. Active metamaterials realize dynamic control of response functions and have produced many influential applications such as ultra-fast switching devices, frequency and phase modulation and memory devices. Introducing active designs to chiral metamaterials will give additional freedom in controlling the optical activity, and therefore enable dynamic manipulation

  7. Carbon Nanoparticles in Nematic Liquid Crystals

    Institute of Scientific and Technical Information of China (English)

    S.Eren San; Mustafa Okutan; O(g)uz K(o)ysal; Yusuf Yer-li

    2008-01-01

    Fullerene G60,C70,single-walled and multi-walled carbon nanotubes and graphene sheets are doped to nematic liquid crystal(LC)host in the same percentage.Planar samples of these mixtures are prepared and our measurements constitute an optimization basis for possible applications.Fullerene balls are found to be the best compatible material for optical aims and reorientation of LC molecules,while the carbon nanotubes experience some reorientation possibility in LC media and graphene layers are good barriers to preserve reorientation.

  8. Thermal diode made by nematic liquid crystal

    Science.gov (United States)

    Melo, Djair; Fernandes, Ivna; Moraes, Fernando; Fumeron, Sébastien; Pereira, Erms

    2016-09-01

    This work investigates how a thermal diode can be designed from a nematic liquid crystal confined inside a cylindrical capillary. In the case of homeotropic anchoring, a defect structure called escaped radial disclination arises. The asymmetry of such structure causes thermal rectification rates up to 3.5% at room temperature, comparable to thermal diodes made from carbon nanotubes. Sensitivity of the system with respect to the heat power supply, the geometry of the capillary tube and the molecular anchoring angle is also discussed.

  9. 冠醚固定相的制备及手性拆分%Crown ether stationary phase for chiral separation

    Institute of Scientific and Technical Information of China (English)

    伍鹏; 汤波; 路振宇; 孔娇; 袁黎明

    2015-01-01

    以 R‐联萘酚为原料合成了 R‐(1,1′‐二萘基)‐20‐冠‐6,并将其涂敷于 C18硅胶(平均粒径5μm ,孔径120 nm)上制成了可用于高效液相色谱手性拆分的 R‐(1,1′‐二萘基)‐20‐冠‐6冠醚固定相(CSP).在以 pH =2的高氯酸溶液为流动相,流速为0.1 mL ・min‐1,柱温为25℃的条件下,研究了 CSP 对9种α‐氨基酸对映体的拆分能力.实验结果表明,有5种手性氨基酸(缬氨酸、苯甘氨酸、对羟基苯甘氨酸、谷氨酸、色氨酸)得到不同程度的拆分,说明 CSP 能对手性氨基酸进行一定的拆分.%In this paper ,R‐(1 ,1′‐ binaphthyl)‐20‐crown‐6 was synthesized and coated on C18 silica gel ,which was used as the chiral stationary phase with pH = 2 perchloric acid solution as mobile phase in high performance liquid chromatography .Five α‐amino acid enantiomers (valine ,phenylglycine ,hydroxyphenylglycine ,glutamate and tryptophan) had been separated . The results showed that the R‐(1 ,1′‐ binaphthyl)‐20‐crown‐6 crown ether stationary phase (CSP) possesses a good enantioselectivity for α‐ amino acid enantiomers .

  10. Online capillary solid-phase microextraction coupled liquid chromatography-mass spectrometry for analysis of chiral secondary alcohol products in yeast catalyzed stereoselective reduction cell culture.

    Science.gov (United States)

    Cheng, Cheanyeh; Nian, Yu-Chuan

    2015-02-06

    An online solid-phase microextraction coupled liquid chromatography-electrospray ionization-ion trap mass spectrometry was developed for the analysis of trace R- and S-4-phenyl-2-butanol (R- and S-pbol) in salt rich cell culture of Saccharomyces cerevisiae catalyzed stereoselective reduction of 4-pheny-2-butanone (pbone). A Supel-Q PLOT capillary column was used for the extraction and deionized distilled water was used as the extraction mobile phase. The extraction flow rate and extraction time were at 0.1 mL min(-1) and 0.95 min, respectively. The three target analytes, pbone, R-pbol, and S-4-pbol, were desorbed and eluted by the mobile phase of water/methanol/isopropanol (55/25/20, v/v/v) with a flow rate of 0.5 mL min(-1) and analyzed by a chiral column. The mass spectrometric detection of the three target analytes was in positive ion mode with the signal [M+Na](+). The matrix-matched external standard calibration curves with linear concentration range between 0 and 50 μg mL(-1) were used for quantitative analysis. The linear regression correlation coefficients (r(2)) of the standard calibration curves were between 0.9950 and 0.9961. The yeast mediated reduction was performed with a recation culture of yeast incubation culture/glycerol (70/30, v/v) for 4 days. This biotransformation possessed 82.3% yield and 92.9% S-enantomeric excess. The limit of detection (LOD)/limit of quantification (LOQ) for pbone, R-pbol, and S-pbol was 0.02/0.067, 0.01/0.033, and 0.01/0.033 μg mL(-1), respectively. The intra-day and inter-day precisions from repeated measurements were 10.8-21.1% and 11.6-18.7%, respectively. The analysis accuracy from spike recovery was 84-91%.

  11. Enhancing and reducing chirality by opposite circularly-polarized light irradiation on crystalline chiral domains consisting of nonchiral photoresponsive W-shaped liquid crystal molecules.

    Science.gov (United States)

    Choi, Suk-Won; Takezoe, Hideo

    2016-09-28

    We found possible chirality enhancement and reduction in chiral domains formed by photoresponsive W-shaped molecules by irradiation with circularly polarized light (CPL). The W-shaped molecules exhibit a unique smectic phase with spontaneously segregated chiral domains, although the molecules are nonchiral. The chirality control was generated in the crystalline phase, which shows chiral segregation as in the upper smectic phase, and the result appeared to be as follows: for a certain chiral domain, right-CPL stimuli enhanced the chirality, while left-CPL stimuli reduced the chirality, and vice versa for another chiral domain. Interestingly, no domain-size change could be observed after CPL irradiation, suggesting some changes in the causes of chirality. In this way, the present system can recognize the handedness of the applied chiral stimuli. In other words, the present material can be used as a sensitive chiral-stimuli-recognizing material and should find invaluable applications, including in chiroptical switches, sensors, and memories as well as in chiral recognition.

  12. Straining soft colloids in aqueous nematic liquid crystals

    Science.gov (United States)

    Mushenheim, Peter C.; Pendery, Joel S.; Weibel, Douglas B.; Spagnolie, Saverio E.; Abbott, Nicholas L.

    2016-05-01

    Liquid crystals (LCs), because of their long-range molecular ordering, are anisotropic, elastic fluids. Herein, we report that elastic stresses imparted by nematic LCs can dynamically shape soft colloids and tune their physical properties. Specifically, we use giant unilamellar vesicles (GUVs) as soft colloids and explore the interplay of mechanical strain when the GUVs are confined within aqueous chromonic LC phases. Accompanying thermal quenching from isotropic to LC phases, we observe the elasticity of the LC phases to transform initially spherical GUVs (diameters of 2-50 µm) into two distinct populations of GUVs with spindle-like shapes and aspect ratios as large as 10. Large GUVs are strained to a small extent (R/r minor radii, respectively), consistent with an LC elasticity-induced expansion of lipid membrane surface area of up to 3% and conservation of the internal GUV volume. Small GUVs, in contrast, form highly elongated spindles (1.54 materials and suggest previously unidentified designs of LC-based responsive and reconfigurable materials.

  13. Synthesis of 1,4-Bis(phenylethynylbenzenes and Their Application as Blue Phase Liquid Crystal Composition

    Directory of Open Access Journals (Sweden)

    Ning Li

    2013-11-01

    Full Text Available A number of 1,4-bis(phenylethynylbenzene derivatives (BPEBs and their analogues with different numbers of side-substitute fluorine atoms on benzene rings, and alkyl chains, ethoxyl groups, fluorine atoms and trifluoromethyl groups as the end groups have been synthesized. The effects of the different substituents on their properties such as thermal behavior of melting point and clearing point, the temperature of nematic phase, optical anisotropy and dielectric anisotropy have been well investigated, and it has been found that some BPEBs have a wide range of the nematic phase temperature with high optical anisotropy (Δn and acceptable dielectric anisotropy (Δε, which have been applied as the crucial compositions to constitute a liquid crystal mixture having the properties of Δε = 29.0 and Δn = 0.283 at 25 °C. With the addition of the chiral dopant to the obtained liquid crystal mixture, blue phase liquid crystal with a blue phase temperature range of 8 °C has been achieved.

  14. Chiral imbalance in QCD

    Directory of Open Access Journals (Sweden)

    Andrianov Alexander

    2017-01-01

    Full Text Available The chiral imbalance (ChI is given by a difference between the numbers of RH and LH quarks which may occur in the fireball after heavy ion collision. To characterize it adiabatically a quark chiral (axial chemical potential must be introduced taking into account emergence of a ChI in such a phase. In this report the phenomenology of formation of Local spatial Parity Breaking (LPB in the hot and dense baryon matter is discussed and its simulation within a number of QCD-inspired models is outlined. The appearance of new states in the spectra of scalar, pseudoscalar and vector particles in such a matter is elucidated. In particular, from the effective vector meson theory in the presence of Chern-Simons interaction it is demonstrated that the spectrum of massive vector mesons splits into three polarization components with different effective masses. The asymmetry in production of longitudinally and transversely polarized states of ρ and ω mesons for various values of the dilepton invariant mass can serve as a characteristic indication of the LPB in PHENIX, STAR and ALICE experiments.

  15. Chirally extended quantum chromodynamics

    CERN Document Server

    Brower, R C; Tan, C I; Richard C Brower; Yue Shen; Chung-I Tan

    1994-01-01

    We propose an extended Quantum Chromodynamics (XQCD) Lagrangian in which the fermions are coupled to elementary scalar %\\sigma and \\pi fields through a Yukawa coupling which preserves chiral invariance. Our principle motivation is to find a new lattice formulation for QCD which avoids the source of critical slowing down usually encountered as the bare quark mass is tuned to the chiral limit. The phase diagram and the weak coupling limit for XQCD are studied. They suggest a conjecture that the continuum limit of XQCD is the same as the continuum limit of conventional lattice formulation of QCD. As examples of such universality, we present the large N solutions of two prototype models for XQCD, in which the mass of the spurious pion and sigma resonance go to infinity with the cut-off. Even if the universality conjecture turns out to be false, we believe that XQCD will still be useful as a low energy effective action for QCD phenomenology on the lattice. Numerical simulations are recommended to further investiga...

  16. Numerical determination of competitive adsorption isotherm of mandelic acid enantiomers on cellulose-based chiral stationary phase.

    Science.gov (United States)

    Zhang, Yan; Rohani, Sohrab; Ray, Ajay K

    2008-08-15

    The use of inverse method for the determination of competitive adsorption isotherm of mandelic acid enantiomers on cellulose tris(3,5-diethylphenyl carbamate) stationary phase is proposed in this work. Non-dominated sorting genetic algorithm with jumping genes (NSGA-II-JG) was applied to acquire the isotherm parameters by minimizing the sum of square deviations of the model predictions from the measured elution profiles. Three different competitive isotherm models, i.e., Langmuir, biLangmuir and Tóth, combined with transport-dispersive chromatographic model were used in predicting the elution profiles. Orthogonal collocation on finite element (OCFE) method was applied to obtain the calculated elution profiles. Results indicate that biLangmuir isotherm and Tóth isotherm give remarkably similar equilibrium isotherms within the investigated liquid concentration range. Band profiles calculated from both isotherm models are in good agreement with the experimental data. The validity of the determined parameters was verified by comparing the model predictions with experimental elution profiles at various experimental conditions.

  17. Effect of the residual silanol group protection on the liquid chromatographic resolution of racemic primary amino compounds on a chiral stationary phase based on optically active (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6.

    Science.gov (United States)

    Hyun, Myung Ho; Han, Sang Cheol; Choi, Hee Jung; Kang, Bu Sung; Ha, Hyun Ju

    2007-01-05

    A liquid chromatographic chiral stationary phase (CSP) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6, which has been utilized in the resolution of alpha-amino acids, amines and amino alcohols, was treated with excess of n-octyltriethoxysilane to prepare a new improved CSP. The residual silanol groups of the original CSP were protected by n-octyl groups in the new CSP. The chiral recognition ability of the new CSP was superior to that of the original CSP in the resolution of alpha-amino acids, amines and amino alcohols. Retention factors (k1) for the resolution of alpha-amino acids were lower on the new CSP than on the original CSP while those for the resolution of amines and amino alcohols were higher on the new CSP than on the original CSP. The improved chiral recognition ability of the new CSP and the retention behaviors of the two enantiomers on the new CSP have been rationalized to stem from the removal of the non-enantioselective interactions between the analytes and the residual silanol groups of the original CSP and the improved lipophilicity of the CSP.

  18. Robustness of the periodic and chaotic orientational behavior of tumbling nematic liquid crystals.

    Science.gov (United States)

    Heidenreich, Sebastian; Ilg, Patrick; Hess, Siegfried

    2006-06-01

    The dynamical behavior of molecular alignment strongly affects physical properties of nematic liquid crystals. A theoretical description can be made by a nonlinear relaxation equation of the order parameter and leads to the prediction that rather complex even chaotic orientational behavior occur. Here the influence of fluctuating shear rates on the orientational dynamics especially on chaotic solutions is discussed. With the help of phase portraits and time evolution diagrams, we investigated the influence of different fluctuation strengths on the flow aligned, isotropic, and periodic solutions. To explore the effect of fluctuations on the chaotic behavior, we calculated the largest Lyapunov exponent for different fluctuation strengths. We found in all cases that small fluctuations of the shear rate do not affect the basic features of the dynamics of tumbling nematics. Furthermore, we present an amended potential modeling the isotropic to nematic transition and discuss the equivalence and difference to the commonly used Landau-de Gennes potential. In contrast to the Landau-de Gennes potential, our potential has the advantage to restrict the order parameter to physically admissible values. In the case of extensional flow, we show that the amended potential leads for increasing extensional rate to a better agreement with experimental results.

  19. Lattice Statistical Models for the Nematic Transitions in Liquid-Crystalline Systems

    Science.gov (United States)

    Nascimento, E. S.; Vieira, A. P.; Salinas, S. R.

    2016-12-01

    We investigate the connections between some simple Maier-Saupe lattice models, with a discrete choice of orientations of the microscopic directors, and a recent proposal of a two-tensor formalism to describe the phase diagrams of nematic liquid-crystalline systems. This two-tensor proposal is used to formulate the statistical problem in terms of fully connected lattice Hamiltonians, with the local nematic directors restricted to the Cartesian axes. Depending on the choice of interaction parameters, we regain all of the main features of the original mean-field two-tensor calculations. With a standard choice of parameters, we obtain the well-known sequence of isotropic, uniaxial, and biaxial nematic structures, with a Landau multicritical point. With another suitably chosen set of parameters, we obtain two tricritical points, according to some recent predictions of the two-tensor calculations. The simple statistical lattice models are quite easy to work with, for all values of parameters, and the present calculations can be carried out beyond the mean-field level.

  20. Three-dimensional modeling of nematic liquid crystal micro-optics structures with complex patterned electrodes

    Science.gov (United States)

    Rong, Xing; Kang, Shengwu; Zhang, Xinyu; Ji, An; Xie, Changsheng; Zhang, Tianxu

    2012-11-01

    In this paper, a three-dimensional (3-D) relaxation method is used to model the dynamic response behavior of liquid crystal (LC) directors in LC micro-optics structures with complex patterned electrodes. The method is based on Frank- Oseen continuum elastic theory by using a vectorial representation. This method can deal with liquid crystal structures with arbitrary patterned electrodes, and it is quite computational stability. Different numerical results obtained according the method are as follows: (1) the nematic LC structures with complex patterned electrodes applied by a constant voltage signal, and (2) the nematic LC structures with different thickness of LC layer, and (3) the nematic LC structures with different signal voltage. The typical results include the distribution of LC directors in LC layers, the distribution of electric potential in LC layers, and the distribution of phase retardation. The results show that the method can be used to effectively predict the formation of disclination lines, which has a strong impact on the performance of LC micro-optics structures.

  1. Optical analysis of spatially periodic patterns in nematic liquid crystals: diffraction and shadowgraphy.

    Science.gov (United States)

    Pesch, Werner; Krekhov, Alexei

    2013-05-01

    Optical methods are most convenient for analyzing spatially periodic patterns with wave vector q in a thin layer of a nematic liquid crystal. In the standard experimental setup a beam of parallel light with a "short" wavelength λ<2π/q passes the nematic layer. Recording the transmitted light the patterns are either directly visualized by shadowgraphy or characterized more indirectly by the diffraction fringes due to the optical-grating effects of the pattern. In this work we present a systematic short-wavelength analysis of these methods for the commonly used planar orientation of the optical axis of liquid crystal at the confining surfaces. Our approach covers general three-dimensional experimental geometries with respect to the relative orientation of q and of the wave vector k of the incident light. In particular, we emphasize the importance of phase-grating effects, which are not accessible in a pure geometric optics approach. Finally, as a by-product we present also an optical analysis of convection rolls in Rayleigh-Bénard convection, where the refraction index of the fluid is isotropic in contrast to its uniaxial symmetry in nematic liquid crystals. Our analysis is in excellent agreement with an earlier physical optics approach by Trainoff and Cannell [Phys. Fluids 14, 1340 (2002)], which is restricted to a two-dimensional geometry and technically much more demanding.

  2. Breatherlike defects and their dynamics in the one-dimensional roll structure of twisted nematics

    Energy Technology Data Exchange (ETDEWEB)

    Skaldin, O. A.; Delev, V. A., E-mail: delev@anrb.ru; Shikhovtseva, E. S.; Lebedev, Yu. A.; Batyrshin, E. S. [Russian Academy of Sciences, Institute of Molecular and Crystal Physics, Ufa Research Center (Russian Federation)

    2015-12-15

    The dynamics of the nonsingular defects in the periodic structures of the rolls that appear in π/2-twisted nematic liquid crystals during electroconvection is studied experimentally and theoretically. The roll structures in twisted nematics are characterized by the presence of an axial component of the hydrodynamic flow velocity with opposite directions in neighboring rolls. The critical oscillation frequency of structural defects is quantitatively estimated using a nonlinear equation of motion for roll displacements. It is found that a pair of edge dislocations with topological charges of +1 and–1 nucleates and annihilates periodically during the oscillations of a defect with a nonsingular core. Oscillating defects with a zero topological charge is shown to correspond to the solution of the sine-Gordon equation in the form of standing breathers. Asymmetry is detected in the full oscillation cycle of a breather defect, and it is related to the twist symmetry of a twist nematic. This asymmetry is taken into account as effective anisotropic friction. The behavior of a breather on a trap, namely, a classical defect (dislocation), is investigated. Dislocation motion is shown to be anisotropic in the oscillation cycle: in one direction, a dislocation moves regularly; in the second phase, the transition into the initial state proceeds via the decay of the breather into a dipole pair of dislocations of opposite signs followed by their annihilation.

  3. Baryons and Chiral Symmetry

    CERN Document Server

    Liu, Keh-Fei

    2016-01-01

    The relevance of chiral symmetry in baryons is highlighted in three examples in the nucleon spectroscopy and structure. The first one is the importance of chiral dynamics in understanding the Roper resonance. The second one is the role of chiral symmetry in the lattice calculation of $\\pi N \\sigma$ term and strangeness. The third one is the role of chiral $U(1)$ anomaly in the anomalous Ward identity in evaluating the quark spin and the quark orbital angular momentum. Finally, the chiral effective theory for baryons is discussed.

  4. Polarization-controlled contrasted images using dye-doped nematic liquid crystals.

    Science.gov (United States)

    Porras Aguilar, R; Ramirez-San-Juan, J C; Baldovino-Pantaleon, O; May-Arrioja, D; Arroyo Carrasco, M L; Iturbe-Castillo, M D; Sánchez-de-la-Llave, D; Ramos-Garcia, R

    2009-03-02

    We explore the polarization dependence of the nonlinear response of a planar nematic liquid crystal cell doped with 1% wt of methyl red dye. The results obtained show that the refractive index change can be switched from a positive value to a negative one as the polarization of the beam changes from parallel to perpendicular with respect to the rubbing direction. This property is exploited in a phase contrast system, where a dynamic phase filter is photoinduced in a liquid crystal cell placed in the system's Fourier plane. Real-time contrast inversion in the resulting images is demonstrated.

  5. Dyakonov-Tamm waves-based optical sensing using sculptured nematic thin film

    Science.gov (United States)

    Abbas, Farhat; Naqvi, Qaisar A.; Faryad, Muhammad

    2015-06-01

    Dyakonov-Tamm (DT) waves are highly sensitive to the constitutive properties of the partnering materials near the interface. DT waves are excited at the interface of two dielectric materials of which at least one is anisotropic and periodically nonhomogeneous normal to their interface. Sculptured nematic thin film (SNTF) is a good candidate for the periodically nonhomogeneous dielectric partner for optical sensing of a fluid due to its porosity. The nanoscale parameters of an uninfiltrated SNTF obtained from the inverse Bruggeman homogenization formalism were used in the forward Bruggeman homogenization formalism to determine the constitutive parameters for the infiltrated SNTF. The sensitivity of DT waves to the refractive index was analyzed for two possible sensing modalities and it was found that the sensitivity was comparable to that of the chiral sculptured thin films (STFs) made of the same material as of the SNTF. This implies that the sensing with DT waves is robust, is independent of the morphology of the partnering nonhomogeneous dielectric material and could make the sensing easier since SNTFs are easier to fabricate than the chiral STFs.

  6. Chiral condensate, susceptibilities, critical coupling and indices in QED$_{4}$

    CERN Document Server

    Azcoiti, V; Galante, A; Grillo, A F; Laliena, V; Piedrafita, C E

    1995-01-01

    We measure chiral susceptibilities in the Coulomb phase of noncompact QED_4 in 8^4, 10^4 and 12^4 lattices. The MFA approach allows simulations in the chiral limit which are therefore free from arbitrary mass extrapolations. Using the critical couplings extracted from these calculations, we study the critical behaviour of the chiral condensate, which we find in disagreement with the predictions of logarithmically improved scalar Mean Field theory.

  7. Chiral Rotational Spectroscopy

    CERN Document Server

    Cameron, Robert P; Barnett, Stephen M

    2015-01-01

    We introduce chiral rotational spectroscopy: a new technique that enables the determination of the individual optical activity polarisability components $G_{XX}'$, $G_{YY}'$, $G_{ZZ}'$, $A_{X,YZ}$, $A_{Y,ZX}$ and $A_{Z,XY}$ of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample whilst yielding an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral by virtue of their isotopic constitution and molecules with multiple chiral centres. The principles that underpin chiral rotational spectroscopy can also be exploited in the search for molecular chirality in space, which, if found, may add weight to hypotheses that biological homochirality and indeed life itself are of cosmic origin.

  8. Optical characterization of the nematic lyotropic chromonic liquid crystals: light absorption, birefringence, and scalar order parameter.

    Science.gov (United States)

    Nastishin, Yu A; Liu, H; Schneider, T; Nazarenko, V; Vasyuta, R; Shiyanovskii, S V; Lavrentovich, O D

    2005-10-01

    We report on the optical properties of the nematic (N) phase formed by lyotropic chromonic liquid crystals (LCLCs) in well aligned planar samples. LCLCs belong to a broad class of materials formed by one-dimensional molecular self-assembly and are similar to other systems such as "living polymers" and "wormlike micelles." We study three water soluble LCLC forming materials: disodium chromoglycate, a derivative of indanthrone called Blue 27, and a derivative of perylene called Violet 20. The individual molecules have a planklike shape and assemble into rodlike aggregates that form the phase once the concentration exceeds about 0.1 M. The uniform surface alignment of the N phase is achieved by buffed polyimide layers. According to the light absorption anisotropy data, the molecular planes are on average perpendicular to the aggregate axes and thus to the nematic director. We determined the birefringence of these materials in the N and biphasic N-isotropic (I) regions and found it to be negative and significantly lower in the absolute value as compared to the birefringence of typical thermotropic low-molecular-weight nematic materials. In the absorbing materials Blue 27 and Violet 20, the wavelength dependence of birefringence is nonmonotonic because of the effect of anomalous dispersion near the absorption bands. We describe positive and negative tactoids formed as the nuclei of the new phase in the biphasic N-I region (which is wide in all three materials studied). Finally, we determined the scalar order parameter of the phase of Blue 27 and found it to be relatively high, in the range 0.72-0.79, which puts the finding into the domain of general validity of the Onsager model. However, the observed temperature dependence of the scalar order parameter points to the importance of factors not accounted for in the athermal Onsager model, such as interaggregate interactions and the temperature dependence of the aggregate length.

  9. Nematic spin order and spin-lattice coupling in Fe-based Superconductors

    Science.gov (United States)

    Hu, Jiangping; Fang, Chen; Tsai, Wei-Feng; Yao, Hong; Kivelson, Steve

    2009-03-01

    We show that the structure transitions observed in Fe-based superconductors are magnetically driven. A quantum Heisenberg model (J1-J2-Jz) exhibits a sequence of two phase transitions: from a high temperature symmetric phase to a narrow region of intermediate ``nematic'' phase, and then to a low temperature spin ordered phase when Jz is small. Identifying phases by their broken symmetries, these phases correspond precisely to the sequence of structural (tetragonal to monoclinic) and magnetic transitions that have been recently revealed in neutron scattering studies of 1111 series of Fe- based superconductors. The structural transition can thus be identified with the existence of incipient (``fluctuating'') magnetic order. We also discuss the effect of spin-lattice coupling on the phase diagram of the model. [3pt] Reference: Chen Fang, Hong Yao, Wei-Feng Tsai, JiangPing Hu and Steven A. Kivelson, Phys. Rev. B 77 224509 (2008).

  10. On chiral and non chiral 1D supermultiplets

    Energy Technology Data Exchange (ETDEWEB)

    Toppan, Francesco, E-mail: toppan@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (TEO/CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Fisica Teorica

    2011-07-01

    In this talk I discuss and clarify some issues concerning chiral and non chiral properties of the one-dimensional supermultiplets of the N-extended supersymmetry. Quaternionic chirality can be defined for N = 4, 5, 6, 7, 8. Octonionic chirality for N = 8 and beyond. Inequivalent chiralities only arise when considering several copies of N = 4 or N = 8 supermultiplets. (author)

  11. Ultra-fast high-efficiency enantioseparations by means of a teicoplanin-based chiral stationary phase made on sub-2 μm totally porous silica particles of narrow size distribution.

    Science.gov (United States)

    Ismail, Omar H; Ciogli, Alessia; Villani, Claudio; De Martino, Michela; Pierini, Marco; Cavazzini, Alberto; Bell, David S; Gasparrini, Francesco

    2016-01-01

    A new ultra-high performance teicoplanin-based stationary phase was prepared starting from sub-2 μm totally porous silica particles of narrow size distribution. Columns of different lengths were packed at high pressure and a deep and systematic evaluation of kinetic performance, in terms of van Deemter analysis, was performed under different elution conditions (HILIC, POM, RP and NP) by using both achiral and chiral probes. For the achiral probes, the efficiency of the columns at the minimum of the van Deemter curves were very high leading to some 278,000, 270,000, 262,000 and 232,000 plates/m in hydrophilic interaction liquid chromatography (HILIC), polar organic mode (POM), normal phase (NP) and reversed phase (RP) respectively. The lowest plate height, Hmin=3.59 μm (h(/)=1.89), was obtained under HILIC conditions at a flow rate of 1.4 mL/min. Efficiency as high as 200,000-250,000 plates/m (at the optimum flow rate) was obtained in the separation of the enantiomers of chiral probes under HILIC/POM conditions. N-protected amino acids, α-aryloxy acids, herbicides, anti-inflammatory agents were baseline separated on short (2-cm) and ultra-short (1-cm) columns, with analysis time in the order of 1 min. The enantiomers of N-BOC-d,l-methionine were successfully baseline separated in only 11s in HILIC mode. Several examples of fast and efficient resolutions in sub/supercritical fluid chromatography were also obtained for a range of chiral carboxylic acids.

  12. A novel twisted nematic alignment and its effects on the electro-optical dynamics of nanoscale liquid crystalline films

    Science.gov (United States)

    Rauzan, Brittany; Lee, Lay Min; Nuzzo, Ralph

    2015-03-01

    Vibrational spectroscopic studies of a surface induced, twisted alignment of the nematic liquid crystal, 4-n-pentyl-4'-cyanobiphenyl (5CB) and its temperature-dependent electro-optical (EO) dynamics were studied near the crystalline-nematic and nematic-isotropic transition temperatures, and at a median temperature in the nematic phase. A 50 nm thick film of 5CB was confined in nanocavities defined by the dimensions of a gold interdigitated electrode array patterned on a unidirectionally polished ZnSe substrate. The film was assembled between two polished substrates bearing extended nanometer-scaled grooves that are oriented orthogonally to one another. The results show that with this anchoring scheme, the molecular director of the LC film undergoes a ninety-degree twist. Step-scan time resolved spectroscopy (TRS) measurements were made to determine the rate constants for the temperature-dependent EO dynamics of both the electric field-induced orientation and thermal relaxation processes of the LC film. The work rationalizes the impacts of organizational anisotropy and illustrates how it can be exploited as a design principle to effectively influence the electric field-induced dynamics of LC systems.

  13. Superconductivity in FeSe Thin Films Driven by the Interplay between Nematic Fluctuations and Spin-Orbit Coupling

    Science.gov (United States)

    Kang, Jian; Fernandes, Rafael M.

    2016-11-01

    The origin of the high-temperature superconducting state observed in FeSe thin films, whose phase diagram displays no sign of magnetic order, remains a hotly debated topic. Here we investigate whether fluctuations arising due to the proximity to a nematic phase, which is observed in the phase diagram of this material, can promote superconductivity. We find that nematic fluctuations alone promote a highly degenerate pairing state, in which both s -wave and d -wave symmetries are equally favored, and Tc is consequently suppressed. However, the presence of a sizable spin-orbit coupling or inversion symmetry breaking at the film interface lifts this harmful degeneracy and selects the s -wave state, in agreement with recent experimental proposals. The resulting gap function displays a weak anisotropy, which agrees with experiments in monolayer FeSe and intercalated Li1 -x(OH )xFeSe .

  14. Chiral symmetry and chiral-symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Peskin, M.E.

    1982-12-01

    These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed. (WHK)

  15. Random matrix model approach to chiral symmetry

    CERN Document Server

    Verbaarschot, J J M

    1996-01-01

    We review the application of random matrix theory (RMT) to chiral symmetry in QCD. Starting from the general philosophy of RMT we introduce a chiral random matrix model with the global symmetries of QCD. Exact results are obtained for universal properties of the Dirac spectrum: i) finite volume corrections to valence quark mass dependence of the chiral condensate, and ii) microscopic fluctuations of Dirac spectra. Comparisons with lattice QCD simulations are made. Most notably, the variance of the number of levels in an interval containing $n$ levels on average is suppressed by a factor $(\\log n)/\\pi^2 n$. An extension of the random matrix model model to nonzero temperatures and chemical potential provides us with a schematic model of the chiral phase transition. In particular, this elucidates the nature of the quenched approximation at nonzero chemical potential.

  16. A Molecular Model for Chiral Symmetry Breaking

    Science.gov (United States)

    Latinwo, Folarin; Stillinger, Frank; Debenedetti, Pablo

    In this work, we present a new class of molecular models for chiral phenomena in condensed matter systems. A key feature of these models is the ability of the four-site (tetramer) ``molecules'' to inter-convert between two distinct chiral forms (enantiomers). Given this feature, we use analytical theory and computer simulations to investigate the emergent chiral properties (including symmetry breaking) over a range of conditions. In particular, we consider the single-molecule level and condensed-phase behavior of our model system. Interestingly, we find that our liquid-phase predictions are in excellent agreement with recent experimental reports on chiral self-sorting in isotropic liquids. From this perspective, our model demonstrates accurate predictive capabilities, as well as a platform for understanding the microscopic origins of a variety of chiral phenomena. In a broader context, we anticipate that this class of models will be relevant to chirality-dominated areas such as the pharmaceutical industry and pre-biotic geochemistry.

  17. Central-to-axial chirality transfer revealed by liquid crystals: a combined experimental and computational approach for the determination of absolute configuration of carboxylic acids with an α chirality centre.

    Science.gov (United States)

    Ferrarini, Alberta; Ferroni, Fiammetta; Pieraccini, Silvia; Rosini, Carlo; Superchi, Stefano; Spada, Gian Piero

    2011-10-01

    The conversion into 6,7-dihydro-5H-dibenz[c,e]azepine (DAZ) N-protected amides is a viable route for the determination of the absolute configuration of chiral 2-substituted carboxylic acids. The biphenyl moiety of DAZ, besides being a probe of chirality for the electronic circular dichroism (ECD) spectroscopy, makes these systems suitable for configuration assignment by exploiting the chirality amplification which occurs in nematic liquid crystals. To assess the reliability of the liquid crystal method in detecting the absolute stereochemistry of chiral amides bound to a biphenyl group, we measured the helical twisting power of a series of DAZ-N-protected amides and compared these data with the results obtained from ECD measurements. We will show that the liquid crystal method, corroborated by HTP predictions, is trustworthy with our biphenyl derivatives, even when ECD spectra are ambiguous for the presence of aryl moieties displaying strong UV absorptions in the same range of the biphenyl chromophore.

  18. 一种新型手性配体交换色谱键合固定相%A Novel Bonded Stationary Phase for Chiral Ligand Exchange-Chromatography

    Institute of Scientific and Technical Information of China (English)

    龙远德; 王群标; 等

    2001-01-01

    A novel chiral bonded stationary phase(CBSP) for ligand exchange chromatography was prepared by bonding (S)-1,2,3,4-tetrahydro-3-isoquinoline carboxylic acid prepared from L-Phe to YWG-80 silica gel via 3-glycidyloxypropyltrimethoxysilane as a coupling agent. Chromatographic resolutions of some DL-amino acids were achieved on the CBSP by using an aqueous solution of 2 mmol/L N(C2H5)3, 2 mmol/L HAc and 0.2 mmol/L Cu(Ac)2 as the mobile phase with a flow rate 1.0 mL/min, column temperature 50 ℃ and detection at 254 nm. The enantioselectivity α of the DL-amino acids on the CBSP was found to be between 1.11 and 1.51. The elution order of D-isomer before L-isomer on the CBSP was observed for all the DL-amino acids resolved except DL-Val. For DL-Pro, DL-Val and DL-Leu the elution order through the CBSP was different from that through the chiral ligand exchange phases prepared from L-Pro or L-hydroxyl proline with a five-membered ring structure.

  19. Extrinsic electromagnetic chirality in metamaterials

    OpenAIRE

    Plum, E.; Fedotov, V. A.; Zheludev, N. I.

    2009-01-01

    Three- and two-dimensional chirality arising from the mutual orientation of non-chiral planar metamaterial structures and the incident electromagnetic wave (extrinsic chirality) lead to pronounced optical activity, circular dichroism and asymmetric transmission indistinguishable from those seen in media consisting of three- and two-dimensionally chiral molecules (intrinsic chirality).

  20. Relation Between Chiral Susceptibility and Solutions of Gap Equation in Nambu--Jona-Lasinio Model

    CERN Document Server

    Zhao, Y; Liu, Y; Yuan, W; Chang, Lei; Liu, Yu-xin; Yuan, Wei; Zhao, Yue

    2006-01-01

    We study the solutions of the gap equation, the thermodynamic potential and the chiral susceptibility in and beyond the chiral limit at finite chemical potential in the Nambu--Jona-Lasinio (NJL) model. We give an explicit relation between the chiral susceptibility and the thermodynamic potential in the NJL model. We find that the chiral susceptibility is a quantity being able to represent the furcation of the solutions of the gap equation and the concavo-convexity of the thermodynamic potential in NJL model. It indicates that the chiral susceptibility can identify the stable state and the possibility of the chiral phase transition in NJL model.