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Sample records for temperature enantiotropic nematic

  1. Temperature tunable optical gratings in nematic elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Sungur, Emel; Mager, Loic; Boeglin, Alex; Dorkenoo, Kokou D. [IPCMS-CNRS UMR 7504, 23 rue du Loess, BP 43, Strasbourg Cedex 2 (France); Li, Min-Hui; Keller, Patrick [Institut Curie, CNRS 168, Paris Cedex 5 (France)

    2010-01-15

    We have investigated the behaviour of temperature dependent periodic-index gratings fabricated in a nematic elastomer. The gratings have been obtained by photopolymerisation under a microscopy apparatus. Contraction properties, as well as diffraction properties, have been studied as a function of temperature. Unidirectional contraction has been demonstrated by means of circular figure deformation and the polarisation dependency of the diffraction by the gratings has been determined. (orig.)

  2. 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.

  3. A twist-bend nematic phase driven by hydrogen bonding

    NARCIS (Netherlands)

    Jansze, S.M.; Martínez-Felipe, A.; Storey, J.M.D.; Marcelis, A.T.M.; Imrie, C.T.

    2015-01-01

    The liquid crystalline phase behavior of 4-[6-(4'-cyanobiphenyl-4-yl)hexyloxy]benzoic acid (CB6OBA) and 4-[5-(4'-cyanobiphenyl-4-yloxy)pentyloxy]benzoic acid (CBO5OBA) is described. Both acids show an enantiotropic nematic phase attributed to the formation of supramolecular complexes by hydrogen

  4. Molecular engineering of discotic nematic liquid crystals

    Indian Academy of Sciences (India)

    The primary objectives of this research programme are: (a) design and synthesis of organic molecules which can form discotic nematic mesophase and (b) synthetic modifi- cations in known discotic nematic phase forming materials to stabilise the nematic phase well below and above the room temperature. 199 ...

  5. A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

    Science.gov (United States)

    Burnell, E. Elliott; Weber, Adrian C. J.; Dong, Ronald Y.; Meerts, W. Leo; de Lange, Cornelis A.

    2015-01-01

    The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche+ gauche+, pp, and gauche+ gauche-, pm), the isotropic trans-gauche energy difference Etg and its temperature coefficient Etg ' are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche+ gauche- conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase.

  6. Nematic Bond Theory of Heisenberg Helimagnets

    Science.gov (United States)

    Schecter, Michael; Syljuâsen, Olav F.; Paaske, Jens

    2017-10-01

    We study classical two-dimensional frustrated Heisenberg models with generically incommensurate ground states. A new theory for the lattice-nematic "order by disorder" transition is developed based on the self-consistent determination of the effective exchange coupling bonds. In our approach, fluctuations of the constraint field imposing conservation of the local magnetic moment drive nematicity at low temperatures. The critical temperature is found to be highly sensitive to the peak helimagnetic wave vector, and vanishes continuously when approaching rotation symmetric Lifshitz points. Transitions between symmetry distinct nematic orders may occur by tuning the exchange parameters, leading to lines of bicritical points.

  7. Distinguishing XY from Ising electron nematics

    Science.gov (United States)

    Basak, S.; Carlson, E. W.

    2017-08-01

    At low temperatures in ultraclean GaAs-AlGaAs heterojunctions, high Landau levels near half-integral filling break rotational symmetry, leading to increasingly anisotropic transport properties as temperature is lowered below ˜150 mK . While the onset of transport anisotropy is well described by an XY model of an electron nematic in the presence of a weak uniform symmetry-breaking term, the low-temperature behavior deviates significantly from this model. We find that inclusion of interactions between the electron nematic and the underlying crystalline lattice in the form of a fourfold symmetry-breaking term is sufficient to describe the entire temperature dependence of the transport anisotropy at ν =9 /2 . This implies that this electron nematic is in the Ising universality class. We propose new experimental tests that can distinguish whether any two-dimensional electron nematic is in the XY or Ising universality class.

  8. Configurational temperature and local properties of the anisotropic Gay-Berne liquid crystal model: applications to the isotropic liquid/vapor interface and isotropic/nematic transition.

    Science.gov (United States)

    Ghoufi, Aziz; Morineau, Denis; Lefort, Ronan; Malfreyt, Patrice

    2011-01-21

    Molecular simulations in the isothermal statistical ensembles require that the macroscopic thermal and mechanical equilibriums are respected and that the local values of these properties are constant at every point in the system. The thermal equilibrium in Monte Carlo simulations can be checked through the calculation of the configurational temperature, k(B)T(conf)=/, where ∇(r) is the nabla operator of position vector r. As far as we know, T(conf) was never calculated with the anisotropic Gay-Berne potential, whereas the calculation of T(conf) is much more widespread with more common potentials (Lennard Jones, electrostatic, ...). We establish here an operational expression of the macroscopic and local configurational temperatures, and we investigate locally the isotropic liquid phase, the liquid / vapor interface, and the isotropic-nematic transition by Monte Carlo simulations.

  9. Spontaneous thermal expansion of nematic elastomers

    Science.gov (United States)

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

    2001-10-01

    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 the isotropic phase. At higher concentration of main chains their behaviour dominates the elastomer properties. At low concentration of main-chain material, we detect two distinct transitions at different temperatures, one attributed to the main-chain, the other to the side-chain component. The effective uniaxial anisotropy of nematic rubber, r(T)=ell_{allel}/ell_{bot} proportional to the effective nematic order parameter Q(T), is given by an average of the two components and thus reflects the two-transition nature of thermal expansion. The experimental data is compared with the theoretical model of ideal nematic elastomers; applications in high-amplitude thermal actuators are discussed in the end.

  10. Field Induced Memory Effects in Random Nematics

    Directory of Open Access Journals (Sweden)

    Amid Ranjkesh

    2014-01-01

    Full Text Available We studied numerically external field induced memory effects in randomly perturbed nematic liquid crystals. Random anisotropy nematic-type lattice model was used. The impurities imposing orientational disorder were randomly spatially distributed with the concentration p below the percolation threshold. Simulations were carried for finite temperatures, where we varied p, interaction strength between LC molecules, and impurities and external field B. In the {B,T} plane we determined lines separating short range—quasi long range and quasi long range—long range order. Furthermore, crossover regime separating external field and random field dominated regime was estimated. We calculated remanent nematic ordering in samples at B=0 as a function of the previously experienced external field strength B.

  11. Molecular engineering of discotic nematic liquid crystals

    Indian Academy of Sciences (India)

    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.

  12. Electric heating effects in nematic liquid crystals

    Science.gov (United States)

    Yin, Y.; Shiyanovskii, S. V.; Lavrentovich, O. D.

    2006-07-01

    Electric heating effects in the nematic liquid crystal change the liquid crystal physical properties and dynamics. We propose a model to quantitatively describe the heating effects caused by dielectric dispersion and ionic conductivity in the nematic liquid crystals upon the application of an ac electric field. The temperature increase of the liquid crystal cell is related to the properties of the liquid crystal such as the imaginary part of the dielectric permittivity, thermal properties of the bounding plates, and the surrounding medium as well as frequency and amplitude of the electric field. To study the temperature dynamics experimentally, we use a small thermocouple inserted directly into the nematic bulk; we assure that the thermocouple does not alter the thermal behavior of the system by comparing the results to those obtained by a noncontact birefringent probing technique recently proposed by Wen and Wu [Appl. Phys. Lett. 86, 231104 (2005)]. We determine how the temperature dynamics and the stationary value of the temperature increase depend on the parameters of the materials and the applied field. We used different surrounding media, from extremely good heat conductors such as aluminum cooling device to extremely poor conductor, Styrofoam; these two provide two limiting cases as compared to typical conditions of nematic cell exploitation in a laboratory or in commercial devices. The experiments confirm the theoretical predictions, namely, that the temperature rise is controlled not only by the heat transfer coefficient of the surrounding medium (as in the previous model) but also by the thickness and the thermal conductivity coefficient of the bounding plates enclosing the nematic layer. The temperature increase strongly depends on the director orientation and can change nonmonotonously with the frequency of the applied field.

  13. Self-assembly of nematic liquid crystal elastomer filaments

    Science.gov (United States)

    Wei, Wei-Shao; Xia, Yu; Yang, Shu; Yodh, A. G.

    In this work we investigate the self-assembly of nematic liquid crystal polymer (NLCP) filaments and their corresponding cross-linked elastomer structures. Specifically, by fine-tuning surfactant concentration, prepolymer chain length, and temperature within a background aqueous phase we can generate filaments composed of oligomerized LC monomers. Filaments with narrowly dispersed diameters ranging from one hundred nanometers to a few micrometers can be obtained. Using polarization optical microscopy, we show that the nematic LCs within the filaments have an escaped radial structure. After photo-cross-linking, nematic liquid crystal elastomer filaments are obtained with well-maintained directors and smooth surface structure. Since these materials are elastomers, the size and mechanical and optical response of the filaments can be ''tuned'' near the nematic to isotropic phase transition temperature. This work is supported by NSF DMR16-07378, PENN MRSEC Grant DMR11-20901, and NASA Grant NNX08AO0G.

  14. Helium-3 gas self-diffusion in a nematically ordered aerogel at low temperatures: enhanced role of adsorption.

    Science.gov (United States)

    Kuzmin, Vyacheslav; Safiullin, Kajum; Stanislavovas, Andrey; Tagirov, Murat

    2017-08-30

    We performed (3)He gas diffusion measurements for the first time in a highly porous ordered Al2O3 aerogel sample at a temperature of 4.2 K using a nuclear magnetic resonance field gradient technique. A strong influence of (3)He adsorption in the aerogel on self-diffusion is observed. The classical consideration of adsorptive gas diffusion in mesopores leads to anomalously high tortuosity factors. The application of a more sophisticated model than the simple combination of empirical two-phase diffusion and the Knudsen gas diffusion models is required to explain our results. Anisotropic properties of the aerogel are not reflected in the observed gas diffusion even at low gas densities where the anisotropic Knudsen regime of diffusion is expected. The observed gas densification indicates the influence of the aerogel attractive potential on the molecular dynamics, which probably explains the reduced diffusion process. Perhaps this behavior is common for any adsorptive gases in nanopores.

  15. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    Directory of Open Access Journals (Sweden)

    Vasily F. Shabanov

    2013-08-01

    Full Text Available Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.

  16. 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

  17. Quantum Hall Electron Nematics

    Science.gov (United States)

    MacDonald, Allan

    In 2D electron systems hosted by crystals with hexagonal symmetry, electron nematic phases with spontaneously broken C3 symmetry are expected to occur in the quantum Hall regime when triplets of Landau levels associated with three different Fermi surface pockets are partially filled. The broken symmetry state is driven by intravalley Coulombic exchange interactions that favor spontaneously polarized valley occupations. I will discuss three different examples of 2D electron systems in which this type of broken symmetry state is expected to occur: i) the SnTe (111) surface, ii) the Bi (111) surface. and iii) unbalanced bilayer graphene. This type of quantum Hall electron nematic state has so far been confirmed only in the Bi (111) case, in which the anisotropic quasiparticle wavefunctions of the broken symmetry state were directly imaged. In the SnTe case the nematic state phase boundary is controlled by a competition between intravalley Coulomb interactions and intervalley scattering processes that increase in relative strength with magnetic field. An in-plane Zeeman field alters the phase diagram by lifting the three-fold Landau level degeneracy, yielding a ground state energy with 2 π/3 periodicity as a function of Zeeman-field orientation angle. I will comment on the possibility of observing similar states in the absence of a magnetic field. Supported by DOE Division of Materials Sciences and Engineering Grant DE-FG03-02ER45958.

  18. Nematic fluctuations balancing the zoo of phases in half-filled quantum Hall systems

    Science.gov (United States)

    Mesaros, Andrej; Lawler, Michael J.; Kim, Eun-Ah

    2017-03-01

    Half-filled Landau levels form a zoo of strongly correlated phases. These include non-Fermi-liquids (NFLs), fractional quantum Hall (FQH) states, nematic phases, and FQH nematic phases. This diversity begs the following question: what keeps the balance between the seemingly unrelated phases? The answer is elusive because the Halperin-Lee-Read description that offers a natural departure point is inherently strongly coupled. However, the observed nematic phases suggest that nematic fluctuations play an important role. To study this possibility, we apply a recently formulated controlled double-expansion approach in large-N composite fermion flavors and small ɛ nonanalytic bosonic action to the case with both gauge and nematic boson fluctuations. In the vicinity of a nematic quantum critical line, we find that depending on the amount of screening of the gauge- and nematic-mediated interactions controlled by ɛ 's, the renormalization-group flow points to all four mentioned correlated phases. When pairing preempts the nematic phase, NFL behavior is possible at temperatures above the pairing transition. We conclude by discussing measurements at low tilt angles, which could reveal the stabilization of the FQH phase by nematic fluctuations.

  19. Monte Carlo simulations of nematic and chiral nematic shells.

    Science.gov (United States)

    Wand, Charlie R; Bates, Martin A

    2015-01-01

    We present a systematic Monte Carlo simulation study of thin nematic and cholesteric shells with planar anchoring using an off-lattice model. The results obtained using the simple model correspond with previously published results for lattice-based systems, with the number, type, and position of defects observed dependent on the shell thickness with four half-strength defects in a tetrahedral arrangement found in very thin shells and a pair of defects in a bipolar (boojum) configuration observed in thicker shells. A third intermediate defect configuration is occasionally observed for intermediate thickness shells, which is stabilized in noncentrosymmetric shells of nonuniform thickness. Chiral nematic (cholesteric) shells are investigated by including a chiral term in the potential. Decreasing the pitch of the chiral nematic leads to a twisted bipolar (chiral boojum) configuration with the director twist increasing from the inner to the outer surface.

  20. Charge transfer reactions in nematic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Wiederrecht, G.P. [Argonne National Lab., IL (United States). Chemistry Div.; Wasielewski, M.R. [Argonne National Lab., IL (United States). Chemistry Div.]|[Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry; Galili, T.; Levanon, H. [Hebrew Univ. of Jerusalem (Israel). Dept. of Physical Chemistry

    1998-07-01

    Ultrafast transient absorption studies of intramolecular photoinduced charge separation and thermal charge recombination were carried out on a molecule consisting of a 4-(N-pyrrolidino)naphthalene-1,8-imide donor (PNI) covalently attached to a pyromellitimide acceptor (PI) dissolved in the liquid crystal 4{prime}-(n-pentyl)-4-cyanobiphenyl (5CB). The temperature dependencies of the charge separation and recombination rates were obtained at temperatures above the nematic-isotropic phase transition of 5CB, where ordered microdomains exist and scattering of visible light by these domains is absent. The authors show that excited state charge separation is dominated by molecular reorientation of 5CB perpendicular to the director within the liquid crystal microdomains. They also show that charge recombination is adiabatic and is controlled by the comparatively slow collective reorientation of the liquid crystal microdomains relative to the orientation of PNI{sup +}-PI{sup {minus}}. They also report the results of time resolved electron paramagnetic resonance (TREPR) studies of photoinduced charge separation in a series of supramolecular compounds dissolved in oriented liquid crystal solvents. These studies permit the determination of the radical pair energy levels as the solvent reorganization energy increases from the low temperature crystalline phase, through the soft glass phase, to the nematic phase of the liquid crystal.

  1. Superconductivity and non-Fermi liquid behavior near a nematic quantum critical point.

    Science.gov (United States)

    Lederer, Samuel; Schattner, Yoni; Berg, Erez; Kivelson, Steven A

    2017-05-09

    Using determinantal quantum Monte Carlo, we compute the properties of a lattice model with spin [Formula: see text] itinerant electrons tuned through a quantum phase transition to an Ising nematic phase. The nematic fluctuations induce superconductivity with a broad dome in the superconducting [Formula: see text] enclosing the nematic quantum critical point. For temperatures above [Formula: see text], we see strikingly non-Fermi liquid behavior, including a "nodal-antinodal dichotomy" reminiscent of that seen in several transition metal oxides. In addition, the critical fluctuations have a strong effect on the low-frequency optical conductivity, resulting in behavior consistent with "bad metal" phenomenology.

  2. Superconductivity and non-Fermi liquid behavior near a nematic quantum critical point

    Science.gov (United States)

    Lederer, Samuel; Schattner, Yoni; Berg, Erez; Kivelson, Steven A.

    2017-05-01

    Using determinantal quantum Monte Carlo, we compute the properties of a lattice model with spin 1212 itinerant electrons tuned through a quantum phase transition to an Ising nematic phase. The nematic fluctuations induce superconductivity with a broad dome in the superconducting TcTc enclosing the nematic quantum critical point. For temperatures above TcTc, we see strikingly non-Fermi liquid behavior, including a “nodal-antinodal dichotomy” reminiscent of that seen in several transition metal oxides. In addition, the critical fluctuations have a strong effect on the low-frequency optical conductivity, resulting in behavior consistent with “bad metal” phenomenology.

  3. Pattern Formation in Active Nematics

    Science.gov (United States)

    Mishra, Prashant

    This thesis presents analytical and numerical studies of the nonequilibrium dynamics of active nematic liquid crystals. Active nematics are a new class of liquid crystals consisting of elongated rod-like units that convert energy into motion and spontaneously organize in large-scale structures with orientational order and self-sustained flows. Examples include suspensions of cytoskeletal filaments and associated motor proteins, monolayers of epithelial cells plated on a substrate, and bacteria swimming in a nematic liquid crystal. In these systems activity drives the continuous generation and annihilation of topological defects and streaming flows, resulting in spatio-temporal chaotic dynamics akin to fluid turbulence, but that occurs in a regime of flow of vanishing Reynolds number, where inertia is negligible. Quantifying the origin of this nonequilibrium dynamics has implications for understanding phenomena ranging from bacterial swarming to cytoplasmic flows in living cells. After a brief review (Chapter 2) of the properties of equilibrium or passive nematic liquid crystals, in Chapter 3 we discuss how the hydrodynamic equations of nematic liquid crystals can be modified to account for the effect of activity. We then use these equations of active nemato-hydrodynamics to characterize analytically the nonequilibrium steady states of the system and their stability. We supplement the analytical work with numerical solution of the full nonlinear equations for the active suspension and construct a phase diagram that identifies the various emergent patterns as a function of activity and nematic stiffness. In Chapter 4 we compare results obtained with two distinct hydrodynamic models that have been employed in previous studies. In both models we find that the chaotic spatio-temporal dynamics in the regime of fully developed active turbulence is controlled by a single active scale determined by the balance of active and elastic stresses. This work provides a unified

  4. Computer simulation study of the nematic-vapour interface in the Gay-Berne model

    Science.gov (United States)

    Rull, Luis F.; Romero-Enrique, José Manuel

    2017-06-01

    We present computer simulations of the vapour-nematic interface of the Gay-Berne model. We considered situations which correspond to either prolate or oblate molecules. We determine the anchoring of the nematic phase and correlate it with the intermolecular potential parameters. On the other hand, we evaluate the surface tension associated to this interface. We find a corresponding states law for the surface tension dependence on the temperature, valid for both prolate and oblate molecules.

  5. History-Dependent Patterns in Randomly Perturbed Nematic Liquid Crystals

    Directory of Open Access Journals (Sweden)

    A. Ranjkesh

    2013-01-01

    Full Text Available We study the characteristics of nematic structures in a randomly perturbed nematic liquid crystal (LC phase. We focus on the impact of the samples history on the universal behavior. The obtained results are of interest for every randomly perturbed system exhibiting a continuous symmetry-breaking phase transition. A semimicroscopic lattice simulation is used where the LC molecules are treated as cylindrically symmetric, rod-like objects interacting via a Lebwohl-Lasher (LL interaction. Pure LC systems exhibit a first order phase transition into the orientationally ordered nematic phase at T=Tc on lowering the temperature T. The orientational ordering of LC molecules is perturbed by the quenched, randomly distributed rod-like impurities of concentration p. Their orientation is randomly distributed, and they are coupled with the LC molecules via an LL-type interaction. Only concentrations below the percolation threshold are considered. The key macroscopic characteristics of perturbed LC structures in the symmetry-broken nematic phase are analyzed for two qualitatively different histories at T≪Tc. We demonstrate that, for a weak enough interaction among the LC molecules and impurities, qualitatively different history-dependent states could be obtained. These states could exhibit either short-range, quasi-long-range, or even long-range order.

  6. Nematicity, magnetism and superconductivity in FeSe

    Science.gov (United States)

    Böhmer, Anna E.; Kreisel, Andreas

    2018-01-01

    Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

  7. Nematicity, magnetism and superconductivity in FeSe.

    Science.gov (United States)

    Böhmer, Anna E; Kreisel, Andreas

    2018-01-17

    Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

  8. Optimization of electrically tunable VCSEL with intracavity nematic liquid crystal.

    Science.gov (United States)

    Belmonte, Carlos; Frasunkiewicz, Leszek; Czyszanowski, Tomasz; Thienpont, Hugo; Beeckman, Jeroen; Neyts, Kristiaan; Panajotov, Krassimir

    2015-06-15

    We optimize the wavelength tuning range of a Vertical-Cavity Surface-Emitting Laser with an intracavity layer of nematic Liquid Crystal (LC-VCSEL) lasing around 1.3 μm. The tunability is obtained by applying voltage to the liquid crystal layer, which esentially is to vary the refractive index from the extraordinary to the ordinary. We achieve 71.6 nm continuous tuning (without mode hopping) with liquid crystal thickness of about 3.2 μm. We investigate the impact of ambient temperature on the LC-VCSEL tuning range and show that mode-hop tuning can be achieved in the temperature range from -10°C to 50°C where the LC is in nematic phase.

  9. Hierarchical elasticity of bimesogenic liquid crystals with twist-bend nematic phase

    Science.gov (United States)

    Yun, Chang-Jun; Vengatesan, M. R.; Vij, Jagdish K.; Song, Jang-Kun

    2015-04-01

    In 2001, Dozov predicted that twist-bend nematic phase can be spontaneously formed when K33 2, and this phase has recently been discovered in bimesogens. To verify Dozov's hypothesis, we have measured precisely the temperature dependence of the elastic constants of CB7CB in the entire temperature range of nematic phase and in twist-bend nematic phase close to the transition temperature by combing the Fréedericksz threshold methods for a twist nematic and an in-plane switching cells. Anomalous changes in K22 and K33 are observed across the phase transition. The elasticity estimated via extrapolation of the data in the high temperature region of the nematic phase seems to fully satisfy Dozov's hypothesis although the elasticity data in the vicinity of the phase transition exhibit opposite trends. This can be explained by the general nature of a hierarchical system where the macroscopic elasticity is governed mostly by the distortion of a higher level structure.

  10. Fluctuation Modes of a Twist-Bend Nematic Liquid Crystal

    Directory of Open Access Journals (Sweden)

    Z. Parsouzi

    2016-06-01

    Full Text Available We report a dynamic light-scattering study of the fluctuation modes in a thermotropic liquid crystalline mixture of monomer and dimer compounds that exhibits the twist-bend nematic (N_{TB} phase. The results reveal a spectrum of overdamped fluctuations that includes two nonhydrodynamic modes and one hydrodynamic mode in the N_{TB} phase, and a single nonhydrodynamic mode plus two hydrodynamic modes (the usual nematic optic axis or director fluctuations in the higher temperature, uniaxial nematic phase. The properties of these fluctuations and the conditions for their observation are comprehensively explained by a Landau-de Gennes expansion of the free-energy density in terms of heliconical director and helical polarization fields that characterize the N_{TB} structure, with the latter serving as the primary order parameter. A “coarse-graining” approximation simplifies the theoretical analysis and enables us to demonstrate quantitative agreement between the calculated and experimentally determined temperature dependence of the mode relaxation rates.

  11. Nematic and chiral superconductivity induced by odd-parity fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Fengcheng; Martin, Ivar

    2017-10-01

    Recent experiments indicate that superconductivity in Bi2Se3 intercalated with Cu, Nb, or Sr is nematic with rotational symmetry breaking. Motivated by this observation, we present a model study of nematic and chiral superconductivity induced by odd-parity fluctuations. We show that odd-parity fluctuations in the two-component E-u representation of D-3d crystal point group can generate attractive interaction in both the even-parity s-wave and odd-parity E-u pairing channels, but repulsive interaction in other odd-parity pairing channels. Coulomb repulsion can suppress s-wave pairing relative to E-u pairing, and thus the latter can have a higher critical temperature. E-u pairing has two distinct phases: a nematic phase and a chiral phase, both of which can be realized in our model. When s-wave and E-u pairings have similar instability temperature, we find an intermediate phase in which both types of pairing coexist.

  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. Molecular dynamics of a binary mixture of twist-bend nematic liquid crystal dimers studied by dielectric spectroscopy

    Science.gov (United States)

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

    2016-06-01

    We report a comprehensive dielectric characterization of a liquid crystalline binary mixture composed of the symmetric mesogenic dimer CB7CB and the nonsymmetric mesogenic dimer FFO9OCB. In addition to the high-temperature nematic phase, such a binary mixture shows a twist-bend nematic phase at room temperature which readily vitrifies on slow cooling. Changes in the conformational distribution of the dimers are reflected in the dielectric permittivity and successfully analyzed by means of an appropriate theoretical model. It is shown that the dielectric spectra of the mixture reflect the different molecular dipole properties of the components, resembling in the present case the characteristic dielectric spectra of nonsymmetric dimers. Comparison of the nematic and twist-bend nematic phases reveals that molecular dynamics are similar despite the difference in the molecular environment.

  14. Active nematic gels as active relaxing solids

    Science.gov (United States)

    Turzi, Stefano S.

    2017-11-01

    I propose a continuum theory for active nematic gels, defined as fluids or suspensions of orientable rodlike objects endowed with active dynamics, that is based on symmetry arguments and compatibility with thermodynamics. The starting point is our recent theory that models (passive) nematic liquid crystals as relaxing nematic elastomers. The interplay between viscoelastic response and active dynamics of the microscopic constituents is naturally taken into account. By contrast with standard theories, activity is not introduced as an additional term of the stress tensor, but it is added as an external remodeling force that competes with the passive relaxation dynamics and drags the system out of equilibrium. In a simple one-dimensional channel geometry, we show that the interaction between nonuniform nematic order and activity results in either a spontaneous flow of particles or a self-organization into subchannels flowing in opposite directions.

  15. Mesoscale structure of chiral nematic shells.

    Science.gov (United States)

    Zhou, Ye; Guo, Ashley; Zhang, Rui; Armas-Perez, Julio C; Martínez-González, José A; Rahimi, Mohammad; Sadati, Monirosadat; de Pablo, Juan J

    2016-11-09

    There is considerable interest in understanding and controlling topological defects in nematic liquid crystals (LCs). Confinement, in the form of droplets, has been particularly effective in that regard. Here, we employ a Landau-de Gennes formalism to explore the geometrical frustration of nematic order in shell geometries, and focus on chiral materials. By varying the chirality and thickness in uniform shells, we construct a phase diagram that includes tetravalent structures, bipolar structures (BS), bent structures and radial spherical structures (RSS). It is found that, in uniform shells, the BS-to-RSS structural transition, in response to both chirality and shell geometry, is accompanied by an abrupt change of defect positions, implying a potential use for chiral nematic shells as sensors. Moreover, we investigate thickness heterogeneity in shells and demonstrate that non-chiral and chiral nematic shells exhibit distinct equilibrium positions of their inner core that are governed by shell chirality c.

  16. Geometry of Thin Nematic Elastomer Sheets

    Science.gov (United States)

    Aharoni, Hillel; Sharon, Eran; Kupferman, Raz

    2014-12-01

    A thin sheet of nematic elastomer attains 3D configurations depending on the nematic director field upon heating. In this Letter, we describe the intrinsic geometry of such a sheet and derive an expression for the metric induced by general nematic director fields. Furthermore, we investigate the reverse problem of constructing a director field that induces a specified 2D geometry. We provide an explicit recipe for how to construct any surface of revolution using this method. Finally, we show that by inscribing a director field gradient across the sheet's thickness, one can obtain a nontrivial hyperbolic reference curvature tensor, which together with the prescription of a reference metric allows dictation of actual configurations for a thin sheet of nematic elastomer.

  17. Solution landscapes in nematic microfluidics

    Science.gov (United States)

    Crespo, M.; Majumdar, A.; Ramos, A. M.; Griffiths, I. M.

    2017-08-01

    We study the static equilibria of a simplified Leslie-Ericksen model for a unidirectional uniaxial nematic flow in a prototype microfluidic channel, as a function of the pressure gradient G and inverse anchoring strength, B. We numerically find multiple static equilibria for admissible pairs (G , B) and classify them according to their winding numbers and stability. The case G = 0 is analytically tractable and we numerically study how the solution landscape is transformed as G increases. We study the one-dimensional dynamical model, the sensitivity of the dynamic solutions to initial conditions and the rate of change of G and B. We provide a physically interesting example of how the time delay between the applications of G and B can determine the selection of the final steady state.

  18. Local nematic susceptibility in stressed BaFe2As2 from NMR electric field gradient measurements

    Science.gov (United States)

    Kissikov, T.; Sarkar, R.; Lawson, M.; Bush, B. T.; Timmons, E. I.; Tanatar, M. A.; Prozorov, R.; Bud'ko, S. L.; Canfield, P. C.; Fernandes, R. M.; Goh, W. F.; Pickett, W. E.; Curro, N. J.

    2017-12-01

    The electric field gradient (EFG) tensor at the 75As site couples to the orbital occupations of the As p orbitals and is a sensitive probe of local nematicity in BaFe2As2 . We use nuclear magnetic resonance to measure the nuclear quadrupolar splittings and find that the EFG asymmetry responds linearly to the presence of a strain field in the paramagnetic phase. We extract the nematic susceptibility from the slope of this linear response as a function of temperature and find that it diverges near the structural transition, in agreement with other measures of the bulk nematic susceptibility. Our work establishes an alternative method to extract the nematic susceptibility which, in contrast to transport methods, can be extended inside the superconducting state.

  19. Two-Dimensional Skyrmion Lattice Formation in a Nematic Liquid Crystal Consisting of Highly Bent Banana Molecules.

    Science.gov (United States)

    Kang, Sungmin; Lee, Eun-Woo; Li, Tianqi; Liang, Xiaobin; Tokita, Masatoshi; Nakajima, Ken; Watanabe, Junji

    2016-09-12

    We synthesized a novel banana-shaped molecule based on a 1,7-naphthalene central core that exhibits a distinct mesomorphism of the nematic-to-nematic phase transition. Both the X-ray profile and direct imaging of atomic force microscopy (AFM) investigations clearly indicates the formation of an anomalous nematic phase possessing a two-dimensional (2D) tetragonal lattice with a large edge (ca. 59 Å) directed perpendicular to the director in the low-temperature nematic phase. One plausible model is proposed by an analogy of skyrmion lattice in which two types of cylinders formed from left- and right-handed twist-bend helices stack into a 2D tetragonal lattice, diminishing the inversion domain wall. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Nuclear magnetic resonance spectroscopic investigations of phase biaxiality in the nematic glass of a shape-persistent V-shaped mesogen.

    Science.gov (United States)

    Figueirinhas, João L; Feio, Gabriel; Cruz, Carlos; Lehmann, Matthias; Köhn, Christiane; Dong, Ronald Y

    2010-11-07

    Deuterium and carbon-13 NMR spectroscopy were used to study both the high temperature uniaxial nematic and the low temperature biaxial nematic glass of a shape-persistent V-shaped mesogen. It was found that biaxial ordering determined in the domains of the latter has symmetry lower than D(2h) and is compatible with C(2h) symmetry or lower. In particular, elements of the ordering matrix including biaxial phase order parameters were determined from (2)H NMR at two temperatures, one just below the glass transition, and the other deep inside the biaxial glass, which allowed for the characterization of the dominant molecular motions at these temperatures. (13)C NMR magic angle spinning sideband patterns, collected both in the high temperature nematic phase and in the nematic glass, clearly show the difference between them in terms of the phase symmetry.

  1. Optical anisotropy in the electronic nematic phase of FeSe

    Science.gov (United States)

    Chinotti, M.; Pal, A.; Degiorgi, L.; Böhmer, A. E.; Canfield, P. C.

    2017-09-01

    At ambient pressure, FeSe undergoes a structural, tetragonal-to-orthorhombic, phase transition at Ts≃90 K without any magnetic ordering on further cooling. FeSe thus provides an arena for examining the nematic phase without the complications following the reconstruction of the Fermi surface due to the antiferromagnetic order within the orthorhombic state. We perform an optical-reflectivity investigation across the structural transition, as a function of uniaxial stress in order to detwin the specimen. These measurements reveal a hysteretic behavior of the anisotropic optical response to uniaxial stress for T ≤Ts , which extends to energy scales of about 0.5 eV. The sign changes of the optical anisotropy between distinct energy intervals suggest a complex evolution of the polarized electronic structure in the nematic phase. The temperature dependence of the optical anisotropy for the fully detwinned specimen is furthermore acting as a proxy for the order parameter of nematicity.

  2. 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

  3. Neutron Scattering Study of Transitions to Convection and Turbulence in Nematic Para-Azoxyanisole

    DEFF Research Database (Denmark)

    Bjerrum Møller, Hans; Riste, T.

    1975-01-01

    The critical temperature gradients for the onset of convection and turbulence were measured in nematic para-azoxyanisole. The transition to turbulence was found to occur through two successive instabilities. The first of these clearly signals the entrance to a periodic-motion regime, and the second...

  4. Nematic fluctuations and resonance in iron-based superconductors

    Science.gov (United States)

    Gallais, Yann

    The spontaneous appearance of nematicity, a state of matter that breaks rotation but not translation symmetry, is ubiquitous in many iron based superconductors (Fe SC), and has relevance for the cuprates as well. Here I will review recent electronic Raman scattering experiments which report the presence of critical nematic fluctuations in the charge channel in the tetragonal phase of several Fe SC systems. In electron doped Co-BaFe2As2 (Co-Ba122), these fluctuations extend over most of the superconducting dome. Their associated nematic susceptibility shows Curie-Weiss behavior, and its doping dependence suggests the presence of a nematic quantum critical point near optimal TC Similar nematic fluctuations are also observed in FeSe despite the absence of magnetic order, raising the question of the link between nematicity and magnetism in Fe SC. In FeSe I will further contrast the evolution of nematic fluctuations under isoelectronic S substitution and hydrostatic pressures up to 8 GPa, with only the former showing evidence for a nematic quantum critical point. In the superconducting state of Co-Ba122, I will show that a resonance emerges in the Raman spectra near the nematic quantum critical point. This nematic resonance is a clear fingerprint of the coupling between nematic fluctuations and Bogoliubov quasiparticles, and can be thought as the nematic counterpart of the spin resonance observed in neutron scattering experiments. Support from Agence Nationale de la Recherche via ANR Grant ''Pnictides'' is acknowledged.

  5. 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.

  6. Nematic phase in the J(1)-J(2) square-lattice Ising model in an external field.

    Science.gov (United States)

    Guerrero, Alejandra I; Stariolo, Daniel A; Almarza, Noé G

    2015-05-01

    The J(1)-J(2) Ising model in the square lattice in the presence of an external field is studied by two approaches: the cluster variation method (CVM) and Monte Carlo simulations. The use of the CVM in the square approximation leads to the presence of a new equilibrium phase, not previously reported for this model: an Ising-nematic phase, which shows orientational order but not positional order, between the known stripes and disordered phases. Suitable order parameters are defined, and the phase diagram of the model is obtained. Monte Carlo simulations are in qualitative agreement with the CVM results, giving support to the presence of the new Ising-nematic phase. Phase diagrams in the temperature-external field plane are obtained for selected values of the parameter κ=J(2)/|J(1)| which measures the relative strength of the competing interactions. From the CVM in the square approximation we obtain a line of second order transitions between the disordered and nematic phases, while the nematic-stripes phase transitions are found to be of first order. The Monte Carlo results suggest a line of second order nematic-disordered phase transitions in agreement with the CVM results. Regarding the stripes-nematic transitions, the present Monte Carlo results are not precise enough to reach definite conclusions about the nature of the transitions.

  7. Synthesis and characterization of three-arm star-shaped glassy ...

    African Journals Online (AJOL)

    The transition temperatures and phase behaviors were studied by Differential Scanning Calorimetry (DSC), Polarizing Optical Microscopy (POM) and X-Ray diffraction analyses. All the synthesized compounds exhibited enantiotropic nematic phase and the stability of the mesophase depends on the length of the terminal ...

  8. 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.

  9. 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.

  10. 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.

  11. Effect of Potential Range in Pressure-Temperature Behavior in Isotropic-Nematic Transition of 4-4´-Bis(EthyloxyAzoxybenzene (P-Azoxyphenetole, Pap, 4-Pentyl-4´-Cyanobiphenyl (5cb, P-Methoxybenzydidene-P-N-Butylaniline (Mbba and P–Ethoxybenzylidene–P–N-Butylaniline (Ebba

    Directory of Open Access Journals (Sweden)

    García-Sánchez E.

    2011-04-01

    Full Text Available In this work we employed the Density Functional Theory (IPCM model to calculate molecular volume and k, and the perturbation theory proposed by García-Sánchez et al. (2002 to predict phase diagram and experimental behavior pressure-temperature for isotropic-nematic transition of 4-4´-bis(ethyloxyazoxybenzene (p-azoxyphenetole, PAP, 4-pentyl-4´-cyanobiphenyl (5CB, p-methoxybenzydidene-p-n-butylaniline (MBBA and p–ethoxybenzylidene–p–n-butylaniline (EBBA at 1 atm. If during the theoretical prediction bigger potential values of potential range of square well (l > k are considered in the theoretical model, it is possible to get better prediction of the experimental behavior. The above mentioned is according with the theoretical formulation of the Second Order Perturbation Theory since Ponce-Renon approximation is included.

  12. Hydrodynamic Effects in Oscillatory Active Nematics

    Science.gov (United States)

    Mikhailov, Alexander S.; Koyano, Yuki; Kitahata, Hiroyuki

    2017-10-01

    Oscillatory active nematics represent nonequilibrium suspensions of microscopic objects, such as natural or artificial molecular machines, that cyclically change their shapes and thus operate as oscillating force dipoles. In this mini-review, hydrodynamic collective effects in such active nematics are discussed. Microscopic stirring at low Reynolds numbers induces non-thermal fluctuating flows and passive particles become advected by them. Similar to advection of particles in macroscopic turbulent flows, this enhances diffusion of tracer particles. Furthermore, their drift and accumulation in regions with stronger activity or higher concentration of force dipoles take place. Analytical investigations and numerical simulations both for 2D and 3D systems were performed.

  13. Functional polypedes—chiral nematic fullerenes

    OpenAIRE

    Campidelli, Stéphane; Eng, Carine; Saez, Isabel M.; Goodby, John W.; Deschenaux, Robert

    2006-01-01

    Self-organising, functional materials created by bottom-up synthesis represent important steps forward in the development of novel materials, here we report on the preparation and properties of a chiral nematic tetrapedal liquid crystal that has been functionalised with C60.

  14. Isotropic-nematic spinodal decomposition dynamics

    NARCIS (Netherlands)

    Dhont, Jan K.G.; Briels, Willem J.

    2005-01-01

    The initial stage of isotropic-nematic spinodal demixing kinetics of suspensions of very long and thin, stiff, repulsive rods is analyzed on the basis of the N -particle Smoluchowski equation. Equations of motion for the reduced probability density function of the position and orientation of a rod

  15. Phase behavior and properties of the liquid-crystal dimer 1'',7''-bis(4-cyanobiphenyl-4'-yl) heptane: a twist-bend nematic liquid crystal.

    Science.gov (United States)

    Cestari, M; Diez-Berart, S; Dunmur, D A; Ferrarini, A; de la Fuente, M R; Jackson, D J B; Lopez, D O; Luckhurst, G R; Perez-Jubindo, M A; Richardson, R M; Salud, J; Timimi, B A; Zimmermann, H

    2011-09-01

    The liquid-crystal dimer 1'',7''-bis(4-cyanobiphenyl-4'-yl)heptane (CB7CB) exhibits two liquid-crystalline mesophases on cooling from the isotropic phase. The high-temperature phase is nematic; the identification and characterization of the other liquid-crystal phase is reported in this paper. It is concluded that the low-temperature mesophase of CB7CB is a new type of uniaxial nematic phase having a nonuniform director distribution composed of twist-bend deformations. The techniques of small-angle x-ray scattering, modulated differential scanning calorimetry, and dielectric spectroscopy have been applied to establish the nature of the nematic-nematic phase transition and the structural features of the twist-bend nematic phase. In addition, magnetic resonance studies (electron-spin resonance and (2)H nuclear magnetic resonance) have been used to investigate the orientational order and director distribution in the liquid-crystalline phases of CB7CB. The synthesis of a specifically deuterated sample of CB7CB is reported, and measurements showed a bifurcation of the quadrupolar splitting on entering the low-temperature mesophase from the high-temperature nematic phase. This splitting could be interpreted in terms of the chirality of the twist-bend structure of the director. Calculations using an atomistic model and the surface interaction potential with Monte Carlo sampling have been carried out to determine the conformational distribution and predict dielectric and elastic properties in the nematic phase. The former are in agreement with experimental measurements, while the latter are consistent with the formation of a twist-bend nematic phase.

  16. 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.

  17. Domain walls and anchoring transitions mimicking nematic biaxiality in the oxadiazole bent-core liquid crystal C7.

    Science.gov (United States)

    Kim, Young-Ki; Cukrov, Greta; Xiang, Jie; Shin, Sung-Tae; Lavrentovich, Oleg D

    2015-05-28

    We investigate the origin of "secondary disclinations" that were recently described as new evidence of a biaxial nematic phase in an oxadiazole bent-core thermotropic liquid crystal C7. Using an assortment of optical techniques such as polarizing optical microscopy, LC PolScope, and fluorescence confocal polarizing microscopy, we demonstrate that the secondary disclinations represent non-singular domain walls formed in a uniaxial nematic phase during the surface anchoring transition, in which surface orientation of the director changes from tangential (parallel to the bounding plates) to tilted. Each domain wall separates two regions with the director tilted in opposite azimuthal directions. At the centre of the wall, the director remains parallel to the bounding plates. The domain walls can be easily removed by applying a moderate electric field. The anchoring transition is explained by the balance of (a) the intrinsic perpendicular surface anchoring produced by the polyimide aligning layer and (b) tangential alignment caused by ionic impurities forming electric double layers. The model is supported by the fact that the temperature of the tangentially tilted anchoring transition decreases as the cell thickness increases and as the concentration of ionic species (added salt) increases. We also demonstrate that the surface alignment is strongly affected by thermal degradation of the samples. This study shows that C7 exhibits only a uniaxial nematic phase and demonstrates yet another mechanism (formation of "secondary disclinations") by which a uniaxial nematic phase can mimic a biaxial nematic behaviour.

  18. Light-controllable linear dichroism in nematics.

    Science.gov (United States)

    Petriashvili, Gia; Hamdi, Ridha; De Santo, Maria Penelope; Gary, Ramla; Barberi, Riccardo

    2015-10-01

    We report a method to obtain a light-controllable dichroism. The main effect is achieved using spiropyran-doped (SP-doped) nematic liquid crystal mixtures. SP molecules exhibit a high solubility in the liquid crystal host, which can vary between 1% and 4% in weight, without destroying the liquid crystalline phase. Due to their elongated shape, SP molecules are oriented along the nematic liquid crystal director. The obtained linear dichroism was measured to be 1.08 with a dichroic ratio of 7.12. Further, a two-direction linear dichroism was obtained by adding a dichroic dye to the mixture. The angle between the two dichroic axes was found to be 11°. Two-direction linear dichroism is also light controllable and can be switched back to one-direction dichroism.

  19. Actuation of Thin Nematic Elastomer Sheets with Controlled Heterogeneity

    Science.gov (United States)

    Plucinsky, Paul; Lemm, Marius; Bhattacharya, Kaushik

    2017-09-01

    Nematic elastomers and glasses deform spontaneously when subjected to temperature changes. This property can be exploited in the design of heterogeneously patterned thin sheets that deform into a non-trivial shape when heated or cooled. In this paper, we start from a variational formulation for the entropic elastic energy of liquid crystal elastomers and we derive an effective two-dimensional metric constraint, which links the deformation and the heterogeneous director field. Our main results show that satisfying the metric constraint is both necessary and sufficient for the deformation to be an approximate minimizer of the energy. We include several examples which show that the class of deformations satisfying the metric constraint is quite rich.

  20. Post-Tanner spreading of nematic droplets

    Energy Technology Data Exchange (ETDEWEB)

    Mechkov, S; Oshanin, G [Laboratoire de Physique Theorique de la Matiere Condensee, Universite Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 5 (France); Cazabat, A M, E-mail: mechkov@lptmc.jussieu.f, E-mail: anne-marie.cazabat@lps.ens.f, E-mail: oshanin@lptmc.jussieu.f [Laboratoire de Physique Statistique, Ecole Normale Superieure, 75252 Paris Cedex 5 (France)

    2009-11-18

    The quasistationary spreading of a circular liquid drop on a solid substrate typically obeys the so-called Tanner law, with the instantaneous base radius R(t) growing with time as Rapproxt{sup 1/10}-an effect of the dominant role of capillary forces for a small-sized droplet. However, for droplets of nematic liquid crystals, a faster spreading law sets in at long times, so that Rapproxt{sup a}lpha with alpha significantly larger than the Tanner exponent 1/10. In the framework of the thin film model (or lubrication approximation), we describe this 'acceleration' as a transition to a qualitatively different spreading regime driven by a strong substrate-liquid interaction specific to nematics (antagonistic anchoring at the interfaces). The numerical solution of the thin film equation agrees well with the available experimental data for nematics, even though the non-Newtonian rheology has yet to be taken into account. Thus we complement the theory of spreading with a post-Tanner stage, noting that the spreading process can be expected to cross over from the usual capillarity-dominated stage to a regime where the whole reservoir becomes a diffusive film in the sense of Derjaguin.

  1. Study of Memory Alignment of Nematic Liquid Crystals on Polyvinyl Alcohol Coatings

    Science.gov (United States)

    Vetter, Peter; Ohmura, Yoshinori; Uchida, Tatsuo

    1993-09-01

    Polymer layers can cause memory alignment of nematic liquid crystals. We describe an experimental method to characterize this effect. We studied the temperature dependence of the memory alignment on polyvinyl alcohol coatings. We also investigated the influence of the time span during which the memory alignment is generated. We propose an adsorption-desorption mechanism by which we can explain our observations in a reasonable way.

  2. Colloidal interactions in two-dimensional nematic emulsions

    Indian Academy of Sciences (India)

    Abstract. We review theoretical and experimental work on colloidal interactions in two- dimensional (2D) nematic emulsions. We pay particular attention to the effects of (i) the nematic elastic constants, (ii) the size of the colloids, and (iii) the boundary conditions at the particles and the container. We consider the interactions ...

  3. Nematic fluctuations, fermiology and the pairing potential in iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kretzschmar, Florian

    2015-08-18

    The thesis comprises a systematic study on the doping, temperature and momentum dependent electron dynamics in iron-based superconductors using inelastic light scattering. The observation of Bardasis-Schrieffer modes in the excitation spectrum of superconducting Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2} is reported and the energy and symmetry dependence of the modes are analyzed. The analysis yields the identification of a strong subdominant component of the interaction potential V(k,k{sup '}). Strong nematic fluctuations are investigated in Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2}. The nature of the fluctuations and the origin of nematicity in Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} are identified.

  4. Ultrafast Critical Nematic Fluctuations and Giant Magnetoelastic Coupling in Iron Pnictide

    Science.gov (United States)

    Patz, Aaron; Li, Tianqi; Ran, Sheng; Fernandes, Rafael; Schmalian, Joerg; Bud'Ko, Sergey; Canfield, Paul; Perakis, Ilias; Wang, Jigang

    2014-03-01

    A ubiquitous anisotropy in the normal state properties of many of the iron pnictides presents a crosscutting challenge important for understanding quantum magnetism and high-temperature superconductivity. Although an electronically-driven nematicity has been invoked, distinguishing this from spin and structural orders is challenging because they all couple together to break the same tetragonal symmetry. Here we use femtosecond-resolved polarimetry to reveal critical fluctuations of nematic correlation in unstrained Ba(Fe1-xCox)2As2. The ultrafast anisotropic response, which arises from the two-fold in-plane anisotropy of the refractive index, displays a characteristic two-step recovery absent in the isotropic response. The fast recovery appears only in the magnetically ordered state, whereas the slow one persists in the paramagnetic phase, with increasing relaxation time, indicative of critical nematic fluctuations approaching the structural transition temperature. The dynamics reveal a gigantic magnetoelastic coupling that far exceeds electron-spin and electron-phonon couplings, opposite to conventional magnetic metals. Supported by the NSF and THALES program NANOPHOS.

  5. 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.

  6. Symmetry breaking in nematic liquid crystals: analogy with cosmology and magnetism.

    Science.gov (United States)

    Repnik, R; Ranjkesh, A; Simonka, V; Ambrozic, M; Bradac, Z; Kralj, S

    2013-10-09

    Universal behavior related to continuous symmetry breaking in nematic liquid crystals is studied using Brownian molecular dynamics. A three-dimensional lattice system of rod-like objects interacting via the Lebwohl-Lasher interaction is considered. We test the applicability of predictions originally derived in cosmology and magnetism. In the first part we focus on coarsening dynamics following the temperature driven isotropic-nematic phase transition for different quench rates. The behavior in the early coarsening regime supports predictions made originally by Kibble in cosmology. For fast enough quenches, symmetry breaking and causality give rise to a dense tangle of defects. When the degree of orientational ordering is large enough, well defined protodomains characterized by a single average domain length are formed. With time subcritical domains gradually vanish and supercritical domains grow with time, exhibiting a universal scaling law. In the second part of the paper we study the impact of random-field-type disorder on a range of ordering in the (symmetry broken) nematic phase. We demonstrate that short-range order is observed even for a minute concentration of impurities, giving rise to disorder in line with the Imry-Ma theorem prediction only for the appropriate history of systems.

  7. 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.

  8. In-plane anisotropy of transport coefficients in electronic nematic states: Universal origin of nematicity in Fe-based superconductors

    Science.gov (United States)

    Onari, Seiichiro; Kontani, Hiroshi

    2017-09-01

    The origin of the electronic nematicity and its remarkable material dependence are famous longstanding unsolved issues in Fe-based superconductors. To attack these issues, we focus on the in-plane anisotropy of the resistivity: In the nematic state in FeSe, the relation ρx>ρy holds, where ρx (y ) is the resistivity along the longer (shorter) Fe-Fe axis. In contrast, the opposite anisotropy ρxρy ) and other undoped compounds (ρxplane anisotropy of the thermoelectric power in the nematic state.

  9. Defect driven shapes in nematic droplets: analogies with cell division

    CERN Document Server

    Leoni, Marco; Bowick, Mark J; Marchetti, M Cristina

    2016-01-01

    Building on the striking similarity between the structure of the spindle during mitosis in living cells and nematic textures in confined liquid crystals, we use a continuum model of two-dimensional nematic liquid crystal droplets, to examine the physical aspects of cell division. The model investigates the interplay between bulk elasticity of the microtubule assembly, described as a nematic liquid crystal, and surface elasticity of the cell cortex, modelled as a bounding flexible membrane, in controlling cell shape and division. The centrosomes at the spindle poles correspond to the cores of the topological defects required to accommodate nematic order in a closed geometry. We map out the progression of both healthy bipolar and faulty multi-polar division as a function of an effective parameter that incorporates active processes and controls centrosome separation. A robust prediction, independent of energetic considerations, is that the transition from a single cell to daughters cells occurs at critical value...

  10. Defect dynamics and ordering in compressible active nematics

    Science.gov (United States)

    Mishra, Prashant; Srivastava, Pragya; Marchetti, M. Cristina

    Active nematics, such as suspensions of biopolymers activated by molecular motors or bacteria swimming in passive liquid crystals, exhibit complex self-sustained flow, excitability and defect generation. Activity renders the defect themselves self-propelled particles, capable of organizing in emergent ordered structures. We have developed a minimal model of compressible active nematics on a substrate. We eliminate the flow velocity in favor of the nematic order parameter via the balance of frictional dissipation and active driving to obtain a dynamical description entirely in terms of the nematic alignment order parameter. Activity renormalizes the bend and splay elastic constants rendering them anisotropic and driving them to zero or even negative, resulting in the appearance of modulated states and defective structures. Using linear stability analysis and numerics we organize the various regimes into a phase diagram and discuss the relation to experiments. This work was supported by NSF-DMR-1305184.

  11. Spherical nematic shells with a threefold valence

    Science.gov (United States)

    Koning, Vinzenz; Lopez-Leon, Teresa; Darmon, Alexandre; Fernandez-Nieves, Alberto; Vitelli, V.

    2016-07-01

    We present a theoretical study of the energetics of thin nematic shells with two charge-one-half defects and one charge-one defect. We determine the optimal arrangement: the defects are located on a great circle at the vertices of an isosceles triangle with angles of 66∘ at the charge-one-half defects and a distinct angle of 48∘, consistent with experimental findings. We also analyze thermal fluctuations around this ground state and estimate the energy as a function of thickness. We find that the energy of the three-defect shell is close to the energy of other known configurations having two charge-one and four charge-one-half defects. This finding, together with the large energy barriers separating one configuration from the others, explains their observation in experiments as well as their long-time stability.

  12. Dancing disclinations in confined active nematics

    Science.gov (United States)

    Shendruk, Tyler N.; Doostmohammadi, Amin; Thijssen, Kristian; Yeomans, Julia M.

    The spontaneous emergence of collective flows is a generic property of active fluids and often leads to chaotic flow patterns characterised by swirls, jets, and topological disclinations in their orientation field. However, the ability to achieve structured flows and ordered disclinations is of particular importance in the design and control of active systems. By confining an active nematic fluid within a channel, we find a regular motion of disclinations, in conjunction with a well defined and dynamic vortex lattice. As pairs of moving disclinations travel through the channel, they continually exchange partners producing a dynamic ordered state, reminiscent of Ceilidh dancing. We anticipate that this biomimetic ability to self-assemble organised topological disclinations and dynamically structured flow fields in engineered geometries will pave the road towards establishing new active topological microfluidic devices.

  13. Isotropic-Nematic Phase Transitions in Gravitational Systems

    Science.gov (United States)

    Roupas, Zacharias; Kocsis, Bence; Tremaine, Scott

    2017-06-01

    We examine dense self-gravitating stellar systems dominated by a central potential, such as nuclear star clusters hosting a central supermassive black hole. Different dynamical properties of these systems evolve on vastly different timescales. In particular, the orbital-plane orientations are typically driven into internal thermodynamic equilibrium by vector resonant relaxation before the orbital eccentricities or semimajor axes relax. We show that the statistical mechanics of such systems exhibit a striking resemblance to liquid crystals, with analogous ordered-nematic and disordered-isotropic phases. The ordered phase consists of bodies orbiting in a disk in both directions, with the disk thickness depending on temperature, while the disordered phase corresponds to a nearly isotropic distribution of the orbit normals. We show that below a critical value of the total angular momentum, the system undergoes a first-order phase transition between the ordered and disordered phases. At a critical point, the phase transition becomes second order, while for higher angular momenta there is a smooth crossover. We also find metastable equilibria containing two identical disks with mutual inclinations between 90° and 180°.

  14. Isotropic–Nematic Phase Transitions in Gravitational Systems

    Energy Technology Data Exchange (ETDEWEB)

    Roupas, Zacharias; Kocsis, Bence [Institute of Physics, Eötvös University, Pázmány P. s. 1/A, Budapest, 1117 (Hungary); Tremaine, Scott [Institute for Advanced Study, Princeton, NJ 08540 (United States)

    2017-06-20

    We examine dense self-gravitating stellar systems dominated by a central potential, such as nuclear star clusters hosting a central supermassive black hole. Different dynamical properties of these systems evolve on vastly different timescales. In particular, the orbital-plane orientations are typically driven into internal thermodynamic equilibrium by vector resonant relaxation before the orbital eccentricities or semimajor axes relax. We show that the statistical mechanics of such systems exhibit a striking resemblance to liquid crystals, with analogous ordered-nematic and disordered-isotropic phases. The ordered phase consists of bodies orbiting in a disk in both directions, with the disk thickness depending on temperature, while the disordered phase corresponds to a nearly isotropic distribution of the orbit normals. We show that below a critical value of the total angular momentum, the system undergoes a first-order phase transition between the ordered and disordered phases. At a critical point, the phase transition becomes second order, while for higher angular momenta there is a smooth crossover. We also find metastable equilibria containing two identical disks with mutual inclinations between 90° and 180°.

  15. Laser damage resistant nematic liquid crystal cell

    Science.gov (United States)

    Raszewski, Z.; Piecek, W.; Jaroszewicz, L.; Soms, L.; Marczak, J.; Nowinowski-Kruszelnicki, E.; Perkowski, P.; Kedzierski, J.; Miszczyk, E.; Olifierczuk, M.; Morawiak, P.; Mazur, R.

    2013-08-01

    There exists a problem in diagnostics of a dense plasma (so-called Thomson diagnostics). For this purpose, the plasma is illuminated by series of high energy laser pulses. Such pulses are generated by several independent lasers operating sequentially, and these pulses are to be directed along an exactly the same optical path. In this case, the energy of each separate pulse is as large as 3 J, so it is impossible to generate a burst of such pulses by a single laser. In this situation, several independent lasers have to be used. To form optical path with λ = 1.064 μm and absolute value of the energy of laser pulse through of 3 J, a special refractive index matched twisted Nematic Liquid Crystal Cell (NLCC) of type LCNP2 with switching on time τON smaller than 5 μs might be applied. High laser damage resistance of NLCC and short τON can be fulfilled by preparation of liquid crystal cells with Liquid Crystal Mixture (LCM), well tuned to twisted nematic electro-optical effect, and well tuned all optical interfaces (Air - Antireflection - Quartz Plate - Electrode - Blocking Film - Aligning Layer - LCM - Aligning Layer - Blocking Film - Electrode - Quartz Plate - Antireflection - Air). In such LCNP2 cell, the transmission is higher than 97% at λ = 1.064 μm, as it is presented by Gooch and Tarry [J. Phys. D: Appl. Phys. 8, 1575 (1975)]. The safe laser density energy is about 0.6 J/cm2 for a train of laser pulses (λ = 1.064 μm, pulse duration 10 ns FWHM, pulse repetition rate 100 pps, train duration 10 s), so the area of liquid crystal cell tolerating 3 J through it shall be as large as 5 cm2. Due to the presence of two blocking film layers between electrodes, LCNP2 can be driven by high voltages. Switching on time smaller than τON = 5 μs was obtained under 200 V switching voltage.

  16. Influence of a magnetic field on the nematic phase of hard colloidal platelets

    NARCIS (Netherlands)

    van der Beek, D.; Davidson, P.; Wensink, H.H.; Vroege, G.J.; Lekkerkerker, H.N.W.

    2008-01-01

    We report on a study of the influence of a magnetic field on the nematic phase and the isotropic-to-nematic (IN) phase transition of hard colloidal gibbsite platelets. We find direct visual evidence of a shift of the IN transition to lower concentrations due to the magnetic field. The nematic phase

  17. SYNTHESIS AND CHARACTERIZATION OF CdS IN DIOL VANILIN LIQUID CRYSTAL MONOMER

    OpenAIRE

    Lee, H. L.; M. Abu Bakar; Ismail, J.; A. M. Issam

    2010-01-01

    Nanocomposites comprising diol-vanilin and cadmium sulfide (CdS) has been synthesized via chemical precipitation method in ethanol at refluxed temperature (160 oC) for 12 hours. CdCl2. 2.5H2O and thiourea as cadmium and sulfide precursors respectively were employed. Diol vanilin is a thermotropic liquid crystal monomer which exhibits enantiotropic nematic metaphase texture when observed under polarizing microscope and confirmed by DSC thermal stability study. A series of different mass compos...

  18. Effect of molecular architecture on the electrorheological behavior of liquid crystal polymers in nematic solvents

    Science.gov (United States)

    Chiang, Yen-Ching

    1998-11-01

    The Miesowicz viscosities of dilute nematic solutions of liquid crystal polymers (LCP) in low molar mass nematic solvents have been measured by a cone-and-plate rheometer in the presence of a saturated electric field applied perpendicular to the shear plane. For mixtures with a positive dielectric anisotropy in the presence of the electric field the nematic director is perpendicular to the velocity gradient and the viscosity measured is the Miesowicz viscosity ηc. With the electric field off the nematic director orients parallel to the shear flow direction and the viscosity measured is closed to the Miesowicz viscosity η b. Specifically, we show that main-chain LCPs strongly increase the magnitude of the electrorheological (ER) response, ηc-ηb, a side-on side chain LCP moderately increases the response, and an end- on side-chain LCP weakly increases the response. The diverse behaviors can be interpreted using theoretical arguments which assume that the LCP conformation is an ellipsoid of revolution whose orientation relative to the flow is determined by the balance between the hydrodynamic and electric torques on the fluid. For the main-chain LCP TPB10 in 5OCB, which has mesogenic groups separated by decamethylene spacers, the intrinsic Miesowicz viscosity [ηc] was found to follow a Mark-Houwink-Sakurada relationship [ηc]/propto M/sp/alpha with α~1 and the configurational relaxation time (τR) shows a strong dependence on molecular weight, τR/propto M/sp/beta with β~2. Applying a theoretical description by Brochard, these results suggest that TPB10 behaves hydrodynamically like a free-draining random coil stretched along the director. The temperature dependence of Miesowicz viscosities η c and η b of LCPs dissolved in nematic solvent E48 was also investigated. The variations in δeta c and δeta c with temperature can be described by the Brochard theory in terms of the corresponding variation of the configurational anisotropy (R///R/sb/perp) with

  19. Dichroism in solutions of C sub 70 in nematic hosts

    Energy Technology Data Exchange (ETDEWEB)

    Marcus, M.A.; Haddon, R.C.; Makhija, A.V.; Zahurak, S.F.; Kortan, A.R. (AT and T Bell Lab., Murray Hill, NJ (United States))

    1991-10-03

    The authors measured the optical absorption and dichroism of parallel-aligned samples of solutions of C{sub 70} and C{sub 60} in nematic hosts. It was found the solutions of C{sub 70} show considerable dichroism, which is attributed to the nonspherical shape of the C{sub 70} molecule. The optical absorption with the {lvec E} vector parallel to the nematic director is greater than that with {lvec E} perpendicular to the director for wavelengths between 380 and 425 nm. The sign is reversed above 425 nm.

  20. Self-assembly in chiral nematic liquid crystal

    Science.gov (United States)

    Evans, Julian; Wang, Nan; Khoo, Iam Choon; He, Sailing

    2017-08-01

    Small molecule chiral nematic LCs contain a variety of defect lines which can cause aggregation of polymers, nanoparticles and small molecule materials such as fluorescent dyes. While normal dyes suffer aggregation induced quenching a class of propeller-like dyes display aggregation induced emission (AIE), which makes them an ideal material for cholesteric lasers. Nanoparticle dispersion is necessary for switchability, while aggregation can be used as a tool to produce assembled structures. Here we discuss strategies to promote or inhibit aggregation of various materials in chiral nematics.

  1. Electrical and thermal tuning of quality factor and free spectral range of optical resonance of nematic liquid crystal microdroplets

    Science.gov (United States)

    Sofi, Junaid Ahmad; Mohiddon, M. A.; Dutta, N.; Dhara, Surajit

    2017-08-01

    We experimentally study the effect of temperature and electric field on the quality (Q ) factor and free spectral range (FSR) of whispering-gallery-mode optical resonance of dye-doped nematic liquid crystal microdroplets. Both the Q factor and the FSR are highly sensitive to the temperature and electric field and are tunable. The Q factor decreases, whereas the FSR increases substantially, with increasing temperature and electric field. The variation of the Q factor and FSR is understood based on the change in the effective refractive index and the dynamic size of the microdroplets.

  2. Binary System Exhibiting the Nematic to Twist-Bend Nematic Transition: Behavior of Permittivity and Elastic Constants.

    Science.gov (United States)

    Parthasarathi, Srividhya; Rao, D S Shankar; Palakurthy, Nani Babu; Yelamaggad, C V; Krishna Prasad, S

    2016-06-09

    We describe measurements of the permittivity and Frank elastic constant in the nematic phase of a binary system displaying a transition between the nematic (N) and the recently discovered twist-bend nematic (NTB) phase. Among the salient features observed are (i) the existence of the NTB phase even when the system is loaded with a high concentration (∼64 mol %) of a rodlike component; (ii) a clear signature in permittivity of the N-NTB transition; and (iii) a lower value of the bend elastic constant compared to the splay over a large phase space, with the difference between the two becoming a maximum for an intermediate mixture. These studies further support the surprising idea that the elastic features associated with bent molecules can be further augmented by suitable rodlike additives.

  3. The electrohydrodynamic instability in homeotropic nematic layers

    Science.gov (United States)

    Hertrich, A.; Decker, W.; Pesch, W.; Kramer, L.

    1992-11-01

    We calculate the threshold for electrohydrodynamic convection in homeotropically oriented nematic layers with negative dielectric anistropy that sets in after the bend-Fréedericksz transition to a quasi-planar alignment has taken place. Oblique rolls are found in a larger range than in the case of planar anchoring. The most interesting prediction is that in the weakly nonlinear analysis all roll solution are in fact unstable so that a direct transition to spatio-temporal chaos becomes possible. In the oblique-roll case this may be accompanied by a permanent local rotation of the director bend axis. Application of a planar magnetic field should stabilize the rolls. Nous calculons le seuil d'apparition de convection électrohydrodynamique dans des couches nématiques orientées homéotropiquement possédant une anisotropie diélectrique négative après que la transition de Fréedericksz de type courbure (bend) vers un alignement quasihorizontal ait eu lieu. Des rouleaux obliques sont observés dans un domaine plus grand que dans le cas de conditions aux limites planes. La prédiction la plus intéressante est que dans le cadre d'une analyse faiblement nonlinéaire toutes les solutions de rouleaux sont en fait instables et un passage direct vers un chaos spatio-temporel a lieu. Dans le cas de rouleaux obliques ceci peut être accompagné d'une rotation permanente locale de l'axe directeur de courbure. L'application d'un champ magnétique plan devrait stabiliser les rouleaux.

  4. Defects in liquid crystal nematic shells

    Science.gov (United States)

    Fernandez-Nieves, A.; Utada, A. S.; Vitelli, V.; Link, D. R.; Nelson, D. R.; Weitz, D. A.

    2006-03-01

    We generate water/liquid crystal (LC)/water double emulsions via recent micro-capillary fluidic devices [A. S. Utada, et.al. Science 308, 537 (2005)]. The resultant objects are stabilized against coalescence by using surfactants or adequate polymers; these also fix the boundary conditions for the director field n. We use 4-pentyl-4-cyanobiphenyl (5CB) and impose tangential boundary conditions at both water/LC interfaces by having polyvinyl alcohol (PVA) dispersed in the inner and outer water phases. We confirm recent predictions [D. R. Nelson, NanoLetters 2, 1125 (2002)] and find that four strength s=+1/2 defects are present; this is in contrast to the two s=+1 defect bipolar configuration observed for bulk spheres [A. Fernandez-Nieves, et.al. Phys. Rev. Lett. 92, 105503 (2004)]. However, these defects do not lie in the vertices of a tetrahedron but are pushed towards each other until certain equilibration distance is reached. In addition to the four defect shells, we observe shells with two s=+1 defects and even with three defects, a s=+1 and two s=+1/2. We argue these configurations arise from nematic bulk distortions that become important as the shell thickness increases. Finally, by adding a different surfactant, sodium dodecyl sulphate (SDS), to the outer phase, we can change the director boundary conditions at the outermost interface from parallel to homeotropic, to induce coalescing of the two pair of defects in the four defect shell configuration to yield two defect bipolar shells.

  5. Elastic interactions and manipulation of wire-shaped inclusions in nematic liquid crystals

    Science.gov (United States)

    Lapointe, Clayton P.

    Anisotropic particles suspended in a nematic liquid crystal disturb the alignment of the liquid crystal molecules and experience small forces and torques mediated by the elasticity of the fluid. These elastic interactions depend upon the orientation of the particle relative to the alignment of the liquid crystal as well as the nature of the molecular-scale alignment at the surface of the particle. In this thesis, I present the results of video microscopy studies on elastic interactions on ferromagnetic nanowires suspended in the nematic liquid crystal 4-pentyl-4-cyanobiphenyl (5CB). In the first part, I describe measurements that characterize the orientation-dependent elastic torque on a nanowire with longitudinal anchoring in uniformly aligned 5CB, its temperature dependence, as well as the elastic repulsion of a nanowire from a flat wall. These measurements were found to be quantitatively consistent with theoretical predictions based on the elastic properties of 5CB. In the second part of this thesis, I demonstrate that distorting the liquid crystal from a state of uniform alignment results in converting the elastic torque on a nanowire into an orientation-dependant translational force that can be utilized to reversibly manipulate the positions of isolated nanowires as well as to assemble suspensions of them into pre-designed arrays on a substrate. First, I describe measurements of an orientation-dependent levitating force on a nanowire in a twisted nematic cell. This force can be used to position nanowires to pre-determined heights above the bottom substrate by controlling their orientation with an external magnetic field. I then describe a series of experiments in which in a liquid crystal cell with a pattern of micron-scale stripe domains was used to drive nanowires held at a fixed orientation with external magnetic fields selectively into the middle of the stripe domains. In the last part of this thesis, I discuss video microscopy experiments to probe the

  6. Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers.

    Science.gov (United States)

    Xia, Yu; Lee, Elaine; Hu, Hao; Gharbi, Mohamed Amine; Beller, Daniel A; Fleischmann, Eva-Kristina; Kamien, Randall D; Zentel, Rudolf; Yang, Shu

    2016-05-18

    Controlling the molecular alignment of liquid crystal monomers (LCMs) within nano- and microstructures is essential in manipulating the actuation behavior of nematic liquid crystal elastomers (NLCEs). Here, we study how to induce uniformly vertical alignment of nematic LCMs within a micropillar array to maximize the macroscopic shape change using surface chemistry. Landau-de Gennes numerical modeling suggests that it is difficult to perfectly align LCMs vertically in every pore within a poly(dimethylsiloxane) (PDMS) mold with porous channels during soft lithography. In an untreated PDMS mold that provides homeotropic anchoring of LCMs, a radially escaped configuration of LCMs is observed. Vertically aligned LCMs, a preferred configuration for actuation, are only observed when using a PDMS mold with planar anchoring. Guided by the numerical modeling, we coat the PDMS mold with a thin layer of poly(2-hydroxyethyl methacrylate) (PHEMA), leading to planar anchoring of LCM. Confirmed by polarized optical microscopy, we observe monodomains of vertically aligned LCMs within the mold, in agreement with modeling. After curing and peeling off the mold, the resulting NLCE micropillars showed a relatively large and reversible radial strain (∼30%) when heated above the nematic to isotropic transition temperature.

  7. Q-tensor model for electrokinetics in nematic liquid crystals

    Science.gov (United States)

    Tovkach, O. M.; Conklin, Christopher; Calderer, M. Carme; Golovaty, Dmitry; Lavrentovich, Oleg D.; Viñals, Jorge; Walkington, Noel J.

    2017-05-01

    We use a variational principle to derive a mathematical model for a nematic electrolyte in which the liquid crystalline component is described in terms of a second-rank order parameter tensor. The model extends the previously developed director-based theory and accounts for the presence of disclinations and possible biaxiality. We verify the model by considering a simple but illustrative example of liquid crystal-enabled electro-osmotic flow around a stationary dielectric spherical particle placed at the center of a large cylindrical container filled with a nematic electrolyte. Assuming homeotropic anchoring of the nematic on the surface of the particle and uniform distribution of the director on the surface of the container, we consider two configurations with a disclination equatorial ring and with a hyperbolic hedgehog, respectively. The computed electro-osmotic flows show a strong dependence on the director configurations and on the anisotropies of dielectric permittivity and electric conductivity of the nematic, characteristic of liquid crystal-enabled electrokinetics. Further, the simulations demonstrate space charge separation around the dielectric sphere, even in the case of isotropic permittivity and conductivity. This is in agreement with the induced-charge electroosmotic effect that occurs in an isotropic electrolyte when an applied field acts on the ionic charge it induces near a polarizable surface.

  8. Nematic liquid crystal boojums with handles on colloidal handlebodies.

    Science.gov (United States)

    Liu, Qingkun; Senyuk, Bohdan; Tasinkevych, Mykola; Smalyukh, Ivan I

    2013-06-04

    Topological defects that form on surfaces of ordered media, dubbed boojums, are ubiquitous in superfluids, liquid crystals (LCs), Langmuir monolayers, and Bose-Einstein condensates. They determine supercurrents in superfluids, impinge on electrooptical switching in polymer-dispersed LCs, and mediate chemical response at nematic-isotropic fluid interfaces, but the role of surface topology in the appearance, stability, and core structure of these defects remains poorly understood. Here, we demonstrate robust generation of boojums by controlling surface topology of colloidal particles that impose tangential boundary conditions for the alignment of LC molecules. To do this, we design handlebody-shaped polymer particles with different genus g. When introduced into a nematic LC, these particles distort the nematic molecular alignment field while obeying topological constraints and induce at least 2g - 2 boojums that allow for topological charge conservation. We characterize 3D textures of boojums using polarized nonlinear optical imaging of molecular alignment and explain our findings by invoking symmetry considerations and numerical modeling of experiment-matching director fields, order parameter variations, and nontrivial handle-shaped core structure of defects. Finally, we discuss how this interplay between the topologies of colloidal surfaces and boojums may lead to controlled self-assembly of colloidal particles in nematic and paranematic hosts, which, in turn, may enable reconfigurable topological composites.

  9. Nematic and Smectic Mesophases from a Novel Triphenylene ...

    African Journals Online (AJOL)

    Salisu Abdulsalam

    phenylazo)azobenzene on to the 2,3,6,7,10,11-hexahydroxytriphenylene nucleus. The presence of a nematic and smectic A ... rod-shaped azobenzene moieties via short (C3) alkyl chains using ester bonds. This compound shows ..... derivatives of hexaalkoxytriphenylene, J. Mol. Liq, Liq Cryst, 411: 1335-1346. Cojocariu C.

  10. Fractional Brownian motion of director fluctuations in nematic ordering

    DEFF Research Database (Denmark)

    Zhang, Z.; Mouritsen, Ole G.; Otnes, K.

    1993-01-01

    Temporal director fluctuations in nematic ordering were studied by computer simulation on the Lebwohl-Lasher model as well as by neutron-scattering experiments on the nematogen d-PAA. The time-series data have been analyzed by the rescaled-range method and in terms of the power spectrum in order ...

  11. Symmetry of Uniaxial Global Landau--de Gennes Minimizers in the Theory of Nematic Liquid Crystals

    KAUST Repository

    Henao, Duvan

    2012-01-01

    We extend the recent radial symmetry results by Pisante [J. Funct. Anal., 260 (2011), pp. 892-905] and Millot and Pisante [J. Eur. Math. Soc. (JEMS), 12 (2010), pp. 1069- 1096] (who show that the equivariant solutions are the only entire solutions of the three-dimensional Ginzburg-Landau equations in superconductivity theory) to the Landau-de Gennes framework in the theory of nematic liquid crystals. In the low temperature limit, we obtain a characterization of global Landau-de Gennes minimizers, in the restricted class of uniaxial tensors, in terms of the well-known radial-hedgehog solution. We use this characterization to prove that global Landau-de Gennes minimizers cannot be purely uniaxial for sufficiently low temperatures. Copyright © by SIAM.

  12. Observation of a new superfluid phase for 3He embedded in nematically ordered aerogel

    Science.gov (United States)

    Zhelev, N.; Reichl, M.; Abhilash, T. S.; Smith, E. N.; Nguyen, K. X.; Mueller, E. J.; Parpia, J. M.

    2016-01-01

    In bulk superfluid 3He at zero magnetic field, two phases emerge with the B-phase stable everywhere except at high pressures and temperatures, where the A-phase is favoured. Aerogels with nanostructure smaller than the superfluid coherence length are the only means to introduce disorder into the superfluid. Here we use a torsion pendulum to study 3He confined in an extremely anisotropic, nematically ordered aerogel consisting of ∼10 nm-thick alumina strands, spaced by ∼100 nm, and aligned parallel to the pendulum axis. Kinks in the development of the superfluid fraction (at various pressures) as the temperature is varied correspond to phase transitions. Two such transitions are seen in the superfluid state, and we identify the superfluid phase closest to Tc at low pressure as the polar state, a phase that is not seen in bulk 3He. PMID:27669660

  13. Photoluminescence analysis of self induced planer alignment in azo dye dispersed nematic liquid crystal complex

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Rishi, E-mail: kkraina@gmail.com; Sood, Srishti, E-mail: kkraina@gmail.com; Raina, K. K., E-mail: kkraina@gmail.com [School of Physics and Materials Science, Thapar University, Patiala-147004 (India)

    2014-04-24

    We have developed azo dye doped nematic liquid crystal complex for advanced photonic liquid crystal display technology aspects. Disperse orange azo dye self introduced planer alignment in the nematic liquid crystal without any surface anchoring treatment. Planer alignment was characterized by optical polarizing microscopy. The electro-optical switching response of dye disperse planer aligned nematic cell was investigated as a function of applied voltage with the help of photoluminescence spectrophotometer for the tuning of photoluminescence contrast.

  14. Phenomenology of polymorphism: The topological pressure-temperature phase relationships of the dimorphism of finasteride

    Energy Technology Data Exchange (ETDEWEB)

    Gana, Ines [EAD Physico-chimie Industrielle du Medicament (EA 4066), Faculte de Pharmacie, Universite Paris Descartes, 4 Avenue de l' Observatoire, 75006 Paris (France) and Etablissement pharmaceutique de l' Assistance Publique - Hopitaux de Paris, Agence Generale des Equipements et Produits de Sante, 7 Rue du Fer a moulin, 75005 Paris (France); Ceolin, Rene [EAD Physico-chimie Industrielle du Medicament (EA 4066), Faculte de Pharmacie, Universite Paris Descartes, 4 Avenue de l' Observatoire, 75006 Paris (France); Rietveld, Ivo B., E-mail: ivo.rietveld@parisdescartes.fr [EAD Physico-chimie Industrielle du Medicament (EA 4066), Faculte de Pharmacie, Universite Paris Descartes, 4 Avenue de l' Observatoire, 75006 Paris (France)

    2012-10-20

    Highlights: Black-Right-Pointing-Pointer The topological pressure-temperature phase diagram for the dimorphism of finasteride. Black-Right-Pointing-Pointer Pressure affects phase equilibria: an enantiotropic phase relationship turning monotropic at high pressure. Black-Right-Pointing-Pointer The influence of pressure on phase behavior inferred from data obtained under ordinary conditions. - Abstract: Knowledge of the phase behavior in the solid state of active pharmaceutical ingredients is important for the development of stable drug formulations. The topological method for the construction of pressure-temperature phase diagrams has been applied to study the phase behavior of finasteride. It is demonstrated that with basic calorimetric measurements and X-ray diffraction sufficient data can be obtained to construct a complete topological pressure-temperature phase diagram. The dimorphism observed for finasteride gives rise to a phase diagram similar to the paradigmatic diagram of sulfur. The solid-solid phase relationship is enantiotropic at ordinary pressure and becomes monotropic at elevated pressure, where solid I is the only stable phase.

  15. 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.

  16. 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.

  17. Creation and manipulation of topological states in chiral nematic microspheres.

    Science.gov (United States)

    Orlova, Tetiana; Aßhoff, Sarah Jane; Yamaguchi, Tadatsugu; Katsonis, Nathalie; Brasselet, Etienne

    2015-07-06

    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 properties of soft matter appears as a relevant strategy to address the challenge, in particular, because it may lead to paradigmatic model systems that allow checking theories experimentally. Here we report experimentally on a wealth of complex free-standing metastable topological architectures at the micron scale, in frustrated chiral nematic droplets. These results support recent works predicting the formation of free-standing knotted and linked disclination structures in confined chiral nematic fluids. We also demonstrate that various kinds of external fields (thermal, electrical and optical) can be used to achieve topological remote control. All this may foster the development of new devices based on topologically structured soft media.

  18. Effect of Pressure on Dielectric and Frank Elastic Constants of a Material Exhibiting the Twist Bend Nematic Phase.

    Science.gov (United States)

    Parthasarathi, Srividhya; Shankar Rao, D S; Palakurthy, Nani Babu; Yelamaggad, C V; Krishna Prasad, S

    2017-02-02

    We report the first investigation on the effect of applied pressure on the now well-known dimer α,ω bis(4,4'-cyanobiphenyl)heptane (CB7CB) that exhibits two types of nematic: the regular uniaxial nematic (N) and the recently discovered twist-bend nematic (NTB) phase. At atmospheric pressure, the thermal behavior of ε⊥, the permittivity normal to the director in the N phase decreases on entering the NTB wherein the value represents permittivity orthogonal to the helical axis. Application of pressure initially decreases the magnitude of the change in ε⊥ and with further increase in pressure exhibits an increase in the value. Such a change in the feature of ε⊥ is similar to that obtained at room pressure when the monomeric heptyloxy cyanobiphenyl (7OCB) is doped to CB7CB at a high concentration of 50%. The dielectric anisotropy exhibits a trend reversal with temperature, the extent of which is affected at high pressures. Another salient feature of the study is the effect that pressure has on the Frank bend elastic constant K33. Over the pressure range studied K33 enhances by a large factor of 5. In contrast, the splay elastic constant exhibits a much smaller change of only 70%. The pressure-temperature phase boundary has a much smaller slope for the N-NTB transformation than for the isotropic-N transition. We propose that all these features can be understood in terms of the relative population of the more energetic horseshoe and lower energy extended conformer adopted by the CB7CB molecule. The extended conformer is favored at lower temperatures or at higher pressures. This argument is validated by X-ray diffraction experiments at atmospheric pressure on the binary mixture of CB7CB and 7OCB, mentioned above.

  19. Isotropic in-plane quenched disorder and dilution induce a robust nematic state in electron-doped pnictides

    Science.gov (United States)

    Liang, Shuhua; Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio

    2015-09-01

    The phase diagram of electron-doped pnictides is studied varying the temperature, electronic density, and isotropic in-plane quenched disorder strength and dilution by means of computational techniques applied to a three-orbital (x z ,y z ,x y ) spin-fermion model with lattice degrees of freedom. In experiments, chemical doping introduces disorder but in theoretical studies the relationship between electronic doping and the randomly located dopants, with their associated quenched disorder, is difficult to address. In this publication, the use of computational techniques allows us to study independently the effects of electronic doping, regulated by a global chemical potential, and impurity disorder at randomly selected sites. Surprisingly, our Monte Carlo simulations reveal that the fast reduction with doping of the Néel TN and the structural TS transition temperatures, and the concomitant stabilization of a robust nematic state, is primarily controlled in our model by the magnetic dilution associated with the in-plane isotropic disorder introduced by Fe substitution. In the doping range studied, changes in the Fermi surface produced by electron doping affect only slightly both critical temperatures. Our results also suggest that the specific material-dependent phase diagrams experimentally observed could be explained as a consequence of the variation in disorder profiles introduced by the different dopants. Our findings are also compatible with neutron scattering and scanning tunneling microscopy, unveiling a patchy network of locally magnetically ordered clusters with anisotropic shapes, even though the quenched disorder is locally isotropic. This study reveals a remarkable and unexpected degree of complexity in pnictides: the fragile tendency to nematicity intrinsic of translational invariant electronic systems needs to be supplemented by quenched disorder and dilution to stabilize the robust nematic phase experimentally found in electron-doped 122 compounds.

  20. Hyperscaling violation at the Ising-nematic quantum critical point in two dimensional metals

    CERN Document Server

    Eberlein, Andreas; Sachdev, Subir

    2016-01-01

    Understanding optical conductivity data in the optimally doped cuprates in the framework of quantum criticality requires a strongly-coupled quantum critical metal which violates hyperscaling. In the simplest scaling framework, hyperscaling violation can be characterized by a single non-zero exponent $\\theta$, so that in a spatially isotropic state in $d$ spatial dimensions, the specific heat scales with temperature as $T^{(d-\\theta)/z}$, and the optical conductivity scales with frequency as $\\omega^{(d-\\theta-2)/z}$ for $\\omega \\gg T$, where $z$ is the dynamic critical exponent. We study the Ising-nematic critical point, using the controlled dimensional regularization method proposed by Dalidovich and Lee (Phys. Rev. B {\\bf 88}, 245106 (2013)). We find that hyperscaling is violated, with $\\theta =1$ in $d=2$. We expect that similar results apply to Fermi surfaces coupled to gauge fields in $d=2$.

  1. Twisted quasiperiodic textures of biaxial nematic liquid crystals.

    Science.gov (United States)

    Golo, V L; Kats, E I; Sevenyuk, A A; Sinitsyn, D O

    2013-10-01

    Textures (i.e., smooth space nonuniform distributions of the order parameter) in biaxial nematics turned out to be much more complex and interesting than expected. Scanning the literature we find only a very few publications on this topic. Thus, the immediate motivation of the present paper is to develop a systematic procedure to study, classify, and visualize possible textures in biaxial nematics. Based on the elastic energy of a biaxial nematic (written in the most simple form that involves the least number of phenomenological parameters) we derive and solve numerically the Lagrange equations of the first kind. It allows one to visualize the solutions and offers a deep insight into their geometrical and topological features. Performing Fourier analysis we find some particular textures possessing two or more characteristic space periods (we term such solutions quasiperiodic ones because the periods are not necessarily commensurate). The problem is not only of intellectual interest but also of relevance to optical characteristics of the liquid-crystalline textures.

  2. Fluctuations and nematic order in collective motion of filamentous bacteria

    Science.gov (United States)

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

    Although there are many numerical and theoretical studies on Vicsek-like models, there have been no convincing experiments that clearly observe predicted properties of collective motion such as giant number fluctuations. To realize such experiments with a biological system, we used filamentous bacteria, which are 20 times as long as usual bacteria. Due to strong alignment interactions arising from their elongated shapes, these bacteria exhibit a nematic state when their dense suspensions are confined in a quasi-two-dimensional plane. We have quantitatively evaluated the nematic order parameter in this ordered state and concluded that it has true long-range order, and we have obtained giant number fluctuations in this true long-range ordered state. All the obtained experimental results are consistent with a Vicsek-like model with the same symmetry as our experiments, namely, the Vicsek-like self-propelled rods model, in which each particle has polarity and their interactions are nematic. This work is supported by a Grant-in-Aid for Japan Society for Promotion of Science (JSPS) Fellows (Grant No. 26-9915) and KAKENHI (No. 25103004, ``Fluctuation & Structure'') from MEXT, Japan.

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

    Science.gov (United States)

    Dan, K; Roy, M; Datta, A

    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.

  4. Enhancement of polar anchoring strength in a graphene-nematic suspension and its effect on nematic electro-optic switching

    Science.gov (United States)

    Basu, Rajratan

    2017-07-01

    A small quantity of monolayer graphene flakes is doped in a nematic liquid crystal (LC), and the effective polar anchoring strength coefficient between the LC and the alignment substrate is found to increase by an order of magnitude. The hexagonal pattern of graphene can interact with the LC's benzene rings via π -π electron stacking, enabling the LC to anchor to the graphene surface homogeneously (i.e., planar anchoring). When the LC cell is filled with the graphene-doped LC, some graphene flakes are preferentially attached to the alignment layer and modify the substrate's anchoring property. These spontaneously deposited graphene flakes promote planar anchoring at the substrate and the polar anchoring energy at alignment layer is enhanced significantly. The enhanced anchoring energy is found to impact favorably on the electro-optic response of the LC. Additional studies reveal that the nematic electro-optic switching is significantly faster in the LC-graphene hybrid than that of the pure LC.

  5. Spiral order by disorder and lattice nematic order in a frustrated Heisenberg antiferromagnet on the honeycomb lattice

    Science.gov (United States)

    Mulder, A.; Ganesh, R.; Capriotti, L.; Paramekanti, A.

    2010-06-01

    Motivated by recent experiments on Bi3Mn4O12(NO3) , we study a frustrated J1-J2 Heisenberg model on the two-dimensional (2D) honeycomb lattice. The classical J1-J2 Heisenberg model on the 2D honeycomb lattice exhibits Néel order for J2J1/6 , it has a family of degenerate incommensurate spin spiral ground states where the spiral wave vector can point in any direction. Spin wave fluctuations at leading order lift this accidental degeneracy in favor of specific wave vectors, leading to spiral order by disorder. For spin S=1/2 , quantum fluctuations are, however, likely to be strong enough to melt the spiral order parameter over a wide range of J2/J1 . Over a part of this range, we argue that the resulting state is a valence bond solid (VBS) with staggered dimer order—this VBS is a lattice nematic which breaks lattice rotational symmetry. Our arguments are supported by comparing the spin wave energy with the energy of the VBS obtained using a bond operator formalism. Turning to the effect of thermal fluctuations on the spiral ordered state, any nonzero temperature destroys the magnetic order, but the discrete rotational symmetry of the lattice remains broken resulting in a thermal analog of the nematic VBS. We present arguments, supported by classical Monte Carlo simulations, that this nematic transforms into the high temperature paramagnet via a thermal phase transition which is in the universality class of the classical three-state Potts (clock) model in 2D. We discuss the relevance of our results for honeycomb magnets, such as Bi3M4O12(NO3) (with M=Mn,V,Cr ), and bilayer triangular lattice magnets.

  6. Experimental realization of crossover in shape and director field of nematic tactoids

    NARCIS (Netherlands)

    Jamali, Vida; Behabtu, Natnael; Senyuk, Bohdan; Lee, J. Alex; Smalyukh, Ivan I.; van der Schoot, Paul; Pasquali, Matteo

    2015-01-01

    Spindle-shaped nematic droplets (tactoids) form in solutions of rod-like molecules at the onset of the liquid crystalline phase. Their unique shape and internal structure result from the interplay of the elastic deformation of the nematic and anisotropic surface forces. The balance of these forces

  7. Local electronic nematicity in the two-dimensional one-band Hubbard model.

    Science.gov (United States)

    Fang, Kun; Fernando, G W; Kocharian, A N

    2013-05-22

    Nematicity is a well-known property of liquid crystals and has been recently discussed in the context of strongly interacting electrons. An electronic nematic phase has been seen in many experiments in certain strongly correlated materials, in particular, in the pseudogap phase generic to many hole-doped cuprate superconductors. Recent measurements in high Tc superconductors have shown that even if the lattice is perfectly rotationally symmetric, the ground state can still have strongly nematic local properties. Our study of the two-dimensional one-band Hubbard model provides strong support for the recent experimental results on local rotational C4 symmetry breaking. The variational cluster approach is used here to show the possibility of an electronic nematic state and the proximity of the underlying symmetry-breaking ground state within the Hubbard model. We identify this nematic phase in the overdoped region and show that the local nematicity decreases with increasing electron filling. Our results also indicate that strong Coulomb interaction may drive the nematic phase into a phase similar to the stripe structure. The calculated spin (magnetic) correlation function in momentum space shows the effects resulting from real-space nematicity.

  8. Droplet snap-off in fluids with nematic liquid crystalline ordering

    NARCIS (Netherlands)

    Verhoeff, A.A.|info:eu-repo/dai/nl/304829579; Lekkerkerker, H.N.W.|info:eu-repo/dai/nl/159054885

    2012-01-01

    We studied the snap-off of nematic liquid crystalline droplets originating from the Rayleigh–Taylor instability at the isotropic–nematic interface in suspensions of charged gibbsite in water and sterically stabilized gibbsite in bromotoluene. We found that droplet snap-off strongly depends on the

  9. Solute NMR study of a bimesogenic liquid crystal with two nematic phases

    Science.gov (United States)

    Dong, R. Y.; Kohlmeier, A.; Tamba, M. G.; Mehl, G. H.; Burnell, E. E.

    2012-11-01

    Recent interest in bimesogenic liquid crystals showing two nematic phases has led us to investigate the nematic mean-field interactions in these nematic phases by using rigid solutes as probes. The nematic potential that is modelled by two independent Maier-Saupe terms is successful in fitting the observed dipolar couplings (molecular order parameters) of para-, meta- and ortho-dichlorobenzene solutes in both nematic phases of 39 wt.% 4-n-pentyl-4'-cyanobiphenyl (5CB) in α,ω-bis (4-4'-cyanobiphenyl) nonane (CBC9CB) to better than the 5% level. The derived liquid-crystal potential parameters G1 and G2 for each solute in the N and Nx phases are discussed.

  10. Antiferroquadrupolar and Ising-nematic orders of a frustrated bilinear-biquadratic Heisenberg model and implications for the magnetism of FeSe.

    Science.gov (United States)

    Yu, Rong; Si, Qimiao

    2015-09-11

    Motivated by the properties of the iron chalcogenides, we study the phase diagram of a generalized Heisenberg model with frustrated bilinear-biquadratic interactions on a square lattice. We identify zero-temperature phases with antiferroquadrupolar and Ising-nematic orders. The effects of quantum fluctuations and interlayer couplings are analyzed. We propose the Ising-nematic order as underlying the structural phase transition observed in the normal state of FeSe, and discuss the role of the Goldstone modes of the antiferroquadrupolar order for the dipolar magnetic fluctuations in this system. Our results provide a considerably broadened perspective on the overall magnetic phase diagram of the iron chalcogenides and pnictides, and are amenable to tests by new experiments.

  11. Temperature Dependence of Light Transmittance in Polymer Dispersed Liquid Crystals

    OpenAIRE

    Bloisi, F.; Ruocchio, C.; Vicari, L

    1997-01-01

    Polymer Dispersed Liquid Crystals (PDLC) axe composite materials made of a dispersion of liquid crystal droplets in a polymeric matrix. When the liquid crystal is in the nematic phase, droplets appeax as optically anisotropic spheres and the material is opaque white. Sample transmittance is a function of the temperature. If the liquid crystal refractive index in the isotropic phase is equal to the one of the polymer, after the nematic-isotropic transition the material is transparent. We prese...

  12. Ellipsometric study of vertically aligned nematic liquid crystals

    Science.gov (United States)

    Marino, A.; Santamato, E.; Bennis, N.; Quintana, X.; Otón, J. M.; Tkachenko, V.; Abbate, G.

    2009-01-01

    The director tilt angle distribution in vertically aligned nematic liquid crystal displays has been investigated by means of variable angle spectroscopic ellipsometry. Liquid crystal vertical alignment has been realized by thermal evaporation of SiOx. By changing the deposition angle, it is possible to control the pretilt angle. The director profile inside the sample was inferred by reflection and transmission ellipsometric measurements. The tilt angle distribution inside the cell versus the applied voltage is reported and eventually, comparing it with the simulations from the elastic theory, the anchoring energy has been obtained.

  13. 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.

  14. Band structures in the nematic elastomers phononic crystals

    Science.gov (United States)

    Yang, Shuai; Liu, Ying; Liang, Tianshu

    2017-02-01

    As one kind of new intelligent materials, nematic elastomers (NEs) represent an exciting physical system that combines the local orientational symmetry breaking and the entropic rubber elasticity, producing a number of unique physical phenomena. In this paper, the potential application of NEs in the band tuning is explored. The band structures in two kinds of NE phononic crystals (PCs) are investigated. Through changing NE intrinsic parameters, the influence of the porosity, director rotation and relaxation on the band structures in NE PCs are analyzed. This work is a meaningful try for application of NEs in acoustic field and proposes a new intelligent strategy in band turning.

  15. Dynamical electronic nematicity from Mott physics

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Satoshi [ORNL; Senechal, D. [University of Sherbrooke; Civelli, M. [Institut Laue-Langevin (ILL); Tremblay, A.-M. [University of Sherbrooke

    2010-01-01

    Very large anisotropies in transport quantities have been observed in the presence of very small in-plane structural anisotropy in many strongly correlated electron materials. By studying the two-dimensional Hubbard model with dynamical-mean-field theory for clusters, we show that such large anisotropies can be induced without static stripe order if the interaction is large enough to yield a Mott transition. Anisotropy decreases at large frequency. The maximum effect on conductivity anisotropy occurs in the underdoped regime, as observed in high temperature superconductors.

  16. Elasticity of nematic phases with fundamental measure theory.

    Science.gov (United States)

    Wittmann, René; Marechal, Matthieu; Mecke, Klaus

    2015-05-01

    In a previous publication [R. Wittmann, M. Marechal, and K. Mecke, Europhys. Lett. 109, 26003 (2015)], we introduced fundamental mixed measure theory (FMMT) for mixtures of anisotropic hard bodies, which shows that earlier results with an empirical parameter are inaccurate. Now we provide a deeper insight into the background of this theory in integral geometry. We study the Frank elastic coefficients in the nematic phase of the hard spherocylinder fluid. The framework of FMMT provides us with the required direct correlation function without additional input of an equation of state. A series representation of the mixed measure gives rise to closed analytical formulas for the elastic constants that only depend on the density, order parameters, and the particle geometry, pointing out a significant advantage of our geometry-based approach compared to other density functionals. Our elastic coefficients are in good agreement with computer simulations and increase with the density and the nematic order parameter. We confirm earlier mean-field predictions in the limits of low orientational order and infinitely long rods.

  17. Key-lock colloids in a nematic liquid crystal

    Science.gov (United States)

    Silvestre, Nuno M.; Tasinkevych, M.

    2017-01-01

    The Landau-de Gennes free energy is used to study theoretically the effective interaction of spherical "key" and anisotropic "lock" colloidal particles. We assume identical anchoring properties of the surfaces of the key and of the lock particles, and we consider planar degenerate and perpendicular anchoring conditions separately. The lock particle is modeled as a spherical particle with a spherical dimple. When such a particle is introduced into a nematic liquid crystal, it orients its dimple at an oblique angle θeq with respect to the far field director n∞. This angle depends on the depth of the dimple. Minimization results show that the free energy of a pair of key and lock particles exhibits a global minimum for the configuration when the key particle is facing the dimple of the lock colloidal particle. The preferred orientation ϕeq of the key-lock composite doublet relative to n∞ is robust against thermal fluctuations. The preferred orientation θeq(2 ) of the dimple particle in the doublet is different from the isolated situation. This is related to the "direct" interaction of defects accompanying the key particle with the edge of the dimple. We propose that this nematic-amplified key-lock interaction can play an important role in self-organization and clustering of mixtures of colloidal particles with dimple colloids present.

  18. Topological Defects in a Living Nematic Ensnare Swimming Bacteria

    Science.gov (United States)

    Genkin, Mikhail M.; Sokolov, Andrey; Lavrentovich, Oleg D.; Aranson, Igor S.

    2017-01-01

    Active matter exemplified by suspensions of motile bacteria or synthetic self-propelled particles exhibits a remarkable propensity to self-organization and collective motion. The local input of energy and simple particle interactions often lead to complex emergent behavior manifested by the formation of macroscopic vortices and coherent structures with long-range order. A realization of an active system has been conceived by combining swimming bacteria and a lyotropic liquid crystal. Here, by coupling the well-established and validated model of nematic liquid crystals with the bacterial dynamics, we develop a computational model describing intricate properties of such a living nematic. In faithful agreement with the experiment, the model reproduces the onset of periodic undulation of the director and consequent proliferation of topological defects with the increase in bacterial concentration. It yields a testable prediction on the accumulation of bacteria in the cores of +1 /2 topological defects and depletion of bacteria in the cores of -1 /2 defects. Our dedicated experiment on motile bacteria suspended in a freestanding liquid crystalline film fully confirms this prediction. Our findings suggest novel approaches for trapping and transport of bacteria and synthetic swimmers in anisotropic liquids and extend a scope of tools to control and manipulate microscopic objects in active matter.

  19. Quantum Hall Ferroelectrics and Nematics in Multivalley Systems

    Directory of Open Access Journals (Sweden)

    Inti Sodemann

    2017-12-01

    Full Text Available We study broken symmetry states at integer Landau-level fillings in multivalley quantum Hall systems whose low-energy dispersions are anisotropic. When the Fermi surface of individual pockets lacks twofold rotational symmetry, like in bismuth (111 [Feldman et al. , Observation of a Nematic Quantum Hall Liquid on the Surface of Bismuth, Science 354, 316 (2016SCIEAS0036-807510.1126/science.aag1715] and in Sn_{1-x}Pb_{x}Se (001 [Dziawa et al., Topological Crystalline Insulator States in Pb_{1-x}Sn_{x}Se, Nat. Mater. 11, 1023 (2012NMAACR1476-112210.1038/nmat3449] surfaces, interactions tend to drive the formation of quantum Hall ferroelectric states. We demonstrate that the dipole moment in these states has an intimate relation to the Fermi surface geometry of the parent metal. In quantum Hall nematic states, like those arising in AlAs quantum wells, we demonstrate the existence of unusually robust Skyrmion quasiparticles.

  20. Geometry of thresholdless active flow in nematic microfluidics

    Science.gov (United States)

    Green, Richard; Toner, John; Vitelli, Vincenzo

    2017-10-01

    Active nematics are orientationally ordered but apolar fluids composed of interacting constituents individually powered by an internal source of energy. When activity exceeds a system-size-dependent threshold, spatially uniform active apolar fluids undergo a hydrodynamic instability leading to spontaneous macroscopic fluid flow. Here we show that a special class of spatially nonuniform configurations of such active apolar fluids display laminar (i.e., time-independent) flow even for arbitrarily small activity. We also show that two-dimensional active nematics confined on a surface of nonvanishing Gaussian curvature must necessarily experience a nonvanishing active force. This general conclusion follows from a key result of differential geometry: Geodesics must converge or diverge on surfaces with nonzero Gaussian curvature. We derive the conditions under which such curvature-induced active forces generate thresholdless flow for two-dimensional curved shells. We then extend our analysis to bulk systems and show how to induce thresholdless active flow by controlling the curvature of confining surfaces, external fields, or both. The resulting laminar flow fields are determined analytically in three experimentally realizable configurations that exemplify this general phenomenon: (i) toroidal shells with planar alignment, (ii) a cylinder with nonplanar boundary conditions, and (iii) a Frederiks cell that functions like a pump without moving parts. Our work suggests a robust design strategy for active microfluidic chips and could be tested with the recently discovered living liquid crystals.

  1. Spherical microparticles with Saturn ring defects and their self-assembly across the nematic to smectic-A phase transition.

    Science.gov (United States)

    Zuhail, K P; Čopar, S; Muševič, I; Dhara, Surajit

    2015-11-01

    We report experimental studies on the Saturn ring defect associated with a spherical microparticle across the nematic (N) to smectic-A (SmA) phase transition. We observe that the director distortion around the microparticle changes rapidly with temperature. The equilibrium interparticle separation and the angle between two quadrupolar particles in the N phase are larger than those of the SmA phase. They are almost independent of the temperature in both phases, except for a discontinuous jump at the transition. We assembled a few particles using a laser tweezer to form a two-dimensional colloidal crystal in the N phase. The lattice structure of the crystal dissolves irreversibly across the N-SmA phase transition. The results on the pretransitional behavior of the defect are supported by the Landau-de Gennes Q-tensor modeling.

  2. Nematic Liquid Crystals: From Maier-Saupe to a Continuum Theory

    KAUST Repository

    Ball, John M.

    2010-07-20

    We define a continuum energy functional that effectively interpolates between the mean-field Maier-Saupe energy and the continuum Landau-de Gennes energy functional and can describe both spatially homogeneous and inhomogeneous systems. In the mean-field approach the main macroscopic variable, the Q-tensor order parameter, is defined in terms of the second moment of a probability distribution function. This definition imposes certain constraints on the eigenvalues of the Q-tensor order parameter, which may be interpreted as physical constraints. We define a thermotropic bulk potential which blows up whenever the eigenvalues of the Q-tensor order parameter approach physically unrealistic values. As a consequence, the minimizers of this continuum energy functional have physically realistic order parameters in all temperature regimes. We study the asymptotics of this bulk potential and show that this model also predicts a first-order nematic-isotropic phase transition, whilst respecting the physical constraints. In contrast, in the Landau-de Gennes framework the Q-tensor order parameter is often defined independently of the probability distribution function, and the theory makes physically unrealistic predictions about the equilibrium order parameters in the low-temperature regime. Copyright © Taylor & Francis Group, LLC.

  3. The radial-hedgehog solution in Landau–de Gennes' theory for nematic liquid crystals

    KAUST Repository

    MAJUMDAR, APALA

    2011-09-06

    We study the radial-hedgehog solution in a three-dimensional spherical droplet, with homeotropic boundary conditions, within the Landau-de Gennes theory for nematic liquid crystals. The radial-hedgehog solution is a candidate for a global Landau-de Gennes minimiser in this model framework and is also a prototype configuration for studying isolated point defects in condensed matter physics. The static properties of the radial-hedgehog solution are governed by a non-linear singular ordinary differential equation. We study the analogies between Ginzburg-Landau vortices and the radial-hedgehog solution and demonstrate a Ginzburg-Landau limit for the Landau-de Gennes theory. We prove that the radial-hedgehog solution is not the global Landau-de Gennes minimiser for droplets of finite radius and sufficiently low temperatures and prove the stability of the radial-hedgehog solution in other parameter regimes. These results contain quantitative information about the effect of geometry and temperature on the properties of the radial-hedgehog solution and the associated biaxial instabilities. © Copyright Cambridge University Press 2011.

  4. Morphogenesis of liquid crystal topological defects during the nematic-smectic A phase transition

    Science.gov (United States)

    Gim, Min-Jun; Beller, Daniel A.; Yoon, Dong Ki

    2017-05-01

    The liquid crystalline phases of matter each possess distinct types of defects that have drawn great interest in areas such as topology, self-assembly and material micropatterning. However, relatively little is known about how defects in one liquid crystalline phase arise from defects or deformations in another phase upon crossing a phase transition. Here, we directly examine defects in the in situ thermal phase transition from nematic to smectic A in hybrid-aligned liquid crystal droplets on water substrates, using experimental, theoretical and numerical analyses. The hybrid-aligned nematic droplet spontaneously generates boojum defects. During cooling, toric focal conic domains arise through a sequence of morphological transformations involving nematic stripes and locally aligned focal conic domains. This simple experiment reveals a surprisingly complex pathway by which very different types of defects may be related across the nematic-smectic A phase transition, and presents new possibilities for controlled deformation and patterning of liquid crystals.

  5. Electric field generation of Skyrmion-like structures in a nematic liquid crystal.

    Science.gov (United States)

    Cattaneo, Laura; Kos, Žiga; Savoini, Matteo; Kouwer, Paul; Rowan, Alan; Ravnik, Miha; Muševič, Igor; Rasing, Theo

    2016-01-21

    Skyrmions are particle-like topological objects that are increasingly drawing attention in condensed matter physics, where they are connected to inversion symmetry breaking and chirality. Here we report the generation of stable Skyrmion-like structures in a thin nematic liquid crystal film on chemically patterned patchy surfaces. Using the interplay of material elasticity and surface boundary conditions, we use a strong electric field to quench the nematic liquid crystal from a fully aligned phase to vortex-like nematic liquid crystal structures, centered on patterned patches, which carry two different sorts of topological defects. Numerical calculations reveal that these are Skyrmion-like structures, seeded from the surface boojum topological defects and swirling towards the second confining surface. These observations, supported by numerical methods, demonstrate the possibility to generate, manipulate and study Skyrmion-like objects in nematic liquid crystals on patterned surfaces.

  6. Final Report: Biaxiality in Nematic and Smectic Liquid Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Satyendra; Quan, Li; Srinivasarao, Mohan; Agra-Kooijman, Dena; Rey, Alejandro

    2017-01-24

    During the award period, the project team explored several phenomena in a diverse group of soft condensed matter systems. These include understanding of the structure of the newly discovered twist-bend nematic phase, solving the mystery of de Vries smectic phases, probing of interesting associations and defect structures in chromonic liquid crystalline systems, dispersions of ferroelectric nanoparticles in smectic liquid crystals, investigations of newly synthesized light sensitive and energy harvesting materials with highly desirable transport properties. Our findings are summarized in the following report followed by a list of 36 publications and 37 conference presentations. We achieved this with the support of Basic Sciences Division of the US DOE for which we are thankful.

  7. Relaxation Dynamics of Spatiotemporal Chaos in the Nematic Liquid Crystal

    Science.gov (United States)

    Nugroho, Fahrudin; Ueki, Tatsuhiro; Hidaka, Yoshiki; Kai, Shoichi

    2011-11-01

    We are working on the electroconvection of nematic liquid crystals, in which a kind of spatiotemporal chaos called as a soft-mode turbulence (SMT) is observed. The SMT is caused by the nonlinear interaction between the convective modes and the Nambu--Goldstone (NG) modes. By applying an external magnetic field H, the NG mode is suppressed and an ordered pattern can be observed. By removing the suppression effect the ordered state relax to its original SMT pattern. We revealed two types of instability govern the relaxation process: the zigzag instability and the free rotation of wavevector q(r). This work is partially supported by Grant-in-Aid for Scientific Research (Nos. 20111003, 21340110, and 21540391) from the Ministry of Education, Culture, Sport, Science, and Technology of Japan and the Japan Society for the Promotion of Science (JSPS).

  8. Chiral power change upon photoisomerization in twisted nematic liquid crystals.

    Science.gov (United States)

    Simoncelli, Sabrina; Aramendía, Pedro F

    2015-05-05

    In this work, we use the photoisomerization of azobenzenes, a phenanthrospirooxazine, and a fulgide in a twisted nematic liquid crystalline phase to change the chiral twisting power of the system. The changes are probed by the rotatory power of linearly polarized light. Time resolved and steady state experiments are carried out. The chiral change and the photoisomerization process have similar characteristic recovery times and activation energy, thus probing that the change is induced by the modification in the chemical composition of the photochromic dopant system. The amplitude of the light twisting power change correlates with the order change in the liquid crystal (LC) but not with the modification in the absorption characteristics of the system. This indicates that the driving force of the chiral change is the microscopic order modification in the LC phase that affects the helical pitch of the phase. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Isotropic-nematic phase transition in aqueous sepiolite suspensions.

    Science.gov (United States)

    Woolston, Phillip; van Duijneveldt, Jeroen S

    2015-01-01

    Aqueous suspensions of sepiolite clay rods in water tend to form gels on increase of concentration. Here it is shown how addition of a small amount (0.1% of the clay mass) of a common stabiliser for clay suspensions, sodium polyacrylate, can allow the observation of an isotropic-nematic liquid crystal phase transition. This transition was found to move to higher clay concentrations upon adding NaCl, with samples containing 10(-3) M salt or above only displaying a gel phase. Even samples that initially formed liquid crystals had a tendency to form gels after several weeks, possibly due to Mg(2+) ions leaching from the clay mineral. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  10. Transparent laser damage resistant nematic liquid crystal cell "LCNP3"

    Science.gov (United States)

    Raszewski, Z.; Piecek, W.; Jaroszewicz, L.; Dąbrowski, R.; Nowinowski-Kruszelnicki, E.; Soms, L.; Olifierczuk, M.; Kędzierski, J.; Morawiak, P.; Mazur, R.; Miszczyk, E.; Mrukiewicz, M.; Kowiorski, K.

    2014-09-01

    There exists the problem in diagnostics of dense plasma (so-called Thomson diagnostics). For this purpose the plasma is illuminated by series of high energy laser pulses. The energy of each separate pulse is as large as 3 J, so it is impossible to generate a burst of such pulses by a single laser. In this situation, the pulses are generated by several independent lasers operating sequentially, and these pulses are to be directed along the same optical path. To form an optical path with λ = 1.064 μm and absolute value of the laser pulse energy of 3 J, a special refractive index matched twisted Nematic Liquid Crystal Cell of type LCNP3, with switching on time τON smaller than 3 μs was applied.

  11. Nematic Equilibria on a Two-Dimensional Annulus

    KAUST Repository

    Lewis, A. H.

    2017-01-16

    We study planar nematic equilibria on a two-dimensional annulus with strong and weak tangent anchoring, in the Oseen–Frank theoretical framework. We analyze a radially invariant defect-free state and compute analytic stability criteria for this state in terms of the elastic anisotropy, annular aspect ratio, and anchoring strength. In the strong anchoring case, we define and characterize a new spiral-like equilibrium which emerges as the defect-free state loses stability. In the weak anchoring case, we compute stability diagrams that quantify the response of the defect-free state to radial and azimuthal perturbations. We study sector equilibria on sectors of an annulus, including the effects of weak anchoring and elastic anisotropy, giving novel insights into the correlation between preferred numbers of boundary defects and the geometry. We numerically demonstrate that these sector configurations can approximate experimentally observed equilibria with boundary defects.

  12. Correlation lengths in hydrodynamic models of active nematics.

    Science.gov (United States)

    Hemingway, Ewan J; Mishra, Prashant; Marchetti, M Cristina; Fielding, Suzanne M

    2016-09-28

    We examine the scaling with activity of the emergent length scales that control the nonequilibrium dynamics of an active nematic liquid crystal, using two popular hydrodynamic models that have been employed in previous studies. In both models we find that the chaotic spatio-temporal dynamics in the regime of fully developed active turbulence is controlled by a single active scale determined by the balance of active and elastic stresses, regardless of whether the active stress is extensile or contractile in nature. The observed scaling of the kinetic energy and enstrophy with activity is consistent with our single-length scale argument and simple dimensional analysis. Our results provide a unified understanding of apparent discrepancies in the previous literature and demonstrate that the essential physics is robust to the choice of model.

  13. Phase biaxiality in nematic liquid crystalline side-chain polymers of various chemical constitutions.

    Science.gov (United States)

    Severing, Kirsten; Stibal-Fischer, Elke; Hasenhindl, Alfred; Finkelmann, Heino; Saalwächter, Kay

    2006-08-17

    In a previous deuterium NMR study conducted on a liquid crystalline (LC) polymer with laterally attached book-shaped molecules as the mesogenic moiety, we have revealed a biaxial nematic phase below the conventional uniaxial nematic phase (Phys. Rev. Lett. 2004, 92, 125501). To elucidate details of its formation, we here report on deuterium NMR experiments that have been conducted on different types of LC side-chain polymers as well as on mixtures with low-molar-mass mesogens. Different parameters that affect the formation of a biaxial nematic phase, such as the geometry of the attachment, the spacer length between the polymer backbone and the mesogenic unit, as well as the polymer dynamics, were investigated. Surprisingly, also polymers with terminally attached mesogens (end-on polymers) are capable of forming biaxial nematic phases if the flexible spacer is short and thus retains a coupling between the polymer backbone and the LC phase. Furthermore, the most important parameter for the formation of a biaxial nematic phase is the dynamics of the polymer backbone, as the addition of a small percentage of low molar mass LC to the biaxial nematic polymer from the original study served to shift both the glass transition and the appearance of detectable biaxiality in a very similar fashion. Plotting different parameters for the investigated systems as a function of T/Tg also reveals the crucial role of the dynamics of the polymer backbone and hence the glass transition.

  14. Isotropic-nematic transition for hard rods on a three-dimensional cubic lattice

    Science.gov (United States)

    Gschwind, A.; Klopotek, M.; Ai, Y.; Oettel, M.

    2017-07-01

    Using grand-canonical Monte Carlo (GCMC) simulations, we investigate the isotropic-nematic phase transition for hard rods of size L ×1 ×1 on a three-dimensional cubic lattice. We observe such a transition for L ≥6 . For L =6 , the nematic state has a negative order parameter, reflecting the co-occurrence of two dominating orientations. For L ≥7 , the nematic state has a positive order parameter, corresponding to the dominance of one orientation. We investigate rod lengths up to L =25 and find evidence for a very weakly first-order isotropic-nematic transition, while we cannot completely rule out a second-order transition. It was not possible to detect a density jump at the transition, despite using large systems containing several 105 particles. The probability density distributions P (Q ) from the GCMC simulations near the transition are very broad, pointing to strong fluctuations. Our results complement earlier results on the demixing (pseudonematic) transition for an equivalent system in two dimensions, which is presumably of Ising type and occurs for L ≥7 . We compare our results to lattice fundamental measure theory (FMT) and find that FMT strongly overestimates nematic order and consequently predicts a strong first-order transition. The rod packing fraction of the nematic coexisting states, however, agree reasonably well between FMT and GCMC.

  15. Interactions of carbon nanotubes in a nematic liquid crystal. II. Experiment.

    Science.gov (United States)

    Agha, Hakam; Galerne, Yves

    2016-04-01

    Multiwall carbon nanotube (CNT) colloids with different anchoring conditions are dispersed in pentyl-cyanobiphenyl (5CB), a thermotropic liquid crystal (LC) that exhibits a room-temperature nematic phase. The experiments make use of CNTs treated for strong planar, homeotropic, or Janus anchorings. Observations with a polarizing microscope show that the CNTs placed in a uniform nematic field stabilize parallel or perpendicular to n depending on their anchoring conditions. In the presence of a splay-bend disclination line, they are first attracted toward it and ultimately, they get trapped on it. Their orientation relative to the line is then found to be parallel or perpendicular to it, again depending on the anchoring conditions. When a sufficient number of particles are deposited on a disclination line, they form a micro- or nanonecklace in the shape of a thin thread or of a bottle brush, with the CNTs being oriented parallel or perpendicular to the disclination line according to the anchoring treatment. The system exhibits a rich versatility, even if until now the weak anchorings appear to be difficult to control. In a next step, the necklaces may be glued by means of pyrrole electropolymerization. In this manner, we realize a true materialization of the disclination lines, and we obtain nanowires capable of conducting the electricity in the place of the initial disclinations that just worked as templates. The advantage of the method is that it finally provides nanowires that are automatically connected to predesignated three-dimensional (3D) electrodes. Such a 3D nanowiring could have important applications, as it could allow one to develop electronic circuits in the third dimension. They could thus help with increasing the transistor density per surface unit, although downsizing of integrated circuits will soon be limited to atomic sizes or so. In other words, the predicted limitation to Moore's law could be avoided. For the moment, the nanowires that we obtain

  16. Electrically induced structure transition in nematic liquid crystal droplets with conical boundary conditions

    Science.gov (United States)

    Rudyak, V. Yu.; Krakhalev, M. N.; Sutormin, V. S.; Prishchepa, O. O.; Zyryanov, V. Ya.; Liu, J.-H.; Emelyanenko, A. V.; Khokhlov, A. R.

    2017-11-01

    Polymer-dispersed liquid crystal composites have been a focus of study for a long time for their unique electro-optical properties and manufacturing by "bottom-up" techniques at large scales. In this paper, nematic liquid crystal oblate droplets with conical boundary conditions (CBCs) under the action of electric field were studied by computer simulations and polarized optical microscopy. Droplets with CBCs were shown to prefer an axial-bipolar structure, which combines a pair of boojums and circular disclinations on a surface. In contrast to droplets with degenerate planar boundary conditions (PBCs), hybridization of the two structure types in droplets with CBCs leads to a two-minima energy profile, resulting in an abrupt structure transition and bistable behavior of the system. The nature of the low-energy barrier in droplets with CBCs makes it highly sensitive to external stimuli, such as electric or magnetic fields, temperature, and light. In particular, the value of the electric field of the structure reorientation in droplets with CBCs was found to be a few times smaller than the one for droplets with PBCs, and the droplet state remained stable after switching off the voltage.

  17. Two-dimensional coherent random laser in photonic crystal fiber with dye-doped nematic liquid crystal.

    Science.gov (United States)

    Nagai, Yusuke; Shao-Chieh, Chen; Kajikawa, Kotaro

    2017-11-10

    A random laser of a photonic crystal fiber (PCF) with holes filled with laser dye-doped nematic liquid crystal (NLC) is reported. When the excitation polarization was along the PCF axis, the measured laser threshold was 80  μJ/mm(2) per pulse, which is much lower than the previously reported random laser of PCF filled with laser dye-doped organic solvent. This low threshold is due to the high refractive index of the NLC, which produces a greater scattering efficiency. In contrast, when the excitation polarization is perpendicular to the PCF axis, the threshold was much higher or the laser oscillation was absent. This is because of the lower refractive index of the NLC for the perpendicular polarization. The laser oscillation was absent in the isotropic phase because of a low fluorescence efficiency at high temperatures.

  18. Polar-horizontal versus polar-vertical reverse-tilt-domain walls: influence of a pretilt angle below the nematic-isotropic phase transition.

    Science.gov (United States)

    Lee, Ji-Hoon; Atherton, Timothy J; Kang, Daeseung; Petschek, Rolfe G; Rosenblatt, Charles

    2008-08-01

    On cooling through the isotropic-to-nematic phase transition in a cell whose substrates induce a large pretilt angle theta0 from the vertical direction, but with no preferential azimuthal orientation, tilt domains appear. The boundary walls between reverse tilt domains are found to be bendlike and twistlike when theta0(T=TNI) is sufficiently large just below the isotropic-nematic phase transition temperature TNI--i.e., for a nearly planar orientation. Here the director becomes planar approximately midway through the wall, and we refer to this type of wall as "polar horizontal," which is topologically stable. However, if theta0(T=TNI) is sufficiently small just below TNI--i.e., closer to vertical orientation--a splay like and twistlike domain wall obtains, where the director is vertically oriented approximately midway through the wall; we refer to this type of wall as "polar vertical," whose stability depends on the anchoring. On cooling through the nematic phase, the pretilt angle theta0 decreases, with the director aligning closer to the vertical orientation. Nevertheless, the structures of both types of domain walls remain unchanged on variation of theta0 with temperature owing to topological constraints and also are unchanged after the application and removal of a large electric field. We examine the structure of domain walls for the liquid crystal ZLI-4330 (Merck) as a function of pretilt angle theta0(T=TNI) and calculate a critical value theta0c(T=TNI) of the pretilt angle just below TNI for which the predominance of domain walls crosses over from polar horizontal to polar vertical.

  19. 3D structure of nematic and columnar phases of hard colloidal platelets

    Energy Technology Data Exchange (ETDEWEB)

    Op Reinink, A B G M Leferink; Meijer, J M; Kleshchanok, D; Byelov, D V; Vroege, G J; Petukhov, A V; Lekkerkerker, H N W, E-mail: A.B.G.M.LeferinkopReinink@uu.nl [Van' t Hoff Laboratory for Physical and Colloid Chemistry, Utrecht University, PO Box 80.051, 3508 TB Utrecht (Netherlands)

    2011-05-18

    We present small angle x-ray scattering data of single-domain nematic and columnar liquid crystal phases in suspensions of sterically stabilized gibbsite platelets. The measurements are performed with different sample orientations to obtain information about the three-dimensional structure of the liquid crystalline phases. With the x-ray beam incident along the director of the nematic phase a strong correlation peak is observed corresponding to the side-to-side interparticle correlations, which suggests a columnar nematic structure. Upon sample rotation this side-to-side correlation peak of the nematic shifts to higher Q-values, suggesting the presence of strong fluctuations of small stacks of particles with different orientations, while the overall particle orientation is constant. In the hexagonal columnar phase, clear Bragg intercolumnar reflections are observed. Upon rotation, the Q-value of these reflections remains constant while their intensity monotonically decreases upon rotation. This indicates that the column orientation fluctuates together with the particle director in the columnar phase. This difference between the behaviour of the columnar and the nematic reflections upon sample rotation is used to assign the liquid crystal phase of a suspension consisting of larger platelets, where identification can be ambiguous due to resolution limitations.

  20. The determination of the phase transition temperatures of a semifluorinated liquid crystalline biphenyl ester by impedance spectroscopy as an alternative method

    Energy Technology Data Exchange (ETDEWEB)

    Yıldız, Alptekin [Istanbul Technical University, Department of Physics Engineering, Maslak, 34469 Istanbul (Turkey); Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Canli, Nimet Yilmaz, E-mail: niyilmaz@yahoo.com [Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Karanlık, Gürkan; Ocak, Hale [Yildiz Technical University, Department of Chemistry, 34220 Istanbul (Turkey); Okutan, Mustafa [Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Eran, Belkız Bilgin [Yildiz Technical University, Department of Chemistry, 34220 Istanbul (Turkey)

    2016-12-15

    Dielectric spectroscopy (DS) is a very powerful and important for better understanding of the molecular dynamics and relaxation phenomena in liquid crystals. The dielectric and impedance characteristics Ethyl 4-(7,7,8,8,9,9,10,10,10-nonafluorodecyloxy)biphenyl-4′-carboxylate (ENBC) liquid crystal have been analyzed over the frequency range of 100 Hz to MHz in the temperature region from room temperature to 180 °C. The compound ENBC shows enantiotropic a smectic mesophase in a wide temperature range. The phase transition temperatures T (°C) of the liquid crystal ENBC, which were characterized by Differential Scanning Calorimetry (DSC), have been verified by the dielectric measurements and conductivity mechanisms of the ENBC. The activation energies for some selected angular frequencies have also been calculated.

  1. From Networks to Nematics -- Carbon Nanotubes as Soft Matter

    Science.gov (United States)

    Hobbie, Erik K.

    2006-03-01

    Carbon nanotubes represent just one example of an emerging paradigm in condensed matter physics and materials science: traditionally ``hard'' materials appearing in new ``soft'' applications and environments. In part, this trend being is being fueled by the desire to exploit solution and fluid-based approaches, such as self assembly and flow processing, in an effort to streamline the engineering and commercialization of new materials and applications. In this talk I will review our recent work on dispersing, aligning and manipulating carbon nanotubes in complex fluids and polymer melts. Due to the large aspect ratios and strong attractive interaction potentials intrinsic to such materials, a number of scientific and technical challenges become immediately apparent. In particular, I will focus on the subtle interplay of rheological influences, such as externally applied shear and elongation stresses, with the inherent ``stickiness'' of carbon nanotube suspensions and melts, where the latter typically favors the formation of disordered networks or ``gels'' over the more desirable liquid-crystalline order. For simple shear, the strength of the applied stress is found to be a critical factor in dictating carbon nanotube morphology, which varies from a quiescent network to macroscopic aggregates to a fully dispersed, flow-aligned (para)nematic state. Although we find remarkably low loading thresholds for elastic percolation, our results highlight a fundamental dilemma for the engineering of conducting carbon nanotube polymer composites; dispersion stability will often be achieved at the expense of electrical conductivity.

  2. Anomalous swimming behavior of bacteria in nematic liquid crystals

    Science.gov (United States)

    Sokolov, Andrey; Zhou, Shuang; Lavrentovich, Oleg; Aranson, Igor

    2015-03-01

    Flagellated bacteria stop swimming in isotropic media of viscosity higher than 0.06kgm-1s-1. However, Bacillus Subtilis slows down by only about 30% in a nematic chromonic liquid crystal (CLC, 14wt% DSCG in water), where the anisotropic viscosity can be as high as 6kgm-1s-1. The bacteria velocity (Vb) is linear with the flagella rotation frequency. The phase velocity of the flagella Vf ~ 2Vb in LC, as compared to Vf ~ 10Vb in water. The flow generated by the bacteria is localized along the bacterial body axis, decaying slowly over tens of micrometers along, but rapidly over a few micrometers across this axis. The concentrated flow grants the bacteria new ability to carry cargo particles in LC, ability not seen in their habitat isotropic media. We attribute these anomalous features to the anisotropy of viscosity of the CLC, namely, the viscosities of splay and twist is hundreds times higher than that of bend deformation, which provides extra boost of swimming efficiency and enables the bacteria swim at considerable speed in a viscous medium. Our findings can potentially lead to applications such as particle transportation in microfluidic devices. A.S and I.A are supported by the US DOE, Office of Science, BES, Materials Science and Engineering Division. S.Z. and O.D.L are supported by NSF DMR 1104850, DMS-1434185.

  3. Snakes on a plane: modeling flexible active nematics

    Science.gov (United States)

    Selinger, Robin

    Active soft matter systems of self-propelled rod-shaped particles exhibit ordered phases and collective behavior that are remarkably different from their passive analogs. In nature, many self-propelled rod-shaped particles, such as gliding bacteria and kinesin-driven microtubules, are flexible and can bend. We model these ``living liquid crystals'' to explore their phase behavior, dynamics, and pattern formation. We model particles as short polymers via molecular dynamics with a Langevin thermostat and various types of activity, substrate, and environments. For self-propelled polar particles gliding on a solid substrate, we map out the phase diagram as a function of particle density and flexibility. We compare simulated defect structures to those observed in colonies of gliding myxobacteria; compare spooling behavior to that observed in microtubule gliding assays; and analyze emergence of nematic and polar order. Next we explore pattern formation of self-propelled polar particles under flexible encapsulation, and on substrates with non-uniform Gaussian curvature. Lastly, we impose an activity mechanism that mimics extensile shear, study flexible particles both on solid substrates and coupled to a lipid membrane, and discuss comparisons to relevant experiments. Work performed in collaboration with Michael Varga (Kent State) and Luca Giomi (Universiteit Leiden.) Work supported by NSF DMR-1409658.

  4. Anomalous Brownian motion of colloidal particle in a nematic environment: effect of the director fluctuations

    Directory of Open Access Journals (Sweden)

    T. Turiv

    2015-06-01

    Full Text Available As recently reported [Turiv T. et al., Science, 2013, Vol. 342, 1351], fluctuations in the orientation of the liquid crystal (LC director can transfer momentum from the LC to a colloid, such that the diffusion of the colloid becomes anomalous on a short time scale. Using video microscopy and single particle tracking, we investigate random thermal motion of colloidal particles in a nematic liquid crystal for the time scales shorter than the expected time of director fluctuations. At long times, compared to the characteristic time of the nematic director relaxation we observe typical anisotropic Brownian motion with the mean square displacement (MSD linear in time τ and inversly proportional to the effective viscosity of the nematic medium. At shorter times, however, the dynamics is markedly nonlinear with MSD growing more slowly (subdiffusion or faster (superdiffusion than τ. These results are discussed in the context of coupling of colloidal particle's dynamics to the director fluctuation dynamics.

  5. Magnetic-field tuning of whispering gallery mode lasing from ferromagnetic nematic liquid crystal microdroplets.

    Science.gov (United States)

    Mur, Maruša; Sofi, Junaid Ahmad; Kvasić, Ivan; Mertelj, Alenka; Lisjak, Darja; Niranjan, Vidur; Muševič, Igor; Dhara, Surajit

    2017-01-23

    We report magnetic field tuning of the structure and Whispering Gallery Mode lasing from ferromagnetic nematic liquid crystal micro-droplets. Microlasers were prepared by dispersing a nematic liquid crystal, containing magnetic nanoparticles and fluorescent dye, in a glycerol-lecithin matrix. The droplets exhibit radial director structure, which shows elastic distortion at a very low external magnetic field. The fluorescent dye doped ferromagnetic nematic droplets show Whispering Gallery Mode lasing, which is tunable by the external magnetic field. The tuning of the WGM lasing modes is linear in magnetic field with a wavelength-shift of the order of 1 nm/100 mT. Depending on the lasing geometry, the WGMs are red- or blue-shifted.

  6. Hydrodynamics Defines the Stable Swimming Direction of Spherical Squirmers in a Nematic Liquid Crystal

    Science.gov (United States)

    Lintuvuori, J. S.; Würger, A.; Stratford, K.

    2017-08-01

    We present a study of the hydrodynamics of an active particle—a model squirmer—in an environment with a broken rotational symmetry: a nematic liquid crystal. By combining simulations with analytic calculations, we show that the hydrodynamic coupling between the squirmer flow field and liquid crystalline director can lead to reorientation of the swimmers. The preferred orientation depends on the exact details of the squirmer flow field. In a steady state, pushers are shown to swim parallel with the nematic director while pullers swim perpendicular to the nematic director. This behavior arises solely from hydrodynamic coupling between the squirmer flow field and anisotropic viscosities of the host fluid. Our results suggest that an anisotropic swimming medium can be used to characterize and guide spherical microswimmers in the bulk.

  7. Melting in temperature sensitive suspensions

    Science.gov (United States)

    Alsayed, Ahmed M.

    We describe two experimental studies about melting in colloidal systems. In particular we studied melting of 1-dimensional lamellar phases and 3-dimensional colloidal crystals. In the first set of experiments we prepared suspensions composed of rodlike fd virus and the thermosensitive polymer, poly(N-isopropylacrylamide). The phase diagram of this systems is temperature and concentration dependent. Using video microscopy, we directly observed melting of lamellar phases and single lamellae into nematic phase. We found that lamellar phases swell with increasing temperature before melting into the nematic phase. The highly swollen lamellae can be superheated as a result of topological nucleation barriers that slow the formation of the nematic phase. In another set of experiments we prepared colloidal crystals from thermally responsive microgel spheres. The crystals are equilibrium close-packed three-dimensional structures. Upon increasing the temperature slightly above room temperature, particle volume fraction decreased from 0.74 to less than 0.5. Using video microscopy, we observed premelting at grain boundaries and dislocations within bulk colloidal crystals. Premelting is the localized loss of crystalline order at surfaces and defects at sample volume fractions above the bulk melting transition. Particle tracking revealed increased disorder in crystalline regions bordering defects, the amount of which depends on the type of defect, distance from the defect, and particle volume fraction. In total these observations suggest that interfacial free energy is the crucial parameter for premelting in colloidal and in atomic scale crystals.

  8. Asymmetric electrooptic response in a nematic liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Dascalu, Constanta [Politechnica University of Bucharest, Bucharest (Romania)

    2001-06-01

    An asymmetric electrooptic response in nematic liquid crystal (LC) has been obtained. The liquid crystal hybrid cell was made by using a standard configuration. One of the ITO (Indium Tin Oxide) electrodes was covered with a surfactant, which induces a homeotropic alignment. The second of the indium tin oxide electrodes was covered by a thin layer of photopolymer, which was previously mixed with an acid, which favours a process of release of protons. Such cations are responsible of electrochemical process in the LC leading to an asymmetric electrooptic response, which depend on the polarity of the applied electric field. This fact is due to an internal field, which change the effective voltage thresholds for the reorientation of the liquid crystal. During the anodic polarization, the optical switching is inhibited because the effective field decreases below the threshold value. On contrary for the opposite polarization the effective field is enough to determine a homeotropic alignment. [Spanish] Se ha obtenido una respuesta electro-optica asimetrica en cristales liquidos neumaticos. La celula hibrida de cristal liquido fue construida utilizando una configuracion estandar. Uno de los electrodos ITO fue cubierto con una pelicula delgada de material organico para inducir una alineacion homeotropa. El otro electrodo ITO fue cubierto con una pelicula delgada de fotopolimero anteriormente mezclada con un acido para favorecer la emision de protones. Estos cationes son responsables del proceso electroquimico en LC, conduciendo a una respuesta electro-optica asimetrica que depende de la polaridad del campo electrico aplicado. Este efecto es originado por un campo interno que cambia el umbral efectivo del voltaje para la reorientacion del cristal liquido. Durante la polarizacion anodica, la conmutacion optica se inhibe debido a que el campo efectivo disminuye abajo del valor del umbral. Por el contrario, para la polarizacion opuesta el campo efectivo es suficiente para

  9. The magnetic and nematic phase diagram of Ba1-xSrxFe2-yNiyAs2

    Science.gov (United States)

    Gong, Dongliang; Li, Shiliang; SC8, National Lab for superconductivity, IOP, CAS Team

    The correlation between magnetic and nematic orders has been widely studied in iron-based superconductors. The magnetic and nematic phase transitions may be both first order as in SrFe2As2,o or both second order as in BaFe2-xNixAs2. Within spin-nematic scenario, it is possible for a system to establish the nematic phase as second order while keeping the magnetic transition first-ordered. Experimentally, it is rather hard to distinguish a second-order transition from a weakly first-order transition. Here we have systematically studied the nematic susceptibility and magnetic susceptibility in the iron-based superconductor Ba1-xSrxFe2-yNiyAs2 by elastoresistivity and magnetic susceptibility measurements, respectively. The evolutions of the nematic and magnetic transitions from first order to second order can be continuously tuned by the substitution of Sr by Ba. Our results give a phase diagram that is consistent with the spin-nematic theory. Chinese Academy of Sciences, Ministry of Science and Technology of China, e National Science Foundation of China, China Academy of Engineering Physics.

  10. Possible nematic spin liquid in spin-1 antiferromagnetic system on the square lattice: Implications for the nematic paramagnetic state of FeSe

    Science.gov (United States)

    Gong, Shou-Shu; Zhu, W.; Sheng, D. N.; Yang, Kun

    2017-05-01

    The exotic normal state of iron chalcogenide superconductor FeSe, which exhibits vanishing magnetic order and possesses an electronic nematic order, triggered extensive explorations of its magnetic ground state. To understand its novel properties, we study the ground state of a highly frustrated spin-1 system with bilinear-biquadratic interactions using an unbiased large-scale density matrix renormalization group. Remarkably, with increasing biquadratic interactions, we find a paramagnetic phase between Néel and stripe magnetic ordered phases. We identify this phase as a candidate of nematic quantum spin liquid by the compelling evidences, including vanished spin and quadrupolar orders, absence of lattice translational symmetry breaking, and a persistent nonzero lattice nematic order in the thermodynamic limit. The established quantum phase diagram naturally explains the observations of enhanced spin fluctuations of FeSe in neutron scattering measurement and the phase transition with increasing pressure. This identified paramagnetic phase provides a possibility to understand the novel properties of FeSe.

  11. Disclination elastica model of loop collision and growth in confined nematic liquid crystals.

    Science.gov (United States)

    Shams, Alireza; Yao, Xuxia; Park, Jung Ok; Srinivasarao, Mohan; Rey, Alejandro D

    2015-07-21

    Theory and modeling are used to characterize disclination loop-loop interactions in nematic liquid crystals under capillary confinement with strong homeotropic anchoring. This defect process arises when a mesogen in the isotropic phase is quenched into the stable nematic state. The texture evolution starts with +1/2 disclination loops that merge into a single loop through a process that involves collision, pinching and relaxation. The process is characterized with a combined Rouse-Frank model that incorporates the tension and bending elasticity of disclinations and the rotational viscosity of nematics. The Frank model of disclinations follows the Euler elastica model, whose non-periodic solution, known as Poleni's curve, is shown to locally describe the loop-loop collision and to shed light on why loop-loop merging results in a disclination intersection angle of approximately 60°. Additional Poleni invariants demonstrate how tension and bending pinch the two loops into a single +1/2 disclination ring. The Rouse model of disclination relaxation yields a Cahn-Hilliard equation whose time constant combines the confinement, tension/bending stiffness ratio and disclination diffusivity. Based on predictions made using this three stage process, a practical procedure is proposed to find viscoelastic parameters from defect geometry and defect dynamics. These findings contribute to the evolving understanding of textural transformations in nematic liquid crystals under confinement using the disclination elastica methodology.

  12. Optical tuning of photonic bandgaps in dye-doped nematic liquid crystal photonic crystal fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard; Hermann, David Sparre

    2005-01-01

    An all-optical modulator is demonstrated, which utilizes a pulsed 532 nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid crystal. In order to investigate the time response of the LCPBG fiber device, a low-power CW probe...

  13. Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez-Hernández, Abelardo; Hur, Su-Mi; Armas-Pérez, Julio; Cruz, Monica; de Pablo, Juan

    2017-03-01

    Liquid crystalline polymers exhibit a particular richness of behaviors that stems from their rigidity and their macromolecular nature. On the one hand, the orientational interaction between liquid-crystalline motifs promotes their alignment, thereby leading to the emergence of nematic phases. On the other hand, the large number of configurations associated with polymer chains favors formation of isotropic phases, with chain stiffness becoming the factor that tips the balance. In this work, a soft coarse-grained model is introduced to explore the interplay of chain stiffness, molecular weight and orientational coupling, and their role on the isotropic-nematic transition in homopolymer melts. We also study the structure of polymer mixtures composed of stiff and flexible polymeric molecules. We consider the effects of blend composition, persistence length, molecular weight and orientational coupling strength on the melt structure at the nano-and mesoscopic levels. Conditions are found where the systems separate into two phases, one isotropic and the other nematic. We confirm the existence of non-equilibrium states that exhibit sought-after percolating nematic domains, which are of interest for applications in organic photovoltaic and electronic devices.

  14. Orbital nematic order and interplay with magnetism in the two-orbital Hubbard model.

    Science.gov (United States)

    Wang, Zhentao; Nevidomskyy, Andriy H

    2015-06-10

    Motivated by the recent angle-resolved photoemission spectroscopy (ARPES) on FeSe and iron pnictide families of iron-based superconductors, we have studied the orbital nematic order and its interplay with antiferromagnetism within the two-orbital Hubbard model. We used random phase approximation (RPA) to calculate the dependence of the orbital and magnetic susceptibilities on the strength of interactions and electron density (doping). To account for strong electron correlations not captured by RPA, we further employed non-perturbative variational cluster approximation (VCA) capable of capturing symmetry broken magnetic and orbitally ordered phases. Both approaches show that the electron and hole doping affect the two orders differently. While hole doping tends to suppress both magnetism and orbital ordering, the electron doping suppresses magnetism faster. Crucially, we find a realistic parameter regime for moderate electron doping that stabilizes orbital nematicity in the absence of long-range antiferromagnetic order. This is reminiscent of the non-magnetic orbital nematic phase observed recently in FeSe and a number of iron pnictide materials and raises the possibility that at least in some cases, the observed electronic nematicity may be primarily due to orbital rather than magnetic fluctuations.

  15. Correlation and disorder-enhanced nematic spin response in superconductors with weakly broken rotational symmetry

    DEFF Research Database (Denmark)

    Andersen, Brian Møller; Graser, S.; Hirschfeld, P. J.

    2012-01-01

    Recent experimental and theoretical studies have highlighted the possible role of an electronic nematic liquid in underdoped cuprate superconductors. We calculate, within a model of d-wave superconductor with Hubbard correlations, the spin susceptibility in the case of a small explicitly broken...

  16. H-3 NMR of the tritiated isotopologues of methane in nematic liquid-crystal solvents

    NARCIS (Netherlands)

    Burnell, E.E.; de Lange, C.A.; Capitani, D.; Angelini, G.

    2010-01-01

    The NMR spectra of the tritiated isotopologues of methane dissolved in several nematic liquid-crystalline solvents are measured. The spectral parameters obtained agree extremely well with those predicted from earlier NMR studies of the deuterated isotopologues, providing excellent confirmation of

  17. Elastic and hydrodynamic torques on a colloidal disk within a nematic liquid crystal.

    Science.gov (United States)

    Rovner, Joel B; Borgnia, Dan S; Reich, Daniel H; Leheny, Robert L

    2012-10-01

    The orientationally dependent elastic energy and hydrodynamic behavior of colloidal disks with homeotropic surface anchoring suspended in the nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) have been investigated. In the absence of external torques, the disks align with the normal of the disk face â parallel to the nematic director n[over ^]. When a magnetic field is applied, the disks rotate â by an angle θ so that the magnetic torque and the elastic torque caused by distortion of the nematic director field are balanced. Over a broad range of angles, the elastic torque increases linearly with θ in quantitative agreement with a theoretical prediction based on an electrostatic analogy. When the disks are rotated to angles θ>π/2, the resulting large elastic distortion makes the disk orientation unstable, and the director undergoes a topological transition in which θ→π-θ. In the transition, a defect loop is shed from the disk surface, and the disks spin so that â sweeps through π radians as the loop collapses back onto the disk. Additional measurements of the angular relaxation of disks to θ=0 following removal of the external torque show a quasi-exponential time dependence from which an effective drag viscosity for the nematic can be extracted. The scaling of the angular time dependence with disk radius and observations of disks rotating about â indicate that the disk motion affects the director field at surprisingly modest Ericksen numbers.

  18. Rheological properties of a nematic cell oriented in a planar manner

    Energy Technology Data Exchange (ETDEWEB)

    Barbero, G., E-mail: giovanni.barbero@polito.i [Dipartimento di Fisica and C. N. I. S. M., Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)] [Universite de Picardie Jules Verne, Laboratoire de Physique des Systemes Complexes, 33 rue Saint-Leu 80039, Amiens (France); Meyer, C.; Lelidis, I. [Universite de Picardie Jules Verne, Laboratoire de Physique des Systemes Complexes, 33 rue Saint-Leu 80039, Amiens (France)

    2010-05-17

    We propose a simple model to investigate the rheological properties of a nematic cell oriented in a planar manner. The storage and loss modulus are evaluated in the case of strong and weak anchoring conditions. The contribution of the surface viscosity to the rheological parameters is also considered.

  19. Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers

    Directory of Open Access Journals (Sweden)

    Abelardo Ramírez-Hernández

    2017-03-01

    Full Text Available Liquid crystalline polymers exhibit a particular richness of behaviors that stems from their rigidity and their macromolecular nature. On the one hand, the orientational interaction between liquid-crystalline motifs promotes their alignment, thereby leading to the emergence of nematic phases. On the other hand, the large number of configurations associated with polymer chains favors formation of isotropic phases, with chain stiffness becoming the factor that tips the balance. In this work, a soft coarse-grained model is introduced to explore the interplay of chain stiffness, molecular weight and orientational coupling, and their role on the isotropic-nematic transition in homopolymer melts. We also study the structure of polymer mixtures composed of stiff and flexible polymeric molecules. We consider the effects of blend composition, persistence length, molecular weight and orientational coupling strength on the melt structure at the nano- and mesoscopic levels. Conditions are found where the systems separate into two phases, one isotropic and the other nematic. We confirm the existence of non-equilibrium states that exhibit sought-after percolating nematic domains, which are of interest for applications in organic photovoltaic and electronic devices.

  20. Monotonicity of a Key Function Arised in Studies of Nematic Liquid Crystal Polymers

    Directory of Open Access Journals (Sweden)

    Hongyun Wang

    2007-01-01

    Full Text Available We revisit a key function arised in studies of nematic liquid crystal polymers. Previously, it was conjectured that the function is strictly decreasing and the conjecture was numerically confirmed. Here we prove the conjecture analytically. More specifically, we write the derivative of the function into two parts and prove that each part is strictly negative.

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

    Indian Academy of Sciences (India)

    vigorous attempts to find it in various systems resulted in mis-identifications. The results of X-ray diffraction and .... the four peaks arise from a single domain of this biaxial nematic phase. Upon application of the electric field, no changes occur until the field strength exceeds a minimum value of 6x106 V/m at 500 Hz. Above ...

  2. Dielectric relaxation studies in 5CB nematic liquid crystal at 9 GHz ...

    Indian Academy of Sciences (India)

    5CB nematic liquid crystal are measured using microwave cavity technique under the influence of an external magnetic field at 9 GHz ... Dielectric relaxation; phase transition; liquid crystals; microwaves. PACS Nos 64.70.-p; 65.40. ... liquids, are preferentially aligned along a common axis, called director. The dielectric prop-.

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

    Indian Academy of Sciences (India)

    core liquid crystals. Abstract. 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 ...

  4. Optical sensor platform based on cellulose nanocrystals (CNC) - 4'-(hexyloxy)-4-biphenylcarbonitrile (HOBC) bi-phase nematic liquid crystal composite films.

    Science.gov (United States)

    Santos, Moliria V; Tercjak, Agnieszka; Gutierrez, Junkal; Barud, Hernane S; Napoli, Mariana; Nalin, Marcelo; Ribeiro, Sidney J L

    2017-07-15

    The preparation of composite materials has gained tremendous attention due to the potential synergy of the combined materials. Here we fabricate novel thermal/electrical responsive photonic composite films combining cellulose nanocrystals (CNC) with a low molecular weight nematic liquid crystal (NLC), 4'-(hexyloxy)-4-biphenylcarbonitrile (HOBC). The obtained composite material combines both intense structural coloration of photonic cellulose and thermal and conductive properties of NLC. Scanning electron microscopy (SEM) results confirmed that liquid crystals coated CNC films maintain chiral nematic structure characteristic of CNC film and simultaneously, transversal cross-section scanning electron microscopy images indicated penetration of liquid crystals through the CNC layers. Investigated composite film maintain NLC optical properties being switchable as a function of temperature during heating/cooling cycles. The relationship between the morphology and thermoresponsive in the micro/nanostructured materials was investigated by using transmission optical microscopy (TOM). Conductive response of the composite films was proved by Electrostatic force microscopy (EFM) measurement. Designed thermo- and electro-responsive materials open novel simple pathway of fabrication of CNC-based materials with tunable properties. Copyright © 2017. Published by Elsevier Ltd.

  5. Spontaneous electrorheological effect in nematic liquid crystals under Taylor-Couette flow configuration

    Science.gov (United States)

    Dhar, Jayabrata; Chakraborty, Suman

    2017-09-01

    Electrorheological (ER) characteristics of Nematic Liquid Crystals (NLCs) have been a topic of immense interest in the field of soft matter physics owing to its rheological modulation capabilities. Here we explore the augmentation in rheological characteristics of the nematic fluid confined within the annular region of the concentric cylindrical space with an Electrical Double Layer (EDL) induced at the fluid-substrate interface due to certain physico-chemical interactions. Using a Taylor-Couette flow configuration associated with an EDL induced at the inner cylinder wall, we show that a spontaneous electrorheological effect is generated owing to the intrinsic director anisotropy and structural order of complex nematic fluids. We seek to find the enhancement in torque transfer capability due to the inherent electrorheological nature of the nematic medium, apart from exploiting the innate nature of such homogeneous media to remain free of coagulation, a fact which makes it an excellent candidate for the applications in microfluidic environment. Our analysis reveals that with stronger induced charge density within the EDL, the apparent viscosity enhances, which, in turn, augments torque transfer across the concentric cylinder. The velocity profile tends to flatten in comparison to the classical circular Couette flow in annular geometry as one increases the surface charge density. We further observe a more pronounced ER effect for the nematic medium having larger electrical permittivity anisotropy. Besides the torque transfer qualifications, we also explore the distinct scenarios, wherein the same NLC medium exhibits shear thinning and shear thickening characteristics. The present configuration of the efficient torque transfer mechanism may be proficiently downscaled to micro-level and is relevant in the fabrication of micro-clutch and micro-dampers.

  6. Mesogenic benzothiazole derivatives with methoxy substituents

    Indian Academy of Sciences (India)

    In series I, -butyloxy to -tetradecyloxy derivatives exhibit nematic mesophase. Smectic A mesophase commences from the -dodecyloxy derivative as a monotropic phase and is retained up to the last member synthesized. All the members of series II exhibit enantiotropic nematic mesophase. The mesomorphic properties ...

  7. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with g-Alumina Nanoparticles

    Directory of Open Access Journals (Sweden)

    Sergio Diez-Berart

    2015-06-01

    Full Text Available In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy-ω-(1-pyrenimine-benzylidene-4′-oxy undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

  8. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with γ-Alumina Nanoparticles

    Science.gov (United States)

    Diez-Berart, Sergio; López, David O.; Salud, Josep; Diego, José Antonio; Sellarès, Jordi; Robles-Hernández, Beatriz; de la Fuente, María Rosario; Ros, María Blanca

    2015-01-01

    In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy)-ω-(1-pyrenimine-benzylidene-4′-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

  9. The nematicity induced d-symmetry charge density wave in electron-doped iron-pnictide superconductors

    Science.gov (United States)

    Chou, Chung-Pin; Chen, Hong-Yi; Ting, C. S.

    2018-03-01

    The interplay among the nematicity, the stripe spin-density-wave (SDW) order and superconductivity in iron-pnictides is studied in a self-consistent Bogoliubov-de Gennes equations. Our calculations have shown that the nematic-order breaks the degeneracy of dxz and dyz orbitals and causes the elliptic Fermi surface near the Γ point in the normal state. In addition, the appearance of the orthorhombic magnetic fluctuations generates two uneven pairs of peaks at ( ± π, 0) and (0, ± π) in its Fourier transformation. All these are comparing favorably with experimental measurements. In the nematic phase, our results indicate that the charge density and its spatial image in the local density of states exhibit a dx2 -y2-like symmetry. Finally, the complete phase diagram is obtained and the nematic phase is found to be in a narrow region close to the SDW transition in the electron-doped iron-pnictide superconductors.

  10. Temperature independent low voltage polymer stabilized blue phase liquid crystals

    Science.gov (United States)

    Kemiklioglu, E.; Hwang, J. Y.; Chien, L.-C.

    2012-03-01

    Blue phases are types of liquid crystal phase which can appear in a narrow temperature range between a chiral nematic phase and isotropic liquid phase. Blue Phase (BP) liquid crystals have been known to exist in a small temperature range. Recently, broadening the temperature range of a BP liquid crystal has occurred by using a mixture of nematic bimesogenic liquid crystals or by polymerizing a small amount of monomer in a BP to stabilize the cubic lattice against temperature variation. In this study, we report a low switching voltage polymer stabilized blue phase (PSBP) liquid crystal device. We showed the stabilization of blue phases over a temperature range of 30.4 °C including room temperature. We observed the temperature independent of Bragg wavelength. Furthermore, the polymer effect on the electo-optic properties of a self assembled nanostructured blue phase liquid crystal composites have been investigated. As well as the ratio between two monomers, the overall monomers concentration is controlled.

  11. Electro-optic studies of the flexoelectric effect in chiral nematic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Musgrave, B

    2000-01-01

    With the advent of global telecommunications networks and the Internet, the development of portable display technology has gained a new impetus. Liquid crystal devices have played a major role in this area, most conspicuously as displays in laptop computers. To date, these liquid crystalline devices have been generally based on the rather slow ({approx} 30 ms) dielectric response of the achiral nematic liquid crystal phase, although more expensive devices based on the faster (< 100 {mu}s) ferroelectric switching of the smectic C* phase are in production. The research presented in this thesis relates to a new switching effect recently discovered in the chiral nematic phase. The flexoelectrically-driven rotation of the chiral nematic phase's optic axis is fast - of the order 10 {mu}s to lms - proportional to the applied field amplitude and completely in-plane. The optic axis has been deflected by over 30 deg. from the equilibrium position in some materials. These electro-optic properties make the 'flexoelectro-optic' effect a potential contender in the liquid crystal device market. The present thesis contains the first studies of the effect of molecular structure on flexoelectric coupling in the chiral nematic phase. Several homologous series of estradiol-cyanobiphenyl bimesogenic materials synthesized for this work have been characterized and their electro-optic properties investigated. The chiral nematic phases of these materials have unusually strong flexoelectro-optic effects and respond on a sub-millisecond timescale. The ratios of the effective flexoelectric coefficient to the mean splay-bend elastic constant, e-bar/K, in the present materials lie in the range 0.3 to 0.6 C N{sup -1} m{sup -1}, and are the highest measured to date: the highest value previously published is 0.12 C N{sup -1} m{sup -1}, measured for the commercial mixture TM216. In order to interpret the effect of the bimesogens' molecular structure, achiral nematic monomesogens

  12. Curvature-induced defect unbinding and dynamics in active nematic toroids

    Science.gov (United States)

    Ellis, Perry W.; Pearce, Daniel J. G.; Chang, Ya-Wen; Goldsztein, Guillermo; Giomi, Luca; Fernandez-Nieves, Alberto

    2018-01-01

    Nematic order on curved surfaces is often disrupted by the presence of topological defects, which are singular regions in which the orientational order is undefined. In the presence of force-generating active materials, these defects are able to migrate through space like swimming microorganisms. We use toroidal surfaces to show that despite their highly chaotic and non-equilibrium dynamics, pairs of defects unbind and segregate in regions of opposite Gaussian curvature. Using numerical simulations, we find that the degree of defect unbinding can be controlled by tuning the system activity, and even suppressed in strongly active systems. Furthermore, by using the defects as active microrheological tracers and quantitatively comparing our experimental and theoretical results, we are able to determine material properties of the active nematic. Our results illustrate how topology and geometry can be used to control the behaviour of active materials, and introduce a new avenue for the quantitative mechanical characterization of active fluids.

  13. Splitting, linking, knotting, and solitonic escape of topological defects in nematic drops with handles.

    Science.gov (United States)

    Tasinkevych, Mykola; Campbell, Michael G; Smalyukh, Ivan I

    2014-11-18

    Topologically nontrivial field excitations, including solitonic, linked, and knotted structures, play important roles in physical systems ranging from classical fluids and liquid crystals, to electromagnetism, classic, and quantum field theories. These excitations can appear spontaneously during symmetry-breaking phase transitions. For example, in cosmological theories, cosmic strings may have formed knotted configurations influencing the Early Universe development, whereas in liquid crystals transient tangled defect lines were observed during isotropic-nematic transitions, eventually relaxing to defect-free states. Knotted and solitonic fields and defects were also obtained using optical manipulation, complex-shaped colloids, and frustrated cholesterics. Here we use confinement of nematic liquid crystal by closed surfaces with varied genus and perpendicular boundary conditions for a robust control of appearance and stability of such field excitations. Theoretical modeling and experiments reveal structure of defect lines as a function of the surface topology and material and geometric parameters, establishing a robust means of controlling solitonic, knotted, linked, and other field excitations.

  14. Landau–De Gennes Theory of Nematic Liquid Crystals: the Oseen–Frank Limit and Beyond

    KAUST Repository

    Majumdar, Apala

    2009-07-07

    We study global minimizers of a continuum Landau-De Gennes energy functional for nematic liquid crystals, in three-dimensional domains, subject to uniaxial boundary conditions. We analyze the physically relevant limit of small elastic constant and show that global minimizers converge strongly, in W1,2, to a global minimizer predicted by the Oseen-Frank theory for uniaxial nematic liquid crystals with constant order parameter. Moreover, the convergence is uniform in the interior of the domain, away from the singularities of the limiting Oseen-Frank global minimizer. We obtain results on the rate of convergence of the eigenvalues and the regularity of the eigenvectors of the Landau-De Gennes global minimizer. We also study the interplay between biaxiality and uniaxiality in Landau-De Gennes global energy minimizers and obtain estimates for various related quantities such as the biaxiality parameter and the size of admissible strongly biaxial regions. © Springer-Verlag (2009).

  15. Generalized nematohydrodynamic boundary conditions with application to bistable twisted nematic liquid-crystal displays

    KAUST Repository

    Fang, Angbo

    2008-12-08

    Parallel to the highly successful Ericksen-Leslie hydrodynamic theory for the bulk behavior of nematic liquid crystals (NLCs), we derive a set of coupled hydrodynamic boundary conditions to describe the NLC dynamics near NLC-solid interfaces. In our boundary conditions, translational flux (flow slippage) and rotational flux (surface director relaxation) are coupled according to the Onsager variational principle of least energy dissipation. The application of our boundary conditions to the truly bistable π -twist NLC cell reveals a complete picture of the dynamic switching processes. It is found that the thus far overlooked translation-rotation dissipative coupling at solid surfaces can accelerate surface director relaxation and enhance the flow rate. This can be utilized to improve the performance of electro-optical nematic devices by lowering the required switching voltages and reducing the switching times. © 2008 The American Physical Society.

  16. Topological defect launches 3D mound in the active nematic sheet of neural progenitors

    CERN Document Server

    Kawaguchi, Kyogo; Sano, Masaki

    2016-01-01

    Cultured stem cells have become a standard platform not only for regenerative medicine and developmental biology but also for biophysical studies. Yet, the characterization of cultured stem cells at the level of morphology and macroscopic patterns resulting from cell-to-cell interactions remain largely qualitative, even though they are the simplest features observed in everyday experiments. Here we report that neural progenitor cells (NPCs), which are multipotent stem cells that give rise to cells in the central nervous system, rapidly glide and stochastically reverse its velocity while locally aligning with neighboring cells, thus showing features of an active nematic system. Within the two-dimensional nematic pattern, we find interspaced topological defects with +1/2 and -1/2 charges. Remarkably, we identified rapid cell accumulation leading to three-dimensional mounds at the +1/2 topological defects. Single-cell level imaging around the defects allowed quantification of the evolving cell density, clarifyin...

  17. Propagation of optical spatial solitary waves in bias-free nematic-liquid-crystal cells

    Energy Technology Data Exchange (ETDEWEB)

    Minzoni, Antonmaria A. [Fenomenos Nonlineales y Mecanica (FENOMEC), Department of Mathematics and Mechanics, Instituto de Investigacion en Matematicas Aplicadas y Sistemas, Universidad Nacional Autonoma de Mexico, 01000 Mexico D.F. (Mexico); Sciberras, Luke W.; Worthy, Annette L. [School of Mathematics and Applied Statistics, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522 (Australia); Smyth, Noel F. [School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom)

    2011-10-15

    The propagation of a bulk optical solitary wave in a rectangular cell filled with a nematic liquid crystal--a nematicon--is mathematically modelled. In order to overcome the Freedricksz threshold the cell walls are rubbed to pretilt the nematic. A modulation theory, based on a Lagrangian formulation, is developed for the (2+1)-dimensional propagation of the solitary wave beam down the cell. This modulation theory is based on two different formulations of the director distribution. The relative advantages and disadvantages of these two methods are discussed. A previously unexplored method based on images is found to possess significant advantages. Excellent agreement with full numerical solutions of the nematicon equations is found for both methods. Finally, the implications of the results obtained for some widely used approximations to the nematicon equations are discussed, particularly their use in comparisons with experimental results.

  18. Nematic effects and strain coupling in entangled polymer melts under strong flow

    DEFF Research Database (Denmark)

    Kirkensgaard, Jacob J K; Hengeller, Ludovica; Dorokhin, Andriy

    2016-01-01

    We use small-angle neutron scattering (SANS) to study labeled short chains with and without the influence of an entangled and highly stretched surrounding environment of longer chains. We find unequivocal evidence of nematic effects as the blend chains in steady state flow are stretched a factor ...... explanation for the two first regimes of the nonlinear relaxation, particularly a transition regime where the long chains are relaxing in a sea of reptating short chains....

  19. Do shape invariant solitons in highly nonlocal nematic liquid crystals really exist?

    CERN Document Server

    Petrovic, Milan S; Aleksic, Najdan B; Belic, Milivoj R

    2011-01-01

    We question physical existence of shape invariant solitons in three dimensional nematic liquid crystals. Using modified Petviashvili's method for finding eigenvalues and eigenfunctions, we determine shape invariant solitons in a realistic physical model that includes the highly nonlocal nature of the liquid crystal system. We check the stability of such solutions by propagating them for long distances. We establish that any noise added to the medium or to the fundamental solitons induces them to breathe, rendering them practically unobservable.

  20. Nematic ordering in pyrochlore antiferromagnets: high-field phase of chromium spinel oxides

    OpenAIRE

    Takata, Emika; Momoi, Tsutomu; Oshikawa, Masaki

    2015-01-01

    Motivated by recent observation of a new high field phase near saturation in chromium spinels $A$Cr$_2$O$_4$ ($A=$ Zn, Cd, Hg), we study the $S = 3/2$ pyrochlore Heisenberg antiferromagnet with biquadratic interactions. Magnon instability analysis at the saturation field reveals that a very small biquadratic interaction can induce magnon pairing in pyrochlore antiferromagnets, which leads to the emergence of a ferro-quadrupolar phase, or equivalently a spin nematic phase, below the saturation...

  1. Measurement of birefringence of nematic liquid crystal material by multiple-wavelength interferometry using nearly common-path single-stage Mach-Zehnder interferometer.

    Science.gov (United States)

    Inam, M; Srivastava, V; Mehta, D S

    2013-11-20

    We report the measurement of birefringence of nematic liquid crystal (NLC) material using multiple-wavelength interferometry. A nearly common path single-stage Mach-Zehnder interferometer was used for recording interferograms of high stability. The Fourier transform fringe analysis technique was used to reconstruct the two-dimensional phase maps of interferograms consisting of the entire active area of the liquid crystal cell. Change in phase as a function of applied voltage to a liquid-crystal cell was measured for blue, green, and red color laser light, keeping the temperature constant during the experiment. From the change in phase, the birefringence for three colors, i.e., red, green, and blue light, was determined. It is found that the birefringence of NLC material for red, green, and blue colors decreases with the increase in wavelength in the visible range. The present method is noncontact, nonmechanical scanning and highly stable due to a common path interferometer.

  2. Cholesteric Polymer Scaffolds Filled with Azobenzene-Containing Nematic Mixture with Phototunable Optical Properties.

    Science.gov (United States)

    Ryabchun, Alexander; Raguzin, Ivan; Stumpe, Joachim; Shibaev, Valery; Bobrovsky, Alexey

    2016-10-12

    The past two decades witnessed tremendous progress in the field of creation of different types of responsive materials. Cholesteric polymer networks present a very promising class of smart materials due to the combination of the unique optical properties of cholesteric mesophase and high mechanical properties of polymer networks. In the present work we demonstrate the possibility of fast and reversible photocontrol of the optical properties of cholesteric polymer networks. Several cholesteric photopolymerizable mixtures are prepared, and porous cholesteric network films with different helix pitches are produced by polymerization of these mixtures. An effective and simple method of the introduction of photochromic azobenzene-containing nematic mixture capable of isothermal photoinducing the nematic-isotropic phase transition into the porous polymer matrix is developed. It is found that cross-linking density and degree of polymer network filling with a photochromic nematic mixture strongly influence the photo-optical behavior of the obtained composite films. In particular, the densely cross-linked films are characterized by a decrease in selective light reflection bandwidth, whereas weakly cross-linked systems display two processes: the shift of selective light reflection peak and decrease of its width. It is noteworthy that the obtained cholesteric materials are shown to be very promising for the variety applications in optoelectronics and photonics.

  3. Electro-osmosis of nematic liquid crystals under weak anchoring and second-order surface effects

    Science.gov (United States)

    Poddar, Antarip; Dhar, Jayabrata; Chakraborty, Suman

    2017-07-01

    Advent of nematic liquid crystal flows has attracted renewed attention in view of microfluidic transport phenomena. Among various transport processes, electro-osmosis stands as one of the efficient flow actuation mechanisms through narrow confinements. In the present study, we explore the electrically actuated flow of an ordered nematic fluid with ionic inclusions, taking into account the influences from surface-induced elasticity and electrical double layer (EDL) phenomena. Toward this, we devise the coupled flow governing equations from fundamental free-energy analysis, considering the contributions from first- and second-order elastic, dielectric, flexoelectric, charged surface polarization, ionic and entropic energies. The present study focuses on the influence of surface charge and elasticity effects in the resulting linear electro-osmosis through a slit-type microchannel whose surfaces are chemically treated to display a homeotropic-type weak anchoring state. An optical periodic stripe configuration of the nematic director has been observed, especially for higher electric fields, wherein the Ericksen number for the dynamic study is restricted to the order of unity. Contrary to the isotropic electrolytes, the EDL potential in this case was found to be dependent on the external field strength. Through a systematic investigation, we brought out the fact that the wavelength of the oscillating patterns is dictated mainly by the external field, while the amplitude depends on most of the physical variables ranging from the anchoring strength and the flexoelectric coefficients to the surface charge density and electrical double layer thickness.

  4. Chiral amplification in a cyanobiphenyl nematic liquid crystal doped with helicene-like derivatives

    Directory of Open Access Journals (Sweden)

    Alberta Ferrarini

    2009-10-01

    Full Text Available The addition of a chiral non-racemic dopant to a nematic liquid crystal (LC has the effect of transferring the molecular chirality to the phase organization and a chiral nematic phase is formed. This molecular chirality amplification in the LC provides a unique possibility for investigating the relationship between molecular structure, intermolecular interactions, and mesoscale organization. It is known that axially chiral or helical-shaped molecules with reduced conformational disorder are good candidates for high helical twisting power derivatives. In particular, biaryl derivatives are known to be efficient chiral inducers in biaryl nematic mesophases. In this paper, we focus on a new series of helicene-like molecules of known absolute configuration. We have integrated cholesteric pitch measurements with geometry optimization by DFT calculations and analysis of the twisting ability by the Surface Chirality model to shed light on the structural features responsible for the analogies and differences exhibited by these derivatives. The investigation of these dopants with well-defined geometry, by virtue of the low conformational freedom, and the substituents variously distributed around the core, allows us to extend our knowledge of the molecular origin of the chirality amplification in liquid crystals and to confirm the simple relationship “molecular P-helicity” → “cholesteric P-handedness” for helical-shaped helicene-like derivatives.

  5. Topological polymer dispersed liquid crystals with bulk nematic defect lines pinned to handlebody surfaces.

    Science.gov (United States)

    Campbell, Michael G; Tasinkevych, Mykola; Smalyukh, Ivan I

    2014-05-16

    Polymer dispersed liquid crystals are a useful model system for studying the relationship between surface topology and defect structures. They are comprised of a polymer matrix with suspended spherical nematic drops and are topologically constrained to host defects of an elementary hedgehog charge per droplet, such as bulk or surface point defects or closed disclination loops. We control the genus of the closed surfaces confining such micrometer-sized nematic drops with tangential boundary conditions for molecular alignment imposed by the polymer matrix, allowing us to avoid defects or, on the contrary, to generate them in a controlled way. We show, both experimentally and through numerical modeling, that topological constraints in nematic microdrops can be satisfied by hosting topologically stable half-integer bulk defect lines anchored to opposite sides of handlebody surfaces. This enriches the interplay of topologies of closed surfaces and fields with nonpolar symmetry, yielding new unexpected configurations that cannot be realized in vector fields, having potential implications for topologically similar defects in cosmology and other fields.

  6. Field-driven dynamics of microcapillaries filled with nematic liquid crystal

    Science.gov (United States)

    Fu, Fred; Khayyatzadeh, Pouya; Abukhdeir, Nasser M.

    Polymer-dispersed liquid crystal (PDLC) composites have long been a focus of study for their unique electro-optical properties and the feasibility of manufacturing them on a large scale, resulting in applications such as switchable windows. LC domains within PDLCs are typically spheroidal, as opposed to rectangular in LCD technology, and thus exhibit substantially different behaviour in the presence of an external field. In this work, continuum simulations were performed in order to capture the complex formation and electric field-driven switching dynamics of approximations of PDLC domains. A simplified elliptic cylinder (microcapillary) geometry is used and the effects of varying aspect ratio, surface anchoring, and external field strength were studied using the Landau-de Gennes model. The observed nematic formation and reorientation dynamics were found to be governed by the presence and motion of defects within the domain. Aspect ratio was found to strongly influence domain texture by providing regions of high curvature to which defects are attracted. Simulations also predict the presence of a geometry-controlled transition from nematic order enhanced by an external field (low aspect ratio) to nematic order frustrated by an external field (high aspect ratio). This work was made possible by the Natural Sciences and Engineering Research Council of Canada and Compute Ontario.

  7. Topological defects in an unconfined nematic fluid induced by single and double spherical colloidal particles

    Science.gov (United States)

    Wang, Yiwei; Zhang, Pingwen; Chen, Jeff Z. Y.

    2017-10-01

    We present numerical solutions to the Landau-de Gennes free-energy model under the one-constant approximation for systems of single and double spherical colloidal particles immersed in an otherwise uniformly aligned nematic liquid crystal. A perfect homeotropic surface anchoring of liquid-crystal molecules on the spherical surface is considered. A large parameter space is carefully examined, including those in the free-energy model and those describing the dimer configurations and the background liquid-crystal orientation. The stability of the resulting liquid-crystal defects appearing in the neighborhood of the colloidal dimer pair is analyzed in light of the numerical results for their free energies. A number of scenarios are considered: a free dimer pair in a nematic fluid where the free-energy ground states are described in terms of a phase diagram, and a constrained dimer pair where the interparticle distance and the relative orientation of the distance vector to the nematic director can be manipulated. We pay particular attention to the nonsymmetric solutions, which yield several metastable defect states that can be observed in real systems. The high-precision numerical calculations are based on a spectral method, which is an enabling factor that allows us to compare the subtle difference in the free energies of different defect structures.

  8. Transverse fields to tune an Ising-nematic quantum phase transition

    Science.gov (United States)

    Maharaj, Akash V.; Rosenberg, Elliott W.; Hristov, Alexander T.; Berg, Erez; Fernandes, Rafael M.; Fisher, Ian R.; Kivelson, Steven A.

    2017-12-01

    The paradigmatic example of a continuous quantum phase transition is the transverse field Ising ferromagnet. In contrast to classical critical systems, whose properties depend only on symmetry and the dimension of space, the nature of a quantum phase transition also depends on the dynamics. In the transverse field Ising model, the order parameter is not conserved, and increasing the transverse field enhances quantum fluctuations until they become strong enough to restore the symmetry of the ground state. Ising pseudospins can represent the order parameter of any system with a twofold degenerate broken-symmetry phase, including electronic nematic order associated with spontaneous point-group symmetry breaking. Here, we show for the representative example of orbital-nematic ordering of a non-Kramers doublet that an orthogonal strain or a perpendicular magnetic field plays the role of the transverse field, thereby providing a practical route for tuning appropriate materials to a quantum critical point. While the transverse fields are conjugate to seemingly unrelated order parameters, their nontrivial commutation relations with the nematic order parameter, which can be represented by a Berry-phase term in an effective field theory, intrinsically intertwine the different order parameters.

  9. Unconventional non-Fermi liquid state caused by nematic criticality in cuprates

    Science.gov (United States)

    Wang, Jing-Rong; Liu, Guo-Zhu; Zhang, Chang-Jin

    2016-07-01

    At the nematic quantum critical point that exists in the {d}{x2-{y}2}-wave superconducting dome of cuprates, the massless nodal fermions interact strongly with the quantum critical fluctuation of nematic order. We study this problem by means of the renormalization group approach and show that, the fermion damping rate | {Im}{{{Σ }}}R(ω )| vanishes more rapidly than the energy ω and the quasiparticle residue {Z}f\\to 0 in the limit ω \\to 0. The nodal fermions thus constitute an unconventional non-Fermi liquid that represents an even weaker violation of Fermi liquid theory than a marginal Fermi liquid. We also investigate the interplay of quantum nematic critical fluctuation and gauge-potential-like disorder, and find that the effective disorder strength flows to the strong coupling regime at low energies. Therefore, even an arbitrarily weak disorder can drive the system to become a disorder controlled diffusive state. Based on these theoretical results, we are able to understand a number of interesting experimental facts observed in curpate superconductors.

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

    Energy Technology Data Exchange (ETDEWEB)

    Tartan, Chloe C., E-mail: chloe.tartan@eng.ox.ac.uk, E-mail: steve.elston@eng.ox.ac.uk; Salter, Patrick S.; Booth, Martin J.; Morris, Stephen M.; Elston, Steve J., E-mail: chloe.tartan@eng.ox.ac.uk, E-mail: steve.elston@eng.ox.ac.uk [Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ (United Kingdom)

    2016-05-14

    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.

  11. Equilibrium state of a cylindrical particle with flat ends in nematic liquid crystals.

    Science.gov (United States)

    Hashemi, S Masoomeh; Ejtehadi, Mohammad Reza

    2015-01-01

    A continuum theory is employed to numerically study the equilibrium orientation and defect structures of a circular cylindrical particle with flat ends under a homeotropic anchoring condition in a uniform nematic medium. Different aspect ratios of this colloidal geometry from thin discotic to long rodlike shapes and several colloidal length scales ranging from mesoscale to nanoscale are investigated. We show that the equilibrium state of this colloidal geometry is sensitive to the two geometrical parameters: aspect ratio and length scale of the particle. For a large enough mesoscopic particle, there is a specific asymptotic equilibrium angle associated to each aspect ratio. Upon reducing the particle size to nanoscale, the equilibrium angle follows a descending or ascending trend in such a way that the equilibrium angle of a particle with the aspect ratio bigger than 1:1 (a discotic particle) goes to a parallel alignment with respect to the far-field nematic, whereas the equilibrium angle for a particle with the aspect ratio 1:1 and smaller (a rodlike particle) tends toward a perpendicular alignment to the uniform nematic direction. The discrepancy between the equilibrium angles of the mesoscopic and nanoscopic particles originates from the significant differences between their defect structures. The possible defect structures related to mesoscopic and nanoscopic colloidal particles of this geometry are also introduced.

  12. Cross-talk between topological defects in different fields revealed by nematic microfluidics.

    Science.gov (United States)

    Giomi, Luca; Kos, Žiga; Ravnik, Miha; Sengupta, Anupam

    2017-07-18

    Topological defects are singularities in material fields that play a vital role across a range of systems: from cosmic microwave background polarization to superconductors and biological materials. Although topological defects and their mutual interactions have been extensively studied, little is known about the interplay between defects in different fields-especially when they coevolve-within the same physical system. Here, using nematic microfluidics, we study the cross-talk of topological defects in two different material fields-the velocity field and the molecular orientational field. Specifically, we generate hydrodynamic stagnation points of different topological charges at the center of star-shaped microfluidic junctions, which then interact with emergent topological defects in the orientational field of the nematic director. We combine experiments and analytical and numerical calculations to show that a hydrodynamic singularity of a given topological charge can nucleate a nematic defect of equal topological charge and corroborate this by creating [Formula: see text], [Formula: see text], and [Formula: see text] topological defects in four-, six-, and eight-arm junctions. Our work is an attempt toward understanding materials that are governed by distinctly multifield topology, where disparate topology-carrying fields are coupled and concertedly determine the material properties and response.

  13. Density-functional theory of surfacelike elasticity of nematic liquid crystals

    Science.gov (United States)

    Yokoyama, Hiroshi

    1997-03-01

    Based on the density-functional theory, we show that the splay-bend surfacelike bulk elastic constant K13 is an artifact of the phenomenological as well as the gradient expansion construction of the curvature elastic free energy of nematic liquid crystals, while the saddle-splay constant K24 is real and approximately obeys an extended Nehring-Saupe relation K24 >=(K11 -K22 )/2, with K11 and K22 being the splay and twist Frank constants, respectively. The result K13 =0 automatically resolves the Oldano-Barbero pathology, which inevitably accompanies a nonzero K13 , and gives a concrete rationale for the conventional approaches in the continuum theory disregarding the surfacelike elasticity. The source of an apparently nonzero K13 in previous microscopic theories is discussed in detail and is demonstrated to be a result of an inconsistent use of a nonlocal-to-local mapping of the elastic free-energy functional at the boundary. The absence of K13 can be regarded as a type of Cauchy relation in the nematic continuum theory in the sense that it is not directly rooted in any of the macroscopic symmetries existing in the nematic phase, but is a general consequence of the particular algebraic form of the nonlocal free-energy term from which K13 derives; its linearity in the distortion amplitude and the symmetry of the relevant direct correlation function with respect to the permutation of a molecular pair leads always to the vanishing K13 . In this respect, K13 =0 applies not only to nematic liquid crystals but also to a more general class of phases such as cholesteric liquid crystals, whose structure can be viewed as a weak modulation of a translationally invariant phase. We finally consider the elastic description of nematic liquid crystals in the presence of real interfaces. The present formulation allows a straightforward decomposition of the elastic excess free energy into the bulk contribution and the interfacial excess in the Gibbs sense. The bulk part yields the

  14. Nutrição e crescimento do fungo nematófago Arthrobotrys oligospora

    Directory of Open Access Journals (Sweden)

    Eliane R. Cardoso

    2009-12-01

    Full Text Available As condições de crescimento e os requerimentos nutricionais de Arthrobotrys oligospora, um fungo nematófago, foram investigados em meio líquido. O organismo foi incubado em meio sintético, a 30º C e em cultura estacionária. O perfil da curva de crescimento do fungo ajustou-se a uma equação de 3º grau, mesmo após 15 dias de incubação. A temperatura e o pH ótimos para produção de micélio foram observados a 25º C e pH 5,0, respectivamente. Contudo, não foram observadas diferenças significativas entre a produção de biomassa nas temperaturas de 25º C e 30º C ou pH 5.0 e 6.0. Várias fontes de carbono foram utilizadas pelo fungo, porém a maior produção de biomassa foi verificada com maltose e sacarose. Das fontes de nitrogênio testadas, várias proteínas (triptona, extrato de levedura, caseína, peptona e casaminoácidos e fontes inorgânicas (nitrato de sódio e cloreto de amônio estimularam a maior produção de biomassa. Das várias vitaminas experimentadas, o crescimento do fungo aumentou 2,2 vezes com riboflavina e 2,3 vezes com a mistura biotina e tiamina em relação ao controle, sem vitamina. De modo geral, constatou-se, após o período de incubação, que o pH inicial do meio de cultura pode aumentar até 8,4. Estes resultados sugerem que as variáveis estudadas podem ter papel importante no crescimento do organismo no solo.The growth conditions and the nutritional requirements of Arthrobotrys oligospora, a nematophagous fungus, were investigated in liquid culture. The organism was incubated in a synthetic medium, at 30º C in a static culture. Time course of growth was adjusted to a 3º degree equation, even after 15 days of incubation. Optimal temperature and pH for mycelium production were observed at 25º C and pH 5.0, respectively. However, significant differences were not found among the biomass production at temperatures 25º C and 30º C or pH 5.0 and 6.0. Several carbon sources were used by the fungus

  15. Global strong solution to the two-dimensional density-dependent nematic liquid crystal flows with vacuum

    Science.gov (United States)

    Li, Lin; Liu, Qiao; Zhong, Xin

    2017-11-01

    We are concerned with the Cauchy problem of the two-dimensional (2D) nonhomogeneous incompressible nematic liquid crystal flows on the whole space {R}2 with vacuum as far field density. It is proved that the 2D nonhomogeneous incompressible nematic liquid crystal flows admits a unique global strong solution provided the initial data density and the gradient of orientation decay not too slow at infinity, and the basic energy \\Vert \\sqrt{ρ_0}{u}_0\\Vert L^2^2+\\Vert \

  16. Semi-analytical approach to supermode spatial solitons formation in nematic liquid crystals.

    Science.gov (United States)

    Jung, Pawel S; Krolikowski, Wieslaw; Laudyn, Urszula A; Karpierz, Miroslaw A; Trippenbach, Marek

    2017-10-02

    We study light propagation in nematic liquid crystals in the context of spatial optical solitons formation. We propose a simple analytical model with multiplicative nonlinearity, which represents (qualitatively) the liquid crystal response by comprising the competition between focusing (reorientational) and defocusing (thermal) nonlocal nonlinearities. We show that at sufficiently high input power the interplay between both nonlinearities leads to the formations of two-peak solitons, which represent supermodes of the self-induced extended waveguide structure. We explain the beam splitting mechanism, discuss threshold effects and conclude that similar phenomena might be present in other media with competing nonlocal nonlinearities.

  17. Communication: Orientational structure manipulation in nematic liquid crystal droplets induced by light excitation of azodendrimer dopant

    Science.gov (United States)

    Shvetsov, Sergey A.; Emelyanenko, Alexander V.; Boiko, Natalia I.; Liu, Jui-Hsiang; Khokhlov, Alexei R.

    2017-06-01

    Reversible orientational transitions in the droplets of a nematic liquid crystal (NLC) caused by the change of boundary conditions under the low intensity diode illumination are investigated. Photosensitivity of NLC is achieved by the addition of the dendrimer compound with azobenzene terminal groups. Two types of NLC droplets in glycerol are considered: the spherical droplets in the bulk of glycerol and the droplets laid-down onto the solid substrate. In the second case, the first order phase transition is revealed. The effects described can be useful for the development of highly sensitive chemical detectors and microsized photo-tunable optical devices.

  18. Electrical Properties of Zn-Phthalocyanine and Poly (3-hexylthiophene Doped Nematic Liquid Crystal

    Directory of Open Access Journals (Sweden)

    Y. Karakuş

    2011-01-01

    Full Text Available An E7 coded nematic liquid crystal was doped with zinc phthalocyanine and poly (3-hexylthiophene. A variety of properties including relaxation time, absorption coefficient, and critical frequency of this doped system were investigated using impedance spectroscopy. The doped systems displayed increased absorption coefficients in the range 0.22–0.55 and relaxation times from 5.05×10−7 s to 3.59×10−6 s with a decrease in the critical frequency from 3.54 MHz to 2.048 MHz.

  19. Surface tension of isotropic-nematic interfaces: fundamental measure theory for hard spherocylinders.

    Science.gov (United States)

    Wittmann, René; Mecke, Klaus

    2014-03-14

    A fluid constituted of hard spherocylinders is studied using a density functional theory for non-spherical hard particles, which can be written as a function of weighted densities. This is based on an extended deconvolution of the Mayer f-function for arbitrarily shaped convex hard bodies in tensorial weight functions, which depend each only on the shape and orientation of a single particle. In the course of an examination of the isotropic-nematic interface at coexistence the functional is applied to anisotropic and inhomogeneous problems for the first time. We find good qualitative agreement with other theoretical predictions and also with Monte Carlo simulations.

  20. Convection in a nematic liquid crystal with homeotropic alignment and heated from below

    Energy Technology Data Exchange (ETDEWEB)

    Ahlers, G. [Univ. of California, Santa Barbara, CA (United States)

    1995-12-31

    Experimental results for convection in a thin horizontal layer of a homeotropically aligned nematic liquid crystal heated from below and in a vertical magnetic field are presented. A subcritical Hopf bifurcation leads to the convecting state. There is quantitative agreement between the measured and the predicted bifurcation line as a function of magnetic field. The nonlinear state near the bifurcation is one of spatio-temporal chaos which seems to be the result of a zig-zag instability of the straight-roll state.

  1. Polarization properties of polymer-dispersed liquid-crystal film with small nematic droplets.

    Science.gov (United States)

    Lisinetskaya, Polina G; Konkolovich, Alexander A; Loiko, Valery A

    2009-06-10

    The polarization state of light transmitted through a polymer-dispersed liquid-crystal film with small, spherical, nonabsorbing, partially oriented nematic droplets is theoretically investigated. The model used is based on the effective medium approach. Scattering properties of a single droplet are described by the Rayleigh-Gans approximation. Propagation of coherent light is described within the framework of the Twersky theory. To describe the orientation of liquid-crystal molecules inside droplets and liquid-crystal droplets in a sample, the concept of multilevel order parameters is employed. Conditions for circular and linear polarization of the transmitted light are determined and investigated.

  2. Electrically Rotatable Polarizer Using One-Dimensional Photonic Crystal with a Nematic Liquid Crystal Defect Layer

    Directory of Open Access Journals (Sweden)

    Ryotaro Ozaki

    2015-09-01

    Full Text Available Polarization characteristics of defect mode peaks in a one-dimensional (1D photonic crystal (PC with a nematic liquid crystal (NLC defect layer have been investigated. Two different polarized defect modes are observed in a stop band. One group of defect modes is polarized along the long molecular axis of the NLC, whereas another group is polarized along its short axis. Polarizations of the defect modes can be tuned by field-induced in-plane reorientation of the NLC in the defect layer. The polarization properties of the 1D PC with the NLC defect layer is also investigated by the finite difference time domain (FDTD simulation.

  3. Confined Electroconvective and Flexoelectric Instabilities Deep in the Freedericksz State of Nematic CB7CB.

    Science.gov (United States)

    Krishnamurthy, Kanakapura S; Palakurthy, Nani Babu; Yelamaggad, Channabasaveshwar V

    2017-06-01

    We report wormlike flexoelectric structures evolving deep in the Freedericksz state of a nematic layer of the liquid crystal cyanobiphenyl-(CH2)7-cyanobiphenyl. They form in the predominantly splay-bend thin boundary layers and are built up of solitary flexoelectric domains of the Bobylev-Pikin type. Their formation is possibly triggered by the gradient flexoelectric surface instability that remains optically discernible up to unusually high frequencies. The threshold voltage at which the worms form scales as square root of the frequency; in their extended state, worms often appear as labyrinthine structures on a section of loops that separate regions of opposite director deviation. Such asymmetric loops are also derived through pincement-like dissociation of ring-shaped walls. Formation of isolated domains of bulk electroconvection precedes the onset of surface instabilities. In essence, far above the Freedericksz threshold, the twisted nematic layer behaves as a combination of two orthogonally oriented planar half-layers destabilized by localized flexoelectric distortion.

  4. Curvature-driven stability of defects in nematic textures over spherical disks

    Science.gov (United States)

    Duan, Xiuqing; Yao, Zhenwei

    2017-06-01

    Stabilizing defects in liquid-crystal systems is crucial for many physical processes and applications ranging from functionalizing liquid-crystal textures to recently reported command of chaotic behaviors of active matters. In this work, we perform analytical calculations to study the curvature-driven stability mechanism of defects based on the isotropic nematic disk model that is free of any topological constraint. We show that in a growing spherical disk covering a sphere the accumulation of curvature effect can prevent typical +1 and +1/2 defects from forming boojum textures where the defects are repelled to the boundary of the disk. Our calculations reveal that the movement of the equilibrium position of the +1 defect from the boundary to the center of the spherical disk occurs in a very narrow window of the disk area, exhibiting the first-order phase-transition-like behavior. For the pair of +1/2 defects by splitting a +1 defect, we find the curvature-driven alternating repulsive and attractive interactions between the two defects. With the growth of the spherical disk these two defects tend to approach and finally recombine towards a +1 defect texture. The sensitive response of defects to curvature and the curvature-driven stability mechanism demonstrated in this work in nematic disk systems may have implications towards versatile control and engineering of liquid-crystal textures in various applications.

  5. Faster in-plane switching and reduced rotational viscosity characteristics in a graphene-nematic suspension

    Energy Technology Data Exchange (ETDEWEB)

    Basu, Rajratan, E-mail: basu@usna.edu; Kinnamon, Daniel; Skaggs, Nicole; Womack, James [Soft Matter and Nanomaterials Laboratory, Department of Physics, The United States Naval Academy, Annapolis, Maryland 21402 (United States)

    2016-05-14

    The in-plane switching (IPS) for a nematic liquid crystal (LC) was found to be considerably faster when the LC was doped with dilute concentrations of monolayer graphene flakes. Additional studies revealed that the presence of graphene reduced the rotational viscosity of the LC, permitting the nematic director to respond quicker in IPS mode on turning the electric field on. The studies were carried out with several graphene concentrations in the LC, and the experimental results coherently suggest that there exists an optimal concentration of graphene, allowing a reduction in the IPS response time and rotational viscosity in the LC. Above this optimal graphene concentration, the rotational viscosity was found to increase, and consequently, the LC no longer switched faster in IPS mode. The presence of graphene suspension was also found to decrease the LC's pretilt angle significantly due to the π-π electron stacking between the LC molecules and graphene flakes. To understand the π-π stacking interaction, the anchoring mechanism of the LC on a CVD grown monolayer graphene film on copper substrate was studied by reflected crossed polarized microscopy. Optical microphotographs revealed that the LC alignment direction depended on monolayer graphene's hexagonal crystal structure and its orientation.

  6. Nematic topological superconducting phase in Nb-doped Bi2Se3

    Science.gov (United States)

    Shen, Junying; He, Wen-Yu; Yuan, Noah Fan Qi; Huang, Zengle; Cho, Chang-woo; Lee, Seng Huat; Hor, Yew San; Law, Kam Tuen; Lortz, Rolf

    2017-10-01

    A nematic topological superconductor has an order parameter symmetry, which spontaneously breaks the crystalline symmetry in its superconducting state. This state can be observed, for example, by thermodynamic or upper critical field experiments in which a magnetic field is rotated with respect to the crystalline axes. The corresponding physical quantity then directly reflects the symmetry of the order parameter. We present a study on the superconducting upper critical field of the Nb-doped topological insulator NbxBi2Se3 for various magnetic field orientations parallel and perpendicular to the basal plane of the Bi2Se3 layers. The data were obtained by two complementary experimental techniques, magnetoresistance and DC magnetization, on three different single crystalline samples of the same batch. Both methods and all samples show with perfect agreement that the in-plane upper critical fields clearly demonstrate a two-fold symmetry that breaks the three-fold crystal symmetry. The two-fold symmetry is also found in the absolute value of the magnetization of the initial zero-field-cooled branch of the hysteresis loop and in the value of the thermodynamic contribution above the irreversibility field, but also in the irreversible properties such as the value of the characteristic irreversibility field and in the width of the hysteresis loop. This provides strong experimental evidence that Nb-doped Bi2Se3 is a nematic topological superconductor similar to the Cu- and Sr-doped Bi2Se3.

  7. A charge transfer complex nematic liquid crystalline gel with high electrical conductivity

    Science.gov (United States)

    Bhargavi, R.; Nair, Geetha G.; Krishna Prasad, S.; Majumdar, R.; Bag, Braja G.

    2014-10-01

    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.

  8. 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.

  9. Faster in-plane switching and reduced rotational viscosity characteristics in a graphene-nematic suspension

    Science.gov (United States)

    Basu, Rajratan; Kinnamon, Daniel; Skaggs, Nicole; Womack, James

    2016-05-01

    The in-plane switching (IPS) for a nematic liquid crystal (LC) was found to be considerably faster when the LC was doped with dilute concentrations of monolayer graphene flakes. Additional studies revealed that the presence of graphene reduced the rotational viscosity of the LC, permitting the nematic director to respond quicker in IPS mode on turning the electric field on. The studies were carried out with several graphene concentrations in the LC, and the experimental results coherently suggest that there exists an optimal concentration of graphene, allowing a reduction in the IPS response time and rotational viscosity in the LC. Above this optimal graphene concentration, the rotational viscosity was found to increase, and consequently, the LC no longer switched faster in IPS mode. The presence of graphene suspension was also found to decrease the LC's pretilt angle significantly due to the π-π electron stacking between the LC molecules and graphene flakes. To understand the π-π stacking interaction, the anchoring mechanism of the LC on a CVD grown monolayer graphene film on copper substrate was studied by reflected crossed polarized microscopy. Optical microphotographs revealed that the LC alignment direction depended on monolayer graphene's hexagonal crystal structure and its orientation.

  10. Large-Scale Patterns in a Minimal Cognitive Flocking Model: Incidental Leaders, Nematic Patterns, and Aggregates

    Science.gov (United States)

    Barberis, Lucas; Peruani, Fernando

    2016-12-01

    We study a minimal cognitive flocking model, which assumes that the moving entities navigate using the available instantaneous visual information exclusively. The model consists of active particles, with no memory, that interact by a short-ranged, position-based, attractive force, which acts inside a vision cone (VC), and lack velocity-velocity alignment. We show that this active system can exhibit—due to the VC that breaks Newton's third law—various complex, large-scale, self-organized patterns. Depending on parameter values, we observe the emergence of aggregates or millinglike patterns, the formation of moving—locally polar—files with particles at the front of these structures acting as effective leaders, and the self-organization of particles into macroscopic nematic structures leading to long-ranged nematic order. Combining simulations and nonlinear field equations, we show that position-based active models, as the one analyzed here, represent a new class of active systems fundamentally different from other active systems, including velocity-alignment-based flocking systems. The reported results are of prime importance in the study, interpretation, and modeling of collective motion patterns in living and nonliving active systems.

  11. 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.

  12. Large-Scale Patterns in a Minimal Cognitive Flocking Model: Incidental Leaders, Nematic Patterns, and Aggregates.

    Science.gov (United States)

    Barberis, Lucas; Peruani, Fernando

    2016-12-09

    We study a minimal cognitive flocking model, which assumes that the moving entities navigate using the available instantaneous visual information exclusively. The model consists of active particles, with no memory, that interact by a short-ranged, position-based, attractive force, which acts inside a vision cone (VC), and lack velocity-velocity alignment. We show that this active system can exhibit-due to the VC that breaks Newton's third law-various complex, large-scale, self-organized patterns. Depending on parameter values, we observe the emergence of aggregates or millinglike patterns, the formation of moving-locally polar-files with particles at the front of these structures acting as effective leaders, and the self-organization of particles into macroscopic nematic structures leading to long-ranged nematic order. Combining simulations and nonlinear field equations, we show that position-based active models, as the one analyzed here, represent a new class of active systems fundamentally different from other active systems, including velocity-alignment-based flocking systems. The reported results are of prime importance in the study, interpretation, and modeling of collective motion patterns in living and nonliving active systems.

  13. Lattice Boltzmann simulation of asymmetric flow in nematic liquid crystals with finite anchoring.

    Science.gov (United States)

    Zhang, Rui; Roberts, Tyler; Aranson, Igor S; de Pablo, Juan J

    2016-02-28

    Liquid crystals (LCs) display many of the flow characteristics of liquids but exhibit long range orientational order. In the nematic phase, the coupling of structure and flow leads to complex hydrodynamic effects that remain to be fully elucidated. Here, we consider the hydrodynamics of a nematic LC in a hybrid cell, where opposite walls have conflicting anchoring boundary conditions, and we employ a 3D lattice Boltzmann method to simulate the time-dependent flow patterns that can arise. Due to the symmetry breaking of the director field within the hybrid cell, we observe that at low to moderate shear rates, the volumetric flow rate under Couette and Poiseuille flows is different for opposite flow directions. At high shear rates, the director field may undergo a topological transition which leads to symmetric flows. By applying an oscillatory pressure gradient to the channel, a net volumetric flow rate is found to depend on the magnitude and frequency of the oscillation, as well as the anchoring strength. Taken together, our findings suggest several intriguing new applications for LCs in microfluidic devices.

  14. 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.

  15. 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.

  16. Molecules with large-amplitude torsional motion partially oriented in a nematic liquid crystal: Ethane and isotopomers

    NARCIS (Netherlands)

    Burnell, E.E.; de Lange, C.A.; Barnhoorn, J.B.S.; Aben, I.; Levelt, P.F.

    2005-01-01

    An NMR study on ethane and five isotopomers dissolved in the nematic liquid crystal Merck ZLI 1132 is performed. A consistent set of dipolar and quadrupolar couplings is obtained. The dipolar couplings are corrected for harmonic vibrational effects, while the contribution from the torsional motion

  17. Distinct Chiral Nematic Self-Assembling Behavior Caused by Different Size-Unified Cellulose Nanocrystals via a Multistage Separation.

    Science.gov (United States)

    Hu, Yang; Abidi, Noureddine

    2016-09-27

    Cellulose nanocrystals (CNCs) are perfect rodlike nanofibers that can self-assemble and form a chiral nematic phase. We found that different self-assembling morphologies could be formed by different size-unified CNCs. This study reported a facile and new approach of fractionating raw (unseparated) CNCs in a wide particle size distribution (9-1700 nm) into a series of narrower size ranges to obtain size-unified CNCs via a well-designed multistage separation process composed of layered filter membranes with different pore size cutoffs followed by a fast pressurized filtration. The smaller size-unified CNCs readily self-assembled into polish chiral nematic phases with larger pitch value as compared to larger size-unified CNCs. Such a distinction among different chiral nematic phases and pitch values as functions of size was addressed by a mathematical evaluation, which suggested that the reduced volume fraction of the anisotropic phase as a function of both increased ionic strength and reduced crystallinity of rigid-rod-like CNCs is a critical factor. In addition, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction results revealed that different size-unified CNCs exhibited particular thermal stabilities and crystallinities even though their chemical and crystalline structures remained unchanged. The discrepancies in physicochemical characteristics and self-assembling chiral nematic behavior among different size-unified CNCs may benefit the specific functionalization of cellulose materials using size-unified fibers instead of raw CNCs containing mixed small and large fibers.

  18. Extensional flow of nematic liquid crystal with an applied electric field

    KAUST Repository

    CUMMINGS, L. J.

    2013-10-17

    Systematic asymptotic methods are used to formulate a model for the extensional flow of a thin sheet of nematic liquid crystal. With no external body forces applied, the model is found to be equivalent to the so-called Trouton model for Newtonian sheets (and fibres), albeit with a modified \\'Trouton ratio\\'. However, with a symmetry-breaking electric field gradient applied, behaviour deviates from the Newtonian case, and the sheet can undergo finite-time breakup if a suitable destabilizing field is applied. Some simple exact solutions are presented to illustrate the results in certain idealized limits, as well as sample numerical results to the full model equations. Copyright © Cambridge University Press 2013.

  19. Silicon oxides as alignment surfaces for vertically-aligned nematics in photonic devices

    Science.gov (United States)

    Oton, E.; López-Andrés, S.; Bennis, N.; Otón, J. M.; Geday, M. A.

    2014-06-01

    A comparative study on alignment performance and microstructure of inorganic layers used for liquid crystal cell conditioning has been carried out. The study has focused on two specific materials, SiOx and SiO2, deposited under different conditions. The purpose was to establish a relationship between layer microstructure and liquid crystal alignment. The surface morphology has been studied by FESEM and AFM. An analysis on liquid crystal alignment, pretilt angle, response time, contrast ratio and the conditions to develop backflow effect (significant rise time increase due to pure homeotropic alignment) on vertically-aligned nematic cells has been carried out. A technique to overcome the presence of backflow has been identified. The full comparative study of SiOx and SiO2 layer properties and their influence over liquid crystal alignment and electrooptic response is presented.

  20. Optically driven translational and rotational motions of microrod particles in a nematic liquid crystal

    Science.gov (United States)

    Eremin, Alexey; Hirankittiwong, Pemika; Chattham, Nattaporn; Nádasi, Hajnalka; Stannarius, Ralf; Limtrakul, Jumras; Haba, Osamu; Yonetake, Koichiro; Takezoe, Hideo

    2015-01-01

    A small amount of azo-dendrimer molecules dissolved in a liquid crystal enables translational and rotational motions of microrods in a liquid crystal matrix under unpolarized UV light irradiation. This motion is initiated by a light-induced trans-to-cis conformational change of the dendrimer adsorbed at the rod surface and the associated director reorientation. The bending direction of the cis conformers is not random but is selectively chosen due to the curved local director field in the vicinity of the dendrimer-coated surface. Different types of director distortions occur around the rods, depending on their orientations with respect to the nematic director field. This leads to different types of motions driven by the torques exerted on the particles by the director reorientations. PMID:25624507

  1. Electric-field variations within a nematic-liquid-crystal layer.

    Science.gov (United States)

    Cummings, L J; Mema, E; Cai, C; Kondic, L

    2014-07-01

    A thin layer of nematic liquid crystal (NLC) across which an electric field is applied is a setup of great industrial importance in liquid crystal display devices. There is thus a large literature modeling this situation and related scenarios. A commonly used assumption is that an electric field generated by electrodes at the two bounding surfaces of the layer will produce a field that is uniform: that is, the presence of NLC does not affect the electric field. In this paper, we use calculus of variations to derive the equations coupling the electric potential to the orientation of the NLC's director field, and use a simple one-dimensional model to investigate the limitations of the uniform field assumption in the case of a steady applied field. The extension of the model to the unsteady case is also briefly discussed.

  2. Light scattering by a nematic liquid crystal droplet: Wentzel–Kramers–Brillouin approximation

    Energy Technology Data Exchange (ETDEWEB)

    Loiko, V. A., E-mail: loiko@dragon.bas-net.by; Konkolovich, A. V.; Miskevich, A. A. [National Academy of Science of Belarus, Stepanov Institute of Physics (Belarus)

    2016-01-15

    Light scattering by an optically anisotropic liquid crystal (LC) droplet of a nematic in an isotropic polymer matrix is considered in the Wentzel–Kramers–Brillouin (WKB) approximation. General relations are obtained for elements of the amplitude matrix of light scattering by a droplet of arbitrary shape and for the structure of the director field. Analytic expressions for the amplitude matrices are derived for spherical LC droplets with a uniformly oriented structure of local optical axes for strictly forward and strictly backward scattering. The efficiency factors of extinction and backward scattering for a spherical nonabsorbing LC droplet depending on the LC optical anisotropy, refractive index of the polymer, illumination conditions, and orientation of the optical axis of the droplet are analyzed. Verification of the obtained solutions has been performed.

  3. FDTD modelling of gold nanoparticle pairs in a nematic liquid crystal cell

    Energy Technology Data Exchange (ETDEWEB)

    Dridi, Montacer; Vial, Alexandre, E-mail: montacer.dridi@utt.f, E-mail: alexandre.vial@utt.f [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Institut Charles Delaunay, UMR CNRS 6279, Universite de Technologie de Troyes, 12, rue Marie Curie, BP 2060, 10010 Troyes Cedex (France)

    2010-10-20

    In this paper, we numerically investigate a grating of gold dimer in a nematic liquid crystal (LC) media. We show that the plasmon resonance exhibits a high sensitivity to the distance between nanoparticles for all orientations of molecules of LCs. The behaviour of plasmon resonance can be described by a simple function called compressed hyperbola that overcomes the limitation of describing this behaviour by the well-known exponential function. Also we show that the orientation of the optical axis leads to an important spectral tunability. We demonstrate then that for certain orientations of the optical axis, we can induce a diffraction coupling featuring an additional narrow resonance peak. Finally near-field properties of the structure are investigated, and we demonstrate that by rotating the director we can control the local field enhancement.

  4. All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers

    DEFF Research Database (Denmark)

    Alkeskjold, Thomas Tanggaard; Lægsgaard, Jesper; Bjarklev, Anders Overgaard

    2004-01-01

    Photonic crystal fibers (PCFs) have attracted significant attention during the last years and much research has been devoted to develop fiber designs for various applications, hereunder tunable fiber devices. Recently, thermally and electrically tunable PCF devices based on liquid crystals (LCs......) have been demonstrated. However, optical tuning of the LC PCF has until now not been demonstrated. Here we demonstrate an all-optical modulator, which utilizes a pulsed 532nm laser to modulate the spectral position of the bandgaps in a photonic crystal fiber infiltrated with a dye-doped nematic liquid...... crystal. We demonstrate a modulation frequency of 2kHz for a moderate pump power of 2-3mW and describe two pump pulse regimes in which there is an order of magnitude difference between the decay times....

  5. The Landau-de Gennes theory of nematic liquid crystals: Uniaxiality versus Biaxiality

    KAUST Repository

    Majumdar, Apala

    2011-12-01

    We study small energy solutions within the Landau-de Gennes theory for nematic liquid crystals, subject to Dirichlet boundary conditions. We consider two-dimensional and three-dimensional domains separately. In the two-dimensional case, we establish the equivalence of the Landau-de Gennes and Ginzburg-Landau theory. In the three-dimensional case, we give a new definition of the defect set based on the normalized energy. In the threedimensional uniaxial case, we demonstrate the equivalence between the defect set and the isotropic set and prove the C 1,α-convergence of uniaxial small energy solutions to a limiting harmonic map, away from the defect set, for some 0 < a < 1, in the vanishing core limit. Generalizations for biaxial small energy solutions are also discussed, which include physically relevant estimates for the solution and its scalar order parameters. This work is motivated by the study of defects in liquid crystalline systems and their applications.

  6. Electrically Controlled Plasmonic Lasing Resonances with Silver Nanoparticles Embedded in Amplifying Nematic Liquid Crystals

    CERN Document Server

    Wang, Chin

    2014-01-01

    We demonstrate an electrically controlled coherent random lasing with silver nano-particles dispersed in a dye-doped nematic liquid crystal (NLC), in which external electric field dependent emission intensity and frequency-splitting are recorded. A modified rate equation model is proposed to interpret the observed coherent lasing, which is a manifestation of double enhancements, caused by the plasmon-polariton near-fields of Ag particles, on the population inversion of laser dye molecules and the optical energy density of lasing modes. The noticeable quenching of lasing resonances in a weak applied field is due to the dynamic light scattering by irregular director fluctuations of the NLC host, which wash out the coherent interference among different particle palsmon-polariton fields. This provides a proof to support that the present lasing resonances are very sensitive to the dielectric perturbations in the host medium and thus are likely associated with some coupled plasmonic oscillations of metal nanopartic...

  7. Worms on a plane: simulation studies of an active nematic phase of flexible chains

    Science.gov (United States)

    Varga, Michael; Najafi, Mohammad; Selinger, Robin

    2015-03-01

    We present simulation studies of flexible nematogen ``worms'' composed of soft spheres assembled into flexible polymer-like chains. These elongated, flexible chains are confined to a planar substrate with periodic boundary conditions or else confined within bounding walls. We consider a variety of driving mechanisms including unidirectional gliding and gliding with random reversals. We also model actuation via kinesin motor clusters which attach and travel along a pair of neighboring chains of opposite polarity, producing inter-chain sliding forces and driving the chains in opposite directions. We examine resulting nematic order, defect nucleation, motion, and annihilation, and density fluctuations as a function of chain length, flexibility, density, and driving mechanism. In a geometry where the chains are constrained to move in tandem with tight spacing, we observe spontaneous formation of organized beating. We compare our results to experimental and theoretical studies of gliding bacteria and kinesin-driven microtubules. Supported by NSF DMR-1409658 and NSF DMR-1106014.

  8. Zigzag line defects and manipulation of colloids in a nematic liquid crystal in microwrinkle grooves.

    Science.gov (United States)

    Ohzono, Takuya; Fukuda, Jun-ichi

    2012-02-28

    Spatially confined liquid crystals exhibit non-uniform alignment, often accompanied by self-organised topological defects of non-trivial shape in response to imposed boundary conditions and geometry. Here we show that a nematic liquid crystal, when confined in a sinusoidal microwrinkle groove, exhibits a new periodic arrangement of twist deformations and a zigzag line defect. This periodic ordering results from the inherent liquid crystal elastic anisotropy and the antagonistic boundary conditions at the flat liquid crystal-air and the curved liquid crystal-groove interfaces. The periodic structure can be tuned by controlling the groove geometry and the molecular chirality, which demonstrates the importance of boundary conditions and introduced asymmetry for the engineering of topological defects. Moreover, the kinks in the zigzag defects can trap small particles, which may afford a new method for manipulation of colloids. Our system, which uses easily fabricated microwrinkle grooves, provides a new microfabrication method based on the arrangement of controllable defects.

  9. Isotropic-to-nematic phase transition of liquid crystals confined in nanoemulsion droplets

    Science.gov (United States)

    Bono, S.; Takanishi, Y.; Yamamoto, J.

    2015-01-01

    We fabricated liquid crystalline nanoemulsions (LCNEs) by introducing low molecular weight liquid crystals (LMWLCs) into the core of nanoemulsions, and investigated the phase transition behavior of LMWLCs in the core part with the various weight ratios of LMWLCs to surfactants. The polarized dynamic light scattering measurement was performed to estimate the radii of LCNEs, and it is found that their radii can be controlled by the weight ratio of LMLCs to surfactant polymers. In the depolarized light scattering, it was revealed that the order of the isotropic-nematic phase transition behavior changes from the first order to biased second order with decreasing radius of LCNEs because of the three-dimensional confinement effect surrounded by an anchoring surface.

  10. Quantum decoherence and quasi-equilibrium in open quantum systems with few degrees of freedom: application to 1H NMR of nematic liquid crystals.

    Science.gov (United States)

    Segnorile, Héctor H; Zamar, Ricardo C

    2011-12-28

    the coupling with an infinite quantum environment. The reversible part can be represented by a semiclassical model, similar to standard line-shape adiabatic models. By exploiting the separation existing between the time scales of the spin coherences and the irreversible decoherence, we present a novel technique to obtain the orientational molecular distribution function for a nematic liquid crystal. The procedure is based on the comparison of the observed coherence time evolution and numerical calculation under the adiabatic quantum decoherence approach. As an example, it is used the experimental free induction decay from a nematic PAA(d6) sample to extract such an orientational distribution. This is the first theoretical description of the experimental liquid crystal NMR signal in the time domain. On the contrary, the irreversible decoherence is intrinsically full-quantum mechanical, as it is governed by the commutation properties of the environment and the spin-lattice Hamiltonians. Consistently, it depends on the molecular correlation in a decisive way, since it vanishes under a mean-field model for the molecular dynamics. The results of this work can contribute to the understanding of the open question of the applicability of the spin-temperature concept in spin systems with few degrees of freedom.

  11. Origin of Biquadratic Exchange Interactions in a Mott Insulator as a Driving Force of Spin Nematic Order

    Science.gov (United States)

    Tanaka, Katsuhiro; Yokoyama, Yuto; Hotta, Chisa

    2018-02-01

    We consider a series of Mott insulators in unit of two orbitals each hosting spin-1/2 electron, and by pairing two spin-1/2 into spin-1 triplet, derive the effective exchange interaction between the adjacent units via fourth order perturbation theory. It turns out that the biquadratic exchange interaction between spin-1, which is one of the origins of the nematic order, arises only in processes where the four different electrons exchange cyclically along the twisted loop, which we call "twisted ring exchange" processes. We show that the term becomes the same order with the Heisenberg exchange interactions when the on-orbital Coulomb interaction is not too large. Whereas, the inter-orbital Coulomb interactions give rise to additional processes that cancel the twisted ring exchange, and strongly suppresses the biquadratic term. The Mott insulator with two electrons on degenerate two orbitals is thus not an ideal platform to study such nematic orders.

  12. Non-Newtonian rheological properties of shearing nematic liquid crystal model systems based on the Gay-Berne potential.

    Science.gov (United States)

    Sarman, Sten; Wang, Yong-Lei; Laaksonen, Aatto

    2015-07-07

    The viscosities and normal stress differences of various liquid crystal model systems based on the Gay-Berne potential have been obtained as functions of the shear rate in the non-Newtonian regime. Various molecular shapes such as regular convex calamitic and discotic ellipsoids and non-convex shapes such as bent core molecules and soft ellipsoid strings have been examined. The isotropic phases were found to be shear thinning with the shear rate dependence of the viscosity following a power law in the same way as alkanes and other non-spherical molecules. The nematic phases turned out to be shear thinning but the logarithm of the viscosity proved to be an approximately linear function of the square root of the shear rate. The normal stress differences were found to display a more or less parabolic dependence on the shear rate in the isotropic phase whereas this dependence was linear at low to intermediate shear rates in the nematic phase.

  13. Anchoring behavior, orientational order, and reorientation dynamics of nematic liquid crystal droplets dispersed in cross-linked polymer networks.

    Science.gov (United States)

    Roussel, Frédérick; Fung, Bing M

    2003-04-01

    The orientational ordering and the electro-optical properties of nematic liquid crystal (LC) droplets confined to cross-linked polymer networks are investigated as a function of the anchoring conditions at the polymer-liquid crystal interface. Normal alignment (homeotropic) or parallel alignment (planar) inside LC droplets was controlled by using acrylate polymers with appropriate side chains. Drastic changes in the reorientation dynamics of the confined nematic liquid crystal phase are observed, as well as in the orientational ordering of the phase-separated LC which was investigated by 13C-NMR (nuclear magnetic resonance) spectroscopy. The cross-link density of the polymer network also affects the orientational ordering and the electro-optical properties of the confined LC phase. Faster switching times and higher-order parameters were found for samples with LC droplets exhibiting planar anchoring.

  14. Comparison of photoinduced reorientation of ortho-, meta-, and para-methyl red-doped nematic liquid crystals on rubbed polyimide.

    Science.gov (United States)

    Statman, David; Statman, Ariel T; Wozniak, Kaitlin; Brennan, Christopher

    2015-08-01

    We compare the photoinduced reorientation of the easy axis on rubbed polyimide surfaces for the nematic E7 doped with three isomers of methyl red; ortho, meta, and para. Using optical techniques, the angle and the pitch of the director at the polymer surface were measured before, during, and after photoexcitation of the dye. Optical absorbances were also measured before and after photoexcitation. Extrapolation lengths, hence anchoring energies, were determined with the on/off application of a magnetic field for meta- and para-methyl red-doped nematics. Because of an elastic reorientation of the easy axis in the presence of the magnetic field, we could not determine the extrapolation length of the ortho-methyl red-doped nematic. Our results confirm that photoinduced reorientation is facilitated by desorption of all dyes from the polymer surface. While there is little evidence of weak photoinduced adsorption of meta- and para-methyl red to the surface during photoexcitation, there is strong evidence of photoinduced adsorption of ortho-methyl red, which is long lasting.

  15. Effects of size and ligand density on the chirality transfer from chiral-ligand-capped nanoparticles to nematic liquid crystals

    Science.gov (United States)

    Mori, Taizo; Sharma, Anshul; Nemati, Ahlam; Bergquist, Leah; Hegmann, Torsten

    2017-08-01

    Studies of chiroptical effects of chiral ligand-capped gold nanoparticles (Au NPs) are a fascinating and rapidly evolving field in nanomaterial research with promising applications of such chiral metal NPs in catalysis and metamaterials as well as chiral sensing and separation. The aim of our studies was to seek out a system that not only allows the detection and understanding of Au NP chirality but also permits visualization and ranking — considering size, shape and nature as well as density of the ligand shell — of the extent of chirality transfer to a surrounding medium. Nematic liquid crystal (N-LC) phases are an ideal platform to examine these effects, exhibiting characteristic defect textures upon doping with a chiral additive. To test this, we synthesized series of Au NPs capped with two structurally different chiral ligands and studied well-dispersed mixtures in two nematic liquid crystal hosts. Induced circular dichroism (ICD) spectropolarimetry and polarized light optical microscopy (POM) confirmed that all Au NPs induce chiral nematic (N*-LC) phases, and measurements of the helical pitch as well as calculation of the helical twisting power (HTP) in various cell geometries allowed for an insightful ranking of the efficiency of chirality transfer of all Au NPs as well as their free ligands.

  16. A small-angle X-ray scattering study of the lyotropic nematic phase of vanadium pentoxide gels

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, P. [Universite de Paris-Sud, Orsay (France). Lab. de Phys. des Solides; Bourgaux, C.; Sergot, P.; Livage, J.

    1997-10-01

    Aqueous suspensions of vanadium pentoxide (V{sub 2}O{sub 5}) ribbons, also called Zocher phases, are known to display a lyotropic nematic phase. In this paper, it is shown how the small-angle X-ray scattering (SAXS) technique can provide useful information on the building blocks and their organization in this phase. SAXS experiments were performed either on unoriented samples or on samples aligned by a magnetic field or by shear flow. The scattering is comparable to that of the other classic lyotropic nematic phases displayed by stiff organic rod-like particles such as the tobacco mosaic virus. Scattering studies show that the building blocks have a ribbon shape, that their thickness is 9(1) A and indirectly that their width is several 100 A. Their length is known to be around a few thousand A and therefore could not be measured by SAXS. By following the average distance between the ribbons as a function of concentration, it is shown that the swelling of the phase is one-dimensional at large concentrations and two-dimensional at low concentrations. Finally, estimates of the nematic order parameter of a single domain sample and of samples sheared in a Couette cell have been obtained. (orig.). 24 refs.

  17. Critical Slowing of Density Fluctuations Approaching the Isotropic-Nematic Transition in Liquid Crystals: 2D IR Measurements and Mode Coupling Theory.

    Science.gov (United States)

    Sokolowsky, Kathleen P; Bailey, Heather E; Hoffman, David J; Andersen, Hans C; Fayer, Michael D

    2016-07-21

    Two-dimensional infrared (2D IR) data are presented for a vibrational probe in three nematogens: 4-cyano-4'-pentylbiphenyl, 4-cyano-4'-octylbiphenyl, and 4-(trans-4-amylcyclohexyl)-benzonitrile. The spectral diffusion time constants in all three liquids in the isotropic phase are proportional to [T*/(T - T*)](1/2), where T* is 0.5-1 K below the isotropic-nematic phase transition temperature (TNI). Rescaling to a reduced temperature shows that the decays of the frequency-frequency correlation function (FFCF) for all three nematogens fall on the same curve, suggesting a universal dynamic behavior of nematogens above TNI. Spectral diffusion is complete before significant orientational relaxation in the liquid, as measured by optically heterodyne detected-optical Kerr effect (OHD-OKE) spectroscopy, and before any significant orientational randomization of the probe measured by polarization selective IR pump-probe experiments. To interpret the OHD-OKE and FFCF data, we constructed a mode coupling theory (MCT) schematic model for the relationships among three correlation functions: ϕ1, a correlator for large wave vector density fluctuations; ϕ2, the orientational correlation function whose time derivative is the observable in the OHD-OKE experiment; and ϕ3, the FFCF for the 2D IR experiment. The equations for ϕ1 and ϕ2 match those in the previous MCT schematic model for nematogens, and ϕ3 is coupled to the first two correlators in a straightforward manner. Resulting models fit the data very well. Across liquid crystals, the temperature dependences of the coupling constants show consistent, nonmonotonic behavior. A remarkable change in coupling occurs at ∼5 K above TNI, precisely where the rate of spectral diffusion in 5CB was observed to deviate from that of a similar nonmesogenic liquid.

  18. Cholesteric Liquid Crystalline Copolymers for Gas Chromatographic Separation of Polycyclic Aromatic Compounds

    Directory of Open Access Journals (Sweden)

    Chih-Hung Lin

    2012-01-01

    Full Text Available A novel series of side-chain liquid crystalline copolysiloxanes containing [S]-1-(2-naphthyl ethyl 6-[4-(10-undecen-1-yloxy biphenyl--carbonyloxy]-2-naphthoate mesogenic and 4-biphenyl -allyloxybenzoate mesogenic side groups in the backbone and side chains liquid crystalline copolymers were prepared and evaluated as possible stationary phases for gas chromatography capillary columns. All copolymers display enantiotropic cholesteric phases. These mesomorphic polysiloxanes specimens with the widest temperature range were used as the stationary phase in a gas chromatography capillary column, and it showed good thermal and physical stability, excellent chemical inertness, and unique separation properties for polycyclic aromatic compounds. These cholesteric LC copolysiloxane stationary phases show much better separation effect for the polycyclic aromatic compound than those of the nematic and smectic LC copolysiloxanes.

  19. On the Landau-de Gennes Elastic Energy of a Q-Tensor Model for Soft Biaxial Nematics

    Science.gov (United States)

    Mucci, Domenico; Nicolodi, Lorenzo

    2017-12-01

    In the Landau-de Gennes theory of liquid crystals, the propensities for alignments of molecules are represented at each point of the fluid by an element Q of the vector space S_0 of 3× 3 real symmetric traceless matrices, or Q-tensors. According to Longa and Trebin (1989), a biaxial nematic system is called soft biaxial if the tensor order parameter Q satisfies the constraint tr(Q^2) = {const}. After the introduction of a Q-tensor model for soft biaxial nematic systems and the description of its geometric structure, we address the question of coercivity for the most common four-elastic-constant form of the Landau-de Gennes elastic free-energy (Iyer et al. 2015) in this model. For a soft biaxial nematic system, the tensor field Q takes values in a four-dimensional sphere S^4_ρ of radius ρ ≤ √{2/3} in the five-dimensional space S_0 with inner product = tr(QP). The rotation group it{SO}(3) acts orthogonally on S_0 by conjugation and hence induces an action on S^4_ρ \\subset {S}_0. This action has generic orbits of codimension one that are diffeomorphic to an eightfold quotient S^3/H of the unit three-sphere S^3, where H={± 1, ± i, ± j, ± k} is the quaternion group, and has two degenerate orbits of codimension two that are diffeomorphic to the projective plane RP^2. Each generic orbit can be interpreted as the order parameter space of a constrained biaxial nematic system and each singular orbit as the order parameter space of a constrained uniaxial nematic system. It turns out that S^4_ρ is a cohomogeneity one manifold, i.e., a manifold with a group action whose orbit space is one-dimensional. Another important geometric feature of the model is that the set Σ _ρ of diagonal Q-tensors of fixed norm ρ is a (geodesic) great circle in S^4_ρ which meets every orbit of S^4_ρ orthogonally and is then a section for S^4_ρ in the sense of the general theory of canonical forms. We compute necessary and sufficient coercivity conditions for the elastic energy by

  20. Optical monitoring of surface anchoring changes for nematic liquid crystal based chemical and biological sensors

    Science.gov (United States)

    Zou, Yang

    In this dissertation, optically monitoring the surface anchoring changes of liquid crystal (LC) due to the chemical or biological bindings is presented. The deformation of LC director with different anchoring energies is simulated using Finite Element Method and continuum theory of nematic LC. The optical properties of the LC film are simulated using the Finite Difference Time Domain method. First, the interference color method was used to monitor the anchoring change. The calculated and experimental interference colors of liquid crystal films due to the optical retardation of two orthogonal electromagnetic components at different surface anchoring conditions and applied voltages are studied. The calculated colors were converted into sRGB parameters so that the corresponding colors can be displayed on a color computer monitor and printed out on a color printer. A gold micro-structure was fabricated and used to control the optical retardation. Polarizing micrographs were collected and compared with the calculated colors. Second, the influence of a bias voltage on the surface-driven orientational transition of liquid crystals resulted from the weakening anchoring and anchoring transition is analyzed theoretically and experimentally. The same interdigitated Au micro-structure was used in the nematic LC based chemical and biological sensors. With a suitable bias electric field, the process of the weakening anchoring energy and the uniform surface-driven orientational transition due to targeted molecules binding to a functionalized surface were observed optically. Finally, measurement of optical transmission was used to monitor the anchoring change. Polarizing micrographs were collected and compared with simulated textures. Experimental and simulation results both demonstrate the optical method can effectively monitor the surface anchoring change due to the presence of targeted analytes. These results show that these optical techniques are suitable for LC based sensing

  1. Competing Spin Liquids and Hidden Spin-Nematic Order in Spin Ice with Frustrated Transverse Exchange

    Directory of Open Access Journals (Sweden)

    Mathieu Taillefumier

    2017-12-01

    Full Text Available Frustration in magnetic interactions can give rise to disordered ground states with subtle and beautiful properties. The spin ices Ho_{2}Ti_{2}O_{7} and Dy_{2}Ti_{2}O_{7} exemplify this phenomenon, displaying a classical spin-liquid state, with fractionalized magnetic-monopole excitations. Recently, there has been great interest in closely related “quantum spin-ice” materials, following the realization that anisotropic exchange interactions could convert spin ice into a massively entangled, quantum spin liquid, where magnetic monopoles become the charges of an emergent quantum electrodynamics. Here we show that even the simplest model of a quantum spin ice, the XXZ model on the pyrochlore lattice, can realize a still-richer scenario. Using a combination of classical Monte Carlo simulation, semiclassical molecular-dynamics simulation, and analytic field theory, we explore the properties of this model for frustrated transverse exchange. We find not one, but three competing forms of spin liquid, as well as a phase with hidden, spin-nematic order. We explore the experimental signatures of each of these different states, making explicit predictions for inelastic neutron scattering. These results show an intriguing similarity to experiments on a range of pyrochlore oxides.

  2. Confinement effects on lyotropic nematic liquid crystal phases of graphene oxide dispersions

    Science.gov (United States)

    Al-Zangana, Shakhawan; Iliut, Maria; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2017-12-01

    Graphene oxide (GO) forms well ordered liquid crystal (LC) phases in polar solvents. Here, we map the lyotropic phase diagram of GO as a function of the lateral dimensions of the GO flakes, their concentration, geometrical confinement configuration and solvent polarity. GO flakes were prepared in water and transferred into other polar solvents. Polarising optical microscopy (POM) was used to determine the phase evolution through the isotropic-biphasic-nematic transitions of the GO LC. We report that the confinement volume and geometry relative to the particle size is critical for the observation of the lyotropic phase, specifically, this determines the low-end concentration limit for the detection of the GO LC. Additionally, a solvent with higher polarisability stabilises the LC phases at lower concentrations and smaller flake sizes. GO LCs have been proposed for a range of applications from display technologies to conductive fibres, and the behaviour of LC phase formation under confinement imposes a limit on miniaturisation of the dimensions of such GO LC systems which could significantly impact on their potential applications.

  3. The shape of bubbles and Drops rising in a Nematic Liquid Crystal

    Science.gov (United States)

    Zhou, Chunfeng; Yue, Pengtao; Feng, James J.; Liu, Chun; Shen, Jie

    2006-11-01

    This work is motivated by recent experimental observation of unusual ``inverted-heart" shapes that a bubble assumes when rising in an anisotropic fluid. A possible explanation is in terms of the molecular orientation of the matrix fluid with respect to the bubble surface. In this work, we use numerical simulations to test such a hypothesis. The moving interface problem is formulated in a diffuse-interface framework. The anisotropic fluid is represented by a simplified Leslie-Ericksen theory for nematic liquid crystals, with director anchoring on the surface of an isotropic drop. The simulations are carried out using axisymmetric finite elements. Results show an array of drop shapes, depending on the interplay among inertial, capillary, anchoring and elastic effects. Drops with sufficiently strong planar anchoring and moderate elasticity rising in a medium with vertical far-field orientation assume the inverted-heart observed in experiments. This is shown to be mainly due to the competition between interfacial tension, anchoring energy and bulk elastic energy. Furthermore, two boojum defects appear on the upper and lower poles. The size of the defects plays an significant role in shaping the rising bubble.

  4. Tuning the defect configurations in nematic and smectic liquid crystalline shells.

    Science.gov (United States)

    Liang, Hsin-Ling; Noh, JungHyun; Zentel, Rudolf; Rudquist, Per; Lagerwall, Jan P F

    2013-04-13

    Thin liquid crystalline shells surrounding and surrounded by aqueous phases can be conveniently produced using a nested capillary microfluidic system, as was first demonstrated by Fernandez-Nieves et al. in 2007. By choosing particular combinations of stabilizers in the internal and external phases, different types of alignment, uniform or hybrid, can be ensured within the shell. Here, we investigate shells in the nematic and smectic phases under varying boundary conditions, focusing in particular on textural transformations during phase transitions, on the interaction between topological defects in the director field and inclusions in the liquid crystal (LC), and on the possibility to relocate defects within the shell by rotating the shell in the gravitational field. We demonstrate that inclusions in a shell can seed defects that cannot form in a pristine shell, adding a further means of tuning the defect configuration, and that shells in which the internal aqueous phase is not density matched with the LC will gently rearrange the internal structure upon a rotation that changes the influence of gravity. Because the defects can act as anchor points for added linker molecules, allowing self-assembly of adjacent shells, the various arrangements of defects developing in these shells and the possibility of tuning the result by modifying boundary conditions, LC phase, thickness and diameter of the shell or applying external forces make this new LC configuration very attractive.

  5. Lasing in a nematic liquid crystal cell with an interdigitated electrode system

    Energy Technology Data Exchange (ETDEWEB)

    Shtykov, N M; Palto, S P; Umanskii, B A; Geivandov, A R [Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow (Russian Federation)

    2015-04-30

    Waveguide lasing in a layer of a dye-doped nematic liquid crystal has been observed. The liquid-crystal layer was sandwiched between a quartz substrate and a glass cover plate on whose surface was deposited an interdigitated electrode system. This system had a period of 3.75 μm and played a dual role, namely, it created a spatial periodicity of the waveguide medium refractive index (thus creating distributed feedback) and served as a diffraction grating coupling out a part of waveguide radiation into the glass cover plate. The distributed feedback ensured lasing in the 18th diffraction order for the TE modes and in the 19th order for the TM modes of the waveguide. The generated radiation was observed at the exit from the glass plate end face at the angles to the waveguide plane of 33.1 ± 1.5° for TM modes and 21.8 ± 1.8° for TE modes. The intensity and position of the TE emission line showed no regular dependence on the voltage on the electrodes. In the case of TM radiation, an increase in the voltage led to a short-wavelength shift of the laser line and to a decrease in its intensity. (lasers)

  6. Poincaré-sphere representation of phase-mostly twisted nematic liquid crystal spatial light modulators

    Science.gov (United States)

    Durán, V.; Clemente, P.; Martínez-León, Ll; Climent, V.; Lancis, J.

    2009-08-01

    We establish necessary conditions in order to build a phase-only wavefront modulation system from a liquid crystal display. These conditions determine the dependence of the polarization state of the light emerging from the display on the addressing gray level. The analysis, which is carried out by means of the coherence-matrix formalism, includes the depolarization properties of the device. Two different types of polarization distributions at the output of the liquid crystal cells are found. This approach is applied to a twisted nematic liquid crystal display. In this case, an optimization algorithm must be designed in order to select the input polarization state that leads to the required distributions. We show that the Poincaré-sphere representation provides a convenient framework to design the optimization algorithm as it allows for a reduced number of degrees of freedom. This feature significantly decreases the computation time. Laboratory results are presented for a liquid crystal on silicon display showing a phase modulation depth greater than 2π rad with an intensity variation lower than 6%. In addition, a hybrid ternary modulation (HTM), an operation regime employed in holographic data storage, is achieved.

  7. Nanocomposites of Polyaniline and Cellulose Nanocrystals Prepared in Lyotropic Chiral Nematic Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Dawei Zhang

    2013-01-01

    Full Text Available Stable lyotropic chiral nematic liquid crystals (N*-LCs of cellulose nanocrystals (CNs were prepared via hydrolysis using sulfuric acid. The lyotropic N*-LCs were used as an asymmetric reaction field to synthesize polyaniline (PANI onto CNs by in situ polymerization. As a primary step, we examined the mesophase transition of the N*-LCs of CNs suspension before and after in situ polymerization of aniline (ANI by polarizing optical microscopy. The structure of nanocomposites of PANI/CNs was investigated at a microscopic level using Fourier transform infrared spectroscopy and X-ray diffraction. Influence of the CNs-to-ANI ratio on the morphology of the nanocomposites was also investigated at macroscopic level by scanning electron and transmission electron microscopies. It is found that the weight ratio of CNs to aniline in the suspension significantly influenced the size of the PANI particles and interaction between CNs and PANI. Moreover, electrical properties of the obtained PANI/CNs films were studied using standard four-probe technique. It is expected that the lyotropic N*-LCs of CNs might be available for an asymmetric reaction field to produce novel composites of conjugated materials.

  8. Alignment techniques for preparation of protein-containing surfactant nematic cells

    Science.gov (United States)

    Omelchenko, M. M.; Boiko, O. P.; Nazarenko, V. G.; Vlokh, R. O.; Nastishin, Yu. A.

    2007-07-01

    We report on first successful alignment of a surfactant lyotropic nematic between rubbed glass substrates either clean or spin-coated with a polymer layer. Worsening of the alignment either at small number of rubbings (less than 60), at long time delay before filling the cell or when washing the rubbed substrates in deionized water, suggest that the rubbinginduced electrostatic charging of the substrate surface is the main alignment mechanism. Prepared surfonematic cells have good optical quality allowing us to perform optical characterization of the studied surfonematic. The surfonematic is optically negative with the weak light wavelengths dispersion. The absolute value of the birefringence is low: -(6x10 -4). For the first time we report that hemoglobin molecules can be dissolved in the surfonematic matrix. Hemoglobin dissolved in well-aligned surfonematic matrix display polarization spectra which differ from its spectrum in water: 1) wide absorption band in the spectral range 540-640nm for hemoglobin in the surfonematic is different from that for water solutions of hemoglobin; 2) polarization spectra of hemoglobin in aligned surfonematic display weak dichroism leading to the estimation of the orientation order parameter for hemoglobin molecules to be about 10 -2. These spectral features indicate that hemoglobin residues form anisotropic complexes with positively charged surfactant residues. At the studied concentration these complexes are weakly aligned by the surfonematic matrix but are not birefringent and do not affect the orientational order of the surfonematic matrix.

  9. Note on the hydrodynamic description of thin nematic films: Strong anchoring model

    KAUST Repository

    Lin, Te-Sheng

    2013-01-01

    We discuss the long-wave hydrodynamic model for a thin film of nematic liquid crystal in the limit of strong anchoring at the free surface and at the substrate. We rigorously clarify how the elastic energy enters the evolution equation for the film thickness in order to provide a solid basis for further investigation: several conflicting models exist in the literature that predict qualitatively different behaviour. We consolidate the various approaches and show that the long-wave model derived through an asymptotic expansion of the full nemato-hydrodynamic equations with consistent boundary conditions agrees with the model one obtains by employing a thermodynamically motivated gradient dynamics formulation based on an underlying free energy functional. As a result, we find that in the case of strong anchoring the elastic distortion energy is always stabilising. To support the discussion in the main part of the paper, an appendix gives the full derivation of the evolution equation for the film thickness via asymptotic expansion. © 2013 AIP Publishing LLC.

  10. Circular Dichroism of Chiral Nematic Films of Cellulose Nanocrystals Loaded with Plasmonic Nanoparticles.

    Science.gov (United States)

    Querejeta-Fernández, Ana; Kopera, Bernd; Prado, Karen S; Klinkova, Anna; Methot, Myriam; Chauve, Grégory; Bouchard, Jean; Helmy, Amr S; Kumacheva, Eugenia

    2015-10-27

    In the search for induced chiral plasmonic activity, cholesteric films formed by cellulose nanocrystals have attracted great interest as potential hosts for plasmonic nanoparticles. Circular dichroism (CD) spectra of the composite films exhibit two peaks, one of which is ascribed to the cholesteric host and the other one to plasmonic chiroptical activity of the plasmonic nanoparticles. Here we report the results of comprehensive studies of extinction and CD properties of composite films formed by different types of cellulose nanocrystals and different types of plasmonic nanoparticles. We show that the second peak in the CD spectra acquired using CD spectrometers appears as the result of the local reduction of the CD signal of the host material, due to excessive absorption by the nanoparticles, and thus it cannot be interpreted as induced plasmonic chiroptical activity. Instead, we propose an alternative way to measure CD spectra of plasmonic cholesteric films by using Mueller matrix transmission ellipsometry. The results of this study are important for ongoing research in the field of chiral plasmonics and for the optical characterization of a broad range of chiral nematic nanostructured materials.

  11. Dynamic electro-optic response of graphene/graphitic flakes in nematic liquid crystals.

    Science.gov (United States)

    Tie, Weiwei; Bhattacharyya, Surjya Sarathi; Lim, Young Jin; Lee, Sang Won; Lee, Tae Hoon; Lee, Young Hee; Lee, Seung Hee

    2013-08-26

    Electric field induced dynamic reorientation phenomenon of graphene/graphitic flakes in homogeneously aligned nematic liquid crystal (NLC) medium has been demonstrated by optical microscopy. The flakes reorient from parallel to perpendicular configuration with respect to boundary plates of confining cells for an applied field strength of as low as tens of millivolt per micrometer. After field removal the reoriented flakes recover to their initial state with the help of relaxation of NLC. Considering flake reorientation phenomenon both in positive and negative dielectric anisotropy NLCs, the reorientation process depends on interfacial Maxwell-Wagner polarization and NLC director reorientation. We propose a phenomenological model based on electric field induced potential energy of graphitic flakes and coupling contribution of positive NLC to generate the rotational kinetic energy for flake reorientation. The model successfully explains the dependence of flake reorientation time over flake shape anisotropy, electric-field strength, and flake area. Using present operating scheme it is possible to generate dark field-off state and bright field-on state, having application potential for electro-optic light modulation devices.

  12. Investigation of the interaction of alkali ions with surfactant head groups for the formation of lyotropic biaxial nematic phase via optical birefringence measurements

    Science.gov (United States)

    Akpinar, Erol; Reis, Dennys; Figueiredo Neto, Antonio Martins

    2013-03-01

    Lyotropic liquid crystals exhibiting nematic phases were obtained from the mixtures potassium laurate/alkali sulfate salts (M2SO4)/1-undecanol (UndeOH)/water and sodium dodecyl sulfate (SDS)/M2SO4/1-dodecanol (DDeOH)/water, where M2SO4 represents the alkali sulfate salts being Li2SO4, Na2SO4, K2SO4, Rb2SO4 or Cs2SO4. The birefringences measurements were performed via laser conoscopy. Our results indicated that cosmotropic and chaotropic behaviors of both ions and head groups are very important to obtain lyotropic biaxial nematic phase. To obtain the biaxial nematic phase, surfactant head group and ion present in lyotropic mixture have relatively opposite behavior, e.g. one more cosmotropic (more chaotropic) other less cosmotropic (less chaotropic) or vice versa.

  13. Virulência de nematóides entomopatogênicos (Nematoda: Rhabditida a Sphenophorus levis (Coleoptera: Curculionidae

    Directory of Open Access Journals (Sweden)

    Fernando Henrique Carvalho Giometti

    2011-01-01

    Full Text Available O bicudo da cana-de-açúcar, Sphenophorus levis (Coleoptera: Curculionidae, é uma importante praga de solo dos canaviais no Estado de São Paulo, ocasionando prejuízos de até 30 t de cana/ha/ano. Visando ao controle biológico desta praga, esse estudo teve por objetivo avaliar a virulência de 17 isolados de nematóides entomopatogênicos do gênero Steinernema e Heterorhabditis contra adultos de S. levis, e o efeito dos quatro nematóides mais virulentos em três dosagens cada um. A pesquisa foi realizada em condições de laboratório, sendo realizados quatro ensaios para o estudo de virulência. Os nematóides selecionados como mais virulentos em cada teste foram S. brazilense IBCB n6, Heterorhabditis sp. IBCB n10, Heterorhabditis sp. IBCB n24 e Heterorhabditis sp. IBCB n44, sendo os únicos que diferenciaram significativamente das respectivas testemunhas com 45%, 40%, 20% e 31% de mortalidade do inseto na concentração de 240 juvenis infectivos (JI/inseto. No teste de dose, os isolados de Heterorhabditis identificados como IBCB n10, IBCB n24 e IBCB n44 destacaram-se quanto à virulência para os adultos do bicudo da cana-de-açúcar, diferindo significativamente da testemunha na maior dose avaliada (1200 JI/inseto com níveis de mortalidade do inseto de 60%, 65,7% e 74,3% respectivamente.

  14. Conoscopic evidence of the UV light-induced flexoelectric effect in homeotropic layers of nematic liquid crystal doped with azobenzene derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Marinov, Y G; Hadjichristov, G B; Petrov, A G; Sridevi, S; Hiremath, U S; Yelamaggad, C V; Prasad, S K, E-mail: ymarinov@issp.bas.b

    2010-11-01

    A digitalized version of the standard method of conoscopy was employed to register the bend deformation of molecular orientation in homeotropic nematic layers caused by an in-plane applied DC electric field, and influenced by UV light illumination. Two guest-host systems prepared by mixing of a nematic liquid crystal and an azobenzene-containing photochromic liquid crystalline material featuring a longitudinal molecular asymmetry, were studied. Upon continuous UV irradiation, a photo-isomerization of the photochromic molecules occurs resulting in an enhanced flexoelectric response of the guest-host mixtures. The dependence of the photoflexoeffect on the field strength and UV light intensity was also examined.

  15. Voltage-induced defect mode coupling in a one-dimensional photonic crystal with a twisted-nematic defect layer

    Science.gov (United States)

    Timofeev, Ivan V.; Lin, Yu-Ting; Gunyakov, Vladimir A.; Myslivets, Sergey A.; Arkhipkin, Vasily G.; Vetrov, Stepan Ya.; Lee, Wei; Zyryanov, Victor Ya.

    2012-01-01

    Defect modes are investigated in a band gap of an electrically tunable one-dimensional photonic crystal infiltrated with a twisted-nematic liquid crystal. Their frequency shift and interference under applied voltage are studied both experimentally and theoretically. We deal with the case where the defect layer thickness is much larger than the wavelength (i.e., the Mauguin condition). It is shown theoretically that the defect modes could have a complex structure with elliptic polarization. Two series of polarized modes are coupled with each other and exhibit an avoided crossing phenomenon in the case of opposite parity.

  16. Coupled effects of director orientations and boundary conditions on light induced bending of monodomain nematic liquid crystalline polymer plates

    Science.gov (United States)

    You, Yue; Xu, Changwei; Ding, Shurong; Huo, Yongzhong

    2012-12-01

    A photo-chromic liquid crystal polymers (LCPs) is a smart material for large light-activated variation or bending to transfer luminous energy into mechanical energy. We study the light induced behavior by modeling planar and homeotropic nematic network polymer plates. We effectively illustrate some reported experimental outcomes and theoretically predict some possible bending patterns. This paper constructs an understanding between the bending behaviors and interactions among the alignments, aspect ratios and boundary conditions, etc. Our work provides information on optimizing light induced bending in the process of micro-opto-mechanical system (MOMS) design.

  17. A fast Huygens sweeping method for capturing paraxial multi-color optical self-focusing in nematic liquid crystals

    Science.gov (United States)

    Kwan, Wingfai; Leung, Shingyu; Wang, Xiao-Ping; Qian, Jianliang

    2017-11-01

    We propose a numerically efficient algorithm for simulating the multi-color optical self-focusing phenomena in nematic liquid crystals. The propagation of the nematicon is modeled by a parabolic wave equation coupled with a nonlinear elliptic partial differential equation governing the angle between the crystal and the direction of propagation. Numerically, the paraxial parabolic wave equation is solved by a fast Huygens sweeping method, while the nonlinear elliptic PDE is handled by the alternating direction explicit (ADE) method. The overall algorithm is shown to be numerically efficient for computing high frequency beam propagations.

  18. Tunable microwave bandpass filter integrated power divider based on the high anisotropy electro-optic nematic liquid crystal.

    Science.gov (United States)

    Liu, Yupeng; Liu, Yang; Li, Haiyan; Jiang, Di; Cao, Weiping; Chen, Hui; Xia, Lei; Xu, Ruimin

    2016-07-01

    A novel, compact microwave tunable bandpass filter integrated power divider, based on the high anisotropy electro-optic nematic liquid crystal, is proposed in this letter. Liquid crystal, as the electro-optic material, is placed between top inverted microstrip line and the metal plate. The proposed structure can realize continuous tunable bandpass response and miniaturization. The proposed design concept is validated by the good performance of simulation results and experimental results. The electro-optic material has shown great potential for microwave application.

  19. A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups

    Directory of Open Access Journals (Sweden)

    Kalpana Upadhyaya

    2013-01-01

    Full Text Available Non-symmetrically substituted four-ring achiral bent-core compounds with polar substituents, i.e.., chloro in the bent or transverse direction in the central core and cyano in the lateral direction at one terminal end of the molecule, are designed and synthesized. These molecules possess an alkoxy chain attached at only one end of the bent-core molecule. The molecular structure characterization is consistent with data from elemental and spectroscopic analysis. The materials thermal behaviour and phase characterization have been investigated by differential scanning calorimetry and polarizing microscopy. All the compounds exhibit a wide-ranging monotropic nematic phase.

  20. DNA origami nanoneedles on freestanding lipid membranes as a tool to observe isotropic-nematic transition in two dimensions.

    Science.gov (United States)

    Czogalla, Aleksander; Kauert, Dominik J; Seidel, Ralf; Schwille, Petra; Petrov, Eugene P

    2015-01-14

    We introduce a simple experimental system to study dynamics of needle-like nanoobjects in two dimensions (2D) as a function of their surface density close to the isotropic-nematic transition. Using fluorescence correlation spectroscopy, we find that translational and rotational diffusion of rigid DNA origami nanoneedles bound to freestanding lipid membranes is strongly suppressed upon an increase in the surface particle density. Our experimental observations show a good agreement with results of Monte Carlo simulations of Brownian hard needles in 2D.

  1. The applicability of a percolation model to photoconductivity in guest–host thermotropic nematic liquid crystal systems

    DEFF Research Database (Denmark)

    Chapoy, L. Lawrence

    1986-01-01

    Photoconductivity is investigated for a thermotropic nematic low molar mass liquid crystal which has been doped with carbazole, a known photoconductor. The dopant is oriented by a guest–host mechanism and is studied as a function of concentration. Threshold levels of photoconductivity occur at le...... at levels three orders of magnitude below that predicted from simple percolation theory. Some possible explanations for this as well as its implications are proposed. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

  2. Spin Nematics, Valence-Bond Solids, and Spin Liquids in SO(N) Quantum Spin Models on the Triangular Lattice.

    Science.gov (United States)

    Kaul, Ribhu K

    2015-10-09

    We introduce a simple model of SO(N) spins with two-site interactions which is amenable to quantum Monte Carlo studies without a sign problem on nonbipartite lattices. We present numerical results for this model on the two-dimensional triangular lattice where we find evidence for a spin nematic at small N, a valence-bond solid at large N, and a quantum spin liquid at intermediate N. By the introduction of a sign-free four-site interaction, we uncover a rich phase diagram with evidence for both first-order and exotic continuous phase transitions.

  3. A coupled map lattice model for rheological chaos in sheared nematic liquid crystals.

    Science.gov (United States)

    Kamil, S M; Menon, Gautam I; Sinha, Sudeshna

    2010-12-01

    A variety of complex fluids under shear exhibit complex spatiotemporal behavior, including what is now termed rheological chaos, at moderate values of the shear rate. Such chaos associated with rheological response occurs in regimes where the Reynolds number is very small. It must thus arise as a consequence of the coupling of the flow to internal structural variables describing the local state of the fluid. We propose a coupled map lattice model for such complex spatiotemporal behavior in a passively sheared nematic liquid crystal using local maps constructed so as to accurately describe the spatially homogeneous case. Such local maps are coupled diffusively to nearest and next-nearest neighbors to mimic the effects of spatial gradients in the underlying equations of motion. We investigate the dynamical steady states obtained as parameters in the map and the strength of the spatial coupling are varied, studying local temporal properties at a single site as well as spatiotemporal features of the extended system. Our methods reproduce the full range of spatiotemporal behavior seen in earlier one-dimensional studies based on partial differential equations. We report results for both the one- and two-dimensional cases, showing that spatial coupling favors uniform or periodically time-varying states, as intuitively expected. We demonstrate and characterize regimes of spatiotemporal intermittency out of which chaos develops. Our work indicates that similar simplified lattice models of the dynamics of complex fluids under shear should provide useful ways to access and quantify spatiotemporal complexity in such problems, in addition to representing a fast and numerically tractable alternative to continuum representations. © 2010 American Institute of Physics.

  4. Finite-element analysis of the optical-texture-mediated photoresponse in a nematic strip

    Science.gov (United States)

    Chung, Hayoung; Yun, Jung-Hoon; Choi, Joonmyung; Cho, Maenghyo

    2017-01-01

    In a nematic solid, wherein liquid crystal molecules are incorporated into polymeric chains, the chromophore phase is projected onto the polymer conformation, changing the stress-free configuration metric. Stimulated actuation cannot be separated from the structure itself, since the mesoscopic polymer properties dictate the degree and type of shape change. In this research, we focused on self-deforming device programming, inspired by recent optical techniques, to pattern nontrivial alignment textures and induce exotic strain fields on specimens. A finite-element framework incorporating a light-thermo-order coupled constitutive relation and geometric nonlinearities was utilized to compute mechanical deformations for given external stimuli. The distortion of planar strips into various exotic 3D shapes was simulated, and disclination-defect-like liquid crystal texture topographies with different defect strengths produced various many-poled shapes upon irradiation, as observed experimentally. The effects of the boundary conditions and geometric nonlinearities were also examined, exemplifying the need for a comprehensive finite-element-based framework. The same method was applied to textures naturally emerging due to static distortion, and the effects of the prescribed inhomogeneities on the overall deformations, which is the basis of inverse design, were observed. Furthermore, we analyzed the local Poisson-effect-induced instability resulting from inscribing a hedgehog disclination texture onto a solid; the onset of buckling-like deformations was observed energetically, and the relations between this onset and other physical properties were elucidated to enable microstate design while maintaining structural stability. These results will facilitate the development and comprehension of the mechanisms of remotely light-controlled self-assembly and propulsion systems that may soon be realized.

  5. Dynamic Response of Graphitic Flakes in Nematic Liquid Crystals: Confinement and Host Effect

    Directory of Open Access Journals (Sweden)

    Weiwei Tie

    2017-09-01

    Full Text Available Electric field-induced reorientation of suspended graphitic (GP flakes and its relaxation back to the original state in a nematic liquid crystal (NLC host are of interest not only in academia, but also in industrial applications, such as polarizer-free and optical film-free displays, and electro-optic light modulators. As the phenomenon has been demonstrated by thorough observation, the detailed study of the physical properties of the host NLC (the magnitude of dielectric anisotropy, elastic constants, and rotational viscosity, the size of the GP flakes, and cell thickness, are urgently required to be explored and investigated. Here, we demonstrate that the response time of GP flakes reorientation associated with an NLC host can be effectively enhanced by controlling the physical properties. In a vertical field-on state, higher dielectric anisotropy and higher elasticity of NLC give rise to quicker reorientation of the GP flakes (switching from planar to vertical alignment due to the field-induced coupling effect of interfacial Maxwell-Wagner polarization and NLC reorientation. In a field off-state, lower rotational viscosity of NLC and lower cell thickness can help to reduce the decay time of GP flakes reoriented from vertical to planar alignment. This is mainly attributed to strong coupling between GP flakes and NLC originating from the strong π-π interaction between benzene rings in the honeycomb-like graphene structure and in NLC molecules. The high-uniformity of reoriented GP flakes exhibits a possibility of new light modulation with a relatively faster response time in the switching process and, thus, it can show potential application in field-induced memory and modulation devices.

  6. Aplicação de formulação do fungo predador de nematóides Monacrosporium thaumasium (Drechsler, 1937 no controle de nematóides de bovinos

    Directory of Open Access Journals (Sweden)

    Alves P.H.

    2003-01-01

    Full Text Available A viabilidade de uma formulação do fungo Monacrosporium thaumasium (Drechsler, 1937 foi avaliada no controle biológico de nematóides parasitos gastrintestinais de bovinos. Dois grupos de sete bezerras cada, mestiças Holandês ´ Zebu, de quatro a seis meses de idade, foram colocados em pastagens de Cynodon dactilon. No grupo A, cada animal recebeu 20g de pellets (formulação granulada de M. thaumasium via oral, duas vezes por semana, durante quatro meses, com início na estação chuvosa (outubro, 2001. No grupo B (controle, as bezerras não receberam nenhum tratamento. As contagens de ovos por grama de fezes (OPG e das larvas infectantes encontradas na pastagem do grupo B foram significativamente maiores (P<0,05 do que as do grupo A e a diferença entre o OPG dos animais dos grupos A e B, no final do experimento, foi de 88,8%. O gênero Cooperia foi o mais prevalente em ambas as pastagens. Conclui-se que a aplicação de pellets de M. thaumasium na dosagem e periodicidade de aplicação usadas foi eficiente no controle de nematóides parasitos gastrintestinais de bovinos.

  7. Electrolyte effects on the stability of nematic and lamellar lyotropic liquid crystal phases: colligative and ion-specific aspects.

    Science.gov (United States)

    Dawin, Ute C; Lagerwall, Jan P F; Giesselmann, Frank

    2009-08-20

    We investigated the electrolyte effects on the stability of nematic and lamellar lyotropic liquid crystalline (LLC) phases formed by the simple anionic surfactant cesium pentadecafluorooctanoate (CsPFO) in water. To the lyotropic guest phase, at the constant CsPFO-mass fraction of 0.55, the series of electrolytes LiCl, NaCl, KCl, CsCl, CsI, and Cs(2)SO(4), respectively, was added at concentrations ranging from 0.5 to 2.5 mol %. With increasing electrolyte concentration two substantially different effects were observed. At low concentrations all added electrolytes caused an increase of the thermal stability of the LLC phases, favoring the lamellar phase over the nematic phase. This behavior is, at least qualitatively, understood within the packing parameter model. The extent of the stabilization clearly depends on the chemical nature of the added cation. For a given cation, however, the effect is colligative, i.e., independent of the chemical nature of the added anion. At higher salt concentrations a salting-out-like phase separation was induced. This effect is clearly ion-specific as the salting-out concentration varied for each cation following the order of the Hofmeister series for cations.

  8. Influence of virtual surfaces on Frank elastic constants in a polymer-stabilized bent-core nematic liquid crystal.

    Science.gov (United States)

    Madhuri, P Lakshmi; Hiremath, Uma S; Yelamaggad, C V; Madhuri, K Priya; Prasad, S Krishna

    2016-04-01

    Effect of a polymer network on the threshold voltage of the Fréedericksz transition, Frank elastic constants, switching speed, and the rotational viscosity are investigated in a polymer-stabilized bent-core nematic liquid crystal with different polymer concentrations. These polymer networks form virtual surfaces with a finite anchoring energy. The studies bring out several differences in comparison to similar studies with a calamitic liquid crystal as the nematic host. For example, on varying the polymer content the threshold voltage decreases initially, but exhibits a drastic increase above a critical concentration. A similar feature-reaching a minimum before rising-is seen for the bend elastic constant, which gets enhanced by an order of magnitude for a polymer content of 2.5 wt %. In contrast, the splay elastic constant has a monotonic variation although the overall enhancement is comparable to that of the bend elastic constant. The behavior changing at a critical concentration is also seen for the switching time and the associated rotational viscosity. The presence of the polymer also induces a shape change in the thermal dependence of the bend elastic constant. We explain the features observed here on the basis of images obtained from the optical and atomic force microscopy.

  9. 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.

  10. A comparison between size dependent paraelectric and ferroelectric BaTiO3 nanoparticle doped nematic and ferroelectric liquid crystals

    Science.gov (United States)

    Al-Zangana, S.; Turner, M.; Dierking, I.

    2017-02-01

    The electro-optic and dielectric properties of barium titanate, BaTiO3, and nanoparticle (NP) doped nematic and ferroelectric liquid crystal materials were examined with respect to different size and concentrations of the NPs. Smaller size paraelectric NPs (≈80 nm) are compared to larger, ferroelectric NPs (≈240 nm). It is found that for concentrations larger than 0.5 vol. %, the ferroelectric NPs exhibit an increasing effect on the electro-optic response of the nematic liquid crystal, which is demonstrated by the enhancement of the dielectric anisotropy. This could be induced by the coupling of the electrical dipole moments in the spherical NPs with the LC director field. The electro-optical properties of the SmC* phase, such as the tilt angle Θ, switching time τ s , and spontaneous polarisation P s , are found to be independent of the concentration and size of the NPs. The rotational viscosity η calculated from response times, polarization reversal current, and dielectric properties is comparable for all three methods employed and practically independent of particle concentration and size. The relaxation frequency f R of the Goldstone mode is higher in the ferroelectric NPs suspensions of 2.0 vol. % as compared to the smaller paraelectric NPs.

  11. The spin-1/2 Kagome XXZ model in a field: competition between lattice nematic and solid orders

    CERN Document Server

    Kshetrimayum, Augustine; Orus, Roman; Poilblanc, Didier

    2016-01-01

    We study numerically the spin-1/2 XXZ model in a field on an infinite Kagome lattice. We use different algorithms based on infinite Projected Entangled Pair States (iPEPS) for this, namely: (i) an approach with simplex tensors and 9-site unit cell, and (ii) an approach based on coarse-graining three spins in the Kagome lattice and mapping it to a square-lattice model with local and nearest-neighbor interactions, with usual PEPS tensors, 6- and 12-site unit cells. We observe the emergence of a plateau in the magnetization at $m_z = \\frac{1}{3}$ as a function of the magnetic field, and focus on characterizing it as a function of the anisotropy, including the XY, Heisenberg, and Ising points. We find that the 9-site simplex-method produces degenerate -- within our accuracy -- (lattice) nematic and $\\sqrt{3} \\times \\sqrt{3}$ VBC-Solid states up to the Ising point. The 6- and 12-site coarse-grained PEPS methods also produce (almost) degenerate nematic and $\\sqrt{2} \\times \\sqrt{2}$ VBC-Solid order, although with a...

  12. Effect of temperature on the morphology and electro-optical properties of liquid crystal physical gel

    Energy Technology Data Exchange (ETDEWEB)

    Leaw, W.L. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Mamat, C.R., E-mail: che@kimia.fs.utm.my [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Triwahyono, S. [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Jalil, A.A. [Department of Chemical Engineering, Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Centre of Hydrogen Energy, Institute of Future Energy, Univerisiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia); Bidin, N. [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310, UTM Johor Bahru, Johor (Malaysia)

    2016-12-01

    Liquid crystal physical gels were (thermally) prepared with cholesteryl stearate as a gelator in nematic liquid crystal, 4-cyano-4′-pentylbiphenyl. The electro-optical performance of liquid crystal physical gels is almost entirely dependent on the gels' inherent morphology. This study involved an empirical investigation of the relationships among all of the gelation temperature, morphology, and electro-optical properties. Besides continuous cooling at room temperature, isothermal cooling was also performed at both 18 and 0 °C, corresponding to near-solid and solid phases of 4-cyano-4′-pentylbiphenyl respectively. Nevertheless, the liquid crystal physical gel was also isothermally rapidly cooled using liquid nitrogen. Polarizing optical microscopy showed that the gel structure became thinner when isothermal cooling was carried out. These thinner gel aggregates then interconnected to form larger liquid crystal domains. Moreover, it was also revealed that the gel networks were randomized. Electron spin resonance results showed that the liquid crystal director orientation was severely randomized in the presence of gel networks. Conversely, isothermal cooling using liquid nitrogen generated a higher liquid crystal director orientation order. The 6.0 wt% cholesteryl stearate/4-cyano-4′-pentylbiphenyl physical gel that was isothermally cooled using liquid nitrogen showed the lowest response time in a twisted nematic mode optical cell. - Graphical abstract: Liquid crystal physical gel was prepared using nematic liquid crystal, 4-cyano-4′-pentylbiphenyl and cholesteryl stearate as gelator. Isothermal cooling at lower temperature produced thinner gel network and larger liquid crystal domain. - Highlights: • 5CB nematic liquid crystal was successfully gelled by cholesteryl stearate gelator. • The morphology of gel network was controlled by different cooling conditions. • Thinner gel network was formed by the rapid cooling using liquid nitrogen.

  13. Global characterization of nematic liquid crystal display Sony LCX038ARA with applied electric field in the modulation amplitude-coupled regime

    Science.gov (United States)

    Cuevas Cely, C. J.; Acevedo Cáceres, C. H.; Torres Moreno, Y.

    2017-06-01

    In this work, we showed experimental and theoretical results of the characterization of a spatial light modulator based in a nematic liquid crystal display Sony model LCX038ARA with electric field excitation. The parameters: effective molecular twist and equivalent retardation are determinated using the retarder-rotor technique in the amplitude-coupled regime.

  14. Modeling out-of-plane actuation in thin-film nematic polymer networks: From chiral ribbons to auto-origami boxes via twist and topology

    Science.gov (United States)

    Gimenez-Pinto, Vianney; Ye, Fangfu; Mbanga, Badel; Selinger, Jonathan V.; Selinger, Robin L. B.

    2017-03-01

    Various experimental and theoretical studies demonstrate that complex stimulus-responsive out-of-plane distortions such as twist of different chirality, emergence of cones, simple and anticlastic bending can be engineered and pre-programmed in a liquid crystalline rubbery material given a well-controlled director microstructure. Via 3-d finite element simulation studies, we demonstrate director-encoded chiral shape actuation in thin-film nematic polymer networks under external stimulus. Furthermore, we design two complex director fields with twisted nematic domains and nematic disclinations that encode a pattern of folds for an auto-origami box. This actuator will be flat at a reference nematic state and form four well-controlled bend distortions as orientational order changes. Device fabrication is applicable via current experimental techniques. These results are in qualitative agreement with theoretical predictions, provide insight into experimental observations, and demonstrate the value of finite element methods at the continuum level for designing and engineering liquid crystal polymeric devices.

  15. Novos assinalamentos de nematóides de parte aérea (Aphelenchoides spp. em plantas de begônia no Brasil.

    Directory of Open Access Journals (Sweden)

    Claudio Marcelo G. Oliveira

    2006-06-01

    Full Text Available Os nematóides da parte aérea, Aphelenchoides besseyi e A. ritzemabosi, foram detectados causando lesões pardo-escuras em todo o limbo foliar de plantas de begônia (Begonia sp. no Brasil. rata-se da primeira ocorrência de A. besseyi parasitando essa planta ornamental.

  16. On the theory of Rayleigh-Bénard convection in homeotropic nematic liquid crystals

    Science.gov (United States)

    Feng, Q.; Decker, W.; Pesch, W.; Kramer, L.

    1992-06-01

    A rigorous linear and weakly nonlinear analysis of Rayleigh-Bénard convection in homeotropically aligned nematic liquid crystals is presented for both adverse convection (heating from above) and normal convection (heating from below) allowing for th presence of magnetic fields. In adverse convection we find a transition from forward to backward bifurcation with increasing vertical (stabilizing) field. The stability analysis of roll solutions explains the experimentally observed transition between roll and square patterns for weak horizontal (destabilizing) fields. In a range of high vertical magnetic fields two steady convective modes with different wavelengths and symmetries become critical at nearly the same threshold giving rise to competition and resonant interaction. For the oscillatory instability in normal convection the nature of the bifurcation for both traveling and standing rolls is determined. Comparison with previous theories and with experiments is made wherever possible. Nous reconsidérons la description théorique du comportement au seuil et près du seuil de convection de Rayleigh-Bénard dans un cristal liquide nématique en géometrie homéotrope. Lorsque le système est chauffé par le haut et soumis à un champ magnétique faiblement déstabilisant, une analyse de stabilité des rouleaux explique leur transition dans les échantillons rectangulaires connus expérimentalement. Dans la même configuration mais avec un champ vertical stabilisant, nous observons le passage d'une bifurcation directe à une bifurcation inverse. On trouve, dans un intervalle de grands champs magnetiques, un regime où deux modes stationnaires convectifs avec différentes longueurs d'onge et de symmetrie opposée ont le même seuil critique. Cela conduit à une compétition et une interaction résonnante. En cas de chauffage par le bas une instabilité oscillante se développe comme on sait. La nature de la bifurcation est analysée pour des rouleaux stationnaires et

  17. Order reconstruction phenomena and temperature-driven dynamics in a 3D zenithally bistable device

    KAUST Repository

    Raisch, A.

    2014-07-01

    We model the zenithally bistable device (ZBD) in three dimensions (3D), within the Landau-de Gennes theory, and find three stable static states in 3D without an applied field: the vertically aligned nematic (VAN) state, the hybrid aligned nematic (HAN) state and a third, high-tilt state, which we call the THAN state, with an interior and a surface defect. We recover the order reconstruction (OR) phenomenon around the defects in the HAN and THAN states and the 3D THAN and HAN solutions exhibit stable biaxial cylinders connecting defects on opposite faces of the ZBD device. We demonstrate a two-way temperature-driven switching between high-tilt and low-tilt states through controlled heating and cooling procedures in two dimensions (2D), with no applied fields. © CopyrightEPLA, 2014.

  18. Voltage- and temperature- controlled LC:PDMS waveguide channels

    Science.gov (United States)

    Rutkowska, Katarzyna A.; Asquini, Rita; d'Alessandro, Antonio

    2017-08-01

    In this paper, we present our studies on electrical and thermal tuning of light propagation in waveguide channels, made for the scope from a polydimethylsiloxane (PDMS) substrate infiltrated with nematic liquid crystal (LC). We demonstrated, via numerical simulations, the changes of the waveguide optical parameters when solicited by temperature changes or electric fields. Moreover, the paper goes through the fabrication process of a waveguide channel sample and its characterization, as well as some preliminary experimental trials of sputtering indium tin oxide (ITO) and chromium layers on PDMS substrate to obtain flat electrodes.

  19. Optical Properties of a One-Dimensional Photonic Crystal Containing a Twisted Nematic Liquid Crystal Defect Layer

    Science.gov (United States)

    Tagashira, Kenji; Yoshida, Hiroyuki; Fujii, Akihiko; Ozaki, Masanori

    We analyze the optical properties of a one-dimensional photonic crystal containing a twisted nematic liquid crystal (NLC) defect layer. For randomly polarized light incidence, two photonic defect modes were found to appear in the photonic band gap of the one-dimensional photonic crystal, and were associated either with the molecular long axis experiencing the averaged extraordinary refractive index or the molecular short axis experiencing the averaged ordinary refractive index, of the defect NLC layer. Numerical analyses also revealed that the transmitted light at the defect mode is linearly-polarized light at an angle which is determined both from the twist angle of the twisted NLC and the resulting optical rotatory power. When the thickness of the defect layer is sufficiently thin, optical rotation can be ignored and the output polarization angle is at half the twist angle for the long axis mode and at 90 degrees to that for the short axis mode.

  20. Zig-zag wall lattice in a nematic liquid crystal with an in-plane switching configuration.

    Science.gov (United States)

    Andrade-Silva, I; Clerc, M G; Odent, V

    2014-08-01

    Liquid crystals displays with tailoring electrodes exhibit complex spatiotemporal dynamics when a large voltage is applied. We report experimental observations of the appearance of a programmable zig-zag lattice using an in-plane-switching cell filled with a nematic liquid crystal. Applying a small voltage to a wide range of frequencies, the system exhibits an Ising wall lattice. Increasing the voltage, this lattice presents a spatial instability generating an undulating wall lattice, and to higher voltages it becomes zig-zag type. Experimentally, we characterize the bifurcations and phase diagram of the wall lattice. Theoretically, we develop, from first principles, a descriptive model. This model has a good qualitative agreement with experimental observations.

  1. Strong flexoelectric behavior in bimesogenic liquid crystals

    Science.gov (United States)

    Coles, H. J.; Clarke, M. J.; Morris, S. M.; Broughton, B. J.; Blatch, A. E.

    2006-02-01

    In this paper, we demonstrate strong flexoelectric coupling in bimesogenic liquid crystals. This strong coupling is determined via the flexoelectro-optic effect in chiral nematic liquid crystals based on bimesogenic mixtures that are doped with low concentrations of high twisting power chiral additive. Two mixtures were examined: one had a pitch length of p~300 nm, the other had a pitch length of p~600 nm. These mixtures exhibit enantiotropic chiral nematic phases close to room temperature. We found that full-intensity modulation, that is, a rotation of the optic axis of 45° between crossed polarizers, could be achieved at significantly lower applied electric fields (E<5 V μm-1) than previously reported. In fact, for the condition of full-intensity modulation, the lowest electric-field strength recorded was E=2 V μm-1. As a result of a combination of the strong flexoelectric coupling and a divergence in the pitch, tilt angles of the optic axis up to 87°, i.e., a rotation of the optic axis through 174°, were observed. Furthermore, the flexoelastic ratios, which may be considered as a figure-of-merit parameter, were calculated from the results and found to be large, ranging from 1.3 to 2 C/Nm for a temperature range of up to 40 °C.

  2. Relação entre desempenho e infecções por nematódeos gastrintestinais em bovinos Nelore em crescimento

    Directory of Open Access Journals (Sweden)

    Nicolau C.V.J.

    2002-01-01

    Full Text Available Este estudo teve por objetivo verificar a associação entre o desempenho e a carga parasitária de 28 machos inteiros da raça Nelore (a partir de um ano de idade, naturalmente infectados por nematódeos gastrintestinais. De novembro de 1999 a junho de 2000, os animais foram pesados quinzenalmente, período no qual foram colhidas amostras de fezes e de sangue para a realização, respectivamente, de exames coprológicos e sangüíneos. Os dados da contagem de ovos por grama de fezes (OPG ajustaram-se ao modelo de distribuição binomial negativa, indicando que a distribuição de nematódeos no rebanho é agregada. Não ficou evidenciada associação entre ganho de peso e contagem de OPG, e entre contagem de OPG e volume globular (VG. De 10 coeficientes de correlação entre ganho de peso e VG, oito foram negativos, mas apenas dois significativos (P<0,05. As estimativas de repetibilidade da contagem de OPG, LOG (OPG+1 e VG foram de 0,26, 0,25 e 0,33, respectivamente. Cooperia punctata foi a espécie mais freqüentemente encontrada parasitando os animais. Além dessa espécie, foram detectados os seguintes nematódeos: Haemonchus placei, Haemonchus similis, Trichostrongylus axei, Bunostomum phlebotomum e Oesophagostomum radiatum. O parasitismo por nematódeos gastrintestinais aparentemente não prejudicou o desenvolvimento dos animais estudados.

  3. Control of infective larvae of gastrointestinal nematodes in heifers using different isolates of nematophagous fungi Controle de larvas infectantes de nematóides gastrintestinais de novilhas por diferentes isolados dos fungos nematófagos

    Directory of Open Access Journals (Sweden)

    Manoel Eduardo da Silva

    Full Text Available The effect of different nematophagous fungi [Duddingtonia flagrans (AC001 and CG722 and Monacrosporium thaumasium (NF34] with regard to controlling infective larvae (L3 of nematodes after gastrointestinal transit in female cattle (3/4 Holstein × Zebu was evaluated. A total of 24 pubescent female cattle were used, weighing approximately 320 kg each one. There were three treatment groups, each contained six animals that received 150 g of pellets (0.2 g of mycelium, orally in a single dose, in a sodium alginate matrix containing mycelial mass of the fungus D. flagrans (AC001 or CG722 or M. thaumasium (NF34; and one control group (without fungi. Fecal samples were collected from the animals at intervals of 12, 15, 18, 21, 24, 48, and 72 hours. At the end of 17 days, the L3 not subjected to predation were recovered by means of the Baermann method. The fungal isolates tested were capable of destroying the L3 after gastrointestinal transit. It was observed that within 72 hours, the isolates AC001, CG722, and NF34 showed a higher predatory activity (81.2%, 97.3%, and 98.3%, respectively. The results justify the need for studies in the field, and over longer intervals, in order to observe the efficiency of the fungus D. flagrans, or even M. thaumasium, for environmental control over nematodes in naturally infected cattle.No presente estudo, foi avaliado o efeito de diferentes fungos nematófagos [Duddingtonia flagrans (AC001 e CG722 e Monacrosporium thaumasium (NF34] no controle de larvas infectantes (L3 de nematóides após o trânsito gastrointestinal em fêmeas bovinas (3/4 Holandês x Zebu. Um total de 24 fêmeas bovinas pubescentes foram utilizadas, pesando aproximadamente 320 kg cada. Foram utilizados três grupos de tratamento; cada um contendo seis animais que receberam por via oral de 150 g de péletes (0,2 g de micélio, em dose única, em uma matriz de alginato de sódio contendo massa micelial dos fungos D. flagrans (AC001 ou

  4. SYNTHESIS AND CHARACTERIZATION OF CdS IN DIOL VANILIN LIQUID CRYSTAL MONOMER

    Directory of Open Access Journals (Sweden)

    H. L. Lee

    2010-06-01

    Full Text Available Nanocomposites comprising diol-vanilin and cadmium sulfide (CdS has been synthesized via chemical precipitation method in ethanol at refluxed temperature (160 oC for 12 hours. CdCl2. 2.5H2O and thiourea as cadmium and sulfide precursors respectively were employed. Diol vanilin is a thermotropic liquid crystal monomer which exhibits enantiotropic nematic metaphase texture when observed under polarizing microscope and confirmed by DSC thermal stability study. A series of different mass composition  of diol vanilin and CdS nanocomposites ranging from  0.1:1.0 till 1.0:1.0(w/w were prepared and characterized using XRD, TEM, SEM-EDX, POM and DSC. The X-ray diffraction pattern (XRD showed broad peaks due to the formation of cubic CdS nanoparticles in diol vanilin matrix. The nanocomposites at low mass composition  of CdS still maintained their nematic phase. However, the liquid crystal property was affected when the mass  composition  of CdS in nanocomposite was increased and the liquid crystal characteristic vanished when the mass composition  was at 0.6:1.0. .    Keywords: CdS, diol vanilin, thermotropic liquid crystal, nanocomposite.

  5. Binary Mass Diffusion Constants in Nematic Liquid Crystals Studied by Forced Rayleigh Scattering

    Science.gov (United States)

    Hara, Masahiko; Ichikawa, Seiji; Takezoe, Hideo; Fukuda, Atsuo

    1984-11-01

    The binary mass diffusion constants of methyl red in the nematogens MBBA and 5CB were measured by forced Rayleigh scattering (FRS). The diffusion constants in the direction parallel to the director orientation, D//, are always larger than those perpendicular to it, D\\bot; D///D\\bot=1.6 for both MBBA and 5CB at room temperature. The temperature dependence is of the Arrhenius type except near the phase transition temperature of 5CB, where the values tend to deviate downwards. A comparison between the results obtained by other methods and those obtained by the present method suggests that the binary mass diffusion constant of methyl red obtained by FRS is a good measure of the self-diffusion constant.

  6. Steady state-Hopf mode interactions at the onset of electroconvection in the nematic liquid crystal Phase V.

    Science.gov (United States)

    Acharya, Gyanu; Dangelmayr, Gerhard; Gleeson, James; Oprea, Iuliana

    2011-01-01

    We report on a new mode interaction found in electroconvection experiments on the nematic liquid crystal mixture Phase V in planar geometry. The mode interaction (codimension two) point occurs at a critical value of the frequency of the driving AC voltage. For frequencies below this value the primary pattern-forming instability at the onset voltage is an oblique stationary instability involving oblique rolls, and above this value it is an oscillatory instability giving rise to normal traveling rolls (oriented perpendicular to and traveling in the director direction). The transition has been confirmed by measuring the roll angle and the dominant frequency of the time series, as both quantities exhibit a discontinuous jump across zero when the AC frequency is varied near threshold. The globally coupled system of Ginzburg-Landau equations that qualitatively describe this mode interaction is constructed, and the resulting normal form, in which slow spatial variations of the mode amplitudes are ignored, is analyzed. This analysis shows that the Ginzburg-Landau system provides the adequate theoretical description for the experimentally observed phenomenon. The experimentally observed patterns at and higher above the onset allow us to narrow down the range of the parameters in the normal form.

  7. Steady State–Hopf Mode Interactions at the Onset of Electroconvection in the Nematic Liquid Crystal Phase V

    Directory of Open Access Journals (Sweden)

    Iuliana Oprea

    2011-07-01

    Full Text Available We report on a new mode interaction found in electroconvection experiments on the nematic liquid crystal mixture Phase V in planar geometry. The mode interaction (codimension two point occurs at a critical value of the frequency of the driving AC voltage. For frequencies below this value the primary pattern-forming instability at the onset voltage is an oblique stationary instability involving oblique rolls, and above this value it is an oscillatory instability giving rise to normal traveling rolls (oriented perpendicular to and traveling in the director direction. The transition has been confirmed by measuring the roll angle and the dominant frequency of the time series, as both quantities exhibit a discontinuous jump across zero when the AC frequency is varied near threshold. The globally coupled system of Ginzburg–Landau equations that qualitatively describe this mode interaction is constructed, and the resulting normal form, in which slow spatial variations of the mode amplitudes are ignored, is analyzed. This analysis shows that the Ginzburg–Landau system provides the adequate theoretical description for the experimentally observed phenomenon. The experimentally observed patterns at and higher above the onset allow us to narrow down the range of the parameters in the normal form.

  8. Molecular dynamics simulation of planar elongational flow in a nematic liquid crystal based on the Gay-Berne potential.

    Science.gov (United States)

    Sarman, Sten; Laaksonen, Aatto

    2015-02-07

    Molecular dynamics simulations of planar elongational flow in a nematic liquid crystal model system based on the Gay-Berne fluid were undertaken by applying the SLLOD equations of motion with an elongational velocity field or strain rate. In order to facilitate the simulation, Kraynik-Reinelt periodic boundary conditions allowing arbitrarily long simulations were used. A Lagrangian constraint algorithm was utilized to fix the director at different angles relative to the elongation direction, so that the various pressure tensor elements could be calculated as a function of this angle. This made it possible to obtain accurate values of the shear viscosities which were found to agree with results previously obtained by shear flow simulations. The torque needed to fix the director at various angles relative to the elongation direction was evaluated in order to determine the stable orientation of the director, where this torque is equal to zero. This orientation was found to be parallel to the elongation direction. It was also noted that the irreversible entropy production was minimal when the director attained this orientation. Since the simulated system was rather large and fairly long simulation runs were undertaken it was also possible to study the cross coupling between the strain rate and the order tensor. It turned out to be very weak at low strain rates but at higher strain rates it could lead to break down of the liquid crystalline order.

  9. Electro-optical study of chiral nematic liquid crystal/chiral ionic liquid composites with electrically controllable selective reflection characteristics.

    Science.gov (United States)

    Hu, Wang; Zhang, Lipei; Cao, Hui; Song, Li; Zhao, Haiyan; Yang, Zhou; Cheng, Zihui; Yang, Huai; Guo, Lin

    2010-03-20

    A chiral nematic liquid crystal (N*-LC)/chiral ionic liquid (CIL) composite with unique electro-optical characteristics was prepared and filled into a planar treated cell. When an electric field was applied to the cell, the anions and the cations of CIL moved towards the anode and the cathode of the power supply, respectively, thus forming a density gradient of the chiral groups, which resulted in wideband reflection. By adjusting the intensity of the electric field, the reflection bandwidth can be controlled accurately and reversibly. Moreover, the electric field-induced states can be memorized after the applied electric field is turned off. The reflective properties of the composite are investigated in the visible and near-infrared region, respectively. Additionally, the changes of the reflection bandwidths with the intensity and the applied time of the electric field were also investigated. From scanning electron microscopy (SEM) investigations, the mechanism of the electrically controllable reflection was demonstrated. Potential applications of the composite are related to reflective, color electronic paper (E-paper) and smart reflective windows for the solar light management.

  10. Hierarchical self-assembly: Self-organized nanostructures in a nematically ordered matrix of self-assembled polymeric chains

    Science.gov (United States)

    Mubeena, Shaikh; Chatterji, Apratim

    2015-03-01

    We report many different nanostructures which are formed when model nanoparticles of different sizes (diameter σn) are allowed to aggregate in a background matrix of semiflexible self-assembled polymeric wormlike micellar chains. The different nanostructures are formed by the dynamical arrest of phase-separating mixtures of micellar monomers and nanoparticles. The different morphologies obtained are the result of an interplay of the available free volume, the elastic energy of deformation of polymers, the density (chemical potential) of the nanoparticles in the polymer matrix, and, of course, the ratio of the size of self-assembling nanoparticles and self-avoidance diameter of polymeric chains. We have used a hybrid semi-grand-canonical Monte Carlo simulation scheme to obtain the (nonequilibrium) phase diagram of the self-assembled nanostructures. We observe rodlike structures of nanoparticles which get self-assembled in the gaps between the nematically ordered chains, as well as percolating gel-like network of conjoined nanotubes. We also find a totally unexpected interlocked crystalline phase of nanoparticles and monomers, in which each crystal plane of nanoparticles is separated by planes of perfectly organized polymer chains. We identified the condition which leads to such interlocked crystal structure. We suggest experimental possibilities of how the results presented in this paper could be used to obtain different nanostructures in the laboratory.

  11. The static and dynamic behaviors of the topological defects in a nematic liquid crystal reveal its material characteristics

    Science.gov (United States)

    Zhang, Rui; Yanagimachi, Takuya; Kumar, Nitin; Gardel, Margaret; Nealey, Paul; de Pablo, Juan

    Topological defects in nematic liquid crystals (LCs) play a key role in phase transitions, domain growth, and morphology evolution. Their ability to absorb impurities offers promise for design of self-assembled, hierarchical materials. Past work has primarily studied defects in thermotropic LCs. In this work, we focus on lyotropic chromonic LCs and biopolymer LCs, and investigate how the static and dynamic properties of topological defects depend on the LC's material characteristics. Specifically, we rely on a Landau-de Gennes free energy model that accounts for variable material constants and back-flow effects, and adopt a hybrid lattice Boltzmann simulation method. We first show that the fine structure of half-charge defects is a function of the ratio of splay and bend constants. This morphological information is in turn used to infer the elasticity of an in vitro, actin-based LC suspension. We then examine the annihilation process of a defect pair of opposite topological charge. We find that the ratio of the two defect velocities is an outcome of the interplay between the LC's elastic moduli, its viscosities, and the organization of the defects. Our calculations predict a strong post-annihilation transverse flow that is further confirmed by our experiments with non-equilibrium LCs. An analysis of the asymptotic behavior of the elastic moduli allows us to elucidate the material at phase transitions. Our modelling provides a general, unified framework within which a wide class of LC materials can be understood.

  12. Formation of nematic liquid crystals of sterically stabilized layered double hydroxide platelets

    NARCIS (Netherlands)

    Mourad, M.C.D.|info:eu-repo/dai/nl/304837563; Devid, E.J.; van Schooneveld, M.M.|info:eu-repo/dai/nl/315032863; Vonk, Ch.; Lekkerkerker, H.N.W.|info:eu-repo/dai/nl/159054885

    2008-01-01

    Colloidal platelets of hydrotalcite, a layered double hydroxide, have been prepared by coprecipitation at pH 11−12 of magnesium nitrate and aluminum nitrate at two different magnesium to aluminum ratios. Changing the temperature and ionic strength during hydrothermal treatment, the platelets were

  13. Synthesis, optical and thermal behaviour of palladium(II) complexes ...

    Indian Academy of Sciences (India)

    shows that all the ligands and Pd(II) complexes exhibit enantiotropic mesophases. The ligands with n-octyloxy and n-decyloxy flexible chains exhibit the nematic (N) and smectic A (SmA) phases whilst the Pd(II) complexes show exclusive SmA phase. The SmA phase observed in Pd(II) complexes can be supported by the ...

  14. Temperature dependence of optical anisotropy of holographic polymer-dispersed liquid crystal transmission gratings.

    Science.gov (United States)

    Drevensek-Olenik, I; Fally, M; Ellabban, M A

    2006-08-01

    We measured the angular dependence of the 0th, +/-1 st, and +/-2 nd optical diffraction orders from a 50 microm thick transmission grating recorded in a UV-curable holographic polymer-dispersed liquid crystal (HPDLC) made from commercially available constituents. The analysis was performed for two orthogonal polarizations of the probe beams. The emphasis was laid on the temperature dependence of the grating anisotropy. Above the nematic-isotropic phase transition, the grating is optically isotropic. At lower temperatures the grating strength for the optical polarization perpendicular to the grating vector decreases with decreasing temperature, while for orthogonal polarization it increases with decreasing temperature. As a consequence, a regime of diffraction with strongly overmodulated gratings is observed. Our investigations indicate that the anisotropy of the refractive-index modulation scales with the optical anisotropy of the liquid crystal medium forming the phase-separated domains. We further demonstrate that light scattering effects, which are profound only in the nematic phase, must not be neglected and can be taken into account via a Lorentzian line-shape broadening of the probing wave vector directions in the framework of the diffraction theory for anisotropic optical phase gratings.

  15. Influence of a change in helical twisting power of photoresponsive chiral dopants on rotational manipulation of micro-objects on the surface of chiral nematic liquid crystalline films.

    Science.gov (United States)

    Thomas, Reji; Yoshida, Yohei; Akasaka, Takehito; Tamaoki, Nobuyuki

    2012-09-24

    Herein we report a group of five planar chiral molecules as photon-mode chiral switches for the reversible control of the self-assembled superstructures of doped chiral nematic liquid crystals. The chiral switches are composed of an asymmetrically substituted aromatic moiety and a photoisomerizing azobenzene unit connected in a cyclic manner through methylene spacers of varying lengths. All the molecules show conformational restriction in the rotation of the asymmetrically substituted aromatic moiety in both the E and Z states of the azobenzene units resulting in planar chirality with separable enantiomers. Our newly synthesized compounds in pure enantiomeric form show high helical twisting power (HTP) in addition to an improved change in HTP between the E and Z states. The molecule with a diphenylnaphthalene unit shows the highest ever known initial helical twisting power among chiral dopants with planar chirality. In addition to the reversible tuning of reflection colors, we employed the enantiomers of these five compounds in combination with four nematic liquid crystalline hosts to study their properties as molecular machines; the change in HTP of the chiral dopant upon photoisomerization induces rotation of the texture of the liquid crystal surfaces. Importantly, this study has revealed a linear dependence of the ratio of the difference between HTPs before and after irradiation against the absolute value of the initial HTP, not the absolute value of the change in helical twisting power between two states, on the angle of rotation of micro-objects on chiral nematic liquid crystalline films. This study has also revealed that a change in irradiation intensity does not affect the maximum angle of rotation, but it does affect the speed of rotational reorganization of the cholesteric helix. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Combinação de drogas antiparasitárias como uma alternativa para o controle de nematódeos gastrintestinais multirresistentes em ovinos

    Directory of Open Access Journals (Sweden)

    Alfredo Skrebsky Cezar

    2011-02-01

    Full Text Available Este estudo foi realizado com o objetivo de encontrarem-se tratamentos anti-helmínticos eficazes sobre uma população de nematódeos gastrintestinais de ovinos, a qual desenvolveu resistência a todas as classes de drogas com ação nematicida disponíveis para ruminantes no mercado brasileiro. Valendo-se da eficácia calculada de tratamentos convencionais a partir de um estudo prévio e, assim, conhecendo-se sua ação sobre diferentes gêneros de nematódeos presentes no rebanho, selecionaram-se drogas as quais, utilizadas em combinações ou em altas doses, pudessem aumentar significativamente a eficácia dos tratamentos. Utilizou-se o percentual de redução da contagem de ovos nas fezes e as culturas de larvas para avaliar a ação anti-helmíntica dos tratamentos testados. A combinação de moxidectina 1% + disofenol 20% apresentou 99% de eficácia, e as combinações de moxidectina 1% + triclorfon 10% e de moxidectina 1% + fosfato de levamisol 22,3% superaram os 90% de eficácia. A utilização de combinações de princípios ativos, com diferentes mecanismos de ação, pode promover a recuperação da eficácia dos tratamentos anti-helmínticos sobre populações multirresistentes de nematódeos gastrintestinais de ovinos.

  17. Avaliação in vitro da patogenicidade de fungos predadores de nematóides parasitos de animais domésticos

    OpenAIRE

    Graminha, Érika Barbosa Neves; Universidade Estadual Paulista; Maia, Arlete Silveira; Centro de Pesquisas em Sanidade Animal; Santos, Jaime Maia dos; Universidade Estadual Paulista; Cândido, Regina Célia; Universidade de São Paulo; Silva, Giane Serafim da; Centro de Pesquisas em Sanidade Animal; Costa, Alvimar José da; Centro de Pesquisas em Sanidade Animal

    2001-01-01

    O controle biológico é uma alternativa promissora no controle dos estágios pré-parasitários de helmintos, por meio da ação de fungos nematófagos. Com este propósito, o presente estudo avaliou in vitro a patogenicidade dos fungos Arthrobotrys musiformis e A. conoides sobre larvas infectantes de Haemonchus contortus, Ancylostoma spp. e ovos larvados de Ascaridia galli. Foram utilizados nove grupos: seis tratamentos (G1A e G2A: L3 de H. contortus; G1B e G2B: L3 de Ancylostoma spp.; G1C e G2C: ov...

  18. Efeitos do suco de alho (Allium sativum Linn. sobre nematódeos gastrintestinais de caprinos Effects of garlic juice (Allium sativum Linn. on gastrintestinal nematodes of goats

    Directory of Open Access Journals (Sweden)

    Maria José Moreira Batatinha

    2004-08-01

    Full Text Available O objetivo deste trabalho foi avaliar os efeitos do suco de alho sobre nematódeos gastrintestinais de caprinos. Foram utilizados 20 animais, distribuídos em dois grupos tratados com o suco de alho, um grupo tratado com ivermectina e um grupo controle sem tratamento. Os percentuais de redução do número de ovos e larvas de Strongyloidea foram inferiores a 95% para todos os grupos. O tratamento de caprinos com o suco de alho não foi eficiente no controle de nematódeos gastrintestinais.The objective of this work was to evaluate the effects of the garlic juice on goat gastrointestinal nematodes. Twenty animals were alocated into two groups and treated with garlic juice. One group was treated with ivermectin and one control group was not treated. The percentage reductions in egg and larvae counts of the Strongyloidea were under 95% for all groups. The treatment of goats with garlic juice was not an effective control of gastrointestinal nematodes.

  19. Dynamic light scattering and viscosity measurements in a ternary and quaternary discotic lyotropic nematic liquid crystal: Tuning the backflow with salt

    Science.gov (United States)

    Risi, C. L. S.; Figueiredo Neto, A. M.; Akpinar, E.; Santos, M. B. Lacerda

    2013-08-01

    Using a dynamic light scattering technique, we measure the damping rate of thermal fluctuations of the nematic director for the so-called disklike nematic ND phase of both the ternary lyotropic K-laurate-1-decanol-H2O system and the quaternary one of similar composition except for the addition of salt (K2SO4). By varying the scattering angle in suitable geometries and polarizations, we are able to measure the orientational diffusivities associated with the pure deformations of splay and twist. A previous study made in the ND phase of the same ternary system yielded a large deviation between the splay and twist diffusivities. The effect was then interpreted in terms of the anisotropy between their associated viscosities due to induced flows, or backflow. In the present work we observe a strong increase of the backflow as an effect of the added salt. In addition, we make auxiliary measurements of shear viscosity and magnetic instabilities, which help to characterize the effect of the salt in the orientational diffusivities as they are mixed quantities involving elastic constants and viscosity coefficients.

  20. Nematóides associados a plantas daninhas na Região de Jaboticabal, SP Nematodes associated with weeds in the Region of Jaboticabal

    Directory of Open Access Journals (Sweden)

    L.C.C.B. Ferraz

    1982-06-01

    Full Text Available Realizou-se, na região de Jaboticabal, SP, levantamento dos gêneros e espécies de nematóides fitoparasitos encontrados associados a plantas daninhas de ocorrência muito comum nas principais culturas locais . Para tal, utilizaram-se como materiais, amostras do solo da rizosfera e raízes das plantas daninhas. Foram identificadas 11 espécies de nematóides de interesse agrícola , pertencentes a sete diferentes gêneros, em 19 espécies daninhas.This paper deals with the associations between plant parasitic nematodes and weeds at the region of Jaboticabal, Sao Paulo State, Brazil . Nineteen weed species were included in the survey. Soil c ollected at the rhizosphere zone and roots of weeds constituted the samples for nematological study. Eleven nematode spe cies were identified on the weeds, belonging to seven different genera, namely Helicotylenchus, Macroposthonia, Meloidogyne, Paratrichodorus, Pratylenchus, Rotylenchulus, and Xiphinema.

  1. Fungos e nematóides fitopatogênicos associados ao cultivo de flores tropicais em São Luís - MA

    Directory of Open Access Journals (Sweden)

    Diogo Herison Silva Sardinha

    2012-06-01

    Full Text Available Considerando a importância do cultivo de flores tropicais no contexto nacional e internacional, buscou-se realizar um levantamento da ocorrência de fungos e nematóides associados às mesmas, em áreas de cultivos de flores tropicais em São Luís - MA. Foram realizadas visitas periódicas, em intervalos bimestrais, nos locais onde a principal atividade era o cultivo de flores tropicais, para o monitoramento e coleta de plantas ou partes de plantas das espécies: Heliconia spp., Alpinia purpurata e Etlingera elatior com sintomatologia típica de doenças. Realizou-se, ainda, o teste de patogenicidade dos principais fungos detectados como agentes causais das manchas foliares. Os resultados obtidos confirmaram a existência de fungos associados aos cultivos de flores tropicais em São Luís, com destaque para Curvularia eragrostides (78 %, Pestalotiopsis sp. (68 % e Colletotrichum gloeosporioides (47 % como agentes causais de manchas foliares em espécies da família Heliconiaceae, e Curvularia eragrostides (75 %, Pestalotiopsis sp. (37 % em espécies da família Zingiberaceae. Foram registrados oito gêneros de nematóides, tanto na família Heliconiaceae, quanto na Zingiberaceae, destacando-se o gênero Meloidogyne.

  2. Tris(β-diketonato) Ru(III) complexes as chiral dopants for nematic liquid crystals: the effect of the molecular structure on the helical twisting power.

    Science.gov (United States)

    Yoshida, Jun; Watanabe, Go; Kakizawa, Kaori; Kawabata, Yasuhiro; Yuge, Hidetaka

    2013-10-07

    Doping nematic liquid crystals with optically active compounds transforms them into chiral nematic phases with helical structures. In this phenomenon, the chirality of the dopant molecules is transferred or amplified to the bulk of the liquid crystals. Δ-[Ru(acac)3] (acac = acetylacetonato) is known to work as one of the dopants with a strong helical twisting power (HTP). In this study, we have systematically modified [Ru(acac)3] to clarify the correlation between the molecular structure and HTP; we have designed and synthesized five new Ru(III) complexes, [Ru(acac)2(acacC8)] (RuC8-1, acac = acetylacetonate, acacC8 = 3-(4'-octyloxy-phenylalkynyl)-pentane-2,4-dionato), [Ru(acac)(acacC8)2] (RuC8-2), [Ru(acacC8)3] (RuC8-3), [Ru(acacC0)3] (RuC0-3, acacC0 = 3-(phenylalkynyl)-pentane-2,4-dionato), and [Ru(acacC24)3] (RuC24-3, acacC24 = 3-(3',4',5'-tri(octyloxy)-phenylalkynyl)-pentane-2,4-dionato). All the complexes, except for RuC0-3, could be separated into Δ, Λ isomers by HPLC on a chiral column and were examined as chiral dopants for a nematic liquid crystal, N-(4-methoxybenzilidene)-4-butylaniline (MBBA). The Δ isomers of RuC8-1, RuC8-2, RuC8-3, and RuC24-3 induced a right-handed (P) helix and the magnitudes of the HTPs (/μm(-1)) were determined as follows: RuC8-1 (+60) RuC8-3 (+78) > RuC24-3 (+41). The HTPs of the ruthenium dopants were not simply proportional to their size. The highest HTP observed in biaxial RuC8-2 was attributed to the balance of the molecular helicity and high ordering in MBBA based on the surface chirality model.

  3. Control of bovine gastrointestinal nematode parasites using pellets of the nematode-trapping fungus Monacrosporium thaumasium Controle de nematóides parasitos gastrintestinais de bovinos com pellets do fungo predador de nematóides Monacrosporium thaumasium

    Directory of Open Access Journals (Sweden)

    Jackson Victor de Araújo

    2004-04-01

    Full Text Available The viability of a formulation of the fungus Monacrosporium thaumasium associated with ivermectin was evaluated for the biological control of bovine gastrointestinal nematode parasites. Four groups of five calves each were placed in pastures with a stocking rate of 1.6 animal/hectare. In group 1 (control, the calves did not receive any treatment. In group 2, each animal received 20g of pellets of M. thaumasium orally twice a week during a six-month period that began with the onset of the rainy season (October 23, 2000. In group 3, each animal received 20g of pellets of M. thaumasium orally twice a week during the same period as 2, as well as two strategic treatments with ivermectin (200 mcg/kg on May 10, 2001 and July 5, 2001. In group 4, the animals were treated with ivermectin alone as described for group 3. EPG counts for group 1 were significantly greater (PA viabilidade de uma formulação do fungo Monacrosporium thaumasium associada com ivermectina foi avaliada no controle biológico de nematóides parasitos gastrintestinais de bovinos. Quatro grupos de cinco bezerros foram colocados em pastagens com uma taxa de lotação de 1,6 animal/hectare. No grupo 1 (controle, os bezerros não receberam nenhum tratamento. No grupo 2, cada animal recebeu 20 g de pellets de M. thaumasium, via oral, duas vezes por semana e durante um período de seis meses que começou na estação chuvosa (23 de outubro, 2000. No grupo 3, cada animal recebeu 20g de pellets de M. thaumasium, via oral, duas vezes por semana e durante o mesmo período do grupo 2, assim como dois tratamentos estratégicos com ivermectina (200 mcg/kg em 10 de maio de 2001 e em 5 de julho de 2001. No grupo 4, os animais foram tratados somente com ivermectina como descrito no grupo 3. As contagens de OPG dos animais do grupo 1 foram significativamente maiores (P< 0,01 do que os animais dos grupos 2 e 3 e a diferença no final do experimento foi próxima de 100%. Os OPGs dos animais do grupo 4

  4. Deuteron and proton NMR study of D2, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases

    Science.gov (United States)

    Burnell, E. E.; Ahmed, Z.; Welch, C.; Mehl, G. H.; Dong, R. Y.

    2016-08-01

    The solutes dideuterium, 1,3,5-trichlorobenzene and p-dichlorobenzene (pdcb) are co-dissolved in a 61/39 wt% mixture of CBC9CB/5CB, a bimesogenic liquid crystal with two nematic phases. NMR spectra are collected for each solute. The local electric field gradient (FZZ) is obtained from the dideuterium spectrum. A double Maier-Saupe potential (MSMS) is used to rationalize the order parameters of pdcb. The liquid-crystal fields G1 and G2 are taken to be due to size and shape interactions and interactions between the solute molecular quadrupole and the mean FZZ of the medium. The FZZ 's obtained from D2 and G2 (from pdcb) are compared and discussed.

  5. Photo-alignment of low-molecular mass nematic liquid crystals on photochemically bifunctional chalcone-epoxy film by irradiation of a linearly polarized UV light

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Dong Hoon; Cha, Young Kwan [Kyunghee Univ., Yongin (Korea, Republic of)

    2002-04-01

    Photocrosslinkable chalcone-epoxy compound comprising 1,3-bis-(4-hydroxy-phenyl)-propenone was synthesized for fabricating the photo-alignment layer of liquid crystals. Chalcone group was introduced into the main chain unit of the epoxy oligomer. We observed a photodimerization behavior and an optical anisotropy of this material by irradiation of a linearly polarized UV(LP-UV) light. With a trace amount of cationic photo initiator (TRS-HFA), polymerization of epoxy groups was also conducted at the similar wavelength range used for photodimerization . Linearly polarized UV irradiation on the chalcone-epoxy films with cationic photoinitiator induced optical anisotropy of the film and the resultant film can be used for alignment layers for low molecular weight nematic liquid crystals.

  6. Orientational order of near D(3h) solutes in nematic liquid crystals. II. Description via Gay-Berne model with embedded quadrupoles.

    Science.gov (United States)

    Sokolovskii, R O; Burnell, E Elliott

    2009-04-21

    We perform Monte Carlo simulations of a mixture of soft ellipsoids with embedded quadrupoles as a model of various chloro- and methyl-substituted benzenes dissolved in nematic liquid crystals. We find that oblate Gay-Berne ellipsoids with multiple embedded quadrupoles qualitatively reproduce the trend in the order parameter asymmetry experimentally observed in NMR spectra. The trend is opposite to what is expected on the basis of the interaction of the solute's quadrupole with the solvent's average electric field gradient "felt" by dissolved dihydrogen molecules. We identify the specific minimum of the solute-solvent interaction energy landscape that may produce the unexpected sign of the order parameter asymmetry that is seen in the experiment and the simulation.

  7. Photo-alignment of low-molecular mass nematic liquid crystals on photochemically bifunctional chalcone-epoxy film by irradiation of a linearly polarized UV light

    CERN Document Server

    Choi, D H

    2002-01-01

    Photocrosslinkable chalcone-epoxy compound comprising 1,3-bis-(4-hydroxy-phenyl)-propenone was synthesized for fabricating the photo-alignment layer of liquid crystals. Chalcone group was introduced into the main chain unit of the epoxy oligomer. We observed a photodimerization behavior and an optical anisotropy of this material by irradiation of a linearly polarized UV(LP-UV) light. With a trace amount of cationic photo initiator (TRS-HFA), polymerization of epoxy groups was also conducted at the similar wavelength range used for photodimerization . Linearly polarized UV irradiation on the chalcone-epoxy films with cationic photoinitiator induced optical anisotropy of the film and the resultant film can be used for alignment layers for low molecular weight nematic liquid crystals.

  8. Formation of temperature dependable holographic memory using holographic polymer-dispersed liquid crystal.

    Science.gov (United States)

    Ogiwara, Akifumi; Watanabe, Minoru; Moriwaki, Retsu

    2013-04-01

    Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization controllable optical devices, such as the holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) that the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is discussed with two types of LC composites comprised of isotropic and LC diacrylate monomers. The holographic memory formed by the LC and LC diacrylate monomer performs precise reconstruction of the context information for ORGAs at high temperatures more than 150°C.

  9. Temperature dependence of anisotropic diffraction in holographic polymer-dispersed liquid crystal memory.

    Science.gov (United States)

    Ogiwara, Akifumi; Watanabe, Minoru; Moriwaki, Retsu

    2013-09-10

    Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization-controllable optical devices, such as a holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) where the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is investigated using four types of LC composites comprised of LCs and monomers having different physical properties such as T(ni) and anisotropic refractive indices. The holographic memory formed by the LC with low anisotropic refractive index and LC diacrylate monomer implements optical reconfiguration for ORGAs at a high temperature beyond T(ni) of LC.

  10. 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

    2010-01-01

    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. PMID:20876125

  11. Relato de nematóides da família Anisakidae em bacalhau comercializado em Ribeirão Preto, SP Report of nematodes of the Anisakidae family in codfish commercialized in Ribeirão Preto, SP

    Directory of Open Access Journals (Sweden)

    Sonia de Paula Toledo Prado

    2006-12-01

    Full Text Available A anisaquíase é uma parasitose gastrointestinal dos seres humanos, resultante da ingestão acidental de larvas infectantes de nematóides da família Anisakidae. Foram analisadas 11 amostras de bacalhau sendo que 64% estavam em desacordo com a legislação em vigor por conter nematóides da família Anisakidae e, portanto, impróprias para o consumo.Anisakiasis is a human gastrointestinal parasitosis that results from accidental ingestion of infective larvae belonging to the Anisakidae family. Eleven codfish samples were analyzed and 64% did not conform to the present legislation, because they contained nematode larvae from the Anisakidae family and were therefore unfit for consumption.

  12. Nematóide de galha em rabanete: suscetibilidade de cultivares e patogenicidade Root-knot nematode: cultivars reaction and damage to radish

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo Rossi

    2004-03-01

    Full Text Available Pesquisaram-se as reações de 11 cultivares de rabanete a Meloidogyne javanica e sua patogenicidade a uma dessas cultivares. No estudo de reações, os tratamentos/cultivares foram 'Comprido Branco', 'Crimson Gigante', 'Ponta Branca', 'Comprido Vermelho', 'Serrano', 'Gigante Wurzburgo', 'Saxa', 'Redondo Vermelho', 'Redondo Gigante', 'Cometo' e 'Akamaru Hatsuka'. Determinaram-se os índices de galhas (IG e de massas de ovos (IMO, o número de nematóides no sistema radicular (NSR e por grama de raiz (NGR e o fator de reprodução (FR 53 dias após a inoculação artificial com 2.000 ovos do parasito. Em outro experimento, avaliaram-se os efeitos de três densidades populacionais do nematóide [0, 500 (nível populacional baixo e 10.000 (nível populacional alto ovos/planta] sobre as massas frescas e secas de túberas e de parte aérea da cultivar 'Redondo Gigante', 39 dias após a inoculação. Os resultados mostraram que todas as cultivares permitiram a reprodução de M. javanica, sendo portanto consideradas suscetíveis. Valores de IG e IMO foram maiores ou iguais a 2,5 e os de FR, maiores do que 8,0 para todas as cultivares estudadas. O parasito causou diminuição significativa nas massas frescas e secas de túberas e de partes aéreas nos dois níveis populacionais estudados comparados com o controle não inoculado. As médias dos tratamentos contendo níveis populacionais baixo e alto do nematóide também diferiram estatisticamente entre si, comprovando-se, assim, a sua ação patogênica sobre a cultivar avaliada.Experiments were conducted under greenhouse conditions to determine the reaction of eleven radish (Raphanus sativus cultivars to Meloidogyne javanica and the pathogenicity of this nematode to a previously selected cultivar. The cultivars tested were 'Comprido Branco', 'Crimson Gigante', 'Ponta Branca', 'Comprido Vermelho', 'Serrano', 'Gigante Wurzburgo', 'Saxa', 'Redondo Vermelho', 'Redondo Gigante', 'Cometo' and 'Akamaru

  13. Diagnóstico do controle e perfil de sensibilidade de nematódeos de ovinos ao albendazol e ao levamisol no norte de Minas Gerais

    Directory of Open Access Journals (Sweden)

    Eduardo R. Duarte

    2012-02-01

    Full Text Available A resistência anti-helmíntica é um dos principais entraves para o controle da verminose em ruminantes e a presença de nematódeos multiresistentes pode inviabilizar a atividade em uma determinada área. Neste trabalho o objetivo foi avaliar a eficácia anti-helmíntica do levamisol e do albendazol em rebanhos ovinos do norte de Minas Gerais. O teste foi realizado em dez propriedades, onde foram selecionados três grupos de 12 borregos cada. Dois desses grupos foram tratados respectivamente com levamisol (5 mg/kg pc ou albendazol (10 mg/kg pc e o terceiro grupo não foi tratado. Fezes foram coletadas antes do tratamento e no sétimo dia após, para a realização do teste de redução de ovos por grama de fezes. Foi realizado o cultivo de larvas provenientes dos grupos avaliados para a identificação dos principais gêneros de nematódeos gastrintestinais antes e após os tratamentos. Para todos os rebanhos avaliados no norte de Minas Gerais, o levamisol apresentou eficácia anti-helmíntica elevada, variando de 90% a 100%. Apenas para um rebanho o albendazol seria efetivo e para seis propriedades as eficácias dessa droga foram inferiores a 80%, sendo considerada insuficientemente ativa. Após as coproculturas foram identificadas, em maior ocorrência, larvas dos gêneros Haemonchus e Trichostrongylus. O gênero Haemonchus foi o mais prevalente mesmo após o tratamento dos ovinos. Ressalta-se neste estudo a importância do teste de eficácia in vivo para a escolha das bases anti-helmínticas nas propriedades, pois foi observado que o perfil de susceptibilidade variou entre os diferentes rebanhos.

  14. Temperature measurement

    Science.gov (United States)

    ... an oral temperature. Other factors to take into account are: In general, rectal temperatures are considered to ... urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows ...

  15. Optical-to-optical interface device. [consisting of two transparent electrodes on glass substrates that enclose thin film photoconductor and thin layer of nematic liquid crystal

    Science.gov (United States)

    Jacobson, A. D.

    1973-01-01

    Studies were conducted on the performance of a photoactivated dc liquid crystal light valve. The dc light valve is a thin film device that consists of two transparent electrodes, deposited on glass substrates, that enclose a thin film photoconductor (cadmium sulfide) and a thin layer of a nematic liquid crystal that operates in the dynamic scattering mode. The work was directed toward application of the light valve to high resolution non-coherent light to coherent light image conversion. The goal of these studies was to improve the performance and quality of the already existing dc light valve device and to evaluate quantitatively the properties and performance of the device as they relate to the coherent optical data processing application. As a result of these efforts, device sensitivity was improved by a factor of ten, device resolution was improved by a factor of three, device lifetime was improved by two-orders of magnitude, undesirable secondary liquid crystal scattering effects were eliminated, the scattering characteristics of the liquid crystal were thoroughly documented, the cosmetic quality of the devices was dramatically improved, and the performance of the device was fully documented.

  16. Direct visualization of phase separation between superconducting and nematic domains in Co-doped CaFe2As2 close to a first-order phase transition

    Science.gov (United States)

    Fente, Antón; Correa-Orellana, Alexandre; Böhmer, Anna E.; Kreyssig, Andreas; Ran, S.; Bud'ko, Sergey L.; Canfield, Paul C.; Mompean, Federico J.; García-Hernández, Mar; Munuera, Carmen; Guillamón, Isabel; Suderow, Hermann

    2018-01-01

    We show that biaxial strain induces alternating tetragonal superconducting and orthorhombic nematic domains in Co-substituted CaFe2As2 . We use atomic force, magnetic force, and scanning tunneling microscopy to identify the domains and characterize their properties, finding in particular that tetragonal superconducting domains are very elongated, more than several tens of micrometers long and about 30 nm wide; have the same Tc as unstrained samples; and hold vortices in a magnetic field. Thus, biaxial strain produces a phase-separated state, where each phase is equivalent to what is found on either side of the first-order phase transition between antiferromagnetic orthorhombic and superconducting tetragonal phases found in unstrained samples when changing Co concentration. Having such alternating superconducting domains separated by normal conducting domains with sizes of the order of the coherence length opens opportunities to build Josephson junction networks or vortex pinning arrays and suggests that first-order quantum phase transitions lead to nanometric-size phase separation under the influence of strain.

  17. Soluções de alho (Allium sativum L. no controle de nematódeos gastrintestinais em bovinos jovens da raça Holandesa

    Directory of Open Access Journals (Sweden)

    C.L.C. Parra

    2014-09-01

    Full Text Available Para avaliar o efeito da atividade anti-helmíntica do alho suplementado, foram utilizadas 24 bezerras e novilhas da raça Holandesa, naturalmente infectadas. As soluções foram preparadas triturando-se o alho, (50%, mais água ou álcool 92º, (50%, administrando-se oralmente aos animais. Os tratamentos (T foram constituídos pelo grupo controle negativo (T1; extrato alcoólico de alho a 60g e 120g/100Kg de peso vivo (T2 e (T3; extrato aquoso de alho a 60 e 120g/100kg de peso vivo (T4 e (T5; e o grupo controle positivo com albendazol a 10% (T6. Os tratamentos fitoterápicos foram repetidos a cada 14 dias, caso a infecção fosse superior a 400 ovos por grama de fezes (OPG. A técnica de coprocultura quantitativa e qualitativa foi empregada para avaliar a eficácia anti-helmíntica dos tratamentos. Foram observadas diferenças entre os grupos controle e tratados para OPG e na porcentagem relativa de larvas infectantes e desenvolvimento larval. O uso das soluções de alho demonstrou controle parcial de nematódeos gastrintestinais.

  18. Single-layer dual-phase nematic elastomer films with bending, accordion-folding, curling and buckling motions.

    Science.gov (United States)

    Liu, Li; Geng, Bin; Sayed, Sayed Mir; Lin, Bao-Ping; Keller, Patrick; Zhang, Xue-Qin; Sun, Ying; Yang, Hong

    2017-02-02

    In this communication, we describe a two-stage temperature-varied photopatterning protocol to synthesize a series of single-layer dual-phase liquid crystalline elastomer films, which have the capabilities to perform versatile three-dimensional motions, such as bending, accordion-folding, wrinkling, curling, and buckling, under thermal stimulus.

  19. Electrode Placement for Active Tuning of Silicon-on-Insulator (SOI) Ring Resonator Structure Clad in Nematic Liquid Crystals

    Science.gov (United States)

    2014-08-01

    1.573, and its threshold voltage is Vt = 1.61V, and saturation voltage Vsat = 2.51 V. LIXON’s clearing point temperature is 123 °C. Figure 4 depicts...applied potential. The field for most of the sample is 1.68 V/μm, which is above the threshold voltage of LIXON™. Saturation voltage, Vsat = 2.51 V

  20. Observation of a temperature dependent asymmetry in the domain structure of a Pd-doped FeRh epilayer

    Science.gov (United States)

    Kinane, C. J.; Loving, M.; de Vries, M. A.; Fan, R.; Charlton, T. R.; Claydon, J. S.; Arena, D. A.; Maccherozzi, F.; Dhesi, S. S.; Heiman, D.; Marrows, C. H.; Lewis, L. H.; Langridge, Sean

    2014-11-01

    Using x-ray photoelectron emission microscopy we have observed the coexistence of ferromagnetic and antiferromagnetic phases in a (3 at%)Pd-doped FeRh epilayer. By quantitatively analyzing the resultant images we observe that as the epilayer transforms there is a change in magnetic domain symmetry from predominantly twofold at lower temperatures through to an equally weighted combination of both four and twofold symmetries at higher temperature. It is postulated that the lowered symmetry Ising-like nematic phase resides at the near-surface of the epilayer. This behavior is different to that of undoped FeRh suggesting that the variation in symmetry is driven by the competing structural and electronic interactions in the nanoscale FeRh film coupled with the effect of the chemical doping disorder.

  1. Infecções naturais em cervídeos (Mammalia: Cervidae procedentes dos Estados do Mato Grosso do Sul e São Paulo, por nematódeos Trichostrongyloidea Cram, 1927

    Directory of Open Access Journals (Sweden)

    Adjair Antonio do Nascimento

    2000-01-01

    Full Text Available No período compreendido entre 1985 e 1996 foram necropsiados, para pesquisa de helmintos, 42 cervídeos, sendo sete Mazama americana, 16 M. gouazoubira, 13 Ozotoceros bezoarticus e seis Blastocerus dichotomus. Desses animais, foram colhidos 14.426 nematódeos Trichostrongyloidea, sendo 13.281 (92,06% parasitos de abomaso e 1.145 (7,94%, de intestino delgado. Nesses órgãos, foram identificadas seis espécies de nematódeos: Haemonchus contortus, H. similis, Trichostrongylus axei, T. colubriformis, Cooperia punctata e C. pectinata. Todos os animais apresentaram infecções helmínticas por uma ou mais espécies, ocorrendo grande variação na intensidade de infecção (1 a 4.345 nematódeos. Ainda com relação à intensidade de infecção, os dados expressavam valores menores que 100 parasitos em 25 (59,52% animais. Os valores mais altos de intensidade média das infecções foram observados em M. gouazoubira (596,37 helmintos e em O. bezoarticus (331, e os menores, em M. americana (17,57 e B. dichotomus (75,5. Os dados mais expressivos de intensidade de infecção, abundância e prevalência foram observados para Haemonchus (larvas de 4º estágio, H. contortus, H. similis e T. axei. O gênero Haemonchus foi constatado em 35 animais, com prevalência de 83,33%; apresentou carga parasitária de 11.616 exemplares, representando 80,52% dos nematódeos verificados, sendo a maioria (8.903 constituída por formas imaturas. Por outro lado, H. similis foi a espécie predominante nas infecções e, portanto, a que apresentou maiores valores de abundância. Verificou-se o gênero Trichostrongylus em 24 (57,14% animais, com carga parasitária de 2.444 exemplares, sendo 1.665 espécimes de T. axei, que representou 11,54% da carga parasitária obtida. As seis espécies de vermes identificadas nos cervídeos são comuns aos ruminantes domésticos nos Estados de São Paulo e Mato Grosso do Sul e dessa maneira não se observou nenhuma espécie de

  2. Atividade predatória, crescimento radial e esporulação de fungos predadores de nematóides Monacrosporium spp, submetidos à criopreservação

    OpenAIRE

    Campos, Artur Kanadani; Mota, Marcelo de Andrade; Araújo, Jackson Victor de; Cecon, Paulo Roberto

    2004-01-01

    Testes in vitro foram realizados para avaliar o efeito da criopreservação em nitrogênio líquido com e sem adição de crioprotetores (DMSO ou glicerol), na atividade predatória sobre larvas infectantes de Cooperia sp e Haemonchus sp, crescimento radial e produção de conídios de dois isolados de fungos predadores de nematóides (Monacrosporium sinense e Monacrosporium appendiculatum). A capacidade predatória dos fungos sobre larvas infectantes de Cooperia sp e Haemonchus sp dos fungos previamente...

  3. Substrates for storing entomopathogenic nematodes (Rhabditida: Steinernematidae, Heterorhabditidae Substratos para armazenar nematóides entomopatogênicos (Rhabditida: Steinernematidae, Heterorhabditidae

    Directory of Open Access Journals (Sweden)

    Vanessa Andaló

    2010-01-01

    Full Text Available The survival of entomopathogenic nematodes under laboratory conditions is low. With the aim of evaluating substrates to extend the survival of entomopathogenic nematodes, suspensions of Heterorhabditis sp. JPM4 and Steinernema carpocapsae All (3,000 IJ mL-1 were added to dirt, fine sand, coarse sand, foam, expanded clay, phenolic foam, agar, corn starch, Plantmax®, and water. The substrates were placed on Petri dishes (5 cm and kept at 16 ± 1°C. Survival evaluations were made after 30, 60, 90, 120, 150, and 180 days, with three replicates. After 180 d, a greater percentage of S. carpocapsae infective juveniles (IJs were still alive in the foam treatment (57.5% as compared to other treatments, while expanded clay (28.4%, Plantmax® (9.3% and phenolic foam (11% were not effective in maintaining the survival rate. Foam (55.6%, coarse sand (53.1%, and fine sand (50.6% provided greater Heterorhabditis sp. JPM4 IJ survival at 180 days. Agar (19.3%, phenolic foam (11.6%, and Plantmax® (10.7% had lower survival indices than the control (29.7%. The use of an appropriate substrate can provide greater IJ survival.Os nematóides entomopatogênicos apresentam baixa viabilidade em condições de laboratório. Com o objetivo de avaliar substratos para prolongar a sobrevivência dos nematóides entomopatogênicos, suspensões de Heterorhabditis sp. JPM4 e Steinernema carpocapsae All (3.000 JI mL-1 foram adicionadas aos substratos solo, areia fina, areia grossa, espuma, argila expandida, esponja fenólica, ágar, amido de milho, Plantmax® e água. Estes foram colocados em placas de Petri (5 cm e mantidos a 16 ± 1°C. As avaliações foram feitas após 30, 60, 90, 120, 150 e 180 dias, com três repetições para cada dia. Após 180 dias, para S. carpocapsae All o substrato espuma (57,5% manteve maior porcentagem de juvenis infectantes (JI vivos; argila expandida (28,4%, Plantmax® (9,3% e esponja fenólica (11% não foram eficientes para manutenção da

  4. Evaluación in vitro de hongos nematófagos en zonas arroceras de Costa Rica contra el nematodo agallador Meloidogyne javanica

    Directory of Open Access Journals (Sweden)

    Walter Peraza Padilla

    2014-12-01

    Full Text Available Se evaluó el parasitismo in vitro de 14 aislamientos de hongos nematófagos (6 Trichoderma sp., 4 Paecilomyces sp., 2 Fusarium oxysporum, y 2 Monacrosporium sp. contra juveniles y huevos del nematodo agallador Meloidogyne javanica. Los hongos, de 3 regiones productoras de arroz en Costa Rica, (Pacífico Central, Huetar Atlántica y Chorotega, se aislaron mediante el método de espolvoreado en placas, durante abril del 2008 a agosto de 2009. Se utilizó un diseño completamente al azar con 10 repeticiones por hongo, en agar-agua (AA. Se inoculó una suspensión de 1 a 1,5x10 6 conidios (ufc.ml -1 por plato Petri, y al cuarto día se depositó en 0,5 ml una suspensión de 150 juveniles y 100 huevos de M. javanica previamente desinfectados, a temperatura ambiente (23-26°C y con luz natural. Transcurridas 96 h se contó en cada plato el número de nematodos vivos, muertos ó parasi- tados y de huevos parasitados o no parasitados. Se realizó un análisis de regresión logística (RL para las variables evaluadas, el cual mostró diferencias significativas (p<0,0001 en el desempeño de los hongos evaluados, presentando rangos de entre 10% a 56% en nematodos muertos, de 13% a 79% en nematodos parasitados y de 1% a 96% en huevos parasitados. En general, los hongos del género Trichoderma (Tri1, Tri2, Tri3 y Tri4 fueron los más eficientes en el parasitismo sobre juveniles y huevos de M. javanica.

  5. A Novel High-Sensitivity, Low-Power, Liquid Crystal Temperature Sensor

    Directory of Open Access Journals (Sweden)

    José Francisco Algorri

    2014-04-01

    Full Text Available A novel temperature sensor based on nematic liquid crystal permittivity as a sensing magnitude, is presented. This sensor consists of a specific micrometric structure that gives considerable advantages from other previous related liquid crystal (LC sensors. The analytical study reveals that permittivity change with temperature is introduced in a hyperbolic cosine function, increasing the sensitivity term considerably. The experimental data has been obtained for ranges from −6 °C to 100 °C. Despite this, following the LC datasheet, theoretical ranges from −40 °C to 109 °C could be achieved. These results have revealed maximum sensitivities of 33 mVrms/°C for certain temperature ranges; three times more than of most silicon temperature sensors. As it was predicted by the analytical study, the micrometric size of the proposed structure produces a high output voltage. Moreover the voltage’s sensitivity to temperature response can be controlled by the applied voltage. This response allows temperature measurements to be carried out without any amplification or conditioning circuitry, with very low power consumption.

  6. A novel high-sensitivity, low-power, liquid crystal temperature sensor.

    Science.gov (United States)

    Algorri, José Francisco; Urruchi, Virginia; Bennis, Noureddine; Sánchez-Pena, José Manuel

    2014-04-09

    A novel temperature sensor based on nematic liquid crystal permittivity as a sensing magnitude, is presented. This sensor consists of a specific micrometric structure that gives considerable advantages from other previous related liquid crystal (LC) sensors. The analytical study reveals that permittivity change with temperature is introduced in a hyperbolic cosine function, increasing the sensitivity term considerably. The experimental data has been obtained for ranges from -6 °C to 100 °C. Despite this, following the LC datasheet, theoretical ranges from -40 °C to 109 °C could be achieved. These results have revealed maximum sensitivities of 33 mVrms/°C for certain temperature ranges; three times more than of most silicon temperature sensors. As it was predicted by the analytical study, the micrometric size of the proposed structure produces a high output voltage. Moreover the voltage's sensitivity to temperature response can be controlled by the applied voltage. This response allows temperature measurements to be carried out without any amplification or conditioning circuitry, with very low power consumption.

  7. A Novel High-Sensitivity, Low-Power, Liquid Crystal Temperature Sensor

    Science.gov (United States)

    Algorri, José Francisco; Urruchi, Virginia; Bennis, Noureddine; Sánchez-Pena, José Manuel

    2014-01-01

    A novel temperature sensor based on nematic liquid crystal permittivity as a sensing magnitude, is presented. This sensor consists of a specific micrometric structure that gives considerable advantages from other previous related liquid crystal (LC) sensors. The analytical study reveals that permittivity change with temperature is introduced in a hyperbolic cosine function, increasing the sensitivity term considerably. The experimental data has been obtained for ranges from −6 °C to 100 °C. Despite this, following the LC datasheet, theoretical ranges from −40 °C to 109 °C could be achieved. These results have revealed maximum sensitivities of 33 mVrms/°C for certain temperature ranges; three times more than of most silicon temperature sensors. As it was predicted by the analytical study, the micrometric size of the proposed structure produces a high output voltage. Moreover the voltage's sensitivity to temperature response can be controlled by the applied voltage. This response allows temperature measurements to be carried out without any amplification or conditioning circuitry, with very low power consumption. PMID:24721771

  8. First report of five nematode species in Phasianus colchicus Linnaeus (Aves, Galliformes, Phasianidae in Brazil Primeiro registro de cinco espécies de nematóides em Phasianus colchicus Linnaeus (Aves, Galliformes, Phasianidae no Brasil

    Directory of Open Access Journals (Sweden)

    Roberto Magalhães Pinto

    2004-12-01

    Full Text Available This paper deals with the first report of the nematodes Dispharynx nasuta (Rudolphi, 1819 Stiles & Hassall, 1920, Gongylonema ingluvicola Ransom, 1904, Oxyspirura mansoni (Cobbold, 1879 Ransom, 1904, Subulura brumpti (Lopez-Neyra, 1922 Cram, 1923 and Tetrameres fissipina (Diesing, 1860 Travassos, 1914, parasitizing the ring-necked pheasant, Phasianus colchicus Linnaeus, 1758 in Brazil. Morphological data on the parasites as well as on the prevalence, mean intensity, mean abundance and range of intensity of the nematodes in the infected birds are provided.O presente trabalho diz respeito à primeira referência dos nematóides Dispharynx nasuta (Rudolphi, 1819 Stiles & Hassall, 1920, Gongylonema ingluvicola Ransom, 1904, Oxyspirura mansoni (Cobbold, 1879 Ransom, 1904, Subulura brumpti (Lopez-Neyra, 1922 Cram, 1923 e Tetrameres fissipina (Diesing, 1860 Travassos, 1914, parasitando o faisão-coleira, Phasianus colchicus Linnaeus, 1758 no Brasil. São fornecidos dados morfológicos sobre os parasitos, bem como sobre a prevalência, intensidade média, abundância média e amplitude de variação da intensidade de infecção dos nematóides nas aves parasitadas.

  9. Atividade ovicida de dois fármacos em caprinos naturalmente parasitados por nematódeos gastrintestinais, RS, Brasil Ovicidal activity of two medicaments against goat gastrointestinal nematode in RS, Brazil

    Directory of Open Access Journals (Sweden)

    Mary Jane Tweedie de Mattos

    2000-10-01

    Full Text Available A eficácia comparativa entre levamisole em duas doses diferentes e closantel foi avaliada sobre ovos de nematódeos gastrintestinais de caprinos naturalmente parasitados. Observou-se que a redução de ovos de nematódeos gastrintestinais foi de 93,23%, 91,25% e 70,42% nos grupos medicados com levamisole 8mg/kg, levamisole 11mg/kg e closantel 10mg/kg, respectivamente. O teste de desenvolvimento embrionário revelou que levamisole, nas duas doses, foi eficaz sobre Haemonchus spp., Ostertagia spp., Cooperia spp. e Oesophagostomum spp. O closantel não foi eficaz para Cooperia spp e Oesophagostomum spp.The efficacy of the anthelmintics levamisole in two different doses (8mg/kg and 11mg/kg and closantel (10mg/kg were compared against gastrointestinal nematodes in naturally infected goats. The reduction on the faecal egg count was 93.23% in the group treated with levamisole at the dose of 8mg/kg, 91.25% in the group treated with the dose of 11mg/kg and 70.42% in the group treated with closantel. The anthelmintic levamisole was effective against Haemonchus spp., Ostertagia spp., Cooperia spp and Oesophagostomum spp. However, closantel wasn't effective against Cooperia spp and Oesophagostomum spp.

  10. Occurrences of Eimeria spp. and gastrointestinal nematodes in dairy calves in southern Minas Gerais, Brazil Ocorrência de Eimeria spp. e nematódeos gastrintestinais em bezerros no sul de Minas Gerais, Brasil

    Directory of Open Access Journals (Sweden)

    Fábio Raphael Pascoti Bruhn

    2012-06-01

    Full Text Available The aim of this cross-sectional observational study was to determine the frequency and factors associated with infection by Eimeria spp. and gastrointestinal nematodes in 356 calves on 20 dairy farms located in southern Minas Gerais, Brazil. Ten species of Eimeria spp. were identified, of which E. bovis (37.6% and E. zuernii (17.9% were the most frequent. From fecal cultures, four genera of gastrointestinal nematodes were recovered, of which Cooperia spp. (74.6% and Haemonchus (19.4% were the most frequent. Variables relating to higher levels of technology used on dairy farms showed a significant association (p O objetivo deste estudo foi determinar a frequência e os fatores associados à infecção por Eimeria spp. e nematódeos gastrintestinais, em 356 bezerras provenientes de 20 rebanhos leiteiros, localizados no sul de Minas Gerais, Brasil. Foram identificadas dez espécies de Eimeria spp., sendo E. bovis (37,6% e E. zuernii (17,9% as mais frequentes. Nas coproculturas, foram recuperados quatro gêneros de nematódeos gastrintestinais, sendo os mais frequentes Cooperia spp. (74,6% e Haemonchus spp. (19,4%.Variáveis relacionadas a um maior nível de tecnificação das propriedades leiteiras apresentaram associação significativa (p < 0,05, com maiores contagens de OoPG e OPG, e são discutidas neste estudo.

  11. New Lyotropic Mixtures with Non-Chiral N-Acylamino Acid Surfactants Presenting the Biaxial Nematic Phase Investigated by Laser Conoscopy, Polarized Optical Microscopy and X-ray Diffraction

    Directory of Open Access Journals (Sweden)

    Erol Akpinar

    2014-05-01

    Full Text Available Amino acid-based surfactants were used as the main surfactants to prepare new lyotropic mixtures presenting three nematic phases. One of them is biaxial (NB, and the two others are uniaxial, discotic (ND and calamitic (NC. These surfactants were the non-chiral molecules, potassium N-dodecanoyl-DL-alaninate (DL-KDDA, potassium N-dodecanoyl-DL-serinate (DL-KDDS, disodium N-dodecanoyl-DL-aspartate (DL-NaDDAs and potassium N-dodecanoyl-glycinate (KDDGly. Measurements of the optical birefringences and X-ray diffraction analysis were used to characterize the nematic phases and phase transitions. Mixtures with DL-KDDS exhibited the largest biaxial phase domain (~9 °C with respect to the other mixtures in this study. The results obtained with the KDDGly mixture showed that the existence of hydrogen bonding between the head groups of the surfactant molecules seems to hinder the orientation of the micelles under the action of an external magnetic field.

  12. Sensing temperature.

    Science.gov (United States)

    Sengupta, Piali; Garrity, Paul

    2013-04-22

    Temperature is an omnipresent physical variable reflecting the rotational, vibrational and translational motion of matter, what Richard Feynman called the "jiggling" of atoms. Temperature varies across space and time, and this variation has dramatic effects on the physiology of living cells. It changes the rate and nature of chemical reactions, and it alters the configuration of the atoms that make up nucleic acids, proteins, lipids and other biomolecules, significantly affecting their activity. While life may have started in a "warm little pond", as Charles Darwin mused, the organisms that surround us today have only made it this far by devising sophisticated systems for sensing and responding to variations in temperature, and by using these systems in ways that allow them to persist and thrive in the face of thermal fluctuation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Rheo-NMR studies of the behavior of a nematic liquid crystal in a low-shear-rate regime: the transition from director alignment to reorientation.

    Science.gov (United States)

    Lepper, C; Edwards, P J B; Schuster, E; Brown, J R; Dykstra, R; Callaghan, P T; Williams, M A K

    2010-10-01

    Deuterium NMR spectroscopy has been used to study the director dynamics of the nematic liquid-crystal system cetyl trimethylammonium bromide/D2O under the action of applied viscous torques. Shear forces were applied using a custom-built Couette cell that was introduced into an NMR superconducting magnet, so that its rotational axis was parallel to the magnetic field direction, along which the liquid-crystal director originally aligned. Subsequently, the inner cylinder of the cell was rotated continuously at different rates using a stepper motor. The resulting time evolution and ultimate steady-state orientation of the director, governed by the competition between the applied viscous torque with elastic and magnetic terms, was measured via observed changes in the deuterium spectrum. Using a simple gearbox allowed unprecedented access to a low-shear-rate regime in which, above a threshold shear rate, the director of part of the sample was observed to reorient, while the remaining part still aligned with the magnetic field. Subsequent increases in the applied rotational rate were found to increase the relative proportion of the orienting fraction. Spatially resolved NMR spectra showed that the orienting and field-aligned fractions formed separated bands across the gap of the Couette cell, with director reorientation being initiated at the moving inner wall. The behavior was found to be consistent with the often ignored variation in velocity gradient manifest across the gap of a cylindrical cell, so that as the angular frequency of the inner cylinder was increased the radial location of the critical shear rate required for reorientation traversed the gap. Once the applied rotational rate was sufficient to reorient the director of the entire sample, the dependence of the exhibited steady-state orientation on the average applied shear rate was measured. These results could be fitted to an analytical solution of the force-balance equation, made tractable by the assumption

  14. Low temperature (

    NARCIS (Netherlands)

    Rath, J.K.; de Jong, M.; Schropp, R.E.I.

    2008-01-01

    Amorphous silicon films have been made by HWCVD at a very low substrate temperature of ≤ 100 °C (in a dynamic substrate heating mode) without artificial substrate cooling, through a substantial increase of the filament–substrate distance ( 80 mm) and using one straight tantalum filament. The

  15. Reação de clones de bananeira(Musa spp. ao nematóide Meloidogyne incognita (Kofoid & White, 1919 Chitwood, 1949, Raça 2

    Directory of Open Access Journals (Sweden)

    Vilas Boas Lenisa Cezar

    2002-01-01

    Full Text Available O trabalho teve por objetivo estudar em condições de casa de vegetação a reação de clones de bananeira, em relação a Meloidogyne incognita raça 2. Mudas micropropagadas foram inoculadas, utilizando-se da suspensão de M. incognita, formada de ovos e de juvenis do segundo estádio, totalizando 20.000 / muda. A inoculação foi feita após cinco dias do transplante das mudas para sacos de plástico preto de cinco litros de capacidade, contendo solo, areia e esterco, na proporção 3:1:1, esterilizado em caldeira a 100ºC, por duas horas. O delineamento experimental foi o inteiramente casualizado, com quatro repetições. Após 120 dias, os clones foram avaliados. Determinou-se o número de ovos e juvenis contido no sistema radicular, sendo utilizado o clone CPA-34, a cultivar Grande Naine, como padrão de suscetibilidade. Amostras de 200 cm³ de solo foram coletadas para a determinação do número de nematóides no solo. De acordo com os fatores de reprodução (Pf/Pi, verificou-se que o clone CPA-34 apresentou-se suscetível ao nematóide, como era esperado, com o maior fator de reprodução, seguido do clone CPA-49, da cultivar Maçã, com índice superior a um. Os demais clones testados apresentaram fator de reprodução menor que um, indicando certa resistência ao nematóide M. incognita raça 2. Entretanto, nas análises estatísticas, foram verificadas diferenças significativas entre o clone-padrão CPA-34, quando comparado com os clones CPA-58 e CPA-54. Para os resultados de peso de raízes e peso da parte aérea, a diferença foi significativa (1% para todos os clones testados, apresentando os maiores valores para os clones não inoculados.

  16. Formulation of a room temperature ferroelectric liquid crystal mixture with sub-millisecond switching time

    Science.gov (United States)

    Debnath, A.; Sinha, D.; Mandal, P. K.; Dabrowski, R.

    2015-06-01

    Ferroelectric liquid crystal (FLC) based display devices show faster response compared to nematic LC based devices. Since pure FLC compounds are high temperature LCs and do not possess optimum parameters necessary for display devices, a room temperature FLC mixture has been formulated, first time by any Indian group. The mixture is prepared by doping an appropriate chiral compound in a four-component LC based achiral host mixture. Resulting mixture was characterized using optical polarizing microscopy, frequency domain dielectric spectroscopy and electro-optic methods. It shows very wide range ferroelectric SmC* phase followed by paraelectric SmA* phase (Crbook shelf geometry alignment in display devices. Dielectric spectroscopy study reveals Goldstone (in kHz region) and soft mode (in hundred kHz region) relaxations in SmC* and SmA* phases respectively. The mixture possesses moderate tilt angle (34.5° - 13°), low viscosity (0.9 - 0.05 N.s.m-2) and moderately high spontaneous polarization (112 - 36 nC.cm-2) which decrease with temperature. These result in very fast switching, slowest response time being 475 µs at ambient temperature.

  17. Robusta coffee rootstocks resistants to Meloidogyne paranaensis and M. incognita races 1 and 2/ Porta-enxertos de café robusta resistentes aos nematóides Meloidogyne paranaensis e M. incognita raças 1 e 21

    Directory of Open Access Journals (Sweden)

    Inês Cristina de Batista Fonseca

    2006-06-01

    Full Text Available The Meloidogyne paranaensis and M. incognita races 1 and 2 are the most pathogenic root knot nematodes of coffee crop in Paraná state, Brazil. The use of susceptible arabica cultivars on resistant rootstock robusta cultivars, especially cultivar Apoatã IAC-2258 of Coffea canephora var. robusta, has been successful, but there are segregations to susceptible ones. The aim of this research was to identify C. canephora var. robusta coffee trees with simultaneous resistance to M. paranaensis, M. incognita races 1 and 2. Twenty-four C. canephora genotypes were evaluated using Taylor´s evaluation method, conducted in randomized blocks design with three replications and 30 plants per plot. The cultivar Mundo Novo IAC 376-4 was used as susceptible standard. The variables evaluated were nematodes incidence and root volume. The resistance levels founded among plants were resistant, moderately resistant and susceptible. Six genotypes of C. canephora var. robusta with simultaneous resistance, probably in homozygous, to M. paranaensis, M. incognita race 1 and M. incognita race 2 were found, all with good root volume. The mother plants of these six better treatments will be vegetatively propagated and used to begin seed production of rootstock cultivars.No Estado do Paraná, os nematóides mais danosos para o café são Meloidogyne paranaensis e M. incognita raças 1 e 2. A enxertia de cultivares suscetíveis de Coffea arabica sobre C. canephora resistentes tem sido bem sucedida, especialmente com o porta-enxerto Apoatã IAC-2258, porém existe segregação para a resistência. O objetivo deste trabalho foi identificar cafeeiros de C. canephora var. robusta com resistência simultânea aos nematóides M. paranaensis e M. incognita raças 1 e 2. Avaliaramse 24 genótipos de C. canephora na metodologia de Taylor, no delineamento em blocos ao acaso com três repetições e parcelas de 30 plantas. Como testemunha suscetível utilizou-se a cultivar Mundo Novo

  18. Metabolismo oxidativo de neutrófilos em ovelhas naturalmente infectadas por nematódeos gastrintestinais e correlação entre nível sérico de cortisol e carga parasitária

    OpenAIRE

    P.C. Ciarlini; Ciarlini,L.D.R.P.; Alencar, N.X.; Hohayagawa, A. [UNESP; Rodrigues, C.F.C.

    2002-01-01

    Estudaram-se as relações entre o metabolismo oxidativo dos neutrófilos, os níveis séricos de cortisol e a carga parasitária estimada pela contagem de ovos por grama de fezes (OPG) no final da gestação, durante a lactação e após o desmame de ovelhas naturalmente infectadas por nematódeos gastrintestinais. Utilizaram-se 22 ovelhas da raça Suffolk, homogêneas quanto à idade (três a quatro anos), número de parições (terceira) e época de parição. O cortisol sérico foi determinado por radioimunoens...

  19. Efeito da fermentação aeróbia na viabilidade de ovos de nematódeos trichostrongilídeos Viability of trichostrongylid nematode eggs after aerobic fermentation

    Directory of Open Access Journals (Sweden)

    Terezinha Padilha Charles

    1996-04-01

    Full Text Available O efeito da fermentação aeróbia na viabilidade de avos de nematódeos trichostrongilídeos foi avaliado em um sistema em que fezes de ovinos contendo ovos de Haemonchus contortus foram imersas em um tanque de fermentação dotado de aerador mecânico intermitente e fezes de bovinos com ovos de nematódeos trichostrongilídeos havendo predomínio de Cooperia sp. foram deixadas fermentar em depósitos a campo. Amostras dos ovos submetidas aos dois processos de fermentação foram colhidas em diferentes intervalos e cultivadas para extração das larvas infectantes. Ambos os processos de fermentação reduziram o número de ovos viáveis. Esterilização superior a 99% dos ovos foi obtida com 14 dias pós-exposição nos dois processos.The viability of gastrointestinal nematode eggs after aerobicfermentation was evaluated in two experiments. In the first, feces of sheep containing Haemonchus contorts eggs were submitted to aerobic fermentation by mechanical air pumping in a 300m³-capacity tank. In the second, bovine feces positive for eggs of the most common gastrointestinal nematodes were kept in a bovine fecal deposit in the field. Fecal samples from the two experiments were cultivated for the extraction of infective larvae. Both processes reduced the number of viable eggs. Reduction in the number of viable eggs were higher than 99% in both cases after 14 days of exposure.

  20. Modulational instability of nematic phase

    Indian Academy of Sciences (India)

    2014-02-08

    Feb 8, 2014 ... Abstract. We numerically observe the effect of homogeneous magnetic field on the modulation- ally stable case of polar phase in F = 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 ...

  1. Modulational instability of nematic phase

    Indian Academy of Sciences (India)

    2014-02-08

    Feb 8, 2014 ... 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 ...

  2. Hyperparasitism by helminths: new records of cestodes and nematodes in proteocephalid cestodes from South American siluriform fishes Hiperparasitismo por helmintos: novas ocorrências de cestóides e nematóides em cestóides proteocefalídeos de peixes siluriformes da América do Sul

    Directory of Open Access Journals (Sweden)

    Amilcar Arandas Rego

    1989-09-01

    Full Text Available Proteocephalid cestode hyperparasite are reported from numerous proteocephalids occurring in pimelodid fishes in different regions of Brazil. In addition, three specimens of a nematode hyperparasite are reported from the proteocephalid cestode Choanoscolex abscissus from the pimelodid fish Pseudoplatystoma corruscans in Brazil. Previous records of cestode and nematode hyperparasite of cestode are listed, and the possible identities of the Brazilian records are discussed.Cestóides hiperparasitos são descritos de espécies de proteocefalídeos, que ocorrem em peixes pimelodídeos de diferentes regiões do Brasil. Referimos ainda, a ocorrência de nematóide hiperparasito em espécimes de Choanoscolex abscissus, do peixe pimelodídeo, Pseudoplatystoma carruscans. São citadas as referências anteriores de cestóides e nematóides hiperparasitos, e discutida a possível identificação dos mesmos.

  3. Viabilidade de formulação peletizada do fungo nematófago Monacrosporium sinense, no controle biológico de nematóides parasitos gastrintestinais de bezerros Viability of pellet formulation of Monacrosporium sinense as biological control of gastrointestinal nematodes of calves

    Directory of Open Access Journals (Sweden)

    A.K. Campos

    2007-02-01

    Full Text Available A viabilidade de uma formulação do fungo Monacrosporium sinense foi avaliada no controle de nematóides parasitos gastrintestinais de bovinos. Dois grupos de 10 bezerros cada um, mestiços Holandês x Zebu, de seis a nove meses de idade, foram colocados em pastagem de Brachiaria brizantha. Em um dos grupos, cada animal recebeu 20g de péletes em matriz de alginato de sódio, contendo massa miceliana do fungo M. sinense via oral, duas vezes por semana, durante seis meses, com início no mês de outubro; no outro grupo, controle, os bezerros não receberam esse tratamento. As contagens de ovos por grama de fezes (OPG e de larvas infectantes por kg de matéria seca foram maiores (PThe viability of a formulation of the fungus Monacrosporium sinense was evaluated as control of bovine gastrointestinal nematodes parasites. Two groups were used and they were made up of 10 Holstein X Zebu crossbred, six to eight-month-old. They were grazing on Brachiaria brizantha pasture. In the treated group, each animal received orally, twice a week 20g of pellets of sodium alginate containing mycelial of the fungus M. sinense, during six months, with the onset in October. In the control group, the calves did not receive that treatment. The counting of eggs per gram of faeces (EPG and the counting of infective larvae per kg of dry matter were higher (P<0.05 in the control group than in the treated group. The difference of the EPG between the groups at the end of the experimental period was 79%. The viability of the pellets germination and the predatory activity of the fungus after the encapsulation were evaluated in vitro. The percentage of pellets with positive culture for fungus varied between 90-100% and the percentage of reduction of infective larvae varied between 90.6-100%. The use of that dose and the periodic application of M. sinense pellets were efficient as control of bovine gastrointestinal nematode parasites.

  4. Highly anisotropic conductivity in organosiloxane liquid crystals

    Science.gov (United States)

    Gardiner, D. J.; Coles, H. J.

    2006-12-01

    In this paper, we present the conductivity and dielectric characterization of three homologous series of smectic A siloxane containing liquid crystals. The materials studied include one monomesogenic series, which consists of a 4-(ω-alkyloxy)-4'-cyanobiphenyl unit terminated by pentamethyldisiloxane, and two bimesogenic series, which consist of twin 4-(ω-alkyloxy)-4'-cyanobiphenyls joined via tetramethyldisiloxane or decamethylpentasiloxane. All of the compounds exhibit wide temperature range enantiotropic smectic A phases; the effect of the siloxane moiety is to suppress nematic morphology even in the short chain homologs. We find that these compounds exhibit a highly anisotropic conductivity: the value perpendicular to the director is to up to 200 times that parallel to the director. For the nonsiloxane analog 4-(ω-octyl)-4'-cyanobiphenyl (8CB), this value is approximately 2. It is also found that the dielectric anisotropy is reduced significantly; a typical value is ˜1 compared to 8.4 for 8CB. We propose that the origin of these unusual properties is in the smectic structure; the microphase separation of the bulky, globular siloxane moieties into liquidlike regions severely inhibits the mobility parallel to the director and across the smectic layers. Further, the inclusion of this unit acts to increase the antiparallel correlations of molecular dipoles in the aromatic and alkyloxy sublayers, reducing the dielectric anisotropy significantly compared to nonsiloxane analogs. The highly anisotropic conductivity suggests that these materials are particularly suitable for application in electro-optic effects which exploit this property, e.g., the bistable electro-optic effect in smectic A liquid crystals.

  5. Resíduos de frutos de pequi no controle do nematóide das galhas em tomateiro Pequi fruit waste in the control of root-knot nematodes in tomato

    Directory of Open Access Journals (Sweden)

    Hudson B Ribeiro

    2012-09-01

    Full Text Available Durante a extração do mesocarpo interno do pequi que corresponde à parte comestível e possui valor comercial, são descartados no ambiente o exocarpo e o mesocarpo externo. Objetivou-se neste trabalho investigar o uso do extrato aquoso e do pó moído dos resíduos de pequi no controle do nematóide das galhas (Meloidogyne javanica. Do exocarpo e do mesocarpo externo foram obtidos extrato aquoso e o pó moído. Cinco doses do extrato aquoso (0,0; 2,5; 5; 10 ou 20% foram avaliadas quanto ao efeito na eclosão e mortalidade de juvenis de segundo estádio (J2 do nematóide das galhas in vitro. Os ensaios foram montados em delineamento inteiramente casualizado com 10 repetições por tratamento. O teste de eclosão foi feito em câmaras de eclosão às quais foram adicionados 800 ovos do nematoide e 10 mL das diferentes doses do extrato. Durante 14 dias contou-se o número de J2 eclodidos com auxílio do microscópio ótico. O ensaio de mortalidade de J2 do nematóide das galhas foi avaliado colocando-se 100 μL de cada dose do extrato em cada célula da placa Elisa e 20 μL contendo 20 J2. Após 24 h contou-se o número de nematoides vivos e mortos. O pó de pequi moído foi testado em tomateiro em casa de vegetação em quatro doses (0; 7,5; 15 ou 30 g/4 kg de solo em delineamento em blocos ao acaso com 10 repetições por tratamento. O pó de pequi foi incorporado sete dias antes do plantio do tomateiro e a inoculação de ovos do nematoide foi feita após o plantio. Após 40 dias foram avaliados: o número de galhas, massas de ovos, ovos por raiz e J2/200 cm³ de solo e altura e peso de massa seca de parte aérea do tomateiro. O extrato aquoso reduziu significativamente a eclosão e aumentou a mortalidade de J2 do nematóide das galhas. O aumento das doses do pó reduziu o número de galhas, massas de ovos e ovos do nematóide das galhas por sistema radicular, bem como o peso da massa seca de parte aérea e da altura do tomateiro os quais s

  6. Nematóides que parasitam a soja na região de Bauru Nematode parasites of soybean in the Bauru region

    Directory of Open Access Journals (Sweden)

    Luiz Gonzaga E. Lordello

    1956-01-01

    Full Text Available Entre os sérios fatôres que atuam contra a expansão da cultura da soja no Estado de São Paulo, acha-se o representado por nematóides parasitos. Dêstes, os que mais têm atraído a atenção dos cultivadores e fitopatologistas são as espécies formadoras de galhas no sistema radicular (Meloidogyne spp.. O estudo do material atacado coligido em Bauru revelou que, naquela região, três formas se acham envolvidas, a saber : Pratylenchus sp., Meloidogyne incognita (Kofoid & White, 1919 Chitwood, 1949 e M. javanica bauruensis n. subsp. Neste trabalho é estudada a nova subespécie, sendo também apresentadas algumas observações sobre a população de M. incognita.One of the serious detriments to soybean (Glycine max (L. Merr. cultivation in the State of S. Paulo, Brazil, are root-parasitic nematodes. A study of infected material collected at Bauru, where at least two distinct soybean varieties were cultivated, disclosed that three forms were involved: a meadow nematode (Pralylenchus sp. and two root-knot nematodes (Meloidogyne incognita (Kofoid & White, 1919 Chitwood, 1949, and M. javanica bauruensis n. subsp.. Silva, Lordello & Miyasaka (3 published some observations about the resistance of several soybean varieties to the attacks by root-knot nematodes in Campinas. A detailed study of the nematodes involved in those experiments, which were considered as related do M. incognita, has not yet been made. One of the varieties tested, La 41-1219, proved to be resistant, thereby providing promising material for further studies and breeding. Unfortunately, such a variety when planted in Bauru, was severely attacked by a root-knot species, which is identified as M. incognita. Attacks by M. javanica bauruensis was not noted in that variety but was noted in another variety (Abura growing adjacent in the same field. The host preference of those two nematodes was specific and very marked. M. incognita attacked only var. La 41-1219 and M. javanica

  7. Combate aos nematóides pela aplicação de fumigantes no solo: efeito do d-d e dowfume w-40 no combate aos nematóides formadores de galhas, em tubérculos de batatinha

    Directory of Open Access Journals (Sweden)

    O. J. Boock

    1951-03-01

    Full Text Available No presente trabalho relatamos os resultados a que pudemos chegar com o emprêgo dos fumigantes "D-D" (Dicloropropeno-Dicloropropano, e "Dowfume W-40", na base de dibrometo de etileno, no combate aos nematóides formadores de galhas, em tubérculos de batatinha. As experiências foram efetuadas em Campinas, em terreno do tipo "Glacial", e divididas em duas fases distintas. Na primeira, tratamos o terreno com os fumigantes 18 dias antes do plantio e adubamos alguns lotes, ena segunda fase, que foi realizada no mesmo terreno, não adubamos e nem tratamos o terreno, com o fim de verificar o efeito residual dos produtos, empregando, além disso, duas variedades ao invés de uma, como na fase inicial. Os resultados apresentados vieram indicar que : a tanto o "D-D" como o "Dowfume W-40" não prejudicaram a brotação dos tubérculos ; b entre produções, houve, na primeira fase da experiência, uma ligeira superioridade dos lotes com fumigantes e adubados sobre o "sem tratamento com fumigante mas com adubação", e dêste, por sua vez, sôbre o "sem fumigante- e sem adubação". Na segunda fase quase não houve diferenças entre tratados e adubados ; c tanto o "D-D" como o "Dowfume W-40" foram eficientes na redução dos nematóides formadores das galhas nos tubérculos, pois enquanto na primeira fase os canteiros "sem tratamento e sem adubação" produziram, em média, 49,5% de galhas, a maioria de caráter grave, e os "adubados mas sem fumigante" deram 20%, já nos tratados e adubados, houve apenas uma leve incidência de 1,5% para o "D-D" e 0% para o "W-40". No segundo plantio, no mesmo terreno, observamos que, além de uma reinfestação do solo, os restos da adubação não impediram a formação das galhas como na primeira fase. Para confirmação dêstes resultados, novas experiências serão executadas com fumigantes no solo.Results are reported on the application of the soil fumigants "D-D" (dichloropropene-dichloropropane and "Dowfume W-40

  8. Controle biológico de nematóides gastrintestinais de caprinos em clima semi-árido pelo fungo Monacrosporium thaumasium Biological control of gastrointestinal nematodes of goats in semiarid climate by Monacrosporium thaumasium

    Directory of Open Access Journals (Sweden)

    Jackson Victor de Araújo

    2007-08-01

    Full Text Available O objetivo deste trabalho foi avaliar a viabilidade do fungo nematófago Monacrosporium thaumasium, no controle de larvas infectantes de nematóides gastrintestinais de caprinos em campo, no Semi-Árido cearense. Uma área de 20 ha, com pasto recém-formado, livre de vermes, foi dividida em quatro piquetes de 5 ha. Em cada piquete, foi formado um grupo constituído por nove caprinos, onde cada animal recebeu os seguintes tratamentos, durante os meses de abril a junho de 2002: grupo 1, 10 g de péletes por via oral, semanalmente; grupo 2, 10 g de péletes por via oral, quinzenalmente; grupo 3, 0,5 mL de moxidectin por 25 kg de peso vivo; grupo 4, controle, não tratado. Mensalmente, dois caprinos traçadores foram colocados junto ao rebanho por 30 dias, e após esse período, foram sacrificados e necropsiados. O grupo de animais que recebeu o tratamento com o fungo uma vez por semana apresentou redução no número de ovos por grama de fezes, menor carga parasitária e maior ganho de peso, em relação aos animais dos demais grupos. O fungo M. thaumasium é eficiente no controle de larvas infectantes nas pastagens e pode ser utilizado no controle e profilaxia de nematóides gastrintestinais de caprinos, no Semi-Árido cearense.The present study aimed to evaluate the viability of the nematophagous fungus Monacrosporium thaumasium in the control of gastrointestinal nematodes larvae of goats in the field, in semiarid climate in Ceará State, Brazil. An area of 20 ha, free of worms, was divided into four paddocks of 5 ha. In each paddock, one group consisting of nine goats was formed and received the following treatment, individually, from April to June 2002: group 1, each animal received, orally, 10 g of pellets, weekly; group 2, the animals received 10 g of pellets, each 15 days; group 3, the animals received 0.5 mL moxidectin per 25 kg of live weight; group 4, control, not treated. Monthly, two tracer goats were introduced into the flock per 30

  9. Disponibilidade de larvas infectantes de nematódeos gastrintestinais parasitas de ovinos deslanados no semi-ârido pernambucano Seasonal availability of sheep gastrointestinal nematode infection in the semi-arid areas of Pernambuco state

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    Terezinha Padilha Charles

    1995-01-01

    Full Text Available A cada período médio de 30 dias (25 a 56 dias compreendidos entre 08 de janeiro de 1988 e 11 de maio de 1990, dois ovinos deslanados, machos, com idade entre três a seis meses de idade, livres de vermes, eram colocados para pastejar juntamente com um rebanho naturalmente infectado. Após o período de pastejo, os animais permaneciam estabulados por 14-21 dias quando eram submetidos à necropsia para coleta, contagem e identificação dos nematódeos adquiridos. Haemonchus contortus foi o nematódeo mais prevalente (80,0%, seguido do Trichostrongylus spp. (T. axei e T. colubriformis e Oxperia spp. (C. pectinata e C. punctata presentes em 72,0% dos animais examinados, Oesophagostomum radiatum e Stcoagyloides papillosus estavam presentes em 56,0% e 38,0% dos animais examinados, respectivamente. O número médio de H. contortus variou de 510 na estação seca a 2157 na chuvosa, sendo o número médio de larvas de quarto estágio desse nematódeo de 499 na estação chuvosa (23% do total adquirido no período e 416 na seca (81,6% do total médio adquirido no período. O número médio de Trichostrongylus spp. (T. axei e T. colubriformis, Cooperia spp. (C. pectinata and C. punctata, O. columbianum e S. papillous variou de 89, 89, 17 e 5 na estação seca a 497, 109, 93 e 284 na chuvosa, respectivamente. A transmissão das várias espécies ocorreu principalmente no meado da estação chuvosa até o início da estação seca.During each of 25-56 days periods from January 08, 1988 to May 05, 1990, two male sheep three to six month old, shown to be free of gastrointestinal nematode infection, were grazed with a flock of naturally infected sheep (tracer sheep. At the end of each grazing period, these sheep were placed on a cement floored pen and were maintained there for two to three weeks prior to necropsy and examination for gastrointestinal nematodes. Haemonchus contortus was the most prevalent nematode found (80%. The mean number of this nematode

  10. Comportamento de diversas plantas daninhas, de ocorrência comum no estado de São Paulo, em relação a duas espécies de nematóides das galhas: primeira parte

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    L.C.C.B. Ferraz

    1985-12-01

    Full Text Available Estudou-se o comportamento de 10 espécies de plantas daninhas, comuns no Estado de São Paulo, quando o solo em que vegetavam foi inoculado com os nematóides das galhas Meloidogyne incognita raça 4 ou M. javanica. As avaliações foram feitas 50 dias após a inoculação dos parasitos, baseando-se nos números de galha s e ootec as pre sentes nas raízes e nos valores de altura e de pesos secos da parte aérea e sistemas radiculares das plantas. Em relação as duas espécies de nematóides, comportaram-se como alta mente suscetíveis Alternaria ficoidea (apaga -fogo e Ipomoea acuminata (cordade -viola , como olerantes Amaranthus hybridus var. patulus (caruru e Commelina virgunica (trapoeraba, como pouco suscetível Euphorbia heterophylla (amendoim bravo e como altamente resistentes Blainvillea rhomboidea (erva - palha, Crotonn glandulosus (gervãobranco, Emilia sonchifolia (serralha e Tagetes minuta (cravo-de-defunto. O carrapicho-de-carneiro, Acant horpermum hispidum, mostrou-se altamente resis tente a M. incognita raça 4 e moderadamente suscetível a M. javanica.The behaviour of ten different weed species belonging to Amaranthaceae, Commelinaceae, Compositae, Convolvulaceae and Euphorbiaceae in relation to the root-knot nematodes Meloidogyne incognita race 4 and M. javanica was studied under greenhouse conditions. Evaluations were carried out 50 days after the nematode inoculations, by means of gall and egg masses indexes observed in the root systems and through the determination of height and/or top dry weight of the plants. Alternanthera ficoidea and Ipomoea acuminate were considered highly suscetible to both nematode species; Amaranthus hybridus var. patul us and Commelina virgunica were tolerant to the arasites whereas Euphorbia heterophylla showed low susceptibility; Acanthospernum hispidum was conside red moderately suscetible to M. javanica and highly resistant to M. incognita race 4; all other weeds - Blainvillea rhomboidea

  11. Control of Strongyloides westeri by nematophagous fungi after passage through the gastrointestinal tract of donkeys Controle de Strongyloides westeri por fungos nematófagos após trânsito gastrintestinal em jumentas

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    Juliana Milani Araujo

    2012-06-01

    Full Text Available Strongyloides westeri is the most prevalent nematode among equines aged up to four months and causes gastrointestinal disorders. The objective of this study was to observe the control of infective S. westeri larvae (L3 by the nematophagous fungi Duddingtonia flagrans (AC001 and Monacrosporium thaumasium (NF34 after passage through the gastrointestinal tract of female donkeys. Twelve dewormed female donkeys that were kept in stables were used. Two treatment groups each comprising four animals received orally 100 g of pellets made of sodium alginate matrix containing a mycelial mass of either D. flagrans (AC001 or M. thaumasium (NF34. The control group consisted of four animals that received pellets without fungus. Feces samples were then collected from the animal groups at different times (after 12, 24, 48 and 72 hours. These feces were placed in Petri dishes containing 2% water-agar medium and 1000 L3 of S. westeri. AC001 and NF34 isolates showed the ability to destroy the L3, after gastrointestinal transit, thus demonstrating their viability and predatory activity.O Strongyloides westeri é o nematóide de maior prevalência entre equídeos com idade até quatro meses, causando distúrbios gastrintestinais. O objetivo do presente trabalho foi observar o controle de larvas infectantes (L3 de Strongyloides westeri pelos fungos nematófagos Duddingtonia flagrans (AC001 e Monacrosporium thaumasium (NF34 após trânsito gastrintestinal em jumentas. Foram utilizadas 12 jumentas, estabuladas e previamente vermifugadas. A seguir, dois grupos tratados, contendo cada um 4 animais receberam por via oral 100 g de péletes em matriz de alginato de sódio, contendo massa miceliana dos fungos D. flagrans (AC001 ou M. thaumasium (NF34. O grupo controle foi constituído de 4 animais que receberam péletes sem fungo. A seguir, amostras de fezes dos grupos de animais foram coletadas em distintos intervalos de horas (12, 24, 48 e 72. Essas fezes foram vertidas em

  12. Investigation of drug polymorphism: Case of artemisinin

    Energy Technology Data Exchange (ETDEWEB)

    Horosanskaia, E., E-mail: horosanskaia@mpi-magdeburg.mpg.de; Seidel-Morgenstern, A.; Lorenz, H.

    2014-02-01

    Highlights: • The Artemisinin dimorphic system was found to be enantiotropic. • The Orthorhombic modification is the form stable at low-temperatures and the triclinic modification the form stable at high-temperatures. • The polymorphic phase transition occurs at ∼130 °C. - Abstract: The polymorphism of the anti-malarial compound artemisinin was examined. The phase behavior of solid artemisinin has experimentally been investigated using differential scanning calorimetry and temperature-resolved X-Ray powder diffraction. In addition, complementary solution studies and suspension experiments were performed. The results clearly confirm the existence of two modifications of artemisinin, which are related enantiotropically. The orthorhombic modification is the thermodynamically stable form at low temperatures, while the triclinic form is the stable one at higher temperatures with a transition temperature of ∼130 °C. Problems associated with analysis of the polymorphic phase behavior are comprehensively addressed.

  13. Atividade predatória, crescimento radial e esporulação de fungos predadores de nematóides Monacrosporium spp, submetidos à criopreservação

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    Campos Artur Kanadani

    2004-01-01

    Full Text Available Testes in vitro foram realizados para avaliar o efeito da criopreservação em nitrogênio líquido com e sem adição de crioprotetores (DMSO ou glicerol, na atividade predatória sobre larvas infectantes de Cooperia sp e Haemonchus sp, crescimento radial e produção de conídios de dois isolados de fungos predadores de nematóides (Monacrosporium sinense e Monacrosporium appendiculatum. A capacidade predatória dos fungos sobre larvas infectantes de Cooperia sp e Haemonchus sp dos fungos previamente submetidos aos diferentes métodos de preservação não foi afetada. O crescimento radial dos fungos criopreservados com glicerol 10% foi mais expressivo(p<0,05, quando comparado ao apresentado pelos fungos congelados com DMSO 10 % ou água. A produção de esporos foi maior (p< 0,05 no fungo M. appendiculatum preservado a 4masculineC em geladeira.

  14. Body temperature norms

    Science.gov (United States)

    Normal body temperature; Temperature - normal ... Morrison SF. Regulation of body temperature. In: Boron WF, Boulpaep EL, eds. Medical Physiology . 3rd ed. Philadelphia, PA: Elsevier; 2017:chap 59. Sajadi MM, Mackowiak ...

  15. Photo-controllable thermal diffusivity and thermal conductivity driven by the orientation change of nematic liquid crystal with azo-dendrimers

    Science.gov (United States)

    Ryu, Meguya; Takezoe, Hideo; Haba, Osamu; Yonetake, Koichiro; Morikawa, Junko

    2015-11-01

    We measured the temperature dependences of anisotropic thermal properties, i.e., thermal diffusivity, thermal effusivity, thermal conductivity, and heat capacity per unit volume, of a nematogen 4'-n-pentyloxybiphenyl-4-carbonitrile (5OCB) containing a small amount (0.02 wt. %) of dendritic azobenzene derivatives (azo-dendrimer), using a temperature wave method. The azo-dendrimers spontaneously adsorb on cell surfaces and act as a command surface, i.e., photo-induced planar/homeotropic alignment by ultraviolet/visible light illumination. By using this effect, we demonstrated thermal property changes except for the heat capacity by almost two times within a few tens of seconds. The phenomenon can be applied to a sheet with photo-controllable thermal diffusivity or thermal conductivity.

  16. Observation of NanoDNA Liquid Crystal Phases from Four Base Pair Duplexes at Subambient Temperatures

    Science.gov (United States)

    Smith, Gregory; Fraccia, Tommaso; Bellini, Tommaso; Walba, David; Clark, Noel

    2014-03-01

    Based upon conventional Onsager model considerations, liquid crystal (LC) formation in DNA-water mixtures was originally thought to be impossible for DNA polymers of very short length (discovery of chiral nematic (N*), columnar CU and C2 LC phases in NanoDNA oligomers as short as 6 bases in length and have since described additional LC phases involving DNA with random sequences and various blunt or sticky-end duplex architecture, all in the regime of motif where hydrophobic forces or hydrogen bond mediated base-pairing enable unusually short polymers to stack into functionally longer units that permit them to exhibit LC phase behavior. We report now the existence of LC phases of ultra short duplexed NanoDNA, 4 bases in length, in blunt-end, sticky-end and random sequence configurations, all observed at temperatures of ~ 5 °C and not stable >13-15 °C. These oligomers demonstrate an unusual wealth of phase behavior, including the typical N*, CU and C2 phases as well as higher order dark and bright phases, including what we believe to be a Blue Phase. Grant support: NSF DMR 1207606 and NSF MRSEC DMR 0820579.

  17. Efeito da solarização, adubação química e orgânica no controle de nematóides em alface sob cultivo protegido Effect of solarization, chemical and organic fertilization on the control of nematode on greenhouse lettuce

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    Marlene G da Silva

    2006-12-01

    Full Text Available Os efeitos da solarização do solo associados à adubação no controle de nematóides e na produtividade da alface cultivar "Verônica" foram avaliados em solo naturalmente infestado. Dois experimentos foram conduzidos, um com e outro sem solarização, em casa de vegetação, ambos com cinco tratamentos: adubação orgânica; nitrogênio na forma amoniacal (NH4; adubação com NPK; adubação orgânica mais NPK; testemunha (sem adubação. No experimento solarizado, o solo foi coberto durante 132 dias com filme plástico transparente. A população de nematóides foi avaliada em duas camadas (0-10 cm e 10-20 cm, e as coletas de solo foram feitas em três épocas (antes da implantação do experimento; após a solarização; após a colheita. O delineamento experimental foi o de blocos ao acaso com três repetições em parcelas sub-subdivididas, com medidas no espaço e no tempo (5 adubações x 2 camadas x 3 épocas, e a comparação entre experimentos foi feita pela análise conjunta. O efeito da solarização sobre o controle de nematóides dependeu da adubação e camada do solo. A solarização reduziu a população de nematóides na camada de 0-10 cm em todos os tratamentos de adubação. A solarização associada ao NH4 reduziu a diversidade na camada de 10-20 cm. A solarização combinada às adubações orgânica, N-NH4, NPK e orgânica mais NPK reduziu de maneira eficiente o número de galhas, o número de massas de ovos e a população de nematóides fitoparasitas nas raízes, em especial de Meloidogyne spp. Solarização combinada à adubação orgânica apresenta potencial para controle de nematóides e redução do uso de agrotóxicos.The effect of soil solarization and fertilization was evaluated for nematode control in 'Veronica' lettuce in naturally infested soil. The two greenhouse experiments consisted of five fertilization treatments: organic fertilization; ammoniacal nitrogen (ammonium sulphate; NPK fertilization; organic

  18. Disposição do nematóide Bursaphelenchus cocophilus (Cobb baujard, em coqueiros portadores da doença anel-vermelho Disposition of the nematode bursaphelenchus cocophilus (Cobb baujard, in coconut palm trees with the red ring disease

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    Adriana Guimarães Duarte

    2008-09-01

    Full Text Available Este trabalho teve o objetivo de conhecer como o nematóide Bursaphelenchus cocophilus tende a se distribuir no interior das plantas de coqueiros em estágios avançados da doença anel-vermelho. Nas amostras de raízes coletadas junto à base da estipe de coqueiros doentes, o número de nematóides foi consideravelmente maior que encontrado em raízes situadas entre um e três metros de distância da estipe. Observou-se que, à medida que se afasta da estipe, a possibilidade de encontrar nematóides na raiz é mínima, de forma que as chances de transmissão da doença, de uma planta para outra, através das raízes, devem ser muito pequenas. Na região do palmito, onde o tecido é mais tenro, é possível encontrar o nematóide tanto nas áreas avermelhadas quanto nas áreas aparentemente sadias. Nos tecidos do pecíolo, foram encontrados nematóides em pequena quantidade. Portanto, práticas profiláticas, visando à desinfecção do facão utilizado na colheita e despalma, devem ser realizadas com a finalidade de eliminar a transmissão da doença. Nenhuma das amostras obtidas dos tecidos da ráquis e dos folíolos estava contaminada. A população de nematóide é mais alta nos excrementos de túneis larvais das regiões apicais do coqueiro, o que confere maior chance de serem transportados para outras plantas, aderidos ao corpo do seu principal vetor, os adultos de Rhynchophorus palmarum.The aim of this work was to investigate how the nematode Bursaphelenchus cocophilus tends to distribute itself inside the coconut palm trees in advanced stages of the red ring disease. In the samples of the roots collected at the base of the stem of sick trees, the number of nematodes was considerably higher when compared to the number found in the roots situated between one and three meters away from the stem. It was observed that, as it stands back of the sick plant, the possibility to find nematodes in the root is remote, so that the chances of

  19. Orbital superconductivity, defects, and pinned nematic fluctuations in the doped iron chalcogenide FeSe0.45Te0.55

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Saheli; Van Dyke, John; Sprau, Peter O.; Massee, Freek; Welp, Ulrich; Kwok, Wai-Kwong; Davis, J. C. Seamus; Morr, Dirk K.

    2017-08-01

    We demonstrate that the differential conductance, dI/dV, measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe0.45Te0.55, possesses a series of characteristic features that allow one to extract the orbital structure of the superconducting gaps. This yields nearly isotropic superconducting gaps on the two holelike Fermi surfaces, and a strongly anisotropic gap on the electronlike Fermi surface. Moreover, we show that the pinning of nematic fluctuations by defects can give rise to a dumbbell-like spatial structure of the induced impurity bound states, and explains the related C-2 symmetry in the Fourier transformed differential conductance.

  20. Nematodes of zoonotic importance in Cynoscion guatucupa (Pisces in the state of Rio de Janeiro Nematóides de importância zoonótica em Cynoscion guatucupa (Pisces no estado do Rio de Janeiro

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    Gabrielle Fontenelle

    Full Text Available Between January and August 2012, thirty specimens of Cynoscion guatucupa (Cuvier, 1830 caught off coast of the municipality of Itajaí, state of Santa Catarina, Brazil (26° 54′ 28″ S and 48° 39′ 43″ W and commercialized in the state of Rio de Janeiro were investigated for the presence of zoonotic nematodes. In total 853 larvae of four nematode parasite species were found. There were three species of Anisakidae: three larvae of Anisakis sp., with prevalence (P of 10%, mean intensity (MI of 1.0, mean abundance (MA of 0.1 and infection site (IS in the mesentery; five of Terranova sp. with P = 13.3%, MI = 1.25, MA = 0.17, range of infection (RI from 1 to 2 and IS = mesentery; and seven of Contracaecum sp. with P = 6.6%, MI = 3.5, MA = 0.23, RI = 1 to 4 and IS = mesentery and abdominal cavity. There was one species of Raphidascarididae: 838 larvae of Hysterothylacium deardorffoverstreetorum with P = 83.3%, MI = 33.52, MA = 27.93, RI = 1 to 219 and IS = mesentery, liver serosa and abdominal cavity. This is the first report of larvae of Anisakis sp. and Contracaecum sp in C. guatucupa in Brazil. Hysterothylacium deardorffoverstreetorum; Anisakis sp.; Terranova sp.; Contracaecum sp.; Cynoscion guatucupaEntre janeiro e agosto de 2012, 30 espécimes de Cynoscion guatucupa (Cuvier, 1830 pescados no litoral do município de Itajaí, estado de Santa Catarina, Brasil (26° 54′ 28″ S and 48° 39′ 43″ W e comercializados no estado do Rio de Janeiro, foram investigados quanto à presença de nematóides zoonóticos. Foram encontradas 853 larvas de quatro espécies de nematóides parasitos. Três espécies pertencem à Anisakidae, sendo três larvas de Anisakis sp., com prevalência (P de 10%, intensidade média (IM de 1, abundância média (AM de 0,1 e sítio de infecção (SI o mesentério; cinco de Terranova sp., com P = 13,3%, IM = 1,25, AM = 0,17, amplitude de variação da intensidade de infecção (AI de 1 a 2 e SI = mesentério; e sete

  1. Resistência do cafeeiro a nematóides: I - Testes em progênies e híbridos, para Meloidogyne exigua Coffee breeding for resistance to Meloidogyne exigua: I - Screening test using arabica progenies and interespecific hybrids

    Directory of Open Access Journals (Sweden)

    L. C. Fazuoli

    1977-01-01

    Full Text Available Procurou-se identificar fontes de resistência ao nematóide Meloidogyne exígua em cafeeiros derivados de híbridos interespecíficos e em progênies de café arábica oriundas da Etiópia, em experimentos estabelecidos em duas localidades. A infestação foi feita por dois processos usados com freqüência nesse tipo de trabalho. As avaliações do grau de ataque foram feitas quatro e 12 meses após a infestação, em Campinas e Ribeirão Preto, respectivamente, adotando-se escala variando de zero, para ausência de galhas, a cinco pontos para grande intensidade de ataque. Verificou-se que a leitura feita aos quatro meses é tão eficiente quanto aos 12 meses, indicando a possibilidade de abreviar consideravelmente a duração dessas avaliações. Notou-se, no experimento de Ribeirão Preto, uma redução de aproximadamente 8% no crescimento das mudas infestadas e verificou-se, também, uma redução de 11,5% e 12% nos pesos verde e seco das plantas, devido ao ataque do nematóide. De 1.692 plantas examinadas nos dois experimentos, selecionaram-se 106 (6,3%, caracterizadas pela ausência de galhas. As populações derivadas dos híbridos entre Coffea arabica e C. canephora revelaram-se mais promissoras, contribuindo com maior número de plantas resistentes. As plantas do experimento instalado em Campinas foram inoculadas também com a raça II de Hemileia vastatrix para o estudo da resistência conjunta aos dois patógenos. Essas seleções, em número de 38, representam valioso material para o programa de melhoramento do cafeeiro.Two coffee screening tests were undertaken in order to find out sources of resistance to the nematode M. exigua. Arabica progenies from Ethiopia origin and advanced popu-lations derived from interspecific crosses (Coffea arabica x C. canephora and C. arabica x C. dewevrei were evaluated. A five point scale (0 point to the roots without galls and 5 points to severely attacked roots was used for determination of the

  2. Resistência de porta-enxertos para pessegueiro e ameixeira aos nematóides causadores de galhas (Meloidogyne spp. Resistance of rootstock for peach tree and plum to root-knot nematodes (Meloidogyne spp.

    Directory of Open Access Journals (Sweden)

    José Carlos Fachinello

    2000-03-01

    Full Text Available O trabalho foi realizado com o objetivo de comparar o comportamento de cinco diferentes porta-enxertos para frutas de caroço em frente a duas espécies de nematóides do gênero Meloidogyne (Meloidogyne javanica e Meloidogyne incognita. O cultivar GF 677 foi obtido a partir do cultivo in vitro e os demais porta-enxertos a partir de sementes. Aos dois meses, as plântulas foram repicadas e inoculadas com uma mistura de Meloidogyne javanica e M. incognita aos 30, 60 e 70 dias após o plantio em canteiros incorporando-se 0,2kg de solo altamente infestado com os nematóides ao redor de cada planta. Ao final do experimento, avaliaram-se o desenvolvimento das plantas e o grau de infecção de cada cultivar. O grau de resistência dos cultivares foi estimado a partir do índice de galhas, obtido através de uma escala de grau ou nota, a qual varia de 0 a 5, em função do número de galhas ou ootecas. Os resultados obtidos demonstraram que o cultivar Okinawa não apresentou galhas no sistema radicular e na análise de crescimento foi superior aos demais cultivares. Os cultivares R-15-2 e Aldrighi foram considerados resistentes aos fitonematóides por apresentarem pequeno número de galhas no sistema radicular. Já o cultivar GF 677 apresentou maior número de galhas no sistema radicular, chegando a 126 galhas/g de raiz.The work was carried out with the objective of comparing the response of five different stone fruit rootstocks to two nematode species (Meloidogyne javanica and Meloidogyne incognita. The cultivar GF677, which was obtained from in vitro cultivation and the others rootstocks, were obtained from seedlings. Two month old plants were transplanted and inoculated with a mixture of both nematode species at 30, 60, 70 days after planting, by incorporating 0.2kg of highly infested soil around each cultivar. The development of the roststocks were evaluated at the end of the experiment. Number of galls, ranging from 0 to 5 was used to score the

  3. Controle de nematóides parasitos gastrintestinais por Arthrobotrys musiformis em ovinos naturalmente infestados mantidos em pastagens Control of gastrintestinal parasitic nematodes by Arthrobotrys musiformis in naturally infested sheep maintained on pastures

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    Érika Barbosa Neves Graminha

    2005-09-01

    Full Text Available Este trabalho objetivou avaliar, in vitro e in vivo, o fungo predador Arthrobotrys musiformis, administrado via oral na forma de conídios microencapsulados em alginato ou in natura em meio líquido, após passagem pelo trato gastrintestinal de ovinos. No teste in vitro, avaliou-se a manutenção da atividade predatória, e no teste in vivo, a capacidade de controlar nematóides parasitos de ovinos naturalmente infectados, mantidos em pastagens. O resultado do teste in vitro confirmou a viabilidade de A. musiformis (95,5%, mesmo após a passagem pelo trato gastrintestinal. Na avaliação in vivo, não houve diferença estatística entre o número de ovos por grama de fezes dos grupos tratados e controle, provavelmente em razão da baixa lotação dos piquetes, da quantidade e periodicidade insuficientes de oferecimento de conídios aos ovinos, o que teria proporcionado dispersão e migração das larvas na pastagem. Contudo, os helmintos recuperados na necropsia dos animais traçadores mostraram que A. musiformis reduziu em 50,9% e 57,6% o número de Trichostrongylus colubriformis dos grupos tratados com conídios microencapsulados e in natura, respectivamente, e em 95% o número de L4 de Haemonchus do grupo tratado com conídios in natura. Embora os resultados não sejam conclusivos, A. musiformis mostrou-se promissor agente no biocontrole de nematóides parasitos gastrintestinais.The objective of the present study was to assess in vitro and in vivo the predatory fungus Arthrobotrys musiformis administered orally, in the form of alginate-microencapsulated conidia, or in natura in liquid medium after passage through the gastrointestinal tract of sheep. Maintenance of the predatory activity of the fungus was evaluated in the in vitro test, and its ability to control parasitic nematodes in naturally infested sheep maintained on pastures was analyzed in the in vivo test. The result of the in vitro test confirmed the viability of A. musiformis (95

  4. In vitro evaluation of nematophagous fungi patogenicity against nematode of domestic animals/ Avaliação in vitro da patogenicidade de fungos predadores de nematóides parasitos de animais domésticos

    Directory of Open Access Journals (Sweden)

    Alvimar José da Costa

    2001-08-01

    Full Text Available Biological control is a promising alternative for the control of pre-parasitic stages through the action of nematophagous fungi’s. The present study evaluated in vitro the patogenicity of both Arthrobotrys musiformis and A. conoides fungi on “infective larvae (or L3 state larvae” of Haemonchus contortus, L3 larvae of Ancylostoma spp. And larvated eggs of the nematode Ascaridia galli. Nine groups were formed: six treated groups (G1A and G2A: L3 of H. contortus; G1B and G2B: L3 of Ancylostoma spp.; G1C and G2C: larvated eggs of A. galli, being that G1 with A. musiformis and G2 with A. conoides and three untreated groups (G3A, G3B and G3C: larvae of H. contortus, Ancylostoma spp. And eggs of A. galli, respectively, without fungi. Each treatment had ten repetitions (ten Petri dishes with an average of 120 larvae of H. contortus and 200 larvae of Ancylostoma spp. and, approximately, 100 larvated A. galli eggs. The results showed A. musiformis plundered 66% and 94% of Ancylostoma spp. L3 larvae and H. contortus L3 larvae, respectively. While that A. conoides plundered 51,7% and 89,4% at the same larvae. The nematophagous fungi evaluated have not presented any predation type on A. galli larvated eggs. Afterwards, both are promising fungi as to their use for biological control of parasitic helminths of animal hosts.O controle biológico é uma alternativa promissora no controle dos estágios pré-parasitários de helmintos, por meio da ação de fungos nematófagos. Com este propósito, o presente estudo avaliou in vitro a patogenicidade dos fungos Arthrobotrys musiformis e A. conoides sobre larvas infectantes de Haemonchus contortus, Ancylostoma spp. e ovos larvados de Ascaridia galli. Foram utilizados nove grupos: seis tratamentos (G1A e G2A: L3 de H. contortus; G1B e G2B: L3 de Ancylostoma spp.; G1C e G2C: ovos larvados de A. galli, com A. musiformis (G1 e A. conoides (G2, respectivamente e três testemunhos (G3A, G3B e G3C: larvas de H

  5. Nematóides resistentes a alguns anti-helmínticos em rebanhos caprinos no Cariri Paraibano Nematode resistant to some anthelmintics in dairy goats in Cariri Paraibano, Brazil

    Directory of Open Access Journals (Sweden)

    Wagner C. Lima

    2010-12-01

    Full Text Available Objetivou-se avaliar a resistência de nematódeos a alguns anti-helmínticos em rebanhos caprinos no Cariri Paraibano. Foram utilizados 144 animais no período seco e 120 animais no período chuvoso, fêmeas com idade acima de oito meses de vida e lactantes, distribuídos em 4 grupos: Grupo I não tratado, Grupo II tratado com albendazole a 10%, Grupo III tratado com ivermectina a 1% e Grupo IV tratado com fosfato de levamisole a 18,8%, nas doses recomendadas pelos fabricantes. Para avaliar a resistência, aplicou-se o teste de redução na contagem de ovos por grama de fezes (RCOF e o cultivo de larvas de helmintos. As amostras fecais foram coletadas no dia do tratamento (dia base e 7, 14 e 21 dias após o tratamento. No grupo tratado com Albendazole, observaram-se eficácias de 61%, 11% e 24% no período seco e de 55%, 14% e 12% no período chuvoso, aos 7, 14, e 21 dias, respectivamente. No grupo tratado com Ivermectina, a eficácia foi de 14%, 70% e 66% para o período seco, e de 76%, 34% e 71% para o período chuvoso, aos 7, 14 e 21 dias, respectivamente. O grupo tratado com fosfato de Levamisole apresentou percentuais de eficácia de 89%, 79% e 73% no período seco e de 76%, 69% e 67% no período chuvoso, aos 7, 14 e 21 dias, respectivamente. Os resultados obtidos indicam que os nematódeos gastrintestinais de alguns rebanhos caprinos no Cariri Paraibano não são sensíveis aos princípios ativos Albendazole, Levamisole e Ivermectina. Durante o período de estudo foi identificada a presença de parasitas dos gêneros Haemonchus, Trichostrongylus, Oesophagostomum e Strongyloides.The aim of this paper was to evaluate the resistance of nematodes to some anthelmintics in dairy goats in Cariri Paraibano, Brazil. A total of 144 female goats, over 8 months of age, were used in the dry season and 120 ones during the rainy season, divided into four groups: Group I untreated, Group II treated with albendazole 10%, Group III treated with ivermectin

  6. Neem (Azadirachta Indica effect in gastrointestinal nematodes control in supplemented sheep during dry season grazingEfeito do neem (Azadirachta Indica no controle de nematódeos gastrintestinais em ovinos suplementados a pasto no período seco

    Directory of Open Access Journals (Sweden)

    Mauricio Nobuyuki Miyashita Piona

    2013-03-01

    Full Text Available The aim of this study was to evaluated the effect of Azadirachta indica (Neem extracts upon the productive response and control of gastrointestinal nematodes in Santa Inês sheep during the dry season grazing. Twenty four sheep, were divided in three groups according to the following treatments: SP – Control (Animals receiving protein supplement; SP- Oil (Animals receiving protein supplement and Neem oil extract and SP – Leaf (Animals receiving protein supplement and Neem dry leaves. The animals received daily protein supplement, while the oil and the dry leaves treatments were offered at interval of 15 days, a total of 4 doses ministred. Each day of supply of oil and leaves, feces samples were collected (day 0, 15, 30, 45, 60 for egg count per gram and subsequent larval cultivation for identifying genres. The protein supplement directly influenced the reduction of nematode eggs obtained per gram of feces (FEC of sheep on quality grazing, consequently bringing benefits for the worms control. A indica present in the oil and leaves did not obtain any statistical difference between the treatments when compared to the animals receiving only protein supplement. The association of Neem derivatives with protein supplement have not been able to increase animal performance even after decreasing the rates of FEC, showing that protein supplement were more able to provide effects on internal parasites control, when compared with to Neem oil or Neem dry leaves treatments. Avaliou-se o efeito de extratos de Azadirachta indica (Neem sobre a resposta produtiva e o controle de nematódeos gastrintestinais em ovinos Santa Inês mantidos em pastagem no período seco. Vinte e quatro ovinos foram divididos em três tratamentos: SP – Controle (Animais recebendo suplemento protéico; SP – Óleo (Animais recebendo suplemento protéico e extrato de óleo de Neem e SP – Folha (Animais recebendo suplemento protéico e folhas secas de Neem. Os animais receberam

  7. Nematódeos de ruminantes em pastagem com diferentes sistemas de pastejo com ovinos e bovinos Ruminant nematodes in pasture under different grazing systems with sheep and cattle

    Directory of Open Access Journals (Sweden)

    Sônia Emília Figueiredo de Araújo Torres

    2009-09-01

    Full Text Available O objetivo deste trabalho foi avaliar os efeitos de diferentes sistemas de pastejo, com ovinos e bovinos, sobre a quantidade de larvas no estágio L3 de nematódeos de ruminantes. O delineamento experimental foi inteiramente ao acaso, em arranjo fatorial com quatro sistemas de pastejo e quatro períodos de rotação de pastagem. A duração do experimento foi de 91 dias, com sistema rotacionado (7 dias de ocupação e 21 de descanso, em 8 ha de Panicum maximum cv. Tanzânia. Foram avaliados os sistemas de pastejo: alternado, simultâneo e isolado, com ovinos e com bovinos. Foram utilizados 20 bovinos (mestiços, 30 cordeiros e 15 ovelhas adultas (raça Santa Inês. As amostras do capim, para recuperação e identificação dos nematódeos, foram realizadas semanalmente no pré e pós-pastejo dos piquetes. Na média geral de todos os manejos, a ordem decrescente de número de larvas foi: Haemonchus spp., Trichostrongylus spp., Oesophagostomum spp., Strongyloides spp. e Cooperia spp. Correlações médias foram encontradas entre as quantidades de larvas L3 no pré e pós-pastejo. Com o aumento do número de rotações, houve aumento no grau de contaminação da pastagem pelas larvas, independentemente do sistema adotado. O sistema de pastejo simultâneo foi o que apresentou maior controle da carga parasitária de Haemonchus spp. na pastagem de capim-tanzânia.The objective of this work was to evaluate the effect of different grazing management systems on the parasitic nematode load (L3 larvae in ruminants. The experimental design was completely randomized, in a factorial arrangement with four grazing systems and four rotations. The experimental period was 91 days, in a rotational system (7 days of occupation and 21 of days rest, in 8-ha pasture cultivated with Panicum maximum cv. Tanzânia. The different management systems evaluated were: alternate, simultaneous and isolate whit cattle and sheep. Twenty mixed breed cattle, 30 lambs and 15 ewes

  8. Phase transition analysis of V-shaped liquid crystal: Combined temperature-dependent FTIR and density functional theory approach.

    Science.gov (United States)

    Singh, Swapnil; Singh, Harshita; Karthick, T; Tandon, Poonam; Prasad, Veena

    2018-01-05

    Temperature-dependent Fourier transform infrared spectroscopy (FTIR) combined with density functional theory (DFT) is employed to study the mechanism of phase transitions of V-shaped bent-core liquid crystal. Since it has a large number of flexible bonds, one-dimensional potential energy scan (PES) was performed on the flexible bonds and predicted the most stable conformer I. A detailed analysis of vibrational normal modes of conformer I have been done on the basis of potential energy distribution. The good agreement between the calculated spectrum of conformer I and observed FTIR spectrum at room temperature validates our theoretical structure model. Furthermore, the prominent changes observed in the stretching vibrational bands of CH3/CH2, CO, ring CC, ring CO, ring CH in-plane bending, and ring CH out-of-plane bending at Iso→nematic phase transition (at 155°C) have been illustrated. However, the minor changes in the spectral features observed for the other phase transitions might be due to the shape or bulkiness of molecules. Combined FTIR and PES study beautifully explained the dynamics of the molecules, molecular realignment, H-bonding, and conformational changes at the phase transitions. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Phase transition analysis of V-shaped liquid crystal: Combined temperature-dependent FTIR and density functional theory approach

    Science.gov (United States)

    Singh, Swapnil; Singh, Harshita; Karthick, T.; Tandon, Poonam; Prasad, Veena

    2018-01-01

    Temperature-dependent Fourier transform infrared spectroscopy (FTIR) combined with density functional theory (DFT) is employed to study the mechanism of phase transitions of V-shaped bent-core liquid crystal. Since it has a large number of flexible bonds, one-dimensional potential energy scan (PES) was performed on the flexible bonds and predicted the most stable conformer I. A detailed analysis of vibrational normal modes of conformer I have been done on the basis of potential energy distribution. The good agreement between the calculated spectrum of conformer I and observed FTIR spectrum at room temperature validates our theoretical structure model. Furthermore, the prominent changes observed in the stretching vibrational bands of CH3/CH2, Cdbnd O, ring CC, ring CO, ring CH in-plane bending, and ring CH out-of-plane bending at Iso → nematic phase transition (at 155 °C) have been illustrated. However, the minor changes in the spectral features observed for the other phase transitions might be due to the shape or bulkiness of molecules. Combined FTIR and PES study beautifully explained the dynamics of the molecules, molecular realignment, H-bonding, and conformational changes at the phase transitions.

  10. Anthelmintic activity of Melia azedarach fruits in lambs naturally infected with gastrointestinal nematodes / Atividade anti-helmíntica do fruto da Melia azedarach em cordeiros naturalmente infectados com nematódeos gastrintestinais

    Directory of Open Access Journals (Sweden)

    Daniela Guzzo

    2008-08-01

    Full Text Available The aim of this study was to evaluate the anthelmintic activity of Melia azedarach grounded dry fruits, in lambs naturally infected with gastrointestinal nematodes. Twenty four (24 mixed-breed Ile de France x Corriedale, male lambs, aged 3 month, were separeted into three (3 groups of eight (8 animals: the first group was medicated with 5mg.Kg-1 of albendazole orally, in a single dose, the second group was medicated with 2g.Kg-1 of Melia azedarach fruits orally, in a single dose, and the third group remained untreated, as control. The results showed that the group that presented the best efficacy was the one treated with albendazole (51.96%, followed by the group treated with Melia azedarach fruits that presented 33.21% of efficacy.Objetivou-se neste trabalho avaliar a atividade anti-helmíntica dos frutos secos e moídos da planta Melia azedarach, em cordeiros naturalmente infectados com nematódeos gastrintestinais. Utilizou-se 24 cordeiros, com 90 dias de idade, machos, mestiços Ile de France x Corridale, os quais foram divididos em 3 grupos de oito animais cada, sendo: grupo 1, medicado com 5mg.Kg-1 em dose única, de albendazole pela via oral (V.O; grupo 2, com 2g.Kg-1 (V.O, em dose única, do fruto do cinamomo (Melia azedarach e o grupo 3, controle, não recebeu nenhum tipo de tratamento. Os resultados encontrados demonstraram que o grupo tratado com albendazole foi o que apresentou melhor eficácia 51.96%, seguido do grupo tratado com frutos de cinamomo o qual apresentou eficácia de 33.21%.

  11. Seleção para resistência de genótipos de cenoura aos nematóides-das-galhas Selection for carrot genotypes resistance to root-knot nematodes in field and greenhouse

    Directory of Open Access Journals (Sweden)

    Giovani O da Silva

    2011-09-01

    Full Text Available Foi verificada a relação entre caracteres avaliados em campo e casa-de-vegetação, relativos à avaliação de genótipos de cenoura quanto à resistência ao nematóide-das-galhas (Meloidogyne spp., visando identificar quais caracteres possibilitam a diferenciação entre os genótipos e verificar a possibilidade de avaliação apenas em um ambiente ou a eliminação de caracteres que apresentem correlação alta. Avaliaram-se 38 progênies da população '0812518' e 31 progênies da população '0812519', além das cultivares Brasília e Kuronan como testemunhas tolerante e suscetível, respectivamente. Em campo naturalmente infestado por uma mistura de Meloidogyne incognita raça 1 e Meloidoigyne javanica, a seleção para resistência ao nematóide-das-galhas foi realizada com base na menor porcentagem de infecção na raiz principal dos genótipos de cenoura, rendimento de raiz e o fator de reprodução, enquanto que em casa-de-vegetação, para cada uma das mesmas espécies de nematóides e também para a mistura de ambas, foi medido o índice de galhas e índice de massa de ovos. Verificou-se que não houve possibilidade de seleção em apenas um dos ambientes testados ou a eliminação de caracteres, indicando que para a obtenção de cultivares mais produtivas e mais tolerantes é necessária a seleção combinada nos diferentes caracteres e ambientes. Para o experimento realizado em campo foi possível diferenciar os genótipos apenas para o rendimento de raiz. No experimento em casa-de-vegetação, para todos os caracteres foi possível identificar genótipos superiores. Porém, as médias das populações não foram melhores que a testemunha 'Brasília' da qual estas se originaram, confirmando a necessidade da busca por métodos mais eficientes de seleção.We verified the relation among the evaluated characters in field and greenhouse, concerning to the evaluation to root-knot nematode (Meloidogyne spp. for the carrot crop, to

  12. Complex free-energy landscapes in biaxial nematic liquid crystals and the role of repulsive interactions: A Wang-Landau study

    Science.gov (United States)

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

    2017-09-01

    General quadratic Hamiltonian models, describing the interaction between liquid-crystal molecules (typically with D2 h symmetry), take into account couplings between their uniaxial and biaxial tensors. While the attractive contributions arising from interactions between similar tensors of the participating molecules provide for eventual condensation of the respective orders at suitably low temperatures, the role of cross coupling between unlike tensors is not fully appreciated. Our recent study with an advanced Monte Carlo technique (entropic sampling) showed clearly the increasing relevance of this cross term in determining the phase diagram (contravening in some regions of model parameter space), the predictions of mean-field theory, and standard Monte Carlo simulation results. In this context, we investigated the phase diagrams and the nature of the phases therein on two trajectories in the parameter space: one is a line in the interior region of biaxial stability believed to be representative of the real systems, and the second is the extensively investigated parabolic path resulting from the London dispersion approximation. In both cases, we find the destabilizing effect of increased cross-coupling interactions, which invariably result in the formation of local biaxial organizations inhomogeneously distributed. This manifests as a small, but unmistakable, contribution of biaxial order in the uniaxial phase. The free-energy profiles computed in the present study as a function of the two dominant order parameters indicate complex landscapes. On the one hand, these profiles account for the unusual thermal behavior of the biaxial order parameter under significant destabilizing influence from the cross terms. On the other, they also allude to the possibility that in real systems, these complexities might indeed be inhibiting the formation of a low-temperature biaxial order itself—perhaps reflecting the difficulties in their ready realization in the laboratory.

  13. Maine River Temperature Monitoring

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — We collect seasonal and annual temperature measurements on an hourly or quarter hourly basis to monitor habitat suitability for ATS and other species. Temperature...

  14. High temperature measuring device

    Science.gov (United States)

    Tokarz, Richard D.

    1983-01-01

    A temperature measuring device for very high design temperatures (to 2,000.degree. C.). The device comprises a homogenous base structure preferably in the form of a sphere or cylinder. The base structure contains a large number of individual walled cells. The base structure has a decreasing coefficient of elasticity within the temperature range being monitored. A predetermined quantity of inert gas is confined within each cell. The cells are dimensionally stable at the normal working temperature of the device. Increases in gaseous pressure within the cells will permanently deform the cell walls at temperatures within the high temperature range to be measured. Such deformation can be correlated to temperature by calibrating similarly constructed devices under known time and temperature conditions.

  15. GISS Surface Temperature Analysis

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The GISTEMP dataset is a global 2x2 gridded temperature anomaly dataset. Temperature data is updated around the middle of every month using current data files from...

  16. Rescaling Temperature and Entropy

    Science.gov (United States)

    Olmsted, John, III

    2010-01-01

    Temperature and entropy traditionally are expressed in units of kelvin and joule/kelvin. These units obscure some important aspects of the natures of these thermodynamic quantities. Defining a rescaled temperature using the Boltzmann constant, T' = k[subscript B]T, expresses temperature in energy units, thereby emphasizing the close relationship…

  17. Evaluation of Eucalyptus citriodora essential oil on goat gastrointestinal nematodes Avaliação do óleo essencial de Eucalyptus citriodora sobre nematóides gastrintestinais de caprinos

    Directory of Open Access Journals (Sweden)

    Iara Tersia Freitas Macedo

    2011-09-01

    Full Text Available Phytotherapy may be an alternative strategy for controlling gastrointestinal parasites. This study evaluated the anthelmintic efficacy of Eucalyptus citriodora essential oil (EcEO. The in vitro effects of EcEO were determined through testing the inhibition of egg hatching and larval development of Haemonchus contortus. EcEO was subjected to acute toxicity testing on mice, orally and intraperitoneally. The in vivo effects of EcEO were determined by the fecal egg count reduction test (FECRT in goats infected with gastrointestinal nematodes. The results showed that 5.3 mg.mL-1 EcEO inhibited egg hatching by 98.8% and 10.6 mg.mL-1 EcEO inhibited H. contortus larval development by 99.71%. The lethal doses for 50% of the mice were 4153 and 622.8 mg.kg-1, for acute toxicity orally and intraperitoneally. In the FECRT, the efficacy of EcEO and ivermectin was 66.25 and 79.16% respectively, on goat gastrointestinal nematodes eight days after treatment. EcEO showed in vitro and in vivo anthelmintic activity.Fitoterapia pode ser uma estratégia alternativa para o controle de parasitas gastrintestinais. Este estudo avaliou a eficácia anti-helmintica do óleo essencial de Eucalyptus citriodora (OeEc. Os efeitos in vitro do OeEc foram determinados através do teste de eclosão de ovos e inibição do desenvolvimento larvar de Haemonchus contortus. O OeEc foi submetido ao teste de toxicidade aguda oral e intraperitoneal, em camundongos. Os efeitos in vivo do OeEc foram avaliados através do teste de redução da contagem de ovos nas fezes (FECRT com caprinos infectados com nematóides gastrintestinais. Os resultados mostraram que 5,3 mg.mL-1 OeEc inibiram 98,8% a eclosão de ovos e 10,6 mg.mL-1 OeEc inibiram 99,71% o desenvolvimento larvar de H. contortus. As doses letais para 50% dos camundongos foram de 4153 e 622,8 mg.kg-1 pela via oral e intraperitoneal. No FECRT, a eficácia de OeEc e ivermectina foi de 66,25 e 79,16%, respectivamente, em caprinos 8 dias

  18. Viabilidade de ovos de nematódeos gastrintestinais de bovinos após passagem em biodigestor anaeróbio Inactivation of trichostrongylid nematode eggs by anaerobic digestion of cattle slurry

    Directory of Open Access Journals (Sweden)

    John Furlong

    1996-08-01

    Full Text Available Em um estudo realizado no Centro Nacional de Pesquisa de Gado de Leite (CNPGL da EMBRAPA, em Coronel Pacheco, Zona da Mata de Minas Gerais, utilizou-se um biodigestor modelo indiano, com o objetivo de estimar o efeito inativante da fermentação anaeróbica em ovos de nematódeos gastrintestinais de bovinos. Amostras de fezes foram contidas em cilindros metálicos telados com malha de 22m e submersas no biodigestor por períodos de 7, 14, 21, 28, 42 e 56 dias. Os resultados do número de larvas recuperadas foi comparado com amostras padrão, submetidas a condições ótimas para o desenvolvimento dos ovos. Somente foram conseguidos níveis de motivação de ovos maiores que 80%, em amostras retidas por períodos superiores a 30 dias. Os efluentes de biodigestores podem veicular contaminação para culturas e pastagens fornecidas verdes, especialmente os oriundos de biodigestores mesofílicos operados com períodos de retenção menores que 30 dias.An experiment was carried out at the National Dairy Cattle Research Center, of EMBRAPA (Brazilian Agricultural Research Organization, in Coronel Pacheco, Zona da Mata Region of Minas Gerais State. To estimate the rate of inactivity of gastro-intestinal worm eggs submitted to anaerobic conditions on a biodigester (Indian model, fecal samples were contained in metallic cylinders with 22m openings and submerged in the anaerobic digester for 7. 14. 21. 28 and 56 days. The number of larvae extracted from culture of the feces after digester passage was compared with cultures mantained in optimal conditions. Levels of inactivation of eggs were greater than 80% only in samples retained for more than 30 days in the biodigester. Effluents of anaerobic digester are potential contaminators of gastro-intestinal worm eggs to crops and fodders, specially in mesophilic digesters, with small chambers, in which the retention period is less than 30 days.

  19. Chapter 6: Temperature

    Science.gov (United States)

    Jones, Leslie A.; Muhlfeld, Clint C.; Hauer, F. Richard; F. Richard Hauer,; Lamberti, G.A.

    2017-01-01

    Stream temperature has direct and indirect effects on stream ecology and is critical in determining both abiotic and biotic system responses across a hierarchy of spatial and temporal scales. Temperature variation is primarily driven by solar radiation, while landscape topography, geology, and stream reach scale ecosystem processes contribute to local variability. Spatiotemporal heterogeneity in freshwater ecosystems influences habitat distributions, physiological functions, and phenology of all aquatic organisms. In this chapter we provide an overview of methods for monitoring stream temperature, characterization of thermal profiles, and modeling approaches to stream temperature prediction. Recent advances in temperature monitoring allow for more comprehensive studies of the underlying processes influencing annual variation of temperatures and how thermal variability may impact aquatic organisms at individual, population, and community based scales. Likewise, the development of spatially explicit predictive models provide a framework for simulating natural and anthropogenic effects on thermal regimes which is integral for sustainable management of freshwater systems.

  20. Automatic temperature adjustment apparatus

    Science.gov (United States)

    Chaplin, James E.

    1985-01-01

    An apparatus for increasing the efficiency of a conventional central space heating system is disclosed. The temperature of a fluid heating medium is adjusted based on a measurement of the external temperature, and a system parameter. The system parameter is periodically modified based on a closed loop process that monitors the operation of the heating system. This closed loop process provides a heating medium temperature value that is very near the optimum for energy efficiency.

  1. Temperature measurement and control

    CERN Document Server

    Leigh, JR

    1988-01-01

    This book treats the theory and practice of temperature measurement and control and important related topics such as energy management and air pollution. There are no specific prerequisites for the book although a knowledge of elementary control theory could be useful. The first half of the book is an application oriented survey of temperature measurement techniques and devices. The second half is concerned mainly with temperature control in both simple and complex situations.

  2. Cardiac arrhythmogenesis and temperature.

    Science.gov (United States)

    Shah, Ujas; Bien, Harold; Entcheva, Emilia

    2006-01-01

    Fast processes in cardiac electrophysiology are often studied at temperatures lower than physiological. Extrapolation of values is based on widely accepted Q10 (Arrhenius) model of temperature dependence (ratio of kinetic properties for a 10 degrees C change in temperature). In this study, we set out to quantify the temperature dependence of essential parameters that define spatiotemporal behavior of cardiac excitation. Additionally, we examined temperature's effects on restitution dynamics. We employed fast fluorescence imaging with voltage-and calcium-sensitive dyes in neonatal rat cardiomyocyte sheets. Conduction velocity (CV), calcium transient duration (CTD), action potential duration (APD) and wavelength (W=CV*duration) change as functions of temperature were quantified. Using 24 degrees C as a reference point, we found a strong temperature-driven increase of CV (Q10=2.3) with smaller CTD and APD changes (Q10=1.33, 1.24, respectively). The spatial equivalents of voltage and calcium duration, wavelength, were slightly less sensitive to temperature with Q10=2.05 and 1.78, respectively, due to the opposing influences of decreasing duration with increased velocity. More importantly, we found that Q10 varies as a function of diastolic interval. Our results indicate the importance of examining temperature sensitivity across several frequencies. Armed with our results, experimentalists and modelers alike have a tool for reconciling different environmental conditions. In a broader sense, these data help better understand thermal influences on arrhythmia development or suppression such as during hibernation or cardiac surgery.

  3. High temperature materials; Materiaux a hautes temperatures

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    The aim of this workshop is to share the needs of high temperature and nuclear fuel materials for future nuclear systems, to take stock of the status of researches in this domain and to propose some cooperation works between the different research organisations. The future nuclear systems are the very high temperature (850 to 1200 deg. C) gas cooled reactors (GCR) and the molten salt reactors (MSR). These systems include not only the reactor but also the fabrication and reprocessing of the spent fuel. This document brings together the transparencies of 13 communications among the 25 given at the workshop: 1) characteristics and needs of future systems: specifications, materials and fuel needs for fast spectrum GCR and very high temperature GCR; 2) high temperature materials out of neutron flux: thermal barriers: materials, resistance, lifetimes; nickel-base metal alloys: status of knowledge, mechanical behaviour, possible applications; corrosion linked with the gas coolant: knowledge and problems to be solved; super-alloys for turbines: alloys for blades and discs; corrosion linked with MSR: knowledge and problems to be solved; 3) materials for reactor core structure: nuclear graphite and carbon; fuel assembly structure materials of the GCR with fast neutron spectrum: status of knowledge and ceramics and cermets needs; silicon carbide as fuel confinement material, study of irradiation induced defects; migration of fission products, I and Cs in SiC; 4) materials for hydrogen production: status of the knowledge and needs for the thermochemical cycle; 5) technologies: GCR components and the associated material needs: compact exchangers, pumps, turbines; MSR components: valves, exchangers, pumps. (J.S.)

  4. Measuring body temperature.

    Science.gov (United States)

    McCallum, Louise; Higgins, Dan

    Body temperature is one of the four main vital signs that must be monitored to ensure safe and effective care. Temperature measurement is recommended by the National Institute of Clinical Excellence a part of the initial assessment in acute illness in adults (NICE, 2007) and by the Scottish Intercollegiate Guidelines Network guidelines for post-operative management in adults (SIGN, 2004). Despite applying in all healthcare environments, wide variations exist on the methods and techniques used to measure body temperature. It is essential to use the most appropriate technique to ensure that temperature is measured accurately. Inaccurate results may influence diagnosis and treatment, lead to a failure to identify patient deterioration and compromise patient safety. This article explains the importance of temperature regulation and compares methods of its measurement.

  5. High temperature structural silicides

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, J.J.

    1997-03-01

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi{sub 2}-based materials, which are borderline ceramic-intermetallic compounds. MoSi{sub 2} single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi{sub 2} possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi{sub 2}-Si{sub 3}N{sub 4} composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi{sub 2}-based materials include furnace heating elements, molten metal lances, industrial gas burners, aerospace turbine engine components, diesel engine glow plugs, and materials for glass processing.

  6. Plastic substrates for active matrix liquid crystal display incapable of withstanding processing temperature of over 200.degree. C and method of fabrication

    Science.gov (United States)

    Carey, Paul G.; Smith, Patrick M.; Havens, John; Jones, Phil

    1999-01-01

    Bright-polarizer-free, active-matrix liquid crystal displays (AMLCDs) are formed on plastic substrates. The primary components of the display are a pixel circuit fabricated on one plastic substrate, an intervening liquid-crystal material, and a counter electrode on a second plastic substrate. The-pixel circuit contains one or more thin-film transistors (TFTs) and either a transparent or reflective pixel electrode manufactured at sufficiently low temperatures to avoid damage to the plastic substrate. Fabrication of the TFTs can be carried out at temperatures less than 100.degree. C. The liquid crystal material is a commercially made nematic curvilinear aligned phase (NCAP) film. The counter electrode is comprised of a plastic substrate coated with a transparent conductor, such as indium-doped tin oxide (ITO). By coupling the active matrix with NCAP, a high-information content can be provided in a bright, fully plastic package. Applications include any low cost portable electronics containing flat displays where ruggedization of the display is desired.

  7. Plastic substrates for active matrix liquid crystal display incapable of withstanding processing temperature of over 200 C and method of fabrication

    Science.gov (United States)

    Carey, P.G.; Smith, P.M.; Havens, J.H.; Jones, P.

    1999-01-05

    Bright-polarizer-free, active-matrix liquid crystal displays (AMLCDs) are formed on plastic substrates. The primary components of the display are a pixel circuit fabricated on one plastic substrate, an intervening liquid-crystal material, and a counter electrode on a second plastic substrate. The-pixel circuit contains one or more thin-film transistors (TFTs) and either a transparent or reflective pixel electrode manufactured at sufficiently low temperatures to avoid damage to the plastic substrate. Fabrication of the TFTs can be carried out at temperatures less than 100 C. The liquid crystal material is a commercially made nematic curvilinear aligned phase (NCAP) film. The counter electrode is comprised of a plastic substrate coated with a transparent conductor, such as indium-doped tin oxide (ITO). By coupling the active matrix with NCAP, a high-information content can be provided in a bright, fully plastic package. Applications include any low cost portable electronics containing flat displays where ruggedization of the display is desired. 12 figs.

  8. About thermometers and temperature

    Science.gov (United States)

    Baldovin, M.; Puglisi, A.; Sarracino, A.; Vulpiani, A.

    2017-11-01

    We discuss a class of mechanical models of thermometers and their minimal requirements to determine the temperature for systems out of the common scope of thermometry. In particular we consider: (1) anharmonic chains with long time of thermalization, such as the Fermi-Pasta-Ulam (FPU) model; (2) systems with long-range interactions where the equivalence of ensembles does not always hold; (3) systems featuring absolute negative temperatures. We show that for all the three classes of systems a mechanical thermometer model can be designed: a temporal average of a suitable mechanical observable of the thermometer is sufficient to get an estimate of the system’s temperature. Several interesting lessons are learnt from our numerical study: (1) the long thermalization times in FPU-like systems do not affect the thermometer, which is not coupled to normal modes but to a group of microscopic degrees of freedom; (2) a thermometer coupled to a long-range system measures its microcanonical temperature, even at values of the total energy where its canonical temperature would be very different; (3) a thermometer to read absolute negative temperatures must have a bounded total energy (as the system), otherwise it heavily perturbs the system changing the sign of its temperature. Our study shows that in order to also work in a correct way in ‘non standard’ cases, the proper model of thermometer must have a special functional form, e.g. the kinetic part cannot be quadratic.

  9. Control of supply temperature

    Energy Technology Data Exchange (ETDEWEB)

    Madsen, H.; Nielsen, T.S.; Soegaard, H.T.

    1996-09-01

    For many district heating systems, e.g. the system in Hoeje Taastrup, it is desirable to minimize the supply temperature from the heat production unit(s). Lower supply temperature implies lower costs in connection with the production and distribution of heat. Factors having impact on the heat demand are for instance solar radiation, wind speed, wind direction and a climate independent part, which is a function of the time of the day/week/year. By applying an optimization strategy, which minimizes the supply temperature, it is assumed that optimal economical operation can be obtained by minimizing the supply temperature and thereby the heat losses in the system. The models and methods described in this report take such aspects into account, and can therefore be used as elements in a more efficient minimization of the supply temperature. The theoretical part of this report describes models and methods for optimal on-line control of the supply temperature in district heating systems. Some of the models and methods have been implemented - or are going to be implemented - in the computer program PRESS which is a tool for optimal control of supply temperature and forecasting of heat demand in district heating systems. The principles for using transfer function models are briefly described. The ordinary generalized predictive control (OGPC) method is reviewed, and several extensions of this method are suggested. New controller, which is called the extended generalized predictive controller (XGPC), is described. (EG) 57 refs.

  10. Temperature estimation with ultrasound

    Science.gov (United States)

    Daniels, Matthew

    Hepatocelluar carcinoma is the fastest growing type of cancer in the United States. In addition, the survival rate after one year is approximately zero without treatment. In many instances, patients with hepatocelluar carcinoma may not be suitable candidates for the primary treatment options, i.e. surgical resection or liver transplantation. This has led to the development of minimally invasive therapies focused on destroying hepatocelluar by thermal or chemical methods. The focus of this dissertation is on the development of ultrasound-based image-guided monitoring options for minimally invasive therapies such as radiofrequency ablation. Ultrasound-based temperature imaging relies on relating the gradient of locally estimated tissue displacements to a temperature change. First, a realistic Finite Element Analysis/ultrasound simulation of ablation was developed. This allowed evaluation of the ability of ultrasound-based temperature estimation algorithms to track temperatures for three different ablation scenarios in the liver. It was found that 2-Dimensional block matching and a 6 second time step was able to accurately track the temperature over a 12 minute ablation procedure. Next, a tissue-mimicking phantom was constructed to determine the accuracy of the temperature estimation method by comparing estimated temperatures to that measured using invasive fiber-optic temperature probes. The 2-Dimensional block matching was able to track the temperature accurately over the entire 8 minute heating procedure in the tissue-mimicking phantom. Finally, two separate in-vivo experiments were performed. The first experiment examined the ability of our algorithm to track frame-to-frame displacements when external motion due to respiration and the cardiac cycle were considered. It was determined that a frame rate between 13 frames per second and 33 frames per second was sufficient to track frame-to-frame displacements between respiratory cycles. The second experiment examined

  11. High Temperature Electrolysis

    DEFF Research Database (Denmark)

    Elder, Rachael; Cumming, Denis; Mogensen, Mogens Bjerg

    2015-01-01

    High temperature electrolysis of carbon dioxide, or co-electrolysis of carbon dioxide and steam, has a great potential for carbon dioxide utilisation. A solid oxide electrolysis cell (SOEC), operating between 500 and 900. °C, is used to reduce carbon dioxide to carbon monoxide. If steam is also...... input to the cell then hydrogen is produced giving syngas. This syngas can then be further reacted to form hydrocarbon fuels and chemicals. Operating at high temperature gives much higher efficiencies than can be achieved with low temperature electrolysis. Current state of the art SOECs utilise a dense...

  12. Host immune responses to nematodes: benefit or cost? Implications for future development of sustainable methods of control Resposta imune a nematódeos: vantagem ou custo? Implicações para o desenvolvimento futuro de métodos sustentáveis de controle

    Directory of Open Access Journals (Sweden)

    Andrew R. Sykes

    2010-07-01

    Full Text Available The nutritional and production costs associated with the development of a competent immune response against nematode parasites is described, based on data from sheep. Anorexia and changes in metabolism are considered to be driven by the host immune response itself and the question is raised about the wisdom of seeking to strengthen immune responses by genetic selection. Several phases of the immune response are identified with different implications for loss of productivity and opportunity for moderation of immune responses and production losses by nutrition. Many animals are able to manage nematode infections with little loss of productivity. In an era when attempts are being made to reduce anthelmintic use and create refugia to reduce the rate of development of drench resistance, treatments based on individual animal performance relative to production targets set by assessment of the prevailing nutritional environment will become more common. These developments, have already occurred in relation to the haematophagic nematodes, for example the "Famacha" technique. Computer-aided weighing and drafting has potential for use with the less pathogenic nematodes prevalent in temperate regions though we need to know more about the pathophysiology and nutritional costs of infections with Nematodirus spp.Os custos nutricionais e de produção associados ao desenvolvimento de uma resposta imune competente contra parasitas nematódeos estão descritos nesta revisão, com base em dados com ovinos. Anorexia e mudanças no metabolismo são consideradas o resultado da própria resposta imune do hospedeiro, e a questão é levantada quando se busca o fortalecimento da resposta imune pela seleção genética. Várias fases da resposta imune são identificadas com diferentes implicações, pela perda de produtividade e oportunidade para moderação da resposta imune e pela perda da produção pela nutrição. Muitos animais são capazes de lidar com as infec

  13. Methodological adaptation for nematodes extration in forest soils of the southern Mata Atlântica Adaptação metodológica para extração de nematódeos em solos florestais da Mata Atlântica do Sul do Brasil

    Directory of Open Access Journals (Sweden)

    Thomas Moser

    2009-08-01

    Full Text Available The objective of this work was to clarify whether the method to extract nematodes from European soils is suitable for forest soils and litter in the eastern of Paraná state, Brazil, and whether nematode abundance differs between sites with different ecosystems and levels of human interference. The study sites were situated in the coastal area of the Serra do Mar, near the town of Antonina, in Eastern Paraná, Brazil. Cobb's sieving and decanting method was more appropriate than ISO method, since extraction efficiency was higher and intra-sample variability was significantly lower. In order to achieve an extraction efficiency higher than 90%, Cobb's method was modified. For the extraction of nematodes from litter, the Baermann funnel, with an extraction time of 48 hours, yielded an extraction efficiency higher than 90%. Nematode abundance in litter was higher than in soil. The mean number of individuals extracted from the litter increased with the age stage of the forest sites sampled, and there was no difference in the number of individuals in the soil of the four forest sites. Mean nematode abundance in soil in banana plantations was about twice as high compared to the banana-palmito mixed stands and to the forest sites.O objetivo deste trabalho foi verificar se o método de extração de nematódeos, aplicado em solos europeus, é apropriado para solos de florestas e para serapilheira do leste do Estado do Paraná, e se a abundância de nematódeos difere entre os diversos ecossistemas e os níveis de interferência humana. Os locais estudados situam-se na área costeira da Serra do Mar, próximo do Município de Antonina, no Leste do Paraná. O método Cobb de peneiramento e decantação foi considerado mais apropriado do que o método ISO, pois a eficiência da extração foi maior, e a variabilidade intra-amostral foi significativamente menor. Para conseguir uma eficiência de extração acima de 90%, o método Cobb foi modificado. Para a

  14. Metabolismo oxidativo de neutrófilos em ovelhas naturalmente infectadas por nematódeos gastrintestinais e correlação entre nível sérico de cortisol e carga parasitária Neutrophils oxidative metabolism in sheep naturally infected by gastrointestinal nematodes and correlation between serum level of cortisol and parasitary burden

    OpenAIRE

    P.C. Ciarlini; Ciarlini,L.D.R.P.; Alencar, N.X.; Hohayagawa, A. [UNESP; Rodrigues, C.F.C.

    2002-01-01

    Estudaram-se as relações entre o metabolismo oxidativo dos neutrófilos, os níveis séricos de cortisol e a carga parasitária estimada pela contagem de ovos por grama de fezes (OPG) no final da gestação, durante a lactação e após o desmame de ovelhas naturalmente infectadas por nematódeos gastrintestinais. Utilizaram-se 22 ovelhas da raça Suffolk, homogêneas quanto à idade (três a quatro anos), número de parições (terceira) e época de parição. O cortisol sérico foi determinado por radioimunoens...

  15. High Temperature QCD

    CERN Document Server

    Lombardo, M P

    2012-01-01

    I review recent results on QCD at high temperature on a lattice. Steady progress with staggered fermions and Wilson type fermions allow a quantitative description of hot QCD whose accuracy in many cases parallels that of zero temperature studies. Simulations with chiral quarks are coming of age, and togheter with theoretical developments trigger interesting developments in the analysis of the critical region. Issues related with the universality class of the chiral transition and the fate of the axial symmetry are discussed in the light of new numerical and analytical results. Transport coefficients and analysis of bottomonium spectra compare well with results of heavy ion collisions at RHIC and LHC. Model field theories, lattice simulations and high temperature systematic expansions help building a coherent picture of the high temperature phase of QCD. The (strongly coupled) Quark Gluon Plasma is heavily investigated, and asserts its role as an inspiring theoretical laboratory.

  16. QUARKONIUM AT FINITE TEMPERATURE.

    Energy Technology Data Exchange (ETDEWEB)

    PETRECZKY,P.

    2003-07-21

    The author discusses quarkonium spectral functions at finite temperature reconstructed using the Maximum Entropy Method. The author shows in particular that the J/{psi} survives in the deconfined phase up to 1.5T{sub c}.

  17. Surface Temperature Data Analysis

    Science.gov (United States)

    Hansen, James; Ruedy, Reto

    2012-01-01

    Small global mean temperature changes may have significant to disastrous consequences for the Earth's climate if they persist for an extended period. Obtaining global means from local weather reports is hampered by the uneven spatial distribution of the reliably reporting weather stations. Methods had to be developed that minimize as far as possible the impact of that situation. This software is a method of combining temperature data of individual stations to obtain a global mean trend, overcoming/estimating the uncertainty introduced by the spatial and temporal gaps in the available data. Useful estimates were obtained by the introduction of a special grid, subdividing the Earth's surface into 8,000 equal-area boxes, using the existing data to create virtual stations at the center of each of these boxes, and combining temperature anomalies (after assessing the radius of high correlation) rather than temperatures.

  18. Anisotropic Unruh temperatures

    Science.gov (United States)

    Arias, Raúl E.; Casini, Horacio; Huerta, Marina; Pontello, Diego

    2017-11-01

    The relative entropy between very high-energy localized excitations and the vacuum, where both states are reduced to a spatial region, gives place to a precise definition of a local temperature produced by vacuum entanglement across the boundary. This generalizes the Unruh temperature of the Rindler wedge to arbitrary regions. The local temperatures can be read off from the short distance leading have a universal geometric expression that follows by solving a particular eikonal type equation in Euclidean space. This equation generalizes to any dimension the holomorphic property that holds in two dimensions. For regions of arbitrary shapes the local temperatures at a point are direction dependent. We compute their explicit expression for the geometry of a wall or strip.

  19. Sediment Temperature, 2015

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data table contains summary data for temperature time series in near-surface sediments in high and low tidal marsh at 7 sites during 2015. These data support...

  20. Temperatures of exploding nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Serfling, V.; Schwarz, C.; Begemann-Blaich, M.; Fritz, S.; Gross, C.; Kleinevoss, U.; Kunze, W.D; Lynen, U.; Mahi, M.; Mueller, W.F.J.; Odeh, T.; Schnittker, M.; Trautmann, W.; Woerner, A.; Xi, H. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Bassini, R.; Iori, I.; Moroni, A.; Petruzzelli, F. [Milan Univ. (Italy). Ist. di Scienze Fisiche]|[Istituto Nazionale di Fisica Nucleare, Milan (Italy); Gaff, S.J.; Kunde, G.J. [Michigan State Univ., East Lansing, MI (United States). Dept. of Physics and Astronomy]|[Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab.; Imme, G.; Maddalena, V.; Nociforo, C.; Raciti, G.; Riccobene, G.; Romano, F.P.; Saija, A.; Sfienti, C.; Verde, G. [Catania Univ. (Italy). Dipt. di Fisica]|[Istituto Nazionale di Fisica Nucleare, Catania (Italy); Moehlenkamp, T.; Seidel, W. [Forschungszentrum Rossendorf e.V. (FZR), Dresden (Germany); Ocker, B.; Schuettauf, A. [Frankfurt Univ. (Germany). Inst. fuer Kernphysik; Pochodzalla, J. [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Trzcinski, A.; Zwieglinski, B. [Soltan Inst. for Nuclear Studies, Warsaw (Poland)

    1998-01-01

    Breakup temperatures in central collisions of {sup 197}Au+{sup 197}Au at bombarding energies E/A=50 to 200 MeV were determined with two methods. Isotope temperatures, deduced from double ratios of hydrogen, helium, and lithium isotopic yields, increase monotonically with bombarding energy from 5 MeV to 12 MeV, in qualitative agreement with a scenario of chemical freeze-out after adiabatic expansion. Excited-state temperatures, derived from yield ratios of states in {sup 4}He, {sup 5,6}Li, and {sup 8}Be, are about 5 MeV, independent of the projectile energy, and seem to reflect the internal temperature of fragments at their final separation from the system. (orig.)

  1. High temperature battery. Hochtemperaturbatterie

    Energy Technology Data Exchange (ETDEWEB)

    Bulling, M.

    1992-06-04

    To prevent heat losses of a high temperature battery, it is proposed to make the incoming current leads in the area of their penetration through the double-walled insulating housing as thermal throttle, particularly spiral ones.

  2. Confinement at Finite Temperature

    Science.gov (United States)

    Cardoso, Nuno; Bicudo, Pedro; Cardoso, Marco

    2017-05-01

    We show the flux tubes produced by static quark-antiquark, quark-quark and quark-gluon charges at finite temperature. The sources are placed on the lattice with fundamental and adjoint Polyakov loops. We compute the squared strengths of the chromomagnetic and chromoelectric fields above and below the critical temperature. Our results are for pure gauge SU(3) gauge theory, they are invariant and all computations are done with GPUs using CUDA.

  3. Portable Body Temperature Conditioner

    Science.gov (United States)

    2014-12-01

    patients become hypothermic after severe injury due to environmental exposure during transport. These patients also have decreased thermoregulation due to...based on the load demand to conserve power consumption 4 Requires glycol solution to prevent H20 freezing at cold ambient temperatures 3. Product...three days. To encompass the range of the temperature to be used during the Patient Simulation testing (15oC – 40oC); cold (15oC), neutral (25oC

  4. Temperature in the throat

    Directory of Open Access Journals (Sweden)

    Dariush Kaviani

    2016-09-01

    Full Text Available We study the temperature of extended objects in string theory. Rotating probe D-branes admit horizons and temperatures a la Unruh effect. We find that the induced metrics on slow rotating probe D1-branes in holographic string solutions including warped Calabi–Yau throats have distinct thermal horizons with characteristic Hawking temperatures even if there is no black hole in the bulk Calabi–Yau. Taking the UV/IR limits of the solution, we show that the world volume black hole nucleation depends on the deformation and the warping of the throat. We find that world volume horizons and temperatures of expected features form not in the regular confining IR region but in the singular nonconfining UV solution. In the conformal limit of the UV, we find horizons and temperatures similar to those on rotating probes in the AdS throat found in the literature. In this case, we also find that activating a background gauge field form the U(1 R-symmetry modifies the induced metric with its temperature describing two different classes of black hole solutions.

  5. Temperature in the throat

    Science.gov (United States)

    Kaviani, Dariush; Mosaffa, Amir Esmaeil

    2016-09-01

    We study the temperature of extended objects in string theory. Rotating probe D-branes admit horizons and temperatures a la Unruh effect. We find that the induced metrics on slow rotating probe D1-branes in holographic string solutions including warped Calabi-Yau throats have distinct thermal horizons with characteristic Hawking temperatures even if there is no black hole in the bulk Calabi-Yau. Taking the UV/IR limits of the solution, we show that the world volume black hole nucleation depends on the deformation and the warping of the throat. We find that world volume horizons and temperatures of expected features form not in the regular confining IR region but in the singular nonconfining UV solution. In the conformal limit of the UV, we find horizons and temperatures similar to those on rotating probes in the AdS throat found in the literature. In this case, we also find that activating a background gauge field form the U (1) R-symmetry modifies the induced metric with its temperature describing two different classes of black hole solutions.

  6. Atividade predatória dos fungos nematófagos Duddingtonia flagrans, Monacrosporium thaumasium e Artrobotrys robusta sobre larvas infectantes de Strongyloides stercoralis Predatory activity of the nematophagous fungi Duddingtonia flagrans, Monacrosporium thaumasium and Arthrobotrys robusta on Strongyloides stercoralis infective larvae

    Directory of Open Access Journals (Sweden)

    Fabio Ribeiro Braga

    2010-10-01

    Full Text Available INTRODUÇÃO: Strongyloides stercoralis é um nematoide que infecta grande parte da população mundial. MÉTODOS: O objetivo deste trabalho foi comparar a capacidade predatória dos fungos nematófagos Duddingtonia flagrans (AC001, Monacrosporium thaumasium (NF34 e Arthrobotrys robusta (I-31 sobre larvas infectantes (L3 de Strongyloides stercoralis em condições laboratoriais no meio ágar-água 2%. RESULTADOS: Ao final do experimento, os percentuais de redução de L3 de Strongyloides stercoralis observados foram de: 83,7% (AC001; 75,5% (NF34 e 73,2% (I-31. CONCLUSÕES: Os fungos nematófagos foram capazes de capturar e destruir in vitro as L3, podendo ser utilizados como controladores biológicos de Strongyloides stercoralis.INTRODUCTION: Strongyloides stercoralis is a nematode that infects much of the population worldwide. METHODS: This study aimed to compare the ability of predatory nematophagous fungi Duddingtonia flagrans (AC001, Monacrosporium thaumasium (NF34 and Arthrobotrys robusta (I-31 on infective larvae (L3 of Strongyloides stercoralis in laboratory conditions on 2% water-agar. RESULTS: At the end of the experiment, the percentage reductions in Strongyloides stercoralis L3 were 83.7% (AC001, 75.5% (NF34 and 73.2% (I-31. CONCLUSIONS: The nematophagous fungi were able to capture and destroy the L3 in vitro and may be used as biological controls of Strongyloides stercoralis.

  7. Compatibility of entomopathogenic nematodes and aqueous plant extracts aiming at the control of fruit fly Ceratitis capitata (Wiedemann (Diptera: TephritidaeCompatibilidade de nematóides entomopatogênicos e extratos vegetais aquosos visando o controle da mosca-das-frutas Ceratitis capitata (Wiedemann (Diptera: Tephritidae

    Directory of Open Access Journals (Sweden)

    Cristhiane Rohde

    2013-06-01

    vezes, tem sido ineficiente, devido ao desenvolvimento de populações de insetos resistentes. Assim, tem surgido a necessidade de pesquisas com novas formas de controle eficazes e menos impactantes. Nesse sentido, a utilização de nematóides entomopatogênicos e extratos vegetais tem se mostrado eficiente para o controle dessa praga. No entanto, são necessários estudos para avaliar a compatibilidade entre esses métodos, visando o seu uso, em programas de manejo integrado, para essa praga. O objetivo desse trabalho foi avaliar a compatibilidade dos nematóides Steinernema carpocapsae ALL e Heterorhabditis sp. JPM4 com os extratos aquosos, preparados com vegetais secos da folha, ramo e fruto de cinamomo (Melia azedarach, folha de arruda (Ruta graveolens, gengibre (Zingiber officinales e alho (Allium sativum visando o controle de C. capitata. O bioensaio foi conduzido em delineamento inteiramente casualizado, com quatro repetições, por tratamento. Cada repetição foi constituída de um tubo de vidro, contendo 1 mL de extrato vegetal, 40% p/v e 1 mL de suspensão de nematóide entomopatogênico, com 1800 JI/mL, para S. carpocapsae ALL e 600 JI/mL, para Heterorhabditis sp. JPM4. Foi avaliada a viabilidade dos nematóides e a infectividade desses sobre larvas de C. capitata, após 48 e 120 horas. Verificou-se que todos os extratos reduziram a viabilidade e a infectividade de ambos os nematóides, sendo incompatíveis, após 120 horas de exposição. O nematóide Heterorhabditis sp. JPM4 foi mais sensível em relação ao S. carpocapsae ALL, pois apresentou, nas primeiras 48 horas redução na viabilidade e infectividade superior a 80 e 75%, respectivamente, quando exposto a todos os extratos, exceto o de gengibre.

  8. Measuring Nematic Susceptibilities from the Elastoresistivity Tensor

    Science.gov (United States)

    Hristov, A. T.; Shapiro, M. C.; Hlobil, Patrick; Maharaj, Akash; Chu, Jiun-Haw; Fisher, Ian

    The elastoresistivity tensor mijkl relates changes in resistivity to the strain on a material. As a fourth-rank tensor, it contains considerably more information about the material than the simpler (second-rank) resistivity tensor; in particular, certain elastoresistivity coefficients can be related to thermodynamic susceptibilities and serve as a direct probe of symmetry breaking at a phase transition. The aim of this talk is twofold. First, we enumerate how symmetry both constrains the structure of the elastoresistivity tensor into an easy-to-understand form and connects tensor elements to thermodynamic susceptibilities. In the process, we generalize previous studies of elastoresistivity to include the effects of magnetic field. Second, we describe an approach to measuring quantities in the elastoresistivity tensor with a novel transverse measurement, which is immune to relative strain offsets. These techniques are then applied to BaFe2As2 in a proof of principle measurement. This work is supported by the Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under Contract DE-AC02-76SF00515.

  9. Temperature measurement: Thermocouples

    Science.gov (United States)

    1982-11-01

    This Data Item is available as part of the ESDU Sub-series on Heat Transfer. Background information and practical guidance on designing temperature measuring systems using thermocouples is provided. The nominal temperature range covered is -200 degrees C to 2000 degrees C but the comments apply, in general terms, to all thermocouple systems. The information is aimed at the user who wishes to design and install a practical thermocouple system using improved techniques that will allow temperatures to be measured within known tolerances. The selection, preparation, and installation of thermocouples, the use of compensating or extension cables, methods of referencing to a known temperature and measurement system are considered. The requirements for reliable systems operating to commercial tolerances are also described. Various factors that might impair the accuracy and stability of thermocouples are identified together with methods of reducing their effect. A check list for the design of a thermocouple system is given and a flow chart procedure for selecting appropriate thermocouple materials is provided as well. The employment of the techniques described will ensure that the temperature of the measuring junction is within known tolerances.

  10. Temperature Data Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Gillespie, David

    2003-03-01

    Groundwater temperature is sensitive to the competing processes of heat flow from below the advective transport of heat by groundwater flow. Because groundwater temperature is sensitive to conductive and advective processes, groundwater temperature may be utilized as a tracer to further constrain the uncertainty of predictions of advective radionuclide transport models constructed for the Nevada Test Site (NTS). Since heat transport, geochemical, and hydrologic models for a given area must all be consistent, uncertainty can be reduced by devaluing the weight of those models that do not match estimated heat flow. The objective of this study was to identify the quantity and quality of available heat flow data at the NTS. One-hundred-forty-five temperature logs from 63 boreholes were examined. Thirteen were found to have temperature profiles suitable for the determination of heat flow values from one or more intervals within the boreholes. If sufficient spatially distributed heat flow values are obtained, a heat transport model coupled to a hydrologic model may be used to reduce the uncertainty of a nonisothermal hydrologic model of the NTS.

  11. DETERMINING SURFACE TEMPERATURE AND CLOUD TEMPERATURE FROM METEOROLOGICAL EARTH SATELLITES,

    Science.gov (United States)

    ATMOSPHERIC TEMPERATURE, *METEOROLOGICAL SATELLITES), SURFACE TEMPERATURE , CLOUDS, BLACKBODY RADIATION, PERIODIC VARIATIONS, INTEGRALS, BOUNDARY LAYER, INTENSITY, ERRORS, CORRECTIONS, FUNCTIONS(MATHEMATICS), USSR

  12. Elevated temperature deformation analysis

    Science.gov (United States)

    Nelson, J. M.

    The paper demonstrates a novel nondestructive test and data analysis technique for quantitative measurement of circumferentially varying flexural moduli of 2D involute carbon-carbon tag rings containing localized wrinkles and dry plies at room and rocket nozzle operating temperatures. Room temperature computed tomography (CT) deformation tests were performed on 11 carbon-carbon rings selected from the cylinders and cones fabricated under the NDE data application program and two plexiglass rings fabricated under this program. This testing and analysis technique is found to have primary application in validation of analytical models for carbon-carbon performance modeling. Both effects of defects assumptions, the effects of high temperature environments, and failure-related models can be validated effectively. The testing and analysis process can be interwoven in a manner that increases the engineering understanding of the material behavior and permits rapid resolution of analysis questions. Specific recommendations for the development and implementation of this technique are provided.

  13. Do `negative' temperatures exist?

    Science.gov (United States)

    Lavenda, B. H.

    1999-06-01

    A modification of the second law is required for a system with a bounded density of states and not the introduction of a `negative' temperature scale. The ascending and descending branches of the entropy versus energy curve describe particle and hole states, having thermal equations of state that are given by the Fermi and logistic distributions, respectively. Conservation of energy requires isentropic states to be isothermal. The effect of adiabatically reversing the field is entirely mechanical because the only difference between the two states is their energies. The laws of large and small numbers, leading to the normal and Poisson approximations, characterize statistically the states of infinite and zero temperatures, respectively. Since the heat capacity also vanishes in the state of maximum disorder, the third law can be generalized in systems with a bounded density of states: the entropy tends to a constant as the temperature tends to either zero or infinity.

  14. Temperature-reflection I

    DEFF Research Database (Denmark)

    McGady, David A.

    2017-01-01

    -temperature path integrals for quantum field theories (QFTs) should be T-reflection invariant. Because multi-particle partition functions are equal to Euclidean path integrals for QFTs, we expect them to be T-reflection invariant. Single-particle partition functions though are often not invariant under T......In this paper, we revisit the claim that many partition functions are invariant under reflecting temperatures to negative values (T-reflection). The goal of this paper is to demarcate which partition functions should be invariant under T-reflection, and why. Our main claim is that finite...... that T-reflection is unrelated to time-reversal. Finally, we study the interplay between T-reflection and perturbation theory in the anharmonic harmonic oscillator in quantum mechanics and in Yang-Mills in four-dimensions. This is the first in a series of papers on temperature-reflections....

  15. Fiber optic temperature sensor

    Science.gov (United States)

    Sawatari, Takeo (Inventor); Gaubis, Philip A. (Inventor)

    2000-01-01

    A fiber optic temperature sensor uses a light source which transmits light through an optical fiber to a sensor head at the opposite end of the optical fiber from the light source. The sensor head has a housing coupled to the end of the optical fiber. A metallic reflective surface is coupled to the housing adjacent the end of the optical fiber to form a gap having a predetermined length between the reflective surface and the optical fiber. A detection system is also coupled to the optical fiber which determines the temperature at the sensor head from an interference pattern of light which is reflected from the reflective surface.

  16. Fluorescent temperature sensor

    Science.gov (United States)

    Baker, Gary A [Los Alamos, NM; Baker, Sheila N [Los Alamos, NM; McCleskey, T Mark [Los Alamos, NM

    2009-03-03

    The present invention is a fluorescent temperature sensor or optical thermometer. The sensor includes a solution of 1,3-bis(1-pyrenyl)propane within a 1-butyl-1-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid solvent. The 1,3-bis(1-pyrenyl)propane remains unassociated when in the ground state while in solution. When subjected to UV light, an excited state is produced that exists in equilibrium with an excimer. The position of the equilibrium between the two excited states is temperature dependent.

  17. High-temperature phase transitions and domain structures of KLiSO{sub 4}. Studied by polarisation-optics, X-ray topography and liquid-crystal surface decoration

    Energy Technology Data Exchange (ETDEWEB)

    Scherf, Christian; Chung, Su Jin; Hahn, Theo; Klapper, Helmut [RWTH Aachen Univ. (Germany). Inst. fuer Kristallographie; Ivanov, Nicolay R. [Russian Academy of Sciences, Moscow (Russian Federation). Shubnikov Inst. of Crystallography

    2017-07-01

    The transitions between the room temperature phase III (space group P6{sub 3}) and the two high-temperature phases II (Pcmn) and I (P6{sub 3}/mmc) of KLiSO{sub 4} and the domain structures generated by them were investigated by high-temperature polarisation optics (birefringence) and room-temperature X-ray topography, optical activity and nematic-liquid-crystal (NLC) surface decoration. The transition from the polar hexagonal phase III into the centrosymmetric orthorhombic phase II at 708 K leads, due to the loss of the trigonal axis and the radial temperature gradient of the optical heating chamber used, to a roughly hexagonal arrangement of three sets of thin orthorhombic {110} lamelleae with angles of 60 (120 ) between them. The associated twin law ''reflection m{110}{sub orth}'' corresponds to the frequent growth twin m{10 anti 10}{sub hex} of phase III. The domains are easily ferroelastically switched. Upon further heating above 949 K into phase I (P6{sub 3}/mmc) all domains vanish. Upon cooling back into phase II the three domain states related by 60 (120 ) reflections m{110}{sub orth} re-appear, however (due to the higher thermal agitation at 949 K) with a completely different domain structure consisting of many small, irregularly arranged {110}{sub orth} domains. Particular attention is paid to the domain structure of the hexagonal room temperature phase III generated during the re-transition from the orthorhombic phase II. Curiously, from the expected three twin laws inversion anti 1, rotation 2 perpendicular to [001]{sub hex} and reflection m{10 anti 10}{sub hex} only the latter, which corresponds to the frequent growth twinning, has been found. Finally a short treatise of the structural relations of the KLiSO{sub 4} high-temperature polymorphs is given.

  18. Nimbus-7 SMMR Antenna Temperatures

    Data.gov (United States)

    National Aeronautics and Space Administration — The SMMR Antenna Temperatures (Nimbus-7) data set consists of antenna temperatures from passive microwave radiometers aboard NOAA's Nimbus-7 satellite. The...

  19. TEMPERATURE INDEPENDENT PHOTOLUMINESCENCE ...

    Indian Academy of Sciences (India)

    8

    [1] C.A.K. Gouvˆea, F. Wypych, S.G. Moraes, N. Dur´an, P. Peralta-Zamora, Semiconductor- assisted photocatalytic degradation of reactive dyes in aqueous solution, Chemosphere. 427(2000) 40. [2] D.C Look, Equation of state for the study of temperature dependence of volume thermal expansion of nanomaterials, Mater.

  20. Life at High Temperatures

    Indian Academy of Sciences (India)

    2005-09-15

    Sep 15, 2005 ... or more in the vicinity of geothermal vents in the deep sea and the plant Tidestromia oblongifolia (Amaranthaceae) found in Death. Valley in California, where the hottest temperature on earth ever recorded during 43 consecutive days in 1917 was >48 °C. (Guinness Book of W orId Records, 1999).

  1. High temperature superconducting materials

    Energy Technology Data Exchange (ETDEWEB)

    Alario-Franco, M.A. [Universidad Complutense de Madrid (Spain). Facultad de Ciencias Quimicas

    1995-02-01

    The perovskite structure is the basis of all known high-temperature superconducting materials. Many of the most successful (highest T{sub c}) materials are based on mercury and thallium phases but, due to the high toxicity of the component compounds effort has been invested in the substitution of these elements with silver. Progress is reviewed. (orig.)

  2. Measuring Temperature: The Thermometer

    Science.gov (United States)

    Chamoun, Mirvette

    2005-01-01

    The author discusses the historical development of the thermometer with the view of helping children understand the role that mathematics plays in society. A model thermometer that is divided into three sections, each displaying one of the three temperature scales used today (Fahrenheit, Celsius and Kelvin) is highlighted as a project to allow…

  3. High-temperature superconductors

    CERN Document Server

    Saxena, Ajay Kumar

    2010-01-01

    The present book aims at describing the phenomenon of superconductivity and high-temperature superconductors discovered by Bednorz and Muller in 1986. The book covers the superconductivity phenomenon, structure of high-Tc superconductors, critical currents, synthesis routes for high Tc materials, superconductivity in cuprates, the proximity effect and SQUIDs, theories of superconductivity and applications of superconductors.

  4. High temperature superconductivity: Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Bedell, K.S.; Coffey, D. (Los Alamos National Lab., NM (USA)); Meltzer, D.E. (Florida Univ., Gainesville, FL (USA)); Pines, D. (Illinois Univ., Urbana, IL (USA)); Schrieffer, J.R. (California Univ., Santa Barbara, CA (USA)) (eds.)

    1990-01-01

    This book is the result of a symposium at Los Alamos in 1989 on High Temperature Superconductivity. The topics covered include: phenomenology, quantum spin liquids, spin space fluctuations in the insulating and metallic phases, normal state properties, and numerical studies and simulations. (JF)

  5. Low Temperature Plasma Medicine

    Science.gov (United States)

    Graves, David

    2013-10-01

    Ionized gas plasmas near room temperature are used in a remarkable number of technological applications mainly because they are extraordinarily efficient at exploiting electrical power for useful chemical and material transformations near room temperature. In this tutorial address, I will focus on the newest area of low temperature ionized gas plasmas (LTP), in this case operating under atmospheric pressure conditions, in which the temperature-sensitive material is living tissue. LTP research directed towards biomedical applications such as sterilization, surgery, wound healing and anti-cancer therapy has seen remarkable growth in the last 3-5 years, but the mechanisms responsible for the biomedical effects have remained mysterious. It is known that LTP readily create reactive oxygen species (ROS) and reactive nitrogen species (RNS). ROS and RNS (or RONS), in addition to a suite of other radical and non-radical reactive species, are essential actors in an important sub-field of aerobic biology termed ``redox'' (or oxidation-reduction) biology. I will review the evidence suggesting that RONS generated by plasmas are responsible for their observed therapeutic effects. Other possible bio-active mechanisms include electric fields, charges and photons. It is common in LTP applications that synergies between different mechanisms can play a role and I will review the evidence for synergies in plasma biomedicine. Finally, I will address the challenges and opportunities for plasma physicists to enter this novel, multidisciplinary field.

  6. Temperature responsive cooling apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Weker, M.L.; Stearns, R.M.

    1987-08-11

    A temperature responsive cooling apparatus is described for an air conditioner or refrigeration system in operative association with a reservoir of fluid, the air conditioner or refrigeration system having an air cooled coil and means for producing a current of air for cooling the coil, the temperature responsive cooling apparatus comprising: (a) means for transferring the fluid from the reservoir to the air conditioner temperature responsive cooling apparatus, (b) a fluid control device activated by the current of air for cooling the coil; (c) a temperature activated, nonelectrical device for terminating and initiating the flow of fluid therethrough in an intermittent fashion for enhancing the operability of the compressor associated with the refrigeration system and for reducing the quantity of fluid required to cool the coil of the refrigeration system, (d) a fluid treatment device for preventing, reducing or mitigating the deposition of nonevaporative components on the air cooled coil, and (e) means for dispersing the fluid to the air cooled coil from the fluid control device for cooling the coil and increasing the efficiency of the air conditioner thereby reducing the cost of operating and maintaining the air conditioner without damaging the air conditioner and without the deposition of nonevaporative components thereupon.

  7. Fast Air Temperature Sensors

    DEFF Research Database (Denmark)

    Hendricks, Elbert

    1998-01-01

    The note documents briefly work done on a newly developed sensor for making fast temperature measurements on the air flow in the intake ports of an SI engine and in the EGR input line. The work reviewed has been carried out in close cooperation with Civ. Ing. Michael Føns, the author (IAU...

  8. Life at High Temperatures

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 9. Life at High Temperatures. Ramesh Maheshwari. General Article Volume 10 Issue 9 September 2005 pp 23-36. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/010/09/0023-0036. Keywords.

  9. High temperature storage loop :

    Energy Technology Data Exchange (ETDEWEB)

    Gill, David Dennis; Kolb, William J.

    2013-07-01

    A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650ÀC) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOEs SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort

  10. Temperature differential detection device

    Science.gov (United States)

    Girling, P.M.

    1986-04-22

    A temperature differential detection device for detecting the temperature differential between predetermined portions of a container wall is disclosed as comprising a Wheatstone bridge circuit for detecting resistance imbalance with a first circuit branch having a first elongated wire element mounted in thermal contact with a predetermined portion of the container wall, a second circuit branch having a second elongated wire element mounted in thermal contact with a second predetermined portion of a container wall with the wire elements having a predetermined temperature-resistant coefficient, an indicator interconnected between the first and second branches remote from the container wall for detecting and indicating resistance imbalance between the first and second wire elements, and connector leads for electrically connecting the wire elements to the remote indicator in order to maintain the respective resistance value relationship between the first and second wire elements. The indicator is calibrated to indicate the detected resistance imbalance in terms of a temperature differential between the first and second wall portions. 2 figs.

  11. Temperature crossovers in cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Chubukov, Andrey V. [Department of Physics, University of Wisconsin, Madison, WI (United States); Pines, David; Stojkovic, Branko P. [Department of Physics, University of Illinois, Urbana, IL (United States)

    1996-11-25

    We study the temperature crossovers seen in the magnetic and transport properties of cuprates using a nearly antiferromagnetic Fermi-liquid model (NAFLM). We distinguish between underdoped and overdoped systems on the basis of their low-frequency magnetic behaviour and so classify the optimally doped cuprates as a special case of the underdoped cuprates. For the overdoped cuprates, we find, in agreement with earlier work, mean-field z=2 behaviour of the magnetic variables associated with the fact that the damping rate of their spin fluctuations is essentially independent of temperature, while the resistivity exhibits a crossover from Fermi-liquid behaviour at low temperature to linear-in-T behaviour above a certain temperature T{sub o}. We demonstrate that above T{sub o} the proximity of the quasiparticle Fermi surface to the magnetic Brillouin zone boundary brings about the measured linear-in-T resistivity. For the underdoped cuprates we argue that the sequence of crossovers identified by Barzykin and Pines in the low-frequency magnetic behaviour (from mean-field z=2 behaviour at high temperatures, T>T{sub cr}, to non-universal z=1 scaling behaviour at intermediate temperatures, T{sub *}temperature-dependent spin damping and ends at T{sub *} where the Fermi surface has lost pieces near corners of the magnetic Brillouin zone. For T{sub *}

  12. Couleurs, etoiles, temperatures.

    Science.gov (United States)

    Spite, F.

    The eye is able to distinguish very tiny color differences of contiguous objects (at high light level, cones vision), but it is not a reliable colorimeter. Hot objects (a heated iron rod) emits some red light, a hotter object would provide a yellow-orange light (the filament of a bulb) and a still hotter one a white or even bluish light : this may be at reverse of common life codes, where "red" means hot water and/or danger, and "blue" cool water or cool air. Stars are a good illustration of the link between temperatures and colors. A heated iron rod has a temperature of about 800 K. Let us recall that K is a temperature unit (Kelvin) such that the Kelvin temperature is the Celsius temperature +273).The so called red stars (or cool stars) have temperature around 3000 K, higher than "white-hot iron". The Sun has a still higher temperature (5800 K) and its color is white : the solar light is by definition the "white light", and includes violet, blue, green, yellow, orange and red colors in balanced proportions (the maximum in the yellow-green). It is often said that the Sun is a yellow star. Admittedly, a brief glimpse at the Sun (take care ! never more than a VERY brief glimpse !) provides a perception of yellow light, but such a vision, with the eye overwhelmed by a fierce light, is not able to provide a good evaluation of the solar color : prefer a white sheet of paper illuminated by the Sun at noon and conclude that "the Sun is a white star". It is sometimes asked why red, white and bluish stars are seen in the sky, but no green stars : the solar light has its maximum intensity in the green, but such a dominant green light, equilibrated by some blue and some red light, is what we call "white", so that stars similar to the Sun, with a maximum in the green, are seen as white stars. Faint stars (rods vision of the eye) are also seen as white stars. Spots on the Sun (never look at the Sun ! let us say spots on "projected images of the Sun") appear as black spots

  13. Estimation of bare soil surface temperature from air temperature and ...

    African Journals Online (AJOL)

    Soil surface temperature has critical influence on climate, agricultural and hydrological activities since it serves as a good indicator of the energy budget of the earth's surface. Two empirical models for estimating soil surface temperature from air temperature and soil depth temperature were developed. The coefficient of ...

  14. High temperature materials and mechanisms

    CERN Document Server

    2014-01-01

    The use of high-temperature materials in current and future applications, including silicone materials for handling hot foods and metal alloys for developing high-speed aircraft and spacecraft systems, has generated a growing interest in high-temperature technologies. High Temperature Materials and Mechanisms explores a broad range of issues related to high-temperature materials and mechanisms that operate in harsh conditions. While some applications involve the use of materials at high temperatures, others require materials processed at high temperatures for use at room temperature. High-temperature materials must also be resistant to related causes of damage, such as oxidation and corrosion, which are accelerated with increased temperatures. This book examines high-temperature materials and mechanisms from many angles. It covers the topics of processes, materials characterization methods, and the nondestructive evaluation and health monitoring of high-temperature materials and structures. It describes the ...

  15. Temperature Measurement and Monitoring Devices

    Science.gov (United States)

    1988-08-01

    feasibility based on potential usefulness in clinical medicine ’ias explored. All information herein wasn obtained from literature rrv’iew only. No...measurements, applications for temperature measuring devices, and description of several modern body temperature monitoring devices (techniques). Finally...gynecology, drug therapy, and ophthalmology. TEMPERATURE SENSING DEVICES Hippocrates is believed to be the first person Lo associate body temperature as

  16. High Temperature Piezoelectric Drill

    Science.gov (United States)

    Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

    2012-01-01

    Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460 deg C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500 deg C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper

  17. Core Outlet Temperature Study

    Energy Technology Data Exchange (ETDEWEB)

    Moisseytsev, A. [Argonne National Laboratory (ANL), Argonne, IL (United States); Hoffman, E. [Argonne National Laboratory (ANL), Argonne, IL (United States); Majumdar, S. [Argonne National Laboratory (ANL), Argonne, IL (United States)

    2008-07-28

    It is a known fact that the power conversion plant efficiency increases with elevation of the heat addition temperature. The higher efficiency means better utilization of the available resources such that higher output in terms of electricity production can be achieved for the same size and power of the reactor core or, alternatively, a lower power core could be used to produce the same electrical output. Since any nuclear power plant, such as the Advanced Burner Reactor, is ultimately built to produce electricity, a higher electrical output is always desirable. However, the benefits of the higher efficiency and electricity production usually come at a price. Both the benefits and the disadvantages of higher reactor outlet temperatures are analyzed in this work.

  18. High temperature future

    Energy Technology Data Exchange (ETDEWEB)

    Sheinkopf, K. [Solar Energy Research and Education Foundation, Washington, DC (United States)

    1994-09-01

    During the past few years, there have been dramatic accomplishments and success of high temperature solar thermal systems and significant development of these systems. High temperature technologies, about 500 F and higher, such as dish engines, troughs, central receiver power towers and solar process heat systems, have been tested, demonstrated and used in an array of applications, including many cost-effective utility bulk power production and demand side supply projects in the United States. Large systems provide power and hot water to prisons, schools, nursing homes and other institutions. Joint ventures with industry, utility projects, laboratory design assistance and other activities are building a solid industry of US solar thermal systems ready for use today.

  19. The temperature hydration kinetics

    Directory of Open Access Journals (Sweden)

    Mircea Oroian

    2017-07-01

    Full Text Available The aim of this study is to evaluate the hydration kinetics of lentil seeds (Lens culinaris in water at different temperatures (25, 32.5, 40, 55, 70 and 80 °C for assessing the adequacy of models for describing the absorption phenomena during soaking. The diffusion coefficient values were calculated using Fick’s model for spherical and hemispherical geometries and the values were in the range of 10−6 m2/s. The experimental data were fitted to Peleg, Sigmoidal, Weibull and Exponential models. The models adequacy was determined using regression coefficients (R2, root mean square error (RMSE and reduced chi-square (χ2. The Peleg model is the suitable one for predicting the experimental data. Temperature had a positive and significant effect on the water absorption capacities and absorption was an endothermic process.

  20. Ultrahigh temperature intermetallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.; Walker, L.R. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1997-12-01

    A new family of Cr-Cr{sub 2}X based alloys with fabricability, mechanical properties, and oxidation resistance superior to previously developed Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys has been identified. The new alloys can be arc-melted/cast without cracking, and exhibit excellent room temperature and high-temperature tensile strengths. Preliminary evaluation of oxidation behavior at 1100 C in air indicates that the new Cr-Cr{sub 2}X based alloys form an adherent chromia-based scale. Under similar conditions, Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys suffer from extensive scale spallation.

  1. Fast Air Temperature Sensors

    DEFF Research Database (Denmark)

    Hendricks, Elbert

    1998-01-01

    The note documents briefly work done on a newly developed sensor for making fast temperature measurements on the air flow in the intake ports of an SI engine and in the EGR input line. The work reviewed has been carried out in close cooperation with Civ. Ing. Michael Føns, the author (IAU......) and Spencer C. Sorenson (ET). The theory which decribes in detail the overall dynamic chracteristics of the sensor was developed at IAU, DTU....

  2. Fuel Temperature Fluctuations During Storage

    Science.gov (United States)

    Levitin, R. E.; Zemenkov, Yu D.

    2016-10-01

    When oil and petroleum products are stored, their temperature significantly impacts how their properties change. The paper covers the problem of determining temperature fluctuations of hydrocarbons during storage. It provides results of the authors’ investigations of the stored product temperature variations relative to the ambient temperature. Closeness and correlation coefficients between these values are given. Temperature variations equations for oil and petroleum products stored in tanks are deduced.

  3. Crowdsourcing urban air temperatures from smartphone battery temperatures

    Science.gov (United States)

    Overeem, Aart; Robinson, James C. R.; Leijnse, Hidde; Steeneveld, Gert-Jan; Horn, Berthold K. P.; Uijlenhoet, Remko

    2014-05-01

    Accurate air temperature observations in urban areas are important for meteorology and energy demand planning. They are indispensable to study the urban heat island effect and the adverse effects of high temperatures on human health. However, the availability of temperature observations in cities is often limited. Here we show that relatively accurate air temperature information for the urban canopy layer can be obtained from an alternative, nowadays omnipresent source: smartphones. In this study, battery temperatures were collected by an Android application for smartphones. It has been shown that a straightforward heat transfer model can be employed to estimate daily mean air temperatures from smartphone battery temperatures for eight major cities around the world. The results demonstrate the enormous potential of this crowdsourcing application for real-time temperature monitoring in densely populated areas. Battery temperature data were collected by users of an Android application for cell phones (opensignal.com). The application automatically sends battery temperature data to a server for storage. In this study, battery temperatures are averaged in space and time to obtain daily averaged battery temperatures for each city separately. A regression model, which can be related to a physical model, is employed to retrieve daily air temperatures from battery temperatures. The model is calibrated with observed air temperatures from a meteorological station of an airport located in or near the city. Time series of air temperatures are obtained for each city for a period of several months, where 50% of the data is for independent verification. The methodology has been applied to Buenos Aires, London, Los Angeles, Paris, Mexico City, Moscow, Rome, and Sao Paulo. The evolution of the retrieved air temperatures often correspond well with the observed ones. The mean absolute error of daily air temperatures is less than 2 degrees Celsius, and the bias is within 1 degree

  4. Risk analysis of climate change on coffee nematodes and leaf miner in Brazil Análise de risco da mudança climática sobre nematóides e o bicho-mineiro do cafeeiro no Brasil

    Directory of Open Access Journals (Sweden)

    Raquel Ghini

    2008-02-01

    Full Text Available The objective of this work was to assess the potential impact of climate change on the spatial distribution of coffee nematodes (races of Meloidogyne incognita and leaf miner (Leucoptera coffeella, using a Geographic Information System. Assessment of the impacts of climate change on pest infestations and disease epidemics in crops is needed as a basis for revising management practices to minimize crop losses as climatic conditions shift. Future scenarios focused on the decades of the 2020's, 2050's, and 2080's (scenarios A2 and B2 were obtained from five General Circulation Models available on Data Distribution Centre from Intergovernmental Panel on Climate Change. Geographic distribution maps were prepared using models to predict the number of generations of the nematodes and leaf miner. Maps obtained in scenario A2 allowed prediction of an increased infestation of the nematode and of the pest, due to greater number of generations per month, than occurred under the climatological normal from 1961-1990. The number of generations also increased in the B2 scenario, but was lower than in the A2 scenario for both organisms.O objetivo deste trabalho foi avaliar os impactos potenciais da mudança climática sobre a distribuição espacial de nematóides (raças de Meloidogyne incognita e do bicho-mineiro (Leucoptera coffeella da cultura de café, com uso de Sistema de Informações Geográficas. O conhecimento dos impactos da mudança climática na ocorrência de pragas e doenças é de grande importância para o setor agrícola, pois permite a elaboração de estratégias para minimizar prejuízos futuros. Cenários futuros centrados nas décadas de 2020, 2050 e 2080 (cenários A2 e B2, foram obtidos a partir de cinco Modelos Climáticos Globais, disponibilizados pelo Centro de Distribuição de Dados do Painel Intergovernamental sobre Mudança do Clima. Por meio de modelos para previsão do número de gerações anuais do nematóide e do bicho

  5. Efeito anti-helmíntico dos extratos aquosos e etanólicos da Annona squamosa L. (fruta-do-conde sobre o nematóide Ascaridia galli Anthelmintic effect of aqueous and ethanolic extracts from Annona squamosa L. (sweetsop on the nematode Ascaridia galli

    Directory of Open Access Journals (Sweden)

    M.Z.L.C.M. Fernandes

    2009-01-01

    Full Text Available As plantas são fontes importantes de produtos naturais biologicamente ativos. Dentre as plantas usadas na medicina popular a Anonna squamosa conhecida como fruta-do-conde é citada como tendo várias ações medicinais, dentre elas a atividade inseticida e anti-helmíntica. Dentro desta perspectiva, objetivou-se determinar a atividade anti-helmíntica dos extratos aquosos (EA e etanólicos (EE das folhas da fruta-do-conde sobre o nematóide de aves Ascaridia galli, in vitro e in vivo. No primeiro, os nematóides foram colocados em placa de Petri contendo diferentes concentrações dos extratos e no segundo foram utilizadas seis galinhas poedeiras por grupo, as quais foram administrados10 mL Kg-1 dos extratos. No teste in vitro o EA da A. squamosa nas concentrações 2,4 e 9,6 mg mL-1 foi capaz de matar 63,33% e 53,33% dos nematóides, respectivamente. O EE não produziu efeito significativo. No teste in vivo, o percentual de eliminação do EA foi de 39% e do EE de 20%. Estes dados sugerem que neste caso a substância responsável pela mortalidade dos parasitos esteja em maior concentração na fração aquosa. Desta maneira, acredita-se que o EA de A. squamosa apresenta uma atividade anti-helmíntica potencial sobre o A. galli.Plants are important sources of biologically active natural products. Among the plants used in popular medicine, Annona squamosa, known as sweetsop, is reported to have several medicinal actions such as insecticidal and anthelmintic activity. Therefore, this study aimed to assess the anthelmintic activity of aqueous (AE and ethanolic (EE extracts from sweetsop leaves on the chicken roundworm Ascaridia galli, both in vitro and in vivo. In the former, nematodes were placed on a Petri plate containing different concentrations of the extracts; in the in vivo test, six egg-laying chickens per group received 10 mL Kg-1 of the extracts. In vitro results indicated that A. squamosa AE at the concentrations 2.4 and 9.6 mg mL-1

  6. Residential Indoor Temperature Study

    Energy Technology Data Exchange (ETDEWEB)

    Booten, Chuck [National Renewable Energy Lab. (NREL), Golden, CO (United States); Robertson, Joseph [National Renewable Energy Lab. (NREL), Golden, CO (United States); Christensen, Dane [National Renewable Energy Lab. (NREL), Golden, CO (United States); Heaney, Mike [Arrow Electronics, Centennial, CO (United States); Brown, David [Univ. of Virginia, Charlottesville, VA (United States); Norton, Paul [Norton Energy Research and Development, Boulder, CO (United States); Smith, Chris [Ingersoll-Rand Corp., Dublin (Ireland)

    2017-04-07

    In this study, we are adding to the body of knowledge around answering the question: What are good assumptions for HVAC set points in U.S. homes? We collected and analyzed indoor temperature data from US homes using funding from the U.S. Department of Energy's Building America (BA) program, due to the program's reliance on accurate energy simulation of homes. Simulations are used to set Building America goals, predict the impact of new building techniques and technologies, inform research objectives, evaluate home performance, optimize efficiency packages to meet savings goals, customize savings approaches to specific climate zones, and myriad other uses.

  7. Room Temperature Curing Polymers

    Science.gov (United States)

    1977-05-01

    UJ LU LU LU UJ LU W -Q U "O 26 -- - -■- — ■ ■- ■ MBti ^L. IIIIIIII.IHI.I|.UHI,IW’I»;I.!I"IT,U» mpwi«ŕ "^Wl be 190,000 psi which is consistent...was added to the mixture. After 1 hour benzene and water were added and the mixture was stirred until the salt was dissolved. The organic ...for 15 minutes and then cooled to room temperature. The mixture was extracted with two 100 ml portions of water. The organic layer was dried (MgS04

  8. High temperature superconductors

    CERN Document Server

    Paranthaman, Parans

    2010-01-01

    This essential reference provides the most comprehensive presentation of the state of the art in the field of high temperature superconductors. This growing field of research and applications is currently being supported by numerous governmental and industrial initiatives in the United States, Asia and Europe to overcome grid energy distribution issues. The technology is particularly intended for densely populated areas. It is now being commercialized for power-delivery devices, such as power transmission lines and cables, motors and generators. Applications in electric utilities include current limiters, long transmission lines and energy-storage devices that will help industries avoid dips in electric power.

  9. The relationship between body and ambient temperature and corneal temperature

    DEFF Research Database (Denmark)

    Kessel, Line; Johnson, Leif; Arvidsson, Henrik Sven

    2010-01-01

    Exposure to elevated ambient temperatures has been mentioned as a risk factor for common eye diseases, primarily presbyopia and cataract. The aim of the present study was to examine the relationship among ambient, cornea, and body core temperature....

  10. Evaluation of reduction in egg shedding of gastrointestinal nematodes in cattle following administration of anthelmintics Avaliação na redução de ovos de nematódeos gastrintestinais em bovinos após a administração de anti-helmínticos

    Directory of Open Access Journals (Sweden)

    Ricardo Velludo Gomes de Soutello

    2010-09-01

    Full Text Available To evaluate the necessary time and to identify the differences among anthelmintics for the reduction of parasite eggs shed in feces, five groups of cattle were treated with moxidectin, ivermectin, levamisole phosphate, and albendazole sulphoxide. Levamisole promoted a reduction in egg count per gram (EPG-R of 97.4% after 24 hours, moxidectin 98.3% after 36 hours, and albendazole sulphoxide 95.9% after 36 hours post- treatment. Cooperia spp. and Haemonchus spp. showed resistance to ivermectin. The results demonstrated that the diagnosis of parasite resistance in cattle can be based on a count of eggs per gram (EPG carried out as soon as seven days after the treatment.No intuito de avaliar o tempo necessário para redução dos valores de OPG visando identificar o início de atuação dos anti-helmínticos, cinco grupos de novilhos, naturalmente infectados por nematódeos gastrintestinais foram tratados com moxidectina, ivermectina, fosfato de levamisol e sulfóxido de albendazol. O levamisol promoveu redução no número de ovos de nematódeos eliminados nas fezes (R-OPG de 97,4% 24 horas após a aplicação, a moxidectina de 98,3% após 36 horas, e o sulfóxido de albendazol de 95,9% após 36 horas. Foi registrada a presença de Cooperia spp. e Haemonchus spp. com resistência a ivermectina. A contagem de OPG realizada aos sete dias pós-tratamento apresentou resultados similares aos obtidos nas contagens realizadas 10 e 14 dias após a aplicação dos anti-helmínticos avaliados, demonstrando que o intervalo adequado entre o tratamento anti-helmíntico e o exame para verificar a redução do OPG pode ser de 7 dias.

  11. Nematódeos resistentes a anti-helmíntico em rebanhos de ovinos e caprinos do estado do Ceará, Brasil Nematodes resistant to anthelmintics in sheep and goat flock in the State of Ceará, Brazil

    Directory of Open Access Journals (Sweden)

    Ana Carolina Fonseca Lindoso Melo

    2003-04-01

    Full Text Available O controle do parasitismo por nematódeos gastrintestinais é feito basicamente com a utilização de anti-helmínticos. Falhas no controle são o primeiro sinal do aparecimento de resistência anti-helmíntica. A real situação da prevalência da resistência anti-helmíntica, em fazendas comerciais de criação de ovinos e caprinos no Brasil, é desconhecida. Esse experimento teve como objetivo, estimar a ocorrência de resistência ao oxfendazol, levamisol e ivermectina em propriedades comerciais de criação de ovinos e caprinos, na região do médio e baixo Jaguaribe, através do teste de redução na contagem de ovos nas fezes acompanhados de coproculturas. O trabalho foi realizado em 25 criações, sendo 16 de ovinos, 7 de caprinos e uma de ovinos e caprinos. Os dados obtidos foram analisados pelo programa estatístico RESO (1989. A prevalência de nematódeos resistentes ao oxfendazol, levamisol e ivermectina em ovinos foi de 88%, 41% e 59%, e em caprinos de 87,5%, 75% e 37,5%, respectivamente. Observou-se que o gênero Haemonchus foi o mais prevalente na população resistente a todos os anti-helmínticos, tanto em ovinos quanto em caprinos, seguido de Trichostrongylus e Oesophagostomum.The control of gastrointestinal nematodes parasitism is made basically with anthelmintics. Control failure is the first sign of anthelmintic resistance development. The actual situation of anthelmintic resistance prevalence in commercial farms of sheep and goats in Brazil is unknown. The aim of this work was to estimate the occurrence of oxfendazole, levamisole and ivermectin resistance in sheep and goats from medio and baixo Jaguaribe region by faecal egg count reduction followed by coprocultures. The work involved 25 farms (16 sheep farms, 7 goat farms and one of sheep and goats. Data were analysed by RESO (1989. The prevalence of resistant nematodes to oxfendazole, levamisole and ivermectin was respectively 88%, 41% and 59% in sheep and 87.5%, 75

  12. Diagnosis of first stage larvae of gastrointestinal nematodes of dairy calves in the city of Paty do Alferes-RJ/ Diagnóstico de larvas de primeiro estágio de nematóides gastrintestinais de bezerros leiteiros do município de Paty do Alferes – RJ

    Directory of Open Access Journals (Sweden)

    Argemiro Sanavria

    Full Text Available An epidemiologycal survey were carried out using the filter of Visser technique for the diagnosis of first-stage larvae (L1 of gastrointestinal nematodes in faecal samples from 150 dairy calves in Paty do Alferes city, Rio de Janeiro state. Feces were individually collected directly of the rectal flask of 150 calves, with age varying between three and 12 months, coming from 15 rural properties in the municipal district Paty do Alferes-RJ. The following genera of nematodes were identified: Haemonchus spp, Trichostrongylus spp., Cooperia spp., Bunostomum spp., Strongyloides and Oesophagostomum spp. The genera of greater occurrence were Cooperia spp. (54%, Haemonchus spp. (50.6% and Trichostrongylus spp. (48.7%. Of the total of inspected properties, 86.7% presented positive animals for Haemonchus spp. and Trichostrongylus spp. The genera Bunostomum spp. had presented smaller occurrence, with 12,7% of cases. The genera identified with the highest medium values of first-stage larvae in 15mL of faeces were: Cooperia spp. (812 and Haemonchus spp. (489. Foi realizado um levantamento epidemiológico utilizando-se a técnica coproparasitologica do filtro de Visser para o diagnóstico de larvas de primeiro estágio (L1 de nematóides gastrintestinais em amostras fecais de 150 bezerros leiteiros do município de Paty do Alferes, estado do Rio de Janeiro. Amostras individuais de fezes foram coletadas diretamente da ampola retal de 150 bezerros, com idade variando entre três e 12 meses, procedentes de 15 propriedades rurais no município de Paty do Alferes-RJ. Destas amostras, foram identificados os seguintes gêneros de nematóides: Haemonchus spp., Trichostrongylus spp., Cooperia spp., Bunostomum spp., Strongyloides e Oesophagostomum spp. Os gêneros de maior ocorrência foram Cooperia spp. (54%, Haemonchus spp. (50,6% e Trichostrongylus spp. (48,7%. Do total de propriedades vistoriadas, 86,7% apresentaram animais positivos para Haemonchus spp. e

  13. The relationship between body and ambient temperature and corneal temperature

    DEFF Research Database (Denmark)

    Kessel, Line; Johnson, Leif; Arvidsson, Henrik Sven

    2010-01-01

    Exposure to elevated ambient temperatures has been mentioned as a risk factor for common eye diseases, primarily presbyopia and cataract. The aim of the present study was to examine the relationship among ambient, cornea, and body core temperature.......Exposure to elevated ambient temperatures has been mentioned as a risk factor for common eye diseases, primarily presbyopia and cataract. The aim of the present study was to examine the relationship among ambient, cornea, and body core temperature....

  14. Core temperature affects scalp skin temperature during scalp cooling.

    Science.gov (United States)

    Daanen, Hein A M; Peerbooms, Mijke; van den Hurk, Corina J G; van Os, Bernadet; Levels, Koen; Teunissen, Lennart P J; Breed, Wim P M

    2015-08-01

    The efficacy of hair loss prevention by scalp cooling to prevent chemotherapy induced hair loss has been shown to be related to scalp skin temperature. Scalp skin temperature, however, is dependent not only on local cooling but also on the thermal status of the body. This study was conducted to investigate the effect of body temperature on scalp skin temperature. We conducted experiments in which 13 healthy subjects consumed ice slurry to lower body temperature for 15 minutes after the start of scalp cooling and then performed two 12-minute cycle exercise sessions to increase body core temperature. Esophageal temperature (Tes ), rectal temperature (Tre ), mean skin temperature (eight locations, Tskin ), and mean scalp temperature (five locations, Tscalp ) were recorded. During the initial 10 minutes of scalp cooling, Tscalp decreased by >15 °C, whereas Tes decreased by 0.2 °C. After ice slurry ingestion, Tes , Tre , and Tskin were 35.8, 36.5, and 31.3 °C, respectively, and increased after exercise to 36.3, 37.3, and 33.0 °C, respectively. Tscalp was significantly correlated to Tes (r = 0.39, P scalp cooling contributes to the decrease in scalp temperature and may improve the prevention of hair loss. This may be useful if the desired decrease of scalp temperature cannot be obtained by scalp cooling systems. © 2015 The International Society of Dermatology.

  15. Crowdsourcing urban air temperatures from smartphone battery temperatures

    NARCIS (Netherlands)

    Overeem, A.; Robinson, J.C.R.; Leijnse, H.; Steeneveld, G.J.; Horn, B.K.P.; Uijlenhoet, R.

    2013-01-01

    [1] Accurate air temperature observations in urban areas are important for meteorology and energy demand planning. They are indispensable to study the urban heat island effect and the adverse effects of high temperatures on human health. However, the availability of temperature observations in

  16. Effect of irrigation fluid temperature on body temperature during ...

    African Journals Online (AJOL)

    ... of dogs were hypothermic (<37oC). The addition of warmed irrigation fluids to a temperature management protocol in dogs undergoing elbow arthroscopy during general anaesthesia did not lead to decreased temperature losses. Keywords: Arthroscopy, Hypothermia, Irrigation fluid temperature, Thermoregulation.

  17. High Temperature Aquifer Storage

    Science.gov (United States)

    Ueckert, Martina; Niessner, Reinhard; Baumann, Thomas

    2016-04-01

    Combined heat and power generation (CHP) is highly efficient because excess heat is used for heating and/or process energy. However, the demand of heat energy varies considerably throughout the year while the demand for electrical energy is rather constant. It seems economically and ecologically highly beneficial for municipalities and large power consumers such as manufacturing plants to store excess heat in groundwater aquifers and to recuperate this energy at times of higher demand. Within the project High Temperature Aquifer Storage, scientists investigate storage and recuperation of excess heat energy into the bavarian Malm aquifer. Apart from high transmissivity and favorable pressure gradients, the hydrochemical conditions are crucial for long-term operation. An enormous technical challenge is the disruption of the carbonate equilibrium - modeling results indicated a carbonate precipitation of 10 - 50 kg/d in the heat exchangers. The test included five injection pulses of hot water (60 °C up to 110 °C) and four tracer pulses, each consisting of a reactive and a conservative fluorescent dye, into a depth of about 300 m b.s.l. resp. 470 m b.s.l. Injection and production rates were 15 L/s. To achieve the desired water temperatures, about 4 TJ of heat energy were necessary. Electrical conductivity, pH and temperature were recorded at a bypass where also samples were taken. A laboratory container at the drilling site was equipped for analysing the concentration of the dyes and the major cations at sampling intervals of down to 15 minutes. Additional water samples were taken and analysed in the laboratory. The disassembled heat exchanger prooved that precipitation was successfully prevented by adding CO2 to the water before heating. Nevertheless, hydrochemical data proved both, dissolution and precipitation processes in the aquifer. This was also suggested by the hydrochemical modelling with PhreeqC and is traced back to mixture dissolution and changing

  18. High temperature superconductor accelerator magnets

    NARCIS (Netherlands)

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and

  19. Temperature measurement in the sea

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnamacharyulu, R.J.; Rao, L.V.G.

    meters with temperature sensors, moored data buoys and drifting buoys) are described in brief. Specialised equipment used for studying oceanic features like internal waves, thermal fronts and temperature microstructure (thermistor chain, isotherm follower...

  20. Temperature Measurement for the LSST

    OpenAIRE

    Czekala, Ian; Paul O'Connor

    2014-01-01

    We explore the various means of temperature measurement to search for a low-cost accurate temperature measuring device.  This poster was completed as part of the Brookhaven National Laboratory High School intern program in 2005.

  1. Safe Minimum Internal Temperature Chart

    Science.gov (United States)

    ... JSR 286) Actions ${title} Loading... Safe Minimum Internal Temperature Chart Safe steps in food handling, cooking, and ... from other foods. Cook —Cook to the right temperature. Chill —Refrigerate food promptly. Cook all food to ...

  2. Melting temperature of archaeometallurgical slag

    Directory of Open Access Journals (Sweden)

    Jozef Petrík

    2013-12-01

    Full Text Available The aim of submitted work is to search the softening and melting temperature of archeometallurgy bloomery and blast furnace slag using high – temperature microscope. The high values of melting temperature of bloomery slag is a result of secondary oxidation of wüstite in the chamber of a microscope. The melting temperature increases with an increase in SiO2 and decreases with increasing basicity of the slag.

  3. Fiber Sagnac interferometer temperature sensor

    Energy Technology Data Exchange (ETDEWEB)

    Starodumov, A.N.; Zenteno, L.A.; Monzon, D.; De La Rosa, E. [Centro de Investigaciones en Optica, 37150 Leon, Gto (Mexico)

    1997-01-01

    A modified Sagnac interferometer-based fiber temperature sensor is proposed. Polarization independent operation and high temperature sensitivity of this class of sensors make them cost effective instruments for temperature measurements. A comparison of the proposed sensor with Bragg grating and long-period grating fiber sensors is derived. A temperature-induced spectral displacement of 0.99 nm/K is demonstrated for an internal stress birefringent fiber-based Sagnac interferometer. {copyright} {ital 1997 American Institute of Physics.}

  4. Modeling Temperature and Pricing Weather Derivatives Based on Temperature

    Directory of Open Access Journals (Sweden)

    Birhan Taştan

    2017-01-01

    Full Text Available This study first proposes a temperature model to calculate the temperature indices upon which temperature-based derivatives are written. The model is designed as a mean-reverting process driven by a Levy process to represent jumps and other features of temperature. Temperature indices are mainly measured as deviations from a base temperature, and, hence, the proposed model includes jumps because they may constitute an important part of this deviation for some locations. The estimated value of a temperature index and its distribution in this model apply an inversion formula to the temperature model. Second, this study develops a pricing process over calculated index values, which returns a customized price for temperature-based derivatives considering that temperature has unique effects on every economic entity. This personalized price is also used to reveal the trading behavior of a hypothesized entity in a temperature-based derivative trade with profit maximization as the objective. Thus, this study presents a new method that does not need to evaluate the risk-aversion behavior of any economic entity.

  5. High temperature autoclave vacuum seals

    Science.gov (United States)

    Hoffman, J. R.; Simpson, W. G.; Walker, H. M.

    1971-01-01

    Aluminum sheet forms effective sealing film at temperatures up to 728 K. Soft aluminum wire rings provide positive seal between foil and platen. For applications at temperatures above aluminum's service temperature, stainless steel is used as film material and copper wire as sealant.

  6. Temperature dependence of surface nanobubbles

    NARCIS (Netherlands)

    Berkelaar, R.P.; Seddon, James Richard Thorley; Zandvliet, Henricus J.W.; Lohse, Detlef

    2012-01-01

    The temperature dependence of nanobubbles was investigated experimentally using atomic force microscopy. By scanning the same area of the surface at temperatures from 51 °C to 25 °C it was possible to track geometrical changes of individual nanobubbles as the temperature was decreased.

  7. High Temperature Superconductor Machine Prototype

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech; Træholt, Chresten

    2011-01-01

    A versatile testing platform for a High Temperature Superconductor (HTS) machine has been constructed. The stationary HTS field winding can carry up to 10 coils and it is operated at a temperature of 77K. The rotating armature is at room temperature. Test results and performance for the HTS field...

  8. Battery system with temperature sensors

    Science.gov (United States)

    Wood, Steven J.; Trester, Dale B.

    2012-11-13

    A battery system to monitor temperature includes at least one cell with a temperature sensing device proximate the at least one cell. The battery system also includes a flexible member that holds the temperature sensor proximate to the at least one cell.

  9. High Temperature Hybrid Elastomers

    Science.gov (United States)

    Drake, Kerry Anthony

    Conventional high temperature elastomers are produced by chain polymerization of olefinic or fluorinated olefinic monomers. Ultimate thermal stabilities are limited by backbone bond strengths, lower thermal stability of cross-link sites relative to backbone bonds, and depolymerization or "unzipping" at high temperatures. In order to develop elastomers with enhanced thermal stability, hybrid thermally cross-linkable polymers that consisted only of organic-inorganic and aromatic bonds were synthesized and evaluated. The addition of phenylethynyl or phenylacetylinic functional groups to these polymers resulted in conversion of the polymers into high temperature elastomers when cross-linked by thermal curing. Polyphenyoxydiphenylsilanes were synthesized via several different condensation reactions. Results of these synthetic reactions, which utilized both hydroquinone and biphenol as monomers, were systematically evaluated to determine the optimal synthetic conditions for subsequent endcapping reactions. It was determined that dichlorodiphenylsilane condensations with biphenol in toluene or THF were best suited for this work. Use of excess dichlorodiphenylsilane yielded polymers of appropriate molecular weights with terminal reactive chlorosilane groups that could be utilized for coupling with phenylethynyl reagents in a subsequent reaction. Two new synthetic routes were developed to endcap biphenoxysilanes with ethynyl containing substituents, to yield polymers with cross-linkable end groups. Endcapping by lithiumphenylacetylide and 4[(4-fluorophenylethynyl))phenol yielded two new polymers that could be thermally cross-linked on heating above 300 °C. Successful endcapping was verified chemically by 13C NMR, FTIR and Raman analysis. Exothermic peaks consistent with ethynyl curing reactions were observed in endcapped polymers by DSC. A new diacetylinic polymer was prepared through reaction of 4,4'-buta-1,3-diyne-1,4-diyldiphenol and dichlorodiphenylsilane. This

  10. Hadrons at finite temperature

    CERN Document Server

    Mallik, Samirnath

    2016-01-01

    High energy laboratories are performing experiments in heavy ion collisions to explore the structure of matter at high temperature and density. This elementary book explains the basic ideas involved in the theoretical analysis of these experimental data. It first develops two topics needed for this purpose, namely hadron interactions and thermal field theory. Chiral perturbation theory is developed to describe hadron interactions and thermal field theory is formulated in the real-time method. In particular, spectral form of thermal propagators is derived for fields of arbitrary spin and used to calculate loop integrals. These developments are then applied to find quark condensate and hadron parameters in medium, including dilepton production. Finally, the non-equilibrium method of statistical field theory to calculate transport coefficients is reviewed. With technical details explained in the text and appendices, this book should be accessible to researchers as well as graduate students interested in thermal ...

  11. Temperature integration and DIF in cut chrysanthemum

    NARCIS (Netherlands)

    Korner, O.; Challa, H.

    2003-01-01

    To reduce energy consumption in greenhouses, temperature integration can be used. However, the temperature integration principle considers only average temperatures and does not comply with the DIF concept (difference between mean day temperature and mean night temperature). With DIF, stem

  12. Advances in high temperature chemistry

    CERN Document Server

    Eyring, Leroy

    1969-01-01

    Advances in High Temperature Chemistry, Volume 2 covers the advances in the knowledge of the high temperature behavior of materials and the complex and unfamiliar characteristics of matter at high temperature. The book discusses the dissociation energies and free energy functions of gaseous monoxides; the matrix-isolation technique applied to high temperature molecules; and the main features, the techniques for the production, detection, and diagnosis, and the applications of molecular beams in high temperatures. The text also describes the chemical research in streaming thermal plasmas, as w

  13. Bradycardia During Targeted Temperature Management

    DEFF Research Database (Denmark)

    Thomsen, Jakob Hartvig; Nielsen, Niklas; Hassager, Christian

    2016-01-01

    OBJECTIVES: Bradycardia is common during targeted temperature management, likely being a physiologic response to lower body temperature, and has recently been associated with favorable outcome following out-of-hospital cardiac arrest in smaller observational studies. The present study sought...... to confirm this finding in a large multicenter cohort of patients treated with targeted temperature management at 33°C and explore the response to targeted temperature management targeting 36°C. DESIGN: Post hoc analysis of a prospective randomized study. SETTING: Thirty-six ICUs in 10 countries. PATIENTS......: We studied 447 (targeted temperature management = 33°C) and 430 (targeted temperature management = 36°C) comatose out-of-hospital cardiac arrest patients with available heart rate data, randomly assigned in the targeted temperature management trial from 2010 to 2013. INTERVENTIONS: Targeted...

  14. Micro-Mechanical Temperature Sensors

    DEFF Research Database (Denmark)

    Larsen, Tom

    Temperature is the most frequently measured physical quantity in the world. The field of thermometry is therefore constantly evolving towards better temperature sensors and better temperature measurements. The aim of this Ph.D. project was to improve an existing type of micro-mechanical temperature...... sensor or to develop a new one. Two types of micro-mechanical temperature sensors have been studied: Bilayer cantilevers and string-like beam resonators. Both sensor types utilize thermally generated stress. Bilayer cantilevers are frequently used as temperature sensors at the micro-scale, and the goal....... The reduced sensitivity was due to initial bending of the cantilevers and poor adhesion between the two cantilever materials. No further attempts were made to improve the sensitivity of bilayer cantilevers. The concept of using string-like resonators as temperature sensors has, for the first time, been...

  15. High-Temperature Piezoelectric Sensing

    Directory of Open Access Journals (Sweden)

    Xiaoning Jiang

    2013-12-01

    Full Text Available Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented.

  16. HIGH TEMPERATURE VACUUM MIXER

    Directory of Open Access Journals (Sweden)

    E. D. Chertov

    2015-01-01

    Full Text Available The work is devoted to the creation of a new type of mixer to produce homogeneous mixtures of dissimilar materials applied to recycling of housing and communal services waste. The article describes the design of a dual-chamber device of the original high-temperature vacuum mixer, there investigated the processes occurring in the chambers of such devices. The results of theoretical and experimental research of the process of mixing recycled polyethylene with a mixture of "grinded food waste – Eco wool” are presented. The problem of the optimum choice of bending the curvilinear blades in the working volume of the seal, which is achieved by setting their profile in the form of involute arc of several circles of different radii, is examined . The dependences, allowing to define the limits of the changes of the main mode parameters the angular velocity of rotation of the working body of the mixer using two ways of setting the profile of the curvilinear blade mixer are obtained. Represented design of the mixer is proposed to use for a wide range of tasks associated with the mixing of the components with a strongly pronounced difference of physic al chemical properties and, in particular, in the production of composites out of housing and communal services waste.

  17. Measurement of thermodynamic temperature of high temperature fixed points

    Energy Technology Data Exchange (ETDEWEB)

    Gavrilov, V. R.; Khlevnoy, B. B.; Otryaskin, D. A.; Grigorieva, I. A.; Samoylov, M. L.; Sapritsky, V. I. [All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI), 46 Ozernaya St., Moscow 119361 (Russian Federation)

    2013-09-11

    The paper is devoted to VNIIOFI's measurements of thermodynamic temperature of the high temperature fixed points Co-C, Pt-C and Re-C within the scope of the international project coordinated by the Consultative Committee for Thermometry working group 5 'Radiation Thermometry'. The melting temperatures of the fixed points were measured by a radiance mode radiation thermometer calibrated against a filter radiometer with known irradiance spectral responsivity via a high temperature black body. This paper describes the facility used for the measurements, the results and estimated uncertainties.

  18. Measurement of thermodynamic temperature of high temperature fixed points

    Science.gov (United States)

    Gavrilov, V. R.; Khlevnoy, B. B.; Otryaskin, D. A.; Grigorieva, I. A.; Samoylov, M. L.; Sapritsky, V. I.

    2013-09-01

    The paper is devoted to VNIIOFI's measurements of thermodynamic temperature of the high temperature fixed points Co-C, Pt-C and Re-C within the scope of the international project coordinated by the Consultative Committee for Thermometry working group 5 "Radiation Thermometry". The melting temperatures of the fixed points were measured by a radiance mode radiation thermometer calibrated against a filter radiometer with known irradiance spectral responsivity via a high temperature black body. This paper describes the facility used for the measurements, the results and estimated uncertainties.

  19. Hall Sensors for Extreme Temperatures

    Directory of Open Access Journals (Sweden)

    Maciej Oszwaldowski

    2011-01-01

    Full Text Available We report on the preparation of the first complete extreme temperature Hall sensor. This means that the extreme-temperature magnetic sensitive semiconductor structure is built-in an extreme-temperature package especially designed for that purpose. The working temperature range of the sensor extends from −270 °C to +300 °C. The extreme-temperature Hall-sensor active element is a heavily n-doped InSb layer epitaxially grown on GaAs. The magnetic sensitivity of the sensor is ca. 100 mV/T and its temperature coefficient is less than 0.04 %/K. This sensor may find applications in the car, aircraft, spacecraft, military and oil and gas industries.

  20. Temperature Monitoring and Perioperative Thermoregulation

    Science.gov (United States)

    Sessler, Daniel I.

    2008-01-01

    Most clinically available thermometers accurately report the temperature of whatever tissue is being measured. The difficulty is that no reliably core-temperature measuring sites are completely non-invasive and easy to use — especially in patients not having general anesthesia. Nonetheless, temperature can be reliably measured in most patients. Body temperature should be measured in patients having general anesthesia exceeding 30 minutes in duration, and in patients having major operations under neuraxial anesthesia. Core body temperature is normally tightly regulated. All general anesthetics produce a profound dose-dependent reduction in the core temperature triggering cold defenses including arterio-venous shunt vasoconstriction and shivering. Anesthetic-induced impairment of normal thermoregulatory control, and the resulting core-to-peripheral redistribution of body heat, is the primary cause of hypothermia in most patients. Neuraxial anesthesia also impairs thermoregulatory control, although to a lesser extant than general anesthesia. Prolonged epidural analgesia is associated with hyperthermia whose cause remains unknown. PMID:18648241

  1. Temperature based Restricted Boltzmann Machines

    Science.gov (United States)

    Li, Guoqi; Deng, Lei; Xu, Yi; Wen, Changyun; Wang, Wei; Pei, Jing; Shi, Luping

    2016-01-01

    Restricted Boltzmann machines (RBMs), which apply graphical models to learning probability distribution over a set of inputs, have attracted much attention recently since being proposed as building blocks of multi-layer learning systems called deep belief networks (DBNs). Note that temperature is a key factor of the Boltzmann distribution that RBMs originate from. However, none of existing schemes have considered the impact of temperature in the graphical model of DBNs. In this work, we propose temperature based restricted Boltzmann machines (TRBMs) which reveals that temperature is an essential parameter controlling the selectivity of the firing neurons in the hidden layers. We theoretically prove that the effect of temperature can be adjusted by setting the parameter of the sharpness of the logistic function in the proposed TRBMs. The performance of RBMs can be improved by adjusting the temperature parameter of TRBMs. This work provides a comprehensive insights into the deep belief networks and deep learning architectures from a physical point of view.

  2. TEMPERATURE TOLERANCES AND OSMOREGULATION IN ...

    African Journals Online (AJOL)

    MQCOmQ IItora/I' and P,ammotelllllll capelUis) have upper lethal temperatures of 4l-46°C when heated at a rate of 1 CO/lO minutes. TWo species have upper lethal temperatures of 37°C and 39°C when heated at a rate of 1 CO/day. It has been concluded that they can tolerate much hisher temperatures thaD they normally ...

  3. Rare Earth Optical Temperature Sensor

    Science.gov (United States)

    Chubb, Donald L. (Inventor); Jenkins, Phillip (Inventor)

    2004-01-01

    A rare earth optical temperature sensor is disclosed for measuring high temperatures. Optical temperature sensors exist that channel emissions from a sensor to a detector using a light pipe. The invention uses a rare earth emitter to transform the sensed thermal energy into a narrow band width optical signal that travels to a detector using a light pipe. An optical bandpass filter at the detector removes any noise signal outside of the band width of the signal from the emitter.

  4. Sensors for low temperature application

    Science.gov (United States)

    Henderson, Timothy M.; Wuttke, Gilbert H.

    1977-01-01

    A method and apparatus for low temperature sensing which uses gas filled micro-size hollow glass spheres that are exposed in a confined observation area to a low temperature range (Kelvin) and observed microscopically to determine change of state, i.e., change from gaseous state of the contained gas to condensed state. By suitable indicia and classification of the spheres in the observation area, the temperature can be determined very accurately.

  5. Low-temperature tracking detectors

    CERN Document Server

    Niinikoski, T O; Anbinderis, P; Anbinderis, T; D'Ambrosio, N; de Boer, Wim; Borchi, E; Borer, K; Bruzzi, M; Buontempo, S; Chen, W; Cindro, V; Dezillie, B; Dierlamm, A; Eremin, V; Gaubas, E; Gorbatenko, V; Granata, V; Grigoriev, E; Grohmann, S; Hauler, F; Heijne, Erik H M; Heising, S; Hempel, O; Herzog, R; Härkönen, J; Ilyashenko, Yu S; Janos, S; Jungermann, L; Kalesinskas, V; Kapturauskas, J; Laiho, R; Li, Z; Luukka, Panja; Mandic, I; De Masi, R; Menichelli, D; Mikuz, M; Militaru, O; Nüssle, G; O'Shea, V; Pagano, S; Paul, S; Perea-Solano, B; Piotrzkowski, K; Pirollo, S; Pretzl, K; Rahman, M; Rato-Mendes, P; Rouby, X; Ruggiero, G; Smith, K; Sousa, P; Tuominen, E; Tuovinen, E; Vaitkus, J; Verbitskaya, E; Da Vià, C; Vlasenko, L; Vlasenko, M; Wobst, E; Zavrtanik, M

    2004-01-01

    RD39 collaboration develops new detector techniques for particle trackers, which have to withstand fluences up to 10/sup 16/ cm/sup -2 / of high-energy particles. The work focuses on the optimization of silicon detectors and their readout electronics while keeping the temperature as a free parameter. Our results so far suggest that the best operating temperature is around 130 K. We shall also describe in this paper how the current-injected mode of operation reduces the polarization of the bulk silicon at low temperatures, and how the engineering and materials problems related with vacuum and low temperature can be solved. (9 refs).

  6. Core temperature affects scalp skin temperature during scalp cooling

    NARCIS (Netherlands)

    Daanen, H.A.M.; Peerbooms, M.; van den Hurk, C.J.G.; van Os, B.; Levels, K.; Teunissen, L.P.J.; Breed, W.P.M.

    2015-01-01

    Background: The efficacy of hair loss prevention by scalp cooling to prevent chemotherapy induced hair loss has been shown to be related to scalp skin temperature. Scalp skin temperature, however, is dependent not only on local cooling but also on the thermal status of the body. Objectives: This

  7. High Temperature Solid Lubricant Coating for High Temperature Wear Applications

    Science.gov (United States)

    DellaCorte, Christopher (Inventor); Edmonds, Brian J (Inventor)

    2014-01-01

    A self-lubricating, friction and wear reducing composite useful over a wide temperature range is described herein. The composite includes metal bonded chromium oxide dispersed in a metal binder having a substantial amount of nickel. The composite contains a fluoride of at least one Group I, Group II, or rare earth metal, and optionally a low temperature lubricant metal.

  8. (Krauss) at constant high temperatures

    African Journals Online (AJOL)

    Snail Research Unit of the SAMRC and Department of Zoology, Potchefstroom University for CHE,. Potchefstroom. The survival of the freshwater snail species Bulinus africanus, Bulinus g/obosus and Biompha/aria pfeifferi at extreme high temperatures was experimentally investigated. Snails were exposed to temperatures ...

  9. Spectroscopy of Low Temperature Plasma

    CERN Document Server

    Ochkin, Vladimir N

    2009-01-01

    Providing an up-to-date overview on spectroscopical diagnostics of low temperature plasma Spectroscopy of Low Temperature Plasma covers the latest developments and techniques. Written by a distinguished scientist and experienced book author this text is applicable to many fields in materials and surface science as well as nanotechnology and contains numerous appendices with indispensable reference data.

  10. Embedded Temperature-Change Sensors

    Science.gov (United States)

    Thakoor, Sarita; Thakoor, Anil; Karmon, Dan

    1995-01-01

    Transducers sensitive to rates of change of temperature embedded in integrated circuits and discrete electronic components damaged by overheating, according to proposal. Used to detect onset of rapid heating and to trigger shutoffs of power or other corrective actions before temperatures rise beyond safe limits. Sensors respond fast and reliably to incipient overheating because they are in direct thermal contact with vulnerable circuit elements.

  11. Multiple Waveband Temperature Sensor (MWTS)

    Science.gov (United States)

    Bandara, Sumith V.; Gunapala, Sarath; Wilson, Daniel; Stirbl, Robert; Blea, Anthony; Harding, Gilbert

    2006-01-01

    This slide presentation reviews the development of Multiple Waveband Temperature Sensor (MWTS). The MWTS project will result in a highly stable, monolithically integrated, high resolution infrared detector array sensor that records registered thermal imagery in four infrared wavebands to infer dynamic temperature profiles on a laser-irradiated ground target. An accurate surface temperature measurement of a target in extreme environments in a non-intrusive manner is required. The development challenge is to: determine optimum wavebands (suitable for target temperatures, nature of the targets and environments) to measure accurate target surface temperature independent of the emissivity, integrate simultaneously readable multiband Quantum Well Infrared Photodetectors (QWIPs) in a single monolithic focal plane array (FPA) sensor and to integrate the hardware/software and system calibration for remote temperature measurements. The charge was therefore to develop and demonstrate a multiband infrared imaging camera with the detectors simultaneously sensitive to multiple distinct color bands for front surface temperature measurements Wavelength ( m) measurements. Amongst the requirements are: that the measurement system will not affect target dynamics or response to the laser irradiation and that the simplest criterion for spectral band selection is to choose those practically feasible spectral bands that create the most contrast between the objects or scenes of interest in the expected environmental conditions. There is in the presentation a review of the modeling and simulation of multi-wave infrared temperature measurement and also a review of the detector development and QWIP capacities.

  12. Certification testing at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Noss, P.W. [Packaging Technology, Tacoma, WA (United States); Ammerman, D.J. [Sandia National Labs., Albuquerque, NM (United States)

    2004-07-01

    Regulations governing the transport of radioactive materials require that most hypothetical accident condition tests or analyses consider the effects of the environmental temperature that most challenges package performance. For many packages, the most challenging temperature environment is the cold condition (-29 C according to U.S. regulations), primarily because the low temperature causes the highest free drop impact forces due to the higher strength of many energy-absorbing materials at this temperature. If it is decided to perform low temperature testing, it is only necessary that the relevant parts of the package have the required temperature prior to the drop. However, the details of performing a drop at low temperature can have a large influence on testing cost and technical effectiveness. The selection of the test site, the chamber and type of chilling equipment, instrumentation, and even the time of year are all important. Control of seemingly minor details such as the effect on internal pressure, placement of monitoring thermocouples, the thermal time constant of the test article, and icing of equipment are necessary to ensure a successful low temperature test. This paper will discuss these issues and offer suggestions based on recent experience.

  13. Temperature, light and the tomato

    NARCIS (Netherlands)

    Verkerk, K.

    1955-01-01

    In good illumination, six tomato varieties all responded to an increase in day or/and night temperature by faster stem and fruit growth, earlier but smaller fruit yield with fewer fruits in shorter and lighter clusters, and a reduction in root, stem and leaf weight. Optimum temperatures for moderate

  14. HIGH TEMPERATURE POLYMER FUEL CELLS

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf; Qingfeng, Li; He, Ronghuan

    2003-01-01

    This paper will report recent results from our group on polymer fuel cells (PEMFC) based on the temperature resistant polymer polybenzimidazole (PBI), which allow working temperatures up to 200°C. The membrane has a water drag number near zero and need no water management at all. The high working...

  15. Temperature rise of installed FCC

    Science.gov (United States)

    Hankins, J. D.

    1976-01-01

    Report discusses temperature profiles of installed FCC for wood and tile surfaces. Three-conductor FCC was tested at twice nominal current-carrying capacity over bare floor and under carpet, with result indicating that temperature rise is not a linear function of current with FCC at this level.

  16. Temperature evolution during dissipative collapse

    Indian Academy of Sciences (India)

    Abstract. We investigate the gravitational collapse of a radiating sphere evolving into a final static configuration described by the interior Schwarzschild solution. The temperature profiles of this particular model are obtained within the framework of causal thermodynamics. The overall temperature evolution is enhanced by ...

  17. The Kelvin and Temperature Measurements

    Science.gov (United States)

    Mangum, B. W.; Furukawa, G. T.; Kreider, K. G.; Meyer, C. W.; Ripple, D. C.; Strouse, G. F.; Tew, W. L.; Moldover, M. R.; Johnson, B. Carol; Yoon, H. W.; Gibson, C. E.; Saunders, R. D.

    2001-01-01

    The International Temperature Scale of 1990 (ITS-90) is defined from 0.65 K upwards to the highest temperature measurable by spectral radiation thermometry, the radiation thermometry being based on the Planck radiation law. When it was developed, the ITS-90 represented thermodynamic temperatures as closely as possible. Part I of this paper describes the realization of contact thermometry up to 1234.93 K, the temperature range in which the ITS-90 is defined in terms of calibration of thermometers at 15 fixed points and vapor pressure/temperature relations which are phase equilibrium states of pure substances. The realization is accomplished by using fixed-point devices, containing samples of the highest available purity, and suitable temperature-controlled environments. All components are constructed to achieve the defining equilibrium states of the samples for the calibration of thermometers. The high quality of the temperature realization and measurements is well documented. Various research efforts are described, including research to improve the uncertainty in thermodynamic temperatures by measuring the velocity of sound in gas up to 800 K, research in applying noise thermometry techniques, and research on thermocouples. Thermometer calibration services and high-purity samples and devices suitable for “on-site” thermometer calibration that are available to the thermometry community are described. Part II of the paper describes the realization of temperature above 1234.93 K for which the ITS-90 is defined in terms of the calibration of spectroradiometers using reference blackbody sources that are at the temperature of the equilibrium liquid-solid phase transition of pure silver, gold, or copper. The realization of temperature from absolute spectral or total radiometry over the temperature range from about 60 K to 3000 K is also described. The dissemination of the temperature scale using radiation thermometry from NIST to the customer is achieved by

  18. The Kelvin and Temperature Measurements.

    Science.gov (United States)

    Mangum, B W; Furukawa, G T; Kreider, K G; Meyer, C W; Ripple, D C; Strouse, G F; Tew, W L; Moldover, M R; Johnson, B C; Yoon, H W; Gibson, C E; Saunders, R D

    2001-01-01

    The International Temperature Scale of 1990 (ITS-90) is defined from 0.65 K upwards to the highest temperature measurable by spectral radiation thermometry, the radiation thermometry being based on the Planck radiation law. When it was developed, the ITS-90 represented thermodynamic temperatures as closely as possible. Part I of this paper describes the realization of contact thermometry up to 1234.93 K, the temperature range in which the ITS-90 is defined in terms of calibration of thermometers at 15 fixed points and vapor pressure/temperature relations which are phase equilibrium states of pure substances. The realization is accomplished by using fixed-point devices, containing samples of the highest available purity, and suitable temperature-controlled environments. All components are constructed to achieve the defining equilibrium states of the samples for the calibration of thermometers. The high quality of the temperature realization and measurements is well documented. Various research efforts are described, including research to improve the uncertainty in thermodynamic temperatures by measuring the velocity of sound in gas up to 800 K, research in applying noise thermometry techniques, and research on thermocouples. Thermometer calibration services and high-purity samples and devices suitable for "on-site" thermometer calibration that are available to the thermometry community are described. Part II of the paper describes the realization of temperature above 1234.93 K for which the ITS-90 is defined in terms of the calibration of spectroradiometers using reference blackbody sources that are at the temperature of the equilibrium liquid-solid phase transition of pure silver, gold, or copper. The realization of temperature from absolute spectral or total radiometry over the temperature range from about 60 K to 3000 K is also described. The dissemination of the temperature scale using radiation thermometry from NIST to the customer is achieved by calibration of

  19. Pricing of temperature index insurance

    Directory of Open Access Journals (Sweden)

    Che Mohd Imran Che Taib

    2012-01-01

    Full Text Available The aim of this paper is to study pricing of weather insurance contracts based on temperature indices. Three different pricing methods are analysed: the classical burn approach, index modelling and temperature modelling. We take the data from Malaysia as our empirical case. Our results show that there is a significant difference between the burn and index pricing approaches on one hand, and the temperature modelling method on the other. The latter approach is pricing the insurance contract using a seasonal autoregressive time series model for daily temperature variations, and thus provides a precise probabilistic model for the fine structure of temperature evolution. We complement our pricing analysis by an investigation of the profit/loss distribution from the contract, in the perspective of both the insured and the insurer.

  20. Small Cold Temperature Instrument Packages

    Science.gov (United States)

    Clark, P. E.; Millar, P. S.; Yeh, P. S.; Feng, S.; Brigham, D.; Beaman, B.

    We are developing a small cold temperature instrument package concept that integrates a cold temperature power system with ultra low temperature ultra low power electronics components and power supplies now under development into a 'cold temperature surface operational' version of a planetary surface instrument package. We are already in the process of developing a lower power lower temperature version for an instrument of mutual interest to SMD and ESMD to support the search for volatiles (the mass spectrometer VAPoR, Volatile Analysis by Pyrolysis of Regolith) both as a stand alone instrument and as part of an environmental monitoring package. We build on our previous work to develop strategies for incorporating Ultra Low Temperature/Ultra Low Power (ULT/ULP) electronics, lower voltage power supplies, as well as innovative thermal design concepts for instrument packages. Cryotesting has indicated that our small Si RHBD CMOS chips can deliver >80% of room temperature performance at 40K (nominal minimum lunar surface temperature). We leverage collaborations, past and current, with the JPL battery development program to increase power system efficiency in extreme environments. We harness advances in MOSFET technology that provide lower voltage thresholds for power switching circuits incorporated into our low voltage power supply concept. Conventional power conversion has a lower efficiency. Our low power circuit concept based on 'synchronous rectification' could produce stable voltages as low as 0.6 V with 85% efficiency. Our distributed micro-battery-based power supply concept incorporates cold temperature power supplies operating with a 4 V or 8 V battery. This work will allow us to provide guidelines for applying the low temperature, low power system approaches generically to the widest range of surface instruments.