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Sample records for frustrated phase separation

  1. Single Sublattice Endotaxial Phase Separation Driven by Charge Frustration in a Complex Oxide

    PubMed Central

    2013-01-01

    Complex transition-metal oxides are important functional materials in areas such as energy and information storage. The cubic ABO3 perovskite is an archetypal example of this class, formed by the occupation of small octahedral B-sites within an AO3 network defined by larger A cations. We show that introduction of chemically mismatched octahedral cations into a cubic perovskite oxide parent phase modifies structure and composition beyond the unit cell length scale on the B sublattice alone. This affords an endotaxial nanocomposite of two cubic perovskite phases with distinct properties. These locally B-site cation-ordered and -disordered phases share a single AO3 network and have enhanced stability against the formation of a competing hexagonal structure over the single-phase parent. Synergic integration of the distinct properties of these phases by the coherent interfaces of the composite produces solid oxide fuel cell cathode performance superior to that expected from the component phases in isolation. PMID:23750709

  2. Frustrated phase separation in the momentum distribution of field-driven light-heavy Fermi-Fermi mixtures of ultracold atoms

    NASA Astrophysics Data System (ADS)

    Fotso, H. F.; Vicente, J.; Freericks, J. K.

    2014-11-01

    Time-of-flight images are a common tool in ultracold atomic experiments, employed to determine the quasimomentum distribution of the interacting particles. If one introduces a constant artificial electric field, then the quasimomentum distribution evolves in time as Bloch oscillations are generated in the system and then are damped, showing a complex series of patterns. In different-mass Fermi-Fermi mixtures, these patterns are formed from a frustrated phase separation in momentum space that is driven by Mott physics for large electric fields which stabilize them for long times.

  3. Quantum phase transitions in frustrated magnetic systems

    NASA Astrophysics Data System (ADS)

    Wölfle, P.; Schmitteckert, P.

    2015-07-01

    We review our recent work on quantum phase transitions in frustrated magnetic systems. In the first part a Pseudo Fermion Functional Renormalization Group (PFFRG) method is presented. By using an exact representation of spin 1/2 operators in terms of pseudofermions a quantum spin Hamiltonian may be mapped onto an interacting fermion system. For the latter an FRG treatment is employed. The results for the J1-J2 model and similar models of frustrated interaction show phase diagrams in agreement with those obtained by other methods, but give more detailed information on the nature of correlations, in particular in the non-magnetic phases. Applications of PFFRG to geometrically frustrated systems and to highly anisotropic Kitaev type models are also reported. In the second part the derivation of quantum spin models from the microscopic many-body Hamiltonian is discussed. The results for multiband systems with strong spin-orbit interaction encountered in the iridates class of compounds are shown to resolve some of the questions posed by experiment.

  4. Frustration and curvature - Glasses and the cholesteric blue phase

    NASA Technical Reports Server (NTRS)

    Sethna, J. P.

    1983-01-01

    An analogy is drawn between continuum elastic theories of the blue phase of cholesteric liquid crystals and recent theories of frustration in configurational glasses. Both involve the introduction of a lattice of disclination lines to relieve frustration; the frustration is due to an intrinsic curvature in the natural form of parallel transport. A continuum theory of configurational glasses is proposed.

  5. Geometric frustration phases of diblock copolymers in nanoparticles.

    PubMed

    Li, Shiben; Chen, Peng; Zhang, Linxi; Liang, Haojun

    2011-04-19

    The geometric frustration phases are investigated for diblock copolymers in nanoparticles with neutral surfaces using real-space self-consistent field theory. First, a rich variety of geometric frustration phases with specific symmetries are observed in the polymer nanoparticles with invariable diameters by constructing the phase diagrams arranged as the volume fraction and Flory-Huggins interaction parameter. Most of the space in the phase diagram is filled with phases with strong symmetries, such as spherical or cubic symmetries, while a number of asymmetric or axisymmetric phases are located in a narrow space in the diagram. Then the geometric frustration phases are examined systematically for the diblock copolymers with special polymer parameters, and a rich variety of novel frustration phases with multilayered structures are observed by varying the diameters of the nanoparticles. Furthermore, the investigations on the free energies indicate that the transitions between these frustrated phases are first-order, and the formation mechanism of the frustration phases is reasonably elucidated. PMID:21417241

  6. Quantum phase transition in the frustrated anisotropic honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Pires, A. S. T.

    2015-12-01

    We study the spin -1 Heisenberg antiferromagnet on the two dimensional honeycomb lattice at zero temperature, with nearest-neighbor J1 and next-to-nearest neighbor J2 exchange interactions and single-ion easy plane anisotropy, using the SU(3) Schwinger boson formalism. A disordered spin-liquid phase may appear in a narrow regime of intermediate frustration, in between an ordered antiferromagnetic phase and a collinear one. This quantum paramagnetic state is characterized by a finite gap in the excitation spectrum.

  7. Thermodynamic phase transitions in a frustrated magnetic metamaterial

    PubMed Central

    Anghinolfi, L.; Luetkens, H.; Perron, J.; Flokstra, M. G.; Sendetskyi, O.; Suter, A.; Prokscha, T.; Derlet, P. M.; Lee, S. L.; Heyderman, L. J.

    2015-01-01

    Materials with interacting magnetic degrees of freedom display a rich variety of magnetic behaviour that can lead to novel collective equilibrium and out-of-equilibrium phenomena. In equilibrium, thermodynamic phases appear with the associated phase transitions providing a characteristic signature of the underlying collective behaviour. Here we create a thermally active artificial kagome spin ice that is made up of a large array of dipolar interacting nanomagnets and undergoes phase transitions predicted by microscopic theory. We use low energy muon spectroscopy to probe the dynamic behaviour of the interacting nanomagnets and observe peaks in the muon relaxation rate that can be identified with the critical temperatures of the predicted phase transitions. This provides experimental evidence that a frustrated magnetic metamaterial can be engineered to admit thermodynamic phases. PMID:26387444

  8. Thermodynamic phase transitions in a frustrated magnetic metamaterial.

    PubMed

    Anghinolfi, L; Luetkens, H; Perron, J; Flokstra, M G; Sendetskyi, O; Suter, A; Prokscha, T; Derlet, P M; Lee, S L; Heyderman, L J

    2015-01-01

    Materials with interacting magnetic degrees of freedom display a rich variety of magnetic behaviour that can lead to novel collective equilibrium and out-of-equilibrium phenomena. In equilibrium, thermodynamic phases appear with the associated phase transitions providing a characteristic signature of the underlying collective behaviour. Here we create a thermally active artificial kagome spin ice that is made up of a large array of dipolar interacting nanomagnets and undergoes phase transitions predicted by microscopic theory. We use low energy muon spectroscopy to probe the dynamic behaviour of the interacting nanomagnets and observe peaks in the muon relaxation rate that can be identified with the critical temperatures of the predicted phase transitions. This provides experimental evidence that a frustrated magnetic metamaterial can be engineered to admit thermodynamic phases. PMID:26387444

  9. Geometrically-frustrated pseudogap phase of Coulomb liquids

    NASA Astrophysics Data System (ADS)

    Pramudya, Y.; Terletska, H.; Pankov, S.; Manousakis, E.; Dobrosavljević, V.

    2012-06-01

    We study a class of models with long-range repulsive interactions of the generalized Coulomb form V(r)∼1/rα. We show that decreasing the interaction exponent in the regime αfrustration produced by long-range interactions. A nearly frozen Coulomb liquid then survives in a broad pseudogap phase found at T>Tc, which is characterized by an unusual temperature dependence of all quantities. In contrast, the leading critical behavior very close to the charge-ordering temperature remains identical as in models with short-range interactions.

  10. Griffiths phase behaviour in a frustrated antiferromagnetic intermetallic compound

    PubMed Central

    Ghosh, Krishanu; Mazumdar, Chandan; Ranganathan, R.; Mukherjee, S.

    2015-01-01

    The rare coexistence of a Griffiths phase (GP) and a geometrically frustrated antiferromagnetism in the non-stoichiometric intermetallic compound GdFe0.17Sn2 (the paramagnetic Weiss temperature θp ~ −59 K) is reported in this work. The compound forms in the Cmcm space group with large structural anisotropy (b/c ~ 4). Interestingly, all the atoms in the unit cell possess the same point group symmetry (Wycoff position 4c), which is rather rare. The frustration parameter, f = |θp|/TN has been established as 3.6, with the Néel temperature TN and Griffiths temperature TG being 16.5 and 32 K, respectively. The TG has been determined from the heat capacity measurement and also from the magnetocaloric effect (MCE). It is also shown that substantial difference in GP region may exist between zero field and field cooled measurements - a fact hitherto not emphasized so far. PMID:26515256

  11. Coupling among three chemical oscillators: Synchronization, phase death, and frustration

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Minoru; Yoshikawa, Kenichi; Mori, Yoshihito

    1993-02-01

    Various modes in three coupled chemical oscillators in a triangular arrangement were observed. As a well-defined nonlinear oscillator, the Belousov-Zhabotinsky reaction was studied in a continuous-flow stirred tank reactor (CSTR). Coupling among CSTR's was performed by mass exchange. The coupling strength was quantitatively controlled by changing the flow rate of reacting solutions among the three CSTR's using peristaltic pumps between each pair of the reactors. As a key parameter to control the model of coupling, we changed the symmetry of the interaction between the oscillators. In the case of the symmetric coupling, a quasiperiodic state or a biperiodic mode, an all-death mode and two kinds of synchronized modes appeared, depending on the coupling strength. On the other hand, under the asymmetric coupling, a quasiperiodic state or a biperiodic mode, an all death mode and four kinds of synchronized modes appeared. Those modes have been discussed in relation to the idea of ``frustration'' in the Ising spin system, where the three-phase mode appears as a transition from the Ising spin system to the XY spin system.

  12. Quantum phase diagram of a frustrated antiferromagnet on the bilayer honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Lamas, Carlos A.; Arlego, Marcelo; Brenig, Wolfram

    2016-06-01

    We study the spin-1/2 Heisenberg antiferromagnet on a bilayer honeycomb lattice including interlayer frustration. Using a set of complementary approaches, namely, Schwinger bosons, dimer series expansion, bond operators, and exact diagonalization, we map out the quantum phase diagram. Analyzing ground-state energies and elementary excitation spectra, we find four distinct phases, corresponding to three collinear magnetic long-range ordered states, and one quantum disordered interlayer dimer phase. We detail that the latter phase is adiabatically connected to an exact singlet product ground state of the bilayer, which exists along a line of maximum interlayer frustration. The order within the remaining three phases will be clarified.

  13. Magnetic properties and magnetic phase diagram of frustrated Co1 - xFexPt3 compounds

    NASA Astrophysics Data System (ADS)

    Kim, T. H.; Cadeville, M. C.; Dinia, A.; Rakoto, H.

    1997-04-01

    The investigation of the magnetic properties of the pseudobinary Co1-xFexPt3 L12 ordered compounds resulting from alloying ferromagnet CoPt3 and frustrated antiferromagnet FePt3 is reported. The magnetic phase diagram of this system shows the presence of a pure spin glass phase that separates the ferromagnetic region from the antiferromagnetic one. On the Co-rich side (x<0.6), two re-entrant spin glass phases are found to emerge at low temperature in the ferromagnetic region. On the iron-rich side, an antiferromagnetic region with two antiferromagnetic [1/2 1/20] and [1/200] structures is observed for 1⩾x⩾0.8. This magnetic phase diagram is discussed comparatively with the previously determined (Fe-Mn)Pt3 and (Co-Mn)Pt3 phase diagrams. The randomness of the average exchange interaction is suggested to arise from a competition between the three dominant magnetic interactions JCoCo, JFeFe, and JCoFe of 3d atoms in sites of second nearest neighbors in the L12 structure.

  14. Quantum phases and phase transitions of frustrated hard-core bosons on a triangular ladder

    NASA Astrophysics Data System (ADS)

    Mishra, Tapan; Pai, Ramesh V.; Mukerjee, Subroto; Paramekanti, Arun

    2013-05-01

    Kinetically frustrated bosons at half filling in the presence of a competing nearest-neighbor repulsion support a wide supersolid regime on the two-dimensional triangular lattice. We study this model on a two-leg ladder using the finite-size density-matrix renormalization-group method, obtaining a phase diagram which contains three phases: a uniform superfluid (SF), an insulating charge density wave (CDW) crystal, and a bond ordered insulator (BO). We show that the transitions from SF to CDW and SF to BO are continuous in nature, with critical exponents varying continuously along the phase boundaries, while the transition from CDW to BO is found to be first order. The phase diagram is also found to contain an exactly solvable Majumdar Ghosh point, and reentrant SF to CDW phase transitions.

  15. Process for phase separation

    DOEpatents

    Comolli, Alfred G.

    1979-01-01

    This invention provides a continuous process for separating a gaseous phase from a hydrocarbon liquid containing carbonaceous particulates and gases. The liquid is fed to a cylindrical separator, with the gaseous phase being removed therefrom as an overhead product, whereas the hydrocarbon liquid and the particulates are withdrawn as a bottoms product. By feeding the liquid tangentially to the separator and maintaining a particulate-liquid slurry downward velocity of from about 0.01 to about 0.25 fps in the separator, a total solids weight percent in the slurry of from about 0.1 to about 30%, a slurry temperature of from about 550.degree. to about 900.degree. F., a slurry residence time in the separator of from about 30 to about 360 seconds, and a length/diameter ratio for the separator of from about 20/1 to about 50/1, so that the characterization factor, .alpha., defined as ##STR1## DOES NOT EXCEED ABOUT 48 (.degree.R sec.sup.2)/ft, the deposit of carbonaceous materials on the interior surface of the separator may be substantially eliminated.

  16. Low gravity phase separator

    NASA Technical Reports Server (NTRS)

    Smoot, G. F.; Pope, W. L.; Smith, L. (Inventor)

    1977-01-01

    An apparatus is described for phase separating a gas-liquid mixture as might exist in a subcritical cryogenic helium vessel for cooling a superconducting magnet at low gravity such as in planetary orbit, permitting conservation of the liquid and extended service life of the superconducting magnet.

  17. Phase Diagram of the Frustrated Square-Lattice Hubbard Model: Variational Cluster Approach

    NASA Astrophysics Data System (ADS)

    Misumi, Kazuma; Kaneko, Tatsuya; Ohta, Yukinori

    2016-06-01

    The variational cluster approximation is used to study the frustrated Hubbard model at half filling defined on the two-dimensional square lattice with anisotropic next-nearest-neighbor hopping parameters. We calculate the ground-state phase diagrams of the model in a wide parameter space for a variety of lattice geometries, including square, crossed-square, and triangular lattices. We examine the Mott metal-insulator transition and show that, in the Mott insulating phase, magnetic phases with Néel, collinear, and spiral orders appear in relevant parameter regions, and in an intermediate region between these phases, a nonmagnetic insulating phase caused by the quantum fluctuations in the geometrically frustrated spin degrees of freedom emerges.

  18. Novel Quantum Phase Transition in the Frustrated Spin Nanotube

    NASA Astrophysics Data System (ADS)

    Sakai, Toru; Nakano, Hiroki

    The S=1/2 three-leg quantum spin tube is investigated using the numerical diagonalization. The study indicated a new quantum phase transition between the 1/3 magnetization plateau phase and the plateauless one, with respect to the spin anisotropy. The phase diagram is also presented.

  19. Classification of ground states and normal modes for phase-frustrated multicomponent superconductors

    NASA Astrophysics Data System (ADS)

    Weston, Daniel; Babaev, Egor

    2013-12-01

    We classify ground states and normal modes for n-component superconductors with frustrated intercomponent Josephson couplings, focusing on n=4. The results should be relevant not only to multiband superconductors, but also to Josephson-coupled multilayers and Josephson-junction arrays. It was recently discussed that three-component superconductors can break time-reversal symmetry as a consequence of phase frustration. We discuss how to classify frustrated superconductors with an arbitrary number of components. Although already for the four-component case there are a large number of different combinations of phase-locking and phase-antilocking Josephson couplings, we establish that there are a much smaller number of equivalence classes where properties of frustrated multicomponent superconductors can be mapped to each other. This classification is related to the graph-theoretical concept of Seidel switching. Numerically, we calculate ground states, normal modes, and characteristic length scales for the four-component case. We report conditions of appearance of new accidental continuous ground-state degeneracies.

  20. Supersolid phase induced by correlated hopping in spin-1/2 frustrated quantum magnets.

    PubMed

    Schmidt, K P; Dorier, J; Läuchli, A M; Mila, F

    2008-03-01

    We show that correlated hopping of triplets, which is often the dominant source of kinetic energy in dimer-based frustrated quantum magnets, produces a remarkably strong tendency to form supersolid phases in a magnetic field. These phases are characterized by simultaneous modulation and ordering of the longitudinal and transverse magnetization, respectively. Using quantum Monte Carlo and a semiclassical approach for an effective hard-core boson model with nearest-neighbor repulsion on a square lattice, we prove, in particular, that a supersolid phase can exist even if the repulsion is not strong enough to stabilize an insulating phase at half-filling. Experimental implications for frustrated quantum antiferromagnets in a magnetic field at zero and finite temperature are discussed. PMID:18352679

  1. Microgravity Passive Phase Separator

    NASA Technical Reports Server (NTRS)

    Paragano, Matthew; Indoe, William; Darmetko, Jeffrey

    2012-01-01

    A new invention disclosure discusses a structure and process for separating gas from liquids in microgravity. The Microgravity Passive Phase Separator consists of two concentric, pleated, woven stainless- steel screens (25-micrometer nominal pore) with an axial inlet, and an annular outlet between both screens (see figure). Water enters at one end of the center screen at high velocity, eventually passing through the inner screen and out through the annular exit. As gas is introduced into the flow stream, the drag force exerted on the bubble pushes it downstream until flow stagnation or until it reaches an equilibrium point between the surface tension holding bubble to the screen and the drag force. Gas bubbles of a given size will form a front that is moved further down the length of the inner screen with increasing velocity. As more bubbles are added, the front location will remain fixed, but additional bubbles will move to the end of the unit, eventually coming to rest in the large cavity between the unit housing and the outer screen (storage area). Owing to the small size of the pores and the hydrophilic nature of the screen material, gas does not pass through the screen and is retained within the unit for emptying during ground processing. If debris is picked up on the screen, the area closest to the inlet will become clogged, so high-velocity flow will persist farther down the length of the center screen, pushing the bubble front further from the inlet of the inner screen. It is desired to keep the velocity high enough so that, for any bubble size, an area of clean screen exists between the bubbles and the debris. The primary benefits of this innovation are the lack of any need for additional power, strip gas, or location for venting the separated gas. As the unit contains no membrane, the transport fluid will not be lost due to evaporation in the process of gas separation. Separation is performed with relatively low pressure drop based on the large surface

  2. Electrical switching to probe complex phases in a frustrated manganite

    NASA Astrophysics Data System (ADS)

    Asthana, Saket; Fujiwara, Kohei; Tanaka, Hidekazu

    2014-06-01

    Electrical switching was used to investigate complex phases induced by Cr-substitution in (Pr1/3Sm2/3)2/3Sr1/3MnO3. This system was expected to transform from a Type I (Mn4+/Mn3+≈3/7) to Type II (Mn4+/Mn3+≈1) manganite at critical Cr content, satisfying a virtual Mn4+/Mn3+ ratio close to unity. The phase diagram of (Pr1/3Sm2/3)2/3Sr1/3Mn0.8Cr0.2O3 including charge/spin ordered/disordered phases was probed by electrical switching. The ferromagnetic insulating phase at <~100 K, located next to the charge-ordered antiferromagnetic phase, exhibited a sudden rise in conductivity upon electric-field biasing. This resulted from the melting of charge ordering, and demonstrated the presence of a crossover regime of two coexisting magnetic orderings.

  3. Frustrated polaritons

    NASA Astrophysics Data System (ADS)

    Schmidt, Sebastian

    2016-07-01

    Artificially engineered light–matter systems constitute a novel, versatile architecture for the quantum simulation of driven, dissipative phase transitions and non-equilibrium quantum many-body systems. Here, we discuss recent experimental as well as theoretical works on the simulation of geometrical frustration in interacting photonic systems out of equilibrium. In particular, we review two recent discoveries at the interface of quantum optics and condensed matter physics: (i) the experimental achievement of Bosonic condensation into a flat energy band and (ii) the theoretical prediction of crystalline phases of light in a frustrated qubit-cavity array. We show that this new line of research leads to novel and unique tools for the experimental investigation of frustrated systems and holds the potential to create new phases of light and matter with interesting spatial structure.

  4. Global Stability and the Magnetic Phase Diagram of a Geometrically-Frustrated Triangular Lattice Antiferromagnet

    SciTech Connect

    Fishman, Randy Scott; Haraldsen, Jason T

    2011-01-01

    While a magnetic phase may be both locally stable and globally unstable, global stability always implies local stability. The distinction between local and global stability is studied on a geometrically-frustrated triangular lattice antiferromagnet with easy axis, single-ion anisotropy D along the z axis. Whereas the critical value Dloc c for local stability may be discontinuous across a phase boundary, the critical value Dglo c Dloc c for global stability must be continuous. We demonstrate this behavior across the phase boundary between collinear 3 and 4 sublattice phases that are stable for large D.

  5. Emergent excitation in the paramagnetic phase of geometrically frustrated GdMn2O5

    NASA Astrophysics Data System (ADS)

    Bukhari, Syed Hamad; Ahmad, Javed

    2016-07-01

    We have measured dielectric constant (ε) as well as magnetic susceptibility (χ) of GdMn2O5 in order to elucidate magnetoelectric phase transitions slightly above and below Néel temperature (TN). Our measurements clearly show that above TN there are short range magnetic correlations arising from geometrically frustrated Mn moments, which fluctuate with respect to field and frequency. These well-defined magnetoelectric phase transitions, together with other transitions below TN, have been observed and discussed in the light of the χ. Magnetoelectric phase diagram is drawn which corresponds well to polarization flip phenomenon as induced by 90° rotation of Gd moments in low temperature phase.

  6. Phase and vortex correlations in superconducting Josephson-junction arrays at irrational magnetic frustration.

    PubMed

    Granato, Enzo

    2008-07-11

    Phase coherence and vortex order in a Josephson-junction array at irrational frustration are studied by extensive Monte Carlo simulations using the parallel-tempering method. A scaling analysis of the correlation length of phase variables in the full equilibrated system shows that the critical temperature vanishes with a power-law divergent correlation length and critical exponent nuph, in agreement with recent results from resistivity scaling analysis. A similar scaling analysis for vortex variables reveals a different critical exponent nuv, suggesting that there are two distinct correlation lengths associated with a decoupled zero-temperature phase transition. PMID:18764218

  7. Vector chiral phases in the frustrated 2D XY model and quantum spin chains.

    PubMed

    Schenck, H; Pokrovsky, V L; Nattermann, T

    2014-04-18

    The phase diagram of the frustrated 2D classical and 1D quantum XY models is calculated analytically. Four transitions are found: the vortex unbinding transitions triggered by strong fluctuations occur above and below the chiral transition temperature. Vortex interaction is short range on small and logarithmic on large scales. The chiral transition, though belonging to the Ising universality class by symmetry, has different critical exponents due to nonlocal interaction. In a narrow region close to the Lifshitz point a reentrant phase transition between paramagnetic and quasiferromagnetic phase appears. Applications to antiferromagnetic quantum spin chains and multiferroics are discussed. PMID:24785067

  8. Pinball liquid phase from Hund's coupling in frustrated transition-metal oxides

    NASA Astrophysics Data System (ADS)

    Ralko, Arnaud; Merino, Jaime; Fratini, Simone

    2015-04-01

    The interplay of nonlocal Coulomb repulsion and Hund's coupling in the d -orbital manifold in frustrated triangular lattices is analyzed by a multiband extended Hubbard model. We find a rich phase diagram with several competing phases, including a robust pinball liquid phase, which is an unconventional metal characterized by threefold charge order, bad metallic behavior, and the emergence of high-spin local moments. Our results naturally explain the anomalous charge-ordered metallic state observed in the triangular layered compound AgNiO2. The potential relevance to other triangular transition-metal oxides is discussed.

  9. Chemical Frustration. A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases, Final Report

    SciTech Connect

    Fredrickson, Daniel C

    2015-06-23

    Final technical report for "Chemical Frustration: A Design Principle for the Discovery of New Complex Alloy and Intermetallic Phases" funded by the Office of Science through the Materials Chemistry Program of the Office of Basic Energy Sciences.

  10. Laws of formation of polar smectic phases under a frustrated interaction

    SciTech Connect

    Dolganov, P. V.; Zhilin, V. M.; Kats, E. I.

    2012-12-15

    The Landau theory of phase transitions with a two-component order parameter is used to systematically calculate the structures and phase diagrams of polar liquid crystals. Commensurate and incommensurate structures with a layer-type period form as a result of a frustration interaction. Phase diagrams are calculated when various short- and long-range interlayer interactions are sequentially introduced. As a result, the nature of formation of various structures is revealed. The calculated phase diagrams explain the formation of various phases, their temperature sequence (including so-called 'unusual' sequence of phases), and the nature of forces responsible for the formation of a certain structure and the shape of a phase diagram.

  11. Degeneracies and exotic phases in an isotropic frustrated spin-1/2 chain

    NASA Astrophysics Data System (ADS)

    Parvej, Aslam; Kumar, Manoranjan

    2016-03-01

    In the presence of an axial magnetic field, a frustrated isotropic J1 - J2 model system shows many exotic phases, such as vector chiral and multipolar phases. In this paper, the phase boundaries of these exotic phases are calculated based on the order parameters, energy level crossings and magnetization jumps in the system. The order parameter of the vector chiral phase is calculated using the broken symmetry states at a finite magnetic field. The exact diagonalization and the density matrix renormalization group results are used to show that the vector chiral phase exists only in a narrow range of J2/J1 parameter space. In the quadrupolar phase, the magnetization jumps can be associated with the binding energy of two magnons localized at two different legs of the zigzag chain. The energy level crossings and degeneracies in the presence of the axial magnetic field are studied in detail using the exact diagonalization method.

  12. Random exchange interaction effects on the phase transitions in frustrated classical Heisenberg model

    SciTech Connect

    Li, W. C.; Song, X.; Feng, J. J.; Zeng, M.; Gao, X. S.; Qin, M. H.; Jia, X. T.

    2015-07-07

    In this work, the effects of the random exchange interaction on the phase transitions and phase diagrams of classical frustrated Heisenberg model are investigated by Monte Carlo simulation in order to simulate the chemical doping effect in real materials. It is observed that the antiferromagnetic transitions shift toward low temperature with the increasing magnitude of the random exchange interaction, which can be qualitatively understood from the competitions among local spin states. This study is related to the magnetic properties in the doped iron-based superconductors.

  13. Symmetry-protected topological phases and transition in a frustrated spin-1/2 XXZ chain

    NASA Astrophysics Data System (ADS)

    Ueda, Hiroshi; Onoda, Shigeki

    2014-12-01

    A frustrated spin-1/2 XXZ zigzag chain relevant to Rb2Cu2Mo3O12 is revisited in the light of symmetry-protected topological (SPT) phases. Using a density-matrix renormalization group method for infinite systems, we identify projective representations for four distinct time-reversal invariant SPT phases; two parity-symmetric dimer phases near the Heisenberg and XX limits and two parity-broken vector-chiral (VC) dimer phases in between. A small bond alternation in the nearest-neighbor ferromagnetic exchange coupling induces a direct SPT transition between the two distinct VC dimer phases. It is also found numerically that two Berezinskii-Kosterlitz-Thouless transitions, which occur from the gapless to the two distinct gapped VC phases in the case of δ =0 , meet each other in the case of δ >0 at a Gaussian criticality of the same Tomonaga-Luttinger parameter value as in the SU(2)-symmetric case.

  14. Geometrical aspects of the frustration in the cubic phases of lyotropic liquid crystals.

    PubMed Central

    Anderson, D M; Gruner, S M; Leibler, S

    1988-01-01

    Bicontinuous cubic phases, composed of bilayers arranged in the geometries of periodic minimal surfaces, are found in a variety of different lipid/water systems. It has been suggested recently that these cubic structures arrive as the result of competition between two free-energy terms: the curvature energy of each monolayer and the stretching energy of the lipid chains. This scenario, closely analogous to the one that explains the origin of the hexagonal phases, is investigated here by means of simple geometrical calculations. It is first assumed that the lipid bilayer is of constant thickness and the distribution of the (local) mean curvature of the phospholipid-water interfaces is calculated. Then, assuming the mean curvature of these interfaces is constant, the distribution of the bilayer's thickness is calculated. Both calculations quantify the fact that the two energy terms are frustrated and cannot be satisfied simultaneously. However, the amount of the frustration can be smaller for the cubic phase than for the lamellar and hexagonal structures. Therefore, this phase can appear in the phase diagram between the other two, as observed in many recent experiments. PMID:3399497

  15. Self-similarity of phase-space networks of frustrated spin models and lattice gas models

    NASA Astrophysics Data System (ADS)

    Peng, Yi; Wang, Feng; Han, Yilong

    2013-03-01

    We studied the self-similar properties of the phase-spaces of two frustrated spin models and two lattice gas models. The frustrated spin models included (1) the anti-ferromagnetic Ising model on a two-dimensional triangular lattice (1a) at the ground states and (1b) above the ground states and (2) the six-vertex model. The two lattice gas models were (3) the one-dimensional lattice gas model and (4) the two-dimensional lattice gas model. The phase spaces were mapped to networks so that the fractal analysis of complex networks could be applied, i.e. the box-covering method and the cluster-growth method. These phase spaces, in turn, establish new classes of networks with unique self-similar properties. Models 1a, 2, and 3 with long-range power-law correlations in real space exhibit fractal phase spaces, while models 1b and 4 with short-range exponential correlations in real space exhibit nonfractal phase spaces. This behavior agrees with one of untested assumptions in Tsallis nonextensive statistics. Hong Kong GRC grants 601208 and 601911

  16. Three phase downhole separator process

    DOEpatents

    Cognata, Louis John

    2008-06-24

    Three Phase Downhole Separator Process (TPDSP) is a process which results in the separation of all three phases, (1) oil, (2) gas, and (3) water, at the downhole location in the well bore, water disposal injection downhole, and oil and gas production uphole.

  17. Phase Diagram of a Geometrically-Frustrated Triangular-Lattice Antiferromagnet in a Magnetic Field

    SciTech Connect

    Fishman, Randy Scott

    2011-01-01

    The magnetic phase diagram of a geometrically-frustrated triangular-lattice antiferromagnet is evaluated as a function of external magnetic field and anisotropy using a trial spin state built from harmonics of a fundamental ordering wavevector. A non-collinear incommensurate state, observed to be chiral and ferroelectric in CuFeO2, is sandwiched between a collinear state with 4 sublattices (SLs) and a 5-SL state. Chiral and non-collinear 5-SL states are predicted to appear at fields above and below the collinear 5-SL states.

  18. Quantum entanglement and quantum phase transitions in frustrated Majumdar-Ghosh model

    NASA Astrophysics Data System (ADS)

    Liu, Guang-Hua; Wang, Chun-Hai; Deng, Xiao-Yan

    2011-01-01

    By using the density matrix renormalization group technique, the quantum phase transitions in the frustrated Majumdar-Ghosh model are investigated. The behaviors of the conventional order parameter and the quantum entanglement entropy are analyzed in detail. The order parameter is found to peak at J2∼0.58, but not at the Majumdar-Ghosh point ( J2=0.5). Although, the quantum entanglements calculated with different subsystems display dissimilarly, the extremes of their first derivatives approach to the same critical point. By finite size scaling, this quantum critical point JC2 converges to around 0.301 in the thermodynamic limit, which is consistent with those predicted previously by some authors (Tonegawa and Harada, 1987 [6]; Kuboki and Fukuyama, 1987 [7]; Chitra et al., 1995 [9]). Across the JC2, the system undergoes a quantum phase transition from a gapless spin-fluid phase to a gapped dimerized phase.

  19. Microcellular foams via phase separation

    SciTech Connect

    Young, A.T.

    1985-01-01

    A study of wide variety of processes for making plastic foams shows that phase separation processes for polymers from solutions offers the most viable methods for obtaining rigid plastic foams which met the physical requirements for fusion target designs. Four general phase separation methods have been shown to give polymer foams with densities less than 0.1 g/cm/sup 3/ and cell sizes of 30..mu..m or less. These methods involve the utilization of non-solvent, chemical or thermal cooling processes to achieve a controlled phase separation wherein either two distinct phases are obtained where the polymer phase is a continuous phase or two bicontinuous phases are obtained where both the polymer and solvent are interpenetrating, continuous, labyrinthine phases. Subsequent removal of the solvent gives the final foam structure.

  20. Quantum Phase Transitions with Spin Frustration in a Trapped Ion System

    NASA Astrophysics Data System (ADS)

    Kim, Kihwan; Chang, Ming-Shien; Korenblit, Simcha; Rajibul Islam, Kazi; Monroe, Christopher

    2009-05-01

    We discuss the use of a linear array of trapped ions for quantum simulations of spin chains with long range interactions [1,2]. In particular, we study interesting phase diagrams with only a few ions that involve multiple normal modes of motion and can feature spin frustration. With trapped ions, there is a potential to directly study the entanglement structure in such exotic ground state spin phases. This work is supported by the DARPA OLE Program under ARO contract, IARPA under ARO contract, the NSF PIF Program, and the NSF Physics Frontier Center at JQI. [1] D. Porras and J. I. Cirac, PRL 92, 207901 (2004); X.-L. Deng, D. Porras, and J. I. Cirac, PRA 72, 063407 (2005). [2] A. Friedenauer, H. Schmitz, J. T. Glueckert, D. Porras & T. Schaetz, Nature Physics 4, 757 (2008).

  1. Spin-stripe phase in a frustrated zigzag spin-1/2 chain

    PubMed Central

    Pregelj, M.; Zorko, A.; Zaharko, O.; Nojiri, H.; Berger, H.; Chapon, L. C.; Arčon, D.

    2015-01-01

    Motifs of periodic modulations are encountered in a variety of natural systems, where at least two rival states are present. In strongly correlated electron systems, such behaviour has typically been associated with competition between short- and long-range interactions, for example, between exchange and dipole–dipole interactions in the case of ferromagnetic thin films. Here we show that spin-stripe textures may develop also in antiferromagnets, where long-range dipole–dipole magnetic interactions are absent. A comprehensive analysis of magnetic susceptibility, high-field magnetization, specific heat and neutron diffraction measurements unveils β-TeVO4 as a nearly perfect realization of a frustrated (zigzag) ferromagnetic spin-1/2 chain. Notably, a narrow spin-stripe phase develops at elevated magnetic fields due to weak frustrated short-range interchain exchange interactions, possibly assisted by the symmetry-allowed electric polarization. This concept provides an alternative route for the stripe formation in strongly correlated electron systems and may help understanding of other widespread, yet still elusive, stripe-related phenomena. PMID:26068618

  2. Phase Separation in Cuprate Superconductors - Proceedings of the Workshop

    NASA Astrophysics Data System (ADS)

    Müller, K. A.; Benedek, G.

    1993-01-01

    The Table of Contents for the full book PDF is as follows: * Preface and Scope * Frustrated Phase Separation and High Temperature Superconductivity * Phase Separation and Photo-Induced High Tc Superconductivity in the Cuprates * Neutron Scattering Studies of the Spin Dynamics in La2-xSrxCuO4 * Percolative Phase Separation and High Tc Superconductivity * Phase Separation in Cuprate Superconductors from NMR and Microwave Absorption Measurements * Electronic Structure and Phase Separation in Superconducting Cuprates * The Virtual Exciton Mechanism of Superconductivity * Linear Arrays of Non Homogeneous Cu Sites in the CuO2 Plane: A New Scenario for Pairing Mechanisms in a Corrugated-Iron-Like Plane * Phase Separation, Structure and Superconductivity in Oxygen-Annealed La2CuO4+δ * Phase Separation in La2-xSrxCuO4 and YBa2Cu3Ox Studied by Mössbauer Spectroscopy * Phase Diagram and Transport Studies on La2-xSrxCuO4 * Static and Dynamic Transport Aspects of Phase Separation * Phase Separation in the Superconducting La2Cu4+δ Phases (0 < δ < 0.09) Prepared by Electrochemical Oxidation * Neutron Scattering Study of the YBa2Cu3O6+x System * NMR Investigation of Low Energy Excitations in YBa2Cu3O6+x Single Crystals * Aspects of the Spin Dynamics in the Cuprate Superconductors * Oxygen Order and Spin Structure in YBa2Cu3Ox Deduced from Copper NMR and NQR * Static and Dynamic Magnetic Properties of Ba, Cu and O in YBa2Cu4O8 and Y2Ba4Cu7O15.1 * Positional Splitting of Apex Oxygen and Nonlinear Excitations in Cuprates * Cooper Pair Formation by Distortive Electron-Lattice Coupling * Bipolaronic Charge Density Waves, Polaronic Spin Density Waves, and High Tc Superconductivity * Phase Separation as Result of a Thermodynamical Variational Method for the Emery Model * General Discussion led by G. Benedek and K. A. Müller

  3. Co-operative and frustration effects in novel perovskite-related phases

    NASA Astrophysics Data System (ADS)

    Ebbinghaus, S. G.; Riegg, S.; Götzfried, T.; Reller, A.

    2009-12-01

    We report on magnetic and electronic properties of various perovskite-type oxides containing 4d- and 5d-transition metals. The compounds under investigation crystallize in (distorted) cubic, layered, and hexagonal perovskite-related structures. These changes in structural dimensionality are reflected by different ordering phenomena. (Pseudo-) cubic perovskites ACu3B4O12 (with A = alkali, alkaline earth or rare earth; B = Ru, Ti) possess an A-site ordered structure with copper on modified A-positions. Structural investigations as well as XANES (X-ray absorption near edge structure) measurements indicate a valence degeneracy, which is keeping the oxidation state of Ru close to +4. Upon replacing Ru by Ti, the itinerant magnetism and metallic conductivity of the pure ruthenates successively change to a localized magnetic moment and a semiconducting behavior. The pure titanates like Ln2/3Cu3Ti4O12 or CaCu3Ti4O12are insulators with colossal dielectric constants. The cation-deficient Cu2+xTa4O12+δ shows a large compositional flexibility with 0.125 ≤ x ≤ 0.500. Both copper content and cooling speed have a strong impact on the crystal structure and the observed magnetic ordering. This behavior can be explained by uncompensated Cu2+-moments resulting from different site occupations. Quasi-2D La2RuO5 undergoes a structural and magnetic phase transition at roughly 160 K, leading to a diminishing magnetic moment and a semiconductor-semiconductor transition. LDA calculations reveal an antiferromagnetic coupling within pairs of neighboring Ru4+-ions, leading to a spin-Peierls like transition. New hexagonal perovskites containing Ru, Ir, and Pt crystallize in the [AO1+δ][A2BO6] structure type and contain peroxide ions (O) in the [AO1+δ] layers. La1.2Sr2.7IrO7.33 exhibits a small temperature-independent paramagnetism, which can be explained on basis of the crystal-field splitting and the strong spin-orbit coupling. The isostructural La1.2Sr2.7RuO7.33 shows a frustrated

  4. Analysis of the phase transition for the Ising model on the frustrated square lattice

    NASA Astrophysics Data System (ADS)

    Kalz, Ansgar; Honecker, Andreas; Moliner, Marion

    2011-11-01

    We analyze the phase transition of the frustrated J1-J2 Ising model with antiferromagnetic nearest- and strong next-nearest-neighbor interactions on the square lattice. Using extensive Monte Carlo simulations we show that the nature of the phase transition for 1/2phase transitions via field-theoretic methods; i.e., we calculate the central charge of the underlying field theory via transfer-matrix techniques and present, furthermore, a field-theoretic discussion on the phase-transition behavior of the model. Starting from the conformally invariant fixed point of two decoupled critical Ising models (J1=0), we calculate the effect of the nearest-neighbor coupling term perturbatively using operator product expansions. As an effective action we obtain the Ashkin-Teller model.

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

    NASA Astrophysics Data System (ADS)

    Brzezicki, Wojciech; Oleś, Andrzej M.

    2016-06-01

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

  6. Nematic phase in two-dimensional frustrated systems with power-law decaying interactions

    NASA Astrophysics Data System (ADS)

    Barci, Daniel G.; Ribeiro, Leonardo; Stariolo, Daniel A.

    2013-06-01

    We address the problem of orientational order in frustrated interaction systems as a function of the relative range of the competing interactions. We study a spin model Hamiltonian with short-range ferromagnetic interaction competing with an antiferromagnetic component that decays as a power law of the distance between spins, 1/rα. These systems may develop a nematic phase between the isotropic disordered and stripe phases. We evaluate the nematic order parameter using a self-consistent mean-field calculation. Our main result indicates that the nematic phase exists, at mean-field level, provided 0<α<4. We analytically compute the nematic critical temperature and show that it increases with the range of the interaction, reaching its maximum near α˜0.5. We also compute a coarse-grained effective Hamiltonian for long wavelength fluctuations. For 0<α<4 the inverse susceptibility develops a set of continuous minima at wave vectors |k⃗|=k0(α) which dictate the long-distance physics of the system. For α→4, k0→0, making the competition between interactions ineffective for greater values of α.

  7. Competing Ferri- and Antiferromagnetic Phases in Geometrically Frustrated LuFe2O4

    SciTech Connect

    De Groot, J.; Marty, Karol J; Lumsden, Mark D; Christianson, Andrew D; Nagler, Stephen E; Adiga, Shilpa; Borghols, Wouter; Schmalzl, Karin; Yamani, Z.; Bland, S. R.; de Souza, R.; Staub, U.; Schweika, Werner; Su, Y.; Angst, Manuel

    2012-01-01

    We present a detailed study of magnetism in LuFe2O4, combining magnetization measurements with neutron and soft x-ray diffraction. The magnetic phase diagram in the vicinity of TN involves a metamagnetic transition separating an antiferro- and a ferrimagnetic phase. For both phases the spin structure is refined by neutron diffraction. Observed diffuse magnetic scattering far above TN is explained in terms of near degeneracy of the magnetic phases.

  8. XY-like frustrated magnetic phase transitions in α-RuCl3

    NASA Astrophysics Data System (ADS)

    Tanaka, Hidekazu

    It is known that a honeycomb-lattice antiferromagnet with the nearest-neighbor exchange interaction undergoes a conventional magnetic ordering even for the spin-1/2 case. However, when a certain amount of second-neighbor exchange interaction or anisotropic exchange interaction exists, the honeycomb-lattice quantum magnet exhibits an unusual ground state. In the last decade, spin-1/2 quantum magnets on honeycomb lattices have been attracting considerable attention from the viewpoints of the frustrated J1 -J2 model and the Kitaev-Heisenberg model, both of which can exhibit the spin liquid state in some parameter range. α-RuCl3 is a layered compound, in which magnetic Ru3+ ions with the 4d5 electronic state form a honeycomb lattice. We have investigated the magnetic properties of α-RuCl3 via magnetization and specific heat measurements using single crystals. It was observed that α-RuCl3 undergoes a structural phase transition at Tt ~= 150 K accompanied by fairly large hysteresis. The magnetizations and magnetic susceptibilities are strongly anisotropic, which mainly arise from the anisotropic g-factors. These g-factors and the obtained entropy indicate that the effective spin of Ru3+ is one-half, which results from the low-spin state. Specific heat data show that magnetic ordering occurs in four steps at zero magnetic field. The magnetic phase diagram is obtained. The successive magnetic phase transitions can be ascribed to the competition among exchange interactions. We discuss the strongly anisotropic g-factors and deduce that the exchange interaction is strongly XY-like. Main results of this talk was published in Phys. Rev. B 91, 094422 (2015).

  9. Colossal negative thermal expansion induced by magnetic phase competition on frustrated lattices in Laves phase compound (Hf,Ta)Fe2

    NASA Astrophysics Data System (ADS)

    Li, B.; Luo, X. H.; Wang, H.; Ren, W. J.; Yano, S.; Wang, C.-W.; Gardner, J. S.; Liss, K.-D.; Miao, P.; Lee, S.-H.; Kamiyama, T.; Wu, R. Q.; Kawakita, Y.; Zhang, Z. D.

    2016-06-01

    Competition between ferromagnetic and antiferromagnetic phases on frustrated lattices in hexagonal Laves phase compound Hf0.86Ta0.14Fe2 is investigated by using neutron diffraction as a function of temperature and magnetic fields and density-functional-theory calculations. At 325 K, the compound orders into the 120° frustrated antiferromagnetic state with a well-reduced magnetic moment, and an in-plane lattice contraction simultaneously sets in. With further cooling down, however, the accumulated distortion in turn destabilizes this susceptible frustrated structure. The frustration is completely relieved at 255 K when the first-order transition to the ferromagnetic state takes place, where a colossal negative volumetric thermal expansion, -123 ×10-6 /K, is obtained. Meanwhile, the antiferromagnetic state can be suppressed by few-tesla magnetic fields, which results in a colossal positive magnetostriction. Such delicate competition is attributed to the giant magnetic fluctuation inherent in the frustrated antiferromagnetic state. Therefore, the magnetoelastic instability is approached even under a small perturbation.

  10. Global phase diagram of the stacked frustrated triangular Ising system in a transverse field: a quantum Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Ma, Han; Lou, Jie; Tsvelik, Alexei; Kawashima, Naoki; Chen, Yan

    2014-03-01

    The global phase diagram of the stacked frustrated triangular Ising magnet in a transverse field is obtained by using continuous time quantum Monte Carlo method. As the inter-plane interaction is strengthened, an first-order transition from a ferrimagnetic phase with two equivalent sublattices (FR2) to a partially disordered antiferrimagnetic phase (AF) occurs at small transverse field. In the quasi-one dimensional case, i.e. antiferromagnetically coupled transverse Ising chains, which corresponds to the realistic material CoNb2O6, our simulation reveals the existence of the low-field FR2 phase. In contrast, in the quasi-two dimensional limit, i.e. weakly coupled triangular Ising magnet, upon increasing the transverse magnetic field, the FR2 and AF phases successively appear in the order. In the vicinity of the ordered-disordered phase transition, the nature of phases can hardly be identified within our computational ability. At large transverse field, the paramagnetic phase trivially appears. Future experiments on CoNb2O6 at low temperature are expected to evidence the different magnetic patterns of this frustrated magnet based on our results in the quasi-one dimensional limit.

  11. Derivation and assessment of phase-shifted, disordered vector field models for frustrated solvent interactions

    PubMed Central

    Weber, Jeffrey K.; Pande, Vijay S.

    2013-01-01

    The structure and properties of water at biological interfaces differ drastically from bulk due to effects including confinement and the presence of complicated charge distributions. This non-bulk-like behavior generally arises from water frustration, wherein all favorable interactions among water molecules cannot be simultaneously satisfied. While the frustration of interfacial water is ubiquitous in the cell, the role this frustration plays in mediating biophysical processes like protein folding is not well understood. To investigate the impact of frustration at interfaces, we here derive a general field theoretic model for the interaction of bulk and disordered vector fields at an embedded surface. We calculate thermodynamic and correlation functions for the model in two and three dimensions, and we compare our results to Monte Carlo simulations of lattice system analogs. In our analysis, we see that field-field cross correlations near the interface in the model give rise to a loss in entropy like that seen in glassy systems. We conclude by assessing our theory's utility as a coarse-grained model for water at polar biological interfaces. PMID:23464179

  12. Theory of supersymmetry ``protected'' topological phases of isostatic lattices and highly frustrated magnets

    NASA Astrophysics Data System (ADS)

    Lawler, Michael

    I generalize the theory of phonon topological band structures of isostatic lattices to highly frustrated antiferromagnets. I achieve this with a discovery of a many-body supersymmetry (SUSY) in the phonon problem of balls and springs which also applies to geometrically frustrated magnets. The Witten index of the SUSY model, when restricted to the single body problem (meaningful for linearized phonons), is then shown to be the Calladine-Kane-Lubensky index of mechanical structures that forms the cornerstone of the phonon topological band structure theory. ``Spontaneous supersymmetry breaking'' is then identified as the need to gap all modes in the bulk to create the topological state. The many-body SUSY formulation shows that the topology is not restricted to a band structure problem but extends to systems of coupled bosons and fermions that are in principle also realizable in solid state systems. The analogus supersymmetry of the magnon problem turns out to be particularly useful for highly frustrated magnets with the kagome family of antiferromagnets an analog of topological isostatic lattices. Thus, a solid state realization of the theory of phonon topological band structure may be found in highly frustrated magnets. However, our results show that this topology is protected not

  13. Novel Magnetic Phases Revealed by Ultra-High Magnetic Field in the Frustrated Magnet ZnCr2O4

    NASA Astrophysics Data System (ADS)

    Miyata, Atsuhiko; Ueda, Hiroaki; Ueda, Yutaka; Motome, Yukitoshi; Shannon, Nic; Penc, Karlo; Takeyama, Shojiro

    2011-07-01

    The Faraday rotation technique is used to map out the finite-temperature phase diagram of the prototypical frustrated magnet ZnCr2O4, in magnetic fields of up to 190 T generated by the single-turn coil method. We find evidence for a number of magnetic phase transitions, which are well-described by the theory based on spin--lattice coupling. In addition to the 1/2 plateau and a 3:1 canted phase, a 2:1:1 canted phase is found for the first time in chromium spinel oxides, which has been predicted by a theory of Penc et al. to realize in a small spin--lattice coupling limit. Both the new 2:1:1 and the 3:1 phases are regarded as the supersolid phases according to a magnetic analogy of Matsuda and Tsuneto, and Liu and Fisher.

  14. Giant barocaloric effect enhanced by the frustration of the antiferromagnetic phase in Mn3GaN.

    PubMed

    Matsunami, Daichi; Fujita, Asaya; Takenaka, Koshi; Kano, Mika

    2015-01-01

    First-order phase transitions are accompanied by a latent heat. Consequently, manipulating them by means of an external field causes a caloric effect. Although transitions from antiferromagnetic to paramagnetic states are not controlled by a magnetic field, a large barocaloric effect is expected when strong cross-correlations between the volume and magnetic order occur. Here we examine how geometric frustration in itinerant antiferromagnetic compounds can enhance the barocaloric effect. We study the thermodynamic behaviour of the frustrated antiferromagnet Mn3GaN, and report an entropy change of 22.3 J kg(-1) K(-1) that is concomitant with a hydrostatic pressure change of 139 MPa. Furthermore, the calculated value of the adiabatic temperature change reaches 5 K by depressurization of 93 MPa. The giant barocaloric effect in Mn3GaN is caused by a frustration-driven enhancement of the ratio of volume change against the pressure coefficient of the Néel temperature. This mechanism for enhancing the barocaloric effect can form the basis for a new class of materials for solid-state refrigerants. PMID:25344781

  15. Low-temperature magnetic phase transitions of the geometrically frustrated isosceles triangular Ising antiferromagnet CoNb2O6

    NASA Astrophysics Data System (ADS)

    Kobayashi, S.; Mitsuda, S.; Prokes, K.

    2001-01-01

    Low-temperature magnetic phase transitions of the geometrically frustrated isosceles triangular Ising antiferromagnet CoNb2O6 have been investigated by means of neutron diffraction down to T=0.2 K under applied fields up to H∥c=4.4 kOe. Below T~0.6 K, the relaxation time of the system becomes extremely long compared with our observation time, being responsible for all the anomalous low-temperature magnetic properties observed in the bulk measurements [T. Hanawa et al., J. Phys. Soc. Jpn. 63, 2706 (1994)]. In addition to confirmation of the triple point where the antiferromagnetic, field-induced ferrimagnetic, and incommensurate phases meet together in the H∥c-T magnetic phase diagram, we also found various ordered phases that are field induced between the ferrimagnetic and saturated paramagnetic phases.

  16. The effect of position of (S)-2-octyloxy tail on the formation of frustrated blue phase and antiferroelectric phase in Schiff base liquid crystals.

    PubMed

    Huang, Chiung-Cheng; Hsu, Ching-Chung; Chen, Li-Wen; Cheng, Yu-Lun

    2014-12-14

    Two series of chiral salicylaldimine-based liquid crystals which differ from each other in the position of the (S)-2-octyloxy tail have been synthesized and characterized by polarizing optical microscopy, differential scanning calorimetry, and electrical switching. Compounds OH I (n = 6-7) having (S)-2-octyloxy tail close to the salicylaldimine core and compounds OH II (n = 6-11) having (S)-2-octyloxy tail far from the salicylaldimine core exhibit polymorphism of mesophases including frustrated blue phase and antiferroelectric (SmC*(A)) phases. Notably, as compared with structurally similar Schiff base compounds H I (n = 7), intramolecular hydrogen bonding in antiferroelectric salicylaldimine-based compounds OH I (n = 7) induces the frustrated blue phase. However, as compared with structurally similar Schiff base compounds OH II (n = 8), the lack of intramolecular hydrogen bonding in Schiff base compounds H II (n = 8) suppresses antiferroelectric properties. PMID:25341417

  17. Two-Phase Flow Separator Investigation

    NASA Video Gallery

    The goal of the Two-Phase Flow Separator investigation is to help increase understanding of how to separate gases and liquids in microgravity. Many systems on the space station contain both liquids...

  18. Binary Colloidal Alloy Test-5: Phase Separation

    NASA Technical Reports Server (NTRS)

    Lynch, Matthew; Weitz, David A.; Lu, Peter J.

    2008-01-01

    The Binary Colloidal Alloy Test - 5: Phase Separation (BCAT-5-PhaseSep) experiment will photograph initially randomized colloidal samples onboard the ISS to determine their resulting structure over time. This allows the scientists to capture the kinetics (evolution) of their samples, as well as the final equilibrium state of each sample. BCAT-5-PhaseSep studies collapse (phase separation rates that impact product shelf-life); in microgravity the physics of collapse is not masked by being reduced to a simple top and bottom phase as it is on Earth.

  19. Competition between supersolid phases and magnetization plateaus in the frustrated easy-axis antiferromagnet on a triangular lattice

    NASA Astrophysics Data System (ADS)

    Seabra, Luis; Shannon, Nic

    2011-04-01

    The majority of magnetic materials possess some degree of magnetic anisotropy, either at the level of a single ion, or in the exchange interactions between different magnetic ions. Where these exchange interactions are also frustrated, the competition between them and anisotropy can stabilize a wide variety of new phases in applied magnetic field. Motivated by the hexagonal delafossite 2H-AgNiO2, we study the Heisenberg antiferromagnet on a layered triangular lattice with competing first- and second-neighbor interactions and single-ion easy-axis anisotropy. Using a combination of classical Monte Carlo simulation, mean-field analysis, and Landau theory, we establish the magnetic phase diagram of this model as a function of temperature and magnetic field for a fixed ratio of exchange interactions, but with values of easy-axis anisotropy D extending from the Heisenberg (D=0) to the Ising (D=∞) limits. We uncover a rich variety of different magnetic phases. These include several phases which are magnetic supersolids (in the sense of Matsuda and Tsuneto or Liu and Fisher), one of which may already have been observed in AgNiO2. We explore how this particular supersolid arises through the closing of a gap in the spin-wave spectrum, and how it competes with rival collinear phases as the easy-axis anisotropy is increased. The finite temperature properties of this phase are found to be different from those of any previously studied magnetic supersolid.

  20. Mechanisms and Consequences of Macromolecular Phase Separation.

    PubMed

    Bergeron-Sandoval, Louis-Philippe; Safaee, Nozhat; Michnick, Stephen W

    2016-05-19

    Over a century ago, colloidal phase separation of matter into non-membranous bodies was recognized as a fundamental organizing principal of cell "protoplasm." Recent insights into the molecular properties of such phase-separated bodies present challenges to our understanding of cellular protein interaction networks, as well as opportunities for interpreting and understanding of native and pathological genetic and molecular interactions. Here, we briefly review examples of and discuss physical principles of phase-separated cellular bodies and then reflect on how knowledge of these principles may direct future research on their functions. PMID:27203111

  1. Study Of Phase Separation In Glass

    NASA Technical Reports Server (NTRS)

    Neilson, George F.; Weinberg, Michael C.; Smith, Gary L.

    1989-01-01

    Report describes an experimental study of effect of hydroxide content on phase separation in soda/silica glasses. Ordinary and gel glasses melted at 1,565 degree C, and melts stirred periodically. "Wet" glasses produced by passing bubbles of N2 saturated with water through melts; "dry" glasses prepared in similar manner, except N2 dried before passage through melts. Analyses of compositions of glasses performed by atomic-absorption and index-of-refraction measurements. Authors conclude hydroxide speeds up phase separation, regardless of method (gel or ordinary) by which glass prepared. Eventually helps material scientists to find ways to control morphology of phase separation.

  2. Incommensurate phase of a triangular frustrated Heisenberg model studied via Schwinger-boson mean-field theory

    NASA Astrophysics Data System (ADS)

    Li, Peng; Su, Haibin; Dong, Hui-Ning; Shen, Shun-Qing

    2009-08-01

    We study a triangular frustrated antiferromagnetic Heisenberg model with nearest-neighbor interactions J1 and third-nearest-neighbor interactions J3 by means of Schwinger-boson mean-field theory. By setting an antiferromagnetic J3 and varying J1 from positive to negative values, we disclose the low-temperature features of its interesting incommensurate phase. The gapless dispersion of quasiparticles leads to the intrinsic T2 law of specific heat. The magnetic susceptibility is linear in temperature. The local magnetization is significantly reduced by quantum fluctuations. We address possible relevance of these results to the low-temperature properties of NiGa2S4. From a careful analysis of the incommensurate spin wavevector, the interaction parameters are estimated as J1≈-3.8755 K and J3≈14.0628 K, in order to account for the experimental data.

  3. Thermodynamic modeling of phase separation in manganites

    NASA Astrophysics Data System (ADS)

    Sacanell, J.; Parisi, F.; Campoy, J. C. P.; Ghivelder, L.

    2006-01-01

    We present a phenomenological model based on the thermodynamics of the phase separated state of manganites, accounting for its static and dynamic properties. Through calorimetric measurements on La0.225Pr0.4Ca0.375MnO3 the low temperature free energies of the coexisting ferromagnetic and charge ordered phases are evaluated. The phase separated state is modeled by free energy densities uniformly spread over the sample volume. The calculations contemplate the out of equilibrium features of the coexisting phase regime, to allow a comparison between magnetic measurements and the predictions of the model. A phase diagram including the static and dynamic properties of the system is constructed, showing the existence of blocked and unblocked regimes which are characteristics of the phase separated state in manganites.

  4. Polymer solution phase separation: Microgravity simulation

    NASA Technical Reports Server (NTRS)

    Cerny, Lawrence C.; Sutter, James K.

    1989-01-01

    In many multicomponent systems, a transition from a single phase of uniform composition to a multiphase state with separated regions of different composition can be induced by changes in temperature and shear. The density difference between the phase and thermal and/or shear gradients within the system results in buoyancy driven convection. These differences affect kinetics of the phase separation if the system has a sufficiently low viscosity. This investigation presents more preliminary developments of a theoretical model in order to describe effects of the buoyancy driven convection in phase separation kinetics. Polymer solutions were employed as model systems because of the ease with which density differences can be systematically varied and because of the importance of phase separation in the processing and properties of polymeric materials. The results indicate that the kinetics of the phase separation can be performed viscometrically using laser light scattering as a principle means of following the process quantitatively. Isopycnic polymer solutions were used to determine the viscosity and density difference limits for polymer phase separation.

  5. Vapor-liquid phase separator studies

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Lee, J. M.; Kim, Y. I.; Hepler, W. A.; Frederking, T. H. K.

    1983-01-01

    Porous plugs serve as both entropy rejection devices and phase separation components separating the vapor phase on the downstream side from liquid Helium 2 upstream. The liquid upstream is the cryo-reservoir fluid needed for equipment cooling by means of Helium 2, i.e Helium-4 below its lambda temperature in near-saturated states. The topics outlined are characteristic lengths, transport equations and plug results.

  6. Gas-Liquid Flows and Phase Separation

    NASA Technical Reports Server (NTRS)

    McQuillen, John

    2004-01-01

    Common issues for space system designers include:Ability to Verify Performance in Normal Gravity prior to Deployment; System Stability; Phase Accumulation & Shedding; Phase Separation; Flow Distribution through Tees & Manifolds Boiling Crisis; Heat Transfer Coefficient; and Pressure Drop.The report concludes:Guidance similar to "A design that operates in a single phase is less complex than a design that has two-phase flow" is not always true considering the amount of effort spent on pressurizing, subcooling and phase separators to ensure single phase operation. While there is still much to learn about two-phase flow in reduced gravity, we have a good start. Focus now needs to be directed more towards system level problems .

  7. Phase Separation in Solutions of Monoclonal Antibodies

    NASA Astrophysics Data System (ADS)

    Benedek, George; Wang, Ying; Lomakin, Aleksey; Latypov, Ramil

    2012-02-01

    We report the observation of liquid-liquid phase separation (LLPS) in a solution of humanized monoclonal antibodies, IgG2, and the effects of human serum albumin, a major blood protein, on this phase separation. We find a significant reduction of phase separation temperature in the presence of albumin, and a preferential partitioning of the albumin into the antibody-rich phase. We provide a general thermodynamic analysis of the antibody-albumin mixture phase diagram and relate its features to the magnitude of the effective inter-protein interactions. Our analysis suggests that additives (HSA in this report), which have moderate attraction with antibody molecules, may be used to forestall undesirable protein condensation in antibody solutions. Our findings are relevant to understanding the stability of pharmaceutical solutions of antibodies and the mechanisms of cryoglobulinemia.

  8. Phase separations in a copolymer copolymer mixture

    NASA Astrophysics Data System (ADS)

    Zhang, Jin-Jun; Jin, Guojun; Ma, Yuqiang

    2006-01-01

    We propose a three-order-parameter model to study the phase separations in a diblock copolymer-diblock copolymer mixture. The cell dynamical simulations provide rich information about the phase evolution and structural formation, especially the appearance of onion-rings. The parametric dependence and physical reason for the domain growth of onion-rings are discussed.

  9. Electronic phase separation in iron pnictides

    NASA Astrophysics Data System (ADS)

    Sboychakov, A. O.; Rozhkov, A. V.; Kugel, K. I.; Rakhmanov, A. L.; Nori, Franco

    2013-11-01

    A mechanism for electronic phase separation in iron pnictides is proposed. It is based on the competition between commensurate and incommensurate spin-density-wave phases in a system with an imperfect doping-dependent nesting of a multisheeted Fermi surface. We model the Fermi surface by two elliptical electron pockets and three circular hole pockets. The interaction between a charge carrier in a hole band and a carrier in an electron band leads to the formation of spin-density-wave order. The commensurate spin density wave in the parent compound transforms to the incommensurate phase when doping is introduced. We show that, for certain parameter values, the uniform state is unstable with respect to phase separation. The resulting inhomogeneous state consists of regions of commensurate and incommensurate spin-density-wave phases. Our results are in qualitative agreement with recent observations of incommensurate spin density waves and electronic inhomogeneity in iron pnictides.

  10. Thermodynamic properties of frustrated arbitrary spin-S J1-J2 quantum Heisenberg antiferromagnet on the body-centered-cubic lattice in random phase approximation

    NASA Astrophysics Data System (ADS)

    Mi, Bin-Zhou

    2016-07-01

    The thermodynamic properties of the frustrated arbitrary spin-S J1-J2 Heisenberg antiferromagnet on the body-centered-cubic lattice for Néel phase are systematically calculated by use of the double-time Green's function method within the random phase approximation (RPA). The role of spin quantum number and frustration strength on sublattice magnetization, Néel temperature, internal energy, and free energy are carefully analyzed. The curve of zero-temperature sublattice magnetization / S versus frustration strength J2/J1 values are almost flat at the larger spin quantum number S=10. With the increase of normalized temperature T/TN, the larger the spin quantum number S, the faster the / S drops, and the smaller influence of J2/J1 on the / S versus T/TN curve. Under the RPA approach, the Néel temperature TN /Sp and the internal energy E/Sp at the Néel point are independent of spin quantum number S. The numerical results show that the internal energy E/Sp at the Néel point seems independent of the frustration strength J2/J1. This indicates that thermodynamic quantities have universal characteristics for large spin quantum number.

  11. Quantum phase transitions, frustration, and the Fermi surface in the Kondo lattice model

    NASA Astrophysics Data System (ADS)

    Eidelstein, Eitan; Moukouri, S.; Schiller, Avraham

    2011-07-01

    The quantum phase transition from a spin-Peierls phase with a small Fermi surface to a paramagnetic Luttinger-liquid phase with a large Fermi surface is studied in the framework of a one-dimensional Kondo-Heisenberg model that consists of an electron gas away from half filling, coupled to a spin-1/2 chain by Kondo interactions. The Kondo spins are further coupled to each other with isotropic nearest-neighbor and next-nearest-neighbor antiferromagnetic Heisenberg interactions which are tuned to the Majumdar-Ghosh point. Focusing on three-eighths filling and using the density-matrix renormalization-group (DMRG) method, we show that the zero-temperature transition between the phases with small and large Fermi momenta appears continuous, and involves a new intermediate phase where the Fermi surface is not well defined. The intermediate phase is spin gapped and has Kondo-spin correlations that show incommensurate modulations. Our results appear incompatible with the local picture for the quantum phase transition in heavy fermion compounds, which predicts an abrupt change in the size of the Fermi momentum.

  12. Common features in phase-space networks of frustrated spin models and lattice-gas models

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Peng, Yi; Han, Yilong

    2012-02-01

    We mapped the phase spaces of the following four models into networks: (1a) the Ising antiferromagnet on triangular lattice at the ground state and (1b) above the ground state, (2) the six-vertex model (i.e. square ice or spin ice), (3) 1D lattice gas and (4) 2D lattice gas. Their phase-space networks share some common features including the Gaussian degree distribution, the Gaussian spectral density, and the small-world properties. Models 1a, 2 and 3 with long-range correlations in real space exhibit fractal phase spaces, while models 1b and 4 with short-range correlations in real space exhibit non-fractal phase spaces. This result supports one of the untested assumptions in Tsallis's non-extensive statistics.

  13. Phase stability frustration on ultra-nanosized anatase TiO2.

    PubMed

    Patra, Snehangshu; Davoisne, Carine; Bouyanfif, Houssny; Foix, Dominique; Sauvage, Frédéric

    2015-01-01

    This work sheds light on the exceptional robustness of anatase TiO2 when it is downsized to an extreme value of 4 nm. Since at this size the surface contribution to the volume becomes predominant, it turns out that the material becomes significantly resistant against particles coarsening with temperature, entailing a significant delay in the anatase to rutile phase transition, prolonging up to 1000 °C in air. A noticeable alteration of the phase stability diagram with lithium insertion is also experienced. Lithium insertion in such nanocrystalline anatase TiO2 converts into a complete solid solution until almost Li1TiO2, a composition at which the tetragonal to orthorhombic transition takes place without the formation of the emblematic and unwished rock salt Li1TiO2 phase. Consequently, excellent reversibility in the electrochemical process is experienced in the whole portion of lithium content. PMID:26042388

  14. Phase diagram of the anisotropic frustrated spin-one J1-J2-J3 ferromagnet

    NASA Astrophysics Data System (ADS)

    Pires, A. S. T.

    2015-05-01

    I study the spin one J1-J2-J3 Heisenberg model with easy plane single- ion anisotropy on the square lattice with ferromagnetic 1st neighbor and antiferromagnetic 2nd and 3rd neighbor interactions by means of the SU(3) Schwinger boson formalism. I show that quantum fluctuations lead to a strong modification of the classical phase diagram. A nematic phase was found at T=0. Although the system behaves like an XY model, in the nematic phase the single ion anisotropy term leads to strong quantum fluctuations and induces a net nematic component. As a consequence the quadrupole structure factor <(Sqz)2(S-qz)2 > has a strong peak at the wave vector q =(0,0).

  15. Phase transition of anisotropic frustrated Heisenberg model on the square lattice.

    PubMed

    Hu, Ai-Yuan; Wang, Huai-Yu

    2016-01-01

    We have investigated the J_{1}-J_{2} Heisenberg model with exchange anisotropy on a square lattice and focused on possible AF1-AF2 phase transition below the Néel point and its dependence on the exchange anisotropy, where AF1 and AF2 represent Néel state and collinear state, respectively. We use the double-time Green's-function method and adopt the random-phase approximation. The less the exchange anisotropy, the stronger the quantum fluctuation of the system will be. Both the Néel state and collinear state can exist and have the same Néel temperature for arbitrary anisotropy and spin quantum number S when J_{2}/J_{1}=0.5. Under such parameters, the calculated free energies show that there may occur a first-order phase transition between the Néel state and collinear state for an arbitrary S when anisotropy is not strong. PMID:26871025

  16. Phase stability frustration on ultra-nanosized anatase TiO2

    PubMed Central

    Patra, Snehangshu; Davoisne, Carine; Bouyanfif, Houssny; Foix, Dominique; Sauvage, Frédéric

    2015-01-01

    This work sheds light on the exceptional robustness of anatase TiO2 when it is downsized to an extreme value of 4 nm. Since at this size the surface contribution to the volume becomes predominant, it turns out that the material becomes significantly resistant against particles coarsening with temperature, entailing a significant delay in the anatase to rutile phase transition, prolonging up to 1000 °C in air. A noticeable alteration of the phase stability diagram with lithium insertion is also experienced. Lithium insertion in such nanocrystalline anatase TiO2 converts into a complete solid solution until almost Li1TiO2, a composition at which the tetragonal to orthorhombic transition takes place without the formation of the emblematic and unwished rock salt Li1TiO2 phase. Consequently, excellent reversibility in the electrochemical process is experienced in the whole portion of lithium content. PMID:26042388

  17. Tuning Membrane Phase Separation Using Nonlipid Amphiphiles

    PubMed Central

    Muddana, Hari S.; Chiang, Homer H.; Butler, Peter J.

    2012-01-01

    Lipid phase separation may be a mechanism by which lipids participate in sorting membrane proteins and facilitate membrane-mediated biochemical signaling in cells. To provide new tools for membrane lipid phase manipulation that avoid direct effects on protein activity and lipid composition, we studied phase separation in binary and ternary lipid mixtures under the influence of three nonlipid amphiphiles, vitamin E (VE), Triton-X (TX)-100, and benzyl alcohol (BA). Mechanisms of additive-induced phase separation were elucidated using coarse-grained molecular dynamics simulations of these additives in a liquid bilayer made from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-diundecanoyl-sn-glycero-phosphocholine (DUPC). From simulations, the additive's partitioning preference, changes in membrane thickness, and alterations in lipid order were quantified. Simulations showed that VE favored the DPPC phase but partitioned predominantly to the domain boundaries and lowered the tendency for domain formation, and therefore acted as a linactant. This simulated behavior was consistent with experimental observations in which VE promoted lipid mixing and dispersed domains in both gel/liquid and liquid-ordered/liquid-disordered systems. From simulation, BA partitioned predominantly to the DUPC phase, decreased lipid order there, and thinned the membrane. These actions explain why, experimentally, BA promoted phase separation in both binary and ternary lipid mixtures. In contrast, TX, a popular detergent used to isolate raft membranes in cells, exhibited equal preference for both phases, as demonstrated by simulations, but nonetheless, was a strong domain promoter in all lipid mixtures. Further analysis showed that TX increased membrane thickness of the DPPC phase to a greater extent than the DUPC phase and thus increased hydrophobic mismatch, which may explain experimental observation of phase separation in the presence of TX. In summary, these nonlipid amphiphiles

  18. Spin Hamiltonian, order out of a Coulomb phase, and pseudocriticality in the frustrated pyrochlore Heisenberg antiferromagnet FeF3

    NASA Astrophysics Data System (ADS)

    Sadeghi, Azam; Alaei, Mojtaba; Shahbazi, Farhad; Gingras, Michel J. P.

    2015-04-01

    FeF3, with its half-filled Fe3 +3 d orbital, hence zero orbital angular momentum and S =5 /2 , is often put forward as a prototypical highly frustrated classical Heisenberg pyrochlore antiferromagnet. By employing ab initio density functional theory, we obtain an effective spin Hamiltonian for this material. This Hamiltonian contains nearest-neighbor antiferromagnetic Heisenberg, biquadratic, and Dzyaloshinskii-Moriya interactions as dominant terms and we use Monte Carlo simulations to investigate the nonzero temperature properties of this minimal model. We find that upon decreasing temperature, the system passes through a Coulomb phase, composed of short-range correlated coplanar states, before transforming into an "all-in/all-out" (AIAO) state via a very weakly first-order transition at a critical temperature Tc≈22 K, in good agreement with the experimental value for a reasonable set of Coulomb interaction U and Hund's coupling JH describing the material. Despite the transition being first order, the AIAO order parameter evolves below Tc with a power-law behavior characterized by a pseudo "critical exponent" β ≈0.18 in accord with experiment. We comment on the origin of this unusual β value.

  19. Vapor-liquid phase separator permeability results

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Frederking, T. H. K.

    1981-01-01

    Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

  20. Frustrated quantum phase diffusion and increased coherence of solitons due to nonlocality

    SciTech Connect

    Batz, Sascha; Peschel, Ulf

    2011-03-15

    We investigate the quantum properties of solitons with nonlocal self-interaction. We find significant changes when compared to the local interaction. Quantum phase diffusion of nonlocal solitons is always reduced with respect to the local interaction and vanishes in the strongly nonlocal limit. Thus, coherence is increased in the nonlocal case. Furthermore, we compare the intrinsic quantum wave packet spreading to the recently discussed classical Gordon-Haus effect for nonlocal solitons [V. Folli and C. Conti, Phys. Rev. Lett. 104, 193901 (2010)].

  1. Critical space-time networks and geometric phase transitions from frustrated edge antiferromagnetism.

    PubMed

    Trugenberger, Carlo A

    2015-12-01

    Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension d(H)=4. The model has a geometric quantum phase transition with disorder parameter (d(H)-d(s)), where d(s) is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions. PMID:26764755

  2. Critical space-time networks and geometric phase transitions from frustrated edge antiferromagnetism

    NASA Astrophysics Data System (ADS)

    Trugenberger, Carlo A.

    2015-12-01

    Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension dH=4 . The model has a geometric quantum phase transition with disorder parameter (dH-ds) , where ds is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions.

  3. Does dynamic vulcanization induce phase separation?

    PubMed

    Abolhasani, Mohammad Mahdi; Zarejousheghani, Fatemeh; Naebe, Minoo; Guo, Qipeng

    2014-08-14

    Immiscible and miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) were subjected to dynamic vulcanization to investigate the effect of crosslinking on phase separation. As a result of different processability, mixing torque behavior of miscible and immiscible blends was significantly different from one another. Scanning electron microscopy (SEM) was used to investigate the morphology of the system. After dynamic vulcanization, submicron ACM droplets were observed in the samples near the binodal curve of the system under mixing conditions. Small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) analysis were used to investigate the effect of dynamic vulcanization on the lamellar structure of the system. It was shown that for samples near the boundary of phase separation, increasing the crosslink density led to a decrease in the lamellar long period (L) as a sign of increment of crosslink density induced phase decomposition. Effects of shear rate on the final morphology of the system were investigated by changing the mixing temperature and by comparing the results of dynamic vulcanization at one phase and two phase regions. PMID:24957793

  4. Crystallization And Phase Separation In Fluoride Glasses

    NASA Astrophysics Data System (ADS)

    Boehm, L.; Chung, K.-H.; Crichton, S. N.; Moynihan, C. T.

    1987-01-01

    We report here two studies relevant to these phenomena. Phase separation was unambiguously shown to occur in a ZrF4-based glass containing a small amount of PbF2 and prepared under a chloride-containing reactive atmosphere. Partial replacement of ZrF4 by HfF4 in a ZBLAN glass appears to improve the resistance to crystallization. The reason for this improvement seems to be a change in the crystalline phases and compositions first appearing on reheating.

  5. PREFACE: Geometrically frustrated magnetism Geometrically frustrated magnetism

    NASA Astrophysics Data System (ADS)

    Gardner, Jason S.

    2011-04-01

    Frustrated magnetism is an exciting and diverse field in condensed matter physics that has grown tremendously over the past 20 years. This special issue aims to capture some of that excitement in the field of geometrically frustrated magnets and is inspired by the 2010 Highly Frustrated Magnetism (HFM 2010) meeting in Baltimore, MD, USA. Geometric frustration is a broad phenomenon that results from an intrinsic incompatibility between some fundamental interactions and the underlying lattice geometry based on triangles and tetrahedra. Most studies have centred around the kagomé and pyrochlore based magnets but recent work has looked at other structures including the delafossite, langasites, hyper-kagomé, garnets and Laves phase materials to name a few. Personally, I hope this issue serves as a great reference to scientist both new and old to this field, and that we all continue to have fun in this very frustrated playground. Finally, I want to thank the HFM 2010 organizers and all the sponsors whose contributions were an essential part of the success of the meeting in Baltimore. Geometrically frustrated magnetism contents Spangolite: an s = 1/2 maple leaf lattice antiferromagnet? T Fennell, J O Piatek, R A Stephenson, G J Nilsen and H M Rønnow Two-dimensional magnetism and spin-size effect in the S = 1 triangular antiferromagnet NiGa2S4 Yusuke Nambu and Satoru Nakatsuji Short range ordering in the modified honeycomb lattice compound SrHo2O4 S Ghosh, H D Zhou, L Balicas, S Hill, J S Gardner, Y Qi and C R Wiebe Heavy fermion compounds on the geometrically frustrated Shastry-Sutherland lattice M S Kim and M C Aronson A neutron polarization analysis study of moment correlations in (Dy0.4Y0.6)T2 (T = Mn, Al) J R Stewart, J M Hillier, P Manuel and R Cywinski Elemental analysis and magnetism of hydronium jarosites—model kagome antiferromagnets and topological spin glasses A S Wills and W G Bisson The Herbertsmithite Hamiltonian: μSR measurements on single crystals

  6. Thermocapillary-Induced Phase Separation with Coalescence

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.

    2003-01-01

    Research has been undertaken on interactions of two or more deformable drops (or bubbles) in a viscous fluid and subject to a temperature, gravitational, or flow field. An asymptotic theory for nearly spherical drops shows that small deformations reduce the coalescence and phase separation rates. Boundary-integral simulations for large deformations show that bubbles experience alignment and enhanced coalescence, whereas more viscous drops may break as a result of hydrodynamic interactions. Experiments for buoyancy motion confirm these observations. Simulations of the sedimentation of many drops show clustering phenomena due to deformations, which lead to enhanced phase separation rates, and simulations of sheared emulsions show that deformations cause a reduction in the effective viscosity.

  7. Phase separation kinetics in immiscible liquids

    NASA Technical Reports Server (NTRS)

    Sadoway, D. R.

    1986-01-01

    The kinetics of phase separation in the succinonitrile-water system are being investigated. Experiments involve initial physical mixing of the two immiscible liquids at a temperature above the consolute, decreasing the temperature into the miscibility gap, followed by imaging of the resultant microstructure as it evolves with time. Refractive index differences allow documentation of the changing microstructures by noninvasive optical techniques without the need to quench the liquid structures for analysis.

  8. Phase separation kinetics in immiscible liquids

    NASA Technical Reports Server (NTRS)

    Ng, Lee H.; Sadoway, Donald R.

    1987-01-01

    The kinetics of phase separation in the succinonitrile-water system are being investigated. Experiments involve initial physical mixing of the two immiscible liquids at a temperature above the consolute, decreasing the temperature into the miscibility gap, followed by iamging of the resultant microstructure as it evolves with time. Refractive index differences allow documentation of the changing microstructures by noninvasive optical techniques without the need to quench the liquid structures for analysis.

  9. Quantum fidelity, string order parameter, and topological quantum phase transition in a spin-1/2 dimerized and frustrated Heisenberg chain

    NASA Astrophysics Data System (ADS)

    Liu, Jin Hua; Wang, Hai Tao

    2015-10-01

    Topological quantum phase transitions are numerically investigated in a spin-1/2 dimerized and frustrated Heisenberg chain by using infinite matrix product state representation with the infinite time evolving block decimation method. Quantum fidelity approach is employed to detect the degenerate ground states and quantum phase transitions. By calculating the long-range string order parameters, we find two topological Haldane phases characterized by two long-range string orders. Also, continuous and discontinuous behaviors of von Neumann entropy show that phase transitions between two topological Haldane phases are topologically continuous and discontinuous quantum phase transitions. For the topologically continuous phase transition, the central charge at the critical point is obtained as c = 1, which means that the topologically continuous quantum phase transition belongs to the Gaussian universality class.

  10. Experimental study of phase separation in dividing two phase flow

    SciTech Connect

    Qian Yong; Yang Zhilin; Xu Jijun

    1996-12-31

    Experimental study of phase separation of air-water two phase bubbly, slug flow in the horizontal T-junction is carried out. The influences of the inlet mass quality X1, mass extraction rate G3/G1, and fraction of extracted liquid QL3/QL1 on phase separation characteristics are analyzed. For the first time, the authors have found and defined pulsating run effect by the visual experiments, which show that under certain conditions, the down stream flow of the T-junction has strangely affected the phase redistribution of the junction, and firstly point out that the downstream geometric condition is very important to the study of phase separation phenomenon of two-phase flow in a T-junction. This kind of phenomenon has many applications in the field of energy, power, petroleum and chemical industries, such as the loss of coolant accident (LOCA) caused by a small break in a horizontal coolant pipe in nuclear reactor, and the flip-flop effect in the natural gas transportation pipeline system, etc.

  11. Phase separation of comb polymer nanocomposite melts.

    PubMed

    Xu, Qinzhi; Feng, Yancong; Chen, Lan

    2016-02-01

    In this work, the spinodal phase demixing of branched comb polymer nanocomposite (PNC) melts is systematically investigated using the polymer reference interaction site model (PRISM) theory. To verify the reliability of the present method in characterizing the phase behavior of comb PNCs, the intermolecular correlation functions of the system for nonzero particle volume fractions are compared with our molecular dynamics simulation data. After verifying the model and discussing the structure of the comb PNCs in the dilute nanoparticle limit, the interference among the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions between the comb polymer and nanoparticles in spinodal demixing curves is analyzed and discussed in detail. The results predict two kinds of distinct phase separation behaviors. One is called classic fluid phase boundary, which is mediated by the entropic depletion attraction and contact aggregation of nanoparticles at relatively low nanoparticle-monomer attraction strength. The second demixing transition occurs at relatively high attraction strength and involves the formation of an equilibrium physical network phase with local bridging of nanoparticles. The phase boundaries are found to be sensitive to the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions. As the side chain length is fixed, the side chain number has a large effect on the phase behavior of comb PNCs; with increasing side chain number, the miscibility window first widens and then shrinks. When the side chain number is lower than a threshold value, the phase boundaries undergo a process from enlarging the miscibility window to narrowing as side chain length increases. Once the side chain number overtakes this threshold value, the phase boundary shifts towards less miscibility. With increasing nanoparticle-monomer size ratio, a crossover of particle size occurs, above which the phase separation

  12. Arrested segregative phase separation in capillary tubes.

    PubMed

    Tromp, R Hans; Lindhoud, Saskia

    2006-09-01

    Phase separation in a capillary tube with one of the phases fully wetting the capillary wall is arrested when the typical size of the phase domains reaches the value of the diameter of the tube. The arrested state consists of an alternating sequence of concave-capped and convex-capped cylindrical domains, called "plugs," "bridges," or "lenses," of wetting and nonwetting phase, respectively. A description of this arrested plug state for an aqueous mixture of two polymer solutions is the subject of this work. A phase separating system consisting of two incompatible polymers dissolved in water was studied. The phase volume ratio was close to unity. The initial state from which plugs evolve is characterized by droplets of wetting phase in a continuous nonwetting phase. Experiments show the formation of plugs by a pathway that differs from the theoretically well-described instabilities in the thickness of a fluid thread inside a confined fluid cylinder. Plugs appear to form after the wetting layer (the confined fluid cylinder) has become unstable after merging of droplet with the wetting layer. The relative density of the phases could be set by the addition of salt, enabling density matching. As a consequence, the capillary length can in principle be made infinitely large and the Bond number (which represents the force of gravity relative to the capillary force) zero, without considerably changing the interfacial tension. Using the possibility of density matching, the relations among capillary length and capillary diameter on the one hand, and the presence of plugs and their average size on the other were studied. It was found that stable plugs are present when the capillary radius does not exceed a certain value, which is probably smaller than the capillary length. However, the average plug size is independent of capillary length. At constant capillary length, average plug size was found to scale with the capillary diameter to a power 1.3, significantly higher than the

  13. Artificial frustrated spin systems

    NASA Astrophysics Data System (ADS)

    Perrin, Y.; Chioar, I. A.; Nguyen, V. D.; Lacour, D.; Hehn, M.; Montaigne, F.; Canals, B.; Rougemaille, N.

    2015-09-01

    Complex architectures of nanostructures are routinely elaborated using bottom-up or nanofabrication processes. This technological capability allows scientists to engineer materials with properties that do not exist in nature, but also to manufacture model systems to explore fundamental issues in condensed matter physics. Two-dimensional frustrated arrays of magnetic nanostructures are one class of systems for which theoretical predictions can be tested experimentally. These systems have been the subject of intense research in the last few years and allowed the investigation of a rich physics and fascinating phenomena, such as the exploration of the extensively degenerate ground-state manifolds of spin ice systems, the evidence of new magnetic phases in purely two-dimensional lattices, and the observation of pseudoexcitations involving classical analogues of magnetic monopoles. We show here, experimentally and theoretically, that simple magnetic geometries can lead to unconventional, non-collinear spin textures. For example, kagome arrays of inplane magnetized nano-islands do not show magnetic order. Instead, these systems are characterized by spin textures with intriguing properties, such as chirality, coexistence of magnetic order and disorder, and charge crystallization. Magnetic frustration effects in lithographically patterned kagome arrays of nanomagnets with out-of-plane magnetization also lead to an unusal, and still unknown, magnetic ground state manifold. Besides the influence of the lattice geometry, the micromagnetic nature of the elements constituting the arrays introduce the concept of chiral magnetic monopoles, bringing additional complexity into the physics of artificial frustrated spin systems.

  14. Wetting and phase separation in soft adhesion

    PubMed Central

    Jensen, Katharine E.; Sarfati, Raphael; Style, Robert W.; Boltyanskiy, Rostislav; Chakrabarti, Aditi; Chaudhury, Manoj K.; Dufresne, Eric R.

    2015-01-01

    In the classic theory of solid adhesion, surface energy drives deformation to increase contact area whereas bulk elasticity opposes it. Recently, solid surface stress has been shown also to play an important role in opposing deformation of soft materials. This suggests that the contact line in soft adhesion should mimic that of a liquid droplet, with a contact angle determined by surface tensions. Consistent with this hypothesis, we observe a contact angle of a soft silicone substrate on rigid silica spheres that depends on the surface functionalization but not the sphere size. However, to satisfy this wetting condition without a divergent elastic stress, the gel phase separates from its solvent near the contact line. This creates a four-phase contact zone with two additional contact lines hidden below the surface of the substrate. Whereas the geometries of these contact lines are independent of the size of the sphere, the volume of the phase-separated region is not, but rather depends on the indentation volume. These results indicate that theories of adhesion of soft gels need to account for both the compressibility of the gel network and a nonzero surface stress between the gel and its solvent. PMID:26553989

  15. Phase Separation: Linking Cellular Compartmentalization to Disease.

    PubMed

    Aguzzi, Adriano; Altmeyer, Matthias

    2016-07-01

    Eukaryotic cells are complex structures capable of coordinating numerous biochemical reactions in space and time. Key to such coordination is the subdivision of intracellular space into functional compartments. Compartmentalization can be achieved by intracellular membranes, which surround organelles and act as physical barriers. In addition, cells have developed sophisticated mechanisms to partition their inner substance in a tightly regulated manner. Recent studies provide compelling evidence that membraneless compartmentalization can be achieved by liquid demixing, a process culminating in liquid-liquid phase separation and the formation of phase boundaries. We discuss how this emerging concept may help in understanding dynamic reorganization of subcellular space and highlight its potential as a framework to explain pathological protein assembly in cancer and neurodegeneration. PMID:27051975

  16. Phase behaviour and phase separation kinetics measurement using acoustic arrays

    NASA Astrophysics Data System (ADS)

    Khammar, M.; Shaw, J. M.

    2011-10-01

    Speed of sound and acoustic wave attenuation are sensitive to fluid phase composition and to the presence of liquid-liquid interfaces. In this work, the use of an acoustic array comprising 64 elements as a non-intrusive sensor for liquid-liquid interface, phase separation kinetics measurement in bulk fluids, and local composition measurement in porous media is illustrated. Three benchmark examples: the phase behaviour of methanol + mixed hexanes and methanol + heptane mixtures at 25.0 °C and 1 bar, and Athabasca bitumen + heptane in a synthetic silica porous medium at 22.5 °C and 1 bar, illustrate the accuracy of liquid-liquid interface and potential research and industrial applications of the technique. Liquid-liquid interfaces can be detected independently using both speed of sound and acoustic wave attenuation measurements. The precision of the interface location measurement is 300 μm. As complete scans can be performed at a rate of 1 Hz, phase separation kinetics and diffusion of liquids within porous media are readily tracked. The technique is expected to find application where the fluids or porous media are opaque to visible light and where other imaging techniques are not readily applied, or are too costly. A current limitation is that the acoustic probes must be cooled to less than 315 K in order for them to operate.

  17. Highly frustrated spin-lattice models of magnetism and their quantum phase transitions: A microscopic treatment via the coupled cluster method

    SciTech Connect

    Bishop, R. F.; Li, P. H. Y.; Campbell, C. E.

    2014-10-15

    We outline how the coupled cluster method of microscopic quantum many-body theory can be utilized in practice to give highly accurate results for the ground-state properties of a wide variety of highly frustrated and strongly correlated spin-lattice models of interest in quantum magnetism, including their quantum phase transitions. The method itself is described, and it is shown how it may be implemented in practice to high orders in a systematically improvable hierarchy of (so-called LSUBm) approximations, by the use of computer-algebraic techniques. The method works from the outset in the thermodynamic limit of an infinite lattice at all levels of approximation, and it is shown both how the 'raw' LSUBm results are themselves generally excellent in the sense that they converge rapidly, and how they may accurately be extrapolated to the exact limit, m → ∞, of the truncation index m, which denotes the only approximation made. All of this is illustrated via a specific application to a two-dimensional, frustrated, spin-half J{sub 1}{sup XXZ}−J{sub 2}{sup XXZ} model on a honeycomb lattice with nearest-neighbor and next-nearest-neighbor interactions with exchange couplings J{sub 1} > 0 and J{sub 2} ≡ κJ{sub 1} > 0, respectively, where both interactions are of the same anisotropic XXZ type. We show how the method can be used to determine the entire zero-temperature ground-state phase diagram of the model in the range 0 ≤ κ ≤ 1 of the frustration parameter and 0 ≤ Δ ≤ 1 of the spin-space anisotropy parameter. In particular, we identify a candidate quantum spin-liquid region in the phase space.

  18. Jahn-Teller solitons, structural phase transitions, and phase separation.

    PubMed

    Clougherty, Dennis P

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like nontopological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudorotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn-Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids. PMID:16486846

  19. Jahn-Teller Solitons, Structural Phase Transitions, and Phase Separation

    NASA Astrophysics Data System (ADS)

    Clougherty, Dennis P.

    2006-02-01

    It is demonstrated that under common conditions a molecular solid subject to Jahn-Teller interactions supports stable Q-ball-like nontopological solitons. Such solitons represent a localized lump of excess electric charge in periodic motion accompanied by a time-dependent shape distortion of a set of adjacent molecules. The motion of the distortion can correspond to a true rotation or to a pseudorotation about the symmetric shape configuration. These solitons are stable for Jahn-Teller coupling strengths below a critical value; however, as the Jahn-Teller coupling approaches this critical value, the size of the soliton diverges signaling an incipient structural phase transition. The soliton phase mimics features commonly attributed to phase separation in complex solids.

  20. Griffiths phase and temporal effects in phase separated manganites

    NASA Astrophysics Data System (ADS)

    Krivoruchko, V. N.; Marchenko, M. A.

    2016-08-01

    Phenomenological description of relaxation phenomena in magnetic and transport properties of perovskite manganites has been presented. The approach is based on generalization of some hypotheses appropriate to the Preisach picture of magnetization process for half-metallic ferromagnets and on an assumption that in doped manganites the phase separated state exists near the magnetic ordering temperature. For systems with the percolation type of a ferromagnet-paramagnet transition, distinctive features in relaxation of magnetization and resistivity have been found. The relaxation is shown to be most pronounced near the transition temperature, and to be an approximately logarithmic function of time. The theoretical results replicate a broad spectrum of behavior observed experimentally on time dependence of magnetization and resistivity of CMR systems and allow a direct comparison with available experimental data. We propose an additional experimental test to distinguish between the percolation scenario of magnetic and transport transitions in doped manganites, and the ferromagnetic polaron picture. In particular, an anomalously slow relaxation to zero of the order parameter can be considered as a key feature of the Griffiths-like phase transition in doped manganites. It is also shown that a system with the Griffiths-like state will exhibit nonequilibrium aging and rejuvenation phenomena, which in many aspects resemble that of a spin glass. We hope that experimental observation of a set of time decay properties will provide a settlement of apparently conflicting results obtained for different characteristics of phase-separated manganites.

  1. Gelation and phase separation of attractive colloids

    NASA Astrophysics Data System (ADS)

    Lu, Peter James

    2008-07-01

    I present several scientific and technical contributions in this thesis. I demonstrate that the gelation of spherical particles with isotropic, short-range attractive interactions is initiated by spinodal decomposition, a thermodynamic instability that triggers the formation of clusters that span and dynamically arrest to create a gel. This simple, universal gelation picture does not depend on microscopic system-specific details---thus broadly describing any particle system with short-range attractions---and suggests that gelation, often considered a purely kinetic phenomenon, is in fact a direct consequence of equilibrium liquid-gas phase separation. I also demonstrate that spherical particles with isotropic attractive interactions exhibit a stable phase---a fluid of particle clusters---that persists on experimental timescales even in the absence of any long-range Coulombic charge repulsion; this contrasts some expectations based on simulation and theory. I describe a new capability I created by integrating accelerated image processing software that I wrote into a high-speed confocal microscope system that I developed: active target-locking, the ability to follow freely-moving complex objects within a microscope sample, even as they change size, shape, and orientation---in real time. Finally, I report continuous, month-long observations of near-critical spinodal decomposition of colloids with isotropic attractions, aboard the International Space Station. I also include detailed descriptions, with examples and illustrations, of the tools and techniques that I have developed to produce these results.

  2. Separation of aqueous two-phase polymer systems in microgravity

    NASA Technical Reports Server (NTRS)

    Vanalstine, J. M.; Harris, J. M.; Synder, S.; Curreri, P. A.; Bamberger, S. B.; Brooks, D. E.

    1984-01-01

    Phase separation of polymer systems in microgravity is studied in aircraft flights to prepare shuttle experiments. Short duration (20 sec) experiments demonstrate that phase separation proceeds rapidly in low gravity despite appreciable phase viscosities and low liquid interfacial tensions (i.e., 50 cP, 10 micro N/m). Ostwald ripening does not appear to be a satisfactory model for the phase separation mechanism. Polymer coated surfaces are evaluated as a means to localize phases separated in low gravity. Contact angle measurements demonstrate that covalently coupling dextran or PEG to glass drastically alters the 1-g wall wetting behavior of the phases in dextran-PEG two phase systems.

  3. Decoupled phase of frustrated spin-(1)/(2) antiferromagnetic chains with and without long-range order in the ground state

    NASA Astrophysics Data System (ADS)

    Kumar, Manoranjan; Soos, Z. G.

    2013-10-01

    The quantum phases of one-dimensional spin s=1/2 chains are discussed for models with two parameters, frustrating exchange g=J2>0 between second neighbors and normalized nonfrustrating power-law exchange with exponent α and distance dependence r-α. The ground state (GS) at g=0 has a long-range order (LRO) for α<2 and long-range spin fluctuations for α>2. The models conserve total spin S=SA+SB, have singlet GS for any g, α≥0 and decouple at 1/g=0 to linear Heisenberg antiferromagnets on sublattices A and B of odd- and even-numbered sites. Exact diagonalization of finite chains gives the sublattice spin , the magnetic gap Em to the lowest triplet state, and the excitation Eσ to the lowest singlet with opposite inversion symmetry to the GS. An analytical model that conserves sublattice spin has a first-order quantum transition at gc=1/4ln2 from a GS with perfect LRO to a decoupled phase with SA=SB=0 for g≥4/π2 and no correlation between spins in different sublattices. The model with α=1 has a first-order transition to a decoupled phase that closely resembles the analytical model. The bond order wave (BOW) phase and continuous quantum phase transitions of finite models with α≥2 are discussed in terms of GS degeneracy where Eσ(g)=0, excited state degeneracy where Eσ(g)=Em(g), and . The decoupled phase at large frustration has nondegenerate GS for any exponent α and excited states related to sublattice excitations.

  4. Optical Bragg, atomic Bragg and cavity QED detections of quantum phases and excitation spectra of ultracold atoms in bipartite and frustrated optical lattices

    SciTech Connect

    Ye, Jinwu; Zhang, K.Y.; Li, Yan; Chen, Yan; Zhang, W.P.

    2013-01-15

    Ultracold atoms loaded on optical lattices can provide unprecedented experimental systems for the quantum simulations and manipulations of many quantum phases and quantum phase transitions between these phases. However, so far, how to detect these quantum phases and phase transitions effectively remains an outstanding challenge. In this paper, we will develop a systematic and unified theory of using the optical Bragg scattering, atomic Bragg scattering or cavity QED to detect the ground state and the excitation spectrum of many quantum phases of interacting bosons loaded in bipartite and frustrated optical lattices. The physically measurable quantities of the three experiments are the light scattering cross sections, the atom scattered clouds and the cavity leaking photons respectively. We show that the two photon Raman transition processes in the three detection methods not only couple to the density order parameter, but also the valence bond order parameter due to the hopping of the bosons on the lattice. This valence bond order coupling is very sensitive to any superfluid order or any valence bond (VB) order in the quantum phases to be probed. These quantum phases include not only the well-known superfluid and Mott insulating phases, but also other important phases such as various kinds of charge density waves (CDW), valence bond solids (VBS), and CDW-VBS phases with both CDW and VBS orders unique to frustrated lattices, and also various kinds of supersolids. We analyze respectively the experimental conditions of the three detection methods to probe these various quantum phases and their corresponding excitation spectra. We also address the effects of a finite temperature and a harmonic trap. We contrast the three scattering methods with recent in situ measurements inside a harmonic trap and argue that the two kinds of measurements are complementary to each other. The combination of both kinds of detection methods could be used to match the combination of

  5. Phase change in an opinion-dynamics model with separation of time scales

    NASA Astrophysics Data System (ADS)

    Iñiguez, Gerardo; Kertész, János; Kaski, Kimmo K.; Barrio, R. A.

    2011-01-01

    We define an opinion formation model of agents in a one-dimensional ring, where the opinion of an agent evolves due to its interactions with close neighbors and due to its either positive or negative attitude toward the overall mood of all the other agents. While the dynamics of the agent’s opinion is described with an appropriate differential equation, from time to time pairs of agents are allowed to change their locations to improve the homogeneity of opinion (or comfort feeling) with respect to their short-range environment. In this way the timescale of transaction dynamics and that of environment update are well separated and controlled by a single parameter. By varying this parameter we discovered a phase change in the number of undecided individuals. This phenomenon arises from the fact that too frequent location exchanges among agents result in frustration in their opinion formation. Our mean field analysis supports this picture.

  6. Phase transitions in a frustrated biquadratic Heisenberg model with coupled orbital degrees of freedom for iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Zhuo, W. Z.; Qin, M. H.; Dong, S.; Li, X. G.; Liu, J.-M.

    2016-03-01

    In this paper, we study a biquadratic Heisenberg model with coupled orbital degrees of freedom by using a Monte Carlo simulation to investigate the phase transitions in iron-based superconductors. The antiferroquadrupolar state, which may be related to the magnetism of FeSe [R. Yu and Q. Si, Phys. Rev. Lett. 115, 116401 (2015), 10.1103/PhysRevLett.115.116401], is stabilized by the anisotropic biquadratic interaction induced by a ferro-orbital-ordered state. It is revealed that the orbital and nematic transitions occur at the same temperature for all the cases, supporting the mechanism of the orbital-driven nematicity as revealed in most recent experiments [S. H. Baek, D. V. Efremov, J. M. Ok, J. S. Kim, J. van den Brink, and B. Büchner, Nat. Mater. 14, 210 (2015), 10.1038/nmat4138]. In addition, it is suggested that the orbital interaction may lead to the separation of the structural and magnetic phase transitions, as observed in many families of iron pnictides.

  7. Frustration in biomolecules.

    PubMed

    Ferreiro, Diego U; Komives, Elizabeth A; Wolynes, Peter G

    2014-11-01

    Biomolecules are the prime information processing elements of living matter. Most of these inanimate systems are polymers that compute their own structures and dynamics using as input seemingly random character strings of their sequence, following which they coalesce and perform integrated cellular functions. In large computational systems with finite interaction-codes, the appearance of conflicting goals is inevitable. Simple conflicting forces can lead to quite complex structures and behaviors, leading to the concept of frustration in condensed matter. We present here some basic ideas about frustration in biomolecules and how the frustration concept leads to a better appreciation of many aspects of the architecture of biomolecules, and especially how biomolecular structure connects to function by means of localized frustration. These ideas are simultaneously both seductively simple and perilously subtle to grasp completely. The energy landscape theory of protein folding provides a framework for quantifying frustration in large systems and has been implemented at many levels of description. We first review the notion of frustration from the areas of abstract logic and its uses in simple condensed matter systems. We discuss then how the frustration concept applies specifically to heteropolymers, testing folding landscape theory in computer simulations of protein models and in experimentally accessible systems. Studying the aspects of frustration averaged over many proteins provides ways to infer energy functions useful for reliable structure prediction. We discuss how frustration affects folding mechanisms. We review here how the biological functions of proteins are related to subtle local physical frustration effects and how frustration influences the appearance of metastable states, the nature of binding processes, catalysis and allosteric transitions. In this review, we also emphasize that frustration, far from being always a bad thing, is an essential feature

  8. Interplay of quantum criticality and geometric frustration in columbite

    NASA Astrophysics Data System (ADS)

    Lee, Sungbin; Kaul, Ribhu K.; Balents, Leon

    2010-09-01

    CoNb2O6 is a material with remarkable properties that are determined by an exciting interplay of quantum mechanics and geometric frustration. On the one hand, weakly coupled ferromagnetic Ising chains of Co2+ ions can be tuned by an applied magnetic field through a quantum critical point to be paramagnetic; on the other hand, the Ising chains must contend with residual interactions on a frustrated triangular lattice in their choice of how to order. Motivated by the material, we theoretically study the phase diagram of quantum ferromagnetic Ising chains coupled antiferromagnetically on a triangular lattice in the plane perpendicular to the chain direction. We combine exact solutions of the quantum criticality in the isolated chains with perturbative approximations for the frustrated interchain couplings. When the triangular lattice has an isosceles distortion, which occurs in the real material, the phase diagram at absolute zero temperature is rich with five different states of matter: ferrimagnetic, Néel, antiferromagnetic, paramagnetic and incommensurate phases, separated by quantum phase transitions. Implications of our results on experiments in CoNb2O6 are discussed.

  9. Frustration in Biomolecules

    PubMed Central

    Ferreiro, Diego U.; Komives, Elizabeth A.; Wolynes, Peter G.

    2014-01-01

    Biomolecules are the prime information processing elements of living matter. Most of these inanimate systems are polymers that compute their own structures and dynamics using as input seemingly random character strings of their sequence, following which they coalesce and perform integrated cellular functions. In large computational systems with a finite interaction-codes, the appearance of conflicting goals is inevitable. Simple conflicting forces can lead to quite complex structures and behaviors, leading to the concept of frustration in condensed matter. We present here some basic ideas about frustration in biomolecules and how the frustration concept leads to a better appreciation of many aspects of the architecture of biomolecules, and how biomolecular structure connects to function. These ideas are simultaneously both seductively simple and perilously subtle to grasp completely. The energy landscape theory of protein folding provides a framework for quantifying frustration in large systems and has been implemented at many levels of description. We first review the notion of frustration from the areas of abstract logic and its uses in simple condensed matter systems. We discuss then how the frustration concept applies specifically to heteropolymers, testing folding landscape theory in computer simulations of protein models and in experimentally accessible systems. Studying the aspects of frustration averaged over many proteins provides ways to infer energy functions useful for reliable structure prediction. We discuss how frustration affects folding mechanisms. We review here how a large part of the biological functions of proteins are related to subtle local physical frustration effects and how frustration influences the appearance of metastable states, the nature of binding processes, catalysis and allosteric transitions. We hope to illustrate how Frustration is a fundamental concept in relating function to structural biology. PMID:25225856

  10. Capillary electrokinetic separations: Influence of mobile phase composition on performance

    SciTech Connect

    Sepaniak, M.J.; Swaile, D.F.; Powell, A.C.; Cole, R.O.

    1990-01-01

    The composition of the mobile phase employed in capillary zone electrophoresis and the related technique, micellar electrokinetic capillary chromatography, is an important factor in determining separation performance. The influences of ionic salt, surfactant, and organic solvent mobile phase additives on separation efficiency, retention, and elution range are discussed and demonstrated. 23 refs., 2 figs., 2 tabs.

  11. Superfluid helium 2 liquid-vapor phase separation: Technology assessment

    NASA Technical Reports Server (NTRS)

    Lee, J. M.

    1984-01-01

    A literature survey of helium 2 liquid vapor phase separation is presented. Currently, two types of He 2 phase separators are being investigated: porous, sintered metal plugs and the active phase separator. The permeability K(P) shows consistency in porous plug geometric characterization. Both the heat and mass fluxes increase with K(P). Downstream pressure regulation to adjust for varying heat loads and both temperatures is possible. For large dynamic heat loads, the active phase separator shows a maximum heat rejection rate of up to 2 W and bath temperature stability of 0.1 mK. Porous plug phase separation performance should be investigated for application to SIRTF and, in particular, that plugs of from 10 to the minus ninth square centimeters to 10 to the minus eighth square centimeters in conjunction with downstream pressure regulation be studied.

  12. Spontaneous liquid-liquid phase separation of water.

    PubMed

    Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki

    2014-02-01

    We report a molecular dynamics simulation demonstrating a fast spontaneous liquid-liquid phase separation of water and a subsequent slow crystallization to ice. It is found that supercooled water separates rapidly into low- and high-density domains so as to reduce the surface energy in the rectangular simulation cell at certain thermodynamic states. The liquid-liquid phase separation, which is about two orders of magnitude faster than the crystallization, suggests a possibility to observe this phenomenon experimentally. PMID:25353404

  13. Stable phase separation and heterogeneity away from the coexistence curve

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, T. R.; Belitz, D.

    2016-04-01

    Phase separation, i.e., the coexistence of two different phases, is observed in many systems away from the coexistence curve of a first-order transition, leading to a stable heterogeneous phase or region. Examples include various quantum ferromagnets, heavy-fermion systems, rare-earth nickelates, and others. These observations seem to violate basic notions of equilibrium thermodynamics, which state that phase separation can occur only on the coexistence curve. We show theoretically that quenched disorder allows for phase separation away from the coexistence curve even in equilibrium due to the existence of stable minority-phase droplets within the majority phase. Our scenario also answers a related question: How can a first-order transition remain sharp in the presence of quenched disorder without violating the rigorous lower bound ν ≥2 /d for the correlation-length exponent? We discuss this scenario in the context of experimental results for a large variety of systems.

  14. Vapor-liquid phase separator studies

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Hepler, W. A.; Frederking, T. H. K.

    1985-01-01

    A study of porous plug use for vapor-liquid phase seperation in spaceborne cryogenic systems was conducted. The three main topics addressed were: (1) the usefulness of porous media in designs that call for variable areas and flow rates; (2) the possibility of prediction of main parameters of porous plugs for a given material; and (3) prediction of all parameters of the plug, including secondary parameters.

  15. Colossal piezoresistance in phase separated manganites.

    PubMed

    Tosado, Jacob; Dhakal, Tara; Biswas, Amlan

    2009-05-13

    We have measured the strain dependent transport properties of phase separated manganite thin films. We subjected (La(1-y)Pr(y))(1-x)Ca(x)MnO(3) thin films grown on NdGaO(3)(110) substrates to direct external mechanical stress using a three-point beam bending method. The resultant change in resistance reveals a colossal piezoresistance (CPR) in manganites. Our experiments reveal that phase separation is a necessary but not sufficient condition for CPR. The maximum CPR is observed only when the phase boundaries are free to move in the fluid-like phase separated state. Our results show that both long-range strain interactions and quenched disorder play an important role in micrometer scale phase separation in manganites, albeit in different temperature ranges. PMID:21825473

  16. Phase Separators And Fountain-Effect Pumps For He 11

    NASA Technical Reports Server (NTRS)

    Whitehouse, Paul L.

    1989-01-01

    Fused-glass microchannel arrays for use as HE 11 phase separators and fountain-effect pumps. Microchannel devices for use in low-gravity storage and cooling systems containing superfluid helium. Phase separators and pumps take advantage of thermomechanical effect peculiar to He 11 in restricted spaces. By creating thermal gradient in porous plug, direction of flow reversed, turning phase separator into pump. However, addition of heat disadvantage. Thermal gradient created by using Peltier effect to transfer heat across array, removing heat from He 11 supply and overcoming undesirable addition of heat.

  17. Phase separation and the formation of cellular bodies

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Broedersz, Chase P.; Meir, Yigal; Wingreen, Ned S.

    Cellular bodies in eukaryotic cells spontaneously assemble to form cellular compartments. Among other functions, these bodies carry out essential biochemical reactions. Cellular bodies form micron-sized structures, which, unlike canonical cell organelles, are not surrounded by membranes. A recent in vitro experiment has shown that phase separation of polymers in solution can explain the formation of cellular bodies. We constructed a lattice-polymer model to capture the essential mechanism leading to this phase separation. We used both analytical and numerical tools to predict the phase diagram of a system of two interacting polymers, including the concentration of each polymer type in the condensed and dilute phase.

  18. Separation of Chloroplast Pigments Using Reverse Phase Chromatography.

    ERIC Educational Resources Information Center

    Reese, R. Neil

    1997-01-01

    Presents a protocol that uses reverse phase chromatography for the separation of chloroplast pigments. Provides a simple and relatively safe procedure for use in teaching laboratories. Discusses pigment extraction, chromatography, results, and advantages of the process. (JRH)

  19. Thus We Frustrate Charlemagne

    ERIC Educational Resources Information Center

    Lafferty, R. A.

    1973-01-01

    Topic 2, The Age of Charlemagne, from a theme issue on Teaching World History Through Science Fiction, motivates student discussion on tampering with history. The story is an excerpt from Thus We Frustrate Charlemagne, copyright in 1967. (JB)

  20. Centrifugal Liquid/Gas Separator With Phase Detectors

    NASA Technical Reports Server (NTRS)

    Schneider, Steven J.

    1994-01-01

    Centrifugal liquid/gas separator that includes phase (liquid or gas) detectors helps ensure exclusiveness of each phase at its assigned outlet. Acoustic sensors in centrifugal liquid/gas separator measure speeds of sound in nominally pure liquid and nominally pure gas at liquid and gas outlets respectively. When speed of sound is that of pure liquid or gas, valve opens to let liquid or gas flow out.

  1. Phase separation in the crust of accreting neutron stars.

    PubMed

    Horowitz, C J; Berry, D K; Brown, E F

    2007-06-01

    Nucleosynthesis, on the surface of accreting neutron stars, produces a range of chemical elements. We perform molecular dynamics simulations of crystallization to see how this complex composition forms new neutron star crust. We find chemical separation, with the liquid ocean phase greatly enriched in low atomic number elements compared to the solid crust. This phase separation should change many crust properties such as the thermal conductivity and shear modulus. PMID:17677319

  2. Phase-Locked Semiconductor Lasers With Separate Contacts

    NASA Technical Reports Server (NTRS)

    Katz, Joseph; Yariv, Amnon; Margalit, Shlomo

    1988-01-01

    Individual current feeds enable better uniformity and flexible control. Separate contacts for lasers in array enable control of output radiation pattern and compensation of manufacturing nonuniformities among lasers. Concept of separate current control described for two-laser array in "Semiconductor Laser Phased Array" (NPO-15963).

  3. Protein crystals on phase-separating model membranes

    NASA Astrophysics Data System (ADS)

    Manley, Suliana; Horton, Margaret; Leszczynski, Szymon; Gast, Alice

    2006-03-01

    We study the interplay between the crystallization of proteins tethered to membranes and separation within the membranes of giant unilamellar vesicles (GUVs) composed of DOPC, sphingomyelin (SM), and cholesterol. These model membranes phase separate into coexisting liquid domains below a miscibility transition temperature. This phase separation captures some aspects of the formation of lipid rafts in cell membranes and demonstrates the influence of membrane composition on raft formation. Real cell membranes have a much more complicated structure. There are additional physical constraints present in cell membranes, such as their attachment to the cytoskeleton and the presence of membrane bound proteins. The self-association of membrane proteins can influence the membrane phase behavior. We begin to investigate these effects on model tethered protein- loaded membranes by incorporating a small amount of biotin-X- DPPE into our GUVs. The biotinylated lipid partitions into a cholesterol-poor phase; thus, streptavidin binds preferentially to one of the membrane phases. As streptavidin assembles to form crystalline domains, it restricts the membrane mobility. We examine the effect of this protein association on lipid phase separation, as well as the effect of the lipid phase separation on the crystallization of the tethered proteins.

  4. A Simple Algorithm for Calculation of Phase Separation.

    ERIC Educational Resources Information Center

    Eubank, Philip T.; Barrufet, Maria A.

    1988-01-01

    Describes an algorithm that provides more rapid convergence for more complicated forms of phase separation requiring the use of a digital computer. Demonstrates that this "inside-out" algorithm remains efficient for determination of the equilibrium states for any type of phase transition for a binary system. (CW)

  5. Texas A&M vortex type phase separator

    NASA Astrophysics Data System (ADS)

    Best, Frederick

    2000-01-01

    Phase separation is required for regenerative biological and chemical process systems as well as thermal transport and rejection systems. Liquid and gas management requirements for future spacecraft will demand small, passive systems able to operate over wide ranges of inlet qualities. Conservation and recycling of air and water is a necessary part of the construction and operation of the International Space Station as well as future long duration space missions. Space systems are sensitive to volume, mass, and power. Therefore, it is necessary to develop a method to recycle wastewater with minimal power consumption. Regenerative life support systems currently being investigated require phase separation to separate the liquid from the gas produced. The microgravity phase separator designed and fabricated at Texas A&M University relies on centripetal driven buoyancy forces to form a gas-liquid vortex within a fixed, right-circular cylinder. Two-phase flow is injected tangentially along the inner wall of this cylinder producing a radial acceleration gradient. The gradient produced from the intrinsic momentum of the injected mixture results in a rotating flow that drives the buoyancy process by the production of a hydrostatic pressure gradient. Texas A&M has flown several KC-135 flights with separator. These flights have included scaling studies, stability and transient investigations, and tests for inventory instrumentation. Among the hardware tested have been passive devices for separating mixed vapor/liquid streams into single-phase streams of vapor only and liquid only. .

  6. Simultaneous Vapor Deposition and Phase Separation of Polymer Films

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Anthamatten, Mitchell

    2012-02-01

    Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique used predominately to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. The major goal of this research is to force and arrest phase separation of deposited species by co-depositing non-reactive molecules (porogens) with reactive monomers and crosslinkers. We introduce these species during iCVD to force and quench polymer induced phase separation (PIPS) during film growth as a step toward tunable pore-size, density, and morphology. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. Cahn-Hilliard theory predicts that the length scale of phase separation depends on the polymer-porogen interaction energy, the polymerization rate and the species' mobility. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Crosslinkers were introduced to limit the growth of phase separated domains and to provide mechanical support during porogen removal. To elucidate how phase separation competes with polymerization and film growth, deposited films were studied using a combination of electron microscopy, profilometry and spectroscopic techniques.

  7. Novel Detection Method of Liquid-Liquid Phase Separation

    NASA Astrophysics Data System (ADS)

    Kato, Hitoshi; Katayanagi, Hideki; Koga, Yoshikata; Nishikawa, Keiko

    2004-12-01

    A novel method of determining a liquid-liquid phase boundary was developed. This method is based on our discovery that a nascent low-density phase is attracted to the center of a Rankine vortex at the onset of phase separation. Thus a liquid-liquid phase boundary is detected easily, rapidly, and accurately. The phase diagrams of the ternary systems NaCl-H2O-1-propanol and NaCl-H2O-1-butanol were obtained by this method. The results matched well with literature values.

  8. Probing quantum frustrated systems via factorization of the ground state.

    PubMed

    Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

    2010-05-21

    The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physical problems such as stochastic gene expression and the stability of long-period modulated structures. PMID:20867055

  9. Frustrated phases under three-dimensional confinement simulated by a set of coupled Cahn-Hilliard equations.

    PubMed

    Avalos, Edgar; Higuchi, Takeshi; Teramoto, Takashi; Yabu, Hiroshi; Nishiura, Yasumasa

    2016-07-01

    We numerically study a set of coupled Cahn-Hilliard equations as a means to find morphologies of diblock copolymers in three-dimensional spherical confinement. This approach allows us to find a variety of energy minimizers including rings, tennis balls, Janus balls and multipods among several others. Phase diagrams of confined morphologies are presented. We modify the size of the interface between microphases to control the number of holes in multipod morphologies. Comparison to experimental observation by transmission electron microtomography of multipods in polystyrene-polyisoprene diblock copolymers is also presented. PMID:27337660

  10. Continuous flow system for controlling phases separation near λ transition

    SciTech Connect

    Chorowski, M.; Poliński, J.; Kempiński, W.; Trybuła, Z.; Łoś, Sz.; Chołast, K.; Kociemba, A.

    2014-01-29

    As demands on 3He are increasing and conventional 3He production through tritium decay is decreasing, alternative 3He production methods are becoming economically viable. One such possibility is to use entropy filters for extraction of the 3He isotope from natural gas. According to the phase diagram of the 3He, its solidification is impossible by only lowering of the temperature. Hence during the cooling process at stable pressure we can reach λ-point and pass to the special phase - He II. The total density of HeII is a sum of the two phases: normal the superfluid ones. It is possible to separate these two phases with an entropy filter - the barrier for the classically-behaving normal phase. This barrier can also be used to separate the two main isotopes of He: 4He and 3He, because at temperatures close to the 4He-λ-point the 3He isotope is part of the normal phase. The paper presents continuous flow schemes of different separation methods of 3He from helium commodity coming from natural gas cryogenic processing. An overall thermodynamic efficiency of the 3He/4He separation process is presented. A simplified model of continuous flow HeI -HeII recuperative heat exchanger is given. Ceramic and carbon porous plugs have been tested in entropy filter applications.

  11. Phase-separation inhibitors and prevention of selenite cataract.

    PubMed Central

    Clark, J I; Steele, J E

    1992-01-01

    The variation of the phase-separation temperature (Tc) was studied in lenses during formation of cataracts induced by a subcutaneous injection of sodium selenite. In normal control animals, the Tc decreased monotonically with increasing age. Approximately 2 days after administration of the selenite the Tc decreased sharply to a minimum, and then at day 4 the Tc increased dramatically toward body temperature. Mature irreversible cataracts formed approximately 6 days after injection of the selenite. Intraperitoneal administration of WR-77913, a phase-separation inhibitor, prevented the abnormal variation of Tc in vivo. When injected into control animals without selenite, WR-77913 produced no abnormal variation in Tc. The results confirm that Tc is a sensitive measure of early changes in the lens and that opacification associated with abnormal variation in Tc can be prevented in vivo by using a phase-separation inhibitor. Images PMID:1311849

  12. Phase separation and emergent structures in an active nematic fluid

    PubMed Central

    Putzig, Elias; Baskaran, Aparna

    2015-01-01

    We consider a phenomenological continuum theory for an active nematic fluid and show that there exists a universal, model independent instability which renders the homogeneous nematic state unstable to order fluctuations. Using numerical and analytic tools we show that, in the vicinity of a critical point, this instability leads to a phase separated state in which the ordered regions form bands in which the direction of nematic order is perpendicular to the direction of density gradient. We argue that the underlying mechanism that leads to this phase separation is a universal feature of active fluids of different symmetries. PMID:25375491

  13. Phase separation of X-irradiated lenses of rabbit

    SciTech Connect

    Clark, J.I.; Giblin, F.J.; Reddy, V.N.; Benedek, G.B.

    1982-02-01

    The phase separation temperature (Tcat) was studied as a function of time (age) after the administration of a single dose of radiation (2000 rad), which induces cataract in the rabbit lens. In the normal unirradiated lens, Tcat decreases linearly with age at a rate (DTcat/dt) approximately 2.2 degrees/week. In the irradiated lens, Tcat initially decreases with age much less than the normal lens, then rises sharply with age at the time of the appearance of opacity in the living rabbit eye. We suggest that the phase separation temperature may serve as a sensitive and early indicator of cataractogenic processes in the lens.

  14. Phase separation in thin films: Effect of temperature gradients

    NASA Astrophysics Data System (ADS)

    Jaiswal, Prabhat K.; Puri, Sanjay; Binder, Kurt

    2013-09-01

    We study the phase-separation kinetics of a binary (AB) mixture confined in a thin film of thickness D with a temperature gradient. Starting from a Kawasaki-exchange kinetic Ising model, we use a master-equation approach to systematically derive an extension of the Cahn-Hilliard model for this system. We study the effect of temperature gradients perpendicular to the film with “neutral” (no preference for either A or B) surfaces. We highlight the rich phenomenology and pattern dynamics which arises from the interplay of phase separation and the temperature gradient.

  15. Phase separation in biological membranes: integration of theory and experiment

    PubMed Central

    Elson, Elliot L.; Fried, Eliot; Dolbow, John E.; Genin, Guy M.

    2013-01-01

    Lipid bilayer model membranes can undergo transitions between ordered and disordered phases, and membranes that contain a mixture of lipid species can undergo phase separations. Studies of these transformations are of interest for what they can tell us about the interaction energies of lipid molecules of different species and conformations. Nanoscopic phases can provide a model for membrane rafts, which have important biological functions in cell membranes. Important questions are whether lipid nanodomains can exist in stable equilibrium in membranes and what is the distribution of their sizes in membranes of different composition. It is also important to know the lifetimes of nanodomains. Theoretical methods have supplied much important information on these questions, but better experimental methods are needed to detect and characterize nanodomains under normal membrane conditions. This review summarizes linkages between theoretical and experimental studies of phase separation in lipid bilayer model membranes. PMID:20192775

  16. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  17. Separation of synchronous sources through phase locked matrix factorization.

    PubMed

    Almeida, Miguel S B; Vigário, Ricardo; Bioucas-Dias, José

    2014-10-01

    In this paper, we study the separation of synchronous sources (SSS) problem, which deals with the separation of sources whose phases are synchronous. This problem cannot be addressed through independent component analysis methods because synchronous sources are statistically dependent. We present a two-step algorithm, called phase locked matrix factorization (PLMF), to perform SSS. We also show that SSS is identifiable under some assumptions and that any global minimum of PLMFs cost function is a desirable solution for SSS. We extensively study the algorithm on simulated data and conclude that it can perform SSS with various numbers of sources and sensors and with various phase lags between the sources, both in the ideal (i.e., perfectly synchronous and nonnoisy) case, and with various levels of additive noise in the observed signals and of phase jitter in the sources. PMID:25291741

  18. Phase transition in Caenorhabditis elegans: A classical oil-water phase separation?

    NASA Astrophysics Data System (ADS)

    Weber, Christoph; Tony Hyman Collaboration; Andrés Delgadillo Collaboration; Frank Jülicher Team

    2014-03-01

    In Caenorhabditis elegans droplets form before the cell divides. These droplets, also referred to as P-granules, consist of a variety of unstructured proteins and mRNA. Brangwynne et al. [Science, 2009] showed that the P-granules exhibit fluid-like behavior and that the phase separation is controlled spatially by a gradient of a component called Mex-5. It is believed that this system exhibits the same characteristics as a classical oil-water phase separation. Here we report the recent experimental investigations on the phase separation in Caenorhabditis elegans and compare our findings with a classical oil-water phase separation. Specifically, we consider the underlying coarsening mechanisms as well as the impact of temperature and species composition. Finally, we present a preliminary model incorporating the characteristics of the phase separation kinetics for Caenorhabditis elegans.

  19. Azimuthal Frustration and Bundling in Columnar DNA Aggregates

    PubMed Central

    Harreis, H. M.; Likos, C. N.; Löwen, H.

    2003-01-01

    The interaction between two stiff parallel DNA molecules is discussed using linear Debye-Hückel screening theory with and without inclusion of the dielectric discontinuity at the DNA surface, taking into account the helical symmetry of DNA. The pair potential furthermore includes the amount and distribution of counterions adsorbed on the DNA surface. The interaction does not only depend on the interaxial separation of two DNA molecules, but also on their azimuthal orientation. The optimal mutual azimuthal angle is a function of the DNA-DNA interaxial separation, which leads to azimuthal frustrations in an aggregate. On the basis of the pair potential, the positional and orientational order in columnar B-DNA assemblies in solution is investigated. Phase diagrams are calculated using lattice sums supplemented with the entropic contributions of the counterions in solution. A variety of positionally and azimuthally ordered phases and bundling transitions is predicted, which strongly depend on the counterion adsorption patterns. PMID:12770870

  20. Ruthenium Behavior at Phase Separation of Borosilicate Glass-12259

    SciTech Connect

    Enokida, Youichi; Sawada, Kayo

    2012-07-01

    The Rokkasho reprocessing plant (RRP) located in Aomori, Japan, vitrifies high level waste (HLW) into a borosilicate glass. The HLW is generated from the reprocessing of spent fuel and contains ruthenium (Ru) and other platinum group metals (PGMs). Based on the recent consequences after a huge earthquake that occurred in Japan, a hypothetical blackout was postulated for the RRP to address additional safety analysis requirements. During a prolonged blackout, the borosilicate glass could phase separate due to cooling of the glass in the melter. The Ru present in the glass matrix could migrate into separate phases and impact the durability of the borosilicate glass. The durability of the glass is important for quality assurance and performance assessment of the vitrified HLW. A fundamental study was performed at an independent university to understand the impact of a prolonged blackout. Simulated HLW glasses were prepared for the RRP, and the Ru behavior in phase separated glasses was studied. The simulated HLW glasses contained nonradioactive elements and PGMs. The glass compositions were then altered to enhance the formation of the phase-separated glasses when subjected to thermal treatment at 700 deg. C for 24 hours. The synthesized simulated glasses contained 1.1 % Ru by weight as ruthenium dioxide (RuO{sub 2}). A portion of the RuO{sub 2} formed needle-shaped crystals in the glass specimens. After the thermal treatment, the glass specimen had separated into two phases. One of the two phases was a B{sub 2}O{sub 3} rich phase, and the other phase was a SiO{sub 2} rich phase. The majority of the chemical species in the B{sub 2}O{sub 3} rich phase was leached away with the Material Characterization Center-3 (MCC-3) protocol standardized by the Pacific Northwest National Laboratory using an aqueous low-concentrated nitric acid solution, but the leaching of the Ru fraction was very limited; less than 1% of the original Ru content. The Ru leaching was much less than

  1. Phase separation in transparent liquid-liquid miscibility gap systems

    NASA Technical Reports Server (NTRS)

    Gelles, S. H.; Bhat, B. N.; Laub, R. J.

    1979-01-01

    A program to be carried out on transparent liquid-phase miscibility gap materials was developed for the purpose of acquiring additional insight into the separation process occurring in these systems. The transparency feature allows the reaction to be viewed directly through light scattering and holographic methods.

  2. Microscale extraction and phase separation using a porous capillary.

    PubMed

    Phillips, Thomas W; Bannock, James H; deMello, John C

    2015-07-21

    We report the use of a porous polytetrafluoroethylene capillary for the inline separation of liquid-liquid segmented flows, based on the selective wetting and permeation of the porous capillary walls by one of the liquids. Insertion of a narrow flow restriction at the capillary outlet allows the back pressure to be tuned for multiple liquid-liquid combinations and flow conditions. In this way, efficient separation of aqueous-organic, aqueous-fluorous and organic-fluorous segmented flows can be readily achieved over a wide range of flow rates. The porous-capillary-separator enables the straightforward regeneration of a continuous flow from a segmented flow, and may be applied to various applications, including inline analysis, biphasic reactions, and purification. As a demonstration of the latter, we performed a simple inline aqueous-organic extraction of the pH indicator 2,6-dichloroindophenol. An aqueous solution of the conjugate base was mixed with hydrochloric acid in continuous flow to protonate the indicator and render it organic-soluble. The indicator was then extracted from the aqueous feed into chloroform using a segmented flow. The two liquids were finally separated inline using a porous PTFE capillary, with the aqueous phase emerging as a continuous stream from the separator outlet. UV-visible absorption spectroscopy showed the concentration of indicator in the outflowing aqueous phase to be less than one percent of its original value, confirming the efficacy of the extraction and separation process. PMID:26054926

  3. Demixing kinetics of phase separated polymer solutions in microgravity

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.; Bamberger, S. B.; Harris, J. M.; Vanalstine, J.; Snyder, R. S.

    1988-01-01

    Phase separated solutions of two neutral polymers in buffer provide a useful and versatile medium for the partition separation of biological cells. However, the efficiency of such separations is orders of magnitude lower than the thermodynamic limit. To test the hypothesis that this inefficiency is at least partially due to the convection and sedimentation that occur during the gravity driven demixing that follows introduction of cells to the systems, a series of experiments were begun aimed at performing cell partition in a low g environment. Demixing of isopycnic three polymer solvent systems was studied, experiments were performed on KC-135 aircraft and one shuttle middeck experiment was completed. Analysis of the results of these experiments and comparisons with the predictions of scaling relations for the dependence of phase domain size on time, derived for a number of possible demixing mechanisms, are presented.

  4. Confined phase separation in SiOX nanometric thin layers

    NASA Astrophysics Data System (ADS)

    Roussel, M.; Talbot, E.; Pareige, C.; Pratibha Nalini, R.; Gourbilleau, F.; Pareige, P.

    2013-11-01

    Phase separation in silicon-rich silica/silica multilayers was investigated using Atom Probe Tomography and Atomistic Kinetic Monte Carlo simulation. It is shown that the thickness of silicon-rich silicon oxide sublayers plays an important role during phase transformation. It determines the morphology of Si-rich phase formed after subsequent annealing, which is of prime interest for microelectronic and optoelectronic applications. Monte Carlo simulation reveals that the formation of isolated Si clusters can be achieved even in the case of spinodal decomposition and is directly related to the ratio between the spinodal wavelength and the sublayer thickness.

  5. Assemblages: Functional units formed by cellular phase separation

    PubMed Central

    Wright, Peter E.

    2014-01-01

    The partitioning of intracellular space beyond membrane-bound organelles can be achieved with collections of proteins that are multivalent or contain low-complexity, intrinsically disordered regions. These proteins can undergo a physical phase change to form functional granules or other entities within the cytoplasm or nucleoplasm that collectively we term “assemblage.” Intrinsically disordered proteins (IDPs) play an important role in forming a subset of cellular assemblages by promoting phase separation. Recent work points to an involvement of assemblages in disease states, indicating that intrinsic disorder and phase transitions should be considered in the development of therapeutics. PMID:25179628

  6. Diagnostic immunoassay by solid phase separation for digoxin

    SciTech Connect

    Grenier, F.C.; Pry, T.A.; Kolaczkowski, L.

    1988-11-29

    A method is described for conducting a diagnostic immunoassay for digoxin, comprising: (a) forming a reaction mixture of a test sample with a molar excess of labeled anti-digoxin antibodies whereby the labeled antibodies are capable of forming complex with digoxin present in the sample; (b) contacting the reaction mixture with a solid phase material having immobilized thereon a compound; (c) separating the solid phase material from the reaction mixture; and (d) determining the presence of digoxin in the test sample by measuring the amount of complex present in the liquid phase.

  7. Analysis of Phase Separation in Czochralski Grown Single Crystal Ilmenite

    NASA Technical Reports Server (NTRS)

    Wilkins, R.; Powell, Kirk St. A.; Loregnard, Kieron R.; Lin, Sy-Chyi; Muthusami, Jayakumar; Zhou, Feng; Pandey, R. K.; Brown, Geoff; Hawley, M. E.

    1998-01-01

    Ilmenite (FeTiOs) is a wide bandgap semiconductor with an energy gap of 2.58 eV. Ilmenite has properties suited for radiation tolerant applications, as well as a variety of other electronic applications. Single crystal ilmenite has been grown from the melt using the Czochralski method. Growth conditions have a profound effect on the microstructure of the samples. Here we present data from a variety of analytical techniques which indicate that some grown crystals exhibit distinct phase separation during growth. This phase separation is apparent for both post-growth annealed and unannealed samples. Under optical microscopy, there appear two distinct areas forming a matrix with an array of dots on order of 5 pm diameter. While appearing bright in the optical micrograph, atomic force microscope (AFM) shows the dots to be shallow pits on the surface. Magnetic force microscope (MFM) shows the dots to be magnetic. Phase identification via electron microprobe analysis (EMPA) indicates two major phases in the unannealed samples and four in the annealed samples, where the dots appear to be almost pure iron. This is consistent with micrographs taken with a scanning probe microscope used in the magnetic force mode. Samples that do not exhibit the phase separation have little or no discernible magnetic structure detectable by the MFM.

  8. A phase-separation kinetic model for coke formation

    SciTech Connect

    Wiehe, I.A. . Corporate Research Lab.)

    1993-11-01

    Coke formation during the thermolysis of petroleum residua is postulated to occur by a mechanism that involves the liquid-liquid phase separation of reacted asphaltenes to form a phase that is lean in abstractable hydrogen. This mechanism provides the basis of a model that quantitatively describes the kinetics for the thermolysis of Cold Lake vacuum residuum and its deasphalted oil in an open-tube reactor at 400 C. The previously unreacted asphaltenes were found to be the fraction with the highest rate of thermal reaction but with the least extent of reaction. This not only described the appearance and disappearance of asphaltenes but also quantitatively described the variation in molecular weight and hydrogen content of the asphaltenes with reaction time. Further evidence of the liquid-liquid phase separation was the observation of spherical particles of liquid crystalline coke and the preferential conversion of the most associated asphaltenes to coke.

  9. A phase separation kinetic model for coke formation

    SciTech Connect

    Wiehe, I.A.

    1993-12-31

    Coke formation during the thermolysis of petroleum residua is postulated to occur by a mechanism that involves the liquid-liquid phase separation of reacted asphaltenes to form a phase that is lean in abstractable hydrogen. This mechanism provides the basis of a model the quantitatively describes the kinetics for the thermolysis of Cold Lake vacuum residuum and its deasphalted oil in an open tube reactor at 400{degrees}C. The previously unreacted asphaltenes were found to be the fraction with the highest rate of thermal reaction but with the least extent of reaction. Further evidence of the liquid-liquid phase separation was the observation of spherical particles of liquid crystalline coke and the preferential conversion of the most associated asphaltenes to coke.

  10. Prediction of phase separation during the drying of polymer shells

    SciTech Connect

    Wilemski, G.; Cook, R.; Boone, T.; Cheung, L.; Nelson, D.

    1995-12-01

    During the drying of polymer shells formed by microencapsulation, vacuole formation is believed to occur as a result of phase separation. To better understand and control this process, we have used a multicomponent diffusion formalism to predict compositional changes in the layer as organic solvents diffuse out and water diffuses into the layer. Formation of thermodynamically unstable compositions can lead to phase separation by condensation of water on submicron foreign particles present in the shell wall. We used statistical mechanics, the UNIFAP methodology, and empirical data to deduce the required values of transport coefficients and equilibrium phase compositions. The results suggest that vacuole formation can be eliminated or reduced by removing submicron and larger particles from the shell wall and by using solvents with lower intrinsic water solubilities. 21 refs., 7 figs.

  11. Metallic and semiconducting carbon nanotubes separation using an aqueous two-phase separation technique: a review

    NASA Astrophysics Data System (ADS)

    Tang, Malcolm S. Y.; Ng, Eng-Poh; Juan, Joon Ching; Ooi, Chien Wei; Ling, Tau Chuan; Woon, Kai Lin; Loke Show, Pau

    2016-08-01

    It is known that carbon nanotubes show desirable physical and chemical properties with a wide array of potential applications. Nonetheless, their potential has been hampered by the difficulties in acquiring high purity, chiral-specific tubes. Considerable advancement has been made in terms of the purification of carbon nanotubes, for instance chemical oxidation, physical separation, and myriad combinations of physical and chemical methods. The aqueous two-phase separation technique has recently been demonstrated to be able to sort carbon nanotubes based on their chirality. The technique requires low cost polymers and salt, and is able to sort the tubes based on their diameter as well as metallicity. In this review, we aim to provide a review that could stimulate innovative thought on the progress of a carbon nanotubes sorting method using the aqueous two-phase separation method, and present possible future work and an outlook that could enhance the methodology.

  12. Metallic and semiconducting carbon nanotubes separation using an aqueous two-phase separation technique: a review.

    PubMed

    Tang, Malcolm S Y; Ng, Eng-Poh; Juan, Joon Ching; Ooi, Chien Wei; Ling, Tau Chuan; Woon, Kai Lin; Show, Pau Loke

    2016-08-19

    It is known that carbon nanotubes show desirable physical and chemical properties with a wide array of potential applications. Nonetheless, their potential has been hampered by the difficulties in acquiring high purity, chiral-specific tubes. Considerable advancement has been made in terms of the purification of carbon nanotubes, for instance chemical oxidation, physical separation, and myriad combinations of physical and chemical methods. The aqueous two-phase separation technique has recently been demonstrated to be able to sort carbon nanotubes based on their chirality. The technique requires low cost polymers and salt, and is able to sort the tubes based on their diameter as well as metallicity. In this review, we aim to provide a review that could stimulate innovative thought on the progress of a carbon nanotubes sorting method using the aqueous two-phase separation method, and present possible future work and an outlook that could enhance the methodology. PMID:27396920

  13. Phase discrimination method for simultaneous two-phase separation in time-resolved stereo PIV measurements

    NASA Astrophysics Data System (ADS)

    Cheng, Y.; Pothos, S.; Diez, F. J.

    2010-12-01

    A phase discrimination method for two-phase PIV is presented that is capable of simultaneously separating the two phases from time-resolved stereoscopic PIV images taken in a particle-laden jet. The technique developed expands on previous work done by Khalitov and Longmire (Exp Fluids 32:252-268, 2002), where by means of image processing techniques, a raw two-phase PIV image can be separated into two single-phase images according to particle size and intensity distributions. The technique is expanded through the use of three new image processing algorithms to separate particles of similar size (up to an order of magnitude better than published work) for fields of view much larger than previously considered. It also addresses the known problem of noisy background images produced by high-speed CMOS cameras, which makes the particle detection and separation from the noisy background difficult, through the use of a novel fast Fourier transform background filter.

  14. Excitations from a chiral magnetized state of a frustrated quantum spin liquid

    SciTech Connect

    Garlea, Vasile O; Zheludev, Andrey I; Tsvelik, A.; Regnault, L.-P.; Habicht, Klaus; Kiefer, K.; Roessli, Bertrand

    2009-01-01

    We study excitations in weakly interacting pairs of quantum spin ladders coupled through geometrically frustrated bonds. The ground state is a disordered spin liquid, at high fields replaced by an ordered chiral helimagnetic phase. The spectra observed by high-field inelastic neutron scattering experiments on the prototype compound Sul Cu2Cl4 are qualitatively different from those in the previously studied frustration-free spin liquids. Beyond the critical field Hc = 3.7 T, the soft mode that drives the quantum phase transition spawns two separate excitations: a gapless Goldstone mode and a massive magnon. Additional massive quasiparticles are clearly visible below Hc, but are destroyed in the ordered phase. In their place one observes a sharply bound excitation continuum.

  15. Polymerization-Induced Phase Separation in Vinyl Ester Resins

    NASA Astrophysics Data System (ADS)

    Ganglani, Manisha; Torkelson, John; Carr, Stephen

    2000-03-01

    In certain multi-component, crosslinking polymer systems, phase separation is induced by polymerization, a process call polymerization-induced phase separation (PIPS) in which there exists a competition between reaction rate and phase separation rate. The final morphology and properties of a system that experiences PIPS depend on the outcome of this competition. Thus, by controlling these rates, it would be possible to control end properties. In fact, this theory has been applied for the creation of polymer-dispersed liquid crystals (PDLCs) where cure occurs via condensation reactions or via free radical polymerization initiated by UV light. This research examines PIPS in the vinyl ester (VE) resins, which are popular as matrix materials in polymer composites. Cure of the VE resins is more complicated because it uses initiators and therefore requires more time and offers less control than cure by photopolymerization. To better understand the PIPS process in the VE resins, this research separates the two competitive effects and examines each one in turn. Initial experiments use a model system to focus on the effect of PIPS in the absence of crosslinking.

  16. An overview of multidimensional liquid phase separations in food analysis.

    PubMed

    Franco, Maraíssa Silva; Padovan, Rodrigo Nogueira; Fumes, Bruno Henrique; Lanças, Fernando Mauro

    2016-07-01

    Food safety is a priority public health concern that demands analytical methods capable to detect low concentration level of contaminants (e.g. pesticides and antibiotics) in different food matrices. Due to the high complexity of these matrices, a sample preparation step is in most cases mandatory to achieve satisfactory results being usually tedious, lengthy, and prone to the introduction of errors. For this reason, many research groups have focused efforts on the development of online systems capable to do the cleanup, concentration, and separation steps at once through multidimensional separation techniques (MDS). Among several possible setups, the most popular are the multidimensional chromatographic techniques (MDC) that consist in combining more than one mobile and/or stationary phase to provide a satisfactory separation. In the present review, we selected a variety of multidimensional separation systems used for food contaminant analysis in order to discuss the instrumentation aspects, the concept of orthogonality, column approaches used in these systems, and new materials that can be used in these columns. Selected classes of contaminants present in food matrices are introduced and discussed as example of the potential applications of multidimensional liquid phase separation techniques in food safety. PMID:27030380

  17. Phase separation in solutions with specific and nonspecific interactions

    SciTech Connect

    Jacobs, William M.; Frenkel, Daan; Oxtoby, David W.

    2014-05-28

    Protein solutions, which tend to be thermodynamically stable under physiological conditions, can demix into protein-enriched and protein-depleted phases when stressed. Using a lattice-gas model of proteins with both isotropic and specific, directional interactions, we calculate the critical conditions for phase separation for model proteins with up to four patches via Monte Carlo simulations and statistical associating fluid theory. Given a fixed specific interaction strength, the critical value of the isotropic energy, which accounts for dispersion forces and nonspecific interactions, measures the stability of the solution with respect to nonspecific interactions. Phase separation is suppressed by the formation of protein complexes, which effectively passivate the strongly associating sites on the monomers. Nevertheless, we find that protein models with three or more patches can form extended aggregates that phase separate despite the assembly of passivated complexes, even in the absence of nonspecific interactions. We present a unified view of the critical behavior of model fluids with anisotropic interactions, and we discuss the implications of these results for the thermodynamic stability of protein solutions.

  18. Evidence of Phase Separation during Vapor Deposition Polymerization

    NASA Astrophysics Data System (ADS)

    Tao, Ran; Anthamatten, Mitchell

    2013-03-01

    Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique predominately used to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. We are developing multicomponent iCVD techniques to induce phase separation during film growth. Small molecule porogens and crosslinkers are introduced into the iCVD process during film growth of poly(glycidyl methacrylate). Analogous to well established polymerization induced phase separation (PIPS) processes, porogens, such as dimethyl phthalate, are well mixed at the growing gas-film interface but are immiscible with high molecular weight polymer. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Deposited films were studied by electron microscopy and spectroscopic techniques. Experiments are compared to Cahn-Hilliard theory predictions that relate the length and time scale of the phase separation to the polymer-porogen interaction energy, the rate of polymerization and the species mobility.

  19. Separate-contact phase-locked semiconductor laser arrays

    NASA Technical Reports Server (NTRS)

    Katz, J.; Kapon, E.; Lindsey, C.; Margalit, S.; Yariv, A.

    1985-01-01

    The novel optoelectronic devices discussed, phase-locked semiconductor laser arrays with separate contacts can perform a variety of near field and far field pattern tailoring functions and control mutual coherence among array elements, as well as lasing wavelength selectivity and tunability. Attention is presently given to experimental results from such arrays, which indicate that the threshold currents of the 4-micron wide lasers employed are typically 60 mA. The separate contacts to each one of them are provided by means of two-level metallization.

  20. Re-entrant phase behavior for systems with competition between phase separation and self-assembly

    NASA Astrophysics Data System (ADS)

    Reinhardt, Aleks; Williamson, Alexander J.; Doye, Jonathan P. K.; Carrete, Jesús; Varela, Luis M.; Louis, Ard A.

    2011-03-01

    In patchy particle systems where there is a competition between the self-assembly of finite clusters and liquid-vapor phase separation, re-entrant phase behavior can be observed, with the system passing from a monomeric vapor phase to a region of liquid-vapor phase coexistence and then to a vapor phase of clusters as the temperature is decreased at constant density. Here, we present a classical statistical mechanical approach to the determination of the complete phase diagram of such a system. We model the system as a van der Waals fluid, but one where the monomers can assemble into monodisperse clusters that have no attractive interactions with any of the other species. The resulting phase diagrams show a clear region of re-entrance. However, for the most physically reasonable parameter values of the model, this behavior is restricted to a certain range of density, with phase separation still persisting at high densities.

  1. Growth and Morphology of Phase Separating Supercritical Fluids

    NASA Technical Reports Server (NTRS)

    Hegseth, John; Beysens, Daniel; Perrot, Francoise; Nikolayev, Vadim; Garrabos, Yves

    1996-01-01

    The scientific objective is to study the relation between the morphology and the growth kinetics of domains during phase separation. We know from previous experiments performed near the critical point of pure fluids and binary liquids that there are two simple growth laws at late times. The 'fast' growth appears when the volumes of the phases are nearly equal and the droplet pattern is interconnected. In this case the size of the droplets grows linearly in time. The 'slow' growth appears when the pattern of droplets embedded in the majority phase is disconnected. In this case the size of the droplets increases in proportion to time to the power 1/3. The volume fraction of the minority phase is a good candidate to determine this change of behavior. All previous attempts to vary the volume fraction in a single experimental cell have failed because of the extreme experimental difficulties.

  2. Lattice-gas models of phase separation: interfaces, phase transitions, and multiphase flow

    SciTech Connect

    Rothman, D.H. ); Zaleski, S. )

    1994-10-01

    Momentum-conserving lattice gases are simple, discrete, microscopic models of fluids. This review describes their hydrodynamics, with particular attention given to the derivation of macroscopic constitutive equations from microscopic dynamics. Lattice-gas models of phase separation receive special emphasis. The current understanding of phase transitions in these momentum-conserving models is reviewed; included in this discussion is a summary of the dynamical properties of interfaces. Because the phase-separation models are microscopically time irreversible, interesting questions are raised about their relationship to real fluid mixtures. Simulation of certain complex-fluid problems, such as multiphase flow through porous media and the interaction of phase transitions with hydrodynamics, is illustrated.

  3. Liquid mixture convection during phase separation in a temperature gradient

    NASA Astrophysics Data System (ADS)

    Lamorgese, A. G.; Mauri, R.

    2011-03-01

    We simulate the phase separation of a low-viscosity binary mixture, assuming that the fluid system is confined between two walls that are cooled down to different temperatures below the critical point of the mixture, corresponding to quenches within the unstable range of its phase diagram. Spinodal decomposition patterns for off-critical mixtures are studied numerically in two dimensions in the creeping flow limit and for a large Lewis number, together with their dependence on the fluidity coefficient. Our numerical results reproduce the large-scale unidirectional migration of phase-separating droplets that was observed experimentally by Califano et al. ["Large-scale, unidirectional convection during phase separation of a density-matched liquid mixture," Phys. Fluids 17, 094109 (2005)], who measured typical speeds that are quite larger than the Marangoni velocity. To understand this finding, we then studied the temperature-gradient-induced motion of an isolated droplet of the minority phase embedded in a continuous phase, showing that when the drop is near local equilibrium, its speed is of the same order as the Marangoni velocity, i.e., it is proportional to the unperturbed temperature gradient and the fluidity coefficient. However, far from local equilibrium, i.e., for very large unperturbed temperature gradients, the drop first accelerates to a speed that is larger than the Marangoni velocity, then, later, it decelerates, exhibiting an increase-decrease behavior, as described by Yin et al. ["Thermocapillary migration of nondeformable drops," Phys. Fluids 20, 082101 (2008)]. Such behavior is due to the large nonequilibrium, Korteweg-driven convection, which at first accelerates the droplets to relatively large velocities, and then tends to induce an approximately uniform inside temperature distribution so that the drop experiences an effective temperature gradient that is much smaller than the unperturbed one and, consequently, decelerates.

  4. Phase-locked semiconductor laser array with separate contacts

    NASA Technical Reports Server (NTRS)

    Katz, J.; Kapon, E.; Lindsey, C.; Margalit, S.; Shreter, U.; Yariv, A.

    1983-01-01

    A new monolithic phase-locked semiconductor laser array has been fabricated. Employing two-level metallization, each of the eight elements in the array has a separate contact, thus making it possible to compensate for device nonuniformities and control the near-field and far-field patterns. Threshold currents are approximately 60 mA for each 5-micron-wide laser in the array. Phase locking has been observed via the narrowing of the far-field pattern. Experimental results are compared to those obtained from the same arrays operated with all the lasers connected in parallel.

  5. Fibril Formation and Phase Separation in Aqueous Cellulose Ethers

    NASA Astrophysics Data System (ADS)

    Maxwell, Amanda; Schmidt, Peter; McAllister, John; Lott, Joseph; Bates, Frank; Lodge, Timothy

    Aqueous solutions of many cellulose ethers are known to undergo thermoreversible gelation and phase separation upon heating to form turbid hydrogels, but the mechanism and resulting structures have not been well understood. Turbidity, light scattering and small-angle neutron scattering (SANS) are used to show that hydroxypropyl methylcellulose (HPMC) chains are dissolved in water below 50 °C and undergo phase separation at higher temperatures. At 70 °C, at sufficiently high concentrations in water, HPMC orders into fibrillar structures with a well-defined radius of 18 +/- 2 nm, as characterized by cryogenic transmission electron microscopy and SANS. The HPMC fibril structure is independent of concentration and heating rate. However, HPMC fibrils do not form a percolating network as readily as is seen in methylcellulose, resulting in a lower hot-gel modulus, as demonstrated by rheology.

  6. Correlated lateral phase separations in stacks of lipid membranes

    NASA Astrophysics Data System (ADS)

    Hoshino, Takuma; Komura, Shigeyuki; Andelman, David

    2015-12-01

    Motivated by the experimental study of Tayebi et al. [Nat. Mater. 11, 1074 (2012)] on phase separation of stacked multi-component lipid bilayers, we propose a model composed of stacked two-dimensional Ising spins. We study both its static and dynamical features using Monte Carlo simulations with Kawasaki spin exchange dynamics that conserves the order parameter. We show that at thermodynamical equilibrium, due to strong inter-layer correlations, the system forms a continuous columnar structure for any finite interaction across adjacent layers. Furthermore, the phase separation shows a faster dynamics as the inter-layer interaction is increased. This temporal behavior is mainly due to an effective deeper temperature quench because of the larger value of the critical temperature, Tc, for larger inter-layer interaction. When the temperature ratio, T/Tc, is kept fixed, the temporal growth exponent does not increase and even slightly decreases as a function of the increased inter-layer interaction.

  7. Exploration of phase separation in heterogeneous lipid monolayers

    NASA Astrophysics Data System (ADS)

    Decaro, Curt; Bera, Sambhunath; Jiang, Zhang; Mukhopadhyay, Mrinmay; Thompson, Carol

    2012-02-01

    A Langmuir monolayer is a well established model of a single leaflet of a lipid membrane. In this work, we investigate the phase separation behavior of a model Langmuir monolayer as a function of both Langmuir surface pressure and ratio of saturated lipid : unsaturated lipid : cholesterol. The specifics of domain separation behavior, or ``rafting,'' in membranes are generally thought to be responsible for much of the behavior of living membranes, specifically in protein integration and transport. Off-specular x-ray scattering is used to probe in-plane structure of the membrane at the sub-micron scale. Additionally, atomic force microscopy imaging is taken on samples transferred to a rigid support. In-plane order is found to grow as a function of surface pressure. Also, the in-plane order is found to depend on cholesterol concentration in the monolayer. The phase space of the in-plane order as a function of lipid and cholesterol concentration is presented.

  8. Phase separation of metallic hydrogen-helium alloys

    NASA Technical Reports Server (NTRS)

    Straus, D. M.; Ashcroft, N. W.; Beck, H.

    1976-01-01

    Calculations are presented for the thermodynamic functions and phase separation boundaries of solid metallic hydrogen helium alloys at temperatures between 0 K and 19,000 K and at pressures between 15 and 90 megabars. Expressions for the band structure energy of a randomly disordered alloy (including third order in the electron ion interaction) are derived and evaluated. Short and long range order are included by the quasi-chemical method, and lattice dynamics in the virtual crystal harmonic approximation. We conclude that at temperatures below 4,000 K there is complete phase separation of hydrogen helium alloys, and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

  9. Phase separation of metallic hydrogen-helium alloys

    NASA Technical Reports Server (NTRS)

    Straus, D. M.; Ashcroft, N. W.; Beck, H.

    1977-01-01

    Calculations are presented for the thermodynamic functions and phase-separation boundaries of solid metallic hydrogen-helium alloys at temperatures between zero and 19,000 K and at pressures between 15 and 90 Mbar. Expressions for the band-structure energy of a randomly disordered alloy (including third order in the electron-ion interaction) are derived and evaluated. Short- and long-range orders are included by the quasi-chemical method, and lattice dynamics in the virtual-crystal harmonic approximation. It is concluded that at temperatures below 4000 K, there is essentially complete phase separation of hydrogen-helium alloys and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

  10. Separation of granulocytes from whole blood by leukoadhesion, phase 1

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Capillary glass tubes are investigated for the separation and retrieval of large quantities of viable granulocytes and monocytes from whole blood on a continuous basis from a single donor. This effort represented the feasibility demonstration of a three phase program for development of a capillary tube cell separation device. The activity included the analysis and parametric laboratory testing with subscale models required to design a prototype device. Capillary tubes 40 cm long with a nominal 0.030 cm internal diameter yielded the highest total process efficiency. Recovery efficiencies as high as 89% of the adhering cell population were obtained. Granulocyte phagocytosis of latex particles indicated approximately 90% viability. Monocytes recovered from the separation column retained their capability to stimulate human bone marrow colony growth, as demonstrated in an in vitro cell culture assay.

  11. Rationale for two phase polymer system microgravity separation experiments

    NASA Technical Reports Server (NTRS)

    Brooks, D. E.; Bamberger, S. B.; Harris, J. M.; Vanalstine, J.

    1984-01-01

    The two-phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) are mixed at concentrations above a few percent are discussed. They provide useful media for the partition and isolation of macromolecules and cell subpopulations. By manipulating their composition, separations based on a variety of molecular and surface properties are achieved, including membrane hydrophobic properties, cell surface charge, and membrane antigenicity. Work on the mechanism of cell partition shows there is a randomizing, nonthermal energy present which reduces separation resolution. This stochastic energy is probably associated with hydrodynamic interactions present during separation. Because such factors should be markedly reduced in microgravity, a series of shuttle experiments to indicate approaches to increasing the resolution of the procedure are planned.

  12. Activity induced phase separation in particles and (bio)polymers

    NASA Astrophysics Data System (ADS)

    Grosberg, Alexander

    It was recently shown that the non-equilibrium steady state of the mixture of two types of particles exposed to two different thermostats can phase separate (A.Y.Grosberg, J.-F.Joanny, PRE, v. 91, 032118, 2015). similar result is valid also in the case when particles in question are monomers of two different polymer chains, or blocks of a co-polymer. We discuss the implications of these results for the physics of chromatin.

  13. Separating homeologs by phasing in the tetraploid wheat transcriptome

    PubMed Central

    2013-01-01

    Background The high level of identity among duplicated homoeologous genomes in tetraploid pasta wheat presents substantial challenges for de novo transcriptome assembly. To solve this problem, we develop a specialized bioinformatics workflow that optimizes transcriptome assembly and separation of merged homoeologs. To evaluate our strategy, we sequence and assemble the transcriptome of one of the diploid ancestors of pasta wheat, and compare both assemblies with a benchmark set of 13,472 full-length, non-redundant bread wheat cDNAs. Results A total of 489 million 100 bp paired-end reads from tetraploid wheat assemble in 140,118 contigs, including 96% of the benchmark cDNAs. We used a comparative genomics approach to annotate 66,633 open reading frames. The multiple k-mer assembly strategy increases the proportion of cDNAs assembled full-length in a single contig by 22% relative to the best single k-mer size. Homoeologs are separated using a post-assembly pipeline that includes polymorphism identification, phasing of SNPs, read sorting, and re-assembly of phased reads. Using a reference set of genes, we determine that 98.7% of SNPs analyzed are correctly separated by phasing. Conclusions Our study shows that de novo transcriptome assembly of tetraploid wheat benefit from multiple k-mer assembly strategies more than diploid wheat. Our results also demonstrate that phasing approaches originally designed for heterozygous diploid organisms can be used to separate the close homoeologous genomes of tetraploid wheat. The predicted tetraploid wheat proteome and gene models provide a valuable tool for the wheat research community and for those interested in comparative genomic studies. PMID:23800085

  14. Phase separation and coarsening in electrostatically driven granular media.

    SciTech Connect

    Aranson, I. S.; Meerson, B.; Sasorov, P. V.; Vinokur, V. M.; Materials Science Division; Hebrew Univ. of Jerusalem; Inst. of Theoretical and Experimental Physics

    2002-05-20

    A continuum model for the phase separation and coarsening in electrostatically driven granular media is formulated in terms of a Ginzburg-Landau equation subject to conservation of the total number of grains. In the regime of well-developed clusters, the continuum model is used to derive 'sharp-interface' equations that govern the dynamics of the interphase boundary. The model captures the essential physics of this system.

  15. Ligand-Driven Phase Separation in Binary Particle Brush Materials

    NASA Astrophysics Data System (ADS)

    Bockstaller, Michael; Schmitt, Michael; Zhang, Jianan; Yan, Jiajun; Matyjaszewski, Krzysztof

    The tethering of polymer chains to the surface of nanoparticles (to form so-called `particle brush materials') has emerged as an effective means to enable the bottom-up assembly of one-component hybrid materials with controlled microstructure and improved mechanical stability as well as novel optical or acoustic properties. The polymer-like interactions and response of these particle-brush materials suggest intriguing new opportunities to control structure formation in multicomponent particle mixtures. This contribution will demonstrate that polymer-ligand interactions can drive phase separation processes in mixed particle systems that share analogies to those of regular binary polymer blends. The role of particle size, density and degree of polymerization of tethered chains as well as the interaction parameter between the distinct tethered chains on the mechanism and kinetics of phase separation processes in mixed particle brush systems will be discussed. Ligand-driven phase separation will be shown to enable the efficient fabrication of monochromatic domain structured in mixed quantum dot systems that might find application in next generation quantum dot-enabled LEDs. Support by the National Science Foundation (via Grant DMR-1410845) is gratefully acknowledged.

  16. Phase-separation models for swimming enhancement in complex fluids

    NASA Astrophysics Data System (ADS)

    Man, Yi; Lauga, Eric

    2015-08-01

    Swimming cells often have to self-propel through fluids displaying non-Newtonian rheology. While past theoretical work seems to indicate that stresses arising from complex fluids should systematically hinder low-Reynolds number locomotion, experimental observations suggest that locomotion enhancement is possible. In this paper we propose a physical mechanism for locomotion enhancement of microscopic swimmers in a complex fluid. It is based on the fact that microstructured fluids will generically phase-separate near surfaces, leading to the presence of low-viscosity layers, which promote slip and decrease viscous friction near the surface of the swimmer. We use two models to address the consequence of this phase separation: a nonzero apparent slip length for the fluid and then an explicit modeling of the change of viscosity in a thin layer near the swimmer. Considering two canonical setups for low-Reynolds number locomotion, namely the waving locomotion of a two-dimensional sheet and that of a three-dimensional filament, we show that phase-separation systematically increases the locomotion speeds, possibly by orders of magnitude. We close by confronting our predictions with recent experimental results.

  17. Phase-separation models for swimming enhancement in complex fluids.

    PubMed

    Man, Yi; Lauga, Eric

    2015-08-01

    Swimming cells often have to self-propel through fluids displaying non-Newtonian rheology. While past theoretical work seems to indicate that stresses arising from complex fluids should systematically hinder low-Reynolds number locomotion, experimental observations suggest that locomotion enhancement is possible. In this paper we propose a physical mechanism for locomotion enhancement of microscopic swimmers in a complex fluid. It is based on the fact that microstructured fluids will generically phase-separate near surfaces, leading to the presence of low-viscosity layers, which promote slip and decrease viscous friction near the surface of the swimmer. We use two models to address the consequence of this phase separation: a nonzero apparent slip length for the fluid and then an explicit modeling of the change of viscosity in a thin layer near the swimmer. Considering two canonical setups for low-Reynolds number locomotion, namely the waving locomotion of a two-dimensional sheet and that of a three-dimensional filament, we show that phase-separation systematically increases the locomotion speeds, possibly by orders of magnitude. We close by confronting our predictions with recent experimental results. PMID:26382500

  18. Novel Resistive Switching Behavior in Phase Separated Manganites

    NASA Astrophysics Data System (ADS)

    Guo, Hangwen; Ward, T. Zac; Sun, Dali; Snijders, Paul C.; Gai, Zheng; Shen, Jian

    2011-03-01

    Electronic phase separation plays a key role in many novel phenomena in complex materials. Manganites are a prime example of this class of materials and have recently come under increase scrutiny for possible application in resistive random-access memory (RRAM) technology. Here, we will discuss our recent work on spatially confined La5/8-xPrxCa3/8MnO3. We have discovered that it is possible to drive single electronic domain formation/annihilation through electric field pulsing. By measuring the I-V curve, we find such resistive switching is different from normal RRAM mechanisms in manganites and is closely related to the nature of electronic phase separation. These findings open these systems to a new understanding of the nature of electronic phase separation and begin the development of manganites for future applications in RRAM devices. Research sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy.

  19. Phase separated microstructure and dynamics of polyurethane elastomers under strain

    NASA Astrophysics Data System (ADS)

    Iacob, Ciprian; Padsalgikar, Ajay; Runt, James

    The molecular mobility of polyurethane elastomers is of the utmost importance in establishing physical properties for uses ranging from automotive tires and shoe soles to more sophisticated aerospace and biomedical applications. In many of these applications, chain dynamics as well as mechanical properties under external stresses/strains are critical for determining ultimate performance. In order to develop a more complete understanding of their mechanical response, we explored the effect of uniaxial strain on the phase separated microstructure and molecular dynamics of the elastomers. We utilize X-ray scattering to investigate soft segment and hard domain orientation, and broadband dielectric spectroscopy for interrogation of the dynamics. Uniaxial deformation is found to significantly perturb the phase-separated microstructure and chain orientation, and results in a considerable slowing down of the dynamics of the elastomers. Attenuated total reflectance Fourier transform infrared spectroscopy measurements of the polyurethanes under uniaxial deformation are also employed and the results are quantitatively correlated with mechanical tensile tests and the degree of phase separation from small-angle X-ray scattering measurements.

  20. Anisotropic phase separation in amorphous Fe--Ge alloys

    SciTech Connect

    Regan, M.J.; Bienenstock, A.

    1993-04-01

    Magnetron sputtered amorphous Fe{sub x}Ge{sub 100-x} films have been examined with anomalous small-angle x-ray scattering (ASAXS) in an attempt to characterize composition fluctuations which have been previously reported in this system. Films grown under various deposition conditions have been studied, with the scattering vector both in and oblique to the plane of the films, to search for anisotropy. By manipulating the deposited power flux and rates of growth, films which have the same composition can be grown to different states of phase separation. The total correlation functions have been calculated from the oblique scattering experiments. The anisotropy can be successfully modeled as a close-packing of oriented prolate ellipsoidal particles, with the elongated axis along the direction of film growth. A method for using these measurements to determine the compositions of the phase-separating species has been developed and utilized. The results indicate phase separation into a-Ge and a-FeGe{sub 2} for the a-Fe{sub x}Ge{sub 100-x} (x<33) alloy.

  1. Anisotropic phase separation in amorphous Fe--Ge alloys

    SciTech Connect

    Regan, M.J.; Bienenstock, A.

    1993-04-01

    Magnetron sputtered amorphous Fe[sub x]Ge[sub 100-x] films have been examined with anomalous small-angle x-ray scattering (ASAXS) in an attempt to characterize composition fluctuations which have been previously reported in this system. Films grown under various deposition conditions have been studied, with the scattering vector both in and oblique to the plane of the films, to search for anisotropy. By manipulating the deposited power flux and rates of growth, films which have the same composition can be grown to different states of phase separation. The total correlation functions have been calculated from the oblique scattering experiments. The anisotropy can be successfully modeled as a close-packing of oriented prolate ellipsoidal particles, with the elongated axis along the direction of film growth. A method for using these measurements to determine the compositions of the phase-separating species has been developed and utilized. The results indicate phase separation into a-Ge and a-FeGe[sub 2] for the a-Fe[sub x]Ge[sub 100-x] (x<33) alloy.

  2. Uphill diffusion and phase separation in partially miscible multicomponent mixtures

    NASA Astrophysics Data System (ADS)

    He, Ping; Raghavan, Ashwin; Ghoniem, Ahmed

    2015-11-01

    The partially miscible multicomponent mixtures, which are frequently encountered in green chemistry processes, often exhibit complicated behaviors, and are critical to the production rate, energy efficiency, and pollution controls. Recent studies have been mainly focused on phase behaviors. However, the coupled phase equilibrium and transport process, which may be the answer to phase separations observed in experiments, is not well researched. Here, we present a numerical and theoretical study on coupled mixing of heavy oil and supercritical water, and the results of our state-of-art modeling agree with experimental measurements. We find that due to the non-ideal diffusion driving force, (1) strong uphill diffusion of heavy oil fractions occurs, (2) a new heavy oil phase is separated starting from the plait point, and heavy fractions become highly concentrated, and (3) water diffusion initially overshoots in oil, and is expelled lately. Finally, we conclude our analysis applicable to different molecules and conditions. The authors thank Saudi Aramco for supporting this work (contract number 6600023444).

  3. Source separation and clustering of phase-locked subspaces.

    PubMed

    Almeida, Miguel; Schleimer, Jan-Hendrik; Bioucas-Dias, José Mario; Vigário, Ricardo

    2011-09-01

    It has been proven that there are synchrony (or phase-locking) phenomena present in multiple oscillating systems such as electrical circuits, lasers, chemical reactions, and human neurons. If the measurements of these systems cannot detect the individual oscillators but rather a superposition of them, as in brain electrophysiological signals (electro- and magneoencephalogram), spurious phase locking will be detected. Current source-extraction techniques attempt to undo this superposition by assuming properties on the data, which are not valid when underlying sources are phase-locked. Statistical independence of the sources is one such invalid assumption, as phase-locked sources are dependent. In this paper, we introduce methods for source separation and clustering which make adequate assumptions for data where synchrony is present, and show with simulated data that they perform well even in cases where independent component analysis and other well-known source-separation methods fail. The results in this paper provide a proof of concept that synchrony-based techniques are useful for low-noise applications. PMID:21791409

  4. Quadruple-junction lattice coherency and phase separation in a binary-phase system

    NASA Astrophysics Data System (ADS)

    Chung, Sung-Yoon; Choi, Si-Young; Kim, Jin-Gyu; Kim, Young-Min

    2015-09-01

    If each phase has an identical crystal structure and small misfit in the lattice parameters in a binary-phase crystalline system, coherent phase boundaries usually form during separation. Although there have been numerous studies on the effect of coherency elastic energy, no attempt has been made to demonstrate how the phase-separation behaviour varies when multiple interfaces meet at a junction. Here we show that a comprehensively different phase-separation morphology is induced, to release the high coherency strain confined to quadruple junctions. High-temperature in-situ transmission electron microscopy reveals that phase boundaries with a new crystallographic orientation emerge over twinned crystals to provide strain relaxation at quadruple junctions. The high coherency strain and the formation of different phase boundaries can be understood in terms of the force equilibrium between interface tensions at a junction point. Visualizing the quadruple points at atomic resolution, our observations emphasize the impact of multiple junctions on the morphology evolution during phase separation.

  5. Quadruple-junction lattice coherency and phase separation in a binary-phase system

    PubMed Central

    Chung, Sung-Yoon; Choi, Si-Young; Kim, Jin-Gyu; Kim, Young-Min

    2015-01-01

    If each phase has an identical crystal structure and small misfit in the lattice parameters in a binary-phase crystalline system, coherent phase boundaries usually form during separation. Although there have been numerous studies on the effect of coherency elastic energy, no attempt has been made to demonstrate how the phase-separation behaviour varies when multiple interfaces meet at a junction. Here we show that a comprehensively different phase-separation morphology is induced, to release the high coherency strain confined to quadruple junctions. High-temperature in-situ transmission electron microscopy reveals that phase boundaries with a new crystallographic orientation emerge over twinned crystals to provide strain relaxation at quadruple junctions. The high coherency strain and the formation of different phase boundaries can be understood in terms of the force equilibrium between interface tensions at a junction point. Visualizing the quadruple points at atomic resolution, our observations emphasize the impact of multiple junctions on the morphology evolution during phase separation. PMID:26346223

  6. Phase diagram of van der Waals-like phase separation in a driven granular gas.

    PubMed

    Khain, Evgeniy; Meerson, Baruch; Sasorov, Pavel V

    2004-11-01

    Equations of granular hydrostatics are used to compute the phase diagram of the recently discovered van der Waals-like phase separation in a driven granular gas. The model two-dimensional system consists of smooth hard disks in a rectangular box, colliding inelastically with each other and driven by a "thermal" wall at zero gravity. The spinodal line and the critical point of the phase separation are determined. Close to the critical point, the spinodal and binodal (coexistence) lines are determined analytically. Effects of the finite size of the confining box in the direction parallel to the thermal wall are investigated. These include suppression of the phase separation by heat conduction in the lateral direction and a change from supercritical to subcritical bifurcation. PMID:15600606

  7. Separable pairing force for relativistic quasiparticle random-phase approximation

    SciTech Connect

    Tian Yuan; Ma Zhongyu; Ring, Peter

    2009-06-15

    We have introduced a separable pairing force, which was adjusted to reproduce the pairing properties of the Gogny force in nuclear matter. This separable pairing force is able to describe in relativistic Hartree-Bogoliubov (RHB) calculations the pairing properties in the ground state of finite nuclei on almost the same footing as the original Gogny interaction. In this work we investigate excited states using the Relativistic Quasiparticle Random-Phase Approximation (RQRPA) with the same separable pairing force. For consistency the Goldstone modes and the convergence with various cutoff parameters in this version of RQRPA are studied. The first excited 2{sup +} states for the chain of Sn isotopes with Z=50 and the chain of isotones with N=82 isotones are calculated in RQRPA together with the 3{sup -} states of Sn isotopes. By comparing our results with experimental data and with the results of the original Gogny force we find that this simple separable pairing interaction is very successful in depicting the pairing properties of vibrational excitations.

  8. Silk fibroin gelation via non-solvent induced phase separation.

    PubMed

    Kasoju, Naresh; Hawkins, Nicholas; Pop-Georgievski, Ognen; Kubies, Dana; Vollrath, Fritz

    2016-03-01

    Tissue engineering benefits from novel materials with precisely tunable physical, chemical and mechanical properties over a broad range. Here we report a practical approach to prepare Bombyx mori silk fibroin hydrogels using the principle of non-solvent induced phase separation (NIPS). A combination of reconstituted silk fibroin (RSF) and methanol (non-solvent), with a final concentration of 2.5% w/v and 12.5% v/v respectively, maintained at 22 °C temperature turned into a hydrogel within 10 hours. Freeze-drying of this gel gave a foam with a porosity of 88%, a water uptake capacity of 89% and a swelling index of 8.6. The gelation kinetics and the loss tangent of the gels were investigated by rheometry. The changes in the morphology of the porous foams were visualized by SEM. The changes in RSF chemical composition and the relative fraction of its secondary structural elements were analyzed by ATR-FTIR along with Fourier self-deconvolution. And, the changes in the glass transition temperature, specific heat capacity and the relative fraction of crystallinity of RSF were determined by TM-DSC. Data suggested that RSF-water-methanol behaved as a polymer-solvent-non-solvent ternary phase system, wherein the demixing of the water-methanol phases altered the thermodynamic equilibrium of RSF-water phases and resulted in the desolvation and eventual separation of the RSF phase. Systematic analysis revealed that both gelation time and the properties of hydrogels and porous foams could be controlled by the ratios of RSF and non-solvent concentration as well as by the type of non-solvent and incubation temperature. Due to the unique properties we envisage that the herein prepared NIPS induced RSF hydrogels and porous foams can possibly be used for the encapsulation of cells and/or for the controlled release of both hydrophilic and hydrophobic drugs. PMID:26730413

  9. Phase Separation of Model Segmented Poly(Carbonate Urethanes)

    NASA Astrophysics Data System (ADS)

    Hernandez, Rebeca; Hung, Elena; Runt, James

    2006-03-01

    The present paper focuses on the phase separated morphology and segment demixing of model poly(carbonate urethanes) [PCU] with hard segment contents ranging from 30 -- 65% and soft segments composed of 1,6 poly(hexamethylene carbonate) [MW = 1K]. Hard segments were formed from 4,4'-methylenediphenyl diisocyanate and 1,4 butanediol. This family of materials represents a recent approach in the development of polyurethanes with improved long-term biostability, and is under clinical investigation in a number of biomedical devices. Only a single glass transition temperature was observed for each copolymer, increasing in temperature with increasing hard segment content. However, loss spectra from dynamic mechanical analysis showed clear evidence of two mixed phases. The results of small-angle X-ray scattering and tapping mode AFM experiments were consistent with these observations and will be discussed. Finally, these results will be compared with initial findings on phase separation in another family of polyurethane copolymers of current interest as blood-contact materials in biomedical devices having mixed poly(dimethylsiloxane) -- poly(hexamethyleneoxide) soft segments.

  10. Spin Glasses and Frustration

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, Scott

    The 1975 EA paper by Sam Edwards and Phil Anderson proposed to understand a class of real materials as frustrated, glassy magnets with a novel type of weak order in time. It launched an exciting period of intense exploration of new directions for understanding random and composite materials. This work has had a lasting impact well beyond materials science, contributing powerful new methods for optimization of complex many-parameter systems as well as codes offering Shannon-bounded communications in extremely noisy channels.

  11. The phase reversal phenomenon at flow separation and reattachment

    NASA Technical Reports Server (NTRS)

    Stack, J. Pete; Mangalam, S. M.; Kalburgi, V.

    1988-01-01

    Tests were conducted on two different airfoils, one of them in a low-turbulence tunnel, to detect laminar separation and turbulent reattachment locations. A 'nonintrusive' multielement sensor consisting of a large number of closely spaced individual nickel films was vacuum deposited on a thin substrate and bonded to the airfoil model surface. Each sensor element was a part of an independent constant temperature anemometer system. Time history as well as spectral analysis of signals from surface film gauges were used to determine the surface shear flow characteristics. A major breakthrough was achieved with the discovery of phase reversal in low-frequency dynamic shear stress signals across regions of flow separation and reattachment.

  12. Self-assembly of amorphous biophotonic nanostructures by phase separation

    SciTech Connect

    Dufresne, Eric R.; Noh, Heeso; Saranathan, Vinodkumar; Mochrie, Simon G.J.; Cao, Hui; Prum, Richard O.

    2009-04-23

    Some of the most vivid colors in the animal kingdom are created not by pigments, but by wavelength-selective scattering of light from nanostructures. Here we investigate quasi-ordered nanostructures of avian feather barbs which produce vivid non-iridescent colors. These {beta}-keratin and air nanostructures are found in two basic morphologies: tortuous channels and amorphous packings of spheres. Each class of nanostructure is isotropic and has a pronounced characteristic length scale of variation in composition. These local structural correlations lead to strong backscattering over a narrow range of optical frequencies and little variation with angle of incidence. Such optical properties play important roles in social and sexual communication. To be effective, birds need to precisely control the development of these nanoscale structures, yet little is known about how they grow. We hypothesize that multiple lineages of birds have convergently evolved to exploit phase separation and kinetic arrest to self-assemble spongy color-producing nanostructures in feather barbs. Observed avian nanostructures are strikingly similar to those self-assembled during the phase separation of fluid mixtures; the channel and sphere morphologies are characteristic of phase separation by spinodal decomposition and nucleation and growth, respectively. These unstable structures are locked-in by the kinetic arrest of the {beta}-keratin matrix, likely through the entanglement or cross-linking of supermolecular {beta}-keratin fibers. Using the power of self-assembly, birds can robustly realize a diverse range of nanoscopic morphologies with relatively small physical and chemical changes during feather development.

  13. Phase Separation of Superconducting Phases in the Penson-Kolb-Hubbard Model

    NASA Astrophysics Data System (ADS)

    Jerzy Kapcia, Konrad; Czart, Wojciech Robert; Ptok, Andrzej

    2016-04-01

    In this paper, we determine the phase diagrams (for T = 0 as well as T > 0) of the Penson-Kolb-Hubbard model for two dimensional square lattice within Hartree-Fock mean-field theory focusing on an investigation of superconducting phases and on a possibility of the occurrence of the phase separation. We obtain that the phase separation, which is a state of coexistence of two different superconducting phases (with s- and η-wave symmetries), occurs in definite ranges of the electron concentration. In addition, increasing temperature can change the symmetry of the superconducting order parameter (from η-wave into s-wave). The system considered exhibits also an interesting multicritical behaviour including bicritical points. The relevance of the results to experiments for real materials is also discussed.

  14. Phase/Shape Transitions and the Two Neutron Separation Energies

    SciTech Connect

    Zamfir, N. V.; Anghel, Sabina; Cata-Danil, G.

    2008-11-11

    We investigated the evolution of experimental two-neutron separation energies (S{sub 2n}) along the isotopic chains for the even-even nuclei. In order to enhance the sensitivity of our search, differential variation of the S{sub 2n} has been investigated. The emphasis is on finding nonmonotonic behaviors which can be correlated with phase/shape transition. Correlations of the ground state S{sub 2n} values with the excited states energies R{sub 4/2} ratio are also discussed.

  15. Vapors-liquid phase separator. [infrared telescope heat sink

    NASA Technical Reports Server (NTRS)

    Frederking, T. H. K.; Brown, G. S.; Chuang, C.; Kamioka, Y.; Kim, Y. I.; Lee, J. M.; Yuan, S. W. K.

    1980-01-01

    The use of porous plugs, mostly with in the form of passive devices with constant area were considered as vapor-liquid phase separators for helium 2 storage vessels under reduced gravity. The incorporation of components with variable cross sectional area as a method of flow rate modification was also investigated. A particular device which uses a shutter-type system for area variation was designed and constructed. This system successfully permitted flor rate changes of up to plus or minus 60% from its mean value.

  16. Nanopatterns by phase separation of patterned mixed polymer monolayers

    DOEpatents

    Huber, Dale L; Frischknecht, Amalie

    2014-02-18

    Micron-size and sub-micron-size patterns on a substrate can direct the self-assembly of surface-bonded mixed polymer brushes to create nanoscale patterns in the phase-separated mixed polymer brush. The larger scale features, or patterns, can be defined by a variety of lithographic techniques, as well as other physical and chemical processes including but not limited to etching, grinding, and polishing. The polymer brushes preferably comprise vinyl polymers, such as polystyrene and poly(methyl methacrylate).

  17. Phase separation as a key to a thermoelectric high efficiency.

    PubMed

    Schwall, Michael; Balke, Benjamin

    2013-02-14

    This work elucidates the possible reasons for the outstanding, but never reproduced thermoelectric properties of the doped Ti(0.5)Zr(0.25)Hf(0.25)NiSn Heusler compounds. The structural investigations done via synchrotron X-ray diffraction measurements and scanning electron microscope measurements, which clearly show that the microstructure consists of three temperature stable C1(b) phases with possible semi-coherent interfaces, are presented. The exceptional thermoelectric properties are due to this intrinsic phase separation. It is possible to reproduce the high Figure of Merit values with ZT = 1.2 at 830 K. Furthermore, the influence of doping different elements on the Sn position in this Heusler material system is investigated. PMID:23247074

  18. Accelerated sintering in phase-separating nanostructured alloys

    PubMed Central

    Park, Mansoo; Schuh, Christopher A.

    2015-01-01

    Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W–Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs. PMID:25901420

  19. Accelerated sintering in phase-separating nanostructured alloys.

    PubMed

    Park, Mansoo; Schuh, Christopher A

    2015-01-01

    Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W-Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs. PMID:25901420

  20. Vortex motion phase separator for zero gravity liquid transfer

    NASA Technical Reports Server (NTRS)

    Howard, Frank S. (Inventor); Fraser, Wilson M., Jr. (Inventor)

    1989-01-01

    A vortex motion phase separator is disclosed for transferring a liquid in a zero gravity environment while at the same time separating the liquid from vapors found within either the sender or the receiving tanks. The separator comprises a rigid sender tank having a circular cross-section and rigid receiver tank having a circular cross-section. A plurality of ducts connects the sender tank and the receiver tank. Disposed within the ducts connecting the receiver tank and the sender tank is a pump and a plurality of valves. The pump is powered by an electric motor and is adapted to draw either the liquid or a mixture of the liquid and the vapor from the sender tank. Initially, the mixture drawn from the sender tank is directed through a portion of the ductwork and back into the sender tank at a tangent to the inside surface of the sender tank, thereby creating a swirling vortex of the mixture within the sender tank. As the pumping action increases, the speed of the swirling action within the sender tank increases creating an increase in the centrifugal force operating on the mixture. The effect of the centrifugal force is to cause the heavier liquid to migrate to the inside surface of the sender tank and to separate from the vapor. When this separation reaches a predetermined degree, control means is activated to direct the liquid conveyed by the pump directly into the receiver tank. At the same time, the vapor within the receiver tank is directed from the receiver tank back into the sender tank. This flow continues until substantially all of the liquid is transferred from the sender tank to the receiver tank.

  1. Studies on Phase Separation in a-PMMA/PEG Gels

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoliang

    2005-03-01

    Stereo-irregular atactic poly(methyl methacrylate) (a-PMMA) is known incapable of forming gels in common solvents, irrespective of the solvent quality. However, we recently found a rigid opaque thermal-reversible a-PMMA gel in the solvent of the polyethyl glycol oligomer (PEG) (the PEG molecule mass differ from 400 to 4000 were used). FT-IR, dynamic mechanical temperature analysis and Solid state NMR measurements were used to study the gel properties and gelation mechanism. The in situ IR studies in a-PMMA/PEG gel suggested that some a-PMMA segments were in the aggregated state in solution, which became a node in the solution. With decreasing temperature, the fraction of aggregated a-PMMA in solution increases, resulting in the formation of physical network finally. Spin diffusion was used to determine the size (ξ) of domains in the gels. We found that, a-PMMA/PEG4000 was miscible (ξ ˜ 9nm), while a-PMMA/PEG1000 was micro phase separated (ξ ˜ 57nm) and a-PMMA/PEG400 was macro phase separated (ξ > 300nm). The a-PMMA self-aggregation was attributed to the depletion interaction that becomes important in the case of middle-sized solvents.

  2. Phase Separation in Lean-Grade Duplex Stainless Steel 2101

    NASA Astrophysics Data System (ADS)

    Garfinkel, David A.; Poplawsky, Jonathan D.; Guo, Wei; Young, George A.; Tucker, Julie D.

    2015-08-01

    The use of duplex stainless steels (DSS) in nuclear power generation systems is limited by thermal instability that leads to embrittlement in the temperature range of 204°C to 538°C. New lean-grade alloys, such as 2101, offer the potential to mitigate these effects. Thermal embrittlement was quantified through impact toughness and hardness testing on samples of alloy 2101 after aging at 427°C for various durations (1-10,000 h). Additionally, atom probe tomography (APT) was utilized in order to observe the kinetics of α-α' separation and G-phase formation. Mechanical testing and APT data for two other DSS alloys, 2003 and 2205, were used as a reference to 2101. The results show that alloy 2101 exhibits superior performance compared to the standard-grade DSS alloy 2205 but inferior to the lean-grade alloy 2003 in mechanical testing. APT data demonstrate that the degree of α-α' separation found in alloy 2101 closely resembles that of 2205 and greatly exceeds 2003. Additionally, contrary to what was observed in 2003, 2101 demonstrated G-phase like precipitates after long aging times, although precipitates were not as abundant as was observed in 2205.

  3. Phase Separation in Lean Grade Duplex Stainless Steel 2101

    SciTech Connect

    Garfinkel, D.; Poplawsky, Jonathan D.; Guo, Wei; Young, Jr., George A.; Tucker, Julie

    2015-08-19

    The use of duplex stainless steels (DSS) in nuclear power generation systems is limited by thermal instability that leads to embrittlement in the temperature range of 204°C - 538°C. New lean grade alloys, such as 2101, offer the potential to mitigate these effects. Thermal embrittlement was quantified through impact toughness and hardness testing on samples of alloy 2101 after aging at 427°C for various durations (1-10,000 hours). Additionally, atom probe tomography (APT) was utilized in order to observe the kinetics of α-α’ separation and G-phase formation. Mechanical testing and APT data for two other DSS alloys, 2003 and 2205 were used as a reference to 2101. The results show that alloy 2101 exhibits superior performance compared to the standard grade DSS alloy, 2205, but inferior to the lean grade alloy, 2003, in mechanical testing. APT data demonstrates that the degree of α-α’ separation found in alloy 2101 closely resembles that of 2205, and greatly exceeds 2003. Additionally, contrary to what was observed in 2003, 2101 demonstrated G-phase like precipitates after long aging times, though precipitates were not as abundant as was observed in 2205.

  4. Phase Separation in Lean Grade Duplex Stainless Steel 2101

    DOE PAGESBeta

    Garfinkel, D.; Poplawsky, Jonathan D.; Guo, Wei; Young, Jr., George A.; Tucker, Julie

    2015-08-19

    The use of duplex stainless steels (DSS) in nuclear power generation systems is limited by thermal instability that leads to embrittlement in the temperature range of 204°C - 538°C. New lean grade alloys, such as 2101, offer the potential to mitigate these effects. Thermal embrittlement was quantified through impact toughness and hardness testing on samples of alloy 2101 after aging at 427°C for various durations (1-10,000 hours). Additionally, atom probe tomography (APT) was utilized in order to observe the kinetics of α-α’ separation and G-phase formation. Mechanical testing and APT data for two other DSS alloys, 2003 and 2205 weremore » used as a reference to 2101. The results show that alloy 2101 exhibits superior performance compared to the standard grade DSS alloy, 2205, but inferior to the lean grade alloy, 2003, in mechanical testing. APT data demonstrates that the degree of α-α’ separation found in alloy 2101 closely resembles that of 2205, and greatly exceeds 2003. Additionally, contrary to what was observed in 2003, 2101 demonstrated G-phase like precipitates after long aging times, though precipitates were not as abundant as was observed in 2205.« less

  5. The mechanical properties of phase separated protein droplets

    NASA Astrophysics Data System (ADS)

    Jawerth, Louise; Ijavi, Mahdiye; Patel, Avinash; Saha, Shambaditya; Jülicher, Frank; Hyman, Anthony

    In vivo, numerous proteins associate into liquid compartments by de-mixing from the surrounding solution, similar to oil molecules in water. Many of these proteins and their corresponding liquid compartments play a crucial role in important biological processes, for instance germ line specification in C. elegans or in neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS). However, despite their importance, very little is known about the physical properties of the resulting droplets as well as the physical mechanisms that control their phase separation from solution. To gain a deeper understanding of these aspects, we study a few such proteins in vitro. When these proteins are purified and added to a physiological buffer, they phase separate into droplets ranging in size from a few to tens of microns with liquid-like behavior similar to their physiological counterparts. By attaching small beads to the surface of the droplets, we can deform the droplets by manipulating the beads directly using optical tweezers. By measuring the force required to deform the droplets we determine their surface tension, elasticity and viscosity as well as the frequency response of these properties. We also measure these properties using passive micro-rheology.

  6. Correlated lateral phase separations in stacks of lipid membranes

    SciTech Connect

    Hoshino, Takuma; Komura, Shigeyuki; Andelman, David

    2015-12-28

    Motivated by the experimental study of Tayebi et al. [Nat. Mater. 11, 1074 (2012)] on phase separation of stacked multi-component lipid bilayers, we propose a model composed of stacked two-dimensional Ising spins. We study both its static and dynamical features using Monte Carlo simulations with Kawasaki spin exchange dynamics that conserves the order parameter. We show that at thermodynamical equilibrium, due to strong inter-layer correlations, the system forms a continuous columnar structure for any finite interaction across adjacent layers. Furthermore, the phase separation shows a faster dynamics as the inter-layer interaction is increased. This temporal behavior is mainly due to an effective deeper temperature quench because of the larger value of the critical temperature, T{sub c}, for larger inter-layer interaction. When the temperature ratio, T/T{sub c}, is kept fixed, the temporal growth exponent does not increase and even slightly decreases as a function of the increased inter-layer interaction.

  7. Liquid-Liquid Phase Separation of Oil Bodies from Seeds.

    PubMed

    Nykiforuk, Cory L

    2016-01-01

    Fundamentally, oil bodies are discrete storage organelles found in oilseeds, comprising a hydrophobic triacylglycerol core surrounded by a half-unit phospholipid membrane and an outer shell of specialized proteins known as oleosins. Oil bodies possess a number of attributes that were exploited by SemBioSys Genetics to isolate highly enriched fractions of oil bodies through liquid-liquid phase separation for a number of commercial applications. The current chapter provides a general guide for the isolation of oil bodies from Arabidopsis and/or safflower seed, from which protocols can be refined for different oilseed sources. For SemBioSys Genetic's recombinant technology, therapeutic proteins were covalently attached to oleosins or fused in-frame with ligands which bound oil bodies, facilitating their recovery to high levels of purity during "upstream processing" of transformed seed. Core to this technology was oil body isolation consisting of simple manipulation including homogenization of seeds to free the oil bodies, followed by the removal of insoluble fractions, and phase separation to recover the oil bodies. During oil body enrichment (an increase in oil body content concomitant with removal of impurities), a number of options and tips are provided to aid researchers in the manipulation and monitoring of these robust organelles. PMID:26614290

  8. Binary-liquid phase separation of lens protein solutions.

    PubMed Central

    Broide, M L; Berland, C R; Pande, J; Ogun, O O; Benedek, G B

    1991-01-01

    We have determined the coexistence curves (plots of phase-separation temperature T versus protein concentration C) for aqueous solutions of purified calf lens proteins. The proteins studied, calf gamma IIIa-, gamma IIIb-, and gamma IVa-crystallin, have very similar amino acid sequences and three-dimensional structures. Both ascending and descending limbs of the coexistence curves were measured. We find that the coexistence curves for each of these proteins and for gamma II-crystallin can be fit, near the critical point, to the function /(Cc-C)/Cc/ = A [(Tc - T)/Tc]beta, where beta = 0.325, Cc is the critical protein concentration in mg/ml, Tc is the critical temperature for phase separation in K, and A is a parameter that characterizes the width of the coexistence curve. We find that A and Cc are approximately the same for all four coexistence curves (A = 2.6 +/- 0.1, Cc = 289 +/- 20 mg/ml), but that Tc is not the same. For gamma II- and gamma IIIb-crystallin, Tc approximately 5 degrees C, whereas for gamma IIIa- and gamma IVa-crystallin, Tc approximately 38 degrees C. By comparing the published protein sequences for calf, rat, and human gamma-crystallins, we postulate that a few key amino acid residues account for the division of gamma-crystallins into low-Tc and high-Tc groups. Images PMID:2062844

  9. Understanding the Impact of User Frustration Intensities on Task Performance Using the OCC Theory of Emotions

    NASA Technical Reports Server (NTRS)

    Washington, Gloria

    2012-01-01

    Have you heard the saying "frustration is written all over your falce"? Well this saying is true, but that is not the only place. Frustration is written all over your face and your body. The human body has various means to communicate an emotion without the utterance of a single word. The Media Equation says that people interact with computers as if they are human: this includes experiencing frustration. This research measures frustration by monitoring human body-based measures such as heart rate, posture, skin temperature. and respiration. The OCC Theory of Emotions is used to separate frustration into different levels or intensities. The results of this study showed that individual intensities of frustration exist, so that task performance is not degraded. Results from this study can be used by usability testers to model how much frustration is needed before task performance measures start to decrease.

  10. Quantitative analysis of aqueous phase composition of model dentin adhesives experiencing phase separation

    PubMed Central

    Ye, Qiang; Park, Jonggu; Parthasarathy, Ranganathan; Pamatmat, Francis; Misra, Anil; Laurence, Jennifer S.; Marangos, Orestes; Spencer, Paulette

    2013-01-01

    There have been reports of the sensitivity of our current dentin adhesives to excess moisture, for example, water-blisters in adhesives placed on over-wet surfaces, and phase separation with concomitant limited infiltration of the critical dimethacrylate component into the demineralized dentin matrix. To determine quantitatively the hydrophobic/hydrophilic components in the aqueous phase when exposed to over-wet environments, model adhesives were mixed with 16, 33, and 50 wt % water to yield well-separated phases. Based upon high-performance liquid chromatography coupled with photodiode array detection, it was found that the amounts of hydrophobic BisGMA and hydrophobic initiators are less than 0.1 wt % in the aqueous phase. The amount of these compounds decreased with an increase in the initial water content. The major components of the aqueous phase were hydroxyethyl methacrylate (HEMA) and water, and the HEMA content ranged from 18.3 to 14.7 wt %. Different BisGMA homologues and the relative content of these homologues in the aqueous phase have been identified; however, the amount of crosslinkable BisGMA was minimal and, thus, could not help in the formation of a crosslinked polymer network in the aqueous phase. Without the protection afforded by a strong crosslinked network, the poorly photoreactive compounds of this aqueous phase could be leached easily. These results suggest that adhesive formulations should be designed to include hydrophilic multimethacrylate monomers and water compatible initiators. PMID:22331596

  11. Dual Phase Membrane for High Temperature CO2 Separation

    SciTech Connect

    Jerry Lin

    2007-06-30

    This project aimed at synthesis of a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2} separation. Metal-carbonate dual-phase membranes were prepared by the direct infiltration method and the synthesis conditions were optimized. Permeation tests for CO{sub 2} and N{sub 2} from 450-750 C showed very low permeances of those two gases through the dual-phase membrane, which was expected due to the lack of ionization of those two particular gases. Permeance of the CO{sub 2} and O{sub 2} mixture was much higher, indicating that the gases do form an ionic species, CO{sub 3}{sup 2-}, enhancing transport through the membrane. However, at temperatures in excess of 650 C, the permeance of CO{sub 3}{sup 2-} decreased rapidly, while predictions showed that permeance should have continued to increase with temperature. XRD data obtained from used membrane indicated that lithium iron oxides formed on the support surface. This lithium iron oxide layer has a very low conductivity, which drastically reduces the flow of electrons to the CO{sub 2}/O{sub 2} gas mixture; thus limiting the formation of the ionic species required for transport through the membrane. These results indicated that the use of stainless steel supports in a high temperature oxidative environment can lead to decreased performance of the membranes. This revelation created the need for an oxidation resistant support, which could be gained by the use of a ceramic-type membrane. Work was extended to synthesize a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2} separation. Helium permeance of the support before and after infiltration of molten carbonate are on the order of 10{sup -6} and 10{sup -10} moles/m{sup 2} {center_dot} Pa {center_dot} s respectively, indicating that the molten carbonate is able to sufficiently infiltrate the membrane. It was found that La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (LSCF) was a suitable candidate for the support

  12. Geometrically Frustrated Fracture Mechanics

    NASA Astrophysics Data System (ADS)

    Mitchell, Noah; Koning, Vinzenz; Vitelli, Vincenzo; Irvine, William T. M.

    2015-03-01

    When a flat elastic sheet is forced to conform to a surface with Gaussian curvature, stresses arise in the sheet. The mismatch between initial and final metrics gives rise to new fracture behavior which cannot be achieved by boundary loading alone. Using experiments of PDMS sheets frustrated on 3D-printed surfaces and a linearized analytical model, we demonstrate the ability of curvature to govern the sheets' fracture phenomenology. In this talk, we first show that curvature can both stimulate and suppress fracture initiation, depending on the position and orientation of the initial slit. Secondly, we show that curvature can steer the path of a crack as it propagates through the material. Lastly, the curvature can arrest cracks which would otherwise continue to propagate.

  13. Phase separation and doped-hole segregation in La{sub 2}CuO{sub 4+{delta}} and La{sub 2-x}Sr{sub x}CuO{sub 4+{delta}}

    SciTech Connect

    Johnston, D.C.; Bayless, W.R.; Borsa, F. |

    1994-05-01

    This paper reviews the magnetic, superconducting and structural phase diagrams of the title systems, with an emphasis on recent results from magnetic and structural neutron diffraction, magnetic susceptibility and {sup 139}La nuclear quadrupole resonance measurements. Results clarify the miscibility gap in the La{sub 2}CuO{sub 4+{delta}} system and indicate the occurrence of frustrated phase separation on a nanoscopic length scale in the La{sub 2{minus}x}Sr{sub x}CuO{sub 4} system with 0 < x {approx_lt} 0.05.

  14. The evolutionary significance of phase-separated microsystems

    NASA Technical Reports Server (NTRS)

    Fox, S. W.

    1976-01-01

    The source, preparation, and properties of phase-separated systems such as lipid layers, coacervate droplets, sulphobes, and proteinoid microspheres are reviewed. These microsystems are of interest as partial models for the cell and as partial or total models for the protocell. Conceptual benefits from the study of such models include clues to experiments on origins, insights into principles of action, and, in some instances, presumable models of the origin of the protocell. The benefits to evolution of organized chemical units are many, and can in part be analyzed. Ease of formation suggests that such units would have arisen early in primordial organic evolution. Integration of these various concepts and the results of consequent experiments have contributed to the developing theory of the origins of primordial and contemporary life.

  15. Phase Separation from Electron Confinement at Oxide Interfaces.

    PubMed

    Scopigno, N; Bucheli, D; Caprara, S; Biscaras, J; Bergeal, N; Lesueur, J; Grilli, M

    2016-01-15

    Oxide heterostructures are of great interest for both fundamental and applicative reasons. In particular, the two-dimensional electron gas at the LaAlO_{3}/SrTiO_{3} or LaTiO_{3}/SrTiO_{3} interfaces displays many different properties and functionalities. However, there are clear experimental indications that the interface electronic state is strongly inhomogeneous and therefore it is crucial to investigate possible intrinsic mechanisms underlying this inhomogeneity. Here, the electrostatic potential confining the electron gas at the interface is calculated self-consistently, finding that such confinement may induce phase separation, to avoid a thermodynamically unstable state with a negative compressibility. This provides a robust mechanism for the inhomogeneous character of these interfaces. PMID:26824560

  16. Ostwald-Driven Phase Separation in Bimetallic Nanoparticle Assemblies.

    PubMed

    Prévot, Geoffroy; Nguyen, Nhat Tai; Alloyeau, Damien; Ricolleau, Christian; Nelayah, Jaysen

    2016-04-26

    The compositional stability of bimetallic nanoparticles (NPs) is crucial for many applications. We have studied the coarsening of amorphous carbon-supported Au-Pd NPs during annealing at 873 K. Using scanning transmission electron microscopy and energy-dispersive spectroscopy measurements, we show that, despite a complete miscibility of the two metals, the particle assembly undergoes a phase separation during annealing, which leads to two distinct populations: Au-rich NPs with a mean radius of 3.5 nm and large Pd-rich NPs with a mean radius of 25 nm. Thermodynamic calculations and kinetic Monte Carlo simulations explain this behavior that is driven by the competition between surface and mixing energy and by the different mobilities of the two atomic species. PMID:26989906

  17. Model system studies with a phase separated membrane bioreactor

    NASA Technical Reports Server (NTRS)

    Petersen, G. R.; Seshan, P. K.; Dunlop, Eric H.

    1989-01-01

    The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestial simulation.

  18. Phase separated membrane bioreactor - Results from model system studies

    NASA Technical Reports Server (NTRS)

    Petersen, G. R.; Seshan, P. K.; Dunlop, E. H.

    1989-01-01

    The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestrial simulation.

  19. Micro-phase Separation via Spinodal-like Decomposition in Hexamethylynediisocyanate (HDI)-polyurea

    SciTech Connect

    Kulkarni, Amit S.; Beaucage, Gregory; Wilkes, Garth L.; Das, Sudipto; Yilgor, Iskander

    2012-04-03

    We found that micro-phase separation in hexamethylynediisocyanate-polyurea was studied using small-angle X-ray scattering and infrared absorption. Moreover, it was found that phase separation in this system followed spinodal-like decomposition on a 3–4 nm size scale with phase separation occuring on a time scale of days.

  20. Evolution of a phase separated gravity independent bioreactor

    NASA Technical Reports Server (NTRS)

    Villeneuve, Peter E.; Dunlop, Eric H.

    1992-01-01

    The evolution of a phase-separated gravity-independent bioreactor is described. The initial prototype, a zero head-space manifold silicone membrane based reactor, maintained large diffusional resistances. Obtaining oxygen transfer rates needed to support carbon-recycling aerobic microbes is impossible if large resistances are maintained. Next generation designs (Mark I and II) mimic heat exchanger design to promote turbulence at the tubing-liquid interface, thereby reducing liquid and gas side diffusional resistances. While oxygen transfer rates increased by a factor of ten, liquid channeling prevented further increases. To overcome these problems, a Mark III reactor was developed which maintains inverted phases, i.e., media flows inside the silicone tubing, oxygen gas is applied external to the tubing. This enhances design through changes in gas side driving force concentration and liquid side turbulence levels. Combining an applied external pressure of 4 atm with increased Reynolds numbers resulted in oxygen transfer intensities of 232 mmol O2/l per hr (1000 times greater than the first prototype and comparable to a conventional fermenter). A 1.0 liter Mark III reactor can potentially deliver oxygen supplies necessary to support cell cultures needed to recycle a 10-astronaut carbon load continuously.

  1. Order From disorder in Frustrated Spin Systems

    NASA Astrophysics Data System (ADS)

    Coleman, Piers

    This talk will review the phemomenon of ''Order from disorder'': the mechanism by which fluctuations remove a degeneracy within a frustrated spin system. An important consequence of order-from-disorder, is the ability of frustrated Heisenberg spin systems to overcome the Mermin-Wagner theorem, developing new forms of discrete order, even when the spins themselves remain disordered with a finite correlation length. The most well-known example, is the two-dimensional frustrated J1 -J2 Heisenberg model, which undergoes a finite temperature Ising phase transition into a stripy or ''nematic'' state, even though the spins do not order until absolute zero. Nematic ordering of this kind is believed to occur in the iron-based superconductors, such as BaFe2 As2 . More recently, it has been possible to theoretically study the triangular-honeycomb versions of the J1 -J2 model, called a windmill model, in which order-from disorder drives the development of six-state clock order. Remarkably, in this case, order-from-disorder leads to an intermediate power-law spin phase, despite the underlying Heisenerg spins. This research was supported by DOE Basic Energy Sciences Grant DE-FG02-99ER45790.

  2. DUAL PHASE MEMBRANE FOR HIGH TEMPERATURE CO2 SEPARATION

    SciTech Connect

    Jerry Y.S. Lin; Seungjoon Chung; Matthew Anderson

    2005-12-01

    This project is intended to expand upon the previous year's research en route to the development of a sustainable dual phase membrane for CO{sub 2} separation. It was found that the pores within the supports had to be less than 9 {micro}m in order to maintain the stability of the dual phase membrane. Pores larger than 9 {micro}m would be unable to hold the molten carbonate phase in place, rendering the membrane ineffective. Calculations show that 80% of the pore volume of the 0.5 media grade metal support was filled with the molten carbonate. Information obtained from EDS and SEM confirmed that the molten carbonate completely infiltrated the pores on both the contact and non-contact size of the metal support. Permeation tests for CO{sub 2} and N{sub 2} at 450-750 C show very low permeance of those two gases through the dual phase membrane, which was expected due to the lack of ionization of those two gases. Permeance of the CO{sub 2} and O{sub 2} mixture was much higher, indicating that the gases do form an ionic species, CO{sub 3}{sup 2-}, enhancing transport through the membrane. However, at temperatures in excess of 650 C, the permeance of CO{sub 3}{sup 2-} decreased quite rapidly, while predictions showed that permeance should have continued to increase. XRD data obtained form the surface of the membrane indicated the formation of lithium iron oxides on the support. This layer has a very low conductivity, which drastically reduces the flow of electrons to the CO{sub 2}/O{sub 2} gas mixture, limiting the formation of the ionic species. These results indicate that the use of stainless steel supports in a high temperature oxidative environment can lead to decreased performance of the membranes. This revelation has created the need for an oxidation resistant support, which can be gained by the use of a ceramic-type membrane. Future research efforts will be directed towards preparation of a new ceramic-carbonate dual phase membrane. The membrane will based on an

  3. Frustrated total internal reflection acoustic field sensor

    DOEpatents

    Kallman, Jeffrey S.

    2000-01-01

    A frustrated total internal reflection acoustic field sensor which allows the acquisition of the acoustic field over an entire plane, all at once. The sensor finds use in acoustic holography and acoustic diffraction tomography. For example, the sensor may be produced by a transparent plate with transparent support members tall enough to support one or more flexible membranes at an appropriate height for frustrated total internal reflection to occur. An acoustic wave causes the membrane to deflect away from its quiescent position and thus changes the amount of light that tunnels through the gap formed by the support members and into the membrane, and so changes the amount of light reflected by the membrane. The sensor(s) is illuminated by a uniform tight field, and the reflection from the sensor yields acoustic wave amplitude and phase information which can be picked up electronically or otherwise.

  4. Protein Phase Behavior in Aqueous Solutions: Crystallization, Liquid-Liquid Phase Separation, Gels, and Aggregates

    PubMed Central

    Dumetz, André C.; Chockla, Aaron M.; Kaler, Eric W.; Lenhoff, Abraham M.

    2008-01-01

    The aggregates and gels commonly observed during protein crystallization have generally been considered disordered phases without further characterization. Here their physical nature is addressed by investigating protein salting-out in ammonium sulfate and sodium chloride for six proteins (ovalbumin, ribonuclease A, soybean trypsin inhibitor, lysozyme, and β-lactoglobulin A and B) at 4°C, 23°C, and 37°C. When interpreted within the framework of a theoretical phase diagram obtained for colloidal particles displaying short-range attractive interactions, the results show that the formation of aggregates can be interpreted theoretically in terms of a gas-liquid phase separation for aggregates that are amorphous or gel-like. A notable additional feature is the existence of a second aggregation line observed for both ovalbumin and ribonuclease A in ammonium sulfate, interpreted theoretically as the spinodal. Further investigation of ovalbumin and lysozyme reveals that the formation of aggregates can be interpreted, in light of theoretical results from mode-coupling theory, as a kinetically trapped state or a gel phase that occurs through the intermediate of a gas-liquid phase separation. Despite the limitations of simple theoretical models of short-range attractive interactions, such as their inability to reproduce the effect of temperature, they provide a framework useful to describe the main features of protein phase behavior. PMID:18160663

  5. Research on the two-phase flow and separation mechanism in the oil-gas cyclone separator

    NASA Astrophysics Data System (ADS)

    Wang, L. Z.; Gao, X.; Feng, J. M.; Peng, X. Y.

    2015-08-01

    The cyclone separator has attracted increasing attention due to its small size, rapid construction and high separation efficiency. This study investigated its gas-liquid two-phase flow and separation characteristics experimentally and numerically. A numerical model of two- phase flow in the cyclone separator was proposed using the Euler-Lagrange method. The distribution of pressure, tangential and axial velocity in the gas-phase flow field was obtained, and the oil droplet movement was traced. Separation efficiency was also studied experimentally, and the diameter distributions of oil droplets at the inlet and the outlet of the separator were measured by a Malvern laser particle size analyser to verify the simulation model. Based on high-speed photography technology, the oil film distribution and flow pattern on the wall of the cyclone separator were visualised. The variation of oil-gas two-phase flow in the cyclone separator was compared under various inlet flow rates. Based on the results, an improved structure was proposed, and the performance of the improved separator was investigated experimentally.

  6. Frustrated Lewis Pairs.

    PubMed

    Stephan, Douglas W

    2015-08-19

    The articulation of the notion of "frustrated Lewis pairs" (FLPs), which emerged from the discovery that H2 can be reversibly activated by combinations of sterically encumbered Lewis acids and bases, has prompted a great deal of recent activity. Perhaps the most remarkable consequence has been the development of FLP catalysts for the hydrogenation of a range of organic substrates. In the past 9 years, the substrate scope has evolved from bulky polar species to include a wide range of unsaturated organic molecules. In addition, effective stereoselective metal-free hydrogenation catalysts have begun to emerge. The mechanism of this activation of H2 has been explored, and the nature and range of Lewis acid/base combinations capable of effecting such activation have also expanded to include a variety of non-metal species. The reactivity of FLPs with a variety of other small molecules, including olefins, alkynes, and a range of element oxides, has also been developed. Although much of this latter chemistry has uncovered unique stoichiometric transformations, metal-free catalytic hydroamination, CO2 reduction chemistry, and applications in polymerization have also been achieved. The concept is also beginning to find applications in bioinorganic and materials chemistry as well as heterogeneous catalysis. This Perspective highlights many of these developments and discusses the relationship between FLPs and established chemistry. Some of the directions and developments that are likely to emerge from FLP chemistry in the future are also presented. PMID:26214241

  7. Dementia, Caregiving, and Controlling Frustration

    MedlinePlus

    ... for you. Behaviors often associated with dementia, like wandering or asking questions repeatedly, can be frustrating for ... or tasks you need help with. Keep in mind that people feel useful and gratified when they ...

  8. Nanoparticle-Mediated, Light-Induced Phase Separations.

    PubMed

    Neumann, Oara; Neumann, Albert D; Silva, Edgar; Ayala-Orozco, Ciceron; Tian, Shu; Nordlander, Peter; Halas, Naomi J

    2015-12-01

    Nanoparticles that both absorb and scatter light, when dispersed in a liquid, absorb optical energy and heat a reduced fluid volume due to the combination of multiple scattering and optical absorption. This can induce a localized liquid-vapor phase change within the reduced volume without the requirement of heating the entire fluid. For binary liquid mixtures, this process results in vaporization of the more volatile component of the mixture. When subsequently condensed, these two steps of vaporization and condensation constitute a distillation process mediated by nanoparticles and driven by optical illumination. Because it does not require the heating of a large volume of fluid, this process requires substantially less energy than traditional distillation using thermal sources. We investigated nanoparticle-mediated, light-induced distillation of ethanol-H2O and 1-propanol-H2O mixtures, using Au-SiO2 nanoshells as the absorber-scatterer nanoparticle and nanoparticle-resonant laser irradiation to drive the process. For ethanol-H2O mixtures, the mole fraction of ethanol obtained in the light-induced process is substantially higher than that obtained by conventional thermal distillation, essentially removing the ethanol-H2O azeotrope that limits conventional distillation. In contrast, for 1-propanol-H2O mixtures the distillate properties resulting from light-induced distillation were very similar to those obtained by thermal distillation. In the 1-propanol-H2O system, a nanoparticle-mediated, light-induced liquid-liquid phase separation was also observed. PMID:26535465

  9. Dual Phase Membrane for High Temperature CO2 Separation

    SciTech Connect

    Jerry Y.S. Lin; Matthew Anderson

    2006-09-29

    Dual-phase membranes consisting of stainless steel supports infiltrated with molten carbonate have been shown to be selective to CO{sub 2} at high temperatures (400-650 C). However, over time at high temperatures, the formation of iron oxides on the surface of the stainless steel supports render the membranes ineffective. This report details synthesis and characteristics of dual-phase carbonate membrane with an oxidation resistant perovskite type ceramic (lanthanum-strontium-cobaltite-iron; LSCF) support. Porous LSCF supports were prepared from its powder synthesized by the citrate method. Both steady state permeation and mercury porosimetry confirmed that the LSCF membrane sintered at 900 C has pores large enough to absorb molten carbonate, yet small enough to retain the molten carbonate under high pressure conditions. Results of XRD analysis have shown that LSCF and the molten carbonate mixture do not react with each other at temperatures below 700 C. Four-point method conductivity tests indicate that the support material has sufficiently high electronic conductivity for this application. Li-Na-K carbonate was coated to the porous LSCF support by a liquid infiltration method. Helium permeance of the support before and after infiltration of molten carbonate are on the order of 10{sup -6} and 10{sup -10} moles/m{sup 2} {center_dot} Pa {center_dot} s respectively, indicating that the molten carbonate is able to sufficiently infiltrate the membrane. Preliminary high temperature permeation experiments indicate that the membrane does separate CO{sub 2} in the presence of O{sub 2}, with a maximum flux of 0.623 ml/cm{sup 2} {center_dot} min obtained at 850 C.

  10. Confinement-driven phase separation of quantum liquid mixtures.

    PubMed

    Prisk, T R; Pantalei, C; Kaiser, H; Sokol, P E

    2012-08-17

    We report small-angle neutron scattering studies of liquid helium mixtures confined in Mobil Crystalline Material-41 (MCM-41), a porous silica glass with narrow cylindrical nanopores (d=3.4 nm). MCM-41 is an ideal model adsorbent for fundamental studies of gas sorption in porous media because its monodisperse pores are arranged in a 2D triangular lattice. The small-angle scattering consists of a series of diffraction peaks whose intensities are determined by how the imbibed liquid fills the pores. Pure (4)He adsorbed in the pores show classic, layer-by-layer film growth as a function of pore filling, leaving the long range symmetry of the system intact. In contrast, the adsorption of (3)He-(4)He mixtures produces a structure incommensurate with the pore lattice. Neither capillary condensation nor preferential adsorption of one helium isotope to the pore walls can provide the symmetry-breaking mechanism. The scattering is consistent with the formation of randomly distributed liquid-liquid microdomains ∼2.3 nm in size, providing evidence that confinement in a nanometer scale capillary can drive local phase separation in quantum liquid mixtures. PMID:23006380

  11. Phase separation in antisymmetric films: A molecular dynamics study

    SciTech Connect

    Krishnan, Raishma; Puri, Sanjay; Jaiswal, Prabhat K.

    2013-11-07

    We have used molecular dynamics (MD) simulations to study phase-separation kinetics in a binary fluid mixture (AB) confined in an antisymmetric thin film. One surface of the film (located at z = 0) attracts the A-atoms, and the other surface (located at z = D) attracts the B-atoms. We study the kinetic processes which lead to the formation of equilibrium morphologies subsequent to a deep quench below the miscibility gap. In the initial stages, one observes the formation of a layered structure, consisting of an A-rich layer followed by a B-rich layer at z = 0; and an analogous structure at z = D. This multi-layered morphology is time-dependent and propagates into the bulk, though it may break up into a laterally inhomogeneous structure at a later stage. We characterize the evolution morphologies via laterally averaged order parameter profiles; the growth laws for wetting-layer kinetics and layer-wise length scales; and the scaling properties of layer-wise correlation functions.

  12. Dual Phase Membrane for High temperature CO2 Separation

    SciTech Connect

    Jerry Y.S. Lin; Matthew Anderson

    2005-12-01

    Research in the previous years in this project found that stainless steel supports are oxidized during high temperature, dual phase membrane separation of carbon dioxide (with oxygen). Consequently, a new material has been sought to alleviate the problems with oxidation. Lanthanum cobaltite oxide is a suitable candidate for the support material in the dual phase membrane due to its oxidation resistance and electronic conductivity. Porous lanthanum cobaltite membranes were prepared via the citrate method, using nitrate metal precursors as the source of La, Sr, Co and Fe. The material was prepared and ground into a powder, which was subsequently pressed into disks for sintering at 900 C. Conductivity measurements were evaluated using the four-probe DC method. Support pore size was determined by helium permeation. Conductivity of the lanthanum cobaltite material was found to be at a maximum of 0.1856 S/cm at 550 C. The helium permeance of the lanthanum cobaltite membranes for this research was on the order of 10{sup -6} moles/m{sup 2} {center_dot} Pa {center_dot} s, proving that the membranes are porous after sintering at 900 C. The average pore size based on steady state helium permeance measurements was found to be between 0.37 and 0.57 {micro}m. The lanthanum cobaltite membranes have shown to have desired porosity, pore size and electric conductivity as the support for the dual-phase membranes. Molten carbonate was infiltrated to the pores of lanthanum cobaltite membranes support. After infiltration with molten carbonate, the helium permeance of the membranes decreased by three orders of magnitude to 10{sup -9} moles/m{sup 2} {center_dot} Pa {center_dot} s. This number, however, is one order of magnitude larger than the room temperate permeance of the stainless steel supports after infiltration with molten carbonate. Optimization of the dip coating process with molten carbonate will be evaluated to determine if lower permeance values can be obtained with the

  13. Effect of OH content on phase separation behavior of soda-silica glasses

    NASA Technical Reports Server (NTRS)

    Neilson, G. F.; Weinberg, M. C.; Smith, G. L.

    1986-01-01

    The kinetics of phase separation in a gel and ordinary soda-silica glass are followed by use of small angle X-ray scattering. Also, the influence of OH on the phase separation behavior is studied. It is found that OH accelerates the growth of the secondary phase, and that gel and ordinary glasses of similar composition and OH concentration exhibit similar phase separation characteristics.

  14. Solidification Behavior of Polymer Solution during Membrane Preparation by Thermally Induced Phase Separation

    PubMed Central

    Ishigami, Toru; Nii, Yoko; Ohmukai, Yoshikage; Rajabzadeh, Saeid; Matsuyama, Hideto

    2014-01-01

    The solidification behavior of poly(vinylidene fluoride) (PVDF) solution during membrane preparation by thermally induced phase separation (TIPS) was investigated. Apparatus newly developed in our laboratory was used to quantitatively measure membrane stiffness during phase separation. In this apparatus, a cooling polymer solution, placed on a stage, is moved upwards and the surface of the polymer solution contacts a sphere attached to the tip of a needle. The displacement of a blade spring attached to the needle is then measured by a laser displacement sensor. Different phase separation modes, such as liquid-liquid (L-L) phase separation and solid-liquid (S-L) phase separation (polymer crystallization) were investigated. In the case of S-L phase separation, the stiffness of the solution surface began to increase significantly just before termination of crystallization. In contrast, L-L phase separation delayed solidification of the solution. This was because mutual contact of the spherulites was obstructed by droplets of polymer-lean phase formed during L-L phase separation. Thus, the solidification rate was slower for the L-L phase separation system than for the S-L phase separation system. PMID:24957124

  15. Frustration and multicriticality in the antiferromagnetic spin-1 chain

    NASA Astrophysics Data System (ADS)

    Pixley, J. H.; Shashi, Aditya; Nevidomskyy, Andriy H.

    2014-12-01

    The antiferromagnetic spin-1 chain has a venerable history and has been thought to be well understood. Here, we show that inclusion of both next-nearest-neighbor (α ) and biquadratic (β ) interactions results in a rich phase diagram with a multicritical point that has not been observed before. We study the problem using a combination of the density matrix renormalization group (DMRG), an analytic variational matrix product state wave function, and conformal field theory. For negative β <β* , we establish the existence of a spontaneously dimerized phase, separated from the Haldane phase by the critical line αc(β ) of second-order phase transitions. In the opposite regime, β >β* , the transition from the Haldane phase becomes first order into the next-nearest-neighbor (NNN) AKLT phase. Based on the field theoretical arguments and DMRG calculations, we find that these two regimes are separated by a multicritical point (β*,α*) of a different universality class, described by the level-4 SU(2) Wess-Zumino-Witten conformal theory. From the DMRG calculations, we estimate this multicritical point to lie in the range -0.2 <β*<-0.15 and 0.47 <α*<0.53 . We further find that the dimerized and NNN-AKLT phases are separated from each other by a line of first-order phase transitions that terminates at the multicritical point. We establish that transitions out of the Haldane phase into the dimer or NNN-AKLT phases are topological in nature and occur either with or without closing of the bulk gap, respectively. We also study short-range incommensurate-to-commensurate transitions in the resulting phase diagram. Inside the Haldane phase, we show the existence of two incommensurate crossovers: the Lifshitz transition and the disorder transition of the first kind, marking incommensurate correlations in momentum and real space, respectively. Notably, these crossover lines stretch across the entire (β ,α ) phase diagram, merging into a single incommensurate

  16. Dissipative particle dynamics simulation study on the binary mixture phase separation coupled with polymerization.

    PubMed

    Liu, Hong; Qian, Hu-Jun; Zhao, Ying; Lu, Zhong-Yuan

    2007-10-14

    The influence of polymerization on the phase separation of binary immiscible mixtures has been investigated by the dissipative particle dynamics simulations in two dimensions. During polymerization, the bulk viscosity increases, which consequently slows down the spinodal decomposition process. The domain size growth is monitored in the simulations. The absence of 23 exponent for inertial hydrodynamic mechanism clearly reflects the suppressing effect of polymerization on the phase separation. Due to the increasing viscosity, the individual phase may be trapped in a metastable stage instead of the lamellar morphology identified for symmetric mixtures. Moreover, the polymerization induced phase separation in the binary miscible mixture has been studied. The domain growth is strongly dependent on the polymerization probability, which is naturally related to the activation energy for polymerization. The observed complex phase separation behavior is attributed to the interplay between the increasing thermodynamic driving force for phase separation and the increasing viscosity that suppresses phase separation as the polymerization proceeds. PMID:17935435

  17. Selective Metal Deposition on a Phase-Separated Polymer Blend Surface

    NASA Astrophysics Data System (ADS)

    Tsujioka, Tsuyoshi; Yamaguchi, Koji

    2013-07-01

    We report selective metal deposition on a phase-separated polymer blend surface. A polymer blend film consisting of polystyrene (PS) and a polystyrene-block-polybutadiene copolymer (PS-BR) was annealed, and a micro-phase-separated film was obtained. Pb was evaporated onto the phase-separated surface without an evaporation mask and was selectively deposited on the PS phase but not on the PS-BR phase. We achieved fine metal patterns corresponding to the microphase separation. This result suggests a novel method of preparing fine metal patterns for electronics and photonics.

  18. Carbon Dioxide Separation from Flue Gas by Phase Enhanced Absorption

    SciTech Connect

    Tim Fout

    2007-06-30

    A new process, phase enhanced absorption, was invented. The method is carried out in an absorber, where a liquid carrier (aqueous solution), an organic mixture (or organic compound), and a gas mixture containing a gas to be absorbed are introduced from an inlet. Since the organic mixture is immiscible or at least partially immiscible with the liquid carrier, the organic mixture forms a layer or small parcels between the liquid carrier and the gas mixture. The organic mixture in the absorber improves mass transfer efficiency of the system and increases the absorption rate of the gas. The organic mixture serves as a transportation media. The gas is finally accumulated in the liquid carrier as in a conventional gas-liquid absorption system. The presence of the organic layer does not hinder the regeneration of the liquid carrier or recovery of the gas because the organic layer is removed by a settler after the absorption process is completed. In another aspect, the system exhibited increased gas-liquid separation efficiency, thereby reducing the costs of operation and maintenance. Our study focused on the search of the organic layer or transportation layer to enhance the absorption rate of carbon dioxide. The following systems were studied, (1) CO{sub 2}-water system and CO{sub 2}-water-organic layer system; (2) CO{sub 2}-Potassium Carbonate aqueous solution system and CO{sub 2}-Potassium Carbonate aqueous solution-organic layer system. CO{sub 2}-water and CO{sub 2}-Potassium Carbonate systems are the traditional gas-liquid absorption processes. The CO{sub 2}-water-organic layer and CO{sub 2}-Potassium Carbonate-organic layer systems are the novel absorption processes, phase enhanced absorption. As we mentioned early, organic layer is used for the increase of absorption rate, and plays the role of transportation of CO{sub 2}. Our study showed that the absorption rate can be increased by adding the organic layer. However, the enhanced factor is highly depended on the

  19. Nematic quantum liquid crystals of bosons in frustrated lattices

    NASA Astrophysics Data System (ADS)

    Zhu, Guanyu; Koch, Jens; Martin, Ivar

    2016-04-01

    The problem of interacting bosons in frustrated lattices is an intricate one due to the absence of a unique minimum in the single-particle dispersion where macroscopic number of bosons can condense. Here, we consider a family of tight-binding models with macroscopically degenerate lowest energy bands, separated from other bands by a gap. We predict the formation of exotic states that spontaneously break rotational symmetry at relatively low filling. These states belong to three nematic phases: Wigner crystal, supersolid, and superfluid. The Wigner crystal phase is established exactly at low filling. Supersolid and superfluid phases, at larger filling, are obtained by making use of a projection onto the flat band, construction of an appropriate Wannier basis, and subsequent mean-field treatment. The nematic superfluid that we predict is uniform in real space but has an anisotropic momentum distribution, providing a novel scenario for Bose condensation with an additional nematic order. Our findings open up a promising direction of studying microscopic quantum liquid crystalline phases of bosons.

  20. Fluid Phase Separation (FPS) experiment for flight on a space shuttle Get Away Special (GAS) canister

    NASA Technical Reports Server (NTRS)

    Peters, Bruce; Wingo, Dennis; Bower, Mark; Amborski, Robert; Blount, Laura; Daniel, Alan; Hagood, Bob; Handley, James; Hediger, Donald; Jimmerson, Lisa

    1990-01-01

    The separation of fluid phases in microgravity environments is of importance to environmental control and life support systems (ECLSS) and materials processing in space. A successful fluid phase separation experiment will demonstrate a proof of concept for the separation technique and add to the knowledge base of material behavior. The phase separation experiment will contain a premixed fluid which will be exposed to a microgravity environment. After the phase separation of the compound has occurred, small samples of each of the species will be taken for analysis on the Earth. By correlating the time of separation and the temperature history of the fluid, it will be possible to characterize the process. The experiment has been integrated into space available on a manifested Get Away Special (GAS) experiment, CONCAP 2, part of the Consortium for Materials Complex Autonomous Payload (CAP) Program, scheduled for STS-42. The design and the production of a fluid phase separation experiment for rapid implementation at low cost is presented.

  1. Excitations in the quantum paramagnetic phase of the quasi-one-dimensional Ising magnet CoNb2O6 in a transverse field: Geometric frustration and quantum renormalization effects

    NASA Astrophysics Data System (ADS)

    Cabrera, I.; Thompson, J. D.; Coldea, R.; Prabhakaran, D.; Bewley, R. I.; Guidi, T.; Rodriguez-Rivera, J. A.; Stock, C.

    2014-07-01

    The quasi-one-dimensional (1D) Ising ferromagnet CoNb2O6 has recently been driven via applied transverse magnetic fields through a continuous quantum phase transition from spontaneous magnetic order to a quantum paramagnet, and dramatic changes were observed in the spin dynamics, characteristic of weakly perturbed 1D Ising quantum criticality. We report here extensive single-crystal inelastic neutron scattering measurements of the magnetic excitations throughout the three-dimensional (3D) Brillouin zone in the quantum paramagnetic phase just above the critical field to characterize the effects of the finite interchain couplings. In this phase, we observe that excitations have a sharp, resolution-limited line shape at low energies and over most of the dispersion bandwidth, as expected for spin-flip quasiparticles. We map the full bandwidth along the strongly dispersive chain direction and resolve clear modulations of the dispersions in the plane normal to the chains, characteristic of frustrated interchain couplings in an antiferromagnetic isosceles triangular lattice. The dispersions can be well parametrized using a linear spin-wave model that includes interchain couplings and further neighbor exchanges. The observed dispersion bandwidth along the chain direction is smaller than that predicted by a linear spin-wave model using exchange values determined at zero field, and this effect is attributed to quantum renormalization of the dispersion beyond the spin-wave approximation in fields slightly above the critical field, where quantum fluctuations are still significant.

  2. Crystalline Phase Separation in Phosphate Containing Waste Glasses: Relevance to INEEL HAW

    SciTech Connect

    Jantzen, C.M.

    2000-09-21

    As part of the Tanks Focus Area's (TFA) effort to increase waste loading for high-level waste vitrification at various facilities in the Department of Energy (DOE) complex, the occurrence of phase separation in waste glasses spanning the Savannah River Site (SRS) and Idaho National Engineering and Environmental Laboratory (INEEL) composition ranges have been studied. The type of phase separation that occurs in the phosphate rich borosilicate waste glasses, such as those investigated for INEEL, crystallizes upon cooling. This type of phase separation mechanism is less well studied than amorphous phase separation in phosphate poor borosilicate waste glasses. Therefore, the type of phase separation, extent, and impact of phase separation on glass durability for a series of INEEL-type glasses were examined and the data statistically analyzed in this study.

  3. Frustration in Condensed Matter and Protein Folding

    NASA Astrophysics Data System (ADS)

    Li, Z.; Tanner, S.; Conroy, B.; Owens, F.; Tran, M. M.; Boekema, C.

    2014-03-01

    By means of computer modeling, we are studying frustration in condensed matter and protein folding, including the influence of temperature and Thomson-figure formation. Frustration is due to competing interactions in a disordered state. The key issue is how the particles interact to reach the lowest frustration. The relaxation for frustration is mostly a power function (randomly assigned pattern) or an exponential function (regular patterns like Thomson figures). For the atomic Thomson model, frustration is predicted to decrease with the formation of Thomson figures at zero kelvin. We attempt to apply our frustration modeling to protein folding and dynamics. We investigate the homogeneous protein frustration that would cause the speed of the protein folding to increase. Increase of protein frustration (where frustration and hydrophobicity interplay with protein folding) may lead to a protein mutation. Research is supported by WiSE@SJSU and AFC San Jose.

  4. Interlay of Quantum Criticality and Geometric Frustration in Columbite

    NASA Astrophysics Data System (ADS)

    Kaul, Ribhu

    2011-10-01

    CoNb2O6 is a remarkable magnetic material. The interplay between two of the most exciting features of correlated quantum physics, quantum criticality and geometric frustration, results in a rich phase diagram which reflects the fundamental underlying quantum many-body physics in this complex oxide material. Many aspects of the theoretically calculated phase diagram and expectations for quantum criticality have already been observed in beautiful neutron scattering experiments on this material.[4pt] Ref: Interplay of Quantum Criticality and Geometric Frustration in Columbite, SungBin Lee, Ribhu K. Kaul, Leon Balents, Nature Physics 6, 702-706 (2010)

  5. A novel route for fabricating metal-polymer composite nanoparticles with phase-separated structures.

    PubMed

    Yabu, Hiroshi; Koike, Kazutaka; Motoyoshi, Kiwamu; Higuchi, Takeshi; Shimomura, Masatsugu

    2010-07-15

    Au nanoparticles (NPs) and polymer composite particles with phase-separation structures were prepared based on phase separation structures. Au NPs were successfully synthesized in amphiphilic block-copolymer micelles, and then composite particles were formed by a simple solvent evaporation process from Au NPs and polymer solution. The phase separated structures (Janus and Core-shell) were controlled by changing the combination of polymers having differing hydrophobicity. PMID:21567522

  6. A novel mechanical model for phase-separation in debris flows

    NASA Astrophysics Data System (ADS)

    Pudasaini, Shiva P.

    2015-04-01

    Understanding the physics of phase-separation between solid and fluid phases as a two-phase mass moves down slope is a long-standing challenge. Here, I propose a fundamentally new mechanism, called 'separation-flux', that leads to strong phase-separation in avalanche and debris flows. This new model extends the general two-phase debris flow model (Pudasaini, 2012) to include a separation-flux mechanism. The new flux separation mechanism is capable of describing and controlling the dynamically evolving phase-separation, segregation, and/or levee formation in a real two-phase, geometrically three-dimensional debris flow motion and deposition. These are often observed phenomena in natural debris flows and industrial processes that involve the transportation of particulate solid-fluid mixture material. The novel separation-flux model includes several dominant physical and mechanical aspects that result in strong phase-separation (segregation). These include pressure gradients, volume fractions of solid and fluid phases and their gradients, shear-rates, flow depth, material friction, viscosity, material densities, boundary structures, gravity and topographic constraints, grain shape, size, etc. Due to the inherent separation mechanism, as the mass moves down slope, more and more solid particles are brought to the front, resulting in a solid-rich and mechanically strong frontal surge head followed by a weak tail largely consisting of the viscous fluid. The primary frontal surge head followed by secondary surge is the consequence of the phase-separation. Such typical and dominant phase-separation phenomena are revealed here for the first time in real two-phase debris flow modeling and simulations. However, these phenomena may depend on the bulk material composition and the applied forces. Reference: Pudasaini, Shiva P. (2012): A general two-phase debris flow model. J. Geophys. Res., 117, F03010, doi: 10.1029/2011JF002186.

  7. On the phase form of a deformation quantization with separation of variables

    NASA Astrophysics Data System (ADS)

    Karabegov, Alexander

    2016-06-01

    Given a star product with separation of variables on a pseudo-Kähler manifold, we obtain a new formal (1, 1)-form from its classifying form and call it the phase form of the star product. The cohomology class of a star product with separation of variables equals the class of its phase form. We show that the phase forms can be arbitrary and they bijectively parametrize the star products with separation of variables. We also describe the action of a change of the formal parameter on a star product with separation of variables, its formal Berezin transform, classifying form, phase form, and canonical trace density.

  8. Frustration-induced nanometre-scale inhomogeneity in a triangular antiferromagnet

    PubMed Central

    Zorko, A.; Adamopoulos, O.; Komelj, M.; Arčon, D.; Lappas, A.

    2014-01-01

    Phase inhomogeneity of otherwise chemically homogenous electronic systems is an essential ingredient leading to fascinating functional properties, such as high-Tc superconductivity in cuprates, colossal magnetoresistance in manganites and giant electrostriction in relaxors. In these materials distinct phases compete and can coexist owing to intertwined ordered parameters. Charge degrees of freedom play a fundamental role, although phase-separated ground states have been envisioned theoretically also for pure spin systems with geometrical frustration that serves as a source of phase competition. Here we report a paradigmatic magnetostructurally inhomogenous ground state of the geometrically frustrated α-NaMnO2 that stems from the system’s aspiration to remove magnetic degeneracy and is possible only due to the existence of near-degenerate crystal structures. Synchrotron X-ray diffraction, nuclear magnetic resonance and muon spin relaxation show that the spin configuration of a monoclinic phase is disrupted by magnetically short-range-ordered nanoscale triclinic regions, thus revealing a novel complex state of matter. PMID:24477185

  9. Excitations in the quantum paramagnetic phase of the quasi-one-dimensional Ising magnet CoNb2O6 in a transverse field: Geometric frustration and quantum renormalization effects

    NASA Astrophysics Data System (ADS)

    Cabrera, Ivelisse; Thompson, J. D.; Coldea, R.; Prabhakaran, D.; Bewley, R. I.; Guidi, T.; Rodriguez-Rivera, J. A.; Stock, C.

    We report extensive single-crystal inelastic neutron scattering measurements of the magnetic excitations in the quasi 1D Ising ferromagnet CoNb2O6 in the quantum paramagnetic phase to characterize the effects of the finite interchain couplings. In this phase, we observe that excitations have a sharp, resolution-limited line shape at low energies and over most of the dispersion bandwidth, as expected for spin-flip quasiparticles. We map the full bandwidth along the strongly dispersive chain direction and resolve clear modulations of the dispersions in the plane normal to the chains, characteristic of frustrated interchain couplings in an antiferromagnetic isosceles triangular lattice. The dispersions can be well parametrized using a linear spin-wave model that includes interchain couplings and further neighbor exchanges. The observed dispersion bandwidth along the chain direction is smaller than that predicted by a linear spin-wave model using exchange values determined at zero field. We attribute this effect to quantum renormalization of the dispersion beyond the spin-wave approximation in fields slightly above the critical field, where quantum fluctuations are still significant. We acknowledge support from EPSRC Grant No. EP/H014934/1, the Oxford Clarendon Fund Scholarship and NSERC of Canada.

  10. On separability of A-phases during the cyclic alternating pattern.

    PubMed

    Mendez, M O; Alba, A; Chouvarda, I; Milioli, G; Grassi, A; Terzano, M G; Parrino, L

    2014-01-01

    A statistical analysis of the separability of EEG A-phases, with respect to basal activity, is presented in this study. A-phases are short central events that build up the Cyclic Alternating Pattern (CAP) during sleep. The CAP is a brain phenomenon which is thought to be related to the construction, destruction and instability of sleep stages dynamics. From the EEG signals, segments obtained around the onset and offset of the A-phases were used to evaluate the separability between A-phases and basal sleep stage oscillations. In addition, a classifier was trained to separate the different A-phase types (A1, A2 and A3). Temporal, energy and complexity measures were used as descriptors for the classifier. The results show a percentage of separation between onset and preceding basal oscillations higher than 85 % for all A-phases types. For Offset separation from following baseline, the accuracy is higher than 80 % but specificity is around 75%. Concerning to A-phase type separation, A1-phase and A3-phase are well separated with accuracy higher than 80, while A1 and A2-phases show a separation lower than 50%. These results encourage the design of automatic classifiers for Onset detection and for separating among A-phases type A1 and A3. On the other hand, the A-phase Offsets present a smooth transition towards the basal sleep stage oscillations, and A2-phases are very similar to A1-phases, suggesting that a high uncertainty may exist during CAP annotation. PMID:25570436