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Sample records for liquid 3d transition

  1. Magnetic Properties of Liquid 3d Transition Metal-Ge Alloys

    NASA Astrophysics Data System (ADS)

    Ohno, Satoru; Shimakura, Hironori; Tahara, Shuta; Okada, Tatsuya

    2015-07-01

    The magnetic susceptibilities (χ) of liquid Ti-Ge and V-Ge alloys show a weak and positive temperature dependence in restricted regions of up to 30 at. % Ti and 40 at. % V, respectively. This suggests that the Ti and V ions in these liquid alloys are in a nonmagnetic state. The χ values of liquid TM-Ge (TM = Fe, Co, Ni) alloys on the Ge-rich side exhibit a similar temperature dependence. The data in the nonmagnetic state were analyzed using the Anderson model. In the nonmagnetic state, we found smooth variations in which both the effective intra-atomic d-d interaction and the density of 3d states at the Fermi level EF decrease with increasing EF of liquid TM0.1M0.9 (M = Sn → Ge → Si) alloys. Liquid Cr1-cGec with c ≥ 0.7 and Mn1-cGec with c ≥ 0.3 obeyed the Curie-Weiss law with regard to the temperature dependence of their χ. The composition dependences of the χ of liquid Cr-Ge and Mn-Ge alloys show maxima at compositions of 50 at. % Cr and 70 at. % Mn, respectively. The magnetic susceptibilities of liquid Fe1-cGec with c ≤ 0.7, liquid Co1-cGec with c ≤ 0.3, and liquid Ni1-cGec with c ≤ 0.1 also exhibited a Curie-Weiss-type behavior. We compared the effective number of Bohr magnetons of liquid TM-Ge alloys with those of liquid TM-Sn and TM-Si alloys at the same TM composition and also investigated the relationship between χ3d and EF for liquid TM0.5M0.5 alloys.

  2. Dimensional phase transition from an array of 1D Luttinger liquids to a 3D Bose-Einstein condensate.

    PubMed

    Vogler, Andreas; Labouvie, Ralf; Barontini, Giovanni; Eggert, Sebastian; Guarrera, Vera; Ott, Herwig

    2014-11-21

    We study the thermodynamic properties of a 2D array of coupled one-dimensional Bose gases. The system is realized with ultracold bosonic atoms loaded in the potential tubes of a two-dimensional optical lattice. For negligible coupling strength, each tube is an independent weakly interacting 1D Bose gas featuring Tomonaga Luttinger liquid behavior. By decreasing the lattice depth, we increase the coupling strength between the 1D gases and allow for the phase transition into a 3D condensate. We extract the phase diagram for such a system and compare our results with theoretical predictions. Because of the high effective mass across the periodic potential and the increased 1D interaction strength, the phase transition is shifted to large positive values of the chemical potential. Our results are prototypical to a variety of low-dimensional systems, where the coupling between the subsystems is realized in a higher spatial dimension such as coupled spin chains in magnetic insulators.

  3. 3D Kitaev spin liquids

    NASA Astrophysics Data System (ADS)

    Hermanns, Maria

    The Kitaev honeycomb model has become one of the archetypal spin models exhibiting topological phases of matter, where the magnetic moments fractionalize into Majorana fermions interacting with a Z2 gauge field. In this talk, we discuss generalizations of this model to three-dimensional lattice structures. Our main focus is the metallic state that the emergent Majorana fermions form. In particular, we discuss the relation of the nature of this Majorana metal to the details of the underlying lattice structure. Besides (almost) conventional metals with a Majorana Fermi surface, one also finds various realizations of Dirac semi-metals, where the gapless modes form Fermi lines or even Weyl nodes. We introduce a general classification of these gapless quantum spin liquids using projective symmetry analysis. Furthermore, we briefly outline why these Majorana metals in 3D Kitaev systems provide an even richer variety of Dirac and Weyl phases than possible for electronic matter and comment on possible experimental signatures. Work done in collaboration with Kevin O'Brien and Simon Trebst.

  4. LASTRAC.3d: Transition Prediction in 3D Boundary Layers

    NASA Technical Reports Server (NTRS)

    Chang, Chau-Lyan

    2004-01-01

    Langley Stability and Transition Analysis Code (LASTRAC) is a general-purpose, physics-based transition prediction code released by NASA for laminar flow control studies and transition research. This paper describes the LASTRAC extension to general three-dimensional (3D) boundary layers such as finite swept wings, cones, or bodies at an angle of attack. The stability problem is formulated by using a body-fitted nonorthogonal curvilinear coordinate system constructed on the body surface. The nonorthogonal coordinate system offers a variety of marching paths and spanwise waveforms. In the extreme case of an infinite swept wing boundary layer, marching with a nonorthogonal coordinate produces identical solutions to those obtained with an orthogonal coordinate system using the earlier release of LASTRAC. Several methods to formulate the 3D parabolized stability equations (PSE) are discussed. A surface-marching procedure akin to that for 3D boundary layer equations may be used to solve the 3D parabolized disturbance equations. On the other hand, the local line-marching PSE method, formulated as an easy extension from its 2D counterpart and capable of handling the spanwise mean flow and disturbance variation, offers an alternative. A linear stability theory or parabolized stability equations based N-factor analysis carried out along the streamline direction with a fixed wavelength and downstream-varying spanwise direction constitutes an efficient engineering approach to study instability wave evolution in a 3D boundary layer. The surface-marching PSE method enables a consistent treatment of the disturbance evolution along both streamwise and spanwise directions but requires more stringent initial conditions. Both PSE methods and the traditional LST approach are implemented in the LASTRAC.3d code. Several test cases for tapered or finite swept wings and cones at an angle of attack are discussed.

  5. Thermomechanical properties of 3d transition metals

    SciTech Connect

    Karaoglu, B.; Rahman, S.M.M. . Dept. of Physics)

    1994-05-15

    The authors have investigated the density variation of the Einstein temperatures and elastic constants of the 3d transition metals. In this respect they have employed the transition metal (TM) pair potentials involving the sp contribution with an appropriate exchange and correlation function, the d-band broadening contribution and the d-band hybridization term. These calculations are aimed at testing the TM pair potentials in generating the quasilocal and local thermomechanical properties.

  6. 3D printing of a multifunctional nanocomposite helical liquid sensor

    NASA Astrophysics Data System (ADS)

    Guo, Shuang-Zhuang; Yang, Xuelu; Heuzey, Marie-Claude; Therriault, Daniel

    2015-04-01

    A multifunctional 3D liquid sensor made of a PLA/MWCNT nanocomposite and shaped as a freeform helical structure was fabricated by solvent-cast 3D printing. The 3D liquid sensor featured a relatively high electrical conductivity, the functionality of liquid trapping due to its helical configuration, and an excellent sensitivity and selectivity even for a short immersion into solvents.A multifunctional 3D liquid sensor made of a PLA/MWCNT nanocomposite and shaped as a freeform helical structure was fabricated by solvent-cast 3D printing. The 3D liquid sensor featured a relatively high electrical conductivity, the functionality of liquid trapping due to its helical configuration, and an excellent sensitivity and selectivity even for a short immersion into solvents. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00278h

  7. 3D printing of free standing liquid metal microstructures.

    PubMed

    Ladd, Collin; So, Ju-Hee; Muth, John; Dickey, Michael D

    2013-09-25

    This paper describes a method to direct-write 3D liquid metal microcomponents at room temperature. The thin oxide layer on the surface of the metal allows the formation of mechanically stable structures strong enough to stand against gravity and the large surface tension of the liquid. The method is capable of printing wires, arrays of spheres, arches, and interconnects. PMID:23824583

  8. 3D printing of liquid metals as fugitive inks for fabrication of 3D microfluidic channels.

    PubMed

    Parekh, Dishit P; Ladd, Collin; Panich, Lazar; Moussa, Khalil; Dickey, Michael D

    2016-05-21

    This paper demonstrates a simple method to fabricate 3D microchannels and microvasculature at room temperature by direct-writing liquid metal as a sacrificial template. The formation of a surface oxide skin on the low-viscosity liquid metal stabilizes the shape of the printed metal for planar and out-of-plane structures. The printed structures can be embedded in a variety of soft (e.g. elastomeric) and rigid (e.g. thermoset) polymers. Both acid and electrochemical reduction are capable of removing the oxide skin that forms on the metal, which destabilizes the ink so that it withdraws from the encapsulating material due to capillary forces, resulting in nearly full recovery of the fugitive ink at room temperature. Whereas conventional fabrication procedures typically confine microchannels to 2D planes, the geometry of the printed microchannels can be varied from a simple 2D network to complex 3D architectures without using lithography. The method produces robust monolithic structures without the need for any bonding or assembling techniques that often limit the materials of construction of conventional microchannels. Removing select portions of the metal leaves behind 3D metal features that can be used as antennas, interconnects, or electrodes for interfacing with lab-on-a-chip devices. This paper describes the capabilities and limitations of this simple process. PMID:27025537

  9. 3D printing of liquid metals as fugitive inks for fabrication of 3D microfluidic channels.

    PubMed

    Parekh, Dishit P; Ladd, Collin; Panich, Lazar; Moussa, Khalil; Dickey, Michael D

    2016-05-21

    This paper demonstrates a simple method to fabricate 3D microchannels and microvasculature at room temperature by direct-writing liquid metal as a sacrificial template. The formation of a surface oxide skin on the low-viscosity liquid metal stabilizes the shape of the printed metal for planar and out-of-plane structures. The printed structures can be embedded in a variety of soft (e.g. elastomeric) and rigid (e.g. thermoset) polymers. Both acid and electrochemical reduction are capable of removing the oxide skin that forms on the metal, which destabilizes the ink so that it withdraws from the encapsulating material due to capillary forces, resulting in nearly full recovery of the fugitive ink at room temperature. Whereas conventional fabrication procedures typically confine microchannels to 2D planes, the geometry of the printed microchannels can be varied from a simple 2D network to complex 3D architectures without using lithography. The method produces robust monolithic structures without the need for any bonding or assembling techniques that often limit the materials of construction of conventional microchannels. Removing select portions of the metal leaves behind 3D metal features that can be used as antennas, interconnects, or electrodes for interfacing with lab-on-a-chip devices. This paper describes the capabilities and limitations of this simple process.

  10. Magnetism In 3d Transition Metals at High Pressures

    SciTech Connect

    Iota, V

    2006-02-09

    This research project examined the changes in electronic and magnetic properties of transition metals and oxides under applied pressures, focusing on complex relationship between magnetism and phase stability in these correlated electron systems. As part of this LDRD project, we developed new measurement techniques and adapted synchrotron-based electronic and magnetic measurements for use in the diamond anvil cell. We have performed state-of-the-art X-ray spectroscopy experiments at the dedicated high-pressure beamline HP-CAT (Sector 16 Advanced Photon Source, Argonne National Laboratory), maintained in collaboration with of University of Nevada, Las Vegas and Geophysical Laboratory of The Carnegie Institution of Washington. Using these advanced measurements, we determined the evolution of the magnetic order in the ferromagnetic 3d transition metals (Fe, Co and Ni) under pressure, and found that at high densities, 3d band broadening results in diminished long range magnetic coupling. Our experiments have allowed us to paint a unified picture of the effects of pressure on the evolution of magnetic spin in 3d electron systems. The technical and scientific advances made during this LDRD project have been reported at a number of scientific meetings and conferences, and have been submitted for publication in technical journals. Both the technical advances and the physical understanding of correlated systems derived from this LDRD are being applied to research on the 4f and 5f electron systems under pressure.

  11. Correlated electron pseudopotentials for 3d-transition metals

    SciTech Connect

    Trail, J. R. Needs, R. J.

    2015-02-14

    A recently published correlated electron pseudopotentials (CEPPs) method has been adapted for application to the 3d-transition metals, and to include relativistic effects. New CEPPs are reported for the atoms Sc − Fe, constructed from atomic quantum chemical calculations that include an accurate description of correlated electrons. Dissociation energies, molecular geometries, and zero-point vibrational energies of small molecules are compared with all electron results, with all quantities evaluated using coupled cluster singles doubles and triples calculations. The CEPPs give better results in the correlated-electron calculations than Hartree-Fock-based pseudopotentials available in the literature.

  12. Additive manufacturing. Continuous liquid interface production of 3D objects.

    PubMed

    Tumbleston, John R; Shirvanyants, David; Ermoshkin, Nikita; Janusziewicz, Rima; Johnson, Ashley R; Kelly, David; Chen, Kai; Pinschmidt, Robert; Rolland, Jason P; Ermoshkin, Alexander; Samulski, Edward T; DeSimone, Joseph M

    2015-03-20

    Additive manufacturing processes such as 3D printing use time-consuming, stepwise layer-by-layer approaches to object fabrication. We demonstrate the continuous generation of monolithic polymeric parts up to tens of centimeters in size with feature resolution below 100 micrometers. Continuous liquid interface production is achieved with an oxygen-permeable window below the ultraviolet image projection plane, which creates a "dead zone" (persistent liquid interface) where photopolymerization is inhibited between the window and the polymerizing part. We delineate critical control parameters and show that complex solid parts can be drawn out of the resin at rates of hundreds of millimeters per hour. These print speeds allow parts to be produced in minutes instead of hours.

  13. Voltage controlled magnetism in 3d transitional metals

    NASA Astrophysics Data System (ADS)

    Wang, Weigang

    2015-03-01

    Despite having attracted much attention in multiferroic materials and diluted magnetic semiconductors, the impact of an electric field on the magnetic properties remains largely unknown in 3d transitional ferromagnets (FMs) until recent years. A great deal of effort has been focused on the voltage-controlled magnetic anisotropy (VCMA) effect where the modulation of anisotropy field is understood by the change of electron density among different d orbitals of FMs in the presence of an electric field. Here we demonstrate another approach to alter the magnetism by electrically controlling the oxidation state of the 3d FM at the FM/oxide interface. The thin FM film sandwiched between a heavy metal layer and a gate oxide can be reversibly changed from an optimally-oxidized state with a strong perpendicular magnetic anisotropy to a metallic state with an in-plane magnetic anisotropy, or to a fully-oxidized state with nearly zero magnetization, depending on the polarity and time duration of the applied electric fields. This is a voltage controlled magnetism (VCM) effect, where both the saturation magnetization and anisotropy field of the 3d FM layer can be simultaneously controlled by voltage in a non-volatile fashion. We will also discuss the impact of this VCM effect on magnetic tunnel junctions and spin Hall switching experiments. This work, in collaboration with C. Bi, Y.H. Liu, T. Newhouse-Illige, M. Xu, M. Rosales, J.W. Freeland, O. Mryasov, S. Zhang, and S.G.E. te Velthuis, was supported in part by NSF (ECCS-1310338) and by C-SPIN, one of six centers of STARnet, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA.

  14. High pressure behavior of 3d transition metal carbonates

    NASA Astrophysics Data System (ADS)

    Farfan, G. A.; Wang, S.; Boulard, E.; Mao, W. L.

    2012-12-01

    Understanding the behavior of carbon-rich phases in Earth's lower mantle is critical for modeling the global carbon cycle since the lower mantle may be the major repository for carbon in our planet. We were interested in the behavior of carbonates containing 3d transition metals, which can exhibit unusual properties at extreme conditions. Thus, we studied siderite (FeCO3) and rhodochrosite (MnCO3) at high pressure using a diamond anvil cell coupled with Raman spectroscopy, X-ray diffraction (XRD) and X-ray emission spectroscopy. In siderite we observed a high to low spin transition and associated volume collapse at approximately 46 GPa which is consistent with previous reports. Our Raman data show that the C-O bonds soften when the Fe2+ volume collapses (Farfan et al, 2012). In contrast, our XES results indicate that the Mn2+ in rhodochrosite does not undergo a spin transition like siderite up to 50 GPa. We observed a new Raman peak emerging above 48 GPa, which is a similar pressure at which a new structure was found in a previous XRD study.

  15. Tensorial analysis of Eshelby stresses in 3D supercooled liquids.

    PubMed

    Lemaître, Anaël

    2015-10-28

    It was recently proposed that the local rearrangements governing relaxation in supercooled liquids impress on the liquid medium long-ranged (Eshelby) stress fluctuations that accumulate over time. From this viewpoint, events must be characterized by elastic dipoles, which are second order tensors, and Eshelby fields are expected to show up in stress and stress increment correlations, which are fourth order tensor fields. We construct here an analytical framework that permits analyzing such tensorial correlations in isotropic media in view of accessing Eshelby fields. Two spherical bases are introduced, which correspond to Cartesian and spherical coordinates for tensors. We show how they can be used to decompose stress correlations and thus test such properties as isotropy and power-law scalings. Eshelby fields and the predicted stress correlations in an infinite medium are shown to belong to an algebra that can conveniently be described using the spherical tensor bases. Using this formalism, we demonstrate that the inherent stress field of 3D supercooled liquids is power law correlated and carries the signature of Eshelby fields, thus supporting the idea that relaxation events give rise to Eshelby stresses that accumulate over time. PMID:26520535

  16. An Efficient 3D Stochastic Model for Predicting the Columnar-to-Equiaxed Transition in Alloy 718

    NASA Astrophysics Data System (ADS)

    Nastac, L.

    2015-06-01

    A three-dimensional (3D) stochastic model for simulating the evolution of dendritic crystals during the solidification of alloys was developed. The model includes time-dependent computations for temperature distribution, solute redistribution in the liquid and solid phases, curvature, and growth anisotropy. The 3D model can run on PCs with reasonable amount of RAM and CPU time. 3D stochastic mesoscopic simulations at the dendrite tip length scale were performed to simulate the evolution of the columnar-to-equiaxed transition in alloy 718. Comparisons between simulated microstructures and segregation patterns obtained with 2D and 3D stochastic models are also presented.

  17. 3D printed metal columns for capillary liquid chromatography.

    PubMed

    Sandron, S; Heery, B; Gupta, V; Collins, D A; Nesterenko, E P; Nesterenko, P N; Talebi, M; Beirne, S; Thompson, F; Wallace, G G; Brabazon, D; Regan, F; Paull, B

    2014-12-21

    Coiled planar capillary chromatography columns (0.9 mm I.D. × 60 cm L) were 3D printed in stainless steel (316L), and titanium (Ti-6Al-4V) alloys (external dimensions of ~5 × 30 × 58 mm), and either slurry packed with various sized reversed-phase octadecylsilica particles, or filled with an in situ prepared methacrylate based monolith. Coiled printed columns were coupled directly with 30 × 30 mm Peltier thermoelectric direct contact heater/cooler modules. Preliminary results show the potential of using such 3D printed columns in future portable chromatographic devices. PMID:25285334

  18. Models for a liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Buldyrev, S. V.; Franzese, G.; Giovambattista, N.; Malescio, G.; Sadr-Lahijany, M. R.; Scala, A.; Skibinsky, A.; Stanley, H. E.

    2002-02-01

    We use molecular dynamics simulations to study two- and three-dimensional models with the isotropic double-step potential which in addition to the hard core has a repulsive soft core of larger radius. Our results indicate that the presence of two characteristic repulsive distances (hard core and soft core) is sufficient to explain liquid anomalies and a liquid-liquid phase transition, but these two phenomena may occur independently. Thus liquid-liquid transitions may exist in systems like liquid metals, regardless of the presence of the density anomaly. For 2D, we propose a model with a specific set of hard core and soft core parameters, that qualitatively reproduces the phase diagram and anomalies of liquid water. We identify two solid phases: a square crystal (high density phase), and a triangular crystal (low density phase) and discuss the relation between the anomalies of liquid and the polymorphism of the solid. Similarly to real water, our 2D system may have the second critical point in the metastable liquid phase beyond the freezing line. In 3D, we find several sets of parameters for which two fluid-fluid phase transition lines exist: the first line between gas and liquid and the second line between high-density liquid (HDL) and low-density liquid (LDL). In all cases, the LDL phase shows no density anomaly in 3D. We relate the absence of the density anomaly with the positive slope of the LDL-HDL phase transition line.

  19. On the shear viscosity of 3D Yukawa liquids

    SciTech Connect

    Donko, Z.; Hartmann, P.

    2008-09-07

    We report calculations of the shear viscosity of three-dimensional strongly-coupled Yukawa liquids, based on two different non-equilibrium molecular dynamics methods. The present simulations intend to improve the accuracy of shear viscosity data, compared to those obtained in earlier studies.

  20. Effects of microalloying with 3d transition metals on glass formation in AlYFe alloys

    SciTech Connect

    Bondi, K.S.; Gangopadhyay, A.K.; Marine, Z.; Kim, T.H.; Mukhopadhyay, Anindita; Goldman, A.I.; Buhro, William E.; Kelton, K.F.

    2008-05-20

    The effects of microalloying on glass formation and stability were systematically investigated by substituting 0.5 at.% of all 3d transition metals for Al in Al{sub 88}Y{sub 7}Fe{sub 5} alloys. X-ray diffraction and isothermal differential scanning calorimetry studies indicate that samples containing microadditions of Ti, V, Cr, Mn, Fe and Co were amorphous, while those alloyed with Ni and Cu were not. The onset temperatures for crystallization (devitrification) of the amorphous alloys were increased with microalloying and some showed a supercooled liquid region ({Delta}T{sub x} = T{sub x} - T{sub g}) of up to 40 C. In addition, microalloying changes the glass structure and the devitrification sequence, as determined by differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA) and high energy X-ray diffraction. The results presented here suggest that the order induced in the alloy by the transition metal microaddition decreases the atomic mobility in the glass and raises the barrier for the nucleation of {alpha}-Al, the primary devitrifying phase in most cases. New intermetallic phases also appear with microalloying and vary for different transition metal additions.

  1. Magnetic and Lattice Interaction in 3d Transition Metal Compounds

    NASA Astrophysics Data System (ADS)

    Jassim, Ishmaeel Khalil

    Available from UMI in association with The British Library. The importance and nature of magnetic and lattice degrees of freedom and their interaction in transition metal magnets has been investigated. As an example of localised behaviour, Heusler alloys in which the magnetic moment was confined to Mn atoms were chosen, e.g. Pd_2MnIn. The manganese atoms are separated by more than 4.6A. By systematically changing Pd for either Ag or Au the electron concentration can be varied in a continuous manner. Dependent upon the electron concentration several different antiferromagnetic structures consistent with an fcc lattice are observed at low temperatures. The type of magnetic order gives rise to distinct lattice distortion characteristic of the magnetic symmetry. A wide range of bulk measurements was carried out to characterise the materials, e.g. X-ray, neutron diffraction, magnetic susceptibility and specific heat (using both pulse and continuous heating techniques). The magnetic structures were, in some instances, frustrated as may be expected for antiferromagnetism on an fcc lattice. As an example of itinerant behaviour the Fe-Ni system was chosen. rm Fe_{1 -x}Ni_ x alloy systems have long been of considerable interest since rm Fe_ {65}Ni_{35} shows an anomalously small thermal expansion below T_ {rm c}. Numerous experiments have been carried out to understand this phenomenon, the Invar effect. The effect is most pronounced close to the composition defining the phase boundary between the bcc and fcc structures. The interplay between the magnetic and lattice degrees of freedom were investigated on an atomic scale using inelastic polarised neutron scattering. The polarisation dependence of the magneto vibrational scattering of the one phonon cross-sections has been investigated as a continuous function of q throughout the Brillouin zone in the Invar alloy rm Fe_{65 }Ni_{35}, and in two other FeNi samples out side the Invar region. The magneto vibrational scattering is

  2. XUV spectra of 2nd transition row elements: identification of 3d-4p and 3d-4f transition arrays

    NASA Astrophysics Data System (ADS)

    Lokasani, Ragava; Long, Elaine; Maguire, Oisin; Sheridan, Paul; Hayden, Patrick; O'Reilly, Fergal; Dunne, Padraig; Sokell, Emma; Endo, Akira; Limpouch, Jiri; O'Sullivan, Gerry

    2015-12-01

    The use of laser produced plasmas (LPPs) in extreme ultraviolet/soft x-ray lithography and metrology at 13.5 nm has been widely reported and recent research efforts have focused on developing next generation sources for lithography, surface morphology, patterning and microscopy at shorter wavelengths. In this paper, the spectra emitted from LPPs of the 2nd transition row elements from yttrium (Z = 39) to palladium (Z = 46), with the exception of zirconium (Z = 40) and technetium (Z = 43), produced by two Nd:YAG lasers which delivered up to 600 mJ in 7 ns and 230 mJ in 170 ps, respectively, are reported. Intense emission was observed in the 2-8 nm spectral region resulting from unresolved transition arrays (UTAs) due to 3d-4p, 3d-4f and 3p-3d transitions. These transitions in a number of ion stages of yttrium, niobium, ruthenium and rhodium were identified by comparison with results from Cowan code calculations and previous studies. The theoretical data were parameterized using the UTA formalism and the mean wavelength and widths were calculated and compared with experimental results.

  3. 2D to 3D transition of polymeric carbon nitride nanosheets

    SciTech Connect

    Chamorro-Posada, Pedro; Vázquez-Cabo, José; Martín-Ramos, Pablo; Martín-Gil, Jesús; Navas-Gracia, Luis M.; Dante, Roberto C.

    2014-11-15

    The transition from a prevalent turbostratic arrangement with low planar interactions (2D) to an array of polymeric carbon nitride nanosheets with stronger interplanar interactions (3D), occurring for samples treated above 650 °C, was detected by terahertz-time domain spectroscopy (THz-TDS). The simulated 3D material made of stacks of shifted quasi planar sheets composed of zigzagged polymer ribbons, delivered a XRD simulated pattern in relatively good agreement with the experimental one. The 2D to 3D transition was also supported by the simulation of THz-TDS spectra obtained from quantum chemistry calculations, in which the same broad bands around 2 THz and 1.5 THz were found for 2D and 3D arrays, respectively. This transition was also in accordance with the tightening of the interplanar distance probably due to an interplanar π bond contribution, as evidenced also by a broad absorption around 2.6 eV in the UV–vis spectrum, which appeared in the sample treated at 650 °C, and increased in the sample treated at 700 °C. The band gap was calculated for 1D and 2D cases. The value of 3.374 eV for the 2D case is, within the model accuracy and precision, in a relative good agreement with the value of 3.055 eV obtained from the experimental results. - Graphical abstract: 2D lattice mode vibrations and structural changes correlated with the so called “2D to 3D transition”. - Highlights: • A 2D to 3D transition has been detected for polymeric carbon nitride. • THz-TDS allowed us to discover and detect the 2D to 3D transition of polymeric carbon nitride. • We propose a structure for polymeric carbon nitride confirming it with THz-TDS.

  4. Prediction of spin-dependent electronic structure in 3d-transition-metal doped antimonene

    NASA Astrophysics Data System (ADS)

    Yang, L. F.; Song, Y.; Mi, W. B.; Wang, X. C.

    2016-07-01

    We investigate the geometric structure and electronic and magnetic properties of 3d-transition-metal atom doped antimonene using spin-polarized first-principles calculations. Strong orbital hybridization exhibits between 3d-transition-metal and Sb atoms, where covalent bonds form in antimonene. A spin-polarized semiconducting state appears in Cr-doped antimonene, while half-metallic states appear by doping Ti, V, and Mn. These findings indicate that once combined with doping states, the bands of antimonene systems offer a variety of features. Specific dopants lead to half-metallic characters with high spin polarization that has potential application in spintronics.

  5. Height-dependent transition from 3-D to 2-D turbulence in the hurricane boundary layer

    NASA Astrophysics Data System (ADS)

    Byrne, David; Zhang, Jun A.

    2013-04-01

    Here we show, from in situ aircraft measurements in the hurricane boundary layer, a height-dependent transition of the flow from 3-D to 2-D turbulence. This marks a fundamental change in the energy dynamics of the hurricane boundary layer due to the fact that in 3-D, energy flows downscale from larger to smaller scales, whereas in 2-D, it flows upscale, from smaller to larger scales. These results represent the first measurement of the 2-D upscale energy flux in the atmosphere and also the first to characterize the transition from 3-D to 2-D. It is shown that the large-scale parent vortex may gain energy directly from small scales in tropical cyclones.

  6. 3-D printing of liquid metals for stretchable and flexible conductors

    NASA Astrophysics Data System (ADS)

    Trlica, Chris; Parekh, Dishit Paresh; Panich, Lazar; Ladd, Collin; Dickey, Michael D.

    2014-06-01

    3-D printing is an emerging technology that has been used primarily on small scales for rapid prototyping, but which could also herald a wider movement towards decentralized, highly customizable manufacturing. Polymers are the most common materials to be 3-D printed today, but there is great demand for a way to easily print metals. Existing techniques for 3-D printing metals tend to be expensive and energy-intensive, and usually require high temperatures or pressures, making them incompatible with polymers, organics, soft materials, and biological materials. Here, we describe room temperature liquid metals as complements to polymers for 3-D printing applications. These metals enable the fabrication of soft, flexible, and stretchable devices. We survey potential room temperature liquid metal candidates and describe the benefits of gallium and its alloys for these purposes. We demonstrate the direct printing of a liquid gallium alloy in both 2-D and 3-D and highlight the structures and shapes that can be fabricated using these processes.

  7. Laboratory rotational ground state transitions of NH3D+ and CF+

    NASA Astrophysics Data System (ADS)

    Stoffels, A.; Kluge, L.; Schlemmer, S.; Brünken, S.

    2016-09-01

    Aims: This paper reports accurate laboratory frequencies of the rotational ground state transitions of two astronomically relevant molecular ions, NH3D+ and CF+. Methods: Spectra in the millimetre-wave band were recorded by the method of rotational state-selective attachment of He atoms to the molecular ions stored and cooled in a cryogenic ion trap held at 4 K. The lowest rotational transition in the A state (ortho state) of NH3D+ (JK = 10-00), and the two hyperfine components of the ground state transition of CF+ (J = 1-0) were measured with a relative precision better than 10-7. Results: For both target ions, the experimental transition frequencies agree with recent observations of the same lines in different astronomical environments. In the case of NH3D+ the high-accuracy laboratory measurements lend support to its tentative identification in the interstellar medium. For CF+ the experimentally determined hyperfine splitting confirms previous quantum-chemical calculations and the intrinsic spectroscopic nature of a double-peaked line profile observed in the J = 1-0 transition towards the Horsehead photon-dominated region (PDR).

  8. On a particular solution to the 3D Navier-Stokes equations for liquids with cavitation

    NASA Astrophysics Data System (ADS)

    Rabinowitch, Alexander S.

    2016-08-01

    The 3D Navier-Stokes equations for incompressible viscous liquids are examined. In the axially symmetric case, they are represented in the form of three nonlinear partial differential equations. These equations are studied and their particular solution is found. In it, the velocity components are sinusoidal in the direction of their axis of symmetry. As to the pressure, it can reach a sufficiently small value at which the phenomenon of cavitation takes place in a liquid. The found solution describes some flows of viscous liquids outside vapor-filled regions in them.

  9. 3D motion of DNA-Au nanoconjugates in graphene liquid cell electron microscopy.

    PubMed

    Chen, Qian; Smith, Jessica M; Park, Jungwon; Kim, Kwanpyo; Ho, Davy; Rasool, Haider I; Zettl, Alex; Alivisatos, A Paul

    2013-09-11

    Liquid-phase transmission electron microscopy (TEM) can probe and visualize dynamic events with structural or functional details at the nanoscale in a liquid medium. Earlier efforts have focused on the growth and transformation kinetics of hard material systems, relying on their stability under electron beam. Our recently developed graphene liquid cell technique pushed the spatial resolution of such imaging to the atomic scale but still focused on growth trajectories of metallic nanocrystals. Here, we adopt this technique to imaging three-dimensional (3D) dynamics of soft materials instead, double strand (dsDNA) connecting Au nanocrystals as one example, at nanometer resolution. We demonstrate first that a graphene liquid cell can seal an aqueous sample solution of a lower vapor pressure than previously investigated well against the high vacuum in TEM. Then, from quantitative analysis of real time nanocrystal trajectories, we show that the status and configuration of dsDNA dictate the motions of linked nanocrystals throughout the imaging time of minutes. This sustained connecting ability of dsDNA enables this unprecedented continuous imaging of its dynamics via TEM. Furthermore, the inert graphene surface minimizes sample-substrate interaction and allows the whole nanostructure to rotate freely in the liquid environment; we thus develop and implement the reconstruction of 3D configuration and motions of the nanostructure from the series of 2D projected TEM images captured while it rotates. In addition to further proving the nanoconjugate structural stability, this reconstruction demonstrates 3D dynamic imaging by TEM beyond its conventional use in seeing a flattened and dry sample. Altogether, we foresee the new and exciting use of graphene liquid cell TEM in imaging 3D biomolecular transformations or interaction dynamics at nanometer resolution. PMID:23944844

  10. Spectroscopic investigation of the 3d 2D → nf 2F transitions in lithium

    NASA Astrophysics Data System (ADS)

    Shahzada, S.; Shah, M.; Haq, S. U.; Nawaz, M.; Ahmed, M.; Nadeem, Ali

    2016-05-01

    We report term energies and effective quantum numbers of the odd parity 3d 2D → nf 2F series of lithium using multi-step and multi-photon laser excitation schemes. The experiments were performed using three dye lasers simultaneously pumped by the second harmonic (532 nm) of a Q-switched Nd:YAG laser in conjunction with an atomic beam apparatus and thermionic diode ion detector. The first ionization potential of lithium has been determined as 43,487.13 ± 0.02 cm- 1 from the much extended 3d 2D → nf 2F (17 ≤ n ≤ 70) series. In addition, the oscillator strengths of the 3d 2D → nf 2F (15 ≤ n ≤ 48) transitions have been determined, showing a decreasing trend with the increase in principal quantum number n.

  11. Liquid crystal materials and structures for image processing and 3D shape acquisition

    NASA Astrophysics Data System (ADS)

    Garbat, K.; Garbat, P.; Jaroszewicz, L.

    2012-03-01

    The image processing supported by liquid crystals device has been used in numerous imaging applications, including polarization imaging, digital holography and programmable imaging. Liquid crystals have been extensively studied and are massively used in display and optical processing technology. We present here the main relevant parameters of liquid crystal for image processing and 3D shape acquisition and we compare the main liquid crystal options which can be used with their respective advantages. We propose here to compare performance of several types of liquid crystal materials: nematic mixtures with high and medium optical and dielectrical anisotropies and relatively low rotational viscosities nematic materials which may operate in TN mode in mono and dual frequency addressing systems.

  12. Extended Moment Formation in Monolayer WS2 Doped with 3d Transition-Metals.

    PubMed

    Singh, Nirpendra; Schwingenschlögl, Udo

    2016-09-14

    First-principles calculations with onsite Coulomb interaction and spin-orbit coupling are used to investigate the electronic structure of monolayer WS2 doped substitutionally with 3d transition-metals. While neither W vacancies nor strain induce spin polarization, we demonstrate an unprecedented tendency to extended moment formation under doping. The extended magnetic moments are characterized by dopant-specific spin density patterns with rich structural features involving the nearest neighbor W and S atoms. PMID:27571717

  13. Melting points and chemical bonding properties of 3d transition metal elements

    NASA Astrophysics Data System (ADS)

    Takahara, Wataru

    2014-08-01

    The melting points of 3d transition metal elements show an unusual local minimal peak at manganese across Period 4 in the periodic table. The chemical bonding properties of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper are investigated by the DV-Xα cluster method. The melting points are found to correlate with the bond overlap populations. The chemical bonding nature therefore appears to be the primary factor governing the melting points.

  14. A theoretical study of the structure and stability of borohydride on 3d transition metals

    NASA Astrophysics Data System (ADS)

    Arevalo, Ryan Lacdao; Escaño, Mary Clare Sison; Gyenge, Elod; Kasai, Hideaki

    2012-12-01

    The adsorption of borohydride on 3d transition metals (Cr, Mn, Fe, Co, Ni and Cu) was studied using first principles calculations within spin-polarized density functional theory. Magnetic effect on the stability of borohydride is noted. Molecular adsorption is favorable on Co, Ni and Cu, which is characterized by the strong s-dzz hybridization of the adsorbate-substrate states. Dissociated adsorption structure yielding one or two H adatom fragments on the surface is observed for Cr, Mn and Fe.

  15. Deconfinement Phase Transition in a 3D Nonlocal U(1) Lattice Gauge Theory

    SciTech Connect

    Arakawa, Gaku; Ichinose, Ikuo; Matsui, Tetsuo; Sakakibara, Kazuhiko

    2005-06-03

    We introduce a 3D compact U(1) lattice gauge theory having nonlocal interactions in the temporal direction, and study its phase structure. The model is relevant for the compact QED{sub 3} and strongly correlated electron systems like the t-J model of cuprates. For a power-law decaying long-range interaction, which simulates the effect of gapless matter fields, a second-order phase transition takes place separating the confinement and deconfinement phases. For an exponentially decaying interaction simulating matter fields with gaps, the system exhibits no signals of a second-order transition.

  16. Electric-dipole allowed and intercombination transitions among the 3d{sup 5}, 3d{sup 4}4s and 3d{sup 4}4p levels of Fe IV

    SciTech Connect

    Deb, Narayan C.; Hibbert, Alan

    2010-07-15

    Oscillator strengths and transition rates for the electric-dipole (E1) allowed and intercombination transitions among 3d{sup 5}, 3d{sup 4}4s and 3d{sup 4}4p levels of Fe IV are calculated using the CIV3 code of Hibbert and coworkers. Using the Hartree-Fock functions up to 3d orbitals we have also optimized 4s, 4p, 4d, 4f, 5s, 5p and 5d orbitals of which 4s and 4p are taken to be spectroscopic and the remaining orbitals represent corrections to the spectroscopic orbitals or the correlation effects. The J-dependent levels of 108 LS states are included in the calculation and the relativistic effects are accounted for via the Breit-Pauli operator. Configurations are chosen in two steps: (a) two promotions were allowed from the 3p, 3d, 4s and 4p subshells, using all the orbitals; and (b) selective promotions from the 3s subshell are included, but only to the 3s and 4s orbitals. The ab initio fine-structure levels are then fine tuned to reproduce observed energy levels as closely as possible, and the resulting wavefunctions are used to calculate oscillator strengths and transition rates for all possible E1 transitions. For many of these transitions, the present results show good agreement between the length and velocity forms while for some transitions, some large disagreements are found with other available results. The complete list of weighted oscillator strengths, transition rates, and line strengths for transitions among the fine structure levels of the three lowest configurations are presented in ascending order of wavelength.

  17. Optimization of liquid overlay technique to formulate heterogenic 3D co-cultures models.

    PubMed

    Costa, Elisabete C; Gaspar, Vítor M; Coutinho, Paula; Correia, Ilídio J

    2014-08-01

    Three-dimensional (3D) cell culture models of solid tumors are currently having a tremendous impact in the in vitro screening of candidate anti-tumoral therapies. These 3D models provide more reliable results than those provided by standard 2D in vitro cell cultures. However, 3D manufacturing techniques need to be further optimized in order to increase the robustness of these models and provide data that can be properly correlated with the in vivo situation. Therefore, in the present study the parameters used for producing multicellular tumor spheroids (MCTS) by liquid overlay technique (LOT) were optimized in order to produce heterogeneous cellular agglomerates comprised of cancer cells and stromal cells, during long periods. Spheroids were produced under highly controlled conditions, namely: (i) agarose coatings; (ii) horizontal stirring, and (iii) a known initial cell number. The simultaneous optimization of these parameters promoted the assembly of 3D characteristic cellular organization similar to that found in the in vivo solid tumors. Such improvements in the LOT technique promoted the assembly of highly reproducible, individual 3D spheroids, with a low cost of production and that can be used for future in vitro drug screening assays.

  18. Transitions of the 3D medial axis under a one-parameter family of deformations.

    PubMed

    Giblin, Peter J; Kimia, Benjamin B; Pollitt, Anthony J

    2009-05-01

    The instabilities of the medial axis of a shape under deformations have long been recognized as a major obstacle to its use in recognition and other applications. These instabilities, or transitions, occur when the structure of the medial axis graph changes abruptly under deformations of shape. The recent classification of these transitions in 2D for the medial axis and for the shock graph was a key factor in the development of an object recognition system where the classified instabilities were utilized to represent deformation paths. The classification of generic transitions of the 3D medial axis could likewise potentially lead to a similar representation in 3D. In this paper, these transitions are classified by examining the order of contact of spheres with the surface, leading to an enumeration of possible transitions which are then examined on a case-by-case basis. Some cases are ruled out as never occurring in any family of deformations, while others are shown to be nongeneric in a one-parameter family of deformations. Finally, the remaining cases are shown to be viable by developing a specific example for each. Our work is inspired by that of Bogaevsky, who obtained the transitions as part of an investigation of viscosity solutions of Hamilton-Jacobi equations. Our contribution is to give a more down-to-earth approach, bringing this work to the attention of the computer vision community, and to provide explicit constructions for the various transitions using simple surfaces. We believe that the classification of these transitions is vital to the successful regularization of the medial axis in its use in real applications. PMID:19299863

  19. 3-D patterning of silicon by laser-initiated, liquid-assisted colloidal (LILAC) lithography.

    PubMed

    Ulmeanu, M; Grubb, M P; Jipa, F; Quignon, B; Ashfold, M N R

    2015-06-01

    We report a comprehensive study of laser-initiated, liquid-assisted colloidal (LILAC) lithography, and illustrate its utility in patterning silicon substrates. The method combines single shot laser irradiation (frequency doubled Ti-sapphire laser, 50fs pulse duration, 400nm wavelength) and medium-tuned optical near-field effects around arrays of silica colloidal particles to achieve 3-D surface patterning of silicon. A monolayer (or multilayers) of hexagonal close packed silica colloidal particles act as a mask and offer a route to liquid-tuned optical near field enhancement effects. The resulting patterns are shown to depend on the difference in refractive index of the colloidal particles (ncolloid) and the liquid (nliquid) in which they are immersed. Two different topographies are demonstrated experimentally: (a) arrays of bumps, centred beneath the original colloidal particles, when using liquids with nliquidliquids with nliquid>ncolloid - and explained with the aid of complementary Mie scattering simulations. The LILAC lithography technique has potential for rapid, large area, organized 3-D patterning of silicon (and related) substrates.

  20. Prediction of positive and negative elastic dilatancy in 2D and 3D liquid foams

    NASA Astrophysics Data System (ADS)

    Rognon, P.; Molino, F.; Gay, C.

    2010-05-01

    Liquid foams have been observed to behave like immersed granular materials in at least one respect: deformation tends to raise their liquid contents, a phenomenon called dilatancy. While experimental observations evidenced the effect of a continuous deformation rate (dynamic dilatancy), we present a geometrical interpretation of both main contributions to elastic dilatancy (during elastic deformation) in foams squeezed between two solid plates (2D GG foams), which contain pseudo Plateau borders along the plates, and in 3D foams. The positive contribution is related to the increase in total Plateau border length while the negative contribution reflects the increase in total surface area of the foam. In 2D, we show that the negative dilatancy predicted by Weaire and Hutzler (Philos. Mag., 83 (2003) 2747) at very low liquid fractions is specific to ideal 2D foams (with no glass plates). In 3D, we predict that dilatancy should be positive at low liquid fractions (below 1%) and negative at moderate liquid fractions (above 4%).

  1. Signatures of topological phase transition in 3 d topological insulators from dynamical axion response

    NASA Astrophysics Data System (ADS)

    Makhfudz, Imam

    2016-04-01

    Axion electrodynamics, first proposed in the context of particle physics, manifests itself in condensed matter physics in the topological field theory description of 3 d topological insulators and gives rise to magnetoelectric effect, where applying magnetic (electric) field B (E ) induces polarization (magnetization) p (m ) . We use linear response theory to study the associated topological current using the Fu-Kane-Mele model of 3 d topological insulators in the presence of time-dependent uniform weak magnetic field. By computing the dynamical current susceptibility χij jpjp(ω ) , we discover from its static limit an `order parameter' of the topological phase transition between weak topological (or ordinary) insulator and strong topological insulator, found to be continuous. The χij jpjp(ω ) shows a sign-changing singularity at a critical frequency with suppressed strength in the topological insulating state. Our results can be verified in current noise experiment on 3 d TI candidate materials for the detection of such topological phase transition.

  2. Regional Gastrointestinal Transit Times in Patients With Carcinoid Diarrhea: Assessment With the Novel 3D-Transit System

    PubMed Central

    Gregersen, Tine; Haase, Anne-Mette; Schlageter, Vincent; Gronbaek, Henning; Krogh, Klaus

    2015-01-01

    Background/Aims The paucity of knowledge regarding gastrointestinal motility in patients with neuroendocrine tumors and carcinoid diarrhea restricts targeted treatment. 3D-Transit is a novel, minimally invasive, ambulatory method for description of gastrointestinal motility. The system has not yet been evaluated in any group of patients. We aimed to test the performance of 3D-Transit in patients with carcinoid diarrhea and to compare the patients’ regional gastrointestinal transit times (GITT) and colonic motility patterns with those of healthy subjects. Methods Fifteen healthy volunteers and seven patients with neuroendocrine tumor and at least 3 bowel movements per day were investigated with 3D-Transit and standard radiopaque markers. Results Total GITT assessed with 3D-Transit and radiopaque markers were well correlated (Spearman’s rho = 0.64, P = 0.002). Median total GITT was 12.5 (range: 8.5–47.2) hours in patients versus 25.1 (range: 13.1–142.3) hours in healthy (P = 0.007). There was no difference in gastric emptying (P = 0.778). Median small intestinal transit time was 3.8 (range: 1.4–5.5) hours in patients versus 4.4 (range: 1.8–7.2) hours in healthy subjects (P = 0.044). Median colorectal transit time was 5.2 (range: 2.9–40.1) hours in patients versus 18.1 (range: 5.0–134.0) hours in healthy subjects (P = 0.012). Median frequency of pansegmental colonic movements was 0.45 (range: 0.03–1.02) per hour in patients and 0.07 (range: 0–0.61) per hour in healthy subjects (P = 0.045). Conclusions Three-dimensional Transit allows assessment of regional GITT in patients with diarrhea. Patients with carcinoid diarrhea have faster than normal gastrointestinal transit due to faster small intestinal and colorectal transit times. The latter is caused by an increased frequency of pansegmental colonic movements. PMID:26130638

  3. Local electronic structure and magnetic properties of 3d transition metal doped GaAs

    NASA Astrophysics Data System (ADS)

    Lin, He; Duan, Haiming

    2008-05-01

    The local electronic structure and magnetic properties of GaAs doped with 3d transition metal (Sc, Ti, V, Cr, Mn, Fe, Co, Ni) were studied by using discrete variational method (DVM) based on density functional theory. The calculated result indicated that the magnetic moment of transition metal increases first and then decreases, and reaches the maximum value when Mn is doped into GaAs. In the case of Mn concentration of 1.4%, the magnetic moment of Mn is in good agreement with the experimental result. The coupling between impure atoms in the system with two impure atoms was found to have obvious variation. For different transition metal, the coupling between the impure atom and the nearest neighbor As also has different variation.

  4. Thermal Performance Mapping of Direct Liquid Cooled 3d Chip Stacks

    NASA Astrophysics Data System (ADS)

    Geisler, Karl J. L.; Bar-Cohen, Avram

    Chip stacks are a crucial building block in advanced 3D microsystem architectures and can accommodate shorter interconnect distances between devices, leading to reduced power dissipation and improved electrical performance. Although enhanced conduction can serve to transfer the dissipated heat to the top and sides of the package and/or down to the underlying PCB, effective thermal management of stacked chips remains a most difficult challenge. Immersion cooling techniques, which provide convective and/or ebullient heat transfer, along with buoyant fluid flow, in the narrow gaps separating adjacent chips, are a most promising alternative to conduction cooling of threedimensional chip stacks. Application of the available theories, correlations, and experimental data are shown to reveal that passive immersion cooling--relying on natural convection and/or pool boiling--could provide the requisite thermal management capability for 3D chip stacks anticipated for use in much of the portable equipment category. Alternatively, pumped flow of dielectric liquids through the microgaps in 3D stacks, providing single phase and/or flow boiling heat absorption, could meet many of the most extreme thermal management requirements for high-performance 3D microsystems.

  5. Mimicking Natural Laminar to Turbulent Flow Transition: A Systematic CFD Study Using PAB3D

    NASA Technical Reports Server (NTRS)

    Pao, S. Paul; Abdol-Hamid, Khaled S.

    2005-01-01

    For applied aerodynamic computations using a general purpose Navier-Stokes code, the common practice of treating laminar to turbulent flow transition over a non-slip surface is somewhat arbitrary by either treating the entire flow as turbulent or forcing the flow to undergo transition at given trip locations in the computational domain. In this study, the possibility of using the PAB3D code, standard k-epsilon turbulence model, and the Girimaji explicit algebraic stresses model to mimic natural laminar to turbulent flow transition was explored. The sensitivity of flow transition with respect to two limiters in the standard k-epsilon turbulence model was examined using a flat plate and a 6:1 aspect ratio prolate spheroid for our computations. For the flat plate, a systematic dependence of transition Reynolds number on background turbulence intensity was found. For the prolate spheroid, the transition patterns in the three-dimensional boundary layer at different flow conditions were sensitive to the free stream turbulence viscosity limit, the reference Reynolds number and the angle of attack, but not to background turbulence intensity below a certain threshold value. The computed results showed encouraging agreements with the experimental measurements at the corresponding geometry and flow conditions.

  6. Reactive Flow Modeling of Liquid Explosives via ALE3D/Cheetah Simulations

    SciTech Connect

    Kuo, I W; Bastea, S; Fried, L E

    2010-03-10

    We carried out reactive flow simulations of liquid explosives such as nitromethane using the hydrodynamic code ALE3D coupled with equations of state and reaction kinetics modeled by the thermochemical code Cheetah. The simulation set-up was chosen to mimic cylinder experiments. For pure unconfined nitromethane we find that the failure diameter and detonation velocity dependence on charge diameter are in agreement with available experimental results. Such simulations are likely to be useful for determining detonability and failure behavior for a wide range of experimental conditions and explosive compounds.

  7. Decay of the 3D viscous liquid-gas two-phase flow model with damping

    NASA Astrophysics Data System (ADS)

    Zhang, Yinghui

    2016-08-01

    We establish the optimal Lp - L2(1 ≤ p < 6/5) time decay rates of the solution to the Cauchy problem for the 3D viscous liquid-gas two-phase flow model with damping and analyse the influences of the damping on the qualitative behaviors of solution. It is observed that the fraction effect of the damping affects the dispersion of fluids and enhances the time decay rate of solution. Our method of proof consists of Hodge decomposition technique, Lp - L2 estimates for the linearized equations, and delicate energy estimates.

  8. Quantum anomalous Hall effect and tunable topological states in 3d transition metals doped silicene.

    PubMed

    Zhang, Xiao-Long; Liu, Lan-Feng; Liu, Wu-Ming

    2013-01-01

    Silicene is an intriguing 2D topological material which is closely analogous to graphene but with stronger spin orbit coupling effect and natural compatibility with current silicon-based electronics industry. Here we demonstrate that silicene decorated with certain 3d transition metals (Vanadium) can sustain a stable quantum anomalous Hall effect using both analytical model and first-principles Wannier interpolation. We also predict the quantum valley Hall effect and electrically tunable topological states could be realized in certain transition metal doped silicene where the energy band inversion occurs. Our findings provide new scheme for the realization of quantum anomalous Hall effect and platform for electrically controllable topological states which are highly desirable for future nanoelectronics and spintronics application. PMID:24105063

  9. Effect of dimensionality on vapor-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Singh, Sudhir Kumar

    2014-04-01

    Dimensionality play significant role on `phase transitions'. Fluids in macroscopic confinement (bulk or 3-Dimensional, 3D) do not show significant changes in their phase transition properties with extent of confinement, since the number of molecules away from the surrounding surfaces is astronomically higher than the number of molecules in close proximity of the confining surfaces. In microscopic confinement (quasi 3D to quasi-2D), however, the number of molecules away from the close proximity of the surface is not as high as is the case with macroscopic (3D) confinement. Hence, under the same thermodynamic conditions `phase transition' properties at microscopic confinement may not remain the same as the macroscopic or 3D values. Phase transitions at extremely small scale become very sensitive to the dimensions as well as the surface characteristics of the system. In this work our investigations reveal the effect of dimensionality on the phase transition from 3D to quasi-2D to 2D behavior. We have used grand canonical transition matrix Monte Carlo simulation to understand the vapor-liquid phase transitions from 3D to quasi-2D behavior. Such studies can be helpful in understanding and controlling the fluid film behaviour confined between solid surfaces of few molecular diameters, for example, in lubrication applications.

  10. Rapid and low-cost prototyping of medical devices using 3D printed molds for liquid injection molding.

    PubMed

    Chung, Philip; Heller, J Alex; Etemadi, Mozziyar; Ottoson, Paige E; Liu, Jonathan A; Rand, Larry; Roy, Shuvo

    2014-01-01

    Biologically inert elastomers such as silicone are favorable materials for medical device fabrication, but forming and curing these elastomers using traditional liquid injection molding processes can be an expensive process due to tooling and equipment costs. As a result, it has traditionally been impractical to use liquid injection molding for low-cost, rapid prototyping applications. We have devised a method for rapid and low-cost production of liquid elastomer injection molded devices that utilizes fused deposition modeling 3D printers for mold design and a modified desiccator as an injection system. Low costs and rapid turnaround time in this technique lower the barrier to iteratively designing and prototyping complex elastomer devices. Furthermore, CAD models developed in this process can be later adapted for metal mold tooling design, enabling an easy transition to a traditional injection molding process. We have used this technique to manufacture intravaginal probes involving complex geometries, as well as overmolding over metal parts, using tools commonly available within an academic research laboratory. However, this technique can be easily adapted to create liquid injection molded devices for many other applications. PMID:24998993

  11. Rapid and Low-cost Prototyping of Medical Devices Using 3D Printed Molds for Liquid Injection Molding

    PubMed Central

    Chung, Philip; Heller, J. Alex; Etemadi, Mozziyar; Ottoson, Paige E.; Liu, Jonathan A.; Rand, Larry; Roy, Shuvo

    2014-01-01

    Biologically inert elastomers such as silicone are favorable materials for medical device fabrication, but forming and curing these elastomers using traditional liquid injection molding processes can be an expensive process due to tooling and equipment costs. As a result, it has traditionally been impractical to use liquid injection molding for low-cost, rapid prototyping applications. We have devised a method for rapid and low-cost production of liquid elastomer injection molded devices that utilizes fused deposition modeling 3D printers for mold design and a modified desiccator as an injection system. Low costs and rapid turnaround time in this technique lower the barrier to iteratively designing and prototyping complex elastomer devices. Furthermore, CAD models developed in this process can be later adapted for metal mold tooling design, enabling an easy transition to a traditional injection molding process. We have used this technique to manufacture intravaginal probes involving complex geometries, as well as overmolding over metal parts, using tools commonly available within an academic research laboratory. However, this technique can be easily adapted to create liquid injection molded devices for many other applications. PMID:24998993

  12. Rapid and low-cost prototyping of medical devices using 3D printed molds for liquid injection molding.

    PubMed

    Chung, Philip; Heller, J Alex; Etemadi, Mozziyar; Ottoson, Paige E; Liu, Jonathan A; Rand, Larry; Roy, Shuvo

    2014-06-27

    Biologically inert elastomers such as silicone are favorable materials for medical device fabrication, but forming and curing these elastomers using traditional liquid injection molding processes can be an expensive process due to tooling and equipment costs. As a result, it has traditionally been impractical to use liquid injection molding for low-cost, rapid prototyping applications. We have devised a method for rapid and low-cost production of liquid elastomer injection molded devices that utilizes fused deposition modeling 3D printers for mold design and a modified desiccator as an injection system. Low costs and rapid turnaround time in this technique lower the barrier to iteratively designing and prototyping complex elastomer devices. Furthermore, CAD models developed in this process can be later adapted for metal mold tooling design, enabling an easy transition to a traditional injection molding process. We have used this technique to manufacture intravaginal probes involving complex geometries, as well as overmolding over metal parts, using tools commonly available within an academic research laboratory. However, this technique can be easily adapted to create liquid injection molded devices for many other applications.

  13. Decay of the 3D inviscid liquid-gas two-phase flow model

    NASA Astrophysics Data System (ADS)

    Zhang, Yinghui

    2016-06-01

    We establish the optimal {Lp-L2(1 ≤ p < 6/5)} time decay rates of the solution to the Cauchy problem for the 3D inviscid liquid-gas two-phase flow model and analyze the influences of the damping on the qualitative behaviors of solution. Compared with the viscous liquid-gas two-phase flow model (Zhang and Zhu in J Differ Equ 258:2315-2338, 2015), our results imply that the friction effect of the damping is stronger than the dissipation effect of the viscosities and enhances the decay rate of the velocity. Our proof is based on Hodge decomposition technique, the {Lp-L2} estimates for the linearized equations and an elaborate energy method.

  14. 3D multi-view system using electro-wetting liquid lenticular lenses

    NASA Astrophysics Data System (ADS)

    Won, Yong Hyub; Kim, Junoh; Kim, Cheoljoong; Shin, Dooseub; Lee, Junsik; Koo, Gyohyun

    2016-06-01

    Lenticular multi-view system has great potential of three dimensional image realization. This paper introduces a fabrication of liquid lenticular lens array and an idea of increasing view points with a same resolution. Tunable liquid lens array can produce three dimensional images by using electro-wetting principle that changes surface tensions by applying voltage. The liquid lenticular device consists of a chamber, two different liquids and a sealing plate. To fabricate the chamber, an <100> silicon wafer is wet-etched by KOH solution and a trapezoid shaped chamber can be made after a certain time. The chamber having slanted walls is advantageous for electro-wetting achieving high diopter. Electroplating is done to make a nikel mold and poly methyl methacrylate (PMMA) chamber is fabricated through an embossing process. Indium tin oxide (ITO) is sputtered and parylene C and Teflon AF1600 is deposited for dielectric and hydrophobic layer respectively. Two immiscible liquids are injected and a glass plate as a sealing plate is covered with polycarbonates (PC) gaskets and sealed by UV adhesive. Two immiscible liquids are D.I water and a mixture of 1-chloronaphthalene and dodecane. The completed lenticular lens shows 2D and 3D images by applying certain voltages. Dioptric power and operation speed of the lenticular lens array are measured. A novel idea that an increment of viewpoints by electrode separation process is also proposed. The left and right electrodes of lenticular lens can be induced by different voltages and resulted in tilted optical axis. By switching the optical axis quickly, two times of view-points can be achieved with a same pixel resolution.

  15. 3D Imaging of Transition Metals in the Zebrafish Embryo by X-ray Fluorescence Microtomography

    PubMed Central

    Bourassa, Daisy; Gleber, Sophie-Charlotte; Vogt, Stefan; Yi, Hong; Will, Fabian; Richter, Heiko; Shin, Chong Hyun; Fahrni, Christoph J.

    2014-01-01

    Synchrotron X-ray fluorescence (SXRF) microtomography has emerged as a powerful technique for the 3D visualization of the elemental distribution in biological samples. The mechanical stability, both of the instrument and the specimen, is paramount when acquiring tomographic projection series. By combining the progressive lowering of temperature method (PLT) with femtosecond laser sectioning, we were able to embed, excise, and preserve a zebrafish embryo at 24 hours post fertilization in an X-ray compatible, transparent resin for tomographic elemental imaging. Based on a data set comprised of 60 projections, acquired with a step size of 2 μm during 100 hours of beam time, we reconstructed the 3D distribution of zinc, iron, and copper using the iterative maximum likelihood expectation maximization (MLEM) reconstruction algorithm. The volumetric elemental maps, which entail over 124 million individual voxels for each transition metal, revealed distinct elemental distributions that could be correlated with characteristic anatomical features at this stage of embryonic development. PMID:24992831

  16. Interaction of 3d transition metal atoms with charged ion projectiles from Electron Nuclear Dynamics computation

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank

    2003-03-01

    Computational results on atomic scattering between charged projectiles and transition metal target atoms are presented. This work aims at obtaining detailed information about charge, spin and energy transfer processes that occur between the interacting particles. An in-depth understanding of these phenomena is expected to provide a theoretical basis for the interpretation of various types of ion beam experiments, ranging from gas phase chromatography to spectroscopic observations of fast ions in ferromagnetic media. This contribution focuses on the scattering of light projectiles ranging from He to O, that are prepared in various initial charge states, by 3d transition metal atoms. The presented computations are performed in the framework of Electron Nuclear Dynamics (END)^1 theory which incorporates the coupling between electronic and nuclear degrees of freedom without reliance on the computationally cumbersome and frequently intractable determination of potential energy surfaces. In the present application of END theory to ion - transition metal atom scattering, a supermolecule approach is utilized in conjunction with a spin-unrestricted single determinantal wave function describing the electronic system. Integral scattering, charge and spin exchange cross sections are discussed as functions of the elementary parameters of the problem, such as projectile and target atomic numbers as well as projectile charge and initial kinetic energy. ^1 E.Deumens, A.Diz, R.Longo, Y.Oehrn, Rev.Mod.Phys. 66, 917 (1994)

  17. Boundary Layer Control of Rotating Convection Systems: the Transition from 2D to 3D Turbulence

    NASA Astrophysics Data System (ADS)

    King, Eric; Stellmach, S.; Noir, J.; Hansen, U.; Aurnou, J.

    2008-09-01

    Recent studies have reproduced the patterns of zonal flow and thermal emission on the Giant Planets using deep convection models. For example, it has been shown that the fundamental differences between the winds of the Ice Giants, Uranus and Neptune, and the Gas Giants, Jupiter and Saturn, may be explained by the breakdown of the influence of rotation on convection. Here, we present results from a coupled suite of laboratory experiments and numerical simulations of rotating convection which span a broad range of parameter space. We observe distinct transitions from rotationally controlled, quasi-2D dynamics to strongly 3D, non-rotating style convection. We quantify the boundary between these two regimes as a function of the Rayleigh and Ekman numbers. The transition is not determined, as long assumed, by the convective Rossby number, but instead is controlled by boundary layer dynamics. It may then be easier than previously thought for convection systems to break free from the constraints of rotation. We are presently investigating how this transition correlates with zonal flows and magnetic field generation on the Giant Planets. Funding provided by NSF Geophysics Program (EAR/IF) and NASA Planetary Atmospheres Program.

  18. Electron enrichment in 3d transition metal oxide hetero-nanostructures.

    PubMed

    Kronawitter, Coleman X; Bakke, Jonathan R; Wheeler, Damon A; Wang, Wei-Cheng; Chang, Chinglin; Antoun, Bonnie R; Zhang, Jin Z; Guo, Jinghua; Bent, Stacey F; Mao, Samuel S; Vayssieres, Lionel

    2011-09-14

    Direct experimental observation of spontaneous electron enrichment of metal d orbitals in a new transition metal oxide heterostructure with nanoscale dimensionality is reported. Aqueous chemical synthesis and vapor phase deposition are combined to fabricate oriented arrays of high-interfacial-area hetero-nanostructures comprised of titanium oxide and iron oxide nanomaterials. Synchrotron-based soft X-ray spectroscopy techniques with high spectral resolution are utilized to directly probe the titanium and oxygen orbital character of the interfacial region's occupied and unoccupied densities of states. These data demonstrate the interface to possess electrons in Ti 3d bands and an emergent degree of orbital hybridization that is absent in parent oxide reference crystals. The carrier dynamics of the hetero-nanostructures are studied by ultrafast transient absorption spectroscopy, which reveals the presence of a dense manifold of states, the relaxations from which exhibit multiple exponential decays whose magnitudes depend on their energetic positions within the electronic structure.

  19. Magnetic ordering in digital alloys of group-IV semiconductors with 3d-transition metals

    SciTech Connect

    Otrokov, M. M.; Tugushev, V. V.; Ernst, A.; Ostanin, S. A.; Kuznetsov, V. M.; Chulkov, E. V.

    2011-04-15

    The ab initio investigation of the magnetic ordering in digital alloys consisting of monolayers of 3d-transition metals Ti, V, Cr, Mn, Fe, Co, and Ni introduced into the Si, Ge, and Si{sub 0.5}Ge{sub 0.5} semiconductor hosts is reported. The calculations of the parameters of the exchange interactions and total-energy calculations indicate that the ferromagnetic order appears only in the manganese monolayers, whereas the antiferromagnetic order is more probable in V, Cr, and Fe monolayers, and Ti, Co, and Ni monolayers are nonmagnetic. The stability of the ferromagnetic phase in digital alloys containing manganese monolayers has been analyzed using the calculations of magnon spectra.

  20. 3-D High-Lift Flow-Physics Experiment - Transition Measurements

    NASA Technical Reports Server (NTRS)

    McGinley, Catherine B.; Jenkins, Luther N.; Watson, Ralph D.; Bertelrud, Arild

    2005-01-01

    An analysis of the flow state on a trapezoidal wing model from the NASA 3-D High Lift Flow Physics Experiment is presented. The objective of the experiment was to characterize the flow over a non-proprietary semi-span three-element high-lift configuration to aid in assessing the state of the art in the computation of three-dimensional high-lift flows. Surface pressures and hot-film sensors are used to determine the flow conditions on the slat, main, and flap. The locations of the attachments lines and the values of the attachment line Reynolds number are estimated based on the model surface pressures. Data from the hot-films are used to determine if the flow is laminar, transitional, or turbulent by examining the hot-film time histories, statistics, and frequency spectra.

  1. Dirac cones in artificial structures of 3d transitional-metals doped Mg-Al spinels

    SciTech Connect

    Lu, Yuan; Zuo, Xu; Feng, Min; Shao, Bin

    2014-05-07

    Motivated by recent theoretical predications for Dirac cone in two-dimensional (2D) triangular lattice [H. Ishizuka, Phys. Rev. Lett. 109, 237207 (2012)], first-principles studies are performed to predict Dirac cones in artificial structures of 3d transitional-metals (TM = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) doped Mg-Al spinels. In investigated artificial structures, TM dopants substitute specific positions of the B sub-lattice in Mg-Al spinel, and form a quasi-2D triangular lattice in the a-b plane. Calculated results illustrate the existence of the spin-polarized Dirac cones formed in d-wave bands at (around) the K-point in the momentum space. The study provides a promising route for engineering Dirac physics in condensed matters.

  2. 3d Transition Metal Adsorption Induced the valley-polarized Anomalous Hall Effect in Germanene

    PubMed Central

    Zhou, P.; Sun, L. Z.

    2016-01-01

    Based on DFT + U and Berry curvature calculations, we study the electronic structures and topological properties of 3d transition metal (TM) atom (from Ti to Co) adsorbed germanene (TM-germanene). We find that valley-polarized anomalous Hall effect (VAHE) can be realized in germanene by adsorbing Cr, Mn, or Co atoms on its surface. A finite valley Hall voltage can be easily detected in their nanoribbon, which is important for valleytronics devices. Moreover, different valley-polarized current and even reversible valley Hall voltage can be archived by shifting the Fermi energy of the systems. Such versatile features of the systems show potential in next generation electronics devices. PMID:27312176

  3. Dipole approximation in the L2,3 electron excited spectra in 3d transition metals

    NASA Astrophysics Data System (ADS)

    Nuroh, K.

    2008-12-01

    A theoretical model based on the autoionization and characteristic decay processes following electron impact ionization of a core electron in solids that has previously been used in calculating electron-energy-loss spectra of transition metals near the 3p -excitation edge has been extended to the 2p -excitation edge for S21c through N27i as well. In the first set of calculations, magnetic effects were ignored and the relative scattering intensity was formulated in terms of the electrostatic interaction U(p,d) between the 3p and 3d electrons of the intermediate resonant configuration state p5dn+1 , using many-body perturbation theory that led to a generalized Fano-type formula for the intensity profiles. In the second set of calculations in which magnetic effects were included as well, an analysis based on the Bethe-Born formalism of inelastic scattering of electrons on atoms was used. The nature of the relative magnitudes of U(p,d) and the spin-orbit parameters ς3p and ς3d and the localized nature of the 3p state necessitated the diagonalization of the intermediate configuration state p5dn+1 to determine the multiplet splitting and their corresponding intensities in the LS -coupling limit using fractional parentage scheme. The nonrelativistic multiconfiguration Hartree-Fock (MCHF) code was used in determining the ground and continuum state wave functions, and the itinerant 3d states in the solid were approximated with an atomic MCHF-wave function. The outline above is applied to the 2p -excitation edge, except that because of the relative magnitudes of U(p,d) , ς2p , and ς3d , it is found that LK coupling is suitable for Sc, Ti, and V, while jK coupling is appropriate for Cr to Ni when it comes to the diagonalization of the configuration p5dn+1 to determine the multiplet splitting and their associated scattering intensities. In the dipole approximation, the scattering intensities separate into two distinct manifolds that arise from the p3/2 and p1/2 states. The

  4. Best fit refractive index of matching liquid for 3D NIPAM gel dosimeters using optical CT

    NASA Astrophysics Data System (ADS)

    Chen, Chin-Hsing; Wu, Jay; Hsieh, Bor-Tsung; Chen, De-Shiou; Wang, Tzu-Hwei; Chien, Sou-Hsin; Chang, Yuan-Jen

    2014-11-01

    The accuracy of an optical computed tomography (CT)-based dosimeter is significantly affected by the refractive index (RI) of the matching liquid. Mismatched RI induces reflection and refraction as the laser beam passes through the gel phantom. Moreover, the unwanted light rays collected by the photodetector produce image artifacts after image reconstruction from the collected data. To obtain the best image quality, this study investigates the best-fit RI of the matching liquid for a 3D NIPAM gel dosimeter. The three recipes of NIPAM polymer gel used in this study consisted of 5% gelatin, 5% NIPAM and 3% N,N'-methylene bisacrylamide, which were combined with three compositions (5, 10, and 20 mM) of Tetrakis (hydroxymethyl) phosphonium chloride. Results were evaluated using a quantitative evaluation method of the gamma evaluation technique. Results showed that the best-fit RI for the non-irradiated NIPAM gel ranges from 1.340 to 1.346 for various NIPAM recipes with sensitivities ranging from 0.0113 to 0.0227. The greatest pass rate of 88.00% is achieved using best-fit RI=1.346 of the matching liquid. The adoption of mismatching RI decreases the gamma pass rate by 2.63% to 16.75% for all three recipes of NIPAM gel dosimeters. In addition, the maximum average deviation is less than 0.1% for the red and transparent matching liquids. Thus, the color of the matching liquid does not affect the measurement accuracy of the NIPAM gel dosimeter, as measured by optical CT.

  5. Liquid immersion thermal crosslinking of 3D polymer nanopatterns for direct carbonisation with high structural integrity

    PubMed Central

    Kang, Da-Young; Kim, Cheolho; Park, Gyurim; Moon, Jun Hyuk

    2015-01-01

    The direct pyrolytic carbonisation of polymer patterns has attracted interest for its use in obtaining carbon materials. In the case of carbonisation of nanopatterned polymers, the polymer flow and subsequent pattern change may occur in order to relieve their high surface energies. Here, we demonstrated that liquid immersion thermal crosslinking of polymer nanopatterns effectively enhanced the thermal resistance and maintained the structure integrity during the heat treatment. We employed the liquid immersion thermal crosslinking for 3D porous SU8 photoresist nanopatterns and successfully converted them to carbon nanopatterns while maintaining their porous features. The thermal crosslinking reaction and carbonisation of SU8 nanopatterns were characterised. The micro-crystallinity of the SU8-derived carbon nanopatterns was also characterised. The liquid immersion heat treatment can be extended to the carbonisation of various polymer or photoresist nanopatterns and also provide a facile way to control the surface energy of polymer nanopatterns for various purposes, for example, to block copolymer or surfactant self-assemblies. PMID:26677949

  6. Liquid immersion thermal crosslinking of 3D polymer nanopatterns for direct carbonisation with high structural integrity

    NASA Astrophysics Data System (ADS)

    Kang, Da-Young; Kim, Cheolho; Park, Gyurim; Moon, Jun Hyuk

    2015-12-01

    The direct pyrolytic carbonisation of polymer patterns has attracted interest for its use in obtaining carbon materials. In the case of carbonisation of nanopatterned polymers, the polymer flow and subsequent pattern change may occur in order to relieve their high surface energies. Here, we demonstrated that liquid immersion thermal crosslinking of polymer nanopatterns effectively enhanced the thermal resistance and maintained the structure integrity during the heat treatment. We employed the liquid immersion thermal crosslinking for 3D porous SU8 photoresist nanopatterns and successfully converted them to carbon nanopatterns while maintaining their porous features. The thermal crosslinking reaction and carbonisation of SU8 nanopatterns were characterised. The micro-crystallinity of the SU8-derived carbon nanopatterns was also characterised. The liquid immersion heat treatment can be extended to the carbonisation of various polymer or photoresist nanopatterns and also provide a facile way to control the surface energy of polymer nanopatterns for various purposes, for example, to block copolymer or surfactant self-assemblies.

  7. Effect of dimensionality on vapor-liquid phase transition

    SciTech Connect

    Singh, Sudhir Kumar

    2014-04-24

    Dimensionality play significant role on ‘phase transitions’. Fluids in macroscopic confinement (bulk or 3-Dimensional, 3D) do not show significant changes in their phase transition properties with extent of confinement, since the number of molecules away from the surrounding surfaces is astronomically higher than the number of molecules in close proximity of the confining surfaces. In microscopic confinement (quasi 3D to quasi-2D), however, the number of molecules away from the close proximity of the surface is not as high as is the case with macroscopic (3D) confinement. Hence, under the same thermodynamic conditions ‘phase transition’ properties at microscopic confinement may not remain the same as the macroscopic or 3D values. Phase transitions at extremely small scale become very sensitive to the dimensions as well as the surface characteristics of the system. In this work our investigations reveal the effect of dimensionality on the phase transition from 3D to quasi-2D to 2D behavior. We have used grand canonical transition matrix Monte Carlo simulation to understand the vapor–liquid phase transitions from 3D to quasi-2D behavior. Such studies can be helpful in understanding and controlling the fluid film behaviour confined between solid surfaces of few molecular diameters, for example, in lubrication applications.

  8. Photonic liquid crystal fibers tuning by four electrode system produced with 3D printing technology

    NASA Astrophysics Data System (ADS)

    Ertman, Slawomir; Bednarska, Karolina; Czapla, Aleksandra; Woliński, Tomasz R.

    2015-09-01

    Photonic liquid crystal fiber has been intensively investigated in last few years. It has been proved that guiding properties of such fibers could be tuned with an electric field. In particular efficient tuning could be obtained if multi-electrode system allowing for dynamic change of not only intensity of the electric field, but also its direction. In this work we report a simple to build four electrode system, which is based on a precisely aligned four cylindrical microelectrodes. As an electrodes we use enameled copper wire with diameter adequate to the diameter of the fiber to be tuned. To ensure uniform and parallel alignment of the wires a special micro-profiles has been designed and then produced with filament 3D printer. The possibility of the dynamic change of the electric field direction in such scalable and cost effective electrode assembly has been experimentally confirmed.

  9. Recipe for High Moment Materials with Rare-earth and 3d Transition Metal Composites.

    PubMed

    Autieri, Carmine; Kumar, P Anil; Walecki, Dirk; Webers, Samira; Gubbins, Mark A; Wende, Heiko; Sanyal, Biplab

    2016-01-01

    Materials with high volume magnetization are perpetually needed for the generation of sufficiently large magnetic fields by writer pole of magnetic hard disks, especially for achieving increased areal density in storage media. In search of suitable materials combinations for this purpose, we have employed density functional theory to predict the magnetic coupling between iron and gadolinium layers separated by one to several monolayers of 3d transition metals (Sc-Zn). We demonstrate that it is possible to find ferromagnetic coupling for many of them and in particular for the early transition metals giving rise to high moment. Cr and Mn are the only elements able to produce a significant ferromagnetic coupling for thicker spacer layers. We also present experimental results on two trilayer systems Fe/Sc/Gd and Fe/Mn/Gd. From the experiments, we confirm a ferromagnetic coupling between Fe and Gd across a 3 monolayers Sc spacer or a Mn spacer thicker than 1 monolayer. In addition, we observe a peculiar dependence of Fe/Gd magnetic coupling on the Mn spacer thickness. PMID:27381456

  10. Recipe for High Moment Materials with Rare-earth and 3d Transition Metal Composites

    NASA Astrophysics Data System (ADS)

    Autieri, Carmine; Kumar, P. Anil; Walecki, Dirk; Webers, Samira; Gubbins, Mark A.; Wende, Heiko; Sanyal, Biplab

    2016-07-01

    Materials with high volume magnetization are perpetually needed for the generation of sufficiently large magnetic fields by writer pole of magnetic hard disks, especially for achieving increased areal density in storage media. In search of suitable materials combinations for this purpose, we have employed density functional theory to predict the magnetic coupling between iron and gadolinium layers separated by one to several monolayers of 3d transition metals (Sc-Zn). We demonstrate that it is possible to find ferromagnetic coupling for many of them and in particular for the early transition metals giving rise to high moment. Cr and Mn are the only elements able to produce a significant ferromagnetic coupling for thicker spacer layers. We also present experimental results on two trilayer systems Fe/Sc/Gd and Fe/Mn/Gd. From the experiments, we confirm a ferromagnetic coupling between Fe and Gd across a 3 monolayers Sc spacer or a Mn spacer thicker than 1 monolayer. In addition, we observe a peculiar dependence of Fe/Gd magnetic coupling on the Mn spacer thickness.

  11. Multigrid direct numerical simulation of the whole process of flow transition in 3-D boundary layers

    NASA Technical Reports Server (NTRS)

    Liu, Chaoqun; Liu, Zhining

    1993-01-01

    A new technology was developed in this study which provides a successful numerical simulation of the whole process of flow transition in 3-D boundary layers, including linear growth, secondary instability, breakdown, and transition at relatively low CPU cost. Most other spatial numerical simulations require high CPU cost and blow up at the stage of flow breakdown. A fourth-order finite difference scheme on stretched and staggered grids, a fully implicit time marching technique, a semi-coarsening multigrid based on the so-called approximate line-box relaxation, and a buffer domain for the outflow boundary conditions were all used for high-order accuracy, good stability, and fast convergence. A new fine-coarse-fine grid mapping technique was developed to keep the code running after the laminar flow breaks down. The computational results are in good agreement with linear stability theory, secondary instability theory, and some experiments. The cost for a typical case with 162 x 34 x 34 grid is around 2 CRAY-YMP CPU hours for 10 T-S periods.

  12. Recipe for High Moment Materials with Rare-earth and 3d Transition Metal Composites

    PubMed Central

    Autieri, Carmine; Kumar, P. Anil; Walecki, Dirk; Webers, Samira; Gubbins, Mark A.; Wende, Heiko; Sanyal, Biplab

    2016-01-01

    Materials with high volume magnetization are perpetually needed for the generation of sufficiently large magnetic fields by writer pole of magnetic hard disks, especially for achieving increased areal density in storage media. In search of suitable materials combinations for this purpose, we have employed density functional theory to predict the magnetic coupling between iron and gadolinium layers separated by one to several monolayers of 3d transition metals (Sc-Zn). We demonstrate that it is possible to find ferromagnetic coupling for many of them and in particular for the early transition metals giving rise to high moment. Cr and Mn are the only elements able to produce a significant ferromagnetic coupling for thicker spacer layers. We also present experimental results on two trilayer systems Fe/Sc/Gd and Fe/Mn/Gd. From the experiments, we confirm a ferromagnetic coupling between Fe and Gd across a 3 monolayers Sc spacer or a Mn spacer thicker than 1 monolayer. In addition, we observe a peculiar dependence of Fe/Gd magnetic coupling on the Mn spacer thickness. PMID:27381456

  13. Microscopic magnetic nature of K2NiF4-type 3d transition metal oxides

    NASA Astrophysics Data System (ADS)

    Sugiyama, J.; Nozaki, H.; Umegaki, I.; Higemoto, W.; Ansaldo, E. J.; Brewer, J. H.; Sakurai, H.; Kao, T.-H.; Yang, H.-D.; Månsson, M.

    2014-12-01

    In order to elucidate the magnetic nature of K2NiF4-type 3d transition metal oxides, we have measured μ+SR spectra for Sr2VO4, LaSrVO4, and Sr2CrO4 using powder samples. ZF- and wTF-μ+SR measurements propose that Sr2VO4 enters into the static antiferromagnetic (AF) order phase below 8 K. In addition, TF-μ+SR measurements evidence that the transition at 105 K is not magnetic but structural and/or electronic in origin. For LaSrVO4, static long-range order has not been observed down to 20 K, while, as T decreases from 145 K, wTF asymmetry starts to decrease below 60 K, suggesting the appearance and evolution of localized magnetic moments below 60 K. For Sr2CrO4, by contrast, both ZF- and wTF-μ+SR have confirmed the presence of antiferromagnetic order below 117 K, as predicted in the χ(T) curve.

  14. Electronic and magnetic structure of 3d-transition-metal point defects in silicon calculated from first principles

    NASA Astrophysics Data System (ADS)

    Beeler, F.; Andersen, O. K.; Scheffler, M.

    1990-01-01

    We describe spin-unrestricted self-consistent linear muffin-tin-orbital (LMTO) Green-function calculations for Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu transition-metal impurities in crystalline silicon. Both defect sites of tetrahedral symmetry are considered. All possible charge states with their spin multiplicities, magnetization densities, and energy levels are discussed and explained with a simple physical picture. The early transition-metal interstitial and late transition-metal substitutional 3d ions are found to have low spin. This is in conflict with the generally accepted crystal-field model of Ludwig and Woodbury, but not with available experimental data. For the interstitial 3d ions, the calculated deep donor and acceptor levels reproduce all experimentally observed transitions. For substitutional 3d ions, a large number of predictions is offered to be tested by future experimental studies.

  15. Switchable 3D liquid crystal grating generated by periodic photo-alignment on both substrates.

    PubMed

    Nys, I; Beeckman, J; Neyts, K

    2015-10-21

    A planar liquid crystal (LC) cell is developed in which two photo-alignment layers have been illuminated with respectively a horizontal and a vertical diffraction pattern of interfering left- and right-handed circularly polarized light. In the bulk of the cell, a complex LC configuration is obtained with periodicity in two dimensions. Remarkably, the period of the structure is larger than the period of the interference pattern, indicating that lowering of the symmetry allows a reduction in the elastic energy. The liquid crystal configuration depends on the periodicity of the alignment but also on the thickness of the cell. By applying a voltage over the electrodes, the power going into the different diffracted orders can be tuned. Finite element (FE) simulations based on Q-tensor theory are used to find the 3D equilibrium director distribution, which is used to simulate the near-field transmission profile based on the Jones calculus. A 2D Fourier transform is performed for both the x- and y-component of the transmitted wave to find the diffraction efficiency. PMID:26313442

  16. Potentiometric and spectroscopic study of the interaction of 3d transition metal ions with inositol hexakisphosphate

    NASA Astrophysics Data System (ADS)

    Veiga, Nicolás; Macho, Israel; Gómez, Kerman; González, Gabriel; Kremer, Carlos; Torres, Julia

    2015-10-01

    Among myo-inositol phosphates, the most abundant in nature is the myo-inositol hexakisphosphate, InsP6. Although it is known to be vital to cell functioning, the biochemical research into its metabolism needs chemical and structural analysis of all the protonation, complexation and precipitation processes that it undergoes in the biological media. In view of its high negative charge at physiological level, our group has been leading a thorough research into the InsP6 chemical and structural behavior in the presence of the alkali and alkaline earth metal ions essential for life. The aim of this article is to extend these studies, dealing with the chemical and structural features of the InsP6 interaction with biologically relevant 3d transition metal ions (Fe(II), Fe(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)), in a non-interacting medium and under simulated physiological conditions. The metal-complex stability constants were determined by potentiometry, showing under ligand-excess conditions the formation of mononuclear species in different protonation states. Under metal ion excess, polymetallic species were detected for Fe(II), Fe(III), Zn(II) and Cu(II). Additionally, the 31P NMR and UV-vis spectroscopic studies provided interesting structural aspects of the strong metal ion-InsP6 interaction.

  17. Accurate nonrelativistic ground-state energies of 3d transition metal atoms

    SciTech Connect

    Scemama, A.; Applencourt, T.; Giner, E.; Caffarel, M.

    2014-12-28

    We present accurate nonrelativistic ground-state energies of the transition metal atoms of the 3d series calculated with Fixed-Node Diffusion Monte Carlo (FN-DMC). Selected multi-determinantal expansions obtained with the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) method and including the most prominent determinants of the full configuration interaction expansion are used as trial wavefunctions. Using a maximum of a few tens of thousands determinants, fixed-node errors on total DMC energies are found to be greatly reduced for some atoms with respect to those obtained with Hartree-Fock nodes. To the best of our knowledge, the FN-DMC/(CIPSI nodes) ground-state energies presented here are the lowest variational total energies reported so far. They differ from the recently recommended non-variational values of McCarthy and Thakkar [J. Chem. Phys. 136, 054107 (2012)] only by a few percents of the correlation energy. Thanks to the variational property of FN-DMC total energies, our results provide exact lower bounds for the absolute value of all-electron correlation energies, |E{sub c}|.

  18. Understanding the spin-driven polarizations in Bi MO3 (M = 3 d transition metals) multiferroics

    NASA Astrophysics Data System (ADS)

    Kc, Santosh; Lee, Jun Hee; Cooper, Valentino R.

    Bismuth ferrite (BiFeO3) , a promising multiferroic, stabilizes in a perovskite type rhombohedral crystal structure (space group R3c) at room temperature. Recently, it has been reported that in its ground state it possess a huge spin-driven polarization. To probe the underlying mechanism of this large spin-phonon response, we examine these couplings within other Bi based 3 d transition metal oxides Bi MO3 (M = Ti, V, Cr, Mn, Fe, Co, Ni) using density functional theory. Our results demonstrate that this large spin-driven polarization is a consequence of symmetry breaking due to competition between ferroelectric distortions and anti-ferrodistortive octahedral rotations. Furthermore, we find a strong dependence of these enhanced spin-driven polarizations on the crystal structure; with the rhombohedral phase having the largest spin-induced atomic distortions along [111]. These results give us significant insights into the magneto-electric coupling in these materials which is essential to the magnetic and electric field control of electric polarization and magnetization in multiferroic based devices. Research is supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division and the Office of Science Early Career Research Program (V.R.C) and used computational resources at NERSC.

  19. Tensile strengths of polyamide based 3D printed polymers in liquid nitrogen

    NASA Astrophysics Data System (ADS)

    Cruz, P.; Shoemake, E. D.; Adam, P.; Leachman, J.

    2015-12-01

    Advances in additive manufacturing technology have made 3D printing a viable solution for many industries, allowing for the manufacture of designs that could not be made through traditional subtractive methods. Applicability of additive manufacturing in cryogenic applications is hindered, however, by a lack of accurate material properties information. Nylon is available for printing using fused deposition modeling (FDM) and selective laser sintering (SLS). We selected 5 SLS (DuraForm® EX, DuraForm® HST, DuraForm® PA, PA 640-GSL, and PA 840-GSL) and 2 FDM (Nylon 12, ULTEM) nylon variants based on the bulk material properties and printed properties at room temperature. Tensile tests were performed on five samples of each material while immersed in liquid nitrogen at approximately 77 Kelvin. Samples were tested in XY and, where available, Z printing directions to determine influence on material properties. Results show typical SLS and FDM nylon ultimate strength retention at 77 K, when compared to (extruded or molded) nylon ultimate strength.

  20. Thermal characterization of a liquid resin for 3D printing using photothermal techniques

    NASA Astrophysics Data System (ADS)

    Jiménez-Pérez, José L.; Pincel, Pavel Vieyra; Cruz-Orea, Alfredo; Correa-Pacheco, Zormy N.

    2016-05-01

    Thermal properties of a liquid resin were studied by thermal lens spectrometry (TLS) and open photoacoustic cell (OPC), respectively. In the case of the TLS technique, the two mismatched mode experimental configuration was used with a He-Ne laser, as a probe beam and an Argon laser was used as the excitation source. The characteristic time constant of the transient thermal lens was obtained by fitting the theoretical expression to the experimental data in order to obtain the thermal diffusivity ( α) of the resin. On the other hand, the sample thermal effusivity ( e) was obtained by using the OPC technique. In this technique, an Argon laser was used as the excitation source and was operated at 514 nm with an output power of 30 mW. From the obtained thermal diffusivity ( α) and thermal effusivity ( e) values, the thermal conductivity ( k) and specific heat capacity per unit volume ( ρc) of resin were calculated through the relationships k = e( α)1/2 and ρc = e/( α)1/2. The obtained thermal parameters were compared with the thermal parameters of the literature. To our knowledge, the thermal characterization of resin has not been reported until now. The present study has applications in laser stereo-lithography to manufacture 3D printing pieces.

  1. Potential energy curves and electronic structure of 3d transition metal hydrides and their cations

    NASA Astrophysics Data System (ADS)

    Goel, Satyender; Masunov, Artëm E.

    2008-12-01

    We investigate gas-phase neutral and cationic hydrides formed by 3d transition metals from Sc to Cu with density functional theory (DFT) methods. The performance of two exchange-correlation functionals, Boese-Martin for kinetics (BMK) and Tao-Perdew-Staroverov-Scuseria (TPSS), in predicting bond lengths and energetics, electronic structures, dipole moments, and ionization potentials is evaluated in comparison with available experimental data. To ensure a unique self-consistent field (SCF) solution, we use stability analysis, Fermi smearing, and continuity analysis of the potential energy curves. Broken-symmetry approach was adapted in order to get the qualitatively correct description of the bond dissociation. We found that on average BMK predicted values of dissociation energies and ionization potentials are closer to experiment than those obtained with high level wave function theory methods. This agreement deteriorates quickly when the fraction of the Hartree-Fock exchange in DFT functional is decreased. Natural bond orbital (NBO) population analysis was used to describe the details of chemical bonding in the systems studied. The multireference character in the wave function description of the hydrides is reproduced in broken-symmetry DFT description, as evidenced by NBO analysis. We also propose a new scheme to correct for spin contamination arising in broken-symmetry DFT approach. Unlike conventional schemes, our spin correction is introduced for each spin-polarized electron pair individually and therefore is expected to yield more accurate energy values. We derive an expression to extract the energy of the pure singlet state from the energy of the broken-symmetry DFT description of the low spin state and the energies of the high spin states (pentuplet and two spin-contaminated triplets in the case of two spin-polarized electron pairs). The high spin states are build with canonical natural orbitals and do not require SCF convergence.

  2. First Principles Study of Effect of 3d Transition Metal-Doped Zinc Oxide on Gas Sensitivity

    NASA Astrophysics Data System (ADS)

    Qiu, Zhiyong; Murakami, Ri-Ichi

    Two series models were developed in order to investigate the gas sensitivity of 3d transition metal-doped zinc oxide (ZnO) materials. Software based on a discrete variation method (DVM) within the framework of density functional theory was used to calculate the electronic structures of the models. It was possible to determine gas sensitivity using the calculated results, from which a relationship between electronic properties and gas sensitivity was formed. The results showed that doping the transition metals greatly affected the gas sensitivity of ZnO-based materials. The main effect was attributed to the change in carrier concentration. On the contrary, the doping of transition metals had a negligible effect on the mobility of ZnO-based materials. Titanium or iron doped-ZnO is thus expected to have the best gas sensitivity of all of the 3d transition metal-doped ZnO materials.

  3. Electronic spectroscopy and electronic structure of the smallest metal clusters: the diatomic 3D transition metal aluminides

    NASA Astrophysics Data System (ADS)

    Behm, Jane M.; Morse, Michael D.

    1994-06-01

    A systematic study of the electronic spectroscopy, electronic structure, and chemical bonding has been initiated for the 3d series of diatomic transition metal aluminides. This report provides a review of the progress to date, with specific emphasis on AlCa, AlV, AlCr, AlMn, AlCo, AlNi, AlCu, and AlZn.

  4. Transition to Turbulence and Effect of Initial Conditions on 3D Compressible Mixing in Planar Blast-wave-driven Systems

    SciTech Connect

    Miles, A R; Edwards, M J; Greenough, J A

    2004-11-08

    Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, results from three-dimensional numerical simulations of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams, 9(2), 209 (1991)] are presented. Using the multi-physics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J.A. Greenough, J. Comp. Phys. 184, 53 (2003)], the late nonlinear instability evolution, including transition to turbulence, is considered for various multimode perturbation spectra. The 3D post-transition state differs from the 2D result, but the process of transition proceeds similarly in both 2D and 3D. The turbulent mixing transition results in a reduction in the growth rate of the mixing layer relative to its pre-transition value and, in the case of the bubble front, relative to the 2D result. The post-transition spike front velocity is approximately the same in 2D and 3D. Implications for hydrodynamic mixing in core-collapse supernova are discussed.

  5. Repumping of ultracold strontium atoms using the ^3P2 - ^3D2 transition

    NASA Astrophysics Data System (ADS)

    Mickelson, P. G.; Martinez de Escobar, Y. N.; Traverso, A. J.; Killian, T. C.

    2008-05-01

    We discuss recent experiments involving ultracold strontium. Using a commercially-available 3 micron laser, we repump atoms out of the ^3P2 level via the ^3D2 state and gain almost a factor of 10 in the number of atoms in our system. This increase in the signal-to-noise ratio enables improved spectroscopy of strontium in our optical trap.

  6. Epithelial-to-mesenchymal transition in pancreatic ductal adenocarcinoma: Characterization in a 3D-cell culture model

    PubMed Central

    Gagliano, Nicoletta; Celesti, Giuseppe; Tacchini, Lorenza; Pluchino, Stefano; Sforza, Chiarella; Rasile, Marco; Valerio, Vincenza; Laghi, Luigi; Conte, Vincenzo; Procacci, Patrizia

    2016-01-01

    AIM: To analyze the effect of three-dimensional (3D)-arrangement on the expression of epithelial-to-mesenchymal transition markers in pancreatic adenocarcinoma (PDAC) cells. METHODS: HPAF-II, HPAC, and PL45 PDAC cells were cultured in either 2D-monolayers or 3D-spheroids. Ultrastructure was analyzed by transmission electron microscopy. The expression of E-cadherin, β-catenin, N-cadherin, collagen type I (COL-I), vimentin, α-smooth muscle actin (αSMA), and podoplanin was assayed by confocal microscopy in cells cultured on 12-mm diameter round coverslips and in 3D-spheroids. Gene expression for E-cadherin, Snail, Slug, Twist, Zeb1, and Zeb2 was quantified by real-time PCR. E-cadherin protein level and its electrophoretic pattern were studied by Western blot in cell lysates obtained from cells grown in 2D-monolayers and 3D-spheroids. RESULTS: The E-cadherin/β-catenin complex was expressed in a similar way in plasma membrane cell boundaries in both 2D-monolayers and 3D-spheroids. E-cadherin increased in lysates obtained from 3D-spheroids, while cleavage fragments were more evident in 2D-monolayers. N-cadherin expression was observed in very few PDAC cells grown in 2D-monolayers, but was more evident in 3D-spheroids. Some cells expressing COL-I were observed in 3D-spheroids. Podoplanin, expressed in collectively migrating cells, and αSMA were similarly expressed in both experimental conditions. The concomitant maintenance of the E-cadherin/β-catenin complex at cell boundaries supports the hypothesis of a collective migration for these cells, which is consistent with podoplanin expression. CONCLUSION: We show that a 3D-cell culture model could provide deeper insight into understanding the biology of PDAC and allow for the detection of marked differences in the phenotype of PDAC cells grown in 3D-spheroids. PMID:27182158

  7. 3s- and 3p-core level excitations in 3d-transition metal oxides from electron-energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Steiner, P.; Zimmermann, R.; Reinert, F.; Engel, Th.; Hüfner, S.

    1995-03-01

    3s- and 3p-core level excitations for a large number of 3d-transition metal oxides, with a formal 3d occupation from 3d0 to 3d10, have been measured by electron energy loss spectroscopy in reflection geometry (REELS) with primary energies 200 eV≤ E 0≤1600 eV. Their intensities decrease systematically with the formal 3d-count, classifying them as transitions to empty 3d-states. The structure of the 3s excitations is analysed in detail and is compared to the 3s-XPS photoemission spectra of the samples. This 3s-REELS structure and its change with the 3d occupation can be explained by the assumption that the excitation arises mainly from a 3s23dn→3s13dn+1 quadrupole transition.

  8. 3D microband boundary alignments and transitions in a cold rolled commercial purity aluminum alloy

    SciTech Connect

    George, C.; Soe, B.; King, K.; Quadir, M.Z.; Ferry, M.; Bassman, L.

    2013-05-15

    In the study of microband formation during plastic deformation of face centered cubic metals and alloys, two theories have been proposed regarding the orientations of their boundaries: (i) they are aligned parallel to crystallographic planes associated with dislocation glide (i.e. (111) planes in FCC metals), or (ii) they are aligned in accordance with the macroscopic stress state generated during deformation. In this study, high resolution 3D electron backscatter diffraction (3D EBSD) was used to investigate the morphology and crystallographic nature of microband boundaries within a 19 × 9 × 8.6 μm volume of a deformed grain in commercial purity aluminum cold rolled to 22% reduction. It was found that microband boundaries correspond to both theories of orientation. Additionally, a single surface may contain both crystallographic and non-crystallographic alignments. Misorientations across boundaries in the regions of microband triple junctions have been identified for both boundary alignments. - Highlights: ► Reconstruction of a 3D volume of crystallographic orientations from EBSD data ► Subgrain features accurately reconstructed using specially designed strategies. ► Microband boundaries contain crystallographic and non-crystallographic alignments. ► Boundaries form by crystallographic process but rotate to non-crystallographic.

  9. High refractive index immersion liquid for superresolution 3D imaging using sapphire-based aplanatic numerical aperture increasing lens optics.

    PubMed

    Laskar, Junaid M; Shravan Kumar, P; Herminghaus, Stephan; Daniels, Karen E; Schröter, Matthias

    2016-04-20

    Optically transparent immersion liquids with refractive index (n∼1.77) to match the sapphire-based aplanatic numerical aperture increasing lens (aNAIL) are necessary for achieving deep 3D imaging with high spatial resolution. We report that antimony tribromide (SbBr3) salt dissolved in liquid diiodomethane (CH2I2) provides a new high refractive index immersion liquid for optics applications. The refractive index is tunable from n=1.74 (pure) to n=1.873 (saturated), by adjusting either salt concentration or temperature; this allows it to match (or even exceed) the refractive index of sapphire. Importantly, the solution gives excellent light transmittance in the ultraviolet to near-infrared range, an improvement over commercially available immersion liquids. This refractive-index-matched immersion liquid formulation has enabled us to develop a sapphire-based aNAIL objective that has both high numerical aperture (NA=1.17) and long working distance (WD=12  mm). This opens up new possibilities for deep 3D imaging with high spatial resolution. PMID:27140083

  10. High refractive index immersion liquid for superresolution 3D imaging using sapphire-based aplanatic numerical aperture increasing lens optics.

    PubMed

    Laskar, Junaid M; Shravan Kumar, P; Herminghaus, Stephan; Daniels, Karen E; Schröter, Matthias

    2016-04-20

    Optically transparent immersion liquids with refractive index (n∼1.77) to match the sapphire-based aplanatic numerical aperture increasing lens (aNAIL) are necessary for achieving deep 3D imaging with high spatial resolution. We report that antimony tribromide (SbBr3) salt dissolved in liquid diiodomethane (CH2I2) provides a new high refractive index immersion liquid for optics applications. The refractive index is tunable from n=1.74 (pure) to n=1.873 (saturated), by adjusting either salt concentration or temperature; this allows it to match (or even exceed) the refractive index of sapphire. Importantly, the solution gives excellent light transmittance in the ultraviolet to near-infrared range, an improvement over commercially available immersion liquids. This refractive-index-matched immersion liquid formulation has enabled us to develop a sapphire-based aNAIL objective that has both high numerical aperture (NA=1.17) and long working distance (WD=12  mm). This opens up new possibilities for deep 3D imaging with high spatial resolution.

  11. Duality between the dynamics of line-like brushes of point defects in 2D and strings in 3D in liquid crystals

    NASA Astrophysics Data System (ADS)

    Digal, Sanatan; Ray, Rajarshi; Saumia, P. S.; Srivastava, Ajit M.

    2013-10-01

    We analyze the dynamics of dark brushes connecting point vortices of strength ±1 formed in the isotropic-nematic phase transition of a thin layer of nematic liquid crystals, using a crossed polarizer set up. The evolution of the brushes is seen to be remarkably similar to the evolution of line defects in a three-dimensional nematic liquid crystal system. Even phenomena like the intercommutativity of strings are routinely observed in the dynamics of brushes. We test the hypothesis of a duality between the two systems by determining exponents for the coarsening of total brush length with time as well as shrinking of the size of an isolated loop. Our results show scaling behavior for the brush length as well as the loop size with corresponding exponents in good agreement with the 3D case of string defects.

  12. Spectroscopic Investigation of the Odd-Parity 3 d 2 D → nf 2 F Transitions of Neutral Sodium

    NASA Astrophysics Data System (ADS)

    Nadeem, A.; Shah, M.; Shahzada, S.; Ahmed, M.; Haq, S. U.

    2015-11-01

    We report new experimental data on term energies and effective quantum numbers of the odd parity Rydberg states of sodium in the 40687-41408 cm-1 energy range. The experiment was performed using a two-color scheme of three-photon laser excitation in conjunction with a thermionic diode ion detector. The new observation includes much extended nf 2 F (12 ≤ n ≤ 51) series excited from the 3 d 2 D intermediate state. In addition, oscillator strengths of the 3 d 2 D → nf 2 F (16 ≤ n ≤ 45) Rydberg transitions have been determined and a complete picture is presented from n = 4-45 incorporating the present work and earlier computed results.

  13. Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System

    PubMed Central

    Xu, Limei; Buldyrev, Sergey V.; Giovambattista, Nicolas; Stanley, H. Eugene

    2010-01-01

    We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses. PMID:21614201

  14. Comparison of 3D Classical Trajectory and Transition-State Theory Reaction Cross Sections

    DOE R&D Accomplishments Database

    Koeppl, G. W.; Karplus, Martin

    1970-10-01

    Although there is excellent agreement for a system such as H+H{sub 2} --> H{sub 2}+H, in which both the potential and the particle masses are symmetric, significant deviations occur for more asymmetric reactions. A detailed analysis show that the calculated differences are from the violation of two assumptions of transition-state theory.

  15. Ferromagnetic interactions between transition-metal impurities in topological and 3D Dirac semimetals

    NASA Astrophysics Data System (ADS)

    Dietl, Tomasz

    The magnitude of ferromagnetic coupling driven by inter-band (Bloembergen-Rowland - BR) and intra-band (Ruderman-Kittel-Kasuya-Yoshida - RKKY) spin polarization is evaluated within kp theory for topological semimetals Hg1-xMnxTe and Hg1-xMnxSe as well as for 3D Dirac semimetal (Cd1-xMnx)3As2. In these systems Mn2+ ions do not introduce any carriers. Since, however, both conduction and valence bands are built from anion p-type wave functions, hybridization of Mn d levels with neighboring anion p states leads to spin-dependent p - d coupling of both electrons and holes to localized Mn spins, resulting in sizable inter-band spin polarization and, thus in large BR interactions. We demonstrate that this ferromagnetic coupling, together with antiferromagnetic superexchange, elucidate a specific dependence of spin-glass freezing temperature on x, determined experimentally for these systems. Furthermore, by employing a multi-orbital tight-binding method, we find that superexchange becomes ferromagnetic when Mn is replaced by Cr or V. Since Cr should act as an isoelectronic impurity in HgTe, this opens a road for realization of ferromagnetic topological insulators based on (Hg,Cr)Te.

  16. Can symmetry transitions of complex fields enable 3-d control of fluid vorticity?

    SciTech Connect

    Martin, James E.; Solis, Kyle Jameson

    2015-08-01

    Methods of inducing vigorous noncontact fluid flow are important to technologies involving heat and mass transfer and fluid mixing, since they eliminate the need for moving parts, pipes and seals, all of which compromise system reliability. Unfortunately, traditional noncontact flow methods are few, and have limitations of their own. We have discovered two classes of fields that can induce fluid vorticity without requiring either gravity or a thermal gradient. The first class we call Symmetry-Breaking Rational Fields. These are triaxial fields comprised of three orthogonal components, two ac and one dc. The second class is Rational Triad Fields, which differ in that all three components are alternating. In this report we quantify the induced vorticity for a wide variety of fields and consider symmetry transitions between these field types. These transitions give rise to orbiting vorticity vectors, a technology for non-contact, non-stationary fluid mixing.

  17. Liquid-liquid phase transition in supercooled silicon

    NASA Astrophysics Data System (ADS)

    Sastry, Srikanth; Austen Angell, C.

    2003-11-01

    Silicon in its liquid and amorphous forms occupies a unique position among amorphous materials. Obviously important in its own right, the amorphous form is structurally close to the group of 4-4, 3-5 and 2-6 amorphous semiconductors that have been found to have interesting pressure-induced semiconductor-to-metal phase transitions. On the other hand, its liquid form has much in common, thermodynamically, with water and other `tetrahedral network' liquids that show density maxima. Proper study of the `liquid-amorphous transition', documented for non-crystalline silicon by both experimental and computer simulation studies, may therefore also shed light on phase behaviour in these related materials. Here, we provide detailed and unambiguous simulation evidence that the transition in supercooled liquid silicon, in the Stillinger-Weber potential, is thermodynamically of first order and indeed occurs between two liquid states, as originally predicted by Aptekar. In addition we present evidence to support the relevance of spinodal divergences near such a transition, and the prediction that the transition marks a change in the liquid dynamic character from that of a fragile liquid to that of a strong liquid.

  18. Adsorption of alkali, alkaline-earth, and 3d transition metal atoms on silicene

    NASA Astrophysics Data System (ADS)

    Sahin, H.; Peeters, F. M.

    2013-02-01

    The adsorption characteristics of alkali, alkaline-earth, and transition metal adatoms on silicene, a graphene-like monolayer structure of silicon are analyzed by means of first-principles calculations. In contrast to graphene, interaction between the metal atoms and the silicene surface is quite strong due to its highly reactive buckled hexagonal structure. In addition to structural properties, we also calculate the electronic band dispersion, net magnetic moment, charge transfer, work function, and dipole moment of the metal adsorbed silicene sheets. Alkali metals, Li, Na, and K, adsorb to hollow sites without any lattice distortion. As a consequence of the significant charge transfer from alkalis to silicene, metalization of silicene takes place. Trends directly related to atomic size, adsorption height, work function, and dipole moment of the silicene/alkali adatom system are also revealed. We found that the adsorption of alkaline-earth metals on silicene is entirely different from their adsorption on graphene. The adsorption of Be, Mg, and Ca turns silicene into a narrow gap semiconductor. Adsorption characteristics of eight transition metals Ti, V, Cr, Mn, Fe, Co, Mo, and W are also investigated. As a result of their partially occupied d orbital, transition metals show diverse structural, electronic, and magnetic properties. Upon the adsorption of transition metals, depending on the adatom type and atomic radius, the system can exhibit metal, half-metal, and semiconducting behavior. For all metal adsorbates, the direction of the charge transfer is from adsorbate to silicene, because of its high surface reactivity. Our results indicate that the reactive crystal structure of silicene provides a rich playground for functionalization at nanoscale.

  19. Transition from Ignition to Flame Growth under External Radiation in 3D

    NASA Technical Reports Server (NTRS)

    Kashiwagi, Takashi; Nakamura, Yuji; Mell, William E.; Olson, Sandra L.

    2004-01-01

    This study focuses on localized ignition by external radiant flux and subsequent flame growth over thin polymeric materials (plastic and paper) in microgravity. Two transition stages were observed. The first transition stage covers the period from the onset of ignition to the formation of stabilized flame near the ignited area. This is followed by the second transition of the flame growth stage from the initial stabilized flame to sustained fire growth away from the ignited area. For the first stage, ignition experiments of thin PMMA sheets were conducted using a CO2 laser as an external source in the 10 s drop tower. The results of front side surface ignition and of backside surface ignition were observed. The effects of imposed flow velocity, sample thickness, and ambient oxygen concentration on ignition are obtained. Numerical study was conducted to investigate to understand and predict ignition behavior observed in the experiments. For the second stage, numerical study is being conducted to describe the effects of gravity on heat release rate of a PMMA sheet. The gravity level was varied from zero to normal gravity. The preliminary results show that the maximum heat release occurs at around 0.02 g.

  20. Dimensional phase transition from 1D behavior to a 3D Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Pelster, Axel; Morath, Denis; Straßel, Dominik; Eggert, Sebastian

    The emergence of new properties from low-dimensional building blocks is a universal theme in different areas in physics. The investigation of transitions between isolated and coupled low-dimensional systems promises to reveal new phenomena and exotic phases. Interacting 1D bosons, which are coupled in a two-dimensional array, are maybe the most fundamental example of a system which illustrates the concept of a dimensional phase transition. However, recent experiments using ultracold gases have shown a surprising discrepancy between theory and experiment and it is far from obvious if the power laws from the underlying 1D theory can predict the transition temperature and order parameter correctly for all interaction strengths. Using a combination of large-scale Quantum Monte-Carlo simulations and chain mean-field calculations, we show that the behavior of the ordering temperature as a function of inter-chain coupling strength does not follow a universal powerlaw, but also depends strongly on the filling

  1. Transition from Ignition to Flame Growth under External Radiation in Three Dimensions (TIGER-3D)

    NASA Technical Reports Server (NTRS)

    Kashiwagi, Takashi; Nakamura, Yuji; Olson, Sandra L.; Mell, William

    2004-01-01

    This study focuses on localized ignition by external radiant flux and subsequent flame growth over thin polymeric materials (plastic and paper) in microgravity. Two transition stages were observed. The first transition stage covers the period from the onset of ignition to the formation of stabilized flame near the ignited area. This is followed by the second transition of the flame growth stage from the initial stabilized flame to sustained fire growth away from the ignited area. For the first stage, ignition experiments of thin PMMA sheets were conducted using a CO2 laser as an external source in the 10 s drop tower. The results of front side surface ignition and of backside surface ignition were observed. The effects of imposed flow velocity, sample thickness, and ambient oxygen concentration on ignition are obtained. Numerical study was conducted to investigate to understand and predict ignition behavior observed in the experiments. For the second stage, numerical study is being conducted to describe the effects of gravity on heat release rate of a PMMA sheet. The gravity level was varied from zero to normal gravity. The preliminary results show that the maximum heat release occurs at around 0.02 g.

  2. 3d-transition metal induced enhancement of molecular hydrogen adsorption on Mg(0001) surface: An Ab-initio study

    NASA Astrophysics Data System (ADS)

    Banerjee, Paramita; Das, G. P.

    2016-05-01

    In our effort to do first principles design of suitable materials for hydrogen storage, we have explored the interaction characteristics of a hydrogen molecule with pure as well as a 3d-transition metal (TM) atom doped Mg(0001) surface using density functional theory (DFT) based approach. Doping of a 3d-TM atom by creating a vacancy on the top most layer of Mg(0001) surface, enhances the molecular hydrogen adsorption efficiency of this surface by ~ 6 times. The TM atom gains some charge from the defected site of the Mg(0001) surface, becomes anionic and adsorbs the hydrogen molecule via Anti Kubas-type interaction. The interaction energy of this H2 molecule, including van der Waals dispersion correction, turns out to be ~ 0.4 eV, which falls in the right energy window between physisorption and chemisorption. On full coverage of this 3d-TM atom doped Mg(0001) surface with hydrogen molecules, the gravimetric density of hydrogen has been estimated to be ~ 5.6 wt %, thereby satisfying the criteria set by the department of energy (DOE) for efficient hydrogen storage.

  3. Numerical simulation in 3D of atomizing coaxial gas-liquid jets

    NASA Astrophysics Data System (ADS)

    Agbaglah, Gilou; Fuster, Daniel; McBain, Geordie; Popinet, Stephane; Zaleski, Stephane

    2012-11-01

    We investigate three-dimensional multiphase flows using the Volume of Fluid method. We are in particular focusing on the problem of jet atomizaton. We use a Volume of Fluid method with oct-tree adaptive finite volume discretization, mostly using the Gerris free code. Surface tension is computed by a balanced-force method. Coaxial, 3D, round and planar air-water jets similar to those investigated experimentally are studied and compared to the equivalent jets in 2D axisymetric and 2D planar setups. A mechanism for large-scale jet disruption is observed. The distribution of droplet sizes is compared to experimental measurements. The effect of grid resolution and of the presence of an explicitly modelled solid separator plate is discussed.

  4. Fabrication of 3D microstructures from interactions of immiscible liquids with a structured surface.

    PubMed

    Balowski, Joseph J; Wang, Yuli; Allbritton, Nancy L

    2013-08-14

    A new lithography technique is presented that exploits the interactions of immiscible liquids with a structured surface. This highly parallel, "low-tech" method requires no dedicated equipment and easily produces curved and/or multi-level structures out of a variety of photoactive and non-photoactive materials. PMID:23798498

  5. The influence of 3d3 type transition metals on light scattering properties of sulfur cycle bacteria Desulfuromonas acetoxidans

    NASA Astrophysics Data System (ADS)

    Bilyi, Oleksandr I.; Vasyliv, Oresta M.; Hnatush, Svitlana O.; Getman, Vasyl B.; Kotsyumbas, Galyna I.

    2011-07-01

    Light scattering properties of bacterial cells mostly depend on their sizes, refractive indexes of their components and surrounding environment. Interaction between bacterial cells and 3d3 type transition metals causes their optical characteristics' changes. Desulfuromonas acetoxidans are uncolored gram-negative obligatory anaerobic sulfur reducing bacteria that can be used as microbial fuel cells with high electron recovery from different organic compounds oxidation to electric current as a result of electrons transfer in the processes of sulfur and some 3d3 type transition metals reduction, such as Ferrum and Manganese. In this study size distribution and relative content in the chosen interval of sizes (0.2 - 2.0 μm) of sulfur reducing D. acetoxidans bacterial cells under the influence of different concentrations of manganese chloride (II) hexahydrate, ferrous chloride (III) hexahydrate and ferrous sulfate (II) have been investigated by the new method of measuring. A method includes sounding of flow suspended bacterial cells by monochromatic coherent light, registration of signals of co-operation of sounding radiation with the explored microbiological objects by detects amplitudes and durations of scattered light impulses. Correlation between changes of light-scattering properties and growth of Desulfuromonas acetoxidans cells under these conditions has been shown.

  6. Determination of mass attenuation coefficients and effective atomic numbers for compounds of the 3d transition elements

    NASA Astrophysics Data System (ADS)

    Yılmaz, Demet; Boydaş, Elif; Cömert, Esra

    2016-08-01

    In this study, we aimed to determine mass attenuation coefficient (μm) and effective atomic number (Zeff) for some compounds of the 3d transition elements such as CoO, CoF2, CoF3, Cr2O3, CrF2, CrF3, FeO, Fe2O3, MnO2, TiO2, V2O3, VF3, V2O5, VF4 and ZnO at 19.63 and 22.10 keV photon energies by using an HPGe detector with a resolution of 182 eV at 5.9 keV. The experimental results of μm are compared with the theoretical results. Also, effective atomic numbers of compounds of the 3d transition elements have been determined by using experimental and theoretical mass attenuation coefficients. The agreement of measured values of effective atomic numbers with theoretical calculations is quite satisfactory.

  7. Development of a cryo-FIB technique for the 3D structural characterization of liquid samples

    NASA Astrophysics Data System (ADS)

    Tsuchiya, M.; Iwahori, T.; Morikawa, A.; Sato, T.; Nagakubo, Y.

    2015-10-01

    The observation of three-dimensional distributions in some liquids or colloids is important, for example in cosmetics, functional paints and a catalyst. Furthermore, there is increasing demand to microscopically investigate the structures inside a liquid colloid, such as the interface of a dispersoid and dispersant. In order to meet these requirements, we have developed a cryo-transfer holder which is fully compatible between FIB and TEM/STEM. The cross section of frozen emulsions and a thin film sample were made by FIB-SEM (NB5000). As a result, the dispersion state of a dispersoid was observed by sequential FIB and SEM. Furthermore a 100nm thick sample was made by FIB and observed by 200 kV STEM (HD- 2700). The dispersoid (TiO2 and Fe2O3) morphology and distribution were shown at nanometer level.

  8. Two phase liquid helium flow testing to simulate the operation of a cryocondensation pump in the D3-D tokamak

    NASA Astrophysics Data System (ADS)

    Laughon, G. J.; Baxi, C. B.; Campbell, G. L.; Mahdavi, M. A.; Makariou, C. C.; Smith, J. P.; Schaffer, M. J.; Schaubel, K. M.; Menon, M. M.

    1994-06-01

    A liquid helium-cooled cryocondensation pump has been installed in the D3-D tokamak fusion energy research experiment at General Atomics. The pump is located within the tokamak vacuum chamber beneath the divertor baffle plates and is utilized for plasma density and contamination control. Two-phase helium flows through the pump at 5 to 10 g/s utilizing the heat transfer and constant temperature characteristics of boiling liquid . helium. The pump is designed for a pumping speed of 32,000 1/s. Extensive testing was performed with a prototypical pump test fixture. Several pump geometries (simple tube, coaxial flow plug, and coaxial slotted insert) were tested, in an iterative process, to determine which was the most satisfactory for stable cryocondensation pumping. Results from the different tests illustrating the temperature distribution and flow characteristics for each configuration are presented.

  9. Giant perpendicular magnetocrystalline anisotropy of 3d transition-metal thin films on MgO

    SciTech Connect

    Nakamura, Kohji Ikeura, Yushi; Akiyama, Toru; Ito, Tomonori

    2015-05-07

    Magnetocrystalline anisotropy (MCA) of the Fe-based transition-metal thin films was investigated by means of first principles full-potential linearized augmented plane wave method. A giant perpendicular MCA (PMCA), up to 3 meV, was confirmed in a 7-layer Fe-Ni film/MgO(001), where an Fe{sub 2}/Ni/Fe/Ni/Fe{sub 2} atomic-layer alignment with a bcc-like-layer stacking and the Fe/MgO interfaces play key roles for leading to the large PMCA. Importantly, we find that the PMCA overcomes enough over the magnetic dipole-dipole anisotropy that favors the in-plane magnetization even when the film thickness increases.

  10. Linear and nonlinear instability and ligament dynamics in 3D laminar two-layer liquid/liquid flows

    NASA Astrophysics Data System (ADS)

    Ó Náraigh, Lennon; Valluri, Prashant; Scott, David; Bethune, Iain; Spelt, Peter

    2013-11-01

    We consider the linear and nonlinear stability of two-phase density-matched but viscosity contrasted fluids subject to laminar Poiseuille flow in a channel, paying particular attention to the formation of three-dimensional waves. The Orr-Sommerfeld-Squire analysis is used along with DNS of the 3D two-phase Navier-Stokes equations using our newly launched TPLS Solver (http://edin.ac/10cRKzS). For the parameter regimes considered, we demonstrate the existence of two distinct mechanisms whereby 3D waves enter the system, and dominate at late time. There exists a direct route, whereby 3D waves are amplified by the standard linear mechanism; for certain parameter classes, such waves grow at a rate less than but comparable to that of most-dangerous two-dimensional mode. Additionally, there is a weakly nonlinear route, whereby a purely spanwise wave couples to a streamwise mode and grows exponentially. We demonstrate these mechanisms in isolation and in concert. Consideration is also given to the ultimate state of these waves: persistent three-dimensional nonlinear waves are stretched and distorted by the base flow, thereby producing regimes of ligaments, ``sheets,'' or ``interfacial turbulence.'' HECToR RAP/dCSE Project e174, HPC-Europa 2.

  11. Coaxial electrospray of liquid core-hydrogel shell microcapsules for encapsulation and miniaturized 3D culture of pluripotent stem cells

    PubMed Central

    Zhao, Shuting; Agarwal, Pranay; Rao, Wei; Huang, Haishui; Zhang, Renliang; Liu, Zhenguo; Yu, Jianhua; Weisleder, Noah; Zhang, Wujie; He, Xiaoming

    2014-01-01

    A novel coaxial electrospray technology is developed to generate microcapsules with a hydrogel shell of alginate and an aqueous liquid core of living cells using two aqueous fluids in one step. Approximately 50 murine embryonic stem (ES) cells encapsulated in the core with high viability (92.3 ± 2.9%) can proliferate to form a single ES cell aggregate of 128.9 ± 17.4 μm in each microcapsule within 7 days. Quantitative analyses of gene and protein expression indicate that ES cells cultured in the miniaturized 3D liquid core of the core-shell microcapsules have significantly higher pluripotency on average than the cells cultured on 2D substrate or in the conventional 3D alginate hydrogel microbeads without a core-shell architecture. The higher pluripotency is further suggested by their significantly higher capability of differentiation into beating cardiomyocytes and higher expression of cardiomyocyte specific gene markers on average after directed differentiation under the same conditions. Considering its wide availability, easiness to set up and operate, reusability, and high production rate, the novel coaxial electrospray technology together with the microcapsule system is of importance for mass production of ES cells with high pluripotency to facilitate translation of the emerging pluripotent stem cell-based regenerative medicine into the clinic. PMID:25036382

  12. 3-D Numerical Simulation for Gas-Liquid Two-Phase Flow in Aeration Tank

    NASA Astrophysics Data System (ADS)

    Xue, R.; Tian, R.; Yan, S. Y.; Li, S.

    In the crafts of activated sludge treatment, oxygen supply and the suspending state of activated sludge are primary factors to keep biochemistry process carrying on normally. However, they are all controlled by aeration. So aeration is crucial. The paper focus on aeration, use CFD software to simulate the field of aeration tank which is designed by sludge load method. The main designed size of aeration tank is: total volume: 20 000 m3; corridor width: 8m; total length of corridors: 139m; number of corridors: 3; length of one single corridor: 48m; effective depth: 4.5m; additional depth: 0.5m. According to the similarity theory, a geometrical model is set up in proportion of 10:1. The way of liquid flow is submerge to avoid liquid flow out directly. The grid is plotted by dividing the whole computational area into two parts. The bottom part which contains gas pipe and gas exit hole and the above part which is the main area are plotted by tetrahedron and hexahedron respectively. In boundary conditions, gas is defined as the primary-phase, and liquid is defined as the secondary-phase. Choosing mixture model, two-phase flow field of aeration tank is simulated by solved the Continuity equation for the mixture, Momentum equation for the mixture, Volume fraction equation for the secondary phases and Relative velocity formula when gas velocity is 10m/s, 20m/s, 30m/s. what figure shows is the contour of velocity magnitude for the mixture phase when gas velocity is 20m/s. Through analysis, the simulation tendency is agreed with actual running of aeration tank. It is feasible to use mixture model to simulate flow field of aeration tank by fluent software. According to the simulation result, the better velocity of liquid or gas (the quantity of inlet air) can be chosen by lower cost, and also the performance of aeration tank can be forecast. It will be helpful for designing and operation.

  13. Heterobimetallic coordination polymers involving 3d metal complexes and heavier transition metals cyanometallates

    SciTech Connect

    Peresypkina, Eugenia V.; Samsonenko, Denis G.; Vostrikova, Kira E.

    2015-04-15

    The results of the first steps in the design of coordination polymers based on penta- and heptacyanometallates of heavier d transitions metals are presented. The 2D structure of the coordination polymers: [(Mn(acacen)){sub 2}Ru(NO)(CN){sub 5}]{sub n} and two complexes composed of different cyanorhenates, [Ni(cyclam)]{sub 2}[ReO(OH)(CN){sub 4}](ClO{sub 4}){sub 2}(H{sub 2}O){sub 1.25} and [Cu(cyclam)]{sub 2}[Re(CN){sub 7}](H{sub 2}O){sub 12}, was confirmed by single crystal XRD study, the rhenium oxidation state having been proved by the magnetic measurements. An amorphism of [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2} (M=Ni, Cu) polymers does not allow to define strictly their dimensionality and to model anisotropic magnetic behavior of the compounds. However, with high probability a honey-comb like layer structure could be expected for [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2} complexes, studied in this work, because such an arrangement is the most common among the bimetallic assemblies of hexa- and octacyanometallates with a ratio [M(cyclam)]/[M(CN){sub n}]=3/2. For the first time was prepared and fully characterized a precursor (n-Bu{sub 4}N){sub 2}[Ru(NO)(CN){sub 5}], soluble in organic media. - Graphical abstract: The very first results in the design of 2D coordination polymers based on penta- and heptacyanometallates of 4d and5d transitions metals are presented. - Highlights: • Design of coordination polymers based on penta- and heptacyanometallates. • New Ru and Re cyanide based heterobimetallic coordination complexes. • Hydrolysis and ox/red processes involving [Re(CN){sub 7}]{sup 3+} during crystallization. • High magnetic anisotropy of [M(cyclam)]{sub 3}[Re(CN){sub 7}]{sub 2}(H{sub 2}O){sub n}, M=Cu, Ni, complexes.

  14. Liquid-Liquid phase transition in a single component system

    NASA Astrophysics Data System (ADS)

    Franzese, Giancarlo; Skibinsky, Anna; Buldyrev, Sergey; Stanley, H. Eugene

    2001-06-01

    Recent experimental results indicate that phosphorus, a single-component system, can have a high-density liquid (HDL) and a low-density liquid (LDL) phase. A first-order LDL-HDL transition line ending in a critical point is consistent with experimental data and Molecular Dynamics (MD) simulations for a variety of single-component systems such as water, silica and carbon, but a coherent and general interpretation of the LDL-HDL transition is lacking. By means of MD, we show that the LDL-HDL transition can be directly related to an interaction potential with an attractive part and with not one but `two' preferred short-range repulsive distances. This kind of interaction is common to other single-component materials in the liquid state, in particular liquid metals. For the fisrt time, we show that the LDL-HDL transition can occur in systems with no density anomaly, opening an experimental challenge to uncover a liquid-liquid transition in systems like liquid metals, regardless of the presence of the density anomaly.

  15. 3D Behavior of Schottky Barriers of 2D Transition-Metal Dichalcogenides.

    PubMed

    Guo, Yuzheng; Liu, Dameng; Robertson, John

    2015-11-25

    The transition metal dichalcogenides (TMDs) are two-dimensional layered solids with van der Waals bonding between layers. We calculate their Schottky barrier heights (SBHs) using supercell models and density functional theory. It is found that the SBHs without defects are quite strongly pinned, with a pinning factor S of about S = 0.3, a similar value for both top and edge contact geometries. This arises because there is direct bonding between the contact metal atoms and the TMD chalcogen atoms, for both top and edge contact geometries, despite the weak interlayer bonding in the isolated materials. The Schottky barriers largely follow the metal induced gap state (MIGS) model, like those of three-dimensional semiconductors, despite the bonding in the TMDs being largely constrained within the layers. The pinning energies are found to be lower in the gap for edge contact geometries than for top contact geometries, which might be used to obtain p-type contacts on MoS2.

  16. Along-axis transition between narrow and wide rifts: Insights from 3D numerical experiments

    NASA Astrophysics Data System (ADS)

    Koptev, Alexander; Calais, Eric; Burov, Evgueni; Leroy, Sylvie; Gerya, Taras

    2016-04-01

    Based on performed high-resolution rheologically consistent three-dimensional thermo-mechanical numerical models, we show that there is a significant difference in the influence of the rheological profile on rifting style in the case of dominant active (plume-activated) rifting compared to dominant passive (far-field tectonic stresses) rifting. Narrow rifting, conventionally attributed to cold strong lithosphere in passive rifting mode, may develop in weak hot ultra-stretched lithosphere during active rifting, after plume impingement on a tectonically pre-stressed lithosphere. In that case, initially ultra-wide small-amplitude rift patterns focus, in a few Myr, in large-scale faults that form a narrow rift. Also, wide rifting may develop during ultra-slow spreading of strong lithosphere, and "switch" to the narrow rifting upon plume impingement. For further understanding the mechanisms behind the interactions between the mantle plume and far-field stresses in case of realistic horizontally heterogeneous lithosphere, we have tested our models on the case of the central East African Rift system (EARS). The EARS south of the Ethiopian Rift Valley bifurcates in two branches (eastern, magma-rich and western, magma-poor) surrounding the strong Tanzanian craton. Broad zones of low seismic velocity observed throughout the upper mantle beneath the central part of the EARS are consistent with the spreading of a deep mantle plume. The extensional features and topographic expression of the Eastern rift varies significantly north-southward: in northern Kenya the area of deformation is very wide (some 150-250 km in E-W direction), to the south the rift narrows to 60-70 km, yet further to the south this localized deformation widens again. Here we investigate this transition between localized and wide rifting using thermo-mechanical numerical modeling that couples, in a dynamic sense, the rise of the upper mantle material with the deformation of the African lithosphere below the

  17. Efficient Nonlinear Atomization Model for Thin 3D Free Liquid Films

    NASA Astrophysics Data System (ADS)

    Mehring, Carsten

    2007-03-01

    Reviewed is a nonlinear reduced-dimension thin-film model developed by the author and aimed at the prediction of spray formation from thin films such as those found in gas-turbine engines (e.g., prefilming air-blast atomizers), heavy-fuel-oil burners (e.g., rotary-cup atomizers) and in the paint industry (e.g., flat-fan atomizers). Various implementations of the model focusing on different model-aspects, i.e., effect of film geometry, surface tension, liquid viscosity, coupling with surrounding gas-phase flow, influence of long-range intermolecular forces during film rupture are reviewed together with a validation of the nonlinear wave propagation characteristics predicted by the model for inviscid planar films using a two-dimensional vortex- method. An extension and generalization of the current nonlinear film model for implementation into a commercial flow- solver is outlined.

  18. A liquid-liquid transition can exist in monatomic transition metals with a positive melting slope

    PubMed Central

    Lee, Byeongchan; Lee, Geun Woo

    2016-01-01

    Liquid-liquid transitions under high pressure are found in many elemental materials, but the transitions are known to be associated with either sp-valent materials or f-valent rare-earth elements, in which the maximum or a negative slope in the melting line is readily suggestive of the transition. Here we find a liquid-liquid transition with a positive melting slope in transition metal Ti from structural, electronic, and thermodynamic studies using ab-initio molecular dynamics calculations, showing diffusion anomaly, but no density anomaly. The origin of the transition in liquid Ti is a pressure-induced increase of local structures containing very short bonds with directionality in electronic configurations. This behavior appears to be characteristic of the early transition metals. In contrast, the late transition metal liquid Ni does not show the L-L transition with pressure. This result suggests that the possibility of the L-L transition decreases from early to late transition metals as electronic structures of late transition metals barely have a Jahn-Teller effect and bond directionality. Our results generalize that a phase transition in disordered materials is found with any valence band regardless of the sign of the melting slope, but related to the symmetry of electronic structures of constituent elements. PMID:27762334

  19. Generic mechanism for generating a liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Franzese, Giancarlo; Malescio, Gianpietro; Skibinsky, Anna; Buldyrev, Sergey V.; Stanley, H. Eugene

    2001-02-01

    Recent experimental results indicate that phosphorus-a single-component system-can have a high-density liquid (HDL) and a low-density liquid (LDL) phase. A first-order transition between two liquids of different densities is consistent with experimental data for a variety of materials, including single-component systems such as water, silica and carbon. Molecular dynamics simulations of very specific models for supercooled water, liquid carbon and supercooled silica predict a LDL-HDL critical point, but a coherent and general interpretation of the LDL-HDL transition is lacking. Here we show that the presence of a LDL and a HDL can be directly related to an interaction potential with an attractive part and two characteristic short-range repulsive distances. This kind of interaction is common to other single-component materials in the liquid state (in particular, liquid metals), and such potentials are often used to describe systems that exhibit a density anomaly. However, our results show that the LDL and HDL phases can occur in systems with no density anomaly. Our results therefore present an experimental challenge to uncover a liquid-liquid transition in systems like liquid metals, regardless of the presence of a density anomaly.

  20. Solid-liquid phase transition in argon

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Tang, H. T.

    1978-01-01

    Starting from the Lennard-Jones interatomic potential, a modified cell theory has been used to describe the solid-liquid phase transition in argon. The cell-size variations may be evaluated by a self-consistent condition. With the inclusion of cell-size variations, the transition temperature, the solid and liquid densities, and the liquid-phase radial-distribution functions have been calculated. These ab initio results are in satisfactory agreement with molecular-dynamics calculations as well as experimental data on argon.

  1. Defect energetics and magnetic properties of 3 d-transition-metal-doped topological crystalline insulator SnTe

    NASA Astrophysics Data System (ADS)

    Wang, Na; Wang, JianFeng; Si, Chen; Gu, Bing-Lin; Duan, WenHui

    2016-08-01

    The introduction of magnetism in SnTe-class topological crystalline insulators is a challenging subject with great importance in the quantum device applications. Based on the first-principles calculations, we have studied the defect energetics and magnetic properties of 3 d transition-metal (TM)-doped SnTe. We find that the doped TM atoms prefer to stay in the neutral states and have comparatively high formation energies, suggesting that the uniform TMdoping in SnTe with a higher concentration will be difficult unless clustering. In the dilute doping regime, all the magnetic TMatoms are in the high-spin states, indicating that the spin splitting energy of 3 d TM is stronger than the crystal splitting energy of the SnTe ligand. Importantly, Mn-doped SnTe has relatively low defect formation energy, largest local magnetic moment, and no defect levels in the bulk gap, suggesting that Mn is a promising magnetic dopant to realize the magnetic order for the theoretically-proposed large-Chern-number quantum anomalous Hall effect (QAHE) in SnTe.

  2. Liquid-Liquid Phase Transition in Nanoconfined Silicon Carbide.

    PubMed

    Wu, Weikang; Zhang, Leining; Liu, Sida; Ren, Hongru; Zhou, Xuyan; Li, Hui

    2016-03-01

    We report theoretical evidence of a liquid-liquid phase transition (LLPT) in liquid silicon carbide under nanoslit confinement. The LLPT is characterized by layering transitions induced by confinement and pressure, accompanying the rapid change in density. During the layering transition, the proportional distribution of tetracoordinated and pentacoordinated structures exhibits remarkable change. The tricoordinated structures lead to the microphase separation between silicon (with the dominant tricoordinated, tetracoordinated, and pentacoordinated structures) and carbon (with the dominant tricoordinated structures) in the layer close to the walls. A strong layer separation between silicon atoms and carbon atoms is induced by strong wall-liquid forces. Importantly, the pressure confinement phase diagram with negative slopes for LLPT lines indicates that, under high pressure, the LLPT is mainly confinement-induced, but under low pressure, it becomes dominantly pressure-induced.

  3. Liquid-Liquid Phase Transition in Nanoconfined Silicon Carbide.

    PubMed

    Wu, Weikang; Zhang, Leining; Liu, Sida; Ren, Hongru; Zhou, Xuyan; Li, Hui

    2016-03-01

    We report theoretical evidence of a liquid-liquid phase transition (LLPT) in liquid silicon carbide under nanoslit confinement. The LLPT is characterized by layering transitions induced by confinement and pressure, accompanying the rapid change in density. During the layering transition, the proportional distribution of tetracoordinated and pentacoordinated structures exhibits remarkable change. The tricoordinated structures lead to the microphase separation between silicon (with the dominant tricoordinated, tetracoordinated, and pentacoordinated structures) and carbon (with the dominant tricoordinated structures) in the layer close to the walls. A strong layer separation between silicon atoms and carbon atoms is induced by strong wall-liquid forces. Importantly, the pressure confinement phase diagram with negative slopes for LLPT lines indicates that, under high pressure, the LLPT is mainly confinement-induced, but under low pressure, it becomes dominantly pressure-induced. PMID:26859609

  4. Multigrid mapping and box relaxation for simulation of the whole process of flow transition in 3-D boundary layers

    SciTech Connect

    Liu, C.; Liu, Z.

    1994-12-31

    A new multilevel technology was developed in this study which provides a successful numerical simulation for the whole process of flow transition in 3-D flat plate boundary layers, including linear growth, secondary instability, breakdown, and transition on a relatively coarse grid with low CPU cost. A fourth-order finite difference scheme on stretched and staggered grids, a fully implicit time-marching technique, a semi-coarsening multigrid based on the so-called approximate line-box relaxation, and a buffer domain for the outflow boundary conditions were all employed for high-order accuracy, good stability, and fast convergence. A new fine-coarse-fine grid mapping technique was developed to catch the large eddies and represent main roles of small eddies to keep the code running after the laminar flow breaks down. The computational results are in good agreement with linear stability theory, secondary instability theory, and some experiments. The computation also reproduced the K-type and C-type transition observed by laboratory experiments. The CPU cost for a typical case is around 2-9 CRAY-YMP hours.

  5. Plate deformation at the transition between collision and subduction: insights from 3D thermo-mechanical laboratory experiments

    NASA Astrophysics Data System (ADS)

    Boutelier, D. A.; Cruden, A. R.; Oncken, O.

    2012-04-01

    3-D thermo-mechanical laboratory experiments of arc-continent collision investigate plate deformation at the transition between collision and subduction. Deformation in the collision area propagates into the subduction-collision transition zone via along-strike coupling of the neighboring segments of the plate boundary. The largest along-strike gradient of trench-perpendicular compression produced by a passive margin turning by 90 degrees does not generate sufficiently localized shear strain in the transition zone to cause a strike-slip system. This is because of the fast propagation of lithosphere failure in the arc area. Deformation is thus continuous along-strike, but the deformation mechanism is three-dimensional and progressive structural variations arise because the coupling between neighboring segments induces either advanced or delayed failure of the arc lithosphere and passive margin. During the initial stage of collision, the accretionary wedge is partially subducted, the interplate zone is lubricated, and shear traction drops. Thus large convergence obliquity does not produce a migrating fore-arc sliver. Instead, the fore-arc motion is due to the pressure force generated by subduction of the buoyant continental crust. It follows that convergence obliquity does not yield trench-parallel deformation of the fore-arc and its influence on the collision process is limited. However, convergence obliquity may have shaped the active margin during the stage of oceanic subduction stage, prior to collision, and inherited structures may impact the propagation mechanism.

  6. First-Principles Study of Electronic Structure and Hydrogen Adsorption of 3d Transition Metal Exposed Paddle Wheel Frameworks

    SciTech Connect

    Bak, J. H.; Le, V. D.; Kang, J.; Wei, S. H.; Kim, Y. H.

    2012-04-05

    Open-site paddle wheels, comprised of two transition metals bridged with four carboxylate ions, have been widely used for constructing metal-organic frameworks with large surface area and high binding energy sites. Using first-principles density functional theory calculations, we have investigated atomic and electronic structures of various 3d transition metal paddle wheels before and after metal exposure and their hydrogen adsorption properties at open metal sites. Notably, the hydrogen adsorption is impeded by covalent metal-metal bonds in early transition metal paddle wheels from Sc to Cr and by the strong ferromagnetic coupling of diatomic Mn and Fe in the paddle wheel configurations. A significantly enhanced H{sub 2} adsorption is predicted in the nonmagnetic Co{sub 2} and Zn{sub 2} paddle wheel with the binding energy of {approx}0.2 eV per H{sub 2}. We also propose the use of two-dimensional Co{sub 2} and Zn{sub 2} paddle wheel frameworks that could have strongly adsorbed dihydrogen up to 1.35 wt % for noncryogenic hydrogen storage applications.

  7. Calculations with spectroscopic accuracy for the ground configuration (3 d9 ) forbidden transition in Co-like ions

    NASA Astrophysics Data System (ADS)

    Guo, X. L.; Si, R.; Li, S.; Huang, M.; Hutton, R.; Wang, Y. S.; Chen, C. Y.; Zou, Y. M.; Wang, K.; Yan, J.; Li, C. Y.; Brage, T.

    2016-01-01

    We present systematic and large-scale calculations for the fine-structure energy splitting and transition rate between the 3 d93/2,5/2,2D levels of Co-like ions with 28 ≤Z ≤100 . Two different fully relativistic approaches are used, based on the multiconfiguration Dirac-Hartree-Fock (MCDHF) theory and the relativistic many-body-perturbation theory (RMBPT). Especially the former gives results of similar accuracy as experiments for a large range of ions. Our calculations are therefore accurate enough to probe Breit and quantum-electro-dynamic effects. To obtain spectroscopic accuracy, we show that it is important to include deep core-valence correlation, down to and including the n =2 shell. We estimate that the uncertainties of our wavelengths are within the uncertainty of experiments, i.e., 0.02%. We also show that the frequently used flexible atomic code has an inaccurate treatment of the self-energy (SE) contribution and of the M 1 -transition properties for lower-Z ions. After correcting for the SE calculation, the resulting RMBPT transition energies are in good agreement with the MCDHF ones, especially for the high-Z end of the Co-like sequence.

  8. Experimental wavelengths for intrashell transitions in tungsten ions with partially filled 3p and 3d subshells

    NASA Astrophysics Data System (ADS)

    Lennartsson, Thomas; Clementson, Joel; Beiersdorfer, Peter

    2013-06-01

    Spectra and measured wavelengths of intrashell n=3 transitions in highly charged tungsten ions with partially filled 3p and 3d valence shells, Al-like W61+ through Fe-like W48+, are presented. The ions were created and excited at the electron-beam ion-trap facility at the Lawrence Livermore National Laboratory and measured with a high-resolution grazing-incidence spectrometer. The spectral lines were studied in the 27-41 Å range and were analyzed by a comparison with synthetic spectra based on a collisional-radiative model. We determined that the emission includes not only electric-dipole-allowed transitions, but also several electric-quadrupole and magnetic-dipole transitions. Line-position uncertainties as low as 25 ppm were achieved. Thus, our measurements provide much-needed benchmarks for calculations of the atomic structure of highly charged ions with a partially filled subshell, since these ions are difficult to calculate due to electron-correlation effects.

  9. Electronic structure of the chiral helimagnet and 3 d -intercalated transition metal dichalcogenide C r1 /3Nb S2

    NASA Astrophysics Data System (ADS)

    Sirica, N.; Mo, S.-K.; Bondino, F.; Pis, I.; Nappini, S.; Vilmercati, P.; Yi, J.; Gai, Z.; Snijders, P. C.; Das, P. K.; Vobornik, I.; Ghimire, N.; Koehler, M. R.; Li, L.; Sapkota, D.; Parker, D. S.; Mandrus, D. G.; Mannella, N.

    2016-08-01

    The electronic structure of the chiral helimagnet C r1 /3Nb S2 has been studied with core level and angle-resolved photoemission spectroscopy (ARPES). Intercalated Cr atoms are found to be effective in donating electrons to the Nb S2 layers but also cause significant modifications of the electronic structure of the host Nb S2 material. In particular, the data provide evidence that a description of the electronic structure of C r1 /3Nb S2 on the basis of a simple rigid band picture is untenable. The data also reveal substantial inconsistencies with the predictions of standard density functional theory. The relevance of these results to the attainment of a correct description of the electronic structure of chiral helimagnets, magnetic thin films/multilayers, and transition metal dichalcogenides intercalated with 3 d magnetic elements is discussed.

  10. Modeling STM tips by single absorbed atoms on W(100) films: 3d and 4d transition-metal atoms

    NASA Astrophysics Data System (ADS)

    Hofer, W. A.; Redinger, J.; Podloucky, R.

    2001-09-01

    In order to provide comprehensive data on the electronic structure of realistic STM tips we have studied tungsten (100) films with adsorbed single 3d and 4d transition-metal atoms by ab initio molecular-dynamics and full potential methods. Molecular dynamics using ultrasoft pseudopotentials has been used to determine the relaxation of adsorbate and surface layers. Subsequently the electronic structure of the relaxed model tip has been calculated with an all-electron full potential method. The results suggest that the chemical nature of the tip apex to a high degree determines achievable corrugations and that results for current and corrugation values in a perturbation approach might be considerably improved by including the electronic structure of the tip.

  11. The K x-ray line structures of the 3d-transition metals in warm dense plasma

    NASA Astrophysics Data System (ADS)

    Szymańska, E.; Syrocki, Ł.; Słabkowska, K.; Polasik, M.; Rzadkiewicz, J.

    2016-09-01

    The shapes and positions of the Kα1 and Kα2 x-ray lines for 3d-transition metals can vary substantially as electrons are stripped from the outer-shells. This paper shows the detailed line shapes for nickel and zinc, obtained by calculations with a multiconfiguration Dirac-Fock method that includes Breit interaction and quantum electrodynamics corrections. The line shapes can be useful in interpreting hot, dense plasmas with energetic electrons for which the K x-ray lines are optically thin, as may be produced by pulsed power machines such as the plasma-filled rod pinch diode or the plasma focus, or in short-pulsed high power laser plasmas.

  12. Relative stability of normal vs. inverse spinel for 3d transition metal oxides as lithium intercalation cathodes.

    PubMed

    Bhattacharya, Jishnu; Wolverton, C

    2013-05-01

    Spinel oxides represent an important class of cathode materials for Li-ion batteries. Two major variants of the spinel crystal structure are normal and inverse. The relative stability of normal and inverse ordering at different stages of lithiation has important consequences in lithium diffusivity, voltage, capacity retention and battery life. In this paper, we investigate the relative structural stability of normal and inverse structures of the 3d transition metal oxide spinels with first-principles DFT calculations. We have considered ternary spinel oxides LixM2O4 with M = Ti, V, Cr, Mn, Fe, Co and Ni in both lithiated (x = 1) and delithiated (x = 0) conditions. We find that for all lithiated spinels, the normal structure is preferred regardless of the metal. We observe that the normal structure for all these oxides has a lower size mismatch between octahedral cations compared to the inverse structure. With delithiation, many of the oxides undergo a change in stability with vanadium in particular, showing a tendency to occupy tetrahedral sites. We find that in the delithiated oxide, only vanadium ions can access a +5 oxidation state which prefers tetrahedral coordination. We have also calculated the average voltage of lithiation for these spinels. The calculated voltages agree well with the previously measured and calculated values, wherever available. For the yet to be characterized spinels, our calculation provides voltage values which can motivate further experimental attention. Lastly, we observe that all the normal spinel oxides of the 3d transition metal series have a driving force for a transformation to the non-spinel structure upon delithiation.

  13. Modeling liquid-liquid phase transitions and quasicrystal formation

    NASA Astrophysics Data System (ADS)

    Skibinsky, Anna

    In this thesis, studies which concern two different subjects related to phase transitions in fluids and crystalline solids are presented. Condensed matter formation, structure, and phase transitions are modeled using molecular dynamics simulations of simple discontinuous potentials with attractive and repulsive interactions. Novel phase diagrams are proposed for quasicrystals, crystals, and liquids. In the first part of the thesis, the formation of a quasicrystal in a two dimensional monodisperse system is investigated using molecular dynamics simulations of hard sphere particles interacting via a two-dimensional square-well potential. It is found that for certain values of the square-well parameters more than one stable crystalline phase can form. By quenching the liquid phase at a very low temperature, an amorphous phase is obtained. When this the amorphous phase is heated, a quasicrystalline structure with five-fold symmetry forms. From estimations of the Helmholtz potentials of the stable crystalline phases and of the quasicrystal, it is concluded that within a specific temperature range, the observed quasicrystal phase can be the stable phase. The second part of the thesis concerns a study of the liquid-liquid phase transition for a single-component system in three dimensions, interacting via an isotropic potential with a repulsive soft-core shoulder at short distance and an attractive well at an intermediate distance. The potential is similar to potentials used to describe such liquid systems as colloids, protein solutions, or liquid metals. It is shown that the phase diagram for such a potential can have two lines of first-order fluid-fluid phase transitions: one separating a gas and a low-density liquid (LDL), and another between the LDL and a high-density liquid (HDL). Both phase transition lines end in a critical point, a gas-LDL critical point and, depending on the potential parameters, either a gas-HDL critical point or a LDL-HDL critical point. A

  14. A full 3D model of fluid flow and heat transfer in an E.B. heated liquid metal bath

    NASA Astrophysics Data System (ADS)

    Matveichev, A.; Jardy, A.; Bellot, J. P.

    2016-07-01

    In order to study the dissolution of exogeneous inclusions in the liquid metal during processing of titanium alloys, a series of dipping experiments has been performed in an Electron Beam Melting laboratory furnace. Precise determination of the dissolution kinetics requires knowing and mastering the exact thermohydrodynamic behavior of the melt pool, which implies full 3D modeling of the process. To achieve this goal, one needs to describe momentum and heat transfer, phase change, as well as the development of flow turbulence in the liquid. EB power input, thermal radiation, heat loss through the cooling circuit, surface tension effects (i.e. Marangoni-induced flow) must also be addressed in the model. Therefore a new solver dealing with all these phenomena was implemented within OpenFOAM platform. Numerical results were compared with experimental data from actual Ti melting, showing a pretty good agreement. In the second stage, the immersion of a refractory sample rod in the liquid pool was simulated. Results of the simulations showed that the introduction of the sample slightly disturbs the flow field inside the bath. The amount of such disturbance depends on the exact location of the dipping.

  15. 3D structures of liquid-phase GaIn alloy embedded in PDMS with freeze casting.

    PubMed

    Fassler, Andrew; Majidi, Carmel

    2013-11-21

    Liquid phase electronic circuits are created by freeze casting gallium-indium (GaIn) alloys, such as eutectic gallium-indium (EGaIn), and encapsulating these frozen components within an elastomer. These metal alloys are liquid at room temperature, and can be cast using either injection or a vacuum to fill a PDMS mold and placing the mold in a freezer. Once solidified, a GaIn alloy segment can be manipulated, altered, or bonded to other circuit elements. A stretchable circuit can be fabricated by placing frozen components onto an elastomer substrate, which can be either patterned or flat, and sealing with an additional layer of elastomer. Circuits produced in this fashion are soft, stretchable, and can have complex 3D channel geometries. In contrast, current fabrication techniques, including needle injection, mask deposition, and microcontact printing, are limited to 2D planar designs. Additionally, freeze casting fabrication can create closed loops, multi-terminal circuits with branching features, and large area geometries. PMID:24067934

  16. 3D printed titanium micro-bore columns containing polymer monoliths for reversed-phase liquid chromatography.

    PubMed

    Gupta, Vipul; Talebi, Mohammad; Deverell, Jeremy; Sandron, Sara; Nesterenko, Pavel N; Heery, Brendan; Thompson, Fletcher; Beirne, Stephen; Wallace, Gordon G; Paull, Brett

    2016-03-01

    The potential of 3D selective laser melting (SLM) technology to produce compact, temperature and pressure stable titanium alloy chromatographic columns is explored. A micro bore channel (0.9 mm I.D. × 600 mm long) was produced within a 5 × 30 × 30 mm titanium alloy (Ti-6Al-4V) cuboid, in form of a double handed spiral. A poly(butyl methacrylate-co-ethyleneglycoldimethacrylate) (BuMA-co-EDMA) monolithic stationary phase was thermally polymerised within the channel for application in reversed-phase high-performance liquid chromatography. The prepared monolithic column was applied to the liquid chromatographic separation of intact proteins and peptides. Peak capacities of 69-76 (for 6-8 proteins respectively) were observed during isothermal separation of proteins at 44 °C which were further increased to 73-77 using a thermal step gradient with programmed temperature from 60 °C to 35 °C using an in-house built direct-contact heater/cooler platform based upon matching sized Peltier thermoelectric modules. Rapid temperature gradients were possible due to direct-contact between the planar metal column and the Peltier module, and the high thermal conductivity of the titanium column as compared to a similar stainless steel printed column. The separation of peptides released from a digestion of E.coli was also achieved in less than 35 min with ca. 40 distinguishable peaks at 210 nm. PMID:26873472

  17. 3D printed titanium micro-bore columns containing polymer monoliths for reversed-phase liquid chromatography.

    PubMed

    Gupta, Vipul; Talebi, Mohammad; Deverell, Jeremy; Sandron, Sara; Nesterenko, Pavel N; Heery, Brendan; Thompson, Fletcher; Beirne, Stephen; Wallace, Gordon G; Paull, Brett

    2016-03-01

    The potential of 3D selective laser melting (SLM) technology to produce compact, temperature and pressure stable titanium alloy chromatographic columns is explored. A micro bore channel (0.9 mm I.D. × 600 mm long) was produced within a 5 × 30 × 30 mm titanium alloy (Ti-6Al-4V) cuboid, in form of a double handed spiral. A poly(butyl methacrylate-co-ethyleneglycoldimethacrylate) (BuMA-co-EDMA) monolithic stationary phase was thermally polymerised within the channel for application in reversed-phase high-performance liquid chromatography. The prepared monolithic column was applied to the liquid chromatographic separation of intact proteins and peptides. Peak capacities of 69-76 (for 6-8 proteins respectively) were observed during isothermal separation of proteins at 44 °C which were further increased to 73-77 using a thermal step gradient with programmed temperature from 60 °C to 35 °C using an in-house built direct-contact heater/cooler platform based upon matching sized Peltier thermoelectric modules. Rapid temperature gradients were possible due to direct-contact between the planar metal column and the Peltier module, and the high thermal conductivity of the titanium column as compared to a similar stainless steel printed column. The separation of peptides released from a digestion of E.coli was also achieved in less than 35 min with ca. 40 distinguishable peaks at 210 nm.

  18. Experiments performed with bubbly flow in vertical pipes at different flow conditions covering the transition region: simulation by coupling Eulerian, Lagrangian and 3D random walks models

    NASA Astrophysics Data System (ADS)

    Muñoz-Cobo, José; Chiva, Sergio; El Aziz Essa, Mohamed; Mendes, Santos

    2012-08-01

    Two phase flow experiments with different superficial velocities of gas and water were performed in a vertical upward isothermal cocurrent air-water flow column with conditions ranging from bubbly flow, with very low void fraction, to transition flow with some cap and slug bubbles and void fractions around 25%. The superficial velocities of the liquid and the gas phases were varied from 0.5 to 3 m/s and from 0 to 0.6 m/s, respectively. Also to check the effect of changing the surface tension on the previous experiments small amounts of 1-butanol were added to the water. These amounts range from 9 to 75 ppm and change the surface tension. This study is interesting because in real cases the surface tension of the water diminishes with temperature, and with this kind of experiments we can study indirectly the effect of changing the temperature on the void fraction distribution. The following axial and radial distributions were measured in all these experiments: void fraction, interfacial area concentration, interfacial velocity, Sauter mean diameter and turbulence intensity. The range of values of the gas superficial velocities in these experiments covered the range from bubbly flow to the transition to cap/slug flow. Also with transition flow conditions we distinguish two groups of bubbles in the experiments, the small spherical bubbles and the cap/slug bubbles. Special interest was devoted to the transition region from bubbly to cap/slug flow; the goal was to understand the physical phenomena that take place during this transition A set of numerical simulations of some of these experiments for bubbly flow conditions has been performed by coupling a Lagrangian code, that tracks the three dimensional motion of the individual bubbles in cylindrical coordinates inside the field of the carrier liquid, to an Eulerian model that computes the magnitudes of continuous phase and to a 3D random walk model that takes on account the fluctuation in the velocity field of the

  19. Liquid-liquid phase transition in a two-dimensional system with anomalous liquid properties.

    PubMed

    Urbic, Tomaz

    2013-12-01

    The phase diagram of the two-dimensional particles interacting through a smooth version of Stell-Hemmer interaction was studied using Monte Carlo computer simulations. By evaluating the pressure-volume isotherms, we observed liquid-liquid, liquid-gas phase transitions and three stable crystal phases. The model shows the liquid-liquid critical point in stable liquid phase and is confirmed by observing properties of other thermodynamic functions such as heat capacity and isothermal compressibility, for example. The liquid-gas and the liquid-liquid critical points were estimated within the thermodynamic limit.

  20. Orientational transitions in antiferromagnetic liquid crystals

    NASA Astrophysics Data System (ADS)

    Zakhlevnykh, A. N.; Petrov, D. A.

    2016-09-01

    The orientational phases in an antiferromagnetic liquid crystal (ferronematic) based on the nematic liquid crystal with the negative anisotropy of diamagnetic susceptibility are studied in the framework of the continuum theory. The ferronematic was assumed to be compensated; i.e., in zero field, impurity ferroparticles with the magnetic moments directed parallel and antiparallel to the director are equiprobably distributed in it. It is established that under the action of a magnetic field the ferronematic undergoes orientational transitions compensated (antiferromagnetic) phase-non-uniform phase-saturation (ferrimagnetic) phase. The analytical expressions for threshold fields of the transitions as functions of material parameters are obtained. It is shown that with increasing magnetic impurity segregation parameter, the threshold fields of the transitions significantly decrease. The bifurcation diagram of the ferronematic orientational phases is built in terms of the energy of anchoring of magnetic particles with the liquid-crystal matrix and magnetic field. It is established that the Freedericksz transition is the second-order phase transition, while the transition to the saturation state can be second- or first-order. In the latter case, the suspension exhibits orientational bistability. The orientational and magnetooptical properties of the ferronematic in different applied magnetic fields are studied.

  1. The role of 3D microenvironmental organization in MCF-7 epithelial–mesenchymal transition after 7 culture days

    SciTech Connect

    Foroni, Laura; Vasuri, Francesco; Valente, Sabrina; Gualandi, Chiara; Focarete, Maria Letizia; Caprara, Giacomo; Scandola, Mariastella; D'Errico-Grigioni, Antonia; Pasquinelli, Gianandrea

    2013-06-10

    We present a multi-technique study on in vitro epithelial–mesenchymal transition (EMT) in human MCF-7 cells cultured on electrospun scaffolds of poly(L-lactic acid) (PLA), with random and aligned fiber orientations. Our aim is to investigate the morphological and genetic characteristics induced by extracellular matrix in tumor cells cultured in different 3D environments, and at different time points. Cell vitality was assessed with AlamarBlue at days 1, 3, 5 and 7. Scanning electron microscopy was performed at culture days 3 and 7. Immunohistochemistry (for E-cadherin, β-catenin, cytokeratins, nucleophosmin, tubulin, Ki-67 and vimentin), immunofluorescence (for F-actin) western blot (for E-cadherin, β-catenin and vimentin) and transmission electron microscopy were carried out at day 7. An EMT gene array followed by PCR analysis confirmed the regulation of selected genes. At day 7, scanning electron microscopy on aligned-PLA revealed spindle-shaped cells gathered in buds and ribbon-like structures, with a higher nucleolar/nuclear ratio and a loss in E-cadherin and β-catenin at immunohistochemistry and western blot. An up-regulation of SMAD2, TGF-β2, TFPI2 and SOX10 was found in aligned-PLA compared to random-PLA cultured cells. The topography of the extracellular matrix has a role in tumor EMT, and a more aggressive phenotype characterizes MCF-7 cells cultured on aligned-PLA scaffold. -- Highlights: • After 7 culture days an aligned-PLA scaffold induces a spindle shape to MCF-7 cells. • Despite these changes, the aligned MCF-7 cells keep an epithelial phenotype. • The extracellular environment alone influences the E-cadherin/β-catenin axis. • The extracellular environment can promote the epithelial–mesenchymal transition.

  2. Verification of proton range, position, and intensity in IMPT with a 3D liquid scintillator detector system

    SciTech Connect

    Archambault, L.; Poenisch, F.; Sahoo, N.; Robertson, D.; Lee, A.; Gillin, M. T.; Mohan, R.; Beddar, S.

    2012-03-15

    Purpose: Intensity-modulated proton therapy (IMPT) using spot scanned proton beams relies on the delivery of a large number of beamlets to shape the dose distribution in a highly conformal manner. The authors have developed a 3D system based on liquid scintillator to measure the spatial location, intensity, and depth of penetration (energy) of the proton beamlets in near real-time. Methods: The detector system consists of a 20 x 20 x 20 cc liquid scintillator (LS) material in a light tight enclosure connected to a CCD camera. This camera has a field of view of 25.7 by 19.3 cm and a pixel size of 0.4 mm. While the LS is irradiated, the camera continuously acquires images of the light distribution produced inside the LS. Irradiations were made with proton pencil beams produced with a spot-scanning nozzle. Pencil beams with nominal ranges in water between 9.5 and 17.6 cm were scanned to irradiate an area of 10 x 10 cm square on the surface of the LS phantom. Image frames were acquired at 50 ms per frame. Results: The signal to noise ratio of a typical Bragg peak was about 170. Proton range measured from the light distribution produced in the LS was accurate to within 0.3 mm on average. The largest deviation seen between the nominal and measured range was 0.6 mm. Lateral position of the measured pencil beam was accurate to within 0.4 mm on average. The largest deviation seen between the nominal and measured lateral position was 0.8 mm; however, the accuracy of this measurement could be improved by correcting light scattering artifacts. Intensity of single proton spots were measured with precision ranging from 3 % for the smallest spot intensity (0.005 MU) to 0.5 % for the largest spot (0.04 MU). Conclusions: Our LS detector system has been shown to be capable of fast, submillimeter spatial localization of proton spots delivered in a 3D volume. This system could be used for beam range, intensity and position verification in IMPT.

  3. Effect of 3d-transition metal doping on the shielding behavior of barium borate glasses: a spectroscopic study.

    PubMed

    ElBatal, H A; Abdelghany, A M; Ghoneim, N A; ElBatal, F H

    2014-12-10

    UV-visible and FT infrared spectra were measured for prepared samples before and after gamma irradiation. Base undoped barium borate glass of the basic composition (BaO 40%-B2O3 60mol.%) reveals strong charge transfer UV absorption bands which are related to unavoidable trace iron impurities (Fe(3+)) within the chemical raw materials. 3d transition metal (TM)-doped glasses exhibit extra characteristic absorption bands due to each TM in its specific valence or coordinate state. The optical spectra show that TM ions favor generally the presence in the high valence or tetrahedral coordination state in barium borate host glass. Infrared absorption bands of all prepared glasses reveal the appearance of both triangular BO3 units and tetrahedral BO4 units within their characteristic vibrational modes and the TM-ions cause minor effects because of the low doping level introduced (0.2%). Gamma irradiation of the undoped barium borate glass increases the intensity of the UV absorption together with the generation of an induced broad visible band at about 580nm. These changes are correlated with suggested photochemical reactions of trace iron impurities together with the generation of positive hole center (BHC or OHC) within the visible region through generated electrons and positive holes during the irradiation process.

  4. 3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2.

    PubMed

    Jin, Z; Xia, Z-C; Wei, M; Yang, J-H; Chen, B; Huang, S; Shang, C; Wu, H; Zhang, X-X; Huang, J-W; Ouyang, Z-W

    2016-10-01

    The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration. PMID:27485370

  5. First-principles study of nitric oxide oxidation on Pt(111) versus Pt overlayer on 3d transition metals

    SciTech Connect

    Arevalo, Ryan Lacdao; Escaño, Mary Clare Sison; Kasai, Hideaki

    2015-03-15

    Catalytic oxidation of NO to NO{sub 2} is a significant research interest for improving the quality of air through exhaust gas purification systems. In this paper, the authors studied this reaction on pure Pt and Pt overlayer on 3d transition metals using kinetic Monte Carlo simulations coupled with density functional theory based first principles calculations. The authors found that on the Pt(111) surface, NO oxidation proceeds via the Eley–Rideal mechanism, with O{sub 2} dissociative adsorption as the rate-determining step. The oxidation path via the Langmuir–Hinshelwood mechanism is very slow and does not significantly contribute to the overall reaction. However, in the Pt overlayer systems, the oxidation of NO on the surface is more thermodynamically and kinetically favorable compared to pure Pt. These findings are attributed to the weaker binding of O and NO on the Pt overlayer systems and the binding configuration of NO{sub 2} that promotes easier N-O bond formation. These results present insights for designing affordable and efficient catalysts for NO oxidation.

  6. First-principle study of the electronic structure and magnetism of lithium-adsorbed 3d transition-metal phthalocyanines

    NASA Astrophysics Data System (ADS)

    Wang, M.; Hu, Y.; Zhang, Z.; Li, Y.; Zhou, T.; Ren, J.

    2016-02-01

    Based on density functional theory (DFT) calculations, the electronic structures and magnetic properties of 3d transition-metal phthalocyanine (TMPc, TM = Ti, V, Cr, Mn, Fe, Co, Ni and Cu), as well as Li-adsorbed phthalocyanines have been studied. The results show that the pristine TMPcs all have a good D4h symmetry. When there is one Li atom adsorbed on TMPcs directly over (LiTMPc-α) or slantly above (LiTMPc-β) the TM atoms, the geometries and electronic structures will be changed. For LiTMPc-α systems, the central TM atoms will deviate from the molecular plane and the molecules exhibit good C4v symmetry. LiTMPc-β systems are more stable than LiTMPc-α systems but it do not possess D4h and C4v symmetries. The total and local magnetic moments and the charge transfer are also presented. Finally, by using the orbit mixing and splitting theory under D4h and C4v symmetry, we get the ordering of the energy levels of the central TM atoms.

  7. Electronic and magnetic properties of monolayer SiC sheet doped with 3d-transition metals

    NASA Astrophysics Data System (ADS)

    Bezi Javan, Masoud

    2016-03-01

    We theoretically studied the electronic and magnetic properties of the monolayer SiC sheet doped by 3d transition-metal (TM) atoms. The structural properties, induced strain, electronic and magnetic properties were studied for cases that a carbon or silicon of the SiC sheet replaced with TM atoms. We found that the mount of induced strain to the lattice structure of the SiC sheet with substituting TM atoms is different for Si (TMSi) and C (TMC) sites as the TMSi structures have lower value of the strain. Also the TM atoms can be substituted in the lattice of the SiC sheet with different binding energy values for TMSi and TMC structures as the TMSi structures have higher value of the binding energies. Dependent to the structural properties, the TM doped SiC sheets show magnetic or nonmagnetic properties. We found that some structures such as MnSi, CuSi and CoC configurations have significant total magnetic moment about 3 μB.

  8. 3D spin-flop transition in enhanced 2D layered structure single crystalline TlCo2Se2

    NASA Astrophysics Data System (ADS)

    Jin, Z.; Xia, Z.-C.; Wei, M.; Yang, J.-H.; Chen, B.; Huang, S.; Shang, C.; Wu, H.; Zhang, X.-X.; Huang, J.-W.; Ouyang, Z.-W.

    2016-10-01

    The enhanced 2D layered structure single crystalline TlCo2Se2 has been successfully fabricated, which exhibits field-induced 3D spin-flop phase transitions. In the case of the magnetic field parallel to the c-axis (B//c), the applied magnetic field induces the evolution of the noncollinear helical magnetic coupling into a ferromagnetic (FM) state with all the magnetization of the Co ion parallel to the c-axis. A striking variation of the field-induced strain within the ab-plane is noticed in the magnetic field region of 20-30 T. In the case of the magnetic field perpendicular to the c-axis (B  ⊥  c), the inter-layer helical antiferromagnetic (AFM) coupling may transform to an initial canted AFM coupling, and then part of it transforms to an intermediate metamagnetic phase with the alignment of two-up-one-down Co magnetic moments and finally to an ultimate FM coupling in higher magnetic fields. The robust noncollinear AFM magnetic coupling is completely destroyed above 30 T. In combination with the measurements of magnetization, magnetoresistance and field-induced strain, a complete magnetic phase diagram of the TlCo2Se2 single crystal has been depicted, demonstrating complex magnetic structures even though the crystal geometry itself gives no indication of the magnetic frustration.

  9. A Novel Liquid-Liquid Transition in Undercooled Ti-Zr-Ni Liquids

    NASA Technical Reports Server (NTRS)

    Lee, G. W.; Gangopadhyay, A. K.; Kelton, K. F.; Bradshaw, R. C.; Hyers, R. W.; Rathz, T. J.; Rogers, J. R.

    2004-01-01

    If crystallization can be avoided, liquids enter a metastable (undercooled) state below their equilibrium liquidus temperatures, T(sub l), finally 'freezing' into a glass below a characteristic temperature called the glass transition temperature, T(sub g). In rare cases, the undercooled liquid may undergo a liquid-liquid phase transition (liquid polymorphism) before entering the glassy state. This has been suggested from experimental studies of H2O and Si. Such phase transitions have been predicted in some stable liquids, ie. above T(sub l) at atmospheric pressure, for SiO2 and BeF2, but these have not been verified experimentally. They have been observed in liquids of P, Si and C, but only under high pressure. In this letter we present the first experimental evidence for a phase transition in a low viscosity metallic liquid that is driven by an approach to a constant entropy configuration state and correlated with a growing icosahedral order in the liquid. A maximum in the specific heat at constant pressure, similar to what is normally observed near T(sub g), is reported for undercooled liquids of quasicrystal-forming Ti-Zr-Ni alloys. A two-state excitation model that includes cooperativity by incorporating a temperature-dependent excitation energy, fits the specific heat data well, signaling a phase transition. An inflection in the liquid density with decreasing temperature instead of a discontinuity indicates that this is not a typical first order phase transition; it could be a weakly first order or higher order transition. While showing many similarities to a glass transition, this liquid-liquid phase transition occurs in a mobile liquid, making it novel.

  10. Micro-wires self-assembled and 3D-connected with the help of a nematic liquid crystal.

    PubMed

    Agha, H; Fleury, J-B; Galerne, Y

    2012-09-01

    We discuss a method for producing automatic 3D connections at right places between substrates in front of one another. The idea is based on the materialization of disclination lines working as templates. The lines are first created in the nematic liquid crystal (5CB) at the very place where microwires have to be synthesized. Due to their anchoring properties, colloids dispersed into the nematic phase produce orientational distortions around them. These distortions, which may be considered as due to topological charges, result in a nematic force, able to attract the colloids towards the disclinations. Ultimately, the particles get trapped onto them, forming micro- or nano-necklaces. Before being introduced in the nematic phase, the colloids are covered with an adhering and conducting polypyrrole film directly synthesized at the surface of the particles (heterogeneous polymerization). In this manner, the particles become conductive so that we may finally perform an electropolymerization of pyrrole monomers solved in 5CB, and definitely stick the whole necklace. The electric connection thus synthesized is analyzed by AFM, and its strength is checked by means of hydrodynamic tests. This wiring method could allow Moore's law to overcome the limitations that arise when down-sizing the electronic circuits to nanometer scale.

  11. 3D numerical modeling of subduction dynamics: plate stagnation and segmentation, and crustal advection in the mantle transition zone

    NASA Astrophysics Data System (ADS)

    Yoshida, M.; Tajima, F.

    2012-04-01

    Water content in the mantle transition zone (MTZ) has been broadly debated in the Earth science community as a key issue for plate dynamics [e.g., Bercovici and Karato, 2003]. In this study, a systematic series of three-dimensional (3D) numerical simulation are performed in an attempt to verify two hypotheses for plate subduction with effects of deep water transport: (1) the small-scale behavior of subducted oceanic plate in the MTZ; and (2) the role of subducted crust in the MTZ. These hypotheses are postulated based on the seismic observations characterized by large-scale flattened high velocity anomalies (i.e., stagnant slabs) in the MTZ and discontinuity depth variations. The proposed model states that under wet conditions the subducted plate main body of peridotite (olivine rich) is abutted by subducted crustal materials (majorite rich) at the base of the MTZ. The computational domain of mantle convection is confined to 3D regional spherical-shell geometry with a thickness of 1000 km and a lateral extent of 10° × 30° in the latitudinal and longitudinal directions. A semi-dynamic model of subduction zone [Morishige et al., 2010] is applied to let the highly viscous, cold oceanic plate subduct. Weak (low-viscosity) fault zones (WFZs), which presumably correspond to the fault boundaries of large subduction earthquakes, are imposed on the top part of subducting plates. The phase transitions of olivine to wadsleyite and ringwoodite to perovskite+magnesiowüstite with Clapeyron slopes under both "dry" and "wet" conditions are considered based on recent high pressure experiments [e.g., Ohtani and Litasov, 2006]. Another recent experiment provides new evidence for lower-viscosity (weaker strength) of garnet-rich zones than the olivine dominant mantle under wet conditions [Katayama and Karato, 2008]. According to this, the effect of viscosity reduction of oceanic crust is considered under wet condition in the MTZ. Results show that there is a substantial difference

  12. Co-culture of 3D tumor spheroids with fibroblasts as a model for epithelial–mesenchymal transition in vitro

    SciTech Connect

    Kim, Sun-Ah; Lee, Eun Kyung; Kuh, Hyo-Jeong

    2015-07-15

    Epithelial–mesenchymal transition (EMT) acts as a facilitator of metastatic dissemination in the invasive margin of malignant tumors where active tumor–stromal crosstalks take place. Co-cultures of cancer cells with cancer-associated fibroblasts (CAFs) are often used as in vitro models of EMT. We established a tumor–fibroblast proximity co-culture using HT-29 tumor spheroids (TSs) with CCD-18co fibroblasts. When co-cultured with TSs, CCD-18co appeared activated, and proliferative activity as well as cell migration increased. Expression of fibronectin increased whereas laminin and type I collagen decreased in TSs co-cultured with fibroblasts compared to TSs alone, closely resembling the margin of in vivo xenograft tissue. Active TGFβ1 in culture media significantly increased in TS co-cultures but not in 2D co-cultures of cancer cells–fibroblasts, indicating that 3D context-associated factors from TSs may be crucial to crosstalks between cancer cells and fibroblasts. We also observed in TSs co-cultured with fibroblasts increased expression of α-SMA, EGFR and CTGF; reduced expression of membranous β-catenin and E-cadherin, together suggesting an EMT-like changes similar to a marginal region of xenograft tissue in vivo. Overall, our in vitro TS–fibroblast proximity co-culture mimics the EMT-state of the invasive margin of in vivo tumors in early metastasis. - Highlights: • An adjacent co-culture of tumor spheroids and fibroblasts is presented as EMT model. • Activation of fibroblasts and increased cell migration were shown in co-culture. • Expression of EMT-related factors in co-culture was similar to that in tumor tissue. • Crosstalk between spheroids and fibroblasts was demonstrated by secretome analysis.

  13. Repumping and spectroscopy of laser-cooled Sr atoms using the (5s5p)3P2-(5s4d)3D2 transition

    NASA Astrophysics Data System (ADS)

    Mickelson, P. G.; Martinez de Escobar, Y. N.; Anzel, P.; De Salvo, B. J.; Nagel, S. B.; Traverso, A. J.; Yan, M.; Killian, T. C.

    2009-12-01

    We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms using the (5s5p)3P2-(5s4d)3D2 transition. Atom number in a magneto-optical trap is enhanced by driving this transition because Sr atoms that have decayed into the (5s5p)3P2 dark state are repumped back into the (5s2)1S0 ground state. Spectroscopy of 84Sr, 86Sr, 87Sr and 88Sr improves the value of the (5s5p)3P2-(5s4d)3D2 transition frequency and determines the isotope shifts for the transition accurately enough to guide laser-cooling experiments with less abundant isotopes.

  14. The complex 3-D transition from continental crust to backarc magmatism and exhumed mantle in the Central Tyrrhenian basin

    NASA Astrophysics Data System (ADS)

    Prada, M.; Sallares, V.; Ranero, C. R.; Vendrell, M. G.; Grevemeyer, I.; Zitellini, N.; de Franco, R.

    2015-10-01

    Geophysical data from the MEDOC experiment across the Northern Tyrrhenian backarc basin has mapped a failed rift during backarc extension of cratonic Variscan lithosphere. In contrast, data across the Central Tyrrhenian have revealed the presence of magmatic accretion followed by mantle exhumation after continental breakup. Here we analyse the MEDOC transect E-F, which extends from Sardinia to the Campania margin at 40.5°N, to define the distribution of geological domains in the transition from the complex Central Tyrrhenian to the extended continental crust of the Northern Tyrrhenian. The crust and uppermost mantle structure along this ˜400-km-long transect have been investigated based on wide-angle seismic data, gravity modelling and multichannel seismic reflection imaging. The P-wave tomographic model together with a P-wave-velocity-derived density model and the multichannel seismic images reveal seven different domains along this transect, in contrast to the simpler structure to the south and north. The stretched continental crust under Sardinia margin abuts the magmatic crust of Cornaglia Terrace, where accretion likely occurred during backarc extension. Eastwards, around Secchi seamount, a second segment of thinned continental crust (7-8 km) is observed. Two short segments of magmatically modified continental crust are separated by the ˜5-km-wide segment of the Vavilov basin possibly made of exhumed mantle rocks. The eastern segment of the 40.5°N transect E-F is characterized by continental crust extending from mainland Italy towards the Campania margin. Ground truthing and prior geophysical information obtained north and south of transect E-F was integrated in this study to map the spatial distribution of basement domains in the Central Tyrrhenian basin. The northward transition of crustal domains depicts a complex 3-D structure represented by abrupt spatial changes of magmatic and non-magmatic crustal domains. These observations imply rapid variations

  15. Mechanochemical and thermal formation of 1H-benzotriazole coordination polymers and complexes of 3d-transition metals with intriguing dielectric properties.

    PubMed

    Brede, Franziska A; Mühlbach, Friedrich; Sextl, Gerhard; Müller-Buschbaum, Klaus

    2016-07-14

    Liquid-assisted grinding (LAG) reactions have been successfully applied to achieve a series of complexes and coordination polymers based on divalent 3d-transition metal chlorides (TM chlorides) and the aromatic ligand 1H-benzotriazole (BtzH). The obtained substances were investigated via single crystal X-ray, powder X-ray determination and simultaneous DTA/TG analysis as model compounds for structural and chemical influences on their dielectric properties. Depending on the synthesis method, different constitutions and structures are observed. Two polymorphous forms of the 1D polymer [MnCl2(BtzH)2] (1 and 2) as well as the complexes [ZnCl2(BtzH)2]·BtzH (3) and [CoCl2(BtzH)2]·BtzH (4) have been obtained as phase-pure bulk substances via the mechanochemical LAG route, and even single crystals are available. For comparison, thermal reactions were also carried out and have led to the formation of the neutral complexes: [CoCl2(BtzH)2] (5) and [CoCl2(BtzH)4]·4BtzH (6), [ZnCl2(BtzH)2] (7) and the anionic complex BtzH2[CoCl3BtzH] (8). In addition, thermal treatment of 3 yields the benzotriazolium salt {(BtzH)2H}Cl (9). The transition metal compounds were additionally analysed regarding their dielectric properties by frequency-dependent as well as temperature-dependent permittivity investigations. It is intriguing that compounds 1 and 3 show remarkably low dielectric constants and loss factors up to 50 °C highlighting them as potential "low-k materials".

  16. Synthesizing 2D and 3D Selenidostannates in Ionic Liquids: The Synergistic Structure-Directing Effects of Ionic Liquids and Metal-Amine Complexes.

    PubMed

    Du, Cheng-Feng; Shen, Nan-Nan; Li, Jian-Rong; Hao, Min-Ting; Wang, Zi; Huang, Xiao-Ying

    2016-05-20

    Presented are the ionothermal syntheses, characterizations, and properties of a series of two- and three-dimensional selenidostannate compounds synergistically directed by metal-amine complex (MAC) cations and ionic liquids (ILs) of [Bmmim]Cl (Bmmim=1-butyl-2,3-dimethylimidazolium). Four selenidostannates, namely, 2D-(Bmmim)3 [Ni(en)3 ]2 [Sn9 Se21 ]Cl (1, en=ethylenediamine), 2D-(Bmmim)8 [Ni2 (teta)2 (μ-teta)]Sn18 Se42 (2, teta=triethylenetetramine), 2D-(Bmmim)4 [Ni(tepa)Cl]2 [Ni(tepa)Sn12 Se28 ] (3, tepa=tetraethylenepentamine), and 3D-(Bmmim)2 [Ni(1,2-pda)3 ]Sn8 Se18 (4, 1,2-pda=1,2-diaminopropane), were obtained. Single-crystal X-ray diffraction analyses revealed that compounds 1 and 2 possess a lamellar anionic [Sn3 Se7 ]n (2n-) structure comprising distinct eight-membered ring units, whereas 3 features a MAC-decorated anionic [Ni(tepa)Sn12 Se28 ]n (6n-) layered structure. In contrast to 1-3, compound 4 exhibits a 3D open framework of anionic [Sn4 Se9 ]n (2n-) . The structural variation from 1 to 4 clearly indicates that on the basis of the synergistic structure-directing ability of the MACs and ILs, variation of the organic polyamine ligand has a significant impact on the formation of selenidostannates. PMID:27037731

  17. A Liquid-Liquid Transition in an Undercooled Ti-Zr-Ni Liquid

    NASA Technical Reports Server (NTRS)

    Lee, G. W.; Gangopadhyay, A. K.; Kelton, K. F.; Hyers, R. W.; Rathz, T. J.; Rogers, J. R.

    2003-01-01

    If crystallization can be avoided, liquids enter a metastable (undercooled) state below their equilibrium liquidus temperatures, TI, finally freezing into a glass below a characteristic temperature called the glass transition temperature, T,. In rare cases, the undercooled liquid may undergo a liquid-liquid phase transition (liquid polymorphism) before entering the glassy state. This has been suggested from experimental studies of HzO and Si4. Such phase transitions have been predicted in some stable liquids, i.e. above TI at atmospheric pressure, for Si02 and BeF;, but these have not been verified experimentally. They have been observed in liquids of P7, Sis and C9, but only under high pressure. All of these transitions are driven by an anomalous density change, i.e. change in local structure, with temperature or pressure. In this letter we present the first experimental evidence for a phase transition in a low viscosity liquid that is not driven by an anomalous density change, but by an approach to a constant configuration state. A maximum in the specific heat at constant pressure, similar to what is normally observed near T,, is reported here for undercooled low viscosity liquids of quasicrystal- forming Ti-Zr-Ni alloys. that includes cooperativity, by incorporating a temperature dependent excitation energy fits the data well, signaling a phase transition.

  18. Structural Transitions at Ionic Liquid Interfaces.

    PubMed

    Rotenberg, Benjamin; Salanne, Mathieu

    2015-12-17

    Recent advances in experimental and computational techniques have allowed for an accurate description of the adsorption of ionic liquids on metallic electrodes. It is now well-established that they adopt a multilayered structure and that the composition of the layers changes with the potential of the electrode. In some cases, potential-driven ordering transitions in the first adsorbed layer have been observed in experiments probing the interface on the molecular scale or by molecular simulations. This perspective gives an overview of the current understanding of such transitions and of their potential impact on the physical and (electro)chemical processes at the interface. In particular, peaks in the differential capacitance, slow dynamics at the interface, and changes in the reactivity have been reported in electrochemical studies. Interfaces between ionic liquids and metallic electrodes are also highly relevant for their friction properties, the voltage-dependence of which opens the way to exciting applications. PMID:26722704

  19. Experimental quantification of a granular crater induced by a liquid-to-granular impact using a 3D scanner

    NASA Astrophysics Data System (ADS)

    Wyser, Emmanuel; Abellan, Antonio; Carrea, Dario; Rudaz, Benjamin; Jaboyedoff, Michel

    2015-04-01

    Granular impacts have been extensively studied but much remains to be investigated regarding the complex topic of liquid-to-granular impact. Its applications to Geosciences are of interest regarding recent advances in the investigation of the raindrop erosion or the sediment flux. In our study, we focus on the quantification of both the excavated and deposited volumes resulting from a water-droplet impact onto a fine granular. The quantification of the existing relationships between the impact energy, the packing fraction and the excavated volume is also of interest. Indeed, the relationship between the packing fraction and the excavated volume has still to be investigated for constant impact energy (fixed height of fall and droplet size). Moreover, the volume distribution of the granular matter around the impact target has still to be achieved regarding the previous studies. Much of the previous work was focused on the ejected particles distribution but less is known about the volume distribution of the ejected mass. In this study, we have developed a specific methodology in order to investigate these two topics, as follows: a) First of all, we carried out experimental investigations in laboratory on a setup inspired by the previous works of Long et al. (2014) and Furbish et al. (2007). Granular samples were prepared using a compaction device in order to produce various packing fractions. Pre- and post-impact surface geometries were recorded using a high precision 3D scanner (KONICA MINOLTA VIVID 9i). This provided an accurate point cloud of the impact crater and ejecta deposits. b) Afterwards, we processed each point cloud pairs using different softwares (PolyWorks & MATLAB). We used an accurate change detection method by computing orthogonal distance from points (post-geometry) to reference meshed surface (pre-geometry) to extract the points belonging to deposits (positive distance) or crater (negative distance). Then, we used the computational geometry toolbox

  20. Liquid-solid transitions with applications to self-assembly

    NASA Astrophysics Data System (ADS)

    Keys, Aaron S.

    We study the thermodynamic and kinetic pathways by which liquids transform into solids, and their relation to the metastable states that commonly arise in self-assembly applications. As a case study in the formation of ordered metastable solids, we investigate the atomistic mechanism by which quasicrystals form. We show that the aperiodic growth of quasicrystals is controlled by the ability of the growing quasicrystal "nucleus" to incorporate kinetically trapped atoms into the solid phase with minimal rearrangement. In a related study, we propose a two-part mechanism for forming 3d dodecagonal quasicrystals by self-assembly. Our mechanism involves (1) attaching small mobile particles to the surface of spherical particles to encourage icosahedral packing and (2) allowing a subset of particles to deviate from the ideal spherical shape, to discourage close-packing In addition to studying metastable ordered solids, we investigate the phenomenology and mechanism of the glass transition. We report measurements of spatially heterogeneous dynamics in a system of air-driven granular beads approaching a jamming transition, and show that the dynamics in our granular system are quantitatively indistinguishable from those for a supercooled liquid approaching a glass transition. In a second study of the glass transition, we use transition path sampling to study the structure, statistics and dynamics of localized excitations for several model glass formers. We show that the excitations are sparse and localized, and their size is temperature-independent. We show that their equilibrium concentration is proportional to exp[- Ja (1/T-1/T o)], where Ja is the energy scale for irreversible particle displacements of length a, and T o is an onset temperature. We show that excitation dynamics is facilitated by the presence of other excitations, causing dynamics to slow in a hierarchical way as temperature is lowered. To supplement our studies of liquid-solid transitions, we introduce a

  1. Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid

    NASA Astrophysics Data System (ADS)

    Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

    2015-02-01

    Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014 K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL).

  2. Basis set limit electronic excitation energies, ionization potentials, and electron affinities for the 3d transition metal atoms: Coupled cluster and multireference methods

    NASA Astrophysics Data System (ADS)

    Balabanov, Nikolai B.; Peterson, Kirk A.

    2006-08-01

    Recently developed correlation consistent basis sets for the first row transition metal elements Sc-Zn have been utilized to determine complete basis set (CBS) scalar relativistic electron affinities, ionization potentials, and 4s23dn -2-4s1dn -1 electronic excitation energies with single reference coupled cluster methods [CCSD(T), CCSDT, and CCSDTQ] and multireference configuration interaction with three reference spaces: 3d4s, 3d4s4p, and 3d4s4p3d'. The theoretical values calculated with the highest order coupled cluster techniques at the CBS limit, including extrapolations to full configuration interaction, are well within 1kcal/mol of the corresponding experimental data. For the early transition metal elements (Sc-Mn) the internally contracted multireference averaged coupled pair functional method yielded excellent agreement with experiment; however, the atomic properties for the late transition metals (Mn-Zn) proved to be much more difficult to describe with this level of theory, even with the largest reference function of the present work.

  3. Selective imaging of 3D director fields and study of defects in biaxial smectic A liquid crystals.

    PubMed

    Smalyukh, I I; Pratibha, R; Madhusudana, N V; Lavrentovich, O D

    2005-02-01

    We report on the selective imaging of different director fields in a biaxial smectic A (SmAb) liquid crystal using Fluorescence Confocal Polarizing Microscopy (FCPM) and Polarizing Microscopy (PM). The patterns of two directors, namely the director n(a) perpendicular to the lamellae and the director n(b) in their planes are visualized by doping the liquid crystal with two fluorescent dyes with different orientation of the transition dipoles with respect to the lamellar matrix. The properties of defects such as disclinations and focal conic domains (FCDs) are consistent with the non-polar D2h-symmetry of the SmA(b) mesophase in the studied mixture of bent-core and rod-like molecules: (1) majority of defects in the director n(b) are half-integer "+/-1/2" disclinations; (2) the integer-strength "+/-1" defects tend to split into the "+/-1/2" disclinations. We compare the vertical cross-sections of the "+/-1" disclinations in the field in SmA(b) and uniaxial nematic samples. In SmA(b), the "+/-1" disclinations do not escape into the third dimension, while in the nematic samples with Schlieren textures they do despite the surface anchoring at the plates; the experimentally determined director field around the escaped disclination capped by a pair of surface point defects--boojums matches the one predicted recently [C. Chiccoli et al., Phys. Rev. E 66, 030701 (2002)]. The FCD structure in SmA(b) is similar to that in SmA and SmC in terms of the normal to the layers but differs significantly in terms of the director n(b) field parallel to the smectic layers. The FCDs in SmA(b) can be associated with topologically non-trivial configurations of n(b) in the surrounding matrix that are equivalent to the disclination lines.

  4. 3D printing of soft and wet systems benefit from hard-to-soft transition of transparent shape memory gels (presentation video)

    NASA Astrophysics Data System (ADS)

    Furukawa, Hidemitsu; Gong, Jin; Makino, Masato; Kabir, Md. Hasnat

    2014-04-01

    Recently we successfully developed novel transparent shape memory gels. The SMG memorize their original shapes during the gelation process. In the room temperature, the SMG are elastic and show plasticity (yielding) under deformation. However when heated above about 50˚C, the SMG induce hard-to-soft transition and go back to their original shapes automatically. We focus on new soft and wet systems made of the SMG by 3-D printing technology.

  5. Detection of antibodies against foot-and-mouth disease virus using a liquid-phase blocking sandwich ELISA (LPBE) with a bioengineered 3D protein.

    PubMed

    O'Donnell, V K; Boyle, D B; Sproat, K; Fondevila, N A; Forman, A; Schudel, A A; Smitsaart, E N

    1996-04-01

    A liquid-phase blocking sandwich enzyme-linked immunosorbent assay (ELISA-3D) was developed to detect specific antibodies to the 3D protein in sera from foot-and-mouth disease (FMD) virus (FMDV)-infected animals. The assay uses a nonstructural 3D recombinant protein and two polyclonal antisera, one for capture (bovine) and the other for detector (guinea pig). The specificity of the assay was demonstrated by negative results with 101 sera of cattle from the FMD-free zone in Argentina and with bovine and porcine sera raised against various RNA and DNA viruses. The ELISA-3D was able to detect antibodies in cattle after natural or experimental infection with FMDV of A, O, or C types as early as 5 days postinfection and at later stages in persistently infected animals. Comparison of the results with those obtained with the routinely used agar gel immunodiffusion test and a previously described ELISA, both employing a partially purified virus-infection-associated antigen, shows that the ELISA-3D is highly sensitive and specific and gives reproducible results. Its use as a tool for monitoring viral activity and for certification of FMDV-free animals is recommended. PMID:8744733

  6. Detection of antibodies against foot-and-mouth disease virus using a liquid-phase blocking sandwich ELISA (LPBE) with a bioengineered 3D protein.

    PubMed

    O'Donnell, V K; Boyle, D B; Sproat, K; Fondevila, N A; Forman, A; Schudel, A A; Smitsaart, E N

    1996-04-01

    A liquid-phase blocking sandwich enzyme-linked immunosorbent assay (ELISA-3D) was developed to detect specific antibodies to the 3D protein in sera from foot-and-mouth disease (FMD) virus (FMDV)-infected animals. The assay uses a nonstructural 3D recombinant protein and two polyclonal antisera, one for capture (bovine) and the other for detector (guinea pig). The specificity of the assay was demonstrated by negative results with 101 sera of cattle from the FMD-free zone in Argentina and with bovine and porcine sera raised against various RNA and DNA viruses. The ELISA-3D was able to detect antibodies in cattle after natural or experimental infection with FMDV of A, O, or C types as early as 5 days postinfection and at later stages in persistently infected animals. Comparison of the results with those obtained with the routinely used agar gel immunodiffusion test and a previously described ELISA, both employing a partially purified virus-infection-associated antigen, shows that the ELISA-3D is highly sensitive and specific and gives reproducible results. Its use as a tool for monitoring viral activity and for certification of FMDV-free animals is recommended.

  7. Laser gain on 3p-3d and 3s-3p transitions and X-ray line ratios for the nitrogen isoelectronic sequence

    NASA Technical Reports Server (NTRS)

    Feldman, U.; Seely, J. F.; Bhatia, A. K.

    1989-01-01

    Results are presented on calculations of the 72 levels belonging to the 2s(2)2p(3), 2s2p(4), 2p(5), 2s(2)2p(2)3s, 2s(2)2p(2)3p, and 2s(2)2p(2)3d configurations of the N I isoelectronic sequence for the ions Ar XII, Ti XVI, Fe XX, Zn XXIV, and Kr XXX, for electron densities up to 10 to the 24th/cu cm. It was found that large population inversions and gain occur between levels in the 2s(2)2p(2)3p configuration and levels in the 2s(2)2p(2)3d configuration that cannot decay to the ground configuration by an electric dipole transition. For increasing electron densities, the intensities of the X-ray transitions from the 2s(2)2p(2)3p configuration to the ground configuration decrease relative to the transitions from the 2s(2)2p(2)3s and 2s(2)2p(2)3d configurations to the ground configuration. The density dependence of these X-ray line ratios is presented.

  8. Liquid-liquid phase transition in a family of simple models of tetrahedral liquid

    NASA Astrophysics Data System (ADS)

    Buldyrev, Sergey; Franzese, Giancarlo; Giovambattista, Nicolas

    2013-03-01

    Liquids with tetrahedral symmetry of the first coordination shell often display anomalous thermodynamic and dynamic behavior. Sometimes, these anomalies are associated with the liquid-liquid phase transition at high pressures and low temperatures. We study a family of simple models with few parameters and investigate the conditions for the existence of the liquid-liquid phase transition. A molecule in these models consists of a hard sphere with a square well and four point particles attached to the center of the hard sphere by directional bonds arranged in tetrahedral geometry. We also impose a condition which does not allow a point particle in one molecule to include in its attractive well more than one point particle belonging to different molecules. We find an optimal range of flexibility of the bonds created by the point particles for which the model displays a clear liquid-liquid critical point in the accessible region of the phase diagram: too flexible bonds weaken the anomalies and destroy the critical point, while too rigid bonds slow down the diffusion and shift the critical point beyond the glass transition. We also investigate how minor changes in the model parameters influence crystallization which might make liquid-liquid unobservable.

  9. Liquid-type cathode enabled by 3D sponge-like carbon nanotubes for high energy density and long cycling life of Li-S batteries.

    PubMed

    Pu, Xiong; Yang, Gang; Yu, Choongho

    2014-11-26

    High energy density and long-term stability of Li-S batteries are achieved by employing a 3D sponge-like carbon nanotube cathode and a liquid-type polysulfide catholyte. Carbon nanotubes not only provide excellent electron pathways and polysulfide reservoirs, but they can also be used as a standalone cathode without current collectors, which greatly alleviates problems arising from insulating sulfur and polysulfide shuttles as well as remarkably increasing the energy density.

  10. A novel orthogonal transmission-virtual grating method and its applications in measuring micro 3-D shape of deformed liquid surface

    NASA Astrophysics Data System (ADS)

    Liu, Zhanwei; Huang, Xianfu; Xie, Huimin

    2013-02-01

    Deformed liquid surface directly involves the surface tension, which can always be used to account for the kinematics of aquatic insects in gas-liquid interface and the light metal floating on the water surface. In this paper a novel method based upon deformed transmission-virtual grating is proposed for determination of deformed liquid surface. By addressing an orthogonal grating (1-5 line/mm) under the transparent water groove and then capturing images from upset of the deformed water surface, a displacement vector of full-field which directly associates the 3-D deformed liquid surface then can be evaluated by processing the recorded deformed fringe pattern in the two directions (x- and y-direction). Theories and equations for the method are thoroughly delivered. Validation test to measure the deformed water surface caused by a Chinese 1-cent coin has been conducted to demonstrate the ability of the developed method. The obtained results show that the method is robust in determination of micro 3-D surface of deformed liquid with a submicron scale resolution and with a wide range application scope.

  11. Structural Transitions in Cholesteric Liquid Crystal Droplets.

    PubMed

    Zhou, Ye; Bukusoglu, Emre; Martínez-González, José A; Rahimi, Mohammad; Roberts, Tyler F; Zhang, Rui; Wang, Xiaoguang; Abbott, Nicholas L; de Pablo, Juan J

    2016-07-26

    Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates.

  12. Liquid-liquid transition in ST2 water

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Palmer, Jeremy C.; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

    2012-12-01

    We use the weighted histogram analysis method [S. Kumar, D. Bouzida, R. H. Swendsen, P. A. Kollman, and J. M. Rosenberg, J. Comput. Chem. 13, 1011 (1992), 10.1002/jcc.540130812] to calculate the free energy surface of the ST2 model of water as a function of density and bond-orientational order. We perform our calculations at deeply supercooled conditions (T = 228.6 K, P = 2.2 kbar; T = 235 K, P = 2.2 kbar) and focus our attention on the region of bond-orientational order that is relevant to disordered phases. We find a first-order transition between a low-density liquid (LDL, ρ ≈ 0.9 g/cc) and a high-density liquid (HDL, ρ ≈ 1.15 g/cc), confirming our earlier sampling of the free energy surface of this model as a function of density [Y. Liu, A. Z. Panagiotopoulos, and P. G. Debenedetti, J. Chem. Phys. 131, 104508 (2009), 10.1063/1.3229892]. We demonstrate the disappearance of the LDL basin at high pressure and of the HDL basin at low pressure, in agreement with independent simulations of the system's equation of state. Consistency between directly computed and reweighted free energies, as well as between free energy surfaces computed using different thermodynamic starting conditions, confirms proper equilibrium sampling. Diffusion and structural relaxation calculations demonstrate that equilibration of the LDL phase, which exhibits slow dynamics, is attained in the course of the simulations. Repeated flipping between the LDL and HDL phases in the course of long molecular dynamics runs provides further evidence of a phase transition. We use the Ewald summation with vacuum boundary conditions to calculate long-ranged Coulombic interactions and show that conducting boundary conditions lead to unphysical behavior at low temperatures.

  13. Reduced serum content and increased matrix stiffness promote the cardiac myofibroblast transition in 3D collagen matrices.

    PubMed Central

    Galie, Peter A.; Westfall, Margaret V.; Stegemann, Jan P.

    2011-01-01

    Introduction The fibroblast-myofibroblast transition is an important event in the development of cardiac fibrosis and scar formation initiated after myocardial ischemia. The goals of the present study were to better understand the contribution of environmental factors to this transition and determine whether myofibroblasts provide equally important feedback to the surrounding environment. Methods The influence of matrix stiffness and serum concentration on the myofibroblast transition was assessed by measuring message levels of a panel of cardiac fibroblast phenotype markers using quantitative rtPCR. Cell-mediated gel compaction measured the influence of environmental factors on cardiac fibroblast contractility. Immunohistochemistry characterized α-SMA expression and cell morphology, while static and dynamic compression testing evaluated the effect of the cell response on the mechanical properties of the cell-seeded collagen hydrogels. Results Both reduced serum content and increased matrix stiffness contributed to the myofibroblast transition, as indicated by contractile compaction of the gels, increased message levels of col3α1 and α-SMA, and a less stellate morphology. However, the effects of serum and matrix stiffness were not additive. Mechanical testing indicated the cell-seeded gels became less viscoelastic with time, and that reduced serum content also increased the initial elastic properties of the gel. Conclusions The results suggest that reduced serum and increased matrix stiffness promote the myofibroblast phenotype in the myocardium. This transition both enhances and is promoted by matrix stiffness, indicating the presence of positive feedback that may contribute to the pathogenesis of cardiac fibrosis. Summary Lower serum content and increased matrix stiffness accelerated the transition of cardiac fibroblasts seeded in collagen hydrogels to a myofibroblast phenotype, though their effects were not additive. Reduced serum also affected mechanical

  14. Liquid to quasicrystal transition in bilayer water

    NASA Astrophysics Data System (ADS)

    Johnston, Jessica C.; Kastelowitz, Noah; Molinero, Valeria

    2010-10-01

    The phase behavior of confined water is a topic of intense and current interest due to its relevance in biology, geology, and materials science. Nevertheless, little is known about the phases that water forms even when confined in the simplest geometries, such as water confined between parallel surfaces. Here we use molecular dynamics simulations to compute the phase diagram of two layers of water confined between parallel non hydrogen bonding walls. This study shows that the water bilayer forms a dodecagonal quasicrystal, as well as two previously unreported bilayer crystals, one tiled exclusively by pentagonal rings. Quasicrystals, structures with long-range order but without periodicity, have never before been reported for water. The dodecagonal quasicrystal is obtained from the bilayer liquid through a reversible first-order phase transition and has diffusivity intermediate between that of the bilayer liquid and ice phases. The water quasicrystal and the ice polymorphs based on pentagons are stabilized by compression of the bilayer and are not templated by the confining surfaces, which are smooth. This demonstrates that these novel phases are intrinsically favored in bilayer water and suggests that these structures could be relevant not only for confined water but also for the wetting and properties of water at interfaces.

  15. The formation of Colloidal 2D/3D MoS2 Nanostructures in Organic Liquid Environment

    NASA Astrophysics Data System (ADS)

    Durgun, Engin; Sen, H. Sener; Oztas, Tugba; Ortac, Bulend

    2015-03-01

    2D MoS2 nanosheets (2D MoS2 NS) and fullerene-like MoS2 nanostructures (3D MoS2 NS) with varying sizes are synthesized by nanosecond laser ablation of hexagonal crystalline 2H-MoS2 powder in methanol. Structural, chemical, and optical properties of MoS2 NS are characterized by optical microscopy, SEM, TEM, XRD, Raman and UV/VIS/NIR absorption spectroscopy techniques. Results of structural analysis show that the obtained MoS2 NS mainly present layered morphology from micron to nanometer surface area. Detailed analysis of the product also proves the existence of inorganic polyhedral fullerene-like 3D MoS2 NS generated by pulsed laser ablation in methanol. The possible factors which may lead to formation of both 2D and 3D MoS2 NS in methanol are examined by ab initio calculations and shown that it is correlated with vacancy formation. The hexagonal crystalline structure of MoS2 NS was determined by XRD analysis. The colloidal MoS2 NS solution presents broadband absorption edge tailoring from UV region to NIR region. Investigations of MoS2 NS show that the one step physical process of pulsed laser ablation-bulk MoS2 powder interaction in organic solution opens doors to the formation of ``two scales'' micron- and nanometer-sized layered and fullerene-like morphology MoS2 structures. This work was partially supported by TUBITAK under the Project No. 113T050 and Bilim Akademisi - The Science Academy, Turkey under the BAGEP program.

  16. On the transition towards slow manifold in shallow-water and 3D Euler equations in a rotating frame

    NASA Technical Reports Server (NTRS)

    Mahalov, A.

    1994-01-01

    The long-time, asymptotic state of rotating homogeneous shallow-water equations is investigated. Our analysis is based on long-time averaged rotating shallow-water equations describing interactions of large-scale, horizontal, two-dimensional motions with surface inertial-gravity waves field for a shallow, uniformly rotating fluid layer. These equations are obtained in two steps: first by introducing a Poincare/Kelvin linear propagator directly into classical shallow-water equations, then by averaging. The averaged equations describe interaction of wave fields with large-scale motions on time scales long compared to the time scale 1/f(sub o) introduced by rotation (f(sub o)/2-angular velocity of background rotation). The present analysis is similar to the one presented by Waleffe (1991) for 3D Euler equations in a rotating frame. However, since three-wave interactions in rotating shallow-water equations are forbidden, the final equations describing the asymptotic state are simplified considerably. Special emphasis is given to a new conservation law found in the asymptotic state and decoupling of the dynamics of the divergence free part of the velocity field. The possible rising of a decoupled dynamics in the asymptotic state is also investigated for homogeneous turbulence subjected to a background rotation. In our analysis we use long-time expansion, where the velocity field is decomposed into the 'slow manifold' part (the manifold which is unaffected by the linear 'rapid' effects of rotation or the inertial waves) and a formal 3D disturbance. We derive the physical space version of the long-time averaged equations and consider an invariant, basis-free derivation. This formulation can be used to generalize Waleffe's (1991) helical decomposition to viscous inhomogeneous flows (e.g. problems in cylindrical geometry with no-slip boundary conditions on the cylinder surface and homogeneous in the vertical direction).

  17. Liquid-liquid phase transitions and water-like anomalies in liquids

    NASA Astrophysics Data System (ADS)

    Lascaris, Erik

    In this thesis we employ computer simulations and statistical physics to understand the origin of liquid-liquid phase transitions and their relationship with anomalies typical of liquid water. Compared with other liquids, water has many anomalies. For example the density anomaly: when water is cooled below 4 °C the density decreases rather than increases. This and other anomalies have also been found to occur in a few other one-component liquids, sometimes in conjunction with the existence of a liquid-liquid phase transition (LLPT) between a low-density liquid (LDL) and a high-density liquid (HDL). Using simple models we explain how these anomalies arise from the presence of two competing length scales. As a specific example we investigate the cut ramp potential, where we show the importance of "competition" in this context, and how one length scale can sometimes be zero. When there is a clear energetic preference for either LDL or HDL for all pressures and temperatures, then there is insufficient competition between the two liquid structures and no anomalies occur. From the simple models it also follows that anomalies can occur without the presence of a LLPT and vice versa. It remains therefore unclear if water has a LLPT that ends in a liquid-liquid critical point (LLCP), a hypothesis that was first proposed based on simulations of the ST2 water model. We confirm the existence of a LLCP in this model using finite size scaling and the Challa-Landau-Binder parameter, and show that the LLPT is not a liquid-crystal transition, as has recently been suggested. Previous research has indicated the possible existence of a LLCP in liquid silica. We perform a detailed analysis of two different silica models (WAC and BKS) at temperatures much lower than was previously simulated. Within the accessible temperature range we find no LLCP in either model, although in the case of WAC potential it is closely approached. We compare our results with those obtained for other

  18. Metastable liquid-liquid transition in a molecular model of water.

    PubMed

    Palmer, Jeremy C; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2014-06-19

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in

  19. Metastable liquid-liquid transition in a molecular model of water.

    PubMed

    Palmer, Jeremy C; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2014-06-19

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in

  20. Metastable liquid-liquid transition in a molecular model of water

    NASA Astrophysics Data System (ADS)

    Palmer, Jeremy C.; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

    2014-06-01

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in

  1. Polymorphism of iron at high pressure: A 3D phase-field model for displacive transitions with finite elastoplastic deformations

    NASA Astrophysics Data System (ADS)

    Vattré, A.; Denoual, C.

    2016-07-01

    A thermodynamically consistent framework for combining nonlinear elastoplasticity and multivariant phase-field theory is formulated at large strains. In accordance with the Clausius-Duhem inequality, the Helmholtz free energy and time-dependent constitutive relations give rise to displacive driving forces for pressure-induced martensitic phase transitions in materials. Inelastic forces are obtained by using a representation of the energy landscape that involves the concept of reaction pathways with respect to the point group symmetry operations of crystal lattices. On the other hand, additional elastic forces are derived for the most general case of large strains and rotations, as well as nonlinear, anisotropic, and different elastic pressure-dependent properties of phases. The phase-field formalism coupled with finite elastoplastic deformations is implemented into a three-dimensional Lagrangian finite element approach and is applied to analyze the iron body-centered cubic (α-Fe) into hexagonal close-packed (ɛ-Fe) phase transitions under high hydrostatic compression. The simulations exhibit the major role played by the plastic deformation in the morphological and microstructure evolution processes. Due to the strong long-range elastic interactions between variants without plasticity, a forward α → ɛ transition is energetically unfavorable and remains incomplete. However, plastic dissipation releases considerably the stored strain energy, leading to the α ↔ ɛ ↔α‧ (forward and reverse) polymorphic phase transformations with an unexpected selection of variants.

  2. Thermodynamic precursors, liquid-liquid transitions, dynamic and topological anomalies in densified liquid germania

    SciTech Connect

    Pacaud, F.; Micoulaut, M.

    2015-08-14

    The thermodynamic, dynamic, structural, and rigidity properties of densified liquid germania (GeO{sub 2}) have been investigated using classical molecular dynamics simulation. We construct from a thermodynamic framework an analytical equation of state for the liquid allowing the possible detection of thermodynamic precursors (extrema of the derivatives of the free energy), which usually indicate the possibility of a liquid-liquid transition. It is found that for the present germania system, such precursors and the possible underlying liquid-liquid transition are hidden by the slowing down of the dynamics with decreasing temperature. In this respect, germania behaves quite differently when compared to parent tetrahedral systems such as silica or water. We then detect a diffusivity anomaly (a maximum of diffusion with changing density/volume) that is strongly correlated with changes in coordinated species, and the softening of bond-bending (BB) topological constraints that decrease the liquid rigidity and enhance transport. The diffusivity anomaly is finally substantiated from a Rosenfeld-type scaling law linked to the pair correlation entropy, and to structural relaxation.

  3. Interplay of the Glass Transition and the Liquid-Liquid Phase Transition in Water

    PubMed Central

    Giovambattista, Nicolas; Loerting, Thomas; Lukanov, Boris R.; Starr, Francis W.

    2012-01-01

    Water has multiple glassy states, often called amorphous ices. Low-density (LDA) and high-density (HDA) amorphous ice are separated by a dramatic, first-order like phase transition. It has been argued that the LDA-HDA transformation connects to a first-order liquid-liquid phase transition (LLPT) above the glass transition temperature Tg. Direct experimental evidence of the LLPT is challenging to obtain, since the LLPT occurs at conditions where water rapidly crystallizes. In this work, we explore the implications of a LLPT on the pressure dependence of Tg(P) for LDA and HDA by performing computer simulations of two water models – one with a LLPT, and one without. In the absence of a LLPT, Tg(P) for all glasses nearly coincide. When there is a LLPT, different glasses exhibit dramatically different Tg(P) which are directly linked with the LLPT. Available experimental data for Tg(P) are only consistent with the scenario including a LLPT. PMID:22550566

  4. 3D Global PIC simulation of Alfvenic transition layers at the cusp outer boundary during IMF rotations from north to south

    NASA Astrophysics Data System (ADS)

    Cai, D. S.; Lembege, B.; Esmaeili, A.; Nishikawa, K.

    2013-12-01

    Statistical experimental observations of the cusp boundaries from CLUSTER mission made by Lavraud et al. (2005) have clearly evidenced the presence of a transition layer inside the magnetosheath near the outer boundary of the cusp. This layer characterized by Log(MA)~ 1 allows a transition from super-Alfvenic to sub-Alfvenic bulk flow from the exterior to the interior side of the outer cusp and has been mainly observed experimentally under northward interplanetary magnetic field (IMF). The role of this layer is important in order to understand the flow variations (and later the entry and precipitation of particles) when penetrating the outer boundary of the cusp. In order to analyze this layer, a large 3D PIC simulation of the global solar wind-terrestrial magnetosphere interaction have been performed, and the attention has been focused on the cusp region and its nearby surrounding during IMF rotation from north to south. Present results retrieve quite well the presence of this layer within the meridian plane for exactly northward IMF, but its location differs in the sense that it is located slightly below the X reconnection region associated to the nearby magnetopause (above the outer boundary of the cusp). In order to clarify this question, an extensive study has been performed as follows: (i) a 3D mapping of this transition layer in order to analyze more precisely the thickness, the location and the spatial extension of this layer on the magnetosphere flanks for a fixed Northward IMF configuration; (ii) a parametric study in order to analyze the impact of the IMF rotation from north to south on the persistence and the main features of this transition layer. The locations of this transition layer slightly radially expand and shrink during the IMF rotation and the thickness of the layer increases during the rotation. We show how these transition layers render the flow from super to sub Alfvenic and allow the particles enter into the magnetic cusp region. Alfven

  5. New opportunities for quantitative and time efficient 3D MRI of liquid and solid electrochemical cell components: Sectoral Fast Spin Echo and SPRITE.

    PubMed

    Romanenko, Konstantin; Forsyth, Maria; O'Dell, Luke A

    2014-11-01

    The ability to image electrochemical processes in situ using nuclear magnetic resonance imaging (MRI) offers exciting possibilities for understanding and optimizing materials in batteries, fuel cells and supercapacitors. In these applications, however, the quality of the MRI measurement is inherently limited by the presence of conductive elements in the cell or device. To overcome related difficulties, optimal methodologies have to be employed. We show that time-efficient three dimensional (3D) imaging of liquid and solid lithium battery components can be performed by Sectoral Fast Spin Echo and Single Point Imaging with T1 Enhancement (SPRITE), respectively. The former method is based on the generalized phase encoding concept employed in clinical MRI, which we have adapted and optimized for materials science and electrochemistry applications. Hard radio frequency pulses, short echo spacing and centrically ordered sectoral phase encoding ensure accurate and time-efficient full volume imaging. Mapping of density, diffusivity and relaxation time constants in metal-containing liquid electrolytes is demonstrated. 1, 2 and 3D SPRITE approaches show strong potential for rapid high resolution (7)Li MRI of lithium electrode components.

  6. New opportunities for quantitative and time efficient 3D MRI of liquid and solid electrochemical cell components: Sectoral Fast Spin Echo and SPRITE

    NASA Astrophysics Data System (ADS)

    Romanenko, Konstantin; Forsyth, Maria; O'Dell, Luke A.

    2014-11-01

    The ability to image electrochemical processes in situ using nuclear magnetic resonance imaging (MRI) offers exciting possibilities for understanding and optimizing materials in batteries, fuel cells and supercapacitors. In these applications, however, the quality of the MRI measurement is inherently limited by the presence of conductive elements in the cell or device. To overcome related difficulties, optimal methodologies have to be employed. We show that time-efficient three dimensional (3D) imaging of liquid and solid lithium battery components can be performed by Sectoral Fast Spin Echo and Single Point Imaging with T1 Enhancement (SPRITE), respectively. The former method is based on the generalized phase encoding concept employed in clinical MRI, which we have adapted and optimized for materials science and electrochemistry applications. Hard radio frequency pulses, short echo spacing and centrically ordered sectoral phase encoding ensure accurate and time-efficient full volume imaging. Mapping of density, diffusivity and relaxation time constants in metal-containing liquid electrolytes is demonstrated. 1, 2 and 3D SPRITE approaches show strong potential for rapid high resolution 7Li MRI of lithium electrode components.

  7. New opportunities for quantitative and time efficient 3D MRI of liquid and solid electrochemical cell components: Sectoral Fast Spin Echo and SPRITE.

    PubMed

    Romanenko, Konstantin; Forsyth, Maria; O'Dell, Luke A

    2014-11-01

    The ability to image electrochemical processes in situ using nuclear magnetic resonance imaging (MRI) offers exciting possibilities for understanding and optimizing materials in batteries, fuel cells and supercapacitors. In these applications, however, the quality of the MRI measurement is inherently limited by the presence of conductive elements in the cell or device. To overcome related difficulties, optimal methodologies have to be employed. We show that time-efficient three dimensional (3D) imaging of liquid and solid lithium battery components can be performed by Sectoral Fast Spin Echo and Single Point Imaging with T1 Enhancement (SPRITE), respectively. The former method is based on the generalized phase encoding concept employed in clinical MRI, which we have adapted and optimized for materials science and electrochemistry applications. Hard radio frequency pulses, short echo spacing and centrically ordered sectoral phase encoding ensure accurate and time-efficient full volume imaging. Mapping of density, diffusivity and relaxation time constants in metal-containing liquid electrolytes is demonstrated. 1, 2 and 3D SPRITE approaches show strong potential for rapid high resolution (7)Li MRI of lithium electrode components. PMID:25442778

  8. Granular Solid-liquid Transition: Experiment and Simulation

    NASA Astrophysics Data System (ADS)

    Fei, M.; Xu, X.; Sun, Q.

    2015-12-01

    Granular media are amorphous materials, which differs from traditional solid or liquid. In different circumstance, granular behavior varies from solid-like to liquid-like, and the transitions between these regimes are always related to many complex natural progresses such as the failure of soil foundation and the occurrence of landslide and debris flow. The mechanic of elastic instability during the transition from solid-like to liquid-like regime, and the quantitative description of irreversible deformation during flow are the key problems to interpret these transition phenomena. In this work, we developed a continuum model with elastic stable condition and irreversible flow rule of granular material based on a thermal dynamical model, the Two-Granular-Temperature model (TGT). Since infinitesimal elastic deformation in solid-like regime and significant plastic large deformation in liquid-like regime can coexist in the granular solid-liquid transition process, the material point method (MPM) was used to build an effective numerical model. Collapse of rectangular granular pile contains both the transition from granular solid to granular liquid and the inverse process, thus in this work we carried out collapse experiment with clay particles, and simulated the experiment with our continuum model and an open-source DEM model YADE to study the transition processes. Results between experiment and simulations were compared and good agreements on collapse shape and velocity profiles were achieved, and the new model proposed in this work seems to work well on the description of granular solid-liquid transition.

  9. Monitoring the formation of carbide crystal phases during the thermal decomposition of 3d transition metal dicarboxylate complexes

    SciTech Connect

    Huba, ZJ; Carpenter, EE

    2014-06-06

    Single molecule precursors can help to simplify the synthesis of complex alloys by minimizing the amount of necessary starting reagents. However, single molecule precursors are time consuming to prepare with very few being commercially available. In this study, a simple precipitation method is used to prepare Fe, Co, and Ni fumarate and succinate complexes. These complexes were then thermally decomposed in an inert atmosphere to test their efficiency as single molecule precursors for the formation of metal carbide phases. Elevated temperature X-ray diffraction was used to identify the crystal phases produced upon decomposition of the metal dicarboxylate complexes. Thermogravimetric analysis coupled with an infrared detector was used to identify the developed gaseous decomposition products. All complexes tested showed a reduction from the starting M2+ oxidation state to the M oxidation state, upon decomposition. Also, each complex tested showed CO2 and H2O as gaseous decomposition products. Nickel succinate, iron succinate, and iron fumarate complexes were found to form carbide phases upon decomposition. This proves that transition metal dicarboxylate salts can be employed as efficient single molecule precursors for the formation of metal carbide crystal phases.

  10. Electron energy-loss near-edge structures of 3d transition metal oxides recorded at high-energy resolution.

    PubMed

    Mitterbauer, C; Kothleitner, G; Grogger, W; Zandbergen, H; Freitag, B; Tiemeijer, P; Hofer, F

    2003-09-01

    Near-edge fine structures of the metal L(2,3) and O K-edges in transition metal-oxides have been studied with a transmission electron microscope equipped with a monochromator and a high-resolution imaging filter. This system enables the recording of EELS spectra with an energy resolution of 0.1eV thus providing new near-edge fine structure details which could not be observed previously by EELS in conventional TEM instruments. EELS-spectra from well-defined oxides like titanium oxide (TiO(2)), vanadium oxide (V(2)O(5)), chromium oxide (Cr(2)O(3)), iron oxide (Fe(2)O(3)), cobalt oxide (CoO) and nickel oxide (NiO) have been measured with the new system. These spectra are compared with EELS data obtained from a conventional microscope and the main spectral features are interpreted. Additionally, the use of monochromised TEMs is discussed in view of the natural line widths of K and L(2,3) edges. PMID:12871809

  11. 3d electron transitions in Co- and Ni-doped MgSO3·6H2O

    NASA Astrophysics Data System (ADS)

    Petkova, P.; Bunzarov, Zh; Iliev, I.; Dimov, T.; Tzoukrovsky, Y.

    2012-05-01

    Absorption spectra of magnesium sulfite hexahydrate (MgSO3·6H2O), doped with Co and Ni, have been studied in the spectral region 1.46-3.1 eV. Investigations have been carried out with linear polarized light E||c, E⊥c (c is the optical axis of MgSO3·6H2O) that propagates in the (1210) direction. The Co structure manifests in the spectral region 2.06-3.1 eV and the Ni structures manifest in the spectral region 1.46-2.26 eV. The peculiarities of the Jahn-Teller effect and spin-orbit interaction with respect to the impurity ions in the crystal lattice of MgSO3·6H2O are analyzed and discussed. The electron transitions in Co2+ and Ni2+ ions are determined for E||c, E⊥c. The crystal field parameter Dq and Racah parameters B and C are also calculated.

  12. Pore-scale modeling of Capillary Penetration of Wetting Liquid into 3D Fibrous Media: A Critical Examination of Equivalent Capillary Concept

    NASA Astrophysics Data System (ADS)

    Palakurthi, Nikhil Kumar; Ghia, Urmila; Comer, Ken

    2013-11-01

    Capillary penetration of liquid through fibrous porous media is important in many applications such as printing, drug delivery patches, sanitary wipes, and performance fabrics. Historically, capillary transport (with a distinct liquid propagating front) in porous media is modeled using capillary-bundle theory. However, it is not clear if the capillary model (Washburn equation) describes the fluid transport in porous media accurately, as it assumes uniformity of pore sizes in the porous medium. The present work investigates the limitations of the applicability of the capillary model by studying liquid penetration through virtual fibrous media with uniform and non-uniform pore-sizes. For the non-uniform-pore fibrous medium, the effective capillary radius of the fibrous medium was estimated from the pore-size distribution curve. Liquid penetration into the 3D virtual fibrous medium at micro-scale was simulated using OpenFOAM, and the numerical results were compared with the Washburn-equation capillary-model predictions. Preliminary results show that the Washburn equation over-predicts the height rise in the early stages (purely inertial and visco-inertial stages) of capillary transport.

  13. Phenotypic transition maps of 3D breast acini obtained by imaging-guided agent-based modeling

    SciTech Connect

    Tang, Jonathan; Enderling, Heiko; Becker-Weimann, Sabine; Pham, Christopher; Polyzos, Aris; Chen, Chen-Yi; Costes, Sylvain V

    2011-02-18

    We introduce an agent-based model of epithelial cell morphogenesis to explore the complex interplay between apoptosis, proliferation, and polarization. By varying the activity levels of these mechanisms we derived phenotypic transition maps of normal and aberrant morphogenesis. These maps identify homeostatic ranges and morphologic stability conditions. The agent-based model was parameterized and validated using novel high-content image analysis of mammary acini morphogenesis in vitro with focus on time-dependent cell densities, proliferation and death rates, as well as acini morphologies. Model simulations reveal apoptosis being necessary and sufficient for initiating lumen formation, but cell polarization being the pivotal mechanism for maintaining physiological epithelium morphology and acini sphericity. Furthermore, simulations highlight that acinus growth arrest in normal acini can be achieved by controlling the fraction of proliferating cells. Interestingly, our simulations reveal a synergism between polarization and apoptosis in enhancing growth arrest. After validating the model with experimental data from a normal human breast line (MCF10A), the system was challenged to predict the growth of MCF10A where AKT-1 was overexpressed, leading to reduced apoptosis. As previously reported, this led to non growth-arrested acini, with very large sizes and partially filled lumen. However, surprisingly, image analysis revealed a much lower nuclear density than observed for normal acini. The growth kinetics indicates that these acini grew faster than the cells comprising it. The in silico model could not replicate this behavior, contradicting the classic paradigm that ductal carcinoma in situ is only the result of high proliferation and low apoptosis. Our simulations suggest that overexpression of AKT-1 must also perturb cell-cell and cell-ECM communication, reminding us that extracellular context can dictate cellular behavior.

  14. Aerogels with 3D ordered nanofiber skeletons of liquid-crystalline nanocellulose derivatives as tough and transparent insulators.

    PubMed

    Kobayashi, Yuri; Saito, Tsuguyuki; Isogai, Akira

    2014-09-22

    Aerogels of high porosity and with a large internal surface area exhibit outstanding performances as thermal, acoustic, or electrical insulators. However, most aerogels are mechanically brittle and optically opaque, and the structural and physical properties of aerogels strongly depend on their densities. The unfavorable characteristics of aerogels are intrinsic to their skeletal structures consisting of randomly interconnected spherical nanoparticles. A structurally new type of aerogel with a three-dimensionally ordered nanofiber skeleton of liquid-crystalline nanocellulose (LC-NCell) is now reported. This LC-NCell material is composed of mechanically strong, surface-carboxylated cellulose nanofibers dispersed in a nematic LC order. The LC-NCell aerogels are transparent and combine mechanical toughness and good insulation properties. These properties of the LC-NCell aerogels could also be readily controlled.

  15. Probing the 3D structure of cornea-like collagen liquid crystals with polarization-resolved SHG microscopy.

    PubMed

    Teulon, Claire; Tidu, Aurélien; Portier, François; Mosser, Gervaise; Schanne-Klein, Marie-Claire

    2016-07-11

    This work aims at characterizing the three-dimensional organization of liquid crystals composed of collagen, in order to determine the physico-chemical conditions leading to highly organized structures found in biological tissues such as cornea. To that end, we use second-harmonic generation (SHG) microscopy, since aligned collagen structures have been shown to exhibit intrinsic SHG signals. We combine polarization-resolved SHG experiments (P-SHG) with the theoretical derivation of the SHG signal of collagen molecules tilted with respect to the focal plane. Our P-SHG images exhibit striated patterns with variable contrast, as expected from our analytical and numerical calculations for plywood-like nematic structures similar to the ones found in the cornea. This study demonstrates the benefits of P-SHG microscopy for in situ characterization of highly organized biopolymers at micrometer scale, and the unique sensitivity of this nonlinear optical technique to the orientation of collagen molecules. PMID:27410876

  16. Theoretical study of inverted sandwich type complexes of 4d transition metal elements: interesting similarities to and differences from 3d transition metal complexes.

    PubMed

    Kurokawa, Yusaku I; Nakao, Yoshihide; Sakaki, Shigeyoshi

    2012-03-01

    Inverted sandwich type complexes (ISTCs) of 4d metals, (μ-η(6):η(6)-C(6)H(6))[M(DDP)](2) (DDPH = 2-{(2,6-diisopropylphenyl)amino}-4-{(2,6-diisopropylphenyl)imino}pent-2-ene; M = Y, Zr, Nb, Mo, and Tc), were investigated with density functional theory (DFT) and MRMP2 methods, where a model ligand AIP (AIPH = (Z)-1-amino-3-imino-prop-1-ene) was mainly employed. When going to Nb (group V) from Y (group III) in the periodic table, the spin multiplicity of the ground state increases in the order singlet, triplet, and quintet for M = Y, Zr, and Nb, respectively, like 3d ISTCs reported recently. This is interpreted with orbital diagram and number of d electrons. However, the spin multiplicity decreases to either singlet or triplet in ISTC of Mo (group VI) and to triplet in ISTC of Tc (group VII), where MRMP2 method is employed because the DFT method is not useful here. These spin multiplicities are much lower than the septet of ISTC of Cr and the nonet of that of Mn. When going from 3d to 4d, the position providing the maximum spin multiplicity shifts to group V from group VII. These differences arise from the size of the 4d orbital. Because of the larger size of the 4d orbital, the energy splitting between two d(δ) orbitals of M(AIP) and that between the d(δ) and d(π) orbitals are larger in the 4d complex than in the 3d complex. Thus, when occupation on the d(δ) orbital starts, the low spin state becomes ground state, which occurs at group VI. Hence, the ISTC of Nb (group V) exhibits the maximum spin multiplicity.

  17. The putative liquid-liquid transition is a liquid-solid transition in atomistic models of water. II

    SciTech Connect

    Limmer, David T.; Chandler, David

    2013-06-07

    This paper extends our earlier studies of free energy functions of density and crystalline order parameters for models of supercooled water, which allows us to examine the possibility of two distinct metastable liquid phases [D. T. Limmer and D. Chandler, J. Chem. Phys.135, 134503 (2011) and preprint http://arxiv.org/abs/arXiv:1107.0337 (2011)]. Low-temperature reversible free energy surfaces of several different atomistic models are computed: mW water, TIP4P/2005 water, Stillinger-Weber silicon, and ST2 water, the last of these comparing three different treatments of long-ranged forces. In each case, we show that there is one stable or metastable liquid phase, and there is an ice-like crystal phase. The time scales for crystallization in these systems far exceed those of structural relaxation in the supercooled metastable liquid. We show how this wide separation in time scales produces an illusion of a low-temperature liquid-liquid transition. The phenomenon suggesting metastability of two distinct liquid phases is actually coarsening of the ordered ice-like phase, which we elucidate using both analytical theory and computer simulation. For the latter, we describe robust methods for computing reversible free energy surfaces, and we consider effects of electrostatic boundary conditions. We show that sensible alterations of models and boundary conditions produce no qualitative changes in low-temperature phase behaviors of these systems, only marginal changes in equations of state. On the other hand, we show that altering sampling time scales can produce large and qualitative non-equilibrium effects. Recent reports of evidence of a liquid-liquid critical point in computer simulations of supercooled water are considered in this light.

  18. On transit time instability in liquid jets

    NASA Technical Reports Server (NTRS)

    Grabitz, G.; Meier, G.

    1982-01-01

    A basic transit time instability in flows with disturbances of speed is found. It was shown that the mass distribution is established by and large by the described transit time effects. These transit time effects may also be involved for gas jets.

  19. Spectroscopy of jet-cooled AlMn and trends in the electronic structure of the 3d transition metal aluminides

    NASA Astrophysics Data System (ADS)

    Behm, Jane M.; Morse, Michael D.

    1994-10-01

    Jet-cooled diatomic AlMn has been spectroscopically investigated and is shown to possess a 5Πi ground state deriving from the Al (3s23p1,2P0)+Mn (3d54s2,6S) separated atom limit. This implies that the aluminum atom favors a 3pπ approach to the manganese atom, a result that is in agreement with previous studies on the related AlCa and AlZn molecules. The ground state bond length has been measured as 2.6384±0.0010 Å, a value which includes corrections due to spin-uncoupling effects in the X 5Πi state. It is suggested that the 5Πi state emerges as the ground state due to a particularly favorable configuration interaction with a low-lying 5Πi state that derives from the interaction of Al (3s23p1,2P0)+Mn [3d6(5D)4s1,6D]. Combination of the atoms in this excited state leads to a strong σ2 covalent bond via a 3pσAl-4sσMn interaction, which causes this excited electronic state to drop in energy so that it is expected to lie within a few thousand cm-1 of the ground electronic state. Following a discussion of the spectroscopic results on AlMn, an overall summary of the spectroscopic results on the 3d series of transition metal aluminides is presented, along with predictions of the ground electronic states of the as yet unobserved AlSc, AlTi, and AlFe molecules.

  20. Liquid Crystalline Assembly of Coil-Rod-Coil Molecules with Lateral Methyl Groups into 3-D Hexagonal and Tetragonal Assemblies

    PubMed Central

    Wang, Zhuoshi; Lan, Yu; Zhong, Keli; Liang, Yongri; Chen, Tie; Jin, Long Yi

    2014-01-01

    In this paper, we report the synthesis and self-assembly behavior of coil-rod-coil molecules, consisting of three biphenyls linked through a vinylene unit as a conjugated rod segment and poly(ethylene oxide) (PEO) with a degree of polymerization (DP) of 7, 12 and 17, incorporating lateral methyl groups between the rod and coil segments as the coil segment. Self-organized investigation of these molecules by means of differential scanning calorimetry (DSC), thermal polarized optical microscopy (POM) and X-ray diffraction (XRD) reveals that the lateral methyl groups attached to the surface of rod and coil segments, dramatically influence the self-assembling behavior in the liquid-crystalline mesophase. Molecule 1 with a relatively short PEO coil length (DP = 7) self-assembles into rectangular and oblique 2-dimensional columnar assemblies, whereas molecules 2 and 3 with DP of 12 and 17 respectively, spontaneously self-organize into unusual 3-dimensional hexagonal close-packed or body-centered tetragonal assemblies. PMID:24699045

  1. Fore-arc deformation at the transition between collision and subduction: results from first 3D thermo-mechanical laboratory experiments

    NASA Astrophysics Data System (ADS)

    Boutelier, D. A.; Oncken, O.; Ustaszewski, K. M.; Cruden, A. R.

    2011-12-01

    3-D thermo-mechanical laboratory experiments of arc-continent collision investigate the deformation of the fore-arc at the transition between collision and subduction. The deformation of the plates in the collision area propagates into the subduction-collision transition zone via along-strike coupling of the neighboring segments of the plate boundary. The largest along-strike gradient of trench-perpendicular compression produced by a passive margin turning by 90 degrees does not generate sufficiently localized shear strain in the transition zone to cause a strike-slip system because of the fast propagation of arc lithosphere failure. Deformation is thus continuous along-strike, but the deformation mechanism is three-dimensional and progressive structural variations arise because the coupling between neighboring segment induces either advanced or delayed failure of the arc lithosphere and passive margin. During the initial stage of collision, the accretionary wedge is partially subducted, the interplate zone is lubricated, and shear traction drops. Thus large convergence obliquity does not produce a migrating fore-arc sliver. Instead, the fore-arc motion is due to the pressure force generated by subduction of the buoyant continental crust. It follows that convergence obliquity does not yield trench-parallel deformation of the fore-arc and its influence on the collision process is limited. However, convergence obliquity may have shaped the active margin during the stage of oceanic subduction stage, prior to collision, and inherited structures may impact the propagation mechanism.

  2. Electronic structure of the chiral helimagnet and 3d-intercalated transition metal dichalcogenide Cr1/3NbS2

    DOE PAGES

    Sirca, N.; Mo, S. -K.; Bondino, F.; Pis, I.; Nappini, S.; Vilmercati, P.; Yi, Jieyu; Gai, Zheng; Snijders, Paul C.; Das, P. K.; et al

    2016-08-18

    The electronic structure of the chiral helimagnet Cr1/3NbS2 has been studied with core level and angle-resolved photoemission spectroscopy (ARPES). Intercalated Cr atoms are found to be effective in donating electrons to the NbS2 layers but also cause significant modifications of the electronic structure of the host NbS2 material. Specifically, the data provide evidence that a description of the electronic structure of Cr1/3NbS2 on the basis of a simple rigid band picture is untenable. The data also reveal substantial inconsistencies with the predictions of standard density functional theory. In conclusion, the relevance of these results to the attainment of a correctmore » description of the electronic structure of chiral helimagnets, magnetic thin films/multilayers, and transition metal dichalcogenides intercalated with 3d magnetic elements is discussed.« less

  3. Dopant-induced 2D-3D transition in small Au-containing clusters: DFT-global optimisation of 8-atom Au-Ag nanoalloys.

    PubMed

    Heiles, Sven; Logsdail, Andrew J; Schäfer, Rolf; Johnston, Roy L

    2012-02-21

    A genetic algorithm (GA) coupled with density functional theory (DFT) calculations is used to perform global optimisations for all compositions of 8-atom Au-Ag bimetallic clusters. The performance of this novel GA-DFT approach for bimetallic nanoparticles is tested for structures reported in the literature. New global minimum structures for various compositions are predicted and the 2D-3D transition is located. Results are explained with the aid of an analysis of the electronic density of states. The chemical ordering of the predicted lowest energy isomers are explained via a detailed analysis of the charge separation and mixing energies of the bimetallic clusters. Finally, dielectric properties are computed and the composition and dimensionality dependence of the electronic polarizability and dipole moment is discussed, enabling predictions to be made for future electric beam deflection experiments.

  4. Adsorption of alkali, alkaline-earth, simple and 3d transition metal, and nonmetal atoms on monolayer MoS{sub 2}

    SciTech Connect

    Li, X. D.; Fang, Y. M.; Wu, S. Q. E-mail: wsq@xmu.edu.cn; Zhu, Z. Z. E-mail: wsq@xmu.edu.cn

    2015-05-15

    Single adsorption of different atoms on pristine two-dimensional monolayer MoS{sub 2} have been systematically investigated by using density functional calculations with van der Waals correction. The adatoms cover alkali metals, alkaline earth metals, main group metal, 3d-transition metals, coinage metal and nonmetal atoms. Depending on the adatom type, metallic, semimetallic or semiconducting behavior can be found in direct bandgap monolayer MoS{sub 2}. Additionally, local or long-range magnetic moments of two-dimensional MoS{sub 2} sheet can also attained through the adsorption. The detailed atomic-scale knowledge of single adsorption on MoS{sub 2} monolayer is important not only for the sake of a theoretical understanding, but also device level deposition technological application.

  5. Spectroscopic analysis of the open 3d subshell transition metal aluminides: AlV, AlCr, and AlCo

    NASA Astrophysics Data System (ADS)

    Behm, Jane M.; Brugh, Dale J.; Morse, Michael D.

    1994-10-01

    Three open 3d subshell transition metal aluminides, AlV, AlCr, and AlCo, have been investigated by resonant two-photon ionization spectroscopy to elucidate the chemical bonding in these diatomic molecules. The open nature of the 3d subshell results in a vast number of excited electronic states in these species, allowing bond strengths to be measured by the observation of abrupt predissociation thresholds in a congested optical spectrum, giving D00(AlV)=1.489±0.010 eV, D00(AlCr)=2.272±0.009 eV, and D00(AlCo)=1.844±0.002 eV. At lower excitation energies the presence of discrete transitions has permitted determinations of the ground state symmetries and bond lengths of AlV and AlCo through rotationally resolved studies, giving r0` (AlV, Ω`=0)=2.620±0.004 Å and r0` (AlCo, Ω`=3)=2.3833±0.0005 Å. Ionization energies were also measured for all three species, yielding IE(AlV)=6.01±0.10 eV, IE(AlCr)=5.96±0.04 eV, and IE(AlCo)=6.99±0.17 eV. A discussion of these results is presented in the context of previous work on AlCu, AlNi, AlCa, and AlZn.

  6. Oriental transitions in nematic liquid crystals on grooved substrates

    SciTech Connect

    Krekhov, A.P.; Khasimullin, M.V.; Lebedev, Y.A.

    1995-12-31

    An expression for the surface energy of a nematic liquid crystal (NLC) on a fine-grooved substrate is obtained with the phenomenological approach. Temperature-induced orientational transitions in nematic liquid crystals are analyzed as functions of the surface-profile parameters. A planar{yields}tilted{yields}homeotropic alignment transition was observed near the clearing point of an MBBA layer sandwiched between two grooved glass substrates, with a microrelief obtained by oblique evaporation of silicon monoxide. 15 refs., 1 fig.

  7. Thermodynamical and structural properties of some liquid transition metals near melting point

    NASA Astrophysics Data System (ADS)

    Uçar, Sevilay; Kartal, Sehban; Armaǧan, Turgay

    2016-03-01

    Structure factor S(q) and thermodynamic properties like entropy (S), isothermal compressibility (χT), specific heat (CV) have been calculated for liquid 3d (Ti, V, Cr and Mn), 4d (Pd, Zr) and 5d (Pt) transition metals. In this work, we have used newly constructed Bretonnet-Silbert potential to describe electron-ion and ion-ion interaction using different reference systems. It is observed that our results are found to be in good agreement with experimental data as well as with other theoretical results.

  8. 3D interconnected ionic nano-channels formed in polymer films: self-organization and polymerization of thermotropic bicontinuous cubic liquid crystals.

    PubMed

    Ichikawa, Takahiro; Yoshio, Masafumi; Hamasaki, Atsushi; Kagimoto, Junko; Ohno, Hiroyuki; Kato, Takashi

    2011-02-23

    Thermotropic bicontinuous cubic (Cub(bi)) liquid-crystalline (LC) compounds based on a polymerizable ammonium moiety complexed with a lithium salt have been designed to obtain lithium ion-conductive all solid polymeric films having 3D interconnected ionic channels. The monomer shows a Cub(bi) phase from -5 to 19 °C on heating. The complexes retain the ability to form the Cub(bi) LC phase. They also form hexagonal columnar (Col(h)) LC phases at temperatures higher than those of the Cub(bi) phases. The complex of the monomer and LiBF(4) at the molar ratio of 4:1 exhibits the Cub(bi) and Col(h) phases between -6 to 19 °C and 19 to 56 °C, respectively, on heating. The Cub(bi) LC structure formed by the complex has been successfully preserved by in situ photopolymerization through UV irradiation in the presence of a photoinitiator. The resultant nanostructured film is optically transparent and free-standing. The X-ray analysis of the film confirms the preservation of the self-assembled nanostructure. The polymer film with the Cub(bi) LC nanostructure exhibits higher ionic conductivities than the polymer films obtained by photopolymerization of the complex in the Col(h) and isotropic phases. It is found that the 3D interconnected ionic channels derived from the Cub(bi) phase function as efficient ion-conductive pathways.

  9. Role of surfactant during microemulsion photopolymerization for the creation of three-dimensional (3D) liquid crystal elastomer microsphere spatial cell scaffolds

    NASA Astrophysics Data System (ADS)

    Hegmann, Elda; Bera, Tanmay; Malcuit, Christopher; Clements, Robert

    2016-06-01

    Three-dimensional (3D) cell scaffolds based on connected nematic liquid crystal elastomer microsphere architectures support the attachment and proliferation of C2C12 myoblasts, neuroblastomas (SHSY5Y) and human dermal fibroblasts (hDF). The microsphere spatial cell scaffolds were prepared by an oil-in-water microemulsion photopolymerization of reactive nematic mesogens in the presence of various surfactants, and the as-prepared scaffold constructs are composed of smooth surface microspheres with diameter ranging from 10 to 30 μm. We here investigate how the nature and type of surfactant used during the microemulsion photopolymerization impacts both the size and size distribution of the resulting microspheres as well as their surface morphology, i.e. the surface roughness.

  10. Nuclear Liquid-Gas Phase Transition: Experimental Signals

    NASA Astrophysics Data System (ADS)

    D'Agostino, M.; Bruno, M.; Gulminelli, F.; Cannata, F.; Chomaz, Ph.; Casini, G.; Geraci, E.; Gramegna, F.; Moroni, A.; Vannini, G.

    2005-03-01

    The connection between the thermodynamics of charged finite nuclear systems and the asymptotically measured partitions in heavy ion collisions is discussed. Different independent signals compatible with a liquid-to-gas-like phase transition are reported. In particular abnormally large fluctuations in the measured observables are presented as a strong evidence of a first order phase transition with negative heat capacity.

  11. Analysis of structural correlations in a model binary 3D liquid through the eigenvalues and eigenvectors of the atomic stress tensors.

    PubMed

    Levashov, V A

    2016-03-01

    It is possible to associate with every atom or molecule in a liquid its own atomic stress tensor. These atomic stress tensors can be used to describe liquids' structures and to investigate the connection between structural and dynamic properties. In particular, atomic stresses allow to address atomic scale correlations relevant to the Green-Kubo expression for viscosity. Previously correlations between the atomic stresses of different atoms were studied using the Cartesian representation of the stress tensors or the representation based on spherical harmonics. In this paper we address structural correlations in a 3D model binary liquid using the eigenvalues and eigenvectors of the atomic stress tensors. This approach allows to interpret correlations relevant to the Green-Kubo expression for viscosity in a simple geometric way. On decrease of temperature the changes in the relevant stress correlation function between different atoms are significantly more pronounced than the changes in the pair density function. We demonstrate that this behaviour originates from the orientational correlations between the eigenvectors of the atomic stress tensors. We also found correlations between the eigenvalues of the same atomic stress tensor. For the studied system, with purely repulsive interactions between the particles, the eigenvalues of every atomic stress tensor are positive and they can be ordered: λ1 ≥ λ2 ≥ λ3 ≥ 0. We found that, for the particles of a given type, the probability distributions of the ratios (λ2/λ1) and (λ3/λ2) are essentially identical to each other in the liquids state. We also found that λ2 tends to be equal to the geometric average of λ1 and λ3. In our view, correlations between the eigenvalues may represent "the Poisson ratio effect" at the atomic scale. PMID:26957166

  12. Analysis of structural correlations in a model binary 3D liquid through the eigenvalues and eigenvectors of the atomic stress tensors.

    PubMed

    Levashov, V A

    2016-03-01

    It is possible to associate with every atom or molecule in a liquid its own atomic stress tensor. These atomic stress tensors can be used to describe liquids' structures and to investigate the connection between structural and dynamic properties. In particular, atomic stresses allow to address atomic scale correlations relevant to the Green-Kubo expression for viscosity. Previously correlations between the atomic stresses of different atoms were studied using the Cartesian representation of the stress tensors or the representation based on spherical harmonics. In this paper we address structural correlations in a 3D model binary liquid using the eigenvalues and eigenvectors of the atomic stress tensors. This approach allows to interpret correlations relevant to the Green-Kubo expression for viscosity in a simple geometric way. On decrease of temperature the changes in the relevant stress correlation function between different atoms are significantly more pronounced than the changes in the pair density function. We demonstrate that this behaviour originates from the orientational correlations between the eigenvectors of the atomic stress tensors. We also found correlations between the eigenvalues of the same atomic stress tensor. For the studied system, with purely repulsive interactions between the particles, the eigenvalues of every atomic stress tensor are positive and they can be ordered: λ1 ≥ λ2 ≥ λ3 ≥ 0. We found that, for the particles of a given type, the probability distributions of the ratios (λ2/λ1) and (λ3/λ2) are essentially identical to each other in the liquids state. We also found that λ2 tends to be equal to the geometric average of λ1 and λ3. In our view, correlations between the eigenvalues may represent "the Poisson ratio effect" at the atomic scale.

  13. The liquid to vapor phase transition in excited nuclei

    SciTech Connect

    Elliott, J.B.; Moretto, L.G.; Phair, L.; Wozniak, G.J.; Beaulieu, L.; Breuer, H.; Korteling, R.G.; Kwiatkowski, K.; Lefort, T.; Pienkowski, L.; Ruangma, A.; Viola, V.E.; Yennello, S.J.

    2001-05-08

    For many years it has been speculated that excited nuclei would undergo a liquid to vapor phase transition. For even longer, it has been known that clusterization in a vapor carries direct information on the liquid-vapor equilibrium according to Fisher's droplet model. Now the thermal component of the 8 GeV/c pion + 197 Au multifragmentation data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model, thus providing the strongest evidence yet of the liquid to vapor phase transition.

  14. Three-dimensional distribution of the ISM in the Milky Way Galaxy. IV. 3D molecular fraction and Galactic-scale H I-to-H2 transition

    NASA Astrophysics Data System (ADS)

    Sofue, Yoshiaki; Nakanishi, Hiroyuki

    2016-08-01

    Three-dimensional (3D) distribution of the volume-density molecular fraction, defined by f_mol^ρ =ρ _H_2/(ρ _{H I}+ρ _H_2), is studied in the Milky Way Galaxy. The molecular front appears at galacto-centric distance of R ˜ 8 kpc, where the galactic-scale phase transition from atomic to molecular hydrogen occurs with f_mol^ρ dropping from ˜0.8 to 0.2 within a radial interval as narrow as ˜0.5 kpc. The f_mol^ρ front is much sharper than that of the surface density molecular fraction. The f_mol^ρ front also appears in the direction vertical to the galactic plane with a full width of the high-f_mol^ρ disk to be ˜100 pc. The radial and vertical f_mol^ρ profiles, particularly the front behavior, are fitted by theoretical curves calculated using the observed density profile and assumed radiation field and metallicity with exponential gradients. The molecular fraction was found to be enhanced along spiral arms at radii R ˜ 6 to 10 kpc, such as the Perseus arm. This implies that the molecular clouds are produced from H I in the arms and are dissociated in the interarm regions in the transition region around the molecular front. We also show that there is a threshold value of mean H I density, over which H I is transformed into molecular gas.

  15. A theoretical study on the structures and energetics of hypothetical TiM(NCN)3 compounds of the 3d transition metals.

    PubMed

    Launay, Maxence; Dronskowski, Richard

    2005-08-01

    Quasi-ternary cyanamides and carbodiimides of general formula AB(NCN)(3) with A not equal B have neither been predicted nor synthesized. Thus, hypothetical compounds of that kind containing 3d transition metals were considered (A = Ti, B = Mn, Fe, Co, Ni, Cu) by means of density-functional calculations on 34 structural models, most of which were derived from chemically related phases. After performing structure optimizations based on the local-density approximation, the relative energetic orderings are rationalized in terms of geometrical factors such as molar volumes and polyhedral connections. Total-energy generalized-gradient calculations evidence that the most stable models are enthalpically favored with respect to the elements. Even at ambient temperatures, the ternary phases are predicted as being thermodynamically stable in terms of their Gibbs free formation energies, especially if energetically competing and low-lying binaries (TiC, TiN) can be excluded by a kinetic reaction control. The best models are characterized by low-spin magnetic transition metals found in octahedral coordination, and the TiN(6) and MN(6) polyhedra either share faces or edges.

  16. Study of morphology effects on magnetic interactions and band gap variations for 3d late transition metal bi-doped ZnO nanostructures by hybrid DFT calculations

    NASA Astrophysics Data System (ADS)

    Datta, Soumendu; Kaphle, Gopi Chandra; Baral, Sayan; Mookerjee, Abhijit

    2015-08-01

    Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO)24 nanostructures with the impurity dopant atoms of the 3d late transition metals—Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO)24 nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.

  17. Study of morphology effects on magnetic interactions and band gap variations for 3d late transition metal bi-doped ZnO nanostructures by hybrid DFT calculations.

    PubMed

    Datta, Soumendu; Kaphle, Gopi Chandra; Baral, Sayan; Mookerjee, Abhijit

    2015-08-28

    Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO)24 nanostructures with the impurity dopant atoms of the 3d late transition metals-Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO)24 nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.

  18. Accurate electronic and chemical properties of 3d transition metal oxides using a calculated linear response U and a DFT + U(V) method

    SciTech Connect

    Xu, Zhongnan; Kitchin, John R.; Joshi, Yogesh V.; Raman, Sumathy

    2015-04-14

    We validate the usage of the calculated, linear response Hubbard U for evaluating accurate electronic and chemical properties of bulk 3d transition metal oxides. We find calculated values of U lead to improved band gaps. For the evaluation of accurate reaction energies, we first identify and eliminate contributions to the reaction energies of bulk systems due only to changes in U and construct a thermodynamic cycle that references the total energies of unique U systems to a common point using a DFT + U(V ) method, which we recast from a recently introduced DFT + U(R) method for molecular systems. We then introduce a semi-empirical method based on weighted DFT/DFT + U cohesive energies to calculate bulk oxidation energies of transition metal oxides using density functional theory and linear response calculated U values. We validate this method by calculating 14 reactions energies involving V, Cr, Mn, Fe, and Co oxides. We find up to an 85% reduction of the mean average error (MAE) compared to energies calculated with the Perdew-Burke-Ernzerhof functional. When our method is compared with DFT + U with empirically derived U values and the HSE06 hybrid functional, we find up to 65% and 39% reductions in the MAE, respectively.

  19. Study of morphology effects on magnetic interactions and band gap variations for 3d late transition metal bi-doped ZnO nanostructures by hybrid DFT calculations

    SciTech Connect

    Datta, Soumendu Baral, Sayan; Mookerjee, Abhijit; Kaphle, Gopi Chandra

    2015-08-28

    Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO){sub 24} nanostructures with the impurity dopant atoms of the 3d late transition metals—Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO){sub 24} nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.

  20. Study of morphology effects on magnetic interactions and band gap variations for 3d late transition metal bi-doped ZnO nanostructures by hybrid DFT calculations.

    PubMed

    Datta, Soumendu; Kaphle, Gopi Chandra; Baral, Sayan; Mookerjee, Abhijit

    2015-08-28

    Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO)24 nanostructures with the impurity dopant atoms of the 3d late transition metals-Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO)24 nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties. PMID:26328845

  1. 1D to 3D dimensional crossover in the superconducting transition of the quasi-one-dimensional carbide superconductor Sc3CoC4.

    PubMed

    He, Mingquan; Wong, Chi Ho; Shi, Dian; Tse, Pok Lam; Scheidt, Ernst-Wilhelm; Eickerling, Georg; Scherer, Wolfgang; Sheng, Ping; Lortz, Rolf

    2015-02-25

    The transition metal carbide superconductor Sc(3)CoC(4) may represent a new benchmark system of quasi-one-dimensional (quasi-1D) superconducting behavior. We investigate the superconducting transition of a high-quality single crystalline sample by electrical transport experiments. Our data show that the superconductor goes through a complex dimensional crossover below the onset T(c) of 4.5 K. First, a quasi-1D fluctuating superconducting state with finite resistance forms in the [CoC(4)](∞) ribbons which are embedded in a Sc matrix in this material. At lower temperature, the transversal Josephson or proximity coupling of neighboring ribbons establishes a 3D bulk superconducting state. This dimensional crossover is very similar to Tl(2)Mo(6)Se(6), which for a long time has been regarded as the most appropriate model system of a quasi-1D superconductor. Sc(3)CoC(4) appears to be even more in the 1D limit than Tl(2)Mo(6)Se(6).

  2. Antiferromagnetic spin chain behavior and a transition to 3D magnetic order in Cu(D,L-alanine)2: Roles of H-bonds

    NASA Astrophysics Data System (ADS)

    Calvo, Rafael; Sartoris, Rosana P.; Calvo, Hernán L.; Chagas, Edson F.; Rapp, Raul E.

    2016-05-01

    We study the spin chain behavior, a transition to 3D magnetic order and the magnitudes of the exchange interactions for the metal-amino acid complex Cu(D,L-alanine)2•H2O, a model compound to investigate exchange couplings supported by chemical paths characteristic of biomolecules. Thermal and magnetic data were obtained as a function of temperature (T) and magnetic field (B0). The magnetic contribution to the specific heat, measured between 0.48 and 30 K, displays above 1.8 K a 1D spin-chain behavior that can be fitted with an intrachain antiferromagnetic (AFM) exchange coupling constant 2J0=(-2.12±0.08) cm-1 (defined as ℋex(i,i+1) = -2J0SiṡSi+1), between neighbor coppers at 4.49 Å along chains connected by non-covalent and H-bonds. We also observe a narrow specific heat peak at 0.89 K indicating a phase transition to a 3D magnetically ordered phase. Magnetization curves at fixed T = 2, 4 and 7 K with B0 between 0 and 9 T, and at T between 2 and 300 K with several fixed values of B0 were globally fitted by an intrachain AFM exchange coupling constant 2J0=(-2.27±0.02) cm-1 and g = 2.091±0.005. Interchain interactions J1 between coppers in neighbor chains connected through long chemical paths with total length of 9.51 Å cannot be estimated from magnetization curves. However, observation of the phase transition in the specific heat data allows estimating the range 0.1≤|2J1|≤0.4 cm-1, covering the predictions of various approximations. We analyze the magnitudes of 2J0 and 2J1 in terms of the structure of the corresponding chemical paths. The main contribution in supporting the intrachain interaction is assigned to H-bonds while the interchain interactions are supported by paths containing H-bonds and carboxylate bridges, with the role of the H-bonds being predominant. We compare the obtained intrachain coupling with studies of compounds showing similar behavior and discuss the validity of the approximations allowing to calculate the interchain

  3. Anchoring transition in confined discotic columnar liquid crystal films

    NASA Astrophysics Data System (ADS)

    Brunet, Thomas; Thiebaut, Olivier; Charlet, Émilie; Bock, Harald; Kelber, Julien; Grelet, Éric

    2011-01-01

    We report the achievement of ultrathin films (down to 25 nm thick) of thermotropic columnar liquid crystals in homeotropic alignment (columns normal to the interface) confined between a glass slide and a thin metallic electrode (about 150 nm thick). The face-on orientation of the discotic compound is obtained by anchoring transition of a columnar liquid crystalline phase from a degenerate planar orientation to the homeotropic alignment without any phase transition to the isotropic liquid phase. The kinetic dependence on temperature of such anchoring transition is investigated revealing various diffusive growth regimes of the homeotropic domains. Finally, confining effects are also considered by varying the thickness of the columnar liquid crystal film to reach the typical value required in organic solar cells thus demonstrating the reliability of such alignment process in a photovoltaic context.

  4. Distinct metallization and atomization transitions in dense liquid hydrogen.

    PubMed

    Mazzola, Guglielmo; Sorella, Sandro

    2015-03-13

    We perform molecular dynamics simulations driven by accurate quantum Monte Carlo forces on dense liquid hydrogen. There is a recent report of a complete atomization transition between a mixed molecular-atomic liquid and a completely dissociated fluid in an almost unaccessible pressure range [Nat. Commun. 5, 3487 (2014)]. Here, instead, we identify a different transition between the fully molecular liquid and the mixed-atomic fluid at ∼400  GPa, i.e., in a much more interesting pressure range. We provide numerical evidence supporting the metallic behavior of this intermediate phase. Therefore, we predict that the metallization at finite temperature occurs in this partially dissociated molecular fluid, well before the complete atomization of the liquid. At high temperature this first-order transition becomes a crossover, in very good agreement with the experimental observation. Several systematic tests supporting the quality of our large scale calculations are also reported.

  5. 3d transition metal doped Zn0.95 Tm 0.05O (Tm = Mn, Co, Ni, Cu): structure, microstructure, Raman, dielectric constant and magnetism

    NASA Astrophysics Data System (ADS)

    Varshney, Dinesh; Dwivedi, Sonam

    2015-10-01

    We present the structural, microstructural, optical, dielectric, and magnetic behavior of 3d transition metal (Tm) doped Zn0.95 Tm 0.05O (Tm = Mn, Co, Ni, Cu) diluted magnetic semiconducting samples as synthesized by solid-state route reaction method. X-ray diffraction (XRD) pattern infers that the sample of Zn0.95 TM 0.05O (Tm = Mn, Co, Ni, Cu) is in single-phase wurtzite structure (hexagonal phase, P63 mc). The average particle size obtained for different compositions of Zn0.95 TM 0.05O (TM = Mn, Co, Ni, Cu) are 0.499, 0.517, 0.568, and 0.572 μm, respectively. Ni-doped ZnO has obtained the lowest band gap (˜3.1 eV) as compared to other transition metal (Tm = Mn, Co, Cu) ion-doped ZnO. The effect of Tm ions substitution on dielectric constant, and loss tangent, is also studied at room temperature in a wide range of frequencies between 50 Hz-1 MHz. The dielectric parameters were enhanced by the replacement of Zn ions with transition metal ions. Room temperature magnetization-magnetic field (M-H) measurements show the paramagnetic behavior of Zn0.95Mn0.05O and Zn0.95Cu0.05O, diamagnetic characteristic of Zn0.95Co0.05O, and ferromagnetic response of Zn0.95Ni0.05O. In Zn0.95Ni0.05O samples the saturation occurs at 2 kOe, while the small value of coercive field is about 100 Oe at room temperature and is attributed to the soft nature of Zn0.95Ni0.05O.

  6. Using the Flow-3D General Moving Object Model to Simulate Coupled Liquid Slosh - Container Dynamics on the SPHERES Slosh Experiment: Aboard the International Space Station

    NASA Technical Reports Server (NTRS)

    Schulman, Richard; Kirk, Daniel; Marsell, Brandon; Roth, Jacob; Schallhorn, Paul

    2013-01-01

    The SPHERES Slosh Experiment (SSE) is a free floating experimental platform developed for the acquisition of long duration liquid slosh data aboard the International Space Station (ISS). The data sets collected will be used to benchmark numerical models to aid in the design of rocket and spacecraft propulsion systems. Utilizing two SPHERES Satellites, the experiment will be moved through different maneuvers designed to induce liquid slosh in the experiment's internal tank. The SSE has a total of twenty-four thrusters to move the experiment. In order to design slosh generating maneuvers, a parametric study with three maneuvers types was conducted using the General Moving Object (GMO) model in Flow-30. The three types of maneuvers are a translation maneuver, a rotation maneuver and a combined rotation translation maneuver. The effectiveness of each maneuver to generate slosh is determined by the deviation of the experiment's trajectory as compared to a dry mass trajectory. To fully capture the effect of liquid re-distribution on experiment trajectory, each thruster is modeled as an independent force point in the Flow-3D simulation. This is accomplished by modifying the total number of independent forces in the GMO model from the standard five to twenty-four. Results demonstrate that the most effective slosh generating maneuvers for all motions occurs when SSE thrusters are producing the highest changes in SSE acceleration. The results also demonstrate that several centimeters of trajectory deviation between the dry and slosh cases occur during the maneuvers; while these deviations seem small, they are measureable by SSE instrumentation.

  7. Nature of the first-order liquid-liquid phase transition in supercooled silicon

    NASA Astrophysics Data System (ADS)

    Zhao, G.; Yu, Y. J.; Tan, X. M.

    2015-08-01

    The first-order liquid-liquid phase transition in supercooled Si is revisited by long-time first-principle molecular dynamics simulations. As the focus of the present paper, its nature is revealed by analyzing the inherent structures of low-density liquid (LDL) and high-density liquid (HDL). Our results show that it is a transition between a sp3-hybridization LDL and a white-tin-like HDL. This uncovers the origin of the semimetal-metal transition accompanying it and also proves that HDL is the metastable extension of high temperature equilibrium liquid into the supercooled regime. The pressure-temperature diagram of supercooled Si thus can be regarded in some respects as shifted reflection of its crystalline phase diagram.

  8. A universal reduced glass transition temperature for liquids

    NASA Technical Reports Server (NTRS)

    Fedors, R. F.

    1979-01-01

    Data on the dependence of the glass transition temperature on the molecular structure for low-molecular-weight liquids are analyzed in order to determine whether Boyer's reduced glass transition temperature (1952) is a universal constant as proposed. It is shown that the Boyer ratio varies widely depending on the chemical nature of the molecule. It is pointed out that a characteristic temperature ratio, defined by the ratio of the sum of the melting temperature and the boiling temperature to the sum of the glass transition temperature and the boiling temperature, is a universal constant independent of the molecular structure of the liquid. The average value of the ratio obtained from data for 65 liquids is 1.15.

  9. Antiferromagnetic half metallicity in codoped chalcopyrite semiconductors Cu(Al 1 - 2 xAxBx)Se2 (A and B are 3d transition-metal atoms)

    NASA Astrophysics Data System (ADS)

    Shahjahan, M.; Oguchi, T.

    2016-06-01

    Electronic structures and magnetic properties of group I-III-VI2 chalcopyrite-type compounds Cu(Al 1 - 2 xAxBx)Se2 are calculated using the Korringa-Kohn-Rostoker Green's function method, where A (Ti, V, Cr, Mn) and B (Fe, Co, Ni) are 3d transition metal atoms, and x is atomic concentration. We found that codoping of Cr-Co and V-Ni pairs at Al site of host CuAlSe2 exhibit antiferromagnetic (AF) half metallicity with low Curie temperature (TC). The AF half metallic property is supported by nullified net magnetic moment and compensated density of states in the minority spin direction. On the other hand, codoping of Cr-Ni, Mn-Co, V-Co, and Ti-Co pairs at Al site of host CuAlSe2 manifest ferrimagnetic half metallicity with a small net magnetization and keeping antiparallel local spin moments. In Mn-Co case TC is close to room temperature. Besides, Cr-Fe, V-Fe, and Ti-Ni codoping cases lead to an instable magnetic ordering and therefore obtain a disordered local moment (spin-glass like) state.

  10. Magnetization of ternary alloys based on Fe0.65Ni0.35 invar with 3d transition metal additions: An ab initio study

    NASA Astrophysics Data System (ADS)

    Onoue, Masatoshi; Trimarchi, Giancarlo; Freeman, Arthur J.; Popescu, Voicu; Matsen, Marc R.

    2015-01-01

    Smart susceptors are being developed for use as tooling surfaces in molding machines that use apply electro-magnetic induction heating to mold and form plastics or metal powders into structural parts, e.g., on aerospace and automotive manufacturing lines. The optimal magnetic materials for the induction heating process should have large magnetization, high magnetic permeability, but also small thermal expansion coefficient. The Fe0.65Ni0.35 invar alloy with its negligible thermal expansion coefficient is thus a natural choice for this application. Here, we use density functional theory as implemented through the Korringa-Kohn-Rostoker method within the coherent-potential approximation, to design new alloys with the large magnetization desired for smart susceptor applications. We consider the Fe0.65-xNi0.35-yMx+y alloys derived from Fe0.65Ni0.35 invar adding a third element M = Sc, Ti, V, Cr, Mn, or Co with concentration (x + y) reaching up to 5 at. %. We find that the total magnetization depends linearly on the concentration of M. Specifically, the early 3d transition metals from Sc to Cr decrease the magnetization with respect to that of the invar alloy whereas Mn and Co increase it.

  11. Optical and infrared absorption spectra of 3d transition metal ions-doped sodium borophosphate glasses and effect of gamma irradiation.

    PubMed

    Abdelghany, A M; ElBatal, F H; Azooz, M A; Ouis, M A; ElBatal, H A

    2012-12-01

    Undoped and transition metals (3d TM) doped sodium borophosphate glasses were prepared. UV-visible absorption spectra were measured in the region 200-900nm before and after gamma irradiation. Experimental optical data indicate that the undoped sodium borophosphate glass reveals before irradiation strong and broad UV absorption and no visible bands could be identified. Such UV absorption is related to the presence of unavoidable trace iron impurities within the raw materials used for preparation of this base borophosphate glass. The TMs-doped glasses show absorption bands within the UV and/or visible regions which are characteristic to each respective TM ion in addition to the UV absorption observed from the host base glass. Infrared absorption spectra of the undoped and TMs-doped glasses reveal complex FTIR consisting of extended characteristic vibrational bands which are specific for phosphate groups as a main constituent but with the sharing of some vibrations due to the borate groups. This criterion was investigated and approved using DAT (deconvolution analysis technique). The effects of different TMs ions on the FTIR spectra are very limited due to the low doping level (0.2%) introduced in the glass composition. Gamma irradiation causes minor effect on the FTIR spectra specifically the decrease of intensities of some bands. Such behavior is related to the change of bond angles and/or bond lengths of some structural building units upon gamma irradiation.

  12. A first-principles investigation of the effect of relaxation on the alloy formation in the aluminum-3 d-transition-metal system

    NASA Astrophysics Data System (ADS)

    Nikitin, N. Yu.

    2012-05-01

    The aim of this investigation is to establish the effect of relaxation on the formation of ordered substitutional solid solutions in Al1 - x M x alloys ( M = 3 d metal; x = 1.6 at %). As the main parameters of the process of formation of the aluminum-based solution, thermodynamic quantities such as the energy of dissolution and the cohesive energy have been chosen; for choosing the most appropriate substitutional element, an analysis of the relaxation energy and deviations of empirical atomic radii of the impurity from the radius of the matrix-forming element has been suggested. It has been shown that there is a correlation between these thermodynamic quantities through the behavior of the density of electronic states and the Fermi energy. A regular relation has also been demonstrated to exist between the relaxation and stability of arising solid solutions, which supports the applicability of the analysis of relaxation energy depending on the atomic radius of the matrix-substituting element. The presence of anomalies in the behavior of magnetic properties of some aluminum alloys with transition metals has been shown and their explanation is given.

  13. First-principles modeling of 3d-transition-metal-atom adsorption on silicene: a linear-response DFT + U approach.

    PubMed

    Le, Hung M; Pham, Tan-Tien; Dinh, Thach S; Kawazoe, Yoshiyuki; Nguyen-Manh, Duc

    2016-04-01

    By employing DFT  +  U calculations with the linear response method, we investigate the interactions between various 3d transition-metal atoms (Cr, Mn, Fe, Co) and silicene. In the cases of two-dimensional (2D) FeSi2 and CoSi2, the metal atoms tend to penetrate into the silicene layer. While CoSi2 is non-magnetic, FeSi2 exhibits a total magnetic moment of 2.21 μ(B)/cell. Upon the examination of 2D MSi6, a trend in anti-ferromagnetic (AFM) favorability in the z-direction is observed according to our DFT  +  U calculations. In the ferromagnetic (FM) states (less stable), each primary unit cell of CrSi6, MnSi6, and FeSi6 possesses different levels of total magnetization (4.01, 5.18, and 2.00 μ B/cell, respectively). The absolute magnetization given by AFM MSi6 structures varies in the range of 5.33-5.84 μ(B)/cell. A direct band gap in AFM MnSi6 (0.2 eV) is predicted, while the metastable FM FeSi6 structure has a wider band gap (0.85 eV). Interestingly, there are superexchange interactions between metal atoms in the MSi6 systems, which result in the AFM alignments. PMID:26940978

  14. First-principles study of site occupancy of 3d, 4d and 5d transition-metal elements in L10TiAl

    SciTech Connect

    Jiang, Chao

    2008-01-01

    Using a statistical-mechanical Wagner-Schottky model parametrized by first-principles density-functional (DFT-GGA) calculations on 32-atom supercells, we predict the lattice site occupancy of 3d (Ti-Cu), 4d (Zr-Ag) and 5d (Hf-Au) transition-metal elements in L10 TiAl intermetallic compound as a function of both alloy composition and temperature. The effects of local atomic relaxations, anisotropic lattice distortions, as well as magnetism on point defect energetics are fully taken into account. Our calculations show that, at all alloy compositions and temperatures, Zr and Hf consistently show a preference for the Ti sublattice, while Co, Ru, Rh, Pd, Ag, Re, Os, Ir, Pt and Au consistently show a preference for the Al sublattice. In contrast, the site preference of V, Cr, Mn, Fe, Ni, Cu, Nb, Mo, Tc, Ta and W strongly depend on both alloy stoichiometry and temperature. Our calculated results compare favorably with the existing theoretical and experimental studies in the literature.

  15. Single-Crystal to Single-Crystal Phase Transition and Segmented Thermochromic Luminescence in a Dynamic 3D Interpenetrated Ag(I) Coordination Network.

    PubMed

    Yan, Zhi-Hao; Li, Xiao-Yu; Liu, Li-Wei; Yu, Si-Qi; Wang, Xing-Po; Sun, Di

    2016-02-01

    A new 3D Ag(I)-based coordination network, [Ag2(pz)(bdc)·H2O]n (1; pz = pyrazine and H2bdc = benzene-1,3-dicarboxylic acid), was constructed by one-pot assembly and structurally established by single-crystal X-ray diffraction at different temperatures. Upon cooling from 298 to 93 K, 1 undergo an interesting single-crystal to single-crystal phase transition from orthorhombic Ibca (Z = 16) to Pccn (Z = 32) at around 148 K. Both phases show a rare 2-fold-interpenetrated 4-connected lvt network but incorporate different [Ag2(COO)2] dimeric secondary building units. It is worth mentioning that complex 1 shows red- and blue-shifted luminescences in the 290-170 and 140-80 K temperature ranges, respectively. The variable-temperature single-crystal X-ray crystallographic studies suggest that the argentophilic interactions and rigidity of the structure dominated the luminescence chromism trends at the respective temperature ranges. Upon being mechanically ground, 1 exhibits a slight mechanoluminescence red shift from 589 to 604 nm at 298 K.

  16. Structure of liquid phosphorus: A liquid-liquid phase transition via constant-pressure first-principles molecular dynamics

    NASA Astrophysics Data System (ADS)

    Morishita, Tetsuya

    2001-12-01

    Constant-pressure first-principles molecular dynamics simulations have been carried out to study structural phase transitions of liquid black phosphorus. By compressing the tetrahedral molecular liquid (a low-pressure phase), a structural phase transition from the molecular to polymeric liquid (a high-pressure phase) was successfully realized just as observed in the recent experiment by Katayama et al. [Nature 170 (2000) 403]. Structural properties in the polymeric liquid were investigated and it is found that the covalent p-state bonds are dominant within the first nearest neighbors of each atom. However, further compression of the polymeric liquid shows that the covalent bonding is weakened as pressure is increased. As a result, liquid phosphorus becomes similar to the simple liquid in which atoms form a close-packed structure at very high pressure.

  17. Improved model for the transit entropy of monatomic liquids

    NASA Astrophysics Data System (ADS)

    Wallace, Duane C.; Chisolm, Eric D.; Bock, Nicolas

    2009-05-01

    In the original formulation of vibration-transit (V-T) theory for monatomic liquid dynamics, the transit contribution to entropy was taken to be a universal constant, calibrated to the constant-volume entropy of melting. This model suffers two deficiencies: (a) it does not account for experimental entropy differences of ±2% among elemental liquids and (b) it implies a value of zero for the transit contribution to internal energy. The purpose of this paper is to correct these deficiencies. To this end, the V-T equation for entropy is fitted to an overall accuracy of ±0.1% to the available experimental high-temperature entropy data for elemental liquids. The theory contains two nuclear motion contributions: (a) the dominant vibrational contribution Svib(T/θ0) , where T is temperature and θ0 is the vibrational characteristic temperature, and (b) the transit contribution Str(T/θtr) , where θtr is a scaling temperature for each liquid. The appearance of a common functional form of Str for all the liquids studied is a property of the experimental data, when analyzed via the V-T formula. The resulting Str implies the correct transit contribution to internal energy. The theoretical entropy of melting is derived in a single formula applying to normal and anomalous melting alike. An ab initio calculation of θ0 , based on density-functional theory, is reported for liquid Na and Cu. Comparison of these calculations with the above analysis of experimental entropy data provides verification of V-T theory. In view of the present results, techniques currently being applied in ab initio simulations of liquid properties can be employed to advantage in the further testing and development of V-T theory.

  18. Liquid-Crystal Phase Transition Probed by Fluorescent Molecules

    NASA Astrophysics Data System (ADS)

    Hattori, Toshiaki; Hanai, Nobuhiko; Inouye, Hideyuki; Nakatsuka, Hiroki

    2001-08-01

    Phase transition of four liquid crystal materials have been studied by measuring the decay times of time-resolved intensity of fluorescence from two kind of dyes, malachite green and cryptocyanine, doped in these materials. It was found that the observed fluorescence lifetimes observed depend strongly on the doped molecules and that they change depending on the phase transition of the liquid-crystal materials. These results show that the fluorescence lifetime measurements are effective molecular probes for estimating the microscopic dynamics in these materials.

  19. Intrinsic response of polymer liquid crystals in photochemical phase transition

    SciTech Connect

    Ikeda, Tomiki; Sasaki, Takeo; Kim, Haengboo )

    1991-01-24

    Time-resolved measurements were performed on the photochemically induced isothermal phase transition of polymer liquid crystals (PLC) with mesogenic side chains of phenyl benzoate (PAPB3) and cyanobiphenyl (PACB3) under conditions wherein the photochemical reaction of the doped photoresponsive molecule (4-butyl-4-{prime}-methoxyazobenzene, BMAB) was completed within {approximately} 10 ns, and the subsequent phase transition of the matrix PLC from nematic (N) to isotropic (I) state was followed by time-resolved measurements of the birefringence of the system. Formation of a sufficient amount of the cis isomer of BMAB with a single pulse of a laser lowered the N-I phase transition temperature of the mixture, inducing the N-I phase transition of PLCs isothermally in a time range of {approximately} 200 ms. This time range is comparable to that of low molecular weight liquid crystals, indicating that suppression in mobility of mesogens in PLCs does not affect significantly the thermodynamically controlled process.

  20. Organic solvent-based graphene oxide liquid crystals: a facile route toward the next generation of self-assembled layer-by-layer multifunctional 3D architectures.

    PubMed

    Jalili, Rouhollah; Aboutalebi, Seyed Hamed; Esrafilzadeh, Dorna; Konstantinov, Konstantin; Moulton, Simon E; Razal, Joselito M; Wallace, Gordon G

    2013-05-28

    We introduce soft self-assembly of ultralarge liquid crystalline (LC) graphene oxide (GO) sheets in a wide range of organic solvents overcoming the practical limitations imposed on LC GO processing in water. This expands the number of known solvents which can support amphiphilic self-assembly to ethanol, acetone, tetrahydrofuran, N-dimethylformamide, N-cyclohexyl-2-pyrrolidone, and a number of other organic solvents, many of which were not known to afford solvophobic self-assembly prior to this report. The LC behavior of the as-prepared GO sheets in organic solvents has enabled us to disperse and organize substantial amounts of aggregate-free single-walled carbon nanotubes (SWNTs, up to 10 wt %) without compromise in LC properties. The as-prepared LC GO-SWNT dispersions were employed to achieve self-assembled layer-by-layer multifunctional 3D hybrid architectures comprising SWNTs and GO with unrivalled superior mechanical properties (Young's modulus in excess of 50 GPa and tensile strength of more than 500 MPa).

  1. 3D hierarchical assembly of ultrathin MnO2 nanoflakes on silicon nanowires for high performance micro-supercapacitors in Li- doped ionic liquid

    PubMed Central

    Dubal, Deepak P.; Aradilla, David; Bidan, Gérard; Gentile, Pascal; Schubert, Thomas J.S.; Wimberg, Jan; Sadki, Saïd; Gomez-Romero, Pedro

    2015-01-01

    Building of hierarchical core-shell hetero-structures is currently the subject of intensive research in the electrochemical field owing to its potential for making improved electrodes for high-performance micro-supercapacitors. Here we report a novel architecture design of hierarchical MnO2@silicon nanowires (MnO2@SiNWs) hetero-structures directly supported onto silicon wafer coupled with Li-ion doped 1-Methyl-1-propylpyrrolidinium bis(trifluromethylsulfonyl)imide (PMPyrrBTA) ionic liquids as electrolyte for micro-supercapacitors. A unique 3D mesoporous MnO2@SiNWs in Li-ion doped IL electrolyte can be cycled reversibly across a voltage of 2.2 V and exhibits a high areal capacitance of 13 mFcm−2. The high conductivity of the SiNWs arrays combined with the large surface area of ultrathin MnO2 nanoflakes are responsible for the remarkable performance of these MnO2@SiNWs hetero-structures which exhibit high energy density and excellent cycling stability. This combination of hybrid electrode and hybrid electrolyte opens up a novel avenue to design electrode materials for high-performance micro-supercapacitors. PMID:25985388

  2. 3D hierarchical assembly of ultrathin MnO2 nanoflakes on silicon nanowires for high performance micro-supercapacitors in Li- doped ionic liquid.

    PubMed

    Dubal, Deepak P; Aradilla, David; Bidan, Gérard; Gentile, Pascal; Schubert, Thomas J S; Wimberg, Jan; Sadki, Saïd; Gomez-Romero, Pedro

    2015-05-18

    Building of hierarchical core-shell hetero-structures is currently the subject of intensive research in the electrochemical field owing to its potential for making improved electrodes for high-performance micro-supercapacitors. Here we report a novel architecture design of hierarchical MnO2@silicon nanowires (MnO2@SiNWs) hetero-structures directly supported onto silicon wafer coupled with Li-ion doped 1-Methyl-1-propylpyrrolidinium bis(trifluromethylsulfonyl)imide (PMPyrrBTA) ionic liquids as electrolyte for micro-supercapacitors. A unique 3D mesoporous MnO2@SiNWs in Li-ion doped IL electrolyte can be cycled reversibly across a voltage of 2.2 V and exhibits a high areal capacitance of 13 mFcm(-2). The high conductivity of the SiNWs arrays combined with the large surface area of ultrathin MnO2 nanoflakes are responsible for the remarkable performance of these MnO2@SiNWs hetero-structures which exhibit high energy density and excellent cycling stability. This combination of hybrid electrode and hybrid electrolyte opens up a novel avenue to design electrode materials for high-performance micro-supercapacitors.

  3. The liquid-liquid phase transition in silicon revealed by snapshots of valence electrons.

    PubMed

    Beye, Martin; Sorgenfrei, Florian; Schlotter, William F; Wurth, Wilfried; Föhlisch, Alexander

    2010-09-28

    The basis for the anomalies of water is still mysterious. Quite generally tetrahedrally coordinated systems, also silicon, show similar thermodynamic behavior but lack--like water--a thorough explanation. Proposed models--controversially discussed--explain the anomalies as a remainder of a first-order phase transition between high and low density liquid phases, buried deeply in the "no man's land"--a part of the supercooled liquid region where rapid crystallization prohibits any experimental access. Other explanations doubt the existence of the phase transition and its first-order nature. Here, we provide experimental evidence for the first-order-phase transition in silicon. With ultrashort optical pulses of femtosecond duration we instantaneously heat the electronic system of silicon while the atomic structure as defined by the much heavier nuclear system remains initially unchanged. Only on a picosecond time scale the energy is transferred into the atomic lattice providing the energy to drive the phase transitions. With femtosecond X-ray pulses from FLASH, the free-electron laser at Hamburg, we follow the evolution of the valence electronic structure during this process. As the relevant phases are easily distinguishable in their electronic structure, we track how silicon melts into the low-density-liquid phase while a second phase transition into the high-density-liquid phase only occurs after the latent heat for the first-order phase transition has been transferred to the atomic structure. Proving the existence of the liquid-liquid phase transition in silicon, the hypothesized liquid-liquid scenario for water is strongly supported.

  4. Europeana and 3D

    NASA Astrophysics Data System (ADS)

    Pletinckx, D.

    2011-09-01

    The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.

  5. Suppression of phase transitions in a confined rodlike liquid crystal.

    PubMed

    Grigoriadis, Christos; Duran, Hatice; Steinhart, Martin; Kappl, Michael; Butt, Hans-Jürgen; Floudas, George

    2011-11-22

    The nematic-to-isotropic, crystal-to-nematic, and supercooled liquid-to-glass temperatures are studied in the liquid crystal 4-pentyl-4'-cyanobiphenyl (5CB) confined in self-ordered nanoporous alumina. The nematic-to-isotropic and the crystal-to-nematic transition temperatures are reduced linearly with the inverse pore diameter. The finding that the crystalline phase is completely suppressed in pores having diameters of 35 nm and below yields an estimate of the critical nucleus size. The liquid-to-glass temperature is reduced in confinement as anticipated by the model of rotational diffusion within a cavity. These results provide the pertinent phase diagram for a confined liquid crystal and are of technological relevance for the design of liquid crystal-based devices with tunable optical, thermal, and dielectric properties.

  6. Structural crossover in a supercooled metallic liquid and the link to a liquid-to-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Lan, S.; Blodgett, M.; Kelton, K. F.; Ma, J. L.; Fan, J.; Wang, X.-L.

    2016-05-01

    Time-resolved synchrotron measurements were carried out to capture the structure evolution of an electrostatically levitated metallic-glass-forming liquid during free cooling. The experimental data shows a crossover in the liquid structure at ˜1000 K, about 115 K below the melting temperature and 150 K above the crystallization temperature. The structure change is characterized by a dramatic growth in the extended-range order below the crossover temperature. Molecular dynamics simulations have identified that the growth of the extended-range order was due to an increased correlation between solute atoms. These results provide structural evidence for a liquid-to-liquid-phase-transition in the supercooled metallic liquid.

  7. An improved model for the transit entropy of monatomic liquids

    SciTech Connect

    Wallace, Duane C; Chisolm, Eric D; Bock, Nicolas

    2009-01-01

    In the original formulation of V-T theory for monatomic liquid dynamics, the transit contribution to entropy was taken to be a universal constant, calibrated to the constant-volume entropy of melting. This model suffers two deficiencies: (a) it does not account for experimental entropy differences of {+-}2% among elemental liquids, and (b) it implies a value of zero for the transit contribution to internal energy. The purpose of this paper is to correct these deficiencies. To this end, the V-T equation for entropy is fitted to an overall accuracy of {+-}0.1% to the available experimental high temperature entropy data for elemental liquids. The theory contains two nuclear motion contributions: (a) the dominant vibrational contribution S{sub vib}(T/{theta}{sub 0}), where T is temperature and {theta}{sub 0} is the vibrational characteristic temperature, and (b) the transit contribution S{sub tr}(T/{theta}{sub tr}), where {theta}{sub tr} is a scaling temperature for each liquid. The appearance of a common functional form of S{sub tr} for all the liquids studied is a property of the experimental data, when analyzed via the V-T formula. The resulting S{sub tr} implies the correct transit contribution to internal energy. The theoretical entropy of melting is derived, in a single formula applying to normal and anomalous melting alike. An ab initio calculation of {theta}{sub 0}, based on density functional theory, is reported for liquid Na and Cu. Comparison of these calculations with the above analysis of experimental entropy data provides verification of V-T theory. In view of the present results, techniques currently being applied in ab initio simulations of liquid properties can be employed to advantage in the further testing and development of V-T theory.

  8. Tests of Exchange-Correlation Functional Approximations Against Reliable Experimental Data for Average Bond Energies of 3d Transition Metal Compounds.

    PubMed

    Zhang, Wenjing; Truhlar, Donald G; Tang, Mingsheng

    2013-09-10

    One of the greatest challenges for the theoretical study of transition-metal-containing compounds is the treatment of intrinsically multiconfigurational atoms and molecules, which require a multireference (MR) treatment in wave function theory. The accuracy of density functional theory for such systems is still being explored. Here, we continue that exploration by presenting the predictions of 42 exchange-correlation (xc) functionals of 11 types [local spin density approximation (LSDA), generalized gradient approximation (GGA), nonseparable gradient approximation (NGA), global-hybrid GGA, meta-GGA, meta-NGA, global-hybrid meta-GGA, range-separated hybrid GGA, range-separated hybrid meta-GGA, range-separated hybrid meta-NGA, and DFT augmented with molecular mechanics damped dispersion (DFT-D)]. DFT-D is tested both for Grimme's DFT-D3(BJ) model with Becke-Johnson damping and for ωB97X-D, which has the empirical atom-atom dispersion parametrized by Chai and Head-Gordon. The Hartree-Fock (HF) method has also been included because it can be viewed as a functional with 100% HF exchange and no correlation. These methods are tested against a database including 70 first-transition-row (3d) transition-metal-containing molecules (19 single-reference molecules and 51 MR molecules), all of which have estimated experimental uncertainties equal to or less than 2.0 kcal/mol in the heat of formation. We analyze the accuracy in terms of the atomization energy per bond instead of the enthalpy of formation of the molecule because it allows us to test electronic energies without the possibility of cancellation of errors in electronic energies with errors in vibrational energies. All the density functional and HF wave functions have been optimized to a stable solution, in which the spatial symmetry is allowed to be broken to minimize the energy to a stable solution. We find that τ-HCTHhyb has the smallest mean unsigned error (MUE) in average bond energy, in particular 2.5 kcal

  9. Improved model for the transit entropy of monatomic liquids

    NASA Astrophysics Data System (ADS)

    Chisolm, Eric; Bock, Nicolas; Wallace, Duane

    2010-03-01

    In the original formulation of vibration-transit (V-T) theory for monatomic liquid dynamics, the transit contribution to entropy was taken to be a universal constant, calibrated to the constant-volume entropy of melting. This implied that the transit contribution to energy vanishes, which is incorrect. Here we develop a new formulation that corrects this deficiency. The theory contains two nuclear motion contributions: (a) the dominant vibrational contribution Svib(T/θ0), where T is temperature and θ0 is the vibrational characteristic temperature, and (b) the transit contribution Str(T/θtr), where θtr is a scaling temperature for each liquid. The appearance of a common functional form of Str for all the liquids studied is deduced from the experimental data, when analyzed via the V-T formula. The theoretical entropy of melting is derived, in a single formula applying to normal and anomalous melting alike. An ab initio calculation of θ0 for Na and Cu, based on density functional theory, provides verification of our analysis and V-T theory. In view of the present results, techniques currently being applied in ab initio simulations of liquid properties can be employed to advantage in the further testing and development of V-T theory.

  10. Electronic and Sturctural Transitions in Dense Liquid Sodium

    SciTech Connect

    Raty, J Y; Schwegler, E R; Bonev, S A

    2007-08-06

    At ambient conditions, the light alkali metals are free-electron like crystals with a highly symmetric structure. However, they were shown recently to exhibit unexpected complexity under pressure. It was predicted from theory and later confirmed by experiment that Li and Na undergo a sequence of symmetry breaking transitions driven by a Peierls mechanism. Most recently, measurements of the Na melting curve revealed an unprecedented and still unexplained drop in the melting temperature from 1000 K at 30 GPa to room temperature at 120 GPa. Here we report results from ab initio calculations that explain the unusual melting behavior in dense Na. We show that molten Na undergoes a series of pressure-induced structural and electronic transitions analogous to that observed in solid Na, but commencing at much lower pressure in the presence of disorder. With increasing pressure, liquid Na initially evolves by assuming a more compact local structure. However, a transition to a lower coordinated liquid takes place at a pressure around 65 GPa, accompanied by a threefold drop in electrical conductivity. A pseudogap opening at the Fermi level, an effect previously not observed in a liquid metal, drives this transition. Remarkably, the lower coordinated liquid emerges at rather elevated temperatures and above the stability region of a closed packed free electron-like metal. We predict that similar exotic behavior is possible in other materials as well.

  11. Structural, mechanical and electronic properties of 3d transition metal nitrides in cubic zincblende, rocksalt and cesium chloride structures: a first-principles investigation.

    PubMed

    Liu, Z T Y; Zhou, X; Khare, S V; Gall, D

    2014-01-15

    We report systematic results from ab initio calculations with density functional theory on three cubic structures, zincblende (zb), rocksalt (rs) and cesium chloride (cc), of the ten 3d transition metal nitrides. We computed lattice constants, elastic constants, their derived moduli and ratios that characterize mechanical properties. Experimental measurements exist in the literature of lattice constants for rs-ScN, rs-TiN and rs-VN and of elastic constants for rs-TiN and rs-VN, all of which are in good agreement with our computational results. Similarly, computed Vickers hardness (HV) values for rs-TiN and rs-VN are consistent with earlier experimental results. Several trends were observed in our rich data set of 30 compounds. All nitrides, except for zb-CrN, rs-MnN, rs-FeN, cc-ScN, cc-CrN, cc-NiN and cc-ZnN, were found to be mechanically stable. A clear correlation in the atomic density with the bulk modulus (B) was observed with maximum values of B around FeN, MnN and CrN. The shear modulus, Young's modulus, HV and indicators of brittleness showed similar trends and all showed maxima for cc-VN. The calculated value of HV for cc-VN was about 30 GPa, while the next highest values were for rs-ScN and rs-TiN, about 24 GPa. A relation (H(V) is proportional to θ(D)(2)) between HV and Debye temperature (θD) was investigated and verified for each structure type. A tendency for anti-correlation of the elastic constant C44, which strongly influences stability and hardness, with the number of electronic states around the Fermi energy was observed.

  12. Characterization by combined optical and FT infrared spectra of 3d-transition metal ions doped-bismuth silicate glasses and effects of gamma irradiation.

    PubMed

    ElBatal, F H; Abdelghany, A M; ElBatal, H A

    2014-03-25

    Optical and infrared absorption spectral measurements were carried out for binary bismuth silicate glass and other derived prepared samples with the same composition and containing additional 0.2% of one of 3d transition metal oxides. The same combined spectroscopic properties were also measured after subjecting the prepared glasses to a gamma dose of 8 Mrad. The experimental optical spectra reveal strong UV-near visible absorption bands from the base and extended to all TMs-doped samples and these specific extended and strong UV-near visible absorption bands are related to the contributions of absorption from both trace iron (Fe(3+)) ions present as contaminated impurities within the raw materials and from absorption of main constituent trivalent bismuth (Bi(3+)) ions. The strong UV-near visible absorption bands are observed to suppress any further UV bands from TM ions. The studied glasses show obvious resistant to gamma irradiation and only small changes are observed upon gamma irradiation. This observed shielding behavior is related to the presence of high Bi(3+) ions with heavy mass causing the observed stability of the optical absorption. Infrared absorption spectra of the studied glasses reveal characteristic vibrational bands due to both modes from silicate network and the sharing of Bi-O linkages and the presence of TMs in the doping level (0.2%) causes no distinct changes within the number or position of the vibrational modes. The presence of high Bi2O3 content (70 mol%) appears to cause stability of the structural building units towards gamma irradiation as revealed by FTIR measurements.

  13. Ga, Ca, and 3d transition element (Cr through Zn) partitioning among spinel-lherzolite phases from the Lanzo massif, Italy: Analytical results and crystal chemistry

    SciTech Connect

    Wogelius, R.A.; Fraser, D.G.

    1994-06-01

    Ultramafic rocks exposed in Lanzo massif, Italy is a record of mantle geochemistry, melting, sub-solidus re-equilibration. Plagioclase(+ spinel)-lherzolite samples were analyzed by Scanning Proton Microscopy, other techniques. Previous work postulated partial melting events and a two-stage sub-solidus cooling history; this paper notes Ga enrichment on spinel-clinopyroxene grain boundaries, high Ga and transition element content of spinel, and pyroxene zonation in Ca and Al. Trace element levels in olivine and orthopyroxene are also presented. Zoning trends are interpreted as due to diffusion during cooling. Olivine-clinopyroxene Cr and Ca exchange as well as clinopyroxene and spinel zonation trends indicate that the massif experienced at least two sub-solidus cooling episodes, one at 20 kbar to 1000 C and one at 8 kbar <750C. Ga levels in cores of Lanzo high-Cr spinels are high (82-66 ppM) relative to other mantle spinels (66-40 ppM), indicating enrichment. Ga content of ultramafic spinels apparently increases with Cr content; this may be due to: increased Ga solubility stemming from crystal chemical effects and/or higher Ga activities in associated silicate melts. Thus, during melting, high-Cr residual spinel may tend to buffer solid-phase Ga level. These spinels are not only rich in Ga and Cr (max 26.37 el. wt %), but also in Fe (max 21.07 el. wt %), Mn (max 3400 ppM), and Zn (max 2430 ppM). These enrichments are again due to melt extraction and partitioning into spinel structure. Low Ni (min 1050 ppM) levels are due to unsuccessful competition of Ni with Cr for octahedral structural sites caused by crystal field. Comparisons of change in partitioning vs Cr content among several 3d transition elements for spinels from Lanzo, other localities allow us to separate crystal field effects from bulk chemical effects and to show that in typical assemblages, inversion of olivine-spinel partition coefficient for Ni from <1 to >1 should occur at 11% el. wt. Cr in spinel.

  14. Microgravity Studies of Liquid-Liquid Phase Transitions in Alumina-Yttria Melts

    NASA Technical Reports Server (NTRS)

    Guynes, Buddy (Technical Monitor); Weber, Richard; Nordine, Paul

    2004-01-01

    The scientific objective of this research is to increase the fundamental knowledge base for liquid- phase processing of technologically important oxide materials. The experimental objective is to define conditions and hardware requirements for microgravity flight experiments to test and expand the experimental hypotheses that: 1. Liquid phase transitions can occur in undercooled melts by a diffusionless process. 2. Onset of the liquid phase transition is accompanied by a large change in the temperature dependence of melt viscosity. Experiments on undercooled YAG (Y3A15012)- and rare earth oxide aluminate composition liquids demonstrated a large departure from an Arrhenian temperature dependence of viscosity. Liquid YAG is nearly inviscid at its 2240 K melting point. Glass fibers were pulled from melts undercooled by ca. 600 K indicating that the viscosity is on the order of 100 Pans (1000 Poise) at 1600 K. This value of viscosity is 500 times greater than that obtained by extrapolation of data for temperatures above the melting point of YAG. These results show that the liquids are extremely fragile and that the onset of the highly non-Arrhenian viscosity-temperature relationship occurs at a temperature considerably below the equilibrium melting point of the solid phases. Further results on undercooled alumina-yttria melts containing 23-42 mole % yttrium oxide indicate that a congruent liquid-liquid phase transition occurs in the undercooled liquids. The rates of transition are inconsistent with a diffusion-limited process. This research is directed to investigation of the scientifically interesting phenomena of polyamorphism and fragility in undercooled rare earth oxide aluminum oxide liquids. The results bear on the technologically important problem of producing high value rare earth-based optical materials.

  15. 3d-3d correspondence revisited

    NASA Astrophysics Data System (ADS)

    Chung, Hee-Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr

    2016-04-01

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d {N}=2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. We also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

  16. 3d-3d correspondence revisited

    DOE PAGES

    Chung, Hee -Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr

    2016-04-21

    In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d N = 2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. As a result, we also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.

  17. Behavior of supercooled aqueous solutions stemming from hidden liquid-liquid transition in water

    NASA Astrophysics Data System (ADS)

    Biddle, John W.; Holten, Vincent; Anisimov, Mikhail A.

    2014-08-01

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid-liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid-liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H2O-NaCl and H2O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid-liquid transition. We elucidate the non-conserved nature of the order parameter (extent of "reaction" between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

  18. Synthesis, structure and magnetic properties of low dimensional spin systems in the 3d transition metal oxides and superconductivity in magnesium borate

    NASA Astrophysics Data System (ADS)

    Rogado, Nyrissa S.

    The major part of this thesis deals with the synthesis and magnetic characterization of low dimensional spin systems in the 3d transition metal oxides. Such systems are of interest due to the simplicity of their structures, allowing theoretical modeling of their electronic and magnetic behavior. Exotic properties are also often encountered. Studies involving layered magnetic materials based on triangle lattices, in particular, have resulted in many observations of unusual low temperature spin dynamics, and have presented new challenges for the theoretical understanding of magnetic systems. The magnetic properties of some compounds exhibiting these triangle-based lattices are described here in detail. BaNi2V2O8 is a spin-1 antiferromagnet on a honeycomb net. Susceptibility chi(T), specific heat C(T), and neutron diffraction measurements on this compound reveal the onset of antiferromagnetic (AFM) long-range ordering (LRO) close to 50 K. Diffuse diffraction peaks that are characteristic of two-dimensional (2D) short-range order are also observed up to 100 K. chi(T) of Ba(Ni1-xMgx)2V 2O8 shows the gradual disappearance of LRO with doping. Ni3V2O8, Co3V2O 8, and beta-Cu3V2O8 have spin-1, spin-3/2, and spin-1/2 magnetic lattices that are a new anisotropic variant of the Kagome net, wherein edge-sharing MO6 octahedra form the rises and rungs of a "Kagome staircase". The anisotropy largely relieves the geometric frustration, but results in rich magnetic behavior. Characterization of the magnetization of polycrystalline samples of Ni 3V2O8 and Co3V2O8 reveals that the compounds are ferrimagnetic in character. C(T) show four distinct magnetic phase transitions below 9 K for Ni3V2O 8 and two below 11 K for Co3V2O8. In the case of beta-Cu3V2O8, chi(T) and C(T) show the onset of short-range ordering at approximately 75 K, and a magnetic phase transition with the characteristics of antiferromagnetism at around 29 K. The second part of this thesis describes the bulk synthesis of

  19. Electronic and structural transitions in dense liquid sodium

    NASA Astrophysics Data System (ADS)

    Raty, Jean-Yves; Schwegler, Eric; Bonev, Stanimir A.

    2007-09-01

    At ambient conditions, the light alkali metals are free-electron-like crystals with a highly symmetric structure. However, they were found recently to exhibit unexpected complexity under pressure. It was predicted from theory-and later confirmed by experiment-that lithium and sodium undergo a sequence of symmetry-breaking transitions, driven by a Peierls mechanism, at high pressures. Measurements of the sodium melting curve have subsequently revealed an unprecedented (and still unexplained) pressure-induced drop in melting temperature from 1,000K at 30GPa down to room temperature at 120GPa. Here we report results from ab initio calculations that explain the unusual melting behaviour in dense sodium. We show that molten sodium undergoes a series of pressure-induced structural and electronic transitions, analogous to those observed in solid sodium but commencing at much lower pressure in the presence of liquid disorder. As pressure is increased, liquid sodium initially evolves by assuming a more compact local structure. However, a transition to a lower-coordinated liquid takes place at a pressure of around 65GPa, accompanied by a threefold drop in electrical conductivity. This transition is driven by the opening of a pseudogap, at the Fermi level, in the electronic density of states-an effect that has not hitherto been observed in a liquid metal. The lower-coordinated liquid emerges at high temperatures and above the stability region of a close-packed free-electron-like metal. We predict that similar exotic behaviour is possible in other materials as well.

  20. Magnetic and structural phase transitions of multiferroic boracites M3B7O13X (M =3 d transition metal Cr-Zn or Mg; X =halogen Cl, Br, I)

    NASA Astrophysics Data System (ADS)

    Schnelle, Walter; Schmid, Hans

    2015-05-01

    The specific heat capacity of mostly single-crystalline samples of 21 boracite compounds M3B7O13X with M a 3 d transition metal (Cr, Mn, Fe, Co, Ni, Cu, Zn) or Mg and X a halogen (Cl, Br, I) is determined. In combination with magnetic susceptibility data the magnetic ordering of the M2 + ions at TN is investigated in detail. The fully ferroelectric/fully ferroelastic structural phase transitions at higher temperatures are measured by differential scanning calorimetry. In the Cr-Br, Cr-I, Cu-Cl, and Cu-Br compounds, previously unknown magnetic phases were found. Magnetic order in the boracites is characterized by the quantum and classical spin states of the M2 + ions, a variable degree of structural distortion, orbital effects, and competing exchange interactions. The Cu-Cl, Cu-Br, and Ni-Cl boracites exhibit broad maxima of magnetic specific heat and of magnetic susceptibility above TN caused by low-dimensional or frustrated magnetic interactions. Co boracites display additional broad anomalies below TN originating from continuous spin reorientations and effective S =1 /2 ground states. Indications for spin reorientations are also observed for Fe boracites. New phases appear in high magnetic fields for some Co and Fe boracites, which is not the case for the Mn compounds. Stronger magnetic frustration is deduced for the cubic Cr compounds. For the latter compounds and Ni-I boracite magnetostructural phase transitions are observed.

  1. Relationship between the liquid liquid phase transition and dynamic behaviour in the Jagla model

    NASA Astrophysics Data System (ADS)

    Xu, Limei; Ehrenberg, Isaac; Buldyrev, Sergey V.; Stanley, H. Eugene

    2006-09-01

    Using molecular dynamics simulations, we study a spherically symmetric 'two-scale' Jagla potential with both repulsive and attractive ramps. This potential displays a liquid-liquid phase transition with a positively sloped coexistence line ending at a critical point well above the equilibrium melting line. We study the dynamic behaviour in the vicinity of this liquid-liquid critical point. Below the critical point, we find that the dynamics in the more ordered high density liquid (HDL) are much slower then the dynamics in the less ordered low density liquid (LDL). Moreover, the behaviour of the diffusion constant and relaxation time in the HDL phase follows approximately an Arrhenius law, while in the LDL phase the slope of the Arrhenius fit increases upon cooling. Above the critical pressure, as we cool the system at constant pressure, the behaviour of the dynamics smoothly changes with temperature. It resembles the behaviour of the LDL at high temperatures and resembles the behaviour of the HDL at low temperatures. This dynamic crossover happens in the vicinity of the Widom line (the extension of the coexistence line into the one-phase region) which also has a positive slope. Our work suggests a possible general relation between a liquid-liquid phase transition and the change in dynamics.

  2. String theory, quantum phase transitions, and the emergent Fermi liquid.

    PubMed

    Cubrović, Mihailo; Zaanen, Jan; Schalm, Koenraad

    2009-07-24

    A central problem in quantum condensed matter physics is the critical theory governing the zero-temperature quantum phase transition between strongly renormalized Fermi liquids as found in heavy fermion intermetallics and possibly in high-critical temperature superconductors. We found that the mathematics of string theory is capable of describing such fermionic quantum critical states. Using the anti-de Sitter/conformal field theory correspondence to relate fermionic quantum critical fields to a gravitational problem, we computed the spectral functions of fermions in the field theory. By increasing the fermion density away from the relativistic quantum critical point, a state emerges with all the features of the Fermi liquid.

  3. 3D and Education

    NASA Astrophysics Data System (ADS)

    Meulien Ohlmann, Odile

    2013-02-01

    Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method of initiation to 3D creation that entails the spatial/temporal experience of the holographic visual. She will present some different tools and techniques used for this learning, their advantages and disadvantages, programs and issues of educational policies, constraints and expectations related to the development of new techniques for 3D imaging. Although the creation of display holograms is very much reduced compared to the creation of the 90ies, the holographic concept is spreading in all scientific, social, and artistic activities of our present time. She will also raise many questions: What means 3D? Is it communication? Is it perception? How the seeing and none seeing is interferes? What else has to be taken in consideration to communicate in 3D? How to handle the non visible relations of moving objects with subjects? Does this transform our model of exchange with others? What kind of interaction this has with our everyday life? Then come more practical questions: How to learn creating 3D visualization, to learn 3D grammar, 3D language, 3D thinking? What for? At what level? In which matter? for whom?

  4. Comparing two tetraalkylammonium ionic liquids. II. Phase transitions.

    PubMed

    Lima, Thamires A; Paschoal, Vitor H; Faria, Luiz F O; Ribeiro, Mauro C C; Ferreira, Fabio F; Costa, Fanny N; Giles, Carlos

    2016-06-14

    Phase transitions of the ionic liquids n-butyl-trimethylammonium bis(trifluoromethanesulfonyl)imide, [N1114][NTf2], and methyl-tributylammonium bis(trifluoromethanesulfonyl)imide, [N1444][NTf2], were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, and Raman spectroscopy. XRD and Raman spectra were obtained as a function of temperature at atmospheric pressure, and also under high pressure at room temperature using a diamond anvil cell (DAC). [N1444][NTf2] experiences glass transition at low temperature, whereas [N1114][NTf2] crystallizes or not depending on the cooling rate. Both the ionic liquids exhibit glass transition under high pressure. XRD and low-frequency Raman spectra provide a consistent physical picture of structural ordering-disordering accompanying the thermal events of crystallization, glass transition, cold crystallization, pre-melting, and melting. Raman spectra in the high-frequency range of some specific cation and anion normal modes reveal conformational changes of the molecular structures along phase transitions.

  5. Evidence of a liquid-liquid phase transition in hot dense hydrogen.

    PubMed

    Dzyabura, Vasily; Zaghoo, Mohamed; Silvera, Isaac F

    2013-05-14

    We use pulsed-laser heating of hydrogen at static pressures in the megabar pressure region to search for the plasma phase transition to liquid atomic metallic hydrogen. We heat our samples substantially above the melting line and observe a plateau in a temperature vs. laser power curve that otherwise increases with power. This anomaly in the heating curve appears correlated with theoretical predictions for the plasma phase transition. PMID:23630287

  6. Electrical Freedericksz transitions in nematic liquid crystals containing ferroelectric nanoparticles

    NASA Astrophysics Data System (ADS)

    Cîrtoaje, Cristina; Petrescu, Emil; Stoian, Victor

    2015-03-01

    A new theoretical approach was elaborated to explain the contradictions reported in many papers about the electric threshold for Freedericksz transition in nematic liquid crystal (NLC) with ferroparticles additives. The free energy density of the mixture was estimated and the contributions of the interaction energy of NLC molecules with ferroparticles surface were calculated. Experimental results for 5CB-BaTiO3 mixture are given.

  7. Influence of spinons fluctuations near the spin liquid Mott transition

    NASA Astrophysics Data System (ADS)

    Lee, Tsung-Han; Florens, Serge; Dobrosavljevic, Vladimir

    We investigate the metal to Mott-insulator transition (MIT) in the Hubbard-Heisenberg model using the slave-rotor technique, which allows to combine for the first time the dynamical mean field theory (DMFT) with the Resonating Valence Bond (RVB) approach. In the spin-liquid phase at large Coulomb repulsion, the system shows a RVB transition from a trivial paramagnetic Mott insulator towards a low temperature insulating state with long lived spinons, as seen by the emergence of a linear specific heat. This quenching of the entropy in the spin liquid phase provides strong modifications in the shape of the standard DMFT phase diagram for the MIT occurring at intermediate values of the Coulomb repulsion. We find that the RVB transition happens concomitantly with the first order MIT lines at low temperature. This implies that the Mott insulator always accommodates a spinon Fermi surface, even in the coexistence regime of the MIT, and that the metallic state always stays a Fermi-liquid as it rejects the presence of free spinons, due to their strong scattering onto the holons.

  8. Surface entropy of liquid transition and noble metals

    NASA Astrophysics Data System (ADS)

    Gosh, R. C.; Das, Ramprosad; Sen, Sumon C.; Bhuiyan, G. M.

    2015-07-01

    Surface entropy of liquid transition and noble metals has been investigated using an expression obtained from the hard-sphere (HS) theory of liquid. The expression is developed from the Mayer's extended surface tension formula [Journal of Non-Crystalline Solids 380 (2013) 42-47]. For interionic interaction in metals, Brettonet-Silbert (BS) pseudopotentials and embedded atom method (EAM) potentials have been used. The liquid structure is described by the variational modified hypernetted chain (VMHNC) theory. The essential ingredient of the expression is the temperature dependent effective HS diameter (or packing fraction), which is calculated from the aforementioned potentials together with the VMHNC theory. The obtained results for the surface entropy using the effective HS diameter are found to be good in agreement with the available experimental as well as other theoretical values.

  9. Improved grand canonical sampling of vapour-liquid transitions

    NASA Astrophysics Data System (ADS)

    Wilding, Nigel B.

    2016-10-01

    Simulation within the grand canonical ensemble is the method of choice for accurate studies of first order vapour-liquid phase transitions in model fluids. Such simulations typically employ sampling that is biased with respect to the overall number density in order to overcome the free energy barrier associated with mixed phase states. However, at low temperature and for large system size, this approach suffers a drastic slowing down in sampling efficiency. The culprits are geometrically induced transitions (stemming from the periodic boundary conditions) which involve changes in droplet shape from sphere to cylinder and cylinder to slab. Since the overall number density does not discriminate sufficiently between these shapes, it fails as an order parameter for biasing through the transitions. Here we report two approaches to ameliorating these difficulties. The first introduces a droplet shape based order parameter that generates a transition path from vapour to slab states for which spherical and cylindrical droplets are suppressed. The second simply biases with respect to the number density in a tetragonal subvolume of the system. Compared to the standard approach, both methods offer improved sampling, allowing estimates of coexistence parameters and vapor-liquid surface tension for larger system sizes and lower temperatures.

  10. Non-equilibrium phase transitions in a liquid crystal

    NASA Astrophysics Data System (ADS)

    Dan, K.; Roy, M.; Datta, A.

    2015-09-01

    The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features of the "Nematic-Isotropic" (N-I) phase transition of a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from the effects of heating rate and initial temperature on the transitions, through differential scanning calorimetry (DSC), Fourier transform infrared and fluorescence spectroscopy. Around the vicinity of the glass transition temperature (Tg), while only a change in the baseline of the ΔCp vs T curve is observed for heating rate (β) > 5 K min-1, consistent with a glass transition, a clear peak for β ≤ 5 K min-1 and the rapid reduction in the ΔCp value from the former to the latter rate correspond to an order-disorder transition and a transition from ergodic to non-ergodic behaviour. The ln β vs 1000/T curve for the glass transition shows convex Arrhenius behaviour that can be explained very well by a purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. Fourier transform infrared spectroscopy indicates sudden freezing of the out-of-plane distortion vibrations of the benzene rings around the glass transition temperature and a considerable red shift indicating enhanced coplanarity of the benzene rings and, consequently, enhancement in the molecular ordering compared to room temperature. We further provide a direct experimental evidence of the non-equilibrium nature of the N-I transition through the dependence of this transition temperature (TNI) and associated enthalpy change (ΔH) on the initial temperature (at fixed β-values) for the DSC scans. A plausible qualitative explanation based on Mesquita's extension of Landau-deGennes theory [O. N. de Mesquita, Braz. J. Phys. 28, 257 (1998)] has been put forward. The change in the molecular ordering from nematic to isotropic phase has been investigated through fluorescence anisotropy measurements where the order parameter, quantified by the

  11. Non-equilibrium phase transitions in a liquid crystal.

    PubMed

    Dan, K; Roy, M; Datta, A

    2015-09-01

    The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features of the "Nematic-Isotropic" (N-I) phase transition of a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from the effects of heating rate and initial temperature on the transitions, through differential scanning calorimetry (DSC), Fourier transform infrared and fluorescence spectroscopy. Around the vicinity of the glass transition temperature (Tg), while only a change in the baseline of the ΔCp vs T curve is observed for heating rate (β) > 5 K min(-1), consistent with a glass transition, a clear peak for β ≤ 5 K min(-1) and the rapid reduction in the ΔCp value from the former to the latter rate correspond to an order-disorder transition and a transition from ergodic to non-ergodic behaviour. The ln β vs 1000/T curve for the glass transition shows convex Arrhenius behaviour that can be explained very well by a purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. Fourier transform infrared spectroscopy indicates sudden freezing of the out-of-plane distortion vibrations of the benzene rings around the glass transition temperature and a considerable red shift indicating enhanced coplanarity of the benzene rings and, consequently, enhancement in the molecular ordering compared to room temperature. We further provide a direct experimental evidence of the non-equilibrium nature of the N-I transition through the dependence of this transition temperature (TNI) and associated enthalpy change (ΔH) on the initial temperature (at fixed β-values) for the DSC scans. A plausible qualitative explanation based on Mesquita's extension of Landau-deGennes theory [O. N. de Mesquita, Braz. J. Phys. 28, 257 (1998)] has been put forward. The change in the molecular ordering from nematic to isotropic phase has been investigated through fluorescence anisotropy measurements where the order parameter, quantified by the

  12. Phase transitions for a collective coordinate coupled to Luttinger liquids.

    PubMed

    Horovitz, Baruch; Giamarchi, Thierry; Le Doussal, Pierre

    2013-09-13

    We study various realizations of collective coordinates, e.g., the position of a particle, the charge of a Coulomb box, or the phase of a Bose or a superconducting condensate, coupled to Luttinger liquids with N flavors. We find that for a Luttinger parameter (1/2)transition from a delocalized phase into a phase with a periodic potential at strong coupling. In the delocalized phase the dynamics is dominated by an effective mass, i.e., diffusive in imaginary time, while on the transition line it becomes dissipative. At K=(1/2) there is an additional transition into a localized phase with no diffusion at zero temperature. PMID:24074101

  13. Transition from laminar to turbulent flow in liquid filled microtubes

    NASA Astrophysics Data System (ADS)

    Sharp, K. V.; Adrian, R. J.

    2004-05-01

    The transition to turbulent flow is studied for liquids of different polarities in glass microtubes having diameters between 50 and 247 µm. The onset of transition occurs at Reynolds numbers of ~1,800 2,000, as indicated by greater-than-laminar pressure drop and micro-PIV measurements of mean velocity and rms velocity fluctuations at the centerline. Transition at anomalously low values of Reynolds number was never observed. Additionally, the results of more than 1,500 measurements of pressure drop versus flow rate confirm the macroscopic Poiseuille flow result for laminar flow resistance to within -1% systematic and ±2.5% rms random error for Reynolds numbers less than 1,800.

  14. Excitation-energy dependence of the resonant Auger transitions to the 4p{sup 4}({sup 1}D)np (n=5,6) states across the 3d{sub 3/2}{sup -1}5p and 3d{sub 5/2}{sup -1}6p resonances in Kr

    SciTech Connect

    Sankari, A.; Alitalo, S.; Nikkinen, J.; Kivimaeki, A.; Aksela, S.; Aksela, H.; Fritzsche, S.

    2007-08-15

    The energy dependencies of the intensities and angular distribution parameters {beta} of the resonant Auger final states 4p{sup 4}({sup 1}D)np (n=5,6) of Kr were determined experimentally in the excitation-energy region of the overlapping 3d{sub 3/2}{sup -1}5p and 3d{sub 5/2}{sup -1}6p resonances. The experimental results were compared with the outcome of multiconfiguration Dirac-Fock calculations. Combining experimental and calculated results allowed us to study interference effects between the direct and several resonant channels that populate the 4p{sup 4}({sup 1}D)np states. The inclusion of the direct channel was crucial in order to reproduce the observed energy behavior of the angular distribution parameters. It was also important to take into account experimentally observed shake transitions.

  15. 3D Imaging.

    ERIC Educational Resources Information Center

    Hastings, S. K.

    2002-01-01

    Discusses 3 D imaging as it relates to digital representations in virtual library collections. Highlights include X-ray computed tomography (X-ray CT); the National Science Foundation (NSF) Digital Library Initiatives; output peripherals; image retrieval systems, including metadata; and applications of 3 D imaging for libraries and museums. (LRW)

  16. Contrasting fluvial styles across the mid-Pleistocene climate transition in the northern shelf of the South China Sea: Evidence from 3D seismic data

    NASA Astrophysics Data System (ADS)

    Zhuo, Haiteng; Wang, Yingmin; Shi, Hesheng; He, Min; Chen, Weitao; Li, Hua; Wang, Ying; Yan, Weiyao

    2015-12-01

    Multiple successions of buried fluvial channel systems were identified in the Quaternary section of the mid-shelf region of the northern South China Sea, providing a new case study for understanding the interplay between sea level variations and climate change. Using three commercial 3D seismic surveys, accompanied by several 2D lines and a few shallow boreholes, the sequence stratigraphy, seismic geomorphology and stratal architecture of these fluvial channels were carefully investigated. Based on their origin, dimensions, planform geometries and infill architectures, six classes of channel systems, from Class 1 to Class 6, were recognized within five sequences of Quaternary section (SQ1 to SQ5). Three types of fluvial systems among them are incised in their nature, including the trunk incised valleys (Class 1), medium incised valleys (Class 2) and incised tributaries (Class 3). The other three types are unincised, which comprise the trunk channels (Class 4), lateral migrating channels (Class 5) and the stable channels (Class 6). The trunk channels and/or the major valleys that contain braided channels at their base are hypothesized to be a product of deposition from the "big rivers" that have puzzled the sedimentologists for the last decade, providing evidence for the existence of such rivers in the ancient record. Absolute age dates from a few shallow boreholes indicate that the landscapes that were associated with these fluvial systems changed significantly near the completion of the mid-Pleistocene climate transition (MPT), which approximately corresponds to horizon SB2 with an age of ˜0.6 Ma BP. Below SB2, the Early Pleistocene sequence (SQ1) is dominated by a range of different types of unincised fluvial systems. Evidence of incised valleys is absent in SQ1. In contrast, extensive fluvial incision occurred in the successions above horizon SB2 (within SQ2-SQ5). Although recent studies call for increased incision being a product of climate-controlled increase

  17. Liquid-Liquid Phase Transitions of Phosphorus via Constant-Pressure First-Principles Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Morishita, Tetsuya

    2001-09-01

    Pressure-induced phase transitions in liquid phosphorus have been studied by constant-pressure first-principles molecular dynamics simulations. By compressing a low-pressure liquid which consists of the tetrahedral P4 molecules, a structural phase transition from the molecular to polymeric liquid (a high-pressure phase) observed in the recent experiment by Katayama et al. [Nature (London) 403, 170 (2000)] was successfully realized. It is found that this transition is caused by a breakup of the tetrahedral molecules with large volume contraction. The same transition is also realized by heating. This indicates that only the polymeric liquid can stably exist at high temperature.

  18. In-situ isothermal phase transitions in photochromic liquid crystals

    NASA Astrophysics Data System (ADS)

    Watson, Samantha J.; Gleeson, Helen F.; D'Emanuele, Antony; Serak, Svetlana V.; Grozhik, Vladimir A.

    1998-06-01

    This study examines the optical response and physical properties of the homologous series 4-n-butyl-4'-n-alkoxyazobenzene. The members of this series all exhibit liquid crystalline phase behavior, and have also been used as dopants in 4-cyano-4'- n'pentylbiphenyl (5CB), a room temperature nematic liquid crystal. The guest-host system and the azobenzene series have been characterized using optical microscopy and UV-vis spectrophotometry. Illumination of these systems with light of a suitable wavelength induces a trans-cis isomerization of the azo- dye molecules which results in a reorientation of the liquid crystal director, often to such an extent that the liquid crystal phase is disrupted, causing an in situ isothermal phase transition. The response of the liquid crystal system to a linearly polarized beam of exciting radiation is examined with the use of a probe He:Ne laser. Changes in light transmission are then detected with a photodiode. Responses are discussed in terms of homologue, cell thickness and temperature.

  19. Apparent First-Order Liquid-Liquid Transition with Pre-transition Density Anomaly, in Water-Rich Ideal Solutions.

    PubMed

    Zhao, Zuofeng; Angell, C Austen

    2016-02-12

    The striking increases in response functions observed during supercooling of pure water have been the source of much interest and controversy. Imminent divergences of compressibility etc. unfortunately cannot be confirmed due to pre-emption by ice crystallization. Crystallization can be repressed by addition of second components, but these usually destroy the anomalies of interest. Here we study systems in which protic ionic liquid second components dissolve ideally in water, and ice formation is avoided without destroying the anomalies. We observe a major heat capacity spike during cooling, which is reversed during heating, and is apparently of first order. It occurs just before the glassy state is reached and is preceded by water-like density anomalies. We propose that it is the much-discussed liquid-liquid transition previously hidden by crystallization. Fast cooling should allow the important fluctuations/structures to be preserved in the glassy state for leisurely investigation.

  20. Apparent First-Order Liquid-Liquid Transition with Pre-transition Density Anomaly, in Water-Rich Ideal Solutions.

    PubMed

    Zhao, Zuofeng; Angell, C Austen

    2016-02-12

    The striking increases in response functions observed during supercooling of pure water have been the source of much interest and controversy. Imminent divergences of compressibility etc. unfortunately cannot be confirmed due to pre-emption by ice crystallization. Crystallization can be repressed by addition of second components, but these usually destroy the anomalies of interest. Here we study systems in which protic ionic liquid second components dissolve ideally in water, and ice formation is avoided without destroying the anomalies. We observe a major heat capacity spike during cooling, which is reversed during heating, and is apparently of first order. It occurs just before the glassy state is reached and is preceded by water-like density anomalies. We propose that it is the much-discussed liquid-liquid transition previously hidden by crystallization. Fast cooling should allow the important fluctuations/structures to be preserved in the glassy state for leisurely investigation. PMID:26756943

  1. Glass transition of aqueous solutions involving annealing-induced ice recrystallization resolves liquid-liquid transition puzzle of water.

    PubMed

    Zhao, Li-Shan; Cao, Ze-Xian; Wang, Qiang

    2015-10-27

    Liquid-liquid transition of water is an important concept in condensed-matter physics. Recently, it was claimed to have been confirmed in aqueous solutions based on annealing-induced upshift of glass-liquid transition temperature, T(g) . Here we report a universal water-content, X(aqu) , dependence of T(g) for aqueous solutions. Solutions with X(aqu)>X(cr)(aqu)vitrify/devitrify at a constant temperature, ~T(g) , referring to freeze-concentrated phase with X(aqu)left behind ice crystallization. Those solutions with X(aqu)liquid II phase of water'. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution.

  2. Glass transition of aqueous solutions involving annealing-induced ice recrystallization resolves liquid-liquid transition puzzle of water.

    PubMed

    Zhao, Li-Shan; Cao, Ze-Xian; Wang, Qiang

    2015-01-01

    Liquid-liquid transition of water is an important concept in condensed-matter physics. Recently, it was claimed to have been confirmed in aqueous solutions based on annealing-induced upshift of glass-liquid transition temperature, T(g) . Here we report a universal water-content, X(aqu) , dependence of T(g) for aqueous solutions. Solutions with X(aqu)>X(cr)(aqu)vitrify/devitrify at a constant temperature, ~T(g) , referring to freeze-concentrated phase with X(aqu)left behind ice crystallization. Those solutions with X(aqu)liquid II phase of water'. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution. PMID:26503911

  3. Glass transition of aqueous solutions involving annealing-induced ice recrystallization resolves liquid-liquid transition puzzle of water

    NASA Astrophysics Data System (ADS)

    Zhao, Li-Shan; Cao, Ze-Xian; Wang, Qiang

    2015-10-01

    Liquid-liquid transition of water is an important concept in condensed-matter physics. Recently, it was claimed to have been confirmed in aqueous solutions based on annealing-induced upshift of glass-liquid transition temperature, . Here we report a universal water-content, , dependence of for aqueous solutions. Solutions with vitrify/devitrify at a constant temperature, , referring to freeze-concentrated phase with left behind ice crystallization. Those solutions with totally vitrify at under conventional cooling/heating process though, of the samples annealed at temperatures   to effectively evoke ice recrystallization is stabilized at . Experiments on aqueous glycerol and 1,2,4-butanetriol solutions in literature were repeated, and the same samples subject to other annealing treatments equally reproduce the result. The upshift of by annealing is attributable to freeze-concentrated phase of solutions instead of ‘liquid II phase of water’. Our work also provides a reliable method to determine hydration formula and to scrutinize solute-solvent interaction in solution.

  4. Anomalous properties and the liquid-liquid phase transition in gallium.

    PubMed

    Li, Renzhong; Sun, Gang; Xu, Limei

    2016-08-01

    A group of materials including water and silicon exhibit many anomalous behaviors, e.g., density anomaly and diffusivity anomaly (increase upon compression). These materials are hypothesized to have a liquid-liquid phase transition (LLPT) and the critical fluctuation in the vicinity of the liquid-liquid critical point is considered as the origin of different anomalies. Liquid gallium was also reported to have a LLPT, yet whether it shows similar water-like anomalies is not yet studied. Using molecular dynamics simulations on a modified embedded-atom model, we study the thermodynamic, dynamic, and structural properties of liquid gallium as well as its LLPT. We find that, similar to water-like materials predicted to have the LLPT, gallium also shows different anomalous behaviors (e.g., density anomaly, diffusivity anomaly, and structural anomaly). We also find that its thermodynamic and structural response functions are continuous and show maxima in the supercritical region, the loci of which asymptotically approach to the other and merge to the Widom line. These phenomena are consistent with the supercritical phenomenon in a category of materials with a liquid-liquid critical point, which could be common features in most materials with a LLPT. PMID:27497564

  5. Anomalous properties and the liquid-liquid phase transition in gallium

    NASA Astrophysics Data System (ADS)

    Li, Renzhong; Sun, Gang; Xu, Limei

    2016-08-01

    A group of materials including water and silicon exhibit many anomalous behaviors, e.g., density anomaly and diffusivity anomaly (increase upon compression). These materials are hypothesized to have a liquid-liquid phase transition (LLPT) and the critical fluctuation in the vicinity of the liquid-liquid critical point is considered as the origin of different anomalies. Liquid gallium was also reported to have a LLPT, yet whether it shows similar water-like anomalies is not yet studied. Using molecular dynamics simulations on a modified embedded-atom model, we study the thermodynamic, dynamic, and structural properties of liquid gallium as well as its LLPT. We find that, similar to water-like materials predicted to have the LLPT, gallium also shows different anomalous behaviors (e.g., density anomaly, diffusivity anomaly, and structural anomaly). We also find that its thermodynamic and structural response functions are continuous and show maxima in the supercritical region, the loci of which asymptotically approach to the other and merge to the Widom line. These phenomena are consistent with the supercritical phenomenon in a category of materials with a liquid-liquid critical point, which could be common features in most materials with a LLPT.

  6. Anomalous properties and the liquid-liquid phase transition in gallium.

    PubMed

    Li, Renzhong; Sun, Gang; Xu, Limei

    2016-08-01

    A group of materials including water and silicon exhibit many anomalous behaviors, e.g., density anomaly and diffusivity anomaly (increase upon compression). These materials are hypothesized to have a liquid-liquid phase transition (LLPT) and the critical fluctuation in the vicinity of the liquid-liquid critical point is considered as the origin of different anomalies. Liquid gallium was also reported to have a LLPT, yet whether it shows similar water-like anomalies is not yet studied. Using molecular dynamics simulations on a modified embedded-atom model, we study the thermodynamic, dynamic, and structural properties of liquid gallium as well as its LLPT. We find that, similar to water-like materials predicted to have the LLPT, gallium also shows different anomalous behaviors (e.g., density anomaly, diffusivity anomaly, and structural anomaly). We also find that its thermodynamic and structural response functions are continuous and show maxima in the supercritical region, the loci of which asymptotically approach to the other and merge to the Widom line. These phenomena are consistent with the supercritical phenomenon in a category of materials with a liquid-liquid critical point, which could be common features in most materials with a LLPT.

  7. A Kagomé layer-based 3D Mn(II) framework showing coexistence of spin-canting, spin-frustration, field-induced metamagnetic and spin-flop transitions.

    PubMed

    Yang, En-Cui; Liu, Zhong-Yi; Li, Ya-Ling; Wang, Jing-Yi; Zhao, Xiao-Jun

    2011-09-14

    A novel 3D Mn(II) coordination framework with Kagomé sublattice, [Mn(3)(py)(2)(nip)(2)](n) (py(-) = 2-((1H-tetrazol-5-yl)methyl)pyridine and nip(2-) = 5-nitroisophathalate), was in situ solvothermally synthesized and shows the coexistence of spin-canting, spin-frustration as well as field-induced metamagnetic and spin-flop transitions at 2.9 K.

  8. From 3D view to 3D print

    NASA Astrophysics Data System (ADS)

    Dima, M.; Farisato, G.; Bergomi, M.; Viotto, V.; Magrin, D.; Greggio, D.; Farinato, J.; Marafatto, L.; Ragazzoni, R.; Piazza, D.

    2014-08-01

    In the last few years 3D printing is getting more and more popular and used in many fields going from manufacturing to industrial design, architecture, medical support and aerospace. 3D printing is an evolution of bi-dimensional printing, which allows to obtain a solid object from a 3D model, realized with a 3D modelling software. The final product is obtained using an additive process, in which successive layers of material are laid down one over the other. A 3D printer allows to realize, in a simple way, very complex shapes, which would be quite difficult to be produced with dedicated conventional facilities. Thanks to the fact that the 3D printing is obtained superposing one layer to the others, it doesn't need any particular work flow and it is sufficient to simply draw the model and send it to print. Many different kinds of 3D printers exist based on the technology and material used for layer deposition. A common material used by the toner is ABS plastics, which is a light and rigid thermoplastic polymer, whose peculiar mechanical properties make it diffusely used in several fields, like pipes production and cars interiors manufacturing. I used this technology to create a 1:1 scale model of the telescope which is the hardware core of the space small mission CHEOPS (CHaracterising ExOPlanets Satellite) by ESA, which aims to characterize EXOplanets via transits observations. The telescope has a Ritchey-Chrétien configuration with a 30cm aperture and the launch is foreseen in 2017. In this paper, I present the different phases for the realization of such a model, focusing onto pros and cons of this kind of technology. For example, because of the finite printable volume (10×10×12 inches in the x, y and z directions respectively), it has been necessary to split the largest parts of the instrument in smaller components to be then reassembled and post-processed. A further issue is the resolution of the printed material, which is expressed in terms of layers

  9. Modeling the solid-liquid phase transition in saturated triglycerides

    NASA Astrophysics Data System (ADS)

    Pink, David A.; Hanna, Charles B.; Sandt, Christophe; MacDonald, Adam J.; MacEachern, Ronald; Corkery, Robert; Rousseau, Dérick

    2010-02-01

    We investigated theoretically two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al. [Langmuir 23, 7241 (2007)], in which the average state of each TL molecule in the liquid phase is a discotic "Y" conformer whose three chains are dynamically twisted, with an average angle of ˜120° between them, and those of (2) Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid-state conformation of the TL molecule in the liquid phase is a nematic h∗-conformer whose three chains are in a modified "chair" conformation. We developed two competing models for the two scenarios, in which TL molecules are in a nematic compact-chair (or "h") conformation, with extended, possibly all-trans, chains at low-temperatures, and in either a Y conformation or an h∗ conformation in the liquid state at temperatures higher than the phase-transition temperature, T∗=319 K. We defined an h-Y model as a realization of the proposal of Corkery et al. [Langmuir 23, 7241 (2007)], and explored its predictions by mapping it onto an Ising model in a temperature-dependent field, performing a mean-field approximation, and calculating the transition enthalpy ΔH. We found that the most plausible realization of the h-Y model, as applied to the solid-liquid phase transition in TL, and likely to all saturated triglycerides, gave a value of ΔH in reasonable agreement with the experiment. We then defined an alternative h-h∗ model as a realization of the proposal of Cebula et al. [J. Am. Oil Chem. Soc. 69, 130 (1992)], in which the liquid phase exhibits an average symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h∗ model gave a value of ΔH that was too small by a factor of ˜3-4. We also predicted the temperature dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman

  10. Plethora of transitions during breakup of liquid filaments.

    PubMed

    Castrejón-Pita, José Rafael; Castrejón-Pita, Alfonso Arturo; Thete, Sumeet Suresh; Sambath, Krishnaraj; Hutchings, Ian M; Hinch, John; Lister, John R; Basaran, Osman A

    2015-04-14

    Thinning and breakup of liquid filaments are central to dripping of leaky faucets, inkjet drop formation, and raindrop fragmentation. As the filament radius decreases, curvature and capillary pressure, both inversely proportional to radius, increase and fluid is expelled with increasing velocity from the neck. As the neck radius vanishes, the governing equations become singular and the filament breaks. In slightly viscous liquids, thinning initially occurs in an inertial regime where inertial and capillary forces balance. By contrast, in highly viscous liquids, initial thinning occurs in a viscous regime where viscous and capillary forces balance. As the filament thins, viscous forces in the former case and inertial forces in the latter become important, and theory shows that the filament approaches breakup in the final inertial-viscous regime where all three forces balance. However, previous simulations and experiments reveal that transition from an initial to the final regime either occurs at a value of filament radius well below that predicted by theory or is not observed. Here, we perform new simulations and experiments, and show that a thinning filament unexpectedly passes through a number of intermediate transient regimes, thereby delaying onset of the inertial-viscous regime. The new findings have practical implications regarding formation of undesirable satellite droplets and also raise the question as to whether similar dynamical transitions arise in other free-surface flows such as coalescence that also exhibit singularities.

  11. Glass transition of ionic liquids under high pressure.

    PubMed

    Ribeiro, Mauro C C; Pádua, Agílio A H; Gomes, Margarida F Costa

    2014-06-28

    The glass transition pressure at room temperature, pg, of six ionic liquids based on 1-alkyl-3-methylimidazolium cations and the anions [BF4](-), [PF6](-), and bis(trifluromethanesulfonyl)imide, [NTf2](-), has been obtained from the pressure dependence of the bandwidth of the ruby fluorescence line in diamond anvil cells. Molar volume, Vm(pg), has been estimated by a group contribution model (GCM) developed for the ionic liquids. A density scaling relation, TV(γ), has been considered for the states Vm(pg, 295 K) and Vm(Tg, 0.1 MPa) using the simplifying condition that the viscosity at the glass transition is the same at pg at room temperature and at atmospheric pressure at Tg. Assuming a constant γ over this range of density, a reasonable agreement has been found for the γ determined herein and that of a previous density scaling analysis of ionic liquids viscosities under moderate conditions. Further support for the appropriateness of extrapolating the GCM equation of state to the GPa pressure range is provided by comparing the GCM and an equation of state previously derived in the power law density-scaling regime.

  12. Glass transition of ionic liquids under high pressure

    NASA Astrophysics Data System (ADS)

    Ribeiro, Mauro C. C.; Pádua, Agílio A. H.; Gomes, Margarida F. Costa

    2014-06-01

    The glass transition pressure at room temperature, pg, of six ionic liquids based on 1-alkyl-3-methylimidazolium cations and the anions [BF4]-, [PF6]-, and bis(trifluromethanesulfonyl)imide, [NTf2]-, has been obtained from the pressure dependence of the bandwidth of the ruby fluorescence line in diamond anvil cells. Molar volume, Vm(pg), has been estimated by a group contribution model (GCM) developed for the ionic liquids. A density scaling relation, TVγ, has been considered for the states Vm(pg, 295 K) and Vm(Tg, 0.1 MPa) using the simplifying condition that the viscosity at the glass transition is the same at pg at room temperature and at atmospheric pressure at Tg. Assuming a constant γ over this range of density, a reasonable agreement has been found for the γ determined herein and that of a previous density scaling analysis of ionic liquids viscosities under moderate conditions. Further support for the appropriateness of extrapolating the GCM equation of state to the GPa pressure range is provided by comparing the GCM and an equation of state previously derived in the power law density-scaling regime.

  13. Plethora of transitions during breakup of liquid filaments

    PubMed Central

    Castrejón-Pita, José Rafael; Castrejón-Pita, Alfonso Arturo; Thete, Sumeet Suresh; Sambath, Krishnaraj; Hutchings, Ian M.; Hinch, John; Lister, John R.; Basaran, Osman A.

    2015-01-01

    Thinning and breakup of liquid filaments are central to dripping of leaky faucets, inkjet drop formation, and raindrop fragmentation. As the filament radius decreases, curvature and capillary pressure, both inversely proportional to radius, increase and fluid is expelled with increasing velocity from the neck. As the neck radius vanishes, the governing equations become singular and the filament breaks. In slightly viscous liquids, thinning initially occurs in an inertial regime where inertial and capillary forces balance. By contrast, in highly viscous liquids, initial thinning occurs in a viscous regime where viscous and capillary forces balance. As the filament thins, viscous forces in the former case and inertial forces in the latter become important, and theory shows that the filament approaches breakup in the final inertial–viscous regime where all three forces balance. However, previous simulations and experiments reveal that transition from an initial to the final regime either occurs at a value of filament radius well below that predicted by theory or is not observed. Here, we perform new simulations and experiments, and show that a thinning filament unexpectedly passes through a number of intermediate transient regimes, thereby delaying onset of the inertial–viscous regime. The new findings have practical implications regarding formation of undesirable satellite droplets and also raise the question as to whether similar dynamical transitions arise in other free-surface flows such as coalescence that also exhibit singularities. PMID:25825761

  14. Dynamical and structural heterogeneities close to liquid-liquid phase transitions: The case of gallium

    NASA Astrophysics Data System (ADS)

    Antonelli, Alex; Cajahuaringa, Samuel; de Koning, Maurice

    2013-03-01

    Liquid-liquid phase transitions (LLPT) have been proposed in order to explain the thermodynamic anomalies exhibited by some liquids. Recently, it was found, through molecular dynamics simulations, that liquid elemental gallium, described by a modified embedded-atom model, exhibits a LLPT between a high-density liquid (HDL) and a low-density liquid (LDL), about 60 K below the melting temperature. In this work, we studied the dynamics of supercooled liquid gallium close to the LLPT. Our results show a large increase in the plateau of the self-intermediate scattering function (β-relaxation process) and in the non-Gaussian parameter, indicating a pronounced dynamical heterogeneity upon the onset of the LLPT. The dynamical heterogeneity of the LDL is closely correlated to its structural heterogeneity, since the fast diffusing atoms belong to high-density domains of predominantly 9-fold coordinated atoms, whereas the slow diffusing ones are mostly in low-density domains of 8-fold coordinated atoms. The energetics suggests that the reason for the sluggish dynamics of LDL is due to its larger cohesive energy as compared to that of the HDL. Work supported by FAPESP, CNPq, CAPES, and FAEPEX/UNICAMP

  15. A random first order theory of liquid-glass transition

    NASA Astrophysics Data System (ADS)

    Xia, Xiaoyu

    It is believed that all classical fluids could form glasses if cooled sufficiently fast so as to avoid crystallization. Various phenomena including violation of the usual Arrhenius law, stretched relaxations, deviations from the Stokes-Einstein relation in hydrodynamics, and aging have been observed in the laboratory. In this thesis, a microscopically motivated theory of glassy dynamics based on an underlying random first order transition is developed to explain the magnitude and variation of free energy barriers for glassy relaxation. A variety of empirical correlations embodied in the concept of liquid "fragility" are shown to be quantitatively explained by such a model. Fragility parameters, the size of heterogeneities, the degree of stretching of relaxations, and the enhancement of translational diffusion are derived from theory. The wide variety of kinetic behaviors in liquids of quite disparate chemical nature reflects quantitative rather than qualitative differences in their energy landscapes as it turns out.

  16. Semiphenomenological model for gas-liquid phase transitions

    NASA Astrophysics Data System (ADS)

    Benilov, E. S.; Benilov, M. S.

    2016-03-01

    We examine a rarefied gas with inter-molecular attraction. It is argued that the attraction force amplifies random density fluctuations by pulling molecules from lower-density regions into high-density regions and thus may give rise to an instability. To describe this effect, we use a kinetic equation where the attraction force is taken into account in a way similar to how electromagnetic forces in plasma are treated in the Vlasov model. It is demonstrated that the instability occurs when the temperature T is lower than a certain threshold value Ts depending on the gas density. It is further shown that, even if T is only marginally lower than Ts, the instability generates clusters with density much higher than that of the gas. These results suggest that the instability should be interpreted as a gas-liquid phase transition, with Ts being the temperature of saturated vapor and the high-density clusters representing liquid droplets.

  17. Frederiks transition in ferroelectric liquid-crystal nanosuspensions

    NASA Astrophysics Data System (ADS)

    Shelestiuk, Sergii M.; Reshetnyak, Victor Yu.; Sluckin, Timothy J.

    2011-04-01

    We construct a theoretical model of the dielectric properties of a ferroelectric LC nanosuspension (FLCNS), using a generalized Maxwell-Garnett picture. The theory supposes that an FLCNS may as a first approximation be considered as a complex homogeneous dielectric ceramic, thus neglecting positional correlations of the colloidal particles. The FLCNS then consists of an anisotropic matrix with a very low concentration (<1% by volume) of impurity particles. The impurity particles possess both shape and dielectric anisotropy, as well as a permanent electric polarization and strong liquid-crystal director anchoring on the particle surface. We show that the effective dielectric properties for capacitance properties and for effective liquid-crystal free energies do not coincide. We calculate the effect of doping a liquid crystal with ferroelectric impurities on the Frederiks transition. The theory takes account of inclusion shape, dielectric susceptibility, and local field effects. We neglect the possibility of dielectric particle chaining, which appears experimentally not to occur in general. Our calculations suggest, in qualitative agreement with experiment, that doping a nematic liquid crystal with ferroelectric particles, even at very low particle concentration, can in some cases significantly decrease the electric Frederiks threshold field.

  18. Phase transitions and separations in a distorted liquid crystalline mixture.

    PubMed

    Kasch, Nicholas; Dierking, Ingo

    2015-08-14

    A theoretical method is proposed for modelling phase transitions and phase ranges in a multi-component liquid crystalline mixture where the liquid crystal structure is distorted and defects are formed. This method employs the Maier-Saupe and Kobayashi-McMillan theories of liquid crystalline ordering and the Flory-Huggins theory of mixtures. It builds on previous work on mixed systems that can form smectic-A and nematic phases by incorporating "distortion factors" into the expression for the local free energy of the mixture, which account for the effects of a deviation of the liquid crystal structure from the uniform nematic and smectic-A states. The method allows a simple description of chiral defect phases such as the blue phase and the twist grain boundary phase. In a previous work, it was shown that a model of the blue phase along these lines could effectively explain the observed effect whereby an added guest compound can stabilize the phase by separating into the high energy defect regions of the structure. It is shown here that with the correct choice of guest material a similar effect could be observed for the twist grain boundary phase.

  19. Phase transitions and separations in a distorted liquid crystalline mixture

    NASA Astrophysics Data System (ADS)

    Kasch, Nicholas; Dierking, Ingo

    2015-08-01

    A theoretical method is proposed for modelling phase transitions and phase ranges in a multi-component liquid crystalline mixture where the liquid crystal structure is distorted and defects are formed. This method employs the Maier-Saupe and Kobayashi-McMillan theories of liquid crystalline ordering and the Flory-Huggins theory of mixtures. It builds on previous work on mixed systems that can form smectic-A and nematic phases by incorporating "distortion factors" into the expression for the local free energy of the mixture, which account for the effects of a deviation of the liquid crystal structure from the uniform nematic and smectic-A states. The method allows a simple description of chiral defect phases such as the blue phase and the twist grain boundary phase. In a previous work, it was shown that a model of the blue phase along these lines could effectively explain the observed effect whereby an added guest compound can stabilize the phase by separating into the high energy defect regions of the structure. It is shown here that with the correct choice of guest material a similar effect could be observed for the twist grain boundary phase.

  20. Volume phase transitions of cholesteric liquid crystalline gels

    SciTech Connect

    Matsuyama, Akihiko

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  1. Phase diagrams of orientational transitions in absorbing nematic liquid crystals

    SciTech Connect

    Zolot’ko, A. S. Ochkin, V. N.; Smayev, M. P.; Shvetsov, S. A.

    2015-05-15

    A theory of orientational transitions in nematic liquid crystals (NLCs), which employs the expansion of optical torques acting on the NLC director with respect to the rotation angle, has been developed for NLCs with additives of conformationally active compounds under the action of optical and low-frequency electric and magnetic fields. Phase diagrams of NLCs are constructed as a function of the intensity and polarization of the light field, the strength of low-frequency electric field, and a parameter that characterizes the feedback between the rotation of the NLC director and optical torque. Conditions for the occurrence of first- and second-order transitions are determined. The proposed theory agrees with available experimental data.

  2. 3D Printable Graphene Composite.

    PubMed

    Wei, Xiaojun; Li, Dong; Jiang, Wei; Gu, Zheming; Wang, Xiaojuan; Zhang, Zengxing; Sun, Zhengzong

    2015-07-08

    In human being's history, both the Iron Age and Silicon Age thrived after a matured massive processing technology was developed. Graphene is the most recent superior material which could potentially initialize another new material Age. However, while being exploited to its full extent, conventional processing methods fail to provide a link to today's personalization tide. New technology should be ushered in. Three-dimensional (3D) printing fills the missing linkage between graphene materials and the digital mainstream. Their alliance could generate additional stream to push the graphene revolution into a new phase. Here we demonstrate for the first time, a graphene composite, with a graphene loading up to 5.6 wt%, can be 3D printable into computer-designed models. The composite's linear thermal coefficient is below 75 ppm·°C(-1) from room temperature to its glass transition temperature (Tg), which is crucial to build minute thermal stress during the printing process.

  3. Confinement effects on the liquid-liquid phase transition and anomalous properties of a monatomic water-like liquid.

    PubMed

    Sun, Gang; Giovambattista, Nicolas; Xu, Limei

    2015-12-28

    We use molecular dynamics simulations to study the effects of confinement on the phase behavior of a water-like monatomic liquid that exhibits a liquid-liquid phase transition (LLPT) and a liquid-liquid critical point (LLCP). The liquid is confined between parallel walls and we focus on the effects of wall separation and surface chemistry (solvophobicity/solvophilicity) on the location of the LLCP, temperature of maximum density (TMD) line, and loci of compressibility maxima (CM). It is found that, independently of the surface solvophobicity/solvophilicity, the LLCP, TMD, and CM lines shift rapidly towards higher pressures and lower temperatures as the wall separation is reduced. It follows that the effects of confinement on the TMD and CM lines are indicative of the confinement effects on the LLCP/LLPT. Confinement effects are observable already when the liquid particles form ≈15 layers between the walls. For the case of water, this corresponds to a separation of ≈4-5 nm between the surfaces, larger than the confining dimension of the nanopores commonly used to study the hypothesized LLPT in confined water. Hence, our results suggest that such experiments should not be interpreted in terms of the phase diagrams proposed for bulk water.

  4. Experimental investigation of off-stoichiometry and 3d transition metal (Mn, Ni, Cu)-substitution in single-crystalline FePt thin films

    NASA Astrophysics Data System (ADS)

    Ono, Takuya; Nakata, Hitoshi; Moriya, Tomohiro; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2016-05-01

    In L10 (fct)-FePt thin films, both tuning Fe and Pt concentrations and substitution with third-metal were studied for magnetic characteristic optimization. We investigated single-crystalline FePt-X (X = Mn, Ni, Cu) thin films grown epitaxially on MgO(001) substrates at a substrate temperature of 350 °C by changing Fe, Pt, and X contents, and explored the effects of off-stoichiometry and 3d-metal-substitution. The magnetic moment per atom (m) of FePt-X films as a function of the effective number of valence electrons (neff) in 3d metal sites follows the Slater-Pauling-type trend, by which m decreases by the neff deviation from neff = 8, independently of the X metal and the Pt concentration. The magnetic anisotropy (Ku) exhibits neff dependence similar to m. This trend was almost independent of the Pt concentration after compensation using the theoretical prediction on the relation between Ku and Fe/Pt concentrations. Such a trend has been proved for stoichiometric FePt-X films, but it was clarified as robust against off-stoichiometry. The compensated Ku ( Ku comp ) of FePt-Mn and FePt-Cu followed a similar trend to that predicted by the rigid-band model, although the Ku comp of the FePt-Mn thin films dropped more rapidly than the rigid band calculation. However, it followed the recent first-principles calculation.

  5. Supercritical phenomenon of hydrogen beyond the liquid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Li, Renzhong; Chen, Ji; Li, Xinzheng; Wang, Enge; Xu, Limei

    2015-06-01

    Using ab initio molecular dynamics simulation, we investigate the supercritical phenomenon associated with the liquid-liquid phase transition of hydrogen by studying the isothermal response functions, such as electric conductivity, molecular dissociation coefficient and isothermal compressibility, with respect to pressure. We find that, along each isotherm in the supercritical region, each of these response functions shows a maximum, the location of which is different for different response functions. As temperature decreases, the loci of these maxima asymptotically converge to a line of zero ordering field, known as the Widom line along which the magnitude of the response function maxima becomes larger and larger until it diverges as the critical point is approached. Thus, our study provides a possible way to locate the liquid-liquid critical point of hydrogen from the supercritical region at lower pressures. It also indicates that the supercritical phonomenon near the critical point of hydrogen is a rather general feature of second-order phase transition, it is not only true for classical systems with weak interactions but also true for highly condensed system with strong inter-atomic interactions.

  6. Radiochromic 3D Detectors

    NASA Astrophysics Data System (ADS)

    Oldham, Mark

    2015-01-01

    Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.

  7. 3-D Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Moore, Gregory F.

    2009-05-01

    This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three-dimensional (3-D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3-D seismic data acquisition and processing. Standard 3-D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple-azimuth and wide-azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.

  8. Synthesis and liquid crystal phase transitions of zirconium phosphate disks

    NASA Astrophysics Data System (ADS)

    Shuai, Min

    Solvent-mediated self-assembly of nanoparticles is an effective and efficient way for the bottom-up organization of functional structures. The primary object of this work is to build up a model system for the study of suspensions of disk-shaped nanoparticles, and use it for the study of self-assembly and discotic liquid crystal phase transitions of discotic particles. The work was introduced by the control over the size and polydispersity of zirconium phosphate (ZrP) disks through synthesis. Systematic experiments revealed that regular-shaped alpha-zirconium phosphate crystalline disks with a size-to-thickness ratio from 1 to 50 and size polydispersity as low as 0.2 can be obtained through hydrothermal treatment in 3 M to 15 M phosphoric acid solutions. Transmission and scanning electron micrographs revealed that the growth of the disks is mediated by oriented attachment, which happened continuously throughout the hydrothermal treatment between various sized disks. Ostwald ripening is effective in improving the regularity of the shape of the disks, especially under prolonged hydrothermal treatment. Under the microwave assisted hydrothermal conditions, the rate of attachment on the flat surfaces of the disks is accelerated, which leads to the formation of the column-shaped crystals. With the ability to adjust the size, aspect ratio, and polydispersity of ZrP disks, the study on self-assembly behavior and the discotic liquid crystal phases was enabled. Firstly, liquid crystal phases of aqueous suspensions of ZrP disks were investigated. Iridescent smectic phase and the critical points of phase transitions were found. Moreover, monolayer ZrP nanosheets with extremely high aspect ratio, which were achieved by exfoliating the ZrP crystals, were also used in this study. The high aspect ratio of nanosheets produces a laminar phase at low nanosheet concentration. Chiral liquid crystal phases were demonstrated when increased the concentration of the nanosheets. The

  9. Growth Kinetics of Intracellular RNA/Protein Droplets: Signature of a Liquid-Liquid Phase Transition?

    NASA Astrophysics Data System (ADS)

    Berry, Joel; Weber, Stephanie C.; Vaidya, Nilesh; Zhu, Lian; Haataja, Mikko; Brangwynne, Clifford P.

    2015-03-01

    Nonmembrane-bound organelles are functional, dynamic assemblies of RNA and/or protein that can self-assemble and disassemble within the cytoplasm or nucleoplasm. The possibility that underlying intracellular phase transitions may drive and mediate the morphological evolution of some membrane-less organelles has been supported by several recent studies. In this talk, results from a collaborative experimental-theoretical study of the growth and dissolution kinetics of nucleoli and extranucleolar droplets (ENDs) in C. elegans embryos will be presented. We have employed Flory-Huggins solution theory, reaction-diffusion kinetics, and quantitative statistical dynamic scaling analysis to characterize the specific growth mechanisms at work. Our findings indicate that both in vivo and in vitro droplet scaling and growth kinetics are consistent with those resulting from an equilibrium liquid-liquid phase transition mediated by passive nonequilibrium growth mechanisms - simultaneous Brownian coalescence and Ostwald ripening. This supports a view in which cells can employ phase transitions to drive structural organization, while utilizing active processes, such as local transcriptional activity, to fine tune the kinetics of these phase transitions in response to given conditions.

  10. Bootstrapping 3D fermions

    DOE PAGES

    Iliesiu, Luca; Kos, Filip; Poland, David; Pufu, Silviu S.; Simmons-Duffin, David; Yacoby, Ran

    2016-03-17

    We study the conformal bootstrap for a 4-point function of fermions <ψψψψ> in 3D. We first introduce an embedding formalism for 3D spinors and compute the conformal blocks appearing in fermion 4-point functions. Using these results, we find general bounds on the dimensions of operators appearing in the ψ × ψ OPE, and also on the central charge CT. We observe features in our bounds that coincide with scaling dimensions in the GrossNeveu models at large N. Finally, we also speculate that other features could coincide with a fermionic CFT containing no relevant scalar operators.

  11. Topological transitions in unidirectional flow of nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Cummings, Linda; Anderson, Thomas; Mema, Ensela; Kondic, Lou

    2015-11-01

    Recent experiments by Sengupta et al. (Phys. Rev. Lett. 2013) revealed interesting transitions that can occur in flow of nematic liquid crystal under carefully controlled conditions within a long microfluidic channel of rectangular cross-section, with homeotropic anchoring at the walls. At low flow rates the director field of the nematic adopts a configuration that is dominated by the surface anchoring, being nearly parallel to the channel height direction over most of the cross-section; but at high flow rates there is a transition to a flow-dominated state, where the director configuration at the channel centerline is aligned with the flow (perpendicular to the channel height direction). We analyze simple channel-flow solutions to the Leslie-Ericksen model for nematics. We demonstrate that two solutions exist, at all flow rates, but that there is a transition between the elastic free energies of these solutions: the anchoring-dominated solution has the lowest energy at low flow rates, and the flow-dominated solution has lowest energy at high flow rates. NSF DMS 1211713.

  12. Structure, Hydrodynamics, and Phase Transition of Freely Suspended Liquid Crystals

    NASA Technical Reports Server (NTRS)

    Clark, Noel A.

    2000-01-01

    Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enable the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable condensed phase fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new liquid crystal physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and

  13. Venus in 3D

    NASA Astrophysics Data System (ADS)

    Plaut, J. J.

    1993-08-01

    Stereographic images of the surface of Venus which enable geologists to reconstruct the details of the planet's evolution are discussed. The 120-meter resolution of these 3D images make it possible to construct digital topographic maps from which precise measurements can be made of the heights, depths, slopes, and volumes of geologic structures.

  14. 3D reservoir visualization

    SciTech Connect

    Van, B.T.; Pajon, J.L.; Joseph, P. )

    1991-11-01

    This paper shows how some simple 3D computer graphics tools can be combined to provide efficient software for visualizing and analyzing data obtained from reservoir simulators and geological simulations. The animation and interactive capabilities of the software quickly provide a deep understanding of the fluid-flow behavior and an accurate idea of the internal architecture of a reservoir.

  15. 3D-printed polylactic acid supports for enhanced ionization efficiency in desorption electrospray mass spectrometry analysis of liquid and gel samples.

    PubMed

    Elviri, Lisa; Foresti, Ruben; Bianchera, Annalisa; Silvestri, Marco; Bettini, Ruggero

    2016-08-01

    The potential of 3D printing technology was here exploited to prepare tailored polylactic acid (PLA) supports for desorption electrospray ionization (DESI) experiments. PLA rough solid supports presenting wells of different shape (i.e. cylindrical, cubic and hemispherical cavities) were designed to accommodate samples of different physical state. The potentials of such supports in terms of sample loading capacity, sensitivity, signal stability were tested by analysing a peptide (i.e. insulin) and an aminoglycoside antibiotic (i.e. gentamicin sulphate) from solution and a chitosan-based gel. The results obtained were compared with those obtained by using a traditional polytetrafluoroethylene (PTFE) support and discussed. By using PLA support on the flat side, signal intensity improved almost twice with respect to PTFE support, whereas with spherical wells a five times improved signal sensitivity and good stability (RSD<6%) were obtained for the analysis of two model molecules. Limits of detection were in the 3-10nM range and linearity was demonstrated for both analytes in the 0.05-0.5μM range for semi-quantitative or quantitative purposes. The use of a well and the set-up of optimal source parameters allowed the analysis of samples in a gel state with good precision (RSD<10%) and accuracy (86±6-102±9%), otherwise difficult to analyse on a flat smooth surface. These findings are of great interest and stimulus to exploit the advantages of 3D printing technology for the development of devices for a DESI source, presenting different shapes or configuration as a function of the sample types.

  16. The effect of 4,4'-bis(N,N-diethylamino) benzophenone on the degree of conversion in liquid photopolymer for dental 3D printing

    PubMed Central

    Lee, Du-Hyeong; Mai, Hang Nga; Yang, Jin-Chul

    2015-01-01

    PURPOSE The purpose of this preliminary study was to investigate the effects of adding 4,4'-bis(N,N-diethylamino) benzophenone (DEABP) as a co-initiator to a binary photoinitiating system (camphorquinone-amine) to analyze on the degree of conversion (DC) of a light-cured resin for dental 3D printing. MATERIALS AND METHODS Cylindrical specimens (N=60, n=30 per group, ø5 mm × 1 mm) were fabricated using bisphenol A glycerolate dimethacrylate (BisGMA) both with and without DEABP. The freshly mixed resins were exposed to light in a custom-made closed chamber with nine light-emitting diode lamps (wavelength: 405 nm; power: 840 mW/cm2) for polymerization at each incidence of light-irradiation at 10, 30, 60, 180, and 300 seconds, while five specimens at a time were evaluated at each given irradiation point. Fourier-transform infrared (FTIR) spectroscopy was used to measure the DC values of the resins. Two-way analysis of variance and the Duncan post hoc test were used to analyze statistically significant differences between the groups and given times (α=.05). RESULTS In the DEABP-containing resin, the DC values were significantly higher at all points in time (P<.001), and also the initial polymerization velocity was faster than in the DEABP-free resin. CONCLUSION The addition of DEABP significantly enhanced the DC values and, thus, could potentially become an efficient photoinitiator when combined with a camphorquinone-amine system and may be utilized as a more advanced photopolymerization system for dental 3D printing. PMID:26576255

  17. Specific features of insulator-metal transitions under high pressure in crystals with spin crossovers of 3d ions in tetrahedral environment

    SciTech Connect

    Lobach, K. A. Ovchinnikov, S. G.; Ovchinnikova, T. M.

    2015-01-15

    For Mott insulators with tetrahedral environment, the effective Hubbard parameter U{sub eff} is obtained as a function of pressure. This function is not universal. For crystals with d{sup 5} configuration, the spin crossover suppresses electron correlations, while for d{sup 4} configurations, the parameter U{sub eff} increases after a spin crossover. For d{sup 2} and d{sup 7} configurations, U{sub eff} increases with pressure in the high-spin (HS) state and is saturated after the spin crossover. Characteristic features of the insulator-metal transition are considered as pressure increases; it is shown that there may exist cascades of several transitions for various configurations.

  18. On 3d bonding in the transition metal trimers - The electronic structure of equilateral triangle Ca3, Sc3, Sc3(+), and Ti3(+)

    NASA Technical Reports Server (NTRS)

    Walch, S. P.; Bauschlicher, C. W., Jr.

    1985-01-01

    It is pointed out that transition metals and transition metal (TM) compounds are currently of considerable interest because of their relevance to catalysis and to materials science problems such as hydrogen embrittlement and crack propagation in metals. The present paper is concerned with complete active space Self-Consistent Field (SCF) externally contracted configuration interaction (CASSCF/CCI) calculations for the low-lying states of Sc3 and Sc3(+). A comparison is conducted regarding the bonding in the Ca3, Sc3, and Cu3 molecules. This comparison makes it possible to predict general trends for the TM trimers. Attention is given to the qualitative features of the bonding in the TM trimers, the basis sets and other technical details of the calculations, the calculated results for Sc3 and Sc3(+), and conclusions from this work.

  19. Semiphenomenological model for gas-liquid phase transitions.

    PubMed

    Benilov, E S; Benilov, M S

    2016-03-01

    We examine a rarefied gas with inter-molecular attraction. It is argued that the attraction force amplifies random density fluctuations by pulling molecules from lower-density regions into high-density regions and thus may give rise to an instability. To describe this effect, we use a kinetic equation where the attraction force is taken into account in a way similar to how electromagnetic forces in plasma are treated in the Vlasov model. It is demonstrated that the instability occurs when the temperature T is lower than a certain threshold value T(s) depending on the gas density. It is further shown that, even if T is only marginally lower than T(s), the instability generates clusters with density much higher than that of the gas. These results suggest that the instability should be interpreted as a gas-liquid phase transition, with T(s) being the temperature of saturated vapor and the high-density clusters representing liquid droplets.

  20. 3D rapid mapping

    NASA Astrophysics Data System (ADS)

    Isaksson, Folke; Borg, Johan; Haglund, Leif

    2008-04-01

    In this paper the performance of passive range measurement imaging using stereo technique in real time applications is described. Stereo vision uses multiple images to get depth resolution in a similar way as Synthetic Aperture Radar (SAR) uses multiple measurements to obtain better spatial resolution. This technique has been used in photogrammetry for a long time but it will be shown that it is now possible to do the calculations, with carefully designed image processing algorithms, in e.g. a PC in real time. In order to get high resolution and quantitative data in the stereo estimation a mathematical camera model is used. The parameters to the camera model are settled in a calibration rig or in the case of a moving camera the scene itself can be used for calibration of most of the parameters. After calibration an ordinary TV camera has an angular resolution like a theodolite, but to a much lower price. The paper will present results from high resolution 3D imagery from air to ground. The 3D-results from stereo calculation of image pairs are stitched together into a large database to form a 3D-model of the area covered.

  1. Hyperfine structure of {sup 87,89}Sr 5s4d{sup 3}D-5snf transitions in collinear fast beam RIMS

    SciTech Connect

    Bushaw, B. A.; Kluge, H.-J.; Lantzsch, J.; Schwalbach, R.; Schwarz, M.; Stenner, J.; Stevens, H.; Wendt, K.; Zimmer, K.

    1995-04-01

    The title transition, with n=20, 23, and 32 were measured for stable {sup 87}Sr and the observed hfs was interpreted and strong hyperfine mixing of all four terms {sup 1}F3 and {sup 3}F2,3,4 in the upper configuration. The results of the analysis were used to predict the hfs for the radioactive isotope {sup 89}Sr. Measurement were then performed on samples containing 10{sup 9} atoms {sup 89}Sr. The positions and intensities of the hfs components selected for study were found to agree well with the predicted values.

  2. Modeling nuclear 'pasta' and the transition to uniform nuclear matter with the 3D Skyrme-Hartree-Fock method at finite temperature: Core-collapse supernovae

    SciTech Connect

    Newton, W. G.; Stone, J. R.

    2009-05-15

    The first results of a new three-dimensional, finite temperature Skyrme-Hartree-Fock+BCS study of the properties of inhomogeneous nuclear matter at densities and temperatures leading to the transition to uniform nuclear matter are presented. Calculations are carried out in a cubic box representing a unit cell of the locally periodic structure of the matter. A constraint is placed on the two independent components of the quadrupole moment of the neutron density to investigate the dependence of the total energy density of matter on the geometry of the nuclear structure in the unit cell. This approach allows self-consistent modeling of effects such as (i) neutron drip, resulting in a neutron gas external to the nuclear structure; (ii) shell effects of bound and unbound nucleons; (iii) the variety of exotic nuclear shapes that emerge, collectively termed nuclear pasta; and (iv) the dissolution of these structures into uniform nuclear matter as density and/or temperature increase. In Part I of this work the calculation of the properties of inhomogeneous nuclear matter in the core collapse of massive stars is reported. Emphasis is on exploring the effects of the numerical method on the results obtained; notably, the influence of the finite cell size on the nuclear shapes and energy-density obtained. Results for nuclear matter in {beta} equilibrium in cold neutrons stars are the subject of Part II. The calculation of the band structure of unbound neutrons in neutron star matter, yielding thermal conductivity, specific heat, and entrainment parameters, is outlined in Part III. Calculations are performed at baryon number densities of n{sub b}=0.04-0.12 fm{sup -3}, a proton fraction of y{sub p}=0.3 and temperatures in the range 0-7.5 MeV. A wide variety of nuclear shapes are shown to emerge. It is suggested that thermodynamical properties change smoothly in the pasta regime up to the transition to uniform matter; at that transition, thermodynamic properties of the matter

  3. Do Practical Standard Coupled Cluster Calculations Agree Better than Kohn–Sham Calculations with Currently Available Functionals When Compared to the Best Available Experimental Data for Dissociation Energies of Bonds to 3d Transition Metals?

    SciTech Connect

    Xu, Xuefei; Zhang, Wenjing; Tang, Mingsheng; Truhlar, Donald G.

    2015-05-12

    Coupled-cluster (CC) methods have been extensively used as the high-level approach in quantum electronic structure theory to predict various properties of molecules when experimental results are unavailable. It is often assumed that CC methods, if they include at least up to connected-triple-excitation quasiperturbative corrections to a full treatment of single and double excitations (in particular, CCSD(T)), and a very large basis set, are more accurate than Kohn–Sham (KS) density functional theory (DFT). In the present work, we tested and compared the performance of standard CC and KS methods on bond energy calculations of 20 3d transition metal-containing diatomic molecules against the most reliable experimental data available, as collected in a database called 3dMLBE20. It is found that, although the CCSD(T) and higher levels CC methods have mean unsigned deviations from experiment that are smaller than most exchange-correlation functionals for metal–ligand bond energies of transition metals, the improvement is less than one standard deviation of the mean unsigned deviation. Furthermore, on average, almost half of the 42 exchange-correlation functionals that we tested are closer to experiment than CCSD(T) with the same extended basis set for the same molecule. The results show that, when both relativistic and core–valence correlation effects are considered, even the very high-level (expensive) CC method with single, double, triple, and perturbative quadruple cluster operators, namely, CCSDT(2)Q, averaged over 20 bond energies, gives a mean unsigned deviation (MUD(20) = 4.7 kcal/mol when one correlates only valence, 3p, and 3s electrons of transition metals and only valence electrons of ligands, or 4.6 kcal/mol when one correlates all core electrons except for 1s shells of transition metals, S, and Cl); and that is similar to some good xc functionals (e.g., B97-1 (MUD(20) = 4.5 kcal/mol) and PW6B95 (MUD(20) = 4.9 kcal/mol)) when the same basis set is used

  4. Continuous On-Chip Cell Separation Based on Conductivity-Induced Dielectrophoresis with 3D Self-Assembled Ionic Liquid Electrodes.

    PubMed

    Sun, Mingrui; Agarwal, Pranay; Zhao, Shuting; Zhao, Yi; Lu, Xiongbin; He, Xiaoming

    2016-08-16

    Dielectrophoresis (DEP) has been widely explored to separate cells for various applications. However, existing DEP devices are limited by the high cost associated with the use of noble metal electrodes, the need of high-voltage electric field, and/or discontinuous separation (particularly for devices without metal electrodes). We developed a DEP device with liquid electrodes, which can be used to continuously separate different types of cells or particles based on positive DEP. The device is made of polydimethylsiloxane (PDMS), and ionic liquid is used to form the liquid electrodes, which has the advantages of low cost and easy fabrication. Moreover, the conductivity gradient is utilized to achieve the DEP-based on-chip cell separation. The device was used to separate polystyrene microbeads and PC-3 human prostate cancer cells with 94.7 and 1.2% of the cells and microbeads being deflected, respectively. This device is also capable of separating live and dead PC-3 cancer cells with 89.8 and 13.2% of the live and dead cells being deflected, respectively. Moreover, MDA-MB-231 human breast cancer cells could be separated from human adipose-derived stem cells (ADSCs) using this device with high purity (81.8 and 82.5% for the ADSCs and MDA-MB-231 cells, respectively). Our data suggest the great potential of cell separation based on conductivity-induced DEP using affordable microfluidic devices with easy operation.

  5. Charge-compensation in 3d-transition-metal-oxide intercalation cathodes through the generation of localized electron holes on oxygen.

    PubMed

    Luo, Kun; Roberts, Matthew R; Hao, Rong; Guerrini, Niccoló; Pickup, David M; Liu, Yi-Sheng; Edström, Kristina; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

    2016-07-01

    During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of (18)O-labelled Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2, which demonstrates that oxygen is extracted from the lattice on charging a Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2 cathode, although we detected no O2 evolution. Combined soft X-ray absorption spectroscopy, resonant inelastic X-ray scattering spectroscopy, X-ray absorption near edge structure spectroscopy and Raman spectroscopy demonstrates that, in addition to oxygen loss, Li(+) removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn(4+) and Li(+) ions, which serve to promote the localization, and not the formation, of true O2(2-) (peroxide, O-O ~1.45 Å) species. The quantity of charge compensated by oxygen removal and by the formation of electron holes on the O atoms is estimated, and for the case described here the latter dominates. PMID:27325095

  6. Understanding ferromagnetism and optical absorption in 3d transition metal-doped cubic ZrO{sub 2} with the modified Becke-Johnson exchange-correlation functional

    SciTech Connect

    Boujnah, M.; Zaari, H.; El Kenz, A.; Labrim, H.; Benyoussef, A.; Mounkachi, O.

    2014-03-28

    The electronic structure, magnetic, and optical properties in cubic crystalline phase of Zr{sub 1−x}TM{sub x}O{sub 2} (TM = V, Mn, Fe, and Co) at x = 6.25% are studied using density functional theory with the Generalized Gradient Approximation and the modified Becke-Johnson of the exchange-correlation energy and potential. In our calculations, the zirconia is a p-type semiconductor and has a large band gap. We evaluated the possibility of long-range magnetic order for transition metal ions substituting Zr. Our results show that ferromagnetism is the ground state in V, Mn, and Fe-doped ZrO{sub 2} and have a high value of energy in Mn-doped ZrO{sub 2}. However, in Co-doped ZrO{sub 2}, antiferromagnetic ordering is more stable than the ferromagnetic one. The exchange interaction mechanism has been discussed to explain the responsible of this stability. Moreover, it has been found that the V, Mn, and Fe transition metals provide half-metallic properties considered to be the leading cause, responsible for ferromagnetism. Furthermore, the optical absorption spectra in the TM -doped cubic ZrO{sub 2} are investigated.

  7. Charge-compensation in 3d-transition-metal-oxide intercalation cathodes through the generation of localized electron holes on oxygen.

    PubMed

    Luo, Kun; Roberts, Matthew R; Hao, Rong; Guerrini, Niccoló; Pickup, David M; Liu, Yi-Sheng; Edström, Kristina; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

    2016-07-01

    During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of (18)O-labelled Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2, which demonstrates that oxygen is extracted from the lattice on charging a Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2 cathode, although we detected no O2 evolution. Combined soft X-ray absorption spectroscopy, resonant inelastic X-ray scattering spectroscopy, X-ray absorption near edge structure spectroscopy and Raman spectroscopy demonstrates that, in addition to oxygen loss, Li(+) removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn(4+) and Li(+) ions, which serve to promote the localization, and not the formation, of true O2(2-) (peroxide, O-O ~1.45 Å) species. The quantity of charge compensated by oxygen removal and by the formation of electron holes on the O atoms is estimated, and for the case described here the latter dominates.

  8. Recent developments in DFD (depth-fused 3D) display and arc 3D display

    NASA Astrophysics Data System (ADS)

    Suyama, Shiro; Yamamoto, Hirotsugu

    2015-05-01

    We will report our recent developments in DFD (Depth-fused 3D) display and arc 3D display, both of which have smooth movement parallax. Firstly, fatigueless DFD display, composed of only two layered displays with a gap, has continuous perceived depth by changing luminance ratio between two images. Two new methods, called "Edge-based DFD display" and "Deep DFD display", have been proposed in order to solve two severe problems of viewing angle and perceived depth limitations. Edge-based DFD display, layered by original 2D image and its edge part with a gap, can expand the DFD viewing angle limitation both in 2D and 3D perception. Deep DFD display can enlarge the DFD image depth by modulating spatial frequencies of front and rear images. Secondly, Arc 3D display can provide floating 3D images behind or in front of the display by illuminating many arc-shaped directional scattering sources, for example, arcshaped scratches on a flat board. Curved Arc 3D display, composed of many directional scattering sources on a curved surface, can provide a peculiar 3D image, for example, a floating image in the cylindrical bottle. The new active device has been proposed for switching arc 3D images by using the tips of dual-frequency liquid-crystal prisms as directional scattering sources. Directional scattering can be switched on/off by changing liquid-crystal refractive index, resulting in switching of arc 3D image.

  9. X-ray-absorption near-edge structure of 3d transition elements in tetrahedral coordination: The effect of bond-length variation

    NASA Astrophysics Data System (ADS)

    Bianconi, A.; Fritsch, E.; Calas, G.; Petiau, J.

    1985-09-01

    The x-ray-absorption near-edge structure (XANES) of transition elements in tetrahedral coordination in crystals and glasses has been studied. We have identified the XANES features in the continuum that can be assigned to multiple scattering within the first coordination shell. The energy positions Er of the XANES peaks in the continuum follow the rule (Er-Eb)d2= const, where Eb is the energy of the prepeak, defined as the first core excitation to the bound antibonding state of T2 symmetry, and d is the interatomic distance. This plot allows us to determine the tetrahedral coordination of a vanadium impurity in a SiO2 glass and to get an estimation of the vanadium-oxygen distance (1.77+/-0.05 Å).

  10. Taming supersymmetric defects in 3d-3d correspondence

    NASA Astrophysics Data System (ADS)

    Gang, Dongmin; Kim, Nakwoo; Romo, Mauricio; Yamazaki, Masahito

    2016-07-01

    We study knots in 3d Chern-Simons theory with complex gauge group {SL}(N,{{C}}), in the context of its relation with 3d { N }=2 theory (the so-called 3d-3d correspondence). The defect has either co-dimension 2 or co-dimension 4 inside the 6d (2,0) theory, which is compactified on a 3-manifold \\hat{M}. We identify such defects in various corners of the 3d-3d correspondence, namely in 3d {SL}(N,{{C}}) CS theory, in 3d { N }=2 theory, in 5d { N }=2 super Yang-Mills theory, and in the M-theory holographic dual. We can make quantitative checks of the 3d-3d correspondence by computing partition functions at each of these theories. This Letter is a companion to a longer paper [1], which contains more details and more results.

  11. 3D Audio System

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Ames Research Center research into virtual reality led to the development of the Convolvotron, a high speed digital audio processing system that delivers three-dimensional sound over headphones. It consists of a two-card set designed for use with a personal computer. The Convolvotron's primary application is presentation of 3D audio signals over headphones. Four independent sound sources are filtered with large time-varying filters that compensate for motion. The perceived location of the sound remains constant. Possible applications are in air traffic control towers or airplane cockpits, hearing and perception research and virtual reality development.

  12. Spin Liquid State in the 3D Frustrated Antiferromagnet PbCuTe_{2}O_{6}: NMR and Muon Spin Relaxation Studies.

    PubMed

    Khuntia, P; Bert, F; Mendels, P; Koteswararao, B; Mahajan, A V; Baenitz, M; Chou, F C; Baines, C; Amato, A; Furukawa, Y

    2016-03-11

    PbCuTe_{2}O_{6} is a rare example of a spin liquid candidate featuring a three-dimensional magnetic lattice. Strong geometric frustration arises from the dominant antiferromagnetic interaction that generates a hyperkagome network of Cu^{2+} ions although additional interactions enhance the magnetic lattice connectivity. Through a combination of magnetization measurements and local probe investigations by NMR and muon spin relaxation down to 20 mK, we provide robust evidence for the absence of magnetic freezing in the ground state. The local spin susceptibility probed by the NMR shift hardly deviates from the macroscopic one down to 1 K pointing to a homogeneous magnetic system with a low defect concentration. The saturation of the NMR shift and the sublinear power law temperature (T) evolution of the 1/T_{1} NMR relaxation rate at low T point to a nonsinglet ground state favoring a gapless fermionic description of the magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics is witnessed, which may signal a reconstruction of spinon Fermi surface. Nonetheless, the compound remains in a fluctuating spin liquid state down to the lowest temperature of the present investigation. PMID:27015508

  13. Spin liquid state in the 3D frustrated antiferromagnet PbCuTe2O6: NMR and muon spin relaxation studies

    DOE PAGES

    Khuntia, P.; Bert, F.; Mendels, P.; Koteswararao, B.; Mahajan, A. V.; Baenitz, M.; Chou, F. C.; Baines, C.; Amato, A.; Furukawa, Y.

    2016-03-11

    In this study, PbCuTe2O6 is a rare example of a spin liquid candidate featuring a three-dimensional magnetic lattice. Strong geometric frustration arises from the dominant antiferromagnetic interaction that generates a hyperkagome network of Cu2+ ions although additional interactions enhance the magnetic lattice connectivity. Through a combination of magnetization measurements and local probe investigations by NMR and muon spin relaxation down to 20 mK, we provide robust evidence for the absence of magnetic freezing in the ground state. The local spin susceptibility probed by the NMR shift hardly deviates from the macroscopic one down to 1 K pointing to a homogeneousmore » magnetic system with a low defect concentration. The saturation of the NMR shift and the sublinear power law temperature (T) evolution of the 1/T1 NMR relaxation rate at low T point to a nonsinglet ground state favoring a gapless fermionic description of the magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics is witnessed, which may signal a reconstruction of spinon Fermi surface. Nonetheless, the compound remains in a fluctuating spin liquid state down to the lowest temperature of the present investigation.« less

  14. Spin Liquid State in the 3D Frustrated Antiferromagnet PbCuTe_{2}O_{6}: NMR and Muon Spin Relaxation Studies.

    PubMed

    Khuntia, P; Bert, F; Mendels, P; Koteswararao, B; Mahajan, A V; Baenitz, M; Chou, F C; Baines, C; Amato, A; Furukawa, Y

    2016-03-11

    PbCuTe_{2}O_{6} is a rare example of a spin liquid candidate featuring a three-dimensional magnetic lattice. Strong geometric frustration arises from the dominant antiferromagnetic interaction that generates a hyperkagome network of Cu^{2+} ions although additional interactions enhance the magnetic lattice connectivity. Through a combination of magnetization measurements and local probe investigations by NMR and muon spin relaxation down to 20 mK, we provide robust evidence for the absence of magnetic freezing in the ground state. The local spin susceptibility probed by the NMR shift hardly deviates from the macroscopic one down to 1 K pointing to a homogeneous magnetic system with a low defect concentration. The saturation of the NMR shift and the sublinear power law temperature (T) evolution of the 1/T_{1} NMR relaxation rate at low T point to a nonsinglet ground state favoring a gapless fermionic description of the magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics is witnessed, which may signal a reconstruction of spinon Fermi surface. Nonetheless, the compound remains in a fluctuating spin liquid state down to the lowest temperature of the present investigation.

  15. Determination of the liquid crystals phase transition temperatures using optical rotation effect

    NASA Astrophysics Data System (ADS)

    Niu, Xiao-ling; Liu, Wei-guo; Liu, Peng; Cai, Chang-long

    2011-11-01

    Using optical rotation effect, a sensitive, simple optical analytical system is developed for determining the phase transition temperatures of liquid crystals (LCs). When a monochromatic polarized light passes through LCs sample and analyzer, the light intensity changes with temperature. Especially, during the phase transition process, the intensity varies greatly due to optical rotation effect. The variation of light intensity versus variation of temperature curve shows the phase transition temperatures of LCs clearly. The phase transition temperatures of three cholesteric liquid crystals (ChLCs) and a nematic liquid crystals (NLCs) were detected by this method, and compared with those of the differential scanning calorimetry (DSC) and polarized light microscope (PLM) methods.

  16. Disorder-driven phase transition in La{sub 0.37}D{sub 0.30}Ca{sub 0.33}MnO{sub 3} (D = Bi, Sm) manganites

    SciTech Connect

    Ade, Ramesh; Singh, R.

    2015-08-15

    In the present work we report the structural, electron spin resonance (ESR) and magnetic properties of La{sub 0.37}D{sub 0.30}Ca{sub 0.33}MnO{sub 3} (D = Bi, Sm) manganites synthesized by sol-gel method. The critical behavior at the critical point, where the system undergoes phase transition from paramagnetic (PM) to ferromagnetic (FM) state, is investigated by using modified-Arrott plots, Kouvel-Fisher method and critical isotherm analysis. Both the samples show second-order phase transition near the critical point. The decrease in magnetization (M), Curie temperature (T{sub C}), evolution of spin or cluster glass behavior and the nature of second-order phase transition compared to the first-order transition reported in the literature for La{sub 0.67}Ca{sub 0.33}MnO{sub 3} are ascribed to disorder caused by the size mismatch of the A-site cations with Bi and Sm doping at La-site.

  17. Inferring transit time distributions from atmospheric tracer data: Assessment of the predictive capacities of Lumped Parameter Models on a 3D crystalline aquifer model

    NASA Astrophysics Data System (ADS)

    Marçais, J.; de Dreuzy, J.-R.; Ginn, T. R.; Rousseau-Gueutin, P.; Leray, S.

    2015-06-01

    While central in groundwater resources and contaminant fate, Transit Time Distributions (TTDs) are never directly accessible from field measurements but always deduced from a combination of tracer data and more or less involved models. We evaluate the predictive capabilities of approximate distributions (Lumped Parameter Models abbreviated as LPMs) instead of fully developed aquifer models. We develop a generic assessment methodology based on synthetic aquifer models to establish references for observable quantities as tracer concentrations and prediction targets as groundwater renewal times. Candidate LPMs are calibrated on the observable tracer concentrations and used to infer renewal time predictions, which are compared with the reference ones. This methodology is applied to the produced crystalline aquifer of Plœmeur (Brittany, France) where flows leak through a micaschists aquitard to reach a sloping aquifer where they radially converge to the producing well, issuing broad rather than multi-modal TTDs. One, two and three parameters LPMs were calibrated to a corresponding number of simulated reference anthropogenic tracer concentrations (CFC-11, 85Kr and SF6). Extensive statistical analysis over the aquifer shows that a good fit of the anthropogenic tracer concentrations is neither a necessary nor a sufficient condition to reach acceptable predictive capability. Prediction accuracy is however strongly conditioned by the use of a priori relevant LPMs. Only adequate LPM shapes yield unbiased estimations. In the case of Plœmeur, relevant LPMs should have two parameters to capture the mean and the standard deviation of the residence times and cover the first few decades [0; 50 years]. Inverse Gaussian and shifted exponential performed equally well for the wide variety of the reference TTDs from strongly peaked in recharge zones where flows are diverging to broadly distributed in more converging zones. When using two sufficiently different atmospheric tracers like

  18. Inhibitory effect of quercetin on epithelial to mesenchymal transition in SK-MEL-28 human melanoma cells defined by in vitro analysis on 3D collagen gels

    PubMed Central

    Patel, Dhairya H; Sharma, Neeti

    2016-01-01

    Considering the emerging concept of complementary and alternative medicine under the paucity of effective treatment for melanoma, we aimed to understand the effect of quercetin (Qu) on collagen I-induced epithelial–mesenchymal transition (EMT) in melanoma cells. To investigate the effect of Qu in melanoma cells, we used multiple methods, including real-time reverse transcription polymerase chain reaction, migration assay, and wound healing assay. We found that EMT was altered by Qu in melanoma cells. Qu-treated cells exhibited decreased migration and invasion activities. Mechanistically, a high expression of epithelial markers and a decrease in the expression of mesenchymal markers were found to be associated with reversal of EMT in melanoma cells. Time-dependent apoptosis was observed in Qu-treated melanoma cells, which was further confirmed by the upregulation in the protein levels of Caspase 3, a proapoptotic marker. Thus, our findings suggest Qu as a promising dietary compound under the new complementary and alternative medicine category of therapeutic drugs in the chemoprevention of melanoma. PMID:27799792

  19. Equation of state and phase transition of deuterated ammonia monohydrate (ND3.D2O) measured by high-resolution neutron powder diffraction up to 500 MPa

    NASA Astrophysics Data System (ADS)

    Fortes, A. Dominic; Suard, Emmanuelle; Lemée-Cailleau, Marie-Hélène; Pickard, Christopher J.; Needs, Richard J.

    2009-10-01

    We describe the results of a neutron powder diffraction study of perdeuterated ammonia monohydrate (AMH, ND3ṡD2O) carried out in the range 102transition from AMH I to AMH II occurred over a period of 90 min, with an associated reduction in molar volume of 4.6% and an increase in the incompressibility of 19.6%.

  20. Strong magnetoelastic coupling at the transition from harmonic to anharmonic order in NaFe(WO 4)2 with 3 d5 configuration

    NASA Astrophysics Data System (ADS)

    Holbein, S.; Ackermann, M.; Chapon, L.; Steffens, P.; Gukasov, A.; Sazonov, A.; Breunig, O.; Sanders, Y.; Becker, P.; Bohatý, L.; Lorenz, T.; Braden, M.

    2016-09-01

    The crystal structure of the double tungstate NaFe (WO4)2 arises from that of the spin-driven multiferroic MnWO4 by inserting nonmagnetic Na layers. NaFe (WO4)2 exhibits a three-dimensional incommensurate spin-spiral structure at low temperature and zero magnetic field, which, however, competes with commensurate order induced by magnetic field. The incommensurate zero-field phase corresponds to the condensation of a single irreducible representation but it does not imply ferroelectric polarization because spirals with opposite chirality coexist. Sizable anharmonic modulations emerge in this incommensurate structure, which are accompanied by large magnetoelastic anomalies, while the onset of the harmonic order is invisible in the thermal-expansion coefficient. In magnetic fields applied along the monoclinic axis, we observe a first-order transition to a commensurate structure that again is accompanied by large magnetoelastic effects. The large magnetoelastic coupling, a reduction of the b lattice parameter, is thus associated only with the commensurate order. Upon releasing the field at low temperature, the magnetic order transforms to another commensurate structure that considerably differs from the incommensurate low-temperature phase emerging upon zero-field cooling. The latter phase, which exhibits a reduced ordered moment, seems to be metastable.

  1. Growth-dissolution-regrowth transitions of Fe3O4 nanoparticles as building blocks for 3D magnetic nanoparticle clusters under hydrothermal conditions.

    PubMed

    Lin, Mouhong; Huang, Haoliang; Liu, Zuotao; Liu, Yingju; Ge, Junbin; Fang, Yueping

    2013-12-10

    Magnetic nanoparticle clusters (MNCs) are a class of secondary structural materials that comprise chemically defined nanoparticles assembled into clusters of defined size. Herein, MNCs are fabricated through a one-pot solvothermal reaction featuring self-limiting assembly of building blocks and the controlled reorganization process. Such growth-dissolution-regrowth fabrication mechanism overcomes some limitations of conventional solvothermal fabrication methods with regard to restricted available feature size and structural complexity, which can be extended to other oxides (as long as one can be chelated by EDTA-2Na). Based on this method, the nanoparticle size of MNCs is tuned between 6.8 and 31.2 nm at a fixed cluster diameter of 120 nm, wherein the critical size for superparamagnetic-ferromagnetic transition is estimated from 13.5 to 15.7 nm. Control over the nature and secondary structure of MNCs gives an excellent model system to understand the nanoparticle size-dependent magnetic properties of MNCs. MNCs have potential applications in many different areas, while this work evaluates their cytotoxicity and Pb(2+) adsorption capacity as initial application study.

  2. Quasi-liquid layer theory based on the bulk first-order phase transition

    SciTech Connect

    Ryzhkin, I. A. Petrenko, V. F.

    2009-01-15

    The theory of the superionic phase transition (bulk first-order transition) proposed in [1] is used to explain the existence of a quasi-liquid layer at an ice surface below its melting point. An analytical expression is derived for the quasi-liquid layer thickness. Numerical estimates are made and compared with experiment. Distinction is made between the present model and other quasi-liquid layer theories.

  3. 3D Printable Graphene Composite

    PubMed Central

    Wei, Xiaojun; Li, Dong; Jiang, Wei; Gu, Zheming; Wang, Xiaojuan; Zhang, Zengxing; Sun, Zhengzong

    2015-01-01

    In human being’s history, both the Iron Age and Silicon Age thrived after a matured massive processing technology was developed. Graphene is the most recent superior material which could potentially initialize another new material Age. However, while being exploited to its full extent, conventional processing methods fail to provide a link to today’s personalization tide. New technology should be ushered in. Three-dimensional (3D) printing fills the missing linkage between graphene materials and the digital mainstream. Their alliance could generate additional stream to push the graphene revolution into a new phase. Here we demonstrate for the first time, a graphene composite, with a graphene loading up to 5.6 wt%, can be 3D printable into computer-designed models. The composite’s linear thermal coefficient is below 75 ppm·°C−1 from room temperature to its glass transition temperature (Tg), which is crucial to build minute thermal stress during the printing process. PMID:26153673

  4. 3D Printable Graphene Composite

    NASA Astrophysics Data System (ADS)

    Wei, Xiaojun; Li, Dong; Jiang, Wei; Gu, Zheming; Wang, Xiaojuan; Zhang, Zengxing; Sun, Zhengzong

    2015-07-01

    In human being’s history, both the Iron Age and Silicon Age thrived after a matured massive processing technology was developed. Graphene is the most recent superior material which could potentially initialize another new material Age. However, while being exploited to its full extent, conventional processing methods fail to provide a link to today’s personalization tide. New technology should be ushered in. Three-dimensional (3D) printing fills the missing linkage between graphene materials and the digital mainstream. Their alliance could generate additional stream to push the graphene revolution into a new phase. Here we demonstrate for the first time, a graphene composite, with a graphene loading up to 5.6 wt%, can be 3D printable into computer-designed models. The composite’s linear thermal coefficient is below 75 ppm·°C-1 from room temperature to its glass transition temperature (Tg), which is crucial to build minute thermal stress during the printing process.

  5. Inferring Transit Time Distributions from Atmospheric Tracer Data: Assessment of Predictive Capacities of Lumped Parameter Models on a 3D Crystalline Aquifer Model

    NASA Astrophysics Data System (ADS)

    Marçais, J.; De Dreuzy, J. R.; Ginn, T. R.; Gueutin, P.; Leray, S.

    2014-12-01

    Transit time distributions (TTDs) play a key role in the transport processes, the interpretation of atmospheric tracer data and the predictions made on groundwater resources. However TTDs are not accessible from field measurements. Only hints on these TTDs can be obtained from anthropogenic tracer concentrations, also commonly called "groundwater ages". We evaluate the predictive capabilities of the information contained in anthropogenic tracer concentrations on groundwater renewal times through the use of Lumped Parameter Models (LPMs) instead of fully developed aquifer models. Towards this end, we develop an assessment methodology in three steps. First, a synthetic crystalline aquifer model representing the site of Plœmeur (Brittany, France) is used to give, at any point, references for observables quantities (anthropogenic tracer concentrations of CFC-11, 85Kr and SF6), for non-observables quantities (the TTDs), and for the prediction objective (groundwater renewal times). Second, several LPMs are considered with one, two or three parameters, and are parameterized by fitting the reference anthropogenic concentrations. Third, the reference renewal times obtained from the synthetic model are compared to the renewal times obtained independently from the LPMs. Statistical analyses over the aquifer show that a good fit of the anthropogenic tracer concentrations is a necessary but not sufficient condition for acceptable predictions. The use of only one anthropogenic tracer gives poor predictions differing by 7 to 12 years to the references. The use of two sufficiently different anthropogenic tracers not only reduce the errors but surprisingly yield to very accurate predictions with errors smaller than 3 years. The additional use of a third anthropogenic tracer does not improve the predictive capabilities. Careful a posteriori analyses reveal that reference TTDs have widely varying shapes from well peaked in recharge zones where flows are diverging to broadly

  6. Combustion characteristics in the transition region of liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Cernansky, N. P.; Namer, I.; Tidona, R. J.

    1986-01-01

    A number of important effects have been observed in the droplet size transition region in spray combustion systems. In this region, where the mechanism of flame propagation is transformed from diffusive to premixed dominated combustion, the following effects have been observed: (1) maxima in burning velocity; (2) extension of flammability limits; (3) minima in ignition energy; and (4) minima in NOx formation. A monodisperse aerosol generator has been used to form and deliver a well controlled liquid fuel spray to the combustion test section where measurements of ignition energy have been made. The ignition studies were performed on monodisperse n-heptane sprays at atmospheric pressure over a range of equivalence ratios and droplet diameters. A capacitive discharge spark ignition system was used as the ignition source, providing independent control of spark energy and duration. Preliminary measurements were made to optimize spark duration and spark gap, optimum conditions being those at which the maximum frequency or probability of ignition was observed. Using the optimum electrode spacing and spark duration, the frequency of ignition was determined as a function of spark energy for three overall equivalence ratios (0.6, 0.8, and 1.0) and for initial droplet diameters of 25, 40, 50, 60, and 70 micro m.

  7. Nature of the gel to liquid crystal transition of synthetic phosphatidylcholines.

    PubMed Central

    Albon, N; Sturtevant, J M

    1978-01-01

    High sensitivity differential scanning calorimetry is employed in the study of the gel to liquid crystal phase transition of a highly purified sample of dipalmitoylphosphatidylcholine in multilamellar bilayer suspension. It is concluded from the calorimetric data that the purity of the sample is better than 99.94 mol % and that the transition closely approximates an isothermal first-order transition. PMID:276866

  8. Cationic amino acids specific biomimetic silicification in ionic liquid: a quest to understand the formation of 3-D structures in diatoms.

    PubMed

    Ramanathan, Rajesh; Campbell, Jos L; Soni, Sarvesh K; Bhargava, Suresh K; Bansal, Vipul

    2011-03-03

    The intricate, hierarchical, highly reproducible, and exquisite biosilica structures formed by diatoms have generated great interest to understand biosilicification processes in nature. This curiosity is driven by the quest of researchers to understand nature's complexity, which might enable reproducing these elegant natural diatomaceous structures in our laboratories via biomimetics, which is currently beyond the capabilities of material scientists. To this end, significant understanding of the biomolecules involved in biosilicification has been gained, wherein cationic peptides and proteins are found to play a key role in the formation of these exquisite structures. Although biochemical factors responsible for silica formation in diatoms have been studied for decades, the challenge to mimic biosilica structures similar to those synthesized by diatoms in their natural habitats has not hitherto been successful. This has led to an increasingly interesting debate that physico-chemical environment surrounding diatoms might play an additional critical role towards the control of diatom morphologies. The current study demonstrates this proof of concept by using cationic amino acids as catalyst/template/scaffold towards attaining diatom-like silica morphologies under biomimetic conditions in ionic liquids.

  9. Cationic Amino Acids Specific Biomimetic Silicification in Ionic Liquid: A Quest to Understand the Formation of 3-D Structures in Diatoms

    PubMed Central

    Ramanathan, Rajesh; Campbell, Jos L.; Soni, Sarvesh K.; Bhargava, Suresh K.; Bansal, Vipul

    2011-01-01

    The intricate, hierarchical, highly reproducible, and exquisite biosilica structures formed by diatoms have generated great interest to understand biosilicification processes in nature. This curiosity is driven by the quest of researchers to understand nature's complexity, which might enable reproducing these elegant natural diatomaceous structures in our laboratories via biomimetics, which is currently beyond the capabilities of material scientists. To this end, significant understanding of the biomolecules involved in biosilicification has been gained, wherein cationic peptides and proteins are found to play a key role in the formation of these exquisite structures. Although biochemical factors responsible for silica formation in diatoms have been studied for decades, the challenge to mimic biosilica structures similar to those synthesized by diatoms in their natural habitats has not hitherto been successful. This has led to an increasingly interesting debate that physico-chemical environment surrounding diatoms might play an additional critical role towards the control of diatom morphologies. The current study demonstrates this proof of concept by using cationic amino acids as catalyst/template/scaffold towards attaining diatom-like silica morphologies under biomimetic conditions in ionic liquids. PMID:21408611

  10. Multiple Ordering Transitions in a Liquid Stabilized by Low Symmetry Structures

    NASA Astrophysics Data System (ADS)

    Ronceray, Pierre; Harrowell, Peter

    2014-01-01

    We present a numerical study of a lattice model of a liquid characterized by a low-symmetry favored local structure. We find that the freezing point is depressed far enough to reveal an exotic liquid-liquid transition characterized by the appearance of an extended chirality, prior to freezing. The ordered liquid can be readily supercooled to zero temperature, as the combination of critical slowing down and competing crystal polymorphs results in a dramatically slow crystallization process. These results provide an explicit scenario by which the ordering of a liquid can proceed via an intermediate liquid-liquid transition, a scenario that may prove helpful in the analysis of low temperature liquids interacting by more realistic interactions.

  11. Multiple ordering transitions in a liquid stabilized by low symmetry structures.

    PubMed

    Ronceray, Pierre; Harrowell, Peter

    2014-01-10

    We present a numerical study of a lattice model of a liquid characterized by a low-symmetry favored local structure. We find that the freezing point is depressed far enough to reveal an exotic liquid-liquid transition characterized by the appearance of an extended chirality, prior to freezing. The ordered liquid can be readily supercooled to zero temperature, as the combination of critical slowing down and competing crystal polymorphs results in a dramatically slow crystallization process. These results provide an explicit scenario by which the ordering of a liquid can proceed via an intermediate liquid-liquid transition, a scenario that may prove helpful in the analysis of low temperature liquids interacting by more realistic interactions. PMID:24483932

  12. Tuning the Liquid-Liquid Transition by Modulating the Hydrogen-Bond Angular Flexibility in a Model for Water

    NASA Astrophysics Data System (ADS)

    Smallenburg, Frank; Sciortino, Francesco

    2015-07-01

    We propose a simple extension of the well known ST2 model for water [F. H. Stillinger and A. Rahman, J. Chem. Phys. 60, 1545 (1974)] that allows for a continuous modification of the hydrogen-bond angular flexibility. We show that the bond flexibility affects the relative thermodynamic stability of the liquid and of the hexagonal (or cubic) ice. On increasing the flexibility, the liquid-liquid critical point, which in the original ST2 model is located in the no-man's land (i.e., the region where ice is the thermodynamically stable phase) progressively moves to a temperature where the liquid is more stable than ice. Our study definitively proves that the liquid-liquid transition in the ST2 model is a genuine phenomenon, of high relevance in all tetrahedral network-forming liquids, including water.

  13. Tuning the Liquid-Liquid Transition by Modulating the Hydrogen-Bond Angular Flexibility in a Model for Water.

    PubMed

    Smallenburg, Frank; Sciortino, Francesco

    2015-07-01

    We propose a simple extension of the well known ST2 model for water [F. H. Stillinger and A. Rahman, J. Chem. Phys. 60, 1545 (1974)] that allows for a continuous modification of the hydrogen-bond angular flexibility. We show that the bond flexibility affects the relative thermodynamic stability of the liquid and of the hexagonal (or cubic) ice. On increasing the flexibility, the liquid-liquid critical point, which in the original ST2 model is located in the no-man's land (i.e., the region where ice is the thermodynamically stable phase) progressively moves to a temperature where the liquid is more stable than ice. Our study definitively proves that the liquid-liquid transition in the ST2 model is a genuine phenomenon, of high relevance in all tetrahedral network-forming liquids, including water.

  14. In Situ Monitoring of Microstructures during Subsequent Phase Transitions in the Olivine System up to 30 GPa and 1100 K Using 3D-XRD Single-Grain Analysis. Effects of Grain Size Evolution on the Stagnation of Slab.

    NASA Astrophysics Data System (ADS)

    Rosa, A. D.; Hilairet, N.; Ghosh, S.; Jacobs, J.; Perrillat, J. P.; Vaughan, G. B. M.; Garbarino, G.; Mezouar, N.; Merkel, S.

    2014-12-01

    Microstructures significantly influence the rheological properties of rocks and are important to understand geodynamical processes such as the descent of slabs. For example, grain size reductions during phase transitions in the dominant upper mantle constituent, olivine, to its high-pressure polymorphs wadsleyite and ringwoodite have been related to the stagnation of slabs in the transition zone. Detailed studies of the microstructure development, underlying transformation mechanism and transformation kinetics are needed in order to assess the effects of these phase transformations on the rheological properties of the slab material and to build reliable models of mantle flow and slab subduction behaviors. So far, the experimental studies dedicated to this theme were mostly based on ex situ techniques (e.g. electron microscopy of quenched products).In this contribution, we present detailed results form in situ single-grain analysis on the evolution of microstructures during the succession of phase transitions in Mg2SiO4*H2O. We used a new approach based on in situ three dimensional-X-ray diffraction (3D-XRD) experiments performed up to 30 GPa and 1100 K using a resistively heated diamond anvil cell at the beam lines ID11 and ID27 of the ESRF. The individual orientations, crystallographic parameters and growth rates of numerous grains inside a polycrystalline sample have been monitored in situ at the high pressure and temperature conditions and while the material was transforming. These parameters have been used to infer grain size distributions, textural relations between parent and newly formed phase and their evolution with ongoing transformation, as well as changing PT conditions and transformation kinetics. This original dataset allows drawing a refined picture of phase transitions in the most abundant minerals of the Earth's upper mantle, shed new light on the origin of seismic anomalies at transition zone depth and provide new grounds for complex simulations

  15. Magnetic and orbital orders coupled to negative thermal expansion in Mott insulators, Ca2Ru1--xM xO4 (M = 3d transition metal ion)

    NASA Astrophysics Data System (ADS)

    Qi, Tongfei

    Ca2RuO4 is a structurally-driven Mott insulator with a metal-insulator (MI) transition at TMI = 357K, followed by a well-separated antiferromagnetic order at T N = 110 K. Slightly substituting Ru with a 3d transition metal ion M effectively shifts TMI and induces exotic magnetic behavior below TN. Moreover, M doping for Ru produces negative thermal expansion in Ca2Ru1-- xMxO4 (M = Cr, Mn, Fe or Cu); the lattice volume expands on cooling with a total volume expansion ratio, DeltaV/V, reaching as high as 1%. The onset of the negative thermal expansion closely tracks TMI and TN, sharply contrasting classic negative thermal expansion that shows no relevance to electronic properties. In addition, the observed negative thermal expansion occurs near room temperature and extends over a wide temperature interval. These findings underscores new physics driven by a complex interplay between orbital, spin and lattice degrees of freedom. These materials constitute a new class of Negative Thermal Expansion (NTE) materials with novel electronic and magnetic functions. KEYWORDS: Transition Metal Oxide, Ruthenate, Negative Thermal Expansion, Single crystal XRD, Invar Effect, Orbital Ordering, Magnetic Ordering, Jahn-Teller Effect.

  16. Investigation of anchoring transition of liquid crystals on crown ether monolayers by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Dong, Xiao; Yang, Xiaomin; Zhu, Yangming; Lu, Zuhong; Wei, Yu

    1994-10-01

    The homeotropic and homogeneous alignment of a liquid crystal material, 4'-n-pentyl-4-cyanobiphenyl (5CB), were achieved by Langmuir monolayers of a double-armed crown ether liquid crystal, N,N-bis(4-(4-heptoxybenzoyloxy)benzo-yl)-1,10-diaza-4,7,13,16- tetracyclooxaotad ecane (CELC) . We found that when the monolayer was deposited before the phase transition during monolayer compression, it induced liquid crystal alignment homogeneously; when the monolayer was transferred after the transition, homeotropic liquid crystal alignment was produced. Atomic force microscopy was used to examine the morphology and microstructure of the alignment agent. The results show a conformational change of the alignment agent before and after the transition. The anchoring transition is interpreted as the result of orientational change of the CELC monolayer. We present strong evidence that the orientational change of dipoles in the alignment agent can induce an anchoring transition.

  17. Evidence of a Liquid-Liquid Phase Transition Hot Dense Hydrogen

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac; Dzyabura, Vasily; Zaghoo, Mohamed

    2013-03-01

    We use pulsed laser heating of hydrogen at static pressures in the megabar pressure region generated in a diamond anvil cell to search for the plasma phase transition (PPT) to liquid atomic metallic hydrogen. Heating the sample substantially above the melting line we observe a plateau in a temperature vs laser power curve that otherwise increases with power. This anomaly in the heating curve is closely correlated with theoretical predictions for the PPT, falling within the theoretically predicted range and having a negative slope with increasing pressure. Details will be presented. The NSF, grant DMR-0804378 and the DOE Stockpile Stewardship Academic Alliance program, grant DE-FG52-10NA29656 supported this research.

  18. Unusual liquid-liquid phase transition in aqueous mixtures of a well-known dendrimer.

    PubMed

    da Costa, Viviana C P; Annunziata, Onofrio

    2015-11-21

    Liquid-liquid phase separation (LLPS) has been extensively investigated for polymer and protein solutions due to its importance in mixture thermodynamics, separation science and self-assembly processes. However, to date, no experimental studies have been reported on LLPS of dendrimer solutions. Here, it is shown that LLPS of aqueous solutions containing a hydroxyl-functionalized poly(amido amine) dendrimer of fourth generation is induced in the presence of sodium sulfate. Both the LLPS temperature and salt-dendrimer partitioning between the two coexisting phases at constant temperature were measured. Interestingly, our experiments show that LLPS switches from being induced by cooling to being induced by heating as the salt concentration increases. The two coexisting phases also show opposite temperature response. Thus, this phase transition exhibits a simultaneous lower and upper critical solution temperature-type behavior. Dynamic light-scattering and dye-binding experiments indicate that no appreciable conformational change occurs as the salt concentration increases. To explain the observed phase behavior, a thermodynamic model based on two parameters was developed. The first parameter, which describes dendrimer-dendrimer interaction energy, was determined by isothermal titration calorimetry. The second parameter describes the salt salting-out strength. By varying the salting-out parameter, it is shown that the model achieves agreement not only with the location of the experimental binodal at 25 °C but also with the slope of this curve around the critical point. The proposed model also predicts that the unusual temperature behavior of this phase transition can be described as the net result of two thermodynamic factors with opposite temperature responses: salt thermodynamic non-ideality and salting-out strength.

  19. Unusual liquid-liquid phase transition in aqueous mixtures of a well-known dendrimer.

    PubMed

    da Costa, Viviana C P; Annunziata, Onofrio

    2015-11-21

    Liquid-liquid phase separation (LLPS) has been extensively investigated for polymer and protein solutions due to its importance in mixture thermodynamics, separation science and self-assembly processes. However, to date, no experimental studies have been reported on LLPS of dendrimer solutions. Here, it is shown that LLPS of aqueous solutions containing a hydroxyl-functionalized poly(amido amine) dendrimer of fourth generation is induced in the presence of sodium sulfate. Both the LLPS temperature and salt-dendrimer partitioning between the two coexisting phases at constant temperature were measured. Interestingly, our experiments show that LLPS switches from being induced by cooling to being induced by heating as the salt concentration increases. The two coexisting phases also show opposite temperature response. Thus, this phase transition exhibits a simultaneous lower and upper critical solution temperature-type behavior. Dynamic light-scattering and dye-binding experiments indicate that no appreciable conformational change occurs as the salt concentration increases. To explain the observed phase behavior, a thermodynamic model based on two parameters was developed. The first parameter, which describes dendrimer-dendrimer interaction energy, was determined by isothermal titration calorimetry. The second parameter describes the salt salting-out strength. By varying the salting-out parameter, it is shown that the model achieves agreement not only with the location of the experimental binodal at 25 °C but also with the slope of this curve around the critical point. The proposed model also predicts that the unusual temperature behavior of this phase transition can be described as the net result of two thermodynamic factors with opposite temperature responses: salt thermodynamic non-ideality and salting-out strength. PMID:26451401

  20. 3D stability analysis of Rayleigh-Bénard convection of a liquid metal layer in the presence of a magnetic field—effect of wall electrical conductivity

    NASA Astrophysics Data System (ADS)

    Dimopoulos, Dimitrios; Pelekasis, Nikos A.

    2014-10-01

    Rayleigh-Bénard stability of a liquid metal layer of rectangular cross section is examined in the presence of a strong magnetic field that is aligned with the horizontal direction of the cross section. The latter is much longer than the vertical direction and the cross section assumes a large aspect ratio. The side walls are treated as highly conducting. Linear stability analysis is performed allowing for three-dimensional instabilities that develop along the longitudinal direction. The finite element methodology is employed for the discretization of the stability analysis formulation while accounting for the electrical conductivity of the cavity walls. The Arnoldi method provides the dominant eigenvalues and eigenvectors of the problem. In order to facilitate parallel implementation of the numerical solution at large Hartmann numbers, Ha, domain decomposition is employed along the horizontal direction of the cross section. As the Hartmann number increases a real eigenvalue emerges as the dominant unstable eigenmode, signifying the onset of thermal convection, whose major vorticity component in the core of the layer is aligned with the direction of the magnetic field. Its wavelength along the longitudinal direction of the layer is on the order of twice its height and increases as Ha increases. The critical Grashof was obtained for large Ha and it was seen to scale like Ha 2 signifying the balance between buoyancy and Lorentz forces. For well conducting side walls, the nature of the emerging flow pattern is determined by the combined conductivity of Hartmann walls and Hartmann layers, cH + Ha -1. When poor conducting Hartmann walls are considered, cH ≪ 1, the critical eigensolution is characterized by well defined Hartmann and side layers. The side layers are characterized by fast fluid motion in the magnetic field direction as a result of the electromagnetic pumping in the vicinity of the Hartmann walls. Increasing the electrical conductivity of the Hartmann

  1. Prominent rocks - 3D

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Many prominent rocks near the Sagan Memorial Station are featured in this image, taken in stereo by the Imager for Mars Pathfinder (IMP) on Sol 3. 3D glasses are necessary to identify surface detail. Wedge is at lower left; Shark, Half-Dome, and Pumpkin are at center. Flat Top, about four inches high, is at lower right. The horizon in the distance is one to two kilometers away.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

    Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right

  2. 'Diamond' in 3-D

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 3-D, microscopic imager mosaic of a target area on a rock called 'Diamond Jenness' was taken after NASA's Mars Exploration Rover Opportunity ground into the surface with its rock abrasion tool for a second time.

    Opportunity has bored nearly a dozen holes into the inner walls of 'Endurance Crater.' On sols 177 and 178 (July 23 and July 24, 2004), the rover worked double-duty on Diamond Jenness. Surface debris and the bumpy shape of the rock resulted in a shallow and irregular hole, only about 2 millimeters (0.08 inch) deep. The final depth was not enough to remove all the bumps and leave a neat hole with a smooth floor. This extremely shallow depression was then examined by the rover's alpha particle X-ray spectrometer.

    On Sol 178, Opportunity's 'robotic rodent' dined on Diamond Jenness once again, grinding almost an additional 5 millimeters (about 0.2 inch). The rover then applied its Moessbauer spectrometer to the deepened hole. This double dose of Diamond Jenness enabled the science team to examine the rock at varying layers. Results from those grindings are currently being analyzed.

    The image mosaic is about 6 centimeters (2.4 inches) across.

  3. Martian terrain - 3D

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This area of terrain near the Sagan Memorial Station was taken on Sol 3 by the Imager for Mars Pathfinder (IMP). 3D glasses are necessary to identify surface detail.

    The IMP is a stereo imaging system with color capability provided by 24 selectable filters -- twelve filters per 'eye.' It stands 1.8 meters above the Martian surface, and has a resolution of two millimeters at a range of two meters.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

    Click below to see the left and right views individually. [figure removed for brevity, see original site] Left [figure removed for brevity, see original site] Right

  4. Going full circle: phase-transition thermodynamics of ionic liquids.

    PubMed

    Preiss, Ulrich; Verevkin, Sergey P; Koslowski, Thorsten; Krossing, Ingo

    2011-05-27

    We present the full enthalpic phase transition cycle for ionic liquids (ILs) as examples of non-classical salts. The cycle was closed for the lattice, solvation, dissociation, and vaporization enthalpies of 30 different ILs, relying on as much experimental data as was available. High-quality dissociation enthalpies were calculated at the G3 MP2 level. From the cycle, we could establish, for the first time, the lattice and solvation enthalpies of ILs with imidazolium ions. For vaporization, lattice, and dissociation enthalpies, we also developed new prediction methods in the course of our investigations. Here, as only single-ion values need to be calculated and the tedious optimization of an ion pair can be circumvented, the computational time is short. For the vaporization enthalpy, a very simple approach was found, using a surface term and the calculated enthalpic correction to the total gas-phase energy. For the lattice enthalpy, the most important constituent proved to be the calculated conductor-like screening model (COSMO) solvation enthalpy in the ideal electric conductor. A similar model was developed for the dissociation enthalpy. According to our assessment, the typical error of the lattice enthalpy would be 9.4 kJ mol(-1), which is less than half the deviation we get when using the (optimized) Kapustinskii equation or the recent volume-based thermodynamics (VBT) theory. In contrast, the non-optimized VBT formula gives lattice enthalpies 20 to 140 kJ mol(-1) lower than the ones we assessed in the cycle, because of the insufficient description of dispersive interactions. Our findings show that quantum-chemical calculations can greatly improve the VBT approaches, which were parameterized for simple, inorganic salts with ideally point-shaped charges. In conclusion, we suggest the term "augmented VBT", or "aVBT", to describe this kind of theoretical approach.

  5. Mechanism of Phase Transition from Liquid to Gas Under Dielectric Barrier Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Wang, Qiuying; Li, Sen; Gu, Fan

    2010-10-01

    Liquid gasification phenomenon was observable in liquid-solid dielectric barrier discharge (DBD) experiments. Starting from classical thermodynamics, this study aimed at finding the reason of liquid gasification in the DBD experiments. Fluid statics and electrohydrodynamics were adopted to analyze the mechanism of phase transition from liquid to gas. The Sumoto effect was also employed to visually explain the change in the pressure of fluid due to the electric field. It was concluded from both theoretical analysis and experiment that the change in liquid pressure was a key factor causing liquid to gasify in DBD conditions. Furthermore, it was stressed that the liquid pressure was affected by many parameters including liquid permittivity, voltage, electric intensity, size of the discharge space and uniformity of the electric field distribution, etc. All of them affected DBD liquid gasification. The related results would provide useful theoretical evidence for multi-phase DBD applications.

  6. Novel approach to study liquid crystal phase transitions using Legendre moments

    NASA Astrophysics Data System (ADS)

    Sreehari Sastry, S.; Mallika, K.; Gowri Sankara Rao, B.; Tiong Ha, Sie; Lakshminarayana, S.

    2012-08-01

    A novel approach is proposed to investigate the phase transitions of cholesteric liquid crystals using the Legendre moments. The textures of cholesteric liquid crystals (cholesteryl butyrate, cholesteryl n-valerate, cholesteryl decanoate, and cholesteryl myristate) are captured as a function of temperature using high-resolution camera attached to the arthroscopic mode of polarizing optical microscope with hot stage. A recurrence formula is used to compute the Legendre moments of the liquid crystal textures based on the Legendre polynomial using MATLAB software. The abrupt change in the values of Legendre moments as a function of temperature gives the phase transitions of liquid crystals. The investigated transition temperatures of cholesteric liquid crystals are compared with other techniques.

  7. Shear Flow Induced Transition from Liquid-Crystalline to Polymer Behavior in Side-Chain Liquid Crystal Polymers

    SciTech Connect

    Noirez, L.; Lapp, A.

    1997-01-01

    We determine the structure and conformation of side-chain liquid-crystalline polymers subjected to shear flow in the vicinity of the smectic phase by neutron scattering on the velocity gradient plane. Below the nematic-smectic transition we observe a typical liquid-crystal behavior; the smectic layers slide, leading to a main-chain elongation parallel to the velocity direction. In contrast,a shear applied above the transition induces a tilted main-chain conformation which is typical for polymer behavior. {copyright} {ital 1996} {ital The American Physical Society}

  8. Detection of first-order liquid/liquid phase transitions in yttrium oxide-aluminum oxide melts.

    PubMed

    Greaves, G N; Wilding, M C; Fearn, S; Langstaff, D; Kargl, F; Cox, S; Van, Q Vu; Majérus, O; Benmore, C J; Weber, R; Martin, C M; Hennet, L

    2008-10-24

    We combine small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) with aerodynamic levitation techniques to study in situ phase transitions in the liquid state under contactless conditions. At very high temperatures, yttria-alumina melts show a first-order transition, previously inferred from phase separation in quenched glasses. We show how the transition coincides with a narrow and reversible maximum in SAXS indicative of liquid unmixing on the nanoscale, combined with an abrupt realignment in WAXS features related to reversible shifts in polyhedral packing on the atomic scale. We also observed a rotary action in the suspended supercooled drop driven by repetitive transitions (a polyamorphic rotor) from which the reversible changes in molar volume (1.2 +/- 0.2 cubic centimeters) and entropy (19 +/- 4 joules mole(-1) kelvin(-1)) can be estimated. PMID:18948535

  9. Effects of carbon nanotubes on liquid crystal order parameter and Freedericksz transition in electro-optic cells

    NASA Astrophysics Data System (ADS)

    Georgiev, Georgi; Gombos, Erin; McIntyre, Michael; Mattera, Michael; Gati, Peter; Cabrera, Yaniel; Cebe, Peggy

    2010-03-01

    We studied the effects of multiwalled carbon nanotubes (MWCTs) at low concentrations (0.01 wt %) on the Freedericksz transition of a 4-Cyano-4'-pentylbipenyl (5CB) liquid crystal using transmission ellipsometry. In addition, we calibrated the altitudinal angle of CNTs as a function of the electric field and directed the azimuthal angle which gave us complete control of the 3D orientation of the CNTs. Our results show that in the presence of CNTs the voltage and width for the Freedericksz transition are reduced by a factor of 1.8 as compared to the control electro-optic cell without CNTs. The shift in transition voltage correlates with increase in order parameter of the electro-optic cell as measured by our polarized UV/Vis absorption spectroscopy results. Research supported by: Assumption College Faculty Development Grant, funding for students' stipends, instrumentation and supplies, the NSF Polymers Program of the DME, grant (DMR-0602473) and NASA grant (NAG8-1167).

  10. Using Peltier Cells to Study Solid-Liquid-Vapour Transitions and Supercooling

    ERIC Educational Resources Information Center

    Torzo, Giacomo; Soletta, Isabella; Branca, Mario

    2007-01-01

    We propose an apparatus for teaching experimental thermodynamics in undergraduate introductory courses, using thermoelectric modules and a real-time data acquisition system. The device may be made at low cost, still providing an easy approach to the investigation of liquid-solid and liquid-vapour phase transitions and of metastable states…

  11. Reentrant Solid-Liquid Transition in Ionic Colloidal Dispersions by Varying Particle Charge Density

    NASA Astrophysics Data System (ADS)

    Yamanaka, Junpei; Yoshida, Hiroshi; Koga, Tadanori; Ise, Norio; Hashimoto, Takeji

    1998-06-01

    The influence of the particle surface charge density on the solid-liquid phase transition in electrostatically stabilized colloidal silica and polymer latex dispersions is examined. Both systems show a reentrant transition with increasing charge density. This is not explainable in terms of the Yukawa potential and the charge-renormalization model.

  12. On the existence of vapor-liquid phase transition in dusty plasmas

    SciTech Connect

    Kundu, M.; Sen, A.; Ganesh, R.; Avinash, K.

    2014-10-15

    The phenomenon of phase transition in a dusty-plasma system (DPS) has attracted some attention in the past. Earlier Farouki and Hamaguchi [J. Chem. Phys. 101, 9876 (1994)] have demonstrated the existence of a liquid to solid transition in DPS where the dust particles interact through a Yukawa potential. However, the question of the existence of a vapor-liquid (VL) transition in such a system remains unanswered and relatively unexplored so far. We have investigated this problem by performing extensive molecular dynamics simulations which show that the VL transition does not have a critical curve in the pressure versus volume diagram for a large range of the Yukawa screening parameter κ and the Coulomb coupling parameter Γ. Thus, the VL phase transition is found to be super-critical, meaning that this transition is continuous in the dusty plasma model given by Farouki and Hamaguchi. We provide an approximate analytic explanation of this finding by means of a simple model calculation.

  13. Connection between the glass transition temperature Tg and the Arrhenius temperature TA in supercooled liquids

    NASA Astrophysics Data System (ADS)

    Novikov, V. N.

    2016-08-01

    At high temperatures the structural relaxation time in liquids has Arrhenius temperature dependence. At lowering temperature, temperature dependence changes to a super Arrhenius at some temperature TA. This temperature is an important point for the structural relaxation dynamics in supercooled liquids because it reflects the transition to collective relaxation. Here we derive a relation between TA, the glass transition temperature Tg and fragility. We show that the ratio Tg/TA increases with increasing fragility of a liquid. The derived relation is in agreement with the experimental data in a series of molecular, hydrogen bonding and two inorganic glass-formers.

  14. Undercooling, local structure and phase transition in icosahedral quasicrystals forming titanium-zirconium-nickel alloy liquids

    NASA Astrophysics Data System (ADS)

    Lee, Geun Woo

    While lacking the long-range translationally periodic order of crystalline solids, liquids contain a significant amount of short-range order (SRO), which distinguishes them from gases. The local structure of a liquid is important to understand its chemical and physical properties. One of the remarkable phenomena related to the short-range order of liquids is undercooling. That is, liquids can be retained below their melting temperature for a long time without crystallization. Turnbull first demonstrated this for metallic liquids in 1952. To explain the surprising results, Frank hypothesized in 1952 that the local structure of liquid metals is icosahedral. This structure is quite different from those of crystal phases giving a large nucleation barrier and making the undercooling of liquids possible. However, a complete verification of Frank's hypothesis has not been possible thus far. In this dissertation, this goal has been achieved by demonstrating a direct connection between the nucleation barrier and the icosahedral SRO (ISRO) in Ti-Zr-Ni alloy liquids. Containerless environments and in-situ x-ray scattering experiments, essential for such studies, were possible because of the development of electrostatic levitation (ESL) and Beamline-ESL techniques. In addition, distorted icosahedral SRO in liquids will be shown, which has been expected but never observed. The other important topic related to the undercooled liquids is a liquid-liquid (L-L) transition. Since the undercooled liquids are essentially metastable, the L-L transition could be expected. However, L-L transitions in undercooled liquids have not been observed experimentally, although elemental liquids of P, C, and Si have shown first order transitions above the liquidus temperatures under high pressure. From specific heat measurements of a series of Ti-Zr-Ni alloys by the ESL technique, a maximum in the specific heat at constant pressure was observed in a few quasicrystal forming alloy compositions in

  15. Full-color holographic 3D printer

    NASA Astrophysics Data System (ADS)

    Takano, Masami; Shigeta, Hiroaki; Nishihara, Takashi; Yamaguchi, Masahiro; Takahashi, Susumu; Ohyama, Nagaaki; Kobayashi, Akihiko; Iwata, Fujio

    2003-05-01

    A holographic 3D printer is a system that produces a direct hologram with full-parallax information using the 3-dimensional data of a subject from a computer. In this paper, we present a proposal for the reproduction of full-color images with the holographic 3D printer. In order to realize the 3-dimensional color image, we selected the 3 laser wavelength colors of red (λ=633nm), green (λ=533nm), and blue (λ=442nm), and we built a one-step optical system using a projection system and a liquid crystal display. The 3-dimensional color image is obtained by synthesizing in a 2D array the multiple exposure with these 3 wavelengths made on each 250mm elementary hologram, and moving recording medium on a x-y stage. For the natural color reproduction in the holographic 3D printer, we take the approach of the digital processing technique based on the color management technology. The matching between the input and output colors is performed by investigating first, the relation between the gray level transmittance of the LCD and the diffraction efficiency of the hologram and second, by measuring the color displayed by the hologram to establish a correlation. In our first experimental results a non-linear functional relation for single and multiple exposure of the three components were found. These results are the first step in the realization of a natural color 3D image produced by the holographic color 3D printer.

  16. The transition from vortex liquid to vortex slush in YB2Cu3Oy superconductors

    NASA Astrophysics Data System (ADS)

    Liu, S. L.; Wu, G. J.; Tan, H. J.; Xu, X. B.; Shao, H. M.

    2006-06-01

    The phase transition from vortex liquid to vortex slush has been confirmed in resistance measurements for YBCO crystal superconductors, on the basis of scaling analysis. The temperature dependence of the resistivity under various magnetic fields collapses onto two branches in the scaling behaviour, associated with the vortex slush and the vortex liquid states. The lower branch, for temperatures below the transition point, has a negative curvature, while the upper one shows a plateau above the transition point. The critical exponents are estimated from the scaling result. The phase diagram in the H-T plane is presented and compared with previous reports.

  17. 3D Elevation Program—Virtual USA in 3D

    USGS Publications Warehouse

    Lukas, Vicki; Stoker, J.M.

    2016-01-01

    The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) uses a laser system called ‘lidar’ (light detection and ranging) to create a virtual reality map of the Nation that is very accurate. 3D maps have many uses with new uses being discovered all the time.  

  18. 3D Elevation Program—Virtual USA in 3D

    USGS Publications Warehouse

    Lukas, Vicki; Stoker, J.M.

    2016-04-14

    The U.S. Geological Survey (USGS) 3D Elevation Program (3DEP) uses a laser system called ‘lidar’ (light detection and ranging) to create a virtual reality map of the Nation that is very accurate. 3D maps have many uses with new uses being discovered all the time.  

  19. Pulsating-gliding transition in the dynamics of levitating liquid nitorgen droplets.

    SciTech Connect

    Snezhko, A.; Jacob, E. B.; Aranson, I. S.; Materials Science Division; Tel-Aviv Univ.

    2008-04-21

    Hot surfaces can cause levitation of small liquid droplets if the temperature is kept above the Leidenfrost point (220 C for water) due to the pressure formed because of rapid evaporation. Here, we demonstrate a new class of pulsating-gliding dynamic transitions in a special setting of the Leidenfrost effect at room temperatures and above a viscous fluid for droplets of liquid nitrogen. A whole range of highly dynamic patterns unfolds when droplets of liquid nitrogen are poured on the surface of another, more viscous liquid at room temperature. We also discovered that the levitating droplets induce vortex motion in the supporting viscous liquid. Depending on the viscosity of the supporting liquid, the nitrogen droplets either adopt an oscillating (pulsating) star-like shape with different azimuthal symmetries (from 2-9 petals) or glide on the surface with random trajectories. Thus, by varying the viscosity of the supporting liquid, we achieve controlled morphology and dynamics of Leidenfrost droplets.

  20. A Liquid-to-Solid Phase Transition of the ALS Protein FUS Accelerated by Disease Mutation.

    PubMed

    Patel, Avinash; Lee, Hyun O; Jawerth, Louise; Maharana, Shovamayee; Jahnel, Marcus; Hein, Marco Y; Stoynov, Stoyno; Mahamid, Julia; Saha, Shambaditya; Franzmann, Titus M; Pozniakovski, Andrej; Poser, Ina; Maghelli, Nicola; Royer, Loic A; Weigert, Martin; Myers, Eugene W; Grill, Stephan; Drechsel, David; Hyman, Anthony A; Alberti, Simon

    2015-08-27

    Many proteins contain disordered regions of low-sequence complexity, which cause aging-associated diseases because they are prone to aggregate. Here, we study FUS, a prion-like protein containing intrinsically disordered domains associated with the neurodegenerative disease ALS. We show that, in cells, FUS forms liquid compartments at sites of DNA damage and in the cytoplasm upon stress. We confirm this by reconstituting liquid FUS compartments in vitro. Using an in vitro "aging" experiment, we demonstrate that liquid droplets of FUS protein convert with time from a liquid to an aggregated state, and this conversion is accelerated by patient-derived mutations. We conclude that the physiological role of FUS requires forming dynamic liquid-like compartments. We propose that liquid-like compartments carry the trade-off between functionality and risk of aggregation and that aberrant phase transitions within liquid-like compartments lie at the heart of ALS and, presumably, other age-related diseases. PMID:26317470

  1. 3D culture for cardiac cells.

    PubMed

    Zuppinger, Christian

    2016-07-01

    This review discusses historical milestones, recent developments and challenges in the area of 3D culture models with cardiovascular cell types. Expectations in this area have been raised in recent years, but more relevant in vitro research, more accurate drug testing results, reliable disease models and insights leading to bioartificial organs are expected from the transition to 3D cell culture. However, the construction of organ-like cardiac 3D models currently remains a difficult challenge. The heart consists of highly differentiated cells in an intricate arrangement.Furthermore, electrical “wiring”, a vascular system and multiple cell types act in concert to respond to the rapidly changing demands of the body. Although cardiovascular 3D culture models have been predominantly developed for regenerative medicine in the past, their use in drug screening and for disease models has become more popular recently. Many sophisticated 3D culture models are currently being developed in this dynamic area of life science. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

  2. Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li0.2Ni0.2Mn0.6]O2.

    PubMed

    Luo, Kun; Roberts, Matthew R; Guerrini, Niccoló; Tapia-Ruiz, Nuria; Hao, Rong; Massel, Felix; Pickup, David M; Ramos, Silvia; Liu, Yi-Sheng; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

    2016-09-01

    Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn(3+/4+) in LiMn2O4, and this limits the energy storage of Li-ion batteries. Compounds such as Li[Li0.2Ni0.2Mn0.6]O2 exhibit a capacity to store charge in excess of the transition metal redox reactions. The additional capacity occurs at and above 4.5 V versus Li(+)/Li. The capacity at 4.5 V is dominated by oxidation of the O(2-) anions accounting for ∼0.43 e(-)/formula unit, with an additional 0.06 e(-)/formula unit being associated with O loss from the lattice. In contrast, the capacity above 4.5 V is mainly O loss, ∼0.08 e(-)/formula. The O redox reaction involves the formation of localized hole states on O during charge, which are located on O coordinated by (Mn(4+)/Li(+)). The results have been obtained by combining operando electrochemical mass spec on (18)O labeled Li[Li0.2Ni0.2Mn0.6]O2 with XANES, soft X-ray spectroscopy, resonant inelastic X-ray spectroscopy, and Raman spectroscopy. Finally the general features of O redox are described with discussion about the role of comparatively ionic (less covalent) 3d metal-oxygen interaction on anion redox in lithium rich cathode materials. PMID:27498756

  3. Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li0.2Ni0.2Mn0.6]O2.

    PubMed

    Luo, Kun; Roberts, Matthew R; Guerrini, Niccoló; Tapia-Ruiz, Nuria; Hao, Rong; Massel, Felix; Pickup, David M; Ramos, Silvia; Liu, Yi-Sheng; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

    2016-09-01

    Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn(3+/4+) in LiMn2O4, and this limits the energy storage of Li-ion batteries. Compounds such as Li[Li0.2Ni0.2Mn0.6]O2 exhibit a capacity to store charge in excess of the transition metal redox reactions. The additional capacity occurs at and above 4.5 V versus Li(+)/Li. The capacity at 4.5 V is dominated by oxidation of the O(2-) anions accounting for ∼0.43 e(-)/formula unit, with an additional 0.06 e(-)/formula unit being associated with O loss from the lattice. In contrast, the capacity above 4.5 V is mainly O loss, ∼0.08 e(-)/formula. The O redox reaction involves the formation of localized hole states on O during charge, which are located on O coordinated by (Mn(4+)/Li(+)). The results have been obtained by combining operando electrochemical mass spec on (18)O labeled Li[Li0.2Ni0.2Mn0.6]O2 with XANES, soft X-ray spectroscopy, resonant inelastic X-ray spectroscopy, and Raman spectroscopy. Finally the general features of O redox are described with discussion about the role of comparatively ionic (less covalent) 3d metal-oxygen interaction on anion redox in lithium rich cathode materials.

  4. Mechanochemical Synthesis of 3d Transition-Metal-1,2,4-Triazole Complexes as Precursors for Microwave-Assisted and Thermal Conversion to Coordination Polymers with a High Influence on the Dielectric Properties.

    PubMed

    Brede, Franziska A; Heine, Johanna; Sextl, Gerhard; Müller-Buschbaum, Klaus

    2016-02-18

    The complexes [MCl2 (TzH)4] (M=Mn (1), Fe (2); TzH=1,2,4-1H-triazole) and [ZnCl2 (TzH)2] (3) have been obtained by mechanochemical reactions of the corresponding divalent metal chloride and 1,2,4-1H-triazole. They were successfully used as precursors for the formation of coordination polymers either by a microwave-assisted reaction or by thermal conversion. For manganese, the conversion directly yielded 1∞ [MnCl2 TzH] (4), whereas for the iron-containing precursor, 1∞ [FeCl2 TzH] (6), was formed via the intermediate coordination polymer 1∞ [FeCl(TzH)2]Cl (5). For cobalt, the isotypic polymer 1∞ [CoCl(TzH)2]Cl (7) was obtained, but exclusively by a microwave-induced reaction directly from CoCl2 . The crystal structures were resolved from single crystals and powders. The dielectric properties were determined and revealed large differences in permittivity between the precursor complexes and the rigid chain-like coordination polymers. Whereas the monomeric complexes exhibit very different dielectric behaviour, depending on the transition metal, from "low-k" to "high-k" with the permittivity ranging from 4.3 to >100 for frequencies of up to 1000 Hz, the coordination polymers and complexes with strong intermolecular interactions are all close to "low-k" materials with very low dielectric constants up to 50 °C. Therefore, the conversion procedures can be used to deliberately influence the dielectric properties from complex to polymer and for different 3d transition-metal ions.

  5. Effect of gold subsurface layer on the surface activity and segregation in Pt/Au/Pt3M (where M = 3d transition metals) alloy catalyst from first-principles

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Eun; Lim, Dong-Hee; Jang, Jong Hyun; Kim, Hyoung Juhn; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo; Hong, Seong-Ahn; Soon, Aloysius; Ham, Hyung Chul

    2015-01-01

    The effect of a subsurface hetero layer (thin gold) on the activity and stability of Pt skin surface in Pt3M system (M = 3d transition metals) is investigated using the spin-polarized density functional theory calculation. First, we find that the heterometallic interaction between the Pt skin surface and the gold subsurface in Pt/Au/Pt3M system can significantly modify the electronic structure of the Pt skin surface. In particular, the local density of states projected onto the d states of Pt skin surface near the Fermi level is drastically decreased compared to the Pt/Pt/Pt3M case, leading to the reduction of the oxygen binding strength of the Pt skin surface. This modification is related to the increase of surface charge polarization of outmost Pt skin atoms by the electron transfer from the gold subsurface atoms. Furthermore, a subsurface gold layer is found to cast the energetic barrier to the segregation loss of metal atoms from the bulk (inside) region, which can enhance the durability of Pt3M based catalytic system in oxygen reduction condition at fuel cell devices. This study highlights that a gold subsurface hetero layer can provide an additional mean to tune the surface activity toward oxygen species and in turn the oxygen reduction reaction, where the utilization of geometric strain already reaches its practical limit.

  6. Effect of gold subsurface layer on the surface activity and segregation in Pt/Au/Pt{sub 3}M (where M = 3d transition metals) alloy catalyst from first-principles

    SciTech Connect

    Kim, Chang-Eun; Lim, Dong-Hee; Jang, Jong Hyun; Kim, Hyoung Juhn; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo; Hong, Seong-Ahn; Soon, Aloysius E-mail: hchahm@kist.re.kr; Ham, Hyung Chul E-mail: hchahm@kist.re.kr

    2015-01-21

    The effect of a subsurface hetero layer (thin gold) on the activity and stability of Pt skin surface in Pt{sub 3}M system (M = 3d transition metals) is investigated using the spin-polarized density functional theory calculation. First, we find that the heterometallic interaction between the Pt skin surface and the gold subsurface in Pt/Au/Pt{sub 3}M system can significantly modify the electronic structure of the Pt skin surface. In particular, the local density of states projected onto the d states of Pt skin surface near the Fermi level is drastically decreased compared to the Pt/Pt/Pt{sub 3}M case, leading to the reduction of the oxygen binding strength of the Pt skin surface. This modification is related to the increase of surface charge polarization of outmost Pt skin atoms by the electron transfer from the gold subsurface atoms. Furthermore, a subsurface gold layer is found to cast the energetic barrier to the segregation loss of metal atoms from the bulk (inside) region, which can enhance the durability of Pt{sub 3}M based catalytic system in oxygen reduction condition at fuel cell devices. This study highlights that a gold subsurface hetero layer can provide an additional mean to tune the surface activity toward oxygen species and in turn the oxygen reduction reaction, where the utilization of geometric strain already reaches its practical limit.

  7. Photo-stimulated phase and anchoring transitions of chiral azo-dye doped nematic liquid crystals.

    PubMed

    Kundu, Sudarshan; Kang, Shin-Woong

    2013-12-16

    We report concurring phase and anchoring transitions of chiral azo-dye doped nematic liquid crystals. The transitions are induced by photo-stimulation and stable against light and thermal treatments. Photochromic trans- to cis-isomerization of azo-dye induces an augmented dipole moment and strong dipole-dipole interaction of the cis-isomers, resulting in the formation of nano-sized dye-aggregates. Consequent phase separation of the aggregates of a chiral azo-dye induces phase transition from a chiral to nonchiral nematic phase. In addition, the deposition of dye-aggregates at the surfaces brings about anchoring transition of LC molecules. The stability and irreversibility of the transition, together with no need of pretreatments for LC alignment, provide fascinating opportunity for liquid crystal device applications.

  8. Physical model of the vapor-liquid (insulator-metal) transition in an exciton gas

    SciTech Connect

    Khomkin, A. L. Shumikhin, A. S.

    2015-04-15

    We propose a simple physical model describing the transition of an exciton gas to a conducting exciton liquid. The transition occurs due to cohesive coupling of excitons in the vicinity of the critical point, which is associated with transformation of the exciton ground state to the conduction band and the emergence of conduction electrons. We calculate the cohesion binding energy for the exciton gas and, using it, derive the equations of state, critical parameters, and binodal. The computational method is analogous to that used by us earlier [5] for predicting the vapor-liquid (insulator-metal) phase transition in atomic (hypothetical, free of molecules) hydrogen and alkali metal vapors. The similarity of the methods used for hydrogen and excitons makes it possible to clarify the physical nature of the transition in the exciton gas and to predict more confidently the existence of a new phase transition in atomic hydrogen.

  9. Simple and Versatile Turbidimetric Monitoring of Bacterial Growth in Liquid Cultures Using a Customized 3D Printed Culture Tube Holder and a Miniaturized Spectrophotometer: Application to Facultative and Strictly Anaerobic Bacteria

    PubMed Central

    Maia, Margarida R. G.; Marques, Sara; Cabrita, Ana R. J.; Wallace, R. John; Thompson, Gertrude; Fonseca, António J. M.; Oliveira, Hugo M.

    2016-01-01

    Here we introduce a novel strategy for turbidimetric monitoring of bacterial growth in liquid culture. The instrumentation comprises a light source, a customized 3D printed culture tube holder and a miniaturized spectrophotometer, connected through optical cables. Due to its small footprint and the possibility to operate with external light, bacterial growth was directly monitored from culture tubes in a simple and versatile fashion. This new portable measurement technique was used to monitor the growth of facultative (Escherichia coli ATCC/25922, and Staphylococcus aureus ATCC/29213) and strictly (Butyrivibrio fibrisolvens JW11, Butyrivibrio proteoclasticus P18, and Propionibacterium acnes DSMZ 1897) anaerobic bacteria. For E. coli and S. aureus, the growth rates calculated from normalized optical density values were compared with those ones obtained using a benchtop spectrophotometer without significant differences (P = 0.256). For the strictly anaerobic species, a high precision (relative standard deviation < 3.5%) was observed between replicates up to 48 h. Regarding its potential for customization, this manifold could accommodate further developments for customized turbidimetric monitoring, such as the use of light-emitting diodes as a light source or flow cells.

  10. Simple and Versatile Turbidimetric Monitoring of Bacterial Growth in Liquid Cultures Using a Customized 3D Printed Culture Tube Holder and a Miniaturized Spectrophotometer: Application to Facultative and Strictly Anaerobic Bacteria.

    PubMed

    Maia, Margarida R G; Marques, Sara; Cabrita, Ana R J; Wallace, R John; Thompson, Gertrude; Fonseca, António J M; Oliveira, Hugo M

    2016-01-01

    Here we introduce a novel strategy for turbidimetric monitoring of bacterial growth in liquid culture. The instrumentation comprises a light source, a customized 3D printed culture tube holder and a miniaturized spectrophotometer, connected through optical cables. Due to its small footprint and the possibility to operate with external light, bacterial growth was directly monitored from culture tubes in a simple and versatile fashion. This new portable measurement technique was used to monitor the growth of facultative (Escherichia coli ATCC/25922, and Staphylococcus aureus ATCC/29213) and strictly (Butyrivibrio fibrisolvens JW11, Butyrivibrio proteoclasticus P18, and Propionibacterium acnes DSMZ 1897) anaerobic bacteria. For E. coli and S. aureus, the growth rates calculated from normalized optical density values were compared with those ones obtained using a benchtop spectrophotometer without significant differences (P = 0.256). For the strictly anaerobic species, a high precision (relative standard deviation < 3.5%) was observed between replicates up to 48 h. Regarding its potential for customization, this manifold could accommodate further developments for customized turbidimetric monitoring, such as the use of light-emitting diodes as a light source or flow cells.

  11. Simple and Versatile Turbidimetric Monitoring of Bacterial Growth in Liquid Cultures Using a Customized 3D Printed Culture Tube Holder and a Miniaturized Spectrophotometer: Application to Facultative and Strictly Anaerobic Bacteria.

    PubMed

    Maia, Margarida R G; Marques, Sara; Cabrita, Ana R J; Wallace, R John; Thompson, Gertrude; Fonseca, António J M; Oliveira, Hugo M

    2016-01-01

    Here we introduce a novel strategy for turbidimetric monitoring of bacterial growth in liquid culture. The instrumentation comprises a light source, a customized 3D printed culture tube holder and a miniaturized spectrophotometer, connected through optical cables. Due to its small footprint and the possibility to operate with external light, bacterial growth was directly monitored from culture tubes in a simple and versatile fashion. This new portable measurement technique was used to monitor the growth of facultative (Escherichia coli ATCC/25922, and Staphylococcus aureus ATCC/29213) and strictly (Butyrivibrio fibrisolvens JW11, Butyrivibrio proteoclasticus P18, and Propionibacterium acnes DSMZ 1897) anaerobic bacteria. For E. coli and S. aureus, the growth rates calculated from normalized optical density values were compared with those ones obtained using a benchtop spectrophotometer without significant differences (P = 0.256). For the strictly anaerobic species, a high precision (relative standard deviation < 3.5%) was observed between replicates up to 48 h. Regarding its potential for customization, this manifold could accommodate further developments for customized turbidimetric monitoring, such as the use of light-emitting diodes as a light source or flow cells. PMID:27630632

  12. Simple and Versatile Turbidimetric Monitoring of Bacterial Growth in Liquid Cultures Using a Customized 3D Printed Culture Tube Holder and a Miniaturized Spectrophotometer: Application to Facultative and Strictly Anaerobic Bacteria

    PubMed Central

    Maia, Margarida R. G.; Marques, Sara; Cabrita, Ana R. J.; Wallace, R. John; Thompson, Gertrude; Fonseca, António J. M.; Oliveira, Hugo M.

    2016-01-01

    Here we introduce a novel strategy for turbidimetric monitoring of bacterial growth in liquid culture. The instrumentation comprises a light source, a customized 3D printed culture tube holder and a miniaturized spectrophotometer, connected through optical cables. Due to its small footprint and the possibility to operate with external light, bacterial growth was directly monitored from culture tubes in a simple and versatile fashion. This new portable measurement technique was used to monitor the growth of facultative (Escherichia coli ATCC/25922, and Staphylococcus aureus ATCC/29213) and strictly (Butyrivibrio fibrisolvens JW11, Butyrivibrio proteoclasticus P18, and Propionibacterium acnes DSMZ 1897) anaerobic bacteria. For E. coli and S. aureus, the growth rates calculated from normalized optical density values were compared with those ones obtained using a benchtop spectrophotometer without significant differences (P = 0.256). For the strictly anaerobic species, a high precision (relative standard deviation < 3.5%) was observed between replicates up to 48 h. Regarding its potential for customization, this manifold could accommodate further developments for customized turbidimetric monitoring, such as the use of light-emitting diodes as a light source or flow cells. PMID:27630632

  13. Monolithic 3D CMOS Using Layered Semiconductors.

    PubMed

    Sachid, Angada B; Tosun, Mahmut; Desai, Sujay B; Hsu, Ching-Yi; Lien, Der-Hsien; Madhvapathy, Surabhi R; Chen, Yu-Ze; Hettick, Mark; Kang, Jeong Seuk; Zeng, Yuping; He, Jr-Hau; Chang, Edward Yi; Chueh, Yu-Lun; Javey, Ali; Hu, Chenming

    2016-04-01

    Monolithic 3D integrated circuits using transition metal dichalcogenide materials and low-temperature processing are reported. A variety of digital and analog circuits are implemented on two sequentially integrated layers of devices. Inverter circuit operation at an ultralow supply voltage of 150 mV is achieved, paving the way to high-density, ultralow-voltage, and ultralow-power applications. PMID:26833783

  14. The Boson peak in confined water: An experimental investigation of the liquid-liquid phase transition hypothesis

    NASA Astrophysics Data System (ADS)

    Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Wang, Zhe; Chen, Sow-Hsin

    2015-10-01

    The Boson peak (BP) of deeply cooled confined water is studied by using inelastic neutron scattering (INS) in a large interval of the ( P, T) phase plane. By taking into account the different behavior of such a collective vibrational mode in both strong and fragile glasses as well as in glass-forming materials, we were able to determine the Widom line that characterizes supercooled bulk water within the frame of the liquid-liquid phase transition (LLPT) hypothesis. The peak frequency and width of the BP correlated with the water polymorphism of the LLPT scenario, allowing us to distinguish the "low-density liquid" (LDL) and "high-density liquid" (HDL) phases in deeply cooled bulk water.Moreover, the BP properties afford a further confirmation of theWidom line temperature T W as the ( P, T) locus in which the local structure of water transforms from a predominately LDL form to a predominately HDL form.

  15. Market study: 3-D eyetracker

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A market study of a proposed version of a 3-D eyetracker for initial use at NASA's Ames Research Center was made. The commercialization potential of a simplified, less expensive 3-D eyetracker was ascertained. Primary focus on present and potential users of eyetrackers, as well as present and potential manufacturers has provided an effective means of analyzing the prospects for commercialization.

  16. 3D World Building System

    ScienceCinema

    None

    2016-07-12

    This video provides an overview of the Sandia National Laboratories developed 3-D World Model Building capability that provides users with an immersive, texture rich 3-D model of their environment in minutes using a laptop and color and depth camera.

  17. 3D World Building System

    SciTech Connect

    2013-10-30

    This video provides an overview of the Sandia National Laboratories developed 3-D World Model Building capability that provides users with an immersive, texture rich 3-D model of their environment in minutes using a laptop and color and depth camera.

  18. LLNL-Earth3D

    SciTech Connect

    2013-10-01

    Earth3D is a computer code designed to allow fast calculation of seismic rays and travel times through a 3D model of the Earth. LLNL is using this for earthquake location and global tomography efforts and such codes are of great interest to the Earth Science community.

  19. [3-D ultrasound in gastroenterology].

    PubMed

    Zoller, W G; Liess, H

    1994-06-01

    Three-dimensional (3D) sonography represents a development of noninvasive diagnostic imaging by real-time two-dimensional (2D) sonography. The use of transparent rotating scans, comparable to a block of glass, generates a 3D effect. The objective of the present study was to optimate 3D presentation of abdominal findings. Additional investigations were made with a new volumetric program to determine the volume of selected findings of the liver. The results were compared with the estimated volumes of 2D sonography and 2D computer tomography (CT). For the processing of 3D images, typical parameter constellations were found for the different findings, which facilitated processing of 3D images. In more than 75% of the cases examined we found an optimal 3D presentation of sonographic findings with respect to the evaluation criteria developed by us for the 3D imaging of processed data. Great differences were found for the estimated volumes of the findings of the liver concerning the three different techniques applied. 3D ultrasound represents a valuable method to judge morphological appearance in abdominal findings. The possibility of volumetric measurements enlarges its potential diagnostic significance. Further clinical investigations are necessary to find out if definite differentiation between benign and malign findings is possible.

  20. Euro3D Science Conference

    NASA Astrophysics Data System (ADS)

    Walsh, J. R.

    2004-02-01

    The Euro3D RTN is an EU funded Research Training Network to foster the exploitation of 3D spectroscopy in Europe. 3D spectroscopy is a general term for spectroscopy of an area of the sky and derives its name from its two spatial + one spectral dimensions. There are an increasing number of instruments which use integral field devices to achieve spectroscopy of an area of the sky, either using lens arrays, optical fibres or image slicers, to pack spectra of multiple pixels on the sky (``spaxels'') onto a 2D detector. On account of the large volume of data and the special methods required to reduce and analyse 3D data, there are only a few centres of expertise and these are mostly involved with instrument developments. There is a perceived lack of expertise in 3D spectroscopy spread though the astronomical community and its use in the armoury of the observational astronomer is viewed as being highly specialised. For precisely this reason the Euro3D RTN was proposed to train young researchers in this area and develop user tools to widen the experience with this particular type of data in Europe. The Euro3D RTN is coordinated by Martin M. Roth (Astrophysikalisches Institut Potsdam) and has been running since July 2002. The first Euro3D science conference was held in Cambridge, UK from 22 to 23 May 2003. The main emphasis of the conference was, in keeping with the RTN, to expose the work of the young post-docs who are funded by the RTN. In addition the team members from the eleven European institutes involved in Euro3D also presented instrumental and observational developments. The conference was organized by Andy Bunker and held at the Institute of Astronomy. There were over thirty participants and 26 talks covered the whole range of application of 3D techniques. The science ranged from Galactic planetary nebulae and globular clusters to kinematics of nearby galaxies out to objects at high redshift. Several talks were devoted to reporting recent observations with newly

  1. 3D printing in dentistry.

    PubMed

    Dawood, A; Marti Marti, B; Sauret-Jackson, V; Darwood, A

    2015-12-01

    3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery. PMID:26657435

  2. PLOT3D user's manual

    NASA Technical Reports Server (NTRS)

    Walatka, Pamela P.; Buning, Pieter G.; Pierce, Larry; Elson, Patricia A.

    1990-01-01

    PLOT3D is a computer graphics program designed to visualize the grids and solutions of computational fluid dynamics. Seventy-four functions are available. Versions are available for many systems. PLOT3D can handle multiple grids with a million or more grid points, and can produce varieties of model renderings, such as wireframe or flat shaded. Output from PLOT3D can be used in animation programs. The first part of this manual is a tutorial that takes the reader, keystroke by keystroke, through a PLOT3D session. The second part of the manual contains reference chapters, including the helpfile, data file formats, advice on changing PLOT3D, and sample command files.

  3. 3D printing in dentistry.

    PubMed

    Dawood, A; Marti Marti, B; Sauret-Jackson, V; Darwood, A

    2015-12-01

    3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery.

  4. Glass-to-cryogenic-liquid transitions in aqueous solutions suggested by crack healing.

    PubMed

    Kim, Chae Un; Tate, Mark W; Gruner, Sol M

    2015-09-22

    Observation of theorized glass-to-liquid transitions between low-density amorphous (LDA) and high-density amorphous (HDA) water states had been stymied by rapid crystallization below the homogeneous water nucleation temperature (∼235 K at 0.1 MPa). We report optical and X-ray observations suggestive of glass-to-liquid transitions in these states. Crack healing, indicative of liquid, occurs when LDA ice transforms to cubic ice at 160 K, and when HDA ice transforms to the LDA state at temperatures as low as 120 K. X-ray diffraction study of the HDA to LDA transition clearly shows the characteristics of a first-order transition. Study of the glass-to-liquid transitions in nanoconfined aqueous solutions shows them to be independent of the solute concentrations, suggesting that they represent an intrinsic property of water. These findings support theories that LDA and HDA ice are thermodynamically distinct and that they are continuously connected to two different liquid states of water. PMID:26351671

  5. Glass-to-cryogenic-liquid transitions in aqueous solutions suggested by crack healing

    PubMed Central

    Kim, Chae Un; Tate, Mark W.; Gruner, Sol M.

    2015-01-01

    Observation of theorized glass-to-liquid transitions between low-density amorphous (LDA) and high-density amorphous (HDA) water states had been stymied by rapid crystallization below the homogeneous water nucleation temperature (∼235 K at 0.1 MPa). We report optical and X-ray observations suggestive of glass-to-liquid transitions in these states. Crack healing, indicative of liquid, occurs when LDA ice transforms to cubic ice at 160 K, and when HDA ice transforms to the LDA state at temperatures as low as 120 K. X-ray diffraction study of the HDA to LDA transition clearly shows the characteristics of a first-order transition. Study of the glass-to-liquid transitions in nanoconfined aqueous solutions shows them to be independent of the solute concentrations, suggesting that they represent an intrinsic property of water. These findings support theories that LDA and HDA ice are thermodynamically distinct and that they are continuously connected to two different liquid states of water. PMID:26351671

  6. Glass-to-cryogenic-liquid transitions in aqueous solutions suggested by crack healing.

    PubMed

    Kim, Chae Un; Tate, Mark W; Gruner, Sol M

    2015-09-22

    Observation of theorized glass-to-liquid transitions between low-density amorphous (LDA) and high-density amorphous (HDA) water states had been stymied by rapid crystallization below the homogeneous water nucleation temperature (∼235 K at 0.1 MPa). We report optical and X-ray observations suggestive of glass-to-liquid transitions in these states. Crack healing, indicative of liquid, occurs when LDA ice transforms to cubic ice at 160 K, and when HDA ice transforms to the LDA state at temperatures as low as 120 K. X-ray diffraction study of the HDA to LDA transition clearly shows the characteristics of a first-order transition. Study of the glass-to-liquid transitions in nanoconfined aqueous solutions shows them to be independent of the solute concentrations, suggesting that they represent an intrinsic property of water. These findings support theories that LDA and HDA ice are thermodynamically distinct and that they are continuously connected to two different liquid states of water.

  7. Combustion characteristics in the transition region of liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Cernansky, N. P.; Namer, I.; Tidona, R. J.

    1984-01-01

    A number of important effects were observed in the droplet size transition region in spray combustion systems. In this region, where the mechanism of flame propagation is transformed from diffusive to premixed dominated combustion, the following effects have been observed: (1) maxima in burning velocity; (2) extension of flammability limits; (3) minima in ignition energy; and (4) minima in NO(x) formation. Unfortunately, because of differences in experimental facilities and limitations in the ranges of experimental data, a unified description of these transition region effects is not available at this time. Consequently, a fundamental experimental investigation was initiated to study the effect of droplet size, size distribution, and operating parameters on these transition region phenomena in a single well controlled spray combustion facility.

  8. High-resolution calorimetric study of phase transitions in chiral smectic-C liquid crystalline phases.

    PubMed

    Sasaki, Y; Le, K V; Aya, S; Isobe, M; Yao, H; Huang, C C; Takezoe, H; Ema, K

    2012-12-01

    We carried out an improved characterization of phase transitions among chiral smectic-C subphases observed for various antiferroelectric liquid crystals by precise heat capacity measurements. It was found that the phase transitions are intrinsically first order exhibiting a remarkable heat anomaly which involves little pretransitional thermal fluctuation and a finite thermal hysteresis. On the other hand, we also noticed that the critical point of the smectic-C(α)(*)-smectic-C* transition is induced by the destabilization of the smectic-C(α)(*) phase which couples with the fluctuation associated with the smectic-A-smectic-C(α)(*) phase transition.

  9. Liquid-to-glass transition of tetrahydrofuran and 2-methyltetrahydrofuran

    NASA Astrophysics Data System (ADS)

    Tan, Rong-Ri; Shen, Xin; Hu, Lin; Zhang, Feng-Shou

    2012-08-01

    Both tetrahydrofuran (THF) and 2-methyltetrahydrofuran (MTHF) are studied systematically at desired temperatures using molecular dynamics simulations. The results show that the calculated densities are well consistent with experiment. Their glass transition temperatures are obtained: 115 K ~ 130 K for THF and 131 K ~ 142 K for MTHF. The calculated results from the dipolar orientational time correlation functions indicate that the “long time" behavior is often associated with a glass transition. From the radial and spatial distributions, we also find that the methyl has a direct impact on the structural symmetry of molecules, which leads to the differences of physical properties between THF and MTHF.

  10. Transitional liquid crystalline phases between the hexagonal and lamellar phases in ternary cesium N-tetradecanoate-water-additive mixtures

    SciTech Connect

    Blackburn, J.C.; Kilpatrick, P.K. )

    1993-04-01

    The effects of added salt (CsOH, CsCl), long-chain carboxylic acid, and long-chain alcohol on the lyotropic liquid crystalline phase behavior in the cesium n-tetradecanoate (CsTD)-water system is reported. The transitional region between the hexagonal (H) and lamellar (L) phases was the compositional range of focus. Three transitional phases were observed: (i) the ribbon (R) phase, a biaxial phase consisting of cylinders of ellipsoidal cross section; (ii) the viscous isotropic (VI) phase, an isotropic phase thought to consist of interconnected rods on an Ia3d lattice; and (iii) the intermediate (Int) phase, a uniaxial anisotropic phase thought to consist of interconnected rods on a planar lattice. The effect of the additives was to decrease the interfacial curvature of the surfactant head group layer by varying head group repulsion and by varying the surfactant tail volume relative to the surfactant head group area. These changes resulted in formation of transitional phases seeming to possess curvature between that of the cylindrical H phase and the planar L phase. The ionic repulsion between carboxylate head groups was reduced by the addition of CsOH or CsCl, and resulted in destabilization of the VI phase and the formation of the anisotropic Int phase. With the addition of cosurfactants, n-tetradecanoic acid (TDA) and 1-tetradecanol (TDOH), no Int phase was observed. With 7 wt% added TDA the R phase was stabilized up to temperatures of 336 K, above the 330 K temperature limit in the binary CsTD-D[sub 2]O system. In all four systems, sufficient additive (5-10 wt%) resulted in a transition to the L phase, which was stable over a large portion of the compositional range. In order of apparently decreasing mean curvature, the phase sequence is: hexagonal, ribbon, viscous isotropic, intermediate, and lamellar.

  11. PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITHOUT TURB3D)

    NASA Technical Reports Server (NTRS)

    Buning, P.

    1994-01-01

    PLOT3D is an interactive graphics program designed to help scientists visualize computational fluid dynamics (CFD) grids and solutions. Today, supercomputers and CFD algorithms can provide scientists with simulations of such highly complex phenomena that obtaining an understanding of the simulations has become a major problem. Tools which help the scientist visualize the simulations can be of tremendous aid. PLOT3D/AMES offers more functions and features, and has been adapted for more types of computers than any other CFD graphics program. Version 3.6b+ is supported for five computers and graphic libraries. Using PLOT3D, CFD physicists can view their computational models from any angle, observing the physics of problems and the quality of solutions. As an aid in designing aircraft, for example, PLOT3D's interactive computer graphics can show vortices, temperature, reverse flow, pressure, and dozens of other characteristics of air flow during flight. As critical areas become obvious, they can easily be studied more closely using a finer grid. PLOT3D is part of a computational fluid dynamics software cycle. First, a program such as 3DGRAPE (ARC-12620) helps the scientist generate computational grids to model an object and its surrounding space. Once the grids have been designed and parameters such as the angle of attack, Mach number, and Reynolds number have been specified, a "flow-solver" program such as INS3D (ARC-11794 or COS-10019) solves the system of equations governing fluid flow, usually on a supercomputer. Grids sometimes have as many as two million points, and the "flow-solver" produces a solution file which contains density, x- y- and z-momentum, and stagnation energy for each grid point. With such a solution file and a grid file containing up to 50 grids as input, PLOT3D can calculate and graphically display any one of 74 functions, including shock waves, surface pressure, velocity vectors, and particle traces. PLOT3D's 74 functions are organized into

  12. PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITH TURB3D)

    NASA Technical Reports Server (NTRS)

    Buning, P.

    1994-01-01

    PLOT3D is an interactive graphics program designed to help scientists visualize computational fluid dynamics (CFD) grids and solutions. Today, supercomputers and CFD algorithms can provide scientists with simulations of such highly complex phenomena that obtaining an understanding of the simulations has become a major problem. Tools which help the scientist visualize the simulations can be of tremendous aid. PLOT3D/AMES offers more functions and features, and has been adapted for more types of computers than any other CFD graphics program. Version 3.6b+ is supported for five computers and graphic libraries. Using PLOT3D, CFD physicists can view their computational models from any angle, observing the physics of problems and the quality of solutions. As an aid in designing aircraft, for example, PLOT3D's interactive computer graphics can show vortices, temperature, reverse flow, pressure, and dozens of other characteristics of air flow during flight. As critical areas become obvious, they can easily be studied more closely using a finer grid. PLOT3D is part of a computational fluid dynamics software cycle. First, a program such as 3DGRAPE (ARC-12620) helps the scientist generate computational grids to model an object and its surrounding space. Once the grids have been designed and parameters such as the angle of attack, Mach number, and Reynolds number have been specified, a "flow-solver" program such as INS3D (ARC-11794 or COS-10019) solves the system of equations governing fluid flow, usually on a supercomputer. Grids sometimes have as many as two million points, and the "flow-solver" produces a solution file which contains density, x- y- and z-momentum, and stagnation energy for each grid point. With such a solution file and a grid file containing up to 50 grids as input, PLOT3D can calculate and graphically display any one of 74 functions, including shock waves, surface pressure, velocity vectors, and particle traces. PLOT3D's 74 functions are organized into

  13. Unassisted 3D camera calibration

    NASA Astrophysics Data System (ADS)

    Atanassov, Kalin; Ramachandra, Vikas; Nash, James; Goma, Sergio R.

    2012-03-01

    With the rapid growth of 3D technology, 3D image capture has become a critical part of the 3D feature set on mobile phones. 3D image quality is affected by the scene geometry as well as on-the-device processing. An automatic 3D system usually assumes known camera poses accomplished by factory calibration using a special chart. In real life settings, pose parameters estimated by factory calibration can be negatively impacted by movements of the lens barrel due to shaking, focusing, or camera drop. If any of these factors displaces the optical axes of either or both cameras, vertical disparity might exceed the maximum tolerable margin and the 3D user may experience eye strain or headaches. To make 3D capture more practical, one needs to consider unassisted (on arbitrary scenes) calibration. In this paper, we propose an algorithm that relies on detection and matching of keypoints between left and right images. Frames containing erroneous matches, along with frames with insufficiently rich keypoint constellations, are detected and discarded. Roll, pitch yaw , and scale differences between left and right frames are then estimated. The algorithm performance is evaluated in terms of the remaining vertical disparity as compared to the maximum tolerable vertical disparity.

  14. Solidification mechanism transition of liquid Co-Cu-Ni ternary alloy

    NASA Astrophysics Data System (ADS)

    Zang, D. Y.; Wang, H. P.; Dai, F. P.; Langevin, D.; Wei, B.

    2011-01-01

    We report a solidification mechanism transition of liquid ternary Co45Cu45Ni10 alloy when it solidifies at a critical undercooling of about 344 K. When undercooling at Δ T<344 K, the solidification process is characterized by primary S (Co) dendritic growth and a subsequent peritectic transition. The dendritic growth velocity of S (Co) dendrite increases with the rise of undercooling. However, once Δ T>344 K, the solidification velocity decreases with the increase of undercooling. In this case, liquid/liquid phase separation takes place prior to solidification. The minor L2 (Cu) droplets hinder the motion of the solidification front, and a monotectic transition may occur in the major L1 phase. These facts caused by metastable phase separation are responsible for the slow growth at high undercoolings.

  15. Confinement transition to density wave order in metallic doped spin liquids

    NASA Astrophysics Data System (ADS)

    Patel, Aavishkar A.; Chowdhury, Debanjan; Allais, Andrea; Sachdev, Subir

    2016-04-01

    Insulating quantum spin liquids can undergo a confinement transition to a valence bond solid via the condensation of topological excitations of the associated gauge theory. We extend the theory of such transitions to fractionalized Fermi liquids (FL*): These are metallic doped spin liquids in which the Fermi surfaces only have gauge neutral quasiparticles. Using insights from a duality transform on a doped quantum dimer model for the U(1)-FL* state, we show that projective symmetry group of the theory of the topological excitations remains unmodified, but the Fermi surfaces can lead to additional frustrating interactions. We propose a theory for the confinement transition of Z2-FL* states via the condensation of visons. A variety of confining, incommensurate density wave states are possible, including some that are similar to the incommensurate d -form factor density wave order observed in several recent experiments on the cuprate superconductors.

  16. Nonlinear vibrational spectroscopy of water structures utilizing laser-induced phase transition phenomena in liquid water

    NASA Astrophysics Data System (ADS)

    Yui, Hiroharu; Sawada, Tsuguo

    2003-01-01

    Anomalous enhancement of the stimulated Raman scattering (SRS) of water molecules in the OH stretching vibrational region is observed when a laser-induced phase transition from liquid to plasma takes place in liquid water. The SRS is emitted before the phase transition and has a duration of several tens of picoseconds full width at half maximum. From the spectroscopic analysis of the SRS, it is suggested that the excess electrons, which are generated in a few picoseconds before the phase transition, play an important role in the transient SRS enhancement through the change of the nonlinear polarizability induced around the electrons in liquid water. Several applications of the enhanced vibrational spectra in the OH stretching vibrational region to the spectroscopic analyses of local water structures in various environments are also described.

  17. Entropy, local order, and the freezing transition in Morse liquids.

    PubMed

    Chakraborty, Somendra Nath; Chakravarty, Charusita

    2007-07-01

    The behavior of the excess entropy of Morse and Lennard-Jones liquids is examined as a function of temperature, density, and the structural order metrics. The dominant pair correlation contribution to the excess entropy is estimated from simulation data for the radial distribution function. The pair correlation entropy (S2) of these simple liquids is shown to have a threshold value of (-3.5+/-0.3)kB at freezing. Moreover, S2 shows a T(-2/5) temperature dependence. The temperature dependence of the pair correlation entropy as well as the behavior at freezing closely correspond to earlier predictions, based on density functional theory, for the excess entropy of repulsive inverse power and Yukawa potentials [Rosenfeld, Phys. Rev. E 62, 7524 (2000)]. The correlation between the pair correlation entropy and the local translational and bond orientational order parameters is examined, and, in the case of the bond orientational order, is shown to be sensitive to the definition of the nearest neighbors. The order map between translational and bond orientational order for Morse liquids and solids shows a very similar pattern to that seen in Lennard-Jones-type systems. PMID:17677432

  18. The New Realm of 3-D Vision

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Dimension Technologies Inc., developed a line of 2-D/3-D Liquid Crystal Display (LCD) screens, including a 15-inch model priced at consumer levels. DTI's family of flat panel LCD displays, called the Virtual Window(TM), provide real-time 3-D images without the use of glasses, head trackers, helmets, or other viewing aids. Most of the company initial 3-D display research was funded through NASA's Small Business Innovation Research (SBIR) program. The images on DTI's displays appear to leap off the screen and hang in space. The display accepts input from computers or stereo video sources, and can be switched from 3-D to full-resolution 2-D viewing with the push of a button. The Virtual Window displays have applications in data visualization, medicine, architecture, business, real estate, entertainment, and other research, design, military, and consumer applications. Displays are currently used for computer games, protein analysis, and surgical imaging. The technology greatly benefits the medical field, as surgical simulators are helping to increase the skills of surgical residents. Virtual Window(TM) is a trademark of Dimension Technologies Inc.

  19. Polymerization transition in liquid AsS under pressure: An ab initio molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Ohmura, Satoshi; Shimojo, Fuyuki

    2011-12-01

    We study the pressure dependence of the structural and electronic properties of liquid AsS by ab initio molecular dynamics simulations. We confirm that liquid AsS consists of As4S4 molecules at ambient pressure, as in the crystalline state. With increasing pressure, a structural transition from molecular to polymeric liquid occurs near 2 GPa, which is eventually followed by metallization. The pressure dependence of the density and diffusion coefficients changes qualitatively with this transition. We find that, during metallization in the polymeric phase at higher pressures, the remnants of covalent interactions between atoms play an important role in the dynamics, i.e., the As-S bond length becomes longer with increasing pressure and the diffusion coefficients have a local maximum near 5 GPa. When the pressure approaches about 15 GPa, the covalent nature of the liquid becomes quite weak. These results explain recent experiments on the pressure dependence of the viscosity.

  20. Combustion characteristics in the transition region of liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Cernansky, N. P.; Namer, I.; Tidona, R. J.; Sarv, H.

    1984-01-01

    A monodisperse aerosol generator was modified to study ignition requirements, flammability limits, and flame speeds in the transition region. An ignition system was developed and tested. The fabrication of an optical drop sizing system is nearly complete. Preliminary measurements of droplet size effects on the minimum ignition energy for n-heptane sprays performed. Parameteric studies of droplet size effects on minimum ignition energies of various fuels including alcohols are in progress.

  1. Effects of confinement on the glass transition temperature of molecular liquids

    SciTech Connect

    Zhang, J.; Liu, G.; Jonas, J.

    1992-04-16

    Differential scanning calorimetry was used to analyze the effects of confinement on the glass transition of temperature, T{sub g}, of several molecular liquids in porous silica glasses. For all the liquids, confinement lowers the observed T{sub g}. A linear relationship between the inverse of the silica glass pore radius and T{sub g} was also observed. The relative temperature depression due to confinement was less than the freezing point depression. 40 refs., 1 fig., 1 tab.

  2. Mechanism of phase transition, from vapor to solid: Transient liquid phase is between the two

    NASA Astrophysics Data System (ADS)

    Mahapatra, A. K.; Wang, Junyong; Zhang, Hongwei; Han, Min

    2016-08-01

    The mechanism of phase transition, from vapor to solid, is studied by producing non-stoichiometric ZnO and CdS nanoclusters (NCs) by low-energy cluster beam deposition technique, and examining their morphological and compositional evolution over a long span of time. It is concluded that the transition of vapor to solid goes through a transient liquid phase: coagulation of a large number of atomic clusters first forms liquid NCs which then solidify. The nature of the material and the experimental conditions determine crystallinity and shape of the NCs during the solidification process.

  3. Inverse correlation between cohesive energy and thermal expansion coefficient in liquid transition metal alloys.

    PubMed

    Gangopadhyay, A K; Bendert, J C; Mauro, N A; Kelton, K F

    2012-09-19

    The volume expansion coefficients (α) of twenty-five glass-forming transition metal alloy liquids, measured using the electrostatic levitation technique, are reported. An inverse correlation between α and the cohesive energy is found. The predicted values of α from this relationship agree reasonably well with the published data for thirty other transition metal and alloy liquids; some disagreement was found for a few alloys containing significant amounts of group III and IV elements. A theoretical argument for this empirical relationship is presented. PMID:22842287

  4. Field-induced phase transitions in chiral smectic liquid crystals studied by the constant current method

    NASA Astrophysics Data System (ADS)

    H, Dhaouadi; R, Zgueb; O, Riahi; F, Trabelsi; T, Othman

    2016-05-01

    In ferroelectric liquid crystals, phase transitions can be induced by an electric field. The current constant method allows these transition to be quickly localized and thus the (E,T) phase diagram of the studied product can be obtained. In this work, we make a slight modification to the measurement principles based on this method. This modification allows the characteristic parameters of ferroelectric liquid crystal to be quantitatively measured. The use of a current square signal highlights a phenomenon of ferroelectric hysteresis with remnant polarization at null field, which points out an effect of memory in this compound.

  5. Amphiphilic Liquid Crystal Exhibiting the Smectic A to Smectic C Phase Transition without Layer Contraction

    NASA Astrophysics Data System (ADS)

    Ishida, Norihiro; Takanishi, Yoichi; Yamamoto, Jun; Yoshizawa, Atsushi

    2011-02-01

    We prepared an amphiphilic liquid crystal composed of a semiperfluorinated alkyl chain and a 2,3-difluoro-1,4-diphenylbenzene core, and investigated its physical properties using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction analysis. The compound was found to exhibit the smectic A to smectic C phase transition without layer contraction. The compound doped with a ferroelectric liquid crystal exhibited a fast electro-optical switching with a response time of 10 µs in the chiral smectic A phase in spite of the absence of a chiral smectic C phase. The phase transition behavior is interpreted using the de Vries cone model.

  6. Micellar-shape anisometry near isotropic-liquid-crystal phase transitions

    NASA Astrophysics Data System (ADS)

    Itri, R.; Amaral, L. Q.

    1993-04-01

    Micellar phases of the sodium dodecyl (lauryl) sulfate (SLS)-water-decanol system have been studied by x-ray scattering in the isotropic (I) phase, with emphasis on the I-->hexagonal (Hα) and I-->nematic-cylindrical (Nc) lyotropic liquid-crystal phase transitions. Analysis of the scattering curves is made through modeling of the product P(q)S(q), where P(q) is the micellar form factor and S(q) is the intermicellar interference function, calculated from screened Coulombic repulsion in a mean spherical approximation. Results show that micelles grow more by decanol addition near the I-->Nc transition (anisometry ν~=3) than by increased amphiphile concentration in the binary system near the I-->Hα phase transition (ν~=2.4). These results compare well with recent theories for isotropic-liquid-crystal phase transitions.

  7. Anchoring transitions of transversely polar liquid-crystal molecules on perfluoropolymer surfaces.

    PubMed

    Dhara, Surajit; Kim, Jin Ki; Jeong, Soon Moon; Kogo, Reiri; Araoka, Fumito; Ishikawa, Ken; Takezoe, Hideo

    2009-06-01

    We report a strong discontinuous orientational transition (anchoring transition) of liquid-crystal molecules with a large transverse dipole moment. A perfluoropolymer was used as an alignment layer and the transition was observed from planar to homeotropic with decreasing temperature in the nematic phase. Conversely a gradual variation in tilt angle from homeotropic to conical was observed in a liquid crystal with a comparatively smaller transverse dipole moment on the same alignment layer. The experimental results clearly demonstrate the competition between a short-range dipolar force and long-range van der Waals force at the interfacial region. Using discontinuous anchoring transition in the sample, we demonstrate a possible bistable device for memory and light-driven display. PMID:19658464

  8. Direct observation of an abrupt insulator-to-metal transition in dense liquid deuterium

    NASA Astrophysics Data System (ADS)

    Knudson, M. D.; Desjarlais, M. P.; Becker, A.; Lemke, R. W.; Cochrane, K. R.; Savage, M. E.; Bliss, D. E.; Mattsson, T. R.; Redmer, R.

    2015-06-01

    Eighty years ago, it was proposed that solid hydrogen would become metallic at sufficiently high density. Despite numerous investigations, this transition has not yet been experimentally observed. More recently, there has been much interest in the analog of this predicted metallic transition in the dense liquid, due to its relevance to planetary science. Here, we show direct observation of an abrupt insulator-to-metal transition in dense liquid deuterium. Experimental determination of the location of this transition provides a much-needed benchmark for theory and may constrain the region of hydrogen-helium immiscibility and the boundary-layer pressure in standard models of the internal structure of gas-giant planets.

  9. Quantum spin liquids and the metal-insulator transition in doped semiconductors.

    PubMed

    Potter, Andrew C; Barkeshli, Maissam; McGreevy, John; Senthil, T

    2012-08-17

    We describe a new possible route to the metal-insulator transition in doped semiconductors such as Si:P or Si:B. We explore the possibility that the loss of metallic transport occurs through Mott localization of electrons into a quantum spin liquid state with diffusive charge neutral "spinon" excitations. Such a quantum spin liquid state can appear as an intermediate phase between the metal and the Anderson-Mott insulator. An immediate testable consequence is the presence of metallic thermal conductivity at low temperature in the electrical insulator near the metal-insulator transition. Further, we show that though the transition is second order, the zero temperature residual electrical conductivity will jump as the transition is approached from the metallic side. However, the electrical conductivity will have a nonmonotonic temperature dependence that may complicate the extrapolation to zero temperature. Signatures in other experiments and some comparisons with existing data are made. PMID:23006401

  10. Spatially resolved 3D noise

    NASA Astrophysics Data System (ADS)

    Haefner, David P.; Preece, Bradley L.; Doe, Joshua M.; Burks, Stephen D.

    2016-05-01

    When evaluated with a spatially uniform irradiance, an imaging sensor exhibits both spatial and temporal variations, which can be described as a three-dimensional (3D) random process considered as noise. In the 1990s, NVESD engineers developed an approximation to the 3D power spectral density (PSD) for noise in imaging systems known as 3D noise. In this correspondence, we describe how the confidence intervals for the 3D noise measurement allows for determination of the sampling necessary to reach a desired precision. We then apply that knowledge to create a smaller cube that can be evaluated spatially across the 2D image giving the noise as a function of position. The method presented here allows for both defective pixel identification and implements the finite sampling correction matrix. In support of the reproducible research effort, the Matlab functions associated with this work can be found on the Mathworks file exchange [1].

  11. Autofocus for 3D imaging

    NASA Astrophysics Data System (ADS)

    Lee-Elkin, Forest

    2008-04-01

    Three dimensional (3D) autofocus remains a significant challenge for the development of practical 3D multipass radar imaging. The current 2D radar autofocus methods are not readily extendable across sensor passes. We propose a general framework that allows a class of data adaptive solutions for 3D auto-focus across passes with minimal constraints on the scene contents. The key enabling assumption is that portions of the scene are sparse in elevation which reduces the number of free variables and results in a system that is simultaneously solved for scatterer heights and autofocus parameters. The proposed method extends 2-pass interferometric synthetic aperture radar (IFSAR) methods to an arbitrary number of passes allowing the consideration of scattering from multiple height locations. A specific case from the proposed autofocus framework is solved and demonstrates autofocus and coherent multipass 3D estimation across the 8 passes of the "Gotcha Volumetric SAR Data Set" X-Band radar data.

  12. Accepting the T3D

    SciTech Connect

    Rich, D.O.; Pope, S.C.; DeLapp, J.G.

    1994-10-01

    In April, a 128 PE Cray T3D was installed at Los Alamos National Laboratory`s Advanced Computing Laboratory as part of the DOE`s High-Performance Parallel Processor Program (H4P). In conjunction with CRI, the authors implemented a 30 day acceptance test. The test was constructed in part to help them understand the strengths and weaknesses of the T3D. In this paper, they briefly describe the H4P and its goals. They discuss the design and implementation of the T3D acceptance test and detail issues that arose during the test. They conclude with a set of system requirements that must be addressed as the T3D system evolves.

  13. Successive disorder to disorder phase transitions in ionic liquid [HMIM][BF4] under high pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Xiang; Yuan, Chaosheng; Li, Haining; Zhu, Pinwen; Su, Lei; Yang, Kun; Wu, Jie; Yang, Guoqiang; Liu, Jing

    2016-02-01

    In situ high-pressure Raman spectroscopy and synchrotron X-ray diffraction have been employed to investigate the phase behavior of ionic liquid, 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM][BF4]) under high pressure up to 20 GPa at room temperature. With increasing pressure, some characteristic bands of [HMIM][BF4] disappear, and some characteristic bands of [HMIM][BF4] display non-monotonic pressure-induced frequency shift and non-monotonic variation of full width at half-maximum. Two successive phase transitions at ˜1.7 GPa and 7.3 GPa have been corroborated by the results above. The glass transition pressure (Pg) of [HMIM][BF4] at ˜7.3 GPa has been obtained by ruby R1 line broadening measurements and analysis of synchrotron X-ray diffraction patterns, and its glass transition mechanism is also analyzed in detail. These facts are suggestive of two successive disorder to disorder phase transitions induced by compression, that is, [HMIM][BF4] serves as a superpressurized glass under the pressure above 7.3 GPa, which is similar to the glassy state at low temperature, and a compression-induced liquid to liquid phase transition in [HMIM][BF4] occurs at ˜1.7 GPa. Besides, the conformational equilibrium of the GAAA conformer and AAAA conformer was converted easily in liquid [HMIM][BF4], while it was difficult to be influenced in glassy state.

  14. Combinatorial 3D Mechanical Metamaterials

    NASA Astrophysics Data System (ADS)

    Coulais, Corentin; Teomy, Eial; de Reus, Koen; Shokef, Yair; van Hecke, Martin

    2015-03-01

    We present a class of elastic structures which exhibit 3D-folding motion. Our structures consist of cubic lattices of anisotropic unit cells that can be tiled in a complex combinatorial fashion. We design and 3d-print this complex ordered mechanism, in which we combine elastic hinges and defects to tailor the mechanics of the material. Finally, we use this large design space to encode smart functionalities such as surface patterning and multistability.

  15. Evidence of a liquid–liquid phase transition in hot dense hydrogen

    PubMed Central

    Dzyabura, Vasily; Zaghoo, Mohamed; Silvera, Isaac F.

    2013-01-01

    We use pulsed-laser heating of hydrogen at static pressures in the megabar pressure region to search for the plasma phase transition to liquid atomic metallic hydrogen. We heat our samples substantially above the melting line and observe a plateau in a temperature vs. laser power curve that otherwise increases with power. This anomaly in the heating curve appears correlated with theoretical predictions for the plasma phase transition. PMID:23630287

  16. Liquid-crystal solid interface structure at the antiferroelectric-ferroelectric phase transition

    NASA Astrophysics Data System (ADS)

    Coleman, D.; Bardon, S.; Radzihovsky, L.; Danner, G.; Clark, N. A.

    2002-12-01

    Total internal reflection is used to probe the molecular organization at the surface of a tilted chiral smectic liquid crystal at temperatures in the vicinity of the bulk antiferroelectric-ferroelectric phase transition. Data are interpreted using an exact analytical solution of a real model for ferroelectric order at the surface. In the mixture T3, ferroelectric surface order is expelled with the bulk ferroelectric-antiferroelectric transition. The conditions for ferroelectric order at the surface of an antiferroelectric bulk are presented.

  17. Surface alignment and anchoring transitions in nematic lyotropic chromonic liquid crystal.

    PubMed

    Nazarenko, V G; Boiko, O P; Park, H-S; Brodyn, O M; Omelchenko, M M; Tortora, L; Nastishin, Yu A; Lavrentovich, O D

    2010-07-01

    The surface alignment of lyotropic chromonic liquid crystals can not only be planar (tangential) but also homeotropic, with self-assembled aggregates perpendicular to the substrate, as demonstrated by mapping optical retardation and by three-dimensional imaging of the director field. With time, the homeotropic nematic undergoes a transition into a tangential state. The anchoring transition is discontinuous and can be described by a double-well anchoring potential with two minima corresponding to tangential and homeotropic orientation. PMID:20867479

  18. Origin of the {lambda} Transition in Liquid Sulfur

    SciTech Connect

    Scopigno, T.; Yannopoulos, S. N.; Andrikopoulos, K. S.; Fioretto, D.; Ruocco, G.

    2007-07-13

    Developing a novel experimental technique, we applied photon correlation spectroscopy using infrared radiation in liquid sulfur around T{sub {lambda}}, i.e., in the temperature range where an abrupt increase in viscosity by 4 orders of magnitude is observed upon heating within few degrees. This allowed us--overcoming photoinduced and absorption effects at visible wavelengths--to reveal a chain relaxation process with characteristic time in the millisecond range. These results do rehabilitate the validity of the Maxwell relation in sulfur from an apparent failure, allowing rationalizing of the mechanical and thermodynamic behavior of this system within a viscoelastic scenario.

  19. The Galicia 3D experiment: an Introduction.

    NASA Astrophysics Data System (ADS)

    Reston, Timothy; Martinez Loriente, Sara; Holroyd, Luke; Merry, Tobias; Sawyer, Dale; Morgan, Julia; Jordan, Brian; Tesi Sanjurjo, Mari; Alexanian, Ara; Shillington, Donna; Gibson, James; Minshull, Tim; Karplus, Marianne; Bayracki, Gaye; Davy, Richard; Klaeschen, Dirk; Papenberg, Cord; Ranero, Cesar; Perez-Gussinye, Marta; Martinez, Miguel

    2014-05-01

    In June and July 2013, scientists from 8 institutions took part in the Galicia 3D seismic experiment, the first ever crustal -scale academic 3D MCS survey over a rifted margin. The aim was to determine the 3D structure of a critical portion of the west Galicia rifted margin. At this margin, well-defined tilted fault blocks, bound by west-dipping faults and capped by synrift sediments are underlain by a bright reflection, undulating on time sections, termed the S reflector and thought to represent a major detachment fault of some kind. Moving west, the crust thins to zero thickness and mantle is unroofed, as evidence by the "Peridotite Ridge" first reported at this margin, but since observed at many other magma-poor margins. By imaging such a margin in detail, the experiment aimed to resolve the processes controlling crustal thinning and mantle unroofing at a type example magma poor margin. The experiment set out to collect several key datasets: a 3D seismic reflection volume measuring ~20x64km and extending down to ~14s TWT, a 3D ocean bottom seismometer dataset suitable for full wavefield inversion (the recording of the complete 3D seismic shots by 70 ocean bottom instruments), the "mirror imaging" of the crust using the same grid of OBS, a single 2D combined reflection/refraction profile extending to the west to determine the transition from unroofed mantle to true oceanic crust, and the seismic imaging of the water column, calibrated by regular deployment of XBTs to measure the temperature structure of the water column. We collected 1280 km2 of seismic reflection data, consisting of 136533 shots recorded on 1920 channels, producing 260 million seismic traces, each ~ 14s long. This adds up to ~ 8 terabytes of data, representing, we believe, the largest ever academic 3D MCS survey in terms of both the area covered and the volume of data. The OBS deployment was the largest ever within an academic 3D survey.

  20. Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

    DOE PAGES

    Wang, Zhe; Kolesnikov, Alexander I.; Ito, Kanae; Podlesnyak, Andrey; Chen, Sow-Hsin

    2015-12-03

    We studied the boson peak in deeply cooled water confined in nanopores in order to examine the liquid-liquid transition (LLT). Below ~180 K, the boson peaks at pressures P higher than ~3.5 kbar are evidently distinct from those at low pressures by higher mean frequencies and lower heights. Moreover, the higher-P boson peaks can be rescaled to a master curve while the lower-P boson peaks can be rescaled to a different one. Moreover, these phenomena agree with the existence of two liquid phases with different densities and local structures and the associated LLT in the measured (P, T) region. Additionally,more » the P dependence of the librational band also agrees with the above conclusion.« less

  1. Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

    SciTech Connect

    Wang, Zhe; Kolesnikov, Alexander I.; Ito, Kanae; Podlesnyak, Andrey; Chen, Sow-Hsin

    2015-12-03

    We studied the boson peak in deeply cooled water confined in nanopores in order to examine the liquid-liquid transition (LLT). Below ~180 K, the boson peaks at pressures P higher than ~3.5 kbar are evidently distinct from those at low pressures by higher mean frequencies and lower heights. Moreover, the higher-P boson peaks can be rescaled to a master curve while the lower-P boson peaks can be rescaled to a different one. Moreover, these phenomena agree with the existence of two liquid phases with different densities and local structures and the associated LLT in the measured (P, T) region. Additionally, the P dependence of the librational band also agrees with the above conclusion.

  2. Transition in fluctuation behaviour of normal liquids under high pressures

    NASA Astrophysics Data System (ADS)

    Postnikov, Eugene B.; Chora&zcedildot; ewski, Mirosław

    2016-05-01

    We explore the behaviour of the inverse reduced density fluctuations and the isobaric expansion coefficient using α , ω-dibromoalkanes as an example. Two different states are revealed far from the critical point: the region of exponentially decaying fluctuations near the coexistence curve and the state with longer correlations under sufficiently high pressures. The crossing of the isotherms of the isobaric expansion coefficient occurs within the PVT range of the mentioned transition. We discuss the interplay of this crossing with the changes in molecular packing structure connected with the analysed function of the density, which represents inverse reduced volume fluctuations.

  3. Paraelectric-antiferroelectric phase transition in achiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Pociecha, Damian; Gorecka, Ewa; Čepič, Mojca; Vaupotič, Nataša; Gomola, Kinga; Mieczkowski, Jozef

    2005-12-01

    Critical freezing of molecular rotation in an achiral smectic phase, which leads to polar ordering through the second order paraelectric-antiferroelectric (Sm-A→Sm-APA) phase transition is studied theoretically and experimentally. Strong softening of the polar mode in the Sm-A phase and highly intensive dielectric mode in the Sm-APA phase are observed due to weak antiferroelectric interactions in the system. In the Sm-APA phase the dielectric response behaves critically upon biasing by a dc electric field. Such a behavior is found general for the antiferroelectric smectic phase with significant quadrupolar interlayer coupling.

  4. Molecular-scale remnants of the liquid-gas transition in supercritical polar fluids.

    PubMed

    Sokhan, V P; Jones, A; Cipcigan, F S; Crain, J; Martyna, G J

    2015-09-11

    An electronically coarse-grained model for water reveals a persistent vestige of the liquid-gas transition deep into the supercritical region. A crossover in the density dependence of the molecular dipole arises from the onset of nonpercolating hydrogen bonds. The crossover points coincide with the Widom line in the scaling region but extend farther, tracking the heat capacity maxima, offering evidence for liquidlike and gaslike state points in a "one-phase" fluid. The effect is present even in dipole-limit models, suggesting that it is common for all molecular liquids exhibiting dipole enhancement in the liquid phase.

  5. Acoustic and thermal anomalies in a liquid-glass transition of racemic S(+)-R(-) ketoprofen

    NASA Astrophysics Data System (ADS)

    Shibata, Tomohiko; Takayama, Haruki; Kim, Tae Hyun; Kojima, Seiji

    2014-01-01

    Acoustic and thermal properties of pharmaceutical racemic S(+)-R(-) ketoprofen were investigated in wide temperature range including glassy, supercooled liquid and liquid states by Brillouin scattering and temperature modulated DSC. Sound velocity and acoustic attenuation exhibited clear changes at 265 K indicating a liquid-glass transition and showed the typical structural relaxation above Tg. The high value of the fragility index m = 71 was determined by the dispersion of the complex heat capacity. New relaxation map was suggested in combination with previous study of dielectric measurement.

  6. Density Affects the Nature of the Hexatic-Liquid Transition in Two-Dimensional Melting of Soft-Core Systems

    NASA Astrophysics Data System (ADS)

    Zu, Mengjie; Liu, Jun; Tong, Hua; Xu, Ning

    2016-08-01

    We find that both continuous and discontinuous hexatic-liquid transitions can happen in the melting of two-dimensional solids of soft-core disks. For three typical model systems, Hertzian, harmonic, and Gaussian-core models, we observe the same scenarios. These systems exhibit reentrant crystallization (melting) with a maximum melting temperature Tm happening at a crossover density ρm. The hexatic-liquid transition at a density smaller than ρm is discontinuous. Liquid and hexatic phases coexist in a density interval, which becomes narrower with increasing temperature and tends to vanish approximately at Tm. Above ρm, the transition is continuous, in agreement with the Kosterlitz-Thouless-Halperin-Nelson-Young theory. For these soft-core systems, the nature of the hexatic-liquid transition depends on density (pressure), with the melting at ρm being a plausible transition point from discontinuous to continuous hexatic-liquid transition.

  7. Density Affects the Nature of the Hexatic-Liquid Transition in Two-Dimensional Melting of Soft-Core Systems.

    PubMed

    Zu, Mengjie; Liu, Jun; Tong, Hua; Xu, Ning

    2016-08-19

    We find that both continuous and discontinuous hexatic-liquid transitions can happen in the melting of two-dimensional solids of soft-core disks. For three typical model systems, Hertzian, harmonic, and Gaussian-core models, we observe the same scenarios. These systems exhibit reentrant crystallization (melting) with a maximum melting temperature T_{m} happening at a crossover density ρ_{m}. The hexatic-liquid transition at a density smaller than ρ_{m} is discontinuous. Liquid and hexatic phases coexist in a density interval, which becomes narrower with increasing temperature and tends to vanish approximately at T_{m}. Above ρ_{m}, the transition is continuous, in agreement with the Kosterlitz-Thouless-Halperin-Nelson-Young theory. For these soft-core systems, the nature of the hexatic-liquid transition depends on density (pressure), with the melting at ρ_{m} being a plausible transition point from discontinuous to continuous hexatic-liquid transition.

  8. Evidence of liquid–liquid transition in glass-forming La50Al35Ni15 melt above liquidus temperature

    PubMed Central

    Xu, Wei; Sandor, Magdalena T.; Yu, Yao; Ke, Hai-Bo; Zhang, Hua-Ping; Li, Mao-Zhi; Wang, Wei-Hua; Liu, Lin; Wu, Yue

    2015-01-01

    Liquid–liquid transition, a phase transition of one liquid phase to another with the same composition, provides a key opportunity for investigating the relationship between liquid structures and dynamics. Here we report experimental evidences of a liquid–liquid transition in glass-forming La50Al35Ni15 melt above its liquidus temperature by 27Al nuclear magnetic resonance including the temperature dependence of cage volume fluctuations and atomic diffusion. The observed dependence of the incubation time on the degree of undercooling is consistent with a first-order phase transition. Simulation results indicate that such transition is accompanied by the change of bond-orientational order without noticeable change in density. The temperature dependence of atomic diffusion revealed by simulations is also in agreement with experiments. These observations indicate the need of two-order parameters in describing phase transitions of liquids. PMID:26165855

  9. Density Affects the Nature of the Hexatic-Liquid Transition in Two-Dimensional Melting of Soft-Core Systems.

    PubMed

    Zu, Mengjie; Liu, Jun; Tong, Hua; Xu, Ning

    2016-08-19

    We find that both continuous and discontinuous hexatic-liquid transitions can happen in the melting of two-dimensional solids of soft-core disks. For three typical model systems, Hertzian, harmonic, and Gaussian-core models, we observe the same scenarios. These systems exhibit reentrant crystallization (melting) with a maximum melting temperature T_{m} happening at a crossover density ρ_{m}. The hexatic-liquid transition at a density smaller than ρ_{m} is discontinuous. Liquid and hexatic phases coexist in a density interval, which becomes narrower with increasing temperature and tends to vanish approximately at T_{m}. Above ρ_{m}, the transition is continuous, in agreement with the Kosterlitz-Thouless-Halperin-Nelson-Young theory. For these soft-core systems, the nature of the hexatic-liquid transition depends on density (pressure), with the melting at ρ_{m} being a plausible transition point from discontinuous to continuous hexatic-liquid transition. PMID:27588868

  10. Liquid-liquid phase transition in hydrogen by coupled electron-ion Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Pierleoni, Carlo; Morales, Miguel A.; Rillo, Giovanni; Holzmann, Markus

    2016-05-01

    The phase diagram of high-pressure hydrogen is of great interest for fundamental research, planetary physics, and energy applications. A first-order phase transition in the fluid phase between a molecular insulating fluid and a monoatomic metallic fluid has been predicted. The existence and precise location of the transition line is relevant for planetary models. Recent experiments reported contrasting results about the location of the transition. Theoretical results based on density functional theory are also very scattered. We report highly accurate coupled electron-ion Monte Carlo calculations of this transition, finding results that lie between the two experimental predictions, close to that measured in diamond anvil cell experiments but at 25-30 GPa higher pressure. The transition along an isotherm is signaled by a discontinuity in the specific volume, a sudden dissociation of the molecules, a jump in electrical conductivity, and loss of electron localization.

  11. Liquid-liquid phase transition in hydrogen by coupled electron-ion Monte Carlo simulations.

    PubMed

    Pierleoni, Carlo; Morales, Miguel A; Rillo, Giovanni; Holzmann, Markus; Ceperley, David M

    2016-05-01

    The phase diagram of high-pressure hydrogen is of great interest for fundamental research, planetary physics, and energy applications. A first-order phase transition in the fluid phase between a molecular insulating fluid and a monoatomic metallic fluid has been predicted. The existence and precise location of the transition line is relevant for planetary models. Recent experiments reported contrasting results about the location of the transition. Theoretical results based on density functional theory are also very scattered. We report highly accurate coupled electron-ion Monte Carlo calculations of this transition, finding results that lie between the two experimental predictions, close to that measured in diamond anvil cell experiments but at 25-30 GPa higher pressure. The transition along an isotherm is signaled by a discontinuity in the specific volume, a sudden dissociation of the molecules, a jump in electrical conductivity, and loss of electron localization. PMID:27099295

  12. Reconfigurable 3D plasmonic metamolecules

    NASA Astrophysics Data System (ADS)

    Kuzyk, Anton; Schreiber, Robert; Zhang, Hui; Govorov, Alexander O.; Liedl, Tim; Liu, Na

    2014-09-01

    A reconfigurable plasmonic nanosystem combines an active plasmonic structure with a regulated physical or chemical control input. There have been considerable efforts on integration of plasmonic nanostructures with active platforms using top-down techniques. The active media include phase-transition materials, graphene, liquid crystals and carrier-modulated semiconductors, which can respond to thermal, electrical and optical stimuli. However, these plasmonic nanostructures are often restricted to two-dimensional substrates, showing desired optical response only along specific excitation directions. Alternatively, bottom-up techniques offer a new pathway to impart reconfigurability and functionality to passive systems. In particular, DNA has proven to be one of the most versatile and robust building blocks for construction of complex three-dimensional architectures with high fidelity. Here we show the creation of reconfigurable three-dimensional plasmonic metamolecules, which execute DNA-regulated conformational changes at the nanoscale. DNA serves as both a construction material to organize plasmonic nanoparticles in three dimensions, as well as fuel for driving the metamolecules to distinct conformational states. Simultaneously, the three-dimensional plasmonic metamolecules can work as optical reporters, which transduce their conformational changes in situ into circular dichroism changes in the visible wavelength range.

  13. Reconfigurable 3D plasmonic metamolecules.

    PubMed

    Kuzyk, Anton; Schreiber, Robert; Zhang, Hui; Govorov, Alexander O; Liedl, Tim; Liu, Na

    2014-09-01

    A reconfigurable plasmonic nanosystem combines an active plasmonic structure with a regulated physical or chemical control input. There have been considerable efforts on integration of plasmonic nanostructures with active platforms using top-down techniques. The active media include phase-transition materials, graphene, liquid crystals and carrier-modulated semiconductors, which can respond to thermal, electrical and optical stimuli. However, these plasmonic nanostructures are often restricted to two-dimensional substrates, showing desired optical response only along specific excitation directions. Alternatively, bottom-up techniques offer a new pathway to impart reconfigurability and functionality to passive systems. In particular, DNA has proven to be one of the most versatile and robust building blocks for construction of complex three-dimensional architectures with high fidelity. Here we show the creation of reconfigurable three-dimensional plasmonic metamolecules, which execute DNA-regulated conformational changes at the nanoscale. DNA serves as both a construction material to organize plasmonic nanoparticles in three dimensions, as well as fuel for driving the metamolecules to distinct conformational states. Simultaneously, the three-dimensional plasmonic metamolecules can work as optical reporters, which transduce their conformational changes in situ into circular dichroism changes in the visible wavelength range.

  14. Interplay Between Two Phase Transitions: Crystallization and Liquid-Liquid Phase Separation in a Polyolefin Blend

    NASA Astrophysics Data System (ADS)

    Han, Charles C.; Zhang, Xiaohua

    2006-03-01

    The correlation between liquid-liquid phase separation (LLPS) and crystallization at several compositions in statistical copolymer blends of poly (ethylene-co-hexene) (PEH) and poly (ethylene-co-butene) (PEB) has been examined by optical microscopy (OM), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). The overwhelming change in the crystallization kinetics due to the density fluctuation caused by the spontaneous spinodal LLPS is observed. This coupling mechanism suggests a new mechanism in the nucleation-crystallization process. All evidences are pointing to a cross-over mechanism from the spinodal fluctuations (of liquid-liquid phase separation) to the nucleation and than crystallization. The detailed experimental evidences and a suggested physical model will be presented.

  15. Theoretical Studies of Liquid He-4 Near the Superfluid Transition

    NASA Technical Reports Server (NTRS)

    Manousakis, Efstratios

    2002-01-01

    We performed theoretical studies of liquid helium by applying state of the art simulation and finite-size scaling techniques. We calculated universal scaling functions for the specific heat and superfluid density for various confining geometries relevant for experiments such as the confined helium experiment and other ground based studies. We also studied microscopically how the substrate imposes a boundary condition on the superfluid order parameter as the superfluid film grows layer by layer. Using path-integral Monte Carlo, a quantum Monte Carlo simulation method, we investigated the rich phase diagram of helium monolayer, bilayer and multilayer on a substrate such as graphite. We find excellent agreement with the experimental results using no free parameters. Finally, we carried out preliminary calculations of transport coefficients such as the thermal conductivity for bulk or confined helium systems and of their scaling properties. All our studies provide theoretical support for various experimental studies in microgravity.

  16. YouDash3D: exploring stereoscopic 3D gaming for 3D movie theaters

    NASA Astrophysics Data System (ADS)

    Schild, Jonas; Seele, Sven; Masuch, Maic

    2012-03-01

    Along with the success of the digitally revived stereoscopic cinema, events beyond 3D movies become attractive for movie theater operators, i.e. interactive 3D games. In this paper, we present a case that explores possible challenges and solutions for interactive 3D games to be played by a movie theater audience. We analyze the setting and showcase current issues related to lighting and interaction. Our second focus is to provide gameplay mechanics that make special use of stereoscopy, especially depth-based game design. Based on these results, we present YouDash3D, a game prototype that explores public stereoscopic gameplay in a reduced kiosk setup. It features live 3D HD video stream of a professional stereo camera rig rendered in a real-time game scene. We use the effect to place the stereoscopic effigies of players into the digital game. The game showcases how stereoscopic vision can provide for a novel depth-based game mechanic. Projected trigger zones and distributed clusters of the audience video allow for easy adaptation to larger audiences and 3D movie theater gaming.

  17. Remote 3D Medical Consultation

    NASA Astrophysics Data System (ADS)

    Welch, Greg; Sonnenwald, Diane H.; Fuchs, Henry; Cairns, Bruce; Mayer-Patel, Ketan; Yang, Ruigang; State, Andrei; Towles, Herman; Ilie, Adrian; Krishnan, Srinivas; Söderholm, Hanna M.

    Two-dimensional (2D) video-based telemedical consultation has been explored widely in the past 15-20 years. Two issues that seem to arise in most relevant case studies are the difficulty associated with obtaining the desired 2D camera views, and poor depth perception. To address these problems we are exploring the use of a small array of cameras to synthesize a spatially continuous range of dynamic three-dimensional (3D) views of a remote environment and events. The 3D views can be sent across wired or wireless networks to remote viewers with fixed displays or mobile devices such as a personal digital assistant (PDA). The viewpoints could be specified manually or automatically via user head or PDA tracking, giving the remote viewer virtual head- or hand-slaved (PDA-based) remote cameras for mono or stereo viewing. We call this idea remote 3D medical consultation (3DMC). In this article we motivate and explain the vision for 3D medical consultation; we describe the relevant computer vision/graphics, display, and networking research; we present a proof-of-concept prototype system; and we present some early experimental results supporting the general hypothesis that 3D remote medical consultation could offer benefits over conventional 2D televideo.

  18. Speaking Volumes About 3-D

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In 1999, Genex submitted a proposal to Stennis Space Center for a volumetric 3-D display technique that would provide multiple users with a 360-degree perspective to simultaneously view and analyze 3-D data. The futuristic capabilities of the VolumeViewer(R) have offered tremendous benefits to commercial users in the fields of medicine and surgery, air traffic control, pilot training and education, computer-aided design/computer-aided manufacturing, and military/battlefield management. The technology has also helped NASA to better analyze and assess the various data collected by its satellite and spacecraft sensors. Genex capitalized on its success with Stennis by introducing two separate products to the commercial market that incorporate key elements of the 3-D display technology designed under an SBIR contract. The company Rainbow 3D(R) imaging camera is a novel, three-dimensional surface profile measurement system that can obtain a full-frame 3-D image in less than 1 second. The third product is the 360-degree OmniEye(R) video system. Ideal for intrusion detection, surveillance, and situation management, this unique camera system offers a continuous, panoramic view of a scene in real time.

  19. Water in Inhomogeneous Nanoconfinement: Coexistence of Multilayered Liquid and Transition to Ice Nanoribbons.

    PubMed

    Qiu, Hu; Zeng, Xiao Cheng; Guo, Wanlin

    2015-10-27

    Phase behavior and the associated phase transition of water within inhomogeneous nanoconfinement are investigated using molecular dynamics simulations. The nanoconfinement is constructed by a flat bottom plate and a convex top plate. At 300 K, the confined water can be viewed as a coexistence of monolayer, bilayer, and trilayer liquid domains to accommodate the inhomogeneous confinement. With increasing liquid density, the confined water with uneven layers transforms separately into two-dimensional ice crystals with unchanged layer number and rhombic in-plane symmetry for oxygen atoms. The monolayer water undergoes the transition first into a puckered ice nanoribbon, and the bilayer water transforms into a rhombic ice nanoribbon next, followed by the transition of trilayer water into a trilayer ice nanoribbon. The sequential localized liquid-to-solid transition within the inhomogeneous confinement can also be achieved by gradually decreasing the temperature at low liquid densities. These findings of phase behaviors of water under the inhomogeneous nanoconfinement not only extend the phase diagram of confined water but also have implications for realistic nanofluidic systems and microporous materials.

  20. School Physical Education in the Transition from Solid Modernity to Liquid Modernity: The Brazilian Case

    ERIC Educational Resources Information Center

    Bracht, Valter; Gomes, Ivan Marcelo; de Almeida, Felipe Quintão

    2015-01-01

    This article discusses the implications of the contemporary transition from a solid modernity to a liquid modernity for school physical education, according to the metaphors adopted by the Polish sociologist and English resident Zygmunt Bauman. By leveraging Bauman's sociological theory, this article pursues two aims: (1) to examine how physical…

  1. The EISCAT_3D Science Case

    NASA Astrophysics Data System (ADS)

    Tjulin, A.; Mann, I.; McCrea, I.; Aikio, A. T.

    2013-05-01

    EISCAT_3D will be a world-leading international research infrastructure using the incoherent scatter technique to study the atmosphere in the Fenno-Scandinavian Arctic and to investigate how the Earth's atmosphere is coupled to space. The EISCAT_3D phased-array multistatic radar system will be operated by EISCAT Scientific Association and thus be an integral part of an organisation that has successfully been running incoherent scatter radars for more than thirty years. The baseline design of the radar system contains a core site with transmitting and receiving capabilities located close to the intersection of the Swedish, Norwegian and Finnish borders and five receiving sites located within 50 to 250 km from the core. The EISCAT_3D project is currently in its Preparatory Phase and can smoothly transit into implementation in 2014, provided sufficient funding. Construction can start 2016 and first operations in 2018. The EISCAT_3D Science Case is prepared as part of the Preparatory Phase. It is regularly updated with annual new releases, and it aims at being a common document for the whole future EISCAT_3D user community. The areas covered by the Science Case are atmospheric physics and global change; space and plasma physics; solar system research; space weather and service applications; and radar techniques, new methods for coding and analysis. Two of the aims for EISCAT_3D are to understand the ways natural variability in the upper atmosphere, imposed by the Sun-Earth system, can influence the middle and lower atmosphere, and to improve the predictivity of atmospheric models by providing higher resolution observations to replace the current parametrised input. Observations by EISCAT_3D will also be used to monitor the direct effects from the Sun on the ionosphere-atmosphere system and those caused by solar wind magnetosphere-ionosphere interaction. In addition, EISCAT_3D will be used for remote sensing the large-scale behaviour of the magnetosphere from its

  2. Physical understanding of gas-liquid annular flow and its transition to dispersed droplets

    NASA Astrophysics Data System (ADS)

    Kumar, Parmod; Das, Arup Kumar; Mitra, Sushanta K.

    2016-07-01

    Transformation from annular to droplet flow is investigated for co-current, upward gas-liquid flow through a cylindrical tube using grid based volume of fluid framework. Three transitional routes, namely, orificing, rolling, and undercutting are observed for flow transformation at different range of relative velocities between the fluids. Physics behind these three exclusive phenomena is described using circulation patterns of gaseous phase in the vicinity of a liquid film which subsequently sheds drop leading towards transition. Orifice amplitude is found to grow exponentially towards the core whereas it propagates in axial direction in a parabolic path. Efforts have been made to fit the sinusoidal profile of wave structure with the numerical interface contour at early stages of orificing. Domination of gas inertia over liquid flow has been studied in detail at the later stages to understand the asymmetric shape of orifice, leading towards lamella formation and droplet generation. Away from comparative velocities, circulations in the dominant phase dislodge the drop by forming either a ligament (rolling) or a bag (undercut) like protrusion in liquid. Study of velocity patterns in the plane of droplet dislodge reveals the underlying physics behind the disintegration and its dynamics at the later stages. Using numerical phase distributions, rejoining of dislodged droplet with liquid film as post-rolling consequences has been also proposed. A flow pattern map showing the transitional boundaries based on the physical mechanism is constructed for air-water combination.

  3. Theory of bent-core liquid-crystal phases and phase transitions

    NASA Astrophysics Data System (ADS)

    Lubensky, T. C.; Radzihovsky, Leo

    2002-09-01

    We study phases and phase transitions that can take place in the recently discovered bow-shaped or bent-core liquid-crystal molecules. We show that to completely characterize phases exhibited by such bent-core molecules a third-rank tensor Tijk order parameter is necessary in addition to the vector and the nematic (second-rank) tensor order parameters. We present an exhaustive list of possible liquid phases, characterizing them by their space-symmetry group and order parameters, and catalog the universality classes of the corresponding phase transitions that we expect to take place in such bent-core molecular liquid crystals. In addition to the conventional liquid-crystal phases such as the nematic phase, we predict the existence of other liquid phases, including the spontaneously chiral nematic (NT+2)* and chiral polar (VT+2)* phases, the orientationally ordered but optically isotropic tetrahedratic T phase, and a nematic NT phase with D2d symmetry that is neither uniaxial nor biaxial. Interestingly, the isotropic-tetrahedratic transition is continuous in mean-field theory, but is likely driven first order by thermal fluctuations. We conclude with a discussion of smectic analogs of these phases and their experimental signatures.

  4. Theory of bent-core liquid-crystal phases and phase transitions.

    PubMed

    Lubensky, T C; Radzihovsky, Leo

    2002-09-01

    We study phases and phase transitions that can take place in the recently discovered bow-shaped or bent-core liquid-crystal molecules. We show that to completely characterize phases exhibited by such bent-core molecules a third-rank tensor T(ijk) order parameter is necessary in addition to the vector and the nematic (second-rank) tensor order parameters. We present an exhaustive list of possible liquid phases, characterizing them by their space-symmetry group and order parameters, and catalog the universality classes of the corresponding phase transitions that we expect to take place in such bent-core molecular liquid crystals. In addition to the conventional liquid-crystal phases such as the nematic phase, we predict the existence of other liquid phases, including the spontaneously chiral nematic (N(T)+2)(*) and chiral polar (V(T)+2)(*) phases, the orientationally ordered but optically isotropic tetrahedratic T phase, and a nematic N(T) phase with D(2d) symmetry that is neither uniaxial nor biaxial. Interestingly, the isotropic-tetrahedratic transition is continuous in mean-field theory, but is likely driven first order by thermal fluctuations. We conclude with a discussion of smectic analogs of these phases and their experimental signatures. PMID:12366133

  5. Direct observation of an abrupt insulator-to-metal transition in dense liquid deuterium

    NASA Astrophysics Data System (ADS)

    Knudson, Marcus; Desjarlais, Michael; Becker, Andeas; Lemke, Raymond; Cochrane, Kyle; Savage, Mark; Bliss, David; Mattsson, Thomas; Redmer, Ronald

    2015-06-01

    Recently a so-called shock-ramp platform has been developed on the Sandia Z Accelerator to access off-Hugoniot states in liquids. The accelerator delivers a two-step current pulse; the first accelerates the electrode to a reasonably constant velocity, which upon impact with the sample cell creates a well-defined shock, the subsequent current rise produces ramp compression from the initially shocked state. This technique generates relatively cool (~1-2 kK), high pressure (>300 GPa), high compression (~10-15 fold compression) states, allowing experimental access to the region of phase space where hydrogen is predicted to undergo a first-order phase transition from an insulating molecular-like liquid to a conducting atomic-like liquid. In this talk we will discuss the experimental platform, survey the various theoretical predictions for the liquid-liquid, insulator-to-metal transition in hydrogen, and present the results of experiments that clearly show an abrupt transition to a metallic state. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  6. Thermalization calorimetry: A simple method for investigating glass transition and crystallization of supercooled liquids

    NASA Astrophysics Data System (ADS)

    Jakobsen, Bo; Sanz, Alejandro; Niss, Kristine; Hecksher, Tina; Pedersen, Ib H.; Rasmussen, Torben; Christensen, Tage; Olsen, Niels Boye; Dyre, Jeppe C.

    2016-05-01

    We present a simple method for fast and cheap thermal analysis on supercooled glass-forming liquids. This "Thermalization Calorimetry" technique is based on monitoring the temperature and its rate of change during heating or cooling of a sample for which the thermal power input comes from heat conduction through an insulating material, i.e., is proportional to the temperature difference between sample and surroundings. The monitored signal reflects the sample's specific heat and is sensitive to exo- and endothermic processes. The technique is useful for studying supercooled liquids and their crystallization, e.g., for locating the glass transition and melting point(s), as well as for investigating the stability against crystallization and estimating the relative change in specific heat between the solid and liquid phases at the glass transition.

  7. Two-dimensional melting: from liquid-hexatic coexistence to continuous transitions.

    PubMed

    Kapfer, Sebastian C; Krauth, Werner

    2015-01-23

    The phase diagram of two-dimensional continuous particle systems is studied using the event-chain Monte Carlo algorithm. For soft disks with repulsive power-law interactions ∝r^{-n} with n≳6, the recently established hard-disk melting scenario (n→∞) holds: a first-order liquid-hexatic and a continuous hexatic-solid transition are identified. Close to n=6, the coexisting liquid exhibits very long orientational correlations, and positional correlations in the hexatic are extremely short. For n≲6, the liquid-hexatic transition is continuous, with correlations consistent with the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) scenario. To illustrate the generality of these results, we demonstrate that Yukawa particles likewise may follow either the KTHNY or the hard-disk melting scenario, depending on the Debye-Hückel screening length as well as on the temperature. PMID:25659008

  8. Near infrared light-driven liquid crystal phase transition enabled by hydrophobic mesogen grafted plasmonic gold nanorods.

    PubMed

    Gutierrez-Cuevas, Karla G; Wang, Ling; Xue, Chenming; Singh, Gautam; Kumar, Satyendra; Urbas, Augustine; Li, Quan

    2015-06-18

    Light-driven phase transition in liquid crystals is a fascinating endeavour from both scientific and technological points of view. Here we demonstrate the proof-of-principle that the photothermal effect of organo-soluble plasmonic gold nanorods can introduce the phase transition of thermotropic liquid crystals upon near infrared laser irradiation. Interestingly, the reverse process occurs when the laser is switched off.

  9. 3D-Printed Microfluidics.

    PubMed

    Au, Anthony K; Huynh, Wilson; Horowitz, Lisa F; Folch, Albert

    2016-03-14

    The advent of soft lithography allowed for an unprecedented expansion in the field of microfluidics. However, the vast majority of PDMS microfluidic devices are still made with extensive manual labor, are tethered to bulky control systems, and have cumbersome user interfaces, which all render commercialization difficult. On the other hand, 3D printing has begun to embrace the range of sizes and materials that appeal to the developers of microfluidic devices. Prior to fabrication, a design is digitally built as a detailed 3D CAD file. The design can be assembled in modules by remotely collaborating teams, and its mechanical and fluidic behavior can be simulated using finite-element modeling. As structures are created by adding materials without the need for etching or dissolution, processing is environmentally friendly and economically efficient. We predict that in the next few years, 3D printing will replace most PDMS and plastic molding techniques in academia.

  10. Disappearance of Widom Line for Liquid-Liquid Phase Transition with Horizontal Coexistence Line

    NASA Astrophysics Data System (ADS)

    Luo, Jiayuan; Xu, Limei; Buldyrev, Sergey; Angell, Austen; Stanley, Gene

    2012-02-01

    The study of spherically symmetric two-scale Jagla model with both repulsive and attractive ramps has been very successful in demonstrating the anomalous behavior of liquids (especially water) and its relation with respect to the existence of a liquid-liquid (LL) critical point. However, the co-existence line of Jagla model shows a positive slope, which is opposite to what has been found in the simulations of water. To more convincingly link the result of the study on Jagla model with that of water, we applied discrete molecular dynamics to Gibson and Wilding's modified Jagla model and found that by shrinking both the attractive and repulsive ramps, the slope of the coexistence line can be reduced to zero. However, at these values of the parameters, the LL critical point becomes completely unstable with respect to crystal and glass. We further studied the Widom line, defined as extreme of response functions and also continuation of the coexistence line into one phase region, and found Widom line disappeared in the case of zero slope of the coexistence line, due to the equal enthalpy of low-density liquid (LDL) and high-density liquid (HDL).

  11. Computer-aided 3D display system and its application in 3D vision test

    NASA Astrophysics Data System (ADS)

    Shen, XiaoYun; Ma, Lan; Hou, Chunping; Wang, Jiening; Tang, Da; Li, Chang

    1998-08-01

    The computer aided 3D display system, flicker-free field sequential stereoscopic image display system, is newly developed. This system is composed of personal computer, liquid crystal glasses driving card, stereoscopic display software and liquid crystal glasses. It can display field sequential stereoscopic images at refresh rate of 70 Hz to 120 Hz. A typical application of this system, 3D vision test system, is mainly discussed in this paper. This stereoscopic vision test system can test stereoscopic acuity, cross disparity, uncross disparity and dynamic stereoscopic vision quantitatively. We have taken the use of random-dot- stereograms as stereoscopic vision test charts. Through practical test experiment between Anaglyph Stereoscopic Vision Test Charts and this stereoscopic vision test system, the statistical figures and test result is given out.

  12. Evidence for liquid water during the high-density to low-density amorphous ice transition

    PubMed Central

    Kim, Chae Un; Barstow, Buz; Tate, Mark W.; Gruner, Sol M.

    2009-01-01

    Polymorphism of water has been extensively studied, but controversy still exists over the phase transition between high-density amorphous (HDA) and low-density amorphous (LDA) ice. We report the phase behavior of HDA ice inside high-pressure cryocooled protein crystals. Using X-ray diffraction, we demonstrate that the intermediate states in the temperature range from 80 to 170 K can be reconstructed as a linear combination of HDA and LDA ice, suggesting a first-order transition. We found evidence for a liquid state of water during the ice transition based on the protein crystallographic data. These observations open the possibility that the HDA ice induced by high-pressure cryocooling is a genuine glassy form of high-density liquid. PMID:19258453

  13. Efficient separation of transition metals from rare earths by an undiluted phosphonium thiocyanate ionic liquid.

    PubMed

    Rout, Alok; Binnemans, Koen

    2016-06-21

    The ionic liquid trihexyl(tetradecyl)phosphonium thiocyanate has been used for the extraction of the transition metal ions Co(ii), Ni(ii), Zn(ii), and the rare-earth ions La(iii), Sm(iii) and Eu(iii) from aqueous solutions containing nitrate or chloride salts. The transition metal ions showed a high affinity for the ionic liquid phase and were efficiently extracted, while the extraction efficiency of the rare-earth ions was low. This difference in extraction behavior enabled separation of the pairs Co(ii)/Sm(iii), Ni(ii)/La(iii) and Zn(ii)/Eu(iii). These separations are relevant for the recycling of rare earths and transition metals from samarium cobalt permanent magnets, nickel metal hydride batteries and lamp phosphors, respectively. The extraction of metal ions from a chloride or nitrate solution with a thiocyanate ionic liquid is an example of "split-anion extraction", where different anions are present in the aqueous and ionic liquid phase. Close to 100% loading was possible for Co(ii) and Zn(ii) up to a concentration of 40 g L(-1) of the transition metal salt in the initial aqueous feed solution, whereas the extraction efficiency for Ni(ii) gradually decreased with increase in the initial feed concentration. Stripping of Co(ii), Zn(ii) and Ni(ii) from the loaded ionic liquid phase was possible by a 15 wt% NH3 solution. The ionic liquid could reused after extraction and stripping. PMID:27243450

  14. 3D Computations and Experiments

    SciTech Connect

    Couch, R; Faux, D; Goto, D; Nikkel, D

    2004-04-05

    This project consists of two activities. Task A, Simulations and Measurements, combines all the material model development and associated numerical work with the materials-oriented experimental activities. The goal of this effort is to provide an improved understanding of dynamic material properties and to provide accurate numerical representations of those properties for use in analysis codes. Task B, ALE3D Development, involves general development activities in the ALE3D code with the focus of improving simulation capabilities for problems of mutual interest to DoD and DOE. Emphasis is on problems involving multi-phase flow, blast loading of structures and system safety/vulnerability studies.

  15. Spontaneous bond orientational ordering in liquids: An intimate link between glass transition and crystallization

    NASA Astrophysics Data System (ADS)

    Tanaka, Hajime; Russo, John; Leocmach, Mathieu; Kawasaki, Takeshi

    2013-02-01

    The origin of slow dynamics near glass transition and the mechanism of crystal nucleation are two unsolved fundamental problems associated with the metastable supercooled state of a liquid. So far these phenomena have been considered rather independently, however, we have revealed an intimate link between them. Recently we found that crystallike bond orientational order develops in the supercooled state of (nearly) single-component systems such as spin liquids and weakly polydisperse colloidal liquids. In these liquids, low free-energy configurations in a supercooled liquid have a link to the rotational symmetry which is going to be broken upon crystallization. We argue that this is a direct consequence of that the same free energy governs both glass transition and crystallization at least in this type of liquids. We found that it is such structural ordering at least in this type of liquids that causes glassy slow dynamics and dynamic heterogeneity. Furthermore, we revealed that such structural order also plays a crucial role in crystal nucleation: Crystallization is a process of the enhancement of spatial coherence of crystal-like bond orientational order and `not' driven by translational order at least in the nucleation stage. These results clearly indicate that the theoretical description at the two-body level is not enough to describe these phenomena and it is crucial to take into account many body correlations, particularly, bond orientational correlations. We argue that there is an intrinsic link between glass transition and crystallization if crystallization does not accompany other processes such as phase separation. If crystallization involves phase separation, on the other hand, such a direct link may be lost. We speculate that even in such a case glassy structural order may still be associated with low free-energy local configurations.

  16. Complex light in 3D printing

    NASA Astrophysics Data System (ADS)

    Moser, Christophe; Delrot, Paul; Loterie, Damien; Morales Delgado, Edgar; Modestino, Miguel; Psaltis, Demetri

    2016-03-01

    3D printing as a tool to generate complicated shapes from CAD files, on demand, with different materials from plastics to metals, is shortening product development cycles, enabling new design possibilities and can provide a mean to manufacture small volumes cost effectively. There are many technologies for 3D printing and the majority uses light in the process. In one process (Multi-jet modeling, polyjet, printoptical©), a printhead prints layers of ultra-violet curable liquid plastic. Here, each nozzle deposits the material, which is then flooded by a UV curing lamp to harden it. In another process (Stereolithography), a focused UV laser beam provides both the spatial localization and the photo-hardening of the resin. Similarly, laser sintering works with metal powders by locally melting the material point by point and layer by layer. When the laser delivers ultra-fast focused pulses, nonlinear effects polymerize the material with high spatial resolution. In these processes, light is either focused in one spot and the part is made by scanning it or the light is expanded and covers a wide area for photopolymerization. Hence a fairly "simple" light field is used in both cases. Here, we give examples of how "complex light" brings additional level of complexity in 3D printing.

  17. Anomalous viscoelasticity near the isotropic-nematic phase transition in liquid crystals.

    PubMed

    Jose, Prasanth P; Bagchi, Biman

    2004-10-01

    Recent optical Kerr effect experiments have shown that orientational relaxation of nematogens shows a pronounced slow down of the response function at intermediate times and also a power law decay near the isotropic-nematic (I-N) transition. In many aspects, this behavior appears to be rather similar to the ones observed in the supercooled liquid near-glass transition. We have performed molecular dynamics simulations of model nematogens (Gay-Berne with aspect ratio 3) to explore the viscoelasticity near the I-N transition and also investigated the correlation of viscoelasticity (if any) with orientational relaxation. It is found that although the viscosity indeed undergoes a somewhat sharper than normal change near the I-N transition, it is not characterized by any divergence-like behavior (like the ones observed in the supercooled liquid). The rotational friction, on the other hand, shows a much sharper rise as the I-N transition is approached. Interestingly, the probability distribution of the amplitude of the three components of the stress tensor shows anisotropy near the I-N transition-similar anisotropy has also been seen in the deeply supercooled liquid. Frequency dependence of viscosity shows several unusual behaviors: (a) There is a weak, power law dependence on frequency [eta(')(omega) approximately omega(-alpha)] at low frequencies and (b) there is a rapid increase in the sharp peak observed in eta(')(omega) in the intermediate frequency on approach to the I-N transition density. These features can be explained from the stress-stress time correlation function. The angular velocity correlation function also exhibits a power law decay in time. The reason for this is discussed. PMID:15473759

  18. Making Inexpensive 3-D Models

    ERIC Educational Resources Information Center

    Manos, Harry

    2016-01-01

    Visual aids are important to student learning, and they help make the teacher's job easier. Keeping with the "TPT" theme of "The Art, Craft, and Science of Physics Teaching," the purpose of this article is to show how teachers, lacking equipment and funds, can construct a durable 3-D model reference frame and a model gravity…

  19. SNL3dFace

    2007-07-20

    This software distribution contains MATLAB and C++ code to enable identity verification using 3D images that may or may not contain a texture component. The code is organized to support system performance testing and system capability demonstration through the proper configuration of the available user interface. Using specific algorithm parameters the face recognition system has been demonstrated to achieve a 96.6% verification rate (Pd) at 0.001 false alarm rate. The system computes robust facial featuresmore » of a 3D normalized face using Principal Component Analysis (PCA) and Fisher Linear Discriminant Analysis (FLDA). A 3D normalized face is obtained by alighning each face, represented by a set of XYZ coordinated, to a scaled reference face using the Iterative Closest Point (ICP) algorithm. The scaled reference face is then deformed to the input face using an iterative framework with parameters that control the deformed surface regulation an rate of deformation. A variety of options are available to control the information that is encoded by the PCA. Such options include the XYZ coordinates, the difference of each XYZ coordinates from the reference, the Z coordinate, the intensity/texture values, etc. In addition to PCA/FLDA feature projection this software supports feature matching to obtain similarity matrices for performance analysis. In addition, this software supports visualization of the STL, MRD, 2D normalized, and PCA synthetic representations in a 3D environment.« less

  20. SNL3dFace

    SciTech Connect

    Russ, Trina; Koch, Mark; Koudelka, Melissa; Peters, Ralph; Little, Charles; Boehnen, Chris; Peters, Tanya

    2007-07-20

    This software distribution contains MATLAB and C++ code to enable identity verification using 3D images that may or may not contain a texture component. The code is organized to support system performance testing and system capability demonstration through the proper configuration of the available user interface. Using specific algorithm parameters the face recognition system has been demonstrated to achieve a 96.6% verification rate (Pd) at 0.001 false alarm rate. The system computes robust facial features of a 3D normalized face using Principal Component Analysis (PCA) and Fisher Linear Discriminant Analysis (FLDA). A 3D normalized face is obtained by alighning each face, represented by a set of XYZ coordinated, to a scaled reference face using the Iterative Closest Point (ICP) algorithm. The scaled reference face is then deformed to the input face using an iterative framework with parameters that control the deformed surface regulation an rate of deformation. A variety of options are available to control the information that is encoded by the PCA. Such options include the XYZ coordinates, the difference of each XYZ coordinates from the reference, the Z coordinate, the intensity/texture values, etc. In addition to PCA/FLDA feature projection this software supports feature matching to obtain similarity matrices for performance analysis. In addition, this software supports visualization of the STL, MRD, 2D normalized, and PCA synthetic representations in a 3D environment.

  1. 3D Printing: Exploring Capabilities

    ERIC Educational Resources Information Center

    Samuels, Kyle; Flowers, Jim

    2015-01-01

    As 3D printers become more affordable, schools are using them in increasing numbers. They fit well with the emphasis on product design in technology and engineering education, allowing students to create high-fidelity physical models to see and test different iterations in their product designs. They may also help students to "think in three…

  2. Fragilities of liquids predicted from the random first order transition theory of glasses

    NASA Astrophysics Data System (ADS)

    Xia, Xiaoyu; Wolynes, Peter G.

    2000-03-01

    A microscopically motivated theory of glassy dynamics based on an underlying random first order transition is developed to explain the magnitude of free energy barriers for glassy relaxation. A variety of empirical correlations embodied in the concept of liquid "fragility" are shown to be quantitatively explained by such a model. The near universality of a Lindemann ratio characterizing the maximal amplitude of thermal vibrations within an amorphous minimum explains the variation of fragility with a liquid's configurational heat capacity density. Furthermore, the numerical prefactor of this correlation is well approximated by the microscopic calculation. The size of heterogeneous reconfiguring regions in a viscous liquid is inferred and the correlation of nonexponentiality of relaxation with fragility is qualitatively explained. Thus the wide variety of kinetic behavior in liquids of quite disparate chemical nature reflects quantitative rather than qualitative differences in their energy landscapes.

  3. Observation of shear-induced nematic-isotropic transition in side-chain liquid crystal polymers

    NASA Astrophysics Data System (ADS)

    Pujolle-Robic, Caroline; Noirez, Laurence

    2001-01-01

    Flow-induced phase transitions are a fundamental (but poorly understood) property of non-equilibrium systems, and are also of practical importance for tuning the processing conditions for plastics, petroleum products, and other related materials. Recognition that polymers may exhibit liquid crystal properties has led to the discovery of the first tailored side-chain liquid crystal polymers (SCLCPs), which are formed by inserting a spacer between the main polymer chain and the lateral mesogen liquid-crystalline graftings. Subsequent research has sought to understand the nature of the coupling between the main polymer chain and the mesogens, with a view to obtaining better control of the properties of these tailored structures. We show here that the parallel or perpendicular orientation of the mesogens with respect to the main chain can be reversed by the application of an external field produced by a shear flow, demonstrating the existence of an isotropic nematic phase transition in SCLCPs. Such a transition, which was theoretically predicted for low-molecular-weight liquid crystals but never observed, is shown to be a general property of SCLCPs too. We expect that these SCLCPs will prove to be good candidate systems for the experimental study of these non-equilibrium phenomena.

  4. Behavior of supercooled aqueous solutions stemming from hidden liquid–liquid transition in water

    SciTech Connect

    Biddle, John W.; Holten, Vincent; Anisimov, Mikhail A.

    2014-08-21

    A popular hypothesis that explains the anomalies of supercooled water is the existence of a metastable liquid–liquid transition hidden below the line of homogeneous nucleation. If this transition exists and if it is terminated by a critical point, the addition of a solute should generate a line of liquid–liquid critical points emanating from the critical point of pure metastable water. We have analyzed thermodynamic consequences of this scenario. In particular, we consider the behavior of two systems, H{sub 2}O-NaCl and H{sub 2}O-glycerol. We find the behavior of the heat capacity in supercooled aqueous solutions of NaCl, as reported by Archer and Carter [J. Phys. Chem. B 104, 8563 (2000)], to be consistent with the presence of the metastable liquid–liquid transition. We elucidate the non-conserved nature of the order parameter (extent of “reaction” between two alternative structures of water) and the consequences of its coupling with conserved properties (density and concentration). We also show how the shape of the critical line in a solution controls the difference in concentration of the coexisting liquid phases.

  5. TACO3D. 3-D Finite Element Heat Transfer Code

    SciTech Connect

    Mason, W.E.

    1992-03-04

    TACO3D is a three-dimensional, finite-element program for heat transfer analysis. An extension of the two-dimensional TACO program, it can perform linear and nonlinear analyses and can be used to solve either transient or steady-state problems. The program accepts time-dependent or temperature-dependent material properties, and materials may be isotropic or orthotropic. A variety of time-dependent and temperature-dependent boundary conditions and loadings are available including temperature, flux, convection, and radiation boundary conditions and internal heat generation. Additional specialized features treat enclosure radiation, bulk nodes, and master/slave internal surface conditions (e.g., contact resistance). Data input via a free-field format is provided. A user subprogram feature allows for any type of functional representation of any independent variable. A profile (bandwidth) minimization option is available. The code is limited to implicit time integration for transient solutions. TACO3D has no general mesh generation capability. Rows of evenly-spaced nodes and rows of sequential elements may be generated, but the program relies on separate mesh generators for complex zoning. TACO3D does not have the ability to calculate view factors internally. Graphical representation of data in the form of time history and spatial plots is provided through links to the POSTACO and GRAPE postprocessor codes.

  6. 3D Model of Surfactant Replacement Therapy

    NASA Astrophysics Data System (ADS)

    Grotberg, James; Tai, Cheng-Feng; Filoche, Marcel

    2015-11-01

    Surfactant Replacement Therapy (SRT) involves instillation of a liquid-surfactant mixture directly into the lung airway tree. Though successful in neonatal applications, its use in adults had early success followed by failure. We present the first mathematical model of 3D SRT where a liquid plug propagates through the tree from forced inspiration. In two separate modeling steps, the plug first deposits a coating film on the airway wall which subtracts from its volume, a ``coating cost''. Then the plug splits unevenly at the airway bifurcation due to gravity. The steps are repeated until a plug ruptures or reaches the tree endpoint alveoli/acinus. The model generates 3D images of the resulting acinar distribution and calculates two global indexes, efficiency and homogeneity. Simulating published literature, the earlier successful adult SRT studies show comparatively good index values, while the later failed studies do not. Those unsuccessful studies used smaller dose volumes with higher concentration mixtures, apparently assuming a well mixed compartment. The model shows that adult lungs are not well mixed in SRT due to the coating cost and gravity effects. Returning to the higher dose volume protocols could save many thousands of lives annually in the US. Supported by NIH Grants HL85156, HL84370 and Agence Nationale de la Recherche, ANR no. 2010-BLAN-1119-05.

  7. Kerr-AdS analogue of triple point and solid/liquid/gas phase transition

    NASA Astrophysics Data System (ADS)

    Altamirano, Natacha; Kubizňák, David; Mann, Robert B.; Sherkatghanad, Zeinab

    2014-02-01

    We study the thermodynamic behavior of multi-spinning d = 6 Kerr-anti de Sitter black holes in the canonical ensemble of fixed angular momenta J1 and J2. We find, dependent on the ratio q = J2/J1, qualitatively different interesting phenomena known from the ‘every day thermodynamics’ of simple substances. For q = 0 the system exhibits recently observed reentrant large/small/large black hole phase transitions, but for 0 < q ≪ 1 we find an analogue of a ‘solid/liquid’ phase transition. Furthermore, for q ∈ (0.00905, 0.0985) the system displays the presence of a large/intermediate/small black hole phase transition with two critical and one triple (or tricritical) points. This behavior is reminiscent of the solid/liquid/gas phase transition except that the coexistence line of small and intermediate black holes does not continue for an arbitrary value of pressure (similar to the solid/liquid coexistence line) but rather terminates at one of the critical points. Finally, for q > 0.0985 we observe the ‘standard liquid/gas behavior’ of the Van der Waals fluid.

  8. Phase transition in the vortex liquid and the critical endpoint in YBa2Cu3Oy

    NASA Astrophysics Data System (ADS)

    Shibata, Kenji; Nishizaki, Terukazu; Sasaki, Takahiko; Kobayashi, Norio

    2002-12-01

    The vortex phase diagram of optimally doped untwinned YBa2Cu3Oy is studied. We find a first-order transition TL(H) in the vortex liquid above the terminal point Hmcp (≃7 T) of both the vortex glass line Tg(H) and the field-driven disordering transition line H*(T). The obtained small entropy change (˜0.02 kB/vortex/layer) and the critical endpoint Hcep (≃11 T) of the TL(H) line indicate that the vortex liquid undergoes the vortex slush regime before the solidification into the vortex glass phase. Below Hmcp, the vortex liquid phase shows the first-order melting transition into the Bragg glass phase. We also study the oxygen content y dependence of the vortex phase diagram and find that the vortex slush regime is located in the borderline (i.e., 6.90⩽y⩽6.92) below which the vortex lattice melting transition disappears. The result indicates that the point disorder with the intermediate strength plays an important role in the vortex slush regime.

  9. Determining Transition State Geometries in Liquids Using 2D-IR

    SciTech Connect

    Harris, Charles; Cahoon, James F.; Sawyer, Karma R.; Schlegel, Jacob P.; Harris, Charles B.

    2007-12-11

    Many properties of chemical reactions are determined by the transition state connecting reactant and product, yet it is difficult to directly obtain any information about these short-lived structures in liquids. We show that two-dimensional infrared (2D-IR) spectroscopy can provide direct information about transition states by tracking the transformation of vibrational modes as a molecule crossed a transition state. We successfully monitored a simple chemical reaction, the fluxional rearrangement of Fe(CO)5, in which the exchange of axial and equatorial CO ligands causes an exchange of vibrational energy between the normal modes of the molecule. This energy transfer provides direct evidence regarding the time scale, transition state, and mechanism of the reaction.

  10. Successive disorder to disorder phase transitions in ionic liquid [HMIM][BF4] under high pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Xiang; Yuan, Chaosheng; Li, Haining; Zhu, Pinwen; Su, Lei; Yang, Kun; Wu, Jie; Yang, Guoqiang; Liu, Jing

    2016-02-01

    In situ high-pressure Raman spectroscopy and synchrotron X-ray diffraction have been employed to investigate the phase behavior of ionic liquid, 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM][BF4]) under high pressure up to 20 GPa at room temperature. With increasing pressure, some characteristic bands of [HMIM][BF4] disappear, and some characteristic bands of [HMIM][BF4] display non-monotonic pressure-induced frequency shift and non-monotonic variation of full width at half-maximum. Two successive phase transitions at ∼1.7 GPa and 7.3 GPa have been corroborated by the results above. The glass transition pressure (Pg) of [HMIM][BF4] at ∼7.3 GPa has been obtained by ruby R1 line broadening measurements and analysis of synchrotron X-ray diffraction patterns, and its glass transition mechanism is also analyzed in detail. These facts are suggestive of two successive disorder to disorder phase transitions induced by compression, that is, [HMIM][BF4] serves as a superpressurized glass under the pressure above 7.3 GPa, which is similar to the glassy state at low temperature, and a compression-induced liquid to liquid phase transition in [HMIM][BF4] occurs at ∼1.7 GPa. Besides, the conformational equilibrium of the GAAA conformer and AAAA conformer was converted easily in liquid [HMIM][BF4], while it was difficult to be influenced in glassy state.

  11. Unraveling wetting transition through surface textures with X-rays: Liquid meniscus penetration phenomena

    PubMed Central

    Antonini, C.; Lee, J. B.; Maitra, T.; Irvine, S.; Derome, D.; Tiwari, Manish K.; Carmeliet, J.; Poulikakos, D.

    2014-01-01

    In this report we show that synchrotron X-ray radiography is a powerful method to study liquid-air interface penetration through opaque microtextured surface roughness, leading to wetting transition. We investigate this wetting phenomenon in the context of sessile drop evaporation, and establish that liquid interface sinking into the surface texture is indeed dictated by the balance of capillary and Laplace pressures, where the intrinsically three-dimensional nature of the meniscus must be accounted for. Air bubble entrapment in the texture underneath impacting water drops is also visualized and the mechanisms of post-impact drop evaporation are discussed. PMID:24514762

  12. Nonlinear absorption in ionic liquids with transition metallic atoms in the anion

    NASA Astrophysics Data System (ADS)

    Nóvoa-López, José A.; López Lago, Elena; Seijas, Julio A.; Pilar Vázquez-Tato, M.; Troncoso, Jacobo; de la Fuente, Raúl; Salgueiro, José R.; Michinel, Humberto

    2016-02-01

    Nonlinear absorption has been investigated by open aperture Z-scan in ionic liquids obtained by combination of 1-butyl-3-methyl-imidazolium cations with anions containing a transition metal (Co, Zn, Cu or Ni) and thiocyanate groups. The laser source was a Ti:Sapphire oscillator (80-fs pulses, λ = 810 nm, repetition rate of 80.75 MHz). All liquids present quite low heat capacities that favor the development of strong thermal effects. Thermal effects and nonlinear absorption make them potential materials for optical limiting purposes.

  13. Investigating the solid-liquid phase transition of water nanofilms using the generalized replica exchange method

    NASA Astrophysics Data System (ADS)

    Lu, Qing; Kim, Jaegil; Farrell, James D.; Wales, David J.; Straub, John E.

    2014-11-01

    The generalized Replica Exchange Method (gREM) was applied to study a solid-liquid phase transition in a nanoconfined bilayer water system using the monatomic water (mW) model. Exploiting optimally designed non-Boltzmann sampling weights with replica exchanges, gREM enables an effective sampling of configurations that are metastable or unstable in the canonical ensemble via successive unimodal energy distributions across phase transition regions, often characterized by S-loop or backbending in the statistical temperature. Extensive gREM simulations combined with Statistical Temperature Weighted Histogram Analysis Method (ST-WHAM) for nanoconfined mW water at various densities provide a comprehensive characterization of diverse thermodynamic and structural properties intrinsic to phase transitions. Graph representation of minimized structures of bilayer water systems determined by the basin-hopping global optimization revealed heterogeneous ice structures composed of pentagons, hexagons, and heptagons, consistent with an increasingly ordered solid phase with decreasing density. Apparent crossover from a first-order solid-liquid transition to a continuous one in nanoconfined mW water with increasing density of the system was observed in terms of a diminishing S-loop in the statistical temperature, smooth variation of internal energies and heat capacities, and a characteristic variation of lateral radial distribution functions, and transverse density profiles across transition regions.

  14. Investigating the solid-liquid phase transition of water nanofilms using the generalized replica exchange method

    SciTech Connect

    Lu, Qing; Kim, Jaegil; Straub, John E.; Farrell, James D.; Wales, David J.

    2014-11-14

    The generalized Replica Exchange Method (gREM) was applied to study a solid-liquid phase transition in a nanoconfined bilayer water system using the monatomic water (mW) model. Exploiting optimally designed non-Boltzmann sampling weights with replica exchanges, gREM enables an effective sampling of configurations that are metastable or unstable in the canonical ensemble via successive unimodal energy distributions across phase transition regions, often characterized by S-loop or backbending in the statistical temperature. Extensive gREM simulations combined with Statistical Temperature Weighted Histogram Analysis Method (ST-WHAM) for nanoconfined mW water at various densities provide a comprehensive characterization of diverse thermodynamic and structural properties intrinsic to phase transitions. Graph representation of minimized structures of bilayer water systems determined by the basin-hopping global optimization revealed heterogeneous ice structures composed of pentagons, hexagons, and heptagons, consistent with an increasingly ordered solid phase with decreasing density. Apparent crossover from a first-order solid-liquid transition to a continuous one in nanoconfined mW water with increasing density of the system was observed in terms of a diminishing S-loop in the statistical temperature, smooth variation of internal energies and heat capacities, and a characteristic variation of lateral radial distribution functions, and transverse density profiles across transition regions.

  15. Forensic 3D scene reconstruction

    NASA Astrophysics Data System (ADS)

    Little, Charles Q.; Small, Daniel E.; Peters, Ralph R.; Rigdon, J. B.

    2000-05-01

    Traditionally law enforcement agencies have relied on basic measurement and imaging tools, such as tape measures and cameras, in recording a crime scene. A disadvantage of these methods is that they are slow and cumbersome. The development of a portable system that can rapidly record a crime scene with current camera imaging, 3D geometric surface maps, and contribute quantitative measurements such as accurate relative positioning of crime scene objects, would be an asset to law enforcement agents in collecting and recording significant forensic data. The purpose of this project is to develop a fieldable prototype of a fast, accurate, 3D measurement and imaging system that would support law enforcement agents to quickly document and accurately record a crime scene.

  16. Forensic 3D Scene Reconstruction

    SciTech Connect

    LITTLE,CHARLES Q.; PETERS,RALPH R.; RIGDON,J. BRIAN; SMALL,DANIEL E.

    1999-10-12

    Traditionally law enforcement agencies have relied on basic measurement and imaging tools, such as tape measures and cameras, in recording a crime scene. A disadvantage of these methods is that they are slow and cumbersome. The development of a portable system that can rapidly record a crime scene with current camera imaging, 3D geometric surface maps, and contribute quantitative measurements such as accurate relative positioning of crime scene objects, would be an asset to law enforcement agents in collecting and recording significant forensic data. The purpose of this project is to develop a feasible prototype of a fast, accurate, 3D measurement and imaging system that would support law enforcement agents to quickly document and accurately record a crime scene.

  17. 3D Printed Robotic Hand

    NASA Technical Reports Server (NTRS)

    Pizarro, Yaritzmar Rosario; Schuler, Jason M.; Lippitt, Thomas C.

    2013-01-01

    Dexterous robotic hands are changing the way robots and humans interact and use common tools. Unfortunately, the complexity of the joints and actuations drive up the manufacturing cost. Some cutting edge and commercially available rapid prototyping machines now have the ability to print multiple materials and even combine these materials in the same job. A 3D model of a robotic hand was designed using Creo Parametric 2.0. Combining "hard" and "soft" materials, the model was printed on the Object Connex350 3D printer with the purpose of resembling as much as possible the human appearance and mobility of a real hand while needing no assembly. After printing the prototype, strings where installed as actuators to test mobility. Based on printing materials, the manufacturing cost of the hand was $167, significantly lower than other robotic hands without the actuators since they have more complex assembly processes.

  18. 3D light scanning macrography.

    PubMed

    Huber, D; Keller, M; Robert, D

    2001-08-01

    The technique of 3D light scanning macrography permits the non-invasive surface scanning of small specimens at magnifications up to 200x. Obviating both the problem of limited depth of field inherent to conventional close-up macrophotography and the metallic coating required by scanning electron microscopy, 3D light scanning macrography provides three-dimensional digital images of intact specimens without the loss of colour, texture and transparency information. This newly developed technique offers a versatile, portable and cost-efficient method for the non-invasive digital and photographic documentation of small objects. Computer controlled device operation and digital image acquisition facilitate fast and accurate quantitative morphometric investigations, and the technique offers a broad field of research and educational applications in biological, medical and materials sciences. PMID:11489078

  19. Liquid-crystal-solid interface structure at the antiferroelectric-ferroelectric phase transition.

    PubMed

    Coleman, D; Bardon, S; Radzihovsky, L; Danner, G; Clark, N A

    2002-12-01

    Total internal reflection is used to probe the molecular organization at the surface of a tilted chiral smectic liquid crystal at temperatures in the vicinity of the bulk antiferroelectric-ferroelectric phase transition. Data are interpreted using an exact analytical solution of a real model for ferroelectric order at the surface. In the mixture T3, ferroelectric surface order is expelled with the bulk ferroelectric-antiferroelectric transition. The conditions for ferroelectric order at the surface of an antiferroelectric bulk are presented. PMID:12513307

  20. Liquid-crystal anchoring transitions on aligning substrates processed by a plasma beam.

    PubMed

    Yaroshchuk, Oleg V; Kiselev, Alexei D; Kravchuk, Ruslan M

    2008-03-01

    We have studied a sequence of anchoring transitions observed in nematic liquid crystals (NLCs) sandwiched between hydrophobic polyimide substrates treated with a plasma beam. There is a pronounced continuous transition from a homeotropic to a slightly tilted (nearly planar) alignment with the easy axis parallel to the incidence plane of the plasma beam (the zenithal transition) which takes place as the exposure dose increases. In NLCs with positive dielectric anisotropy, a further increase in the exposure dose results in in-plane reorientation of the easy axis by 90 degrees (the azimuthal transition). This transition occurs through the twofold degenerate alignment characteristic of second-order anchoring transitions. In contrast to the critical behavior of anchoring, the contact angle of the NLC and water on the treated substrates declines monotonically with increasing exposure dose. It follows that the surface concentration of hydrophobic chains decreases continuously. The anchoring transitions under consideration are qualitatively interpreted by using a simple phenomenological model of competing easy axes which is studied by analyzing anchoring diagrams of generalized polar and nonpolar anchoring models.