Mesoporous phases based on SnO2 and TiO2

A hexagonal mesoporous phase based on SnO2 is synthesized for the first time by using an anionic surfactant; hexagonal phases of TiO2 are prepared with neutral amine surfactants.

Transmembrane domains participate in functions of integral membrane proteins

Integral membrane proteins have one or more transmembrane a-helical domains and carry out a variety of functions such as enzyme catalysis, transport across membranes, transducing signals as receptors of hormones and growth factors, and energy transfer in ATP synthesis. These transmembrane domains are not mere structural units anchoring the protein to the lipid bilayer but seem to-contribute in the overall activity. Recent findings in support of this are described using some typical examples-LDL receptor, growth factor receptor tyrosine kinase, HMG-CoA reductase, F-0-ATPase and adrenergic receptors. The trends in research indicate that these transmembrane domains participate in a variety of ways such as a linker, a transducer or an exchanger in the overall functions of these proteins in transfer of materials, energy and signals.

Synthesis and structure of oxygen-deficient La2NiCoO5 and LaSrCo2O5 phases

The La2NiCoO5 and LaSrCo2O5 phases have been synthesized by the temperature-programmed reduction (TPR) of the parent mixed perovskites LaNi0.5Co0.5O3 and La0.5Sr0.5CoO3, respectively, under an ammonia atmosphere. While La2NiCoO5 adopts a structure similar to the vacancy-ordered La2Ni2O5, LaSrCo2O5 crystallized in a brownmillerite-like structure. The reactivity of the perovskite oxides towards reduction by ammonia and the structure of the product oxides are found to be guided by factors such as the coordination and oxidation state of the transition-metal cations.

The formation of ?-FeSiAl5 and Be---Fe phases in Al---7Si---0.3Mg alloy containing Be

Thermal analysis and interrupted quench experiments have been carried out to study the formation of beta-FeSiAl5 and (Be-Fe)-BeSiFe2Al8 phases in Al-7Si-0.3Mg alloy with and without Be addition. In the base alloy with 0.6% Fe (without Be addition), a needle- and plate-shaped beta-phase is present in the interdendritic regions and is formed by a ternary eutectic reaction. In the Be- added alloy with 0.6% Fe, a Be-Fe phase of Chinese script and polygon shapes grows along with the primary alpha-Al dendrites, leading to superior mechanical properties. It is proposed that this Be-Fe phase is formed by a peritectic reaction. Be addition has also resulted in some grain refinement.

Electrical and magnetic properties of pure and Li intercalated Bi1.7-xPbxV8O16 phases

Hollandite oxides of the type Bi1.7-xPbxV8O16 have been synthesized. The electrical resistivity studies show that the conductivity improves upon Pb substitution. The feasibility of Li intercalation in the system has been established. Magnetic susceptibility studies on the pure and Li intercalated phases show that except for pure Bi1.7V8O16, all phases exhibit Pauli paramagnetism. No superconductivity is encountered down to 12 K in any of the phases. (C) 1998 Elsevier Science B.V. All rights reserved.

Nonaxisymmetric convection in stationary Gas Tungsten Arc Weld Pools

Observations of surface flow patterns of steel and aluminum GTAW pools have been made using a pulsed laser visualization system. The weld pool convection is found to be three-dimensional with the azimuthal circulation depending on the location of the clamp with respect to the torch. Oscillation of steel pools and undulating motion in aluminum weld pools are also observed even with steady process parameters. Current axisymmetric numerical models are unable to explain such phenomena. A three-dimensional computational study is carried out in this study to explain the rotational flow in aluminum weld pools.

On the existence of hydrotalcite-like phases in the absence of trivalent cations

alpha-Hydroxides of nickel(II) and cobalt(II) are hydrotalcite-like phases, possessing a layered double hydroxide (LDH) structure even though there are no trivalent cations in the lattice. While the LDHs acquire a positive charge on the hydroxide layers by the incorporation of trivalent cations, we suggest that the alpha-hydroxides acquire a positive charge by partial protonation of the hydroxyl ions according to the equation M(OH)(2)+xH(+) --> [M(OH)(2-x)(H2O)(x)](x+). As in the LDHs, charge balance is restored by the incorporation of anions in the interlayer region. (C) 1997 Academic Press.

Synthesis and vesicle formation from novel pseudoglyceryl dimeric lipids. Evidence of formation of widely different membrane organizations with exceptional thermotropic properties

Eight new bis-cationic dimeric lipids 2a-h have been synthesized; TEM of their aqueous dispersions confirmed the vesicle formation and from the thermal, spectroscopic, DLS and XRD studies it has been revealed that they form three different kinds of membranous aggregate depending on the m-value.

Synthesis of nanodispersed phases during rapid solidification and crystallization of glasses in Ti75Ni25 alloys

The formation of the metallic glass and crystalline phases and related microstructures and the decomposition behavior of rapidly solidified Ti75Ni25 alloys obtained under different processing conditions have been investigated in detail. The competition between glass transition and nucleation of beta-Ti during rapid solidification leads to the possibility of synthesizing the nanocomposites of beta-Ti and glass. Additionally, it is shown that the presence of a small amount of Si also promotes simultaneous nucleation of fine Ti2Ni intermetallic compound. Thermodynamic calculation of the metastable phase diagram indicates the presence of a metastable eutectic reaction between alpha-Ti and Ti2Ni. Evidence of this reaction at lower cooling rates has been presented. On heating, the glass decomposes through this reaction. Finally, on the basis of understanding of the microstructural evolution during decomposition, a new approach has been adopted to synthesize a nanodispersed composite of alpha-Ti in the crystalline Ti2Ni matrix with a narrow size distribution by controlling the devitrification heat treatment of the metallic glass.

Nonequilibrium stationary states of a particle in a gravitational field driven by a vibrating surface

Stationary velocity distribution functions are determined for a particle in a gravitational field driven by a vibrating surface in the limit of small dissipation. It is found that the form of the distribution function is sensitive to the mechanism of energy dissipation, inelastic collisions or viscous drag, and also to the form of the amplitude function of the vibrating surface. The velocity distributions obtained analytically are found to be in excellent agreement with the results of computer simulations in the limit of low dissipation. [S0031-9007(99)08898-5].

Growth mechanism of phases, Kirkendall voids, marker plane position, and indication of the relative mobilities of the species in the interdiffusion zone

Often, wrong conclusions about the mobilities of species are drawn from the position of the Kirkendall marker plane or voids in the interdiffusion zone. To clarify, I have discussed the growth mechanism of the phases and the position of the marker plane depending on the relative mobilities of the species. The formation of different kinds of voids in the interdiffusion zone is discussed. Further, the microstructure that could be found because of the Kirkendall effect is also explained.

Topological phases, Majorana modes and quench dynamics in a spin ladder system

We explore the salient features of the `Kitaev ladder', a two-legged ladder version of the spin-1/2 Kitaev model on a honeycomb lattice, by mapping it to a one-dimensional fermionic p-wave superconducting system. We examine the connections between spin phases and topologically non-trivial phases of non-interacting fermionic systems, demonstrating the equivalence between the spontaneous breaking of global Z(2) symmetry in spin systems and the existence of isolated Majorana modes. In the Kitaev ladder, we investigate topological properties of the system in different sectors characterized by the presence or absence of a vortex in each plaquette of the ladder. We show that vortex patterns can yield a rich parameter space for tuning into topologically non-trivial phases. We introduce and employ a new topological invariant for explicitly determining the presence of zero energy Majorana modes at the boundaries of such phases. Finally, we discuss dynamic quenching between topologically non-trivial phases in the Kitaev ladder and, in particular, the post-quench dynamics governed by tuning through a quantum critical point.

Growth mechanism of phases by interdiffusion and atomic mechanism of diffusion in the molybdenum-silicon system

Tracer diffusion coefficients are calculated in different phases in the Mo-Si system from diffusion couple experiments using the data available on thermodynamic parameters. Following, possible atomic diffusion mechanism of the species is discussed based on the crystal structure. Unusual diffusion behaviour is found in the Mo(5)Si(3) and Mo(3)Si phases, which indicate the nature of defects present on different sublattices. Further the growth mechanism of the phases is discussed and morphological evolution during interdiffusion is explained. (C) 2011 Elsevier Ltd. All rights reserved.