Twinning of quasicrystals and related structures

We consider for the first time twinning in quasicrystals and related structures in a systematic manner. The twinning operations are considered in the framework of six-dimensional crystallography. The number of twin variants and the symmetry of twinned aggregates are also discussed. It is shown that essentially two different types of interface can arise between any two twin variants.

Application of scaled particle theory to alkyl-aryl surfactants: a two zone model of micellar core

Scaled Particle Theory (SPT) has been applied to predict the total free energies of micellization of ionic as well as nonionic micellar systems containing an aryl ring. A modification of the previously developed model has been made, proposing a two-zone model of micellar core which corroborates with the structural information available for such systems. The results are in good agreement with experimental data and also confirm the dictating role of cavity forming free energies for such systems

Role of zirconium addition on stability of UAl3 phase in Al-U system

The microstructural changes of Al-22 wt%U and Al-46 wt%U alloys containing 3 wt% Zr were investigated after heat treatment at 620 degrees C for 1 to 45 days, Though it is reported that addition of similar to 3 wt% Zr stabilizes the (U,Zr)Al-3 phase at room temperature, the present investigation shows that the (U,Zr)Al-3 phase is not stable but slowly transforms to the U0.9Al4 phase, The high temperature creep curves generated for these ternary alloys showed a wavy pattern which also suggests that the (U,Zr)Al-3 phase is not stable.

Structure of 9[alpha],19-dihydroxy-4-androstene-3,17-dione

C19H26O4, M(r) = 318.41, orthorhombic, P2(1)2(1)2(1), a = 10.591 (1), b = 11.133 (1), c = 13.657 (2) angstrom, V = 1610.29 angstrom 3, Z = 4, D(m) (flotation in KI) = 1.301, D(x) = 1.313 g cm-3, Mo K-alpha, lambda = 0.7107 angstrom, mu = 0.85 cm-1, F(000) = 688, T = 293 K, R = 0.057 for 1253 significant reflections. The A ring is disordered with atoms C(2) and O(19) occupying two possible sites. The molecules are held together by a hydrogen bond [O(9)...O(17) = 2.89 angstrom].

Forecasting rain for groundnut farmers�how good is good enough

: We illustrate how climatological information about adverse weather events and meteorological forecasts (when available) can be used to decide between alternative strategies so as to maximize the long-term average returns for rainfed groundnut in semi-arid parts of Karnataka, We show that until the skill of the forecast, i.e. probability of an adverse event occurring when it is forecast, is above a certain threshold, the forecast has no impact on the optimum strategy, This threshold is determined by the loss in yield due to the adverse weather event and the cost of the mitigatory measures, For the specific case of groundnut, it is found that while for combating some pests/diseases, climatological information is adequate, for others a forecast of sufficient skill would have a significant impact on the productivity.

Diaphragmless shock wave generators for industrial applications of shock waves

The prime focus of this study is to design a 50 mm internal diameter diaphragmless shock tube that can be used in an industrial facility for repeated loading of shock waves. The instantaneous rise in pressure and temperature of a medium can be used in a variety of industrial applications. We designed, fabricated and tested three different shock wave generators of which one system employs a highly elastic rubber membrane and the other systems use a fast acting pneumatic valve instead of conventional metal diaphragms. The valve opening speed is obtained with the help of a high speed camera. For shock generation systems with a pneumatic cylinder, it ranges from 0.325 to 1.15 m/s while it is around 8.3 m/s for the rubber membrane. Experiments are conducted using the three diaphragmless systems and the results obtained are analyzed carefully to obtain a relation between the opening speed of the valve and the amount of gas that is actually utilized in the generation of the shock wave for each system. The rubber membrane is not suitable for industrial applications because it needs to be replaced regularly and cannot withstand high driver pressures. The maximum shock Mach number obtained using the new diaphragmless system that uses the pneumatic valve is 2.125 +/- 0.2%. This system shows much promise for automation in an industrial environment.

Barkhausen jumps and related magnetic properties of iron nanowires encapsulated in aligned carbon nanotube bundles

Iron nanowires encapsulated in aligned carbon nanotube bundles show interesting magnetic properties. Besides the increased coercivity, Barkhausen jumps with 5 emu/g steps in magnetization are observed due to magnetization reversal or depinning of domains. (C) 2002 Elsevier Science B.V. All rights reserved.

FE analysis of piezo-laminate composites under thermal loads

A shear flexible 4-noded finite element formulation, having five mechanical degrees of freedom per node, is presented for modeling the dynamic as well as the static thermal response of laminated composites containing distributed piezoelectric layers. This element has been developed to have one electrical degree of freedom per piezoelectric layer. The mass, stiffness and thermo-electro-mechanical coupling effects on the actuator and sensor layers have been considered. Numerical studies have been conducted to investigate both the sensory and active responses on piezoelectric composite beam and plate structures. It is. concluded that both the thermal and pyroelectric effects are important and need to be considered in the precision distributed control of intelligent structures.

Understanding glassy dynamics from the free-energy landscape

Many interesting features of the dynamics of simple liquids near the glass transition may be understood in terms of properties of the free-energy landscape obtained from numerical studies of a model free-energy functional. Main results obtained from this approach are summarized and a list of references to relevant publications is provided. (C) 2002 Elsevier Science B.V. All rights reserved.

Dynamics and transport properties of Kondo insulators

A many-body theory of paramagnetic Kondo insulators is described, focusing specifically on single-particle dynamics, scattering rates, dc transport and optical conductivities. This is achieved by development of a non-perturbative local moment approach to the symmetric periodic Anderson model within the framework of dynamical mean-field theory. Our natural focus is the strong-coupling, Kondo lattice regime, in particular the resultant 'universal' scaling behaviour in terms of the single, exponentially small low-energy scale characteristic of the problem. Dynamics/transport on all relevant (ω, T)-scales are considered, from the gapped/activated behaviour characteristic of the low-temperature insulator through to explicit connection to single-impurity physics at high ω and/or T; and for optical conductivities emphasis is given to the nature of the optical gap, the temperature scale responsible for its destruction and the consequent clear distinction between indirect and direct gap scales. Using scaling, explicit comparison is also made to experimental results for dc transport and optical conductivities of Ce3Bi4Pt3, SmB6 and YbB12. Good agreement is found, even quantitatively; and a mutually consistent picture of transport and optics results.

Bacterial transformation using micro-shock waves

Shock waves are one of the most competent mechanisms of energy dissipation observed in nature. We have developed a novel device to generate controlled micro-shock waves using an explosive-coated polymer tube. In this study, we harnessed these controlled micro-shock waves to develop a unique bacterial transformation method. The conditions were optimized for the maximum transformation efficiency in Escherichia coli. The maximum transformation efficiency was obtained when we used a 30 cm length polymer tube, 100 mu m thick metal foil, 200 mM CaCl(2), 1 ng/mu l plasmid DNA concentration, and 1 x 10(9) cell density. The highest transformation efficiency achieved (1 x 10(-5) transformants/cell) was at least 10 times greater than the previously reported ultrasound-mediated transformation (1 x 10(-6) transformants/cell). This method was also successfully employed for the efficient and reproducible transformation of Pseudomonas aeruginosa and Salmonella typhimurium. This novel method of transformation was shown to be as efficient as electroporation with the added advantage of better recovery of cells, reduced cost (40 times cheaper than a commercial electroporator), and growth phase independent transformation. (C) 2011 Elsevier Inc. All rights reserved.

Thermodynamics of oxide sulfate melts: The system PbO PbSO4

Activities in the PbO-PbSO4 melts at 1253 K have been measured by emf and gas-equilibration techniques. The activity of PbO was directly obtained from the emf of the solid oxide cell, Pt, Ni-NiO/CaO-ZrO2/Auo.92PbO.08, PbOx-PbSO4(1-x), Ir, Pt for 1.0 >XPbO > 0.6. The melt and the alloy were contained in closed zirconia crucibles. Since the partial pressure of SO2 gas in equilibrium with the melt and alloy was appreciable (>0.08 atm) atXPbO < 0.6, activities at lower PbO concentrations were derived from measurements of the weight gain of pure PbO under controlled gas streans of Ar + SO2 + O2. The partial and integral free energies of mixing at 1253 K were calculated and found to fit a subregular model: ΔGEPbO =X2PbSO4 {-42,450 + 20,000X2PbSO4} J mol-1 ΔGEPbO =X2pbSO {-12,450 - 20,000XPbS} J mol-1 ΔGEpbSOXPbSO4 {-32,450XPbS - 22,450XPbSO4 } J mol-1. The standard free energy of formation of liquid PbSO4 from pure liquid PbO and gaseous SO3 at 1 atm at 1253 K was evaluated as -88.02 (±0.72) kJ mol-1.