Interaction of rat testis protein, TP, with nucleosome core particle

Circular dichroism studies have revealed that addition of testis specific protein, TP in vitro, to rat testes nucleosome core particle resulted in a decrease in the compaction of the core particle DNA. This was also corroborated by thermal denaturation analysis. Addition of TP to nucleosome core particle resulted in the conversion of a biphasic transition towards a single phase. However, at the same time there was a 20% reduction in the overall hyperchromicity of core particle DNA at core particle to TP molar ratios of 1:2 and 1:3. These observations along with our earlier report, showing the DNA melting properties of TP, suggest that TP may play an important role in the disassembly process of nucleosome core particle during spermiogenesis.

Combustion synthesis of rare earth cuprates

Rare earth cuprates, La2CuO4 Nd2CuO4, La1.8M0.2CuO4 (M=Ca.Sr) and Nd1.85Ce0.15CuO4 have been prepared by the combustion of redox mixtures containing corresponding metal nitrates and maleic hydrazide, C4H4N2O2, at 350°C. The solid combustion products are submicron size amorphous powders which on heat treatment (700°C, 30 minutes) yield crystalline single phase cuprates. Strontium doped lanthanum cuprate, La1.8Sr0.2CuO4, shows an onset of superconductivity at 36K.

A new perovskite series based on lanthanum chromite [LaCr1−xMxO3−δ]

A new series of substituted perovskites of the type LaCr1−xMxO3−δ, where M=Cu or Mg have been synthesised by the citrate gel process and characterized by means of powder X-ray diffraction, infrared spectroscopy, selected area diffraction and also by electron paramagnetic resonance spectroscopy. The general powder morphology was also observed using scanning electron microscopy. 40 mole percent substitution of Cr3+ by Cu2+ or Mg2+ have shown to result in single phase perovskite structure. Beyond x=0.5, a new phase has been identified in a narrow compositional range. Effect of Cu and Mg substitution on the sinterability of pure LaCrO3 has also been studied. It is possible to get near theoretically dense materials at a temperature as low as 1200°C in air by copper substitution.

Combustion synthesis and properties of fine-particle rare-earth-metal zirconates, Ln2Zr2O7

Fine-particle rare-earth-metal zirconates, Ln2Zr2O7, where Ln = La, Ce, Pr, Nd, Sm, Gd and Dy having the pyrochlore structure have been prepared using a novel combustion process. The process employs aqueous solutions of the corresponding rare-earth-metal nitrate, zirconium nitrate and carbohydrazide/urea in the required molar ratio. When the solution is rapidly heated to 350–500 °C it boils, foams and burns autocatalytically to yield voluminous oxides. The formation of single-phase Ln2Zr2O7 has been confirmed by powder X-ray diffraction, infrared and fluorescence spectroscopy. The solid combustion products are fine, having surface areas in the range 6–20 m2 g–1. The cold-pressed Pr2Zr2O7 compact when sintered at 1500 °C, 4 h in air, achieved 99% theoretical density.

Combustion Synthesis and Properties of Fine Particle Spinel Manganites

Fine particle spinel manganites have been prepared by thermal decomposition of the precursors N2H5M1/3Mn2/3(N2H3COO)3 · H2O (M = Co and Ni) and M1/3 Mn2/3(N2H3COO)2 · 2H2O (M = Mg and Zn), as well as by the combustion of redox mixtures containing M(II) nitrate (M = Mg, Co, Ni, Cu, and Zn), Mn(II) nitrate, and maleic hydrazide (MH) in the required molar ratio. Both the precursor and redox mixtures undergo self-propagating, gas-producing, exothermic reactions once ignited at 250-375°C to yield corresponding manganites in less than 5 min. Formation of single phase products was confirmed by X-ray powder diffraction patterns. The manganites are of submicrometer size and have surface area in the range 20-76 m2/g.

Effect of Substitution of Ca on Thermal Expansion of Cordierite (Mg2Al4Si5O18)

The effect of substitution of calcium on the anisotropic axial thermal expansion of cordierite was investigated by using a high-temperature X-ray diffraction technique. The compositions were prepared by the sol–gel route. In the Mg2-xCax-Al4Si5O18 system, single-phase cordierite can be prepared for x up to 0.5. Thermal expansion anisotropy (αa–αc) of cordierites reduces progressively by the substitution of increasing amounts of Ca for Mg.

Observations on transition in plane bubble plumes

Flow visualization studies of plane laminar bubble plumes have been conducted to yield quantitative data on transition height, wavelength and wave velocity of the most unstable disturbance leading to transition. These are believed to be the first results of this kind. Most earlier studies are restricted to turbulent bubble plumes. In the present study, the bubble plumes were generated by electrolysis of water and hence very fine control over bubble size distribution and gas flow rate was possible to enable studies with laminar bubble plumes. Present observations show that (a) the dominant mode of instability in plane bubble plumes is the sinuous mode, (b) transition height and wavelength are related linearly with the proportionality constant being about 4, (c) wave velocity is about 40 % of the mean plume velocity, and (d) normalized transition height data correlate very well with a source Grashof number. Some agreement and some differences in transition characteristics of bubble plumes have been observed compared to those for similar single-phase flows.

Some features of spray breakup in effervescent atomizers

The near orifice spray breakup at low GLR (gas to liquid ratio by mass) values in an effervescent atomizer is studied experimentally using water as a simulant and air as atomizing gas. From the visualizations, the near orifice spray structures are classified into three modes: discrete bubble explosions, continuous bubble explosions and annular conical spray. The breakup of the spray is quantified in terms of the mean bubble bursting distance from the orifice. The parametric study indicates that the mean bubble bursting distance mainly depends on airflow rate, jet diameter and mixture velocity. It is also observed that the jet diameter has a dominant effect on the bubble bursting distance when compared to mixture velocity at a given airflow rate. The mean bubble bursting distance is shown to be governed by a nondimensional two-phase flow number consisting of all the aforementioned parameters. The location of bubble bursting is found to be highly unsteady spatially, which is influenced by flow dynamics inside the injector. It is proposed that this unsteadiness in jet breakup length is a consequence of varying degree of bubble expansion caused due to the intermittent occurrence of single phase and two-phase flow inside the orifice.

Combustion synthesis and properties of Ln3Fe5O12 and yttrium aluminium garnets

The rare earth iron garnets Ln3Fe5O12 and Y3AlxFe5-xO12, where x=1.0-5.0, and Y1.5Gd1.5Al0.2Fe4.8O12 have been prepared by the combustion of redox mixtures containing corresponding metal nitrates and oxalyl dihydrazide, i.e. C2H6N4O2 at 350-degrees-C. The solid combustion products are amorphous, submicrometre-sized powders which, on heating at 750-degrees-C for 3 h, yield crystalline single-phase garnets. The particle size of the garnets is below 1 mum and the surface area ranges from 16 to 90 m2 g-1. Yttrium iron garnet could be sintered to a density of more than 95% at 1200-degrees-C for 3 h, giving an average grain size of 3-5 mum.

Synthesis and properties of tialite, beta-AL2TIO5

Tialite, beta-Al2TiO5, a low expansion material, has been synthesised by the combustion of corresponding metal nitrates and carbohydrazide (CH) or urea redox mixtures at 500-degrees-C. As prepared powders contained tialite, rutile, and corundum in the mole ratios of 50:25:25 (CH) and 20:40:40 (urea). The combustion derived powders, when calcined 30 min at 1300-degrees-C, gave single phase beta-tialite having a surface area of 20-25 m2 g-1 and a particle size of 0.79-1.03 mum.

Analysis of texture evolution in pure magnesium and the magnesium alloy AM30 during rod and tube extrusion

The evolution of microstructure and texture during extrusion of pure magnesium and its single phase alloy AM30 has been studied experimentally as well as by crystal plasticity simulation. Microstructure and micro-texture were characterized by electron back scattered diffraction (EBSD), bulk-texture was measured using X-ray diffraction and deformation texture simulations were carried out using visco-plastic self consistent (VPSC) model. In spite of clear indications of the occurrence of dynamic recrystallization (DRX), simulations were able to reproduce the experimental textures successfully. This was attributed to the fact that the textures were c-type fibers with their axis of rotation parallel to the c-axis and DRX leads to simply rotate the texture around the c-axis. (C) 2011 Elsevier B.V. All rights reserved.

Constrained optimization of heat exchangers

Optimizing a shell and tube heat exchanger for a given duty is an important and relatively difficult task. There is a need for a simple, general and reliable method for realizing this task. The authors present here one such method for optimizing single phase shell-and-tube heat exchangers with given geometric and thermohydraulic constraints. They discuss the problem in detail. Then they introduce a basic algorithm for optimizing the exchanger. This algorithm is based on data from an earlier study of a large collection of feasible designs generated for different process specifications. The algorithm ensures a near-optimal design satisfying the given heat duty and geometric constraints. The authors also provide several sub-algorithms to satisfy imposed velocity limitations. They illustrate how useful these sub-algorithms are with several examples where the exchanger weight is minimized.

Preparation, structure, and properties of strontium-doped lanthanum chromites: La1−xSrxCrO3

Strontium-doped lanthanum chromites, La1−xSrxCrO3, have been synthesised to investigate the effect of strontium doping on the stability and physico-chemical characteristics of the perovskite LaCrO3. Both microscopic and X-ray examinations show that the materials exist as single phase perovskite structure for all compositions up to 50 mole% strontium substitution. The materials have been further characterized by infrared and electron paramagnetic resonance spectra. These materials show a good sinterability even in air at 1773 K. Electrical conductivity of thse perovskites has been measured as a function of temperature. Electrical conductivity has been found to be a maximum at x=0.2. The observed electrical and magnetic properties are consistent with activated polaron transport as the mechanism for electrical conduction in these materials.

Combustion synthesis and properties of nanostructured ceria-zirconia solid solutions

Nanostructured ceria-zirconia solid solutions (Ce1 − xZrxO2, X = 0 to 0.9) have been synthesized by a single step solution combustion process using cerous nitrate, zirconyl nitrate and oxalyl dihydrazide (ODH) / carbohydrazide (CH). The as-synthesized powders show extensive XRD line broadening and the crystallite sizes calculated from the XRD line broadening are in the nanometer range (6–11 nm). The combustion derived ceria zirconia solid solutions have high surface area in the range of 36–120 m2/g. Calcination of Ce1 −xZrxO2 at 1350 °C showed three distinct solid solution regions: single phase cubic (x ≤ 0.2), biphasic cubic-tetragonal (0.2 < x Image .8) and tetragonal (x > 0.8). When x ≥ 0.9, the metastable tetragonal phase formed transforms to monoclinic phase on cooling after calcination above 1100 °C. The homogeneity of Ce1 − xZrxO2 has been confirmed by EDAX analysis. The Temperature Programmed Reduction (TPR) measurement of Ce0.5Zr0.5O2 was carried out with H2 and the TPR profile showed two water formation peaks corresponding to the utilization of surface and bulk oxygen.

Microstructural stability and superplasticity in an electrodeposited nanocrystalline Ni-P alloy

Stabilization of nanocrystalline grain sizes by second phase particles can facilitate superplasticity at high strain rates and/or low temperatures. A metastable single phase nano-Ni-P alloy prepared by electrodeposition, with a grain size of similar to 6 nm, transforms to a nanoduplex structure at T> 673 K, with similar to 4 vol.% Ni3P particles at triple junctions and within Ni grains. The nanoduplex microstructure is reasonably stable up to 777 K, and the growth of Ni grains occurs in a coupled manner with the growth of Ni3P particles such that the ratio of the two mean sizes (Z) is essentially constant. High temperature tests for a grain size of 290 nm reveal superplastic behavior with an optimum elongation to failure of 810% at a strain rate of 7 x 10(-4) s(-1) and a relatively low temperature of 777 K. Superplastic deformation enhances both grain growth and the ratio Z, implying that grain boundary sliding (GBS) significantly influences the microstructural dynamics. Analysis of the deformation processes suggests that superplasticity is associated with GBS controlled by the overcoming of intragranular particles by dislocations, so that deformation is independent of the grain size. The nano-Ni-P alloy exhibits lower ductility than nano-Ni due to concurrent cavitation caused by higher stresses. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.