The effect of halogen atom on the molecular quadratic nonlinearity of half sandwich complexes in the presence of an acceptor

Half sandwich complexes of the type [CpM(CO)(n)X] {X=Cl, Br, I; If, M=Fe, Ru; n=2 and if M=Mo; n=3} and [CpNiPPh3X] {X=Cl, Br, I} have been synthesized and their second order molecular nonlinearity (beta) measured at 1064 nm in CHCl3 by the hyper-Rayleigh scattering technique. Iron complexes consistently display larger beta values than ruthenium complexes while nickel complexes have marginally larger beta values than iron complexes. In the presence of an acceptor ligand such as CO or PPh3, the role of the halogen atom is that of a pi donor. The better overlap of Cl orbitals with Fe and Ni metal centres make Cl a better pi donor than Br or I in the respective complexes. Consequently, M-pi interaction is stronger in Fe/Ni-Cl complexes. The value of beta decreases as one goes down the halogen group. For the complexes of 4d metal ions where the metal-ligand distance is larger, the influence of pi orbital overlap appears to be less important, resulting in moderate changes in beta as a function of halogen substitution. (C) 2006 Elsevier B.V. All rights reserved.

Effect of process parameters on transport phenomena during solidification in the presence of electromagnetic stirring

In the present work, a numerical study is performed to predict the effect of process parameters on transport phenomena during solidification of aluminium alloy A356 in the presence of electromagnetic stirring. A set of single-phase governing equations of mass, momentum, energy and species conservation is used to represent the solidification process and the associated fluid flow, heat and mass transfer. In the model, the electromagnetic forces are incorporated using an analytical solution of Maxwell equation in the momentum conservation equations and the slurry rheology during solidification is represented using an experimentally determined variable viscosity function. Finally, the set of governing equations is solved for various process conditions using a pressure based finite volume technique, along with an enthalpy based phase change algorithm. In present work, the effect of stirring intensity and cooling rate are considered. It is found that increasing stirring intensity results in increase of slurry velocity and corresponding increase in the fraction of solid in the slurry. In addition, the increasing stirring intensity results uniform distribution of species and fraction of solid in the slurry. It is also found from the simulation that the distribution of solid fraction and species is dependent on cooling rate conditions. At low cooling rate, the fragmentation of dendrites from the solid/liquid interface is more.

Effect of cold exposure on the metabolism of ubiquinone in the rat

1. Accumulation of ubiquinone in the livers of rats exposed to a cold environment was shown to be due to both decreased catabolism during the entire experimental period and increased synthesis during an intermediate stage (10–20 days). 2. The increased endogenous synthesis in the cold-exposed rats was eliminated when ubiquinone accumulated in the liver after exposure for 40 days (coinciding with cclimatization), or by absorption of the exogenous dietary supply, possibly by the mechanism of end-product regulation.

Effect of soil tillage on erosion and nutrient transport in plough layer runoff

Yhteenveto: Viljelymenetelmien vaikutus eroosioon ja ravinteiden huuhtoutumiseen

Effect of La modification on antiferroelectricity and dielectric phase transition in sol-gel grown PbZrO3 thin films

Antiferroelectricity of sol-gel grown pure and La modified PbZrO3 thin films, with a maximum extent of 6 mol%, has been characterized by temperature dependent P-E hysteresis loops within the applied electric field of 60 MV/m. It has been seen that on extent of La modification electric field induced phase transformation can be altered and at 40 degrees C its maximum value has been observed at +/- 38 MV/m on 6 mol% modifications whereas the minimum value is +/- 22 MV/m on 1 mol%. On La modification the variation of electric field induced phase transformations at 40 degrees C has been correlated with the temperature of ntiferroelectric phase condensation on cooling. The critical electric fields for saturated P-E hysteresis loops have been defined from field dependent maximum polarizations and their variations on La modification show a similar trend as found in their dielectric phase transition temperatures. (C) 2010 Elsevier Ltd. All rights reserved.

Effect of Strain Rate on Evolution of the Deformation Microstructure and Texture in Polycrystalline Copper and Nickel

The evolution of crystallographic texture in polycrystalline copper and nickel has been studied. The deformation texture evolution in these two materials over seven orders of magnitude of strain rate from 3 x 10(-4) to similar to 2.0 x 10(+3) s(-1) show little dependence on the stacking fault energy (SFE) and the amount of deformation. Higher strain rate deformation in nickel leads to weakerh < 101 > texture because of extensive microband formation and grain fragmentation. This behavior, in turn, causes less plastic spin and hence retards texture evolution. Copper maintains the stable end < 101 > component over large strain rates (from 3 x 10(-4) to 10(+2) s(-1)) because of its higher strain-hardening rate that resists formation of deformation heterogeneities. At higher strain rates of the order of 2 x 10(+3) s(-1), the adiabatic temperature rise assists in continuous dynamic recrystallization that leads to an increase in the volume fraction of the < 101 > component. Thus, strain-hardening behavior plays a significant role in the texture evolution of face-centered cubic materials. In addition, factors governing the onset of restoration mechanisms like purity and melting point govern texture evolution at high strain rates. SFE may play a secondary role by governing the propensity of cross slip that in turn helps in the activation of restoration processes.

Effect of process variables on die-billet temperature history in a slow speed hot coining type process

A computer code is developed as a part of an ongoing project on computer aided process modelling of forging operation, to simulate heat transfer in a die-billet system. The code developed on a stage-by-stage technique is based on an Alternating Direction Implicit scheme. The experimentally validated code is used to study the effect of process specifics such as preheat die temperature, machine ascent time, rate of deformation, and dwell time on the thermal characteristics in a batch coining operation where deformation is restricted to surface level only.

Effect of Li+-ion on enhancement of photoluminescence in Gd2O3:Eu3+ nanophosphors prepared by combustion technique

Gd2O3:Eu3+ (4 mol%) nanophosphor co-doped with Li+ ions have been synthesized by low-temperature solution combustion technique in a short time. Powder X-ray diffractometer (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-VIS and photoluminescence (PL) techniques have been employed to characterize the synthesized nanoparticles. It is found that the lattice of Gd2O3:Eu3+ phosphor transforms from monoclinic to cubic as the Li+-ions are doped. Upon 254 nm excitation, the phosphor showed characteristic luminescence D-5(0) -> F-7(J) (J= 0-4) of the Eu3+ ions. The electronic transition located at 626 nm (D-5(0) -> F-7(2)) of Eu3+ ions was stronger than the magnetic dipole transition located at 595 nm (D-5(0) -> F-7(1)). Furthermore, the effects of the Li+ co-doping as well as calcinations temperature on the PL properties have been studied. The results show that incorporation of Li+ ions in Gd2O3:Eu3+ lattice could induce a remarkable improvement of their PL intensity. The emission intensity was observed to be enhanced four times than that of with out Li+-doped Gd2O3:Eu3+. (C) 2010 Elsevier B.V. All rights reserved,

Effect of anchor width on pullout capacity of strip anchors in sand

By incorporating the variation of peak soil friction angle (phi) with mean principal stress (sigma(m)), the effect of anchor width (B) on vertical uplift resistance of a strip anchor plate has been examined. The anchor was embedded horizontally in a granular medium. The analysis was performed using lower bound finite element limit analysis and linear programming. An iterative procedure, proposed recently by the authors, was implemented to incorporate the variation of phi with sigma(m). It is noted that for a given embedment ratio, with a decrease in anchor width (B), (i) the uplift factor (F-gamma) increases continuously and (ii) the average ultimate uplift pressure (q(u)) decreases quite significantly. The scale effect becomes more pronounced at greater embedment ratios.