Kinetic studies on saponification of ethyl acetate using an innovative conductivity‐monitoring instrument with a pulsating sensor

An innovative conductometric measurement technique using a nonconventional but high‐performance (high‐precision, high‐resolution, rapid response features for online graphic display) in house–built pulsating conductivity monitoring instrument has been deployed to study the kinetic behavior during the reaction of ethyl acetate and NaOH. A laboratory‐made constant temperature reaction bath with the facility of continuous stirring of solution for homogeneous mixing was used to carry out experiments at desired solution temperatures. Rate constants of the saponification reaction in the temperature range at various temperatures (30–55°C) were determined, and the results were compared with the reported values. Although the reported data exhibit wide scatter, our data are in agreement with some of the literature data. From these data, thermodynamic parameters such as activation energy, activation enthalpy, activation entropy, and activation free energy have been evaluated. With the introduction of this novel conductometric measurement technique, the determination of rate constants at various solution temperatures becomes much simpler and faster. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 648–656, 2011     

Harmonic manifolds with minimal horospheres

For a non-compact harmonic manifold M, we establish an integral formula for the derivative of a harmonic function on M. As an application we show that for the harmonic spaces having minimal horospheres, bounded harmonic functions are constant. The main result of this article states that the harmonic spaces having polynomial volume growth are flat. In other words, if the volume density function Θ of M has polynomial growth, then M is flat. This partially answers a question of Szabo namely, which density functions determine the metric of a harmonic manifold. Finally, we give some natural conditions which ensure polynomial growth of the volume function.     

Evidence for an anomalous redox ionic pair between Ru and Mn in SrRu0.5Mn0.5O3: an X-ray absorption spectroscopy approach

X-ray absorption spectroscopy studies of the polycrystalline SrRu0.5Mn0.5O3 have been performed at Ru, Mn-L2,3 edges. The 2p-->t2g related peak at the Ru-L2 edge is more intense than the Ru-L3 edge and a shift of the 2p-->eg related peak by approximately 0.8 eV to higher energy than that of the Ru(IV) compound, SrRuO3 is observed. In combination with a crystal field multiplet calculation approach, a possible anomalous change in the spectral features is explained based on the existence of a redox ionic pair involving Ru(IV)/Ru(v)<-->Mn(III)/Mn(IV).     

Synthesis of 2,2-dimethyl-5-hydroxy-3-(3-oxobutyl)-7-pentyl-4-chromone

Alkylation and deformylation of 2,2-dimethyl-3-hydroxymethylene-5-hydroxy-7-pentyl-4-chromone occurs in the same step to give the title compound.     

Perpendicular exchange bias and its control by magnetic,stress and electric fields

Perpendicular exchange bias (PEB) involving perpendicular magnetic anisotropy (PMA) in both the antiferromagnetic (AF) pinning and the ferromagnetic (FM) sensor layer is expected to become important in future perpendicular recording and sensing devices. Further, because of the reduced spin dimensionality, PEB promises to be easier understandable than the conventional planar exchange bias (EB). In addition to its first realization using the Ising-type AF compounds FeF2 and FeCl2 we have tested control strategies of EB being alternative to the conventional magnetic and thermal ones. Indeed, specific symmetry properties of the pinning layer have been shown to enable mechanical (viz. piezomagnetic via FeF2) and electric control (viz. magneto-electric via Cr2O3) of EB, respectively. Electric control promises to become relevant for TMR devices in MRAM technology.     

Comparative studies of the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of 25Mg+

We have employed the relativistic coupled cluster theory to calculate the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of singly ionized magnesium. Comparison with experimental and the other theoretical results are done and predictions are also made for a few low lying excited states which could be of interest. We have made comparative studies of the important many body effects contributing to the hyperfine constants for the different states of the ion.