Water Pollution Threat to the Environment by a Urea Plant

Disposal of untreated industrial effluents is drastically deteriorating the quality of underground water. Research work has been conducted to analyze the effect of disposal of urea plant effluent on the quality of ground water of the District Mianwali Daudkhail, Pakistan. For this purpose the effluent and ground water samples were analyzed for pH, TDS, TSS, Cl, F, COD, BOD, Fe, Zn, Pb, Cu, Cr, Cd, Mn, and As. Results obtained were compared with WHO and NEQS standards for drinking and effluent emission limits, respectively. Moreover, effluent samples were also evaluated for irrigation purposes and results compared with criteria recommended for irrigation water. Results showed though the effluents were according to the standards given by National Environmental Quality Standards (NEQS) for liquid emission and fit for irrigation purposes, the quality of underground water was below standard due to having a higher quantity of total dissolved solids than permissible.     

Addendum to “Unstable crack motion is predictable” [2005. JMPS 53, 1071]

Using a scaling relationship discussed in an earlier paper [Abraham, F. F., 2005. Unstable crack motion is predictable. J. Mech. Phys. Solids 53, 1071-1075], we find that the steady-state speed of a unidirectional crack moving in a hyperelastic solid equals the crack speed in a linear solid with our “effective spring constant”.     

Monte Carlo simulation using the Fourier transform of the interatomic potential

When doing Monte Carlo simulations using continuous potentials, the evaluation of the configurational potential energy ink-space by Fourier transformation is shown to be a computationally attractive scheme for systems where the long-range interatomic interaction spans a dimension comparable to the size of the simulated system.     

Synthesis and protein degradation capacity of photoactivated enediynes

[structure: see text] The viability of proteins as targets of thermally and photoactivated enediynes has been confirmed at the molecular level. Model studies using a labeled substrate confirmed the efficacy of atom transfer from diyl radicals produced from enediynes to form captodatively stabilized carbon centered aminoacyl radicals, which then undergo either fragmentation or dimerization. To exploit this finding, a family of enediynes was developed using an intramolecular coupling strategy. Derivatives were prepared and used to target specific proteins, showing good correlation between affinity and photoinduced protein degrading activity. The findings have potential applications in the design of artificial chemical proteases and add to our understanding of the mechanism of action of the clinically important enediyne antitumor antibiotics.     

On the validity of the capillarity approximation in the rate theory of homogeneous nucleation

An Einstein model is used to calculate the internal vibrational free energy of approximately spherical fcc crystallites as a function of crystallite size at T/θ = 1. It is found that the free energy per surface atom does not become convergent until a size of about 3 × 10⁷ atoms is reached. The excess free energy at convergence is used to define the macroscopic surface tension for use in the capillarity approximation. The internal free energy of microcrystallites containing of the order of 100 atoms is fortuitously well described by the capillarity approximation. A good estimate of the total free energy of the microcrystallite (nucleus) is obtained from the capillarity approximation only by adding the contributions from free translation and rotation and the replacement partition function.     

A computer simulation of an amorphous thin film on a crystalline substrate

We employ the Monte Carlo simulation method of classical statistical mechanics to study the structure and energetics of the crystal/amorphous interface. The interface is found to be approximately four atomic layers thick and provides good bonding between the amorphous and crystalline phases.     

A synthetic route to thionolactones

The treatment of O-alkyllactonium tetrafluoroborate salts with anh. NaSH in CH₃CN at 0°C led to five-, six-, and seven-membered thionolactones (44– 90% yield).     

A degenerate elliptic-parabolic system arising in competitive contaminant transport

The objective of this work is to study a coupled system of degenerate and nonlinear partial differential equations governing the transport of reactive solutes in groundwater. We show that this system admits a unique weak solution provided the nonlinear adsorption isotherm associated with the reaction process satisfies certain physically reasonable structural conditions, by addressing a more general problem. In addition, we conclude, that the solute concentrations stay non-negative if the source term is componentwise non-negative and investigate numerically the finite speed of propagation of compactly supported initial concentrations, in a two-component test case.