A Mössbauer and electrochemical study of mononuclear iron(III) complexes with benzimidazole-based flexible bidentate ligands

A series of FeIII complexes of stoichiometry [FeLX3].nH2O have been synthesized, where X=Cl–, HCO–2 and L is a flexible bidentate ligand, 1,3(bis-benzimidazolyl) propane and 1,4(bis-benzimidazolyl)butane. Mössbauer data reveals that the isomer shift values lie in the range typically observed for high spin FeIII complexes, while the slightly large quadrupole splitting parameter indicates a rhombically distorted FeIII centre. Cyclic voltammetric studies reveal that the E1/2 for the FeIII/FeII couple for the formate complex shifts more cathodically than for the chloride complex; implying that HCO–2 is more effective at lowering the Lewis acidity of the FeIII centre.     

Etching and Dissolution Mechanism of Cadmium Oxalate Trihydrate Crystals

Dislocation etching and dissolution of gel-grown cadmium oxalate trihydrate crystals are carried out using different etchants. The study revealed the existence of dislocation network in the body of the crystal and shallow dislocation loops in the substructure. Faster dissolution of the crystal at elevated temperatures revealed that the rate of dissolution in the initial part of the dissolution time is much lesser, which increases fast to attain a steady value. This observation is related to the available specific surface area of the crystal.     

Growth and properties of calcium tungstate

CaWO₄ single crystals have been grown and compared by three different high temperature solution methods, viz. the normal flux-cooling procedure, the indirect flux-reaction technique and the isothermal flux-evaporation method. The typical as-grown bipyramidal crystals obtained by these methods have been found to be mostly large and perfect with varying degree of transparency. The crystals are characterised by using EDAX, X-ray diffraction, electrical conduction, micromechanical tests and chemical etching. The assessment of various characteristics of the grown crystals is likely to show enormous usefulness of the flux grown crystals.     

Cell theory and equation‐of‐state of chain molecular systems: Application to polymer solids

We use the Lennard‐Jones and Devonshire cell theory without any ad hoc simplification of the cell potential to obtain the equation‐of‐state (EOS) for chain molecular systems. The interactions of the central segment with second and third shells of neighbors are taken into account. Numerical values of the cell integrals are given in tabular form along with interpolation expressions that cover the range of PVT variables appropriate to polymers. Results of comparison with EOS based on square‐well form are also discussed. Application of the theory to polymer glasses of diverse structures is found to be quite successful in explaining the PVT behavior over a wide range of temperatures both at atmospheric and elevated pressures. Further, scaled volume at the glass‐transition temperature is discovered to be a corresponding state property. Turning to crystals, the theory is generally in good accordance with the PVT data of three well‐studied polymers both at atmospheric and elevated pressures. For linear polyethylene the agreement is good up to 42 kbar for the room‐temperature isotherm. On the other hand, at higher temperatures where the data are limited to 5 kbar, the agreement is determined to be satisfactory for the three polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 515–530, 2001     

A Convenient One Step Synthesis of 1,3-Diaryl-6-methyl-4-oxo-1,2,3,4-tetrahydro-2-thioxofuro [2,3-d] Pyrimidines

1,3-Diaryl-6-methyl-4-oxo-1,2,3,4-tetrahydro-2-thioxofuro (2,3-d) pyrimidines have been synthesised in one step in good yield by the reaction of 1,3-diaryl-1,3-dihydro-2-thioxo-2H,5H-pyrimidine-4,6-diones with chloroacetone in presence of triethylamine.     

Photochemical Transformations of Some 2‐(5‐Methylthiophen‐2‐yl)‐3‐[(naphthalen‐2‐yl)methoxy]‐4H‐chromen‐4‐ones Involving Type‐II Process

Photo‐irradiation of 2‐(5‐methylthiophen‐2‐yl)‐3‐[(naphthalen‐2‐yl)methoxy]‐4H‐chromen‐4‐ones yielded the fascinating angular tetracyclic products via cyclization involving both 2‐thienyl ring and naphthylmethoxy group via 1,4‐biradical generated in the Norrish type‐II process. The stereochemical dispositions of the products were determined by MM2 energy minimized programme and spectroscopic analysis.     

Cross layer based fast handover for IEEE 802.16e networks

To guarantee the QoS in real time applications in wireless networks, handover delay is one of the most important parameters to be considered while mobile users are changing their point of attachment to the access networks. This calls for a fast handover mechanism that will be able to offer uninterrupted services to mobile users. In this paper, a cross layer based fast handover mechanism is proposed to reduce handover delay and signaling load in IEEE 802.16e wireless metropolitan area networks. This is achieved by overlapping the functions of Medium Access Control (MAC) Layer and Internet Protocol (IP) layer. The analytical results show that the proposed mechanism significantly enhances the handover performance in terms of handover delay and signaling load thus resulting into fast handover.