Efficient Elemental Iodine Catalyzed One-Pot Synthesis of 2,4,5-Triarylimidazoles

Elemental iodine is used as an efficient catalyst for the synthesis of 2,4,5-triarylimidazoles in excellent yields via condensation of benzoin, ammonium acetate, and aromatic aldehydes. This is a simple, one-pot, high yielding technique using cheap, non-toxic iodine in catalytic amounts.     

Copper(II) complexes of acid amide derivatives of 2-aminopyridineand an exogenous ligand

The bidentate ligands, 2-[(N-acetyl)aminopyridine] (AAPH, A) and 2-[(N-benzoyl)aminopyridine] (BAPH, B) have been used to synthesize copper(II) complexes including an exogenous ligand X (X = AcO^–, HCO₂ ^–, N₃ ^– and benzimidazole). The complexes were characterized by elemental analysis, electronic and vibrational spectroscopy, magnetic and e.s.r. studies. E.s.r. parameters and visible spectra indicated that all the complexes are monomers and exist in distorted octahedral geometry except for benzimidazole. With benzimidazole as an exogenous ligand, a five coordinate complex is formed.     

Spectroscopic study of overtone and combination bands in aliphatic aldehydes

Overtone spectra of C–H stretching vibrations of formaldehyde, acetaldehyde and n-butyraldehyde have been studied in liquid phase using conventional absorption and thermal lens techniques. The overtone bands up to Δν = 4 have been monitored using the conventional IR and NIR techniques and the band involving Δν = 7 of the C–H stretching vibration with thermal lens technique. The vibrational frequencies and the anharmonicity constants for C–H stretching vibrations of the methyl as well as of the aldehyde groups for all the three molecules have been determined using these data. We have also calculated the vibrational frequencies of fundamental bands and charge distribution on carbon and hydrogen atoms using ab initio methods and the results are compared with the experimental data.     

Effect of injecting electrodes on TSD behaviour of vacuum deposited PVF films

Depolarization behaviour of vacuum deposited polyvinyl fluoride (PVF) films has been studied as a function of nature of the electrode materials used during polarization such as copper, silver, aluminium and indium using the thermally stimulated discharge current (TSD) technique. TSD spectra of these films show a single relaxation peak centered around 430 ± 1 K with activation energies of ∼ 0.65 eV. The peak current and the charge associated with the relaxation peak depend strongly on the electrode material used. This has been attributed to the electrode-polymer interface barrier controlling the injection of the charge carriers into PVF films that results into space charge effects by subsequent trapping of the injected charge carriers at macroscopic distances. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Thermal stresses in an elastic sphere containing a penny-shaped crack

Zusammenfassung Es wird der Spannungszustand in einer elastischen Kugel untersucht, die im Zentrum einen münzenförmigen Riss mit konstanter Oberflächentemperatur besitzt, während die sphärische Oberfläche auf der Temperatur null gehalten wird. Dabei wird angenommen, dass an der Oberfläche a) die Schubspannung und die radiale Verschiebung, b) die Normalspannung und die Schubspannung null sind.

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This work was supported by a C.S.I.R. grant No. 3(277)/69-GAU-II.     

Structure of poly(methyl methacrylate) chains adsorbed on sapphire probed using infrared-visible sum frequency generation spectroscopy

We have studied the orientation of the train segments of a poly(methyl methacrylate) (PMMA) adsorbed layer at the CCl4-sapphire interface using surface-sensitive IR-visible sum frequency generation (SFG) spectroscopy. The SFG spectra of PMMA chains adsorbed on sapphire indicate ordered ester methyl groups. In comparison, we did not observe any significant contributions from the backbone methylene and alpha methyl groups, suggesting that these groups are disordered. No change in the structure of the adsorbed layer is observed upon cooling the solvent below the theta temperature; this is consistent with the picture of flat adsorbed chains on the surface. Interestingly, the orientation of the ester methyl groups of a spin-coated PMMA film at the PMMA-sapphire interface is similar to that of the same groups in the chains adsorbed from solution.     

Parameter adaptation technique for rapid synchronization and secure communication

An effort is made here to show how parameter adaptation can be used for achieving rapid synchronization between two chaotic systems in a time much smaller than the time scale of chaotic oscillations. This rapid synchronization can be used for faster and more secure communication of digital messages. Different symbols of the message are coded by assigning different values to a parameter set. At the receiving end the parameter values quickly adapt to the changing transmitter parameters, thereby permitting the messages to be decoded. The technique presented here is significantly more secure compared to other similar schemes because in our scheme the transmitting parameters change so rapidly that an intruder cannot infer any information about the attractors corresponding to the different parameter values. Another feature, which enhances security, is that a subsystem of the transmitter can be changed, without having to convey this information to the bona fide recipient. Thus for the same plaintext and the same key, several different cipher-texts can be generated. Further, the variables, whose evolution equations contain the coding parameters, are not transmitted.     

Analysing factors affecting the choice of emergent human resource capital

Ever since the announcement that UK higher education (HE) fees were to increase up to £9000, many universities have expressed concern about how to attract the best students while offering choice and promoting student mobility through broader access. This in turn has led to questioning how such complexity might be modelled using sophisticated operational research (OR) techniques. Because higher education institutions (HEIs) are now beginning to compete ‘against’ rather than ‘with’ each other, potential students are paying increased attention to where and what they will study, as well as graduate opportunities after their degree. Hence, the quality of education services becomes increasingly vital for HEIs in order to attract potential students. This study seeks to develop a framework of those factors affecting international (non-EU) students’ choice of institution. A number of factors were identified and collated from the existing literature providing a solid foundation on which to base this research. A survey approach was utilised to determine the importance of identified factors based on data collected from students of two different types of institutions (a university and a feeder institution). Through a better understanding of factors such as social influence, financial and career opportunities, universities should be well placed to construct models underpinned by OR principles that will promote scenario modelling and planning within HE.     

Efficacy of Organophosphorus Derivatives Containing Substituted Chalcone Thiosemicarbazones and Dithiocarbazates Against Fungal Pathogens of Sugarcane

Ten novel organophosphorus derivatives have been prepared by the reactions of O,O-diethylchlorophosphate with two important series of substituted chalcones viz., substituted chalcone thiosemicarbazones and substituted chalcone dithiocarbazates. The derivatives have been characterized on the basis of analysis and spectral (IR, 1 H NMR) data. Fungicidal activity of these derivatives against Colletotrichum falcatum , Fusarium oxysporum , and Curvularia pallescens have been evaluated. The screening results have been correlated with the structural features of the tested compounds. Organophosphorus derivatives containing 2,2'-dihydroxybenzalacetophenone thiosemicarbazone, 2-chlorobenzal-2'-hydroxyacetophenone thiosemicarbazone, 2-chlorobenzal-2'-hydroxy acetophenone-S-benzyldithiocarbazate proved more active than some prevalent commercial synthetic fungicides.