NOPR Collection:

Some recent results in the theory of the Wiener number

1993-08-01T00:00:00Z

Title: Some recent results in the theory of the Wiener number Authors: Gutman, Ivan; Yeh, Yeong-Nan; Lee, Shyi-Long; Luo, Yeung-Long Abstract: The Wiener number (W) is equal to the some of distances between all pairs of vertices of the molecular graph. This important topological index was invented in the 1940, but vigorous research on both its theory and its applications is still going on. The aim of this article is to outline the state of the art of the theory of the Wiener number, with emphasis on the progress achieved in the last few years. In particular, we present (a) the recent results on the relation between W and intermolecular forces (which, for the first time, provide a sound physico-chemical basis for various applications of W), (b) several novel techniques for the calculation of W, (c) methods for the calculation of W of composite and highly branched molecular graphs, (d) the problem of isomer degeneracy of W, and (e) some novel mathematical results relevant to the theory of W. Page(s): 651-661

Vibrational relaxation studies on C – H and C - S stretching modes of dimethyl sulphoxide

1993-08-01T00:00:00Z

Title: Vibrational relaxation studies on C – H and C - S stretching modes of dimethyl sulphoxide Authors: Sastry, M I S; Singh, Surjit Abstract: Vibrational relaxation studies have been performed on solutions of dimethyl sulphoxide (DMSO) With various protic and aprotic solvents and metal perchlorates. Vibrational relaxation times are calculate using isotropic part of the Raman spectra of these solutions for symmetric CH₃ stretching and C - S stretching vibrations. The results are interpreted in terms of interactions of DMSO with neighbouring molecules and ions. Page(s): 662-666

A glucose sensor based on graphite paste modified with tetracyanoquinodimethane

1993-08-01T00:00:00Z

Title: A glucose sensor based on graphite paste modified with tetracyanoquinodimethane Authors: Pandey, P C; Pandey, V; Mehta, S Abstract: An arnperometric enzyme electrode for glucose based on glucose oxidase (GOD) incorporated into a graphite paste modified with tetracyanoquinodimethane (TCNQ) shows long term stability (65% loss of initial response after 26d). The sensor provides a linear response to glucose over a wide concentration range (linear=0.5-100 mmol and non-linear = 100-300 mmol). The response time of the sensor is 15-50 sec and the detection limit is 0.5 mmol. Stable response to the substrate is obtained over a period of several weeks upon storage in 0.1M phosphate buffer (pH 7.0) at room temperature. Data are presented on the influence of binder composition, anodic potential, pH, and temperature upon the electrode. A qualitative approach to the kinetic analysis of the electrode response is reported based on cyclic voltammetric data. Comparison of the electrode response is made with the data obtained using ferrocene-mediated graphite paste glucose sensor and it is concluded that TCNQ has better compatibility with the graphite paste than ferrocene derivatives though ferrocene is more efficient mediator than TCNQ. Page(s): 667-672

Synthesis and characterization of some polyalkyl- and polyalkoxy-anilines

1993-08-01T00:00:00Z

Title: Synthesis and characterization of some polyalkyl- and polyalkoxy-anilines Authors: Ahmad, Naseer; Feng, Ping; Schursky, Helen; Shah, Sharmila; Antonacci, Desiree; Cichowicz, Melissa B; Kohli, Rakesh K; MacDiarmid, Alan G Abstract: Since poly-3-alkylthiophenes are more processible than polythiophene, it is expected that poly-o-alkyl and poly-o-alkoxyanilines will evince better processibility than polyaniline. Hence, poly-o-alkyl and poly-o-alkoxyanilines (alkyl = CH₃, C₂H₅, C₃H₇, alkoxy = OCH₃, OC₂H₅, OC₃H₇) have been synthesized. The polyaniline salt is insoluble in organic solvents but these polymers are soluble both in salt and base forms. The solubility increases with increase in the length of the side chain but conductivity decreases. The polypropyl and polypropoxyanilines have been synthesized for the first time. Page(s): 673-678