Self consistent field MO studies of the vinylguanidinium ion

Ab initio Hartree–Fock calculations are used to predict the effect of substituting one hydrogen on the guanidinium ion by a vinyl group. The results show no overlap between the π-electron system of the guanidinium moiety and that of the vinyl group.     

Chemical effects of heavy metals on the hydration of calcium sulphoaluminate 4CaO·3Al2O3·SO3

The system 4CaO·3Al₂O₃·SO₃-CaSO₄·2H₂O-Ca(OH)₂ was hydrated in the presence of ten dopants, specifically soluble salts of heavy metals.When added in 10% amount, the effect of each salt is strongly evident at shorter curing times, the hydration kinetics being more favoured in the order Pb(NO₃)₂2CrO₄< Cd(NO₃)₂< Zn(NO₃)₂t~Mn(NO₃)₃=K₂MoO₄3)₂3)₂3)₃3)₃. At longer curing times the differences among the systems decrease significantly.The 28-day compressive strength is almost the same for all the systems except those containing Pb(NO₃)₂, K₂MoO₄ and K₂CrO₄.     

Vibronic coupling in electronic transitions with significant Duschinsky effect

Conceptual and mathematical difficulties arise in the study of transitions between vibronic states belonging to crossing Born-Oppenheimer hypersurfaces with significantly different positions and shapes of the minimum-energy nuclear configurations (Duschinsky effect). This article presents an analytic procedure for the evaluation of the pertinent coupling integrals, adopting a normal coordinate reference system for the internal nuclear motion and harmonic approximation. The Duschinsky effect is properly considered. The procedure was applied to the dynamics of electron transfer in neutral mixed valence monoradicals, using the diabatic representation. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 233–244, 1997     

Dynamics of beams with uncertain crack depth: stochastic versus interval analysis

Meccanica - The present paper deals with the evaluation of the structural response of single-cracked beam-like structures under deterministic time variant excitations assuming the crack depth as an...     

Development and validation of a chiral liquid chromatographic method for the determination of atenolol and metoprolol enantiomers in tablet preparations.

Atenolol (AT) and metoprolol (MT) are predominantly used in the treatment of angina pectoris, certain arrhythmias, systemic hypertension, and several other cardiovascular disorders. Both compounds are produced commercially in the racemic form, although the S-form is responsible for the desired biological effect. This paper describes a simple, rapid, precise, and accurate method for separating the enantiomers of AT and MT. AT isomers are separated by using a Chiralcel OD column (250 x 4.6 mm, 10 microm), hexane-ethanoldiethylamine-acetic acid (60 + 40 + 0.2 + 0.2, v/v/v/v) as the mobile phase, and a flow rate of 1.0 mL/min. MT isomers are separated by using a mobile phase with the same components in the following proportions (40 + 60 + 0.2 + 0.2, v/v/v/v) and a flow rate of 0.8 mL/min. Ultraviolet detection was at 276 nm for both analytes. The coefficients of variation (CVs) and average recoveries (ARs) for the R-enantiomers in samples A, B, C, D, and E were 1.15 and 101.06%, 0.74 and 99.25%, 1.05 and 102.57%, 0.84 and 101.57%, and 0.86 and 98.62%, respectively. The CVs and ARs for the S-enantiomers in samples A, B, C, D, and E were 1.33 and 98.87%, 0.99 and 100.76%, 1.17 and 101.69%, 1.26 and 100.39%, and 1.40 and 99.39%, respectively. The standard curves of R-AT, S-AT, R-MT, and S-MT showed good linearity over the concentration range studied with correlation coefficients of 0.9991, 0.998, 0.9988, and 0.999, respectively.     

Atomic force microscopy study of lymphoblastoid cells under 50-Hz 2-mT magnetic field irradiation

Received: 18 December 1997/Accepted: 5 January 1998