Infrared detection of a phenylboronic acid terminated alkane thiol monolayer on gold surfaces

Polarization modulation infrared reflectance absorption spectroscopy (PM-IRRAS) and infrared reflectance absorption spectroscopy (IRRAS) have been used to characterize the formation of a self-assembled monolayer of N-(3-dihydroxyborylphenyl)-11-mercaptoundecanamide) (abbreviated PBA) on a gold surface and the subsequent binding of various sugars to the PBA adlayer through the phenylboronic acid moiety to form a phenylboronate ester. Vibrationally resonant sum frequency generation (VR-SFG) spectroscopy confirmed the ordering of the substituted phenyl groups of the PBA adlayer on the gold surface. Solution FTIR spectra and density functional theory were used to confirm the identity of the observed vibrational modes on the gold surface of PBA with and without bound sugar. The detection of the binding of glucose on the gold surface was confirmed in part by the presence of a C-O stretching mode of glucose and the observed O-H stretching mode of glucose that is shifted in position relative to the O-H stretching mode of boronic acid. An IR marker mode was also observed at 1734 cm(-1) upon the binding of glucose. Additionally, changes in the peak profile of the B-O stretching band were observed upon binding, confirming formation of a phenylboronate ester on the gold surface. The binding of mannose and lactose were also detected primarily through the IR marker mode at approximately 1736 to 1742 cm(-1) depending on the identity of the bound sugar.     

Synthetic approaches to an isostructural series of redox-active, metal tris(bipyridine) core dendrimers

Several types of six-armed, metal tris(bipyridine) core dendrimers were synthesized. Bis-4,4'-alkoxy bipyridine dendrons were prepared and employed to make tris(bipyridine) dendrimers. Although the ruthenium-centered and iron-centered dendrimers displayed quasi-reversible cyclic voltammetry, the analogous cobalt-centered complex did not. The synthesis of 4,4'-disubstituted bipyridines containing -CH(2)OR groups proceeded in low yield. The reactions of the dicarbanion of 4,4'-dimethyl bipyridine prepared with LDA and mesylate, triflate, and bromide groups were found to result in no or poor yields of carbon-carbon bond formation. Use of KDA in place of LDA resulted in much higher yields of dendritic bipyridines.     

Vibration analysis of variable thickness discs subjected to centrifugal and thermal stresses

The paper presents a numerical technique whereby the natural frequencies of transverse vibration of a disc of varying thickness profile may be determined when the disc is subject to the combined actions of centrifugal loading and complex radial temperature distribution. The study includes an optimizing programme for the generation of the most representative temperature gradient across the disc surface, resulting from peripheral heating and surface convection.In-plane stress levels, arising from the thermal gradient and rotational effects, are determined at a number of radially spaced points across the disc and, by means of annular finite elements, the effect of the resulting stress distribution upon the natural frequencies of the disc is examined.     

Free vibration analysis of rectangular plates with symmetrically distributed point supports along the edges

In this paper a highly accurate mathematical technique for establishing the free vibration eigenvalues and mode shapes of rectangular plates with symmetrically distributed point supports is introduced. The method is based on the principle of superposition and it constitutes, in essence, an extension of a technique described earlier for the analysis of completely free plates. Eigenvalues, covering numerous modes and aspect ratios, are tabulated for corner supported rectangular plates. It is seen that with some modifications the method is equally applicable to problems where the point supports are not symmetrically distributed.     

Experimental analysis of transverse vibration in thermally stressed rotating discs

Details and results are presented of an experimental analysis of the natural frequencies of free transverse vibration of two annular discs subjected to the combined action of centrifugal and thermal stressing. One disc is of constant thickness form, whilst the other is of linearly varying thickness form. The results obtained experimentally are subsequently compared with those as predicted by a finite element technique previously described by the first two authors. In general the comparisons are found to be favourable, when account is taken of the sources of error in the experimental analysis.