Vibrational analyses,vibronic coupling and identification of electronic origins in the lower 1nπ* and 1ππ* states of phenazine and acrid

The spectra of the lowest ¹ nπ2 and ¹ ππ2 singlets of phenazine and acridine were studied in a biphenyl matrix at 2 K. The major findings are: (1) The lowest ππ2 singlets L^a and L^b in phenazine and acridine are clearly located and the vibrational analysis of these states support their assignments. (2) Good evidence is presented that a ¹ nπ2 state is the lowest excited singlet in acridine. The ¹nπ2 origin. The fact that the ¹L^a spectrum of acridine is twenty times broder than the ¹ L^a spectrum of antharacone which is otherwise very similar, is additional evidence that the nπ2 is the lowest excited singlet. (3) Three b^2g and three b^1g out-of-plane modes act as false origins for the long- and short-axis nπ2 spectra of phenazine. (4)Sharp lines in the region of phenazine's second singlet are shown to come from the lower ¹B^3u state and appear to be the same type of vibration interference as described by Wessel. (5) The vibrational analysis of the pure crystal spectra of phenazine published previously has been resigned.     

Photoelasticity for stress analysis under high hydrostatic pressure

Experimental research relative to pressure effects on the mechanical behavior of materials is frequently handicapped by the difficulties associated with making load and deformation measurements in a hostile environment. The application of photoelasticity in high-pressure experiments provides a means for studying the effect of hydrostatic stress on varying stress fields. The purpose of this paper is to examine the feasibility of using the photoelastic method of stress analysis in a high-pressure environment. The unusual feature of this application is the finite elastic deformations suffered by the photoelastic model under high pressure. As a result, the mechanical and stress-optical properties of the model materials are functions of pressure. Another important feature in this study is the selection of a suitable model material. Since the model must come into contact with the liquid pressure media, chemical and absorption resistance are essential considerations. Although it was found that photoelastic investigations can be carried out at high pressure, limitations are imposed by the presence of the optical vessel and pressurized fluid.     

Effects of a serum spreading factor on growth and morphology of cells in serum-free medium

A heat-sensitive, trypsin-sensitive factor that promoted growth and spreading of cells in serum-free, hormone-supplemented medium was partially purified from human serum. The major portion of the proteins in these preparations migrated upon SDS-polyacrylamide gel electrophoresis with a mobility consistent with molecular weights between 60,000 and 90,000. The spreading activity, which we have termed serum spreading factor, stimulated growth and spreading of a wide variety of cell types. The serum spreading factor was similar to fibronectin in that it showed an affinity for the plastic cell culture substrate but was shown to be distinct from fibronectin by several criteria. This factor may prove useful in studies of cell attachment and spreading and in studies of the relationship of cell shape and cell proliferation.     

Evidence for molecularly chemisorbed oxygen on TiO2 supported gold nanoclusters and Au(111)

In this study, we present evidence for the existence of a molecularly chemisorbed oxygen species on a Au/TiO2 model catalyst and a Au(111) single crystal following exposure of these samples to an oxygen plasma-jet molecular beam. We present evidence for the molecularly chemisorbed oxygen species from thermal desorption, collision-induced desorption, and heat of adsorption/reaction-induced desorption measurements. Thermal desorption measurements reveal a peak desorption temperature at approximately 145 K which corresponds to an activation energy for desorption of approximately 0.35 eV.     

2-azabicyclo[2.2.2]octa-3,5-dione via a nitrile Diels-Alder reaction

The hetero-Diels-Alder reaction of an electron-deficient nitrile, p-toluenesulfonyl cyanide, with the silyl enol ether of cyclohexenone produced a hydrolytically sensitive [4 + 2] adduct in good yield. Use of Mander's reagent, ethyl cyanoformate, with the same diene, produced an unstable adduct. Hydrolysis of the tosyl cyanide adduct resulted in the isoquinuclidinone 2-aza[2.2.2]octa-3,5-dione as a crystalline compound in excellent yield from the nitrile.