Viscosity of Alkali–Metal Iodides in Propionitrile and Acetonitrile Mixtures at 25°C

The relative viscosities were measured for LiI, NaI, KI, RbI, Bu₄NBPh₄, and Bu₄NI in a wide range of mixtures of propionitrile and acetonitrile at 25°C to obtain Jones–Dole Bcoefficients. The Bcoefficients of these electrolytes were large and positive. The values of ionic Bcoefficients allow us to assess the behavior of ions in the solvent mixtures.     

The Fitting of Luminescence Rises and Decays

This review presents a number of mathematical expressions which the experimental scientist may find useful to fit to time-dependent luminescence intensity (and concentration) data for both decay and rise situations. Some of these expressions have been drawn from literature sources and are presented here in a unified form. In compiling these expressions, a number of gaps were found in the literature, and, in this review, new expressions have been derived to fill some of these gaps. The final section of the review summarizes both the existing and the new kinetic expressions and provides an explanation of how to use them. Some of the subtleties and pitfalls of using kinetic data fitting to determine reaction mechanisms are also discussed.     

SPECTRAL AND TIME DEPENDENCE STUDIES OF THE ULTRA WEAK BIOLUMINESCENCE EMITTED BY THE BACTERIUM Escherichia coli

Abstract— Weak luminescence was detected using photon counting equipment, from oxygenated, liquid cultures of Escherichia coli during two stages of its growth cycle. The first period of emission occurred during the exponential phase of growth and comprised a UV(210–330 nm) band and a visible region(450–620 nm) band, the total intensity being (1.65 ± 0.12) x 10³ counts s^-1. The second period of emission occurred during the stationary phase of growth and comprised only a visible region(450–620 nm) band of intensity (8.72 ± 0.15) x 10³ counts s^-1. When the growth temperature was raised from 306.15 to 310.15 K, the above emission intensities were approximately halved, but the spectra were not changed significantly. No luminescence was observed at either temperature when the E. coli was grown anaerobically. The visible region luminescence was attributed to excited carbonyl groups and excited singlet O₂ dimers formed during the decomposition of lipid peroxides. The UV component was tentatively assigned to oxidative side reactions accompanying the synthesis of proteins.     

DOES LOW-INTENSITY He-Ne LASER RADIATION PRODUCE A PHOTOBIOLOGICAL GROWTH RESPONSE IN Escherichia coli?

Abstract A photobiological study was camed out on the bacterium Escherichia coli in order to determine whether stimulation of growth occurred after irradiation of an inoculum with coherent red light. No enhancement or inhibition of growth was observed for cultures of the bacterium following irradiation of inocula with a Helium-neon laser (continuous wave, λ= 632.8 nm) at irradiances of 7.7 × 10¹⁵ and 1.8 × 10¹⁶ photons cm⁻² s⁻¹ using fluences of 4.5 × 10^−-1 and 4.5 J cm⁻² at each irradiance. Bacterial growth in irradiated and control cultures was monitored during a growth period of ca 2 h using a viable count technique after inocula in the early exponential phase had been diluted with fresh growth medium. These results do not provide support for the work of Kam et al . (1983, Nuov. Cim . 2D, 1138–1144), and Tiphlova and Karu (1988, Photochem. Photobiol . 48 , 467–471), which appear to show substantial enhancement of E. coli growth under these conditions.     

Hydration of monosaccharides: A study by dielectric and nuclear magnetic relaxation

NMR studies indicate that the relaxation rate of¹⁷O-enriched water is enhanced in monosaccharide solutions, and it is greater in hexose solutions than with a pentose, ribose. Three dielectric relaxations have been isolated and assigned to bulk water相似文献   

Infrared measurements and calculations on H2O.HO

We have measured the infrared spectrum of H2O.HO in argon matrices at 11.5 +/- 0.5 K. We have also calculated the vibrational frequencies and intensities of the H2O.HO complex. As a result of these measurements and calculations, we have assigned a previously unassigned absorption band at 3442.1 cm-1 to the OH stretch in the radical complexed to the water molecule. This absorption originates from a complex that is situated in a different site within the argon matrix to those absorptions already assigned to this vibration at 3452.2 and 3428.0 cm-1. We observe a decrease in intensity of the OH radical stretching vibration of the H2O.HO complex upon isotopic substitution of D for H that agrees well with our calculations.     

Viscosity B Coefficients for Alkali–Metal Bromides in 3-Hydroxypropionitrile–Acetonitrile Mixtures at 25°C

The viscosity B coefficients were measured for LiBr, NaBr, KBr, RbBr, CsBr, Bu₄NBPh₄ and Bu₄NBr in 3-hydroxypropionitrile–acetonitrile mixtures over the entire composition range at 25°C. The B coefficients of these electrolytes were large and positive and were split into their respective ionic values using the method of Gill and Sharma. The ionic B coefficients were positive for all the electrolytes.     

Luminescence spectra of exponential and stationary phase cultures of respiratory deficient Saccharomyces cerevisiae

The spectral distributions of the luminescences emitted by the respiratory-deficient mutant of Saccharomyces cerevisiae and the normal yeast have been determined during the exponential phase of growth and during the stationary phase. The respiratory-deficient mutant gave a more intense emission in the visible region than did the normal yeast, but the UV intensities from the two yeasts did not differ greatly. These differences were explained in terms of higher O2- concentrations in the respiratory-deficient mutant which lead to enhanced visible region chemiluminescence from lipid peroxidation reactions.     

THE SPECTRAL DISTRIBUTION OF THE LUMINESCENCE EMITTED DURING GROWTH OF THE YEAST SACCHAROMYCES CEREVISIAE AND ITS RELATIONSHIP TO MITOGENETIC RADIATION

Abstract— The spectral distributions of two previously reported weak luminescences from liquid cultures of the yeast Saccharomyces cerevisiae have been determined. During the logarithmic phase of growth, emission was observed as a broad UV band between 200 and 425 nm, and as a visible region band between 525 and 700 nm. During the stationary phase, there were two narrow bands centred at 250 and 650 nm, and a broad band extending from 325 to 525 nm. The UV components are compared with Gurwitsch's mitogenetic radiation, and possible chemical and radiolytic sources of the luminescences are discussed.     

ATTEMPTED BIOSTIMULATION OF DIVISION IN Saccharomyces cerevisiae USING RED COHERENT LIGHT

Replicate cultures of the yeast, Saccharomyces cerevisiae were irradiated with 632.8 nm coherent light from He-Ne lasers at irradiances of 6.5 times 10¹⁵ and 1.0 times 10¹⁶ photons s^?1 cm^?2. Irradiation periods ranged from 0 to 652 min, and cultures were grown until well into the exponential phase. Unirradiated control cultures were grown alongside the irradiated cultures under otherwise identical conditions. The extents of growth in the control and irradiated cultures were compared spectrophotometrically at the end of each experiment. contrary to the expectations of Karu et al. (e.g. Karu, 1988, Lasers Life Sci. 2 , 53–74) no growth enhancement was found in the irradiated cultures, but a mild inhibitory effect was observed.