Properties of C60 polymerized under high pressure and temperature

60 polymers. Pure and mixed phase polymeric samples were synthesized by simultaneously subjecting microcrystalline C₆₀ powder or pellets to various pressures () and temperatures (). The optical spectra of the orthorhombic, tetragonal, and rhombohedral C₆₀ polymer phases are observed to be quite distinct and rich. These spectra exhibit numerous lines and an overall downshift in frequency relative to C₆₀ is observed, consistent with a loss of double bonds from the fullerene cage. The LDMS spectra of a sample synthesized at under hydrostatic conditions and , exhibited a succession of clear peaks at mass numbers corresponding to , similar to the LDMS data on the C₆₀ photopolymer. This is taken as further evidence for interfullerene bonds in these high-pressure polymers. The XRD pattern of this sample indicates the presence of a strong texture in the sample. Received: 14 November 1996/Accepted: 8 January 1997     

The Gay-Berne mesogen: a paradigm shift?

A Commentary on the paper “Computer simulation studies of anisotropic systems XIX. Mesophases formed by the Gay-Berne model mesogen„, by G.R. Luckhurst, R.A. Stephens and R.W. Phippen. First published in Liquid Crystals, 8, 451-464 (1990).     

Palladium-catalysed coupling of terminal alkynes with aryl halides aided by catalytic zinc

The palladium-catalysed coupling of aryl halides with terminal alkynes can be performed using base, zinc chloride and sodium iodide. This protocol represents a convenient method for the generation of nucleophilic acetylides in situ.     

An instrumental method of solution preconcentration

Aerosol concentration before atomic-absorption measurement is achieved by use of an electrostatic trapping technique. The effects of various experimental parameters are examined, including those of voltage, trap dimensions, gas flow-rate through the trap and trapping time. It is concluded that the technique offers an inherently clean method of solution preconcentration which is capable of enhancing the signal by an order of magnitude or more.     

Hearing and personality: A review

The personality of individuals has been shown to interact with their auditory system in a variety of ways. Subjects with different personalities may differ in their physiological responses to sounds, in their perception of sounds and in the way in which noise influences their performance of a variety of tasks. Severe deafness appears to influence the personality of patients, and fairly characteristic changes are found in specific auditory disorders. The annoyance caused by a variety of noises is influenced by the person's personality and in the past a noise annoyance scale has been used as a measure of neuroticism.     

Lifetimes of unresolved transitions from very high spin states in nuclei nearN=82

Average lifetimes of unresolved transitions deexciting very high spin states populated in²⁸Si(^{136, 129}Xe,xn)^164? x, 157?xEr reactions have been determined by a Doppler shift attenuation method. We find that the yrast bump region between 1.0 and 1.6 MeV contains a majority of strongly collectiveE2 transitions with very short lifetimes (a few tens of fsec) in the well deformed nuclei around¹⁵⁹Er and, with less certainty, almost comparably short lifetimes in the more spherical nuclei around¹⁵²Er. In the high energy region of 2.0–3.2 MeV we observe transitions which depopulate longer lived states in the nuclei nearN=82 than in the well deformed systems.     

Comparison of BJT and MESFET front ends in broadband optical transimpedance preamplifiers

We show in this paper that little noise penalty is incurred by using readily available bipolar junction transistors in place of GaAs MESFETs in the first stage of high-speed optical transimpedance preamplifiers.     

Kinetics of the reaction of hydroxyl radicals with 2-(dimethylamino)ethanol from 234–364 K

The temperature dependence of the rate of the reaction of OH with 2-(dimethylamino)-ethanol, (CH₃)₂NCH₂CH₂OH (DMAE) was investigated over the temperature range, 234 to 364 K. The reaction was studied using the flash photolysis-resonance fluorescence technique. The room temperature rate constant determined for this reaction was (10.3 ± 2.0) × 10^?11 cm³ molecule^?1 s^?1, with essentially no temperature dependence evident within the uncertainty in the experiments. A value of (9.0 ± 2.0) × 10^?11 cm³ molecule^?1 s^?1 is believed to best describe the reaction over the entire temperature range. The room temperature rate constant is about twice the value reported previously for this reaction. The overall reaction of OH with DMAE was apportioned to the reactivity of OH for abstracting individual H- atoms from different types of C? H bonds and the O? H bond within the molecule. This technique predicts the overall rate constant for the OH-DMAE reaction to within about 15% of the experimental value and makes it possible to estimate the yields of the initial radical products of the OH attack on DMAE. A mechanism is proposed for the subsequent atmospheric reactions that would occur in the photooxidation of DMAE.     

Some observations on the interdependence of cyanide concentration and atomization efficiency in the nitrous oxide-acetylene flame

A relationship is derived between CN concentration and atomization efficiency in the C₂H₂-N₂O flame. The relationship is examined under various experimental conditions and β values are estimated for a number of elements. The possibility of complex vapour phase oxide formation by U is considered.