Characterisation of some sparse binary sequential arrays

A periodic binary array is said to besequential if and only if every line of the array is occupied by a given periodic binary sequence or by some cyclic shift or reversal of this sequence. This paper extends earlier results for arrays built on the square grid, characterising further sequential arrays with two ones per period, and those with three consecutive ones per period.     

Non-radiative recombination in chalcogenide glasses

Non-radiative recombination of electron-hole pairs in chalcogenide glasses is described using a mechanism of a strong electron-phonon coupling. Recombination proceeds through a transient bonding rearrangement that creates a defect similar to those giving localized electronic states. Incomplete recombination which leaves the defect in a metastable state explains the reversible photostructural change.     

An automated high precision calorimeter for the temperature range 200K–400K. Part 1: Design and performance

A fully automated calorimeter has been designed and tested over the temperature range 200K–400K. The system may be used for measurements with an absolute accuracy of 0.2% of samples of approximate mass 50g and thermal capacity 15 JK⁻¹. The temperature of the sample is determined by a quartz crystal thermometer of resolution 100 μK which is not in direct thermal contact with the sample. The performance of the system is illustrated by results obtained on high purity copper, distilled water and K₂PbCu(NO₂)₆ which exhibits very sharp first order phase transitions at about 273.4K and 281.8K.     

Interaction between explosive and analyte layers in explosive matrix-assisted plasma desorption mass spectrometry

An HMX/insulin two-layer system was chosen as a model for further investigation of the matrix properties of explosive materials for protein analytes in plasma desorption mass spectrometry. The dependencies of the molecular ion yield and average charge state as a function of the analyte thickness were studied. An increase in the charge state of multiply protonated molecular species was confirmed as the major matrix effect, with the average charge state z at the smallest thickness studied being higher than in matrix-assisted laser desorption/ionization and closer to the value obtained in electrospray ionization under standard acidic conditions. Observed charge state distributions are significantly narrower than the corresponding Poisson distributions, which suggests that the protonation of insulin is limited in plasma desorption by the number of basic sites in the molecule, similar to electrospray ionization. Both the curve displaying total molecular ion yield and the one showing the total charge (proton) yield as a function of the insulin thickness have maxima at a thickness different from an insulin monolayer. These observations diminish the significance of a matrix/analyte interface mechanism for the explosive matrix assistance. Instead, a mechanism related to the chemical energy release during conversion of the explosive after the ion impact is proposed. As additional mechanisms, enhanced protonation of the analyte through collisions with products of the explosive decay is considered, as well as electron scavenging by other products, which leads to a higher survival probability of positively charged protein molecular ions. Copyright 1999 John Wiley & Sons, Ltd.     

Structure-property relationships in high-performance thermoset-thermoplastic blends

Semi-crystalline and amorphous aromatic polymers have become well established as high-performance engineering polymers and composite matrices. Such polymers with functional groups introduced, may be used to toughen, and modify the processing properties of, a range of thermosetting resins, in addition to being copolymerisable, crosslinkable and/or chain-extendable. This paper describes structure/property relationships which have been established for functionalised polyaromatics and systems which utilise them.     

An Economical Large Scale Preparation of (2S,3S)-4,5-Dimethyl-2-Phenyl-L,3-Dioxolan

An economical 5-step synthesis of (2s,5s)-4,5-dimethyl-2-phenyl-l,3-dioxolan from (2R,3R)-tartaric acid is described.     

Maximum packings ofK n with copies ofK 4 − e

For eachn, we determine the maximum number of pairwise edge disjoint copies ofK ₄ – e inK _n , and all possible graphs that arise from the unused edges.     

The structure of the turbulent boundary layer over a mobile and deformable boundary

The structure of the velocity field above a propagating water wave of fixed frequency was investigated in order to evaluate the transport of wind momentum to water waves and the influence of a mobile and deformable boundary on the bursting cycle. The vertical and horizontal velocities were measured in a transformed Eulerian wave-following frame of reference with the aid of a cross hot film, in a wind-wave research facility at Stanford University.The mean velocity profiles have a log-linear form with a wake free-stream characteristic. The wave-coherent motion in the free-stream is irrotational; in the boundary layer, it has a strong shear behavior related to the wave-associated stress. The wave-induced velocity field and the wave-perturbed turbulence depend strongly on the ratio of the wave-speed to the mean free-stream velocity, c/U ₀.The presence of the propagating waves affects the bursting cycle, making the contribution of sweeps and ejections almost equal and dependent on the ratio c/U ₀. The magnitudes of the contribution of the bursting events are generally enhanced by the presence of water waves. The time interval between ejections or sweeps does not scale with either the inner and/or outer flow variables.This paper was presented at the Ninth Symposium on Turbulence, University of Missouri-Rolla, October 1–3, 1984