A simple carbon dioxide laser amplifier suitable for optically pumped infra-red laser applications

A simple amplifier tube has been designed which, when used with already well-developed, stable single-frequency CO₂ laser oscillators, produces a cw power output of up to 40 W suitable for pumping far infra-red lasers.     

Calcium and magnesium ATPases of the spectrin fraction of human erythrocytes.

Using a rapid method of preparation, spectrin has been isolated from human erythrocytes and its ATPase activity investigated. The ATPase activity with calcium has two distinct components, one with optimal activity when calcium and ATP are of equal concentration (low-Ca-ATPase) and another which is activated above 1 mM CaCl2 and is maximal at 100 mM CaCl2. There is also a Mg-ATPase with maximal activity at 10 mM MgCl2. The high-Ca-ATPase of spectrin, but not the low-Ca-ATPase, is inhibited by magnesium, while the Mg-ATPase is inhibited by Ca in excess of ATP. None of these activities exhibits the calcium-stimulated magnesium-dependent activity characteristic of the red cell calcium pump.     

Analytical Chemistry in the Republic of Ireland training and employment of chemists and technicians

Summary Based on the results of surveys carried out throughout the country the following topics are discussed: employment of chemists in Ireland, employment of chemists and technicians in the field of Analytical Chemistry, training requirements, types of courses and syllabus outlines.Presented at Euroanalysis III conference, Dublin, August 20–25, 1978     

Signal detection in computer-synthesized noise.

Human observers detected sinusoidal and pulse-train signals in noise derived from two computer-synthesized sources and from a Gaussian noise source. The synthesized noise stimuli were generated from sequences of pulses whose amplitudes were drawn from two divergent types of probability distributions: a centrally peaked distribution and a bimodal distribution. No differences in the detectability of signals in these noise stimuli were evident at pulse rates of 1000, 2000, 4000, or 10 000 Hz. subjects could not discriminate between the two types of computer-generated maskers at any pulse rate. The data support a spectrum-analyzer model of detection in which multiband filtering of the input smooths the masker energy in each spectral region to approximate the Gaussian case.     

Experimental and theoretical studies related to a dye laser differential lidar system for the determination of atmospheric So2 and NO2 concentrations

Laboratory measurements of the absorption coefficients of NO₂ at wavelengths suitable for the operation of differential absorption lidar (DIAL) systems, at around 446 nm and 489 nm are reported. Such measurements are necessary for the valid determination of absolute levels of concentration of NO₂ in the atmosphere and have been made in order to assess anomalies in existing data. A theoretical assessment of some of the optional systems currently available for the application of DIAL to the measurement of atmospheric concentrations of SO₂ is described.     

Continuity properties of the representations of the canonical commutation relations

We prove that a given representation of the canonical commutation relations can be extended uniquely by continuity to larger test function spaces which are maximal in the sense that no further extension is possible. For irreducible tensor product representations of the canonical commutation relations we give a necessary and a sufficient condition for the admissible test functions. We consider the problem of finding topologies on the test function spaces such that this extension can be obtained by a topological completion. Various examples are discussed.Supported in part by the National Research Council of Canada.An earlier version of the present work was distributed as a preprint entitled Topologies for Test Function Spaces for Representations of the Canonical Commutation Relations.     

Automated, fluorescence-based approach for the specific diagnosis of chicken coccidiosis.

We have established a fluorescence-based electrophoretic approach for the specific identification of all seven currently recognised species of Eimeria infecting chickens. The second internal transcribed spacer (ITS-2) of ribosomal DNA is amplified by polymerase chain reaction (PCR) from any of the seven species using a single set of oligonucleotide primers (of which the reverse one is fluorescently labelled). The amplicons are heat-denatured, subjected to denaturing polyacrylamide gel electrophoresis in a 377 DNA sequencer (ABI). The chromatograms produced are stored electronically and then analysed using GeneScan 3.1 software. Using control DNA samples representing monospecific lines of Eimeria, regions in the chromatograms have been defined for the specific identification of each of the seven species, although some variation in the chromatograms (reflecting population variation) was detectable within two species. Electrophoretic reading and analysis is carried out automatically using a computer imaging system, thus making it a time- and cost-effective approach. It is well suited for high-throughput diagnostic screening of oocyst samples and should find applicability as a tool for prevalence studies, monitoring of coccidiosis outbreaks and the quality control of vaccines.     

Isothiourea‐Mediated Asymmetric O‐ to C‐Carboxyl Transfer of Oxazolyl Carbonates: Structure–Selectivity Profiles and Mechanistic Studies

The structural motif within a series of tetrahydropyrimidine‐based isothioureas necessary for generating high asymmetric induction in the asymmetric Steglich rearrangement of oxazolyl carbonates is fully explored, with crossover and dynamic ¹⁹F NMR experiments used to develop a mechanistic understanding of this transformation.     

Thermal racemization of biaryl atropisomers

Many biaryl compounds possess atropisomerism due to the steric hindrance of substituents at the ortho-position of the two aromatic moieties. Upon heating, atropisomers may have enough energy to surpass the rotational energy barrier and racemize. The thermal stability of five atropisomers was studied using chiral chromatography by following the change in enantiomeric excess ratio at different temperatures. The first order racemization reaction rate was obtained at a given temperature as the slope of the change in enantiomeric excess ratio versus time. For each atropisomer, the racemization rates at different temperatures led to the value of the rotational energy barrier for racemization, ΔG³, and to the racemization half lifetime, t_1/2, indicating the atropisomer thermal stability. Binaphthol started to racemize significantly at temperature of 190 °C and above while binaphthyldiamine was much more stable showing little or very minor racemization up to 210 °C. A chloro-substituted phenylamino-naphthol was very sensitive to thermal racemization starting at a low 40 °C.