Search

Dramatic increase in demand for virgin olive oil over the past few years can be attributed not only to its potential health benefits, but also to reports of its fragrant flavour. Supercritical fluid extraction (SFE) was applied to the extraction of volatile compounds of virgin olive oil and olive fruit samples. The volatiles extracted were concentrated in Tenax TA traps attached to the venting valve of the supercritical fluid extractor. The traps were desorbed onto a GC column by thermal desorption with cryofocusing and then analysed by high-resolution GC–MS. Volatile compounds were identified and compared with those obtained by applying a dynamic headspace procedure. The presence of semivolatile compounds was higher in the extracts obtained by SFE. Different profiles of volatile compounds, from flavours to off-flavours were obtained changing SFE experimental parameters. Volatiles were then characterised by sensory descriptors in order to evaluate the effect of this extraction technique on the virgin olive oil flavour.

Highly achromatic operation of a computer-optimized distributed feedback dye laser is reported. Linewidths of between 320 and 500 MHz, a factor of up to 100 less than the pump laser linewidth, have been measured across a scanning range of 70 nm. The dependence of the laser linewidth on pump laser parameters such as linewidth and energy has also been studied. The wavelength dependence of the laser linewidth was well represented by a computer model, and the measured threshold was close to the value predicted by a rate equation model. A conversion efficiency of 20% was obtained. >

A pulsed, grazing incidence dye laser has been designed to oscillate at a repetition rate of 6·5 kHz in a single, narrow and stable, axial mode with a high excitation conversion efficiency. A single mode efficiency of 12% has been measured in a near diffraction limited beam. No measurable fluctuations of the central laser wavelength or the 100–150 MHz single mode linewidth were observed during an hour of observation. The effect of grating incident angle and dye flow rate on laser operation have been investigated and a correlation has been found between the state of polarization of the dye laser output and the polarization of the pump laser.

A distributed-feedback dye laser has been designed and computer-optimized to produce very narrow linewidth, broadly tunable, nanosecond pulses when pumped by a broad bandwidth laser. Details of the computer optimization and construction of the laser are presented along with preliminary measurements of the laser output.

We have designed and tested a pulsed single-mode dye laser for use as the master oscillator in a laser isotope separation (LIS) system. The design features a grazing incidence, or Littman type, cavity which is pumped at a repetition rate of up to 6 kHz by a copper vapour laser to produce a single-mode nearly diffraction-limited beam at over 1% efficiency. Operating on the dye Rhodamine B the laser can be tuned over the range 570–590 nm of interest for LIS.

An actively Q-switched NdYAG laser, using a telescopic resonator configuration has produced single longitudinal mode, TEM 00 outputs of 100 mJ with output pulses free from any observable mode-beating.

A rapid method for the preparation of crystalline 5'-adenylic acid deaminase from rabbit skeletal muscle is presented. The enzyme remains bound to cellulose phosphate under conditions at which apparently no other proteins are bound; thus it was possible to develop, in essence, a one-step method for its purification. The crystalline preparation is homogeneous as indicated by its elution profile, by ultracentrifugation, and by acrylamide gel electrophoresis. The new method results in enzyme that has 5 times the specific activity of the previously reported crystalline preparation and differs in stability and kinetic properties. The enzyme is stable in dilute solution for extended periods at room temperature provided the diluting medium is of high ionic strength and contains β-mercaptoethanol. The enzyme follows normal Michaelis-Menten kinetics with respect to adenosine monophosphate concentration when assayed in the presence of KCl, and with respect to potassium concentration. Sodium and potassium, at 0.15 m, function equally efficiently as cation activators.

The use of a fused silica capillary for reduction of stimulated Raman scattering threshold in H2 gas has been investigated A threshold pump power at 1.06µm of 70 kW has been obtained, a twentyfold reduction over free space propagation. Further threshold reduction should be possible by taking care over capillary straightness.