Daniel McStay

Photosensitive changes in Ge-doped fibres observed by raman spectroscopy

Raman spectroscopy has been used to study photosensitive effects in Ge-doped optical fibres. The spectrum obtained for a sample of the original fibre used by Hill et al is shown to have a large broadband fluorescence. A rapid photobleaching of a fluorescence band at 570nm has been observed in the photosensitive fibre. It is shown that the Ge(1) and Ge(2) defects have appropriate properties to produce a refractive index grating via a photobleaching process. A weak photosensitive production of SiH occurs in Ge-doped fibres subjected to 488nm, which have previously been subjected to hydrogen diffusion, the rate of production is found to be linear with the power squared.

A Comparative Study of Rotational Relaxations of an Eosin-protein Complex Using Delayed Fluorescence and Phosphorescence

Abstract The slow rotational diffusion of a macromolecule bovine serum albumin in solution has been investigated by measuring the decay of dichroism in laser-pulse induced transient emissions from triplet probes covalently bound to the protein. A comparison of the anisotropy parameters of phosphorescence and delayed fluorescence from eosin-bound bovine serum albumin is described. The results indicate that the measurement of delayed fluorescence is often the preferable option for investigating the rotational diffusion of the eosin-bound macromolecules.

Novel dual-channel time-domain phosphorimeter for time-resolved spectroscopic studies of biomolecules

A newly developed dual-channel time domain phosphorimeter is described in this paper. This employs a pulsed, frequency doubled Nd:YAG laser as a linear polarized pumping source. The resulting orthogonally polarized emission components are then simultaneously collected by two oppositely positioned photomultiplier tubes (PMTs), digitized by a digital storage adaptor, and then transferred to an IBM PC microcomputer where the intensity or the depolarization (anisotropy) of the emission is calculated. The range of lifetimes or rotational correlation times that can be routinely determined with this instrument extends from a few microseconds to milliseconds. The instrument has an 8 bit magnitude resolution and a signal sampling rate of 20 mesa-samples per second. The averaging function of the instrument yields a single measurement with an average of over 2 to 255 excitation transients. To demonstrate the utility of the new instrument, studies of the emission properties of the triplet probe eosin immobilized in a polymer matrix and covalently bound to a membrane protein are reported.

Comparison of E1 and E2 Conformers of Membrane Bound Na+/K+-ATPase Using Time-Resolved Phosphorescence Anisotropy Measurements

Na+/K+-ATPase is known to form oligomeric complexes in the membrane bilayer. On the other hand, there are strong evidence that monomelic form possesses all of the main hydrolytic and transport properties of the Na+-pump. This raises the question as to whether formation of oligomeric complexes is a the necessary step in the biochemical processes associated with the translocation of cations across the membrane or simply an architectural feature of the intercalation of the proteins into the phospholipid bilayer. We have addressed this question by measuring the rotational relaxation of the ATPase in different conformational states of the pump cycle using flash-photolysis methods.

New method for the simultaneous measurement of fluorescence and phosphorescence depolarizations

A new technique for the simultaneous measurement of fluorescence and phosphorescence depolarization is reported. The technique is based on a newly developed photomultiplier gain suppression technique. The gain suppression characteristics of the circuit were studied by applying a constant level of incident light. To demonstrate this new technique, a solid sample of the triplet probe eosin was excited by a pulsed, frequency doubled Nd:YAG laser; the resulting orthogonally-polarized emissions were collected by two balanced photomultiplier (PMTs). The gains of the PMTs were suppressed for the duration of the fluorescence emission, and subsequently returned to normal, in order to keep the measured fluorescence and phosphorescence signals at the same level. The suppression of the gain was controlled by using a specially designed dual-channel PMT gain suppression circuit. The signals from the PMTs were recorded by two digital oscilloscopes, one set at a fast sweep time in order to measure the transient fluorescence depolarization and the other set at a slow sweep time in order to measure the slow phosphorescence depolarization. The anisotropies can then be deduced from the two sets of recordings.

Delayed fluorescence of eosin-bound protein: a probe for measurement of slow-rotational mobility

The slow rotational diffusion of macromolecules has been investigated by measuring the decay of dichroism in laser-pulse induced transient emissions for triplet probes bound to the molecules. A comparison of the anisotropy parameters of phosphorescence and delayed fluorescence from eosin-bound bovine serum albumin (BSA) is described. The results indicate that the measurement of delayed fluorescence is often the preferable option for investigating the rotational diffusion of the macromolecules.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Miniature HiBi current sensor

Electric current sensing using Faraday coupling in a highly birefringent optical fiber is reported. The sensor is potentially less susceptible to environmental perturbations, such as vibration and stress, than conventional optical-fiber sensors. The performance of the sensor using a laser diode as the source and when the fiber is subjected to a distributed load is reported.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Temperature Compensation of a Highly Birefringent Optical-fibre Current Sensor

ABSTRACT A technique for the measurement of electric current using highly-birefingent optical-fibre is reported. The technique involves a resonant coupling between the fibre beat length and the period of a spatially-varying magnetic field. The resonant nature of the coupling makes the sensor less susceptible to environmental perturbations, than conventional low- birefringence optical-fibre current sensors. The response of the coupling to distributed loads, and temperature compensation of the coupling are reported.INTRODUCTION Optical-fibre based current sensors have a number of important advantages over traditional current measurement techniques which make them an auractive alternative in a range of applications. The fact that the sensing element is adielectric, thus providing substantial isolation in the presence of large electric fields, makes them useful in electric current monitoring in power stations and other ES! sites. Other important advantages for this application include the linear