Department of Physics (Fredericton)

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 pulsed NMR study of water adsorption on methylcellulose
pulsed NMR study of water adsorption on methylcellulose
by Thomas J. Lees, The proton magnetic resonance relaxation times T1. T1p, T2FID, and T2cp for water adsorbed on methylcellulose have been measured at a Larmor frequency of 30MHz over the temperature range from 293K to 153K. The spin locking field pulse used to measure T1p was 10 Gauss. The relaxation times are consistent with those found in previous studies of water-cellulose systems, but with added components attributable to the ethyl group due to the slowness of spin diffusion. The relaxation times were roughly fit to a cross-relaxation model considering anisotropic motion as well. The fits are similar to those found for water-cellulose systems.
A computer-controlled digital pulse programmer for pulse NMR
A computer-controlled digital pulse programmer for pulse NMR
by Michael Edward Hale, A versatile and flexible digital pulse programmer for pulse NMR experiments is described. Independently variable controls for pulse widths (0.1 μsec to 999.9 sec), delay between pulses (0.1μ sec to 999. 9 sec), sequence period (0.1μ sec to 9999.9 sec) and trigger delay (0.1 μsec to 9999.9 sec) are brought to the front panel. The programmer can be used under computer as well as manual control. The programmer is designed to be used with a DEC LSI-11 microcomputer having a Heathkit H11-2 parallel interface.
A mid-infrared tunable diode laser (TDL) system for atmospheric applications
A mid-infrared tunable diode laser (TDL) system for atmospheric applications
by Kjetil Våge, A tunable diode laser (TDL) system operating in the mid-infrared region has been used for studies related to several aspects of atmospheric applications. To characterize the operation of the laser diode, the mode structure was mapped over the full temperature tuning range. For use as a reference, a segment of the broadband OCS spectrum was obtained from 1997.5 cm-1 to 2000.5 cm-1 at a pressure of 1.8 Torr. The spectrum is rich and has previously been reported in detail, so it is well suited as a standard reference for the TDL system in this spectral window. Many rare isotopic lines of OCS appeared in natural abundance, indicating a high sensitivity of the system. Experiments were then carried out in which OCS was mixed with air at varying pressures from 0 Torr to atmospheric conditions. By monitoring a 160 13C34S transition appearing in natural abundance at 2000.1467 cm-1, the detection limit of the system was estimated to be about 4 ppm by volume at an optical path length of 4 m. Pressure broadening and shift of OCS and H20 transitions were also investigated. Finally a sample of car exhaust was obtained and introduced into the sample cell as a direct atmospheric application. Absorption lines due to H20 and OCS were observed as well as more than 15 additional "unknown" lines. By comparison of their wavenumbers against the HITRAN standard atmospheric database (1), some of the unknown lines are identified with H2S.
A neutron technique for detection of explosive-like materials
A neutron technique for detection of explosive-like materials
by Paul Michel Lord, A method for detecting explosives in luggage using a combination of neutron scattering and transmission measurements was investigated. Ammonium nitrate (commercial fertilizer) was used in the laboratory as an explosive- like material. By empirical mapping of the measurements, the method was shown to be able to detect the presence of fertilizer, even when surrounded by other materials. A series of simulations was carried out using the COMMM (Center-Of-Mass Multi-Media) Monte Carlo Neutron Transport Code. The results of these simulations further confirmed the feasibility of the technique., 5 unnumbered pages before first numbered page
A numerical analysis of NMR spin echo attenuation due to variations in magnetic susceptibility
A numerical analysis of NMR spin echo attenuation due to variations in magnetic susceptibility
by Steven D. Beyea, Variations in the susceptibility of a heterogeneous sample will produce background microscopic field gradients when the sample is inserted into a magnetic field. These field gradients frequently alter the signal intensity observed in a nuclear magnetic resonance (NMR) image. A random walk simulation of the NMR spin echo experiment, with several model geometries, has been performed using Mathematica. Using this procedure a qualitative/ quantitative study has been done in an attempt to examine the role of diffusion in diminishing the observed signal intensity. The simulations will be compared to several MRI images of materials containing varying magnetic susceptibility, and various applications of this technique will be discussed.
A numerical analysis of a dynamic model pertaining to ionospheric research
A numerical analysis of a dynamic model pertaining to ionospheric research
by Andrew M. Smith, Appendix irregularly numbered.
A patch clamp system for cell-attached recordings from crayfish giant axons
A patch clamp system for cell-attached recordings from crayfish giant axons
by Martin Bakota, A patch-clamping system consisting of a computer controlled pA amplifier and signal averager was designed to measure currents through single ionic channels. Techniques were established for reliable micropipette (tip 0.0. <2μ) manufacture and tungsten microelectrode use in patch-clamping. Attempts were made to measure single channel currents in giant axons of crayfish (Orconectes). These were unsuccessful due to a failure to establish GΩ seals between the pipette and the plasma membrane. The failure is attributed to unclean plasma membrane surface (it was not digested with proteolytic enzymes)., 4unnumbered pages before first numbered page
A study of the infrared absorption spectra of nitric acid vapour
A study of the infrared absorption spectra of nitric acid vapour
Charles Paul W. Smith, Nitric Acid is an important molecule in the stratosphere and is involved in photochemical reactions with ozone and the freons. Measurements of nitric acid have been made using balloon borne infrared spectrometers. Laboratory measurements at room and stratospheric temperatures are required to obtain the molecular parameters needed to reduce the balloon measurements and obtain absolute nitric acid amounts. This project proceeds to carry out the necessary measurements in an attempt to arrive at the integrated band intensity for nitric acid.
A study of the radiation induced attenuation in optical fibres
A study of the radiation induced attenuation in optical fibres
by Tony D. Teakles, Several papers on the radiation induced effects on optical fibres were s tudied and a series of properties were observed. The formation, annealing and properties of colour centres were studied. The published results on radiation induced attenuation have been examined in relation to the colour centres causing it. The potential uses, advantages and disadvantages for radiation environment fibre sensors have been studied. The use of a fibre sensor system as a personal radiation detector has been suggested.
An analysis of the ß-delayed a spectrum of 16N and the 12C (a,y) 16O cross section at stellar helium burning energies
An analysis of the ß-delayed a spectrum of 16N and the 12C (a,y) 16O cross section at stellar helium burning energies
by D. Gregory Hunter, The rate of 12C(a,y)16O reaction that occurs in helium burning stars is critical to the evolution of stars over twenty-five solar masses. By K-matrix analysis of the ß -delayed spectrum of 16N it is possible to precisely measure the astrophysical S-factor at centre-of-mass energies around 300 keV, corresponding to a temperature of 1 billion Kelvins. An updated analysis of the data from the TISOL isotope separator is presented here. Using the TISOL data and the previous y-ray data, the K-matrix parameters have been simultaneously fitted, giving a value of S(E = 300 keV) = 83 ± 16 keV b for the El part of the 12C(a,y)16.
An experimental search for optical bistability
An experimental search for optical bistability
by Michael Patrick Bradley, An unsuccessful attempt was made to experimentally observe dispersive optical bistability. Following this attempt, nonlinear absorption was sought. A dye solution was found which exhibited an absorption which increased with increasing input power. Transient and steady-state effects were examined experimentally and are discussed qualitatively. Unfortunately, no bistability was observed, though this can be explained. Finally, control of one laser beam by another via the nonlinear absorber was demonstrated., No numbered pages.

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