Filters
Availability
Publication Year
Resource Type
Faculty
School/Institute
Publication Search Results
Sort
Results per page
1 - 10 of 549
-
-
(1998)Journal ArticleThe first results obtained using a SOI device for microdosimetry applications are presented. Microbeam and broadbeam spectroscopy methods are used for determining minority carrier lifetime and radiation damage constants. A spectroscopy model is presented which includes the majority of effects that impact spectral resolution. Charge collection statistics were found to substantially affect spectral resolution. Lateral diffusion effects significantly complicate charge collection
-
-
-
(1998)Journal ArticleGrowth under elevated [CO2] promoted spring frost damage in field grown seedlings of snow gum (Eucalyptus pauciflora Sieb. ex Spreng.), one of the most frost tolerant of eucalypts. Freezing began in the leaf midvein, consistent with it being a major site of frost damage under field conditions. The average ice nucleation temperature was higher in leaves grown under elevated [CO2] (– 5.7 oC versus – 4.3 oC), consistent with the greater incidence of frost damage in these leaves (34% versus 68% of leaves damaged). These results have major implications for agriculture, forestry and vegetation dynamics, as an increase in frost susceptibility may reduce potential gains in productivity from CO2 fertilization and may affect predictions of vegetation change based on increasing temperature.
-
Freezing-Induced Hydration Forces Between Phospatidylcholine Bilayers-The Effect of Osmotic Pressure(1997)Journal ArticleQuantitative nuclear magnetic resonance was used to measure the freezing behaviour of lamellar phases of phosphatidylcholine in water and in solutions of sorbitol. Both solute and solvent were deuterated in different series of experiments to allow the calculation of the partitioning of solute and solvent molecules between the lamellar phase and unfrozen bulk solution. Sorbitol, as well as water, was found to redistribute between these phases as a function of temperature. The results show a strong, repulsive, interlamellar force which decreases approximately exponentially with hydration. Compared to measurements on lipid/water systems and solute/water systems, the hydration of the lamellar phase containing solutes is slightly less than the sum of the hydrations of lipid and solute at any given chemical potential of water. For a lamellar phase with a given quantity of lipid, interlamellar sorbitol and water, reduction of chemical potential of water is greater than that due to lipid acting alone plus that due to solute acting alone.
-
(1997)Journal ArticleThe acoustic impedance Z(f) of the flute has a range of around 70 dB. We report the use of a novel impedance spectrometer to measure the acoustic impedance of the flute with a resolution of +/- 1 1 Hz, a dynamic range of over 80 dB and which makes the measurement in 1 second. We report Z(f) for the standard fingerings over the range C4 to C7, and for selected non-standard fingerings as well. These results explain some of the idiosyncracies of the instrument well known to flutists, and in some cases suggest ways in which these may be overcome.
-
(1997)Journal ArticleAcoustic resonances of the vocal tract give rise to formants (broad bands of acoustic power) in the speech signal when the vocal tract is excited by a periodic signal from the vocal folds. This paper reports a novel instrument which uses a real-time, non-invasive technique to measure these resonances accurately during phonation. A broadband acoustic current source is located just outside the mouth of the subject and the resulting acoustic pressure is measured near the lips. The contribution of the speech signal in the pressure spectrum is then digitally suppressed and the resonances are calculated from the input impedance of the vocal tract as a function of frequency. The external excitation signal has a much smaller harmonic spacing than the periodic signal from the vocal folds and consequently the resonances are determined much more accurately due to the closer sampling. This is particularly important for higher pitched voices and we demonstrate that this technique can be markedly superior to the curve-fitting technique of linear prediction. The superior frequency resolution of this instrument which results from external vocal tract excitation can provide the precise, stable, effective, articulatory feedback considered essential for some language-learning and speech therapy applications.
-
-
(1997)Journal ArticleClose-to-theoretical-density compacts of Fe3Al intermetallic and its composite with 4 vol% A12O3 were made by mechanical smearing of powders, followed by Hot Isostatic Pressing. Mechanical characterisation of the compacts were carried out, predominantly, by ultramicro-indentation technique. The materials exhibited very high mechanical properties, and in particular, the composite compact appeared to possess 50% more strength than, and the same modulus of elasticity as, ultra high strength steels. The A12O3 in the composite preferentially occupied the grain boundary positions giving rise to a grain boundary hardness of 9 GPa. The hardness decreased to 6 GPa in the interior, and a functionally graded zone, 0.6-1.0 μm in thickness was observed. Electron probe microanalysis profiles showed good correlation with the results of the mechanical study.