[en] Optically stimulated luminescence (OSL) signals from various insulators including quartz, Al₂O₃:C, BeO and NaCl have been studied using the linear modulation OSL (LM-OSL) technique. LM-OSL is based on the linear increase of the stimulation light power from zero to a maximum during the measurement. The resultant OSL curve initially increases and then decays after reaching a maximum. The analysis of LM-OSL data usually assumes a linear relationship between the detrapping rate and the stimulation light intensity. However, experiments carried out using various insulators have shown that this assumption is not always correct. The initial decay rates of the blue (∼470 nm) light stimulated constant power OSL decay curves were examined to test the relation between the detrapping rates and the stimulation light intensity. In SiO₂, Al₂O₃ : C and BeO a linear relation between the detrapping rates and the stimulation light intensity was observed. However the detrapping rate of the OSL signal from NaCl was non-linear. Assuming that this non-linearity can be described using a saturating exponential function, a new more general expression for the LM-OSL signal has been derived. The validity of this expression was checked using curve fitting and it was found that the new expression could describe the LM-OSL curves successfully

[en] Luminescence dating of single grains requires a method of distinguishing between quartz and feldspar based solely on their luminescence behaviour. Several methods are tested, including the shape of optically stimulated luminescence (OSL) decay curve, the effect of infrared stimulation upon the OSL signal, and the change in OSL decay curve shape and OSL intensity as a function of the temperature of the sample during stimulation. Of these, the last requires a large number of additional measurements, whilst the first is a poor discriminant. The most efficient means of distinguishing quartz and feldspar grains is by taking the ratio of the OSL signal when measured with and without prior infrared stimulation. This is termed the OSL IR depletion ratio

[en] Spatially-resolved measurements of optically stimulated luminescence (OSL) were performed using a two-dimensional scanning system designed for use with planar samples. The scanning system employs a focused laser beam to stimulate a selected area of the sample, which is moved under the beam by a motorised stage. Exposure of the sample is controlled by an electronic shutter. Mapping of the distribution of OSL using a continuous wave laser source was obtained with sub-millimeter resolution for samples of sliced brick, synthetic single crystal quartz, concrete and dental ceramic. These revealed sporadic emission in the case of brick or concrete and significant spatial variation of emission for quartz and dental ceramic slices. Determinations of absorbed dose were performed for quartz grains within a slice of modern brick. Reconfiguration of the scanner with a pulsed laser source enabled quartz and feldspathic minerals within a ceramic sample to be thinner region. about 6 nm from the extrapolation of themeasuring the time-resolved luminescence spectrum

[en] The luminescence properties of NaCl are discussed. Attention is focussed predominantly upon the optically stimulated luminescence (OSL) signal (UV emission) of NaCl (420-560 nm stimulation). The results from experiments relevant to geological dating applications, such as signal resetting, dose response and thermal stability, are described. The behaviour of the OSL signal observed was found to be favourable for dating, with both the thermal stability and dose response suggesting a range of at least 10 ka. Signal resetting via optical exposure was found to be extremely rapid and no evidence of either thermoluminescence or OSL signals was found following re-crystallization. The potential for dating natural salt deposits, as found in various arid environments, appears to be good

[en] The slow component of quartz OSL displays a number of properties that clearly distinguish it from the main ('rapidly bleachable') part of the quartz OSL signal traditionally used for dating. These properties include an extremely high thermal stability, dose saturation level and a charge concentration dependence in both signal form and decay rate. The physical mechanism responsible for the slow component is thought at present to involve a direct donor-acceptor recombination component, possibly associated with competing pathways below, and possibly up to, the conduction band. The thermal stability and high dose saturation characteristics of the slow component suggest much potential for long-range dating exists although at present it is uncertain whether difficulties associated with partial resetting may preclude routine use of the slow component for dating sedimentary deposits. A single-aliquot additive dose method was however used to obtain an estimate of D_e from the slow component for an Egyptian quartz sample that was in broad agreement with previous estimates based on the standard multiple-aliquot additive dose method. The slow component is often small in magnitude compared to the initial portion of the quartz OSL decay. However, this is not always the case and for some samples significant inaccuracies in D_e estimation may occur when deriving ages from the initial 'rapidly bleaching' portion of the OSL decay if the effect of the slow component is ignored or taken to be constant

[en] The development of a new well stimulation technique that uses propellant technology was discussed. The enhanced oil production process involves igniting a cylinder of solid rocket propellant positioned across a perforated zone to disrupt clogging sand. The StimGun assembly is a hybrid method of perforating with simultaneous propellant stimulation. High pressure gas enters the perforated zone and breaks through damage around the tunnel creating fractures. Data recorders can also run with the StimGun to record downhole pressure and provide a data model for estimating rock properties and propellant penetration. The StimGun assembly was developed by Marathon Oil, Computalog Ltd., Owen Oil Tools, and HTH Technical Services Inc., and is available in Canada from Computalog. 1 fig

[en] The time to reach the maximum response of arterial pressure, heart rate and vascular resistance (hindquarter and mesenteric) was measured in conscious male spontaneously hypertensive (SHR) and normotensive control rats (NCR; Wistar; 18-22 weeks) subjected to electrical stimulation of the aortic depressor nerve (ADN). The parameters of stimulation were 1 mA intensity and 2 ms pulse length applied for 5 s, using frequencies of 10, 30, and 90 Hz. The time to reach the hemodynamic responses at different frequencies of ADN stimulation was similar for SHR (N = 15) and NCR (N = 14); hypotension = NCR (4194 ± 336 to 3695 ± 463 ms) vs SHR (3475 ± 354 to 4494 ± 300 ms); bradycardia = NCR (1618 ± 152 to 1358 ± 185 ms) vs SHR (1911 ± 323 to 1852 ± 431 ms), and the fall in hindquarter vascular resistance = NCR (6054 ± 486 to 6550 ± 847 ms) vs SHR (4849 ± 918 to 4926 ± 646 ms); mesenteric = NCR (5574 ± 790 to 5752 ± 539 ms) vs SHR (5638 ± 648 to 6777 ± 624 ms). In addition, ADN stimulation produced baroreflex responses characterized by a faster cardiac effect followed by a vascular effect, which together contributed to the decrease in arterial pressure. Therefore, the results indicate that there is no alteration in the conduction of the electrical impulse after the site of baroreceptor mechanical transduction in the baroreflex pathway (central and/or efferent) in conscious SHR compared to NCR

[en] Thorium oxide doped with trivalent terbium ions offers itself as a novel phosphor with its photo- and thermally-stimulated luminescence (PL and TSL) characteristics showing a marked change on sustained exposure to 254 and 365 nm ultraviolet (UV) radiation. The reduction in luminescence intensity of Tb³⁺ ions, on irradiation with 254 nm photons and subsequent restoration on exposure to 365 nm, has been correlated with the complimentary behaviour in UV-induced TSL. These changes are, in turn, ascribed to inter-configurational (f-d) transitions and e-h formation and recombination processes. UV radiation induced TSL output increases linearly with incident UV radiant energy at a constant radiation flux; however, for a fixed exposure, TSL output increases with increase in radiant flux

[en] Pulsed stimulation has earlier been proven useful for several applications in dosimetry and luminescence research. Pulsed stimulation has been integrated in the Riso TL/OSL reader along with a software control built into the Sequence Editor. To facilitate research of the lifetime or delay involved in the OSL/IRSL process, a Photon Timer attachment to the Riso reader has been developed which measures data at 100 ps resolution. Furthermore a post-processing program has been developed to present the data in a compressed 3D form that gives a useful overview of the data before further analysis of relevant data. An example of how the Photon Timer has been used to characterise the performance of the pulsed stimulation unit is presented.

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