OSL SENSITIVITY OF QUARTZ EXTRACTED FROM FIRED BRICKS FOR RETROSPECTIVE DOSIMETRY.

Optically stimulated luminescence of quartz extracted from fired materials has been used for retrospective dosimetry for about 40 years. Quartz sensitivity to thermoluminescence and optically stimulated luminescence can vary over few orders of magnitude. These discrepancies in sensitivity for the quartz originating from different parts of the world are still not yet fully understood. We have extracted quartz from bricks produced by three different companies in the Czech Republic. Quartz was extracted from fired bricks, as well as from the bricks before firing. Significant changes in quartz sensitivity were observed after firing process. Sensitivity can either increase or decrease, depending mainly on the maximum temperature achieved during firing process. For some samples, the sensitivity increased significantly after firing (7 times). Sensitivity also increased after repeated irradiation exposures. On the other hand, there were also samples for which the sensitivity did not increase after repeated cycles of irradiation.

A new fully integrated X-ray irradiator system for dosimetric research.

A fully housed X-ray irradiator was developed for use within lexsyg or Magnettech desktop equipment. The importance of hardening of the low energy photon radiation is discussed, its performance and feasibility is empirically shown and sustained by basic numerical simulations. Results of the latter for various materials are given for different X-ray source settings in order to provide estimates on the required setup for the irradiation of different geometries and materials. A Si-photodiode provides real-time monitoring of the X-ray-irradiator designed for use in dosimetric dating and other dosimetric application where irradiation of small samples or dosemeters is required.

Energy output reduction and surface alteration of quartz tips following Er:YAG laser contact irradiation on soft and hard tissues in vitro.

Though the Er:YAG laser (ErL) has been used in periodontal therapy, the irradiated tip damage has not been studied in detail. In this study, the change in the energy output, surface morphology, and temperature of quartz tips was evaluated following contact irradiation. Soft tissue, calculus on extracted human teeth, and porcine bone were irradiated by ErL for 60 min at 14.2 or 28.3 J/cm(2)/pulse and 20 Hz with or without water spray. The energy output ratio declined the most in the calculus group, followed by the bone and soft tissue groups with and/or without water spray. Carbon contamination was detected in all groups, and contamination by P, Ca, and/or other inorganic elements was observed in the calculus and bone groups. The rate of energy output reduction and the degree of surface alteration/contamination is variously influenced by the targeting tissue, temperature elevation of the tip and water spray.

Anisotropy of the acoustic plate modes in ST-quartz and 128°Y-LiNbO(3).

Orientation dependences of the phase velocity vn, coupling coefficient Kn(2), and power flow angle Ψ(n) for zero-order and high-order acoustic modes are calculated numerically in ST-quartz and 128°Y-LiNbO(3) plates with normalized thickness h/λ = 0.1, 0.25, 0.5, 1.0, 1.25, 1.5, and 1.67 (n is the mode order, θ is the angle between propagation direction and the x-axis, h is the thickness, and λ is the wavelength). Results of the calculations are experimentally verified using 128°YLiNbO(3) plates with h/λ = 1.0, 1.67 and θ = 0°, 30°, 60°, 90° as examples.

Degradation of glycine and alanine on irradiated quartz.

Recent researches suggest participation of minerals in the formation of life under primordial conditions. Among all of the minerals, quartz seems to be one of the most probable to take part in such processes. However, an external source of energy is needed, e.g. electric discharge. A device simulating the proposed conditions was designed and was used to simulate prebiotic conditions. Investigation of processes occurring during the stimulation of quartz with electric discharge was studied by means of Ultraviolet-visible (UV-VIS) spectroscopy, in order to monitor the generation kinetics of free radicals. Additionally, infrared spectroscopy was applied to identify chemical reaction products created in a solution of alanine or glycine, in the presence of quartz treated with electric discharge. Formation of increased amounts of free radicals, compared to experiments performed without quartz and/or amino acid, is reported, along with identification of possible degradation products of alanine. No synthetic reactions were observed.

Comparison of thermoluminescence (TL) and cathodoluminescence (ESEM-CL) properties between hydrothermal and metamorphic quartzes.

This paper reports on the Thermoluminescence (TL) and Cathodoluminescence (CL) emission of well-characterized hydrothermal milky quartz specimens from Hakkari in Turkey, labeled THQ, and Madrid in Spain, labeled SHQ, and metamorphic quartz from Madrid, in Spain, labeled SMQ. Both hydrothermal and metamorphic quartz samples display similar UV-IR CL spectra consisting of five groups of components centered at 330 nm and 380 nm linked to [AlO(4)]° centers, 420 nm due to intrinsic defects such as oxygen vacancies, lattice defects, and impurities which modify the crystal structure, 480 nm associated with [AlO(4)]° centers of substitutional Al(3+), and a red broad band related to the hydroxyl defects in the quartz lattice as precursors of non-bridging oxygen hole centers (NBOHC) and substitutional point defects. The Turkish quartz specimen exhibits higher CL intensity in the UV region (up to 330 nm) than the Spanish specimens probably linked to the presence of Ca (0.95% in THQ and less than 0.1% in SHQ and SMQ). At wavelengths greater than 330 nm, SMQ (formed at high pressure 6000 bars and temperatures over 500-600°C) shows higher intensity than the hydrothermal (growth at 2000 bars and temperatures 200-300°C) samples associated with the formation process. The natural blue TL glow curves of both THQ and SHQ display a weaker TL intensity than the SMQ, attributable to the Al (0.32%), Ti (0.14%), K (0.01%) and Zr (76 ppm) content. It is shown that mineralogical formation, crystallinity index and the content of the impurities seem to be the main parameters of influence in the shape intensity of the CL and TL glow curve emission.

Energy output reduction and surface alteration of quartz and sapphire tips following Er:YAG laser contact irradiation for tooth enamel ablation.

BACKGROUND: Despite the recent increase in application of Er:YAG laser for various dental treatments, limited information is available regarding the contact tips. This study examined the changes in energy output and surface condition of quartz and sapphire contact tips after Er:YAG laser contact irradiation for tooth enamel ablation. MATERIALS AND METHODS: Ten sets of unused quartz or sapphire contact tips were employed for contact irradiation to sound enamel of extracted teeth. The teeth were irradiated with Er:YAG laser at approximately 75 J/cm(2)/pulse and 20 Hz under water spray for 60 minutes. The energy output was measured before and every 5 minutes after irradiation, and the changes in morphology and chemical composition of the contact surface were analyzed. RESULTS: The energy output significantly decreased with time in both tips. The energy output from the sapphire tips was generally higher on average than that of the quartz. The contact surfaces of all the used quartz tips were concave and irregular. Most of the sapphire tips also appeared rough with crater formation and fractures, except for a few tips in which a high energy output and the original smooth surface were maintained. Spots of melted tooth substances were seen attached to the surface of both tips. CONCLUSION: In contact enamel ablation, the sapphire tip appeared to be more resistant than the quartz tip. The quartz tips showed similar patterns of energy reduction and surface alteration, whereas the sapphire tips revealed a wider and more characteristic variation among tips. Lasers Surg. Med. 41:595-604, 2009. (c) 2009 Wiley-Liss, Inc.

Effectiveness of different substrate materials for in vitro sunscreen tests.

BACKGROUND: In vitro measurements of sunscreen products are used to assess their reliability in terms of photoprotection and photo-stability. OBJECTIVE: In this study, several substrates have been fully characterized for in vitro sunscreen testing. METHODS: The following different substrates have been utilised in the study: roughened PMMA plates, Transpore, Vitro-Skin, roughened quartz plate and a laboratory prepared roughened PTFE plate. The suitability of these substrates for SPF evaluation has been investigated by performing total absorbance measurements of seven sunscreen products with different SPF values produced by the same manufacturer. RESULTS AND CONCLUSIONS: Application of sunscreen products on Transpore, roughened quartz plate, PMMA, PTFE and Vitro-Skin was performed efficiently. With regard to photo-stability of the substrate materials, only PMMA plate, PTFE and roughened quartz plate showed to be photo-stable after UV irradiation. With regard to SPF tests, our results indicate that Transpore, roughened quartz plate and Vitro-Skin are preferable to assess SPF values because of a better correlation between in vitro and in vivo measurements. Our study also confirms that an initial calibration must be performed for sunscreen products labelled with different SPF values. Finally, the results of our measurements demonstrate that, although a correlation between in vitro and in vivo SPF results can be established, it is never exactly 1:1.

An in vitro evaluation of effect of ionizing radiotherapy on push-out strength of fiber posts under cyclic loading.

Ionizing radiotherapy has a deleterious effect on all vital cells and thus might affect the collagen fibril network of dentin and formation of hybrid layer of composite resins. The present study evaluated the effect of ionizing x-ray radiotherapy on push-out bond strength of fiber posts. Sixty mandibular premolar roots were divided into 4 groups: group I, control group with no irradiation, restored with a quartz fiber post system with cyclic loading; group II, samples were exposed to 60 Gy radiation dosage and than restored; group III, samples were restored and then irradiated; and group IV, samples were restored during irradiation. A push-out bond strength test was done. Radiotherapy significantly reduced the push-out bond strength of fiber posts. Patients undergoing ionizing radiotherapy might have a less than ideal prognosis of fiber posts luted with dual cure resin cement with total etch bonding system, if restorations are done after radiotherapy.

Light-transmitting ability of marketed fiber posts.

If proper polymerization of resin-based cements is to be achieved for fiber post luting, light activation is needed for photo-curing agents, recommended for self-curing materials. The study was aimed at verifying whether the light-transmitting ability of marketed fiber posts reflected the manufacturers' claims for translucency. Ten posts per type were light-irradiated with a curing unit. Spectrophotometric measurements of the amount of photons reaching different post levels were taken. Data were statistically analyzed (linear regression, two-way ANOVA; alpha = 0.05). No light transmission was recorded through FibreKleer and Tech21 X-OP. For the other posts, light intensity decreased from coronal to apical and rose again at the apical tip, where it peaked for GC Fiber Post, Macrolock Illusion Post, and Radix Fiber Post. Light transmission was significantly higher at the coronal level. A statistically significant difference in translucency was found for Dentin Post X and FRC Postec Plus in comparison with Reforpost, FibreKleer, Tech21 X-OP, and Composipost.

Dedicated finite elements for electrode thin films on quartz resonators.

The accuracy of the finite element analysis for thickness shear quartz resonators is a function of the mesh resolution; the finer the mesh resolution, the more accurate the finite element solution. A certain minimum number of elements are required in each direction for the solution to converge. This places a high demand on memory for computation, and often the available memory is insufficient. Typically the thickness of the electrode films is very small compared with the thickness of the resonator itself; as a result, electrode elements have very poor aspect ratios, and this is detrimental to the accuracy of the result. In this paper, we propose special methods to model the electrodes at the crystal interface of an AT cut crystal. This reduces the overall problem size and eliminates electrode elements having poor aspect ratios. First, experimental data are presented to demonstrate the effects of electrode film boundary conditions on the frequency-temperature curves of an AT cut plate. Finite element analysis is performed on a mesh representing the resonator, and the results are compared for testing the accuracy of the analysis itself and thus validating the results of analysis. Approximations such as lumping and Guyan reduction are then used to model the electrode thin films at the electrode interface and their results are studied. In addition, a new approximation called merging is proposed to model electrodes at the electrode interface.

Short- and long-term stability of resonant quartz temperature sensors.

A new miniaturized design of the thermosensitive quartz resonator (TSQR) using an NLC cut (yxl/ -31 degrees 30') with a fundamental frequency of 29.3 MHz was created in the Acoustoelectronics Laboratory of ISSPBAS for use in a wide temperature range (4.2 K to 450 K) as highly sensitive quartz temperature sensors (QTS). This paper presents the results of the investigations of the short- and long-term frequency stability of QTS. The short-term frequency stability of QTS was measured for averaging times up to 150 s at three constant temperatures: liquid helium (4.2 K), liquid nitrogen (77 K), and melting ice (0 degrees C). The short-term frequency stability is 6.8 * 10(-9) at 0 degrees C for t = 15 s, which permits a temperature sensitivity of 2 * 10(-4) K. The long-term stability (aging) was investigated at room temperature and at 80 degrees C for 500 days. The aging characteristics at 25 degrees C and 80 degrees C are compared. It was observed that the frequency change does not exceed 5 * 10(-7) after the 25th day of accelerated aging at 80 degrees C. This guarantees a reliable operation of the sensor, without additional calibration, for several years.

Effects of electrodes with varying thickness on energy trapping in thickness-shear quartz resonators.

We study the possibility of using electrodes of varying thickness for strong energy trapping in quartz thickness-shear resonators as an alternative for contoured resonators. A theoretical analysis is performed. Results show that nonuniform electrodes can produce strong trapping of thickness-shear modes.

Design and properties of STW asynchronous resonators on quartz.

In a surface transverse wave (STW) asynchronous resonator, grating phase shifters are placed between interdigital transducers and reflectors to obtain the incident and reflected waves in phase, and the resonance frequency is located near the center frequency of the reflectors. In this paper, the scattering matrix method is used for design of such resonators with one dominant longitudinal mode. At a frequency of about 509.5 MHz, insertion loss, and loaded and unloaded quality factors of about 6 dB, 5,300 and 11,000, respectively, were obtained. The measured and calculated parameters of this resonator are in good agreement. Design guidelines and comparison of synchronous and asynchronous resonators are presented. Compared to synchronous resonators, low spurious signals' level, location of the resonance frequency near the center frequency of the reflectors, and simple design method make the asynchronous resonators more attractive for manufacture and practical applications.

Usability of VTL from natural quartz grains for retrospective dosimetry.

To develop retrospective dosimetry of unexpected radiation accident, basic studies on violet thermoluminescence (VTL) phenomena were conducted using natural quartz grains. All VTL glowcurves of as-received samples did not exhibit peaks <250 degrees C, although for artificially irradiated quartz samples there were VTL peaks in the temperature region <250 degrees C. Therefore, accident doses could be estimated without the interference of naturally accumulated doses by VTL measurements from natural quartz. The mean lives of VTL were evaluated by the various heating rates method and the range of values was found to be between some days and ten thousands of years depending on each peak. Especially, the mean life of VTL peak at 200 degrees C was years order. Furthermore, the lower detection limit was calculated to be tens of mGy from the response curve. This value was lower than that of other methods such as ESR dosimetry. From these results, we conclude that VTL dosimetry can be preferred for accidental evaluation.

Thermal pre-treatment in the OSL dating of quartz: is it necessary?

Thermal treatment before optically stimulated luminescence (OSL) measurement is an important step in all widely accepted OSL dating procedures used with quartz. This is a major constraint on the design of a portable luminescence instrument for estimating ages in the field. Preliminary experiments show that using a standard dating protocol without heating caused a 30-50% underestimation of equivalent dose. This underestimate arises mainly from OSL derived from the 110 degrees C thermoluminescence (TL) trap; because of the thermal instability of this trap, this OSL contribution is only present in unheated laboratory-regenerated signals, but not in the natural signal. An alternative to thermal pre-treatment is investigated, based on the mathematical separation of the stable dosimetry OSL signal from the total OSL; the latter is the sum of signals from several traps, including the 110 degrees C TL trap. Our results show consistency with dose estimates obtained using a standard measurement protocol including pre-heating.

A system to irradiate and measure luminescence at low temperatures.

We have developed a system to irradiate samples and record radioluminescence (RL), optically stimulated luminescence (OSL), and thermoluminescence (TL) at temperatures ranging from -150 degrees C to 200 degrees C. The system consists of a cryostat, an irradiation/stimulation unit fitted with an X-ray tube (40 kV Moxtek) and a quartz window for optical stimulation, and a detection unit that utilises a photomultiplier tube and an interchangeable filter pack. Experiments have been conducted with quartz and albite (a feldspar). TL and OSL experiments show that several optically sensitive trapping states are stable below -50 degrees C. In addition, an increase in OSL is seen as the OSL stimulation temperature is lowered below -50 degrees C, and an increase in RL is apparent as the temperature is lowered during irradiation. This indicates that not only are optically sensitive low temperature traps present but that luminescence becomes more efficient at low temperatures.

A comprehensive comparative study of the predose effect for three quartz crystals of different origin.

The study of the thermoluminiscence (TL) sensitivity of quartz due to heat and irradiation treatments is of importance in dating and retrospective dosimetry. A comprehensive comparative study of the predose effect was carried out for three types of quartz of different origin. Complete TL vs. dose and sensitivity S vs. predose curves were obtained for the dose range of 0.1 < D < 400 Gy. Additional complete sensitivity vs. predose curves were obtained for samples which underwent a combined predose irradiation and a subsequent heat treatment to 500 degrees C. Although the TL vs. dose curves showed very different behaviours, the sensitivity vs. predose curves showed several common characteristics. The sensitivity vs. predose curves showed abrupt changes approximately 10 Gy. The sensitivity after a combined predose irradiation and heat treatment to 500 degrees C showed a very gradual change in the whole dose range studied. These results are explained qualitatively by using the modified Zimmerman model for quartz.

A comparison of quartz OSL and isothermal TL measurements on Chinese loess.

The reliability of equivalent doses (De) from Chinese loess, measured using isothermal thermoluminescence (ITL) is tested. Dose calculations use the single-aliquot regenerative-dose (SAR) procedure. Despite good reproducibility of laboratory-induced signals and negligible response at zero dose, a significant overestimation of De is observed, compared with OSL measurements. Measurement of a known laboratory dose administered after optical bleaching, but before any heating, demonstrates that the first heating during measurement of the natural signal causes a significant sensitivity change, undetected by SAR. Using the single-aliquot regeneration and added (SARA) dose procedure, which allows for initial sensitivity change, good agreement with OSL is obtained after allowance is made for initial incomplete bleaching. It is concluded that SAR-ITL, in its present form, is not a suitable method for dating Chinese loess; it is very important to undertake a dose recovery test before any TL procedure is used to date sediments.