TL Curves Research Articles

Simultaneous Detection of Thermostimulated Luminescence and Exoelectronic Emission Between 77 and 650 K: Application to Alpha Alumina

Detection apparatus which allows the simultaneous recording of TL and TSEE curves up to 650 K after X or UV irradiations at 77 K is described. Various samples of a-alumina were studied in these conditions. It is shown that this approach avoids some measurement errors and compares accurately the TL and TSEE peaks related to the same trapping centre.

A TL model based on deep traps competition

TL appears as a very complex phenomenon. However, some general features are widely presented by TL materials: low TL yields, nonlinear growth with dose (supralinearity or saturation), lower efficiency for high LET particles etc., which are not explained by the well-known classical one-trap band model. In the past, the competition between TL traps and deep (thermally disconnected) traps was proposed in theoretical models accounting for some specific TL features. Arguments are presented here for a more general role of deep traps, in order to get an overall satisfying (at least qualitatively) description of the TL phenomenon either in the irradiation stage (TL or ESR) or in the heating one. A corresponding theoretical model is proposed. It is outlined that the competition between TL and deep traps leads to spatial correlations between electrons in TL traps and recombination centres (trapped holes). On the other hand, occurrence of recombination is taken into account as well in the irradiation step as during the heating one. As a result, on a very simple basis, the model accounts for supralinear behaviour of TL output with dose, non-exponential shape of TL or ESR growth curves, slight temperature shift of glow peaks with dose and scarceness of observed second-order kinetics.

Thermal and field excitation of filled traps in CaS:Zn phosphors

CaS phosphors with varying concentration of Zn +2 have been prepared and their thermo- and electrothermo-luminescence have been studied systematically. It has been found that the variation of Zn +2 impurity considerably affects the general features of glow curves. The intensities of the two peaks observed have been altered in such a way that the population of trapping states corresponding to the first peak initially increases and then decreases in preference to the second one. The shape of glow curve has been modified remarkably when electric field is applied during the thermal excitation. The values of activation energy evaluated from ELTL curves are found to be lower than those evaluated from TL curves while the values of escape frequency factor estimated from ELTL curves are higher in comparison with those evaluated from TL studies. An attempt has been made to explain the effect on the basis of Thornton's theory.

Kinetic analysis of monochromatic TL curves

In the kinetic analysis of thermoluminescence, ‘monochromatic’ curves are more useful and give more reliable information than the polychromatic glow curve. This is demonstrated for two specific cases. In one case (TL of albite) the kinetic analysis of monochromatic curves did not enable us to determine whether the red and blue emissions involved one recombination process or two independent processes. In the second case (TL of zircon) the prominent 110°C peak was found to involve three independent recombination processes.

THERMOLUMINESCENCE STUDY OF PET FIBERS FOR TIRE-CORD USE

Commercial PET fibers for tire-cord use were characterized by Thermoluminescence method (TL). TL experiments were performed separately at low and high temperatures: In the low temperature experiment, samples were irradiated by x-ray from a Copper-tube at -180°C for 1 hour and then heated up to room temperature at a rate of 3°C/min. to measure the TL intensity as a function of temperature. In the high temperature experiment, the x-ray irradiation was made at room temperature and heated up at the same rate of heating as in the low temperature experiment. In the Low temperature TL, asymmetric-shaped intensity curves with the maxima between -150°C and -130°C were observed commonly for all specimens. However, big difference was observed in the magnitude of the low temperature TL intensity among the specimens: the intensity of a specimen with the strongest TL was one order of magnitude larger than that of the specimen with the weakest TL. The high temperature TL curves had maxima at about 80°C corresponding to the Tg, and the specimens with very weak low temperature TL had another maxima at 160°C as well as at 80°C. The fibers were repeatedly extended to a fixed strain at a rate of 105 rep./min. at room temperature, and the change of TL with the extension was measured. The high temperature TL intensity increased with extension but decreased with time after the stop of the repeated extension: the intensity measured after long time was weaker than before extension, with an exception of the specimen from FII company. In this fiber the increase in the TL intensity with the extension was much larger than in other specimens, and the intensity did not become weaker than before extension even after a long time. Low temperature TL intensity remarkably increased in the specimens with weak low temperature TL before extension, while it almost remained as before in the specimens with strong TL intensity before extension. The results obtained in the study suggested that TL method may be effectively used for the characterization of PET tire-cord fiber and also the study on the fatigue properties of the fibers.

Trapping parameters for non-saturation doses

In recent papers the authors (see ibid., vol.16, p.425, 1983) have described methods for obtaining trapping parameters from thermoluminescence curves. The methods are applicable when the traps are filled to saturation concentration. Here, the problem of obtaining trapping parameters from TL curves recorded under non-saturation conditions is discussed.

Correlations between elephantiasis and thermoluminescence of volcanic soil

Abstract There is clinical evidence to link non-filarial elephantiasis with soil from alcalic type volcanoes but no other correlation between properties of the soils and endemic regions have been found. This paper reports the use of thermoluminescence to distinguish between endemic and non-endemic soils from Cameroon and Ethiopia. The grouping of soils by the form of the glow curve is simple and a correlation with clinical data is at least 90% successful. The link between the TL and volcanic soil is thought to involve intrinsic lattice defects which are frozen in during the cooling of volcanic material. These defects influence both TL and chemical, or biological reactivity. After annealing, the TL curves of endemic and non-endemic areas are very similar which confirms that intrinsic defects are the major source of their differences.

ANTIARRHYTHMIC DRUGS AND IN VIVO MYOCARDIAL EXCITABILITY IN THE DOG

SUMMARY1. It has been demonstrated in an earlier study that the threshold for capturing the canine ventricle in situ varies at each time interval during the relative refractory period with a wide range of current levels. Thus, there is no single threshold curve, as is commonly accepted, but rather a range defined by upper limit of threshold (TU) and a lower limit (TL). TU is the minimal current level which always produced a generalized ventricular response. A wide range of lesser current levels produced a local response but with inconsistent propagation throughout the ventricle. TL is the maximal current level which was never able to elicit a generalized response.2. Applying the method used for the determination of these limits, the present study was undertaken to characterize the effect of quinidine, lignocaine, procainamide and verapamil in therapeutic doses on TU and TL.3. It was found that quinidine, lignocaine and procainamide elevated TU and TL during the relative refractory period, but only quinidine did so during diastole as well. Verapamil, however, did not have any significant influence on excitability. Procainamide had the least effect on the absolute refractoriness of the ventricular muscle as judged by the rightward displacement of the TU and TL curves, while quinidine and lignocaine exhibited a significant displacement regarding TU but much less so for TL.4. The proposition is entertained that TL represents true local excitability of the ventricular muscle and TU represents the stimulus needed for propagation throughout the heart during the most unfavourable conditions for such spread.5. Relative changes of TU/TL as a function of TU are considered to express the capability of the locally induced potential to evoke a generalized response: quinidine diminished, procainamide increased, and lignocaine had no effect on this parameter.

In vivo atrial excitability and anti-arrhythmic drugs

The threshold of excitability of the atrial muscle was studied in the in vivo beating canine heart. Unipolar cathodal and anodal strength-interval curves were constructed and found to be dissimilar in shape. It was found that at any interval within the relative refractory period of the atrium, as in the ventricle, there is a wide range of current levels delineated by an upper (TU) and lower (TL) limit of threshold which can stimulate the atrial myocardium. Within these limits the threshold varies spontaneously and can be reduced to TL level by a run of extrasystoles. Such TU and TL curves were repeatedly determined following administration of therapeutic doses of quinidine, procaine amide or lidocaine. It was observed that all three drugs prolonged the refractory period. The TU values increased following each of the drugs, and mostly after quinidine, while the TL curve was less affected by quinidine. It is suggested that the exit block thus produced is the principal mechanism whereby quinidine depresses atrial disrhythmias.

Trapping and emission centres in thermoluminescent barium sulphate

Abstract The nature of trapping and emission centres in various impurity doped BaSO4 phosphors has been investigated by thermoluminescence (glow curves and emission spectra) and esr techniques. The results indicate that anion radicals (such as SO4 −, SO3 −, O3 − etc) that act as trapped hole centres are formed by γ-irradiation. It has been found that corresponding to the temperatures at which the above centres are annihilated there are glow peaks in the TL curves. It is, therefore, suggested that the thermally released holes from each of such centres are mobile and recombine at some trapped electron centres. The energy thus released excite the impurity ion present, which on returning to the normal state gives its characteristic emission.

Thermoluminescence study of radiation-induced defects in alkaline earth sulfates

Since these processes can be accompanied by thermoluminescen ce, we have carried out a study of the thermoluminescen ce (TL) curves of alkaline earth sulfates in both the unactivated and activated (with europium and manganese) forms. Excitation was by means of the radioactive isotopes 45Ca and 35S, which were introduced both separately and together during synthesis. Nonradioactive samples were excited by irradiation with a 9~176 source. The absorbed dose was determined using the ferrous sulfate dosimeter and was 103 rad for the nonradioactive sulfates. The isotopes listed are pure fl-emitters with maximum energies: 45Ca 0.254 MeV, 35S 0.167 MeV, 9~176 0.61 and 2.18 MeV, respectively. The radioactive samples: 45CASO4. Eu, 45CASO4-Mn, 45CASO4" Eu. Mn, Ca3SSO4 �9 Eu, CaZSSO4 �9 Mn, Ca3~SO4 - Eu- 1Vln, 45Ca35SO4 - Eu, 45Ca35SOr �9 Mn, 45Ca35SO4 �9 Eu. Mn, Sr35SO4 �9 Eu, Ba35SO4, Ba35SO4 �9 Eu and nonradioactive samples of the unactivated sulfates of strontium and barium were synthesized in sealed quartz tubes by growing them from solution in a sodium chloride melt. The TL curves of these substances were obtained on standard equipment using the generally accepted

Effect of Shape of Transmission-Loss Curve on Subjective Reaction to Transmitted Noise

The use of single-number ratings is quite common in describing the acoustic performance of various building elements, e.g., the sound-transmission class of a wall or the impact-noise rating of a floor. The determination of single-number ratings involves certain assumptions regarding the relative importance of various frequency bands. In the sound transmission class (STC) rating system, for instance, a TL curve of irregular shape must be compared to a standard reference curve. The contribution of various frequency bands depends on the shape of the reference curve and on the method of comparison. An experiment has been carried out to determine subjectively the effect of various irregularities in TL curves as compared to a standard curve such as the STC contour. Results so far show that for frequencies in the range 500, 1000, and 2000 Hz, a dip 1 oct wide would effectively reduce the STC rating by 5 as compared to a dip 13 oct wide of the same depth.