TL Curve Research Articles

THE STRUCTURE OF THERMOLUMINESCENCE TRAPS IN AQUEOUS GROWN KCl

The results of TL studies in aqueous grown undoped KCl crystals are reported. A de-convolution of TL curve into five component peaks has been performed and trap depths have been obtained. The importance of bi-vacancy has been established as a fundamental trap and its anion vacancy end has also been proposed as a suitable trap for thermoluminescence in KCl crystals. The traps at anion vacancies linked to impurity vacancy I-V pairs have also been envisaged and the shift in the depths of traps is attributed to the electric field of I-V pairs in the lattice caused by inherent divalent ions. Some traps linked to hydroxyl groups have also been identified.

Optically stimulated luminescence of K2SO4:Ce and its relationship with TL glow-curves

K2SO4:Ce was investigated with respect to its OSL and TL properties. Due to the doping with Ce3+ ions, the material shows strong emission in the range of 300–400 nm with a maximum of approx. 330 nm. The spectrum of OSL stimulation is wide and enables stimulation with visible light and infrared. When comparing the 550 nm and 900 nm stimulation, differences in the initial intensity, decay rate and total counts can be seen. The higher total counts are obtained for 550 nm green light, with the initial intensity being higher for 900 nm infrared. The OSL signal, for both stimulations, is sensitive to preheat, however, this relationship is different in both cases. The study of the mutual correlation of the TL and OSL signal showed that only a part of the peaks in the TL curve are bleached by optical stimulation. The result indicates that there are both optically active and non-optically active traps in the material. The OSL-TL correlation study involves the deconvolution of the TL curves and the estimation of the bleaching of two main TL peaks and one minor peak. At least three traps are optically active but are emptied to varying degrees by different stimulations.

Fractional Curve in Adult Spinal Deformity: Is it a Driver of or a Compensation for Coronal Malalignment?

This was a retrospective review of the multicenter adult spine deformity database. The objective of this study was to investigate the role of the fractional curve (FC) on global coronal malalignment. Despite being very common, the role of the coronal FC as either a driver or compensation for global coronal malalignment is not well documented. Patients with the following characteristics were extracted from a prospective multicenter database: lumbar/thoracolumbar (TL) major coronal curve >15 degrees, apex at T11-L3, lower end vertebra at L3 or L4, above 45 years old, and FC >5 degrees. In addition to the classic radiographic parameters, baseline analysis included Cobb angle, pelvic obliquity (PO), fractional ratio (fractional Cobb/main Cobb), the sum of PO and FC, as well as the coronal Qiu classification. Curves distribution (TL vs. FC) were compared across the 3 Qui types, and the role of the FC was investigated. A total of 404 patients (63 y old, 83.3% female) were included: 43 patients were classified as type B, 120 as type C, and 241 were coronally balanced (type A). Compared with the balanced patients, type C patients had similar major TL Cobb angles but significantly larger fractional Cobb angles (17.5 vs. 22.3 degrees, P<0.001). By opposition, type B patients had significantly larger major TL Cobb angles (49 vs. 41 degrees, P=0.001) but smaller fractional Cobb angles (P<0.001). PO>5 degrees in the same direction as FC was more common in type B patients (20%) than in type C patients (7.5%), which suggests the preferential role of pelvic compensation. Our findings challenge the idea that FC is only a compensatory curve below a main lumbar or TL curve. In type B patients, FC acts as a compensation mechanism but fails to maintain coronal alignment despite the presence of PO. In type C patients, however, the lumbosacral FC acts as a primary driver of coronal malalignment. Level III.

Impact of Supine Radiographs to Assess Curve Flexibility in the Treatment of Adolescent Idiopathic Scoliosis.

Study Design:Retrospective cohort study.Objectives:The purpose of the study is to evaluate the role of supine radiographs in determining flexibility of thoracic and thoracolumbar curves.Methods:Ninety operative AIS patients with 2-year follow-up from a single institution were queried and classified into MT structural and TL structural groups. Equations were derived using linear regression to compute cut-off values for MT and TL curves. Thresholds were externally validated in a separate database of 60 AIS patients, and positive and negative predictive values were determined for each curve.Results:MT supine values were highly predictive of MT side-bending values (TL group: 0.63, P < 0.001; MT group: 0.66, P = 0.006). Similarly, TL supine values were highly predictive of TL side-bending values (TL group: 0.56, P = 0.001 MT group: 0.68, P = 0.001). From our derived equations, MT and TL curves were considered structural on supine films if they were ≥ 30° and 35°, respectively. Contingency table analysis of external validity sample showed that supine films were highly predictive of structurality of MT curve (Sensitivity = 0.91, PPV = 0.95, NPV = 0.81) and TL curve (Sensitivity = 0.77, PPV = 0.81, NPV = 0.94). ROC analysis revealed that the area under curve for MT structurality from supine films was 0.931 (SEM: 0.03, CI: 0.86-0.99, P < 0.001) and TL structurality from supine films was 0.922 (SEM: 0.03, CI- 0.84-0.98, P < 0.001).Conclusions:A single preoperative supine radiograph is highly predictive of side-bending radiographs to assess curve flexibility in AIS. A cut-off of ≥ 30° for MT and ≥ 35° for TL curves in supine radiographs can determine curve structurality.

Theory and Design of the Double-Tuned Coaxial and Flow-Reversal Mufflers: A New Perspective

Double-tuning an expansion chamber consists in extending the inlet–outlet pipes into the chamber by certain specific lengths so that the TL peaks due to the quarter-wave resonances of the annular cavities cancel or tune out the TL troughs due to the axial standing waves in the simple expansion chamber. The transfer matrix method is combined with the direct electroacoustic analogies in this paper to derive simple analytical expressions for the TL spectra of the double-tuned coaxial chamber (DTCAC) muffler or the axial-inlet, axial-outlet muffler, the double-tuned flow-reversal chamber (DTFRC) muffler or the inlet–outlet same-end muffler and the semi-tuned coaxial chamber (STCAC) or axial-inlet, axial-outlet muffler. It has been shown that barring the rather inconsequential sharp narrow peaks, the underlying overarching wide-band TL curve corresponds to a hypothetical simple expansion chamber, the effective lengths and diameter of which for the DTCAC muffler, DTFRC muffler and STCAC muffler have been tabulated at the end of this paper. This novel approach would simplify analysis and facilitate synthesis of mufflers with more than one semi-tuned as well as double-tuned chambers. Finally, some guidelines for design of these tuned mufflers for the HVAC systems have been given where it has been emphasized that physical lengths of the extended pipes would be different from the acoustic lengths to the extent of the end corrections.

Dose-rate dependence of natural TL signals from feldspars extracted from bedrock samples

The influence of dose rate on feldspar thermoluminescence shape is considered for a range of natural dose rates. The geologic dose rate experienced by bedrock samples is observed to control the position of the low-temperature edge of the bulk TL signal (the T1/2 parameter), with higher dose rates producing natural TL signals that begin to emit at lower measurement temperatures. This behavior can be explained in terms of the natural equilibrium between electron trapping and detrapping rates, as the trapping rate depends directly on the dose rate. The role of anomalous fading is more subtle. While a wide range of T1/2 values is found at low fading rates, only high T1/2 values are found when the fading rate is greater. This suggests that high fading rates may also influence the natural T1/2 value by making low-temperature regions of the TL curve unstable. Our results illustrate the need to consider dose-rate and fading-rate variations between bedrock samples before interpreting the minimum stability of each natural TL signal, a consequential result for future low-temperature thermochronology applications.

Thermoluminescence of new Al2O3-BeO ceramics after exposure to high radiation doses

New Al2O3-BeO ceramics were synthesized from alumina nanopowder in BeO crucibles by high-temperature treatment in reducing conditions. It was found that the TL curve of these ceramics is characterized by a dosimetric peak at 520–530 K for a heating rate of 2 K/s. The integrated TL of the peak is not influenced by the heating rate of the samples, unlike that in anion-defective alumina and beryllia crystals. The presence of an energy distribution of the traps which cause dosimetric TL peak is verified by Tm-Tstop and initial rise methods. Linear dependence on dose of the intensity of TL peak at 520–530 K is observed in the 10–300 Gy gamma-dose range. The diversity of TL sensitivity of the ceramic samples synthesized in one cycle does not exceed 10%. The results obtained show that the newly synthesized Al2O3-BeO ceramics are promising materials for TL dosimetry of high doses of ionizing radiation.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P29. Does the true AP radiograph for scoliosis differ from ancient convention? Lessons from 3D imaging

BACKGROUND CONTEXT Scoliosis is a three-dimensional deformity. As such, the rotational component must be considered during its evaluation and management. However, the severity of scoliosis has long been measured in the 2D coronal plane using the Cobb angle – a modality unable to account for axial vertebral rotation (VR). In the past, the Stagnara lateral radiograph has attempted to compensate for VR. To date, no similar radiographic view has been described for the AP plane. Recent advances in 3D CT imaging may allow clinicians to more accurately measure Cobb angles in scoliosis by compensating for axial VR. Here, we present a retrospective study comparing Cobb angle measurements taken from both traditional 2D radiographs, and rotationally compensated CT images. PURPOSE The purpose of this study is to compare Cobb angle measurements routinely made for AIS in both rotationally compensated and standard imaging. STUDY DESIGN/SETTING Retrospective matched cohort study. PATIENT SAMPLE A total of 66 patients diagnosed with AIS. OUTCOME MEASURES PT, MT, and TL/L curve Cobb angle values, coronal balance, thoracic and lumbar apical vertebral translation (T/L-AVT), thoracic and lumbar apical vertebral rotation (T/L-AVR), thoracic kyphosis, and sagittal balance. METHODS In this retrospective study, standard AP, lateral, and bending radiographs of 66 patients age 10-19 with AIS were obtained. Using multiplanar 3D CT, the coronal plane was reconstructed within the plane of the vertebral axis to form a rotationally compensated 3D CT image (RC-3DCT). The following measurements were made on both imaging modalities: PT, MT, TL/L curve, coronal balance, T/L-AVT, T/L-AVR, thoracic kyphosis, and sagittal balance. RESULTS Mean MT curve was found to be 40.56° on AP radiograph versus 35.39° on RC-3DCT (n=63, P=.00039). In 28 patients (42.4%), rotational compensation altered the end vertebra of the major curve by at least 1 level. The mean TL curve obtained on radiograph, was significantly larger than that of RC-3DCT (n=62; 35.34° vs. 30.98° ; P=.0046). AP films overstated coronal balance by over 50% when compared to RC-3DCT Mean T-AVT was measured to be 25.28 mm on conventional films and 19.46 mm on RC-3DCT (n=62; P=.00033). RC-3DCT L-AVT was significantly smaller than that of standard films (P=.0094). Mean T-AVT on standing film was 26.2±31.0°. The mean proximal thoracic kyphosis did not differ between the two modalities: 20.66° on radiograph versus 21.062° on RC-3DCT (P=.41). CONCLUSIONS Measurements traditionally made on AP radiograph to evaluate scoliosis may be inaccurate due to VR. Our data suggest that axial rotation of a patient 19° per Nash–Moe grade with respect to the coronal plane may adequately compensate for the rotational component of deformity without the need for CT. Additionally, rotational compensation may yield end vertebrae levels different from those obtained traditionally. In 42% of patients, VR compensation altered end vertebral designation by at least 1 level.

Effect of N doping on Tl2Ga2S3Se single crystals: Thermoluminescence characterization of defect centers

Thermoluminescence study on nitrogen doped Tl 2 Ga 2 S 3 Se single crystals was achieved by performing the experiments with different stopping temperatures of 10−24 K and various heating rates between 0.4 and 1.2 K/s below room temperature. Thermoluminescence peak with peak maximum temperature of 54 K was detected from the emitted luminescence. Two trap levels were obtained from the observed spectra. Curve fitting and initial rise methods were applied to compute the activation energies and the values of 34 and 70 meV were found. Thermal cleaning process was applied to separate the overlapping peaks and so true energy region of trapping levels was corroborated. Moreover, variation of shape and position of TL curve were studied by investigating the heating rate behavior of trap levels. The best known behavior which the peak maximum temperature increases while the thermoluminescence intensity decreases with raising heating rate was observed. The effect of the N doping on the existed defects was discussed.

Evidence of luminescence modification with structure of zirconia phases

Three crystallographic phases of nanocrystalline zirconium oxide (ZrO2) are prepared by solution combustion technique. Tetragonal and cubic phases are stabilized at low temperature by adding yttrium content. Phase stabilization is confirmed by X-ray diffraction and Raman spectroscopy. The XRD results are analyzed using rietveld refinement and average crystallite size is found to be 50−60nm. Characteristic PL emission of Dy3+ ions are observed at 490, 578, 672 and 764nm corresponding to 44F9/2→6H15/, 4F9/2→6H13/2, 4F9/2→6H11/2 and 4F9/2→6H9/2 transitions respectively. The spectral peak shape changes and variation of blue to yellow intensity ratio in different symmetry of ZrO2 has been discussed. CIE chromaticity color coordinates (x, y) are calculated for Dy3+ doped zirconia phosphors and fall near white light region. A high intense TL glow peak at 441K and a less intense peak at 550K are observed in monoclinic ZrO2. The intensity of 441K TL glow peak is drastically reduced and a new TL peak at 703K is found in tetragonal ZrO2. Whereas, cubic ZrO2 exhibit a single TL glow with peak at 703K. Dy3+ doped ZrO2 (monoclinic) exhibit two prominent TL peaks at 457 and 695K whereas tetragonal and cubic samples shows only high temperature peak. It is concluded that TL curve is modified in three zirconia system and TL kinetic parameters are discussed.

Luminescence properties of long-lasting phosphor SrMg2(PO4)2:Eu2+, Ho3+, Zr4+

Novel long lasting phosphors SrMg2(PO4)2:Eu2+, SrMg2(PO4)2:Eu2+, Zr4+, SrMg2(PO4)2:Eu2+, Ho3+ and SrMg2(PO4)2:Eu2+, Ho3+, Zr4+ were synthesized by conventional solid-state reaction method. The luminescent properties were systematically characterized by X-ray diffraction, photoluminescent excitation and emission spectra, as well as thermoluminescence spectrum and decay curves. The XRD patterns indicated that the samples belonged to monoclinic phase and co-doping Eu2+, Ho3+ and Zr4+ ions had no effect on the basic crystal structure. These phosphors emitting purplish blue light is related to the characteristic emission of Eu2+. The afterglow time of Eu2+ activated SrMg2(PO4)2 can be greatly enhanced by the co-doping of Ho3+, Zr4+. After the 365 nm UV light excitation source switching off, the Sr0.92Mg1.95(PO4)2:Eu2+0.01, Zr4+0.05, Ho3+0.07 phosphorescence can be observed for more than 1013 s in the limit of light perception of dark-adapted human eyes (0.32 mcd/m2). Different kinds of TL peaks at 423, 448 and 473 K have appeared, and traps densities have increased compared with the Eu2+ single doped SrMg2(PO4)2 phosphor. By analyzing the TL curve the depths of traps were calculated to be 0.846, 0.896 and 0.946 eV, respectively, which suggested that the co-doping of Ho3+, Zr4+ improved the electron storage ability of material. Besides, the mechanism was discussed in this report.

Light-induced gradual activation of photosystem II in dark-grown Norway spruce seedlings

Gymnosperms, unlike angiosperms, are able to synthesize chlorophyll and form photosystems in complete darkness. Photosystem I (PSI) formed under such conditions is fully active, but photosystem II (PSII) is present in its latent form with inactive oxygen evolving complex (OEC). In this work we have studied light-induced gradual changes in PSII function in dark-grown cotyledons of Norway spruce (Picea abies) via the measurement of chlorophyll a fluorescence rise, absorption changes at 830nm, thermoluminescence glow curves (TL) and protein analysis. The results indicate that in dark-grown cotyledons, alternative reductants were able to act as electron donors to PSII with inactive OEC. Illumination of cotyledons for 5min led to partial activation of PSII, which was accompanied by detectable oxygen evolution, but still a substantial number of PSII centers remained in the so called PSII-QB-non-reducing form. Interestingly, even 24h long illumination was not sufficient for the full activation of PSII centers. This was evidenced by a weak attachment of PsbP protein and the absence of PsbQ protein in PSII particles, the absence of PSII supercomplexes, the suboptimal maximum yield of PSII photochemistry, the presence of C band in TL curve and also the presence of up-shifted Q band in TL in DCMU-treated cotyledons. This slow light-induced activation of PSII in dark-grown cotyledons could contribute to the prevention of PSII overexcitation before the light-induced increase in PSI/PSII ratio allows effective operation of linear electron flow.

Luminescence properties of Eu2+ doped SrB4O7 phosphor for radiation dosimetry

In this report, we presented the TL/OSL properties of Eu doped SrB4O7 phosphor under β-irradiation. This phosphor was synthesized by using solid state method. The phosphor shows OSL sensitivity about 33% than that of commercially available α-Al2O3: C phosphor. CW-OSL curve possess two components having photoionization cross-sections 0.707×10−17 and 18.58×10−17cm2 respectively and TL sensitivity about 200 times higher than TLD-500. The kinetic parameters such as activation energy, frequency factor and order of kinetics of TL curve were calculated by using peak shape method. In TL/OSL mode dose-response was almost linear in the range of measurements. The MDD was found to be 1.26mGy with 3σ of background. Also reusability studies showed the phosphor can be reused for 10 cycles with 1% change in the OSL output. The PL spectra of SrB4O7 showed emission in NUV region when excited with 318nm under UV source.

단순확장관 내부 파티션 위치에 따른 음향투과손실 계산식의 개발

This paper proposed a new formula for predicting acoustic power transmission loss of simple expansion chamber with two internal partitions. Seventeen cases of computational results were performed and the database was constructed for the TL according to the various positions of internal partitions. Using this database, firstly, the formula for the peak values of TL at certain frequencies was developed using the least square estimation. Secondly, the formula for the TL curve could be obtained automatically with the input data of the positions of two internal partitions. The formula of TL developed in this paper showed good agreement with computational results. This formula will be helpful for the positioning of internal partitions to improve TL at target frequencies.

Dosimetric studies in combustion synthesized LiSr4(BO3)3:Sm (III) under X-ray irradiation

In this paper, combustion synthesis of samarium III (Sm)-doped LiSr4(BO3)3 (LSBS) and mechanism during the reaction was discussed. The structural characterization was done through X-ray diffraction, Fourier transformed infrared spectroscopy studies and morphology of prepared material was highlighted by scanning electron microscope (SEM) results. Dosimetric characteristics were studied through thermoluminescence analysis under X-ray irradiation. Glow curve fitting, dose response and fading effect were also reported in detail. The observation supports that LSBS may be a promising material for environmental radiation monitoring. The LSBS show two peak nature TL curve with P1 at 165 and P2 at 303 °C. Also, the material gives linear dose response in the range of measurement.

Low-Temperature Thermoluminescence Studies on TlInS2Layered Single Crystals

Thermoluminescence characteristics of TlInS2 layered single crystals grown by the Bridgman method were investigated in the low temperature range of 10 300 K. The illuminated sample with blue light (≈ 470 nm) at 10 K was heated at constant heating rate. Curve tting, initial rise and various heating rate methods were used to determine the activation energy of the trap levels. All applied methods showed good consistency about the presence of ve trapping centers located at 14, 19, 350, 420, and 520 meV. Behavior of the TL curve for various heating rates was investigated. Traps distribution has also been studied. The activation energies of the distributed trapping centers were found to be increasing from 14 to 46 meV.

Theoretical derivation of a simplified form of the OTOR/GOT differential equation

A simplified form of the OTOR/GOT differential equation has been derived, which may be employed in the evaluation of TL curves for saturated (N = no) and non-saturated cases (N > no). The present eqn. is found to be theoretically correct and physically sound in comparison with empirical general order kinetics. It has been found that the TL curve evaluated using the present eqn. matches the TL curves evaluated using differential eqn. formalism, and spans the region from α = no/(100N) to α = 0.999 (where α is the ratio of the retrapping probability to the recombination probability). The simulated curve resembles a first order kinetics curve when α = no/(100N) and a second order kinetics curve when α = 0.999. However, comparison with general order kinetics for the intermediate range is not possible as a one- to-one correspondence between α and b cannot be made. Also, calculation in the saturated case is made simpler since only three unknown parameters (E, s and α) are required.

Controlled synthesis of Li2B4O7:Cu for temperature sensing

With the aim of developing a new phosphor for temperature sensing, the effect of different annealing processes and co-dopants (Ag, In, Dy or Ti) on the TL properties of copper-doped Li2B4O7 synthesized by Solution Combustion Synthesis was investigated. Compared with slow annealing, fast annealing induces a high temperature peak (∼310 °C) in the TL curve of Li2B4O7:Cu. The defect structure of Li2B4O7:Cu synthesized by fast annealing is not reproducible, resulting in high sample-to-sample variability in the TL curves. We tested In, Dy, Ti or Ag as co-dopants in Li2B4O7:Cu and found that Ag co-doping resulted in increased TL intensity and reproducible TL curves from sample to sample. In addition, the relative intensity of the main TL peak at ∼200 °C can be controlled by adjusting the Ag doping concentration. Finally, the effect of light exposure on irradiated samples and the room temperature fading over time have been examined. Li2B4O7:Cu,Ag showed low room light sensitivity and almost no fading over a 24 h storage period in the dark. These features support the application of Li2B4O7:Cu,Ag for temperature sensing.

Reddish orange long lasting phosphorescence of Sm 3+ in Sr 2ZnSi 2O 7:Sm 3+ phosphors

Long lasting phosphorescence phosphors with composition of (Sr 1- x Sm x) 2ZnSi 2O 7 were prepared by conventional high-temperature solid-state method. Their properties were systematically investigated utilizing XRD, photoluminescence, phosphorescence and thermoluminescence spectra. The results showed that these phosphors emitted reddish orange light that corresponds to the characteristic emission due to the 4G 5/2→ 6H 5/2, 6H 7/2 and 6H 9/2 transitions of Sm 3+. After the UV light excitation source was switched off, the bright reddish orange long lasting phosphorescence could be observed and it could last for about 30 min in the limit of light perception of dark-adapted human eyes (0.32 mcd/m 2). A wide TL band raging from room temperature to 700 K with two dominating peaks at 340 and 602 K appeared in the TL spectrum. The TL curve could be fitted to five TL peaks and the low temperature TL peak at 340 K was found to be responsible for the long lasting phosphorescence. Also, the mechanism was discussed.

The effect of preheating on the IRSL signal from feldspar

It is difficult to relate the IRSL signal from feldspar to a particular region of the TL curve; prior IR stimulation reduces the TL signal over a wide range of temperatures. Such data are apparently consistent with the observation from pulse anneal experiments that a laboratory-induced IRSL signal is detectably eroded by a relatively low temperature preheat. These results can be explained by a distribution of trap depths of IR sensitive traps, and/or by changes in recombination probability induced by IR exposure. To investigate the relative importance of these processes, we first examine the relationship between the loss of blue IRSL and TL signals with preheating, and the effect of prior IRSL on the TL signal. Using IRSL measured at 50 °C and a SAR protocol, we then examine the dependence on preheat temperature of equivalent dose (D e), laboratory fading rate ( g), and the resulting luminescence age, from three sedimentary potassium-rich feldspar extracts. We demonstrate that there is no systematic increase in D e for a preheat temperature range from ∼80 °C to ∼320 °C (60 s duration). After fading correction, age plateaus vary slightly over the temperature range examined, but there is no evidence for an increase in age with preheat temperature. We therefore conclude that the main dosimetry trap(s) in feldspar are not significantly eroded by laboratory heating for up to 60 s at 320 °C, and we tentatively identify the source of this IRSL as a TL peak lying between 410 and 420 °C; this suggestion is consistent with a kinetic analysis of sensitivity-corrected IRSL data. The corollary to our observations is that shallow (unstable) traps do not give rise to a significant IRSL signal.