Investigation of some commercial TLD chips/discs as UV dosimeters

Using a deuterium UV source, we have investigated the response of a number of commercially available thermoluminescence (TL) dosimeters (TLDs) to UV radiation (UVR), including LiF : Mg, Cu, P (TLD-100 H), CaF₂ : Dy (TLD-200), CaF₂ : Mn (TLD-400), Al₂O₃ (TLD-500), ⁷LiF : Mg, Cu, P (TLD-700 H) and CaSO₄ : Dy (TLD-900). The intrinsic method was used to detect UVR, while trap depth and frequency factors were estimated using the initial rise method. We have studied TL intensity as a function of exposure time, observing high sensitivity of TLD-500 to UVR. Conversely, TLD-400 displays weak sensitivity to these same radiations. Although TLD-900 and TLD-200 are both less sensitive to UVR than TLD-500, they each provide a linear response to UVR. The possible use of these phosphors as UV dosimeters has been further appraised, examining thermal fading effects and fading due to light exposure.     

一种基于分形结构的复合左右手传输线及其在小型化功分器中应用

首先提出了一种基于互补开口单环谐振器对(CSSRRP)的新型谐振式复合左右手传输线(CRLH TL)和其等效电路模型. 采用Bloch理论对等效电路进行了深入研究, 推导了CRLH TL工作于平衡态的计算公式. 通过等效电磁参数提取, 证明了该结构的负折射率与后向波传输特性. 其次在CSSRRP中引入Koch分形结构, 设计了工作于WiMAX波段的电小平衡零相移传输线. 最后基于设计的零相移传输线制作了一分四串联功分器. 对其进行测试, 测试结果与仿真结果完全符合, 从而验证了设计方法的正确性. 与传统统蜿蜒线状一分四功分器相比, 本文提出的功分器带宽有效展宽56%且尺寸缩减了42%. 基于分形CSSRRP的左手传输线必将在小型化无线通信系统中得到广泛应用.     

紫外分光光度法表征Lipozyme TL IM脂肪酶转酯化活性

建立了一种新的有机相脂肪酶转酯化活性测定方法. 以正己烷为溶剂,脂肪酶催化棕榈酸对硝基苯酯和正丁醇的转酯化反应为模型反应,通过测定反应液中310 nm下吸光值的变化计算反应转化率. 以气相色谱法对新建的紫外分光光度法进行验证,分别采用这两种方法测定了七种商品化脂肪酶的转酯化活性,两种方法所得实验结果基本一致. 利用紫外分光光度检测法考察了Lipozyme TL IM脂肪酶催化转酯化的时间进程及合成活性与酶量的关系,并对Lipozyme TL IM催化转酯化的性质（最适溶剂、酰基受体特异性、醇耐受性、最优反应温度和热力学稳定性）进行了表征.     

A new mathematical approximation of sunlight attenuation in rocks for surface luminescence dating

The attenuation of sunlight through different rock surfaces and the thermoluminescence (TL) or Optical stimulated luminescence (OSL) residuals clock resetting derived from sunlight induced eviction of electrons from electron traps, is a prerequisite criterion for potential dating. The modeling of change of residual luminescence as a function of two variables, the solar radiation path length (or depth) and exposure time offers further insight into the dating concept. The double exponential function modeling based on the Lambert-Beer law, valid under certain assumptions, constructed by a quasi-manual equation fails to offer a general and statistically sound expression of the best fit for most rock types. A cumulative log-normal distribution fitting provides a most satisfactory mathematical approximation for marbles, marble schists and granites, where absorption coefficient and residual luminescence parameters are defined per each type of rock or marble quarry. The new model is applied on available data and age determination tests.     

Electron paramagnetic resonance and the thermoluminescence emission mechanism of the 280 °C peak in natural andalusite crystal

Samples of natural andalusite (Al₂SiO₅) crystal have been investigated in terms of thermoluminescence (TL) and electron paramagnetic resonance (EPR) measurements. The TL glow curves of samples previously annealed at 600 °C for 30 min and subsequently gamma-irradiated gave rise to four glow peaks at 150, 210, 280 and 350 °C. The EPR spectra of natural samples heat-treated at 600 °C for 30 min show signals at g=5.94 and 2.014 that do not change after gamma irradiation and thermal treatments. However, it was observed that the appearance of a paramagnetic center at g=1.882 for the samples annealed at 600 °C for 30 min followed gamma irradiation. This line was attributed to Ti³⁺ centers. The EPR signals observed at g=5.94 and 2.014 are due to Fe³⁺. Correlations between EPR and TL results of these crystals show that the EPR line at g=1.882 and the TL peak at 280 °C can be attributed to the same defect center.     

Thermoluminescence mechanism in rare-earth-doped magnesium tetra borate phosphors

Magnesium tetra borate (MTB) doped with rare earths (REs) was prepared by the solid state sintering technique. Among the different RE dopants studied in this phosphor, gadolinium-doped phosphors resulted in a dosimetric peak at a relatively higher temperature. The thermoluminescence (TL) emission spectra of RE-doped MTB showed characteristic RE ³⁺ emissions. Electron paramagnetic resonance measurements were carried out in these phosphors to identify the defect centers formed during gamma irradiation and to establish a mechanism for the TL process. Signals corresponding to (BO ₃)^2?, O _v^? were seen upon irradiation which vanished on annealing at 250 °C, showing the role of these centers in the TL process. The thermal activation energies calculated based on the decay of these signals matched well with those calculated on the basis of the usual conventional method showing the validity of the mechanism of TL.     

ESR and TL studies of irradiated Anatolian laurel leaf (Laurus nobilis L.)

Laurel leaf (Laurus nobilis L.) samples that originated from Turkey were analyzed by electron spin resonance (ESR) and thermoluminescence (TL) techniques before and after γ-irradiation. Unirradiated (control) laurel leaf samples exhibit a weak ESR singlet centered at g=2.0020. Besides this central signal were two weak satellite signals situated about 3 mT left and right to it in radiation-induced spectra. The dose–response curve of the radiation-induced ESR signal at g=2.0187 (the left satellite signal) was found to be described well by a power function. Variation of the left satellite ESR signal intensity of irradiated samples at room temperature with time in a long term showed that cellulosic free radicals responsible for the ESR spectrum of laurel leaves were not stable but detectable even after 100 days. Annealing studies at four different temperatures were used to determine the kinetic behavior and activation energy of the radiation-induced cellulosic free radicals responsible from the left satellite signal (g=2.0187) in laurel leaves. TL measurements of the polymineral dust isolated from the laurel leaf samples allowed distinguishing between irradiated and unirradiated samples.     

Thermoluminescence characteristics of Na3 SO4 Cl:X (X=Ce,Dy, Mn) phosphor

In the present paper Na₃SO₄Cl:Ce, Na₃SO₄Cl:Dy, Na₃SO₄Cl:Mn, of Na₃SO₄Cl:Ce, Dy and Na₃SO₄Cl:Ce, Mn phosphor were synthesized by the wet chemical method. Thermoluminescence (TL) characteristics of Na₃SO₄Cl:Ce, Na₃SO₄Cl:Dy, Na₃SO₄Cl:Mn, Na₃SO₄Cl:Ce, Dy and Na₃SO₄Cl:Ce, Mn phosphors were studied for 5 Gy γ-ray dose. In TL glow curve, two peaks have been observed at 129°C and 224°C for different concentrations of Ce and Dy, whereas Mn peaks at 212°C. The same host is also tried for Ce, Dy (peaks at 126, 219) and Ce, Mn (248°C). A significant single peak is observed in the case of Na₃SO₄Cl:Mn and Na₃SO₄Cl:Ce, Mn. This may be due to the effect of activators. It is found that intensity tends to be increase with increased concentrations of the activators. The TL glow curves of the phosphors have been recorded and irradiated at a rate of 0.39 kGy h^?1 for 5 Gy γ-rays dose. It is also found that all the phosphors are less sensitive as compared with Thermoluminescence dosimetry-CaSO₄: Dy for the same γ-rays dose. The paper discuses the preliminary TL characteristics and effect of γ-rays on Na₃SO₄Cl:Ce, Na₃SO₄Cl:Dy, Na₃SO₄Cl:Mn, Na₃SO₄Cl:Ce, Dy and Na₃SO₄Cl:Ce, Mn phosphors.     

Facets of Luminescence for Dating

The aim of this article is to introduce luminescence dating and relate it to luminescence and Raman spectroscopy of minerals. The physical bases of luminescence signals used in dating and their relationships to other radiation-induced luminescence and Raman signals are briefly reviewed. The manner in which these signals are applied to evaluate luminescence ages is described. Archaeological and geological case studies from the author's experience are used to illustrate potentialities and issues related to different contexts, techniques, and materials.