Temperature-dependent photoluminescence of novel Eu3+, Tb3+, and Dy3+ doped LaCa4O(BO3)3: Insights at low and room temperatures

This study explores the structural and optical qualities of LaCa4O(BO3)3 (LACOB) phosphors doped with Eu3+, Dy3+, and Tb3+ using a microwave-assisted sol-gel technique. It uncovers oxygen-related luminescence defects in LACOB, highlighting emission peaks at 489 and 585 nm for Dy3+, a distinct sharp peak at 611 nm for Eu3+ in the red spectrum, and a notable green emission for Tb3+ due to specific transitions. The photoluminescence (PL) analysis indicates that luminescence is optimized through precise doping, leveraging dipole interactions, and localized resonant energy transfer, which are influenced by dopant concentration and spatial configuration. Temperature studies show emission intensity variations, particularly noticeable below 100 K for Tb3+ doped samples, demonstrating the nuanced balance between thermal quenching and luminescence efficiency. This temperature dependency, alongside the identified optimal doping conditions, underscores the potential of these materials for advanced photonic applications, offering insights into their thermal behavior and emission mechanisms under different conditions.

Beta irradiation-induced thermoluminescence: Glow curve analysis and kinetic parameters in combustion-synthesized undoped Ca4YO(BO3)3

This study examines the thermoluminescent (TL) properties of undoped Ca4YO(BO3)3 phosphor, focusing on how it behaves under a variety of experimental conditions. The IRSL-TL 565 nm was chosen as the appropriate detection filter among various optical detection filter combinations. During the preheating trials conducted at a rate of 2 °C/s, the TL peak exhibited increased intensity, particularly around 200 °C. The experimental outcomes demonstrated a reliable linear relationship (R2 = 0.996 and b = 1.015) in the dose response of undoped preheated Ca4YO(BO3)3 within the range of 1-200 Gy. The investigation encompasses a range of techniques, including the TM-Tstop method, computerized glow curve deconvolution (CGCD) analysis, and theoretical modelling. The application of the TM-Tstop method to samples irradiated with a 5 Gy dose revealed distinct zones on the TM versus Tstop diagram, signifying the presence of at least two discernible components within the TL glow curve, specifically, a single general order kinetics peak and a continuous distribution. The analysis of activation energy versus preheated temperature exhibited a stepwise curve, indicating five trap levels with depths ranging between 1.13 eV and 1.40 eV. The CGCD method also revealed the superposition of at least five distinct TL glow peaks. It was observed that their activation energies were consistent with the Tm-Tstop experiment. Furthermore, the low Figure of Merit (FOM) value of 1.18% indicates high reliability in the goodness-of-fit measure. These findings affirm the reliability and effectiveness of the employed methods in characterizing the TL properties of the Ca4YO(BO3)3 phosphor under investigation. Theoretical models, including the semi-localized transition model, were introduced to explain anomalous observations in TL glow peak intensities and heating rate patterns. While providing a conceptual framework, these models may require adjustments to accurately capture the specific characteristics uncovered through CGCD analysis. As a potential application, the study suggests that the characterized TL properties of Ca4YO(BO3)3 phosphor could be utilized in dosimetric applications, such as radiation dose measurements, owing to its reliable linear response within a broad dose range.

Temperature-responsive insights: Investigating Eu3+ and Dy3+ activated yttrium calcium oxyborate phosphors for structure and luminescence

An investigation into the luminescent behavior of YCOB (Yttrium Calcium Oxyborate) doped with Eu3+ and Dy3+ ions, synthesized via the combustion method, is presented. The study, employing X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Energy-Dispersive X-ray Spectroscopy (EDS) analyses, confirms the structural integrity and purity of the synthesized nanophosphors. An XRD pattern exhibiting distinct crystalline peaks indicates that the dopant ions were successfully integrated into the YCOB lattice. The photoluminescence (PL) response of YCOB with Eu3+ and Dy3+ ions is thoroughly examined, uncovering distinct excitation and emission spectra. In the case of Eu3+ doping, excitation spectra reveal a significant charge transfer (CT) band at 254 nm, indicative of electron transfer between oxygen and europium ions. This CT transition enhances our understanding of the excitation behavior, with the dominant and Laporte-forbidden 5D0 → 7F2 transition. Characteristic peaks at 345 nm in the excitation spectra efficiently stimulate YCOB:Dy3+ when Dy3+ is used as a dopant. The primary emission peak at 585 nm corresponds to the hypersensitive electric dipole transition 4F9/2-6H13/2. Concentration quenching phenomena are observed, with a maximum Eu3+ concentration of 7 wt % attributed to the dipole-quadrupole interaction. Dy3+ doping, with a maximum concentration of 2 wt % primarily shows multipolar interactions, especially dipole-dipole interactions. The study extends to CIE chromaticity analysis, emphasizing Eu3+ doping's suitability for white light-emitting diode (WLED) applications and ensuring color stability. Conversely, varying Dy3+ concentrations do not yield consistent chromaticity coordinates. These findings have significant implications for the development of advanced phosphor materials across diverse applications, offering a roadmap for optimizing their optical performance.

Europium-doped strontium gadolinium oxide phosphor: Investigating structural and photoluminescence characteristics via sol-gel combustion synthesis

SrGd2O4 phosphors doped with Eu3+ were successfully synthesized through a sol-gel combustion method, covering a range of dopant concentrations from 0.25 mol% to 3 mol%. The structural analysis of these phosphor materials was comprehensively conducted utilizing various techniques, including X-ray powder diffraction analysis (XRD), Energy Dispersive X-ray (EDX), and Fourier-transform infrared spectroscopy (FTIR). In addition to unveiling the structural characteristics, these analyses provide valuable insights into the compositional aspects, enhancing our understanding of the synthesized SrGd2O4:Eu3+ phosphors across different doping levels. XRD analysis findings validate the successful generation of the intended SrGd2O4 host, demonstrating orthorhombic system structures consistent with JPCD card number 98-019-3592. FTIR analyses conducted on the phosphor samples not only identify bending modes but also reveal intricate details about small vibration bonds within the material. When excited by the 349 nm laser, SrGd2O4:xEu3+ phosphors exhibit distinct photoluminescence (PL) properties like red emission at 614 nm from Eu3+. From the emission spectra, one can clearly observe that Eu3+ with an ionic radius close to the Gd3+ ion preferentially occupies the symmetry sites of the host lattice. The optimal doping concentration was determined to be 0.5 mol%, as revealed by the data in our study. Additionally, a deeper understanding of the luminescence quenching mechanism was attained, pinpointing the involvement of dipole-dipole (d-d) energy transfer in this intriguing phenomenon. This optimal concentration not only enhances the material's properties but also underscores the pivotal role of d-d interactions in governing the luminescence behavior within the doped system.

Novel Sm3+ doped YCa4O(BO3)3 phosphors: Structural and, low and room temperature luminescent insights

Inorganic phosphors, known for their ability to capture energy from various sources and emit visible light, have become essential in the development of advanced lighting and display technologies. This study explores YCa4O(BO3)3 (YCOB) as a potential host material for phosphors, focusing on the luminescent properties of YCOB phosphors doped with Sm3+ ions. The successful integration of Sm3+ ions into the YCOB host lattice is confirmed through structural characterization using X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Energy-Dispersive X-ray Spectroscopy (EDS). Photoluminescence (PL) studies reveal distinct emission spectra with Stark energy level splitting, indicating a cooperative effect between Y3+ and Sm3+ ions. Concentration quenching, mainly attributed to dipole-dipole (d-q) interactions, is observed at higher Sm3+ concentrations. Temperature-dependent PL measurements demonstrate thermal quenching at lower temperatures and increased emission intensity with higher laser power. Thermal quenching is explained by reduced lattice vibrations and electron-phonon interactions, leading to decreased radiative recombination of charge carriers. The CIE chromaticity data position the samples in the orange-red region, emitting vibrant orange-red light. This comprehensive investigation provides insights into the synthesis and luminescent properties of YCOB:Sm3+ phosphors, highlighting their potential applications in luminescent devices.

Tb-doped MgAl2O4 phosphors: A study of structural and luminescence characteristics

In the MgO-Al2O3 system, magnesium aluminate spinel (MgAl2O4) is a technologically significant compound due to its unique properties, including a high melting point, low thermal conductivity, excellent thermal shock resistance, chemical inertness, and robust mechanical strength. This compound has diverse applications in refractory materials, catalyst supports, moisture sensors, nuclear techniques, insulating materials, and even military applications. While rare-earth elements are commonly used as dopants in luminescent materials, limited research exists on doping of Tb3+ ions in magnesium aluminate. This study investigates the luminescence properties of Tb3+ doped synthesis magnesium aluminate materials, shedding light on this underexplored area. The combustion method is employed for synthesis, known for producing nano-sized powders with exceptional luminescent properties. Additionally, this study explores Sm3+ ion doping in magnesium aluminate materials and their luminescence properties. Using the combustion synthesis method, structural attributes of Tb3+-doped MgAl2O4 nanophosphors are meticulously examined. Through X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analyses, coupled with excitation and emission spectra, a comprehensive investigation of the luminescent provide behavior at room temperature is provided. The XRD data reveal Tb3+ doped MgAl2O4 phosphors exhibit a single phase with face centred cubic structure belonging to the Fd3m‾ space group, consistent with the standard JCPDS files (No. 21-1152). Excitation and emission spectra offer valuable insights into the energy transitions within the Tb3+-doped MgAl2O4 phosphors. Furthermore, the study explores the effects of varying Tb3+ ion concentrations on the luminescent properties, revealing an optimal doping concentration of 5 wt% Tb for maximizing emission intensity. Concentration quenching, primarily attributed to dipole-dipole (d-q) interactions, is observed at higher Sm3+ concentrations. In conclusion, this research enhances our understanding of rare-earth ion doping in luminescent materials and highlights the potential applications of Tb3+-doped MgAl2O4 nanophosphors, which offer promise for various technological applications, including lighting and displays.

Luminescence of undoped and Eu3+ activated zinc gallate phosphor: Synthesis, unusual intense 5D0 → 7F4 red emission

A series of Eu³⁺-doped ZnGa₂O₄ samples were synthesized via the urea-glycine combustion route. Powder X-ray diffraction (XRD) was used to investigate the crystallinity of the samples, energy dispersive spectroscopy (EDS) to explore the elemental composition, Fourier transform infrared (FTIR), to observe the vibrational modes of the samples, photoluminescence (PL) to determine the luminescence properties. The XRD data prove that the samples remain single cubic structure even at high concentrations of Eu³⁺, enabling the formation of a unique emission spectrum. The active ion concentration was varied to examine the influence of concentration on luminescent properties. This study revealed a ⁵D₀ →⁷F₄ transition located at 700 nm with unusual intensity that has not been documented in the literature, which suggests that the active ion concentration can influence the luminescent characteristics of the phosphors. The increasing Eu³⁺ content increases the number of Eu³⁺ ions in ZnGa₂O₄ host lattice, which enhances the luminescence efficiency of the phosphor. However, beyond a certain level of Eu³⁺content (i.e., 3 wt% Eu³⁺), the number of Eu³⁺ ions becomes excessive, resulting in a reduction in luminescence efficiency due to concentration quenching. The dipole dipole interaction is elucidated to play a prominent role in the mechanism of Eu³⁺ quenching in the ZnGa₂O₄. An assessment of color coordinates based on emission spectra reveals that the coordinates shift from blue to the white light region, and then to red as Eu³⁺ content increases. This suggests that there is a substantial relationship between the Eu³⁺ concentration and the measured color coordinates.

Thermoluminescence in GdAl3(BO3)4 phosphors: Unusual heating rate dependencies, dose responses and kinetic parameters

The current study focuses on the production of GdAl₃(BO₃)₄ (GAB) phosphors using gel combustion. X-ray diffraction (XRD) and thermoluminescent (TL) methods were used to investigate the structural and thermoluminescence (TL) features of the samples. XRD results revealed that GAB phosphors were crystallized in a rhombohedral crystal system. TL experimental data exhibited an unusual heating rate behaviour, which was explained by the semi-localized transition model, and this provides valuable insight into the properties of the GAB sample. Beta-irradiated GAB hosts exhibit two primary peaks at 106 °C and 277 °C on their TL glow curves. We have employed a variety of heating rates (VHRs), T_M-T_stop method, and computerized glow curve deconvolution (CGCD) techniques. By using a combination of these techniques, we can identify the kinetic parameters of the GAB samples more accurately, including peak numbers, activation energy, and frequency factors. Both T_m-T_stop and CGCD techniques produce similar results in terms of trap numbers and trap depths. In the trap centers, electrons were trapped at 1.05 eV, 0.84 eV, 1.12 eV, 1.20 eV, 1.42 eV, 1.63 eV and 1.42 eV. There was a linear behaviour of GAB samples over a dose range of 0.1 Gy-10 Gy. GAB phosphors did not show any significant changes in TL response with repeated irradiation cycles, suggesting that it is a reliable radiation dosimeter. GAB is therefore a potential candidate for radiotherapy dose measurement based on these findings.

Adsorption of thorium (IV) ions using a novel borate-based nano material Ca3Y2B4O12: Application of response surface methodology and Artificial Neural Network

Since nuclear wastes are the most important wastes in terms of health and the environment, they are evaluated differently within nuclear reactors as well as in terms of their use in medical and industrial applications. In some cases, emergency intervention is necessary due to the amount of radioactivity or the physical and/or chemical conditions. . The purpose of this study is to investigate the adsorption properties of nano Ca₃Y₂B₄O₁₂ (CYBO) material synthesized by the sol-gel combustion method for the adsorption of Thorium (IV) from an aqueous medium. We tested how pH (3-8), the concentration of Th (IV) (25-125 mg/L), amount of adsorbent value (0.005-0.08 g) and temperature (20-60 °C), affect adsorption efficiency. The best possible combinations of these parameters were examined by Response Surface Methodology (RSM) and Artificial Neural Network (ANN). R² values for RSM and ANN were 0.9964 and 0.9666, respectively. According to the models, the adsorption capacity under the optimum conditions determined for the RSM and ANN model was found to be 134.62 mg/g and 125.12 mg/g, respectively.

Synthesis and beta particle excited thermoluminescence of BaSiF6 phosphor

BaSiF₆ phosphor was synthesized by a gel combustion method. The crystalline size was found to be 54.17 ± 4.36 nm using Williamson-Hall (W-H) approximation. The TL data collected by means of a combination of a commercial BG39 and HC575/25 filters was studied to evaluate basic kinetic parameters. Three TL glow peaks of BaSiF₆ phosphors are centered at around 84, 190 and 322 °C. T_m-T_stop, various heating rate (VHR) and computerized glow-curve deconvolution (CGCD) method were utilized to analyse collected data. Our findings indicate that luminescence process in scrutinized material may obey second order kinetics. The TL dose response of the TL glow peaks exhibits a linear characteristic up to 100 Gy. Deconvolution of the glow curve reveals that the number of the component TL glow peaks in the complex glow curve is composed of well-isolated six overlapping glow peaks. The FOM value is 2.32.

SURVIVIN POSITIVITY AND PROGNOSTIC FACTORS IN PAPILLARY THYROID CARCINOMAS

CONTEXT

Papillary thyroid carcinoma(PTC)s are the indolent progressive tumours. Survivin is a unique bifunctional protein with cell cycle regulation and apoptosis inhibition. The expression of this protein has been shown to be increased in thyroid tumours correlated with aggressive behavior from well differentiated to anaplastic.

OBJECTIVE

In this study, we aimed to investigate the relationship between immunohistochemically survivin expression and tumour-associated prognostic factors in papillary thyroid carcinomas.

DESIGN

In patients with thyroidectomy, we compared the clinicopathological findings and immunohistochemical positivity for survivin.

SUBJECTS AND METHODS

In 109 patients, sex, age, tumour size, histological tumour variant, tumour focality, tumour border pattern, tumour peripheral/intratumoural lymphocytic and stromal response, intraglandular spread, extrathyroideal spread, lymph node metastases, lymphocytic tiroiditis and relationships of these findings with survivin positivity were investigated.

RESULTS

When we indicated the tumour size and compared it with survivin expression, tumour size correlates with, survivin expression (p = 0.016). Survivin expression was correlated statistically significant with lymphovascular invasion, without stromal response and with intraglandular extension respectively (p<0.001, p = 0.043, p<0.001). No significant correlation was found between other clinicopathological parameters and survival.

CONCLUSION

Few studies have investigated the relationship of survivin expression with prognosis in thyroid papillary carcinomas and showed that survivin was a poor prognostic marker. If its expression is detected in preoperative cytology smears, it may affects the surgical treatment strategy. When it is detected in the tissue, postoperative radioactive iodine treatment plan may be modified and the need for more aggressive follow-up may be considered.

Adsorption of thorium (IV) ions by metal ion doped ZnO nanomaterial prepared with combustion synthesis: Empirical modelling and process optimization by response surface methodology (RSM)

Environmental problems have reached enormous dimensions, driving efforts to remove and recycle waste from energy and industrial production. In particular, removing the radionuclide contamination that occurs as the nuclear industry grows is difficult and costly, but it is vital. Technologic and economical methods and advanced facilities are needed for the separation and purification of radioactive elements arising from the nuclear industry and uranium and thorium mining. With the adsorption method, which is the most basic separation and recovery method, the use of high-capacity nanomaterials has recently gained great importance in reducing the activity of the waste, reducing its volume by transforming it into solid form, and recovering and removing liquid radioactive wastes that might harm the ecological environment. This study aimed to determine the adsorption properties of metal ion-doped nano ZnO (nano-ZnO:Al) material synthesized by the microwave-assisted gel combustion method for the adsorption of thorium (IV) from aqueous media. First, characterization processes such as XRD, SEM, BET and zeta potential were performed to observe changes in the host ZnO adsorbent structure caused by the doping process. Later, this was optimized via the response surface method (RSM), which is widely used in the characterization of the adsorption properties of thorium (IV) from aqueous solutions. Such characterization is commonly used in industrial research. We tested how pH (3-8), temperature (20-60 °C), Th (IV) concentration (25-125 mg/L) and adsorbent amount (0.01-0.1 g) affect adsorption efficiency. The best possible combinations of these parameters were determined by RSM. It was calculated by RSM that the design fits the second order (quadratic) model using the central composite design (CCD) for the design of experimental conditions. R² and R² adjusted values from the parameters showing the model fit were 0.9923 and 0.9856, respectively. According to the model, the experimental adsorption capacity was 192.3 mg/g for the doped-ZnO nanomaterial under the theoretically specified optimum conditions. Also, the suitability of Th (IV) adsorption to isotherms was examined and thermodynamic parameters were calculated.

Synthesis and photoluminescence characteristics of a novel Eu and Tb doped Li2MoO4 phosphor

Li₂MoO₄:x Eu³⁺ and Li₂MoO₄:xTb³⁺ phosphors, where x = 0.5, 1, 2, 3, 5 and 7 wt%, were synthesized through a gel-combustion method. The XRD data reveals that Eu³⁺ and Tb³⁺ doped Li₂MoO₄ phosphors exhibit a Rhombohedral structure belonging to the space group R3 which matched well with the standard JCPDS files (No.012-0763). We present photoluminescence (PL) spectra from Eu and Tb doped Li₂MoO₄ under 349 nm Nd:YLF pulses laser excitation over the temperature range of 10-300 K. Undoped Li₂MoO₄ shows a wide broad band around 600 nm because of the intrinsic PL emission of tetrahedral of MoO₄^2- which was in good agreement with previous findings. Under the excitation of 394 nm, the as-synthesized phosphors exhibited sharp and strong intensity PL emission signals in the red (612 nm, ⁵D₀→⁷F₂ transition) and green (544 nm, ⁵D₄→⁷F₅ transition), respectively. The critical doping concentration of Eu³⁺ and Tb³⁺ ions in the Li₂MoO₄ were estimated to be 2 wt%. The concentration quenching phenomena were discussed, and the critical distances for energy transfer have also been evaluated by the concentration quenching.

Characterization of thermoluminescence kinetic parameters of beta irradiated B doped Ca5(PO4)3OH powder obtained from eggshell

In this study, we have synthesized B doped Ca5(PO4)3OH (HAP) by a sonication chemical method. The thermoluminescence (TL) properties of the family of synthesized samples (B doped Ca5(PO4)3OH (HAP) were investigated using an IRSL-TL 565 nm filter. This gave the highest TL intensity of each phosphor after 2 Gy β-irradiation. Three TL glow peaks of B doped Ca5(PO4)3OH (HAP) are centered at around 84, 208 and 324 °C (with a heating rate of 2 °Cs-1). The trapping parameters such as activation energy (E), order of kinetics (b), frequency factor (s) were calculated by using initial rise (IR), various heating rates (VHR) and computerized glow curve deconvolution (CGCD) method. The response of TL glow curves remained constant within ±5% deviation from the initial value after 9 cycles of reuse; but only at tenth cycle the deviation goes up to 6%.

Cathodoluminescence properties of La2MoO6:Ln3+ (Ln: Eu, Dy, and Sm) phosphors

La₂MoO₆ orange-red phosphors with high efficiency incorporated with Eu, Dy and Sm have been synthesized through a gel combustion method. The influences of rare earth doping in synthesized samples were analysed by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and cathodoluminescence. Rare earth doped La₂MoO₆ samples show strong emission bands in the range of 400-750 nm and optimal doping concentration for all samples was 2 mol%. La₂MoO₆ host doped Eu ion showed intense and predominant emission peaks in 450-750 nm range. The electrical multipolar interaction contributed to the non-radiative energy transfer between Eu³⁺ ions in La₂MoO₆ host matrix. Sm doped La₂MoO₆ host exhibited orange-red CL emission peaks at 564, 608, 652 and 708 nm La₂MoO₆:Dy³⁺ phosphor displayed emissions at 484, 574 and 670 nm, respectively. The observed intense and sharp emission peaks indicate that La₂MoO₆ is promising host for lanthanides doped phosphor materials in the applications of optoelectronic.

Synthesis and photoluminescence characteristics of Dy incorporated MoO3 phosphor: Suppression concentration quenching

A series of MoO₃:Dy³⁺ phosphors have been synthesized via the gel-combustion method. The X-ray and photoluminescence (PL) emission spectra were employed to characterize the obtained phosphors. The prepared samples were characterized through XRD measurements and exhibited that Dy³⁺ ions can be successfully incorporated into the host material. The PL emission bands of Dy³⁺ doped MoO₃ were observed at 486 nm, 574 nm and 666 nm which are assigned to the transitions of ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2, respectively. Concentration quenching were largely taken into consideration as one of the crucial aspects limiting the application range of phosphors in today's modern world. An abnormal thermal quenching dependence was reported when Dy³⁺ ions were incorporated into MoO₃ host matrix. In order to understand the origin of this beneficial behaviour, energy transfer processes occurring via radiative and nonradiative mechanisms were investigated to elucidate this suppression of the concentration quenching.

Structural and spectroscopic properties of LaAlBO3 doped with Eu3+ ions

In this study, we performed X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) techniques to examine the structure and morphological observation of the samples and thermoluminescence (TL) experiments to extract the trapping parameters and dosimetric properties of LaAlBO₃ phosphors doped with Eu at various doping concentrations. Diffraction patterns of obtained sample were well consistent JCPDS card No 98-009-7945, indicating the formation of pure phase. The TL kinetic parameters were estimated by CGCD software. TL glow curves of LaAlBO₃:Eu³⁺ consist of 12 trap levels and exhibited dominantly first order kinetics. Photoluminescence (PL) emission was observed in the range 400-800 nm for LaAlBO₃ phosphor doped with Eu³⁺. The dominant emission of Eu³⁺ corresponding to the electric dipole transition ⁵D₀ → ⁷F₂ is located at 616 nm. The sharp emission properties exhibited demonstrate that the LaAlBO₃ is a suitable host for rare-earth ion doped phosphor material. It is observed that for the variable concentration of Eu³⁺ on PL studies, the PL intensity augments with increase in the dopant concentration and the concentration quenching was found after 1 mass% of Eu³⁺. The PL experimental results reveal that LaAlBO₃:Eu³⁺ phosphor as an red emitting phosphor may be promising luminescence materials for the optoelectronic applications.

Thermoluminescence spectra of Tm doped ZnB2O4 phosphor prepared via a wet-chemical synthesis

In this paper we describe the thermoluminescence (TL) characteristics of 0.8 mol% Tm³⁺ doped ZnB₂O₄phosphors prepared by a wet-chemical method. The TL glow curves of the phosphor sample consisted of three peaks located at 181 °C, 213 °C and 351 °C. The glow peak TL temperature (T_m) at which the TL glow peak occurs shifts toward the higher temperature side whilst the heating ramp rate increases and also the peak TL intensity (I_m) decreases. The TL glow curves are characterized by evaluating various dosimetric characteristics of scrutinized samples. The T_m-T_stopinvestigations on regenerated TL signals revealed that there are five different traps in the phosphor with energy values in the range of 0.61-1.71 eV. The dose responses increased in a linear way for 3 peaks with the beta-ray exposure in the dose range of 0.11-60 Gy. The process of applying 10 Gy dose was repeated for ten successive irradiation cycles to check reproducibility and the maximum variation was found to be less than 1% from the average value. These results provide valuable knowledge for use of the characteristics of T_m doped ZnB₂O₄ in dosimetry research.

The role of calcination temperature on structural and luminescence behaviour of novel apatite-based Ca2Y 8(SiO4)6O2: Ce3+,Tb3+ phosphors

A series of novel apatite-based Ca₂Y₈(SiO₄)₆O₂ phosphors doped with Ce³⁺ and Tb³⁺ were synthesized by a solid-state reaction method at different calcination temperatures and times. The comparative results of thermal analysis (TG-DTA), FTIR, X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) reveal that the firing temperature for Ca ₂Y ₈ (SiO₄)₆O₂:Ce³⁺, Tb³⁺ was optimized to be 1200°C. The systematic studies on the influences of thermal treatment conditions on photoluminescence (PL) and cathodoluminescence (CL) properties were also reported. The excitation spectra of Ca₂Y₈(SiO₄)₆O₂:Ce³⁺, Tb³⁺exhibited one strong excitation band at 325nm. The PL and CL results indicated that the violet-blue emission intensities about 400nm from the Ce³⁺ and efficient green emission at 544nm from Tb³⁺ were highly dependent on the calcination conditions.

Thermoluminescence characterization of Ag-doped Li2 B4 O7 single crystal materials

In this study, the thermoluminescence (TL) characteristics of Ag-doped and undoped lithium tetraborate (Li₂ B₄ O₇ , LTB) materials, grown using the Czochralski method, were reported. The TL properties of LTB:Ag, such as glow curve structure, dose response, fading and reproducibility, were investigated. The glow curve of the Li₂ B₄ O₇ :Ag single crystal consists of four peaks located at approximately 75, 130, 190 and 275°C; in undoped LTB, the single crystal shows a broad glow curve with peaks at 65, 90, 125, 160 and 190°C using a heating rate of 5°C/s in the 50-350°C temperature region. The high temperature peak of Ag-doped sample at 275°C has a nonlinear dose response within the range from 33 mGy to 9 Gy. There is a linear response in the range of 33-800 mGy; after which, a sublinear region appears up to 9 Gy for Ag-doped LTB single crystal. For undoped single crystal, the dose response is supralinear for low doses and linear for the region between 1 and 9 Gy. The thermal fading ratio of the undoped material is almost 60% for the high temperature peak after 7 days. Ag-doped LTB single crystal exhibits different behaviour over a period of 7 days.

Pedobarographic measurements after repair of Achilles tendon by minimal invasive surgery

The aim of the current study was to assess the changes of plantar foot pressures with pedobarography in -patients with Achilles tendon repair by minimally -invasive surgical technique. This retrospective study consisted of 15 consecutive patients who were treated for acute Achilles' tendon repair with minimally invasive technique in our clinic in a two year period between 2010 and 2012. All patients were male. The mean age was 28.7 years (24-42) and the mean follow-up time was 2.3 years (1.5- 3). All patients had sports related Achilles' tendon rupture and all had undergone surgery in 24-48 hours. After surgery, extremity was immobilized with short leg cast for 6 weeks. Peak and mean heel and forefoot pressures in injured extremity were measured by -pedobarograph and compared with noninvolved foot. There wasn't any complication associated with -surgery such as wound problems, re rupture or -neurologic injury. Only three patients had some numbness at the incision site. When we compare the mean foot pressures between the operated foot and the normal foot, there was no statistical difference about peak and mean heel and forefoot plantar pressure between involved site and non involved site. As a result, Achilles tendon repair with minimal invasive technique and early rehabilitation may prevent changes of plantar foot pressure distribution.

Optical spectroscopy of the Ce-doped multicomponent garnets

Here, we report our results referring to the preparation of Ce doped Y2.22MgGa2Al2SiO12, Y1.93MgAl4SiO12 and Y2.22Gd0.75Ga2Al3O12 using solid state reaction at high temperature. Several complementary methods (i.e. powder x-ray diffraction (XRPD), energy dispersive analysis of X-rays (EDX), scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR)) were studied to examine the effects of the synthesis procedure on the morphology and structure. XRD analyses revealed that all compounds include yttrium aluminate phase with garnet structure. Cathodoluminescence (CL), radioluminescence (RL) and photoluminescence (PL) measurements were carried out for clarification of relationship between host lattice defects and the spectral luminescence emissions. Luminescence emission of phosphors is peaked at 530nm assigned to 5d-4f transitions of the dopant Ce(3+) ions with a broad emission band in 400-700nm range. Under electron irradiation, the emission spectrum of Ce doped (YGd)3Ga2Al3O12 is well defined and has a characteristic fairly narrow and sharp emission band peaking at 312nm and 624nm corresponding to transition of (6)P7/2 →(8)S7/2 and (6)GJ→(6)PJ (Gd(3+)), respectively. We suggest some of phosphors might be excellent phototherapy phosphor materials under electron excitation.

A RARE CLINICAL PRESENTATION: A PATIENT WITH CHRONIC RENAL FAILURE, SECONDARY HYPERPARATHYROIDISM AND CALCIPHYLAXIS

Calciphylaxis, also known as calcific uremic arteriolopathy (CUA), is usually observed in women and it is a serious complication of hyperparathyroidism secondary to chronic renal failure. CUA is characterized by ischemic tissue loss secondary to progressive vascular degeneration. Although it is rare, it may end up with sepsis and organ failure and can be fatal. Its pathogenesis is not fully understood, but it is thought that it occurs secondary to increased calcification activators such as oxidized LDL, TNF- α, calcitriol, fibronectin, collagen-I, and TGF-1α. The most effective treatment is managing underlying pathology and decreasing serum calcium and phosphorus levels. In this report, we aimed to present an end stage renal failure case with coexisting hyperparathyroidism, hyperthyroidism and calciphylaxis in whom cutaneous manifestations were healed 6 months after parathyroidectomy.

CLINICALLY UNDETECTABLE OCCULT THYROID PAPILLARY CARCINOMA PRESENTING WITH CERVICAL LYMPH NODE METASTASIS

Background

Occult papillary thyroid carcinoma presented as isolated cervical lymphadenopathy without clinical and radiologic findings has been rarely reported.

Case report

A 47 years old female patient admitted to otorhinolaryngology clinic with 4X3 cm sized cervical mass. Physical examination of the patient was noted as a nontender, firm, mobile lymph node at right lateral cervical region. There was no inflammatory or infection disease in the history of patients anamnesis and no abnormal value on laboratory tests. Ultrasound screening of the neck detected a lymph node with suspicious features for malignancy. Head and neck examination was normal and there is no evidence of a tumoral mass or nodule in the thyroid gland. Whole body scan of MRI showed no pathologic sign both in the neck and body. Excisional biopsy was performed and revealed a carcinoma with papillary morphology. Immunohistochemical staining features of the tumor confirmed a papillary carcinoma derived from the thyroid gland. Second look USG of the neck and thyroid was performed but it revealed no tumoral mass. The patient underwent total thyroidectomy with right functional and central lymph node dissection. Histological examination of the thyroid gland showed multicentric 2 mm sized, three foci of papillary carcinoma located in bilateral thyroid lobes and metastatic lymph nodes in the right side of the neck.

Conclusion

A metastatic cervical lymph node can be evidence of a clinically undetected occult papillary thyroid carcinoma. Specific immunohistochemistry staining of specimen may lead to appropriate surgery and progression of carcinoma may be hindered by application of additional RAI therapy.

The possibility of previous epidemiological data to serve as baseline for future national oral health surveys--a study in Vietnam

AIM

The purpose of this paper is to review the most recent epidemiological data (1985-2000) on dental caries and periodontal diseases in Vietnam in an attempt to obtain a 'baseline' for future national oral health surveys.

METHODS

Studies on periodontal diseases and caries were included when CPITN and WHO caries criteria had been applied and when the sample size was at least n = 200 for each age group.

RESULTS

Almost all subjects had calculus. The median number of sextants with calculus in the 15-19-year- and in the 35-44-year-olds was 4.2 and 5.0, respectively. Only 2-7% of the 35-44-year-olds had one or more deep periodontal pockets. The estimated DMFT of the 12-, 15- and 35-44-year-olds was 1.8, 2.0 and 5.4, respectively, in the years around 1990.

CONCLUSION

This review shows that (often neglected) epidemiological studies from the past on caries and periodontal diseases can contain comprehensive data sets that provide an estimate of the past oral health status which may serve as a baseline for future national surveys.