[en] The Gd₂(WO₄)₃:Tb³⁺ phosphors have been successfully prepared using the hydrothermal method calcined at 900°C in this work. The crystal structure, PLE/PL and fluorescence decay behavior of samples were investigated in detail. Under the 270 nm excitation (4f⁸→4f⁷⁵d¹ transition of Tb³⁺), the (Gd_2-xTb_x)(WO₄)₃ (x=0.01-0.15) phosphors emit the strong green emission at 547 nm (5D₄→⁷F₅ transition of Tb³⁺). The quenching concentration was found to be ∼10% owing to the exchange reaction between Tb³⁺. The Tb³⁺ addition did not influence the CIE chromaticity coordinates (∼0.33±0.02, ∼0.60±0.02) and color temperatures (∼5542 K) of the (Gd_2-xTb_x)(WO₄)₃ phosphors. However, due to the energy transfer between Tb³⁺, the fluorescence lifetime for 547 nm emission decreased with the Tb³⁺ content increasing. The Gd₂(WO₄)₃:Tb³⁺ phosphors with strong green emission are expected to be widely used in white light LED and display areas. (paper)

[en] The nonlinearity of fibre-reinforced polymer (FRP) composites have significant effects on the analysis of composite structures. This article proposes a phenomenological intralaminar plasticity model to represent the nonlinearity of FRP composite materials. Based on the model presented by Ladeveze et al., the plastic potential and hardening functions are improved to give a more rational description of phenomenological nonlinearity behavior. A four-parameter hardening model is built to capture important features of the hardening curve and consequently gives the good matching of the experiments. Within the frame of plasticity theory, the detailed constitutive model, the numerical algorithm and the derivation of the tangent stiffness matrix are presented in this study to improve model robustness. This phenomenological model achieved excellent agreement between the experimental and simulation results in element scale respectively for glass fibre-reinforced polymer (GFRP) and carbon fibre-reinforced polymer (CFRP). Moreover, the model is capable of simulating the nonlinear phenomenon of laminates, and good agreement is achieved in nearly all cases. (paper)

[en] Objective: To investigate the diagnostic value of ¹⁸F-FDG PET/CT for thyroid nodules. Methods: From January 2008 to May 2012, 34 patients (13 males, 21 females; age range: 21-73 years, mean (53.00± 12.57) years) with thyroid nodules on ¹⁸F-FDG PET/CT and with histopathological results were retrospectively analyzed. From January 2011 to December 2011, 20 cases (9 males, 11 females; age range: 40-55 years, mean (45.00±4.72) years) were selected as control group. Wilcoxon rank sum test and ROC analysis (AUC ≥0.7 was considered the standard of medium-high accuracy) were used. PET/CT features taken to suggest malignant thyroid nodules were: focally high uptake on PET, indistinct boundary or heterogeneous density on CT with punctuate, round or curved calcifications, or with hypermetabolic cervical lymph nodes as ancillary supportive findings of metastasis. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of PET/CT for diagnosing thyroid nodules were calculated. Results: (1) There were 18 patients with malignant and 16 with benign thyroid nodules. The SUV_max of benign, malignant nodules and normal controls were 7.59±8.69, 5.75±4.48 and 1.38±0.57, respectively. The differences between malignant thyroid nodules and controls, between benign nodules and controls were significant (u=3.553, 3.408, both P<0.01). There was no significant difference between benign and malignant thyroid nodules (u =0.207, P>0.05). (2) The AUC for the differentiation of benign and malignant thyroid nodules by ROC analysis was 0.557 (<0.70). (3) The sensitivity, specificity, positive predictive value,negative predictive value and accuracy of ¹⁸F-FDG PET/CT for the differentiation of benign and malignant thyroid nodules were 72.2% (13/18), 75.0% (12/16), 76.5% (13/17), 70.6% (12/17) and 73.5% (25/34), respectively. Conclusions: ¹⁸F-FDG PET/CT has limited value for the differentiation between benign and malignant thyroid nodules based alone on the degree of metabolic intensity. It may have improved diagnostic certainty if combined with the morphological features on CT. (authors)

[en] The (Gd_0.98−xTb_0.02Eu_x)₂O₃ phosphors have been successfully obtained using the urea-based homogeneous precipitation method in the present work. The particle growth of the precursors with mono-dispersion spherical morphology is surface-diffusion controlled and precipitated in the order of the Tb(OH)CO₃ > Gd(OH)CO₃ > Eu(OH)CO₃, and the formation process has been also studied in detail. Partially replacing the pure water with ethylene glycol (EG) can control the particle size and morphology owing to its lower permittivity constant and interface energy. By monitoring the excitation at 314 nm (4f⁸ → 4f⁷5d¹ transition of Tb³⁺), the (Gd_0.98−xTb_0.02Eu_x)₂O₃ phosphors exhibit both Tb³⁺ (green) and Eu³⁺ (red) emissions at 547 and 613 nm, respectively. The presence of Gd³⁺ and Tb³⁺ excitation bands on the PLE spectra by monitoring the Eu³⁺ emission directly provides an evidence of the Tb³⁺ → Eu³⁺ and Gd³⁺ → Eu³⁺ energy transfer, respectively. The quenching concentration is determined to be 2.0 at.%, and the quenching mechanism is determined to be the exchange reaction between Eu³⁺. The emission color can be readily tuned from approximately green to red via adjusting the Eu³⁺ content. The temperature-dependent analysis has been performed, and the results indicate that the (Gd_0.98−xTb_0.02Eu_x)₂O₃ samples possess good thermal stability. Owing to the Tb³⁺ → Eu³⁺ energy transfer, the lifetime for the Tb³⁺ emission rapidly decreases, and the energy transfer efficiency has been calculated. The EG addition does not bring appreciable changes to the lifetime values for the both Tb³⁺ and Eu³⁺ emissions, but enhances remarkably the luminescent intensity which confirms the variation of the particle morphology/size, and the reason can be explained by the scattering of the light. The (Gd_0.98−xTb_0.02Eu_x)₂O₃ phosphors developed in this work hopefully meet the requirements of various lighting and optical display applications.

[en] Objective: To explore the diagnostic value of PET-CT and PET-CT combined with lung volume computed assisted reading (Lung VCAR) software in hilar area lymph nodes. Methods: Preoperative whole body PET-CT imaging was performed in 49 patients who were highly suspicious of non-small cell lung cancer. PET-CT images of the hilar area lymph nodes and the PET-CT images of the hilar area lymph nodes from Lung VCAR software were evaluated by two experienced doctors, and then compared with the pathological diagnosis. Results: There was no significant difference between the CT values of benign and malignant lymph nodes (t=-1.40, P>0.05). But a significant difference was existed between the benign and malignant hilar lymph nodes with the density visual analysis, the lymph short diameter and the maximum of standardized uptake value (SUV_max) (χ²=30.37, 27.40, 20.06, all P<0.05). The sensibility,specificity and accuracy of PET-CT in diagnosis of the hilar area lymph nodes were 76.5%, 90.7%, 88.3% respectively, and the accuracy of the diagnosis was significantly higher than that of CT and PET alone (χ²=15.27, P<0.05) using the lymph short diameter ≥1 cm of CT, the density of lymph node is equal to (slightly lower than) the same layer vascular density and the lymph node SUV_max ≥2.5 of PET as the diagnostic criteria. One hundred and three hilar area lymph nodes were diagnosed by PET-CT and four nodes were not hilar lymph nodes proved by the Lung VCAR software (3 hilar vascular uptake,1 bronchial cartilage). Conclusion: The methods of PET-CT lymph visual density analysis plus lymph node diameter and SUV_max had a high diagnostic accuracy of non-small cell lung hilar lymph. For the PET-CT,the pulmonary vascular uptake was the main cause affecting the discrimination of hilar lymph nodes,while Lung VCAR software was helpful to diagnosis. (authors)

[en] Objective: To study the consistency of the results between of MR myocardial perfusion imaging and DSA coronary arteriography. Methods: MR myocardial perfusion imaging and DSA coronary artery imaging were performed to 51 patients with coronary heart disease with typical clinical symptoms and typical cardiogram. Dynamic contrast enhanced myocardial imaging (DCEMI) myocardial perfusion imaging analysis software for GE AW4.0 working station was employed to analyze the first pass phase images of the myocardial perfusion of the left ventricle short axle. A curve of the time-intensity of the cardiac muscle perfusion was obtained and the rising slope and the peak value of signal intensity were observed. According to the description of the relation between the position of the short axle of left ventricle and the distribution of the coronary artery blood vessels, the existence of narrowed coronary artery was determined. DSA machine of DAR 1200 double C arm was employed in the coronary artery imaging. Judkin method employing Seldinger's method of femoral centesis was carried out and the value ≤50% of the diameter of the coronary artery was determined as the diagnostic standard of narrowness of clinical significance. Results: The results of the two methods in 43 cases were consistent and 8 not, the rate of consistency was 84.3%. Conclusion: High consistency of the results was found between MR myocardial perfusion imaging and DSA coronary arteriography. MR myocardial perfusion imaging is a non-traumatic method to determine the blood flow of myocardium and it can supply valuable information and guidance for the diagnosis and treatment for the patients

[en] The poor stability of CsPbX${}_3$ (X = Cl, Br, I) perovskite quantum dots (PQDs) in polar solvents such as water, seriously hinders their practical application. Herein, 5-Bromovaleric acid (BVA) is used to replace oleic acid (OA), the most common surface ligand in CsPbX${}_3$ PQDs synthesis. Under the synergic action of oleylamine (OLA), CsPbX${}_3$ PQDs with high water stability can be synthesized directly in water. Because the carboxyl ligands provided by BVA, and the long chain amines provided by OLA formed hydrophobic shells on the surface of CsPbBr${}_3$ PQDs, the obtained CsPbBr${}_3$ PQDs still has high luminescence intensity and photoluminescence quantum yield after being dispersed in water for several days, and the luminescence peak is always maintained at 518 nm. In contrast, the luminescence intensity of CsPbBr${}_3$ PQDs synthesized with OA and OLA is <1% of the initial intensity after only 30 min. CsPbCl${}_3$ and CsPbI${}_3$ PQDs synthesized directly in water by this method also show high water stability. In this study, for the first time the synthesis method of CsPbX${}_3$ PQDs with high water stability using BVA/OLA as surface ligands is proposed, which provides an effective way to explore the synthesis of PQDs that can maintain stability in water. (© 2023 Wiley‐VCH GmbH)

[en] The Dy³⁺ doped Gd₂(WO₄)₃ phosphors have been successfully obtained through calcining the precursor prepared via hydrothermal method at 900°C. The structure, morphology and luminescent properties of the resultant products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence excitation/photo-luminescence spectroscopy (PLE/PL), and fluorescence decay analysis. The (Gd_1-xDy_x)₂(WO₄)₃ (x=0.01-0.10) solid solutions, exhibit strong yellow luminescence at 575 nm (the ⁴F_9/2→⁶H_13/2 electric dipole transition of Dy³⁺) optimal UV excitation into the ⁶H_15/2→ ⁴H_11/2 of Dy³⁺ at ∼452 nm. The quenching concentration was determined to be ∼7at.%, and the quenching was due to the exchange reaction between Dy³⁺. The emission intensity decreased monotonically with the used temperature increasing while the fluorescence lifetime (0.5±0.05 ms) does not alter appreciably. All the (Gd_1-xDy_x)₂(WO₄)₃ phosphors have similar CIE chromaticity coordinates and color temperatures of (∼0.43±0.02, ∼0.47±0.02) and ∼3550 K respectively, but the lifetime for 575 nm emission decreased with the Dy³⁺ increasing ascribed to the energy transfer between Dy³⁺. The Gd₂(WO₄)₃:Dy³⁺ yellow phosphors are expected to be widely used in white light LED and display areas. (paper)

[en] The new system of [(Gd_0.9Y_0.1)_0.9-xTb_0.1Ce_x]AG phosphors have been successfully obtained by using a modified co-precipitation method which include the precursor synthesis and post treatment at 1300 °C. The crystal structure stabilization, morphology, PL/PLE spectra, fluorescence decay analysis and thermal property have been studied in detail. The metastable GdAG:Tb³⁺/Ce³⁺ samples could be effectively stabilized via smaller 10 at% Y³⁺ doping, which can develop a new phosphor of [(Gd_0.9Y_0.1)_0.9-xTb_0.1Ce_x]AG for exploring the field of the opto-functionality. The presence of Gd³⁺ and Tb³⁺ excitation bands in the PLE spectra monitoring the Ce³⁺ yellow emission directly provides an evidence of Gd³⁺→Ce³⁺ and Tb³⁺→Ce³⁺ energy transfer. The [(Gd_0.9Y_0.1)_0.9-xTb_0.1Ce_x]AG phosphors with good dispersion show various luminescence properties monitoring at 275 nm, 331 nm and 452 nm excitation, respectively. The optimized (Gd_0.9Y_0.1)_0.89Tb_0.1Ce_0.01]AG phosphor has a red-shifted emission and the applicable emission intensity because of the energy transfer of Gd³⁺→Ce³⁺ and Tb³⁺→Ce³⁺, thus being more suitable for the application of warm-white lighting than YAG:Tb³⁺/Ce³⁺ and LuAG:Tb³⁺/Ce³⁺. The Stokes shift have been calculated through the Gaussian fitted curves of emission spectra, indicating that the doping of Ce³⁺ does not obviously change the splitting degree of 5d orbit. The quenching concentration was determined to be 1.0 at%, and the quenching mechanism was determined to be the exchange reaction between Ce³⁺. The temperature-dependent analysis has been performed and the results indicated that the [(Gd_0.9Y_0.1)_0.89Tb_0.1Ce_0.01]AG phosphors possesses good thermal stability. The fluorescence decay analysis shows that the lifetimes of Tb³⁺ and Ce³⁺ emission decrease with the Ce³⁺ content increasing. The [(Gd_0.9Y_0.1)_0.89Tb_0.1Ce_0.01]AG phosphors developed in this work are expected to be widely used in the lighting and optical display areas.

[en] The new systems of the (Gd_0.95-xDy_0.05Tb_x)₂(WO₄)₃ (x = 0–0.1) and (Gd_0.95-yDy_0.05Eu_y)₂(WO₄)₃ (y = 0–0.2) phosphors have been successfully obtained using the hydrothermal method at 900 °C in this work. The crystal structure, morphology, PL/PLE spectra, fluorescence and decay analysis have been studied in detail via the combined techniques of XRD, FE-SEM, PLE/PL spectra and decay kinetic. The phase-pure of the (Gd_0.95-xDy_0.05Tb_x)₂(WO₄)₃ and (Gd_0.95-yDy_0.05Eu_y)₂(WO₄)₃ with good dispersions have been formed at the lower sintering temperature of 900 °C. Under 273 nm and 270 nm excitation (the ⁶P_7/2→⁸S_7/2 transitions of Gd³⁺), the Gd₂(WO₄)₃:Dy³⁺/Tb³⁺ and Gd₂(WO₄)₃:Dy³⁺/Eu³⁺ phosphors exhibit both Dy³⁺ (yellow, at 574 nm) and Tb³⁺ (green, at 547 nm) as well as Dy³⁺ (yellow, at 574 nm) and Eu³⁺ (red, at 616 nm) emissions, respectively. The presences of WO₄^2-, Gd³⁺ and Dy³⁺ excitation bands on the PLE spectra by monitoring the Tb³⁺ and Eu³⁺ emissions directly provide an evidence of energy transfer of WO₄^2-→Tb³⁺, Gd³⁺→Tb³⁺ and Dy³⁺→Tb³⁺, as well as WO₄^2-→Eu³⁺, Gd³⁺→Eu³⁺ and Dy³⁺→Eu³⁺, respectively. The quenching concentrations of both two systems are determined to be 7 at% (x = 0.07 for Tb³⁺) and 10 at% (y = 0.10 for Eu³⁺), and the quenching mechanisms of both two systems are mainly due to the Tb³⁺-Tb³⁺ and Eu³⁺-Eu³⁺ energy transfers, respectively. The color-tunable emission can be achieved though adjusting the relative content ratios of Dy³⁺/Tb³⁺ or Dy³⁺/Eu³⁺, which has been verified by the CIE chromaticity coordinates analysis. The energy transfer efficiencies of Dy³⁺→Tb³⁺ and Dy³⁺→Eu³⁺ have been calculated, and the energy transfer mechanisms have been analyzed in detail. The (Gd_0.95-xDy_0.05Tb_x)₂(WO₄)₃ and (Gd_0.95-yDy_0.05Eu_y)₂(WO₄)₃ phosphors with color-tunable emission may have a potential application for w-LEDs.