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The VUV-UV-vis photoluminescence, X-ray radioluminescence, energy transfer dynamics of Ce3+ and Eu2+ in Sr2MgSi2O7 and the dependencies of Ce3+ 4f–5d transitions on the local structure of Sr2MgSi2O7, Ba2MgSi2O7 and BaMg2Si2O7 are discussed.

In this study, the regulation of Al3+/Ga3+ on Sr2(Ga,Al)2SiO7:Ce3+ phosphors is demonstrated to enhance the photoluminescence and persistent luminescence (PersL) performances of Ce3+. With the replacement of Al3+, the emission band of Ce3+ shifts to the longer wavelength side, thermal stability of Ce3+ emission becomes better, and Ce3+ persistent luminescence shows stronger intensity and longer lifetime. To get insight into the structure-luminescence relationship, the influences of Al3+/Ga3+ on the structure of Sr2(Ga,Al)2SiO7:Ce3+, 4f–5di (i = 1–5) transition energies of Ce3+ and trap distributions are discussed. With the construction of the vacuum referred binding energy scheme and analysis of a series of thermoluminescence (TL) spectra, the increase of band gap is found to tune the trap depths and change persistent luminescence performances of Ce3+ in Sr2(Ga,Al)2SiO7. Finally, with the stimulation of a 1060 nm laser, the optimized Sr2(Ga,Al)2SiO7:Ce3+ phosphors show strong persistent luminescence of Ce3+, suggesting the potential for application in optical storage.

Ce3+ and Eu2+ single- and double-doped CaMgSi2O6 phosphors have been prepared by a high-temperature solid-state reaction approach. The VUV–UV–vis luminescence properties are investigated at cryogen...

Luminescent materials with controllable colour evolution features are demanded for the development of multi-level anti-counterfeiting technologies. Here we report the structural and luminescence properties of CaMgSi2O6:Ln (Ln = Eu2+, Eu3+, Eu2+/3+) samples in detail and reveal their excitation-wavelength/temperature driven colour evolution characteristics. By tuning either the excitation-wavelength (276, 304, 343, 394 nm) or temperature (in the 330-505 K range), the designed samples with co-existing Eu2+/Eu3+ ions can achieve diverse and controllable colour evolution from red, to pink, purple and blue. This shows their potential application in anti-counterfeiting with the help of sophisticated pattern design. In addition, the underlying mechanism of the Stokes shift of the Eu2+ emission and valence stability of both Eu2+/Eu3+ ions in CaMgSi2O6 are also studied in depth. These results are valuable for designing colour-controllable luminescent materials based on the co-existence of the Eu2+/Eu3+ ions for anti-counterfeiting applications.

Ce

Ce3+-doped LiSr4(BO3)3 phosphors have been prepared by a high-temperature solid-state reaction method, and structural refinement of the host compound has been performed. The excitation and emission spectra in the vacuum ultraviolet-ultraviolet-visible range at cryogenic temperatures reveal that Ce3+ ions preferentially occupy eight-coordinated Sr2+ sites in LiSr4(BO3)3. Such experimental attribution is well corroborated by the calculated 4f-5d transition energies and defect formation energies of Ce3+ ions at two distinct Sr2+ sites in the first-principles framework. In addition, the doping concentration-dependent luminescence and the temperature-dependent luminescence are systematically investigated by luminescence intensity and lifetime measurements, respectively. This shows that concentration quenching does not occur in the investigated doping range, but inhomogeneous broadening exists in the concentrated samples. With the estimated thermal quenching activation energy, the discussions on the thermal quenching mechanisms suggest that the thermal-ionization process of the 5d electron is a dominant channel for thermal quenching of Ce3+ luminescence, despite the fact that thermally activated concentration quenching cannot be excluded for the highly doped samples. Finally, the X-ray excited luminescence measurement demonstrates the promising applications of the phosphors in X-ray detection.

To explore the interventional effect of exercise therapy on idiopathic scoliosis and identify an optimal intervention window, we did a prospective controlled cohort study. The results shows the efficacy of our exercise protocol, and younger patients with a lower Risser grade are most likely to respond., Study Design. A prospective controlled cohort study. Objective. The aim of this study was to explore the interventional effect of exercise therapy on idiopathic scoliosis (IS) and identify an optimal intervention window. Summary of Background Data. Early conservative treatment is helpful for IS. In addition to bracing, current evidence suggests that exercise can play an important role. Methods. We included 99 patients with IS who were treated at the Guangdong Xinmiao Scoliosis Center from August 2013 to September 2017. The inclusion criteria were: new IS diagnosis, Cobb angle 10° to 25°, Risser 0 to 3 grade, only treated with the Xinmiao treatment system (XTS; >3 days/week, >1 h/day), and follow-up >1 year. Patients were divided into three age groups: A

Luminescent materials with controllable colour evolution features are demanded for the development of multi-level anti-counterfeiting technologies. Here we report the structural and luminescence properties of CaMgSi2O6:Ln (Ln = Eu2+, Eu3+, Eu2+/3+) samples in detail and reveal their excitation-wavelength/temperature driven colour evolution characteristics. By tuning either the excitation-wavelength (276, 304, 343, 394 nm) or temperature (in the 330-505 K range), the designed samples with co-existing Eu2+/Eu3+ ions can achieve diverse and controllable colour evolution from red, to pink, purple and blue. This shows their potential application in anti-counterfeiting with the help of sophisticated pattern design. In addition, the underlying mechanism of the Stokes shift of the Eu2+ emission and valence stability of both Eu2+/Eu3+ ions in CaMgSi2O6 are also studied in depth. These results are valuable for designing colour-controllable luminescent materials based on the co-existence of the Eu2+/Eu3+ ions for anti-counterfeiting applications.

© 2018 Elsevier B.V. The contribution of this paper is to enable solid conclusions to be drawn about the existence of momentum effects in China as the current evidence is unsatisfactory. We review and analyse the existing empirical studies on momentum and contrarian strategies in China and show that many of the findings in these studies appear inconsistent, if not actually contradictory. To clarify this confused situation we initially identify common findings in the diverse and seemingly contradictory body of existing empirical evidence. Subsequently, we systematically assess how the design of empirical studies affects the results of investigations in this area. We do this by conducting an empirical analysis of monthly data on Chinese A shares, varying one factor in the research design at a time (sample period, equally or value-weighed portfolios, skipping a period between portfolio formation and holding periods, and exclusion of post-IPO observations). This allows us to pinpoint directly how each of these factors affects momentum profits and thus when these profits are likely to be observed. It also indicates why studies using different designs might have arrived at seemingly inconsistent conclusions. Overall, we draw a number of conclusions: there appear to exist medium- and longer-term reversals in the pre-2001 period and short-term reversals and longer-term momentum effects thereafter; there is substantial time-variation in the profits to momentum strategies; small stocks exhibit stronger reversals than their larger counterparts; a large fraction of portfolio returns occur in the first month after formation; there is evidence of post-IPO price drifts. In summary, this study reconciles and explains the inconsistent evidence on the existence of momentum and contrarian effects in China allowing clear conclusions to be drawn.