Search

NaY(WO4)2:Eu3+ phosphors were synthesized using high-temperature solid state method. The effects of Eu3+ doping concentrations on structure and photoluminescence properties of the powders were investigated. The results indicate that the pure NaY(WO4)2:Eu3+ phase can be produced by calcining at 800°C where Eu3+ doping does not alter the main phase structure. Eu3+ ions were successfully incorporated into the crystal lattice, replacing Y3+ at the B-site. This caused gradual shifts of the characteristic X-ray diffraction peaks to lower 2θ angles. Morphological characterization revealed that the sample particles had irregular polygonal shapes with sizes ranging from 100 to 300 nm. There was minimal variation in morphology among samples with different doping concentrations. The samples exhibited the characteristic spectral emission of Eu3+ and emitted red light at a wavelength of 616 nm when excited by 394 nm near-ultraviolet light. The luminescence intensity of the nanophosphor gradually increased with increasing Eu3+ doping concentration, reaching its maximum at a doping ratio of 0.6, followed by a decrease due to the concentration quenching. The quenching mechanism was analysed to be primarily dipole-dipole interaction, in accordance with the Dexter’s theory of doping concentration. The luminescence positions of the phosphors slightly changed with varying Eu3+ doping concentrations, and the colour coordinates closely matched the standard value of the red colour in the National Television Standards Committee, confirming the stability of the obtained powders as red phosphors.

【Objective】In Free Space Optical (FSO) communication, atmospheric turbulence can cause a decrease in communication link performance.【Methods】In this paper, a polar coding channel coding scheme is proposed for this problem, and Monte Carlo algorithm is used to construct polar codes for Gamma-Gamma distribution atmospheric turbulence channels commonly used in FSO communication. By comparing the Block Error Rates (BER) of the proposed polar coding scheme, uncoded transmission, and Low Density Parity Check (LDPC) codes with similar code lengths under Gamma-Gamma distribution atmospheric turbulence channels.【Results】The simulation results show that when the Signal-to-Noise Ratio (SNR) is greater than 6.7 dB in weak turbulence, 10.3 dB in moderate turbulence, and 11.5 dB in strong turbulence, the proposed polar coding scheme performs better than uncoded transmission. Compared with LDPC codes, under weak turbulence conditions, when the SNR is greater than 7.1 dB, the overall performance of the proposed polar coding scheme is better than that of LDPC codes. Under moderate turbulence conditions, when the SNR is greater than 10.6 dB, the overall performance of the proposed polar coding scheme is better than that of LDPC codes. Under strong turbulence conditions, when the SNR is greater than 12 dB, the overall performance of the proposed polar coding scheme is better than that of LDPC codes. In addition, it is found that when the code length is short, the code rate is low, and the decoding width is small, the proposed polar coding scheme has better performance.【Conclusion】The use of the proposed polar coding scheme effectively improves the atmospheric turbulence effect in FSO communication systems. Moreover, in the harsh atmospheric turbulence channel environment of moderate and high turbulence intensities, the proposed polar coding scheme exhibits more obvious advantages than LDPC codes. This indicates that polar codes have good development prospects in FSO communication.

Myocardial ischemia-reperfusion injury (MIRI) is one of the leading causes of death from cardiovascular disease in humans, especially in individuals exposed to cold environments. Long non-coding RNAs (lncRNAs) regulate MIRI through multiple mechanisms.This study explored the regulatory effect of lncRNA-AK138945 on myocardial ischemia-reperfusion injury and its mechanism.

Objective To explore the pharmacokinetic changes of single dose of fentanyl in rats in a simulated high-altitude and contributing factors. Methods Thirty-six healthy female SD rats (6~8 weeks old, 250±20 g) were randomly divided into high-altitude-acute-exposure group (group A), high-altitude-chronic-exposure group (group S) and control group (group C) through random number table, with 12 rats in each group.The group A and S were housed in a low-pressure chamber simulating the high altitude of 5 000 m above sea level for 3 and 30 d respectively, and the group C was housed out of the chamber (at an altitude of 300 m).A single dose of fentanyl was administered through the femoral vein to 6 rats randomly selected from each group.Liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to detect blood concentrations of fentanyl and WinNonlin 8.2 software was used to calculate the pharmacokinetic parameters, while blood samples were taken through the femoral artery before and in 1, 2, 4, 8, 15, 30, 60, 120 and 180 min after administration.The remaining 6 rats were ultrasonographically assessed for portal vein internal diameter (PVD), peak flow velocity (PVV) and blood flow (PVF), and liver tissues were collected for CYP3A1 protein content assay. Results The blood drug concentrations of fentanyl in the group A and group S were significantly lower than those in the group C at 60, 120, and 180 min (P=0.002, P < 0.001, P=0.001).Compared with the group C, the clearance rate (CL) of the group A was increased by 54.06%(P=0.021), and the mean residence time (MRTlast) was shortened by 24.21%(P=0.033);CL of the group S was increased by 50.10%(P=0.041), the area under the concentration-time curve (AUC0-t, AUC0-∞) and MRTlast were reduced by 18.92%(P=0.039), 27.54%(P=0.018) and 33.61%(P=0.004), respectively.PVD and PVF in the group S increased by 10.87%(P=0.006) and 42.50%(P=0.006) when compared with the group C.The CYP3A1 protein content in the group A was 28.74%, which was higher than that in the group C (P=0.048). Conclusion Fentanyl is cleared significantly faster after a single dose in rats in simulated high-altitude, which may be related to the increased liver blood flow and increased CYP3A1 protein expression in liver.

Background: Social annotation (SA) allows users to collaboratively highlight important texts, make comments and discuss with each other on the same online document. This would not only accelerate and deepen learners' cognitive understanding of information, but also help build a sense of rapport, which is critical especially because of the worldwide shift from face-to-face class to remote education as a response to the COVID-19 pandemic. Objective: To provide a systematic review of empirical SA studies, so that current development as well as issues in SA practices and research are identified. Methods: A total of 32 studies were identified and bibliometrical, instructional, and methodological analysis were conducted. Results and Conclusions: The United States has published the most SA research and technology-related journals are most receptive of SA research; one-shot quantitative designs with a sample size between 30 and 100 have been adopted most often; there is a lack of theoretical support for SA studies; higher education settings have been more frequently researched than other educational levels; SA technological features and activities have focused more on student uses and outcomes than on those of instructors; self-designed technologies were more preferred than commercial ones; both cognitive and affective outcomes were emphasized and nearly all studies reported positive findings. Implications: Future SA studies may conduct blended designs with larger sample sizes that is grounded upon solid theoretical frameworks; more customized and affordable SA technologies that support both students and teachers should be developed. Learning analytics and emotional design may be capitalized more to meet the demand of remote education during the pandemic.