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Background: After a 920-day hiatus, COVID-19 resurged in the Tibet Autonomous Region of China in August 2022. This study compares the characteristics of COVID-19 between high-altitude residents and newcomers, as well as between newcomers and lowlanders., Methods: This multi-center cohort study conducted at the Third People's Hospital of Tibet Autonomous Region and Beijing University Shenzhen Hospital, included 520 high-altitude resident patients, 53 high-altitude newcomer patients, and 265 lowlander patients infected with the Omicron variant. Initially, we documented epidemiological, clinical, and treatment data across varying residency at admission. We compared the severity of COVID-19 and various laboratory indicators, including hemoglobin concentration and SpO2%, over a 14-day period from the date of the first positive nucleic acid test, as well as the differences in treatment methods and disease outcomes between highlanders and high-altitude newcomers. We also compared several characteristics of COVID-19 between high-altitude newcomers and lowlanders. Univariate analysis, multivariable logistic regression, and the generalized linear mixed model were utilized for the analysis., Results: No fatalities were observed. The study found no significant differences in COVID-19 severity or in the physiological measures of hemoglobin concentration and SpO 2 % between high-altitude and lowland residents. Similarly, there were no statistically significant differences in the values or trends of hemoglobin and SpO 2 % between high-altitude residents and newcomers throughout the 14-day observation period. However, compared to age- and sex-matched lowlander patients (1:5 ratio), high-altitude newcomers exhibited higher heart rates, respiratory rates, and average hemoglobin concentrations, along with lower platelet counts. There were no significant differences in hospital stays between the two groups., Conclusions: High-altitude residents and newcomer patients exhibit clinical similarities. However, the clinical characteristics of high-altitude newcomers and lowlander patients differ due to the impact of the high-altitude environment. These results highlight potential considerations for public health strategies in high-altitude regions such as Tibet., (© 2024. The Author(s).)

Mid-infrared (MIR) pulsed lasers near a 3 µm waveband show great potential for the high absorption of water molecules and many important gas molecules. A passively Q -switched mode-locked (QSML) E r 3+ -doped fluoride fiber laser with a low laser threshold and high slope efficiency around a 2.8 µm waveband is reported. The improvement is achieved by depositing bismuth sulfide ( B i 2 S 3 ) particles onto the cavity mirror directly as a saturable absorber and using the cleaved end of the fluoride fiber as output directly. -QSML pulses begin to appear with the pump power of 280 mW. The repetition rate of the QSML pulses reaches a maximum of 33.59 kHz with the pump power of 540 mW. When the pump power is further increased, the output of the fiber laser switches from the QSML to the continuous-wave mode-locked operation with the repetition rate of 28.64 MHz and the slope efficiency of 12.2%. The results indicate that B i 2 S 3 is a promising modulator for the pulsed lasers near a 3 µm waveband, which paves the way for further development of various applications in MIR wavebands, including material processing, MIR frequency combs, and modern healthcare.

We experimentally demonstrate a fiber laser with different linewidths based on self-injection locking (SIL) and the stimulated Brillouin scattering effect. Based on the homemade fiber laser, the error origin, resolution, and applicable range of delayed self-heterodyne interferometry (DSHI), self-correlation envelope linewidth detection (SCELD) and Voigt fitting are investigated numerically and experimentally. The selection of the linewidth measuring method should meet the following conclusions: an approximately Lorentzian self-heterodyne spectrum without the pedestal and high-intensity sinusoidal jitter is a prerequisite for DSHI; the SCELD needs a suitable length of delay fiber for eliminating flicker noise and dark noise of the electrical spectrum analyzer; a non-Lorentzian self-heterodyne spectrum without a pedestal is an indispensable element for Voigt fitting. According to the experimental results, the laser Lorentzian linewidth of SIL changes from 1.7 kHz to 587 Hz under different injection powers. When the Brillouin erbium fiber laser is utilized, the Lorentzian linewidth is measured to be 60 ± 5 Hz.

The ultra-wideband supercontinuum generation (SCG) in a Te-based chalcogenide (ChG) photonic crystal fiber (PCF) is simulated in the mid-infrared (MIR) waveband. The PCF core and cladding materials are G e 20 A s 20 S e 15 T e 45 and G e 20 A s 20 S e 17 T e 43 , respectively. The supercontinuum (SC) broadening affected by the core diameter and fiber absorption is considered. The selected PCFs at different pumping wavelengths can demonstrate the generation of ultra-wideband MIR supercontinuum according to the simulated results. We consider SC broadening with and without fiber absorption. A SC range from 3 to 25 µm is demonstrated by simulation in a PCF with a core diameter of 8 µm and a pump wavelength of 6 µm considering the fiber absorption. With the increase of the peak power and the pulse width and the decrease of the core diameter, the degree of coherence gradually degraded. To the best of our knowledge, this is the first demonstration of the possibility of SCG up to the waveband of 25 µm in fiber. Our results highlight the potential of a novel Te-based chalcogenide multi-material PCF for SCG. We also provide a way to generate the SCs to longer wavebands than 20 µm in fiber, especially up to the far-infrared waveband.

As the best adapted high altitude population, Tibetans feature a relatively high offspring survival rate. Genome-wide studies have identified hundreds of candidate SNPs related to high altitude adaptation of Tibetans, although most of them have unknown functional relevance. To explore the mechanisms behind successful reproduction at high altitudes, we compared the placental transcriptomes of Tibetans, sea level Hans (SLHan), and Han immigrants (ImHan). Among the three populations, placentas from ImHan showed a hyperactive gene expression pattern. Their increased activation demonstrates a hypoxic stress response similar to sea level individuals experiencing hypoxic conditions. Unlike ImHan, Tibetan placentas were characterized by the significant up-regulation of placenta-specific genes, and the activation of autophagy and the tricarboxylic acid (TCA) cycle. Certain conserved hypoxia response functions, including the antioxidant system and angiogenesis, were activated in both ImHan and Tibetans, but mediated by different genes. The coherence of specific transcriptome features linked to possible genetic contribution was observed in Tibetans. Furthermore, we identified a novel Tibetan-specific EPAS1 isoform with a partial deletion at exon six, which may be involved in the adaption to hypoxia through the EPAS1-centred gene network in the placenta. Overall, our results show that the placenta grants successful pregnancies in Tibetans by strengthening the natural functions of the placenta itself. On the other hand, the placenta of ImHan was in an inhabiting time-dependent acclimatization process representing a common hypoxic stress response pattern., (© The Author(s) 2022. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.)