Microwave frequency transfer over a 112-km urban fiber link based on electronic phase compensation

We demonstrate the transmission of a microwave frequency signal at 10 GHz over a 112-km urban fiber link based on a novel simple-architecture electronic phase compensation system.The key element of the system is the low noise frequency divider by 4 to differentiate the frequency of the forward signal from that of the backward one,thus suppressing the effect of Brillouin backscattering and parasitic reflection along the link.In terms of overlapping Allan deviation,the frequency transfer instability of 4.2×10-15 at 1-s integration time and 1.6×10-18 at one-day integration time was achieved.In addition,its sensitivity to the polarization mode dispersion in fiber is analyzed by comparing the results with and without laser polarization scrambling.Generally,with simplicity and robustness,the system can offer great potentials in constructing cascaded frequency transfer system and facilitate the building of fiber-based microwave transfer network.

Photoluminescence and cathodoluminescence properties of CaLaGa_3O_7:Eu^(3+) phosphors

The CaLaGa3O7:Eu3+ phosphor was prepared by a chemical co-precipitation method.Field emission scanning electron microscopy(FE-SEM),laser particle size analysis,X-ray diffraction(XRD),photoluminescence(PL),and cathodoluminescence(CL) spectra were util-ized to characterize the synthesized phosphor.The results revealed that the phosphor was composed of microspheres with a slight agglomer-ate phenomenon and was spherically shaped.The average grain size was about 1.0 μm.Eu3+ ions,as luminescent centers,substituted La3+ ions into the single crystal lattice of CaLaGa3O7 with the sites of Cs.Although the CL spectrum was greatly different from the PL spec-trum,it had the strongest red emission corresponding to the 5D0 →7F2 transition of Eu3+.Under the excitation of UV light(287 nm) and elec-tron beams(1.0-7.0 kV),the chromaticity coordinates of the phosphor were found to be in the nearly red and orange light regions,respec-tively.

Residual Phase Noise and Time Jitters of Single-Chip Digital Frequency Dividers

In this paper, we demonstrate the residual phase noise of a few microwave frequency dividers which usually limit the performance of frequency synthesizers. In order to compare these dividers under different operation frequencies, we calculate additional time jitters of these dividers by using the measured phase noise. The time jitters are various from ~0.1 fs to 43 fs in a bandwidth from 1 Hz to 100 Hz in dependent of models and operation frequencies. The HMC series frequency dividers exhibit outstanding performance for high operation frequencies, and the time jitters can be sub-fs. The time jitters of SP8401, MC10EP139, and MC100LVEL34 are comparable or even below that of HMC series for low operation frequencies.

Meta analysis of Masquelet technology and Llizarov technology in the treatment of infectious bone defects

Objective: To systematically evaluate the clinical efficacy and safety of Masquelet technology and Llizarov group technology in the treatment of infectious bone defects by meta-analysis. Methods: The computer searched China Knowledge Network (CNKI), Wanfang, VIP, Chinese Biomedical Literature Database (CBM), Pubmed, Medline, Cochrane Llibrary databases. The retrieval time was from the time of the establishment of the database to January 2020. According to the inclusion and exclusion criteria, randomized controlled trials on the treatment of infectious bone defects using Masquelet technology and Llizarov technology were collected, and the retrieved literature was independently screened, evaluated, and data extracted by two researchers, and then RevMan5.3 software was used so for meta-analysis. Results: A total of 10 RCT documents were included, with a total of 496 patients, including 242 in the Masquelet group and 254 in the Llizarov group. The results of the meta-analysis showed that: in terms of bone defect healing time, total weight bearing time, treatment cost, and complication rate, the Masquelet group was significantly different from the Llizarov group, and the Masquelet group was better than the Llizarov group (P <0.05);In terms of knee joint Lowa score and SF-36 score, Masquelet group has significant differences compared with Llizarov group, Llizarov group is better than Masquelet group (P <0.05);in excellent rate, number of operations, ankle Lowa score, infection control rate In terms of excellent rate of affected limb function, there was no significant difference between Masquelet group and Llizarov group (P> 0.05). Conclusion:Compared with Llizarov technology, Masquelet technology has obvious advantages in the treatment of infectious bone defects in terms of bone defect healing time, total weight-bearing time, treatment cost, and complication rate. In terms of scoring, it has advantages over Masquelet technology, but in terms of excellent treatment rate, number of operations, and ankle lowa score. In terms of infection control rate and excellent function of affected limbs, there was no significant difference between Masquelet technology and Llizarov technology,However, due to the low quality of the included studies and the small sample size, the exact efficacy still needs to be confirmed by higher quality RCT studies.

A review of CoSb_(3)-based skutterudite thermoelectric materials

The binary skutterudite CoSb_(3) is a narrow bandgap semiconductor thermoelectric(TE)material with a relatively flat band structure and excellent electrical performance.However,thermal conductivity is very high because of the covalent bond between Co and Sb,resulting in a very low ZT value.Therefore,researchers have been trying to reduce its thermal conductivity by the different optimization methods.In addition,the synergistic optimization of the electrical and thermal transport parameters is also a key to improve the ZT value of CoSb_(3) material because the electrical and thermal transport parameters of TE materials are closely related to each other by the band structure and scattering mechanism.This review summarizes the main research progress in recent years to reduce the thermal conductivity of CoSb_(3)-based materials at atomic-molecular scale and nano-mesoscopic scale.We also provide a simple summary of achievements made in recent studies on the non-equilibrium preparation technologies of CoSb_(3)-based materials and synergistic optimization of the electrical and thermal transport parameters.In addition,the research progress of CoSb_(3)-based TE devices in recent years is also briefly discussed.

Observed permafrost thawing and disappearance near the altitudinal limit of permafrost in the Qilian Mountains

Permafrost degradation has been widely reported on the Tibetan Plateau(TP).However,directly observed evidence of permafrost thawing processes and degradation rates are very limited,although it is expected to be prevalent near the periphery of a permafrost area.Here,we report permafrost changes and disappearance in the Qilian Mountains(northeastern TP)based on three boreholes instrumented along a 100 m transect during 2014–2021.Our results show that permafrost has significantly degraded in the study area:the mean downward thawing rate from the permafrost table was about 0.16 m per year while the mean upward thawing rate from the permafrost base was about 0.23 m per year.We estimate the mean lateral degradation rate of permafrost in this area was∼4.14 m per year.More dramatically,the 1.5 m thick permafrost layer at one of the boreholes thawed completely between April of 2018 and December of 2019.Our results indicate that changes in climatic condition may have played only a limited role in controlling the active layer thickness in the vicinity of the altitudinal limit of permafrost;moisture content and soil conditions play key roles in site-specific permafrost thawing.This study provides new quantitative insights for understanding changes near the altitudinal limit of permafrost,and we suggest that land surface models or Earth system model studies of the lateral heat exchanges should be implemented in order to better represent permafrost thawing processes.

Uncarialins J-M from Uncaria rhynchophylla and Their Anti-depression Mechanism in Unpredictable Chronic Mild Stress-Induced Mice via Activating 5-HT_(1A) Receptor

Uncaria rhynchophylla has been widely used to treat central nervous system diseases for a long history.After investigation of U.rhynchophylla,eleven monoterpene indole alkaloids,including four new compounds uncarialins J-M(1-4)and seven known analogues(5-11),were isolated and identified.Their structural characterization was conducted using HRESIMS,1D and 2D NMR,electronic circular dichroism(ECD)spectra,and quantum chemical computations.Compounds 1,2,7,and 9-11 displayed significant ag-onistic effects towards 5-HT_(1A) receptor,and their EC_(50) values were 7.86,732,2.24,1.18,1.52,and 3.75μmol/L,respectively.Furthermore,in vivo experimental results fully revealed that hirsuteine(7)displayed a significant antidepression effect in unpredictable chronic mild stress(UCMS)-induced depression mice mainly via regulating 5-HT_(1A) signaling pathway.Molecular docking and site-directed amino acid mutation verified that amino acid residues Aspll6 and Asn386 were the binding sites of hirsuteine(7)with 5-HT_(1A) receptor.In addition,pre-treatment of mice with WAY 100635 also blocked the anti-depression effect of hirsuteine(7),which further demonstrated that 5-HT_(1A) receptor was a potential target of hirsuteine(7)to effectively treat depression.These findings indicated the therapeutic material basis of U.rhynchophylla and the anti-depression underlying mechanism of hirsuteine(7),and further provided the useful guidance for the development of hirsuteine(7)as a potential antidepressant candidate.

Discovery of New Iridoids as Farnesoid X Receptor Agonists from Morinda officinalis: Agonistic Potentials and Molecular Stimulation

The investigation of Morinda officinalis led to the isolation of twelve compounds(1-12),including three new iridoid glycosides morindallns A-C(1-3)and nine known compounds(4-12).Their structural identifications were conducted using HRMS,1D and 2D NMR,and electronic circular dichroism(ECD)spectra as well as quantum chemical computations.Compound 6 displayed the most significantly agonistic activity against farnesoid X receptor(FXR)with an EC_(50) value of 7.18 μM,and its agonistic effect was verified through the investigation of FXR downstream target genes including small heterodimer partner 1(SHP1),bile salt export pump(BSEP),and organic solute transporter subunit alpha and beta(OSTα and OSTβ).The potential interaction of compound 6 with FXR was analyzed by molecular docking and molecular dynamics stimulation,revealing that amino acid residues Leu287;Thr288,and Ser332 played a crucial role in the activation of compound 6 towards FXR.These findings suggested that compound 6 could be regarded as a potential candidate for the development of FXR agonists.