In-situ emb e dding zeolitic imidazolate framework derived Co–N–C bifunctional catalysts in carbon nanotube networks for flexible Zn–air batteries

Recently, the development of high-performance bifunctional oxygen catalysts integrated with flexible conductive scaffolds f or rechargeable metal-air batteries has attracted considerable interest, driving by fastgrowing wearable electronics. Herein, we report a flexible bifunctional oxygen catalyst thin film consisting of Co–N–C bifunctional catalysts embedding in carbon nanotube(CNT) networks. The catalyst is readily prepared by pyrolysis of cobalt-based zeolitic imidazolate frameworks(ZIF-67) that are in-situ synthesized in CNT networks. Such catalyst film demonstrates very high catalytic activities for oxygen reduction(onset potential: 0.91 V, and half-wave potential: 0.87 V vs. RHE) and oxygen evolution(10 m Acm^-2 at 1.58 V) reactions, high methanol tolerance property, and long-term stability(97% current retention). Moreover, our integrated catalyst film shows very good structure flexibility and robustness. Based on the obtained film air electrodes, flexible Zn–air batteries demonstrate low charging and discharging overpotentials(0.82 V at 1 m A cm^-1) and excellent structure stability in the bending tests. These results indicate that presently reported catalyst films are potential air electrodes for flexible metal–air batteries.

Novel polybenzimidazole/graphitic carbon nitride nanosheets composite membrane for the application of acid-alkaline amphoteric water electrolysis

It is a great challenge to develop membrane materials with high performance and long durability for acidalkaline amphoteric water electrolysis.Hence,the graphitic carbon nitride(g-C_(3)N_(4))nanosheets were compounded with the(2,2'-m-phenylene)-5,5'-benzimidazole(m-PBI)matrix for the preparation of m-PBI/g-C_(3)N_(4) composite membranes.The synthesis of g-C_(3)N_(4) nanosheets and m-PBI matrix have been confirmed by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscoy(TEM)and ^(1)H nuclear magnetic resonance spectra(^(1)H NMR),respectively.The fourier transform infrared spectroscopy(FT-IR)and SEM of the composite membranes showed the g-C_(3)N_(4) nanosheets were well dispersed in the m-PBI/g-C_(3)N_(4) composite membrane.The mechanical properties test exhibited the good mechanical strength,and the TGA curves of m-PBI showed the high thermal stability of composite membranes.Besides,the m-PBI/g-C_(3)N_(4) composite membrane showed excellent proton and hydroxide ion conductivity,which was higher than pure m-PBI and Nafion 115 membrane.The acid-alkaline amphoteric water electrolysis test showed m-PBI/1%g-C_(3)N_(4) composite membrane has the best performance with a current density of 800 mA cm^(-2) at cell voltage of 1.98 V at 20℃.It showed that m-PBI/g-C_(3)N_(4) composite membrane has a good application prospect for acid-alkaline amphoteric water electrolysis.

CoNi nanoparticles anchored inside carbon nanotube networks by transient heating:Low loading and high activity for oxygen reduction and evolution

Transitional metal alloy and compounds have been developed as the low cost and efficient bifunctional electrocatalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).However,a high mass loading of these catalysts is commonly needed to achieve acceptable catalytic performance,which could cause such problems as battery weight gain,mass transport blocking,and catalyst loss.We report herein the preparation of fine CoNi nanoparticles(5-6 nm)anchored inside a nitrogendoped defective carbon nanotube network(CoNi@N-DCNT)by a transient Joule heating method.When utilized as an electrocatalyst for oxygen reduction and evolution in alkaline media,the CoNi@N-DCNT film catalyst with a very low mass loading of 0.06 mg cm^(-2) showed excellent bifunctional catalytic performance.For ORR,the onset potential(Eonset)and the half-wave potential(E_(1/2))were 0.92 V versus reversible hydrogen electrode(vs.RHE)and 0.83 V(vs.RHE),respectively.For OER,the potential at the current density(J)of 10 mA cm^(-2)(E_(10))was 1.53 V,resulting in an overpotential of 300 mV much lower than that of the commercial RuO_(2) catalyst(320 mV).The potential gap between E_(1/2) and E_(10) was as small as 0.7 V.Considering the low mass loading,the mass activity at E_(10) reached at 123.2 A g^(-1),much larger than that of the RuO_(2) catalyst and literature results of transitional metal-based bifunctional catalysts.Moreover,the CoNi@N-DCNT film catalyst showed very good long-term stability during the ORR and OER test.The excellent bifunctional catalytic performance could be attributed to the synergistic effect of the bimetal alloy.

Pulmonary thromboembolism after distal ulna and radius fractures surgery: A case report and a literature review

BACKGROUND Pulmonary thromboembolism(PTE)is a serious postoperative complication that can occur after a fracture.Generally,PTE is caused by the falling off of lower extremity deep vein thrombosis(LEDVT)after lower limb fracture surgery.LEDVT and PTE after upper extremity fracture surgery are very rare.PTE is one of the most common clinical causes of sudden death.Venous thromboembolism includes PTE and DVT.We experienced one case of LEDVT and PTE after distal ulna and radius fracture surgery.The purpose of our report is to raise awareness for orthopedic surgeons that PTE can occur after distal ulna and radius fracture surgery,and patients with high risk factors should be considered for prevention and treatment of thrombosis in a timely manner.CASE SUMMARY We report a 51-year-old Chinese male who had severe fractures of the left distal ulna,radius and little finger after a motorcycle accident.The patient underwent external fixation,open reduction and internal fixation.On the third post-operative day,computed tomographic pulmonary angiography showed PTE.Doppler ultrasonography showed thrombus formation in the bilateral posterior tibial veins.After a period of anticoagulation therapy,on the 25th d after the PTE,computed tomographic pulmonary angiography showed that thrombus in both sides of the pulmonary artery disappeared.Furthermore,about 4 mo after the PTE,thrombosis in the deep veins of the lower limbs disappeared.About 1 year after the surgery,X-rays showed good fracture healing,and the function of the wrist joint recovered well.CONCLUSION Though rare,PTE can occur after distal ulna and radius fracture surgery and patients with high risk factors should be considered for prevention and treatment of thrombosis in a timely manner.

CaCO_(3)纳米晶体稳定非水相泡沫实验研究

非水相泡沫在油田开发、功能材料、食品工业和日化等领域有着广泛的应用,对非水相泡沫性能的调控在相关行业的发展中发挥着重要的影响。然而,由于非水相溶剂具有的低界面张力和低介电常数,导致其发泡难度较大。为解决非水相溶剂发泡困难的问题,文章通过制备CaCO_(3)纳米晶体,并经TEM,FT-IR及XRD等对晶体颗粒进行了表征,采用1H,1H,2H,2H-全氟癸基三乙氧基硅烷对CaCO_(3)纳米晶体的润湿性进行了调控,研究CaCO_(3)纳米晶体对非水相溶剂发泡性能的影响。研究发现:随CaCO_(3)纳米晶体质量分数的增加,不同接触角的CaCO_(3)纳米晶体所产生的泡沫体积呈现先增后减的趋势,当晶体质量分数为5%时,非水相溶剂发泡性能最佳,泡沫体积最高可达到120 mL;非水相泡沫的稳定性随CaCO_(3)纳米晶体接触角的增加呈现先增强后减弱的趋势,当接触角范围在47.5°~73.9°时,非水相泡沫的稳定性最佳,排液半衰期最高可达到100 h。

Runaway electron dynamics in Experimental Advanced Superconducting Tokamak helium plasmas

The generation of runaway electrons(REs)is observed during the low-density helium ohmic plasma discharge in the Experimental Advanced Superconducting Tokamak(EAST).The growth rate of hard x-ray(HXR)is inversely proportional to the line-average density.Besides,the RE generation in helium plasma is higher than that in deuterium plasma at the same density,which is obtained by comparing the growth rate of HXR with the same discharge conditions.The potential reason is the higher electron temperature of helium plasma in the same current and electron density plateau.Furthermore,two Alfvén eigenmodes driven by REs have been observed.The frequency evolution of the mode is not fully satisfied with the Alfvén scaling and when extension of the Alfvén frequency is towards 0,the high frequency branch is~50 kHz.The different spatial position of the two modes and the evolution of the helium concentration could be used to understand deviation between theoretical and experimental observation.

Synthesis and Anti-Cancer Activities of Resveratrol Derivatives

A novel series of resveratrol derivatives were synthesized according to Wittig-Horner reaction with 3,5-dihydroxybenzyl alcohol or 3,5-dimethoxybenzyl alcohol or 4-hydroxybenzyl alcohol as raw material and the inhibitory activities on breast carcinoma (MDA-MB-231) and gastric carcinoma cell lines (SGC-7901) in vitro were evaluated by the standard methyl thiazole tetrazolium (MTT) method. The result of biological test shows that some of resveratrol derivatives possess stronger anti-cancer activities than 5-FU. Compound 5c shows the strongest activity against breast carcinoma (MDA-MB-231) and gastric carcinoma cell lines (SGC-7901) with IC50 value of 50.19 ± 1.02 μM, 122.68.27 ± 2.04 μM, compared to that IC50 value of 5-FU is 98.59±3.61 μM,156.74±6.16 μM, respectively.

基于DYNAMICS软件的透平膨胀机临界转速计算与分析

本文用转子动力学分析软件DYNAMICS计算了两种气体轴承支撑的不同结构的透平膨胀机转子系统的临界转速,并与ANSYS计算结果和实验数据进行了对比。ANSYS与DYNAMICS对两种材质(铍青铜、不锈钢)双层鼓泡箔片动压轴承支撑的Φ_1=25mm双盘转子系统前4阶临界转速计算结果差异较大,随转速提高差异较低,5,6两阶临界转速计算结果差异小于1%,DYNAMICS对临界转速计算结果与转子非同步涡动振动频率实验值基本吻合。ANSYS与DYNAMICS对小孔供气静压轴承支撑的Φ_2=17mm单盘转子系统各阶临界转速差异均小于2%,DYNAMICS对临界转速计算结果略大于实验结果。ANSYS计算Φ_1=25mm双盘转子系统耗时分别为109s和105s,计算Φ_2=17mm单盘转子系统耗时约70s,DYNAMICS计算耗时均小于1s。通过对两种结构转子系统的计算对比,表明DYNAMICS计算准确度高,运算速度快,适用于多种转子、轴承系统。

Medium-term efficacy of arthroscopic debridement vs conservative treatment for knee osteoarthritis of Kellgren-Lawrence grades I-III

BACKGROUND Arthroscopic debridement is a mature treatment for knee osteoarthritis(KOA).Due to the differences in the research subjects,methods,and efficacy evaluation indexes,there are great differences in the surgical efficacy reported in the literature.AIM To compare the medium-term efficacy of arthroscopic debridement and conservative treatment for KOA of Kellgren-Lawrence grades I-III.METHODS Patients with KOA of Kellgren-Lawrence grades I-III who were admitted to the orthopedic clinic of our hospital from July 2018 to December 2018 and agreed to undergo arthroscopic surgery were included in an arthroscopic debridement group,and those who refused surgical treatment were included in a conservative treatment group.Gender,age,body mass index(BMI),side of KOA,American hospital for special surgery knee score(HSS score)before treatment,visual analogue scale(VAS)score during walking and rest before treatment,conservative treatment content,and surgical procedure were recorded.Outpatient visits were conducted at the 1st,3rd,6th,12th,and 24th mo after treatment in the two groups.The changes of HSS score and VAS score in each group before and after treatment were statistically analyzed,and the differences of HSS score and VAS score in different treatment stages between the two groups were also compared.RESULTS In the conservative treatment group,there were 80 patients with complete followup data,including 20 males and 60 females,aged 58.75±14.66 years old.And in the knee arthroscopic debridement group,there were 98 patients with complete follow-up data,including 24 males and 74 females,aged 59.27±14.48 years old.There was no statistically significant difference in the general data(gender,age,BMI,side of KOA,Kellgren-Lawrence grade distribution,HSS score,and VAS score)between the two groups before treatment.The HSS scores of the conservative treatment group at the 1st,3rd,6th,12th,and 24th mo after treatment were significantly higher than that before treatment(P<0.05).There was no statistical difference in HSS score of the conservative treatment group among the 1st,3rd,6th,12th,and 24th mo(P>0.05).The HSS score of the knee arthroscopic debridement group at the 1st mo after surgery was significantly higher than that before surgery(P<0.05).HSS scores of the knee arthroscopic debridement group at the 3rd,6th,12th,and 24th mo were significantly higher than those before surgery and at the 1st mo after surgery(P<0.05).There were no statistically significant differences in HSS scores at the 3rd,6th,12th,and 24th mo after surgery(P>0.05).HSS scores at the 3rd,6th,12th,and 24th mo were significantly higher in the arthroscopic debridement group than in the conservative treatment group(P<0.05).There was no statistical difference in HSS scores between the two groups before treatment and at the 1st mo of follow-up(P>0.05).VAS scores during walking and rest were significantly decreased in both groups,and the VAS score during rest was significantly lower in the arthroscopic debridement group than in the conservative treatment group,but there was no significant difference in the VAS score during walking between the two groups after treatment.CONCLUSION Compared with conservative treatment,arthroscopic debridement can significantly improve the knee resting pain and knee functional status of patients with KOA of Kellgren-Lawrence grades I-III within 2 years after treatment.

Fast estimation of ion temperature from EAST charge exchange recombination spectroscopy using neural network

Ion temperature, as one of the most critical plasma parameters, can be diagnosed by charge exchange recombination spectroscopy (CXRS). Iterative least-squares fitting is conventionally used to analyze CXRS spectra to identify the active charge exchange component, which is the result of local interaction between impurity ions with a neutral beam. Due to the limit of the time consumption of the conventional approach (~100 ms per frame), the Experimental Advanced Superconducting Tokamak CXRS data is now analyzed in-between shots. To explore the feasibility of real-time measurement, neural networks are introduced to perform fast estimation of ion temperature. Based on the same four-layer neural network architecture, two neural networks are trained for two central chords according to the ion temperature data acquired from the conventional method. Using the TensorFlow framework, the training procedures are performed by an error back-propagation algorithm with the regularization via the weight decay method. Good agreement in the deduced ion temperature is shown for the neural networks and the conventional approach, while the data processing time is reduced by 3 orders of magnitude (~0.1 ms per frame) by using the neural networks.

Numerical simulation and experimental validation of multiphysics field coupling mechanisms for a high power ICP wind tunnel

We take the established inductively coupled plasma(ICP) wind tunnel as a research object to investigate the thermal protection system of re-entry vehicles. A 1.2-MW high power ICP wind tunnel is studied through numerical simulation and experimental validation. The distribution characteristics and interaction mechanism of the flow field and electromagnetic field of the ICP wind tunnel are investigated using the multi-field coupling method of flow, electromagnetic, chemical, and thermodynamic field. The accuracy of the numerical simulation is validated by comparing the experimental results with the simulation results. Thereafter, the wind tunnel pressure, air velocity, electron density, Joule heating rate, Lorentz force, and electric field intensity obtained using the simulation are analyzed and discussed. The results indicate that for the 1.2-MW ICP wind tunnel, the maximum values of temperature, pressure, electron number density, and other parameters are observed during coil heating. The influence of the radial Lorentz force on the momentum transfer is stronger than that of the axial Lorentz force. The electron number density at the central axis and the amplitude and position of the Joule heating rate are affected by the radial Lorentz force. Moreover, the plasma in the wind tunnel is constantly in the subsonic flow state, and a strong eddy flow is easily generated at the inlet of the wind tunnel.

Numerical simulation of the thermal non-equilibrium flow-field characteristics of a hypersonic Apollo-like vehicle

In order to investigate the relationship between the flow-field parameters outside the vehicle and the altitude,this paper takes the Atmospheric Reentry Demonstrator(ARD)with an angle of attack of-20°as the research object and adopts a two-temperature model coupled with the shear-stress transport k-ωturbulence model to focus on the variation of flow-field parameters including flow-field pressure,Mach number and temperature with the reentry altitude.It is found that the flow-field high-pressure region and low-Mach region both appear in the shock layer near the head of the ARD,while the maximum pressure of the surface appears on the windward side of the ARD's head with a toroidal distribution,and the numerical magnitude is inversely proportional to the radius of the torus.With fluid through the shoulder of the ARD flow expansion plays a dominant role,the airflow velocity increases,the Mach number of the windward side of the rear cone increases and the flow-field pressure and surface pressure rapidly decrease.When the fluid passes through the shock layer,the translational-rotation temperature will increase before the vibration-electron temperature,there is a thermal non-equilibrium effect and the two temperatures will rapidly decrease again when approaching the surface of the ARD due to the existence of temperature gradient.At the same time,both the windward side of the shoulder and the back cover of the ARD suffer from a large thermal load and require thermal protection.

Transmissive 2-bit anisotropic coding metasurface

Coding metasurfaces have attracted tremendous interests due to unique capabilities of manipulating electromagnetic wave.However,archiving transmissive coding metasurface is still challenging.Here we propose a transmissive anisotropic coding metasurface that enables the independent control of two orthogonal polarizations.The polarization beam splitter and the orbital angular momentum(OAM)generator have been studied as typical applications of the anisotropic 2-bit coding metasurface.The simulated far field patterns illustrate that the x and y polarized electromagnetic waves are deflected into two different directions,respectively.The anisotropic coding metasurface has been experimentally verified to realize an OAM beam with l=2 of right-handed polarized wave,resulting from both contributions from linear-to-circular polarization conversion and the phase profile modulation.This work is beneficial to enrich the polarization manipulation field and develop transmissive coding metasurfaces.

The effect of Wujiadan Recipe on serum sex hormone and expression of Kiss-1, GPR54 and GnRH in arcuate nucleus of hypothalamus in ovariectomized rats

Objective:To explore the effect of wujiadan Recipe on the expression of FSH,E2 in serum and KiSS-1,GPR54,GnRH mRNA in hypothalamic arcuate nucleus tissue homogenate of ovariectomized rats,and to further explore the mechanism of wujiadan Recipe on menopausal syndrome.Methods:Sixty-four adult female rats were randomly divided into three groups:blank group,model group,Chinese medicine control group,western medicine control group,and wujiadan high,medium and low dose groups.Except for the blank group,all the other groups were ovariectomized.The rats in the normal group and the model group were given the same dose of saline once a day.One rat in the blank group died during the experiment.After 4 weeks of continuous administration,blood was collected from abdominal aorta and brain stereotaxic localization was performed to preserve the arcuate nucleus of hypothalamus.The levels of FSH and E2 in serum were detected by enzyme-linked immunosorbent assay(ELISA),and the expression of Kiss-1,GPR54 and GnRH mRNA in arcuate nucleus of hypothalamus were detected by PCR.Results:1.Compared with the blank group,FSH level in the model group was significantly higher(P<0.01),and E2 level was significantly lower(P<0.01).Compared with the model group,the level of serum E2 in the western medicine control group increased significantly(P.The serum FSH content in each group decreased,especially in the high dose group and the western medicine control group(P<0.01),and in the Chinese medicine control group,the middle dose group and the low dose group(P<0.05).Compared with the blank group,the expression of KiSS-1 mRNA,GPR54 mRNA and GnRH mRNA in the model group increased significantly(P<0.01);compared with the model group,the expression of KiSS-1 mRNA and GPR54 mRNA in the high dose group,middle dose group and Western medicine control group of wujiadan prescription decreased significantly(P<0.05).Compared with the model group,the expression of GnRH mRNA in the high dose group and the western medicine control group decreased significantly(P<0.01);the middle dose group of wujiadan decreased significantly(P<0.05).Conclusion:Wujiadan recipe can improve the serum sex hormone level of castrated rats,and reduce the over expression of KiSS-1,GPR54 and GnRH mRNA in hypothalamic arcuate nucleus of castrated rats,which may be the reproductive endocrine mechanism of wujiadan recipe in the treatment of menopausal syndrome.

Stormwater Quality Characteristics and Reuse Analysis of Different Underlying Surfaces at Wanzhou North Station

In response to the water shortage in Wanzhou North Station(WNS),the authors investigated the stormwater quality characteristics with different underlying surfaces of WNS and carried out stormwater reuse analysis in conjunction with the InfoWorks ICM model.The results show that during heavy,torrential,and moderate rainfall,the road stormwater runoff has the highest concentrations of pollutants,with an average EMC(event mean concentration)value of 206 mg/L for COD.For the square runoff,the average EMC values of COD,SS,TN,and TP are 108 mg/L,395 mg/L,2.113 mg/L,and 0.128 mg/L,in comparison,the average EMC values of the corresponding indexes for the roof runoff are 65 mg/L,212 mg/L,1.449 mg/L,and 0.086 mg/L,respectively,demonstrating their potential for reuse.The R2(coefficient of determination)of SS and COD in both roof and square runoff are greater than 0.85,with a good correlation,indicating that SS removal is the key to stormwater purification.InfoWorks ICM analysis shows that the recyclable volume of rainwater from WNS in 2018 is 29,410 m3,accounting for 61.8%of the total annual rainfall.This study is expected to provide an ideal reference for the stormwater management of public buildings in mountainous areas.

Independent control of circularly polarized light with exceptional topological phase coding metasurfaces:erratum

The funding in this article[1]needs to be supplemented.Coupled-mode theory analysis has been supported by the Priority 2030 Federal Academic Leadership Program.CST simulations have been supported by Russian Science Foundation(project 23-72-10059).

Independent control of circularly polarized light with exceptional topological phase coding metasurfaces

Exceptional points,as degenerate points of non-Hermitian parity-time symmetric systems,have many unique physical properties.Due to its flexible control of electromagnetic waves,a metasurface is frequently used in the field of nanophotonics.In this work,we developed a parity-time symmetric metasurface and implemented the 2πtopological phase surrounding an exceptional point.Compared with Pancharatnam-Berry phase,the topological phase around an exceptional point can achieve independent regulation of several circular polarization beams.We combined the Pancharatnam-Berry phase with the exceptional topological phase and proposed a composite coding metasurface to achieve reflection decoupling of different circular polarizations.This work provides a design idea for polarimetric coding metasurfaces in the future.

Secondary organic aerosols in Jinan, an urban site in North China: Significant anthropogenic contributions to heavy pollution

Secondary organic aerosols(SOAs) are an important component of particulates, but whether biogenic SOAs(BSOAs) or anthropogenic SOAs(ASOAs) are the dominant contributors to haze pollution remains poorly characterized. In this study, particulate samples were collected from September 2014 to August 2015 at an urban site in Jinan, which is the capital of Shandong Province and a typical city in the North China Plain. The PM2.5 samples were analyzed for BSOA(isoprene(SOAI) and monoterpenes(SOAM)) and ASOA(aromatic(SOAA)) tracers. The concentrations of the SOAAtracer(1.1 ± 1.0 ng/m3) were lowest, and those of SOAItracers(41.8 ± 86.2 ng/m3) were highest, with the concentrations of SOAMtracers(19.4 ± 9.9 ng/m3) being intermediate. The SOAItracers were more abundant in the summer and less abundant in the winter. Both SOAIand SOAMincreased with increasing ozone level but decreased with increasing NOx level. Correlation analysis revealed a good correlation between 2,3-dihydroxy-4-oxopentanoic acid and levoglucosan levels in three seasons. These results suggested that biomass burning activities occurring in the NCP can enhance the emissions of aromatics and should be controlled, especially in the autumn and winter. SOA tracers were classified according to pollution degree, and the results showed that as pollution increases, the contributions of SOAAincrease. These results indicate that reducing anthropogenic emissions is necessary to prevent SOA pollution, especially during heavy pollution episodes.

Source apportionment of PM_(2.5)and visibility in Jinan,China

Atmospheric extinction is impacted by the chemical composition of particles.To better understand the chemical composition of PM_(2.5)(particles with diameters of less than 2.5μm)and its relationship with extinction,one-month sampling campaigns were carried out in four different seasons from 2013 to 2014 in Jinan,China.The seasonal average concentrations of PM_(2.5)were 120.9(autumn),156.6(winter),102.5(spring),and 111.8μg/m^(3)(summer).The reconstructed PM_(2.5)chemical composition showed that sulfate,nitrate,chlorine salt,organic matter(OM),mineral dust,elemental carbon(EC)and others accounted for 25%,14%,2%,24%,22%,3%and 10%,respectively.The relationship between the chemical composition of PM_(2.5)and visibility was reconstructed by the IMPROVE method,and ammonium sulfate,ammonium nitrate,OM and EC dominated the visibility.Seven main sources were resolved for PM_(2.5),including secondary particles,coal combustion,biomass burning,industry,motor vehicle exhaust,soil dust and cooking,which accounted for 37%,21%,13%,13%,12%,3%and 1%,respectively.The contributions of different sources to visibility were similar to those to PM_(2.5).With increasing severity of air pollution,the contributions of secondary particles and coal combustion increased,while the contribution of motor vehicle exhaust decreased.The results showed that coal combustion and biomass burning were still the main sources of air pollution in Jinan.

O-glycosyltransferases from Homo sapiens contributes to the biosynthesis of Glycyrrhetic Acid 3-O-mono-β-D-glucuronide and Glycyrrhizin in Saccharomyces cerevisiae

Glycyrrhizin(GL)and Glycyrrhetic Acid 3-O-mono-β-D-glucuronide(GAMG)are the typical triterpenoid glycosides found in the root of licorice,a popular medicinal plant that exhibits diverse physiological effects and pharmacological manifestations.However,only few reports are available on the glycosylation enzymes involved in the biosynthesis of these valuable compounds with low conversion yield so far.In mammals,glycosyltransferases are involved in the phase II metabolism and may provide new solutions for us to engineer microbial strains to produce high valued compounds due to the substrate promiscuity of these glycosyltransferases.In this study,we mined the genomic databases of mammals and evaluated 22 candidate genes of O-glycosyltransferases by analyzing their catalytic potential for O-glycosylation of the native substrate,glycyrrhetinic acid(GA)for its glycodiversification.Out of 22 selected glycosyltransferases,only UGT1A1 exhibited high catalytic performance for biosynthesis of the key licorice compounds GL and GAMG.Molecular docking results proposed that the enzymatic activity of UGT1A1 was likely owing to the stable hydrogen bonding interactions and favorite conformations between the amino acid residues around substrate channels(P82~R85)and substrates.Furthermore,the complete biosynthesis pathway of GL was reconstructed in Saccharomyces cerevisiae for the first time,resulting in the production of 5.98±0.47 mg/L and 2.31±0.21 mg/L of GL and GAMG,respectively.