Tungsten oxide/nitrogen-doped carbon nanotubes composite catalysts for enhanced redox kinetics in lithium-sulfur batteries

The sluggish redox kinetics of polysulfides in lithium-sulfur(Li-S)batteries are a significant obstacle to their widespread adoption as energy storage devices.However,recent studies have shown that tungsten oxide(WO_(3))can facilitate the conversion kinetics of polysulfides in Li-S batteries.Herein,we fabricated host materials for sulfur using nitrogen-doped carbon nanotubes(N-CNTs)and WO_(3).We used low-cost components and simple procedures to overcome the poor electrical conductivity that is a disadvantage of metal oxides.The composites of WO_(3) and N-CNTs(WO_(3)/N-CNTs)create a stable framework structure,fast ion diffusion channels,and a 3D electron transport network during electrochemical reaction processes.As a result,the WO_(3)/N-CNT-Li2S6 cathode demonstrates high initial capacity(1162 mA·h·g^(-1) at 0.5℃),excellent rate performance(618 mA·h·g^(-1) at 5.5℃),and a low capacity decay rate(0.093%up to 600 cycles at 2℃).This work presents a novel approach for preparing tungsten oxide/carbon composite catalysts that facilitate the redox kinetics of polysulfide conversion.

Calculation of Mass Concrete Temperature Containing Cooling Water Pipe Based on Substructure and Iteration Algorithm

Mathematical physics equations are often utilized to describe physical phenomena in various fields of science and engineering.One such equation is the Fourier equation,which is a commonly used and effective method for evaluating the effectiveness of temperature control measures for mass concrete.One important measure for temperature control in mass concrete is the use of cooling water pipes.However,the mismatch of grids between large-scale concrete models and small-scale cooling pipe models can result in a significant waste of calculation time when using the finite element method.Moreover,the temperature of the water in the cooling pipe needs to be iteratively calculated during the thermal transfer process.The substructure method can effectively solve this problem,and it has been validated by scholars.The Abaqus/Python secondary development technology provides engineers with enough flexibility to combine the substructure method with an iteration algorithm,which enables the creation of a parametric modeling calculation for cooling water pipes.This paper proposes such a method,which involves iterating the water pipe boundary and establishing the water pipe unit substructure to numerically simulate the concrete temperature field that contains a cooling water pipe.To verify the feasibility and accuracy of the proposed method,two classic numerical examples were analyzed.The results showed that this method has good applicability in cooling pipe calculations.When the value of the iteration parameterαis 0.4,the boundary temperature of the cooling water pipes can meet the accuracy requirements after 4∼5 iterations,effectively improving the computational efficiency.Overall,this approach provides a useful tool for engineers to analyze the temperature control measures accurately and efficiently for mass concrete,such as cooling water pipes,using Abaqus/Python secondary development.

Growth of covellite crystal onto azurite surface during sulfurization and its response to flotation behavior

In this work,the growth of copper sulfide crystal onto azurite surfaces during sulfurization and its response to flotation are investigated.Filed emission scanning electron microscopy-energy dispersive X-ray spectroscopy(FESEM) and X-ray diffraction(XRD) studies confirmed that the sulfurization of azurite is not limited to the mineral surface,but rather penetrates into the bulk to form covellite crystal(synCuS),creating favorable conditions for the stable adsorption of xanthate and greatly promoting the azurite flotation.Additionally,as demonstrated by X-ray photoelectron spectroscopy(XPS) and time of flight secondary ion mass spectrometry(TOF-SIMS) analyses,a redox reaction occurred during this process,and Cu(Ⅱ) onto the mineral surface was reduced to Cu(Ⅰ).Correspondingly,reduced S^(2-) was oxidized to(S_(2))^(2-),(S_n)^(-2),and even to deeper oxidation state S~0,(S_(x)O_(y))^(n-) and SO_(4)^(2-).Excess sodium sulfide strengthens copper sulfide to form onto the azurite surface,and provides enough raw material for crystal copper sulfide to grow,resulting in the formation of "flake-like" covellite with a better crystallinity.However,the floatability of azurite decreased dramatically under this condition,because the generated massive colloidal copper sulfide in flotation pulp deteriorates the flotation environment,resulting in a decreased effective adsorption of collector onto azurite surfaces.

Role of ammonium sulfate in sulfurization flotation of azurite:Inhibiting the formation of copper sulfide colloid and its mechanism

In this study,the role of(NH_(4))_(2)SO_(4)during the sulfurization of azurite and its response to flotation were investigated.The flotation results showed that adding(NH_(4))_(2)SO_(4)prior to sulfurization decreased the formation of colloid in flotation pulp,and the floatability of the suppressed azurite caused by excess sodium sulfide was restored.After adding(NH_(4))_(2)SO_(4)prior to sulfurization,the formation of Cu(NH_(3))_(n) ^(2+)intermediate products changed the path of the sulfurization reaction,which slowed the direct impact of HSon the azurite surface.The nucleation rate was reduced,and the growth of copper sulfide crystal was improved.Covellite(syn,CuS)with larger crystal grains was formed on the azurite surface,thereby enhancing the mechanical stability of copper sulfide products onto the mineral surface.Therefore,the generated copper sulfide colloid significantly reduced,ultimately promoting the effective adsorption of xanthate on the azurite surface.

氧气和硫化钠对赤铜矿浮选的影响及作用机理

通过浮选试验、场发射扫描电子显微镜(FESEM)、电子探针(EPMA)以及X射线光电子能谱(XPS)等研究氧气和硫化钠对赤铜矿浮选的影响。浮选试验表明,用适量的硫化钠预处理赤铜矿表面后可大幅提升赤铜矿的可浮性。FESEM显示硫化后的赤铜矿表面覆盖有大量碎片,在Na_(2)S浓度为5.0×10^(−4)mol/L时,这些碎片的形状更加规则和完整。结合EPMA和EDS分析发现,这些碎片是新形成的铜硫化物,是促进赤铜矿高效浮选的关键。XPS分析表明,赤铜矿暴露于空气中表面极易被氧化成CuO,硫化钠优先与表面的CuO膜发生氧化还原反应,此过程中,Cu^(2+)被还原为Cu^(+),S^(2-)主要被氧化为(S_(2))^(2-)和(S_(n))^(2−)。

Recent advances and perspectives of fluorite and perovskite-based dual-ion conducting solid oxide fuel cells

High-temperature solid-state electrolyte is a key component of several important electrochemical devices,such as oxygen sensors for automobile exhaust control,solid oxide fuel cells(SOFCs) for power generation,and solid oxide electrolysis cells for H_(2) production from water electrolysis or CO_(2) electrochemical reduction to value-added chemicals.In particular,internal diffusion of protons or oxygen ions is a fundamental and crucial issue in the research of SOFCs,hypothetically based on either oxygen-ionconducting electrolytes or proton-conducting electrolytes.Up to now,some electrolyte materials based on fluorite or perovskite structure were found to show certain degree of dual-ion transportation capability,while in available electrolyte database,particularly in the field of SOFCs,such dual-ion conductivity was seriously overlooked.Actually,few concerns arising to the simultaneous proton and oxygen-ion conductivities in electrolyte of SOFCs inevitably induce various inadequate and confusing results in literature.Understanding dual-ion transportation behavior in electrolyte is indisputably of great importance to explain some unusual fuel cell performance as reported in literature and enrich the knowledge of solid state ionics.On the other hand,exploration of novel dual-ion conducting electrolytes will benefit the development of SOFCs.In this review,we provide a comprehensive summary of the understanding of dual-ion transportation in solid electrolyte and recent advances of dual-ion conducting SOFCs.The oxygen ion and proton conduction mechanisms at elevated temperature inside oxide-based electrolyte materials are first introduced,and then(mixed) oxygen ion and proton conduction behaviors of fluorite and perovskite-type oxides are discussed.Following on,recent advances in the development of dual-ion conducting SOFCs based on fluorite and perovskite-type single-phase or composite electrolytes,are reviewed.Finally,the challenges in the development of dual-ion conducting SOFCs are discussed and future prospects are proposed.

Solid oxide fuel cells in combination with biomass gasification for electric power generation

Biomass,a source of renewable energy,represents an effective substitute to fossil fuels.Gasification is a process that organics are thermochemically converted into valuable gaseous products(e.g.biogas).In this work,the catalytic test demonstrated that the biogas produced from biomass gasification mainly consists of H2,CH4,CO,and CO2,which were then be used as the fuel for solid oxide fuel cell(SOFC).Planar SOFCs were fabricated and adopted.The steam reforming of biogas was carried out at the anode of a SOFC to obtain a hydrogen-rich fuel.The performance of the SOFCs operating on generated biogas was investigated by I-V polarization and electrochemical impedance spectra characterizations.An excellent cell performance was obtained,for example,the peak power density of the SOFC reached 1391 mW·cm-2 at 750℃when the generated biogas was used as the fuel.Furthermore,the SOFC fuelled by simulated biogas delivered a very stable operation.

肺结核空洞伴曲霉菌感染并咯血的外科治疗

目的探讨外科手术治疗肺结核空洞伴曲霉菌感染并咯血的原则、方法及疗效。方法回顾性分析该院2013年1月-2016年12月收治的施行外科手术治疗肺结核空洞伴曲霉菌感染并咯血的25例患者临床资料。行胸腔镜辅助小切口治疗23例,标准后外侧切口2例。其中,右肺上叶切除13例,右肺下叶切除2例,左肺上叶切除6例,左肺下叶切除1例,左全肺切除1例,右肺上叶合并右肺下叶背段切除1例,右肺上中叶合并右肺下叶背段切除1例,全组未作胸廓成形术。结果围手术期死亡1例,为健肺肺部感染导致呼吸衰竭。局限性肺不张8例,心律失常7例,胸腔渗血1例,反复少量咯血1例,均采用相应治疗痊愈,复查胸部CT肺复张良好。术后失访2例,其余22例随访3~36个月,咯血、痰血消失,痰抗酸杆菌涂片均转阴,咳嗽、咳痰、胸闷和胸痛等症状明显缓解,生活质量提高,效果满意。结论外科手术治疗肺结核空洞伴曲霉菌感染并咯血的效果确切,安全可行,对于符合指征的患者应不失时机地进行手术治疗。

3D amorphous carbon and graphene co-modified LiFePO_4 composite derived from polyol process as electrode for high power lithium-ion batteries

Amorphous carbon and graphene co-modified LiFePO4 nanocomposite has been synthesized via a facile polyol process in connection with a following thermal treatment.Various characterization techniques,including XRD.Mossbauer spectra,Raman spectra,SEM,TEM,BET,O2-TPO,galvano charge-discharge,CV and EIS were applied to investigate the phase composition,carbon content,morphological structure and electrochemical performance of the synthesized samples.The effect of introducing way of carbon sources on the properties and performance of LiFePO4/C/graphene composite was paid special attention.Under optimized synthetic conditions,highly crystalized olivine-type LiFePO4was successfully obtained with electron conductive Fe2P and FeP as the main impurity phases.SEM and TEM analyses demonstrated the graphene sheets were randomly distributed inside the sample to create an open structured LiFePO4 with respect to graphene,while the glucosederived carbon mainly coated over LiFeP04 particles which effectively connected the graphene sheets and LiFePO4 particles to result in a more efficient charge transfer process.As a result,favorable electrochemical performance was achieved.The performance of the amorphous carbon-graphene co-modified LiFePO4 was further progressively improved upon cycling in the first 200 cycles to reach a reversible specificcapacity as high as 97 mAh·g-1 at 10 C rate.

New strategy for boosting cathodic performance of low temperature solid oxide fuel cells via chlorine doping

To enhance the performance and widespread use of solid oxide fuel cells(SOFCs),addressing the low-temperature(<650℃)electrochemical performance and operational stability issues of cathode materials is crucial.Here,we propose an innovative approach to enhance oxygen ion mobility and electrochemical performance of perovskite oxide by substituting some oxygen sites with chlorine anions.The designed SrTa_(0.1)Fe_(0.9)O_(3-δ-x)Clx(x=0.05 and 0.10)exhibits improved performance compared to SrTa_(0.1)Fe_(0.9)O_(3-δ)(STF).SrTa_(0.1)Fe_(0.9)O_(2.95-δ)Cl_(0.05)(STFCl0.05)shows the lowest area-specific resistance(ASR)value on Sm0.2Ce0.8O1.9(SDC)electrolyte.At 600℃,STFCl0.05 achieves an ASR value of 0.084Ω·cm^(2),and a single cell with STFCl0.05 reaches a higher peak power density(PPD)value(1143 mW·cm^(-2))than that with STF(672 mW·cm^(-2)).Additionally,besides exhibiting excellent oxygen reduction reaction(ORR)activity at lower temperatures,the STFCl0.05 cathode demonstrates good CO_(2)tolerance and operational stability.Symmetrical cell operation lasts for 150 h,and single cell operation endures for 720 h without significant performance decline.The chlorine doping approach effectively enhances ORR activity and stability,making STFCl0.05 a promising cathode material for low-temperature SOFCs.

Statistical characteristics and mechanism analysis of adhered particle on surface under strong electric field

Insulators on high-voltage Uansmission lines are almost the only man-made structures on the Earth's surface intended for long-term operation under strong electric fields. After samples of natural contaminant particles were collected from insulator surfaces in China, it was found that the particle diameter distribution (PDD) was mainly concentrated in the 5-50 μm range. To analyze the statistical characteristics of these particles, this work studies the physical processes of particle collision and adhesion using the theories of hydrodynamics and collision dynamics. The physical model considers coupling of the fluid field and the electric field, introduces an adhesion criterion, and establishes a particle and surface collision model. The effects of relative humidity, wind speed, aerodynamic shape, electric field type, and electric field strength on particle adhesion were analyzed. The results show that the relative humidity and wind speed have very significant effects and the influences of the electric field type and the electric field strength are obvious, but the in fluence of the aerodynamic shape is relatively weak. The simulation results support the statistical characteristics determined in this work. The physical model established here provides reference values for study of the adhesion characteristics of particles on surfaces under electric fields.

Rational construction of high-active CO_(3)O_(4) electrocatalysts for oxygen evolution reaction

Rational construction of high-efficiency electrocatalysts for oxygen evolution reaction(OER)is critical for renewable-energy technologies,but it is highly challenging to rationally regulate their surface structures to improve the OER performance.Herein,we proposed a“model-etching”strategy to investigate chemical etching of CO_(3)O_(4).The cubic CO_(3)O_(4)nanocrystals enclosed by well-defined facets are synthesized as model crystals,whose uniform surface structures allow us to study the etching mechanism at atomic level.Etching kinetics study together with DFT calculations discloses that{111}facets,the highly active facets for OER,serve as etch-stop facets in the etching reaction and H_(2)SO_(4)molecules play a special role in creating surface Co2^(+),the active center of OER.These results direct us to rationally optimize the surface structures of CO_(3)O_(4) to develop highly active OER electrocatalysts.The favorable performance of overpotential(η)and the Tafel slope decrease even to 268 mV@10 mA·cm−2 and 74 mV·dec−1,respectively.In general,our study shows that chemical etching of model crystals could help us rationally construct high-efficiency electrocatalysts.

Highly active and durable triple conducting composite air electrode for low-temperature protonic ceramic fuel cells

Protonic ceramic fuel cells(PCFCs)are more suitable for operation at low temperatures due to their smaller activation energy(Ea).Unfortunately,the utilization of PCFC technology at reduced temperatures is limited by the lack of durable and high-activity air electrodes.A lot number of cobalt-based oxides have been developed as air electrodes for PCFCs,due to their high oxygen reduction reaction(ORR)activity.However,cobalt-based oxides usually have more significant thermal expansion coefficients(TECs)and poor thermomechanical compatibility with electrolytes.These characteristics can lead to cell delamination and degradation.Herein,we rationally design a novel cobalt-containing composite cathode material with the nominal composition of Sr_(4)Fe_(4)Co_(2)O_(13)+δ(SFC).SFC is composed of tetragonal perovskite phase(Sr_(8)Fe_(8)O_(23)+δ,I4/mmm,81 wt.%)and spinel phase(Co_(3)O_(4),Fd3m,19 wt.%).The SFC composite cathode displays an ultra-high oxygen ionic conductivity(0.053 S·cm^(-1)at 550℃),superior CO_(2)tolerance,and suitable TEC value(17.01×10^(-6)K^(-1)).SFC has both the O_(2)^(-)/e^(-)conduction function,and the triple conducting(H^(+)/O_(2)^(-)/e^(-))capability was achieved by introducing the protonic conduction phase(BaZr_(0.2)Ce_(0.7)Y_(0.1)O_(3-δ),BZCY)to form SFC+BZCY(70 wt.%:30 wt.%).The SFC+BZCY composite electrode exhibits superior ORR activity at a reduced temperature with extremely low area-specific resistance(ASR,0.677Ω·cm^(2)at 550℃),profound peak power density(PPD,535 mW·cm^(-2)and 1.065 V at 550℃),extraordinarily long-term durability(>500 h for symmetrical cell and 350 h for single cell).Moreover,the composite has an ultra-low TEC value(15.96×10^(-6)K^(-1)).This study proves that SFC+BZCY with triple conducting capacity is an excellent cathode for low-temperature PCFCs.

Investigation and optimization of high-valent Ta-doped SrFeO_(3-δ)as air electrode for intermediate-temperature solid oxide fuel cells

To explore highly active and thermomechanical stable air electrodes for intermediate-temperature solid oxide fuel cells(ITSOFCs),10mol%Ta5+doped in the B site of strontium ferrite perovskite oxide(SrTa_(0.1)Fe_(0.9)O_(3-δ),STF)is investigated and optimized.The effects of Ta^(5+)doping on structure,transition metal reduction,oxygen nonstoichiometry,thermal expansion,and electrical performance are evaluated systematically.Via 10mol%Ta^(5+)doping,the thermal expansion coefficient(TEC)decreased from 34.1×10^(-6)(SrFeO_(3-δ))to 14.6×10^(-6) K^(-1)(STF),which is near the TEC of electrolyte(13.3×10^(-6) K^(-1) for Sm_(0.2)Ce_(0.8)O_(1.9),SDC),indicates excellent thermomechanical compatibility.At 550-750℃,STF shows superior oxygen vacancy concentrations(0.262 to 0.331),which is critical in the oxygen-reduction reaction(ORR).Oxygen temperature-programmed desorption(O_(2)-TPD)indicated the thermal reduction onset temperature of iron ion is around 420℃,which matched well with the inflection points on the thermos-gravimetric analysis and electrical conductivity curves.At 600℃,the STF electrode shows area-specific resistance(ASR)of 0.152Ω·cm^(2) and peak power density(PPD)of 749 mW·cm^(-2).ORR activity of STF was further improved by introducing 30wt%Sm_(0.2)Ce_(0.8)O_(1.9)(SDC)powder,STF+SDC composite cathode achieving outstanding ASR value of 0.115Ω·cm2 at 600℃,even comparable with benchmark cobalt-containing cathode,Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF).Distribution of relaxation time(DRT)analysis revealed that the oxygen surface exchange and bulk diffusion were improved by forming a composite cathode.At 650℃,STF+SDC composite cathode achieving an outstanding PPD of 1117 mW·cm^(-2).The excellent results suggest that STF and STF+SDC are promising air electrodes for IT-SOFCs.

Calculation of Mass Concrete Temperature and Creep Stress under the Influence of Local Air Heat Transfer

Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.The problem of heat transfer between the air and concrete has been simplified to the concrete’s heat dissipation boundary.However,in the case of tubular concrete structures,where air inlet and outlet are relatively limited,the internal air temperature does not dissipate promptly to the external environment as it rises.To accurately simulate the temperature and creep stress in tubular concrete structures with enclosed air spaces during construction,we establish an air–concrete coupled heat transfer model according to the principles of conjugate heat transfer,and the accuracy of the model is verified through experiments.Furthermore,we conduct a case study to analyze the impact of airflow within the ship lock corridor on concrete temperature and creep stress.The results demonstrate that enhancing airflow within the corridor can significantly reduce the maximum concrete temperature.Compared with cases in which airflow within the corridor is neglected,the maximum concrete temperature and maximum tensile stress can be reduced by 12.5℃ and 0.7 MPa,respectively,under a wind speed of 4 m/s.The results of the traditional calculation method are relatively close to those obtained at a wind speed of 1 m/s.However,the temperature reduction process in the traditional method is faster,and the method yields greater tensile stress values for the corridor location.

Chromosome-Level Reference Genome and Population Genomic Analysis Provide Insights into the Evolution and Improvement of Domesticated Mulberry (Morns alba)

Mulberry(Morns spp.)is the sole plant consumed by the domesticated silkworm.However,the genome of domesticated mulberry has not yet been sequenced,and the ploidy level of this species remains unclear.Here,we report a high-quality,chromosome-level domesticated mulberry(Morus alba)genome.Analysis of genomic data and karyotype analyses confirmed that M.alba is a diploid with 28 chromosomes(2/7=2x=28).Population genomic analysis based on resequencing of 134 mulberry accessions classified domesticated mulberry into three geographical groups,namely,Taihu Basin of southeastern China(Hu mulberry),northern and southwestern China,and Japan.Hu mulberry had the lowest nucleotide diversity among these accessions and demonstrated obvious signatures of selection associated with environmental adaptation.Further phylogenetic analysis supports a previous proposal that multiple domesticated mulberry accessions previously classified as different species actually belong to one species.This study expands our understanding of genome evolution of the genus Morus and population structure of domesticated mulberry,which would facilitate mulberry breeding and improvement.

A GmNINa-miR172c-NNC1 Regulatory Network Coordinates the Nodulation and Autoregulation of Nodulation Pathways in Soybean

Symbiotic root nodules are root lateral organs of plants in which nitrogen-fixing bacteria(rhizobia)convert atmospheric nitrogen to ammonia.The formation and number of nodules in legumes are precisely controlled by a rhizobia-induced signal cascade and host-controlled autoregulation of nodulation(AON).However,how these pathways are integrated and their underlying mechanisms are unclear.Here,we report that microRNA172c(miR172c)activates soybean(Glycine max)R hizobia-induced CLE1(GmRICI)and GmRIC2 by removing the transcriptional repression of these genes by Nodule Number Control 1(NNC1),leading to the activation of the AON pathway.NNC1 interacts with GmNINa,the soybean ortholog of Lotus NODULE INCEPTION(NIN),and hampers its transcriptional activation o i G m RICI and GmRIC2.Importantly,GmNINa acts as a transcriptional activator of miR172c.Intriguingly,NNC1 can transcriptionally repress miR172c expression,adding a negative feedback loop into the NNC1 regulatory network.Moreover,GmNINa interacts with NNC1 and can relieve the NNC1-mediated repression of miR172c transcription.Thus,the GmNINa-miR172c-NNC1 network is a master switch that coordinately regulates and optimizes NF and AON signaling,supporting the balance between nodulation and AON in soybean.

Climate change induced eutrophication of cold-water lake in an ecologically fragile nature reserve

Aquatic ecosystem sustainability around the globe is facing crucial challenges because of increasing anthropogenic and natural disturbances. In this study, the Tianchi Lake, a typical cold-water lake and a UNESCO/MAB(Man and Biosphere) nature reserve located in high latitude and elevation with the relatively low intensity of human activity was chosen as a system to examine the linkages between climate change and eutrophication. As a part of the UNESCO Bogda Man and Biosphere Reserve, Tianchi Lake has been well preserved for prevention from human intervention, but why has it been infected with eutrophication recent years? Our results show that climate change played a significant role in the eutrophication in the Tianchi Lake. Increased temperature, changed precipitation pattern and wind-induced hydrodynamic fluctuations in the summer season were suggested to make a major contribution to the accelerated eutrophication. The results also showed that the local temperature and precipitation changes were closely linked to the large-scale atmospheric circulation, which opens the door for the method to be applied in other regions without local climatic information. This study suggests that there is an urgent need to take into consideration of climate change adaptation into the conservation and management of cold-water lakes globally.

Dewetting Behavior of Hydrogen Bonded Polymer Complex Film under Hydrothermal Condition

Hydrogen-bonded polymer complex films with the thickness ranging from 50 nm to 2400 nm were prepared by layer-by-layer （LbL） assembly of poly（2-ethyl-2-oxazoline） （PEOX） and poly（acrylic acid） （PAA）. The dewetting behavior of PEOX/PAA films under hydrothermal condition was investigated. It was found that the dewetting occurred at solid-liquid interface, and the typical morphologies such as holes, irregular cellular structure, and droplets were observed. Atomic force microscopy （AFM） revealed the initial rupture of the film. Microscopic Raman and infrared （IR） imaging demonstrated that the PEOX and PAA chains remained association during the dewetting process.

Genomic Perspectives on the Emerging SARS-CoV-2 Omicron Variant

A new variant of concern for SARS-CoV-2,Omicron(B.1.1.529),was designated by the World Health Organization on November 26,2021.This study analyzed the viral genome sequencing data of 108 samples collected from patients infected with Omicron.First,we found that the enrichment efficiency of viral nucleic acids was reduced due to mutations in the region where the primers anneal to.Second,the Omicron variant possesses an excessive number of mutations compared to other variants circulating at the same time(median:62 vs.45),especially in the Spike gene.Mutations in the Spike gene confer alterations in 32 amino acid residues,more than those observed in other SARS-CoV-2 variants.Moreover,a large number of nonsynonymous mutations occur in the codons for the amino acid residues located on the surface of the Spike protein,which could potentially affect the replication,infectivity,and antigenicity of SARS-CoV-2.Third,there are 53 mutations between the Omicron variant and its closest sequences available in public databases.Many of these mutations were rarely observed in public databases and had a low mutation rate.In addition,the linkage disequilibrium between these mutations was low,with a limited number of mutations concurrently observed in the same genome,suggesting that the Omicron variant would be in a different evolutionary branch from the currently prevalent variants.To improve our ability to detect and track the source of new variants rapidly,it is imperative to further strengthen genomic surveillance and data sharing globally in a timely manner.