Mechanical behaviors of mylonitic granite and granitic protomylonite in a deep ductile shear zone

For projects near the tectonic belt,mylonite of varying metamorphic degrees may be present.The matrix proportion of rock reflects its internal microscopic characteristics,thus it is beneficial for engineering geology to study the effect of the matrix proportion on the mechanical properties and rupture behaviors of rock.Samples of mylonitic granite and granitic protomylonite with varying matrix proportions were obtained from a ductile shear zone for a series of uniaxial compression and acoustic emission(AE)tests.The results showed that with the increase in matrix proportion,the average strength and elastic modulus of the samples increased,and the rock sample with the largest matrix proportion exhibited the maximum peak stress of 244.42 MPa,which was 45.86%greater than the average peak stress of the rock samples with the smallest matrix proportions.For the rock samples with larger matrix proportion,their mechanical parameters exhibited greater dispersion and the large-scale appearance of AE events occurred earlier,showing a relatively gradual failure process.These samples had larger accumulated AE parameter values and greater degree of failure.In contrast,for samples with smaller matrix proportions,the large-scale appearance of AE events occurred close to the peak stress,indicating that the occurrence of damage and fractures was centralized and instantaneous.These samples had lower accumulated AE parameter values and fewer cracks after failure.Additionally,for the rock samples with more matrix proportion,the average variance of the b-value was 1.1,which was lower than that of rock samples with the smallest matrix proportion(the average variance of the b-value was 3.7).Furthermore,it can be predicted that under certain stress,the failure depth around a tunnel is generally smaller when the strength of rock samples with larger matrix proportion is greater.

Mechanical behaviors and rupture processes of a typical granitic stratum

Granitic veins(GVs)have a significant influence on the mechanical responses of tunnels excavated in granitic strata.Distinguishing the mechanical properties of host granites(HGs),GVs and vein-granite interfaces(VGIs)is critical.For this,this paper analyzed the mechanical behaviors and rupture processes of typical HG,GV,and VGI samples under uniaxial compression condition.For the rocks studied,although the linear axial stress‒strain relation can be identified and the deformation modulus can be determined,the transverse deformation developed nonlinearly with axial stress.As a result,the instantaneous Poisson’s ratio increases continuously and may even exceed 0.5,making it extremely difficult to accurately determine the Poisson’s ratio.In addition,the studied GV samples were found to be significantly brittle,indicating that large-scale GVs cannot be ignored when assessing rockburst hazards in granitic strata with brittle GVs.In terms of the rupture process,the HG and GV samples were gradually damaged by the formation of small-scale cracks and then ruptured by large cracks formed from smallscale cracks,whereas the VGI samples ruptured along large cracks with significant energy release.By examining the characteristic stress thresholds of these three granites,it is noted that the crack closure stress scc exceeds both the crack initiation stress sci and the crack damage stress scd for the HG and VGI samples.The transverse damage to a tested sample appears to be significantly greater than the axial damage,which is essentially related to the rock grain size and grain size distribution.

基于计算控制通信融合的车联网资源协同优化技术研究

车联网高度动态且业务种类多样,安全业务和非安全业务并存。如何同时满足差异化的业务需求,是车联网面临的重大挑战。分析了计算、控制与通信等要素在车联网中的融合方式,并指出以协同管理多维资源提升驾驶安全性和业务体验质量的必要性。针对业务特点分别介绍了面向自动驾驶的控制与通信融合机制、面向信息娱乐业务的计算与通信资源协同管理机制以及面向差异化业务并发的多维资源协同管理机制,最后基于相关挑战展望了该领域未来的技术发展趋势。

Clinical effects of Xingnao Kaiqiao acupuncture on neurological impairment following cerebral infarction

BACKGROUND： Although the curative effects of acupuncture have been confirmed by various treatments of cerebral infarction, few studies have investigated when acupuncture can attain the best clinical effect. OBJECTIVE： Four different time points were selected for acupuncture treatment of cerebral infarction to evaluate the appropriate time course for Xingnao Kaiqiao therapy in terms of improved neurological function. DESIGN： Controlled observation. SETTING： Department of Traditional Chinese Medicine Rehabilitation and Physiotherapy of the Affiliated Hospital of Medical College of Chinese Armed Police Forces. PARTICIPANTS： A total of 120 inpatients with cerebral infarction of different stages, including 75 males and 45 females, aged 41-75 years, were selected from November 2005 to December 2006 at the Department of Traditional Chinese Medicine Rehabilitation and Physiotherapy in Affiliated Hospital of Medical College of Chinese Armed Police Forces. Diagnostic criteria： in accordance with ＂main points of diagnosis on different cerebrovascular disease＂ secondly revised in the Second Cerebrovascular Disease Academic Meeting of Chinese Medicine Association in 1986. All accepted subjects provided confirmed consent, and the experiment received ethical permission from the hospital＇s ethics committee. METHODS： ① Experiment grouping： All inpatients were divided into four groups with non-stochastic concurrent control method according to the disease course： Group Ⅰ （onset within 7 hours）, group Ⅱ （onset from 7 hours to 3 days）, group Ⅲ （onset within 4-7 days）, and group IV （onset within 21-180 days）. On the basis of symptomatic treatment with western medicine, each group received Xingnao Kaiqiao therapy after onset within 7 hours, 7 hours to 3 days, 4 to 7days, and 21 to 180 days. ① The principal acupoints were Neiguan, Renzhong, and Sanyinfiao. ② The auxiliary acupoints were Jiquan, Chize, and Weizhong. ③Acupuncture manipulations： initially, Neiguan （PC6, bilateral） was needled at 0.5-1.0 cun vertically with a reducing technique achieved by rotating-swirling and lifting-inserting for l minute. Subsequently, Renzhong （GV26） was needled at 0.3-0.5 cun obliquely towards the nasal septum, with a heavy bird-pecking method until eyeballs were moist or shed tears. Sanyinjiao （SP6, affected limb） was needled at 1.0-1.5 cun obliquely along the medial border of the tibia with a 45° angle between the needle and skin. The technique of reinforcing was achieved by a lifting-inserting method until the affected lower limb twitched three times. The auxiliary acupoint, Jiquan, was selected when the patient extended the affected upper limb abduction. Jiquan was along the downward channel, l cun from the quondam Jiquan （HT1） acupoint; the armpit hair was avoided. Jiquan （affected limb） was needled vertically at 1.0-1.5 cun. The technique of reduction was achieved by lifting-inserting until the affected upper limb twitched three times. Chize （LU5） was selected when the patient flexed the elbow at 120°. Chize was vertically needled at l cun with a lifting-inserting reducing technique until the affected forearm and fingers twitched three times. Weizhong （BL40） was selected when the patient＇s leg was raised straight in a supine position. Weizhong was vertically needled at 0.5 1.0 cun with a lifting-inserting reducing technique until the affected lower limb twitched three times. ⑤ Acupuncture manipulations were achieved by the doctor who is an associate chief physician and doctor of acupuncture and moxibustion and has aptitude for the post＇s specification. ⑥One course of treatment lasted for 10 days and each group was treated for two courses of treatment. ⑦Experiment evaluation： To apply neurological impairment scores for evaluating clinical curative effects before and after treatment with Xingnao Kaiqiao therapy on day 7, 14, and 21（range of 0 45; decreasing score indicates functional improvement）.To evaluate clinical curative effect by clinical effective power： Basic recovery： equal to or more than 81%; significant improvement： 56% to 81% （including 56%）; Improvement： between 36% to 56% （including 36%）; Slight Improvement： 11% to 36% （including 11%）; No change： less than 11%; Aggravation （including death）： negative value. Total effective rate was computed at the same time. MAIN OUTCOME MEASURES： The total effective rate and amelioration of neurological impairment of the patients after treatment. RESULTS： All 120 patients with cerebral infarction were included in the final analysis, without deletion. ① Comparison of the total effective rate： the total effective rate of group Ⅰ, group Ⅱ, group Ⅲ and group IV was 97%, 93%, 93%, and 67%, respectively. There were significant differences of interclass synthetic curative effects （x^2 = 36.351 7, P 〈 0.01）. ② Amelioration of neurological impairment： A decreased neurological impairment score was observed in group Ⅰ on day 7, 14, and 21 after Xingnao Kaiqiao therapy. The differences between group Ⅳ and the remaining three groups were significant （P 〈 0.05）. CONCLUSION： Xingnao Kaiqiao therapy is helpful for amelioration of neurological impairment in patients during the acute stage cerebral infarction.

Cluster-Based Interference-Free MAC Protocol with Load Aware in Software Defined VANET

In order to reduce the interference,a novel,cluster-based medium access control(MAC)protocol with load aware for VANETs is proposed in this paper.First,all vehicles on roads are grouped into stable clusters in the light of their direction,number of neighbors,link reliability,and traffic load.By utilizing the advantages of centralized control in software defined VANETs(SDVN),cluster stability can be maintained in real-time.Second,a contention-free MAC mechanism composed of inter-cluster multi-channel allocation and intra-cluster dynamic TDMA frame allocation is proposed to prevent co-channel interference and hidden terminal interference.Simulation results show that the proposed protocol outperforms some existing protocols in cluster stability,delivery ratio,throughput and delay performance.

CFD Analysis and Optimization of an Engine with a Restrictor Valve in the Intake System

In some competitions the rules clearly state that all participating cars must install a restrictor valve structure in the intake system of the engine.The intake air volume of the engine is considerably affected due to the existence of such a valve.Indeed,a small interface diameter through which gas flows can lead to considerable flow resistance and loss.In this study,a four-cylinder engine for FSC racing is analyzed using a combined method based on numerical simulation and experiments.The analysis reveals that the main factors affecting the intake air volume are the intake manifold and the volume of the resonance chamber.The influence of such factors is assessed using a single variable method and an optimal model and parameters are obtained accordingly.Comparison of different results show that the maximum torque for the optimized system is increased from the original 42.6 N·m to 46.9 N·m,thus demonstrating an increase of 10.6%.These findings provide a theoretical basis for the design of the intake system and the improvement of engine performance.

Design and development of the deep-rock in-situ condition-preserved coring calibration platform

To systematically validate and calibrate the theory and technology of the deep in-situ conditionpreserved coring, the in-situ conditions at different depths should be simulated, and the full-size coring tests should be carried out in this simulated environment. Therefore, a deep-rock in-situ conditionpreserved coring calibration platform was designed and developed. The self-tightening sealing structure and the quick-disassembly structure were designed on the basis of an innovative segmented nonuniformdiameter structure, which was a breakthrough from the traditional high-pressure vessel frame and was verified by finite element simulation and actual testing under extreme working conditions, respectively.To simulate the actual deep in-situ environment with a temperature of 150℃ and pressure of 140 MPa for a large Φ450 mm×H1400 mm core, temperature and pressure control systems were designed by coupling, and a pre-embedded high-pressure-resistant temperature sensor was designed. Finally, highprecision assembly automation, complex movement coordination of the coring device with the platform,and rotary dynamic sealing were achieved by utilizing the combination of adaptive cabin body servo control and an adaptive mechanical structure in a limited space, laying a solid foundation for the calibration of in-situ condition-preserved coring.

Deformation behavior of in situ permafrost on the Qinghai-Tibetan Plateau

Creep is an important mechanical behavior of frozen soils, one which can cause many problems for the infrastructures in permafrost regions on the Qinghai-Tibetan Plateau. To access the natural creep properties of in situ permafrost for explaining the engineering instability and predicting long-term deformation, conducting field tests is necessary. The paper reports on a group of plate loading tests we carried out over many years on the Qinghai-Tibetan Plateau. The results show that the ground temperature at the loading plates ranged from-0.29 °C to-3.03 °C, and the mean annual ground temperature increased year by year in a linear fashion. Affected by the ground-temperature variations, two forms of deformation curves, a step-form and a wave-form occurred, depending on the relative extent of settlement in warm seasons and frost heave in cold seasons. Overall, the deformations of permafrost were characterized by settlement. The deformation magnitudes and curve styles of permafrost are different at different locations attributing to the influence of ground temperature and moisture content. Due to the existence of much unfrozen water in warm frozen soils, consolidation resulting from migration of unfrozen water along seepage channels may play a significant role in the settlement of permafrost. The research can provide a credible reference for engineering in the permafrost regions and the numerical computation of settlement.

Real-time digital image stabilization based on regional field image gray projection

Digital image stabilization technique plays important roles in video surveillance and object acquisition.Many useful electronic image stabilization algorithms have been studied.A real-time algorithm is proposed based on field image gray projection which enables the regional odd and even field image to be projected into x and y directions and thus to get the regional gray projection curves in x and y directions,respectively.For the odd field image channel,motion parameters can be estimated via iterative minimum absolute difference based on two successive field image regional gray projection curves.Then motion compensations can be obtained after using the Kalman filter method.Finally,the odd field image is adjusted according to the compensations.In the mean time,motion compensation is applied to the even field image channel with the odd field image gray projection curves of the current frame.By minimizing absolute difference between odd and even field image gray projection curves of the current frame,the inter-field motion parameters can be estimated.Therefore,the even field image can be adjusted by combining the inter-field motion parameters and the odd field compensations.Finally,the stabilized image sequence can be obtained by synthesizing the adjusted odd and even field images.Experimental results show that the proposed algorithm can run in real-time and have a good stabilization performance.In addition,image blurring can be improved.

A Study on the Relationship between Anodic Oxidation and the Thermal Load on the Aluminum Alloy Piston of a Gasoline Engine

In order to analyze the influence of the anodizing process on the thermal load of an aluminum alloy piston,dedicated temperature tests have been carried out using the Hardness Plug method and the results for the anodized piston have been compared with those obtained separately for an original aluminum piston.In addition,numerical simulations have been conducted to analyze the temperature field and thermal stress distribution.Simulations and experiments show that the maximum temperature of the anodized piston is 16.36%and 5.4%smaller than that of the original piston under the condition of maximum torque and maximum power,respectively.The thermal stress of the temperature field of both pistons is within 50 Mpa,which meets the strength requirements of the material at high temperature.However,the area with significant thermal stress of the anodized piston is significantly smaller than that of the original piston.Combined with the fatigue analysis data,it can be seen that the safety factor of the anodized piston greater than 1.8 is 99.13%.Therefore,adopting the anodizing process not only reduces the piston thermal load,but also helps to extend its life and improve its reliability.

White light emission in 0D halide perovskite[(CH_(3))_(3)S]_(2)SnCl_(6)·H_(2)O crystals through variation of doping ns^(2) ions

With the rapid development of white LEDs,the research of new and efficient white light emitting materials has attracted increasing attention.Zero dimensional(0D)organic–inorganic hybrid metal halide perovskites with superior luminescent property are promising candidates for LED application,due to their abundant and tailorable structure.Herein,[(CH_(3))_(3)S]_(2)SnCl_(6)・H_(2)O is synthesized as a host for dopant ions Bi^(3+)and Sb^(3+).The Sb^(3+)doped,or Bi^(3+)/Sb^(3+)co-doped,[(CH_(3))3S]_(2)SnCl_(6)・H_(2)O has a tunable optical emission spectrum by means of varying dopant ratio and excitation wavelength.As a result,we can achieve single-phase materials suitable for emission ranging from cold white light to warm white light.The intrinsic mechanism is examined in this work,to clarify the dopant effect on the optical properties.The high stability of title crystalline material,against water,oxygen and heat,makes it promising for further application.

comLinking flowering and reproductive allocation in response to nitrogen addition in an alpine meadow

Aims Plants can change in phenology and biomass allocation in response to environmental change.It has been demonstrated that nitrogen is the most limiting resource for plants in many terrestrial ecosystems.Previous studies have usually focused on either flowering phenology or biomass allocation of plants in response to nitrogen addition;how-ever,attempts to link flowering phenology and biomass allocation are still rare.In this study,we tested the effects of nitrogen addition on both flowering phenology and reproductive allocation in 34 common species.We also examined the potential linkage between flowering time and reproductive allocation in response to nitrogen addition.Methods We conducted a 3-year nitrogen addition experiment in Tibetan alpine meadow.We measured first flowering date and the repro-ductive allocation for 34 common plant species in control,low and high nitrogen added plots,respectively.one-way analysis of variance was used to examine differences of first flowering date and reproductive allocation among treatments.The relationships between the change in species first flowering date and change in reproductive allocation in response to nitrogen addition were examined by calculating Pearson correlation coefficients.Important Findings For most species,both first flowering date and reproductive alloca-tion significantly responded to nitrogen addition.Nitrogen addition significantly delayed the first flowering date and reduced the repro-ductive allocation for all graminoid species,but accelerated flower-ing and increased reproductive allocation for most forb species.We found that changes in first flowering date significantly negatively correlated with the changes in reproductive allocation over spe-cies in response to nitrogen,which indicated a positive relationship between flowering response and plant performance in reproductive allocation.species that advanced their flowering time with nitrogen addition increased their reproductive allocation,whereas those that delayed flowering time tended to decline in reproductive allocation with nitrogen addition.our results suggest that species-specific switch from vegetative growth to reproductive growth could influence species performance.

Design and experiment of automatic garlic seed directing device

Garlic planting requires a single seed with a scaly bud upward and vertically.In this study,an automatic garlic seed directing device was designed for auxiliary garlic seeding by utilizing a seed placed funnel,a correcting mechanism,and an automatic control system.Three factors influenced device performance:characteristics of garlic seeds,limited notch diameter of the seed placed funnel,and funnel taper of the seed placed funnel.The most optimal structural parameters of the seed placed funnel were determined via theoretical analysis.The research samples of Lanling and Jinxiang garlic were divided into three groups according to their respective sizes.3D design software(Solidworks)was used to simulate the above three factors and analyze their rules of action.The obtained simulation results demonstrated that the suitable range of funnel taper and limited notch diameter of seed placed funnel for the three groups of seed were from 40°to 60°and 6-8 mm,respectively.The bench test showed that when the funnel taper was 60°and the limited notch diameter was 10 mm,the success rates of the three groups’seeds in terms of scaly bud directing were 89.8%,91.6%and 96.6%respectively,which satisfied the agricultural requirements of garlic planting.Accordingly,the corresponding results may promote the study and improvement of garlic intelligent planting equipment.

Synthesis,formation mechanism,and intrinsic physical properties of several As/P-containing MAX phases

321 phases are an atypical series of MAX phases,in which A=As/P,with superior elastic properties,fea-turing in the MA-triangular-prism bilayers in the crystal structure.Until now,besides Nb 3 As 2 C,the pure phases of the other 321 compounds have not been realized,hampering the study of their intrinsic prop-erties.Here,molten-salt sintering(MSS)and solid-state synthesis(SSS)were applied to synthesize As/P-containing 321 phases and 211 phases.Analyzing the phase composition of the end-product via multiple-phase Rietveld refinement,we found that MSS can effectively improve the purity of P-containing MAX phases,with the phase content up to 99%in Nb_(3)P_(2)C and 75.4(5)%in Nb 2 PC.In contrast,MSS performed poorly on As-containing MAX phases,only 8.9(4)%for Nb 3 As 2 C and 64(2)%for Nb 2 AsC,as opposed to the pure phases obtained by SSS.The experimental analyses combined with first-principles calculations reveal that the dominant formation route of Nb_(3)P_(2)C is through NbP+Nb+C→Nb_(3)P_(2)C.Moreover,we found that the benefits of MSS on P-containing MAX phases are on the facilitation of three consid-ered chemical reaction routes,especially on Nb 2 PC+NbP→Nb_(3)P_(2)C.Furthermore,the intrinsic physical properties and Fermi surface topology of two 321 phases consisting of electron,hole,and open orbits are revealed theoretically and experimentally,in which the electron carriers are dominant in electrical trans-port.The feasible synthesis methods and the formation mechanism are instructive to obtain high-purity As/P-containing MAX phases and explore new MAX phases.Meanwhile,the intrinsic physical properties will give great support for future applications on 321 phases.

Observation of low thermal expansion behavior and weak thermal anisotropy in M_(3)A_(2)C phases

M_(3)A_(2)X phases,named 321 phases,are an atypical series of MAX phases featuring in the MA-triangular-prism bilayers,with the A=As/P,exhibiting excellent elastic properties.This work systematically studies the thermal expansion properties of 321 phases.We found their average linear thermal expansion coefficients(TECs),α_(L)=5-6μK^(–1),are the lowest among the reported values of MAX phases.The lowest average TEC was found in Nb_(3)As_(2)C(αa=4.46(4)μK^(–1),αc=5.09(4)μK–1,αL=5.09(4)μK–1).The average TEC and anisotropy factor(αc/αa)of Nb_(3)As_(2)C and Nb_(3)P_(2)C were lower than the ones of the corresponding 211 phases.The best isotropy performance was found in Nb_(3)P_(2)C (αc/αa=1.11).Moreover,our first-principles calculations demonstrate that the weaker chemical bonding between Nb-As/P than Nb-C induces thermal expansion in M_(3)A_(2)X phases.Furthermore,a relatively weaker anharmonic effect in 321 phases than in the 211 phases was revealed by the as-calculated average Grüneisen parameters,which account for the lower TECs in 321 phases.The low TECs and enhanced thermal isotropy make 321 phases outstanding among MAX phases,which could be sound candidates for varying-temperature structural-functional components.

Impact of grazing on germination trait selection in an alpine grassland on the Tibet Plateau

Previous studies indicated that grazing can cause significant changes in abiotic and biotic environment in grassland.However,how these changes impact germination trait selection in grassland has not been well studied.Thus,we aimed to explore whether grazing can significantly change germination trait diversity and composition of grasslands community.We measured the germination traits of species in the laboratory,and compared their performance in grazed and nongrazed grasslands.Then,we compared the community-weighted means of germination traits and functional diversity of grazed and nongrazed grasslands based on these germination traits to know whether grazed and nongrazed grasslands differed in their germination trait structures.At the species level,we found that the changes of abundance in grazed and nongrazed grasslands were not related to species’germination traits.However,at the community level,compared with nongrazed grasslands,species in the grazed grasslands generally exhibited a higher seed germination percentage.Moreover,seed germination response in grazed grasslands was more positively related to alternating temperature than in nongrazed grasslands,and breadth of the germination temperature niche was narrower in grazed than in nongrazed grasslands.Compared with nongrazed grasslands,seed germination trait diversity was increased and germination trait evenness decreased in grazed grasslands.Grazing can change microhabitat conditions,thereby changing germination trait selection by environmental filtering,resulting in a significant difference in germinate trait composition at the community level.

A conservative distribution of tridomain NDP-heptose synthetases in actinobacteria

Heptoses are important structural components of Gram-negative bacterium cell wall and participate in bacterial colonization,infection,and immune recognition.Current knowledge of NDP-heptose originating from D-sedoheptulose 7-phosphate in Grampositive bacterium remains limited.Here,in silico analysis suggested that the special tridomain NDP-heptose synthetases with isomerase,kinase,and nucleotidyltransferase activities are conservatively distributed in Actinobacteria class of Gram-positive bacterium.Enzymatical characterization of the tridomain proteins from different strains showed that they are involved in ADPD-glycero-β-D-manno-heptose biosynthesis despite the unexpected discovery of kinase activities deficient in some proteins.The presence of three types of NDP-heptose synthetases in Gram-positive bacterium suggests that it is also a rich source of heptoses and the heptose moieties may play important roles in vivo.Our work updates the understanding of NDP-heptose biosynthesis in Gram-positive bacterium and lays a solid foundation for further physiological function explorations.

Dynamic detection method for falling ears of maize harvester based on improved YOLO-V4

Traditional maize ear harvesters mainly rely on manual identification of fallen maize ears,which cannot realize real-time detection of ear falling.The improved You Only Look Once-V4(YOLO-V4)algorithm is combined with the channel pruning algorithm to detect the dropped ears of maize harvesters.K-means clustering algorithm is used to obtain a prior box matching the size of the dropped ears,which improves the Intersection Over Union(IOU).Compare the effect of different activation functions on the accuracy of the YOLO-V4 model,and use the Mish activation function as the activation function of this model.Improve the calculation of the regression positioning loss function,and use the CEIOU loss function to balance the accuracy of each category.Use improved Adam optimization function and multi-stage learning optimization technology to improve the accuracy of the YOLO-V4 model.The channel pruning algorithm is used to compress the model and distillation technology is used in the fine-tuning of the model.The final model size was only 10.77%before compression,and the test set mean Average Precision(mAP)was 93.14%.The detection speed was 112 fps,which can meet the need for real-time detection of maize harvester ears in the field.This study can provide technical reference for the detection of the ear loss rate of intelligent maize harvesters.

(S)-3-aminopiperidine-2,6-dione is a biosynthetic intermediate of microbial blue pigment indigoidine

The biosynthetic investigations of microbial natural products continuously provide powerful biocatalysts for the preparation of valuable chemicals.Practical methods for preparing(S)-3-aminopiperidine-2,6-dione(2),the pharmacophore of thalidomide(1)and its analog drugs,are highly desired.To develop a biocatalyst for producing(S)-2,we dissected the domain functions of IdgS,which is responsible for the biosynthesis of indigoidine(3),a microbial blue pigment that consists of two 2-like moieties.Our data supported that the L-glutamine tethered to the indigoidine assembly line is first offloaded and cyclized by the thioesterase domain to form(S)-2,which is then dehydrogenated by the oxidation(Ox)domain and finally dimerized to yield 3.Based on this,we developed an IdgS-derived enzyme biocatalyst,IdgS-Ox^(*)R539A,for preparing enantiomerically pure(S)-2.As a proof of concept,one-pot chemoenzymatic synthesis of 1 was achieved by combining the biocatalytic and chemical approaches.