Hypoxic preconditioning has been shown to improve hypoxic tolerance in mice,accompanied by the downregulation of DNA methyltransferases(DNMTs)in the brain.However,the roles played by DNMTs in the multiple neuroprotect...Hypoxic preconditioning has been shown to improve hypoxic tolerance in mice,accompanied by the downregulation of DNA methyltransferases(DNMTs)in the brain.However,the roles played by DNMTs in the multiple neuroprotective mechanisms associated with hypoxic preconditioning remain poorly understood.This study aimed to establish an in vitro model of hypoxic preconditioning,using a cultured mouse hippocampal neuronal cell line(HT22 cells),to examine the effects of DNMTs on the endogenous neuroprotective mechanisms that occur during hypoxic preconditioning.HT22 cells were divided into a control group,which received no exposure to hypoxia,a hypoxia group,which was exposed to hypoxia once,and a hypoxic preconditioning group,which was exposed to four cycles of hypoxia.To test the ability of hypoxic preadaptation to induce hypoxic tolerance,cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium assay.Cell viability improved in the hypoxic preconditioning group compared with that in the hypoxia group.The effects of hypoxic preconditioning on the cell cycle and apoptosis in HT22 cells were examined by western blot assay and flow cytometry.Compared with the hypoxia group,the expression levels of caspase-3 and spectrin,which are markers of early apoptosis and S-phase arrest,respectively,noticeably reduced in the hypoxic preconditioning group.Finally,enzyme-linked immunosorbent assay,real-time polymerase chain reaction,and western blot assay were used to investigate the changes in DNMT expression and activity during hypoxic preconditioning.The results showed that compared with the control group,hypoxic preconditioning downregulated the expression levels of DNMT3A and DNMT3B mRNA and protein in HT22 cells and decreased the activities of total DNMTs and DNMT3B.In conclusion,hypoxic preconditioning may exert anti-hypoxic neuroprotective effects,maintaining HT22 cell viability and inhibiting cell apoptosis.These neuroprotective mechanisms may be associated with the inhibition of DNMT3A and DNMT3B.展开更多
Erosion wear is a common failure mode in the oil and gas industry.In the hydraulic fracturing,the fracturing pipes are not only in high-pressure working environment,but also suffer from the impact of the high-speed so...Erosion wear is a common failure mode in the oil and gas industry.In the hydraulic fracturing,the fracturing pipes are not only in high-pressure working environment,but also suffer from the impact of the high-speed solid particles in the fracturing fluid.Beneath such complex conditions,the vulnerable components of the pipe system are prone to perforation or even burst accidents,which has become one of the most serious risks at the fracturing site.Unfortunately,it is not yet fully understood the erosion mechanism of pipe steel for hydraulic fracturing.Therefore,this article provides a detailed analysis of the erosion behavior of fracturing pipes under complex working conditions based on experiments and numerical simulations.Firstly,we conducted erosion experiments on AISI 4135 steel for fracturing pipes to investigate the erosion characteristics of the material.The effects of impact angle,flow velocity and applied stress on erosion wear were comprehensively considered.Then a particle impact dynamic model of erosion wear was developed based on the experimental parameters,and the evolution process of particle erosion under different impact angles,impact velocities and applied stress was analyzed.By combining the erosion characteristics,the micro-structure of the eroded area,and the micro-mechanics of erosion damage,the erosion mechanism of pipe steel under fracturing conditions was studied in detail for the first time.Under high-pressure operating conditions,it was demonstrated through experiments and numerical simulations that the size of the micro-defects in the eroded area increased as the applied stress increased,resulting in more severe erosion wear of fracturing pipes.展开更多
The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture ...The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture mechanism of hollow particles in cement sheath was firstly analyzed by discrete element method, and the effect of hollow particles in cement on casing deformation was investigated by laboratory experiment method. Finally, field test was carried out to verify the improvement effect of the casing deformation based on cement slurry modification. The results show that the formation displacement can be absorbed effectively by hollow particles inside the cement transferring the excessive deformation away from casing. The particles in the uncemented state provide deformation space during formation slipping. The casing with diameter of 139.7 mm could be passed through by bridge plug with the diameter of 99 mm when the mass ratio of particle/cement reaches 1:4. According to the field test feedback, the method based on optimization of cement slurry can effectively reduce the risk of casing deformation, and the recommended range of hollow microbeads content in the cement slurry is between 15% and 25%.展开更多
Litsea,a non-monophyletic group of the tribe Laureae(Lauraceae),plays important roles in the tropical and subtropical forests of Asia,Australia,Central and North America,and the islands of the Pacific.However,intergen...Litsea,a non-monophyletic group of the tribe Laureae(Lauraceae),plays important roles in the tropical and subtropical forests of Asia,Australia,Central and North America,and the islands of the Pacific.However,intergeneric relationships between Litsea and Laurus,Lindera,Parasassafras and Sinosassafras of the tribe Laureae remain unresolved.In this study,we present phylogenetic analyses of seven newly sequenced Litsea plastomes,together with 47 Laureae plastomes obtained from public databases,representing six genera of the Laureae.Our results highlight two highly supported monophyletic groups of Litsea taxa.One is composed of 16 Litsea taxa and two Lindera taxa.The 18 plastomes of these taxa were further compared for their gene structure,codon usage,contraction and expansion of inverted repeats,sequence repeats,divergence hotspots,and gene evolution.The complete plastome size of newly sequenced taxa varied between 152,377 bp(Litsea auriculata)and 154,117 bp(Litsea pierrei).Seven of the 16 Litsea plastomes have a pair of insertions in the IRa(trnL-trnH)and IRb(ycf2)regions.The 18 plastomes of Litsea and Lindera taxa exhibit similar gene features,codon usage,oligonucleotide repeats,and inverted repeat dynamics.The codons with the highest frequency among these taxa favored A/T endings and each of these plastomes had nine divergence hotspots,which are located in the same regions.We also identified six protein coding genes(accD,ndhJ,rbcL,rpoC2,ycf1 and ycf2)under positive selection in Litsea;these genes may play important roles in adaptation of Litsea species to various environments.展开更多
Fungi of the family Boletaceae are of great importance in both ecology and economy.Our previous molecular phylogenetic studies have shown this family to have an extremely high species diversity in China.To further doc...Fungi of the family Boletaceae are of great importance in both ecology and economy.Our previous molecular phylogenetic studies have shown this family to have an extremely high species diversity in China.To further document the Chinese boletes,morphological studies and phylogenetic analyses were conducted including species of Boletaceae from China and other parts of the world.The results indicate that seven subfamily-level major clades and 62 generic clades can be retrieved,52 of which are found in China.Furthermore,100 species(comprising 32 genera)common in China are illustrated and described here in detail.Among them,four genera and 46 species are new to science,and 26 new combinations are proposed.To interpret the species concepts consistently,epitypes for five species are designated based on collections made from or near the type localities.Notes on eight extralimital species are also provided.Among the species reported here,most of the species are known only from East Asia.Only Leccinum scabrum(Bull.)Gray,Porphyrellus porphyrosporus(Fr.&Hok)E.-J.Gilbert and Tylopilus felleus(Bull.)P.Karst.are widely distributed in the Holarctic,and Buchwaldoboletus lignicola(Kallenb.)Pila´t;Strobilomyces strobilaceus(Scop.)Berk.are in Eurasia;while Aureoboletus mirabilis(Murrill)Halling,Harrya chromapes(Frost)Halling et al.,and Sutorius eximius(Peck)Halling et al.are found throughout East Asia-North America based on morphological and molecular phylogenetic evidences.展开更多
基金supported by the National Natural Science Foundation of China,Nos.81460283(to GS),81660307(to GS),31860307(to WX)the Science Foundation of Inner Mongolia Autonomous Region of China,Nos.2018LH08078(to GS),2018LH03029(to JHS)+2 种基金the Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region of China,No.NJYT-18-B26(to WX)the Scientific Research Foundation of Baotou Medical College of China,Nos.BYJJ-YF 201717(to SCY),BYJJ-YF 201606(to WX)the National Key Research and Development Program of China,No.2017YFC1308405(to GS)。
文摘Hypoxic preconditioning has been shown to improve hypoxic tolerance in mice,accompanied by the downregulation of DNA methyltransferases(DNMTs)in the brain.However,the roles played by DNMTs in the multiple neuroprotective mechanisms associated with hypoxic preconditioning remain poorly understood.This study aimed to establish an in vitro model of hypoxic preconditioning,using a cultured mouse hippocampal neuronal cell line(HT22 cells),to examine the effects of DNMTs on the endogenous neuroprotective mechanisms that occur during hypoxic preconditioning.HT22 cells were divided into a control group,which received no exposure to hypoxia,a hypoxia group,which was exposed to hypoxia once,and a hypoxic preconditioning group,which was exposed to four cycles of hypoxia.To test the ability of hypoxic preadaptation to induce hypoxic tolerance,cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyphenol)-2-(4-sulfophenyl)-2H-tetrazolium assay.Cell viability improved in the hypoxic preconditioning group compared with that in the hypoxia group.The effects of hypoxic preconditioning on the cell cycle and apoptosis in HT22 cells were examined by western blot assay and flow cytometry.Compared with the hypoxia group,the expression levels of caspase-3 and spectrin,which are markers of early apoptosis and S-phase arrest,respectively,noticeably reduced in the hypoxic preconditioning group.Finally,enzyme-linked immunosorbent assay,real-time polymerase chain reaction,and western blot assay were used to investigate the changes in DNMT expression and activity during hypoxic preconditioning.The results showed that compared with the control group,hypoxic preconditioning downregulated the expression levels of DNMT3A and DNMT3B mRNA and protein in HT22 cells and decreased the activities of total DNMTs and DNMT3B.In conclusion,hypoxic preconditioning may exert anti-hypoxic neuroprotective effects,maintaining HT22 cell viability and inhibiting cell apoptosis.These neuroprotective mechanisms may be associated with the inhibition of DNMT3A and DNMT3B.
基金supported by the National Natural Scienceof China (No.52175208)Scientific Research and Technology Development Project of CNPC (No.2023ZZ11)+1 种基金Fundamental Research and Strategic Reserve Technology Research Fund Project of CNPC (No.2023DQ03-03)Study on Key Technologies of Production Increase and Transformation of Gulong Shale Oil (2021ZZ10-04)。
文摘Erosion wear is a common failure mode in the oil and gas industry.In the hydraulic fracturing,the fracturing pipes are not only in high-pressure working environment,but also suffer from the impact of the high-speed solid particles in the fracturing fluid.Beneath such complex conditions,the vulnerable components of the pipe system are prone to perforation or even burst accidents,which has become one of the most serious risks at the fracturing site.Unfortunately,it is not yet fully understood the erosion mechanism of pipe steel for hydraulic fracturing.Therefore,this article provides a detailed analysis of the erosion behavior of fracturing pipes under complex working conditions based on experiments and numerical simulations.Firstly,we conducted erosion experiments on AISI 4135 steel for fracturing pipes to investigate the erosion characteristics of the material.The effects of impact angle,flow velocity and applied stress on erosion wear were comprehensively considered.Then a particle impact dynamic model of erosion wear was developed based on the experimental parameters,and the evolution process of particle erosion under different impact angles,impact velocities and applied stress was analyzed.By combining the erosion characteristics,the micro-structure of the eroded area,and the micro-mechanics of erosion damage,the erosion mechanism of pipe steel under fracturing conditions was studied in detail for the first time.Under high-pressure operating conditions,it was demonstrated through experiments and numerical simulations that the size of the micro-defects in the eroded area increased as the applied stress increased,resulting in more severe erosion wear of fracturing pipes.
基金the supports of project funded by China Postdoctoral Science Foundation(2023M743886)Project of Shale Gas Evaluation and Exploitation Key Laboratory of Sichuan Province(YSK2023004)youth project funded by Shaanxi Province Natural Science Basic Research Program(2024JC-YBQN-0522)。
文摘The casing deformation prevention technology based on the optimization of cement slurry is proposed to reduce the casing deformation of shale oil and gas wells during hydraulic fracturing. In this paper, the fracture mechanism of hollow particles in cement sheath was firstly analyzed by discrete element method, and the effect of hollow particles in cement on casing deformation was investigated by laboratory experiment method. Finally, field test was carried out to verify the improvement effect of the casing deformation based on cement slurry modification. The results show that the formation displacement can be absorbed effectively by hollow particles inside the cement transferring the excessive deformation away from casing. The particles in the uncemented state provide deformation space during formation slipping. The casing with diameter of 139.7 mm could be passed through by bridge plug with the diameter of 99 mm when the mass ratio of particle/cement reaches 1:4. According to the field test feedback, the method based on optimization of cement slurry can effectively reduce the risk of casing deformation, and the recommended range of hollow microbeads content in the cement slurry is between 15% and 25%.
基金supported by the National Natural Science Foundation of China(Grant No.32060710,31970223,31860005,31860620)Applied Basic Research Projects of Yunnan(Grant No.2019FB057).
文摘Litsea,a non-monophyletic group of the tribe Laureae(Lauraceae),plays important roles in the tropical and subtropical forests of Asia,Australia,Central and North America,and the islands of the Pacific.However,intergeneric relationships between Litsea and Laurus,Lindera,Parasassafras and Sinosassafras of the tribe Laureae remain unresolved.In this study,we present phylogenetic analyses of seven newly sequenced Litsea plastomes,together with 47 Laureae plastomes obtained from public databases,representing six genera of the Laureae.Our results highlight two highly supported monophyletic groups of Litsea taxa.One is composed of 16 Litsea taxa and two Lindera taxa.The 18 plastomes of these taxa were further compared for their gene structure,codon usage,contraction and expansion of inverted repeats,sequence repeats,divergence hotspots,and gene evolution.The complete plastome size of newly sequenced taxa varied between 152,377 bp(Litsea auriculata)and 154,117 bp(Litsea pierrei).Seven of the 16 Litsea plastomes have a pair of insertions in the IRa(trnL-trnH)and IRb(ycf2)regions.The 18 plastomes of Litsea and Lindera taxa exhibit similar gene features,codon usage,oligonucleotide repeats,and inverted repeat dynamics.The codons with the highest frequency among these taxa favored A/T endings and each of these plastomes had nine divergence hotspots,which are located in the same regions.We also identified six protein coding genes(accD,ndhJ,rbcL,rpoC2,ycf1 and ycf2)under positive selection in Litsea;these genes may play important roles in adaptation of Litsea species to various environments.
基金supported by the Funds for International Cooperation and Exchange of the National Natural Science Foundation of China(31210103919)the Fundamental Research Program of the Ministry of Science and Technology,China(2013FY110400)+4 种基金the CAS/SAFEA International Partnership Program for Creative Research Teamsthe National Natural Science Foundation of China(Nos.31370001,31570025,31560011)the National Natural Science Foundation for Young Scientists of China(31500023)the Natural Science Foundation of Yunnan Province(2013FB066)the Youth Innovation Promotion Association,CAS(2016348).
文摘Fungi of the family Boletaceae are of great importance in both ecology and economy.Our previous molecular phylogenetic studies have shown this family to have an extremely high species diversity in China.To further document the Chinese boletes,morphological studies and phylogenetic analyses were conducted including species of Boletaceae from China and other parts of the world.The results indicate that seven subfamily-level major clades and 62 generic clades can be retrieved,52 of which are found in China.Furthermore,100 species(comprising 32 genera)common in China are illustrated and described here in detail.Among them,four genera and 46 species are new to science,and 26 new combinations are proposed.To interpret the species concepts consistently,epitypes for five species are designated based on collections made from or near the type localities.Notes on eight extralimital species are also provided.Among the species reported here,most of the species are known only from East Asia.Only Leccinum scabrum(Bull.)Gray,Porphyrellus porphyrosporus(Fr.&Hok)E.-J.Gilbert and Tylopilus felleus(Bull.)P.Karst.are widely distributed in the Holarctic,and Buchwaldoboletus lignicola(Kallenb.)Pila´t;Strobilomyces strobilaceus(Scop.)Berk.are in Eurasia;while Aureoboletus mirabilis(Murrill)Halling,Harrya chromapes(Frost)Halling et al.,and Sutorius eximius(Peck)Halling et al.are found throughout East Asia-North America based on morphological and molecular phylogenetic evidences.
