Physics-informed neural networks(PINNs)have become an attractive machine learning framework for obtaining solutions to partial differential equations(PDEs).PINNs embed initial,boundary,and PDE constraints into the los...Physics-informed neural networks(PINNs)have become an attractive machine learning framework for obtaining solutions to partial differential equations(PDEs).PINNs embed initial,boundary,and PDE constraints into the loss function.The performance of PINNs is generally affected by both training and sampling.Specifically,training methods focus on how to overcome the training difficulties caused by the special PDE residual loss of PINNs,and sampling methods are concerned with the location and distribution of the sampling points upon which evaluations of PDE residual loss are accomplished.However,a common problem among these original PINNs is that they omit special temporal information utilization during the training or sampling stages when dealing with an important PDE category,namely,time-dependent PDEs,where temporal information plays a key role in the algorithms used.There is one method,called Causal PINN,that considers temporal causality at the training level but not special temporal utilization at the sampling level.Incorporating temporal knowledge into sampling remains to be studied.To fill this gap,we propose a novel temporal causality-based adaptive sampling method that dynamically determines the sampling ratio according to both PDE residual and temporal causality.By designing a sampling ratio determined by both residual loss and temporal causality to control the number and location of sampled points in each temporal sub-domain,we provide a practical solution by incorporating temporal information into sampling.Numerical experiments of several nonlinear time-dependent PDEs,including the Cahn–Hilliard,Korteweg–de Vries,Allen–Cahn and wave equations,show that our proposed sampling method can improve the performance.We demonstrate that using such a relatively simple sampling method can improve prediction performance by up to two orders of magnitude compared with the results from other methods,especially when points are limited.展开更多
预训练语言模型(pre-trained languages model,PTLM)在自然语言处理(natural language processing,NLP)领域取得了令人瞩目的成功,并由此引发了下游任务从监督学习到预训练-微调范式的转变。在此之后,一系列预训练模型的创新研究涌现出...预训练语言模型(pre-trained languages model,PTLM)在自然语言处理(natural language processing,NLP)领域取得了令人瞩目的成功,并由此引发了下游任务从监督学习到预训练-微调范式的转变。在此之后,一系列预训练模型的创新研究涌现出来。本文系统性、全面的回顾了自然语言处理的代表性工作和最新进展,并按照类别系统性的介绍了自然语言处理领域的预训练模型。首先我们简要介绍了预训练模型,以及不同的模型特点和框架。之后,我们介绍并分析了预训练模型的影响和挑战以及下游任务中的应用。最后,我们简要总结并阐述了预训练模型未来的研究方向。展开更多
Flower development is one of the most vital pathways in plant development, during which the epigenetic regulation of gene expression is essential. DNA methylation, the most conserved epigenetic modification, participa...Flower development is one of the most vital pathways in plant development, during which the epigenetic regulation of gene expression is essential. DNA methylation, the most conserved epigenetic modification, participates in gene expression regulation and transposable element silencing. Honeysuckle(Lonicera japonica) is an important medicinal plant renowned for its colorful and fragrant flowers. Honeysuckle flowers change color from white to gold as a result of carotenoid accumulation during development. However, the role of DNA methylation in flower color changes is not well understood in L. japonica. Here, we performed whole-genome bisulfite sequencing and transcriptome sequencing during flowering development in honeysuckle. The results showed that a decrease in the levels of genome-wide average DNA methylation during flower development and changes in DNA methylation were associated with the expression of demethylase genes. Moreover, many genes involved in carotenoid biosynthesis and degradation, such as Lj PSY1, LjPDS1, LjLCYE, and LjCCD4, have altered expression levels because of hypomethylation, indicating that DNA methylation plays an important role in flower color changes in honeysuckle. Taken together, our data provide epigenetic insights into flower development and color change in honeysuckles.展开更多
Somaclonal variation in tissue culture is a common phenomenon induced by various external or internal environmental conditions,resulting in heritable or non-heritable alterations in gene expression. One crucial mechan...Somaclonal variation in tissue culture is a common phenomenon induced by various external or internal environmental conditions,resulting in heritable or non-heritable alterations in gene expression. One crucial mechanism involved in plant growth and development is epigenetic regulation. A highly dynamic epigenome can respond to environmental changes by regulating gene expression. DNA methylation is one of these epigenetic modifications that can alter gene expression in tissue-cultured pineapple plants. The underlying mechanism of such somaclonal variations in pineapple and the epigenetic regulation involvement in somaclonal variations has not been studied. This study performed DNA methylome and transcriptome sequencing of wild-type(WT) and mutant pineapple plants(WS, HW, and TW). We observed altered DNA methylation patterns in chlorophyll development in the mutants. Specifically, we noticed that the methylation levels in the CHG and CHH contexts were lower in the gene body regions compared to the upstream and downstream regions. We identified several thousand differentially methylated regions(DMRs) located at the gene body regions, some of which overlapped with the differentially expressed genes(DEGs). Functional enrichment analyses suggested that these genes were involved in chlorophyll metabolism. Thus, our results revealed that the transcriptional regulation of many chlorophyll metabolic essential genes could be regulated by DNA methylation caused by somaclonal variations and provided insights into epigenetic mechanisms underlying the regulation of chlorosis in pineapple plants.展开更多
Objective:To explore the effect of 3-dimensional(3D)printing-assisted cognitive fusion on improvement of the positive rate in prostate biopsy.Methods:From August to December 2014,16 patients with suspected prostatic l...Objective:To explore the effect of 3-dimensional(3D)printing-assisted cognitive fusion on improvement of the positive rate in prostate biopsy.Methods:From August to December 2014,16 patients with suspected prostatic lesions detected by multiparametric magnetic resonance imaging(MRI)were included.Targeted prostate biopsy was performed with the use of prostate 3D reconstruction modeling,computersimulated biopsy,3D printing,and cognitive fusion biopsy.All patients had received 3.0 T multiparametric MRI before biopsy.The DICOM MRI files were imported to medical imaging processing software for 3D reconstruction modeling to generate a printable.stl file for 3D printing with use of transparent resin as raw material.We further performed a targeted 2-to 3-core biopsy at suspected lesions spotted on MRI.Results:For the 16 patients in the present study,3D modeling with cognitive fusion-based targeted biopsy was successfully performed.For a single patient,1e2 lesions(average:1.1 lesions)were discovered,followed by 2-6 cores(average:2.4 cores)added as targeted biopsy.Systematic biopsies accounted for 192 cores in total,with a positive rate of 22.4%;targeted biopsies accounted for 39 cores in total,with a positive rate of 46.2%.Among these cases,10 patients(62.5%)were diagnosed with prostate adenocarcinoma,in which seven were discovered by both systematic and targeted biopsy,one was diagnosed by systematic biopsy only,and two were diagnosed by targeted biopsy only.For systematic biopsy,Gleason score ranged from 6 to 8(average:7),while that for targeted biopsy ranged from 6 to 9(average:7.67).Among the seven patients that were diagnosed by both systematic and targeted biopsy,three(42.8%)were reported with a higher Gleason score in targeted therapy than in systematic biopsy.Conclusion:3D printing-assisted cognitive fusion technique markedly promoted positive rate in prostate biopsy,and reduced missed detection in high-risk prostate cancer.展开更多
The EMMS/bubbling model originally proposed for fluidization of monodisperse particles is extended to fluidization of binary particle mixture in this study.The dense and dilute phases are considered to comprise of two...The EMMS/bubbling model originally proposed for fluidization of monodisperse particles is extended to fluidization of binary particle mixture in this study.The dense and dilute phases are considered to comprise of two types of particles differing in size and/or density.Governing equations and the stability condition are then formulated and solved by using an optimization numerical scheme.The effects of bubble diameter are first investigated and a suitable bubble diameter correlation is chosen.Preliminary validation for steady state behavior shows the extended model can fairly capture the overall hydrodynamic behaviors in terms of volume fraction of bubbles and average bed voidage for both monodisperse and binary particle systems.This encourages us to integrate this model with CFD for more validations in the future.展开更多
Gut homeostasis is of importance to host health and imbalance of the gut usually leads to disorders or diseases for both human and animal.Postbiotics have been applied in manipulating of gut health,and utilization of ...Gut homeostasis is of importance to host health and imbalance of the gut usually leads to disorders or diseases for both human and animal.Postbiotics have been applied in manipulating of gut health,and utilization of postbiotics threads new lights into the host health.Compared with the application of probiotics,the characteristics such as stability and safety of postbiotics make it a potential alternative to probiotics.Studies have reported the beneficial effects of components derived from postbiotics,mainly through the mechanisms including inhibition of pathogens,strengthen gut barrier,and/or regulation of immunity of the host.In this review,we summarized the characteristics of postbiotics,main compounds of postbiotics,potential mechanisms in gut health,and their application in animal production.展开更多
The traditional modeling method of rotor system with a slant crack considers only integer-order calculus.However,the model of rotor system based on integer-order calculus can merely describe local characteristics,not ...The traditional modeling method of rotor system with a slant crack considers only integer-order calculus.However,the model of rotor system based on integer-order calculus can merely describe local characteristics,not historical dependent process.The occur of fractional order calculus just makes up for the deficiency in integer-order calculus.Therefore,a new dynamic model with a slant crack based on fractional damping is proposed.Here,the stiffness of rotor system with a slant crack is solved by zero stress intensity factor method.The proposed model is simulated by Runge-Kutta method and continued fraction Euler method.The influence of the fractional order,rotating speed,and crack depth on the dynamic characteristics of rotor system is discussed.The simulation results show that the amplitude of torsional excitation frequency increases significantly with the increase of the fractional order.With the increase of the rotating speed,the amplitude of first harmonic component becomes gradually larger,the amplitude of the second harmonic becomes smaller,while the amplitude of the other frequency components is almost invariant.The shaft orbit changes gradually from an internal 8-type shape to an ellipse-type shape without overlapping.With the increase of the slant crack depth,the amplitude of the transverse response frequency in the rotor system with a slant crack increases,and the amplitude in the second harmonic component also increases significantly.In addition,the torsional excitation frequency and other coupling frequency components also occur.The proposed model is further verified by the experiment.The valuable conclusion can provide an important guideline for the fault diagnosis of rotor system with a slant crack.展开更多
Histone deacetylation is a key modulator involved in cell proliferation,apoptosis,and mRNA transcription.However,the effects of histone deacetylation on C17.2 neural stem cells(NSCs)remain unclear.Here,the histone dea...Histone deacetylation is a key modulator involved in cell proliferation,apoptosis,and mRNA transcription.However,the effects of histone deacetylation on C17.2 neural stem cells(NSCs)remain unclear.Here,the histone deacetylase inhibitors nicotinamide and trichostatin A(TSA)were used to determine the role of histone deacetylation on gene transcription in NSCs.The results showed that the mRNA expression of p53,Sox1,Sox2,and Bax were significantly higher in E14.5 NSCs than in C17.2 NSCs.Nestin,a marker gene of neuronal differentiation,did not differ significantly between E14.5 NSCs and C17.2 NSCs.The transcription levels of p53 and Nestin were significantly higher in C17.2 NSCs than in differentiated brain tissues,and the expression of Bax,Sox1,and Sox2 was higher in the olfactory bulb than in other brain tissues.Nicotinamide and TSA treatment decreased the transcription of Sox2,p53,Nestin,and Bax in C17.2 NSCs,although the difference was statistically significant only for Sox2 and Nestin,Sox1 transcription was not detected.These results demonstrated that mRNA expression profiles differ between C17.2 NSCs,E14.5 NSCs,and adult mouse brain tissues,and HDAC inhibitors regulate gene expression by modulating histone acetylation.展开更多
DNA methylation participates in regulating the expression of coding and non-coding regions in plants. To investigate the association between DNA methylation and pathogen infection, we used whole-genome bisulfite seque...DNA methylation participates in regulating the expression of coding and non-coding regions in plants. To investigate the association between DNA methylation and pathogen infection, we used whole-genome bisulfite sequencing to survey temporal DNA methylation changes in rice after infection with the rice blast fungus Magnaporthe oryzae. In contrast to previous findings in Arabidopsis, global DNA methylation levels in rice increased slightly after rice blast infection. We identified over 38,000 differentially methylated regions(DMRs), and hypermethylated DMRs far outnumbered hypomethylated DMRs. Most DMRs were located in transposable element regions. Using transcriptome analysis, we identified 8830 differentially expressed genes(DEGs) after 1, 3, and 5 days of infection. Over one-third of DEGs, most of which were CHH-type DMRs, were associated with DMRs. Functional analysis of the CHH DMR-DEGs indicated their involvement in many important biological processes, including cell communication and response to external stimulus. The transcription of many NBS-LRR family genes was affected by changes in DNA methylation, suggesting that DNA methylation plays essential roles in the response of rice to M. oryzae infection. More broadly, the DNA methylation analysis presented here sheds light on epigenomic involvement in plant defense against fungal pathogens.展开更多
After more than 70 years of evolution,great achievements have been made in machine translation.Especially in recent years,translation quality has been greatly improved with the emergence of neural machine translation(...After more than 70 years of evolution,great achievements have been made in machine translation.Especially in recent years,translation quality has been greatly improved with the emergence of neural machine translation(NMT).In this article,we first review the history of machine translation from rule-based machine translation to example-based machine translation and statistical machine translation.We then introduce NMT in more detail,including the basic framework and the current dominant framework,Transformer,as well as multilingual translation models to deal with the data sparseness problem.In addition,we introduce cutting-edge simultaneous translation methods that achieve a balance between translation quality and latency.We then describe various products and applications of machine translation.At the end of this article,we briefly discuss challenges and future research directions in this field.展开更多
Two kinds of films were prepared to study the effect of microstructure on helium migration in Ti tritides. Both films showed different release behaviors and helium bubble distributions. In the film consisting of colum...Two kinds of films were prepared to study the effect of microstructure on helium migration in Ti tritides. Both films showed different release behaviors and helium bubble distributions. In the film consisting of columnar grains, a twolayered structure was observed. Inclusions with a strip feature were found at the grain boundary, and no helium bubbles were distributed in these inclusions. However, helium preferred to migrate to the boundaries of these inclusions. Bubble linkage as a ribbon-like feature developed parallel to the film surface in the film consisting of columnar grains. More cracks were developed at the grain boundaries of the film consisting of columnar grains, although the helium content in the film consisting of columnar grains was less than that in the film consisting of equiaxed grains. A surface region with a small number of bubbles, or ＂depleted zone＂, was observed near the surface. The cracks extending to the film surface were the pathways of the critical helium released from the film. The helium migration was strongly influenced by the grain microstructure.展开更多
We study a simplified(3+1)-dimensional model equation and construct a lump solution for the special case of z=y using the Hirota bilinear method.Then,a more general form of lump solution is constructed,which contains ...We study a simplified(3+1)-dimensional model equation and construct a lump solution for the special case of z=y using the Hirota bilinear method.Then,a more general form of lump solution is constructed,which contains more arbitrary autocephalous parameters.In addition,a lumpoff solution is also derived based on the general lump solutions and a stripe soliton.Furthermore,we figure out instanton/rogue wave solutions via introducing two stripe solitons.Finally,one can better illustrate these propagation phenomena of these solutions by analyzing images.展开更多
基金Project supported by the Key National Natural Science Foundation of China(Grant No.62136005)the National Natural Science Foundation of China(Grant Nos.61922087,61906201,and 62006238)。
文摘Physics-informed neural networks(PINNs)have become an attractive machine learning framework for obtaining solutions to partial differential equations(PDEs).PINNs embed initial,boundary,and PDE constraints into the loss function.The performance of PINNs is generally affected by both training and sampling.Specifically,training methods focus on how to overcome the training difficulties caused by the special PDE residual loss of PINNs,and sampling methods are concerned with the location and distribution of the sampling points upon which evaluations of PDE residual loss are accomplished.However,a common problem among these original PINNs is that they omit special temporal information utilization during the training or sampling stages when dealing with an important PDE category,namely,time-dependent PDEs,where temporal information plays a key role in the algorithms used.There is one method,called Causal PINN,that considers temporal causality at the training level but not special temporal utilization at the sampling level.Incorporating temporal knowledge into sampling remains to be studied.To fill this gap,we propose a novel temporal causality-based adaptive sampling method that dynamically determines the sampling ratio according to both PDE residual and temporal causality.By designing a sampling ratio determined by both residual loss and temporal causality to control the number and location of sampled points in each temporal sub-domain,we provide a practical solution by incorporating temporal information into sampling.Numerical experiments of several nonlinear time-dependent PDEs,including the Cahn–Hilliard,Korteweg–de Vries,Allen–Cahn and wave equations,show that our proposed sampling method can improve the performance.We demonstrate that using such a relatively simple sampling method can improve prediction performance by up to two orders of magnitude compared with the results from other methods,especially when points are limited.
文摘预训练语言模型(pre-trained languages model,PTLM)在自然语言处理(natural language processing,NLP)领域取得了令人瞩目的成功,并由此引发了下游任务从监督学习到预训练-微调范式的转变。在此之后,一系列预训练模型的创新研究涌现出来。本文系统性、全面的回顾了自然语言处理的代表性工作和最新进展,并按照类别系统性的介绍了自然语言处理领域的预训练模型。首先我们简要介绍了预训练模型,以及不同的模型特点和框架。之后,我们介绍并分析了预训练模型的影响和挑战以及下游任务中的应用。最后,我们简要总结并阐述了预训练模型未来的研究方向。
基金supported by the National Natural Science Foundation of China (Grant Nos. 32160142, 81873095)。
文摘Flower development is one of the most vital pathways in plant development, during which the epigenetic regulation of gene expression is essential. DNA methylation, the most conserved epigenetic modification, participates in gene expression regulation and transposable element silencing. Honeysuckle(Lonicera japonica) is an important medicinal plant renowned for its colorful and fragrant flowers. Honeysuckle flowers change color from white to gold as a result of carotenoid accumulation during development. However, the role of DNA methylation in flower color changes is not well understood in L. japonica. Here, we performed whole-genome bisulfite sequencing and transcriptome sequencing during flowering development in honeysuckle. The results showed that a decrease in the levels of genome-wide average DNA methylation during flower development and changes in DNA methylation were associated with the expression of demethylase genes. Moreover, many genes involved in carotenoid biosynthesis and degradation, such as Lj PSY1, LjPDS1, LjLCYE, and LjCCD4, have altered expression levels because of hypomethylation, indicating that DNA methylation plays an important role in flower color changes in honeysuckle. Taken together, our data provide epigenetic insights into flower development and color change in honeysuckles.
基金supported by the Science and Technology Major Project of Guangxi (Grant No. Guike AA22068096)Guangxi Distinguished Experts Fellowship to YQ, Science and Technology Major Project of Guangxi (Grant No. Guike 2018-266-Z01)+4 种基金Project of Guangxi featured fruit innovation team on pineapple breeding and cultivation post under national modern agricultural industry technology system (Grant No. nycytxgxcxtd-17-05)Science and Technology Program of Fujian Province (Grant No. 2019N5008)Science and technology innovation project of Pingtan Science and Technology Research Institute (Grant Nos. PT2021007, PT2021003)China Postdoctoral Science Foundation (Grant No. 2018M632564)the National Natural Science Foundation of China (31970333, U1605212)。
文摘Somaclonal variation in tissue culture is a common phenomenon induced by various external or internal environmental conditions,resulting in heritable or non-heritable alterations in gene expression. One crucial mechanism involved in plant growth and development is epigenetic regulation. A highly dynamic epigenome can respond to environmental changes by regulating gene expression. DNA methylation is one of these epigenetic modifications that can alter gene expression in tissue-cultured pineapple plants. The underlying mechanism of such somaclonal variations in pineapple and the epigenetic regulation involvement in somaclonal variations has not been studied. This study performed DNA methylome and transcriptome sequencing of wild-type(WT) and mutant pineapple plants(WS, HW, and TW). We observed altered DNA methylation patterns in chlorophyll development in the mutants. Specifically, we noticed that the methylation levels in the CHG and CHH contexts were lower in the gene body regions compared to the upstream and downstream regions. We identified several thousand differentially methylated regions(DMRs) located at the gene body regions, some of which overlapped with the differentially expressed genes(DEGs). Functional enrichment analyses suggested that these genes were involved in chlorophyll metabolism. Thus, our results revealed that the transcriptional regulation of many chlorophyll metabolic essential genes could be regulated by DNA methylation caused by somaclonal variations and provided insights into epigenetic mechanisms underlying the regulation of chlorosis in pineapple plants.
文摘Objective:To explore the effect of 3-dimensional(3D)printing-assisted cognitive fusion on improvement of the positive rate in prostate biopsy.Methods:From August to December 2014,16 patients with suspected prostatic lesions detected by multiparametric magnetic resonance imaging(MRI)were included.Targeted prostate biopsy was performed with the use of prostate 3D reconstruction modeling,computersimulated biopsy,3D printing,and cognitive fusion biopsy.All patients had received 3.0 T multiparametric MRI before biopsy.The DICOM MRI files were imported to medical imaging processing software for 3D reconstruction modeling to generate a printable.stl file for 3D printing with use of transparent resin as raw material.We further performed a targeted 2-to 3-core biopsy at suspected lesions spotted on MRI.Results:For the 16 patients in the present study,3D modeling with cognitive fusion-based targeted biopsy was successfully performed.For a single patient,1e2 lesions(average:1.1 lesions)were discovered,followed by 2-6 cores(average:2.4 cores)added as targeted biopsy.Systematic biopsies accounted for 192 cores in total,with a positive rate of 22.4%;targeted biopsies accounted for 39 cores in total,with a positive rate of 46.2%.Among these cases,10 patients(62.5%)were diagnosed with prostate adenocarcinoma,in which seven were discovered by both systematic and targeted biopsy,one was diagnosed by systematic biopsy only,and two were diagnosed by targeted biopsy only.For systematic biopsy,Gleason score ranged from 6 to 8(average:7),while that for targeted biopsy ranged from 6 to 9(average:7.67).Among the seven patients that were diagnosed by both systematic and targeted biopsy,three(42.8%)were reported with a higher Gleason score in targeted therapy than in systematic biopsy.Conclusion:3D printing-assisted cognitive fusion technique markedly promoted positive rate in prostate biopsy,and reduced missed detection in high-risk prostate cancer.
基金Supported by the National Natural Science Foundation of China(21576263,21625605,91334204)the Youth Innovation Promotion Association CAS(2015033)
文摘The EMMS/bubbling model originally proposed for fluidization of monodisperse particles is extended to fluidization of binary particle mixture in this study.The dense and dilute phases are considered to comprise of two types of particles differing in size and/or density.Governing equations and the stability condition are then formulated and solved by using an optimization numerical scheme.The effects of bubble diameter are first investigated and a suitable bubble diameter correlation is chosen.Preliminary validation for steady state behavior shows the extended model can fairly capture the overall hydrodynamic behaviors in terms of volume fraction of bubbles and average bed voidage for both monodisperse and binary particle systems.This encourages us to integrate this model with CFD for more validations in the future.
基金supported by grants from the Key R&D Projects ofZhejiang Province (2022C04034)the Natural Science Foundation of Zhejiang Province(Z19C170001)+2 种基金the National Natural Science Foundation of China (31672430)the National Key Research and Development Program of China(2017YFD0500502)the Funds of Ten Thousand People Plan
文摘Gut homeostasis is of importance to host health and imbalance of the gut usually leads to disorders or diseases for both human and animal.Postbiotics have been applied in manipulating of gut health,and utilization of postbiotics threads new lights into the host health.Compared with the application of probiotics,the characteristics such as stability and safety of postbiotics make it a potential alternative to probiotics.Studies have reported the beneficial effects of components derived from postbiotics,mainly through the mechanisms including inhibition of pathogens,strengthen gut barrier,and/or regulation of immunity of the host.In this review,we summarized the characteristics of postbiotics,main compounds of postbiotics,potential mechanisms in gut health,and their application in animal production.
基金supported by National Natural Science Foundation of China(Grant Nos.51675258,51261024,51265039)State Key Laboratory of Mechani-cal System and Vibration(Grant No.MSV201914)Laboratory of Science and Technology on Integrated Logistics Support,National University of Defense Technology(Grant No.6142003190210).
文摘The traditional modeling method of rotor system with a slant crack considers only integer-order calculus.However,the model of rotor system based on integer-order calculus can merely describe local characteristics,not historical dependent process.The occur of fractional order calculus just makes up for the deficiency in integer-order calculus.Therefore,a new dynamic model with a slant crack based on fractional damping is proposed.Here,the stiffness of rotor system with a slant crack is solved by zero stress intensity factor method.The proposed model is simulated by Runge-Kutta method and continued fraction Euler method.The influence of the fractional order,rotating speed,and crack depth on the dynamic characteristics of rotor system is discussed.The simulation results show that the amplitude of torsional excitation frequency increases significantly with the increase of the fractional order.With the increase of the rotating speed,the amplitude of first harmonic component becomes gradually larger,the amplitude of the second harmonic becomes smaller,while the amplitude of the other frequency components is almost invariant.The shaft orbit changes gradually from an internal 8-type shape to an ellipse-type shape without overlapping.With the increase of the slant crack depth,the amplitude of the transverse response frequency in the rotor system with a slant crack increases,and the amplitude in the second harmonic component also increases significantly.In addition,the torsional excitation frequency and other coupling frequency components also occur.The proposed model is further verified by the experiment.The valuable conclusion can provide an important guideline for the fault diagnosis of rotor system with a slant crack.
基金supported by the Key Scientific Research Projects of Higher Education Institutions in Henan Province under grant number 19A180021the Young Key Teachers Training Program of Yellow River Conservancy Technical Institute+2 种基金the Campus Scientific and Research Fund Project of Yellow River Conservancy Technical Institute under grant number 2017QNKY012the Research Projects of Employment and Entrepreneurship of Secondary and Higher Education Institutions in Henan Province under grant number JYB2018534National Natural Sciences Foundation of China under grant number 31070954.
文摘Histone deacetylation is a key modulator involved in cell proliferation,apoptosis,and mRNA transcription.However,the effects of histone deacetylation on C17.2 neural stem cells(NSCs)remain unclear.Here,the histone deacetylase inhibitors nicotinamide and trichostatin A(TSA)were used to determine the role of histone deacetylation on gene transcription in NSCs.The results showed that the mRNA expression of p53,Sox1,Sox2,and Bax were significantly higher in E14.5 NSCs than in C17.2 NSCs.Nestin,a marker gene of neuronal differentiation,did not differ significantly between E14.5 NSCs and C17.2 NSCs.The transcription levels of p53 and Nestin were significantly higher in C17.2 NSCs than in differentiated brain tissues,and the expression of Bax,Sox1,and Sox2 was higher in the olfactory bulb than in other brain tissues.Nicotinamide and TSA treatment decreased the transcription of Sox2,p53,Nestin,and Bax in C17.2 NSCs,although the difference was statistically significant only for Sox2 and Nestin,Sox1 transcription was not detected.These results demonstrated that mRNA expression profiles differ between C17.2 NSCs,E14.5 NSCs,and adult mouse brain tissues,and HDAC inhibitors regulate gene expression by modulating histone acetylation.
基金supported by the Natural Science Foundation of Fujian Province(2018J06006)National Key Research and Development Program of China(2016YFD0300700)+4 种基金National Natural Science Foundation of China(31770156)State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops(SKL2018006)the Program for New Century Excellent Talents of Fujian Province Universitythe Pre-eminent Youth Fund and Distinguished Young Scholars of Fujian Provincesupported by the Supercomputing Center at the College of Plant Protection of Fujian Agriculture and Forestry University。
文摘DNA methylation participates in regulating the expression of coding and non-coding regions in plants. To investigate the association between DNA methylation and pathogen infection, we used whole-genome bisulfite sequencing to survey temporal DNA methylation changes in rice after infection with the rice blast fungus Magnaporthe oryzae. In contrast to previous findings in Arabidopsis, global DNA methylation levels in rice increased slightly after rice blast infection. We identified over 38,000 differentially methylated regions(DMRs), and hypermethylated DMRs far outnumbered hypomethylated DMRs. Most DMRs were located in transposable element regions. Using transcriptome analysis, we identified 8830 differentially expressed genes(DEGs) after 1, 3, and 5 days of infection. Over one-third of DEGs, most of which were CHH-type DMRs, were associated with DMRs. Functional analysis of the CHH DMR-DEGs indicated their involvement in many important biological processes, including cell communication and response to external stimulus. The transcription of many NBS-LRR family genes was affected by changes in DNA methylation, suggesting that DNA methylation plays essential roles in the response of rice to M. oryzae infection. More broadly, the DNA methylation analysis presented here sheds light on epigenomic involvement in plant defense against fungal pathogens.
文摘After more than 70 years of evolution,great achievements have been made in machine translation.Especially in recent years,translation quality has been greatly improved with the emergence of neural machine translation(NMT).In this article,we first review the history of machine translation from rule-based machine translation to example-based machine translation and statistical machine translation.We then introduce NMT in more detail,including the basic framework and the current dominant framework,Transformer,as well as multilingual translation models to deal with the data sparseness problem.In addition,we introduce cutting-edge simultaneous translation methods that achieve a balance between translation quality and latency.We then describe various products and applications of machine translation.At the end of this article,we briefly discuss challenges and future research directions in this field.
文摘Two kinds of films were prepared to study the effect of microstructure on helium migration in Ti tritides. Both films showed different release behaviors and helium bubble distributions. In the film consisting of columnar grains, a twolayered structure was observed. Inclusions with a strip feature were found at the grain boundary, and no helium bubbles were distributed in these inclusions. However, helium preferred to migrate to the boundaries of these inclusions. Bubble linkage as a ribbon-like feature developed parallel to the film surface in the film consisting of columnar grains. More cracks were developed at the grain boundaries of the film consisting of columnar grains, although the helium content in the film consisting of columnar grains was less than that in the film consisting of equiaxed grains. A surface region with a small number of bubbles, or ＂depleted zone＂, was observed near the surface. The cracks extending to the film surface were the pathways of the critical helium released from the film. The helium migration was strongly influenced by the grain microstructure.
基金Project supported by the National Natural Science Foundation of China(Grant No.11971475)。
文摘We study a simplified(3+1)-dimensional model equation and construct a lump solution for the special case of z=y using the Hirota bilinear method.Then,a more general form of lump solution is constructed,which contains more arbitrary autocephalous parameters.In addition,a lumpoff solution is also derived based on the general lump solutions and a stripe soliton.Furthermore,we figure out instanton/rogue wave solutions via introducing two stripe solitons.Finally,one can better illustrate these propagation phenomena of these solutions by analyzing images.
