检索结果-南通市图书馆

Reconstitution of Gametogenesis In Vitro:Meiosis Is the Biggest Obstacle

在线全文

学校读者我要写书评

暂无评论

Journal of Genetics and Genomics 2014年第3期41卷 87-95页

作者： Yuan-chao sun Shun-Feng Cheng Rui sun Yong Zhao Wei Shen Key Laboratory of Animal Reproduction and Germplasm Enhancement in Universities of Shandong Qingdao Agricultural University National Laboratory for Physical Sciences at Microscale School of Life SciencesUniversity of Science and Technology of China

Germ-line cells are responsible for transmitting genetic and epigenetic information across generations, and ensuring the creation of new individuals from one generation to the next. Gametogenesis process requires several rigorous steps, including primordial germ cell （PGC） specification, proliferation, migration to the gonadal ridges and differentiation into mature gametes such as sperms and oocytes. But this process is not clearly explored because a small number of PGCs are deeply embedded in the developing embryo. In the attempt to establish an in vitro model for understanding gametogenesis process well, several groups have made considerable progress in differen- tiating embryonic stem cells （ESCs） and adult stem cells （ASCs） into germ-like cells over the past ten years. These stem cell-derived germ cells appear to he capable of undergoing meiosis and generating both male and female gametes. But most of gametes turn out to be not fully functional due to their abnormal meiosis process compared to endogenous germ cells. Therefore, a robust system of differentiating stem cells into germ cells would enable us to investigate the genetic, epigenetic and environmental factors associated with germ cell development. Here, we review the stem cell-derived germ cell development, and discuss the potential and challenges in the differentiation of functional germ cells from stem cells.

关键词： Stem cells Germ cells Gametogenesis Differentiation Meiosis

Near field 3-D imaging approach for joint high-resolution imaging and phase error correction

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2017年第2期28卷 199-211页

作者： Yang Fang Baoping Wang chao sun Zuxun Song Shuzhen Wang School of Electronics and Information Northwestern Polytechnical University Xi’an 710072 China National Key Laboratory of Science and Technology on UAV Xi’an 710065 China School of Computer Science and Technology Xidian University Xi’an 710071 China

This paper combines compressed sensing (CS) imaging theory and range migration algorithm (RMA), and then proposes a near-field three-dimensional (3-D) imaging approach for joint high-resolution imaging and phase error correction. Firstly, a sparse measurement matrix construction method based on a logistic sequence is proposed, which conducts nonlinear transformation for the determined logistic sequence, making it obey uniform distribution, then conducts sign function mapping, and generates the pseudorandom sequence with Bernoulli distribution, thus leading to good signal recovery under down-sampling and easy availability for engineering realization. Secondly, in combination with the RMA imaging approach, the dictionary with all scene information and phase error correction is constructed for CS signal recovery and error correction. Finally, the non-quadratic solution model jointing imaging and phase error correction based on regularization is built, and it is solved by two steps - the separable surrogate functionals (SSF) iterative shrinkage algorithm is adopted to realize target scattering estimate; the iteration mode is adopted for the correction of the dictionary model, so as to achieve the goal of error correction and highly-focused imaging. The proposed approach proves to be effective through numerical simulation and real measurement in anechoic chamber. The results show that, the proposed approach can realize high-resolution imaging in the case of less data; the designed measurement matrix has better non-coherence and easy availability for engineering realization. The proposed approach can effectively correct the phase error, and achieve highly-focused target image. © 2017 Beijing Institute of Aerospace Information.

关键词： Compressed sensing Error correction Image reconstruction Iterative methods Linear transformations Mathematical transformations Signal reconstruction Signal sampling

Research of transient rotor dynamic characteristic of magnetic liquid double suspension bearing in double collision state

在线全文

学校读者我要写书评

暂无评论

High Technology Letters 2024年第2期30卷 146-157页

作者：刘洪美 LI Shengguo sun chao sun Yanan ZHAO Jianhua Shijiazhuang Rail Transit Group Co.Ltd Shijiazhuang 050011P.R.China Shijiazhuang Haishan Industrial Development Co.Ltd Shijiazhuang 050200P.R.China Hebei Provincial Key Laboratory of Heavy Machinery Fluid Power Transmission and Control Yanshan UniversityQinhuangdao 066004P.R.China

During the operation of magnetic liquid double suspension bearing(MLDSB),due to rotor resonance,assembly error and other factor,the vibration amplitude of the rotor in resonance state exceeds the original design clearance,resulting in the collision damage between the rotor and the stator,the rotor and the *** paper presents a method to simulate the influence of different factors on the dynamic characteristics of 5 degrees of freedom(DOF)rotor based on the dynamic model of ***,according to the second Lagrange equation,the dynamic equation of 5 DOF rotor is derived,and the mathematical model is ***,based on 5 DOF rotor dynamic equation,the rotor transient dynamic equation under collision state is obtained,and the rotor transient collision dynamic simulation model is ***,the key influencing factors of rotor dynamic characteristics are extracted,and the influence mapping relationship of rotor displacement,axis locus and stress distribution under different factors is simulated by using ANSYS Workbench *** experimental results show that this method can effectively reflect the influence of various factors on the dynamic characteristics of the *** method can provide theoretical reference for the design and control of MLDSB.

关键词： displacement response axis trajectory radial excitation peak radial excitationtimes transient dynamic characteristics

Reduced graphene oxide-modified Ni Co-phosphates on Ni foam enabling high areal capacitances for asymmetric supercapacitors

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第31期90卷 255-263页

作者： chao sun Li sun Yuanxing Zhang Haochen Si Kaifeng Fan Yan Shi Jialin Gu Yihe Zhang Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes National Laboratory of Mineral MaterialsSchool of Materials Science and TechnologyChina University of Geosciences.Beijing100083China

NiCo-phosphates can deliver high specific capacitances and high electrochemical activities as pseudocapacitive electrode material for *** this study,The NiCo-phosphates@reduced graphene oxide(NCPO@rGO)composite is directly loaded on Ni foam by a simple one-step hydrothermal *** conductive rGO sheets provides continuous electron pathways between NCPO flowers and Ni foam,allowing active electrochemical reactions throughout the whole *** can solve the difficulty of low active material utility and small areal capacitances in the Ni foam-supported *** the same time,the rGO sheets creates large amount of mesopores within the electrode,which can ensure a highly open structure for electrolyte attachment and ion *** of the positive effect of rGO in improving charge transfe r,the NiCo-phosphates can be fully involved in the electrochemical reactions with high utility,ensuring high specific capacitances(1416.7 F g^(-1)at 1 A g^(-1))and high-rate ***,the areal capacitance of the NCPO@rGO electrode can reach as large as 3.69 F cm^(-2)at 1 A g^(-1),which is among the highest ones in Ni foam supported *** asymmetric supercapacitor is then fabricated by NCPO@rGO as the positive material with attractive energy densities and power densities,further proving its excellent electrochemical performance.

关键词： NiCo-phosphates High areal capacitance Reduced graphene oxide Ni foam Asymmetric supercapacitor

Effect of Enhanced Plasma Density on the Properties of Aluminium Doped Zinc Oxide Thin Films Produced by DC Magnetron Sputtering

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2011年第5期27卷 393-397页

作者： Jun Gong Xiaobo Zhang Zhiliang Pei chao sun Lishi Wen Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Aluminum doped zinc oxide （AZO） thin films were prepared by DC magnetron sputtering at low substrate temperature. A coaxial solenoid coil was placed near the magnetron target to enhance the plasma density （Ji）. The enhanced plasma density improved significantly the bulk resistivity （p） and its homogeneity in spatial distribution of AZO films. X-ray diffraction （XRD） analysis revealed that the increased Ji had influenced the crystallinity, stress relaxation and other material properties. The AZO films deposited in low plasma density （LPD） mode showed marked variation in p （ranging from -6.5x10-2 to 1.9x10-3 Ω.cm）, whereas those deposited in high plasma density （HPD） mode showed a better homogeneity of films resistivity （ranging from ~1.3x10-3 to 3.3x10-3 ~.cm） at different substrate positions. The average visible transmittance in the wavelength range of 500-800 nm was over 80%, irrespective of the deposition conditions. The atomic force microscopy （AFM） surface morphology showed that AZO films deposited in HPD mode were smoother than that in LPD mode. The high plasma density produced by the coaxial solenoid coil improved the electrical property, surface morphology and the homogeneity in spatial distribution of AZO films deposited at low substrate temperature.

关键词： Sputtering Electronic conductivity Ion bombardmentPlasma density

Adipose-derived stem cells and obesity: The spear and shield relationship

在线全文

学校读者我要写书评

暂无评论

Genes & Diseases 2023年第1期10卷 175-186页

作者： Hong Yang chaowei Li Yizhou Li Ruiqing Tai chao sun Key Laboratory of Animal Genetics Breeding and Reproduction of Shaanxi ProvinceCollege of Animal Science and TechnologyNorthwest A&F UniversityYanglingShaanxi 712100China

With the transformation of modern lifestyles and population ageing,obesity has become a global epidemic,as one of the important threat to human health of chronic noncommunicable diseases(NCD).Stem cell therapy seems promising as an alternative strategy for managing obesity and related metabolic *** tissue-derived stem cells(ADSCs)have received widespread attention,which provides new ideas for the treatment of obesity and various metabolic-related diseases,due to their abundant reserves,easy acquisition,rapid expansion,and multi-directional differentiation potential,low immunogenicity and many other ***,there seems to be a"shield and spear paradox"in the relationship between ADsCs and *** this review,we emphatically summarized the role of ADsCs in the occurrence and development of obesity and related metabolic disease processes,in order to pave the way for clinical practice.

关键词： Adipose-derived stem cells Differentiation Inflammation Insulin resistance Metabolic syndrome Obesity

Exploring the Spatiotemporal Changes and Driving Forces of Ecosystem Services of Zhejiang Coasts,China,Under Sustainable Development Goals

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Geographical Science 2024年第4期34卷 647-661页

作者： ZHANG Shu sun chao ZHANG Yixin HU Ming SHEN Xingru Department of Geography and Spatial Information Techniques Ningbo UniversityNingbo 315211China Donghai Academy Ningbo UniversityNingbo 315211China Zhejiang Collaborative Innovation Center&Ningbo Universities Collaborative Innovation Center for Land and Marine Spatial Utilization and Governance Research Ningbo UniversityNingbo 315211China Xiangshan High School Ningbo 315700China

Ecosystem services(ESs)refer to the continuous provisioning of ecosystem goods and services that benefit human *** recent decades,rapid urbanization has exerted significant pressure on coastal ecosystems,resulting in biodiversity and habitat loss,environmental pollution,and the depletion of natural *** response to these environmental challenges,the Sustainable Development Goals(SDGs)were *** the pressing need to address these issues,understanding the changes in ESs under the SDGs is crucial for formulating specific ecological *** this study,we first analyzed land use and cover change in the Zhejiang coasts of China during 2000–***,we investigated the spatiotemporal configuration of ESs by integrating carbon storage(CS),soil retention(SR),habitat quality(HQ)and water yield(WY)using the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)*** driving mechanisms of ESs,which varied by space and time,were also explored using the Geo-detector *** results revealed that,over the past two decades:1)the Zhejiang coasts have experienced a significant increase of 2783.72 km^(2) in built-up land areas and a continuous decrease in farmland areas due to rapid urbanization;2)owing to higher precipitation,extensive vegetation cover,and reduced anthropogenic disturbances,forests emerge as a crucial land use type for maintaining ecosystem services such as HQ,CS,WY,and SR;3)ESs have generally declined across the entire Zhejiang coasts,with a significant decrease observed in the northern areas and an increase in the southern areas spatially;4)the expansion of built-up land areas emerged as the primary factor affecting ecosystem services,while the vegetation factor has been increasingly significant and is expected to become predominant in the near *** study provides insights of understanding of ecosystem service theory and emphasizing the importance of preserving biodiversity for long-term sustainable development

关键词： ecosystem services(ESs) Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)model Geo-detector land use and cover change(LUCC) Zhejiang coasts China

Response of vegetation variation to climate change and human activities in the Shiyang River Basin of China during 2001-2022

在线全文

学校读者我要写书评

暂无评论

Journal of Arid Land 2024年第8期16卷 1044-1061页

作者： sun chao BAI Xuelian WANG Xinping ZHAO Wenzhi WEI Lemin Northwest Institute of Eco-Environment and Resources Chinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China Gansu Provincial Academy of Water Sciences Lanzhou 730000China

Understanding the response of vegetation variation to climate change and human activities is critical for addressing future conflicts between humans and the environment,and maintaining ecosystem ***,we aimed to identify the determining factors of vegetation variation and explore the sensitivity of vegetation to temperature(SVT)and the sensitivity of vegetation to precipitation(SVP)in the Shiyang River Basin(SYRB)of China during *** climate data from climatic research unit(CRU),vegetation index data from Moderate Resolution Imaging Spectroradiometer(MODIS),and land use data from Landsat images were used to analyze the spatial-temporal changes in vegetation indices,climate,and land use in the SYRB and its sub-basins(i.e.,upstream,midstream,and downstream basins)during *** regression analysis and correlation analysis were used to explore the SVT and SVP,revealing the driving factors of vegetation *** increasing trends(P<0.05)were detected for the enhanced vegetation index(EVI)and normalized difference vegetation index(NDVI)in the SYRB during 2001-2022,with most regions(84%)experiencing significant variation in vegetation,and land use change was determined as the dominant factor of vegetation ***-significant decreasing trends were detected in the SVT and SVP of the SYRB during *** were spatial differences in vegetation variation,SVT,and *** NDVI and EVI exhibited increasing trends in the upstream,midstream,and downstream basins,the change slope in the downstream basin was lower than those in the upstream and midstream basins,the SVT in the upstream basin was higher than those in the midstream and downstream basins,and the SVP in the downstream basin was lower than those in the upstream and midstream *** and precipitation changes controlled vegetation variation in the upstream and midstream basins while human activities(land use change)dominated vegetation variation in the d

关键词： vegetation variation climate change land use change normalized difference vegetation index(NDVI) enhanced vegetation index(EVI) Shiyang River Basin

Effects of Cr and Al Contents on the Preparation of SiC Fiber-Reinforced NiCrAl Alloy Matrix Composite

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2020年第10期33卷 1416-1422页

作者： Haoqiang Zhang Xixi Niu Zhiliang Pei Nanlin Shi Jun Gong chao sun Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China University of Chinese Academy of Sciences Beijing 100049China

In this work,the effects of Cr and Al contents on the preparation of SiC fiber-reinforced NiCrAl alloy matrix composites(SiCf/Ni-20Cr-5Al,SiCf/Ni-15Cr-5Al,SiCf/Ni-10Cr-5Al and SiCf/Ni-10Cr-3Al)were thoroughly *** composites were prepared by vacuum hot pressing process using matrix-coated *** was found that Cr solute atoms played a significant role in retarding the recrystallization of NiCrAl alloy matrix,and the Al elements in the form of γ'-Ni3Al phase had a suppression effect on the plastic flow of the ***,the reduction in Cr and Al contents was conductive to the recrystallization and plastic flow of NiCrAl alloy matrix,thereby reduced the size and number of micro-voids in the *** addition,this work provides some guidance for designing and manufacturing reasonable SiC fiber-reinforced Ni alloy matrix composites.

关键词： SiC fiber NiCrAl alloy Composite Recrystallization Plastic flow