检索结果-南通市图书馆

Megafossils of Betulaceae from the Oligocene of Qaidam Basin and their paleoenvironmental and phytogeographic implications

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

Plant Diversity 2024年第1期46卷 101-115页

作者： Tao Yang Jia-Hao Cai Yan-Zhi Dai Hong-Yu Chen Lei Han Li Zhang Wei-Yu Liang xu-Jun Li Wen-Jia Li Jing-Yu Wu san-Ping Xie De-Fei Yan School of Earth Sciences and Key Laboratory of Mineral Resources in Western China(Gansu Province) Lanzhou UniversityLanzhou 730000China Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijing 100044China State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and PaleoenvironmentChinese Academy of SciencesNanjing 210008China Center for Research and Education on Biological Evolution and Environments School of Earth Sciences and EngineeringNanjing UniversityNanjing 210023China

Understanding the paleoenvironment and phytogeographical history of the Tibetan Plateau,China relies on discovering new plant fossils.The Qaidam Basin has long been regarded as an ideal‘field laboratory’to investigate the paleoclimate and paleobiological evolution of the northern Tibetan Plateau.However,fossil angiosperms from the Qaidam Basin are rare,and our knowledge of its paleovegetation is poor.Here,we report fossil leaves and fruits of Betulaceae found from the Oligocene Shangganchaigou Formation of northwestern Qaidam Basin(Huatugou area).Comparative morphological analysis led us to assign the fruits to the Betula subgenus Betula and the leaves to Carpinus grandis.These findings,together with other reported fossil plants from the same locality,reveal a close floristic linkage between the Qaidam Basin and Europe during the Oligocene.The northern pathway of this floristic exchange may have crossed through the Qaidam Basin during the late Paleogene.This floristic linkage may have been facilitated by the continuous narrowing of the Turgai Strait and stronger westerlies,which transported moisture and provided favorable climatic conditions.Indeed,fossil plants collected from the Qaidam Basin suggest that during the Oligocene this region had warm and humid deciduous broad-leaf forest,which differs from the region’s modern vegetation and indicates that the Qaidam Basin may have been a suitable region for these plants to flourish and spread during the Oligocene.

关键词： Paleoenvironment Biogeography Betulaceous fossil Qaidam basin Tibetan Plateau Oligocene

A seismic elastic moduli module for the measurements of low-frequency wave dispersion and attenuation of fluid-saturated rocks under different pressures

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第1期21卷 162-181页

作者： Yan-Xiao He Shang-xu Wang Gen-Yang Tang Chao Sun Hong-Bing Li san-Yi Yuan Xian Wei Li-Deng Gan Xiao-Feng Dai Qiang Ge Peng-Peng Wei Hui-Qing Zhang National Key Laboratory of Petroleum Resources and Engineering CNPC Key Lab of Geophysical ExplorationCollege of GeophysicsChina University of Petroleum(Beijing)Beijing102249China School of Resources and Geosciences China University of Mining and TechnologyXuzhou221116JiangsuChina Research Institute of Petroleum Exploration and Development CNPCBeijing100083China Beijing Vocational College of Labour and Social Security Beijing100029China PetroChina Dagang Oilfield Exploration and Development Research Institute CNPCTianjin300280China

Knowledge about the seismic elastic modulus dispersion,and associated attenuation,in fluid-saturated rocks is essential for better interpretation of seismic observations taken as part of hydrocarbon identification and time-lapse seismic surveillance of both conventional and unconventional reservoir and overburden performances.A Seismic Elastic Moduli Module has been developed,based on the forced-oscillations method,to experimentally investigate the frequency dependence of Young's modulus and Poisson's ratio,as well as the inferred attenuation,of cylindrical samples under different confining pressure conditions.Calibration with three standard samples showed that the measured elastic moduli were consistent with the published data,indicating that the new apparatus can operate reliably over a wide frequency range of f∈[1-2000,10^(6)]Hz.The Young's modulus and Poisson's ratio of the shale and the tight sandstone samples were measured under axial stress oscillations to assess the frequency-and pressure-dependent effects.Under dry condition,both samples appear to be nearly frequency independent,with weak pressure dependence for the shale and significant pressure dependence for the sandstone.In particular,it was found that the tight sandstone with complex pore microstructure exhibited apparent dispersion and attenuation under brine or glycerin saturation conditions,the levels of which were strongly influenced by the increased effective pressure.In addition,the measured Young's moduli results were compared with the theoretical predictions from a scaled poroelastic model with a reasonably good agreement,revealing that the combined fluid flow mechanisms at both mesoscopic and microscopic scales possibly responsible for the measured dispersion.

关键词： Low-frequency measurements Dispersion and attenuation Rock physics Fluid flow

在线全文

学校读者我要写书评

暂无评论

基于分解和聚类的昂贵高维多目标进化算法

控制与决策 2024年第2期39卷 440-448页

作者：徐三水李军华李凌黎明南昌航空大学江西省图像处理与模式识别重点实验室南昌330063

使用进化算法解决昂贵高维多目标优化问题时,因目标维数较高,导致收敛性和多样性平衡困难,并且消耗成本过高,使得计算资源有限时难以收敛.为此,提出一种基于分解和聚类的昂贵高维多目标进化算法(DC-EMEA),使用克里金模型近似目标函数,... 详细信息

使用进化算法解决昂贵高维多目标优化问题时,因目标维数较高,导致收敛性和多样性平衡困难,并且消耗成本过高,使得计算资源有限时难以收敛.为此,提出一种基于分解和聚类的昂贵高维多目标进化算法(DC-EMEA),使用克里金模型近似目标函数,减少昂贵函数的评价次数.在优化器对模型的最优解集搜索时,借助参考向量分解目标空间,有利于收敛性和多样性的平衡,同时采取两轮选择的方式,保证后代种群规模与父代相同,为填充准则选择真实评价的个体时,提供更多选择,提升搜索效率.同时,提出一种自适应填充准则,首先使用K均值算法将种群划分为k个子种群.通过划分邻域,将子种群自适应地分成不同类型,根据子种群的类型选择个体,提升计算资源的利用率.在选择个体时,侧重于对收敛性压力的维持,提升收敛速度.将选出的个体用于更新模型和档案.实验结果表明, DC-EMEA能够很好地平衡收敛性和多样性,同时具有较强的收敛能力.

关键词：克里金模型高维昂贵优化填充准则参考向量进化算法聚类算法

Regulation of AMPK activation by extracellular matrix stiffness in pancreatic cancer

在线全文

学校读者我要写书评

暂无评论

Genes & Diseases 2024年第3期11卷 338-350页

作者： Xin xu Yuan Fang Somaira Nowsheen Ye-Xiong Li Zhenkun Lou Min Deng State Key Laboratory of Molecular Oncology and Department of Radiation Oncology National Cancer Center/National Clinical Research Center for Cancer/Cancer HospitalChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing 100021China Department of General Surgery Shanghai General HospitalShanghai Jiaotong University School of MedicineShanghai 200080China Department of General Surgery Zhongshan HospitalFudan UniversityShanghai 200032China Department of Dermatology University of California San DiegoSan DiegoCA 92093USA Department of Oncology Mayo ClinicRochesterMN 55905USA

The adenosine monophosphate(AMP)-activated protein kinase(AMPK)sits at a cen-tral node in the regulation of energy metabolism and tumor progression.AMPK is best known to sense high cellular ADP or AMP levels,which indicate the depletion of energy stores.Previous studies have shown that the low expression of phosphorylated AMPK is associated with a poor prognosis of pancreatic cancer.In this study,we report that AMPK is also highly sensitive to extracellular matrix(ECM)stiffness.We found that AMPK is activated in cells when cultured under low ECM stiffness conditions and is functionally required for the metabolic switch induced by ECM stiffness.This regulation of AMPK requires the Hippo kinases but not LKB1/CaMKKp.Hippo kinases directly phosphorylate AMPKa at Thr172 to activate AMPK at low ECM stiffness.Furthermore,we found AMPK activity is inhibited in patients with pancreatic ductal adenocarcinoma(PDAC)with high ECM stiffness and is associated with a poor survival outcome.The activation of Hippo kinases by ROCK inhibitor Y-27632 in combination with the mitochondrial inhibitor metformin synergistically activates AMPK and dramatically inhibits PDAC growth.Together,these findings establish a novel model for AMPK regulation by the mechanical properties of ECMs and provide a rationale for simultaneously targeting the ECM stiffness-Hippo kinases-AMPK signaling and low glucose-LKB1-AMPK signaling pathways as an effective therapeutic strategy against PDAC.

关键词： AMPKactivity Cellularmetabolic switch ECM stiffness Hippokinase signaling Pancreaticductal adenocarcinoma

New insights into the effects of APP gene dose on synapse in Down syndrome

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

Neural Regeneration Research 2024年第5期19卷 961-962页

作者： xu-Qiao Chen Xinxin Zuo Department of Neurosciences University of California San DiegoLa JollaCAUSA

Synaptic dysfunction:Alzheimer’s disease(AD)is a prevalent form of dementia,affecting over 35 million people worldwide(Tzioras et al.,2023).A synapse serves as the connection point between neurons,facilitating the transmission of information from one neuron to another.Dynamic alterations in synapses,known as synaptic plasticity,play a pivotal role in cognitive processes such as learning and memory.Synaptic loss has been identified as a key contributor to cognitive decline in AD patients.Studies have shown that the soluble forms of amyloid-beta(Aβ)and tau proteins are toxic to synapses,leading to cognitive impairment in animal models(Spires-Jones and Hyman,2014).Additionally,the formation of oligomers of tau and Aβcan spread pathology through synaptic connections in the brain,emphasizing the vital role of synapses in disease progression.

关键词： alterations Aβ tau

基于自适应参考向量和参考点的高维多目标进化算法

在线全文

学校读者我要写书评

暂无评论

控制与决策 2024年第3期39卷 759-767页

作者：覃灏李军华黎明徐三水南昌航空大学江西省图像处理与模式识别重点实验室南昌330063

研究表明,现有的多目标进化算法在处理具有不同Pareto前沿的优化问题时难以有效平衡种群的收敛性与多样性.鉴于此,提出一种基于自适应参考向量和参考点的高维多目标进化算法(adaptive reference vector and reference point based many-... 详细信息

研究表明,现有的多目标进化算法在处理具有不同Pareto前沿的优化问题时难以有效平衡种群的收敛性与多样性.鉴于此,提出一种基于自适应参考向量和参考点的高维多目标进化算法(adaptive reference vector and reference point based many-objective evlolutionary algorithm, ARVRPMEA). ARVRPMEA主要利用种群稀疏性自适应调整参考向量和参考点以提高种群多样性,首先,生成均匀分布的参考向量子集和参考点子集,并利用该参考向量子集分解种群;然后,根据规模最大子种群中解的分布情况生成新的参考向量和参考点,直至满足参考向量集和参考点集规模;最后,为进一步提高种群收敛性,该算法结合指标进行环境选择以保存收敛性较高的个体进入下一代种群.实验结果表明, ARVRP算法在求解具有不同Pareto前沿的问题方面具有良好的性能.

关键词：进化算法高维多目标进化算法自适应参考向量和参考点分解种群

基于非线性定向降维的k近邻致密砂岩储层含气性预测方法

在线全文

学校读者我要写书评

暂无评论

Applied Geophysics 2024年第2期21卷 221-231,418页

作者：宋朝辉桑文镜袁三一王尚旭中国石油大学(北京) 地球物理学院北京102249

本文提出利用全连接人工神经网络(FANN)进行非线性定向降维并结合k近邻方法分类的致密砂岩储层含气性预测方法。k近邻方法能够依据样本间相似性,针对性地选取对应的部分训练样本建立局部模型,但缺乏含气敏感属性的提取能力,并面临“维... 详细信息

本文提出利用全连接人工神经网络(FANN)进行非线性定向降维并结合k近邻方法分类的致密砂岩储层含气性预测方法。k近邻方法能够依据样本间相似性,针对性地选取对应的部分训练样本建立局部模型,但缺乏含气敏感属性的提取能力,并面临“维度灾难”问题。由于样本中的含气性特征虽然是重要特征,但不一定是主要特征。线性降维方法难以准确提取这些特征。我们通过训练一个合理搭建的FANN并输出其中间低维特征实现对训练样本和待预测样本的非线性定向降维。这种做法既能够增加样本的可分性,同时避免了通过样本低维空间中的最大差异实现降维而改变样本固有分布特征的问题。另外,k近邻方法对降维数据进行分类,还等效于用k近邻方法替代FANN中具有线性分类作用的深层结构,有利于白化FANN的黑箱问题。本方法在具体的物理场景中挖掘机器学习算法的物理内涵,提高了智能方法的可解释性。将本方法应用在实际数据中,预测结果显示本方法能够一定程度上挖掘局部波形属性中蕴含的含气敏感信息,实现小范围的致密砂岩储层精确刻画。

关键词： k近邻方法致密砂岩储层预测非线性定向降维可解释性

On the analytic and geometric aspects of obstruction flatness

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2024年

作者： Peter EBENFELT Ming XIAO Hang xu Department of Mathematics University of California at San Diego School of Mathematics (Zhuhai) Sun Yat-sen University

In this paper, we investigate analytic and geometric properties of obstruction flatness of strongly pseudoconvex CR hypersurfaces of dimension 2n-1. Our first two results concern local aspects. One asserts that any strongly pseudoconvex CR hypersurface M ? Cncan be osculated at a given point p ∈ M by an obstruction flat one up to order 2n + 4 generally and 2n + 5 if and only if p is an obstruction flat point. In the other result, we show that locally there are non-spherical but obstruction flat CR hypersurfaces with transverse symmetry for n = 2. The final main result in this paper concerns the existence of obstruction flat points on compact, strongly pseudoconvex, 3-dimensional CR hypersurfaces. It asserts that the unit sphere in a negative line bundle over a Riemann surface X always has at least one circle of obstruction flat points.

关键词：

Activation of the Ig la I promoter by the transcription factor Ets-1 triggers Ig lal-Cal germline transcription in epithelial cancer cells

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Cellular & Molecular Immunology 2014年第2期11卷 197-205页

作者： Zhi Duan Hui Zheng san xu Yiqun Jiang Haidan Liu Ming Li Duosha Hu Wei Li Ann M. Bode Zigang Dong Ya Cao Laboratory of Tumor Molecular Biology Cancer Research Institute Central South University Changsha China Key Laboratory of Carcinogenesis andCancer Invasion Ministry of Education Changsha China Key Laboratory of Carcinogenesis Ministry of Health Changsha China Center of Clinical Gene rDiagnosis and Theralav Department of Cardiothoracic Surgery The Second Xian~:ya Hospital Central South University Changsha China Department ofimmunology Xiangya Medical College Central South University Changsha China The Hormel Institute University of Minnesota Austin MN USACorrespondence: Dr Y Cao Laboratory of Tumor Molecular Biology Cancer Research Institute Central South University Changsha 410078 China.

Immunoglobulins （Igs） are known to be synthesized and secreted only by B lymphocytes. Class switch recombination （CSR） is a key event that enables B cells to express Igs, and one of the crucial steps for CSR initiation is the germline transcription of Iggenes. Surprisingly, recent studies have demonstrated that the Iggenes are also expressed in some epithelial cancer cells; however, the mechanisms underlying how cancer cells initiate CSR and express Igs are still unknown. In this study, we confirmed that the Ig la I promoter in cancer cell lines was activated by the Ets- 1 transcription factor, and the activity of the Ig la I promoter and ig lal-C^l germiine transcription were attenuated after knockdown of Ets-1 by specific small interfering RNAs （siRNA）. Furthermore, the expression of Ets-1 and Iga heavy chain in cancer cells was dose dependently upregulated by TGF-I^I. These results indicate that activation of the Ig lal promoter by the transcriotion factor Ets-1 is a critical Dathwav and orovides a novel mechanism for le exoression in non-B cell cancers.

关键词： epithelial cancer cells Ets-1 Ig I^1 promoter