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短链脂肪酸介导的肠骨轴在骨代谢中的研究进展

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食品科学 2025年第2期46卷 260-267页

作者：张萱杨雪李新科孟璐王加启郑楠中国农业科学院北京畜牧兽医研究所农业农村部奶及奶制品质量安全控制重点实验室北京100193 中国农业科学院北京畜牧兽医研究所农业农村部奶产品质量安全风险评估实验室(北京)北京100193

随着全球老龄化加剧,骨质疏松症等与年龄相关的骨骼代谢疾病发病率不断上升,寻求安全有效的治疗干预方法至关重要。目前肠道微生物及其代谢产物调节骨代谢已成为研究的热点。短链脂肪酸(short-chain fatty acids,SCFAs)如乙酸、丙酸和... 详细信息

随着全球老龄化加剧,骨质疏松症等与年龄相关的骨骼代谢疾病发病率不断上升,寻求安全有效的治疗干预方法至关重要。目前肠道微生物及其代谢产物调节骨代谢已成为研究的热点。短链脂肪酸(short-chain fatty acids,SCFAs)如乙酸、丙酸和丁酸等,能够通过肠-骨轴发挥骨形成和骨吸收的调节作用,对骨稳态调节具有一定的积极作用,并能改善炎症性骨丢失。本文综述SCFAs通过内分泌、免疫、改善营养吸收等途径调控骨代谢稳态,以期为老年代谢性骨病的预防和治疗提供科学依据。

关键词：肠-骨轴短链脂肪酸肠道微生物骨代谢骨质疏松症

Optimal restructuring strategies under various dynamic factors

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第6期8卷 932-938页

作者： MENG Qing-xuan Department of Management Science and Engineering Stanford University CA 94305 USA College ofEconomtcs Zhejiang University Hangzhou 310027 China

Corporate restructuring was identified as a new industrial force that has great impact on economic values and that therefore has become central in daily financial decision making. This article investigates the optimal restructuring strategies under different dynamic factors and their numerous impacts on firm value. The concept of quasi-leverage is introduced and valuation models are built for corporate debt and equity under imperfect market conditions. The model’s input variables include the quasi-leverage and other firm-specific parameters, the output variables include multiple corporate security values. The restruc- turing cost is formulated in the form of exponential function, which allows us to observe the sensitivity of the variation in security values. The unified model and its analytical solution developed in this research allow us to examine the continuous changes of security values by dynamically changing the coupon rates, riskless interest rate, bankruptcy cost, quasi-leverage, personal tax rate, corporate taxes rate, transaction cost, firm risk, etc., so that the solutions provide useful guidance for financing and restructuring decisions.

关键词： Restructuring Capital structure Financial decisions

First principles study of Fenton reaction catalyzed by FeOCl:reaction mechanism and location of active site

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Rare Metals 2019年第8期38卷 783-792页

作者： xuan-xuan Ji Hai-Feng Wang Pei-Jun Hu Key Laboratory for Advanced Materials Research Institute of Industrial Catalysis and Centre for Computational Chemistry School of Chemical and Molecular Engineering East China University of Science and Technology Shanghai 200237 China School of Chemistry and Chemical Engineering The Queen’s University of Belfast Belfast BT9 5AZ UK

Fe-based solid catalysts in promoting Fenton reaction to generate ·OH radical has drawn much attention,and interestingly,FeOCl was reported to have superior activity compared with the traditional Fe2 O3 ***,the mechanism of Fenton reaction on FeOCl and the origin of high activity remain ***,by virtue of DFT+ U calculations,the H2 O2 decomposition and conversion mechanism on FeOCl(100)surface were systematically *** is found that on clean FeOCl(100)surface,the exposed[Fe^3+-Fe^3+]sites can hardly break O-O bond of H2 O2 into OH groups,but instead H2 O2 tends to dehydrogenate by the surface lattice O,resulting in a series of side reactions and final conversion into O2,while the left H atoms gradually saturate the surface lattice O and reduce Fe^3+ into Fe^2+.On fully H-covered FeOCl(100),H2O2 can efficiently dissociate at[Fe^2+-Fe^2+]sites into two OH,but OH binds with Fe^2+ so strongly that it cannot desorb as OH radical as easily as that on Fe^3+.Interestingly,FeOCl(100)tends to be partially protonated in the real acid solution,which,along with H2 O2 dehydrogenation,results in the formation of active unit [Fe^2+-Fe^3+].On[Fe^2+-Fe^3+]unit,H2 O2 can easily break its O-O bond and OH at Fe3+ can desorb as OH radical,while the other OH at Fe^2+ couples with the surface H into H2O and finish the catalytic *** comparison,Fe2 O3(012)cannot provide enough [Fe^2+-Fe^3+] active units due to the relative difficulty in H2 O2 dehydrogenation,which accounts for its inferior catalytic efficiency for Fenton reaction.

关键词： Fenton reaction FeOCl Density functional theory H2O2 Active site

Evolution of Transitional Institutions for Urban Land Redevelopment in China——Case in Guangzhou

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Chinese Geographical Science 2009年第1期19卷 1-7页

作者： LIU xuan School of Geography and Planning SUN Yat-Sen University Guangzhou 510275 China

Building effective institutions for markets is a great challenge to China's transitional economy. China's experience in establishing urban land markets is characterized by trial and error and the gradual evolution of transitional institutions. Based on archive data and interviews in a neighborhood(Jinhuajie) of Guangzhou,this research reveals that China's land redevelopment in the past two decades has followed an approach of partial and gradual reform,which was structured by the gradual evolution of transitional institutions to speed up local land redevelopment within the existing property rights system. Transitional institutions,including highly compensated residents' land use rights,in-kind land lease payment,flexible control on development rights of developers and short-term actual ownership of work units,are generated by the local government sequentially to dispel existing land use rights of different land users and make further development be able to follow market mechanisms.

关键词： land redevelopment evolution of transitional institutions property rights Guangzhou

Light-Driven Dinitrogen Activation with Transition Metal Complexes:Mechanisms and Applications

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Chinese Journal of Chemistry 2023年第18期41卷 2400-2407页

作者： xuan-xuan Zhao Junnian Wei Zhenfeng Xi Bejing National Laboratory for Molecular Sciences Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of EducationCollege of Chemistryand Molecular EngineeringPeking UniversityBeijing 100871China

Comprehensive Summary,The Haber-Bosch process,which is used for ammonia(NH3)synthesis,requires vast amounts of energy,accounting for approximately 1%—2%of the world's annual energy ***,researchers in both industry and academia are interested in developing sustainable and environmentally friendly methods for synthesizing nitrogenous compounds at ambient conditions using renewable energy sources such as visible *** several examples of thermal activation of dinitrogen molecules have been demonstrated using various transition metals and ligand frameworks,the use of light to weaken or split the strong N—N bond has been less *** article presents an overview of molecular complexes capable of dinitrogen photocleavage and provides mechanistic insights into the photoactivation process through experimental and theoretical *** believe this review will provide readers with an in-depth understanding of the current state-of-the-art and future research perspectives,particularly in the use of visible light for dinitrogen activation and transformation.

关键词： Photochemistry N_(2)reduction Dinitrogen complexes Photoactivation Dinitrogen transformation Photoredox catalysis

Unimodality of Independence Polynomials of the Cycle Cover Product of Graphs

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Acta Mathematica Sinica,English Series 2022年第5期38卷 858-868页

作者： Bao xuan ZHU School of Mathematics and Statistics Jiangsu Normal UniversityXuzhou 221116P.R.China

An independent set in a graph G is a set of pairwise non-adjacent *** ik(G)denote the number of independent sets of cardinality k in *** its generating function I(G;x)=∑^(α(G))^(k=0)ik(G)x^(k),is called the independence polynomial of G(Gutman and Harary,1983).In this paper,we introduce a new graph operation called the cycle cover product and formulate its independence *** also give a criterion for formulating the independence polynomial of a *** on the exact formulas,we prove some results on symmetry,unimodality,reality of zeros of independence polynomials of some *** applications,we give some new constructions for graphs having symmetric and unimodal independence polynomials.

关键词： Independence polynomials unimodality log-concavity real zeros symmetry cycle cover product of graphs

Low lighting image enhancement using local maximum color value prior

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Frontiers of Computer Science 2016年第1期10卷 147-156页

作者： xuan DONG Jiangtao WEN Department of Computer Science and Technology Tsinghua University Beijing 100084 China

We study the problem of low lighting image en- hancement. Previous enhancement methods for images un- der low lighting conditions usually fail to consider the factor of image degradation during image formation. As a result, the lost contrast could not be recovered after enhancement. This paper will adaptively recover the contrast and adjust the exposure for low lighting images. Our first contribution is the modeling of image degradation in low lighting con- ditions. Then, the local maximum color value prior is pro- posed, i.e., in most regions of well exposed images, the lo- cal maximum color value of a pixel will be very high. By combining the image degradation model and local maximum color value prior, we propose to recover the un-degraded im- ages under low lighting conditions. Last, an adaptive expo- sure adjustment module is proposed to obtain the final result. We show that our approach enables better enhancement com- paring with popular image editing tools and academic algo- rithms.

关键词： low lighting enhancement image degradationmodel

Incompressible Limit of the Compressible Q-tensor System of Liquid Crystals

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Acta Mathematicae Applicatae Sinica 2023年第1期39卷 179-201页

作者： Yi-xuan WANG University of Pittsburgh PA 15260USA

We study the connection between the compressible Navier-Stokes equations coupled by the Qtensor equation for liquid crystals with the incompressible system in the periodic case, when the Mach number is low. To be more specific, the convergence of the weak solutions of the compressible nematic liquid crystal model to the incompressible one is proved as the Mach number approaches zero, and we also obtain the similar results in the stochastic setting when the equations are driven by a stochastic force. Our approach is based on the uniform estimates of the weak solutions and the martingale solutions, then we justify the limits using various compactness criteria.

关键词： compressible liquid crystal system Q-tensor weak solutions martingale solution stochastic compactness Mach number incompressible limit

A pixel-based outlier-free motion estimation algorithm for scalable video quality enhancement

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Frontiers of Computer Science 2015年第5期9卷 729-740页

作者： xuan DONG Jiangtao WEN Department of Computer Science and Technology Tsinghua University Beijing 100084 China

Scalable video quality enhancement refers to the process of enhancing low quality frames using high quality ones in scalable video bitstreams with time-varying qualities. A key problem in the enhancement is how to search for correspondence between high quality and low quality frames. Previous algorithms usually use block-based motion estimation to search for correspondences. Such an approach can hardly estimate scale and rotation transforms and always in- troduces outliers to the motion estimation results. In this paper, we propose a pixel-based outlier-free motion estimation algorithm to solve this problem. In our algorithm, the motion vector for each pixel is calculated with respect to estimate translation, scale, and rotation transforms. The motion relationships between neighboring pixels are considered via the Markov random field model to improve the motion estimation accuracy. Outliers are detected and avoided by taking both blocking effects and matching percentage in scale- invariant feature transform field into consideration. Experiments are conducted in two scenarios that exhibit spatial scalability and quality scalability, respectively. Experimental results demonstrate that, in comparison with previous algorithms, the proposed algorithm achieves better correspondence and avoids the simultaneous introduction of outliers, especially for videos with scale and rotation transforms.

关键词： motion estimation scalable video coding videosuper resolution.