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Recruitment and reinforcement: maintaining epigenetic silencing

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Science China(Life Sciences) 2018年第5期61卷 515-522页

作者： chengzhi wang Bing Zhu Jun Xiong National Laboratory of Biomacromolecules CAS Center for Excellence in Biomacromolecules Institute of BiophysicsChinese Academy of Sciences College of Life Sciences University of Chinese Academy of Sciences

Cells need to appropriately balance transcriptional stability and adaptability in order to maintain their identities while responding robustly to various stimuli. Eukaryotic cells use an elegant "epigenetic" system to achieve this functionality. "Epigenetics" is referred to as heritable information beyond the DNA sequence, including histone and DNA modifications, nc RNAs and other chromatin-related components. Here, we review the mechanisms of the epigenetic inheritance of a repressive chromatin state,with an emphasis on recent progress in the field. We emphasize that(i) epigenetic information is inherited in a relatively stable but imprecise fashion;(ii) multiple cis and trans factors are involved in the maintenance of epigenetic information during mitosis; and(iii) the maintenance of a repressive epigenetic state requires both recruitment and self-reinforcement *** mechanisms crosstalk with each other and form interconnected feedback loops to shape a stable epigenetic system while maintaining certain degrees of flexibility.

关键词： heterochromatin heterochromatin maintenance polycomb H3K27me3 H3K9me2/3

Phase field modeling of dendrite growth

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Acta Metallurgica Sinica(English Letters) 2009年第3期22卷 197-201页

作者： Yutuo ZHANG chengzhi wang Dianzhong LI Yiyi LI Shenyang Ligong University Shenyang 110168 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Single dendrite and multi-dendrite growth for Al-2 mol pct Si alloy during isothermal solidification are simulated by phase field method. In the case of single equiaxed dendrite growth, the secondary and the necking phenomenon can be observed. For multi-dendrite growth, there exists the competitive growth among the dendrites during solidification. As solidification proceeds, growing and coarsening of the primary arms occurs, together with the branching and coarsening of the secondary arms. When the diffusion fields of dendrite tips come into contact with those of the branches growing from the neighboring dendrites, the dendrites stop growing and being to ripen and thicken.

关键词： Phase field modeling Dendrite growth Al-Si alloy Isothermal solidification

Co-or Ni-modified Sn-MnO_(x) low-dimensional multi-oxides for high-efficient NH_(3)-SCR De-NO_(x):Performance optimization and reaction mechanism

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Journal of Environmental Sciences 2022年第3期34卷 204-218页

作者： Fengyu Gao Chen Yang Xiaolong Tang Honghong Yi chengzhi wang School of Energy and Environmental Engineering University of Science and Technology BeijingBeijing 100083China Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants University of Science and Technology BeijingBeijing 100083China

NH_(3)-SCR performances were explored to the relationship between structure morphology and physio-chemical properties over low-dimensional ternary Mn-based catalysts prepared by one-step synthesis *** to its strong oxidation performance,Sn-MnO_(x) was prone to side reactions between NO,NH_(3)and O_(2),resulting in the generation of more NO_(2)and N_(2)O,here most of N_(2)O was driven from the non-selective oxidation of NH_(3),while a small part generated from the side reaction between NH_(3)and NO_(2).Co or Ni doping into Sn-MnO_(x) as solid solution components obviously stronged the electronic interaction for actively mobilization and weakened the oxidation performance for signally reducing the selective tendency of side reactions to N_(2)*** optimal modification resulted in improving the surface area and enhancing the strong interaction between polyvalent cations in Co/Ni-Mn-SnO_(2)to provide more surface adsorbed oxygen,active sites of Mn^(3+) and Mn^(4+),high-content Sn^(4+) and plentiful Lewis-acidity for more active intermediates,which significantly broadened the activity window of Sn-MnOx,improved the N^(2) selectivity by inhibiting N_(2)O formation,and also contributed to an acceptable resistances to water and *** low reaction temperatures,the SCR reactions over three catalysts mainly obeyed the typical Elye-rideal(E-R)routs via the reactions of adsorbed L-NH_(x)(x=3,2,1)and B-NH_(4)^(+) with the gaseous NO to generate N_(2) but also N_(2)O *** for the above basic E-R reactions,as increasing the reaction temperature,the main adsorbed NO_(x)-species were bidentate nitrates that were also active in the Langmuir-Hinshelwood reactions with adsorbed L-NH_(x) species over Co/Ni modified Mn-SnO_(2) catalyst.

关键词： Low-dimensional catalysts One-step synthesis Mn-SnO_(2)nanosheet Ni or Co modification SCR performances Promotional mechanism

Analysis of antibiotic resistance of Escherichia coli isolated from the Yitong River in North-east China

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Frontiers of Environmental Science & Engineering 2019年第3期13卷 127-135页

作者： Yangyang Yu Xiaolin Zhu Guanlan Wu chengzhi wang Xing Yuan School of Environment Northeast Normal University Changchun 130117 China

The Yitong River is one of the largest secondary tributaries of the Songhua River. The area where the Yitong River flows is densely populated and contains the livestock and poultry breeding areas of northeast China. These areas introduce a high risk of antibiotic contamination. In this study, the concentrations of four types of typical antibiotics including quinolones, tetracyclines, sulfonamides, and trimethoprim were determined by solid phase extraction-high performance liquid chromatography. The antibiotic resistance of Escherichia coli caused by antibiotic pollution was investigated. The concentration of total coliforms in the Yitong River was detected by the plate counting method. The antibiotic resistance of E. coli to quinolones, tetracyclines, sulfonamides, and trimethoprim was analyzed by the Kirby-Bauer method. The results showed that the concentration of total coliforms in the summer was higher than that in the spring. There was a seasonal difference in the resistance rate of E. coli to antibiotics except trimethoprim. The antibiotic resistance to fluoroquinolones was relatively low. The resistance rate to tetracyclines was higher during the summer. Moreover, resistance to several antibiotics was observed in all sections. This study provides basic data for research on pollution characteristics and prevention of antibiotic exposure in rivers.

关键词： Yitong River Coliform bacteria Antibiotic resistance Escherichia coli

Parameters Sensitivity Analysis and Correction for Concrete Damage Plastic Model

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Journal of Beijing Institute of Technology 2018年第1期27卷 103-108页

作者： Yaqin Jiang Pengfei Xu chengzhi wang Dianshu Liu School of Mechanics and Civil Engineering China University of Mining and Technology College of Civil Engineering and Architecture Henan University of Technology School of Materials Science and Engineering Beijing Institute of Technology

In order to understand the effect of hardening ductility parameters and softening ductility parameters of the concrete damage plastic model in LS-DYNA,a sensitivity and reliability analysis of these parameters through a convenient cube unit test was conducted. The results showed that the peak strength strain was independent of the hardening ductility parameter DH,but affected by AH,BH,and CH. The softening ductility was mainly related to the softening ductility parameter AS,but not affected by the damage ductility exponent BS. In case that the model with default parameters failed to match the AS-controlled damage softening phase,an optimized model with an AS correction was developed. The corrected model with the AS value of 2 matched well with the code model,and exhibited good feasibility in predicting the stress-strain curve of different grades of concrete. Moreover,the practicability of the corrected model was further validated by the conventional triaxial test. The simulated curve exhibited favorable consistence with the trial curve. Therefore,the model with parameter correction could provide a prospective reference for predicting the mechanical properties of concrete.

关键词： damage-plastic model concrete sensitivity analysis parameter correction

New filling system design for bolster casting and computer simulation

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China Foundry 2010年第4期7卷 349-351页

作者： Zhang Yutuo Li Guimao Zhang Wanning wang chengzhi Shenyang Ligong University Shenyang 110159 China Key Laboratory of National Education Ministry for Electromagnetic Processing of Material Northeastern University Shenyang 110004 China Shenyang Government Investment Project Evaluation Center Shenyang 110014 China

The new filling system is smooth filling without gas gap. It works well in avoiding the generation of defects such as porosity and inclusion. The pouring basin, sprue, runner and the gate of the bolster casting were designed according to the principle of the new filling system. The filling and solidifciation process of the bolster casting were also simulated. It was found that the filling process was smooth, and air entrapment and shrinkage were avoided. Finally, a further validation of the new filling system of bolster casting was carried out in a foundry.

关键词： new filling system bolster casting filling and solidifciation computer simulation

Phase field modeling of dendritic coarsening during isothermal solidification

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China Foundry 2011年第3期8卷 313-315页

作者： Zhang Yutuo Zhang Wanning wang Tie Fan Liyan wang chengzhi Shenyang Ligong University Shenyang 110159 China Shenyang Government Investment Project Evaluation Center Shenyang 110014 China Dalian Jinzhou Cable Co. Ltd. Liaoning Baolin Group Dalian 116100 China

Dendritic coarsening in AI-2mol%Si alloy during isothermal solidification at 880K was investigated by phase field modeling. Three coarsening mechanisms operate in the alloy：（a） melting of small dendrite arms; （b） coalescence of dendrites near the tips leading to the entrapment of liquid droplets; （c） smoothing of dendrites. Dendrite melting is found to be dominant in the stage of dendritic growth, whereas coalescence of dendrites and smoothing of dendrites are dominant during isothermal holding. The simulated results provide a better understanding of dendrite coarsening during isothermal solidification.

关键词： phase field dendritic coarsening Al-Si alloy isothermal solidification

Model Test and Numerical Analysis on Long-Term Mechanical Properties of Stepped Reinforced Retaining Wall

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Transactions of Tianjin University 2012年第1期18卷 62-68页

作者： wang chengzhi LUAN Maotian ZHU Zeqi School of Civil Engineering Dalian University of TechnologyDalian 116024China School of River and Ocean Engineering Chongqing Jiaotong UniversityChongqing 400074China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China

Model tests and numerical analyses of stepped reinforced retaining wall were performed to investigate the effects of rheology of backfill and creep of geogrids on the long-term performance of the *** geogrid tensions,soil pressures,wall deformations and foundation pressure were measured during model construction and loading.A visco-elasto-plastic model and an empirical nonlinear visco-elastic model were utilized to simulate the stresses and deformations of geogrid-reinforced earth-retaining wall under long-term *** comparing test data with numerical results,it is shown that the foundation pressure distribution is nonlinear,and the lateral constraint of geogrids for backfill can cause a redistribution of foundation *** curve of soil pressure is outside convex at each step initially,and it is close to the distribution for the case of vertical wall *** variation trend of geogrid tensions at different heights is ***,the failure mechanism and development mode of potential slip surface in retaining wall are proposed.

关键词： model test geogrid stepped reintbrced retaining wall finite element method visco-elasto-plasticity model

Phase field modeling of multiple dendrite growth of Al-Si binary alloy under isothermal solidification

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China Foundry 2008年第4期5卷 265-267页

作者： Sun Qiang Zhang Yutuo Cui Haixia wang chengzhi Shenyang Ligong University Shenyang 110168 China

Phase field method offers the prospect of being able to perform realistic numerical experiments on dendrite growth in metallic systems. In this study, the growth process of multiple dendrites in AI-2-mole-%-Si binary alloy under isothermal solidification was simulated using phase field model. The simulation results showed the impingement of arbitrarily oriented crystals and the competitive growth among the grains during solidification. With the increase of growing time, the grains begin to coalesce and impinge the adjacent grains. When the dendrites start to impinge, the dendrite growth is obviously inhibited.

关键词： phase field model multiple dendrite growth binary alloy isothermal solidification