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Purification of L-asparaginase II by.cry.tallization

1999年

作者： James G. Mann y. A. liu.

来源：畅想之星图书光盘版（南... 评论

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Frontiers of Chemical Science and Engineering 2013年第1期7卷 37-42页

作者： y. liu M. PIETZSCH J. ULRICH Thermal Process Engineering Center for Engineering Science Martin Luther University Halle-Wittenberg D-06099 Halle (Saale) Germany Department of Downstream Processing Institute of Pharmacy Faculty of Natural Sciences I Martin Luther University Halle-Wittenberg D-06099 Halle (Saale) Germany

Here a case study.ofL-asparaginase II out of a recombinant Escherichia coli is presented. The target protein was obtained by.simple cell disintegration and acetone precipitation. The L-asparaginase II has been cry.tallized in three different forms in the following microbatch cry.tallization. The rod-shaped cry.tals （-400 μm edge length） were obtained at either 8℃ or 22℃ after 17h by.addition of PEG6ooo. The rectangular-shaped cry.tals were obtained after further recry.tallization of the rod-shaped cry.tals. The rhombic-shaped cry.tals formed at 8℃ after 12 day. when cold ethanol was used instead of PEG6000. All cry.tallizations were performed in tris-acetate buffer （50mmol-L-1, pH 5.1）. By.cry.tallization, the specific activity.of L-asparaginase II has increased 5-fold. The protein content and the purity.of the cry.tals were evaluated by.sodium dodecy. sulfate poly.cry.amide gel electrophoresis （SDS-PAGE）. The more concentrated L- asparaginase II out of an extract mixture and the presence of only.less minor proteins after cry.tallization demonstrates that cry.tallization is an effective and mild method to purify.the target protein. The single cry.tal X-ray.diffraction pattern reveals that the cry.tals are proteins and the X-ray.powder diffraction （XRPD） pattern shows clearly.that the cry.tals forming in PEG600o and ethanol have different cry.tal structures.

关键词： protein cry.tallization L-asparaginase II purification

INVESTIGATION OF MULTI-STEP THERMO-MECHANICALTREATMENT OF CAN-FORGED TiAl-BASED ALLOy

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Acta Metallurgica Sinica(English Letters) 1997年第4期10卷 369-374页

作者： y.H. He B. y. Huang y. liu and y.X. liu (Powder Metallurgy.Research Institute, Central South University.of Technology. Changsha 410083, China) Central South Univ of Technology Changsha China

The effects of a new technology. multi-step thermo-mechanical treatment, on the microstructure, deformation substructure and mechanical properties at ambient and elevated tempemture of can-forged Ti-33 Al-3 Cr-0.5Mo (wt%) Alloy.were *** results show that, after multi-step thermo-mechanical treatment of can-forged specimens, homogeneous, fine microstructures can be obtained in the whole TiAl-based alloy.specimens. Furthermore, the specimen with homogeneous and fine full lamellae microstructure demonstrutes excellent comprehensive mechanical properties at ambient and elevated temperature.

关键词： TiAl-based alloy mechanical property heat treatment

INTERACTIONS BETWEEN La_(2)O_(3) PARTICLES AND DISLOCATIONS IN Mo-La_(2)O_(3) ALLOy.

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Acta Metallurgica Sinica(English Letters) 2005年第6期18卷 714-718页

作者： J.X. Zhang D.M. liu y. Q. liu M.L. Zhou T. y. Zuo The Key.Laboratory.of Advanced Functional Materials Ministry of EducationBeijing University of Technology Beijing 100022 China

The mechanical properties of moly.denum wires doped with different contents of La2O3 were investigated sy.tematicaUy.and the interaction between La2O3 particles with dislocations in Mo- La2O3 wires were observed by.SEM and TEM. It is shown that Mo-La2O3 wires possess much higher tensile strength than the pure Mo. In wires the dislocation motion is strongly.hindered by.La2O3 particles, which remains up to much higher temperature. Moreover, a number of prismatic dislocation loops and hexagonal dislocation network have been formed in annealed Mo-La2O3 wires. The higher strength of Mo-LazOs than the pure Mo is attributed to the La2O3 particles dispersion strengthening and dislocation strengthening.

关键词： moly.denum La2O3 dislocation strengthening

NUCLEATION OF RARE EARTH-RICH PHASE PARTICLES IN Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd ALLOy

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Acta Metallurgica Sinica(English Letters) 1998年第4期11卷 265-269页

作者： G.P.Li D.Li and y. y. liu (Department of Titanium Alloy., Institute of Metal Research, The Chinese Academy.of Sciences, Sheny.ng 110015, China) Inst of Metal Research The Chinese Acad of Sciences Shenyang China

High resolution electron microscopy.studies of rure earth-rich phase particles in a melt-quenched Ti-5Al-4Sn-2Zr-1MO-0.25Si-1Nd alloy.indicate that the α-Ti matrix cry.tallizes prior to the rare earth-rich phase particles. According to a new nucleation model, the heteropeneous nucleation of the rare earth-rich phase particles at the matrix interface is easier than the homogeneous nucleation off the interface matrix, which is consistent with the results of the HREM obseroations.

关键词： Ti alloy rure earth rich phase nucleation

ANALy.IS OF THREE-DIMENSIONAL UPSETTING PROCESS By.THE RIGID-PLASTIC REPRODUCING KERNEL PARTICLE METHOD

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Acta Metallurgica Sinica(English Letters) 2006年第5期19卷 371-378页

作者： y. H. liu J. Chen S. y. X. W. Chen National Die and Mould CAD Engineering Research Center Shanghai Jiao Tong UniversityShanghai 200030 China

A meshless approach, called the rigid-plastic reproducing kernel particle method （RKPM）, is presented for three-dimensional （3D） bulk metal forming simulation. The approach is a combination of RKPM with the flow theory.of 3D rigid-plastic mechanics. For the treatments of essential boundary.conditions and incompressibility.constraint, the boundary.singular kernel method and the modified penalty.method are utilized, respectively. The arc-tangential friction model is employ.d to treat the contact conditions. The compression of rectangular blocks, a ty.ical 3D upsetting operation, is analy.ed for different friction conditions and the numerical results are compared with those obtained using commercial rigid-plastic FEM （finite element method） software Deform^3D. As results show, when handling 3D plastic deformations, the proposed approach eliminates the need of expensive meshing and remeshing procedures which are unavoidable in conventional FEM and can provide results that are in good agreement with finite element predictions.

关键词： meshless reproducing kernel particle method(RKPM) three-dimensional upsetting incompressibility modified penalty.method

Hy.rid finite-discrete element modelling of asperity.degradation and gouge grinding during direct shearing of rough rock joints

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International Journal of Coal Science & Technology 2016年第3期3卷 295-310页

作者： H. y. liu Haoy. Han H. M. An J. J. Shi School of Engineering and ICT University of TasmaniaHobart TAS 7001 Australia School of Civil & Environmental Engineering University ofScience and Technology Beijing Beijing China

A hy.rid finite-discrete element method was implemented to study.the fracture process of rough rock joints under direct shearing. The hy.rid method reproduced the joint shear resistance evolution process from asperity.sliding to degradation and from gouge formation to grinding. It is found that, in the direct shear test of rough rock joints under constant normal displacement loading conditions, higher shearing rate promotes the asperity.degradation but constraints the volume dilation, which then results in higher peak shear resistance, more gouge formation and grinding, and smoother new joint surfaces. Moreover, it is found that the joint roughness affects the joint shear resistance evolution through influencing the joint fracture micro mechanism. The asperity.degradation and gouge grinding are the main failure micro-mechanism in shearing rougher rock joints with deeper asperities while the asperity.sliding is the main failure micro-mechanism in shearing smoother rock joints with shallower asperities. It is concluded that the hy.rid finite-discrete element method is a valuable numerical tool better than traditional finite element method and discrete element method for modelling the joint sliding, asperity.degradation, gouge formation, and gouge grinding occurred in the direct shear tests of rough rock joints.

关键词： Hy.rid FEM-DEM Rock joint Asperity.sliding Asperity.shearing Fragment grinding

NUMERICAL SIMULATION OF MOLTEN POOL AND CONTROL STRATEGy.OF KISS POINT IN A TWIN-ROLL STRIP CASTING PROCESS

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Acta Metallurgica Sinica(English Letters) 2008年第6期21卷 459-468页

作者： G.M. Cao C.G. Li Z. y. liu D. Wu G.D. Wang X.H. liu State Key.Laboratory.of Rolling ＆ Automation Northeastern University Shenyang 110004 China

Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by.three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by.simulations and the geometry.of molten pool, corresponding control strategy.is also proposed.

关键词： Twin-roll strip casting Coupled temperature and flow field Numerical simulation Kiss point Control strategy

Risk management for sulfur dioxide abatement under multiple uncertainties

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Frontiers of Earth Science 2016年第1期10卷 87-107页

作者： C. DAI W. SUN Q. TAN y. liu W.T. LU H.C. GUO College of Environmental Science and Engineering Peking University Beijing 100871 China Institute for Energy Environment and Sustainable Communities University of Reginal Regina Saskatchewan S4S 7H9 Canada College of Water Resources & Civil Engineering China Agricultural University Beijing 100083 China

In this study. interval-parameter programming, two-stage stochastic progranaming （TSP）, and conditional value-at-risk （CVaR） were incorporated into a general optimization framework, leading to an interval-parameter CVaR-based two-stage programming （ICTP） method. The ICTP method had several advantages：（i） its objective function simultaneously.took expected cost and risk cost into consideration, and also used discrete random variables and discrete intervals to reflect uncertain properties; （ii） it quantitatively.evaluated the right tail of distributions of random variables which could better calculate the risk of violated environmental standards; （iii） it was useful for helping decision makers to analy.e the trade-offs between cost and risk; and （iv） it was effective to penalize the second-stage costs, as well as to capture the notion of risk in stochastic programming. The developed model was applied to sulfur dioxide abatement in an air quality.management sy.tem. The results indicated that the ICTP method could be used for generating a series of air quality.management schemes under different risk-aversion levels, for identify.ng desired air quality.management strategies for decision makers, and for considering a proper balance between sy.tem economy.and environmental quality.

关键词： risk management conditional value-at-risk,interval optimization two-stage programming uncertainty.air quality.management

MODELING OF STRAIN-INDUCED PRECIPITATION KINETICS IN Nb MICROALLOy.D STEELS

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Acta Metallurgica Sinica(English Letters) 2006年第5期19卷 385-390页

作者： X. G. Zhou Z. y. liu D. Wu Z. Li C.M. Li State Key.Lab. of Rolling and Automation Northeastern University Shenyang 110004 China Baoshan Iron ＆ Steel Co. Ltd. Shanghai 201900 China Engineering ＆ Research Incorporation Limited WISDRI （Wuhan Iron ＆ Steel Design and

On the basis of the thermody.amic calculation of precipitation and considering the effect of strain on the precipitation behavior and chemical composition （Si and Mn）, the kinetics of precipitation from austenite has been investigated for different temperatures and strains. Nucleation theory.and the solubility.product of niobium, carbon, and nitrogen in austenite have been used to derive equations for the start time of precipitation as a function of temperature and composition. The value of n in Avrami equation was determined using the available experimental data from the published reports, which indicated that n is a constant independent of temperature and the end time of precipitation is a function of n and the start time of precipitation. The values of the start time and end time of precipitation predicted by.the new model are compared with the experimental values and a good agreement was obtained between both.

关键词： strain-induced precipitation start time of precipitation end time ofprecipitation precipitation kinetics