AM80-0.2Sr-1.5Ca镁合金高温压缩过程动态再结晶模拟

在Gleeble-1500热压缩实验机上对AM80-0.2Sr-1.5Ca镁合金进行高温压缩实验，得到了该合金在温度为300~450 ℃、应变速率为0.01~1 s-1条件下的流变应力曲线.结合改进的Laasraoui-Jonas（L-J）位错密度模型和Kock-Mecking（K-M）位错密度模型，获得AM80-0.2Sr-1.5Ca镁合金在改进的L-J位错密度模型中的应变硬化参数和应变软化参数，建立该合金的动态再结晶模型.利用DEFORM-3D软件，实现了对AM80-0.2Sr-1.5Ca镁合金在450 ℃热压缩实验时微观组织演变和位错密度变化过程的有限元模拟，并与实际热压缩实验微观组织进行对比.研究结果表明：在相同的温度和应变量下，应变速率较低时，AM80-0.2Sr-1.5Ca镁合金组织粗大且晶粒分布不均，随着应变速率增大，再结晶组织细小均匀模拟与实验结果一致，说明求解的应变硬化参数和应变软化参数准确，所建立的动态再结晶模型能准确预测该合金高温压缩过程动态再结晶过程.     

基于P300高性能BCI打字机的研究与实现

利用Gleeble-3800数字控制热/力模拟试验机研究了Q690低碳微合金钢在变形温度850~1150 ℃，应变速率0.01~30 s-1条件下的高温单道次压缩变形行为.建立了基于动态材料模型(DMM)的加工图，结合OM观察变形体微观组织确定了该钢种的高温热变形机制.结果表明：应变量0.7及以下的加工图中包含2个峰区(1 000~1 120 ℃，0.01~0.37 s-1和1 100~1 150 ℃，3.16~30 s-1)和3个加工失稳区(850~900 ℃，0.01~0.32 s-1和850~900 ℃，10~30 s-1以及1 000~1 085 ℃，1~30 s-1).应变量超过0.8的加工图包含2个峰区(1 025~1 100 ℃，0.01~0.38 s-1和1 100~1 150 ℃，3~30 s-1)，失稳区为低温(850~900 ℃，0.01~30 s-1)以及应变速率1 s-1以上的中低温度(850~1 100 ℃)范围，在这两个峰区峰值点附近的热变形显微组织为均匀的完全动态再结晶组织，因此，这两个区域均适合Q690钢的热加工变形.     

Pedogenic carbonate recrystallization assessed by isotopic labeling: a comparison of 13C and 14C tracers

The C isotopic composition (δ¹³C) of pedogenic carbonates reflects the photosynthetic pathway of the predominant local vegetation because pedogenic (secondary) CaCO₃ is formed in isotopic equilibrium with soil CO₂ released by root and rhizomicrobial respiration. Numerous studies show the importance of pedogenic carbonates as a tool for reconstructing paleoecological conditions in arid and semiarid regions. The methodological resolution of these studies strongly depends on the time scale of pedogenic carbonate formation, which remains unknown. The initial formation rate can be assessed by ¹⁴C labeling of plants grown on loess and subsequent incorporation of ¹⁴C from rhizosphere CO₂ into newly formed carbonate by recrystallization of loess CaCO₃. We tested the feasibility of ¹⁴C and ¹³C tracers for estimating CaCO₃ recrystallization rates by simultaneous ¹⁴C and ¹³C labeling and comparison with literature data. ¹⁴C labeling was more efficient and precise in assessing recrystallization rates than ¹³C labeling. This is connected with higher sensitivity of ¹⁴C liquid scintillation counting when compared with δ¹³C measurement by IRMS. Further, assessment of very low amounts of incorporated tracer is more precise with low background signal (natural abundance), which is true for ¹⁴C, but is rather high for ¹³C. Together, we obtained better reproducibility, higher methodological precision, and better plausibility of recrystallization rates calculated based on ¹⁴C labeling. Periods for complete CaCO₃ recrystallization, extrapolated from rates based on ¹⁴C labeling, ranged from 130 (125–140) to 240 (225–255) y, while it was ≈ 600 (365–1600) y based on the ¹³C approach. In terms of magnitude, data from late‐Holocene soil profiles of known age provide better fit with modeled recrystallization periods based on the ¹⁴C approach.     

植物抗冻蛋白及其高级结构研究进展

抗冻蛋白是一类能控制冰晶生长和抑制冰晶之间发生重结晶的蛋白质．并具有两种明显不同的活性——热滞活性和重结晶抑制活性．植物抗冻蛋白的抗冻特性是低热滞活性和高重结晶抑制活性．植物抗冻蛋白虽然在DNA和氨基酸水平上具有较大的差异-几乎没有同源性，但却拥有相似的高级结构．冰晶结合位点也有一定的相似性．而且都可以通过“表面互补”模型较好地解释它们与冰晶之间的相互作用．全面介绍了植物抗冻蛋白的种类及特性，以及它们的高级结构和冰晶结合位点．     

Improvement on Refining Process of Chloroquilonine Sulfate Monohydrate

Effects of solvents such as ethanol, isopropanol and acetone on the qualities of chloroquinoline sulfate such as color, clarity, melting point and crystalline form are studied in detail. The results indicat that a single solvent of ethanol or isopropanol makes end_product greenish with an indefinite melting point but an excellent clarity and a relatively high yield; a single solvent of acetone, however, greatly improved the color and the stability of melting point, but decreased the yield and the clarity. Based on the results above, the mixture of these solvents are required to get the optimum of this product. An optimum solvent composed of V (ethanol(95%)): V (acetone)=1:4 are determined and used to prepare chloroquinoline sulfate, whose qualities are up to BP93.     

冰糖规模化生产工艺探析

冰糖可以以精炼糖厂精炼车间的中间制品---精制糖浆为生产原料,也可以以白砂糖为原料,经过再溶、清净、重结晶生产工艺而制成。其有白色、微黄、微红、深红等色,结晶如冰状,故名为冰糖。因冰糖的成分是含结晶水的葡萄糖,与白糖在体内分解的成分一样,所以它可以代替白糖;又因为它的纯度较高,并拥有自身特有的食疗功效,所以其更优于白糖,在市场上颇具竞争力。目前中国规模化生产冰糖的企业并不多,文章从冰糖规模化生产方面论述冰糖的生产工艺。     

穿心莲内酯超临界CO2重结晶工艺初探

采用单因素实验法探讨超临界CO₂重结晶压力、温度、时间对穿心莲内酯的纯度和结晶率的影响，并借助扫描电镜进行晶体形貌考察，利用高效液相色谱仪进行纯度检测。结果表明，采用超临界CO₂重结晶技术得到的穿心莲内酯晶体形貌更加细小，并呈絮状分布在结晶板上；选择较佳纯化工艺参数为重结晶压力14 MPa，温度55℃，时间60 min，CO₂流量20 L/min时，得到的穿心莲内酯纯度达90%以上，结晶率超过45%。     

酶法生产α-熊果苷的纯化工艺

采用乙醇发酵去除酶法合成α-熊果苷反应液中大部分糖类杂质,以活性炭纤维吸附分离α-熊果苷,选择甲醇-乙酸乙酯混合溶剂重结晶精制。结果表明,50%乙醇溶液洗脱部分α-熊果苷含量最高,此部分经甲醇-乙酸乙酯混合溶剂反复重结晶精制,可制备得到α-熊果苷无色针状结晶,HPLC检测纯度达到99%以上,收率达到80%。该工艺简单可行,稳定性高、重复性好,适合大规模制备高纯度α-熊果苷。     

The structure of local transgranular deformation in polycrystalline pure aluminium

The micro hardness method was used to achieve plastic deformation in grain scales in polycrystalline pure aluminums. Characteristics of the deformation structure near indentations were investigated before and after annealing. The different morphologies of slipbands near indentation areas were viewed only after annealing. Within the slipband areas the numerous orderly arranged ends of the dislocations were identified. During experiments, we observed the phenomenon of slipbands across aggregate areas in grains. We discuss reasons for not discovering recrystallization in the deformed specimen after annealing. We also discuss factors such as temperature and time of annealing, reduction and grain orientation, which have influence on the formation of slipbands. The experimental results show that, being different from global deformation for materials, the mode of transgranular deformation can be used conveniently to study the morphological features of deformation and recrystallization of polycrystalline materials and related influencing factors.      

Antifreeze Peptides and Glycopeptides,and Their Derivatives: Potential Uses in Biotechnology

Antifreeze proteins (AFPs) and glycoproteins (AFGPs), collectively called AF(G)Ps, constitute a diverse class of proteins found in various Arctic and Antarctic fish, as well as in amphibians, plants, and insects. These compounds possess the ability to inhibit the formation of ice and are therefore essential to the survival of many marine teleost fishes that routinely encounter sub-zero temperatures. Owing to this property, AF(G)Ps have potential applications in many areas such as storage of cells or tissues at low temperature, ice slurries for refrigeration systems, and food storage. In contrast to AFGPs, which are composed of repeated tripeptide units (Ala-Ala-Thr)_n with minor sequence variations, AFPs possess very different primary, secondary, and tertiary structures. The isolation and purification of AFGPs is laborious, costly, and often results in mixtures, making characterization difficult. Recent structural investigations into the mechanism by which linear and cyclic AFGPs inhibit ice crystallization have led to significant progress toward the synthesis and assessment of several synthetic mimics of AFGPs. This review article will summarize synthetic AFGP mimics as well as current challenges in designing compounds capable of mimicking AFGPs. It will also cover our recent efforts in exploring whether peptoid mimics can serve as structural and functional mimics of native AFGPs.