重组毕赤酵母高密度发酵表达水蛭素过程中产物的生成和降解

目的　研究重组毕赤酵母高密度发酵表达水蛭素过程中产物的生成和降解。方法　通过质谱和氨基酸序列分析确定水蛭素的 4种活性异构体 ,再用HPLC监测发酵过程中水蛭素的降解情况。结果　发酵过程中产生了 4种具有较高比活的水蛭素异构体 ,它们分别是目的产物水蛭素Hir6 5及Hir6 5的C 末端降解 1～ 3个氨基酸的产物。发酵时细胞干重达到 16 2g/L ,水蛭素的总活性一直在增加 ,最高为 2 .4 5× 10 4ATU/ml,相当于总产量1.8g/L。但Hir6 5在 4种水蛭素异构体总量中的比例一直在下降。Hir6 5的产量先升高再降低 ,最高为 2 80mg/L。结论　毕赤酵母发酵过程中水蛭素存在降解 ,Hir6 5降解产生了Hir6 2和Hir6 3。     

Syntheses and Properties of Novel Copolymers of Polylactide and Aliphatic Polycarbonate Based on Ketal-Protected Dihydroxyacetone

The novel random copolymers of L-LA and 2, 2-ethylenedioxy-1, 3-propanediol carbonate (EOPDC) were synthesized in bulk using Sn(Oct)₂ as a catalyst. The poly(EOPDC -co- L-LA)s obtained were characterized by FT IR, ¹H NMR, ¹³C NMR, GPC and DSC. The copolymers were obtained with yield of 87.9–95.6%. The number average molecular weight of the copolymer is 1.85–6.18 × 10⁴ with a polydispersity of 1.41–1.73. The properties of the copolymer including the enzymatic degradation by proteinase K and drug-controlled release property were also investigated. The results show that the degradation rate of the copolymers increases with increasing LA content in the copolymers.     

Control on the topological structure of polyolefin elastomer by reactive processing

The feasibility of preliminary tailoring of the long chain branched (LCB) polymer through complex flow field was evaluated in the torque rheometer, for the reaction of melt polyolefin elastomer (POE) with peroxides at elevated temperatures. With the compensation of temperature, the strength of complex shear flow could be the only factor affecting the reaction kinetics and mechanism. The results of sample characterization by the rheological and dilute polymer solution methods indicated that the degradation mainly made the length of LCB arm shorter and shorter as the rotational speed increases. Extremely, a certain amount of LCB degraded to be linear chains again due to the scission approaching the branching point at intense mixing condition. One new LCB index (D_LCB) was defined from nonlinear oscillatory shear, and a nearly linear relationship between it and long chain branching index (LCBI) was found, which can be a map to quantify LCB level by Fourier Transform Rheology (FTR).     

Long-term tests of a Jülich planar short stack with reversible solid oxide cells in both fuel cell and electrolysis modes

A two-cell planar stack in the Jülich F-design with solid oxide cells has been built and the reversible operation between fuel cell and electrolysis modes has been demonstrated. The cells were anode supported cells (ASC) with yttria-stabilized zirconia (YSZ) electrolytes, Ni/YSZ hydrogen electrodes and perovskite oxygen electrodes with lanthanum strontium cobalt ferrite (LSCF). This paper summarizes and discusses the preliminary experimental results on the long-term aging tests of the reversible solid oxide planar short stack for fuel cell operation (4000 h) at a current density of 0.5 A cm⁻² which shows a degradation of 0.6% per 1000 h and for steam electrolysis operation (3450 h) and co-electrolysis operation of CO₂ and H₂O (640 h) under different current densities from −0.3 to −0.875 A cm⁻² which show different degradation rates depending on current density and on steam or co-electrolysis.     

多孔Fe-Mn合金表面微纳形貌调控及其生物相容性评价

铁基可降解金属因其良好的生物相容性和优异的机械性能,在骨科植入物领域具有广阔的应用前景,但必须突破其降解速率过慢的瓶颈问题。本研究通过电化学技术对3D打印多孔铁锰合金(Fe-30Mn)支架表面进行去合金化处理。通过扫描电镜观察发现,以盐酸和氯化钠分别作为去合金化处理介质溶液,可以在支架表面形成多微孔网络结构和片状纳米结构。接触角和粗糙度测试显示,2种微纳结构的构建均显著改善了Fe-30Mn支架表面亲水性,并提升了其表面粗糙度,多微孔网络结构更加粗糙并且亲水性更好。利用静态浸泡法和电化学耐腐蚀实验评估合金化处理前后支架的腐蚀速率,发现表面微纳结构的形成可加速Fe-30Mn支架的降解。建立体外成骨细胞培养模型,通过激光共聚焦观察及细胞增殖测试发现,经合金化处理的2种支架均能支撑细胞的贴附和增殖,具有良好的细胞相容性。结果表明,经电化学去合金化处理后,Fe-30Mn支架的降解速度得以增强,同时保持了良好的生物相容性,有望在骨修复领域得到较好应用。     

Irreversible dilation of NaCl contaminated lime-cement mortar due to crystallization cycles

The mechanism of damage occurring in NaCl contaminated materials has not been clarified yet. Apart from crystallization pressure, other hypotheses have been proposed to explain the cause of decay. Irreversible dilation has been observed in a few cases but has never been studied in a more systematic way. The aim of the research is to contribute to the modeling of this phenomenon.In the present paper the effect of NaCl on the hydric and hygric behavior of a lime-cement mortar is extensively studied. The results indicate that NaCl influences the hydric and hygric dilation behavior of the material. The material contaminated with NaCl shrinks during dissolution and dilates during crystallization of the salt. This dilation is irreversible and sufficient to damage the material after few dissolution/crystallization cycles. This behavior is not restricted to NaCl, but is observed in the presence of other salts as well (NaNO₃ and KCl). Outcomes of electron microscopy studies suggest that salts causing irreversible dilation tend to crystallize as layers on the pore wall.     

Miscibility and hydrolytic degradation in alkaline solution of poly(l-lactide) and poly(methyl methacrylate) blends

Poly(l-lactide) (PLLA) was melt blended with poly(methyl methacrylate) (PMMA) using a two-roll mill. The miscibility and hydrolytic degradation of the blend films were characterized. It was found that PLLA/PMMA blend has high miscibility in the amorphous state because only single T_g was observed in the DSC and DMA measurements. In alkaline solution, the hydrolytic degradation rate of the blends whose PMMA content is higher than 30 wt% was decelerated while the rate of the blends whose PMMA content is lower than 30 wt% was accelerated. That is, the hydrolytic degradation rate of the blends could be widely controlled by PMMA content in the blend. It was also found that only PLLA was hydrolyzed and eluted into alkaline solution, while PMMA remained during alkaline hydrolysis.     

Decolorization of methylene blue by heterogeneous Fenton reaction using Fe3−xTixO4 (0 ≤ x ≤ 0.78) at neutral pH values

In this work, a series of Fe_3−xTi_xO₄ (0 ≤ x ≤ 0.78) was synthesized using a new soft chemical method. The synthetic Fe_3−xTi_xO₄ were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, thermogravimetric and differential scanning calorimetry (TG–DSC) analyses. The results showed that they were spinel structures and Ti was introduced into their structures.Then, decolorization of methylene blue (MB) by Fe_3−xTi_xO₄ in the presence of H₂O₂ at neutral pH values was studied using UV–vis spectra, dissolved organic carbon (DOC) and element C analyses. Furthermore, the degradation products remained in reaction solution after the decolorization were identified using ionic chromatography (IC), ¹³C nuclear magnetic resonance spectra (NMR), liquid chromatography and mass spectrometry (LC–MS). Although small amounts of MB were mineralized, the aromatic rings in MB were destroyed completely after the decolorization. Decolorization of MB by Fe_3−xTi_xO₄ in the presence of H₂O₂ was promoted remarkably with the increase of Ti content in Fe_3−xTi_xO₄ due to the enhancement of both adsorption and degradation of MB on Fe_3−xTi_xO₄.     

Degradation of phthalate esters in an activated sludge wastewater treatment plant

Efficient removal of phthalate esters (PE) in wastewater treatment plants (WWTP) is becoming an increasing priority in many countries. In this study, we examined the fate of dimethyl phthalate (DMP), dibutyl phthalate (DBP), butylbenzyl phthalate (BBP), and di-(2-ethylhexyl) phthalate (DEHP) in a full scale activated sludge WWTP with biological removal of nitrogen and phosphorus. The mean concentrations of DMP, DBP, BBP, and DEHP at the WWTP inlet were 1.9, 20.5, 37.9, and 71.9 μg/L, respectively. Less than 0.1%, 42%, 35%, and 96% of DMP, DBP, BBP, and DEHP was associated with suspended solids, respectively. The overall microbial degradation of DMP, DBP, BBP, and DEHP in the WWTP was estimated to be 93%, 91%, 90%, and 81%, respectively. Seven to nine percent of the incoming PE were recovered in the WWTP effluent. Factors affecting microbial degradation of DEHP in activated sludge were studied using [U-¹⁴C-ring] DEHP as tracer. First order rate coefficients for aerobic DEHP degradation were 1.0×10⁻², 1.4×10⁻², and 1.3×10⁻³ at 20, 32, and 43 °C, respectively. Aerobic degradation rates decreased dramatically under aerobic thermophilic conditions (<0.1×10⁻² h⁻¹ at 60 °C). The degradation rate under anoxic denitrifying conditions was 0.3×10⁻² h⁻¹, whereas the rate under alternating conditions (aerobic-anoxic) was 0.8×10⁻² h⁻¹. Aerobic DEHP degradation in activated sludge samples was stimulated 5-9 times by addition of a phthalate degrading bacterium. The phthalate degrading bacterium was isolated from activated sludge, and maintained a capacity for DEHP degradation while growing on vegetable oil. Collectively, the results of the study identified several controls of microbial PE degradation in activated sludge. These controls may be considered to enhance PE degradation in activated sludge WWTP with biological removal of nitrogen and phosphorus.     

Reliability of multilayer ceramic capacitors with nickel electrodes

The reliability of multilayer ceramic capacitors (MLCCs) with Ni internal electrodes has been studied trom the viewpoint of partial oxygen pressure (P_O2) during firing. It is shown that the load-life time of the insulation resistance (1R) was prolonged by firing under low Po₂ annealing after firing, and the addition of dopants. It is also shown that the generation of oxygen vacancies led to the degradation of IR. Annealing treatment for the oxidation of the dielectric body accelerates the dielectric aging of MLCCs. It is found that the appropriate control of the P_O2 during firing can improve the reliability of MLCCs with Ni electrodes to a level as high as that of MLCCs with precious metal electrodes. Thus, we have developed an MLCC with Ni electrodes that features high reliability and a large capacitance of 10 μF for the Y5V characteristic and 4.7 μF for the X7R characteristic, both in the case of the C3216 (3.2 mm × 1.6 mm × 1.4 mm) form.