Influence of pH on recombinant human growth hormone production by Pichia pastoris

BACKGROUND: Effect of pH on recombinant human growth hormone (rhGH) production by Pichia pastoris hGH‐Mut⁺ was investigated at pH = 4.2, 5.0, 5.5, and 6.0. RESULTS: The highest cell concentration was obtained at pH = 6.0 with 53 g L^?1, while the highest rhGH concentration was attained at pH = 5.0 as 0.27 g L^?1. Total protease secretion increased with increase in pH and with the cultivation time. Oxygen uptake rate increased with increasing pH up to pH = 6.0, having the maximum value, 37 mmol m^?3 s^?1, at pH = 5.5. K_La values were similar at all the conditions, having a maximum value of 0.14 s^?1 at pH = 5.0. Taking the final rhGH concentration into account, the most favourable pH was 5.0; where AOX1 expression level showed a similar trend to AOX activity profiles, having the highest value of 9.4 × 10¹⁰ copy mg^?1 CDW at t = 15 h; in parallel to AOX1 expression profile, hGH expression level increased until t = 15 h, with the highest value of 4.0 × 10¹⁰ copy mg^?1 CDW, where a sharp increase in rhGH concentration was obtained. The expression levels of pep4, prb1 and prc1 genes, responsible from the production of proteinase A, proteinase B and, carboxypeptidase Y, were parallel to each other. CONCLUSION: Since it was shown that pH is a crucial operating parameter in fermentation processes using P. pastoris, keeping pH constant at its determined optimum value, pH = 5.0, during the bioprocess is vital in terms of recombinant protein production. Copyright © 2010 Society of Chemical Industry     

病险水工建筑物可靠性评估方法初探

 水工建筑物可靠性评估是水利工程管理中急需解决的问题，将水工建筑物分解为由分部工程组成的层次结构，引入子系统概率重要性系数，用层次分析法导出水工建筑物系统可靠度指标的实用计算方法。     

涉水工程装备用聚合物摩擦副材料改性技术研究进展

聚合物作为摩擦副材料在涉水工程装备上应用前景广阔,然而与金属材料相比,聚合物材料存在强度低、蠕变、老化以及吸水等固有缺陷,并且在低速重载工况下难以形成完整的润滑水膜而导致零部件出现严重的磨损与振动问题,随着涉水工程装备运动副所面临复杂多样的极端环境和苛刻工况,极大地限制了聚合物材料作为摩擦副部件在涉水工程装备领域的应用。分析了聚合物材料在涉水极端环境中的主要摩擦学问题和面临的挑战,并从辐照与等离子体表面改性技术、填料共混复合改性技术、织构化表面调控技术,以及功能化水润滑表面调控技术4个方面,综述目前国内外关于涉水工程装备用聚合物摩擦副材料改性技术的研究进展,最后对涉水工程装备用聚合物摩擦副材料的制备技术和摩擦学研究方向进行总结和展望。     

符号资本在大学社会评价中的作用

大学社会评价是高等教育评价体系中重要的一环,它可以满足政府之外社会上其他利益相关者对高校的认知需要。目前,由于诸多大学排行榜无视大学的符号资本,已陷入了纯粹＂数字游戏＂的误区。然而,符号资本在大学社会评价体系中有着极为重要的作用,它不但是大学社会评价与大学学科评估界分的基础,更是大学社会评价合法性与公信力的保障;它能更好地解决不同类型大学之间的比较,更公允地评价特色大学和不同规模的大学。理解符号资本在大学社会评价中的作用,有利于帮助大学排名走出误区,促进大学社会评价的发展。     

Estimation of the soil parameters in Balçova region using multiple geophysical approach

This study aimed to reveal the soil properties in the research area by using various geophysical methods. Physical parameters determining soil characteristics give us a chance to approach how the soil behaves during an earthquake. Thus, precautions can be taken to minimize earthquake damage. Also, safe construction against earthquake effects is important. The studied area is a tectonically and geothermally active area. İzmir Fault zone is passing through the investigation area and trending E–W direction. To investigate soil parameters at this active tectonic region, microtremor method data were recorded and the multichannel analysis of surface waves (MASW) method at 27 profiles was implemented in the study area. Additionally, these methods were supported by the spatial auto correlation (SPAC) method in center spot. Shear wave velocities up to 30 m, soil classification according to the National Earthquake Hazards Reduction Program (NEHRP), site amplification, predominant site period, amplification factor, ground vulnerability index, and shear wave velocity changes up to 300 m were obtained by evaluating the data collected from the applied geophysical methods. V_S30 values varied between 700 and 1100 m/s in the southernmost part of the study area, corresponding to a C and B type as soil classification. While the predominant period values were taken as the lowest value of 0.2 s, it was observed to increase up to 5.5 s on the alluvial unit in the northern parts of the study area. The ground vulnerability index, which is directly related to the probability of earthquake damage, was found to be quite high in some parts of the study area. In this paper, we propose microzonation maps for the Balçova district, based on the variation of the soil dynamic parameters.

     

Neutronic study on the effect of first wall material thickness on tritium production and material damage in a fusion reactor

In this study, the effects of changing first wall materials and their thicknesses on a reactor were investigated to determine the displacement per atom（DPA） and gas production（helium and hydrogen） in the first wall, as well as the tritium breeding ratio（TBR） in the coolant and tritium breeding zones. Therefore, the modeling of the magnetic fusion reactor was determined based on the blanket parameters of the International Thermonuclear Experimental Reactor（ITER）. Stainless steel（SS 316 LNIG）, Oxi...     

Construction of Microfluidic Chip Structure for Cell Migration Studies in Bioactive Ceramics

Cell migration is an essential bioactive ceramics property and critical for bone induction, clinical application, and mechanism research. Standardized cell migration detection methods have many limitations, including a lack of dynamic fluid circulation and the inability to simulate cell behavior in vivo. Microfluidic chip technology, which mimics the human microenvironment and provides controlled dynamic fluid cycling, has the potential to solve these questions and generate reliable models of cell migration in vitro. In this study, a microfluidic chip is reconstructed to integrate the bioactive ceramic into the microfluidic chip structure to constitute a ceramic microbridge microfluidic chip system. Migration differences in the chip system are measured. By combining conventional detection methods with new biotechnology to analyze the causes of cell migration differences, it is found that the concentration gradients of ions and proteins adsorbed on the microbridge materials are directly related to the occurrence of cell migration behavior, which is consistent with previous reports and demonstrates the effectiveness of the microfluidic chip model. This model provides in vivo environment simulation and controllability of input and output conditions superior to standardized cell migration detection methods. The microfluidic chip system provides a new approach to studying and evaluating bioactive ceramics.     

Dark fermentative hydrogen production from sucrose and molasses

There are many factors affecting the dark fermentative hydrogen production. The interaction of these factors, that is, their combined effects, should be investigated for better design of the systems with stable and higher hydrogen yields. This study aimed to investigate the combined effects of initial substrate, pH, and biomass (or initial substrate to biomass) values on hydrogen production from sucrose and sugar‐beet molasses. Therefore, optimum initial chemical oxygen demand (COD), pH, and volatile suspended solids (VSS) or initial substrate to biomass (VSS) ratio (S/X_o) values leading to the highest dark fermentative hydrogen production were investigated in batch reactors. An experimental design approach (response surface methodology) was used. Results revealed that when sucrose was the substrate, maximum hydrogen production yield (HY) of 2.3 mol H₂/mol sucrose_added was obtained at initial pH of 7 and COD of 10 g/L. Initial S/X_o values studied (4–20 g COD/g VSS) had no effect on HY, while the initial pH was found as the parameter mostly affecting both HY and hydrogen production rate (HPR). When substrate was molasses, initial COD concentration was the only variable affecting HY and HPR. Maximum of both was achieved at 10 g/L initial COD. Initial VSS values studied (2.5–7.5 g/L) had no effect on HPR and HY. This study also indicated that molasses leads to homoacetogenesis for potentially containing intrinsic microorganism and/or natural constituents; thus, sucrose is more advantageous for hydrogen production via fermentation. Homoacetogenesis should be prevented for effective optimization via response surface methodology, if substrate is a natural carbon source potential to have intrinsic microorganisms. Copyright © 2017 John Wiley & Sons, Ltd.     

带高速电流舵DAC的直接数字频率合成器

本文给出了一种高速SiGe BiCMOS直接数字频率合成器设计。该数字频率合成器单片集成了高速DDS数字核,10位差分电流舵 DAC,串/并接口和时钟控制逻辑。芯片采用0.35μm SiGe BiCMOS标准工艺流片,工作在1GHz系统频率。测试结果显示,该DDS能够生成高达400+ MHz的捷变模拟sine波形。     

Test bed for power amplifier behavioral characterization and modeling

Traditional test bed of power amplifier (PA) behavioral characterization and modeling based on vector signal analyzer (VSA) and often equipped with specialized software is both expensive and inflexible to modify to suit different scenarios. In this paper, a new test bed based on an oscilloscope or other general purpose data acquisition systems, which works as analog to digital converter (ADC) with a proper (radio frequency) RF bandwidth and maximum sampling rate, is proposed. The common impairments, e.g. transmitter IQ imbalances, channel delay, frequency offset, and carrier phase offset, are all well compensated. The accurately recovered envelopes of the PA’s input and output signals are used for a PA behavioral characterization and modeling. Furthermore, Relative envelope error (REE) parameter is proposed to evaluate the accuracy of envelope recovery. The experiment shows a very accurate RF signal envelope recovery, and a good performance of PA behavioral modeling.