抗人CD25人鼠嵌合抗体在CHO细胞中的稳定表达及初步鉴定

目的在CHO细胞中稳定表达抗人CD25人鼠嵌合抗体,并对抗体活性进行初步鉴定。方法采用脂质体法将嵌合抗体真核表达质粒pOptiVEC-H和pcDNA3.3-L共转染CHO-DHFR-细胞,通过去除HT和在培养基中加入500μg/ml的Geneticine进行阳性克隆的筛选,有限稀释法对阳性克隆进行亚克隆,通过在培养基中加入浓度逐步增加的MTX提高克隆的抗体表达量。采用流式细胞术(FCM)检测嵌合抗体的抗原结合活性及人抗体重链Fc段、轻链κ链;提取细胞基因组进行PCR鉴定;抗体经超滤浓缩后,采用蛋白G亲和纯化法进行纯化,并进行Westernblot分析;体外连续培养细胞株2个月及冻存、复苏后,采用ELISA法检测抗体分泌的稳定性。结果获得稳定分泌嵌合抗体的细胞株1C1,ELISA检测抗体表达量为103ng/ml;PCR结果表明,表达的质粒已整合入细胞基因组中;FCM及Westernblot结果显示,嵌合抗体含有人抗体重链Fc段及轻链κ链,且保留了鼠抗体V区的抗原结合特异性;经蛋白G亲和纯化后,获得抗体220μg,纯度>97%;体外连续培养细胞株2个月及冻存、复苏后,抗体分泌保持稳定。结论获得了稳定表达人CD25人鼠嵌合抗体的CHO细胞株,其具有鼠源抗体的抗原结合特异性及人抗体的恒定区。     

Mobility of Pb in salt marshes recorded by total content and stable isotopic signature

Total lead and its stable isotopes were analysed in sediment cores, leaves, stem and roots of Sacorconia fruticosa and Spartina maritima sampled from Tagus (contaminated site) and Guadiana (low anthropogenic pressure) salt marshes. Lead concentration in vegetated sediments from the Tagus marsh largely exceeded the levels in non-vegetated sediments. Depth profiles of (206)Pb/(207)Pb and (206)Pb/(208)Pb showed a decrease towards the surface ((206)Pb/(207)Pb=1.160-1.167) as a result of a higher proportion of pollutant Pb components. In contrast, sediments from Guadiana marsh exhibited low Pb concentrations and an uniform isotopic signature ((206)Pb/(207)Pb=1.172+/-0.003) with depth. This suggests a homogeneous mixing of mine-derived particles and pre-industrial sediments with minor inputs of anthropogenic Pb. Lead concentrations in roots of plants from the two marshes were higher than in leaves and stems, indicating limited transfer of Pb to aerial parts. A similar Pb isotopic signature was found in roots and in vegetated sediments, indicating that Pb uptake by plants reflects the input in sediments as determined by a significant anthropogenic contribution of Pb at Tagus and by mineralogical Pb phases at Guadiana. The accumulation in roots from Tagus marsh (max. 2870 microg g(-1) in S. fruticosa and max. 1755 microg g(-1) in S. maritima) clearly points to the dominant role of belowground biomass in the cycling of anthropogenic Pb. The fraction of anthropogenic Pb in belowground biomass was estimated based on the signature of anthropogenic Pb components in sediments ((206)Pb/(207)Pb=1.154). Since no differences exist between Pb signature in roots and upper sediments, the background and anthropogenic levels of Pb in roots were estimated. Interestingly, both background and anthropogenic Pb in roots exhibited a maximum at the same depth, although the proportion of anthropogenic Pb was relatively constant with depth (83+/-4% for S. fruticosa and 74+/-8% for S. maritima).     

Local Image Features Resulting from 3-Dimensional Geometric Features,Illumination, and Movement: I

We study images of smooth or piecewise smooth objects illuminated by a single light source, with only background illumination from other sources. The objects may have geometric features (F), namely surface markings, boundary edges, creases and corners; and shade features (S), namely shade curves and cast shadow curves. We determine the local stable interactions between these and apparent contours (C) for the various configurations of F, S, C, and we concisely summarize them using an “alphabet” of local curve configurations. We further determine the generic transitions for the configurations resulting from viewer movement. These classifications are obtained using the methods of singularity theory, which allows us to ensure that our lists are complete, in some cases correcting earlier attempts at similar classifications. Authors were partially supported by Insight 2+ grant from the European Commission. J. Damon was partially supported by the National Science Foundation grants DMS-0405947 and DMS-0706941.     

Statistical scatter of fracture toughness in the ductile-brittle transition of a structural steel

The statistical scatter of fracture toughness in the ductile-brittle transition temperature range was experimentally examined on a 500 MPa class low carbon steel. Fracture toughness tests were replicatedly performed at −60 °C, −20 °C and −10 °C. The tests at −60 °C resulted in a single modal Weibull distribution with a shape parameter of 4 for the critical stress intensity factor converted from J-integral, whereas the Weibull distributions of the critical stress intensity factor at −20 °C and −10 °C showed a bilinear pattern with an elbow point, which caused a wider scatter than that at −60 °C. Such scatter transition behavior was discussed with reference to stable crack initiation. A model of the statistical scatter transition has been proposed in this work and the model reasonably explains the experimental results.     

Lake Superior herring gulls benefit from anthropogenic food subsidies in a prey–impoverished aquatic environment

Herring gulls (Larus argentatus) are used as ecological indicators of the coastal Lake Superior ecosystem in Pukaskwa National Park, Ontario, Canada. Their populations have declined by 70 % over the last 40 years, suggesting changes in the park ecosystem. Previous studies highlighted declining prey abundance as a possible contributing factor to population declines. Here, we assess herring gull diets via stable isotope (nitrogen, carbon) and fatty acid indicators to investigate how diet may influence population trends through effects on physiology (stress-related hormones), reproduction (egg size) and behavior (nest attentiveness). Diets were variable among individual herring gulls. Gulls utilizing anthropogenic food sources exhibited reduced levels of stress-associated hormones, increased egg size, and increased nest attentiveness. Anthropogenic food sources are likely buffering the impacts of declines in aquatic food availability; however, populations are still declining. Understanding factors contributing to population trends in ecological indicator species is critical for species management and for identifying stressors that are likely affecting the broader ecosystem. Herring gulls are archetypal examples of the “canary in a coalmine” indicator but in an ecosystem context. Changes in their diets and in variables associated with their physiology, reproduction, and behavior point to very significant changes occurring in the Lake Superior ecosystem. Integrated research across the Great Lakes is required to understand the extent of this change and its implications for the sustainability of wildlife populations.     

Efficient cathode contacts through Ag-doping in multifunctional strong nucleophilic electron transport layer for high performance inverted OLEDs

This paper presents an efficient and stable green inverted organic light emitting diode (IOLED) using multifunctional and strong nucleophilic quality electron transport material (1,3-bis(2-phenyl-1,10-phenanthrolin-4-yl)benzene (m-bPPhenB)) with silver (Ag) as an n-dopant. By the energy level alignment study using in-situ ultraviolet photoelectron spectroscopy measurement, negligible electron injection barrier between indium tin oxide (ITO) and Ag-doped m-bPPhenB (Φ_e ≈ 0.03 eV) is observed and the electrons can be easily tunneled from ITO into Ag-doped m-bPPhenB layer. Also, Ag dopant forms coordination bonds with phenanthroline based unit, which improves electron injection from ITO. Fabricated IOLED devices using an Ag-doped m-bPPhenB have an extremely low driving voltage of 3.6 V and external quantum efficiency of 29.0%. Such good performances of IOLED are attributed to negligible electron injection barrier at the interface between ITO and Ag-doped m-bPPhenB. The Ag-doped IOLED device also shows a good air stability owing to the stable Ag n-dopant. The doping of Ag into special electron transport layer in the IOLED structure could be applicable to various displays and lighting applications.     

基于ABAQUS的显式动力学分析方法研究

显式动力学(The Explicit Dynamic)是针对隐式求解器的一个补充,其分析方法对于求解广泛、各类非线性结构力学问题是一个非常有效的工具,显式方法中的单个增量步取决于模型的最高固有频率,与持续时间、载荷类型无关。ABAQUS/Explicit主要用于碰撞、接触以及失效分析。探讨了ABAQUS显式动力学的基本理论、求解的问题,对显示动力学分析方法中的求解算法、稳定时间极限和能量平衡问题进行研究,给出了显示动力学分析的一般性分析方法。通过案例验证了该方法的可行性,应用该方法可有效解决实际工业生产中的碰撞问题、复杂的接触问题以及复杂的后屈曲问题,可为显式动力学分析方法应用于工程实践奠定理论与方法基础。     

能带混合量子阱的触发功能和异质谷间转移电子放大器件的研究

运用MonteCarlo理论模拟、二极管除穿伏安特性、器件振荡性能和射频输入信号激励下的放大功能研究了异质谷间转移电子器件中能带混合量子阱的触发功能。理论和实验研究发现，当能带混合量子讲中没有产生足够的异质谷间转移电子效应时，即使有源层中加有足够的电场仍然不能产生振荡。异质谷间转移电子效应成为器件进行射频工作的必要条件。在适当设计的器件中，运用输入射频信号也能激励异质谷间转移电子效应而触发输出放大信号。应用这一原理研制成8mm波段工作的稳态放大器，解决了二极管稳态放大器中的自激振荡问题。最后讨论了利用能带混合量子讲的触发功能来制作新的三端器件和各类功能器件的可能性。     

Impact of Divalent Ions on Heavy Oil Recovery by in situ Emulsification

Many reservoir formation brines are characterized by high salinity and contain high concentrations of divalent ions such as calcium, magnesium, and potassium. These challenging conditions can render the surfactants ineffective during chemical flooding for enhanced heavy oil recovery. Various brine types can have an impact on the stability of emulsions generated with chemicals as chemicals have various resistant levels toward hard divalent ions and salinities. To investigate the impact of brine hardness on heavy oil-in-water emulsion stability, glass tube experiments, microscopic visualization and sandpack flooding experiments, and Hele-Shaw visualization experiments were conducted in this study under low-salinity/hard-brine, high-salinity/hard-brine conditions using commercial chemicals, which are designed for specific reservoir brine conditions. Recovery results demonstrated that complex colloidal solution introduced in the previous study with silica and Dodecyltrimethylammonium bromide (DTAB) along with screened chemicals from glass tube tests in this study can enhance heavy oil recovery significantly with an addition of low concentration of xanthan gum (Lee and Babadagli 2018). The results confirmed the robustness of the complex colloidal solution formula to enhance oil recovery with low concentration of polymer under any reservoir brine conditions. The study also demonstrates the potential of polymer as an emulsion stabilization additive for enhanced heavy oil recovery by in situ emulsion generation. Polymer effects seemed to be particularly dominant under the low-salinity conditions than high-salinity conditions.     

Lead isotopes reveal different sources of lead in balsamic and other vinegars

Fifty-eight brands of balsamic vinegars were analyzed for lead concentrations and isotopic compositions (²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb) to test the findings of a previous study indicating relatively high levels of lead contamination in some of those vinegars — more than two thirds (70%) of them exceeded California's State Maximum Level (34 μg/L) based on consumption rates ≥ 0.5 μg Pb per day. The Lead isotopic fingerprints of all those vinegars with high lead concentrations were then found to be primarily anthropogenic. This isotopic analysis unquestionably reveals multiple contamination sources including atmospheric pollutant Pb and an unidentified contamination source, likely occurring after grape harvest. Organically grown grape vinegars display the same Pb content and isotopic signatures as other vinegars. This implies that pesticides might not be a significant source of pollutant Pb in vinegars. A significant post-harvest contamination would be inherited from chemicals added during production and/or material used during transport, processing or storage of these vinegars. This is consistent with the highest Pb levels being found in aged vinegars (112 ± 112 μg/L) in contrast to other vinegars (41.6 ± 28.9 μg/L) suggesting contamination during storage. It is, therefore, projected that lead levels in most vinegars, especially aged balsamic and wine vinegars, will decrease with improvements in their manufacture and storage processes consequential to recent concerns of elevated levels of lead in some vinegars.