Electrochemical corrosion behavior of 2A02 Al alloy under an accelerated simulation marine atmospheric environment

The corrosion behavior of 2A02 Al alloy under simulated marine atmospheric environment has been studied using mass-gain, scanning electron microscope/energy dispersive spectroscopy (SEM/EDS), laser scanning confocal microscopy, X-ray diffraction spectroscopy and localized electrochemical methods. The results demonstrate that the relationship between the corrosion induced mass-gain and the corrosion time is in accordance with the power rule. The mass-gain increases gradually during the corrosion time, while the corrosion rate decreases. With ongoing of the corrosion, corrosion products film changed from a porous to a compact structure. The various spectroscopic data show that the corrosion products films composed mainly of Al(OH)₃, Al₂O₃ and AlCl₃. The electrochemical corrosion behavior of the 2A02 Al alloy was studied by electrochemical impedance spectroscopy (EIS).     

Evaluation of hydrogels for soft tissue adhesives <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis> analyses

In this study, natural materials (sodium alginate, dextran, gelatin and carboxymethyl chitosan) were modified to get aldehyde components and amino components. Upon mixing the two-component solutions together, four kinds of Schiff base hydrogels formed successfully within 5-300 s and could seal the wound tissue. The cytotoxicity tests of hydrogel extraction solution confirmed that the hydrogels are nontoxic materials. The adhesive ability was evaluated in vivo by measuring the adhesive strength after sealing the skin incisions on the back of rats. All the hydrogels showed higher adhesive strength than that of commercial fibrin glue and the blank control. The histological staining observation by hematoxylin and eosin staining (HE) and Masson’s trichrome staining (MTC) methods suggested that the hydrogels had good biocompatibility and biodegradation in vivo. They have only normal initial inflammation to skin tissue and could improve the formation of new collagen in the incision section. So, the prepared hydrogels were both safe and effective tissue adhesive, which had the great potentials to be used as skin tissue adhesive.     

基于无线传感器网络的比例导引优化信息融合研究

在分析反舰导弹比例导引控制规律的基础上,将无线传感器网络信息融合思想引入到比例导引优化辅助决策控制过程中,通过将无线传感器网络信息融合中的数据、特征、决策概念对应于比例导引的具体数学模型,构建了基于无线传感器网络的比例导引优化信息融合辅助决策架构;利用VB6.0语言对基于无线传感器网络辅助决策的反舰导弹优化信息融合制导控制规则进行了模拟仿真,命中距离缩短约37.1%,命中时间节省约10.9%;仿真实验结果实现了反舰导弹自适应优化比例系数的比例制导律,验证了该方法的有效性。     

天然活性包装膜在冷冻肉贮藏中的应用研究进展

目的 对天然活性包装膜在冷冻肉贮藏中的应用研究进展进行总结,为后续研究提供理论参考。方法 在介绍反复冻融对冷冻肉品质影响的基础上,围绕天然活性包装膜的功能成分、成膜工艺及其在冷冻肉贮藏中的应用研究予以阐述,讨论现有研究的局限性和今后的研究方向。结果 冻融过程中冰晶的反复形成影响冷冻肉体系的细胞结构和理化性质,加剧肉品品质下降;天然活性包装膜可以通过降低干耗、抑制氧化等延长肉品货架期。结论 天然活性包装膜可有效保护冷冻肉品,在肉品保鲜领域具有广阔的应用前景。     

不完全观测数据下混合效应模型的正交投影估计

基于矩阵的QR分解技术,对一类含有不完全观测数据的线性混合效应模型提出了一种基于正交投影的估计方法。在一些正则条件下,证明了固定效应参数的估计渐近服从标准正态分布,得到了固定效应参数的置信区间。另外,所提出的固定效应参数的估计过程不受随机效应的任何影响,具有较好的有效性和稳健性。最后,通过一些数值模拟和一个实例分析研究了所提出估计方法的有限样本性质。     

Medical image contrast enhancement based on improved sparrow search algorithm

The collection or transmission of medical images is often disturbed by various factors, such as insufficient brightness and noise pollution, which will result in the deterioration of image quality and significantly affect the clinical diagnosis. To improve the quality of medical images, a contrast enhancement method based on improved sparrow search algorithm is proposed in this paper. The method is divided into two steps to enhance the medical images. First, a new transform function is introduced to improve the brightness or contrast of medical images, and two parameters in the transform function are optimized by the improved sparrow search algorithm. Second, adaptive histogram equalization method with contrast limited is used to equalize the result image of the previous step to make the pixel distribution of the image more uniform. Finally, a large number of experiments and qualitative and quantitative analyses were conducted on the common data sets. The analysis results demonstrate that the presented approach outperforms some existing medical image processing approaches.     

DNA-Directed alkylating agents. 7. Synthesis, DNA interaction, and antitumor activity of bis(hydroxymethyl)- and bis(carbamate)-substituted pyrrolizines and imidazoles

A series of bis(hydroxymethyl)-substituted imidazoles, thioimidazoles, and pyrrolizines and related bis(carbamates), linked to either 9-anilinoacridine (intercalating) or 4-(4-quinolinylamino)benzamide (minor groove binding) carriers, were synthesized and evaluated for sequence-specific DNA alkylation and cytotoxicity. The imidazole and thioimidazole analogues were prepared by initial synthesis of [(4-aminophenyl)alkyl]imidazole-, thioimidazole-, or pyrrolizine dicarboxylates, coupling of these with the desired carrier, and reduction to give the required bis(hydroxymethyl) alkylating moiety. The pyrrolizines were the most reactive alkylators, followed by the thioimidazoles, while the imidazoles were unreactive. The pyrrolizines and some of the thioimidazoles cross-linked DNA, as measured by agarose gel electrophoresis. Strand cleavage assays showed that none of the compounds reacted at purine N7 or N3 sites in the gpt region of the plasmid gpt2Eco, but the polymerase stop assay showed patterns of G-alkylation in C-rich regions. The corresponding thioimidazole bis(carbamates) were more selective than the bis(hydroxymethyl) pyrrolizines, with high-intensity bands at 5'-NCCN, 5'-NGCN and 5'-NCGN sequences in the PCR stopping assay ( indicates block sites). The data suggest that these targeted compounds, like the known thioimidazole bis(carbamate) carmethizole, alkylate exclusively at guanine residues via the 2-amino group, with little or no alkylation at N3 and N7 guanine or adenine sites. The cytotoxicities of the compounds correlated broadly with their reactivities, with the bis(hydroxymethyl)imidazoles being the least cytotoxic (IC50s >1 microM; P388 leukemia) and with the intercalator-linked analogues being more cytotoxic than the corresponding minor-groove-targeted ones. This was true also for the more reactive thioimidazole bis(carbamates) (IC50s 0.8 and 11 microM, respectively), but both were more active than the analogous "untargeted" carmethizole (IC50 20 microM). The bis(hydroxymethyl)pyrrolizine analogues were the most cytotoxic, with IC50s as low as 0.03 microM.     

冲击式机组动能参数在线监测

鉴于冲击式水轮机结构上的特殊性,其流量效率等动能参数在线监测目前在国内还是项空白,针对冲击式机组的具体情况,探讨了基于压差理论的监测途径,在此基础上结合一个冲击式电站的实例,设计出了利用单片机来实现的方案．     

图的正交(g,f)-因子分解

设ｇ和ｆ分别是定义在图Ｇ的顶点集合Ｖ（Ｇ）上的整数值函数且对每一个ｘ∈Ｖ（Ｇ）有２≤ｇ（ｘ）≤ｆ（ｘ）．证明了若Ｇ是（ｍｇ＋ｍ－１,ｍｆ－ｍ＋１）—图,则对Ｇ中任意一个给定的有ｍ条边的子图Ｈ,Ｇ有一个（ｇ,ｆ）—因子分解与Ｈ正交．