Study on surface and mechanical fiber characteristics and their effect on the adhesion properties to a polycarbonate matrix tuned by anodic carbon fiber oxidation

Polyacrylonitrile (PAN) based high strength carbon fibers were anodically oxidized using the galvanostatic mode in alkaline electrolyte solutions to influence the chemical surface composition. The change of chemical and physical properties was investigated using scanning electron microscopy (SEM), photoelectron spectroscopy (XPS), energy dispersive X-ray analysis (EDX) and contact angle as well as zeta (ζ)-potential measurements.

An initially improved wettability for polar liquids, particularly water, was observed for oxidized carbon fibers. This result was confirmed by ζ-potential measurements. The chemical state of the oxygen containing surface groups changes during anodic oxidation in K₂CO₃/KOH due to further oxidation of C–OH and C=O groups to COOH groups. Therefore the surface acidity increases, which leads to a shift of the isoelectric point to lower pH values and increases the negative ζ_plateau value. The ζ–pH as well as the ζ–concentration dependence show the same tendency. During anodic oxidation of carbon fibers in KNO₃/KOH electrolyte solution beside ‘normal’ (like C–OH, C=O and COOH) surface oxides also carboxylate groups (COO⁻K⁺) were formed at the fiber surface in contrast to an oxidation in K₂CO₃/KOH which introduces ‘normal' surface oxides. No influence could be observed of such an anodic oxidation on the single fiber tensile strength. Contact angle measurements of polycarbonate melt droplets onto single carbon fibers show no dependence of the surface composition. The interfacial shear strength, measured using the microdroplet pull-off test were compared with the thermodynamic work of adhesion. The calculated as well as the measured adhesion show the same absence of any influence of fiber treatment.     

多菌灵抗性基因在球毛壳中的转化

利用PEG方法将多菌灵抗性基因通过质粒pRB129转化到球毛壳原生质体，并在含0.5μg/ml多菌灵浓度下筛选转化子，转化率可达6－7个转化子／μgDNA。转化子可在1000μg/ml多菌灵处理条件下正常生长。将转化子在非选择压力下连续培养10代，其抗性稳定不变。     

Selective Coloration of Melanin Nanospheres through Resonant Mie Scattering

Black melanin inks are prepared to selectively exhibit colors under strong light, inspired by human hair. High absorbance of melanin suppresses multiple scattering, causing resonant Mie scattering predominant. Various colors can be developed as the resonant wavelength dictated by nanosphere diameter. Therefore, the melanin inks can be used to encrypt and selectively disclose multicolor patterns for anticounterfeiting applications.     

Characterization of residual stresses from cold expansion using spatial statistics

Residual stress fields from cold expansion have been widely used to extend the fatigue life of aircraft structures. However, the spatial statistical character of these residual stress fields has not been established and has not been incorporated in current analysis methods. The objective of this study was to establish a spatial statistical method to quantify the residual stress field around a cold expanded hole. A framework called the Spatial Analysis of Residual Stress (SpARS) was developed utilizing spatial correlation, response surface modelling techniques and statistical resampling methods to characterize the residual stress field. Our results showed that tolerance bounds on residual stress can be quantified using this method. We also demonstrated the SpARS method using recently published round robin case studies. The newly developed model will be useful for aircraft structural fatigue crack growth analyses to incorporate residual stress fields for extending inspection intervals for fatigue and fracture critical structures.     

Biomimetic Robust Starch Composite Films with Super-Hydrophobicity and Vivid Structural Colors

The starch composite films (SCFs) will be one of the best alternative packaging materials to petroleum based plastic films, which mitigates white pollution and energy consumption. However, weak mechanical stability, water resistance, and dyeability has hindered the application of SCFs. Herein, a bioinspired robust SCFs with super-hydrophobicity and excellent structural colors were prepared by fiber-reinforcement and assembling SiO₂/Polydimethylsiloxane (PDMS) amorphous arrays on the surface of SCFs. The properties of the designed SCFs were investigated by various methods including scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), a tensile test, contact angle (CA) test, and an optical test. The results showed that the obtained SCFs possessed a higher tensile strength (55.17 MPa) attributed to the formed abundant hydrogen bonds between the molecular chains of the starch, cellulose fiber, and polyvinyl alcohol. Benefiting from the nanostructure with rough surface which were modified by materials with low surface free energy, the contact angle and sliding angle of the film reached up to 154° and 2°, respectively. The colors which were produced by the constructive interference of the coherent scattered light could cover all of the visible regions by tuning the diameters of the SiO₂ nanoparticles. The strategy in the present study not only reinforces the mechanical strength and water resistance of SCFs but also provides an environmentally friendly way to color the them, which shows unprecedented application potential in packaging materials of the starch composite films.     

Genome-Wide Association Study Identifies a Rice Panicle Blast Resistance Gene,Pb2, Encoding NLR Protein

Rice blast is one of the main diseases in rice and can occur in different rice growth stages. Due to the complicated procedure of panicle blast identification and instability of panicle blast infection influenced by the environment, most cloned rice resistance genes are associated with leaf blast. In this study, a rice panicle blast resistance gene, Pb2, was identified by genome-wide association mapping based on the panicle blast resistance phenotypes of 230 Rice Diversity Panel 1 (RDP1) accessions with 700,000 single-nucleotide polymorphism (SNP) markers. A genome-wide association study identified 18 panicle blast resistance loci (PBRL) within two years, including 9 reported loci and 2 repeated loci (PBRL2 and PBRL13, PBRL10 and PBRL18). Among them, the repeated locus (PBRL10 and PBRL18) was located in chromosome 11. By haplotype and expression analysis, one of the Nucleotide-binding domain and Leucine-rich Repeat (NLR) Pb2 genes was highly conserved in multiple resistant rice cultivars, and its expression was significantly upregulated after rice blast infection. Pb2 encodes a typical NBS-LRR protein with NB-ARC domain and LRR domain. Compared with wild type plants, the transgenic rice of Pb2 showed enhanced resistance to panicle and leaf blast with reduced lesion number. Subcellular localization of Pb2 showed that it is located on plasma membrane, and GUS tissue-staining observation found that Pb2 is highly expressed in grains, leaf tips and stem nodes. The Pb2 transgenic plants showed no difference in agronomic traits with wild type plants. It indicated that Pb2 could be useful for breeding of rice blast resistance.     

智能控制--超越世纪的目标--国际自动控制联合会第14次代表大会报告

国际自动控制联合会（ＩＦＡ）第１４次代表大会是本世纪最后一次,能在北京召开,中国科学界和工程界都无比高兴。我代表中国科学界和工程界的同行们,向世界各国来京出席会议的同行和朋友们以及他们的家属表示最热烈的欢迎。今年是ＩＦＡＣ成立４２周年。１９５７年在巴黎成立了第一届理事会,中国是发起国之一。我有幸参加过在莫斯科召开的第一次代表大会。记得,那是一次盛大的科学集会,向全世界宣布了ＩＦＡＣ的诞生。２０世纪对控制论科学做出过重大贡献的杰出科学家们,如ＮｏｒｂｅｒｔＷｉｅｎｅｒ,ＬｅｖＰｏｎｔｒｙａ－ｇｉｎ…     

几种起爆技术在水下爆破中的应用

文章综合介绍了水下爆破采用的几种先进的起爆技术,着重阐述电磁感应遥控起爆、超声波遥控起爆、导爆索起爆技术和控制震动技术的基本原理、装置和结构等.