Sample Size Dependence of Second Magnetization Peak in Type－II Superconductors

We show that the second magnetization peak (SMP), i. e., an increase in the magnetization hysteresis loop width in type-II superconductors,vanishes for samples smaller than a critical size. We argue that the SMP is not related to the critical current enhancement but can be well explained within a framework of the thermomagnetic flux-jump instability theory, where flux jumps reduce the absolute irreversible magnetization relative to the isothermal critical state value at low enough magnetic fields. The recovering of the isothermal critical state with increasing field leads to the SMP. The low-field SMP takes place in both Iow-Tc conventional and high-Tc unconventional superconductors. Our results show that the restoration of the isothermal critical state is responsible for the SMP occurrence in both cases.     

Size effect in nanoadhesion of fibrillar structure

The gecko has incredible climbing ability for its nanoscale hierarchical fibrillar structure foot-hair. Can we fabricate a new type of adhesive by mimicking the gecko mechanism? In this paper, we consider a simplified case of an elastic cylinder with hemispherical shape terminals adhering to a rigid substrate. By using the classical JKR model to calculate the adhesive strength, we find that the strong size effect arises when the cylinder's radius is in nanoscale. This finding may help us to design a biomemetic adhesive.     

Nanoengineering of Flux Pinning Sites in High－Tc Superconductors

Volume pinning forces were determined for a variety of bulk high-Tc superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd-based superconductors and some YBCO crystals exhibited a dominating pinning of the δTc-type (i.e., small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δl-type; providing effective pinning in the entire temperature range acting as a “background” pinning mechanism for the peak effect. Due to the small coherence lengths of the high-Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ε^3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high-Tccompounds were spatially inhomogeneous, which could becaused by oxygen deficiency (YBCO), solid solutions of Nd/Ba (NdBCO and other light rare earth compounds), intergrowths (Bi-based superconductors), and doping by pair-breaking dopants like Zn, Pr. This implies that the superconducting sample consists of stronger and weaker superconducting areas, coupled together. In large applied fields, this coupling gets broken and the magnetization versus temperature curves revealed more than one superconducting transition. In contrast, irradiation experiments by neutrons, protons,and heavy-ions enabled the artificial introduction of very effective pinning sites into the high-Tc superconductors, thus creating a large variety of different observations using magnetic data. From all these observations, we construct a pinning diagram for bulk high-Tc superconductors explaining many featuresobserved in high-Tc samples.     

Hemingway＇ s Political Views in His Second Period of Creation

Based on the influence of different relationship between general ideology and authorial ideology on Hemingway＇s works in the second period of his creation, the thesis aims to study the different reflection of his political interest from the perspective of ideology.     

Grading Standards of the Coefficient of Variation in the Electronic Raw Silk Size Testing

In order to shorten the difference between the raw silk size grading standards of the world and that of China, to quicken the step of the electronic raw silk testing process, the distribution of the coefficient of variation （CV50m%） of the raw silk size in the electronic testing and the development of the new standards are studied according to the sampling and grading theory. By the theoretical deduction and the simulating experiments, the distribution of the coefficient of variation of the raw silk size is given, and the grading scheme whose quality index is the coefficient of variation（CV50m%）of the raw silk size and the grading precisions of all grades are proposed. Moreover, the rightness and the feasibility of the grading scheme are testified by the sampling and grading simulation.     

Size distribution and element composition of dust aerosol in Chinese Otindag Sandland

Dust aerosol is one important component of atmos-pheric aerosols, and plays important roles in the Earth’s climate system and the biogeochemical cycle. Large amounts of dust aerosols produced from windblown soils and deserts are emitted annually into the atmosphere and transported over long distance to downwind land and ocean areas[1]. The deserts and desertification soils in northern China are important sources of East Asia dust aerosols. It is estimated that 800 Mt of dust aerosols emit-t…     

An Analysis of Michael Long＇ s Interaction Hypothesis in Second Language Acquisition

The Interaction Hypothesis, which was first advanced by Michael Long, is considered as a further supplement or extension of the Input Hypothesis in the field of second language acquisition. This paper explains the main claims of Michael Long＇s Interaction Hypothesis, the three steps to study how input and interaction affect the acquisition of a second language, and the importance of the interactional modifications applied by both participants of the interaction. Emphasis is placed on the evaluation of the theory as well as its relation to second language teaching, with many researchers＇ findings and arguments discussed as supporting evidence. It aims to help the effective application of this theory in second language teaching.     

Hyperspectral retrieval model of phycocyanin in case Ⅱ waters

Phycocyanin, a functional protein found in blue-green algae, with characteristic absorption peak around 620 nm, can be used to detect the quantity of blue-green algae in waters. Spectral characteristics of phycocyanin were studied by measuring hyperspectral water leaving radiance and absorption curve, and the results showed that the absorption peak of phycocyanin around 620 nm was evident in the curve of water leaving radiance. Bio-optical model of phycocyanin was set up with analytical methods and calibrated with error analysis. Linear relationship between phycocyanin concentration measured and that retrieved with calibrated bio-optical model （R = 0.755） was better than that retrieved with the band ratio of 709 nm/620 nm （R = 0.729）, which proved that the calibration was necessary for improving the accuracy of phycocyanin concentration.     

Thermal stability of oxygen evolution in photosystem Ⅱ core complex in the presence of digalactosyl diacylglyceroli

The influence of digalactosyldiacylglycerol (DGDG), one of the photosynthetic membrane lipids, on heat inactivation of the process of oxygen evolution has been studied in vitro in photosystem Ⅱ (PSⅡ) core complex. It was found that the temperature of semi-inactivation of oxygen evolution in the complex increased from 40.0 to about 43.0℃ in the presence of DGDG with 5-min heat treatment in the dark. Furthermore, when PSⅡ core complex was incubated for 5 min at 45.0℃, the oxygen evolution in the complex was completely lost, whilst the DGDG-complexed PSⅡ core complex still retained a 16% of activity (100% for 25.0℃). In addition, a 1-h incubation at 38.0℃ inactivated absolutely the oxygen evolution for the PSⅡ core complex. By contrast, there remained about 20% of activity (zero time for 100%) for the complex in the presence of DGDG under the same condition. These results indicate a new role of DGDG in the protection of PSⅡ core complex against the deleterious effects of temperature. It was most likely that DGDG-mediated stability toward thermal denaturation of oxygen evolution in PSⅡ core complex is due to the protective effect of DGDG on the release of the 33 kD protein from PSⅡ core complex.     

Effect of Mn cluster on the formation of superoxide radicals in photoinhibition of photosystem Ⅱ

To further realize the action of superoxide radicals (O₂^{− .}) in photoinhibition of photosystem Ⅱ (PSⅡ), we employed 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap, associated with EPR spectroscopy, to study the effect of illumination time on O₂^{− .} formation during high light photoinhibition in PSⅡ membranes and Mn-depleted PSⅡ membranes. Results indicated that the removal of Mn cluster from PS
membranes has a strong influence on the dynamics of superoxide formation. The relative mechanism was also discussed. These novel findings may further promote the studies of the structure and function of PSⅡ and the mechanism of photoinhibition.     

Effect of Phosphatidylcholine on the Steady State Fluorescence of Chlorophyll in Photosystem Ⅱ Particles

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｐｈｏｔｏｓｙｎｔｈｅｓｉｓｌｉｇｈｔｒｅａｃｔｉｏｎｉｎ ｐｌａｎｔｓｏｃｃｕｒｓｉｎｔｈｅｔｈｙｌａｋｏｉｄｍｅｍｂｒａｎｅｏｆｔｈｅｃｈｌｏｒｏｐｌａｓｔｓ .Ｔｈｅｐｒｏｔｅｉｎｃｏｍｐｌｅｘｅｓｉｎｔｈｅｔｈｙｌａｋｏｉｄｍｅｍｂｒａｎｅｓａｒｅｓｕｐｅｒｍｏｌｅｃｕｌａｒｓｙｓｔｅｍｓｃｏｎｓｉｓｔｉｎｇｏｆ ｐｒｏｔｅｉｎｓ ,ｌｉｐｉｄｓａｎｄ ｐｉｇｍｅｎｔｓｗｈｉｃｈｒｅｇｕｌａｔｅａｎｄｃｏｎｔｒｏｌｔｈｅｌｉｇｈｔｅｎｅｒｇｙａｂｓｏｒｐｔｉｏｎ ,…     

Low pH-induced conformational changes in 33 kD protein of photosystem Ⅱ

33 kD protein, located on the lumen side ofthylakoid membranes, is one of three extrinsic proteins ofphotosystem Ⅱ (PS Ⅱ ). Previous study showed that NBSmodification of W241, the only tryptophan in 33 kD protein,is helpful for understanding the function of W241 in main-taining functional conformation of 33 kD protein. In thispaper, studies of both circular dichroism and fluorescencespectra showed that upon decreasing pH from 6.2 to 2.5, theconformation of soluble 33 kD protein changed significantly,with an increase or a decrease in percentage of random coilor (z-helix and turns. The changes in secondary structures ofthis protein are pH reversible. After NBS modification at pH2.5, the conformational change of 33 kD protein was keptfixed. The CD ellipticity at 200 nm for NBS-modified 33 kDprotein is much lower than that for control, indicating that the unfolding degree of 33 kD protein was enhanced after the NBS modification. Moreover, the conformational flexibility islost in NBS-modified 33 kD protein, and the conformationalchange becomes pH irreversible, indicating that NBS modi-fication blocked the reversibility of conformational change of33 kD protein. The specific binding capability of NBS-modi-fled 33 kD protein is much lower than that of low pH-treatedcontrol. Furthermore, the rebinding of modified protein on PS Ⅱ membranes cannot restore the activity of oxygen evo-lution. We suggest that it is low pH but not NBS modificationof W241 that leads to the conformational change of 33 kDprotein from one functional to another non-functional state.The significant capability of proton transport of 33 kD pro-tein is discussed.     

Simulation for the primary electronic donor of photosystem Ⅱ in vitro

Histidine coordinated to Chl a is a distinct characteristic of Chl a in vivo. By using histidine analogue of 1-methylimidazole (C4H6N2) and measuring the UV/vis absorption, CD and MCD spectra of the interaction between C4H6N2 and Chl a in CCl4, we have obtained that: (ⅰ) In pure CCl4 solvent, Chl a molecule is in five-coordinate state, and two Chl a molecules form an asymmetric compact-dimer with strong coupling interaction. We propose that the two Chl a molecules are connected by two unequally coordinated Mg-O bonds (the two oxygen atoms come from the C== O of C131 keto and C17 ester, respectively); (ⅱ) when the molar ratio of C4H6N2/Chl a is 0.5 or 1 (corresponding to 2Chl a·1C4H6N2 and 2Chl a·2C4H6N2, respectively), significant changes have been observed in the absorption, CD and MCD spectra, which indicate that the Chl a remains in dimer form, but the coupling interaction between them reduces greatly. We postulate that C4H6N2 replaces the ligation of C== O of C17 ester and C131 keto to Mg atoms sequentially. The two Chl a molecules linked by two weakly interacted Mg...O bonds form a relaxed-dimer. The structure of the model is essentially similar to that of the primary electronic donor, P680, of photosystem Ⅱ in high plants and algae.     

Improved Methods for Process Routing in Enterprise Production Processes in Terms of Sustainable Development Ⅱ

Introduction Manufacturing is the main process consuming re- sources, polluting the environment, and causing occu- pational health and safety problems in a product life cycle[1]. In recent years, the International Standards Organization has issued a seque…     

Electrooxidation of Mn(Ⅱ) on Pb-Sb-As Electrode in Sulfuric Acid

The electrooxidation of Mn(Ⅱ) on Pb-Sb-As alloy electrode in sulfuric acid has been investigated.In order to make the two steps of indirect electrosynthesis of benzaldehyde carried out in the same sulfuric acid concentration and also obtain high current efficiency of Mn(Ⅱ) to Mn(Ⅲ) and high yield of Mn(Ⅲ) oxidizing toluene to benzaldehyde in the mean time,the electrooxidation of Mn(Ⅱ) in 60% H2SO4 has been studied.Experimental results show that high current efficiency of Mn(Ⅲ) (about 75%) is obtained in 60%H2SO4 at 60℃.The reason affecting the current efficiency of Mn(Ⅲ) is discussed,and it is the coordination of sulfuric acid concentration and electrolytic temperature.The law is found that it is suitable for electrolysis at low temperature when sulfuric acid concentration is low and at high temperature when sulfuric acid concentration is high.     

Quantitative analysis of icariside Ⅱ in rabbit bile by LC-MS/MS

建立能定量分析家兔胆汁中淫羊藿次苷Ⅱ的液相色谱-串联质谱联用法(LC-MS/MS).以水饱和乙酸乙酯萃取为家兔胆汁样本前处理方法,采用OSD柱(150×4.6 mm,i.d.,5μm),以乙腈-水(各含0.1％的甲酸)为流动相进行梯度洗脱,采用电喷雾离子源(ESI),二级质谱全扫描,负离子方式下检测.方法学考察结果显示,该方法专属性良好;日内精密度(RSD)不大于10.6％,日间精密度(RSD)不大于8.3％,准确度(RE)在-4.4％～+5.0％范围以内;胆汁样本稳定性良好;基质效应对测定影响可以忽略不计且提取率较高并稳定.该方法快速而灵敏,可用于家兔灌胃给以淫羊藿总黄酮后胆汁中的活性代谢物淫羊藿次苷Ⅱ的动态变化研究.