Conformations and adsorption behavior of poly（allylamine hydrochloride） studied by single molecule force spectroscopy

Poly（allylamine hydrochloride） （PAH）, which is frequently used in fabricating polyelectrolyte multilayer films, was studied by single molecule force spectroscopy （SMFS）. Plenty of force-extension curves with a long plateau were obtained in water, indicating that train-like structure was predominant when PAH was adsorbed on the substrate. It was found that the peak-type force-extension curves of PAH in water were not able to be fitted by the modified freely-jointed chain model. Additionally, there was a flat region in the derivative of force-extension curves. Thus, it was inferred that PAH chain in water was in a special conformation and underwent a ＂conformational transition＂ under the stretching of an external force. This phenomenon did not appear in the SMFS experiment in 1 mol/L urea solution, which indicated that urea was able to break the special conformation.     

Grenvillian orogeny in the Southern Cathaysia Block: Constraints from U-Pb ages and Lu-Hf isotopes in zircon from metamorphic basement

Metamorphic basement rocks in the Cathaysia Block are composed mainly of meta-sediments with different ages. New zircon U-Pb geochronological results from the meta-sedimentary rocks exposed in the Zengcheng and Hezi areas, southern Cathaysia Block, show that they consist dominantly of early Neoproterozoic （1.0-0.9 Ga） materials with minor Paleo- to Mesoproterozoic and late Neoproterozoic （0.8-0.6 Ga） components, suggesting that the detritus mostly come from a Grenvillian orogen. The youngest detrital zircon ages place a constraint on the deposition time of these sediments in Late Neoproterozoic. Zircon Hf isotopic compositions indicate that the Grenvillian zircons were derived from the reworking of Mesoproterozoic arc magmatic rocks and Paleoproterozoic continental crust, implying an arc-continent collisional setting. Single-peak age spectra and the presence of abundant euhedral Grenvillian zircons suggest that the sedimentary provenance is not far away from the sample location. Thus, the Grenvillian orogen probably preexisted along the southern margin of the Cathaysia Block, or very close to the south. Similarity in the ages of Grenvillian orogeny and the influence of the assembly of Gondwana in South China with India and East Antarctic are discussed, with suggestion that South China was more likely linked with the India-East Antarctica continents in Early Neoproterozoic rather than between western Laurentia and eastern Australia.     

A theoretical model for mid- and low-latitude ionospheric electric fields in realistic geomagnetic fields

The geomagnetic fields, which play important roles in the ionospheric dynamo, can greatly affect the global distribution of ionospheric electric fields, currents and other ionospheric electrodynamics phenomena. In the study of ionospheric electrodynamics phenomena, such as the longitudinal variations of ionospheric electric fields, the non-dipolar component of the geomagnetic fields must be taken into account. In this paper, we deduce a theoretical electric field model for ionospheric dynamo at mid- and low-latitude which adopt a modified magnetic apex coordinates system. In the new electric field model, the geomagnetic fields can be calculated from either the IGRF model or the dipole field model, and the neutral winds and conductivities are calculated based on empirical models. Then the dynamo equation for the electric potential is finally solved in terms of the line-by-line iteration method, and the ionospheric electric fields and currents are derived from the calculated potential. Our model can reproduce the main features of the ionospheric electrodynamics processes, so it will be a useful tool for the investigation of the upper atmosphere and ionosphere.     

Effective identification of the three particle modes generated during pulverized coal combustion

Based on the mass fraction size distribution of aluminum （AI）, an improved method for effectively identifying the modes of particulate matter from pulverized coal combustion is proposed in this study. It is found that the particle size distributions of coal-derived particulate matter actually have three modes, rather than just mere two. The ultrafine mode is mainly generated through the vaporization and condensation processes. The coarse mode is primarily formed by the coalescence of molten minerals, while the newly-found central mode is attributed to the heterogeneous condensation or adsorption of vaporized species on fine residual ash particles. The detailed investigation of the mass fraction size distribution of sulfur （S） further demonstrates the rationality and effectiveness of the mass fraction size distribution of the AI in identifying three particle modes. The results show that not only can the number of particle modes be identified in the mass fraction size distributions of the AI but also can their size boundaries be more accurately defined. This method provides new insights in elucidating particle formation mechanisms and their physico-chemical characteristics.     

Synthesis and luminescent properties of a Schiff-base-boron-quinacridone compound

A novel Schiff-base-boron-quinacridone compound （4） has been synthesized. The absorption and emission properties of 4 have been studied carefully. Experimental results demonstrated that the introduction of Schiff-base-boron moieties could suppress the aggregation of molecules 4 in solution and enhance the photoluminescent efficiency in relatively high concentration solution. The energy transfer from the Schiff-base-boron moieties to quinacridone cores could take place in 4 system.     

Development of a middle and low latitude theoretical ionospheric model and an observation system data assimilation experiment

On the basis of previous work, we develop a middle and low latitude theoretical ionospheric model in this paper, named Theoretical Ionospheric Model of the Earth in the Institute of Geology and Geophysics, Chinese Academy of Sciences （TIME-IGGCAS）. TIME-IGGCAS solves the equations of mass continuity, motion and energy of electron and ions self-consistently and uses an eccentric dipole field approximation to the Earth＇s magnetic field. We combine the Eulerian and Lagrangian approaches in the model and take account of the plasma ExB drift velocity. Calculation results reveal that the model is steady and credible and can reproduce most large-scale features of ionosphere. By using TIME-IGGCAS, we carried out an observation system data assimilation experiment. Assimilation results show that the ExB drift velocity can be accurately estimated by ingesting the observed foF2 and hmF2 into the model applying nonlinear least-square fit method. We suggest that this work is of great significance in the development of ionospheric data assimilation model to give better nowcast and forecast of ionosphere.     

Rearrangements of microtubule cytoskeleton in stomatal closure of <Emphasis Type=Italic>Arabidopsis</Emphasis> induced by nitric oxide

NO （nitric oxide）, known as a key signal molecule in plant, plays important roles in regulation of stomatal movement. In this study, microtubule dynamics and its possible mechanism in the NO signal pathway were investigated. The results were as follows： （i） In vivo stomatsl aperture assays revealed that both vinblastine （microtubule-disrupUng drug） and SNP （exogenous NO donor） prevented stomatsl opening in the light, and vinblastine even could enhance the inhibitory effect of SNP, whereas tsxol （a microtubule-stsbilizing agent） was able to reduce this effect; （ii） microtubules in the opening Arabi-dopsis guard cells expressing GFP：a-tubulin-6 （AtGFP：a-tubulin-6） were organized in parallel, straight and dense bundles, radiating from the ventral side to the dorsal side, and most of them were localized perpendicularly to the ventral wall; （iii） under the same environmental conditions, treated with SNP for 30 min, the radial arrays of microtubules in guard cells began to break down, twisted partially and be- came oblique or exhibited a random pattern; （iv） furthermore, the involvement of cytosolic Ca^2＋ in this event was tested. Stomatal aperture assays revealed that BAPTA-AM （a chelator of Ca^2＋） greatly suppressed the effect of NO on stomatal closure; however, it did not show the same function on stomatal closure induced by vinblastine. When BAPTA-AM was added to the SNP-pretreated solution, the SNP-induced disordered microtubulue cytoskeleton in guard cells underwent rearrangement in a time-dependent manner. After 30 min of treatment with BAPTA-AM, the cortical microtubules resumed the original radial distribution, almost the same as the control. All this indicates that NO may promote rearrangement of microtubule cytoskeleton via elevation of [Ca^2＋]cyt （free Ca^2＋ concentration in the cytoplasm）, finally leading to stomatsl closure.     

综合运输网络中合理路径优化模型

为了提高多式联运经营人运输决策的科学性和可行性,建立了一个含路径合理性约束的联合运输路径优化模型.从货运生产实践角度出发,提出了联合运输合理路径概念.基于联合运输的实现流程,指出除了运输效益最大化外,合理的换装序列和换装次数限制是联合运输路径选择和优化必须要考虑的另外2个重要特性.对于一般联合运输问题,研究了运输总费用的构成,即直线运输费用、节点中转费用和超期惩罚费用.通过构建直观的联合运输网络图,以总运输成本最少为优化目标,将多方式联合运输合理路径的选择和优化问题转化为含有超期惩罚因子的广义最短路模型,对模型的假设和数学形式做了详细的描述,并提供了简要的求解思路和参考算法.     

有源电力滤波器谐波电流检测的MATLAB仿真研究

随着电力电子技术的迅猛发展,电力电子装置产生的谐波对公用电网产生的危害,引起了人们越来越多的关注。文章对基于瞬时无功功率理论的ip-iq检测算法设计的有源电力滤波器模型进行了MATLAB仿真,并对仿真结果进行了分析。     

A note on abelian extensions

Let K/Q be any abelian extension where Q is the field of rational numbers. By Galois theory and the Frobenius formula for induced characters, we prove that there exists a metabelian group G and an irreducible character X of G such that K=Q（X）.