Culture and chemical-induced fusion of tobacco mesophyll protoplasts in a microfluidic device

Microfluidic systems provide a powerful platform for biological analysis and have been applied in many disciplines. However, few efforts have been devoted to plant cell study. In this article, an optimized culture of tobacco mesophyll protoplasts and their first polyethylene glycol-induced fusion in a microfluidic device are presented. Culture medium optimization and dynamics of protoplast growth including size change, organelle motion, and cell mass formation were also investigated microscopically in real-time. On-chip protoplast culture showed that the first division percentage of tobacco mesophyll protoplasts could be improved as high as up to 85.6% in 5 days using NT1 medium, and the percentage of small cell mass formation was more than 48.0% in 10 days. Meanwhile, chemical-induced fusion of tobacco mesophyll protoplasts was realized in 3–5 min and a 28.8% fusion rate was obtained, which was similar to the conventional fusion in a macro-scale environment. These results will be helpful for the development of microfluidics-based studies on manipulation and analysis of plant cells in a miniaturized environment, including cell growth and differentiation, gene isolation, and cloning.     

Ant colony optimization for unrelated parallel machine scheduling

Meeting due dates is a major issue in most manufacturing systems, and one effective measure for due dates is total weighted tardiness. In this research, we consider an ant colony optimization (ACO) algorithm incorporating a number of new ideas (heuristic initial solution, machine reselection step, and local search procedure) to solve the problem of scheduling unrelated parallel machines to minimize total weighted tardiness. The problem is NP-hard in the strong sense, because the single machine case is already NP-hard in the strong sense. Computational results show that the proposed ACO algorithm outperforms other existing algorithms in terms of total weighted tardiness.     

Compression molding of biodegradable drug‐eluting implants for sustained release of metronidazole and doxycycline

The purpose of this report was to develop solvent‐free biodegradable drug‐eluting implants that provide sustained release of metronidazole and doxycycline. The drug‐eluting implants were prepared using the compression molding technique. To fabricate the implants, polylactide‐polyglycolide copolymers were premixed with metronidazole or doxycycline. The mixture was then compression molded and sintered to form implants of various sizes and geometries. An elution method and an HPLC assay were used to characterize the in vitro release rates of the antibiotics over a 28‐day period. A bacterial inhibition test was also carried out to determine the bioactivity of released antibiotics. The concentrations of both metronidazole and doxycycline were much greater than the minimum inhibitory concentration of Escherichia coli for up to 3 and 4 weeks, respectively, and the bioactivities of the antibiotics remained high after the fabrication process. Furthermore, the initial burst could be minimized and the release rate could be reduced by increasing the size of the implants and by adopting low drug to polymer ratios. By using this compression molding technique and appropriate processing parameters, we will be able to fabricate biodegradable implants of various types of antibacterial drugs for long‐term local deliveries. Eventually, biodegradable drug‐eluting implants may be used to treat various periodontal diseases. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

世界城市转型的一般规律与上海的创新战略

从中国经济发展的趋势上看,目前中国经济社会的发展已经进入转型的关键时期,各方面的约束条件日益增多,经济结构调整和优化已经成为落实科学发展观的重中之重。同时,经济改革的关键还要在稳定投资和出口的同时扩大消费,实现消费快速增长,从而形成内需主导型经济。"创新驱动、转型发展",应该是像上海这样的特大型城市的发展新战略。     

Stochastic simulations of ErbB homo and heterodimerisation: potential impacts of receptor conformational state and spatial segregation

ErbB overexpression is linked to carcinogenesis. It is hypothesised that this is due to increased receptor density and receptor clustering, leading to increased receptor dimerisation and activation. Herein, spatial stochastic simulations have been performed to shed light receptor dimerisation processes. First, ligand- independent homodimerisation, is considered, based upon constitutive oligomerisation estimates (14%) in A431 cells that overexpress epidermal growth factor receptor (EGFR). When autocrine stimulation is blocked, ligand-independent EGFR activation is demonstrated by persistent, low levels of phosphorylation. The possibility that ligand-independent signalling is due to the fluctuation of EGFR conformation is considered. The agent-based model predicts the frequency (expressed as a probability) that uniformly distributed receptors would need to flux to the open conformation to reach 14% EGFR dimers at high receptor density. Simulations suggest that ligand-independent EGFR homodimerisation is highly density dependent, since collisions between 'open', dimerisation-competent receptors are a rare event at low receptor levels. Simulations that incorporate receptor clustering lower the threshold for homodimerisation of unoccupied receptors as well as the estimate of the probability for fluxing to the dimer-competent conformation. The impact of ErbB receptor clustering patterns on hetero and homodimerisation rates is also considered, using immunoelectron microscopy data derived from SKBR3 breast cancer cells that express ErbB2 Gt EGFR > ErbB3. Partial spatial segregation of ErbB receptors has a profound effect on simulated heterodimerisation rates. Despite the general assumption that ErbB2 is a preferred heterodimerising partner for other ErbBs, it is predicted that most ErbB2 will form homodimers. Overall, it is proposed that both receptor density and membrane spatial organisation contribute to the carcinogenesis process.     

An improved mesh simplification method using additional attributes with optimal positioning

The use of highly detailed models is continuously increasing in computer-aided design (CAD) design and computer graphics field as the technology of range scanners advances. Real-time rendering and manipulating applications are also increasing to support applications in various areas such as collaborative design and scientific visualization. Although graphics hardware technology has been improved rapidly, more attributes such as color, material property, texture coordinate, and curvature are added to CAD models, and it becomes a challenge to handle and render such heavy models. Consequently, the models with complex mesh need to be approximated to improve the efficiency of rendering and manipulation and to reduce computation time. A considerable amount of work has been done regarding geometry preservation, but relatively little research has been performed to preserve both geometry and additional attributes. We present a feature sensitive simplification method using curvature color as an additional attribute. We also use curvature color filtering and optimal positioning methods after edge collapse to preserve feature more sensitively. Our method is applied to several models, and the performance is demonstrated by comparing it with other methods.     

“军事通信基础”PPT的创意与实现

在"军事通信基础"课件的设计和制作中,详细分析了课程标准、课程特点和授课内容,得出该课件的创意流程。以现代通信技术发展趋势的PPT创意与实现等内容为例,运用三维效果、自定义动画、结构图插入、设置放映方式和旁白录音等PPT设计要素,实现了递进式展示、动画讲解、对比重现、组合说明等创意效果。用简练、生动、新颖的方式展示繁琐、枯燥、复杂的授课内容,调动感官接受知识的兴奋点,以期达到良好的教学效果。     

Micellar layer-by-layer synthesis of TiO2/Ag hybrid particles for bactericidal and photocatalytic activities

Silver nanoparticles prepared by a reverse micelle process were sequentially deposited on rutile-structured TiO₂ particles via an electrostatic layer-by-layer (LbL) deposition together with a hydrophilic/hydrophobic interaction. The TiO₂ surface was first mediated by a preferential adsorption of poly(allylamine hydrochloride) (PAH) cationic molecules, before being mixed with the Ag nanoparticles encapsulated in reverse micelles consisting of anionic surfactant of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in isooctane. The deposition of Ag nanoparticles was not of a uniform coverage on the TiO₂ surface, but of a heterogeneous growth of the Ag particles on the TiO₂ surface. Antibacterial activity of the composites against gram-negative bacteria, i.e., Escherichia coli (E. coli), was found to increase with the deposition cycle, resulted mainly from the increased Ag concentration. The bactericidity is persistent in the absence of ultraviolet (UV) light. Over the concentration range of Ag examined, i.e., Ag/Ti atomic ratio varies from 0.28% to 0.53%, photocatalytic efficiency of the composites against methylene blue (MB) dye in an aqueous solution also improved pronouncedly with the silver concentration under UV exposure.     

Atomic structure and mechanical properties of BC2N superlattice

Structural motifs for the BC₂N superlattices were identified from a systematic search based on a greedy algorithm. Using a tree data structure, we have retrieved seven structural models for c-BC₂N 1 × 1 × 1 lattice which were identified previously by Sun et al. [Phys. Rev. B 64, 094108 (2001)]. Furthermore, the atomic structures with the maximum number of C–C bonds for c-BC₂N 2 × 2 × 2, 3 × 3 × 3, and 4 × 4 × 4 superlattices were found by imposing the greedy algorithm in the tree data structure. This new structural motif has not been previously proposed in the literature. A total of up to 512 atoms in the c-BC₂N superlattice are taken into consideration. The atoms in these superlattices are in diamond-like structural form. Furthermore, the C atoms, as well as B and N atoms, form the octahedral motif separately. The octahedral structure consisting of C is bounded with {111} facets, and each facet is interfaced to a neighboring octahedral structure consisting of B and N atoms. The electronic and mechanical properties of newly identified low energy structures were analyzed.     

EMG-based measures of fatigue during a repetitive squat exercise

We have demonstrated a technique to calculate the EMG instantaneous median frequency to assess muscle fatigue during a dynamic exercise commonly prescribed in patients with ACL deficiency. We used Cohen-Posch time-frequency representations to improve upon the variability of the instantaneous median frequency estimates derived using Cohen Class transformations. The technique was applied to surface EMG data recorded from the quadriceps and hamstring muscles of a control subject and a patient with ACL deficiency during a repetitive squat exercise. Instantaneous median frequency values were derived for the knee-extension phases of the exercise. Ensemble average and standard deviation of the instantaneous median frequency were computed for the portion of the cycle associated with the lowest variability of the mechanics