Membrane-assisted revelation of the spatial nanoarchitecture of dislocation networks

We propose a method of direct visualization of the spatial nanoarchitecture of dislocation networks which is based on etching away the regions with low density of structural defects from the bulk of GaN epilayers, keeping intact only the threading dislocations and a thin surface film pre-treated with low-energy Ar⁺ ions. The formation of nanometer-thick suspended membrane to which the dislocations are genetically attached provides conditions for the revelation of the spatial nanoarchitecture of dislocation networks using conventional scanning electron microscopy. Complementary monochromatic and panchromatic micro-cathodoluminescence images are presented.     

Synthesis of optical transparent and electrical conductive polymer/nanocarbon composite films by infiltration method

Optical transparent and electrical conductive (PMMA)/nanocarbon composite films can be prepared through the infiltration of the polymer between the carbon aggregates of a preformed percolation cluster. This cluster is prepared by Langmuir-Blodgett technique as a thick film (2-20 μm in thickness). The performed direct current electrical measurements have shown that PMMA/Multiwall Nanotubes present a lower electrical surface resistivity and a higher optical transmittance than PMMA/carbon nanoparticles composite films. Much simpler and cheaper than other methods, the infiltration method allowed us to prepare composite films with a 75% in transparency and 1 MΩ/square in surface electrical resistivity. The composite films prepared by infiltration method have a good adhesion to the glass substrates but in some specific conditions can be integrally removed as free-standing films.     

Production and Electrostatic Precipitation of Combustion Nuclei by an Electrified Propane?Air Flame

The results are given of an investigation into the production and electrostatic precipitation of combustion nuclei by an electrified propane-air flame. The apparatus consisted of a burner with a dc potential applied which was supported inside a grounded metal combustion chamber where the generation and removal of particles could be studied. A mathematical and experimental analysis of transient combustion nuclei concentrations inside the combustion chamber was carried out to evaluate the nuclei precipitation and production rates as a function of flame potentials and air flow rates. Two new theoretical equations containing production, precipitation, and flow parameters are derived to describe these transient concentrations. The constants of the equations were determined by experiment. These lead directly to the important parameters of nuclei production and precipitation rates, which are difficult to assess individually using previously known techniques. The experiments show that the concentration of combustion nuclei in the exhaust gas can be significantly decreased by the simple electrification of the flame. For combustion processes that generate aerosols, the method has the advantage of using the flame itself to affect the removal of the particles from the exhaust gases. Since combustion nuclei are receiving increased attention as air pollutants, this study could have important practical applications.     

The Impact of the Azo-Chromophore Sort on the Features of the Supramolecular Azopolyimide Films Desired to Be Used as Substrates for Flexible Electronics

High-performance supramolecular polyimide systems were synthesized via a simple and innovative approach using two types of azo-chromophores, leading to concomitant special properties: high thermostability, the ability to be processed in the form of films with high flexibility, adequate morphological features, and good structuring capacity via phase mask ultraviolet (UV) laser irradiation, induced by the presence of the azo groups (–N=N–). The dimension and the anisotropy degree of the micro/nano patterns obtained on the surface of the flexible films (determined by atomic force microscopy) depend on the azo-dye type used in the supramolecular azopolyimide synthesis, which were higher when the azo-chromophore containing a –cyano group (–C≡N) was used. The molecular dynamics method, an excellent tool for an in-depth examination of the intermolecular interactions, was used to explain the morphological aspects. Energetic, dynamic and structural parameters were calculated for the two systems containing azo-chromophores, as well as for the pristine polymer system. It was highlighted that the van der Waals forces make a major contribution to the intermolecular interactions. The results from the combination of the dynamic analysis and the concentration profile explain the better mobility of the polyimide chains with a maximum content of azo groups in the cis configuration compared to the other systems. Taking all these data into account, the surfaces of the films can be tuned as required for the proposed applications, namely as substrates for flexible electronis.     

Sodium Alginate-g-acrylamide/acrylic Acid Hydrogels Obtained by Electron Beam Irradiation for Soil Conditioning

Being both a cause and a victim of water scarcity and nutrient deficiency, agriculture as a sustainable livelihood is dependent now on finding new suport solutions. Biodegradable hydrogels usage as soil conditioners may be one of the most effective solutions for irrigation efficiency improvement, reducing the quantity of soluble fertilizers per crop cycle and combating pathogens, due to their versatility assured by both obtaining method and properties. The first goal of the work was the obtaining by electron beam irradiation and characterization of some Sodium Alginate-g-acrylamide/acrylic Acid hydrogels, the second one being the investigation of their potential use as a soil conditioner by successive experiments of absorption and release of two different aqueous nutrient solutions. Alginate-g-acrylamide/acrylic Acid hydrogels were obtained by electron beam irradiation using the linear accelerator ALID 7 at 5.5 MeV at the irradiation doses of 5 and 6 kGy. For this were prepared monomeric solutions that contained 1 and 2% sodium alginate, acrylamide and acrylic acid in ratios of 1:1 and 1.5:1, respectively, for the obtaining of materials with hybrid properties derived from natural and synthetic components. Physical, chemical, structural and morphological characteristics of the obtained hydrogels were investigated by specific analysis using swelling, diffusion and network studies and Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. Four successive absorption and release experiments of some synthetic and natural aqueous solutions with nutrients were performed.     

Scanning transmission ion microscopy on Fudan SPM facility

In this paper,we report a novel measurement system based on the development of Fudan Scanning Proton Microscopy(SPM) facility.By using Si-PIN diode(Hamamatsu S1223-01) detector,scanning transmission ion microscopy(STIM) measurement system has been set up.It can provide density and structural images with high probing efficiency and non-destruction by utilizing the energy loss of high energy(MeV) and focused ions penetrating through a thin sample.STIM measurement is able to map the density distribution of organic elements which mostly compose biology materials,such information can not be detected by using conventional Be-windowed Si(Li) X-ray detector in Particle Induced X-ray Emission(PIXE) technique.The spatial resolution capability of STIM is higher than PIXE technique at same accelerator status.As a result of STIM measurement,Paramecium attached on the top of Kapton tube was measured by STIM.     

Poisson Shot Noise Removal by an Oracular Non-Local Algorithm

Journal of Mathematical Imaging and Vision - In this paper, we address the problem of denoising images obtained under low-light conditions for the Poisson shot noise model. Under such conditions,...     

北京大学6MV串列静电加速器的运行及其应用

北京大学６ＭＶ串列静电加速器上建成４条束流输运线，加速＾１Ｈ，＾１２Ｃ，＾１６Ｏ，＾１９Ｆ，＾３５Ｃｌ，＾７９Ｂｒ等离子，并开展物理实验研究。首次利用Ｄ（＾１２Ｃ，ｐ）＾１３Ｃ核反应建立起高灵敏度的氘分析法；利用共振核反应＾１Ｈ（＾１９Ｆ，αγ）＾１６Ｏ分析材料中氢的深度分布；用重离子背散射分析超导材料ＹＢａ２Ｃｕ３Ｏ７－ｘ；用３５ＭｅＶ＾３５Ｃｌ和４５ＭｅＶ＾７９Ｂｒ的弹性前冲分析不同材料中的轻     

A new system for computer-aided preoperative planning and intraoperative navigation during corrective jaw surgery.

A new system for computer-aided corrective surgery of the jaws has been developed and introduced clinically. It combines three-dimensional (3-D) surgical planning with conventional dental occlusion planning. The developed software allows simulating the surgical correction on virtual 3-D models of the facial skeleton generated from computed tomography (CT) scans. Surgery planning and simulation include dynamic cephalometry, semi-automatic mirroring, interactive cutting of bone and segment repositioning. By coupling the software with a tracking system and with the help of a special registration procedure, we are able to acquire dental occlusion plans from plaster model mounts. Upon completion of the surgical plan, the setup is used to manufacture positioning splints for intraoperative guidance. The system provides further intraoperative assistance with the help of a display showing jaw positions and 3-D positioning guides updated in real time during the surgical procedure. The proposed approach offers the advantages of 3-D visualization and tracking technology without sacrificing long-proven cast-based techniques for dental occlusion evaluation. The system has been applied on one patient. Throughout this procedure, we have experienced improved assessment of pathology, increased precision, and augmented control.