Synthesis of Mg-Al and Zn-Al-layered double hydroxide nanocrystals using laser ablation in water

In this paper, we report our results on the synthesis of Mg-Al and Zn-Al-layered double hydroxides using the laser ablation in the liquid technique. To prepare these layered double hydroxides (LDH) we first began with the laser generation of a Mg (or zinc) target submerged in deionized water and then ablated an aluminum target submerged in the previously prepared Mg-deionized water suspensions (Mg-dw) to produce Mg-Al LDH and in Zn-dw to prepare Zn-Al LDH. In these ablation tests, the Mg ablation duration was selected to vary from 5 to 60 min, while the Al ablation duration was kept constant at 30 min for all samples. The generated Mg-Al LDH was a gel-like and well crystallized nanoparticles of a rod-like shape and were arranged in a well-organized pattern. When the Mg ablation duration between 25 and 35 min, the synthesized nanocrystals were stoichiometric with a formula of Mg₆Al₂(OH)₁₈4.5(H₂O), the interlayer distance (d_(0 0 3)-spacing) was 7.8 Å and the average grain size was 8.0 nm. The synthesized Zn-Al LDH revealed various lamellar thin plate-like nanostructures of hexagonal morphologies. The average diameters of these structures was about 500 nm and the thickness of a single layer was approximately about 6.0 nm. The XRD diffraction peaks were indexed in hexagonal lattice with a_o=3.07 Å and c_o=15.12 Å. These indexes were (0 0 2), (0 0 4), and (0 0 8) and the corresponding interlayer distances, d-spacing (Å), were 7.56 (0 0 2), 3.782 (0 0 4), and 1.891 (0 0 8), respectively.     

Electro-mechanical behavior of single twisted high-temperature superconducting tape under transverse Lorentz force

In recent years, several cabling methods of high temperature superconducting (HTS) cable have been proposed; e.g., the conductor on a round core cable (CORC), the Roebel assembled coated conductor cable, the helical twisted stacking-tape cable (TSTC) and the twisted-stack slotted core HTS cable (TSSC). These cabling methods allow the high temperature superconducting tapes widely used in the high-field magnets. The single superconducting tape performance under applied loads directly relates to the transport performance of the cable and the choice of the cabling method. In this paper, we investigate the effect of twisting morphology on the electro-mechanical properties of HTS tapes. Particular attention is given to the transverse Lorentz force of a pre-twisted HTS tape. The analytical solution of the deflection of the HTS tape under transverse Lorentz force is derived. Then, the current distribution and AC loss of the tape are calculated by using H-formulation. The effects of twist angle and loading conditions are examined for different HTS tape lengths. The results show that the stiffness resistance ability to Lorentz force of the HTS tape can be increased in several ranges by increasing the twist angle. The twisting structure can also reduce current degradation and AC loss, and thus enhance the transport capacity of HTS tape. This study helps understand the electro-mechanical properties of pre-twisted HTS tapes and provides theoretical reference for the design of novel HTS cable structures.     

Increasing the crystallite and conductivity of polypyrrole with dopant used

The chemical polymerization method is very convenient for obtaining a plurality of the polymer. Chemical synthesizes of polypyrrole (PPy) were performed in acetonitrile solutions containing different dopants: dodecylbenzene sulphonic acid (DBSA), tetrafluoroborate (BF₄ ^?), perchlorate (ClO₄ ^?) and oxalate (C₂O₄ ^2?). These polymers were characterized by using scanning electron microscopy (SEM), ultraviolet–visible (UV–Vis) spectrophotometer, Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD) techniques and dry conducting measurement. It was observed that the interactions between the polymers and dopant materials are completely different from each other. As a result of this interaction, the conductivities and crystal structures of PPy are also different from each other. Results in this work showed that the dopants used affected both electrical conductivities and crystal structures of PPy.     

Boron nitride nanotubes as templates for half-metal nanowires

We investigate by means of a GGA + U implementation of density functional theory the electronic and structural properties of magnetic nanotubes composed of an iron oxide monolayer and (n,0) boron nitride (BN) nanotubes, with n ranging from 6 to 14. The formation energy per FeO molecule of FeO covered tubes is smaller than the formation energy of small FeO nanoparticles, which suggests that the FeO molecules may cover the BN nanotubes rather than aggregating locally. Both GGA (PBE) and Van der Waals functionals predict an optimal FeO-BN interlayer distance of 2.94 ?. Depending on the diameter of the tube, novel electronic properties for the FeO covered BN nanotubes were found. They can be semiconductors, intrinsic half-metals or semi-half-metals that can become half-metals if charged with either electrons or holes. Such results are important in the spintronics context.     

Development and validation of a HPAE-PAD method for the quantification of CGP69669A, a sialyl Lewis(x) mimetic, in skin permeation studies

A simple, rapid, precise and specific isocratic HPAE‐PAD method for quantification of CGP69669A was developed and validated. CGP69669A is a glycomimetic of sialyl Lewis^x and an antagonist of E‐selectin with potential application in the treatment of inflammatory skin disease. Quantification was performed using a Dionex CarboPac^TM PA‐200 anion‐exchange column (3 × 250 mm) with 100 mm NaOH solution as mobile phase, a flow rate of 0.50 mL/min and an injection volume of 10 μL. A quadruple potential waveform was used to detect the carbohydrate (+0.1 V from 0.00 to 0.40 s, ?2.0 V from 0.41 to 0.42 s, +0.6 V at 0.43 s and ?0.1 V from 0.44 to 0.50 s with current integrated between 0.20 and 0.40 s for detection) and rafinose was employed as an internal standard. The optimized conditions enabled rapid elution of CGP69669A (at 3.0 min) without interference from solvent peaks or substances present in the skin. The method showed good intra‐ and inter‐day precision and accuracy and the response was linear from 1.0 to 25 µg/mL. This is the first validated direct method for the quantification of CGP69669A. It will now be employed in studies investigating the topical and transdermal delivery of CGP69669A in vitro and in vivo and it should also be of use for other applications of this molecule. Copyright © 2011 John Wiley & Sons, Ltd.     

Some characteristic behavior of mixed spin-1/2 and spin-1 Ising nano-tube

The magnetization of a cylindrical Ising nano-tube is investigated by the use of the effective field theory with correlations. The effects of the crystal field couplings at the surface shell to the order parameters, susceptibility, internal energy, specific heat and free energy are investigated. Some characteristic phenomena are examined in the thermal variations, depending on crystal field term. Moreover, tricritical and critical points are found on the (D/J,kT/J) plane, where D/J and kT/J are reduced crystal-field and temperature, respectively.     

悬浮振子对中耳声传播特性影响的数值研究

为研究悬浮式中耳植入式助听装置中悬浮振子对中耳声传播特性的一些影响,建立了包括绑定悬浮振子的中耳有限元模型. 该模型基于一无任何听力损伤病史的成年志愿者的左耳,利用CT扫描和逆向成型技术建成. 模型的可靠性通过鼓膜及镫骨底板的位移计算结果与国外文献实验测得数据进行对比加以验证. 研究结果表明:悬浮振子的绑定会显著恶化中耳的高频传输特性;振子输出8.9\times10^5N的激振力才能激起100dB声压所对应的激振效果;振子在砧骨长突上的绑定位置离砧镫关节越近,高频段激振效果越好.      

CFD by first order PDEs

This research originally was aimed at modeling all flows (except free-molecular) by systems of hyperbolic-relaxation equations (moments of the Boltzmann equation), and developing efficient numerical methods for these. Such systems have many potential numerical advantages, mainly because there are no second or higher derivatives to be approximated. This avoids accuracy problems on adaptive unstructured grids, and the source terms, though often stiff, are only local; the compact stencils facilitate code parallelization. A single code could simulate flows up to intermediate Knudsen numbers, and be hybridized with DSMC where needed. In this project, one major problem arose that we have not yet solved: the accurate representation of shock structures. This makes the methodology currently unsuited for, e.g., re-entry flows. We have validated it for subsonic and transonic flows and are concentrating on applications to MEMS-related flows. We discuss the challenges of our approach, present numerical algorithms and results based on the 10-moment model, and report progress in our latest research topic: formulating accurate solid-boundary conditions.