Development of novel synthetic method of carbon nanotubes from electrospun polystyrene fibers by using microwave heating

We have developed a novel synthetic method that enables us to easily synthesize metal‐capsulated carbon nanotubes (CNTs) in a laboratory by using a combined technology of electrospinning‐metallization and microwave heating. These techniques greatly shorten the time for the synthesis of the CNTs in comparison with the conventional methods. TEM analysis confirmed a successful formation of the CNTs, and the resulting CNTs were multi‐walled and found to be about 25–100 nm in diameters. The products prepared by heating at 600 and 900°C exhibited less‐developed and strongly curved CNTs, whereas the products prepared by heating at 700 and 800°C relatively well‐developed long CNTs. Copyright © 2010 John Wiley & Sons, Ltd.     

Regularization of a two-dimensional strongly damped wave equation with statistical discrete data

In this paper, we consider an inverse problem for a strongly damped wave equation in two dimensional with statistical discrete data. Firstly, we give a representation for the solution and then present a discretization form of the Fourier coefficients. Secondly, we show that the solution does not depend continuously on the data by stating a concrete example, which makes the solution be not stable and thus the present problem is ill-posed in the sense of Hadamard. Next, we use the trigonometric least squares method associated with the Fourier truncation method to regularize the instable solution of the problem. Finally, the convergence rate of the error between the regularized solution and the sought solution is estimated and also investigated numerically.     

Finite element simulation of a layout optimisation technique by photoelastic stress minimisation

Layout optimisation to minimise maximum Tresca stress by photoelastic stress minimisation technique is simulated by finite element method: elements in the design domain that are lowly stressed are slowly removed resulting in a structure having minimum Tresca stress. The FEM simulation consists of analysing-monitoring the Tresca stress of elements in the design domain and “removing” material by declaring the element stiffness matrix of those possessing small stress values as of negligible stiffness in the subsequent step of the optimisation process. The lower bounds and upper bounds of stress limits for the “removal” criterion have to be appropriately chosen and effects of sharp notches introduced by removing finite elements should be properly taken into account for successful optimisation. The FEM simulation can be made fully automatic and can be extended to cases of complex geometry, loading material properties as well as to other objective functions of the optimisation problem.     

Regularization of a final value problem for a nonlinear biharmonic equation

In this paper, we consider the nonlinear biharmonic equation. The problem is ill‐posed in the sense of Hadamard. To obtain a stable numerical solution, we consider a regularization method. We show rigourously, with error estimates provided, that the corresponding regularized solutions converge to the true solution strongly in uniformly with respect to the space coordinate under some a priori assumptions on the solution.     

A consistent local linear estimator of the covariate adjusted correlation coefficient

Consider the correlation between two random variables (X, Y), both not directly observed. One only observes X? = φ(1)(U)X + φ(2)(U) and ? = ψ(1)(U)Y + ψ(2)(U), where all four functions {φ(l)(·),ψ(l)(·), l = 1, 2} are unknown/unspecified smooth functions of an observable covariate U. We consider consistent estimation of the correlation between the unobserved variables X and Y, adjusted for the above general dual additive and multiplicative effects of U, based on the observed data (X?, ?, U).     

Dosage rapide des alliages cuivre-palladium par electrolyse a tension controlee

The optimum conditions for separation by controlled potential electrolysis were determined by linear chronoamperometry. This method can be applied to any alloy which, can be deposited on platinum electrodes. For Cu-Pd alloys, the palladium was deposited at 50° in N sulphuric acid medium at +640 mV (with respect to the normal hydrogen electrode). Copper was deposited in several stages at ambient temperature after adding hydroxylammonium chloride. For ca. 100 mg of deposited metal, the errors were less than l%; they could be reduced by using bigger samples. The two successive electrolyses required less than 3 h.     

A vibration isolation system in low frequency excitation region using negative stiffness structure for vehicle seat

This paper designs and fabricates a vibration isolation model for improving vibration isolation effectiveness of the vehicle seat under low excitation frequencies. The feature of the proposed system is to use two symmetric negative stiffness structures (NSS) in parallel to a positive stiffness structure. Here, theoretical analysis of the proposed system is clearly presented. Then, the design procedure is derived so that the resonance peak of frequency-response curve drifts to the left, the load support capacity of the system is maintained, the total size of the system is reduced for easy practical application and especially, the bending of the frequency-response curve is minimized. Next the dynamic equation of the proposed system is set up. Then, the harmonic balance (HB) method is employed to seek the characteristic of the motion transmissibility of the proposed system at the steady state for each of the excitation frequency. From this characteristic, the curves of the motion transmission are predicted according to the various values of the configurative parameters of the system. Then, the time responses to the sinusoidal, multi frequency and random excitations are also investigated by simulation and experiment. In addition, the isolation performance comparison between the system with NSS and system without NSS is realized. The simulation results reveal that the proposed system has larger frequency region of isolation than that of the system without NSS. The experimental results confirm also that with a random excitation mainly spreading from 0.1 to 10 Hz, the isolation performance of the system with NSS is greatly improved, where the RMS values of the mass displacement may be reduced to 67.2%, whereas the isolation performance of the system without NSS is bad. Besides, the stability of the steady-state response is also studied. Finally, some conclusions are given.     

Nanostars on Nanopipette Tips: A Raman Probe for Quantifying Oxygen Levels in Hypoxic Single Cells and Tumours

Multiple sharp‐edged gold nanostars were efficiently assembled on nanopipette tips through electrostatic interactions for use as a potent intracellular hypoxia‐sensing Raman probe. Colloidal stability and surface immobilization were checked using scanning electron microscopy, light scattering, and zeta potential measurements. Site‐specific intracellular hypoxia levels can be estimated in vitro and in vivo using Raman lancets (RL). Distinct Raman spectral changes for the nitro‐(NO₂) functional group of the redox marker 4‐nitrothiophenol (4NTP) can be quantified according to the intracellular oxygen (O₂) content, ranging from 1 % to 10 %. Redox potential changes in mitochondrial respiration were also examined through serial injections of inhibitors. 3D‐cultured cells and in vivo tests were used to validate our method, and its application in the assessment of the aggressiveness of cancer cells by differentiating spectral changes between malignant and benign cells was demonstrated.     

Phenolic,Carotenoid and Saccharide Compositions of Vietnamese Camellia sinensis Teas and Herbal Teas

Tea (Camellia sinensis) and herbal tea have been recognized as rich sources of bioactive constituents with the ability to exert antioxidant actions. The aims of this study were to analyze phenolic, carotenoid and saccharide contents in a set of Vietnamese tea and herbal tea and compare the results with those of green and black teas marketed in the U.S. In total, 27 phenolics, six carotenoids and chlorophylls, and three saccharides were quantitatively identified. Catechins, quercetin glycosides and chlorogenic acid were the predominating phenolics in the teas, with the concentrations following the order: jasmine/green teas > oolong tea > black tea. Lutein was the dominant carotenoid in the teas and its concentrations were generally found to be higher in the jasmine and green teas than in the oolong and black teas. The study showed that the green teas originating in Vietnam had much higher levels of phenolics and carotenoids than their counterparts stemming from another country. The application of partial least squares discriminant analysis (PLS-DA) as a chemometric tool was able to differentiate phenolic profiles between methanolic extracts and tea infusions. Through principal component analysis (PCA), the similarities and dissimilarities among the jasmine, green, oolong, black teas and herbal teas were depicted.