Damage Evolution In Cement Mortar Due To Erosion Of Sulphate

Ultrasonic technique is used to detect the velocity change of stress wave propagated in the cement mortar immersed in the solution of sodium sulfate for 425 days. Also the density change of specimens at different erosion time is measured. By curve fitting, the effect of solutions' concentration and water/cement ratio on the damage evolution is analyzed. The SEM observation on the growth of delayed ettringite is also performed. It shows that the damage evolution of specimens attacked by sulphate solution is dominantly induced by the nucleation and growth of delayed ettringite, and the average size of microvoids in cement mortar affects the damage evolution significantly. (c) 2008 Elsevier Ltd. All rights reserved.

Measuring Binding Kinetics Of Surface-Bound Molecules Using The Surface Plasmon Resonance Technique

Surface plasmon resonance (SPR) technology and the Biacore biosensor have been widely used to measure the kinetics of biomolecular interactions in the fluid phase. In the past decade, the assay was further extended to measure reaction kinetics when two counterpart molecules are anchored on apposed surfaces. However, the cell binding kinetics has not been well quantified. Here we report development of a cellular kinetic model, combined with experimental procedures for cell binding kinetic measurements, to predict kinetic rates per cell. Human red blood cells coated with bovine serum albumin and anti-BSA monoclonal antibodies (mAbs) immobilized on the chip were used to conduct the measurements. Sensor-grams for BSA-coated RBC binding onto and debinding from the anti-BSA mAb-immobilized chip were obtained using a commercial Biacore 3000 biosensor, and analyzed with the cellular kinetic model developed. Not only did the model fit the data well, but it also predicted cellular on and off-rates as well as binding affinities from curve fitting. The dependence of flow duration, flow rate, and site density of BSA on binding kinetics was tested systematically, which further validated the feasibility and reliability of the new approach. Crown copyright (c) 2008 Published by Elsevier Inc. All rights reserved.

Extraction of intrinsic frequency response of p-i-n photodiodes

This letter presents a new method for extracting the intrinsic frequency response of a p-i-n photodiode (PD) from the measured frequency response of the PD at different bias voltages. This method is much simpler than the conventional calibration method, since only the measured scattering parameters are required, and there is no need to calibrate the test fixtures and the lightwave source. Experiment shows that the proposed method is as accurate as the calibration method.

Extraction of intrinsic response from S-parameters of laser diodes

We describe a new method for extracting the intrinsic response of a laser diode from S-parameters measured using a calibrated vector network analyzer. The experimental results obtained using the new method are compared with those obtained using the optical modulation method and the frequency response subtraction method. Good agreement has been obtained, confirming the new method validity and accuracy. The new method has the advantages of obtaining the intrinsic characteristics of a laser diode with conventional measurements using a network analyzer.

Sputtering induced by Arq+ impact on Nb surface

The relative sputtering yield induced by highly charged Arq+ impacting on Nb surface is investigated. The yield increases drastically as the incidence angle increases. A formula Y=A* tan(B) (theta) + C, developed from classical sputtering theory, fits well with the yield. By analysing a series of coefficients A and C extracted by curve fitting, the results demonstrate the presence of a synergy of the linear cascade collision and potential energy deposition.

Observation of a Possible New Isomer in Ir-175

The neutron deficient nuclide Ir-175 was produced by irradiation of Nd-146 with 210 MeV Cl-35 via a fusion-evaporation reaction channel. The reaction products were transported to a low-background location using a helium-jet recoil fast-moving tape-transport system for measurement. The experimental devices and data analysis method are introduced. Based on the decay-curve fitting of the beta-delayed gamma ray from Ir-175, realized by the least-square method, a new long-lived isomeric state of Ir-175 is proposed and briefly discussed.

FTIR study of poly(propylene carbonate)/bisphenol A blends

A systematic investigation by FTIR spectroscopy was undertaken on blends of poly(propylene carbonate) (PPC) and bisphenol A (BPA). It provided direct evidence of the hydrogen bond (H-bond) between BPA O-H groups and PPC C=O groups. Using a curve-fitting method, qualitative as well as quantitative information concerning this H-bond interaction was obtained. The inter-H-bond in PPC/BPA blends was weaker than the self-H-bond in BPA. The absorptivities of the free and the H-bonded C=O groups were nearly equal. The fraction of H-bonded C=O in the blends increased with BPA content and leveled off at a value close to 40%. Finally, FTIR-temperature measurements of pure PPC and a representative blend were reported: by monitoring the peak areas of C=O absorptions, the dissociation of the inter-H-bonds and the thermal degradation of PPC were observed. It revealed that the presence of BPA clearly retarded the thermal degradation of PPC.

Quantitative FTIR study of PHBV/bisphenol A blends

FTIR spectroscopy was used to verify the presence of intermolecular hydrogen bond (inter-H-bond) between poly-(3-hydroxybutyrate co-3-hydroxyvalerate) (PHBV) and bisphenol A (BPA). By monitoring the spectral changes during PHBV crystallization and blends dissociation, the absorptivity ratio of C=O bonds in crystalline and amorphous regions in PHBV and that of H-bonded and free C=O in PHBV/BPA blends were experimentally determined as 1.40 and 1.68, respectively. Using curve-fitting program, the C=O absorptions in spectra of blends were ascribed to three types of bonds: amorphous, crystalline and H-bonded C=O. The crystallinity of PHBV and the fraction of H-bonded C=O were calculated. These results indicated that the H-bond clearly suppressed the PHBV crystallization. Furthermore, the fraction of BPA molecules that simultaneously formed two hydrogen bonds (H-bonds) with C=O was estimated. It revealed that there existed a H-bond network in PHBV/BPA blends. This network was compared with the covalent network by estimating the number of atoms between every two adjacent crosslink points in chain. Up to the high density of H-bond discussed in this paper, there was always a certain part in PHBV that crystallized due to the dynamic character of hydrogen bonds; however, the hydrogen bonds significantly reduced the crystallization rate of PHBV.

Deconvolution of overlapped peaks based on the exponentially modified Gaussian model in comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GC x GC) has attracted much attention for the analys is of complex samples. Even with a large peak capacity in GC x GC, peak overlapping is often met. In this paper, a new method was developed to resolve overlapped peaks based on the mass conservation and the exponentially modified Gaussian (EMG) model. Linear relationships between the calculated sigma, tau of primary peaks with the corresponding retention time (t(R)) were obtained, and the correlation coefficients were over 0.99. Based on such relationships, the elution profile of each compound in overlapped peaks could be simulated, even for the peak never separated on the second-dimension. The proposed method has proven to offer more accurate peak area than the general data processing method. (c) 2005 Elsevier B.V. All rights reserved.

Calculating the equation of state parameters and predicting the spinodal curve of isotactic polypropylene/poly(ethylene-co-octene) blend by molecular dynamics simulations combined with Sanchez-Lacombe lattice fluid theory

Molecular dynamics simulations are adopted to calculate the equation of state characteristic parameters P*, rho*, and T* of isotactic polypropylene (iPP) and poly(ethylene-co-octene) (PEOC), which can be further used in the Sanchez-Lacombe lattice fluid theory (SLLFT) to describe the respective physical properties. The calculated T* is a function of the temperature, which was also found in the literature. To solve this problem, we propose a Boltzmann fitting of the data and obtain T* at the high-temperature limit. With these characteristic parameters, the pressure-volume-temperature (PVT) data of iPP and PEOC are predicted by the SLLFT equation of state. To justify the correctness of our results, we also obtain the PVT data for iPP and PEOC by experiments. Good agreement is found between the two sets of data. By integrating the Euler-Lagrange equation and the Cahn-Hilliard relation, we predict the density profiles and the surface tensions for iPP and PEOC, respectively. Furthermore, a recursive method is proposed to obtain the characteristic interaction energy parameter between iPP and PEOC. This method, which does not require fitting to the experimental phase equilibrium data, suggests an alternative way to predict the phase diagrams that are not easily obtained in experiments.

Complex potentials and singular integral equation for curve crack problem in antiplane elasticity

Four types of the fundamental complex potential in antiplane elasticity are introduced: (a) a point dislocation, (b) a concentrated force, (c) a dislocation doublet and (d) a concentrated force doublet. It is proven that if the axis of the concentrated force doublet is perpendicular to the direction of the dislocation doublet, the relevant complex potentials are equivalent. Using the obtained complex potentials, a singular integral equation for the curve crack problem is introduced. Some particular features of the obtained singular integral equation are discussed, and numerical solutions and examples are given.

Numerical estimate of the stability curve for the flow past a rotating cylinder

It is demonstrated that the primary instability of the wake of a two-dimensional circular cylinder rotating with constant angular velocity can be qualitatively well described by the Landau equation. The coefficients of the Landau equation are determined by means of numerical simulations for the Navier-Stokes equations. The critical Reynolds numbers, which depend on the angular velocity of the cylinder, are evaluated correctly by linear regression. (C) 2004 American Institute of Physics.

基于U型塑料光纤和邻啡咯啉钌的溶解氧传感器

本文提出了一种基于U型塑料光纤和邻啡咯啉钌的溶解氧传感器。光纤传感头放在样品池中，测量了不同氮氧体积比情况下荧光强度和寿命。研究了邻啡咯啉钌的浓度、传感头的退火时间和U型光纤的弯曲半径对系统灵敏度的影响。我们提出了双层模型来解释实验结果不符合S-V方程的实验现象，并用双层模型分析了弯曲半径对系统灵敏度的影响。通过对溶解氧浓度和荧光寿命亚线性曲线的拟合，我们得出敏感层的厚度和S-V系数分别为0.59和0.61。