Characterization of the surface properties of xylan by FT-Raman spectroscopy and wicking technique

Using FT-Raman spectroscopy, column wicking technique and the equations of Washburn as well as van Oss et al., the surface properties of xylan, the main component in hemicelluloses, has been characterized and estimated. Raman spectrum showed that xylan has been structured by acetyl group and methyl-bonded glucurono group. Obtained results show that the surface free energy of xylan is higher in comparison with literature reported values for cellulose because the former has a larger Lifshitz–van der Waals component than the latter. However, xylan has been found to have very smaller polarity and orientation data than that of cellulose.     

Fabrication of alternating polycation and albumin multilayer coating onto stainless steel by electrostatic layer-by-layer adsorption

Multilayer films consisting of polyethylenimine (PEI) and albumin were successfully prepared on biomedical 316L stainless steel surface via electrostatic self-assembly of the PEI and albumin. The process of electrostatic self-assembly of PEI/albumin was monitored by125I radiolabeling, electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The EIS data revealed that the multilayer coating was stable in Tris-HCl (pH 7.35) buffer solution for 21 days. 125I radiolabeling experiments indicated that less than 10% albumin was eluted by PBS in 45 days. Static platelet adhesion experiments indicated that the PEI/albumin deposited on stainless steel could resist platelet adhesion effectively. Such an easy processing and shape-independent method may have good potential for surface modification of cardiovascular devices.     

A simplified approach for evaluation of the polarity parameters for polymer using the K coefficient of the Mark-Houwink-Sakurada equation

Since two solvent polarity parameters, e.g., the Et(30) defined by Reichardt and the pi* defined by Kamlet and Taft, respectively, plotted with the K coefficient of the Mark-Houwink-Sakurada equation, presented good linear fits, this paper suggests applying the extrapolating method in the same way as the Zisman plot to obtain similar polarity parameters for polymers. In order to verify those obtained polarity parameter values for various polymers, literature-reported polarity values determined using other techniques are referenced and indicate that this paper introduced a simplified approach that can be applied to evaluate the polarity parameters for polymers. In this paper, since we observe that various polymers are of interest to present absolutely different slope tendencies, e.g., positive and negative, it is also suggested that polarity properties of polymers may be reinterpreted.     

The first regioselective palladium-catalyzed indolization of 2-bromo- or 2-chloroanilines with internal alkynes: a new approach to 2,3-disubstituted indoles

[reaction: see text] The first practical and economical process for synthesis of 2,3-disubstituted indole compounds has been developed with high regioselectivity by palladium-catalyzed indolization of 2-bromo- or chloroanilines and their derivatives with internal alkynes.     

Semi-cooperative strategies for differential games

The paper is concerned with a non-cooperative differential game for two players. We first consider Nash equilibrium solutions in feedback form. In this case, we show that the Cauchy problem for the value functions is generically ill-posed. Looking at vanishing viscosity approximations, one can construct special solutions in the form of chattering controls, but these also appear to be unstable. In the second part of the paper we propose an alternative semi-cooperative pair of strategies for the two players, seeking a Pareto optimum instead of a Nash equilibrium. In this case, we prove that the corresponding Hamiltonian system for the value functions is always weakly hyperbolic.Revised: May 2004     

On the error estimates for the rotational pressure-correction projection methods

In this paper we study the rotational form of the pressure-correction method that was proposed by Timmermans, Minev, and Van De Vosse. We show that the rotational form of the algorithm provides better accuracy in terms of the -norm of the velocity and of the -norm of the pressure than the standard form.

     

Regularity Results for the Generalized Beltrami System

Abstract For the generalized Beltrami system with two characteristic matrices, we deal with the regularity of its very weak solutions in the Sobolev class (1 < r < n). By changing the generalized Beltrami system into a class of a divergent elliptic system with nonhomogeneous items, we obtain that each of its very weak solutions is essentially a classical weak solution of a usual Sobolev class. Furthermore, we also establish a higher regularity of its weak solution if the regularity hypotheses of two characteristic matrices are improved. Supported by the National Natural Science Foundation of China (49805005) and by the research foundation of Northern Jiaotong University (2002SM061)     

Demonstration of a simple technique for determining the M/# of a holographic substrate by use of a single exposure

We propose and demonstrate a simple technique for determining the M/# parameter of a holographic recording material. In this method, divergent object and reference beams are used to produce a spatially varying index modulation. One can analyze the resultant diffraction pattern to find M/# by using only a single grating; existing techniques require many gratings.     

Large-area broadband saturable Bragg reflectors by use of oxidized AlAs

Broadband saturable Bragg reflectors (SBRs) are designed and fabricated by monolithic integration of semiconductor saturable absorbers with broadband Bragg mirrors. The wet oxidation of AlAs creates low-index AlxOy layers for broadband, high-index-contrast AlGaAs/AlxOy or InGaAlP/AlxOy mirrors. SBR mirror designs indicate greater than 99% reflectivity over bandwidths of 294, 466, and 563 nm for center wavelengths of 800, 1300, and 1550 nm, respectively. Highly strained and unstrained absorbers are stably integrated with the oxidized mirrors. Large-scale lateral oxidation techniques permit the fabrication of SBRs with diameters of 500 microm. Large-area, broadband SBRs are used to self-start and mode lock a variety of laser systems at wavelengths from 800 to 1550 nm.     

High-temperature sustainability of strong fiber Bragg gratings written into Sb-Ge-codoped photosensitive fiber: decay mechanisms involved during annealing

An antimony--germanium- (Sb--Ge-) codoped fiber specially designed for the fabrication of fiber Bragg gratings (FBGs) with high temperature sustainability has been developed. The photosensitivity and the high-temperature sustainability of FBGs that have been written into this fiber were tested. The results obtained showed that the FBG written into this fiber has a very high temperature sustainability of 900 degrees C. A decay mechanism that involves cation hopping is presented to explain the observed high temperature sustainability of the grating written into this fiber.