Synthesis and characterization of a novel chitosan‐based network prepared using naturally occurring crosslinker

Novel chitosan‐based polymeric networks were synthesized and characterized by FTIR, UV and C¹³ NMR. A naturally occurring crosslinking reagent—genipin, which has been used in herbal medicine and in the fabrication of food dyes, was used to prepare crosslinked chitosan hydrogel. The heterocyclic compound of genipin crosslinked chitosan was formed by a nucleophilic attack by amino group on the olefinic carbon atom at C‐3 of deoxyloganin aglycone, followed by opening of the dihydropyran ring and attack by the secondary amine group on the intermediate aldehyde group. Additional, secondary amide linkages could be established in the genipin crosslinked chitosan network by the reaction of ester group of genipin with amino group of chitosan. This bifunctional linkages of genipin with amino group of chitosan leads to form crosslinked networks. Genipin reacted with nucleophilic reagent such as chitosan could further go through a polymerization to form oligomer‐bridge in the crosslinked network. The finally formed chitosan networks are blue color, elastic and exhibits pH‐dependent swelling characteristics. The swelling ratio of the chitosan hydrogel increased at pH lower than 3 and higher than 11 due to the hydrolysis of amide linkage in the genipin crosslinked chitosan network by acid or alkaline, followed by the protonation of amine group or ionization of carboxyl acid group in the network. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2804–2814, 2000     

Whirling of a forced cantilevered beam with static deflection. I: Primary resonance

The response of a slender, clastic, cantilevered beam to a transverse, vertical, harmonic excitation is investigated. The effects of nonlinear curvature, nonlinear inertia, viscous damping and static load are included. Previous work often has neglected the static deflection caused by the weight of the beam, which adds quadratic terms in the governing equations of motion. Galerkin's method is used with three modes and approximate solutions of the temporal equations are obtained by the method of multiple scales. Primary resonance is treated here, and out-of-plane motion is possible in the first and second modes when the principal moments of inertia of the beam cross-section are approximately equal. In Parts II and III, secondary resonances and nonstationary passages through various resonances are considered.     

Residual thermal birefringence in freely quenched plates of amorphous polymers: Simulation and experiment

Free quenching experiments were performed on thin plates of polystyrene (PS) and polycarbonate (PC). The thermal birefringence distribution along the thickness direction of the plates was measured. The birefringence data were compared with the results of a numerical simulation based on the linear viscoelastic and photoviscoelastic constitutive equations for the mechanical and optical properties, respectively, and the first‐order rate equation for volume relaxation. The effects of the initial temperature, quenching temperature, and quenching media on the development of residual thermal stresses and birefringence were evaluated. At higher initial temperatures (>105 °C), the thermal birefringence in quenched PS plates was negative at the center and positive at the surface, whereas at lower temperatures (close to the glass‐transition temperature), the birefringence became positive at the core and negative at the surface or positive through the entire cross section of the plate. The birefringence in freely quenching PC plates was positive at the center and negative at the surface at any initial temperature. These observations were in fair agreement with predicted data. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1850–1867, 2003     

Decomposition of Complete Graphs into Cycles and Stars

Let C _k denote a cycle of length k and let S _k denote a star with k edges. As usual K _n denotes the complete graph on n vertices. In this paper we investigate decomposition of K _n into C _l ’s and S _k ’s, and give some necessary or sufficient conditions for such a decomposition to exist. In particular, we give a complete solution to the problem in the case l = k = 4 as follows: For any nonnegative integers p and q and any positive integer n, there exists a decomposition of K _n into p copies of C ₄ and q copies of S ₄ if and only if ${4(p + q)={n \choose 2}, q\ne 1}$ if n is odd, and ${q\geq max\{3, \lceil{\frac{n}{4}\rceil}\}}$ if n is even.     

The Visual Design and Control of Trellis Display

Abstract

Trellis display is a framework for the visualization of data. Its most prominent aspect is an overall visual design, reminiscent of a garden trelliswork, in which panels are laid out into rows, columns, and pages. On each panel of the trellis, a subset of the data is graphed by a display method such as a scatterplot, curve plot, boxplot, 3-D wireframe, normal quantile plot, or dot plot. Each panel shows the relationship of certain variables conditional on the values of other variables. A number of display methods employed in the visual design of Trellis display enable it to succeed in uncovering the structure of data even when the structure is quite complicated. For example, Trellis display provides a powerful mechanism for understanding interactions in studies of how a response depends on explanatory variables. Three examples demonstrate this; in each case, we make important discoveries not appreciated in the original analyses. Several control methods are also essential to Trellis display. A control method is a technique for specifying information so that a display can be drawn. The control methods of Trellis display form a basic conceptual framework that can be used in designing software. We have demonstrated the viability of the control methods by implementing them in the S/S-PLUS system for graphics and data analysis, but they can be implemented in any software system with a basic capability for drawing graphs.     

Theoretical Calculations of Combination of Hydrogen Atoms

A resonance-complex set was developed to investigate the process of combination of hydrogen atoms with a modified resonance-complex theory and Monte-Carlo trajectory method over the temperature range 40-300 K. The obtained ratios of ortho to para at 300 K and at 77 K agree satisfactorily with experimental results. Unlike previous results, a maximum of the rate coefficient as a function of temperature is found near 150 K.     

电子器件包封用聚硅氧烷树脂的合成

电子器件包封用的聚硅氧烷包封料一般都是由聚硅氧烷树脂、固化剂、着色剂、脱模剂以及无机填料等制成的聚硅氧烷模塑粉。这种模塑粉在工艺性能和工作性能上必须满足一系列苛刻的要求。聚硅氧烷模塑粉能否满足这些要求,关键在聚硅氧烷树脂。本文将简要报导一种适合于制造这类模塑粉的NJ-7401聚硅氧烷树脂的合成。     

Synthesis of Heterobimetallic Phosphido-Bridged W-Mo Complexes with Chelating dppe and dppm Ligands

Reactions between and bidentate phosphines (dppm and dppe) produced complexes and with chelating dppm and dppe ligands as only products. No bridging bidentate phosphine complex was observed. Both complexes were spectroscopically characterized.     

High-resolution through-focus metric with two-pitch grating target

Through-focus focus-metric is a method that is used to analyze images on a fixed plane with the help of focus-metric values when the target moves through the focus. In this study, an optical microscope having a magnification of 250× is constructed. A two-pitch grating target is imaged on a CCD detector and through-focus image data are measured. In addition, the optical field on the CCD detector is simulated using the boundary element method and physical optics propagation. By comparing the measured focus-metric signatures with the simulated signatures, information regarding the linewidth is obtained. The results show that the through-focus focus-metric method is a very sensitive method that can be used for measuring parameters such as the linewidth. Thus, a nanoscale resolution can be achieved.