Solid state characterization of the structure of chitosan films

Films of chitosan, prepared by different fabrication processes, were examined at several structural levels, from the molecular to the macroscopic. This revealed the presence of polymorphic crystal forms, which varied with film treatment. Similarly, morphological structures varying from spherulites to rods were formed, depending on film processing conditions. The effect of structure on the mechanical properties, as well as the orientability of the films, were also investigated.     

Simple preparation of iron stabilized carboxonium ions. Concurrent complexation,rearrangement and alcohol addition to terminal acetylenes

CpFe(CO)₂[C(OEt)R]BF₄ complexes can be prepared by reaction of CpFe(CO)₂(isobutylene)BF₄ with monoalkylated acetylenes in methylene chloride/ethanol solutions. Methyl propiolate yields methyl trans-2-ethoxy-acrylate, in a reaction catalytic in CpFe(CO)₂(isobutylene)BF₄, and internal acetylenes can be transformed to CpFe(CO)₂(vinyl ether)BF₄ complexes.     

The influence of hydrogen chloride doping level on the complex refractive indices of anisotropic polyaniline film: Application of a new internal reflection waveguide coupling technique

Nondestructive three‐dimensional refractive‐index measurements are used for the determination of both crystallinity and orientation in thin polymer films. The prism waveguide coupler is particularly suitable for three‐dimensional isotropic and anisotropic thin‐film studies because of the quantitative character of the information obtained and the ease of data acquisition. It has been limited, however, to measuring the refractive index of optically transparent or weakly absorbing films. This study shows that a modified prism waveguide coupler can be used to determine the complex refractive index over a range from transparent to highly absorbing films from the internally reflected light intensity. Thus, both the refractive index, n, and the extinction coefficient, k, can be obtained. This method is used to determine the anisotropic three‐dimensional n and k values of spin‐coated emeraldine base and hydrogen chloride doped emeraldine salt polyaniline films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2481–2490, 2001     

Metric Mahler measures over number fields

For an algebraic number α, the metric Mahler measure \({m_1(\alpha)}\) was first studied by Dubickas and Smyth [4] and was later generalized to the t-metric Mahler measure \({m_t(\alpha)}\) by the author [16]. The definition of \({m_t(\alpha)}\) involves taking an infimum over a certain collection N-tuples of points in \(\overline{\mathbb{Q}}\), and from previous work of Jankauskas and the author, the infimum in the definition of \({m_t(\alpha)}\) is attained by rational points when \({\alpha\in \mathbb{Q}}\). As a consequence of our main theorem in this article, we obtain an analog of this result when \({\mathbb{Q}}\) is replaced with any imaginary quadratic number field of class number equal to 1. Further, we study examples of other number fields to which our methods may be applied, and we establish various partial results in those cases.     

抗坏血酸有机锗倍半氧化物的合成及抗癌活性研究

通过三氯锗仿与抗坏血酸分子的加成反应,合成了一种新型有机锗倍半氧化物,产物的结构通过元素分析、IR及UV光谱等方法进行了表征．生物活性实验表明合成物对小鼠S-180肿瘤生长具有显著的抑制作用．     

High-spin structure of yrast-band in 78Kr

Lifetime of levels up to 22⁺, have been measured in ⁷⁸Kr and an oblate shape is assigned to the ground state using the CSM and the configuration dependent shell correction calculations. Calculations further show that ⁷⁸Kr is highly γ-soft nucleus. The experimental Q _t values coupled with theoretical calculations indicate an oblate shape for ⁷⁸Kr at low spins and triaxial shape at higher spins     

Prediction of DNA far-IR absorption spectra based on normal mode analysis

 We present a computational method which couples normal mode analysis in internal coordinates of a molecule with very far IR spectroscopy. The analytical expression for the dependence of IR absorption on frequency incorporates frequencies and optical activities of each normal mode. In order to predict far-IR spectra of a molecule we evaluate the optical activity of each normal mode. This optical activity is determined by the vibration amplitude of the dipole moment produced by a normal mode. We calculated normal modes of DNA double-helical fragments (dA)₁₂ · (dT)₁₂ and (dA-dT)₆ · (dA-dT)₆ and evaluated their optical activities. These were found to be very sensitive to the DNA base-pair sequence. The positions of the resonance peaks in the calculated absorption spectrum of (dA)₁₂ · (dT)₁₂ are in a good agreement with those obtained by Fourier transform IR spectroscopy (Powell JW et al. 1987 Phys Rev A 35: 3929–3939). Received: 20 June 2000 / Accepted: 5 January 2001/ Published online: 3 May 2001