Thermal stabilisation of PVC—An alternative approach

Although the Frye and Horst^1–3 theory of PVC stabilisation has been widely accepted, it has also been subject to some criticism. An alternative approach to the stabilisation of PVC, based on polar interactions within the PVC matrix, is postulated. Some of the results of research in this area which may be explained more convincingly on the basis of this approach are discussed in this paper.     

Comment on “On the original proof by reductio ad absurdum of the Hohenberg–Kohn theorem for many‐electron Coulomb systems”

We argue with Kryachko's criticism [Int J Quantum Chem 2005, 103, 818] of the original proof of the second Hohenberg‐Kohn theorem. The Kato cusp condition can be used to refute a “to‐be‐refuted” statement as an alternative to the original proof by Hohenberg and Kohn applicable for Coulombic systems. Since alternative ways to prove falseness of the “to‐be‐refuted” statement in a reduction ad absurdum proof do not exclude each other, Kryachko's criticism is not justified. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Comment on gas phase infrared spectrum and ab initio calculations of phosphorus(III) thiocyanide, SPCN

We show that two of the three bands assigned to SPCN are assignable to cyanogen and that the bands assigned to SPCl are done so in error, with the 712 cm(-1) band in the spectrum of Allaf and Odeh assignable to HCN. There is no evidence for either ClPS or SPCN in the spectra shown. Finally low resolution IR spectroscopy by itself, whilst useful in assisting in the identification of pyrolysis products does not provide unambiguous identification and requires support by rigorous computation, band modelling and correct use of the literature. None of these are evidenced in the present paper of Allaf and Odeh nor indeed in the work that was the subject of our previous criticism and re-analysis.     

Klein on the origin of the concept of chemical compound

Ursula Klein has argued that Geoffroy’s table of chemical affinities, published in 1718, marked the emergence of the concepts of chemical compound and chemical combination central to chemistry. In this paper her position is summarised and then modified to render it immune to criticism that has been levelled against it. The essentials of Geoffroy’s chemistry are clarified and adapted to Klein’s picture by way of a detailed comparison of it with Boyle’s corpuscular chemistry that proceeded Geoffroy’s by over half a century. The idea that Geoffroy’s notion of chemical combination marked a significant turning point in the emergence of modern chemistry is defended against the charge that it is Whiggish.     

Kaolinite-genetic and thermoanalytical parameters

Different genetic types of kaolinite were investigated from the point of view of crystallinity. The measurements were carried out by means of different methods of thermal analysis, infrared spectroscopy and X-ray diffraction. The different parameters of the degree of crystallinity based on a series of 85 nearly monomineralic samples were critically studied. The estimated parameters of the different methods show relatively bad correlation. The reason for the difference in the data come from the fact that the methods give information about different parts and/or features of the mineral structure. The results are better if several parameters are simultaneously used. In the present paper the results of thermal parameters are summarized.     

A variational treatment of the potential of impurity ions in semiconductors with spatially variable dielectric constants

The primary purpose of the present paper consists in obtaining a correction to Dingle's potential for a (point) impurity ion (embedded) in Si or Ge. This goal is accomplished by making use of a variational principle in taking into account the effect of the spatial variation of the dielectric constant in the respective medium. It is found that the resulting impurity-ion potential can be represented as the product of Dingle's potential and a factor which, with increasing distance from the charged impurity, approaches unity. The secondary purpose of the present paper consists in suggesting a way for the modification of an impurity-ion potential that has been obtained previously with a boundary condition, that, in retrospect, is open to criticism. It is shown that the modified impurity-ion potential can be represented as the product of the author's previous potential and a factor which, with increasing distance from the charged impurity, approaches unity.     

《植物纤维化学》中的天然高分子教学的改革实践

天然高分子作为一种资源,由于它们来源丰富且可再生利用,越来越显示出其重要地位.本文介绍了作者将培养学生的创新能力理念贯穿于教学实践中,对天然高分子教学实践采取了一些改革措施.以纤维素、木质素及半纤维素的结构-性质及其相互关系为主线展开教学内容,加强学生的高分子理论的基础知识,培养高素质的科学技术人才;选修课以研究式教学为主,加强培养学生自学能力和创新理念.改革教学模式,在教学过程中提高学生的学习兴趣,加强"教"与"学"的互动,提倡科学的批评精神,培养创新精神,以达到良好的教学目的.     

“Comment” on the Reply to the Paper “On the Elber–Karplus Reaction Path-Following Method and Related Procedures”

The flaws in the Reply [1] to our paper [2] have been pointed out. Elber and Karplus (EK) have not disproved our irrefutable global statement that the energy average cannot be minimized which rebuts the theoretical background of EK-type calculations. Another statement of ours has shown that even a curve for which the average energy is locally minimal for all directional perturbations in the sense of classical variational calculus cannot be identical with the reaction path (RP) defined as a steepest descent path (SDP). EK found an error in the early preprint of our theoretical paper [3] and because of this error they qualified our correct variational statement as false for all the SDPs consisting of a straight line each. Mixing global and variational arguments, EK refuted our criticism in a logically incorrect manner. In this Comment we prove that both of our earlier statements invariably remain in force and the criticism included in those has been as well-established and solid as was before.     

Thermodynamic analysis of the hydrogen peroxide decomposition parameters

This paper discusses the estimation of the decomposition parameters of the liquid–gas-steam system, which is produced by the hydrogen peroxide decomposition at isobar conditions. The thermodynamic analysis calculates the two critical concentrations, which mark the phase transitions of the system depending on the initial pressure and hydrogen peroxide concentration.     

A reply to: “Bis-pericyclic retrocycloaddition and the importance of avoiding piecewise analysis”

Recent criticism of a tentative interpretation of the cheletropic response of the aza-bicyclo[4.2.]nona-2,4,7-triene frame is shown to be invalid.     

Calculation of the kinetic parameters

The paper reports the calculation of kinetic parameters (activation energy, pre-exponent and reaction order) of thermodegradation of some phenol stabilizers. For this purpose, a software package for IBM-compatible personal computers is proposed. The first calculation of kinetic parameters (E, Z, n) was carried out for these compounds. The package can be applied for kinetic calculations on the thermodegradation of other substances.     

Reply to “Comments on the paper entitled ‘The formulation and modelling of the anodic dissolution of zinc through adsorbed intermediates’ ” by C. Cachet et al.

The points raised in the paper entitled “Comments on the paper entitled ‘The formulation and modelling of the anodic dissolution of zinc through adsorbed intermediates”’ have been discussed. It has been shown that, in contrast to the statements in the “Comments”, most of the papers concerning the reaction schemes suggested for the interpretation of the dissolution or deposition of metals, which were considered as a support for the opinion of the Authors of the “Comments”, support the views expressed in our original paper [J. Electroanal. Chem. 583 (2005) 148]. On the other hand, it has been stressed again that the criticism expressed in the original paper refers to dubious conclusions drawn on the basis of transient measurements.     

应用化学专业新生研讨课教学实践

针对中学传统应试教育与大学创新教育的矛盾,西北农林科技大学应用化学专业开设新生研讨课,加强培养学生创新意识与创新能力以及学术探索和批判精神。教学内容包括专业介绍以及应用化学学科的9个学术领域,教学方式以小班讨论为主。本文探讨了该课程的教学模式、教学内容、考核方式以及教学效果,为相关专业开设新生研讨课提供了新思路。     

Chemiluminescence from oxidation of polypropylene: Some comments on a kinetic approach

We present a detailed criticism of the kinetic approach to the analysis of data obtained from measurements of the very weak chemiluminescence accompanying the oxidation of polypropylene. It is shown that a kinetic model proposed by other workers is based upon invalid assumptions, leads to kinetic parameters which are not sensible, and requires measurement of the properties which it claims to predict.     

Correlation among parameters of the extended-Rydberg potential energy function

This paper reports a remarkable correlation among parameters of extended-Rydberg potential function by recasting the Morse potential in the form of extended-Rydberg function via the application of infinite series expansion to the exponential terms of the Morse function. By using linear regression, a reasonable band that encompasses 90% of the diatomic combination given by Huxley and Murrell [J. Chem. Soc. Faraday Trans. II 79 (1983) 323] is furnished in a plotted characteristic map.     

A Constrained Disorder Refinement: “Reinvestigation of “Single‐Crystal X‐ray Structure of 1,3‐Dimethylcyclobutadiene” by M. Shatruk and I. V. Alabugin”

Shatruk and Alabugin propose an alternative structural model for the observed electron density that we have attributed to the photochemical formation of 1,3‐dimethylcyclobutadiene in a protective solid crystalline matrix. The main criticism from Shatruk and Alabugin concerns the modeling of the disorder in the calixarene cavity and in particular the neglect of a residual electron density close to the O1 atom. We published (Chem. Eur. J. 2011 , 17, 10021) our opinion concerning this “ignored peak” in the Supporting Information of the paper. The current response to the Correspondence demonstrates that Shatruk and Alabugin have over‐modeled our data by assigning a small electron density peak, which is hardly more than the density corresponding to a hydrogen atom, to an under‐occupied oxygen site, using inappropriate refinement contraints.     

Paper conservation methods: a literature review

The main paper conservation methods are presented, classified in the following categories: preparation of the intervention, disinfestation and disinfection/sterilization, surface/dry cleaning, wet cleaning, chemical stabilization, paper repairs, consolidation and strengthening. Treatment documentation is also discussed. The targets, the historical aspects, the general principles, the materials and equipment, the acceptance and criticism pertaining to each method are briefly reviewed, and the most important research for their evaluation is presented. Several paper stabilization strategies, such as deacidification and iron gall ink stabilization, applicable to paper are elucidated. Specific consolidation and strengthening methods for paper, such as lamination and paper splitting are also discussed. The review mainly focuses on the established methods, but experimental, abandoned or insufficiently documented methods are also included. Shortcomings and limitations of several methods were found in the literature, concerning health issues, limited effectiveness, adverse side-effects on the treated artefacts and restricted applicability.     

Statistical adjustment of parameters for potentiometric titration data

The paper deals with the statistical problem of adjusting parameters to the experimental data from potentiometric titrations. The parameters to be refined are, first, the value of the stability constant of the titration reaction, and, second, the equivalence volume. The paper discusses the selection of the error variable and the need for weighting in the optimization procedure. The case where both parameters are refined at the same time is also considered. Special reference is made to linearized titration curves for the determination of the equivalence volume.     

Short-and long-range interaction parameters for polydimethylsiloxanes with different terminal groups

The paper discusses the behaviour of polydimethylsiloxanes with different terminal groups as induced by polymer molecular weight and solvent mixture composition in dilute solution.