Dew- and bubble-point measurements for the mixtures of dichlorodifluoromethane and bromotrifluoromethane

The dew and bubble points for the mixtures of dichlorodifluoromethane (CCl₂F₂; R 12) and bromotrifluoromethane (CBrF₃; R13B1) were measured with the use of a constant-volume method coupled with an expansion procedure and visual observation of the meniscus at the vapor-liquid interface. In order to check the reliability of the apparatus used, vapor pressure measurements were conducted for carbon dioxide at 273.15 K and for two pure components, CCl₂F₂ and CBrF₃. Thirty-eight dew and bubble points of the CCl₂F₂+CBrF₃ system were determined for four different compositions of 0, 21, 45, and 70 mol % CBrF₃ in the range of temperatures from 299 to 384 K, pressures up to 4.2 MPa, and densities from 89 to 1228 kg · m^–1.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Simultaneous Edge‐on to Face‐on Reorientation and 1D Alignment of Small π‐Conjugated Molecules Using Room‐Temperature Mechanical Rubbing

In this study, room‐temperature mechanical rubbing is used to control the 3D orientation of small π‐conjugated molecular systems in solution‐processed polycrystalline thin films without using any alignment substrate. High absorption dichroic ratio and significant anisotropy in charge carrier mobilities (up to 130) measured in transistor configuration are obtained in rubbed organic films based on the ambipolar quinoidal quaterthiophene (QQT(CN)4). Moreover, a solvent vapor annealing treatment of the rubbed film is found to improve the optical and charge transport anisotropy due to an increased crystallinity. X‐ray diffraction and atomic force microscopy measurements demonstrate that rubbing does not only lead to an excellent 1D orientation of the QQT(CN)4 molecules over large areas but also modifies the orientation of the crystals, moving molecules from an edge‐on to a face‐on configuration. The reasons why a mechanical alignment technique can be used at room temperature for such a polycrystalline film are rationalized, by the plastic characteristics of the QQT(CN)4 layer and the role of the flexible alkyl side chains in the molecular packing. This nearly complete conversion from edge‐on to face‐on orientation by mechanical treatment in polycrystalline small‐molecule‐based thin films opens perspectives in terms of fundamental research and practical applications in organic optoelectronics.     

A survey of usability capability maturity models: implications for practice and research

Improving the position and effectiveness of user-centred design (UCD) in software and product development is a challenge in many companies. One step towards improvements is to carry out a usability capability maturity (UCM) assessment to evaluate the strengths and weaknesses of a development organisation in UCD. While several diverse UCM models have been introduced, little research has been published in the public domain on these models. The paper aims to fill this gap by analysing the main features of the models. The results show that most models represent different approaches - although some of them have the same roots - meaning that understanding one model is not enough to understand the basics of another model. All models can be used for examining the status of UCD in individual development projects. In addition, models provide various means for assessment of the status of UCD in other organisational areas. The level of documentation of models varies a lot, and very few empirical research results exist. Based on the results, implications for practice and research are suggested.     

A Defect Localization Scheme for Cellular Nanocomputers

Computers with device feature sizes of a few nanometers—so-called nanocomputers—are expected within a few decades, but this expectation is accompanied by the realization that the boundary conditions of such systems differ substantially from those of current VLSI-based computers. Prominent among the concerns is the increased degree of permanent defects that will affect nanocomputers, such as defects caused by imperfections at the manufacturing stage, but also defects occurring later, possibly even during the use of these systems. New techniques to deal with defects are called for, but given the huge number of devices involved, such techniques may need to be self-contained: they need be applicable at local levels without outside control, even while computations continue to take place. This paper proposes an important element in such techniques, i.e. the localization of defects among a huge number of devices. It employs a cellular automaton-based architecture, and uses statistical techniques combined with randomly moving configurations in the cellular space to estimate defect locations.

Structure-activity relationships of phomactin derivatives as platelet activating factor antagonists

Phomactins, natural products isolated from the culture broth of marine fungus Phoma sp., were found to be active as PAF antagonists. This unique carbon skeleton led us to investigate the structure-activity relationship demonstrating that the lipophilicity at C-(7-8), acetoxy, (methoxycarbonyl)oxy, and 3-isoxazolyloxy substitution at C-20, and 2-beta-OH configuration at C-2 are all required for the enhancement of inhibitor activity.     

A perspective on the contribution of surfactants and lipids toward “Green Chemistry”: Present states and future potential

“Green Chemistry” has become a subject of increasing interest in recent years. The goal of efforts in this area is to develop environmentally friendly methods and processes to replace traditional reactions that use organic solvents, consume much energy, and generate undesirable by-products and/or waste. Utilization of renewable resources is an important component of Green Chemistry. Fats and oils represent one such resource. They can give rise to many types of surfactants and lipids that can modify properties of boundary phases between different phases. Thus, phase-transfer catalysts (PTC) based on surfactants or lipids have been reported to be useful in reactions such as oxidation and hydration reactions and in glycidyl ether formation. Another approach to satisfying Green Chemistry requirements is the recovery and recycling of reactants and/or substrates used. In the preparation of alkyl glyceryl ethers, the intermediate 1,3-dioxolane compounds prepared by addition of acetone to alkyl glycidyl ethers can be hydrolyzed to regenerate reusable acetone. Other examples of methodologies based on surfactants or lipids are summarized, and their potential contribution to Green Chemistry is discussed.     

EXACT THERMOELECTROELASTICITY SOLUTION FOR A PENNY-SHAPED CRACK IN PIEZOELECTRIC MATERIALS

This paper investigates the electromechanical fracture behavior of a penny-shaped crack in piezoelectric materials subjected to a uniform heat flow far away from the crack region. The crack is treated as isothermal. First, the temperature field is obtained by using the Hankel transform technique. The thermoelectromechanical field is then investigated by solving the themopiezoelectoelasticity governing equations. The explicit solutions for the stress intensity factors near the crack tip are presented. The exact solution for the whole-field stresses and electric displacements are obtained.     

STEADY THERMAL STRESSES IN AN INFINITE NONHOMOGENEOUS ELASTIC SOLID CONTAINING A CRACK

This article considers the crack problem for an infinite nonhomogeneous elastic solid subjected to steady heat flux over the crack surfaces. The aim is to understand the effect of nonhomogeneities of materials on stress intensity factors. By using the Fourier transforms, the problem is reduced to a Fredholm integral equation of the second kind which is solved numerically. Results are presented illustrating the influence of the nonhomogeneity of the material on the stress intensity factors. For some groups of the material constants, there exist minimum stress intensity factors, which is very interesting for the understanding of compositions of advanced functionally gradient materials.     

PIEZOTHERMOELASTIC ANALYSIS OF A CROSS-PLY LAMINATE CONSIDERING THE EFFECTS OF TRANSVERSE SHEAR AND COUPLING

In this study, we treat the behavior of a piezothermoelastic composite plate taking into account the effects of transverse shear and coupling among mechanical, thermal, and electrostatic fields. As an analytical model, we consider a rectangular laminate composed of several fiber-reinforced laminae and a piezoelectric layer. All the laminae are assumed to exhibit 2-mm symmetry and the principal axes of anisotropy to coincide with coordinate axes, that is, a cross-ply laminate is considered. We assume that the laminate is subjected to mechanical, thermal, and electrical loads with all edges simply supported and treat the problem as a coupled piezothermoelastic one. Numerical calculation is carried out to examine the effects of transverse shear and coupling on the behavior of the laminate. Moreover, the control of the deflection by applied voltage is examined.     

Applications of protecting groups in the synthesis of surfactants, lipids, and related compounds

Several types of alkyl ether lipids were prepared in high yield and high purity using protecting groups such as 1,3-dioxolane compounds or allyl ethers. We also succeeded in the industrial production of alkyl glyceryl ethers using the reaction of alkyl glycidyl ethers with acetone to give 1,3-dioxolane compounds, from which the desired alkyl glyceryl ethers were obtained in high quantities. 1,3-Dioxolane (ketal) compounds based on acetone were used in the enzymatic preparation of monoglyceride on an industrial scale. On the basis of these protecting groups, we extended our studies concerning both the preparations and properties of novel polyol ether compounds, beginning with alkyl glycidyl ethers. Another typical property of surfactants containing 1,3-dioxolane units and acetal is degradability under acidic conditions. Several types of destructible/cleavable surfactants based on polyols, such as carbohydrates and polyethyleneglycol, were prepared. As for natural products containing polyol skeletons, much attention has been paid to their molecular design, in which protecting groups such as 1,3-dioxolane compounds or allyl ether have contributed to synthetic strategies.