Electrical conductivity and contact phenomena in porous metallic materials

The change in electrical resistance of copper fiber and powder compacts upon heating from room to the sintering temperature was studied. It was found that different regimes of heating in vacuum did not affect the temperature dependence of electrical resistance. A relationship between electrical conductivity and the relative size of interparticle contacts was derived for a model fiber body. This was in good agreement with data on the tensile strength of real fiber materials.     

Ethics and new technological applications in animals

Cloning and genetic engineering of animals are in the picture of public debate. The intrinsic value is an important issue in the ethical debate about both new technologies. The intrinsic value is introduced during the seventies as counterpart of the instrumental use of animals. The introduction of two new aspects, 'the ability to function independently' and 'naturalness', gives more insight in the meaning of intrinsic value. In two cases the consequences of the recognition of intrinsic value is discussed. The author concludes that cloning and genetic engineering are an infringement of the intrinsic value. The ethical debate about the transgenic bull Herman is the first experience in practice.     

Surface phenomena and continuous casting

Understanding the transformation of liquid steel to solid steel is the most fundamental aspect of continuous casting;however,it remains a complex subject with a number of unresolved issues.In this paper,the following aspects of mold operation which give rise to sub-surface defects will be discussed;meniscus solidification,surface and interfacial energies,effects of gas bubbles,and the dynamic nature of the liquid slag-liquid steel interface.     

表面现象与连铸

了解钢从液态到固态的转变是连铸最基础的方面,然而它还是一个很多问题尚未解决的复杂课题。论述了结晶器操作导致皮下缺陷的形成,包括钢液在弯月面凝固、表面能和界面能变化、气泡的影响以及钢液与液渣界面的动力学现象。     

Development of new functional immobilized microbial cell systems and their applications

Immobilized cell technology has been playing a vital role in the development of fermentation processes. For the past several years, I have been working on immobilized cell systems with an aim of developing novel immobilized biosystems where physical, chemical as well as biological functions are incorporated into the immobilization carrier. By efficiently integrating these new functions with the innate abilities of immobilized cells, the area where immobilized cell systems can be utilized will expand, and the process efficiency will be greatly improved.     

Dynamic and equilibrium interfacial phenomena in liquid steel-slag systems

The equilibrium interfacial energy between a liquid iron alloy and a liquid slag is a key physical parameter in the design of steel-refining processes as high interfacial energies are desired to avoid emulsification of slag in steel and the creation of casting defects. During a chemical reaction between a liquid iron alloy droplet and a liquid slag, it is possible to observe by X-ray photography a number of dynamic interfacial phenomena such as droplet flattening, interfacial turbulence, and spontaneous emulsification that can potentially lead to serious processing problems. These dynamic phenomena have been studied during reactions between Fe-Al and Fe-Ti alloys and silica-containing slags, and the presence of significant interfacial disturbance has been observed during the times of high reaction rate between the slag and the metal. It is suggested that interfacial chemical reactions induce Marangoni and natural convection at the slag-metal interface. This interfacial flow gives rise to interfacial waves due to a Kelvin-Helmholtz instability. The waves grow, become unstable, and lead to spontaneous emulsification of slag in steel and steel in slag. Experiments using industrial samples and controlled laboratory tests have indicated that this phenomenon may be more common than once thought and could lead to some serious problems in the processing of steel alloys containing high quantities of aluminum and/or titanium. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

Disposable contact lenses and their complications

Disposable soft contact lenses (DSCLs) have been marketed as a safer alternative to conventional soft lenses. Extended-wear DSCLs are designed for one or two weeks of continuous use before disposal. Those for daily wear are designed for use as conventional daily wear soft lenses, with daily removal and storage for 2 to 4 weeks before disposal. Beside minor complications, such as corneal abrasion, giant papillary conjunctivitis and toxic epithelial reactions to contact lens solutions, the most serious complication occurring in contact lens users is ulcerative keratitis. Several case-control studies performed over the last years, demonstrated that disposable contact lenses were associated with a 14-fold excess risk of ulcerative keratitis compared with that for patients wearing conventional daily-wear soft contact lenses and a 13-fold excess risk compared with that for wearers of rigid gas permeable contact lenses. However, the major risk factor for corneal ulceration in contact lens wearers is overnight lens wear of 1 to 3 nights. It was estimated that 49 to 74% of cases of contact lens associated ulcerative keratitis could be prevented by eliminating overnight wear.     

Highly fluorinated amphiphiles and colloidal systems, and their applications in the biomedical field. A contribution

Fluorocarbons and fluorocarbon moieties are uniquely characterized by very strong intramolecular bonds and very weak intermolecular interactions. This results in a combination of exceptional thermal, chemical and biological inertness, low surface tension, high fluidity, excellent spreading characteristics, low solubility in water, and high gas dissolving capacities, which are the basis for innovative applications in the biomedical field. Perfluoroalkyl chains are larger and more rigid than their hydrogenated counterparts. They are considerably more hydrophobic, and are lipophobic as well. A large variety of well-defined, modular fluorinated surfactants whose polar head groups consist of polyols, sugars, sugar phosphates, amino acids, amine oxides, phosphocholine, phosphatidylcholine, etc, has recently been synthesized. Fluorinated surfactants are significantly more surface active than their hydrocarbon counterparts, both in terms of effectiveness and of efficiency. Despite this, they are less hemolytic and less detergent. Fluorosurfactants appear unable to extract membrane proteins. Fluorinated chains confer to surfactants a powerful driving force for collecting and organizing at interfaces. As compared to non-fluorinated analogs, fluorosurfactants have also a much stronger capacity to self-aggregate into discrete molecular assemblies when dispersed in water and other solvents. Even very short, single-chain fluorinated amphiphiles can form highly stable, heat-sterilizable vesicles, without the need for supplementary associative interactions. Sturdy microtubules were obtained from non-chiral, non-hydrogen bonding single-chain fluorosurfactants. Fluorinated amphiphiles can be used to engineer a variety of colloidal systems and manipulate their morphology, structure and properties. Stable fluorinated films, membranes and vesicles can also be prepared from combinations of standard surfactants with fluorocarbon/hydrocarbon diblock molecules. In bilayer membranes made from fluorinated amphiphiles the fluorinated tails segregate to form an internal teflon-like hydrophobic and lipophobic film that increases the stability of the membrane and reduces its permeability. This fluorinated film can also influence the behavior of fluorinated vesicles in a biological milieu. For example, it can affect the in vivo recognition and fate of particles, or the enzymatic hydrolysis of phospholipid components. Major applications of fluorocarbons currently in advanced clinical trials include injectable emulsions for delivering oxygen to tissues at risk of hypoxia; a neat fluorocarbon for treatment of acute respiratory failure by liquid ventilation; and gaseous fluorocarbon-stabilized microbubbles for use as contrast agents for ultrasound imaging. Fluorosurfactants also allow the preparation of a range of stable direct and reverse emulsions, microemulsions, multiple emulsions, and gels, some of which may include fluorocarbon and hydrocarbon and aqueous phases simultaneously. Highly fluorinated systems have potential for the delivery of drugs, prodrugs, vaccines, genes, markers, contrast agents and other materials.