Viewpoints [computing in the 1990s]

Fifteen academic and industry leaders share their views on current and future computer and related technology. They discuss Europe 1992 and its impact on information technology, 25 years of MITI and its influence on computing research in Japan, concurrent engineering, the scientific data decade, information systems, superconductivity and computing technology, semiconductor technology at middle age, past and future computer networks, testing and design verification of electronic components, operating systems in the year 2000, data parallel computing, computer-aided software prototyping, and object-oriented software technology     

On the evolution of Internet technologies

The Internet has been evolving from its origins in the early 1970s, based on work sponsored by the U.S. Defense Advanced Research Projects Agency. While the basic design was known in 1973 and first published in 1974 and the system essentially deployed in the academic and military communities on January 1, 1983, much has happened in the intervening 20 years. The first commercial Internet services emerged in 1989 after the interconnection of the Internet to commercial e-mail services. By 1993, commercial versions of the World Wide Web had appeared, and by 2003, voice over IP service was growing rapidly, after its first commercial introduction around 1995 (See Vocaltec: http://www.vocaltec.com/html/about/company.shtml). The Internet of the future will be shaped by the tectonic forces of regulation, commercialization, technological change, and a wide range of policy concerns expressed at local, national, regional and international levels. In this paper, the effect of these forces is considered and an attempt made to project their effects into the future.     

Polyimide asymmetric membranes: Elaboration,morphology, and gas permeation performance

Asymmetric 2,2‐bis‐(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride (6FDA)‐2‐methyl‐1,3‐phenylenediamine (mPDA) polyimide membranes were prepared according to a phase‐inversion mechanism by using different solvent/nonsolvent blends. The membrane formation mechanism and the final performances of the asymmetric membranes have been found both nonsolvent and solvent nature dependent. From the visualization of cross sections of asymmetric membranes by scanning electron microscopy and the study of the permeation of two gases (N₂, CO₂) through asymmetric membranes, a relationship between elaboration conditions and asymmetric membranes characteristics could be drawn. The organization of polymer chains in solution strongly affects the final polymer arrangement and thus the final performances of the membrane. The influence of preliminary solvent evaporation before immersion has been shown to be dependent on the structure of the asymmetric membrane: finger‐like or sponge‐like structures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1838–1848, 2003     

Closed and noise-tolerant patterns in n-ary relations

Binary relation mining has been extensively studied. Nevertheless, many interesting 0/1 data naturally appear as n-ary relations with n ≥ 3. A timely challenge is to extend local pattern extraction, eg, closed pattern mining, to such contexts. When considering higher arities, faint noise affects more and more the quality of the extracted patterns. We study a declarative specification of error-tolerant patterns by means of new primitive constraints and the design of an efficient algorithm to extract every solution pattern. It exploits the enumeration principles of the state-of-the-art Data-Peeler algorithm for n-ary relation mining. Efficiently enforcing error-tolerance crucially depends on innovative strategies to incrementally compute partial information on the data. Our prototype is tested on both synthetic and real datasets. It returns relevant collections of patterns even in the case of noisy ternary or 4-ary relations, eg, in the context of pattern discovery from dynamic networks.     

Stiffness xanthan hydrogels: synthesis,swelling characteristics and controlled release properties

Summary  New xanthan hydrogels were synthesized at 90 C in water acid media using adipic acid dihydrazide (ADH) as crosslinking agent, in the presence of 1-ethyl-3[3-dimethyl amino] propyl carbodiimide hydrochloride (EDCI) as reagent. In these conditions, xanthan chains are in a predominantly helical conformation and through rheological measurements the influence of the temperature over the helix-coil transition was assessed. Xanthan hydrogels with different concentration in polysaccharide and ADH were obtained and characterised by elemental analysis and swelling properties. High concentration of xanthan (i.e. 25gL^-1) is needed to obtain gel due to the low available carboxylic functions in the helical conformation. During the swelling analysis, it was noted that high temperature (i.e. 90 C) favoured the conformational transitions within the network. The drug loading and releasing properties were estimated using methylene blue as model molecule and different experimental pH and ionic strength conditions.     

Adsorption of amphiphilic polysaccharides onto polystyrene latex particles

Adsorption properties of hydrophobically modified carboxymethylpullulans (HMCMP) with different degree of modification of alkyl chains (C8) onto polystyrene latex particles have been investigated. Hydrophobic interactions between the grafted alkyl chains and the surface are responsible for the adsorption of these polymers. Their adsorption isotherms are Langmuir type, therefore, there is only a monolayer of adsorbed polymer chains. Variations of plateau adsorbed amounts and adsorbed layer thicknesses show a competition between the number of anchors (alkyl chains) and size of loops. Desorption of adsorbed polymer chains has been tested in three different media (0.1 M NaCl, pure water and 0.01 M NaOH). The greater desorbed amount has been obtained in 0.01 M NaOH (hydrolysis of ester bonds).     

Delay-tolerant networking: an approach to interplanetary Internet

Increasingly, network applications must communicate with counterparts across disparate networking environments characterized by significantly different sets of physical and operational constraints; wide variations in transmission latency are particularly troublesome. The proposed Interplanetary Internet, which must encompass both terrestrial and interplanetary links, is an extreme case. An architecture based on a "least common denominator" protocol that can operate successfully and (where required) reliably in multiple disparate environments would simplify the development and deployment of such applications. The Internet protocols are ill suited for this purpose. We identify three fundamental principles that would underlie a delay-tolerant networking (DTN) architecture and describe the main structural elements of that architecture, centered on a new end-to-end overlay network protocol called Bundling. We also examine Internet infrastructure adaptations that might yield comparable performance but conclude that the simplicity of the DTN architecture promises easier deployment and extension.     

Evolution of the water–monomer dynamic interfacial properties during methyl methacrylate radical polymerization in a single monomer droplet: dependence on the chemical structure of the surfactant

This paper deals with the monitoring of the methyl methacrylate (MMA) droplet interface during its polymerization in one single monomer droplet by using a drop tensiometer. The droplet is stabilized by various molecular and polymer surfactants, in particular Pluronic® F68 and pullulan‐block‐Jeffamine®. The polymerization in one single droplet of the tensiometer can be seen as a way to study the interface of polymer nanoparticles during a mini‐emulsion polymerization assuming the concept of a perfect nanoreactor. It was found that the experimental results (surface tension and interfacial rheology) can be connected with MMA radical polymerization. These results demonstrate that the drop tensiometer technique enables interface evolution to be followed during polymer polymerization. © 2013 Society of Chemical Industry     

Developing Biceps to completely compute in subquadratic time a new generic type of bicluster in dense and sparse matrices

Data Mining and Knowledge Discovery - Given an m-by-n real matrix, biclustering aims to discover relevant submatrices. This article defines a new type of bicluster. In any of its columns, the...