Renewed interest

The power of optical spectroscopies is that they are often much better developed than their electron-, ion- and atom-based counterparts, and therefore provide results that are easier to interpret. Furtlienuore, photon-based teclmiques are uniquely poised to help in the characterization of liquid-liquid, liquid-solid and even solid-solid interfaces generally inaccessible by other means. There has certainly been a renewed interest in the use of optical spectroscopies for the study of more realistic systems such as catalysts, adsorbates, emulsions, surfactants, self-assembled layers, etc. 

In solid state materials, single-step electron transport between dopant species is well known. For example, electron-hole recombination accounts for luminescence in some materials [H]. Multistep hopping is also well known. Models for single and multistep transport are enjoying renewed interest in tlie context of DNA electron transfer [12, 13, 14 and 15]. Indeed, tliere are strong links between tire ET literature and tire literature of hopping conductivity in polymers [16]. 

As PWB technology is refined to provide greater integration using finer conductor lines, there is renewed interest in hquid resists. The absence of a cover sheet and the abihty to apply thinner films both contribute to improved resolution and to an intrinsically lower consumables cost (16,17). 

Sodium Hydroxide. Before World War 1, nearly all sodium hydroxide [1310-93-2], NaOH, was produced by the reaction of soda ash and lime. The subsequent rapid development of electrolytic production processes, resulting from growing demand for chlorine, effectively shut down the old lime—soda plants except in Eastern Europe, the USSR, India, and China. Recent changes in chlorine consumption have reduced demand, putting pressure on the price and availabiHty of caustic soda (NaOH). Because this trend is expected to continue, there is renewed interest in the lime—soda production process. EMC operates a 50,000 t/yr caustic soda plant that uses this technology at Green River it came onstream in mid-1990. Other U.S. soda ash producers have aimounced plans to constmct similar plants (1,5). 

Transesterification. There has been renewed interest in the transesterification process for preparation of polycarbonate because of the desire to transition technology to environmentally friendly processes. The transesterification process utilizes no solvent during polymerization, producing neat polymer direcdy and thus chlorinated solvents may be entirely eliminated. General Electric operates a polycarbonate plant in Chiba, Japan which produces BPA polycarbonate via this melt process. 

Photochemical Reactions. Increased knowledge of the centraUty of quinone chemistry in photosynthesis has stimulated renewed interest in their photochemical behavior. Synthetically interesting work has centered on the 1,4-quinones and the two reaction types most frequentiy observed, ie [2 A 2] cycloaddition and hydrogen abstraction. Excellent reviews of these reactions, along with mechanistic discussion, are available (34,35). 

Because the nickel—iron cell system has a low cell voltage and high cost compared to those of the lead—acid battery, lead—acid became the dorninant automotive and industrial battery system except for heavy-duty appHcations. Renewed interest in the nickel—iron and nickel—cadmium systems, for electric vehicles started in the mid-1980s using other cell geometries. 

Tanc alloys are finding renewed interest for lower cost and better wear life as replacements for SAE 660 and other bron2es (17). About 10—30% aluminum is introduced for improved properties in both oscillating and many rotating appHcations at speeds up to 7 m/s (1400 ft/min) at temperatures up to 90-125°C. 

With the renewed interest in environmentally friendly products, ceUulose esters are being re-evaluated as a natural source of biodegradable thermoplastics. CeUulose acetates are potentiaUy biodegradable (152). Films prepared from a ceUulose acetate with a DS of 2.5 were shown to require only a 10—12 day incubation period for extensive degradation in an in vitro enrichment assay. Similarly, films prepared from a ceUulose acetate with a DS of 1.7 saw 70% degradation in 27 days in a wastewater treatment facUity, whereas films prepared from a ceUulose acetate with a DS of 2.5 required approximately 10 weeks for similar degradation to occur. The results of this work demonstrate that ceUulose acetate fibers and films are potentiaUy environmentally nonpersistant. 

Chemical Oxidation This process has not been widely utihzed because of its high cost. Onlv wEere the concentration of the target compound is very low will tlie quantity of oxidant required be low enough to justify treatment by chemical oxidation. The efficiency of this process is also low, as many side reactions can occur that will consume the oxidant. In addition, complete oxidation of organics to carbon dioxide and water often will not occur unless a significant overdose is used. However, renewed interest has recently occurred for two reasons. 

Railroad Transport Renewed interest is developing in the use of railroads for hauling sohd wastes, especially in heavily populated areas where landfill space is scarce and tipping fees are high. Containerized waste on piggyback rail cars are used. Fiill-size bulk material cars are also used for shipping solid wastes. 

There has been renewed interest in pipeline toughness in recent years. Pipeline flaws have caused failures, and increased toughness makes pipelines more tolerant of flaws thus helping to prevent or mitigate ruptures. 

In the United States and in Mexico there has been recent renewed interest in the guayule shrub as a source of natural rubbber. Whilst this shrub could provide an indigenous source of supply to these countries the rubber is more difficult to obtain. At present it is necessary to pull up the bush, macerate it, extract the rubber with solvent and then to preeipitate it from solvent. 

In the late 1970s several developments occurred causing renewed interest in poly(ethylene terephthalate) as a plastics material. These included the development of a new mouldable grade by ICI (Melinar) and the development of a blow moulding technique to produce biaxially oriented PET bottles. In addition there appeared a glass-fibre filled, ionomer nucleated, dibenzoate plasticised material by Du Pont (Rynite) (see Chapter 26). 

Renewed interest in the fluorination of quaternary ammonium salts is prompted by the need for rapid fluorination techniques to incorporate 110... 

A renewed interest attaches to alloxan since E. Fischer s discovery of the new synthesis of mic acid. The steps in the synthesis are briefly the following. Alloxan and amnioniuin sulphite foim thionuiic acid, which is decomposed by hydio-chloric or sulphuric acid into tiramil. 

This review is an attempt to collect under one heading and to present in a systematic manner the large body of work which deals with the chemistry of the carboline ring systems. Some three hundred papers in this field have been published during the last decade, more than twice as many as appeared during the preceding fifty years. The renewed interest in the chemistry of the carbolines is due in no small measure to the discovery of serotonin and to the recent developments in the chemistry and pharmacology of the Rauwolfia and related alkaloids. 

There has been some renewed interest in the use of tin-zinc alloy electroplate as a substitute for cadmium coatings on steel . It has been pointed out that tin-zinc coatings produce less loose corrosion product than zinc during full outdoor exposure... 

There has been renewed interest over the last few years in erosion-corrosion, i.e. essentially velocity-assisted corrosion since it appeared in the feed systems of certain nuclear plant. This prompted extensive experimental investigations . Erosion-corrosion is influenced by many factors-chemistry, flow, temperature, heat flux, and whether one or two phases exist. It also varies with the material, resistance increasing from mild steel, through 1% Cr-Mo to 2% Cr-Mo. 

Taxol s journey to the clinic was slow and arduous. Initial difficulties with aqueous solubility and lack of knowledge regarding its mechanism, of action delayed its development until 1979 when, in another seminal paper in the field, S.B.Horwitz and her collaborators disclosed their findings on the interaction of taxol with microtubules.4 Taxol s unique biological action, which includes promotion of microtubule formation and microtubule stabilization, stimulated a renewed interest in taxol as a potential drug candidate. The problem of procuring adequate supplies of taxol became even... 

Uses It is one active ingredient present in water which has been purified by chlorination (Ref 6). It is used as an intermediate for.the prepn of hydrazine and substituted hydrazines. Recentiy there has been a renewed interest in chloramine as a possible intermediate for the prepn of UDMH (see Vol 7, H203-R) which avoids handling the highly carcinogenic dimethyl-nitrosamine (Refs 5 7)... 

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