Carbon fiber structure and stability studies

A study has been made of the thermal-oxidative stability of several commercially available carbon fibers. Significant differences in the weight loss behavior were observed in air aging studies run on the bare fibers at 600°F (589 K). The stability of high temperature laminates, such as those based on NR-150 polyimide precursor solutions, was found to be directly affected by the stability of the reinforcing carbon fibers. In studies carried out to determine the reasons for carbon fiber instability, residual sodium sulfate was found to be the principle destabilizing factor. A mechanism whereby the sodium sulfate promotes the oxidation of carbon in the presence of air is proposed.     

Electrosynthesis in systems of two immiscible liquids and a phase transfer catalyst. V. The anodic chlorination of naphthalene

The anodic chlorination of naphthalene in a water/methylene chloride emulsion and using tetrabutylammonium ion as the phase transfer catalyst is demonstrated; in conditions where the aqueous phase is saturated NaCl, the organic yield of 1-chloronaphthalene is 56% and the current yield is 33% after the passage of 2.33 F mol^–1 of naphthalene. It is shown, however, that when the aqueous phase also contains zinc chloride so that the species transferred is [(C₄H₉)₄N⁺]₂ZnCl ₄ ^–– , the yields can be increased to 92% and 49% respectively. The mechanism of these chlorinations is discussed.     

Impact of H+ ion irradiation on Matrimid®. I. Evolution in chemical structure

Ion beam irradiation can be used to modify the structure and gas transport properties of glassy polymers. This is the first of two studies that focus on the impact of H⁺ ion irradiation on the structure and permeation properties of the polyimide Matrimid®. Specifically, the evolution in chemical structure after H⁺ irradiation over a range of fluences was analyzed using FTIR spectroscopy and dissolution studies. Although H⁺ ion irradiation at very low ion fluences induced little modification in the chemical structure, irradiation at relatively high ion fluences resulted in crosslinking of the irradiated films. The branched structure of the aliphatic methyl (CH₃) was the most sensitive to the H⁺ ion irradiation. The para‐disubstituted aromatic ring showed the strongest resistance toward ion irradiation and required fairly high doses to induce degradation. Two potential crosslinking mechanisms related to the degradation of the aliphatic methyl and the benzophenone carbonyl were presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2010–2019, 2003     

Industrially interesting approaches to “low-CO2” cements

This article discusses the practicality of replacing portland cements with alternative hydraulic cements that could result in lower total CO₂ emissions per unit volume of concrete of equivalent performance. Currently, the cement industry is responding rapidly to the perceived societal need for reduced CO₂ emissions by increasing the production of blended portland cements using supplementary cementitious materials that are principally derived from industrial by-products, such as blast-furnace slags and coal combustion fly ashes. However, the supplies of such by-products of suitable quality are limited. An alternative solution is to use natural pozzolans, although they must still be activated either by portland cement or lime or by alkali silicates or hydroxides, the production of all of which still involves significant CO₂ emissions. Moreover, concretes based on activated pozzolans often require curing at elevated temperatures, which significantly limits their field of application.The most promising alternative cementing systems for general concrete applications at ambient temperatures currently appear to be those based at least in part on calcium sulfates, the availability of which is increasing due to the widespread implementation of sulfur dioxide emission controls. These include calcium sulfoaluminate-belite-ferrite cements of the type developed in China under the generic name “Third Cement Series” (TCS) and other similar systems that make good use of the potential synergies among calcium sulfate, calcium silicate and calcium aluminate hydrates. However, a great deal more research is required to solve significant unresolved processing and reactivity questions and to establish the durability of concretes made from such cements. If we are to use these potentially more CO₂-efficient technologies on a large enough scale to have a significant global impact, we will also have to develop the performance data needed to justify changes to construction codes and standards.     

Electro-winning of chromium from chromic oxide by chlorination in fused salt and subsequent electrolysis

The electro-winning of chromium from chromic oxide after chlorination in a carbon-containing fused sodium chloride flux is described. Only low values of current efficiency (based on the reaction Cr³⁺ + 3e ← Cr) can be attained. The effects of concentration of chromic and chromous chlorides in the melt, of current density and of melt temperature are reported. The conclusion is reached that the major factor responsible for the low current efficiency is the re-solution of deposited metal by anodic chlorine.     

Laminated paper-based analytical devices (LPAD): fabrication, characterization, and assays

Paper-based microfluidic devices have recently garnered an increasing interest in the literature. The majority of these devices were produced by patterning hydrophobic zones in hydrophilic paper via photoresist or wax. Others were created by cutting paper using a laser. Here, we present a fabrication method for producing devices by simple craft-cutting and lamination, in a way similar to making an identification (ID) card. The method employs a digital craft cutter and roll laminator to produce laminated paper-based analytical devices (LPAD). Lamination with a plastic backing provides the mechanical strength for a paper device. The approach of using a craft cutter and laminator makes it possible to rapid-prototype LPAD with no more difficulty than producing a typical ID card, at very low cost. Devices constructed using this method have been exploited for simultaneous detection of bovine serum albumin (BSA) and glucose in synthetic urine with colorimetric assays. Both BSA and glucose are detectable at clinically relevant concentrations, with the detection limit at 2.5 μM for BSA and 0.5 mM for glucose.     

Observed finger behaviour during computer mouse use

Two-button computer mouse users may exhibit sustained, static finger lifting behaviours to prevent inadvertent activations by avoiding finger pressure on the buttons, which leads to prolonged, static finger extensor muscle loading. One hundred graduate students were observed during normal computer work in a university computer facility to qualify and quantify the prevalence of lifted finger behaviours and extended finger postures, as well as wrist/forearm and grip behaviour, during specific mouse activities. The highest prevalences observed were 48% of the students lifted their middle finger during mouse drag activities, and 23% extended their middle finger while moving the mouse. In addition, 98% of the students rested their wrist and forearm (77%) or wrist only (21%) on the workstation surface, and 97% had an extended wrist posture (15 degrees -30 degrees ) when using the mouse. Potential applications of these findings include future computer input device designs to reduce finger lifting behaviour and exposures to risk factors of hand/forearm musculoskeletal pain.     

Targeted Nanoparticle Thermometry: A Method to Measure Local Temperature at the Nanoscale Point Where Water Vapor Nucleation Occurs

An optical nanothermometer technique based on laser trapping, moving and targeted attaching an erbium oxide nanoparticle cluster is developed to measure the local temperature. The authors apply this new nanoscale temperature measuring technique (limited by the size of the nanoparticles) to measure the temperature of vapor nucleation in water. Vapor nucleation is observed after superheating water above the boiling point for degassed and nondegassed water. The average nucleation temperature for water without gas is 560 K but this temperature is lowered by 100 K when gas is introduced into the water. The authors are able to measure the temperature inside the bubble during bubble formation and find that the temperature inside the bubble spikes to over 1000 K because the heat source (optically‐heated nanorods) is no longer connected to liquid water and heat dissipation is greatly reduced.     

Post-craniectomy intracranial hypotension: potential impact on rehabilitation

The process of active dissociation or "DNA clearing" of not covalently binding agents from DNA in living HeLa cells was shown by the flow cytometry technique. The vital fluorescent bisbenzimidazole dye Hoechst 33342, which binds tightly but not covalently to DNA in a minor groove, was used as a basic model to study the interaction of not covalently binding agents with DNA. In this paper, we continue to analyse the "DNA clearing" process in the living fibroblasts of different rodent species (mouse, rat, Chinese hamster). The obtained data suggest that the processes of active dissociation or "DNA clearing" of Hoechst 33342 have some common features in all investigated mammalian cells. Nevertheless, some differences in the process were found in these lines. The role of nucleotide excision repair genes in the process of DNA clearing was not established.