An improved photographic process for convergent beam electron diffraction applications

The use of a surface developer, pyrocatechol, to process transmission electron microscope negatives has been shown to have significant advantages over the conventional D-19 process. The process described here is tolerant of a large margin of error in the electron exposure and produces a negative that not only retains details both in the highlight as well as the faint regions, but also preserves local contrast. These characteristics are particularly useful in convergent beam electron diffraction applications where one encounters a wide contrast range. Improved acuteness and an enhanced signal to noise ratio due to the prolonged exposures associated with this process have also been observed.     

Hydrothermal synthesis of chromium dioxide powders and their characterisation

Chromium dioxide (CrO₂) powders have been synthesised by decomposing CrO₃ and Cr₂O₅ powders under hydrothermal conditions in the temperature range of 300–500°C and pressure range of 250–1200 bars. Oxides of antimony and iron have been used as modifiers to induce acicular morphology. A novel method of using alkali metal salts such as chlorides and carbonates as mineralisers produces CrO₂ with superior magnetic characteristics. The particle size distributions have been correlated with the magnetic properties of the materials. The products obtained have properties rendering them useful for magnetic recording applications.     

Nonsteroidal anti-inflammatory drug induced duodenal web

Duodenal webs represent an unusual cause of intestinal obstruction in adults. These anomalies are generally considered to be congenital in origin and usually present in infancy. However, they occasionally become symptomatic in adulthood. In these cases, because of the delay in symptoms, the etiology of duodenal webs in adults is uncertain. Gastrointestinal webs in adults have also been reported in the small intestine and colon. It is generally accepted that these lesions are an acquired defect related to long term nonsteroidal anti-inflammatory drug (NSAID) use. We report a patient with a history of long term NSAID use who presented with symptoms of gastric outlet obstruction due to the presence of a duodenal web.     

Probability of first passage analysis of a two-stage transfer-line production system with storage and rework

In this paper, we study some of the transient state characteristics of a two-stage transfer-line production system subject to an initial storage of unlimited capacity and reworking the defective products in the respective stages. This paper provides a complete analysis to consider manufacturing, inspection and reworking in two-stage transfer-line production systems. The first stage of the system is never starved and the second stage is never blocked. A stochastic model is developed to analyse the system and explicit analytical expressions for some of the system characteristics have been obtained using the state space method and regeneration point technique. All the random variables involved in the analysis are assumed to be arbitrary (general).     

Novel AB crosslinked polymer networks based on 1‐vinylimidazole‐ terminated polyurethane and poly(methyl methacrylate)

1‐Vinylimidazole‐terminated telechelic polyurethanes were prepared from 1‐vinylimidazole and bromine‐terminated polyurethane. This vinyl‐terminated telechelic polyurethane (VTPU) and methyl methacrylate were polymerized in the presence of benzoyl peroxide to prepare novel AB crosslinked polymer networks (ABCPs). These were characterized by spectral, thermal and mechanical studies. The absence of the characteristic peak of vinyl group in infrared spectra of ABCP films confirms the occurrence of crosslinking. Static mechanical testing showed that the tensile strength of ABCP increases with increasing poly(methyl methacrylate) content. Dynamic mechanical studies revealed that ABCPs, at equal compositions of VTPU and methyl methacrylate, show good damping properties. Copyright © 2006 Society of Chemical Industry     

A COAL PYROLYSIS REACTOR SYSTEM WITH FAST ON-LINE COMPOSITION ANALYSIS BY GAS CHROMATOGRAPHY

The development of a coal pyrolysis reactor and a novel gas chromatography method for fast on-line composition analysis of pyrolysis products are presented. The annular fluidized bed reactor system minimizes particle agglomeration during the pyrolysis of plastic coals and the new column switching technique significantly reduces the time required for measuring the composition of low-volatile pyrolysis gases on a conventional gas chromatograph. Data from representative pyrolysis runs are presented and discussed.     

A generalization of atom location by channelling enhanced microanalysis

The technique of atom location by channelling enhanced microanalysis (ALCHEMI), has limitations in practical application. A generalization of this technique, with the underlying idea that additional relationships can be generated by performing these experiments at an appropriate number of orientations depending upon the stoichiometry of the original compound has been developed. The precise number of orientations required to solve the distributions in a whole class of related compounds is expressed in terms of the stoichiometry of the original compound along with the alloying additions.     

R.F. sputtering system for the preparation of multilayer optical filters

Thin film multilayer optical filters are usually prepared by vacuum evaporation of successive layers. The deposition of thin films by sputtering has many advantages over the vacuum evaporation technique and hence it is employed for the fabrication of better quality optical filters. However, the filters may be more time consuming to prepare if a single-target sputtering system is used because two different materials are required for alternate layers. For the preparation of multilayer optical filters, a special r.f. sputtering jig arrangement with two target holders is fabricated. Using this the successive layers can be deposited in one pumpdown. A simple coupling arrangement used to match the r.f. generator output impedance to the load is explained. With all the sputtering parameters such as the pressure, the temperature and the power maintained constant except the time, control of the thickness of the multilayers is achieved. A calibration chart of sputtering time versus thickness of the materials to be deposited is prepared for TiO₂ and SiO₂ for the above purpose. Using this calibration chart, the deposition time of different layers of any optical filters based on these dielectric materials can be fixed to obtain optical filters of acceptable quality and reproducibility.