Scaling laws for diamond chemical-vapor deposition. I. Diamond surface chemistry

A simplified model of the gas-surface chemistry occurring during chemical-vapor deposition of diamond thin films is presented. The model results in simple scaling relations, useful for process scale-up and optimization, for growth rate and defect density in terms of the local chemical environment at the substrate. A simple two-parameter expression for growth rate is obtained, which with suitable parameter choices reproduces the results of more detailed mechanisms and experiment over two orders of magnitude in growth rate. The defect formation model suggests that the achievable growth rate at specified defect density scales approximately quadratically with the atomic hydrogen concentration at the substrate

Cylindrical claw clamp has quick release feature

Claw clamp grasps cylindrical shapes by pressing its jaws around the object. The clamp is released by retraction of a release pin which extends beyond the clamp handle on both sides for better purchase

The role of the horse in Europe. Editorial

The horse has a unique place in European society. Historically, it has played a major part in shaping political and agricultural advances. Today, the horse has diverse roles ranging from the companion and leisure horse, to the sporting athlete. The horse continues to work on the land in many European countries, it serves in the police and the armed forces, and in some regions is a source of food. This has resulted in a vast range of horse-human interactions and relationships. Despite the long association between man and the horse we still have a great deal to learn about their behaviour and the constraints that domestication has placed on them. The WATHAM Symposium on “The Role of the Horse in Europe”, organized in association with the Anthrozoology Institute at the University of Southampton, brought together researchers involved in the student of equine behaviour management and horsehuman interactions to present some of their recent work and to identify fruitful areas for future research. In addition to the main programme papers, the Symposium also featured a series of poster presentations on a range of topics including the evolution and domestication of horses; their husbandry, behaviour and welfare; and the role of the horse in modern society. The horse industry, and indeed, equine research, appears to be very fragmented by both discipline and country; and European collaboration provides a greater research potential than exists within countries or disciplines. The WALTHAM Symposium was successful, not only in highlighting common areas of interest, but also in revealing gaps in our knowledge where the paucity of information stands a barrier to the advancement of the equine industry, as a whole, across Europe

Defining and delineating the central areas of towns for statistical monitoring using continuous surface representations

The increasing availability of very high spatial resolution data using the unit postcode as its geo-reference is making possible new kinds of urban analysis andmodelling. However, at this resolution the granularity of the data used to representurban functions makes it difficult to apply traditional analytical and modellingmethods. An alternative suggested here is to use kernel density estimation totransform these data from point or area 'objects' into continuous surfaces of spatialdensities. The use of this transformation is illustrated by a study in which we attemptto develop a robust, generally applicable methodology for identifying the centralareas of UK towns for the purpose of statistical reporting and comparison.Continuous density transformations from unit post code data relating to a series ofindicators of town centredness created using ArcView are normalised and thensummed to give a composite ?Index of Town Centredness?. Selection of key contourson these index surfaces enables town centres to be delineated. The work results froma study on behalf of DETR

The first record of Merycomyia whitneyi (Johnson), tribe Bouvieromyiini (Diptera: Tabanidae), from Texas and from west of the Mississippi River

The first collections of Merycomyia whitneyi (Johnson), (Diptera: Tabanidae: Chrysopsinae: Bouvieromyiini) from Texas and from west of the Mississippi River are reported, and the Nearctic species of the Tribe Bouvieromyiini are discussed

Diamond growth in a novel low pressure flame

Diamond growth using a new low-pressure combustion technique is reported. A large-area hydrogen/oxygen flame is used as the source of atomic hydrogen. Methane diluted in hydrogen is injected into the flame near a heated silicon substrate, on which diamond crystallites nucleate and grow. This technique is potentially capable of large-area film growth, since atomic hydrogen can be generated uniformly over arbitrarily large areas

Temperature dependence of species concentrations near the substrate during diamond chemical vapor deposition

Measurements have been made of the temperature dependence of CH3, CH4, and C2H2 very near the substrate during filament-assisted diamond growth. CH3 was detected using (2+1) resonance-enhanced multiphoton ionization (REMPI), and CH4 and C2H2 concentrations were measured using sampling mass spectrometry. A strong dependence of the CH3 REMPI signal on substrate temperature was observed, which at low temperatures may be characterized as having an activation energy of approximately 4±1 kcal/mole. Methane and acetylene, on the other hand, are relatively independent of substrate temperature. These results are most likely due to recombination of methyl to methane or ethane in the cool gas layer near the substrate or on the surface at low substrate temperatures

Magnetoplasmadynamic (MPD) accelerator assisted synthesis of diamond

The use of a magnetoplasmadynamic (MPD) accelerator for diamond synthesis is investigated. The acceleration process in an MPD device is reviewed and results presented for a test in which a low power (15 kW) MPD accelerator was used as the gas activation source for diamond deposition. A hydrogen–argon mixture was used in the discharge with externally injected methane as the carbon precursor. Results, including SEM images, Raman and x-ray diffraction spectra are presented for a 3.3 µm thick film deposited over a 100 min period. The Raman spectra include a broad background and shift in the diamond peak, indicative of contamination and stresses in the deposited film. Potential scaling benefits of the MPD accelerator as well as some of the drawbacks associated with methane injection and sample contamination underscored by the experiments are identified and discussed