Chemical mechanical polishing of thin film diamond

The demonstration that Nanocrystalline Diamond (NCD) can retain the superior Young's modulus (1,100 GPa) of single crystal diamond twinned with its ability to be grown at low temperatures (<450 {\deg}C) has driven a revival into the growth and applications of NCD thin films. However, owing to the competitive growth of crystals the resulting film has a roughness that evolves with film thickness, preventing NCD films from reaching their full potential in devices where a smooth film is required. To reduce this roughness, films have been polished using Chemical Mechanical Polishing (CMP). A Logitech Tribo CMP tool equipped with a polyurethane/polyester polishing cloth and an alkaline colloidal silica polishing fluid has been used to polish NCD films. The resulting films have been characterised with Atomic Force Microscopy, Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy. Root mean square roughness values have been reduced from 18.3 nm to 1.7 nm over 25 {\mu}m$^2$, with roughness values as low as 0.42 nm over ~ 0.25 {\mu}m$^2$. A polishing mechanism of wet oxidation of the surface, attachment of silica particles and subsequent shearing away of carbon has also been proposed.Comment: 6 pages, 6 figure

Alveolar Rhabdomyosarcoma of the foot metastasizing to the Iris: report of a rare case

BACKGROUND: Intraocular iris rhabdomyosarcoma is extremely rare, and in the 3 cases reported to date occurred as the primary site of tumour growth. We report a case of rhabdomyosarcoma of the foot metastasizing to the iris. CASE PRESENTATION: An 18-year-old white female was referred to the London Ocular Oncology Service for management of a metastatic rhabdomyosarcomatous deposit in the iris, a metastasis from alveolar rhabdomyosarcoma of the foot. She was diagnosed nearly 2 years earlier with the primary sarcoma with extensive systemic spread and treated by resection of the foot lesion and chemotherapy, and achieved a partial remission. The left iris deposit was noted while she was receiving systemic chemotherapy, heralding a relapse. However, anterior uveitis and raised intraocular pressure developed and she was referred to our service for further management. A left iris secondary rhabdomyosarcoma deposit was noticed and in addition a lacrimal gland mass, as indicated by ultrasound B scan of the eye and orbit. The patient was treated with external beam radiotherapy to the globe and orbit, but died 2 months after treatment completion. CONCLUSION: Rhabdomyosarcoma of the iris is very rare and was previously documented only as a primary malignancy in this location. We report that secondary spread to the iris can also occur, in this case as the first sign of widely disseminated systemic relapse

Anomalous material-dependent transport of focused, laser-driven proton beams.

Intense lasers can accelerate protons in sufficient numbers and energy that the resulting beam can heat materials to exotic warm (10 s of eV temperature) states. Here we show with experimental data that a laser-driven proton beam focused onto a target heated it in a localized spot with size strongly dependent upon material and as small as 35 μm radius. Simulations indicate that cold stopping power values cannot model the intense proton beam transport in solid targets well enough to match the large differences observed. In the experiment a 74 J, 670 fs laser drove a focusing proton beam that transported through different thicknesses of solid Mylar, Al, Cu or Au, eventually heating a rear, thin, Au witness layer. The XUV emission seen from the rear of the Au indicated a clear dependence of proton beam transport upon atomic number, Z, of the transport layer: a larger and brighter emission spot was measured after proton transport through the lower Z foils even with equal mass density for supposed equivalent proton stopping range. Beam transport dynamics pertaining to the observed heated spot were investigated numerically with a particle-in-cell (PIC) code. In simulations protons moving through an Al transport layer result in higher Au temperature responsible for higher Au radiant emittance compared to a Cu transport case. The inferred finding that proton stopping varies with temperature in different materials, considerably changing the beam heating profile, can guide applications seeking to controllably heat targets with intense proton beams

Enhanced mass activity and stability of bimetallic Pd-Ni nanoparticles on boron-doped diamond for direct ethanol fuel cell applications

In this work, electrochemical deposition of Pd (palladium) and bimetallic Pd-Ni (nickel) nanoparticles on oxygen-terminated boron-doped diamond (BDD) substrate is described for use as electrocatalyst in direct ethanol fuel cell. A potentiostatic two-step electrochemical method involving the electrodeposition of Ni nanoparticles on BDD followed by mono-dispersed Pd nanoparticles was used for the fabrication of Pd-Ni/BDD electrode. The electrocatalytic activity of the bimetallic Pd-Ni nanoparticles was evaluated in an alkaline solution containing ethanol and compared to that of the Pd nanoparticles alone. The bimetallic Pd-Ni nanoparticles showed 2.4 times higher mass activity than the similar systems from literature as well as stability when operated in alkaline media. Higher electrochemical response towards the electrooxidation of ethanol observed for the bimetallic electrocatalysts was due to the synergistic effects of the electron interaction at the interface of the two metals. Chronopotentiometric measurements revealed that Pd is more stable when anchored to the Ni nanoparticles. The optimised loading of mono-dispersed Pd on a foreign Ni metal as nanoparticles plays a crucial role in achieving a high mass (3.63 x 106 mA/g) and specific (10.53 mA/cm2) electrocatalytic activity of Pd towards ethanol electrooxidation in alkaline media

Surrogates of spider diversity, leveraging the conservation of a poorly known group in the Savanna Biome of South Africa (Arachnida : Araneae)

The inclusion of spiders in conservation planning initiatives is confounded by several factors. Surrogates could facilitate their incorporation. In this paper we investigate the performance of a number of surrogate measures, such as higher taxa (genus, family), cross-taxon surrogates that are subsets of the spider assemblages (certain spider families) or non-overlapping groups (woody vegetation and birds), and the use of morphospecies. Birds and woody vegetation were included because they often form the focus of conservation planning initiatives. We assessed the surrogate measures based on their predictive power for species richness and extent to which conservation planning that maximizes representation of the surrogate is effective in representing spider diversity. A measure for the latter is the Species Accumulation Index (SAI). Generic richness as a higher taxon surrogate and the combined richness of the families Thomisidae and Salticidae were the best estimators of total species richness. Based on the surrogacy efficiency criterion, genera and the family Salticidae had species accumulation indices (SAIs) that were significantly larger than 95% confidence intervals of a random curve, while woody vegetation and birds turned out to be poor surrogates for spider diversity. The use of morphospecies as estimators is cautiously supported (adjusted R2 = 0.85, for species richness, SAI = 0.73). The surrogates identified here provide a viable alternative to whole assemblage analysis but should be used with caution. The use of genera is confounded by unstable taxonomy and the difficulty of identifying specimens up to genus level. Geographic location and varying sampling effort between surveys did not have an effect on the surrogate performance of the two spider families, viz. Salticidae and Thomisidae. The former family has seen a flood of recent systematic work, whereas the latter’s taxonomy is fairly well developed. These two families comprise ca. 20% of spider species observed in the Savanna Biome of South Africa and could provide a viable handle on spider diversity in this region.This research was funded by the University of Venda and an NRF grant (GUN 2054390) to the first author. SHF also acknowledges support from the DST-NRF Centre of Excellence for Invasion Biology.http://www.elsevier.com/ locate/bioconhb201

Faunistic diversity of spiders (Arachinda: Araneae) of the Savanna Biome in South Africa

Invertebrates include more than 80% of all animals, yet they are severely under-represented in studies of southern African diversity. Site biodiversity estimates that ignore invertebrates, not only omit the greatest part of what they are attempting to measure, but also neglect major contributions to essential ecosystem processes. All available information on spider species distribution in the South African Savanna Biome was compiled. This is the largest biome in the country, occupying over one third of the surface area. A total of 23 739 records from 1260 localities were recorded in the South African Savanna Biome until the end of 2010. This include 1230 species represented by 381 genera and 62 families. The last decade has seen an exponential growth in the knowledge of the group in South Africa, but there certainly are several more species that have to be discovered, and the distribution patterns of those listed are partly unknown. Information is summarised for all quarter-degree squares for the biome and reveals considerable inequalities in knowledge. At a large scale the eastern region is much better surveyed than the western parts, but at finer scales throughout the region, several areas have little information. The Salticidae is the most diverse family (162 spp.) and also has the most endemic savannah species (42 spp.). An endemicity index indicates that 366 species are endemic to the biome, with 322 species that are near endemics, i.e., also occurring in an adjacent biome. An abundance index (1-3) was also calculated for each species based on numbers sampled. A rarity index for each species gives a preliminary indication of their conservation importance. Patterns of guild composition are summarised and species known to play a role as predators in agro-ecosystems found within the biome are also discussed.The Agricultural Research Council (ARC) and the South African National Biodiversity Institute (SANBI), Threatened Species Programme for funding the South African National Survey of Arachnida (SANSA) phase 2.http://www.tandfonline.com/loi/ttrs20ab201

X-ray Astronomy in the Laboratory with a Miniature Compact Object Produced by Laser-Driven Implosion

Laboratory spectroscopy of non-thermal equilibrium plasmas photoionized by intense radiation is a key to understanding compact objects, such as black holes, based on astronomical observations. This paper describes an experiment to study photoionizing plasmas in laboratory under well-defined and genuine conditions. Photoionized plasma is here generated using a 0.5-keV Planckian x-ray source created by means of a laser-driven implosion. The measured x-ray spectrum from the photoionized silicon plasma resembles those observed from the binary stars Cygnus X-3 and Vela X-1 with the Chandra x-ray satellite. This demonstrates that an extreme radiation field was produced in the laboratory, however, the theoretical interpretation of the laboratory spectrum significantly contradicts the generally accepted explanations in x-ray astronomy. This model experiment offers a novel test bed for validation and verification of computational codes used in x-ray astronomy.Comment: 5 pages, 4 figures are included. This is the original submitted version of the manuscript to be published in Nature Physic