We observed several H ii regions in the dwarf irregular galaxy NGC 6822 using the infrared spectrograph on the Spitzer Space Telescope. Our aim is twofold: first, to examine the neon to sulfur abundance ratio in order to determine how much it may vary and whether or not, it is fairly ‘universal’; second, to discriminate and test the predicted ionizing spectral energy distribution between various stellar atmosphere models by comparing with our derivation of the ratio of fractional ionizations involving neon and sulfur. This work extends our previous similar studies of H ii regions in M83 and M33 to lower metallicities.

Evidence of past zoonotic infection was investigated serologically in randomly selected Northern Ireland farmers. The percentage of farmers with antibody was: Brucella abortus (0·7), Leptospira interrogans serovars (8·1), Borrelia burgdorferi (14·3), Toxoplasma gondii (73·5), Coxiella burnetii (28·0), Chlamydia psittaci (11·1) and Hantavirus (1·2).

The results show that Northern Ireland farmers have been exposed in the past to zoonotic infections. It is not known if these infections contributed to ill health in farmers but it is now time for the health of farm workers and their medical services to be reassessed.

Nanocrystalline silicon (n-Si) is formed in a silicon dioxide thin-film matrix by ion implantation followed by thermal annealing in forming gas at 1100 °C for 1 hour. The ion implantation is performed using multiple implants with different implantation energies and doses to create a quasi-flat concentration of silicon atoms throughout the silicon dioxide film. These samples are then analyzed using spectroscopic ellipsometry to characterize their linear optical properties. Implantations with small doses (5 × 1020 Si atoms/cm3) increase the refractive index by a small amount (δn∼0.006 at 600nm), while implantations with moderate dose (5 × 1021 Si atoms/cm3) have a larger increase in refractive index and exhibit optical absorption above ∼1.9 eV (650 nm).

Two layer co-sputtered Bi over In thin films (40 nm/layer) act as a microfabrication resist with many potential applications. Their physical, chemical and optical characteristics change after laser exposures that produce a rapid thermal anneal in selected areas. Unlike organic photoresists, Bi/In is a bimetallic thermal resist whose sensitivity shows a near wavelength invariance for wavelengths from Near IR to UV. The laser-induced patterns are developed by an etch that selectively removes unexposed areas and retains converted ones. The optical density (OD) of 40 nm thick Bi/In films on quartz substrates, for example, changes from 3.3 OD to 0.37 OD in the annealed area. This has enabled the creation of direct-write photomasks for standard photoresist exposures. In this paper, the composition, morphology, and nanostructure of the resist before and after laser processing were studied in order to determine the mechanism of the laser-induced material conversion. AFM, XRD, and TEM show that the as-deposited films are polycrystalline, continuous, but with a rough, island morphology. Furnace anneals in air above the eutectic temperature (150–250°C, 3 hours) result in the formation of the tetragonal phase BiIn with a small degree of oxidation. The island morphology is maintained but there is evidence of melting and recrystallization. Transparency is much lower than after laser annealing. RBS and NRA depth profile analysis show that Bi/In films exposed to laser annealing in air contain a large fraction of oxygen and suggest that the converted film may be a BiIn0.6O6 /Bi0.3InO6 bilayer.

Individual tall fescue (Festuca arundinacea) plants infected with both Neotyphodium coenophialum and N. lolii endophytes, and individual perennial ryegrass (Lolium perenne) plants infected with both N. lolii and Neotyphodium LpTG-2, were obtained following inoculation of naturally infected seedlings with the second endophyte. Differences in the ability of the endophytes to produce conidia, together with colony characteristics, enabled the endophytes in plants to be identified following incubation of excised leaf tissue on potato dextrose agar. Most tillers of dually infected plants were infected with just a single endophyte, but tillers infected with two endophytes were identified in three tall fescue plants. In these tillers one endophyte was always present at a much higher concentration than the other. Over time the incidence of dually infected tillers decreased and no tillers with both N. coenophialum and N. lolii were present 5 months after the associations were established. No evidence was obtained of exchange of nuclei between different endophytes present in dually infected tillers giving rise to heterokaryons or interspecific hybrids.

A ceramic waste form is being developed by Argonne National Laboratory* (ANL) as part of the demonstration of the electrometallurgical treatment of spent nuclear fuel [1]. The halide, alkaline earth, alkali, transuranic, and rare earth fission products are stabilized in zeolite which is combined with glass and processed in a hot isostatic press (HIP) to form a ceramic composite. The mineral sodalite is formed in the HIP from the zeolite precursor. The process, from starting materials to final product, is relatively simple. An overview of the processing operations is given. The metrics that have been developed to measure the success or completion of processing operations are developed and discussed. The impact of variability in processing metrics on the durability of the final product is presented. The process is demonstrated to be robust for the type and range of operation metrics considered and the performance metric (PCT durability test) against which the operation metrics are evaluated.

The active form of platelet derived growth factor (PDGF) is a dimeric combination of two polypeptide chains: PDGF-A and PDGF-B. The protein can exist as a heterodimer (PDGF-AB) or as one of two homodimers (PDGF-AA, PDGF-BB), resulting in three isoforms. Two types of PDGF receptors also exist: PDGFRα and PDGFRß. The PDGFRß binds only the PDGF-B chain, while PDGFRα can bind both PDGF-A and -B chains. Both of these receptors show specific temporal and spatial expression patterns that are related to cellular responses including mitogenesis, cell migration, chemotaxis, adhesion and differentiation in a variety of cell types.

Spontaneous mutants in which the PDGFRα is absent exhibit fatal defects during fetal development in mice. Some of these malformities include cardiac septal, valve, and outflow tract defects. Similar defects occur when the function of PDGF-A is disrupted by blocking antibodies. Disruption of PDGF-B function, results in ventricular and atrial dilation, hyper-trabeculation and reduction of the ventricular wall to the thickness of a single cell layer.

Understanding has advanced significantly in the interpretation of the thermal release of self interstitials into a silicon lattice from a region, e.g. ion implanted, which is rich in point defects. Progress has been accelerated through the use of delta doped layer structures, especially of boron doping type, where the transient enhanced diffusion (TED) of the dopant marks the arrival of the self interstitial species from a physically separate damage region. Frequently observed in such TED experiments is an immobile, electrically inactive, boron peak on top of the spreading diffusion profile. This signature boron peak has been attributed to the Si-interstitial driven clustering of boron. It has been observed that this feature occurs for high boron concentrations and implant fluences; however, a complete understanding of the clustering mechanism has remained elusive.

We present new data from experiments where the self implant fluence has been varied to allow the intensity of the transient flux to be adjusted and where repeat distances in the MBE structure have been adjusted to test for trapping. This has led to some clarifications to the current picture of boron clustering during TED. These results seem to be important in the context of the search for engineering control over dopant redistribution in Si during post-implantation annealing.

A study has been made of B transient enhanced diffusion (TED) in heavily P-doped Si using secondary ion mass spectroscopy (SIMS) and positron annihilation spectroscopy (PAS). The Pdoped silicon was implanted with boron ions of 40 keV energy to a dose of 3 × 1014 cm-2, and then annealed at temperatures ranging from 700–1000°C in a N2 ambient for varying durations. As P doping concentration increased from 3 × 1019 to 1 × 1020 cm-3, boron diffusivity and the immobile boron fraction decreased. Our experimental results are inconsistent with the predictions of the Fermi-level model and suggest that the clustering between B atoms and Si interstitials should be invoked in order to explain the immobile portion of the B peak during TED.

Delta-doped boron marker layers in silicon have been used to test further the relationship between B transient enhanced diffusion (TED) and the flux of silicon interstitials released during the annealing stage following self implantation. We present new data which address a number of questions raised by the present models. We show that in our experiments bulk trapping of interstitials is significant only for low implant fluences (˜1012 cm2). The origin of the observed diffusion-like profiles for the interstitial flux is instead found to lie in local trapping within the δ-doped layers themselves. Boron trapped in immobile clusters may be associated with Si interstitials in approximately a 1:1 ratio; nevertheless this trapping contribution alone may not entirely account for the observed gradient. We suggest that some part of the observed TED response with depth is attributable to local trapping of silicon interstitials within the boron doped layers.

Changes in the defect structure in carbon rich a-SiC:H films deposited on various substrates using ditertiary butyl silane were investigated as a function of thermal treatment. Films grown at high deposition rates exhibit hydrogen trapped in voids. The incorporation of CHn, groups is thought to be the origin for these microvoids. With increasing annealing temperature the effusion of CHn, groups as determined by thermal desorption experiments promotes void growth which was studied using a variable energy positron beam. At annealing temperatures above 600 °C the films densify due to the breaking of C-H bonds and the formation of additional C-C bonds when the voids anneal out.

A study has been made of B transient enhanced diffusion (TED) in heavily P-doped Si using secondary ion mass spectroscopy (SIMS) and positron annihilation spectroscopy (PAS). The Pdoped silicon was implanted with boron ions of 40 keV energy to a dose of 3 x 1014 cm-2, and then annealed at temperatures ranging from 700–1000°C in a N2 ambient for varying durations. As P doping concentration increased from 3 x 1019 to 1 x 1020 cm-3, boron diffusivity and the immobile boron fraction decreased. Our experimental results are inconsistent with the predictions of the Fermi-level model and suggest that the clustering between B atoms and Si interstitials should be invoked in order to explain the immobile portion of the B peak during TED.

Delta-doped boron marker layers in silicon have been used to test further the relationship between B transient enhanced diffusion (TED) and the flux of silicon interstitials released during the annealing stage following self implantation. We present new data which address a number of questions raised by the present models. We show that in our experiments bulk trapping of interstitials is significant only for low implant fluences (∼1012 cm −2). The origin of the observed diffusion-like profiles for the interstitial flux is instead found to lie in local trapping within the δ-doped layers themselves. Boron trapped in immobile clusters may be associated with Si interstitials in approximately a 1:1 ratio; nevertheless this trapping contribution alone may not entirely account for the observed gradient. We suggest that some part of the observed TED response with depth is attributable to local trapping of silicon interstitials within the boron doped layers.

Variable energy positron annihilation and Rutherford backscattering spectroscopy have been used to investigate the evolution of secondary defects during the annealing of self-ion irradiated silicon. Evidence supporting the existence of both vacancy- and interstitially-based defects after high temperature anneals is presented. Dopant type and irradiation temperature have both been shown to influence the structure of the defects whose onset can be manipulated via the implantation flux.

We report new measurements of the regrowth behaviour of Pb-implanted SrTiO3 crystals in the presence of water vapour. Doubly labelled water vapour, D218O, at greater than 95% enrichment in each isotope has been added to the annealing ambient and depth profiles of D and 18O have been obtained from the regrown crystals using secondary ion mass spectrometry (SIMS). The D and 18O content has also been measured by nuclear reaction analysis (NRA) using the reactions D(3He,p)4 He and 18O(p,α)15 N. The crystals were regrown in a conventional furnace under a controlled gas ambient and time-resolved optical reflectivity (TRR) was used to dynamically monitor the regrowth rate during the anneal. An enhancement of the solid-phase epitaxial regrowth rate is observed when water vapour is added to the annealing ambient. This rate increase is accompanied by incorporation of D throughout the regrown layer. 18O is incorporated into the lattice but does not appear to penetrate deep enough to influence the regrowth rate.