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High Speed Sintering (HSS) is a novel additive manufacturing technology which currently uses Nylon 12 as the standard feedstock material. To expand the number of processable materials, the preferred characteristics of polymeric powder as a feedstock powder are presented, appropriate materials identified, parts made, and mechanical properties measured. Two commercially available laser sintering (LS) grade powders previously untested for HSS were selected, DuraForm® HST10 and ALM TPE 210-S. Tensile test specimens were manufactured using each material and mechanical properties analyzed and compared to the manufacturers' specification for LS. Tensile test specimens built using DuraForm® PA show higher tensile strength and elongation at break than LS whereas DuraForm® HST10 shows somewhat reduced tensile strength but slightly increased elongation at break. ALM TPE 210-S shows elongation at break of more than double that of LS demonstrating the capability of HSS to process viscous materials. The results indicate that HSS is capable of processing LS grade polymeric powders and may extend beyond.
Understanding the finite volume throughout which plastic deformation begins is necessary to understand the mechanics of small-scale deformation. In indentation using spherical indenters, conventional yield criteria predict that yield starts at a point on the axis and at a depth of half the contact radius. However, Jayaweera et al (Proc. Roy. Soc. 2003) concluded that yield occurs over a finite volume at least 100 nm thick. Semiconductor superlattice structures, in which the stress and thickness of individual layers can be varied and in which known internal stresses can be incorporated, open up new possibilities for investigation that cannot be achieved by varying external stresses on a homogenous specimen. We have designed samples with bands of highly strained InGaAs superlattice, which are essentially bands of low yield-stress material devoid of other metallurgical artifacts. These bands are placed at different depths in a series of samples. Spherical indenters with a range of radii were used to determine the elastic-plastic transition. The stress field from different sized indenters interacts with the low yield-stress material at different depths below the surface to map out the size of the initial yield volume.
A new methodology has been developed to measure the maximum pressure that can be withstood by a bilayer lipid membrane (BLM) formed over porous substrates. A custom test fixture was fabricated to pressurize BLMs in very fine increasing increments until they fail. This experiment was performed on 1-Stearoyl-2-Oleoyl-sn-Glycero-3-Phosphatidylocholine (SOPC) BLMs formed over polycarbonate substrates with a single pore ranging from 5 to 20 microns in diameter. Failure pressure was found to be inversely proportional to pore diameter. The same set of experiments was repeated for BLMs that were formed from a mixture of SOPC and 50 mol% cholesterol (CHOL). The presence of cholesterol was found to increase the failure pressure of the BLMs by 56% on average. A model of the characteristic pressure curve from this experiment was developed based on the pressurization and flow of fluid through a porous substrate. The model was found to accurately fit the experimental pressure curves.
A continuum model is used for the description of the mechanical response of bilayer lipid membranes (BLMs) subjected to hydrostatic pressure. The model is formulated under the assumption that the BLMs are Smectic A liquid crystals. The mean orientation of the amphiphilic molecules is postulated to be perpendicular to the lipid layers and each layer is idealized as a two dimensional liquid. The permeation process governs the motion of the molecules through the smectic layers. The approach taken in this study is based on the seminal works of Helfrich  and de Gennes  on Smectic A liquid crystals. The failure process of the BLMs, which is observed in the experimental studies, is considered to be due to extrusion of the BLMs through the pores of the polycarbonate filters.
As a signatory of the Convention on Biological Diversity, the United Kingdom (UK) Government is obliged to conserve and enhance biodiversity. One step towards addressing this goal is to determine the level of biodiversity conservation already achieved within the current array of protected areas. We used national distribution data for ten taxonomic groups, and location information for three reserve networks, to assess the contribution of nature reserves to biodiversity conservation in Great Britain at the 10 km square (=100 km2) resolution. For several taxonomic groups, 10 km squares containing nature reserves had a significantly greater overlap than random networks with both hotspots (areas of high species richness) and complementary areas (sets of sites within which all species are represented). In addition, more than 94% of species from each taxonomic group have been recorded within the 10 km squares of the three reserve networks. These results provide some encouragement in terms of the UK meeting its commitment to conserve biodiversity.
Serpentinized ultramafic rocks recovered from beneath the southern Iberia Abyssal Plain (Ocean Drilling Programme Leg 173) provide the first record of fractal carbonate replacement patterns in a serpentinite. The patterns are expressed as microscopic branching aggregates (clusters) of aragonite disseminated throughout the serpentinites. Aragonite growth was the final mineralization event. The aragonite diminishes rapidly in quantity from an essential to a trace component of the serpentinite over a distance of ∼40 m from a normal fault. Decreasing abundance of aragonite away from the normal fault links the growth of the carbonate to the multistage hydrothermal mineralization associated with the fault.
Aragonite clusters are concentrated in picrolite, where they are interwoven with colloid-sized chrysotile, and show fractal growth habits. Areas adjacent to the clusters are sites of Mg enrichment of the serpentine medium relative to aragonite-free picrolite. It is interpreted that the aragonite clusters result from incursions of reactive seawater solutions through fine-scale pore structures in and around the fault in response to pressure gradients emanating from active tectonism. Cluster growth is interpreted to be a percolation phenomenon and provides a novel source of information on the nature of fine-scale reactive fluid flow, pore-space connectivity, and carbonate replacement processes in serpentinites.
The interest in the phenomenon of islanding in a range of semiconductor systems is in part due to the fundamental importance of the Stranski-Krastanow transition but also driven by potential device applications of self-organized quantum dot arrays. However, the mechanism underlying the island formation is still to a significant degree unclear. In the present work, we focus on the epitaxial InGaAs / GaAs(001) system, with layer deposition by molecular beam epitaxy. Atomic force microscopy is used to measure the surface topography of nominally 4nm thick InxGa1-xAs films. It is shown that the growth mode switches abruptly from flat layer to island growth if a critical Indium composition of x(In)≍0.25 is reached. The structure of such layers during early stages of growth is examined using energy-filtered transmission electron microscopy. Indium gradients in the islanded layers are measured and the driving force for the islanding transition itself is considered.
Patients with chronic obstructive airways disease (COAD) or asthma who have a tracheostomy tube or tracheal stoma have difficulty using metered dose inhalers (MDIs) because of a failure to achieve a good seal between the tracheostomy tube or stoma and the MDI or spacer device mouthpiece. Many such patients therefore utilize nebulizers. MDIs in comparison to nebulizers have the advantages of being more compact, portable, easy to use, less time-consuming, and cheaper. We present the case of a 74-year-old man who underwent a laryngectomy with tracheal stoma formation who had a poor response with nebulizers and required oral steroids. He was subsequently, with the help of a number of attached devices, able to use his MDIs to good effect. We describe a number of devices and adaptors to enable patients with laryngectomy stomas or tracheostomy tubes to utilize MDIs and undergo respiratory function tests. We recommend that all such patients should have the benefit of a consultation with a dedicated respiratory nurse who can provide the appropriate MDIs, devices and adaptors to optimize the treatment of their lower respiratory tract condition.
Phosphoglucomutase 1 (PGM1) deficiency is a stable characteristic
line, K562, whereas the activity of the isozymes of the other two PGM loci
(PGM2 and PGM3) is
slightly elevated. In this study the molecular basis of PGM1 deficiency
investigated by a
combined approach utilising protein electrophoresis, immunodetection,
cytogenetic techniques, and
DNA and RNA analysis. Isoelectric focusing and activity staining confirmed
that K562 has no
detectable PGM1 activity. Immunoblot analysis of extracts, separated by
isoelectric focusing, starch
gel and SDS gel electrophoresis, using monospecific anti-PGM1 antibodies
showed that K562
contained no detectable immunoreactive material. Karyotype analysis revealed
the presence of two
intact chromosomes 1 and a derivative chromosome 1,
der(1)t(1; 11), each of which carried a copy
of the PGM1 gene as demonstrated by fluorescence in situ
hybridization using a PGM1 cosmid as
probe. Southern blot analysis using a PGM1 cDNA clone as probe
that the PGM1 genes
had not been subject to any gross structural rearrangements. We were also
able to determine that K562 is type PGM1 2+1+
by restriction endonuclease analysis of genomic DNA. Very low levels
of PGM1 mRNA which appeared to be full length transcripts were detected
K562 using a reverse
transcriptase PCR technique. We conclude that the most likely cause of
enzyme deficiency in K562 is abnormal regulation of transcription.
Mast cells are a rich source of potent biologically active mediators and are found in connective tissue, associated with blood vessels in many varied inflammatory conditions. Mast cells have been described in nasal polyps and turbinates and in adenoidal tissue in the upper aerodigestive tract. As the middle ear lining is contiguous with the nose and the nasopharynx, the presence of mast cells in aural polyps is interesting.
This preliminary study investigated the presence of mast cells in inflammatory aural polyps using light microscopy. All patients presenting to the department in one year were included. Patients with previous ear disease or surgery and in whom cholesteatoma was suspected were excluded. Except for one patient mast cells were seen in all aural polyps. The implications of these findings is discussed. Further work is needed using electron microscopy.
An auto-antibody screen for SLE, which included anti-nuclear antibodies, was performed on 296 patients admitted to acute psychiatric and psychogeriatric wards. Three cases (1% of those screened) of previously undiagnosed SLE were found, and one patient was found to have autoimmune chronic active hepatitis. An auto-antibody screen may be a useful investigation in psychiatric practice.
On p. 240 sqq. of the B.S.A. Annual, vol. viii., Mr. R. C. Bosanquet has described a tomb opened by him at Praesos during the excavations of 1901. The tomb had originally been of the ‘beehive’ type though the upper portion had been broken before the excavators opened it. The layer of earth constituting the original floor of the tomb was covered to a depth of nearly two feet with a tightly packed deposit of broken pottery, whilst in a small vestibule leading into the tomb from the dromos a few better preserved vases were found. Owing to the confusion caused by the later use of the tomb and by the fall of the roofing stones it is difficult to make out any stratification in the deposit, but on the analogy of the Menidi tomb Mr. Bosanquet would explain the large quantity of pottery found here as the result of a long period of hero-worship. The bulk of the pottery is of the Geometric period and comprises a sequence of at least several generations. Nothing of indisputably Mycenaean date was found in the tomb, and the latest objects that came to light were two small fragments of red-figure ware.
The importance of the ‘Melian Amphorae’ in the history of early vase-painting has long been recognised, but the difficulty of locating an isolated fabric which in itself consisted of only five complete examples, all of uncertain provenance, has hitherto prevented any adequate treatment. Any extension of the class would therefore have been welcome. But the amphora which is now added to the list (vide Appendix) has a value in itself beyond its cumulative importance. Not only is there stronger evidence in this case than in any of the others that the vase was actually found in Melos, but the decoration of the vase adds new figure-subjects and new schemes of ornament to those previously recognised as characteristic of the class. Indeed the whole ‘Melian’ class as at present constituted consists of large and elaborate vases, ceramic masterpieces, each of which possesses its own individual scheme of decoration. This appears very clearly in a comparison of the present amphora with two typical examples from those previously published, namely, the Herakles and the Artemis amphorae. In the Herakles vase the painter has produced his effect by an elaborate and ornate treatment both of the figure-scenes and of the ornament forms.
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