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Micromachined diaphragm transducers for miniaturised ultrasound arrays
Get PDFMiniaturised ultrasound transducer arrays with integrated electronics will in future enable significant advances in high resolution medical imaging and in acoustic tweezing for bioscience research. However, their development has been limited by challenges in scaling down conventional piezoelectric ultrasound transducer fabrication and interconnection techniques. Piezoelectric thin film transducers on silicon substrates can overcome these challenges by reducing dimensional constraints in fabrication and facilitating integration with electronics, including allowing low drive voltages in transmission. We present the design, fabrication and testing of diaphragm transducers to evaluate the feasibility of integrated piezoelectric micromachined ultrasonic transducers (PMUTs). Transducers have been designed, then fabricated with 80 µm and 130 µm diameter diaphragms, the latter in arrays with ~500 diaphragms. Receive measurements demonstrate functionality of both devices, with pulse-echo bandwidths of approximately 90% for the 80 ?m diaphragms, demonstrating initial feasibility for ultrasound imaging
Prototype energy autonomous studio in Dundee, Scotland
No full textPrototype Energy Autonomous Studio’ is a net-zero energy, PV- and wind-powered configurable off-grid demonstrator building, located in Dundee University’s Botanical Gardens. It was developed and constructed as a self-build collaborative student project, led by the Department of Architecture’s Macro Micro Master of Architecture research unit, with contributions from masters’ students in Civil Engineering, Renewable Energy and Applied Computing. A consortium of some 50 manufacturers and suppliers contributed specialist knowhow and donations of in-kind materials. The prototype represents a ‘live’ test-bed, monitoring energy generation and storage technologies and performance of the Passivhaus timber frame construction. This enables the feasibility of ultra-low energy and off-grid buildings powered solely by renewable sources to be assessed in the context of the Scottish Government’s strategy for a low-carbon future. We describe the research rationale, the processes and decision-making in the development of the formal and technical design of the building and energy generation, monitoring and management systems, and review present status and future expectations
DESIGN IN ACTION. (Research that builds a model for knowledge exchange between industry and academia, using design as a strategy for business growth in Scotland. Disseminated through: Follett G. Marra M. Leading innovation through design. Presentation & Proceedings of the Design Management Institute, DMI 2012, International Research Conference, Boston USA. 8/08/12 - 9/08/12)
No full textFollett and Marra propose a model for improving knowledge exchange in order to meet the complex demands of industrial R & D in Scotland. As the UK government and public policy bodies seek routes back to economic growth, the domestic higher education sector has been identified as a source for innovation. The Scottish economy’s particular weaknesses in industrial R&D mean that resultant knowledge exchange is critical. The proposed model to meet these complex demands is based upon the funded AHRC Knowledge Exchange Hub, Design in Action, led by Follett at the University of Dundee
Metastable effects in silicon thin films:atmospheric adsorption and light-induced degradation
No full textThe effects of exposure to atmosphere (ageing) and light-soaking on coplanar dark- and photo-conductivity of silicon films of varying crystallinity are examined. Dark conductivity generally increases on ageing in films with significant amorphous fraction and decreases in largely crystalline films, and may be reversed by annealing under vacuum at 130 °C consistent with adsorption and desorption of atmospheric components. Thinner films are more strongly affected by ageing. Boron doping appears to compensate charge introduced by ageing, though there are disagreements in detail. In comparison with ageing, moderate light-soaking affects dark conductivity in transitional microcrystalline silicon films only slightly. Both processes change the majority carrier mu–tau product in line with shifts in Fermi level position
Continuous wave terahertz radiation from an InAs/GaAs quantum-dot photomixer device
No full textGeneration of continuous wave radiation at terahertz (THz) frequencies from a heterodyne source based on quantum-dot (QD) semiconductor materials is reported. The source comprises an active region characterised by multiple alternating photoconductive and QD carrier trapping layers and is pumped by two infrared optical signals with slightly offset wavelengths, allowing photoconductive device switching at the signals’ difference frequency ~1 THz.(C) 2012 American Institute of Physics
Three-dimensional null point reconnection regimes
No full textRecent advances in theory and computational experiments have shown the need to refine the previous categorization of magnetic reconnection at three-dimensional null points-points at which the magnetic field vanishes. We propose here a division into three different types, depending on the nature of the flow near the spine and fan of the null. The spine is an isolated field line which approaches the null (or recedes from it), while the fan is a surface of field lines which recede from it (or approach it). So-called torsional spine reconnection occurs when field lines in the vicinity of the fan rotate, with current becoming concentrated along the spine so that nearby field lines undergo rotational slippage. In torsional fan reconnection field lines near the spine rotate and create a current that is concentrated in the fan with a rotational flux mismatch and rotational slippage. In both of these regimes, the spine and fan are perpendicular and there is no flux transfer across spine or fan. The third regime, called spine-fan reconnection, is the most common in practice and combines elements of the previous spine and fan models. In this case, in response to a generic shearing motion, the null point collapses to form a current sheet that is focused at the null itself, in a sheet that locally spans both the spine and fan. In this regime the spine and fan are no longer perpendicular and there is flux transfer across both of them.</p
Effect of high-dose allopurinol on exercise in patients with chronic stable angina:a randomised, placebo controlled crossover trial
No full textBackground Experimental evidence suggests that xanthine oxidase inhibitors can reduce myocardial oxygen consumption for a particular stroke volume. If such an effect also occurs in man, this class of inhibitors could become a new treatment for ischaemia in patients with angina pectoris. We ascertained whether high-dose allopurinol prolongs exercise capability in patients with chronic stable angina. Methods 65 patients (aged 18-85 years) with angiographically documented coronary artery disease, a positive exercise tolerance test, and stable chronic angina pectoris (for at least 2 months) were recruited into a double-blind, randomised, placebo-controlled, crossover study in a hospital and two infirmaries in the UK. We used computer-generated randomisation to assign patients to allopurinol (600 mg per day) or placebo for 6 weeks before crossover. Our primary endpoint was the time to ST depression, and the secondary endpoints were total exercise time and time to chest pain. We did a completed case analysis. This study is registered as an International Standard Randomised Controlled Trial, number IS RCTN 82040078. Findings In the first treatment period, 31 patients were allocated to allopurinol and 28 were analysed, and 34 were allocated to placebo and 32 were analysed. In the second period, all 60 patients were analysed. Allopurinol increased the median time to ST depression to 298 s (IQR 211-408) from a baseline of 232 s (182-380), and placebo increased it to 249 s (200-375; p=0.0002). The point estimate (absolute difference between allopurinol and placebo) was 43 s (95% CI 31-58). Allopurinol increased median total exercise time to 393 s (IQR 280-519) from a baseline of 301 s (251-447), and placebo increased it to 307s (232-430; p=0.0003); the point estimate was 58 s (95% Cl 45-77). Allopurinol increased the time to chest pain from a baseline of 234 s (IQR 189-382) to 304 s (222-421), and placebo increased it to 272 s (200-380; p=0.001); the point estimate was 38s (95% Cl 17-55). No adverse effects of treatment were reported. Interpretation Allopurinol seems to be a useful, inexpensive, well tolerated, and safe anti-ischaemic drug for patients with angina.</p
Isolation of the human genes encoding the pyst1 and Pyst2 phosphatases:characterisation of Pyst2 as a cytosolic dual-specificity MAP kinase phosphatase and its catalytic activation by both MAP and SAP kinases
No full textWe have isolated the human genes encoding the Pyst1 (MKP-3) and Pyst2 (MKP-X) MAP kinase phosphatases. Both genes consist of three exons interrupted by two introns and lack an intron which is conserved in all the other members of this gene family characterised to date. This reinforces the conclusion that Pyst1 and Pyst2 are members of a distinct and structurally homologous subfamily of dual-specificity (Thr/Tyr) MAP kinase phosphatases. We find that Pyst2 mRNA is constitutively expressed in a wide variety of human cell lines including those derived from ovarian, bladder and breast cancers. While there is no evidence for inducible expression of Pyst2 mRNA in human skin fibroblasts in response to cellular stress, Pyst2 mRNA levels are moderately increased in response to serum stimulation. Pyst2 protein is predominantly cytosolic when expressed in COS-1 cells. In common with Pyst1, Pyst2 shows substrate selectivity for the classical p42 (ERK2) isoform of MAP kinase both in vitro and in vivo, displaying much reduced activity towards stress activated MAP kinase isoforms such as JNK-1 and p38/RK. Pyst2 binds p42 MAP kinase in vivo and both MAP kinase binding and substrate selectivity correlate with the ability of different recombinant MAP and SAP kinases to cause catalytic activation of the Pyst2 phosphatase in vitro
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