After X-radiography, ultrasound is now the most common of all the medical imaging technologies. For millennia, manual palpation has been used to assist in diagnosis, but it is subjective and ...restricted to larger and more superficial structures. Following an introduction to the subject of elasticity, the elasticity of biological soft tissues is discussed and published data are presented. The basic physical principles of pulse-echo and Doppler ultrasonic techniques are explained. The history of ultrasonic imaging of soft tissue strain and elasticity is summarized, together with a brief critique of previously published reviews. The relevant techniques—low-frequency vibration, step, freehand and physiological displacement, and radiation force (displacement, impulse, shear wave and acoustic emission)—are described. Tissue-mimicking materials are indispensible for the assessment of these techniques and their characteristics are reported. Emerging clinical applications in breast disease, cardiology, dermatology, gastroenterology, gynaecology, minimally invasive surgery, musculoskeletal studies, radiotherapy, tissue engineering, urology and vascular disease are critically discussed. It is concluded that ultrasonic imaging of soft tissue strain and elasticity is now sufficiently well developed to have clinical utility. The potential for further research is examined and it is anticipated that the technology will become a powerful mainstream investigative tool.
This paper argues that there is a powerful tendency in forecasting of socio-technical change to focus on the causes and consequences of change at the cost of greater understanding of the reasons for ...and significance of continuity. Taking the case of the global automotive industry, the paper therefore analyses the evidence for systemic continuity in technologies, economic structures, cultural positioning and embedded social function through the lens of transition theory and the multi-level perspective. It is concluded that the observable processes are as much about enduring technologies and social practices as they are about systemic change. That is, the industry has shown resistance to change notwithstanding the apparent imperatives for radical action or the multitude of attempts via socio-technical experimentation to nurture strategic niches. At a theoretical level, it is concluded that greater attention must be paid to understanding how change can be nullified. Moreover, theoretical expectations of systemic change need a greater emphasis on the way in which technological transition as a process may mean that many existing practices and structures are retained more or less intact rather than entirely replaced by new practices and structures. The future research agenda needs therefore to understand more fully how embedded practices and technological change inter-relate in specific concrete conditions.
► The paper identifies an urgent need to understand non-change. ► Six mechanisms for regime stability are identified. ► Questions whether technological change brings organizational change ► Core technologies and business models may be retained.
This commentary reviews the position articulated in an article published in 2004 that the business model prevalent in the automotive industry was inadequate to meeting the challenge of ...sustainability, and reviews the key developments since then. The most noticeable developments the commentary traces are the growth in academic interest in business models, a more responsive government policy particularly in respect of new technologies, and the practical application of the concepts and ideas mooted in the original paper, notably with respect to electric vehicles.
March 2017 marks the 50th anniversary of the SS Torrey Canyon oil spill and cleanup, off the Cornwall coast in the English Channel. It was the world's first major supertanker disaster. It was a ...signature event in the marine pollution field, especially related to oil spill response and the initiation of scientific studies of monitoring and researching the fate and effects of oil in the sea. This paper recalls this event, notes our growing understanding of marine pollution and global efforts for cleaner seas, and encourages further work on both oil and the many emerging environmental issues affecting the marine environment.
It is widely accepted that electrification of the transport sector is one of several technological trajectories that could redress some of the environmental issues associated with the growth in ...travel demand including climate change and oil demand at a global scale, and air quality and noise pollution at the urban scale. Electric vehicles have been considered a promising technology at repeated intervals over the last century, but this promise has not been realised. This paper is a contribution to understanding the key tools and strategies that might enable the successful introduction of new technologies and innovations by exploring the key barriers to electric vehicles encountered in two countries (UK and Germany) where the automobile industry has been historically significant. The study evaluates stakeholders' opinions on relevant regulation, infrastructure investment, R&D incentives, and consumer incentives. The key findings of the research are that the introduction and penetration of EVs is confronted by several barriers that inhibit a larger market penetration under current conditions, which in turn casts doubt on the assumptions of strategic niche management and transitions theory.
•Immature developing technology reason behind non-commercialisation of EVs.•EVs currently do not present a significant benefit to the electricity sector.•EVs rely on a mix of regulatory and government measures for their development.•EVs face lock-in problem of unsustainable technologies and related barriers.•Positive milieu for innovation in vehicle technology and business models are required.
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•Pd/ZnO is a poor methanol synthesis catalyst showing RWGS.•Reduction produces PdZn alloy nanoparticles.•PdZn shows high selectivity to methanol.•Sol immobilisation produces smaller, ...more stable particles.
The direct hydrogenation of CO2 into methanol is crucial for providing a means of CO2 fixation and a way to store cleanly produced hydrogen in a more energy-dense and transportable form. Here we have prepared two series of Pd/ZnO catalysts, both by immobilisation of PVA-protected Pd colloids and by Pd impregnation of PdCl2 to investigate structure activity relationships for direct CO2 hydrogenation. Very different performances were found for the different preparation methods, and the Pd loading and pre-reduction of the catalysts were shown to be important factors for optimising methanol yield. The crucial factor for high methanol yield is the formation of a Pd–Zn alloy, either during the reaction itself, or better by high temperature pre-reduction. The formation of the alloy greatly reduces CO production by the reverse water gas shift reaction. The catalysts prepared by sol-immobilisation were relatively stable to thermal treatment. In contrast, the impregnated catalysts were much less thermally stable, due to the presence of remnant chloride on the surface of the catalyst, which was absent for the case of sol immobilisation preparation. The results illustrate the importance of controlling the PdZn particle size and its surface structure for the catalysts to achieve high methanol selectivity (60%, the rest being CO) and conversion (11%) at 250°C and 20bar. Selectivity for sol-immobilised catalysts decreases from 60% at 3nm average diameter, to 20% at 7nm.
There remains considerable debate over the active form of gold under operating conditions of a recently validated gold catalyst for acetylene hydrochlorination. We have performed an in situ x-ray ...absorption fine structure study of gold/carbon (Au/C) catalysts under acetylene hydrochlorination reaction conditions and show that highly active catalysts comprise single-site cationic Au entities whose activity correlates with the ratio of Au(I):Au(III) present. We demonstrate that these Au/C catalysts are supported analogs of single-site homogeneous Au catalysts and propose a mechanism, supported by computational modeling, based on a redox couple of Au(I)-Au(III) species.
For more than 3500 years, urinary catheters have been used to drain the bladder when it fails to empty. For people with impaired bladder function and for whom the method is feasible, clean ...intermittent self-catheterization is the optimal procedure. For those who require an indwelling catheter, whether short- or long-term, the self-retaining Foley catheter is invariably used, as it has been since its introduction nearly 80 years ago, despite the fact that this catheter can cause bacterial colonization, recurrent and chronic infections, bladder stones and septicaemia, damage to the kidneys, the bladder and the urethra, and contribute to the development of antibiotic resistance. In terms of medical, social and economic resources, the burden of urinary retention and incontinence, aggravated by the use of the Foley catheter, is huge. In the UK, the harm resulting from the use of the Foley catheter costs the National Health Service between £1.0-2.5 billion and accounts for ∼2100 deaths per year. Therefore, there is an urgent need for the development of an alternative indwelling catheter system. The research agenda is for the new catheter to be easy and safe to insert, either urethrally or suprapubically, to be retained reliably in the bladder and to be withdrawn easily and safely when necessary, to mimic natural physiology by filling at low pressure and emptying completely without damage to the bladder, and to have control mechanisms appropriate for all users.
Bioassays are among the ecotoxicologist's most effective weapons in the evaluation of water quality and the assessment of ecological impacts of effluents, chemicals, discharges, and emissions on the ...aquatic environment. Information on these assessment aids is needed throughout the international scientific and environmental management community. This comprehensive reference provides an excellent overview of the small-scale aquatic bioassay techniques and applications currently in use around the world. This special volume is the result of several years of collaboration between Environment Canada and Fisheries and Oceans Canada. Internationally recognized research scientists at many institutions have contributed to this state-of-the-art examination of the exciting, environmentally important field of microscale testing in aquatic toxicology. Microscale Testing in Aquatic Toxicology contains over forty chapters covering relevant principles, new techniques and recent advancements, and applications in scientific research, environmental management, academia, and the private sector.
Microbubble Axial Localization Errors in Ultrasound Super-Resolution Imaging Christensen-Jeffries, Kirsten; Harput, Sevan; Brown, Jemma ...
IEEE transactions on ultrasonics, ferroelectrics and frequency control/IEEE transactions on ultrasonics, ferroelectrics, and frequency control,
11/2017, Letnik:
64, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Acoustic super-resolution imaging has allowed the visualization of microvascular structure and flow beyond the diffraction limit using standard clinical ultrasound systems through the localization of ...many spatially isolated microbubble signals. The determination of each microbubble position is typically performed by calculating the centroid, finding a local maximum, or finding the peak of a 2-D Gaussian function fit to the signal. However, the backscattered signal from a microbubble depends not only on diffraction characteristics of the waveform, but also on the microbubble behavior in the acoustic field. Here, we propose a new axial localization method by identifying the onset of the backscattered signal. We compare the accuracy of localization methods using in vitro experiments performed at 7-cm depth and 2.3-MHz center frequency. We corroborate these findings with simulation results based on the Marmottant model. We show experimentally and in simulations that detecting the onset of the returning signal provides considerably increased accuracy for super-resolution. Resulting experimental crosssectional profiles in super-resolution images demonstrate at least 5.8 times improvement in contrast ratio and more than 1.8 times reduction in spatial spread (provided by 90% of the localizations) for the onset method over centroiding, peak detection, and 2-D Gaussian fitting methods. Simulations estimate that these latter methods could create errors in relative bubble positions as high as 900 μm at these experimental settings, while the onset method reduced the interquartile range of these errors by a factor of over 2.2. Detecting the signal onset is, therefore, expected to considerably improve the accuracy of super-resolution.
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