Ignition of dust-air atmospheres by ultrasonic waves

This paper shows the results of our investigations on the ignition source ultrasound in dust-air atmospheres. Ultrasound is, on the one hand, considered to be an ignition source according to international safety standards (EN 1127–1 (2011)). On the other hand, though, ultrasound is used for various applications in gases and air, such as level and flow measurement, or in the process industry, but no explosion accidents have yet been reported. Our research now shows that it is indeed possible to ignite dust-air mixtures in ultrasound fields under certain conditions. We conducted our experiments in an ultrasound standing wave field and used maize starch, calcium stearate and sulfur dust. For ignitions, an absorbing target was needed to convert the acoustic energy into heat. From theoretical estimations and experiments critical conditions that provoke ultrasonically triggered explosions are identified.     

Analytical solution for Joule–Thomson cooling during CO2 geo-sequestration in depleted oil and gas reservoirs

Mathematical tools are needed to screen out sites where Joule–Thomson cooling is a prohibitive factor for CO₂ geo-sequestration and to design approaches to mitigate the effect. In this paper, a simple analytical solution is developed by invoking steady-state flow and constant thermophysical properties. The analytical solution allows fast evaluation of spatiotemporal temperature fields, resulting from constant-rate CO₂ injection. The applicability of the analytical solution is demonstrated by comparison with non-isothermal simulation results from the reservoir simulator TOUGH2. Analysis confirms that for an injection rate of 3 kg s^?1 (0.1 MT yr^?1) into moderately warm (>40 °C) and permeable formations (>10^?14 m² (10 mD)), JTC is unlikely to be a problem for initial reservoir pressures as low as 2 MPa (290 psi).     

Strong Patient Advocacy and the Fundamental Ethical Role of Veterinarians

This essay examines the fundamental role of veterinarians in companion animal practice by developing the idea of veterinarians as strong advocates for their nonhuman animal patients. While the practitioner-patient relationship has been explored extensively in medical ethics, the relation between practitioner and animal patient has received relatively less attention in the expanding but still young field of veterinary ethics. Over recent decades, social and professional ethical perspectives on human-animal relationships have undergone major change. Today, the essential role of veterinarians is not entirely clear. Furthermore, veterinarians routinely face pressure, often insidious, to refrain from pursuing their patients’ vital interests. In exploring the concept of strong patient advocacy, this essay investigates the increasingly common suggestion that veterinarians have ‘primary obligation’ and ‘first allegiance’ to their animal patients rather than to other parties, such as their clients or employers. The related concept of a fiduciary duty, which is sometimes encountered in medical ethics, is similarly explored as it applies to companion animal practice. The resultant idea of a strong patient advocate places companion animal veterinarians conceptually and ethically close to human health professionals, not least pediatricians.