Prediction of far-field acoustic emissions from cavitation clouds during shock wave lithotripsy for development of a clinical device

This study presents the key simulation and decision stage of a multi-disciplinary project to develop a hospital device for monitoring the effectiveness of kidney stone fragmentation by shock wave lithotripsy (SWL). The device analyses, in real time, the pressure fields detected by sensors placed on the patient's torso, fields generated by the interaction of the incident shock wave, cavitation, kidney stone and soft tissue. Earlier free-Lagrange simulations of those interactions were restricted (by limited computational resources) to computational domains within a few centimetres of the stone. Later studies estimated the far-field pressures generated when those interactions involved only single bubbles. This study extends the free-Lagrange method to quantify the bubble–bubble interaction as a function of their separation. This, in turn, allowed identification of the validity of using a model of non-interacting bubbles to obtain estimations of the far-field pressures from 1000 bubbles distributed within the focus of the SWL field. Up to this point in the multi-disciplinary project, the design of the clinical device had been led by the simulations. This study records the decision point when the project's direction had to be led by far more costly clinical trials instead of the relatively inexpensive simulations. <br/

Particulate airborne impurities

The cumulative effects of air pollutants are of principal concern in research on environmental protection in Sweden. Post-industrial society has imposed many limits on emitted air pollutants, yet the number of reports on the negative effects from them is increasing, largely due to human activity in the form of industrial emissions and increased traffic flows. Rising concerns over the health effects from airborne particulate matter (PM) stem from in vitro, in vivo, and cohort studies revealing effects of mostly negative nature. Full insight into the health effects from PM can only be achieved through practical investigation of the mode of toxicity from distinct types of particles and requires techniques for their identification, monitoring, and the production of model fractions for health studies. To this effect, comprehensive collection and chemical analysis of particulates at the origin of emission was performed in order to provide clearer insight into the nature of the particulates at exposure and add detail to aid risk assessment. Methods of capturing particles and analyzing their chemical nature were devised using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). Furthermore, taking the approach of in vitro cytotoxicity testing, nanoparticles of types typical to automotive emissions, were synthesized and extensively characterized using SEM-EDS, X-ray diffraction (XRD), transmission electron microscopy (TEM),dynamic light scattering (DLS), and nanoparticle tracking analysis (NTA). The produced model magnetite and palladium nanoparticles were found to induce toxicity in human pulmonary epithelial cells (A549 and PBEC) as well as impact severely on immunological and renal cells (221 B- and 293T-cells) in a dose-dependent manner

Advanced optical smoke meters for jet engine exhaust measurement

Smoke meters with increased sensitivity, improved accuracy, and rapid response are needed to measure the smoke levels emitted by modern jet engines. The standard soiled tape meter in current use is based on filtering, which yields long term averages and is insensitive to low smoke levels. Two new optical smoke meter techniques that promise to overcome these difficulties have been experimentally evaluated: modulated transmission (MODTRAN) and photothermal deflection spectroscopy (PDS). Both techniques are based on light absorption by smoke, which is closely related to smoke density. They are variations on direct transmission measurements which produce a modulated signal that can be easily measured with phase sensitive detection. The MODTRAN and PDS techniques were tested on low levels of smoke and diluted samples of NO2 in nitrogen, simulating light adsorption due to smoke. The results are evaluated against a set of ideal smoke meter criteria that include a desired smoke measurement range of 0.1 to 12 mg cu.m. (smoke numbers of 1 to 50) and a frequency response of 1 per second. The MODTRAN instrument is found to be inaccurate for smoke levels below 3 mg/cu.m. and is able to make a only about once every 20 seconds because of its large sample cell. The PDS instrument meets nearly all the characteristics of an ideal smoke meter: it has excellent sensitivity over a range of smoke levels from 0.1 to 20 mg/cu.m. (smoke numbers of 1 to 60) and good frequency response (1 per second)

Air pollution monitoring instrumentation A survey

Air pollution monitoring instrumentation developed for aerospace uses surveyed for industrial application

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

Laser diagnostics and minor species detection in combustion using resonant four-wave mixing

Peer reviewedPostprin

The adsorptive properties of oligomeric, non-ionic surfactants from aqueous solution

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Surfactants from the 'Triton' range, manufactured by Rohm and Haas, Germany, were used to study the adsorptive behaviour of non-ionic surfactants (of the alkyl polyoxyethylene type) from aqueous solution onto mineral oxide surfaces. The oligomeric distributions of the surfactants were characterised using the HPLC technique. Two gradients were used: a normal phase gradient was used to study the surfactants from non-aqueous solution; an unusual gradient, which could not be definitively categorised as either normal or reversed phase and which was developed at Brunel, was used to analyse surfactants directly from aqueous solution. Quartz was used as a model mineral oxide surface. The quartz surface was characterised using a range of techniques: scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, X-ray fluorescence -analysis, Fourier transform-infra red spectroscopy and BET analysis. It was found that washing the quartz with concentrated HCI removed any calcium ions present on the surface and also removed 02- ions. Calcining the sample removed carbonaceous materials from the surface and also caused a decrease in the surface area. The quartz was shown to be non-porous by SEM and BET analysis. The adsorption experiments for this study were carried out using a simple tumbling method for which known ratios of surfactant in aqueous solution and quartz silica were mixed together for a known length of time. The amounts of surfactant present were measured using ultra-violet analysis and the HPLC techniques mentioned above. It was found that the smallest oligomers were adsorbed the most. An addition of salt to the system caused an overall increase in adsorption of the bulk surfactant, and increase in temperature caused an initial decrease in adsorbed amounts before the plateau of the isotherm and a final increase in bulk adsorption at the plateau of the isotherm. The oligomeric adsorption generally appeared to mirror the behaviour of the bulk surfactant. Atomic force microscopy (AFM), dynamic light and neutron scattering studies were used to analyse the character of the adsorbed surfactant layer. It was shown that the layer reached a finite thickness that corresponded to a bilayer of adsorbed surfactant. According to AFM data, this value of thickness was not consistent over the whole of the quartz surface.E

Study of atmospheric and AAP objectives of cross beam experiments Final report, 23 Jan. 1967 - 9 Jan. 1968

Light beam triangulation technique for atmospheric measurement