An Audible Demonstration Of The Speed Of Sound In Bubbly Liquids

The speed of sound in a bubbly liquid is strongly dependent upon the volume fraction of the gas phase, the bubble size distribution, and the frequency of the acoustic excitation. At sufficiently low frequencies, the speed of sound depends primarily on the gas volume fraction. This effect can be audibly demonstrated using a one-dimensional acoustic waveguide, in which the flow rate of air bubbles injected into a water-filled tube is varied by the user. The normal modes of the waveguide are excited by the sound of the bubbles being injected into the tube. As the flow rate is varied, the speed of sound varies as well, and hence, the resonance frequencies shift. This can be clearly heard through the use of an amplified hydrophone and the user can create aesthetically pleasing and even musical sounds. In addition, the apparatus can be used to verify a simple mathematical model known as Wood's equation that relates the speed of sound of a bubbly liquid to its void fraction. (c) 2008 American Association of Physics Teachers.Mechanical Engineerin

Measurement of Both Gas and Particle Velocity in Turbulent Two-Phase Flow

A laser-Doppler anemometer was used to measure the velocity of both the gas and particles in a turbulent two-phase flow for conditions when the distribution of the velocities of the two phases overlaps. The velocities from the two phases are separated by comparing the Doppler amplitude to the pedestal amplitude. Results of the measure of the gas-particle flow downstream of a nozzle mounted in a circular pipe are presented

Electron-impact ionization of atomic hydrogen at 2 eV above threshold

The convergent close-coupling method is applied to the calculation of fully differential cross sections for ionization of atomic hydrogen by 15.6 eV electrons. We find that even at this low energy the method is able to yield predictive results with small uncertainty. As a consequence we suspect that the experimental normalization at this energy is approximately a factor of two too high.Comment: 10 page

Forehead reflectance photoplethysmography to monitor heart rate: preliminary results from neonatal patients

Around 5%–10% of newborn babies require some form of resuscitation at birth and heart rate (HR) is the best guide of efficacy. We report the development and first trial of a device that continuously monitors neonatal HR, with a view to deployment in the delivery room to guide newborn resuscitation. The device uses forehead reflectance photoplethysmography (PPG) with modulated light and lock-in detection. Forehead fixation has numerous advantages including ease of sensor placement, whilst perfusion at the forehead is better maintained in comparison to the extremities. Green light (525 nm) was used, in preference to the more usual red or infrared wavelengths, to optimize the amplitude of the pulsatile signal. Experimental results are presented showing simultaneous PPG and electrocardiogram (ECG) HRs from babies (n = 77), gestational age 26–42 weeks, on a neonatal intensive care unit. In babies ≥32 weeks gestation, the median reliability was 97.7% at ±10 bpm and the limits of agreement (LOA) between PPG and ECG were +8.39 bpm and −8.39 bpm. In babies <32 weeks gestation, the median reliability was 94.8% at ±10 bpm and the LOA were +11.53 bpm and −12.01 bpm. Clinical evaluation during newborn deliveries is now underway

Qualitative protocol for understanding the contribution of Australian policy in the urban planning, justice, energy and environment sectors to promoting health and health equity

Introduction: A well-established body of literature demonstrates that health and equity are strongly influenced by the consequences of governments’ policy and resultant actions (or inactions) outside the health sector. Consequently, the United Nations, and its agency the WHO, have called for national leadership and whole-of-government action to understand and address the health impacts of policies in all sectors. This research responds to that call by investigating how policymaking in four sectors—urban planning, justice, energy and environment—may influence the social determinants of health and health equity (SDH/HE). Methods and analysis: The research design is informed by a critical qualitative approach. Three successive stages are included in the design. The first involves analysing all strategic policy documents and selected legislative documents from the four sectors (n=583). The document analysis is based on a coding framework developed to identify alignment between the documents and the SDH/HE. Two policies that demonstrate good practice in regard to SDH/HE will be selected from each sector during the second stage for embedded case study analysis (total n=8). This is intended to illuminate which factors have supported recognition and action on SDH/HE in the selected policies. The third stage involves progressive theoretical integration and development to understand political and institutional facilitators and barriers to action on SDH/HE, both within and between sectors. Ethics and dissemination: The research will provide much needed evidence about how coherent whole-of-government action on SDH/HE can be advanced and contribute knowledge about how health-enhancing policy activity in the four sectors may be optimised. Learnings from the research will be shared via a project advisory group, policy briefings, academic papers, conference presentations and research symposia. Ethics approval has been secured for the embedded case studies, which involve research participants

Eulerian simulation of the fluid dynamics of helicopter brownout

A computational model is presented that can be used to simulate the development of the dust cloud that can be entrained into the air when a helicopter is operated close to the ground in desert or dusty conditions. The physics of this problem, and the associated pathological condition known as ‘brownout’ where the pilot loses situational awareness as a result of his vision being occluded by dust suspended in the flow around the helicopter, is acknowledged to be very complex. The approach advocated here involves an approximation to the full dynamics of the coupled particulate-air system. Away from the ground, the model assumes that the suspended particles remain in near equilibrium under the action of aerodynamic forces. Close to the ground, this model is replaced by an algebraic sublayer model for the saltation and entrainment process. The origin of the model in the statistical mechanics of a distribution of particles governed by aerodynamic forces allows the validity of the method to be evaluated in context by comparing the physical properties of the suspended particulates to the local properties of the flow field surrounding the helicopter. The model applies in the Eulerian frame of reference of most conventional Computational Fluid Dynamics codes and has been coupled with Brown’s Vorticity Transport Model. Verification of the predictions of the coupled model against experimental data for particulate entrainment and transport in the flow around a model rotor are encouraging. An application of the coupled model to analyzing the differences in the geometry and extent of the dust clouds that are produced by single main rotor and tandem-rotor configurations as they decelerate to land has shown that the location of the ground vortex and the size of any regions of recirculatory flow, should they exist, play a primary role in governing the extent of the dust cloud that is created by the helicopter

Transition phenomena in unstably stratified turbulent flows

We study experimentally and theoretically transition phenomena caused by the external forcing from Rayleigh-Benard convection with the large-scale circulation (LSC) to the limiting regime of unstably stratified turbulent flow without LSC whereby the temperature field behaves like a passive scalar. In the experiments we use the Rayleigh-B\'enard apparatus with an additional source of turbulence produced by two oscillating grids located nearby the side walls of the chamber. When the frequency of the grid oscillations is larger than 2 Hz, the large-scale circulation (LSC) in turbulent convection is destroyed, and the destruction of the LSC is accompanied by a strong change of the mean temperature distribution. However, in all regimes of the unstably stratified turbulent flow the ratio $\big[(\ell_x \nabla_x T)^2 + (\ell_y \nabla_y T)^2 + (\ell_z \nabla_z T)^2\big] /$ varies slightly (even in the range of parameters whereby the behaviour of the temperature field is different from that of the passive scalar). Here $\ell_i$ are the integral scales of turbulence along x, y, z directions, T and \theta are the mean and fluctuating parts of the fluid temperature. At all frequencies of the grid oscillations we have detected the long-term nonlinear oscillations of the mean temperature. The theoretical predictions based on the budget equations for turbulent kinetic energy, turbulent temperature fluctuations and turbulent heat flux, are in agreement with the experimental results.Comment: 14 pages, 14 figures, REVTEX4-1, revised versio

Living with sub-optimal glycaemic control: the experiences of Type 2 diabetes diagnosis and education

Aim The aim of this study was to explore the experiences of diagnosis and education for people living with Type 2 diabetes who have sub-optimal glycaemic control. Background The increasing prevalence of Type 2 diabetes is a global concern. Many people have difficulty maintaining optimal glycaemic control with up to 50% having HbA1c levels higher than recommended. A range of factors that have been suggested as possibly contributing to this, however, little is known about how their experience of diagnosis, education and support to attempt to understand the context of their self-management practices. Design A qualitative thematic analysis of interviews conducted with people with sub-optimal glycaemic control prior to their participation in an intervention study. Method Thirty participants taking part in a psychosocial/educational intervention for people with sub-optimal glycaemic control were interviewed in 2012 before the intervention commenced. These interviews explored each participant's experience of the diagnosis and associated education. The interviews were transcribed and a thematic analysis was conducted. Findings Almost all the participants had been shocked at receiving the diagnosis and felt it had been a moral indictment on their lifestyle. Many had been given the impression that they had a mild form of diabetes and most had been given very little information on self-management that they had found useful. Conclusion The findings suggest that for the participants there was a considerable gap between the rhetoric of person-centred services and the reality of the experiences of diagnosis and education for the self-management of Type 2 diabetes