4,202 research outputs found
Paravertebral blocks and enhanced recovery after surgery protocols in breast reconstructive surgery: Patient selection and perspectives
Quantitative determination of engine water ingestion
A nonintrusive optical technique is described for determination of liquid mass flux in a droplet laden airstream. The techniques were developed for quantitative determination of engine water ingestion resulting from heavy rain or wheel spray. Independent measurements of the liquid water content (LWC) of the droplet laden airstream and of the droplet velocities were made at the stimulated nacelle inlet plane for the liquid mass flux determination. The LWC was measured by illuminating and photographing the droplets contained within a thin slice of the flow field by means of a sheet of light from a pulsed laser. A fluorescent dye introduced in the water enchanced the droplet image definition. The droplet velocities were determined from double exposed photographs of the moving droplet field. The technique was initially applied to a steady spray generated in a wind tunnel. It was found that although the spray was initially steady, the aerodynamic breakup process was inherently unsteady. This resulted in a wide variation of the instantaneous LWC of the droplet laden airstream. The standard deviation of ten separate LWC measurements was 31% of the average. However, the liquid mass flux calculated from the average LWC and droplet velocities came within 10% of the known water ingestion rate
A window into the neutron star: Modelling the cooling of accretion heated neutron star crusts
In accreting neutron star X-ray transients, the neutron star crust can be
substantially heated out of thermal equilibrium with the core during an
accretion outburst. The observed subsequent cooling in quiescence (when
accretion has halted) offers a unique opportunity to study the structure and
thermal properties of the crust. Initially crust cooling modelling studies
focussed on transient X-ray binaries with prolonged accretion outbursts (> 1
year) such that the crust would be significantly heated for the cooling to be
detectable. Here we present the results of applying a theoretical model to the
observed cooling curve after a short accretion outburst of only ~10 weeks. In
our study we use the 2010 outburst of the transiently accreting 11 Hz X-ray
pulsar in the globular cluster Terzan 5. Observationally it was found that the
crust in this source was still hot more than 4 years after the end of its short
accretion outburst. From our modelling we found that such a long-lived hot
crust implies some unusual crustal properties such as a very low thermal
conductivity (> 10 times lower than determined for the other crust cooling
sources). In addition, we present our preliminary results of the modelling of
the ongoing cooling of the neutron star in MXB 1659-298. This transient X-ray
source went back into quiescence in March 2017 after an accretion phase of ~1.8
years. We compare our predictions for the cooling curve after this outburst
with the cooling curve of the same source obtained after its previous outburst
which ended in 2001.Comment: 4 pages, 1 figure, to appear in the proceedings of "IAUS 337: Pulsar
Astrophysics - The Next 50 Years" eds: P. Weltevrede, B.B.P. Perera, L. Levin
Preston & S. Sanida
Tunnelling Effect and Hawking Radiation from a Vaidya Black Hole
In this paper, we extend Parikh' work to the non-stationary black hole. As an
example of the non-stationary black hole, we study the tunnelling effect and
Hawking radiation from a Vaidya black hole whose Bondi mass is identical to its
mass parameter. We view Hawking radiation as a tunnelling process across the
event horizon and calculate the tunnelling probability. We find that the result
is different from Parikh's work because is the function of
Bondi mass m(v)
Using heat maps to identify areas prone to violence against women in the public sphere
The lack of accessible crime data, especially geolocations, in developing countries often acts as a barrier to identifying environmental or situational factors in high crime areas that might contribute to the facilitation of those crimes. This paper presents a methodology for conducting fieldwork for creating heat maps to identify areas prone to violence against women (VAW) in Corregidora, Mexico. Heat maps were produced based on household survey data. The results were used to select specific high concentration locations to conduct structured observations and inductive visual analysis at street level in order to identify if and what situational factors might influence the perpetration of VAW in those locations. Four broad features were identified in the urban built environment during the site visits linked to the facilitation of opportunities for the commission of VAW: (1) lacking infrastructure, (2) presence of physical obstacles, (3) poor visibility and (4) restricted pedestrian mobility. The paper demonstrates the utility of this method for aiding situational crime prevention strategies in areas where official spatial crime data is unavailable or lacking. This study presents a relatively low cost (although labour intensive) and independent method of aiding crime prevention strategies, which will hopefully be of practical value for organisations in areas with poor crime recording practices and limited access to expensive mapping technologies
Multiple and complex links between babyWASH and stunting: An evidence synthesis
Studies have shown linkages between water, sanitation and hygiene (WASH) and stunting in children under 2 years in sub-Saharan Africa. WASH interventions have been shown to reduce stunting rates; however, the biological mechanisms and socio-economic influences responsible for this trend remain poorly understood. This paper reviews the literature regarding these links, and the efficacy of both general WASH interventions and those targeted at children in their first 1,000 days, known as babyWASH, for stunting reduction. Fifty-nine papers published between 2008 and 2019 were reviewed, retrieved from Science Direct, Scopus and Web of Science databases, comprising field trials and data analysis, and literature and systematic reviews. Key findings showed that stunting is directly attributed to diarrhoea, environmental enteric dysfunction and undernutrition although a more comprehensive understanding of these biological mechanisms is necessary. Interventions to interrupt the faecal transmission cycle proved to effectively reduce stunting rates, particularly improved sanitation facilities to reduce open defaecation, increased proximity to water and widespread behavioural change. Methodologies should move away from randomised controlled trials towards selected contexts, mixed data collection methods and inclusion of broader social, cultural and environmental conditions. Improved cross-sectoral collaboration is encouraged, particularly to ensure the complexity of social and contextual factors is fully considered
Barriers and opportunities for participatory environmental upgrading: Case study of Havelock informal settlement, Durban
Urbanisation is one of the key challenges of this decade with 68% of the global population likely to be living in urban areas by 2050. This challenge is particularly acute in sub-Saharan Africa where future towns and cities will see an influx of residents living in spontaneous human settlements. As cities struggle to keep up with the speed of growth and spread of informal settlements, associated environmental challenges such as air and water pollution and waste management have been significantly increasing posing a health risk in high density settings. Using the case of Havelock informal settlement in Durban, the authors identified key challenges associated with poor environmental conditions, lack of basic infrastructure, and the implications for settlement upgrading. The study uses mixed methods combining transect walks, priority mapping, seasonal calendar, focus group discussions and household interviews to explore the households' most challenging environmental issues faced daily by informal dwellers. This paper seeks to make the case for targeted participatory environmental infrastructure and management delivery in urban settlements in South Africa. The research also highlights the value of adopting a holistic approach to infrastructure provision to effectively enhance the living conditions of communities. Targeted participatory processes are vital to ensure that holistic infrastructure interventions are acceptable, appropriate and embedded in local communities to create sustainable habitats
Quantum fields in gravity
We give a brief description of some compelling connections between general
relativity and thermodynamics through i) the semi-classical tunnelling
method(s) and ii) the field-theoretical modelling of Unruh-DeWitt detectors. In
both approaches it is possible to interpret some quantities in a
thermodynamical frame.Comment: 4 pages, no figures, contribution to the proceedings of the
conference "Relativity and Gravitation - 100 years after Einstein in Prague
Simulation and Analysis of Natural Rain in a Wind Tunnel via Digital Image Processing Techniques
It is desired to simulate natural rain in a
wind tunnel in order to investigate its influence
on the aerodynamic characteristics of aircraft.
Rain simulation nozzles have been developed and
tested at JPL. Pulsed laser sheet illumination is
used to photograph the droplets in the moving
airstream. Digital image processing techniques are
applied to these photographs for calculation of
rain statistics to evaluate the performance of the
nozzles. It is found that fixed hypodermic type
nozzles inject too much water to simulate natural
rain conditions. A modification uses two aerodynamic
spinners to flex a tube in a pseudo-random
fashion to distribute the water over a larger area
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