25 research outputs found
Asean plus guidelines: management of diabetic foot wounds
a reference guide on best practices in the management of diabetic foot woun
GAMBUT field experiment of peatland wildfires in Sumatra: from ignition to spread and suppression
Peat wildfires can burn over large areas of peatland, releasing ancient carbon and toxic gases into the atmosphere over prolonged periods. These emissions cause haze episodes of pollution and accelerate climate change. Peat wildfires are characterised by smouldering - the flameless, most persistent type of combustion. Mitigation strategies are needed in arctic, boreal, and tropical areas but are hindered by incomplete scientific understanding of smouldering. Here, we present GAMBUT, the largest and longest to-date field experiment of peat wildfires, conducted in a degraded peatland of Sumatra. Temperature, emission and spread of peat fire were continuously measured over 4-10 days and nights, and three major rainfalls. Measurements of temperature in the soil provide field experimental evidence of lethal fire severity to the biological system of the peat up to 30 cm depth. We report that the temperature of the deep smouldering is 13% hotter than shallow layer during daytime. During night-time, both deep and shallow smouldering had the same level of temperature. The experiment was terminated by suppression with water. Comparison of rainfall with suppression confirms the existence of a critical water column height below which extinction is not possible. GAMBUT provides a unique understanding of peat wildfires at field conditions that can contribute to mitigation strategies
The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set
Background
Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables.
Methods
Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set.
Results
Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001).
Conclusions
The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy
An experimental apparatus to measure soot morphology at high pressures using multi-angle light scattering
Investigating Soot Parameters in an Ethane/Air Counterflow Diffusion Flame at Elevated Pressures
Soot emissions from diesel engines and gas turbines are influenced by the combustion environment. Pressure is one of the parameters, which affects particulate emissions, and these effects are poorly understood on soot parameters. In this work, pressurized counterflow diffusion flame of ethane and air has been investigated using two angle light scattering and extinction technique. A counterflow diffusion flame has been stabilized from 2 to 5 atm in a pressure vessel, which can provide optical access from 10 to 165° in angular direction. Global strain rate (a) of 30 s−1 is maintained at all pressures by adjusting the inlet flows. Scattering measurements are performed at two angles (45° and 135°) and Rayleigh-Debye-Gans theory for Fractal Aggregates (RDG-FA) has been used to determine soot parameters from light scattering and extinction data. By combining the scattering at 135° with laser extinction measurements, path averaged soot volume fraction (fv), mean primary particle diameter (dp¯¯¯¯¯) and particle number densities (np), along the axis of the counterflow flame are calculated. Local soot volume fraction (fv,local) profiles are also measured using diffuse light 2D line of sight attenuation technique. Peak value of fv increases from 0.3 to 8 ppm as the pressure is raised from 2 to 5 atm. Primary particle size (dp¯¯¯¯¯) also increases with pressure where peak primary particle size of 11 nm at 2 atm rises to 38 nm at 5 atm. Population average radius of gyration (Rg) increases with pressure while the number densities (np) of primary particles decrease due to coalescence.</p
Determining fractal properties of soot aggregates and primary particle size distribution in counterflow flames up to 10 atm
Morphology of soot sampled from N<sub>2</sub>-diluted methane/air counterflow flames at elevated pressures via TEM imaging
Measurements of Pressure Effects on PAH Distribution and 2D Soot Volume Fraction Diagnostics in a Laminar Non-premixed Coflow Flame
The soot formation
process has been investigated at pressures up
to 16 bar using a non-premixed laminar coflow flame with nitrogen-diluted
ethylene. 2D diffuse line-of-sight attenuation (2D LOSA) and planar
laser-induced incandescence (PLII) were used to measure soot volume
fraction (SVF). The peak SVF increased exponentially with increasing
pressure, and the spatial distribution of soot volume fraction changed
substantially. At pressures below 6 bar, the two techniques agreed
well. At pressures above 6 bar, the techniques began to disagree,
with 2D LOSA showing higher peak SVF values at a location lower in
the wings of the flame compared to PLII. Errors in the LOSA measurements
due to the molecular absorption of PAHs were assessed by performing
measurements with bandpass filters centered at 435 nm and at 647 nm.
Furthermore, the evolution of polycyclic aromatic hydrocarbons (PAH)
in the flame was studied using planar laser-induced fluorescence (PLIF)
with the excitation laser set at 282.85 nm and compared to LOSA measurements.
Fluorescence signals were captured using bandpass filters (350, 400,
450, and 510 nm) corresponding to increasing PAH size. The peak concentration
of PAHs moved closer to the burner nozzle as pressure increased. Absorption
by PAH was unable to explain discrepancies between LOSA measurements
and PLII measurements. Using the Rayleigh–Debye–Gans
approximation for polydisperse fractal aggregates (RDG-PFA), the differences
between LOSA and PLII measurements were analyzed, and it was found
that LOSA is more sensitive to the soot primary particle diameter
due to changes in the scattering-to-absorption ratio (ρ<sub>sa</sub>). The effect of gate duration on SVF imaging with PLII is
also reported
Experimental study of moisture content effects on the transient gas and particle emissions from peat fires
Peat fires are a global-scale source of carbon emissions and a leading cause of regional air quality deterioration, especially in Southeast Asia. The ignition and spread of peat fires are strongly affected by moisture, which acts as an energy sink. However, moisture effects on peat fire emissions are poorly understood in the literature. Here we present the first experimental work to investigate transient gas and particle emissions for a wide range of peat moisture contents (MCs). We include drying, ignition, smouldering spread, and even flaming stages. Peat samples conditioned to different MCs were burnt in the laboratory where a suite of diagnostics simultaneously measured mass loss rate, temperature profiles, real-time concentration of 20 gas species, and size-fractioned particle mass. It was found that MC affects emissions, in addition to peat burning dynamics. An increase in MC below a smouldering threshold of 160% in dry basis leads to a decrease in NH 3 and greenhouse gas emissions, including CO 2 and CH 4. The burning of wet peat emits more coarse particles (between 1 and 10 µm) than dry peat, especially during the ignition stage. In contrast, flaming stage emits mostly soot particles less than 1 µm, and releases 100% more fully oxidised gas species including CO 2, NO 2 and SO 2 than smouldering. The examination of the resulting modified combustion efficiency (MCE) reveals that it fails to recongnise smouldering combustion with sufficient accuracy, especially for wet peat with MC > 120%. MCE confuses drying and flaming, and has significant variations during the ignition stage. As a result, MCE is not valid as a universal fire mode indicator used in the field. This work fills the knowledge gap between moisture and emissions, and provides a better understanding which can help mitigate peat fires