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Surrogate chemical kinetics for drying of biomass and influence of moisture content on the burning behaviour of wood
No full textSolid phase burning models are necessary to understand fire dynamics of wood. Its thermal degradation produces pyrolysate and char which burn during flaming and smouldering respectively, but drying is the first thermophysical process to occur when wood, or biomass in general, burns. This study characterises the behaviour of drying via a single-step first-order Arrhenius-type reaction. A kinetic model is optimised using inverse modelling on TGA data, taken from the literature, from five different biomass types at different heating rates and moisture contents. Two clusters of biomass are identified: one of high lignin and low cellulose and hemicellulose content for which drying occurs faster at around 60 ◦C, and another of low lignin and high cellulose and hemicellulose content for which drying occurs slower at around 80 ◦C. The model is validated against further TGA data, yielding errors of 8% for the prediction of the faster drying cluster and 13% for the slower drying cluster. The resulting kinetics are used in combination with a one-dimensional meso-scale model for wood burning using Gpyro, a generalised pyrolysis model for porous fuels, to study the influence of kinetics,
heat transfer and mass transfer of moisture on the burning behaviour of wood. The model is compared against
experimental temperature data from the literature. The relationship between the position of the pyrolysis
and drying fronts with moisture content is shown. As the moisture content increases from 6% to 18%, the
pyrolysis rate decreases. The drying process acts thus as a heat sink which significantly delays pyrolysis. We
hence demonstrate that there exist two clusters of biomass drying behaviour and extract generalised drying
kinetics for each of them
Progesterone sulfates are enterohepatically recycled and stimulate G protein-coupled bile acid receptor 1-mediated gut hormone release
No full textSulfated progesterone metabolites (PMxSs) increase during gestation and are raised further in intrahepatic cholestasis of pregnancy (ICP), a disorder characterized by pruritus and elevated serum bile acids. PMxSs interact with bile acid receptor G protein-coupled bile acid receptor 1 (GPBAR1) to cause itch. We investigated whether PMxS could undergo enterohepatic recycling and stimulate intestinal GPBAR1-mediated release of gut hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). PMxSs were quantified in pre-/postprandial serum samples (n = 21) and feces (n = 18) by ultra performance liquid chromatography-tandem mass spectrometry in prospectively recruited third trimester of pregnancy outpatients with uncomplicated pregnancy or ICP. Ussing chambers were used to evaluate colonic ion secretion changes (ΔIsc) in wildtype, GPBAR1−/−, and PYY−/− mice by PMxS metabolites, 5β‐pregnan‐3α,‐20α‐diol‐3-sulfate (PM3S) and 5α-pregnan-3β-ol-20-one-sulfate (PM5S), and in wildtype mice with or without apical sodium bile acid transporter (ASBT) inhibition (n = 6/condition). PM3S/PM5S stimulation of GLP-1 release from wildtype and GPBAR1−/− murine crypts and human colonoids was measured by ELISA (n = 3). Serum PMxSs increase postprandially in women with ICP but are unaltered in uncomplicated pregnancies. PMxSs are present in feces. Apical and basolateral PM3S and PM5S stimulated PYY-mediated −ΔIsc in wildtype (P < 0.01) but not GPBAR1−/− or PYY−/− colons. PM3S and PM5S caused GLP-1 secretion in murine crypts and human colonoids (P < 0.001). ASBT inhibition blunted −ΔIsc by 68% after apical PM3S and PM5S addition (P < 0.001). Serum PMxS, elevated in women with ICP and particularly postprandially, can undergo ASBT-mediated intestinal reuptake and activate GPBAR1 to stimulate gut hormone release. PMxS may therefore augment GPBAR1-mediated metabolic responses during pregnancy.
NEW & NOTEWORTHY Sulfated progesterone species (PMxSs) increase postprandially in women with intrahepatic cholestasis of pregnancy (ICP) but not in women with uncomplicated pregnancy. PMxS can be enterohepatically recycled via active transport from the gut lumen by apical sodium-dependent bile acid transporter (ASBT) and stimulate gut hormone secretion. Active reabsorption of PMxS may play a role in the pruritus suffered by women with ICP. ASBT inhibition is a plausible therapy for ICP-associated pruritus
The drag length is key to quantifying tree canopy drag
No full textThe effects of trees on urban flows are often determined in computational fluid dynamics simulations using a
quadratic drag formulation based on the leaf-area density and a volumetric drag coefficient
. We develop
an analytical model for the flow within a vegetation canopy and identify the drag length = (
)
−1 as the
key metric to describe the local tree drag, which represents the adjustment lengthscale for the mean velocity
inside the canopy due to tree drag. A detailed literature survey suggests that the median observed in
field experiments is 21 m for trees and 0.7 m for low vegetation (crops). Total 168 large-eddy simulations
are conducted to obtain a closed form of the analytical model which allows determining and
from the
wind-tunnel experiments that typically present the drag characteristics in terms of the classical drag coefficient
and the aerodynamic porosity
. We show that geometric scaling of
is the appropriate scaling of trees
in wind tunnels. Evaluation of
for numerical simulations and wind-tunnel experiments (assuming geometric
scaling 1 ∶ 100) in literature shows that the median
in both these cases is about 5 m, suggesting a potential
overestimation of vegetative drag
Reflections on the tobacco-free generation: methodological challenges and global implications
No full textStrong screening rules for group-based SLOPE models
No full textTuning the regularization parameter in penalized regression models is an expensive task, requiring multiple models to be fit along a path of parameters. Strong screening rules
drastically reduce computational costs by lowering the dimensionality of the input prior to fitting. We develop strong screening rules for group-based Sorted L-One Penalized Estimation (SLOPE) models: Group SLOPE and Sparse-group SLOPE. The developed rules are applicable to the wider family of group-based OWL models, including OSCAR. Our
experiments on both synthetic and real data show that the screening rules significantly accelerate the fitting process. The screening rules make it accessible for group SLOPE and
sparse-group SLOPE to be applied to high-dimensional datasets, particularly those encountered in genetics
Insight into hysteretic drying and wetting in unsaturated granular soil from fully resolved computational fluid dynamics analysis
No full textThe hysteresis of soil water retention curves (WRCs) originates from multiple factors including the pore geometry, contact angles at the solid–liquid interface, and pore-water morphology. This study exploits high-resolution computational fluid dynamics (CFD) to explore the mechanisms underlying this hysteresis in wetting and drying and the development of scanning curves. We consider the role of pore geometry on the processes, i.e., the ink-bottle effect, and we focus on capillary rise. Drying and wetting in single pores were simulated using fully resolved CFD, and the results are summarized in the form of WRCs. A detailed analysis of the force balance in the system reveals the role of the angle between the fluid–fluid interface and the vertical direction as the water surface moves into the bulb during drying. In wetting, residual water remaining in the pore after a drying cycle plays a key role. This difference in mechanisms contributes to the observed hysteresis. Scanning curves emerged from simulations of a single pore and a composite pore comprising two types of double-bulb systems. The analyses were expanded to simulate wetting and drying in a face-centered cubic packing of uniform spheres. The study shows that CFD simulations can elucidate the mechanisms at key transition points and capture the influence of factors including residual water on the emergent WRCs
Survival of patients with solid tumours and sepsis admitted to intensive care in a tertiary oncology centre: a retrospective analysis
No full textIntroduction:
Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Patients with cancer are at risk of developing sepsis and requiring intensive care unit (ICU) admission. We aimed to assess survival of patients with a solid tumour admitted to ICU as an emergency with sepsis, and to identify predictors of 90-day survival at admission.
Materials and Methods:
We conducted a retrospective cohort survival analysis. We identified adults with a solid tumour admitted to ICU with sepsis between 01/01/2011 and 31/12/2020 at a tertiary oncology centre with two hospitals (London and Surrey, UK). We defined sepsis using the Sepsis-3 definition. The primary outcome was 90-day survival. We used the parametric accelerated failure time model for multivariate analysis to generate acceleration factors (AF).
Results:
625 patients were identified and the 90-day survival rate was 59.5%(353/593).Multivariate analysis identified the presence of localized (AF 0.13, 95% CI 0.06-0.25) or regionalized disease (AF 0.21, 95% CI 0.12-0.36) compared to distant metastatic disease, unplanned surgery on the day of admission (AF 0.15, 95% CI 0.07-0.31), lactate (AF 1.25 95% CI 1.15-1.35), Sequential Organ Failure Assessment Score (AF 1.19, 95% CI 1.12-1.27), previous radiotherapy (AF 1.89, 95% CI 1.14-3.125), previous systemic anti-cancer treatment (excluding hormonal therapy) (AF 1.49, 95% CI 0.93-2.38), bacteraemia (AF 0.47, 95% CI 0.27-0.81) and serum albumin (AF 0.94, 95% CI 0.91-0.98) as independent predictors of 90-day survival.
Conclusions:
This study of solid tumour patients admitted to ICU is one of the largest providing survival data to inform clinicians and patients. This data provides information on factors that should be considered when deliberating the possible outcome of ICU admission for a patient with solid malignancy and sepsis and highlights that the presence of cancer itself should not limit ICU admission for sepsis
Urodynamics tests for the diagnosis and management of bladder outlet obstruction in men: the UPSTREAM non-inferiority RCT
No full textBackground: Lower urinary tract symptoms are common in older men and can be bothersome, leading to treatment. The UPSTREAM randomised controlled trial (Phase I) investigated whether assessment of these symptoms with invasive urodynamic testing could improve symptoms when guiding treatment options.
Objective: To assess the long-term lower urinary tract symptoms and rates of surgery for bladder outlet obstruction in men participating in the UPSTREAM study (Phase I).
Design: Pragmatic, multi-centre, parallel group, two-group open randomised controlled study, with outcome assessors blinded to aggregate data.
Setting: Urology departments of 26 NHS hospitals in England.
Participants: Men ≥18-years, seeking further treatment for their bothersome lower urinary tract symptoms, which may include surgery, who were existing participants of the UPSTREAM study (Phase I). Men were excluded if they were unable to pass urine without a catheter, had a relevant neurological disease, were currently undergoing treatment for prostate or bladder cancer, had previous prostate surgery or were unfit for surgery.
Interventions: Routine care plus invasive urodynamics (intervention) or non-invasive routine care.
Main outcome measures: The primary outcome was patient reported International Prostate Symptom Score five years post-randomisation. Rates of surgery was the key secondary outcome. Patient Reported Outcomes included measures of lower urinary tract symptoms, sexual function, overall quality of life and cost-effectiveness from a secondary care perspective.
Data sources: Questionnaires to participants for patient reported outcome measures, and NHS England Hospital Episode Statistics and mortality data.
Results: Of 820 men randomised in UPSTREAM (Phase I) between October 2014 and December 2016, 211/427 men randomised to the intervention group completed Phase II questionnaires (49.4%) and 205/363 in the routine care group (56.5%). There was no difference between International Prostate Symptom scores in the two groups at five years (adjusted difference 0.41, 95% CI -1.10, 1.93). There was also no difference in other lower urinary tract symptoms, sexual function or quality of life. Routine data was received for 98% of men. 347 (43.3%) men with routine data available had received at least one related surgical procedure for the treatment of LUTS. Over the five year time horizon, incremental mean costs were slightly higher (£176.63, 95% CI £-464.06 to £817.32) in the intervention group and incremental mean QALYs were slightly lower (-0.039, 95% CI -0.152 to 0.073) in the intervention group. This suggests routine care is the cost-effective option.
Limitations: Around half of the men from Phase I completed questionnaires at five years, although their characteristics were similar to those of non-responders, withdrawn participants or those who had died. The majority of men were of white ethnicity, so results may be less applicable to other ethnicities.
Conclusions: Five year follow up does not support the introduction of invasive urodynamics in reducing lower urinary tract symptoms or rates of prostate surgery, from a clinical or cost-effectiveness perspective.
Future work: This should identify if there are sub-groups of patients who might benefit from the addition of urodynamics to routine care for bothersome lower urinary tract symptoms
Assessment of healthcare providers’ knowledge, attitude, and practice toward medical research in southwest Saudi Arabia: a cross-sectional study
No full textBackground:
Medical research plays a crucial role in advancing the treatment and prevention of diseases, in addition to enhancing public health.
Objectives:
This study aims to assess knowledge, attitude, and practice (KAP) of healthcare providers (HCPs) in relation to medical research, identify motivating factors and barriers that prevent them from conducting research, and identify associated factors with good knowledge, practice and positive attitude.
Methods:
In this cross-sectional study, a validated questionnaire was employed to gather data of HCPs who work at healthcare institutions affiliated with MOH. The Proportionate stratified random sampling method was used to recruit HCPS. Proportion (%), and median and interquartile range (IQR) were used to represent the data. Logistic regression analysis was carried out to identify associated factors with good knowledge, positive attitude, and good practice.
Results:
A total of 285 HCPs were included in the analysis. The median score for knowledge was 43%, with scores ranging from 14 to 57%, for most participants showing variability in their knowledge levels. For attitude, the median score was 100%, indicating a generally positive outlook, with scores between 80% and 100% for most participants. The practice score had a median of 59%, with scores ranging from 33 to 83%, showing a wide range in research activity among the HCPS. The most reported motivators were strength of the resume (91.80%) and fulfilment of work requirements (90.80%). The most reported barriers were lack of financial support (82.3%), poor time management (78.7%), no enough research facilities (75.2%), lack of motivation (74.8%), inadequate skills and knowledge (72.3%), and lack of rewards (71.6%). Good knowledge was significantly associated with taken research methodology course (p. value = 0.001) and qualification (p. values = < 0.05). Positive attitude was significantly associated with workplace and qualification. Nationality (p. value = 0.005) and taking a research methodology course (p. value = 0.001) were significantly associated with good practice.
Conclusion:
Although HCPs showed a positive attitude towards medical research, their knowledge and practice were inadequate. They are necessarily needed for amelioration. This improvement can be achieved through effective and regular research methodology courses, workshops, and enhancement of the research environment