173 research outputs found
Chapter 10 The effect of topography on ash-cloud surge generation and propagation
AbstractThe relationship between valley morphology and ash-cloud surge development for 12 pyroclastic density currents (PDCs) at Soufrière Hills Volcano (SHV), Montserrat is investigated. Channel slope, sinuosity and cross-sectional area were measured from high-resolution digital elevation models (DEMs) using geographical information system (GIS) software; and were compared to geometric parameters of the deposits. The data illustrate three surge-generation regimes: a proximal area of rapid expansion; a medial deflation zone; and a steadier distal surge ‘fringe'. The extent to which these regimes develop varies with flow volume. For larger flows, within the proximal and medial regimes, a strong inverse correlation exists between surge detachment and valley cross-sectional area. Surge detachment is also correlated with observed and modelled flow velocities. Areas of topography-induced increases in velocity are interpreted to result in more pervasive fragmentation and fluidization, and thus enhanced surge generation. Distally, surge deposits appear as fringes with decaying extents, indicative of more passive expansion and decreasing velocity. The results indicate that surge mobility and detachment are a complex product of flow mass flux and topography, and that future efforts to model dense–dilute coupled flows will need to account for and integrate several mechanisms acting on different parts of the flow.</jats:p
Presentation and analysis of a worldwide database for lava dome collapse events: the Global Archive of Dome Instabilities (GLADIS)
Lava dome collapses generate hazardous pyroclastic flows, rockfalls and debris avalanches. Despite advances in understanding lava dome collapses and their resultant products, the conditions that occur prior to collapse are still poorly understood. Here we introduce the Global Archive of Dome Instabilities (GLADIS), a database that compiles worldwide historical dome collapses and their reported properties, including original dome volume (at the time of collapse), dome morphology, emplacement conditions, precursory activity, dome geometry and deposit characteristics. We determine the collapse magnitude for events where possible, using both absolute deposit volumes and relative collapse volume ratios (this being deposit volume as a proportion of original dome volume).
We use statistical analysis to explore whether relationships exist between collapse magnitude and extrusion rate, dome growth style, original dome volume, and causal mechanism of collapse. We find that relative collapse magnitude is independent of both the extrusion rate and the original dome volume. Relative collapse volume ratio is dependent on dome growth style, where endogenous growth is found to precede the largest collapses (~75% original volume). Collapses that comprise a higher proportion (<50%) of original dome volume are particularly attributed to both gravitational loading and the development of gas overpressure, whilst collapses comprising a small proportion (<10%) of original dome volume are associated with the topography surrounding the dome, and variations in extrusion direction. By providing validation and/or source data, we intend these data on various dome growth and collapse events, and their associated mechanisms, to be the focus of future numerical modelling efforts, whilst the identified relationships with relative collapse volume ratios can inform collapse hazard assessment based on observations of a growing dome
Post-depositional fracturing and subsidence of pumice flow deposits: Lascar Volcano, Chile
Unconsolidated pyroclastic flow deposits of the
1993 eruption of Lascar Volcano, Chile, have, with time,
become increasingly dissected by a network of deeply
penetrating fractures. The fracture network comprises
orthogonal sets of decimeter-wide linear voids that form a
pseudo-polygonal grid visible on the deposit surface. In this
work, we combine shallow surface geophysical imaging
tools with remote sensing observations and direct field
measurements of the deposit to investigate these fractures
and their underlying causal mechanisms. Based on ground
penetrating radar images, the fractures are observed to have
propagated to depths of up to 10 m. In addition, orbiting radar interferometry shows that deposit subsidence of up to
1 cm/year occurred between 1993 and 1996 with continued
subsidence occurring at a slower rate thereafter. In situ
measurements show that 1 m below the surface, the 1993
deposits remain 5°C to 15°C hotter, 18 years after
emplacement, than adjacent deposits. Based on the observed
subsidence as well as estimated cooling rates, the fractures are
inferred to be the combined result of deaeration, thermal
contraction, and sedimentary compaction in the months to
years following deposition. Significant environmental factors,
including regional earthquakes in 1995 and 2007, accelerated
settling at punctuated moments in time. The spatially variable
fracture pattern relates to surface slope and lithofacies
variations as well as substrate lithology. Similar fractures
have been reported in other ignimbrites but are generally
exposed only in cross section and are often attributed to
formation by external forces. Here we suggest that such
interpretations should be invoked with caution, and deformation
including post-emplacement subsidence and fracturing of
loosely packed ash-rich deposits in the months to years postemplacement
is a process inherent in the settling of pyroclastic
material
Dietary inflammatory index and inflammatory biomarkers in adolescents from LabMed physical activity study
Background/objectives The dietary inflammatory index (DII) is a tool to measure the diet’s inflammatory potential and has
been used with adults to predict low-grade inflammation. The present study aims to assess whether this dietary score predicts
low-grade inflammation in adolescents.
Subjects/methods The sample comprises 329 adolescents (55.9% girls), aged 12–18 years, from LabMed Physical Activity
Study. DII score was calculated based on a food-frequency questionnaire and categorized into tertiles. We collected blood
samples to determine the follow inflammatory biomarkers: C-reactive protein (CRP), interleukin-6 (IL-6), complement
component 3 (C3), and 4 (C4). In addition we calculated an overall inflammatory biomarker score. Odds ratios (OR) and
95% confidence intervals (95%CI) were computed from binary logistic regression models.
Results DII score, comparing first with third tertile, was positively associated with IL-6 in crude model (OR = 1.88, 95%
CI:1.09–3.24, ptrend = 0.011) and in fully adjusted (for biological and lifestyle variables) (OR = 3.38, 95%CI:1.24–9.20,
ptrend = 0.023). Also, DII score was positively associated with C4, when fully adjusted (OR = 3.12, 95%CI:1.21–8.10, ptrend
= 0.016). DII score was negatively associated with C3 in crude model, comparing first with second but not with third tertile,
and no significant associations in fully adjusted model were observed, although a trend was found (OR = 1.71, 95%
CI:0.63–4.66, ptrend = 0.044). No significant associations were observed between DII score and CRP. However, DII score
was positively associated with the overall inflammatory biomarker score, when fully adjusted (OR = 5.61, 95%
CI:2.00–15.78, ptrend = 0.002).
Conclusions DII score can be useful to assess the diet’s inflammatory potential and its association with low-grade inflammation in adolescents.The authors gratefully acknowledged the participation
of all adolescents and their parents, teachers and schools of
the LabMed and Physical Activity Study, the cooperation of volunteer’s,
the Department of Hygiene and Epidemiology (University of
Porto) for the conversion food frequency questionnaire data into
nutrients, and the Research Centre in Physical Activity, Health and
Leisure (University of Porto) for the sponsoring the LabMed and
Physical Activity Study.info:eu-repo/semantics/publishedVersio
Generation and dietary modulation of anti-inflammatory electrophilic omega-3 fatty acid derivatives
Dietary ω-3 polyunsaturated fatty acids (PUFAs) decrease cardiovascular risk via suppression of inflammation. The generation of electrophilic α,β-unsaturated ketone derivatives of the ω-3 PUFAs docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA) in activated human macrophages is catalyzed by cyclooxygenase-2 (Cox-2). These derivatives are potent pleiotropic anti-inflammatory signaling mediators that act via mechanisms including the activation of Nrf2- dependent phase 2 gene expression and suppression of pro-inflammatory NF-κB-driven gene expression. Herein, the endogenous generation of ω-3 PUFAs electrophilic ketone derivatives and their hydroxy precursors was evaluated in human neutrophils. In addition, their dietary modulation was assessed through a randomized clinical trial. Methods: Endogenous generation of electrophilic omega-3 PUFAs and their hydroxy precursors was evaluated by mass spectrometry in neutrophils isolated from healthy subjects, both at baseline and upon stimulation with calcium ionophore. For the clinical trial, participants were healthy adults 30-55 years of age with a reported EPA+DHA consumption of ≤ 300 mg/day randomly assigned to parallel groups receiving daily oil capsule supplements for a period of 4 months containing either 1.4 g of EPA+DHA (active condition, n = 24) or identical appearing soybean oil (control condition, n = 21). Participants and laboratory technicians remained blinded to treatment assignments. Results: 5-lypoxygenase-dependent endogenous generation of 7-oxo-DHA, 7-oxo-DPA and 5-oxo-EPA and their hydroxy precursors is reported in human neutrophils stimulated with calcium ionophore and phorbol 12-myristate 13-acetate (PMA). Dietary EPA+DHA supplementation significantly increased the formation of 7-oxo-DHA and 5-oxo-EPA, with no significant modulation of arachidonic acid (AA) metabolite levels. Conclusions: The endogenous detection of these electro.©2014 Cipollina et al
Percutaneous & Mini Invasive Achilles tendon repair
Rupture of the Achilles tendon is a considerable cause of morbidity with reduced function following injury. Recent studies have shown little difference in outcome between the techniques of open and non-operative treatment using an early active rehabilitation programme. Meta-analyses have shown that non-operative management has increased risk of re-rupture whereas surgical intervention has risks of complications related to the wound and iatrogenic nerve injury. Minimally invasive surgery has been adopted as a way of reducing infections rates and wound breakdown however avoiding iatrogenic nerve injury must be considered. We discuss the techniques and outcomes of percutaneous and minimally invasive repairs of the Achilles tendon
Allometry of the Duration of Flight Feather Molt in Birds
Replacement of flight feathers takes disproportionately more time for large birds than it does for small birds, because feather length increases with body size almost twice as fast as feather growth rate increases
A framework for evolutionary systems biology
<p>Abstract</p> <p>Background</p> <p>Many difficult problems in evolutionary genomics are related to mutations that have weak effects on fitness, as the consequences of mutations with large effects are often simple to predict. Current systems biology has accumulated much data on mutations with large effects and can predict the properties of knockout mutants in some systems. However experimental methods are too insensitive to observe small effects.</p> <p>Results</p> <p>Here I propose a novel framework that brings together evolutionary theory and current systems biology approaches in order to quantify small effects of mutations and their epistatic interactions <it>in silico</it>. Central to this approach is the definition of fitness correlates that can be computed in some current systems biology models employing the rigorous algorithms that are at the core of much work in computational systems biology. The framework exploits synergies between the realism of such models and the need to understand real systems in evolutionary theory. This framework can address many longstanding topics in evolutionary biology by defining various 'levels' of the adaptive landscape. Addressed topics include the distribution of mutational effects on fitness, as well as the nature of advantageous mutations, epistasis and robustness. Combining corresponding parameter estimates with population genetics models raises the possibility of testing evolutionary hypotheses at a new level of realism.</p> <p>Conclusion</p> <p>EvoSysBio is expected to lead to a more detailed understanding of the fundamental principles of life by combining knowledge about well-known biological systems from several disciplines. This will benefit both evolutionary theory and current systems biology. Understanding robustness by analysing distributions of mutational effects and epistasis is pivotal for drug design, cancer research, responsible genetic engineering in synthetic biology and many other practical applications.</p
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