Measurement and analysis of air quality in temporary shelters on three continents

Millions of displaced people are housed in shelters that generally consist of a single room, meaning that activities including cooking, sleeping and socialising all take place in the same space. Therefore, indoor air quality can be poor, resulting in estimated 20,000 displaced people dying prematurely every year. Very few studies considered the issue and all within one country. This paper describes the first comprehensive study investigating air quality in shelters by looking at Volatile Organic Compounds (VOCs), Particulate Matter (PM), and CO2 in ten locations within Peru, Ethiopia, Djibouti, Jordan, Turkey and Bangladesh. It has the aim of: (i) discovering how widespread the issue is, (ii) identifying some of the causes, (iii) whether it is linked to cultural and behavioural factors, (iv) location and climate, or (v) shelters’ materials or design. Results revealed very harmful levels of pollutants that are often linked to excess mortality - with total VOC concentrations as high as 102400μgm-3 and PM over 3000μgm-3. The reasons for these concentrations were complex, multifaceted and setting-specific. However, it was an issue in both simple self-built shelters and mass-manufactured designs, and across all climates and cultures. In all cases, conditions could be greatly improved by improving airflow as windows were frequently blocked for various reasons. Therefore, airflow should be explicitly considered, whilst being cognisant of the local context; and when cooking is likely to occur indoors, chimneys must be fitted

Measurement and analysis of air quality in temporary shelters on three continents

Millions of displaced people are housed in shelters that generally consist of a single room, meaning that activities including cooking, sleeping and socializing all take place in the same space. Therefore, indoor air quality can be poor, resulting in estimated 20,000 displaced people dying prematurely every year. Very few studies considered the issue and all within one country. This paper describes the first comprehensive study investigating air quality in shelters by looking at Volatile Organic Compounds (VOCs), Particulate Matter (PM), and CO2 in ten locations within Peru, Ethiopia, Djibouti, Jordan, Turkey and Bangladesh. It has the aim of: (i) discovering how widespread the issue is, (ii) identifying some of the causes, (iii) whether it is linked to cultural and behavioural factors, (iv) location and climate, or (v) shelters’ materials or design. Results revealed very harmful levels of pollutants that are often linked to excess mortality - with total VOC concentrations as high as 102400 µgm-3 and PM over 3000 µgm-3. The reasons for these concentrations were complex, multifaceted and setting-specific. However, it was an issue in both simple self-built shelters and mass-manufactured designs, and across all climates and cultures. In all cases, conditions could be greatly improved by improving airflow as windows were frequently blocked for various reasons. Therefore, airflow should be explicitly considered, whilst being cognisant of the local context; and when cooking is likely to occur indoors, chimneys must be fitted

Properties of bio-based insulation materials and their potential impact on indoor air quality

Significantly decreasing energy consumption in buildings requires more air-tight construction combined with much higher insulation levels. A potential unintended consequence of this approach has been deterioration in the indoor air quality, resulting from significantly reduced ventilation rates and the accumulation of airborne pollutants, and this has proven to be a bottleneck to successful implementation of legislation. The use of natural bio-based insulation materials has increased in recent years, largely driven by concerns over the embodied energy and whole-life environmental impact of insulation materials. This has led to their increased use, typically within breathable wall constructions. A breathable wall construction allows the insulation material to directly contribute to the indoor air quality.Volatile Organic Compounds (VOCs) having boiling points within the range 60-280 °C contribute to the indoor air contamination in buildings, and at certain concentrations can contribute to building-related illnesses. This paper presents some findings from the early stages of a phased experimental study to explore use of bio-based insulation materials, including hemp-lime and sheep’s wool, to reduce VOCs from the room atmosphere. There are many different volatile organic compounds and this study will consider the Total Volatile Organic Compound (TVOC) emissions expressed as toluene, as well as the formaldehyde emissions separately.Insulation specimens with nominal dimensions 200 x 60 x 50 mm were prepared and placed in horizontally mounted cylindrical chambers. Air maintained at 23 °C (±2 °C) and 50 % (±5 %) RH was fed in coaxially to one end of the cylinder. The exhaust air was sampled for VOCs and for formaldehyde following 3 and 28 day of exposure. The results of this paper will help inform the design of holistic indoor environments that consider more than just the hygrothermal properties of insulation materials

Bio-based plaster for improved indoor air quality

People in industrialised countries spend approximately 80% of their time indoors. As such, the internal environment quality can have a significant impact on occupant health and wellbeing. Additionally, the demand for increased building energy efficiency has the potential to degrade Indoor Air Quality (IAQ) through a reduction of air exchange rates. In many forms of construction, the walls and ceilings are plastered, providing a large surface area exposed to the indoor environment. There is a growing recognition of the important role this surface may have on IAQ through regulation of relative humidity. Another, less well known, impact is that porous coatings have the potential to adsorb Volatile Organic Compounds (VOCs) from the air, which offers further potential to improve IAQ.This paper presents work from the development of a novel bio-based plaster with improved hygrothermal performance and VOC sorption characteristics. Cellulose flakes, used for blown insulation, were added into a cement-lime substrate in three different proportions. A range of mechanical, hygrothermal, VOC emission and VOC adsorption properties were investigated to evaluate the potential of the bio-based cement-lime plaster to improve IAQ. The bio-based cement-lime plaster resulted in an improved thermal conductivity and an improvement in the material’s moisture buffering capacity and VOC adsorption capacity. With 5% addition of cellulose flakes, the hygrothermal performance increased by over 25%. This material also showed the ability to capture VOCs and formaldehyde from the air, reducing the concentrations of these compounds by up to 22% and 70 % respectively. Therefore, the impact of the implementation of this plaster includes potential benefits regarding better operational performance of the building and improved occupant health and wellbeing.<br/

Analysis and computer program for rupture-risk prediction of abdominal aortic aneurysms

BACKGROUND: Ruptured abdominal aortic aneurysms (AAAs) are the 13(th )leading cause of death in the United States. While AAA rupture may occur without significant warning, its risk assessment is generally based on critical values of the maximum AAA diameter (>5 cm) and AAA-growth rate (>0.5 cm/year). These criteria may be insufficient for reliable AAA-rupture risk assessment especially when predicting possible rupture of smaller AAAs. METHODS: Based on clinical evidence, eight biomechanical factors with associated weighting coefficients were determined and summed up in terms of a dimensionless, time-dependent severity parameter, SP(t). The most important factor is the maximum wall stress for which a semi-empirical correlation has been developed. RESULTS: The patient-specific SP(t) indicates the risk level of AAA rupture and provides a threshold value when surgical intervention becomes necessary. The severity parameter was validated with four clinical cases and its application is demonstrated for two AAA cases. CONCLUSION: As part of computational AAA-risk assessment and medical management, a patient-specific severity parameter 0 < SP(t) < 1.0 has been developed. The time-dependent, normalized SP(t) depends on eight biomechanical factors, to be obtained via a patient's pressure and AAA-geometry measurements. The resulting program is an easy-to-use tool which allows medical practitioners to make scientific diagnoses, which may save lives and should lead to an improved quality of life

Non-linear viscoelastic behavior of abdominal aortic aneurysm thrombus

The objective of this work was to determine the linear and non-linear viscoelastic behavior of abdominal aortic aneurysm thrombus and to study the changes in mechanical properties throughout the thickness of the thrombus. Samples are gathered from thrombi of seven patients. Linear viscoelastic data from oscillatory shear experiments show that the change of properties throughout the thrombus is different for each thrombus. Furthermore the variations found within one thrombus are of the same order of magnitude as the variation between patients. To study the non-linear regime, stress relaxation experiments are performed. To describe the phenomena observed experimentally, a non-linear multimode model is presented. The parameters for this model are obtained by fitting this model successfully to the experiments. The model cannot only describe the average stress response for all thrombus samples but also the highest and lowest stress responses. To determine the influence on the wall stress of the behavior observed the model proposed needs to implemented in the finite element wall stress analysis

Fluid-structure interaction in abdominal aortic aneurysms: effects of asymmetry and wall thickness

BACKGROUND: Abdominal aortic aneurysm (AAA) is a prevalent disease which is of significant concern because of the morbidity associated with the continuing expansion of the abdominal aorta and its ultimate rupture. The transient interaction between blood flow and the wall contributes to wall stress which, if it exceeds the failure strength of the dilated arterial wall, will lead to aneurysm rupture. Utilizing a computational approach, the biomechanical environment of virtual AAAs can be evaluated to study the affects of asymmetry and wall thickness on this stress, two parameters that contribute to increased risk of aneurysm rupture. METHODS: Ten virtual aneurysm models were created with five different asymmetry parameters ranging from β = 0.2 to 1.0 and either a uniform or variable wall thickness to study the flow and wall dynamics by means of fully coupled fluid-structure interaction (FSI) analyses. The AAA wall was designed to have a (i) uniform 1.5 mm thickness or (ii) variable thickness ranging from 0.5 – 1.5 mm extruded normally from the boundary surface of the lumen. These models were meshed with linear hexahedral elements, imported into a commercial finite element code and analyzed under transient flow conditions. The method proposed was then compared with traditional computational solid stress techniques on the basis of peak wall stress predictions and cost of computational effort. RESULTS: The results provide quantitative predictions of flow patterns and wall mechanics as well as the effects of aneurysm asymmetry and wall thickness heterogeneity on the estimation of peak wall stress. These parameters affect the magnitude and distribution of Von Mises stresses; varying wall thickness increases the maximum Von Mises stress by 4 times its uniform thickness counterpart. A pre-peak systole retrograde flow was observed in the AAA sac for all models, which is due to the elastic energy stored in the compliant arterial wall and the expansion force of the artery during systole. CONCLUSION: Both wall thickness and geometry asymmetry affect the stress exhibited by a virtual AAA. Our results suggest that an asymmetric AAA with regional variations in wall thickness would be exposed to higher mechanical stresses and an increased risk of rupture than a more fusiform AAA with uniform wall thickness. Therefore, it is important to accurately reproduce vessel geometry and wall thickness in computational predictions of AAA biomechanics

DNA Barcoding Bromeliaceae: Achievements and Pitfalls

<div><h3>Background</h3><p>DNA barcoding has been successfully established in animals as a tool for organismal identification and taxonomic clarification. Slower nucleotide substitution rates in plant genomes have made the selection of a DNA barcode for land plants a much more difficult task. The Plant Working Group of the Consortium for the Barcode of Life (CBOL) recommended the two-marker combination <em>rbcL</em>/<em>matK</em> as a pragmatic solution to a complex trade-off between universality, sequence quality, discrimination, and cost.</p> <h3>Methodology/Principal Findings</h3><p>It is expected that a system based on any one, or a small number of plastid genes will fail within certain taxonomic groups with low amounts of plastid variation, while performing well in others. We tested the effectiveness of the proposed CBOL Plant Working Group barcoding <em>markers</em> for land plants in identifying 46 bromeliad species, a group rich in endemic species from the endangered Brazilian Atlantic Rainforest. Although we obtained high quality sequences with the suggested primers, species discrimination in our data set was only 43.48%. Addition of a third marker, <em>trnH–psbA</em>, did not show significant improvement. This species identification failure in Bromeliaceaecould also be seen in the analysis of the GenBank's <em>matK</em> data set. Bromeliaceae's sequence divergence was almost three times lower than the observed for Asteraceae and Orchidaceae. This low variation rate also resulted in poorly resolved tree topologies. Among the three Bromeliaceae subfamilies sampled, Tillandsioideae was the only one recovered as a monophyletic group with high bootstrap value (98.6%). Species paraphyly was a common feature in our sampling.</p> <h3>Conclusions/Significance</h3><p>Our results show that although DNA barcoding is an important tool for biodiversity assessment, it tends to fail in taxonomy complicated and recently diverged plant groups, such as Bromeliaceae. Additional research might be needed to develop markers capable to discriminate species in these complex botanical groups.</p> </div

Inference of reticulate evolutionary histories by maximum likelihood: the performance of information criteria

Background: Maximum likelihood has been widely used for over three decades to infer phylogenetic trees from molecular data. When reticulate evolutionary events occur, several genomic regions may have conflicting evolutionary histories, and a phylogenetic network may provide a more adequate model for representing the evolutionary history of the genomes or species. A maximum likelihood (ML) model has been proposed for this case and accounts for both mutation within a genomic region and reticulation across the regions. However, the performance of this model in terms of inferring information about reticulate evolution and properties that affect this performance have not been studied. Results: In this paper, we study the effect of the evolutionary diameter and height of a reticulation event on its identifiability under ML. We find both of them, particularly the diameter, have a significant effect. Further, we find that the number of genes (which can be generalized to the concept of "non-recombining genomic regions") that are transferred across a reticulation edge affects its detectability. Last but not least, a fundamental challenge with phylogenetic networks is that they allow an arbitrary level of complexity, giving rise to the model selection problem. We investigate the performance of two information criteria, the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC), for addressing this problem. We find that BIC performs well in general for controlling the model complexity and preventing ML from grossly overestimating the number of reticulation events. Conclusion: Our results demonstrate that BIC provides a good framework for inferring reticulate evolutionary histories. Nevertheless, the results call for caution when interpreting the accuracy of the inference particularly for data sets with particular evolutionary features