Differential Inflammatory Cytokine Elaboration in Serum from Brick Kiln Workers in Bhaktapur, Nepal.

Previous studies involving workers at brick kilns in the Kathmandu Valley of Nepal have investigated chronic exposure to hazardous levels of fine particulate matter (PM2.5) common in ambient and occupational environments. Such exposures are known to cause and/or exacerbate chronic respiratory diseases, including chronic obstructive pulmonary disease (COPD) and asthma. However, there is a paucity of data regarding the status of systemic inflammation observed in exposed workers at brick manufacturing facilities within the country. In the current study, we sought to elucidate systemic inflammatory responses by quantifying the molecular cytokine/chemokine profiles in serum from the study participants. A sample of participants were screened from a kiln in Bhaktapur, Nepal (n = 32; 53% female; mean ± standard deviation: 28.42 ± 11.47 years old) and grouped according to job category. Blood was procured from participants on-site, allowed to clot at room temperature, and centrifuged to obtain total serum. A human cytokine antibody array was used to screen the inflammatory mediators in serum samples from each of the participants. For the current study, four job categories were evaluated with n = 8 for each. Comparisons were generated between a control group of administration workers vs. fire master workers, administration workers vs. green brick hand molders, and administration workers vs. top loaders. We discovered significantly increased concentrations of eotaxin-1, eotaxin-2, GCSF, GM-CSF, IFN-γ, IL-1α, IL-1ß, IL-6, IL-8, TGF-ß1, TNF-α, and TIMP-2 in serum samples from fire master workers vs. administration workers (p < 0.05). Each of these molecules was also significantly elevated in serum from green brick hand molders compared to administration workers (p < 0.05). Further, each molecule in the inflammatory screening with the exception of TIMP-2 was significantly elevated in serum from top loaders compared to administration workers (p < 0.05). With few exceptions, the fire master workers expressed significantly more systemic inflammatory molecular abundance when compared to all other job categories. These results reveal an association between pulmonary exposure to PM2.5 and systemic inflammatory responses likely mediated by cytokine/chemokine elaboration. The additional characterization of a broader array of inflammatory molecules may provide valuable insight into the susceptibility to lung diseases among this population.

Magnetic resonance imaging based finite element modelling of the proximal femur: a short-term in vivo precision study.

Proximal femoral fractures are a serious life-threatening injury with high morbidity and mortality. Magnetic resonance (MR) imaging has potential to non-invasively assess proximal femoral bone strength in vivo through usage of finite element (FE) modelling (a technique referred to as MR-FE). To precisely assess bone strength, knowledge of measurement error associated with different MR-FE outcomes is needed. The objective of this study was to characterize the short-term in vivo precision errors of MR-FE outcomes (e.g., stress, strain, failure loads) of the proximal femur for fall and stance loading configurations using 13 participants (5 males and 8 females; median age: 27 years, range: 21-68), each scanned 3 times. MR-FE models were generated, and mean von Mises stress and strain as well as principal stress and strain were calculated for 3 regions of interest. Similarly, we calculated the failure loads to cause 5% of contiguous elements to fail according to the von Mises yield, Brittle Coulomb-Mohr, normal principal, and Hoffman stress and strain criteria. Precision (root-mean squared coefficient of variation) of the MR-FE outcomes ranged from 3.3% to 11.8% for stress and strain-based mechanical outcomes, and 5.8% to 9.0% for failure loads. These results provide evidence that MR-FE outcomes are a promising non-invasive technique for monitoring femoral strength in vivo.

Respirable dust and crystalline silica concentrations among workers at a brick kiln in Bhaktapur, Nepal.

Exposure to respirable dust and crystalline silica (SiO2) has been linked to chronic obstructive pulmonary disease, silicosis, cancer, heart disease, and other respiratory diseases. Relatively few studies have measured respirable dust and SiO2 concentrations among workers at brick kilns in low- and middle-income countries. The purpose of this study was to measure personal breathing zone (PBZ) respirable dust and SiO2 concentrations among workers at one brick kiln in Bhaktapur, Nepal. A cross-sectional study was conducted among 49 workers in five job categories: administration, fire master, green (unfired) brick hand molder, green brick machine molder, and top loader. PBZ air samples were collected from each worker following Methods 0600 (respirable dust) and 7500 (respirable crystalline SiO2: cristobalite, quartz, tridymite) of the U.S. National Institute for Occupational Safety and Health. Eight-hour time-weighted average (TWA) respirable dust and quartz concentrations were also calculated. SiO2 percentage was measured in one bulk sample each of wet clay, the release agent used by green brick hand molders, and top coat soil at the brick kiln. The geometric mean (GM) sample and TWA respirable dust concentrations were 0.20 (95% confidence interval [CI]: 0.16, 0.27) and 0.12 (95% CI: 0.09, 0.16) mg/m3, respectively. GM sample and TWA quartz concentrations were 15.28 (95% CI: 11.11, 21.02) and 8.60 (95% CI: 5.99, 12.34) µg/m3, respectively. Job category was significantly associated with GM sample and TWA respirable dust and quartz concentrations (all p < 0.0001). Top loaders had the highest GM sample and TWA respirable dust concentrations of 1.49 and 0.99 mg/m3, respectively. Top loaders also had the highest GM sample and TWA quartz concentrations of 173.08 and 114.39 µg/m3, respectively. Quartz percentages in bulk samples were 16%-27%. Interventions including using wet methods to reduce dust generation, administrative controls, personal protective equipment, and education and training should be implemented to reduce brick kiln worker exposures to respirable dust and SiO2.

Food texture and vitamin D influence mouse mandible form and molar roots.

Industrialization influenced several facets of lifestyle, including softer nutrient-poor diets that contributed to vitamin D deficiency in post-industrzialized populations, with concomitantly increased dental problems. Here we simulated a post-industrialized diet in a mouse model to test the effects of diet texture and vitamin D level on mandible and third molar (M3) forms. Mice were raised on a soft diet with vitamin D (VitD) or without it (NoD), or on a hard diet with vitamin D. We hypothesized that a VitD/hard diet is optimal for normal mandible and tooth root form, as well as for timely M3 initiation. Subsets of adult NoD/soft and VitD/soft groups were bred to produce embryos that were micro-computed tomography (µCT) scanned to stage M3 development. M3 stage did not differ between embryos from mothers fed VitD and NoD diets, indicating that vitamin D does not affect timing of M3 onset. Sacrificed adult mice were µCT-scanned, their mandibles 3D-landmarked and M3 roots were measured. Principal component (PC) analysis described the largest proportion of mandible shape variance (PC1, 30.1%) related to diet texture, and nominal shape variance (PC2, 13.8%) related to vitamin D. Mice fed a soft diet had shorter, relatively narrower, and somewhat differently shaped mandibles that recapitulated findings in human populations. ANOVA and other multivariate tests found significantly wider M3 roots and larger root canals in mice fed a soft diet, with vitamin D having little effect. Altogether our experiments using a mouse model contribute new insights about how a post-industrial diet may influence human craniodental variation.

Printing tissue-engineered scaffolds made of polycaprolactone and nano-hydroxyapatite with mechanical properties appropriate for trabecular bone substitutes.

BACKGROUND: Bone tissue engineering, based on three-dimensional (3D) printing technology, has emerged as a promising approach to treat bone defects using scaffolds. The objective of this study was to investigate the influence of porosity and internal structure on the mechanical properties of scaffolds. METHODS: We fabricated composite scaffolds (which aimed to replicate trabecular bone) from polycaprolactone (PCL) reinforced with 30% (wt.) nano-hydroxyapatite (nHAp) by extrusion printing. Scaffolds with various porosities were designed and fabricated with and without an interlayer offset, termed as staggered and lattice structure, respectively. Mechanical compressive testing was performed to determine scaffold elastic modulus and yield strength. Linear regression was used to evaluate mechanical properties as a function of scaffold porosity. RESULTS: Different relationships between mechanical properties and porosities were noted for the staggered and lattice structures. For elastic moduli, the two relationships intersected (porosity = 55%) such that the lattice structure exhibited higher moduli with porosity values greater than the intersection point; vice versa for the staggered structure. The lattice structure exhibited higher yield strength at all porosities. Mechanical testing results also indicated elastic moduli and yield strength properties comparable to trabecular bone (elastic moduli: 14-165 MPa; yield strength: 0.9-10 MPa). CONCLUSIONS: Taken together, this study demonstrates that scaffolds printed from PCL/30% (wt.) nHAp with lattice and staggered structure offer promise for treating trabecular bone defects. This study identified the effect of porosity and internal structure on scaffold mechanical properties and provided suggestions for developing scaffolds with mechanical properties for substituting trabecular bone.

Investigation into relationships between design parameters and mechanical properties of 3D printed PCL/nHAp bone scaffolds.

BACKGROUND: Scaffolds are of great importance in tissue engineering applications as they provide a mechanically supportive environment for cellular activity, which is particularly necessary for hard tissues such as bone. Notably, the mechanical properties of a scaffold vary with differing design parameters such as those related to scaffold height and internal structure. Thus, the present study aimed to explore the relationship between design parameters and mechanical properties of composite polycaprolactone (PCL) and nano-hydroxyapatite (nHAp) scaffolds fabricated by three-dimensional (3D) printing. METHODS: We designed and printed scaffolds with different internal structures (lattice and staggered) and varying heights (4, 6, 8 and 10 layers), and consistent porosity (50%) for the purpose of comparison. Then, we examined the scaffold microstructure (pore size and penetration between layers) using scanning electron microscopy (SEM) and mechanical properties (elastic modulus and yield strength) using compressive testing. RESULTS: Our results illustrated that the microstructural parameters were related to scaffold design. At higher heights, pore size increased while penetration between layers decreased; thus, mechanical properties were affected. Results of mechanical testing demonstrated that for lattice scaffolds, elastic modulus was similar for 6 vs 4, and 8 vs 4 layers but ~33% lower for 10 layers vs 4 layers. Similarly, yield strength was comparable for 6 vs 4, and 8 vs 4 layers but ~27% lower for 10 layers vs 4 layers. With staggered scaffolds, when compared to 4-layer results, elastic modulus was similar for 6 layers but was ~43% lower for 8 layers and ~38% lower for 10 layers. Staggered scaffolds had ~38%, ~51%, and ~76% lower yield strength when the number of layers were increased from 4 to 6, 8, and 10 layers, respectively. When comparing lattice and staggered scaffolds with the same layer number, elastic modulus was similar, apart from 8-layer scaffolds where the staggered design was ~42% lower than lattice. Yield strength was similar between 4-layer staggered and lattice scaffolds, while staggered scaffolds with 6, 8, and 10 number of layers showed ~43%, ~45%, ~68% lower strength, respectively, than those found in lattice scaffolds with the same layer numbers. CONCLUSIONS: Mechanical properties of 3D printed scaffolds depended on scaffold height for both lattice and staggered internal structures. Staggered scaffolds had lower mechanical properties than the lattice scaffolds with the same height and were more sensitive to the change in scaffold height. Taken together, lattice scaffolds demonstrated the advantages of more stable mechanical properties over staggered scaffolds. Also, scaffolds with lower height were more promising in terms of mechanical properties compared to scaffolds with greater height.

Too hot, too cold, or just right: Can wildfire restore dry forests of the interior Pacific Northwest?

As contemporary wildfire activity intensifies across the western United States, there is increasing recognition that a variety of forest management activities are necessary to restore ecosystem function and reduce wildfire hazard in dry forests. However, the pace and scale of current, active forest management is insufficient to address restoration needs. Managed wildfire and landscape-scale prescribed burns hold potential to achieve broad-scale goals but may not achieve desired outcomes where fire severity is too high or too low. To explore the potential for fire alone to restore dry forests, we developed a novel method to predict the range of fire severities most likely to restore historical forest basal area, density, and species composition in forests across eastern Oregon. First, we developed probabilistic tree mortality models for 24 species based on tree characteristics and remotely sensed fire severity from burned field plots. We applied these estimates to unburned stands in four national forests to predict post-fire conditions using multi-scale modeling in a Monte Carlo framework. We compared these results to historical reconstructions to identify fire severities with the highest restoration potential. Generally, we found basal area and density targets could be achieved by a relatively narrow range of moderate-severity fire (roughly 365-560 RdNBR). However, single fire events did not restore species composition in forests that were historically maintained by frequent, low-severity fire. Restorative fire severity ranges for stand basal area and density were strikingly similar for ponderosa pine (Pinus ponderosa) and dry mixed-conifer forests across a broad geographic range, in part due to relatively high fire tolerance of large grand (Abies grandis) and white fir (Abies concolor). Our results suggest historical forest conditions created by recurrent fire are not readily restored by single fires and landscapes have likely passed thresholds that preclude the effectiveness of managed wildfire alone as a restoration tool.

Gaseous Air Pollutants and Respirable Crystalline Silica Inside and Outside Homes at Brick Kilns in Bhaktapur, Kathmandu Valley, Nepal.

Household and ambient air pollution remain public health problems in much of the world. Brick kiln employees in Nepal may be particularly at risk of high air pollution exposures and resulting health effects due to high levels of outdoor air pollution, substandard housing, and indoor biomass cooking. We conducted a cross-sectional study of indoor and outdoor air pollution concentrations at workers' homes at four fixed chimney Bull's trench brick kilns in Bhaktapur, Kathmandu Valley, Nepal. We measured air concentrations of carbon monoxide (CO), carbon dioxide (CO2), nitrogen dioxide (NO2), sulfur dioxide (SO2), and respirable crystalline silica (SiO2; cristobalite, quartz, tridymite) using established methods and conducted a survey about characteristics of homes or samples that may be associated with air pollution concentrations. Geometric mean concentrations of CO, CO2, and SiO2 (quartz) were 0.84 ppm, 1447.34 ppm, and 6.22 µg/m3, respectively, whereas concentrations of all other air pollutants measured below lower detection limits. Most characteristics of homes or samples were not associated with air pollution concentrations. We found a positive association between the variable how long lived in house and SiO2 (quartz) concentrations, which may reflect sustained take-home exposure to SiO2 (quartz) over time. Interventions should focus on administrative controls to reduce take-home exposure to SiO2 (quartz) in this population.

Bioaerosol and microbial exposures from residential evaporative coolers and their potential health outcomes: A review.

Evaporative cooling is an energy efficient form of air conditioning in dry climates that functions by pulling hot, dry outdoor air across a wet evaporative pad. While evaporative coolers can help save energy, they also have the potential to influence human health. Studies have shown residential evaporative coolers may pull outdoor air pollutants into the home or contribute to elevated levels of indoor bioaerosols that may be harmful to health. There is also evidence that evaporative coolers can enable a diverse microbial environment that may confer early-life immunological protection against the development of allergies and asthma or exacerbate these same hypersensitivities. This review summarizes the current knowledge of bioaerosol and microbiological studies associated with evaporative coolers, focusing on harmful and potentially helpful outcomes from their use. We evaluate the effects of evaporative coolers on indoor bacterial endotoxins, fungal ß-(1 → 3)-D-glucans, dust mite antigens, residential microbial communities, and Legionella pneumophila. To our knowledge, this is the first review to summarize and evaluate studies on the influence that evaporative coolers have on the bioaerosol and microbiological profile of homes. This brings to light a gap in the literature on evaporative coolers, which is the lack of data on health effects associated with their use.

3D Bioprinted Scaffolds for Bone Tissue Engineering: State-Of-The-Art and Emerging Technologies.

Treating large bone defects, known as critical-sized defects (CSDs), is challenging because they are not spontaneously healed by the patient's body. Due to the limitations associated with conventional bone grafts, bone tissue engineering (BTE), based on three-dimensional (3D) bioprinted scaffolds, has emerged as a promising approach for bone reconstitution and treatment. Bioprinting technology allows for incorporation of living cells and/or growth factors into scaffolds aiming to mimic the structure and properties of the native bone. To date, a wide range of biomaterials (either natural or synthetic polymers), as well as various cells and growth factors, have been explored for use in scaffold bioprinting. However, a key challenge that remains is the fabrication of scaffolds that meet structure, mechanical, and osteoconductive requirements of native bone and support vascularization. In this review, we briefly present the latest developments and discoveries of CSD treatment by means of bioprinted scaffolds, with a focus on the biomaterials, cells, and growth factors for formulating bioinks and their bioprinting techniques. Promising state-of-the-art pathways or strategies recently developed for bioprinting bone scaffolds are highlighted, including the incorporation of bioactive ceramics to create composite scaffolds, the use of advanced bioprinting technologies (e.g., core/shell bioprinting) to form hybrid scaffolds or systems, as well as the rigorous design of scaffolds by taking into account of the influence of such parameters as scaffold pore geometry and porosity. We also review in-vitro assays and in-vivo models to track bone regeneration, followed by a discussion of current limitations associated with 3D bioprinting technologies for BTE. We conclude this review with emerging approaches in this field, including the development of gradient scaffolds, four-dimensional (4D) printing technology via smart materials, organoids, and cell aggregates/spheroids along with future avenues for related BTE.

3D printing PCL/nHA bone scaffolds: exploring the influence of material synthesis techniques.

BACKGROUND: It is known that a number of parameters can influence the post-printing properties of bone tissue scaffolds. Previous research has primarily focused on the effect of parameters associated with scaffold design (e.g., scaffold porosity) and specific scaffold printing processes (e.g., printing pressure). To our knowledge, no studies have investigated variations in post-printing properties attributed to the techniques used to synthesize the materials for printing (e.g., melt-blending, powder blending, liquid solvent, and solid solvent). METHODS: Four material preparation techniques were investigated to determine their influence on scaffold properties. Polycaprolactone/nano-hydroxyapatite 30% (wt.) materials were synthesized through melt-blending, powder blending, liquid solvent, and solid solvent techniques. The material printability and the properties of printed scaffolds, in terms of swelling/degradation, mechanical strength, morphology, and thermal properties, were examined and compared to one another using Kruskal-Wallis nonparametric statistical analysis. RESULTS: Material prepared through the liquid solvent technique was found to have limited printability, while melt-blended material demonstrated the highest degree of uniformity and lowest extent of swelling and degradation. Scaffolds prepared with powder-blended material demonstrated the highest Young's modulus, yield strength, and modulus of resilience; however, they also demonstrated the highest degree of variability. The higher degree of inhomogeneity in the material was further supported by thermal gravimetric analysis. While scaffolds printed from melt-blended, powder-blended, and solid solvent materials demonstrated a high degree of micro-porosity, the liquid solvent material preparation technique resulted in minimal micro-porosity. CONCLUSIONS: Study results indicate that specific techniques used to prepare materials influence the printing process and post-printing scaffold properties. Among the four techniques examined, melt-blended materials were found to be the most favorable, specifically when considering the combination of printability, consistent mechanical properties, and efficient preparation. Techniques determined to be favourable based on the properties investigated should undergo further studies related to biological properties and time-dependent properties beyond 21-days.

QCT-FE modeling of the proximal tibia: Effect of mapping strategy on convergence time and model accuracy.

Quantitative computed tomography (QCT) based finite element (FE) modeling, referred to as QCT-FE, has seen rapid growth and application for modeling bone mechanics. With this approach, varying bone material properties are set via experimentally-derived density-modulus equations. One challenge though associated with QCT-FE is to identify the appropriate mapping strategy for assigning elastic moduli to elements. The goal of this study was to evaluate different QCT-FE mapping strategies to identify the optimum approach with fastest convergence rate and highest accuracy. Four proximal tibial medial compartments were imaged using QCT and experimentally tested to characterize proximal tibial subchondral bone stiffness at four surface points, resulting in a total of 16 indentation measures. Three material mapping methods were analyzed: (1) constant-E where an average elastic modulus was assigned to each element; (2) node-based where the material properties were first mapped on nodes then interpolated to Gaussian integration points; and (3) element-based in which the material properties were directly assigned to Gaussian integration points. Different element sizes were assessed with edge-lengths ranging from 0.9 to 3 mm. Results indicated that all converged models showed similar coefficient-of-determination (R2) and normalized root-mean-square errors (RMSE%). Though, the constant-E and node-based methods converged with the element edge-length of 1.5 mm (prediction error of 4.8% and 2.5%, respectively) whereas the element-based method converged with a larger element having an edge-length 2.5 mm (error = 4.9%). In conclusion, the element-based method, with a larger element size, resulted in similar predictive accuracy, faster convergence and shorter run-times relative to the constant-E and node-based approaches. As such, we recommend the element-based method for future subject-specific QCT-FE modeling.

Correction: Predicting the influence of climate on grassland area burned in Xilingol, China with dynamic simulations of autoregressive distributed lag models.

[This corrects the article DOI: 10.1371/journal.pone.0229894.].

Associations Between School Characteristics and Classroom Radon Concentrations in Utah's Public Schools: A Project Completed by University Environmental Health Students.

Radon (²²²Rn), a radioactive gas, is the second leading cause of lung cancer deaths in the U.S. Classroom radon concentrations in public schools in our target area had never been measured or had not been measured in many years. We had university students, primarily enrolled in environmental health courses, measure radon concentrations in 2289 classrooms in 66 of Utah's public schools and identify school characteristics associated with classroom radon concentrations. The geometric mean (GM) classroom radon concentration was 31.39 (95% confidence interval (CI): 27.16, 36.28) Bq/m3 (GM: 0.85; 95% CI: 0.72, 0.98 pCi/L). Thirty-seven (2%) classrooms in 13 (20%) schools had radon concentrations at or above the U.S. Environmental Protection Agency's (EPA) recommended action level of 148 Bq/m3 (4.0 pCi/L). Number of classrooms had a u-shaped association with classroom radon concentrations. The year the heating, ventilation, and air conditioning (HVAC) system was installed was inversely associated with having classroom radon concentrations at or above the EPA's recommended action level. Number of classrooms and number of students had u-shaped associations with having classroom radon concentrations at or above the EPA's recommended action level. Classroom radon concentrations decreased when schools' HVAC systems were on. Replacing HVAC systems and turning/keeping them on may be effective radon mitigation strategies to prevent radon-associated lung cancer, especially for small and large schools.

Distal radius sections offer accurate and precise estimates of forearm fracture load.

BACKGROUND: Forearm fracture risk can be estimated via factor-of-risk: the ratio of applied impact force to forearm fracture load. Simple techniques are available for estimating impact force associated with a fall; estimating forearm fracture load is more challenging. Our aim was to assess whether failure load estimates of sections of the distal radius (acquired using High-Resolution peripheral Quantitative Computed Tomography and finite element modeling) offer accurate and precise estimates of forearm fracture load. METHODS: We scanned a section of the distal radius of 19 cadaveric forearms (female, mean age 83.7, SD 8.3), and 34 women (75.0, 7.7). Sections were converted to finite element models and failure loads were acquired for different failure criteria. We assessed forearm fracture load using experimental testing simulating a fall on the outstretched hand. We used linear regression to derive relationships between ex vivo forearm fracture load and finite element derived distal radius failure load. We used derived regression coefficients to estimate forearm fracture load, and assessed explained variance and prediction error. We used root-mean-squared coefficients of variation to assess in vivo precision errors of estimated forearm fracture load. FINDINGS: Failure load estimates of sections of the distal radius, used in conjunction with derived regression coefficients, explained 89-90% of the variance in experimentally-measured forearm fracture load with prediction errors <6.8% and precision errors <5.0%. INTERPRETATION: Failure load estimates of distal radius sections can reliably estimate forearm fracture load experienced during a fall. Forearm fracture load estimates can be used to improve factor-of-risk predictions for forearm fracture.

Comparison of Liquefied Petroleum Gas Cookstoves and Wood Cooking Fires on PM2.5 Trends in Brick Workers' Homes in Nepal.

Prior studies document a high prevalence of respiratory symptoms among brick workers in Nepal, which may be partially caused by non-occupational exposure to fine particulate matter (PM2.5) from cooking. In this study, we compared PM2.5 levels and 24 h trends in brick workers' homes that used wood or liquefied petroleum gas (LPG) cooking fuel. PM2.5 filter-based and real-time nephelometer data were collected for approximately 24 h in homes and outdoors. PM2.5 was significantly associated with fuel type and location (p < 0.0001). Pairwise comparisons found significant differences between gas, indoor (geometric mean (GM): 79.32 µg/m3), and wood, indoor (GM: 541.14 µg/m3; p = 0.0002), and between wood, indoor, and outdoor (GM: 48.38 µg/m3; p = 0.0006) but not between gas, indoor, and outdoor (p = 0.56). For wood fuel homes, exposure peaks coincided with mealtimes. For LPG fuel homes, indoor levels may be explained by infiltration of ambient air pollution. In both wood and LPG fuel homes, PM2.5 levels exceeded the 24 h limit (25.0 µg/m3) proposed by the World Health Organization. Our findings suggest that increasing the adoption of LPG cookstoves and decreasing ambient air pollution in the Kathmandu valley will significantly lower daily PM2.5 exposures of brick workers and their families.

Predicting the influence of climate on grassland area burned in Xilingol, China with dynamic simulations of autoregressive distributed lag models.

The influence of climate change on wildland fire has received considerable attention, but few studies have examined the potential effects of climate variability on grassland area burned within the extensive steppe land of Eurasia. We used a novel statistical approach borrowed from the social science literature-dynamic simulations of autoregressive distributed lag (ARDL) models-to explore the relationship between temperature, relative humidity, precipitation, wind speed, sunlight, and carbon emissions on grassland area burned in Xilingol, a large grassland-dominated landscape of Inner Mongolia in northern China. We used an ARDL model to describe the influence of these variables on observed area burned between 2001 and 2018 and used dynamic simulations of the model to project the influence of climate on area burned over the next twenty years. Our analysis demonstrates that area burned was most sensitive to wind speed and temperature. A 1% increase in wind speed was associated with a 20.8% and 22.8% increase in observed and predicted area burned respectively, while a 1% increase in maximum temperature was associated with an 8.7% and 9.7% increase in observed and predicted future area burned. Dynamic simulations of ARDL models provide insights into the variability of area burned across Inner Mongolia grasslands in the context of anthropogenic climate change.

Off-axis loads cause failure of the distal radius at lower magnitudes than axial loads: A side-to-side experimental study.

Off-axis loading associated with a fall onto the outstretched hand has been hypothesized to induce distal radius failure at lower magnitudes than axially directed loading commonly used in biomechanical models for estimating fracture risk. However, this hypothesis has not been tested with side-to-side experimental testing. The objective of this study was to compare distal radius failure loads between forearm pairs experimentally tested in an axial or off-axis loading configuration. We acquired 18 pairs of cadaveric forearms from 18 female donors (mean age (standard deviation): 84.4 (7.9) years). Each forearm pair was tested to failure using either an axial compression test (vertical orientation with 0° dorsal inclination, 3°-6° radial inclination) or an off-axis test corresponding to the hand position during a fall (15° dorsal inclination, 3°-6° radial inclination). Failure testing was performed at 3 mm/s onto the palm of the hand until fracture occurred. Of the 18 pairs, 11 sustained a distal radius fracture. We compared failure loads between the two groups using a paired t test. Results indicated that failure load under off-axis loading was 29% lower than failure load under axial compressive loading (mean difference: -0.31 kN; 95% confidence interval: -0.47 to -0.16 kN, P = .001). In conclusion, off-axis loading associated with a fall onto the outstretched hand resulted in a 29% lower failure load. Integrating an off-axis loading configuration into current biomechanical models of distal radius bone strength may prevent overestimating of failure load and may offer a clinically relevant option to estimate distal radius fracture risk and monitor therapy efficacy.

An exclusion approach for addressing partial volume artifacts with quantititive computed tomography-based finite element modeling of the proximal tibia.

INTRODUCTION: Quantitative computed tomography based finite element modeling (QCT-FE) has potential to clarify the role of subchondral bone stiffness in osteoarthritis. The limited spatial resolution of clinical QCT systems, however, results in partial volume (PV) artifacts and low contrast between cortical and trabecular bone, which adversely affects the accuracy of QCT-FE models. The objective of this research was to evaluate the agreement between stiffness predictions offered by QCT-FE models of proximal tibial subchondral bone (constructed with and without a new voxel-exclusion algorithm) with experimentally-derived local subchondral bone structural stiffness. METHODS: Thirteen proximal tibial compartments were obtained and imaged using QCT. Two types of QCT-FE models were developed: (1) standard model, which employed the standard procedure for QCT-FE modeling; and (2) "voxel exclusion (VE)" model, which addressed PV artifacts by excluding low density voxels during the material mapping stage of construction. We assessed agreement between QCT-FE stiffness estimates (using standard and VE approaches) with experimental stiffness by reporting predicted variance from linear regression and mean bias with 95% Limits of Agreement (LOA). RESULTS: The standard and VE models explained 81% and 84% of the variance in experimentally measured stiffness, respectively. The standard model showed a mean bias of -268 N/mm (LOA -1210 to 679 N/mm); the VE model showed a mean bias of +59 N/mm (LOA -762 to 910 N/mm). INTERPRETATION: The VE model explained more variance in subchondral bone stiffness with less bias. Our findings indicate that the VE method has potential to improve QCT-FE models of bone affected by PV artifacts.

Air-Quality Assessment of On-Site Brick-Kiln Worker Housing in Bhaktapur, Nepal: Chemical Speciation of Indoor and Outdoor PM2.5 Pollution.

Brick workers and their families in Nepal generally live in poorly ventilated on-site housing at the brick kiln, and may be at higher risk for non-occupational exposure to fine particulate matter air pollution and subsequent respiratory diseases due to indoor and outdoor sources. This study characterized non-occupational exposure to PM2.5 by comparing overall concentrations and specific chemical components of PM2.5 inside and outside of brick workers' on-site housing. For all samples, the geometric mean PM2.5 concentration was 184.65 µg/m3 (95% confidence interval: 134.70, 253.12 µg/m3). PM2.5 concentrations differed by kiln number (p = 0.009). Kiln number was significantly associated with 16 of 29 (55%) air pollutant, temperature, or relative humidity variables. There was not a significant interaction between kiln number and location of sample for PM2.5 (p = 0.16), but there was for relative humidity (p = 0.02) and temperature (p = 0.01). Results were qualitatively similar when we repeated analyses using indoor samples only. There was no difference in the chemical makeup of indoor and outdoor PM2.5 in this study, suggesting that outdoor PM2.5 air pollution easily infiltrates into on-site brick worker housing. Outdoor and indoor PM2.5 concentrations found in this study far exceed recommended levels. These findings warrant future interventions targeted to this vulnerable population.