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Due to a change in capital funding formula, many school boards across the Province of Ontario engaged in Accommodation Reviews to rationalize the supply of school capacity. This process led to numerous school closures and raised important policy questions regarding the economic value of a school in terms of its capitalization into property values and, by extension, how the closure of a school might affect local neighborhoods. To explore these questions, this research uses spatial hedonic methods to estimate the implicit value of accessibility to schools in the City of Hamilton, Ontario. Spatial Durbin model results provide evidence of a significant negative correlation between distance to schools and housing prices in the Canadian context. This suggests that accessibility to schools is capitalized into property values and that the closure of a neighborhood school may result in potentially significant losses of economic value in communities. [ABSTRACT FROM AUTHOR]

Mass timber construction has seen a growing interest in North America and worldwide. In the US, code provisions allow mass timber buildings to be up to 82 m tall, but with floor slabs requiring a noncombustible, usually cementitious, topping over mass timber panels (MTPs). Designing the MTP and concrete topping to act compositely can increase the strength and stiffness compared to noncomposite MTP floors. Several connections are available to create composite action between an MTP and a concrete topping, with self-tapping screws being the most widely considered practice. A new test fixture and testing method were developed to characterize connection properties and facilitate the selection of fasteners most suitable for developing composite action. Three conventional self-tapping screws were experimentally investigated at the single-fastener scale. The screws were subjected to withdrawal at 90° and 45° orientations to the interface plane between the MTP and concrete. Withdrawal from both the MTP substrate and concrete topping was investigated. Three MTP materials were tested: cross-laminated timber (CLT) consisting of two different wood species and a mass ply panel (MPP). Results demonstrated that the pullout failure of the screwhead from the concrete was the limiting failure mode. Comparisons were made between the experimental results and analytical models for screw withdrawal to assess the applicability of available models to the different MTPs. These models underestimated the capacity of the tested fasteners for all samples except for the fully threaded screws. [ABSTRACT FROM AUTHOR]

New building code changes enable mass timber panels (MTP), including cross-laminated timber (CLT), to be used in moderate and tall buildings as a floor system, usually with a concrete topping. A floor system of CLT composite with a reinforced concrete topping slab can provide increased stiffness and strength, making the system more advantageous. Present connection methods used to produce composite action within timber-concrete composites (TCC) have limitations when considering constructability or performance. This study presents experimental results from four (4) shear connectors for CLT-concrete composite floor systems, including three developed for this study. The connectors included self-tapping screws (STS) at 45-degrees, a modified lag screw with an integral plate washer that bears on the CLT surface at installation, a steel angle anchored only at the end of the span, and an inverted-T steel section with stem perforations. Different tests were performed on the different connectors including individual fastener tests, push-off group tests, and full-scale one-way bending tests. The push-off group tests showed that the proposed washer-screw exhibited higher stiffness and strength than a conventional STS. The full-scale one-way bending testing showed that the STS specimen exhibited the lowest strength of the alternatives. The inverted-T section exhibited the highest stiffness, while the other three connections had similar stiffness to the STS. [ABSTRACT FROM AUTHOR]

Experimental tests of cross-laminated timber (CLT)-concrete composite floor panels were conducted. The tests consisted of linear-elastic tests of square CLT-concrete composite panels with a novel shear connector to determine elastic orthotropic plate properties. After the linear-elastic tests, the panels were subjected to a patch load at the center of the panel and tested to failure. To investigate load transfer across longitudinal joints between adjacent panels, nonuniform bending tests were conducted. Results from the experimentally measured orthotropic plate properties showed that the shear connector increased the bending stiffness in the weak direction of the panel compared to prior test results using conventional shear connectors. The tests to failure exhibited larger differences in behavior between the strong and weak orientations of the specimens, with both showing substantial inelastic behavior prior to failure. Numerical finite element models of the patch-load test showed good agreement with experimental results. Analytical formulas using the obtained orthotropic plate properties did not agree with experimental results for the patch-load at linear scales, suggesting the simplified method is currently not suited for CLT-concrete two-way bending. Load-transfer tests found that the reinforced concrete topping is capable of transferring load across the longitudinal joint of two parallel panels to enable two-way bending of composite timber–concrete floors and that the addition of a plywood spline with closely spaced screws enables a higher degree of force transfer. [ABSTRACT FROM AUTHOR]

While cities have become gradually more vertical and complex over the past century, our methods for conceptualising their characteristics and measuring their forms and functions are still largely based in a horizontal mindset. Recent work has sought to shift urban discourse towards understanding cities according to their volumetric properties. Moving the debate further, this paper approaches volumetric urbanism from a morphological perspective, setting out a research agenda that operationalises the concept as a means of better capturing the morphological characteristics of cities as volumetric entities. First, we deconstruct volumetric urbanism into the five basic building blocks that define volumetric morphologies: density, functional mix, compaction and compression, complex networks and interaction intensity. Next, we propose two methods for capturing the urban volumetrics of cities based on spatial and network interaction and apply them to a hypothetical case and a preliminary study of Hong Kong. We conclude by arguing that a volumetric approach is required to capture the complex form of compressed, multi-layered and highly connected cities. In response, urban morphological and planning discourses must move away from the horizontal analytical mindset, embrace a multi-layered three-dimensional view of cities and place greater emphasis on spatial configurations and network relations by measuring interaction. [ABSTRACT FROM AUTHOR]

Designing structures resistant to tsunami-like flood flow impacts is contingent on the ability to accurately predict dynamic loading effects on building components. To characterize these effects, two metal building cladding subassembly test specimens, designed for Risk Category II and Category IV wind loading, were experimentally subjected to surges and bores with various wave height and initial water levels. The results reveal that maximum structural responses, quantified by curvatures and displacements, occur after initial wave impact, as splash up on the structure subsides. Furthermore, consistent pressure–time histories between specimens in equivalent flow conditions, despite significantly different strains and displacements, suggest structural flexibility does not influence which wave forcing produces the maximum structural response. Lastly, structural analysis of the specimens, based on measured pressures at maximum strain conditions, reveals that loading conditions ranged between hydrostatic and hydrodynamic depending on the initial flooding conditions. With these findings, a method to predict pressure magnitude and distribution on the cladding at the time of maximum structural response for tsunami-like flood flow impacts is proposed. [ABSTRACT FROM AUTHOR]

Floating Catchment Area (FCA) methods are a popular tool to investigate accessibility to public facilities, in particular health care services. FCA approaches are attractive because, unlike other accessibility measures, they take into account the potential for congestion of facilities. This is done by 1) considering the population within the catchment area of a facility to calculate a variable that measures level of service, and then 2) aggregating the level of service by population centers subject to catchment area constraints. In this paper we discuss an effect of FCA approaches, an artifact that we term demand and level of service inflation. These artifacts are present in previous implementations of FCA methods. We argue that inflation makes interpretation of estimates of accessibility difficult, which has possible deleterious consequences for decision making. Next, we propose a simple and intuitive approach to proportionally allocate demandand and level of service in FCA calculations. The approach is based on a standardization of the impedance matrix, similar to approaches popular in the spatial statistics and econometrics literature. The result is a more intiuitive measure of accessibility that 1) provides a local version of the provider-to-population ratio; and 2) preserves the level of demand and the level of supply in a system. We illustrate the relevant issues with some examples, and then empirically by means of a case study of accessibility to family physicians in the Hamilton Census Metropolitan Area (CMA), in Ontario, Canada. Results indicate that demand and supply inflation/deflation affect the interpretation of accessibility analysis using existing FCA methods, and that the proposed adjustment can lead to more intuitive results. [ABSTRACT FROM AUTHOR]

The study presents a multi-group structural equation modelling exercise to identify differences in the mindset of individuals towards electric vehicles (EVs) across seven vehicle body types in Canada. The study utilizes a sample of 15,392 households and grounds the psychographic orientation of potential EV adopters on an extended version of the Theory of Planned Behaviour. Specifically, the study measures the impact of five latent constructs; environmental concerns, attitude, subjective norm, personal moral norm, and perceived behavioural control on the intention to adopt EVs along with socio-economic-demographic (SED) variables. The results highlight that both attitude and perceived behaviour control are the strongest factors influencing individual intention to adopt EVs. However, the multi-group invariance analysis indicates that the psychographic orientation and the SED traits of potential adopters of different EV body types are significantly different, with particular standouts in the luxury and pickup truck classes. We follow this up with an analysis of mindshare towards EVs over the seven vehicle types. Insights derived from the analysis can help define potential submarkets for EVs and accelerate their adoption. [ABSTRACT FROM AUTHOR]

Rapid transit projects that increase accessibility should result in a localised land value uplift (LVU) benefit for locations near stations. A rich history of research has tested this hypothesis, generally operationalising transit accessibility by proxy through distance from a transit station. However, a growing body of research has also demonstrated LVU effects from transit-oriented development (TOD) as individuals sort themselves into locations that best match their preferences and willingness to pay. Considering the interdependence of transportation and land use in the urban system, we argue that these benefits create a spatial bundle of TOD goods around transit stations and hypothesise that households are willing to pay a premium for locations in more transit-oriented station catchment areas. Utilising latent class analysis, we quantify station area TOD submarkets. Next, interactions between these submarkets and station proximity in spatial hedonic regressions reveal that TOD is capitalised into land values in Toronto, though the maximum amount and spatial impact area of this capitalisation differs by TOD context. [ABSTRACT FROM AUTHOR]

Little work has accounted for congestion, using data that reflects driving patterns, traffic volume, and speed, to examine the association between traffic emissions and human health. In this study, we performed a health risk assessment of PM 2.5 emissions during congestion periods in the Greater Toronto and Hamilton Area (GTHA), Canada. Specifically, we used a micro-level approach that combines the Stochastic User Equilibrium Traffic Assignment Algorithm with a MOVES emission model to estimate emissions considering congestion conditions. Subsequently, we applied a concentration-response function to estimate PM 2.5 -related mortality, and the associated health costs. Our results suggest that traffic congestion has a substantial impact on human health and the economy in the GTHA, especially at the most congested period (7:00 am). Considering daily mortality, our results showed an impact of 206 (boundary test 95%: 116; 297) and 119 (boundary test 95%: 67; 171) deaths per year (all-cause and cardiovascular mortality, respectively). The economic impact from daily mortality is approximately $1.3 billion (boundary test 95%: 0.8; 1.9), and $778 million (boundary test 95%: 478; 981), for all-cause and cardiovascular mortality, respectively. Our study can guide reliable projections of transportation and air pollution levels, improving the capability of the medical community to prepare for future trends. [ABSTRACT FROM AUTHOR]

Contemporary examination of community structure requires analyzing multiple dimensions of biodiversity to provide a more holistic understanding of the ecological and historical factors involved in the formation and maintenance of local communities. We used empirical data on bat communities across Mexico to investigate patterns of taxonomic and phylogenetic diversities. More specifically, we 1) characterized phylogenetic structure using multiple measures of diversity and identified environmental factors that serve as potential drivers of the underlying structure, 2) determined whether any bat community showed evidence of phylogenetic overdispersion or underdispersion and characterized how taxonomic structure differed among overdispersed, randomly dispersed, and underdispersed sites, and 3) examined the relationship between phylogenetic diversity and size of the regional species pool. We used 3 indices of phylogenetic diversity (Faith's index [FI], mean nearest neighbor distance [MNND], and mean pairwise distance [MPD]) to quantify patterns of evolutionary relatedness in bat communities across Mexico. To determine whether a particular community was overdispersed, randomly dispersed, or underdispersed, we used randomization procedures with latitudinal and longitudinal constraints to define the regional species pool for each bat community. We used regression trees to investigate which climatic factors explained variation for each measure of phylogenetic diversity. Precipitation and longitude were correlated with FI, temperature was correlated with MNND, and temperature along with latitude and longitude were correlated with MPD. We found that just over one-half of the communities were underdispersed, just under one-half were randomly dispersed, and only 1 was overdispersed. Each measure of phylogenetic diversity was differently affected by the size of the regional species pool. [ABSTRACT FROM AUTHOR]

• Transit travel times to OAT clinics are modeled for 2019 and 2020. • The average resident faces a 24.3 to 25.6 min transit trip to their closest clinic. • Transit changes increased travel times beyond 30 min travel thresholds for thousands of households. • Travel times for transit-riding patients making daily visits may exceed 5.5 h per week. Public transport disruptions caused by the COVID-19 pandemic had wide-ranging impacts on the ability of individuals to access health care. Individuals with opioid use disorder represent an especially vulnerable population due to the necessity of frequent, supervised doses of opioid agonists. Focused on Toronto, a major Canadian city suffering from the opioid epidemic, this analysis uses novel realistic routing methodologies to quantify how travel times to individuals\220 nearest clinics changed due to public transport disruptions from 2019 to 2020. Individuals seeking opioid agonist treatment face very constrained windows of access due to the need to manage work and other essential activities. We find that thousands of households in the most materially and socially deprived neighbourhoods crossed 30 and 20-minute travel time thresholds to their nearest clinic. As even small changes to travel times can lead to missed appointments and heighten the chances of overdose and death, understanding the distribution of those most impacted can help inform future policy measures to ensure adequate access to care. [ABSTRACT FROM AUTHOR]

Low-income residents are often reliant on public transit for daily travel. In North American cities, they have also historically concentrated in centrally located neighbourhoods with relatively higher levels of transit accessibility. However, during the late 20th and early 21st century, regions have witnessed trends of inner-city neighbourhood change and gentrification and the suburbanization of poverty, raising concerns that low-income residents are disproportionately moving away from relied upon transit service. In this paper, we investigate what occurs when low-income residents change dwellings within a region: do they experience a reduction in their levels of transit accessibility, how does this compare to higher-income movers, and how has this changed over time? We examine this by linking historical transit accessibility measures to annual individual-level panel data representing 20% of tax filers in Toronto, Canada from 1988 to 2018. We then analyze changes in transit accessibility for over 2 million intra-urban movers during this time period via descriptive statistics and regression models to answer whether there are significant differences in individual changes in transit accessibility by income level. We find that low-income residents do, on average, experience reductions in their levels of transit accessibility when moving within the region, suggesting a growth in people at risk of transport poverty. Nevertheless, they do not undergo as great of a reduction in transit accessibility as higher-income movers, although this gap in experienced changes in transit accessibility between higher- and low-income movers is converging over time. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) hold great promise for reducing greenhouse gas emissions, yet achieving their environmental benefits depends on greater market uptake. While a growing body of literature has sought to offer information on consumer stated preferences for EVs, to date no research has examined how preferences for hybrid, plug-in hybrid, and battery electric vehicles are shaped by vehicle body size or type. The automobile market is differentiated with vehicle attributes that respond to heterogeneous consumer demands. We hypothesize that each bundle of attributes as it relates to vehicle body size also shapes demand for EVs. Using a large primary dataset, we segment respondents according to their preferred next vehicle body type (economy, intermediate, full-size sedan, luxury, minivan, sport utility, and pickup). Multivariate analysis of variance (MANOVA) results show significant differences in the socioeconomic, demographic, and psychological profile of consumers across the seven vehicle segments. From this, discrete choice models detail how vehicle type plays a significant role in the choicemaking behaviour of potential EV consumers. While factors like age, education, and the importance of fuel economy and reduced or eliminated emissions generally play a consistent role in improving the utility of EVs, our results also reveal significant heterogeneity in choice of powertrain across vehicle segments, with luxury and pickup buyers among the most distinct. The results offer useful information for marketing, policy, and research. [ABSTRACT FROM AUTHOR]

Many rapid transit projects are justified by a desire to achieve intangible city image and branding goals such as promoting messages of modernity, economic growth, global competitiveness, and world city status. The relationship between rapid transit and city image is poorly understood in the planning literature. In response, this article presents a theoretical framework of rapid transit in image-led planning. The framework and examples of rapid transit in image-led planning in practice reveal that while important, rapid transit alone is not a sufficient condition for wholesale image change, and image-led planning must be mindful of a host of important practical considerations. [ABSTRACT FROM AUTHOR]

Identifying and measuring the land value uplift (LVU) impacts of rapid transit are important for a number of reasons. However, despite the general notion that rapid transit does confer positive LVU benefits, our comprehensive and critical review of more than 130 analyses across 60 studies completed in North America over the past 40 years finds significant heterogeneity in research outcomes, leaving many significant questions unanswered. Beyond high-level differences in study inputs, we argue that a fundamental source of variability is a lack of empirical specificity from the use of proximity as the dominant way in which LVU benefits are captured. This use of a proxy leads to the potential for omitted variables and unobserved relationships, and exposes previous work to the potential for misvalued results. To overcome this issue, we outline recommendations for future research, namely a recognition of relative accessibility and the possibility of LVU impacts from transit-oriented development. Incorporating measures related to these factors into LVU models can reveal their implicit prices, resulting in research that is more theoretically inclusive, empirically comprehensive, comparable, and able to provide important information to inform policy analysis and prescription. [ABSTRACT FROM AUTHOR]

Summary Apical constriction is a change in cell shape that drives key morphogenetic events including gastrulation and neural tube formation. Apical force-producing actomyosin networks drive apical constriction by contracting while connected to cell-cell junctions. The mechanisms by which developmental patterning regulates these actomyosin networks and associated junctions with spatial precision are not fully understood. Here we identify a myosin light-chain kinase MRCK-1 as a key regulator of C. elegans gastrulation that integrates spatial and developmental patterning information. We show that MRCK-1 is required for activation of contractile actomyosin dynamics and elevated cortical tension in the apical cell cortex of endoderm precursor cells. MRCK-1 is apically localized by active Cdc42 at the external, cell-cell contact-free surfaces of apically constricting cells, downstream of cell fate determination mechanisms. We establish that the junctional components α-catenin, β-catenin, and cadherin become highly enriched at the apical junctions of apically constricting cells and that MRCK-1 and myosin activity are required in vivo for this enrichment. Taken together, our results define mechanisms that position a myosin activator to a specific cell surface where it both locally increases cortical tension and locally enriches junctional components to facilitate apical constriction. These results reveal crucial links that can tie spatial information to local force generation to drive morphogenesis. [ABSTRACT FROM AUTHOR]

Transit oriented development (TOD), which is generally understood as the provision of higher-density, mixed-use, amenity-rich, and walkable development around rapid transit stations, has been championed as one of the most effective solutions for maximizing the potential return on investment for existing and future rapid transit infrastructure projects. But it is clear that not all implementations of TOD are the same in every station catchment area across a transit network. This heterogeneity in station area contexts presents significant complexity for planners and policymakers interested in understanding existing TOD conditions, an area's TOD potential, and the relevant policy and planning interventions required to achieve planning goals. It also creates complications for researchers interested in associating station contexts with various TOD outcomes. In response, the present paper develops a model-based latent class method for distilling measures of station area TOD inputs into a set of more homogeneous station types. Its application to 372 existing and planned rapid transit stations in the Toronto region reveals a typology of 10 distinct TOD contexts across a number of present and future transit lines. The end result is an empirical tool for policy evaluation and prescription that can be used to benchmark and compare performance of TOD inputs around existing and planned transit stations and offers a foundation for further research into the relationship between TOD inputs and outcomes. Furthermore, the use of latent class analysis improves on the previous literature in this area by offering model results that are easily interpretable and extendable to other applications. [ABSTRACT FROM AUTHOR]

The strength and behavior of large-diameter reinforcing steel bars with straight anchorages were experimentally investigated. The anchorage details are typical of monolithic girder-column connections used in bridges and buildings in the midcentury. Eleven subassemblage column specimens were examined with different anchorage lengths, bar groupings, amount of transverse steel, and externally applied column axial forces. Test results showed an increase in anchorage capacity because of the presence of transverse steel and externally applied axial force. Experimental results were compared with contemporary design specifications which do not currently account for the beneficial effects of column axial compression acting transverse to the splitting plane. A modification factor was developed to account for the presence of active force applied transverse to the splitting plane to determine anchorage capacity that better estimated the available capacity of the anchorages. [ABSTRACT FROM AUTHOR]

This study focuses on interactions between aerobic soil-derived hydrocarbon degrading bacteria and a suite of perfluorocarboxylic adds and perfluoroalkylsulfonates that are found in aqueous film-forming foams used for fire suppression. No effect on toluene degradation rate or induction time was observed when active cells of Rhodococcus jostii strain RHA1 were exposed to toluene and a mixture of perfluoroalkyl adds (PFAAs) including perfluorooctanoic add (PFOA) and perfluorooctanesulfonate (PFOS) at concentrations near the upper bounds of groundwater relevance ( 11 PFAAs at 10 mg/L each). However, exposure to aqueous PFAA concentrations above 2 mg/L (each) was assodated with enhanced aggregation of bacterial cells and significant increases in extracellular polymeric substance production. Flocculation was only observed during exponential growth and not elicited when PFAAs were added to resting incubations; analogous flocculation was also observed in soil enrichments. Aggregation was accompanied by 2- to 3-fold upregulation of stress-assodated genes, sigF3 and prmA, during growth of this Rhodococcus in the presence of PFAA. These results suggest that biological responses, such as microbial stress and biofilm formation, could be more prominent than suppression of co-contaminant biodegradation in subsurface locations where poly- and perfluoroalkyl substances occur with hydrocarbon fuels. [ABSTRACT FROM AUTHOR]

The last three decades have witnessed substantial growth in the literature on excess commuting. Researchers have proposed and applied a number of commuting benchmarks and excess commuting indices that aim to evaluate the commuting efficiency and jobs-housing balance of cities. A comprehensive review and comparative evaluation of the proposed metrics in terms of their ability to capture the intended phenomena, while controlling for the other general characteristics of cities, has yet to be performed. This article attempts to fill this gap by examining four commuting benchmarks ( minimum commute , maximum commute , random commute , and proportionally matched commute ) and five excess commuting indices ( excess commute , commuting potential utilized , commuting economy , normalized commuting economy , and effort ). Our conceptual analysis of the indices is complemented with a comparative empirical analysis of commuting in thirty Canadian cities. We explore relationships between the indices and point out the strengths and limitations of each. The findings suggest that no single index can adequately capture the commuting performance of an urban area, while each index can be employed to address a specific policy question. Used together, the indices can provide a reasonably good understanding of urban form and commuting behavior. [ABSTRACT FROM AUTHOR]

Floating Catchment Area (FCA) methods are a popular choice for modelling accessibility to healthcare services because of their ability to consider both supply and demand. However, FCA methods do not fully consider aspects of travel and choicemaking behaviour as the only behavioural component is the impedance function. FCA approaches also tend to assign population demand to clinics and levels-of-service to population zones in an overlapping manner that has been shown to inflate/deflate supply and demand. While the adjustments proposed in the recent "Balanced FCA" method can rectify this, it apportions population and levels of service in a fractional manner. In response, this research proposes a utility-based measure of healthcare accessibility based on a multinomial logit (MNL) destination choice model that avoids the multiple-counting issue in FCA methods. It also considers additional behavioural aspects that define the appeal of clinics in addition to the travel time required to reach them, including their capacity and level of crowding. Comparisons of the MNL approach with the original and balanced FCA models using data for the City of Hamilton, Canada, suggest that while the accessibility patterns produced by each method are broadly similar, some key differences exist in the calculated accessibilities and their spatial patterns. The MNL model in particular estimates higher accessibilities in suburban and rural areas. After considering their strengths and weaknesses, we argue that both the FCA and MNL approaches offer merit for planning and policy. • Develops a multinomial logit based method for healthcare accessibility. • Compares floating catchment-based with utility-based accessibility. • Balanced floating catchment method corrects for inflation of supply and demand. • Utility-based approach accounts for more aspects of travel behaviour. • Each method has merit for health planning and policy. [ABSTRACT FROM AUTHOR]

Abstract: The near ubiquitous presence of poly- and perfluoroalkyl substances (PFASs) in humans has raised concerns about potential human health effects from these chemicals, some of which are both extremely persistent and bioaccumulative. Because some of these chemicals are highly water soluble, one major pathway for human exposure is the consumption of contaminated drinking water. This study measured concentrations of PFASs in 18 raw drinking water sources and 2 treated wastewater effluents and evaluated 15 full-scale treatment systems for the attenuation of PFASs in water treatment utilities throughout the U.S. A liquid-chromatography tandem mass-spectrometry method was used to enable measurement of a suite of 23 PFASs, including perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs). Despite the differences in reporting levels, the PFASs that were detected in >70% of the source water samples (n = 39) included PFSAs, perfluorobutane sulfonic acid (74%), perfluorohexane sulfonic acid (79%), and perfluorooctane sulfonic acid (84%), and PFCAs, perfluoropentanoic acid (74%), perfluorohexanoic acid (79%), perfluoroheptanoic acid (74%), and perfluorooctanoic acid (74%). More importantly, water treatment techniques such as ferric or alum coagulation, granular/micro-/ultra- filtration, aeration, oxidation (i.e., permanganate, ultraviolet/hydrogen peroxide), and disinfection (i.e., ozonation, chlorine dioxide, chlorination, and chloramination) were mostly ineffective in removing PFASs. However, anion exchange and granular activated carbon treatment preferably removed longer-chain PFASs and the PFSAs compared to the PFCAs, and reverse osmosis demonstrated significant removal for all the PFASs, including the smallest PFAS, perfluorobutanoic acid. [Copyright &y& Elsevier]

Median arcuate ligament syndrome, a rarely reported condition, is characterized by postprandial abdominal pain, nausea, vomiting, and weight loss. Its cause is unclear. We present the case of a 45-year-old woman who had intermittent chronic positional abdominal pain without weight loss. Magnetic resonance angiograms and computed tomograms revealed stenosis of the celiac artery. Ostial compression was confirmed on catheter angiographic and intravascular ultrasonographic images. Intravascular ultrasound revealed far greater stenosis than did the initial imaging methods and confirmed a diagnosis of median arcuate ligament syndrome. In lieu of surgery, the patient underwent a celiac ganglion block procedure that substantially relieved her symptoms. To our knowledge, this is the first report of the use of intravascular ultrasound in the diagnosis of median arcuate ligament syndrome. We recommend using this imaging method preoperatively in other suspected cases of the syndrome, to better identify patients who might benefit from corrective surgery. [ABSTRACT FROM AUTHOR]

Several classes of polyfluorinated chemicals that are potential precursors to the perfluorinated carboxylates and sulfonates are present in aqueous film-forming foams (AFFF). To assess the persistence of these AFFF-derived precursors, groundwater, soil, and aquifer solids were obtained in 2011 from an unlined firefighter training area at a U.S. Air Force Base where AFFF was regularly used between 1970 and 1990. To measure the total concentration of perfluorinated carboxylate and sulfonate precursors in archived AFFF formulations and AFFF-impacted environmental samples, a previously developed assay that uses hydroxyl radical to oxidize precursors to perfluorinated carboxylates was adapted for these media. This assay was employed along with direct measurement of 22 precursors found in AFFF and a suite of other poly- and perfluoroalkyl substances (PFASs). On a molar basis, precursors accounted for 41-100% of the total concentration of PFASs in archived AFFF formulations. In the training area, precursors measured by the oxidation assay accounted for an average of 23% and 28% of total PFASs (i.e., precursors and perfluorinated carboxylates and sulfonates) in groundwater and solids samples, respectively. One precursor in AFFF, perfluorohexane sulfonamide amine, was observed on several highly contaminated soil and aquifer solids samples, but no other precursors present in AFFF formulations were detected in any samples at this field site. Suspected intermediate transformation products of precursors in AFFF that were directly measured accounted for approximately half of the total precursor concentration in samples from the training site. The fraction of PFASs consisting of perfluorinated carboxylates and sulfonates was greater in groundwater and solid samples than in any archived AFFF formulations, suggesting that much of the mass of precursors released at the site was converted to perfluorinated carboxylates and sulfonates. The precursors that have persisted at this site may generate significant amounts of additional perfluorinated carboxylates and sulfonates upon remediation of contaminated groundwater or aquifer solids. [ABSTRACT FROM AUTHOR]

Subsurface transport potential of a suite of perfluoroalkyl acids (PFAAs) was studied in batch sorption experiments with various soils and in the presence of co-contaminants relevant to aqueous film-forming foam (AFFF)-impacted sites. Specifically, PFAA sorption to multiple soils in the presence of nonaqueous phase liquid (NAPL) and nonfluorinated AFFF surfactants was examined. This study is the first to report on sorption of perfluorobutanoate (PFBA) and perfluoropentanoate (PFPeA) (log Kac = 1.88 and 1.37, respectively) and found that sorption of these compounds does not follow the chain-length dependent trend observed for longer chain-length PFAAs. Sorption of PFBA was similar to that of perfluorooctanoate (PFOA, log Kac = 1.89). NAPL and nonfluorinated AFFF surfactants all had varying impacts on sorption of longer chain (>6 CF2 groups) PFAAs. The primary impact of NAPL was observed in low J soil (soil A) where Freundlich n-values increased when NAPL was present. Impacts of nonfluorinated AFFF surfactants varied with surfactant and soil. The anionic surfactant sodium decy] sulfate (SDS) illicited PFAA chain-length dependent impacts in two negatively charged soils with varying In soil A, Kj values for perfluoroheptanoate (PFHpA) increased 9196 with SDS, whereas values for perfluorodecanoate (PFDA) increased only 2896. An amphoteric surfactant, dimcthyidodecylamine n-oiide (AO), had die most notable impact on PFAA sorption to a positively charged soil (soil C). In this soil, AO oxide significancy increased sorption for the longer chain PFAAs (Lc., 528% increase in Kj for PFDA). Changes in sorption caused by SDS and AO may be due to mixed hemimicelle formation, competitive sorption, or changes to PFAA solubility. Short-chain PFAA behavior in die presence of NAPL, SDS, and AO was again notable. Co-contaminants generally increased the sorption of diesc compounds to all soils. Log Kd values of PFBA in soil A increased 8S%, 372%, and 32% in the presence of NAPL, SDS, and AO, respectively. Use of Kj values to calculate retardation factors (Rf) of PFAAs demonstrates the variability of co-contaminant impacts on PFAA transport. Whereas NAPL and nonfluorinated surfactants decreased the sorption of perfmorooctancsulfbnate (PFOS) at lower PFOS concentrations (l μg/L), they led to increases in sorption at higher PFOS concentrations (500 μg/L). These results demonstrate that PFAA groundwater transport will depend on bSe solid phase characteristics as well as PFAA concentration and chain length. Detailed site-specific information will likely be needed to accurately predict PFAA transport at AFFF-impacted sites. [ABSTRACT FROM AUTHOR]

We present a new method for whole slide darkfield imaging. Whole Slide Imaging (WSI), also sometimes called virtual slide or virtual microscopy technology, produces images that simultaneously provide high resolution and a wide field of observation that can encompass the entire section, extending far beyond any single field of view. For example, a brain slice can be imaged so that both overall morphology and individual neuronal detail can be seen. We extended the capabilities of traditional whole slide systems and developed a prototype system for darkfield internal reflection illumination (DIRI). Our darkfield system uses an ultra-thin light-emitting diode (LED) light source to illuminate slide specimens from the edge of the slide. We used a new type of side illumination, a variation on the internal reflection method, to illuminate the specimen and create a darkfield image. This system has four main advantages over traditional darkfield: (1) no oil condenser is required for high resolution imaging (2) there is less scatter from dust and dirt on the slide specimen (3) there is less halo, providing a more natural darkfield contrast image, and (4) the motorized system produces darkfield, brightfield and fluorescence images. The WSI method sometimes allows us to image using fewer stains. For instance, diaminobenzidine (DAB) and fluorescent staining are helpful tools for observing protein localization and volume in tissues. However, these methods usually require counter-staining in order to visualize tissue structure, limiting the accuracy of localization of labeled cells within the complex multiple regions of typical neurohistological preparations. Darkfield imaging works on the basis of light scattering from refractive index mismatches in the sample. It is a label-free method of producing contrast in a sample. We propose that adapting darkfield imaging to WSI is very useful, particularly when researchers require additional structural information without the use of further staining. [ABSTRACT FROM AUTHOR]

Corrosion of embedded carbon steel is a leading factor in deterioration of ageing conventional reinforced concrete structures. Methods to accurately predict remaining capacity of corrosion damaged elements, especially shear capacity, are lacking. In this paper, ACI-AASHTO approach, strut and tie method, modified compression field theory, and Response 2000™ were used to predict the shear strength of corrosion damaged and undamaged test beams. The methods were modified to account for the corrosion induced damage to both the concrete section and stirrups. Each of the methods considered, with the proposed modifications, reasonably estimated the remaining shear capacity of large-size laboratory specimens subjected to accelerated corrosion of embedded stirrups. [ABSTRACT FROM AUTHOR]

Detection and sizing of metal-containing engineered nanoparticles (ENPs) was achieved at concentrations predicted for environmental samples (part-per trillion levels) using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Silver nanowires, titanium dioxide and cerium oxide nanoparticles were found to be detectable by this technique, while zinc oxide dissolved too quickly for analysis at these concentrations. In addition to the potential dissolution of particles, other considerations affecting ENP analysis include: instrumental background, mass interferences, percent metal in a nanoparticle, and isotopic abundance of the analyte element. Sizing of these metal-containing nanoparticles was done by correlating ICP-MS response (pulses) from ENPs entering the plasma to mass of metal in dissolved standards. The resulting particle size distributions compared well with results from sedimentation field-flow fractionation. Coincidence in ENP pulses may be difficult to detect in the broad size distributions that arise from polydisperse samples. Comparison of data obtained by combination of multiple analyses of dilute solutions to single analyses of higher concentration allowed discrimination between coincidence and polydispersity. The ratio of ENP pulse detections to the total number of readings during analysis was optimized at 2.5% or less to minimize coincident pulses while still allowing definition of a size distribution. [ABSTRACT FROM AUTHOR]

Stent thrombosis is a potentially lethal complication of percutaneous coronary intervention. We describe the case of a 51-year-old man who presented with acute anterior ST-segment-elevation myocardial infarction and underwent successful percutaneous transluminal coronary angioplasty and placement of 3 drug-eluting stents in the left anterior descending coronary artery. Despite receiving dual antiplatelet therapy, the patient presented a week later with a non-ST-segment-elevation myocardial infarction and was found to have nonocclusive thrombosis of the left anterior descending coronary artery stents and his ostial left main and left circumflex coronary arteries. Subsequently, bone marrow biopsy analysis indicated that the patient had acute myelogenous leukemia, which we believe was the underlying cause of his prothrombotic state and stent thrombosis. [ABSTRACT FROM AUTHOR]

Orthotropic plates are widely used in bridge deck systems. However, these are not commonly treated as such within design specifications, and semianalytical solutions are not presently available for all deck types. This paper develops deflection equations for infinitely wide and simply supported thin plates considering each of the three cases of orthotropy: (1) relatively torsionally stiff, flexurally soft; (2) uniformly thick plate; and (3) torsionally soft, flexurally stiff; subjected to arbitrary patch loading. These are common boundary and loading conditions encountered for bridge deck applications. The reported analytical solutions enable rapid evaluation of multiple moving patch loads to determine maximum design load effects and permit validation of numerical and finite-element methods. Application of the solutions will produce guidelines that can prescribe design demands and establish practical design simplifications for treatment of different bridge deck and slab systems in a uniform and consistent manner. [ABSTRACT FROM AUTHOR]

The presence of the antimicrobial chemicals triclocarban (TCC) and triclosan (TCS) in municipal biosolids has raised concerns about the potential impacts of these chemicals on soil ecosystems following land application of municipal biosolids. The relative persistence of TCC and TCS in agricultural fields receiving yearly applications of biosolids at six different loading rates over a three-year period was investigated. Soil and biosolids samples were collected, extracted, and analyzed for TCC and TCS using liquid chromatography-tandem mass spectrometry. In addition, the potential for bioaccumulation of TCC and TCS from the biosolids-amended soils was assessed over 28 d in the earthworm Eisenia foetida. Standard 28-d bioaccumulation tests were conducted for three biosolids loading rates from two sites, representing agronomic and twice the agronomic rates of biosolids application plots as well as control plots receiving no applications of biosolids. Additional bioaccumulation kinetic data were collected for the soils receiving the high biosolids loadings to ensure attainment of quasi steady-state conditions. The results indicate that TCC is relatively more persistent in biosolids-amended soil than TCS. In addition, TCC bioaccumulated in E. foetida, reaching body burdens of 25 ± 4 and 133 ± 17 ng/g in worms exposed for 28 d to the two soils amended with biosolids at agronomic rates. The 28-d organic carbon and lipid-normalized biota soil accumulation factors (BSAFs) were calculated for TCC and ranged from 0.22 ± 0.12 to 0.71 ± 0.13. These findings suggest that TCC bioaccumulation is somewhat consistent with the traditional hydrophobic organic contaminant (HOC) partitioning paradigm. However, these data also suggest substantially reduced bioavailability of TCC in biosolids-amended soils compared with HOC partitioning theory. Environ. Toxicol. Chem. 2011; 30:556-563. © 2011 SETAC [ABSTRACT FROM AUTHOR]

The primary objective of this study was to determine whether total biodiversity (γ) is partitioned into within-community (α) and among-community (β) components differently for taxonomic and functional organization. I hypothesized that α diversity will contribute more to the functional organization of γ diversity and that β diversity will contribute more to the taxonomic organization of γ diversity. A secondary objective was to determine whether the relationship between taxonomic and functional diversity is scale dependent. Species abundance data was obtained from fisheries surveys conducted by the Texas Parks and Wildlife Dept that focused on least disturbed streams from 11 different ecoregions of Texas, including 62 localities from 18 drainages. Functional and taxonomic organization of assemblages was quantified with two different measures of biodiversity, including richness and the numbers equivalent of Shannon diversity. Scale-dependent effects on these indices were assessed by multiplicatively partitioning γ into α and β components. The contribution of α and β components to γ diversity differed between functional and taxonomic organization and among different measures of biodiversity. Among-community components were more influential in structuring the taxonomic organization of stream-fish assemblages, whereas within-community components were more important in structuring the functional organization of assemblages. The relationship between taxonomic and functional diversity differed between α and β components and between spatial scales. Indeed, ecological patterns not only change with spatial scale, but how they change is dependent on which aspect of biodiversity is considered. [ABSTRACT FROM AUTHOR]

The metacommunity framework is a powerful platform for evaluating patterns of species distribution in geographic or environmental space. Idealized patterns (checkerboard, Clementsian, evenly spaced, Gleasonian and nested distributions) give the framework shape. Each pattern represents an area in a multidimensional continuum of metacommunity structures; however, the current approach to analysis of spatial structure of metacommunities is incomplete. To address this, we describe additional non-random structures and illustrate how they may be discerned via objective criteria. First, we distinguish three distinct forms of species loss in nested structures, which should improve identification of structuring mechanisms for nested patterns. Second, we define six quasi-structures that are consistent with the conceptual underpinnings of Clementsian, Gleasonian, evenly spaced and nested distributions. Finally, we demonstrate how combinations of structures at smaller spatial extents may aggregate to form Clementsian structure at larger extents. These refinements should facilitate the identification of best-fit patterns, associated structuring mechanisms, and informative scales of analysis and interpretation. This conceptual and analytical framework may be applied to network properties within communities (i.e. structure of interspecific interactions) and has broad application in ecology and biogeography. [ABSTRACT FROM AUTHOR]

Transportation agencies expend large amounts of money annually to maintain highway wearing surfaces. Wear depends mainly on axle weight, vehicle speed, temperature, surface type, and the type of tires mounted on vehicles. When studded tires are used, wear is increased significantly. Past studies on the use of studded tires have highlighted the need for a tool to better estimate the number of vehicles with studded tires that travel a road network. Currently, there is no such tool available. This paper presents a detection methodology using acoustic emission techniques to identify vehicles operating with studded tires. Data from an in-service test on a highway bridge were used for developing and evaluating two proposed detection schemes. It was found that using relatively simple detection algorithms, vehicles with studded tires could be discriminated reliably. Finally, a practicable integrated system is proposed that could be implemented for detection and monitoring of studded snow tire use on highway systems. [ABSTRACT FROM AUTHOR]

The antimicrobial triclocarban (TCC) has been detected in streams and municipal biosolids throughout the United States. In addition, TCC and potential TCC transformation products have been detected at high levels (ppm range) in sediments near major cities in the United States. Previous work has suggested that TCC is relatively stable in these environments, thereby raising concerns about the potential for bioaccumulation in sediment-dwelling organisms. Bioaccumulation of TCC from sediments was assessed using the freshwater oligochaete Lumbriculus variegatus. Worms were exposed to TCC in sediment spiked to 22.4 ppm to simulate the upper bound of environmental concentrations. Uptake from laboratory-spiked sediment was examined over 56 d for TCC and 4,4′- dichlorocarbanilide (DCC), a chemical impurity in and potential transformation product of TCC. The clearance of TCC from worms placed in clean sediment was also examined over 21 d after an initial 35-d exposure to TCC in laboratory-spiked sediment. Concentrations of TCC and DCC were monitored in the worms, sediment, and the overlying water using liquid chromatography/tandem mass spectrometry. Experimental data were fitted using a standard biodynamic model to generate uptake and elimination rate constants for TCC in L. variegatus. These rate constants were used to estimate steady-state lipid (lip)- and organic carbon (OC)- normalized biota-sediment accumulation factors (BSAFs) for TCC and DCC of 2.2 ± 0.2 and 0.3 ± 0.1 g OC/g lip (goc/glip), respectively. Alternatively, directly measured BSAFs for TCC and DCC after 56 d of exposure were 1.6 ± 0.6 and 0.5 ± 0.2 goc/glip, respectively. Loss of TCC from pre-exposed worms followed first-order kinetics, and the fitted elimination rate constant was identical to that determined from the uptake portion of the present study. Overall, study observations indicate that TCC bioaccumulates from sediments in a manner that is consistent with the traditional hydrophobic organic contaminant paradigm. [ABSTRACT FROM AUTHOR]

Techniques to evaluate elements of metacommunity structure (EMS; coherence, species turnover and range boundary clumping) have been available for several years. Such approaches are capable of determining which idealized pattern of species distribution best describes distributions in a metacommunity. Nonetheless, this approach rarely is employed and such aspects of metacommunity structure remain poorly understood. We expanded an extant method to better investigate metacommunity structure for systems that respond to multiple environmental gradients. We used data obtained from 26 sites throughout Paraguay as a model system to demonstrate application of this methodology. Using presence–absence data for bats, we evaluated coherence, species turnover and boundary clumping to distinguish among six idealized patterns of species distribution. Analyses were conducted for all bats as well as for each of three feeding ensembles (aerial insectivores, frugivores and molossid insectivores). For each group of bats, analyses were conducted separately for primary and secondary axes of ordination as defined by reciprocal averaging. The Paraguayan bat metacommunity evinced Clementsian distributions for primary and secondary ordination axes. Patterns of species distribution for aerial insectivores were dependent on ordination axis, showing Gleasonian distributions when ordinated according to the primary axis and Clementsian distributions when ordinated according to the secondary axis. Distribution patterns for frugivores and molossid insectivores were best described as random. Analysis of metacommunities using multiple ordination axes can provide a more complete picture of environmental variables that mold patterns of species distribution. Moreover, analysis of EMS along defined gradients (e.g., latitude, elevation and depth) or based on alternative ordination techniques may complement insights based on reciprocal averaging because the fundamental questions addressed in analyses are contingent on the ordination technique that is employed. [ABSTRACT FROM AUTHOR]

Tests were performed on full-size prefabricated steel stair assemblies to assess seismic interstory drift response combined with factored gravity loads. The stair assemblies were production-run units of a standard system and were designed for a typical steel frame building. Two different stair assembly units were tested: one with checker plate and one with concrete-filled pans. A loading system and testing protocol were developed to evaluate the seismic performance using seismic and gravity load combinations. Lateral drifts were imposed in both orthogonal stair directions followed by factored live and dead gravity loads. Imposed lateral drift placed high deformation demands on the stair-to-landing connections and overall performance is dependent on the deformability and endurance of these connections. Careful detailing, fabrication, and inspection of the stair-to-landing connections are required to ensure desired system performance. [ABSTRACT FROM AUTHOR]

Public bicycle share programs (PBSPs) can play a role in advancing transportation equity if they make bicycling more accessible to disadvantaged populations. In Ontario, Hamilton Bike Share expanded their program in 2018 by adding twelve "equity" stations with the explicit objective of increasing access for under-serviced neighborhoods. In this case study, we investigate differentials in accessibility to stations using a balanced floating catchment area approach and compare accessibility with and without the equity stations. We analyze population interpolated to small cells to better reflect walking to a station and conduct a sensitivity analysis at several walking time thresholds. We then reaggregate the estimated accessibility by income groups for further analysis. Our findings indicate that equity stations increased accessibility for the serviced population at every threshold examined, but the increase was relatively modest especially for population in the bottom 20% of median total household income. • Balanced floating catchment area method applied to measure accessibility to bike share. • Contribution of stations added to increase equity assessed at different thresholds. • Added stations increased accessibility and reduced inequities, albeit only modestly. • Lowest income group has low levels of accessibility, even with "equity" stations. • Location and size of docking stations matters for increasing equity in accessibility. [ABSTRACT FROM AUTHOR]

In this paper we analyze the changes in accessibility to emergency and community food services before and during the COVID-19 pandemic in the City of Hamilton, Ontario. Many of these food services are the last line of support for households facing food insecurity; as such, their relevance cannot be ignored in the midst of the economic upheaval caused by the pandemic. Our analysis is based on the application of balanced floating catchment areas and concentrates on households with lower incomes (

This study assessed generational differences in human values as measured by the Schwartz Value Survey. It was proposed that the two most recent generations, Millennials and Generation Xers, would value Self-enhancement and Openness to Change more than the two older generations, Baby Boomers and Matures, while the two older generations would value Self-transcendence and Conservation more. The hypotheses were tested with a combined sample of Canadian knowledge workers and undergraduate business students (N= 1,194). Two hypotheses were largely supported, although an unexpectedly large difference was observed between Millennials and Generation Xers with respect to Openness to Change and Self-enhancement. The findings suggest that generation is a useful variable in examining differences in social values. [ABSTRACT FROM AUTHOR]

Bioaccumulation of perfluoroalkyl sulfonates, perfluoro-carboxylates, and 2-(N-ethylperfluorooctane sulfonamido) acetic acid (N-EtFOSAA) from laboratory-spiked and contaminated field sediments was assessed using the freshwater oligochaete, Lumbriculus variegatus. Semi-static batch experiments were conducted to monitor the biological uptake of these perfluorochemicals (PFCs) over 56 days. The elimination of PFCs was measured as the loss of PFCs in L. variegatus exposed to PFC-spiked sediment for 28 days and then transferred to clean sediment. The resultant data suggest that PFCs in sediments are readily bioavailable and that bioaccumulation from sediments does not continually increase with increasing perfluorocarbon chain length. Perfluorooctane sulfonate (PFOS) and perfluorononanoate were the most bioaccumulative PFCs, as measured by laboratory-based estimated steady-state biota sediment accumulation factors (BSAFs) and BSAFs measured using contaminated field sediments. Elimination rate constants for pertluoroalkyl sulfonates and perfluorocaroboxylates were generally smaller than those previously measured for other organic contaminants. Last, a PFOS precursor, N-EtFOSAA, accumulated in the worm tissues and appeared to undergo biotransformation to PFOS and other PFOS precursors. This suggests that N-EtFOSAA, which has been detected in sediments and sludge often at levels exceeding PFOS, may contribute to the bioaccumulation of PFOS in aquatic organisms. [ABSTRACT FROM AUTHOR]

The acquisition of multidrug resistance is a serious impediment to improved healthcare. Multidrug resistance is most frequently due to active transporters that pump a broad spectrum of chemically distinct, cytotoxic molecules out of cells, including antibiotics, antimalarials, herbicides and cancer chemotherapeutics in humans. The paradigm multidrug transporter, mammalian P-glycoprotein, was identified 30 years ago. Nonetheless, success in overcoming or circumventing multidrug resistance in a clinical setting has been modest. Recent structural and biochemical data for several multidrug transporters now provide mechanistic insights into how they work. Organisms have evolved several elegant solutions to ridding the cell of such cytotoxic compounds. Answers are emerging to questions such as how multispecificity for different drugs is achieved, why multidrug resistance arises so readily, and what chance there is of devising a clinical solution. [ABSTRACT FROM AUTHOR]

Distributions of species often exhibit nested structure, such that assemblages at species-poor sites are proper subsets of taxa at more species-rich sites. Traditionally, this has been viewed as a large-scale biogeographic pattern and treated implicitly as static from a temporal perspective. Nonetheless, recent work suggests that nestedness may arise at multiple spatio-temporal scales. A 13-year data set encompassing the effects of two large-scale natural disturbances (hurricanes Hugo and Georges) on terrestrial gastropod assemblages was used to test the hypothesis that changes in species composition resulting from disturbance alter the degree of nestedness exhibited over time at two spatial scales. Gastropod assemblages were least nested immediately following disturbance, and nestedness increased thereafter. Although land-use history influenced the degree of nestedness, trajectories of nestedness following disturbance were similar irrespective of disturbance history or hurricane identity. The effects of hurricanes with respect to nestedness of terrestrial gastropods may be general and predictable, even though species respond to hurricanes in disparate fashions. By damaging some localities within the forest more severely than others, a hurricane dismantles extant patterns of species composition and severs connections among sites, as inhospitable microclimatic conditions limit dispersal of gastropods. As time passes and the forest canopy regenerates, conditions ameliorate, and movement among sites becomes more frequent. Thus, a conclusion based on a single time period may not characterize the study system in general. Consequently, explanations for nested structure that incorporate variability in ecological as well as evolutionary time will improve the applicability and comparability of nested subsets analysis across study systems. [ABSTRACT FROM AUTHOR]

ATP-binding cassette (ABC) transporters are ubiquitous integral membrane proteins that facilitate the transbilayer movement of ligands. They comprise, minimally, two transmembrane domains, which impart ligand specificity, and two nucleotide-binding domains (NBDs), which power the transport cycle. Almost 25 years of biochemistry is reviewed in light of the recent structure analyses resulting in the ATP-switch model for function in which the NBDs switch between a dimeric conformation, closed around two molecules of ATP, and a nucleotide-free, dimeric ‘open’ conformation. The flexibility of this switching mechanism has evolved to provide different kinetic control for different transporters and has also been co-opted to diverse functions other than transmembrane transport. [ABSTRACT FROM AUTHOR]

Fluorochemicals have widespread applications and are released into municipal wastewater treatment plants via domestic wastewater. A field study was conducted at a full-scale municipal wastewater treatment plant to determine the mass flows of selected fluorochemicals. Flow-proportional, 24 h samples of raw influent, primary effluent, trickling filter effluent, secondary effluent, and final effluent and grab samples of primary, thickened, activated, and anaerobically digested sludge were collected over 10 days and analyzed by liquid chromatography electrospray-ionization tandem mass spectrometry. Significant decreases in the mass flows of perfluorohexane sulfonate and perfluorodecanoate occurred during trickling filtration and primary clarification, while activated sludge treatment decreased the mass flow of perfluorohexanoate. Mass flows of the 6:2 fluorotelomer sulfonate and perfluorooctanoate were unchanged as a result of wastewater treatment, which indicates that conventional wastewater treatment is not effective for removal of these compounds. A net increase in the mass flows for perfluorooctane and perfluorodecane sulfonates occurred from trickling filtration and activated sludge treatment. Mass flows for perfluoroalkylsulfonamides and perfluorononanoate also increased during activated sludge treatment and are attributed to degradation of precursor molecules. [ABSTRACT FROM AUTHOR]

The sorption of anionic perfluorochemical (PFC) surfactants of varying chain lengths to sediments was investigated using natural sediments of varying iron oxide and organic carbon content. Three classes of PFC surfactants were evaluated for sorptive potential: perfluorocarboxylates, perfluorosulfonates, and perfluorooctyl sulfonamide acetic acids. PFC surfactant sorption was influenced by both sediment-specific and solution-specific parameters. Sediment organic carbon, rather than sediment iron oxide content, was the dominant sediment-parameter affecting sorption, indicating the importance of hydrophobic interactions. However, sorption also increased with increasing solution [Ca2+] and decreasing pH, suggesting that electrostatic interactions play a role. Perfluorocarbon chain length was the dominant structural feature influencing sorption, with each CF2 moiety contributing 0.50–0.60 log units to the measured distribution coefficients. The sulfonate moiety contributed an additional 0.23 log units to the measured distribution coefficient, when compared to carboxylate analogs. In addition, the perfluorooctyl sulfonamide acetic acids demonstrated substantially stronger sorption than perfluorooctane sulfonate (PFOS). These data should prove useful for modeling the environmental fate of this class of contaminants. [ABSTRACT FROM AUTHOR]

Nestedness has received considerable attention in community ecology and conservation biology from both theoretical and empirical perspectives. This has lead to the creation of various metrics and null models to analyze nested subsets, all of which rely on the random placement of species to assess significance. However, if immigration and extinction are the processes that underlie species distributions on island systems, then null models might be better determined on the basis of randomly placed individuals. Consequently, we examined the effects of species–abundance distributions (uniform, dominance–decay, random–assortment, and dominance–preemption), island–size distributions (uniform and linear decrease), and total abundances (128, 256, 512, 1024, 2048, 4096 and 8192) on the degree of nestedness and its significance. Generally, matrices of species presence and absence created from the random placement of individuals were nested significantly according to null models based on the random placement of species. Island size and abundance had less of an effect on nestedness in systems dominated by only a few species than in systems in which abundances were distributed more evenly. Stochastic processes, such as the random placement of individuals, predispose systems to evince patterns of nestedness at the species level, which may account, in part, for the ubiquity of nestedness in nature. [ABSTRACT FROM AUTHOR]

We used fishery surveys from 1954 to 1957 to determine the relationship between salinity and prairie stream-fish assemblage composition prior to the major drought of the 1950s and subsequent anthropogenic modifications. A total of 78,931 fishes were captured, representing 13 families and 44 species. Species were classified as having low, moderate, or high salinity tolerances based on k-means clustering of detrended correspondence scores. The proportion of species with high salinity tolerances was correlated positively ( r = 0.74) with salinity, whereas the proportion of species with low ( r = −0.69) or moderate ( r = −0.36) tolerances was correlated strongly and negatively with salinity. Many of the low or moderate salinity tolerant species found in the 1950s were not collected in studies conducted 15 and 35 years later. Examination of these studies provides compelling evidence that salinity has been a dominant and persistent factor in affecting the structure of stream-fish assemblages for the past 50 years. [ABSTRACT FROM AUTHOR]

I offer a close reconstruction of John Dewey’s account of vocation in Democracy and Education , bringing out the existential and aesthetic dimensions of Dewey’s idea that vocations constitute perceptual environments for their practitioners. Although Dewey offers this idea to teachers only as an insight about student development, I contend that its most powerful educational implication concerns the growth of teachers. Picking up where Dewey left off, I investigate to what extent teaching constitutes an educative environment for teachers. I conclude that, while the environment of teaching is an exceedingly rich one, the basic working conditions of teachers and the ethos of education often frustrate their attempts to interact with this environment. I conclude with a critique of some of the forces that narrow the range of what teachers notice, feel, and learn in the course of their work. [ABSTRACT FROM AUTHOR]