In the Thousand Islands region of eastern Ontario, Canada, Lyme disease is emerging as a serious health risk. The factors that influence Lyme disease risk, as measured by the number of blacklegged ...tick (Ixodes scapularis) vectors infected with Borrelia burgdorferi, are complex and vary across eastern North America. Despite study sites in the Thousand Islands being in close geographic proximity, host communities differed and both the abundance of ticks and the prevalence of B. burgdorferi infection in them varied among sites. Using this archipelago in a natural experiment, we examined the relative importance of various biotic and abiotic factors, including air temperature, vegetation, and host communities on Lyme disease risk in this zone of recent invasion. Deer abundance and temperature at ground level were positively associated with tick abundance, whereas the number of ticks in the environment, the prevalence of B. burgdorferi infection, and the number of infected nymphs all decreased with increasing distance from the United States, the presumed source of this new endemic population of ticks. Higher species richness was associated with a lower number of infected nymphs. However, the relative abundance of Peromyscus leucopus was an important factor in modulating the effects of species richness such that high biodiversity did not always reduce the number of nymphs or the prevalence of B. burgdorferi infection. Our study is one of the first to consider the interaction between the relative abundance of small mammal hosts and species richness in the analysis of the effects of biodiversity on disease risk, providing validation for theoretical models showing both dilution and amplification effects. Insights into the B. burgdorferi transmission cycle in this zone of recent invasion will also help in devising management strategies as this important vector-borne disease expands its range in North America.
Herein we report the use of a tetrazine-norbornene inverse electron demand Diels–Alder conjugation applied to polymer end-functionalization and polymer–polymer coupling. The reaction was found to be ...applicable to polymer–polymer coupling, as judged by SEC, DOSY NMR, and LCxSEC analyses, giving diblock copolymers by merely mixing the constituent homopolymers together under ambient conditions, using no catalyst, additive, or external stimulus.
Abstract End-functional PLLA nanofibers were fabricated into mats of random or aligned fibers and functionalized post-spinning using metal-free “click chemistry” with the peptide Tyr-Ile-Gly-Ser-Arg ...(YIGSR). Fibers that were both aligned and functionalized with YIGSR were found to significantly increase the fraction of mouse embryonic stem cells (mESC) expressing neuron-specific class III beta-tubulin (TUJ1), the level of neurite extension and gene expression for neural markers compared to mESC cultured on random fiber mats and unfunctionalized matrices. Precise functionalization of degradable polymers with bioactive peptides created translationally-relevant materials that capitalize on the advantages of both synthetic and natural systems, while mitigating the classic limitations of each.
In most synthetic elastomers, changing the physical properties by monomer choice also results in a change to the crystallinity of the material, which manifests through alteration of its mechanical ...performance. Using organocatalyzed stereospecific additions of thiols to activated alkynes, high‐molar‐mass elastomers were isolated via step‐growth polymerization. The resulting controllable double‐bond stereochemistry defines the crystallinity and the concomitant mechanical properties as well as enabling the synthesis of materials that retain their excellent mechanical properties through changing monomer composition. Using this approach to elastomer synthesis, further end group modification and toughening through vulcanization strategies are also possible. The organocatalytic control of stereochemistry opens the realm to a new and easily scalable class of elastomers that will have unique chemical handles for functionalization and post synthetic processing.
Stereochemistry‐controlled stretching: Step‐growth polymerization using organocatalytic nucleophilic thiol–yne addition chemistry is demonstrated to produce elastomeric materials in which the stereochemistry of the double bond controls the mechanical properties of the materials independently of the monomers.
To assess the impacts of different types of human activity on the development of resistant bacteria in the feces of wild small mammals, we compared the prevalences and patterns of antimicrobial ...resistance and resistance genes in generic Escherichia coli and Salmonella enterica isolates from fecal samples collected from wild small mammals living in four environments: swine farms, residential areas, landfills, and natural habitats. Resistance to antimicrobials was observed in E. coli isolates from animals in all environments: 25/52 (48%) animals trapped at swine farms, 6/69 (9%) animals trapped in residential areas, 3/20 (15%) animals trapped at landfills, and 1/22 (5%) animals trapped in natural habitats. Animals trapped on farms were significantly more likely to carry E. coli isolates with resistance to tetracycline, ampicillin, sulfisoxazole, and streptomycin than animals trapped in residential areas. The resistance genes sul2, aadA, and tet(A) were significantly more likely to be detected in E. coli isolates from animals trapped on farms than from those trapped in residential areas. Three S. enterica serotypes (Give, Typhimurium, and Newport) were recovered from the feces of 4/302 (1%) wild small mammals. All Salmonella isolates were pansusceptible. Our results show that swine farm origin is significantly associated with the presence of resistant bacteria and resistance genes in wild small mammals in southern Ontario, Canada. However, resistant fecal bacteria were found in small mammals living in all environments studied, indicating that environmental exposure to antimicrobials, antimicrobial residues, resistant bacteria, or resistance genes is widespread.
Lyme disease is the commonest vector-borne zoonosis in the temperate world, and an emerging infectious disease in Canada due to expansion of the geographic range of the tick vector Ixodes scapularis. ...Studies suggest that climate change will accelerate Lyme disease emergence by enhancing climatic suitability for I. scapularis. Risk maps will help to meet the public health challenge of Lyme disease by allowing targeting of surveillance and intervention activities.
A risk map for possible Lyme endemicity was created using a simple risk algorithm for occurrence of I. scapularis populations. The algorithm was calculated for each census sub-division in central and eastern Canada from interpolated output of a temperature-driven simulation model of I. scapularis populations and an index of tick immigration. The latter was calculated from estimates of tick dispersion distances by migratory birds and recent knowledge of the current geographic range of endemic I. scapularis populations. The index of tick immigration closely predicted passive surveillance data on I. scapularis occurrence, and the risk algorithm was a significant predictor of the occurrence of I. scapularis populations in a prospective field study. Risk maps for I. scapularis occurrence in Canada under future projected climate (in the 2020s, 2050s and 2080s) were produced using temperature output from the Canadian Coupled Global Climate Model 2 with greenhouse gas emission scenario enforcing 'A2' of the Intergovernmental Panel on Climate Change.
We have prepared risk maps for the occurrence of I. scapularis in eastern and central Canada under current and future projected climate. Validation of the risk maps provides some confidence that they provide a useful first step in predicting the occurrence of I. scapularis populations, and directing public health objectives in minimizing risk from Lyme disease. Further field studies are needed, however, to continue validation and refinement of the risk maps.
Glycoside hydrolases cleave the glycosidic linkage between two carbohydrate moieties. They are among the most efficient enzymes currently known. β-Xylosidases from glycoside hydrolase family 43 ...hydrolyze the nonreducing ends of xylooligomers using an inverting mechanism. Although the general mechanism and catalytic amino acid residues of β-xylosidases are known, the nature of the reaction’s transition state and the conformations adopted by the glycon xylopyranosyl ring along the reaction pathway are still elusive. In this work, the xylobiose hydrolysis reaction catalyzed by XynB3, a β-xylosidase produced by Geobacillus stearothermophilus T-6, was explicitly modeled using first-principles quantum mechanics/molecular mechanics Car−Parrinello metadynamics. We present the reaction’s free energy surface and its previously undetermined reaction pathway. The simulations also show that the glycon xylopyranosyl ring proceeds through a 2,5B-type transition state with significant oxacarbenium ion character.
This book provides a readily accessible and practical guide to the increasingly important subject of facilities management. It shows the formal basis for the complex and constantly moving ...requirements of FM and recognises that it is becoming more vital in its role of enabling the core business of a company to function effectively and is fast becoming a methodology for affecting and influencing the profitability of most organisations. Based upon the author's many years of experience, A Practical Guide to Facilities Management gives an overview of most FM theories and applies them in the workplace. It is a thought-provoking approach to FM practice and illustrates what the author has found to work. Throughout the text thematic graphics are used to present helpful tips, key action points, things to avoid and key elements of theory. An aide memoire summarises each chapter to help assimilation of the key parameters. The modern challenges of FM mean that more and more managers need to be innovators and to do more with less. This book will facilitate that process. In addition, it provides useful tips on the issue of sustainability and how a company can profitably benefit by FM actions in this area.
Post‐polymerization modification of polymers derived from sustainable resources using the click reaction between tetrazines and norbornenes is shown to provide a mild and efficient route for the ...synthesis of functional degradable polymers. Norbornene chain‐end functional poly(lactide) was synthesized using organocatalytic methods and functionalized by the addition of 3,6‐di‐2‐pyridyl‐1,2,4,5‐tetrazine without degradation of the polymer backbone. The versatility of this reaction was demonstrated by the application of analogues bearing amine and poly(ethylene oxide) groups to realize amine‐functional polymers and block copolymers. Poly(spiro6‐methyl‐1,4‐dioxane‐2,5‐dione‐3,2′‐bicyclo2.2.1hept5ene) was prepared from lactide. The pendant norbornene group on the backbone of the resultant polymer was modified in a similar manner to produce functional degradable polymers and graft co‐polymers.
The post‐polymerization modification of polymers derived from lactide is reported. Poly(lactide)s with norbornene groups both at the chain‐end and along the backbone are shown to readily undergo reaction with tetrazines in a mild and efficient manner.
Well-defined norbornene-functional poly(carbonate)s were prepared by ring-opening polymerization and utilized as multireactive polymeric scaffolds in a range of postpolymerization modifications. The ...norbornene-functional handles were shown to undergo facile reaction with azides via a 1,3-dipolar cycloaddition, tetrazines in the inverse electron demand Diels–Alder reaction and thiols via radical thiol-ene coupling. Furthermore, the above-mentioned chemistries were demonstrated in a sequential one-pot, three-step modification reaction illustrating the potential of these polymers as scaffolds to access multifunctionalized materials in an undemanding manner.
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