The application of ionizing radiation in reversible addition-fragmentation chain transfer (RAFT) polymerization: Renaissance of a key synthetic and kinetic tool

Ionizing radiation, such as γ, ultraviolet, microwave and X-ray radiation, has long been used in polymer chemistry as a means of initiating polymerization, crosslinking gels and decomposing particular polymer components. More recently, ionizing radiation has found application in tandem with living radical polymerization to form novel polymeric materials with defined molecular weight and narrow molecular weight distribution. In particular, γ-rays and ultraviolet light both have shown promise as sources of initiation in reversible addition-fragmentation chain transfer (RAFT) polymerization. The ability to apply these sources of initiation at low temperatures is useful in applications where elevated temperature is likely to be detrimental to the system, for instance, in preparing protein-polymer conjugates. Similarly, the use of these initiating sources at low temperature is particularly suitable for some monomers, such as allyl compounds, which have not been synthesized using any other living radical approach. The current review examines the development of ionizing radiation as a tool in RAFT polymerization, with particular reference to the elucidation of the polymerization mechanism, the synthesis of high functionality polymers and probing the kinetic parameters of the RAFT process.     

Polymer on Top: Current Limits and Future Perspectives of Quantitatively Evaluating Surface Grafting

Well‐defined polymer strands covalently tethered onto solid substrates determine the properties of the resulting functional interface. Herein, the current approaches to determine quantitative grafting densities are assessed. Based on a brief introduction into the key theories describing polymer brush regimes, a user's guide is provided to estimating maximum chain coverage and—importantly—examine the most frequently employed approaches for determining grafting densities, i.e., dry thickness measurements, gravimetric assessment, and swelling experiments. An estimation of the reliability of these determination methods is provided via carefully evaluating their assumptions and assessing the stability of the underpinning equations. A practical access guide for comparatively and quantitatively evaluating the reliability of a given approach is thus provided, enabling the field to critically judge experimentally determined grafting densities and to avoid the reporting of grafting densities that fall outside the physically realistic parameter space. The assessment is concluded with a perspective on the development of advanced approaches for determination of grafting density, in particular, on single‐chain methodologies.     

Formulation of a Biodegradable Detergent for Cleaning Oily Residues Generated during Industrial Processes

The use of toxic petroleum-based heavy oils is common in industrial processes. The cleaning of machines, equipment, and other surface covered in these oils is achieved with expensive products that are often also toxic and harmful to both the health of workers and the environment. The present paper proposes the development of a sustainable biodetergent made from plant-based materials. Tests were performed to determine the properties of the biodetergent in terms of its surfactant and emulsifying capacities, stability, toxicity, and the removal of heavy oil from glass plates and metallic surfaces. The formulation was composed of a natural solvent (cottonseed oil), a plant-based surfactant agent (saponin), and two natural stabilizers (carboxymethylcellulose and glycerine). The formulation was stable, nontoxic, and highly efficient, removing 100% of the heavy oil from glass and metallic surfaces. This solution developed in this study could be used in diverse industries with the need to clean machines and parts encrusted with oil and grease as well as the cleaning of floors covered with petroleum-based residues. A preliminary analysis of the economic feasibility of using the detergent was carried out at a Brazilian power plant. Besides the reduction in environmental impact due to the use of a nontoxic, biodegradable product as well as the reduction in health risks to workers associated with toxic cleaning products, this new product can have a considerable impact on the market as an environmentally friendly solution.     

Precisely Controlled Microsphere Design via Visible‐Light Cross‐Linking of Functional Prepolymers

A new strategy for particle synthesis is enabled by utilizing modern synthetic, polymer, and photochemical techniques to facilitate the synthesis of highly narrow–disperse multifunctional microspheres from visible‐light induced crosslinking of prepolymers in both a single and dual polymer system. The approach requires no stabilizers, bases, or initiators, and proceeds at ambient temperature to yield microspheres with a tunable size range (0.25–5 µm) in less than 4 h, depending largely on solvent composition, but also polymer concentration (2–10 mg mL^?1), ratio, and irradiation intensity (3–20 W). Critically, the visible‐light induced dimerization reaction exploited herein enables simple functional particle syntheses via a single polymer system. Underpinned by an in‐depth kinetic analysis of the particle formation as well as a detailed small molecule study, the mechanism for particle formation is also elucidated. Importantly, inherent advantages of the system are exploited for surface functionalization of residual acrylate and hydroxyl groups (generating inherently fluorescent particles).     

A framework for governance of public green spaces in cities

Public authorities that seek to transfer the cost of managing green spaces to the private sector face apprehension about the extent of community input in managing of public green spaces in cities. In practice, the governance arrangements for managing public green spaces are neither a purely private or public sector responsibility. They are part of complex and contested governance schemas that involve multiple stakeholder groups with varying interests and responsibilities. This paper proposes a simple framework to support different modes of governance appropriate for the management of public green spaces in cities. The framework classifies stakeholders’ desires for engagement based on ecosystem service characteristics defined on a spectrum of excludability and rivalry. The framework is applied to case studies in Australia and Canada. Finally, we discuss the new insights for governance arrangements for public green space management in cities.     

Out of the Closet: The Importance of Stories and Storytelling in Planning Practice

This article argues that story has a special importance in planning that has neither been fully understood nor sufficiently valued. Planning is performed through story, in a myriad of ways. The aim here is to unpack the many ways we use story: in policy, in process, in pedagogy, in critique, as a foundation, and as a catalyst for change. A better understanding of the work that stories do can make us better planners in at least three ways: by expanding our practical tools, by sharpening our critical judgment and by widening the circle of democratic discourse.     

Cattle, crops and clearing: Regional drivers of landscape change in the Brigalow Belt, Queensland, Australia, 1840–2004

Landscape change occurs through the interaction of a multitude of natural and human driving forces at a range of organisational levels, with humans playing an increasingly dominant role in many regions of the world. Building on the current knowledge of the underlying drivers of landscape change, a conceptual framework of regional landscape change was developed which integrated population, economic and cultural values, policy and science/technology. Using the Southern Brigalow Belt biogeographic region of Queensland as a case study, the role of natural and human drivers in landscape change was investigated in four phases of settlement since 1840. The Brigalow Belt has experienced comparable rates of vegetation clearance over the past 50 years to areas of tropical deforestation. Economic factors were important during all phases of development, but the five regional drivers often acted in synergy. Environmental constraints played a significant role in slowing rates of change. Temporal trends of deforestation followed a sigmoidal curve, with initial slow change accelerating though the middle phases then slowing in recent times. Future landscape management needs to take account of the influence of all the components of the conceptual framework, at a range of organisational levels, if more ecologically sustainable outcomes are to be achieved.     

Molecular basis of the constitutive activity and STI571 resistance of Asp816Val mutant KIT receptor tyrosine kinase

The receptor tyrosine kinase, KIT, displays activating mutations in the kinase domain, which are associated with various cancers. We have used homology modelling based on the crystal structures of the insulin receptor kinase in active and inactive conformations to predict the corresponding structures of the KIT kinase domain. We have prepared four KIT models, one each for the active and inactive conformations of the wild-type and of the Asp816Val mutant proteins. We have also placed ATP into the active conformations and the inhibitor, STI571, into the inactive conformations. All models have been fully energy minimised. The molecular modelling studies described here explain (i) why Asp816Val KIT is constitutively active, (ii) why the nature of the substituting amino acid at residue 816 is relatively unimportant, and (iii) why the Asp816Val substitution confers resistance to the KIT-inhibitory drug STI571. The models will be valuable for predicting other kinase inhibitory drugs that may be active on wild-type and mutant forms of KIT. During the course of this work, a crystal structure of the active conformation of the KIT kinase domain has been published. Our model of the active conformation of the Asp816Val mutant is strikingly similar to this crystal structure, whereas our model of the active conformation of the wild-type kinase domain of KIT differs from the crystal structure in some respects. The reasons for this apparent discrepancy are discussed.