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Caversham, United Kingdom

Rhodes C.J.,Fresh lands Environmental Actions
Chemical Papers

A critical review of zeolites and their use in practical applications is presented. Specificallyconsidered are their role as media for selective light-induced oxidations using molecular O2, and the relationship between this phenomenon and the surface electric fields that exist in zeolites. Methods for the determination of the strength of zeolite surface fields are discussed using sorbed molecules such as CO (with IR detection), spin-probes, di-tert-butyl nitroxide, and NO (measured using EPR spectroscopy). Relationship between the surface fields and molecular reorientation energetics for free radicals sorbed in zeolites, obtained using muonium as a spin-label, is explored. Finally, results obtained from exposing the naturally occurring zeolite, clinoptilolite, to high energy electrons as a means for activating materials toward selective removal of radioactive caesium and strontium cations from wastewaters of nuclear power plants are presented. © Institute of Chemistry, Slovak Academy of Sciences 2015. Source

Rhodes C.J.,Fresh lands Environmental Actions
Annual Reports on the Progress of Chemistry - Section C

The present review focuses mainly on the interaction between molecules and the surfaces of zeolites and opens with Electron Spin Resonance (ESR) spectroscopy in view of the desire to study radical intermediates in catalytic systems. In this aim too, the family of spectroscopic techniques known collectively as μSR (Muon Spin Rotation, Relaxation or Resonance) which employ spin-polarised positive muons, and can probe radicals in porous media, including zeolites, with a unique and remarkable sensitivity are paid due attention. All such methods have undergone appreciable developments in recent years, especially in regard to pulsed-techniques and theoretical methods for data acquisition and analysis. DFT calculations continue to prove their worth in the prediction and interpretation of hyperfine coupling constants in (paramagnetic) radical species. The broader characterization of less fleeting (diamagnetic) molecules hosted in zeolites, either as deliberately introduced probes or as formed during catalytic activity, has been greatly aided by developments in infra-red (IR) spectroscopy, UV/Resonance Raman methods, inelastic neutron scattering techniques and NMR, as are surveyed in their recent applications to this topic. © The Royal Society of Chemistry 2010. Source

Jomova K.,Constantine the Philosopher University | Jenisova Z.,Constantine the Philosopher University | Feszterova M.,Constantine the Philosopher University | Baros S.,Constantine the Philosopher University | And 4 more authors.
Journal of Applied Toxicology

Arsenic (As) is a toxic metalloid element that is present in air, water and soil. Inorganic arsenic tends to be more toxic than organic arsenic. Examples of methylated organic arsenicals include monomethylarsonic acid [MMA(V)] and dimethylarsinic acid [DMA(V)]. Reactive oxygen species (ROS)-mediated oxidative damage is a common denominator in arsenic pathogenesis. In addition, arsenic induces morphological changes in the integrity of mitochondria. Cascade mechanisms of free radical formation derived from the superoxide radical, combined with glutathione-depleting agents, increase the sensitivity of cells to arsenic toxicity. When both humans and animals are exposed to arsenic, they experience an increased formation of ROS/RNS, including peroxyl radicals (ROO), the superoxide radical, singlet oxygen, hydroxyl radical (OH) via the Fenton reaction, hydrogen peroxide, the dimethylarsenic radical, the dimethylarsenic peroxyl radical and/or oxidant-induced DNA damage. Arsenic induces the formation of oxidized lipids which in turn generate several bioactive molecules (ROS, peroxides and isoprostanes), of which aldehydes [malondialdehyde (MDA) and 4-hydroxy-nonenal (HNE)] are the major end products. This review discusses aspects of chronic and acute exposures of arsenic in the etiology of cancer, cardiovascular disease (hypertension and atherosclerosis), neurological disorders, gastrointestinal disturbances, liver disease and renal disease, reproductive health effects, dermal changes and other health disorders. The role of antioxidant defence systems against arsenic toxicity is also discussed. Consideration is given to the role of vitamin C (ascorbic acid), vitamin E (α-tocopherol), curcumin, glutathione and antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase in their protective roles against arsenic-induced oxidative stress. © 2011 John Wiley & Sons, Ltd. Source

Rhodes C.J.,Fresh lands Environmental Actions
Science Progress

September 2015 saw the International Permaculture Conference1, held in London, followed by the Convergence2, which occupied 6 days at Gilwell Park, on the Essex-London border, where its practitioners gave presentations and workshops on various aspects of permaculture, which is a sustainable design system intended to emulate the principles of living ecosystems. While it has been emphasised3 that such terms as sustainable development, and sustainable agriculture, are really oxymorons, since neither untrammelled growth nor our present form of industrial food production can be maintained in perpetuity, permaculture4 has a value-added factor that extends beyond what might be merely maintained or sustained, which is the quality of regeneration. All sustainable solutions are unsustainable over the longer term, if they are not also intrinsically regenerative. Nature offers the ultimate example of a design that is both sustainable and regenerative, and it is logical to appeal to natural principles for solutions to many of our current problems. This is sometimes taken to mean that we need adopt more “simple” lifestyles, abandoning our technology in the process, but the reality is more complex. Within a broader perspective of regenerative design, permaculture identifies the elements of sustainable living which are harmonious with nature. Discordant practices which lead, e.g. to soil erosion3, fret the environment, and are neither sustainable nor regenerative, but degenerative. © 2015, Science Reviews 2000 Ltd, All right reserved. Source

Rhodes C.J.,Fresh lands Environmental Actions
Progress in Reaction Kinetics and Mechanism

Recent progress is surveyed in regard to the importance of molecular species containing unpaired electrons in catalytic systems, as revealed using ESR spectroscopy. The review begins with studies of enzymes and their role directly in biological systems, and then discusses investigations of various artificially created catalysts with potential human and environmental significance, including zeolites. Among the specific types of catalytic media considered are those for photocatalysis, water splitting, the degradation of environmental pollutants, hydrocarbon conversions, fuel cells, ionic liquids and sensor devices employing graphene. Studies of muonium-labelled radicals in zeolites are also reviewed, as a means for determining the dynamics of transient radicals in these nanoporous materials. Source

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