Educational change and discourse communities: representing change in postmodern times

As a consequence of the shift that educational change is experiencing it has begun to focus its energy in the creation of more sophisticated categories. Facing a situation of having to redefine categories, it is necessary to find ways of representing change that grasp the complex and sometimes contradictory expressions of innovations. Concepts such as 'discourse communities' are now being used to capture a sense of the plurality and ambiguity of possible positions. A discourse community refers to an association of identity and discourse that creates its particularity between those persons who think of themselves as members and participants in their discourse. I focus on three main discourse communities in educational change: 'excellence', 'restructuring' and 'cultural politics'. Discourse communities are mapping epistemological positions considering interaction and conflictive areas and are also showing the changeable and unstable nature of their own representations.     

Research Watch: Climate change

Modeling.     

Research Watch: Temperature change

Climate.     

Research Watch: Paleoclimate change

Climate Change.     

An investigation of sources of Campylobacter in a poultry production and packing operation in Barbados

Chicken meat is frequently contaminated with Campylobacter jejuni and is thought to be the major source of organisms causing human Campylobacter enteritis. Genotypic similarities between Campylobacter isolates from chicken meat at retail outlets and patients with gastroenteritis in Barbados suggested that it is a vehicle for infection of humans on the island and prompted this investigation of transmission of Campylobacter in a local poultry operation. Campylobacter testing was conducted at the hatchery, on the broiler farm and in the processing plant for two consecutive production cycles. The genetic relatedness of Campylobacter isolates was determined by RAPD typing with primer OPA 11. Hatchery samples and week-old chicks were negative for Campylobacter. Flocks became colonized as early as three weeks after introduction to the farm. Ten distinct RAPD genotypes were identified among isolates. Some genotypes were similar and may be of clonal origin. There was no evidence of vertical transmission of Campylobacter. The results suggest that the broiler flock was infected from more than one source in the farm environment.     

Research Watch: Climate change effects

Policy.     

Research Watch: Soil-climate change dynamics

Soils.     

Purification and kinetic characterization of polyphenol oxidase from Barbados cherry (Malpighia glabra L.)

Polyphenol oxidase (PPO) of Barbados cherry was extracted and purified through ammonium sulfate precipitation, gel filtration, and affinity chromatography. The purification factor for PPO was 60% with 8.3% yield. The enzyme was characterized for thermal stability, pH and kinetic parameters. The molecular mass of PPO was approximately the sum of 52 and 38 kDa estimated by SDS–PAGE. The purity was checked by native PAGE, showing a single prominent band. The optimum pH was 7.2. The enzyme had a temperature optimum at 40 °C and was relatively stable at 60 °C, with 55% loss of activity. Sodium diethyl dithiocarbamate (SDDC), l-cysteine and ascorbate significantly inhibited PPO activity. 4-Methyl catechol and catechol were found to be efficient diphenolic substrates for cherry PPO, considering the _Vmax/_Km$V_{\text{max}}/K_{\mathrm{m}}$ ratio. The data obtained in this study may help to understand cherry fruit browning.     

Book review: a climate for change

A review of Negotiating Climate Change: The Inside Story of the Rio Convention.     

Water chemistry: fifty years of change and progress

Water chemistry evolved from early foundations in several related disciplines. Although it is difficult to associate a precise date to its founding, several events support the argument that the field as we know it today developed in the mid-20th century--at the dawn of the "environmental era"--that is, ～1960. The field in its modern incarnation thus is about 50 years old. In celebration of this half-centenary, we examine here the origins of water chemistry, how the field has changed over the past 50 years, and the principal driving forces for change, focusing on both the "practice" of water chemistry and ways that teaching the subject has evolved.     

Hydrochloric acid: an overlooked driver of environmental change

Research on the ecosystem impacts of acidifying pollutants, and measures to control them, has focused almost exclusively on sulfur (S) and nitrogen (N) compounds. Hydrochloric acid (HCl), although emitted by coal burning, has been overlooked as a driver of ecosystem change because most of it was considered to redeposit close to emission sources rather than in remote natural ecosystems. Despite receiving little regulatory attention, measures to reduce S emissions, and changes in energy supply, have led to a 95% reduction in United Kingdom HCl emissions within 20 years. Long-term precipitation, surface water, and soil solution data suggest that the near-disappearance of HCl from deposition could account for 30-40% of chemical recovery from acidification during this time, affecting both near-source and remote areas. Because HCl is highly mobile in reducing environments, it is a more potent acidifier of wetlands than S or N, and HCl may have been the major driver of past peatland acidification. Reduced HCl loadings could therefore have affected the peatland carbon cycle, contributing to increases in dissolved organic carbon leaching to surface waters. With many regions increasingly reliant on coal for power generation, HCl should be recognized as a potentially significant constituent of resulting emissions, with distinctive ecosystem impacts.     

Climate change and food safety: A review

Climate change and variability may have an impact on the occurrence of food safety hazards at various stages of the food chain, from primary production through to consumption. There are multiple pathways through which climate related factors may impact food safety including: changes in temperature and precipitation patterns, increased frequency and intensity of extreme weather events, ocean warming and acidification, and changes in contaminants’ transport pathways among others. Climate change may also affect socio-economic aspects related to food systems such as agriculture, animal production, global trade, demographics and human behaviour which all influence food safety.This paper reviews the potential impacts of predicted changes in climate on food contamination and food safety at various stages of the food chain and identifies adaptation strategies and research priorities to address food safety implications of climate change. The paper concludes that there is a need for intersectoral and international cooperation to better understand the changing food safety situation and in developing and implementing adaptation strategies to address emerging risks associated with climate change.     

Climate change and seafood safety: Human health implications

Worldwide, anthropogenic climate change is now a reality and is already affecting the biology and ecology of some organisms, as well as several chemical pathways. Little is known about the consequences of climate change for the food system, particularly seafood, comprising all stages from ‘‘farm to fork” (mainly primary production, processing, transport and trading). In this context, the current review aims to elucidate climate change impacts on seafood safety and its human health implications. Both chemical and biological risks are foreseen to impair seafood safety in the future as a consequence of climate change; in particular, toxic metals, organic chemicals residues, algal toxins and pathogens of both humans and marine organisms. However, different species respond differently to such stresses. Public health authorities will face new challenges to guarantee seafood safety and to sustain consumers’ confidence in eating seafood in a warmer world.