Showing papers by "University of Greenwich published in 2003"

Fipronil: Environmental Fate, Ecotoxicology, and Human Health Concerns

Abstract: Fipronil is a highly effective, broad-spectrum insecticide with potential value for the control of a wide range of crop, public hygiene, amenity, and veterinary pests. It can generally be applied at low to very low dose rates to achieve effective pest control. Application rates vary between 0.6 and 200 g a.i./ha, depending on the target pest and formulation. It belongs to the phenyl pyrazole or fiprole group of chemicals and is a potent disrupter of the insect central nervous system via interference with the gamma-aminobutyric acid (GABA-) regulated chloride channel. Fipronil degrades slowly on vegetation and relatively slowly in soil and in water, with a half-life ranging between 36 hr and 7.3 mon depending on substrate and conditions. It is relatively immobile in soil and has low potential to leach into groundwater. One of its main degradation products, fipronil desulfinyl, is generally more toxic than the parent compound and is very persistent. There is evidence that fipronil and some of its degradates may bioaccumulate, particularly in fish. Further investigation on bioaccumulation is warranted, especially for the desulfinyl degradate. The suitability of fipronil for use in IPM must be evaluated on a case-by-case basis. In certain situations, fipronil may disrupt natural enemy populations, depending on the groups and species involved and the timing of application. The indications are that fipronil may be incompatible with locust IPM; hence, this possibility requires further urgent investigation. It is very highly toxic to termites and has severe and long-lasting negative impacts on termite populations. It thus presents a long-term risk to nutrient cycling and soil fertility where termites are "beneficial" key species in these ecological processes. Its toxicity to termites also increases the risk to the ecology of habitats in which termites are a dominant group, due to their importance as a food source to many higher animals. This risk has been demonstrated in Madagascar, where two endemic species of lizard and an endemic mammal decline in abundance because of their food chain link to termites. Fipronil is highly toxic to bees (LD50 = 0.004 microgram/bee), lizards [LD50 for Acanthodactylus dumerili (Lacertidae) is 30 micrograms a.i./g bw], and gallinaceous birds (LD50 = 11.3 mg/kg for Northern bobwhite quail), but shows low toxicity to waterfowl (LD50 > 2150 mg/kg for mallard duck). It is moderately toxic to laboratory mammals by oral exposure (LD50 = 97 mg/kg for rats; LD50 = 91 mg/kg for mice). Technical fipronil is in toxicity categories II and III, depending on route of administration, and is classed as a nonsensitizer. There are indications of carcinogenic action in rats at 300 ppm, but it is not carcinogenic to female mice at doses of 30 ppm. The acute toxicity of fipronil varies widely even in animals within the same taxonomic groups. Thus, toxicological findings from results on standard test animals are not necessarily applicable to animals in the wild. Testing on local species seems particularly important in determining the suitability of fipronil-based products for registration in different countries or habitats and the potential associated risk to nontarget wildlife. Risk assessment predictions have shown that some fipronil formulations present a risk to endangered bird, fish, and aquatic and marine invertebrates. Great care should thus be taken in using these formulations where they may impact any of these endangered wildlife groups. Work in Madagascar has highlighted field evidence of this risk. The dose levels at which fipronil produces thyroid cancer in rats are very high and are unlikely to occur under normal conditions of use. There is also dispute as to whether this is relevant to human health risk. However, as fipronil is a relatively new insecticide that has not been in use for long enough to evaluate the risk it may pose to human health, from data on human exposure to the product, a precautionary approach may be warranted. The use of some fipronil-based products on domestic animals is not recommended where handlers spend significant amounts of time grooming or handling treated animals. In general, it would appear unwise to use fipronil-based insecticides without accompanying environmental and human health monitoring, in situations, regions, or countries where it has not been used before, and where its use may lead to its introduction into the wider environment or bring it into contact with people. Further work is needed on the impacts of fipronil on nontarget vertebrate fauna (amphibians, reptiles, birds, and mammals) in the field before the risk to wildlife from this insecticide can be adequately validated. Further field study of the effects of fipronil on the nutrient cycling and soil water-infiltration activities of beneficial termites is required to assess the ecological impacts of the known toxicity of fipronil to these insects.

Fatty acids, the immune response, and autoimmunity: A question of n−6 essentiality and the balance between n−6 and n−3

Abstract: The essentiality of n−6 polyunsaturated fatty acids (PUFA) is described in relation to a thymus/thymocyte accretion of arachidonic acid (20∶4n−6, AA) in early development, and the high requirement of lymphoid and other cells of the immune system for AA and linoleic acid (18∶2n−6, LA) for membrane phospholipids. Low n−6 PUFA intakes enhance whereas high intakes decrease certain immune functions. Evidence from in vitro and in vivo studies for a role of AA metabolites in immune cell development and functions shows that they can limit or regulate cellular immune reactions and can induce deviation toward a T helper (Th)2-like immune response. In contrast to the effects of the oxidative metabolites of AA, the longer-chain n−6 PUFA produced by γ-linolenic acid (18∶3n−6, GLA) feeding decreases the Th2 cytokine and immunoglobulin (Ig)G1 antibody response. The n−6 PUFA, GLA, dihomo-γ-linolenic acid (20∶3n−6, DHLA) and AA, and certain oxidative metabolites of AA can also induce T-regulatory cell activity, e.g., transforming growth factor (IGF)-β-producing T cells; GLA feeding studies also demonstrate reduced proinflammatory interleukin (IL)-1 and tumor necrosis factor (TNF)-α production. Low intakes of long-chain n−3 fatty acids (fish oils) enhance certain immune functions, whereas high intakes are inhibitory on a wide range of functions, e.g., antigen presentation, adhesion molecule expression, Th1 and th2 responses, proinflammatory cytokine and eicosanoid production, and they induce lymphocyte apoptosis. Vitamin E has a demonstrable critical role in long-chain n−3 PUFA interactions with immune functions, often reversing the effects of fish oil. The effect of dietary fatty acids on animal autoimmune disease models depends on both the autoimmune model and the amount and type of fatty acids fed. Diets low in fat, essential fatty acid deficient (EFAD), or high in long-chain n−3 PUFA from fish oils increase survival and reduce disease severity in spontaneous autoantibody-mediated disease, whereas high-fat LA-rich diets increase disease severity. In experimentally induced T cell-mediated autoimmune disease, EFAD diets or diets supplemented with long-chain n−3 PUFA augment disease, whereas n−6 PUFA prevent or reduce the severity. In contrast, in both T cell- and antibody-mediated autoimmune disease, the desaturated/elongated metabolites of LA are protective. PUFA of both the n−6 and n−3 families are clinically useful in human autoimmune-inflammatory disorders, but the precise mechanisms by which these fatty acids exert their clinical effects are not well understood. Finally, the view that all n−6 PUFA are proinflammatory requires revision, in part, and their essential regulatory and developmental role in the immune system warrants appreciation.

Job/Work Environment Factors Influencing Training Transfer within a Human Service Agency: Some Indicative Support for Baldwin and Ford's Transfer Climate Construct

Abstract: Despite significant progress in the field of training transfer research over the past two decades very little empirical research in the area has been conducted within human service organisations. As a result, our knowledge of the extent to which those factors posited within the training literature to influence the transfer of training are necessarily those found in these particular work settings very much remains in its infancy. This article presents findings from qualitative research that was undertaken as part of a wider training evaluation strategy to investigate (1) those factors which influenced the transfer of training within a UK social services department; and (2) how these factors compared or differed from those suggested within the literature as influencing training transfer. The findings suggest a range of specific factors as they pertain to both the nature of the jobs and the workplace within such work settings as mediating training transfer. However, a number of these were closely associated with the dimensions of social support and opportunity to use as posited within Baldwin and Ford's (1988) transfer of training model, suggesting that the model is potentially generalisable to human service agencies.

Motherhood, paid work and partnering: values and theories

Abstract: The male breadwinner model, which dominated both policy assumptions and social ideals in the post-war welfare state, is increasingly being supplanted by an adult worker family model. In this new model, both men and women are assumed to be primarily workers in the labour market, who as fathers and mothers pool their earned income in supporting children. In this article we assess this assumption. First, we examine the gendered moral rationalities of particular social groups of partnered mothers, defined in terms of class, conventionality, ethnicity and sexuality, about how mothering is combined with paid work, and how time and labour is allocated with their partners. Second, in the light of this empirical research, we examine three leading approaches to understanding change and decision making in families ‐ new household economics, individualization in late modernity, and ‘post-modern moral negotiation’. We conclude that both the empirical and theoretical assumptions of the adult worker model are severely limited.

Ethical and responsible tourism: Consumer trends in the UK

Abstract: Responsible tourism is emerging as a significant market trend in the UK as wider consumer market trends towards lifestyle marketing and ethical consumption spread to tourism. This paper reviews recent survey evidence about consumer attitudes towards the responsible and ethical aspects of the tourism they consume, and places this in the context of campaigns by Voluntary Service Overseas and Tearfund. Between 1999 and 2001 the percentage of UK holidaymakers aspiring to be willing to pay more for an ethical holiday increased by 7 per cent from 45 per cent to 52 per cent. The evidence for increasing consumer demand for responsible tourism is reported and the paper concludes with a discussion of the implications.

Cassava brown streak disease: A review of present knowledge and research needs

Abstract: Cassava (Manihot esculenta) is an important subsistence food crop in Africa where it is affected by two main virus diseases, cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). CMD occurs in all the cassava-growing countries on the continent and it has been much researched. CBSD occurs mainly on the East African coast, and although the disease was first reported in 1936, it has received much less attention than CMD. The aetiology and epidemiology of CBSD are still not fully elucidated, and no insect vector has been identified. There is renewed interest in CBSD owing to the discovery of its widespread occurrence in southern Tanzania and Mozambique, where the associated symptom of root necrosis is a major cause of economic loss in the cassava crop. In view of the present importance of the disease in eastern Africa, it is timely to produce a review of work carried out on the disease since it was first described.

Women, Work and Equal Opportunities in Post-Communist Transition:

Abstract: This article examines gender, work and equal opportunities (EO) in five central eastern European (CEE) candidates to an enlarged European Union (EU): the Czech Republic, Hungary, Poland, Slovenia and Slovakia It demonstrates how capitalist transition has eroded women’s Communist economic and social legacy, and considers implications for EO of the EU enlargement process Analysis of decline begins with an outline of women’s position under Communism, showing both similarities in gender inequality to those of capitalism, but also significant differences and advances Post-transition is then examined in terms of the UN Gender Development Index, women’s loss of social support, their decline in labour force participation and changes in employment and political representation A limitation in available data is lack of information on unregulated employment and informal work ‐ both major developments in CEEThe objective picture is then set against subjective responses to change ‐ a key factor in gender EO prospects Finally, developments in EO monitoring and enforcement agencies are reviewed, with the conclusion drawing these levels of enquiry together to assess the possibilities of EU enlargement as a spur to greater commitment to gender equality in CEE

How ancient are ancient asexuals

Abstract: Ancient asexual animal groups, such as bdelloid rotifers and darwinuloid ostracods, are excellent model organisms to study the effects of long-term asexuality. However, the absolute length of time that these groups have been fully asexual is mostly ignored. In the case of the darwinuloid ostracods, the fossil record shows that sexual reproduction disappeared almost completely after the end of Permian mass extinction (ca. 245 Myr ago), although several putative records of males from the Mesozoic obscure the exact time-frame of obligate asexuality in darwinuloids. Here, we re-examine the Mesozoic darwinuloid records, with regard to the reproductive mode of the assemblages. Three criteria to distinguish males in fossil populations (lack of brood pouch, position of muscle scars and size dimorphism) are used here to test for the presence of males in darwinuloid assemblages. A large, well-preserved assemblage of Darwinula leguminella (Forbes 1885) from the latest Jurassic (ca. 145 Myr ago) of England is found to be markedly variable in size and shape, but nevertheless turns out to be an all female assemblage. The exceptional preservation of the material also allows the re-assignment of this species to the extant darwinuloid genus Alicenula. All other putative dimorphic darwinuloid records from the Mesozoic are re-examined using the same criteria. The hypothesis that these assemblages represent bisexual populations is rejected for all post-Triassic (ca. 208 Myr ago) records.

Physicochemical Properties of Poly(N-isopropylacrylamide-co-4-vinylpyridine) Cationic Polyelectrolyte Colloidal Microgels

Abstract: Aqueous colloidal poly(N-isopropylacrylamide-co-4-vinylpyridine) [poly(NIPAM-co-4-VP)] copolymer microgels have been synthesized using different percentages of 4-vinylpyridine (4-VP). A surfactant-free emulsion polymerization reaction using N-isopropylacrylamide (NIPAM) and 4-vinylpyridine comonomers cross-linked with N,N‘-methylenebisacrylamide was utilized. The reaction was initiated using the cationic initiator 2,2‘-azobis(2-amidinopropane) dihydrochloride. Transmission electron micrograph data show the copolymer microgels to be monodisperse spheres. The pH and electrolyte sensitivity of the copolymer microgels have been studied, as well as temperature sensitivity, since microgels undergo a reversible volume phase transition in response to heating and cooling. Changes in the hydrodynamic diameters in the system were monitored as a function of temperature (25−60 °C), pH (3−8), and ionic strength (10-3−10-1 mol dm-3 NaCl or NaClO4) using photon correlation spectroscopy. The hydrodynamic diameter of poly(...

Uterine artery function in pregnant rats fed a diet supplemented with animal lard

Abstract: We hypothesised that maternal uterine artery vascular dysfunction could contribute to cardiovascular dysfunction in offspring of rats fed a diet rich in fat. Sprague-Dawley rats were fed for 10 days prior to pregnancy and throughout gestation either: (a) a control breeding diet, or (b) the same diet supplemented with 20 % w/w lard, vitamins, essential micronutrients and protein to control values. At 20 days gestation vascular function was assessed in uterine arteries and third-order mesenteric arteries. Vascular reactivity in response to application of potassium, noradrenaline, the thromboxane analogue U46619, acetylcholine and nitric oxide was assessed. Maternal plasma concentrations of factors likely to contribute to endothelial dysfunction were measured. Maximum acetylcholine-induced relaxation was impaired in the mesenteric arteries of the lard-fed dams (max % relaxation: lard-fed, 69.7 +/- 6.48; control, 85.37 +/- 2.69, P = 0.03). Uterine artery vascular function was similar in the two groups (max % acetylcholine-induced relaxation: lard-fed, 73.7 +/- 4.01; control, 77.5 +/- 4.72, P = 0.98). Concentrations of plasma lipids, 8-epi-PGF(2alpha) and leptin were normal, whereas insulin and corticosterone concentrations were raised in the lard-fed group (insulin (ng ml(-1)): lard-fed, 8.04 +/- 0.47; control, 1.35 +/- 0.37, P < 0.0001; corticosterone (ng ml(-1)): lard-fed, 1164.0 +/- 170.9; control, 541.9 +/- 96.3, P = 0.005). Fetal and placental weights were reduced in lard-fed dams (fetus (g): lard-fed, 4.27 +/- 0.38; control, 2.96 +/- 0.40, P = 0.025; placenta (g): lard-fed, 0.72 +/- 0.06; control, 0.57 +/- 0.04, P = 0.05). Cardiovascular dysfunction in offspring is not associated with reduced uterine artery endothelial function but is associated with activation of the hypothalamic-pituitary-adrenal axis, hyperinsulinaemia and fetoplacental growth retardation.

Utility privatisation in Sub-Saharan Africa: a case study of water

Abstract: Over the past twenty years, the focus of development policy has shifted from the state to the private sector. Privatisation is now central to utility reform in much of SSA. This paper sets out developments in water privatisation and reviews the evidence regarding its impact. Water privatisation has been carried out to some degree in at least fourteen countries in the region, and many other governments are at various stages in the privatisation process. However, in some cases privatisation has been difficult to achieve, and a few countries have successfully provided water under public ownership. Evidence on the impact of privatisation indicates that the performance of privatised utilities has not changed dramatically, but that enterprises have continued to perform well, or not so well, depending both on their state when they were privatised and on the wider economic context. The evidence points to internal improvements in terms of financial management. However, governments face considerable difficulties in attracting investors and regulating private utilities. Furthermore, privatisation fails to address some of the fundamental constraints affecting water utilities in SSA, such as finance, the politicised nature of service delivery, and lack of access for the poor. A preoccupation with ownership may obscure the wider goals of reform.

Rice yield gaps in irrigated systems along an agro‐ecological gradient in West Africa

Abstract: Irrigated rice (Oryza sativa L.) in West Africa covers about 12 % of the regional rice-growing area, and is produced all along the agro-ecological gradient from the forest zone to the Sahara desert margins. Spatial and temporal variability of yield gaps (i.e., difference between actual and potential yield) were determined to set priorities for research and target technologies. On-farm trials were conducted on 191 irrigated lowland fields in the humid forest, the savanna and the Sahel. Farmers' yields were compared with those of super-imposed treatments of improved fertilization and weed management. Farmers' yields varied between 0.2 and 8.7 Mg ha-1, with average yields of 3.4 Mg ha-1 (Guinea savanna), 3.6 Mg ha-1 (humid forest), 3.9 Mg ha-1 (Sahel), and 5.1 Mg ha-1 (Sudan savanna). Simulated potential yields increased from 7 Mg ha-1 in the forest to about 10 Mg ha-1 in the Sahel. Accordingly, yield gaps were large, ranging from 3.2 to 5.9 Mg ha-1. Researcher weed control in the Sahel gave grain yield increases of about 1.0 Mg ha-1. Improved weed and N fertilization management increased yields by 1 to 2 Mg ha-1 in the forest and Guinea savanna sites. A share of 57-80 % of the yield gap could not be accounted for. Improving weed control is likely to have the highest pay-off in the Sahel while improved management of fertilizer N will be most beneficial in the forest and savanna environments. Potenzielle und aktuelle Ertrage von bewassertem Reis in unterschiedlichen agrarokologischen Zonen Westafrikas Etwa 12 % der Reisanbauflache Westafrikas istmit bewassertem Nassreis (Oryza sativa L.) bestellt, der in allen agrarokologischen Zonen zwischen der Sahara und dem Regenwald angebaut wird. Die raumliche und zeitliche Variabilitat der Ertrage und die Differenzen, die zwischen den tatsachlichen, den von Forschern erzielten und den potenziellen (mit ORYZAS simulierten) Ertragen bestehen, wurden in 191 Nassreisfeldern der Regenwald-, der Feuchtsavanne-, der Trockensavanne- und der Sahelzone bestimmt. Ertrage in den Feldern der Reisbauern variierten zwischen 0.2 and 8.7 Mg ha-1, mit durchschnittlich 3.4 Mg ha-1 (Feuchtsavanne), 3.6 Mg ha-1 (Regenwald), 3.9 Mg ha-1 (Sahel) und 5.1 Mg ha-1 (Trockensavanne). Das simulierte Ertragspotential stieg von 7 Mg ha-1 in der Regenwaldzone auf etwa 10 Mg ha-1 im Sahel an. Die daraus resultierenden Ertragsdifferenzen lagen zwischen 3.2 und 5.9 Mg ha-1. Verbesserte Unkrautkontrolle vermochte den Reisertrag im Sahel um etwa 1.0 Mg ha-1 zu erhohen. Ein verbessertes Management der N-Dungung erhohte die Reisertrage in den Regenwald- und Savannenzonen um 1 bis 2 Mg ha-1, was 20-40 % der beobachteten Ertragsdifferenzen zu erklaren vermochte. Die Unkrautkontrolle sollte vorrangig in den Anbausystemen im Sahel verbessert werden. Bei derzeitigen Applikationsmengen durfte ein verbessertes Dungungsmanagement speziell in der Regenwald- und Savannenzone die Nutzungseffizienz von mineralischem N und somit die Reisertrage erhohen.

Modelling Electromagnetically Levitated Liquid Droplet Oscillations

Abstract: This work comprises accurate computational analysis of levitated liquid droplet oscillations in AC and DC magnetic fields. The AC magnetic field interacting with the induced electric current within the liquid metal droplet generates intense fluid flow and the coupled free surface oscillations. The pseudo-spectral technique is used to solve the turbulent fluid flow equations for the continuously dynamically transformed axisymmetric fluid volume. The volume electromagnetic force distribution is updated with the shape and position change. We start with the ideal fluid test case for undamped Rayleigh frequency oscillations in the absence of gravity, and then add the viscous and the DC magnetic field damping. The oscillation frequency spectra are further analysed for droplets levitated against gravity in AC and DC magnetic fields at various combinations. In the extreme case electrically poorly conducting, diamagnetic droplet (water) levitation dynamics are simulated. Applications are aimed at pure electromagnetic material processing techniques and the material properties measurements in uncontaminated conditions.

Solidification of stainless steel slag by accelerated carbonation

Abstract: On exposure to carbon dioxide (CO2) at a pressure of 3 bars, compacts formed from pressed ground slag, and 12.5 weight percent water, were found to react with approximately 18% of their own weight of CO2. The reaction product formed was calcium carbonate causing the slag to self‐cement. Unconfined compressive strengths of 9MPa were recorded in carbonated compacts whereas strengths of <1 MPa were recorded in non‐carbonated slag compacts. As molten stainless steel slag containing dicalcium silicate (C2S) cools it can undergo several phase transitions. The final transformation from the p‐polymorph to γ‐C2S is accompanied by a volume change that causes the slag to self‐pulverise or ‘dust’. As a consequence of this the fine grained portion of the slag contains more of this phase whilst the coarser particles of the slag contain more of the calcium magnesium silicates that contribute the bulk of the waste. The fine fraction (<125μm) of the slag when ground is found to react to the same extent as the gro...

Characterisation of pumpkin yellow vein mosaic virus from India

Abstract: Yellow vein mosaic disease symptoms occur frequently in pumpkin in India. Diseased plants show vein yellowing, which sometimes coalesces to form chlorotic patches. Infected plants are stunted and flowers drop prematurely, greatly reducing yields. Diseased plants are infected by a begomovirus, designated pumpkin yellow vein mosaic virus (PYVMV), which is transmitted readily and in a persistent manner by the whitefly, Bemisia tabaci. Transmission of PYVMV requires minimum acquisition and inoculation access periods of 30 min and 10 min, respectively. The minimum latent period in the insect is 6 h and the virus persists in the vector for at least 8 days. PYVMV has a narrow host range consisting of a small number of cucurbit species and some tobacco cultivars. It was detected serologically in diseased plants and in viruliferous B. tabaci using polyclonal antibodies in a double-antibody sandwich enzyme-linked immunosorbent assay. Reactions with monoclonal antibodies in a triple-antibody sandwich ELISA showed that PYVMV has an epitope profile distinct from those of other begomoviruses from the Indian sub-continent. Polymerase chain reaction amplified fragments from the putative viral coat and movement protein genes. Based on comparative phylogeny of complete coat protein gene sequences, PYVMV was most similar to to the bipartite Tomato leaf curl New Delhi virus from India and appears to be a new strain of this virus.