Flow experiences at work: for high need achievers alone?

Applying Csikszentmihalyi's ( 1990 ) flow theory of optimal experience to the workplace, two studies examined the relationships of employees' perceived skill and challenge at work and need for achievement with their positive mood, intrinsic task interest, and extra‐role performance. Among achievement‐oriented employees only, high skill and challenge was associated with greater positive mood, task interest, and performance than other skill/challenge combinations. Additionally, positive mood mediated the interactive relationship of skill/challenge and need for achievement with performance. Copyright © 2005 John Wiley & Sons, Ltd.     

Mechanism of toxicity of ionic copper and copper complexes to algae

The mechanism of toxicity of ionic copper and copper complexes to growth, photosynthesis, respiration, ATP levels and mitochondrial electron-transport chain-activity in two marine diatoms, Nitzschia closterium (Ehrenberg) W. Smith (Hasle, 1964) and Asterionella glacialis Castracane, and one freshwater green alga, Chlorella pyrenoidosa Chick was investigated. Copper ions depressed both cell division and photosynthesis in A. glacialis and C. pyrenoidosa, whereas ionic copper concentrations which were inhibitory to cell division in N. closterium had no effect on photosynthesis, respiration, ATP production, electron transport or membrane ultrastructure. This suggests that in N. closterium, copper does not act on the chloroplast, the mitochondrion, or the cell membrane, since if it did, the above parameters should be affected. Copper-ethylxanthogenate was exceptional amongst the copper complexes in that it stimulated respiration, mitochondrial electrontransport and ATP formation in N. closterium under conditions of strongly inhibited cell division and slightly stimulated photosynthesis. Ionic copper toxicity may result from an intracellular reaction between copper and reduced glutathione (GSH), leading to a lowering of the GSH:GSSG ratio and suppression of mitosis. In addition, copper inhibits the enzyme catalase and reduces cell defence mechanisms against H₂O₂ and oxygen-free radicals. Lipid-soluble copper complexes are more toxic than ionic copper because both the metal and the ligand are introduced into the cell. Toxicity of ionic copper is ameliorated by trivalent metal ions in the growth medium, including those of Mn, Co, Al, Fe and Cr which form a layer of metal (III) hydroxide around the algal cell, adsorb copper and reduce its penetration into the cell. The degree of insolubility of the metal (III) hydroxide is related to its ability to protect against copper toxicity. In addition, manganese and cobalt catalytically scavenge damaging H₂O₂ and superoxide radicals, respectively, produced by the cell.     

Use patterns of natural resources supporting livelihoods of smallholder communities and implications for climate change adaptation in Zimbabwe

Declining crop and livestock production due to a degrading land resource base and changing climate among other biophysical and socio-economic constraints, is increasingly forcing rural households in Zimbabwe and other parts of Southern Africa to rely on common natural resource pools (CNRPs) to supplement their household food and income. Between 2011 and 2013, we combined farmer participatory research approaches, remote sensing and geographic information systems (GIS) to (1) understand the contribution of CNRPs to household food and income in Dendenyore and Ushe smallholder communities in Hwedza District, eastern Zimbabwe and (2) assess changes of the CNRPs in both space and time, and their implications on climate change adaptation. Across study sites, wetlands and woodlands were ranked as the most important CNRPs. Extraction and use patterns of products from the different pools differed among households of different resource endowment. Resource-constrained households (RG3) sold an average of 183 kg household^?1 year^?1 of wild loquats fruits (Uapaca kirkiana), realising about US$48, while resource-endowed farmers (RG1) had no need to sale any. The RG3 households also realised approximately US$70 household^?1 year^?1 from sale of crafts made from water reeds (Phragmites mauritianus). Empirical data closely supported communities’ perceptions that CNRPs had declined significantly in recent years compared with two to three decades ago. More than 60 % of the respondents perceived that the availability of natural resources drawn from wetlands and woodlands, often used for food, energy and crafts, has decreased markedly since the 1980s. Classification of land cover in a GIS environment indicated that CNRPs declined between 1972 and 2011, supporting farmers’ perceptions. Overall, woodlands declined by 37 % in both communities, while the total area under wetlands decreased by 29 % in Ushe, a drier area and 49 % in Dendenyore, a relatively humid area. The over-reliance in CNRPs by rural communities could be attributed to continued decline in crop yields linked to increased within-season rainfall variability, and the absence of alternative food and income sources. This suggests limited options for rural communities to adapt to the changing food production systems in the wake of climate change and variability and other challenges such as declining soil fertility. There is therefore a need to design adaptive farm management options that enhance both crop and livestock production in a changing climate as well as identifying other livelihood alternatives outside agriculture to reduce pressure on CNRPs. In addition, promotion of alternative sources of energy such as solar power and biogas among rural communities could reduce the cutting of trees for firewood from woodlands.     

Atmospheric pollution in an urban environment by tree bark biomonitoring - part II: Sr, Nd and Pb isotopic tracing

The harmful effect of manmade particles on natural processes and human health is documented by a large number of studies showing a positive correlation between particulate matter (PM) concentration and health effects. Diminution of this health risk necessitates among others the precise knowledge of the particle sources, their physical and chemical properties and their dissemination in the environment. Pb isotope ratios have been successfully used during the past decades as tracers of anthropogenic Pb disseminated in the biosphere. Here we show that tree bark biomonitoring with lead (Pb), strontium (Sr) and neodymium (Nd) isotope ratios as tracers allow a thorough analysis of the impacts of industrial and other anthropogenic emissions on the urban environment. This is the first comprehensive multi-isotope tracer study of atmospheric pollution in an urban environment allowing to identify and to integrate the different plume paths of emissions in a digital map system. This innovative approach might become an important tool for environmental management and policy-making processes dealing especially with risks and surveillance of air quality in the urban environment.     

Different Pla Grafting Techniques on Chitosan

PLA grafting on chitosan has been successfully prepared with two different methods: a direct grafting method and the ROP method. The thermal properties showed that the copolymerization of PLA on the chitosan’s chain by direct grafting is more thermostable than the one obtained by the ROP method.     

Development and evaluation of the Lake Macroinvertebrate Integrity Index (LMII) for New Jersey lakes and reservoirs

In response to the recent focus by the U.S. EnvironmentalProtection Agency on bioassessment of lakes, a multimetric index was developed for New Jersey lakes and reservoirs using benthicmacroinvertebrates. Benthic samples were collected fromreference and impaired lakes with muck and intermediate sedimentsin central and northern New Jersey during summer 1997. We used astepwise process to evaluate properties of candidate metrics andselected five for the Lake Macroinvertebrate Integrity Index(LMII): Hilsenhoff Biotic Index (HBI), percent chironomidindividuals, percent collector-gatherer taxa, percentoligochaetes/leeches, and number of Diptera taxa. We scoredmetrics as the fraction of the best expected value (based on allsites) achieved at a site and summed them into the LMII. Evaluation of the LMII showed that it discriminated well betweenreference and impaired lakes and was strongly related to severalpotential stressors. Chemical and physical gradients distinguished between reference and impaired lakes, and the LMIIsummarized these gradients well. The LMII corresponded stronglywith land use, but some lakes with more urban land use stillachieved high scores. Based on a power analysis, the ability ofthe LMII to detect differences in condition was sensitive to thenumber of samples from each lake.     

Fine atmospheric particles emitted by industrial,traffic and urban sources in France: characterization and genotoxicity

Health risks associated with inhalation of fine particulate matter of 2.5 µm in diameter or smaller depend on their atmospheric levels and physicochemical properties. The relationships between chemical compositions and genotoxic activities of particles emitted by mineral industries, traffic and urban sources during summer and winter in the region of Provence-Alpes-Côte d'Azur (France) were investigated.

The fine particles were separated in respect to water-soluble (13 minerals and metals) and organic-extractable (16 polycyclic aromatic hydrocarbons) components that were quantified. The chromosome damaging properties of the hydrophilic and lipophilic extracts were assessed using the centromeric micronucleus assay on a human lung fibroblast cell line.

The composition of the fine particulate matter was variable and depended upon the sources and seasons. Both the hydrophilic and lipophilic extracts induced chromosome damage: (1) in hydrophilic extracts, Ca and Zn affected chromosome losses induction; (2) acenapthylene affected chromosome damage (breakages and losses) induction and naphthalene affected chromosome damage and losses induction in lipophilic extracts without metabolic activation; and (3) benzo[a]pyrene affected chromosome losses induction in lipophilic extracts with metabolic activation. Fine particulate matter arising from coal-fired power station, road traffic, and other urban sources were the most efficient to induce chromosome breakage.     

Gating in grapevine: relationship between application of the fungicide fludioxonil and circadian rhythm on photosynthesis

The aim of this study was to determine the impact of the fludioxonil (fdx) fungicide on the diurnal fluctuation in grapevine photosynthesis. Therefore, fdx treatment was performed at the end of flowering, at 8 am, 12 am or 7 pm. The study was performed in experimental field and several photosynthesis parameters were followed one day after treatment. Morning fdx treatment induced (i) a significant and simultaneous drop of both photosynthesis (Pn) and stomatal conductance between 8 am and 4 pm and (ii) an increase of intercellular CO₂ concentration when compared to control plants. On the contrary, evening fdx treatment did not affect Pn whereas midday treatment caused Pn increase after 4 pm. These data suggest that (i) morning fdx treatment results in a non-stomatal limitation of Pn, (ii) midday treatment is more suitable to treat grapevine with fdx and (iii) a phenomenon of gating was noticed.