263,213 research outputs found
Sensitive indicators of side-effects of pesticides on the epigeal fauna of Arable land
No full textThe main objective of the present study was to evaluate the possible impact of pesticides on epigeal arthropods in arable land. It was also envisaged to develop a predictive model for possible undesirable effects of pesticides on the epigeal arthropod fauna using an indicator species from the field. The strategy was the following. In the field, species were identified that were (1) sensitive to a number of pesticides, (2) abundant, (3) regular in time and space and (4) easy to sample and identify (Phase I). Two species, the erigonid spiders Oedothorax apicatus (Blackwall) and Erigone atra (Blackwall) were selected for toxicity studies in the laboratory using deltamethrin as a model compound (Phase II). The results of these studies were used to develop a predictive model which was tested under field conditions (Phase III).Phase I: Initial Field ObservationsPhase I was implemented in the South Flevoland Polder, in cooperation with the State Authority for the Development of the Lake IJssel Polders. Observations on the above-ground arthropods were conducted in 17 commercially farmed fields and in one experimental field, from March 1985 to November 1986, during two growing seasons and one winter. The arthropods were sampled by pitfall traps in oilseed rape fields which were treated with a number of insecticides and herbicides, and in cereal fields which were either treated with herbicides or weeded chemically against herbs, at recommended dosages. In the experimental field, dosages were varied and the effect of ploughing was observed. During the treatments in situ bioassays were carried out with captive spiders. From @ 5100 pitfall samples over 200,000 specimens were identified, belonging to 147 taxa. The observed short term effects were the following. A limited number of species were significantly affected by the treatments with insecticides. These were the carabids Clivina fossor after deltamethrin applications and Trechus quadristriatus after fenitrothion, and 7 spider species. The latter were reduced after treatments with either deltamethrin, fenitrothion or bromophos-ethyl. No effects were observed of herbicide treatments. It was also demonstrated, however, that the effect of mechanical disturbance by ploughing was comparable to the strongest effects of insecticides. It was concluded that an assemblage of spider species consisting of Oedothorax apicatus , Erigone atra , E. dentipalpis , Meioneta rurestris and Bathyphantes gracilis may be a sensitive indicator for early detection of side-effects of insecticides. This group represents 80-90% of the erigonid and linyphiid fauna of arable land and they are common throughout North-Western Europe. The most abundant species, E. atra and O.apicatus were selected for further study.Possible long-term effects on the spider fauna have been studied in a transversal study in fields with different cultivation histories. The differences were related to the distance between fields rather than to cultural history. There was one exception: in cereal fields that have, since reclamation, been weeded by harrowing, the spider fauna was considerably poorer than in herbicide treated fields.The effect of deltamethrin on the spiders was observed several times, under different weather conditions. It appeared that the toxicity was highest under hot and dry conditions and low under cold and wet circumstances. This was not in agreement with the known negative temperature-toxicity relationship of pyrethroids and the higher availablity of chemicals from wet surfaces. This relation, therefore, was studied in more detail in the following phase.Phase II: Toxicity studiesThe first step in the analytical phase was the development of new methods for rearing of and toxicity testing with the selected indicators. 0. apicatus females appeared to be the most appropriate species both for rearing and testing.The second step concerned the availablity of deltamethrin to this species under varying environmental conditions. Three routes of exposure were examined: topical application (simulating exposure to spray); uptake via food, and exposure to contaminated surfaces (soil or glass filter). Part of the work was carried out with radio-labelled deltamethrin. It appeared that uptake of residues from a surface by the tarsi is the most important route. Field observations carried out with a fluorescent tracer showed that the direct exposure of the spiders and their prey species to the spray, was very limited. This indicated that in the field as well, direct exposure and oral uptake are of limited importance. The availability of the residue, however, strongly depends on the water content of the soil. A decrease of the soil moisture content to 66 % of the field capacity resulted in a drop of 75 % in availability.The third step concerned the relation between environmental factors, i.e. climate and animal antagonists, and the toxicity of deltamethrin. Toxicity tests carried out under varying moisture and temperature conditions showed that at decreasing air humidity the toxicity increased, at all temperatures tested. The compound is most toxic at a combination of a low air humidity or the absence of drinking water and a high temperature. A negative temperature-effect relationship in the range 10 - 30 °C could be observed only at maximum air humidity. The behaviour of the spiders with regard to the moisture in the environment changed after exposure to sublethal dosages of deltamethrin. Spiders not visibly affected showed an increased preference for wet conditions. Affected spiders, on the other hand, showed a reduced capacity to select moist conditions. Their capacity to escape from predators was also reduced. Analysis of gut contents of the main predator, the carabid beetle P. cupreus , from the fields sampled in Phase I, showed an 8-fold increase in the consumption of linyphiids and erigonids after deltamethrin spraying. A few tests were carried out with both captive and reared spiders. There appeared to be a marked difference in sensitivity between these groups. This was primarily imputed to differences in selection mechanisms between laboratory and field.With these results a regression equation was composed which predicts the toxicity of deltamethrin to O. apicatus females under various weather and soil moisture conditions.Phase III. Validation under field conditionsSimilarly to Phase 1, the field observations of Phase III were carried out in the South Flevoland Polder. A 75 ha field was divided into 27 test plots. These plots were treated three times at different dates, in three replicates, with three dosages of deltamethrin. The following observations were carried out: acute effects in in situ bio assays, activity-density of E. atra and O. apicatus ; deposition of deltamethrin on the soil, on the spiders, on carabid, and on collembola (the main food items of the spiders). Meteorological data were obtained from a near-by meteo station and moisture of the top soil was calculated from data on rainfall, evaporation, and characteristics of the soil and the crop. Only E. atra males were abundant enough at the first and the last spraying date to allow calculation of dose-response relationships. The angles of the regressions appeared to differ for both dates. However, comparison of the observed reduction in O.apicatus females and E. atra males with the toxic effect predicted for O. apicatus females, showed that the laboratory based model had a fair predictive value for the given situation. Apparently erigonid spiders are good indicator species for the assessment of possible undesirable effects of insecticides
Inhibition by lectins of glutamate receptor desensitization is determined by the lectin's sugar specificity at kainate but not AMPA receptors
No full textGroupe B5. - Problèmes régionaux dans les pays à revenu élevé et dans les zones spécifiques
No full textR. Bergmann Denis, Everts I. D. Groupe B5. - Problèmes régionaux dans les pays à revenu élevé et dans les zones spécifiques. In: Économie rurale. N°150-151, 1982. Agriculture et développement régional en Europe, sous la direction de Louis P. Mahé. pp. 118-121
Louis H. Everts: American Atlas Publisher and Entrepreneur
No full textLouis H. Everts was a native of New York, resident of Illinois, and publisher in Chicago, Philadelphia and Buffalo. His life and business practices illustrate the growth and changes in American county map publishing between the post Civil War period and the pre-World War I era
The sugar specificity of lectins affects their influence on the desensitization of glutamate receptor current responses
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Iteratio: Calculating environmental indicator values for species and relevés.
No full textQuestion: Is it possible to translate vegetation maps into reliable thematic maps of site conditions? Method: This paper presents a new method, called Iteratio, by which a coherent spatial overview of specific environmental conditions can be obtained from a comprehensive vegetation survey of a specific area. Iteratio is a database application which calculates environmental indicator values for vegetation samples (relevés) on the basis of known indicator values of a limited number of plant species. The outcome is then linked to a digitalized vegetation map (map of plant communities) which results in a spatial overview of site conditions. Iteratio requires the indicator values of a minimum of 10–20% of the species occurring. The species are given a relative weight according to their amplitudes: species with a narrow range are weighted stronger, species with a broad range are weighted weaker. Conclusion: The method presented here enables a coherent assessment of site conditions on the basis of a vegetation survey and the indicator values of a limited number of plant species
Protecting Animals 36: Author Witi Ihimaera
No full textIn this very special episode of Knowing Animals I am joined by beloved New Zealand author Witi Ihimaera. Witi has written many books featuring nonhuman animals. He offers us a non-colonial lens through which to think about the human/nonhuman relationship
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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