1,410 research outputs found
De week van ... Daniël Rodenburg
No full textDaniel Rodenburg is een eerstejaars student bestuurskunde die vorig jaar enthousiast werd voor de studie na het lopen van de bestuurskunde tweedaagse, georganiseerd door de B .LL. Intussen heeft Daniel zich helemaal gestort in de studentenwereld van Leiden. Naast zijn studie bestuurskunde is Daniel actief bij de B.I.L. en lid van studentenvereniging L.V.V.S. Augustinus. Wij van de Bestuurskundige Berichten mochten een week meelopen
Polychlorinated biphenyls in pigments: inadvertent production and environmental significance
No full textPolychlorobiphenyls are toxic, bioaccumulative, and persistent chemicals whose intentional manufacture has been banned throughout the developed world. Polychlorobiphenyls may be generated inadvertently during the production of certain pigments, including diarylides. This inadvertent production is allowed under various regulatory schemes, such as the Toxic Substances Control Act in the United States and the Stockholm Convention on Persistent Organic Pollutants. Generally, these regulations require polychlorobiphenyl levels in batches of pigment to be less than certain regulatory limits, usually 50 ppm. A growing body of evidence suggests that the use of pigments is dispersing polychlorobiphenyls throughout the environment. Polychlorobiphenyl congeners associated with pigments have been found throughout the United States in sediments and in surface waters at levels exceeding the prevailing water quality standards. A recent Japanese government study reported measured polychlorobiphenyl concentrations well above 50 ppm in several commercial batches of azo pigments. A strong case may thus be argued that pigment manufacturers should modify existing production processes to reduce, ideally prevent, the formation of polychlorobiphenyls, or develop new pigments that a collaboration involving environmental scientists (LR and JG) and a pigment chemist (RC), reviews the evidence for environmental contamination from inadvertent polychlorobiphenyl production in specific pigments, together with a rationalisation of the conclusions based on the reaction mechanisms involved in their manufacture. Broad measures are proposed that might address these issues, both from environmental and from chemical perspectives.Peer reviewe
Adapting weed management in rice to changing climates
No full textThis paper provides some of the scientific background on how projected environmental conditions could affect weeds and weed management in rice in Africa. Elevated CO2 levels may have positive effects on rice competitiveness with C4 weeds, but these are generally outnumbered by C3 species in weed populations of rice in Africa. Moreover, higher temperatures and drought will favor C4 over C3 plants. Increased CO2 levels may also improve tolerance of rice against parasitic weeds, while invasiveness of such species may be stimulated by soil degradation and more frequent droughts or floods. Elevated CO2 may increase belowground relative to aboveground growth, in particular of perennial (C3) species, rendering mechanical control less effective or even counterproductive. Increased CO2 levels, rainfall and temperature may also reduce the effectiveness of chemical control. The implementation of climate change adaptation technologies, such as drought-tolerant germplasm and water-saving irrigation regimes, will also have consequences for rice–weed competition. Rainfed production systems are hypothesized to be most vulnerable to direct effects of climate change (e.g. changes in rainfall patterns) and are likely to face increased competition from C4 and parasitic weeds. Bioticstress- tolerant rice cultivars to be developed for these systems should encompass weed competitiveness and parasitic-weed resistance. In irrigated systems, indirect effects will be more important and weed management strategies should be diversified to lessen dependency on herbicides and mechanical control, and be targeted to perennial rhizotomous (C3) weeds. Water-saving production methods that replace the weed-suppressive flood water layer by intermittent or continuous periods of aerobic conditions, necessitate additional weed management strategies to address the inherent increases in weed competition
A comprehensive Monte Carlo calculation of dopant contrast in secondary electron imaging
No full textTwo-dimensional dopant mapping using secondary electrons in a scanning electron microscope is a useful and rapid technique for studying dopant distributions with high spatial resolution in semiconductor materials and devices. However, it has not yet found wide spread application because the quantification of dopant concentrations currently lacks a firm theoretical model. This paper addresses the issue by means of Monte Carlo modelling. We demonstrate that by taking account of the electron affinity in Monte Carlo simulations to calculate the secondary electron emission from doped silicon the dopant contrast can be explained. This paper also provides a firm theoretical model about the existence of surface effects in dopant contrast imaging
Effect of layers housing system on the quality and microbiological safety of eggs
No full textEffect of layers housing system on the quality and microbiological safety of egg
Bioluminescence in Product Design: Design Guidelines for Cultivation and Perpetuation
No full textIntegrating living organisms in design could offer alternative and more sustainable ways of producing and using products. The use of bioluminescent organisms in design is a relatively new and unknown subject. Because of this, interested designers have a lot of homework to do before starting the actual design process. Successfully changing the organisms habitat from nature to a user’s home and provoking the desired luminescence depends on specific biological and environmental requirements. The aim of this graduation project is to provide interested designers with guidelines on the cultivation and perpetuation of bioluminescent organisms when integrated into a consumer product. The first step is to gather information on two bioluminescent organisms, P. fusiformis and P. phosphoreum, in an extensive literature research. This results in design insights which compare both organisms on the challenges and potential when integrated in a consumer product. The second step continues with the most promising organism, P. phosphoreum. This organism is used within experiments further researching the bioluminescent and perpetuation characteristics, relating them to usage and storage possibilities. The experiment results are translated into design insights. The third step is to combine the design insights from both the literature research and the conducted experiments into guidelines which will help and inspire interested designers in the creation of products with integrated bioluminescent organisms. The guidelines are applied within a future scenario which will act as an example on how P. phosphoreum could be integrated within a design.Integrated Product Desig
Voice work: Synergy of approaches
No full textThis thesis presents a translation of selected texts and excersises concerning voice work shaped by Patsy Rodenburg. Rodenburg is a reknown voice coach and lecturer. The author of this thesis compares Rodenburg's approach, which she got acquainted with during her four-month stay at Regent's University in London in 2013, with an approach taught at the Department of Authorial Creativity and Pedagogy at the Academy of Performing Arts in Prague. This thesis is an attempt to combine different approaches to voice work into a holistic methodology, as the author describes her own experience in this field - both as a student and a lecturer
Vocal schizophrenia or conscious flexibility? : owning the voice in the South African context
No full textIncludes abstract.Includes bibliographical references (leaves 56-60).This thesis questions how and why certain South African performers habitually and unconsciously shift accent in the performance context. I refer to this vocal action as habitual, unconscious accent-based speech adaptation. This examination is made considering that contemporary voice training at the Drama Department of the University of Cape Town (UCT), where the author locates, does not designate any accent as a criterion for performance. Whilst I do not contend habitual, unconscious accent-based speech adaptation to be language-specific this research is English-based. Habitual, unconscious accent-based speech adaptation highlights three primary concerns: the first I term an 'ossification' of sound producing vocal inflexibility; the second is potential class-based exclusion from the performance context; and the third concern is a need for critical awareness in training and performance, evidenced by the preceding concerns. Despite accent-based speech adaptation paradoxically demonstrating the voice's flexibility, when accent-based speech adaptation happens unconsciously and habitually the real flexibility of the voice is negated producing detachment from the performer's own vocal identity or 'vocal schizophrenia' (Rodenburg, 2001: 81)
Challenges for weed management in African rice systems in a changing climate
No full textGlobal changes including increases in temperature, atmospheric greenhouse gases, soil degradation and competition for land and water resources, will have multiple impacts on rice production systems in Africa. These changes will affect weed communities, and management approaches must be adapted to take this into account. Higher temperatures and limited water availability will generally advantage C4 over C3 plants (e.g. rice). Conversely, elevated carbon dioxide (CO2) levels will improve the competitiveness of rice relative to C4 weeds, which comprise many of the problem weeds of rice. Increased atmospheric CO2 levels may also improve tolerance of rice against parasitic weeds, while prevalence of parasitic species may be amplified by soil degradation and more frequent droughts or floods. Elevated CO2 levels tend to promote growth below-ground relative to above-ground, particularly in perennial (C3) species. This may render mechanical control of weeds within a cropping season less effective or even counterproductive. Increased CO2 levels, rainfall and temperature may also reduce the effectiveness of chemical control, while the implementation of adaptation technologies, such as water-saving irrigation regimes, will have negative consequences for rice–weed competition. Rain-fed production systems are prevalent throughout Africa and these are likely to be most vulnerable to direct effects of climate change (e.g. higher temperatures and changes in rainfall patterns). Effective weed management strategies in these environments could encompass off-season tillage, the use of well-adapted cultivars (i.e. those with drought and heat tolerance, high weed competitiveness and parasitic weed resistance or tolerance) and rotations, intercropping or short, off-season fallows with weed-suppressive legumes including those that suppress parasitic weeds. In irrigated, non-flooded rice systems, weeds are expected to become more serious. Specifically, perennial rhizomatous C3 weeds and species adapted to hydromorphic conditions are expected to increase in prevalence. By implementing an integrated weed management strategy primarily targeted at weed prevention, dependency on flood water, herbicides and mechanical control can be lessened. Off-season deep tillage, stale seed bed techniques, use of clean seeds and irrigation water, competitive cultivars, timely transplanting at optimum spacing and judicious fertilizer timings are suitable candidate components for such a strategy. Integrated, novel approaches must be developed to assist farmers in coping with the challenges of weed control in the futur
Across-Line SNP Association Study for Direct and Associative Effects on Feather Damage in Laying Hens
No full textAn association study between SNP markers and feather condition score on the back, rump and belly of laying hens was performed. Feather condition score is a measure of feather damage, which has been shown to be closely related to feather pecking behaviour in hens housed in groups. A population of 662 hens was genotyped for 1536 SNPs of which 1022 could be used for the association study. The analysis was conducted across 9 different lines of White Leghorn and Rhode Island Red origin. Across lines linkage disequilibrium is conserved at shorter distances than within lines; therefore, SNPs significantly associated with feather condition score across lines are expected to be closer to the functional mutations. The SNPs that had a significant across-line effect but did not show significant SNP-by-line interaction were identified, to test that the association was consistent across lines. Both the direct effect of the individual’s genotype on its plumage condition, and the associative effect of the genotype of the cage mates on the individual’s plumage condition were analysed. The direct genetic effect can be considered as the susceptibility to be pecked at, whereas the associative genetic effect can be interpreted as the propensity to perform feather pecking. Finally, 11 significant associations between SNPs and behavioural traits were detected in the direct model, and 81 in the associative model. A role of the gene for the serotonin receptor 2C (HTR2C) on chromosome 4 was found. This supports existing evidence of a prominent involvement of the serotonergic system in the modulation of this behavioural disorder in laying hens. The genes for IL9, IL4, CCL4 and NFKB were found to be associated to plumage condition, revealing relationships between the immune system and behaviour
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