366,834 research outputs found

    The dynamic electric polarizability of a particle bound by a double delta potential

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    In this paper we derive an expression for the dynamic electric polarizability of a particle bound by a double delta potential for frequencies below and above the absolute value of the particle's ground state energy. The derived expression will be used to study some of the fundamental features of the system and its representation of real systems. In addition we derive a general expression of the dynamic electric polarizability for a potential of multi-delta functions.Comment: 11 pages, 5 figure

    The static electric polarizability of a particle bound by a finite potential well

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    In this paper we derive an expression for the static electric polarizability of a particle bound by a finite potential well without the explicit use of the continuum states in our calculations. This will be accomplished by employing the elegant Dalgarno-Lewis perturbative technique.Comment: 14 Pages, 2 Table


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    Intercropped crops represent an important production system in organic farming, especially maize/climbing bean mixture due to its high content of protein in bean seeds for human diet, and producing silage for ruminants. To test this hypothesis, the effects of maize (Zea mays L.) sown as a sole crop and maize/climbing bean (Phaseolus vulgaris L. cv. Cipro) mixtures on maize plant height, maize leaf area index, bean leaf area index and grain yield were investigated in field experiments on an organic farm following accepted rules of certification. The maize/climbing bean mixture increased maize plant height as well as maize and bean leaf area and reduced maize grain yield in comparison with maize sown as sole crop, but 477.5 kg ha-1seed yield of bean sown in mixture was obtained. Maize was a stronger competitor than bean. The overall conclusion is that maize/bean mixture has promise for producing valuable yield of maize and bean, but mixtures needs further investigation

    Terra Nova​: Enacting Videogame Development through Indigenous-Led Creation

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    Indigenous peoples have had a rich tradition of utilizing digital media to tell their stories in new ways. These stories often run counter to popular Western-centric narratives that perpetually position Indigenous peoples as only existing in the past. Indigenous peoples are regularly forgotten as participants of the technological world, but we are also both players and producers of videogames. Indigenous videogames can express something about specific Indigenous communities and cultural contexts or can be made by Indigenous individuals who wish to communicate their own unique narratives through the medium. This research-creation project studies these aspects of Indigenous videogames in detail through the production of my own videogame, ​Terra Nova​, alongside a written survey of the field, contextualization of the videogame itself, and reflections on the game and the creation process. Through the production of a videogame as its primary form of research, this project seeks to draw attention to how and why Indigenous peoples are making videogames on their own terms to answer the question of what makes a videogame Indigenous

    Coping with Ex-ante Regulations for Planting Bt Maize: The Portuguese Experience

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    This article investigates the attitude and practices of Bt and non-Bt maize farmers in Portugal. Thirty-seven Bt maize farmers were interviewed, representing 22.5% of the total number of Bt maize notifications in the country and 31.5% of the total area planted with Bt maize in 2007. Additionally, 66 non-Bt maize farmers were surveyed in an attempt to investigate their opinion on the Bt technology, its viability, and its future. The most interesting finding is that almost half of all the surveyed maize farmers stated that the ex-ante regulations are rigid and difficult to appl

    Co-existence in maize supply chains in Spain and Switzerland

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    The debate about co-existence usually focuses on the situation of neighbouring farms. Organic producers take the position that co-existence affects the whole supply chain. Therefore, this paper compares the maize grain supply chains in Switzerland and Spain in order to identify which factors influence the segregation of genetically modified (GM) maize from non-GM maize, and discusses how organic production copes with the challenge of GM maize. Considerable differences exist between Spain and Switzerland with regard to grain maize as a component of animal feed. In Spain, where GM maize is grown, it is the feed industry that defines standards in the supply chains. Since the trading co-operatives are unable to supply GM-free maize, independent and separate infrastructures have been developed for a GM-free maize supply (e.g. for maize starch). In Switzerland, the retailers define quality standards for suppliers, and these standards exclude the use of GM plants for feed. Therefore, the feed industry has to segregate GM from non-GM feed

    A method to search for optimal field allocations of transgenic maize in the context of co-existence

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    Spatially isolating genetically modified (GM) maize fields from non-GM maize fields is a robust on-farm measure to keep the adventitious presence of GM material in the harvest of neighboring fields due to cross-fertilizations below the European labeling threshold of 0.9%. However, the implementation of mandatory and rigid isolation perimeters can affect the farmers' freedom of choice to grow GM maize on their fields if neighboring farmers do not concur with their respective cropping intentions and crop plans. To minimize the presence of non-GM maize within isolation perimeters implemented around GM maize fields, a method was developed for optimally allocating GM maize to a particular set of fields. Using a Geographic Information System dataset and Monte Carlo analyses, three scenarios were tested in a maize cultivation area with a low maize share in Flanders (Belgium). It was assumed that some farmers would act in collaboration by sharing the allocation of all their arable land for the cultivation of GM maize. From the large number of possible allocations of GM maize to any field of the shared pool of arable land, the best field combinations were selected. Compared to a random allocation of GM maize, the best field combinations made it possible to reduce spatial co-existence problems, since at least two times less non-GM maize fields and their corresponding farmers occurred within the implemented isolation perimeters. In the selected field sets, the mean field size was always larger than the mean field size of the common pool of arable land. These preliminary data confirm that the optimal allocation of GM maize over the landscape might theoretically be a valuable option to facilitate the implementation of rigid isolation perimeters imposed by law.
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