Manejo integrado de plagas al servicio de los pequeños campesinos colombianos

Versión en inglés disponible en la Biblioteca Digital del IDRC: Integrated pest management for Colombian small farmersVersión en francés disponible en la Biblioteca Digital del IDRC: Gestion intégrée ou comment ne plus dépendre des pesticide

Dependence of the Electroluminescence on the Spacer Layer Growth Temperature of Multilayer Quantum-Dot Laser Structures

Electroluminescence (EL) measurements have been performed on a set of In(Ga)As-GaAs quantum-dot (QD) structures with varying spacer layer growth temperature. At room temperature and low injection current, a superlinear dependence of the integrated EL intensity (IEL) on the injection current is observed. This superlinearity decreases as the spacer layer growth temperature increases and is attributed to a reduction in the amount of nonradiative recombination. Temperature-dependent IEL measurements show a reduction of the IEL with increasing temperature. Two thermally activated quenching processes, with activation energies of ˜ 157 meV and ˜ 320 meV, are deduced and these are attributed to the loss of electrons and holes from the QD ground state to the GaAs barriers. Our results demonstrate that growing the GaAs barriers at higher temperatures improves their quality, thereby increasing the radiative efficiency of the QD emission

Investigating Plant Physiological Responses to Global Phylogenetic Diversity of Glomeromycotina

Arbuscular mycorrhizal (AM) fungi are ubiquitous symbionts of terrestrial plant species with associations predominantly characterized as mutualistic. In addition to well-documented enhancement of host growth response, more recent analyses have demonstrated the conferral of host benefits under numerous biotic and abiotic stressors. However, much of the established evidence originates from studies involving limited AM fungal diversity. Accordingly, this study sought to evaluate the potential effects of inoculation on plant host physiological traits within a growth chamber environment, investigate potential correlations between host trait responses, & assess the degree of phylogenetic signal observed in trait responses due to the presence of AM fungi. Overall, inoculation did not result in meaningfully different effects in host trait responses relative to controls. The effects of unique inoculum identity were also not meaningfully different from one another, although some instances of deviation from this trend were observed. Trait correlations were also largely absent after accounting for species relatedness. Further, model selection criteria tended to endorse an effect of unique inoculum identity but was not suggestive of effects due to evolutionary history. The presently described experimental implementation of AM phylogenetic diversity, comprising 36 taxa across 8 families, contributes to a greater contextual understanding of the AM symbiosis and offers an approach suitable for future studies

Modelling and extracting periodically deforming objects by continuous, spatio-temporal shape description

This thesis proposes a new model for describing spatio-temporally deforming objects. Through a novel use of Fourier descriptors, it is shown how arbitrary shape description can be extended to include spatio-temporal shape deformation. It is further demonstrated that these new spatio-temporal Fourier descriptors have the ability to be used as the basis for both the recognition and extraction of deforming objects. Application of this new recognition technique to human gait sequences demonstrates recognition rates of over 86% for individual human subjects, signifying that these descriptors possess unique descriptive properties. Based upon the new spatio-temporal Fourier descriptor model, a new technique for the detection and extraction of deforming shapes from an image sequence is presented through a new variant of the Hough transform (the Continuous Deformable Hough Transform) that utilises spatio-temporal shape correlation within an evidence-gathering context. This new technique demonstrates excellent success rates and tolerance to noise, correctly extracting human subjects in image sequences corrupted with noise levels of up to 80%. The technique is also tested extensively using real-world data, thus demonstrating its worth in a modern-day computer vision system. Both the spatio-temporal Fourier descriptor model, the Continuous Deformable Hough Transform, and aspects of their application are fully discussed throughout the thesis, along with ideas and suggestions for future research and development.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Quantum-ionic features in the absorption spectra of homonuclear diatomic molecules

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).We show that additional features can emerge in the linear absorption spectra of homonuclear diatomic molecules when the ions are described quantum mechanically. In particular, the widths and energies of the peaks in the optical spectra change with the initial configuration, mass, and charge of the molecule. We introduce a model that can describe these features and we provide a quantitative analysis of the resulting peak energy shifts and width broadenings as a function of the mass.We acknowledge financial support from the European Research Council Advanced Grant DYNamo (Grant No. ERC-2010-AdG-267374), Spanish Grants No. FIS2013-46159-C3-1-P and No. PIB2010US-00652, and Grupo Consolidado UPV/EHU del Gobierno Vasco (Grant No. IT578-13). A.C.-U. acknowledges financial support from the Departamento de Educacion, Universidades e Investigacion del Gobierno Vasco (Reference No. BFI-2011-26).Peer Reviewe

Light-emitting GaAs nanowires on a flexible substrate

Semiconductor nanowire-based devices are among the most promising structures used to meet the current challenges of electronics, optics and photonics. Due to their high surface-to-volume ratio and excellent optical and electrical properties, devices with low power, high efficiency and high density can be created. This is of major importance for environmental issues and economic impact. Semiconductor nanowires have been used to fabricate high performance devices, including detectors, solar cells and transistors. Here, we demonstrate a technique for transferring large-area nanowire arrays to flexible substrates while retaining their excellent quantum efficiency in emission. Starting with a defect-free self-catalyzed molecular beam epitaxy (MBE) sample grown on a Si substrate, GaAs core–shell nanowires are embedded in a dielectric, removed by reactive ion etching and transferred to a plastic substrate. The original structural and optical properties, including the vertical orientation, of the nanowires are retained in the final plastic substrate structure. Nanowire emission is observed for all stages of the fabrication process, with a higher emission intensity observed for the final transferred structure, consistent with a reduction in nonradiative recombination via the modification of surface states. This transfer process could form the first critical step in the development of flexible nanowire-based light-emitting devices

Making physics outreach more gender inclusive

“Diversity in the Cultures of Physics” was an Erasmus+ funded Strategic Partnership launching several key actions aimed at improving the gender balance in physics and its subfields. The Strategic Partnership consisted of six universities in four countries: Freie Universität Berlin in Germany, Universitat Autònoma de Barcelona and Universitat de Barcelona in Spain, the University of Manchester and the University of Sheffield in the United Kingdom and Uppsala Universitet in Sweden. This flyer provides recommendations and a checklist to make outreach activities in physics more gender inclusive. It is aimed at people already active in outreach activities for young people. The flyer indicates relevant examples of outreach projects, highlights diversity-relevant questions and topics for planning outreach activities and provides a checklist for how outreach events in physics can be made more gender inclusive

Consumers as mental health providers: First-person accounts of benefits and limitations

Community support programs are increasingly establishing paid service positions designated exclusively for consumers. Project WINS (Work Incentives and Needs Study), a hybrid case management-vocational program for individuals with severe mental illness, used consumers as peer support specialists (PSSs) to supplement professional roles. Semistructured interviews were conducted with PSSs about 12 months after their employment ended. They identified substantial personal benefits specific to consumer-designated roles (e.g., a “safe” employment setting with accommodations) and general benefits from employment. Problems described were just as numerous, encompassing attitudes toward assigned peers and costs to their own well-being. Critical commentary addressed program operations (structure, supervision, and training needs) and problems in the mental health system. The authors discuss the changed sense of self that service provider roles can create for consumers and suggest that mental health administrators provide anticipatory socialization for this service innovation throughout their agencies and ongoing supports for consumers in their new roles.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45767/1/11414_2005_Article_BF02287510.pd

Competitive carrier interactions influencing the emission dynamics of GaAsSb-capped InAs quantum dots

The optical properties of InAs/GaAs quantum dots capped with a GaAsSb quantum well are investigated by means of power-dependent and time-resolved photoluminescence. The structure exhibits the coexistence of a type-I ground state and few type-II excited states, the latter characterized by a simultaneous carrier density shift of the peak position and wavelength-dependent carrier lifetimes. Complex emission dynamics are observed under a high-power excitation regime, with the different states undergoing shifts during specific phases of the measurement. These features are satisfactorily explained in terms of band structure and energy level modifications induced by two competitive carrier interactions inside the structure. (C) 2012 American Institute of Physics. (http://dx.doi.org/10.1063/1.4769431