737 research outputs found
A moment's eigenvalue quantization for difference equation models, 1987
No full textFinite difference equations abound in all areas of physics and engineering. In particular, linear difference equation eigenvalue problems define an important class of systems which have been studied through various traditional approaches adapted from continuum space methods. We studied an important subclass of problems involving strong coupling potential interactions which are not amenable to conventional analysis, such as ordinary perturbation theory. We worked with a powerful eigenvalue moment method, developed by Handy et al (C.R. Handy, D. Bessis and T. Morley, Atlanta University preprint, 1987), for generating rapidly converging lower and upper bounds to the eigenvalues of such systems, as previously described. This type analysis focuses on the signature structure of the intended solution in order to define a moment problem. Through the relevant moment problem theorems, tight constraints can be defined which serve to determine (quantize) the physical parameters of the system
Measurement of eotaxin (CCL11) in induced sputum supernatants: validation and detection in asthma
No full textBackground
Induced sputum is widely used in asthma research; however, for many mediators, the detection methods have not been validated.Objective
We sought to optimize the method of detection of eotaxin, an important chemokine acting through the CCR3 receptor on eosinophils, basophils, and TH2 cells.Methods
Induced sputum from normal and asthmatic subjects was processed with dithioerythritol (DTE) or PBS; recovery of eotaxin was assessed by means of ELISA before and after spiking with recombinant eotaxin. Furthermore, the effects of removing DTE by means of ultrafiltration or the addition of protease inhibitors and high-speed centrifugation on endogenous levels and spiking recovery of eotaxin were assessed.Results
Endogenous eotaxin was undetectable in DTE-processed samples, with a mean of only 30% (SD, 13%) spike recovery. DTE had no effect on the immunoassay capture antibody but dramatically reduced the detection of recombinant eotaxin. Removal of DTE from sputum before immunoassay did not improve detection, although it restored the recovery of a subsequent eotaxin spike. In contrast, PBS-processed sputum resulted in an eotaxin spike recovery of 101% (SD, 20%). Addition of protease inhibitors or high-speed centrifugation had no effect on eotaxin detection. By using this optimized protocol, eotaxin levels in PBS-processed sputum samples were found to be significantly increased in asthmatic sputum (P<.05).Conclusion
Measurement of eotaxin by means of immunoassay is adversely affected by DTE, possibly through irreversible denaturation of epitopes, which makes eotaxin undetectable by using the immunoassay antibody. Sputum samples should be processed into PBS for assessment of eotaxin, which is present at increased levels in asthmatic sputum. <br/
Nanomaterials in the environment: behavior, fate, bioavailability, and effects
No full textArticle first published online: 9 DEC 2009The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed.Stephen J. Klaine, Pedro J.J. Alvarez, Graeme E. Batley, Teresa F. Fernandes, Richard D. Handy, Delina Y. Lyon, Shaily Mahendra, Michael J. McLaughlin, and Jamie R. Lea
INSIdE NANO: a systems biology framework to contextualize the mechanism-of-action of engineered nanomaterials
No full textEngineered nanomaterials (ENMs) are widely present in our daily lives. Despite the efforts to characterize their mechanism of action in multiple species, their possible implications in human pathologies are still not fully understood. Here we performed an integrated analysis of the effects of ENMs on human health by contextualizing their transcriptional mechanism-of-action with respect to drugs, chemicals and diseases. We built a network of interactions of over 3,000 biological entities and developed a novel computational tool, INSIdE NANO, to infer new knowledge about ENM behavior. We highlight striking association of metal and metal-oxide nanoparticles and major neurodegenerative disorders. Our novel strategy opens possibilities to achieve fast and accurate read-across evaluation of ENMs and other chemicals based on their biosignatures
Avaliação do destino e efeitos de nanomateriais metálicos e óxido metálicos em organismos dulçaquícolas
No full textEngineered nanomaterials (ENMs), namely silver (Ag) and copper oxide (CuO) ENMs, are widely applied in diverse fields such as biomedical, sensors, food packaging, textiles, cosmetics, environmental remediation, etc. Through different pathways, these ENMs might enter in freshwater ecosystems and affect aquatic biota, in particular plants and fish. Although their bulk counterparts (salt metals) have well known mechanisms of toxicity, it is crucial to understand if the nano scale properties result in distinct effects to freshwater organisms. Thus, the main objective of this thesis was to assess the effects of ENMs to aquatic biota, using silver (Ag) ENMs and copper oxide (CuO) ENMs as representatives of metal (Me) and (MeO) ENMs, respectively. This work focused on the effect of different characteristics of ENMs (e.g. surface coating) on their toxicity to the aquatic organisms Lemna minor and zebrafish (Danio rerio), as model species of aquatic plants and fish. In particular, this work aimed to address the following questions: Are ENMs more toxic than the respective salt metals (AgNO₃ and CuSO₄)? Is toxicity of Ag ENMs affected by their characteristics (e.g. surface coatings as citrate or polyvinylpyrrolidone (PVP))? Do the effects of Ag ENMs to L. minor change over time? Are the effects of both Ag ENMs and CuO ENMs similar to zebrafish embryos? Can chorion hinder the entry of ENMs inside fish embryos? Do ENMs induce osmoregulatory stress in fish embryos and oxidative stress in both model organisms? Experimental data showed that ENMs were less toxic than the respective salt metals (AgNO₃ and CuSO₄) in both species, L. minor and zebrafish. Surface coating influenced Ag ENMs effects in L. minor, as citrate affected more pronouncedly Guaiacol peroxidase (GPox) and Glutathione-S-transferase (GST) activities, whereas PVP influenced more the growth rate and the number of fronds per colony. The effects of Ag ENMs to L. minor changed over time, as an ameliorative effect was noticed after 14 days (d) of exposure, compared to 7d of exposure.
In zebrafish embryos, chorion had a protective effect against ENMs. Indeed, bioavailability of both Ag ENMs and CuO ENMs to the zebrafish embryos was very low, where most of total metal (>99% and 94%, respectively) was associated to the chorion. the same trend that occurred for AgNO₃ (96% of total metal), but not for CuSO₄, where only 58% (total metal) was associated to the chorion. Osmoregulatory stress showed a nano-specific effect (i.e. more significant effects in ENMs than in the salt metal) for Ag ENMs but not for CuO ENMs. Moreover, a mild oxidative stress was triggered by both Ag and CuO ENMs, where a depletion of total glutathione (GSH) also had a nano-specific effect. Overall, results suggest that ENMs tend to be less toxic than the respective salt metals, and highlight their ability to cause oxidative stress to both aquatic species, further showing that some toxic effects are nano-specific.
The lower toxicity of Ag ENMs compared to the bulk salt was further confirmed using Species Sensitive Distributions (SSD). The hazardous concentration for 5% of species (HC₅) values was 13-fold lower for Ag NMs than for AgNO₃ (0.089 μg L⁻¹ and 0.007 μg L⁻¹, respectively). The most sensitive species for both Ag forms were cladocerans (Daphniidae). Predicted no effect concentration (PNEC) values were 0.045 μg L⁻¹ for Ag ENMs and 0.007 μg L⁻¹ for AgNO₃. Risk quotient (RQ) was 6.3 (>1) for AgNO₃ and 0.03 for Ag ENMs (<1), which suggests that the existing metal risk assessment could be extrapolated to the ENMs. Nevertheless, ENMs have a distinct mechanism of action than the salt metals. Furthermore, the diversity of ENMs characteristics (e.g. surface coating) requires further toxicological studies aiming to improve the knowledge on ENMs toxicity and risk assessment.Os nanomateriais de síntese (ENMs), nomeadamente de prata (Ag) e óxido de cobre (CuO), são amplamente utilizados em diversos campos, como biomedicina, sensores, embalagens de alimentos, têxteis, cosméticos, remediação ambiental, etc. Através de diferentes vias, entram nos ecossistemas dulçaquícolas e afetam a biota aquática, em particular plantas e peixes. Embora os respetivos sais metálicos tenham mecanismos de toxicidade bem conhecidos, é crucial entender se as propriedades da escala nano resultam em efeitos distintos nos organismos dulçaquícolas. Assim, o principal objetivo desta tese foi avaliar os efeitos das ENMs na biota aquática, usando ENMs de prata (Ag ENMs) e ENMs de óxido de cobre (CuO ENMs) como representantes de ENMs metálicas (Me) e ENMs de óxido metálico (MeO), respectivamente. Este trabalho focou-se no efeito de diferentes características dos ENMs (por exemplo, revestimento de superfície) na toxicidade para os organismos aquáticos Lemna minor e zebrafish (Danio rerio), como espécies modelo de plantas aquáticas e peixes. Em particular, este trabalho visou abordar as seguintes questões: os ENMs são mais tóxicos do que os respectivos sais metálicos (AgNO₃ e CuSO₄)? A toxicidade de Ag ENMs é afectada pelas suas características (por exemplo, revestimentos superficiais como citrato ou polivinilpirrolidona (PVP))? Os efeitos dos Ag ENMs sobre a L. minor mudam com o tempo? Os efeitos dos Ag ENMs e de CuO ENMs no organismo dos embriões de peixe-zebra são semelhantes entre si? O córion pode impedir a entrada de ENMs dentro de embriões de peixes? Os ENMs induzem stress osmorregulatório em embriões de peixe e stress oxidativo em ambos os organismos modelo?
Os dados experimentais mostraram que os ENMs foram menos tóxicos do que os respetivos sais metálicos em ambas as espécies, L. minor e peixe-zebra. O revestimento superficial influenciou os efeitos dos ENMs de Ag na L. minor, pois o citrato afetou mais pronunciadamente as atividades da guaiacol peroxidase (GPox) e glutationa-S-transferase (GST), enquanto que o PVP influenciou mais a taxa de crescimento e o número de frondes por colónia. Os efeitos dos Ag ENMs sobre a L. minor mudaram ao longo do tempo, pois após 14 dias (d) de exposição foi notado um efeito atenuador, comparativamente aos 7d de exposição.O córion dos embriões de peixe-zebra teve um efeito protetor contra ENMs. De fato, a biodisponibilidade de Ag ENMs e de CuO ENMs nos embriões de peixe-zebra foi muito baixa, onde a maior parte do metal total (>99% e 94%, respetivamente) foi associada ao córion; a mesma tendência que ocorreu para AgNO₃ (96% do metal total), mas não para CuSO₄, onde apenas 58% (metal total) estava associado ao córion. O stress osmorregulatório mostrou um efeito nanoespecífico (ou seja, efeitos mais significativos nos ENMs do que no sal metálico) para Ag ENMs, mas não para CuO ENMs. Além disso, os Ag ENMs e os CuO ENMs desencadearam stress oxidativo moderado, onde a depleção de glutationa (GSH) total também teve um efeito nanoespecífico. No geral, os resultados sugerem que os ENMs tendem a ser menos tóxicos do que os respetivos sais metálicos e destacam a sua capacidade de causar stress oxidativo para ambas as espécies aquáticas, mostrando ainda que alguns efeitos tóxicos são nanoespecíficos.
A menor toxicidade dos Ag ENMs em comparação com o sal metálico foi ainda confirmada usando a Distribuição da Sensibilidade das Espécies (SSD). O valor da Concentração Perigosa para 5% das Espécies (HC₅) dos Ag ENMs foi 13 vezes inferior ao do AgNO₃ (0,089 μg L⁻¹ e 0,007 μg L⁻¹, respetivamente). As espécies mais sensíveis para ambas as formas de Ag foram os cladóceros (Daphniidae). A Concentração para a qual Não se Prevê a ocorrência de um Efeito (PNEC) foi 0,045 μg L⁻¹ para os Ag ENMs e 0,007 μg L⁻¹ para AgNO₃. O quociente de risco RQ foi de 6,3 (>1) para o AgNO₃ e 0,03 para os Ag ENMs (<1), sugerindo que a avaliação de risco existente para metais poderá ser extrapolada para os ENMs. No entanto, os ENMs têm um mecanismo de ação distinto dos sais metálicos. Além disso, a diversidade de características dos ENMs (por exemplo, revestimento superficial) requer mais estudos toxicológicos com o objetivo de melhorar o conhecimento sobre a toxicidade e avaliação de risco dos ENMs.Programa Doutoral em Biologi
A study of management and organization development in a UK shipping transport and trading company: 1972-80
No full textThe thesis provides an empirical analysis of the role of a management development and training adviser in a major U.K. Shipping, Transport & Trading Group during the decade of the 1970s.The period was characterized by world-wide economic convulsions, political and social change and the emergence of information technology as a key facet of post-industrial society. The decade was to signal the end of British dominance in liner shipping. The study examines how the inter-related processes of management development and organization development were interwoven with the general processes of management. It also illustrates how a managerial system achieved an effective interlocking of the triad of managerial resources -the physical, financial and human resources. An interventions-oriented approach was aimed to achieve individual positive manager involvement for the effective interlocking of business planning with individual performance planning an inter-related performance appraisal system, embracing business and individual performance reviews and assessment the integration of manpower planning and career planning with strategic business objectives and corporate planning the introduction of management development programmes aimed to optimize the contribution of individuals in the achievement of profitability and growth the development of counselling and coaching skills and ongoing action programme to facilitate organization development, through systematic approaches to change the managerial style and behavioural pattern, and to enable managers to acquire competence in decision making skills and managing people
Use of nanotechnology to increase nutrient use efficiency, enhance crop nutrition, and reduce agrochemical pollution
No full textNutrients (e.g., nitrogen, phosphorus, and potassium) are obtained from the soil as part of the natural nutrient cycling process (through the decay of plant and animal matter) and are essential for plant growth and development. Limiting factors such as low availability of key nutrients put a damper on potential growth and reduce the nutritional value of the crop. The absence of key nutrients, which is increasingly occurring as a result of industrial agriculture and intensification of farming, leads to poor quality soils that are unable to supply the required nutrients, causing deficiencies in the plant, stunting their growth and, when sufficiently severe, triggering plant death. To resolve this, fertilizers are extensively used to supplement the soil’s nutritive value and ensure consistent crop growth and quality. Crop quality includes a range of different aspects of a food crop, including nutritional value, which are important to consumers. This chapter will discuss nutrient management and the history of fertilizer, agricultural pollution due to excessive fertilizer use, and potential nanotechnology solutions to improve the use of natural resources (nutrients, water, light) by plants to increase nutrient use efficiency and thus enhance productivity while reducing the negative environmental impacts of agriculture.</p
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