Mesoscopic modelling of bipolar charge evolution in CN-PPV LEDs

Since various chances are possible in the molecular structure of the repeat unit, substituted poly(para-phenylenevinylene) (PPV) has ben used as active component in light-emitting diodes (LEDs) to obtain light emission in a wide range of colours.A major aspect determining device performance is the competition between current flow, trapping and recombination within the polymer layer. By suitable Monte Carlo calculations, we have performed computer experiments in which bipolar charge carriers are injected at constant rate in polymer networks made of cyano-substituted PPV chains with variable length and orientation. The intra-molecular electronic properties used in these simulations were calculated by a quantum molecular dynamics method. In order to assess the influence of cyano-substitution on the properties of single-layer PPV LEDs, we have focused our attention on bipolar charge evolution in time. Specifically addressed are the differences in electric field strength needed for intra-molecular charge mobility of electrons and holes and their consequences at mesoscopic scale. (C) 2004 Elsevier B.V. All rights reserved

Aspects of safety: what should be considered?

Main objectives: 1. To appreciate the core competencies and the radiographer's role as a key element to ensure patient safety at the imaging department. 2. To learn about the main concepts of patient safety related to the radiographer's professional responsibility and ethics outlines at the imaging department level from a public or private hospital or even at the private practice level. 3. To discuss ways to promote patient safety and quality in imaging

Draft genome sequence of Agrobacterium deltaense strain CNPSo 3391, isolated from a soybean nodule in Mozambique

Open Access Article; Published online: 7 March 2019Agrobacterium deltaense strain CNPSo 3391 was isolated from a soybean nodule in Mozambique. Its genome size was estimated at 4,926,588 bp. This isolate carries several coding sequences for stress tolerance, but no identifiable nodulation or virulence genes. Possible ecological roles of bacteria isolated from legume nodules and closely related to Agrobacterium are discussed

Electron-phonon induced spin relaxation in InAs quantum dots

We have calculated spin relaxation rates in parabolic quantum dots due to the phonon modulation of the spin-orbit interaction in presence of an external magnetic field. Both, deformation potential and piezoelectric electron-phonon coupling mechanisms are included within the Pavlov-Firsov spin-phonon Hamiltonian. Our results have demonstrated that, in narrow gap materials, the electron-phonon deformation potential and piezoelectric coupling give comparable contributions as spin relaxation processes. For large dots, the deformation potential interaction becomes dominant. This behavior is not observed in wide or intermediate gap semiconductors, where the piezoelectric coupling, in general, governs the spin relaxation processes. We also have demonstrated that spin relaxation rates are particularly sensitive to the Land\'e $g$-factor.Comment: 4 pages, 2 figures, to be appear in Physica E: Proceedings of the 11 International Conference on Narrow Gap Semiconductor

Effect of molecular properties on the performance of polymer light-emitting diodes

The performance of a single layer polymer light-emitting diode depends on several interdependent factors, although recombination between electrons and holes within the polymer layer is believed to play an important role. Our aim is to carry out computer experiments in which bipolar charge carriers are injected in polymer networks made of poly(p-phenylene vinylene) chains randomly oriented. In these simulations, we follow the charge evolution in time from some initial state to the steady state. The intra-molecular properties of the polymer molecules obtained from self-consistent quantum molecular dynamics calculations are used in the mesoscopic model. The purpose of the present work is to clarify the effects of intra-molecular charge mobility and energy disorder on recombination efficiency. In particular, we find that charge mobility along the polymer chains has a serious influence on recombination within the polymer layer. Our results also show that energy disorder due to differences in ionization potential and electron affinity of neighbouring molecules affects mainly recombinations that occur near the electrodes at polymer chains parallel to them.Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência, Tecnologia, Inovação” - POCTI/CTM/41574/2001Comunidade Europeia (CE). Fundo Europeu de Desenvolvimento Regional (FEDER

Pharmaceutical drugs as emerging pollutants in aqueous media of Northeast Portugal

Emerging pollutants are potentially toxic substances that although found in very small concentrations can produce hazard effects to the environment. Due to their very small concentrations they are not yet included in the water quality monitoring programs neither in national or international environmental control regulations. Pharmaceutical and Personal Care Products (PPCPs) represent an important group of emerging pollutants owing to increased worldwide consumption and to their inherent capacity to induce physiological harmful effects in very low doses, which raises several concerns related with the potential adverse effects on humans, animals and environmental systems. In this work, it will be presented the development and validation of a complete experimental methodology proposed for the monitoring of pharmaceutical drugs. The method is based on solid phase extraction (SPE) followed by analysis with high performance liquid chromatography with a diode array detector (HPLC-DAD). Experimental results obtained with two different columns will be presented. An analytical Nucleosil 100-5 C18 column, 150 mm x 4.6 mm, obtained from Macherey-Nagel for compounds with lower pKa values and a SiliaChrom XT C18 column, 4.6 mm x 250 mm, obtained from SiliCycle for compounds with higher pKa values. The method is validated by the analysis of real aqueous matrices samples obtained from different water media sources, such as, swimming pools, rivers and wastewater treatment plants. To extend the scope of the analytical method and thus obtain a broader study, several drugs were selected, belonging to five different pharmacological classes: non-steroidal anti-inflammatory (ibuprofen, acetylsalicylic acid, ketoprofen, naproxen and diclofenac), analgesic (paracetamol), antibiotic (sulfamethoxazole), an anticonvulsant (carbamazepine) and a central nervous system stimulator (caffeine). These compounds were selected due to their high level of use and medical prescription and, consequently, leading to a high probability of environmental contamination.info:eu-repo/semantics/publishedVersio

Study of Biodiesel Production through Esterification Catalysed by Imidazolium-based Ionic Liquids

Biodiesel is an alternative diesel fuel which is industrially produced from vegetable oils and animal fats, by transesterification reactions. Thus, currently most commercial biodiesel is produced from oils, using alkaline catalysts. On the other hand, conventional mineral acid catalysts like sulfuric acid, are commonly used for catalyzing esterification reactions of fatty acids which also produce biodiesel. However, Ionic Liquids (ILs) offer an alternative solution to classical homogeneous catalysts, because it can be recycled and reused in subsequent runs after recovery steps. An IL is a molten salt consisting of a cation and an anion, with low melting temperature. In this study, a Brønsted acidic IL, 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM][HSO4]) was used as a catalyst in the esterification of oleic acid with methanol into biodiesel. The effect of different operation parameters such as oleic acid to methanol molar ratio, amount of catalyst, reaction temperature, and reaction time were tested. The optimal conditions for esterification of oleic acid were experimentally determined at 1/10 for oleic acid/methanol molar ratio, 2.5 %wt for the amount of catalyst, a reaction time of 4 h and reaction temperature of 90oC. The Fatty Acid Methyl Esters (FAMEs) content was analyzed using Gas Chromatography.info:eu-repo/semantics/publishedVersio

Optimization and kinetic study of esterification reaction of oleic acid using [HMIM]HSO4 as catalyst

Biodiesel Biodiesel is an alternative fuel to petrodiesel. It can be produced from a wide range of raw materials such as vegetable oils and animal fats. Yet, the use of sources that do not compete with the food market, such as waste cooking oils - which usually feature high levels of free fatty acids (FFA’s), can lead to problems in the process of biodiesel production through alkaline transesterification. Therefore, new methodologies to successfully apply acidic oils need to be developed.info:eu-repo/semantics/publishedVersio

Effect of catalyst on the producer gas composition from co-gasification of glycerol/fat mixtures

In this work, steam reforming of crude glycerol and animal fat mixtures was studied. The tests were carried out at temperatures of 700 °C and 750 °C in a fixed bed reactor using activated alumina or dolomite particles, to evaluate the catalytic capacity of these minerals in the removal of tar from the producer gas. The gas produced was quantified and analyzed by gas chromatography, and it was concluded that its composition is greatly influenced by the bed material used. The results obtained showed that dolomite is more effective in reducing the tar content, evidencing its ability to catalyze the tar reform reactions and promoting the water-gas shift reaction. Consequently, using dolomite as a catalyst, a producer gas with 47–48 vol% in H and 27–30 vol% in CO2 was obtained, while using a bed of alumina particles, a gas with a high CO content (45–48 vol%) and lower H content (34–37 vol%) was produced.This work was supported by Portugal 2020 (POCI-01-0145-FEDER-024067) and by Multi-year financing of FCT- Fundação para a Ciência e Tecnologia, Portugal (grant UIDB/04730/2020).info:eu-repo/semantics/publishedVersio

An experimental study on the evolution of modal damping with damage in carbon fiber laminates

Many of the techniques developed to assess structural damage are based on experimental modal analysis. This paper presents a study to extend the current understanding of how increasing damage in a carbon fiber reinforced plastic affects the modal damping factor of a laminated structure. Damage is introduced and quantified in terms of the dissipated energy. It is shown that there is a tendency for the overall damping to increase whereas there is a tendency for the overall stiffness to decrease. While these results are not novel, the former is quite relevant, since the authors are not aware of many other experimental studies on the evolution of the modal damping factor with damage in carbon fiber reinforced plastic. At the same time, a modal-based damage location technique that combines both the natural frequencies and the modal damping factors as damage sensitive features is discussed. The hypothesis that different damage morphologies on composite materials have different contributions to the damage features is drawn. The methods are illustrated with both numerical and experimental examples. One of the problems observed is that, although damping is consistently found to increase globally with damage, the determination of the individual changes of the modal damping factors is still very uncertain. This may be due to concurrent damage types being present at the same time, but most certainly due to uncertainties involved in the identification of the modal damping factors