Origem do efeito de memória e previsão da dimensão das estruturas precursoras em fundidos quiescentes e deformados sob acção de esforços de corte : efeitos do grau de reticulação e do tipo de catalisador

Tese de doutoramento em Engenharia de PolímerosThe aim of this work was to study the effect of melt memory in the solidification of semicrystalline polymers and to identify its origin. It contains three bibliographic critical review chapters, two additional chapters of experimental work, a proposal of future work, and an appendix with more details of experimental results. The first three chapters present the current state of the art in the understanding of the earlier crystallization stages and the effect of flow on crystallization development. The earlier crystallization stages are discussed. Different views are presented for the earlier crystallization mechanisms, namely the nucleation resulting from a spinodal decomposition in the melt, the classical nucleation and growth, and the nucleation and crystallization development resulting from the presence of a mesophase in the molten polymer. The effect of entanglements on the crystallization and melting are also analysed. Particularly critical is a clear understanding of this last process, which requires a deep knowledge of polymer melt morphology. Its change with flow conditions will inevitably affect crystallization development. Because polymer chains in melts are considered ideal, this concept is discussed with detail. The variation with temperature and flow of parameters used to establish dimensions of chain segments in ideal chains is also analysed. Limitations of models used to describe chain dynamics are presented, discussed and their flaws identified. At the end, the study of the effect of flow on polymer melt morphology is presented. Under the assumption that the melt memory effect is originated from thermal and mechanical history imposed to during the processing stage, its origin was studied by making the reverse experiments of those used to erase this effect and to record reproducible crystallization experiments in fully relaxed melts. It was found that pre-shearing polymer melts above their melting temperature accelerates crystallization kinetics until saturation, which is ascribed to the existence in the melt of precursor structures, consisting of chain segments aligned with flow, without crystallographic order. The melt state responsible for this saturation was identified as the steady state in shear flow. The excess in the specific free energy of melts sheared up to steady state and the strain at its onset were evaluated and expressed as a function of precursor structures surface free energies, their length and thickness. For quiescent melts their thickness was found to be maximum. Erasing the melt memory effect is ascribed to the decrease of melt excess specific free energy, which is achieved a randomization and increase in the thickness of the precursor structures existing at steady state. Application of shear fragmentises the precursors and aligns them with flow. The major conclusion of this work is that, despite the differences in the polymers studied, they show universal features concerning their flow and crystallization behaviour.O objectivo deste trabalho é estudar e identificar a origem do efeito da memória na solidificação de polímeros semicristalinos. O trabalho contém três capítulos de revisão bibliográfica. Há ainda dois capítulos de trabalho experimental, um capítulo com propostas de trabalho futuro e um apêndice com detalhes de resultados experimentais. Os primeiros três capítulos apresentam uma análise crítica do estado da arte no estudo dos estágios iniciais da solidificação, do efeito do fluxo no desenvolvimento da cristalização e de modelos de fluxo. Na discussão dos estágios embrionários da cristalização são apresentadas diferentes propostas, nomeadamente o desenvolvimento dos núcleos semicristalinos como resultado da decomposição spinodal no polímero fundido, o processo clássico de nucleação e crescimento e o desenvolvimento da cristalização como resultado de uma mesofase existente no polímero fundido. O efeito dos entrelaçamentos na cristalização e fusão é também analisado. É crítico perceber-se o que lhes acontece, como e quando. Para isso é necessário perceber-se amorfologia do fundido e a sua variação com o fluxo. Admite-se que as cadeias se comportam como ideais em polímeros fundidos. Por esta razão, o conceito de idealidade é discutido com detalhe. A variação com a temperatura e fluxo dos parâmetros utilizados para estabelecer a dimensão de um segmento da cadeia ideal é também analisada. As limitações dos modelos utilizados na descrição da dinâmica de cadeias e as suas limitações são apresentados e discutidos. Finalmente é feita a análise do efeito do fluxo na morfologia do polímero fundido. Partindo do pressuposto que a memória do fundido resulta da história térmica e mecânica imposta durante o processamento, a sua origem é estudada fazendo experiências opostas às utilizadas para apagar esse efeito e registar experiências de cristalização reprodutíveis em fundidos relaxados. Foi observado que deformando polímeros fundidos acima da sua temperatura de fusão resulta na aceleração da cristalização até à sua saturação, efeito atribuído às estruturas precursoras da cristalização. O estado do fundido responsável pela saturação foi identificado como o estado estacionário em fluxos de corte. O excesso de energia livre dos fundidos deformados até esse estado, e a deformação no seu início, foram avaliados e expressos em função das energias livres de superfície dos precursores, do seu comprimento e espessura. A espessura das estruturas precursoras é máxima em fundidos quiescentes. Apagar o efeito de memória resulta na diminuição do excesso de energia livre, o que é conseguido pela randomização e aumento de espessura das estruturas precursoras. A aplicação de um esforço de corte tem como efeito a fragmentação e orientação no sentido do fluxo das estruturas precursoras. A conclusão mais relevante deste trabalho foi a verificação da universalidade do comportamento dos polímeros em fluxo e a sua cristalização, independentemente do grau de ramificação da cadeia e das interacções intermoleculares.Fundação para a Ciência e a Tecnologia (FCT) - projectos POCTI/CTM/46270/2002 e PTDC/CTM/68614/2006FEDER e projecto 3599/PPCD

Variability in clinical profile of asthmatic child referred from allergy clinic - ten years of observation

Wstęp: Astma jest najczęściej występującą chorobą przewlekłą wieku rozwojowego. Niedodiagnozowanie jest częstym zjawiskiem związanym z niedoleczeniem, którego z kolei konsekwencją jest wzrastająca zachorowalność i śmiertelność. Opóźnienie w diagnozowaniu astmy odzwierciedla problemy z prawidłową realizacją celów diagnostycznych wytyczonych przez Global Initiative for Asthma (GINA). Celem pracy jest charakterystyka kliniczna dzieci kierowanych do Poradni Chorób Alergicznych, u których następnie rozpoznano astmę oskrzelową. Oceniono przyczyny zgłaszania się do poradni specjalistycznej, dane demograficzne i społeczne dziecka. Materiał i metody: Analizie poddano grupę 907 dzieci do 18. roku życia, u których rozpoznano astmę w poradni alergologicznej w latach 2000-2009. Było to badanie przekrojowe, w którym analizowano dane demograficzne, socjalne oraz kliniczne pacjentów. Wyniki: Na podstawie wyników ujawniono zmieniony profil kliniczny dziecka kierowanego do poradni alergologicznej na przestrzeni 10 lat, u którego następnie rozpoznana została astma oskrzelowa. Profil ten charakteryzują: młodszy wiek pacjenta, większa częstość nawracających infekcji i mniejsza częstość występowania świstów oraz atopii jako przyczyny skierowań do alergologa. Wnioski: Nowy profil kliniczny dziecka kierowanego do alergologa wskazuje na konieczność przeprowadzenia kosztownej diagnostyki różnicowej astmy w ośrodkach specjalistycznych. Dane te powinny być uwzględnione w wytyczaniu nowych strategii zdrowotnych w Polsce. Pneumonol. Alergol. Pol. 2011; 79, 3: 189-195Introduction: Asthma is the most frequent chronic respiratory disease in children. Underdiagnosis is frequent, which results in undertreatment and, consequently, in rising asthma morbidity and mortality rates. The delay in the diagnosis of asthma seems to precisely reflect problems with a proper realization of the goals of the diagnostic part of the Global Initiative for Asthma guidelines. We attempted to assess the clinical profile of children who were referred to allergy clinic followed by asthma diagnosis, we consider especially demographic and social data. Material and methods: We analyzed the group of 907 children with diagnosis of asthma between 2000 and 2009. This was cross-sectional study assessing demographic, social and clinical characteristic. All variables were tested over time. Results: We observed change in clinical profile of children checking into the clinic over time. The new profile includes: younger age of patient, higher frequency of recurrent infections, lower frequency of wheezes and atopy. Conclusions: New clinical profile of patients referred to allergist reveals the need of costly differential diagnosis of asthma in specialized centers. This should be included in new strategies in the health care system in Poland. Pneumonol. Alergol. Pol. 2011; 79, 3: 189-19

Skrzepliny wewnątrzsercowe w zatorowości płucnej a priori niewysokiego ryzyka: dylematy terapeutyczne

Pulmonary embolism (PE) of a priori non high risk according to ESC guidelines, but coexisting with intracardiac thrombi ispotentially a life threatening disease. The recommendations regarding therapy in such situations are not clear. We report twocases of PE with coexisting intracardiac thrombi. The 74 year-old woman was admitted after previous cardiac arrest in thecourse of PE with the presence of intracardiac thrombi in right ventricle. Due to lack of clinical improvement during heparinadministration she was treated with thrombolysis. The 72 year-old obese woman with hypertension, diabetes and previousstroke with right-sided paresis was admitted after 2 episodes of loss of consciousness, with intracardiac thrombus in bothright and left heart. Due to contraindications to both surgery and thrombolysis, she was treated with heparin. Both womenrecovered successfully. These cases illustrate the importance of individual treatment strategy

Family Tree for Aqueous Organic Redox Couples for Redox Flow Battery Electrolytes: A Conceptual Review

Redox flow batteries (RFBs) are an increasingly attractive option for renewable energy storage, thus providing flexibility for the supply of electrical energy. In recent years, research in this type of battery storage has been shifted from metal-ion based electrolytes to soluble organic redox-active compounds. Aqueous-based organic electrolytes are considered as more promising electrolytes to achieve “green”, safe, and low-cost energy storage. Many organic compounds and their derivatives have recently been intensively examined for application to redox flow batteries. This work presents an up-to-date overview of the redox organic compound groups tested for application in aqueous RFB. In the initial part, the most relevant requirements for technical electrolytes are described and discussed. The importance of supporting electrolytes selection, the limits for the aqueous system, and potential synthetic strategies for redox molecules are highlighted. The different organic redox couples described in the literature are grouped in a “family tree” for organic redox couples. This article is designed to be an introduction to the field of organic redox flow batteries and aims to provide an overview of current achievements as well as helping synthetic chemists to understand the basic concepts of the technical requirements for next-generation energy storage materials

Multi-kinase control of environmental stress responsive transcription

Cells respond to changes in environmental conditions by activating signal transduction pathways and gene expression programs. Here we present a dataset to explore the relationship between environmental stresses, kinases, and global gene expression in yeast. We subjected 28 drug-sensitive kinase mutants to 10 environmental conditions in the presence of inhibitor and performed mRNA deep sequencing. With these data, we reconstructed canonical stress pathways and identified examples of crosstalk among pathways. The data also implicated numerous kinases in novel environment-specific roles. However, rather than regulating dedicated sets of target genes, individual kinases tuned the magnitude of induction of the environmental stress response (ESR)–a gene expression signature shared across the set of perturbations–in environment-specific ways. This suggests that the ESR integrates inputs from multiple sensory kinases to modulate gene expression and growth control. As an example, we provide experimental evidence that the high osmolarity glycerol pathway is an upstream negative regulator of protein kinase A, a known inhibitor of the ESR. These results elaborate the central axis of cellular stress response signaling

Experimental and numerical studies of rotating drum grate furnace

Waste material from the meat industry can be taken into account as a biofuel. Studies confirm, that calorific value is higher and ash content is lower comparing to some conventional fuels. EU directives regulate details of thermal disposal of the waste material from the meat industry - especially in range of the process temperature and time of the particle presence in area of the combustion zone. The paper describes design of the rotating drum grate stove, dedicated to thermal disposal of the meat wastes as well as solid biomass (pellet, small bricket, wood chips) combustion. Device has been developed in frames of cooperation between AGH University of Science and Technology (Krakow, Poland) and producer focused on technologies of energy utilization of biomass in distributed generation. Results of measurements of selected operational parameters performed during startup of the furnace have been presented and discussed. Furthermore, numerical model of the combustion process has been developed to complement experimental results in range of the temperature and oxygen distribution in the area of the combustion chamber. ANSYS CFX solver has been applied to perform simulations including rotational domain related with specifics of operation of the device. Results of numerical modelling and experimental studies have been summarized and compared

A Coordination Chemistry Study of Hydrated and Solvated Cationic Vanadium Ions in Oxidation States +III, +IV, and +V in Solution and Solid State

The coordination chemistry of hydrated and solvated vanadium­(III), oxovanadium­(IV), and dioxovanadium­(V) ions in the oxygen-donor solvents water, dimethyl sulfoxide (DMSO), and <i>N</i>,<i>N</i>′-dimethylpropyleneurea (DMPU) has been studied in solution by extended X-ray absorption fine structure (EXAFS) and large-angle X-ray scattering (LAXS) and in the solid state by single-crystal X-ray diffraction and EXAFS. The hydrated vanadium­(III) ion has a regular octahedral configuration with a mean V–O bond distance of 1.99 Å. In the hydrated and DMSO-solvated oxovanadium­(IV) ions, vanadium binds strongly to an oxo group at ca. 1.6 Å. The solvent molecule trans to the oxo group is very weakly bound, at ca. 2.2 Å, while the remaining four solvent molecules, with a mean V–O bond distance of 2.0 Å, form a plane slightly below the vanadium atom; the mean OVO_perp bond angle is ca. 98°. In the DMPU-solvated oxovanadium­(IV) ion, the space-demanding properties of the DMPU molecule leave no solvent molecule in the trans position to the oxo group, which reduces the coordination number to 5. The OVO bond angle is consequently much larger, 107°, and the mean VO and V–O bond distances decrease to 1.58 and 1.97 Å, respectively. The hydrated and DMSO-solvated dioxovanadium­(V) ions display a very distorted octahedral configuration with the oxo groups in the cis position with a mean VO bond distance of 1.6 Å and a OVO bond angle of ca. 105°. The solvent molecules trans to the oxo groups are weakly bound, at ca. 2.2 Å, while the remaining two have bond distances of 2.02 Å. The experimental studies of the coordination chemistry of hydrated and solvated vanadium­(III,IV,V) ions are complemented by summarizing previously reported crystal structures to yield a comprehensive description of the coordination chemistry of vanadium with oxygen-donor ligands