969 resultados para structural characteristics


Relevância:

60.00% 60.00%

Publicador:

Resumo:

Heparin, a sulfated polysaccharide, was the first compound used as an anticoagulant and antithrombotic agent. Due to their structural characteristics, also has great potential anti-inflammatory, though such use is limited in inflammation because of their marked effects on coagulation. The occurrence of heparin-like compounds that exhibit anticoagulant activity decreased in aquatic invertebrates, such as crab Goniopsis cruentata, sparked interest for the study of such compounds as anti-inflammatory drugs. Therefore, the objective of this study was to evaluate the potential modulator of heparin-like compound extracted from Goniopsis cruentata in inflammatory events, coagulation, and to evaluate some aspects of its structure. The heparin-type compound had a high degree of N-sulphation in its structure, being able to reduce leukocyte migration into the peritoneal cavity at lower doses compared to heparin and diclofenac sodium (anti-inflammatory commercial). Furthermore, it was also able to inhibit the production of nitric oxide and tumor necrosis factor alpha by activated macrophages, inhibited the activation of the enzyme neutrophil elastase in low concentrations and showed a lower anticoagulant effect in high doses as compared to porcine mucosal heparin. Because of these observations, the compound extracted from crab Goniopsis cruentata can be used as a structural model for future anti-inflammatory agents

Relevância:

60.00% 60.00%

Publicador:

Resumo:

In this work commercial filters papers were organomodified with tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (3-APTS), aiming at the development of a new analytical procedure for in-situ speciation of labile and inert metal species in aquatic systems. Parameters that exert influence on the metal lability such as pH, chelating time, concentration and characteristics of the organic matter were studied in the laboratory using tests for metal recuperation. The results showed slower kinetics for Cu ion than for Ni, Mn and Cd in the absence of aquatic humic substances (AHS). The relative lability observed for complexed metals in aquatic humic substances using organomodified filter papers was Cu>>Cd>Ni>Mn. The pH values, structural characteristics and concentration of AHS exert strong influence on the lability of the metals. The results obtained showed that the utilization of organomodified filter papers can be an interesting and promising alternative for in situ characterization of metal lability in aquatic systems.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Cold in-place recycling (CIR) and cold central plant recycling (CCPR) of asphalt concrete (AC) and/or full-depth reclamation (FDR) of AC and aggregate base are faster and less costly rehabilitation alternatives to conventional reconstruction for structurally distressed pavements. This study examines 26 different rehabilitation projects across the USA and Canada. Field cores from these projects were tested for dynamic modulus and repeated load permanent deformation. These structural characteristics are compared to reference values for hot mix asphalt (HMA). A rutting sensitivity analysis was performed on two rehabilitation scenarios with recycled and conventional HMA structural overlays in different climatic conditions using the Mechanistic Empirical Pavement Design (MEPDG). The cold-recycled scenarios exhibited performance similar to that of HMA overlays for most cases. The exceptions were the cases with thin HMA wearing courses and/or very poor cold-recycled material quality. The overall conclusion is that properly designed CIR/FDR/CCPR cold-recycled materials are a viable alternative to virgin HMA materials.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

O Serviço de Referência (SR), incorporando na sua organização, funcionamento e comunicação com o utilizador um conjunto de potencialidades proporcionadas pela tecnologia, assume um papel fundamental na luta contra a desigualdade e o analfabetismo digital, no fomento da literacia da informação e na criação de conhecimento. A percepção do valor e das fragilidades do SR nas bibliotecas públicas em Portugal levanta a questão sobre como contribuir para o seu desenvolvimento. A presente investigação, visando a construção de alicerces numa perspectiva de evolução, parte da análise de documentos orientadores internacionais da RUSA/ALA (Reference and User Services Association / American Library Association) e da IFLA (International Federation of Library Association) e da observação de características estruturais da Rede Nacional de Biblioteca Públicas (RNBP), para a concepção de soluções de desenvolvimento do SR a aplicar a esta realidade concreta. Seguindo um paradigma compreensivo indutivo, com uma orientação baseada na Grounded Theory, esta pesquisa privilegia o contexto da descoberta e a construção de uma teoria. No plano empírico cumpre uma complementaridade de técnicas qualitativas e quantitativas, com recurso a uma triangulação metodológica. O campo de análise abrange a totalidade das bibliotecas públicas portuguesas integradas na RNBP em Portugal. Visando aspectos funcionais e materiais, são analisados dados preexistentes e aplicadas técnicas de observação directa e inquérito por questionário. Visando aspectos sociais, são efectuadas seis entrevistas semi-estruturadas. Os resultados apontam para uma situação de estagnação das bibliotecas da RNBP e para um funcionamento não estruturado e informal do SR, na maioria dos casos em que se verifica a sua disponibilização. Fundamentada a necessidade de evolução, e do investimento que nele possa ser feito, é construído um modelo, seguindo uma estratégia por níveis, flexíveis e adaptáveis às necessidades e aos recursos de cada biblioteca, que visa o desenvolvimento incremental e congruente daquele serviço; Abstract: The Reference Service in public libraries in Portugal. Development model from international guidelines. Incorporating in its organization, procedures and communication with the users a set of tools brought by technology, Reference Service (RS) plays a key role in the struggle against inequality and digital illiteracy, promoting information literacy and creating knowledge. The perception of the value of RS and the weaknesses in public libraries in Portugal raise the question on how to contribute to its development. In order to build RS foundations on an evolutionary perspective, this research analyzes RUSA / ALA (Reference and User Services Association / American Library Association) and IFLA (International Federation of Library Association) international guidelines and the structural characteristics of the Portuguese National Public Library Network (RNBP), with the objective of creating a solution for the development of that service to be applied to this reality. Following an inductive comprehensive paradigm, with an orientation based on Grounded Theory, this research focuses on the context of discovery and the construction of a theory. Empirically it fulfils complementary qualitative and quantitative techniques, using a methodological triangulation. The field of analysis covers Portuguese public libraries integrating the RNBP. Aiming at functional and material aspects, direct observation techniques and a survey by questionnaire are applied. Targeting social aspects, six semistructured interviews are carried out. The results point to a situation of stagnation in the RNBP as well as the unstructured and informal performance of the SR, which justifies the need for evolution and investment. A model is constructed, following a strategy based on levels, flexible and adaptable to the needs and resources of each library, with the perspective of an incremental and consistent development of this service.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Dissertação de Mestrado para obtenção do grau de Mestre em Design de Comunicação, apresentada na Universidade de Lisboa - Faculdade de Arquitectura.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

The structural characteristics of liposomes have been widely investigated and there is certainly a strong understanding of their morphological characteristics. Imaging of these systems, using techniques such as freeze-fracturing methods, transmission electron microscopy, and cryo-electron imaging, has allowed us to appreciate their bilayer structures and factors which can influence this. However, there are few methods which all us to study these systems in their natural hydrated state; commonly the liposomes are visualized after drying, staining, and/or fixation of the vesicles. Environmental Scanning Electron Microscopy (ESEM) offers the ability to image a liposome in its hydrated state without the need for prior sample preparation. Within our studies we were the first to use ESEM to study liposomes and niosomes and we have been able to dynamically follow the hydration of lipid films and changes in liposome suspensions as water condenses on to, or evaporates from, the sample in real time. This provides insight into the resistance of liposomes to coalescence during dehydration, thereby providing an alternative assay of liposome formulation and stability.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

A capacidade coletiva compassiva tem claras implicações no desempenho e no bem-estar dos indivíduos no contexto organizacional (Lilius, Worline, Maitlis, Kanov, Dutton, & Frost, 2008). O presente estudo tem como objetivo descrever a forma como o efeito combinado de práticas e características de flexibilização de estrutura organizacional contribuem para o aumento de respostas coletivas compassivas (RCC) em organizações com missão pró-social, quando comparadas com organizações cuja missão é focada na produtividade. Este objetivo tem como pressuposto que todas as organizações, independentemente da sua missão (pró-social vs. produtiva), podem ter a capacidade de se auto-organizar de forma compassiva para minimizar o sofrimento dos colaboradores, embora o possam fazer através de mecanismos diferentes. Esta resposta poderá, contudo, ser mais facilitada nas organizações com uma estrutura flexível e com valores culturais humanizados.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

In Colombia coffee production is facing risks due to an increase in the variability and amount of rainfall, which may alter hydrological cycles and negatively influence yield quality and quantity. Shade trees in coffee plantations, however, are known to produce ecological benefits, such as intercepting rainfall and lowering its velocity, resulting in a reduced net-rainfall and higher water infiltration. In this case study, we measured throughfall and soil hydrological properties in four land use systems in Cauca, Colombia, that differed in stand structural parameters: shaded coffee, unshaded coffee, secondary forest and pasture. We found that throughfall was rather influenced by stand structural characteristics than by rainfall intensity. Lower throughfall was recorded in the shaded coffee compared to the other systems when rain gauges were placed at a distance of 1.0 m to the shade tree. The variability of throughfall was high in the shaded coffee, which was due to different canopy characteristics and irregular arrangements of shade tree species. Shaded coffee and secondary forest resembled each other in soil structural parameters, with an increase in saturated hydraulic conductivity and microporosity, whereas bulk density and macroporosity decreased, compared to the unshaded coffee and pasture. In this context tree-covered systems indicate a stronger resilience towards changing rainfall patterns, especially in mountainous areas where coffee is cultivated.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Vaults are an architectural element which during construction history have been built with a great variety of different materials, shapes, and sizes. The shape of these structural elements was often dependent by the necessity to cover complex spaces, by the needed loading capacity, or by architectural aesthetics. Within this complex scenario masonry patterns generates also different effects on loading capacity, load percolation and stiffness of the structure. These effects were been extensively investigated, both with empirical observations and with modern numerical methods. While most of them focus on analyzing the load bearing capacity or the texture effect on vaulted structures, the aim of this analysis is to investigate on the effects of the variation of a single structural characteristic on the load percolation in the vault. Moreover, an additional purpose of the work is related to the coding of a parametrical model aiming at generating different masonry vaulted structures. Nevertheless, proposed script can generate different typology of vaulted structure basing on some structural characteristics, such as the span and the length to cover and the dimensions of the blocks.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Marine biomineralizing organisms provide a fundamental link between biology and environment. Calcified structure are important archives that can provide us main means of understanding organism adaptation, habits, environmental characteristics, and to look back in time and explore the past climate and their evolutionary history. In fact, biomineralized structures retain an unparalleled record of current and past ocean conditions through the investigation of their microchemistry and isotopes. This thesis considers aspects of two different biomineralization systems: fish otolith and coral skeletons at macro-, micro- and nanoscale, with the aim to understand how their morphology, structural characteristics and compositions can provide information of their functionality, and the environmental, behavioural, and evolutionary context in which organisms are framed. To this end, I applied a multidisciplinary approach in the scope to investigate calcified structures as “information recorders” and as models to study the phenotypic plasticity.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

OBJECTIVE: To assess by Doppler echocardiography the structural and functional alterations of rat heart with surgical induced extensive myocardial infarction. METHODS: Five weeks after surgical ligature of the left coronary artery, 38 Wistar-EPM rats of both sexes, 10 of them with extensive infarction, undergone anatomical and functional evaluation by Doppler echocardiography and then euthanized for anatomopathological analysis. RESULTS: Echocardiography was 100% sensible and specific to anatomopathological confirmed extensive miocardial infarction. Extensive infarction lead to dilatation of left ventricle (diastolic diameter: 0.89cm vs.0.64cm; systolic: 0.72cm vs. 0.33cm) and left atrium (0.55cm vs. 0.33cm); thinning of left ventricular anterior wall (systolic: 0.14cm vs. 0.23cm, diastolic: 0.11cm vs. 0.14cm); increased mitral E/ A wave relation (6.45 vs. 1.95). Signals of increased end diastolic ventricle pressure, B point in mitral valve tracing in 62.5% and signs of pulmonary hypertension straightening of pulmonary valve (90%) and notching of pulmonary systolic flow (60%) were observed in animals with extensive infarction. CONCLUSION: Doppler echocardiography has a high sensitivity and specificity for detection of chronic extensive infarction. Extensive infarction caused dilatation of left cardiac chambers and showed in Doppler signals of increased end diastolic left ventricular pressure and pulmonary artery pressure.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

The study deals with the diversity in structural and spectural characteristics of some transition metal complexes derived from aldehyde based thiosemicarbazone ligands thiosemicarbazones are a family of compounds with beneficial biological activity viz., anticancer,antitumour, antifungal, antibacterial, antimalarial, antifilarial, antiviral and anti-HIV activities. Many thiosemicarbazone ligands and their complexes have been prepared and screened for their antimicrobial activity against various types of fungi and bacteria. The results prove that the compounds exhibit antimicrobial properties and it is important to note that in some cases metal chelates show more inhibitory effects than the parent ligands. The increased lipophilicity of these complexes seems to be responsible for their enhanced biological potency. Adverse biological activities of thiosemicarbazones have been widely studied in rats and in other species. The parameters measured show that copper complexes caused considerable oxidative stress and zinc zinc complexes behaved as antioxidants. It has applications on analytical field also. Some thiosemicarbazones produce highly colored complexes with metal ions. This thesis aims to synthesis some novel thiosemicarbazone ligands and their transition metal complexes together with their physico-chemical characterization.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

ZnGa2O4:Dy3+ phosphor thin films were deposited on quartz substrates by radio frequency rf magnetron sputtering and the effect of substrate temperature on its structural and luminescent properties was investigated. Polycrystalline film could be deposited even at room temperature. The crystalline behavior, Zn/Ga ratio, and surface morphology of the films were found to be highly sensitive to substrate temperature. Under UV illumination, the as-deposited films at and above 300°C gave white luminescence even without any postdeposition treatments. The photoluminescent PL emission can be attributed to the combined effect of multicolor emissions from the single luminescence center Dy3+ via host-sensitization. Maximum PL emission intensity was observed for the film deposited at 600°C, and the CIE chromaticity coordinates of the emission were determined to be x,y = 0.34, 0.31 .

Relevância:

40.00% 40.00%

Publicador:

Resumo:

An in vitro study was conducted to investigate the effects of condensed tannins (CT) structural properties, i.e. average polymer size (or mean degree of polymerization); percentage of cis flavan-3-ols and percentage of prodelphinidins in CT extracts on methane production (CH4) and fermentation characteristics. CT were extracted from eight plants in order to obtain different CT types: black currant leaves, goat willow leaves, goat willow twigs, pine bark, red currant leaves, sainfoin plants, weeping willow catkins and white clover flowers. They were analysed for CT content and CT composition by thiolytic degradation, followed by HPLC analysis. Grass silage was used as a control substrate. Condensed tannins were added to the substrate at a concentration of 40 g/kg, with or without polyethylene glycol (+ or −PEG 6000 treatment) to inactivate tannins, and then incubated for 72 h in mixed buffered rumen fluid from three different lactating dairy cows per run. Total cumulative gas production (GP) was measured by an automated gas production system. During the incubation, 12 gas samples (10 μl) were collected from each bottle headspace at 0, 2, 4, 6, 8, 12, 24, 30, 36, 48, 56 and 72 h of incubation and analyzed for CH4. A modified Michaelis–Menten model was fitted to the CH4 concentration patterns and model estimates were used to calculate total cumulative CH4 production (GPCH4). Total cumulative gas production and GPCH4 curves were fitted using biphasic and monophasic modified Michaelis-Menten models, respectively. Addition of PEG increased GP, GPCH4, and CH4 concentration compared to the −PEG treatment. All CT types reduced GPCH4 and CH4 concentration. All CT increased the half time of GP and GPCH4. Moreover, all CT decreased the maximum rate of fermentation for GPCH4 and rate of substrate degradation. The correlation between CT structure and GPCH4 and fermentation characteristics showed that the proportion of prodelphinidins within CT had the largest effect on fermentation characteristics, followed by average 27 polymer size and percentage of cis-flavan-3-ols.

Relevância:

40.00% 40.00%

Publicador:

Resumo:

In recent years, Mg-Ni-based metastable alloys have been attracting attention due to their large hydrogen sorption capacities, low weight, low cost, and high availability. Despite the large discharge capacity and high activity of these alloys, the accelerated degradation of the discharge capacity after only few cycles of charge and discharge is the main shortcoming against their commercial use in batteries. The addition of alloying elements showed to be an effective way of improving the electrode performance of Mg-Ni-based alloys. In the present work, the effect of Ti and Pt alloying elements on the structure and electrode performance of a binary Mg-Ni alloy was investigated. The XRD and HRTEM revealed that all the investigated alloy compositions had multi-phase nanostructures, with crystallite size in the range of 6 nm. Moreover, the investigated alloying elements demonstrated remarkable improvements of both maximum discharge capacity and cycling life. Simultaneous addition of Ti and Pd demonstrated a synergetic effect on the electrochemical properties of the alloy electrodes. Among the investigated alloys, the best electrochemical performance was obtained for the Mg(51)Ti(4)Ni(43)Pt(2) composition (in at.%), which achieved 448 mAh g(-1) of maximum discharge capacity and retained almost 66% of this capacity after 10 cycles. In contrast, the binary Mg(55)Ni(45) alloy achieved only 248 mAh g(-1) and retained 11% of this capacity after 10 cycles. (C) 2010 Elsevier By. All rights reserved.