16 resultados para Polymer crystallization, Water crystallization, Dynamics


Relevância:

40.00% 40.00%

Publicador:

Resumo:

Acta Crystallographica Section F Structural Biology and Crystallization Communications Volume 65, Part 8

Relevância:

40.00% 40.00%

Publicador:

Resumo:

Dissertation to obtain a Master Degree in Molecular Genetics and Biomedicine at Faculty of Sciences and Technology,Universidade Nova de Lisboa

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Thesis submitted to the Universidade Nova de Lisboa,Faculdade de Ciências e Tecnologia for the degree of Doctor of Philosophy in Environmental Engineering

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Dissertation presented to obtain a Ph.D. Degree in Chemical Physics

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Dissertation presented to obtain the Ph.D degree in Biology

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Dissertação para obtenção do grau de mestre em Engenharia de Materiais

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Dissertação para obtenção do Grau de Doutor em Engenharia Química, especialidade de Engenharia Bioquímica

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Dissertação para obtenção do Grau de Mestre em Biotecnologia

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Deep-eutectic solvents (DES) are considered novel renewable and biodegradable solvents, with a cheap and easy synthesis, without waste production. Later it was discovered a new subclass of DES that even can be biocompatible, since their synthesis uses primary metabolites such as amino acids, organic acids and sugars, from organisms. This subclass was named natural deep-eutectic solvents (NADES). Due to their properties it was tried to study the interaction between these solvents and biopolymers, in order to produce functionalized fibers for biomedical applications. In this way, fibers were produced by using the electrospinning technique. However, it was first necessary to study some physical properties of NADES, as well as the influence of water in their properties. It has been concluded that the water has a high influence on NADES properties, which can be seen on the results obtained from the rheology and viscosity studies. The fluid dynamics had changed, as well as the viscosity. Afterwards, it was tested the viability of using a starch blend. First it was tested the dissolution of these biopolymers into NADES, in order to study the viability of their application in electrospinning. However the results obtained were not satisfactory, since the starch polymers studied did not presented any dissolution in any NADES, or even in organic solvents. In this way it was changed the approach, and it was used other biocompatible polymers. Poly(ethylene oxide), poly(vinyl alcohol) and gelatin were the others biopolymers tested for the electrospinning, with NADES. All polymers show good results, since it was possible to obtain fibers. However for gelatin it was used only eutectic mixtures, containing active pharmaceutical ingredients (API’s), instead of NADES. For this case it was used mandelic acid (antimicrobial properties), choline chloride, ibuprofen (anti-inflammatory properties) and menthol (analgesic properties). The polymers and the produced fibers were characterized by scanning electron microscope (SEM), Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). With the help of these techniques it was possible to conclude that it was possible to encapsulate NADES within the fibers. Rheology it was also study for poly(ethylene oxide) and poly(vinyl alcohol), in a way to understand the influence of polymer concentration, on the electrospinning technique. For the gelatin, among the characterization techniques, it was also performed cytotoxicity and drug release studies. The gelatin membranes did not show any toxicity for the cells, since their viability was maintained. Regarding the controlled release profile experiment no conclusion could be drawn from the experiments, due to the rapid and complete dissolution of the gelatin in the buffer solution. However it was possible to quantify the mixture of choline chloride with mandelic acid, allowing thus to complete, and confirm, the information already obtained for the others characterization technique.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Evaporative cooling is a traditional strategy to improve summer comfort, which has gained renewed relevance in the context of the transition to a greener economy. Here, the potential for evaporative cooling of two common porous building materials, natural stone and ceramic brick, was evaluated. The work has relevance also to the protection of built heritage becauseevaporation underlies the problems of dampness and salt crystallization, which are so harmful and frequent in this heritage. It was observed that the drying rate of the materials is, in some cases, higher than the evaporation rate of a free water surface. Surface area measurements by a three-dimensional optical technique suggested, as probable cause of this behavior, that surface irregularity gives rise to a large effective surface of evaporation in the material. Surface temperature measurements by infrared were performed afterward during evaporation experiments outside during a hot summer day in Lisbon. Their results indicate that ordinary building materials can be very efficient evaporative media and, thus, may help in achieving higher energy efficiency while maintaining a simultaneous constructive or architectural function.