DSpace Collection:
http://hdl.handle.net/11422/7616
2024-03-28T11:20:33ZMicrofluídica de gotas para o encapsulamento de esferoides de células-tronco em alginato para regeneração tecidual
http://hdl.handle.net/11422/20144
Title: Microfluídica de gotas para o encapsulamento de esferoides de células-tronco em alginato para regeneração tecidual
Author(s)/Inventor(s): Mesquita, Cristiane Raquel Sousa
Advisor: Cotta, Carolina Palma Naveira
Abstract: The chemical, biochemical and mass transfer / heat transfer analysis in segmented droplets, of the droplets type, in microfluidic devices presents more efficiency due to some of its characteristics such as large surface area and monodisperse sizes. Thus, the use of microfluidic systems for encapsulation of spheroids is a promising field because it exhibits important properties such as distribution of controlled and uniform droplet sizes, as well as their relative simplicity and reproducibility, which is not presented in traditional processes. The use of these spheroids encapsulated by hydrogel composite matrices are widely used in regenerative medicine, mainly due to the increase in surface area. Therefore, the present study presents the fabrication and testing of microfluidic devices, the formation of single emulsion droplets and, consequently, the encapsulation of spheroids in separate aqueous microdroplets dispersed in an immiscible carrier oil. Variations in the flow of dispersed and continuous phases are observed generating droplets with diameters varying from 335 ± 1 μm to 733 ± 15 μm, showing that the average size and morphology of the droplets vary with the viscosity and configuration of the capillaries. The encapsulation of spheroids in alginate hydrogels provides a simple and rapid tool for preparing microdroplets for systems related to regenerative medicine.
Publisher: Universidade Federal do Rio de Janeiro
Type: Dissertação2019-06-01T00:00:00ZModificação de pastas de cimentação com nanopartículas de C-S-H sob diferentes temperaturas
http://hdl.handle.net/11422/14024
Title: Modificação de pastas de cimentação com nanopartículas de C-S-H sob diferentes temperaturas
Author(s)/Inventor(s): Pedrosa Consición, Herman Camilo
Advisor: Fairbairn, Eduardo de Moraes Rego
Abstract: This work analyzes the feasibility of adding a commercial product based on C-S-H
nanoparticles used in the construction industry, as nucleation points source, in cement
pastes used in oil and gas wells, with the objective of improving their mechanical
performance. The effects of the nanoparticles on the hydration reaction kinetics and the
mechanical properties of the pastes were studied in Portland cement Class G matrices
under temperature conditions that can be found in oil and gas reservoirs. Acceleration of
the cement hydration reaction and modification of the mechanical properties of the
pastes were identified. Nanomechanical characterization results allowed concluding that
the addition of C-S-H nanoparticles promotes the generation of low-density C-S-H and
decreases the production of high-density C-S-H.
Publisher: Universidade Federal do Rio de Janeiro
Type: Dissertação2019-05-01T00:00:00ZImobilização de β-Galactosidases em membranas de óxido de grafeno
http://hdl.handle.net/11422/14023
Title: Imobilização de β-Galactosidases em membranas de óxido de grafeno
Author(s)/Inventor(s): Luzardo, Jéssica Menezes de Mélo
Advisor: Simão, Renata Antoun
Abstract: The use of enzymes as catalysts requires recovery and reuse to make the process viable. Enzymatic immobilization changes enzyme stability, activity and specificity. There is no single method or support applicable to all enzymes and their various applications. It is very important to explore new substrates for immobilization with appropriate composition and structure in order to improve the efficiency of the immobilized enzymes. In this work, the use of graphene oxide membranes produced by chemical route (GO) and electrochemistry (EG) for immobilization of β-Galactosidases was investigated. For the membrane’s characterization, the techniques of atomic force microscopy, Raman spectroscopy, X-ray excitation and X-ray diffraction spectroscopy were used. The electrochemical technique of cyclic voltammetry was used to monitor the reaction of conversion of lactose to glucose as well as to evaluate the influence of the use of plasma treatment on the membranes. The AFM images showed that the EG membranes had better immobilization of the enzymes on the surface. This membrane was treated with different plasmas to obtain improved substrates, however, the argon plasma was destructive and the plasma jet contributed to the reduction of the defects of the graphene sheets, interfering in the interaction between the same and the active center of the enzymes, making it difficult to evaluate the activity by cyclic voltammetry. Finally, the unmodified EG membrane was the best substrate for immobilization.
Publisher: Universidade Federal do Rio de Janeiro
Type: Dissertação2019-07-01T00:00:00ZFlow visualization of silica nanofluid injection for enhanced oil recovery in a micromodel based on wellsorted grain-size porous media
http://hdl.handle.net/11422/14022
Title: Flow visualization of silica nanofluid injection for enhanced oil recovery in a micromodel based on wellsorted grain-size porous media
Author(s)/Inventor(s): Cruz, Felipe Adrião
Advisor: Balbino, Tiago Albertini
Abstract: Currently, coreflood analysis is considered as the conventional laboratory test to understand fluid flow through porous media. However, this technique possesses disadvantages regarding time-consuming experiments and fluid movement visualization. In this context, microfluidics is emerging as a trend in reservoir engineering, providing fast-paced solutions for old-fashioned problems. Microfluidic chips, or micromodels, are able to directly observe a wide range of transport phenomena in pore-scale and assist in fluid screening for enhanced oil recovery (EOR). In this study, polydimethylsiloxane (PDMS) micromodels were fabricated and applied in a nano-EOR technique with silica nanofluids. Several pore-networks were computationally generated based on statistical parameters of real rocks. An experimental setup was mounted to provide a platform for flow visualization and a fluid injection method was applied similarly to field applications. By digital processing of captured images, oil recovery factors (RF) were calculated during the experiments. Finally, silica nanofluid injection showed additional RFs of 12% as tertiary recovery and 23% as secondary recovery.
Publisher: Universidade Federal do Rio de Janeiro
Type: Dissertação2019-07-01T00:00:00Z