Mechanistic study of menisci motion within homogeneously and heterogeneously wet porous media

textOil reservoirs and soil can be homogeneously wet (water-wet, oil-wet, neutralwet) or heterogeneously wet (mixed wet or fractionally wet). The goal of this research is to model the detailed configuration of wetting and non-wetting phases within homogeneously and heterogeneously wet porous media. We use a dense random pack of equal spheres as a model porous medium. The geometry of the sphere pack is complex but it is known. In homogeneously wet porous media we quantify the effect of low saturations of the wetting phase on the non-wetting phase relative permeability by solving analytically the geometry of the wetting phase. At low saturations (at or near the drainage endpoint) the wetting phase exists largely in the form of pendular rings held at grain contacts. Pore throats correspond to the constriction between groups of three grains, each pair of which can be in contact. Thus the existence of these pendular rings decreases the void area available for the flowing non-wetting phase. Consequently, the existence of the pendular rings decreases the permeability of non-wetting phase. Our model explains the significant permeability reduction of the non-wetting phase with a small change in the wetting phase in a low permeability porous medium. To model heterogeneously wet porous medium, we assume that the porous medium is fractionally wet where each grain is either oil-wet or water-wet. These waterwet or oil-wet grains are distributed randomly within the porous medium. We calculate analytically the stable fluid configuration in individual pores and throats of a fractionally wet medium. The calculation is made tractable by idealizing the configurations as locally spherical (menisci) or toroidal (pendular rings.) Because the calculation of the interface position is entirely local and grain-based, it provides a single, generalized, geometric basis for computing pore-filling events during drainage as well as imbibition. This generality is essential for modeling displacements in fractionally wet media. Pore filling occurs when an interface becomes unstable in a pore throat (analogous to the Haines condition for drainage in a uniformly wet throat), when two or more interfaces come into contact and merge to form a single interface (analogous to the Melrose condition for imbibition in uniformly wet medium), or when a meniscus in a throat touches a nearby grain (a new stability criterion). The concept of tracking the fluid/fluid interfaces on each grain means that a traditional pore network is not used in the model. The calculation of phase saturation or other quantities that are conveniently computed in a network can be done with any approach for defining pore bodies and throats. The fluid/fluid interfaces are mapped from the grain-based model to the network as needed. Consequently, the model is robust as there is no difference in the model between drainage and imbibition, as all criteria are accounted for both increasing and decreasing capillary pressure.Petroleum and Geosystems Engineerin

Chitosan-FastOs® BG membrane-guides for nervous tissue regeneration

Mestrado em Materiais e Dispositivos BiomédicosThree-dimensional (3D) biodegradable composite porous scaffolds made of a biopolymer matrix (chitosan) and a bioactive glass (FastOs®BG-Z4) were fabricated via freeze drying as guides for nerve tissue engineering applications. For this purpose, chitosan was dissolved in aqueous solutions of lactic acid (LA, 1 wt.%) to reach a final concentration of 2 wt.%. Subsequently FastOs®BG-Z4 in powder form was added to chitosan solution in a chitosan/Fasto®BG-Z4 weight ratio of 50/50. The Chitosan/FastOs®BG-Z4 systems were cross-linked via adding different concentrations (0.01, 0.05 and 0.5 wt.%) of two kinds of cross-linking agents, genipin, a natural component, and glutaraldehyde, a synthetic agent, to stiffen the chitosan network. The final mixtures were then frozen at two temperatures, 20ºC and 80ºC followed by freezedrying to obtain porous scaffolds. For achieving the optimal Chitosan/FastOs®BG-Z4 scaffolds, the influences of adding FastOs®BG-Z4 powder and/or different amounts of crosslinking agents on the rheological properties of chitosan/LA solutions were firstly investigated by rheological measurements. The results showed that a strong and stable gel could not be obtained even when the highest amount of cross-linking agents (0.5 wt.%) was added to the 2 wt.% chitosan solution, while effective cross-linking occurred in the presence of FastOs®BG-Z4 powder. Therefore, it was concluded that FastOs®BG-Z4 plays an active role on chitosan complexation. The positive interactions between chitosan and the surface of FastOs®BGZ4 particles and/or the ionic species leached out to the solution needs to be further investigated in future work. The microstructural features of porous scaffolds were investigated by scanning electron microscope (SEM), and the porosity assessment was made by ethanol replacement method. The mechanical properties of porous scaffolds were investigated under compression/swelling tests with samples immersed in phosphate-buffered saline (PBS) solution. In vitro degradation tests were also performed by immersing the samples in iv phosphate-buffered saline (PBS) solution for 2 months tests and the degradation degree was evaluated through the undergone weight changes. The results showed some common features among genipin or glutaraldehyde as crosslinking agents: increasing their amounts from 0.01 to 0.5 wt.% led to reductions in gelling time, porosity fraction, swelling and degradation rate, while cross-linking degree increased. However, their effects on pore size and compression strength of the scaffolds diverged. For genipin pore size decreased and consequently the compression strength increased, while for glutaraldehyde pore size always increased with added amounts, but compression strength was improved with concentration increasing from 0.01 to 0.05 wt.%, decreasing when the added amount was further increased to 0.5 wt.%. Moreover, 20ºC was selected as the most suitable freezing temperature when considering the porous microstructural features and the intended applications.A presente tese relata acerca do fabrico e caracterização de compósitos porosos tridimensionais (3D) biodegradáveis baseados em quitosano, como matriz biopolimérica, carregada com partículas de um vidro bioativo (Fastos®BG-Z4). Para este efeito, o quitosano foi dissolvido em solução aquosa de ácido láctico (LA, 1% em peso) até atingir uma concentração final de 2% em peso. Subsequentemente o Fastos®BG-Z4 em forma de pó foi adicionado à solução de quitosano em uma proporção em peso de quitosano/ Fastos®BG-Z4 de 50/50. Os sistemas quitosano/Fastos®BG-Z4 foram reticulados por meio de adição de diferentes percentagens em peso (0.01, 0.05 e 0.5) de dois tipos de agentes de ligação cruzada, um componente natural, genipin, e um agente sintético, glutaraldeído. As misturas finais foram então reticuladas a 60ºC seguido de congelamento a duas temperaturas diferentes, 20ºC e 80ºC. O gelo foi depois sublimado por liofilização de modo a obter matrizes porosas para aplicações como guias em engenharia de tecidos nervosos periféricos. Com vista à optimização do processo de fabrico e das propriedades das estruturas porosas de suporte (andaimes) de quitosano/Fastos®BG-Z4, estudaram-se os efeitos da adição do Fastos®BG-Z4 em pó e/ou de diferentes quantidades de agentes de reticulação nas propriedades reológicas das soluções de LA/quitosano. Os resultados mostraram a impossibilidade de obter de um gel de quitosano suficientemente forte e estável mesmo quando a quantidade mais elevada de agentes de reticulação (0.5% em peso) foi adicionada à solução de quitosano, em contraste com o que aconteceu com a adição do pó de Fastos®BG-Z4 na ausência de outros agentes de reticulação. Esta descoberta permitiu concluir que o Fastos®BG-Z4 desempenha um papel activo na complexação do quitosano. As interacções positivas entre o quitosano e a superfície das partículas do Fastos®BG-Z4 e/ou as espécies iónicas lixiviadas para a solução precisam de ser melhor investigadas no futuro. vi As características microestruturais dos materiais porosos foram investigadas por microscopia electrónica de varrimento (SEM), e a porosidade foi determinada pelo método de substituição de etanol. As propriedades mecânicas dos compósitos porosos imersos em solução (PBS) de solução salina tamponada com fosfato foram investigadas através de testes de compressão/inchamento. Realizaram-se também testes de degradação in vitro por imersão das amostras na mesma solução de PBS durante 2 meses, e o grau de degradação foi avaliado através das alterações de peso sofridas pelas amostras. Os resultados mostraram algumas características comuns entre o genipin e o glutaraldeído como agentes de reticulação: o aumento das quantidades adicionadas (0.010.5% em peso) levou a reduções no tempo de gelificação, na fracção de porosidade, no grau de inchamento, e na taxa de degradação, enquanto o grau de reticulação aumentou. No entanto, os seus efeitos sobre o tamanho dos poros e a resistência à compressão dos suportes porosos divergiram. O tamanho de poro diminuiu no caso do genipin, o que se traduziu em consequentes aumentos da resistência à compressão; enquanto o tamanho dos poros aumentou sempre com as quantidades adicionadas no caso do glutaraldeído, pelo que só foram registadas melhorias na resistência à compressão na gama de concentrações entre 0.010.05% em peso, diminuindo quando a quantidade adicionada foi aumentada para 0,5 % em peso. Verificou-se ainda que a temperatura de 20ºC era a que permitia obter as microestruturas porosas mais adequadas para as aplicações almejadas

Stimuli-responsive local drug molecule delivery to adhered cells in a 3D nanocomposite scaffold

Drug delivery systems capable of providing controlled and localized drug release are a highly important tool in the biomedical field because they can provide site-specific, sustained, and controlled drug release at the place where the drug is most needed, and they allow for significantly lower doses of the drug at other parts of the body, reducing the drug\u2019s potential side effects. In this respect, we describe pH-responsive PMO/alginate nanocomposite (NC) scaffolds with different pH-responsive strengths for controlled local drug delivery applications. To prepare the PMO/alginate NC scaffolds, PMOs were first loaded with anti-cancer molecules and then coated with a non-biopolymer or a biopolymer, after which the PMOs were embedded into an alginate network. We found that drug release from the PMOs was regulated by the pH of the environment and the surface coating of the PMOs due to the different pHdependent levels of electrostatic interactions between all the charged components of the NC scaffolds. The non-biopolymer-coated formulation of the NC scaffold can be utilized to deliver higher dosages of drug molecules directly to cells, while the biopolymer-coated system is useful for slow and prolonged release of drugs and for enhanced cell adhesion. Nonetheless, both systems can be utilized, in particular, to deliver higher dosages of drug molecules directly to cancer cells while delivering less of the drug to healthy cells

The Correlation between Intersegmental Coordination Variability and Frontal Plane Hip Kinematics during Running in Persons with Patellofemoral Pain

Background: Despite the existing evidence indicating altered hip kinematics as well as the studies showing altered movement coordination variability in persons with patellofemoral pain (PFP), there is no study investigating the correlation between hip joint kinematic and movement coordination variability in persons with patellofemoral pain (PFP).Objective: This study aims to evaluate the correlation between peak hip adduction and variability of thigh frontal-shank transverse coordination during running in persons with PFP.Material and Methods: In this cross-sectional correlational study, kinematic data were collected from 34 females (17 with and 17 without PFP) aged 18-35 years during treadmill running at preferred and fixed speeds, each for 30 s. The continuous relative phase method was used to calculate the coordination of thigh frontal-shank transverse. To calculate the deviation phase as the variability of intersegmental coordination, the standard deviation of the ensemble continuous relative phase curve points was averaged. The parameters of interest were peak hip adduction and coordination variability of thigh frontal-shank transverse. The Pearson Correlation Coefficient (r) was used to calculate the correlation between the variables.Results: The Pearson correlation coefficient showed a significant negative correlation between the peak hip adduction angle and variability of thigh frontal– shank transverse during running at both fixed (r=-0.553, P0.05).  Conclusion: The results indicated that greater adduction of the hip joint in persons with PFP during running is contributed to lesser variability of thigh frontal-shank transverse

Human-based fibrillar nanocomposite hydrogels as bioinstructive matrices to tune stem cell behavior

The extracellular matrix (ECM)-biomimetic fibrillar structure of platelet lysate (PL) gels along with its enriched milieu of biomolecules has drawn significant interest in regenerative medicine applications. However, PL-based gels have poor structural stability which severely limits its performance as a bioinstructive biomaterial. Here, rod-shaped cellulose nanocrystals (CNC) are used as a novel approach to modulate the physical and biochemical microenvironment of PL gels enabling their effective use as injectable human-based cell scaffolds with a level of biomimicry that is difficult to recreate with synthetic biomaterials. The incorporation of CNC (0 to 0.61 wt.%) into the PL fibrillar network during the coagulation cascade leads to decreased fiber branching, increased interfiber porosity (from 66 to 83%) and modulate fiber (from 1.4 ± 0.7 to 27 ± 12 kPa) and bulk hydrogel (from 18 ± 4 to 1256 ± 82 Pa) mechanical properties. As result of these physicochemical alterations, nanocomposite PL hydrogels resist to the typical extensive clot retraction (from 76 ± 1 to 24 ± 3 at Day 7) and show favored retention of PL bioactive molecules. The feedback of these cues on the fate of human adipose-derived stem cells is evaluated, showing how it can be explored to modulate the commitment of encapsulated stem cells toward different genetic phenotypes without the need for additional external biological stimuli. These fibrillar nanocomposite hydrogels allow therefore to explore the outstanding biological properties of human-based PL as an efficient engineered ECM which can be tailored to trigger specific regenerative pathways in minimal invasive strategies.The authors thank the Hospital da Prelada (Porto, Portugal) for providing adipose tissue samples. The authors acknowledge the financial support from project Recognize (UTAP-ICDT/CTM-BIO/0023/2014), project NORTE-01-0145FEDER-000021 supported by the Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF), the European Union Framework Programme for Research and Innovation HORIZON 2020, under the TEAMING Grant agreement No. 739572 – The Discoveries CTR EU, Forecast 668983, Marie Skłodowska-Curie grant agreement No. 706996 (PrinTendon) and CHEM2NATURE 692333; FCT/MCTES (Fundação para a Ciência e a Tecnologia/ Ministério da Ciência, Tecnologia, e Ensino Superior) and the Fundo Social Europeu através do Programa Operacional do Capital Humano (FSE/POCH) in the framework of PhD grant PD/59/2013 – PD/BD/113807/2015 for BBM, Post-Doc grant SFRH/BPD/112459/2015 for R.D.info:eu-repo/semantics/publishedVersio

Advanced therapeutic dressings for effective wound healing

Advanced therapeutic dressings that take active part in wound healing to achieve rapid and complete healing of chronic wounds is of current research interest. There is a desire for novel strategies to achieve expeditious wound healing due to the enormous financial burden worldwide. This paper reviews the current state of wound healing and wound management products, with emphasis on the demand for more advanced forms of wound therapy and some of the current challenges and driving forces behind this demand. The paper reviews information mainly from peer reviewed literature and other publicly available sources such as the FDA. A major focus is the treatment of chronic wounds including amputations, diabetic and leg ulcers, pressure sores, surgical and traumatic wounds (e.g. accidents and burns) where patient immunity is low and the risk of infections and complications are high. The main dressings include medicated moist dressings, tissue engineered substitutes, biomaterials based biological dressings, biological and naturally derived dressings, medicated sutures and various combinations of the above classes. Finally, the review briefly discusses possible prospects of advanced wound healing including some of the emerging approaches such as hyperbaric oxygen, negative pressure wound therapy and laser wound healing, in routine clinical care

Efecto del recubrimiento en el comportamiento mecánico y la bioactividad de andamiajes biocerámicos fabricados mediante moldeo robotizado

Tesis doctoral con la Mención de "Doctor Internacional"El hueso es uno de los tejidos más frecuentemente trasplantado. Los injertos óseos se pueden dividir en varias categorías: autoinjertos, aloinjertos y xenoinjertos. Por otra parte, en este sentido, la ingeniería de tejido óseo surgió hace casi tres décadas como una alternativa para promover la capacidad regenerativa del hueso. Una de las etapas más importantes en la ingeniería de tejidos es el diseño y fabricación de una estructura tridimensional porosa biodegradable (andamiaje) capaz de proporcionar el soporte mecánico necesario durante la regeneración del hueso dañado. Los vidrios bioactivos están atrayendo gran atención para su uso en ingeniería de tejido óseo debido a su alta bioactividad. Entre ellos, el biovidrio 45S5 es probablemente el más estudiado y utilizado como sustituto óseo. La principal desventaja de los andamiajes de 45S5 es su alta fragilidad. El objetivo principal de este trabajo es el desarrollo de andamiajes de 45S5 en combinación con polímeros sintéticos o naturales para superar estos obstáculos. Las tareas realizadas incluyen: (1) Fabricación y caracterización de andamiajes de 45S5 mediante moldeo robotizado (robocasting), se ha utilizado una nueva formulación para la preparación de la tinta a partir de polvos de 45S5. (2) Mejora de las propiedades mecánicas intrínsecas de las barras que constituyen los andamiajes mediante el control de los parámetros de sinterización. (3) Refuerzo mecánico de los andamiajes de 45S5 mediante su recubrimiento con polímeros sintéticos (PCL y PLA) y naturales (quitosano, alginato y gelatina) Determinación de la biodegradabilidad y bioactividad in vitro de andamiajes de 45S5 y 45S5/polímeroBone is one of the most frequently transplanted tissues. The materials used in bone grafting can be divided into several major categories, including autografts, allografts, and xenografts. Each of these options has its own advantages and disadvantages. The field of bone tissue engineering (BTE) was emerged nearly three decades ago as a convenient alternative to promote the regenerative ability of the host body. One of the most important stages of BTE is the design and processing of a porous, biodegradable three-dimensional structure called ‘scaffold’ providing the mechanical support during regeneration of damaged bone. Bioactive glasses are attracting increasing attention for their use as BTE due to their high bioactivity. Among them, 45S5 bioglass is probably the most widely used as bone graft substitute in clinical applications. However, the main disadvantage of bioglass based scaffolds is their high brittleness. The primary objective of this work is to develop 45S5 scaffolds in combination with synthetic or natural polymers to overcome these obstacles. The tasks carried out to fulfill the above aims include: Fabrication and characterization of 45S5 scaffolds by robocasting technique, a new and simple formulation has been used for the preparation of the concentrated suspensions from 45S5 powders. Improving the intrinsic properties of the 45S5 struts by controlling the sintering parameters. Reinforcement of 45S5 scaffolds by polymer coatings by different kind of synthetic (PCL and PLA), and natural (chitosan, alginate, gelatin) polymers. Determination of the in vitro biodegradability and bioactivity of selected bare and coated scaffolds

Controlling Polymer Properties Through Attenuating Intermolecular Interactions

Attenuating intermolecular interactions can result in enhancing properties or even can lead to new properties. Attenuating intermolecular and interchain interactions in polymeric materials can be achieved through the structural design and complex blend preparation. In this study, both approaches have been employed for organic materials with the focus on ion exchange membranes and inorganic materials developed by sol-gel chemistry. Manipulating intermolecular interactions through designing a branched poly(arylene ether sulfone) (BPAES) copolymer with various side-chain lengths led to change in molecular aggregation in solution and affected polymer thermal and mechanical properties in the film. Results showed the existence of optimum side-chain length for achieving highest mechanical robustness. However, a further increase in side-chain length would negatively affect intermolecular interactions and would lead to steric crowding and lowering the toughness of materials. Furthermore, this newly designed structure with sulfonated side-chain (sBPAES) was introduced to the matrix of fully aromatic sulfonated polyphenylene sPP to enhance its properties for proton exchange membrane fuel cell application. The ionic interaction induced by the sulfonated side-chain dramatically improved miscibility between these distinctly different ionomers and affected the polymer morphology and water distribution in the polymer. These modifications led to an increase in fractional free volume and relative free water content in the polymer and consequently resulted in increased conductivity by 4% and decreased water uptake by 25% for sPP:sBPAES(95:5) blend in comparison with pristine sPP. Optimized intermolecular interactions in blend containing 5 wt% sBPAES within sPP led to hydrogen-oxygen peak-power output of 630 mW/cm2 at 1490 mA/cm2, which was greater than its unmodified sPP version at 570 mW/cm2 and 1220 mA/cm2. Effect of intermolecular interactions on polymer properties was further studied for inorganic materials developed via sol-gel chemistry to produce homogenous electrospun nanofibers. Altering the inorganic network by changing the density of Si-O-Ti, Ti-O-Ti ,and Si-O-Si while the extent of network formation was similar resulted in bead formation for samples containing more than 50 mol% of titania. In addition, statistical analysis study on SiO2-TiO2 nanofibers with similar 1:1 molar ratio showed optimizing interactions between electrospinning conditions and extent of network formation can transform broken nanofibers to homogenous continuous nanofibers

Interactive architectural approach (interactive architecture): An effective and adaptive process for architectural design

This research attempts to offer a new approach for architectural design process that the concepts of interaction and multi-relations are being achieved through it. This approach, which is identified as an interactive architecture, suggests a process that a dynamic and mutual relation will create among all factors and parameters of design and the effects of each factor or parameters on final design will be considered. In fact, the main axis of the suggested approach is comprehensive interaction with all various aspects of design, since the design problems have multi-aspects, mostly. Thus, the final design will be resulted based on these mutual relations and it is a production which will have a maximum and optimum adaption with all factors and parameters. What makes this attitude more significant and crucial is the chaotic situation that is produced in architecture and urban designing of most cities especially in developing countries and leads to lack of identity in these cities. So, the interactive approach can be able to eliminate the challenges and create the fields of sustainable architecture and urban development through an effective method. However, this process encounters to some constraints and challenges along with some potentials which are discussed in this essay. The research method is analytical-interpretative and based on qualitative analyses