Design and Early Age Performance of Sustainable One-Part Geopolymers for Well Cementing

One-part geopolymers, known as “just add water” (JAW), alkali-activated formulation is presented in this work. This work reveals the design and development of short-term properties of JAW geopolymers for use in oilwell cementing and well abandonment. Granite-based mix designs normalized with a byproduct slag and a small amount of microsilica as precursors were developed. The solid activator is composed of potassium silicate and potassium hydroxide, which are mixed with the precursors to synthesize the JAW formulation. Zinc oxide is used as a strength booster admixture. The cementing properties of the developed granite-based mix designs were characterized by investigating reaction phases and mechanical properties. Dissolution, heat evolution, pumpability, strength development, and mineralogy are also studied. The results show that a positive correlation among all the given analyses for the final geopolymeric product is quite observable. Zinc oxide is favorable to be added for optimizing the given precursor mix design to enhance the solubility and leads to much higher heat evolutions. Furthermore, it develops early strength up to 16 MPa without any negative effect on the investigated one-part geopolymer slurries.publishedVersio

Poly-Left-Lactic Acid tubular scaffolds via Diffusion Induced Phase Separation (DIPS): control of morphology

n this work, tubular poly-left-lactic acid scaffolds for vascular tissue engineering applications were produced by an innovative two-step method. The scaffolds were obtained by performing a dip-coating around a nylon fiber, followed by a diffusion induced phase separation process. Morphological analysis revealed that the internal lumen of the as-obtained scaffold is equal to the diameter of the fiber utilized; the internal surface is homogeneous with micropores 1–2 μm large. Moreover, a porous open structure was detected across the thickness of the walls of the scaffold. An accurate analysis of the preparation process revealed that it is possible to tune up the morphology of the scaffold (wall thickness, porosity, and average pore dimension), simply by varying some experimental parameters. Preliminary in vitro cell culture tests were carried out inside the scaffold. The results showed that cells are able to grow within the internal surface of the scaffolds and after 3 weeks they begin to form a “primordial” vessel-like structure. Modeling predictions of the dip-coating process display always an underestimate of experimental data (dependence of wall thickness upon extraction rate).In this work, tubular poly-left-lactic acid scaffolds for vascular tissue engineering applications were produced by an innovative two-step method. The scaffolds were obtained by performing a dip-coating around a nylon fiber, followed by a diffusion induced phase separation process. Morphological analysis revealed that the internal lumen of the as-obtained scaffold is equal to the diameter of the fiber utilized; the internal surface is homogeneous with micropores 1–2 lm large. Moreover, a porous open structure was detected across the thickness of the walls of the scaffold. An accurate analysis of the preparation process revealed that it is possible to tune up the morphology of the scaffold (wall thickness, porosity, and average pore dimension), simply by varying some experimental parameters. Preliminary in vitro cell culture tests were carried out inside the scaffold. The results showed that cells are able to grow within the internal surface of the scaffolds and after 3 weeks they begin to form a ‘‘primordial’’ vessel-like structure. Modeling predictions of the dipcoating process display always an underestimate of experimental data (dependence of wall thickness upon extraction rate)

Transfusion-Associated Lyme Disease – Although Unlikely, It Is Still a Concern Worth Considering

Even though hematogenous spread of the Lyme disease spirochete, Borrelia burgdorferi, has been well documented, and there are more than 300,000 cases per year of Lyme disease in the United States, no evidence (anecdotal or published) of transfusion-associated Lyme disease has been reported. Such a possibility would seem to exist but various factors, as discussed in this perspective, make this less likely to occur. Nonetheless, if not done already, safeguards need to be put in place at blood collection and dispensing facilities, possibly with the assistance of diagnostic microbiology and immunology laboratories, to ensure that the potential for the transfer of the Lyme disease spirochete through a blood transfusion remains a theoretical consideration rather than a real possibility

PLLA biodegradable scaffolds for angiogenesis via Diffusion Induced Phase Separation (DIPS)

A critical obstacle in tissue engineering is the inability to maintain large masses of living cells upon transfer from the in vitro culture conditions into the host in vivo. Capillaries, and the vascular system, are required to supply essential nutrients, including oxygen, remove waste products and provide a biochemical communication “highway”. For this reason it is mandatory to manufacture an implantable structure where the process of vessel formation – the angiogenesis – can take place. In this work PLLA scaffolds for vascular tissue engineering were produced by dip-coating via Diffusion Induced Phase Separation (DIPS) technique. The scaffolds, with a vessel-like shape, were obtained by performing a DIPS process around a nylon fibre whose diameter was 700 μm. The fibre was first immersed into a 4% PLLA dioxane solution and subsequently immersed into a second bath containing distilled water. The covered fibre was then rinsed in order to remove the excess of dioxane and dried; finally the internal nylon fibre was pulled out so as to obtain a hollow biodegradable PLLA fiber. SEM analysis revealed that the scaffolds have a lumen of ca. 700 μm. The internal surface is homogeneous with micropores 1–2 μm large. Moreover, a cross section analysis showed an open structure across the thickness of the scaffold walls. A cell culture of endothelial cells was carried out into the as-prepared scaffolds. The result showed that cells are able to grow within the scaffolds and after 3 weeks they begin to form a “primordial” vessel-like structure

3D cultures of primary astrocytes on Poly-L-lactic acid scaffolds

Tissue engineering is an emerging multidisciplinary field that aims at reproducing in vitro tissues with morphological and functional features similar to the biological tissue of the human body. Polymeric materials can be used in contact with biological systems in replacing destroyed tissue by transplantation [1]. Several biopolymers, including poly L (lactic acid) (PLLA), have been used in biomedical applications to set scaffolds with ductile proprieties and biodegradation kinetics [2]. In particular, the PLLA scaffold topography mimics the natural extracellular matrix and makes it a good candidate for neural tissue engineering. We report about of 3D system the PLLA porous scaffolds prepared via thermally-induced phase separation (TIPS) [3], and utilized as substrate for primary rat astrocytes 3D growth. Interestingly astrocytes adapt well to these porous matrices, not only remaining on the surface, but also penetrating inside the scaffolds. They colonize the matrix acquiring a typical star-like morphology; they form cell contacts and, in addition produce EVs as in vivo [4]. These results suggest that the chosen conditions could be a good starting point for 3D brain culture systems. PLLA scaffolds could be further enriched to host two or three different brain cell types, in order to set an in vitro model of blood brain barrier. The future use of co-culture systems may be involved in drug delivery studies, and in the formulation of new therapeutic strategies for the treatment of neurological diseases. [1]Langer R, Vacanti JP. Tissue engineering. Science. 1993; 260: 920 [2]Nejati E, et al. Appl. Sci. Manuf. 2008; 39: 1589–1596 [3]Scaffaro R, et al. J. Mech. Behav. Biomed. Mater. 2016; 54:8-20 [4]Schiera G, et al. Biomed Res Int 2015: 152926, 201

Investimento imobiliário alavancado na banca

A presente Dissertação investiga a prática da alavancagem financeira no contexto dos investimentos imobiliários e qual é o seu impacto no setor bancário. Procurará compreender de que forma os investidores utilizam a Banca, para adquirir imóveis, e escalar o portfólio. Embora esta estratégia seja utilizada no mundo imobiliário, ainda tende a ser alvo de críticas devido aos seus riscos inerentes, o que poderá estar relacionado, de certo modo, com a falta de informação e de educação financeira. Neste sentido, este trabalho abrirá caminho para uma melhor compreensão de como aumentar a carteira de investimentos através dos financiamentos. Investir usando dinheiro emprestado não é a forma correta de abordar o tema, a maneira ideal é afirmar que o investimento imobiliário assente no crédito permite expandir o portfólio, diversificar os ativos e aumentar potencialmente o retorno dos investimentos. Não obstante, deve estar assente que a alavancagem aumenta a vulnerabilidade financeira. Será importante recuar um pouco atrás na história, a fim de entender como se formou a crise do subprime, visto que os ciclos económicos são uma das temáticas mais abordadas nesta matéria. Durante períodos de crescimento económico, a demanda por imóveis e o acesso ao financiamento podem ser mais favoráveis, enquanto nas recessões, os riscos tendem a intensificar-se. Em suma, o trabalho enfatiza a interconexão entre o setor imobiliário e o bancário, que ilustra a alavancagem como a estratégia de investimento mais poderosa, devendo, contudo, ser abordada com cautela e com conhecimentos sólidos dos riscos inerentes.The present Dissertation investigates the practice of financial leverage in the context of real estate investments and its impact on the banking sector. It will seek to understand how investors use banking institutions to acquire real estate and scale their portfolios. Although this strategy is used in the real estate world, it still tends to be criticized due to its inherent risks, which may be related, to some extent, to a lack of information and financial education. In this sense, this work will pave the way for a better understanding of how to expand an investment portfolio through financing. Investing using borrowed money is not the correct way to approach the topic. The ideal way is to state that real estate investment based on credit allows for port folio expansion, asset diversification, and potentially increased investment returns. Nevertheless, it should be noted that leverage increases financial vulnerability. It will be important to step back in history a bit to understand how the subprime crisis formed since economic cycles are one of the most discussed topics in this matter. During periods of economic growth, the demand for real estate and access to financing can be more favourable, while during recessions, risks tend to intensify. In summary, this work emphasizes the interconnection between the real estate and banking sectors, illustrating leverage as the most powerful investment strategy. However, it should be approached with caution and a solid understanding of the inherent risks

Modulation of physical and biological properties of a composite PLLA and polyaspartamide derivative obtained via thermally induced phase separation (TIPS) technique

In the present study, blend of poly l-lactic acid (PLLA) with a graft copolymer based on α,β-poly(N-hydroxyethyl)-dl-aspartamide and PLA named PHEA-PLA, has been used to design porous scaffold by using Thermally Induced Phase Separation (TIPS) technique. Starting from a homogeneous ternary solution of polymers, dioxane and deionised water, PLLA/PHEA-PLA porous foams have been produced by varying the polymers concentration and de-mixing temperature in metastable region. Results have shown that scaffolds prepared with a polymer concentration of 4% and de-mixing temperature of 22.5 °C are the best among those assessed, due to their optimal pore size and interconnection. SEM and DSC analysis have been carried out respectively to study scaffold morphology and the influence of PHEA-PLA on PLLA crystallization, while DMF extraction has been carried out in order to quantify PHEA-PLA into the final scaffolds. To evaluate scaffold biodegradability, a hydrolysis study has been performed until 56 days by incubating systems in a media mimicking physiological environment (pH 7.4). Results obtained have highlighted a progressive increase in weight loss with time in PLLA/PHEA-PLA scaffolds, conceivably due to the presence of PHEA-PLA and polymers interpenetration. Viability and adhesion of bovine chondrocytes seeded on the scaffolds have been studied by MTS test and SEM analysis. From results achieved it appears that the presence of PHEA-PLA increases cells affinity, allowing a faster adhesion and proliferation inside the scaffold