Influence of the rate of cooling in the resistance to corrosion of the alloy Ti6Al4V eli deformed in warms

Este artículo pretende hacer un aporte específico relacionado con la posibilidad de obtener mediante forja en caliente componentes de Ti6Al4V ELI con la microestructura y propiedades aptas para aplicaciones biomédicas. Las muestras fueron sometidas inicialmente a un proceso de forja en caliente a dos niveles de temperatura seleccionadas dentro del intervalo bifásico de la aleación. Se empleó una velocidad de avance de la herramienta de 1.8 cm/s y tres medios de enfriamiento, agua, aire y arcilla, con el fin de determinar su influencia sobre la microestructura y la resistencia a corrosión. Para el análisis microestructural se emplearon las técnicas de microscopía óptica de luz reflejada (MOLR) y microscopia electrónica de barrido (MEB). La resistencia a corrosión de la aleación fue evaluada mediante curvas de polarización cíclica en solución Ringer desaireada a temperatura corporal (37°C). Los resultados de resistencia a corrosión de las muestras deformadas fueron confrontados con los de la condición en el estado de entrega comercial, lo que permitió concluir sobre las condiciones de procesamiento del material con el fin de implementar un procedimiento adecuado de forja en caliente a nivel industrial para su uso como biomaterial.Abstract: The aim of this paper is to discuss the feasibility of manufacturing Ti6Al4V ELI components with proper microstructure and mechanical properties for biomedical applications. The samples were hot forged at two temperature levels, both of them within the dual phase field (α + β). A constant strain rate of 4x10-3 s-1 was employed. The samples were cooled in three different cooling media (water, air and clay) and some correlations between cooling rate and microstructure and corrosion resistance were established. The microstructure was analyzed with the aid of light optical microscopy (LOM) and scanning electron microscopy (SEM) techniques. The corrosion resistance was determined by cyclic polarization tests in Ringer´s solution at 37°C. Comparison between the results obtained for forged and commercial samples allowed concluding about some of the recommended manufacturing conditions of Ti6Al4V for biomedical applications

Decay of weak solutions to the 2D dissipative quasi-geostrophic equation

We address the decay of the norm of weak solutions to the 2D dissipative quasi-geostrophic equation. When the initial data is in $L^2$ only, we prove that the $L^2$ norm tends to zero but with no uniform rate, that is, there are solutions with arbitrarily slow decay. For the initial data in $L^p \cap L^2$, with $1 \leq p < 2$, we are able to obtain a uniform decay rate in $L^2$. We also prove that when the $L^{\frac{2}{2 \alpha -1}}$ norm of the initial data is small enough, the $L^q$ norms, for $q > \frac{2}{2 \alpha -1}$ have uniform decay rates. This result allows us to prove decay for the $L^q$ norms, for $q \geq \frac{2}{2 \alpha -1}$, when the initial data is in $L^2 \cap L^{\frac{2}{2 \alpha -1}}$.Comment: A paragraph describing work by Carrillo and Ferreira proving results directly related to the ones in this paper is added in the Introduction. Rest of the article remains unchange

RICORS2040 : The need for collaborative research in chronic kidney disease

Chronic kidney disease (CKD) is a silent and poorly known killer. The current concept of CKD is relatively young and uptake by the public, physicians and health authorities is not widespread. Physicians still confuse CKD with chronic kidney insufficiency or failure. For the wider public and health authorities, CKD evokes kidney replacement therapy (KRT). In Spain, the prevalence of KRT is 0.13%. Thus health authorities may consider CKD a non-issue: very few persons eventually need KRT and, for those in whom kidneys fail, the problem is 'solved' by dialysis or kidney transplantation. However, KRT is the tip of the iceberg in the burden of CKD. The main burden of CKD is accelerated ageing and premature death. The cut-off points for kidney function and kidney damage indexes that define CKD also mark an increased risk for all-cause premature death. CKD is the most prevalent risk factor for lethal coronavirus disease 2019 (COVID-19) and the factor that most increases the risk of death in COVID-19, after old age. Men and women undergoing KRT still have an annual mortality that is 10- to 100-fold higher than similar-age peers, and life expectancy is shortened by ~40 years for young persons on dialysis and by 15 years for young persons with a functioning kidney graft. CKD is expected to become the fifth greatest global cause of death by 2040 and the second greatest cause of death in Spain before the end of the century, a time when one in four Spaniards will have CKD. However, by 2022, CKD will become the only top-15 global predicted cause of death that is not supported by a dedicated well-funded Centres for Biomedical Research (CIBER) network structure in Spain. Realizing the underestimation of the CKD burden of disease by health authorities, the Decade of the Kidney initiative for 2020-2030 was launched by the American Association of Kidney Patients and the European Kidney Health Alliance. Leading Spanish kidney researchers grouped in the kidney collaborative research network Red de Investigación Renal have now applied for the Redes de Investigación Cooperativa Orientadas a Resultados en Salud (RICORS) call for collaborative research in Spain with the support of the Spanish Society of Nephrology, Federación Nacional de Asociaciones para la Lucha Contra las Enfermedades del Riñón and ONT: RICORS2040 aims to prevent the dire predictions for the global 2040 burden of CKD from becoming true

Long Time Dynamics of Forced Critical SQG

We prove the existence of a compact global attractor for the dynamics of the forced critical surface quasi-geostrophic equation (SQG) and prove that it has finite fractal (box-counting) dimension. In order to do so we give a new proof of global regularity for critical SQG. The main ingredient is the nonlinear maximum principle in the form of a nonlinear lower bound on the fractional Laplacian, which is used to bootstrap the regularity directly from $L^\infty$ to $C^\alpha$, without the use of De Giorgi techniques. We prove that for large time, the norm of the solution measured in a sufficiently strong topology becomes bounded with bounds that depend solely on norms of the force, which is assumed to belong merely to $L^\infty \cap H^1$. Using the fact that the solution is bounded independently of the initial data after a transient time, in spaces conferring enough regularity, we prove the existence of a compact absorbing set for the dynamics in $H^1$, obtain the compactness of the linearization and the continuous differentiability of the solution map. We then prove exponential decay of high yet finite dimensional volume elements in $H^1$ along solution trajectories, and use this property to bound the dimension of the global attractor

Potential of Natural Biomaterials in Nano-scale Drug Delivery

Background: The usage of natural biomaterials or naturally derived materials intended for interface with biological systems has steadily increased in response to the high demand of amenable materials, which are suitable for purpose, biocompatible and biodegradable. There are many naturally derived polymers which overlap in terms of purpose as biomaterials but are equally diverse in their applications. Methods: This review examines the applications of the following naturally derived polymers; hyaluronic acid, silk fibroin, chitosan, collagen and tamarind polysaccharide (TSP); further focusing on the biomedical applications of each as well as emphasising on individual novel applications. Results: Each of the polymer was found to demonstrate a wide variety of successful biomedical applications fabricated as wound dressings, scaffolds, matrices, films, sponges, implants or hydrogels to suit the therapeutic need. Interestingly, blending and amelioration of polymer structures were but two of a selection of strategies to modify the functionality of the polymers to suit the purpose. Further these polymers have shown promise to deliver small molecule drugs, proteins and genes as nano-scale delivery systems. Conclusion: The review highlights the breadth and depth of applications of the aforementioned polymers as biomaterials. Hyaluronic acid, silk fibroin, chitosan, collagen and TSP have been successfully utilised as biomaterials in the subfields of implant enhancement, wound management, drug delivery, tissue engineering and nanotechnology. Whilst there are a number of associated advantages (i.e. biodegradability, biocompatibility, non-toxic, non-antigenic as well as amenability) the select disadvantages of each individual polymer provide significant scope for their further exploration and overcoming challenges like feasibility of mass production at a relatively low cost