Influence of organic phase change materials on the physical and mechanical properties of HDPE and PP polymers

In this work, the compatibility of four commercially available organic phase change materials, with melting points in the temperature range 44–58 °C and with engineering polymers high density polyethylene (HDPE) and polypropylene (PP), is investigated. These polymers are used for the design and manufacture of hot and cold thermal energy storage tanks or encapsulation media. The study involves interaction of polymer specimens with the four different phase change materials for a period of time up to 40 days under high temperature. The mass change, mechanical strength and properties of the polymers were tested. The wt% uptake reached 6.4 wt% for PP and 5.8 wt% for HDPE. The strength of HDPE is immediately decreased by Day 7 but at a significant level restored after Day 28. No such effect was found for PP. The surface wetting as well as thermal properties measured (DSC) on the specimens provided an insight on the interaction of the absorbed phase change materials with the polymer. An in depth distribution over time was observed with significant decrease in the mechanical strength of the polymers. An epoxy-based resin was also evaluated under the same conditions and is suggested as a protective coating.

Organic PCMs affect HDPE and PP mechanical properties. HDPE strength is remarkably partly restored by the homogeneous distribution of absorbed PCM.     

Tendência da Mortalidade por Doenças Cerebrovasculares no Brasil (1996-2015) e Associação com Desenvolvimento Humano e Vulnerabilidade Social

BackgroundCerebrovascular diseases (CBVD) are the second major cause of death in the world.ObjectiveTo analyze the mortality trend of CBVD in Brazil (1996 to 2015) and its association with Human Development Index (HDI) and the Social Vulnerability Index (SVI).MethodsThis is an ecological study. We analyzed the mortality rate standardized by CBVD. Death data were obtained from the Mortality Information System (SIM) and populational data from the Brazilian Institute of Geography and Statistics (IBGE). The model of regression by inflection points (Joinpoint regression) was used to perform the temporal analysis, calculating the Annual Percent Change (APC) and Average Annual Percent Change (AAPC), with 95% of confidence interval and a significance of 5%. Trends were classified as increasing, decreasing or stationary. A multivariate regression model was used to analyze the association between mortality by CBVD, HDI and SVI.ResultsDuring this period, 1,850,811 deaths by CBVD were recorded. We observed a reduction in the national mortality rate (APC -2.4; p = 0.001). Twenty federation units showed a significant trend, of which 13 showed reduction, including all states in the Midwest (n=4), Southeast (n=4) and South (n=3). The HDI was positively associated and the SVI was negatively associated with mortality (p = 0.046 and p = 0.026, respectively).ConclusionAn unequal epidemiological course of mortality was observed between the regions, being higher in the Southeast and South states, with a significative tendency of reduction, and lower in the North and Northeast states, but with a significative tendency of increase. HDI and SVI showed an association with mortality. (Arq Bras Cardiol. 2021; 116(1):89-99)     

Towards Customized Footwear with Improved Comfort

A methodology enabling the customization of shoes for comfort improvement is proposed and assessed. For this aim, 3D printed graded density inserts were placed in one of the critical plantar pressure zones of conventional insoles, the heel. A semi-automated routine was developed to design the 3D inserts ready for printing, which comprises three main stages: (i) the definition of the number of areas with different mesh density, (ii) the generation of 2D components with continuous graded mesh density, and (iii) the generation of a 3D component having the same 2D base mesh. The adequacy of the mesh densities used in the inserts was previously assessed through compression tests, using uniform mesh density samples. Slippers with different pairs of inserts embedded in their insoles were mechanically characterized, and their comfort was qualitatively assessed by a panel of users. All users found a particular pair, or a set, of prototype slippers more comfortable than the original ones, taken as reference, but their preferences were not consensual. This emphasizes the need for shoe customization, and the usefulness of the proposed methodology to achieve such a goal.     

Is lin28a polymorphism associated with endurance performance in soccer players?

Sport Sciences for Health - The aim of this study was to investigate the association of rs6598964 (A?>?G), a molecular marker located in the LIN28A gene, with the performance of...     

Polymerized laminin incorporation into alginate‐based microcapsules reduces pericapsular overgrowth and inflammation

Cell encapsulation coats cells with an artificial membrane to preserve their physical and functional integrity. Different approaches try to develop more functional and biocompatible materials to avoid cell loss after transplantation due to inflammatory reaction, one of the main causes for graft failure. In this study, the LN‐Biodritin biomaterial, based on alginate, chondroitin sulfate, and laminin, previously developed by our group, was further improved by replacing laminin by polylaminin, an artificial laminin polymer with anti‐inflammatory properties, generating the new biomaterial polyLN‐Biodritin. Capsules containing polylaminin are stable, do not induce macrophage activation in vitro, and are also able to prevent macrophage activation by encapsulated human pancreatic islets in vitro, preserving their glucose‐stimulated insulin secretion potential. In addition, when empty capsules containing polylaminin were implanted into immunocompetent mice, the inflammatory response towards the implant was attenuated, when compared with capsules without polylaminin. The results indicate that polylaminin incorporation leads to lower levels of pericapsular growth on the capsules surface, lower infiltration of cells into the peritoneal cavity, and lower production of proinflammatory cytokines, both at the implant site (interleukin‐12p70 (IL‐12p70), tumor necrosis factor‐α (TNF‐α), monocyte chemotactic protein‐1 (MCP‐1), and interferon‐γ (IFN‐γ)) and systemically (IL‐12p70 and TNF‐α). Therefore, polylaminin incorporation into the microcapsules polymer attenuates the host posttransplantation immune response against implanted microcapsules, being likely to favor maintenance of engrafted encapsulated cells.     

Void and gap evaluation using microcomputed tomography of different fiber post cementation techniques

Statement of problem

Few studies have investigated the voids and gaps produced during the cementation of fiber posts using different techniques.