THE EFFECT OF WATER-SOLUBLE POLYMERS ON THE MICROSTRUCTURE AND PROPERTIES OF FREEZE-CAST ALUMINA CERAMICS

Porous ceramics can be divided into three separate classes based on their pore size: microporous ceramics with pores less than 2 nm, mesoporous ceramics with pores in the range of 2-50 nm and macroporous ceramics with pores that are greater than 50 nm. In particular, macroporous ceramics are used in a variety of applications such as refractories, molten metal filtration, diesel particulate filters, heterogeneous catalyst supports and biomedical scaffolds.Freeze casting is a novel method used to create macroporous ceramics. In this method growing ice crystals act as a template for the pores and are solidified, often directionally, through a ceramic dispersion and removed from the green body through a freeze drying procedure. This method has attracted some attention over the past few years due to its relative simplicity, flexibility and environmental friendliness. On top of this freeze casting is capable of producing materials with high pore volume fractions, which is an advantage over processing by packing and necking of particles, where the pore volume fraction is typically less than 50%. Many of the basic processing variables that affect the freeze cast microstructure, such as the temperature gradient, interfacial velocity and solid loading of the dispersion have been well established in the literature. On the other hand, areas such as the effect of additives on the microstructure and mechanical properties have not been covered in great detail.In this study the concept of constitutional supercooling from basic solidification theory is used to explain the effects of two water-soluble polymers, polyethylene glycol and polyvinyl alcohol, on the microstructure of freeze cast alumina ceramics. In addition, changes in the observed microstructure will be related to experimentally determined values of permeability and compressive strength

Surface stiffening and enhanced photoluminescence of ion implanted cellulose - polyvinyl alcohol - silica composite

Novel Cellulose (Cel) reinforced polyvinyl alcohol (PVA)-Silica (Si) composite which has good stability and in vitro degradation was prepared by lyophilization technique and implanted using N3+ ions of energy 24 keV in the fluences of 1 x 10(15), 5 x 10(15) and 1 x 10(16) ions/cm(2). SEM analysis revealed the formation of microstructures, and improved the surface roughness on ion implantation. In addition to these structural changes, the implantation significantly modified the luminescent, thermal and mechanical properties of the samples. The elastic modulus of the implanted samples has increased by about 50 times compared to the pristine which confirms that the stiffness of the sample surface has increased remarkably on ion implantation. The photoluminescence of the native cellulose has improved greatly due to defect site, dangling bonds and hydrogen passivation. Electric conductivity of the ion implanted samples was improved by about 25%. Hence, low energy ion implantation tunes the mechanical property, surface roughness and further induces the formation of nano structures. MG63 cells seeded onto the scaffolds reveals that with the increase in implantation fluence, the cell attachment, viability and proliferation have improved greatly compared to pristine. The enhancement of cell growth of about 59% was observed in the implanted samples compared to pristine. These properties will enable the scaffolds to be ideal for bone tissue engineering and imaging applications.G.M.S. acknowledges CSIR, India (Grant no: 09/468 (0474)/2013-EMR-I) and S.N.K. thanks the award of Erasmus-Mundus Svaagata for providing financial support to carry out this research. G.M.S., N.S. and S.N.K. acknowledge the support of UGC National facility for characterization facility. J.A.G.T. acknowledges the support of the Spanish Ministry of Economy and Competitiveness (MINECO) through the project DPI2015-65401-C3-2-R (including the FEDER financial support). CIBER-BBN, Spain is an initiative funded by the VI National R&D Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. AFM was conducted by the microscopy service of the UPV, whose advice was greatly appreciated.Shanthini, GM.; Sakthivel, N.; Menon, R.; Nabhiraj, PY.; Gómez-Tejedor, JA.; Meseguer Dueñas, JM.; Gómez Ribelles, JL.... (2016). Surface stiffening and enhanced photoluminescence of ion implanted cellulose - polyvinyl alcohol - silica composite. Carbohydrate Polymers. 153:619-630. https://doi.org/10.1016/j.carbpol.2016.08.016S61963015

Differentiation of human-induced pluripotent stem cell under flow conditions to mature hepatocytes for liver tissue engineering

Hepatic differentiation of human?induced pluripotent stem cells (hiPSCs) under flow conditions in a 3D scaffold is expected to be a major step forward for construction of bioartificial livers. The aims of this study were to induce hepatic differentiation of hiPSCs under perfusion conditions and to perform functional comparisons with fresh human precision?cut liver slices (hPCLS), an excellent benchmark for the human liver in vivo. The majority of the mRNA expression of CYP isoenzymes and transporters and the tested CYP activities, Phase II metabolism, and albumin, urea, and bile acid synthesis in the hiPSC?derived cells reached values that overlap those of hPCLS, which indicates a higher degree of hepatic differentiation than observed until now. Differentiation under flow compared with static conditions had a strong inducing effect on Phase II metabolism and suppressed AFP expression but resulted in slightly lower activity of some of the Phase I metabolism enzymes. Gene expression data indicate that hiPSCs differentiated into both hepatic and biliary directions. In conclusion, the hiPSC differentiated under flow conditions towards hepatocytes express a wide spectrum of liver functions at levels comparable with hPCLS indicating excellent future perspectives for the development of a bioartificial liver system for toxicity testing or as liver support device for patients

Out of the Education Desert: How Limited Local College Options are Associated with Inequity in Postsecondary Opportunities

The United States has a stratified hierarchy of colleges and universities. The consequences of this stratification include large disparities in the returns to higher education between the levels of postsecondary institutions, and gaps by race and income in terms of where students enroll that, together, have the potential to reproduce longstanding social inequality. We study one potential cause associated with enrollment disparities, the uneven geographic distribution of colleges around the United States. Specifically, we examine the college application and enrollment decisions of students who live in education deserts—geographic areas where students either do not have access to a broad-access, public college option (access deserts), or where they do not have access to a college that is academically matched to their academic credentials (match deserts). We find that the students in access deserts are more likely to apply to and enroll in colleges farther away from home than the students who have more readily available college options. In contrast, students in match deserts are less likely to apply to and enroll in academically-matched institutions. We discuss the equity implications of these findings and make recommendations for policy and future research

Fencing Africa's protected areas : costs, benefits, and management issues

The fencing of protected areas (PAs) is highly controversial, and much remains unknown about the associated financial, ecological, and social impacts. We surveyed experts on 63 fenced and 121 unfenced PAs across 23 African countries to assess the advantages and drawbacks of fencing. Where fences exist, they are largely supported and widely viewed as effective at demarcating PA boundaries and mitigating human-wildlife conflicts. However, most fences were insufficiently funded, which limited their ability to contain conflict-prone species like elephants and lions. Fences were also frequently vandalised and caused numerous conflicts with local communities. We documented for the first time the distribution of and support for fencing in PAs across Africa. While fencing is largely limited to Southern Africa and East Africa, support for fencing is greatest in West Africa and is associated with high human and livestock densities, and high threats from bushmeat harvesting, livestock encroachment, and logging.JRBM was supported in part by Panthera and National Science Foundation Coupled Human and Natural Systems Grant 115057.http://www.elsevier.com/locate/biocon2020-01-01hj2019Mammal Research InstituteZoology and Entomolog