Novel porous matrix and bioreactors for high density cultures of insulinoma cell lines: Insulin secretion and response to glucose

This paper describes the use of a novel porous matrix, Porocell, for high density, tissue-like culture of two insulinoma cell lines, CRI-D2 and CRI-D11. Both these cell lines have previously been shown not to secrete insulin in response to glucose. Porocell is a macro-porous, polymeric material manufactured in the shape of discs that are 6·2 mm in diameter and 2 mm in thickness. Insulinoma cells were cultured in two different mini-bioreactors, each containing six Porocell discs inoculated with 2·5 × 10⁶ cells per disc. In surface aerated, stirred bioreactors, the insulinoma cells grew as closely packed dense cell sheets penetrating deep into the pores of Porocell. In a second type of system, a packed-bed perfused mini-bioreactor, flat, extended monolayers of cells were observed growing throughout the Porocell matrix. In both bioreactor configurations, viable cell populations were maintained for 30 days because of the excellent oxygen and nutrient transfer properties of Porocell. CRI-D2 insulinoma cells cultured in static flasks and on Porocell did not show any insulin secretion in response to 30 min exposures in media supplemented with 5·5–16·7 mmol dm⁻³ glucose. However, in long term (14–19 day) cultures, CRI-D2 cells growing in Porocell secreted low, but measurable amounts (25–35 pmol dm⁻³) of insulin in medium supplemented with elevated (14·5 mmol dm⁻³) glucose concentrations. The glucose uptake rates of cells cultured in 4·0 mmol dm⁻³ glucose increased linearly from 1·0 to 2·3 mmol dm⁻³ day⁻¹ over a period of 19 days. At 14·5 mmol dm⁻³ glucose concentration, the uptake rate increased from 1·0 to 7·05 mmol dm⁻³ day⁻¹ over the same period of culture. Contrary to previous studies, we have demonstrated that the CRI-D2 cell line cultured at high cell density in Porocell is capable of secreting insulin when exposed to prolonged and elevated concentrations of glucose. The Porocell mini-bioreactors are easy to use, robust systems that can be used for long-term studies of primary and tumorgenic islet cell function and response to secretagogues. © 1998 SCI.     

Slow-crack-growth and indentation damage in calcium magnesium aluminosilicate (CMAS) glass from desert sand

Desert sand from a Middle East country was melted into calcium magnesium aluminosilicate (CMAS) glass. Its chemical composition was analyzed to be 25.2CaO-2.6MgO-8.2Al₂O₃-59.8SiO₂-1.6Fe₂O₃-1.5K₂O weight % using inductively coupled plasma-atomic emission spectrometry. The CMAS glass powder was hot pressed into billets. Slow-crack-growth (SCG) and indentation deformation/fracture of the CMAS glass was investigated. The SCG susceptibility parameter (n) was found to be 25 ± 3 which is within a range of n = 15–35 that has been observed in many silicate glasses and glass ceramics. A similarity in indentation hardness and toughness was found between the CMAS glass and the low-silica content (50–70%) glasses. However, an exception was that significant lateral cracking was typified in the CMAS glass, as quantified via stress analysis in the vicinity of an indent.     

Re‐entrant transition of aluminum‐crosslinked partially hydrolyzed polyacrylamide in a high salinity solvent by rheology and NMR

Linked polymer solution (LPS) is a nanoparticle polymer and designed by crosslinking a high molecular weight partially hydrolyzed polyacrylamide (HPAM) with aluminum (III). It has been applied in the oil industry to enhance oil recovery by improving sweep efficiency and by microscopic diversion in porous media. To achieve good propagation properties, aggregates formed by intermolecular crosslinking and gel formation should be avoided. To our knowledge, there is no established method to distinguish between intra‐ and intermolecular crosslinking for high molecular weight (>10 × 10⁶ Da), low concentration (<1000 ppm), polydisperse solutions of partially hydrolyzed polyacrylamides in high salinity solvents (5 wt % NaCl). The high salinity solvent is relevant to represent for formation water in many oil reservoirs. The main objective of the present study is to establish an experimental method for determining phase transition of LPS from monomeric coiled state to aggregated state in a high salinity solvent. No single experimental methods are conclusive and we have therefore applied a combinatorics approach including two‐dimensional NMR, dynamic rheology, and UV spectroscopy. The different techniques show similar trends, which allow overall interpretations of phase transitions to be made. The experimental results indicated that the LPS solution at high salinity solvent underwent a phase transition by chain re‐expansion, called reentrant transition. The transition point was observed at addition of 100 ppm of Al³⁺. Higher concentrations of Al³⁺ suppressed the rate of reentrant transition, most likely because of intramolecular crosslinking of HPAM chains by Al³⁺. Intermolecular crosslinking reaction was not observed at these conditions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43825.     

In situ characterization of foreign object damage (FOD) in environmental-barrier-coated silicon carbide (SiC) ceramic

Environmental barrier coatings (EBCs) protect advanced ceramics and ceramic matrix composites (CMCs) from oxidation and corrosion in gas turbine engine environments. Foreign object damage (FOD), where debris impact the protective coatings, is a critical hazard which limits the turbine durability. Despite previous efforts to understand FOD in EBCs, a detailed understanding of the fundamental transient damage mechanisms is still lacking. In the current work, the real-time FOD behavior of a mullite/ silicon EBC was visualized via a dynamic synchrotron X-ray source in phase contrast imaging (PCI) configuration. Prior to the in situ FOD experiments, the microstructure and composition of the coating were, respectively, characterized using a scanning electron microscope (SEM) and X-ray diffraction (XRD). The variation in the properties of the debris was modeled by~1.5mm diameter partially stabilized zirconia (PSZ) and silicon nitride (Si₃N₄) spheres. A modified light-gas gun setup, synchronized with the X-ray beam, was used to propel the projectiles at velocities ranging between 300 and 355ms⁻¹. Coated samples were impacted under a fully backed support configuration and at normal incidence. Coating penetration and delamination, as well as projectile deformation at the bond coat resulted for FOD by PSZ spheres. Comparatively, projectile fracture, with subsequent rebound of fragments, as well as complete coating penetration and delamination at the substrate interface occurred for FOD by Si₃N₄ spheres. Only cone cracking was observed for FOD by PSZ spheres, whereas back surface cracking was present for both projectile types. The driving forces for the observed damage mechanisms are qualitatively assessed.     

In-situ synthesis and characterizations of Bi2(O,S)3/Zn(O,S) composites for visible light hexavalent chromium reduction

Heterojunction construction with low band gap materials is an effective way of utilizing UV light active materials under visible light irradiation. Here, we report the synthesis of Bi₂(O,S)₃/Zn(O,S) heterostructure using simple solvothermal method without surfactant. The catalysts were investigated with different characterization techniques. All the composite catalysts showed high light absorption capacity in the whole visible light spectrum. The catalytic activity of the catalysts was evaluated by Cr(VI) reduction. While pure Zn(O,S) catalyst showed no significant Cr(VI) reduction, higher photocatalytic activity than individual components were exhibited after heterojunction construction with Bi₂(O,S)₃. 20-BiZnOS catalyst with Bi/Zn molar percentage of 20% showed the best photocatalytic activity among the composites with 99.5% Cr(VI) reduction within 12 min under visible light irradiation. Heterojunction formation between Bi₂(O,S)₃ and Zn(O,S) nanoparticle, and selective adsorption of Cr(VI) and desorption of Cr(III) on the surface of 20-BiZnOS composite catalyst were ascribed to the enhanced photocatalytic activity of the composite catalyst.     

Chronic poverty in urban Ethiopia: panel data evidence

There are good reasons to think that a substantial proportion of urban poverty is likely to be chronic or persistent in nature, but to date there has been limited quantitative evidence to back up this assertion due to a lack of data tracking the same households over time. In this paper, we analyse a three-wave panel data set in urban Ethiopia over the mid-1990 s. Our results indicate that there is a high level of chronic poverty, and that those who are chronically poor show distinct characteristics that are likely to be important factors underlying their chronic poverty. These include high household dependency rates; low levels of education; lack of asset ownership; and insecure, low return or no employment.     

Resolving the Martensitic Transformation in Q&P Steels In-Situ at Dynamic Strain Rates Using Synchrotron X-ray Diffraction

The dynamic deformation response of two quenching and partitioning (Q&P) steels was investigated using a high strain rate tension pressure bar and in-situ synchrotron radiography and diffraction. This allowed for concurrent measurements of the martensitic transformation, the elastic strains/stresses on the martensite and ferrite, and the bulk mechanical behavior. The steel with the greater fraction of ferrite exhibited greater ductility and lower strength, suggesting that dislocation slip in ferrite enhanced the deformability. Meanwhile, the kinetics of the martensitic transformation appeared similar for both steels, although the steel with a greater ferrite fraction retained more austenite in the neck after fracture.

     

Investigation on culturable microflora in tibetan kefir grains from different areas of china

Four samples of Tibetan kefir grains (TK-ZJUJ 01-04) from Tibet and surrounding areas were investigated via phenotypic and genotypic methods to compare and analyze the diversity of culturable microflora among different origins. As a result, 4 genera of microorganisms from TK-ZJUJ01: Bacillus subtilis (2.9 × 10(7) cfu/mL), Lactococcus lactis (8.2 × 10(7) cfu/mL), Kluyveromyces marxianus (3.0 × 10(6) cfu/mL), Saccharomyces cerevisiae (9.0 × 10(6) cfu/mL); 4 genera from TK-ZJUJ02: Lactobacillus kefiri (1.0 × 10(8) cfu/mL), Pichia kudriavzevii (5.0 × 10(6) cfu/mL), K. marxianus (1.9 × 10(7) cfu/mL), Kazachstania unispora (6.2 × 10(7) cfu/mL); 6 genera from TK-ZJUJ03: Leuconostoc lactis (4.6 × 10(7) cfu/mL), L. lactis (3.0 × 10(7) cfu/mL), Lactobacillus plantarum (3.0 × 10(7) cfu/mL), K. unispora (3.0 × 10(6) cfu/mL), K. marxianus (2.0 × 10(6) cfu/mL), (1.7 × 10(7) cfu/mL); and 4 genera from TK-ZJUJ04: L. plantarum (1.8 × 10(7) cfu/mL), Acetobacter fabarum (5.0 × 10(6) cfu/mL), K. unispora (6.2 × 10(7) cfu/mL), Pichia guilliermondii (6.2 × 10(7) cfu/mL) were identified. Yeasts like P. kudriavzevii and P. guilliermondii isolated in this study were the first time reported in Tibetan kefir grains. For TK-ZJUJ 01-03, lactic acid bacteria were the major microorganisms, which accounted for more than 50% of all the microbial population, while for TK-ZJUJ04, the largest microbial group was yeasts which accounted for more than 50%. In a word, study of diversity and composition of microflora provided us theoretical foundation for further investigation and application of Tibetan kefir grains. Practical Application: This is the basic research in order to develop and industrialize a new kind of yogurt starter which is naturally formed microbiota with both lactic acid bacteria and yeasts in it.