Effects of Titanium Dioxide Nanoparticle Aggregate Size on Gene Expression

Titanium dioxide (titania) nanoparticle aggregation is an important factor in understanding cytotoxicity. However, the effect of the aggregate size of nanoparticles on cells is unclear. We prepared two sizes of titania aggregate particles and investigated their biological activity by analyzing biomarker expression based on mRNA expression analysis. The aggregate particle sizes of small and large aggregated titania were 166 nm (PDI = 0.291) and 596 nm (PDI = 0.417), respectively. These two size groups were separated by centrifugation from the same initial nanoparticle sample. We analyzed the gene expression of biomarkers focused on stress, inflammation, and cytotoxicity. Large titania aggregates show a larger effect on cell viability and gene expression when compared with the small aggregates. This suggests that particle aggregate size is related to cellular effects.     

Interface temperature measurement of M2C and M6C eutectic carbides in the Fe–Mo–C system

The High speed cast iron, which is used for hot rolling parts, needs high fracture toughness and wear resistance. To improve these properties, the control of eutectic carbides, M₃C, M₇C₃,M₆C and MC is important by adding elements such as Cr, W, V and Mo.

The aim of this study is to estimate which carbide will solidify under certain solidification conditions and compositions. This prediction criterion can be gained by measuring the interface temperature of each carbide in various samples with different solute elements, composition and growth rate.

In this report, the solidified temperature of γ + M₂C and γ + M₆C eutectic carbide in the Fe–Mo–C ternary system in the composition range near to the eutectic monovariant line, was measured during the unidirectional solidiication process. The relationship between solidified interface temperature and growth rate was obtained. In eutectic solidification along the γ + M₆C monovariant line, a coefficient of undercooling, the k value, was obtained.

The authors have already measured the k values of other eutectic carbides, such as γ + M₃C, austenite + M₇C₃, and γ + VC in Fe–Cr–C and Fe–V–C system. The paper also discusses the relationships between these properties of eutectic carbides.     

Natural convective heat transfer in uniformly heated vertical pipe annuli

Natural convective heat transfer in vertical concentric pipe annuli is investigated both numerically and experimentally for a fluid having a Prandtl number of 0.7. Numerical calculations for three cases of different heating conditions for pipes (heated inner pipe, heated outer pipe, both pipes heated) are made of laminar flows for different inner‐to‐outer‐pipe diameter ratios d_i/d_o from 0.2 to 0.8. For each case, the thermal entrance length x/b at the modified Grashof numbers Gr^*=10² to 5 × 10⁵ is well correlated with Grashof number Gr^* and annulus length to clearance ratio L/b. Local Nusselt numbers Nu_i and Nu_o in the thermally fully developed region have certain constant values dependent on the diameter ratio d_i/d_o, regardless of Gr^* and L/b. Average Nusselt numbers Nu_i and Nu_o in the thermal entrance region are also independent of Gr^* and L/b. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 676–688, 2001     

Expression of active and inactive recombinant soluble trehalase using baculovirus–silkworm expression system and their glycan structures

Silkworm soluble trehalase was expressed as a fusion protein with an N-terminal or C-terminal hexahistidine tag in a baculovirus–silkworm expression system and assayed for enzymatic activity. Only N-terminally tagged trehalase showed a high activity. This study is the first to report in vitro functional expression of recombinant insect soluble trehalase.