Formation Mechanism of Porous Alumina With Oriented Cylindrical Pores Fabricated by Unidirectional Solidification

Porous alumina whose pores were aligned in one direction was fabricated by the unidirectional solidification method under a pressurized hydrogen atmosphere. The porous structure is formed at the solid–liquid interface during solidification due to a hydrogen solubility gap at the melting point. The hydrogen gas is dissolved into molten alumina according to Sieverts' law and insoluble gas that corresponds to the amount of solubility gap evolves from the solid phase at the solid–liquid interface during the unidirectional solidification to form the pores. The porosity and pore size of the solidified samples decreased with increasing total pressure where the environmental gas consisted of pure hydrogen or hydrogen–argon mixed gases. There is a reverse proportion relation between the pore diameter and the total pressure according to Boyle's law.     

Insolubilization mechanism and lithographic characteristics of a negative electron beam resist iodinated polystyrene

To elucidate the insolubilization mechanism of iodinated polystyrene (IPS) upon exposure to an electron beam and deep UV, the effects of additives on exposure characteristics of IPS and its parent polymer, polystyrene, are clarified. Results indicate the following mechanism. Iodine atoms produced by homolytic dissociation upon exposure undergo competitive reactions: the radical recombination which is the reverse of dissociation and the formation of other radicals that leads to insolubilization. The proposed reaction mechanism can explain the relationship between the sensitivity and degree of iodination. The G values for crosslinking of IPS, G(X), are also obtained according to Charlesby's theory. The calculated lithographic characteristics on the basis of G(X) are discussed.     

Reliable indirect competitive ELISA used for a survey of ochratoxin A in green coffee from the North of Paraná State, Brazil.

The performance of an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) based on a monoclonal antibody (mAb) for ochratoxin A (OTA) detection was evaluated in a comparative study with high-performance liquid chromatography (HPLC) analysis using 68 freshly harvested coffee samples from the North of Paraná State, Brazil. The anti-OTA mAb showed high specificity and low cross-reactivity with OTA analogues (OTB and OTalpha), but cross-reacted with OTC. This ic-ELISA showed a detection limit of 3.75 ngg-1 sample, when compared to 0.80 ngg-1 by HPLC, with an ic-ELISA/HPLC correlation coefficient of 0.90. As regards OTA analysis of these coffee samples, natural contamination was detected in 10 samples (14.7%) by both methods, where the ic-ELISA values (range 3.9-7.3 ngg-1) were 1.1 to 1.6-fold higher than HPLC data (2.7-4.7 ngg-1). Five samples (7.4%) were OTA positive (range 0.84-1.30 ngg-1) only by HPLC assay, probably due to the higher detection limit reached by ic-ELISA. OTA was undetectable in 53 samples (77.9%) by both methods, while all positive samples (range 0.84-7.30 ngg-1) showed OTA levels lower than 8 ngg-1 (maximum limit recommended by the European Union). The matrix interference of green coffee was minimized by dilution of sample extracts before carrying out the ELISA assay. This mAb-based ic-ELISA can be effectively applied for OTA screening in coffee, because it is simple, sensitive and sample preparation is easy.     

Electronic Structures of Two-Phase Microstructures in Pb-doped Bi2Sr2CaCu2O y

We have performed scanning tunneling microscopy/spectroscopy (STM/STS) on single crystals of heavily Pb-doped Bi ₂ Sr ₂ CaCu ₂ O _y (Pb-Bi2212). The obtained STM images clearly demonstrated phase separation into the and phases with lamella-type and new zigzag-like microstructures. From the site-specified tunneling measurements, it was directly confirmed that the phase possesses higher T _c . This suggests that the phase boundaries act as strong pinning sites especially at higher temperatures.