Carbonized hollow fiber membranes were prepared by pyrolyzing an asymmetric hollow fiber
membrane of a polyimide from 3,3‘,4,4‘-biphenyltetracarboxylic dianhydride and aromatic
diamines at temperatures of 500−700 °C under a nitrogen stream. The precursor membrane
was treated in air at 400 °C for 0.5 h before the pyrolysis. This pretreatment was effective for
improvement of gas permeance of the carbonized membranes. The carbonized membranes had
an asymmetric structure with a skin layer of around 200 nm in thickness. They had the
characteristics of larger permeance and lower permselectivity for inorganic gas pairs such as
O2/N2, but this was rather preferable to the separation of olefin/paraffin. The membranes
pyrolyzed at 600−630 °C displayed good stability and excellent performances of propylene/propane and 1,3-butadiene/n-butane separation based on the molecular sieving.
ABSTRACT:Soluble polyimides with polyalicyclic structure were prepared by reactions of 2,3,5-tricarboxycyclopentyl acetic dianhydride (TCA-AH) with aromatic diamines. The two-step polymerization systems including poly(amic acids) synthesis and solution imidization using pyridine and acetic anhydride were performed and soluble polyimides with high inherent viscosities and high imidization ratios were obtained. TCA-AH polyimides exhibited high thermal stability in air and nitrogen, and good solubility in common polar solvents such as NMP (N-methyl-2-pyrrolidone). In comparison with soluble aromatic polyimides based on fluorine containing monomers, TCA-AH polyimides showed slightly less thermal stability and lower solubility in a few solvents.KEY WORDS Polyimide / Soluble Polyimide / Polyalicyclic Structure / 2,3,5-Tricarboxycyclopentyl Acetic Dianhydride / Solution Imidization / Thermal Stability / Solubility / Polyimides exhibit excellent thermal and mechanical properties, and have extensive engineering and microelectronics applications.
The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.
To study the immunological protective system against rickettsial infection, a T-cell line specific for Rickettsia tsutsugamushi antigen was established by long-term culture of splenocytes from mice immunized with live Gilliam strain R. tsutsugamushi and then propagated in the presence of homologous rickettsial antigen and syngeneic filler cells. The characteristics of the T-cell line and its capacity to induce antirickettsial protection in vivo were studied. Flow cytometric analysis demonstrated that the T-cell line showed the phenotype Thy-1.2+ L3T4+ Lyt-2-, suggestive of helper T cells. In a lymphocyte proliferation assay, this cell line showed a specific response to Gilliam antigen, partial cross-reactivity to Karp antigen, but no response to Kato antigen. The proliferative response of this T-cell line was filler cell dependent, and genetic restriction was observed between the T-cell line and filler cells. The T-cell line produced gamma interferon, one of the macrophage-activating factors, in cultures with specific antigen and was able to adoptively mediate antirickettsial protection in vivo. The data presented here suggest that antigen-specific helper T cells play an important role in protection against rickettsial infection.
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