Enhancement of low density lipoprotein binding to both low density lipoprotein receptor-positive and- negative cells by tetracycline antibiotics

Some tetracycline (TC) antibiotics, including TC and anhydrotetracycline, have been found to enhance specific binding of low density lipoprotein (LDL) to both LDL receptor-positive and-negative cells at relatively higher concentrations. When incubated at 37°C, the ability of LDL receptor-negative human fibroblasts to bind ¹²⁵I-LDL was increased from<2 to 45 ng/mg by 170 μM TC. In normal human fibroblasts and Hep G2 cells, ¹²⁵I-LDL binding was elevated 1.4- to 2-fold by 113 μM TC. The ¹²⁵I-LDL binding in the presence of TC was diminished by both heparin and EDTA. The enhancement by TC was not observed when ¹²⁵I-LDL binding was assayed at 4°C. TC enhanced LDL binding to paraformaldehyde-fixed Hep G2 cells, excluding LDL receptor induction in the mechanism. These results demonstrated that TC enhanced cellular LDL binding through a process not involving functional LDL receptors.     

Effects of light guides and optical filters for a high density lead glass counter

Effects of various light guides on energy resolution, position dependence of the output pulse and the hadron suppression factor were studied for a high density lead glass counter with particles of energies between 1 GeV and 16 GeV. The best hadron suppression factor was obtained for a configuration with a plastic light guide and a short wave cutoff filter at little expense to energy resolution. The energy resolution is worse at high energy and is dependent on the hit position of an incident particle for a BK7 light guide.     

Asian dust event observed in Seoul, Korea, during 29-31 May 2008: Analysis of transport and vertical distribution of dust particles from lidar and surface measurements

In this study, we investigate the transport of dust particles, its vertical distribution, and the associated meteorological conditions during an Asian dust event that was observed in Seoul, Korea on May 29-31, 2008. This study analyzes data from ground-based and space-borne 2-wavelength polarization lidars, particulate mass concentrations, and synoptic weather data. Surface meteorological station observations of dust phenomena, dust transport model, and weather maps consistently show that the dust particles were transported from the source regions (Inner Mongolia, Man-Ju, and Ordos areas) to Korea via the northeastern part of China. Network observations of the PM₁₀ concentrations in Korea revealed that a majority of the heavy dust particles traveled across South Korea from the northwest to the southeast direction with a horizontal scale of 250-300 km and a traveling speed of approximately 40 km h^− 1. This extraordinary dust event, in terms of its intensity and timing during the year, occurred due to the blockage of an unusually intensified low-pressure system in the northeastern part of China as well as high-pressure system centered over the Sea of Okhotsk and the Kuril Islands. The low values of the particle depolarization ratio (δ₅₃₂) (≤0.05) and color ratio (CR) during the pre-dust period indicate the presence of spherical, non-dust, and relatively small particles. The mean δ₅₃₂ value was approximately 0.123 ± 0.069 between altitudes of ground ~ 2.8 km, and 0.161 ± 0.049 for near-surface dust layer (ground ~ 1.2 km). This value is quite similar to that obtained during the 3-year SNU-Lidar measurements in Seoul (δ₅₃₂ ~0.136 ± 0.027). The value of δ₅₃₂ during the 2nd multilayered dust episode ranged between 0.081 and 0.120 for near-surface dust layers, and between 0.076 and 0.114 for elevated dust layers. The CALIPSO measurements of β₅₃₂, δ₅₃₂, and CR also revealed the presence of dense dust aerosols along the transport route.     

The effects of di-D-fructofuranose-1,2':2,3'-dianhydride (DFA III) administration on human intestinal microbiota

Di-D-fructofuranose-1,2':2,3'-dianhydride (DFA III) was shown to enhance Ca absorption in rat and human intestine. The effects of DFA III administration (9 g per day for 4 weeks that corresponded to 3-fold the optimal dosage of DFA III) on human intestinal microbiota were studied using denaturing gradient gel electrophoresis (DGGE). The major groups of human intestinal microbiota reported previously: the Bacteroides, the Clostridium coccoides group (Clostridium cluster XIVa), the Clostridium leptum group (Clostridium cluster IV), and the Bifidobacterium group were detected. The similarity of 30 DGGE profiles based on the V3 region (before and after administration to the 15 subjects) of the 16S rDNA were calculated using Pearson's correlation based on numbers, positions and intensity of bands, and then a dendrogram of DGGE profiles was constructed by the unweighted pair group method using arithmetic average (UPGMA) clustering method. By these analyses, no difference in DGGE profiles after DFA III administration was observed in healthy subjects, while two subjects with chronic constipation showed different profiles, namely on numbers, positions and the intensity of some bands. Their stools were softer and stool frequencies increased and they obtained relief from constipation.     

Syntheses of alpha-arbutin-alpha-glycosides and their inhibitory effects on human tyrosinase

Alpha-arbutin is a tyrosinase inhibitor. We synthesized alpha-arbutin-alpha-glycosides by the transglycosylation reaction of cyclomaltodextrin glucanotransferase from Bacillus macerans using alpha-arbutin and starch as acceptor and donor molecules, respectively. We isolated and characterized two major products from the reaction mixture. The structural analyses using 13C- and 1H-NMR spectroscopy proved that they were 4-hydroxyphenyl alpha-maltoside (alpha-Ab-alpha-G1) and 4-hydroxyphenyl alpha-maltotrioside (alpha-Ab-alpha-G2). Both alpha-Ab-alpha-G1 and alpha-Ab-alpha-G2 exhibited competitive-type inhibition on human tyrosinase as alpha-arbutin does. Their K(i) values were calculated to be 0.6 mM and 2.8 mM, respectively, which is slightly and significantly higher than that of alpha-arbutin (0.2 mM).     

Measurements of water distribution in through-plane direction of PEFC by using neutron radiography

Fuel gas (hydrogen gas) and oxidant gas (air) are supplied to a polymer electrolyte fuel cell (PEFC). Protons pass through the electrolyte membrane, and combine with oxygen to form water in the cathode reaction site. The generated water must be supplied appropriately to the membrane for proton conduction. On the other hand, the generated water may affect the fuel cell performances because of the blocking of oxygen from reaching the cathode reaction site. Therefore, water management in the PEFC is important, and water distribution during the operation in the through-plane direction has been of wide concern. In order to obtain the water distributions in a membrane electrode assembly (MEA) and a gas diffusion layer (GDL), a borescope system was newly employed using neutron radiography. The system could obtain the water distribution in the MEA and the GDL, and pixel size of 6.5 μm was achieved. Furthermore, the system was applied for a tilted converter system. The pixel of 1.0 μm at an angle of 81° was achieved, and improvement of the spatial resolution was confirmed.     

Measurement of water thickness in PEM fuel cells and analysis of gas velocity distributions

Fuel gas (hydrogen gas) and oxidant gas (air) are supplied to a polymer electrolyte fuel cell (PEFC). Condensation may occur in the cathode side, since the air might be super-saturated by the fuel cell reactions. If condensed water exists in a gas diffusion layer (GDL) or the gas channels, it may affect the fuel cell performances because it blocks the oxygen from reaching the cathode reaction site. Thus, water management in the PEFC is important. In order to clarify water effects on performances of a PEFC, visualization and quantitative measurements of water distributions in a PEFC were carried out by means of neutron radiography. Two-dimensional water distributions were obtained, and water ejection was confirmed. It was found that the water easily accumulated in the GDL under the rib rather than under the channel at beginning of the operation. Furthermore, a network analysis of gas-velocity distribution is applied for the experimental results. It analyzes the gas-velocity distributions depending on the flow resistance, which is the pressure drop. Applying the measured data of water thickness, gas-velocity distributions were obtained in the channel and the GDL. From the calculation, air supply in the GDL dramatically decreased with increasing of water accumulation.     

Fabrication and electrical properties of SrTiO3/diamond junctions

Strontium titanate (STO) films were directly deposited on Ib (100) single crystal diamond by r.f. magnetron sputtering. The as-deposited STO film was in amorphous state. On the other hand, the crystalline STO film was obtained under the optimized condition of a deposition temperature of 250 °C and a post-annealing temperature of 650 °C. STO/diamond junctions were fabricated on boron-doped homoepitaxial layers grown on p⁺-type single crystal diamond substrates. Electrical properties of the STO/diamond junction were investigated by changing the surface terminations of diamond with hydrogen or oxygen and the crystallinity of the STO film. It was found that the amorphous STO acted like a semi-insulator on H-diamond surface and that the amorphous STO/O-diamond junction behaved like a Schottky diode. The crystalline STO/O-diamond showed a complex rectifying behavior. The crystalline STO film possessed a higher dielectric constant as compared to that of the amorphous one.