Reactions of 26-iodopseudodiosgenin and 26-iodopseudodiosgenone with various nucleophiles and pharmacological activities of the products

26-Iodopseudodiosgenin (8) and 26-iodopseudodiosgenone (9) were reacted with various nucleophiles (KSCN, KOCN, NaCN, NaN(3) and various amines) to give pseudodiosgenin derivatives (4, 12, 16-20, 26) and pseudodiosgenone derivatives (5, 13, 21-25, 27), respectively. The reactions of 8 and 9 with KOCN gave the elimination products (10) and (11), respectively. The reaction of 9 with NaCN gave 5alpha,26- (14) and 5beta,26-dicyanocholestan-3-one (15). The reaction of 8 with NaN3 gave triazepine derivative (30), while that of 9 gave 26-azidopseudodiosgenone (31). Compound 31 was converted into triazepine derivative (32) by heating at 120 degrees C. The cytotoxicity of the pseudodiosgenins and pseudodiosgenones on P-gp-underexpressing HCT 116 cells and P-gp-overexpressing Hep G2 cells was examined by MTT assay. Pseudodiosgenins 2, 4, 12 and 30 showed strong cytotoxic activity (IC50 values: 2.6+/-0.3-6.7+/-1.4 microM), as did pseudodiosgenones 3, 5, 11, 13, 21-25 and 27 (IC50 values: 1.3+/-0.3-6.4+/-0.3 microM) toward HCT 116 cells. Pseudodiosgenins 12, 16 and 30 (IC50 values: 1.2+/-0.7-2.2+/-0.6 microM) and pseudodiosgenones 22, 23, 25 and 27 (IC50 values: 0.6+/-0.1-2.5+/-0.3 microM) were highly cytotoxic to Hep G2 cells. Compounds 3 and 27 showed efficient antibacterial activity (MIC: 15.6, 10.4 microg/ml) and (MIC: 7.8, 15.6 microg/ml) against Bacillus subtilis and Staphylococcus aureus, respectively.     

Effects of bubble size on heat transfer enhancement by sub-millimeter bubbles for laminar natural convection along a vertical plate

Injection of sub-millimeter bubbles is considered a promising technique for enhancing natural convection heat transfer for liquids. So far, we have experimentally investigated heat transfer characteristics of laminar natural convection flows with sub-millimeter bubbles. However, the effects of the bubble size on the heat transfer have not yet been understood. The purpose of this study is to clarify the effects of the bubble size on the heat transfer enhancement for the laminar natural convection of water along a vertical heated plate with uniform heat flux. Temperature and velocity measurements, in which thermocouples and a particle tracking velocimetry technique are, respectively used, are conducted to investigate heat transfer and flow characteristics for different bubble sizes. Moreover, two-dimensional numerical simulations are performed to comprehensively understand the effects of bubble injection on the flow near the heated plate. The result shows that the ratio of the heat transfer coefficient with sub-millimeter-bubble injection to that without injection ranges from 1.3 to 2.2. The result also shows that for a constant bubble flow rate, the heat transfer coefficient ratio increases with a decrease in the mean bubble diameter. It is expected from our estimation based on both experimental data and simulation results that this increase results from an increase in the advection effect due to bubbles.     

Crystal structures of AgAF6 (A = P, As, Sb, Nb, Ta) at ambient temperatures

Structures of AgAF₆ (A=Sb, Ta) have been determined by X-ray single crystal studies at ambient temperatures. AgSbF₆ crystallizes in space group Ia with a=979.85(4) pm, V=9.4076(12)×10⁸ pm³, z=8, and AgTaF₆ crystallizes in space group P4₂/mcm with a=499.49(4) pm, c=960.51(8) pm, V=2.3964(6)×10⁸ pm³, z=2. Only the crystal system and cell parameters were obtained for the isomorphic AgNbF₆; primitive tetragonal, a=497.80(10) pm, b=960.40(10) pm, V=2.3799(12)×10⁸ pm³, z=2. The results of the Raman spectroscopy of AgAF₆ support the obtained structures. The structures are discussed by comparing with that of AgPF₆ and AgAsF₆ which have recently been determined in a series of our study.     

A search for monojet events produced by virtual Z0 bosons in e+e− annihalation at petra

A search was performed for the associated production of two different Higgs bosons via a virtual Z⁰ in e⁺e^? annihilation (e⁺e^? → h₁⁰h₂⁰) using the JADE detector at PETRA. This was motivated by the interpretation of the monojet events observed at the CERN p$\text{p}$ collider as anomalous Z⁰ decays into two neutral Higgs bosons (h₁⁰ and h₂⁰), where h₁⁰ is stable and escapes detection while h₂⁰ decays into hadrons. Single- or di-jet events with large momentum imbalance are then expected at PETRA energies. No evidence for such events was found in our data; this excludes h₂⁰ masses in the range of 1 to 21 GeV with 95% CL, if the branching fraction for Z⁰ → h₁⁰h₂⁰ is a larger than one half that for $\text{Z}{}^0\text{→ v}{}_{\mathrm{\mu }}\text{v}{}_{\mathrm{\mu }}$. The possibility that the monojets could originate from supersymmetric higgsino production from Z⁰ decay is also examined.     

Study on organic pollution parameters for dyes and dyeing auxiliaries

Analytical and Bioanalytical Chemistry -     

Complete removal of paint from metal surface by ablation with a TEA CO2 laser

For high-speed metal surface cleaning, we applied TEA CO₂ laser pulses to ablate painted materials on metal surfaces and examined the efficiency of removal under different surface and irradiation conditions. Surfaces treated with a line-focused laser beam were analyzed with an energy dispersive X-ray analyzer and inspected with optical microscopic observation. Although paints were selectively ablated from the metal surface, the cleaning efficiency was found to depend on surface conditions of substrates. An application of a small amount of dimethyl formamide was effective for completely removing of resin without scorching the surface.     

Enantioselective Denitrogenative Annulation of 1H‐Tetrazoles with Styrenes Catalyzed by Rhodium

Sulfonylation of 1H‐tetrazoles with triflic anhydride in the presence of chiral rhodium(II) carboxylate dimers causes denitrogenation to generate α‐azo rhodium(II) carbenoid species as new types of donor/acceptor carbenoids, which then readily react with styrenes to afford 3,5‐diaryl‐2‐pyrazolines with a high degree of enantioselectivity.