Adsorption of phenol in flow systems by a monolithic carbon cryogel with a microhoneycomb structure

Adsorption of phenol from an aqueous solution in batch and continuous flow systems using carbon gels with a microhoneycomb structure (carbon gel microhoneycombs, CMHs) was studied. The obtained monolithic CMHs had fairly straight channels, 25–45 μm in diameter, and the thickness of the walls which form the channels was around 5 μm. The CMHs showed 370 times lower hydraulic resistance when compared with a column packed with particles having the same diffusion path length as it. The obtained CMHs have a hierarchical micro-meso porous structure giving BET surface area in the range of 513–1070 m²·g^?1.When used for phenol adsorption from an aqueous solution, the CMHs quickly adsorbed phenol at first, and then, the uptake gradually increased, which indicates that the adsorption mechanism is based on not only simple physisorption. The phenol adsorption capacity increased with the increase in carbonization temperature of the CMH and the decrease in its hydrophilicity. CMHs carbonized at temperatures higher than 1073 K showed the highest phenol adsorption capacity which was around 160 mg·g^?1. The CMHs could continuously adsorb phenol from aqueous solutions, and their length of unused bed (LUB) values depended on operation conditions but were in the range of 0.3–0.7 cm. The experimental results indicated that carbon cryogels with a microhoneycomb structure have a high potential to be used for effective separation of phenol.     

Time-resolved absorption spectroscopic studies on the reaction of conformationally fixed o-(9-fluorenyl)phenylnitrenes

Laser-flash photolysis studies have been carried out on a solution of ap- and sp-9-(2-azido-4,6-dimethylphenyl)fluorenes (3) in methanol-ether at 25°C. The rates of formation of azanorcaradiene (5) from ap-nitrene (4) ap, and of 9-methoxyfluorene (7) from o-quinoid intermediate (6) were determined. The deuterium isotope effect on the migration of the hydrogen is discussed.     

Synthesis, Photoreactivity and Cytotoxic Activity of Caged Compounds of L-Leucyl-L-Leucine Methyl Ester, an Apoptosis Inducer

I,-Leucyl-L-leucine methyl ester (Leu-Leu-OMe), an apoptosis inducer in natural killer cells and macro-phages, was caged with trans -o-hydroxycinnamoyl (3ad), trans-o -mercaptocinnamoyl (4) and o -nitrobenzyl derivatives (5a, b), and the photochemical reactivity of these derivatives in phosphate-buffered saline containing 1% dimethyl sulfoxide and their immunological properties were studied. All of the derivatives exhibited absorplion at wavelengths longer than the UVB region. Although 3a–d and 4 were expected to isomerize to a cis isomer, which thgn cyclizes intramolecularly to give Leu-Leu-OMe and a coumarin derivative, cyclization efficiency was not satisfactory except for 3a. However, 3a itself caused necrosis (cell swelling) of U937 cells (a myeloid cell line). In contrast, 5a and b released Leu-Leu-OMe quickly and efficiently and did not affect U937 cells. Although irradiated 5b induced necrosis, irradiated 3a and 5a induced apoptosis in these cells, as evidenced by a decrease in cell size.     

Analytic properties of the Ishida-Yonezawa approximation for liquid and amorphous metals

We generally examine the analytic properties of the Ishida-Yonezawa approximation for the tight binding single s-band model. A sufficient condition is derived on which a solution satisfies the physical conditions; (1) sum rule, (2) reality, (3) definiteness, (4) analyticity, (5) boundary condition and (6) uniqueness.     

Anomalous fluctuations in sliding motion of cytoskeletal filaments driven by molecular motors: model simulations

It has been found in in vitro experiments that cytoskeletal filaments driven by molecular motors show finite diffusion in sliding motion even in the long filament limit [Imafuku, Y. et al. Biophys. J. 1996, 70, 878-886. Noda, N. et al. Biophysics 2005, 1, 45-53]. This anomalous fluctuation can be evidence for cooperativity among the motors in action because fluctuation should be averaged out for a long filament if the action of each motor is independent. In order to understand the nature of the fluctuation in molecular motors, we perform numerical simulations and analyze velocity correlation in three existing models that are known to show some kind of cooperativity and/or large diffusion coefficient, i.e., the Sekimoto-Tawada model [Sekimoto, K.; Tawada, K. Phys. Rev. Lett. 1995, 75, 180], the Prost model [Prost, J. et al. Phys. Rev. Lett. 1994, 72, 2652], and the Duke model [Duke, T. Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 2770]. It is shown that the Prost model and the Duke model do not give a finite diffusion in the long filament limit, in spite of the collective action of motors. On the other hand, the Sekimoto-Tawada model has been shown to give a diffusion coefficient that is independent of filament length, but it comes from the long time correlation whose time scale is proportional to filament length, and our simulations show that such a long correlation time conflicts with the experimental time scales. We conclude that none of the three models represent experimental findings. In order to explain the observed anomalous diffusion, we have to search for a mechanism that will allow both the amplitude and the time scale of the velocity correlation to be independent of the filament length.     

Photochemistry of N-Phenylbenzenecarbohydroxamic acid

N-Phenylbenzenecarbohydroxamic acid undergoes a photoreaction in cyclohexane and methanol to give benzanilide as a major product.

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Photochemie von N-Phenylbenzolcarbohydroxamsäure

Zusammenfassung N-Phenylbenzolcarbohydroxamsäure ergibt in einer Photoreaktion (in Cyclohexan und Methanol) Benzanilid als Hauptprodukt.

     

Molecular design of correlated internal rotation

Disrotatory coupling of the internal rotational degrees of freedom in double rotor molecules has been studied for bis(9-triptycyl)methanes (Tp₂CH₂) and bis-(9-triptycyl) ethers (Tp₂O). These molecules undergo rapid internal rotation in a strictly gear-meshed fashion, giving rise to new stereoisomerism in the 2, 2′- and 3,3′-dichloro derivatives. The racemic and meso isomers which arise due to different phase relationship between the substituted benzene rings were separated by HPLC. The high energy barrier to the gear-slipping process was obtained as 32 - 33 and 42 - 43 kcal mol^?1 for Tp₂CH₂ and Tp₂O, respectively, by the isomerization study. The low energy barrier to the gear-meshing process was determined to be ca. 4.5 kcal mol^?1 by analyzing the exciplex fluorescence dynamics for a Tp₂O carrying the naphthalene chromophore on one Tp unit and the tert-amino group on the other. The molecular structure of Tp₂O has been determined by an X-ray analysis; the molecule adopts a bevel gear-shaped structure with the C_s point group in which the CO bond lengths average 1.412 Å and the ∠COC angle is widened to 135.8°. An attempt at reproducing the observed structural features by means of an empirical force-field calculation is described. A possible extension of the concept and further results on correlated internal rotation and phase isomers are discussed.