Perturbation theory of difference schemes

Summary This paper is to show, if the abstract Cauchy problem has a stable difference scheme, then the Cauchy problem of a perturbed equation has also a stable difference scheme when a perturbing operator and its difference approximation have some suitable properties. And it will be noted this result is applicable to parabolic differential equations and their lower order terms, when parabolic difference schemes are used as original difference schemes.     

Electrical and thermal properties in CuV2S4

The successive phase transitions of the cubic spinel structure CuV₂S₄ have been studied by the electrical resistivity and the specific heat. In the resistivity and the specific heat two anomalies have been observed at T₁～91 K and T₃≈55 K. The specific heat indicates that the phase transition at T₁ is in the vicinity of a tricritical point, where the resistivity has a small sharp peak. On the other hand, the specific heat shows a step at T₃, where a hysteresis of the resistivity indicates the existence of the first-order phase transition.     

Active species transfer-type artificial light harvesting system in the nanosheet – Dye complexes: Utilization of longer wavelength region of sunlight

A novel light harvesting system that captures long-wavelength light of sunlight by the use of hole transfer was newly investigated. Ga phthalocyanine(Ga^IIITMAPc⁴⁺(D)) and Ru porphyrin(Ru^IIDMPyMP²⁺(A)) co-adsorbed reaction system on the synthetic nanosheet was examined as an artificial light harvesting system. By irradiating 660?nm light, where Ga^IIITMAPc⁴⁺(D) absorbs, to the system under a presence of PtCl₆^2? as an electron acceptor, cation radical of Ru^IIDMPyMP²⁺(A) was produced despite that Ru porphyrin adsorbs only 413 and 533?nm light. The efficient hole transfer reaction from Ga^IIITMAPc⁴⁺(D)⁺, that is generated from its excited state, to Ru^IIDMPyMP²⁺(A) takes place on the nanosheet.     

Factors controlling photochemical cleavage of the energetically unfavorable Ph-Se bond of alkyl phenyl selenides

Primary photochemical paths of alkyl phenyl selenides (1) were investigated, and an origin of large deviations in the chemical yields of products obtained by carbon radical reactions induced by photolysis of phenyl selenides was clarified. KrF excimer laser photolyses of n-pentyl phenyl selenide (1a) yielded 1-pentene (2a), n-pentane (3a), n-decane (4a), dipentyl selenide (5a), benzene (6), dipentyl diselenide (7a), and diphenyl diselenide (7) as major photoproducts, with compounds 2a, 3a, 4a, 5a, and 7 formed by pentyl-Se bond cleavage, and 5a, 6, and 7a by Ph-Se bond cleavage. The selectivity of the photoproducts revealed the occurrence of an unexpected amount of Ph-Se bond cleavage (35% in n-hexane at 248 nm) during photolysis. Solvent viscosity, wavelength of light, and the structure of alkyl substituents were the major factors that controlled Ph-Se bond cleavage. The ratio of Ph-Se bond cleavage decreased with increasing solvent viscosity and laser wavelength. The effect of alkyl substituents on the ratio of bond cleavages, Ph-Se/total C-Se, was investigated for five alkyl phenyl selenides; the ratio decreased in the order pentyl > 2-methylallyl > allyl > 1-ethylpropyl > tert-butyl groups. The contribution of Ph-Se bond cleavage is most probably the origin of the large deviations in the yields of radical reactions induced by photolyses of 1, which can be minimized by selecting appropriate solvents and wavelength of light.     

Determination of paclitaxel in human and rat blood samples after administration of low dose paclitaxel by HPLC-UV detection

A simple and sensitive HPLC-UV method was developed for the determination of paclitaxel (TXL) in human and rat blood samples. 4-Hydroxybenzoic acid n-hexyl ester was used as an internal standard. TXL was extracted by a liquid-liquid extraction with tert-butylmethyl ether. The disturbing peaks in the case of serum sample were removed by pre-extraction with hexane. The separation of TXL was achieved within 25 min using an ODS column with 50% acetonitrile aqueous solution as a mobile phase at a flow rate of 1.0 mL/min. The eluent was monitored at 230 nm, and the resulted retention times of TXL and IS were 11.2 and 20.4 min. The detection limits of TXL for human plasma, serum and rat plasma samples at a signal-to-noise ratio of 3 were 10, 9.5 and 7.5 ng/mL, respectively. The proposed methods were applicable to the determination of TXL in human patients' plasma ranging from 15 to 27 ng/mL. Furthermore, monitoring of the time course of TXL after its single administration to rat could be demonstrated.     

Five non‐synonymous SNPs in the gene encoding human deoxyribonuclease I‐like 2 implicated in terminal differentiation of keratinocytes reduce or abolish its activity

Several non‐synonymous SNPs in the human deoxyribonuclease I‐like 2 (DNase 1L2) gene responsible for DNA degradation during terminal differentiation of epidermal keratinocytes have been identified. However, only limited population data are available, and furthermore the effect of these SNPs on the DNase 1L2 activity remains unknown. Genotyping of all of the 17 SNPs was performed using the PCR‐RFLP method in three ethnic groups including 14 different populations. A series of amino acid‐substituted DNase 1L2 corresponding to each SNP was expressed, and its activity was measured. All of the six non‐synonymous SNPs exhibited a mono‐allelic distribution, whereas the distribution of some SNPs other than exonic ones was ethnicity‐dependent. Each of the minor alleles in SNPs, p.Ala20Asp, p.Val104Leu, p.Asp197Ala, p.Glu274Lys and p.Asp287Asn, among the non‐synonymous SNPs produced low or no activity‐harbouring DNase 1L2. DNase 1L2 is well conserved, retaining full levels of enzymatic activity, with regard to these exonic SNPs in human populations. It seems plausible to assume that these SNPs affecting the activity may be one of the factors responsible for a genetic pre‐disposition for failure of differentiation‐associated cell death in various keratinocyte lineages, thereby leading to the development of parakeratosis. Our results may have clinical implications in relation to the pathogenesis of parakeratosis.     

Investigation of adsorption behavior and energy transfer of cationic porphyrins on clay surface at low loading levels by picosecond time-resolved fluorescence measurement

Time-resolved fluorescence and steady-state spectroscopic measurements were performed with +4-charged cationic porphyrins adsorbed on an anionic-type clay (Sumecton SA; SSA) surface at a low molecular loading level (10 % vs. cation-exchange capacity of clay) corresponding to an occupied area of ca 50 nm² per molecule. Absorption spectra indicated no interaction between transition moments of the porphyrins on the clay surface. An efficient energy-transfer process from donor to acceptor porphyrin was observed on the clay surface even under low porphyrin loading conditions. The efficiency of energy transfer obtained from the steady-state measurement was 65 %. Real-time behavior of the porphyrins was successfully captured during energy transfer. The rate constant of the energy transfer obtained from time-resolved fluorescence measurements was found to be 5.3 × 10⁸ s^?1. According to the efficiency and the rate constant, it is proposed that the adsorbed porphyrins did not have a uniform and fixed distribution.     

Novel methodology to control the adsorption structure of cationic porphyrins on the clay surface using the "size-matching rule"

Saponite-type clays that have different cation exchange capacities were successfully synthesized by hydrothermal synthesis. The structure and properties were analyzed by X-ray diffraction, X-ray fluorescence, (27)Al NMR, FT-IR, thermogravimetric and differential thermal analysis, atomic force microscopy, and cation exchange capacity measurement. The intercharge distances on the synthetic saponite (SS) surfaces were calculated to be 0.8-1.9 nm on the basis of a hexagonal array. The complex formation behavior between SS and cationic porphyrins was examined. It turns out that the average intermolecular distance between porphyrin molecules on the SS surface can be controlled, depending on the charge density of the SS. In the case of tetrakis(1-methylpyridinium-4-yl)porphyrin (H(2)TMPyP(4+)), the average intermolecular distances on the SS surface can be controlled from 2.3 to 3.0 nm on the basis of a hexagonal array. It was also found that absorption maxima of porphyrins depend on the charge density of the SS. The adsorption behavior of porphyrin on the SS surface can be rationally understood by the previously reported "size-matching rule". This methodology using host-guest interaction can realize a unique adsorption structure control of the porphyrin molecule on the SS surface, where the gap distance between guest porphyrin molecules is rather large. These findings will be highly valuable to construct photochemical reaction systems such as energy transfer in the complexes.     

Synthesis of (±)-cyclic dehypoxanthine futalosine, the biosynthetic intermediate in an alternative biosynthetic pathway for menaquinones

The first synthesis of (±)-cyclic dehypoxanthine futalosine (cyclic DHFL), a biosynthetic intermediate in the futalosine pathway for menaquinones operating in microorganisms, has been achieved. Efficient growth of the Streptomyces coelicolor mutant, which lacks the cyclic DHFL synthetase gene (mqnC gene) was observed in the presence of synthetic (±)-cyclic DHFL.