Convenient synthesis of 2-alkylamino-6-carboxy-5,7-diarylcyclopenteno[1,2-b]pyridines via direct acylamination with imidoyl chlorides

A robust synthetic method for 2-alkylamino-6-carboxy-5,7-diarylcyclopenteno[1,2-b]pyridines via acylamination at the alpha position of the functionalized pyridine system has been developed. The key step in this method was achieved by treatment of the corresponding pyridine N-oxides with 2.5 equiv of imidoyl chlorides in the presence of triethylamine, thus producing the desired 2-acylaminopyridines in good yields (74-96%).     

Compositional dependence of the valency state of Cr ions in oxide glasses

Absorption spectra of Cr ions in multi-component oxide glasses melted in Ar were measured. The integrated extinction coefficient is used as a parameter to analyze the redox reaction of Cr³⁺ and Cr⁶⁺ in glass samples. The relative content of Cr⁶⁺ increased and that of Cr³⁺ decreased with increasing basicity in silicate and borate glasses; this result is consistent with previous studies. On the contrary, only Cr³⁺ exist in phosphate glasses. Cr⁴⁺ ions were found only in aluminate, gallate and alumino-silicate glasses with modifier contents ≥ 60 mol%. The relationship between point defects and Cr⁴⁺ formation is examined on the basis of electron spin resonance measurements. We concluded that the superoxide ion radical (O₂⁻) and the peroxy bonding (-O-O-) oxidize Cr³⁺ to Cr⁴⁺ in aluminate, gallate, and alumino-silicate glasses.     

Structure changes in amorphous silica by neutron irradiation

Wide angle, small angle, and very-small angle X-ray scatterings (WAXS, SAXS and VSAXS) as well as optical microscopy are observed for amorphous silica before and after neutron irradiation [3×10¹⁰n_th/cm², (48±2)°C]. The results are analyzed by employing the continuous random network (CRN) model [Zachariasen, J. Am. Chem. Soc. 54 (1932) 3841] that is topologically equivalent to the dense random packing (DRP) model for metallic glass (hard spheres being replaced by deformable spheres containing Si₂O₄ structural units).The effects of irradiation, as deduced from the broadening of the innermost haloes in WAXS, are interpreted in terms of an enhancement of randomness in the packing of the spheres materializing the structural unit, and in the internal structures of the spheres. This involves the rearrangements of the OSiO network that results in the local invalidation of the CRN-DRP equivalence. Consequently, small (25 Å) and large ($\text{2×10}{}^5\text{A}\text{?}$) structural inhomogeneities are produced that can effectively be disclosed by WAXS, SAXS, VSAXS, and optical microscopy. Arguments are advanced in which these structural changes are viewed as deviations from the DRP-equivalent CRN model in an analogous way as interpreting the radiation effects of amorphous Pd₈₀Si₂₀ (Doi et al., J. Non-Crystalline Solids 34 (1979) 405).     

A SAXS observation of the crystallization of an Al85Y10Ni5 amorphous alloy in the supercooled liquid state

The medium-range structure of a heat-treated Al₈₅Y₁₀Ni₅ amorphous alloy was investigated by small-angle X-ray scattering, calorimetric analysis, wide-angle X-ray diffraction and transmission electron microscope measurements. It is observed that crystalline particles having a definite boundary are precipitated by annealing at supercooled liquid temperatures and that most of the precipitates consist of the Al fcc crystalline phase. The integrated intensities of the small-angle scattering and the Guinier radii of the precipitates increase on annealing for time duration <5.4 ks. However, as the annealing time becomes > 5.4 ks, the integrated intensities and the Guinier radii are invariant, i.e., growth of the precipitates ceases. After annealing for 518.4 ks, the diameters of the precipitates exhibit a narrow distribution centered around 200 Å.     

铌酸锂晶体的缺陷及其控制

针对铌酸锂晶体中的缺陷研究,本文总结了国内外学者提出的不同晶体缺陷模型及各自的特点,并介绍了我们提出的铌位依赖、锂位敏感模型.在分析晶体缺陷研究的基础上提出了对铌酸锂晶体进行缺陷控制的意义及理论依据,指出缺陷控制的主要任务是保护锂格位.本文还简要概括了铌酸锂晶体缺陷控制的主要手段,并建议从反映铌酸锂晶体性能的角度来研究缺陷结构.     

Water-soluble dendrimer–poly(ethylene glycol) starlike conjugates as potential drug carriers

The design and synthesis of a new dendrimer–poly(ethylene glycol) (PEG) conjugate that may be used as a model drug carrier are described. The starting material is a polyether dendrimer with two different types of chain end functionalities. The dendritic assembly is made water soluble through attachment of short PEG chains to the dendrimer via one type of functionality. The remaining chain end functionalities then were used to incorporate model drug molecules of varying polarity into the modified dendrimer. Cholesterol and two amino acid derivatives were selected as model drugs for attachment through their respective hydroxyl, carboxylic acid, and amino functional groups to the dendrimer via carbonate, ester, and carbamate linkages. The resulting water-soluble dendrimer-model drug conjugates were characterized by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3492–3503, 1999     

Effects of L-tyrosine esters on quenching and photosensitized charge separation using polymers containing ruthenium(II) complex

A series of ruthenium(II) complex-containing partially quaternized poly(1-vinylimidazole)s with various alkyl side chains such as hexyl (C₆RuQPIm), dodecyl (C₁₂RuQPIm), and hexadecyl (C₁₆RuQPIm) were synthesized. The effects of L -tyrosine esters with hexyl (C₆Tyr), octyl (C₈Tyr), and dodecyl (C₁₂Tyr) on the quenching with methylviologen and photosensitized charge separation reactions were investigated using these metallopolymers as polymer photosensitizers. The quenching reaction took place through both a dynamic quenching process and a static quenching one mediated by the L -tyrosine esters. The kinetic parameters for these processes were obtained from a computed curve fitting using a Stern–Volmer equation derived from a combination of dynamic quenching and static quenching. The parameters had a significant dependence on the lengths of the alkyl groups in the L -tyrosine esters and the alkyl side chains on these metallopolymers. During photosensitized charge separation, the reaction proceeded through these quenching processes, referred to as direct and mediated processes. The initial rates of methylviologen radical formation also depended on these lengths; they increased when the lengths of the alkyl side chain on these metallopolymers and alkyl groups in the L -tyrosine esters were long. Such a dependence was caused by a change in the balance of some effects such as the electrostatic and steric effects. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4360–4367, 1999     

Arsenobetaine-decomposing Ability of Marine Microorganisms Occurring in Particles Collected at Depths of 1100 and 3500 Meters

The arsenobetaine-decomposing ability of microorganisms occurring in sinking particles, which play a main role in the vertical transport of organic substances produced in the photic zone, was investigated. The microorganisms in particles collected in the deep sea, 1100 and 3500 m in depth, clearly showed decomposing ability. With the particles from 1100 m, the degradation products were the same as those produced by microorganisms occurring in sources in the photic zone, i.e. trimethylarsine oxide (TMAO), dimethylarsinic acid (DMA) and inorganic arsenic(V). At 3500 m, the degradation activity was diminished, smalls amount of DMA and TMAO being produced. These results suggest that arsenobetaine contained in the animals starts to degrade immediately after the death of the animals and their transformation to particles. The degradation of arsenobetaine to inorganic arsenic in our tentative arsenic cycle in marine ecosystems (inorganic arsenic to inorganic arsenic via the biosynthesis of arsenobetaine) may apply to the deep sea as well as to the photic zone. © 1997 by John Wiley & Sons, Ltd.     

Formation of Giant Liposomes from Crystalline Complexes of Monoalkylammonium Surfactants and 4-Hydroxybiphenyl

A parallel rather than a perpendicular alignment of aromatic compounds with respect to surfactant molecules (see schematic representation) is preferred for the formation of a liposome structure, because the perpendicular alignment would reduce the hydrophilicity of the aggregate. This is the result of studies on crystalline complexes of monoalkylammonium halides and various aromatic compounds.