Hydrogen bonded homo- and heterodimers of tetra urea derivatives of calix[4]arenes

Calix[4]arene ethers fixed in the cone conformation and substituted at the upper rim by various urea residues have been synthesized by reaction of the amino calix[4]arenes with isocyanates. Their dimerisation in apolar solvents has been established by the formation of mixed dimers consisting of two different urea derivatives.     

The effect of nitrogen donors on the reactivity of copper(I) aryloxides: Synthesis of thioncarbonates

Significant changes in the reactivity of copper(I) aryloxides are observed in the presence of nitrogen bases leading to an easy method of synthesizing thioncarbonates.     

Preparation and diels-alder reactions of a pyranoid vinyl glycal:model studies for anthraquinone aglycone and carbohydrate syntheses

The preparation of a conjugated pyranoid vinyl glycal is reported, along with several of its thermal [4+2] cycloaddition reactions with a variety of dienophiles. Applications to the anthraquinone antitumor agents are discussed.     

Photocatalytic properties of [polymerized n-butyl-o-titanate + hydrogen peroxide] complex on the decomposition of water

The electronic structure of the [pol-Ti(OBu)₄ + H₂O₂] complex, which is formed during the photolysis of water over [pol-Ti(OBu)₄ + CH₃OH] complex on silica gel, is elucidated in detail from the photocatalytic standpoint by DV-Xα cluster calculations. The numerical results reveal the appearance of a localized state (active site) similar to that of the [pol-Ti(OBu)₄ + CH₃OH] complex. The [TiOBu)(OH)(OH)₄]²⁻ cluster, which substitutes a hydroxyl group for the (OOH) group, exhibits an electronic structure very close to that of the [Ti(OBu)(OMe)(OH)₄]²⁻ cluster (A₁ or A₂), which was studied previously. A reduction in photocatalytic activity for the water decomposition is discussed.     

Binuclear hydroxo-monopentahalophenyl complexes of palladium(II)

The novel binuclear hydroxo-bridged complexes trans-[R(PPh₃)Pd(μ-OH)₂Pd(PPh₃)R] and cis-[R(PPh₃)Pd(μ-OH)(μ-pz)Pd(PPh₃)R] (R = C₆F₅ or C₆Cl₅; pz = pyrazolate) have been prepared, and their structures assigned on the basis of NMR data.     

Maps preserving the idempotency of products of operators

Let B(X) be the algebra of all bounded linear operators on a complex Banach space X. We give the concrete form of every unital surjective map φ on B(X) such that AB is a non-zero idempotent if and only if φ(A)φ(B) is for all A,B∈B(X) when the dimension of X is at least 3.     

基于多光谱方法对山东海曲汉墓群出土漆盒类漆器研究

山东日照海曲汉墓群是2002年度全国十大考古新发现之一,该墓群共出土漆器约500件,具有较高历史、科学和艺术价值.漆盒是海曲汉墓出土漆器中数量最多的一类,具有造型精美的特点,代表着当时高度发达的髹漆工艺水平.切片显微研究揭示了该批漆盒存在漆灰层→底漆层→面漆(色漆和彩绘层)的髹制工艺特点,且具有较厚的漆灰层和底漆层.漆...     

The Proton-Resonance-Frequency-Shift Method Compared with Molecular Diffusion for Quantitative Measurement of Two-Dimensional Time-Dependent Temperature Distribution in a Phantom

Noninvasive thermometry methods with magnetic resonance imaging usually explore the temperature dependence of the molecular diffusion coefficient of water. A method based on the temperature dependence of the proton resonance frequency is proposed in this study and compared with the diffusion method. The comparison was made with a gel phantom with muscle characteristics and for a voxel size of 0.8 × 0.8 × 10 mm³. The root-mean-square deviation of the temperature images obtained with simulations of the thermal process is between 0.1 and 0.15°C for the proton-resonance-shift-based method with an acquisition time of 1 minute and 0.9-1°C for the diffusion-based method with an acquisition time of 4.5 minutes. Unfortunately, the proton-resonance-shift method is very sensitive to the drift of the external magnetic field and therefore a method of external references was proposed to correct for this drift. The method proves to be adequate as long as the thermal be of interest do not take more than 1 hour.