Spectrophotometric determination of aluminum with m-carboxyphenylfluorone, a novel chemical probe, and its application.

A highly spectrophotometric method for the determination of aluminum was developed. This method used the color reaction between m-carboxyphenylfluorone (MCPF) as a novel chemical probe and aluminum in the presence of a surfactant, poly(N-vinylpyrrolidone) (PVP, K-90) (0.03 - 1.40 microg of aluminum in a final volume of 10 ml at 561 nm). The proposed method showed excellent sensitivity (molar absorptibity of 1.70 x 10(5) l mol(-1) cm(-1)) and reproducibility (within-day precision: RSD = 0.35% n = 6, between-day precision: RSD = 0.44% n = 6). Linearity was achieved over the range 3 - 140 microg L(-1) with a correlation coefficient of 0.9999, and the effects of foreign substances were low.     

Synthesis of 1,3‐Cycloalkadienes from Cycloalkenes: Unprecedented Reactivity of Oxoammonium Salts

Few methods allow for the direct conversion of cycloalkenes into cycloalkadienes with high chemo‐ and regioselectivity. Herein, we report a convenient one‐pot process for this transformation that involves the unprecedented N‐preferential group transfer of N‐oxoammonium salts to cycloalkenes, followed by Cope elimination, to afford cycloalkadienes at room temperature and pressure.     

Graph Neural Networks with Multiple Feature Extraction Paths for Chemical Property Estimation

Feature extraction is essential for chemical property estimation of molecules using machine learning. Recently, graph neural networks have attracted attention for feature extraction from molecules. However, existing methods focus only on specific structural information, such as node relationship. In this paper, we propose a novel graph convolutional neural network that performs feature extraction with simultaneously considering multiple structures. Specifically, we propose feature extraction paths specialized in node, edge, and three-dimensional structures. Moreover, we propose an attention mechanism to aggregate the features extracted by the paths. The attention aggregation enables us to select useful features dynamically. The experimental results showed that the proposed method outperformed previous methods.     

Spectrophotometric determination of spermine and related compounds using o-hydroxyhydroquinonephthalein and manganese(II).

A simple and highly sensitive spectrophotometric method for the determination of spermine (Spm) was established based on the ternary complex formation reaction of Spm with o-hydroxyhydroquinonephthalein (QP) as a xanthene dye and manganese(II) as a metal ion in the presence of a dispersion agent. The apparent molar absorptivity at 555 nm and the relative standard deviation of the proposed method were 1.4 x 10(5) dm(3) mol(-1) cm(-1) and 0.50% (n = 10), respectively. In the method for flow-injection analysis (FIA), which employs a single-channel flow manifold system, a good linear relationship was observed over the 2 - 20 pg microl(-1) range of Spm by direct injection.     

溴化四丁铵催化苯乙烯一步合成苯乙烯环状碳酸酯

以溴化季铵盐为催化剂, 通过苯乙烯的环氧化和CO2的加成反应一步直接合成出苯乙烯环状碳酸酯, 详细考察了催化剂的用量、氧化剂的种类、反应温度、反应时间和CO2压力等因素对反应主产物收率的影响. 结果表明, 以溴化四丁铵为催化剂, 于80 ℃和1 MPa CO2下反应6 h, 环状碳酸酯的收率达到38%, 这是季铵盐阳离子和亲核性阴离子协同催化的结果.     

Zum thermischen Abbau von Poly-?-caprolacton

Ohne Zusammenfassung     

Vortical Structures in Rotating Uniformly Sheared Turbulence

Rotating homogeneous turbulence with and without mean uniform shear is investigated numerically. It is found that in the shearless case the two-dimensionalization process is most effective when the initial small-scale Rossby number is around unity and the resonant triad interactions play a central role in the process. The vortical structures are studied systematically by changing the relative strength of the mean shear and the system rotation as well as the sense of rotation. (The system is called cyclonic (or anti-cyclonic) when the direction of the vorticity associated with the rotation is the same as (or opposite to) that of the mean shear.) A distinct coherent structure appears in the anti-cyclonic system when the vorticities associated with the rotation and the mean shear cancel out, i.e. the absolute vorticity of the mean shear vanishes. For the linearly most unstable case in the anti-cyclonic system, the vortex tubes develop in the sheared direction, which is caused by instability of vortex layers. For linearly stable cases in both the cyclonic and the anti-cyclonic systems, there appear three typical structures, that is, the oblique vortex tubes, the pancake-like structures and the ribbon-like structures. It is interesting that the flow behaves quite differently between the cyclonic and anti-cyclonic systems even at the same Bradshaw number.