A Review of Results on Axially Symmetric Navier-Stokes Equations,with Addendum by X. Pan and Q. Zhang

In this paper, we give a brief survey of recent results on axially symmetric Navier-Stokes equations (ASNS) in the following categories: regularity criterion, Liouville property for ancient solutions, decay and vanishing of stationary solutions. Some discussions also touch on the full 3 dimensional equations. Two results, closing of the scaling gap for ASNS and vanishing of homogeneous D solutions in 3 dimensional slabs will be described in more detail.In the addendum, two new results in the 3rd category will also be presented, which are generalizations of recently published results by the author and coauthors.     

The investigation of ancient pottery

Summary Ancient ceramic samples (single fragments and different parts of pots, unbroken and repaired; total about 180 samples) dated from the transitional period of late Bronze to early Iron Age (VIII-VI centuries BC) and early Iron Age (VII-IV centuries BC) were investigated by thermal analysis, X-ray powder diffraction, petrography, and scanning electron microscopy equipped with the energy-dispersive X-ray analyzer. In addition to that, to identify the clay sources for the ceramic manufacturing, about 15 samples of clays and soils found near archeological digs and taken from the mineralogical museum were investigated. We found out that the calcite content of ceramics is a very informative parameter for the identification of the clay source for the pottery manufactured at low technological level (low-temperature firing).     

One-pot Synthesis of a Truncated Cone-shaped Porphyrin Macrocycle and Its Self-assembly into Permanent Porous Material

Here, we report the synthesis of a truncated cone-shaped triangular porphyrinic macrocycle, P₃L₃ , via a single step imine condensation of a cis-diaminophenylporphyrin and a bent dialdehyde-based linker as building units. X-ray diffraction analysis reveals that the truncated cone-shaped P₃L₃ molecules are stacked on top of each other by π⋯π and CH⋯π interactions, to form 1.7 nm wide hollow columns in the solid state. The formation of the triangular macrocycle is corroborated by quantum chemical calculations. The permanent porosity of the P₃L₃ crystals is demonstrated by several gas sorption experiments and powder X-ray diffraction analysis.     

拉曼光谱技术在中国古玉、古玉器鉴定和研究中的应用

激光拉曼光谱技术是应用于科技考古研究中的高技术之一,属于无损分析研究,但作为一种很好的无损分析方法它在中国古代玉器研究中的应用并不非常广泛。文章首先介绍了激光拉曼光谱技术的基本原理及近几年来国内外的最新进展,然后从矿物结构与拉曼特征峰之间的关系入手比较了目前国内外5种常见玉石的激光拉曼研究结果。然后分别通过对浙江良渚遗址和河南安阳殷墟遗址出土的4件中国古代玉器与新疆和田地区出产的软玉样品进行对比研究,成功地利用激光拉曼光谱技术对一批中国古代玉器进行了无损鉴定,从而阐明该项技术在中国古代玉器结构测试和材质鉴定中是一种很好的无损分析研究方法。最后,讨论了目前激光拉曼光谱技术在中国古玉和古代玉器研究中存在的局限性并对其发展前景进行了展望。     

Protein Secondary Structure Prediction with Partially Recurrent Neural Networks

Abstract

Partially recurrent neural networks with different topologies are applied for secondary structure prediction of proteins. The state of some activations in the network is available after a pattern presentation via feedback connections as additional input during the processing of the next pattern in a sequence. A reference data set containing 91 proteins in the training set and 15 non-homologous proteins in the test set is used for training and testing a network with a modified, hierarchical Elman architecture. The network predicts the secondary structures α-helix, β-sheet, and “coil” for each amino acid. The percentage of correctly classified amino acids is 67.83% on the training set and 63.98% on the test set. The best performance of a three-layer feedforward network is 62.7% on the same test set. A cascaded network, where the outputs of the recurrent network are processed by a second net with 13 × 3 inputs, four hidden and three output units has a predictive performance of 64.49%. The best corresponding feedforward net has a performance of 64.3%.     

Supramolecular architectures in metal(II) (Cd/Zn) halide/nitrate complexes of cytosine/5‐fluorocytosine

Three new metal(II)–cytosine (Cy)/5‐fluorocytosine (5FC) complexes, namely bis(4‐amino‐1,2‐dihydropyrimidin‐2‐one‐κN³)diiodidocadmium(II) or bis(cytosine)diiodidocadmium(II), [CdI₂(C₄H₅N₃O)₂], ( I ), bis(4‐amino‐1,2‐dihydropyrimidin‐2‐one‐κN³)bis(nitrato‐κ²O,O′)cadmium(II) or bis(cytosine)bis(nitrato)cadmium(II), [Cd(NO₃)₂(C₄H₅N₃O)₂], ( II ), and (6‐amino‐5‐fluoro‐1,2‐dihydropyrimidin‐2‐one‐κN³)aquadibromidozinc(II)–6‐amino‐5‐fluoro‐1,2‐dihydropyrimidin‐2‐one (1/1) or (6‐amino‐5‐fluorocytosine)aquadibromidozinc(II)–4‐amino‐5‐fluorocytosine (1/1), [ZnBr₂(C₄H₅FN₃O)(H₂O)]·C₄H₅FN₃O, ( III ), have been synthesized and characterized by single‐crystal X‐ray diffraction. In complex ( I ), the Cd^II ion is coordinated to two iodide ions and the endocyclic N atoms of the two cytosine molecules, leading to a distorted tetrahedral geometry. The structure is isotypic with [CdBr₂(C₄H₅N₃O)₂] [Muthiah et al. (2001). Acta Cryst. E 57 , m558–m560]. In compound ( II ), each of the two cytosine molecules coordinates to the Cd^II ion in a bidentate chelating mode via the endocyclic N atom and the O atom. Each of the two nitrate ions also coordinates in a bidentate chelating mode, forming a bicapped distorted octahedral geometry around cadmium. The typical interligand N—H…O hydrogen bond involving two cytosine molecules is also present. In compound ( III ), one zinc‐coordinated 5FC ligand is cocrystallized with another uncoordinated 5FC molecule. The Zn^II atom coordinates to the N(1) atom (systematic numbering) of 5FC, displacing the proton to the N(3) position. This N(3)—H tautomer of 5FC mimics N(3)‐protonated cytosine in forming a base pair (via three hydrogen bonds) with 5FC in the lattice, generating two fused R₂²(8) motifs. The distorted tetrahedral geometry around zinc is completed by two bromide ions and a water molecule. The coordinated and nonccordinated 5FCs are stacked over one another along the a‐axis direction, forming the rungs of a ladder motif, whereas Zn—Br bonds and N—H…Br hydrogen bonds form the rails of the ladder. The coordinated water molecules bridge the two types of 5FC molecules via O—H…O hydrogen bonds. The cytosine molecules are coordinated directly to the metal ion in each of the complexes and are hydrogen bonded to the bromide, iodide or nitrate ions. In compound ( III ), the uncoordinated 5FC molecule pairs with the coordinated 5FC ligand through three hydrogen bonds. The crystal structures are further stabilized by N—H…O, N—H…N, O—H…O, N—H…I and N—H…Br hydrogen bonds, and stacking interactions.     

Two organic–inorganic hybrid compounds constructed from 12-tungstovanadate and bipyridine

Two rare 12-tungstovanadate-bipyridine inorganic–organic hybrid compounds, [VW₁₂O₄₀] · 2(4,4′-H₂bipy) · 2H₂O (1) and [VW₁₂O₄₀] · 4(2,2′-Hbipy) (2), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction and IR analysis. In 1, a 2-D supramolecular architecture is formed by hydrogen-bonding between [VW₁₂O₄₀]^4? and bipy. Compound 1 shows good activity for photocatalytic reduction of rhodamine B in a liquid–solid system. The electrochemical and electrocatalytic properties of 2-bulk carbon paste electrode modified with 2 were investigated by cyclic voltammetry.     

Study of the circumstance influence on the elemental distribution in ancient animal bone using μ-XRF

Elemental analysis of archaeological bone plays an important role in the study of the dietary habits of ancient animals. The elemental characteristic of diagenetic skeletons depends on the surrounding circum-stance. The study of environmental influence on the elemental concentration of ancient bone is significant. In this paper, the diagenetic influence on archaeological skeletons is analyzed by microbeam X-ray fluorescence (μ-XRF). The results show that the enamel is an excellent barrier to the diagenesis and the element Sr in bone isn’t susceptible to contamination from the buried environment.     

New series of acridines and phenanthrolines: synthesis and characterization

New series of acridines and phenanthrolines have been prepared from β-chlorovinyl aldehydes and various aniline derivatives allowing the installation of valuable substituents, such as ketone, nitro or amino groups at the heterocyclic core. X-ray analyses confirmed the structures of acridines and phenanthrolines as well as the presence of partially hydrogenated rings and their crucial impact on the overall shape of the acridine-based architectures. ¹H NMR revealed the helical behaviour of several acridine motives. Comparison of UV data between architectures and influence of number of partially hydrogenated rings is also described.