On the back-scatter cross-sections of ice spheres

Résumé La section droite de diffusion arrière de sphères de grand diamètre constituées par de la glace ou une matière (Stycast) ayant le même indice de réfraction est envisagée d'une manière à la fois théorique et expérimentale. La section droite est évaluée théoriquement par l'application d'une méthode d'optique géométrique simplifiée dans laquelle on considère seulement les réflexions sur les faces avant et arrière de la sphère. Dans le domaine du rapport diamètre/longueur d'onde de l'ordre de 1,3 à 6,7, les résultats obtenus par cette méthode s'accordent bien avec le calcul rigoureux de la section droite obtenu par la solution de l'équation demie. Pour des diamètres plus grands, la solution approchée sous-estime la section droite demie par un facteur qui est cependant plus petit que 3. La théorie simplifiée est étendue au cas de sphères diélectriques ayant leur surface partiellement couverte par une couche réfléchissante.Des données expérimentales sur la diffusion arrière, à une longuer d'onde de 3,22 cm, par des sphères en Stycast recouvertes d'une calotte sphérique de petite dimension, sont présentées dans le but d'illustrer la théorie précédente. En effet, les résultats obtenus, pour toutes les positions de la calotte sphérique au cours de sa rotation autour d'un axe vertical, sont en plein accord, dans la limite des erreurs expérimentales, avec la théorie faisant intervenir la composition de 3 parcours optiques principaux.

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A summary of this work was presented at the Tenth Weather Radar Conference, Washington, D. C., April 22–25, 1963.     

Energy dependence on fractional charge for strongly interacting subsystems

The energies of a pair of strongly interacting subsystems with arbitrary noninteger charges are examined from closed- and open-system perspectives. An ensemble representation of the charge dependence is derived, valid at all interaction strengths. Transforming from resonance-state ionicity to ensemble charge dependence imposes physical constraints on the occupation numbers in the strong-interaction limit. For open systems, the chemical potential is evaluated using microscopic and thermodynamic models, leading to a novel correlation between ground-state charge and an electronic temperature.     

A bioactive cycloartane triterpene from Garcinia hombroniana

The dichloromethane bark extract of Garcinia hombroniana yielded one new cycloartane triterpene; (22Z,24E)-3β-hydroxycycloart-14,22,24-trien-26-oic acid (1) together with five known compounds: garcihombronane G (2), garcihombronane J (3), 3β acetoxy-9α-hydroxy-17,14-friedolanostan-14,24-dien-26-oic acid (4), (22Z, 24E)-3β, 9α-dihydroxy-17,14-friedolanostan-14,22,24-trien-26-oic acid (5) and 3β, 23α-dihydroxy-17,14-friedolanostan-8,14,24-trien-26-oic acid (6). Their structures were established by the spectral techniques of NMR and ESI-MS. These compounds together with some previously isolated compounds; garcihombronane B (7), garcihombronane D (8) 2,3’,4,5’-tetrahydroxy-6-methoxybenzophenone (9), volkensiflavone (10), 4’’-O-methyll-volkensiflavone (11), volkensiflavone-7-O-glucopyranoside (12), volkensiflavone-7-O-rhamnopyranoside (13), Morelloflavone (14), 3’’-O-methyl-morelloflavone (15) and morelloflavone-7-O-glucopyranoside (16) were evaluated for cholinesterase enzymes inhibitory activities using acetylcholinesterase and butyrylcholinesterase. In these activities, compounds 1–9 showed good dual inhibition on both the enzymes while compounds 10–16 did not reasonably contribute to both the cholinesterases inhibitory effects.     

A Water-Soluble Sodium Pectate Complex with Copper as an Electrochemical Catalyst for Carbon Dioxide Reduction

A selective noble-metal-free molecular catalyst has emerged as a fruitful approach in the quest for designing efficient and stable catalytic materials for CO₂ reduction. In this work, we report that a sodium pectate complex of copper (PG-NaCu) proved to be highly active in the electrocatalytic conversion of CO₂ to CH₄ in water. Stability and selectivity of conversion of CO₂ to CH₄ as a product at a glassy carbon electrode were discovered. The copper complex PG-NaCu was synthesized and characterized by physicochemical methods. The electrochemical CO₂ reduction reaction (CO₂RR) proceeds at −1.5 V vs. Ag/AgCl at ~10 mA/cm² current densities in the presence of the catalyst. The current density decreases by less than 20% within 12 h of electrolysis (the main decrease occurs in the first 3 h of electrolysis in the presence of CO₂). This copper pectate complex (PG-NaCu) combines the advantages of heterogeneous and homogeneous catalysts, the stability of heterogeneous solid materials and the performance (high activity and selectivity) of molecular catalysts.     

Molecular Docking of SP40 Peptide towards Cellular Receptors for Enterovirus 71 (EV-A71)

Enterovirus 71 (EV-A71) is one of the predominant etiological agents of hand, foot and mouth disease (HMFD), which can cause severe central nervous system infections in young children. There is no clinically approved vaccine or antiviral agent against HFMD. The SP40 peptide, derived from the VP1 capsid of EV-A71, was reported to be a promising antiviral peptide that targeted the host receptor(s) involved in viral attachment or entry. So far, the mechanism of action of SP40 peptide is unknown. In this study, interactions between ten reported cell receptors of EV-A71 and the antiviral SP40 peptide were evaluated through molecular docking simulations, followed by in vitro receptor blocking with specific antibodies. The preferable binding region of each receptor to SP40 was predicted by global docking using HPEPDOCK and the cell receptor-SP40 peptide complexes were refined using FlexPepDock. Local molecular docking using GOLD (Genetic Optimization for Ligand Docking) showed that the SP40 peptide had the highest binding score to nucleolin followed by annexin A2, SCARB2 and human tryptophanyl-tRNA synthetase. The average GoldScore for 5 top-scoring models of human cyclophilin, fibronectin, human galectin, DC-SIGN and vimentin were almost similar. Analysis of the nucleolin-SP40 peptide complex showed that SP40 peptide binds to the RNA binding domains (RBDs) of nucleolin. Furthermore, receptor blocking by specific monoclonal antibody was performed for seven cell receptors of EV-A71 and the results showed that the blocking of nucleolin by anti-nucleolin alone conferred a 93% reduction in viral infectivity. Maximum viral inhibition (99.5%) occurred when SCARB2 was concurrently blocked with anti-SCARB2 and the SP40 peptide. This is the first report to reveal the mechanism of action of SP40 peptide in silico through molecular docking analysis. This study provides information on the possible binding site of SP40 peptide to EV-A71 cellular receptors. Such information could be useful to further validate the interaction of the SP40 peptide with nucleolin by site-directed mutagenesis of the nucleolin binding site.     

What controls the thickness of wetting layers near bulk criticality?

We study the thickness of wetting layers in the binary-liquid mixture cyclohexane methanol. Far from the bulk critical point, the wetting layer thickness is independent of temperature, resulting from the competition between van der Waals and gravitational forces. Upon approaching the bulk critical temperature [t=(T(c)-T)/T(c)-->0], we observe that the wetting layer thickness diverges as t(-beta) with effective critical exponent beta=0.23+/-0.06. This is characteristic of a broad, intermediate scaling regime for the crossover from van der Waals wetting to critical scaling. We predict beta=beta/3 approximately 0.11, with beta the usual bulk-order parameter critical exponent, showing a small but significant difference with experiment.     

新型联苯胺基窄带隙共轭聚合物的光学及电化学性能研究

随着化石燃料的日益枯竭,人类社会对能源的需求在不断增长。为了平衡能量应用需求并提升能量使用效率,开发高效能量转换材料与电化学储能材料成为当前研究的重要课题。导电聚合物基电极材料面临着相应储能器件能量密度、功率密度、循环性能不高的挑战,需进行结构改性提高电导率、改善界面性质。鉴于共轭高分子的电子结构、光学及电化学性质由共轭链骨架结构决定,对导电共轭聚合物进行结构修饰以提升其电荷传输性能和载流子迁移率,进而设计合成新型高迁移率导电聚合物基共轭聚合物是提高相应器件特性的关键所在。已有研究大多借助复杂的结构设计来实现提升迁移率,设计合成了结构简单,有助提升电荷迁移的新型窄带隙聚联苯胺基共轭聚合物聚物。通过光谱学及电化学方法对材料结构与性能进行了表征分析。采用核磁共振氢谱、红外光谱,X射线粉末衍射对单体及聚合物进行了结构表征,通过紫外光谱、紫外可见漫反射、循环伏安、计时电位、交流阻抗对其进行了光学及电化学性能测试。结果表明,成功制得具有预期结构的共轭聚合物,所得聚合物结晶性较佳,光学带隙E_g^opt为1.85eV,HOMO及LUMO能级分别为-5.44和...     

Revisiting the nature of the ZnO ground state: Influence of spin–orbit coupling

Relativistic calculations of the low-lying electronic states of the ZnO molecule are performed for the Λ–Σ states, ¹Σ⁺, ¹Π, ¹Δ, ³Π and ³Σ⁻, at the CCSD(T) or MRCI level, using scalar relativistic energy-consistent pseudopotentials, and the EPCISO method for spin–orbit CI coupling. The ZnO ground state is assigned to 0⁺ symmetry and has ¹Σ⁺ character around the equilibrium region. The spectroscopic constants (r_e, ω_e) of the 0⁺ ground state are in good agreement with experimental results. Interpenetration of the vibrational levels of the two lowest 0⁺ states is also shown.