A Novel Dimeric Eremophilane from Ligularia virgaurea spp. oligocephala

A novel dimeric eremophilane, ligulolide B, was isolated from the alcoholic extract of the whole plant of Ligularia virgaurea spp. oligocephala. The structure was elucidated by various spectroscopic methods including intensive 2D NMR techniques （^1H-^1H COSY, gHMQC, gHMBC and ^1H-^1H NOESY） and HR-ESI-MS.     

Synthèse d'arylhydroxyspirocétals. Influence du groupe aryle sur la photocyclisation d'arylcétoacétals en série hétérocyclique et osidique

By irradiation, the tetrahydropyranylarylketoacetal compounds led to isomers of spiro compounds. A competition between Norrish II and Paterno-Buchi reations was observed with unsaturated heterocyclic products. In the osidic series, the reaction was not stereoselective, but the photocyclisation works with rentention of configuration at low temperature. The acidic epimerisation of spiro C-1 sugars mainly yields the trans (α or β) isomers.     

Synthesis of CuCorePtShell Nanoparticles as Model Structures for Core–Shell Electrocatalysts by Direct Platinum Electrodeposition on Copper

The synthesis of Cu(core)Pt(shell) model catalysts by the direct electrochemical deposition of Pt on Cu particles is presented. Cu particles with an average diameter of 200 nm have been deposited on glassy‐carbon electrodes by double pulse electrodeposition from a copper sulfate solution. Subsequent deposition from a platinum nitrate solution under potential control allows for a high selectivity of the Pt deposition towards Cu. Using a combination of cyclic voltammetry, XPS and sputtering, the structure of the generated particles has been analyzed and their core–shell configuration proven. It is shown that the electrocatalytic activity for the oxygen reduction is similar to that of other PtCu catalyst systems. The synthesized structures could allow for the analysis of structure–activity relations of core–shell catalysts on the way to the simple and controlled synthesis of supported Cu(core)Pt(shell) nanoparticles as oxygen reduction catalysts.     

一类齐次对称多项式上的切比雪夫不等式

本文借助于控制不等式及数学归纳法，将著名的切比雪夫不等式推广到m次一般齐次对称多项式上(如文中定理及引理7)，并将此结果用于对称平均等．旨在展示证明解析不等式的一些有效的方法和技巧，同时为数学研究特别是高维几何研究提供一些新的有趣而有用的解析不等式．     

The decay of93g Ru,93m Ru,91g Mo,91m Mo,91g Tc and91m Tc

Decay studies on a number of short-lived odd nuclei in theN=50 region are described. The 59.6-s ⁹³Ru ground state decay was studied in detail for the first time; in these experiments the 10.8-s activity^93m Ru was discovered. The⁹¹Tc activities were also observed for the first time. The ground state and an isomeric state of this nucleus decay with nearby equal half-lives (3.14 and 3.3-min). The activities^91g Mo (16.6-min) and^95m Mo (65.1-s) have been reinvestigated. A number ofγ-rays, previously erroneously assigned to the⁹¹Mo activities, could be eliminated. A strong similarity is noted for the decay schemes of theN=49 isotones^91m Mo and^93m Ru. The energy of the 1/2^? isomeric state in⁹³Ru and theB(M4)-value of the isomeric transition fit well into the systematics of the previously knownN=49 isotones.     

Tests of quantum chromodynamics and a direct measurement of the strong coupling constant αs at √s=30 GeV

We report the measurement of the reaction e⁺ + e^? → hadronic jets at a center-of-mass energy √s=30 GeV using the MARK-J detector at PETRA. By measuring the energy and angular distribution of both neutrals and charged particles we were able to isolate unambiguously the three-jet events in a kinematic region where the backgrounds from q$\text{q}$ and phase space contributions and other processes are small. Various comparisons of the data with quantum chromodynamics were made. The relative yield of three-jet events and the shape distribution of the events enable us to determine α_s = 0.23 ± 0.02 (statistical error) with a systematic error of ± 0.04.     

On the power from phonon fluorescence in superconductors

A vibronic sideband spectrometer is used to detect phonons generated from phonon fluorescence in superconductors. Although previously projected phonon powers are just within the minimum detectivity, no sideband signals were observed. An interpretation of this result is given.