Photochemical formation of silver-gold (Ag?Au) composite colloids in solutions containing sodium alginate

Photochemical formation of colloidal silver, colloidal gold and silver-gold (Ag-Au) composite colloids under mild conditions has been studied. Irradiation of either aqueous AgCIO₄ or HAuCI₄ solution in the presence of sodium alginate (SA) with 253.7 nm light yielded colloidal silver or gold, whose particle diamter was 10-30 nm or 40-60 nm, respectively. The Ag-Au composite colloids consisting of mixtures of silver and gold domains (particle diameter 30-150 nm) have been prepared and their extinction spectra have been examined on the basis of a conventional Mie theory in combination with an effective medium theory to estimate the optical constants of these colloids. It has been shown that the extinction spectra of the Ag-Au composite colloids are completely different from those of Ag-Au alloy colloids, in that the former have two extinction maxima close to the colloidal extinction bands of pure silver and gold, in contrast to a single extinction maximum of the latter. The importance of natural, high-molecular carboxylic acids such as alginic acid in the photochemical formation of metal colloids and thin films has been stressed.     

气相CBr2 自由基的产生及激光诱导荧光色散谱研究

利用双层流动反应管作为束源 ,研究了F与CH2 Br2 反应生成的CBr2 和Br2 的气相激光诱导荧光色散谱 ,将得到的谱线分别指定为CBr2 的 A(0 ,13,0 )→ X(0 ,v2 ″,0 ) (v2 ″ =1～ 6 )跃迁和Br2 的 B3 Π+ u → X1Σ+ g 跃迁 ,从光谱中首次得到气相CBr2 自由基基态弯曲振动频率ν2 ″ =2 15cm-1,实验确认了CBr2 自由基和Br2 是F +CH2 Br2 过程多步反应的产物     

The vapor phase oxidation of 3-picoline on tin and titanium vanadates

The oxidation of 3-picoline with air on fused tin and titanium vanadates gives as the main reaction products nicotinaldehyde and nicotinic acid, the yield of which amounts to 45–50% of theory calculated on the alkylpipidine taken and 75–80% calculated on that which has reacted.Part LXIV of the series Oxidation of organic compounds: for part LXIII, see [1].     

Electrodynamics of solar wind-magnetosphere-ionosphere interactions

The authors present a coherent picture of fundamental physical processes in three basic elements of the SW-I (solar wind-magnetosphere-ionosphere) coupling system: (i) the field-aligned potential structure which leads to the formation of auroral arcs; (ii) the magnetosphere coupling which leads to the onset of magnetospheric substorms; and (iii) the solar wind-magnetosphere dynamo which supplies the power for driving various magnetospheric processes. The field-aligned potential structure on auroral lines is forced into existence by the loss-cone constriction effect when the upward field-aligned current density exceeds the loss-cone thermal flux limit. The substorm onset occurs when the ionosphere responds fully to the enhanced magnetospheric convection driven by the solar wind. The energy is transferred from the solar wind to the magnetosphere by a dynamo process primarily on open field lines