Cardenolides from Ch' an Su

From the toad venom Ch'an Su digitoxigenin (I), periplogenin (IX), and sarmentogenin (XI) were isolated as well as the two new 14, 15 β-epoxy-cardenolides III and VI which — regarding their steroid nucleus — are corresponding to cinobufotalin and marinobufagin, respectively.     

Simultanbestimmung von Si, Mn, P, Cu, Al, Ni, Cr, Mo, V, Ti, Co und As in St?hlen mit ICP-AES

Summary A universal method for quantitative analysis of twelve elements in low-alloy steels is described. The samples are digested in a mixture of sulfuric-/nitric acid/ammonium peroxodisulfate. Si, Mn, P, Cu, Al, Ni, Cr, Mo, V, Ti, Co, As are determined in solution by ICP-AES. The procedure was tested with NBS and BCS reference samples. The analytical results are in good agreement with the certified values. With slight modifications, the method is applicable to the analysis of high-alloy steel samples.     

Power scaling of a side-pumped Nd:YLF laser based on DBMC technology

This work demonstrates the power scalability of double-beam-mode controlling, a technique that has generated the highest optical efficiency reported so far for Nd:YLF lasers. We analyze two types of power scaling possibilities by numerical simulations: multiplication of intracavity pump modules and MOPA configuration. About 44 W of TEM₀₀ output power at 1053 nm was experimentally demonstrated with a beam-parameter product of 1.07 × 1.15. The results show great ease of power scaling without sacrificing beam quality.     

Anatase–silica composite aerogels: a nanoparticle-based approach

Herein we present the synthesis of anatase–silica aerogels based on the controlled gelation of preformed nanoparticle mixtures. The monolithic aerogels with macroscopic dimensions show large specific surface areas, and high and uniform porosities. The major advantage of such a particle-based approach is the great flexibility in pre-defining the compositional and structural features of the final aerogels before the gelation process by fine-tuning the properties of the titania and silica building blocks (e.g., size, composition and crystallinity) and their relative ratio in the dispersion. Specific surface functionalization enables control over the interaction between the nanoparticles and thus over their distribution in the aerogel. Positively charged titania nanoparticles are co-assembled with negatively charged Stoeber particles, resulting in a binary aerogel with a crystalline anatase and amorphous silica framework directly after supercritical drying without any calcination step. Titania–silica aerogels combine the photocatalytic activity of the anatase nanoparticles with the extensive silica chemistry available for silica surface functionalization.     

Water-exchange study revealed unexpected substitution behavior of [(CO)2(NO)Re(H2O)3]2+ in aqueous media

The pH-dependent water-exchange rates of [(CO)2(NO)Re(H2O(cis))2(H2O(trans))]2+ (1) in aqueous media were investigated by means of 17O NMR spectroscopy at 298 K. Because of the low pK(a) value found for 1 (pK(a) = 1.4 +/- 0.3), the water-exchange rate constant k(obs)(H2O(trans/cis)) was analyzed with a two-pathway model in which k(Re)(H2O(trans/cis)) and k(ReOH)(H2O)(trans/cis)) denote the water-exchange rate constants in trans or cis position to the nitrosyl ligand on 1 and on the monohydroxo species [(CO)2(NO)Re(H2O)2(OH)]+ (2), respectively. Whereas the rate constants k(ReOH)(H2O)(trans)) and k(ReOH)(H2O)(cis)) were determined as (4.2 +/- 2) x 10(-3) s(-1) and (5.8 +/- 2) x 10(-4) s(-1), respectively, k(Re)(H2O)(trans)) and k(Re)(H2O)(cis)) were too small to be determined in the presence of the much more reactive species 2. Apart from the water exchange, an unexpectedly fast C identical with 16O --> C identical withO exchange was also observed via NMR and IR spectroscopy. It was found to proceed through 1 and 2, with rate constants k(Re)(CO) and k(ReOH)(CO) of (19 +/- 4) x 10(-3) s(-1) and (4 +/- 3) x 10(-3) s(-1), respectively. On the other hand, N identical with 16O --> N identical with *O exchange was not observed.