Graphene ranks highly as a possible material for future high-speed and flexible electronics. Current fabrication routes, which rely on metal substrates, require post synthesis transfer of the graphene onto a Si wafer or in the case of epitaxial growth on SiC, temperatures above 1000 °C are required. Both the handling difficulty and high temperatures are not best suited to present day silicon technology. We report a facile chemical vapor deposition approach in which nano-graphene and few
In the course of our chemical screening of actinomycetes and other bacteria from terrestrial and marine sources, several extracts showed colourless middle polar bands with strong UV absorption at 254 nm and brown to grey colouration with anisaldehyde/sulphuric acid. Working-up of such strains led to the isolation of a number of isoflavonoids. Daidzein (1a) and genistein (1b) are very wide-spread, however, compounds like kakkatin (2b, Streptomyces sp. GW39/1530) were known only from plant sources. Additionally, three new isoflavonoids were obtained, namely 4',7-bis-(β -cymaropyranosyl)-genistein (1e) and 4'-hydroxy-6,7-methoxyisoflavone (2c) from the actinomycete isolate HKI 129-L, and genistein-4'-(6"-methyl)-salicylate (1d) from Streptomyces sp. isolate GW27/2506. 1d is the first natural 4'-ester of an isoflavonoid and an aromatic acid. For the first time, also two flavonoids were isolated from bacteria, apigenin (5a) and luteolin-3'-methyl ether (5b).
The design and performance of a cluster ionizer of the Bayard–Alpert type which is intended to be used in cluster accelerators is described. Positive cluster ions are formed from neutral hydrogen clusters with an efficiency of up to 80%. The mean size of clusters can be reduced by an order of magnitude by multiple ionization followed by splitting into charged fragments due to the repulsion between the individual charges. The fraction of the electrical current carried by cluster ions exceeds 90% of the total ion current. At low particle density two modes of operation are found. The ’’normal’’ mode A with high efficiency is characterized by space charge compensation of the primary electrons. In mode B this compensation is missing and the efficiency drops to less than 20% of that of mode A.
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