489,790 research outputs found
The pan-European mobile radio system: Part I
No full textFollowing the launch of the Pan-European digital mobile radio (GSM) system its salient features are summarised in this tutorial review [I, 8]. Time Division Multiple Access (TDMA) with eight users per carrier is used at a multi-user rate of 27.1 kbit/s, demanding a channel equaliser to combat dispersion. The error protected chip-rate of the full-rate traffic channels is 22.8 kbit/s, while in half-rate channels is 11.4 kbit/s. There are two speech traffic channels, five different-rate data traffic channels and 14 various control and signalling channels to support the system's operation. A moderately complex, 13 kbit/s Regular Pulse Excited speech codec with long term predictor (LTP) is used, combined with an embedded three-class error correction codec and multi-layer interleaving to provide sensitivity-matched unequal error protection for the speech bits. An overall speech delay of 57.5 ms is maintained. Slow frequency hopping at 217 hops/s yields substantial performance gains for slowly moving pedestrians
Letter from Carl Hayden to L. S. Williams
No full textLetter from Carl Hayden to L. S. Williams about the potential to expand the park boundaries
Mystery Author Stan Jones and Sepculative Fiction Authors Sterling Emmal and L. S. Goulet
No full textSterling Emmal is author of the sci-fi fantasy The Executioner of Rawule and L. S. Goulet is author of the fantasy book Sword of Dragonblood. Tundra Kill is Stan Jones' latest Nathan Active mystery. His other books include White Sky, Black Ice; Shaman Pass, Frozen Sun; Village of the Ghost Bears, and the nonfiction classic, The Spill: Personal Stories from the Exxon Valdez Disaster, coauthored with Sharon Bushell
Clerocidin selectively modifies the gyrase-DNA gate to induce irreversible and reversible DNA damage
No full textClerocidin (CL), a microbial diterpenoid, reacts with DNA via its epoxide group and stimulates DNA cleavage by type II DNA topoisomerases. The molecular basis of CL action is poorly understood. We establish by genetic means that CL targets DNA gyrase in the gram-positive bacterium Streptococcus pneumoniae, and promotes gyrase-dependent single- and double-stranded DNA cleavage in vitro. CL-stimulated DNA breakage exhibited a strong preference for guanine preceding the scission site (-1 position). Mutagenesis of -1 guanines to A, C or T abrogated CL cleavage at a strong pBR322 site. Surprisingly, for double-strand breaks, scission on one strand consistently involved a modified (piperidine-labile) guanine and was not reversed by heat, salt or EDTA, whereas complementary strand scission occurred at a piperidine-stable -1 nt and was reversed by EDTA. CL did not induce cleavage by a mutant gyrase (GyrA G79A) identified here in CL-resistant pneumococci. Indeed, mutations at G79 and at the neighbouring S81 residue in the GyrA breakage-reunion domain discriminated poisoning by CL from that of antibacterial quinolones. The results suggest a novel mechanism of enzyme inhibition in which the -1 nt at the gyrase-DNA gate exhibit different CL reactivities to produce both irreversible and reversible DNA damage
Letter from L. S. Williams to Carl Hayden
No full textLetter from L. S. Williams to Carl Hayden suggesting a boundary amendment to the national park bill
Letter from L. S. Williams to Carl Hayden
No full textLetter from L. S. Williams to Carl Hayden about visiting Mr. Buggeln to discuss proposed park boundary changes
Letter from Carl Hayden to L. S. Williams
No full textLetter from Carl Hayden to L. S. Williams informing the Saginaw and Manistee Lumber Company that a bill extending the timber cutting rights in the Canyon did not pass in Congress
Telegram from L. S. Williams to Carl Hayden
No full textLetter from L. S. Williams to Carl Hayden stating there should be no objection to Saginaw and Manistee Lumber Company having their timber contract extended as it is greatly favored
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