Gökhan, Nesrin | Köksal, Meriç | Küpeli, Esra | Yeşilada, Erdem | Erdoğan, Hakkı

Article | 2005 | Turkish Journal of Chemistry29 ( 4 ) , pp.445 - 454

The synthesis of a novel series of Mannich bases of 5-methyl-3-substituted piperazinomethyl-2-benzoxazolinones is described. The structures attributed to compounds 3c, 3d and 3f-3n were elucidated using IR and 1H NMR spectroscopic techniques as well as elemental analysis. The compounds were examined for their in vivo anti-inflammatory and analgesic activities in 2 different bioassays, namely, carrageenan-induced hind paw edema and p-benzoquinone-induced abdominal constriction tests in mice, respectively. In addition, the ulcerogenic effects of the compounds were determined. Among the derivatives tested the most promising results wer . . .e obtained for the compounds bearing electron-withdrawing substituents (F, Cl, COCH_3) in the para position of the phenyl nucleus on the piperazine ring at the 3 position of benzoxazolinone moiety (3a, 3c, 3i). The analgesic activities of all compounds are higher than their anti-inflammatory activities and therefore these high analgesic activities indicated that the compounds could a show central effect Daha fazlası Daha az

Çekiç, Yalçın | Şenay, Seda | Akan, Aydın | Chaparro, Luis F.

Article | 2005 | Istanbul University Journal of Electrical and Electronics Engineering5 ( 2 ) , pp.1411 - 1417

Multi-carrier spread spectrum (MCSS) communication systems are able to mitigate the effects of fading, interferences and Doppler frequency shifts as well as to support multiple access schemes. It is possible to get optimum performance from MCSS systems by carefully choosing the spreading sequences. However, due to inter-user interferences, performance degrades as the number of users increases unless the transmission channels are modeled and estimated. In this paper, we present a new spreading sequence obtained from a complex quadratic sequence multiplied by a pseudo random noise sequence, thus exploiting the properties of constant e . . .nvelope and statistical independence. Our approach is based on the time-frequency characterization of the wireless communication channel by means of discrete evolutionary transform. The properties of the new spreading sequence enables us to estimate the parameters of multi-user channels, both for uplink and downlink transmission cases, and design a receiver that is robust to channel noise, inter-user interference and intentional jammers. The performance of the proposed system is illustrated by simulations Daha fazlası Daha az