Design Criteria for Non-Orthogonal Space–Time Block Codes in Multipath Channels

We consider the problem of designing high rate space–time block codes in multipath fading channels. For this, both minimizing the effect of the self-interference induced by the code itself, and mitigating the inter-symbol-interference induced by the channel have to be addressed. We translate the problem into an equivalent problem of designing a constrained code in a single-path channel with more antennas, and argue that design criteria derived in single-path apply when optimizing this constrained code. Here we concentrate on an analytic measure pertinent to mutual information maximization and BER-performance optimization. The design program is successfully applied to rate one linear space–time transmissions from four transmit antennas. A family of discrete permutations of the transmitted sequences are considered. Performance is optimized within this family, and the results are seen to effect directly both mutual information and error performance.     

Unaltered agonist potency upon inducible 5-HT7(a) but not 5-HT4(b) receptor expression indicates agonist-independent association of 5-HT7(a) receptor and Gs

We compared adenylyl cyclase (AC) activation by the G protein-coupled human serotonin (5-HT) receptors 5-HT4(b) and 5-HT7(a) using an ecdysone-inducible expression system, which allowed for reproducible expression of increasing receptor densities in clonal HEK293 (EcR293) cell lines. Low constitutive expression of receptors (2-70 fmol/mg protein) was observed and could be titrated up to 50-200-fold (approximately 400-7000 fmol/mg protein) by the ecdysone analogue ponasterone A. Although 5-HT-stimulated AC activity increased with receptor density, interclonal variation precluded comparisons of coupling efficiency. Interestingly, the potency of 5-HT to stimulate AC increased with increasing receptor density only in clones expressing 5-HT4(b) receptors. The potency for 5-HT did not change in clones expressing 5-HT7(a) receptors, even though 5-HT-stimulated AC activity approached asymptotic levels. This indicates that potency of 5-HT for stimulation of AC through the 5-HT7(a) receptor is independent of receptor-Gs stoichiometry and is consistent with a model where the 5-HT7(a) receptors are tightly associated with G protein, independent of agonist binding. This supports the existence of a complex between inactive receptor and G protein, as predicted by the cubic ternary complex model. In such a system, spare receptors do not lead to increased potency of an agonist with increased receptor density.     

Ein Übergang aus der Strychnin- in die Heteroyohimban-Reihe der Indolalkaloide durch oxidative Umlagerung von Isostrychninsäure

A Transformation from the strychnine into the Heteroyohimbane Series of the Indole Alkaloids by Oxidative Rearrangement of Isostrychnic Acid By peroxyacid oxidation of isostrychnic acid there are formed, together with the amine oxide of base 2 , three isomeric lactone bases, C₂₁H₂₀N₂O₄, which are formulated as 3–5. Reduction of the isatogen 5 leads to ring opening on both sides of the indole nitrogen ( 6, 7 ), and hydrochloric acid introduces a chloro atom in p-position to the nitrogen ( 9 ). – Both tautomeric forms of 2 can be fixed by reduction to 8 and 10 , respectively. – The lactone ring of 2 is hydrolyzed by hot dilute hydrochloric acid, followed by rearrangement to the heteroyohimbane type indoloquinolizidine 12 . Compound 12 , featuring as keto-enol and amino acid, can be reduced and cyclised with mineral acid to the lactone 14 (two diasteroisomers) serving for X-ray structural analysis. Treatment of 12 with acetic anhydride afforded the lactone 20 by rearrangement of the double bonds. Further hydrogenation products of 12 are described ( 15 , 16 , 18 ) and their spectra, including mass and CD spectra, are discussed. Biochemical implications are referred, too.