Hydro­gen bonding in two tetracyclic indole alkaloids

3-Acetyl-1,6,7,12b-tetra­hydro­indolo­[2,3-a]­quinolizin-2(12H)-one, C₁₇H₁₆N₂O₂, consists of two symmetry-independent mol­ecules and each forms a layered structure stabilized by N—H⃛O and C—H⃛O hydrogen bonds. In 3-acetyl-6,7-di­hydro­indolo­[2,3-a]­quinolizin-4(12H)-one monohydrate, C₁₇H₁₄N₂O₂·H₂O, the structure is stabilized by O—H⃛O, N—H⃛O and C—H⃛O hydrogen bonds, with the ordered water mol­ecule playing a crucial role in the self-assembly. Contribution from the weak interactions to the strong hydrogen-bonded network is a common feature in both structures.     

An Improved Process for the Enantioselective Synthesis of HCV NS5A Inhibitor Elbasvir (MK-8742) Chiral Amine Intermediate

Russian Journal of General Chemistry - Large-scale enantioselective synthesis of the chiral amine unit of HCV NS5A inhibitor Elbasvir has been accomplished in six steps, with 55% overall yield. The...     

Locally minimax tests in symmetrical distributions

In this paper we give an extension of the theory of local minimax property of Giri and Kiefer (1964, Ann. Math. Statist., 35, 21–35) to the family of elliptically symmetric distributions which contains the multivariate normal distribution as a member.This work was partially supported by the Canadian N.S.E.R.C. grant     

Study of FCNC mediated Z boson effectin the semileptonic rare baryonic decays Λ b → Λl + l -

We study the effect of the FCNC mediated Z boson in the rare semileptonic baryonic decays Λ_b → Λl⁺l^-. We consider the model where the standard model fermion sector is extended by an extra vector-like down quark, as a consequence of which it allows for CP-violating Z mediated flavor changing neutral current at the tree level. We find that due to this non-universal Zbs coupling, the branching ratios of the rare semileptonic Λ_b decays are enhanced reasonably from their corresponding standard model values and the zero point of the forward-backward asymmetry for Λ_b → Λ_μ⁺_μ^- is shifted to the left. Received: 2 June 2005, Published online: 26 October 2005 PACS: 13.30.Ce, 12.60.-i, 11.30.Hv     

Some two body non-leptonicB decays and estimation off D in the heavy quark effective theory

We have studied some of the two body nonleptonic decays ofB meson in the context of heavy quark effective theory using factorization hypothesis. Treatinga ₁ as a free parameter, we have obtained its value asa ₁=0.822±0.045, by correlating the experimental and predicted branching ratio for process. With this value ofa ₁ the branching ratios obtained for other decay channels are in good agreement with the experiment. The decay constant ofD meson is extracted to be 280.82 MeV. Heavy quark spin symmetry has also been tested.     

Investigation of graphite-probe atomisation for carbon-furnace atomic emission spectrometry

A new method of sample introduction for carbon furnace atomic emission spectrometry is described. The sample is deposited on a graphite probe which is inserted into the furnace along its length, after the tube has attained its maximum temperature. The heating rate experienced by the sample in an HGA-72 furnace is considerably increased by use of probe atomisation. Improved detection limits for a number of elements are reported, and the interference of magnesium chloride on the emission signals for lead and cadmium is substantially reduced.     

Shock wave study on the thermal unimolecular decomposition of allyl radicals

We present the first direct study on the thermal unimolecular decomposition of allyl radicals. Experiments have been performed behind shock waves, and the experimental conditions covered temperatures ranging from 1125 K up to 1570 K and pressures between 0.25 and 4.5 bar. Allyl radicals have been generated by thermal decomposition of allyl iodide, and H-atom resonance absorption spectroscopy has been used to monitor the reaction progress. A marked pressure dependence of the rate constant has been observed which is in agreement with the results from a master equation analysis. However, our experimental results as well as our Rice-Ramsperger-Kassel-Marcus calculations seem to contradict the results of Deyerl et al. (J. Chem. Phys. 1999, 110, 1450) who investigated the unimolecular decomposition of allyl radicals upon photoexcitation and tried to deduce specific rate constants for the unimolecular dissociation in the electronic ground state. At pressures around 1 bar we extracted the following rate equation: k(T) = 5.3 x 10(79)(T/K)(-19.29) exp[(-398.9 kJ/mol)/RT] s(-1). The uncertainty of the rate constant calculated from this equation is estimated to be 30%.