Quality of potential harmonics expansion method for dilute Bose-Einstein condensate

We present and examine an approximate but ab initio many-body approach, viz., potential harmonics expansion method (PHEM), which includes two-body correlations for dilute Bose-Einstein condensates. Comparing the total ground state energy for three trapped interacting bosons calculated in PHEM with the exact energy, the new method is shown to be very good in the low density limit which is necessary for achieving Bose-Einstein condensation experimentally.      

Dielectric spectroscopy of an antiferroelectric liquid crystal showing an antiferroelectric-ferrielectric transition

We report the dielectric relaxation behaviour in the antiferroelectric SmC_A* and ferrielectric SmC_γ* phases of the antiferroelectric liquid crystal 4-[5-(4-octloxyphenyl)-2-pyrimidinyl]phenyl 4,4,4-trifluoro-3-(methoxyphenyl)butanoate which shows an antiferroelectric transition at around 88±0.1°C. In the SmC_A* phase, two dielectric relaxation modes have been found, namely the usual antiferroelectric Goldstone mode and another arising from molecular rotation around its short axis. In the SmC_γ* phase, one dielectric relaxation mode has been observed due to the ferrielectric Goldstone mode. Dielectric increments and relaxation frequencies of the antiferroelectric and ferrielectric phases are estimated from the fits of the Cole-Cole function of the dielectric spectrum. The dependence of the bias field in the ferrielectric phase is also discussed.     

Synthesis of combinatorial libraries based on terpenoid scaffolds

Triterpenoid-based scaffolds betulinic acid (1a) and ursolic acid (1b), have been used for the generation of combinatorial libraries in parallel format using solid phase organic synthesis method. These templates have the potential for the synthesis and amplification of triterpenoid-based compounds with one and two-point diversity. This has been demonstrated by the synthesis of two small libraries comprising 18 derivatives each of betulinic acid and ursolic acid with structural diversity at C-3 and C-28 positions. The primary screening of antimalarial activity of these libraries against P. falciparum in vitro led to the identification of four compounds with 5 fold increase in the activity compared to betulinic and ursolic acids.     

Studies in some new initiator systems for vinyl polymerization. II. Ammonia–halogen system as the redox initiator

The ammonia–halogen redox system has proved a promising initiator for polymerizing a number of vinyl monomers in aqueous media. Chlorine and bromine are most efficient, whereas iodine fails to initiate polymerization, probably due to its inhibitive tendency. Endgroups are halogen and amine and total about 0.5 per chain. On the basis of results of endgroup analysis, a mechanism of initiation through halogen and amine radicals, mainly through hydrogen atoms, is suggested. Consistent with the proposed mechanism the endgroup profile changes significantly with changes in pH.     

Studies on triacetic acid lactone-annulated heterocycles: synthesis of 3-aryloxyacetyl-6-methyl-2,3-dihydrothieno[3,2-c]pyran-4-ones by tandem cyclization

The hitherto unreported 3-aryloxyacetyl-6-methyl-2,3-dihydrothieno[3,2-c]pyran-4-ones were synthesized in 62–71% yield by the sulfoxide rearrangement of 4-(4′-aryloxybut-2′-ynylthio)-6-methyl-2-pyrone. The substrates were synthesized by phase-transfer-catalysed alkylation of the hitherto unreported 4-mercapto-6-methylpyran-2-one.