A review of the role of DSC analysis in the design of fluorozirconate glasses for fibre optic applications

The relatively poor thermal stability of fluorozirconate glasses is a major factor preventing the realisation of their true potential for fibre optic applications. A range of methods based on both isothermal and non-isothermal DSC techniques, which can be employed to evaluate the thermal stability of fluorozirconate glasses, are described. The relevance of these thermal stability criteria to the design of fluorozirconate compositions capable of yielding high quality optical fibres is discussed.     

An unusual electron-transfer behavior of ferrocene in aqueous microemulsion systems

The electrochemical behavior of ferrocene in an aqueous microemulsion (pentan-1-ol/sodium dodecyl sulfate (SDS)/aq. H₂SO₄) has been studied using an ultramicroelectrode. Contrary to the generally expected reversible peak, the experiments show the presence of a second oxidation peak during the reverse scan at low scan rates where the peak corresponding to ferricinium ion reduction is nearly absent along with the unanticipated appearance of a current dip. These observations are rationalized using a novel type of coupling between heterogeneous (electrochemical) and homogeneous (chemical) electron transfer processes. The composition of the medium, especially the acid concentration, affects the electron transfer of the solubilized probe and there exists a threshold acid concentration for achieving maximum anodic peak current.     

Über triterpene—XXIX : Zur struktur des avenacins

From the roots of oat (Avena sativa) a second antibiotic active glycoside, avenacine B, was isolated in addition to the main glycoside avenacine A. In the aglycone of A the double bond could not be established contrary to the statement in the literature but an aldehyde group in addition to the keto group was identified and therefore the proposed structure has to be revised. In the aglycone of B the —CH₂OH-group of A has been substituted by CH₃. The structures of the sugar chains in both glycosides have been determined, in avenacine A as [β-d-gluco-pyranosyl(1 → 4)-[β-d-glucopyranosyl (1 → 2)]-α-l-arabinosyl (1)- and in B as [β-d-glucopyranosyl (1 → 4)]-β-d-glucopyranosyl (1)-.     

Temperature Dependent Raman Spectroscopic Study of the Fe Doped La0.67Sr0.33MnO3 Prepared Using Ball Milling Method

Physics of the Solid State - Polycrystalline samples of La0.67Sr0.33Mn0.65Fe0.35O3 (LSMFO) were synthesized using the standard ball mill method with different calcination temperatures ranging from...     

Allylic Hydroxylation Through Acid Catalysed Epoxy Ring Opening of Betulinic Acid Derivatives

Acid catalysed epoxy ring opening of several lupane type triterpenoids leads to unusual allylic hydroxylation. The reaction involves the formation of epoxide by m‐chloroperbenzoic acid followed by the treatment of mineral acid. The simple methodology finds utility to introduce a hydroxyl function at the allylic position in these triterpenoids, which is otherwise quite difficult.     

An Efficient Method for Agrobacterium-Mediated Genetic Transformation and Plant Regeneration in Cumin (Cuminum cyminum L.)

Cumin is an annual herbaceous medicinally important plant having diverse applications. An efficient and reproducible method of Agrobacterium-mediated genetic transformation was herein established for the first time. A direct regeneration method without callus induction was optimised using embryos as explant material in Gamborg’s B5 medium supplemented with 0.5-μM 6-benzyladenine and 2.0-μM α-naphthalene acetic acid. About 1,020 embryos (a mean of 255 embryos per batch) were used for the optimisation of transformation conditions. These conditions were an Agrobacterium cell suspension of 0.6 OD₆₀₀, a co-cultivation time of 72 h, 300-μM acetosyringone and wounding of explants using a razor blade. Pre-cultured elongated embryos were treated using optimised conditions. About 720 embryos (a mean of 180 embryos per batch) were used for transformation and 95 % embryos showed transient β-glucuronidase expression after co-cultivation. Putative transformed embryos were cultured on B5 medium for shoot proliferation and 21 regenerated plants were obtained after selection and allowed to root. T₀ plantlets showed β-glucuronidase expression and gene integration was confirmed via PCR amplification of 0.96 and 1.28 kb fragments of the hygromycin-phosphotransferase II and β-glucuronidase genes, respectively. In this study, a transformation efficiency of 1.5 % was demonstrated and a total of 11 transgenic plants were obtained at the hardening stage, however, only four plants acclimatised during hardening. Gene copy number was analysed by Southern blot analysis of hardened plants and single-copy gene integration was observed. This is the first successful attempt of Agrobacterium-mediated genetic transformation of cumin.     

Stereoselective tandem synthesis of oxazolo-fused pyrroloquinolines from o-alkynylaldehydes via Ag(I)-catalyzed regioselective 5-exo-dig ring closure

A tandem approach for the regio- and stereoselective synthesis of oxazolo-fused pyrroloquinolines 3a–l via the reaction of o-alkynylaldehydes 1a–i with chiral amino alcohols 2a–c under mild reaction conditions is described. The possible participation of the pyridine ring in the regioselective formation of 5-exo-dig cyclized products was supported by the controlled experiments. The structures and stereochemistry of the products were confirmed by NOESY and X-ray crystallographic studies.