Monitoring the production yields of vincristine and vinblastine in Catharanthus roseus from somatic embryogenesis. Semiquantitative determination by flow-injection electrospray ionization mass spectrometry

A semiquantitative determination of two bis-indole antitumor alkaloids, vincristine and vinblastine, has been performed by flow-injection electrospray ionization mass spectrometric analysis of the extracts of Catharanthus roseus. Leaves and flowers of two different phenotypes (pink flower and white flower) obtained from somatic embryogenesis were thus examined and compared with the field-grown mother plant. Different amounts of vincristine and vinblastine were detected depending on the examined samples.     

Lattice-dynamical calculations for tetracene and pentacene

Lattice-dynamical, calculations for evidently non-rigid molecules of aromatic hydrocarbons have been carried out on tetracene and pentacene. In these substances, “out-of plane” vibrations mix extensively with lattice vibrations, and significant differences can be noted between results from a “rigid-body” and a “non-rigid” treatment. For tetracene crystals, whose Raman spectral data are given in the literature, the agreement with experiment is satisfactory. This confirms the validity of such procedures for interpreting and/or predicting spectroscopic behaviour, starting from empirical atom—atom potentials and valence force fields.     

Temperature dependence of the Kerr effect response time of nematogenic liquids

The temperature dependence on the rise time of the Kerr effect is measured in a range of 10°C above T_c for 5CB, 7CB and CPHB. The part played in the response time by the dipole moment is examined.     

Photon channelling in foams

Experiments by Gittings, Bandyopadhyay and Durian (Europhys. Lett. 65, 414 (2004)) demonstrate that light possesses a higher probability to propagate in the liquid phase of a foam due to total reflection. The authors term this observation photon channelling which we investigate in this article theoretically. We first derive a central relation in the work of Gitting et al. without any free parameters. It links the photon's path-length fraction f in the liquid phase to the liquid fraction ɛ. We then construct two-dimensional Voronoi foams, replace the cell edges by channels to represent the liquid films and simulate photon paths according to the laws of ray optics using transmission and reflection coefficients from Fresnel's formulas. In an exact honeycomb foam, the photons show superdiffusive behavior. It becomes diffusive as soon as disorder is introduced into the foams. The dependence of the diffusion constant on channel width and refractive index is explained by a one-dimensional random-walk model. It contains a photon channelling state that is crucial for the understanding of the numerical results. At the end, we shortly comment on the observation that photon channelling only occurs in a finite range of ɛ.     

Evidence for a kaon-bound state K(-)pp produced in K(-) absorption reactions at rest

We have searched for a deeply bound kaonic state by using the FINUDA spectrometer installed at the e(+)e(-) collider DAPhiNE. Almost monochromatic K(-)'s produced through the decay of phi(1020) mesons are used to observe K(-) absorption reactions stopped on very thin nuclear targets. Taking this unique advantage, we have succeeded to detect a kaon-bound state K(-)pp through its two-body decay into a Lambda hyperon and a proton. The binding energy and the decay width are determined from the invariant-mass distribution as 115(+6)(-5)(stat)(+3)(-4)(syst) MeV and 67(+14)(-11)(stat)(+2)(-3)(syst) MeV, respectively.     

Determination of inorganic selenium species in water and garlic samples with on-line ionic liquid dispersive microextraction and electrothermal atomic absorption spectrometry

A non-chromatographic separation and preconcentration method for Se species determination based on the use of an on-line ionic liquid (IL) dispersive microextraction system coupled to electrothermal atomic absorption spectrometry (ETAAS) is proposed. Retention and separation of the IL phase was achieved with a Florisil^®-packed microcolumn after dispersive liquid-liquid microextraction (DLLME) with tetradecyl(trihexyl)phosphonium chloride IL (CYPHOS^® IL 101). Selenite [Se(IV)] species was selectively separated by forming Se-ammonium pyrrolidine dithiocarbamate (Se-APDC) complex followed by extraction with CYPHOS^® IL 101. The methodology was highly selective towards Se(IV), while selenate [Se(VI)] was reduced and then indirectly determined. Several factors influencing the efficiency of the preconcentration technique, such as APDC concentration, sample volume, extractant phase volume, type of eluent, elution flow rate, etc., have been investigated in detail. The limit of detection (LOD) was 15 ng L⁻¹ and the relative standard deviation (RSD) for 10 replicates at 0.5 μg L⁻¹ Se concentration was 5.1%, calculated with peak heights. The calibration graph was linear and a correlation coefficient of 0.9993 was achieved. The method was successfully employed for Se speciation studies in garlic extracts and water samples.     

Lattice-dynamical calculations for fluorene,carbazole, dibenzofuran and dibenzothiophen

For crystalline fluorene, carbazole, dibenzofuran and dibenzothiophen several properties have been calculated using semi-empirical atom-atom potentials Calculated geometrical parameters, Raman-active lattice frequencies, enthalpies of sublimation and crystallographic temperature factors agree with observed values. However, except for dibenzothiophen, infrared-active lattice frequencies are not consistent with any potential so far tried