ESTIMATION OF THE OPTICAL PARAMETERS AND LIGHT GRADIENTS IN LEAVES: MULTI-FLUX versus TWO-FLUX TREATMENT

Abstract
Parameters of light propagation in plant leaves-absorption and scattering coefficients, asymmetry of scattering-have been estimated on the basis of measured transmission and remission as well as internal fluxes. This estimation has been carried through by solving the inverse problem of the 4-flux radiative transfer-a theory considering forward and backward diffuse as well as directed components of the overall radiation in a multiply scattering sample. Using the gained parameters, light flux gradients in a two-layered model leaf have been calculated at different wavelengths. Monte Carlo simulation of absorption spectra performed with the parameters obtained with this treatment is in a good agreement with experimental spectra, thus substantiating the theory. Parallel calculations with the two-flux (Kubelka-Munk) theory provide an estimation of the accuracy and applicability of this more simple treatment. Calculations have been performed for two different plants.     

INVOLVEMENT OF NEAR-UV-INDUCED SYNTHESIS OF SEROTONIN IN PHOTOPROTECTION AND IN POTENTIATION OF FAR-UV LETHALITY IN THE YEAST CANDIDA GUILLIERMONDII

Abstract— This paper considers mechanisms of near-UV (334nm) induced photoprotection as well as potentiation of far-UV (254 nm) lethality in Candida guilliermondii. Using exogenous precursors of serotonin, it appears that the above two mechanisms involve photoactivated synthesis of serotonin. It has been postulated that the serotonin effect could take place by binding to DNA.     

Difference singular perturbations—I. A priori estimates

Difference approximations for differential singular perturbations with small parameter ? are considered. We point out ellipticity and coerciveness conditions which are necessary and sufficient for a two-sided a priori estimate to hold for the solutions of difference singular perturbation uniformly with respect to the ratio of both small parameters: the original one ? and the meshsize h.     

Chemoenzymatic synthesis of HIV-1 V3 glycopeptides carrying two N-glycans and effects of glycosylation on the peptide domain

[structure: see text] A highly efficient chemoenzymatic synthesis of HIV-1 V3 domain glycopeptides carrying two N-linked core tri- and pentasaccharides was achieved. The synthesis consisted of two key steps: a solid-phase synthesis of the cyclic, 47-mer V3 domain peptide containing two GlcNAc residues and a novel endoglycosidase-catalyzed transglycosylation that simultaneously added two N-glycan moieties to the peptide precursor from the oligosaccharide oxazoline donor substrates. The availability of the synthetic glycopeptides allowed the probing of the effects of glycosylation on the HIV-1 V3 domain. It was demonstrated that glycosylation influenced the global conformations of the V3 domain and provided protection of the V3 domain against protease digestion.     

Redox processes in highly yttrium-doped barium titanate

The changes of microstructure occurring during oxidation of the reduced form of yttrium-doped barium titanate have been studied. Samples were sintered under reduction conditions at and oxidized by annealing at high temperatures (1150 and 1350 °C) in air. Depending on yttrium concentration, the oxidation of the reduced form of the yttrium-doped BaTiO₃ caused precipitation of the phase Ba₆Ti₁₇O₄₀ or the phases Ba₆Ti₁₇O₄₀ and Y₂Ti₂O₇. The precipitates had well-defined orientational relationships with the perovskite matrix. Oxidation of the reduced form of doped barium titanate results in formation of the phase responsible for increase in the resistance of outer grain layers, which lie between grain boundaries and grain.