Development of a quantitative spectrophotometric assay for lectins

A new quantitative spectrophotometric assay for lectins has been developed. It involves mixing a copolymer with a lectin solution and measuring the absorbance change as a function of time as the resulting solution becomes turbid. The slope obtained could be correlated quantitatively with the amount of lectin present. The assay has sensitivity problems at low lectin concentrations and also a reproducibility problem. More study is required in these two areas

Electron dephasing near zero temperature: an experimental review

The behavior of the electron dephasing time near zero temperature, $\tau_\phi^0$, has recently attracted vigorous attention. This renewed interest is primarily concerned with whether $\tau_\phi^0$ should reach a finite or an infinite value as $T \to$ 0. While it is accepted that $\tau_\phi^0$ should diverge if there exists only electron-electron (electron-phonon) scattering, several recent measurements have found that $\tau_\phi^0$ depends only very weakly on temperature, if at all, when $T$ is sufficiently low. This article discusses the current experimental status of "the saturation problem", and concludes that the origin(s) for this widely observed saturation are still unresolved

Oxidative degradation of polyvinyl alcohol by the photochemically enhanced Fenton reaction. Evidence for the formation of super-macromolecules

The reaction mechanism of the oxidative degradation of polyvinyl alcohol (PVA) by the photochemically enhanced Fenton reaction has been studied. Fast and efficient degradation was observed in a batch reactor, using a medium pressure mercury arc in a Pyrex envelope and employing 80\% of the stoichiometric amount of H2O2 required for the total oxidation of PVA and a concentration ratio as low as 1 mole of iron(II) sulfate per 20 moles of PVA sub-units (C2H4O). Model PVA polymers of three different molecular weights (15,000, 49,000 and 100,000 g mol(-1)) were found to follow identical degradation patterns. Strong experimental evidence supports the formation of super-macromolecules (MW: 1-5 X 10(6) g mol(-1)) consisting of oxidized PVA and trapped iron(HI) at an early reaction stage. Low molecular weight intermediates, such as oxalic acid, formic acid or formaldehyde were not found during the PVA degradation, and we may deduce that the manifold of degradation reactions is mainly taking place within the super-macromolecules from which CO2 is directly released

Degradation of Polyvinyl Alcohol (PVA) by Homogeneous and Heterogeneous Photocatalysis Applied to the Photochemically Enhanced Fenton Reaction

The reaction mechanism of the oxidative degradation of polyvinyl alcohol (PVA) by the photochemically enhanced Fenton reaction was studied using a homogeneous (Fe-aq(2+) + H2O2) and a heterogeneous reaction system (iron (III)-exchanged zeolite Y+ H2O2). In the homogeneous Fenton system, efficient degradation was observed in a batch reactor, equipped with a medium pressure mercury arc in a Pyrex envelope and employing 80\% of the stoichiometric amount of H2O2 required for the total oxidation of PVA and a concentration ratio as low as 1 mole of iron(II) sulfate per 20 moles of PVA sub-units (C2H4O). Model PVA polymers of three different molecular weights (15,000, 49,000 and 100,000 g mol(-1)) were found to follow identical degradation patterns. Strong experimental evidence supports the formation of super-macromolecules (MW: 1 - 5 x 10(6) g/mol) consisting of oxidized PVA and trapped iron(III) at an early reaction stage. Low molecular weight intermediates, such as oxalic acid, formic acid or formaldehyde were not found during PVA degradation in the homogeneous Fenton system, and we may deduce that the manifold of degradation reactions is mainly taking place within the super-macromolecules from which CO2 is directly released. However, in the heterogeneous Fenton system, the reaction behavior was found to be distinctly different: a decrease of the molecular weights of all three tested monodisperse PVA samples was observed by the broadening of the GPC-traces during irradiation, and oxalic acid was formed. The results lead to the mechanistic hypothesis that during the heterogeneous Fenton process, the cleavage of the PVA-chains may occur at random positions, the reactive centres being located inside the iron(III)-doped zeolite Y photocatalysts

Extensions and Modifications of the Kohonen-SOM and Applications in Remote Sensing Image Analysis

Utilization of remote sensing multi- and hyperspectral imagery has shown a rapid increase in many areas of economic and scientific significance over the past ten years. Hyperspectral sensors, in particular, are capable of capturing the detailed spectral signatures that uniquely characterize a great number of diverse surface materials. Interpretation of these very high-dimensional signatures, however, has proved an insurmountable challenge for many traditional classi¿cation, clustering and visualization methods. This chapter presents spectral image analyses with Self-Organizing Maps (SOMs). Several recent extensions to the original Kohonen SOM are discussed, emphasizing the necessity of faithful topological mapping for correct interpretation. The effectiveness of the presented approaches is demonstrated through case studies on real-life multi- and hyperspectral images