Flash photolysis and antioxidant activity

The photo-chemical behaviour of a number of mono- and polyfunctional commercial phenolic antioxidants has been examined using kinetic micro-second flash photolysis. The technique provides useful information on the relationship between antioxidant structure and the efficiency of phenoxy radical production. The kinetics of decay of the phenoxy radicals are also found to be dependent on structure. Mono-functional antioxidants give phenoxy radicals which decay by a second-order process whereas polyfunctional antioxidants give phenoxy radicals that decay by a first-order process. In the former case dimerisation to give bisphenolic coupling products is observed whereas, with the latter, this process is sterically inhibited. The value of flash photolysis as a probe for studying antioxidant activity is discussed.     

Problems and results of diffusion length investigations by energy-dependent EBIC measurements

The fundamentals of the method are described. From applications of this measuring method the following results were obtained: The determination of the diffusion length on glass-plate bevels with evaporated Schottky contacts is frequently quite difficult and sometimes even impossible. Besides a reduction of the diffusion length with increasing microdefect density surprisingly also the opposite behaviour can be found. Comparative PEM and EBIC investigations yield differences between both diffusion lengths (L_EBIC < < L_PEM) depending on the sample pre-history.     

Charge transfer at F<Subscript>16</Subscript>CoPc and CoPc interfaces to Au

We analyze the electronic properties of the interfaces between cobalt phthalocyanine (CoPc), as well as fluorinated cobalt phthalocyanine (F₁₆CoPc), and an Au(100) single-crystal using X-ray photoemission spectroscopy and valence band ultraviolet photoemission spectroscopy. Our data demonstrate that for the monolayers of both materials a charge transfer occurs from the substrate to the center of the organic molecules resulting in a central Co(I) ion. This leads to the conclusion that this effect essentially is fluorination- and ligand-independent.     

Schottky contact barrier height enhancement on p-type silicon by wet chemical etching

A wet chemical etch preceding the usual cleaning process has been found to yield Schottky barriers of high values on p-type silicon. This procedure produces a passivated surface layer which has resulted in Al/0-Si Schottky diodes with barrier height of 0.75 eV and ideality factor of 1.15. Measurements have confirmed the presence of electrically active donor-like states in this surface layer. The origin of the donor states is explained in terms of the deactivation of the boron acceptor by the formation ofH ⁺ B ^– pairs.     

Eine Mn−Re-Phase mit geordneter α-Mn-Struktur (χ-Phase)

Ohne Zusammenfassung     

ERKALE—A flexible program package for X‐ray properties of atoms and molecules

ERKALE is a novel software program for computing X‐ray properties, such as ground‐state electron momentum densities, Compton profiles, and core and valence electron excitation spectra of atoms and molecules. The program operates at Hartree–Fock or density‐functional level of theory and supports Gaussian basis sets of arbitrary angular momentum and a wide variety of exchange‐correlation functionals. ERKALE includes modern convergence accelerators such as Broyden and ADIIS and it is suitable for general use, as calculations with thousands of basis functions can routinely be performed on desktop computers. Furthermore, ERKALE is written in an object oriented manner, making the code easy to understand and to extend to new properties while being ideal also for teaching purposes. © 2012 Wiley Periodicals, Inc.     

Determination of lysinoalanine by high performance liquid chromatography

This work suggests an HPLC method for qualitative and quantitative determination of N^ε(2-amino-2-carboxyethyl)-L -lysine (LAL). LAL was released from total hydrolysates of various proteins of animal origin and derivatized with dansyl chloride. The performance of two different columns, Spherisorb 3S TG and μ-Bondapack C₁₈, was compared; better resolution and quantitative response were obtained with the former. The mobile phase was a mixture of 0.01 M phosphate buffer (pH 7) and acetonitrile. Linear response and quantitative repeatability were tested for both detectors used (UV-Vis set at 254 nm; fluorimetric set at λ_ex(max) = 360 nm and λ_em(max) = 525 nm). For LAL standard the minimum detectable amount was 0.05 ng, whereas for LAL in actual samples the amount was 0.5 ng (40 μg/g of analyzed proteins). Good analytical repeatability was obtained, resulting in CV % of 4.7 and 3.8 for UV and fluorimetric detectors, respectively. LAL recovery was determined using both detectors; the values obtained were 94 % (fluorimetric) and 92 % (UV). Greater noise levels were observed with the fluorimetric detector and its higher sensitivity could not, therefore, be fully utilized. The highest amounts of LAL were found in the casein (2816 μg/g) and cooked albumin (615 μg/g) samples.     

Photo-stabilising action of a p-hydroxybenzoate compound in polyolefins—Part I: Thermal and photo-chemical behaviour in polypropylene film

The photo-stabilising action of a new aliphatic p-hydroxybenzoate light stabiliser, Cyasorb® UV 2908 (American Cyanamid Company), has been examined in polypropylene film, with the aid of a number of related compounds, by both normal and derivative uv absorption, infra-red techniques and hydroperoxide analysis. During processing and oven ageing the stabiliser operates as an effective chain breaking donor, terminating macroalkyl radicals and inhibiting the formation of hydroperoxides. Under both monochromatic (365 nm) and polychromatic (λ′s > 300 nm) irradiation conditions the decomposition of the stabiliser shows a direct dependence on initial hydroperoxide concentration in the film, indicating that it operates as an effective light stable alkoxy and hydroxy radical scavenger. Under ‘direct photolysis’ conditions (254 nm light) the stabiliser does not undergo unfavourable dimerisation reactions like other related p-alkyl substituted phenols. Evidence is also presented to show that the presence of the long aliphatic hydrocarbon chain has a powerful protective effect on the molecule and this is associated with a radical recombination process due to the polymer cage.