Riesz Bases for p-Subordinate Perturbations of Normal Operators

For p-subordinate perturbations of unbounded normal operators, the change of the spectrum is studied and spectral criteria for the existence of a Riesz basis with parentheses of root vectors are established. A Riesz basis without parentheses is obtained under an additional a priori assumption on the spectrum of the perturbed operator. The results are applied to two classes of block operator matrices.Comment: 30 pages, 4 figures, submitted to J. Funct. Ana

T=0 Neutron-Proton Correlations at High Angular Momenta

The properties of T=0 neutron-proton correlations are discussed within the frame work of different model calculations. Single-j shell calculations reveal that the T=0 correlations remain up to the highest frequencies. They are more complex and cannot be restricted to L=0 pairs only. Whereas it may be difficult to find clear evidence for T=0 pairing at low spins, T=0 correlations are found to induce a new excitation scheme at high angular momenta.Comment: 9 pages, 5 figure

Pesticide and mycotoxin contamination of organic products and strategies for prevention

Consumers generally expect organic food to be produced ecologically and in a way in which they can trust. They further expect it to be healthy, and not or less contaminated with pesticides and/or mycotoxins

Assessing the risk from mycotoxins for the organic food chain: results from Organic HACCP-project and other research

Introduction: Mycotoxins are toxic compounds produced by the secondary metabolism of toxic moulds in the Aspergillus, Penicillium and Fusarium genera occurring in food commodities and foodstuffs. The range and potency of mycotoxins make this group of naturally occurring toxins an ongoing animal health hazard and a constant risk for contamination of the food supply. Mycotoxicoses are diseases caused by exposure to foods or feeds contaminated with mycotoxins. Mycotoxins exhibit a variety of biological effects in animals, such as liver and kidney toxicity, central nervous system effects or estrogenic effects. There are differences between animals with regard to the susceptibility towards different mycotoxins. Poultry secrete mycotoxins relatively fast because of a particular digesting system. Ingredients used for animal feeding should be checked to ensure that adequate quality standards are maintained and that mycotoxins are not present at higher than acceptable levels. Good animal feeding practices also requires that feed is stored in such a way as to avoid contamination. As organically raised livestock are fed greater proportions of hay, grass and silage, there is reduced opportunity for mycotoxin contaminated feed to lead to mycotoxin contaminated milk. Mycotoxins have been reported in organic produce. One theory is that organically-grown products are likely to contain higher concentrations of mycotoxins than conventionally grown products. However, there is little evidence to support this theory (Tamm et al. 2002). Higher or lower mycotoxin contents in feed and food made in different production systems may be caused by i) systematic differences in the production systems during pre-harvest (e.g. use of agrochemicals), ii) differences in post-harvest handling (e.g. storage, transport) and iii) differences during the transformation of raw products into processed foods. Also differences that are in fact due to improper handling procedures during harvest or post-harvest tend to occur systematically if there are systematic differences in the type of equipment used or in the technical qualifications of those who handle the products. Obvious omissions, regarding quality assurance, lead to poor quality but this phenomenon is not linked to organic agriculture in particular (Tamm 2001). Within the 5th EU-framework project “Recommendations for improved procedures for securing consumer oriented food safety and quality of certified organic foods from plough to plate“(QLRT-2002-02245; “Organic HACCP”), a systematic analysis was carried out among selected certified organic food production chains, e.g. milk but also wheat bread. The aim was to investigate current procedures of production management and quality assurance related to the examined chains. For the quality and safety criteria “microbial toxins” (there were six more) the information was analysed to identify Critical Control Points (CCPs) and to suggest ways how the control of quality and safety can be further improved. CCPs were defined as the steps in supply chains where the qualities of the final product can be controlled most efficiently