Waveguide characterization of chiral material: theory

A new procedure to extract all three constitutive parameters of chiral material from waveguide measurements is presented. Two chiral slabs of different length must be measured. Their scattering parameters are inverted in a largely analytical way, complemented by a simple and fast convergent numerical algorithm. Tests with synthetic scattering data show the method to be very accurate and stable     

Simulation of 125I induced DNA strand breaks in a CAP-DNA complex

The E. coli catabolite gene activator protein (CAP)-DNA complex with 125I located at the position of the H5 atom of the cytosine near the centre was incorporated into the PARTRAC track structure code. DNA strand breaks due to irradiation were calculated by track structure and radical attack simulations; strand breaks due to neutralisation of the highly charged 125Te ion were derived from a semi-empirical distribution. According to the calculations, the neutralisation effect dominates the strand breakage frequency at 2 bases away from the 125I decay site on both strands. The first breakage distribution counted from a 32P labelled end on the strand with 125I agreed well with experimental data, but on the opposite strand, the calculated distribution is more concentrated around the decay site and its yield is about 20% larger than the measured data.     

Suppression of nicotine intake during ad libitum cigarette smoking by high-dose transdermal nicotine

Pulmonary hypertension in response to chronic hypoxia is invariably accompanied by remodeling of the pulmonary vessels but the mechanism by which hypoxia increases the replication of vascular cells is unknown. To investigate the hypothesis that hypoxia stimulates intracellular kinase cascades we measured the activity of "classic" mitogen-activated protein (MAP) kinase pathways and "stress- activated" MAP kinase pathways in bovine pulmonary artery fibroblasts subjected to hypoxia for up to 30 h. Hypoxia (1% O2) stimulated strongly the stress-activated protein kinases, c-Jun NH2-terminal kinase (JNK) and p38 MAP kinase. Two peaks of p38 MAP kinase activity at 6 and 24 h were associated with an increase in the activity of mitogen-activated protein kinase-activated protein (MAPKAP) kinase-2, the immediate downstream target of p38 MAP kinase. Furthermore, the second phase of p38 MAP kinase activity could be reversed if cells were reoxygenated after 12 h. These data suggest that hypoxic stimulation of pulmonary artery cells is mediated by activation of the stress-activated protein kinases.     

Prevention of hyperthermia with silk of the oriental hornet, Vespa orientalis: a hypothesis

Wasps apparently develop normally even under extreme thermal conditions, including deserts. We deemed it worthwhile to set up an experiment wherein wasp brood combs containing a full gamut of brood ranging from eggs up to pupae and a few adults were kept in an incubator whose temperature was gradually raised to 45 degrees C, and the response of the disparate brood to such warming was photographed via Infra Red camera. The finding of this experiment showed that for open brood (i.e., eggs, larvae at various instars, and empty cells) the temperature was close to the ambient temperature, but in the silk coated pupae, the temperature was lower than the ambient by up to 4 degrees C. This lower temperature was retained for at least 90 min of incubation. For comparison we evaluated the relative contribution of the pupae to the phenomenon, by warming also a vacant, (i.e., a broodless and silkless comb) in parallel to a comb from which the pupae had been extricated but the silk weave retained and left behind. We found that the totally empty comb heated up under these conditions to nearly 110 degrees C, whereas the silk-containing vacant cells only heated up to about 40 degrees C. These finding are discussed from two aspects, namely the importance for wasps to maintain a constant temperature throughout the pupating process, and the manner in which the silk weave contributes to such a goal.     

The design of S-boxes by simulated annealing

Substitution boxes (S-boxes) are important components in many modern-day symmetric key ciphers. Their study has attracted a great deal of attention over many years. The emergence of a variety of cryptosystem attacks has shown that substitutions must be designed with great care. Some general criteria such as high non-linearity and low autocorrelation have been proposed (providing some protection against attacks such as linear cryptanalysis and differential cryptanalysis). The design of appropriate S-boxes is a difficult task; several criteria must be traded off and the design space is huge. There has been little application of evolutionary search to the development of S-boxes. In this paper we show how a cost function that has found excellent single-out put Boolean functions can be generalised to provide improved results for small S-boxes. John A. Clark: He is Professor of Critical Systems at the University of York, where he leads the software testing, security and cryptography work. Much of this has been concerned with the application of meta-heuristic search. Jeremy L. Jacob: He has a BSc. in Mathematics from the University of Hull, England, M.Sc. and D. Phil. in Computation from the University of Oxford, England and now works for the Univerity of York. His research interests include modelling secure systems and software engineering practices for secure systems. Susan Stepney: She is Professor of computer Science at the University of York, and leads the Non-Standard Computation research group there. She is a member of the ACM, Fellow of the British Computer Society, and moderator of the UKCRC Grand Challenge in Non-Classical Computation. Her main research interests include novel applications of nature-inspired computation, modelling self-organising complex systems and designing and reasoning about emergent properties.