Higher Order Variational Integrators: a polynomial approach

We reconsider the variational derivation of symplectic partitioned Runge-Kutta schemes. Such type of variational integrators are of great importance since they integrate mechanical systems with high order accuracy while preserving the structural properties of these systems, like the symplectic form, the evolution of the momentum maps or the energy behaviour. Also they are easily applicable to optimal control problems based on mechanical systems as proposed in Ober-Bl\"obaum et al. [2011]. Following the same approach, we develop a family of variational integrators to which we refer as symplectic Galerkin schemes in contrast to symplectic partitioned Runge-Kutta. These two families of integrators are, in principle and by construction, different one from the other. Furthermore, the symplectic Galerkin family can as easily be applied in optimal control problems, for which Campos et al. [2012b] is a particular case.Comment: 12 pages, 1 table, 23rd Congress on Differential Equations and Applications, CEDYA 201

Evolutionary estimation of a Coupled Markov Chain credit risk model

There exists a range of different models for estimating and simulating credit risk transitions to optimally manage credit risk portfolios and products. In this chapter we present a Coupled Markov Chain approach to model rating transitions and thereby default probabilities of companies. As the likelihood of the model turns out to be a non-convex function of the parameters to be estimated, we apply heuristics to find the ML estimators. To this extent, we outline the model and its likelihood function, and present both a Particle Swarm Optimization algorithm, as well as an Evolutionary Optimization algorithm to maximize the likelihood function. Numerical results are shown which suggest a further application of evolutionary optimization techniques for credit risk management

Flow properties of driven-diffusive lattice gases: theory and computer simulation

We develop n-cluster mean-field theories (0 < n < 5) for calculating the flow properties of the non-equilibrium steady-states of the Katz-Lebowitz-Spohn model of the driven diffusive lattice gas, with attractive and repulsive inter-particle interactions, in both one and two dimensions for arbitrary particle densities, temperature as well as the driving field. We compare our theoretical results with the corresponding numerical data we have obtained from the computer simulations to demonstrate the level of accuracy of our theoretical predictions. We also compare our results with those for some other prototype models, notably particle-hopping models of vehicular traffic, to demonstrate the novel qualitative features we have observed in the Katz-Lebowitz-Spohn model, emphasizing, in particular, the consequences of repulsive inter-particle interactions.Comment: 12 RevTex page

Arrays of Individual DNA Molecules on Nanopatterned Substrates

Arrays of individual molecules can combine the advantages of microarrays and single-molecule studies. They miniaturize assays to reduce sample and reagent consumption and increase throughput, and additionally uncover static and dynamic heterogeneity usually masked in molecular ensembles. However, realizing single-DNA arrays must tackle the challenge of capturing structurally highly dynamic strands onto defined substrate positions. Here, we create single-molecule arrays by electrostatically adhering single-stranded DNA of gene-like length onto positively charged carbon nanoislands. The nanosites are so small that only one molecule can bind per island. Undesired adsorption of DNA to the surrounding non-target areas is prevented via a surface-passivating film. Of further relevance, the DNA arrays are of tunable dimensions, and fabricated on optically transparent substrates that enable singe-molecule detection with fluorescence microscopy. The arrays are hence compatible with a wide range of bioanalytical, biophysical, and cell biological studies where individual DNA strands are either examined in isolation, or interact with other molecules or cells

Neoclassical transport of tungsten ion bundles in total-f neoclassical gyrokinetic simulations of a whole-volume JET-like plasma

Neoclassical gyrokinetic simulations including tungsten impurities are carried out using multiple gyrokinetic bundles to model the many charge states of tungsten ions present in the whole-volume of a model H-mode plasma in JET geometry. A gyrokinetic bundle regroups tungsten ions of similar charge together in order to decrease the computational cost. The initial radial shape of the bundles and their individual charges are deduced from a coronal approximation and from quasi-neutrality of the plasma. Low-Z tungsten ions move radially inward from SOL into the core region, whereas high-Z tungsten ions move radially outwardly from the core and inwardly from the separatrix. These fluxes lead to an accumulation of tungsten in the pedestal top of our test case. This organization of the fluxes cannot be captured by a single tungsten-ion simulation. Large up/down poloidal asymmetries of tungsten form in the pedestal and strongly influence the direction of these neoclassical fluxes. Future implementation of atomic interactions between bundles is discussed.Comment: 11 pages, 11 figure

Docosahexaenoic acid in Arctic charr (Salvelinus alpinus): The importance of dietary supply and physiological response during the entire growth period

The aim of this 14-month feeding study was to investigate the effects of dietary docosahexaenoic acid (DHA) on tissue fatty acid composition, DHA retention and DHA content per biomass accrual in muscle tissues of Arctic charr (Salvelinus alpinus). A control feed, formulated with a relatively high DHA inclusion level (F1), was compared with feeds containing gradually reduced amounts of DHA (Feeds F2, F3, and F4). Arctic charr were randomly distributed among 12 tanks and fed one of the feeds in triplicate. The DHA content within muscle tissues of fish fed diets F1 and F2 was generally higher compared to fish fed diets F3 and F4. However, there was an interaction between dietary DHA treatment and season, which resulted in fish muscle tissues having similar DHA contents irrespective of dietary supply during specific sampling periods. Although diets F3 and F4 contained ~4-fold less DHA compared to diets F1 and F2, retention of DHA in dorsal and ventral muscle tissue was up to 5-fold higher relative to the diet content in fish fed diets F3 and F4. However, the difference among treatments was dependent on the month sampled. In addition, younger fish retained DHA more efficiently compared to older fish. DHA (&micro;g DHA/g/day) accrual in muscle tissue was independent of somatic growth, and there was no difference among treatments. The results suggested that dietary DHA may be essential throughout the lifecycle of Arctic charr and that the DHA content of muscle tissues was influenced by diet and metabolic/physiological factors, such as specific DHA retention during the entire growth cycle . Finally, this long-term feeding study in Arctic charr indicated a non-linear function in DHA retention in dorsal and ventral muscle tissues throughout the lifecycle, which varied in its relationship to dietary DHA

Effect of partial replacement of dietary fish meal and oil by pumpkin kernel cake and rapeseed oil on fatty acid composition and metabolism in Arctic charr (Salvelinus alpinus)

The aim of this 15-month feeding study was to investigate the effects of more sustainable feeds on specific growth rate, fatty acid composition and metabolism of Arctic charr (Salvelinus alpinus). A control feed, formulated with fish meal and fish oil (F1), was compared with feeds where the marine ingredients were increasingly replaced by pumpkin kernel cake and rapeseed oil (Feeds F2, F3, and F4). Arctic charr were randomly distributed into 12 tanks and fed one of the feeds in triplicate. The biomass of fish fed F1 and F2 diets was significantly higher compared to fish fed diet F4 with highest replacement level. However, the dorsal and ventral muscle tissues had very similar total saturated, monounsaturated, and polyunsaturated fatty acid (PUFA) contents, irrespective of dietary supply. Although diets F3 and F4 contained 6-fold less fish oil than diets F1 and F2, fish fed diets F3 and F4 retained only 2-fold less highly desired omega-3 (n-3) long-chain (LC)-PUFA in their dorsal and ventral muscle tissues. Incubating isolated hepatocytes with 14C-labeled -linolenic acid (18:3n-3) provided evidence that Arctic charr can bioconvert this essential dietary PUFA to n-3 LC-PUFA, including docosahexaenoic acid. The results suggested that tissue fatty acid compositions in Arctic charr are dependent, not only on dietary fatty acid supply, but also on their ability for endogenous synthesis of n-3 LC-PUFA. Finally, this long-term feeding study indicated that feeds containing pumpkinseed press cake and rapeseed oil produced fish with largely similar fatty acid composition to fish fed diets containing higher contents of fish meal and fish oil

Internal conversion coefficients for superheavy elements

The internal conversion coefficients (ICC) were calculated for all atomic subshells of the elements with 104<=Z<=126, the E1...E4, M1...M4 multipolarities and the transition energies between 10 and 1000 keV. The atomic screening was treated in the relativistic Hartree-Fock-Slater model. The Tables comprising almost 90000 subshell and total ICC were recently deposited at LANL preprint server.Comment: 6 pages including 3 figures, needs files myown.sty and epsfig.sty (both included