Trophic flow within the microbial and mesozooplankton foodweb in the North Atlantic: processes indicated by analyses of stable isotopes and biovolume spectra.

The trophic flow from primary producers through the microbial and mesozooplankton food web makes sun energy available in particulate form for higher trophic levels. Pathways through the lower trophic levels are highly variable and determine productivity of the marine pelagic food webs. We analysed spatial variability in food web structure across the North Atlantic by means of stable isotope analyses (SIA) and biovolume spectrum theories (BST). At 7 stations in the Iceland Basin, Reykjanes Ridge, Irminger Basin and Labrador Sea, respectively, chlorophyll a, zooplankton net samples (55 μm and 150 μm) and laser optical plankton counter data were collected in the upper 200 to 500 m during a EURO-BASIN cruise with R/V M.S.Merian in spring (March/April) 2013. Trophic indices were determined by both methods (SIA and BST) for different size groups of the pelagic community. For the smallest fraction, both methods yielded trophic indices around 2 to 3 and agreed reasonable well. Large differences between both methods were observed in the mediumsized fraction, which was dominated by more omnivorous species, with much higher trophic indices estimated by BST. The largest fraction showed slightly higher value by BST, especially in the Labrador Sea. Comparing differences between SIA and BST might allow to trace energy flow through the microbial food web. A conceptual model is developed for the trophic flow through the lower trophic levels and discussed with respect to phytoplankton bloom stage, water mass, and stratification.EUROBASIN (FP7-ENV-2010 Project no. 264933

Nonextensive statistical mechanics applied to protein folding problem: kinetics aspects

A reduced (stereo-chemical) model is employed to study kinetic aspects of globular protein folding process, by Monte Carlo simulation. Nonextensive statistical approach is used: transition probability p i j between configurations i &#8594; j is given by p i j =[1 +(1 - q)&#916;Gi j/kB T ]1/(1-q), where q is the nonextensive (Tsallis) parameter. The system model consists of a chain of 27 beads immerse in its solvent; the beads represent the sequence of amino acids along the chain by means of a 10-letter stereo-chemical alphabet; a syntax (rule) to design the amino acid sequence for any given 3D structure is embedded in the model. The study focuses mainly kinetic aspects of the folding problem related with the protein folding time, represented in this work by the concept of first passage time (FPT). Many distinct proteins, whose native structures are represented here by compact self avoiding (CSA) configurations, were employed in our analysis, although our results are presented exclusively for one representative protein, for which a rich statistics was achieved. Our results reveal that there is a specific combinations of value for the nonextensive parameter q and temperature T, which gives the smallest estimated folding characteristic time (t). Additionally, for q = 1.1, (t) stays almost invariable in the range 0.9 < T < 1.3, slightly oscillating about its average value <img border=0 width=32 height=32 src="../../../../../../../img/revistas/bjp/v39n2a/a16txt01.gif" align=absmiddle > or = 27 ±&#963;, where &#963; = 2 is the standard deviation. This behavior is explained by comparing the distribution of the folding times for the Boltzmann statistics (q &#8594; 1), with respect to the nonextensive statistics for q = 1.1, which shows that the effect of the nonextensive parameter q is to cut off the larger folding times present in the original (q &#8594; 1) distribution. The distribution of natural logarithm of the folding times for Boltzmann statistics is a triple peaked Gaussian, while, for q = 1.1 (Tsallis), it is a double peaked Gaussian, suggesting that a log-normal process with two characteristic times replaced the original process with three characteristic times. Finally we comment on the physical meaning of the present results, as well its significance in the near future works

Simulation of a vibratory system with shape memory alloy under rotating unbalance excitation

This paper presents a numerical simulation of the non-linear dynamic presented by a mechanical vibratory system (MVS) under rotating unbalance and dumped by shape memory alloy (SMA). To do so, a Matlab code was used to solve the respective equations. The results made clear the dissipative capability of this material due its hysteretic behavior.info:eu-repo/semantics/publishedVersio