Summer distribution of marine mammals encountered along transects between South Africa and Antarctica during 2007-2012 in relation to oceanographic features

The at-sea summertime distribution of marine mammals between South Africa and Antarctica was determined along eight transects surveyed between December 2007 and January 2012. During 1930 30-minute transect counts, 1390 marine mammal individuals were attributed to 19 species: eight toothed whales (Odontoceti), six pinnipeds, and five baleen whales (Mysticeti). An additional two toothed-whale species were encountered ‘out of effort’. The four most numerous species accounted for 85% of the total number of individuals encountered: crabeater seal (Lobodon carcinophagus), humpback whale (Megaptera novaeangliae), Antarctic Minke whale (Balaenoptera bonaerensis) and fin whale (B. physalus). The distribution of these species was related to oceanographic features, such as water masses and fronts, pack ice and ice edge: These differences were statistically highly significant. Biodiversity was compared with other polar marine ecosystems

Electromagnetic two-body problem: recurrent dynamics in the presence of state-dependent delay

We study the electromagnetic two-body problem of classical electrodynamics as a prototype dynamical system with state-dependent delays. The equations of motion are analysed with reference to motion along a straight line in the presence of an electrostatic field. We consider the general electromagnetic equations of motion for point charges with advanced and retarded interactions and study two limits, (a) retarded-only interactions (Dirac electrodynamics) and (b) half-retarded plus half-advanced interactions (Wheeler-Feynman electrodynamics). A fixed point is created where the electrostatic field balances the Coulombian attraction, and we use local analysis near this fixed point to derive necessary conditions for a Hopf bifurcation. In case (a), we study a Hopf bifurcation about an unphysical fixed point and find that it is subcritical. In case (b), there is a Hopf bifurcation about a physical fixed point and we study several families of periodic orbits near this point. The bifurcating periodic orbits are illustrated and simulated numerically, by introducing a surrogate dynamical system into the numerical analysis which transforms future data into past data by exploiting the periodicity, thus obtaining systems with only delays

Ethiopian-Netherlands Horticulture Partnership : Mission Report Strategy Development Floriculture Capacity Building October 15 - 21, 2006

The Netherlands’ Government has committed itself to contribute to a balanced growth of the horticulture sector in Ethiopia through a public-private partnership program in line with the WSSD partnership programs in South-east Asia and East-Africa. Jointly with the stakeholders a plan of activities for 2006 for this partnership was formulated. In order to address the topic ‘Capacity building in the floriculture sector in Ethiopia’ a mission was conducted in the period October 16-21, 2006 with the following objectives: • Identify needs and priorities for capacity building in the floriculture sector • Formulate a strategy for capacity building activities in the floriculture sector for the period 2007 - 201

The effects of the nonextensivity on the dimerization process and nematic ordering

The influence of the dimerization process on the nematic ordering is investigated by using a nonextensive thermostatistics, namely Tsallis thermostatistics(TT). A theoretical model taking into account the dimerization influence on the nematic scalar order parameter has been recently presented[1]. Our study considers this model and the theoretical predictions for the nematic order parameter are improved by using TT

A Garside-theoretic approach to the reducibility problem in braid groups

Let $D_n$ denote the $n$-punctured disk in the complex plane, where the punctures are on the real axis. An $n$-braid $\alpha$ is said to be \emph{reducible} if there exists an essential curve system \C in $D_n$, called a \emph{reduction system} of $\alpha$, such that \alpha*\C=\C where \alpha*\C denotes the action of the braid $\alpha$ on the curve system \C. A curve system \C in $D_n$ is said to be \emph{standard} if each of its components is isotopic to a round circle centered at the real axis. In this paper, we study the characteristics of the braids sending a curve system to a standard curve system, and then the characteristics of the conjugacy classes of reducible braids. For an essential curve system \C in $D_n$, we define the \emph{standardizer} of \C as \St(\C)=\{P\in B_n^+:P*\C{is standard}\} and show that \St(\C) is a sublattice of $B_n^+$. In particular, there exists a unique minimal element in \St(\C). Exploiting the minimal elements of standardizers together with canonical reduction systems of reducible braids, we define the outermost component of reducible braids, and then show that, for the reducible braids whose outermost component is simpler than the whole braid (including split braids), each element of its ultra summit set has a standard reduction system. This implies that, for such braids, finding a reduction system is as easy as finding a single element of the ultra summit set.Comment: 38 pages, 18 figures, published versio

The APC network regulates the removal of mutated cells from colonic crypts

Self-renewal is essential for multicellular organisms but carries the risk of somatic mutations that can lead to cancer, which is particularly critical for rapidly renewing tissues in a highly mutagenic environment such as the intestinal epithelium. Using computational modeling and in vivo experimentation, we have analyzed how adenomatous polyposis coli (APC) mutations and β-catenin aberrations affect the maintenance of mutant cells in colonic crypts. The increasing abundance of APC along the crypt axis forms a gradient of cellular adhesion that causes more proliferative cells to accelerate their movement toward the top of the crypt, where they are shed into the lumen. Thus, the normal crypt can efficiently eliminate β-catenin mutant cells, whereas APC mutations favor retention. Together, the molecular design of the APC/β-catenin signaling network integrates cell proliferation and migration dynamics to translate intracellular signal processing and protein gradients along the crypt into intercellular interactions and whole-crypt physiological or pathological behavior

Photon assisted Levy flights of minority carriers in n-InP

We study the photoluminescence spectra of n-doped InP bulk wafers, both in the reflection and the transmission geometries relative to the excitation beam. From the observed spectra we estimate the spatial distribution of minority carriers allowing for the spectral filtering due to re-absorption of luminescence in the wafer. This distribution unambiguously demonstrates a non-exponential drop-off with distance from the excitation region. Such a behavior evidences an anomalous photon-assisted transport of minority carriers enhanced owing to the high quantum efficiency of emission. It is shown that the transport conforms very well to the so-called Levy-flights process corresponding to a peculiar random walk that does not reduce to diffusion. The index gamma of the Levy flights distribution is found to be in the range gamma = 0.64 to 0.79, depending on the doping. Thus, we propose the high-efficiency direct-gap semiconductors as a remarkable laboratory system for studying the anomalous transport.Comment: 12 pages, 9 figure