Impact and extinction signatures in complete Cretaceous-Tertiary (K-T) boundary sections

The Zumaya, Caravaca and Agost sections in Spain, the El Kef section in Tunisia and the Negev (Nahal Avdat) sections in Israel are among the most continuous, expanded and complete K-T boundary sections. The distribution patterns of the planktic faunas were quantitatively analyzed in closely spaced samples across the K-T boundary in these sections, in conjuction with the geochemistry, stable isotopes, mineralogy and magnetostratigraphy. Three hundred foraminiferal specimens were randomly selected and determined. Reliable estimates for the foraminiferal productivity changes across the K-T boundary and for the 1 to 2 Ma interval preceding the K-T boundary were made from the numbers of individuals/gram of sediment corrected for the sedimentation rates (calculated from magnetic reversals and lithology). No gradual or stepwise extinction is seen below the K-T boundary nor any productivity decrease. Stable isotope analyses show a warming just after deposition of the ejecta layer, not cooling as predicted by nuclear winter scenarios, although the duration of such cooling may be too short to be observed even in these complete sections. Low REE values and cpx spherules with quench textures idential to quench-textures in diagenetically altered spherules, strongly indicate an oceanic site of (one of) the impactor(s)

The Quasi-Verbal Dispute Between Kripke and 'Frege-Russell'

Traditional descriptivism and Kripkean causalism are standardly interpreted as rival theories on a single topic. I argue that there is no such shared topic, i.e. that there is no question that they can be interpreted as giving rival answers to. The only way to make sense of the commitment to epistemic transparency that characterizes traditional descriptivism is to interpret Russell and Frege as proposing rival accounts of how to characterize a subject’s beliefs about what names refer to. My argument relies on a development of the distinction between speaker’s reference and semantic reference

Anomalous Hall Effect due to the spin chirality in the Kagom\'{e} lattice

We consider a model for a two dimensional electron gas moving on a kagom\'{e} lattice and locally coupled to a chiral magnetic texture. We show that the transverse conductivity $\sigma\_{xy}$ does not vanish even if spin-orbit coupling is not present and it may exhibit unusual behavior. Model parameters are the chirality, the number of conduction electrons and the amplitude of the local coupling. Upon varying these parameters, a topological transition characterized by change of the band Chern numbers occur. As a consequence, $\sigma\_{xy}$ can be quantized, proportional to the chirality or have a non monotonic behavior upon varying these parameters.Comment: 8 pages, 7 figure

Anomalous Hall effect and weak localization corrections in a ferromagnet

In this paper, we report results on the anomalous Hall effect. First, we summarize analytical calculations based on the Kubo formalism : explicit expressions for both skew-scattering and side-jump are derived and weak-localization corrections are discussed. Next, we present numerical calculations of the anomalous Hall resistivity based on the Dirac equation. Qualitative agreement with experiments is obtained.Comment: Proceeding JEMS'0

Topological Hall effect and Berry phase in magnetic nanostructures

We discuss the anomalous Hall effect in a two-dimensional electron gas subject to a spatially varying magnetization. This topological Hall effect (THE) does not require any spin-orbit coupling, and arises solely from Berry phase acquired by an electron moving in a smoothly varying magnetization. We propose an experiment with a structure containing 2D electrons or holes of diluted magnetic semiconductor subject to the stray field of a lattice of magnetic nanocylinders. The striking behavior predicted for such a system (of which all relevant parameters are well known) allows to observe unambiguously the THE and to distinguish it from other mechanisms.Comment: 5 pages with 4 figure

The Value of Black Monukka, Perlette, Ruby Seedless and Sultanina as parents for breeding Raisin Grapes

The seedless grape cultivars Black Monukka, Perlette, Ruby Seedless and Sultanina were used as pollen parents and hybridized with two muscat flavoured and four neutral flavoured cultivars and selections in an effort to breed seedless table grapes. The progeny of some of these crosses were also evaluated for raisin quality during the 1983/84 season. Ten seedless selections and 21 selections possessing trace seeds (1-2 mm) obtained a quality rating comparable to that of Merbein Seedless, Fiesta, Perlette and Sultanina raisins. Perlette produced four times as many seedlings with satisfactory raisin quality as all the other crosses combined. The cross CG 1272 X Sultanina produced five promising white currant types. Selection CG 1272 appears to be a valuable parent for breeding improved currant types

Phase diagram of patchy colloids: towards empty liquids

We report theoretical and numerical evaluations of the phase diagram for patchy colloidal particles of new generation. We show that the reduction of the number of bonded nearest neighbours offers the possibility of generating liquid states (i.e. states with temperature $T$ lower than the liquid-gas critical temperature) with a vanishing occupied packing fraction ($\phi$), a case which can not be realized with spherically interacting particles. Theoretical results suggest that such reduction is accompanied by an increase of the region of stability of the liquid phase in the ($T$-$\phi$) plane, possibly favoring the establishment of homogeneous disordered materials at small $\phi$, i.e. stable equilibrium gels.Comment: 4 pages, 4 figures, revised version, accepted in Phys. Rev. Let

A Class of Nonperturbative Configurations in Abelian-Higgs Models: Complexity from Dynamical Symmetry Breaking

We present a numerical investigation of the dynamics of symmetry breaking in both Abelian and non-Abelian $[S U (2)]$ Higgs models in three spatial dimensions. We find a class of time-dependent, long-lived nonperturbative field configurations within the range of parameters corresponding to type-1 superconductors, that is, with vector masses ($m_v$) larger than scalar masses ($m_s$). We argue that these emergent nontopological configurations are related to oscillons found previously in other contexts. For the Abelian-Higgs model, our lattice implementation allows us to map the range of parameter space -- the values of $\beta = (m_s /m_v)^2$ -- where such configurations exist and to follow them for times t \sim \O(10^5) m^{-1}. An investigation of their properties for $\hat z$-symmetric models reveals an enormously rich structure of resonances and mode-mode oscillations reminiscent of excited atomic states. For the SU(2) case, we present preliminary results indicating the presence of similar oscillonic configurations.Comment: 21 pages, 19 figures, prd, revte

Molecular Dynamics Simulation of Heat-Conducting Near-Critical Fluids

Using molecular dynamics simulations, we study supercritical fluids near the gas-liquid critical point under heat flow in two dimensions. We calculate the steady-state temperature and density profiles. The resultant thermal conductivity exhibits critical singularity in agreement with the mode-coupling theory in two dimensions. We also calculate distributions of the momentum and heat fluxes at fixed density. They indicate that liquid-like (entropy-poor) clusters move toward the warmer boundary and gas-like (entropy-rich) regions move toward the cooler boundary in a temperature gradient. This counterflow results in critical enhancement of the thermal conductivity

MissForest - nonparametric missing value imputation for mixed-type data

Modern data acquisition based on high-throughput technology is often facing the problem of missing data. Algorithms commonly used in the analysis of such large-scale data often depend on a complete set. Missing value imputation offers a solution to this problem. However, the majority of available imputation methods are restricted to one type of variable only: continuous or categorical. For mixed-type data the different types are usually handled separately. Therefore, these methods ignore possible relations between variable types. We propose a nonparametric method which can cope with different types of variables simultaneously. We compare several state of the art methods for the imputation of missing values. We propose and evaluate an iterative imputation method (missForest) based on a random forest. By averaging over many unpruned classification or regression trees random forest intrinsically constitutes a multiple imputation scheme. Using the built-in out-of-bag error estimates of random forest we are able to estimate the imputation error without the need of a test set. Evaluation is performed on multiple data sets coming from a diverse selection of biological fields with artificially introduced missing values ranging from 10% to 30%. We show that missForest can successfully handle missing values, particularly in data sets including different types of variables. In our comparative study missForest outperforms other methods of imputation especially in data settings where complex interactions and nonlinear relations are suspected. The out-of-bag imputation error estimates of missForest prove to be adequate in all settings. Additionally, missForest exhibits attractive computational efficiency and can cope with high-dimensional data.Comment: Submitted to Oxford Journal's Bioinformatics on 3rd of May 201