Studies in zirconium oxidation

Study provides insight into the oxidation mechanism of zirconium by combining electrical measurements with oxidation data. The measurement of electrical potential across growing scale on zirconium and the determination of conventional weight-change oxidation data were carried out at 550, 700, and 800 degrees C

SUSY transformation of the Green function and a trace formula

An integral relation is established between the Green functions corresponding to two Hamiltonians which are supersymmetric (SUSY) partners and in general may possess both discrete and continuous spectra. It is shown that when the continuous spectrum is present the trace of the difference of the Green functions for SUSY partners is a finite quantity which may or may not be equal to zero despite the divergence of the traces of each Green function. Our findings are illustrated by using the free particle example considered both on the whole real line and on a half line

Topological model of soap froth evolution with deterministic T2-processes

We introduce a topological model for the evolution of 2d soap froth. The topological rearrangements (T2 processes) are deterministic (unlike the standard stochastic model): the final topology depends on the areas of the neighboring cells. The new model gives agreement with experiments in the transient regime, where the previous models failed qualitatively, and also improves agreement in the scaling state.Comment: latex, 12 pages, 2 figure

Ocean acidification changes the male fitness landscape.

Sperm competition is extremely common in many ecologically important marine taxa. Ocean acidification (OA) is driving rapid changes to the marine environments in which freely spawned sperm operate, yet the consequences of OA on sperm performance are poorly understood in the context of sperm competition. Here, we investigated the impacts of OA (+1000 μatm pCO2) on sperm competitiveness for the sea urchin Paracentrotus lividus. Males with faster sperm had greater competitive fertilisation success in both seawater conditions. Similarly, males with more motile sperm had greater sperm competitiveness, but only under current pCO2 levels. Under OA the strength of this association was significantly reduced and there were male sperm performance rank changes under OA, such that the best males in current conditions are not necessarily best under OA. Therefore OA will likely change the male fitness landscape, providing a mechanism by which environmental change alters the genetic landscape of marine species.We acknowledge Catherina Artikis and Yueling Hao for their contributions to the molecular analysis. We thank the team at Exeter Biosciences for their help and support. A.L.C. was supported by a Natural Environment Research Council (NERC) PhD studentship to Exeter, and received additional funding from Exeter CLES PREF and a Santander Postgraduate Research Award (2014/2015). C.L. was supported by a UK-OARP NERC consortium grant NE/H017496/1 and a NERC UK Fellowship: NE/G014728/1. DRL was supported by funding from the United States, National Science Foundation (Grant DEB 1354272) which helped to fund the molecular analysis

Agricultural Plastics: What are they? Why are they 'hard stuff'? Can the challenges be surmounted?

Presentation slides illustrate the array of agricultural plastic products, the plastic resins they are made from, and qualities and practices that increase suitability for recycling. The reasons that agricultural plastics have been difficult to recycle are outlined, including (1) often contamination with a higher percentage of soil, moisture, etc. than typically permissible for recyclable materials; (2) possibility of contamination with equipment-damaging grit, gravel and rocks; (3) perception or possibility of contamination with pesticide residue; and/or (4) with soil pathogens and weed seeds. Also (5) the expense of collecting bulky material dispersed across the rural landscape, which is greater than collecting waste plastic that is neatly contained within a factory or store; (6) agricultural plastics are often dark colored or a mix of black and white, which process into a muddy gray; and (7) products may be an unidentified mix of different plastic resins and additives. Plastic films are increasingly complex, often made with multiple extrusion layers to meet specific technical criteria. However, new equipment and markets are emerging with capability of processing even the most difficult of agricultural films

Discarded Agricultural Plastics: Evolving Infrastructure & Markets for Recycling

Presentation made at the SWANA, NYS Chapter, Technical Training Session: Plastics – Myths & Mysteries, Nov 2, 2011. Covers types of agricultural plastic products, reasons for recycling these materials, organizational structure and objectives of the Recycling Agricultural Plastics Project (RAPP) and marketing options and criteria

Effects of Noise in a Cortical Neural Model

Recently Segev et al. (Phys. Rev. E 64,2001, Phys.Rev.Let. 88, 2002) made long-term observations of spontaneous activity of in-vitro cortical networks, which differ from predictions of current models in many features. In this paper we generalize the EI cortical model introduced in a previous paper (S.Scarpetta et al. Neural Comput. 14, 2002), including intrinsic white noise and analyzing effects of noise on the spontaneous activity of the nonlinear system, in order to account for the experimental results of Segev et al.. Analytically we can distinguish different regimes of activity, depending from the model parameters. Using analytical results as a guide line, we perform simulations of the nonlinear stochastic model in two different regimes, B and C. The Power Spectrum Density (PSD) of the activity and the Inter-Event-Interval (IEI) distributions are computed, and compared with experimental results. In regime B the network shows stochastic resonance phenomena and noise induces aperiodic collective synchronous oscillations that mimic experimental observations at 0.5 mM Ca concentration. In regime C the model shows spontaneous synchronous periodic activity that mimic activity observed at 1 mM Ca concentration and the PSD shows two peaks at the 1st and 2nd harmonics in agreement with experiments at 1 mM Ca. Moreover (due to intrinsic noise and nonlinear activation function effects) the PSD shows a broad band peak at low frequency. This feature, observed experimentally, does not find explanation in the previous models. Besides we identify parametric changes (namely increase of noise or decreasing of excitatory connections) that reproduces the fading of periodicity found experimentally at long times, and we identify a way to discriminate between those two possible effects measuring experimentally the low frequency PSD.Comment: 25 pages, 10 figures, to appear in Phys. Rev.

Convergence of expansions in Schr\"odinger and Dirac eigenfunctions, with an application to the R-matrix theory

Expansion of a wave function in a basis of eigenfunctions of a differential eigenvalue problem lies at the heart of the R-matrix methods for both the Schr\"odinger and Dirac particles. A central issue that should be carefully analyzed when functional series are applied is their convergence. In the present paper, we study the properties of the eigenfunction expansions appearing in nonrelativistic and relativistic $R$-matrix theories. In particular, we confirm the findings of Rosenthal [J. Phys. G: Nucl. Phys. 13, 491 (1987)] and Szmytkowski and Hinze [J. Phys. B: At. Mol. Opt. Phys. 29, 761 (1996); J. Phys. A: Math. Gen. 29, 6125 (1996)] that in the most popular formulation of the R-matrix theory for Dirac particles, the functional series fails to converge to a claimed limit.Comment: Revised version, accepted for publication in Journal of Mathematical Physics, 21 pages, 1 figur

A Tale of Two Democrats: How Authoritarianism Divides the Democratic Party

Authoritarianism has been predominantly used in American politics as a predictor of Republican identification and conservative policy preferences. We argue that this approach has neglected the role authoritarianism plays among Democrats and how it can operate within political parties regardless of their ideological orientation. Drawing from three distinct sets of data, we demonstrate the impact of authoritarianism in the 2016 Democratic Party’s primaries. Authoritarianism consistently predicts differences in primary voting among Democrats, particularly support for Hillary Clinton over Bernie Sanders. This effect is robust across various model specifications including controls for ideology, partisan strength, and other predispositions. These results highlight the potential of authoritarianism to shape leadership preferences within the Democratic Party. We advocate for a reconsideration of authoritarianism as a disposition with meaningful consequences for intraparty dynamics and conclude with practical implications regarding the future of the Democratic Party