Strain analysis of multiferroic BiFeO3-CoFe2O4 nanostructures by Raman scattering

We report a Raman scattering investigation of columnar BiFeO3-CoFe2O4 (BFO-CFO) epitaxial thin film nanostructures, where BFO pillars are embedded in a CFO matrix. The feasibility of a strain analysis is illustrated through an investigation of two nanostructures with different BFO-CFO ratios. We show that the CFO matrix presents the same strain state in both nanostructures, while the strain state of the BFO pillars depends on the BFO/CFO ratio with an increasing tensile strain along the out-of-plane direction with decreasing BFO content. Our results demonstrate that Raman scattering allows monitoring strain states in complex 3D multiferroic pillar/matrix composites.Comment: revised version submitted to Appl. Phys. Let

The magnetic field of the B3V star 16 Pegasi

The Slowly Pulsating B3V star 16 Pegasi was discovered by Hubrig (2006) to be magnetic, based on low-resolution spectropolarimetric observations with FORS1 at the VLT. We have confirmed the presence of a magnetic field with new measurements with the spectropolarimeters Narval at TBL, France and Espadons at CFHT, Hawaii during 2007. The most likely period is about 1.44 d for the modulation of the field, but this could not be firmly established with the available data set. No variability has been found in the UV stellar wind lines. Although the star was reported once to show H alpha in emission, there exists at present no confirmation that the star is a Be star.Comment: 2 pages, 4 figures, contrubuted poster at IAU Symposium 259 "Cosmic Magnetic Fields: from Planets, to Stars and Galaxies", Tenerife, Spain, November 3-7, 200

Herbaceous angiosperms are not more vulnerable to drought-induced embolism than angiosperm trees

The water transport pipeline in herbs is assumed to be more vulnerable to drought than in trees due to the formation of frequent embolisms (gas bubbles), which could be removed by the occurrence of root pressure, especially in grasses. Here, we studied hydraulic failure in herbaceous angiosperms by measuring the pressure inducing 50% loss of hydraulic conductance (P50) in stems of 26 species, mainly European grasses (Poaceae). Our measurements show a large range in P50 from 20.5 to 27.5 MPa, which overlaps with 94% of the woody angiosperm species in a worldwide, published data set and which strongly correlates with an aridity index. Moreover, the P50 values obtained were substantially more negative than the midday water potentials for five grass species monitored throughout the entire growing season, suggesting that embolism formation and repair are not routine and mainly occur under water deficits. These results show that both herbs and trees share the ability to withstand very negative water potentials without considerable embolism formation in their xylem conduits during drought stress. In addition, structure-function trade-offs in grass stems reveal that more resistant species are more lignified, which was confirmed for herbaceous and closely related woody species of the daisy group (Asteraceae). Our findings could imply that herbs with more lignified stems will become more abundant in future grasslands under more frequent and severe droughts, potentially resulting in lower forage digestibility.

SurEau-Ecos v2.0: a trait-based plant hydraulics model for simulations of plant water status and drought-induced mortality at the ecosystem level

A widespread increase in tree mortality has been observed around the globe, and this trend is likely to continue because of ongoing climate-induced increases in drought frequency and intensity. This raises the need to identify regions and ecosystems that are likely to experience the most frequent and significant damage. We present SurEau-Ecos, a trait-based, plant hydraulic model designed to predict tree desiccation and mortality at scales from stand to region. SurEau-Ecos draws on the general principles of the SurEau model but introduces a simplified representation of plant architecture and alternative numerical schemes. Both additions were made to facilitate model parameterization and large-scale applications. In SurEau-Ecos, the water fluxes from the soil to the atmosphere are represented through two plant organs (a leaf and a stem, which includes the volume of the trunk, roots and branches) as the product of an interface conductance and the difference between water potentials. Each organ is described by its symplasmic and apoplasmic compartments. The dynamics of a plant's water status beyond the point of stomatal closure are explicitly represented via residual transpiration flow, plant cavitation and solicitation of plants' water reservoirs. In addition to the “explicit” numerical scheme of SurEau, we implemented a “semi-implicit” and “implicit” scheme. Both schemes led to a substantial gain in computing time compared to the explicit scheme (&gt;10 000 times), and the implicit scheme was the most accurate. We also observed similar plant water dynamics between SurEau-Ecos and SurEau but slight disparities in infra-daily variations of plant water potentials, which we attributed to the differences in the representation of plant architecture between models. A global model's sensitivity analysis revealed that factors controlling plant desiccation rates differ depending on whether leaf water potential is below or above the point of stomatal closure. Total available water for the plant, leaf area index and the leaf water potential at 50 % stomatal closure mostly drove the time needed to reach stomatal closure. Once stomata are closed, resistance to cavitation, residual cuticular transpiration and plant water stocks mostly determined the time to hydraulic failure. Finally, we illustrated the potential of SurEau-Ecos to simulate regional drought-induced mortality over France. SurEau-Ecos is a promising tool to perform regional-scale predictions of drought-induced hydraulic failure, determine the most vulnerable areas and ecosystems to drying conditions, and assess the dynamics of forest flammability.</p

Uniform Selection as a Primary Force Reducing Population Genetic Differentiation of Cavitation Resistance across a Species Range

Background: Cavitation resistance to water stress-induced embolism determines plant survival during drought. This adaptive trait has been described as highly variable in a wide range of tree species, but little is known about the extent of genetic and phenotypic variability within species. This information is essential to our understanding of the evolutionary forces that have shaped this trait, and for evaluation of its inclusion in breeding programs. Methodology: We assessed cavitation resistance (P 50), growth and carbon isotope composition in six Pinus pinaster populations in a provenance and progeny trial. We estimated the heritability of cavitation resistance and compared the distribution of neutral markers (FST) and quantitative genetic differentiation (QST), for retrospective identification of the evolutionary forces acting on these traits. Results/Discussion: In contrast to growth and carbon isotope composition, no population differentiation was found for cavitation resistance. Heritability was higher than for the other traits, with a low additive genetic variance (h 2 ns = 0.4360.18, CVA = 4.4%). QST was significantly lower than FST, indicating uniform selection for P50, rather than genetic drift. Putativ

Trust transfer between contexts

Funding for Open Access provided by the UMD Libraries Open Access Publishing Fund.This paper explores whether trust, developed in one context, transfers into another, distinct context and, if so, attempts to quantify the influence this prior trust exerts. Specifically, we investigate the effects of artificially stimulated prior trust as it transfers across disparate contexts and whether this prior trust can compensate for negative objective information. To study such incidents, we leveraged Berg’s investment game to stimulate varying degrees of trust between a human and a set of automated agents. We then observed how trust in these agents transferred to a new game by observing teammate selection in a modified, four-player extension of the well-known board game, Battleship. Following this initial experiment, we included new information regarding agent proficiency in the Battleship game during teammate selection to see how prior trust and new objective information interact. Deploying these experiments on Amazon’s Mechanical Turk platform further allowed us to study these phenomena across a broad range of participants. Our results demonstrate trust does transfer across disparate contexts and this inter-contextual trust transfer exerts a stronger influence over human behavior than objective performance data. That is, humans show a strong tendency to select teammates based on their prior experiences with each teammate, and proficiency information in the new context seems to matter only when the differences in prior trust between potential teammates are small

Children Base Their Investment on Calculated Pay-Off

To investigate the rise of economic abilities during development we studied children aged between 3 and 10 in an exchange situation requiring them to calculate their investment based on different offers. One experimenter gave back a reward twice the amount given by the children, and a second always gave back the same quantity regardless of the amount received. To maximize pay-offs children had to invest a maximal amount with the first, and a minimal amount with the second. About one third of the 5-year-olds and most 7- and 10-year-olds were able to adjust their investment according to the partner, while all 3-year-olds failed. Such performances should be related to the rise of cognitive and social skills after 4 years

Photon-Photon Physics in Very Peripheral Collisions of Relativistic Heavy Ions

In central collisions at relativistic heavy ion colliders like the Relativistic Heavy Ion Collider RHIC/Brookhaven and the Large Hadron Collider LHC (in its heavy ion mode) at CERN/Geneva, one aims at detecting a new form of hadronic matter - the Quark Gluon Plasma. It is the purpose of this review to discuss a complementary aspect of these collisions, the very peripheral ones. Due to coherence, there are strong electromagnetic fields of short duration in such collisions. They give rise to photon-photon and photon-nucleus collisions with high flux up to an invariant mass region hitherto unexplored experimentally. After a general survey photon-photon luminosities in relativistic heavy ion collisions are discussed. Special care is taken to include the effects of strong interactions and nuclear size. Then photon-photon physics at various gamma-gamma-invariant mass scales is discussed. The region of several GeV, relevant for RHIC is dominated by QCD phenomena (meson and vector meson pair production). Invariant masses of up to about 100 GeV can be reached at LHC, and the potential for new physics is discussed. Photonuclear reactions and other important background effects, especially diffractive processes are also discussed. A special chapter is devoted to lepton-pair production, especially electron-positron pair production; due to the strong fields new phenomena, especially multiple e+-e- pair production, will occur there.Comment: 40 pages, 19 figures, Topical Review, to appear in Journal of Physics G, revised text, updated text/references, one figure replace