1,449 research outputs found

    Two modes of peri-interaction between an aldehyde group and a carboxylate anion in naphthalaldehydate salts

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    Crystal structures of the salts of 1,8-naphthalaldehydic acid (8-formyl-1-naphthoic acid) show one of two types of interaction between the functional groups. In the more commonly observed case, a carboxylate oxygen lies close to the aldehyde carbonyl carbon atom (O⋯C: 2.445–2.630 Å) and makes an n–pi* interaction. However, in two other cases the carboxylate group has rotated so that the aldehyde now directs its hydrogen atom at the face of the carboxylate group and forms a surprisingly short contact with the carbon atom (H⋯C: 2.29 and 2.42 Å). This interaction is likely to be electrostatic in nature

    Influence of site and stand factors on Hymenoscyphus fraxineus-induced basal lesions

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    Hymenoscyphus fraxineus is an invasive fungus in Europe and causes a severe decline affecting ash, which began in the late 1990s. One of the symptoms associated with the disease is lesions in the outer bark of the collar area. However, the aetiology of these basal lesions, and in particular the relative roles of H.fraxineus and Armillaria species, is still controversial; moreover, little is known about the influence of environmental factors on the disease epidemiology.This study therefore surveyed 42 plots located in northeastern France, in an area affected by ash decline since 2008, in order to determine which environmental factors condition the severity of lesions associated with H.fraxineus on ash collar. The spatial pattern that is a consequence of the invasive spread of the disease was taken into account in the analysis, using a spatial hierarchical Bayesian model fitted by integrated nested laplace approximation (INLA).Results show that while basal lesions are tightly associated with H.fraxineus, their severity is influenced by the Armillaria species present in the plot. Sites with vegetation indicating moist conditions, or more humid topographical positions, were associated with more developed basal lesions

    Charge transfer electrostatic model of compositional order in perovskite alloys

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    We introduce an electrostatic model including charge transfer, which is shown to account for the observed B-site ordering in Pb-based perovskite alloys. The model allows charge transfer between A-sites and is a generalization of Bellaiche and Vanderbilt's purely electrostatic model. The large covalency of Pb^{2+} compared to Ba^{2+} is modeled by an environment dependent effective A-site charge. Monte Carlo simulations of this model successfully reproduce the long range compositional order of both Pb-based and Ba-based complex A(BB^{'}B^{''})O_3 perovskite alloys. The models are also extended to study systems with A-site and B-site doping, such as (Na_{1/2}La_{1/2})(Mg_{1/3}Nb_{2/3})O_3, (Ba_{1-x}La_{x})(Mg_{(1+x)/3}Nb_{(2-x)/3})O_3 and (Pb_{1-x}La_{x})(Mg_{(1+x)/3}Ta_{(2-x)/3})O_3. General trends are reproduced by purely electrostatic interactions, and charge transfer effects indicate that local structural relaxations can tip the balance between different B-site orderings in Pb based materials.Comment: 15 pages, 6 figure

    Negative illness perceptions are related to poorer health‐related quality of life among thyroid cancer survivors:Results from the PROFILES registry

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    Background Differentiated thyroid cancer (DTC) reports a poorer health‐related quality of life (HRQoL) than a norm population. Patients' illness perceptions are modifiable and known associates of HRQoL in other cancers. The aim was to examine the relationship between illness perceptions and HRQoL among DTC survivors. Methods DTC survivors registered in the Netherlands Cancer Registry diagnosed between 1990 and 2008, received a survey on illness perceptions (Brief‐Illness Perception Questionnaire; B‐IPQ) and HRQoL (European Organisation for Research and Treatment of Cancer, Quality of Life Questionnaire‐Core 30; EORTC QLQ‐C30). Multiple regression analyses were conducted investigating the relation between illness perceptions and HRQoL, while controlling for sociodemographic and clinical characteristics. Results Two hundred and eighty‐four DTC survivors were included. DTC survivors who believed their illness had many negative consequences; who perceived their illness as controllable by treatment; who had strong beliefs symptoms could be attributed to their illness; and who had strong beliefs their illness causes negative emotions, reported a poorer HRQoL. Conclusions Stronger negative illness perceptions are related to a poorer HRQoL among DTC survivors

    The Rotation of Sub-Populations in omega Centauri

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    We present the first result of the Ital-FLAMES survey of red giant branch (RGB) stars in omega Cen. Radial velocities with a precision of ~0.5 km/s are presented for 650 members of omega Cen observed with FLAMES-Giraffe at the Very Large Telescope. We found that stars belonging to the metal -poor (RGB-MP), metal-intemediate (RGB-MInt) and metal-rich (RGB-a) sub -populations of Omega Cen are all compatible with having the same rotational pattern. Our results appear to contradict past findings by Norris et al., who could not detect any rotational signature for metal -rich stars. The slightly higher precision of the present measurements and the much larger sample size, especially for the metal-richer stars, appear as the most likely explanation for this discrepancy. The result presented here weakens the body of evidence in favour of a merger event in the past history of omega Cen.Comment: 5 pages, 3 fiures, electronic table can be obtained from E. Pancino. Accepted for publication in ApJ Letter

    Leaf Eh and pH: A Novel Indicator of Plant Stress. Spatial, Temporal and Genotypic Variability in Rice (Oryza sativa L.)

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    A wealth of knowledge has been published in the last decade on redox regulations in plants. However, these works remained largely at cellular and organelle levels. Simple indicators of oxidative stress at the plant level are still missing. We developed a method for direct measurement of leaf Eh and pH, which revealed spatial, temporal, and genotypic variations in rice. Eh (redox potential) and Eh@pH7 (redox potential corrected to pH 7) of the last fully expanded leaf decreased after sunrise. Leaf Eh was high in the youngest leaf and in the oldest leaves, and minimum for the last fully expanded leaf. Leaf pH decreased from youngest to oldest leaves. The same gradients in Eh-pH were measured for various varieties, hydric conditions, and cropping seasons. Rice varieties differed in Eh, pH, and/or Eh@pH7. Leaf Eh increases and leaf pH decreases with plant age. These patterns and dynamics in leaf Eh-pH are in accordance with the pattern and dynamics of disease infections. Leaf Eh-pH can bring new insight on redox processes at plant level and is proposed as a novel indicator of plant stress/health. It could be used by agronomists, breeders, and pathologists to accelerate the development of crop cultivation methods leading to agroecological crop protection

    CVM studies on the atomic ordering in complex perovskite alloys

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    The atomic ordering in complex perovskite alloys is investigated by the cluster variation method (CVM). For the 1/3\{111\}-type ordered structure, the order-disorder phase transition is the first order, and the order parameter of the 1:2 complex perovskite reaches its maximum near x=0.25. For the 1/2\{111\}-type ordered structure, the ordering transition is the second order. Phase diagrams for both ordered structures are obtained. The order-disorder line obeys the linear law.Comment: 10 pages, 6 figure

    Synthesising, using, and correcting for telluric features in high-resolution astronomical spectra

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    We present a technique to synthesise telluric absorption and emission features both for in-situ wavelength calibration and for their removal from astronomical spectra. While the presented technique is applicable for a wide variety of optical and infrared spectra, we concentrate in this paper on selected high-resolution near-infrared spectra obtained with the CRIRES spectrograph to demonstrate its performance and limitation. We find that synthetic spectra reproduce telluric absorption features to about 2%, even close to saturated line cores. Thus, synthetic telluric spectra could be used to replace the observation of telluric standard stars, saving valuable observing time. This technique also provides a precise in-situ wavelength calibration, especially useful for high-resolution near-infrared spectra in the absence of other calibration sources.Comment: 11 pages, 11 figures, accepted for publication in A&A (updated version
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