8,732 research outputs found

    The effect of flooding on the exchange of the volatile Câ‚‚-compounds ethanol, acetaldehyde and acetic acid between leaves of Amazonian floodplain tree species and the atmosphere

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    The effect of root inundation on the leaf emissions of ethanol, acetaldehyde and acetic acid in relation to assimilation and transpiration was investigated with 2–3 years old tree seedlings of four Amazonian floodplain species by applying dynamic cuvette systems under greenhouse conditions. Emissions were monitored over a period of several days of inundation using a combination of Proton Transfer Reaction Mass Spectrometry (PTR-MS) and conventional techniques (HPLC, ion chromatography). Under non-flooded conditions, none of the species exhibited measurable emissions of any of the compounds, but rather low deposition of acetaldehyde and acetic acid was observed instead. Tree species specific variations in deposition velocities were largely due to variations in stomatal conductance. Flooding of the roots resulted in leaf emissions of ethanol and acetaldehyde by all species, while emissions of acetic acid were only observed from the species exhibiting the highest ethanol and acetaldehyde emission rates. All three compounds showed a similar diurnal emission profile, each displaying an emission burst in the morning, followed by a decline in the evening. This concurrent behavior supports the conclusion, that all three compounds emitted by the leaves are derived from ethanol produced in the roots by alcoholic fermentation, transported to the leaves with the transpiration stream and finally partly converted to acetaldehyde and acetic acid by enzymatic processes. Co-emissions and peaking in the early morning suggest that root ethanol, after transportation with the transpiration stream to the leaves and enzymatic oxidation to acetaldehyde and acetate, is the metabolic precursor for all compounds emitted, though we can not totally exclude other production pathways. Emission rates substantially varied among tree species, with maxima differing by up to two orders of magnitude (25–1700 nmol m−2 min−1 for ethanol and 5–500 nmol m−2 min−1 for acetaldehyde). Acetic acid emissions reached 12 nmol m−2 min−1. The observed differences in emission rates between the tree species are discussed with respect to their root adaptive strategies to tolerate long term flooding, providing an indirect line of evidence that the root ethanol production is a major factor determining the foliar emissions. Species which develop morphological root structures allowing for enhanced root aeration produced less ethanol and showed much lower emissions compared to species which lack gas transporting systems, and respond to flooding with substantially enhanced fermentation rates and a non-trivial loss of carbon to the atmosphere. The pronounced differences in the relative emissions of ethanol to acetaldehyde and acetic acid between the tree species indicate that not only the ethanol production in the roots but also the metabolic conversion in the leaf is an important factor determining the release of these compounds to the atmosphere

    Fear of campaign violence and support for democracy and autocracy

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    Election violence is common in many developing countries and has potentially detrimental implications for democratic consolidation. Drawing on political psychology, we argue that citizens’ fear of campaign violence undermines support for democracy while increasing support for autocracy. Using individual-level survey data from 21 electoral democracies in Sub-Saharan Africa, we find robust support for our argument. Citizens fearing campaign violence are less likely to support democracy and multi-party competition, more likely to favor a return to autocracy, and less likely to turn out to vote. Our findings have important implications for democratic survival and provide further impetus for reducing electoral violence

    Electroweak Sudakov Logarithms and Real Gauge-Boson Radiation in the TeV Region

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    Electroweak radiative corrections give rise to large negative, double-logarithmically enhanced corrections in the TeV region. These are partly compensated by real radiation and, moreover, affected by selecting isospin-noninvariant external states. We investigate the impact of real gauge boson radiation more quantitatively by considering different restricted final state configurations. We consider successively a massive abelian gauge theory, a spontaneously broken SU(2) theory and the electroweak Standard Model. We find that details of the choice of the phase space cuts, in particular whether a fraction of collinear and soft radiation is included, have a strong impact on the relative amount of real and virtual corrections.Comment: 20 pages, 4 figure

    Reducing decoherence of the confined exciton state in a quantum dot by pulse-sequence control

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    We study the phonon-induced dephasing of the exciton state in a quantum dot excited by a sequence of ultra-short pulses. We show that the multiple-pulse control leads to a considerable improvement of the coherence of the optically excited state. For a fixed control time window, the optimized pulsed control often leads to a higher degree of coherence than the control by a smooth single Gaussian pulse. The reduction of dephasing is considerable already for 2-3 pulses.Comment: Final version (moderate changes

    Porównanie maksymalnego ciśnienia zamknięcia cewki moczowej mierzone cewnikiem typu mikrotip i cewnikiem wypełnionym powietrzem – badanie randomizowane

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    Background: Measurements of maximum urethral closure pressure (MUCP) are a part of urodynamic investigations preceding an incontinence surgery and a part of urethral function tests. Objectives: The aim of the study was to compare maximum urethral closure pressure determined by a microtip catheter with those measured by an air-charged catheter. Material and methods: A prospective randomized study in a tertiary referral centre. 122 female patients with urodynamic stress incontinence were randomly assigned to have their urethral pressure profi les measured at rest by both microtip and air-charged catheters. Intervention and Measurements: Each patient had three measurements taken by each catheter type. Means of the measurements were compared with regard to correlation and repeatability. For statistical analysis, an approach proposed by Bland-Altman was applied to assess the agreement between the two techniques. Results: Correlation coeffi cient between MUCP by the air-charged and the microtip catheter was r=0.8507(95% CI 0.7928 – 0.8934; pCel: Pomiar maksymalnego ciśnienia zamknięcia cewki moczowej (MUCP) jest częścią badania urodynamicznego poprzedzającego operacyjne leczenie nietrzymania moczu i częścią testow czynnościowych cewki moczowej. Celem pracy było porownanie maksymalnego ciśnienia zamknięcia cewki moczowej zmierzonego przy pomocy cewnika microtip i cewnika wypełnionego powietrzem. Materiał i metoda: Przeprowadzono prospektywne, randomizowane badanie w ośrodku trzeciego stopnia referencyjności. Do badania losowo włączono 122 kobiety z nietrzymaniem moczu, u których wykonywano profi l ciśnień w cewce moczowej w spoczynku przy pomocy zarówno cewnika microtip jak i cewnika wypełnionego powietrzem. Każda pacjentka miała wykonane trzy pomiary przy pomocy obu cewników. Średnie z pomiarów porównano w odniesieniu do korelacji i powtarzalności. Do celów statystycznych użyto metody Bland-Altmana oceniającej zgodność obu technik pomiarów. Wyniki: Współczynnik korelacji pomiędzy MUCP mierzonym cewnikiem powietrznym a cewnikiem microtip wynosił r=0,8507(95% CI 0,7928–0,8934;

    Measuring Global Similarity between Texts

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    We propose a new similarity measure between texts which, contrary to the current state-of-the-art approaches, takes a global view of the texts to be compared. We have implemented a tool to compute our textual distance and conducted experiments on several corpuses of texts. The experiments show that our methods can reliably identify different global types of texts.Comment: Submitted to SLSP 201
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