Sunflecks in the upper canopy: dynamics of light-use efficiency in sun and shade leaves of Fagus sylvatica

Sunflecks are transient patches of direct radiation that provide a substantial proportion of the daily irradiance to leaves in the lower canopy. In this position, faster photosynthetic induction would allow for higher sunfleck-use efficiency, as is commonly reported in the literature. Yet, when sunflecks are too few and far between, it may be more beneficial for shade leaves to prioritize efficient photosynthesis under shade. We investigated the temporal dynamics of photosynthetic induction, recovery under shade, and stomatal movement during a sunfleck, in sun and shade leaves of Fagus sylvatica from three provenances of contrasting origin. We found that shade leaves complete full induction in a shorter time than sun leaves, but that sun leaves respond faster than shade leaves due to their much larger amplitude of induction. The core-range provenance achieved faster stomatal opening in shade leaves, which may allow for better sunfleck-use efficiency in denser canopies and lower canopy positions. Our findings represent a paradigm shift for future research into light fluctuations in canopies, drawing attention to the ubiquitous importance of sunflecks for photosynthesis, not only in lower-canopy leaves where shade is prevalent, but particularly in the upper canopy where longer sunflecks are more common due to canopy openness

Sunflecks in the upper canopy : dynamics of light-use efficiency in sun and shade leaves of Fagus sylvatica

Sunflecks are transient patches of direct radiation that provide a substantial proportion of the daily irradiance to leaves in the lower canopy. In this position, faster photosynthetic induction would allow for higher sunfleck-use efficiency, as is commonly reported in the literature. Yet, when sunflecks are too few and far between, it may be more beneficial for shade leaves to prioritize efficient photosynthesis under shade. We investigated the temporal dynamics of photosynthetic induction, recovery under shade, and stomatal movement during a sunfleck, in sun and shade leaves of Fagus sylvatica from three provenances of contrasting origin. We found that shade leaves complete full induction in a shorter time than sun leaves, but that sun leaves respond faster than shade leaves due to their much larger amplitude of induction. The core-range provenance achieved faster stomatal opening in shade leaves, which may allow for better sunfleck-use efficiency in denser canopies and lower canopy positions. Our findings represent a paradigm shift for future research into light fluctuations in canopies, drawing attention to the ubiquitous importance of sunflecks for photosynthesis, not only in lower-canopy leaves where shade is prevalent, but particularly in the upper canopy where longer sunflecks are more common due to canopy openness.Peer reviewe

Collective dynamics of liquid aluminum probed by Inelastic X-ray Scattering

An inelastic X-ray scattering experiment has been performed in liquid aluminum with the purpose of studying the collective excitations at wavevectors below the first sharp diffraction peak. The high instrumental resolution (up to 1.5 meV) allows an accurate investigation of the dynamical processes in this liquid metal on the basis of a generalized hydrodynamics framework. The outcoming results confirm the presence of a viscosity relaxation scenario ruled by a two timescale mechanism, as recently found in liquid lithium.Comment: 8 pages, 7 figure

Evidence of short time dynamical correlations in simple liquids

We report a molecular dynamics (MD) study of the collective dynamics of a simple monatomic liquid -interacting through a two body potential that mimics that of lithium- across the liquid-glass transition. In the glassy phase we find evidences of a fast relaxation process similar to that recently found in Lennard-Jones glasses. The origin of this process is ascribed to the topological disorder, i.e. to the dephasing of the different momentum $Q$ Fourier components of the actual normal modes of vibration of the disordered structure. More important, we find that the fast relaxation persists in the liquid phase with almost no temperature dependence of its characteristic parameters (strength and relaxation time). We conclude, therefore, that in the liquid phase well above the melting point, at variance with the usual assumption of {\it un-correlated} binary collisions, the short time particles motion is strongly {\it correlated} and can be described via a normal mode expansion of the atomic dynamics.Comment: 7 pages, 7 .eps figs. To appear in Phys. Rev.

Inelastic X-ray scattering study of the collective dynamics in liquid sodium

Inelastic X-ray scattering data have been collected for liquid sodium at T=390 K, i.e. slightly above the melting point. Owing to the very high instrumental resolution, pushed up to 1.5 meV, it has been possible to determine accurately the dynamic structure factor, $S(Q,\omega)$, in a wide wavevector range, $1.5 \div 15$ nm$^{-1}$, and to investigate on the dynamical processes underlying the collective dynamics. A detailed analysis of the lineshape of $S(Q,\omega)$, similarly to other liquid metals, reveals the co-existence of two different relaxation processes with slow and fast characteristic timescales respectively. The present data lead to the conclusion that: i) the picture of the relaxation mechanism based on a simple viscoelastic model fails; ii) although the comparison with other liquid metals reveals similar behavior, the data do not exhibit an exact scaling law as the principle of corresponding state would predict.Comment: RevTex, 7 pages, 6 eps figures. Accepted by Phys. Rev.

B. Zur erklärung und kritik der schriftsteller

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Immunotherapeutic targeting of membrane Hsp70-expressing tumors using recombinant human granzyme B

Background: We have previously reported that human recombinant granzyme B (grB) mediates apoptosis in membrane heat shock protein 70 (Hsp70)-positive tumor cells in a perforin-independent manner

ifo Konjunkturprognose 2008: Konjunktur verliert an Fahrt

Am 13. Dezember 2007 stellte das ifo Institut im Rahmen seines vorweihnachtlichen Pressegesprächs seine Prognose für die Jahre 2008 und 2009 vor. Die Weltwirtschaft hat in diesem Jahr mit 5,2% erneut sehr kräftig expandiert. Allerdings sind die Risiken für die Konjunktur im Gefolge der Turbulenzen an den internationalen Finanzmärkten inzwischen merklich gestiegen. So hat sich das vom ifo Institut erhobene Weltwirtschaftsklima im 4. Quartal 2007 deutlich verschlechtert. Sowohl die Einschätzungen der derzeitigen wirtschaftlichen Lage als auch die Erwartungen für die nächsten sechs Monate wurden nach unten revidiert. Die Verschlechterung des ifo Wirtschaftsklimas betrifft alle drei großen Weltregionen, also Westeuropa, Nordamerika und Asien. Dabei ist der stärkste Rückgang des Klimaindikators in Nordamerika, und dort in erster Linie in den USA zu verzeichnen. Diese Datenkonstellation deutet daraufhin, dass sich das Tempo der Weltkonjunktur merklich verlangsamen wird. Die deutsche Konjunktur ist zum Jahresende 2007 weiter aufwärts gerichtet, wenn auch mit nachlassender Kraft. Die Dynamik hatte im vergangenen Winter einen Höhepunkt erreicht und lässt inzwischen wieder deutlich nach. Wie das ifo Institut im Dezember 2006 erwartet hatte, hat sich der seit 2005 laufende Aufschwung trotz der massiven Erhöhung der Mehrwertsteuer fortgesetzt. Die Auftriebskräfte aus dem In- und Ausland waren kräftig genug, um die restriktiven Wirkungen der Finanzpolitik zu verkraften. Konjunkturmotor war weiterhin die Auslandsnachfrage, die trotz der massiven Aufwertung des Euro gegenüber dem US-Dollar aufgrund der dynamischen Weltkonjunktur kräftig blieb. Im Jahresdurchschnitt 2007 expandierte das reale Bruttoinlandsprodukt um 2,5%. Allerdings gab es in diesem Jahr erneut eine etwas geringere Zahl von Arbeitstagen als 2006. Nach Ausschaltung dieser Kalenderschwankung ist die Zuwachsrate der Produktion auf 2,6% zu veranschlagen, was knapp unter dem Durchschnitt der alten EU-Länder liegt