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Search Results: 1 - 10 of 208459 matches for " Lüttge "
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Photosynthetic efficiency of Clusia arrudae leaf tissue with and without Cecidomyiidae galls
Fernandes, GW.;Coelho, MS.;Lüttge, U.;
Brazilian Journal of Biology , 2010, DOI: 10.1590/S1519-69842010000400004
Abstract: leaf galls induced by a still undescribed new species of cecidomyiidae (diptera) are frequent on leaves of clusia arrudae planchon & tirana (clusiaceae) in the rupestrian fields at 1400 m a.s.l. in serra do cipó, minas gerais, brazil. galls were 7.1 ± 0.7 mm in diameter, one chambered with only one larva inside. gall tissue is green and soft. assessments of photosynthetic capacity using chlorophyll-a fluorescence measurements revealed that photosynthetic performance of gall tissue and healthy leaf tissue were rather similar. hence, the morphological changes due to gall development were not associated with significant changes in the photosynthetic capacity of the tissue.
Ecophysiology
Lüttge, Ulrich;Scarano, Fabio R.;
Brazilian Journal of Botany , 2004, DOI: 10.1590/S0100-84042004000100001
Abstract: an attempt to delineate rather than to precisely define what we mean by "ecophysiology" is based on a brief historical overview of what eventually led to development of instrumentation and sampling strategies for analyses that allow description of physiological performance in the field. these techniques are surveyed. ecophysiology originally is aut-ecology dedicated to the behaviour of individual plants, species or higher taxa, viz. "physiotypes", in particular habitats. examples of ecophysiological diversity are developed, which illustrate gradual merging with more integrative considerations of functions and dynamics of habitats or ecosystems, i.e. a trend of research towards physiological syn-ecology. the latter is exemplified by studies with comparisons of a variety of morphotypes and physiotypes within a given habitat or ecosystem and across a range of habitats or ecosystems. the high demand and complexity as well as the excitement of ecology and ecophysiology arise from the quest to cover all conditions of the existence of organisms according to ernst haeckel's original definition of "ecology".
Synecological comparisons sustained by ecophysiological fingerprinting of intrinsic photosynthetic capacity of plants as assessed by measurements of light response curves
Lüttge, Ulrich;Scarano, Fabio Rubio;
Brazilian Journal of Botany , 2007, DOI: 10.1590/S0100-84042007000300002
Abstract: in some literature variations in photosynthetic rates are considered to be of little relevance for individual fitness. this depends among other things on how one defines fitness, i.e. if one takes strictly darwinian fitness as seed production or if one needs to evaluate particular traits and consider plant establishment. it also matters if one takes the darwinian "organism individual" as the central entity in evolution ("individual fitness") or the "species individual" in a modified "structure of evolutionary theory" sensu stephen jay gould. a phenotypically expressed trait like photosynthetic rate, even if intra- and interspecific differences may be small, can matter in habitat performance and niche acquisition. light dependence curves (lcs) of photosynthetic rates are now readily measured under field conditions using miniaturized equipment of pulse amplitude modulated fluorometers. in contrast to actual momentary measurements of quantum yield of photosynthesis under actually prevailing ambient conditions, lc measurements reflect the expressed intrinsic capacity of photosynthesis. in this review we explore the power of lc measurements yielding cardinal points such as maximum apparent electron transport rate of photosystem ii (etrmax) and saturating photosynthetically active radiation (parsat) in making intra- and interspecific comparisons of plant performance and synecological fingerprinting in ecophysiological studies across species, sites, habitats and ecosystems.
Magnetic control of Coulomb scattering and terahertz transitions among excitons
J. Bhattacharyya,S. Zybell,F. E?er,M. Helm,H. Schneider,L. Schneebeli,C. N. B?ttge,B. Breddermann,M. Kira,S. W. Koch,A. M. Andrews,G. Strasser
Physics , 2013, DOI: 10.1103/PhysRevB.89.125313
Abstract: Time-resolved terahertz quenching studies of the magnetoexcitonic photoluminescence from GaAs/AlGaAs quantum wells are performed. A microscopic theory is developed to analyze the experiments. Detailed experiment-theory comparisons reveal a remarkable magnetic-field controllability of the Coulomb and terahertz interactions in the excitonic system.
Computing Reachable Sets as Capture-Viability Kernels in Reverse Time  [PDF]
No?l Bonneuil
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.311219
Abstract: The set SF(x0;T) of states y reachable from a given state x0 at time T under a set-valued dynamic x’(t)∈F(x (t)) and under constraints x(t)∈K where K is a closed set, is also the capture-viability kernel of x0 at T in reverse time of the target {x0} while remaining in K. In dimension up to three, Saint-Pierre’s viability algorithm is well-adapted; for higher dimensions, Bonneuil’s viability algorithm is better suited. It is used on a large-dimensional example.
Three Dimensional Evolution of SN 1987A in a Self-Gravitating Disk  [PDF]
L. Zaninetti
International Journal of Astronomy and Astrophysics (IJAA) , 2013, DOI: 10.4236/ijaa.2013.32010
Abstract:

The introduction of an exponential or power law gradient in the interstellar medium (ISM) allows to produce an asymmetric evolution of the supernova remnant (SNR) when the framework of the thin layer approximation is adopted. Unfortunately both the exponential and power law gradients for the ISM do not have a well defined physical meaning. The physics conversely is well represented by an isothermal self-gravitating disk of particles whose velocity is everywhere Maxwellian. We derived a law of motion in the framework of the thin layer approximation with a control parameter of the swept mass. The photon’s losses, which are often neglected in the thin layer approximation, are modeled trough velocity dependence. The developed framework is applied to SNR 1987A and the three observed rings are simulated.

The Luminosity Function of Galaxies as Modeled by a Left Truncated Beta Distribution  [PDF]
L. Zaninetti
International Journal of Astronomy and Astrophysics (IJAA) , 2014, DOI: 10.4236/ijaa.2014.41013
Abstract: A first new luminosity function of galaxies can be built starting from a left truncated beta probability density function, which is characterized by four parameters. In the astrophysical conversion, the number of parameters increases by one, due to the addition of the overall density of galaxies. A second new galaxy luminosity function is built starting from a left truncated beta probability for the mass of galaxies once a simple nonlinear relationship between mass and luminosity is assumed; in this case the number of parameters is six because the overall density of galaxies and a parameter that regulates mass and luminosity are added. The two new galaxy luminosity functions with finite boundaries were tested on the Sloan Digital Sky Survey (SDSS) in five different bands; the results produce a better fit than the Schechter luminosity function in two of the five bands considered. A modified Schechter luminosity function with four parameters has been also analyzed.
On the Dark Matter’s Halo Theoretical Description  [PDF]
L. M. L. M. Chechin
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.35052
Abstract: We argued that the standard field scalar potential couldn’t be widely used for getting the adequate galaxies’ curve lines and determining the profiles of dark matter their halo. For discovering the global properties of scalar fields that can describe the observable characteristics of dark matter on the cosmological space and time scales, we propose the simplest form of central symmetric potential celestial-mechanical type, i.e. U(φ) = –μ/φ. It was shown that this potential allows get rather satisfactorily dark matter profiles and rotational curves lines for dwarf galaxies. The good agreement with some previous results, based on the N-body simulation method, was pointed out. A new possibility of dwarf galaxies’ masses estimation was given, also.
Analytical Approximation to the Dynamics of a Binary Stars System with Time Depending Mass Variation  [PDF]
Gustavo V. López, Elkin L. López
Journal of Applied Mathematics and Physics (JAMP) , 2018, DOI: 10.4236/jamp.2018.63053
Abstract: We study the classical dynamics of binary stars when there is an interchange of mass between them. Assuming that one of the stars is more massive than others, the dynamics of the lighter one is analyzed as a function of its time depending mass variation. Within our approximations and models for mass transference, we obtain a general result which establishes that if the lightest star looses mass, its period increases. If the lightest star wins mass, its period decreases.
Quantization and Stable Attractors in a DissipativeOrbital Motion  [PDF]
Daniel L. Nascimento, Antonio L. A. Fonseca
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.24030
Abstract: We present a method for determining the motion of an electron in a hydrogen atom, which starts from a field Lagrangean foundation for non-conservative systems that can exhibit chaotic behavior. As a consequence, the problem of the formation of the atom becomes the problem of finding the possible stable orbital attractors and the associated transition paths through which the electron mechanical energy varies continuously until a stable energy state is reached.
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