Tiller recruitment, survival, growth and reproductive effort were monitored in a highly competitive bunchgrass to contrast the demographic effects of nonuse and dormant season burning with and without subsequent defoliation. The number of tillers recruited were largest during the fall, decreased through the winter and spring, and were smallest during the summer. Tiller mortality was highest during the summer, tillers surviving until fall usually completed senescence the following spring. Biomass accumulation and reproductive effort predominantly occurred during the summer rainfall season. Summer growth and reproduction began earlier and were enhanced by dormant season burning. Defoliation increased summer tiller recruitment and advanced by one month fall tiller recruitment. The wide range of tiller weight-density relationships which occurred among treatments followed the -3/2 Power Law. This species' competitiveness and ability to tolerate grazing is attributable to its ability to respond with plasticity along the -3/2 self-thinning line.

Univ., Diss.--Frankfurt/Main, 2001. / Literaturverz. S. [328] - 346.

Thesis--Kiel. / Bibliography of W. Lehmann's works: p. 264-267. Bibliographical references included in "Anmerkungen" (p. 269-324).

Dissertation--Philosophische Fakultät--München, 1972. / Notes bibliogr.

Thesis (doctoral)--Université d'Aix-Marseille I, 1977. / Includes indexes. Includes bibliographical references (v. 2, p. [801]-877).

Diss. med. Bern, 1998.

Inaug.-Diss.--Leipzig. / Vita. "Separat-abdruck aus Wundt, Philosophische studien, 7. Bd., 1. Heft."

Inaug.-Diss.--Leipzig. / Vita. "Separat-abdruck aus Wundt, Philosophische studien, 7. Bd., 1. Heft."

Circular or Angular data occur in many fields of applied statistics. A common problem of interest in circular data is estimating a preferred direction and its corresponding distribution. This problem is complicated by the so-called wrap-around effect, which exists because there is no minimum or maximum on the circle. The usual statistics employed for linear data are inappropriate for directional data, as they do not account for the circular nature of directional data. Common choices for summarizing the preferred direction are the sample circular mean, and sample circular median. A newly proposed circular analog of the Hodges-Lehmann estimator is proposed, as an alternative estimate of preferred direction. The new measure of preferred direction is a robust compromise between circular mean and circular median. Theoretical results show that the new measure of preferred direction is asymptotically more efficient than the circular median and that its asymptotic efficiency relative to the circular mean is quite comparable. Descriptions of how to use the methods for constructing confidence intervals and testing hypotheses are provided. Simulation results demonstrate the relative strengths and weaknesses of the new approach for a variety of distributions. / Ph. D.

Cette thèse porte sur l’effet Lehmann, un effet hors d’équilibre couplant un gradient de température avec la rotation de la texture de gouttes cholestériques ou nématiques coexistant avec la phase isotrope. Nous avons d’abord caractérisé les couplages thermomécaniques de Leslie, Akopyan et Zel’dovich en mesurant en phase cholestérique la vitesse de rotation des molécules dans deux configurations invariantes par translation avec des orientations différentes.Nous avons ensuite caractérisé la texture des gouttes observées dans l’expérience de Lehmann en nous basant sur des observations optiques et des simulations numériques. Plus important, nous avons montré pour la première fois qu’il est possible d’observer l’effet Lehmann dans des gouttes nématiques achirales, à condition que la texture interne soit torsadée. Nous avons aussi utilisé un montage de photoblanchiment afin de montrer qu’il n’y a pas d’écoulements visibles au voisinage des gouttes. Ceci montre que la rotation observée est due à une rotation locale des molécules – pas à une rotation solide des gouttes.Enfin, nous avons proposé un modèle théorique « à la Leslie » de l’effet Lehmann incluant les termes de couplage thermomécanique d’Akopyan et Zel’dovich. En appliquant ce modèle généralisé aux textures calculées numériquement, nous avons ajusté les vitesses de rotation mesurées expérimentalement et avons trouvé des valeurs pour les constantes de couplage thermomécanique bien plus grandes que celles mesurées en dessous de la transition cholestérique/isotrope. Cela montre que ce modèle est faux et que le paradigme de Leslie doit être définitivement abandonné. / This thesis is focused on the Lehmann effect, an out-of-equilibrium effect which couples a temperature gradient with the rotation of the internal texture of liquid crystal droplets in coexistence with the isotropic phase. First, we characterized the thermomechanical couplings of Leslie, Akopyan and Zel'dovich by measuring the rotation velocity of the molecules in two translationally invariant configurations withdifferent orientations, below the cholesteric/isotropic transition.Then, we characterized the texture of the droplets observed in the Lehmann experiment, both usingoptical observations and numerical simulations. More important, we showed for the first time that it is possible to observe the Lehmann effect in achiral nematic droplets, providing that the internal texture ischiral. We also used a photobleaching experiment to show that there is no visible flow in the vicinity ofthe droplet, which implies that the texture rotation is due to a local rotation of the molecules -- not to asolid rotation of the droplet. Finally, we proposed a theoretical model of the Lehmann effect based on the thermomechanical coupling of Leslie, Akopyan and Zel’dovich. By applying this model to the numerically computed textures, we fitted the measured rotation velocities and found values for the thermomechanical coupling constants much bigger than those measured below the cholesteric/isotropic transition. This shows that this model is incorrect and that the Leslie paradigm must be abandoned.