Defects in Chiral Columnar Phases: Tilt Grain Boundaries and Iterated Moire Maps

Biomolecules are often very long with a definite chirality. DNA, xanthan and poly-gamma-benzyl-glutamate (PBLG) can all form columnar crystalline phases. The chirality, however, competes with the tendency for crystalline order. For chiral polymers, there are two sorts of chirality: the first describes the usual cholesteric-like twist of the local director around a pitch axis, while the second favors the rotation of the local bond-orientational order and leads to a braiding of the polymers along an average direction. In the former case chirality can be manifested in a tilt grain boundary phase (TGB) analogous to the Renn-Lubensky phase of smectic-A liquid crystals. In the latter case we are led to a new "moire" state with twisted bond order. In the moire state polymers are simultaneously entangled, crystalline, and aligned, on average, in a common direction. In the moire state polymers are simultaneously entangled, crystalline, and aligned, on average, in a common direction. In this case the polymer trajectories in the plane perpendicular to their average direction are described by iterated moire maps of remarkable complexity, reminiscent of dynamical systems.Comment: plain TeX, (33 pages), 17 figures, some uufiled and included, the remaining available at ftp://ftp.sns.ias.edu/pub/kamien/ or by request to [email protected]

Perspectives and challenges for the use of radar in biological conservation

Radar is at the forefront for the study of broad-scale aerial movements of birds, bats and insects and related issues in biological conservation. Radar techniques are especially useful for investigating species which fly at high altitudes, in darkness, or which are too small for applying electronic tags. Here, we present an overview of radar applications in biological conservation and highlight its future possibilities. Depending on the type of radar, information can be gathered on local- to continental-scale movements of airborne organisms and their behaviour. Such data can quantify flyway usage, biomass and nutrient transport (bioflow), population sizes, dynamics and distributions, times and dimensions of movements, areas and times of mass emergence and swarming, habitat use and activity ranges. Radar also captures behavioural responses to anthropogenic disturbances, artificial light and man-made structures. Weather surveillance and other long-range radar networks allow spatially broad overviews of important stopover areas, songbird mass roosts and emergences from bat caves. Mobile radars, including repurposed marine radars and commercially dedicated ‘bird radars’, offer the ability to track and monitor the local movements of individuals or groups of flying animals. Harmonic radar techniques have been used for tracking short-range movements of insects and other small animals of conservation interest. However, a major challenge in aeroecology is determining the taxonomic identity of the targets, which often requires ancillary data obtained from other methods. Radar data have become a global source of information on ecosystem structure, composition, services and function and will play an increasing role in the monitoring and conservation of flying animals and threatened habitats worldwide

Laboratoire de zoologie marine de Marseille (Station maritime d'Endoume)

Marion , Gourret P. Laboratoire de zoologie marine de Marseille (Station maritime d'Endoume). In: Rapport sur l'École pratique des hautes études, 1888-1889. 1888. pp. 109-113

Laboratoire de zoologie marine de Marseille (Station maritime d'Endoume)

Marion , Gourret P. Laboratoire de zoologie marine de Marseille (Station maritime d'Endoume). In: Rapport sur l'École pratique des hautes études, 1888-1889. 1888. pp. 109-113

6. Laboratoire de zoologie maritime de Marseille (Station maritime d'Endoume)

Marion , Gourret P. 6. Laboratoire de zoologie maritime de Marseille (Station maritime d'Endoume). In: Rapport sur l'École pratique des hautes études, 1893-1894. 1893. pp. 73-74

6. Laboratoire de zoologie maritime de Marseille (Station maritime d'Endoume)

Marion , Gourret P. 6. Laboratoire de zoologie maritime de Marseille (Station maritime d'Endoume). In: Rapport sur l'École pratique des hautes études, 1893-1894. 1893. pp. 73-74

8. Laboratoire de zoologie maritime de Marseille

Marion , Gourret P. 8. Laboratoire de zoologie maritime de Marseille. In: Rapport sur l'École pratique des hautes études, 1892-1893. 1892. p. 64

8. Laboratoire de zoologie maritime de Marseille

Marion , Gourret P. 8. Laboratoire de zoologie maritime de Marseille. In: Rapport sur l'École pratique des hautes études, 1889-1892. 1889. pp. 130-134