King eider wing molt: inferences from stable isotope analyses

Thesis (M.S.) University of Alaska Fairbanks, 2004The western North American population of the king eider is thought to have declined by over 50% between 1974 and 1996 without an apparent cause. The non-breeding period of king eiders consists of 80-100% of their annual cycle if not impossible by observation. I used stable carbon and nitrogen isotope values of feathers and muscle to examine the wing molt and migration ecology of king eiders in 2003. Eider primary feathers were isotopically homogenous along the length of the feather, implying invariable diets during wing molt. Captive eiders in their hatch-year did not fractionate nitrogen isotopes, potentially indicating preferential protein allocation associated with growth. Six percent of female eiders sampled molted primary feathers on their breeding grounds, which had not been previously substantiated. Tissue samples from both genders corroborated dietary shifts inherent in switching from a marine to terrestrial diet. Carbon isotopes of feathers from satellite-transmittered males were correlated with longitude of their known wing molt locations indicating that the gradient of carbon isotopes can be used to draw inferences about molt location of eiders

Elastometry of deflated capsules elastic moduli from shape and wrinkle analysis

Elastic capsules, prepared from droplets or bubbles attached to a capillary (as in a pendant drop tensiometer), can be deflated by suction through the capillary. We study this deflation and show that a combined analysis of the shape and wrinkling characteristics enables us to determine the elastic properties in situ. Shape contours are analyzed and fitted using shape equations derived from nonlinear membrane-shell theory to give the elastic modulus, Poisson ratio and stress distribution of the membrane. We include wrinkles, which generically form upon deflation, within the shape analysis. Measuring the wavelength of wrinkles and using the calculated stress distribution gives the bending stiffness of the membrane. We illustrate this method on two very different capsule materials: polymerized octadecyltrichlorosilane (OTS) capsules and hydrophobin (HFBII) coated bubbles. Our results are in agreement with the available rheological data. For hydrophobin coated bubbles the method reveals an interesting nonlinear behavior consistent with the hydrophobin molecules having\ud a rigid core surrounded by a softer shell

he Effects of Informal Social Structures: A Cognition–Structure–Action Approach

The purpose of this article is to examine the effects of epistemic motives and social structures on individual actions and the implications for organizational outcomes. It has been suggested that the informal social structures that develop within organizations affect the behavior of individuals, perhaps more so than formal structure. If this is true, when studying organizations it may be important to examine the effects of informal social structures on individual actions and organizational outcomes. Drawing on findings from epistemic motive theory and expanding social capital theory, a cognition–structure–action model is introduced as a way to begin systematically examining the informal structure of relations that form within organizations on individual behavior. A multilevel perspective is used to examine the interrelationships between formal organizational structures and epistemic motivation and the formation of informal social structure. This article contributes to network research by examining potential cognitive antecedents to network structure

Surface moisture increases microcracking and water vapour permeance of apple fruit skin

Surface moisture induces microcracking in the cuticle of fruit skins. Our objective was to study the effects of surface moisture on cuticular microcracking, the permeance to water vapour and russeting in developing ‘Pinova’ apple fruit. Surface moisture was applied by fixing to the fruit a plastic tube containing deionized water. Microcracking was quantified by fluorescence microscopy and image analysis following infiltration with acridine orange. Water vapour permeance was determined gravimetrically using skin segments (ES) mounted in diffusion cells. Cumulative water loss through the ES increased linearly with time. Throughout development, surface moisture significantly increased skin permeance. The effect was largest during early development and decreased towards maturity. Recovery time courses revealed that following moisture treatment of young fruit for 12 days, skin permeance continued to increase until about 14 days after terminating the moisture treatment. Thereafter, skin permeance decreased over the next 28 days, then approaching the control level. This behaviour indicates gradual healing of the impaired cuticular barrier. Nevertheless, permeance still remained significantly higher compared with the untreated control. Similar patterns of permeance change were observed following moisture treatments at later stages of development. The early moisture treatment beginning at 23 DAFB resulted in russeting of the exposed surfaces. There was no russet in control fruit without a tube or in control fruit with a tube mounted for 12 days without water. The data demonstrate that surface moisture increases microcracking and water vapour permeance. This may lead to the formation of a periderm and, hence, a russeted fruit surface

Stationary shapes of deformable particles moving at low Reynolds numbers

Lecture Notes of the Summer School ``Microswimmers -- From Single Particle Motion to Collective Behaviour'', organised by the DFG Priority Programme SPP 1726 (Forschungszentrum J{\"{u}}lich, 2015).Comment: Pages C7.1-16 of G. Gompper et al. (ed.), Microswimmers - From Single Particle Motion to Collective Behaviour, Lecture Notes of the DFG SPP 1726 Summer School 2015, Forschungszentrum J\"ulich GmbH, Schriften des Forschungszentrums J\"ulich, Reihe Key Technologies, Vol 110, ISBN 978-3-95806-083-