Nonlinear Dynamics of a Single Ferrofluid-Peak in an Oscillating Magnetic Field

If a magnetic field normal to the surface of a magnetic fluid is increased beyond a critical value a spontaneous deformation of the surface arises (normal field instability). The instability is subcritical and leads to peaks of a characteristic shape. We investigate the neighborhood of this instability experimentally under the influence of a temporal modulation of the magnetic field. We use a small vessel, where only one peak arises. The modulation can either be stabilizing or destabilizing, depending on the frequency and amplitude. We observe a cascade of odd-numbered response-periods up to period 11, and also a domain of even-numbered periods. We propose a minimal model involving a cutoff-condition which captures the essence of the experimental observations. PACS: 47.20.-k, 47.20.Ky, 75.50.Mm Keywords: magnetic fluid; nonlinear oscillator; subharmonic response; surface instability;Comment: 13 pages, 12 Postscript figures, LaTeX, uses elsart.sty, to be published in Physica

Dynamics of a Single Peak of the Rosensweig Instability in a Magnetic Fluid

To describe the dynamics of a single peak of the Rosensweig instability a model is proposed which approximates the peak by a half-ellipsoid atop a layer of magnetic fluid. The resulting nonlinear equation for the height of the peak leads to the correct subcritical character of the bifurcation for static induction. For a time-dependent induction the effects of inertia and damping are incorporated. The results of the model show qualitative agreement with the experimental findings, as in the appearance of period doubling, trebling, and higher multiples of the driving period. Furthermore a quantitative agreement is also found for the parameter ranges of frequency and induction in which these phenomena occur.Comment: 21 pages, 9 figures, using elsart, submitted to Physica D; revised version with 2 figures and references adde

Chemical, Natural, and Cultural Control of \u3ci\u3eHyadaphis Tataricae\u3c/i\u3e (Homoptera: Aphididae) on Honeysuckle

Hyadaphis tataricae is an aphid pest of honeysuckle relatively new to the Great Lakes and midwestern regions of North America. Feeding results in severly deformed terminals (witches\u27 brooms). Studies were conducted on natural, chemical, and cultural control. Foliar-applied systemic insecticides provided excellent knock-down and 3-4 weeks of residual control. Although diazinon also provided good knock-down, its residual activity was shorter. Malathion provided suppression but did not protect plants from injury. A tree and shrub soap wash did not provide control. Oxydemeton methyl provided best results of soil-applied systemics. Of 385 aphidophagous predators collected, 85% were syrphid larvae. The remainder were Coccinellidae and Chrysopidae. About 140,000 aphids were examined microscop- ically without visual evidence of insect pathogens and with only one mummified (parasitized) individual. Dormant pruning of previously broomed terminals resulted in increased vegetative growth of the plants and larger early season aphid populations. There was no visible difference in pruned vs. unpruned plants at the end of the growing season

SWEETENER TRADE ISSUES: A VIEW FROM CAPITOL HILL

International Relations/Trade,

User characteristics for customer involvement in innovation processes : deconstructing the Lead User-concept

Despite the growing evidence of the beneficial nature of customer and user involvement in new product or service development, research into user types and customer characteristics for innovation is still scarce. One notable exception can be found in the literature dealing with the so-called Lead User. Although there is a substantial research corpus dealing with Lead User innovation, the integration of Lead Users or Lead User-methods is definitely not common within most firms. We believe that disentangling the Lead Userconcept into more concrete user types and customer characteristics would benefit and optimize user involvement in innovation processes. Within this paper, we describe six user types based on five dimensions, associated with the Lead User-concept and abstracted from various literature streams. We further propose some guidelines for an optimal integration of these users within innovation methodologies and sketch out some lines for future research

A fourfold typology of living labs: an empirical investigation amongst the ENoLL community

Living Labs can be seen as a means to structure user involvement in innovation processes. However, in this rather young research domain, there is no consensus yet regarding supporting theories and frameworks. This has resulted in a wide variety of projects and approaches being called ‘Living Labs’, which leaves a clear conceptualization and definition a task in progress. Within this research paper we propose a fourfold categorization of Living Labs based on a literature review and validated by an empirical investigation of the characteristics of 64 ICT Living Labs from the European Network of Living Labs (ENoLL). The four types are Living Labs for collaboration and knowledge support activities, original ‘American’ Living Labs, Living Labs as extension to testbeds and Living Labs that support context research and co-creation with users

Prediction Models for Flight Activity of the Cranberry Girdler (Lepidoptera: Pyralidae) in Wisconsin

Cranberry girdler, Chrysoteuchia topiaria, was monitored with pheromone traps in Wisconsin cranberry farms. Cumulative 50% capture was related to degree-days after first catch using air or soil temperature. An air temperature of O°C and soil temperature of 2°C were chosen as base temperatures for calculation of degree-days because they yielded estimates with the lowest coefficients of variation. Weibull functions were fitted to the relation- ship between cumulative percent capture and time or degree-days after first trap catch using air or soil temperatures. The models that predicted the date of 50% capture were evaluated with data from two other farms. Degree-days after first catch using soil temperatures predicted 50% catch with less variability than calendar date or degree-days after thaw of ice. but not significantly less variability than days after first catch or degree-days after first catch using air temperatures

Development of Cranberry Girdler, \u3ci\u3eChrysoteuchia Topiaria\u3c/i\u3e (Lepidoptera: Pyraliadae) in Relation to Temperature

The development of Chrysoteuchia topiaria was studied in controlled-temperature chambers. Estimates of the threshold temperatures for the egg, larval, and prepupal-pupal stages were 9.4,6.8, and 9.8°C, respectively. An overall threshold temperature for egg to adult development was estimated to be 8.8°C. Degree-day summations above thresholds averaged 107, 484, and 388 for the egg, larval, and prepupal-pupal stages, respectively