A note on the magnetic spatial forcing of a ferrofluid layer

We report on the response of a thin layer of ferrofluid to a spatially modulated magnetic field. This field is generated by means of a constant current in a special arrangement of aluminum wires. The full surface profile of the liquid layer is recorded by means of the absorption of X-rays. The outcome is analyzed particularly with regard to the magnetic self focusing effect under a deformable fluid layer

How do farmers research and learn? The example of organic farmers’ experiments and innovations: A research concept

Experimenting, adapting and innovating are central features of farmers’ activities all over the world. Farmers hold valuable knowledge about their environment, they actively do experiments, and have their own research traditions. The development of organic farming systems is continually evolving through the experiments and innovations of organic farmers. So far, there has been little attempt to study the nature, characteristics, and factors associated with the experimental processes of farmers in a systematic, comprehensive way. A current research project investigates learning processes of organic farmers in Austria, Cuba and Israel through researching the multifaceted experiments they conduct and the innovations they obtain as possible results. This paper presents the research concept of the project

Magnetic traveling-stripe-forcing: enhanced transport in the advent of the Rosensweig instability

A new kind of contactless pumping mechanism is realized in a layer of ferrofluid via a spatio-temporally modulated magnetic field. The resulting pressure gradient leads to a liquid ramp, which is measured by means of X-rays. The transport mechanism works best if a resonance of the surface waves with the driving is achieved. The behavior can be understood semi-quantitatively by considering the magnetically influenced dispersion relation of the fluid.Comment: 6 Pages, 8 Figure

Experimente von Biobäuerinnen und Biobauern in Österreich

Farmers’ experiments can be defined as the activity of trying or introducing something totally or partially new at the farm, including evaluation of the success or failure. In this research, topics, motives, methods and evaluation strategies of farmers’ experiments are investigated. Personal interviews were conducted with 73 organic farmers (47 semi-structured interviews, 26 structured questionnaire interviews). Organic farmers in Austria were found to experiment in a broad range of topics. To evaluate the experiments, all farmers conducted observation, and most of them also comparisons. Farmers experiment to find own creative solutions for their specific conditions and emerging problems. It is advisable to support farmers in their experimentation activities, provide room for experimentation within regulatory frameworks and to make active use of the outcomes of farmers’ experiments for the development of local agricultural systems

Structured cooperation in computer based collaborative Learning

Es wird der Frage nachgegangen, inwieweit hochstrukturierte kooperative Lernmethoden zur Förderung computerunterstützten kollaborativen Lernens genutzt werden können. Solche Methoden geben Regeln für das Dialogverhalten vor und haben sich in traditionellen face-to-face-Gruppen bewährt. In einer experimentellen Untersuchung wurde in einem telematischen Setting eine Kooperationsstruktur vorgegeben, die mittels Kommunikationsschnittstelle das Dialogverhalten kooperativer Paare gemäß dem Prinzip des gegenseitigen Erklärens regelt. Teilnehmer waren 30 Studenten verschiedener Fachrichtungen. Es zeigte sich im Vergleich zu einer Kontrollgruppe von ebenfalls 30 Studenten ein geringerer Koordinationsaufwand bei der gemeinsamen Aufgabenbearbeitung und ein effektiveres Dialogverhalten im Sinne eines geringeren Anteils an Aussagen zur Dialogsteuerung. Außerdem ergab sich eine Verbesserung der Problemlöseperformanz und des Wissenserwerbs aufgrund der gemeinsamen Aufgabenbearbeitung. (DIPF/Orig.

Glassy dynamics of polymethylphenylsiloxane in one- and two-dimensional nanometric confinement

Glassy dynamics of polymethylphenylsiloxane (PMPS) is studied by broadband dielectric spectroscopy in one-dimensional (1D) and two-dimensional (2D) nanometric confinement; the former is realized in thin polymer layers having thicknesses down to 5 nm, and the latter in unidirectional (thickness 50 µm) nanopores with diameters varying between 4 and 8 nm. Based on the dielectric measurements carried out in a broad spectral range at widely varying temperatures, glassy dynamics is analyzed in detail in 1D and in 2D confinements with the following results: (i) the segmental dynamics (dynamic glass transition) of PMPS in 1D confinement down to thicknesses of 5 nm is identical to the bulk in the mean relaxation rate and the width of the relaxation time distribution function; (ii) additionally a well separated surface induced relaxation is observed, being assigned to adsorption and desorption processes of polymer segments with the solid interface; (iii) in 2D confinement with native inner pore walls, the segmental dynamics shows a confinement effect, i.e., the smaller the pores are, the faster the segmental dynamics; on silanization, this dependence on the pore diameter vanishes, but the mean relaxation rate is still faster than in 1D confinement; (iv) in a 2D confinement, a pronounced surface induced relaxation process is found, the strength of which increases with the decreasing pore diameter; it can be fully removed by silanization of the inner pore walls; (v) the surface induced relaxation depends on its spectral position only negligibly on the pore diameter; (vi) comparing 1D and 2D confinements, the segmental dynamics in the latter is by about two orders of magnitude faster. All these findings can be comprehended by considering the density of the polymer; in 1D it is assumed to be the same as in the bulk, hence the dynamic glass transition is not altered; in 2D it is reduced due to a frustration of packaging resulting in a higher free volume, as proven by ortho-positronium annihilation lifetime spectroscopy

Data transformation for rank reduction in multi-trait MACE model for international bull comparison

Since many countries use multiple lactation random regression test day models in national evaluations for milk production traits, a random regression multiple across-country evaluation (MACE) model permitting a variable number of correlated traits per country should be used in international dairy evaluations. In order to reduce the number of within country traits for international comparison, three different MACE models were implemented based on German daughter yield deviation data and compared to the random regression MACE. The multiple lactation MACE model analysed daughter yield deviations on a lactation basis reducing the rank from nine random regression coefficients to three lactations. The lactation breeding values were very accurate for old bulls, but not for the youngest bulls with daughters with short lactations. The other two models applied principal component analysis as the dimension reduction technique: one based on eigenvalues of a genetic correlation matrix and the other on eigenvalues of a combined lactation matrix. The first one showed that German data can be transformed from nine traits to five eigenfunctions without losing much accuracy in any of the estimated random regression coefficients. The second one allowed performing rank reductions to three eigenfunctions without having the problem of young bulls with daughters with short lactations