Dynamo quenching due to shear flow

We provide a theory of dynamo (α effect) and momentum transport in three-dimensional magnetohydrodynamics. For the first time, we show that the α effect is reduced by the shear even in the absence of magnetic field. The α effect is further suppressed by magnetic fields well below equipartition (with the large-scale flow) with different scalings depending on the relative strength of shear and magnetic field. The turbulent viscosity is also found to be significantly reduced by shear and magnetic fields, with positive value. These results suggest a crucial effect of shear and magnetic field on dynamo quenching and momentum transport reduction, with important implications for laboratory and astrophysical plasmas, in particular, for the dynamics of the Sun

Effect of solvent, host precursor, dopant concentration and crystallite size on the fluorescence properties of Eu(III) doped yttria

A systematic spectroscopic study of Eu3+ doped yttria powder phosphors are reported. Fluorescence study of this system has been investigated under the different solvent systems, e.g ethanol and water. In this study, the effect of the precursor of yttria, e.g. acetate, nitrate and chloride, on the fluorescence behaviour of Eu3+ have been observed in particular. Attention was paid to their effect on the emission intensity of the 5D0 -> 7F2 transition which is characteristic of the \u27red fluorescence\u27 of the Eu3+ ion. Results show that the CH3COO- ion has a tremendous effect on the enhancement of emission intensity, greater than NO3- and Cl- ions. The Fourier transformed infrared (FTIR) spectroscopy was used for chemical and structural analysis. It has also been stated that the concentration quenching of dopant was more pronounced in the powders derived from yttrium chloride than from yttria precursor. In the case of Y(CH3COO)3 as a precursor, the concentration quenching was totally absent and emission intensity increased with an increase in the concentration of dopant. This paper also includes some interesting results on the effect of modifiers, which are a mixture of Tween-80 with ε-caprolactum/ β-alanine/emulsogen-OG, on the 5D0 -> 7F2 transition of Eu3+ doped yttria in terms of crystallite size in brief

Representation of acoustic communication signals by insect auditory receptor neurons

Despite their simple auditory systems, some insect species recognize certain temporal aspects of acoustic stimuli with an acuity equal to that of vertebrates; however, the underlying neural mechanisms and coding schemes are only partially understood. In this study, we analyze the response characteristics of the peripheral auditory system of grasshoppers with special emphasis on the representation of species-specific communication signals. We use both natural calling songs and artificial random stimuli designed to focus on two low-order statistical properties of the songs: their typical time scales and the distribution of their modulation amplitudes. Based on stimulus reconstruction techniques and quantified within an information-theoretic framework, our data show that artificial stimuli with typical time scales of >40 msec can be read from single spike trains with high accuracy. Faster stimulus variations can be reconstructed only for behaviorally relevant amplitude distributions. The highest rates of information transmission (180 bits/sec) and the highest coding efficiencies (40%) are obtained for stimuli that capture both the time scales and amplitude distributions of natural songs. Use of multiple spike trains significantly improves the reconstruction of stimuli that vary on time scales <40 msec or feature amplitude distributions as occur when several grasshopper songs overlap. Signal-to-noise ratios obtained from the reconstructions of natural songs do not exceed those obtained from artificial stimuli with the same low-order statistical properties. We conclude that auditory receptor neurons are optimized to extract both the time scales and the amplitude distribution of natural songs. They are not optimized, however, to extract higher-order statistical properties of the song-specific rhythmic patterns

Preparing the Ne(x)t Generation: Lessons learnt from Free / Libre Open Source Software Why free and open are pre-conditions and not options for higher

With reference to round table discussions on ‘preparing the new generation’ and ‘renewing knowledge creation’ this paper will illustrate why higher education (HE) needs to reposition itself to be prepared for the ne(x)t generation and which are the lessons to be learnt from well established virtual and informal open participatory learning ecosystems, in particular the Free / Libre Open and Source Software (FLOSS) communities. As has become clear; FLOSS communities succeed in providing and distributing in a sustainable manner the knowledge necessary for the production of good quality software, thereby using a different development approach than proprietary software producers. One characteristic of FLOSS is that it is built by a community of volunteers and frequently backed by companies that generate their revenues by providing services related to FLOSS projects and the software.Peer Reviewe