Feeding ecology of sprat (Sprattus sprattus L.) and sardine (Sardina pilchardus W.) larvae in the German Bight, North Sea

The abundance of the sardine in the North Sea suddenly increased after 1995. Since 2002, the sardine has been spawning regularly in the German Bight, and all its life stages can be found in the area. The larval feeding ecology of two small pelagic clupeiform species with very similar life histories was investigated, the particular aim being to determine signs of food overlap. The distribution and feeding of sprat and sardine larvae were investigated during late spring 2003 on two transects covering a wide range of environmental conditions in the German Bight. Larvae co-occurred at all the stations investigated. Sprat and sardine larvae shared a wide range of prey types. Gut fullness and feeding success were similar in both species; however, potential food competition is avoided to some extent by different habitat preferences

Goldstone Mode Relaxation in a Quantum Hall Ferromagnet due to Hyperfine Interaction with Nuclei

Spin relaxation in quantum Hall ferromagnet regimes is studied. As the initial non-equilibrium state, a coherent deviation of the spin system from the ${\vec B}$ direction is considered and the breakdown of this Goldstone-mode state due to hyperfine coupling to nuclei is analyzed. The relaxation occurring non-exponentially with time is studied in terms of annihilation processes in the "Goldstone condensate" formed by "zero spin excitons". The relaxation rate is calculated analytically even if the initial deviation is not small. This relaxation channel competes with the relaxation mechanisms due to spin-orbit coupling, and at strong magnetic fields it becomes dominating.Comment: 8 page

Key signal contributions in photothermal deflection spectroscopy

We report on key signal contributions in photothermal deflection spectroscopy (PDS) of semiconductors at photon energies below the bandgap energy and show how to extract the actual absorption properties from the measurement data. To this end, we establish a rigorous computation scheme for the deflection signal including semi-analytic raytracing to analyze the underlying physical effects. The computation takes into account linear and nonlinear absorption processes affecting the refractive index and thus leading to a deflection of the probe beam. We find that beside the linear mirage effect, nonlinear absorption mechanisms make a substantial contribution to the signal for strongly focussed pump beams and sample materials with high two-photon absorption coefficients. For example, the measured quadratic absorption contribution exceeds 5% at a pump beam intensity of about ${1.3}\times{10^{5}}\;{W}/{cm^{2}}$ in Si and at ${5}\times{10^{4}}\;{W}/{cm^{2}}$ in GaAs. In addition, our method also includes thermal expansion effects as well as spatial gradients of the attenuation properties. We demonstrate that these effects result in an additional deflection contribution which substantially depends on the distance of the photodetector from the readout point. This distance dependent contribution enhances the surface related PDS signal up to two orders of magnitude and may be misinterpreted as surface absorption if not corrected in the analysis of the measurement data. We verify these findings by PDS measurements on crystalline silicon at a wavelength of 1550 nm and provide guidelines how to extract the actual attenuation coefficient from the PDS signal.Comment: 10 pages, 16 figures, submitted to Journal of Applied Physiv

Exploring standardisation and knowledge networking processes in transnational human resource management.

Purpose – It is argued that a key step in becoming a “transnational” company is to implement transnational HRM (THRM). However, what is meant by THRM and how can it be assessed? The purpose of this paper is to develop the characteristics of THRM along two dimensions: standardisation and knowledge networking, in contrast to many existing studies which focus on IHRM strategies and structures. Standardisation and knowledge networking are to be examined at both the meta and operational levels. Design/methodology/approach – The paper is based on two case studies of major German MNCs, both with significant operations in Spain and the UK. Data were collected by means of semi-structured interviews with senior managers, HR managers and labour representatives. Findings – The findings show that THRM can be operationalised using knowledge networking and standardisation on a meta level, in terms of principles, and at an operational level in terms of practices. The two firms show differences in the process and intensity of HR knowledge networking which have implications for the level of standardisation, local autonomy and innovation capabilities. The findings also suggests that THRM is more about processes than outcomes. Research limitations/implications – A limitation of this study is that the cases were only drawn from Western Europe. The patterns of THRM structures and processes may differ significantly in MNCs from other regions. Originality/value – This paper extends existing research by exploring international HR beyond strategies and structures and focuses on communication and coordination processes. It advocates a refined view of the transnational firm

Quadratic form theory over preordered von Neumann-regular rings

AbstractTo each pair, 〈R,T〉, consisting of a unitary commutative von Neumann-regular ring, R, where 2 is a unit and T is a preorder on R, we associate a reduced special group, GT(R), which faithfully reflects quadratic form theory, modulo T, over free R-modules and then show, using the representation of R as the ring of global sections of its affine scheme, together with results from [M. Dickmann, F. Miraglia, On quadratic forms whose total signature is zero mod 2n. Solution to a problem of M. Marshall, Invent. Math. 133 (1998) 243–278; M. Dickmann, F. Miraglia, Lam's Conjecture, Algebra Colloq. 10 (2003) 149–176; M. Dickmann, F. Miraglia, Algebraic K-theory of special groups, J. Pure Appl. Algebra 204 (2006) 195–234], that GT(R) satisfies a powerful K-theoretic property, the [SMC]-property. From this we conclude that quadratic form theory modulo T over free R-modules verifies Marshall's signature conjecture, Lam's conjecture, as well as a reduced version of Milnor's Witt ring conjecture

Orders and Relative Pythagorean Closures

Orders and Relative Pythagorean Closure

Sensor Concept for Controlled Laser Cleaning via Photodiode

Abstract. In the field of laser cleaning of artworks the effect of “over-cleaning” is a commonly well known problem. The detection of laser induced plasma is one possibility in order to identify the kind of material just being irradiated by the laser beam. LIBS is a powerful method for the extraction of spectral information. Instead the detection of the plasma intensity contains much less information. However, this can be realised by using a fast photodiode. It has turned out that for several applications in laser cleaning of artworks a reliable identification of layers during the cleaning process is possible. In cooperation with restorers we proved that this low-cost method may be used for online monitoring as well as automated closed loop cleaning.

Comment on "Spin relaxation in quantum Hall systems"

W. Apel and Yu.A. Bychkov have recently considered the spin relaxation in a 2D quantum Hall system for the filling factor close to unity [PRL v.82, 3324 (1999)]. The authors considered only one spin flip mechanism (direct spin-phonon coupling) among several possible spin-orbit related ones and came to the conclusion that the spin relaxation time due to this mechanism is quite short: around $10^{-10}$ s at B=10 T (for GaAs). This time is much shorter than the typical time ($10^{-5}$ s) obtained earlier by D. Frenkel while considering the spin relaxation of 2D electrons in a quantizing magnetic field without the Coulomb interaction and for the same spin-phonon coupling. I show that the authors' conclusion about the value of the spin-flip time is wrong and have deduced the correct time which is by several orders of magnitude longer. I also discuss the admixture mechanism of the spin-orbit interaction.Comment: 1 pag