Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSb2−x_{2-x}Tex_x

Substitution of Sb in FeSb$_2$ by less than 0.5% of Te induces a transition from a correlated semiconductor to an unconventional metal with large effective charge carrier mass $m^*$. Spanning the entire range of the semiconductor-metal crossover, we observed an almost constant enhancement of the measured thermopower compared to that estimated by the classical theory of electron diffusion. Using the latter for a quantitative description one has to employ an enhancement factor of 10-30. Our observations point to the importance of electron-electron correlations in the thermal transport of FeSb$_2$, and suggest a route to design thermoelectric materials for cryogenic applications.Comment: 3 pages, 3 figures, accepted for publication in Appl. Phys. Lett. (2011

A class of well-posed parabolic final value problems

This paper focuses on parabolic final value problems, and well-posedness is proved for a large class of these. The clarification is obtained from Hilbert spaces that characterise data that give existence, uniqueness and stability of the solutions. The data space is the graph normed domain of an unbounded operator that maps final states to the corresponding initial states. It induces a new compatibility condition, depending crucially on the fact that analytic semigroups always are invertible in the class of closed operators. Lax--Milgram operators in vector distribution spaces constitute the main framework. The final value heat conduction problem on a smooth open set is also proved to be well posed, and non-zero Dirichlet data are shown to require an extended compatibility condition obtained by adding an improper Bochner integral.Comment: 16 pages. To appear in "Applied and numerical harmonic analysis"; a reference update. Conference contribution, based on arXiv:1707.02136, with some further development

A critique of full reserve banking

Proposals for full reserve banking have been put forward as a radical way of preventing further financial crises. They rest on the argument that crises are caused by excessive money supply growth brought about by inadequately controlled bank credit creation. Our aim is to provide a critique of the theoretical assumptions underlying the plans for full reserve banking. In particular some of the plans rely on the view that the money supply is a key causal variable and that it is feasible for central banks to identify and enforce an optimal quantity. Second, the plans all rely on an unsupported confidence in the efficiency of financial markets outside the centrally controlled banking system. Third, by removing profit-making opportunities from banks, the proposals may unduly tip the balance further in favour of shadow banking. Finally, as the case of 95% liquidity requirements on Kaupthing, Singer and Friedlander in the wake of the Great Financial Crash shows that modern financial engineering makes such policy-making difficult to execute. A Minskyan analysis rather emphasises the inherent instability of the financial system such that it is subject to systemic crises and the indeterminacy of demand for liquidity, while also emphasising the contribution prudent banking can make to financing economic activity and providing a safe money asset. While a return to a traditional separation of retail banking (regulated and supported by the central bank) from investment banking (regulated differently but not supported) would contribute to financial stability, it is argued that the full reserve banking proposals go too far

Vertical migration, feeding and colouration in the mesopelagic shrimp Sergestes arcticus

Intraspecific variation in vertical distribution, timing of vertical migration, and colouration of the mesopelagic shrimp Sergestes arcticus were studied in the >400 m deep part of Masfjorden, Norway. Very few individuals were caught in the upper strata during daytime, and larger individuals occurred deeper during the day than smaller ones. Vertical migration was prominent and no overall trend of increasing length with depth was found at night. Small individuals arrived in the upper layers earlier than larger ones. Animal colouration assessed by digital photography revealed significant variance in individual redness. Depth of capture was the most important factor explaining colouration, with increasing degree of redness with depth. Assessing the gut fullness of the transparent shrimps provided a rapid way of estimating feeding activity and showed that feeding took place mainly at night

Direct analysis of microbial populations in soil and freshwater aquifers using nucleic acid based techniques

The first DNA-based methods for direct quantification of soil protozoa, and a DNA-based quantification method to describe the spread of phenanthrene-degrading bacteria in soil and freshwater aquifers, have recently been developed at the BIOPRO Research Centre at the Geological Survey of Denmark and Greenland (GEUS). Well-known genes for phenoxyalcanoic acid degradation have been used to monitor the in situ degradation of phenoxyalcanoic acid pesticides. Studies have been initiated on the short-lived mRNA molecules that are expected to provide a shortcut to the understanding of low, yet important, microbial activity in geological samples. This article reviews recent developments in techniques based on analysis of nucleic acids from soils and aquifers. Analytical work has been carried out mainly on soil samples from a former asphalt production plant at Ringe (Fig. 1). The Ringe plant constitutes one of the most polluted industrial sites in Denmark, and is a priority site of studies by the BIOPRO Research Centre. Although rich in carbon, the Ringe subsoil is an oligotrophic environment due to the high content of polycyclic aromatic hydrocarbons (PAH). This is an environment where the supply of nutrients to microorganisms is low, leading to slow growth, low total numbers of microorganisms and small cells. To study microbial communities of oligotrophic environments, analytical methods with low detection limits are needed. Until recently, microorganisms of natural environments were mainly studied by cultivation-dependent methods. However, microorganisms that can be cultured on agar plates are now known to represent only a small fraction of the total microbial community. Modern methods, therefore, need to be based on the detection of biomolecules in the microorganisms rather than being dependent on growth of the microorganisms. The best available techniques are based on DNA and RNA molecules (Fig. 2), which due to their high level of resolution allow closely related organisms or functional genes to be distinguished. In the following review, examples are given of applications of these nucleic acid based methods