Combined energy -- diffraction data refinement of decagonal AlNiCo

We incorporate realistic pair potential energies directly into a non-linear least-square fit of diffraction data to quantitatively compare structure models with experiment for the Ni-rich $d$(AlNiCo) quasicrystal. The initial structure models are derived from a few {\it a priori} assumptions (gross features of the Patterson function) and the pair potentials. In place of the common hyperspace approach to the structure refinement of quasicrystals, we use a real-space tile decoration scheme, which does not rely on strict quasiperiodicity, and makes it easy to enforce sensible local arrangements of the atoms. Inclusion of the energies provides information complementary to the diffraction data and protects the fit procedure from converging on spurious solutions. The method pinpoints sites which are likely to break the symmetry of their local environment.Comment: 7 pages, 5 figures, proceedings of the Internation Conference on Quasicrystals, Bangalore, India, August 200

The role of the dentate gyrus and adult neurogenesis in hippocampal-basal ganglia associated behaviour

The ability of the brain to continually generate new neurons throughout life is one of the most intensely researched areas of modern neuroscience. While great advancements in understanding the biochemical mechanisms of adult neurogenesis have been made, there remain significant obstacles and gaps in connecting neurogenesis with behavioural and cognitive processes such as learning and memory. The purpose of the thesis was to examine by review and laboratory experimentation the role of the dentate gyrus and of adult neurogenesis within the hippocampus in the performance of cognitive tasks dependent on the hippocampal formation and hippocampal-basal ganglia interactions. Advancement in understanding the role of neurogenesis in these processes may assist in improving treatments for common brain injury and cognitive diseases that affect this region of the brain. Mild chronic stress reduced the acquisition rate of a stimulus-response task (p=0.043), but facilitated the acquisition of a discrimination between a small and a large reward (p=0.027). In locomotor activity assays, chronic stress did not shift the dose-response to methamphetamine. Analysis of 2,5-bromodeoxyuridine incorporation showed that, overall, chronic mild stress did not effect survival of neuronal progenitors . However, learning of the tasks had a positive influence on cell survival in stressed animals (p=0.038). Microinjections of colchicine produced significant lesions of the dentate gyrus and surrounding CA1-CA3 and neocortex. Damage to these regions impaired hippocampal-dependent reference memory (p=0.054) while preserving hippocampal independent simple discrimination learning. In a delay discounting procedure, the lesions did not induce impulsive-like behaviour when delay associated with a large reward was introduced. The experiments uphold a current theory that learning acts as a buffer to mitigate the negative effects of stress on neurogenesis

Exploring the role of instrument design and instrument interaction for eco-innovation: a survey-based analysis of renewable energy innovation in Germany

Empirical research on eco-innovation has produced a substantive body of literature on the relevance of regulation for stimulating such innovation. Much of this work on the role of policy for eco-innovation relies on econometric analyses of company survey data. In this regard, the eco-innovation module introduced in 2008/9 in the Community Innova-tion Survey serves as an important data source that has helped improve our under-standing of the role of environmental and innovation policy for eco-innovation in the Eu-ropean Union (EU). However, so far, this data source has provided only limited oppor-tunities to generate insights into the role of instrument design and instrument interaction for eco-innovation. In this chapter, we present a first attempt to measure such aspects in a company innovation survey based on the example of renewable energy innovation in Germany. In particular, we explore to what extent the design of the German Renewa-ble Energy Sources Act (and the interaction of its feed-in tariffs with the EU emissions trading system) correlates with innovation in renewable power generation technologies. We find instrument design features but not instrument type to be related to eco-innovation. In addition, our exploratory study provides evidence for an interaction effect between climate policy and renewables support policy. Based on these findings, we discuss implications for future research on the role of policy in eco-innovation

Functionalized Imidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquids for Gas Sensors: Solubility of H2, O2 and SO2

Gas solubilities of non-polar (hydrogen and oxygen) and polar (sulphur dioxide) gases in a set of functionalized alkyl imidazolium ionic liquids with the bis(trifluoromethylsulfonyl)imide ([NTFf2]−) anion are reported between 303 and 333 K at 1 bar. The alkyl side-chains in the imidazolium cations include different functional groups, such as –OH, –CN and benzyl; their effects on gas solubilities were studied. The solubility decreases with temperature for all gases, as expected for an exothermic dissolution. Sulphur dioxide is by far the most soluble gas, with mole fractions between 0.29 and 0.41 in the ionic liquids at 313 K and 1 bar, approximately 2–3 orders of magnitude higher than the two other gases studied. Oxygen is generally more soluble in the ionic liquids than hydrogen with mole fractions ranging from 9 × 10−4 to 21 × 10−4 and 5 × 10−4 to 15 × 10−4 at 313 K and 1 bar for oxygen and hydrogen, respectively. In the case of hydrogen, the solubility increases when the molar volume of the ionic liquid increases, whereas for oxygen, the presence of polar groups in the cation causes a reduction in the solubility. None of the three gases is chemically absorbed in the ionic liquids

Intergranular films in Si3N4 studied by TEM

Like many ceramic materials, Si3N4 contains amorphous intergranular films (IGFs). These films affect or even dominate the properties of the ceramic material. As a result of the sintering process the amorphous IGFs in Si3N4 ceramics contain oxides of silicon and other elements. These additional elements are also observed in amorphous pockets where three or more grains meet. To obtain information about the local atomic structure of the IGFs we employ electron diffraction with a convergent probe focussed on the IGF. This method provides the reduced radial distribution function G(r) within the films and thereby a fingerprint of the atomic structure. We have studied Si3N4 containing oxygen as an additional element. Our first results show that the order in both pockets and IGFs is closely related to amorphous SiO2, with little if any nitrogen. This suggests SiO2 as the main constituent in the pockets as well as in the interfaces. In Y2O3 doped material, the G(r) indicates the presence of yttrium in the IGF