Orbital-selective metal-insulator transition and gap formation above TC in superconducting Rb(1-x)Fe(2-y)Se2

Understanding the origin of high-temperature superconductivity in copper- and iron-based materials is one of the outstanding tasks of current research in condensed matter physics. Even the normal metallic state of these materials exhibits unusual properties. Here we report on a hierarchy of temperatures T(c)<T(gap)<T(met) in superconducting Rb(1-x)Fe(2-y)Se(2) observed by THz spectroscopy (T(c)=critical temperature of the superconducting phase; T(gap)=temperature below which an excitation gap opens; T(met)=temperature below which a metallic optical response occurs). Above T(met)=90 K the material reveals semiconducting characteristics. Below T(met) a coherent metallic THz response emerges. This metal-to-insulator-type, orbital-selective transition is indicated by an isosbestic point in the temperature dependence of the optical conductivity and dielectric constant at THz frequencies. At T(gap)= 61 K, a gap opens in the THz regime and then the superconducting transition occurs at T(c)=32 K. This sequence of temperatures seems to reflect a corresponding hierarchy of the electronic correlations in different bands.

Cadmium uptake in Elodea canadensis leaves and its interference with extra- and intra-cellular pH

This study investigated cadmium (Cd) uptake in Elodea canadensis shoots under different photosynthetic conditions, and its effects on internal (cytosolic) and external pH. The plants were grown under photosynthetic (light) or non-photosynthetic (dark or in the presence of a photosynthetic inhibitor) conditions in the presence or absence of CdCl2 (0.5 μm) in a medium with a starting pH of 5.0. The pH-sensitive dye BCECF-AM was used to monitor cytosolic pH changes in the leaves. Cadmium uptake in protoplasts and leaves was detected with a Cd-specific fluorescent dye, Leadmium Green AM, and with atomic absorption spectrophotometry. During cultivation for 3 days without Cd, shoots of E. canadensis increased the pH of the surrounding water, irrespective of the photosynthetic conditions. This medium alkalisation was higher in the presence of CdCl2 . Moreover, the presence of Cd also increased the cation exchange capacity of the shoots. The total Cd uptake by E. canadensis shoots was independent of photosynthetic conditions. Protoplasts from plants exposed to 0.5 μm CdCl2 for 3 days did not exhibit significant change in cytosolic [Cd(2+)] or pH. However, exposure to CdCl2 for 7 days resulted in increased cytosolic [Cd(2+) ] as well as pH. The results suggest that E. canadensis subjected to a low CdCl2 concentration initially sequesters Cd into the apoplasm, but under prolonged exposure, Cd is transported into the cytosol and subsequently alters cytosolic pH. In contrast, addition of 10-50 μm CdCl2 directly to protoplasts resulted in immediate uptake of Cd into the cytosol.

Trait selection and welfare of genetically engineered animals in agriculture

The release of the Final Guidance from the US Food and Drug Administration on the commercialization of genetically engineered animals has sparked renewed discussion over the ethical, consumer, and regulatory implications of transgenesis in animal agriculture. Animal welfare critiques have focused on unexpected phenotypic effects in animals used in transgenic research, rather than on the health and welfare implications of the intended productivity enhancement. Unless breeding goals are redefined to reflect social concerns, the occurrence and magnitude of undesirable side effects may increase and consumer confidence in the nascent technology may be undermined.

Influence of temperature and salinity on heavy metal uptake by submersed plants

Submersed plants can be useful in reducing heavy metal concentrations in stormwater, since they can accumulate large amounts of heavy metals in their shoots. To investigate the effects of water temperature and salinity on the metal uptake of two submersed plant species, Elodea canadensis (Michx.) and Potamogeton natans (L.), these plants were grown in the presence of Cu, Zn, Cd, and Pb at 5, 11, and 20 degrees C in combination with salinities of 0, 0.5, and 5 per thousand. The metal concentrations in the plant tissue increased with increasing temperature in both species; the exception was the concentration of Pb in Elodea, which increased with decreasing salinity. Metal concentrations at high temperature or low salinity were up to twice those found at low temperature or high salinity. Plant biomass affected the metal uptake, with low biomass plants having higher metal concentrations than did high biomass plants.