Effects of lanthanum and lanthanum-modified clay on growth, survival and reproduction of Daphnia magna

The novel lanthanum-modified clay water treatment technology (Phoslock^®) seems very promising in remediation of eutrophied waters. Phoslock^® is highly efficient in stripping dissolved phosphorous from the water column and in intercepting phosphorous released from the sediments. The active phosphorous-sorbent in Phoslock^® is the Rare Earth Element lanthanum. A leachate experiment revealed that lanthanum could be released from the clay, but only in minute quantities of 0.13-2.13 μg l⁻¹ for a worst-case Phoslock^® dosage of 250 mg l⁻¹. A life-history experiment with the zooplankton grazer Daphnia magna revealed that lanthanum, up to the 1000 μg l⁻¹ tested, had no toxic effect on the animals, but only in medium without phosphorous. In the presence of phosphorous, rhabdophane (LaPO₄ · nH₂O) formation resulted in significant precipitation of the food algae and consequently affected life-history traits. With increasing amounts of lanthanum, in the presence of phosphate, animals remained smaller, matured later, and reproduced less, resulting in lower population growth rates. Growth rates were not affected at 33 μg La l⁻¹, but were 6% and 7% lower at 100 and 330 μg l⁻¹, respectively, and 20% lower at 1000 μg l⁻¹. A juvenile growth assay with Phoslock^® tested in the range 0-5000 mg l⁻¹, yielded EC₅₀ (NOEC) values of 871 (100) and 1557 (500) mg Phoslock^® l⁻¹ for weight and length based growth rates, respectively. The results of this study show that no major detrimental effects on Daphnia are to be expected from Phoslock^® or its active ingredient lanthanum when applied in eutrophication control.     

In vitro safety toxicology data for evaluation of gold nanoparticles-chronic cytotoxicity, genotoxicity and uptake

Safety and toxic effects of nanoparticles are still largely unexplored due to the multiple aspects that influence their behaviour toward biological systems. Here, we focus the attention on 12 nm spherical gold nanoparticle coated or not with hyaluronic acid compared to its precursor counterpart salt. Results ranging from the effects of a 10-days exposure in an in vitro model with BALB/c 3T3 fibroblast cells show how 12 nm spherical gold nanoparticles are internalized from 3T3 cells by endo-lysosomal pathway by an indirect measurement technique; and how gold nanoparticles, though not being a severe cytotoxicant, induce DNA damage probably through an indirect mechanism due to oxidative stress. While coating them with hyaluronic acid reduces gold nanoparticles cytotoxicity and slows their cell internalization. These results will be of great interest to medicine, since they indicate that gold nanoparticles (with or without coating) are suitable for therapeutic applications due to their tunable cell uptake and low toxicity.     

The Nature of the Catalytic Sites for H2 Dissociation

Scanning Tunneling Microscopy (STM) can reveal the nature of active sites on the surface of heterogeneous catalysts. This is shown for the case of the dissociation of molecular hydrogen on Pd(111), which has been studied recently both experimentally and theoretically. STM can image in real time to generate movies of adsorbed atoms diffusing on the catalyst surface and forming aggregates. Of particular interest is the behavior near saturation coverage, a situation that is common when catalysts operate under the gas pressures typical of many industrial reactions. Under these conditions, active catalyst sites are formed as a result of density fluctuations that free atoms at the catalyst surface of adsorbates, so that they become available for new reactions. Little is known about the structure of the sites generated in this process. While the end state of a dissociative adsorption of a diatomic molecule requires at least two empty sites to accommodate the reaction products, the initial state where the molecule adsorbs and dissociates, might be more complicated and its nature is unknown. The review shows how STM can provide an improved understanding of the nature of these initial sites.     

Stabilized solution of the multidimensional advection-diffusion-absorption equation using linear finite elements

A stabilized finite element method (FEM) for the multidimensional steady state advection-diffusion-absorption equation is presented. The stabilized formulation is based on the modified governing differential equations derived via the finite calculus (FIC) method. For 1D problems the stabilization terms act as a nonlinear additional diffusion governed by a single stabilization parameter. It is shown that for multidimensional problems an orthotropic stabilizing diffusion must be added along the principal directions of curvature of the solution. A simple iterative algorithm yielding a stable and accurate solution for all the range of physical parameters and boundary conditions is described. Numerical results for 1D and 2D problems with sharp gradients are presented showing the effectiveness and accuracy of the new stabilized formulation.     

A Bis(Triazolecarboxamido) Ligand for Enantio‐ and Regioselective Molybdenum‐Catalyzed Asymmetric Allylic Alkylation Reactions

A modular, enantiomerically pure bis(1H‐1,2,3‐triazole‐4‐carboxamide) has been assembled from N,N′‐[(1R,2R)‐cyclohexane‐1,2‐diyl]dipropiolamide through a copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) reaction and evaluated as a ligand in the molybdenum‐catalyzed asymmetric allylic alkylation (MoAAA) reaction, very high regio‐ and enantioselectivities being recorded.

     

Electro-thermal characterization of a differential temperature sensor in a 65 nm CMOS IC: Applications to gain monitoring in RF amplifiers

This paper reports on the design solutions and the different measurements we have done in order to characterize the thermal coupling and the performance of differential temperature sensors embedded in an integrated circuit implemented in a 65 nm CMOS technology. The on-chip temperature increases have been generated using diode-connected MOS transistors behaving as heat sources. Temperature measurements performed with the embedded sensor are corroborated with an infra-red camera and a laser interferometer used as thermometer. A 2 GHz linear power amplifier (PA) is as well embedded in the same silicon die. In this paper we show that temperature measurements performed with the embedded temperature sensor can be used to monitor the PA DC behavior and RF activity.     

International scientific collaboration in Latin America

This study attempts to analyse the usability of international databases such as the Science Citation Index (SCI) for the observation of the international collaboration in lesser-developed countries. We have examined the adequacy of this data source (the SCI) in perceiving the international scientific activities of nine Latin American countries. We have studied the relationships of these countries with their main foreign partners in the large fields of science. It has been observed that some of these relationships are not covered by the data source under study. The creation of an information system storing complementary data suited for the identification of existing internatinal collaborative projects is recommended. In the longrange future such a system would provide more appropriate information for the analyses of international collaboration.     

Depletion of cytosolic GSH decreases the ATP levels and viability of synaptosomes from aged mice but not from young mice

The effect of glutathione depletion on the viability of freshly isolated synaptosomes from whole brain was investigated in young and aged mice. Aging did not influence the GSH and ATP levels and the viability of these synaptosomes. However depletion of glutathione caused by the cytosolic glutathione inhibitor diethyl maleate (1 mM) resulted in a significant decline, after 60 min of incubation, in ATP levels and viability in the synaptosomes from aged mice but not in those from young mice. When synaptosomes were incubated in the presence of the mitochondrial glutathione inhibitor ethacrynic acid (0.2 mM) there was a similar decline in glutathione, ATP levels and synaptosomal viability, both in young and aged mice. These results emphasize the relative importance of the cytosolic glutathione pool for the maintenance of the plasma membrane integrity in synaptosomes from aged mice.     

Structure of international collaboration in science: Typology of countries through multivariate techniques using a link indicator

In this article patterns of international collaboration in science are investigated using a specific procedure to analyse data collected from theScience Citation Index. We develop an indicator based on the scientific linkages between countries established through internationally co-authored articles (COPs). The credibility, advantages and uses of this indicator are discussed. We apply the Correspondence Factorial Analysis method and the Minimum Spanning Tree classification to this indicator in order to observe the level of resemblance and the main characteristics of the collaboration structured by 98 countries in eight principal fields of science. The results shown summarize the diverse aspects of countries participating in collaborative works and bring into view the cognitive structure of international research. The use of these methods in the investigation of international collaboration contributes to the analysis of the complex structure of the scientific communities of different countries.