Effects over one year of low-intensity endurance exercise targeted at the level of maximal lipid oxidation

International audienc

Crystal structure of synthetic Mg3Cr2Si3O12, the high-pressure Cr end-member of the knorringite-pyrope garnet series

Knorringite, the Cr-end-member of the pyrope garnet series (Nixon et al. 1968), often occur in high proportions in kimberlite garnets and is thus used for tracing high-pressure deep-earth conditions favorable to the formation of diamonds, in which knorringite-rich garnet can occur as inclusions. However, although the synthesis of knorringite is reported in the literature (Ringwood 1977; Irifune et al. 1982; Taran et al. 2004), the structure of the pure end-member has not been yet determined from experimental data. In this study, the crystal structure of knorringite, Mg3Cr2(SiO4)3, has been refined from high resolution synchrotron X-ray powder diffraction data recorded under ambient conditions on a polycrystalline sample synthesized at 12 GPa in a multi-anvil apparatus. The structure is cubic, space group Ia-3d, a = 11.5935(1), V = 1558.27(4) {\AA}3, dcalc = 3.97 g.cm-3. The Cr-O distance of 1.957(2) {\AA} is consistent with EXAFS results on the same sample. This short distance indicates a substantial compression of the CrO6 octahedron, compared to ambient pressure Cr3+-minerals such as uvarovite ( = 1.99 {\AA}, Andrut and Wildner 2002). Our experimental results thus confirm early empirical predictions based on series of high-pressure Cr-garnet end-members (Fursenko 1981), showing that the values of the Cr-O distance and the Cr-O-Si angle decrease with the augmentation of pressure and with the diminution of the size of the divalent cation

On Limitations of the Ultrasonic Characterization of Pieces Manufactured with Highly Attenuating Materials

Some technical aspects of two Spanish cooperation projects, funded by DPI and Innpacto Programs of the R&D National Plan, are discussed. The objective is to analyze the common belief about than the ultrasonic testing in MHz range is not a tool utilizable to detect internal flaws in highly attenuating pieces made of coarse-grained steel. In fact high-strength steels, used in some safe industrial infrastructures of energy & transport sectors, are difficult to be inspected using the conventional “state of the art” in ultrasonic technology, due to their internal microstructures are very attenuating and coarse-grained. It is studied if this inspection difficulty could be overcome by finding intense interrogating pulses and advanced signal processing of the acquired echoes. A possible solution would depend on drastically improving signal-to-noise-ratios, by applying new advances on: ultrasonic transduction, HV electronics for intense pulsed driving of the testing probes, and an “ad-hoc” digital processing or focusing of the received noisy signals, in function of each material to be inspected. To attain this challenging aim on robust steel pieces would open the possibility of obtaining improvements in inspecting critical industrial components made of highly attenuating & dispersive materials, as new composites in aeronautic and motorway bridges, or new metallic alloys in nuclear area, where additional testing limitations often appear.The Spanish I+D National Plan (MINECO), by funding the Projects: Fundamental Research / DPI2011 – 22438, and INNPACTO Program / IMAAD - IPT-020000-2010-0004

Possible Patient Early Diagnosis by Ultrasonic Noninvasive Estimation of Thermal Gradients into Tissues Based on Spectral Changes Modeling

To achieve a precise noninvasive temperature estimation, inside patient tissues, would open promising research fields, because its clinic results would provide early-diagnosis tools. In fact, detecting changes of thermal origin in ultrasonic echo spectra could be useful as an early complementary indicator of infections, inflammations, or cancer. But the effective clinic applications to diagnosis of thermometry ultrasonic techniques, proposed previously, require additional research. Before their implementations with ultrasonic probes and real-time electronic and processing systems, rigorous analyses must be still made over transient echotraces acquired from well-controlled biological and computational phantoms, to improve resolutions and evaluate clinic limitations. It must be based on computing improved signal-processing algorithms emulating tissues responses. Some related parameters in echo-traces reflected by semiregular scattering tissues must be carefully quantified to get a precise processing protocols definition. In this paper, approaches for non-invasive spectral ultrasonic detection are analyzed. Extensions of author's innovations for ultrasonic thermometry are shown and applied to computationally modeled echotraces from scattered biological phantoms, attaining high resolution (better than 0.1°C). Computer methods are provided for viability evaluation of thermal estimation from echoes with distinct noise levels, difficult to be interpreted, and its effectiveness is evaluated as possible diagnosis tool in scattered tissues like liver

Molecular dynamics simulation of radiation damage in glasses

Molecular dynamics simulations of the ballistic effects arising from displacement cascades in glasses have been investigated in silica and in a SiO 2 -B 2 O 3 -Na 2 O glass. In both glasses the T-O-T′ angle (where T and T′ are network formers) diminishes, despite radiation causes opposite effects: while the ternary glass swells and silica becomes denser. We show that radiation-induced modifications of macroscopic glass properties result from structural change at medium/range, reflecting an increasing disorder and internal energy of the system. A local thermal quenching model is proposed to account for the effects of ballistic collisions. The core of a displacement cascade is heated by the passage of the projectile, then rapidly quenched, leading to a process that mimics a local thermal quenching. The observed changes in both the mechanical and structural properties of glasses eventually reach saturation at 2 10 18 α/g as the accumulated energy increases. The passage of a single projectile is sufficient to reach the maximum degree of damage, confirming the hypothesis postulated in the swelling model proposed by J.A.C. Marples

X-ray Linear Dichroism in cubic compounds: the case of Cr3+ in MgAl2O4

The angular dependence (x-ray linear dichroism) of the Cr K pre-edge in MgAl2O4:Cr3+ spinel is measured by means of x-ray absorption near edge structure spectroscopy (XANES) and compared to calculations based on density functional theory (DFT) and ligand field multiplet theory (LFM). We also present an efficient method, based on symmetry considerations, to compute the dichroism of the cubic crystal starting from the dichroism of a single substitutional site. DFT shows that the electric dipole transitions do not contribute to the features visible in the pre-edge and provides a clear vision of the assignment of the 1s-->3d transitions. However, DFT is unable to reproduce quantitatively the angular dependence of the pre-edge, which is, on the other side, well reproduced by LFM calculations. The most relevant factors determining the dichroism of Cr K pre-edge are identified as the site distortion and 3d-3d electronic repulsion. From this combined DFT, LFM approach is concluded that when the pre-edge features are more intense than 4 % of the edge jump, pure quadrupole transitions cannot explain alone the origin of the pre-edge. Finally, the shape of the dichroic signal is more sensitive than the isotropic spectrum to the trigonal distortion of the substitutional site. This suggests the possibility to obtain quantitative information on site distortion from the x-ray linear dichroism by performing angular dependent measurements on single crystals

Early diagenetic vivianite [Fe-3(PO4)(2) center dot 8H(2)O] in a contaminated freshwater sediment and insights into zinc uptake: a mu-EXAFS, mu-XANES and Raman study

The sediments in the Salford Quays, a heavily-modified urban water body, contain high levels of organic matter, Fe, Zn and nutrients as a result of past contaminant inputs. Vivianite [Fe3(PO4)2 · 8H2O] has been observed to have precipitated within these sediments during early diagenesis as a result of the release of Fe and P to porewaters. These mineral grains are small (<100 μm) and micron-scale analysis techniques (SEM, electron microprobe, μ-EXAFS, μ-XANES and Raman) have been applied in this study to obtain information upon the structure of this vivianite and the nature of Zn uptake in the mineral. Petrographic observations, and elemental, X-ray diffraction and Raman spectroscopic analysis confirms the presence of vivianite. EXAFS model fitting of the FeK-edge spectra for individual vivianite grains produces Fe–O and Fe–P co-ordination numbers and bond lengths consistent with previous structural studies of vivianite (4O atoms at 1.99–2.05 Å; 2P atoms at 3.17–3.25 Å). One analysed grain displays evidence of a significant Fe3+ component, which is interpreted to have resulted from oxidation during sample handling and/or analysis. EXAFS modelling of the Zn K-edge data, together with linear combination XANES fitting of model compounds, indicates that Zn may be incorporated into the crystal structure of vivianite (4O atoms at 1.97 Å; 2P atoms at 3.17 Å). Low levels of Zn sulphate or Zn-sorbed goethite are also indicated from linear combination XANES fitting and to a limited extent, the EXAFS fitting, the origin of which may either be an oxidation artifact or the inclusion of Zn sulphate into the vivianite grains during precipitation. This study confirms that early diagenetic vivianite may act as a sink for Zn, and potentially other contaminants (e.g. As) during its formation and, therefore, forms an important component of metal cycling in contaminated sediments and waters. Furthermore, for the case of Zn, the EXAFS fits for Zn phosphate suggest this uptake is structural and not via surface adsorption

Organisational participation and women - an attitude problem?

Employee participation is a dynamic and contested area of organisational behaviour, attracting continuing academic, practitioner and policy interest and debate. This chapter focuses on organisational participation and women

Basic biochemical investigations as rationale for the design of original antimalarial drugs. An example of phospholipid metabolism

The future of antimalarial chemotherapy is particulary alarming in view of the spread of parasite cross-resistances to drugs that are not even structurally related. Only the availability of new pharmacological models will make it possible to select molecules with novel mechanisms of action, thus delaving resistance and allowing the development of new chemotherapeutic strategies. We reached this objective in mice. Our approach is hunged on fundamental and applied research begun in 1980 to investigate to phospholipid (PL) metabolism of intraerythrocytic Plasmodium. This metabolism is abundant, specific and indispensable for the production of Plasmodium membranes. Any drug to interfere with this metabolism blocks parasitic development. The most effective interference yet found involves blockage of the choline transporter, which supplies Plasmodium with choline for the synthesis of phosphatidylcholine, its major PL, this is a limiting step in the pathway. The drug sensitivity thereshold is much lower for the parasite, which is more dependent on this metabolism than host cells. The compounds show in vitro activity against P. falciparum at 1 to 10 nM. They show a very low toxicity against a lymphblastoid cell line, demonstrating a total abscence of correlation between growth inhibition of parasites and lymphoblastoid cells. They show antimalarial activity in vivo, in the P. berghei or P. chabaudi/mouse system, at doses 20-to 100-fold lower than their in acute toxicity limit. The bioavailability of a radiolabeled form of the product seemed to be advantageous (slow blood clearance and no significant concentration in tissues). Lastly, the compounds are inexpensive to produce. They are stable and water-soluble