Structural Changes in Tribo-Stressed Zinc Polyphosphates

The influences of pressure, shear stress and temperature on the structure of zinc orthophosphate and zinc metaphosphate was investigated. Tribological tests were performed to study the combined effect of pressure and shear stress at two temperatures. Friction tests were carried out in the boundary lubrication regime from dispersions of zinc polyphosphates in base oil. The effects of pressure alone were investigated using a diamond anvil cell in order to separate it from those of shearing. Raman spectroscopy was used to follow in situ or ex situ the structural changes of the zinc polyphosphate powders and the tribo-stressed areas. Tribofilms obtained with both polyphosphates display a partial and full depolymerization of the zinc metaphosphate at ambient and high (120 °C) temperature, respectively. The large stress and strain conditions of the tribological tests are necessary to induce a tribochemical reaction between zinc metaphosphate and iron oxide leading to a depolymerization of the phosphate in the tribofilm. The tribochemical reaction and antiwear tribofilm formation are significantly enhanced by the modest temperature increase from ambient to 120 °C. Pressure alone induces only disordering in the structure of zinc polyphosphates, with only minor changes of the chain length in phosphates and does not contribute significantly to the observed structural changes in tribofilms.     

Ecological risk assessment of urban and industrial systems: a review

Numerous ecological risk assessment methodologies have been developed over the last twenty years around the world for evaluating urban and industrial systems and installations, by both the organisations responsible for implementing regulations and the scientific community. Although these methodologies share the general principle underlying their use, they differ widely with respect to the approaches chosen and the resources employed to apply them. Also, they may even have different objectives: prior assessment as part of an impact study before building a new installation, or retrospective assessment, for example, in view to explaining the reasons for an impact recorded or for forecasting additional expected impacts.This article provides a synthesis of the different approaches used around the world for carrying out each of the major steps common to all ecological risk assessment methodologies. The advantages and limitations of these different options are discussed in order to provide elements for formulating any new methodology adapted to a given scenario. To conclude, perspectives for improving the tools required for these methodologies are proposed, and the research works to which priority should be given are identified.     

Antiwear Chemistry of ZDDP: Coupling Classical MD and Tight-Binding Quantum Chemical MD Methods (TB-QCMD)

Zinc dialkyl dithiophosphate (ZDDP) is an antiwear additive for steel surfaces currently used in most of engine oils. The mechanism by which the additive is active is based on tribochemical reactions. These reactions occur in the contact zone under the combined effects of pressure and shear. These reactions are predictable on the basis of the HSAB principle (or Chemical Hardness model). We show here that computer simulations can describe the reactions much more accurately than the HSAB principle thanks to the use of a hybrid technique, coupling classical MD and tight-binding quantum chemical MD. In this study, we focused on one of the basic tribochemical reactions of ZDDP: the ability of zinc polyphosphate to react with abrasive metal oxides nanoparticles under pressure and shear. Results show that the driving forces for the reaction are mainly the increases of molecular shearing and entropy, besides temperature. We also studied the case of other metal oxide particles that emanate from elements of addition in steel compositions. We show that manganese and chromium oxides are eliminated in the same way as iron oxides, being in agreement with experimental data obtained by X-ray microanalysis and FIB-TEM characterizations. Eventually, we investigated the case of Al/Si alloys and showed that alumina particles can hardly be digested by zinc phosphate, at the opposite of silica particles. This explains very well why ZDDP is not a good antiwear additive for aluminium alloys and why the presence of silicon grain in the alloy is favourable.     

Chemistry of ZDDP Tribofilm by ToF-SIMS

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) (static and dynamic modes) has been applied to chemical characterization of zinc dithiophosphate additives tribofilm. Main result concerns insights in the spatial distribution of phosphate and sulphide species in the whole tribofilm thickness, at a sub-micrometer scale. The disappearance of oxide layer at the interface between steel and the tribofilm is also noticed.     

Bimodal X‐ray and Infrared Imaging of an Organometallic Derivative of Praziquantel in Schistosoma mansoni

An organometallic derivative of praziquantel was studied directly in worms by using inductively coupled plasma‐mass spectrometry (ICP‐MS) for quantification and synchrotron‐based imaging. X‐ray fluorescence (XRF) and IR absorption spectromicroscopy were used for the first time in combination to directly locate this organometallic drug candidate in schistosomes. The detection of both CO (IR) and Cr (XRF) signatures proved that the Cr(CO)₃ core remained intact in the worms. Images showed a preferential accumulation at the worm's tegument, consistent with a possible targeting of the calcium channel but not excluding other biological targets inside the worm.     

Microwave-assisted synthesis of prebiotic di-D-fructose dianhydride-enriched caramels

The synthesis of prebiotic caramels involving the use of microwaves as the activating/heating source has been achieved. The yields in di-fructose dianhydrides (DFAs) in caramels were measured. The aim of this study was twofold: first to check the feasibility of the process, and second to determine the conditions to obtain an optimum response with microwave heating. The study showed that it was possible to obtain a yield of almost 50% of DFAs in a reaction time that was 10 times shorter than a previous study; i.e. 5–10 min for microwave activation compared to 60–120 min for conventional heating. It was shown that the radiation time and the radiation power were linked. The simultaneous determination of the values of these two factors was therefore necessary to obtain significant yields. This technique demonstrates the advantage of activation for mixtures such as caramels.     

Low-friction tribofilm formed by the reaction of ZDDP on iron oxide

An iron oxide layer (mixture of Fe₃O₄ and FeO) was formed by water-vapor treatment on tool steel plates. Bearing steel cylinders were slid against the plates in PAO with and without 1% zinc dialkyldithiophosphate (ZDDP) at 80 °C. The friction coefficient was below 0.06–0.08 with ZDDP, which is more than 20% lower than that without ZDDP and about a half of a steel/steel contact under the same condition. The formation of multi-layered tribofilm of 30–130 nm on the iron oxide was identified by TEM. The bottom part of the tribofilm is a layer of 10–30 nm that contains Zn, Fe, S, P, and O with a gradient composition, where distribution peaks of Zn and S were found by EDX.     

CYP2D6 PCR 基因型与DXT表型和基因芯片检测的比较1

目的: 为了评价 CYP2D6 的基因型和表型的联系以及基因芯片在 CYP2D6 多基因分析中的应用。方法: 242 健康志愿者, 口服 dextromethorphan 后收集尿液测定其代谢率, 收集 20 ml 血提取DNA, 并通过基 因 特 异性 PCR 和/(或) 基 因芯 片 分 析CYP2D6 *2———*11, *17 和多拷贝 CYP2D6 基因, 其中 5 个基因(*3、*4、*6、*7 和 *9) 用 PCR和CYD450 基因芯片同时分析。 结果: CYP2D6 基因型比表型更富有信息和更能反映 CYP2D6 酶的表达。 CYP2D6 *3、*4、*6、*7 和*9 的基因检测在CYP450基因芯片和基因特异性 PCR 中显示高度的一致性。结论: 基因芯片在检测基因多位点的多基因中是一个有发展前途和可靠的方法。     

Hypoxia as a Stimulus for the Maturation of Meniscal Cells: Highway to Novel Tissue Engineering Strategies?

The meniscus possesses low self-healing properties. A perfect regenerative technique for this tissue has not yet been developed. This work aims to evaluate the role of hypoxia in meniscal development in vitro. Menisci from neonatal pigs (day 0) were harvested and cultured under two different atmospheric conditions: hypoxia (1% O₂) and normoxia (21% O₂) for up to 14 days. Samples were analysed at 0, 7 and 14 days by histochemical (Safranin-O staining), immunofluorescence and RT-PCR (in both methods for SOX-9, HIF-1α, collagen I and II), and biochemical (DNA, GAGs, DNA/GAGs ratio) techniques to record any possible differences in the maturation of meniscal cells. Safranin-O staining showed increments in matrix deposition and round-shape “fibro-chondrocytic” cells in hypoxia-cultured menisci compared with controls under normal atmospheric conditions. The same maturation shifting was observed by immunofluorescence and RT-PCR analysis: SOX-9 and collagen II increased from day zero up to 14 days under a hypoxic environment. An increment of DNA/GAGs ratio typical of mature meniscal tissue (characterized by fewer cells and more GAGs) was observed by biochemical analysis. This study shows that hypoxia can be considered as a booster to achieve meniscal cell maturation, and opens new opportunities in the field of meniscus tissue engineering.