Effect of pH and ionic strength on phospholipid nanomechanics and on deposition process onto hydrophilic surfaces measured by AFM

The effect of ion-binding on a zwitterionic phospholipid such as 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) has been studied by measuring the zeta potential value of the unilamellar liposomes present in solution while varying the pH and the ionic strength in independent experiments. We have experimentally confirmed that DMPC binds cations, resulting in an increase of the zeta potential value. The liposome surface charge has been proved to have a strong effect on the supported bilayer formation on hydrophilic, negatively charged surfaces such as mica and silicon oxide as atomic force microscopy images reveal. Furthermore, thanks to force spectroscopy measurements we have proved that ion-binding also affects the nanomechanical response of the system, since it increases the force that has to be exerted on the membrane in order to puncture it. Last but not least, the nanomechanics of the bilayer does not depend on the substrate, thus implying that membrane properties are not influenced by the supporting material.     

Acute ingestion of yerba mate infusion (Ilex paraguariensis) inhibits plasma and lipoprotein oxidation

Yerba mate extract (Ilex paraguariensis) is a source of phenolic compounds that possesses in vitro antioxidant activities and may contribute to a reduction in the risk of cardiovascular disease. In this study we examined the acute effects of the consumption of mate infusion on ex vivo plasma and low-density lipoprotein (LDL) oxidation, plasma antioxidant capacity, and platelet aggregation. Twelve healthy fasted subjects ingested 500 mL of mate infusion and blood samples were collected before and 1 h after mate intake. Lipid peroxidation of plasma and LDL was monitored by the measurement of cholesteryl-ester hydroperoxides (CE-OOH) and cholesterol oxides. The plasma antioxidant capacity was measured as ferric-reducing antioxidant potential (FRAP). Platelet aggregation was evaluated in platelet-rich plasma stimulated with adenosine diphosphate and coagulation was tested in platelet-poor plasma. Ingestion of mate infusion diminished the ex vivo oxidizability of both plasma and LDL particles. After mate intake, the CE-OOH levels were around 50% lower in plasma oxidized with copper or 2,2′-azobis[2-amidine-propane-hydrochloride] (AAPH) and the lag time to plasma oxidation increased 2-fold (P < 0.05). Copper- and AAPH-induced LDL peroxidation were also inhibited by around 50% and 20%, respectively, after mate consumption (P < 0.05). The levels of various oxysterols were significantly reduced in oxidized-plasma and LDL (P < 0.05) and FRAP increased by 7.7% after mate intake (P < 0.01). However, mate consumption did not inhibit platelet aggregation or blood coagulation. In summary, intake of yerba mate infusion improved the antioxidant capacity and the resistance of plasma and LDL particles to ex vivo lipid peroxidation.     

A Novel Flow Profiling Approach Using Permanent Downhole Pressure Gauges

Flow profiling through permanent downhole pressure gauge, a novel and unique application, is proposed in the present paper. Theoretical development of the new technique is first provided. Example studies are then given to illustrate the application of the technique. Application scenarios, practical issues, as well as key impacting parameters are also addressed. Finally, a field case study implementing the new technique for a long horizontal well is performed to demonstrate how the production profiles calculated from permanent downhole gauge (PDG) data compare closely to the results from a recent production logging (PLT) survey which was expensive and mechanically risky yet turned out to be unsatisfactory.

The technique could be applied to real-time production and injection profiling for different well configurations (vertical, horizontal, deviated, and multilateral) and bring tremendous financial benefits through replacing conventional production logging surveys that could be cost-extensive for horizontal or multilateral wells offshore.     

基于多体系统理论的反弧门钢止水修复误差分析

以自制反弧门钢止水修复设备为研究对象,通过分析反弧门钢止水非线性接触密封面机械同步仿形修复误差产生的原因,运用多体系统理论建立了反弧门钢止水非线性接触密封面机械同步仿形修复误差的数学模型,找出了修复过程中的全部误差项,并得出修复过程中的主要误差为原理性误差、导轨精度误差、设备误差、砂轮磨损误差。该模型能为修复设备的优化设计提供参考依据,对反弧门钢止水修复误差补偿及修复精度的提高具有指导意义。     

子午面成型对超临界汽轮机调节级喷嘴固体颗粒冲蚀特性的影响

建立了氧化铁颗粒撞击12Cr材料高温的冲蚀率模型,并与叶栅的三维流场和固体颗粒运动特性的数值计算方法一道,计算与分析了1台超临界汽轮机调节级喷嘴顶部采用平直子午面和收缩子午面两种情况下,氧化铁颗粒对于喷嘴叶片的撞击区域和撞击参数以及喷嘴表面的冲蚀量分布,结果表明:子午面收缩能够有效地减小叶片表面上受严重侵蚀的范围并降低最大当地冲蚀量。与平直子午面喷嘴相比,受严重侵蚀的区域面积降低约60%,最大当地冲蚀量降低约1 3。图13参7     

Oxidation and diffusion study on AlCrVN hard coatings using oxygen isotopes O and O

The present work aims to investigate the oxidation behaviour of AlCrVN hard coatings of equal composition but of different crystal structure. In order to gain more information about the mechanisms that are active during oxidation, a two-stage oxidation procedure has been applied where different isotopes, ¹⁶O and ¹⁸O, were introduced in each step. The analysis by means of secondary ion mass spectrometry depth profiling with its inherent isotope selectivity provided information on the general oxidation behaviour as well as the oxygen diffusion during the oxidation process. The single-phase coating with its face-centred cubic (fcc) structure presents a higher oxidation resistance as compared to the dual-phase coating containing a wurtzite and an fcc phase. After the annealing treatment the surface of the latter is entirely covered by VO₂ and V₂O₅ as evidenced by Raman spectroscopy. The single-phase coating, on the other hand, reveals unoxidised coating material and AlVO₄ crystals. However, even though exhibiting a significantly different oxidation resistance, the oxygen diffusion is similar. In both cases the peak values of ¹⁸O, which was introduced in the second stage, were found near the oxide-nitride interface indicating that O atoms diffused through the already formed oxides. Additional experiments using a gas mixture comprising natural water vapour H₂¹⁶O and ¹⁸O₂ revealed that mainly the presence of molecular oxygen causes oxidation as with increasing water vapour partial pressure the oxide layer thickness was significantly reduced.