稀土离子和肌质网(Ca~(2+)+Mg~(2+))-ATP酶相互作用的研究

研究了稀土离子对肌质网(Ca~(2+)+MG~(2+))-ATP酶活性的影响及其作用机制,结果表明,低浓度Gd~(3+)对肌质网膜上(Ca~(2+)+Mg~(2+)),ATP酶有激活作用,较高浓度Gd~(3+)抑制其活性,Gd~(3+)抑制纯化酶的活性,低浓度Gd~(3+)对磷脂酸(FA)、心磷脂(CL)重组酶有激活作用,而对磷脂酰胆碱(PC)、磷脂酰胆碱(PC)与磷脂酰乙醇胺(Pe)混合物(PC/PE)及磷脂酰丝氨酸(PS)重组酶无激活作用,低浓度Tb~(3+)对肌质网膜与纯化酶上Ca~(2+)结合位点的影响不同。

Influence of strain and polycrystalline ordering on magnetic properties of high moment rare earth metals and alloys

Despite being the most suitable candidates for solenoid pole pieces in state-of-the-art superconductor- based electromagnets, the intrinsic magnetic properties of heavy rare earth metals and their alloys have gained comparatively little attention. With the potential of integration in micro- and nanoscale devices, thin films of Gd, Dy, Tb, DyGd and DyTb were plasma-sputtered and investigated for their in-plane magnetic properties, with an emphasis on magnetisation vs. temperature profiles. Based on crystal structure analysis of the polycrystalline rare earth films, which consist of a low magnetic moment FCC layer at the seed interface topped with a higher moment HCP layer, an experimental protocol is introduced which allows the direct magnetic analysis of the individual layers. In line with the general trend of heavy lanthanides, the saturation magnetisation was found to drop with increasing unit cell size. In-situ annealed rare earth films exceeded the saturation magnetisation of a high-moment Fe65Co35 reference film in the cryogenic temperature regime, proving their potential for pole piece applications; however as-deposited rare earth films were found completely unsuitable. In agreement with theoretical predictions, sufficiently strained crystal phases of Tb and Dy did not exhibit an incommensurate magnetic order, unlike their single-crystal counterparts which have a helical phase. DyGd and DyTb alloys followed the trends of the elemental rare earth metals in terms of crystal structure and magnetic properties. Inter-rare-earth alloys hence present a desirable blend of saturation magnetisation and operating temperature.

Ferromagnetism in DyRh and DyRhX (X = Fe, Ni, Co, Gd) thin films

In an effort to achieve large high-field magnetization and increased Curie temperature, polycrystalline DyRh, (DyRh)95X5 and (DyRh)85X15 (X = Fe, Co, Ni, Gd) thin films have been prepared via ultra-high vacuum DC co-sputtering on SiO2 and Si wafers, using Ta as seed and cap material. A body-centred cubic CsCl-like crystal formation (B2 phase) was achieved for DyRh around the equiatomic equilibrium, known from single crystals. The maximum in-plane spontaneous magnetization at T = 4K in fields of μ0H = 5T of was found to be μ0MS,4K = (1.50 ± 0.09)T with a ferromagnetic transition at TC = (5 ± 1)K and a coercivity of μ0HC,4K[D] = (0.010 ± 0.001)T (at T = 4K) for layers deposited on substrates heated to 350°C. Samples prepared at room temperature exhibited poorer texture, smaller grains and less B2-phase content; this did impact on the Curie temperature which was higher compared to those layers with best crystallisation; however the maximal magnetization stayed unaffected. Ferromagnetic coupling was observed in ternary alloys of DyRhGd and DyRhNi with an increased Curie temperature, larger initial permeability, and
high-field magnetization which was best for (DyRh)85Gd15 with μ0MS,4K[Gd15] = (2.10 ± 0.13)T. DyRhFe and DyRhCo showed antiparallel coupling of the spontaneous magnetic moments.

Organic addittives in zinc electrowinning and electrodeposition of Fe-Mo-P alloys as cathodes for chlorate production

Ce projet de travail est divisé en deux études principales: (a) l’influence des certains additifs organiques sur la consommation d’énergie et la pureté du métal de zinc déposé dans le processus d’extraction électrolytique, et (b) l’électrodéposition des alliages binaires et ternaires de Fe-Mo et Fe-Mo-P sur des substrats d’acier doux afin d’agir comme cathodes pour la production de chlorate. (a) Parmi les sept différents additifs organiques examinés, les sels des liquides ioniques ont réussi à augmenter le rendement du courant jusqu’à 95,1% comparé à 88,7% qui a obtenu à partir de l’électrolyte standard en présence des ions de Sb3+. La réduction maximale de la consommation d’énergie de ~173 kWh tonne-1 a été obtenue en ajoutant de 3 mg dm-3 du chlorure de 1-butyl-3-méthylimidazolium dans le même électrolyte. La teneur en plomb dans le dépôt de zinc est réduite de 26,5 ppm à 5,1-5,6 ppm en utilisant les sels des liquides ioniques. (b) Des différents binaires Fe-Mo et ternaires Fe-Mo-P alliages ont été électrodéposés sur des substrats d’acier doux. Les alliages préparés ont une tenure en Mo entre 21-47 at.% et une tenure en P de 0 à 16 at.%. L’activité électrocatalytique de ces alliages vers la réaction de dégagement d’hydrogène (RDH) a été étudiée dans des solutions de chlorure de sodium. La réduction maximale de la surtension de RDH de ~313 mV a été obtenue par l’alliage ternaire préparé Fe54Mo30P16 par rapport à celle obtenue pour l’acier doux. La rugosité de surface et l’activité intrinsèque des revêtements de Fe-Mo-P peuvent être l’origine du comportement prometteur de ces électrocatalyseurs vers la RDH.

Effect of mechanical coating with Ni and Ni-5% Al on the structure and electrochemical properties of the Mg-50% Ni alloy

The Mg-Ni metastable alloys (with amorphous or nanocrystalline structures) are promising candidates for anode application in nickel-metal hydride rechargeable batteries due to its large hydrogen absorbing capacity, low weight, availability, and relative low price. In spite of these interesting features, improvement on the cycle life performance must be achieved to allow its application in commercial products. In the present paper, the effect of mechanical coating of a Mg-50 at.% Ni alloy with Ni and Ni-5 at.% Al on the structure, powder morphology, and electrochemical properties is investigated. The coating additives, Mg-Ni alloy and resulting nanocomposites (i.e., Mg-Ni alloy + additive) were investigated by means of X-ray diffraction and scanning electron microscopy. The Mg-Ni alloy and nanocomposites were submitted to galvanostatic cycles of charge and discharge to evaluate their electrode performances. The mechanical coating with Ni and Ni-5% Al increased the maximum discharge capacity of the Mg-Ni alloy from of 221 to 257 and 273 mA h g(-1), respectively. Improvement on the cycle life performance was also achieved by mechanical coating.

Structural and electrochemical characteristics of Mg((55-x))Ti(x)Ni((45-y))Pt(y) metal hydride electrodes

In recent years, Mg-Ni-based metastable alloys have been attracting attention due to their large hydrogen sorption capacities, low weight, low cost, and high availability. Despite the large discharge capacity and high activity of these alloys, the accelerated degradation of the discharge capacity after only few cycles of charge and discharge is the main shortcoming against their commercial use in batteries. The addition of alloying elements showed to be an effective way of improving the electrode performance of Mg-Ni-based alloys. In the present work, the effect of Ti and Pt alloying elements on the structure and electrode performance of a binary Mg-Ni alloy was investigated. The XRD and HRTEM revealed that all the investigated alloy compositions had multi-phase nanostructures, with crystallite size in the range of 6 nm. Moreover, the investigated alloying elements demonstrated remarkable improvements of both maximum discharge capacity and cycling life. Simultaneous addition of Ti and Pd demonstrated a synergetic effect on the electrochemical properties of the alloy electrodes. Among the investigated alloys, the best electrochemical performance was obtained for the Mg(51)Ti(4)Ni(43)Pt(2) composition (in at.%), which achieved 448 mAh g(-1) of maximum discharge capacity and retained almost 66% of this capacity after 10 cycles. In contrast, the binary Mg(55)Ni(45) alloy achieved only 248 mAh g(-1) and retained 11% of this capacity after 10 cycles. (C) 2010 Elsevier By. All rights reserved.

Method for determining reaction rate of mild steel containers during melting of magnesium-aluminium alloys and effect of aluminium content on directionally solidified microstructures

A magnesium alloy of eutectic composition (33 wt-'%Al) was directionally solidified in mild steel tubes at two growth rates, 32 and 580 mum s(-1,) in a temperature gradient between 10 and 20 K mm(-1). After directional solidification, the composition of each specimen varied dramatically, from 32'%Al in the region that had remained solid to 18%Al (32 mum s(-1) specimen) and 13%Al (580 mum s(-1) specimen) at the plane that had been quenched from the eutectic temperature. As the aluminium content decreased, the microstructure contained an increasing volume fraction of primary magnesium dendrites and the eutectic morphology gradually changed from lamellar to partially divorced. The reduction in aluminium content was caused by the growth of an Al-Fe phase ahead of the Mg-Al growth front. Most of the growth of the Al-Fe phase occurred during the remelting period before directional solidification. The thickness of the Al-Fe phase increased with increased temperature and time of contact with the molten Mg-Al alloy. (C) 2003 Maney Publishing.

Influence of grain size on hot working stresses and microstructures in Mg-3A1-1Zn

The influence of the grain size on the deformation of Mg–3Al–1Zn was examined in compression at 300 °C. At low strains the flow stress increases with increasing grain size. This is interpreted in terms of dynamic recrystallization. Empirical models of dynamic recrystallization are developed and employed to generate a microstructure map.

Observation of deformation modes in Mg-3Al-1Zn

Since magnesium alloys are the lightest metallic materials, they are very attractive for automotive and aerospace industries. The main problem of these alloys is limited ductility due to a shortage of independent slip systems. In order to improve the formability in these alloys, an understanding of the deformation modes is required. In the present work, different slip systems were investigated in rolled Mg-3Al-IZn by means of in situ tensile tests in the SEM. These permitted electron backscatter diffraction (EBSD) and electron backscatter diffraction imaging (QBSD) to be carried out during the test. The results show that non-basal slip systems are active at room temperature.

Microstructural features of rolled mg-3Al-1Zn

The microstructures of hot- and cold-rolled Mg-3Al-1Zn (AZ31) are examined using scanning electron and optical microscopy. It is shown that the microstructures following multipass hot rolling and annealing are more uniform than those formed by heavy single pass rolling and annealing. The importance of twins in producing intragranular recrystallization is evident, although the most dominant nucleation site is grain boundaries. The cold-rolled structure after a rolling reduction of 15 pct is dominated by the presence of deformation twins. Twin trace analysis suggests that approximately two thirds of the twins are a form of “c-axis compression” twin. A number of “c-axis tension” twins were also observed and additional in-situ scanning electron microscopy experiments were performed to confirm earlier observations that suggest these twins can form after deformation, during unloading.

EBSD analysis of deformation modes in Mg-3A1-1Zn

Wrought magnesium alloys exhibit poor cold formability and the accepted explanation is the shortage of independent slip systems. In order to improve the formability in these alloys, an understanding of the deformation modes is required. In the present work, activation of different slip and twinning systems are investigated in rolled Mg–3Al–1Zn using electron back scattering diffraction. Analysis was performed on deformed surfaces and on metallographically prepared cross-sections following deformation at room temperature. The results reinforce the importance of prismatic slip and c-axis compression double twinning.

In-situ investigation of twinning behaviour in Mg-3Al-1Zn

Magnesium alloys are attractive for automotive and aerospace industries, due to their low density. One problem with these alloys is their limited formability at room temperature. Twinning plays a dominant role in deformation behaviour and it can be expected that an increased understanding of twinning will help improve formability. In the present work, the behaviour of different twinning systems in as-cast Mg-3AI-IZn is investigated using in-situ tensile tests in a scanning electron microscope. Electron backscatter diffraction and back scatter electron imaging were carried out during the tests. The results show both "tension" and "compression" twinning are active at room temperature and that twinning and untwinning occur both during loading and unloading.

Microstructural development during hot working of Mg-3AI-1Zn

he microstructural evolution is examined during the hot compression of magnesium alloy AZ31 for both wrought and as-cast initial microstructures. The influences of strain, temperature, and strain rate on the dynamically recrystallized microstructures are assessed. Both the percentage dynamic recrysallization (DRX) and the dynamically recrystallized grain size were found to be sensitive to the initial microstructure and the applied deformation conditions. Lower Z conditions (lower strain rates and higher temperatures) yield larger dynamically recrystallized grain sizes and increased percentages of DRX, as expected. The rate with which the percentage DRX increases for the as-cast material is considerably lower than for the wrought material. Also, in the as-cast samples, the percentage DRX does not continue to increase toward complete DRX with decreasing Z. These observations may be attributed to the deformation becoming localized in the DRX fraction of the material. Also, the dynamically recrystallized grain size is generally larger in as-cast material than in wrought material, which may be attributed to DRX related to twins and the inhomogeneity of deformation. Orientation maps of the as-cast material (from electron backscattering diffraction (EBSD) data) reveal evidence of discontinuous DRX (DDRX) and DRX related to twins as predominant mechanisms, with some manifestation of continuous DRX (CDRX) and particle-stimulated nucleation (PSN).

Texture changes during uniaxial compression of Mg-3AI-1Zn

The mechanical anisotropy of wrought Mg alloys is very high. For example the yield stress of extruded Mg-3Al-1Zn tested in tension can be as high as twice that obtained in compression [1]. To solve the problems this creates for product design it is necessary to understand the sensitivity of texture to processing parameters. Uniaxial compression tests at different temperatures were performed on cylindrical samples of an extruded Mg-3Al-1Zn bar. The texture
during this deformation changes from a situation where all crystal c-axes are nearly perpendicular to the sample axis to one where the c-axes are all nearly parallel to this axis. Compression was stopped at different strains to examine the rate of this texture change. Textures were examined using EBSD measurements. It was found that different mechanisms operate depending on the temperature of deformation and that a variety of textures can be created. Also it was seen that an annealing treatment performed after compression has an influence on the texture. Afterwards the samples were subjected to another uniaxial compression test to examine the influence of texture on room temperature properties.