Ti-Al-C MAX phases by aluminothermic reduction process

A new approach to synthesis of Ti₂AlC-Ti₃AlC₂/Al₂O₃ compounds is developed based on thermite reaction in the TiO₂-Al-C system. The effect of Al excess is also discussed. XRD analysis has proved that this parameter can be used to improve the product purity, i.e., the amount of TiC in the final product. It has also been shown that, with increasing Al excess, the composition of a major MAX phase undergoes a change from Ti₂AlC to Ti₃AlC₂.      

Multiple ionic conductances of the human dopamine transporter: the actions of dopamine and psychostimulants

Electrophysiological and pharmacological studies of a cloned human dopamine transporter (hDAT) were undertaken to investigate the mechanisms of transporter function and the actions of drugs at this target. Using two-electrode voltage-clamp techniques with hDAT-expressing Xenopus laevis oocytes, we show that hDAT can be considered electrogenic by two criteria. (1) Uptake of hDAT substrates gives rise to a pharmacologically appropriate "transport-associated" current. (2) The velocity of DA uptake measured in oocytes clamped at various membrane potentials was voltage-dependent, increasing with hyperpolarization. Concurrent measurement of transport-associated current and substrate flux in individual oocytes revealed that charge movement during substrate translocation was greater than would be expected for a transport mechanism with fixed stoichiometry of 2 Na+ and 1 Cl- per DA+ molecule. In addition to the transport-associated current, hDAT also mediates a constitutive leak current, the voltage and ionic dependencies of which differ markedly from those of the transport-associated current. Ion substitution experiments suggest that alkali cations and protons are carried by the hDAT leak conductance. In contrast to the transport-associated functions, the leak does not require Na+ or Cl-, and DAT ligands readily interact with the transporter even in the absence of these ions. The currents that hDAT mediates provide a functional assay that readily distinguishes the modes of action of amphetamine-like "DA-releasing" drugs from cocaine-like translocation blockers. In addition, the voltage dependence of DA uptake suggests a mechanism through which presynaptic DA autoreceptor activation may accelerate the termination of dopaminergic neurotransmission in vivo.     

Tunable,Flexible Composite Magnets for Marine Monitoring Applications

This paper presents flexible NdFeB‐PDMS composite magnets with tunable magnetic and mechanical properties optimized for applications in corrosive marine environments. The magnetic and mechanical properties are studied for different NdFeB powder concentrations and the performance of the magnetic composites for different exposure times to sea water investigated systematically. The remanence and saturation magnetizations could be tailored by the powder concentration, whereby up to 70 wt% concentration could be employed without compromising the integrity of the magnets. The elastic modulus of the composite magnets is about 10⁵ times lower than the one of a bulk permanent magnet. This ensures a high bending flexibility, which allows the magnets to be attached to curved surfaces as illustrated for a giant clam, crab, and turtle. At the same time, the weight of the composite magnets is reduced by a factor of about 10, which poses less burden to animals’ natural free movement. Without a protective layer, the composite magnets lose more than 50% of their magnetization after 51 days in seawater. However, the durability of the composite magnets has been improved considerably by using polymer coatings. Parylene C is the most effective for this, providing corrosion resistance, flexibility, and enhanced biocompatibility. Parylene C films of 2 and 4 μm thicknesses provided excellent protection of the magnetic composite in corrosive aqueous environments for 65 and 82 days, respectively. By combining the composite magnets with tunnel magnetoresistance sensors, a magnetic animal monitoring system is established that is used to track the behavior of giant clam, crab, and turtle.

     

Use of a Ring DWTT Specimen for Determination of Steel NDT from Pipe of Diameter Less than DN500

It has become recognized that the drop weight tearing test (DWTT) energy better represents the ductile fracture resistance of pipe steels since it utilizes a specimen that has the full thickness of the pipe and has a fracture path long enough to reach steady-state fracture resistance. However, the API 5L code does not require it for pipe sizes less than DN500. The aim of this paper is to propose a DWTT specific to small diameter pipes based on a new specimen, the ring drop weight tearing test (RDWTT) specimen; to evaluate the transition temperature T _{t, DWTT} and nil ductility temperature of the pipe steel API 5L X65; to introduce the transition temperature T _{t, DWTT} in the transition temperature material master curve of the API 5L X65 steel; and to compare the prediction of the crack ductile extension in a pipe based on the RDWTT’s energy and crack tip opening angle in the case of the steel API 5L X65.     

Multiatlas‐based segmentation of female pelvic organs: Application for computer‐aided diagnosis of cervical cancer

Atlas‐based segmentation is a high level segmentation technique which has become a standard paradigm for exploiting prior knowledge in image segmentation. Recent multiatlas‐based methods have provided greatly accurate segmentations of different parts of the human body by propagating manual delineations from multiple atlases in a data set to a query subject and fusing them. The female pelvic region is known to be of high variability which makes the segmentation task difficult. We propose, here, an approach for the segmentation of magnetic resonance imaging (MRI) called multiatlas‐based segmentation using online machine learning (OML). The proposed approach allows separating regions which may be affected by cervical cancer in a female pelvic MRI. The suggested approach is based on an online learning method for the construction of the dataset of atlases. The experiments demonstrate the higher accuracy of the suggested approach compared to a segmentation technique based on a fixed dataset of atlases and single‐atlas‐based segmentation technique.     

A new topology of hybrid synchronous machine

Permanent-magnet synchronous machines are able to operate over a wide range of speeds at constant power through the use of control laws allowing for flux weakening. Generally, this is performed by applying a strong demagnetizing current in the d axis, yet such an approach involves the risk of irreversible magnet demagnetization and, consequently, a reduction in machine performance. This paper presents a novel structure for a hybrid synchronous machine. The authors' solution provides good flux weakening without introducing the risk of magnet demagnetization. In order to explain the structure's operating principle, they apply a model with a single elementary design; electromotive force measurements are then presented to demonstrate the possibilities of flux weakening, along with a series of simulations to show the contribution of hybrid excitation     

Hydrodynamical modelling and multidimensional approximation of estuarian river flows

We propose a new approach for deriving hydrodynamical models, within the framework of mixed variational formulations. We thus obtain a 2D-horizontal model, as well as a 2D-vertical one and a 1D model taking into account the geometry of the river. We briefly study here the 2D-vertical and the 1D models and we propose (after time discretization) low-order conforming finite element approximations. All the variational problems are well-posed. We justify next a posteriori estimators between the models, which allow us to couple them. Numerical tests, achieved with a realistic bathymetry, are next presented.     

Modification of cation-exchange membrane properties by electro-adsorption of polyethyleneimine

A cation-exchange membrane has been modified by fixation of polyethyleneimine on its surface. This fixation was carried out under an electric field effect, thus it is called electro-adsorption. The polycation formed in an acidic medium migrated toward the membrane and a charged layer was deposited on the surface, and the selectivity towards divalent ions decreased, yielding to the increase of the proton transfer. When the amount of adsorbed PEI increased, the electrical resistance ofthe membrane increased and the transport number of zinc decreased. However, suitable conditions like pH, current density and electro-adsorption time were controlled in the order to obtain membranes with better selectivity and low electrical resistance.     

SHS of high-purity MAX compounds in the Ti-Al-C system

During the synthesis of MAX phases using combustion synthesis (or Self-Propagating High-temperature Synthesis), the main drawback is the presence of binary phases, and especially the simple MX carbide, when X = C. Our experiments were designed in order to check whether the cooling rate of the sample immediately after synthesis might play a key role for obtaining samples with low-level carbide contents. In the best conditions, a TiC content of about 2% only has been observed. A systematic study on the direct effect of the cooling rate on the final composition has then been conducted, and confirms that high cooling rates allow the synthesis of high-purity MAX phases in the Ti-Al-C system.