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81.
Dmitri A. Molodov Tatiana Gorkaya Christoph Günster Günter Gottstein 《Frontiers of Materials Science in China》2010,4(3):291-305
Recent research on the dynamics of planar grain boundaries is reviewed. Novel measuring techniques developed for in situ observation and recording of magnetically and stress driven grain boundary migration are presented. The results of migration
measurements obtained on bismuth, zinc and aluminum bicrystals are addressed. The experiments revealed that the inclination
of a 〈112〉 tilt boundary in Bi has a very strong influence on its mobility. The migration of planar 〈10$
\bar 1
$
\bar 1
0〉 tilt grain boundaries with different misorientation angles was measured in situ in bicrystals of high purity zinc. The
results proved that there is a pronounced misorientation dependence of grain boundary mobility in the investigated angular
range. The shear stress induced migration of planar symmetric 〈100〉 tilt boundaries in aluminum bicrystals was observed to
be accompanied by a lateral translation of the adjacent grains. The coupling between boundary motion and shearing is not confined
to low angle and some low Σ high angle boundaries, but occurs also for noncoincidence high angle 〈100〉 tilt boundaries. It
has been found that also for stress induced grain boundary motion there is a misorientation dependence of the migration activation
parameters. Lower values of the activation enthalpy and the pre-exponential mobility factor can be associated with boundaries
with tilt angles close to low Σ CSL orientation relationships. 相似文献
82.
Injection of Microporous Annealing Particle (MAP) Hydrogels in the Stroke Cavity Reduces Gliosis and Inflammation and Promotes NPC Migration to the Lesion 下载免费PDF全文
Lina R. Nih Elias Sideris S. Thomas Carmichael Tatiana Segura 《Advanced materials (Deerfield Beach, Fla.)》2017,29(32)
With the number of deaths due to stroke decreasing, more individuals are forced to live with crippling disability resulting from the stroke. To date, no therapeutics exist after the first 4.5 h after the stroke onset, aside from rest and physical therapy. Following stroke, a large influx of astrocytes and microglia releasing proinflammatory cytokines leads to dramatic inflammation and glial scar formation, affecting brain tissue's ability to repair itself. Pathological conditions, such as a stroke, trigger neural progenitor cells (NPCs) proliferation and migration toward the damaged site. However, these progenitors are often found far from the cavity or the peri‐infarct tissue. Poststroke tissue remodeling results in a compartmentalized cavity that can directly accept a therapeutic material injection. Here, this paper shows that the injection of a porous hyaluronic acid hydrogel into the stroke cavity significantly reduces the inflammatory response following stroke while increasing peri‐infarct vascularization compared to nonporous hydrogel controls and stroke only controls. In addition, it is shown that the injection of this material impacts NPCs proliferation and migration at the subventricular zone niche and results, for the first time, in NPC migration into the stroke site. 相似文献
83.
84.
Mychelle Vianna Pereira Companhoni Jose Ricardo Gomes Matheus Tatiana Lisboa Marcondes Andre Luiz Pinto 《Journal of Materials Science》2012,47(22):7835-7840
Nanostructured materials have been widely studied due to the improvement of their mechanical properties comparing to those of coarse grain materials. The present work intended to analyze the microstructure and microhardness of Zr-2.5Nb processed by high-pressure torsion (HPT), one of the severe plastic deformation techniques. The deformations were carried out at room temperature using a pressure of 5?GPa and 5 anvil turns. Vickers indentation was used to evaluate the microhardness of the samples. Transmission electron microscopy and X-ray diffraction were used to analyze the microstructure. The results showed a significant refinement from the initial microstructure achieving nanometric grain size around 50?nm and phase transformation α?→?ω?+?βI induced by shear. The Vickers microhardness values of the material submitted to HPT technique were significantly higher than those of non-deformed material. Also, HPT procedure resulted in a huge grain refinement of the material and in phase transformation. 相似文献
85.
86.
Counter-clustering for Training Pattern Selection 总被引:2,自引:0,他引:2
87.
Daniel Errandonea David Santamaria-Perez Tatiana Bondarenko 《Materials Research Bulletin》2010,45(11):1732-1735
We studied the high-pressure effects on the crystalline structure of monoclinic HfTiO4 and ZrTiO4. We found that the compressibility of these ceramics is highly non-isotropic, being the b-axis the most compressible one. In addition, the a-axis is found to have a small and negative compressibility. At 2.7 GPa (10.7 GPa) we discovered the onset of a structural phase transition in HfTiO4 (ZrTiO4), coexisting the low- and high-pressure phases in a broad pressure range. The new high-pressure phase has a monoclinic structure which involves an increase in the Ti-O coordination and a collapse of the cell volume. The equation of state for the low-pressure phase is also determined. 相似文献
88.
Electrochemical studies were carried out to estimate the risks of perchlorate formation in drinking water disinfected by direct electrolysis. Boron Doped Diamond (BDD) anodes were used in laboratory and commercially available cells at 20 °C. The current density was changed between 50 and 500 A m−2. For comparison, other anode materials such as platinum and mixed oxide were also tested. It was found that BDD anodes have a thousandfold higher perchlorate formation potential compared with the other electrode materials that were tested. In long-term discontinuous experiments all the chloride finally reacted to form perchlorate. The same result was obtained when probable oxychlorine intermediates (OCl−, ClO2−, ClO3−) were electrolysed in synthetic waters in the ppm range of concentrations. The tendency to form perchlorate was confirmed when the flow rate of drinking water was varied between 100 and 300 L h−1 and the temperature increased to 30 °C. In a continuous flow mode of operation a higher chloride concentration in the water resulted in a lower perchlorate formation. This can be explained by reaction competition of species near and on the anode surface for experiments both with synthetic and local drinking waters. It is concluded that the use of electrodes producing highly reactive species must be more carefully controlled in hygienically and environmentally oriented applications. 相似文献
89.
90.
Alejandro Vega Tatiana Baidyk Ernst Kussul José Luís Pérez Silva 《Optical Memory & Neural Networks》2011,20(3):168-180
Different types of neural networks can be used to classify images. We propose to apply LIRA (LImited Receptive Area) neural
classifier to work with images. To accelerate the neural network functioning we propose a digital implementation of the LIRA
neural classifier. We begin with a neuron design, and then continue with the neural network simulation. The advantage of neural
network is its parallel structure and possibility of the training. FPGA (Field Programmable Gate Array) allows the implementation
of these parallel algorithms in a single device. Speed of classification is one of the most important requirements in adaptive
control systems based on computer vision. The contribution of this article is LIRA neural classifier implementation with FPGA
for two classes to accelerate the training and recognition processes. 相似文献