scholarly journals Local phenomena at grain boundaries: An alternative approach to grasp the role of oxygen vacancies in metallization of VO2

2018 ◽  
Vol 4 (4) ◽  
pp. 360-367 ◽  
Author(s):  
Wanheng Lu ◽  
Lai-Mun Wong ◽  
Shijie Wang ◽  
Kaiyang Zeng
Keyword(s):  
Grain Boundaries ◽  
Oxygen Vacancies ◽  
Alternative Approach

Investigation of the Sintering Behavior of Ultrapure α-Alumina Containing Low Amounts of SiO2 or CaO

2006 ◽  
Vol 317-318 ◽  
pp. 1-6 ◽  
Author(s):  
Nicolas Louet ◽  
Thierry Epicier ◽  
Gilbert Fantozzi
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Oxygen Vacancies ◽  
Glassy Phase ◽  
Intermediate Stage ◽  
Abnormal Grain Growth ◽  
Sintering Behavior ◽  
Critical Temperatures ◽  
Heterogeneous Microstructures

The target of this work is to investigate the effect of small additions of SiO2 or CaO on the sintering behavior and the microstructure of an ultrapure α-alumina compound. The sintering behavior has been investigated through extensive dilatometric study. SiO2 additions lead to a significant decrease in shrinkage rate during the intermediate stage of sintering whereas CaO is beneficent to densification. It has been found that during this stage which corresponds to the maximum of densification rate, grain boundaries diffusion controls densification through oxygen vacancies. The study of the densification behavior under different atmospheres help us to explain the role of the additives in agreement with electroneutrality equations. S.E.M. investigations confirm the well know correlation between doping and heterogeneous microstructures. After doping with SiO2 or CaO, abnormal grain growth appears at temperatures corresponding to the lowest eutectics given by Al2O3-SiO2 or Al2O3-CaO phase diagrams. H.R.T.E.M. observations show that below the critical temperatures for abnormal grain growth, additives enrichment is observed near grain boundaries (GBs). Above these temperatures, glassy phase for SiO2-doping and calciumhexaluminate (CA6) for CaO-doping are present at grain boundaries.

Analysis of Oxygen Vacancy Trapping at [001] Symmetric Tilt Grain Boundaries in Barium Titanate by Atomistic Simulations

2010 ◽  
Vol 445 ◽  
pp. 39-42 ◽  
Author(s):  
Takashi Oyama ◽  
Nobuyuki Wada ◽  
Hiroshi Takagi
Keyword(s):  
Barium Titanate ◽  
Grain Boundaries ◽  
Atomistic Simulation ◽  
Oxygen Vacancies ◽  
Atomistic Simulations ◽  
Multilayer Ceramic Capacitors ◽  
Simulation Techniques ◽  
Electrical Degradation ◽  
Symmetric Tilt

The role of grain boundaries (GBs) in the diffusion of oxygen vacancies (VO••s) in barium titanate (BaTiO3) and its mechanism were investigated using atomistic simulation techniques. It was found that GBs trapped VO••s at specific sites in the course of the diffusion, and the excess energy reflecting structural distortion of the GB was closely related to the availability of the trapping. GBs therefore act as a resistance of the diffusion of VO••s, suggesting that electrical degradation of multilayer ceramic capacitors (MLCCs), which is derived from vacancy diffusion, enables to be additionally improved by controlling GB structures in BaTiO3-based dielectrics.

Elucidation of block boundaries as the dissolution channels in hydrated cement

1978 ◽  
Vol 36 (1) ◽  
pp. 484-485
Author(s):  
N.V. Belov ◽  
U.I. Papiashwili ◽  
B.E. Yudovich
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Benzoyl Peroxide ◽  
Phase Contrast ◽  
Active Role ◽  
Point Of View ◽  
Hardened Cement ◽  
Hydrated Cement ◽  
Hardened Cement Paste

It has been almost universally adopted that dissolution of solids proceeds with development of uniform, continuous frontiers of reaction.However this point of view is doubtful / 1 /. E.g. we have proved the active role of the block (grain) boundaries in the main phases of cement, these boundaries being the areas of hydrate phases' nucleation / 2 /. It has brought to the supposition that the dissolution frontier of cement particles in water is discrete. It seems also probable that the dissolution proceeds through the channels, which serve both for the liquid phase movement and for the drainage of the incongruant solution products. These channels can be appeared along the block boundaries.In order to demonsrate it, we have offered the method of phase-contrast impregnation of the hardened cement paste with the solution of methyl metacrylahe and benzoyl peroxide. The viscosity of this solution is equal to that of water.

Carbide precipitation and chromium depletion on coherent twin boundaries in deformed 304 stainless steels

1992 ◽  
Vol 50 (2) ◽  
pp. 1216-1217
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D.J. Matlock ◽  
W.W. Fisher ◽  
P.M. Tarin ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Stainless Steels ◽  
Interfacial Free Energy ◽  
Carbide Precipitation ◽  
Twin Boundaries ◽  
Invariant Structure ◽  
Heat Treated ◽  
Constant Structure ◽  
Cr Depletion

Coherent annealing-twin boundaries are constant structure and energy interfaces with an average interfacial free energy of ∼19mJ/m2 versus ∼210 and ∼835mJ/m2 for incoherent twins and “regular” grain boundaries respectively in 304 stainless steels (SS). Due to their low energy, coherent twins form carbides about a factor of 100 slower than grain boundaries, and limited work has also shown differences in Cr-depletion (sensitization) between twin versus grain boundaries. Plastic deformation, may, however, alter the kinetics and thermodynamics of twin-sensitization which is not well understood. The objective of this work was to understand the mechanisms of carbide precipitation and Cr-depletion on coherent twin boundaries in deformed SS. The research is directed toward using this invariant structure and energy interface to understand and model the role of interfacial characteristics on deformation-induced sensitization in SS. Carbides and Cr-depletion were examined on a 20%-strain, 0.051%C-304SS, heat treated to 625°C-4.5h, as described elsewhere.

scholarly journals Robust Universal Inference

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 773
Author(s):  
Amichai Painsky ◽  
Meir Feder
Keyword(s):  
Robust Estimation ◽  
Minimax Estimator ◽  
Worst Case ◽  
Capacity Theory ◽  
Alternative Approach ◽  
True Model ◽  
Finite Set ◽  
Universal Prediction ◽  
Estimation Scheme

Learning and making inference from a finite set of samples are among the fundamental problems in science. In most popular applications, the paradigmatic approach is to seek a model that best explains the data. This approach has many desirable properties when the number of samples is large. However, in many practical setups, data acquisition is costly and only a limited number of samples is available. In this work, we study an alternative approach for this challenging setup. Our framework suggests that the role of the train-set is not to provide a single estimated model, which may be inaccurate due to the limited number of samples. Instead, we define a class of “reasonable” models. Then, the worst-case performance in the class is controlled by a minimax estimator with respect to it. Further, we introduce a robust estimation scheme that provides minimax guarantees, also for the case where the true model is not a member of the model class. Our results draw important connections to universal prediction, the redundancy-capacity theorem, and channel capacity theory. We demonstrate our suggested scheme in different setups, showing a significant improvement in worst-case performance over currently known alternatives.

Balanced performance for β-Ga2O3 solar blind photodetectors: The role of oxygen vacancies

2021 ◽  
Vol 112 ◽  
pp. 110808
Author(s):  
Jiang Wang ◽  
Yuanqiang Xiong ◽  
Lijuan Ye ◽  
Wanjun Li ◽  
Guoping Qin ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Solar Blind

scholarly journals Chemical and Biological Molecules Involved in Differentiation, Maturation, and Survival of Dopaminergic Neurons in Health and Parkinson’s Disease: Physiological Aspects and Clinical Implications

Biomedicines ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 754
Author(s):  
Giulia Gaggi ◽  
Andrea Di Credico ◽  
Pascal Izzicupo ◽  
Giovanni Iannetti ◽  
Angela Di Baldassarre ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Dopaminergic Neurons ◽  
Potential Role ◽  
High Efficiency ◽  
Biological Molecules ◽  
Alternative Approach ◽  
Non Coding Rnas ◽  
Set Up

Parkinson’s disease (PD) is one of the most common neurodegenerative disease characterized by a specific and progressive loss of dopaminergic (DA) neurons and dopamine, causing motor dysfunctions and impaired movements. Unfortunately, available therapies can partially treat the motor symptoms, but they have no effect on non-motor features. In addition, the therapeutic effect reduces gradually, and the prolonged use of drugs leads to a significative increase in the number of adverse events. For these reasons, an alternative approach that allows the replacement or the improved survival of DA neurons is very appealing for the treatment of PD patients and recently the first human clinical trials for DA neurons replacement have been set up. Here, we review the role of chemical and biological molecules that are involved in the development, survival and differentiation of DA neurons. In particular, we review the chemical small molecules used to differentiate different type of stem cells into DA neurons with high efficiency; the role of microRNAs and long non-coding RNAs both in DA neurons development/survival as far as in the pathogenesis of PD; and, finally, we dissect the potential role of exosomes carrying biological molecules as treatment of PD.

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