Mimicking the Brain Extracellular Matrix in Vitro: A Review of Current Methodologies and Challenges

The brain's extracellular matrix (ECM), a 3-dimensional macromolecular network that supports cell growth and viability, has crucial roles in homeostasis and disease. Accurate recapitulation of the chemical, structural, and mechanical properties of the ECM in brain cell cultures is essential for the development of translatable in vitro models; however, thus far, this task has proven highly challenging. This review provides an in-depth discussion of this challenge, including an overview of the properties of the ECM that in vitro models should endeavour to capture, a survey of ECM analogues that are currently used for this purpose, and a discussion of the main hindrances to developing more effective ECM-like coating materials.     

An iterative approach for the discrete‐time dynamic control of Markov jump linear systems with partial information

The , and mixed dynamic output feedback control of Markov jump linear systems in a partial observation context is studied through an iterative approach. By partial information, we mean that neither the state variable x(k) nor the Markov chain θ(k) are available to the controller. Instead, we assume that the controller relies only on an output y(k) and a measured variable coming from a detector that provides the only information of the Markov chain θ(k). To solve the problem, we resort to an iterative method that starts with a state‐feedback controller and solves at each iteration a linear matrix inequality optimization problem. It is shown that this iterative algorithm yields to a nonincreasing sequence of upper bound costs so that it converges to a minimum value. The effectiveness of the iterative procedure is illustrated by means of two examples in which the conservatism between the upper bounds and actual costs is significantly reduced.     

Two-step method to deposit ZrO2 coating on carbon fiber: Preparation,characterization, and performance in SiC composites

Recently, ceramic matrix composites reinforced by short carbon fibers (CFs) attracted increasing attentions. To further improve mechanical properties and oxidation resistances, CFs were subjected to oxidation and acidification followed by sol-gel dip-coating to deposit ZrO₂ on their surfaces. ZrO₂-C_f/SiC composites were fabricated by joint hot compression molding and sintering, compared to C_f/SiC and SiC prepared by the same method. Microstructural analyses indicated that ZrO₂ coatings were successfully deposited on CF surfaces, formed strong bonding and interfaces between CF and the matrix. Meanwhile, CFs were found uniformly distributed in SiC matrix with random orientations. Flexural curves of ZrO₂-C_f/SiC and C_f/SiC revealed the presence of “false plasticity” regions after sharp drops, which were quite different from brittle flexural behavior of SiC ceramic. Compression strength of the three samples showed step-up growth. ZrO₂-C_f/SiC exhibited the highest value, indicating the introduction of CFs and ZrO₂ coatings do have great influence on mechanical performances. After heat treatment, ZrO₂-C_f/SiC exhibited better oxidation resistance than C_f/SiC, with weight loss ratios estimated to ??3.76% and ??6.43%, respectively. These improved properties indicated that ZrO₂-C_f/SiC would be excellent alternatives to other existence materials under ultra-high temperature environments.     

Effects of structural characteristics on microwave dielectric properties of low-loss (Zn1-xNix)ZrNbTaO8 ceramics

Low-loss (Zn_1-xNi_x)ZrNbTaO₈ (0.02?≤?x?≤?0.10) ceramics possessing single wolframite structure are initiatively synthesized by solid-state route. Based on the results of Rietveld refinement, complex chemical bond theory is used to establish the correlation between structural characteristics and microwave performance in this ceramic system. A small amount of Ni²⁺ (x?=?0.06) in A-site with the fixed substitution of Ta⁵⁺ in B-site can effectually raise the Q?×?f value of ZnZrNb₂O₈ ceramic, embodying a dense microstructure and high lattice energy. The dielectric constant and τ_f are mainly affected by bond ionicity and the average octahedral distortion. The (Zn_0.94Ni_0.06)ZrNbTaO₈ ceramic sample sintered at 1150?°C for 3?h exhibits an outstanding combination of microwave dielectric properties: ε_r =?27.88, Q?×?f?=?128,951?GHz, τ_f =?–39.9?ppm/°C. Thus, it is considered to be a candidate material for the communication device applications at high frequency.     

Similarities and differences between male and female novice designers on color‐concept associations for warnings,action required,and signs and equipment status messages

This research examined the male and female novice designers toward color associations for the concepts used for ‘warnings’, ‘action required’, and ‘signs and equipment status’ through a questionnaire‐based study. A total of 178 Hong Kong Chinese final year undergraduate design students (89 males and 89 females) participated in the study. The test used required the participants to indicate their choice of one of nine colors to associations with each of 38 concepts in a color‐concept table, so that any one color could be associated with any one of the concepts. For both male and female groups of novice designers, chi‐square tests revealed a strong color association for each concept tested in this study (P < .05). The results showed males and females agreed on some color‐concept association stereotypes which were therefore gender neutral. The male and female novice designers had the same color associations and similar levels of stereotype strengths for 21 concepts. The nine strongest and therefore most useful color‐concept association stereotypes for both male and female novice designers were: red‐danger, red‐fire, red‐hot, red‐stop, red‐emergency, red‐error, blue‐cold, blue‐male, and green‐exit. However, the male and female novice designers had different color association stereotypes for the standby (green vs. yellow), emergency exit (green vs. red), and toxic (purple vs. black) concepts, and the strengths of the 14 remaining associations for both groups were not at equivalent levels. Overall, it is anticipated that the findings of this study will act as a useful reference for novice designers and other design practitioners to optimize color coding in the design of ‘warnings’, ‘action required’, and ‘signs and equipment status’ messages.     

CMC jackets for metallic pipes – A novel approach to prevent the creep deformation of thermo-mechanically loaded metals

Steel materials suffer extensive creep by the application at temperatures of about 700?°C and pressures about 350?bar in a power plant environment. The presented concept overwraps a steel pipe with a ceramic matrix composite (CMC) jacket in order to support the steel pipe and provide high temperature strength. Finite Element simulations show the influence of the wall thickness of CMC jacket and the coefficient of thermal expansion (CTE) on circumferential stresses within the hybrid metal ceramic pipe. Suitable fiber and matrix materials were studied, composites fabricated and mechanical properties determined. Finally, a prototype was designed in order to confirm the feasibility of the concept. The lifetime of a pure steel pipe was increased by more than four-fold by the additional CMC jacket.     

Mechanical property degradation of high crystalline SiC fiber–reinforced SiC matrix composite neutron irradiated to ∼100 displacements per atom

For the development of silicon carbide (SiC) materials for next-generation nuclear structural applications, degradation of material properties under intense neutron irradiation is a critical feasibility issue. This study evaluated the mechanical properties and microstructure of a chemical vapor infiltrated SiC matrix composite, reinforced with a multi-layer SiC/pyrolytic carbon–coated Hi-Nicalon^TM Type S SiC fiber, following neutron irradiation at 319 and 629?°C to ～100 displacements per atom. Both the proportional limit stress and ultimate flexural strength were significantly degraded as a result of irradiation at both temperatures. After irradiation at 319?°C, the quasi-ductile fracture behavior of the nonirradiated composite became brittle, a result that was explained by a loss of functionality of the fiber/matrix interface associated with the disappearance of the interphase due to irradiation. The specimens irradiated at 629?°C showed increased apparent failure strain because the fiber/matrix interphase was weakened by irradiation-induced partial debonding.     

Mullite-bonded SiC-whisker-reinforced SiC matrix composites: Preparation,characterization, and toughening mechanisms

A novel mullite-bonded SiC-whisker-reinforced SiC matrix composite (SiCw/SiC, SiC whisker-to-SiC powder mass ratio of 1:9) was designed and successfully prepared. Before preparing the composite, the inexpensive lab-made SiCw was first modified by an oxidation/leaching process and then coated with Al₂O₃. The kinetics results indicate that the oxidation process can be described by improved shrinking-cylinder models. The aspect ratio of SiCw improved after modification. Subsequently, raw materials with a SiC–SiO₂–Al₂O₃ triple-layered structure were obtained after the Al₂O₃-coating process and used as feedstocks during the subsequent hot-pressing sintering. Finally, the characterization of the composites indicates that the mullite-bonded sample performs better (relative density of 93.8?±?1.4%, flexural strength of 533.3?±?18.2?MPa, fracture toughness of 13.6?±?2.1?MPa?m^1/2, and Vickers hardness of 20.6?±?2.5?GPa) than the reference sample without the mullite interface. The improved toughness could essentially be attributed to the moderately strong interface bonding and effective load transfer effects of the mullite interface.     

Arabic sign language intelligent translator

ABSTRACT

Arabic sign language (ArSL) is method of communication between deaf communities in Arab countries; therefore, the development of systemsthat can recognize the gestures provides a means for the Deaf to easily integrate into society. In this research we implemented a computational structurefor an intelligent interpreter that automatically recognizes the isolated dynamic gestures. The proposed system recognizes and translates gesturesperformed with one or both hands. It comprises five subsystems, building dataset, video processing, feature extraction, mapping between ArSL and Arabictext, and text generation. To apply the system, 100-signs of ArSL was used, which was applied on 1500 video files. It's were divided into five classes:alphabet, numbers, "prepositions, pronouns and question words", Arabic life expressions, and "nouns and verbs". The evaluation indicated that thesystem automatically recognizes and translates isolated dynamic ArSL gestures by highly accurate manner. The results showed that the system accuracy is 95.8%.     

Preparation and mechanism of active Mo–Mn metallization on ZTA particles surface and interfacial bonding of reinforced iron matrix composite

ZrO₂ toughened Al₂O₃ particles (ZTAp) have poor wettability with iron, and therefore some defects are easily formed at the interface between ZTAp and iron matrix, which may lead to material failure. This paper illustrates that the ZTAp were modified on the surface by the active Mo–Mn metallization, and thus, they were used as the reinforcing phases to prepare the iron-matrix composite (ZTAp/Fe composite). It is concluded that the sponge-like skeleton structure was formed on the surface of ZTAp after the metallization. The interface of ZTAp/Fe composite, which has been proved to have bearing and transitional capacity by scratch test, was formed by chemical bonding with elemental diffusion, besides mechanical bonding. The metallization mechanism of elemental diffusion can be explained by the migration of glass phase, and the elements diffusion between the interface and iron matrix is to form solid solution.