Modification Of Matrix Research Articles

Influence of zinc oxide particles dispersion on the functional and antimicrobial properties of cementitious composites

One of the most important aspects of shaping the antibacterial properties of nano-mixed cementitious composites is the proper dispersion of nanoparticles (NPs) to ensure their sustainable application. Therefore, in the presented article special attention was paid to the method of mixing zinc oxide NPs with the cement matrix. A two-stage modification of the cement matrix was used; in the first stage, zinc oxide NPs were introduced directly in dry form into the cement binder or mixed mechanically, with ultrasound and combined mechanically and with ultrasound. Then, in the second stage, a superplasticizer was added to the mixing methods mentioned above. It was shown that the combined use of premixing and then mixing with superplasticizer influences better dispersion of zinc oxide in the cement matrix, which in turn translates into higher mechanical parameters, better microstructure compaction and resistance to microorganisms. The most homogeneous mixture was obtained with combined mechanical and ultrasonic mixing. On the other hand, better antimicrobial properties were exhibited by composites obtained only by mechanical mixing.

Synthesis of Organoalkoxysilanes: Versatile Organic–Inorganic Building Blocks

Organic–inorganic building blocks are an important class of hybrid materials due to the synergistic versatility of organic compounds with the robust properties of inorganic materials. Currently, the growing interest in silica hybrid materials to modify the physical and chemical properties of the silica network has led to an increasing interest in organoalkoxysilanes. A general formula of R-[Si-(OR’)3]n, with OR’ as a hydrolysable alkoxy group and R acting as the organic functional group (n ≥ 1), has led to precursors for many molecules. By introducing adequate organic moieties (R), organoalkoxysilanes effectively engage in surface and matrix modification of silica-based materials with smart-responsive units, coupling agents, targeting moieties, bioactive moieties etc., opening promising applications, specifically biomedical ones. Several synthetic procedures have been established to introduce the alkoxysilane moieties, including hydrosilylation, coupling reactions, and addition reactions to isocyanates. Herein, we review synthetic routes to organoalkoxysilanes and the relationship between structural features to design appropriate organoalkoxysilanes for specific applications.

Combined effect of fiber hybridization and matrix modification on mechanical properties of polymer composites

Glass/carbon fiber reinforced hybrid composites are great candidates for wind turbine blade manufacturers to make larger blades. Variation of stacking sequences ensures design freedom to the composite engineers to optimize the composite structure's mechanical performance. On the other hand, matrix modification of polymer composites with nanoparticles is also of interest to introduce multifunctional properties. This research aims to scrutinize the influence of simultaneous fiber hybridization and matrix modification on polymer composites’ tensile, flexural, and low-velocity impact properties. Hybrid glass/carbon epoxy composites and hybrid glass/carbon/multi-walled carbon nanotube (MWCNT) multiscale polymer composites of stacking sequences [GCGCGC]S, [CGCGCG]S, and [G6C6] were manufactured. Fiber hybridization dramatically improved tensile strength between 51% and 76% compared to glass fiber composite. Depending on the stacking sequence, the flexural strength of the hybrid composites was improved between 10% and 16% concerning carbon fiber composite. With the introduction of MWCNTs, a slight increase in the tensile strength for unsymmetrical hybrid composites by around 5% and decreases by 7% for symmetrical ones were observed. Similar behavior was seen for bending characteristics. Additionally, low-velocity impact tests showed that it is achievable to bring greater impact peak forces up to 70% for hybrid composites than carbon fiber epoxy composites. MWCNTs modification of the matrix restrained the impact damage propagation, as proved by C-scan analysis.

Investigating the Wear Behaviors of Silane Coated Silica Filled Glass/Epoxy Nanocomposites

Wear behaviors of silane coated silica (SiO2) nanoparticle-filled glass fiber reinforced polymer composites were investigated depending on the type of silane coating (KH550: -Aminopropyl-triethoxy-silane and KH570: -Methacryloxypropyl-trimethoxy-silane) and nanoparticle percentages within the polymer matrix. Unlike the cases given in most research studies, the silanized silica nanoparticles were used as received. Therefore, the synergistic effects of silanization and nanoparticle reinforcement were successfully applied since the silanization process was eliminated. The matrix modification with the nanoparticles was carried out using an ultrasound homogenizer, and then the modified matrix was reinforced with glass fibers. Scanned electron microscopy revealed the disperse ability of silanized silica nanoparticles within the glass/epoxy composites. The wear behaviors of the developed composites were investigated via a ball-on-disc tribology device. Wear track profiles were obtained depending on the width and depth of the wear. The length of wear track and wear mechanisms were determined by a stereomicroscope. The findings have shown that both types of silane coating and silica nanofiller percentages significantly affected the wear rate of the composite structures.

Modification of UHPC Matrix and Fiber Surface for Improving the Mechanical Performance of Ultra-High-Performance Fiber-Reinforced Concrete

In this study, filler and silica fume were substituted by Liquid crystal display glass powder (LCDGP) and nanosilica, respectively, to improve the performance of ultra-high- performance fiber-reinforced concrete. In addition, the surface of steel fiber was modified with ethylenediaminetetraacetic acid (EDTA) solution to improve the interfacial friction between the fiber and Ultra-high-performanceconcrete (UHPC) matrix. Both LCDGP and nanosilica reacted with calcium hydroxide to form hydrates, and the fiber surface roughness increased owing to the EDTA treatment. When LCDGP was used, the compressive strength decreased owing to a decrease in packing density; however, the compressive and tensile strengths of Ultra-high-performance fiber-reinforced-concrete (UHPFRC) were improved on using nanosilica. It was observed that the surface modification of the fiber increased the friction force between the UHPC and fiber interface; therefore, it was more effective in improving the tensile strength than the compressive strength.

Determination of Cr, Se, Ge, and V in Hypothyroidism Patients by Using Graphite Furnace Atomic Absorption Spectrometry and mixture matrix modification

A simple, accurate and rapid method was developed for routine determination of trace elements in blood serum. The method based on the direct determination for Cr, Se, Ge, and V in hypothyroidism patients before therapy. By using atomic absorption spectrometry with graphite surface coated and uncoated pyrolysis GF-AAS, and a mixture of palladium nitrate and magnesium nitrate as the matrix modifier, with deuterium background correction and no sample pretreatment except dilution was necessary. This permitted direct determination hence the risk of sample contamination was reduced. Further, the use of graphite surface-coated GF-AAS decreased the ashing and atomization temperatures of Cr, Ge, and V to values that were lesser than the corresponding values obtained using uncoated pyrolysis GF-AAS, by 100°C; in case of Se, the atomization temperature decreased to a value that was 200°C lesser than that obtained using uncoated pyrolysis GF-AAS.
 A mixture of (3µL) palladium nitrate, and (2µL) magnesium nitrate was successfully applied to improve the sensitivity, reproducibility, recovery, limit of detection and the accuracy of the measurements. The correlation coefficients of the calibration curves of Cr, Se, Ge, and V were found to be (0.9999, 0.9999, 0.9995 and 0.9999) respectively, the relative standard deviation of the measurements for Cr, Se, Ge and V were (0.027, 0.075, 0.054 and 0.068) respectively. The statistical analysis of the acquired data showed acceptable accuracy. The analyses thus performed indicated that the levels of serum trace elements Cr, Se, Ge, and V in hypothyroidism patients were lower than those in the control group.

Intradiscal treatment of the cartilage endplate for improving solute transport and disc nutrition.

Poor nutrient transport through the cartilage endplate (CEP) is a key factor in the etiology of intervertebral disc degeneration and may hinder the efficacy of biologic strategies for disc regeneration. Yet, there are currently no treatments for improving nutrient transport through the CEP. In this study we tested whether intradiscal delivery of a matrix-modifying enzyme to the CEP improves solute transport into whole human and bovine discs. Ten human lumbar motion segments harvested from five fresh cadaveric spines (38-66 years old) and nine bovine coccygeal motion segments harvested from three adult steers were treated intradiscally either with collagenase enzyme or control buffer that was loaded in alginate carrier. Motion segments were then incubated for 18h at 37 °C, the bony endplates removed, and the isolated discs were compressed under static (0.2MPa) and cyclic (0.4-0.8 MPa, 0.2Hz) loads while submerged in fluorescein tracer solution (376Da; 0.1mg/ml). Fluorescein concentrations from site-matched nucleus pulposus (NP) samples were compared between discs. CEP samples from each disc were digested and assayed for sulfated glycosaminoglycan (sGAG) and collagen contents. Results showed that enzymatic treatment of the CEP dramatically enhanced small solute transport into the disc. Discs with enzyme-treated CEPs had up to 10.8-fold (human) and 14.0-fold (bovine) higher fluorescein concentration in the NP compared to site-matched locations in discs with buffer-treated CEPs (p < 0.0001). Increases in solute transport were consistent with the effects of enzymatic treatment on CEP composition, which included reductions in sGAG content of 33.5% (human) and 40% (bovine). Whole disc biomechanical behavior-namely, creep strain and disc modulus-was similar between discs with enzyme- and buffer-treated CEPs. Taken together, these findings demonstrate the potential for matrix modification of the CEP to improve the transport of small solutes into whole intact discs.

Contact force cancelation in robot impedance control by target impedance modification

AbstractA force sensorless impedance controller is proposed in this paper for robot manipulators without using force estimators. From the observation of the impedance control law, the force feedback term can be canceled if the inertia matrix in the target impedance is the same as the robot inertia matrix. However, the inertia matrix in the target impedance is almost always a constant matrix, while the robot inertia matrix is a function of the robot configuration, and hence, they may not be identical in general. A modification of the coefficient matrix for the contact force term in the target impedance is suggested in this paper to enable cancelation of the force feedback term in the impedance control law so that a force sensorless impedance controller without using force estimators can be obtained. The tracking performance in the free space phase and the motion trajectory in the compliant motion phase of the new design are almost the same as those in the traditional impedance control. Modification of the inertia matrix in the target impedance will result in small variations of the contact force which is acceptable in practical applications. For robot manipulators containing uncertainties, an adaptive version of the new controller is also developed in this paper to give satisfactory performance without the need for force sensors. Rigorous mathematical justification in closed-loop stability is given in detail, and computer simulations are performed to verify the efficacy of the proposed design.

The durability performance of waste cardboard kraft fibre reinforced concrete

Despite the high recycling rate of cardboard, a significant amount of this material is disposed of in landfill areas. The conversion of cardboard waste into kraft fibres (KFs) offers potential sustainability benefits when used in the building and construction industry. This study comprehensively analyses the durability of KF reinforced concrete as a partial cement substitution. Durability testing was conducted, exploring the composites microstructure when integrating KFs derived from waste cardboard. Fibre and matrix modification techniques were utilised via silica fume (SF) and metakaolin (MK), respectively. Porosity analysis of the novel composites demonstrated connecting microstructural system, enhancing the knowledge of durable aspects of potential service life of the composites. SF reduced the water permeability of the novel composites as demonstrated via water absorption and immersion testing. At one year, there was a reduction of chloride ion transference for all fibre composites. Composites were aged via wet and dry cycles, then tested for their compressive and tensile strength at each interval. Compressive strength of all samples peaked at 60- 80 day-cycles. Fibre Matrix modified composites demonstrated a tensile strength of 2.5 MPa when subjected to 100 day-cycles, with the control having 2.7 MPa.

Progress in preparation and ablation resistance of ultra-high-temperature ceramics modified C/C composites for extreme environment

Abstract Carbon/carbon (C/C) composites have received considerable attention for one of the most promising materials in thermal-structural applications owing to their low density, excellent mechanical strength at high temperature, and superior thermal shock resistance. However, C/C composites are susceptible to destructive oxidation in atmospheric environment at high temperature. Matrix modification by adding ultra-high-temperature ceramics (UHTCs) into carbon substrate has been proved to be a favorable route to achieve the improved ablation resistance of C/C composites. In this work, the main fabrication approaches of UHTCs-modified C/C composites were summarized, including chemical vapor infiltration/deposition, precursor infiltration and pyrolysis, reactive melt infiltration, and slurry infiltration, and the advantages and drawbacks of each process were also briefly analyzed. In addition, anti-ablation properties of UHTCs-modified C/C composites under different ablation tests with different shape specimens were introduced. Finally, some likely future challenges and research directions in the development and application of these materials were presented.

Endometrial extracellular matrix components do not change over the course of embryonic diapause and reactivation in the roe deer (Capreolus capreolus).

The modification of the endometrial extracellular matrix (ECM) is a crucial step for embryo implantation in many mammalian species. The embryo of the European roe deer (Capreolus capreolus) displays a 4-5 months long temporary reduction of developmental pace termed embryonic diapause. A reduction of epithelial cell height during diapause has previously been described. Co-occurring ECM modifications may contribute to the changes of the intra-uterine milieu during reactivation at which the embryo regains developmental velocity. We assessed the localization of five ECM proteins (collagen I and IV, fibronectin, laminin, and extracellular matrix protein 1) using immunohistochemistry in animals with early, late, and post-diapause (elongating) embryos. While our results confirmed the reduction of epithelial height during diapause, we only detected marginal differences in localization and staining intensities of the selected ECM proteins. Major ECM remodelling events in the roe deer endometrium are thus likely to occur only at implantation.

Significant improvement of ultra-high temperature oxidation resistance of C/SiC composites upon matrix modification by SiHfBCN ceramics

Advanced C/SiC-SiHfBCN composites were prepared by modification of the matrix of C/SiC composites with single-source-precursor derived SiHfBCN ceramics. Ultra-high temperature oxidation behavior of the C/SiC-SiHfBCN composites under laser heating were systematically studied. The influence of temperature, preform structure and precursor on oxidation resistance of the composites were analyzed. The results revealed that the preform structure and precursor can influence the oxidation behavior of C/SiC-SiHfBCN composites by effecting its thermal conductivity in the thickness direction. The Hf-containing oxide layer formed during ultra-high temperature oxidation test can effectively protect the internal carbon fibers from being oxidized. Linear ablation rate of C/SiC-SiHfBCN composites was more than an order of magnitude lower than that of other reported C/SiC composites, indicating an enhanced ablation resistance of the C/SiC-SiHfBCN composites.

Transcriptomic Profiling and Pathway Analysis of Mesenchymal Stem Cells Following Low Dose-Rate Radiation Exposure.

Low dose-rate radiation exposure can occur in medical imaging, as background from environmental or industrial radiation, and is a hazard of space travel. In contrast with high dose-rate radiation exposure that can induce acute life-threatening syndromes, chronic low-dose radiation is associated with Chronic Radiation Syndrome (CRS), which can alter environmental sensitivity. Secondary effects of chronic low dose-rate radiation exposure include circulatory, digestive, cardiovascular, and neurological diseases, as well as cancer. Here, we investigated 1-2 Gy, 0.66 cGy/h, 60Co radiation effects on primary human mesenchymal stem cells (hMSC). There was no significant induction of apoptosis or DNA damage, and cells continued to proliferate. Gene ontology (GO) analysis of transcriptome changes revealed alterations in pathways related to cellular metabolism (cholesterol, fatty acid, and glucose metabolism), extracellular matrix modification and cell adhesion/migration, and regulation of vasoconstriction and inflammation. Interestingly, there was increased hypoxia signaling and increased activation of pathways regulated by iron deficiency, but Nrf2 and related genes were reduced. The data were validated in hMSC and human lung microvascular endothelial cells using targeted qPCR and Western blotting. Notably absent in the GO analysis were alteration pathways for DNA damage response, cell cycle inhibition, senescence, and pro-inflammatory response that we previously observed for high dose-rate radiation exposure. Our findings suggest that cellular gene transcription response to low dose-rate ionizing radiation is fundamentally different compared to high-dose-rate exposure. We hypothesize that cellular response to hypoxia and iron deficiency are driving processes, upstream of the other pathway regulation.

Matrix Tailoring for Polyvinyl Alcohol (PVA) Fiber-Reinforced Ductile Cementitious Composites

The main concern for the limited practical applications of strain-hardening cementitious composite, especially in China, is the high cost of imported materials, mainly polyvinyl alcohol fibers. This study uses local ingredients to develop strain-hardening cementitious composite reinforced with non-oil-coated Chinese polyvinyl alcohol fiber. The cementitious matrix consisting of cement, fly ash, viscosity-modifying agent, and silica fume was prepared, and the matrix tailoring was performed to achieve improved mechanical performance. The prepared composites were evaluated by rheology, three-point bending, and tensile characterizations. It is found that with the given local ingredients and matrix modification, the toughness index value of 100 ( I40) according to the American Society for Testing and Materials can be achieved. Besides, the tensile results showed the improvement of 45% and 60% for first-cracking strength and peak tensile strength values, respectively. The effects of matrix modification are also analyzed statistically using the analysis of variance for the mechanical properties of the cementitious composite. The post hoc statistical analysis using the Tukey–Kramer honestly significant difference illustrated the optimum cementitious mix from the experimental data. The presented results of cost-effective strain-hardening cementitious composite are expected to promote the practical applications of strain-hardening cementitious composite in China.

РОЛЬ ЦИФРОВОЙ ТРАНСФОРМАЦИИ В СТРАТЕГИЧЕСКОМ УПРАВЛЕНИИ

The study deals with the issues of analyzing the internal and external contexts of the company during strategic changes. The relevance of the work is that errors in context research can lead to financial and other losses, reduce competitive positions in the market. Based on the study of the literature on the declared problems, the author concluded that it is necessary to use an integrated approach that takes into account the benefits that the client wants to receive when conducting the analysis. The work presents a model, the difference of which is as follows. The tools used to analyze the context of the company must be rebuilt and take into account the interests of the client. As an example, a fragment showing modification of the SWOT analysis matrix is shown.

Towards freeform manufacturing of ultra-low expansion glass optics

Ultra-Low-Expansion glass (ULE®) has become an important technological enabler of advanced imaging for astronomy and for extreme-UV lithography. A major limitation though, is that ULE® cannot be poured from the fluid state unlike ZERODUR® which renders costly to produce large and/or complex shapes from it. Beside mirrors, optical components are rarely made of ULE® despite it sharing many properties of pure fused silica glass. Here we explore how femtosecond laser processing combined with laser induced reflow can be used to structure ULE® glass with the goal of producing miniature optical components. To fulfil optical roughness requirements, we adopt a strategy based on first producing elementary shapes, such as cubes or cylinders, that we further topologically transform into sphere, ellipsoids or curved surfaces, using a laser-reflow process. The structural modification of the glass matrix induced by the reflow were investigated using Raman spectroscopy. Our result points to a densification of the glass but no apparent sign of crystallization or devitrification. Furthermore, to understand whether the thermo-mechanical properties were affected or not, the thermal expansion coefficient was estimated using a dilatometry technic based on a pseudo-bimorph micro-cantilevers in a temperature-controlled chamber.

Adaptive Self-Supervised SAR Image Registration With Modifications of Alignment Transformation

Considering that deep learning achieves the prominent performance, it has been applied into SAR image registration to improve the registration accuracy. In most methods, a deep registration model is constructed to classify for matched-points and unmatched-points, in which SAR image registration is regarded as a supervised two-classification problem. However, it is difficult to annotate massive matched-points manually in practice, which limits the performance of deep networks. Besides, inevitable differences among SAR images easily cause that some training and testing samples are inconsistent, which probably brings negative effects for training a robust registration model. To address these problems, we propose an adaptive self-supervised SAR image registration method, where SAR image registration is regarded as a self-supervised task rather than the supervised two-classification task. Inspired by self-supervised learning, we consider each point on SAR images as a category-independent instance, which mitigates the requirement of manual annotations. Based on key points from images, a self-supervised model is constructed to explore the latent feature of each key point, and then pairs of match-points are sought via evaluating similarities among key points and used to calculate the alignment transformation matrix. Meanwhile, to enhance the consistency of samples, we design a new strategy that constructs multi-scale samples by transforming key points from one image into another, which avoids inevitable diversities between two images effectively. Specially, the constructed samples feeding to the self-supervised model are adaptively updated with the modification of the transformation matrix in iterations. Moreover, the MPAS indicator is proposed to assist in estimating the transformation. Finally, experimental results illustrate that the proposed method achieves more accurate registrations than other compared methods.

ИССЛЕДОВАНИЕ ВОПРОСОВ СТРАТЕГИЧЕСКОГО АНАЛИЗА ВНЕШНЕЙ И ВНУТРЕННЕЙ СРЕДЫ ОРГАНИЗАЦИИ

The study deals with the issues of analyzing the internal and external contexts of the company during strategic changes. The relevance of the work is that errors in context research can lead to financial and other losses, reduce competitive positions in the market. Based on the study of the literature on the declared problems, the author concluded that it is necessary to use an integrated approach that takes into account the benefits that the client wants to receive when conducting the analysis. The work presents a model, the difference of which is as follows. The tools used to analyze the context of the company must be rebuilt and take into account the interests of the client. As an example, a fragment showing modification of the SWOT analysis matrix is shown.

Application features of microarc oxidation technology

The technology of microarc oxidation of valve metals is one of the promising methods for engineering the working surface of friction units of modern technology. As a result of the versatility of the technology, it is possible to obtain composite ceramic coatings and materials of various types. Their properties are set by the electrical modes of material formation, the chemical composition of the electrolyte, and the possible further modification of the ceramic matrix with micro- and nanosized tribofillers. Based on the practical results of their research in the field of creating coatings of various types by microarc oxidation, an analysis is given of the main areas of application of microplasma electrolytic oxidation technology, their advantages over other methods of surface modification, structure and properties of the materials obtained. It is possible to distinguish the modification of the friction surface of a part by the method of microplasma electrolytic oxidation in order to increase its hardness and wear resistance. Good results were obtained in increasing the wear resistance of the hardened working surface of the spinning machine parts, the number of equipment repairs was reduced by more than 20 times. The use of microarc oxidation is promising for the preparation of composite coatings, which are a ceramic matrix in which solid lubricating dispersed particles are embedded. The technology of forming a matrix on aluminum, modified with dispersed magnetite, graphite and molybdenum disulfide, has been developed. According to the results of comparative tribotechnical tests, it was found that the intensity of linear wear of the material filled with MoS2 is 3 times, and Fe3O4 - 1.6 times lower than that of the coatings without filler. Based on the technology of microplasma electrolytic oxidation, an original technology has been developed for obtaining mineral-ceramic material, which is a matrix of aluminum oxide and dispersed diamond inclusions. Abrasive wheels made from this material have a consistently high volumetric cutting ability, 1.5-3.5 times higher than the traditional analogues and are characterized by high diamond retention. The possibilities of microplasma oxidation have not yet been fully explored, the most promising direction being the creation of nanostructured coatings for a specific technological task.

Development of an optimised method for measurement of iodine-129 in decommissioning wastes using ICP-MS/MS

Tube furnace extraction combined with ICP-MS/MS for low-level 129I measurement in decommissioning samples, combined with matrix modification for improved sensitivity.