Crystallization of GeO2-Al2O3-Bi2O3 glass

In the presented work, two kinds of germanium oxide glass with different compositions, namely GeO2 and GeO2-Al2O3-Bi2O3, were investigated. After controlled crystallization of a glassy sample, the emission in the NIR-range was determined (1165 nm with excitation at 470 nm). To better understanding the kinetics of the glass crystallization, the activation energy was also determined by applying the Kissinger method. The obtained results show that in the case of GeO2-Al2O3-Bi2O3, activation energy value was 400 and 477 kJ/mol, which means that such values are significantly larger than for pure GeO2 (254 kJ/mol). The investigations also show that two phases crystallized in the complex glass matrix: the mullite-like phase and germanium oxide

Crystallization of Lanthanide—Ho3+ and Tm3+ Ions Doped Tellurite Glasses

In the presented work, the tellurite glasses TeO2-WO3-ZnO doped with Tm3+ and Ho3+ ions were prepared by the same glass forming method. X-ray diffraction (XRD) and differential thermal analysis (DTA) techniques were used to study the effects of the forming technology on the thermal and structural properties of the fabricated glasses. After controlled crystallization of investigated glasses, the emission in the VIS- and NIR range was determined. The effect of silver doping on emission intensity was investigated. The value of the activation energy of the glass crystallization process was determined, while the Ea value for pure TeO2 glass was much lower than for tellurite glasses TeO2-WO3-ZnO

Investigation of Praseodymium Ions Dopant on 9/65/35 PLZT Ceramics’ Behaviors, Prepared by the Gel-Combustion Route

In this work, were synthesized (Pb0.91La0.09)(Zr0.65Ti0.35)0.9775O3 ceramic materials with different concentrations of praseodymium (0, 0.1, 0.3, 0.5, 1 wt.%) via gel-combustion route and sintered by the hot uniaxial pressing method. Measurements were conducted on the obtained ceramics using X-ray powder diffraction (XRD), scanning electron microscope (SEM), EDS analysis, and examination of dielectric and ferroelectric optical properties. Results give us a detailed account of the influences of the praseodymium ions on the structural, microstructural, and dielectric properties. 3D fluorescence maps and excitation and emission spectra measurements show how a small admixture changes the ferroelectric relaxor behavior to an optically active ferroelectric luminophore

Investigation of Modified Auxetic Structures from Rigid Rotating Squares

Auxetic structures exhibit unusual changes in size, expanding laterally upon stretching instead of contracting. This paper presents this effect in a failsafe mode in structures made of rigid squares. We applied the concept of auxetic structures made of rigid rotating squares (from Grima and Evans) and offer a novel solution for connecting them. By introducing axes of rotation on the surface of the squares, a reliable working system is obtained, free from stress, in which the squares can come into contact with each other and completely cover the surface of the structure, or, in the open position, form regularly arranged pores. Herein, we present a new 2D auxetic metamaterial that is mathematically generated based on a theoretical relationship of the angle between the edges of a square and the position of the axis of rotation. Physical models were generated in the form of a planar structure and in the form of a circular closed structure. Such physical models confirmed our initial considerations and the geometrical relationships, offering new application possibilities. The novel structure that was designed and manufactured for the purpose of the paper can be considered as a new proposal in the market of auxetic materials

Preparation and characterization of calcium cobaltite for thermoelectric application

Abstract Starting powders of CaCO 3 with different Ca:Co ratio and three different sources of cobalt (II,III) oxide were mixed and calcined at 700-1100 o C. DTA/TG, mass changes, density, grain size distribution, phase composition were examined. It has been found that phase composition of the resulted product was dependent on calcination temperature and properties of starting cobalt oxide. Three stages of cobaltite formation were established: simultaneous decomposition of CaCO 3 with Ca 3 Co 4 O 9 formation (800-900 °C), decomposition of Ca 3 Co 4 O 9 and formation of Ca 3 Co 2 O 6 (about 950 °C) and the last stage at 1050°C was dependent on starting cation ratio and source of cobalt (II,III) oxide. It has been found that total decomposition of the previous phases was observed after calcinations at 1050 °C in the batches with Ca:Co=1:1 ratio if very pure Co 3 O 4 was used for preparation. Replacement of pure Co 3 O 4 by cobalt oxide contaminated by cobalt hydroxide lead to re-formation of Ca 3 Co 4 O 9 phase at 1050 °C in 1:1 batches. Residual Co 3 O 4 and CaO was always present in calcined specimens. It seems that prolonged heat treatment did not lead to better reaction degree

Klotho gene silencing promotes pathology in the mdx

Duchenne muscular dystrophy (DMD) is a lethal muscle disease involving progressive loss of muscle regenerative capacity and increased fibrosis. We tested whether epigenetic silencing of the klotho gene occurs in the mdx mouse model of DMD and whether klotho silencing is an important feature of the disease. Our findings show that klotho undergoes muscle-specific silencing at the acute onset of mdx pathology. Klotho experiences increased methylation of CpG sites in its promoter region, which is associated with gene silencing, and increases in a repressive histone mark, H3K9me2. Expression of a klotho transgene in mdx mice restored their longevity, reduced muscle wasting, improved function and greatly increased the pool of muscle-resident stem cells required for regeneration. Reductions of fibrosis in late, progressive stages of the mdx pathology achieved by transgene expression were paralleled by reduced expression of Wnt target genes (axin-2), transforming growth factor-beta (TGF-β1) and collagens types 1 and 3, indicating that Klotho inhibition of the profibrotic Wnt/TGFβ axis underlies its anti-fibrotic effect in aging, dystrophic muscle. Thus, epigenetic silencing of klotho during muscular dystrophy contributes substantially to lost regenerative capacity and increased fibrosis of dystrophic muscle during late progressive stages of the disease