Optimised phase compositions and improved microwave dielectric properties based on calcium tin silicates

The Ca_(1+2y)Sn_(1-x)Si_(1+y)O_(5-2x+4y) low-permittivity microwave dielectric ceramics were prepared through solid-state reaction at 1350–1450 °C for 5 h. The relations between microwave dielectric properties and phase compositions for non-stoichiometric Ca_(1+2y)Sn_(1-x)Si_(1+y)O_(5-2x+4y) ceramics have been investigated. A single CaSnSiO₅ phase with abnormally positive temperature coefficient of resonant frequency (τ_f = + 62.5 ppm/°C) was synthesised at 1450 °C. This composition was an effective τ_f compensator of CaSiO₃ and Ca₃SnSi₂O₉ phases with typically negative τ_f value. The CaSiO₃ second phase was related to the Sn deficiency in the CaSn_(1-x)SiO_(5-2x) (0 < x < 1.0) composition, whereas the Ca₃SnSi₂O₉ second phase was obtained by controlling the Ca:Sn:Si ratios on the basis of the Ca_(1+2y)SnSi_(1+y)O_(5+4y) (0 < y < 1.0) composition. A promising low-permittivity millimetre-wave ceramic with most excellent microwave dielectric properties (ε_r = 10.2, Q×f = 81,000 GHz and τ_f = −4.8 ppm/°C) was produced from the Ca_(1+2y)SnSi_(1+y)O_(5+4y) (y = 0.4) ceramic.     

冶金过程中复杂夹杂物和钢液化学平衡计算

本文提出一个同温冶炼过程中预测非金属夹杂物沉淀的计算机程序。本研究中，多元硅酸盐溶体的Ｇｉｂｂｓ自由能由基于统计热力学的晶胞模型来计算，该晶胞模型按照氧与周围的阳离子构成的对称和非对称晶胞来描述硅酸盐熔体结构，假定高温冶炼时认与非金属夹杂物平衡，钢液中氧化物元素的活度由Ｗａｇｎｅｒ交互作用系数来计算，利用本程序可以估计炼钢时沉淀的非金属氧化物的成分，为调整冶炼工艺和提高产品质量提供指导，进一步可计     

Preliminary<Emphasis Type="Italic">in vitro</Emphasis> and<Emphasis Type="Italic">in vivo</Emphasis> characterizations of a sol-gel derived bioactive glass-ceramic system

This study investigates quantitatively and qualitatively the sol-gel derived bioactive glass-ceramic system (BGS)—apatite-wollastonite (AW) type granules in the size range of 0.5–1 mm, as an effective graft material for bone augmentation and restoration. Scanning electron micrographs (SEM) of the sintered granules revealed the rough material surface with micropores in the range 10–30 μm. X-ray diffraction (XRD) pattern of the granules revealed the presence of crystalline phases of the hydroxyapatite and wollastonite, and the functional groups of the silicate and phosphates were identified by Fourier transform infrared spectroscopy (FT-IR). Thein vitro cell culture studies with L929 mouse fibroblast cell line showed very few cells adhered on the BGS disc after 24 h. This could be due to the highly reactive surface of the disc concomitant with the crystallization but not due to the cytotoxicity of the material, since the cellular viability (MTT assay) with the material was 80‰ Cytotoxicity and cytocompatibility studies proved that the material was non-toxic and biocompatible. After 12 weeks of implantation of the BGS granules in the tibia bone of New Zealand white rabbits, the granules were found to be well osteointegrated, as observed in the radiographs. Angiogram with barium sulphate and Indian ink after 12 weeks showed the presence of microcapillaries in the vicinity of the implant site implicating high vascularity. Gross observation of the implant site did not show any inflammation or necrosis. SEM of the implanted site after 24 weeks revealed good osteointegration of the material with the newly formed bone and host bone. New bone was also observed within the material, which was degrading. Histological evaluation of the bone healing with the BGS granules in the tibial defect at all time intervals was without inflammation or fibrous tissue encapsulation. After 2 weeks the new bone was observed as a trabeculae network around the granules, and by 6 weeks the defect was completely closed with immature woven bone. By 12 weeks mature woven bone was observed, and new immature woven bone was seen within the cracks of the granules. After 24 weeks the defect was completely healed with lamellar bone and the size of the granules decreased. Histomorphometrically the area percentage of new bone formed was 67.77% after 12 weeks and 63.37% after 24 weeks. Less bone formation after 24 weeks was due to an increased implant surface area contributed by the material degradation and active bone remodeling. The osteostimulative and osteoconductive potential of the BGS granules was established by tetracycline labelling of the mineralizing areas by 2 and 6 weeks. This sol-gel derived BGS granules proved to be bioactive and resorbable which in turn encouraged active bone formation.     

谷氨酰胺(Gln)活性肽营养液的研究进展

对G1n小肽在氨基酸营养液中的使用以及G1n小肽的稳定性和代谢机制进行了论述。G1n是一种“条件必需氨基酸”，但Cln的水溶液不稳定，因而在氨基酸输液或氨基酸营养被中，用G1n小肽代替G1n单体使用。G1n小肽含有取代的α—NH2，使Cln小肽的稳定性大大增加。     

Bioactive compounds in rye flours with different extraction rates

Rye flours with extraction rate of 100% (wholemeal flour), 95% (brown flour), 90% (brown flour) and 70% (light flour) were prepared in order to study the relation between flour extraction rates and content of bioactive compounds. The following compounds were analysed: total phenolic compounds (TPC), total flavonoids (TF), inositol hexaphosphate (IP6), reduced (GSH) and oxidized (GSSG) glutathione, tocopherols (T) and tocotrienols (T3). The reduced/oxidized glutathione status (GSH/GSSG) of the flours was examined as a potential index of flour resistance against oxidative stress. The following observations were made in relation to the flour extraction rates and bioactive compounds contents: (a) milling process caused decrease in content in TPC, TF, IP6, GSH and GSSG, T and T3, (b) the most resistant against oxidation processes were suggested a brown flours, then light and finally wholemeal flour, (c) the ratio of tocotrienols to tocopherols (T3/T) was the highest in rye flours with extraction rate of 100–90% whereas light flour was the poorest source of tocopherols and tocotrienols. The provided data support current trend to increase number of rye products from wholemeal or brown flours.     

Drying of persimmons (Diospyros kaki L.) and the following changes in the studied bioactive compounds and the total radical scavenging activities

Fresh persimmons were subjected to two different processes: sun-drying during 1 month and dehydration at 60 °C during 12 h. To assess the effect of this process on nutritional and health-related properties of persimmons dietary fibers, minerals, trace elements, polyphenols and the total radical scavenging activities (TRSAs) were determined before and after processing. It was found that the contents of dietary fibers, minerals and trace elements in fresh and dried persimmons fruits were comparable. Total polyphenols in fresh persimmons was higher than in dried fruits (1.3 vs. 0.9 and 0.8 mg/100 g FW, respectively) and percentage of inhibition was higher than in dried fruits (70% vs. 59% and 55% and 58% vs. 53% and 46% for 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) [ABTS] radicals, respectively (P>0.05 in all cases). In conclusion: (1) the differences in the contents of dietary fibers, minerals and trace elements in fresh and dried persimmons are not significant; (2) the contents of polyphenols and the level of the TRSA are higher in fresh persimmons than in dried fruits; however, both variables are also high in dried persimmons; (3) when fresh fruits are not available, proper dried persimmons could be used as a valuable substitute.     

Natural rubber-based nanocomposites by latex compounding with layered silicates

Natural rubber (NR) based nanocomposites with 10 wt% natural and synthetic layered silicates were produced via the latex compounding method. As layered silicates, sodium bentonite (natural) and sodium fluorohectorite (synthetic) were selected in addition to a non-layered inert filler (English India clay or commercial clay) as reference material. The nanocomposites were prepared by compounding the dispersions of clays and other latex chemicals necessary for vulcanization. The vulcanized nanocomposites were subjected to mechanical, thermal and swelling tests. The silicate dispersion was studied by transmission electron microscopy. Layered silicates outperformed the reference material (commercial clay) in all aspects. This was attributed to the intercalation/exfoliation of the silicates and to the formation of a skeleton ‘(house of cards)’ silicate network in the NR matrix.     

溶胶-凝胶法CaO-P2O5-SiO2系生物玻璃的制备及机理探讨

以正硅酸乙酯[Si(OC2H5)4]、四水硝酸钙[Ca(NO3)2*4H2O]等作为前驱体,采用溶胶-凝胶工艺制备CaO-P2O5-SiO2系生物活性玻璃,把制备的样品放在模拟体液中浸泡一段时间后取出,以X-射线衍射、红外光谱等手段对其作物相分析,确定在玻璃的表面有羟基磷灰石相生成,同时对其形成机理做了进一步探讨.     

High-temperature Na2SO4 interaction with air plasma sprayed Yb2Si2O7 + Si EBC system: Topcoat behavior

The high-temperature interaction between ~2.5 mg/cm² of Na₂SO₄ and an atmospheric plasma sprayed (APS) Yb₂Si₂O₇ topcoat–Si bond coat system on SiC CMC substrates was studied for times up to 240 h at 1000°C–1316°C in a 0.1% SO₂–O₂ gaseous environment. Yb₂Si₂O₇ reacted with Na₂SO₄ to form Yb₂SiO₅ and an intergranular amorphous Na-silicate phase. Below 1200°C, the reaction was sluggish, needing days to cause morphological changes to the “splat microstructure” associated with APS coatings. The reaction was rapid at 1200°C and above, needing only a few hours for the entire topcoat to transform into a granulated microstructure consisting of Yb₂SiO₅ and Yb₂Si₂O₇ phases. Na₂SO₄ deposits infiltrated the Yb₂Si₂O₇ topcoat and transformed into an amorphous Na-silicate in less than 1 h at all exposure temperatures. Quantitative assessment of the Yb₂SiO₅ area fraction in the topcoat showed a linear decrease over time at 1316°C, attributed to reaction with the SiO₂ thermally grown oxide (TGO) formed on the Si bond coat and rapid transport through the interpenetrating amorphous Na-silicate grain boundary phase. It was predicted that nearly 2 weeks is needed for complete removal of Yb₂SiO₅ from the topcoat at 1316°C for a single applied loading of Na₂SO₄.