Mullitización de mezclas de arcilla caolinítica e hidróxido de aluminio

Se calcinaron mezclas de arcilla caolinítica e hidróxido de aluminio, los ensayos se realizaron entre 900 y 1400°C, a distintos tiempos de calentamiento. Los compuestos obtenidos se estudiaron por técnicas de difracción de rayos X, dejándose establecido que se produce reacción entre la $latex Al_{2}O_{3}$ agregada y la $latex SiO_{2}$ liberada, para formar mullita a temperaturas inferiores a 1400°C, cuando la mezcla se precalienta varias horas a temperaturas próximas a los 1000°C. Se confirmó el fenómeno de nucleación de mullita, por tratamientos térmicos similares en mezclas de ácido silícico e hidróxido de aluminio puros. Es de interés tecnológico lograr la transformación total a mullita, de mezclas arcilla alúmina, a temperaturas no mayores de 1400°C. Por esto, el presente trabajo tuvo por fin comprobar si la $latex \gamma -Al_{2}O_{3}$ que se forma durante el calentamiento del $latex Al(OH)_{3}$ puede entrar en la reacción de mullitización del caolín, combinándose con la sílice remanente.Mixtures of kaolin clay and aluminium hydroxide were heated to temperatures between 900 and 1400°C for different periods. The heat treated samples were studied by X-ray diffraction techniques. It was clearly shown that the added $latex Al_{2}O_{3}$ reacts with the free $latex SiO_{2}$ to form mullite at temperatures below 1400°C when the mixtures were preheated for several hours at temperatures approaching 1000°C. Through similar heating treatments in mixtures of silicic acid and pure aluminium hydroxide, the mullite nucleation phenomenon was confirmed. It is of technological interest to achieve the total transformation to mullite of the clay-alumina mixtures by heating to temperatures not exceeding 1400°C. It was the aim of the present investigation to observe the reaction between the $latex \gamma-Al_{2}O_{3}$ form ed from $latex Al(OH)_{3}$ and the silica freed from the kaolin to form mullite

Nuevo proceso para la producción de mullita

Se desarrolló un nuevo proceso para la obtención de mullita, que consiste en la nucleación de una mezcla de arcilla caolinítica e hidróxido de aluminio por la acción simultánea del tratamiento térmico a 980°C y molienda, seguido del moldeado del polvo obtenido y una única calcinación entre 1 500°C y 1 650°C para obtener productos de mullita pura. El efecto del tiempo de molienda a 980°C y el desarrollo de los cristales de mullita por diferentes tratamientos térmicos a 1 400°C, 1 500°C y 1 650°C fueron estudiados por difracción con rayos X. El polvo nucleado a 980°c fue denominado "premullita”. Con este polvo se hicieron probetas, las que se calcinaron a temperaturas entre 1 500°C y 1 650°C. En todos los casos fueron obtenidos productos de mullita pura de baja porosidad y alta densidad.A new process to obtain mullite has been developed. It consists of the nucléation of a mixture of kaolinitic clay and aluminium hydroxide through simultaneous action of grinding and thermal treatment at 980°C, followed by shaping of ilie powder obtained and one single firing between 1 500°C and 1 650°C to obtain pure mullite products. The êffect of the grinding time at 980°c and development of mullite crystals by different thermal treatments at 1 400°C, 1 500°C and 1 650°C were studied by X-ray difraction. The nucleated powder at 980°C was named "premullite". Alongside with it probes were made and calcinated at temperatures between 1 500ºC and 1 650°C. In all these cases pure mullite products of a low porosity and high density were obtained

Heparan Sulfate Induces Necroptosis in Murine Cardiomyocytes: A Medical-in-Silico Approach Combining In Vitro Experiments and Machine Learning (vol 9, 393, 2018)

A Corrigendum on Heparan Sulfate Induces Necroptosis in Murine Cardiomyocytes: A Medical-In silico Approach Combining In vitro Experiments and Machine Learning by Zechendorf E, Vaßen P, Zhang J, Hallawa A, Martincuks A, Krenkel O, Müller-Newen G, Schuerholz T, Simon T-P, Marx G, Ascheid G, Schmeink A, Dartmann G, Thiemermann C and Martin L (2018). Front. Immunol. 9:393. doi: 10.3389/fimmu.2018.00393 In the original article, there was an error in the Author Contributions section. The wording used to declare the contribution of Elisabeth Zechendorf was not clear. The new Author Contributions section appears below. Conception and design: EZ, LM, GD, AS, and CT. In vitro experiments and data analyses: EZ, LM, TS, T-PS, AM, GM-N, OK, GM, and PV. Medical in silico experiments and data analyses: EZ, PV, JZ, GD, AS, LM, AH, and GA. EZ wrote the manuscript. Correction of the manuscript: EZ, PV, LM, CT, GM, GD, T-PS, and AS. All the authors reviewed and finally approved the manuscript. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated

Biological response of an in vitro human 3D lung cell model exposed to brake wear debris varies based on brake pad formulation

Wear particles from automotive friction brake pads of various sizes, morphology, and chemical composition are significant contributors towards particulate matter. Knowledge concerning the potential adverse effects following inhalation exposure to brake wear debris is limited. Our aim was, therefore, to generate brake wear particles released from commercial low-metallic and non-asbestos organic automotive brake pads used in mid-size passenger cars by a full-scale brake dynamometer with an environmental chamber simulating urban driving and to deduce their potential hazard in vitro. The collected fractions were analysed using scanning electron microscopy via energy-dispersive X-ray spectroscopy (SEM-EDS) and Raman microspectroscopy. The biological impact of the samples was investigated using a human 3D multicellular model consisting of human epithelial cells (A549) and human primary immune cells (macrophages and dendritic cells) mimicking the human epithelial tissue barrier. The viability, morphology, oxidative stress, and (pro-)inflammatory response of the cells were assessed following 24 h exposure to similar to 12, similar to 24, and similar to 48 A mu g/cm(2) of non-airborne samples and to similar to 3.7 A mu g/cm(2) of different brake wear size fractions (2-4, 1-2, and 0.25-1 A mu m) applying a pseudo-air-liquid interface approach. Brake wear debris with low-metallic formula does not induce any adverse biological effects to the in vitro lung multicellular model. Brake wear particles from non-asbestos organic formulated pads, however, induced increased (pro-)inflammatory mediator release from the same in vitro system. The latter finding can be attributed to the different particle compositions, specifically the presence of anatase.Web of Science9272351233

Antifibrotic Effects of the Dual CCR2/CCR5 Antagonist Cenicriviroc in Animal Models of Liver and Kidney Fibrosis

Background & Aims Interactions between C-C chemokine receptor types 2 (CCR2) and 5 (CCR5) and their ligands, including CCL2 and CCL5, mediate fibrogenesis by promoting monocyte/macrophage recruitment and tissue infiltration, as well as hepatic stellate cell activation. Cenicriviroc (CVC) is an oral, dual CCR2/CCR5 antagonist with nanomolar potency against both receptors. CVC’s anti-inflammatory and antifibrotic effects were evaluated in a range of preclinical models of inflammation and fibrosis. Methods Monocyte/macrophage recruitment was assessed in vivo in a mouse model of thioglycollate-induced peritonitis. CCL2-induced chemotaxis was evaluated ex vivo on mouse monocytes. CVC’s antifibrotic effects were evaluated in a thioacetamide-induced rat model of liver fibrosis and mouse models of diet-induced non-alcoholic steatohepatitis (NASH) and renal fibrosis. Study assessments included body and liver/kidney weight, liver function test, liver/kidney morphology and collagen deposition, fibrogenic gene and protein expression, and pharmacokinetic analyses. Results CVC significantly reduced monocyte/macrophage recruitment in vivo at doses ≥20 mg/kg/day (p < 0.05). At these doses, CVC showed antifibrotic effects, with significant reductions in collagen deposition (p < 0.05), and collagen type 1 protein and mRNA expression across the three animal models of fibrosis. In the NASH model, CVC significantly reduced the non-alcoholic fatty liver disease activity score (p < 0.05 vs. controls). CVC treatment had no notable effect on body or liver/kidney weight. Conclusions CVC displayed potent anti-inflammatory and antifibrotic activity in a range of animal fibrosis models, supporting human testing for fibrotic diseases. Further experimental studies are needed to clarify the underlying mechanisms of CVC’s antifibrotic effects. A Phase 2b study in adults with NASH and liver fibrosis is fully enrolled (CENTAUR Study 652-2-203; NCT02217475)

Barrier Tissue Macrophages: Functional Adaptation to Environmental Challenges

Macrophages are found throughout the body, where they have crucial roles in tissue development, homeostasis and remodeling, as well as being sentinels of the innate immune system that can contribute to protective immunity and inflammation. Barrier tissues, such as the intestine, lung, skin and liver, are exposed constantly to the outside world, which places special demands on resident cell populations such as macrophages. Here we review the mounting evidence that although macrophages in different barrier tissues may be derived from distinct progenitors, their highly specific properties are shaped by the local environment, which allows them to adapt precisely to the needs of their anatomical niche. We discuss the properties of macrophages in steady-state barrier tissues, outline the factors that shape their differentiation and behavior and describe how macrophages change during protective immunity and inflammation

CVD-Coating of Fabric Sheets in Combination with the LSI-Process

Due to short processing times and fairly low manufacturing costs the Liquid Silicon Infiltration Process (LSI) developed at the DLR in Stuttgart is a well established process to produce ceramic matrix composites (CMC) without any fiber coating [1]. The key step is the liquid silicon infiltration of porous carbon/carbon composites (C/C) whose distinct microstructure is formed in the preceding pyrolysis step of carbon fiber reinforced plastics (CFRP). These were produced by resin transfer molding (RTM) in a first step. This process leads to C/C-SiC composites being characterized by high mass-specific properties in combination with an extreme thermal shock stability. By applying special process pa-rameters the microstructure as well as the physical properties can be tailor-designed to match spe-cific requirements. However, compared to CMCs reinforced with coated fibers [2-5], C/C-SiC has a low damage tolerance and tensile strength since the fiber matrix bonding (FMB) is too high. An improvement can be achieved by a fiber pretreatment at about 600 °C prior to composite manufacturing [6]. However, the superior properties of composites manufactured with coated fibers cannot be achieved. Unfortunately, single fiber coating increases CMC costs considerably [7]. In order to overcome this problem, woven C-fabrics have been coated with pyrolytic carbon (pyC) and then submitted to the LSI-process yielding dense C/C-SiC. In a first step, C-fabric sheets (30 mm in width and 300 mm in length) were coated with pyC in both a CVD hot wall and alternatively in a CVD cold wall reactor under static condi-tions at about 900 °C. Toluene was used as a precursor whereas argon served as a carrier gas. Deposition times ranging from 10 to 20 min resulted in an increase in weight of 50 to 250 mg corre-sponding to a mean layer thickness of 39 to 189 nm on each single fiber. The pyC-coated C-fabrics exhibited increased stiffness with increased coating thickness as well as reference samples were submitted to the conventional LSI-process. Besides SEM-investigations on the pyC-coating, this paper reports on the physical and the mechanical properties of the composites manufactured via LSI-processing in all stages CFRP, C/C and especially C/C-SiC