7 research outputs found
Preparation and characterization of thermally stabilized Ceria and Ceria containing materials
Ceria, CeO2, is one of the most important catalytic materials that can play multiple roles owing to its ability to release and uptake oxygen under catalytic reaction conditions with the preservation of it fluorite structure. Textural and thermal stability is a critical issue in determining the promoting and metal supporting functions of CeO2 in its catalytic applications in the three way catalysis. Therefore, significant efforts have been made by industry on finding ways to improve the thermal stability of ceria both by modification of the synthesis of CeO2 and by looking at possible stabilizers.
In the first part of this work, thermally stable ceria aggregates were obtained via a two-step sol gel process of cerium isopropoxide dispersed in isopropanol by ultrasonic radiation. The first step involved a hydrolysis reaction. In the second step, the resultant dispersions were mixed under stirring with neutral or basic water isopropanol solutions. The ceria powders obtained via neutral and basic media were shown to be composed of aggregates of fine particles. However, it was found that the type of media affected both particle texture and morphology. Specific surface areas of 33.1 and 44.2 m2g-1 respectively, were obtained for the neutral and basic materials, which calcined at 650 °C for 3 hours. Moreover, the oxidative nature of ceria was found to help in the removal of the organic impurities while the hydroxylated surface of ceria facilitated the formation of thermally stable agglomerates.
In the second part of this work, ceria supported on silica, ceria/silica, materials of 10 and 20% (w/w) were prepared by calcinations, at 650 °C for 3 h, of the xerogels obtained by the mixing of the corresponding amount of a ceria precursor with freshly prepared sols of spherical silica particles (Stober particles) in their mother liquors. Two different ceria precursors were examined in this investigation. The first was a gel produced by prehydrolysis of cerium (IV)-tetra isopropoxide in isopropanol media, and the second was an aqueous solution of ceric (IV) ammonium nitrate. Different textural and morphological characteristics that developed by calcination, were investigated by TGA, FTIR, XRD, SEM and analyses of N2 adsorption isotherms. The results indicated better ceria dispersion and formation of mesoporous textural composites materials produced by the second precursor, ceric (IV) ammonium nitrate, than the first precursor, prehydrolysed cerium (IV)-tetra isopropoxide.
The results show that properties of composite materials are largely related to the preparation method and the precursor type. Moreover, mixing media affect both nucleation and the growth of ceria particles and their protection against sintering upon calcinations at the test temperature
An insight into the paradigms of osteoporosis: From genetics to biomechanics
© 2019 The Authors Considered as one of the major epidemics of the 21st century, osteoporosis affects approximately 200 million people globally, with significant worldwide impact on rates of morbidity and mortality and massive socioeconomic burdens. Mainly characterized by decreased bone mineral density (BMD) and increased risk of bone fragility/deterioration, this devastating silent epidemic typically has no symptoms until a fracture occurs. The multifactorial disease, osteoporosis is instigated by complex interactions between genetic, metabolic and environmental factors, with severe impact on the biomechanics of the musculoskeletal system. This article provides a review of the epidemiology, genetic and biomechanical aspects of primary osteoporosis. The review begins with a summary of the epidemiology and global prevalence of osteoporosis. Sections 1 and 2 discuss the genetic associations and molecular signaling pathways involved in normal and pathological osteogenesis while Section 3 explores the biomechanics of osteoporosis and its quantitative damaging effects on critical bone mechanical properties, and associated bone remodeling. Overall, this review summarizes the recent findings about osteoporosis and emphasizes the importance of an integrative holistic approach in investigating osteoporosis towards providing better informed, more effective preventive and treatment modalities. Importantly, this work also explores the limited available literature on the various aspects of osteoporosis in the United Arab Emirates (UAE), Gulf Cooperation Council (GCC), and Middle East despite its alarming prevalence in the region, and highlights the need for further research and studies taking into consideration the importance of the vitamin D receptor (VDR) gene influencing the development of osteoporosis
Antipathogenic effects of structurally-related Schiff base derivatives: Structure–activity relationship
Eighteen structurally-related Schiff base derivatives, which belong to salicylidenebenzylamine and 2-hydroxy-1-naphthylidenebenzylamine families were prepared and characterized by spectroscopic techniques. All the synthesized compounds were screened in vitro for their antibacterial and antifungal activities. Human pathogenic gram-negative (Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa and Serratia marcescens), gram-positive bacteria (Staphylococcus epidermidis, Staphylococcus aureus and Bacillus subtilis), and fungi (Alternaria alternata, Aspergillus niger, Penicillium roqueforti, and Saccharomyces cerevisiae) were evaluated based on their toxicity to different concentrations of Schiff base compounds. For assessment of toxicity to pathogens, a disc diffusion assay was used to test the antimicrobial properties. The results revealed some antimicrobial activities of some of the synthesized compounds. Among the tested pathogens, the synthesized salicylidinaniline derivatives show highly potent action towards Alternaria alternata. Interestingly, a compound which contains the –Cl group is only effective against gram negative bacteria, but not gram positive bacteria. No remarkable antibacterial or antifungal activities were observed in the presence of –CH3 or –Br group. Furthermore, most of the naphthalene-containing compounds show no growth retardation towards bacterial or fungal pathogens. On the other hand, the presence of –OH or –SH group at para or ortho position, respectively, on the aniline site is correlated with an increased inhibitory drug effect on all pathogens. The importance of our findings to the drug research and developments is discussed in the context of finding a correlation between the structural properties of the new drugs and their biological activities
Ultrasound-mediated drug delivery by gas bubbles generated from a chemical reaction
<p>Highly echogenic and ultrasound-responsive microbubbles such as nitrogen and perfluorocarbons have been exploited as ultrasound-mediated drug carriers. Here, we propose an innovative method for drug delivery using microbubbles generated from a chemical reaction. In a novel drug delivery system, luminol encapsulated in folate-conjugated bovine serum albumin nanoparticles (Fol-BSAN) can generate nitrogen gas (N<sub>2</sub>) by chemical reaction when it reacts with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>), one of reactive oxygen species (ROS). ROS plays an important role in the initiation and progression of cancer and elevated ROS have been observed in cancer cells both <i>in vitro</i> and <i>in vivo</i>. High-intensity focussed ultrasound (HIFU) is used to burst the N<sub>2</sub> microbubbles, causing site-specific delivery of anticancer drugs such as methotrexate. In this research, the drug delivery system was optimised by using water-soluble luminol and Mobil Composition of Matter-41 (MCM-41), a mesoporous material, so that the delivery system was sensitive to micromolar concentrations of H<sub>2</sub>O<sub>2</sub>. HIFU increased the drug release from Fol-BSAN by 52.9 ± 2.9% in 10 minutes. The cytotoxicity of methotrexate was enhanced when methotrexate is delivered to MDA-MB-231, a metastatic human breast cancer cell line, using Fol-BSAN with HIFU. We anticipate numerous applications of chemically generated microbubbles for ultrasound-mediated drug delivery.</p