The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and morta...The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and mortar mixtures was implemented to improve their strength and waterproofing, respectively, using compression and water absorption tests according to their corresponding standards (ASTM C1231, ASTM D2938, and ASTM C1585). The samples were evaluated at different concentrations and curing ages. In addition, different sand/cement ratios were considered for the mortar. The results revealed that there was a 9.4% increase in compressive strength in concrete and a 23.7% reduction in water absorption in mortar for the 5:1 ratio. These changes would be the result of the interaction of the nanoporous additive in the atomic crystal structure of the material demonstrating the nanotechnological nature of allophane.展开更多
Metallo-β-lactamases are bacterial zinc-dependent enzymes involved in the hydrolysis of β-lactamic antibiotics representing the main cause of bacterial resistance to carbapenems, drugs of last resort for treating in...Metallo-β-lactamases are bacterial zinc-dependent enzymes involved in the hydrolysis of β-lactamic antibiotics representing the main cause of bacterial resistance to carbapenems, drugs of last resort for treating infections caused by multiresistant bacteria. We elaborated the hypothesis that it is possible to inhibit the enzymatic activity of metallo-β-lactamases by lowering the availability of zinc in the extracellular medium using metal chelating agents such as EDTA carried on nanoparticles. Chitosan, as linear cationic polysaccharide is frequently used in biomedical and pharmaceutical applications, has been studied as a biocompatible encapsulating agent in drug delivery systems and is an ideal transport agent for bioactive molecular complexes in antibiotic applications due to its ability to associate with negatively charged substances. We developed novel nanoparticles using chitosan as a transport matrix for β-lactamic antibiotics. Nanoparticles were synthesized according to the ion gelation method using tripolyphosphate as crosslinking agent. Nanoparticles were functionalized by the adsorption of EDTA, which acts as complexifying agent for Zn2+ ions causing inhibition of metallo-β-lactamases activity. We evaluate the antimicrobial effects of EDTA-functionalized nanoparticles with an imipenem cargo on the clinical isolate P. aeruginosa AG1, a carbapenem-resistant high-risk clone ST-111 carrying both blaIMP-18 and blaVIM-2 metallo-β-lactamases genes.展开更多
EDITOR'S NOTE: From August 11 through 21, 2005, Fernando Garcia, a reporter of Spain's ABC newspaper, undertook a reporting tour of Tibet at the invitation of China. After he returned home, Interviu, a Spanish maga...EDITOR'S NOTE: From August 11 through 21, 2005, Fernando Garcia, a reporter of Spain's ABC newspaper, undertook a reporting tour of Tibet at the invitation of China. After he returned home, Interviu, a Spanish magazine, carried his story tiffed Viejo Tibet, Nuevos Tibetanos. Following is his story translated from its Chinese version.展开更多
文摘The constant need for high-strength materials in the construction industry promotes the research of additives that improve the properties of masonry materials. The use of allophane as an additive in concrete and mortar mixtures was implemented to improve their strength and waterproofing, respectively, using compression and water absorption tests according to their corresponding standards (ASTM C1231, ASTM D2938, and ASTM C1585). The samples were evaluated at different concentrations and curing ages. In addition, different sand/cement ratios were considered for the mortar. The results revealed that there was a 9.4% increase in compressive strength in concrete and a 23.7% reduction in water absorption in mortar for the 5:1 ratio. These changes would be the result of the interaction of the nanoporous additive in the atomic crystal structure of the material demonstrating the nanotechnological nature of allophane.
基金the Inter-University Fund for Higher Education(FEES)at the National Council of Rectors(CONARE)for financial support to this project through grant agreement No ACUERDO-VI-171-2014
文摘Metallo-β-lactamases are bacterial zinc-dependent enzymes involved in the hydrolysis of β-lactamic antibiotics representing the main cause of bacterial resistance to carbapenems, drugs of last resort for treating infections caused by multiresistant bacteria. We elaborated the hypothesis that it is possible to inhibit the enzymatic activity of metallo-β-lactamases by lowering the availability of zinc in the extracellular medium using metal chelating agents such as EDTA carried on nanoparticles. Chitosan, as linear cationic polysaccharide is frequently used in biomedical and pharmaceutical applications, has been studied as a biocompatible encapsulating agent in drug delivery systems and is an ideal transport agent for bioactive molecular complexes in antibiotic applications due to its ability to associate with negatively charged substances. We developed novel nanoparticles using chitosan as a transport matrix for β-lactamic antibiotics. Nanoparticles were synthesized according to the ion gelation method using tripolyphosphate as crosslinking agent. Nanoparticles were functionalized by the adsorption of EDTA, which acts as complexifying agent for Zn2+ ions causing inhibition of metallo-β-lactamases activity. We evaluate the antimicrobial effects of EDTA-functionalized nanoparticles with an imipenem cargo on the clinical isolate P. aeruginosa AG1, a carbapenem-resistant high-risk clone ST-111 carrying both blaIMP-18 and blaVIM-2 metallo-β-lactamases genes.
文摘EDITOR'S NOTE: From August 11 through 21, 2005, Fernando Garcia, a reporter of Spain's ABC newspaper, undertook a reporting tour of Tibet at the invitation of China. After he returned home, Interviu, a Spanish magazine, carried his story tiffed Viejo Tibet, Nuevos Tibetanos. Following is his story translated from its Chinese version.