Search results for "SILICA"
showing 10 items of 1092 documents
Large-Scale Synthesis of Mammalian Gonadoliberin without protection of side-chain functions
1991
A simple, Large-scale preparation of mammalian gonadoliberin was elaborated using classical solution methods without protecting side-chain functions. At the final stage, a hexapeptide segment was condensed with the corresponding tetrapeptide and the obtained decapeptide was purified by a single chromatographic procedure on silica gel. The total efficiency of the whole synthesis and the purity of the product amounted to 34% and 98.3%, respectively.
NMR and Infrared Spectroscopies of C-S-H and Al-Substituted C-S-H Synthesised in Alkaline Solutions
1998
(C,N)-(S,A)-H samples have been synthesised from mixes of different CaO/SiO2 and AI(OH)3/SiO2 ratios in stirred suspensions in more or less concentrated soda solutions. The stoichiometry and spectroscopic characteristics of samples have been studied by FTIR, 27A1 and 29Si MAS NMR spectroscopies. The structural changes induced by substitutions have been discussed on the basis of the dreiketten structure of the tobermorite silicate chains.
Electrical tree growth in EVA-layered silicate nanocomposites
2006
This work deals with the growth of electrical treeing in different EVA-layered silicate nanostructured compounds. The experimental activity evidenced that the intercalated nanocomposites have longer lifetimes than pure EVA under the same constant AC stress conditions. A monitoring of the tree growth morphology allowed to evidence very interesting features of the intercalated nano-compounds showing a barrier effect to the treeing path. A preliminary investigation on the possible arrangement of the filler particles inside the matrix was also carried out.
Polyfurfuryl alcohol composite as adsorbent of polychlorinated biphenyls and pyrethroid insecticides
2007
Abstract Composites from furfuryl alcohol and silica gel were prepared in dichloromethane using trifluoroacetic acid as catalyst and characterized by means of thermogravimetric analysis, transmission electron microscopy and nitrogen adsorption–desorption isotherms. The polymer content in the composites ranged between 19.5% and 32.9%. The capability to adsorb polychlorinated biphenyls and pyrethroid insecticides was tested for composite samples containing different percentages of polymer. Pyrethroids are retained almost totally by composites containing around 24–33% of polymer, while recovery of PCBs close to 80% is obtained with all the composites. No selectivity between compounds of the sa…
PLASMOGENY, A NEW SCIENCE OF THE ORIGIN OF LIFE
2014
The Church has always hampered the progress of Mankind so as to retain its hold over awareness, which is the basis of secular exploitation of the people.
Atrane complexes chemistry as a tool for obtaining trimodal UVM-7-like porous silica
2018
[EN] The use of atrane complexes as hydrolytic precursors enables the homogeneous incorporation of manganese (25Si/Mn48) throughout the porous walls of the nanoparticles of a surfactant-templated bimodal mesoporous silica (UVM-7). The subsequent leaching of the manganese nanodomains allows adding controlled microporosity to the host silica framework. The resulting final silica material presents three pore systems structured at different length scales: interparticle textural-type macroporosity (ca. 43.2nm), ordered intraparticle mesoporosity (ca. 2.63nm; after template removal), and well-dispersed microporosity (< 2nm; as consequence of the lixiviation of the Mn-rich domains). The good dispe…
CLAYS IN COSMETICS AND PERSONAL-CARE PRODUCTS
2021
Clays are used in various cosmetic formulations, such as sunscreens, toothpastes, deodorants, creams, hair cosmetics, makeups, nail polish, facial masks, and shampoos, among others, to improve the organoleptic and physicochemical characteristics, to increase the stability, or to facilitate elaboration. Together with their technological functionalities, clays are cosmetologically active ingredients with cleaning, anti-aging, anti-wrinkling, and sun-care functionalities. Talc, kaolinite, mica, and some smectites are the clay minerals used most frequently in cosmetic products, but several other phyllosilicates as well as modified and synthetic clays are also used. Sometimes, clays are useful i…
Comparison of adsorption properties of commercial silica and rice husk ash (RHA) silica: A study by NIR spectroscopy
2021
Abstract Adsorption properties of Silica gel (commercial silica), rice husk ash (RHA) silica, and their hydrothermally treated products towards water molecules were studied in this work. RHA silica was prepared by heating rice husk to 650°C for 4 h after pretreatment with hydrochloric acid. Portions of the samples of silica were evacuated at 200℃ and then allowed to adsorb water molecules from the surrounding air at either 42 or 50% humidity. The near infrared spectra of these samples were measured at different time intervals during their adsorption of water molecules. The evolved near infrared spectra were analyzed using second derivative techniques. Adsorption properties of these samples …
Solvated copper(I) hexafluorosilicate π-complexes based on [Cu2(amtd)2]2+ (amtd = 2-allylamino-5-methyl-1,3,4-thiadiazole) dimer
2016
[Cu2(amdt)2]SiF6·C6H6 and [Cu2(amdt)2(H2O)2]SiF6·CH3CN·2H2O (amdt = 2-allylamino-5- methyl-1,3,4-thiadiazole) were obtained by alternating-current electrochemical synthesis, starting from water–acetonitrile–benzene mixtures containing 2-allylamino-5-methyl-1,3,4- thiadiazole and CuSiF6·4H2O. The electrochemical reduction of the saturated copper hexafluorosilicate water solution beneath the neatly poured layer of acetonitrile-benzene amdt solution resulted in the formation of crystalline [Cu2(amdt)2]SiF6·C6H6. The initial stirring of the same mixture before subjecting it to the electrochemical reduction resulted in the formation of [Cu2(amdt)2(H2O)2]SiF6·CH3CN·2H2O. A sluggish hydrolysis of …
(2S,3S)-2-Azaniumyl-4-[(1S,4aS,4bS,6S,7S,8aS,10aS)-6,7-dihydroxy-2,4b,8,8,10a-pentamethyl-1,4,4a,4b,5,6,7,8,8a,9,10,10a-dodecahydrophenanthren-1-yl]-…
2018
The title compound, which crystallized as a methanol and water solvate, C24H41NO5·CH4O·H2O, was obtained by heterologous expression of the brasilicardin gene cluster in the bacterium Amycolatopsis japonicum. In the crystal, the components are linked by numerous hydrogen bonds, generating a three-dimensional network.