Search results for "CARBONATE"
showing 10 items of 920 documents
Common genetic denominators for Ca++-based skeleton in Metazoa: role of osteoclast-stimulating factor and of carbonic anhydrase in a calcareous spong…
2012
Calcium-based matrices serve predominantly as inorganic, hard skeletal systems in Metazoa from calcareous sponges [phylum Porifera; class Calcarea] to proto- and deuterostomian multicellular animals. The calcareous sponges form their skeletal elements, the spicules, from amorphous calcium carbonate (ACC). Treatment of spicules from Sycon raphanus with sodium hypochlorite (NaOCl) results in the disintegration of the ACC in those skeletal elements. Until now a distinct protein/enzyme involved in ACC metabolism could not been identified in those animals. We applied the technique of phage display combinatorial libraries to identify oligopeptides that bind to NaOCl-treated spicules: those oligop…
Natural Compounds as Sustainable Additives for Biopolymers
2020
In the last few decades, the interest towards natural compounds, coming from a natural source and biodegradable, for biopolymers is always increasing because of a public request for the formulation of safe, eco-friendly, and sustainable materials. The main classes of natural compounds for biopolymers are: (i) naturally occurring fillers (nFil), such as nano-/micro- sized layered alumino-silicate: halloysite, bentonite, montmorillonite, hydroxyapatite, calcium carbonate, etc.; (ii) naturally occurring fibers (nFib), such as wood and vegetable fibers; (iii) naturally occurring antioxidant molecules (nAO), such as phenols, polyphenols, vitamins, and carotenoids. However, in this short review, …
Orbital chronology of the lower-middle Aptian: palaeoenvironmental implications (Serre Chaitieu section, Vocontian Basin).
2013
4 pages; International audience; A detailed cyclostratigraphic study conducted on several proxies including spectral gamma ray, magnetic susceptibility, clay minerals, and carbonate content suggests that the return to equilibrium in the carbon cycle after the major disturbance linked with Oceanic Anoxic Event 1a occurred in about 2 Myr. The minimum duration of the D. furcata zone is estimated at 0.46 Myr and that of the E. subnodosocostatum zone at 1.45 Myr. Strengthening of the obliquity record in the furcata zone confirms the cooling that characterizes this period.
( n ‐Bu 2 Sn) 2 O(CO 3 ): An active, robust and recyclable organotin(IV) for the direct synthesis of linear organic carbonates from carbon dioxide an…
2017
Organotin(IV) compounds are known to promote the direct synthesis of organic carbonates from carbon dioxide and alcohols. In the past, structural studies have highlighted that the carbonato moiety is a recurring ligand of tin species collected during CO2 pressurized reactions. In a mimetic approach and in order to achieve an available and recyclable precursor, the title compound (n-Bu2Sn)2O(CO3) (1) was prepared in a single step by reacting commercial di-n-butyltin dichloride with an aqueous solution of sodium carbonate. Compound 1 was characterized using infrared spectroscopy and thermogravimetric and elemental analyses. Multinuclear NMR investigations in solution were also conducted. Comp…
Ferromagnetic coupling through a carbonate bridge in the copper (II) chain [Cu(CO3)(4-apy)2] · H2O (4-apy = 4-aminopyridine)
1999
Abstract Atmospheric CO2 fixation by aqueous solutions containing copper(II) bromide and 4-aminopyridine (4-apy) yields the first carbonatobridged copper(II) chain of formula [Cu(CO3)(4-apy)2] · H2O that exhibits an intrachain ferromagnetic coupling.
Electrochemical reduction of graphene oxide films in aqueous and organic solutions
2013
Abstract Electrochemical reduction of graphene oxide (GO) films cast on tin oxide glass substrates were carried out in aqueous solutions and in propylene carbonate and acetonitrile. Cyclic voltammetric measurements indicate successful reduction of GO films. The reduction process begins in aqueous solutions at less negative potentials than in organic solutions. Additionally the pH value of the aqueous solutions influences the reduction potential. According to spectroscopic analysis the reduction process of the GO film can be controlled by the choice of reduction potential and electrolyte medium. The potential window in this work was made broader by increasing pH or by using organic electroly…
Protonation of Carbonate in Aqueous Tetraalkylammonium Salts at 25°C.
2006
Protonation constants of carbonate were determined in tetramethylammonium chloride (Me4NClaq 0.1≤I/mol kg−1 ≤4) and tetraethylammonium iodide (Et4NIaq 0.1≤I/mol kg−1 ≤1) by potentiometric ([H+]-glass electrode) measurements. Dependence of protonation constants on ionic strength was taken into account by modified specific ion interaction theory (SIT) and by Pitzer models. Literature data on the protonation of carbonate in NaClaq (0.1≤I/mol kg−1 ≤6) were also critically analysed. Both protonation constants of carbonate follow the trend Et4NI>Me4NCl > NaCl. An ion pair formation model designed to take into account the different protonation behaviours of carbonate in different supporting electr…
Antivirale Wirkstoffe, 20. Mitt. 4,6-Dialkylierte 2-Benzylthiopyrimidine
1981
Aus der Kondensation von Benzylisothioharnstoff (1) mit den β-Diketonen 2a–c gehen die 2-Benzylthiopyrimidine 3a–c hervor. Wird die Reaktion 1+2b jedoch in 30proz. wasr. Kaliumcarbonat-Losung/Ethanol/Ether durchgefuhrt, so tritt unter Ethanolyse Bildung von 2-Ethoxy-4,6-diethylpyrimidin (4) ein. 2-Benzylthio-4-ethyl-6-(trifluormethyl)pyrimidin ubt Hemmwirkung gegen Influenza A-Virus aus. Antiviral Agents, XX: 4,6-Dialkylated 2-Benzylthiopyrimidines Condensations of benzylisothiourea (1) with the β-diketones 2a–c yield the 4,6-dialkylated 2-benzylthiopyrimidines 3a–c. However, in 30% aqueous potassium carbonate solution/ethanol/ether, the reaction 1+2b proceeds by ethanolysis to form 2-ethox…
Jurassic evolution of the Arabian carbonate platform edge in the central Oman Mountains
2005
International audience; The Jurassic Sahtan Group exposed in northern Oman was deposited in shallow marine environments at the edge of the Arabian Platform facing the Neo-Tethys (Hamrat Duru Basin). The upper Sahtan Group is made up of a mixed siliciclastic-carbonate unit overlain by pure carbonate deposits, assigned to a Bathonian and Early Callovian age on the basis of brachiopods and foraminifers. These carbonate depositional systems were composed of outer oolitic shoals that underwent subaerial exposure, and a deeper, somewhat restricted, gently dipping shelf interior. Oolitic material was shed off the platform edge into the deep-sea depositional complex of the Guweyza Formation. The Sa…
Primary Cell Culture of Fresh Water Hyriopsis cumingii Mantle/Pearl Sac Tissues and Its Effect on Calcium Carbonate Mineralization
2014
Primary cell cultures of the fresh water Hyriopsis cumingii mantle and pearl sac tissues were produced in this study, and the influence of the tissue, cells, and secreted protein on calcium carbonate crystal nucleation and growth was studied. The study contributes to a further understanding of the influence of organic matrices on CaCO3 crystal formation. This research started from the protein level to the tissue/cell level, which is crucial for understanding the inorganic deposition process. The new data also add relevant theoretical approaches to an overall understanding of biomineralization processes. In the experimental groups with mantle or pearl sac tissue, the growth patterns of arago…