Search results for " carbonate"
showing 10 items of 381 documents
The role of filler type in the photo-oxidation behaviour of micro- and nano-filled polypropylene
2011
The rising interest in polymer nanocomposites leads also to an increasing concern for their photo-oxidation resistance. The main properties and photo-oxidation behaviour of polypropylene-based microcomposites and nanocomposites were investigated. The results show that the use of nanosized calcium carbonate may lead to a higher photo-oxidation rate than that of pristine polypropylene, in a way that is comparable to organo-modified nanoclays. It is also observed that nanosized calcium carbonate causes higher photodegradation rates than microsized calcium carbonate. The main reasons for the increased photo-oxidation rates when using organo-modified nanoclays include the presence of iron ions, …
Thermomechanical degradation of filled polypropylene
2003
The main problem in post-consumer plastics recycling is due to the thermomechanical stress acting on the melt during the reprocessing operations. The macromolecules break because of the temperature and of the mechanical stress. The extent of degradation is then correlated to the level of mechanical stress which, in turn, is proportional to the viscosity of the melt. The presence of fillers increases the viscosity of the polymers and then it is expected that the level of thermomechanical degradation of these systems is larger than that of the unfilled material. In this work the thermomechanical degradation kinetic of a polypropylene sample is investigated as a function of the calcium carbona…
Antivirale Wirkstoffe, 18. Mitt. 2-Aminothiazole durch Spaltung der S-S-Bindung des Disulfidodicarbamidins
1981
Bei der Umsetzung von Disulfidodicarbamidin (1) mit β-Diketonen 2 werden sowohl (2-Amino-5-thiazolyl)ketone 3 als auch 2,2′-Dithiobispyrimidine 4 und Pyrimidinthione 5 gebildet. Unter Verwendung von Ethanol/Kaliumcarbonat entstehen bei Raumtemp. sowohl aus aliphatisch symmetrisch (2a–c) als auch aus aliphatisch unsymmetrisch (2d) substsituierten, ferner aus fluorierten (2e) β-Diketonen, die korrespondierenden (2-Amino-5-thiazolyl)ketone 3a–e als Hauptprodukte. Antiviral Drugs, XVIII: 2-Aminothiazoles by Cleavage of the S-S-Bond of Disulfidodicarbamidine Through the interaction of disulfidodicarbamidine (1) with β-diketones 2, (2-amino-5-thiazolyl)ketones 3 as well as 2,2′-dithiobispyrimidin…
Polymere acroleine. III. Mittteilung. Oximierung und quantitative Bestimmung der Aldehydgruppen
1956
Die Oximierung von Disacryl wird beschrieben. Ferner werden Bedingungen fur eine quantitative Bestimmung von Aldehydgruppen in polymeren Acroleinen mitgeteilt. Es wird festgestellt, das Disacryl und ein durch Redox-Polymerisation gewonnenes Polyacrolein etwa 65% reaktionsfahige Aldehydgruppen enthalten. Bei Polyacroleinen, die mittels Borfluorid-Atherat oder Kaliumcarbonat gewonnen wurden, betragt der Umsatz mit Hydroxylamin nur etwa 20% d. Th. The oximation reaction of disacryl is described. The conditions of a quantitative determination of aldehyde function in polymeric acroleins have been investigated. It has been shown, that disacryl and an other polyacrolein, prepared by a redox-polyme…
Nucleation and Growth of CaCO3 Mediated by the Egg-White Protein Ovalbumin: A Time-Resolved in situ Study Using Small-Angle Neutron Scattering
2008
Mineralization of calcium carbonate in aqueous solutions starting from its initiation was studied by time-resolved small-angle neutron scattering (SANS). SANS revealed that homogeneous crystallization of CaCO 3 involves an initial formation of thin plate-shaped nuclei which subsequently reassemble to 3-dimensional particles, first of fractal and finally of compact structure. The presence of the egg-white protein ovalbumin leads to a different progression of mineralization through several stages; the first step represents amorphous CaCO 3, whereas the other phases are crystalline. The formation and dissolution of the amorphous phase is accompanied by Ca (2+)-mediated unfolding and cross-link…
Evolution of nacre: biochemistry and proteomics of the shell organic matrix of the cephalopod Nautilus macromphalus.
2009
12 pages; International audience; In mollusks, one of the most widely studied shell textures is nacre, the lustrous aragonitic layer that constitutes the internal components of the shells of several bivalves, a few gastropods, and one cephalopod: the nautilus. Nacre contains a minor organic fraction, which displays a wide range of functions in relation to the biomineralization process. Here, we have biochemically characterized the nacre matrix of the cephalopod Nautilus macromphalus. The acid-soluble matrix contains a mixture of polydisperse and discrete proteins and glycoproteins, which interact with the formation of calcite crystals. In addition, a few bind calcium ions. Furthermore, we h…
The skeleton of the staghorn coral Acropora millepora: molecular and structural characterization.
2014
15 pages; International audience; The scleractinian coral Acropora millepora is one of the most studied species from the Great Barrier Reef. This species has been used to understand evolutionary, immune and developmental processes in cnidarians. It has also been subject of several ecological studies in order to elucidate reef responses to environmental changes such as temperature rise and ocean acidification (OA). In these contexts, several nucleic acid resources were made available. When combined to a recent proteomic analysis of the coral skeletal organic matrix (SOM), they enabled the identification of several skeletal matrix proteins, making A. millepora into an emerging model for biomi…
Proteomics of CaCO3 biomineral-associated proteins: how to properly address their analysis.
2013
8 pages; International audience; In a recent editorial (Proc. Natl. Acad. Sci., 2013 110, E2144-E2146) and elsewhere, questions have been raised regarding the experimental practices in relation to the proteomic analysis of organic matrices associated to the biomineralized CaCO3 skeletons of metazoans such as molluscan shells and coral skeletons. Indeed, although the use of new high sensitivity MS technology potentially allows to identify a greater number of proteins, it is also equally (or even more) sensitive to contamination of residual proteins from soft tissues, which are in close contact with the biomineral. Based on our own past and present experimental know-how-observations that are …
The test skeletal matrix of the black sea urchin Arbacia lixula
2015
11 pages; International audience; In the field of biomineralization, the past decade has been marked by the increasing use of high throughput techniques, i.e. proteomics, for identifying in one shot the protein content of complex macromolecular mixtures extracted from mineralized tissues. Although crowned with success, this approach has been restricted so far to a limited set of key-organisms, such as the purple sea urchin Strongylocentrotus purpuratus, the pearl oyster or the abalone, leaving in the shadow non-model organisms. As a consequence, it is still unknown to what extent the calcifying repertoire varies, from group to group, at high (phylum, class), median (order, family) or low (g…
Calcifying zooplankton standing stocks and in the North Pacific from the R/V Kilo Moana cruise KM1712
2022
This dataset compiles the standing stocks (ind/m³), the integrated standing stocks (ind/m²) and the integrated CaCO3 standing stocks (mg/m²) for three groups of zooplanktonic calcifying organisms: pteropods, heteropods and foraminifers. The organisms were collected by oblique towing (Ø 0.5 m, 90 μm mesh size, SeaGear mechanical flowmeter) in the North Pacific between Hawaii and the Gulf of Alaska during the R/V Kilo Moana cruise KM1712 in August 2017. The sampling strategy was designed to capture an integrated sample of all foraminifers, pteropods and heteropods from juveniles to adults living throughout the upper water column. Pteropods and heteropods were quantified and shell diameter mea…