Carbonated hydroxyapatite is the mineral found in vertebrate bones and teeth, whereas invertebrates utilize calcium carbonate in their mineralized organs. In particular, stable amorphous calcium carbonate is found in many crustaceans. Here we report on an unusual, crystalline enamel-like apatite layer found in the mandibles of the arthropod Cherax quadricarinatus (freshwater crayfish). Despite ...

Edison discovered that the coefficient of friction between a metallic plate and a porous material moistened with a dilute electrolyte could be modulated by an electric field. In experiments on the same kind of contacts (clays or chalks on carbon or metals) but without continuous tangential relative motion we measure two electro-mechanical effects at frequencies of the order of 10 kHz. An altern...

The mineralogical investigation, geochemical analysis, and grain size calculation were carried out for floodplain sediment in the Tigris River to identify properties of sediment. average values three main classes, very fine sand, silt, clay are 9.67, 62.53 27.80%, respectively. silt fraction was predominant. classification nomenclature surface types from sandy-silt mud, they dominant Statistica...

Three Moroccan clays, denoted A1, A3 and A5, were sampled from the Fez region with aim of potential use as aluminosilicate precursors for geopolymer synthesis. Each clay was subjected to calcination at 700 °C analyzed using DTA/TG, grain size distribution measurements, XRD, FTIR spectroscopy before after heat treatment. The results showed that three clays contain kaolinite in different proporti...

Several mechanisms have been proposed to explain the interactions between proteins and mineral surfaces, among them a combination of electrostatic, stereochemical interactions and molecular recognition between the protein and the crystal surface. To identify the mechanisms of interaction in the lysozyme– calcium carbonate model system, the effect of this protein on the precipitation kinetics an...

Abstract Microscale diagenetic changes that occur during burial exert a profound influence on the elastic and mechanical properties of sediments—but are poorly quantified. The focus here is how diagenesis influences carbonate-rich mudstones, which subject to wide range physical chemical changes. Nanoindentation data for gas-window (180 $$^\circ$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math...

Effects of carbonation temperature and compacting pressure on basic properties of calcite block were studied using Ca(OH)2 compact made with 0.2-2.0 MPa and their carbonation at 200-800ºC for 1 h. Microporous calcite was obtained only when carbonated at 600ºC using Ca(OH)2 compact made with 0.2 MPa even though thermogravimetry analysis showed that calcite powder was stable up to 920ºC under CO2...

The enzyme urease drives the hydrolysis of urea leading to the release of ammonium ions and bicarbonate; in the presence of calcium, the rise in pH leads to increased calcium carbonate saturation and the subsequent precipitation of calcite. Although such alkalinizing ureolysis is widespread in nature, most studies have focussed on bacteria (i.e. indigenous communities or urease-active Sporosarc...

Secondary, backscattered, high-resolution transmission, and energy-dispersive spectroscopy tools of electron microscopy reexamined Alexander von Humboldt’s field site of “brownish black crust[s]” covering rocks along cataracts of the Orinoco River. Modern tools confirm eighteenth-century analysis that the basic composition includes an abundance of manganese, iron, and carbon. Additional major c...