Search results for "Microscopy"
showing 10 items of 3390 documents
Structure-Dependent Dissolution and Restructuring of Calcite Surfaces by Organophosphonates
2017
Organophosphonates are well-known to strongly interact with the surfaces of various minerals, such as brucite, gypsum, and barite. In this work, we study the influence of six systematically varied organophosphonate molecules (tetraphosphonates and diphosphonates) on the dissolution process of the (10.4) surface of calcite. In order to pursue a systematic study, we have selected organophosphonates that exhibit similar structural features, but also systematic architectural differences. The effect of this class of additives on the dissolution process of the calcite (10.4) surface is evaluated using in situ dynamic atomic force microscopy. For all of the six organophosphonate derivatives, we ob…
Reactivity of gypsum faces according to the relative humidity by scanning force microscopy
1997
Abstract This article reports the experimental observation of the stability of the different faces of calcium sulphate dihydrate (gypsum CaSO 4 .2H 2 O) according to the relative humidity. Scanning Force Microscopy experiments were carried out with a view to discerning the topography of the surfaces, the chemical compositional domains, and in an attempt to evaluate the friction and viscoelastic properties of the surface. Our results indicate that the (010) face of gypsum is hydrophilic and very reactive contrary to the less hydrophilic (120) and (101) faces which remain stable depending on the relative humidity. It is clear from our results that a precipitation like process can be induced b…
Flexible minerals: self-assembled calcite spicules with extreme bending strength.
2013
Flexi-Fibers Glass or metal fibers can show incredible flexibility. Natalio et al. (p. 1298 ; see the Perspective by Sethmann ) used the protein silicatein-α, which is responsible for the biomineralization of silicates in sponges, to guide the formation of spicules made of calcite. These synthetic spicules could be bent to a high degree because of their inherent elasticity, whilst retaining the ability to guide light.
Deposition order controls the first stages of a metal-organic coordination network on an insulator surface
2016
| openaire: EC/FP7/610446/EU//PAMS We report on first stages toward the formation of a surface-confined metal-organic coordination network (MOCN) by sequential deposition of biphenyl-4,4′-dicarboxylic acid and iron atoms on the surface of a bulk insulator, calcite (10.4). The influence of the deposition order on the structure formation is studied by noncontact atomic force microscopy operated in ultrahigh vacuum at room temperature. It is found that sequential deposition facilitates MOCN formation when the organic linker molecules are first adsorbed on the surface, followed by iron deposition. This observation is explained by first-principles computations, indicating that the metal-molecule…
Clear signature of the (2 x 1) reconstruction of calcite (1014).
2010
Calcite is a mineral of fundamental importance that plays a crucial role in many fields of research such as biomineralization, biomolecule adsorption, and reactivity as well as industrial and daily life applications. Consequently, the most stable cleavage plane of calcite has been studied extensively using both direct imaging techniques such as atomic force microscopy as well as spectroscopic and diffraction techniques. Several surface structures have been reported for the (10 (1) over bar4) cleavage plane of calcite differing from the simple bulk-truncated structure and an ongoing controversy exists in literature whether the cleavage plane exhibits a (2 x 1) reconstruction or not. We study…
Crystallized nano-sized alpha-tricalcium phosphate from amorphous calcium phosphate: microstructure, cementation and cell response
2015
New insight on the conversion of amorphous calcium phosphate (ACP) to nano-sized alpha tricalcium phosphate (α-TCP) provides a faster pathway to calcium phosphate bone cements. In this work, synthesized ACP powders were treated with either water or ethanol, dried, crystallized between 700 and 800 °C, and then cooled at different cooling rates. Particle size was measured in a scanning electron microscope, but crystallite size calculated by Rietveld analysis. Phase composition and bonding in the crystallized powder was assessed by x-ray diffraction and Fourier-transform infrared spectroscopy. Results showed that 50 nm sized α-TCP formed after crystallization of lyophilized powders. Water trea…
Influence of β-tricalcium phosphate granule size and morphology on tissue reaction in vivo.
2010
In this study the tissue reaction to five different β-tricalcium phosphate (β-TCP)-based bone substitute materials differing only in size, shape and porosity was analyzed over 60 days, at 3, 10, 15, 30 and 60 days after implantation. Using the subcutaneous implantation model in Wistar rats both the inflammatory response within the implantation bed and the resulting vascularization of the biomaterials were qualitatively and quantitatively assessed by means of standard and special histological staining methods. The data from this study showed that all investigated β-TCP bone substitutes induced the formation of multinucleated giant cells. Changes in size, shape and porosity influenced the int…
Induction of carbonic anhydrase in SaOS-2 cells, exposed to bicarbonate and consequences for calcium phosphate crystal formation.
2013
Ca-phosphate/hydroxyapatite crystals constitute the mineralic matrix of vertebrate bones, while Ca-carbonate dominates the inorganic matrix of otoliths. In addition, Ca-carbonate has been identified in lower percentage in apatite crystals. By using the human osteogenic SaOS-2 cells it could be shown that after exposure of the cells to Ca-bicarbonate in vitro, at concentrations between 1 and 10 mm, a significant increase of Ca-deposit formation results. The crystallite nodules formed on the surfaces of SaOS-2 cells become denser and larger in the presence of bicarbonate if simultaneously added together with the mineralization activation cocktail (β-glycerophosphate/ascorbic acid/dexamethason…
Aqueous two-phase system cold-set gelation using natural and recombinant probiotic lactic acid bacteria as a gelling agent
2016
The present study aimed to entrap probiotic lactic acid bacteria (LAB) in a sodium alginate and sodium caseinate aqueous two-phase gel system. The natural acidifying properties of two therapeutic probiotic LAB were exploited to liberate calcium ions progressively from calcium carbonate (CaCO3), which caused the gelation of the co-existing phases. Bi-biopolymeric matrix gelation of GDL/CaCO3 or LAB/CaCO3 was monitored by dynamic rheological measurements, and the final gels were characterized by frequency dependence measurements and confocal laser scanning microscopy. Weak to strong gels were formed with an elastic modulus G' from 10 to 1.000Pa, respectively. After cold-set gelation of our sy…