Biological control over the formation and storage of amorphous calcium carbonate by earthworms

2008 ◽  
Vol 72 (1) ◽  
pp. 227-231 ◽  
Author(s):  
M. J. I. Briones ◽  
E. López ◽  
J. Méndez ◽  
J. B. Rodríguez ◽  
L. Gago-Duport
Keyword(s):  
Electron Microscopy ◽  
Biological Control ◽  
Calcium Carbonate ◽  
Ostwald Ripening ◽  
High Resolution Electron Microscopy ◽  
Amorphous Calcium Carbonate ◽  
Concentrated Suspension ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Glandular Secretion

AbstractThe earthworm calciferous gland produces a concentrated suspension of calcium carbonate and in certain species precipitates as concretions of CaCO3, which then enter the soil. Here we investigated the initial stages of CaCO3 formation in the earthworm Lumbricus friendi by means of Fourier transform infrared and electron microscopy techniques (field-emission scanning electron microscopy, transmission electron microscopy, high resolution electron microscopy and selected area electron diffraction). In addition, comparisons between the IR spectra of the water-dissolved carbonic anhydrase (CA) and the glandular secretion (‘milky fluid’) were performed in order to investigate the mechanisms involved in CaCO3 precipitation. Our results strongly suggest that carbonation starts with the dissolved CO2, which is transformed via deprotonation to HCO3-, then to CO32- and finally to amorphous calcium carbonate (ACC). While ACC stabilization takes place under the biological control, further transformation stages leading to calcite concretions seem to be inorganically driven by an Ostwald ripening process.

Electron microscopy and diffraction of crystalline dendrimers and macrocycles

1993 ◽  
Vol 51 ◽  
pp. 1218-1219
Author(s):  
C. J. Buchko ◽  
P. M. Wilson ◽  
Z. Xu ◽  
J. Zhang ◽  
S. Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Liquid Crystalline ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
Scanning Calorimetry ◽  
Tertiary Butyl ◽  
Phenyl Acetylene ◽  
Selected Area Electron Diffraction ◽  
Liquid Crystalline Phases ◽  
Resolution Electron

The synthesis of well-defined organic molecules with unique geometries opens new opportunities for understanding and controlling the organization of condensed matter. Here, we study dendrimers and macrocycles which are synthesized from rigid phenyl-acetylene spacer units, Both units are solubilized by the presence of tertiary butyl groups located at the periphery of the molecule. These hydrocarbon materials form crystalline and liquid crystalline phases which have been studied by differential scanning calorimetry, hot stage optical microscopy, and wide-angle x-ray scattering (WAXS).The precisely defined architecture of these molecules makes it possible to investigate systematic variations in chemical architecture on the nature of microstructural organization. Here we report on the transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high resolution electron microscopy (HREM) studies of crystalline thin films formed by deposition of these materials onto carbon substrates from dilute solution. Electron microscopy is very attractive for gaining structural information on new molecules due to the scarcity of material to grow single crystals suitable for conventional crystallography.

Orientation Relationship between Fe2M and Martensite in M50NiL Steel

2013 ◽  
Vol 456 ◽  
pp. 533-536
Author(s):  
Yan Zhi Lou
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Orientation Relationship ◽  
High Resolution Electron Microscopy ◽  
Lattice Parameters ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Martensite Matrix

In this paper, high resolution electron microscopy (HREM) was used to observe nanosized Fe2M precipitates in M50NiL steel, and crystal structure of which was also investigated by selected area electron diffraction (SAED). At the same time, the orientation relationship between the Fe2M and the martensite matrix was also studied. The results suggested that crystal structure of Fe2M is close-packed hexagonal, and lattice parameters about a=b=0.473nm, c=0.772nm, α=β=90°, γ=120°. The orientation relationship between the nanoprecipitates Fe2M and martensite is and .

New nonhydrolytic route to synthesize crystalline BaTiO3 nanocrystals with surface capping ligands

2006 ◽  
Vol 21 (12) ◽  
pp. 3187-3195 ◽  
Author(s):  
Zhuoying Chen ◽  
Limin Huang ◽  
Jiaqing He ◽  
Yimei Zhu ◽  
Stephen O'Brien
Keyword(s):  
Electron Microscopy ◽  
Barium Titanate ◽  
Oleyl Alcohol ◽  
High Resolution Electron Microscopy ◽  
Decanoic Acid ◽  
Nonpolar Solvents ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Capping Ligands ◽  
20 Nm

A new nonhydrolytic route for the preparation of well-crystallized size-tunable barium titanate (BaTiO3) nanocrystals capped with surface ligands is reported. Our approach involves: (i) synthesizing a “pseudo” bimetallic precursor, and (ii) combining the as-synthesized bimetallic precursor with a mixture of oleylamine with different surface coordinating ligands at 320 °C for crystallization and crystal growth. Different alcohols in the precursor synthesis and different carboxylic acids were used to study the effect of size and morphological control over the nanocrystals. Nanocrystals of barium titanate with diameters of 6–10 nm (capped with decanoic acid), 3–5 nm (capped with oleic acid), 10–20 nm (a nanoparticle and nanorod mixture capped with oleyl alcohol), and 2–3 nm (capped with oleyl alcohol) were synthesized, and can be easily dispersed into nonpolar solvents such as hexane or toluene. Techniques including x-ray diffraction, transmission electron microscopy, selected area electron diffraction, and high-resolution electron microscopy confirm the crystallinity and morphology of these as-synthesized nanocrystals.

Gallium ZSM-5 type zeolites: A catalytical and structural electron microscopy study

1988 ◽  
Vol 46 ◽  
pp. 950-951
Author(s):  
Dwight R. Acosta ◽  
Isaac Schifter ◽  
José L. Contreras
Keyword(s):  
Electron Microscopy ◽  
Structural Characteristics ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
X Ray Diffraction ◽  
Modified Method ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Cage Size

Synthesis of stereo selective zeolites using Gallium as partial or total substitute instead of aluminum, may lead to obtention of a novel class of zeo lites with modification of channel apertures, cage size and total acidity. Reaction velocity and selectivity for isomerization and cracking processes, for instance, are influenced by acid force of protonic sites, which may be selective or active for particular catalytic reactions.Zeolites Z-683 and Z-691 with a 50% and 100% of A1 atoms substituted respectively, were synthesized using a modified method for ZSM-5 zeolite crystallization as described in the literature. The samples obtained were studied using ammonia (NH3) thermodesorption techniques. X-ray diffraction, high resolution electron microscopy, selected area electron diffraction and optical diffractometry methods were used in order to determine structural characteristics of zeolites above mentioned.Figure 1 shows the results of NH3 thermodesortion studies for three zeolites: Z-601 (ZSM-5), Z-683 (50% A1 - 50% Ga) and Z-691 (100% Ga).

Characterization of Cadmium Zinc Tellurium Obtained by Modified - Bridgman Technique

1993 ◽  
Vol 324 ◽  
Author(s):  
D.R. Acosta ◽  
F. Rabago
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Bridgman Technique ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Structural Details ◽  
Semiconductor Compounds ◽  
Ternary Semiconductor ◽  
The Stability

AbstractThe growth of ternary semiconductor compounds Cd1-ZZnx. Te leads to possible uses of this material like optoelectronic devices. In the present work we report the structural characterization of Cd0.96Zn0.04Te obtained by modified - Bridgman technique. Structural studies were carried out using Scanning Electron Microscopy (SEM) and Conventional and High Resolution Electron Microscopy (TEM and HREM, respectively). Selected Area Electron Diffraction (SAED) was used to determine local variations in composition. Characteristics of the growth of the bulk samples were observed and structural details that might be related with the stability of ternary phase were derived.

Determination of six new polytypes in parisite-(Ce) by means of high resolution electron microscopy

2001 ◽  
Vol 65 (6) ◽  
pp. 797-806 ◽  
Author(s):  
Meng Dawei ◽  
Wu Xiuling ◽  
Mou Tao ◽  
Li Douxing
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Mineral Deposit ◽  
Space Groups ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Rare Earth Mineral ◽  
Probable Space

AbstractThe ultrastructures of parisite-(Ce) from a rare-earth mineral deposit of Sichuan Province, southwest China, have been observed and investigated by selected area electron diffraction (SAED) and high resolution electron microscopy (HREM). Six new polytypes 4H, 10H, 16H, 18R, 24R and 30R were determined in parisite-(Ce), as were their crystal structure types, subcell (a′c‴, a′c″, a′c′) and supercell (ac) parameters, reflection conditions, polytype features and probable space groups. The HREM studies revealed the complex polytypism in parisite-(Ce) whereby the six new polytypes, formed by long-period ordered stacking, always coexist with the common polytype parisite-(Ce)-6R by syntaxy and thus constitute the complex microstructural ‘syntactic polycrystals’, the host of which is the polytype parisite-(Ce)-6R.

Dislocation mediated lattice bending in 1,6-di (N-carbazolyl)-2,4 hexadiyne (DCHD) polydiacetylene droplets

1992 ◽  
Vol 7 (11) ◽  
pp. 3150-3158 ◽  
Author(s):  
Patricia M. Wilson ◽  
David C. Martin
Keyword(s):  
Molecular Structure ◽  
Electron Microscopy ◽  
Room Temperature ◽  
High Resolution Electron Microscopy ◽  
Droplet Surface ◽  
The Core ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Carbon Coated ◽  
Edge Dislocations

Droplets of 1,6–di (N-carbazolyl)-2,4 hexadiyne (DCHD) polydiacetylene were prepared by room temperature evaporation of dilute (0.01 wt. %) solution of the monomer in chloroform onto amorphous carbon-coated mica substrates. High Resolution Electron Microscopy (HREM) and Selected Area Electron Diffraction (SAED) revealed small crystallographically textured droplets (∼1 μm diameter) with cracks parallel to the [001] chain direction. The droplet geometry allowed us to investigate the organization of the polymer near surfaces. It was found that the curvature of the droplet edge caused a local bending of the polymer crystal lattice. Direct imaging of the molecular structure near the droplet surface revealed that the mechanism of lattice bending was by the formation of edge dislocations. Dislocations were etched in some droplets to gain information about perturbations in structure and reactivity near the core.

Specific twin junctions in doped zirconia

2006 ◽  
Vol 62 (5) ◽  
pp. 761-767 ◽  
Author(s):  
F. M. Morales ◽  
M. Rühle
Keyword(s):  
Electron Microscopy ◽  
Coincidence Site Lattice ◽  
High Resolution Electron Microscopy ◽  
Site Lattice ◽  
Selected Area Electron Diffraction ◽  
Lack Of Information ◽  
Resolution Electron ◽  
Diffraction Patterns ◽  
Electron Back Scattered Diffraction

The effect of different dopant cations on the phase transformations of the initially stabilized supersaturated tetragonal ZrO2 phase during various heat treatments has been studied. The obtained fraction of monoclinic grains develop twinned structures, but there is still a lack of information about the character of grain boundaries formed in doped monoclinic solid solutions. The inspection of particular selected-area electron diffraction patterns provides an alternative method with respect to high-resolution electron microscopy or electron back-scattered diffraction for characterizing different twin junctions in various doped zirconia systems. The classification of these special twins is based on the coincidence site lattice concept.

Recent Applications of High Resolution Electron Microscopy to Crystalline Arrays of Virus Particles

1978 ◽  
Vol 36 (3) ◽  
pp. 470-482 ◽  
Author(s):  
R.W. Horne
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Analytical Techniques ◽  
Staining Technique ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Full Potential ◽  
Virus Particles ◽  
Resolution Electron ◽  
Wide Range

The technique of surrounding virus particles with a neutralised electron dense stain was described at the Fourth International Congress on Electron Microscopy, Berlin 1958 (see Home & Brenner, 1960, p. 625). For many years the negative staining technique in one form or another, has been applied to a wide range of biological materials. However, the full potential of the method has only recently been explored following the development and applications of optical diffraction and computer image analytical techniques to electron micrographs (cf. De Hosier & Klug, 1968; Markham 1968; Crowther et al., 1970; Home & Markham, 1973; Klug & Berger, 1974; Crowther & Klug, 1975). These image processing procedures have allowed a more precise and quantitative approach to be made concerning the interpretation, measurement and reconstruction of repeating features in certain biological systems.

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