Electron microscopical and laser diffraction studies of the nucleation and growth of crystals in the organic matrix of dentine

1971 ◽  
Vol 117 (3) ◽  
pp. 381-393 ◽  
Author(s):  
H. J. H�hling ◽  
F. Scholz ◽  
A. Boyde ◽  
H. G. Heine ◽  
L. Reimer
Keyword(s):  
Organic Matrix ◽  
Nucleation And Growth ◽  
Laser Diffraction ◽  
Electron Microscopical

Genetic Coding in Biomineralization of Microlaminate Composites

1992 ◽  
Vol 292 ◽  
Author(s):  
Daniel E. Morse ◽  
Marios A. Cariolou ◽  
Galen D. Stucky ◽  
Charlotite M. Zaremba ◽  
Paul K. Hansma
Keyword(s):  
Organic Matrix ◽  
Nucleation And Growth ◽  
Direct Crystallization ◽  
Basic Principles ◽  
Shell Matrix ◽  
Additional Protein ◽  
Flexible Deformation ◽  
Abalone Shell ◽  
Crystalline Domains ◽  
Present Understanding

AbstractBiomineralization is precisely controlled by complex templating relationships ultimately encoded in the genes. In the formation of the molluscan shell, polyanionic pleated sheet proteins serve as templates for the nucleation and epitaxial growth of calcium carbonate crystalline domains to yield microlaminate composites of exceptional strength and crystal ordering. The strength and fracture-resistance of these composites far exceed those of the minerals themselves, as a result of both the capacity for flexible deformation of the organic matrix layers and the retardation of crack propagation at each mineral-organic interface. The basic principles controlling low temperature biosynthesis of these materials thus are of both fundamental and applied importance. The abalone shell consists of microlaminates with a remarkable regularity of lamina thickness (ca. 0.5 micron), the formation of which defies present understanding. We have found that shells of abalone larvae formed prior to metamorphosis contain only aragonite, whereas the adult shell made after metamorphosis contains both aragonite and calcite. This transition is accompanied by a switch in genetic expression of the template proteins, suggesting that the premetamorphic protein may serve as a template for aragonite nucleation and growth, while template proteins synthesized after metamorphosis may direct crystallization of calcite. These analyses are based on improvements we recently reported for the detection and purification of proteins from the demineralized shell matrix. Genetic cloning experiments now in progress are aimed at discovering additional protein sequences responsible for the programmed control of crystal phase termination, since it is the termination and reinitiation of mineralization that is responsible for the regularity of highly ordered microlaminates produced in nature.

Texturization Analysis by X-ray Diffraction of Shells of the Mussel Ischadium recurvum (Rafinesque, 1820) (Mollusca Bivalvia)

2001 ◽  
Vol 711 ◽  
Author(s):  
Octavio Gómez-Martínez ◽  
Daniel H. Aguilar ◽  
Juan J. Alvarado-Gil ◽  
Patricia Quintana ◽  
Dalila Aldana-Aranda
Keyword(s):  
Diffraction Study ◽  
Organic Matrix ◽  
Nucleation And Growth ◽  
Preferred Orientation ◽  
Bivalve Mollusk ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Matrix ◽  
Crystallographic Planes ◽  
Chemical Groups

ABSTRACTMost of the inorganic biomineralized materials are deposited on an organic matrix that controls the orientation and structure of the crystals. It is thought that chemical groups at the surface of the matrix may act as a template for the nucleation and growth of the mineral. A x-ray diffraction study of the texturization development of the bivalve mollusk shells is presented; specifically, the mussel Ischadium recurvum (Rafinesque, 1820), in different growing stages. The x-ray reflections show a preferred orientation that changes as the mollusk grows, and at the final stages only two crystallographic planes prevail.

Silk fibroin directs the formation monetite nanocrystals and their assembly into hierarchical composites

2021 ◽  
Author(s):  
Ying Huang ◽  
Hao Xie ◽  
Weijian Fang ◽  
Zhaoyong Zou ◽  
Zhengyi Fu
Keyword(s):  
Composite Materials ◽  
Silk Fibroin ◽  
Organic Matrix ◽  
Nucleation And Growth ◽  
Inorganic Crystals ◽  
Hierarchical Composites

Natural biominerals are usually composite materials produced through mineralization of inorganic crystals within an organic matrix. Silk fibroin is known to be capable of directing the nucleation and growth of...

AEM analysis of crystallization in Ti-based amorphous alloys

1983 ◽  
Vol 41 ◽  
pp. 270-271
Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Isothermal Annealing ◽  
Amorphous Matrix ◽  
Nucleation And Growth ◽  
Current Interest ◽  
Amorphous Films ◽  
Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

Ultrastructural localization of neuropeptides in the rat brain

1978 ◽  
Vol 36 (2) ◽  
pp. 612-613
Author(s):  
F.W. Van Leeuwen
Keyword(s):  
Freeze Substitution ◽  
Ultrastructural Localization ◽  
Serial Sections ◽  
Microscopical Level ◽  
Electron Microscopical Level ◽  
Enzyme Method ◽  
Perfusion Fixation ◽  
Electron Microscopical ◽  
Unlabeled Antibody ◽  
Peroxidase Conjugate

In order to obtain specific and optimal ultrastructural localization of vasopressin and oxytocin in the hypothalamo-neurohypophyseal system of the rat, 2 staining procedures and several tissue treatments were evaluated using neurohypophyseal tissue. It appeared from these studies that post-embedding staining with the unlabeled antibody enzyme method developed by Sternberger allows greater dilution of the first antibody (anti-vasopressin, 1:4800) than the indirect procedure (1:320) using a peroxidase conjugate as second antibody. Immersion fixation with 4% formalin during 24 hours gave better results (general ultrastructure, immunoreactivity) than those obtained by perfusion fixation with 2.5% glutaraldehyde-1% paraformaldehyde or freeze substitution.Since no reliable specificity tests were performed at the electron microscopical level, tests were developed for antibodies against both vasopressin and oxytocin. For anti-vasopressin plasma neural lobes of homozygous Brattleboro rats, that are lacking vasopressin by a genet- ical defect, were used. For antibodies against both hormones serial sections were used that were alternately incubated with the antibodies.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

A Protozoan Model for Golgi-Associated Calcification

1971 ◽  
Vol 29 ◽  
pp. 332-333
Author(s):  
D. C. Williams ◽  
D. E. Outka
Keyword(s):  
Golgi Apparatus ◽  
Organic Matrix ◽  
Model System ◽  
Sequential Formation

Many studies have shown that the Golgi apparatus is involved in a variety of synthetic activities, and probably no Golgi product is more elaborate than the scales produced by various kinds of phytoflagellates. The formation of calcified scales (coccoliths, Fig. 1,2) of the coccolithophorid phytoflagellates provides a particularly interesting model system for the study of biological mineralization, and the sequential formation of Golgi products.The coccoliths of Hymenomonas carterae consist of a scale-like base (Fig. 2 and 4, b) with a highly structured calcified (CaCO3) rim composed of two distinct elements which alternate about the base periphery (Fig. 1 and 3, A, B). Each element is enveloped by a sheath-like organic matrix (Fig. 3; Fig. 4, m).

Electrochemical nucleation and growth of copper on iron and aluminum: A TEM study of industrial copper cementation

1978 ◽  
Vol 36 (1) ◽  
pp. 454-455
Author(s):  
L.E. Murr ◽  
V. Annamalai
Keyword(s):  
Metal Surface ◽  
Copper Deposit ◽  
Nucleation And Growth ◽  
16Th Century ◽  
Electrochemical Reactions ◽  
Mine Shaft ◽  
De Re ◽  
Copper Precipitation ◽  
Electrochemical Nucleation ◽  
Interesting System

Georgius Agricola in 1556 in his classical book, “De Re Metallica”, mentioned a strange water drawn from a mine shaft near Schmölnitz in Hungary that eroded iron and turned it into copper. This precipitation (or cementation) of copper on iron was employed as a commercial technique for producing copper at the Rio Tinto Mines in Spain in the 16th Century, and it continues today to account for as much as 15 percent of the copper produced by several U.S. copper companies.In addition to the Cu/Fe system, many other similar heterogeneous, electrochemical reactions can occur where ions from solution are reduced to metal on a more electropositive metal surface. In the case of copper precipitation from solution, aluminum is also an interesting system because of economic, environmental (ecological) and energy considerations. In studies of copper cementation on aluminum as an alternative to the historical Cu/Fe system, it was noticed that the two systems (Cu/Fe and Cu/Al) were kinetically very different, and that this difference was due in large part to differences in the structure of the residual, cement-copper deposit.

Fundamental Research into Thin Films in a Developing Country

1972 ◽  
Vol 30 ◽  
pp. 500-501
Author(s):  
J.A. Eades ◽  
E. Grünbaum
Keyword(s):  
Thin Films ◽  
Growth Process ◽  
Empirical Process ◽  
Nucleation And Growth ◽  
Research Groups ◽  
Film Research ◽  
Fundamental Research ◽  
Controlled Deposition ◽  
The One ◽  
The University

In the last decade and a half, thin film research, particularly research into problems associated with epitaxy, has developed from a simple empirical process of determining the conditions for epitaxy into a complex analytical and experimental study of the nucleation and growth process on the one hand and a technology of very great importance on the other. During this period the thin films group of the University of Chile has studied the epitaxy of metals on metal and insulating substrates. The development of the group, one of the first research groups in physics to be established in the country, has parallelled the increasing complexity of the field.The elaborate techniques and equipment now needed for research into thin films may be illustrated by considering the plant and facilities of this group as characteristic of a good system for the controlled deposition and study of thin films.

Human Enamel Replication

1976 ◽  
Vol 34 ◽  
pp. 180-181
Author(s):  
Norman L. Dockum ◽  
John G. Dockum
Keyword(s):  
Organic Matrix ◽  
Human Teeth ◽  
Human Enamel ◽  
Straight Line ◽  
Ultrastructural Characteristics

Ultrastructural characteristics of fractured human enamel and acid-etched enamel were compared using acetate replicas shadowed with platinum and palladium. Shadowed replications of acid-etched surfaces were also obtained by the same method.Enamel from human teeth has a rod structure within which there are crystals of hydroxyapatite contained within a structureless organic matrix composed of keratin. The rods which run at right angles from the dentino-enamel junction are considered to run in a straight line perpendicular to the perimeter of the enamel, however, in many areas these enamel rods overlap, interlacing and intertwining with one another.

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