The Nature and Crystal Growth of Otoconia in the Rat

1975 ◽  
Vol 84 (1) ◽  
pp. 22-36 ◽  
Author(s):  
Muriel D. Ross ◽  
Donald R. Peacor
Keyword(s):  
Crystal Growth ◽  
Structural Unit ◽  
Integrated Approach ◽  
Nucleation And Growth ◽  
Organic Substrate ◽  
Crystal Nucleation ◽  
Chemical Factor ◽  
Adult Type ◽  
Inorganic Crystal ◽  
Parallel Growth

Several types of otoconia are present in the macular regions of young rats. These include multifaceted, transitional and rounded body forms, some variant otoconia and a few rhombohedrons. The adult form has typically rounded but nonsmooth body surfaces and pointed ends with three planar faces. The multifaceted and transitional otoconia fracture and etch more readily than do the adult type. The differences in properties of the otoconia are considered in the light of known facts concerning inorganic crystal nucleation and growth. This integrated approach indicates that many otoconia originate by seeding of multiple subunits on an organic substrate and develop by the mechanism of parallel growth. The basic structural unit is the rhombohedron. By analogy to inorganic crystals of calcite, it would seem that the typical otoconium grows on the end faces but growth on the side faces is suppressed by some unknown chemical factor. Some otoconia are exceptions, evidently seeding and growing in the pure rhombohedral form. Decalcification of cleaved otoconia shows that organic material is incorporated during growth. The observations are interpreted to indicate that organic substance influences growth and achievement of the adult otoconial form.

A double cell for controlling nucleation and growth of protein crystals

1989 ◽  
Vol 22 (2) ◽  
pp. 115-118 ◽  
Author(s):  
M. Przybylska
Keyword(s):  
Crystal Growth ◽  
Protein Crystallization ◽  
Heavy Atom ◽  
Nucleation And Growth ◽  
The Other ◽  
Crystal Nucleation ◽  
Diffusion Method ◽  
Vapour Diffusion ◽  
Reservoir Solution ◽  
The Stability

A simple device for protein crystallization is described that consists of two connected cells, one for the hanging- or sitting-drop vapour diffusion method and the other for changing the concentration of the reservoir solution. It has been found useful for decoupling crystal nucleation from crystal growth, for improving the size and the stability of crystals, and in the preparation of heavy-atom derivatives.

scholarly journals The bee Tetragonula builds its comb like a crystal

2020 ◽  
Vol 17 (168) ◽  
pp. 20200187 ◽  
Author(s):  
Silvana S. S. Cardoso ◽  
Julyan H. E. Cartwright ◽  
Antonio G. Checa ◽  
Bruno Escribano ◽  
Antonio J. Osuna-Mascaró ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Lattice Model ◽  
Stingless Bees ◽  
Nucleation And Growth ◽  
Coupled Map Lattice ◽  
Three Dimensions ◽  
Crystal Nucleation ◽  
Target Pattern ◽  
Brood Comb ◽  
Molecular Scale

Stingless bees of the genus Tetragonula construct a brood comb with a spiral or a target pattern architecture in three dimensions. Crystals possess these same patterns on the molecular scale. Here, we show that the same excitable-medium dynamics governs both crystal nucleation and growth and comb construction in Tetragonula , so that a minimal coupled-map lattice model based on crystal growth explains how these bees produce the structures seen in their bee combs.

scholarly journals Molecular Dynamics Simulations of Crystal Nucleation near Interfaces in Incompatible Polymer Blends

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 347
Author(s):  
Wenlin Zhang ◽  
Lingyi Zou
Keyword(s):  
Molecular Dynamics ◽  
Polymer Blends ◽  
Md Simulations ◽  
Nucleation And Growth ◽  
Crystal Nucleation ◽  
Crystalline Order ◽  
Mobile Species ◽  
Deep Supercooling ◽  
Crystallizable Polymer ◽  
Dynamics Simulations

We apply molecular dynamics (MD) simulations to investigate crystal nucleation in incompatible polymer blends under deep supercooling conditions. Simulations of isothermal nucleation are performed for phase-separated blends with different degrees of incompatibility. In weakly segregated blends, slow and incompatible chains in crystallizable polymer domains can significantly hinder the crystal nucleation and growth. When a crystallizable polymer is blended with a more mobile species in interfacial regions, enhanced molecular mobility leads to the fast growth of crystalline order. However, the incubation time remains the same as that in pure samples. By inducing anisotropic alignment near the interfaces of strongly segregated blends, phase separation also promotes crystalline order to grow near interfaces between different polymer domains.

Phase separation in undercooled molten Pd80Si20: Part I

1999 ◽  
Vol 14 (9) ◽  
pp. 3653-3662 ◽  
Author(s):  
K. L. Lee ◽  
H. W. Kui
Keyword(s):  
Growth Rate ◽  
Phase Separation ◽  
Crystal Growth ◽  
Grain Refinement ◽  
Crystallization Temperature ◽  
Sharp Decrease ◽  
Nucleation And Growth ◽  
Crystal Growth Rate ◽  
Large Undercooling ◽  
Kinetic Crystallization

Three different kinds of morphology are found in undercooled Pd80Si20, and they dominate at different undercooling regimens ΔT, defined as ΔT = T1 – Tk, where T1 is the liquidus of Pd80Si20 and Tk is the kinetic crystallization temperature. In the small undercooling regimen, i.e., for ΔT ≤ 190 K, the microstructures are typically dendritic precipitation with a eutecticlike background. In the intermediate undercooling regimen, i.e., for 190 ≤ ΔT ≤ 220 K, spherical morphologies, which arise from nucleation and growth, are identified. In addition, Pd particles are found throughout an entire undercooled specimen. In the large undercooling regimen, i.e., for ΔT ≥ 220 K, a connected structure composed of two subnetworks is found. A sharp decrease in the dimension of the microstructures occurs from the intermediate to the large undercooling regimen. Although the crystalline phases in the intermediate and the large undercooling regimens are the same, the crystal growth rate is too slow to bring about the occurrence of grain refinement. Combining the morphologies observed in the three undercooling regimens and their crystallization behaviors, we conclude that phase separation takes place in undercooled molten Pd80Si20.

scholarly journals Crystal nucleation and growth kinetics of NaF in photo-thermo-refractive glass

2013 ◽  
Vol 378 ◽  
pp. 115-120 ◽  
Author(s):  
I. Dyamant ◽  
A.S. Abyzov ◽  
V.M. Fokin ◽  
E.D. Zanotto ◽  
J. Lumeau ◽  
...  
Keyword(s):  
Growth Kinetics ◽  
Nucleation And Growth ◽  
Crystal Nucleation ◽  
Kinetics Of

Membrane-protein crystals for neutron diffraction

2018 ◽  
Vol 74 (12) ◽  
pp. 1208-1218 ◽  
Author(s):  
Thomas Lykke-Møller Sørensen ◽  
Samuel John Hjorth-Jensen ◽  
Esko Oksanen ◽  
Jacob Lauwring Andersen ◽  
Claus Olesen ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Neutron Diffraction ◽  
Membrane Protein ◽  
Neutron Source ◽  
Nucleation And Growth ◽  
Crystal Nucleation ◽  
Protein Crystals ◽  
Macromolecular Crystallography ◽  
Transport Mechanisms ◽  
Potential Impact

Neutron macromolecular crystallography (NMX) has the potential to provide the experimental input to address unresolved aspects of transport mechanisms and protonation in membrane proteins. However, despite this clear scientific motivation, the practical challenges of obtaining crystals that are large enough to make NMX feasible have so far been prohibitive. Here, the potential impact on feasibility of a more powerful neutron source is reviewed and a strategy for obtaining larger crystals is formulated, exemplified by the calcium-transporting ATPase SERCA1. The challenges encountered at the various steps in the process from crystal nucleation and growth to crystal mounting are explored, and it is demonstrated that NMX-compatible membrane-protein crystals can indeed be obtained.

scholarly journals In situ X-ray Diffraction Investigation of the Crystallisation of Perfluorinated Ce(IV)-based Metal-Organic Frameworks with UiO-66 and MIL-140 architectures

2020 ◽  
Author(s):  
Stephen Shearan ◽  
Jannick Jacobsen ◽  
Ferdinando Costantino ◽  
Roberto D’Amato ◽  
Dmitri Novikov ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Metal Organic Frameworks ◽  
Building Blocks ◽  
Nucleation And Growth ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rate Determining Step ◽  
Wide Range ◽  
Metal Organic

We report on the results of a thorough <i>in situ</i> synchrotron powder X-ray diffraction study of the crystallisation in aqueous medium of two recently discovered perfluorinated Ce(IV)-based metal-organic frameworks (MOFs), analogues of the already well investigated Zr(IV)-based UiO-66 and MIL-140A, namely, F4_UiO-66(Ce) and F4_MIL-140A(Ce). The two MOFs were originally obtained in pure form in similar conditions, using ammonium cerium nitrate and tetrafluoroterephthalic acid as building blocks, and small variations of the reaction parameters were found to yield mixed phases. Here, we investigate the crystallisation of these compounds <i>in situ</i> in a wide range of conditions, varying parameters such as temperature, amount of the protonation modulator nitric acid (HNO<sub>3</sub>) and amount of the coordination modulator acetic acid (AcOH). When only HNO<sub>3</sub> is present in the reaction environment, F4_MIL-140A(Ce) is obtained as a pure phase. Heating preferentially accelerates nucleation, which becomes rate determining below 57 °C, whereas the modulator influences nucleation and crystal growth to a similar extent. Upon addition of AcOH to the system, alongside HNO<sub>3</sub>, mixed-phased products, consisting of F4_MIL-140A(Ce) and F4_UiO-66(Ce), are obtained. In these conditions, F4_UiO-66(Ce) is always formed faster and no interconversion between the two phases occurs. In the case of F4_UiO-66(Ce), crystal growth is always the rate determining step. An increase in the amount of HNO<sub>3</sub> slows down both nucleation and growth rates for F4_MIL-140A(Ce), whereas nucleation is mainly affected for F4_UiO-66(Ce). In addition, a higher amount HNO<sub>3</sub> favours the formation of F4_MIL-140A(Ce). Similarly, increasing the amount of AcOH leads to slowing down of the nucleation and growth rate, but favours the formation of F4_UiO-66(Ce). The pure F4_UiO-66(Ce) phase could also be obtained when using larger amounts of AcOH in the presence of minimal HNO<sub>3</sub>. Based on these <i>in situ</i> results, a new optimised route to achieving a pure, high quality F4_MIL-140A(Ce) phase in mild conditions (60 °C, 1 h) is also identified.

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