GROWTH OF COLLOIDAL CRYSTALS UNDER MICROGRAVITY

2002 ◽  
Vol 16 (01n02) ◽  
pp. 338-345 ◽  
Author(s):  
M. ISHIKAWA ◽  
H. MORIMOTO ◽  
T. OKUBO ◽  
T. MAEKAWA
Keyword(s):  
Fractal Dimension ◽  
Power Law ◽  
Brownian Dynamics ◽  
Normal Gravity ◽  
Colloidal Crystals ◽  
Growth Dynamics ◽  
Sounding Rocket ◽  
Microgravity Experiment ◽  
Colloidal Crystallization ◽  
Number Of Particles

The growth dynamics of colloidal crystallization was evaluated under sedimentation free conditions using sounding rocket and Brownian Dynamics (BD) simulation. The Bragg's reflections of colloidal crystals were measured during microgravity flight and average sizes of crystallites were obtained by the Sherrer's method. Results showed a power-law relationship between size and time, L ∝ tα where L is the size of crystallites and t is time. The obtained α s were 0.33 ± 0.03 in microgravity and 0.25 ± 0.02 in normal gravity, respectively. Browninan Dynamics (BD) simulation showed the time evolution of ordered domains that consisted of connected structures of crystalline clusters. The power law relationship n ∝ t0.5 in post-nucleation period was confirmed between the number of particles (n) in clusters and time. The calculated power was related to α using the fractal dimension of crystalline clusters and α = 0.31 was obtained. The value was matched well with that of the microgravity experiment.

Effects of gravity on processing heavy metal fluoride fibers

1997 ◽  
Vol 12 (9) ◽  
pp. 2223-2225 ◽  
Author(s):  
Dennis S. Tucker ◽  
Gary L. Workman ◽  
Guy A. Smith
Keyword(s):  
Heavy Metal ◽  
Crystallization Temperature ◽  
Normal Gravity ◽  
Crystal Nucleation ◽  
Sounding Rocket ◽  
Metal Fluoride ◽  
Reduced Gravity ◽  
Rocket Flight ◽  
Heavy Metal Fluoride

The effects of gravity on the crystal nucleation of heavy metal fluoride fibers have been studied in preliminary experiments utilizing NASA's KC-135 reduced gravity aircraft and a microgravity sounding rocket flight. Commercially produced fibers were heated to the crystallization temperature in normal and reduced gravity. The fibers processed in normal gravity showed complete crystallization while the fibers processed in reduced gravity did not show signs of crystallization.

scholarly journals The fractal dimension of the tree of life

2014 ◽  
Author(s):  
Xiaofei Lv ◽  
Yuping Wu ◽  
Bin Ma
Keyword(s):  
Fractal Dimension ◽  
Power Law ◽  
Fractal Dimensions ◽  
Predictive Modelling ◽  
Tree Of Life ◽  
Fundamental Question ◽  
Theoretical Studies ◽  
Structure Pattern ◽  
Intermediate Size ◽  
Taxonomic Groups

The structure pattern of the tree of life clues on the key ecological issues; hence knowing the fractal dimension is the fundamental question in understanding the tree of life. Yet the fractal dimension of the tree of life remains unclear since the scale of the tree of life has hypergrown in recent years. Here we show that the tree of life display a consistent power-law rules for inter- and intra-taxonomic levels, but the fractal dimensions were different among different kingdoms. The fractal dimension of hierarchical structure (Dr) is 0.873 for the entire tree of life, which smaller than the values of Dr for Animalia and Plantae but greater than the values of Dr for Fungi, Chromista, and Protozoa. The hierarchical fractal dimensions values for prokaryotic kingdoms are lower than for other kingdoms. The Dr value for Viruses was lower than most eukaryotic kingdoms, but greater than prokaryotes. The distribution of taxa size is governed by fractal diversity but skewed by overdominating taxa with large subtaxa size. The proportion of subtaxa in taxa with small and large sizes was greater than in taxa with intermediate size. Our results suggest that the distribution of subtaxa in taxa can be predicted with fractal dimension for the accumulating taxa abundance rather than the taxa abundance. Our study determined the fractal dimensions for inter- and intra-taxonomic levels of the present tree of life. These results emphases the need for further theoretical studies, as well as predictive modelling, to interpret the different fractal dimension for different taxonomic groups and skewness of taxa with large subtaxa size.

scholarly journals IDEAL-MODIFIED BOSONIC GAS TRAPPED IN AN ARBITRARY THREE-DIMENSIONAL POWER-LAW POTENTIAL

2012 ◽  
Vol 27 (31) ◽  
pp. 1250181 ◽  
Author(s):  
E. CASTELLANOS ◽  
C. LÄMMERZAHL
Keyword(s):  
Dispersion Relation ◽  
Power Law ◽  
Three Dimensional ◽  
Particle Dispersion ◽  
Einstein Condensate ◽  
Gravity Models ◽  
Condensation Temperature ◽  
Bose Einstein Condensate ◽  
Bose Einstein ◽  
Number Of Particles

We analyze the effects caused by an anomalous single-particle dispersion relation suggested in several quantum-gravity models, upon the thermodynamics of a Bose–Einstein condensate trapped in a generic three-dimensional power-law potential. We prove that the shift in the condensation temperature, caused by a deformed dispersion relation, described as a non-trivial function of the number of particles and the shape associated to the corresponding trap, could provide bounds for the parameters associated to such deformation. In addition, we calculate the fluctuations in the number of particles as a criterium of thermodynamic stability for these systems. We show that the apparent instability caused by the anomalous fluctuations in the thermodynamic limit can be suppressed considering the lowest energy associated to the system in question.

scholarly journals Convenient and Efficient Fabrication of Colloidal Crystals Based on Solidification-Induced Colloidal Assembly

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 575 ◽  
Author(s):  
Ting Shao ◽  
Laixi Sun ◽  
Chun Yang ◽  
Xin Ye ◽  
Shufan Chen ◽  
...  
Keyword(s):  
Driving Force ◽  
Crystallization Process ◽  
Colloidal Crystal ◽  
Colloidal Crystals ◽  
Magnetic Interaction ◽  
Colloidal Assembly ◽  
Water Suspension ◽  
Colloidal Crystallization ◽  
New Strategy ◽  
Crystal Grains

The simple yet efficient and versatile fabrication of colloidal crystals was investigated based on the solidification-induced colloidal crystallization process with particle/water suspension as precursor. The resulting colloidal crystals were constituted by crystal grains with sizes ranging from several tens of micrometers to a few millimeters. Each of the grains had a close-hexagonal array of colloids, which endowed the bulk colloidal crystal powders with some specific optical properties. The freezing of water was shown as the major driving force to form colloidal crystal grains, which supersaturated the solution with nanoparticles and thus induced the formation and growth of colloidal crystal seeds. This process is intrinsically different from those conventional methods based on shearing force, surface tension, columbic interaction or magnetic interaction, revealing a new strategy to fabricate colloidal crystals in a convenient and efficient way.

Influence of Gravity Driven Convection on the Directional Solidification of Bi/MnBi Eutectic Composites

1981 ◽  
Vol 9 ◽  
Author(s):  
Ron G. Pirich ◽  
D.J. Larson
Keyword(s):  
Directional Solidification ◽  
Normal Gravity ◽  
Volume Fraction ◽  
Sounding Rocket ◽  
Low Gravity ◽  
Gravity Driven ◽  
Morphological Differences ◽  
Mnbi Phase ◽  
Irregular Interface

ABSTRACTThe role of gravity on Bridgman-Stockharger directional solidification of eutectic Bi/MnBi has been studied in reduced gravity aboard NASA sounding rocket SPAR flight experiments and contrasted with normal gravity investigations. The directional solidification of eutectic Ri/MnBi results in a low volume fraction, faceted/nonfaceted aligned rod eutectic whose MnRi rod size, interrod spacing, thermal and magnetic properties are sensitive functions of solidification processing conditions. The morphology of the low-gravity samples showed striking differences compared with identically processed,normal gravity samples grown in the same apparatus. The MnBi rod diameter and interrod spacing distributions were significantly smaller, approximately 50%, for the lowgravity samples compared with identically processed one gravity samples. Accompanying the smaller MnBi rod diameters observed in the flight samples, was an increase in permanent magnet properties which reached greater than 97% of the theoretical maximum.Gravitationally induced thermal instabilities in one-gravity which result in irregular interface movement and associated difficulty of the faceted MnBi phase to branch are suggested to explain the morphological differences between one and low gravity solidification.

ON THE FRACTAL STRUCTURE OF ELECTRON AVALANCHES

Fractals ◽  
1993 ◽  
Vol 01 (04) ◽  
pp. 939-946 ◽  
Author(s):  
Z. DONKÓ ◽  
I. PÓCSIK
Keyword(s):  
Fractal Dimension ◽  
Power Law ◽  
Inelastic Collision ◽  
Fractal Structure ◽  
Secondary Electrons ◽  
Electron Multiplication ◽  
Helium Gas ◽  
Self Similar ◽  
Collision Processes ◽  
Electron Avalanches

The motion of electrons in helium gas in the presence of a homogeneous external electric field was studied. Moving between the two electrodes, the electrons participate in elastic and inelastic collision processes with gas atoms. In ionizing collisions, secondary electrons are also created and in this way self-similar electron avalanches build up. The statistical distribution of the fractal dimension and electron multiplication of electron avalanches was obtained based on the simulation of a large number of electron avalanches. The fractal dimension shows a power-law dependence on electron multiplication with an exponent of ≈0.33.

scholarly journals The fractal dimension of the tree of life

2014 ◽  
Author(s):  
Bin Ma ◽  
Xiaofei Lv ◽  
Jun Gong
Keyword(s):  
Fractal Dimension ◽  
Power Law ◽  
Fractal Dimensions ◽  
Predictive Modelling ◽  
Tree Of Life ◽  
Fundamental Question ◽  
Theoretical Studies ◽  
Structure Pattern ◽  
Intermediate Size ◽  
Taxonomic Groups

The structure pattern of the tree of life clues on the key ecological issues; hence knowing the fractal dimension is the fundamental question in understanding the tree of life. Yet the fractal dimension of the tree of life remains unclear since the scale of the tree of life has hypergrown in recent years. Here we show that the tree of life display a consistent power-law rules for inter- and intra-taxonomic levels, but the fractal dimensions were different among different kingdoms. The fractal dimension of hierarchical structure (Dr) is 0.873 for the entire tree of life, which smaller than the values of Dr for Animalia and Plantae but greater than the values of Dr for Fungi, Chromista, and Protozoa. The hierarchical fractal dimensions values for prokaryotic kingdoms are lower than for other kingdoms. The Dr value for Viruses was lower than most eukaryotic kingdoms, but greater than prokaryotes. The distribution of taxa size is governed by fractal diversity but skewed by overdominating taxa with large subtaxa size. The proportion of subtaxa in taxa with small and large sizes was greater than in taxa with intermediate size. Our results suggest that the distribution of subtaxa in taxa can be predicted with fractal dimension for the accumulating taxa abundance rather than the taxa abundance. Our study determined the fractal dimensions for inter- and intra-taxonomic levels of the present tree of life. These results emphases the need for further theoretical studies, as well as predictive modelling, to interpret the different fractal dimension for different taxonomic groups and skewness of taxa with large subtaxa size.

scholarly journals Variability of magnetic field spectra in the Earth's magnetotail

2009 ◽  
Vol 16 (6) ◽  
pp. 691-698 ◽  
Author(s):  
A. A. Petrukovich ◽  
D. V. Malakhov
Keyword(s):  
Magnetic Field ◽  
Fractal Dimension ◽  
Power Law ◽  
Plasma Sheet ◽  
Negative Power ◽  
Magnetic Fluctuation ◽  
Power Law Index

Abstract. We investigate the variability of magnetic fluctuation spectra below 1 Hz in the Earth's plasma sheet using specially selected long observation intervals by Geotail spacecraft. The spectra can be generally described by a negative power law with two kinks. The range between kinks ~0.02–0.2 Hz has the most stable power law index ~2.4–2.6. Indices at the lower and the higher frequencies are more variable and generally increase with power of fluctuations. In the sub-second range fluctuations are strongly localized and indices are closer to 3. At the lower-frequency end indices are about 1.5. The lower kink is usually well defined on average spectra and its frequency tends to increase with activity. Combination of spectrum index α and fractal dimension δ is expected to follow the Berry relation α+2δ=5, but actually is ~5.5.

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