scholarly journals The Mesoscale Crystallinity of Nacreous Pearls

2021 ◽  
Author(s):  
Jiseok Gim ◽  
Alden Koch ◽  
Laura Otter ◽  
Benjamin Savitzky ◽  
Sveinung Erland ◽  
...  
Keyword(s):  
Stochastic Processes ◽  
Cross Section ◽  
Topological Defects ◽  
Translational Symmetry ◽  
Natural Phenomena ◽  
Growth Mechanisms ◽  
Naturally Occurring ◽  
Entire Structure ◽  
Medium Range ◽  
Structural Coherence

Abstract A pearl’s distinguished beauty and toughness is attributable to the periodic stacking of aragonite tablets known as nacre. Nacre is a naturally occurring mesocrystal that remarkably arises in the absence of translational symmetry. Gleaning the inspiring biomineral design of a pearl requires quantifying its structural coherence and understanding the stochastic processes that govern formation. By characterizing the entire structure of pearls (~3 mm) in cross-section at high resolution, we show nacre is a medium-range mesocrystal formed through nanoparticle assembly processes. Self-correcting growth mechanisms actively remedy disorder and topological defects of the tablets and act as a countervailing force to paracrystallinity (i.e. long-range disorder). Nacre has a correlation length of roughly 16 tablets (~5.5 µm) despite persistent fluctuations and topological defects. For longer distances (> 25 tablets, ~8.5 µm), the frequency spectrum of nacre tablets follows f-1.5 behavior suggesting growth is coupled to external stochastic processes—a universality found across disparate natural phenomena which now includes pearls.

scholarly journals The mesoscale order of nacreous pearls

2021 ◽  
Vol 118 (42) ◽  
pp. e2107477118
Author(s):  
Jiseok Gim ◽  
Alden Koch ◽  
Laura M. Otter ◽  
Benjamin H. Savitzky ◽  
Sveinung Erland ◽  
...  
Keyword(s):  
Stochastic Processes ◽  
Cross Section ◽  
Topological Defects ◽  
Translational Symmetry ◽  
Natural Phenomena ◽  
Growth Mechanisms ◽  
Naturally Occurring ◽  
Entire Structure ◽  
Medium Range ◽  
Structural Coherence

A pearl’s distinguished beauty and toughness are attributable to the periodic stacking of aragonite tablets known as nacre. Nacre has naturally occurring mesoscale periodicity that remarkably arises in the absence of discrete translational symmetry. Gleaning the inspiring biomineral design of a pearl requires quantifying its structural coherence and understanding the stochastic processes that influence formation. By characterizing the entire structure of pearls (∼3 mm) in a cross-section at high resolution, we show that nacre has medium-range mesoscale periodicity. Self-correcting growth mechanisms actively remedy disorder and topological defects of the tablets and act as a countervailing process to long-range disorder. Nacre has a correlation length of roughly 16 tablets (∼5.5 µm) despite persistent fluctuations and topological defects. For longer distances (>25 tablets , ∼8.5 µm), the frequency spectrum of nacre tablets follows f−1.5 behavior, suggesting that growth is coupled to external stochastic processes—a universality found across disparate natural phenomena, which now includes pearls.

Contribution to the systematic knowledge of Lamium multifidum and L. orientale (Lamiaceae)

Phytotaxa ◽  
2015 ◽  
Vol 203 (2) ◽  
pp. 147 ◽  
Author(s):  
Bayram Atasagun ◽  
Ahmet Aksoy ◽  
Esra Martin
Keyword(s):  
Chromosome Number ◽  
Cross Section ◽  
Pollen Grains ◽  
Morphological Characters ◽  
Previous Description ◽  
Somatic Chromosome Number ◽  
Additional Information ◽  
Naturally Occurring ◽  
First Time ◽  
Systematic Knowledge

Some morphological, anatomical, palynological and karyological features of Lamium multifidum and L. orientale (Lamiaceae) naturally occurring in Turkey have been studied. Additional information was added to the previous description of these species. Anatomically, both L. multifidum and L. orientale had an annual taproot, stems quadrangular in cross-section, leaves bifacial. The nutlets were ovoid in outline and trigonous in cross section, blackish-dark brownish, with glabrous surface. The pollen grains of both species were tricolpate, shape subprolate, ornamentation reticulate. In both species, the somatic chromosome number resulted 2n = 14. The anatomical and palynological features, chromosome number and morphological characters of both species were reported for the first time in this study.

REACTOR NEUTRON CAPTURE CROSS SECTION OF 51-DAY Sr89

1957 ◽  
Vol 35 (10) ◽  
pp. 1215-1219 ◽  
Author(s):  
L. P. Roy ◽  
J. C. Roy
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Neutron Capture ◽  
Capture Cross Section ◽  
High Flux ◽  
Capture Cross ◽  
Neutron Capture Cross Section ◽  
Naturally Occurring ◽  
Reactor Spectrum ◽  
Capture Cross Sections

The neutron capture cross section of Sr89 has been measured by an activation method. Naturally occurring strontium was irradiated in different high flux positions in the NRX reactor at Chalk River and the amount of Sr90 formed by successive neutron capture in Sr88 was determined by separating and measuring its daughter Y90. Using values of 36.6 and 0.005 barns for the respective neutron capture cross sections of Co59 and Sr88, the capture cross section of Sr89 for reactor spectrum neutrons was found to be 0.49 ± 0.10 barn.

Applications of Benford's Law

2015 ◽  
Author(s):  
Arno Berger ◽  
Theodore P. Hill
Keyword(s):  
Computer Science ◽  
Cross Section ◽  
Ad Hoc ◽  
Fraud Detection ◽  
Benford’S Law ◽  
Natural Phenomena ◽  
Pedagogical Tool ◽  
Practical Applications ◽  
Benford's Law ◽  
Main Ideas

This chapter provides a overview of the practical applications of Benford's law. These include fraud detection, detection of natural phenomena, diagnostics and design, computations and computer science, and as a pedagogical tool. In contrast to the rest of the book, this chapter is necessarily expository and informal. It has been organized into a handful of ad hoc categories, which the authors hope will help illuminate the main ideas. None of the conclusions of the experiments or data presented here have been scrutinized or verified by the authors of this book, since the intent here is not to promote or critique any specific application. Rather the goal is to offer a representative cross-section of the related scientific literature, in the hopes that this might continue to facilitate research in both the theory and practical applications of Benford's law.

Luck, Nature and Institutions

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Cynthia A. Stark
Keyword(s):  
Distributive Justice ◽  
Luck Egalitarianism ◽  
Natural Phenomena ◽  
Naturally Occurring ◽  
Luck Egalitarian

AbstractIn addition to having an institutional site or scope, a theory of distributive justice might also have an institutional ‘reach’ or currency. It has the first when it applies to only social (and not natural) phenomena. It has the second when it distributes only socially produced (and not naturally occurring) goods. One objection to luck egalitarianism is that it has absurd implications. In response, Tan has defended a luck egalitarian account that has a strictly institutional reach. I argue, first, that Tan’s view contains two fatal ambiguities and, second, that, to be sound, it requires an institutional currency. This second argument implies that virtually all extant luck egalitarian currencies are incompatible with his approach. I argue, third, that the alleged absurd implications often have little to do with the extent of luck egalitarianism’s reach.

XUV Absorption Spectra of Carbon Ions

1988 ◽  
Vol 102 ◽  
pp. 71-73
Author(s):  
E. Jannitti ◽  
P. Nicolosi ◽  
G. Tondello
Keyword(s):  
Absorption Spectra ◽  
Cross Section ◽  
Theoretical Calculations ◽  
Photoionization Cross Section ◽  
Carbon Ions

AbstractThe photoabsorption spectra of the carbon ions have been obtained by using two laser-produced plasmas. The photoionization cross-section of the CV has been absolutely measured and the value at threshold, σ=(4.7±0.5) × 10−19cm2, as well as its behaviour at higher energies agrees quite well with the theoretical calculations.

The growth of mica polytypes as studied by conventional and high-resolution TEM

1983 ◽  
Vol 41 ◽  
pp. 174-177
Author(s):  
A. Baronnet ◽  
M. Amouric
Keyword(s):  
Water Pressure ◽  
Point Of View ◽  
Temperature Fields ◽  
Natural Occurrence ◽  
Growth Mechanisms ◽  
Long Period ◽  
High Resolution Tem ◽  
Layer Stacking ◽  
Experimental Works ◽  
Potential Use

The origin of mica polytypes has long been a challenging problem for crystal- lographers, mineralogists and petrologists. From the petrological point of view, interest in this field arose from the potential use of layer stacking data to furnish further informations about equilibrium and/or kinetic conditions prevailing during the crystallization of the widespread mica-bearing rocks. From the compilation of previous experimental works dealing with the occurrence domains of the various mica "polymorphs" (1Mr, 1M, 2M1, 2M2 and 3T) within water-pressure vs temperature fields, it became clear that most of these modifications should be considered as metastable for a fixed mica species. Furthermore, the natural occurrence of long-period (or complex) polytypes could not be accounted for by phase considerations. This highlighted the need of a more detailed kinetic approach of the problem and, in particular, of the role growth mechanisms of basal faces could play in this crystallographic phenomenon.

Elastic Scattering in Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 252-253
Author(s):  
J. Langmore ◽  
M. Isaacson ◽  
J. Wall ◽  
A. V. Crewe
Keyword(s):  
Electron Microscopy ◽  
Elastic Scattering ◽  
Cross Section ◽  
Quantum Noise ◽  
Dark Field ◽  
Elastic Cross Section ◽  
Biological Molecules ◽  
Dark Field Microscopy ◽  
Field Systems ◽  
Effects Of Radiation

High resolution dark field microscopy is becoming an important tool for the investigation of unstained and specifically stained biological molecules. Of primary consideration to the microscopist is the interpretation of image Intensities and the effects of radiation damage to the specimen. Ignoring inelastic scattering, the image intensity is directly related to the collected elastic scattering cross section, σɳ, which is the product of the total elastic cross section, σ and the eficiency of the microscope system at imaging these electrons, η. The number of potentially bond damaging events resulting from the beam exposure required to reduce the effect of quantum noise in the image to a given level is proportional to 1/η. We wish to compare η in three dark field systems.

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