Microcrystal Morphology

Mapping Intimacies ◽

10.1093/oso/9780190080112.003.0004 ◽

2021 ◽

pp. 63-89

Author(s):

David Rickard

Keyword(s):

Bimodal Distribution ◽

Frequency Distributions ◽

Crystal Shapes ◽

Size Frequency ◽

Additional Process ◽

The Common ◽

Log Normal ◽

Random Packings

Framboids are constituted by microcrystals with approximately log-normal size-frequency distributions, and 95% of framboidal microcrystals are between 0.1 and 3.1 μ‎m. Nanocrystals are not generally observed in framboids. Packing efficiencies vary between close-packings in which the microcrystals occupy up to 74% of the framboid volume and random packings with a 56% volume of microcrystals. The ratios between framboid diameter and microcrystal size show a clear bimodal distribution which reflects the populations of close-packed ordered framboids and randomly organized framboids. Framboids may contain up to 500,000 microcrystals. The average numbers of microcrystals in both disordered and ordered framboids are similar, which suggests that the organization of microcrystals is the result of an additional process. Minerals that do not commonly produce equant crystals forms are unlikely to display the framboidal texture. Framboid microcrystals are essentially limited to isometric minerals like pyrite which produce equant crystals. Pyrite displays the greatest variety of crystal shapes among the common minerals. This means that pyrite is able to approximate forbidden fivefold symmetries such as the pentagonal dodecahedron, but with asymmetric pentagonal faces, and the icosahedron, again with different-sized triangular faces, as a combination of the octahedron and pyritohedron.

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Determinacy of fecundity in sole (Solea solea) from the Bristol Channel

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400059075 ◽

1990 ◽

Vol 70 (4) ◽

pp. 803-813 ◽

Cited By ~ 21

Author(s):

J. W. Horwood ◽

M. Greer Walker

Keyword(s):

Bay Of Biscay ◽

English Channel ◽

Potential Fecundity ◽

Frequency Distributions ◽

The North ◽

Size Frequency ◽

Solea Solea ◽

The North Sea ◽

The Common ◽

Common Sole

Ovaries of the common sole (Solea solea (Linnaeus)) were collected prior to, or at the beginning of, spawning from the spawning grounds in the Bristol Channel. Size frequency distributions of oocytes over 100 μm are presented. They clearly show a break in the size frequency distributions, at about 170 μm, indicating that the production of new oocytes to be spawned that season had ceased. It indicates that the sole is a determinate spawner and that, at least for this population, an annual potential fecundity can be measured. Estimated annual fecundity at length of Bristol Channel sole is calculated, and values are compared with those found for sole from the North Sea, eastern English Channel and the Bay of Biscay.

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The common origin of family and non-family asteroids: Implications for meteorites and NEAs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318008591 ◽

2018 ◽

Vol 14 (S345) ◽

pp. 281-282

Author(s):

Stanley F. Dermott ◽

Dan Li ◽

Apostolos A. Christou

Keyword(s):

Hierarchical Clustering ◽

Common Origin ◽

Clustering Method ◽

Main Belt ◽

Frequency Distributions ◽

Size Frequency ◽

The Family ◽

The Common ◽

The Mean ◽

Asteroid Families

AbstractThe observed size-frequency distributions (SFDs) of the five major asteroid families in the Inner Main Belt (IMB), defined by Nesvorný (2015) using the Hierarchical Clustering Method (Zappala et al. 1990), are distinctly different and deviate significantly from the linear log-log relation described by Dohnanyi (1969). The existence of these differences in the SFDs, and the fact that the precursor bodies of the major families have distinctly different eccentricities and inclinations, provides an explanation for the observations that the mean sizes of both the family and the non-family asteroids are correlated with their mean proper eccentricities and anti-correlated with their mean proper inclinations. We deduce from this, and from the fact that the SFDs of the family and the non-family asteroids are almost identical, that the family and most of the non-family asteroids in the IMB have a common origin (Dermott et al. 2018).

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Ecological Studies on New Zealand Lacustrine Zooplankton with Special Reference to Boeckella propinqua Sars (Copepoda: Calanoida)

Marine and Freshwater Research ◽

10.1071/mf9620143 ◽

1962 ◽

Vol 13 (2) ◽

pp. 143 ◽

Cited By ~ 21

Author(s):

IAE Bayly

Keyword(s):

New Zealand ◽

Vertical Distribution ◽

Lower Limit ◽

Bimodal Distribution ◽

Zooplankton Biomass ◽

Vertical Variation ◽

Frequency Distributions ◽

Size Frequency ◽

Egg Number ◽

The Vertical Distribution

A study was made of the zooplankton of a small, warm monomictic, closed, alkaline lake. This was located on Mayor Island, an offshore island of the North Island of New Zealand. Morphometric, thermometric, and chemical aspects of this lake are discussed. The vertical distribution of the zooplankton was investigated by the vertical hauling of a closing net and by the horizontal towing of a Clarke Bumpus sampler. The vertical distribution of zooplankton biomass and of the different planktonic crustacean species at different times of the year is discussed. When thermal stratification was well developed, all crustacean and rotatorian species had a very sharply defined lower limit between the upper limit of the metalimnion and the thermocline; minimal population densities existed some distance above this lower limit. A reversed diurnal vertical migration is reported for Daphnia carinata and the mature males of Boeckella propinqua. The following investigations and findings refer to Boeckella propinqua: the vertical distribution of four population components (CI-V, C VI male, male, C VI female, female , and C VI female, female, with eggs) at different times of the year is discussed; departure of sex ratio from 1 : 1 is reported; cyclic seasonal changes, which correlated inversely with temperature during part of the year, occurred in mean length and mean number of eggs in sacs; mean egg number also correlated with mean body length; considerable simultaneous interpopulational variation in mean egg number was found; length measurements of adults from November surface collections showed a bimodal distribution, and at the same time vertical variation occurred in the nature of size-frequency distributions-in both sexes the upper mode was progressively diminished with increasing depth and finally eliminated; in these November collections the percentage of lower modal females with eggs was much smaller than that for upper modal ones; when surface collections showed unimodal size distributions there appeared to be no vertical variation in size-frequency distributions; variation in the lobulation of the last metasomal segment of females is mentioned; the occurrence of a cestode cysticercoid stage in male and female stages CV and VI, and parasitic castration of C VI male, male, is reported. General observations are made on the Rotatoria and the vertical distribution of Filinia longiseta is dealt with. Comparisons are made between the zooplankton of a number of mainland lakes and that of the Mayor Island lake.

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Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽

10.1007/s00338-021-02081-2 ◽

2021 ◽

Author(s):

Liam Lachs ◽

Brigitte Sommer ◽

James Cant ◽

Jessica M. Hodge ◽

Hamish A. Malcolm ◽

...

Keyword(s):

Heat Stress ◽

Size Structure ◽

Temporal Trends ◽

Early Recovery ◽

Size Frequency Distribution ◽

Frequency Distributions ◽

Community Organisation ◽

Size Frequency ◽

Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

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