Slip-resistant silver-feet: shell form and mode of life in lower Pleistocene Argyropeza from Fiji

1986 ◽  
Vol 60 (5) ◽  
pp. 1066-1074 ◽  
Author(s):  
Alan J. Kohn
Keyword(s):  
Grain Size ◽  
Shell Length ◽  
Direct Relationship ◽  
Ventral Side ◽  
Drilling Predation ◽  
Length Range ◽  
Lower Pleistocene ◽  
Mode Of Life ◽  
Enhance Efficiency ◽  
Lines Of Evidence

Asymmetric sculpture in the form of tubercles or ridges on the shells of large (mean shell length ~60 mm) turritelliform gastropods has previously been shown to enhance efficiency of the shell as a penetration anchor in burrowing through coarse sediment. The small (<8 mm) turritelliform shells of all species of Argyropeza (Family Cerithiidae) have both of these ratchetlike sculptural features. Four lines of evidence from Lower Pleistocene A. divina and A. schepmaniana from Fiji support the interpretation that they help resist back-slippage: cross-orientation, frictional asymmetry, allometric shallowing, and allometric densing of sculptural elements. In addition, excellent state of preservation including protoconch sculpture, near coplanarity of aperture and ventral side of shell, and susceptibility to drilling predation by naticids support the conclusion that these gastropods burrowed in the sediment that formed the siltstone in which they are now preserved. A direct relationship is proposed between height of ratchet sculpture on turritelliform gastropod shells of approximate length range 5–100 mm and the grain size of sediments they inhabit ranging from silts to coarse sands.

Machining and Wear of High-Alumina Ceramics for Structural Applications

2009 ◽  
Vol 409 ◽  
pp. 137-144 ◽  
Author(s):  
Stojana Veskovic-Bukudur ◽  
Tanja Leban ◽  
Milan Ambrozic ◽  
Tomaž Kosmač
Keyword(s):  
Grain Size ◽  
Wear Rate ◽  
Abrasive Wear ◽  
Direct Relationship ◽  
Bending Strength ◽  
High Alumina ◽  
Alumina Ceramics ◽  
Large Area ◽  
Structural Applications ◽  
Worn Surfaces

The wear resistances of four standard-grade high-alumina ceramics were evaluated and related to their machining ability. Three of the material grades contained 96% of alumina and 4% of either calcium silicate, or magnesium silicate, or manganese titanate in the starting-powder composition. The nominal alumina content in the fourth material was 99.7%. The specimens were fabricated using a low-pressure injection-molding forming technique, followed by thermal de-binding and sintering. After sintering the four materials differ significantly in their grain size, bending strength and Vickers hardness. No direct relationship between the microstructural parameters and the mechanical properties was found, but there was a grain-size dependence of the surface finish after grinding under industrial conditions. The two silicate-containing ceramics exhibited considerably higher wear resistances than the two silicate-free ceramics, but no direct relationship between the abrasive wear rate during grinding and the cutting time was observed. The cutting ability represents a valuable material characteristic for industrial practice, but it should not be directly used for predicting the wear rate during grinding. Quantitative differences in the cutting time and abrasive wear rate were manifested in the different topographies of the worn surfaces. Cutting resulted in relatively large area fractions of plastically deformed surfaces, whereas pullouts dominated the worn surfaces after grinding.

Commensalism of a Bivalve, Peregrinamor Ohshimai, With a Thalassinidean Burrowing Shrimp, Upogebia Major

1995 ◽  
Vol 75 (4) ◽  
pp. 941-947 ◽  
Author(s):  
Makoto Kato ◽  
Gyo Itani
Keyword(s):  
Shell Length ◽  
Suspended Matter ◽  
Carapace Length ◽  
Anterior Part ◽  
Living Organism ◽  
Ventral Side ◽  
Filter Feeding ◽  
Water Currents ◽  
Veliger Larva ◽  
The Seto Inland Sea

Ecological, behavioural and anatomical observations of a commensal bivalve, Peregrinamor ohshimai (Mollusca: Galeommatoidea), were carried out in a tidal mudflat in the Seto Inland Sea, Japan. The bivalve attached specifically to the longitudinal groove of the ventral side of the cephalothorax of thalassinidean burrowing shrimps, Upogebia major and Lf. narutensis (Crustacea: Decapoda), singly, dorso-ventrally and longitudinally, using its byssus, with its anterior part towards the head of the host. The mantle of the commensal bivalve has wide anterior (branchio-pedal) and narrow posterior (exhalant) apertures. In the living organism, the extended anterior edges of the mantle protrude from the shell and are inserted into the host's filtering basket, which is formed by the setal rows of the first two pairs of pereiopods and utilized for intercepting suspended matter. By beating its pleopods in a U-shaped burrow, the filter-feeding Upogebia shrimp creates water currents, which are also utilized by the commensal bivalve for filter-feeding. The shell length of the commensal bivalve was in proportion to the host's carapace length. This suggests that the veliger larva attaches to a young host and grows, thus maintaining the host-commensal morphological matching. The bivalve is a hermaphrodite and individuals of >8–5 mm in shell length were already producing eggs. Anatomical observations suggest that P. ohshimai is most closely related to the Montacutidae in Galeommatoidea.

The Lower Pleistocene stratigraphy of the Ormesby Borehole, Norfolk, England

1991 ◽  
Vol 128 (6) ◽  
pp. 647-660 ◽  
Author(s):  
R. Harland ◽  
Anne P. Bonny ◽  
M. J. Hughes ◽  
A. N. Morigi
Keyword(s):  
Grain Size ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Post Mortem ◽  
Lower Pleistocene

AbstractThe sedimentology, micropalaepntology and palynology of Lower Pleistocene sediments recovered from a borehole at Ormesby St Margaret, near Great Yarmouth, Norfolk, have been investigated. The sediments, consisting of a lower clay facies overlain by an upper predominantly sandy facies, were deposited in inner neritic environments. Micropalaeontological and palynologicalevidence allows comparisons with the nearby Ludham sequence but an unequivocal correlation cannot be made. The Ormesby Borehole sequence includes representatives of the Pre-Ludhamian to Early Pastonian stage interval and the presence of a late Pre-Ludhamian to late Baventian/Pre-Pastonian a hiatus. Foraminiferal faunas matched to grain size analysis are indicative of transportation and considerable post-mortem sorting.

Inferring substrate preferences from test morphology in echinoids, and interpreting spatial and temporal patterns of diversity

1997 ◽  
Vol 3 ◽  
pp. 121-145 ◽  
Author(s):  
Burchard D. Carter
Keyword(s):  
Grain Size ◽  
Sediment Type ◽  
Spatial And Temporal Patterns ◽  
Thin Sections ◽  
Substrate Preferences ◽  
Sediment Types ◽  
Profile Control ◽  
The Matrix ◽  
Mode Of Life ◽  
Better Than

Preservational style of fossil echinoid tests allows assessment of the likelihood of post-mortem transport out of the preferred sediment type of the living echinoid. Sedimentologic study of the matrix of untransported specimens allows a check on functional morphologic inferences of the species' preferred sediment types. Functional morphologic analysis allows inference of a species preferred sediment type because the petals, fasciolaes, tubercles, ambulacral pores, ambulacral shape, and test profile control the echinoid's ability to burrow, and the grain size of sediment into which it is capable of doing so. Past studies have achieved better than 90% accuracy in predicting the grain size of thin sections of rocks containing echinoids, simply by interpretation of their functional morphology. Most mistaken predictions are attributable to species living in sediments that are less difficult to burrow in (sands) than those to which they are adapted (muds). Other species may live in sediments in which they are not well adapted by assuming an epifaunal mode of life.Relative proportions of species in an echinoid fauna preferring various sediment grain sizes, plotted for each of a number of localities, has proven useful in inferring generalized facies patterns within regions.Plots of temporal changes in echinoid species diversity through time correspond well to changes in proportions of species inferred to have preferred various substrate conditions, suggesting an environmental and taphonomic component to simple diversity curves.

Micropredators skulking in Silurian oceans?

2020 ◽  
Author(s):  
Isabella Leonhard ◽  
Bryan Shirley ◽  
Duncan Murdock ◽  
Emilia Jarochowska
Keyword(s):  
Growth Dynamics ◽  
Backscatter Electron ◽  
Feeding Mode ◽  
Independent Evidence ◽  
X Ray ◽  
Mode Of Life ◽  
Early Vertebrates ◽  
Extinct Group ◽  
Insight Into ◽  
Lines Of Evidence

&lt;p&gt;Predation is potentially one of the most impactful evolutionary traits to have ever developed. Conodonts, an extinct group of early vertebrates, developed the first phosphatic dental tools, known as elements. Elements ranged from simple coniform types to more complex morphologies, predominantly in more derived species. Unlike the teeth of other vertebrates, these continuously grew throughout their lifetime by the periodic accretion of new lamellar tissues. This unique growth process continuously records chemical and physical characteristics throughout its lifespan which, when accessed, gives direct insight into the animal&amp;#8217;s ecology and mode of life. Multiple lines of evidence, such as microwear studies and growth allometry, indicate that adult conodonts fed as predators and/or scavengers. There is little direct independent evidence for feeding ecologies in the earliest conodonts with coniform elements apparatuses, although previous modelling of element position and mechanical properties indicate these were capable of processing or manipulation of food. A direct test would be provided through evidence of tissue damage and its chemical composition. Our research focuses on samples of the coniform genus Panderodus (Family: Panderodontidae) from the Silurian of Poland and Ukraine. Panderodus has the best constrained apparatus reconstruction of any coniform conodont. Here we employ Backscatter electron (BSE) imaging and Energy-dispersive X-Ray spectroscopy (EDX) to identify growth dynamics, microwear, and chemical sclerochronology recorded within this unique mode of growth. Our results have direct implications not just for understanding the feeding mode of Panderodus, but also the origination of predation in the earliest vertebrates in the fossil record.&lt;/p&gt;

Fluency: A trigger of familiarity for relational representations?

2019 ◽  
Vol 42 ◽  
Author(s):  
Talya Sadeh
Keyword(s):  
Memory Model ◽  
Lines Of Evidence

Abstract According to Bastin et al.’s integrative memory model, familiarity may be attributed to both entity representations and relational representations. However, the model does not specify what triggers familiarity for relational representations. I argue that fluency is a key player in the attribution of familiarity regardless of the type of representation. Two lines of evidence are reviewed in support of my claim.

Structuring, Motions and Shapes of Corona Emission Line Profiles

1994 ◽  
Vol 144 ◽  
pp. 421-426
Author(s):  
N. F. Tyagun
Keyword(s):  
Emission Line ◽  
Filling Factor ◽  
Direct Relationship ◽  
Coronal Plasma ◽  
Line Of Sight ◽  
Line Profiles ◽  
The Difference ◽  
Yellow Line ◽  
Red Line

AbstractThe interrelationship of half-widths and intensities for the red, green and yellow lines is considered. This is a direct relationship for the green and yellow line and an inverse one for the red line. The difference in the relationships of half-widths and intensities for different lines appears to be due to substantially dissimilar structuring and to a set of line-of-sight motions in ”hot“ and ”cold“ corona regions.When diagnosing the coronal plasma, one cannot neglect the filling factor - each line has such a factor of its own.

Effect of Shock Loading on the Microstructure of Uniloy 326

1974 ◽  
Vol 32 ◽  
pp. 504-505
Author(s):  
K. P. Staudhammer ◽  
L. E. Murr
Keyword(s):  
Grain Size ◽  
Shock Loading ◽  
Current Investigation ◽  
Two Phase ◽  
05 C ◽  
Shock Deformation ◽  
Heat Treated

The effect of shock loading on a variety of steels has been reviewed recently by Leslie. It is generally observed that significant changes in microstructure and microhardness are produced by explosive shock deformation. While the effect of shock loading on austenitic, ferritic, martensitic, and pearlitic structures has been investigated, there have been no systematic studies of the shock-loading of microduplex structures.In the current investigation, the shock-loading response of millrolled and heat-treated Uniloy 326 (thickness 60 mil) having a residual grain size of 1 to 2μ before shock loading was studied. Uniloy 326 is a two phase (microduplex) alloy consisting of 30% austenite (γ) in a ferrite (α) matrix; with the composition.3% Ti, 1% Mn, .6% Si,.05% C, 6% Ni, 26% Cr, balance Fe.

Aspects of microanalysis in a transmission electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 510-511
Author(s):  
R. Sinclair ◽  
B.E. Jacobson
Keyword(s):  
Grain Size ◽  
Electron Beam ◽  
Electron Microscope ◽  
Chemical Analysis ◽  
Transmission Electron Microscope ◽  
Vapor Deposition ◽  
Critical Currents ◽  
X Ray ◽  
Fine Grain ◽  
Transmission Electron

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3 . Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).

Novel magneto-optical recording materials: Bi-substituted garnet films

1991 ◽  
Vol 49 ◽  
pp. 776-777
Author(s):  
Takao Suzuki ◽  
Hossein Nuri
Keyword(s):  
Grain Size ◽  
Amorphous Film ◽  
Nitrogen Atmosphere ◽  
Optical Recording ◽  
Garnet Film ◽  
Media Noise ◽  
Garnet Films ◽  
Order Of Magnitude ◽  
A New Technique ◽  
A Current

For future high density magneto-optical recording materials, a Bi-substituted garnet film ((BiDy)3(FeGa)5O12) is an attractive candidate since it has strong magneto-optic effect at short wavelengths less than 600 nm. The signal in read back performance at 500 nm using a garnet film can be an order of magnitude higher than a current rare earth-transition metal amorphous film. However, the granularity and surface roughness of such crystalline garnet films are the key to control for minimizing media noise.We have demonstrated a new technique to fabricate a garnet film which has much smaller grain size and smoother surfaces than those annealed in a conventional oven. This method employs a high ramp-up rate annealing (Γ = 50 ~ 100 C/s) in nitrogen atmosphere. Fig.1 shows a typical microstruture of a Bi-susbtituted garnet film deposited by r.f. sputtering and then subsequently crystallized by a rapid thermal annealing technique at Γ = 50 C/s at 650 °C for 2 min. The structure is a single phase of garnet, and a grain size is about 300A.

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