scholarly journals Multiscale approach reveals that Cloudina aggregates are detritus and not in situ reef constructions

2018 ◽  
Vol 115 (11) ◽  
pp. E2519-E2527 ◽  
Author(s):  
Akshay Mehra ◽  
Adam Maloof
Keyword(s):  
Imaging System ◽  
Imaging Techniques ◽  
Minor Role ◽  
Multiscale Approach ◽  
Field Observations ◽  
3D Reconstructions ◽  
Physical Separation ◽  
A Minor ◽  
Globally Distributed

The earliest metazoans capable of biomineralization appeared during the late Ediacaran Period (635–541 Ma) in strata associated with shallow water microbial reefs. It has been suggested that some Ediacaran microbial reefs were dominated (and possibly built) by an abundant and globally distributed tubular organism known as Cloudina. If true, this interpretation implies that metazoan framework reef building—a complex behavior that is responsible for some of the largest bioconstructions and most diverse environments in modern oceans—emerged much earlier than previously thought. Here, we present 3D reconstructions of Cloudina populations, produced using an automated serial grinding and imaging system coupled with a recently developed neural network image classifier. Our reconstructions show that Cloudina aggregates are composed of transported remains while detailed field observations demonstrate that the studied reef outcrops contain only detrital Cloudina buildups, suggesting that Cloudina played a minor role in Ediacaran reef systems. These techniques have wide applicability to problems that require 3D reconstructions where physical separation is impossible and a lack of density contrast precludes tomographic imaging techniques.

Severity of contraction-induced injury is affected by velocity only during stretches of large strain

2001 ◽  
Vol 91 (2) ◽  
pp. 661-666 ◽  
Author(s):  
Susan V. Brooks ◽  
John A. Faulkner
Keyword(s):  
Null Hypothesis ◽  
Isometric Force ◽  
Large Strain ◽  
Minor Role ◽  
Average Force ◽  
Significant Relationships ◽  
Severity Of Injury ◽  
Work Input ◽  
A Minor

Our purpose was to investigate the effect of velocity of stretch on contraction-induced injury to whole skeletal muscles. Single stretches provide an effective method for studying factors that initiate contraction-induced injury. We tested the null hypothesis that the severity of injury is not dependent on the velocity of the stretch. From the plateau of maximum isometric contractions, extensor digitorum longus muscles of mice were administered single stretches in situ of 30–50% strain relative to muscle fiber length ( L f) at rates of 1–16 L f/s. The magnitude of injury was represented by the isometric force deficit 1–10 min after the stretch. Although the null hypothesis was not supported because the force deficit was affected by velocity ( r 2= 0.09), the effect was relatively weak and was not significant except at the largest strain. Velocity had no effect on peak or average force or work input, factors established to have significant relationships with the force deficit. Velocity may play a minor role in contraction-induced injury, but its importance is negligible relative to that of strain.

scholarly journals SOME ASPECTS OF THE CULTURE OF EUCHEMA

1970 ◽  
Vol 17 ◽  
pp. 145-146
Author(s):  
U. Horstman ◽  
A. Colina ◽  
W. Schramm
Keyword(s):  
Growth Rate ◽  
The Philippines ◽  
Minor Role ◽  
Bacterial Disease ◽  
Surrounding Water ◽  
Low Salinity ◽  
In Situ Experiments ◽  
Spraying Plants ◽  
A Minor

Eucheuma striatum and Eucheuma spinosum, are red algae of commercial value because of their carrageenin content, to an increasing extent are cultivated in the Philippines. The influence of environmental factors on growth rate and photosynthesis of these seaweeds were studied through observations in their natural biotope in seaweed farms, from in-situ experiments, and photosynthesis experiments in an incubator. While difference in light intensity and temperature play only a minor role, the algae were found out to be sensitive to low salinity and to the amount of dissolved gases and nutrients in the surrounding seawater. The algae can only be cultured in areas where there is sufficient current but to a cer-tain extent lack of current can be compensated by exposing the plants to wave action. This leads to certain conclusions regarding the most suitable method of commercial Eucheuma culture. Eucheuma can be successfully cultured in small rafts or in floating baskets in areas where there is insufficient current for the use of fixed nets or strings. There is evidence that-the CO2 -02 metabolism in the surrounding water plays an important role in Eucheuma growth. Eucheuma harvest can be further increased by introducing more nutrients. Fertilizing with phosphate caused a bigger increase in growth rate than with nitrogen. The method of spraying plants after temporarily removing them from the water, found to be more effective than fertilizing solutions by the use of clay pots. The presence of a bacterial disease, locally referred to as "ice-ice", was recognized as a clear indication that certain environment conditions were unfavourable for Eucheuma culture. Low salinity, in the first place, but also lack of current favors the attack of "ice-ice". Finally, it was found that Eucheuma adapts itself to its culture site in such a way that after maintaining seedlings in an area for a sufficient length of time, the cultured plants showed better growth rates and were resistent to unfavorable conditions than plants recently transferred to the area.

Characterisation of iron nodules in a Ultisol of central Taiwan

Soil Research ◽  
2003 ◽  
Vol 41 (1) ◽  
pp. 37 ◽  
Author(s):  
C. W. Pai ◽  
M. K. Wang ◽  
H. C. Chiang ◽  
H. B. King ◽  
J.-L. Hwong ◽  
...  
Keyword(s):  
Soil Depth ◽  
Clay Mineralogy ◽  
Minor Role ◽  
Soil Matrix ◽  
Free Iron ◽  
Radiocarbon Age ◽  
Central Taiwan ◽  
A Minor ◽  
In Situ Weathering

The chemical and physical properties, clay mineralogy, and 14C radiocarbon age of iron nodules found in a Ultisol located on a low elevation terrace of Taiwan were investigated. The results indicated that the amount and size of iron nodules increase with soil depth. Free iron contents in nodules were markedly higher than in the surrounding soil matrix. Feo/Fed ratio was low in all iron nodules, indicating that the predominant form of free iron was crystalline. Al-substituted goethite was found as the predominant oxide mineral and Al substitution ranged from 16 to 24% mole. Illite and hydroxy-interlayered vermiculite and kaolinite were the dominant clay minerals in the iron nodules. X-ray fluorescence (XRF) analysis of the iron nodules are composed primarily of Fe, Si, and Al, and minor amounts of Mn. Based on the similarity of clay mineralogical compositions and radiocarbon dating ages, it is suggested that the major driving force promoting the formation of iron nodules was in situ weathering of saprolite by the frequent wetting/drying cycles. We speculate that illuviated iron played only a minor role in their formation.

scholarly journals Spectroscopic evidence of large aspherical <i>β</i>-NAT particles involved in denitrification in the December 2011 Arctic stratosphere

2016 ◽  
Vol 16 (14) ◽  
pp. 9505-9532 ◽  
Author(s):  
Wolfgang Woiwode ◽  
Michael Höpfner ◽  
Lei Bi ◽  
Michael C. Pitts ◽  
Lamont R. Poole ◽  
...  
Keyword(s):  
Gas Phase ◽  
Michelson Interferometer ◽  
Emission Spectra ◽  
Deformation Mode ◽  
Spherical Particles ◽  
Lagrangian Model ◽  
Minor Role ◽  
Aspect Ratios ◽  
A Minor

Abstract. We analyze polar stratospheric cloud (PSC) signatures in airborne MIPAS-STR (Michelson Interferometer for Passive Atmospheric Sounding – STRatospheric aircraft) observations in the spectral regions from 725 to 990 and 1150 to 1350 cm−1 under conditions suitable for the existence of nitric acid trihydrate (NAT) above northern Scandinavia on 11 December 2011. The high-resolution infrared limb emission spectra of MIPAS-STR show a characteristic “shoulder-like” signature in the spectral region around 820 cm−1, which is attributed to the ν2 symmetric deformation mode of NO3− in β-NAT. Using radiative transfer calculations involving Mie and T-Matrix methods, the spectral signatures of spherical and aspherical particles are simulated. The simulations are constrained using collocated in situ particle measurements. Simulations assuming highly aspherical spheroids with aspect ratios (AR) of 0.1 or 10.0 and a lognormal particle mode with a mode radius of 4.8 µm reproduce the observed spectra to a high degree. A smaller lognormal mode with a mode radius of 2.0 µm, which is also taken into account, plays only a minor role. Within the scenarios analyzed, the best overall agreement is found for elongated spheroids with AR  =  0.1. Simulations of spherical particles and spheroids with AR  =  0.5 and 2.0 return results very similar to each other and do not allow us to reproduce the signature around 820 cm−1. The observed “shoulder-like” signature is explained by the combination of the absorption/emission and scattering characteristics of large highly aspherical β-NAT particles. The size distribution supported by our results corresponds to ∼ 9 ppbv of gas-phase equivalent HNO3 at the flight altitude of ∼ 18.5 km. The results are compared with the size distributions derived from the in situ observations, a corresponding Chemical Lagrangian Model of the Stratosphere (CLaMS) simulation, and excess gas-phase HNO3 observed in a nitrification layer directly below the observed PSC. The presented results suggest that large highly aspherical β-NAT particles involved in denitrification of the polar stratosphere can be identified by means of passive infrared limb emission measurements.

scholarly journals Compressibility of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4−x Al x O x N7−x] (x = 2; M = Sr, Ba)

2006 ◽  
Vol 62 (3) ◽  
pp. 424-430 ◽  
Author(s):  
E. A. Juarez-Arellano ◽  
A. Friedrich ◽  
K. Knorr ◽  
A. Lieb ◽  
B. Winkler ◽  
...  
Keyword(s):  
Minor Role ◽  
Third Order ◽  
X Ray ◽  
Compression Behaviour ◽  
Bulk Compressibility ◽  
Diamond Anvil ◽  
A Minor ◽  
Murnaghan Equation ◽  
Structurally Stable

The compressibilities of the nitridosilicate SrYb[Si4N7] and the oxonitridoaluminosilicates MYb[Si4−x Al x O x N7−x ] (x = 2; M = Sr, Ba) were investigated by in situ high-pressure X-ray powder diffraction. Pressures up to 42 GPa were generated using the diamond–anvil cell technique. The title compounds are structurally stable to the highest pressure obtained. A fit of a third-order Birch–Murnaghan equation-of-state to the p–V data results in V 0 = 302.91 (6) Å3, B 0 = 176 (2) GPa and B′ = 4.4 (2) for SrYb[Si4N7]; V 0 = 310.4 (1) Å3, B 0 = 161 (2) GPa and B′ = 4.6 (2) for SrYb[Si4−x Al x O x N7−x ]; and V 0 = 317.3 (5) Å3, B 0 = 168 (2) GPa and B′ = 4.7 (2) for BaYb[Si4−x Al x O x N7−x ]. While the linear compressibilities of the a and c axes of BaYb[Si4−x Al x O x N7−x ] are very similar up to 30 GPa, distinct differences were observed for SrYb[Si4N7] and SrYb[Si4−x Al x O x N7−x ], with the c axis being the most compressible axis. In all of the investigated compounds the bulk compressibility is dominated by the compression behaviour of the tetrahedral network, while the size of the substituted cation plays a minor role.

scholarly journals Spectroscopic evidence for large aspherical β-NAT particles involved in denitrification in the December 2011 Arctic stratosphere

2016 ◽  
Author(s):  
Wolfgang Woiwode ◽  
Michael Höpfner ◽  
Lei Bi ◽  
Michael C. Pitts ◽  
Lamont R. Poole ◽  
...  
Keyword(s):  
Gas Phase ◽  
Michelson Interferometer ◽  
Emission Spectra ◽  
Deformation Mode ◽  
Spherical Particles ◽  
Lagrangian Model ◽  
Minor Role ◽  
Aspect Ratios ◽  
A Minor

Abstract. We analyse polar stratospheric cloud (PSC) signatures in airborne MIPAS-STR (Michelson Interferometer for Passive Atmospheric Sounding – STRatospheric aircraft) observations under conditions suitable for the existence of nitric acid trihydrate (NAT) above northern Scandinavia on 11 December 2011. The high resolution infrared limb emission spectra of MIPAS-STR show a characteristic "shoulder-like" signature in the spectral region around 820 cm−1, which is attributed to the ν2 deformation mode of NO3− in β-NAT. Using radiative transfer calculations involving Mie and T-Matrix methods, the spectral signatures of spherical and aspherical particles are simulated. The simulations are constrained using collocated in-situ particle measurements. Simulations assuming highly aspherical spheroids with aspect ratios (AR) of 0.1 or 10.0 and a lognormal particle mode with a mode radius of 4.8 µm reproduce the observed spectra to a high degree. A smaller lognormal mode with a mode radius of 2.0 µm, which was also taken into account, plays only a minor role. Best overall agreement is found for elongated spheroids with AR = 0.1. Simulations of spherical particles and spheroids with AR = 0.5 and 2.0 return results very similar to each other and do not allow to reproduce the signature around 820 cm−1. The observed “shoulder-like” signature is explained by the combination of the emission and scattering characteristics of large highly aspherical β-NAT particles. The size distribution supported by our results corresponds with ~9 ppbv of gas-phase equivalent HNO3 at the flight altitude of ~18.5 km. The results are compared with the size distributions derived from the in-situ observations, a corresponding Chemical Lagrangian Model of the Stratosphere (CLaMS) simulation, and excess gas-phase HNO3 observed in a nitrification layer directly below the observed PSC. The presented results suggest that large highly aspherical β-NAT particles involved in denitrification of the polar stratosphere can be identified by means of passive infrared limb emission measurements.

scholarly journals Understanding electrochemical switchability of perovskite-type exsolution catalysts

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Alexander K. Opitz ◽  
Andreas Nenning ◽  
Vedran Vonk ◽  
Sergey Volkov ◽  
Florian Bertram ◽  
...  
Keyword(s):  
Interesting Property ◽  
Minor Role ◽  
X Ray Diffraction ◽  
Metallic Particles ◽  
Activity State ◽  
A Minor ◽  
Perovskite Type ◽  
Low Activity ◽  
Perovskite Lattice

Abstract Exsolution of metal nanoparticles from perovskite-type oxides is a very promising approach to obtain catalysts with superior properties. One particularly interesting property of exsolution catalysts is the possibility of electrochemical switching between different activity states. In this work, synchrotron-based in-situ X-ray diffraction experiments on electrochemically polarized La0.6Sr0.4FeO3-δ thin film electrodes are performed, in order to simultaneously obtain insights into the phase composition and the catalytic activity of the electrode surface. This shows that reversible electrochemical switching between a high and low activity state is accompanied by a phase change of exsolved particles between metallic α-­Fe and Fe-oxides. Reintegration of iron into the perovskite lattice is thus not required for obtaining a switchable catalyst, making this process especially interesting for intermediate temperature applications. These measurements also reveal how metallic particles on La0.6Sr0.4FeO3-δ electrodes affect the H2 oxidation and H2O splitting mechanism and why the particle size plays a minor role.

scholarly journals Declining maerl vitality and habitat complexity across a dredging gradient: Insights from in situ sediment profile imagery (SPI)

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Guillaume Bernard ◽  
Alicia Romero-Ramirez ◽  
Adeline Tauran ◽  
Michael Pantalos ◽  
Bruno Deflandre ◽  
...  
Keyword(s):  
Habitat Complexity ◽  
Imaging System ◽  
Imaging Techniques ◽  
Ecosystem Functions ◽  
Long Term Effects ◽  
Form Complex ◽  
High Productivity ◽  
Sediment Profile ◽  
Maerl Beds

Abstract Maerl beds form complex biogenic benthic habitats, characterized by high productivity as well as diverse biological communities. Disturbances associated with extraction and/or fishing activities using mobile bottom-contacting gears such as clam-dredges induce the most severe and long-term effects on these fragile habitats. We here investigated the effects of dredge-fishing on maerl in the bay of Brest (France). We quantified maerl beds structure and vitality across a fine scale quantified dredging intensity gradient through the acquisition of in-situ images of beds cross-section using Sediment Profile Imaging system (SPI). Declines in the proxies of maerl vitality and habitat complexity were measured across the gradient, and were associated with significant changes in the vertical distribution of live and dead maerl as well as of interstitial space. Fishing with dredges caused maerl mortality, substratum compaction, and decreasing habitat complexity. SPI imaging techniques also allowed for an assessment of changes in spatial heterogeneity that dredging created on several aspects of the structure and vitality of maerl beds. It suggests that direct and indirect disturbances induced by dredging are not acting at the same spatial scale, and can thereby differentially affect the ecosystem functions linked to vitality and habitat complexity.

Coherent electron nanodiffraction from clean silver nano particles in a UHV STEM

1993 ◽  
Vol 51 ◽  
pp. 1058-1059
Author(s):  
J. Liu ◽  
M. Pan ◽  
G. E. Spinnler
Keyword(s):  
Supported Catalysts ◽  
Imaging Techniques ◽  
Nano Particles ◽  
Metal Particles ◽  
Shape Structure ◽  
Dynamical Simulations ◽  
Small Metal Particles ◽  
Extract Information

Small metal particles have peculiar chemical and physical properties as compared to bulk materials. They are especially important in catalysis since metal particles are common constituents of supported catalysts. The structural characterization of small particles is of primary importance for the understanding of structure-catalytic activity relationships. The shape and size of metal particles larger than approximately 5 nm in diameter can be determined by several imaging techniques. It is difficult, however, to deduce the shape of smaller metal particles. Coherent electron nanodiffraction (CEND) patterns from nano particles contain information about the particle size, shape, structure and defects etc. As part of an on-going program of STEM characterization of supported catalysts we report some preliminary results of CEND study of Ag nano particles, deposited in situ in a UHV STEM instrument, and compare the experimental results with full dynamical simulations in order to extract information about the shape of Ag nano particles.

The Effect of Path Length and Display Size on Memory for Spatial Information

2012 ◽  
Vol 59 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Katherine Guérard ◽  
Sébastien Tremblay
Keyword(s):  
Path Length ◽  
Potential Role ◽  
Spatial Information ◽  
Recall Performance ◽  
Minor Role ◽  
Length Effect ◽  
Serial Memory ◽  
Fixed Reference ◽  
A Minor

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.

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