scholarly journals Orientations of Mistaken Point fronds indicate morphology impacted ability to survive turbulence

2021 ◽  
Author(s):  
Philip B. Vixseboxse ◽  
Charlotte G. Kenchington ◽  
Frances S. Dunn ◽  
Emily G. Mitchell
Keyword(s):  
Turbulent Flows ◽  
Community Dynamics ◽  
Centre Of Mass ◽  
Flow Conditions ◽  
Multimodal Distributions ◽  
Background Turbulence ◽  
Orientation Distributions ◽  
Animal Communities ◽  
Frond Length ◽  
Insight Into

The Ediacaran organisms of the Mistaken Point E surface have provided crucial insight into early animal communities, including how they reproduced, the importance of Ediacaran height and what the most important factors were to their community dynamics. Here, we use this iconic community to investigate how morphological variation between eight taxa affected their ability to withstand different flow conditions. For each of Beothukis, Bradgatia, Charniodiscus procerus, Charniodiscus spinosus, Plumeropriscum, Primocandelabrum and Fractofusus we measured the orientation and length of their stems (if present) and their fronds. We statistically tested each taxon's stem and frond orientation distributions to see whether they displayed a uniform or multimodal distribution. Where multimodal distributions were identified, the stem/frond length of each cohort was tested to identify if there were differences in size between different orientation groups. We find that Bradgatia and Thectardis show a bimodal felling direction, and infer that they were felled by the turbulent head of the felling flow. In contrast, the frondose rangeomorphs including Beothukis, Plumeropriscum, Primocandelabrum, and the arboreomorphs were felled in a single direction, indicating that they were upright in the water column, and were likely felled by the laminar tail of the felling flow. These differences in directionality suggests that an elongate habit, and particularly possession of a stem, lent greater resilience to frondose taxa against turbulent flows, suggesting that such taxa would have had improved survivability in conditions with higher background turbulence than taxa like Bradgatia and Thectardis, which lacked a stem and which had a higher centre of mass, which may have fared better in quieter water conditions.

scholarly journals Orientations of Mistaken Point Fronds Indicate Morphology Impacted Ability to Survive Turbulence

2021 ◽  
Vol 9 ◽  
Author(s):  
Philip B. Vixseboxse ◽  
Charlotte G. Kenchington ◽  
Frances S. Dunn ◽  
Emily G. Mitchell
Keyword(s):  
Turbulent Flows ◽  
Community Dynamics ◽  
Centre Of Mass ◽  
Flow Conditions ◽  
Multimodal Distributions ◽  
Background Turbulence ◽  
Orientation Distributions ◽  
Animal Communities ◽  
Frond Length ◽  
Insight Into

The Ediacaran fossils of the Mistaken Point E surface have provided crucial insight into early animal communities, including how they reproduced, the importance of Ediacaran height and what the most important factors were to their community dynamics. Here, we use this iconic community to investigate how morphological variation between eight taxa affected their ability to withstand different flow conditions. For each of Beothukis, Bradgatia, Charniodiscus procerus, Charniodiscus spinosus, Plumeropriscum, Primocandelabrum, Thectardis and Fractofusus we measured the orientation and length of their stems (if present) and their fronds. We statistically tested each taxon’s stem and frond orientation distributions to see whether they displayed a uniform or multimodal distribution. Where multimodal distributions were identified, the stem/frond length of each cohort was tested to identify if there were differences in size between different orientation groups. We find that Bradgatia and Thectardis show a bimodal felling direction, and infer that they were felled by the turbulent head of the felling flow. In contrast, the frondose rangeomorphs including Beothukis, Plumeropriscum, Primocandelabrum, and the arboreomorphs were felled in a single direction, indicating that they were upright in the water column, and were likely felled by the laminar tail of the felling flow. These differences in directionality suggests that an elongate habit, and particularly possession of a stem, lent greater resilience to frondose taxa against turbulent flows, suggesting that such taxa would have had improved survivability in conditions with higher background turbulence than taxa like Bradgatia and Thectardis, that lacked a stem and had a higher centre of mass, which may have fared better in quieter water conditions.

scholarly journals Seasonal dynamics of a generalist and a specialist predator on a single prey

2021 ◽  
pp. 1-20
Author(s):  
Noah Bolohan ◽  
Victor LeBlanc ◽  
Frithjof Lutscher
Keyword(s):  
Seasonal Variation ◽  
Community Dynamics ◽  
Alternative Prey ◽  
Ecological Communities ◽  
Season Length ◽  
Simplified Models ◽  
Hunting Behaviour ◽  
Temporal Averaging ◽  
Invasion Analysis ◽  
Insight Into

In ecological communities, the behaviour of individuals and the interaction between species may change between seasons, yet this seasonal variation is often not represented explicitly in mathematical models. As global change is predicted to alter season length and other climatic aspects, such seasonal variation needs to be included in models in order to make reasonable predictions for community dynamics. The resulting mathematical descriptions are nonautonomous models with a large number of parameters, and are therefore challenging to analyze. We present a model for two predators and one prey, whereby one predator switches hunting behaviour to seasonally include alternative prey when available. We use a combination of temporal averaging and invasion analysis to derive simplified models and determine the behaviour of the system, in particular to gain insight into conditions under which the two predators can coexist in a changing climate. We compare our results with numerical simulations of the temporally varying model.

scholarly journals Biofilm formation by group A Streptococcus: a role for the streptococcal regulator of virulence (Srv) and streptococcal cysteine protease (SpeB)

Microbiology ◽  
2009 ◽  
Vol 155 (1) ◽  
pp. 46-52 ◽  
Author(s):  
Christopher D. Doern ◽  
Amity L. Roberts ◽  
Wenzhou Hong ◽  
Jessica Nelson ◽  
Slawomir Lukomski ◽  
...  
Keyword(s):  
Cysteine Protease ◽  
Biofilm Formation ◽  
Group A Streptococcus ◽  
Immunoblot Analysis ◽  
Wild Type ◽  
Flow Conditions ◽  
Group A ◽  
Streptococcus A ◽  
Insight Into ◽  
Western Immunoblot Analysis

Recently, biofilms have become a topic of interest in the study of the human pathogen group A Streptococcus (GAS). In this study, we sought to learn more about the make-up of these structures and gain insight into biofilm regulation. Enzymic studies indicated that biofilm formation by GAS strain MGAS5005 required an extracellular protein and DNA component(s). Previous results indicated that inactivation of the transcriptional regulator Srv in MGAS5005 resulted in a significant decrease in virulence. Here, inactivation of Srv also resulted in a significant decrease in biofilm formation under both static and flow conditions. Given that production of the extracellular cysteine protease SpeB is increased in the srv mutant, we tested the hypothesis that increased levels of active SpeB may be responsible for the reduction in biofilm formation. Western immunoblot analysis indicated that SpeB was absent from MGAS5005 biofilms. Complementation of MGAS5005Δsrv restored the biofilm phenotype and eliminated the overproduction of active SpeB. Inhibition of SpeB with E64 also restored the MGAS5005Δsrv biofilm to wild-type levels.

The Application of Submerged Jets to the Mixing of Slurries

2002 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Growth Rate ◽  
Radioactive Waste ◽  
Rheological Characteristics ◽  
Flow Conditions ◽  
Waste Storage ◽  
Submerged Jets ◽  
Mixing Ability ◽  
Waste Mixture ◽  
Insight Into ◽  
Radioactive Waste Storage

The ongoing cleanup effort at various DOE radioactive waste storage sites heavily relies on submerged jets during the mobilization and mixing phase of the settled sludges. Mobilization and mixing of the waste is a prerequisite for retrieval and transport to separation and processing facilities. The present study attempts to provide an insight into the flow conditions existing during the deployment of submerged jets to create uniform slurry conditions. Simulations that emulate the rheological characteristics of the waste mixture during mobilization are carried out. A particular attention is paid to how a non-Newtonian rheology affects the growth rate and mixing ability of the submerged jets.

scholarly journals Erratum: A pyrosequencing insight into sprawling bacterial diversity and community dynamics in decaying deadwood logs of Fagus sylvatica and Picea abies

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Björn Hoppe ◽  
Dirk Krüger ◽  
Tiemo Kahl ◽  
Tobias Arnstadt ◽  
François Buscot ◽  
...  
Keyword(s):  
Picea Abies ◽  
Bacterial Diversity ◽  
Fagus Sylvatica ◽  
Community Dynamics ◽  
Insight Into

Particle Resuspension From Carpeted Floorings in Indoor Environment in Turbulent Flows

2011 ◽  
Author(s):  
Iman Goldasteh ◽  
Goodarz Ahmadi ◽  
Andrea Ferro
Keyword(s):  
Turbulent Flows ◽  
Indoor Environment ◽  
Adhesion Force ◽  
Spherical Particles ◽  
Graphical Form ◽  
Flow Conditions ◽  
Particle Resuspension ◽  
Roughness Model ◽  
Carpet Fibers

Particle resuspension is an important source of particulate matter in the indoor environment. [1] In this study, a model for resuspension of spherical particles from carpet fibers was developed using the micro-roughness model for simulating the adhesion of rough spherical particles. The Johnson-Kendall-Roberts (JKR) adhesion model was used for modeling the adhesion force between particles and carpet fibers. Adhesion of pollen particles to the carpet fibers was studied, and the pull-off forces predicted by the model are compared with the available experimental data. The effect of the hydrodynamic force of fluid flow on resuspension of particles under turbulent flow conditions was studied and the effect of turbulence bursts was included in the model. In particular, the range of airflow velocity for resuspension of pollen particles from carpet was evaluated and the results are presented in graphical form. The role of airflow on resuspension of particles from carpeted floorings is discussed.

scholarly journals Ecosystem Resilience and Limitations Revealed by Soil Bacterial Community Dynamics in a Bark Beetle-Impacted Forest

mBio ◽  
2017 ◽  
Vol 8 (6) ◽  
Author(s):  
Kristin M. Mikkelson ◽  
Brent M. Brouillard ◽  
Chelsea M. Bokman ◽  
Jonathan O. Sharp
Keyword(s):  
Water Quality ◽  
Bacterial Community ◽  
Tree Mortality ◽  
Community Dynamics ◽  
Watershed Scale ◽  
Microbial Community Dynamics ◽  
Local Soil ◽  
The World ◽  
Water Quality And Quantity ◽  
Insight Into

ABSTRACT Forested ecosystems throughout the world are experiencing increases in the incidence and magnitude of insect-induced tree mortality with large ecologic ramifications. Interestingly, correlations between water quality and the extent of tree mortality in Colorado montane ecosystems suggest compensatory effects from adjacent live vegetation that mute responses in less severely impacted forests. To this end, we investigated whether the composition of the soil bacterial community and associated functionality beneath beetle-killed lodgepole pine was influenced by the extent of surrounding tree mortality. The most pronounced changes were observed in the potentially active bacterial community, where alpha diversity increased in concert with surrounding tree mortality until mortality exceeded a tipping point of ~30 to 40%, after which diversity stabilized and decreased. Community structure also clustered in association with the extent of surrounding tree mortality with compositional trends best explained by differences in NH4 + concentrations and C/N ratios. C/N ratios, which were lower in soils under beetle-killed trees, further correlated with the relative abundance of putative nitrifiers and exoenzyme activity. Collectively, the response of soil microorganisms that drive heterotrophic respiration and decay supports observations of broader macroscale threshold effects on water quality in heavily infested forests and could be utilized as a predictive mechanism during analogous ecosystem disruptions. IMPORTANCE Forests around the world are succumbing to insect infestation with repercussions for local soil biogeochemistry and downstream water quality and quantity. This study utilized microbial community dynamics to address why we are observing watershed scale biogeochemical impacts from forest mortality in some impacted areas but not others. Through a unique “tree-centric” approach, we were able to delineate plots with various tree mortality levels within the same watershed to see if surviving surrounding vegetation altered microbial and biogeochemical responses. Our results suggest that forests with lower overall tree mortality levels are able to maintain “normal” ecosystem function, as the bacterial community appears resistant to tree death. However, surrounding tree mortality influences this mitigating effect with various linear and threshold responses whereupon the bacterial community and its function are altered. Our study lends insight into how microscale responses propagate upward into larger-scale observations, which may be useful for future predictions during analogous disruptions. IMPORTANCE Forests around the world are succumbing to insect infestation with repercussions for local soil biogeochemistry and downstream water quality and quantity. This study utilized microbial community dynamics to address why we are observing watershed scale biogeochemical impacts from forest mortality in some impacted areas but not others. Through a unique “tree-centric” approach, we were able to delineate plots with various tree mortality levels within the same watershed to see if surviving surrounding vegetation altered microbial and biogeochemical responses. Our results suggest that forests with lower overall tree mortality levels are able to maintain “normal” ecosystem function, as the bacterial community appears resistant to tree death. However, surrounding tree mortality influences this mitigating effect with various linear and threshold responses whereupon the bacterial community and its function are altered. Our study lends insight into how microscale responses propagate upward into larger-scale observations, which may be useful for future predictions during analogous disruptions.

Evaluation and Analysis of an Early Inducer Design and its Approach to Backflow Control

2013 ◽  
Author(s):  
Donald P. Sloteman ◽  
Jennifer Redding ◽  
Paul Cooper
Keyword(s):  
Rocket Engine ◽  
Design Flow ◽  
Flow Conditions ◽  
Design Features ◽  
Essential Component ◽  
Operational Characteristics ◽  
Modern Analysis ◽  
Insight Into

The inducer has become an essential component of the modern turbopump. Many investigations have been performed to gain an understanding of the inducer’s adverse operational characteristics that can include fluctuating pressures, unsteady delivery flow and fluctuating loads that compromise reliability. Furthermore, design features have been evaluated that eliminate or attenuate this adverse behavior. This paper describes the first known application of an inducer to a turbopump which fueled a throttleable rocket engine dating from the early 1940’s. The pump is unique in its use of an integral backflow recirculator that corrects the effects of suction recirculation at off-design flow conditions. Modern analysis, including CFD, of this inducer provides insight into its design and operational behavior. The design of this historic inducer offers insight into modern approaches that will correct inducer instabilities.

Temperature and flow conditions of quartz-sand injections at the base of the Esla Nappe (Cantabrian Zone, NW Iberia)

2021 ◽  
Author(s):  
Manuel Ignacio de Paz Álvarez ◽  
Sergio Llana-Fúnez ◽  
Stefano M. Bernasconi ◽  
Juan Luis Alonso ◽  
Heather M. Stoll
Keyword(s):  
Laminar Flow ◽  
Turbulent Flows ◽  
Quartz Sand ◽  
Geothermal Gradient ◽  
Flow Conditions ◽  
Fall Velocity ◽  
Cantabrian Zone ◽  
Bedding Planes ◽  
Nw Iberia ◽  
Flow Velocities

<p>The Esla Nappe is located in the foreland and thrust belt of the Variscan Orogen (Cantabrian Zone, NW Iberia). It is formed by a near-complete Palaeozoic sedimentary succession. With a displacement of around 19 km, the nappe was emplaced along a thin (<2–3 m) basal shear zone (ENSZ) at a minimum depth of 4 km during the Moscovian (ca. 312 Ma). Fault-rock assemblages record a variety of alternating deformation mechanisms and processes, including cataclastic flow, pressure solution and hydrofracturing and vein precipitation.</p><p>Following emplacement, the ENSZ was breached by clastic dykes and sills injected within re-opened previous anisotropies such as bedding planes, thrust surfaces, joints and stylolites. Together, they constitute an interconnected network of quartz sand-rich lithosomes that reach structural heights in excess of 20 m above the ENSZ. The orientation of the dykes suggests that the injection process took place under low differential stress conditions in the hangingwall and near-lithostatic fluid pressure conditions in the footwall. The injected slurry consisted of overpressured pore fluid, quartz-sand grains derived from the footwall and entrained host-rock fragments. The temperature of the fluids estimated from the clumped isotope composition of calcite cements is 71–86 °C, with an average of 80 ± 4 °C. The calcite isotopic composition (δ<sup>13</sup>C = -0.15, δ<sup>18</sup>O = -9.53, both VPDB) is well within the typical values of the host Láncara Fm., which suggests that the fluids achieved equilibrium with the host prior to calcite precipitation. Using this calculated temperature and depth estimates for the base of the Esla Nappe, the geothermal gradient during deformation is estimated to be in the order of 16–24 °C/km, a relatively low value.</p><p>Flow conditions within the injections have been inferred from properties such as the particle drag coefficient, morphology, diameter and concentration, and the fluid density and viscosity, necessary for the calculation of the terminal fall velocity of the particle array. Thin injections formed of pure quartz, with a thickness <1 cm, are consistent with flow velocities of 0.01–0.35 m/s and a laminar flow (Reynolds number (Re) <800). Thicker pure quartz injections (<10 cm), on the other hand, required faster flow velocities (0.35 m/s) and transitional to turbulent flows (800 < Re < 8000). The thicker injections (≈1 m) that entrained larger host-derived fragments would require transitional to turbulent flows (1200 < Re < 1.2×10<sup>4</sup>) at fast velocities (0.35 m/s).</p><p>The estimated geothermal gradient is consistent with the lower estimations for current foreland basins, and very similar to ocean trenches. The velocities and Reynolds numbers derived for the Esla Nappe are larger than usually estimated for deep seated injections without hydraulic connection with the surface, where the vertical pressure gradient driving them is limited. In those cases, laminar flow conditions are usually invoked, but our results suggest that turbulent flow is possible in the thicker injections. Nonetheless, the values are lower than those reported for shallow injections in connection with the surface.</p>

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