scholarly journals The evolution of laminar thermals

2019 ◽  
Vol 878 ◽  
pp. 907-931 ◽  
Author(s):  
J. W. Atkinson ◽  
P. A. Davidson
Keyword(s):  
Life Cycle ◽  
Vortex Ring ◽  
Critical Reynolds Number ◽  
Morphological Changes ◽  
Mathematical Framework ◽  
Initial Condition ◽  
Thermal Transitions ◽  
Left Behind ◽  
Vorticity Flux ◽  
Initial Heat

We consider the life cycle of an axisymmetric laminar thermal starting from the initial condition of a Gaussian buoyant blob. We find that, as time progresses, the thermal transitions through a number of distinct stages, undergoing several morphological changes before ending up as a vortex ring. Whilst each stage is interesting in its own right, one objective of this study is to set out a consistent mathematical framework under which the entire life cycle can be studied. This allows examination of the transition between the different stages, as well as shedding light on some unsolved questions from previous works. We find that the early stages of formation are key in determining the properties of the final buoyant vortex ring and that, since they occur on a time scale where viscosity has little effect, the final properties of the ring display an independence above a critical Reynolds number. We also find that rings consistently contain the same proportion of the initial heat and have a consistent vorticity flux. By considering the effect of Prandtl number, we show that thermal diffusion can have a significant impact on development, smoothing out the temperature field and inhibiting the generation of vorticity. Finally, by considering the wake left behind as well as the vortex ring that is generated, we observe that the wake can itself roll up to form a second mushroom cap and subsequently a secondary vortex ring that follows the first.

Morphological changes during the life cycle ofAureobasidium pullulans (de Bary) Arnaud

1980 ◽  
Vol 25 (1) ◽  
pp. 56-67 ◽  
Author(s):  
A. Kocková-Kratochvílová ◽  
M. Černáková ◽  
E. Sláviková
Keyword(s):  
Life Cycle ◽  
Morphological Changes

scholarly journals Identification of Fis1 Interactors in Toxoplasma gondii Reveals a Novel Protein Required for Peripheral Distribution of the Mitochondrion

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Kylie Jacobs ◽  
Robert Charvat ◽  
Gustavo Arrizabalaga
Keyword(s):  
Life Cycle ◽  
Toxoplasma Gondii ◽  
Morphological Changes ◽  
Dominant Negative Effect ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Content Type ◽  
Membrane Contact Sites ◽  
Intracellular Parasites ◽  
Single Mitochondrion

ABSTRACT Toxoplasma gondii’s single mitochondrion is very dynamic and undergoes morphological changes throughout the parasite’s life cycle. During parasite division, the mitochondrion elongates, enters the daughter cells just prior to cytokinesis, and undergoes fission. Extensive morphological changes also occur as the parasite transitions from the intracellular environment to the extracellular environment. We show that treatment with the ionophore monensin causes reversible constriction of the mitochondrial outer membrane and that this effect depends on the function of the fission-related protein Fis1. We also observed that mislocalization of the endogenous Fis1 causes a dominant-negative effect that affects the morphology of the mitochondrion. As this suggests that Fis1 interacts with proteins critical for maintenance of mitochondrial structure, we performed various protein interaction trap screens. In this manner, we identified a novel outer mitochondrial membrane protein, LMF1, which is essential for positioning of the mitochondrion in intracellular parasites. Normally, while inside a host cell, the parasite mitochondrion is maintained in a lasso shape that stretches around the parasite periphery where it has regions of coupling with the parasite pellicle, suggesting the presence of membrane contact sites. In intracellular parasites lacking LMF1, the mitochondrion is retracted away from the pellicle and instead is collapsed, as normally seen only in extracellular parasites. We show that this phenotype is associated with defects in parasite fitness and mitochondrial segregation. Thus, LMF1 is necessary for mitochondrial association with the parasite pellicle during intracellular growth, and proper mitochondrial morphology is a prerequisite for mitochondrial division. IMPORTANCE Toxoplasma gondii is an opportunistic pathogen that can cause devastating tissue damage in the immunocompromised and congenitally infected. Current therapies are not effective against all life stages of the parasite, and many cause toxic effects. The single mitochondrion of this parasite is a validated drug target, and it changes its shape throughout its life cycle. When the parasite is inside a cell, the mitochondrion adopts a lasso shape that lies in close proximity to the pellicle. The functional significance of this morphology is not understood and the proteins involved are currently not known. We have identified a protein that is required for proper mitochondrial positioning at the periphery and that likely plays a role in tethering this organelle. Loss of this protein results in dramatic changes to the mitochondrial morphology and significant parasite division and propagation defects. Our results give important insight into the molecular mechanisms regulating mitochondrial morphology.

Multi-instar descriptions of cave dwelling Erythraeidae (Trombidiformes: Parasitengona) employing an integrative approach

Zootaxa ◽  
2019 ◽  
Vol 4717 (1) ◽  
pp. 137-184 ◽  
Author(s):  
SAMUEL GEREMIAS DOS SANTOS COSTA ◽  
HANS KLOMPEN ◽  
LEOPOLDO FERREIRA DE OLIVEIRA BERNARDI ◽  
LUCIANA CARDOSO GONÇALVES ◽  
DANTE BATISTA RIBEIRO ◽  
...  
Keyword(s):  
Life Cycle ◽  
Cytochrome Oxidase ◽  
Molecular Analysis ◽  
Species Delimitation ◽  
Morphological Changes ◽  
Molecular Data ◽  
Coi Gene ◽  
Integrative Approach ◽  
Larval Instars ◽  
Individual Host

The life cycle of Parasitengona includes major morphological changes precluding an instar association based only on the morphology. This makes rearing and/or molecular data necessary to associate the heteromorphic instars. Most of the described species are known from either post larval instars or larva. Following a previous study on Palearctic Erythraeidae, in the present study the instar association was made through an integrative approach including rearing trials and molecular analysis of the cytochrome oxidase I (COI) gene with the Bayesian Generalized Mixed Yule Coalescent (bGMYC) algorithm for species delimitation. Two new cave dwelling Erythraeidae (Trombidiformes: Parasitengona) species are described Lasioerythraeus jessicae sp. nov. and Leptus sidorchukae sp. nov. including all active instars. Additionally, a complete description of the previously unknown adults of Charletonia rocciai Treat & Flechtmann, 1979 is provided with notes on the larva and deutonymph. We also demonstrate experimentally that Ch. rocciai larvae are not attached to the same individual host during the entire feeding stage. We discuss the presence of troglomorphisms in Le. sidorchukae sp. nov.; and the distribution of the species. 

Synthesis of Chitosan-Polyvinyl Alcohol Copolymers for Smart Drug Delivery Application

2017 ◽  
Vol 25 (3) ◽  
pp. 241-246 ◽  
Author(s):  
Neha Mulchandani ◽  
Nimish Shah ◽  
Tejal Mehta
Keyword(s):  
Drug Delivery ◽  
Drug Release ◽  
Polyvinyl Alcohol ◽  
Morphological Changes ◽  
Crosslinking Agent ◽  
Ph Responsive ◽  
Thermal Transitions ◽  
Scanning Calorimetry ◽  
Model Drug

Chitosan is a natural polymer obtained from exoskeletons of crustaceans and polyvinyl alcohol (PVA) is a synthetic polymer which has excellent film forming ability along with non-toxic nature. The current work focuses on synthesizing a smart polymer by copolymerization of natural and synthetic polymers and exploring its applications in drug delivery. The copolymers were blended in different ratios and were synthesized using ammonium ceric nitrate as initiator and glutaraldehyde as a crosslinking agent which were converted to films by casting method. Amoxicillin, as a model drug was incorporated to the copolymerized films to study the in-vitro drug release. The films obtained were evaluated by varying the pH to study the pH responsive nature of films. Drug release studies were performed to obtain the release profile of drug; water uptake capacity of the copolymerized film were measured to determine the swelling behaviour of the films. The films were further characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) to identify the structural and morphological changes along with thermal transitions. The results indicate that the synthesized copolymers are pH responsive in nature having great potential for application in controlled and targeted drug delivery.

Composite Vertical Structure of Vertical Velocity in Nonprecipitating Cumulus Clouds

2013 ◽  
Vol 141 (5) ◽  
pp. 1673-1692 ◽  
Author(s):  
Yonggang Wang ◽  
Bart Geerts
Keyword(s):  
Life Cycle ◽  
Vortex Ring ◽  
Vertical Velocity ◽  
Circulation Pattern ◽  
Liquid Water Content ◽  
University Of Wyoming ◽  
High Plains ◽  
Cumulus Clouds ◽  
The University ◽  
Negatively Buoyant

Abstract Vertical transects of Doppler vertical velocity data, obtained from an airborne profiling millimeter-wave cloud radar, are composited for a large number of cumulus clouds (Cu) at various stages of their life cycle, to examine typical circulations patterns. The Cu clouds range in depth between ~500 and 6000 m and are generally nonprecipitating. They were sampled on board the University of Wyoming King Air over a mountain in southern Arizona during the summer monsoon, and over the high plains of southeastern Wyoming. The composite analysis shows clear evidence of an updraft/downdraft dipole in the upper cloud half, consistent with a horizontal vortex ring. A single cloud-scale toroidal circulation emerges notwithstanding the complex finescale structure with multiple vortices, commonly evident in individual transects of Cu clouds. The stratification of all Cu samples as a function of their buoyancy and mean vertical velocity shows that the vortex ring pattern tends to be more pronounced in positively buoyant Cu with rising motion (presumably young clouds) than in negatively buoyant and/or sinking Cu near the end of their life cycle. Yet no reverse vortex ring is observed in the latter Cu, suggesting that the decaying phase is short lived in these dry environments. The vortex-ring circulation pattern is more intense in the shallower Cu, which are also more buoyant and have a liquid water content closer to adiabatic values. Wind shear tends to tilt Cu clouds and their vortex ring, resulting in a broadening of the upshear updraft and downshear downdraft.

scholarly journals 4D visualization study of a vortex ring life cycle using modal analyses

2015 ◽  
Vol 19 (2) ◽  
pp. 237-259 ◽  
Author(s):  
Benjamin Ponitz ◽  
Mark Sastuba ◽  
Christoph Brücker
Keyword(s):  
Life Cycle ◽  
Vortex Ring

scholarly journals In VivoLabelling of Adenovirus DNA Identifies Chromatin Anchoring and Biphasic Genome Replication

2018 ◽  
Vol 92 (18) ◽  
Author(s):  
Tetsuro Komatsu ◽  
Charlotte Quentin-Froignant ◽  
Irene Carlon-Andres ◽  
Floriane Lagadec ◽  
Fabienne Rayne ◽  
...  
Keyword(s):  
Life Cycle ◽  
Real Time ◽  
Viral Genome ◽  
Imaging System ◽  
Morphological Changes ◽  
Host Cells ◽  
Genome Replication ◽  
Equal Distribution ◽  
Viral Genomes

ABSTRACTAdenoviruses are DNA viruses with a lytic infection cycle. Following the fate of incoming as well as recently replicated genomes during infections is a challenge. In this study, we used the ANCHOR3 technology based on a bacterial partitioning system to establish a versatilein vivoimaging system for adenoviral genomes. The system allows the visualization of both individual incoming and newly replicated genomes in real time in living cells. We demonstrate that incoming adenoviral genomes are attached to condensed cellular chromatin during mitosis, facilitating the equal distribution of viral genomes in daughter cells after cell division. We show that the formation of replication centers occurs in conjunction within vivogenome replication and determine replication rates. Visualization of adenoviral DNA revealed that adenoviruses exhibit two kinetically distinct phases of genome replication. Low-level replication occurred during early replication, while high-level replication was associated with late replication phases. The transition between these phases occurred concomitantly with morphological changes of viral replication compartments and with the appearance of virus-induced postreplication (ViPR) bodies, identified by the nucleolar protein Mybbp1A. Taken together, our real-time genome imaging system revealed hitherto uncharacterized features of adenoviral genomesin vivo. The system is able to identify novel spatiotemporal aspects of the adenovirus life cycle and is potentially transferable to other viral systems with a double-stranded DNA phase.IMPORTANCEViruses must deliver their genomes to host cells to ensure replication and propagation. Characterizing the fate of viral genomes is crucial to understand the viral life cycle and the fate of virus-derived vector tools. Here, we integrated the ANCHOR3 system, anin vivoDNA-tagging technology, into the adenoviral genome for real-time genome detection. ANCHOR3 tagging permitted thein vivovisualization of incoming genomes at the onset of infection and of replicated genomes at late phases of infection. Using this system, we show viral genome attachment to condensed host chromosomes during mitosis, identifying this mechanism as a mode of cell-to-cell transfer. We characterize the spatiotemporal organization of adenovirus replication and identify two kinetically distinct phases of viral genome replication. The ANCHOR3 system is the first technique that allows the continuous visualization of adenoviral genomes during the entire virus life cycle, opening the way for further in-depth study.

scholarly journals Biofilms Comprise a Component of the Annual Cycle ofVibrio choleraein the Bay of Bengal Estuary

mBio ◽  
2018 ◽  
Vol 9 (2) ◽  
pp. e00483-18 ◽  
Author(s):  
Marzia Sultana ◽  
Suraia Nusrin ◽  
Nur A. Hasan ◽  
Abdus Sadique ◽  
Kabir U. Ahmed ◽  
...  
Keyword(s):  
Life Cycle ◽  
Vibrio Cholerae ◽  
Causative Agent ◽  
Aquatic Environment ◽  
Morphological Changes ◽  
Living Cells ◽  
Estuarine Environment ◽  
Annual Life Cycle ◽  
Free Living ◽  
Content Type

ABSTRACTVibrio cholerae, an estuarine bacterium, is the causative agent of cholera, a severe diarrheal disease that demonstrates seasonal incidence in Bangladesh. In an extensive study ofV. choleraeoccurrence in a natural aquatic environment, water and plankton samples were collected biweekly between December 2005 and November 2006 from Mathbaria, an estuarine village of Bangladesh near the mangrove forests of the Sundarbans. ToxigenicV. choleraeexhibited two seasonal growth peaks, one in spring (March to May) and another in autumn (September to November), corresponding to the two annual seasonal outbreaks of cholera in this region. The total numbers of bacteria determined by heterotrophic plate count (HPC), representing culturable bacteria, accounted for 1% to 2.7% of the total numbers obtained using acridine orange direct counting (AODC). The highest bacterial culture counts, including toxigenicV. cholerae, were recorded in the spring. The direct fluorescent antibody (DFA) assay was used to detectV. choleraeO1 cells throughout the year, as free-living cells, within clusters, or in association with plankton.V. choleraeO1 varied significantly in morphology, appearing as distinctly rod-shaped cells in the spring months, while small coccoid cells within thick clusters of biofilm were observed during interepidemic periods of the year, notably during the winter months. ToxigenicV. choleraeO1 was culturable in natural water during the spring when the temperature rose sharply. The results of this study confirmed biofilms to be a means of persistence for bacteria and an integral component of the annual life cycle of toxigenicV. choleraein the estuarine environment of Bangladesh.IMPORTANCEVibrio cholerae, the causative agent of cholera, is autochthonous in the estuarine aquatic environment. This study describes morphological changes in naturally occurringV. choleraeO1 in the estuarine environment of Mathbaria, where the bacterium is culturable when the water temperature rises and is observable predominantly as distinct rods and dividing cells. In the spring and fall, these morphological changes coincide with the two seasonal peaks of endemic cholera in Bangladesh.V. choleraeO1 cells are predominantly coccoid within biofilms but are rod shaped as free-living cells and when attached to plankton or to particulate matter in interepidemic periods of the year. It is concluded that biofilms represent a stage of the annual life cycle ofV. choleraeO1, the causative agent of cholera in Bangladesh.

scholarly journals Development of the trailing shear layer in a starting jet during pinch-off

2012 ◽  
Vol 700 ◽  
pp. 382-405 ◽  
Author(s):  
L. Gao ◽  
S. C. M. Yu
Keyword(s):  
Shear Layer ◽  
Vortex Ring ◽  
Critical Time ◽  
Piston Cylinder ◽  
Vortex Ring Formation ◽  
Image Velocimetry ◽  
Formation Number ◽  
Vorticity Flux ◽  
Secondary Vortices ◽  
Starting Jet

AbstractExperiments on a circular starting jet generated by a piston–cylinder arrangement, over a range of Reynolds number from $2600$ to $5600$, are conducted so as to investigate the development of the trailing shear layer during the leading vortex ring formation, as well as the corresponding effects on the pinch-off process. Results obtained by digital particle image velocimetry (DPIV) show that secondary vortices start to develop in the trailing jet only after the critical time scale, the ‘formation number’, is achieved. The subsequent growth of the secondary vortices reduces the vorticity flux being fed into the leading vortex ring and, as a consequence, constrains the growth of leading vortex ring with larger circulation. Evolution of perturbation waves into secondary vortices is found to associate with growth and translation of the leading vortex ring during the formation process. A dimensionless parameter ‘$A$’, defined as ${\Gamma }_{\mathit{ring}} / ({x}_{\mathit{core}} \mrm{\Delta} U$), is therefore proposed to characterize the effect of the leading vortex ring on suppressing the nonlinear development of instability in the trailing shear layer, i.e. the initial roll-up of the secondary vortices. In a starting jet, $A$ follows a decreasing trend with the formation time ${t}^{\ensuremath{\ast} } $. A critical value ${A}_{c} = 1. 1\pm 0. 1$ is identified experimentally, which physically coincides with the initiation of the first secondary vortex roll-up and, therefore, indicates the onset of pinch-off process.

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