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Callum J. Shakespeare - One of the best experts on this subject based on the ideXlab platform.
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Curved Density Fronts: Cyclogeostrophic Adjustment and Frontogenesis
Journal of Physical Oceanography, 2016Co-Authors: Callum J. ShakespeareAbstract:AbstractCurvature can play a significant role in the dynamics of density fronts at small scales and in low-latitude regions of the ocean. Fronts can be displaced from balance by rapid forcing and undergo an adjustment toward a more stable state or be strained and sharpened by surrounding flow in a process known as frontogenesis. This study investigates the role of curvature in adjustment and frontogenesis using the idealized configuration of an axisymmetric eddy and associated circular front. As a result of the curvature, the balanced state of this system is not geostrophic balance, where pressure and Coriolis Forces exactly balance, but cyclogeostrophic balance, where pressure and Coriolis Forces combine to supply a net inwards Centripetal Force on fluid parcels. The parameter range for which cyclogeostrophically balanced states exist for a given unbalanced initial condition is determined. This parameter range is smaller for anticyclonic fronts (i.e., fronts curved around a warm core), which have larger ...
Adrienne M Stilp - One of the best experts on this subject based on the ideXlab platform.
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pressure support in galaxy disks impact on rotation curves and dark matter density profiles
The Astrophysical Journal, 2010Co-Authors: Julianne J Dalcanton, Adrienne M StilpAbstract:Rotation curves constrain a galaxy's underlying mass density profile, under the assumption that the observed rotation produces a Centripetal Force that exactly balances the inward Force of gravity. However, most rotation curves are measured using emission lines from gas, which can experience additional Forces due to pressure. In realistic galaxy disks, the gas pressure declines with radius, providing additional radial support to the disk. The measured tangential rotation speed will therefore tend to lag the true circular velocity of a test particle. The gas pressure is dominated by turbulence, and we evaluate its likely amplitude from recent estimates of the gas velocity dispersion and surface density. We show that where the amplitude of the rotation curve is comparable to the characteristic velocities of the interstellar turbulence, pressure support may lead to underestimates of the mass density of the underlying dark matter halo and the inner slope of its density profile. These effects may be significant for galaxies with rotation speeds 75 km s-1 but are unlikely to be significant in higher-mass galaxies. We find that pressure support can be sustained over long timescales, because any reduction in support due to the conversion of gas into stars is compensated for by an inward flow of gas. However, we point to many uncertainties in assessing the importance of pressure support in real or simulated galaxies. Thus, while pressure support may help to alleviate possible tensions between rotation curve observations and ΛCDM on kiloparsec scales, it should not be viewed as a definitive solution at this time.
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pressure support in galaxy disks impact on rotation curves and dark matter density profiles
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Julianne J Dalcanton, Adrienne M StilpAbstract:Rotation curves constrain a galaxy's underlying mass density profile, under the assumption that the observed rotation produces a Centripetal Force that exactly balances the inward Force of gravity. However, most rotation curves are measured using emission lines from gas, which can experience additional Forces due to pressure. In realistic galaxy disks, the gas pressure declines with radius, providing additional radial support to the disk. The measured tangential rotation speed will therefore tend to lag the true circular velocity of a test particle. The gas pressure is dominated by turbulence, and we evaluate its likely amplitude from recent estimates of the gas velocity dispersion and surface density. We show that where the amplitude of the rotation curve is comparable to the characteristic velocities of the interstellar turbulence, pressure support may lead to underestimates of the mass density of the underlying dark matter halo and the inner slope of its density profile. These effects may be significant for galaxies with rotation speeds <75km/s, but are unlikely to be significant in higher mass galaxies. We find that pressure support can be sustained over long timescales, because any reduction in support due to the conversion of gas into stars is compensated for by an inward flow of gas. However, we point to many uncertainties in assessing the importance of pressure support in galaxies. Thus, while pressure support may alleviate possible tensions between rotation curve observations and LambdaCDM on kiloparsec scales, it should not be viewed as a definitive solution at this time.
Colas-blaise Marion - One of the best experts on this subject based on the ideXlab platform.
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De la posture énonciative à la diathèse. Gestion et gestation du sens
2020Co-Authors: Colas-blaise MarionAbstract:This paper, which analyses extracts of Le balcon en forêt by Julien Gracq, aims to question once more the notion of enunciative posture that has been examined by Alain Rabatel in his point of view theory. Attention is focused on the posture of co-enunciation, which is approached from three different viewing angles: first, we reflect upon the notion of “recessive diathesis”, in relation to a Centripetal Force; second, we distinguish between tonic and low regimes of consensual and dissensual co-enunciation; third, we want to show that the posture of co-enunciation is based on a sensitive proto-posture, which underlies it. Keywords : co-enunciation, diathesis, regimes of consensual and dissensual co-enunciation,, enunciative proto-postur
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De la posture énonciative à la diathèse : gestion et gestation du sens
'OpenEdition', 2020Co-Authors: Colas-blaise MarionAbstract:Cet article, qui s’appuie sur Un balcon en forêt de Julien Gracq, se propose de réinterroger la notion de posture énonciative développée par Alain Rabatel dans sa théorie du point de vue. L’attention est focalisée sur la posture de la co-énonciation, qui est abordée sous différents angles : du point de vue de la diathèse en particulier récessive, qui est mise en relation avec l’opération de l’embrayage et une visée centripète ; du point de vue des régimes tonique et atone de la co-énonciation consensuelle et dissensuelle ; enfin, du point de vue d’une proto-posture énonciative sous-tendant la posture de la co-énonciation, qui permet de rendre compte de la gestation du sens et des couches sensibles du pathique.This paper, which analyses extracts of Le balcon en forêt by Julien Gracq, aims to question once more the notion of enunciative posture that has been examined by Alain Rabatel in his point of view theory. Attention is focused on the posture of co-enunciation, which is approached from three different viewing angles: first, we reflect upon the notion of “recessive diathesis”, in relation to a Centripetal Force; second, we distinguish between tonic and low regimes of consensual and dissensual co-enunciation; third, we want to show that the posture of co-enunciation is based on a sensitive proto-posture, which underlies it
Julianne J Dalcanton - One of the best experts on this subject based on the ideXlab platform.
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pressure support in galaxy disks impact on rotation curves and dark matter density profiles
The Astrophysical Journal, 2010Co-Authors: Julianne J Dalcanton, Adrienne M StilpAbstract:Rotation curves constrain a galaxy's underlying mass density profile, under the assumption that the observed rotation produces a Centripetal Force that exactly balances the inward Force of gravity. However, most rotation curves are measured using emission lines from gas, which can experience additional Forces due to pressure. In realistic galaxy disks, the gas pressure declines with radius, providing additional radial support to the disk. The measured tangential rotation speed will therefore tend to lag the true circular velocity of a test particle. The gas pressure is dominated by turbulence, and we evaluate its likely amplitude from recent estimates of the gas velocity dispersion and surface density. We show that where the amplitude of the rotation curve is comparable to the characteristic velocities of the interstellar turbulence, pressure support may lead to underestimates of the mass density of the underlying dark matter halo and the inner slope of its density profile. These effects may be significant for galaxies with rotation speeds 75 km s-1 but are unlikely to be significant in higher-mass galaxies. We find that pressure support can be sustained over long timescales, because any reduction in support due to the conversion of gas into stars is compensated for by an inward flow of gas. However, we point to many uncertainties in assessing the importance of pressure support in real or simulated galaxies. Thus, while pressure support may help to alleviate possible tensions between rotation curve observations and ΛCDM on kiloparsec scales, it should not be viewed as a definitive solution at this time.
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pressure support in galaxy disks impact on rotation curves and dark matter density profiles
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Julianne J Dalcanton, Adrienne M StilpAbstract:Rotation curves constrain a galaxy's underlying mass density profile, under the assumption that the observed rotation produces a Centripetal Force that exactly balances the inward Force of gravity. However, most rotation curves are measured using emission lines from gas, which can experience additional Forces due to pressure. In realistic galaxy disks, the gas pressure declines with radius, providing additional radial support to the disk. The measured tangential rotation speed will therefore tend to lag the true circular velocity of a test particle. The gas pressure is dominated by turbulence, and we evaluate its likely amplitude from recent estimates of the gas velocity dispersion and surface density. We show that where the amplitude of the rotation curve is comparable to the characteristic velocities of the interstellar turbulence, pressure support may lead to underestimates of the mass density of the underlying dark matter halo and the inner slope of its density profile. These effects may be significant for galaxies with rotation speeds <75km/s, but are unlikely to be significant in higher mass galaxies. We find that pressure support can be sustained over long timescales, because any reduction in support due to the conversion of gas into stars is compensated for by an inward flow of gas. However, we point to many uncertainties in assessing the importance of pressure support in galaxies. Thus, while pressure support may alleviate possible tensions between rotation curve observations and LambdaCDM on kiloparsec scales, it should not be viewed as a definitive solution at this time.
Jay T. Groves - One of the best experts on this subject based on the ideXlab platform.
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Myosin IIA and formin dependent mechanosensitivity of filopodia adhesion.
Nature communications, 2019Co-Authors: Naila O. Alieva, Meenubharathi Natarajan, Artem K. Efremov, Zhongwen Chen, Hui Ting Ong, Antoine Jégou, Guillaume Romet-lemonne, Jay T. GrovesAbstract:Filopodia, dynamic membrane protrusions driven by polymerization of an actin filament core, can adhere to the extracellular matrix and experience both external and cell-generated pulling Forces. The role of such Forces in filopodia adhesion is however insufficiently understood. Here, we study filopodia induced by overexpression of myosin X, typical for cancer cells. The lifetime of such filopodia positively correlates with the presence of myosin IIA filaments at the filopodia bases. Application of pulling Forces to the filopodia tips through attached fibronectin-coated laser-trapped beads results in sustained growth of the filopodia. Pharmacological inhibition or knockdown of myosin IIA abolishes the filopodia adhesion to the beads. Formin inhibitor SMIFH2, which causes detachment of actin filaments from formin molecules, produces similar effect. Thus, Centripetal Force generated by myosin IIA filaments at the base of filopodium and transmitted to the tip through actin core in a formin-dependent fashion is required for filopodia adhesion.
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Force dependence of filopodia adhesion involvement of myosin ii and formins
bioRxiv, 2017Co-Authors: Naila O. Alieva, Meenubharathi Natarajan, Guillaume Rometlemonne, Jay T. Groves, Artem K. Efremov, Zhongwen Chen, Hui Ting Ong, Antoine Jégou, Michael P Sheetz, Jie YanAbstract:Filopodia are dynamic membrane protrusions driven by polymerization of an actin filament core, mediated by formin molecules at the filopodia tips. Filopodia can adhere to the extracellular matrix and experience both external and cell generated pulling Forces. The role of such Forces in filopodia adhesion is however insufficiently understood. Here, we induced sustained growth of filopodia by applying pulling Force to their tips via attached fibronectin-coated beads trapped by optical tweezers. Strikingly, pharmacological inhibition or knockdown of myosin IIA, which localized to the base of filopodia, resulted in weakening of filopodia adherence strength. Inhibition of formins, which caused detachment of actin filaments from formin molecules, produced similar effect. Thus, myosin IIA-generated Centripetal Force transmitted to the filopodia tips through interactions between formins and actin filaments is required for filopodia adhesion. Force-dependent adhesion led to preferential attachment of filopodia to rigid versus fluid substrates, which may underlie cell orientation and polarization.