The Experts below are selected from a list of 277107 Experts worldwide ranked by ideXlab platform
Julie A Theriot - One of the best experts on this subject based on the ideXlab platform.
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surface area to Volume Ratio a natural variable for bacterial morphogenesis
Trends in Microbiology, 2018Co-Authors: Leigh K Harris, Julie A TheriotAbstract:An immediately observable feature of bacteria is that cell size and shape are remarkably constant and characteristic for a given species in a particular condition, but vary quantitatively with physiological parameters such as growth rate, indicating both genetic and environmental regulation. However, despite decades of research, the molecular mechanisms underlying bacterial morphogenesis have remained incompletely characterized. We recently demonstrated that a wide range of bacterial species exhibit a robust surface area to Volume Ratio (SA/V) homeostasis. Because cell size, shape, and SA/V are mathematically interconnected, if SA/V is indeed the natural variable that cells actively monitor, this finding has critical implications for our understanding of bacterial morphogenesis, placing fundamental constraints on the sizes and shapes that cells can adopt. In this Opinion article we discuss the broad implications that this novel perspective has for the field of bacterial growth and morphogenesis.
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a caulobacter mreb mutant with irregular cell shape exhibits compensatory widening to maintain a preferred surface area to Volume Ratio
Molecular Microbiology, 2014Co-Authors: Leigh K Harris, Natalie A Dye, Julie A TheriotAbstract:Summary Rod-shaped bacteria typically elongate at a uniform width. To investigate the genetic and physiological determinants involved in this process, we studied a mutation in the morphogenetic protein MreB in Caulobacter crescentus that gives rise to cells with a variable-width phenotype, where cells have regions that are both thinner and wider than wild-type. During growth, individual cells develop a balance of wide and thin regions, and mutant MreB dynamically localizes to poles and thin regions. Surprisingly, the surface area to Volume Ratio of these irregularly shaped cells is, on average, very similar to wild-type. We propose that, while mutant MreB localizes to thin regions and promotes rod-like growth there, wide regions develop as a compensatory mechanism, allowing cells to maintain a wild-type-like surface area to Volume Ratio. To support this model, we have shown that cell widening is abrogated in growth conditions that promote higher surface area to Volume Ratios, and we have observed individual cells with high Ratios return to wild-type levels over several hours by developing wide regions, suggesting that compensation can take place at the level of individual cells.
Shaun M Kunisaki - One of the best experts on this subject based on the ideXlab platform.
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surveillance of fetal lung lesions using the congenital pulmonary airway malformation Volume Ratio natural history and outcomes
Prenatal Diagnosis, 2016Co-Authors: Catriona A Macardle, Stacey Ehrenbergbuchner, Ethan A Smith, Jonathan R Dillman, George B Mychaliska, Marjorie C Treadwell, Shaun M KunisakiAbstract:OBJECTIVES The congenital pulmonary airway malformation Volume Ratio (CVR) is a widely used sonographic measure of relative mass size in fetuses with lung malformations. The purposes of this study were to examine serial CVR measurements to understand longitudinal growth patterns and to determine correlation with postnatal imaging. METHODS An institutional review board-approved retrospective review was performed on fetuses referred for an echogenic lung malformation between 2002 and 2014. For each fetus, the CVR was prospectively calculated using 2D ultrasound and followed with advancing gestation. RESULTS Based on 40 fetuses, the mean initial CVR was 0.51 ± 0.07 at 20.5 ± 0.3 weeks of gestation. The CVR increased after 24 weeks of gestation (p = 0.0014), peaking at a CVR of 0.96 ± 0.11 at 25.5 ± 0.05 weeks, followed by a significant decrease in the CVR to 0.43 ± 0.07 prior to term (p < 0.0001). However, approximately one third showed no appreciable increase in size. The mean CVR was significantly correlated with postnatal chest computed tomography (CT) size dimensions (p = 0.0032) and likelihood for lung resection (p = 0.0055). CONCLUSIONS Fetal lung malformations tend to follow one of two distinct growth patterns, characterized by either (1) a maximal CVR between 25 and 26 weeks of gestation or (2) minimal change in relative growth. The mean CVR correlates with postnatal CT size and operative management.
Magali Benoit - One of the best experts on this subject based on the ideXlab platform.
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Equilibrium shape of core(Fe)–shell(Au) nanoparticles as a function of the metals Volume Ratio
Journal of Applied Physics, 2020Co-Authors: Anne Ponchet, Segolene Combettes, Patrizio Benzo, Nathalie Tarrat, Marie-josé Casanove, Magali BenoitAbstract:The equilibrium shape of nanoparticles is investigated to elucidate the various core–shell morphologies observed in a bimetallic system associating two immiscible metals, iron and gold, that crystallize in the bcc and fcc lattices, respectively. Fe–Au core–shell nanoparticles present a crystalline Fe core embedded in a polycrystalline Au shell, with core and shell morphologies both depending on the Au/Fe Volume Ratio. A model is proposed to calculate the energy of these nanoparticles as a function of the Fe Volume, Au/Fe Volume Ratio, and the core and shell shape, using the density functional theory-computed energy densities of the metal surfaces and of the two possible Au/Fe interfaces. Three driving forces leading to equilibrium shapes were identified: the strong adhesion of Au on Fe, the minimization of the Au/Fe interface energy that promotes one of the two possible interface types, and the Au surface energy minimization that promotes a 2D–3D Stranski–Krastanov-like transition of the shell. For a low Au/Fe Volume Ratio, the wetting is the dominant driving force and leads to the same polyhedral shape for the core and the shell, with an octagonal section. For a large Au/Fe Ratio, the surface and interface energy minimizations can act independently to form an almost cube-shaped Fe core surrounded by six Au pyramids. The experimental nanoparticle shapes are well reproduced by the model, for both low and large Au/Fe Volume Ratios.
Bowen Xiong - One of the best experts on this subject based on the ideXlab platform.
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effect of Volume Ratio of liquid to solid on the interfacial microstructure and mechanical properties of high chromium cast iron and medium carbon steel bimetal
Journal of Alloys and Compounds, 2011Co-Authors: Bowen Xiong, Baiping LuAbstract:Abstract The high chromium cast iron and medium carbon steel bimetal was fabricated by liquid–solid casting technology. The effect of Volume Ratios of liquid to solid (6:1, 10:1 and 12:1) on the interfacial microstructure and mechanical properties of bimetal was investigated. The interfacial microstructure was analyzed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The shear strength and microhardness in as-cast condition were studied at room temperature. The results show that the Volume Ratios of liquid to solid affect significantly the interfacial microstructure. When liquid–solid Volume Ratio was 6:1, the unbonded region was detected in interface region because the imported heat energy cannot support effectively the diffusion of element, whereas, when liquid–solid Volume Ratios reach 10:1 and 12:1, a sound interfacial microstructure was achieved by the diffusion of C, Cr, Mo, Cu and Mn, and metallurgical bonding without unbonded region, void and hole, etc. was detected. With the increase of liquid–solid Volume Ratio, the elemental diffusion activity improves, resulting in the increase of width of interface transition region. At the same distance from interface, with the increase of liquid–solid Volume Ratio, the microhardness is degraded in HCCI, but increased in MCS. The shear strength is also improved with the increase of liquid–solid Volume Ratio.
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effect of Volume Ratio of liquid to solid on the interfacial microstructure and mechanical properties of high chromium cast iron and medium carbon steel bimetal
Journal of Alloys and Compounds, 2011Co-Authors: Bowen Xiong, Changchun CaiAbstract:Abstract The high chromium cast iron and medium carbon steel bimetal was fabricated by liquid–solid casting technology. The effect of Volume Ratios of liquid to solid (6:1, 10:1 and 12:1) on the interfacial microstructure and mechanical properties of bimetal was investigated. The interfacial microstructure was analyzed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The shear strength and microhardness in as-cast condition were studied at room temperature. The results show that the Volume Ratios of liquid to solid affect significantly the interfacial microstructure. When liquid–solid Volume Ratio was 6:1, the unbonded region was detected in interface region because the imported heat energy cannot support effectively the diffusion of element, whereas, when liquid–solid Volume Ratios reach 10:1 and 12:1, a sound interfacial microstructure was achieved by the diffusion of C, Cr, Mo, Cu and Mn, and metallurgical bonding without unbonded region, void and hole, etc. was detected. With the increase of liquid–solid Volume Ratio, the elemental diffusion activity improves, resulting in the increase of width of interface transition region. At the same distance from interface, with the increase of liquid–solid Volume Ratio, the microhardness is degraded in HCCI, but increased in MCS. The shear strength is also improved with the increase of liquid–solid Volume Ratio.
Catriona A Macardle - One of the best experts on this subject based on the ideXlab platform.
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surveillance of fetal lung lesions using the congenital pulmonary airway malformation Volume Ratio natural history and outcomes
Prenatal Diagnosis, 2016Co-Authors: Catriona A Macardle, Stacey Ehrenbergbuchner, Ethan A Smith, Jonathan R Dillman, George B Mychaliska, Marjorie C Treadwell, Shaun M KunisakiAbstract:OBJECTIVES The congenital pulmonary airway malformation Volume Ratio (CVR) is a widely used sonographic measure of relative mass size in fetuses with lung malformations. The purposes of this study were to examine serial CVR measurements to understand longitudinal growth patterns and to determine correlation with postnatal imaging. METHODS An institutional review board-approved retrospective review was performed on fetuses referred for an echogenic lung malformation between 2002 and 2014. For each fetus, the CVR was prospectively calculated using 2D ultrasound and followed with advancing gestation. RESULTS Based on 40 fetuses, the mean initial CVR was 0.51 ± 0.07 at 20.5 ± 0.3 weeks of gestation. The CVR increased after 24 weeks of gestation (p = 0.0014), peaking at a CVR of 0.96 ± 0.11 at 25.5 ± 0.05 weeks, followed by a significant decrease in the CVR to 0.43 ± 0.07 prior to term (p < 0.0001). However, approximately one third showed no appreciable increase in size. The mean CVR was significantly correlated with postnatal chest computed tomography (CT) size dimensions (p = 0.0032) and likelihood for lung resection (p = 0.0055). CONCLUSIONS Fetal lung malformations tend to follow one of two distinct growth patterns, characterized by either (1) a maximal CVR between 25 and 26 weeks of gestation or (2) minimal change in relative growth. The mean CVR correlates with postnatal CT size and operative management.
