scholarly journals Deviations from classical droplet evaporation theory

2021 ◽  
Vol 477 (2251) ◽  
pp. 20210078
Author(s):  
Joshua Finneran ◽  
Colin P. Garner ◽  
François Nadal
Keyword(s):  
Droplet Evaporation ◽  
Transient Effects ◽  
Predictive Tool ◽  
Transient Regimes ◽  
Wide Range ◽  
Classical Models ◽  
Cold Vapour ◽  
Input Domain ◽  
Steady Temperature Field ◽  
Transient Models

In this article, we show that significant deviations from the classical quasi-steady models of droplet evaporation can arise solely due to transient effects in the gas phase. The problem of fully transient evaporation of a single droplet in an infinite atmosphere is solved in a generalized, dimensionless framework with explicitly stated assumptions. The differences between the classical quasi-steady and fully transient models are quantified for a wide range of the 10-dimensional input domain and a robust predictive tool to rapidly quantify this difference is reported. In extreme cases, the classical quasi-steady model can overpredict the droplet lifetime by 80%. This overprediction increases when the energy required to bring the droplet into equilibrium with its environment becomes small compared with the energy required to cool the space around the droplet and therefore establish the quasi-steady temperature field. In the general case, it is shown that two transient regimes emerge when a droplet is suddenly immersed into an atmosphere. Initially, the droplet vaporizes faster than classical models predict since the surrounding gas takes time to cool and to saturate with vapour. Towards the end of its life, the droplet vaporizes slower than expected since the region of cold vapour established in the early stages of evaporation remains and insulates the droplet.

scholarly journals Subcritical and Supercritical Droplet Evaporation within a Zero Gravity Environment; On the Discrepancies between Theoretical and Experimental Results

2009 ◽  
Vol 1 (3) ◽  
pp. 317-338 ◽  
Author(s):  
Hongtao Zhang ◽  
Vasudevan Raghavan ◽  
George Gogos
Keyword(s):  
High Pressure ◽  
Ambient Pressure ◽  
Local Maximum ◽  
Droplet Evaporation ◽  
Experimental Results ◽  
Spherically Symmetric ◽  
Transient Effects ◽  
Ambient Temperatures ◽  
Wide Range ◽  
Thermo Physical Properties

A comprehensive axisymmetric numerical model has been developed to study high pressure droplet evaporation. In this model, high pressure transient effects, variable thermo-physical properties and inert species solubility in the liquid-phase are considered. First, the axisymmetric model has been utilized to explain the discrepancy between theoretical and experimental results on microgravity droplet evaporation that has been reported in the literature [J.R. Yang and S.C. Wong, Ref. 35]. In addition, this effort led to a thorough validation of the model against the most extensive microgravity experimental data available in the literature on droplet evaporation. Second, the validated model has been utilized to investigate spherically symmetric droplet evaporation for a wide range of ambient pressures and temperatures. The predictions show that the average droplet evaporation constant decreases with ambient pressure at sub-critical ambient temperatures, becomes insensitive to pressure at ambient temperatures around the critical temperature of the fuel and presents a local maximum while increasing with the ambient pressure at super-critical ambient temperatures.

scholarly journals Global analysis of adenylate-forming enzymes reveals β-lactone biosynthesis pathway in pathogenic Nocardia

2020 ◽  
Vol 295 (44) ◽  
pp. 14826-14839
Author(s):  
Serina L. Robinson ◽  
Barbara R. Terlouw ◽  
Megan D. Smith ◽  
Sacha J. Pidot ◽  
Timothy P. Stinear ◽  
...  
Keyword(s):  
Machine Learning ◽  
Natural Product ◽  
Global Analysis ◽  
Gene Clusters ◽  
Divergent Evolution ◽  
Acid Activation ◽  
Biosynthetic Gene ◽  
Biosynthetic Gene Clusters ◽  
Predictive Tool ◽  
Wide Range

Enzymes that cleave ATP to activate carboxylic acids play essential roles in primary and secondary metabolism in all domains of life. Class I adenylate-forming enzymes share a conserved structural fold but act on a wide range of substrates to catalyze reactions involved in bioluminescence, nonribosomal peptide biosynthesis, fatty acid activation, and β-lactone formation. Despite their metabolic importance, the substrates and functions of the vast majority of adenylate-forming enzymes are unknown without tools available to accurately predict them. Given the crucial roles of adenylate-forming enzymes in biosynthesis, this also severely limits our ability to predict natural product structures from biosynthetic gene clusters. Here we used machine learning to predict adenylate-forming enzyme function and substrate specificity from protein sequences. We built a web-based predictive tool and used it to comprehensively map the biochemical diversity of adenylate-forming enzymes across >50,000 candidate biosynthetic gene clusters in bacterial, fungal, and plant genomes. Ancestral phylogenetic reconstruction and sequence similarity networking of enzymes from these clusters suggested divergent evolution of the adenylate-forming superfamily from a core enzyme scaffold most related to contemporary CoA ligases toward more specialized functions including β-lactone synthetases. Our classifier predicted β-lactone synthetases in uncharacterized biosynthetic gene clusters conserved in >90 different strains of Nocardia. To test our prediction, we purified a candidate β-lactone synthetase from Nocardia brasiliensis and reconstituted the biosynthetic pathway in vitro to link the gene cluster to the β-lactone natural product, nocardiolactone. We anticipate that our machine learning approach will aid in functional classification of enzymes and advance natural product discovery.

scholarly journals New methods for predicting and measuring dispersion in rivers

2018 ◽  
Vol 40 ◽  
pp. 05052 ◽  
Author(s):  
Jonathan Nelson ◽  
Richard McDonald ◽  
Carl Legleiter ◽  
Paul Kinzel ◽  
Travis Terrell-Ramos ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Lagrangian Model ◽  
Predictive Tool ◽  
River Flows ◽  
3 Dimensional ◽  
Interacting Particle ◽  
Large Numbers ◽  
Wide Range ◽  
Turbulence Closures ◽  
Rhodamine Wt

To develop a better predictive tool for dispersion in rivers over a range of temporal and spatial scales, our group has developed a simple Lagrangian model that is applicable for a wide range of coordinate systems and flow modeling methodologies. The approach allows dispersion computations for a large suite of discretizations, model dimensions (1-, 2-, or 3-dimensional), spatial and temporal discretization, and turbulence closures. As the model is based on a discrete non-interacting particle approach, parallelization is straightforward, such that simulations with large numbers of particles are tractable. Results from the approach are compared to dispersion measurements made with conventional Rhodamine WT dye experiment in which typical at-a-point sensors are employed to determine concentration. The model performs well, but spatial resolution for experiments over large and or complex river flows was inadequate for model testing. To address this issue, we explored the idea of measuring spatial concentrations in river flows using hyperspectral remote sensing. Experiments both for idealized channels and real rivers show that this technique is viable and can provide high levels of spatial detail in concentration measurements with quantitatively accurate concentrations.

scholarly journals Observations of High-Frequency Activity of EV Lacertae

1995 ◽  
Vol 151 ◽  
pp. 82-84
Author(s):  
B.E. Zhilyaev ◽  
I.A. Verlyuk
Keyword(s):  
High Frequency ◽  
Sudden Onset ◽  
X Rays ◽  
Long Duration ◽  
Cataclysmic Binaries ◽  
Wide Range ◽  
Classical Models ◽  
Low Mass ◽  
Ev Lac ◽  
Short Time

The flare star EV Lac shows a wide variety of activity phenomena on a wide range of time scales. These are the well-known “classical” solar-like flares, the short-time flare events (Gershberg & Petrov 1986, Karapetian & Zalinian 1991, Tovmassian & Zalinian 1988, Tsvetkov et al. 1986, Zhilyaev 1994), and the long-duration variations caused by starspots and rotation (Petterson 1980). However, the “classical” flares are not such a frequent phenomenon as one gets used to think. As noted by Roizman & Kabitchev (1985), a considerable fraction of flares shows a complicated multipeak structure with sudden onset and decay. Their interpretation along the lines of classical models favored for solar-like flares is very problematic.Here, we report the detection of high-frequency chaotic variability (flickering) in EV Lac. Optical flickering is observed in cataclysmic binaries, and in X-rays it is observed in low-mass X-ray binaries. As a rule, flickering is an accretion phenomenon. Strange as it may seem, EV Lac as a visual binary has the analogous property.

Numerical Study of Impact Penetration Shearing Employing Finite Strain Viscoplasticity Model Incorporating Adiabatic Shear Banding

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Patrice Longère ◽  
André Dragon ◽  
Xavier Deprince
Keyword(s):  
Damage Mechanics ◽  
Numerical Study ◽  
Shear Banding ◽  
Three Dimensional ◽  
Adiabatic Shear ◽  
Deformation Model ◽  
Viscoplastic Material ◽  
Predictive Tool ◽  
Adiabatic Shear Banding ◽  
Wide Range

This work brings forward a twofold contribution relevant to the adiabatic shear banding (ASB) process as a part of dynamic plasticity of high-strength metallic materials. The first contribution is a reassessment of a three-dimensional finite deformation model starting from a specific scale postulate and devoted to cover a wide range of dissipative phenomena, including ASB-related material instabilities (strong softening prefailure stage). The model, particularly destined to deal with impacted structures was first detailed by (Longère et al. 2003, “Modelling Adiabatic Shear Banding Via Damage Mechanics Approach,” Arch. Mech., 55, pp. 3–38; 2005, “Adiabatic Shear Banding Induced Degradation in a Thermo-Elastic/Viscoplastic Material Under Dynamic Loading,” Int. J. Impact Eng., 32, pp. 285–320). The second novel contribution concerns numerical solution of a genuine ballistic penetration problem employing the above model for a target plate material. The ASB trajectories are shown to follow a multistage history and complex distribution pattern leading finally to plugging failure mechanism. The corresponding analysis and related parametric study are intended to put to the test the pertinency of the model as an advanced predictive tool for complex shock related problems.

scholarly journals Microbial diversity beyond E. coli: new microbial worlds, new concepts in biology

2011 ◽  
Vol 32 (2) ◽  
pp. 73
Author(s):  
John A Fuerst
Keyword(s):  
Escherichia Coli ◽  
Saccharomyces Cerevisiae ◽  
Influenza Virus ◽  
Microbial Diversity ◽  
Microbial Evolution ◽  
E Coli ◽  
New Concepts ◽  
Wide Range ◽  
Classical Models ◽  
The Universe

Microbial diversity explores the universe of microorganisms beyond classical models such as Escherichia coli, influenza virus, or Saccharomyces cerevisiae. Exploring such new microbial worlds is essential for a microbiology which needs to learn about all the scientific and practical possibilities offered by billions of years of microbial evolution. Here we illustrate some examples of how studying a wide range of microbial diversity can assist microbiology as a fundamental and a practical science.

scholarly journals Topological constraints in early multicellularity favor reproductive division of labor

2019 ◽  
Author(s):  
David Yanni ◽  
Shane Jacobeen ◽  
Pedro Márquez-Zacarías ◽  
Joshua S Weitz ◽  
William C. Ratcliff ◽  
...  
Keyword(s):  
Division Of Labor ◽  
Resource Sharing ◽  
Evolutionary Biology ◽  
Large Body ◽  
Concave Function ◽  
Cellular Interactions ◽  
Wide Range ◽  
Classical Models ◽  
Reproductive Division Of Labor ◽  
Reproductive Division

Reproductive division of labor (e.g., germ-soma specialization) is a hallmark of the evolution of multicellularity, signifying the emergence of a new type of individual and facilitating the evolution of increased organismal complexity. A large body of work from evolutionary biology, economics, and ecology has shown that specialization is beneficial when further division of labor produces an accelerating increase in absolute productivity (i.e., productivity is a convex function of specialization). Here we show that reproductive specialization is qualitatively different from classical models of resource sharing, and can evolve even when the benefits of specialization are saturating (i.e., productivity is a concave function of specialization). Through analytical theory and evolutionary individual based simulations, our work demonstrates that reproductive specialization is strongly favored in sparse networks of cellular interactions, such as trees and filaments, that reflect the morphology of early, simple multicellular organisms, highlighting the importance of restricted social interactions in the evolution of reproductive specialization. More broadly, we find that specialization is strongly favored, despite saturating returns on investment, in a wide range of scenarios in which sharing is asymmetric.

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