scholarly journals A multiscale model of virus pandemic: Heterogeneous interactive entities in a globally connected world

2020 ◽  
Vol 30 (08) ◽  
pp. 1591-1651 ◽  
Author(s):  
Nicola Bellomo ◽  
Richard Bingham ◽  
Mark A. J. Chaplain ◽  
Giovanni Dosi ◽  
Guido Forni ◽  
...  
Keyword(s):  
Critical Analysis ◽  
Large Scale ◽  
Spatial Scales ◽  
Lattice Models ◽  
Multiscale Model ◽  
Small Scale ◽  
The Third ◽  
Research Perspectives ◽  
Complex Features ◽  
Modelling Approach

This paper is devoted to the multidisciplinary modelling of a pandemic initiated by an aggressive virus, specifically the so-called SARS–CoV–[Formula: see text] Severe Acute Respiratory Syndrome, corona virus n.[Formula: see text]. The study is developed within a multiscale framework accounting for the interaction of different spatial scales, from the small scale of the virus itself and cells, to the large scale of individuals and further up to the collective behaviour of populations. An interdisciplinary vision is developed thanks to the contributions of epidemiologists, immunologists and economists as well as those of mathematical modellers. The first part of the contents is devoted to understanding the complex features of the system and to the design of a modelling rationale. The modelling approach is treated in the second part of the paper by showing both how the virus propagates into infected individuals, successfully and not successfully recovered, and also the spatial patterns, which are subsequently studied by kinetic and lattice models. The third part reports the contribution of research in the fields of virology, epidemiology, immune competition, and economy focussed also on social behaviours. Finally, a critical analysis is proposed looking ahead to research perspectives.

Thermohaline layering on the microscale

2019 ◽  
Vol 862 ◽  
pp. 672-695 ◽  
Author(s):  
Timour Radko
Keyword(s):  
Large Scale ◽  
Numerical Models ◽  
Spatial Scales ◽  
Multiscale Model ◽  
Small Scale ◽  
Multiscale Approach ◽  
Flux Gradient ◽  
Gradient Model ◽  
Wide Range ◽  
Local Background

A theoretical model is developed which illustrates the dynamics of layering instability, frequently realized in ocean regions with active fingering convection. Thermohaline layering is driven by the interplay between large-scale stratification and primary double-diffusive instabilities operating at the microscale – temporal and spatial scales set by molecular dissipation. This interaction is described by a combination of direct numerical simulations and an asymptotic multiscale model. The multiscale theory is used to formulate explicit and dynamically consistent flux laws, which can be readily implemented in large-scale analytical and numerical models. Most previous theoretical investigations of thermohaline layering were based on the flux-gradient model, which assumes that the vertical transport of density components is uniquely determined by their local background gradients. The key deficiency of this approach is that layering instabilities predicted by the flux-gradient model have unbounded growth rates at high wavenumbers. The resulting ultraviolet catastrophe precludes the analysis of such basic properties of layering instability as its preferred wavelength or the maximal growth rate. The multiscale model, on the other hand, incorporates hyperdiffusion terms that stabilize short layering modes. Overall, the presented theory carries the triple advantage of (i) offering an explicit description of the interaction between microstructure and layering modes, (ii) taking into account the influence of non-uniform stratification on microstructure-driven mixing, and (iii) avoiding unphysical behaviour of the flux-gradient laws at small scales. While the multiscale approach to the parametrization of time-dependent small-scale processes is illustrated here on the example of fingering convection, we expect the proposed technique to be readily adaptable to a wide range of applications.

scholarly journals Enhancing ecosystem restoration efficiency through spatial and temporal coordination

2015 ◽  
Vol 112 (19) ◽  
pp. 6236-6241 ◽  
Author(s):  
Thomas M. Neeson ◽  
Michael C. Ferris ◽  
Matthew W. Diebel ◽  
Patrick J. Doran ◽  
Jesse R. O’Hanley ◽  
...  
Keyword(s):  
Great Lakes ◽  
Large Scale ◽  
Expert Knowledge ◽  
Spatial Scales ◽  
Small Scale ◽  
Space And Time ◽  
Ecosystem Connectivity ◽  
Breeding Grounds ◽  
Local Expert ◽  
Conservation Projects

In many large ecosystems, conservation projects are selected by a diverse set of actors operating independently at spatial scales ranging from local to international. Although small-scale decision making can leverage local expert knowledge, it also may be an inefficient means of achieving large-scale objectives if piecemeal efforts are poorly coordinated. Here, we assess the value of coordinating efforts in both space and time to maximize the restoration of aquatic ecosystem connectivity. Habitat fragmentation is a leading driver of declining biodiversity and ecosystem services in rivers worldwide, and we simultaneously evaluate optimal barrier removal strategies for 661 tributary rivers of the Laurentian Great Lakes, which are fragmented by at least 6,692 dams and 232,068 road crossings. We find that coordinating barrier removals across the entire basin is nine times more efficient at reconnecting fish to headwater breeding grounds than optimizing independently for each watershed. Similarly, a one-time pulse of restoration investment is up to 10 times more efficient than annual allocations totaling the same amount. Despite widespread emphasis on dams as key barriers in river networks, improving road culvert passability is also essential for efficiently restoring connectivity to the Great Lakes. Our results highlight the dramatic economic and ecological advantages of coordinating efforts in both space and time during restoration of large ecosystems.

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2018 ◽  
Author(s):  
Feng Jie Zheng ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Pressure Fluctuation ◽  
Large Scale ◽  
Three Dimensional ◽  
Industrial Process ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial process. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operation such as rapid valve opening/closing. To investigate the pressure especially the pressure fluctuation in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled by a zero-dimensional virtual point, the pipe is modeled by a one-dimensional MOC, and the valve is modeled by a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted, in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve are obtained. The results show that the proposed model is in good agreement with the full CFD model in both large-scale and small-scale spaces. Moreover, the proposed model is more computationally efficient than the CFD model, which provides a feasibility in the analysis of complex RPV system within an affordable computational time.

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Feng Jie Zheng ◽  
Chao Yong Zong ◽  
William Dempster ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Large Scale ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Dimensional System ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial processes. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operations such as rapid valve opening or closing. To investigate the pressure response, with particular interest in the pressure fluctuations in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled as a zero-dimensional virtual point, the pipe is modeled as a one-dimensional system using the MOC, and the valve is modeled using a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve is obtained. The results show that the proposed model is in good agreement when compared with a high fidelity CFD model used to represent both large-scale and small-scale spaces. As expected, the proposed model is significantly more computationally efficient than the CFD model. This demonstrates the feasibility of analyzing complex RPV systems within an affordable computational time.

scholarly journals Modeling and simulating the spatial spread of an epidemic through multiscale kinetic transport equations

2021 ◽  
pp. 1-39
Author(s):  
Walter Boscheri ◽  
Giacomo Dimarco ◽  
Lorenzo Pareschi
Keyword(s):  
Large Scale ◽  
Scaling Limit ◽  
Propagation Speed ◽  
Multiscale Model ◽  
Transport Equations ◽  
Small Scale ◽  
Spatial Spread ◽  
Model Interpretation ◽  
Mass Migration ◽  
Migration Dynamics

In this paper, we propose a novel space-dependent multiscale model for the spread of infectious diseases in a two-dimensional spatial context on realistic geographical scenarios. The model couples a system of kinetic transport equations describing a population of commuters moving on a large scale (extra-urban) with a system of diffusion equations characterizing the non-commuting population acting over a small scale (urban). The modeling approach permits to avoid unrealistic effects of traditional diffusion models in epidemiology, like infinite propagation speed on large scales and mass migration dynamics. A construction based on the transport formalism of kinetic theory allows to give a clear model interpretation to the interactions between infected and susceptible in compartmental space-dependent models. In addition, in a suitable scaling limit, our approach permits to couple the two populations through a consistent diffusion model acting at the urban scale. A discretization of the system based on finite volumes on unstructured grids, combined with an asymptotic preserving method in time, shows that the model is able to describe correctly the main features of the spatial expansion of an epidemic. An application to the initial spread of COVID-19 is finally presented.

Mycorrhizal fungal community relationship to root nitrogen concentration over a regional atmospheric nitrogen deposition gradient in the northeastern USA

2008 ◽  
Vol 38 (5) ◽  
pp. 1260-1266 ◽  
Author(s):  
Erik A. Lilleskov ◽  
Philip M. Wargo ◽  
Kristiina A. Vogt ◽  
Daniel J. Vogt
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Nitrogen Concentration ◽  
N Deposition ◽  
Small Scale ◽  
N Availability ◽  
Cenococcum Geophilum ◽  
Ectomycorrhizal Morphotypes ◽  
Deposition Gradient ◽  
Northeastern Usa

Increased nitrogen (N) input has been found to alter ectomycorrhizal fungal communities over short deposition gradients and in fertilization experiments; however, its effects over larger spatial scales have not been determined. To address this gap, we reanalyzed data from a study originally designed to examine the effects of soil aluminum/calcium (Al/Ca) ratios on the vitality of red spruce fine roots over a regional acid and N deposition gradient in the northeastern USA. We used root N as an indicator of stand N availability and examined its relationship with the abundance of ectomycorrhizal morphotypes. The dominant morphotypes changed in relative abundance as a function of stand N availability. As root N concentrations increased, Piloderma spp. - like, Cenococcum geophilum Fr., and other unidentified mycorrhizal morphotypes declined in abundance, while other smooth-mantled morphotypes increased. Root N concentration in the 1–2 mm diameter class was the best predictor of the abundance of multiple morphotypes. The morphotype responses were consistent with those found in experimental and small-scale studies, suggesting that N availability is altering ectomycorrhizal communities over broad spatial scales in this region. This finding provides an impetus to conduct a more detailed characterization of mycorrhizal community responses to N deposition across large-scale gradients.

The power distribution between the symmetric and anti-symmetric components of the tropical wavenumber-frequency spectrum

2021 ◽  
Author(s):  
Ofer Shamir ◽  
Chen Schwartz ◽  
Chaim Garfinkel ◽  
Nathan Paldor
Keyword(s):  
Frequency Spectrum ◽  
Power Distribution ◽  
Large Scale ◽  
Spectral Power ◽  
Spatial Scales ◽  
Turbulent Energy ◽  
Heat Fluxes ◽  
Small Scale ◽  
Ample Evidence ◽  
Parity Distribution

<p>A yet unexplained feature of the tropical wavenumber-frequency spectrum is its parity distributions, i.e., the distribution of power between the meridionally symmetric and anti-symmetric components of the spectrum. Due to the linearity of the decomposition to symmetric and anti-symmetric components and the Fourier analysis, the total spectral power equals the sum of the power contained in each of these two components. However, the spectral power need not be evenly distributed between the two components. Satellite observations and reanalysis data provide ample evidence that the parity distribution of the tropical wavenumber-frequency spectrum is biased towards its symmetric component. Using an intermediate-complexity model of an idealized moist atmosphere, we find that the parity distribution of the tropical spectrum is nearly insensitive to large-scale forcing, including topography, ocean heat fluxes, and land-sea contrast. On the other hand, by adding a small-scale (stochastic) forcing, we find that the parity distribution of the tropical spectrum is sensitive to asymmetries on small spatial scales compared to the observed large-scale spectrum. Physically, such forcing can be thought of as small-scale convection, which is believed to trigger some of the Tropics' large-scale features via an upscale (inverse) turbulent energy cascade. These results are qualitatively explained by considering the effects of triad interactions on the parity distribution. According to the proposed mechanism, any small-scale asymmetry (symmetric or anti-symmetric) in the forcing leads to symmetric bias in the spectrum, regardless of the source of variability providing the forcing.</p>

scholarly journals Balanced reconnection intervals: four case studies

2008 ◽  
Vol 26 (12) ◽  
pp. 3897-3912 ◽  
Author(s):  
A. D. DeJong ◽  
A. J. Ridley ◽  
C. R. Clauer
Keyword(s):  
Case Studies ◽  
Large Scale ◽  
The Other ◽  
Small Scale ◽  
Polar Cap ◽  
Reconnection Rate ◽  
Magnetospheric Convection ◽  
The Third ◽  
New Name ◽  
Definition Of

Abstract. During steady magnetospheric convection (SMC) events the magnetosphere is active, yet there are no data signatures of a large scale reconfiguration, such as a substorm. While this definition has been used for years it fails to elucidate the true physics that is occurring within the magnetosphere, which is that the dayside merging rate and the nightside reconnection rate balance. Thus, it is suggested that these events be renamed Balanced Reconnection Intervals (BRIs). This paper investigates four diverse BRI events that support the idea that new name for these events is needed. The 3–4 February 1998 event falls well into the classic definition of an SMC set forth by Sergeev et al. (1996), while the other challenge some previous notions about SMCs. The 15 February 1998 event fails to end with a substorm expansion and concludes as the magnetospheric activity slowly quiets. The third event, 22–23 December 2000, begins with a slow build up of magnetospheric activity, thus there is no initiating substorm expansion. The last event, 17 February 1998, is more active (larger AE, AL and cross polar cap potential) than previously studied SMCs. It also has more small scale activity than the other events studied here.

Enhanced dissipation for quasi-geostrophic motion over small-scale topography

2000 ◽  
Vol 407 ◽  
pp. 105-122 ◽  
Author(s):  
JACQUES VANNESTE
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Additional Term ◽  
Equation Of Motion ◽  
Small Scale ◽  
Two Dimensional ◽  
Turbulent Dissipation ◽  
Dissipative Term ◽  
History Of ◽  
Large Scale Flow

The effect of a small-scale topography on large-scale, small-amplitude oceanic motion is analysed using a two-dimensional quasi-geostrophic model that includes free-surface and β effects, Ekman friction and viscous (or turbulent) dissipation. The topography is two-dimensional and periodic; its slope is assumed to be much larger than the ratio of the ocean depth to the Earth's radius. An averaged equation of motion is derived for flows with spatial scales that are much larger than the scale of the topography and either (i) much larger than or (ii) comparable to the radius of deformation. Compared to the standard quasi-geostrophic equation, this averaged equation contains an additional dissipative term that results from the interaction between topography and dissipation. In case (i) this term simply represents an additional Ekman friction, whereas in case (ii) it is given by an integral over the history of the large-scale flow. The properties of the additional term are studied in detail. For case (i) in particular, numerical calculations are employed to analyse the dependence of the additional Ekman friction on the structure of the topography and on the strength of the original dissipation mechanisms.

scholarly journals Hydrologic-environmental effects of sponge city under different spatial scales

2019 ◽  
Vol 10 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Jiake Li ◽  
Cong Mu ◽  
Chenning Deng ◽  
Menghua Ma
Keyword(s):  
Environmental Effects ◽  
Large Scale ◽  
Peak Flow ◽  
Spatial Scales ◽  
Small Scale ◽  
Pollution Load ◽  
Sponge City ◽  
Medium Scale ◽  
Total Runoff ◽  
Runoff Reduction

Abstract The storm water management models were established at three spatial scales (large, medium, and small) based on a sponge city pilot area in China to explore the hydrological and environmental effects of rainfall conditions and development modes. Results showed the following. (1) Total runoff reduction rates increased from 26.7% to 53.9% for the rainfall event of a 2-year recurrence period as the scale increased. For 5-year and above recurrence periods, total runoff reduction rates were 19.5–49.4%. These rates increased from the small to medium scale and slightly decreased from the medium to large scale. (2) The runoff coefficients were 0.87–0.29, which decreased from the small to medium scale and were basically constant from the medium to large scale. (3) The peak flow reduction rates decreased with increased recurrence periods. The rates increased initially and then decreased at the small scale, whereas the opposite trend occurred at the medium scale. (4) The reduction rates of pollutants were negatively correlated with recurrence periods under the three spatial scales. The pollution load reduction rates were 19.5–54.7%, which increased from the small to medium scale and were basically constant from the medium to large scale.

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