scholarly journals Mechanistic modelling of COVID-19 and the impact of lockdowns on a short-time scale

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258084
Author(s):  
Danish A. Ahmed ◽  
Ali R. Ansari ◽  
Mudassar Imran ◽  
Kamal Dingle ◽  
Michael B. Bonsall
Keyword(s):  
Time Scale ◽  
Population Distribution ◽  
Contact Process ◽  
Time Lag ◽  
Service Industries ◽  
Spatial Proximity ◽  
Short Time Scale ◽  
Susceptible Host ◽  
Short Time ◽  
The Impact

Background To mitigate the spread of the COVID-19 coronavirus, some countries have adopted more stringent non-pharmaceutical interventions in contrast to those widely used. In addition to standard practices such as enforcing curfews, social distancing, and closure of non-essential service industries, other non-conventional policies also have been implemented, such as the total lockdown of fragmented regions, which are composed of sparsely and highly populated areas. Methods In this paper, we model the movement of a host population using a mechanistic approach based on random walks, which are either diffusive or super-diffusive. Infections are realised through a contact process, whereby a susceptible host is infected if in close spatial proximity of the infectious host with an assigned transmission probability. Our focus is on a short-time scale (∼ 3 days), which is the average time lag time before an infected individual becomes infectious. Results We find that the level of infection remains approximately constant with an increase in population diffusion, and also in the case of faster population dispersal (super-diffusion). Moreover, we demonstrate how the efficacy of imposing a lockdown depends heavily on how susceptible and infectious individuals are distributed over space. Conclusion Our results indicate that on a short-time scale, the type of movement behaviour does not play an important role in rising infection levels. Also, lock-down restrictions are ineffective if the population distribution is homogeneous. However, in the case of a heterogeneous population, lockdowns are effective if a large proportion of infectious carriers are distributed in sparsely populated sub-regions.

scholarly journals Mechanistic modelling of coronavirus infections and the impact of confined neighbourhoods on a short time scale

2020 ◽  
Author(s):  
Danish A Ahmed ◽  
Ali R Ansari ◽  
Mudassar Imran ◽  
Kamaludin Dingle ◽  
Naveed Ahmed ◽  
...  
Keyword(s):  
Time Scale ◽  
Contact Process ◽  
Service Industries ◽  
Spatial Proximity ◽  
Infectious Period ◽  
Short Time Scale ◽  
Residential Areas ◽  
Susceptible Host ◽  
Short Time ◽  
The Impact

Background: To mitigate the spread of the COVID-19 coronavirus, some countries have adopted more stringent non-pharmaceutical interventions in contrast to those widely used (for e.g. the state of Kuwait). In addition to standard practices such as enforcing curfews, social distancing, and closure of non-essential service industries, other non-conventional policies such as the total confinement of highly populated areas has also been implemented. Methods: In this paper, we model the movement of a host population using a mechanistic approach based on random walks, which are either diffusive or super-diffusive. Infections are realised through a contact process, whereby a susceptible host may be infected if in close spatial proximity of the infectious host. Our focus is only on the short-time scale prior to the infectious period, so that no further transmission is assumed. Results: We find that the level of infection depends heavily on the population dynamics, and increases in the case of slow population diffusion, but remains stable for a high or super-diffusive population. Also, we find that the confinement of homogeneous or overcrowded sub-populations has minimal impact in the short term. Conclusions: Our results indicate that on a short time scale, confinement restrictions or complete lock down of whole residential areas may not be effective. Finally, we discuss the possible implications of our findings for total confinement in the context of the current situation in Kuwait.

scholarly journals Mechanistic Modelling of Coronavirus Infections and the Impact of Confined Neighbourhoods on a Short Time Scale

2020 ◽  
Author(s):  
Danish Ali Ahmed ◽  
Ali Ansari ◽  
Mudassar Imran ◽  
Kamal Dingle ◽  
Naveed Ahmed ◽  
...  
Keyword(s):  
Time Scale ◽  
Contact Process ◽  
Service Industries ◽  
Spatial Proximity ◽  
Infectious Period ◽  
Short Time Scale ◽  
Residential Areas ◽  
Susceptible Host ◽  
Short Time ◽  
The Impact

Abstract Background: To mitigate the spread of the COVID-19 coronavirus, some countries have adopted more stringent non-pharmaceutical interventions in contrast to those widely used (for e.g. the state of Kuwait). In addition to standard practices such as enforcing curfews, social distancing, and closure of non-essential service industries, other non-conventional policies such as the total confinement of highly populated areas has also been implemented. Methods: In this paper, we model the movement of a host population using a mechanistic approach based on random walks, which are either diffusive or super-diffusive. Infections are realised through a contact process, whereby a susceptible host may be infected if in close spatial proximity of the infectious host. Our focus is only on the short-time scale prior to the infectious period, so that no further transmission is assumed. Results: We find that the level of infection depends heavily on the population dynamics, and increases in the case of slow population diffusion, but remains stable for a high or super-diffusive population. Also, we find that the confinement of homogeneous or overcrowded sub-populations has minimal impact in the short term. Conclusions: Our results indicate that on a short time scale, confinement restrictions or complete lock down of whole residential areas may not be effective. Finally, we discuss the possible implications of our findings for total confinement in the context of the current situation in Kuwait.

scholarly journals Mechanistic modelling of coronavirus infections and the impact of confined neighbourhoods on a short time scale

2020 ◽  
Author(s):  
Danish Ali Ahmed ◽  
Ali Ansari ◽  
Mudassar Imran ◽  
Kamal Dingle ◽  
Naveed Ahmed ◽  
...  
Keyword(s):  
Time Scale ◽  
Contact Process ◽  
Service Industries ◽  
Spatial Proximity ◽  
Infectious Period ◽  
Short Time Scale ◽  
Residential Areas ◽  
Susceptible Host ◽  
Short Time ◽  
The Impact

Abstract Background: To mitigate the spread of the COVID-19 coronavirus, some countries have adopted more stringent non-pharmaceutical interventions in contrast to those widely used (for e.g. the state of Kuwait). In addition to standard practices such as enforcing curfews, social distancing, and closure of non-essential service industries, other non-conventional policies such as the total confinement of highly populated areas has also been implemented.Methods: In this paper, we model the movement of a host population using a mechanistic approach based on random walks, which are either diffusive or super-diffusive. Infections are realised through a contact process, whereby a susceptible host may be infected if in close spatial proximity of the infectious host. Our focus is only on the short-time scale prior to the infectious period, so that no further transmission is assumed.Results: We find that the level of infection depends heavily on the population dynamics, and increases in the case of slow population diffusion, but remains stable for a high or superdiffusive population. Also, we find that the confinement of homogeneous or overcrowded sub-populations has minimal impact in the short term.Conclusion: Our results indicate that on a short time scale, confinement restrictions or complete lock down of whole residential areas may not be effective. Finally, we discuss the possible implications of our findings for total confinement in the context of the current situation in Kuwait.

scholarly journals Mechanistic Modelling of Coronavirus Infections and the Impact of Confined Neighbourhoods on a Short Time Scale

2020 ◽  
Author(s):  
Danish Ahmed ◽  
Ali Ansari ◽  
Mudassar Imran ◽  
Kamaludin Dingle ◽  
Naveed Ahmed ◽  
...  
Keyword(s):  
Time Scale ◽  
Contact Process ◽  
Service Industries ◽  
Spatial Proximity ◽  
Infectious Period ◽  
Short Time Scale ◽  
Susceptible Host ◽  
The State Of Kuwait ◽  
Short Time ◽  
The Impact

To mitigate the spread of the COVID-19 coronavirus, some countries have enforced more stringent non-pharmaceutical interventions in contrast to those widely adopted (for e.g. the state of Kuwait). In addition to standard practices such as enforcing curfews, social distancing, and closure of non-essential service industries, other non-conventional policies such as the total confinement of highly populated areas has also been implemented. In this paper, we model the movement of a host population using a mechanistic approach based on random walks, which are either diffusive or super-diffusive. Infections are realised through a contact process, whereby a susceptible host may be infected if in close spatial proximity of the infectious host. Our focus is only on the short-time scale prior to the infectious period, so that no further transmission is assumed. We find that the level of infection depends heavily on the population dynamics, and increases in the case of slow population diffusion, but remains stable for a high or super-diffusive population. Also, we find that the confinement of homogeneous or overcrowded sub-populations has minimal impact in the short term. Finally, we discuss the possible implications of our findings for total confinement in the context of the current situation in Kuwait.

scholarly journals Phages associated with horses provide new insights into the dominance of lateral gene transfer in virulent bacteriophages evolution in natural systems

2019 ◽  
Author(s):  
V.V. Babenko ◽  
A.K. Golomidova ◽  
P.A. Ivanov ◽  
M.A. Letarova ◽  
E.E. Kulikov ◽  
...  
Keyword(s):  
Time Scale ◽  
Natural Habitat ◽  
Local Population ◽  
Point Mutations ◽  
Major Effect ◽  
Model Systems ◽  
Laboratory Model ◽  
Short Time Scale ◽  
Short Time ◽  
The Impact

AbstractTailed bacteriophages (Caudovirales order) are omnipresent on our planet. Their impressive ecological and evolutionary success largely relies on the bacteriophage potential to adapt to great variety of the environmental conditions found in the Biosphere. It is believed that the adaptation of bacteriophages, including short time scale adaptation, is achieved almost exclusively via the (micro)evolution processes. In order to analyze the major mechanisms driving adaptation of phage genomes in a natural habitat we used comparative genomics of G7C-like coliphage isolates obtained during 7 years period from the feces of the horses belonging to a local population. The data suggest that even at this relatively short time scale the impact of various recombination events overwhelms the impact of the accumulation of point mutations. The access to the large pool of the genes of a complex microbial and viral community of the animal gut had major effect on the evolutionary trajectories of these phages. Thus the “real world” bacteriophage evolution mechanisms may differ significantly from those observed in the simplified laboratory model systems.

Short-Time-Scale Thermal Mapping of Microdevices Using a Scanning Thermoreflectance Technique

1998 ◽  
Vol 120 (2) ◽  
pp. 306-313 ◽  
Author(s):  
Y. S. Ju ◽  
K. E. Goodson
Keyword(s):  
Temperature Distribution ◽  
Time Scale ◽  
Silicon On Insulator ◽  
Temperature Fields ◽  
Scanning Laser ◽  
Transient Temperature ◽  
Drift Region ◽  
Short Time Scale ◽  
Short Time ◽  
The Impact

The performance and reliability of microdevices can be strongly influenced by the peak temperature rise and spatial temperature distribution during brief electrical overstress (EOS) phenomena, which can occur at sub-microsecond time scales. The present study investigates short-time-scale laser reflectance thermometry of micro devices by examining the impact of passivation overlayers on the thermoreflectance signal and by demonstrating a calibration method suitable for metallization. This manuscript also describes a scanning laser thermometry facility that captures temperature fields in microdevices with 10 ns temporal resolution and 1 μm spatial resolution. The facility combines scanning laser optics with electrical stressing capability to allow simultaneous interrogation of the thermal and electrical behavior of devices. Data show the transient temperature distribution along the drift region of silicon-on-insulator (SOI) power transistors and along metal interconnects subjected to brief electrical stresses. The theory and experimental capability developed in this study are useful for studying short-time-scale thermal phenomena in microdevices and verifying models employed for their simulation.

Anomalous Diffusion in Short-Pulse Laser Interactions With Random Media

1996 ◽  
Vol 118 (3) ◽  
pp. 781-786 ◽  
Author(s):  
M. C. Hipwell ◽  
C.-L. Tien
Keyword(s):  
Time Scales ◽  
Anomalous Diffusion ◽  
Time Scale ◽  
Random Media ◽  
Energy Transport ◽  
Short Pulse ◽  
Homogeneous Medium ◽  
Short Time Scale ◽  
Short Time ◽  
The Impact

This work applies fractal percolation theory to examine the impact of anomalous diffusion in short time-scale applications of random media. It is shown that there exist three regimes of heat transport corresponding to transport over the basic percolation unit (particle), the fractal cluster, and the homogeneous medium. Scaling is performed to determine the characteristic time scales of anomalous diffusion. The dependence of these time scales on both material properties and structure is examined to assess the impact of the anomalous diffusion regime on short time-scale energy transport. Additional criteria that determine the importance of anomalous diffusion relative to other transport phenomena and properties, such as radiation and thermal boundary resistance, are established.

An Alternative Test Using Algal Cultures for Testing Chemicals for Toxicity

1993 ◽  
Vol 21 (2) ◽  
pp. 196-201
Author(s):  
Søren Achim Nielsen ◽  
Thomas Hougaard
Keyword(s):  
Size Distribution ◽  
Mitotic Activity ◽  
Time Scale ◽  
Test System ◽  
Short Time Scale ◽  
Toxic Substances ◽  
Alternative Test ◽  
Short Time ◽  
Algal Cultures ◽  
Test Cultures

An alternative test is presented, in which algal cultures are used for testing toxic substances. This test system is based on variations in the size distribution of cells in test cultures as a measurement of growth. Thus, inhibition of mitotic activity is used as a measurement for toxic effects. The test can be performed on a short time-scale and is very sensitive to even weak toxic doses.

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