A model based on a high-resolution flux matrix explains the spread of diseases in a spatial network and the effect of mitigation strategies

Propagation of an epidemic across a spatial network of communities is described by a variant of the SIR model accompanied by an intercommunity infectivity matrix. This matrix is estimated from fluxes between communities, obtained from cell-phone tracking data recorded in the USA between March 2020 and February 2021. We have applied this model to the 2020 dynamics of the SARS-CoV-2 pandemic. We find that the numbers of susceptible and infected individuals predicted by the model agree with the reported cases in each community by fitting just one global parameter representing the frequency of interaction between individuals. The effect of "shelter-in-place" policies introduced across the USA at the onset of the pandemic is clearly seen in our results. We then consider the effect that alternative policies would have had, namely restricting long-range travel. We find that this policy is successful in decreasing the epidemic size and slowing down the spread, at the expense of a substantial restriction on mobility as a function of distance. When long-distance mobility is suppressed, this policy results in a traveling wave of infections, which we characterize analytically. In particular, we show the dependence of the wave velocity and profile on the transmission parameters. Finally, we discuss a policy of selectively constraining travel based on an edge-betweenness criterion.

Spatiotemporal Evolution and Spatial Network Analysis of the Urban Ecological Carrying Capacity in the Yellow River Basin

Based on the panel data of 82 cities in the Yellow River Basin (YRB) during 2008–2017, this paper calculated the urban ecological carrying capacity (UECC) index by means of the entropy method, drew a spatiotemporal evolution map using ArcGIS10.3 software, used a spatial cold–hot spot model to explore the spatial characteristics of the UECC index, and used the revised gravity model to construct the spatial network of the UECC. In addition, through social network analysis, we obtained the spatial network correlation characteristics of the UECC of 82 cities in the YRB. The study found the following: (1) The UECC index of the cities in the YRB increased steadily, and showed strong non-stationarity in space. The cold and hot spot patterns both changed greatly. Overall, the changes of the hot and cold spots were very significant. (2) The spatial correlation and linkage effects of the UECC in the YRB were not significant. The central cities with higher point centrality and closeness centrality showed the same spatial distribution, and most of them are located in the midstream and downstream of the YRB. The central cities in the midstream and downstream of the YRB had high betweenness centrality, and stood in the center of the association network. (3) The four plates in the spatial correlation network of the UECC in the YRB all showed their advantages and functions. The first plate was the net spillover plate, which was principally allocated in the upstream and midstream of the YRB. The second plate was the broker plate, which was principally located in the midstream and downstream of the YRB, and a few cities in the upper reaches. The third plate was the net inflow plate, which was distributed sporadically in the upstream and downstream of the YRB. The fourth plate was the broker plate, which was scattered in upstream, midstream, and downstream of the YRB. Therefore, it is necessary to shorten the gap of and promote the improvement of the UECC in the YRB.

Research on the Influence of Sodium Ion on Mechanism of Polymer Solution Viscosity Loss

The researches on the influence of sodium ion on mechanism of polymer solution viscosity loss were conducted. Scanning electron microscopy was used to analyze the polymer microstructure. Molecular dynamics simulation was employed to reveal the influence of sodium ion on the polymer molecular configuration. The results shown: the polymer viscosity loss was more than 70% when the concentration of sodium ion was above 4000 mg/L. The results of microstructure and molecular conformation analysis indicated that the main reason of viscosity loss was the electrostatic attraction between sodium ion and negatively charged groups of polymer molecule chains, which cause compression of polymer molecular chain. The coil and shrinkage of polymer molecular chain led to the breakage of the spatial network structure of macromolecules.

Unraveling the spatiotemporal spread of COVID-19 in Brazil through spatial network connectivity

Background: Describing and understanding the process of diffusion can allow local managers better plan emergence scenarios. Thus, the main aim of this study was to describe and unveil the spatiotemporal patterns of diffusion of the COVID-19 in Brazil from February 2020 until April 2021. Methods: This is a retrospective purely observational ecologic study including all notified cases and deaths. We used satellite-derived night light imagery and spatiotemporal Empirical Orthogonal Function analysis to quantify the spatial network structure of lighted development and the spatiotemporal transmission of the pathogen through the network. Results: The more populous state capitals within the largest network components presented higher frequency of deaths and earlier onset compared to the increasing numbers of smaller, less populous municipalities trending toward lower frequency of deaths and later onset. By week 48 2020, the full network was almost completely affected. Cases and deaths showed a distinct second wave of wider geographic expansion beginning in early November 2020. Conclusions: The spatiotemporal diffusion in Brazil was characterized by an intertwined process of overseas relocation, hierarchical network transmission and contagious effects. A rapid response as the immediate control of all ports, airports and borders combined with mandatory quarantine are critical to retard disease diffusion.

Bazaar in the 'Burbs: Infilling fine grain of activity in the course grain context of Paraparaumu

<p>The regional townships of New Zealand are losing young people. The township of Paraparaumu, located along the Kapiti Coast, is no exception. As a sprawling, low-density suburban settlement with its town center being Coastlands Shopping Center - the local mall - there are few job opportunities available. As a result, many early career adults choose to settle elsewhere. Tasked with creating more opportunities, the Kapiti Coast District Council plans to build a new commercial district. To make space for it, this will be done by paving over a large expanse of wetland adjacent to the mall. The premise of this thesis is that generating opportunities do not have to be large scale. In more dense urban areas where space is limited, many productive activities occur within the fine grain of a city. Wetlands are also recognized as a critical natural infrastructure and a valuable social amenity. Thus, instead of building large commercial facilities that have to occupy the wetland, the design in this thesis proposes a facility made up of a finer grain and infills the glut of car park spaces in front of Coastlands Mall. The parking spaces displaced will be relocated into a parking tower adjacent to the site. The building type of the Bazaar was looked at in this thesis as a model, for it is fine-grained and also ingrained with its urban context. The spatial network of the Bazaar democratizes access. The spatial network of the Bazaar democratizes access, which is a direct contrast to the singular and hierarchical nature of the mall. The design adopts these ideas and expresses them through a network of modules on a tartan grid plan transforming the design into a rhythmic series of spaces that express compression and expansion, allowing it to be an interlinked network of interior and exterior spaces. The grid is a powerful tool for organizing expanses of space though it is only useful in an architectural sense when accompanied by a fine-grained variation. Though the repetitive grid is suitable in plan, as a 3d form it quickly dissolves into monotony when repeated across a field. Similarly, the site itself is inherently charged with spatial hierarchy. Thus, localized adjustments of the roof and exterior details were made to break the monotony and rest the spatial hierarchy. This thesis explores how fine grain activity can be integrated into a large-grained context through the use of an additive, modular network set on a grid. Though the research findings produced on expression of this in the design outcome, the idea of a dense, fine-grained modular network is applicable in any context that has large inactive open space to be filled.</p>