Spatial heterogeneity of a host population of mobile agents has been shown to be a crucial determinant of many aspects of disease dynamics, ranging from the proliferation of diseases to their ...persistence and to vaccination strategies. In addition, the importance of regional and structural differences grows in our modern world. Little is known, though, about the consequences when traits of a disease vary regionally. In this paper, we study the effect of a spatially varying per capita infection rate on the behaviour of livestock diseases. We show that the prevalence of an infectious livestock disease in a community of animals can paradoxically decrease owing to transport connections to other communities in which the risk of infection is higher. We study the consequences for the design of livestock transportation restriction measures and establish exact criteria to discriminate those connections that increase the level of infection in the community from those that decrease it.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
The location and nature of the percolation transition in random networks is a subject of intense interest. Recently, a series of graph evolution processes have been introduced that lead to ...discontinuous percolation transitions where the addition of a single edge causes the size of the largest component to exhibit a significant macroscopic jump in the thermodynamic limit. These processes can have additional exotic behaviors, such as displaying a "Devil's staircase" of discrete jumps in the supercritical regime. Here we investigate whether the location of the largest jump coincides with the percolation threshold for a range of processes, such as Erdős-Rényipercolation, percolation via edge competition and via growth by overtaking. We find that the largest jump asymptotically occurs at the percolation transition for Erdős-Rényiand other processes exhibiting global continuity, including models exhibiting an "explosive" transition. However, for percolation processes exhibiting genuine discontinuities, the behavior is substantially richer. In percolation models where the order parameter exhibits a staircase, the largest discontinuity generically does not coincide with the percolation transition. For the generalized Bohman-Frieze-Wormald model, it depends on the model parameter. Distinct parameter regimes well in the supercritical regime feature unstable discontinuous transitions-a novel and unexpected phenomenon in percolation. We thus demonstrate that seemingly and genuinely discontinuous percolation transitions can involve a rich behavior in supercriticality, a regime that has been largely ignored in percolation.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Connectivity, or the lack thereof, is crucial for the function of many man-made systems, from financial and economic networks over epidemic spreading in social networks to technical infrastructure. ...Often, connections are deliberately established or removed to induce, maintain, or destroy global connectivity. Thus, there has been a great interest in understanding how to control percolation, the transition to large-scale connectivity. Previous work, however, studied control strategies assuming unlimited resources. Here, we depart from this unrealistic assumption and consider the effect of limited resources on the effectiveness of control. We show that, even for scarce resources, percolation can be controlled with an efficient intervention strategy. We derive such an efficient strategy and study its implications, revealing a discontinuous transition as an unintended side effect of optimal control.
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Taxi services are an integral part of urban transport and are a major contributor to air pollution and traffic congestion, which adversely affect human life and health. Sharing taxi rides is one way ...to reduce the unfavorable effects of cab services on cities. However, this comes at the expense of passenger discomfort, quantified in terms of longer travel times. Taxi ridesharing is a sophisticated mode of urban transport that combines individual trip requests with similar spatiotemporal characteristics into a shared ride. We propose a one-to-one sharing strategy that pairs trips with similar starting and ending points. We examine the method using an open dataset with trip information on over 165 million taxi rides. We show that the cumulative journey time can be reduced by 48 percent while maintaining a relatively low level of passenger inconvenience, with a total average delay compared to an individual mobility case of 6 minutes and 42 seconds. This advantage is accompanied by decreases in emissions of 20.129 tons on an ordinary day and a potential fare reduction of 49 percent, which could point to a widespread passenger acceptance of shared taxi services. Overall, a matching rate of 13 percent is reached while a 27 percent matching rate is attained for high-demand areas. Compared to many-to-many sharing dynamic routing methodologies, our scheme is easier to implement and operate, making fewer assumptions about data availability and customer acceptance.
Protected specimen brushing (PSB), combined with quantitative culture, is now recognized as one of the reference methods for diagnosis of nosocomial pneumonia. However, no criteria exist with which ...to assess the quality of the PSB sample. We studied numbers of inflammatory cells and bronchial cells per microscopic field (magnification: x500, objective x50) in cytospin preparations of PSB samples. Results of cell count and quantitative culture in a first study period were compared with those in a second study period, following adaptation of the PSB technique and collection of samples from more peripheral sites. The cellular content of samples from patients and controls was investigated. We examined 86 samples from patients with suspected nosocomial pneumonia and 15 samples from uninfected controls. The number of samples with a high cellular content was considerably greater in the second study period. No positive cultures were obtained from samples containing < 10 cells per field. The numbers of cells in samples from uninfected controls were comparable to the numbers in samples from patients. Our results indicate that absence of cells probably represents inadequate sampling. Negative PSB cultures with cytospin preparations containing < 10 cells per microscopic field should therefore be considered with caution, and resampling considered.
Microorganisms, particularly parasites, have developed sophisticated swimming mechanisms to cope with a varied range of environments. African Trypanosomes, causative agents of fatal illness in humans ...and animals, use an insect vector (the Tsetse fly) to infect mammals, involving many developmental changes in which cell motility is of prime importance. Our studies reveal that differences in cell body shape are correlated with a diverse range of cell behaviors contributing to the directional motion of the cell. Straighter cells swim more directionally while cells that exhibit little net displacement appear to be more bent. Initiation of cell division, beginning with the emergence of a second flagellum at the base, correlates to directional persistence. Cell trajectory and rapid body fluctuation correlation analysis uncovers two characteristic relaxation times: a short relaxation time due to strong body distortions in the range of 20 to 80 ms and a longer time associated with the persistence in average swimming direction in the order of 15 seconds. Different motility modes, possibly resulting from varying body stiffness, could be of consequence for host invasion during distinct infective stages.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Evolution occurs in populations of reproducing individuals. Reproduction depends on the payoff a strategy receives. The payoff depends on the environment that may change over time, on intrinsic ...uncertainties, and on other sources of randomness. These temporal variations in the payoffs can affect which traits evolve. Understanding evolutionary game dynamics that are affected by varying payoffs remains difficult. Here we study the impact of arbitrary amplitudes and covariances of temporally varying payoffs on the dynamics. The evolutionary dynamics may be "unfair", meaning that, on average, two coexisting strategies may persistently receive different payoffs. This mechanism can induce an anomalous coexistence of cooperators and defectors in the Prisoner's Dilemma, and an unexpected selection reversal in the Hawk-Dove game.
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