Tissue geometry is an important influence on the evolution of many biological tissues. The local curvature of an evolving tissue induces tissue crowding or spreading, which leads to differential tissue growth rates, and to changes in cellular tension, which can influence cell behaviour. Here, we investigate how directed cell motion interacts with curvature control in evolving biological tissues. Directed cell motion is involved in the generation of angled tissue growth and anisotropic tissue material properties, such as tissue fibre orientation. We develop a new cell-based mathematical model of tissue growth that includes both curvature control and cell guidance mechanisms to investigate their interplay. The model is based on conservation principles applied to the density of tissue synthesising cells at or near the tissue's moving boundary. The resulting mathematical model is a partial differential equation for cell density on a moving boundary, which is solved numerically using a hybrid front-tracking method called the cell-based particle method. The inclusion of directed cell motion allows us to model new types of biological growth, where tangential cell motion is important for the evolution of the interface, or for the generation of anisotropic tissue properties. We illustrate such situations by applying the model to simulate both the resorption and infilling components of the bone remodelling process, and to simulate root hair growth. We also provide user-friendly MATLAB code to implement the algorithms.
Tissue geometry is an important influence on the evolution of many biological tissues. The local curvature of an evolving tissue induces tissue crowding or spreading, which leads to differential tissue growth rates, and to changes in cellular tension, which can influence cell behaviour. Here, we investigate how directed cell motion interacts with curvature control in evolving biological tissues. Directed cell motion is involved in the generation of angled tissue growth and anisotropic tissue material properties, such as tissue fibre orientation. We develop a new cell-based mathematical model of tissue growth that includes both curvature control and cell guidance mechanisms to investigate their interplay. The model is based on conservation principles applied to the density of tissue synthesising cells at or near the tissue's moving boundary. The resulting mathematical model is a partial differential equation for cell density on a moving boundary, which is solved numerically using a hybrid front-tracking method called the cell-based particle method. The inclusion of directed cell motion allows us to model new types of biological growth, where tangential cell motion is important for the evolution of the interface, or for the generation of anisotropic tissue properties. We illustrate such situations by applying the model to simulate both the resorption and infilling components of the bone remodelling process, and provide user-friendly MATLAB code to implement the algorithms.
Many endangered species exist in only a single population, and almost all species that go extinct will do so from their last remaining population. Understanding how to best conserve these single population threatened species (SPTS) is therefore a distinct and important task for threatened species conservation science. As a last resort, managers of SPTS may consider taking the entire population into captivity – ex situ, in toto conservation. In the past, this choice has been taken to the great benefit of the SPTS, but it has also lead to catastrophe. Here, we develop a decision-support tool for planning when to trigger this difficult action. Our method considers the uncertain and ongoing decline of the SPTS, the possibility that drastic ex situ action will fail, and the opportunities offered by delaying the decision. Specifically, these benefits are additional time for ongoing in situ actions to succeed, and opportunities for the managers to learn about the system. To illustrate its utility, we apply the decision tool to four retrospective case-studies of declining SPTS. As well as offering support to this particular decision, our tool illustrates why trigger points for difficult conservation decisions should be formulated in advance, but must also be adaptive. A trigger-point for the ex situ, in toto conservation of a SPTS, for example, will not take the form of a simple threshold abundance.
No abstract
Block cave mining is a mining method aimed at achieving a high tonnage output from a single production level. Interactions between production loaders and consequent cycle delays can constrain overall production level performance. Together with access restrictions associated with the control of caving progression and secondary break requirements, these constraints can prevent block cave mines from reaching throughput targets. Careful layout design and development of operating strategies for the production level are critical for minimising equipment interactions and building an optimised block cave operation. In striving for a net zero emissions mining operation, many companies are actively investigating the option of electrification of their mining fleet. This adds another dimension to design considerations and creates new possibilities for block cave designs and operating strategies. The potential impacts for charging of battery electric vehicles requires consideration and ventilation limits on the practical number of production loaders are reduced, giving rise to different design solutions.This paper explores the capability of a number of alternative production level operating strategies for the Carrapateena mine, which is an OZ Minerals owned, South Australian copper-gold mine, ramping up to a rate of 12 Mtpa from 2029 utilising the block cave mining method. A comparison of the performance characteristics for each alternative is assessed using a detailed simulation model of the block cave operations. Relationships between fleet size and production level throughput are developed for each alternative operational strategy to demonstrate relative performance over a target throughput range for the mine. The assessment demonstrates how alternative operating strategies can be used to alleviate production level bottlenecks and improve output for block cave mining operations. Outcomes from the case study are broadly applicable to other block cave operations, particularly those that will move to, or are being designed as an electric mining operation.
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