Search

In this study, we discuss critical issues in modelling the structure and function of lymph nodes (LNs), with emphasis on how LN physiology is related to its multi-scale structural organization. In addition to macroscopic domains such as B-cell follicles and the T cell zone, there are vascular networks which play a key role in the delivery of information to the inner parts of the LN, i.e., the conduit and blood microvascular networks. We propose object-oriented computational algorithms to model the 3D geometry of the fibroblastic reticular cell (FRC) network and the microvasculature. Assuming that a conduit cylinder is densely packed with collagen fibers, the computational flow study predicted that the diffusion should be a dominating process in mass transport than convective flow. The geometry models are used to analyze the lymph flow properties through the conduit network in unperturbed- and damaged states of the LN. The analysis predicts that elimination of up to 60%-90% of edges is required to stop the lymph flux. This result suggests a high degree of functional robustness of the network. [ABSTRACT FROM AUTHOR]

Copyright of Acta Carsologica is the property of Scientific Research Centre of Slovenian Academy of Sciences & Arts and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new three-reservoir model was proposed to simulate complex groundwater flow in a karst system where a short-duration pumping test was conducted. The pumping test was conducted in the Houzhai underground river basin located in Puding County, Southwest China. Three sinkholes were used as a pumping and observation well network in the pumping test. Water was pumped from one sinkhole located in the local matrix reservoir. The response of hydraulic head to the pumping was observed at the other two sinkholes located in the conduit network reservoir. Maréchal and others (Water Resour Res 44:W05401, ) used a two-reservoir model to simulate a long-duration pumping test which provided a good match between the observations and calculations. In this study, a three-reservoir model was developed to represent the local matrix, regional matrix, and conduit network. The regional matrix reservoir was treated as the boundary from which the flow system was recharged. This model can better simulate the site's hydrogeological conditions. The results show that the observed hydraulic heads agree well with the calculated heads in the conduit network [relative root mean square (rRMS) error = 3.32 %] and in the local matrix (rRMS = 8.43 %). The model also calculated the component volumes of groundwater flow, including the exchange among the three reservoirs. The extent of influence of the pumping test was also characterized in the model. Local matrix storage, recharge from the conduit network, and the recharge from the regional matrix account for about 10.46, 61.28 and 28.26 % of the groundwater pumpage, respectively. The appropriate rate and duration of pumping can be estimated using the calibrated model for the water resources management. [ABSTRACT FROM AUTHOR]

A long-duration pumping test performed in the conduit of a mixed flow karst system (MFKS) is analyzed and interpreted. It constitutes a unique experiment of catchment wide response of a karst system, with drawdowns measured both in the pumped conduit and in the matrix. A modeling approach is proposed for this interpretation. The developed double continuum model consists of two reservoirs - karst conduits and the surrounding carbonate rocks - between which flow exchange is modeled using the superposition principle and the hypothesis of Darcian flow in the matrix considered as an equivalent porous media. The karst conduits are assumed to have an infinite hydraulic conductivity. Model calibration results in a very good match (relative root mean square [rRMS] = 2.3 %) with drawdown measured at the pumping well (karst conduit). It shows that the matrix hydrodynamic parameters (hydraulic conductivity and storativity) have a greater influence on the drawdown than the storage capacity of the conduit network. The accuracy of the model relies mostly on a very good knowledge of both pumping rate and natural discharge at the spring (with and without pumping). This type of approach represents an advance in double continuum modeling of karst systems. It also provides a methodology for the management of water resources from karst aquifers. [ABSTRACT FROM AUTHOR]