A general cell-fluid Navier-Stokes model with inclusion of chemotaxis
MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES
Authors: Qiao, Yangyang; Evje, Steinar
Abstract
The main purpose of this work is to explore a general cell-fluid model which is based on a mixture theory formulation that accounts for the interplay between oxytactically (chemotaxis toward gradient in oxygen) moving bacteria cells in water and the buoyance forces caused by the difference in density between cells and fluid. The model involves two mass balance and two general momentum balance equations, respectively, for the cell and fluid phase, combined with a convection-diffusion-reaction equation for oxygen. In particular, the momentum balance equations include interaction terms which describe the cell-fluid drag force effect. Hence, the model is an extension of the classical Navier-Stokes equation in two different ways: (i) inclusion of two phases (cell and fluid) instead of one; (ii) inclusion of a chemotactic transport mechanism. The model can be understood as a natural generalization of the much studied chemotaxis-Stokes model explored by [I. Tuval, L. Cisneros, C. Dombrowski, C. W. Wolgemuth, J. O. Kessler and R. E. Goldstein, Bacterial swimming and oxygen transport near contact lines, Proc. Natl. Acad. Sci. USA 102 (2005) 2277-2282]. First, we explore the model for parameters in a range which ensures that it lies close to the previously studied chemotaxis-Stokes model (essentially very low cell volume fraction). Main observations are (i) formation of sinking finger-shaped plumes and (ii) convergence to plumes that possibly can be stationary (i. e. persist over time). The general cell-fluid model provides new insight into the role played by the cell-fluid interaction term which controls the competition between gravity segregation and chemotaxis effect on the formation of cell plumes. Second, we explore cases with large cell volume fraction (far beyond the regime captured by the chemotaxis-Stokes model), which gives rise to rich pattern-formation behavior. The general cell-fluid model opens for exploring a hierarchy of different "submodels". Hence, it seems to be an interesting model for further investigations of various, general cell-fluid spatio-temporal evolution dynamics, both from an experimental and mathematical point of view.
Subgrouping of Iranian children and adolescents based on cardiometabolic risk factors using latent class analysis: The CASPIAN-V study
CASPIAN JOURNAL OF INTERNAL MEDICINE
Authors: Abbasi-Gharamanloo, Abbas; Heshmat, Ramin; Rafiemanzelat, Amir-Masood; Ghaderi, Kimia; Motlagh, Mohammad Esmaeil; Ahadi, Zeinab; Shafiee, Gita; Mahadavi-Gorabi, Armita; Qorbani, Mostafa; Kelishadi, Roya
Abstract
Background: Cardiometabolic syndrome indicates the clustering of several risk factors. The aims of this study were to identify the subgroups of the Iranian children and adolescents on the basis of the components of the cardio-metabolic syndrome and assess the role of demographic characteristics, socioeconomic status and lifestyle-related behaviors on the membership of participants in each latent class. Methods: This cross-sectional study was performed on 3730 Iranian students in 2015 using stratified cluster. All students in each class completed anonymous and structured questionnaires. Abdominal obesity, high triglyceride (TG), low high-density lipoprotein (HDL), high blood pressure (BP), high fasting blood sugar (FBS), high low-density lipoprotein (LDL), high cholesterol and obesity were used for assessing the pattern of cardio metabolic risk as a latent variable. Data analysis was performed using PROC LCA in SAS software. Results: Four latent classes were identified in this study; namely 1) healthy (59.6%), 2) low risk (20.4%), 3) moderate risk (13.7%) and 4) high risk (6.4%). Being a female (OR=0.59, 95% CI: 0.46-0.74), living in a rural area (01:0.45, 95% CI;0.33-0.60), high screen time (OR=1.56, 95% CI:1.09-2.24), and parental obesity (OR=1.52, 95% CI: 1.18-1.95) were associated with moderate risk class. Only living in rural areas (OR=0.71, 95% CI; 0.51-0.99) was associated with high risk class. Conclusion: About 20% of the students are in the moderate risk and high risk classes. Design and implement interventions according to risk-based class that seem necessary by considering probably risk and protective factors for the prevention of complications of cardiometabolic syndrome.