The effects of internal adaptation dynamics on the self-organized aggregation of chemotactic bacteria are investigated by Monte Carlo (MC) simulations based on a two-stream kinetic transport equation coupled with a reaction-diffusion equation of the chemoattractant that bacteria produce. A remarkable finding is a nonmonotonic behavior of the peak aggregation density with respect to the adaptation time; more specifically, aggregation is the most enhanced when the adaptation time is comparable to or moderately larger than the mean run time of bacteria. Another curious observation is the formation of a trapezoidal aggregation profile occurring at a very large adaptation time, where the biased motion of individual cells is rather hindered at the plateau regimes due to the boundedness of the tumbling frequency modulation. Asymptotic analysis of the kinetic transport system is also carried out, and a novel asymptotic equation is obtained at the large adaptation-time regime while the Keller-Segel type equations are obtained when the adaptation time is moderate. Numerical comparison of the asymptotic equations with MC results clarifies that trapezoidal aggregation is well described by the novel asymptotic equation, and the nonmonotonic behavior of the peak aggregation density is interpreted as the transient of the asymptotic solutions between different adaptation time regimes.
Stiff-response-induced instability for chemotactic bacteria and flux-limited Keller-Segel equation
趋化性细菌如E.在个人层面上，Coli依赖于通过奔跑和翻滚不断地重新定位。它已被确立，运行的长度是由一个僵硬的响应的时间sensingof化学cues along the pathway.We描述了一种新的机制，图案形成源于趋化反应的刚度依赖于动力学趋化模型，其中包括最近发现的形式主义的细菌趋化性。本文证明了在空间速度空间中的非微观描述和近年来引起广泛关注的宏观方程--通量限制的Keller-Segel方程的不稳定性，其显著性质是不稳定频率保持有界，这与Turing不稳定性的情况相同.基于强大的蒙特卡罗方法的数值计算表明，在实际的参数范围内，粒子数密度的平稳均匀态是不稳定的，并且产生周期性的图案。这些理论的发展与一些生物学观察结果是一致的。
Chemotactic Feedback Controls Patterning in Hybrid Tumor--Stroma Model
College of Engineering, Boston University（波士顿大学工程学院）；Department of Mathematics, University of Tennessee（田纳西大学数学系）；Department of Hepatopancreatobiliary Surgery, Fujian Cancer Hospital（福建省肿瘤医院肝胆胰外科）
Transient instability and recurrent aggregation in a two-species chemotaxis-competition system under environmental periodicity
Instituto de Matemática Interdisciplinar, Departamento de Análisis Matemático y Matemática Aplicada, Universidad Complutense de Madrid（马德里康普顿斯大学交叉数学研究所分析数学与应用数学系）；Departamento de Matemática Aplicada, ICAI, Universidad Pontificia de Comillas（科米利亚斯宗座大学ICAI学院应用数学系）
