分类: 生物学 >> 生物物理学 提交时间: 2016-05-15
摘要: A widely appreciated aspect of developmental robustness is pattern formation in proportion to size. But how such scaling features emerge dynamically remains poorly understood. Here we generate a data set of the expression profiles of six gap genes in Drosophila melanogaster embryos that differ significantly in size. Expression patterns exhibit size-dependent dynamics both spatially and temporally. We uncover a dynamic emergence of under-scaling in the posterior, accompanied by reduced expression levels of gap genes near the middle of large embryos. Simulation results show that a size-dependent Bicoid gradient input can lead to reduced Kruppel expression that can have long-range and dynamic effects on gap gene expression in the posterior. Thus, for emergence of scaled patterns, the entire embryo may be viewed as a single unified dynamic system where maternally derived size-dependent information interpreted locally can be propagated in space and time as governed by the dynamics of a gene regulatory network.
分类: 物理学 >> 核物理学 提交时间: 2023-06-09
摘要: 考虑到低能电子(LEEs;020 eV)在放射生物学中的重要性,金纳米颗粒(AuNPs)在亚keV电子照射下作为高通量LEEs发射源的放射增敏潜力已经得到提出。在这项研究中,基于介电函数理论开发了一套径迹结构蒙特卡罗模拟程序来模拟50keV以下电子在金材料中的输运。在该程序中,为了更精确地描述二次电子发射中的LEEs发射,针对非弹性散射、弹性散射和电子-声学声子散射理论进行了改进,并进一步地使用二次电子产额和反向散射系数对该程序进行了验证。在该程序中还开发了剂量计算模块,为了确保剂量学的准确性,我们使用了蒙特卡罗工具包Geant4进一步对比验证了能量沉积的计算。该优化后的蒙特卡罗程序的开发为未来对AuNPs在靶向放射性核素治疗中影响的研究奠定了基础。