The role of trachea, lungs and airsacs in temperature control in sauropods as inferred from finite element and air-flow analysis.

对第一个和第二个资助期获得的形态和生理呼吸参数的异速生长估计得出的结论是：a)鸟类式的肺不仅在蜥脚类动物中可能存在，而且很容易以低能量成本满足快速生长和活跃的幼年动物的代谢需要，以及b)巨大的气囊和长脖子的存在可能共同作用来控制巨大的温度过高。本研究的目的是建立一个基于有限元分析(FEA)的热力学模型，并将其应用于气囊和气管的体积和表面积的异速测量值，以验证这样的假设，即禽类呼吸系统的解剖可能提供了防止由于体表与体体积的比例而引起的体温升高的关键。我们将首先严格测试当前的巨温模型，包括关于蜥脚类栖息地的大气温度、氧分压和相对湿度以及生长速度的最新数据，以及由于细胞代谢、消化活动、发酵和肌肉活动而产生的热量。其次，我们将对气管、肺和气囊的表面积以及温度梯度产生一系列合理的估计，并将它们与导热系数相结合，然后我们将通过一种新的有限元应用来估计热传递。最后，我们将计算气管内的流动模式，并根据湍流或层流的流行程度，估计蒸发冷却和依赖于温度通风的温度控制。

Allometric estimates of morphological and physiological respiratory parameters obtained in the first and second funding periods have lead to the conclusions that a) an avian style lung is not only likely in sauropods, but that it easily would have met the metabolic needs of a rapidly growing and active juvenile animal at low energetic cost and b) the presence of voluminous airsacs and a long neck could have worked together to control gigantothermic hyperthermy. The goal of the present study is to develop a finite element analysis (FEA)-based thermodynamic model and apply it to allometrically estimated values for the volume and surface area of airsacs and trachea in order to test the hypothesis that the anatomy of the avian-like respiratory system could have provided a key to preventing hyperthermy caused by the scaling of body surface vs body volume. We shall begin by critically testing current gigantothermy models, including most recent data on atmospheric temperature, oxygen partial pressure and relative humidity in areas inhabited by sauropods as well as growth rates, and heat production due to cellular metabolism, digestive activity, fermentation and muscular activity. Second we shall generate a range of reasonable estimates of the surface area of the trachea, lung and air sacs as well as temperature gradients, and combine them with coefficients for thermal conductance, We shall then estimate heat transfer by a novel application of FEA. Finally we shall calculate flow patterns in the trachea and depending on the prevalence of turbulent or laminar flow, estimate evaporative cooling and temperature ventilation-dependent temperature control.