SGER: Biomechanical Modeling to Forensic Estimation of Time Since Death

摘要本提案旨在解决这样一个问题：“人类的死亡时间能否通过测量死后特定组织的机械材料特性的变化来估计？”一个由一名法医人类学家、一名解剖学家和一名机械工程师组成的多学科小组已经成立，试图回答这个问题。由于这项研究处于初步阶段，国家科学基金会的“探索性研究小额赠款”是为该项目提供初始资金的适当机制。为了深入了解人体组织在死亡后的机械降解情况，必须从体内分解速度相对较慢的部位选择组织。由于组织包封，我们选择了脊柱椎间盘（纤维环）作为本研究最有可能的测试样本，然而，其他组织（如牙齿）将被考虑作为测试方案的制定。最初，将从已知死亡时间的新鲜（未保存的）尸体上采集三根（受成本限制）人体脊柱。椎间盘将在指定的时间间隔从脊柱的胸椎和腰椎区域手术取出。这些收获的圆盘将在宏观和微观上进行描述，然后通过Instron 8511机械试验机进行准静态、动态和随时间变化的压缩测试来确定机械材料的性能。此外，将调查使用超声技术的试点研究。从力学试验中获得的载荷和变形数据将使用幂律、指数律、单应性或其他适用于生物材料的本构律进行建模，以确定死亡后特定时间的材料参数。预计材料参数与死亡后时间之间将出现一种趋势。

Biomechanical Modeling to Forensic Estimation of Time Since DeathAbstract This proposal is designed to address the question: "Can the time of death for a human be estimated from measured changes in mechanical material properties of specific tissues post-mortem?" A multidisciplinary team, consisting of a Forensic Anthropologist, an Anatomist and a Mechanical Engineer, has been formed to attempt to answer this question. Since this research is at such a preliminary stage the NSF "Small Grants for Exploratory Research" is the appropriate mechanism for initial funding of the project. To gain insight into the mechanical degradation of human tissue after death, the tissue must be chosen from a location in the body which decomposes at a relatively slow rate. Because of tissue encapsulation, we have chosen intervertebral discs (annulus fibrosus) in the spine as the most likely test specimens for this study, however, other tissues (e.g. teeth) will be considered as the testing protocol is developed. Initially, three (limited by cost) human vertebral columns will be harvested from fresh (unpreserved) cadavers for which time of death is known. The intervertebral discs will be surgically extracted from the thoracic and lumbar regions of the spinal columns at specified time intervals. These harvested discs will be described macroscopically and microscopically, then mechanical material properties will be determined from quasi-static, dynamic and time-dependent compression testing imposed by an Instron 8511 Mechanical Testing Machine. Additionally, pilot studies using ultrasound techniques will be investigated. The load and deformation data acquired from the mechanical tests will be modeled using the power law, exponential law, homography or other applicable constitutive laws appropriate for biological material to determine material parameters at specific times since death. It is expected that a trend between the material parameters and time since death will emerge.