New ages for human occupation and climatic change at Lake Mungo,Australia

Australia's oldest human remains, found at Lake Mungo, include the world's oldest ritual ochre burial (Mungo III) and the first recorded cremation (Mungo I). Until now, the importance of these finds has been constrained by limited chronologies and palaeoenvironmental information. Mungo III, the source of the world's oldest human mitochondrial DNA, has been variously estimated at 30 thousand years (kyr) old, 42-45 kyr old and 62 +/- 6 kyr old, while radiocarbon estimates placed the Mungo I cremation near 20-26 kyr ago. Here we report a new series of 25 optical ages showing that both burials occurred at 40 +/- 2 kyr ago and that humans were present at Lake Mungo by 50-46 kyr ago, synchronously with, or soon after, initial occupation of northern and western Australia. Stratigraphic evidence indicates fluctuations between lake-full and drier conditions from 50 to 40 kyr ago, simultaneously with increased dust deposition, human arrival and continent-wide extinction of the megafauna. This was followed by sustained aridity between 40 and 30 kyr ago. This new chronology corrects previous estimates for human burials at this important site and provides a new picture of Homo sapiens adapting to deteriorating climate in the world's driest inhabited continent.     

Electron cryo-microscopy shows how strong binding of myosin to actin releases nucleotide

Muscle contraction involves the cyclic interaction of the myosin cross-bridges with the actin filament, which is coupled to steps in the hydrolysis of ATP. While bound to actin each cross-bridge undergoes a conformational change, often referred to as the "power stroke", which moves the actin filament past the myosin filaments; this is associated with the release of the products of ATP hydrolysis and a stronger binding of myosin to actin. The association of a new ATP molecule weakens the binding again, and the attached cross-bridge rapidly dissociates from actin. The nucleotide is then hydrolysed, the conformational change reverses, and the myosin cross-bridge reattaches to actin. X-ray crystallography has determined the structural basis of the power stroke, but it is still not clear why the binding of actin weakens that of the nucleotide and vice versa. Here we describe, by fitting atomic models of actin and the myosin cross-bridge into high-resolution electron cryo-microscopy three-dimensional reconstructions, the molecular basis of this linkage. The closing of the actin-binding cleft when actin binds is structurally coupled to the opening of the nucleotide-binding pocket.     

把力学扩展到思维：心理学和经济学的力学基础

本书阐述现代理性力学的数学原理在人工智能中的应用并发展成精确的智力模型，这种阐述可以帮助读者把思维理解为力学系统。该系统显示出真实的、非隐喻的力、惯性和运动。作者用力学术语分析了诱导、论证、学习和通告过程。这些分析为心理学和经济学提供了有限合理性的新特征，为力学提供新型的材料，这些材料显示出不同思维类型的本构运动学和动力学特性，也为哲学提供结合离散和连续力学量的杂交系统的严格理论。描述人体的物理科学和描述人类思维的心理科学合成的力学重整体（reintegration）将为传统的哲学和现代的计算问题打开技术分析的新途径。