30 research outputs found
Early Triassic wrinkle structures on land:stressed environments and oases for life
Wrinkle structures in rocks younger than the Permian-Triassic (P-Tr) extinction have been reported repeatedly in marine strata, but rarely mentioned in rocks recording land. Here, three newly studied terrestrial P-Tr boundary rock succession in North China have yielded diverse wrinkle structures. All of these wrinkles are preserved in barely bioturbated shore-shallow lacustrine siliciclastic deposits of the Liujiagou Formation. Conversely, both the lacustrine siliciclastic deposits of the underlying Sunjiagou Formation and the overlying Heshanggou Formation show rich bioturbation, but no wrinkle structures or other microbial-related structures. The occurrence of terrestrial wrinkle structures in the studied sections reflects abnormal hydrochemical and physical environments, presumably associated with the extinction of terrestrial organisms. Only very rare trace fossils occurred in the aftermath of the P-Tr extinction, but most of them were preserved together with the microbial mats. This suggests that microbial mats acted as potential oases for the surviving aquatic animals, as a source of food and oxygen. The new finds suggests that extreme environmental stresses were prevalent both in the sea and on land through most of the Early Triassic
Mechanical transistors for logic-with-memory computing
As a potential revolutionary topic in future information processing,
mechanical computing has gained tremendous attention for replacing or
supplementing conventional electronics vulnerable to power outages, security
attacks, and harsh environments. Despite its potential for constructing
intelligent matter towards nonclassical computing systems beyond the von
Neumann architecture, most works on mechanical computing demonstrated that the
ad hoc design of simple logic gates cannot fully realize a universal mechanical
processing framework involving interconnected arithmetic logic components and
memory. However, such a logic-with-memory computing architecture is critical
for complex and persistent state-dependent computations such as sequential
logic. Here we propose a mechanical transistor (M-Transistor), abstracting
omnipresent temperatures as the input-output mechanical bits, which consists of
a metamaterial thermal channel as the gate terminal driving a nonlinear
bistable soft actuator to selectively connect the output terminal to two other
variable thermal sources. This M-Transistor is an elementary unit to modularly
form various combinational and sequential circuits, such as complex logic
gates, registers (volatile memory), and long-term memories (non-volatile
memory) with much fewer units than the electronic counterparts. Moreover, they
can establish a universal processing core comprising an arithmetic circuit and
a register in a compact, reprogrammable network involving periodic read, write,
memory, and logic operations of the mechanical bits. Our work contributes to
realizing a non-electric universal mechanical computing architecture that
combines multidisciplinary engineering with structural mechanics, materials
science, thermal engineering, physical intelligence, and computational science.Comment: 25 pages, 4 figures, Articl
Integrated Sr isotope variations and global environmental changes through the Late Permian to early Late Triassic
New 87Sr/86Sr data based on 127 well-preserved and well-dated conodont samples from South China were measured using a new technique (LA-MC-ICPMS) based on single conodont albid crown analysis. These reveal a spectacular climb in seawater 87Sr/86Sr ratios during the Early Triassic that was the most rapid of the Phanerozoic. The rapid increase began in Bed 25 of the Meishan section (GSSP of the Permian–Triassic boundary, PTB), and coincided closely with the latest Permian extinction. Modeling results indicate that the accelerated rise of 87Sr/86Sr ratios can be ascribed to a rapid increase (>2.8×) of riverine flux of Sr caused by intensified weathering. This phenomenon could in turn be related to an intensification of warming-driven runoff and vegetation die-off. Continued rise of 87Sr/86Sr ratios in the Early Triassic indicates that continental weathering rates were enhanced >1.9 times compared to those of the Late Permian. Continental weathering rates began to decline in the middle–late Spathian, which may have played a role in the decrease of oceanic anoxia and recovery of marine benthos. The 87Sr/86Sr values decline gradually into the Middle Triassic to an equilibrium values around 1.2 times those of the Late Permian level, suggesting that vegetation coverage did not attain pre-extinction levels thereby allowing higher runoff