在模型系统中，学网我们看到聚合物分子量从58100 g mol?自然周论1降至约400 g mol?1；实际应用中，胺化处理的出版废旧橡胶经6小时反应即可转化为可溶性胺功能化聚合物，该产物可进一步制备具有与商用双酚A型树脂相当刚度的文导闻科环氧热固材料。这项工作证明了C–H胺化与主链重排使消费后材料的读新化学回收成为可能。
▲ Abstract：
Here we apply C–H amination and 学网backbone rearrangement of polymers to deconstruct these materials into precursors for epoxy resins. Specifically, we develop a sulfur diimide reagent that enables up to about 35% allylic amination of diene polymers and rubber. Then, we apply the cationic 2-aza-Cope rearrangement to deconstruct aminated diene polymers. In a model system, we see molecular weight reduction from 58,100 to approximately 400?g?mol?1, and aminated post-consumer rubber is deconstructed over 6?hours into soluble amine-functionalized polymers, which can be utilized to prepare epoxy thermosets with similar stiffnesses to commercial bisphenol A-derived resins. Altogether, this work demonstrates the power of C–H amination and backbone rearrangement to enable chemical recycling of post-consumer materials.
Here we introduce a photonic AI processor that executes advanced AI models, including ResNet and BERT, along with the Atari deep reinforcement learning algorithm originally demonstrated by DeepMind. This processor achieves near-electronic precision for many workloads, marking a notable entry for photonic computing into competition with established electronic AI accelerators and an essential step towards developing post-transistor computing technologies.
地球科学Earth Science
Formation and composition of Earth’s Hadean protocrust
Although Earth, together with other terrestrial planets, must have had an early-formed protocrust, the chemical composition of this crust has received little attention. The protocrust was extracted from an extensive magma ocean formed by accretion and melting of asteroidal bodies. Both experimental and chronological data suggest that the silicate melt ascending from this magma ocean formed in equilibrium with, or after, metal was extracted to form Earth’s core. Here we show that a protocrust formed under these conditions would have had incompatible (with respect to silicate minerals) trace-element characteristics remarkably similar to those of the current average continental crust. This has major implications for subsequent planetary evolution. Many geochemical arguments for when and how plate tectonics began implicitly assume that subduction is required to produce the continental trace-element signature. These arguments are severely compromised if this signature was already a feature of the Hadean protocrust.
Widespread slow growth of acquisitive tree species
Here, by consolidating four independent datasets and classifying the acquisitive and conservative species based on their functional trait values, we show that acquisitive tree species, which are supposedly fast-growing species, generally grow slowly in field conditions. This discrepancy between the current paradigm and field observations is explained by the interactions with environmental conditions that influence growth. Acquisitive species require moist mild climates and fertile soils, conditions that are generally not met in the field. By contrast, conservative species, which are supposedly slow-growing species, show generally higher realized growth due to their ability to tolerate unfavourable environmental conditions. In general, conservative tree species grow more steadily than acquisitive tree species in non-tropical forests. We recommend planting acquisitive tree species in areas where they can realize their fast-growing potential. In other regions, where environmental stress is higher, conservative tree species have a larger potential to fix carbon in their biomass.
地理人类学Geoanthropology
Humans in Africa’s wet tropical forests 150 thousand years ago
Here we report a clear association between late Middle Pleistocene material culture and a wet tropical forest in southern C?te d’Ivoire, a region of present-day rainforest. Twinned optically stimulated luminescence and electron spin resonance dating methods constrain the onset of human occupations at Bété I to around 150?ka, linking them with Homo sapiens. Plant wax biomarker, stable isotope, phytolith and pollen analyses of associated sediments all point to a wet forest environment. The results represent the oldest yet known clear association between humans and this habitat type. The secure attribution of stone tool assemblages with the wet forest environment demonstrates that Africa’s forests were not a major ecological barrier for H. sapiens as early as around 150?ka.
农业Agriculture
Leveraging a phased pangenome for haplotype design of hybrid potato
在此，构建了包含栽培二倍体马铃薯及其野生祖先种60个单倍型的相位化泛基因组图谱，并发现了转座元件在产生结构变异中的广泛存在。与线性参考基因组相比，该图谱呈现更广的遗传多样性（3076 Mb vs 742 Mb）。值得注意的是，栽培二倍体的杂合度显著高于野生种（14.0% vs 9.5%），表明马铃薯驯化过程中存在广泛杂交。
Here we develop a phased potato pangenome graph of 60 haplotypes from cultivated diploids and the ancestral wild species, and find evidence for the prevalence of transposable elements in generating structural variants. Compared with the linear reference, the graph pangenome represents a broader diversity (3,076?Mb versus 742?Mb). Notably, we observe enhanced heterozygosity in cultivated diploids compared with wild ones (14.0% versus 9.5%), indicating extensive hybridization during potato domestication. Using conservative criteria, we identify 19,625 putatively deleterious structural variants (dSVs) and reveal a biased accumulation of deleterious single nucleotide polymorphisms (dSNPs) around dSVs in coupling phase. Based on the graph pangenome, we computationally design ideal potato haplotypes with minimal dSNPs and dSVs. These advances provide critical insights into the genomic basis of clonal propagation and will guide breeders to develop a suite of promising inbred lines.
