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Prethermalization by random multipolar driving on a 78-qubit processor
No full textTime-dependent drives hold promise for realizing non-equilibrium many-body phenomena that are absent in undriven systems1, 2-3. Yet, drive-induced heating normally destabilizes the systems4,5, which can be parametrically suppressed in the high-frequency regime by using periodic (Floquet) drives6,7. It remains largely unknown to what extent highly controllable quantum simulators can suppress heating in non-periodically driven systems. Here, using the 78-qubit superconducting quantum processor, Chuang-tzu 2.0, we report the experimental observation of long-lived prethermal phases in many-body systems with tunable heating rates, driven by structured random protocols, characterized by n-multipolar temporal correlations. By measuring both the particle imbalance and subsystem entanglement entropy, we monitor the entire heating process over 1,000 driving cycles and observe the existence of the prethermal plateau. The prethermal lifetime is 'doubly tunable': one way by driving frequency, the other way by multipolar order; it grows algebraically with the frequency with the universal scaling exponent 2n + 1. Using quantum-state tomography on different subsystems, we demonstrate a non-uniform spatial entanglement distribution and observe a crossover from area-law to volume-law entanglement scaling. With 78 qubits and 137 couplers in a two-dimensional configuration, the entire far-from-equilibrium heating dynamics are beyond the reach of simulation using tensor-network numerical techniques. Our work highlights superconducting quantum processors as a powerful platform for exploring universal scaling laws and non-equilibrium phases of matter in driven systems in regimes where classical simulation faces formidable challenges
Constraining the nature of the most extreme Galactic particle accelerator
No full textContext. Microquasars have emerged as promising candidates to explain the cosmic-ray flux at petaelectronvolt energies. LHAASO observations revealed V4641 Sgr as the most extreme example so far. Its gamma-ray spectrum extends up to 800 TeV, which requires particles with multi-PeV energy. The TeV emission is highly extended, which challenges expectations given the reported low-inclination angle of the V4641 Sgr jets. Aims. We spatially and spectrally resolved the gamma-ray emission from V4641 Sgr and investigated the particle acceleration in the system. Methods. Using ≈100 h of H.E.S.S. data, we performed a spectro-morphological study of the gamma-ray emission around V4641 Sgr. We em- ployed HI and dedicated CO observations of the region to infer the target material for cosmic-ray interactions.Results. We detected multi-TeV emission around V4641 Sgr with a high significance. The emission region is elongated, and its major and minor axes are 0.34±0.01syst◦±0.04stat and 0.06±0.01syst◦±0.01stat, respectively. We found a power-law spectrum with an index ≈1.8, and together with results from other gamma-ray instruments, this reveals a spectral energy distribution (SED) that peaks at energies of ≈100 TeV for the first time. We found indica- tions (3σ) of a two-component morphology, with indistinguishable spectral properties. The position of V4641 Sgr is inconsistent with the best-fit position of the single-component model and with the dip between the two components. We found no significant evidence of an energy-dependent morphology. No dense gas was found at any distance towards V4641 Sgr, which places an upper limit of ngas ≤ 0.2 cm−3 within the gamma-ray emission region.Conclusions. The peak of the SED at ≈100 TeV identifies V4641 Sgr as a candidate cosmic-ray accelerator beyond the so-called knee. The absence of dense target gas places stringent energetic constraints on hadronic interpretations, however. The H.E.S.S. measurement requires an unusually hard (≈1.5) spectral index for the protons. A leptonic scenario faces fewer obstacles if the particle transport is fast enough to avoid losses and to reproduce the observed energy-independent morphology. The absence of bright X-ray emission across the gamma-ray emission region requires a magnetic field strength ≤ 3 μG, however. Our findings favour a leptonic origin of the gamma-ray emission. This conclusion does not exclude hadron acceleration in the V4641 Sgr system
Electric fields enhance Diels–Alderase catalysis in abyssomicin C biosynthesis
No full textNatural Diels–Alderases catalyse [4+2] cycloadditions by preorganizing substrates into reactive conformations. However, the roles of other catalytic factors, such as electrostatic effects, remain elusive. Here, we combine conceptual density functional theory (CDFT) descriptors and electric field analysis to unravel the electrostatic basis of activity in the Diels–Alderase AbyU. Previously, four different enzyme-substrate poses were identified, of which two showed catalytically favorable free energy barriers based on quantum mechanical/molecular mechanical (QM/MM) reaction simulations. Here, we show that atom-condensed Fukui functions can predict the reactivity from reactant conformations alone, focusing on the diene carbons involved in bond formation. The importance of the enzyme-diene interaction is supported by electric field analysis, which shows how reactivity of enzyme-substrate poses correlates with alignment of the enzyme field along the diene moiety. Our findings establish a basis for predicting and engineering Diels–Alderase activity based on electrostatic and electronic reactivity features
Flexible circuits for visually guided flight control in Drosophila
No full textFlight maneuvers in the fruit fly Drosophila have long served as a model for studying principles underlying visual information processing. Advances in genetic targeting of individual types of neurons for manipulation and recording, as well as the publication of the complete connectome, have greatly expanded our knowledge of how behavior is controlled by the fly's nervous system. In this review, I summarize recent findings on how visual information relevant to flight is transformed into a behavioral output, ranging from fast stabilizing reflex-like responses to longer-lasting goal-directed behaviors. I argue that flexibility in the processing of visual information and a hierarchical recruitment of different behavioral modules enable the control of this complex behavior with a comparatively small number of neurons
Chemical and lithological heterogeneity of upwelling mantle plumes inducing Zn isotope variation in Ocean Island Basalts
No full textFrom the latest Cretaceous (late Campanian to Maastrichtian, -75?66 Ma) to the earliest Paleogene, fluctuations in greenhouse climate, inferred primarily from marine sediments, have been linked to volcanism, the Chicxulub asteroid impact, and the Cretaceous-Paleogene (K-Pg) mass extinction. In this paper, we summarize terrestrial climate records in mid-latitude East Asia during the latest Cretaceous and across the K-Pg boundary, based on a multi-proxy approach from the geochronologically well-constrained Sifangtai and Mingshui formations (SMF), accessed by scientific drilling of the Songliao Basin in northeastern China. Evolution of sedimentary environments is characterized by five depositional units of fluvial-deltaic-lacustrine facies. Development of four types of paleosols, including Inceptisols, Aridisols, Vertisols and Alfisols, is interpreted to primarily reflect climatic changes. Correlations among sedimentary facies, paleosol features, illite chemistry index, chemical index of alteration, as well as stable and clumped isotopes of pedogenic carbonates and clay minerals of the SMF validate their reliability for paleoclimate reconstruction, and indicate significant fluctuations in terrestrial climate and sedimentary environment. During global warming intervals possibly triggered by volcanism (e.g. -69.5?68.5 Ma), the Songliao Basin experienced a warmer and wetter climate with stronger terrestrial chemical weathering and more monsoon-derived moisture sourced from the Pacific. In contrast, during global cooling intervals (e.g. -70.5?69.5 Ma and - 68.5?66.5 Ma), the SMF record a cooler and drier climate with less intensive chemical weathering and more westerlies-derived moisture. Across the K-Pg boundary, dramatic changes in land temperatures and hydroclimate correspond to the latest Maastrichtian warming episode (-66.4?66.1 Ma), the transient cooling preceding the K-Pg boundary (-66.1?66.0 Ma), and the earliest Paleogene warming interval (-66.0?65.7 Ma). Temporal correlation of weathering index changes with the Deccan Traps volcanism suggests that volcanism and subsequent intensified weathering played a major role for climatic changes across the K-Pg boundary. The integrated records of sedimentological and geochemical datasets from the Songliao Basin robustly demonstrate that the terrestrial climate of mid-latitude East Asia responded strongly to greenhouse climate changes and to the catastrophic geological events from the latest Cretaceous to the earliest Paleogene
Unfolding and Degradation of Micellar Immunodrug Carriers Derived From End Group Modified Aliphatic Poly(Carbonate)s with Acid-Responsive Ketal Side Groups
No full textComplementarity of long-reads and optical mapping in Parkinson’s disease for structural variants
No full textObjectiveLong-read sequencing and optical genome mapping technologies have the ability to detect large and complex structural variants. This has led to the discovery of novel pathogenic variants in neurodegenerative movement disorders. Thus, we aimed to systematically compare the SV detection capabilities of OGM and ONT in Parkinson's disease.MethodsUltra-high molecular weight DNA was derived from blood and fibroblast cultures of 19 patients with mostly early-onset Parkinson's disease, and used for Nanopore sequencing and optical genome mapping. The size distributions of deletions and insertions were compared, and variants were filtered for rare or potentially pathogenic variants in 134 known movement disorder genes.ResultsBoth methods identified SVs > 50 kb; however, optical mapping identified fewer structural variants (49,677) compared to Nanopore sequencing (94,400), but detected six times more in the range 50–80 kb. In general, it detected significantly larger deletions and insertions (p InterpretationOptical mapping can be a powerful first-line method for detecting large structural variants, but it requires a high-resolution method to refine breakpoint positions. Despite certain limitations, Nanopore sequencing was highly capable of detecting large variants independently and allows for a highly complementary assessment and validation of structural variation in combination with optical mapping
