15 research outputs found
Diff-Transfer: Model-based Robotic Manipulation Skill Transfer via Differentiable Physics Simulation
The capability to transfer mastered skills to accomplish a range of similar
yet novel tasks is crucial for intelligent robots. In this work, we introduce
, a novel framework leveraging differentiable physics
simulation to efficiently transfer robotic skills. Specifically,
discovers a feasible path within the task space that
brings the source task to the target task. At each pair of adjacent points
along this task path, which is two sub-tasks, adapts
known actions from one sub-task to tackle the other sub-task successfully. The
adaptation is guided by the gradient information from differentiable physics
simulations. We propose a novel path-planning method to generate sub-tasks,
leveraging -learning with a task-level state and reward. We implement our
framework in simulation experiments and execute four challenging transfer tasks
on robotic manipulation, demonstrating the efficacy of
through comprehensive experiments. Supplementary and Videos are on the website
https://sites.google.com/view/difftransfe
Experimental quantum adversarial learning with programmable superconducting qubits
Quantum computing promises to enhance machine learning and artificial
intelligence. Different quantum algorithms have been proposed to improve a wide
spectrum of machine learning tasks. Yet, recent theoretical works show that,
similar to traditional classifiers based on deep classical neural networks,
quantum classifiers would suffer from the vulnerability problem: adding tiny
carefully-crafted perturbations to the legitimate original data samples would
facilitate incorrect predictions at a notably high confidence level. This will
pose serious problems for future quantum machine learning applications in
safety and security-critical scenarios. Here, we report the first experimental
demonstration of quantum adversarial learning with programmable superconducting
qubits. We train quantum classifiers, which are built upon variational quantum
circuits consisting of ten transmon qubits featuring average lifetimes of 150
s, and average fidelities of simultaneous single- and two-qubit gates
above 99.94% and 99.4% respectively, with both real-life images (e.g., medical
magnetic resonance imaging scans) and quantum data. We demonstrate that these
well-trained classifiers (with testing accuracy up to 99%) can be practically
deceived by small adversarial perturbations, whereas an adversarial training
process would significantly enhance their robustness to such perturbations. Our
results reveal experimentally a crucial vulnerability aspect of quantum
learning systems under adversarial scenarios and demonstrate an effective
defense strategy against adversarial attacks, which provide a valuable guide
for quantum artificial intelligence applications with both near-term and future
quantum devices.Comment: 26 pages, 17 figures, 8 algorithm
Mechanism of sphingolipid homeostasis revealed by structural analysis of \u3ci\u3eArabidopsis\u3c/i\u3e SPT-ORM1 complex
The serine palmitoyltransferase (SPT) complex catalyzes the first and rate-limiting step in sphingolipid biosynthesis in all eukaryotes. ORM/ORMDL proteins are negative regulators of SPT that respond to cellular sphingolipid levels. However, the molecular basis underlying ORM/ORMDL-dependent homeostatic regulation of SPT is not well understood.We determined the cryo–electron microscopy structure of Arabidopsis SPT-ORM1 complex, composed of LCB1, LCB2a, SPTssa, and ORM1, in an inhibited state. A ceramide molecule is sandwiched between ORM1 and LCB2a in the cytosolic membrane leaflet. Ceramide binding is critical for the ORM1-dependent SPT repression, and dihydroceramides and phytoceramides differentially affect this repression. A hybrid β sheet, formed by the amino termini of ORM1 and LCB2a and induced by ceramide binding, stabilizes the amino terminus of ORM1 in an inhibitory conformation. Our findings provide mechanistic insights into sphingolipid homeostatic regulation via the binding of ceramide to the SPT-ORM/ORMDL complex that may have implications for plant-specific processes such as the hypersensitive response for microbial pathogen resistance
Observation of many-body Fock space dynamics in two dimensions
Quantum many-body simulation provides a straightforward way to understand
fundamental physics and connect with quantum information applications. However,
suffering from exponentially growing Hilbert space size, characterization in
terms of few-body probes in real space is often insufficient to tackle
challenging problems such as quantum critical behavior and many-body
localization (MBL) in higher dimensions. Here, we experimentally employ a new
paradigm on a superconducting quantum processor, exploring such elusive
questions from a Fock space view: mapping the many-body system onto an
unconventional Anderson model on a complex Fock space network of many-body
states. By observing the wave packet propagating in Fock space and the
emergence of a statistical ergodic ensemble, we reveal a fresh picture for
characterizing representative many-body dynamics: thermalization, localization,
and scarring. In addition, we observe a quantum critical regime of anomalously
enhanced wave packet width and deduce a critical point from the maximum wave
packet fluctuations, which lend support for the two-dimensional MBL transition
in finite-sized systems. Our work unveils a new perspective of exploring
many-body physics in Fock space, demonstrating its practical applications on
contentious MBL aspects such as criticality and dimensionality. Moreover, the
entire protocol is universal and scalable, paving the way to finally solve a
broader range of controversial many-body problems on future larger quantum
devices.Comment: 8 pages, 4 figures + supplementary informatio
Pharmacokinetics of oxiracetam and its degraded substance (HOPAA) after oral and intravenous administration in rats
The pharmacokinetics of oxiracetam and its degraded substance (4-hydroxy-2-oxo-1-pyrrolidine acetic acid, HOPAA) after oral and intravenous administration in rats were studied using an established UPLC-MS/MS method. Three groups of rats after an overnight fasted received 10 g/kg (n = 6) oxiracetam suspensions orally, and 2 g/kg (n = 6) normal or degraded oxiracetam injections intravenously via a caudal tail vein, respectively. Before the pharmacokinetic experiment, a simple safety evaluation test was conducted on the degraded oxiracetam injections containing 16.16% HOPAA in mice. There was no mortality by a single intravenous dose of 2 g/kg of degraded oxiracetam injections within two weeks, demonstrating that HOPAA was non-toxic in mice. Following intravenous administration of the normal injections, the plasma concentration-time curves of oxiracetam and HOPAA both showed a rapid elimination phase. The values of t1/2 were 3.1 ± 1.5 h for oxiracetam and 0.8 ± 0.2 h for HOPAA, and the mean residence times (MRT) were 1.2 ± 0.1 h and 0.8 ± 0.1 h, respectively. Oxiracetam and HOPAA after intravenous administration of the degraded oxiracetam injections presented elimination patterns similar to those observed in the normal injections. Oral pharmacokinetic results showed that the Tmax was less than 1.5 h for the two analytes, and both had a longer t1/2 and MRT than those of intravenous administration. Contents of HOPAA in three groups were calculated based on AUC0–t values of the two analytes. The quantitative change of HOPAA in vivo was also evaluated by comparing the plasma concentrations of HOPAA and oxiracetam at the same time for every group. Additionally, the values of absolute bioavailability of oxiracetam were about 8.0% and 7.4% calculated by the normal or degraded oxiracetam injections, which were far less than the value of 75% reported in literature, indicating the necessity of further study
<i>In vitro</i> faecal fermentation outcomes and microbiota shifts of resistant starch spherulites
A Multi-Dimensional Calibration Based on Genetic Algorithm in a 12-Bit 750 MS/s Pipelined ADC
As the preferred architecture for high-speed and high-resolution analog-to-digital converters (ADC), the accuracy of pipelined ADC is limited mainly by various errors arising from multiple digital-to-analog converters (MDAC). This paper presents a multi-dimensional (M-D) MDAC calibration based on a genetic algorithm (GA) in a 12-bit 750 MS/s pipelined ADC. The proposed M-D MDAC compensation model enables capacitor mismatch and static interstage gain error (IGE) compensation on the chip and prepares for subsequent background calibration based on a pseudo-random number (PN) injection to achieve accurate compensation for dynamic IGE. An M-D coefficient extraction scheme based on GA is also proposed to extract the required compensation coefficients of the foreground calibration, which avoids falling into local traps through MATLAB. The above calibration scheme has been verified in a prototype 12-bit 750 MS/s pipelined ADC. The measurement results show that the signal-to-noise and distortion ratio (SNDR) and spurious-free dynamic range (SFDR) are increased from 49.9 dB/66.7 dB to 59.6 dB/77.5 dB with the proposed calibration at 25 °C. With the help of background calibration at 85 °C, the SNDR and SFDR are improved by 3.4 dB and 8.8 dB, respectively
Collaborative regulation of yeast SPT-Orm2 complex by phosphorylation and ceramide
Summary: The homeostatic regulation of serine palmitoyltransferase (SPT) activity in yeast involves N-terminal phosphorylation of Orm proteins, while higher eukaryotes lack these phosphorylation sites. Although recent studies have indicated a conserved ceramide-mediated feedback inhibition of the SPT-ORM/ORMDL complex in higher eukaryotes, its conservation and relationship with phosphorylation regulation in yeast remain unclear. Here, we determine the structure of the yeast SPT-Orm2 complex in a dephosphomimetic state and identify an evolutionarily conserved ceramide-sensing site. Ceramide stabilizes the dephosphomimetic Orm2 in an inhibitory conformation, facilitated by an intramolecular β-sheet between the N- and C-terminal segments of Orm2. Moreover, we find that a phosphomimetic mutant of Orm2, positioned adjacent to its intramolecular β-sheet, destabilizes the inhibitory conformation of Orm2. Taken together, our findings suggest that both Orm dephosphorylation and ceramide binding are crucial for suppressing SPT activity in yeast. This highlights a distinctive regulatory mechanism in yeast involving the collaborative actions of phosphorylation and ceramide