59 research outputs found
Exploring quantum chaos with a single nuclear spin
Most classical dynamical systems are chaotic. The trajectories of two
identical systems prepared in infinitesimally different initial conditions
diverge exponentially with time. Quantum systems, instead, exhibit
quasi-periodicity due to their discrete spectrum. Nonetheless, the dynamics of
quantum systems whose classical counterparts are chaotic are expected to show
some features that resemble chaotic motion. Among the many controversial
aspects of the quantum-classical boundary, the emergence of chaos remains among
the least experimentally verified. Time-resolved observations of quantum
chaotic dynamics are particularly rare, and as yet unachieved in a single
particle, where the subtle interplay between chaos and quantum measurement
could be explored at its deepest levels. We present here a realistic proposal
to construct a chaotic driven top from the nuclear spin of a single donor atom
in silicon, in the presence of a nuclear quadrupole interaction. This system is
exquisitely measurable and controllable, and possesses extremely long intrinsic
quantum coherence times, allowing for the observation of subtle dynamical
behavior over extended periods. We show that signatures of chaos are expected
to arise for experimentally realizable parameters of the system, allowing the
study of the relation between quantum decoherence and classical chaos, and the
observation of dynamical tunneling.Comment: revised and published versio
Navigating the 16-dimensional Hilbert space of a high-spin donor qudit with electric and magnetic fields
Efficient scaling and flexible control are key aspects of useful quantum
computing hardware. Spins in semiconductors combine quantum information
processing with electrons, holes or nuclei, control with electric or magnetic
fields, and scalable coupling via exchange or dipole interaction. However,
accessing large Hilbert space dimensions has remained challenging, due to the
short-distance nature of the interactions. Here, we present an atom-based
semiconductor platform where a 16-dimensional Hilbert space is built by the
combined electron-nuclear states of a single antimony donor in silicon. We
demonstrate the ability to navigate this large Hilbert space using both
electric and magnetic fields, with gate fidelity exceeding 99.8% on the nuclear
spin, and unveil fine details of the system Hamiltonian and its susceptibility
to control and noise fields. These results establish high-spin donors as a rich
platform for practical quantum information and to explore quantum foundations.Comment: 31 pages and 19 figures including Supplementary Material
Late onset of new conduction disturbances requiring permanent pacemaker implantation following TAVI
Background: The timing of onset and associated predictors of late new conduction disturbances (CDs) leading to permanent pacemaker implantation (PPI) following transcatheter aortic valve implantation (TAVI) are still unknown, however, essential for an early and safe discharge. This study aimed to investigate the timing of onset and associated predictors of late onset CDs in patients requiring PPI (LCP) following TAVI. Methods and results: We performed retrospective analysis of prospectively collected data from five large volume centres in Europe. Post-TAVI electrocardiograms and telemetry data were evaluated in patients with a PPI post-TAVI to identify the onset of new advanced CDs. Early onset CDs were defined as within 48 hours after procedure, and late onset CDs as after 48 hours. A total of 2804 patients were included for analysis. The PPI rate was 12%, of which 18% was due to late onset CDs (>48 hours). Independent predictors for LCP were pre-existing non-specific intraventricular conduction delay, pre-existing right bundle branch block, self-expandable valves and predilation. At least one of these risk factors was present in 98% of patients with LCP. Patients with a balloon-expandable valve without predilation did not develop CDs requiring PPI after 48 hours. Conclusions: Safe early discharge might be feasible in patients without CDs in the first 48 hours after TAVI if no risk factors for LCP are present
Contribution of TAT System Translocated PhoX to Campylobacter jejuni Phosphate Metabolism and Resilience to Environmental Stresses
Campylobacter jejuni is a common gastrointestinal pathogen that colonizes food animals; it is transmitted via fecal contamination of food, and infections in immune-compromised people are more likely to result in serious long-term illness. Environmental phosphate is likely an important sensor of environmental fitness and the ability to obtain extracellular phosphate is central to the bacteria's core metabolic responses. PhoX is the sole alkaline phosphatase in C. jejuni, a substrate of the TAT transport system. Alkaline phosphatases mediate the hydrolytic removal of inorganic phosphate (Pi) from phospho-organic compounds and thereby contribute significantly to the polyphosphate kinase 1 (ppk1) mediated formation of poly P, a molecule that regulates bacterial response to stresses and virulence. Similarly, deletion of the tatC gene, a key component of the TAT system, results in diverse phenotypes in C. jejuni including reduced stress tolerance and in vivo colonization. Therefore, here we investigated the contribution of phoX in poly P synthesis and in TAT-system mediated responses. The phoX deletion mutant showed significant decrease (P<0.05) in poly P accumulation in stationary phase compared to the wild-type, suggesting that PhoX is a major contributor to the inorganic phosphate pool in the cell which is essential for poly P synthesis. The phoX deletion is sufficient for a nutrient stress defect similar to the defect previously described for the ΔtatC mutant. Additionally, the phoX deletion mutant has increased resistance to certain antimicrobials. The ΔphoX mutant was also moderately defective in invasion and intracellular survival within human intestinal epithelial cells as well as in chicken colonization. Further, the ΔphoX mutant produced increased biofilm that can be rescued with 1 mM inorganic phosphate. The qRT-PCR of the ΔphoX mutant revealed transcriptional changes that suggest potential mechanisms for the increased biofilm phenotype
Interactions between Type 1 Interferons and the Th17 Response in Tuberculosis: Lessons Learned from Autoimmune Diseases
textabstractThe classical paradigm of tuberculosis (TB) immunity, with a central protective role for Th1 responses and IFN-γ-stimulated cellular responses, has been challenged by unsatisfactory results of vaccine strategies aimed at enhancing Th1 immunity. Moreover, preclinical TB models have shown that increasing IFN-γ responses in the lungs is more damaging to the host than to the pathogen. Type 1 interferon signaling and altered Th17 responses have also been associated with active TB, but their functional roles in TB pathogenesis remain to be established. These two host responses have been studied in more detail in autoimmune diseases (AID) and show functional interactions that are of potential interest in TB immunity. In this review, we first identify the role of type 1 interferons and Th17 immunity in TB, followed by an overview of interactions between these responses observed in systemic AID. We discuss (i) the effects of GM-CSF-secreting Th17.1 cells and type 1 interferons on CCR2+ monocytes; (ii) convergence of IL-17 and type 1 interferon signaling on stimulating B-cell activating factor production and the central role of neutrophils in this process; and (iii) synergy between IL-17 and type 1 interferons in the generation and function of tertiary lymphoid structures and the associated follicular helper T-cell responses. Evaluation of these autoimmune-related pathways in TB pathogenesis provides a new perspective on recent developments in TB research
Autoantibodies against type I IFNs in patients with life-threatening COVID-19
Interindividual clinical variability in the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is vast. We report that at least 101 of 987 patients with life-threatening coronavirus disease 2019 (COVID-19) pneumonia had neutralizing immunoglobulin G (IgG) autoantibodies (auto-Abs) against interferon-w (IFN-w) (13 patients), against the 13 types of IFN-a (36), or against both (52) at the onset of critical disease; a few also had auto-Abs against the other three type I IFNs. The auto-Abs neutralize the ability of the corresponding type I IFNs to block SARS-CoV-2 infection in vitro. These auto-Abs were not found in 663 individuals with asymptomatic or mild SARS-CoV-2 infection and were present in only 4 of 1227 healthy individuals. Patients with auto-Abs were aged 25 to 87 years and 95 of the 101 were men. A B cell autoimmune phenocopy of inborn errors of type I IFN immunity accounts for life-threatening COVID-19 pneumonia in at least 2.6% of women and 12.5% of men
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