Signatures of hybridization of multiple Majorana zero modes in a vortex.

Majorana zero modes (MZMs) are emergent zero-energy topological quasiparticles that are their own antiparticles1,2. Detected MZMs are spatially separated and electrically neutral, so producing hybridization between MZMs is extremely challenging in superconductors3,4. Here, we report the magnetic field response of vortex bound states in superconducting topological crystalline insulator SnTe (001) films. Several MZMs were predicted to coexist in a single vortex due to magnetic mirror symmetry. Using a scanning tunnelling microscope equipped with a three-axis vector magnet, we found that the zero-bias peak (ZBP) in a single vortex exhibits an apparent anisotropic response even though the magnetic field is weak. The ZBP can robustly extend a long distance of up to approximately 100 nm at the (001) surface when the magnetic field is parallel to the ( 1 1 ¯ 0 )-type mirror plane, otherwise it displays an asymmetric splitting. Our systematic simulations demonstrate that the anisotropic response cannot be reproduced with trivial ZBPs. Although the different MZMs cannot be directly distinguished due to the limited energy resolution in our experiments, our comparisons between experimental measurements and theoretical simulations strongly support the existence and hybridization of symmetry-protected multiple MZMs. Our work demonstrates a way to hybridize different MZMs by controlling the orientation of the magnetic field and expands the types of MZM available for tuning topological states.

Graphene nanoribbons grown in hBN stacks for high-performance electronics.

Van der Waals encapsulation of two-dimensional materials in hexagonal boron nitride (hBN) stacks is a promising way to create ultrahigh-performance electronic devices1-4. However, contemporary approaches for achieving van der Waals encapsulation, which involve artificial layer stacking using mechanical transfer techniques, are difficult to control, prone to contamination and unscalable. Here we report the transfer-free direct growth of high-quality graphene nanoribbons (GNRs) in hBN stacks. The as-grown embedded GNRs exhibit highly desirable features being ultralong (up to 0.25 mm), ultranarrow (<5 nm) and homochiral with zigzag edges. Our atomistic simulations show that the mechanism underlying the embedded growth involves ultralow GNR friction when sliding between AA'-stacked hBN layers. Using the grown structures, we demonstrate the transfer-free fabrication of embedded GNR field-effect devices that exhibit excellent performance at room temperature with mobilities of up to 4,600 cm2 V-1 s-1 and on-off ratios of up to 106. This paves the way for the bottom-up fabrication of high-performance electronic devices based on embedded layered materials.

Atomically precise photothermal nanomachines.

Interfacing molecular machines to inorganic nanoparticles can, in principle, lead to hybrid nanomachines with extended functions. Here we demonstrate a ligand engineering approach to develop atomically precise hybrid nanomachines by interfacing gold nanoclusters with tetraphenylethylene molecular rotors. When gold nanoclusters are irradiated with near-infrared light, the rotation of surface-decorated tetraphenylethylene moieties actively dissipates the absorbed energy to sustain the photothermal nanomachine with an intact structure and steady efficiency. Solid-state nuclear magnetic resonance and femtosecond transient absorption spectroscopy reveal that the photogenerated hot electrons are rapidly cooled down within picoseconds via electron-phonon coupling in the nanomachine. We find that the nanomachine remains structurally and functionally intact in mammalian cells and in vivo. A single dose of near-infrared irradiation can effectively ablate tumours without recurrence in tumour-bearing mice, which shows promise in the development of nanomachine-based theranostics.

Vaccination Shapes Within-Host SARS-CoV-2 Diversity of Omicron BA.2.2 Breakthrough Infection.

BACKGROUND: Low-frequency intrahost single-nucleotide variants of SARS-CoV-2 have been recognized as predictive indicators of selection. However, the impact of vaccination on the intrahost evolution of SARS-CoV-2 remains uncertain at present. METHODS: We investigated the genetic variation of SARS-CoV-2 in individuals who were unvaccinated, partially vaccinated, or fully vaccinated during Shanghai's Omicron BA.2.2 wave. We substantiated the connection between particular amino acid substitutions and immune-mediated selection through a pseudovirus neutralization assay or by cross-verification with the human leukocyte antigen-associated T-cell epitopes. RESULTS: In contrast to those with immunologic naivety or partial vaccination, participants who were fully vaccinated had intrahost variant spectra characterized by reduced diversity. Nevertheless, the distribution of mutations in the fully vaccinated group was enriched in the spike protein. The distribution of intrahost single-nucleotide variants in individuals who were immunocompetent did not demonstrate notable signs of positive selection, in contrast to the observed adaptation in 2 participants who were immunocompromised who had an extended period of viral shedding. CONCLUSIONS: In SARS-CoV-2 infections, vaccine-induced immunity was associated with decreased diversity of within-host variant spectra, with milder inflammatory pathophysiology. The enrichment of mutations in the spike protein gene indicates selection pressure exerted by vaccination on the evolution of SARS-CoV-2.

Non-uniformity correction algorithm for DoFP adapted to integration time variations.

Division of the focal plane (DoFP) polarization detector is a pivotal technology in real-time polarization detection. This technology integrates a micropolarization array (MPA) onto the conventional focal plane, introducing a more intricate non-uniformity than traditional focal plane detectors. Current non-uniformity correction algorithms for DoFP are difficult to adapt to changes in integration time and perform poorly in low-polarization scenarios. Analyzing the characteristics of DoFP, formulating a pixel response model, and introducing an adaptive non-uniformity correction algorithm tailored for varying integration time. The DoFP analysis vectors are decomposed into average polarization response and unit analysis vectors for correction separately to improve the performance of the correction algorithm in different polarization scenarios. The performance of modern correction algorithms was tested and evaluated using standard uniform images, and the proposed method outperformed existing algorithms in terms of polarization measurement accuracy under the root mean square error (RMSE) metric. Moreover, in natural scene images, our proposed algorithm shows favorable visual effects and distinguishes itself from its superior stability amid changes in the integration time.

CircOGDH Is a Penumbra Biomarker and Therapeutic Target in Acute Ischemic Stroke.

BACKGROUND: Acute ischemic stroke (AIS) is a leading cause of disability and mortality worldwide. Prediction of penumbra existence after AIS is crucial for making decision on reperfusion therapy. Yet a fast, inexpensive, simple, and noninvasive predictive biomarker for the poststroke penumbra with clinical translational potential is still lacking. We aim to investigate whether the CircOGDH (circular RNA derived from oxoglutarate dehydrogenase) is a potential biomarker for penumbra in patients with AIS and its role in ischemic neuronal damage. METHODS: CircOGDH was screened from penumbra of middle cerebral artery occlusion mice and was assessed in plasma of patients with AIS by quantitative polymerase chain reaction. Magnetic resonance imaging was used to examine the penumbra volumes. CircOGDH interacted with miR-5112 (microRNA-5112) in primary cortical neurons was detected by fluorescence in situ hybridization, RNA immunoprecipitation, and luciferase reporter assay. Adenovirus-mediated CircOGDH knockdown ameliorated neuronal apoptosis induced by COL4A4 (Gallus collagen, type IV, alpha IV) overexpression. Transmission electron microscope, nanoparticle tracking analysis, and Western blot were performed to confirm exosomes. RESULTS: CircOGDH expression was dramatically and selectively upregulated in the penumbra tissue of middle cerebral artery occlusion mice and in the plasma of 45 patients with AIS showing a 54-fold enhancement versus noncerebrovascular disease controls. Partial regression analysis revealed that CircOGDH expression was positively correlated with the size of penumbra in patients with AIS. Sequestering of miR-5112 by CircOGDH enhanced COL4A4 expression to elevate neuron damage. Additionally, knockdown of CircOGDH significantly enhanced neuronal cell viability under ischemic conditions. Furthermore, the expression of CircOGDH in brain tissue was closely related to that in the serum of middle cerebral artery occlusion mice. Finally, we found that CircOGDH was highly expressed in plasma exosomes of patients with AIS compared with those in noncerebrovascular disease individuals. CONCLUSIONS: These results demonstrate that CircOGDH is a potential therapeutic target for regulating ischemia neuronal viability, and is enriched in neuron-derived exosomes in the peripheral blood, exhibiting a predictive biomarker of penumbra in patients with AIS.

Engineering of robust topological quantum phases in graphene nanoribbons.

Boundaries between distinct topological phases of matter support robust, yet exotic quantum states such as spin-momentum locked transport channels or Majorana fermions1-3. The idea of using such states in spintronic devices or as qubits in quantum information technology is a strong driver of current research in condensed matter physics4-6. The topological properties of quantum states have helped to explain the conductivity of doped trans-polyacetylene in terms of dispersionless soliton states7-9. In their seminal paper, Su, Schrieffer and Heeger (SSH) described these exotic quantum states using a one-dimensional tight-binding model10,11. Because the SSH model describes chiral topological insulators, charge fractionalization and spin-charge separation in one dimension, numerous efforts have been made to realize the SSH Hamiltonian in cold-atom, photonic and acoustic experimental configurations12-14. It is, however, desirable to rationally engineer topological electronic phases into stable and processable materials to exploit the corresponding quantum states. Here we present a flexible strategy based on atomically precise graphene nanoribbons to design robust nanomaterials exhibiting the valence electronic structures described by the SSH Hamiltonian15-17. We demonstrate the controlled periodic coupling of topological boundary states18 at junctions of graphene nanoribbons with armchair edges to create quasi-one-dimensional trivial and non-trivial electronic quantum phases. This strategy has the potential to tune the bandwidth of the topological electronic bands close to the energy scale of proximity-induced spin-orbit coupling19 or superconductivity20, and may allow the realization of Kitaev-like Hamiltonians3 and Majorana-type end states21.

Related Factors of CRKP Infection in Neurosurgery and Comparison of Therapeutic Effects of Tigecycline Versus Polymyxin B for CRKP Infection.

Objective: This paper aimed to identify the factors related to Carbapenem-resistant Klebsiella pneumoniae (CRKP) infection in neurosurgical patients, and to compare the therapeutic effects of tigecycline versus polymyxin B against CRKP infection, so as to provide a reliable reference for neurosurgery in future prevention and treatment of CRKP infection. Methods: One hundred and fifty cases of KPN treated in the neurosurgery department of our hospital from January 1, 2019 to December 31, 2021 were selected, 50 of which were found to be infected with CRKP and the other 100 were detected with carbapenem-sensitive Klebsiella pneumoniae (CSKP) by culture, analysis of factors associated with infection with CRKP. Subsequently, CRKP-infected patients were randomized into a group treated with Ti (group Ti) and a group treated with PB (group PB). The clinical efficacy, bacterial clearance, adverse reactions, and pre- and post-treatment hepatorenal function were comparatively analyzed. Results: Based on the Logistic regression analysis, tracheal intubation (or mechanical ventilation), combination of multiple underlying diseases, presence of impaired consciousness, and use of carbapenem antibiotics are independent risk factors for CRKP infection (P < .05). Ti and PB groups had no evident differences in clinical efficacy and bacterial clearance (P > .05); however, Ti group presented a worse hepatorenal function and a higher incidence of adverse reactions than PB group (P < .05). Conclusions: Tracheal intubation (or mechanical ventilation), multiple underlying diseases, consciousness disturbance, and use of carbapenem antibiotics are related factors affecting CRKP infection in neurosurgical patients. Both Ti and PB have excellent therapeutic efficacy, but the former has more obvious toxicity and side effects.

Quantum Phase Transition in Magnetic Nanographenes on a Lead Superconductor.

Quantum spins, also known as spin operators that preserve SU(2) symmetry, lack a specific orientation in space and are hypothesized to display unique interactions with superconductivity. However, spin-orbit coupling and crystal field typically cause a significant magnetic anisotropy in d/f shell spins on surfaces. Here, we fabricate atomically precise S = 1/2 magnetic nanographenes on Pb(111) through engineering sublattice imbalance in the graphene honeycomb lattice. Through tuning the magnetic exchange strength between the unpaired spin and Cooper pairs, a quantum phase transition from the singlet to the doublet state has been observed, consistent with the quantum spin models. From our calculations, the particle-hole asymmetry is induced by the Coulomb scattering potential and gives a transition point about kBTk ≈ 1.6Δ. Our work demonstrates that delocalized π electron magnetism hosts highly tunable magnetic bound states, which can be further developed to study the Majorana bound states and other rich quantum phases of low-dimensional quantum spins on superconductors.

Collective Quantum Magnetism in Nitrogen-Doped Nanographenes.

The emergence of quantum magnetism in nanographenes provides ample opportunities to fabricate purely organic devices for spintronics and quantum information. Although heteroatom doping is a viable way to engineer the electronic properties of nanographenes, the synthesis of doped nanographenes with collective quantum magnetism remains elusive. Here, a set of nitrogen-doped nanographenes (N-NGs) with atomic precision are fabricated on Au(111) through a combination of imidazole [2+2+2]-cyclotrimerization and cyclodehydrogenation reactions. High-resolution scanning probe microscopy measurements reveal the presence of collective quantum magnetism for nanographenes with three radicals, with spectroscopic features which cannot be captured by mean-field density functional theory calculations but can be well reproduced by Heisenberg spin model calculations. In addition, the mechanism of magnetic exchange interaction of N-NGs has been revealed and compared with their counterparts with pure hydrocarbons. Our findings demonstrate the bottom-up synthesis of atomically precise N-NGs which can be utilized to fabricate low-dimensional extended graphene nanostructures for realizing ordered quantum phases.