Experimental Observation of the Yang-Lee Quantum Criticality in Open Quantum Systems.

The Yang-Lee edge singularity was originally studied from the standpoint of mathematical foundations of phase transitions. However, direct observation of anomalous scaling with the negative scaling dimension has remained elusive due to an imaginary magnetic field required for the nonunitary criticality. We experimentally implement an imaginary magnetic field with an open quantum system of heralded single photons, directly measure the partition function, and demonstrate the Yang-Lee edge singularity via the quantum-classical correspondence. We also demonstrate unconventional scaling laws for finite-temperature quantum dynamics.

Observation of the Sign Reversal of the Magnetic Correlation in a Driven-Dissipative Fermi Gas in Double Wells.

We report the observation of the sign reversal of the magnetic correlation from antiferromagnetic to ferromagnetic in a dissipative Fermi gas in double wells, utilizing the dissipation caused by on-site two-body losses in a controlled manner. We systematically measure dynamics of the nearest-neighbor spin correlation in an isolated double-well optical lattice, as well as a crossover from an isolated double-well lattice to a one-dimensional uniform lattice. In a wide range of lattice configurations over an isolated double-well lattice, we observe a ferromagnetic spin correlation, which is consistent with a Dicke type of correlation expected in the long-time limit. This work demonstrates the control of quantum magnetism in open quantum systems with dissipation.

Yang-Lee Zeros, Semicircle Theorem, and Nonunitary Criticality in Bardeen-Cooper-Schrieffer Superconductivity.

Yang and Lee investigated phase transitions in terms of zeros of partition functions, namely, Yang-Lee zeros [Phys. Rev. 87, 404 (1952)PHRVAO0031-899X10.1103/PhysRev.87.404; Phys. Rev. 87, 410 (1952)PHRVAO0031-899X10.1103/PhysRev.87.410]. We show that the essential singularity in the superconducting gap is directly related to the number of roots of the partition function of a BCS superconductor. Those zeros are found to be distributed on a semicircle in the complex plane of the interaction strength due to the Fermi-surface instability. A renormalization-group analysis shows that the semicircle theorem holds for a generic quantum many-body system with a marginal coupling, in sharp contrast with the Lee-Yang circle theorem for the Ising spin system. This indicates that the geometry of Yang-Lee zeros is directly connected to the Fermi-surface instability. Furthermore, we unveil the nonunitary criticality in BCS superconductivity that emerges at each individual Yang-Lee zero due to exceptional points and presents a universality class distinct from that of the conventional Yang-Lee edge singularity.

Exact Liouvillian Spectrum of a One-Dimensional Dissipative Hubbard Model.

A one-dimensional dissipative Hubbard model with two-body loss is shown to be exactly solvable. We obtain an exact eigenspectrum of a Liouvillian superoperator by employing a non-Hermitian extension of the Bethe-ansatz method. We find steady states, the Liouvillian gap, and an exceptional point that is accompanied by the divergence of the correlation length. A dissipative version of spin-charge separation induced by the quantum Zeno effect is also demonstrated. Our result presents a new class of exactly solvable Liouvillians of open quantum many-body systems, which can be tested with ultracold atoms subject to inelastic collisions.

Liouvillian Skin Effect: Slowing Down of Relaxation Processes without Gap Closing.

It is highly nontrivial to what extent we can deduce the relaxation behavior of a quantum dissipative system from the spectral gap of the Liouvillian that governs the time evolution of the density matrix. We investigate the relaxation processes of a quantum dissipative system that exhibits the Liouvillian skin effect, which means that the eigenmodes of the Liouvillian are localized exponentially close to the boundary of the system, and find that the timescale for the system to reach a steady state depends not only on the Liouvillian gap Δ, but also on the localization length ξ of the eigenmodes. In particular, we show that the longest relaxation time τ that is maximized over initial states and local observables is given by τ∼Δ^{-1}(1+L/ξ) with L being the system size. This implies that the longest relaxation time can diverge for L→∞ without gap closing.

Collective Excitations and Nonequilibrium Phase Transition in Dissipative Fermionic Superfluids.

We predict a new mechanism to induce collective excitations and a nonequilibrium phase transition of fermionic superfluids via a sudden switch on of two-body loss, for which we extend the BCS theory to fully incorporate a change in particle number. We find that a sudden switch on of dissipation induces an amplitude oscillation of the superfluid order parameter accompanied by a chirped phase rotation as a consequence of particle loss. We demonstrate that when dissipation is introduced to one of the two superfluids coupled via a Josephson junction, it gives rise to a nonequilibrium dynamical phase transition characterized by the vanishing dc Josephson current. The dissipation-induced collective modes and nonequilibrium phase transition can be realized with ultracold fermionic atoms subject to inelastic collisions.

Dynamical Sign Reversal of Magnetic Correlations in Dissipative Hubbard Models.

In quantum magnetism, the virtual exchange of particles mediates an interaction between spins. Here, we show that an inelastic Hubbard interaction fundamentally alters the magnetism of the Hubbard model due to dissipation in spin-exchange processes, leading to sign reversal of magnetic correlations in dissipative quantum dynamics. This mechanism is applicable to both fermionic and bosonic Mott insulators, and can naturally be realized with ultracold atoms undergoing two-body inelastic collisions. The dynamical reversal of magnetic correlations can be detected by using a double-well optical lattice or quantum-gas microscopy, the latter of which facilitates the detection of the magnetic correlations in one-dimensional systems because of spin-charge separation. Our results open a new avenue toward controlling quantum magnetism by dissipation.

[Spinal Intradural Extramedullary Ependymoma:A Case Report].

Ependymoma is the most common primary intramedullary tumor of the spinal cord, accounting for a quarter of these tumors. We experienced a case of 'ependymoma of the spinal cord with a cystic lesion that presented as an intradural extramedullary tumor extending from the thoracic to lumbar vertebrae. In review of past literature on reports of spinal intradural extramedullary ependymoma, lesions spanning three or more vertebrae with cystic lesions were frequent, and about half were World Health Organization grade II or higher. Dissemination or recurrence of these tumors may occur after surgery. There is no consensus on postoperative adjuvant therapy for intradural extramedullary spinal ependymoma, but careful consideration should be given to the intraoperative findings and the characteristics of the tumor.

Floquet Chiral Magnetic Effect.

A single Weyl fermion, which is prohibited in static lattice systems by the Nielsen-Ninomiya theorem, is shown to be realized in a periodically driven three-dimensional lattice system with a topologically nontrivial Floquet unitary operator, manifesting the chiral magnetic effect. We give a topological classification of Floquet unitary operators in the Altland-Zirnbauer symmetry classes for all dimensions, and use it to predict that all gapless surface states of topological insulators and superconductors can emerge in bulk quasienergy spectra of Floquet systems.

Theory of Non-Hermitian Fermionic Superfluidity with a Complex-Valued Interaction.

Motivated by recent experimental advances in ultracold atoms, we analyze a non-Hermitian (NH) BCS Hamiltonian with a complex-valued interaction arising from inelastic scattering between fermions. We develop a mean-field theory to obtain a NH gap equation for order parameters, which are different from the standard BCS ones due to the inequivalence of left and right eigenstates in the NH physics. We find unconventional phase transitions unique to NH systems: superfluidity shows reentrant behavior with increasing dissipation, as a consequence of nondiagonalizable exceptional points, lines, and surfaces in the quasiparticle Hamiltonian for weak attractive interactions. For strong attractive interactions, the superfluid gap never collapses but is enhanced by dissipation due to an interplay between the BCS-BEC crossover and the quantum Zeno effect. Our results lay the groundwork for studies of fermionic superfluidity subject to inelastic collisions.

Non-Hermitian Kondo Effect in Ultracold Alkaline-Earth Atoms.

We investigate the Kondo effect in an open quantum system, motivated by recent experiments with ultracold alkaline-earth(-like) atoms. Because of inelastic collisions and the associated atom losses, this system is described by a complex-valued Kondo interaction and provides a non-Hermitian extension of the Kondo problem. We show that the non-Hermiticity induces anomalous reversion of renormalization-group flows which violate the g theorem due to nonunitarity and produce a quantum phase transition unique to non-Hermiticity. Furthermore, we exactly solve the non-Hermitian Kondo Hamiltonian using a generalized Bethe ansatz method and find the critical line consistent with the renormalization-group flow.

Spatial-Translation-Induced Discrete Time Crystals.

A discrete time crystal is a phase unique to nonequilibrium systems, where discrete time translation symmetry is spontaneously broken. Most conventional time crystals proposed so far rely on the spontaneous breaking of on-site symmetries and their corresponding on-site symmetry operations. In this Letter, we propose a new time crystal dubbed the "spatial-translation-induced discrete time crystal," which is realized by spatial translation and its symmetry breaking. Owing to the properties of spatial translation, in this new time crystal, various time crystal orders can only emerge by changing the filling but not changing the driving protocol. We demonstrate that the local transport of charges or spins shows a nontrivial oscillation, enabling detection and applications of time crystal orders, and also provide promising platforms including quantum circuits. Our proposal opens up a new avenue of realizing time crystal orders by spatial translation in various quantum simulators.

Laser-Induced Kondo Effect in Ultracold Alkaline-Earth Fermions.

We demonstrate that laser excitations can coherently induce a novel Kondo effect in ultracold atoms in optical lattices. Using a model of alkaline-earth fermions with two orbitals, it is shown that the optically coupled two internal states are dynamically entangled to form the Kondo-singlet state, overcoming the heating effect due to the irradiation. Furthermore, a lack of SU(N) symmetry in the optical coupling provides a peculiar feature in the Kondo effect, which results in spin-selective renormalization of effective masses. We also discuss the effects of interorbital exchange interactions, and reveal that they induce novel crossover or reentrant behavior of the Kondo effect owing to control of the coupling anisotropy. The laser-induced Kondo effect is highly controllable by tuning the laser strength and the frequency, and thus offers a versatile platform to study the Kondo physics using ultracold atoms.

Carotid Artery Stenting via Radial Access with Modified Flow Reversal Method: Case Series.

OBJECTIVE: Neuroendovascular treatment via transradial access (TRA) has gained popularity as a minimally invasive technique. However, the flow reversal (FR) system, reported useful in carotid artery stenting (CAS), cannot be applied via TRA because it requires an access route of more than 8 F. Herein, we report the utility of a modified FR system applied via TRA using a sheathless 8-F balloon guide catheter and a 2.6-F balloon catheter. METHODS: In a retrospective analysis of a single-center consecutive case series, patients with CAS and vulnerable plaques who were treated with CAS via TRA using a modified FR system from June 2022 to August 2022 were examined. High-intensity spots were assessed on postprocedural diffusion-weighted magnetic resonance images. Puncture site complications at discharge and cardiovascular events for 1 year after CAS were also evaluated. RESULTS: Ten patients were included in this study. There were no high-intensity spots on diffusion-weighted magnetic resonance images after CAS. No procedure-related complications, including radial artery occlusion or cardiovascular events, were observed. CONCLUSIONS: This study suggests that CAS with FR using our modified system is feasible via TRA and may be an effective technique with a low rate of vascular complications.

Feasibility, efficacy, and safety of mechanical thrombectomy via sheathless transradial access as a first-line strategy: A case series.

OBJECTIVE: Although mechanical thrombectomy (MT) is primarily performed via transfemoral access (TFA), transradial access (TRA) is a potential alternative in older patients or those with tortuous vessels. However, the small radial artery diameter restricts the use of large-bore balloon guides and aspiration catheters, a limitation that may be overcome using the sheathless technique. Thus, we aimed to explore the feasibility, efficacy, and safety of sheathless TRA-MT as a first-line treatment approach for acute ischemic stroke. METHODS: This single-center retrospective case series included patients who underwent TRA-MT as first-line treatment between September 2020 and June 2023. Per our MT protocol, TRA was not the first-line approach in cases of left anterior circulation lesions with a type 3 aortic arch. We evaluated treatment effectiveness based on the successful recanalization rate, puncture-to-recanalization time, and modified first-pass effect; access route effectiveness based on the puncture-to-first-pass time and switch-to-TFA rate; and procedure safety based on procedure-related and severe puncture site complications. RESULTS: Sheathless 8-F guide catheters were used in 68 % and large-bore aspiration catheters in 70 % of the procedures. Successful recanalization was achieved in 98 % of the patients, with a modified first-pass effect in 54 % of them. The median puncture-to-first-pass and puncture-to-recanalization times were 20.5 and 33 min, respectively. The rate of procedure-related complications was low (4 %), with no severe puncture site complications. CONCLUSION: Sheathless TRA-MT enabled the use of large-bore guide and aspiration catheters, providing a swift approach to the target and satisfactory outcomes, and might be an effective first-line treatment for acute ischemic stroke.

Feasibility and Challenges of Transradial Approach in Neuroendovascular Therapy: A Retrospective Observational Study.

Objective: Transradial approach (TRA) is increasingly used as a viable alternative to the traditional transfemoral approach (TFA) in neuroendovascular therapy (NET) owing to its potential anatomical benefits and lower puncture-site complication rates. However, the real-world challenges of implementing TRA-NET have not been thoroughly studied, particularly those related to guide catheter (GC) placement. In this study, we aimed to explore the feasibility and challenges of TRA-NET, with a specific focus on GC placement. Methods: This retrospective observational study included patients who underwent NET at our institution between December 2019 and May 2022. Procedural success was defined as the successful placement of a GC in the target vessel. Cases in which a Simmons-shaped GC was used or the approach was changed to TFA were classified as difficult. Safety was assessed based on the rate of severe puncture-site complications requiring either blood transfusion or surgical intervention. Results: Among the 310 patients who underwent NET during the study period, 222 (71.6%) with a median age of 74 years were selected for TRA-NET. The target vessel was in the left anterior circulation (LtAC) in 101 (45.5%) patients, and 8-F GCs were the most frequently used (40.1%). TRA-NET achieved a 95.0% success rate, with a switch to TFA required in 5.0% of the cases. Procedural challenges occurred in 42 (18.9%) patients, primarily in those with LtAC lesions. Specifically, a type III aortic arch (p <0.0001) and age ≥80 years (p = 0.01) were significantly associated with procedural difficulties. Radial artery evaluation was confirmed in 66 cases (29.7%), revealing one instance (1.5%) of radial artery occlusion. No severe puncture-site complications were observed. Conclusion: TRA-NET may provide substantial therapeutic benefits without significant limitations in device use. However, it may be challenging, particularly in older patients and those with a type III aortic arch with LtAC lesions. Consequently, careful selection of the approach route is imperative.

Cadaver investigation of the usefulness of the transstyloid diaphragm approach for high-position plaque carotid endarterectomy.

OBJECTIVES: Patients sometimes present with high cervical internal carotid artery (ICA) stenosis. This study demonstrates the usefulness of the transstyloid approach to expose the distal ICA by dissection of the styloid diaphragm covering the distal cervical ICA for carotid endarterectomy (CEA). In particular, the possible exposure length achieved by this approach was investigated using cadaveric heads. METHODS: The procedure of the transstyloid diaphragm approach was confirmed in 10 cadaveric heads (20 sides). After the carotid triangle was opened, both the posterior belly of the digastric muscle (PBDM) and the stylohyoid muscle could be divided. Then, the carotid sheath was dissected, and the glossopharyngeal nerve was identified crossing over the distal ICA. The revealed length of the ICA was measured with or without dissection of both the PBDM and the stylohyoid muscle. The specimens were dissected under the surgical microscope. RESULTS: The transstyloid diaphragm approach was achieved successfully in all specimens. The revealed lengths of the ICA with and without dissection of the styloid diaphragm were 53.7 ± 5.9 mm and 38.8 ± 2.9 mm (mean ± standard deviation), respectively. Therefore, the revealed length of the distal ICA was 14.9 ± 4.5 mm greater using the transstyloid diaphragm approach compared to the regular CEA approach. CONCLUSIONS: More of the ICA can be revealed by dissection of both the PBDM and the stylohyoid muscle. The transstyloid diaphragm approach might be helpful to reveal the distal ICA in cases of high cervical ICA stenosis.

KLC1-ROS1 Fusion Exerts Oncogenic Properties of Glioma Cells via Specific Activation of JAK-STAT Pathway.

Here, we investigated the detailed molecular oncogenic mechanisms of a novel receptor tyrosine kinase (RTK) fusion, KLC1-ROS1, with an adapter molecule, KLC1, and an RTK, ROS1, discovered in pediatric glioma, and we explored a novel therapeutic target for glioma that possesses oncogenic RTK fusion. When wild-type ROS1 and KLC1-ROS1 fusions were stably expressed in the human glioma cell lines A172 and U343MG, immunoblotting revealed that KLC1-ROS1 fusion specifically activated the JAK2-STAT3 pathway, a major RTK downstream signaling pathway, when compared with wild-type ROS1. Immunoprecipitation of the fractionated cell lysates revealed a more abundant association of the KLC1-ROS1 fusion with JAK2 than that observed for wild-type ROS1 in the cytosolic fraction. A mutagenesis study of the KLC1-ROS1 fusion protein demonstrated the fundamental roles of both the KLC1 and ROS1 domains in the constitutive activation of KLC1-ROS1 fusion. Additionally, in vitro assays demonstrated that KLC1-ROS1 fusion upregulated cell proliferation, invasion, and chemoresistance when compared to wild-type ROS1. Combination treatment with the chemotherapeutic agent temozolomide and an inhibitor of ROS1, JAK2, or a downstream target of STAT3, demonstrated antitumor effects against KLC1-ROS1 fusion-expressing glioma cells. Our results demonstrate that KLC1-ROS1 fusion exerts oncogenic activity through serum-independent constitutive activation, resulting in specific activation of the JAK-STAT pathway. Our data suggested that molecules other than RTKs may serve as novel therapeutic targets for RTK fusion in gliomas.

T-817MA, a neuroprotective agent, attenuates the motor and cognitive impairments associated with neuronal degeneration in P301L tau transgenic mice.

Tau pathology is implicated in mechanisms of neurodegenerative tauopathies, including Alzheimer's disease (AD) and hereditary frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). It has been reported that transgenic mice expressing FTDP-17 mutation P301L of human tau (P301L mice) display extensive tau pathology and exhibit behavioral deficits with aging. In this study, we investigated the effects of T-817MA, a neuroprotective agent, on the motor and cognitive impairments associated with neuronal degeneration in P301L mice. T-817MA prevented the progression of motor deficit and the loss of spinal cord motor neurons in P301L mice. Furthermore, T-817MA significantly attenuated the spatial memory impairment and the reduction in synaptic terminal density in the hippocampal dentate gyrus of P301L mice. These results indicate that T-817MA improved the motor and cognitive impairments as a result of inhibiting neuronal degeneration derived from tau pathology in the P301L mice. Therefore, it is expected that T-817MA has a therapeutic potential for tau-related neurodegenerative diseases such as AD.

Neuroprotective effects of T-817MA against noise-induced hearing loss.

Oxidative stress, including reactive oxygen species and other free radicals, is thought to play an important role in neuronal cell death, including noise-induced hearing loss. 1-{3-[2-(1-Benzothiophen-5-yl)ethoxy]propyl}azetidin-3-ol maleate (T-817MA), a novel neurotrophic agent, protects against oxidative stress-induced neurotoxicity. This study examines the effects of T-817MA in noise-induced ototoxicity in the cochlea. Guinea pigs received treatment with T-817MA-enhanced water (0.2, 0.7 mg/ml) or untreated water (control) beginning 10 days prior to noise exposure and continuing through this study. All subjects were exposed to 4-kHz octave-band noise at 120-dB SPL for 5h. Auditory thresholds were assessed by sound-evoked auditory brainstem response at 4, 8, and 16kHz, prior to and 10 days following noise exposure. Hair cell damage was analyzed by quantitative histology. T-817MA significantly reduced threshold deficits and hair cell death. These results suggest T-817MA reduces noise-induced hearing loss and cochlear damage, suggesting functional and morphological protection.