Spin wavepackets in the Kagome ferromagnet Fe3Sn2: Propagation and precursors.

The propagation of spin waves in magnetically ordered systems has emerged as a potential means to shuttle quantum information over large distances. Conventionally, the arrival time of a spin wavepacket at a distance, d, is assumed to be determined by its group velocity, vg. Here, we report time-resolved optical measurements of wavepacket propagation in the Kagome ferromagnet Fe3Sn2 that demonstrate the arrival of spin information at times significantly less than d/vg. We show that this spin wave "precursor" originates from the interaction of light with the unusual spectrum of magnetostatic modes in Fe3Sn2. Related effects may have far-reaching consequences toward realizing long-range, ultrafast spin wave transport in both ferromagnetic and antiferromagnetic systems.

The unexpected influence of legacy conspecific density dependence.

When plants die, neighbours escape competition. Living conspecifics could disproportionately benefit because they are freed from negative intraspecific processes; however, if the negative effects of past conspecific neighbours persist, other species might be advantaged, and diversity might be maintained through legacy effects. We examined legacy effects in a mapped forest by modelling the survival of 37,212 trees of 23 species using four neighbourhood properties: living conspecific, living heterospecific, legacy conspecific (dead conspecifics) and legacy heterospecific densities. Legacy conspecific effects proved nearly four times stronger than living conspecific effects; changes in annual survival associated with legacy conspecific density were 1.5% greater than living conspecific effects. Over 90% of species were negatively impacted by legacy conspecific density, compared to 47% by living conspecific density. Our results emphasize that legacies of trees alter community dynamics, revealing that prior research may have underestimated the strength of density dependent interactions by not considering legacy effects.

Two-Dimensional Cobalt(II) Benzoquinone Frameworks for Putative Kitaev Quantum Spin Liquid Candidates.

The realization and discovery of quantum spin liquid (QSL) candidate materials are crucial for exploring exotic quantum phenomena and applications associated with QSLs. Most existing metal-organic two-dimensional (2D) quantum spin liquid candidates have structures with spins arranged on the triangular or kagome lattices, whereas honeycomb-structured metal-organic compounds with QSL characteristics are rare. Here, we report the use of 2,5-dihydroxy-1,4-benzoquinone (X2dhbq, X = Cl, Br, H) as the linkers to construct cobalt(II) honeycomb lattices (NEt4)2[Co2(X2dhbq)3] as promising Kitaev-type QSL candidate materials. The high-spin d7 Co2+ has pseudospin-1/2 ground-state doublets, and benzoquinone-based linkers not only provide two separate superexchange pathways that create bond-dependent frustrated interactions but also allow for chemical tunability to mediate magnetic coupling. Our magnetization data show antiferromagnetic interactions between neighboring metal centers with Weiss constants from -5.1 to -8.5 K depending on the X functional group in X2dhbq linkers (X = Cl, Br, H). No magnetic transition or spin freezing could be observed down to 2 K. Low-temperature susceptibility (down to 0.3 K) and specific heat (down to 0.055 K) of (NEt4)2[Co2(H2dhbq)3] were further analyzed. Heat capacity measurements confirmed no long-range order down to 0.055 K, evidenced by the broad peak instead of the λ-like anomaly. Our results indicate that these 2D cobalt benzoquinone frameworks are promising Kitaev QSL candidates with chemical tunability through ligands that can vary the magnetic coupling and frustration.

A Lightweight and Efficient Method of Structural Damage Detection Using Stochastic Configuration Network.

With the advancement of neural networks, more and more neural networks are being applied to structural health monitoring systems (SHMSs). When an SHMS requires the integration of numerous neural networks, high-performance and low-latency networks are favored. This paper focuses on damage detection based on vibration signals. In contrast to traditional neural network approaches, this study utilizes a stochastic configuration network (SCN). An SCN is an incrementally learning network that randomly configures appropriate neurons based on data and errors. It is an emerging neural network that does not require predefined network structures and is not based on gradient descent. While SCNs dynamically define the network structure, they essentially function as fully connected neural networks that fail to capture the temporal properties of monitoring data effectively. Moreover, they suffer from inference time and computational cost issues. To enable faster and more accurate operation within the monitoring system, this paper introduces a stochastic convolutional feature extraction approach that does not rely on backpropagation. Additionally, a random node deletion algorithm is proposed to automatically prune redundant neurons in SCNs, addressing the issue of network node redundancy. Experimental results demonstrate that the feature extraction method improves accuracy by 30% compared to the original SCN, and the random node deletion algorithm removes approximately 10% of neurons.

Are the surface Fermi arcs in Dirac semimetals topologically protected?

Motivated by recent experiments probing anomalous surface states of Dirac semimetals (DSMs) Na3Bi and Cd3As2, we raise the question posed in the title. We find that, in marked contrast to Weyl semimetals, the gapless surface states of DSMs are not topologically protected in general, except on time-reversal-invariant planes of surface Brillouin zone. We first demonstrate this finding in a minimal four-band model with a pair of Dirac nodes at [Formula: see text] where gapless states on the side surfaces are protected only near [Formula: see text] We then validate our conclusions about the absence of a topological invariant protecting double Fermi arcs in DSMs, using a K-theory analysis for space groups of Na3Bi and Cd3As2 Generically, the arcs deform into a Fermi pocket, similar to the surface states of a topological insulator, and this pocket can merge into the projection of bulk Dirac Fermi surfaces as the chemical potential is varied. We make sharp predictions for the doping dependence of the surface states of a DSM that can be tested by angle-resolved photoemission spectroscopy and quantum oscillation experiments.

High-Temperature Majorana Corner States.

Majorana bound states often occur at the end of a 1D topological superconductor. Validated by a new bulk invariant and an intuitive edge argument, we show the emergence of one Majorana Kramers pair at each corner of a square-shaped 2D topological insulator proximitized by an s_{±}-wave (e.g., Fe-based) superconductor. We obtain a phase diagram that addresses the relaxation of crystal symmetry and edge orientation. We propose two experimental realizations in candidate materials. Our scheme offers a higher-order and higher-temperature route for exploring non-Abelian quasiparticles.

Strong and Tunable Spin-Lifetime Anisotropy in Dual-Gated Bilayer Graphene.

We report the discovery of a strong and tunable spin-lifetime anisotropy with excellent out-of-plane spin lifetimes up to 7.8 ns at 100 K in dual-gated bilayer graphene. Remarkably, this realizes the manipulation of spins in graphene by electrically controlled spin-orbit fields, which is unexpected due to graphene's weak intrinsic spin-orbit coupling (∼12 µeV). We utilize both the in-plane magnetic field Hanle precession and oblique Hanle precession measurements to directly compare the lifetimes of out-of-plane vs in-plane spins. We find that near the charge neutrality point, the application of a perpendicular electric field opens a band gap and generates an out-of-plane spin-orbit field that stabilizes out-of-plane spins against spin relaxation, leading to a large spin-lifetime anisotropy (defined as the ratio between out-of-plane and in-plane spin lifetime) up to ∼12 at 100 K. This intriguing behavior occurs because of the unique spin-valley coupled band structure of bilayer graphene. Our results demonstrate the potential for highly tunable spintronic devices based on dual-gated 2D materials.

Simulated microgravity increases myocardial susceptibility to ischemia-reperfusion injury via a deficiency of AMP-activated protein kinase.

Gravitation is an important factor in maintaining cardiac contractility. Our study investigated whether simulated microgravity increases myocardial susceptibility to ischemia-reperfusion (IR) injury. Using the Langendorff-perfused heart model with 300 beats/min pacing, 4-week tail suspension (SUS) and control (CON) male Sprague-Dawley rats (n = 10 rats/group) were subjected to 60 min of left anterior descending coronary artery (LAD) occlusion followed by 120 min of reperfusion. Left ventricular end-systolic pressure (LVESP), left ventricular end-diastolic pressure (LVEDP), creatine kinase (CK) and lactate dehydrogenase (LDH) activity, and infarct size were assessed. Data demonstrated that there were significantly increased LVEDP, CK, LDH, and infarct size in SUS compared with CON (P < 0.05), accompanied by decreased LVESP (P < 0.05). Furthermore, TUNEL-positive cardiomyocytes were higher in SUS than that in CON (P < 0.01), and AMP-activated protein kinase (AMPK) phosphorylation and Bcl-2/Bax in SUS were less compared with CON (P < 0.05). Similarly, isolated hearts pre-treated with A-769662 exhibited better recovery of cardiac function, increased AMPK phosphorylation, and reduced necrosis and apoptosis. Furthermore, AMPKα protein showed a significant suppression in 4-week hindlimb unweighting rats. These results suggest that AMPK deficiency increases myocardial susceptibility to IR injury in rats subjected to simulated microgravity.

Space Group Symmetry Fractionalization in a Chiral Kagome Heisenberg Antiferromagnet.

The anyonic excitations of a spin liquid can feature fractional quantum numbers under space group symmetries. Detecting these fractional quantum numbers, which are analogs of the fractional charge of Laughlin quasiparticles, may prove easier than the direct observation of anyonic braiding and statistics. Motivated by the recent numerical discovery of spin-liquid phases in the kagome Heisenberg antiferromagnet, we theoretically predict the pattern of space group symmetry fractionalization in the kagome lattice SO(3)-symmetric chiral spin liquid. We provide a method to detect these fractional quantum numbers in finite-size numerics which is simple to implement in the density matrix renormalization group. Applying these developments to the chiral spin liquid phase of a kagome Heisenberg model, we find perfect agreement between our theoretical prediction and numerical observations.

Topological spinon semimetals and gapless boundary states in three dimensions.

Recently, there has been much effort in understanding topological phases of matter with gapless bulk excitations, which are characterized by topological invariants and protected intrinsic boundary states. Here we show that topological semimetals of Majorana fermions arise in exactly solvable Kitaev spin models on a series of three-dimensional lattices. The ground states of these models are quantum spin liquids with gapless nodal spectra of bulk Majorana fermion excitations. It is shown that these phases are topologically stable as long as certain discrete symmetries are protected. The corresponding topological indices and the gapless boundary states are explicitly computed to support these results. In contrast to previous studies of noninteracting systems, the phases discussed in this work are novel examples of gapless topological phases in interacting spin systems.

Majorana fermions in spin-singlet nodal superconductors with coexisting noncollinear magnetic order.

Realizations of Majorana fermions in solid state materials have attracted great interest recently in connection to topological order and quantum information processing. We propose a novel way to create Majorana fermions in superconductors. We show that an incipient noncollinear magnetic order turns a spin-singlet superconductor with nodes into a topological superconductor with a stable Majorana bound state in the vortex core, at a topologically stable magnetic point defect, and on the edge. We argue that such an exotic non-Abelian phase can be realized in extended t-J models on the triangular and square lattices. It is promising to search for Majorana fermions in correlated electron materials where nodal superconductivity and magnetism are two common caricatures.

[In vitro heart models simulating in vivo cardiac ischemia-reperfusion injury].

The aim of this study was to compare in vivo and several in vitro cardiac ischemia-reperfusion (I-R) myocardial injury models, and choose a superior in vitro cardiac I-R model. Sprague-Dawley (SD) rats were randomly grouped into in vivo, Langendorff, Langendorff + pacing, and working heart groups. Left anterior descending (LAD) coronary artery was ligated for 60 min and then reperfused for 120 min in in vivo and in vitro rat hearts. Cardiac function and myocardial infarct size were measured by using pressure transducer and TTC/Evans blue double staining, respectively. The results showed that heart rate was greater in in vivo model than those in the three in vitro models. Coronary flows were dropped after LAD ligation and could recover at early phase of releasing LAD ligation in I-R models of the isolated working heart, Langendorff and Langendorff with 300 beats/min of electrical stimulation. Left ventricular end-systolic pressure (LVESP) decreased during ischemia, and partially restored during reperfusion in the three in vitro models. Left ventricular end-diastolic pressure (LVEDP) increased during ischemia in the three in vitro models. LVEDP was significantly higher in the isolated working heart than those in Langendorff models during ischemia, whereafter decreased slowly during reperfusion. LVEDP elevated further in the initiation of reperfusion period and then decreased, but did not recover to normal levels during reperfusion in Langendorff and Langendorff + pacing groups. Left ventricular myocardial infarct size was (60.4 ± 5.4)% in in vivo I-R model, which was significantly higher than that in Langendorff model and the isolated working heart. Notably, there was no significant difference in myocardial infarct size between in vivo model and Langendorff model with electrical stimulation. These results suggest that Langendorff I-R model with 300 beats/min of electrical stimulation can simulate the in vivo I-R myocardial injury.

[Four-week simulated weightlessness increases the expression of atrial natriuretic peptide in the myocardium].

One of the major circulatory changes that occur in human during space flight and simulated weightlessness is a cerebral redistribution of body fluids, which is accompanied by an increase of blood volume in the upper body. Therefore, atrial myocardium should increase the secretion of atrial natriuretic peptide (ANP), but the researches lack common conclusion until now. The present study was to investigate the expression level of ANP in simulated weightlessness rats, and to confirm the changes of ANP by observing the associated proteins of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). The tail-suspended rat model was used to simulate weightlessness. Western blots were carried out to examine the expression levels of ANP and SNARE proteins in atrial and left ventricular myocardium. The results showed that ANP expression in atrial myocardium showed an increase in 4-week tail-suspended rats (SUS) compared with that in the synchronous control rats (CON). We only detected a trace amount of ANP in the left ventricular myocardium of the CON, but found an enhanced expression of ANP in left ventricular myocardium of the SUS. Expression of VAMP-1/2 (vesicle associated SNARE) increased significantly in both atrial and left ventricular myocardium in the SUS compared with that in the CON. There was no difference of the expression of syntaxin-4 (target compartment associated SNARE) between the CON and SUS, but the expression of SNAP-23 showed an increase in atrial myocardium of the SUS compared with that in the CON. Synip and Munc-18c as regulators of SNAREs did not show significant difference between the CON and SUS. These results suggest that the expression of ANP shows an increase in atrial and left ventricular myocardium of 4-week tail-suspended rats. Enhanced expression of VAMP-1/2 associated with ANP vesicles confirms the increased expression of ANP in atrial and left ventricular myocardium.

An efficient material search for room-temperature topological magnons.

Topologically protected magnon surface states are highly desirable as an ideal platform to engineer low-dissipation spintronics devices. However, theoretical prediction of topological magnons in strongly correlated materials proves to be challenging because the ab initio density functional theory calculations fail to reliably predict magnetic interactions in correlated materials. Here, we present a symmetry-based approach, which predicts topological magnons in magnetically ordered crystals, upon applying external perturbations such as magnetic/electric fields and/or mechanical strains. We apply this approach to carry out an efficient search for magnetic materials in the Bilbao Crystallographic Server, where, among 198 compounds with an over 300-K transition temperature, we identify 12 magnetic insulators that support room-temperature topological magnons. They feature Weyl magnons with surface magnon arcs and magnon axion insulators with either chiral surface or hinge magnon modes, offering a route to realize energy-efficient devices based on protected surface magnons.

miR-10a induces inflammatory responses in epileptic hippocampal neurons of rats via PI3K/Akt/mTOR signaling pathway.

Epilepsy is a common chronic neurological disorder worldwide. MicroRNAs (miRNAs) play an important role in the pathogenesis of epilepsy. However, the mechanism of the regulatory effect of miR-10a on epilepsy is unclear. In this study, we investigated the effect of miR-10a expression on the PI3K/Akt/mTOR signaling pathway and inflammatory cytokines in epileptic hippocampal neurons of rats. The miRNA differential expression profile of rat epileptic brain was analyzed using bioinformatic approaches. Neonatal Sprague-Dawley rat hippocampal neurons were prepared as epileptic neuron models in vitro by replacing culture medium with magnesium-free extracellular solution. The hippocampal neurons were transfected with miR-10a mimics, and transcript levels of miR-10a, PI3K, Akt and mTOR were detected by quantitative reverse transcription-PCR, and PI3K, mTOR, Akt, TNF-α, IL-1ß, IL-6 protein expression levels were detected by Western blot. Cytokines secretory levels were detected by ELISA. Sixty up-regulated miRNAs were identified in the hippocampal tissue of epileptic rats and might affect the PI3K-Akt signaling pathway. In the epileptic hippocampal neurons model, the expression levels of miR-10a were significantly increased, with decreasing levels of PI3K, Akt and mTOR, and increasing levels of TNF-α, IL-1ß and IL-6. The miR-10a mimics promoted the expression of TNF-α, IL-1ß and IL-6. Meanwhile, miR-10a inhibitor activated PI3K/Akt/mTOR pathway and inhibited cytokines secretion. Finally, cytokine secretion was increased by treated with PI3K inhibitor and miR-10a inhibitor. The miR-10a may promote inflammatory responses in rat hippocampal neurons by inhibiting the PI3K/Akt/mTOR pathway, suggesting that miR-10a may be one of the target therapeutic molecules for epilepsy treatment.

A systematic protocol for the characterization of Hsp90 modulators.

Several Hsp90 modulators have been identified including the N-terminal ligand geldanamycin (GDA), the C-terminal ligand novobiocin (NB), and the co-chaperone disruptor celastrol. Other Hsp90 modulators elicit a mechanism of action that remains unknown. For example, the natural product gedunin and the synthetic anti-spermatogenic agent H2-gamendazole, recently identified Hsp90 modulators, manifest biological activity through undefined mechanisms. Herein, we report a series of biochemical techniques used to classify such modulators into identifiable categories. Such studies provided evidence that gedunin and H2-gamendazole both modulate Hsp90 via a mechanism similar to celastrol, and unlike NB or GDA.

Correlation-hole induced paired quantum Hall states in the lowest Landau level.

A theory is developed for the paired even-denominator fractional quantum Hall states in the lowest Landau level. We show that electrons bind to quantized vortices to form composite fermions, interacting through an exact instantaneous interaction that favors chiral p-wave pairing. There are two canonically dual pairing gap functions related by the bosonic Laughlin wave function (Jastrow factor) due to the correlation holes. We find that the ground state is the Moore-Read Pfaffian in the long-wavelength limit for weak Coulomb interactions, a new Pfaffian with an oscillatory pairing function for intermediate interactions, and a Read-Rezayi composite Fermi liquid beyond a critical interaction strength. Our findings are consistent with recent experimental observations of the 1/2 and 1/4 fractional quantum Hall effects in asymmetric wide quantum wells.

Deaths of colon neuroendocrine tumors are associated with increasing metastatic lymph nodes and lymph node ratio.

BACKGROUND: Colon neuroendocrine tumors (NETs) are uncommon. Currently, the impact of the number of metastatic lymph nodes (LNs) and lymph node ratio (LNR) on survival has been well investigated in other colon malignancies, but both remain nebulous for patients with colon NETs. METHODS: Surgically resected patients with histologically proven nonmetastatic colon NETs were queried from the Surveillance, Epidemiology, and End Results database between 1988 and 2011. Patients with lymph nodes involved were investigated and categorized into four LNs-based classifications (≤4, >4-10, >10-13, and >13) or three LNR-based subgroups (≤0.51, >0.51-0.71, and >0.71) according to the threshold, determined by Harrell's C statistic. Univariate and multivariate survival analyses were performed by log-rank test and Cox stepwise regression analysis, respectively. RESULTS: Eight hundred fifty-one patients met the inclusion criteria. Among them, higher LNR and LNs classification are associated with a worse prognosis. The 10-year NETs-specific survival rate was 78.3% (74.2-82.6%), 61.3% (52.4-71.7%), 40.8% (20.7-80.7%) for patients in the ≤4, >4-10, and 10-13 LNs groups, respectively. When patients were classified with LNR, the observed 10-year NETs-specific survival rate was 79.9% (74.8-85.5%) for ≤0.51, 57.4% (43.8-75.2%) for >0.51-0.71, and 40.0% (31.0-51.5%) for >0.71. In stratified analysis, higher LNs and LNR groups have worse prognosis only in patients with advanced T stage (T3-T4). Regarding stage migration, the LNR-based system did not show superiority to LNs-based classification. CONCLUSIONS: Current TNM staging classification could be improved by considering the count of metastatic nodes and LNR instead of a simple record of lymph node status (N1 or N0) for colon NETs.

The effect of hormonal levels and oxidative stress on bisphenol A and soy isoflavone reproductive toxicity in murine offspring.

Previous studies have suggested that human exposure to bisphenol A (BPA) and soy isoflavones (SIFs) can occur during pregnancy. The combination of these chemicals is hypothesized to have a toxic impact on the fetus. While BPA is an industrial chemical used widely in the manufacture of polycarbonate plastics and epoxy resins, SIFs are naturally occurring estrogen­like phytoestrogens. To determine the impact of the combination of BPA and SIFs on fetal development, the body weight, organ weight, anogenital distance and histopathological changes in the testes of F1 offspring were assessed in mice. Hormonal effects were determined by measuring serum levels of estrogen receptor (ESR), follicle­stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T). Additionally, mitochondrial DNA copy numbers, and the serum levels of malondialdehyde and superoxide dismutase, were determined to evaluate alterations in oxidative stress and potential toxicity. Exposure to BPA increased the body weight of the pups and reduced the ratio of anogenital distance to body weight, as well as testes weight. Moreover, BPA exposure also induced testicular lesions. The seminiferous tubules of testis were denatured in varying degrees and the lumen wall structure was disordered. The levels of ESR in all offspring and the T levels in male offspring significantly increased, compared with controls. Co­exposure to BPA and SIFs exacerbated these changes in body weight, testicular lesions and hormonal levels, relative to BPA exposure alone. Additionally, oxidative damage was only induced by high­dose BPA. Collectively, these findings suggested that BPA and SIFs could have synergistic effect on the reproductive system, which could be mediated by the regulation of ESR expression and testosterone release.

Distinct magneto-Raman signatures of spin-flip phase transitions in CrI3.

The discovery of 2-dimensional (2D) materials, such as CrI3, that retain magnetic ordering at monolayer thickness has resulted in a surge of both pure and applied research in 2D magnetism. Here, we report a magneto-Raman spectroscopy study on multilayered CrI3, focusing on two additional features in the spectra that appear below the magnetic ordering temperature and were previously assigned to high frequency magnons. Instead, we conclude these modes are actually zone-folded phonons. We observe a striking evolution of the Raman spectra with increasing magnetic field applied perpendicular to the atomic layers in which clear, sudden changes in intensities of the modes are attributed to the interlayer ordering changing from antiferromagnetic to ferromagnetic at a critical magnetic field. Our work highlights the sensitivity of the Raman modes to weak interlayer spin ordering in CrI3.