High Simulation Training System for Spinal Full-Endoscopic Surgery, Based on the Combination of VR/AR and Magneto-Optical Navigation Technology.

Objective: Spinal full-endoscopic surgery is a challenging technique with a steep learning curve, limited by inadequate training models and the shortcomings of cadaver-based training. To address this, we propose a high-simulation training system using VR/AR and magneto-optical navigation technology to enhance skill development and reduce the learning curve.

Methods: A new simulation training system for spinal full-endoscopic surgery was established, which was conducted by using the data of Chinese Digital Human with medical image parameters for the three-dimensional (3D) reconstruction, as well as integrating the technical advantages of VR/AR, 3D printing, and magneto-optical navigation technology.

Ferroelectricity with concomitant Coulomb screening in van der Waals heterostructures.

Interfacial ferroelectricity emerges in non-centrosymmetric heterostructures consisting of non-polar van der Waals (vdW) layers. Ferroelectricity with concomitant Coulomb screening can switch topological currents or superconductivity and simulate synaptic response. So far, it has only been realized in bilayer graphene moiré superlattices, posing stringent requirements to constituent materials and twist angles.

Single Molecular Semi-Sliding Ferroelectricity/Multiferroicity.

In recent years, the unique mechanism of sliding ferroelectricity with ultralow switching barriers has been experimentally verified in a series of 2-dimensional (2D) materials. However, its practical applications are hindered by the low polarizations, the challenges in synthesis of ferroelectric phases limited in specific stacking configurations, and the low density for data storage since the switching process involves large-area simultaneous sliding of a whole layer. Herein, through first-principles calculations, we propose a type of semi-sliding ferroelectricity in the single metal porphyrin molecule intercalated in 2D bilayers.

Facile Coordination Transitions in AgCrX (X = S, Se): Unprecedented Electrostrain, Negative Piezoelectricity and Thermal Expansion.

The coefficients of piezoelectricity and thermal expansion are generally positive due to the bond anharmonicity. For converse piezoelectricity, the electrostrain obtained in prevalent ceramics is only around 1%. Here we propose that the coordination transition of metal cations may make a paradigm shift.

Quantized ferroelectricity in multivalent ion conductors with non-polar point groups.

Ferroelectricity with switchable polarizations is generally associated with small ion-displacements and occurs only in 10 specific polar point groups, which is not a necessary requirement for ion conduction where the ions can also be electrically displaced but by much longer distances. Herein, through first-principles calculations, we predict the formation of unconventional ferroelectricity based on previous experimental reports on topotactic reaction with an aliovalent cation between trigonal layers of ion conductors. In such systems, the multivalent cations are surrounded by vacant sites that can simultaneously migrate by a much larger distance compared with conventional displacive ferroelectricity, giving rise to a quantized change in polarization even if the crystal lattices do not belong to the 10 polar groups.

Bevel-edge epitaxy of ferroelectric rhombohedral boron nitride single crystal.

Within the family of two-dimensional dielectrics, rhombohedral boron nitride (rBN) is considerably promising owing to having not only the superior properties of hexagonal boron nitride-including low permittivity and dissipation, strong electrical insulation, good chemical stability, high thermal conductivity and atomic flatness without dangling bonds-but also useful optical nonlinearity and interfacial ferroelectricity originating from the broken in-plane and out-of-plane centrosymmetry. However, the preparation of large-sized single-crystal rBN layers remains a challenge, owing to the requisite unprecedented growth controls to coordinate the lattice orientation of each layer and the sliding vector of every interface. Here we report a facile methodology using bevel-edge epitaxy to prepare centimetre-sized single-crystal rBN layers with exact interlayer ABC stacking on a vicinal nickel surface.

An inorganic liquid crystalline dispersion with 2D ferroelectric moieties.

Electro-optical effect-based liquid crystal devices have been extensively used in optical modulation techniques, in which the Kerr coefficient reflects the sensitivity of the liquid crystals and determines the strength of the device's operational electric field. The Peterlin-Stuart theory and the O'Konski model jointly indicate that a giant Kerr coefficient could be obtained in a material with both a large geometrical anisotropy and an intrinsic polarization, but such a material is not yet reported. Here we reveal a ferroelectric effect in a monolayer two-dimensional mineral vermiculite.

Letter to the editor.

We review the study by Xu et al. (J Clin Monit Comput 37(4):985-992, 2023. https://doi.

Atypical Sliding and Moiré Ferroelectricity in Pure Multilayer Graphene.

Most nonferroelectric two-dimensional materials can be endowed with so-called sliding ferroelectricity via nonequivalent homobilayer stacking, which is not applicable to monoelement systems like pure graphene bilayer with inversion symmetry at any sliding vector. Herein, we show first-principles evidence that multilayer graphene with N>3 can all be ferroelectric, where the polarizations of polar states stem from the symmetry breaking in stacking configurations of across layer instead of adjacent layer, which are electrically switchable via interlayer sliding. The nonpolar states can also be electrically driven to polar states via sliding, and more diverse states with distinct polarizations will emerge in more layers.

Exploitation of mixed-valency chemistry for designing a monolayer with double ferroelectricity and triferroic couplings.

Mixed-valence compounds possess both intriguing chemical and physical properties such as the intervalence charge transfer band and thus have been excellent model systems for the investigation of fundamental electron- and charge-transfer phenomena. Herein, we show that valence stratification can be a source of symmetry breaking and generating ferroelectricity in two-dimensional (2D) materials. We present computation evidence of the monolayer CuCl structure with Cu ions being stratified into two separated layers of Cu(I) and Cu(II).

Two-Dimensional Ultrahigh Unconventional Piezoelectricity Driven by Charge Screening.

In the past decade, piezoelectricity has been explored in a series of two-dimensional (2D) materials for nanoelectromechanical applications, while their piezoelectric coefficients are mostly much lower than those of prevalent piezoceramics. In this paper, we propose an unconventional approach of inducing 2D ultrahigh piezoelectricity dominated by charge screening instead of lattice distortion and show the first-principles evidence of such piezoelectricity in a series of 2D van der Waals bilayers, where the bandgap can be remarkably tuned via applying a moderate vertical pressure. Their polarizations can switch between the screened and unscreened state by a pressure-driven metal-insulator transition, which can be realized via tuning interlayer hybridization or inhomogeneous electrostatic potential by substrate layer to change the band splitting or tuning the relative energy shift between bands utilizing the vertical polarization of the substrate layer.

Covalent-like bondings and abnormal formation of ferroelectric structures in binary ionic salts.

In the Mooser-Pearson diagram, binary ionic compoundss form into nonpolar symmetrical structures with high coordination numbers, while wurtzite structures should appear in the covalent region. Their tetrahedral bonding configurations break the inversion symmetry, with polarizations almost unswitchable due to the high barriers of abrupt breaking and reformation of covalent bonds. Here, through first-principles calculations, we find some exceptional cases of highly ionic ferroelectric binary salts such as lithium halides, which may form into wurtzite structures with covalent-like sp bondings, and the origin of these abnormal formations is clarified.

Spatially Resolved Polarization Manipulation of Ferroelectricity in Twisted hBN.

Robust room-temperature interfacial ferroelectricity has been formed in the 2D limit by simply twisting two atomic layers of non-ferroelectric hexagonal boron nitride (hBN). A thorough understanding of this newly discovered ferroelectric system is required. Here, twisted hBN is used as a tunneling junction and it is studied at the nanometer scale using conductive atomic force microscopy.

Giant ferroelectric polarization in a bilayer graphene heterostructure.

At the interface of van der Waals heterostructures, the crystal symmetry and the electronic structure can be reconstructed, giving rise to physical properties superior to or absent in parent materials. Here by studying a Bernal bilayer graphene moiré superlattice encapsulated by 30°-twisted boron nitride flakes, we report an unprecedented ferroelectric polarization with the areal charge density up to 10cm, which is far beyond the capacity of a moiré band. The translated polarization ~5 pC m is among the highest interfacial ferroelectrics engineered by artificially stacking van der Waals crystals.

Unconventional Ferroelectricity with Quantized Polarizations in Ionic Conductors: High-Throughput Screening.

Ferroelectricity is generally a displacive phenomenon within a unit cell in which ions are placed asymmetrically. In ionic conductors, ions can also be electrically displaced but by much longer distances. They are mostly nonpolar with symmetrical lattices due to the nondirectional character of ionic bondings.

High- Two-Dimensional Ferroelectric CuCrS Grown Chemical Vapor Deposition.

Two-dimensional (2D) ferroelectrics have attracted intensive attention. However, the 2D ferroelectrics remain rare, and especially few of them represent high ferroelectric transition temperature (), which is important for the usability of ferroelectrics. Herein, CuCrS nanoflakes are synthesized by salt-assisted chemical vapor deposition and exhibit switchable ferroelectric polarization even when the thickness is downscaled to 6 nm.

Optimal prophylactic para-aortic radiotherapy in locally advanced cervical cancer: anatomy-based versus margin-based delineation.

Objective: Precise delineation of the para-aortic nodal region is critical for the optimal therapeutic ratio of prophylactic para-aortic radiotherapy. We aimed to evaluate the para-aortic control and patient-reported gastrointestinal toxicity in patients with locally advanced cervical cancer who received anatomy-based or margin-based prophylactic para-aortic radiotherapy.

Methods: We analyzed 160 patients with locally advanced cervical cancer who received prophylactic extended-field radiotherapy between January 2014 and November 2019 at two tertiary centers.

Progressive Skeletal Muscle Loss After Surgery and Adjuvant Radiotherapy Impact Survival Outcomes in Patients With Early Stage Cervical Cancer.

The effect of skeletal muscle loss associated with surgery and adjuvant radiotherapy on survival outcomes in patients with early-stage cervical cancer remains unclear. We analyzed the data of 133 patients with early-stage cervical cancer who underwent surgery and adjuvant radiotherapy between 2013 and 2018 at two tertiary centers. Skeletal muscle changes were measured using computed tomography scans at baseline, at simulation for radiotherapy, and at 3 months post-treatment.

SbCl: An Exceptional Superhalogen as the Building Block of a Mixed Valence Supercrystal with Unconventional Ferroelectricity.

Superhalogens are nanoclusters with high electron affinities, exhibiting behavior similar to that of halogens. Their dimerization yields nonpolar symmetrical clusters, akin to diatomic halogen molecules, and they are unstable in the condensed phase in the absence of charge-compensating cations. Herein, we provide evidence that SbCl superhalogen is an exception: its dimerization yields a polar cluster that can be viewed as a quasi-bonded [SbCl] and [SbCl] Lewis acid-base cluster.

A multiferroic vanadium phosphide monolayer with ferromagnetic half-metallicity and topological Dirac states.

Ferroelasticity, ferromagnetism, half-metallicity, and topological Dirac states are properties highly sought in two-dimensional (2D) materials for advanced device applications. Here, we report first-principles prediction of a dynamically and thermally stable tetragonal vanadium phosphide (t-VP) monolayer that hosts all these desirable properties. This monolayer is substantially ferromagnetic with polarized spins aligned in the in-plane direction a dpd super-exchange coupling mechanism; meanwhile, its tetragonal lattice enables an intrinsic in-plane ferroelasticity with a reversible strain of 23.

Sliding ferroelectricity in 2D van der Waals materials: Related physics and future opportunities.

Near the 100th anniversary of the discovery of ferroelectricity, so-called sliding ferroelectricity has been proposed and confirmed recently in a series of experiments that have stimulated remarkable interest. Such ferroelectricity exists widely and exists only in two-dimensional (2D) van der Waals stacked layers, where the vertical electric polarization is switched by in-plane interlayer sliding. Reciprocally, interlayer sliding and the "ripplocation" domain wall can be driven by an external vertical electric field.