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Cerebellar hemangioblastomas with pregnancy is rare, but coexistence of pregnancy and recurrent cerebellar hemangioblastomas is rather rare. And coexistence of other diseases during pregnancy usually leads to misdiagnosis because of pregnancy reaction. A 29-year-old woman, at the 8th week of pregnancy, complained of nausea, vomiting, and episodic posterior occipital pain and was misdiagnosed pregnancy reaction without any special treatment during her several visits to local hospital. The patient was diagnosed cerebellar hemangioblastomas 14 years ago, after surgery, she received regular re-examination without recurrence. At the 15th week of pregnancy, the situation of the patient got worse, and she was admitted to our hospital. Brain magnetic resonance imaging showed a lesion in cerebellum. It was considered to be cerebellar hemangioblastomas and was confirmed finally by postoperative pathological examination. In clinical practice, differential diagnosis is of great importance during pregnancy because many other diseases can mimic pregnancy reaction. In this patient, the intracranial hypertension caused by recurrent cerebellar hemangioblastomas was misdiagnosed as pregnancy reaction and it was suggested that the change of hormones, neuroendocrine, and cardiovascular function promoted the recurrence of cerebellar hemangioblastomas.

Optical fine-tunable layer-hybridized Moiré excitons are highly in demand for emerging many-body states in two-dimensional semiconductors. We report naturally confined layer-hybridized bright Moiré excitons with long lifetimes in twisted hexagonal GaTe bilayers, using ab initio many-body perturbation theory and the Bethe–Salpeter equation. Due to the hybridization of electrons and holes between layers, which enhances the brightness of excitons, the twisted bilayer system becomes attractive for optical applications. We find that in both R and H-type stacking Moiré superlattices, more than 200 meV lateral quantum confinements occur on exciton energies, which results in two scenarios: (1) The ground state bright excitons XA are found to be trapped at two high-symmetry points, with opposite electric dipoles in the R-stacking Moiré supercell, forming a honeycomb superlattice of nearest-neighbor dipolar attraction. (2) For H-stacking case, the XA is found to be trapped at only one high-symmetry point exhibiting a triangular superlattice. Our results suggest that twisted h-GaTe bilayer is one of the promising systems for optical fine-tunable excitonic devices and provide an ideal platform for realizing strong correlated Bose–Hubbard physics.

Modern laboratory techniques like ultrafast laser excitation and shock compression can bring matter into highly nonequilibrium states with complex structural transformation, metallization and dissociation dynamics. To understand and model the dramatic change of both electronic structures and ion dynamics during such dynamic processes, the traditional method faces difficulties. Here, we demonstrate the ability of deep neural network (DNN) to capture the atomic local-environment dependence of electronic density of states (DOS) for both multicomponent system under exoplanet thermodynamic condition and nonequilibrium system during super-heated melting process. Large scale and time-resolved diagnosis of DOS can be efficiently achieved within the accuracy of ab initio method. Moreover, the atomic contribution to DOS given by DNN model accurately reveals the information of local neighborhood for selected atom, thus can serve as robust order parameters to identify different phases and intermediate local structures, strongly highlights the efficacy of this DNN model in studying dynamic processes., Comment: 7 Figures, accepted by PRB

The newly synthesized two-dimensional polyaniline (C3N) of graphene family attracted extensive research attention due to extraordinary electrical and electron-related properties, but its thermal properties have still been in its infancy although the thermal management is of critical importance for the performance and reliability of electron-related devices. Herein, we investigated the thermal transport properties of single-layer C3N with different system size by utilizing non-equilibrium molecular dynamics simulations. Compared with the graphene, the analysis of lattice dynamics and electron density distribution revealed that the lower thermal conductivity of single-layer C3N stems from the disorders from mass difference and the polarization from asymmetric electrical difference density. Moreover, the temperature dependence of thermal conductivity of single-layer C3N approaches κ ∼ T−1 when the system size increases. Our studies provide more physical insights into the thermal transport of emerging two-dimensional polymeric carbon nitride materials.

Exploring the novel structural phase of van der Waals (vdW) magnets would promote the development of spintronics. Here, through first-principles calculations, we report a novel monoclinic structure of vdW layered 1T-CrTe2, which is one of the popular vdW magnets normally exhibiting a trigonal structure. The new monoclinic phase emerges from a switchable magnetic state between ferromagnetism and antiferromagnetism through changing hole doping concentration, which suggests a practical approach to obtain such a structure. The results of phonon dispersion and energy analysis convince us that the monoclinic structure is a metastable phase even without hole doping. When the hole doping concentration increases, the stability analysis indicates the preference for a novel monoclinic phase rather than a conventional trigonal phase, and meanwhile, the magnetic properties are accordingly tuned. This work provides new insights into the phase engineering of the chalcogenide family and the electrical control of magnetism of vdW layered magnets.

The thermal switch is a device that can modulate the heat flux and create a huge gap between the “On” and “Off” state, which has been widely used in many applications. However, owing to weak biocom...

Lattice thermal conductivity (κ lat) of MgSiO3 perovskite and post-perovskite is an important parameter for the thermal dynamics in the Earth. Here, we develop a deep potential of density functional theory quality under entire thermodynamic conditions in the lower mantle, and calculate the κ lat by the Green–Kubo relation. Deep potential molecular dynamics captures full-order anharmonicity and considers ill-defined phonons in low-κ lat materials ignored in the phonon gas model. The κ lat shows negative temperature dependence and positive linear pressure dependence. Interestingly, the κ lat undergos an increase at the phase boundary from perovskite to post-perovskite. We demonstrate that, along the geotherm, the κ lat increases by 18.2% at the phase boundary. Our results would be helpful for evaluating Earth’s thermal dynamics and improving the Earth model.

Ion dynamics exhibits inherent multiscale characteristics because it contains both atomistic and hydrodynamic behaviors. Although atomic-scale ab initio molecular dynamics is the subject of intense research on warm dense matter, the macroscopic relaxation process contained in the zero-frequency mode of the ionic dynamic structure factor (DSF) cannot be demonstrated due to the limitation of simulation sizes. Here, we fill this gap via the machine-learning deep potential method. To capture the ion dynamics near the hydrodynamic limit with ab initio accuracy, an accurate and efficient electron-temperature-dependent interatomic potential was constructed. We quantitatively verify the consistency of thermal diffusivities obtained from hydrodynamics and the fluctuation-dissipation theorem and further provide a microscopic perspective of energy transport to understand the zero-frequency mode of DSF. As implemented in two temperature states, a competitive mechanism is found to account for the damping of the zero-frequency mode.

Stacking order plays a central role in governing a wide range of properties in layered two-dimensional materials. In the case of few-layer graphene, there are two common stacking configurations: ABA and ABC stacking, which have been proven to exhibit dramatically different electronic properties. However, the controllable characterization and manipulation between them remain a great challenge. Here, we report that ABA- and ABC-stacked domains can be directly visualized in phase imaging by tapping-mode atomic force microscopy with much higher spatial resolution than conventional optical spectroscopy. The contrasting phase is caused by the different energy dissipation by the tip-sample interaction. We further demonstrate controllable manipulation on the ABA/ABC domain walls by means of propagating stress transverse waves generated by the tapping of tip. Our results offer a reliable strategy for direct imaging and precise control of the atomic structures in few-layer graphene, which can be extended to other two-dimensional materials.

In this paper, we investigate a user scheduling algorithm for massive multiple-input multiple-output (MIMO) systems over more general correlated Rician fading channels. To achieve low latency and high throughput, a new user scheduling algorithm based on deep learning (DL) is proposed, which exploits only statistical channel state information. The proposed scheduling network is trained to grasp the mapping from the statistical signal and interference pattern to the user scheduling decision through supervised learning. It can predict the optimal scheduling scheme from statistical CSI without iterative calculation after offline training. Simulation results demonstrate the superior performance of the proposed algorithm in terms of calculation time, and it achieves almost the same throughput as the optimal scheduling algorithm which is obtained through exhaustive search. Furthermore, with the normalization of the input data, the proposed scheduling network is robust to the change of the channel environment and the number of transmit antennas.

Understanding thermal transport in doped organic semiconductors would promote the development of flexible electronics and organic thermoelectrics. Temperature-dependent thermal conductivity of poly...

Neuronal apoptosis is a regulated intrinsic cell mechanism and common pathological phenomenon after seizures, which involves the protein kinase B/cAMP response element binding protein / brain derived neurotrophic factor (AKT/CREB/ BDNF) signaling pathway. In this study, we aimed to identify the effects of salvianolic acid B (Sal B), a major water-soluble component of the Chinese herb, Danshen, on rats in which seizures had been induced by pentylenetetrazole (PTZ) and the underlying molecular mechanisms mediating these effects. For this, 60 adult male Sprague-Dawley rats were divided into a control group, a ‘PTZ’ group and a ‘PTZ + Sal B’ group. The animals in the control group received an intraperitoneal (i.p.) injection of saline on alternate days for a total of 15 injections and saline orally once a day for 29 days. The animals in the ‘PTZ’ group received PTZ (40 mg/kg, i.p.) on alternate days for a total of 15 injections and saline orally once a day for 29 days. Similarly, the animals in the ‘PTZ + Sal B’ group received PTZ (40 mg/kg, i.p.) on alternate days and Sal B (20 mg/kg) orally once a day for 29 days. Neural density was then evaluated using immunofluorescence (IF) staining of microtubule-associated protein 2 (MAP2). Neuronal apoptosis was detected using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining. In addition, the expression of several proteins related to AKT/CREB/BDNF signaling was measured using Western blotting. The results indicated that more severe seizures, decreased neural density, decreased expression of Bcl-2, increased expression of Bax and cleaved caspase-3, and inactivation of AKT/CREB/BDNF signaling occurred in the ‘PTZ’ group in comparison with the control group. However, those changes were suppressed by Sal B. Thus, these data suggest that Sal B has anticonvulsant and anti-apoptotic effects in a PTZ-induced seizure model through activation of the AKT/CREB/BDNF signaling pathways.

In this paper, we investigate the downlink transmission for full-dimension multiple-input multiple-output (FD-MIMO) systems over correlated Rician fading channels. With only statistical channel state information at the BS, the beamforming vectors of each user are decoupled from each other through the maximization of average signal-to-leakage-plus-noise ratio (SLNR) lower bound, and the optimal beamforming vector which involves the line-of-sight component and correlation matrix of both directions is derived. To reduce the time of acquiring the beamforming vector for each user, a deep learning (DL)-based algorithm is proposed. A sub-optimal analytical beamforming algorithm is also proposed for comparison. Based on the proposed beamforming method, the ergodic rate of each user is analyzed and simple closed-form approximations are derived, which are very useful in evaluating the system performance and user scheduling. Moreover, two user scheduling algorithms referred to as most dissimilar and minimum interference-to-signal factor algorithm are proposed, which greatly reduce the complexity compared to the sum rate based greedy scheduling algorithm. Simulation results validate the performance of the proposed beamforming and scheduling algorithms, and verify the accuracy of the derived ergodic rate approximations.

Organic thermoelectric (TE) materials provide a brand new perspective to search for high-efficiency TE materials, due to their low thermal conductivity. The overlap of pz orbitals, commonly existing in organic π-stacking semiconductors, can potentially result in high electron mobility comparable to that of inorganic materials. Here we propose a strategy to utilize the overlap of pz orbitals to increase the TE efficiency of a layered polymeric carbon nitride (PCN). Through first-principles calculations and classical molecular dynamics simulations, we find that an A–A stacked PCN has unexpectedly high cross-plane ZT up to 0.52 at 300 K, and can contribute to n-type TE groups. The high ZT originates from its one-dimensional charge transport and low thermal conductivity. The thermal contribution of the overlap of pz orbitals is investigated, which slightly enhances the thermal transport when compared with that without considering the overlap effect. That is, there is a limited influence of orbital overlap to thermal conductivity. To explore the physical insight behind its TE advantages, we find that the low-dimensional charge transport results from strong pz-overlap interactions and the in-plane electron confinement, by comparing π-stacking carbon nitride derivatives and graphite. This study can provide guidance to search for layered materials with high cross-plane TE performance.

Exploring the mechanism of interfacial thermal transport and reducing the interfacial thermal resistance are of great importance for thermal management and modulation. Herein, the interfacial thermal resistance between overlapped graphene nanoribbons is largely reduced by adding bonded carbon chains as shown by molecular dynamics simulations. And the analytical model (phonon weak couplings model, PWCM) is utilized to analyze and explain the two-dimensional thermal transport mechanism at the cross-interface. An order of magnitude reduction of the interfacial thermal resistance is found as the graphene nanoribbons are bonded by just one carbon chain. Interestingly, the decreasing rate of the interfacial thermal resistance slows down gradually with the increasing number of carbon chains, which can be explained by the proposed theoretical relationship based on analytical model. Moreover, by the comparison of PWCM and the traditional simplified model, the accuracy of PWCM is demonstrated in the overlapped graphene nanoribbons. This work provides a new way to improve the interfacial thermal transport and reveal the essential mechanism for low-dimensional materials applied in thermal management.

Phonon engineering focuses on heat transport modulation in atomic-scale. Different from reported methods, it is shown that electric field can also modulate heat transport in ferroelectric polymers, poly(vinylidene fluoride), by both simulation and measurement. Interestingly, the thermal conductivities of poly(vinylidene fluoride) array can be enhanced by a factor of 3.25 along the polarization direction by simulation. The thermal conductivities of semi-crystalline poly(vinylidene fluoride) film can be also enhanced by a factor of 1.5 which is shown by both simulation and measurement. The mechanism is analyzed by morphology and phonon properties. It is found that the enhancement arises from the higher inter-chain lattice order, stronger inter-chain interaction, higher phonon group velocity and suppressed phonon scattering. This study offers a new modulation strategy with quick response and without fillers.

Recently discovered massive Dirac fermions and room temperature skyrmions in the ferromagnetic kagome metal Fe3Sn2 have attracted extensive attention due to the potential applications in topological and spintronic devices. Because of its centrosymmetric lattice, the topological spin texture in Fe3Sn2 arises primarily from the competition between anisotropy and exchange interaction. In this Letter, we have identified the spin-reorientation at around 80 K by the magnetization and AC-susceptibility measurements. The evolution of the anisotropy is revealed by neutron powder diffraction data from 18 to 700 K, where the “breathing”-like kagome structure evolves into an ideal kagome lattice at higher temperature. Meanwhile, the deviation between the experimental and calculated results on heat capacity at high temperature and the softening of optical phonon modes in Raman spectra suggest the presence of anharmonic phonons in Fe3Sn2, which is responsible for the degeneracy of lattice thermal conductivity at high temperature. Our study indicates that Fe3Sn2 possesses a promising future in the design and development of topological, spintronic as well as thermoelectric devices.

The design of graphene-based composite with high thermal conductivity requires a comprehensive understanding of phonon coupling in nanosized graphene. We extended the two-temperature model to coupled groups of phonons. The study give new physical quantities, the phonon-phonon coupling factor and length, to characterize the couplings quantitatively. Besides, our proposed coupling length has an obvious dependence on system size. Our studies can not only observe the nonequilibrium between different groups of phonons but explain theoretically the thermal resistance inside nanosized graphene.

Due to their exceptional electrical, thermal, and optical properties, low-dimensional (LD) materials are very promising for many applications, such as nanoelectronic devices, energy storage, energy conversion, and thermal management. The thermal performance of LD materials is often an important consideration in these applications. Although freestanding LD materials exhibit interesting thermal properties, they are almost never used in such a form. Instead, they are often integrated into a certain environment; for example, in a composite material or on a substrate. Due to the large surface-to-volume ratio of LD materials, the environment usually has a strong impact on the thermal transport properties of these materials. The thermal behavior of the LD materials can be completely different from the freestanding form. The effect of environmental perturbation on thermal transport properties has recently attracted a lot of research interest. In this article, we aim to provide a comprehensive review of ho...

The application of low-dimensional materials for heat dissipation requires a comprehensive understanding of thermal transport at cross-interfaces, which widely exist in various composite materials and electronic devices. In this work, an analytical model is proposed, named as the cross-interface model (CIM), to accurately reveal the essential mechanism of the two-dimensional thermal transport at cross-interfaces. The applicability of CIM is validated through a comparison of the analytical results with molecular dynamics simulations for a typical cross-interface between two overlapped boron nitride nanoribbons. Besides, it is found that both the thermal resistances and the factor, η, has an important influence on the thermal transport. These investigations would deepen the understanding of the thermal transport at cross-interfaces and also facilitate the application of low-dimensional materials in thermal management.