Josephson Diode Effect Induced by Valley Polarization in Twisted Bilayer Graphene.

Recently, the Josephson diode effect (JDE), in which the superconducting critical current magnitudes differ when the currents flow in opposite directions, has attracted great interest. In particular, it was demonstrated that gate-defined Josephson junctions based on magic-angle twisted bilayer graphene showed a strong nonreciprocal effect when the weak-link region is gated to a correlated insulating state at half filling (two holes per moiré cell). However, the mechanism behind such a phenomenon is not yet understood. In this Letter, we show that the interaction-driven valley polarization, together with the trigonal warping of the Fermi surface, induce the JDE. The valley polarization, which lifts the degeneracy of the states in the two valleys, induces a relative phase difference between the first and the second harmonics of the supercurrent and results in the JDE. We further show that the nontrivial current phase relation, which is responsible for the JDE, also generates the asymmetric Shapiro steps.

Valley-Polarized Quantum Anomalous Hall State in Moiré MoTe_{2}/WSe_{2} Heterobilayers.

Moiré heterobilayer transition metal dichalcogenides (TMDs) emerge as an ideal system for simulating the single-band Hubbard model and interesting correlated phases have been observed in these systems. Nevertheless, the moiré bands in heterobilayer TMDs were believed to be topologically trivial. Recently, it was reported that both a quantum valley Hall insulating state at filling ν=2 (two holes per moiré unit cell) and a valley-polarized quantum anomalous Hall state at filling ν=1 were observed in AB stacked moiré MoTe_{2}/WSe_{2} heterobilayers. However, how the topologically nontrivial states emerge is not known. In this Letter, we propose that the pseudomagnetic fields induced by lattice relaxation in moiré MoTe_{2}/WSe_{2} heterobilayers could naturally give rise to moiré bands with finite Chern numbers. We show that a time-reversal invariant quantum valley Hall insulator is formed at full filling ν=2, when two moiré bands with opposite Chern numbers are filled. At half filling ν=1, the Coulomb interaction lifts the valley degeneracy and results in a valley-polarized quantum anomalous Hall state, as observed in the experiment. Our theory identifies a new way to achieve topologically nontrivial states in heterobilayer TMD materials.

Lattice reconstruction induced multiple ultra-flat bands in twisted bilayer WSe2.

Moiré superlattices in van der Waals heterostructures provide a tunable platform to study emergent properties that are absent in the natural crystal form. Twisted bilayer transition metal dichalcogenides (TB-TMDs) can host moiré flat bands over a wide range of twist angles. For twist angle close to 60°, it was predicted that TB-TMDs undergo a lattice reconstruction which causes the formation of ultra-flat bands. Here, by using scanning tunneling microscopy and spectroscopy, we show the emergence of multiple ultra-flat bands in twisted bilayer WSe2 when the twist angle is within 3° of 60°. The ultra-flat bands are manifested as narrow tunneling conductance peaks with estimated bandwidth less than 10 meV, which is only a fraction of the estimated on-site Coulomb repulsion energy. The number of these ultra-flat bands and spatial distribution of the wavefunctions match well with the theoretical predictions, strongly evidencing that the observed ultra-flat bands are induced by lattice reconstruction. Our work provides a foundation for further study of the exotic correlated phases in TB-TMDs.

Kramers nodal line metals.

Recently, it was pointed out that all chiral crystals with spin-orbit coupling (SOC) can be Kramers Weyl semimetals (KWSs) which possess Weyl points pinned at time-reversal invariant momenta. In this work, we show that all achiral non-centrosymmetric materials with SOC can be a new class of topological materials, which we term Kramers nodal line metals (KNLMs). In KNLMs, there are doubly degenerate lines, which we call Kramers nodal lines (KNLs), connecting time-reversal invariant momenta. The KNLs create two types of Fermi surfaces, namely, the spindle torus type and the octdong type. Interestingly, all the electrons on octdong Fermi surfaces are described by two-dimensional massless Dirac Hamiltonians. These materials support quantized optical conductance in thin films. We further show that KNLMs can be regarded as parent states of KWSs. Therefore, we conclude that all non-centrosymmetric metals with SOC are topological, as they can be either KWSs or KNLMs.

Local Tumor Control for Metastatic Epidural Spinal Cord Compression Following Separation Surgery with Adjuvant CyberKnife Stereotactic Radiotherapy or Image-Guided Intensity-Modulated Radiotherapy.

BACKGROUND: We sought to compare local tumor control after conventionally fractionated image-guided intensity-modulated radiotherapy (IMRT) versus adjuvant CyberKnife stereotactic body radiotherapy (SBRT) in patients who underwent separation surgery for metastatic epidural spinal cord compression (MESCC). METHODS: We retrospectively reviewed patients with MESCC who were treated at our hospital. The Kaplan-Meier method was used to estimate local progression and overall survival. RESULTS: Fifty-six patients with MESCC underwent separation surgery between 2013 and 2018, among whom 6 were lost to follow-up, 24 received conventionally fractionated image-guided IMRT, and 26 were treated with CyberKnife SBRT. The median follow-up was 16.5 months (range, 2.1-47.5 months). Eleven patients experienced local failure including 9 and 2 from the IMRT and SBRT groups, respectively. The local progression-free survival rates were significantly higher in the SBRT group than IMRT group at 6 months (95.5% vs. 82.0%), 1 year (90.9% vs. 71.8%), and 2 years (90.9% vs. 57.6%) (P = 0.035). Multivariate Cox proportional hazards regression analysis identified radiotherapy method (P = 0.034) and receipt of preoperative radiotherapy (P = 0.047) as significant predictors of local control, while visceral metastasis (P = 0.048) and high-malignancy primary tumor type (P = 0.002) were negative predictors of overall survival. Moreover, postoperative SBRT was noninferior to IMRT in terms of pain control, adverse effects, and performance in treating irradiated spinal metastases. CONCLUSIONS: Hybrid surgery-radiosurgery therapy is a safe and effective treatment option for patients with MESCC. SBRT provided higher local control rates compared with IMRT. Thus postoperative SBRT should be considered for patients expected to have relatively long survival.

[Value of 18F-FDG PET/CT Scan Quantization Parameters for Prognostic Evaluation of Patients with Diffuse Large B-cells Lymphoma].

OBJECTIVE: To investigate the prognostic value of 18F-FDG PET/CT scan quantization parameters, max standardized uptake value （SUVmax）, metabolic tumor volume （MTV）, total lesion glycolysis （TLG） and other clinical factors for prognostic evaluation of paticnts with diffuse large B-cell lymphoma （DLBCL）. METHODS: PET/CT scan and clinical data of a total of 65 newly diagnosed DLBCL patients who received Rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisone （R-CHOP） chemotherapy as first-line treatment were analyzed. All patients received a PET/CT scan at diagnosis and an interim PET/CT after 2-4 circles of chemotherapies. The related parameters of SUVmax, MTV and TLG were acquired by analyzing and calculating the scan results. The receiver operating characteristic （ROC） curve was used to determine the optimal cut-off of parameters. Pearson chi-square test, Kaplan-Meier method and COX proportional hazard model were performed to analyze the prognostic value of PET/CT related parameters and clinical factors in progression-free survival （PFS）. RESULTS: Age, B symptom, Ann Arbor stage and extra-nodal involvement in major organs significantly related with PFS （P<0.05）, but the SUVmax didn't relalt with the prognosis. The cut-off values of MTV0, MTV1, TLG0 and TLG1 for disease recurrence or progression were 172.20cm 3, 4.32cm 3, 1043.33g and 14.07g. The lower MTV and TLG groups showed longer PFS significantly. In the multivariate Cox regression model, B symptoms, MTV1 and TLG1 were the independent prognostic risk factors. CONCLUSION: MTV and TLG at baseline and in the interim and NCCN-IPI correlate with disease prognosis. SUVmax related parameters hare no significant relationship with prognosis. Besides MTV and TLG during treatment are the independent prognostic risk factors suggesting more predictive value than NCCN-IPI.

Intraosseous schwannoma of the mobile spine: a report of twenty cases.

PURPOSE: To clarify the clinical features, surgical strategies, and outcomes of intraosseous schwannoma (IOS) of the mobile spine. METHODS: We retrospectively reviewed patients with primary benign spinal schwannoma who underwent surgery in our orthopedic department. RESULTS: A total of 101 patients with primary benign schwannoma located in the mobile spine underwent surgery in our orthopedic department from 2005 to 2015. Twenty-five patients presented with aggressive features. Twenty patients were regularly followed up, twelve with lesions in the cervical spine, six with lesions in the thoracic region, and two with lesions in the lumbar spine. Preoperative CT-guided biopsy was performed in fourteen cases; the accuracy of diagnosis was 100%, and IOS is not histologically different from conventional schwannoma. The computed tomography (CT) scan revealed expansile and osteolytic bone destruction in all these cases, with six patients having pathological fracture. On T2-weighted magnetic resonance imaging, the lobulated schwannomas showed heterogeneous signal intensity and significant heterogeneous enhancement on post-contrast images. Gross total resection was performed in seventeen patients and subtotal resection in three. Tumor-involved nerve roots resection were documented to decrease local recurrence in fourteen cases. The visual analog scale score decreased from 5.66 ± 1.79 preoperatively to 1.16 ± 1.77 at the final follow-up. No local recurrence was noticed at the final follow-up. CONCLUSION: CT-guided biopsy is effective for the preoperative diagnosis of spinal IOS. Total resection is the optimal treatment for IOS, whereas subtotal resection could be an alternative choice for high-risk cases. These slides can be retrieved under electronic supplementary material.

Effect of Femoral Resection on Coronal Overall Alignment after Conventional Total Knee Arthroplasty.

BACKGROUND: A good postoperative alignment in total knee arthroplasty (TKA) is the key to achieving satisfactory results. We assessed the effect of femoral and tibial resection on the overall alignment after conventional TKA. METHODS: We conducted a retrospective analysis of 212 primary TKAs in 188 patients. Intramedullary (IM)-guided resection was applied on the femoral side while extramedullary (EM)-guided resection was used on the tibial side. Using full-length X-ray, the preoperative femoral valgus angle and lower extremity alignment, as well as 2-week postoperative femoral and tibial prosthetic coronal alignment and overall lower extremity alignment, were measured. RESULTS: Postoperatively, good prosthetic alignment was achieved in 191 cases (90.1%) on the tibial side and in 144 cases (67.9%) on the femoral side (χ2 = 5.441, P = 0.02). Multiple linear regression analysis was used to assess the effect of different alignment sides on the overall alignment in the coronal plane. Data were divided into five subgroups based on the valgus or varus status of the prostheses. The standardized regression coefficients of the femoral and tibial prosthetic alignment on the overall alignment were 0.666 and 0.414, respectively; in varus on both sides were 0.658 and 0.377, respectively; in valgus, 0.555 and 0.030; femoral side varus and tibial side valgus, 0.702 and 0.211; femoral side valgus and tibial side varus, -0.416 and 0.287. The study showed that the overall low extremity alignment was statistically influenced by the prosthetic alignment, except for the tibial prosthetic alignment when femoral prosthesis was in valgus (P = 0.153). CONCLUSIONS: In conventional TKA, tibial side EM-guided resection may offer satisfactory postoperative alignment, and femoral resection relying on IM guide may lead to more undesirable results. Postoperative coronal alignment is mainly affected by the femoral resection. Therefore, femoral side operation should receive adequate attention from the surgeons.