ARPES detection of superconducting gap sign in unconventional superconductors.

The superconducting gap symmetry is crucial in understanding the underlying superconductivity mechanism. Angle-resolved photoemission spectroscopy (ARPES) has played a key role in determining the gap symmetry in unconventional superconductors. However, it has been considered so far that ARPES can only measure the magnitude of the superconducting gap but not its phase; the phase has to be detected by other phase-sensitive techniques. Here we propose a method to directly detect the superconducting gap sign by ARPES. This method is successfully validated in a cuprate superconductor Bi2Sr2CaCu2O8+δ with a well-known d-wave gap symmetry. When two bands have a strong interband interaction, the resulted electronic structures in the superconducting state are sensitive to the relative gap sign between the two bands. Our present work provides an approach to detect the gap sign and can be applied to various superconductors, particularly those with multiple orbitals like the iron-based superconductors.

Electronic nature of charge density wave and electron-phonon coupling in kagome superconductor KV3Sb5.

The Kagome superconductors AV3Sb5 (A = K, Rb, Cs) have received enormous attention due to their nontrivial topological electronic structure, anomalous physical properties and superconductivity. Unconventional charge density wave (CDW) has been detected in AV3Sb5. High-precision electronic structure determination is essential to understand its origin. Here we unveil electronic nature of the CDW phase in our high-resolution angle-resolved photoemission measurements on KV3Sb5. We have observed CDW-induced Fermi surface reconstruction and the associated band folding. The CDW-induced band splitting and the associated gap opening have been revealed at the boundary of the pristine and reconstructed Brillouin zones. The Fermi surface- and momentum-dependent CDW gap is measured and the strongly anisotropic CDW gap is observed for all the V-derived Fermi surface. In particular, we have observed signatures of the electron-phonon coupling in KV3Sb5. These results provide key insights in understanding the nature of the CDW state and its interplay with superconductivity in AV3Sb5 superconductors.

Sudden Collapse of Magnetic Order in Oxygen-Deficient Nickelate Films.

Antiferromagnetic order is a common and robust ground state in the parent (undoped) phase of several strongly correlated electron systems. The progressive weakening of antiferromagnetic correlations upon doping paves the way for a variety of emergent many-electron phenomena including unconventional superconductivity, colossal magnetoresistance, and collective charge-spin-orbital ordering. In this study, we explored the use of oxygen stoichiometry as an alternative pathway to modify the coupled magnetic and electronic ground state in the family of rare earth nickelates (RENiO_{3-x}). Using a combination of x-ray spectroscopy and resonant soft x-ray magnetic scattering, we find that, while oxygen vacancies rapidly alter the electronic configuration within the Ni and O orbital manifolds, antiferromagnetic order is remarkably robust to substantial levels of carrier doping, only to suddenly collapse beyond 0.21 e^{-}/Ni without an accompanying structural transition. Our work demonstrates that ordered magnetism in RENiO_{3-x} is mostly insensitive to carrier doping up to significant levels unseen in other transition-metal oxides. The sudden collapse of ordered magnetism upon oxygen removal may provide a new mechanism for solid-state magnetoionic switching and new applications in antiferromagnetic spintronics.

Spectroscopic evidence of superconductivity pairing at 83 K in single-layer FeSe/SrTiO3 films.

Single-layer FeSe films grown on the SrTiO3 substrate (FeSe/STO) have attracted much attention because of their possible record-high superconducting critical temperature (Tc) and distinct electronic structures. However, it has been under debate on how high its Tc can really reach due to the inconsistency of the results from different measurements. Here we report spectroscopic evidence of superconductivity pairing at 83 K in single-layer FeSe/STO films. By preparing high-quality single-layer FeSe/STO films, we observe strong superconductivity-induced Bogoliubov back-bending bands that extend to rather high binding energy ~ 100 meV by high-resolution angle-resolved photoemission measurements. They provide a new definitive benchmark of superconductivity pairing that is directly observed up to 83 K. Moreover, we find that the pairing state can be further divided into two temperature regions. These results indicate that either Tc as high as 83 K is achievable, or there is a pseudogap formation from superconductivity fluctuation in single-layer FeSe/STO films.

Alpha 2-Macroglobulin as Dual Regulator for Both Anabolism and Catabolism in the Cartilaginous Endplate of Intervertebral Disc.

STUDY DESIGN: Basic science study. OBJECTIVE: To illustrate supplemental alpha-2 macroglobulin (α2 M) has beneficial effects on cartilaginous endplates (CEPs) that may slow the progression of intervertebral disc (IVD) degeneration. SUMMARY OF BACKGROUND DATA: CEPs play a vital role in progression of intervertebral disc degenerative diseases. However, the ideal and economic therapies for CEPs degeneration are still urgently required. METHODS: Firstly, we confirmed degenerative CEP characters by H&E and Safranin O fast green staining and detected increasing level of α2 M and matrix metalloproteinase 13(MMP-13) in degenerative CEP by immunohistochemistry. Then, effects of exogenous α2 M on tumor necrosis factor alpha (TNF-α)-induced CEP catabolic enzyme and anabolic molecules were evaluated by qRT-PCR, Western blotting and ELISA in cultured CEP cells obtained from rats. Furthermore, suppression of α2 M on TNF-α-induced activation of NF-кB signaling pathway was measured by Western blotting and immunofluorescence. In addition, function of α2 M on TNF-α-treated ex vivo IVDs from rats lumbar IVDs was estimated by measuring the expression of MMP-13, Sox9, aggrecan, and type II collagen in CEP area. RESULTS: Compared with normal CEP, level of α2 M was slightly increased in CEP from degenerative patients, whereas MMP-13 was sharply elevated. In vitro, α2 M inhibited expression and activity of MMP-3 or MMP-13 in a dose-dependent manner in rat CEP cells stimulated by TNF-α. The α2 M refrained phosphorylation of IκBα and inhibited nuclear translocation of p65. Finally, supplemental α2 M reduced expression of MMP-13, and promoted expression of Sox9, aggrecan, and type II collagen in CEP area of ex vivo IVDs cultured with TNF-α. CONCLUSION: α2 M is not sufficiently produced to inactivate higher concentrations of catabolic factor MMP-13 found in the degenerated CEP. Supplemental α2 M protects against the progression of IVD degeneration by inhibiting effects of proinflammatory cytokines. LEVEL OF EVIDENCE: N/A.

Low virulence bacterial infections in cervical intervertebral discs: a prospective case series.

STUDY DESIGN: A prospective cross-sectional case series study. OBJECTIVE: To investigate the prevalence of low virulence disc infection and its associations with characteristics of patients or discs in the cervical spine. BACKGROUND: Low virulence bacterial infections could be a possible cause of intervertebral disc degeneration and/or back pain. Controversies are continuing over whether these bacteria, predominantly Propionibacterium acnes (P. acnes), represent infection or contamination. However, the current studies mainly focus on the lumbar spine, with very limited data on the cervical spine. METHODS: Thirty-two patients (20 men and 12 women) who underwent anterior cervical fusion for degenerative cervical spondylosis or traumatic cervical cord injury were enrolled. Radiological assessments included X-ray, CT, and MRI of the cervical spine. Endplate Modic changes, intervertebral range of motion, and disc herniation type were evaluated. Disc and muscle tissues were collected under strict sterile conditions. Samples were enriched in tryptone soy broth and subcultured under anaerobic conditions, followed by identification of the resulting colonies by the PCR method. RESULTS: Sixty-six intervertebral discs were excised from thirty-two patients. Positive disc cultures were noted in eight patients (25%) and in nine discs (13.6%). The muscle biopsy (control) cultures were negative in 28 patients and positive in 4 patients (12.5%); three of whom had a negative disc culture. Seven discs (10.6%) were positive for coagulase-negative Staphylococci (CNS) and two discs were positive for P. acnes (3.0%). A younger patient age and the extrusion or sequestration type of disc herniation, which represented a complete annulus fibrous failure, were associated with positive disc culture. CONCLUSIONS: Our data show that CNS is more prevalent than P. acnes in degenerative cervical discs. The infection route in cervical discs may be predominantly through an annulus fissure. Correlation between these infections and clinical symptoms is uncertain; therefore, their clinical significance needs to be investigated in the future. These slides can be retrieved under Electronic Supplementary Material.

[Experimental study of laparoscopical lumbar interbody fusion with polyporus composite phosphate calcium and rhBMP-2 compounds in sheep].

OBJECTIVE: To study the efficacy of polyporus composite phosphate calcium and rhBMP-2 compounds with laparoscopical lumbar interbody fusion in sheep. METHODS: Fourteen uniform-weight adult sheep were randomly divided into three groups for LA-5 interbody fusion with titanium mesh. Autogenous bone and titanium mesh was applied with open anterior technique in group 1 (n=4). In group 2, 4 sheep were operated with laparoscope technique for LA-5 interbody fusion with composite phosphate calcium (CPC) and titanium mesh. In group 3, 6 sheep underwent laparoscopical L4-5 interbody fusion with titanium mesh as well as polyporus composite phosphate calcium and rhBMP-2 compounds. At Weeks 6 and 12 post-operation, the sheep were sacrificed for imaging, biomechanic and morphological examinations. RESULTS: Although there was no statistical difference between open and laparoscopical interbody fusion group when comparing the remaining disc and endplate decorticated, bone fusion occurred in 3 groups after 3 months. A much larger amount of bony callus was observed earlier in laparoscopical L4-5 interbody fusion group with titanium mesh as well as polyporus composite phosphate calcium and rhBMP-2 compounds than two other groups. CONCLUSION: Polyporus composite phosphate calcium and rhBMP-2 compounds are suitable prosthetic materials for clinical trials. When these materials are utilized with a laparoscopical technique, satisfactory interbody fusion may be achieved.

Applied digital signal processing systems for vortex flowmeter with digital signal processing.

The spectral analysis is combined with digital filter to process the vortex sensor signal for reducing the effect of disturbance at low frequency from pipe vibrations and increasing the turndown ratio. Using digital signal processing chip, two kinds of digital signal processing systems are developed to implement these algorithms. One is an integrative system, and the other is a separated system. A limiting amplifier is designed in the input analog condition circuit to adapt large amplitude variation of sensor signal. Some technique measures are taken to improve the accuracy of the output pulse, speed up the response time of the meter, and reduce the fluctuation of the output signal. The experimental results demonstrate the validity of the digital signal processing systems.