Influence of Magnetic and Electric Fields on Universal Conductance Fluctuations in Thin Films of the Dirac Semimetal Cd3As2.

Time-reversal invariance (TRS) and inversion symmetry (IS) are responsible for the topological band structure in Dirac semimetals (DSMs). These symmetries can be broken by applying an external magnetic or electric field, resulting in fundamental changes to the ground state Hamiltonian and a topological phase transition. We probe these changes using universal conductance fluctuations (UCF) in the prototypical DSM, Cd3As2. With increasing magnetic field, the magnitude of the UCF decreases by a factor of 2, in agreement with numerical calculations of the effect of broken TRS. In contrast, the magnitude of the UCF increases monotonically when the chemical potential is gated away from the charge neutrality point. We attribute this to Fermi surface anisotropy rather than broken IS. The concurrence between experimental data and theory provides unequivocal evidence that UCF are the dominant source of fluctuations and offers a general methodology for probing broken-symmetry effects in topological quantum materials.

Idiopathic mesenteric phlebosclerotic colitis associated with Chinese herbal medicine.

Idiopathic mesenteric phlebosclerotic colitis(IMP) is a rare disease. At present, the etiology and pathogenesis are not clear, but the main patients are Asian people, and most of them have a history of taking Chinese herbal medicines. The disease has characteristic endoscopic and imaging manifestations. This paper shares a case of IMP, The patient came to our hospital for one year because of intermittent abdominal pain and diarrhea. It conforms to the typical manifestations of IMP. For patients who take Chinese herbal medicine for a long time, if they have clinical manifestations of gastrointestinal tract, it is necessary to consider the possibility of the disease to avoid serious consequences due to missed diagnosis.

Spin current as a probe of quantum materials.

Spin current historically referred to the flow of electrons carrying spin information, in particular since the discovery of giant magnetoresistance in the 1980s. Recently, it has been found that spin current can also be mediated by spin-triplet supercurrent, superconducting quasiparticles, spinons, magnons, spin superfluidity and so on. Here, we review key progress concerning the developing research direction utilizing spin current as a probe of quantum materials. We focus on spin-triplet superconductivity and spin dynamics in the ferromagnet/superconductor heterostructures, quantum spin liquids, magnetic phase transitions, magnon-polarons, magnon-polaritons, magnon Bose-Einstein condensates and spin superfluidity. The unique characteristics of spin current as a probe will be fruitful for future investigation of spin-dependent properties and the identification of new quantum materials.

"Stomach mass" as the first manifestation of IgG4-related disease: a case report.

BACKGROUND: IgG4-related disease mainly manifests as organomegaly and is accompanied by tissue fibrosis (Mimori, Mod Rheumatol 29(2):213, 2019) which is frequently confused with tumour (Dawei et al., J Gastroenterol Hepatol 29(12):1375-8, 2020). There are few reports with of IgG4-related disease with the first clinical manifestation involving the stomach. CASE PRESENTATION: We present the case of 46-year-old male patient with a "stomach tumour" as the first manifestation of IgG4-related disease. Gastroscopy showed a mass in the stomach, however, the pathology result was chronic inflammation with IgG4 positivity. CT scans of abdomen showed that the stomach wall was thick, the head of the pancreas was swollen, and retroperitoneal fibrosis was severe.The serum IgG4 level was 75 g/L (normal range 0.03-2.01 g/L).After treatment with methylprednisolone for one month, the symptoms were greatly relieved. CONCLUSIONS: To reduce the suffering of patients and relieve their financial burden, we should consider the possibility of IgG4-related disease when the initial manifestation is a stomach mass.

Crossover from 3D to 2D quantum transport in Bi2Se3/In2Se3 superlattices.

The topological insulator/normal insulator (TI/NI) superlattices (SLs) with multiple Dirac channels are predicted to offer great opportunity to design novel materials and investigate new quantum phenomena. Here, we report first transport studies on the SLs composed of TI Bi2Se3 layers sandwiched by NI In2Se3 layers artificially grown by molecular beam epitaxy (MBE). The transport properties of two kinds of SL samples show convincing evidence that the transport dimensionality changes from three-dimensional (3D) to two-dimensional (2D) when decreasing the thickness of building block Bi2Se3 layers, corresponding to the crossover from coherent TI transport to separated TI channels. Our findings provide the possibility to realizing "3D surface states" in TI/NI SLs.

Changes in composition and enamel demineralization inhibition activities of gallic acid at different pH values.

BACKGROUND: Gallic acid (GA) has been shown to inhibit demineralization and enhance remineralization of enamel; however, GA solution is highly acidic. This study was to investigate the stability of GA solutions at various pH and to examine the resultant effects on enamel demineralization. METHODS: The stability of GA in H2O or in phosphate buffer at pH 5.5, pH 7.0 and pH 10.0 was evaluated qualitatively by ultraviolet absorption spectra and quantified by high performance liquid chromatography with diode array detection (HPLC-DAD). Then, bovine enamel blocks were subjected to a pH-cycling regime of 12 cycles. Each cycle included 5 min applications with one of the following treatments: 1 g/L NaF (positive control), 4 g/L GA in H2O or buffered at pH 5.5, pH 7.0 and pH 10.0 and buffers without GA at the same pH (negative control), followed by a 60 min application with pH 5.0 acidic buffers and a 5 min application with neutral buffers. The acidic buffers were analysed for dissolved calcium. RESULTS: GA was stable in pure water and acidic condition, but was unstable in neutral and alkaline conditions, in which ultraviolet spectra changed and HPLC-DAD analysis revealed that most of the GA was degraded. All the GA groups significantly inhibited demineralization (p < 0.05) and there was no significant difference of the inhibition efficacy among different GA groups (p > 0.05). CONCLUSIONS: GA could inhibit enamel demineralization and the inhibition effect is not influenced by pH. GA could be a useful source as an anti-cariogenic agent for broad practical application.

The preface: Toward higher-T c superconductivity under lower pressure-from binary to ternary superhydrides.

This is the Preface to Special Topic: Challenges to Achieving Room-Temperature Superconductivity in Superhydrides under Pressure.

Large intramural hematoma of the esophagus after endoscopic injection sclerotherapy: A case report.

RATIONALE: Endoscopic injection sclerotherapy (EIS) is a common treatment for patients with liver cirrhosis and esophageal varices. It can effectively treat variceal rupture and bleeding caused by liver cirrhosis. However, EIS has many complications, including postoperative bleeding, retrosternal pain, esophageal ulcers, esophageal stenosis, and ectopic embolism. Intramural hematoma of the esophagus (IHE) is a rare complication of EIS that can lead to chest tightness, chest pain, and dysphagia. PATIENTS CONCERNS: A 55-year-old man developed severe nausea and vomiting accompanied by chest pain after EIS. DIAGNOSIS: Comprehensive imaging features, the patient was diagnosed as IHE. INTERVENTIONS: A vascular clamp was used for hemostasia, and a feeding tube was placed in the patient's jejunum. OUTCOMES: After the removal of the jejunal feeding tube and the intake of a semiliquid diet, the patient had no episodes of chest pain, chest tightness, or dysphagia and was discharged after 2 days of observation. LESSONS: Although IHE rarely occurs after EIS, we should not overlook its risk. The occurrence of IHE is not directly related to the number of EISs received or the degree of liver cirrhosis but is more likely related to postoperative nausea and vomiting. Therefore, timely medication and observation are particularly important for patients with nausea and vomiting after endoscopic treatment.

The Effect of the Displacement Amplitude on the Fretting Wear of GCr15 Steel with a TiC Coating.

In the present paper, the effect of mechanical ball milling time on the fretting wear of GCr15 steel balls at different displacement amplitudes is investigated. TiC powder coating was fabricated on the surface of GCr15 steel balls using various process times, and the fretting wear tests were conducted on an AISI 52100 steel disk with the applied force of 80 N. Additionally, various displacement amplitudes (10 µm, 20 µm, and 60 µm) were selected. Specimen attributes and wear scars were characterized using an inverted metallographic microscope, a microhardness tester, an X-ray diffractometry analyzer, a white light interferometer, and a scanning electron microscope. The results showed that thick and continuous coatings could be obtained at the milling time of 18 h. The specimens processed for a longer milling time demonstrated better fretting wear resistance, which we attribute to higher microhardness of the surface layer. The coefficient of friction and wear volume of specimens at each different displacement amplitude significantly decreased with increasing milling time. As the displacement amplitude increased, the three fretting states were: partial slip coordinated by elastic deformation; partial slip state coordinated by plastic deformation; and gross slip condition. Our observations indicate that mechanical ball milling could be an efficient approach to improve the fretting wear resistance of GCr15 steel balls.

Enhanced Strength-Ductility Synergy Properties in Selective Laser Melted 316L Stainless Steel by Strengthening Grinding Process.

Selective laser melted (SLM) 316L stainless steel (SS) has been widely employed in the fields of designing and manufacturing components with complex shapes and sizes. However, the low yield strength, low ultimate tensile stress, and low hardness of SLM 316L SS components hinder its further application. In this work, the strengthening grinding process (SGP) was used to enhance the mechanical properties of SLM 316L SS. The microhardness, residual stress, microstructure, and tensile properties of all the samples were analyzed. The results demonstrate that the SGP induced higher compressive residual stress and microhardness, as well as higher tensile properties. The maximum hardness and residual stress reached 354.5 HV and -446 MPa, respectively, indicating that the SGP resulted in a plastic deformation layer over 150 µm. The possible mechanisms have been discussed in further detail. Compared to the untreated sample, the SGP sample shows a significant improvement in yield strength (YS), ultimate tensile stress (UTS), and elongation (EL), increasing 30%, 25.5%, and 99.1%, respectively. This work demonstrates that SGP treatment could be an efficient approach to simultaneously improving the strength and ductility of the SLM 316L SS, which makes it more suitable for engineering applications.

Giant oscillatory Gilbert damping in superconductor/ferromagnet/superconductor junctions.

Interfaces between materials with differently ordered phases present unique opportunities for exotic physical properties, especially the interplay between ferromagnetism and superconductivity in the ferromagnet/superconductor heterostructures. The investigation of zero- and π-junctions has been of particular interest for both fundamental physical science and emerging technologies. Here, we report the experimental observation of giant oscillatory Gilbert damping in the superconducting niobium/nickel-iron/niobium junctions with respect to the nickel-iron thickness. This observation suggests an unconventional spin pumping and relaxation via zero-energy Andreev bound states that exist not only in the niobium/nickel-iron/niobium π-junctions but also in the niobium/nickel-iron/niobium zero-junctions. Our findings could be important for further exploring the exotic physical properties of ferromagnet/superconductor heterostructures and potential applications of ferromagnet π-junctions in quantum computing, such as half-quantum flux qubits.

Landau quantization of topological surface states in Bi2Se3.

We report the direct observation of Landau quantization in Bi2Se3 thin films by using a low-temperature scanning tunneling microscope. In particular, we discovered the zeroth Landau level, which is predicted to give rise to the half-quantized Hall effect for the topological surface states. The existence of the discrete Landau levels (LLs) and the suppression of LLs by surface impurities strongly support the 2D nature of the topological states. These observations may eventually lead to the realization of quantum Hall effect in topological insulators.

Experimental demonstration of topological surface states protected by time-reversal symmetry.

We report direct imaging of standing waves of the nontrivial surface states of topological insulator Bi2Te3 using a scanning tunneling microscope. The interference fringes are caused by the scattering of the topological states off Ag impurities and step edges on the Bi2Te3(111) surface. By studying the voltage-dependent standing wave patterns, we determine the energy dispersion E(k), which confirms the Dirac cone structure of the topological states. We further show that, very different from the conventional surface states, backscattering of the topological states by nonmagnetic impurities is completely suppressed. The absence of backscattering is a spectacular manifestation of the time-reversal symmetry, which offers a direct proof of the topological nature of the surface states.

Log-periodic quantum magneto-oscillations and discrete-scale invariance in topological material HfTe5.

Discrete-scale invariance (DSI) is a phenomenon featuring intriguing log-periodicity that can be rarely observed in quantum systems. Here, we report the log-periodic quantum oscillations in the longitudinal magnetoresistivity (ρxx ) and the Hall traces (ρyx ) of HfTe5 crystals, which reveal the DSI in the transport-coefficients matrix. The oscillations in ρxx and ρyx show the consistent logB-periodicity with a phase shift. The finding of the logB oscillations in the Hall resistance supports the physical mechanism as a general quantum effect originating from the resonant scattering. Combined with theoretical simulations, we further clarify the origin of the log-periodic oscillations and the DSI in the topological materials. This work evidences the universality of the DSI in the Dirac materials and provides indispensable information for a full understanding of this novel phenomenon.

Enhanced lubricity in mixed alkanethiol monolayers.

The frictional properties of two-component mixed alkanethiol monolayers were investigated with frictional force microscopy. With large chain length differences, the two types of molecules segregated into large islands and reveal similar frictional properties as those of single-component monolayers. With small chain length differences, the completely mixed monolayers display a decreased friction as compared with single-component monolayers. This observation indicates that development of gauche kinks in the top portion of the mixed monolayers can enhance lubrication rather than increase friction, perhaps due to suppression of other energy dissipation channels.