Search

There has been a long-standing debate about the mechanism of the unusual superconductivity in alkali-intercalated fulleride superconductors. In this work, using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structures of superconducting K3C60 thin films. We observe a dispersive energy band crossing the Fermi level with an occupied bandwidth of about 130 meV. The measured band structure shows prominent quasiparticle kinks and a replica band involving high-energy Jahn-Teller active Hg(8) phonon mode, reflecting strong electron-phonon coupling in the system. The electron-phonon coupling constant is estimated to be about 1.2, which dominates the quasiparticle mass renormalization. Moreover, we observe an isotropic nodeless superconducting gap beyond the mean-field estimation. Both the large electron-phonon coupling constant and large reduced superconducting gap suggest a strong-coupling superconductivity in K3C60, while the electronic correlation effect is indicated by the observation of a waterfall-like band dispersion and the small bandwidth compared with the effective Coulomb interaction. Our results not only directly visualize the crucial band structure of superconducting fulleride but also provide important insights into the mechanism of the unusual superconductivity., Accepted by Phys. Rev. Lett

EuTe4 is a newly-discovered van der Waals material exhibiting a novel charge-density wave (CDW) with a large thermal hysteresis in the resistivity and CDW gap. In this work, we systematically study the electronic structure and transport properties of EuTe4 using high-resolution angle-resolved photoemission spectroscopy (ARPES), magnetoresistance measurements, and scanning tunneling microscopy (STM). We observe a CDW gap of about 200 meV at low temperatures that persists up to 400 K, suggesting that the CDW transition occurs at a much higher temperature. We observe a large thermal hysteretic behavior of the ARPES intensity near the Fermi level, consistent with the resistivity measurement. The hysteresis in the resistivity measurement does not change under a magnetic field up to 7 T, excluding the thermal magnetic hysteresis mechanism. Instead, the surface topography measured with STM shows surface domains with different CDW trimerization directions, which may be important for the thermal hysteretic behavior of EuTe4. Interestingly, we observe a large negative magnetoresistance at low temperatures that can be associated with the canting of magnetically ordered Eu spins. Our work shed light on the understanding of magnetic, transport, and electronic properties of EuTe4.

Angle-resolved photoemission spectroscopy with sub-micrometer spatial resolution ({\mu}-ARPES), has become a powerful tool for studying quantum materials. To achieve sub-micrometer or even nanometer-scale spatial resolution, it is important to focus the incident light beam (usually from the synchrotron radiation) using X-ray optics such as the zone plate or ellipsoidal capillary mirrors. Recently, we developed a laser-based {\mu}-ARPES with spin-resolution (LMS-ARPES). The 177 nm laser beam is achieved by frequency doubling a 355 nm beam using a KBBF crystal and subsequently focused using an optical lens with a focal length of about 16 mm. By characterizing the focused spot size using different methods and performing spatial-scanning photoemission measurement, we confirm the sub-micron spatial resolution of the system. Compared with the {\mu}-ARPES facilities based on synchrotron radiation, our LMS-ARPES system is not only more economical and convenient but also with higher photon flux (> 5E13 photons/s), thus enabling the high-resolution and high-statistics measurements. Moreover, the system is equipped with a two-dimensional spin detector based on exchange scattering at a surface-passivated iron film grown on a W(100) substrate. We investigate the spin structure of the prototype topological insulator Bi2Se3 and reveal a high spin-polarization rate, confirming its spin-momentum locking property. This lab-based LMS-ARPES will be a powerful research tool for studying the local fine electronic structures of different condensed matter systems, including topological quantum materials, mesoscopic materials and structures, and phase-separated materials., Comment: To appear in RSI

Recently, magnetic topological quantum materials have attracted substantial research attention due to their great application potential. Here, using high-resolution angle-resolved photoemission spectroscopy and ab initio calculation, we systematically investigate the electronic structure of antiferromagnet Dirac semimetal candidate GdIn3. According to our ab initio calculation, there exist two and one pair(s) of Dirac fermions in the paramagnetic and antiferromagnetic state, respectively. In the antiferromagnetic state, the magnetic Dirac semimetal phase is protected by C4z rotation symmetry in the type-IV magnetic space group. Our experiment above the Néel temperature is well reproduced by the calculated band structure in the paramagnetic state, from which we identify a pair of Dirac fermions at 1.5 eV below the Fermi level. However, we do not observe the signature of electronic reconstruction in the antiferromagnetic state, suggesting a weak interaction between the localized Gd 4f states of spin configuration S=7/2μB and the itinerant conduction electrons. Our results confirm the Dirac semimetal nature of the paramagnetic GdIn3 and provide important insights into its antiferromagnetic Dirac semimetal phase.

Avoiding the plasma instability, especially the disruption instability, is an important problem for the stable operation of tokamak. Large-scale instabilities driven by free energy evolve nonlinearly and lead to the disruption. The microscale turbulence is highly sensitive to the change of free energy. The paper show the electron-scale turbulence evolution in the pre-precursor phase of TMs included disruption with the CO 2 laser coherent scattering system in EAST. In the pre-precursor phase of disruption, it is observed that the characteristics of turbulence (e.g. intensity, spatial correlation) have obviously changed for more than 30 ms. In addition, before TM ( n = 1 ) included major disruption, the spatial-correlation of turbulence in two regions ( ρ = 0–0.4 and ρ = 0.4–0.8) increase obviously, while opposite turbulence spatial-correlation evolution was observed before TM ( n = 1 ) included minor disruption. The warning time for disruption with microscale turbulence is competitive while 30 ms for ITER. According to the experimental results in EAST, it may provide a new experimental evidence for the method improvement of predicting disruption.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a new type of coronavirus that causes the Coronavirus Disease 2019 (COVID-19), which has been the most challenging pandemic in this century. Considering its high mortality and rapid spread, an effective vaccine is urgently needed to control this pandemic. As a result, the academia, industry, and government sectors are working tightly together to develop and test a variety of vaccines at an unprecedented pace. In this review, we outline the essential coronavirus biological characteristics that are important for vaccine design. In addition, we summarize key takeaways from previous vaccination studies of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle East Respiratory Syndrome Coronavirus (MERS-CoV), highlighting the pros and cons of each immunization strategy. Finally, based on these prior vaccination experiences, we discuss recent progress and potential challenges of COVID-19 vaccine development. Original article: Li YD, Chi WY, Su JH, et al. Coronavirus vaccine development: from SARS and MERS to COVID-19. J Biomed Sci. 2020;27(1):104. DOI: 10.1186/s12929-020-00695-2. The article was translated into Russian and published under the terms of the Creative Commons Attribution 4.0 license.

We propose the implementation of the Swap Test using a charge qubit in a double quantum dot. The Swap Test is a fundamental quantum subroutine in quantum machine learning and other applications for estimating the fidelity of two unknown quantum states by measuring an auxiliary qubit. Our proposal uses a controlled three-qubit gate which is natural to quantum-dot charge qubits. It allows us to implement a Swap Test with a circuit depth of six layers, and an estimated gate time of less than 3 ns, that is below the coherence time of double quantum dots. This work paves the way for enhancing the toolbox of quantum machine learning developments in semiconductor qubits., 6 Pages, 9 Figures

Schottky junctions, formed by high work function metals and semiconductors, are important devices in electronics and optoelectronics. The metal deposition in traditional Schottky interfaces usually damages the semiconductor surface and causes defect states, which reduces the Schottky barrier height and device performance. This can be avoided in the atomically smooth interface formed by two-dimensional (2D) metals and semiconductors. For better interface tailoring engineering, it is particularly important to understand various interface effects in such 2D Schottky devices under critical or boundary conditions. Here we report the fabrication and testing of three types of MoS

To determine the parameters of the double-ellipsoidal heat source model (DEHSM) in welding simulations, a technique is developed to extract the parameters of weld pool shape from the simulation results. The technique is developed based on the knowledge of the isoparametric transformation and computer graphics, and its validity is verified by a graphic comparison. It is shown that the technique can effectively extract and reflect the shape of weld pools without interrupting the solution process of the DEHSM parameters. Second, using this technique in conjunction with the optimization method, an approach is proposed to determine the DEHSM parameters. Next, using the proposed method, the DEHSM parameters associated with four different welding conditions are determined. Finally, with these parameters, their corresponding weld widths and penetrations are compared with the measured ones. The results demonstrate that the proposed method can efficiently determine the DEHSM parameters with a relatively high accuracy.

In this study, we developed a SYBR Green I real-time PCR method for the rapid and sensitive detection of novel porcine parvovirus 7 (PPV7). Specific primers were designed based on the highly conserved region within the Capsid gene of PPV7. The established method was 1,000 times more sensitive than the conventional PCR method and had a detection limit of 35.6 copies. This method was specific and had no cross-reactions with PCV2, PCV3, PRV, PEDV, PPV1, and PPV6. Experiments testing the intra and interassay precision demonstrated a high reproducibility. Testing the newly established method with 200 clinical samples revealed a detection rate up to 17.5% higher than that of the conventional PCR assay. The established method could provide technical support for clinical diagnosis and epidemiological investigation of PPV7.

Quasi-one-dimensional (quasi-1D) materials are a newly arising topic in low-dimensional researches. As a result of reduced dimensionality and enhanced anisotropy, the quasi-1D structure gives rise to novel properties and promising applications such as photodetectors. However, it remains an open question whether performance crossover will occur when the channel material is downsized. Here we report on the fabrication and testing of photodetectors based on exfoliated quasi-1D BiSeI thin wires. Compared with the device on bulk crystal, a significantly enhanced photoresponse is observed, which is manifested by a series of performance parameters, including ultrahigh responsivity (7 x 10$^4$ A W$^{-1}$), specific detectivity (2.5 x 10$^{14}$ Jones) and external quantum efficiency (1.8 x 10$^7$%) when $V_{\textrm {ds}}$ = 3 V, $\lambda$ = 515 nm and $P$ = 0.01 mW cm$^{-2}$. The conventional photoconductive effect is unlikely to account for such a superior photoresponse, which is ultimately understood in terms of the increased specific surface area and the photogating effect caused by trapping states. This work provides a perspective for the modulation of optoelectronic properties and performance in quasi-1D materials., Comment: 23 pages, 4 figures and SI

In this study, a SYBR Green-based real-time quantitative polymerase chain reaction (qPCR) assay was developed for rapid detection of porcine parvovirus (PPV) 6. Primer pairs targeting the conserved regions of PPV6 Capsid gene were designed. Sensitivity analyses revealed the lowest detection limit of the SYBR Green-based real-time PCR assay to be 47.8 copies/μL, which indicated it was 1000 times higher than that found in the conventional PCR investigations. This assay was specific and showed no cross-species amplification with other six porcine viruses. The assay demonstrated high repeatability and reproducibility; the intra- and inter-assay coefficients of variation were 0.79% and 0.42%, respectively. The positive detection rates of 180 clinical samples with SYBR Green-based real-time PCR and conventional PCR were 12.22% (22/180) and 4.44% (8/180), respectively. Our method is sensitive, specific, and reproducible. The use of SYBR Green-based real-time PCR may be suitable for the clinical detection and epidemiological investigation of PPV6.

Retinal pigment epithelium (RPE) degenerative death is an evident hallmark of advanced age-related macular degeneration (AMD). The present study aims to evaluate the protective effects of S-allyl L-cysteine (SAC), a bioactive component from aged garlic extracts, on the oxidative stress-related apoptosis of RPE cells and to investigate the potential underlying mechanisms.Cell Counting Kit-8 (CCK-8) assay, flow cytometry, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining were performed to evaluate the effects of SAC on the hydroquinone-treated human ARPE19 cells. The Reactive Oxygen Species (ROS) production was measured by virtue of flow cytometry or determined under an inverted fluorescence microscope. Furthermore, the expression of antioxidant factor Nrf2, as well as downstream antioxidant genes, including NQO1, SOD1, SOD2, and HO1 was assessed in hydroquinone stimulated ARPE19 cells, in the presence or absence of SAC pretreatment.Hydroquinone incitement contributed to a marked decrease in cell viability, but enhanced cell apoptosis, whereas SAC addition did not cause significant alterations. When cells were pre-treated with SAC, cell proliferation was dramatically enhanced whereas apoptosis was mitigated, and the ROS generation induced by hydroquinone was also significantly suppressed, indicating a prominent function of SAC in preventing ARPE19 cells from oxidant-related apoptosis. The elevated expression levels of Nrf2 and other antioxidant genes driven by hydroquinone were downregulated by SAC addition.These data suggest that SAC can effectively attenuate hydroquinone-induced oxidative damage in human RPE cells. Our work is the first to demonstrate that SAC modulates oxidative stress-induced RPE apoptosis, thereby potentially proving new insights into the treatment of AMD.

The local structures and the g factors g

Schottky junctions, formed by high work function metals and semiconductors, are important devices in electronics and optoelectronics. The metal deposition in traditional Schottky interfaces usually damages the semiconductor surface and causes defect states, which reduces the Schottky barrier height and device performance. This can be avoided in the atomically smooth interface formed by two-dimensional (2D) metals and semiconductors. For better interface tailoring engineering, it is particularly important to understand various interface effects in such 2D Schottky devices under critical or boundary conditions. Here we report the fabrication and testing of three types of MoS2 devices, i.e., using PtTe2, Cr and Au as contact materials. While the Cr/MoS2 contact is an ohmic contact, the other two are Schottky contacts. The van-der-Waals interface of PtTe2–MoS2 results in a well-defined OFF state and a significant rectification ratio of 104. This parameter, together with an ideality factor 2.1, outperforms the device based on evaporated Au. Moreover, a device in the intermediate condition is also presented. An abrupt increase in the reverse current is observed and understood based on the enhanced tunneling current. Our work manifests the essential role of doping concentration and provides another example for 2D Schottky interface design.

Gas suspension calciner is a kind of ideal fluidization process equipment for energy economy. In order to improve the effective of gas suspension calciner, a series of effecting factors such as producer gas component, air-fuel ratio, products moisture and heat dissipation on calciner energy consumption were discussed in this paper, which is based on the research of thermal balance calculation of gas suspension calciner. The study of thermal balance calculation has significant meaning on the energy-saving and the whole refinery energy consumption.

At present, China’s energy structure is mainly based on fossil fuels, which has brought serious problems such as environmental pollution, low energy efficiency and poor development quality. In the automotive industry, in order to save energy and protect the environment, many countries are actively promoting the production of new energy vehicles, optimizing the use of resources and benefits, and achieving green development. Based on the idea of sharing economy, this paper constructs a two-stage model. Considering the different quality of new energy vehicles in the two stages, optimization theory, game theory and other methods are used to study the influence of sharing behavior on enterprise operation decisions, and the following conclusions are drawn. First, in the presence of product sharing, product quality is negatively correlated with the optimal profit of the enterprise. Second, there is a negative correlation between the charging rate of the third-party platform and the optimal profit of the enterprise, and with the increase of the charging rate of the platform, the decline of the optimal profit of the enterprise is less and less. Third, when product sharing exists, the ratio of product quality in the two stages is positively correlated with the optimal profit of the enterprise.

For a welding procedure with grooves or filler materials, to avoid underestimating the welding distortion in predictions based on the residual plastic strain, a prediction approach is proposed to estimate the welding distortion based on the local displacement in the weld plastic zone, and the proposed method is verified using the thermal elastic–plastic finite element method. Additionally, the welding distortions of an orthotropic deck are estimated using the proposed method and compared with the experimental measurements. The results show that the proposed method can be used to predict the welding distortion with a high accuracy, and in addition to the welding procedures with grooves or filler materials, the proposed method is also applicable to procedures without them.

The purpose of this study was to examine centromere protein U (CENPU) expression in non-small cell lung cancer (NSCLC) and identify the clinical values of CENPU, as well as investigate the potential molecular mechanisms in NSCLC.The expression levels and clinical significance of CENPU were systematically evaluated in human protein atlas datasets and TCGA datasets. CENPU protein expression was studied by Western blotting. CENPU mRNA expression was studied by Real Time-Polymerase Chain Reaction (RT-PCR). Proliferation, migration, and invasion capacities of CENPU cells were assessed after silencing CENPU. Apoptosis was determined using flow cytometry. Western blotting was performed to assess the protein expression levels.We found that the expression of CENPU at mRNA and protein levels was significantly up-regulated in both NSCLC tissues and cell lines. Overexpression of CENPU was significantly associated with poor prognosis of NSCLC patients. Knockdown of CENPU significantly suppressed proliferation, migration, and invasion, and caused apoptosis of NSCLC cells in vitro. In addition, knockdown of CENPU suppressed epithelial-mesenchymal transition (EMT). Furthermore, our results revealed that the abnormal expression of CENPU could influence the Wnt/β-catenin signaling pathway.CENPU was highly expressed in NSCLC tissues and its knockdown of CENPU strongly suppressed NSCLC cell proliferation and metastasis through modulating Wnt/β-catenin signaling. Targeting CENPU could be a promising therapeutic strategy for patients with CENPU.

The polarized energy dispersive X-ray fluorescence analysis method can effectively reduce detection limits by improving the signal-to-noise ratio. However, the lack of high-power density and small analysis area of the polarized X-ray beam has hindered more accurate analysis of samples in conventional laboratory. A polycapillary X-ray lens can be applied to micro-area analysis. Therefore, a micro-area polarized energy dispersive X-ray fluorescence spectrometer based on a bent highly oriented pyrolytic graphite and a polycapillary X-ray lens is proposed. The polarization degree of the polarized X-ray beam is 99.76% and its focal spot size is 338.8 μm × 404.5 μm. The new spectrometer feasibility was proved by effective production of high-resolution element distribution maps of a holly (Ilex chinensis Sims) leaf sample.

A simulation model is established to simulate the X-ray transmission performance through a polycapillary focusing X-ray lens whose configuration curve was described by a piecewise function. The shape of the lens is segmented, and each segment uses different function curve. The ray tracing principle is used to simulate the transmission performance of X-rays through the polycapillary focusing X-ray lens. And the simulation results were compared with the experimental results.

The dynamics of the core and outer micro-turbulence during the low–intermediate–high (L–I–H) confinement transition have been investigated simultaneously by a tangential CO2 laser collective scattering system on EAST. It is found that, the intensity of micro-turbulence decreases most strongly near the outer region of the plasma, with less dramatic reduction deeper into the plasma. During the transition, the cross-coherence between broadband turbulence at neighboring wave-numbers in the same region of the plasma increase from less than 0.3 to greater than 0.8 just after the I–H transition. Besides, the magnetic fluctuations in the LCO frequency range reaches a maximum just before the final transition to H-mode, indicating the plausible underlying role of the perturbation of the pressure gradient in the triggering of the transition dynamics. These results would help to achieve a more comprehensive understanding of the L–H transition mechanism.

The different crack initiation modes from different internal defects of a high carbon chromium bearing steel are investigated in the present paper. The relative granular bright facet (GBF) size is approximately proportional to . The critical applied stress intensity factor range at the periphery of inclusion ΔKinc,th, above which the GBF will no longer be formed, was obtained. For the present SUJ2 steel, ΔKinc,th = 8 MPa m1/2. The crack growth process in GBF is further investigated by the low–high two-step variable amplitude loading tests. The crack growth process in GBF can be described by . The exponent m0 is a material constant independent of the applied stress amplitude and the inclusion size and increases with increasing of HV.

The dynamics of the turbulent fluctuations during the H–L back transition have been studied on EAST by a CO2 laser collective scattering system. The limit-cycle oscillation (LCO) regime has been frequently observed during the H–L back transition, and the oscillation frequency increases gradually as the back transition is approached. In the LCO regime, both the core and outer fluctuation level have a gradual increase, and reach a maximum near the back transition to L-mode, which mainly result from the appearance and enhancement of a low-frequency (10–20 kHz) quasi-coherent structure. The cross-spectrum analysis suggests that the QC structure could propagate from the core to the outer region.