Spontaneous Ferromagnetism Induced Topological Transition in EuB_{6}.

The interplay between various symmetries and electronic bands topology is one of the core issues for topological quantum materials. Spontaneous magnetism, which leads to the breaking of time-reversal symmetry, has been proven to be a powerful approach to trigger various exotic topological phases. In this Letter, utilizing the combination of angle-resolved photoemission spectroscopy, magneto-optical Kerr effect microscopy, and first-principles calculations, we present the direct evidence on the realization of the long-sought spontaneous ferromagnetism induced topological transition in soft ferromagnetic EuB_{6}. Explicitly, we reveal the topological transition is from Z_{2}=1 topological insulator in paramagnetic state to χ=1 magnetic topological semimetal in low temperature ferromagnetic state. Our results demonstrate that the simple band structure near the Fermi level and rich topological phases make EuB_{6} an ideal platform to study the topological phase physics.

Performance of the BL03U beamline at SSRF.

The vacuum ultraviolet beamline BL03U with a photon energy range from 7 eV upwards has been constructed at the 3.5 GeV Shanghai Synchrotron Radiation Facility. Equipped with an APPLE-Knot undulator, this beamline is dedicated to angle-resolved photoemission spectroscopy. An energy-resolving power of higher than 4.6 × 104 has been achieved in the photon energy range 21.6-48 eV, which is almost the same as the theoretical estimation.

Photoemission Spectroscopic Evidence for the Dirac Nodal Line in the Monoclinic Semimetal SrAs_{3}.

Topological nodal-line semimetals with exotic quantum properties are characterized by symmetry-protected line-contact bulk band crossings in the momentum space. However, in most of identified topological nodal-line compounds, these topological nontrivial nodal lines are enclosed by complicated topological trivial states at the Fermi energy (E_{F}), which would perplex their identification and hinder further applications. Utilizing angle-resolved photoemission spectroscopy and first-principles calculations, we provide compelling evidence for the existence of Dirac nodal-line fermions in the monoclinic semimetal SrAs_{3}, which possesses a simple nodal loop in the vicinity of E_{F} without the distraction from complicated trivial Fermi surfaces. Our calculations revealed that two bands with opposite parities were inverted around Y near E_{F}, resulting in the single nodal loop at the Γ-Y-S plane with a negligible spin-orbit coupling effect. The band crossings were tracked experimentally and the complete nodal loop was identified quantitatively, which provide a critical experimental support for the existence of nodal-line fermions in the CaP_{3} family of materials. Hosting simple topological nontrivial bulk electronic states around E_{F} and without complication from the trivial states, SrAs_{3} is expected to be a potential platform for topological quantum state investigation and applications.

Charge Transfer Effects in Naturally Occurring van der Waals Heterostructures (PbSe)_{1.16}(TiSe_{2})_{m} (m=1, 2).

van der Waals heterostructures (VDWHs) exhibit rich properties and thus has potential for applications, and charge transfer between different layers in a heterostructure often dominates its properties and device performance. It is thus critical to reveal and understand the charge transfer effects in VDWHs, for which electronic structure measurements have proven to be effective. Using angle-resolved photoemission spectroscopy, we studied the electronic structures of (PbSe)_{1.16}(TiSe_{2})_{m} (m=1, 2), which are naturally occurring VDWHs, and discovered several striking charge transfer effects. When the thickness of the TiSe_{2} layers is halved from m=2 to m=1, the amount of charge transferred increases unexpectedly by more than 250%. This is accompanied by a dramatic drop in the electron-phonon interaction strength far beyond the prediction by first-principles calculations and, consequently, superconductivity only exists in the m=2 compound with strong electron-phonon interaction, albeit with lower carrier density. Furthermore, we found that the amount of charge transferred in both compounds is nearly halved when warmed from below 10 K to room temperature, due to the different thermal expansion coefficients of the constituent layers of these misfit compounds. These unprecedentedly large charge transfer effects might widely exist in VDWHs composed of metal-semiconductor contacts; thus, our results provide important insights for further understanding and applications of VDWHs.

Unveiling the Superconducting Mechanism of Ba_{0.51}K_{0.49}BiO_{3}.

The mechanism of high superconducting transition temperatures (T_{c}) in bismuthates remains under debate despite more than 30 years of extensive research. Our angle-resolved photoemission spectroscopy studies on Ba_{0.51}K_{0.49}BiO_{3} reveal an unexpectedly 34% larger bandwidth than in conventional density functional theory calculations. This can be reproduced by calculations that fully account for long-range Coulomb interactions-the first direct demonstration of bandwidth expansion due to the Fock exchange term, a long-accepted and yet uncorroborated fundamental effect in many body physics.Furthermore, we observe an isotropic superconducting gap with 2Δ_{0}/k_{B}T_{c}=3.51±0.05, and strong electron-phonon interactions with a coupling constant λ∼1.3±0.2. These findings solve a long-standing mystery-Ba_{0.51}K_{0.49}BiO_{3} is an extraordinary Bardeen-Cooper-Schrieffer superconductor, where long-range Coulomb interactions expand the bandwidth, enhance electron-phonon coupling, and generate the high T_{c}. Such effects will also be critical for finding new superconductors.

Quasiparticle mass enhancement and temperature dependence of the electronic structure of ferromagnetic SrRuO3 thin films.

We report high-resolution angle-resolved photoemission studies of epitaxial thin films of the correlated 4d transition metal oxide ferromagnet SrRuO(3). The Fermi surface in the ferromagnetic state consists of well-defined Landau quasiparticles exhibiting strong coupling to low-energy bosonic modes which contributes to the large effective masses observed by transport and thermodynamic measurements. Upon warming the material through its Curie temperature, we observe a substantial decrease in quasiparticle coherence but negligible changes in the ferromagnetic exchange splitting, suggesting that local moments play an important role in the ferromagnetism in SrRuO(3).

Genotypic diversity enhances invasive ability of Spartina alterniflora.

Although genetic diversity is very important for alien species, which have to cope with new environments, little is known about the role that genetic diversity plays in their invasive success. In this study, we set up a manipulation experiment including three levels of genotypic diversity to test whether genotypic diversity can enhance the invasive ability of alien species, in our case the invasive Spartina alterniflora in China, and to infer the underlying mechanisms. There was no significant relationship between genotypic diversity and parameters of performance in the first year; however, from the summer of the second year onwards, genotypic diversity enhanced four of the six parameters of performance. After two growing seasons, there were significant positive relationships between genotypic diversity and maximum spread distance, patch size, shoot number per patch, and aboveground biomass. Moreover, abundance of the native dominant species Scirpus mariqueter was marginally significantly decreased with genotypic diversity of S. alterniflora, suggesting that enhanced invasive ability of S. alterniflora may have depressed the growth of the native species. There was no significant difference in most measures of performance among six genotypes, but we observed a transgressive over performance in four measures in multiple-genotype patches. At the end of the experiment, there were significant nonadditive effects of genotypic diversity according to Monte Carlo permutations, in six-genotype, but not three-genotype plots. Our results indicated that both additive and nonadditive effects played roles in the positive relationship between genetic diversity and invasion success, and nonadditive effects were stronger as duration increased.

Temperature dependence of the electronic structure and Fermi-surface reconstruction of Eu(1-x)Gd(x)O through the ferromagnetic metal-insulator transition.

We present angle-resolved photoemission spectroscopy of Eu(1-x)Gd(x)O through the ferromagnetic metal-insulator transition. In the ferromagnetic phase, we observe Fermi surface pockets at the Brillouin zone boundary, consistent with density functional theory, which predicts a half-metal. Upon warming into the paramagnetic state, our results reveal a strong momentum-dependent evolution of the electronic structure, where the metallic states at the zone boundary are replaced by pseudogapped states at the Brillouin zone center due to the absence of magnetic long-range order of the Eu 4f moments.

Effect of miR-126 on intracranial aneurysms and its predictive value for rupture of aneurysms.

OBJECTIVE: This study aimed to investigate the effect of miR-126 on intracranial aneurysm (IA) and its predictive value for aneurysm rupture. PATIENTS AND METHODS: Altogether 102 patients (patient group) with IA diagnosed in the Jinhua Municipal Central Hospital from July 2016 to April 2018, and 80 healthy people (normal group) who underwent physical examination during the same period were collected. QRT-PCR was used to detect the expression of miR-126 in serum, analyze the expression of miR-126 in IA, and explore the predictive value on IA rupture. Potential target genes of miR-126 were analyzed by target gene prediction website, and David was used to analyze the enrichment of miR-126 target gene GO and KEGG. RESULTS: The expression of miR-126 in serum of patient group was significantly higher than that of normal group (p < 0.05), ROC curve area was 0.966. The high expressions of miR-126 were directly related to the possibility of large lesions (p < 0.05). Multivariate analysis showed that lesion size and miR-126 expression were independent risk factors for rupture of IA patients. ROC curve showed that lesion size and miR-126 expression area under the curve were 0.707 and 0.827. Altogether 520 potential target sites were found by Venn diagram of Targetscan, miRDB, and Starbase online miR-126 prediction website. GO enrichment and KEGG analysis by David online software found that miR-126 target genes were mainly enriched in 169 biological processes, such as nucleus, transcription, DNA-templated, transcription factor activity, sequence-specific DNA binding, protein binding, and phosphatidylinositol phosphorylation. KEGG analysis found that miR-126 target genes were significantly enriched in MAPK signaling pathway, pathways in cancer, ErbB signaling pathway, MicroRNAs in cancer, and Thyroid hormone signaling pathway. CONCLUSIONS: MiR-126 can be used as a potential diagnostic and predictive indicator for IA occurrence and IA rupture.

Momentum dependent [Formula: see text] band splitting in LaFeAsO.

The nematic phase in iron based superconductors (IBSs) has attracted attention with a notion that it may provide important clue to the superconductivity. A series of angle-resolved photoemission spectroscopy (ARPES) studies were performed to understand the origin of the nematic phase. However, there is lack of ARPES study on LaFeAsO nematic phase. Here, we report the results of ARPES studies of the nematic phase in LaFeAsO. Degeneracy breaking between the [Formula: see text] and [Formula: see text] hole bands near the [Formula: see text] and M point is observed in the nematic phase. Different temperature dependent band splitting behaviors are observed at the [Formula: see text] and M points. The energy of the band splitting near the M point decreases as the temperature decreases while it has little temperature dependence near the [Formula: see text] point. The nematic nature of the band shift near the M point is confirmed through a detwin experiment using a piezo device. Since a momentum dependent splitting behavior has been observed in other iron based superconductors, our observation confirms that the behavior is a universal one among iron based superconductors.

Human multidrug-resistant cell lines: increased mdr1 expression can precede gene amplification.

The development of simultaneous resistance to multiple structurally unrelated drugs is a major impediment to cancer chemotherapy. Multidrug resistance in human KB carcinoma cells selected in colchicine, vinblastine, or Adriamycin is associated with amplification of specific DNA sequences (the multidrug resistance locus, mdr1). During colchicine selection resistance is initially accompanied by elevated expression of a 4.5-kilobase mdr1 messenger RNA (mRNA) without amplification of the corresponding genomic sequences. During selection for increased levels of resistance, expression of this mRNA is increased simultaneously with amplification of mdr1 DNA. Increased expression and amplification of mdr1 sequences were also found in multidrug-resistant sublines of human leukemia and ovarian carcinoma cells. These results suggest that increased expression of mdr1 mRNA is a common mechanism for multidrug resistance in human cells. Activation of the mdr1 gene by mutations or epigenetic changes may precede its amplification during the development of resistance.

Defects controlled hole doping and multivalley transport in SnSe single crystals.

SnSe is a promising thermoelectric material with record-breaking figure of merit. However, to date a comprehensive understanding of the electronic structure and most critically, the self-hole-doping mechanism in SnSe is still absent. Here we report the highly anisotropic electronic structure of SnSe investigated by angle-resolved photoemission spectroscopy, in which a unique pudding-mould-shaped valence band with quasi-linear energy dispersion is revealed. We prove that p-type doping in SnSe is extrinsically controlled by local phase segregation of SnSe2 microdomains via interfacial charge transferring. The multivalley nature of the pudding-mould band is manifested in quantum transport by crystallographic axis-dependent weak localisation and exotic non-saturating negative magnetoresistance. Strikingly, quantum oscillations also reveal 3D Fermi surface with unusual interlayer coupling strength in p-SnSe, in which individual monolayers are interwoven by peculiar point dislocation defects. Our results suggest that defect engineering may provide versatile routes in improving the thermoelectric performance of the SnSe family.

Multidrug resistance of DNA-mediated transformants is linked to transfer of the human mdr1 gene.

Mouse NIH 3T3 cells were transformed to multidrug resistance with high-molecular-weight DNA from multidrug-resistant human KB carcinoma cells. The patterns of cross resistance to colchicine, vinblastine, and doxorubicin hydrochloride (Adriamycin; Adria Laboratories Inc.) of the human donor cell line and mouse recipients were similar. The multidrug-resistant human donor cell line contains amplified sequences of the mdr1 gene which are expressed at high levels. Both primary and secondary NIH 3T3 transformants contained and expressed these amplified human mdr1 sequences. Amplification and expression of the human mdr1 sequences and amplification of cotransferred human Alu sequences in the mouse cells correlated with the degree of multidrug resistance. These data suggest that the mdr1 gene is likely to be responsible for multidrug resistance in cultured cells.

Double minute chromosomes carrying the human multidrug resistance 1 and 2 genes are generated from the dimerization of submicroscopic circular DNAs in colchicine-selected KB carcinoma cells.

This study characterizes amplified structures carrying the human multidrug resistance (MDR) genes in colchicine-selected multidrug resistant KB cell lines and strongly supports a model of gene amplification in which small circular extrachromosomal DNA elements generated from contiguous chromosomal DNA regions multimerize to form cytologically detectable double minute chromosomes (DMs). The human MDR1 gene encodes the 170-kDa P-glycoprotein, which is a plasma membrane pump for many structurally unrelated chemotherapeutic drugs. MDR1 and its homolog, MDR2, undergo amplification when KB cells are subjected to stepwise selection in increasing concentrations of colchicine. The structure of the amplification unit at each step of drug selection was characterized using both high-voltage gel electrophoresis and pulsed-field gel electrophoresis (PFGE) techniques. An 890-kb submicroscopic extrachromosomal circular DNA element carrying the MDR1 and MDR2 genes was detected in cell line KB-ChR-8-5-11, the earliest step in drug selection in which conventional Southern/hybridization analyses detected MDR gene amplification. When KB-ChR-8-5-11 was subjected to stepwise increases in colchicine, this circular DNA element dimerized as detected by PFGE with and without digestion with Not 1, which linearizes the 890-kb amplicon. This dimerization process, which also occurred at the next step of colchicine selection, resulted in the formation of cytologically detectable DMs revealed by analysis of Giemsa-stained metaphase spreads.

In situ hybridization analysis of acquisition and loss of the human multidrug-resistance gene.

The extent of multidrug-resistance of human KB carcinoma cell lines has been shown to be proportional to the level of expression of the MDR1 gene. Using an in situ hybridization analysis with 35S-labeled RNA probes, we have found that there is some heterogeneity in expression of the MDR1 gene from cell to cell, but that the average level of expression is proportional to the resistance of the cell line. In the absence of selective pressure, a colchicine-selected multidrug-resistant population with a highly amplified MDR1 gene loses its resistance in parallel with the loss of the amplified gene. Loss of resistance also parallels a decrease in MDR1 RNA expression in the whole cell population. Loss of MDR1 expression in this population is highly heterogeneous, with small clusters of cells maintaining expression even after the population as a whole has become relatively sensitive. This heterogenous loss of expression of the MDR1 gene is consistent with random segregation of amplified DNA segments in the selected cells. The analysis of MDR1 RNA expression by in situ hybridization which is validated by this study should be useful in the study of normal human tissue and tumor samples expressing the MDR1 gene.

Direct observation of the Dirac nodes lifting in semimetallic perovskite SrIrO3 thin films.

Perovskite SrIrO3 has long been proposed as an exotic semimetal induced by the interplay between the spin-orbit coupling and electron correlations. However, its low-lying electronic structure is still lacking. We synthesize high-quality perovskite SrIrO3 (100) films by means of oxide molecular beam epitaxy, and then systemically investigate their low energy electronic structure using in-situ angle-resolved photoemission spectroscopy. We find that the hole-like bands around R and the electron-like bands around U(T) intersect the Fermi level simultaneously, providing the direct evidence of the semimetallic ground state in this compound. Comparing with the density functional theory, we discover that the bandwidth of states near Fermi level is extremely small, and there exists a pronounced mixing between the Jeff = 1/2 and Jeff = 3/2 states. Moreover, our data reveal that the predicted Dirac degeneracy protected by the mirror-symmetry, which was theoretically suggested to be the key to realize the non-trivial topological properties, is actually lifted in perovskite SrIrO3 thin films. Our findings pose strong constraints on the current theoretical models for the 5d iridates.

Intrinsic drug resistance in human kidney cancer is associated with expression of a human multidrug-resistance gene.

The cloning of the cDNA for the mdr1 gene, whose expression is associated with the development of multidrug-resistance in cultured cells, has made it possible to explore the mechanism of multidrug resistance in human tumors. We have found that normal human kidney, six of eight adenocarcinomas of the kidney, and four cell lines derived from kidney adenocarcinomas express high levels of mdr1 mRNA. Two criteria suggest that primary multidrug resistance in human adenocarcinomas of the kidney results, at least in part, from expression of the mdr1 gene: (1) mdr1 mRNA levels are elevated in four unselected kidney adenocarcinoma cell lines that show a multidrug-resistant phenotype; and (2) multidrug resistance in these kidney cancer cell lines is reversed by verapamil and quinidine, agents known to reverse mdr1-associated drug resistance in cell lines selected for multidrug resistance in vitro. These results suggest that appropriate pharmacological intervention to reverse multidrug resistance might make adenocarcinomas of the kidney more sensitive to chemotherapy with agents such as Adriamycin (Adria Laboratories, Columbus, OH) and the vinca alkaloids.

Electronic structure of a new layered bismuth oxyselenide superconductor: LaO0.5F0.5BiSe2.

LaO(0.5)F(0.5)BiSe(2) is a new layered superconductor discovered recently, which shows the superconducting transition temperature of 3.5 K. With angle-resolved photoemission spectroscopy, we study the electronic structure of LaO(0.5)F(0.5)BiSe(2) comprehensively. Two electron-like bands are located around the X point of the Brillouin zone, and the outer pockets connect with each other and form large Fermi surface around Γ and M. These bands show negligible k(z) dispersion, indicating their two-dimensional nature. Based on the Luttinger theorem, the carrier concentration is about 0.53 e(-) per unit cell, close to its nominal value. Moreover, the photoemission data and the band structure calculations agree very well, and the renormalization factor is nearly 1.0, indicating the electron correlations in this material are rather weak. Our results suggest that LaO(0.5)F(0.5)BiSe(2) is a conventional BCS superconductor without strong electron correlations.

[Purification of 31/32 kDa proteins of adult Schistosoma japonicum and studies on their protective immunity].

Schistosoma japonicum adult worm 31/32 kDa proteins (Sj 31/32) were separated on polyacrylamide slab gels and purified by electrophoretic elution. These purified proteins were used to immunize mice in order to observe their protective immunity against challenge. The results of SDS-PAGE,EITB and ELISA indicated that the 31/32 kDa proteins separated and purified by means of these methods were pure and active. It was assumed that Sj 31/32 proteins could reduce worm burden and inhibit the fecundity of schistosome and formation of egg granuloma. The results suggested that 31/32 kDa S. japonicum proteins might be an important component of a multivalent vaccine against schistosomiasis japonica (Figs. 1-4).

Novel electronic structure induced by a highly strained oxide interface with incommensurate crystal fields.

The misfit oxide, Bi2Ba1.3K0.6Co2.1O7.94, made of alternating rocksalt-structured [BiO/BaO] layers and hexagonal CoO2 layers, was studied by angle-resolved photoemission spectroscopy, revealing the electronic structure of a highly strained oxide interface. We found that low-energy states are confined within individual sides of the interface, but scattered by the incommensurate crystal field from the other side. Furthermore, the high strain on the rocksalt layer induces large charge transfer to the CoO2 layer, and a novel effect, the interfacial enhancement of electron-phonon interactions, is discovered.