Van Hove annihilation and nematic instability on a kagome lattice.

A nematic phase breaks the point-group symmetry of the crystal lattice and is known to emerge in correlated materials. Here we report the observation of an intra-unit-cell nematic order and associated Fermi surface deformation in the kagome metal ScV6Sn6. Using scanning tunnelling microscopy and scanning tunnelling spectroscopy, we reveal a stripe-like nematic order breaking the crystal rotational symmetry within the kagome lattice itself. Moreover, we identify a set of Van Hove singularities adhering to the kagome-layer electrons, which appear along one direction of the Brillouin zone and are annihilated along other high-symmetry directions, revealing rotational symmetry breaking. Via detailed spectroscopic maps, we further observe an elliptical deformation of the Fermi surface, which provides direct evidence for an electronically mediated nematic order. Our work not only bridges the gap between electronic nematicity and kagome physics but also sheds light on the potential mechanism for realizing symmetry-broken phases in correlated electron systems.

A hybrid topological quantum state in an elemental solid.

Topology1-3 and interactions are foundational concepts in the modern understanding of quantum matter. Their nexus yields three important research directions: (1) the competition between distinct interactions, as in several intertwined phases, (2) the interplay between interactions and topology that drives the phenomena in twisted layered materials and topological magnets, and (3) the coalescence of several topological orders to generate distinct novel phases. The first two examples have grown into major areas of research, although the last example remains mostly unexplored, mainly because of the lack of a material platform for experimental studies. Here, using tunnelling microscopy, photoemission spectroscopy and a theoretical analysis, we unveil a 'hybrid' topological phase of matter in the simple elemental-solid arsenic. Through a unique bulk-surface-edge correspondence, we uncover that arsenic features a conjoined strong and higher-order topology that stabilizes a hybrid topological phase. Although momentum-space spectroscopy measurements show signs of topological surface states, real-space microscopy measurements unravel a unique geometry of topologically induced step-edge conduction channels revealed on various natural nanostructures on the surface. Using theoretical models, we show that the existence of gapless step-edge states in arsenic relies on the simultaneous presence of both a non-trivial strong Z2 invariant and a non-trivial higher-order topological invariant, which provide experimental evidence for hybrid topology. Our study highlights pathways for exploring the interplay of different band topologies and harnessing the associated topological conduction channels in engineered quantum or nano-devices.

Visualizing Higher-Fold Topology in Chiral Crystals.

Novel topological phases of matter are fruitful platforms for the discovery of unconventional electromagnetic phenomena. Higher-fold topology is one example, where the low-energy description goes beyond standard model analogs. Despite intensive experimental studies, conclusive evidence remains elusive for the multigap topological nature of higher-fold chiral fermions. In this Letter, we leverage a combination of fine-tuned chemical engineering and photoemission spectroscopy with photon energy contrast to discover the higher-fold topology of a chiral crystal. We identify all bulk branches of a higher-fold chiral fermion for the first time, critically important for allowing us to explore unique Fermi arc surface states in multiple interband gaps, which exhibit an emergent ladder structure. Through designer chemical gating of the samples in combination with our measurements, we uncover an unprecedented multigap bulk boundary correspondence. Our demonstration of multigap electronic topology will propel future research on unconventional topological responses.

Coexistence of Bulk-Nodal and Surface-Nodeless Cooper Pairings in a Superconducting Dirac Semimetal.

The interplay of nontrivial topology and superconductivity in condensed matter physics gives rise to exotic phenomena. However, materials are extremely rare where it is possible to explore the full details of the superconducting pairing. Here, we investigate the momentum dependence of the superconducting gap distribution in a novel Dirac material PdTe. Using high resolution, low temperature photoemission spectroscopy, we establish it as a spin-orbit coupled Dirac semimetal with the topological Fermi arc crossing the Fermi level on the (010) surface. This spin-textured surface state exhibits a fully gapped superconducting Cooper pairing structure below T_{c}∼4.5 K. Moreover, we find a node in the bulk near the Brillouin zone boundary, away from the topological Fermi arc. These observations not only demonstrate the band resolved electronic correlation between topological Fermi arc states and the way it induces Cooper pairing in PdTe, but also provide a rare case where surface and bulk states host a coexistence of nodeless and nodal gap structures enforced by spin-orbit coupling.

Visualization of Tunable Weyl Line in A-A Stacking Kagome Magnets.

Kagome magnets provide a fascinating platform for a plethora of topological quantum phenomena, in which the delicate interplay between frustrated crystal structure, magnetization, and spin-orbit coupling (SOC) can engender highly tunable topological states. Here, utilizing angle-resolved photoemission spectroscopy, the Weyl lines are directly visualized with strong out-of-plane dispersion in the A-A stacked kagome magnet GdMn6 Sn6 . Remarkably, the Weyl lines exhibit a strong magnetization-direction-tunable SOC gap and binding energy tunability after substituting Gd with Tb and Li, respectively. These results not only illustrate the magnetization direction and valence counting as efficient tuning knobs for realizing and controlling distinct 3D topological phases, but also demonstrate AMn6 Sn6 (A = rare earth, or Li, Mg, or Ca) as a versatile material family for exploring diverse emergent topological quantum responses.

Evidence of a room-temperature quantum spin Hall edge state in a higher-order topological insulator.

Room-temperature realization of macroscopic quantum phases is one of the major pursuits in fundamental physics1,2. The quantum spin Hall phase3-6 is a topological quantum phase that features a two-dimensional insulating bulk and a helical edge state. Here we use vector magnetic field and variable temperature based scanning tunnelling microscopy to provide micro-spectroscopic evidence for a room-temperature quantum spin Hall edge state on the surface of the higher-order topological insulator Bi4Br4. We find that the atomically resolved lattice exhibits a large insulating gap of over 200 meV, and an atomically sharp monolayer step edge hosts an in-gap gapless state, suggesting topological bulk-boundary correspondence. An external magnetic field can gap the edge state, consistent with the time-reversal symmetry protection inherent in the underlying band topology. We further identify the geometrical hybridization of such edge states, which not only supports the Z2 topology of the quantum spin Hall state but also visualizes the building blocks of the higher-order topological insulator phase. Our results further encourage the exploration of high-temperature transport quantization of the putative topological phase reported here.

Observation of a linked-loop quantum state in a topological magnet.

Quantum phases can be classified by topological invariants, which take on discrete values capturing global information about the quantum state1-13. Over the past decades, these invariants have come to play a central role in describing matter, providing the foundation for understanding superfluids5, magnets6,7, the quantum Hall effect3,8, topological insulators9,10, Weyl semimetals11-13 and other phenomena. Here we report an unusual linking-number (knot theory) invariant associated with loops of electronic band crossings in a mirror-symmetric ferromagnet14-20. Using state-of-the-art spectroscopic methods, we directly observe three intertwined degeneracy loops in the material's three-torus, T3, bulk Brillouin zone. We find that each loop links each other loop twice. Through systematic spectroscopic investigation of this linked-loop quantum state, we explicitly draw its link diagram and conclude, in analogy with knot theory, that it exhibits the linking number (2, 2, 2), providing a direct determination of the invariant structure from the experimental data. We further predict and observe, on the surface of our samples, Seifert boundary states protected by the bulk linked loops, suggestive of a remarkable Seifert bulk-boundary correspondence. Our observation of a quantum loop link motivates the application of knot theory to the exploration of magnetic and superconducting quantum matter.

Unconventional chiral charge order in kagome superconductor KV3Sb5.

Intertwining quantum order and non-trivial topology is at the frontier of condensed matter physics1-4. A charge-density-wave-like order with orbital currents has been proposed for achieving the quantum anomalous Hall effect5,6 in topological materials and for the hidden phase in cuprate high-temperature superconductors7,8. However, the experimental realization of such an order is challenging. Here we use high-resolution scanning tunnelling microscopy to discover an unconventional chiral charge order in a kagome material, KV3Sb5, with both a topological band structure and a superconducting ground state. Through both topography and spectroscopic imaging, we observe a robust 2 × 2 superlattice. Spectroscopically, an energy gap opens at the Fermi level, across which the 2 × 2 charge modulation exhibits an intensity reversal in real space, signalling charge ordering. At the impurity-pinning-free region, the strength of intrinsic charge modulations further exhibits chiral anisotropy with unusual magnetic field response. Theoretical analysis of our experiments suggests a tantalizing unconventional chiral charge density wave in the frustrated kagome lattice, which can not only lead to a large anomalous Hall effect with orbital magnetism, but also be a precursor of unconventional superconductivity.

Signatures of Weyl Fermion Annihilation in a Correlated Kagome Magnet.

The manipulation of topological states in quantum matter is an essential pursuit of fundamental physics and next-generation quantum technology. Here we report the magnetic manipulation of Weyl fermions in the kagome spin-orbit semimetal Co_{3}Sn_{2}S_{2}, observed by high-resolution photoemission spectroscopy. We demonstrate the exchange collapse of spin-orbit-gapped ferromagnetic Weyl loops into paramagnetic Dirac loops under suppression of the magnetic order. We further observe that topological Fermi arcs disappear in the paramagnetic phase, suggesting the annihilation of exchange-split Weyl points. Our findings indicate that magnetic exchange collapse naturally drives Weyl fermion annihilation, opening new opportunities for engineering topology under correlated order parameters.

Spin-orbit quantum impurity in a topological magnet.

Quantum states induced by single-atomic impurities are at the frontier of physics and material science. While such states have been reported in high-temperature superconductors and dilute magnetic semiconductors, they are unexplored in topological magnets which can feature spin-orbit tunability. Here we use spin-polarized scanning tunneling microscopy/spectroscopy (STM/S) to study the engineered quantum impurity in a topological magnet Co3Sn2S2. We find that each substituted In impurity introduces a striking localized bound state. Our systematic magnetization-polarized probe reveals that this bound state is spin-down polarized, in lock with a negative orbital magnetization. Moreover, the magnetic bound states of neighboring impurities interact to form quantized orbitals, exhibiting an intriguing spin-orbit splitting, analogous to the splitting of the topological fermion line. Our work collectively demonstrates the strong spin-orbit effect of the single-atomic impurity at the quantum level, suggesting that a nonmagnetic impurity can introduce spin-orbit coupled magnetic resonance in topological magnets.

Quantum-limit Chern topological magnetism in TbMn6Sn6.

The quantum-level interplay between geometry, topology and correlation is at the forefront of fundamental physics1-15. Kagome magnets are predicted to support intrinsic Chern quantum phases owing to their unusual lattice geometry and breaking of time-reversal symmetry14,15. However, quantum materials hosting ideal spin-orbit-coupled kagome lattices with strong out-of-plane magnetization are lacking16-21. Here, using scanning tunnelling microscopy, we identify a new topological kagome magnet, TbMn6Sn6, that is close to satisfying these criteria. We visualize its effectively defect-free, purely manganese-based ferromagnetic kagome lattice with atomic resolution. Remarkably, its electronic state shows distinct Landau quantization on application of a magnetic field, and the quantized Landau fan structure features spin-polarized Dirac dispersion with a large Chern gap. We further demonstrate the bulk-boundary correspondence between the Chern gap and the topological edge state, as well as the Berry curvature field correspondence of Chern gapped Dirac fermions. Our results point to the realization of a quantum-limit Chern phase in TbMn6Sn6, and may enable the observation of topological quantum phenomena in the RMn6Sn6 (where R is a rare earth element) family with a variety of magnetic structures. Our visualization of the magnetic bulk-boundary-Berry correspondence covering real space and momentum space demonstrates a proof-of-principle method for revealing topological magnets.

Fabrication of bio-inspired nitinol alloy surface with tunable anisotropic wetting and high adhesive ability.

In this paper, micro/nano-scale structures were fabricated on nitinol alloy (NiTi) to realize tunable anisotropic wetting and high adhesive capability. Laser texturing and silanization process are utilized to change the morphological and chemical properties of substrates. It is noted that these treated substrates exhibit the joint characteristics of anisotropic wetting and high adhesive capability. In order to investigate the influences of laser-texturing and silanization processes on NiTi, these surfaces were evaluated using scanning electron microscope (SEM), a white light confocal microscope, X-ray photoelectron spectroscopy (XPS) and goniometer. The relationship between water volume and anisotropic wetting was also established. From the experimental testing, we can obtain the following conclusions: (1) the anisotropic wetting characterized by the difference between the water contact angles (WCAs) in the vertical and parallel directions ranges from 0° to 20.3°, which is far more than the value of natural rice leaves. (2) the water sliding angles (WSAs) kept stable at 180°, successfully mimicking the adhesive ability of rose petals. (3) the silanization process could strengthen the hydrophobicity but weaken anisotropic wetting. These bio-inspired NiTi surfaces have a tremendous potential applications such as microfluidic devices, bio-mimetic materials fabrication and lab on chip.

Observations of the Interaction and Transport of Fine Mode Aerosols with Cloud and/or Fog in Northeast Asia from Aerosol Robotic Network (AERONET) and Satellite Remote Sensing.

Analysis of sun photometer measured and satellite retrieved aerosol optical depth (AOD) data has shown that major aerosol pollution events with very high fine mode AOD (>1.0 in mid-visible) in the China/Korea/Japan region are often observed to be associated with significant cloud cover. This makes remote sensing of these events difficult even for high temporal resolution sun photometer measurements. Possible physical mechanisms for these events that have high AOD include a combination of aerosol humidification, cloud processing, and meteorological co-variation with atmospheric stability and convergence. The new development of Aerosol Robotic network (AERONET) Version 3 Level 2 AOD with improved cloud screening algorithms now allow for unprecedented ability to monitor these extreme fine mode pollution events. Further, the Spectral Deconvolution Algorithm (SDA) applied to Level 1 data (L1; no cloud screening) provides an even more comprehensive assessment of fine mode AOD than L2 in current and previous data versions. Studying the 2012 winter-summer period, comparisons of AERONET L1 SDA daily average fine mode AOD data showed that Moderate Resolution Imaging Spectroradiometer (MODIS) satellite remote sensing of AOD often did not retrieve and/or identify some of the highest fine mode AOD events in this region. Also, compared to models that include data assimilation of satellite retrieved AOD, the L1 SDA fine mode AOD was significantly higher in magnitude, particularly for the highest AOD events that were often associated with significant cloudiness.

[Effect of Sunitinib therapy on immune function of patients with advanced renal cell carcinoma].

Objective: To evaluate the effect of Sunitinib therapy on immune function of patient with advanced renal cell carcinoma. Methods: A total of 27 patient with advanced renal cell carcinoma who received Sunitinib therapy in Chongqing Cancer Hospital from July 2010 to July 2014 were recruited in a prospective cohort study.Nineteen were male patients and 8 were female patients aged from 36 to 75 years with mean age of (58±7)years.Twenty-five cases were renal clear cell carcinoma, the other two cases were papillary renal cell carcinoma and Xp11.2 translocation renal cell carcinoma.According to MSKCC terminal prognosis scoring recommend by NCCN: 22 cases were in low risk, 5 cases were in high risk.All the patient took Sunitinib 50 mg orally once daily for 4 weeks, followed-up by 2 weeks.Flow cytometry was used to detect the levels of CD3+ , CD8+ , CD4+ T lymphocyte, NK cell and B lymphocyte in peripheral blood of patients before taking medicine.The levels of CD3+ , CD8+ , CD4+ T lymphocyte, NK cell, B lymphocyte in peripheral blood were detected again after 4 weeks, 6 weeks, 10 weeks and the disease progression.Paired t-test was used to analyze the data comparison of two groups, mean comparison in groups was conducted with repeated measurements analysis of variance, and the pairwise comparison was performed with LSD-t method. Results: The levels of CD3+ , CD8+ T lymphocyte, NK cell, B lymphocyte were significantly increased after the therapy of Sunitinib for 1 cycle(I-J was 212±22, 163±18, 59±12, 13.8±1.4, respectively, all P<0.05). The levels of CD3+ , CD8+ T lymphocyte, NK cell, B lymphocyte were significantly increased after the therapy of Sunitinib for 2 cycles(I-J was 362±43, 299±28, 91±19, 28.1±3.9, respectively, all P<0.05), while the level of CD4+ lymphocyte was decreased, but no significant difference(F=0.873, P>0.05). CD4+ /CD8+ was significantly decreased after the therapy of Sunitinib for 1 cycle, and it went on decreasing after the therapy of Sunitinib for 2 cycles(I-J was -0.31±0.03, -0.44±0.04, respectively, all P<0.05). Disease progression occurred in 10 cases during the follow-up period.The NK cell, CD3+ , CD4+ , CD8+ T lymphocyte were significantly decreased when the disease progressed(t=2.39-5.769, all P<0.05). Conclusions: Sunitinib has effect on the immune function of patients with advanced renal cell carcinoma, and the progression of renal cell carcinoma is related to the immune function.It suggests that targeted drug therapy should be combined with biological immunotherapy, which may be the research direction for the treatment of advanced renal cell carcinoma.

Human leukocyte antigen G expression in breast cancer: role in immunosuppression.

Human leukocyte antigen G (HLA-G) is an immunotolerant nonclassical major histocompatibility complex Class Ib molecule. It is expressed by trophoblastic placental cells during pregnancy to protect the fetus from maternal alloreactivity. HLA-G is overexpressed in tumors and involved in cancer immune evasion. Reverse transcription-polymerase chain reaction and immunohistochemistry (IHC) were used to examine HLA-G expression in normal mammary and breast cancer cell lines and normal and human breast cancer tissues. Reverse transcription-polymerase chain reaction confirmed that normal epithelial MCF-12A cells had no HLA-G mRNA expression, whereas cancer cell lines MCF-7, T47D, and MDA-MB-231 and NCI/Adr-Res had various levels of HLA-G mRNA expression. Twelve (12) normal and 38 breast cancer tissues were examined by IHC. Fifty-eight (58) percent (22/38) of cancers had medium to strong staining to HLA-G, whereas only 8% (1/12) of normal breast tissues had medium to strong staining, and the difference was significant (p < 0.05). HLA-G staining was found in the membranes and cytoplasm of cancer cells. In conclusion, breast cancer cells overexpress HLA-G mRNA and protein, and this probably contributes to immune evasion.

Manipulation of iron transporter genes results in the suppression of human and mouse mammary adenocarcinomas.

Since malignant cells often have a high demand for iron, we hypothesize that breast cancer cells may alter the expression of iron transporter genes including iron importers [transferrin receptor (TFRC) and solute carrier family 11 (proton-coupled divalent metal ion transporters), member 2 (SLC11A2)] and the iron exporter SLC40A1 (ferroportin), and additionally that the growth of breast cancer can be inhibited by manipulating iron transporter gene expression. To test our hypothesis, reverse transcription polymerase chain reaction (RT-PCR) was used to determine mRNA expression of iron transporter genes in normal human mammary epithelial MCF-12A cells and human breast cancer MCF-7 cells. Antisense oligonucleotides were employed to suppress the expression of TFRC gene in the 4T1 mammary adenocarcinoma in both cell culture and a mouse tumor model. We found the following: i) the MCF-7 cells have higher expression of TFRC and SLC11A2 compared with MCF-12A epithelia; ii) SLC40A1 was only expressed in MCF-12A epithelia but not in MCF-7 cells; iii) iron increased mRNA levels of the SLC11A2 gene in both MCF-12A and MCF-7 cells; iv) TFRC antisense oligonucleotides reduced TFRC mRNA levels and intracellular total iron, and inhibited the proliferation of the 4T1 cells in cell culture; v) TFRC antisense oligonucleotide inhibited tumor growth and lung metastases in the 4T1 mammary adenocarcinoma mouse model. In conclusion, breast cancer cells up-regulate the expression of iron importer genes and down-regulate the expression of iron exporter SLC40A1 to satisfy their increased demand for iron. Suppression of transferrin receptor by antisense results in inhibition of tumor growth and lung metastasis in the 4T1 mammary adenocarcinoma mouse model.

Induction of apoptosis by iron depletion in the human breast cancer MCF-7 cell line and the 13762NF rat mammary adenocarcinoma in vivo.

It is known that the interruption of normal iron metabolism with chelators of iron, toxic metals, toxic metals bound to transferrin, or anti-transferrin receptor antibodies leads to significant inhibition of tumor cell growth in cell culture systems and animal models. In the present study, we found that iron depletion was produced by the iron chelator deferoxamine mesylate, the free toxic metals gallium or indium, and the toxic metals gallium or indium bound to transferrin in the MCF-7 human breast cancer cell line, and this induced the condensation and fragmentation of chromatin, and the formation of DNA fragments characteristic of apoptosis. The induction of apoptosis was quantitated with acridine orange and ethidium bromide staining of apoptotic cells, separation of fragmented DNA from radiolabeled cells, and in situ terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) assays. The apoptosis, caused by deferoxamine mesylate, and gallium or indium bound to transferrin in the MCF-7 cells, can be completely inhibited by excess ferric chloride or equimolar iron-loaded transferrin. Gallium-transferrin and indium-transferrin complexes induced more apoptosis than their respective salts in the MCF-7 cells. Deferoxamine mesylate induced a small increase in the endogenous expression of both the bcl-2 and bax genes in the MCF-7 cells and this can be prevented by ferric chloride. In the 13762NF rat mammary adenocarcinoma model, in situ TUNEL assays showed that the iron-deficiency following a low iron diet or intravenous injection of deferoxamine mesylate produced 5.32 +/- 3.90% and 6.46 +/- 3.58% of apoptotic cells, respectively, compared to 2.01 +/- 1.20% of apoptotic cells in the control rats maintained on a normal diet (p < 0.05 and p < 0.01, respectively, Student's t-test). This is the first report of iron depletion caused by a low iron diet or deferoxamine mesylate treatment inducing apoptosis in rats bearing the 13762NF marnmary adenocarcinoma.

[Determination of metabolites of heroin in urine and discrimination of heroin abuse].

This article describes a sensitive method that detects morphine, 6-monoacetylmorphine, morphine-3-glucuronide and codeine in urine for qualifying the abuse of heroin. The analytes were extracted by solid phase C18. The limits of detection (LOD) for morphine and codeine were 50 ng/ml and 50 ng/ml, respectively. The RSD of morphine and codeine were 11.3% (n = 5), and 14.2% (n = 5) respectively. For urine, it does not need to be hydrolyzed before extracted, and for all analytes, also need not to be derivated. The difference ratio of morphine and codeine in the chromatography can be used to discriminate between the abuse of heroin and the administration of compound liquorice mixture.

Byssinosis in Guangzhou, China.

OBJECTIVES: To study the prevalence of byssinosis and other respiratory abnormalities in workers exposed to cotton dust in Guangzhou in two factories that processed purely cotton. METHODS: All the 1320 workers exposed were included. The controls were 1306 workers with no history of occupational dust exposure. Total dust and inhalable dust were measured by Chinese total dust sampler and American vertical elutriator respectively. A World Health Organisation questionnaire was used. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured by a Vitalograph spirometer. RESULTS: The median inhalable dust concentrations ranged from 0.41 to 1.51 mg/m3 and median total dust concentrations from 3.04 to 12.32 mg/m3. The prevalence of respiratory abnormalities in the cotton workers were (a) typical Monday symptoms 9.0%; (b) FEV1 fall by > or = 5% after a shift 16.8%; (c) FEV1 fall by > or = 10% after a shift 4.2%; (d) FEV1 < 80% predicted 6.1%; (e) FEV1/FVC < 75% 4.0%; (f) cough or phlegm 18.2%; (g) chronic bronchitis 10.9%; and (h) byssinosis, defined by (a) plus (b) 1.7%. With the exception of (d), most of the prevalences increased with increasing age, duration of exposure, and cumulative inhalable dust exposure. No increasing trends of respiratory abnormalities were found for current total dust, inhalable dust, and cumulative total dust concentrations. Compared with controls, after adjustment for sex and smoking, with the exception of (d), all the pooled relative risks of respiratory abnormalities were raised for cotton exposure. CONCLUSION: It is concluded that cumulative inhalable cotton is likely to be the cause of byssinotic symptoms, acute lung function decrements, cough, or phlegm, and chronic bronchitis.