Versatile filter membrane for effective sampling and real-time quantitative detection of airborne pathogens.

Construction of air filter membranes bearing prominent collecting and transferring capability is highly desirable for detecting airborne pathogens but remains challenging. Here, a hyaluronic acid air filter membrane (HAFM) with tunable heterogeneous micro-nano porous structures is straightforwardly constructed through the ethanol-induced phase separation strategy. Airborne pathogens can be trapped and collected by HAFM with high performance due to the ideal trade-off between removal efficiency and pressure drop. By exempting the sample elution and extraction processes, the HAFM after filtration sampling can not only directly disperse on the agar plate for colony culture but also turn to an aqueous solution for centrifugal enrichment, which significantly reduces the damage and losses of the captured microorganisms. The following combination with ATP bioluminescence endows the HAFM with a real-time quantitative detection function for the captured airborne pathogens. Benefiting from high-efficiency sampling and non-traumatic transfer of airborne pathogens, the real-world bioaerosol concentration can be facilely evaluated by the HAFM-based ATP assay. This work thus not only provides a feasible strategy to fabricate air filter membranes for efficient microbial collection and enrichment but also sheds light on designing advanced protocols for real-time detection of bioaerosols in the field.

High Accuracy of Clinical Verification of Electrohydrodynamic-Driven Nanobox-on-Mirror Platform for Molecular Identification of Respiratory Viruses.

The molecular detection of multiple respiratory viruses provides evidence for the rational use of drugs and effective health management. Herein, we developed and tested the clinical performance of an electrohydrodynamic-driven nanobox-on-mirror platform (E-NoM) for the parallel, accurate, and sensitive detection of four respiratory viral antigens. The E-NoM platform uses gold-silver alloy nanoboxes as the core material with the deposition of a silver layer as a shell on the core surfaces to amplify and enable a reproducible Raman signal readout that facilitates accurate detection. Additionally, the E-NoM platform employs gold microelectrode arrays as the mirror with electrohydrodynamics to manipulate the fluid flow and enhance molecular interactions for an improved biosensing response. The presence of viral antigens binds the nanobox-based core-shell nanostructure on the gold microelectrode and creates the nanocavity with extremely strong "hot spots" to benefit sensitive analysis. Significantly, in a large clinical cohort with 227 patients, the designed E-NoM platform demonstrates the capability of screening respiratory infection with achieved clinical specificity, sensitivity, and accuracy of 100.0, 96.48, and 96.91%, respectively. It is anticipated that the E-NoM platform can find a position in clinical usage for respiratory disease diagnosis.

The potential role and mechanism of circRNA/miRNA axis in cholesterol synthesis.

Cholesterol levels are an initiating risk factor for atherosclerosis. Many genes play a central role in cholesterol synthesis, including HMGCR, SQLE, HMGCS1, FDFT1, LSS, MVK, PMK, MVD, FDPS, CYP51, TM7SF2, LBR, MSMO1, NSDHL, HSD17B7, DHCR24, EBP, SC5D, DHCR7, IDI1/2. Especially, HMGCR, SQLE, FDFT1, LSS, FDPS, CYP51, and EBP are promising therapeutic targets for drug development due to many drugs have been approved and entered into clinical research by targeting these genes. However, new targets and drugs still need to be discovered. Interestingly, many small nucleic acid drugs and vaccines were approved for the market, including Inclisiran, Patisiran, Inotersen, Givosiran, Lumasiran, Nusinersen, Volanesorsen, Eteplirsen, Golodirsen, Viltolarsen, Casimersen, Elasomeran, Tozinameran. However, these agents are all linear RNA agents. Circular RNAs (circRNAs) may have longer half-lives, higher stability, lower immunogenicity, lower production costs, and higher delivery efficiency than these agents due to their covalently closed structures. CircRNA agents are developed by several companies, including Orna Therapeutics, Laronde, and CirCode, Therorna. Many studies have shown that circRNAs regulate cholesterol synthesis by regulating HMGCR, SQLE, HMGCS1, ACS, YWHAG, PTEN, DHCR24, SREBP-2, and PMK expression. MiRNAs are essential for circRNA-mediated cholesterol biosynthesis. Notable, the phase II trial for inhibiting miR-122 with nucleic acid drugs has been completed. Suppressing HMGCR, SQLE, and miR-122 with circRNA_ABCA1, circ-PRKCH, circEZH2, circRNA-SCAP, and circFOXO3 are the promising therapeutic target for drug development, specifically the circFOXO3. This review focuses on the role and mechanism of the circRNA/miRNA axis in cholesterol synthesis in the hope of providing knowledge to identify new targets.

Modulation of T Cell Responses by Fucoidan to Inhibit Osteogenesis.

Fucoidan has sparked considerable interest in biomedical applications because of its inherent (bio)physicochemical characteristics, particularly immunomodulatory effects on macrophages, neutrophils, and natural killer cells. However, the effect of fucoidan on T cells and the following regulatory interaction on cellular function has not been reported. In this work, the effect of sterile fucoidan on the T-cell response and the subsequent modulation of osteogenesis is investigated. The physicochemical features of fucoidan treated by high-temperature autoclave sterilization are characterized by UV-visible spectroscopy, X-ray diffraction, Fourier transform infrared and nuclear magnetic resonance analysis. It is demonstrated that high-temperature autoclave treatment resulted in fucoidan depolymerization, with no change in its key bioactive groups. Further, sterile fucoidan promotes T cells proliferation and the proportion of differentiated T cells decreases with increasing concentration of fucoidan. In addition, the supernatant of T cells co-cultured with fucoidan greatly suppresses the osteogenic differentiation of MC3T3-E1 by downregulating the formation of alkaline phosphatase and calcium nodule compared with fucoidan. Therefore, our work offers new insight into the fucoidan-mediated T cell and osteoblast interplay.

Chitosan-CaP microflowers and metronidazole loaded calcium alginate sponges with enhanced antibacterial, hemostatic and osteogenic properties for the prevention of dry socket after tooth removal.

Tooth removal, particularly for patients with severe periodontitis, can frequently cause massive bleeding, postoperative infection, and bone resorption, resulting in a dry socket. Thus, developing bio-multifunctional materials with excellent antibacterial, hemostatic, and osteogenic characteristics for the prevention of dry sockets after tooth removal is highly desirable in clinical applications. Herein, chitosan-CaP microflowers (CM) and metronidazole (MD) loaded calcium alginate (CA) sponges (CA@CM/MD) with enhanced antibacterial, hemostatic, and osteogenic properties were developed via Ca2+ crosslinking, lyophilization, and electrostatic interaction for the prevention of dry socket after tooth removal. The fabricated CM particles display 3-dimensional, relatively homogeneous, and flower-shaped architectures. The CA@CM/MD composite sponges were facilely shaped into the tooth root as well as exhibit interconnected porous and lamellar structures with remarkable porosity, suitable maximum swelling ratio, as well as excellent compressive and hemostatic performance. Besides, the in vitro cellular assessment demonstrates that the prepared CA@CM/MD composite sponges possess satisfactory cytocompatibility. Importantly, the designed sponges significantly suppress the growth of S. aureus and E. coli, as well as promote cellular osteogenic differentiation by upregulating the formation of alkaline phosphatase. Our findings indicate that the tooth root-shaped composite sponges hold great promise for wound management after tooth removal.

Modified Acupotomy versus Percutaneous Release for Trigger Thumb: A Retrospective Study.

Background: Acupotomy is now increasingly used for trigger thumb, while recent evidence showed it increased the risk of nerve injury. Based on the close proximity of the neurovascular bundles and the A1 pulley, we designed a modified acupotomy. Given that percutaneous release is the common surgical treatment, this retrospective study aimed to compare the effect and safety of modified acupotomy versus percutaneous release for trigger thumb. Methods: This is a retrospective study. All patients with trigger thumb were retrieved in the electronic records of the Department of Pain Medicine at the Beijing Hospital of Traditional Chinese Medicine from January 2016 to September 2018. Both short-term (3 months) and long-term (2 years) outcomes were evaluated using the criteria established through Gilberts et al.'s questionnaire, including triggering, residual pain, stiffness, digital nerve injury, scar, infection and satisfaction. Chi-square test or Fisher's exact test was used to compare differences between two groups. Results: A total of 305 patients with 334 trigger thumbs treated with either modified acupotomy (n = 194 thumbs) or percutaneous release (n = 140 thumbs) were included. Of them, 221 (72.5%) were female, and the mean age was 56.2 ± 10.0 years. The mean duration of trigger thumb lasted for 7.5 ± 3.6 months. At 3 months, all triggering were alleviated by both therapies. Although more digital nerve injury occurred in the percutaneous release (0 [0%] thumbs vs 5 [3.6%] thumbs, P = 0.012), more residual pain (30 [15.5%] thumbs vs 6 [4.3%] thumbs; rate ratio, 3.61; 95% confidence interval [CI]: 1.54-8.43; P = 0.001) and less satisfaction occurred in the modified acupotomy group. At 2 years, more recurrent triggering, residual pain and digital nerve injury occurred in the percutaneous release group (2 [1.0%] thumbs vs 12 [8.6%] thumbs; rate ratio, 0.12; 95% CI: 0.03-0.53; P = 0.001; 9 [4.6%] thumbs vs 22 [15.7%] thumbs; rate ratio, 0.30; 95% CI: 0.14-0.62 P < 0.001; 0 [0%] thumbs vs 4 [2.9%] thumbs, P = 0.030, respectively). Moreover, satisfaction was significantly better in the modified acupotomy group. Conclusion: The modified acupotomy had better long-term outcomes and satisfaction than the percutaneous release for trigger thumb, although percutaneous release has less residual pain and better satisfaction in the short term. The modified acupotomy is a treatment option for trigger thumb.

A Transcriptome Sequencing Study on Genome-Wide Gene Expression Differences of Lung Cancer Cells Modulated by Fucoidan.

Fucoidan has received increasing attention in anti-(lung) tumors. However, the effect of fucoidan on the gene changes of lung cancer cells (LCCs) has not been examined systematically. Herein, we investigate the effect of fucoidan on the phenotypes of LCCs and their gene expression by transcriptome sequencing analysis. The phenotypes of LCCs are significantly inhibited by fucoidan. Importantly, compared to LCCs, 1 mg/ml fucoidan has no effect on the phenotypes of normal cells. Further, 6,930 differentially expressed genes (DEGs) in the transcriptome of LCCs (3,501 up-regulated and 3,429 down-regulated genes) are detected via RNA-sequencing between the fucoidan and control groups. Gene Ontology analysis confirms that DEGs are reflected in DNA replication, cell-substrate junction, regulation of cell cycle phase transition, apoptosis, focal adhesion, cadherin binding, and cell adhesion molecule binding. Thus, our findings on the transcriptomic level highlight the therapeutic potential of fucoidan for lung cancer treatment.

Recent progress in advanced biomaterials for long-acting reversible contraception.

Unintended pregnancy is a global issue with serious ramifications for women, their families, and society, including abortion, infertility, and maternal death. Although existing contraceptive strategies have been widely used in people's lives, there have not been satisfactory feedbacks due to low contraceptive efficacy and related side effects (e.g., decreased sexuality, menstrual cycle disorder, and even lifelong infertility). In recent years, biomaterials-based long-acting reversible contraception has received increasing attention from the viewpoint of fundamental research and practical applications mainly owing to improved delivery routes and controlled drug delivery. This review summarizes recent progress in advanced biomaterials for long-acting reversible contraception via various delivery routes, including subcutaneous implant, transdermal patch, oral administration, vaginal ring, intrauterine device, fallopian tube occlusion, vas deferens contraception, and Intravenous administration. In addition, biomaterials, especially nanomaterials, still need to be improved and prospects for the future in contraception are mentioned.

The Effects of ATIR Blocker on the Severity of COVID-19 in Hypertensive Inpatients and Virulence of SARS-CoV-2 in Hypertensive hACE2 Transgenic Mice.

Angiotensin-converting enzyme 2 (ACE2) is required for the cellular entry of the severe acute respiratory syndrome coronavirus 2. ACE2, via the Ang-(1-7)-Mas-R axis, is part of the antihypertensive and cardioprotective effects of the renin-angiotensin system. We studied hospitalized COVID-19 patients with hypertension and hypertensive human(h) ACE2 transgenic mice to determine the outcome of COVID-19 with or without AT1 receptor (AT1R) blocker treatment. The severity of the illness and the levels of serum cardiac biomarkers (CK, CK-BM, cTnI), as well as the inflammation markers (IL-1, IL-6, CRP), were lesser in hypertensive COVID-19 patients treated with AT1R blockers than those treated with other antihypertensive drugs. Hypertensive hACE2 transgenic mice, pretreated with AT1R blocker, had increased ACE2 expression and SARS-CoV-2 in the kidney and heart, 1 day post-infection. We conclude that those hypertensive patients treated with AT1R blocker may be at higher risk for SARS-CoV-2 infection. However, AT1R blockers had no effect on the severity of the illness but instead may have protected COVID-19 patients from heart injury, via the ACE2-angiotensin1-7-Mas receptor axis.

Effectiveness and safety of acupotomy for knee osteoarthritis: study protocol for a randomized controlled trial.

BACKGROUND: Knee osteoarthritis (KOA) is one of the most common musculoskeletal disorders. Acupotomy may be effective for KOA, but the evidence is limited. This trial aims to determine the effectiveness and safety of acupotomy for KOA. METHODS/DESIGN: This is a parallel-group, assessor-blinded randomized controlled trial. Two hundred patients with KOA will be recruited and randomly assigned to two groups (group A or group D) in a 1:1 ratio. Patients in group A will receive acupotomy and topical diclofenac diethylamine for 4 weeks, while patients in group D will receive topical diclofenac diethylamine alone for 4 weeks. The primary outcome will be the response rate-the proportion of patients who achieve the minimal clinically important improvement in pain and function at week 4 compared with baseline. Secondary outcomes will include pain, function, quality of life, the use of rescue medicine (loxoprofen sodium), and adverse events at weeks 4, 8, and 24 after randomization. Besides, joint fluid and serum will be collected to assess the level of inflammatory cytokines, like TNF-α, IL-1ß, and MMP-3. DISCUSSION: This study will contribute to a better understanding of the effectiveness and safety of acupotomy in combination with topical nonsteroidal anti-inflammatory drugs. If the hypothesis is confirmed, acupotomy may be recommended as adjunctive therapy for patients with KOA. Results of the study will be of great importance for the guidelines of clinical therapy. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2100043005 Registered on 4 February 2021.

Rapid Detection of COVID-19 by Serological Methods and the Evaluation of Diagnostic Efficacy of IgM and IgG.

BACKGROUND: In December 2019, a novel coronavirus (SARS-CoV-2) causing symptomatic illness (COVID-19) occurred in Wuhan, China. Travel-associated cases were reported in many other countries leading to epidemic transmission. The number of cases has increased rapidly but laboratory diagnosis is limited. METHODS: We collected samples from two groups of patients diagnosed with COVID-19 for experiments. In one group, 63 serum samples were analyzed IgG and IgM antibodies by enzyme-linked immunosorbent assay (ELISA) and 35 healthy serum samples were served as controls. In the other group, 91 plasma samples were analyzed by colloidal gold-immunochromatographic assay (GICA) for IgG and IgM antibodies and 35 healthy plasma samples were served as controls. Throat swab samples for nucleic acids retest were collected from 81/91 of these participant. RESULTS: The sensitivity of the combined ELISA IgM and IgG detection was 55/63 (87.3%). Sensitivity of the com-bined GICA IgM and IgG detection was 75/91 (82.4%). Both methods were negative for healthy controls and had a specificity of 100%. In 81 cases, the follow up throat swab samples were retested by RT-PCR, showing that 42 cases were positive. The sensitivity was 51.9% (42/81). The area under the receiver operating characteristic (ROC) curve for IgG (AUC(IgG)) was 0.934. The area under the ROC curve for IgM (AUC(IgM)) was 0.812. The area under the ROC curve for IgG + IgM (AUC(IgG+IgM)) was 0.983. CONCLUSIONS: The serological test of SARS-CoV-2 can be used as an important supplement to the existing RT-PCR test for the specific and rapid diagnosis of COVID-19. AUC(IgG) > AUC(IgM) indicates that IgG has better classification performance than IgM. AUC(IgG + IgM) > AUC(IgG) indicates that the combination of IgG and IgM has better classification performance than IgG alone.

Biointerface topography regulates phenotypic switching and cell apoptosis in vascular smooth muscle cells.

BACKGROUND: In-stent restenosis (ISR) is a complex disease that occurs after coronary stenting procedures. The development of quality materials and improvement of our understanding on significant factors regulating ISR are essential for enhancing prognosis. Vascular smooth muscle cells (VSMCs) are the main constituent cells of blood vessel walls, and dysfunction of VMSCs can exacerbate ISR. Accordingly, in this study, we explored the influence of wrinkled material topography on the biological functions of VSMCs. METHODS: Polydimethylsiloxane with a wrinkled topography was synthesized using elastomer base and crosslinking and observed by atomic force microscopy. VSMC proliferation, apoptosis, and morphology were determined by Cell Counting Kit-8 assays, fluorescence-assisted cell sorting, and phalloidin staining. α-Smooth muscle actin (α-SMA), major histocompatibility complex (MHC), and calponin 1 (CNN-1) expression levels were measured by quantitative real-time polymerase chain reaction and western blotting. Moreover, p53 and cleaved caspase-3 expression levels were evaluated by western blotting in VSMCs to assess apoptotic induction. RESULTS: Surface topographies were not associated with a clear orientation or elongation of VSMCs. The number of cells was increased on wrinkled surfaces (0.7 µm in amplitude, and 3 µm in wavelength [W3]) compared with that on other surfaces, contributing to continuously increased cell proliferation. Moreover, interactions of VSMCs with the W3 surface suppressed phenotypic switching, resulting in ISR via regulation of α-SMA, calponin-1, and SM-MHC expression. The surface with an amplitude of 0.05 µm and a wavelength of 0.5 µm (W0.5) promoted apoptosis by inducing caspase 3 and p53 activities. CONCLUSION: Introduction of aligned topographies on biomaterial scaffolds could provide physical cues to modulate VSMC responses for engineering vascular constructs. Materials with wrinkled topographies could have applications in the development of stents to reduce ISR.

Comparison of throat swabs and sputum specimens for viral nucleic acid detection in 52 cases of novel coronavirus (SARS-Cov-2)-infected pneumonia (COVID-19).

Objectives In December 2019, a novel coronavirus (SARS-CoV-2)-infected pneumonia (COVID-19) occurred in Wuhan, China. Laboratory-based diagnostic tests utilized real-time reverse transcriptase polymerase chain reaction (RT-PCR) on throat samples. This study evaluated the diagnostic value to analyzing throat and sputum samples in order to improve accuracy and detection efficiency. Methods Paired specimens of throat swabs and sputum were obtained from 54 cases, and RNA was extracted and tested for 2019-nCoV (equated with SARS-CoV-2) by the RT-PCR assay. Results The positive rates of 2019-nCoV from sputum specimens and throat swabs were 76.9% and 44.2%, respectively. Sputum specimens showed a significantly higher positive rate than throat swabs in detecting viral nucleic acid using the RT-PCR assay (p = 0.001). Conclusions The detection rates of 2019-nCoV from sputum specimens were significantly higher than those from throat swabs. We suggest that sputum would benefit for the detection of 2019-nCoV in patients who produce sputum. The results can facilitate the selection of specimens and increase the accuracy of diagnosis.

Silence of cZNF292 suppresses the growth, migration, and invasion of human esophageal cancer Eca-109 cells via upregulating miR-206.

Circular RNA (circRNA) cZNF292 has been previously revealed as a circular oncogenic RNA. This study attempted to illustrate the functions of cZNF292 in human esophageal carcinoma Eca-109 cells. Eca-109 cells were transfected with the short hairpin RNA specific against cZNF292 (sh-cZNF292) and/or miR-206 inhibitor. cZNF292 and miR-206 expression was examined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Cell counting kit-8 and flow cytometry were performed for detecting cell growth including cell viability as well as apoptosis. Various kinds of factors, which are involved in cell development including proliferation, apoptosis, migration, and invasion were determined by western blot analysis. Besides, the activation of AMP-activated protein kinase (AMPK) and PI3K/AKT signaling was measured by western blot analysis. It was found that cZNF292 silencing decreased Eca-109 cell viability and induced apoptosis. In the meantime, cZNF292 silencing inhibited cell migration and invasion. cZNF292 silencing upregulated miR-206 expression. And miR-206 downregulation impaired the suppressive effects of cZNF292 silence toward Eca-109 cell growth, migration, and invasion. cZNF292 silencing activated AMPK signaling and inactivated PI3K/AKT signaling also via regulating miR-206. In conclusion, silencing of cZNF292 abated growth, migration, and invasion of Eca-109 cells by upregulating miR-206, which subsequently modulated AMPK and PI3K/AKT signaling pathways.

Crossover from 2D metal to 3D Dirac semimetal in metallic PtTe2 films with local Rashba effect.

PtTe2 and PtSe2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topological semimetal to 2D atomic thin films is an important scientific question. While a transition from 3D type-II Dirac semimetal in the bulk to 2D semiconductor in monolayer (ML) film has been reported for PtSe2, so far the evolution of electronic structure of atomically thin PtTe2 films still remains unexplored. Here we report a systematic angle-resolved photoemission spectroscopy (ARPES) study of the electronic structure of high quality PtTe2 films grown by molecular beam epitaxy with thickness from 2 ML to 6 ML. ARPES measurements show that PtTe2 films still remain metallic even down to 2 ML thickness, which is in sharp contrast to the semiconducting property of few layer PtSe2 films. Moreover, a transition from 2D metal to 3D type-II Dirac semimetal occurs at film thickness of 4-6 ML. In addition, Spin-ARPES measurements reveal helical spin textures induced by local Rashba effect in the bulk PtTe2 crystal, suggesting that similar hidden spin is also expected in few monolayer PtTe2 films. Our work reveals the transition from 2D metal to 3D topological semimetal and provides new opportunities for investigating metallic 2D films with local Rashba effect.

Evidence for a Quasi-One-Dimensional Charge Density Wave in CuTe by Angle-Resolved Photoemission Spectroscopy.

We report the electronic structure of CuTe with a high charge density wave (CDW) transition temperature T_{c}=335 K by angle-resolved photoemission spectroscopy. An anisotropic charge density wave gap with a maximum value of 190 meV is observed in the quasi-one-dimensional band formed by Te p_{x} orbitals. The CDW gap can be filled by increasing the temperature or electron doping through in situ potassium deposition. Combining the experimental results with calculated electron scattering susceptibility and phonon dispersion, we suggest that both Fermi surface nesting and electron-phonon coupling play important roles in the emergence of the CDW.

Detection of circulating Mycobacterium tuberculosis-specific DNA by droplet digital PCR for vaccine evaluation in challenged monkeys and TB diagnosis.

Mycobacterium tuberculosis (M. tb) is emerging as a more serious pathogen due to the increased multidrug-resistant TB and co-infection of human immunodeficiency virus (HIV). The development of an effective and sensitive detection method is urgently needed for bacterial load evaluation in vaccine development, early TB diagnosis, and TB treatment. Droplet digital polymerase chain reaction (ddPCR) is a newly developed sensitive PCR method for the absolute quantification of nucleic acid concentrations. Here, we used ddPCR to quantify the circulating virulent M. tb-specific CFP10 (10-kDa culture filtrate protein, Rv3874) and Rv1768 DNA copy numbers in the blood samples from Bacille Calmette-Guerin (BCG)-vaccinated and/or virulent M. tb H37Rv-challenged rhesus monkeys. We found that ddPCR was more sensitive compared to real-time fluorescence quantitative PCR (qPCR), as the detection limits of CFP10 were 1.2 copies/µl for ddPCR, but 15.8 copies/µl for qPCR. We demonstrated that ddPCR could detect CFP10 and Rv1768 DNA after 3 weeks of infection and at least two weeks earlier than qPCR in M.tb H37Rv-challenged rhesus monkey models. DdPCR could also successfully quantify CFP10 and Rv1768 DNA copy numbers in clinical TB patients' blood samples (active pulmonary TB, extrapulmonary TB (EPTB), and infant TB). To our knowledge, this study is the first to demonstrate that ddPCR is an effective and sensitive method of measuring the circulating CFP10 and Rv1768 DNA for vaccine development, bacterial load evaluation in vivo, and early TB (including EPTB and infant TB) diagnosis as well.

Lorentz-violating type-II Dirac fermions in transition metal dichalcogenide PtTe2.

Topological semimetals have recently attracted extensive research interests as host materials to condensed matter physics counterparts of Dirac and Weyl fermions originally proposed in high energy physics. Although Lorentz invariance is required in high energy physics, it is not necessarily obeyed in condensed matter physics, and thus Lorentz-violating type-II Weyl/Dirac fermions could be realized in topological semimetals. The recent realization of type-II Weyl fermions raises the question whether their spin-degenerate counterpart-type-II Dirac fermions-can be experimentally realized too. Here, we report the experimental evidence of type-II Dirac fermions in bulk stoichiometric PtTe2 single crystal. Angle-resolved photoemission spectroscopy measurements and first-principles calculations reveal a pair of strongly tilted Dirac cones along the Γ-A direction, confirming PtTe2 as a type-II Dirac semimetal. Our results provide opportunities for investigating novel quantum phenomena (e.g., anisotropic magneto-transport) and topological phase transition.Whether the spin-degenerate counterpart of Lorentz-violating Weyl fermions, the Dirac fermions, can be realized remains as an open question. Here, Yan et al. report experimental evidence of such type-II Dirac fermions in bulk PtTe2 single crystal with a pair of strongly tilted Dirac cones.

Electric-field control of tri-state phase transformation with a selective dual-ion switch.

Materials can be transformed from one crystalline phase to another by using an electric field to control ion transfer, in a process that can be harnessed in applications such as batteries, smart windows and fuel cells. Increasing the number of transferrable ion species and of accessible crystalline phases could in principle greatly enrich material functionality. However, studies have so far focused mainly on the evolution and control of single ionic species (for example, oxygen, hydrogen or lithium ions). Here we describe the reversible and non-volatile electric-field control of dual-ion (oxygen and hydrogen) phase transformations, with associated electrochromic and magnetoelectric effects. We show that controlling the insertion and extraction of oxygen and hydrogen ions independently of each other can direct reversible phase transformations among three different material phases: the perovskite SrCoO3-δ (ref. 12), the brownmillerite SrCoO2.5 (ref. 13), and a hitherto-unexplored phase, HSrCoO2.5. By analysing the distinct optical absorption properties of these phases, we demonstrate selective manipulation of spectral transparency in the visible-light and infrared regions, revealing a dual-band electrochromic effect that could see application in smart windows. Moreover, the starkly different magnetic and electric properties of the three phases-HSrCoO2.5 is a weakly ferromagnetic insulator, SrCoO3-δ is a ferromagnetic metal, and SrCoO2.5 is an antiferromagnetic insulator-enable an unusual form of magnetoelectric coupling, allowing electric-field control of three different magnetic ground states. These findings open up opportunities for the electric-field control of multistate phase transformations with rich functionalities.

Direct observation of spin-layer locking by local Rashba effect in monolayer semiconducting PtSe2 film.

The generally accepted view that spin polarization in non-magnetic solids is induced by the asymmetry of the global crystal space group has limited the search for spintronics materials mainly to non-centrosymmetric materials. In recent times it has been suggested that spin polarization originates fundamentally from local atomic site asymmetries and therefore centrosymmetric materials may exhibit previously overlooked spin polarizations. Here, by using spin- and angle-resolved photoemission spectroscopy, we report the observation of helical spin texture in monolayer, centrosymmetric and semiconducting PtSe2 film without the characteristic spin splitting in conventional Rashba effect (R-1). First-principles calculations and effective analytical model analysis suggest local dipole induced Rashba effect (R-2) with spin-layer locking: opposite spins are degenerate in energy, while spatially separated in the top and bottom Se layers. These results not only enrich our understanding of the spin polarization physics but also may find applications in electrically tunable spintronics.