Helical Topological Superconducting Pairing at Finite Excitation Energies.

We propose helical topological superconductivity away from the Fermi surface in three-dimensional time-reversal-symmetric odd-parity multiband superconductors. In these systems, pairing between electrons originating from different bands is responsible for the corresponding topological phase transition. Consequently, a pair of helical topological Dirac surface states emerges at finite excitation energies. These helical Dirac surface states are tunable in energy by chemical potential and strength of band splitting. They are protected by time-reversal symmetry combined with crystalline twofold rotation symmetry. We suggest concrete materials in which this phenomenon could be observed.

Fluctuations in Planar Magnetotransport Due to Tilted Dirac Cones in Topological Materials.

Fluctuations in planar magnetotransport are ubiquitous in topological HgTe structures, in both tensile (topological insulator) and compressively strained layers (Weyl semimetal phase). We show that the common reason for the fluctuations is the presence of tilted Dirac cones combined with the formation of charge puddles. The origin of the tilted Dirac cones is the mix of the Zeeman term due to the in-plane magnetic field and quadratic contributions to the dispersion relation. We develop a network model that mimics the transport of tilted Dirac fermions in the landscape of charge puddles. The model captures the essential features of the experimental data. It should be relevant for the interpretation of planar magnetotransport in a variety of topological and small band gap materials.

Enhancement of Second-Order Non-Hermitian Skin Effect by Magnetic Fields.

The non-Hermitian skin effect is a unique phenomenon in which an extensive number of eigenstates are localized at the boundaries of a non-Hermitian system. Recent studies show that the non-Hermitian skin effect is significantly suppressed by magnetic fields. In contrast, we demonstrate that the second-order skin effect (SOSE) is robust and can even be enhanced by magnetic fields. Remarkably, SOSE can also be induced by magnetic fields from a trivial non-Hermitian system that does not experience any skin effect at zero field. These properties are intimately related to to the persistence and emergence of topological line gaps in the complex energy spectrum in the presence of magnetic fields. Moreover, we show that a magnetic field can drive a non-Hermitian system from a hybrid skin effect, where the first-order skin effect and SOSE coexist, to pure SOSE. Our results describe a qualitatively new magnetic field behavior of the non-Hermitian skin effect.

Higher-Order Fabry-Pérot Interferometer from Topological Hinge States.

We propose an intrinsic three-dimensional Fabry-Pérot type interferometer, coined "higher-order interferometer," that is based on the chiral hinge states of second-order topological insulators and cannot be mapped to an equivalent two-dimensional setting because of higher-order topological obstructions. Quantum interference patterns in the two-terminal conductance of this interferometer are controllable not only by tuning the strength but also, particularly, by rotating the direction of the magnetic field applied perpendicularly to the transport direction. Remarkably, the conductance exhibits a characteristic beating pattern with multiple frequencies depending on the field strength and direction in a unique fashion. Our novel interferometer thus provides feasible and robust magnetotransport signatures for hinge states of higher-order topological insulators.

Super-Resonant Transport of Topological Surface States Subjected to In-Plane Magnetic Fields.

Magnetic oscillations of Dirac surface states of topological insulators are typically expected to be associated with the formation of Landau levels or the Aharonov-Bohm effect. We instead study the conductance of Dirac surface states subjected to an in-plane magnetic field in the presence of a barrier potential. Strikingly, we find that, in the case of large barrier potentials, the surface states exhibit pronounced oscillations in the conductance when varying the magnetic field, in the absence of Landau levels or the Aharonov-Bohm effect. These novel magnetic oscillations are attributed to the emergence of super-resonant transport by tuning the magnetic field, in which many propagating modes cross the barrier with perfect transmission. In the case of small and moderate barrier potentials, we identify a positive magnetoconductance due to the increase of the Fermi surface by tilting the surface Dirac cone. Moreover, we show that for weak magnetic fields, the conductance displays a shifted sinusoidal dependence on the field direction with period π and phase shift determined by the tilting direction with respect to the field direction. Our predictions can be applied to various topological insulators, such as HgTe and Bi_{2}Se_{3}, and provide important insights into exploring and understanding exotic magnetotransport properties of topological surface states.

Topological Phase Transitions in Disordered Electric Quadrupole Insulators.

We investigate disorder-driven topological phase transitions in quantized electric quadrupole insulators in two dimensions. We show that chiral symmetry can protect the quantization of the quadrupole moment q_{xy}, such that the higher-order topological invariant is well defined even when disorder has broken all crystalline symmetries. Moreover, nonvanishing q_{xy} and consequent corner modes can be induced from a trivial insulating phase by disorder that preserves chiral symmetry. The critical points of such topological phase transitions are marked by the occurrence of extended boundary states even in the presence of strong disorder. We provide a systematic characterization of these disorder-driven topological phase transitions from both bulk and boundary descriptions.

Residues of polychlorinated biphenyls (PCBs) in a wild predatory fish from an e-waste site in South China between 2009 and 2016.

Crude electronic waste (e-waste) recycling has been banned due to the serious environmental pollution it caused, leaving many abandoned e-waste sites. However, information on the current levels and associated ecological risks of e-waste-derived contaminants such as polychlorinated biphenyls (PCBs) in e-waste site is limited. Wild fish, because they can accumulate high pollutant levels, are suitable indicators for environmental pollution monitoring and has been widely employed as biomonitoring. In this study, we investigated the changes in the levels and profiles of PCBs in a wild fish species, the northern snakehead (Channa argus), before (2009) and after (2016) the ban of crude e-waste recycling from a typical e-waste recycling site in South China. The mean total PCB concentration in the northern snakehead sampled in 2016 (343 ng/g ww) declined by 75% compared with that (1410 ng/g ww) in 2009. The contributions of less chlorinated congeners (tri-CBs and tetra-CBs) in the northern snakehead tended to decrease over the years, indicating that the lighter congeners are more easily eliminated than the heavier ones in the environment. Our findings suggested no fresh PCB input in these years, as well as the positive impacts of laws and regulations on the prohibition of e-waste recycling. The ecological risk assessment suggested that PCB exposure may have median to high risks to the wild fish and fish-eating wildlife that inhabit the e-waste site, even after the ban of crude e-waste recycling activities.

Whole-Genome Analysis of blaNDM-Bearing Proteus mirabilis Isolates and mcr-1-Positive Escherichia coli Isolates Carrying blaNDM from the Same Fresh Vegetables in China.

The global spread of colistin or carbapenem-resistant Enterobacteriaceae (CRE) has been a pressing threat to public health. Members of Enterobacteriaceae, especially Proteus mirabilis and Escherichia coli, have been prevalent foodborne pathogens and such pathogens from fresh vegetables have triggered foodborne illness in China. However, reports about CRE, especially P. mirabilis from fresh vegetables, are still lacking. In this study, we identified five blaNDM-positive P. mirabilis and five blaNDM-positive generic E. coli concurrently from five fresh vegetables in two markets from China, and four of the five E. coli also carried mcr-1. The 10 isolates were characterized with methods including antimicrobial susceptibility testing, conjugation, whole-genome sequencing and phylogenetic analysis. All 10 isolates were multidrug-resistant (MDR). blaNDM-5 in five E. coli isolates and one P. mirabilis carrying blaNDM-5 was located on similarly transferable IncX3 plasmids, while transferably untypable plasmids were the carriers of blaNDM-1 in four P. mirabilis isolates from different types of vegetables/markets. mcr-1 in the four blaNDM-5-positive E. coli was located on similarly non-conjugative IncHI2 MDR plasmids lacking transfer region. Notably, ISCR1 complex class 1 integron capable of capturing blaNDM-1 was found on all untypable plasmids from P. mirabilis, and five copies of ISCR1 complex class 1 integron containing blaNDM-1 even occurred in one P. mirabilis, which showed high-level carbapenem resistance. Plasmid and phylogenetic analysis revealed that the blaNDM-positive P. mirabilis and E. coli from fresh vegetables might be derived from animals and transmitted to humans via the food chain. The concurrence of blaNDM-positive P. mirabilis and E. coli carrying both mcr-1 and blaNDM in different types of fresh vegetables eaten raw is alarming and threatens food safety. Sustained surveillance of these foodborne pathogens among fresh vegetables is urgent to ensure the health of food consumers. We report for the first time the concurrence of blaNDM-positive P. mirabilis and mcr-1-bearing E. coli carrying blaNDM from the same fresh vegetables.

Characterized of class I integron in Acinetobacter baumannii isolated from upper respiratory tract.

OBJECTIVE: To characterize the class I integron in Acinetobacter baumannii and to analyze the correlation between integron and drug resistance. METHODS: In total 187 strains were collected between 2008 and 2009. All strains were tested by Kirb-Bauer disk diffusion test for drug resistance. PCR and DNA sequencing were used to detected class I integrase gene and to clarify the context of gene cassette. RESULTS: Class I integrase gene was detected in 100 (53.4%) of the isolates analyzed. Seven different gene cassettes were identified, including a new integron (GenBank: HQ322622) carrying an unknown protein probably associated with recombination. The vast majority of the cassettes encoded amonoglycoside resistance gene, including aacA4, aadA1, aacC1, aac6 II , aadA2. Susceptibility data show that strains carrying class I integron were significantly more resistant to all of the antibiotics tested than isolates lacking class I integron. The correlation between the presence of integron and the multidrug-resistance of A. baumannii was statistically significant. CONCLUSION: Drug resistance genes integrated by Class I integron were widespread in A. baumannii. Class I integron plays an important role in resistance of A. baumannii.

Double tracheal stents reduce side effects of progression of malignant tracheoesophageal fistula treated with immunotherapy: A case report.

BACKGROUND: The protective effect of tracheal stents is reported to relieve airway obstruction and reduce side effects of rapid progression of malignant tracheoesophageal fistula (MTEF) after immunotherapy in this case with 10 mo follow-up. CASE SUMMARY: Two kinds of silicone stents were placed in the main airway of a 58-year-old male to relieve the airway obstruction caused by advanced esophageal carcinoma. The patient then received four doses of toripalimab. Subsequently, rapid, progressive deterioration of the original fistula was found. Although the fistula enlarged rapidly after immunotherapy, it remained covered completely, and likely because of this, his condition remained stable. Therefore, immunotherapy could be continued to treat the primary tumor. Despite these efforts, the patient died of the advancement of his esophageal cancer. CONCLUSION: Appropriately-sized tracheal stent placement combined with immune checkpoint inhibitors may improve the quality of life and survival of patients with MTEF.

Quantum Monte Carlo study of topological phases on a spin analogue of Benalcazar-Bernevig-Hughes model.

We study the higher-order topological spin phases based on a spin analogue of Benalcazar-Bernevig-Hughes model in two dimensions using large-scale quantum Monte Carlo simulations. A continuous Néel-valence bond solid quantum phase transition is revealed by tuning the ratio between dimerized spin couplings, namely, the weak and strong exchange couplings. Through the finite-size scaling analysis, we identify the phase critical points, and consequently, map out the full phase diagrams in related parameter spaces. Particularly, we find that the valence bond solid phase can be a higher-order topological spin phase, which has a gap for spin excitations in the bulk while demonstrates characteristic gapless spin modes at corners of open lattices. We further discuss the connection between the higher-order topological spin phases and the electronic correlated higher-order phases, and find both of them possess gapless spin corner modes that are protected by higher-order topology. Our result exemplifies higher-order physics in the correlated spin systems and will contribute to further understandings of the many-body higher-order topological phenomena.

Secondary infection in severe and critical COVID-19 patients in China: a multicenter retrospective study.

BACKGROUND: Since 2020 COVID-19 pandemic became an emergent public sanitary incident. The epidemiology data and the impact on prognosis of secondary infection in severe and critical COVID-19 patients in China remained largely unclear. METHODS: We retrospectively reviewed medical records of all adult patients with laboratory-confirmed COVID-19 who were admitted to ICUs from January 18th 2020 to April 26th 2020 at two hospitals in Wuhan, China and one hospital in Guangzhou, China. We measured the frequency of bacteria and fungi cultured from respiratory tract, blood and other body fluid specimens. The risk factors for and impact of secondary infection on clinical outcomes were also assessed. RESULTS: Secondary infections were very common (86.6%) when patients were admitted to ICU for >72 hours. The majority of infections were respiratory, with the most common organisms being Klebsiella pneumoniae (24.5%), Acinetobacter baumannii (21.8%), Stenotrophomonas maltophilia (9.9%), Candida albicans (6.8%), and Pseudomonas spp. (4.8%). Furthermore, the proportions of multidrug resistant (MDR) bacteria and carbapenem resistant Enterobacteriaceae (CRE) were high. We also found that age ≥60 years and mechanical ventilation ≥13 days independently increased the likelihood of secondary infection. Finally, patients with positive cultures had reduced ventilator free days in 28 days and patients with CRE and/or MDR bacteria positivity showed lower 28-day survival rate. CONCLUSIONS: In a retrospective cohort of severe and critical COVID-19 patients admitted to ICUs in China, the prevalence of secondary infection was high, especially with CRE and MDR bacteria, resulting in poor clinical outcomes.

Pseudo chiral anomaly in zigzag graphene ribbons.

As the three-dimensional analogs of graphene, Weyl semimetals display signatures of chiral anomaly which arises from charge pumping between the lowest chiral Landau levels of the Weyl nodes in the presence of parallel electric and magnetic fields. In this work, we study the pseudo chiral anomaly and its transport signatures in graphene ribbon with zigzag edges. Here 'pseudo' refers to the case where the inverse of width of zigzag graphene ribbon plays the same role as magnetic field in three-dimensional Weyl semimetals. The valley chiral bands in zigzag graphene ribbons can be introduced by edge potentials, giving rise to the nonconservation of chiral current, i.e. pseudo chiral anomaly, in the presence of a longitudinal electric field. Further numerical results reveal that pseudo magnetoconductivity of zigzag graphene ribbons is positive and has a nearly quadratic dependence on the pseudofield, which is regarded as the transport signature of pseudo chiral anomaly.

Biodegradable Materials and Green Processing for Green Electronics.

There is little question that the "electronic revolution" of the 20th century has impacted almost every aspect of human life. However, the emergence of solid-state electronics as a ubiquitous feature of an advanced modern society is posing new challenges such as the management of electronic waste (e-waste) that will remain through the 21st century. In addition to developing strategies to manage such e-waste, further challenges can be identified concerning the conservation and recycling of scarce elements, reducing the use of toxic materials and solvents in electronics processing, and lowering energy usage during fabrication methods. In response to these issues, the construction of electronic devices from renewable or biodegradable materials that decompose to harmless by-products is becoming a topic of great interest. Such "green" electronic devices need to be fabricated on industrial scale through low-energy and low-cost methods that involve low/non-toxic functional materials or solvents. This review highlights recent advances in the development of biodegradable materials and processing strategies for electronics with an emphasis on areas where green electronic devices show the greatest promise, including solar cells, organic field-effect transistors, light-emitting diodes, and other electronic devices.

Investigating the urbanization process and its impact on vegetation change and urban heat island in Wuhan, China.

Rapid urbanization significantly changes vegetation coverage and heat distribution, which threatens the sustainable development and the quality of life. As the largest developing city in Central China, Wuhan was chosen as the experimental region. This study investigated the urbanization process of Wuhan from 1989 to 2917 based on Landsat data. Combined with MODIS EVI (Enhanced Vegetation Index) and LST (Land Surface Temperature) data, vegetation disturbance and surface urban heat island (SUHI) caused by urbanization were discussed for 2001-2017. Furthermore, correlation between ∆EVI (urban EVI minus rural EVI) and ∆LST (urban LST minus rural LST) was also conducted. The results were as follows: (1) Wuhan experienced a strong urbanization over the past 29 years, with an increasing urban expansion rate and the altered dominant urban expansion pattern (edge expansion and infilling). After the enhanced vegetation functions and urban increased structures, the urbanization finally caused the fragmented patches and irregular urban shapes. (2) Urbanization had a positive effect on LST but a negative effect on EVI. From 2001 to 2017, the highest increasing rate of ∆LST for the old urban area (OUA) and urbanized area (UA) was both observed in summer daytime (OUA, 0.106 °C/a; UA, 0.207 °C/a). The decreasing rate of ∆EVI reached the highest value in summer (OUA, 0.00697/a; UA, 0.00298/a). (3) There was a strong negative correlation (except spring and winter for OUA) between ∆EVI and ∆LST in daytime, which proved that the activity of vegetation in daytime could relieve LST to a certain extent. This study clarifies the dynamic urbanization process of Wuhan and discusses its impacts on vegetation change and SUHI. Efficiently investigating urbanization process and quantifying its impacts on urban environment are critical for regional ecological conservation.

Eu-TiO2 Nanocomposite with High Photoelectrochemical Activity for Enhanced Photocatalysis of Rhodamine B.

A novel Eu-TiO2 nanocomposite prepared by a sol-gel method is used for the degradation of rhodamine B (RhB) present in dyes wastewater. The X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) show the anatase phase and globular shape of Eu- TiO2 nanocomposite, UV-vis diffuse reflectance spectroscopy and low temperature N2 adsorption (BET) indicate Eu-TiO2 possesses a narrow band gap (2.98 eV) and a high specific surface area (112.1 m² · g-1), respectively. Furthermore, the prepared Eu-TiO2 exhibits unprecedented higher photocatalytic activity towards RhB than P25 TiO2. The degradation ratio of RhB is up to 93% within 100 min irradiation of simulated solar lights by the obtained Eu-TiO2, which demonstrated firstly by the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis. The high photocatalytic performance may be ascribed to the efficient Eu loading in favor of the absorption of visible-light and the separation of photogenerated charges.

A linear trinuclear ferrous single molecule magnet.

A linear trinuclear ferrous complex [FeII3(pymp)4(MeOH)2][BPh4]2·2MeOH (1) (Hpymp = 2-[(pyridine-2-ylimine)-methyl]phenol) was isolated and characterized both structurally and magnetically. A magnetic study revealed the ferromagnetic coupling (J = +3.54 cm-1) within the [FeII3] units and uniaxial magnetic anisotropy (D = -1.21 cm-1) of the molecule. Slow relaxation of the magnetization at below 5 K and an effective energy barrier of 26.0(2) cm-1 under a 1200 Oe applied dc field were evidenced. Moreover, clear magnetic hysteresis loops were observed at below 2.5 K, which further corroborated the single-molecule magnet behavior of 1.