Moiré Superlattice-Induced Superconductivity in One-Unit-Cell FeTe.

In this work, we demonstrate that the nonsuperconducting single-layer FeTe can become superconducting when its structure is properly tuned by epitaxially growing it on Bi2Te3 thin films. The properties of the single-layer FeTe deviate strongly from its bulk counterpart, as evidenced by the emergence of a large superconductivity gap (3.3 meV) and an apparent 8 × 2 superlattice (SL). Our first-principles calculations indicate that the 8 × 2 SL and the emergence of the novel superconducting phase are essentially the result of the structural change in FeTe due to the presence of the underlying Bi2Te3 layer. The structural change in FeTe likely suppresses the antiferromagnetic order in the FeTe and leads to superconductivity. Our work clearly demonstrates that moiré pattern engineering in a heterostructure is a reachable dimension for investigating novel materials and material properties.

Superconductivity in Single-Quintuple-Layer Bi2Te3 Grown on Epitaxial FeTe.

How an interfacial superconductivity emerges during the nucleation and epitaxy is of great importance not only for unveiling the physical insights but also for finding a feasible way to tune the superconductivity via interfacial engineering. In this work, we report the nanoscale creation of a robust and relatively homogeneous interfacial superconductivity (TC ≈ 13 K) on the epitaxial FeTe surface, by van der Waals epitaxy of single-quintuple-layer topological insulator Bi2Te3. Our study suggests that the superconductivity in the Bi2Te3/FeTe heterostructure is generated at the interface and that the superconductivity at the interface does not enhance or weaken with the increase of the Bi2Te3 thickness beyond 1 quintuple layer (QL). The observation of the topological surface states crossing Fermi energy in the Bi2Te3/FeTe heterostructure with the average Bi2Te3 thickness of about 20 QL provides further evidence that this heterostructure may potentially host Majorana zero modes.

The HrpW protein of Lonsdalea quercina N-5-1 has pectate lyase activity and is required for full bacterial virulence.

Lonsdalea quercina N-5-1 is a bacterial pathogen that causes poplar bark cankers. It has been isolated from the branch of Populus × euramericana cv. "74/76" in Henan, China. Previous studies have revealed that the Type III secretion system (T3SS) acts as an essential pathogenic factor in L. quercina N-5-1. HrpW is a putative effector of T3SS in strain N-5-1, which has a typical harpin domain at the amino terminal and a pectate lyase (Pel) domain at its carboxyl terminal. Genetic evidence had shown that, compared to the wild-type and the complementary strain, the hrpW mutation causes a small but significant reduction in virulence when inoculated on the poplar branches. The amino terminal domain of HrpW was found to trigger tobacco hypersensitive response, but the carboxyl terminal domain of HrpW was not. Unlike most HrpW homologs in other bacteria, the carboxyl terminal domain of HrpW of strain N-5-1 exhibited detectable pectate lyase activity. Site-direction mutations (W104A, W171M) further demonstrated that two tryptophan residues were essential to its pectate lyase activity. The results of the present work suggest that HrpW in L. quercina N-5-1 possesses pectate lyase activity and acts as a nonessential but important pathogenic factor in poplar bark canker disease.

Tidal inundation and plant growth/decay impact redox-sensitive metal geochemistry and fluxes in salt marsh porewater.

In dynamic coastal ecosystems, environmental factors can play important roles in the biogeochemical cycle of redox-sensitive metals. This work is focused on the impact of tidal inundation, plant growth and decay on the biogeochemical cycle of redox-sensitive metals (e.g., Fe, Mn, Mo, V and U) in salt marsh wetlands. Samples were collected from the salt marsh wetlands of the Yellow River Estuary under different tidal states and growth stages of plants (Phragmites australis). Compared to the concentration of redox-sensitive metals in the river water and seawater near the study area, Fe, Mn and U were enriched in salt marsh wetland, which might become a potential source of Fe, Mn and U in the coastal sea. Tidal inundation, plant growth and decay can affect redox-sensitive metals through changes in redox conditions; the plant can also affect them directly via root absorption or plant residue decomposition, especially for Mo. Calculations of diffusion flux between sediment porewater and tidal water show that these processes can increase diffusion by at least 16.7 % or decrease it by at least 65.7 %, even reversing the direction of diffusion, which can affect the accumulation of redox-sensitive metals in salt marsh wetlands. The results showed that tidal inundation and the decay of plant residue were not conducive to the accumulation of Fe and Mn but were beneficial to the accumulation of V and U in salt marsh wetlands. The plant growth showed the opposite pattern. The accumulation of Mo in salt marsh wetlands largely depends on ingestion by plants and the decay of plant residue. This research provides a scientific basis for the budget calculation of redox-sensitive metals in salt marsh wetlands.

How the Water-Sediment Regulation Scheme in the Yellow River affected the estuary ecosystem in the last 10 years?

The Yellow River, renowned as the most sediment-laden river globally, grapples with sediment deposition issues compromising reservoir functionality and elevating downstream riverbeds, posing threats to human life and property safety. In response, the Water-Sediment Regulation Scheme (WSRS) has been innovatively implemented to address these challenges. While effectively mitigating sediment deposition, WSRS has concurrently disrupted the equilibrium of the estuarine ecosystem. This paper addresses the understudied but crucial topic of the interannual impact of WSRS on the estuarine ecosystem. Drawing upon physical, chemical, and biological data gathered through field surveys conducted before, during, and after WSRS from 2011 to 2022, the analysis delves into the interannual changes in the estuarine environment, fish eggs and larvae abundance, and species diversity under the influence of WSRS. The findings reveal an interannual decreasing trend in terrestrial material input due to WSRS, juxtaposed with an interannual increasing trend in fish eggs and larvae around the estuary, as well as the species diversity index. Notably, these trends became more pronounced post-2014. Compared to pre-2014, nutrient concentrations experienced a ~20 % decrease, chlorophyll-a concentration increased by 44 %, fish eggs proliferated approximately 1 time, and the species diversity index transitioned from a declining trend to an ascending trajectory. After 12 years of continuous WSRS implementation, the impact on the estuarine ecosystem has demonstrably diminished. This research aims to furnish reference experience and scientific basis for water and sediment regulation in major rivers around the world in terms of estuarine ecology.

Measurement of 224Ra in water via pulsed ionization chamber (PIC) radon detector.

224Ra (t1/2 = 3.6 d) has been widely used as a tracer in environmental water research. Here, we present a new method for measuring 224Ra in natural waters using a pulsed ionization chamber (PIC)-based radon detector. This method is based on the measurement of the 224Ra daughter isotope 220Rn (thoron) after reaching secular equilibrium within 7 min. Radium isotopes are concentrated on ''Mn-fibers'' before measurement of 220Rn, which can be distinguished from 222Rn by the difference in their half-lives. The measurement efficiency of the method is 0.20 ± 0.01 cps/Bq at an optimum airflow rate of 1.0 L/min and a water/Mn-fiber weight ratio of 1.0. Results from natural water samples obtained by this method agree well with analysis via RaDeCC, an established technique for 224Ra assessments. Since the PIC system is lighter compared to RaDeCC, easier to operate, and does not require the usage of helium carrier gas and desiccant, this method is recommended for in-situ 224Ra measurement in long-term fieldwork with limited logistical support.

A Review of Temperature Effects on Membrane Filtration.

Membrane technology plays a vital role in drinking water and wastewater treatments. Among a number of factors affecting membrane performance, temperature is one of the dominant factors determining membrane performance. In this review, the impact of temperature on membrane structure, fouling, chemical cleaning, and membrane performance is reviewed and discussed with a particular focus on cold temperature effects. The findings from the literature suggest that cold temperatures have detrimental impacts on membrane structure, fouling, and chemical cleaning, and thus could negatively affect membrane filtration operations and performance, while warm and hot temperatures might expand membrane pores, increase membrane flux, improve membrane chemical cleaning efficiency, and interfere with biological processes in membrane bioreactors. The research gaps, challenges, and directions of temperature effects are identified and discussed indepth. Future studies focusing on the impact of temperature on membrane processes used in water and wastewater treatment and the development of methods that could reduce the adverse effect of temperature on membrane operations are needed.

The complete chloroplast genome of Agave amaniensis (Asparagales: Asparagaceae: Agavoideae).

Agave amaniensis Trel. & W. Nowell (1933) has long been used for phytosteroid production, which is also one of the parents of the famous Agave hybrid cultivar 11648 for sisal fiber production. However, its systematic position and phylogenetic relationship remains unknown at the chloroplast (cp) genome level. Therefore, we have sequenced and assembled the cp genome of A. amaniensis via Illumina sequencing. The cp genome is 157,282 bp in length with a GC content of 37.84%. A large single-copy region of 85,899 bp, a small single-copy region of 18,233 bp, and inverted repeat regions of 26,575 bp were found in the cp genome. Based on the annotation, 86 protein-coding genes, eight rRNAs, and 38 tRNAs were identified in the cp genome with total lengths of 78,981 bp, 9050 bp, and 2867 bp, respectively. The phylogenetic tree indicates that A. amaniensis is closely related with A. H11648, A. angustifolia, and A. americana.

A global assessment of the mixed layer in coastal sediments and implications for carbon storage.

The sediment-water interface in the coastal ocean is a highly dynamic zone controlling biogeochemical fluxes of greenhouse gases, nutrients, and metals. Processes in the sediment mixed layer (SML) control the transfer and reactivity of both particulate and dissolved matter in coastal interfaces. Here we map the global distribution of the coastal SML based on excess 210Pb (210Pbex) profiles and then use a neural network model to upscale these observations. We show that highly dynamic regions such as large estuaries have thicker SMLs than most oceanic sediments. Organic carbon preservation and SMLs are inversely related as mixing stimulates oxidation in sediments which enhances organic matter decomposition. Sites with SML thickness >60 cm usually have lower organic carbon accumulation rates (<50 g C m-2 yr-1) and total organic carbon/specific surface area ratios (<0.4 mg m-2). Our global scale observations reveal that reworking can accelerate organic matter degradation and reduce carbon storage in coastal sediments.

Nutrient-rich submarine groundwater discharge fuels the largest green tide in the world.

One of the largest "green tide" (Ulva prolifera) outbreaks in the world has occurred every year from 2007 to present in the Southern Yellow Sea, China. Currently, the coastal area around Jiangsu Province (Subei Shoal region) is thought to be the origination point of these giant green tide blooms. The combination of high nutrient demand but low river discharge and other inputs suggests that there is a significant flux of submarine groundwater discharge (SGD) in this area. By using a radium mass balance model, we estimated the SGD flux in the area to be (0.7-1.4) × 109 m3 d-1 (6.1-12 cm d-1), at the high end of SGD fluxes worldwide. Geographically, Subei Shoal is less than 5% of the entire Southern Yellow Sea area, while our calculated SGD flux just for the shoal area is ~3 times larger than previously documented for the whole Southern Yellow Sea. Therefore, Subei Shoal may be considered a SGD hotspot that plays an important role in SGD associated material fluxes. Compared to inputs from local rivers, atmospheric deposition, and anthropogenic activities, SGD-derived nutrients are the main source term that can support the growth of macroalgae. We specifically highlight that this type of areas that are shallow, intensively mixed, anthropogenically polluted, sandy or muddy with heavy bio-irrigation, may have a higher risk of suffering harmful ecological problems, even with limited terrestrial runoff.

Colossal Magnetoresistance without Mixed Valence in a Layered Phosphide Crystal.

Materials with strong magnetoresistive responses are the backbone of spintronic technology, magnetic sensors, and hard drives. Among them, manganese oxides with a mixed valence and a cubic perovskite structure stand out due to their colossal magnetoresistance (CMR). A double exchange interaction underlies the CMR in manganates, whereby charge transport is enhanced when the spins on neighboring Mn3+ and Mn4+ ions are parallel. Prior efforts to find different materials or mechanisms for CMR resulted in a much smaller effect. Here an enormous CMR at low temperatures in EuCd2 P2 without manganese, oxygen, mixed valence, or cubic perovskite structure is shown. EuCd2 P2 has a layered trigonal lattice and exhibits antiferromagnetic ordering at 11 K. The magnitude of CMR (104 %) in as-grown crystals of EuCd2 P2 rivals the magnitude in optimized thin films of manganates. The magnetization, transport, and synchrotron X-ray data suggest that strong magnetic fluctuations are responsible for this phenomenon. The realization of CMR at low temperatures without heterovalency leads to a new regime for materials and technologies related to antiferromagnetic spintronics.

Does submarine groundwater discharge contribute to summer hypoxia in the Changjiang (Yangtze) River Estuary?

The Changjiang (Yangtze) River Estuary (CJE) is one of the largest and most intense seasonal hypoxic zones in the world. Here we examine the possibility that submarine groundwater discharge (SGD) may contribute to the summer hypoxia. Spatial distributions of bottom water 222Rn suggest a hotspot discharge area in the northern section of the CJE. SGD fluxes were estimated based on a 222Rn mass balance model and were found to range from 0.002 ± 0.004 to 0.022 ± 0.011 m3/m2/day. Higher SGD fluxes were observed during summer hypoxia period. The well-developed overlap of the distribution patterns for SGD flux and dissolved oxygen (DO) implies that SGD could be an important contributor to summer hypoxia in the region off the CJE. We suggest that SGD contributes to the seasonal hypoxia either: (1) directly via discharge of anoxic groundwaters together with reducing substances; and/or (2) indirectly by delivering excess nutrients that stimulate primary productivity with consequent consumption of DO during organic matter decomposition.

Radium isotopes-suspended sediment relationships in a muddy river.

Radium isotopes are known to be excellent geochemical tracers for study of oceanographic processes. We show here that radium isotopes can also be used to assess adsorption/desorption and transport processes in rivers. The Yellow River (Huanghe), one of the longest, most turbid and heavily regulated rivers in the world, is used as an example. We first investigated the temporal and spatial behavior of radium isotopes (224Ra and 226Ra) in the lower reaches of the river, and found that this zone displayed some of the highest known riverine radium concentrations and fluxes in the world. Suspended particulate matter (SPM) is shown to be the dominant factor controlling radium activities. Laboratory simulation experiments showed that radium desorption from SPM obeys an exponential relationship in fresh water (S = 0). When salinities are >10, the increase in radium concentration follows a linear increase with respect to the amounts of SPM added. Significantly higher radium concentrations (3-5 times), especially for short-lived 224Ra, were observed during the "Water-Sediment Regulation Scheme" (WSRS), an annual management event when ∼15%-55% of the annual water discharge and ∼30%-75% of the annual sediment load are released from a reservoir to control sedimentation in the Yellow River. The radium fluxes during WSRS periods (∼2 weeks long) accounted for more than half of the entire annual load during the periods studied. Sediment erosion and pore water release are also thought to be important processes supplying radium to the river. After a WSRS, Ra desorption from SPM increases and becomes the prevailing process.

Hydro-biogeochemical processes and their implications for Ulva prolifera blooms and expansion in the world's largest green tide occurrence region (Yellow Sea, China).

The hydro-biogeochemical processes in the world's largest area of green tide occurrence, off the Jiangsu coast in the Yellow Sea, are investigated in the summer, and their implications for Ulva prolifera blooms are discussed. The results show that the offshore transport of coastal water and the inshore upwelling of offshore bottom water both occur off the Jiangsu coast, and the upwelling position is consistent with the 20- to 30-m isobath off the Subei Shoal. The upwelling results in nutrient supplementation off the shoal, where a rapid decrease in the suspended particulate matter content contributes to good light conditions. As a result, a high-value area of phytoplankton is formed within the 20- to 30-m isobath. Eutrophication in the shoal has provided nutrients for the frequent occurrence of Ulva prolifera in recent years, whereas the upwelling area off the shoal has served as a "service station" or "courier station" for floating Ulva prolifera and promoted the species' propagation. The propagation of Ulva prolifera in the upwelling area and its blooms within the Subei Shoal can have a spatially synergistic effect, leading to its large-scale development. Our findings reveal the mechanisms that trigger the world's largest green tides from the perspective of physical-biogeochemical interactions.

Biogenic silica composition and δ13C abundance in the Changjiang (Yangtze) and Huanghe (Yellow) Rivers with implications for the silicon cycle.

The study was carried out to address a method for separation of terrestrial and marine biogenic silica (BSi) in estuaries based on BSi compositions and δ13C values in BSi associated organic matter (δ13CBSi). We used two world-class major rivers - the Changjiang (Yangtze) and Huanghe (Yellow) Rivers as examples to illustrate our approach. Our results for these rivers indicate that riverine BSi is comprised mainly of phytoliths and diatoms. River BSi concentrations vary with terrestrial inputs and in-stream primary production. Although the fluvial BSi sources are complex, the terrestrial δ13CBSi signals are quite unique (-24.7±0.8), significantly lower than the marine δ13CBSi values (-21.3±0.07, central Yellow Sea) (p<0.01). Thus, the variation of δ13C within BSi organic matter can provide terrestrial source information on the biogeochemistry of silicon in estuaries and the adjacent shelf. The δ13CBSi combination could potentially act as an efficient tool to study environmental change in coastal areas on decadal time-scales since this index may respond to variable terrestrial fluxes from land, as well as to changed phytoplankton assemblages in the coastal ocean.

Phosphorus speciation, transformation, and preservation in the coastal area of Rushan Bay.

Phosphorus (P) speciation, burial, and transformation are poorly constrained under low-oxygen conditions. Sequential chemical extraction techniques, in-situ incubation, and laboratory incubation were employed to explore P cycling in the low-oxygen area of coastal Rushan. The study determined that the total P concentrations in the coastal area of Rushan Bay were higher than those of other China shelf seas, and largely affected by anthropogenic activities. The phosphate (DRP) fluxes in the study area calculated using an incubation method (0-1960µmolm(-2)day(-)(1)) and measured based on pore water gradients (1.5-50.4µmolm(-2)day(-)(1)) were both highly correlated with oxygen conditions. Sediment incubations showed that DRP diffusion from the sediment mainly originates from Fe-P and Auth-P dissolution and that Org-P recycling contributed only a small portion of the total released P pool. The benthic phosphate flux can be 60 times higher under low bottom-water oxygen levels of 63-150µmolL(-1) than under oxygen levels exceeding 150µmolL(-1) in the study area. The P accumulation rates and burial efficiencies in this study area ranged from 16.5-33.3µmolcm(-2)year(-1) and 81.1-83.4%, respectively, and were regulated by the oxygen level and diffusive DRP flux. This study indicates that low oxygen levels between 63 and 150µmol significantly govern P transformation and preservation in the sediment and P pools in the water column.

Detrital phosphorus as a proxy of flooding events in the Changjiang River Basin.

In this study, sediment grain size (MGS), specific surface area (SSA), total organic carbon (TOC) contents, C/N molar ratios, stable carbon isotope, and P species in a sediment core, collected from the East China Sea (ECS) inner-shelf were measured to explore the applicability of detrital phosphorus (De-P) as a potential indicator of past flooding events in the Changjiang River Basin (CRB). In particular, we examined the linkages between the evolution of floods with regional climate changes and anthropogenic activities in the CRB. Peaks of De-P concentrations in sediments corresponded well with the worst flooding events of the CRB over the past two centuries (e.g., 1850s, 1860s, 1900s, 1920s, 1950s, 1980s, and 2000s). Moreover, De-P also corresponded well with the extreme hypoxic events in 1981 and 1998 in the Changjiang Estuary as indicated by Mo/Al ratios, indicating potential linkages between De-P as a flooding proxy to flood-induced hypoxia events in this region. In addition, a robust relationship was found among De-P, the floods in 1950s, 1980s, and 2000s of the CRB, the intensive El Niño-Southern Oscillation (ENSO), the abnormally weak East Asian Summer Monsoon (EASM) and the warm phase of Pacific Decadal Oscillation (PDO), suggesting that De-P also provided insights to linkages between regional climate change and flooding events in this region.