Transport Mechanism Research Articles

Emerging Advances around Nanofluidic Transport and Mass Separation under Confinement in Atomically Thin Nanoporous Graphene.

Membrane separation stands as an environmentally friendly, high permeance and selectivity, low energy demand process that deserves scientific investigation and industrialization. To address intensive demand, seeking appropriate membrane materials to surpass trade-off between permeability and selectivity and improve stability is on the schedule. 2Dmaterials offer transformational opportunities and a revolutionary platform for researching membrane separation process. Especially, the atomically thin graphene with controllable porosity and structure, as well as unique properties, is widely considered as a candidate for membrane materials aiming to provide extreme stability, exponentially large selectivity combined with high permeability. Currently, it has shown promising opportunities to develop separation membranes to tackle bottlenecks of traditional membranes, and it has been of great interest for tremendously versatile applications such as separation, energy harvesting, and sensing. In this review, starting from transport mechanisms of separation, the material selection bank is narrowed down to nanoporous graphene. The study presents an enlightening overview of very recent developments in the preparation of atomically thin nanoporous graphene and correlates surface properties of such 2D nanoporous materials to their performance in critical separation applications. Finally, challenges related to modulation and manufacturing as well as potential avenues for performance improvements are also pointed out.

Polymer nanotherapeutics: A promising approach toward microglial inhibition in neurodegenerative diseases.

Nanoparticles (NPs) that target multiple transport mechanisms facilitate targeted delivery of active therapeutic agents to the central nervous system (CNS) and improve therapeutic transport and efficacy across the blood-brain barrier (BBB). CNS nanotherapeutics mostly target neurons and endothelial cells, however, microglial immune cells are the first line of defense against neuronal damage and brain infections. Through triggering release of inflammatory cytokines, chemokines and proteases, microglia can however precipitate neurological damage-a significant factor in neurodegenerative diseases. Thus, microglial inhibitory agents are attracting much attention among those researching and developing novel treatments for neurodegenerative disorders. The most established inhibitors of microglia investigated to date are resveratrol, curcumin, quercetin, and minocycline. Thus, there is great interest in developing novel agents that can bypass or easily cross the BBB. One such approach is the use of modified-nanocarriers as, or for, delivery of, therapeutic agents to the brain and wider CNS. For microglial inhibition, polymeric NPs are the preferred vehicles for choice. Here, we summarize the immunologic and neuroinflammatory role of microglia, established microglia inhibitor agents, challenges of CNS drug delivery, and the nanotherapeutics explored for microglia inhibition to date. We also discuss applications of the currently considered "most useful" polymeric NPs for microglial-inhibitor drug delivery in CNS-related diseases.

Identification of reversible OATP1B1 and time-dependent CYP3A4 inhibition as the major risk factors for drug-induced cholestasis (DIC).

Hepatic bile acid regulation is a multifaceted process modulated by several hepatic transporters and enzymes. Drug-induced cholestasis (DIC), a main type of drug-induced liver injury (DILI), denotes any drug-mediated condition in which hepatic bile flow is impaired. Our ability in translating preclinical toxicological findings to human DIC risk is currently very limited, mainly due to important interspecies differences. Accordingly, the anticipation of clinical DIC with available in vitro or in silico models is also challenging, due to the complexity of the bile acid homeostasis. Herein, we assessed the in vitro inhibition potential of 47 marketed drugs with various degrees of reported DILI severity towards all metabolic and transport mechanisms currently known to be involved in the hepatic regulation of bile acids. The reported DILI concern and/or cholestatic annotation correlated with the number of investigated processes being inhibited. Furthermore, we employed univariate and multivariate statistical methods to determine the important processes for DILI discrimination. We identified time-dependent inhibition (TDI) of cytochrome P450 (CYP) 3A4 and reversible inhibition of the organic anion transporting polypeptide (OATP) 1B1 as the major risk factors for DIC among the tested mechanisms related to bile acid transport and metabolism. These results were consistent across multiple statistical methods and DILI classification systems applied in our dataset. We anticipate that our assessment of the two most important processes in the development of cholestasis will enable a risk assessment for DIC to be efficiently integrated into the preclinical development process.

A Review: Application of Doped Hydrogenated Nanocrystalline Silicon Oxide in High Efficiency Solar Cell Devices.

Due to the unique microstructure of hydrogenated nanocrystalline silicon oxide (nc-SiOx:H), the optoelectronic properties of this material can be tuned over a wide range, which makes it adaptable to different solar cell applications. In this work, the authors review the material properties of nc-SiOx:H and the versatility of its applications in different types of solar cells. The review starts by introducing the growth principle of doped nc-SiOx:H layers, the effect of oxygen content on the material properties, and the relationship between optoelectronic properties and its microstructure. A theoretical analysis of charge carrier transport mechanisms in silicon heterojunction (SHJ) solar cells with wide band gap layers is then presented. Afterwards, the authors focus on the recent developments in the implementation of nc-SiOx:H and hydrogenated amorphous silicon oxide (a-SiOx:H) films for SHJ, passivating contacts, and perovskite/silicon tandem devices.

Ion transport mechanisms in covalent organic frameworks: implications for technology.

Covalent organic frameworks (COFs) have emerged as promising materials for ion conduction due to their highly tunable structures and excellent electrochemical stability. This review paper explores the mechanisms of ion conduction in COFs, focusing on how these materials facilitate ion transport across their ordered structures, which is crucial for applications such as solid electrolytes in batteries and fuel cells. We discuss the design strategies employed to enhance ion conductivity, including pore size optimization, functionalization with ionic groups, and the incorporation of solvent molecules and salts. Additionally, we examine the various applications of ion-conductive COFs, particularly in energy storage and conversion technologies, highlighting recent advancements and future directions in this field. This review paper aims to provide a comprehensive overview of the current state of research on ion-conductive COFs, offering insights into their potential to design highly ion-conductive COFs considering not only fundamental studies but also practical perspectives for advanced electrochemical devices.

Analysis of Climate Risk in Panama’s Urban Areas

To mitigate the effects of climate change and increase the resilience of cities, climate risks in urban areas are crucial issues to be addressed. This study analyzes the risks, vulnerability, capacity, degree of exposure, and characteristics of the threats to Panama’s urban areas that result from climate change. Data from DesInventar—a conceptual and methodological tool developed for the construction of databases regarding losses, damages, or effects caused by emergencies or disasters—were analyzed. The main current impacts are floods, landslides, and extreme winds in that order. From 1933 to 2019, Panama recorded 1903 flood reports, 625 landslide reports, and numerous extreme wind events. The affected population totaled 527,394 people, with 101,738 homes impacted. The most affected provinces are Panama, Panama Oeste, and Chiriquí, based on the number of reports. It is expected that in the future, the current effects will increase, and the country’s energy and water security will be put at risk. Strategies to address climate change include enhancing early warning systems and investing in climate-resilient infrastructure. Key measures involve developing public policies for renewable energy and sustainable transportation, preserving ecosystems, and financial mechanisms to support a transition to a sustainable economy.

Development of Lead‐Free Defect Brownmillerite Perovskite Ceramic LiBiFeMnO5 Solid Solution for Electronic Devices

This article reports the fabrication (synthesis) and characterizations (structural, microstructural topographic surface, dielectric, transport, impedance, current–voltage, and resistive properties) of a complex lead‐free defect perovskite material of composition LiBiFeMnO5. A preliminary structural investigation of the X‐ray diffraction pattern using N‐TREOR09 methods shows monoclinic symmetry. The scanning electron microscopic spectrum examines the sample's microstructural topographic surface, fractal study, and roughness (using the standard ISO25178). The analysis of Maxwell–Wagner dielectric dispersion, relaxation, and transport mechanisms is investigated utilizing dielectric, impedance, and conductivity spectrum accumulated within the experimental frequency of (1 kHz–1 MHz) at different temperatures (30–500 °C). A nonoverlapping small polaron tunneling conduction mechanism and correlated barrier hopping mechanism in the material have helped to understand its conduction phenomena. The Ohmic and space–charge limited conduction mechanisms are investigated by the slope of the logarithmic electric field (E) and current density (J). The thermistor constant (β) is determined to be 1982.87. The temperature coefficient of resistance is found to be −0.00419, which may be suitable for negative temperature coefficient thermistors, sensors, and other related devices.

Cell-Penetrating Peptide-Mediated Biomolecule Transportation in Artificial Lipid Vesicles and Living Cells.

Signal transduction and homeostasis are regulated by complex protein interactions in the intracellular environment. Therefore, the transportation of impermeable macromolecules (nucleic acids, proteins, and drugs) that control protein interactions is essential for modulating cell functions and therapeutic applications. However, macromolecule transportation across the cell membrane is not easy because the cell membrane separates the intra/extracellular environments, and the types of molecular transportation are regulated by membrane proteins. Cell-penetrating peptides (CPPs) are expected to be carriers for molecular transport. CPPs can transport macromolecules into cells through endocytosis and direct translocation. The transport mechanism remains largely unclear owing to several possibilities. In this review, we describe the methods for investigating CPP conformation, translocation, and cargo transportation using artificial membranes. We also investigated biomolecular transport across living cell membranes via CPPs. Subsequently, we show not only the biochemical applications but also the synthetic biological applications of CPPs. Finally, recent progress in biomolecule and nanoparticle transportation via CPPs into specific tissues is described from the viewpoint of drug delivery. This review provides the opportunity to discuss the mechanism of biomolecule transportation through these two platforms.

Implementing the finite element numerical approach to optimize thermosolutal convection (TSC) energy imparted by discrete heat and solute sources in generalized Newtonian fluid flow in square enclosure

AbstractMesmerizing utilizations of thermosolutal convection (TSC) have been found in metallurgical and petrochemical procedures, crystal growth, thermal exchangers, nuclear waste disposal, and building environment control. In the current study, we considered three heat and solute sources on the left boundary of the cavity, which raises the significance of studying multiple chemical and civil engineering phenomena. Therefore, the prime motivation to commence this work is to attain the optimization of thermosolutal attributes characterized by non-Newtonian (power–law) liquid in the presence of installed sources. For this purpose, the natural convective flow governed by the nonpersistent impact of buoyancy forces is encompassed in the square enclosure. In addition to the source location, the vertical boundaries are considered to be cold, whereas the horizontal boundaries are kept insulated. Owing to the free convective flow, no compositional and thermal gradients are induced by lid movement, and all walls are prescribed with no-slip constraints. To examine the transport mechanism, structuring of problem is attained in the form of dimensional governing expressions by employing conservation laws. Subsequently, constitutive equations in a dimensionless format are accessed through similar variables. The finite element approach is employed to find the solution using COMSOL Multiphysics software. The deviations in the thermal and solutal fields are examined against the involved physical parameters by illustrating graphs and tables. Quantities of interest, such as the mean Nusselt and Sherwood numbers, are also computed against sundry parameters. The assurance of the computed results is validated by constructing a comparison with published studies. A grid sensitivity test is also executed to ensure the credibility of the built-in software (COMSOL). It is observed that the averaged heat and mass flux coefficient diminishes with an elevation in the magnitude of the power-law index (n), irrespective of the change in other involved parameters. The average Sherwood number tends to increase for a positive magnitude of (N) in contrast to negative values of (N). The average heat flux and average mass flux coefficients increase until the Prandtl number (Pr) reaches a value of 5 in shear thinning case at $$Ra\ge {10}^{5},$$ R a ≥ 10 5 , whereas, for n > 1 there is no substantial effect on either the average heat flux coefficient or average mass flux coefficient.

Design and modelling of SiC MPS diodes with superior surge current robustness

The investigation and modelling of the 4H–SiC merged PiN/Schottky (MPS) diode are presented for superior surge current capability design. A bipolar current transmission (BCT) model is proposed for investigating the current transport mechanism of MPS diodes under bipolar operation. The knee voltage (Vturn) defining the conversion from unipolar to bipolar operation is precisely modelled for controlling surge current. According to the proposed model, the method of designing a SiC MPS diode with high robustness against surge current is discussed and concluded primarily, which has great significance for improving the reliability of SiC MPS diodes. Meanwhile, we propose a new hybrid stripe cell design according model calculation and simulation for enhancing the surge current capability of the diode while maintaining high forward current capability. The proposed model and design method are verified by experimental results. And the proposed hybrid stripe cell design has superior surge current robustness while it almost avoids the forward current degradation in experiment.

Strong heterologous electron sink outcompetes alternative electron transport pathways in photosynthesis.

Improvement of photosynthesis requires a thorough understanding of electron partitioning under both natural and strong electron sink conditions. We applied a wide array of state-of-the-art biophysical and biochemical techniques to thoroughly investigate the fate of photosynthetic electrons in the engineered cyanobacterium Synechocystis sp. PCC 6803, a blueprint for photosynthetic biotechnology, expressing the heterologous gene for ene-reductase, YqjM. This recombinant enzyme catalyses the reduction of an exogenously added substrate into the desired product by utilising photosynthetically produced NAD(P)H, enabling whole-cell biotransformation. Through coupling the biotransformation reaction with biophysical measurements, we demonstrated that the strong artificial electron sink, outcompetes the natural electron valves, the flavodiiron protein-driven Mehler-like reaction and cyclic electron transport. These results show that ferredoxin-NAD(P)H-oxidoreductase is the preferred route for delivering photosynthetic electrons from reduced ferredoxin and the cellular NADPH/NADP+ ratio as a key factor in orchestrating photosynthetic electron flux. These insights are crucial for understanding molecular mechanisms of photosynthetic electron transport and harnessing photosynthesis for sustainable bioproduction by engineering the cellular source/sink balance. Furthermore, we conclude that identifying the bioenergetic bottleneck of a heterologous electron sink is a crucial prerequisite for targeted engineering of photosynthetic biotransformation platforms.

Sediment Transport Mechanism and Provenance of Unconsolidated Sediments in Opak River Channel, Yogyakarta, Indonesia

This study focuses on the Opak River, which crosses administratively through two regencies, Sleman and Bantul. This research aims to reveal the sedimentation mechanism and provenance of Opak River sediment based on textural and sedimentary composition. Sediment samples were collected from ten points along the river channel, spanning from upstream to downstream. Granulometric and grain morphology analysis were conducted which the followed by QFL analysis wherein the presence of light detrital minerals (quartz, feldspar, lithic) was observed. The sediment texture of Opak River Channel generally consists of coarse-grained sand, poorly sorted, with varying degrees of roundness and sphericity, which are angular to sub-rounded and intermediate to sub-equant, respectively. Opak River sediment predominantly comprises Feldspar (20-48%), Quartz (4-17,9%) and Lithic (13,5-19,6%) which implies arkose-lithic arkose type. The sedimentation process in Opak River is mainly driven by the traction process, which is indicated by a 48-79% traction fraction on the probability log curve. Based on QFL analysis, it is inferred that the Opak River sediment originated tectonically derived from a magmatic arc setting, specifically a transitional arc subtype. The primary sediment source could have been derived from Mount Merapi with a potentially strong influence by the Oyo River, especially in the downstream of Opak River.

Turbulence-reduced high-performance scenarios in Wendelstein 7-X

In the Wendelstein 7-X (W7-X) stellarator, turbulence is the dominant transport mechanism in most discharges. This leads to a ‘clamping’ of ion temperature over a wide range of heating power, predominantly flat density profiles where hollow profiles driven by neoclassical thermo-diffusion would be expected and by rapid impurity transport in injection experiments. Significantly reduced turbulent transport is observed in the presence of strong core density gradients found transiently after core pellet injection and irregularly after boronisation or boron pellet injection. Density peaking is also achieved in a controlled manner in purely neutral beam heated discharges where particle transport analysis reveals an abrupt reduction in the main-ion particle flux leading to significant density profile peaking not explained by the NBI particle source alone. The plasmas exhibit a heat diffusivity of around χ=0.25±0.1m2 s−1 at mid radius, a factor of around 4 lower than ECRH dominated discharges. Despite the improved confinement, the achieved ion temperature is limited by broader heat deposition and the lower power-per-particle given the higher density. This is overcome with limited reintroduction of ECRH power, where the low heat diffusivity diffusivity is maintained, the density rise supressed and ion temperatures above the clamping limit are achieved. The applicability of these plasmas for a high performance scenario on transport relevant time scales is assessed, including initial predictions for planned heating upgrades of W7-X, based on a range of assumptions about particle transport.

Anticancer Effect of PtIIPHENSS, PtII5MESS, PtII56MESS and Their Platinum(IV)-Dihydroxy Derivatives against Triple-Negative Breast Cancer and Cisplatin-Resistant Colorectal Cancer.

Development of resistance to cisplatin, oxaliplatin and carboplatin remains a challenge for their use as chemotherapies, particularly in breast and colorectal cancer. Here, we compare the anticancer effect of novel complexes [Pt(1,10-phenanthroline)(1S,2S-diaminocyclohexane)](NO3)2 (PtIIPHENSS), [Pt(5-methyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)](NO3)2 (PtII5MESS) and [Pt(5,6-dimethyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)](NO3)2 (PtII56MESS) and their platinum(IV)-dihydroxy derivatives with cisplatin. Complexes are greater than 11-fold more potent than cisplatin in both 2D and 3D cell line cultures with increased selectivity for cancer cells over genetically stable cells. ICP-MS studies showed cellular uptake occurred through an active transport mechanism with considerably altered platinum concentrations found in the cytoskeleton across all complexes after 24 h. Significant reactive oxygen species generation was observed, with reduced mitochondrial membrane potential at 72 h of treatment. Late apoptosis/necrosis was shown by Annexin V-FITC/PI flow cytometry assay, accompanied by increased sub-G0/G1 cells compared with untreated cells. An increase in S and G2+M cells was seen with all complexes. Treatment resulted in significant changes in actin and tubulin staining. Intrinsic and extrinsic apoptosis markers, MAPK/ERK and PI3K/AKT activation markers, together with autophagy markers showed significant activation of these pathways by Western blot. The proteomic profile investigated post-72 h of treatment identified 1597 MDA-MB-231 and 1859 HT29 proteins quantified by mass spectroscopy, with several differentially expressed proteins relative to no treatment. GO enrichment analysis revealed a statistically significant enrichment of RNA/DNA-associated proteins in both the cell lines and specific additional processes for individual drugs. This study shows that these novel agents function as multi-mechanistic chemotherapeutics, offering promising anticancer potential, and thereby supporting further research into their application as cancer therapeutics.

Targeting zincosomes to unveil lysosomal zinc ion dynamics and their role in exacerbating Alzheimer's pathology

Maintaining lysosomal zinc (Zn2+) homeostasis is crucial for cellular functionality, with its dysregulation implicated in the progression of neurodegenerative disorders, notably Alzheimer's disease (AD). The paucity of effective tools for precise lysosomal Zn2+ visualization has been a significant barrier to elucidating its role in AD. In response, a highly sensitive and selective novel fluorescent probe based on a salicylaldehyde Schiff base derivative, SSb, was developed to visualize Zn2+ dynamics. Our findings unveil a previously uncharacterized Zn2+ transport mechanism via zincosomes, highlighting their engulfment by mitochondria during autophagy, facilitated by SSb. Significantly, Zn2+ levels were found to be elevated in the brains of AD model mice, associated with amyloid-β (Aβ) deposits. Additionally, our study indicates an abnormal activation of autophagy in AD models, suggesting that Zn2+ increment may exacerbate AD pathology by fostering Aβ deposition and toxicity. This investigation provides valuable insights into Zn2+ homeostasis and its impact on AD, laying the groundwork for novel diagnostic and therapeutic avenues in combating AD, further reflecting the interdisciplinary nature of chemical engineering and biomedical research.

Exploring superionic conduction in lithium oxyhalide solid electrolytes considering composition and structural factors

Lithium (Li) oxyhalides have emerged as promising solid electrolyte candidates for all-solid-state batteries (ASSBs) due to their superior ionic conductivity and excellent cathode capability. However, the mechanism of Li transport in oxyhalides has remained unclear due to the complex nature of these compounds, which often comprise multiple phases such as crystalline and amorphous structures. Herein, a first-principles study using density functional theory and ab initio molecular dynamic simulation is performed to gain a theoretical insight into the structural behavior and conduction pathway in oxyhalide electrolytes. Li2.5ZrCl5.5O0.5 electrolyte, as a case of study, is comprehensively investigated by considering various phases. It’s revealed that the P3̅m1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\rm{P}}\\bar{3}{\\rm{m}}1$$\\end{document} phase is energetically more stable and exhibits one order of magnitude higher Li conductivity compared to the C2/m phase among potential crystalline phases (1.63 mS cm−1 versus 0.24 mS cm−1 at room temperature). Interestingly, an amorphous phase with even higher ionic conductivity (~40 mS cm−1) can be generated by creating LiCl-deficient Li-Zr-O-Cl compounds. The remarkably high ionic conductivity suggests that the amorphous structure is likely the dominant conducting pathway, facilitating fast Li transport due the weak bonding between Li and other atoms. Cl anion mobility is also observed in the amorphous phase through mean square displacement (MSD) calculation, although further analyses revealed this to be localized vibration. This study sheds light on the nature of oxychloride structures and promotes a deeper understanding of the superionic conduction mechanism in oxychlorides, which will contribute to the development of advanced solid electrolytes and ASSBs.

Ultrahigh proton conductivity of four ionic hydrogen-bonded organic frameworks based on functionalized terephthalates

Recently, the utilization of hydrogen-bonded organic frameworks (HOFs) with high crystallinity and inherent well-defined H-bonding networks in the field of proton conduction has received increasing attention, but obtaining HOFs with excellent water stability and prominent proton conductivity (σ) remains challenging. Herein, by employing functionalized terephthalic acids, 2,5-dihydroxyterephthalic acid, 2-hydroxyterephthalic acid, 2-nitro terephthalic acid, and terephthalic acid, respectively, four highly water-stable ionic HOFs (iHOFs), [(C8H5O6)(Me2NH2)]∙2H2O (iHOF 1), [(C8H5O5)(Me2NH2)] (iHOF 2), [(C8H4NO6)(Me2NH2)] (iHOF 3) and [(C8H5O4)(Me2NH2)] (iHOF 4) were efficiently prepared by a straightforward synthesis approach in DMF and H2O solutions. The alternating-current (AC) impedance testing in humid conditions revealed that all four iHOFs were temperature- and humidity-dependent σ, with the greatest value reaching 10-2 S·cm−1. As expected, the high density of free carboxylic acid groups, crystallization water, and protonated [Me2NH2]+ units offer adequate protons and hydrophilic environments for effective proton transport. Furthermore, the σ values of these iHOFs with different functional groups were compared. It was discovered that it dropped in the following order under 100 °C and 98 % relative humidity (RH): σ iHOF 1 (1.72 × 10−2 S·cm−1) > σ iHOF 2 (4.03 × 10−3 S·cm−1) > σ iHOF 3 (1.46 × 10−3 S·cm−1) > σ iHOF 4 (4.86 × 10−4 S·cm−1). Finally, we investigated the causes of the above differences and the proton transport mechanism inside the framework using crystal structure data, water contact angle tests, and activation energy values. This study provides new motivation to develop highly proton-conductive materials.

Experimental and numerical simulation research on the transport process of bubble clusters in aeration system

Improving gas-liquid mass transfer efficiency in aeration systems contributes to energy savings, cost reduction, and enhanced efficiency in wastewater treatment. However, due to the complex nonlinear interactions among bubbles in turbulence, understanding the transport mechanisms of non-uniform bubble clusters in turbulence remains unclear. This study employs a combined approach of experimental research and numerical simulations to investigate the shape, diameter distribution, trajectory, and velocity of bubbles under different aeration port sizes and flow rates. The diameter distribution of bubble clusters exhibits a bimodal distribution. Bubble trajectories during ascent mainly exhibit two types of motion patterns: “Z” shaped and linear. Increasing aeration port size and flow rate both lead to an increase in the maximum bubble diameter. Higher initial flow rates and smaller port sizes induce greater lateral velocity fluctuations in bubbles. The proposed numerical simulation method serves as a reference for simulating the transport of non-uniform bubble clusters.

Seasonal dynamics, tidal influences, and anthropogenic impacts on microplastic distribution in the Yangtze River estuary: A comprehensive characterization and comparative analysis

Microplastics (MPs) are emerging contaminants with significant ecological and human health implications. This study examines the abundance, characteristics, and distribution of MPs in the Yangtze River estuary, focusing on seasonal variations, tidal cycles, and anthropogenic influences. Surface samples were collected using the Manta trawl method to ensure consistency with previous marine MP research. The study found an average MP concentration of 1.01 (± 0.65) n m−3, predominantly comprising low-density polymers such as polystyrene (38 %), polypropylene (33 %), and polyethylene (29 %). MPs were mainly fragments (34.9 %) and foam (30.7 %), with a prevalence of white particles. Seasonal analysis indicated significantly higher MP concentrations during flood seasons (1.32 ± 1.09 n m−3), nearly 1.9 times higher than during non-flood seasons (0.70 ± 0.28 n m−3). Tidal cycles also impacted MP distribution, with ebb tides showing increased concentrations (2.44 ± 1.30 n m−3) compared to flood tides (1.48 ± 2.07 n m−3). Furthermore, MP abundance showed a decreasing trend with increasing distance from urban centers, with significant correlations (0.52 < R2 < 0.65, P < 0.001). These findings underscore the necessity for seasonally adjusted monitoring and robust management strategies to combat MP pollution. The study advocates for the integration of diverse sampling methods and the consideration of environmental factors in future MP assessments, laying the groundwork for understanding the MP transport mechanism in the Yangtze River estuary and similar estuarine systems worldwide.

A highly-selective biomimetic potassium channel

Abstract Reproducing the outstanding selectivity achieved by biological ion channels in artificial channel systems can revolutionize applications ranging from membrane filtration to single-molecule sensing technologies, but achieving this goal remains a challenge. Herein, inspired by the selectivity filter structure of the KcsA potassium channel, we propose a design of biomimetic potassium nanochannels by functionalizing the wall of carbon nanotubes with an array of arranged carbonyl oxygen atoms. Our extensive molecular dynamics simulations show that the biomimetic nanochannel exhibits a high K+ permeation rate and meanwhile a high K+/Na+ selectivity ratio. The free energy calculations suggest that the low Na+ permeability is the result of the higher energy barrier for Na+ than K+ at the channel entrance and ion binding sites. In addition, reducing the number of ion binding sites leads to an increase in the permeation rate but a decrease in the selectivity. These findings not only hold promise for the design of high-performance membranes but also help understand the mechanism of selective ion transport in biological ion channels.