Transport Behavior Research Articles

IMulch: an investigation of the influence of polymers on a terrestrial ecosystem using the example of mulch films used in agriculture

BackgroundThis article provides an overview of the iMulch joint project, which analysed the use of polyethylene (PE) and biodegradable mulch films made of a polylactide (PLA) and polybutylene adipate terephthalate (PBAT) on agricultural land as a source of microplastic. The development of a detection methodology using Raman spectroscopy and thermo-extraction desorption gas chromatography mass–spectrometry (TED-GC–MS), the adsorption behaviour, ageing in drainage water and soil, their transport behaviour in lysimeters, ecotoxicity, uptake in plants, a life cycle assessment (LCA) and upcycling were considered.ResultsThe PE film tested showed hardly any degradation or fragmentation during the ageing tests. The biodegradable films showed incipient degradation after 8 weeks in drainage water and initial degradation after 12 weeks in soil ageing experiments. Additionally no degradation could be detected in the lysimeter test within the 24 months analysed. The biodegradable films could be metabolized in laboratory tests with some microorganisms present in the soil. This indicates that these films can be degraded in the environment if the conditions for degradation are optimal. No microorganisms or fungi that could degrade the PE film within a respective period of time were detected in the soil. Adsorption of the tested substances was not observed. Incorporated in soil, mulch film microplastic showed retention of extractable pesticides. In the ecotoxicological tests, both film types showed no acute toxic effects in the earthworm Eisenia fetida and the springtail Folsomia candida. Endocrine activity was observed in eluate samples from both films. However, aged films showed fewer effects than non-aged films.ConclusionBoth types of film show no transport or degradation in the tests under real conditions, which means that they remain in the upper soil layer, where they are available to soil organisms and can lead to high concentrations in the future. As the biodegradable film could be degraded, at least under ideal conditions, we recommend its use. However, proof of degradation must first be verified under real field conditions. In addition, we recommend the use of thicker conventional mulch films to minimize the emission of plastic particles. For this purpose, a minimum lower limit for the material thickness should be defined.Graphical

Direct Observation of Dipole Interlocking Effect Occurrence in Two-Dimensional Ferroelectricity.

The electric dipole in materials is closely associated with their electronic transport, optical properties, and mechanical behavior. Here, we have employed the differential phase contrast (DPC) technique of the scanning transmission electron microscopy technique (STEM) to directly analyze the local electric dipole at the sub-Angstrom scale. By utilizing DPC-STEM technology, we successfully visualized the ferroelectric polarization of van der Waals material 3R α-In2Se3 and directly confirmed the dipole interlocking effect (DIE) between in-plane (IP) and out-of-plane (OOP) polarizations. Through density functional theory (DFT) calculations and structural analysis, we discovered that this DIE is caused by the central asymmetry of the middle Se atoms of each monolayer and that the reversal of polarization is accompanied by the emergence of an intermediate phase, β-In2Se3. Leveraging the DIE, we developed a multidirectional ferroelectric memristor that can effectively modulate the IP polarization by applying an OOP pulse voltage.

Mapping the Energy Carrier Diffusion Tensor in Perovskite Semiconductors.

Understanding energy transport in semiconductors is critical for the design of electronic and optoelectronic devices. Semiconductor material properties, such as charge carrier mobility or diffusion length, are commonly measured in bulk crystals and determined using models that describe transport behavior in homogeneous media, where structural boundary effects are minimal. However, most emerging semiconductors exhibit nano- and microscale heterogeneity. Therefore, experimental techniques with high spatial resolution paired with models that capture anisotropy and domain boundary behavior are needed. We develop a diffusion tensor-based framework to analyze experimental photoluminescence (PL) diffusion maps accounting for material nano- and microstructure. Specifically, we quantify both carrier transport and recombination in single crystal and polycrystalline lead halide perovskites by globally fitting diffusion maps with spatial, temporal, and PL intensity data. We reveal a 29% difference in principal diffusion coefficients and alignment between electronically coupled grains for CH3NH3PbI3 polycrystalline films. This framework allows for understanding and optimizing anisotropic energy transport in heterogeneous materials.

Continuous Near-Bed Movements of Microplastics in Open Channel Flows: Statistical Analysis.

The ubiquitous distribution of microplastics (MPs) in aquatic environments is linked to their transport in rivers and streams. However, the specific mechanism of bedload microplastic (MP) transport, notably their stochastic behaviors, remains an underexplored area. To investigate this, particle tracking velocimetry was employed to examine the continuous near-bed movements of four types of MPs under nine setups with different experimental conditions in a laboratory flume, with an emphasis on their streamwise transport. It was found that the streamwise velocity of MPs follows a normal distribution, which can be characterized using the proposed equations to estimate the ensemble mean and standard deviation of MP streamwise velocity. The proposed equations show low relative errors of ∼5% when compared to experimental data. This study also revealed similarities in the continuous movement of MPs and sediments in the streamwise diffusion process. A superdiffusive regime was observed, with particle inertia identified as the primary source of this anomalous diffusion. These results indicate that adopting a probabilistic framework may provide a promising avenue for improving numerical models and enhancing the understanding of MP transport behavior.

Dipole-Modulated Carrier Dynamics and Charge Transport Behavior of Ligand-Protected Metal Chalcogenide Nanoclusters.

Atomically precise nanoclusters, distinguished by their unique nuclearity- and structure-dependent properties, hold great promise for applications of energy conversion and electronic transport. However, the relationship between ligands and their properties remains a mystery yet to be unrevealed. Here, the influence of ligands on the electronic structures, optical properties, excited-state dynamics, and transport behavior of Re12S16 dimer clusters with different ligands is explored using density functional theory combined with time-domain nonadiabatic molecular dynamic simulations. The correlation between ligands and the excited-state dynamics of nanoclusters is elucidated. The ligand replacement introduces a built-in electric field at the dimer interface, inhibiting the recombination of excited carriers and increasing the voltage threshold. This study paints a physical picture of the ligand effect on nanoclusters in terms of geometric configuration, electronic structure, optical properties, carrier dynamics, and transport behavior, paving a pathway toward their applications in optoelectronic materials.

An evolution model for the mobility of urban societal classes based on complex networks

Abstract Cities serve as the main platform for human socio-economic activities, where large crowds, products, and information converge, forming complex societal interactions and the space for human to interact with each other. Like traditional geographical space, in cities, cyberspace and societal space also offer diverse channels for human interactions. While urban mobility in geographical space has been extensively studied across disciplines such as geography, economics, transportation and human behavior, mobility within societal space in cities has rarely been examined in depth. This paper focuses on the self-organized consolidation of mobility within urban societal spaces. Based on the rational person hypothesis and Dunbar's number, we construct a simple model to explain why urban societal classes spontaneously emerge in the evolution of societal space. We also find that the mobility within urban societal space decreases spontaneously over time, and eventually outstanding individuals potentially can be trapped in lower classes, resulting in an inefficient matching of urban resources.

Asymmetric ion transport through heterogeneous bilayers of covalent organic frameworks

In recent years, with the development of interfacial polymerization methodologies, the successful preparation of covalent organic framework (COF) monolayers featuring ultrahigh pore density and molecule-scale thickness has become a reality. This advancement has enabled ion transport with ultrahigh flux across extremely short paths. Owing to these processes, the COF monolayers have shown wide potential applications ranging from energy conversion and artificial mechanosensing to ion sieving. To date, nanofluidic systems based on COF monolayers are homogeneous, leading to nearly symmetric ion transport properties. Studies on the ionic transport behavior within ultrathin COF heterojunctions are limited and remain challenging. Herein, using a two-step sequential self-assembly and subsequent interfacial polymerization strategy, bi-layered heterogeneous tetraphenylporphyrin-based COF membranes composed of negatively charged and positively charged monolayers were prepared. Using an electric field as a driving force, rectified ion transport was observed for the first time. Notably, this ionic current rectification property could be modulated by the salt concentration and the structural composition of the membrane, and it was universal for various COF heterojunctions with different chemical ingredients. These findings are beneficial for promoting the development of innovative nanofluidic materials and devices.

Lattice Boltzmann modeling of droplet actuation via temperature gradient and electrowetting

Droplet manipulation under various physical fields is crucial for microfluidics. Theoretical models are key to understand the physics. In this work, by extending the binary phase lattice Boltzmann model to fully coupled thermodynamics and electrostatics, we systematically explore the behaviors of droplet transport driven by temperature-dependent surface tension, thermocapillary, and electrowetting effects. It is shown that electrowetting enables bidirectional transport of the droplet, determined by various physical parameters such as electric voltage, wettability, viscosity, thermal conductivity, and surface tension. Specifically, the physics revealed in this work is more than simply electrowetting modified wettability. Actually, the droplet transport is controlled further by contact angle hysteresis and thermocapillary-induced temperature gradient.

Sorption and Transport of Antibiotics in Manured Upland Agricultural Soils

Sorption and transport are important environmental behaviors of antibiotics in soils and can determine the fate of antibiotics in environments； however, limited relevant studies have been conducted on long-term manured soils. In this study, batch and repacked soil column experiments were conducted to examine the sorption and transport behavior of four veterinary antibiotics, including sulfamethazine （SMT）, florfenicol （FFC）, doxycycline （DOX）, and enrofloxacin （ENR）, in red soils, yellow soils, and calcareous soils with long-term amendment of chicken or pig manure collected in Zhejiang Province. The results showed that the sorption isothermal data of the four target antibiotics all conformed well to the linear and Freundlich models. The performance of the linear model was better for the weakly-sorbing antibiotics （SMT and FFC）, whereas the performance of the Freundlich model was better for the strongly-sorbing antibiotics （DOX and ENR）. The sorption of target antibiotics was governed by both soil and manure types. The linear sorption parameter （Kd） of SMT and FFC were positively related to the organic carbon content and pH of soils, and their sorption was mainly controlled by soil organic matter, indicating that non-electrostatic interactions （e.g., hydrogen bonding, hydrophobic interactions） played dominant roles in their sorption to the soils. Contrastingly, DOX and ENR did not show significant relationships with soil pH, organic carbon content, and cation exchange capacity, indicating that multiple mechanisms （e.g., hydrophobic interactions, hydrogen bonding, and electrostatic interactions） worked jointly in their sorption into the soils. SMT and FFC exhibited high recoveries of breakthrough curves （in ranges of 37.5%-92.3% and 45.8%-112.6%, respectively） in column transport experiments, reflecting their high leaching potentials. Contrastingly, no soil column breakthrough of DOX and ENR was observed, reflecting that the injected antibiotics were completely retained inside the soil columns. The maximum relative concentrations and breakthrough recoveries of SMT and FFC showed significant negative linear relationships with Kd. This indicates that the leaching potential of antibiotics can be predicted from sorption parameters using the regression equations established by batch and column experiments.

Reversed rectification of ionic liquid/water mixtures in conical nanochannels

Because of their remarkable properties, room-temperature ionic liquids (RTILs) are used widely in electrochemistry, fuel cells, supercapacitors, and even DNA sequencing, and many of these applications involve the transport of RTILs in nanoscale media. Particularly for single-molecule detection, the RTIL must be mixed with a solvent (e.g., water) so that the electrolyte has both high viscosity and conductivity to obtain excellent signals. If a RTIL contains a quantity of water in bulk, this has a significant effect on its properties (e.g., the electrochemical window), thereby limiting some applications. However, the physicochemical properties of RTILs containing water in nanoconfined spaces remain unclear, especially their ionic transport behavior. Therefore, reported here is a study of the ionic transport behavior of mixed RTIL/water solutions at the nanoscale using a single conical nanochannel as a nanofluidic platform. The conductivity of the mixtures in the nanoconfined space was closely related to the nanochannel size, and highly diluted mixed solutions resulted in a nonlinear rectification-reversed current, which was possibly due to the adsorption of cations on the nanochannel wall. The maximum rectification ratio was 114, showing excellent rectification that could be used to realize newly conceptualized nanofluidic diodes. In summary, this work provides an exhaustive understanding of the nonlinear ion transport of RTIL/water mixtures and a theoretical foundation for applying RTILs in energy storage and conversion and bio-sensing.

Multifunctional Native Defects Boosting the Thermoelectric Transport in Few‐Layer PdPS

AbstractAs a unique Cairo pentagonal 2D material, palladium phosphide sulfide (PdPS) has garnered immense interests due to its excellent optoelectronic properties, anisotropic electronic transport behavior, and good air‐stability. In addition, its puckered pentagon structure renders an ultralow thermal conductivity, making it a promising candidate for thermoelectrics applications. However, its thermoelectric transport has not been studied until now due to challenges in obtaining the atomic thin PdPS flake and further measurement. In this work, the thermoelectric performance of 2D PdPS is investigated. It is found that thermoelectric property of PdPS can be effectively manipulated via the delicate annealing treatment, which effectively regulate the defect concentrations. Remarkably, beyond regulating carrier concentrations and shifting the Fermi level closer to the conduction band, these defects also produce a large number of defect states. Consequently, ultra‐high power factor of 0.648 mW m−1 K−2 at room temperature is achieved, outperfoming other 2D materials reported to date. Furthermore, the anisotropic electronic transport properties of few‐layer PdPS are further studied and an extremely high electron anisotropic ratio of 47.37 are obtained at 20 K. The findings provide a new pathway for the development of nanoelectronic devices based on emerging 2D materials with high electronic anisotropy and thermoelectric performance.

Mix-Charged Nanofiltration Membrane for Efficient Organic Removal from High-Salinity Wastewater: The Role of Charge Spatial Distribution.

The efficient removal of organic contaminants from high-salinity wastewater is crucial for resource recovery and achieving zero discharge. Nanofiltration (NF) membranes are effective in separating organic compounds and monovalent salts, but they typically exhibit an excessive rejection of divalent salts. Modifying the charge characteristics of NF membranes can improve salt permeation; however, the role of charge spatial distribution in governing salt transport behavior is not fully understood. In this study, we developed a mix-charged NF membrane with a horizontal charge distribution by employing interfacial polymerization combined with a polyester template etching and solvent-induced polyamine intercalation strategy. The ratio of positive to negative charge domains in the membrane can be precisely controlled by adjusting the aqueous monomer ratio and polyamine modifier type. X-ray photoelectron spectroscopy (XPS) depth profiling and separation layer thickness analysis confirmed the complete penetration of polyamines into the separation layer, providing direct evidence of the formation of horizontally distributed charge domains. This unique charge distribution results in a high charge density and a near-electroneutral surface, which facilitates the permeation of the divalent salts. The size-dependent "plug-in" modification and covalent cross-linking further reduce pore size, enhancing rejection of small organic molecules. Additionally, the membrane demonstrated exceptional antifouling performance against both negatively and positively charged pollutants, attributed to its unique charge distribution and smooth surface. Molecular dynamics (MD) simulations further revealed that weak electrostatic interactions and a tightly bound hydration layer contribute to the membrane's superior antifouling properties. This work provides valuable insights into the design of NF membranes with tailored microstructures and charge distributions for improved water treatment performance.

Sub-5 Ångstrom Porosity Tuning in Calixarene-Derived Porous Liquids via Supramolecular Complexation Construction.

Precise sub-Ångstrom-level porosity engineering, which is appealing in gas separations, has been demonstrated in solid carbon, polymer, and framework materials but rarely achieved in the liquid phase. In this work, a gas molecular sieving effect in the liquid phase at sub-5 Ångstrom scale is created via sophisticated porosity tuning in calixarene-derived porous liquids (PLs). Type II PLs are constructed via supramolecular complexation between the sodium salts of calixarene derivatives and crown ether solvents. The chemical structure variation and assembly behavior of the porous host upon PL construction are monitored by spectroscopy-, X-ray-, and neutron-scattering techniques. The presence of permanent porosity in calixarene-derived PLs is verified by pressure swing gas uptake, altered CO2 physisorption behavior, and dynamic theoretical simulation. Sub-5 Ångstrom porosity tuning within the PL phase is achieved by introducing bulky substituted groups on the benzene ring of the calixarene host, which then greatly affects the dynamic motion and transport behavior of CO2 molecules and the Xe uptake performance. The approach being demonstrated in this work represents a promising pathway to tune and leverage the porosity effect for enhanced gas uptake capacity and selectivity in liquid sorbents.

A Laboratory‐Validated, Graph‐Based Flow and Transport Model for Naturally Fractured Media

AbstractFractures are a primary feature controlling flow, transport, and coupled processes in geologic systems. To date, experimental image‐based observations of these processes have been challenging. Here, we use pulse‐tracer experiments with a conservative radiotracer ([18F]‐fludeoxyglucose) spanning multiple flow rates with simultaneous positron emission tomography imaging to characterize transport in a 5.08 cm fractured Sierra granite core. A graph‐based, laboratory‐validated flow and transport model is successfully demonstrated to describe the conservative solute transport in the natural fracture. Model network complexity, determined by the number of nodes and edges, significantly impacts model fit to observed data. Large graphs over‐describe a fracture plane and act similarly to a porous medium while small graphs oversimplify the solute transport behavior. To our knowledge, this work provides the first validation of graph‐based flow and transport models across a range of experimental conditions and sets the groundwork for upscaling to more complex and computationally efficient fracture models.

Bioinspired solid-state nanochannels for molecular analysis.

The acute sensory behaviour in living organisms relies on the highly efficient transport behaviour of ions in biological nanochannels, which has inspired the design and applications of artificial solid-state nanochannels in the field of sensitive analysis. The application of nanochannels for analysis is now widely investigated, and a variety of sensors have been developed. By coupling reliable nanochannel fabrication techniques with a multitude of surface modification strategies, novel sensors with customized sensing capabilities are generated by the integration of recognition elements and nanochannels. The altered physicochemical properties of these solid-state nanochannel sensors will be manifested by steady-state currents when they are affected by the target analyte. In this mini-review, we focus on emerging solid-state nanochannels based on different fabrication processes such as electron-beam etching, anodic oxidation, ion track etching, and self-assembly. Also, modifications of recognition elements are discussed, including nucleic acids, proteins, small molecules, and responsive materials. The key factors of ion transport behaviour during detection are also reviewed, including surface charge, channel size, and wettability. The applications of these bioinspired nanochannels in the exploration of analysis of small molecules (gas molecules, drug molecules and biological molecules) are concisely presented. Furthermore, we discuss the future developments and challenges.

Percolative phase transition in few-layered MoSe2 field-effect transistors using Co and Cr contacts.

The metal-to-insulator phase transition (MIT) in two-dimensional (2D) materials under the influence of a gating electric field has revealed interesting electronic behavior and the need for a deeper fundamental understanding of electron transport processes, while attracting much interest in the development of next-generation electronic and optoelectronic devices. Although the mechanism of the MIT in 2D semiconductors is a topic under debate in condensed matter physics, our work demonstrates the tunable percolative phase transition in few-layered MoSe2 field-effect transistors (FETs) using different metallic contact materials. Here, we attempted to understand the MIT through temperature-dependent electronic transport measurements by tuning the carrier density in a MoSe2 channel under the influence of an applied gate voltage. In particular, we have examined this phenomenon using the conventional chromium (Cr) and ferromagnetic cobalt (Co) as two metal contacts. For both Cr and Co, our devices demonstrated n-type behavior with a room-temperature field-effect mobility of 16 cm2 V-1 s-1 for the device with Cr-contacts and 92 cm2 V-1 s-1 for the device with Co-contacts, respectively. With low temperature measurements at 50 K, the mobilities increased significantly to 65 cm2 V-1 s-1 for the device with Cr and 394 cm2 V-1 s-1 for the device with Co-contacts. By fitting our experimental data to the percolative phase transition theory, the temperature-dependent conductivity data show a transition from an insulating-to-metallic behavior at a bias of ∼28 V for Cr-contacts and ∼20 V for Co-contacts. This cross-over of the conductivity can be attributed to an increase in carrier density as a function of the gate bias in temperature-dependent transfer characteristics. By extracting the critical exponents, we find that the transport behavior in the device with Co-contacts aligns closely with the 2D percolation theory. In contrast, the devices with Cr-contacts deviate significantly from the 2D limit at low temperatures.

Coupling analysis of transient cuttings transport and tubular mechanical behaviors in extended-reach drilling

Coupling analysis of transient cuttings transport and tubular mechanical behaviors in extended-reach drilling

Microplastics in soils: A comprehensive review.

Microplastics (MPs) have become pervasive pollutants in terrestrial ecosystems, raising significant ecological risks and human health concerns. Despite growing attention, a comprehensive understanding of their quantification, sources, emissions, transport, degradation, and accumulation in soils remains incomplete. This review synthesizes the current knowledge on the anthropogenic activities contributing to soil MP contamination, both intentional and unintentional behaviors, spanning sectors including agriculture, domestic activities, transportation, construction, and industry. Furthermore, it examines the spatial distribution, accumulation, and abundance of MPs across various land use types, alongside a critical assessment of existing quantification methodologies. While the predominant metric for MP quantification is particle number concentration, integrating mass and area concentration enhances the ability to compare pollution levels, assess fluxes, and conduct risk analyses. Additionally, the review explores the transport behavior of MPs in soil, distinguishing between external mechanisms (abiotic factors: wind, leaching, and runoff, biotic factors: soil bioturbation and food chain interactions), and internal mechanisms that are impacted by the characteristics of MPs themselves (e.g., shape, color, size, density, surface properties), soil properties (e.g., porosity, pH, ionic strength, organic matter and mineral content), coexisting substances, and soil structural dynamics. The study of MP transport in soil remains in its early stages, with substantial gaps in knowledge. Future research should focus on integrating number, mass concentration, and area concentration for the more holistic quantification of MP abundance, and prioritize the development of more accurate and efficient methodologies. In addition, the investigation of MP transport and degradation processes under varying environmental conditions and soil management practices is critical for addressing this emerging environmental challenge.

Transport of lithium droplets between two nonparallel iron plates: A molecular dynamics study

The use of bionic structures for the efficient and passive directional transportation of liquid droplets is crucial in numerous industrial applications. Compared with conventional fluids, liquid metals are stable under a wide range of environmental conditions owing to their excellent physicochemical properties. However, the directional transportation of liquid metals remains challenging. Herein, inspired by the pecking feeding mode of shorebirds, we performed a series of systematic molecular dynamics simulations to study the directional transport of liquid lithium (Li) between non-parallel iron (Fe) plates. The simulations demonstrate that cyclically closing and opening the Fe plates induces the movement of Li droplets toward the tip of the beak-shaped plate. Increasing the opening angle and applying a positive strain of the Fe plates can increase the transport velocity of the Li droplets. Nevertheless, the dissolution of Fe atoms in the liquid Li due to corrosion hinders the transportation of Li droplet across the Fe plate. We simulated the impact of two surface nanostructures on Li transport behavior and found that saw-tooth nanostructures decrease transport efficiency and lead to droplet breakup, whereas nanogrooves improve transport capacity by promoting the capillary effect. This work indicates that understanding the mechanism and influencing factors of liquid Li transport between non-parallel plates is essential for the design of bionic structures for the efficient transport of liquid metals.

Retraction notice to “Nondestructive measurement of the capillary water absorption coefficient and water transport behaviors of porous building materials by using single-sided NMR” Constr. Build. Mater. 414 (2024) 134819

Retraction notice to “Nondestructive measurement of the capillary water absorption coefficient and water transport behaviors of porous building materials by using single-sided NMR” Constr. Build. Mater. 414 (2024) 134819