Transport Mechanism Research Articles

A bamboo 'PeSAPK4-PeMYB99-PeTIP4-3' regulatory model involved in water transport.

Water plays crucial roles in expeditious growth and osmotic stress of bamboo. Nevertheless, the molecular mechanism of water transport remains unclear. In this study, an aquaporin gene, PeTIP4-3, was identified through a joint analysis of root pressure and transcriptomic data in moso bamboo (Phyllostachys edulis). PeTIP4-3 was highly expressed in shoots, especially in the vascular bundle sheath cells. Overexpression of PeTIP4-3 could increase drought and salt tolerance in transgenic yeast and rice. A co-expression pattern of PeSAPK4, PeMYB99 and PeTIP4-3 was revealed by WGCNA. PeMYB99 exhibited an ability to independently bind to and activate PeTIP4-3, which augmented tolerance to drought and salt stress. PeSAPK4 could interact with and phosphorylate PeMYB99 in vivo and in vitro, wherein they synergistically accelerated PeTIP4-3 transcription. Overexpression of PeMYB99 and PeSAPK4 also conferred drought and salt tolerance in transgenic rice. Further ABA treatment analysis indicated that PeSAPK4 enhanced water transport in response to stress via ABA signaling. Collectively, an ABA-mediated cascade of PeSAPK4-PeMYB99-PeTIP4-3 is proposed, which governs water transport in moso bamboo.

A Comprehensive Review on Biotransformation, Interaction, and Health of Gut Microbiota and Bioactive Components.

The relationship between gut microbiota and bioactive components has become the research focus in the world. We attempted to clarify the relationship between biotransformation and metabolites of gut microbiota and bioactive components, and explore the metabolic pathway and mechanism of bioactive ingredients in vivo, which will provide an important theoretical basis for the clinical research of bioactive ingredients and rationality of drugs, and also provide an important reference for the development of new drugs with high bioavailability. The related references of this review on microbiota and bioactive components were collected from both online and offline databases, such as ScienceDirect, PubMed, Elsevier, Willy, SciFinder, Google Scholar, Web of Science, Baidu Scholar, SciHub, Scopus, and CNKI. This review summarized the biotransformation of bioactive components under the action of gut microbiota, including flavonoids, terpenoids, phenylpropanoids, alkaloids, steroids, and other compounds. The interaction of bioactive components and gut microbiota is a key link for drug efficacy. Relevant research is crucial to clarify bioactive components and their mechanisms, which involve the complex interaction among bioactive components, gut microbiota, and intestinal epithelial cells. This review also summarized the individualized, precise, and targeted intervention of gut microbiota in the field of intestinal microorganisms from the aspects of dietary fiber, microecological agents, fecal microbiota transplantation, and postbiotics. It will provide an important reference for intestinal microecology in the field of nutrition and health for people. To sum up, the importance of human gut microbiota in the research of bioactive components metabolism and transformation has attracted the attention of scholars all over the world. It is believed that with the deepening of research, human gut microbiota will be more widely used in the pharmacodynamic basis, drug toxicity relationship, new drug discovery, drug absorption mechanism, and drug transport mechanism in the future.

Indium Tin Oxide Induced Internal Positive Feedback and Indium Ion Transport in Perovskite Solar Cells.

Stability is the most pressing challenge hindering the commercialization of perovskite solar cells (PSCs), and previous efforts focused more on enhancing the resistance of PSCs to external stimulus. Here, we found that the indium tin oxide (ITO) will deteriorate the photovoltaic performance of PSCs through positive feedback cycles. Specifically, the perovskite degradation products will cross the electron transport layer to chemically etch the electrode ITO to generate In3+, which will migrate upwards into the perovskite film. Then, the reaction that corrodes ITO consumes the decomposition products of perovskite and shifts the balance of the perovskite decomposition reaction, further promoting the degradation and thus falling into a positive feedback cycle. Moreover, the In3+ in the perovskite film was found to accumulate at the upper surface, which would lead to n-type doping of perovskite film to form the energy barrier for interface carrier extraction. Subsequently, the chelating molecule ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) was introduced onto ITO to firmly chelate the In3+ and prevent it from migrating upward, thus breaking this internal positive feedback cycle and significantly enhancing the efficiency and stability of PSCs. This work provides new perspectives for understanding the mechanism of photovoltaic performance loss and ionic transport in PSCs.

Indium Tin Oxide Induced Internal Positive Feedback and Indium Ion Transport in Perovskite Solar Cells

AbstractStability is the most pressing challenge hindering the commercialization of perovskite solar cells (PSCs), and previous efforts focused more on enhancing the resistance of PSCs to external stimulus. Here, we found that the indium tin oxide (ITO) will deteriorate the photovoltaic performance of PSCs through positive feedback cycles. Specifically, the perovskite degradation products will cross the electron transport layer to chemically etch the electrode ITO to generate In3+, which will migrate upwards into the perovskite film. Then, the reaction that corrodes ITO consumes the decomposition products of perovskite and shifts the balance of the perovskite decomposition reaction, further promoting the degradation and thus falling into a positive feedback cycle. Moreover, the In3+ in the perovskite film was found to accumulate at the upper surface, which would lead to n‐type doping of perovskite film to form the energy barrier for interface carrier extraction. Subsequently, the chelating molecule ethylenediaminetetraacetic acid disodium salt (EDTA‐2Na) was introduced onto ITO to firmly chelate the In3+ and prevent it from migrating upward, thus breaking this internal positive feedback cycle and significantly enhancing the efficiency and stability of PSCs. This work provides new perspectives for understanding the mechanism of photovoltaic performance loss and ionic transport in PSCs.

Charge-Transfer Complexes: Halogen-Doped Anthracene as a Case of Study.

Charge transfer (CT) crystals exhibit unique electronic and magnetic properties with interesting applications. We present a rational and easy guide which allows to foresee the effective charge transfer co-crystal production and that is based on the comparison of the frontier molecular orbital (MO) energies of a donor and acceptor couple. For the sake of comparison, theoretical calculations have been carried out by using the cheap and fast PM6 semiempirical Hamiltonian and pure HF/cc-pVTZ level of the theory. The results are then compared with experimental results obtained both by chemical (bromine and iodine were used as the acceptor) and electrochemical doping (exploiting an original experimental set-up by this laboratory: the electrochemical transistor). Infra-red vibrational experimental results and theoretically calculated spectra are compared to assess both the effective donor-acceptor (D/A) charge-transfer and transport mechanism (giant IRAV polaron signature). XPS spectra have been collected (carbon (1 s) and iodine (3d5/2)) signals, yielding further evidence of the effective formation of the CT anthracene:iodine complex.

Diffusive lensing as a mechanism of intracellular transport and compartmentalization.

While inhomogeneous diffusivity has been identified as a ubiquitous feature of the cellular interior, its implications for particle mobility and concentration at different length scales remain largely unexplored. In this work, we use agent-based simulations of diffusion to investigate how heterogeneous diffusivity affects the movement and concentration of diffusing particles. We propose that a nonequilibrium mode of membrane-less compartmentalization arising from the convergence of diffusive trajectories into low-diffusive sinks, which we call 'diffusive lensing,' is relevant for living systems. Our work highlights the phenomenon of diffusive lensing as a potentially key driver of mesoscale dynamics in the cytoplasm, with possible far-reaching implications for biochemical processes.

Solvation Structures and Transport Mechanisms of Cations in Water-in-Bisalt Electrolytes for High-Concentration Lithium-Ion Batteries Revealed by Molecular Dynamics Simulations.

The development of safe and cost-effective electrolytes for rechargeable batteries is currently underway. While water-based electrolytes hold promise, their restricted electrochemical stability window poses a challenge. Combining multiple ionic species emerges as a promising strategy to broaden this stability window and optimize Li-ion battery performance. This study focuses on dual-cation electrolytes, which blend lithium and potassium acetates to enhance the electrochemical characteristics of the solution at high concentrations. We investigated the solvation structure of each ion and its interactions on a molecular level. Our analysis reveals that ion clusters and aggregates are formed through shared acetate and water molecules at high salt concentrations. Furthermore, the residence time analyses of atom pairs indicate that cations diffuse in vehicular mode at low concentrations. In contrast, they switch to a structural mode at high concentrations due to diminishing water content. This study offers a comprehensive model for exploring diverse solvation structures of cations and gaining insights into their diffusion mechanisms within water-in-bisalt electrolytes for aqueous Li-ion batteries.

Electrokinetic Desalting and Salting of Water-in-Oil Droplets.

Droplet-based microfluidic platforms demand modifications to the droplet composition to facilitate reactions and analyses. However, limited techniques exist to modify the droplet contents post their generation. Here, ion transport across two ion-exchange membranes possessing distinct selectivity is employed to introduce ions into (salt) or extract ions from (desalt) water-in-oil droplets. The ion concentration distribution and transport mechanisms are visualized using a precipitation reaction and a charged fluorescent tracer. Furthermore, current measurements reveal characteristic regimes in desalting and salting modes and demonstrate that the rates of ion transport linearly correlate with applied voltage and the ionic strength of the droplets. Importantly, up to 98% desalting efficiency is achieved. This technique advances droplet-based sample preparation through the straightforward manipulation of droplet contents.

Excited State Dynamics and Transport of Self-Trapped Excitons in Bi-Doped Cs2Na0.4Ag0.6In(1-y)BiyCl6 Double Perovskites.

Lead-free double perovskites (DPs) have become notable in white light emission applications due to the self-trapped exciton (STE) formation in the excited state. However, the mechanism understanding of the excited state dynamics and transport of STE remains ambiguous. Here, we demonstrate a new STE (Bi-STE) forming in tiny Bi-doped Cs2Na0.4Ag0.6InCl6, alongside its intrinsic STE (i-STE), resulting in the DPs photoluminescence quantum yield (PLQY) increasing to as high as >90%. The i-STE exhibits faster formation (60 fs) and slower relaxation dynamics (2.8 μs) compared to the Bi-STE. Moreover, we unveil that the Bi doping can augment the i-STE diffusion properties to attain a diffusion coefficient (diffusion length) of 0.012 cm2 s-1 (1.7 μm) at room temperature, indicating their promise in photovoltaic applications. Our results shed light on significant STE dynamics and transport mechanisms in DPs, providing a new roadmap for advancing existing and crafting new DPs in light emission applications.

Expanding the π-system of fatty acid-anion transporter conjugates modulates their mechanism of proton transport and mitochondrial uncoupling activity.

Mitochondrial uncoupling by small molecule protonophores is a promising strategy for developing novel anticancer agents. Recently, aryl urea substituted fatty acids (aryl ureas) were identified as a new class of protonophoric anticancer agents. To mediate proton transport these molecules self-assemble into membrane-permeable anionic dimers in which intermolecular hydrogen bonds between the carboxylate and aryl-urea anion receptor delocalise the negative charge across the aromatic π-system. In this work, we extend the aromatic π-system by introducing a second phenyl substituent to the aryl urea scaffold and compare the proton transport mechanisms and mitochondrial uncoupling actions of these compounds to their monoaryl analogues. It was found that incorporation of meta-linked phenyl substituents into the aryl urea scaffold enhanced proton transport in vesicles and demonstrated superior capacity to depolarise mitochondria, inhibit ATP production and reduce the viability of MDA-MB-231 breast cancer cells. In contrast, diphenyl ureas linked through a 1,4-distribution across the phenyl ring displayed diminished proton transport activity, despite both diphenyl urea isomers possessing similar binding affinities for carboxylates. Mechanistic studies suggest that inclusion of a second aryl ring changes the proton transport mechanism, presumably due to steric factors that impose higher energy penalties for dimer formation.

Probing particle acceleration in Abell 2256: from 16 MHz to gamma rays

Merging galaxy clusters often host spectacular diffuse radio synchrotron sources. These sources can be explained by a non-thermal pool of relativistic electrons that are accelerated by shocks and turbulence in the intracluster medium. The origin of the pool and details of the cosmic ray transport and acceleration mechanisms in clusters are still open questions. Due to the often extremely steep spectral indices of diffuse radio emission, it is best studied at low frequencies. However, the lowest frequency window available to ground-based telescopes (10-30 MHz) has remained largely unexplored as radio frequency interference and calibration problems related to the ionosphere become severe. Here, we present LOFAR observations from 16 to 168 MHz targeting the famous cluster Abell 2256. In the deepest-ever images at decametre wavelengths, we detected and resolved the radio halo, radio shock, and various steep spectrum sources. We measured standard single power-law behaviour for the radio halo and radio shock spectra, with spectral indices of $ from 24 to 1500 MHz and $ from 24 to 3000 MHz, respectively. Additionally, we found significant spectral index and curvature fluctuations across the radio halo, indicating an inhomogeneous emitting volume. In contrast to the straight power-law spectra of the large-scale diffuse sources, the various AGN-related sources showed extreme steepening towards higher frequencies and flattening towards low frequencies. We also discovered a new fossil plasma source with a steep spectrum between 23 and 144 MHz, with $ 0.1$. Finally, by comparing radio and gamma-ray observations, we ruled out purely hadronic models for the radio halo origin in Abell 2256, unless the magnetic field strength in the cluster is exceptionally high, which is unsupportable by energetic arguments and inconsistent with the knowledge of other cluster magnetic fields.

Modeling multi-source plastic pollution yield and transport driven by catchment hydrometeorological processes

Plastic pollution has emerged as a global environmental concern, impacting both terrestrial and marine ecosystems. However, understanding of plastic sources and transport mechanism at the catchment scale remains limited. This study introduces a multi-source plastic yield and transport model, which integrates catchment economic activities, climate data, and hydrological processes. Model parameters were calibrated using a combination of field observations, existing literature, and statistical random sampling techniques. The model demonstrated robust performance in simulating both plastic yield and transport from 2010 to 2020 in the upper and middle Mulan River Catchment, located in southeast China. The annual average yield coefficients were found to closely align with existing estimations, and the riverine outflow exhibited a high correlation coefficient of 0.97, with biases ranging from -63.0 % to -21.4 % across all monitoring stations. The analysis reveals that, on average, 12.5 ± 2.5 % of the total plastic yield is transported to rivers annually, with solid waste identified as the primary source, accounting for 37.8 ± 20.7 % of the total load to rivers, followed by agricultural film (26.4 ± 9.8 %), impermeable surfaces (21.5 ± 10.3 %), urban and rural sewage (10.4 ± 5.0 % and 3.0 ± 1.5 %, respectively), and industrial wastewater (0.9 ± 0.7 %). The annual average outflow was estimated to between 9.3 and 43.0 ton/year (median: 23.1) at a 95 % confidence level. This study not only provides insights into the primary sources and transport pathways of plastic pollution at the catchment scale, but also offers a valuable tool for informing effective plastic pollution mitigation strategies.

Comparison of the H2O, HDO and δD stratospheric climatologies between the MIPAS-ESA V8, MIPAS-IMK V5 and ACE-FTS V4.1/4.2 satellite datasets

Abstract. Variations in the isotopologic composition of water vapour are fundamental for understanding the relative importance of different mechanisms of water vapour transport from the tropical upper troposphere to the lower stratosphere. Previous comparisons obtained from observations of H2O and HDO by satellite instruments showed discrepancies. In this work, newer versions of H2O and HDO retrievals from Envisat/MIPAS and SCISAT/ACE-FTS are compared. Specifically, MIPAS-IMK V5, MIPAS-ESA V8 and ACE-FTS V4.1/4.2 for the common period from February 2004 to April 2012 are compared for the first time through a profile-to-profile approach and comparison based on climatological structures. The comparison is essential for the scientific community to assess the quality of new satellite data products, a necessary procedure to validate further scientific work. Averaged stratospheric H2O profiles reveal general good agreement between 16 and 30 km. Biases derived from the profile-to-profile comparison are around zero between 16 and 30 km for MIPAS-IMK and ACE-FTS comparison. For HDO and δD, low biases are found in the MIPAS-ESA and ACE-FTS comparison in the same range of altitudes, even if associated with a larger de-biased standard deviation. The zonally averaged cross sections of H2O and HDO exhibit the expected distribution that has been established in previous studies. For δD the tropical depletion in MIPAS-ESA occurs at the top of the dynamical tropopause, but this minimum is found at higher altitudes in the ACE-FTS and MIPAS-IMK dataset. The tape recorder signal is present in H2O and HDO for the three databases with slight quantitative differences. The δD annual variation for ACE-FTS data and MIPAS-ESA data is weaker compared to the MIPAS-IMK dataset, which shows a coherent tape recorder signal clearly detectable up to at least 30 km. The observed differences in the climatological δD composites between databases could lead to different interpretations regarding the water vapour transport processes toward the stratosphere. Therefore, it is important to further improve the quality of level 2 products.

Small electron polarons bound to interstitial tantalum defects in lithium tantalate

The absorption features of optically generated, short-lived small bound electron polarons are inspected in congruent lithium tantalate, LiTaO3 (LT), in order to address the question whether it is possible to localize electrons at interstitial Ta V :V Li defect pairs by strong, short-range electron–phonon coupling. Solid-state photoabsorption spectroscopy under light exposure and density functional theory are used for an experimental and theoretical access to the spectral features of small bound polaron states and to calculate the binding energies of the small bound Ta Li4+ (antisite) and Ta V4+ :V Li (interstitial site) electron polarons. As a result, two energetically well separated ( ΔE≈0.5 eV) absorption features with a distinct dependence on the probe light polarization and peaking at 1.6 eV and 2.1 eV are discovered. We contrast our results to the interpretation of a single small bound Ta Li4+ electron state with strong anisotropy of the lattice distortion and discuss the optical generation of interstitial Ta V4+ :V Li small polarons in the framework of optical gating of Ta V4+ :Ta Ta4+ bipolarons. We can conclude that the appearance of carrier localization at Ta V :V Li must be considered as additional intermediate state for the 3D hopping transport mechanisms at room temperature in addition to Ta Li , as well, and, thus, impacts a variety of optical, photoelectrical and electrical applications of LT in nonlinear photonics. Furthermore, it is envisaged that LT represents a promising model system for the further examination of the small-polaron based photogalvanic effect in polar oxides with the unique feature of two, energetically well separated small polaron states.

Amorphization transition and electrical properties of La2−xCexCuO4 polycrystalline materials

In contrast to crystals, amorphous materials exhibit distinctive properties and applications due to their unique electronic structure and surface energy. Moreover, the amorphous modification of crystalline materials also results in numerous notable and unique properties. In this study, we propose the amorphous modification of polycrystal La2CuO4 with CeO2, examining the composition of the two phases and changes in the crystal structure. Our findings indicate that the degree of ordering of the La2CuO4 phase significantly decreases as the CeO2 content increases, leading to a resistivity increase in 3–4 orders of magnitude. Furthermore, within the 40–400 K, the transition of the Efros–Shklovskii variable range hopping (E–S VRH) transport mechanism between localized states to the Mott 3D VRH and the crossover around 230 K is observed. The method presented here has great potential in modifying polycrystalline materials by using amorphization to make a sudden increase in resistivity.

Passive accumulation of alkaloids in non-toxic frogs challenges paradigms of the origins of acquired chemical defenses.

Understanding the origins of novel, complex phenotypes is a major goal in evolutionary biology. Poison frogs of the family Dendrobatidae have evolved the novel ability to acquire alkaloids from their diet for chemical defense at least three times. However, taxon sampling for alkaloids has been biased towards colorful species, without similar attention paid to inconspicuous ones that are often assumed to be undefended. As a result, our understanding of how chemical defense evolved in this group is incomplete. Here we provide new data showing that, in contrast to previous studies, species from each undefended poison frog clade have measurable yet low amounts of alkaloids. We confirm that undefended dendrobatids regularly consume mites and ants, which are known sources of alkaloids. Further, we confirm the presence of alkaloids in two putatively non-toxic frogs from other families. Our data suggest the existence of a phenotypic intermediate between toxin consumption and sequestration-passive accumulation-that differs from active sequestration in that it involves no derived forms of transport and storage mechanisms yet results in low levels of toxin accumulation. We discuss the concept of passive accumulation and its potential role in the origin of chemical defenses in poison frogs and other toxin-sequestering organisms.

Superoxide dismutase and oxygen transport mechanism in endemic fish Delminichthys ghetaldii (Steindachner, 1882) under mild hypoxia

Superoxide dismutase and oxygen transport mechanism in endemic fish Delminichthys ghetaldii (Steindachner, 1882) under mild hypoxia

Small polaron hopping and tunneling transport in Maxwell–Wagner relaxation dominated Al2O3/TiO2 subnanometric laminates

Maxwell–Wagner relaxation dominated Al2O3/TiO2 nanolaminates (ATA NLs) have recently demonstrated their potential for high-density energy storage applications. In this report, we have unraveled the defect-mediated transport mechanisms prevailing in Al2O3/TiO2 sub-nanometric laminates. Temperature-dependent ac conductivity measurements revealed the signature of small polaron hopping in TiO2 active layers and trap-assisted tunneling transport through Al2O3 barrier layers, which was corroborated by resonant photoelectron spectroscopy and temperature-dependent current–voltage measurement. The polaronic defect states, found ∼1 eV below the Fermi level, served as the hopping centers and leakage paths for current. The signature of quantum tunneling transport and the negative differential conductance observed toward higher electric field was attributed to the splitting of delocalized minibands. These transport properties of Al2O3/TiO2 nanolaminates will help in tailoring these materials for next-generation storage capacitors.

A Microporous Gel Polymer Electrolyte with High Mg2+ Ionic Conductivity at Room Temperature

AbstractRechargeable magnesium batteries have attracted much attention due to the high theoretical volumetric capacity, abundance, and safety. However, solid‐state Mg batteries have been rarely studied because of limited choices of solid‐state electrolyte materials. In this research, poly(vinylidene fluoride)/poly(propylene carbonate) (PVDF/PPC) as matrix were prepared using a simple solution casting method. Ethylene carbonate (EC), diethyl carbonate (DEC), and magnesium(II) bis(trifluoromethanesulfonyl) imide [Mg(TFSI)2] were selected to prepare liquid electrolyte. A classification of novel gel polymer electrolytes (GPEs), PVDF/PPC/Mg(TFSI)2, was synthesized and investigated. The electrochemical measurements show that PVDF/PPC/Mg(TFSI)2 polymer electrolytes exhibit a high ionic conductivity, close to 10−2 S cm−1, at room temperature. The electrochemical stability window of PVDF/PPC‐based GPE was up to 3 V (versus Mg2+/Mg). Materials characterization shows that these GPEs have a porous structure, providing a pathway for magnesium ion transport. Thermal analysis and crystal structure results indicate that PVDF crystallinity was affected by the addition of PPC. Additionally, the ion transport mechanism in the gel polymer electrolyte has been discussed.

Predictive modeling of NSTX discharges with the updated multi-mode anomalous transport module

The objective of this study is twofold: firstly, to demonstrate the consistency between the anomalous transport results produced by updated Multi-Mode Model (MMM) version 9.0.4 and those obtained through gyrokinetic simulations; and secondly, to showcase MMM’s ability to predict electron and ion temperature profiles in low aspect ratio, high beta NSTX discharges. MMM encompasses a range of transport mechanisms driven by electron and ion temperature gradients, trapped electrons, kinetic ballooning, peeling, microtearing, and drift resistive inertial ballooning modes. These modes within MMM are being verified through corresponding gyrokinetic results. The modes that potentially contribute to ion thermal transport are stable in MMM, aligning with both experimental data and findings from linear CGYRO simulations. The isotope effects on these modes are also studied and higher mass is found to be stabilizing, consistent with the experimental trend. The electron thermal power across the flux surface is computed within MMM and compared to experimental measurements and nonlinear CGYRO simulation results. Specifically, the electron temperature gradient modes (ETGM) within MMM account for 2.0 MW of thermal power, consistent with experimental findings. It is noteworthy that the ETGM model requires approximately 5.0 ms of computation time on a standard desktop, while nonlinear CGYRO simulations necessitate 8.0 h on 8 K cores. MMM proves to be highly computationally efficient, a crucial attribute for various applications, including real-time control, tokamak scenario optimization, and uncertainty quantification of experimental data.