Transport Mechanism Research Articles

Confinement effects and manipulation strategies of nanocomposite membranes towards molecular separation.

Materials featuring well-defined nanoscale channels have demonstrated inherent advantages in the selective transport of gases, liquids, and ions, making them pivotal in applications such as molecular separation, catalysis and energy storage. A crucial challenge lies in the assembly of ordered nanochannel structures and the transformation of such microscopic ordered structures into macroscopic regular distributions to achieve performance improvements. Nanocomposites provide a promising solution by incorporating nanoscale material (e.g., filler) that significantly enhance macroscale properties of matrix (e.g., polymer). In this review, we spotlight nanocomposite membranes that leverage the confinement effects between filler and matrix to construct precise nanochannels and regulate the nanochannel distribution. We discussed the underlying design principles, channel architectures, and the manipulation strategies for integrating filler and polymers into functional membranes. Emphasis is placed on the fundamental mechanisms of mass transport, and the structure-property-performance relationships within the nanocomposite membranes towards molecular separation. This work aims to provide a comprehensive understanding of how these nanocomposite membranes can be further developed to meet the demands of industrial and environmental applications.

Critical factors influencing electron and phonon thermal conductivity in metallic materials using first-principles calculations.

Understanding the thermal transport of various metals is crucial for many energy-transfer applications. However, due to the complex transport mechanisms varying among different metals, current research on metallic thermal transport has been focusing on case studies of specific types of metallic materials. Ageneral understanding of the transport mechanisms across a broad spectrum of metallic materials is still lacking. In this work, we perform first-principles calculations to determine the thermal conductivity of 40 representative metallic materials, within a range of 8-456 W/mK. Our predicted values of electrical and thermal conductivity are in good agreement with available experimental results. Based on the data of separated electron and phonon thermal conductivity, we employ a statistical approach to examine nine factors derived from previous understandings and identify the critical factors determining these properties. For electrons, although a high electron density of states around the Fermi level implies more conductive electrons, we find it counterintuitively correlates with low electron thermal conductivity. This is attributed to the enlarged electron-phonon scattering channels induced by substantial electrons around the Fermi level. Regarding phonons, we demonstrate that among all the studied factors, Debye temperature plays the most significant role in determining the phonon thermal conductivity, despite the phonon-electron scattering being non negligible in- sometransition metals. Correlation analysis suggeststhat Debye temperature has the highest positive correlation coefficient with phonon thermal conductivity, as it corresponds to a large phonon group velocity. Additionally, Young's modulus is found to be closely correlated with high phonon thermal conductivity and contribution. Our findings of simple factors that closely correlate with the electron and phonon thermal conductivity provide a general understanding of various metallic materials. They may facilitate the discovery of novel materials with extremely high or low thermal conductivity, or be used as descriptors in machine learning to accurately predict the thermal conductivity of metals in the future.&#xD.

Pathogenic Mechanisms of Collagen TypeⅦA1 (COL7A1) and Transporter Protein Transport and Golgi Organization 1 (TANGO1) in Rheumatoid Arthritis: A New Therapeutic Target

Rheumatoid arthritis (RA) is an autoimmune disorder causing chronic inflammation primarily due to collagen regulation and transport imbalances. Collagen VII A1(COL7A1), a major component of anchoring fibrils, regulates inflammation via interacting with its transporter protein Transport and Golgi organization 2 homologs (TANGO1). The study revealed a significant increase in COL7A1 levels in both the plasma and PBMCs of RA patients. Additionally, a positive correlation between COL7A1 and ACCPA (anti-cyclic citrullinated peptide antibody) levels was observed among RA patients. TANGO1 mRNA expression was also found to be elevated in PBMCs. The knockdown of COL7A1 in RA synoviocytes using siRNA affected the expression of TANGO1 and inflammatory genes. Western blot analysis showed that COL7A1 si-RNA in TNF-α-induced SW982 cells reduced the expression of COL7A1, TANGO1, and NF-kBp65. The mRNA expression of inflammatory genes TNF-α, NF-kB p65, and IL-6 simultaneously decreased after the knockdown of COL7A1, as measured by qRT-PCR. An in silico analysis found 20 common interacting proteins of COL7A1 and TANGO1, with pathway enrichment analysis linking them to antigen presentation, class I and II MHC, and adaptive immunity pathways in RA. Among the common proteins, The DisGeNET database depicted that COL1A1, MIA3, SERPINH1, and GORASP1 are directly linked to RA. The molecular docking analysis of COL7A1 and TANGO1 revealed strong interaction with a −1013.4 energy-weighted score. Common RA-used drugs such as Adalimumab, Golimumab, and Infliximab were found to inhibit the interaction between COL7A1 and TANGO1, which can further impede the transport of COL7A1 from ER exit sites, indicating COL7A1 and TANGO1 as potential therapeutic targets to diminish RA progression.

Design and Synthesis of Multipath Compact Cyclophanes for Quantum Interference Studies

To investigate interference phenomena and con­duc­tance properties in mechanically controlled break junctions (MCBJs), macrocycles 1 and 2 (BMCs: for BenzeneMacroCycles), containing a meta‐substituted benzene moiety with solubilizing tert‐butyl groups, as well as structures 3 and 4 (TMCs: for ThiopheneMacroCycles), featuring 2,5‐connected 3,4‐hexyl‐thio­phene corners, were synthesized. Macrocycles 1 and 2 respect­ively 3 and 4 differ in the positions of the acetyl‐protected sulfur anchoring groups, which impacts both, the individual transport efficiency of their parallel electronic pathways and their overall molecular wire lengths. All macrocycles were synthesized based on a series of Sonogashira cross‐coupling reactions. For 3 and 4, a 2‐(4‐pyridin­yl)ethyl protecting group for the sulfur atoms was successful, while for macrocycles 1 and 2 the more common tert‐butyl protecting group did the job. To our delight, proof‐of‐concept charge transport studies conducted in an MCBJ setup demon­strated the expected trends regarding improved conductance intensities for the TMCs compared to the BMCs. Furthermore, the corres­ponding molecular plateaus from the breaking experiments were in the expected length range of the S‐S distances for all compounds. We also found that the overall conductance seems to follow a more complex transport mechanism than just the sum of contributions from both channels.

Enzymes Repertoires and Genomic Insights into Lycium Barbarum Pectin Polysaccharides Biosynthesis.

Lycium barbarum, a member of the Solanaceae family, represents an important eudicot lineage with homology of food and medicine. Lycium barbarum pectin polysaccharides (LBPPs) are key bioactive ingredients of Lycium barbarum, and are among the few polysaccharides with both biocompatibility and biomedical activity. While previous studies have primarily focused on the functional properties of LBPPs, the mechanisms of biosynthesis and transport by key enzymes remain poorly understood. Here, we reported the completion of a 2.18-gigabase reference genome of Lycium barbarum, reconstructed the first entire biosynthesis of pectin polysaccharides and sugar transport, and characterized the important genes responsible for backbone extending, sidechain synthesis, and modification of pectin polysaccharides. Additionally, we characterized long non-coding RNAs (lncRNAs) associated with polysaccharide metabolism and identified a specific rhamnogalacturonan I (RG-I) rhamnosyltransferase, RRT3020, which enhances RG-I biosynthesis in LBPPs. These newly identified enzymes and pivotal genes endow L. barbarum with specific pectin biosynthesis capabilities, distinguishing it from other Solanaceae species. Our findings provide a foundation for evolutionary studies and molecular breeding to enhance the diverse applications of L. barbarum.

Variable‐Range Hopping Conduction in Amorphous, Non‐Stoichiometric Gallium Oxide

AbstractAmorphous, non‐stoichiometric gallium oxide (a‐GaOx, x < 1.5) is a promising material for many electronic devices, such as resistive switching memories, neuromorphic circuits and photodetectors. So far, all respective measurements are interpreted with the explicit or implicit assumption of n‐type band transport above the conduction band mobility edge. In this study, the experimental and theoretical results consistently show for the first time that for an O/Ga ratio x of 0.8 to 1.0 the dominating electron transport mechanism is, however, variable‐range hopping (VRH) between localized states, even at room temperature and above. The measured conductivity exhibits the characteristic exponential temperature dependence on T−1/4, in remarkable agreement with Mott's iconic law for VRH. Localized states near the Fermi level are confirmed by photoelectron spectroscopy and density of states (DOS) calculations. The experimental conductivity data is reproduced quantitatively by kinetic Monte Carlo (KMC) simulations of the VRH mechanism, based on the ab‐initio DOS. High electric field strengths F cause elevated electron temperatures and an exponential increase of the conductivity with F1/2. Novel results concerning surface oxidation, magnetoresistance, Hall effect, thermopower and electron diffusion are also reported. The findings lead to a new understanding of a‐GaOx devices, also with regard to metal|a‐GaOx Schottky barriers.

FREE FATTY ACIDS INHIBIT AN ION-COUPLED MEMBRANE TRANSPORTER BY DISSIPATING THE ION GRADIENT

Glutamate is the main excitatory transmitter in the mammalian central nervous system; glutamate transporters keep the synaptic glutamate concentrations at bay for normal brain function. Arachidonic acid (AA), docosahexaenoic acid (DHA), and other unsaturated fatty acids modulate glutamate transporters in cell- and tissue slices-based studies. Here, we investigated their effect and mechanism using a purified archaeal glutamate transporter homolog reconstituted into the lipid membranes. AA, DHA, and related fatty acids irreversibly inhibited the sodium-dependent concentrative substrate uptake into lipid vesicles within the physiologically relevant concentration range. In contrast, AA did not inhibit amino acid exchange across the membrane. The length and unsaturation of the aliphatic tail affect inhibition, and the free carboxylic headgroup is necessary. The inhibition potency did not correlate with the fatty acid effects on the bilayer deformation energies. AA does not affect the conformational dynamics of the protein, suggesting it does not inhibit structural transitions necessary for transport. Single-transporter and membrane voltage assays showed that AA and related fatty acids mediate cation leak, dissipating the driving sodium gradient. Thus, such fatty acids can act as cation ionophores, suggesting a general modulatory mechanism of membrane channels and ion-coupled transporters.

Controlled growth of two-dimensional MoS2/WSe2 heterostructure solar cell by chemical vapor deposition

The development of high-quality type II semiconductor heterostructures is crucial for solar energy conversion applications. Here, we report the sequential growth of MoS2/WSe2 two-dimensional semiconductor type II heterostructure using a one-step chemical vapor deposition. The morphological, Raman, and chemical analysis revealed that the WSe2 layer is deposited on the rhombus-shaped MoS2, forming a vertical MoS2/WSe2 heterostructure. The solar cell fabricated using the grown heterostructure exhibits a photovoltaic response with a conversion efficiency of 2.5 % and an open circuit voltage of 0.22 V, respectively. The numerical simulation study unravels the mechanism of charge separation and transport in the MoS2/WSe2 heterostructure solar cell.

Tensile strain-induced disorder and weak localization in SrRuO3 thin films on (100) KTaO3 substrates

Abstract SrRuO3 (SRO) thin (~12 nm) films have been grown on KTaO3 (001) substrates by RF magnetron sputtering. The as-prepared films are under enormous in-plane tensile strain, which corresponds to the elastic energy of ~1.5 MJ. Annealing in oxygen at 900 C for 6 hr relaxes strain, partially lowering the elastic energy. The surface topography shows a transition from granularity as the Ar+O2 pressure increases from 5 mTorr to 200 mTorr, with a simultaneous change in the average surface roughness from 4 nm to 0.8 nm. Annealing transforms the topography to island-type and enhances surface roughness. The films deposited at 5 mTorr are semiconducting, and annealing further enhances the resistivity. The -T of films grown at 200 mTorr shows a metallic behavior with an inflection in the -T at TC~150 K, FM transition. The low-temperature resistivity upturn shows the disordered nature of these films. The eq. ρ(T)=1/(σ_0+aT^(1/2)+a_1 T^(p/2) )+bT^α (p=2 & =2) describes the transport behavior from 2K to 300K of 5 mTorr deposited films. In the 200 mTorr deposited film, the above eq. is valid at T<95 K with p=2 and =1.5. At TC<T300 K, the -T follows eq. ρ(T)=ρ_0+ ρ_1 T^α with =1.3 and 1.5 for the as-grown and annealed films. The lower temperature -T upturn appears to have contributions from the disorder-enhanced renormalized e-e interaction (REEI) and weak localization (WL) effects. The magnetoresistance behavior supports a substantial WL effect in the films grown at 200 mTorr. Our results establish a strong correlation between the nature of strain, surface topography, and carrier transport mechanisms.

Copper in Human Health and Disease: A Comprehensive Review.

This comprehensive review discusses the crucial role of copper in human health and disease as an essential trace mineral. It emphasizes the significance of copper while addressing potential risks from imbalances in copper levels, be it excessive or inadequate. The review outlines various challenges in copper research, including toxicity concerns, data limitations, metabolic complexities, genetic influences, nutrient interactions, and resource constraints. Despite these challenges, the review identifies specific research areas needing exploration, such as copper homeostasis regulation, transport mechanisms, gut microbiome interactions, immune function, neurodegenerative diseases, cardiovascular health, cancer, fertility, and reproductive health. The purpose of this review is to explore the important role of copper in human health and disease, which highlights the delicate balance required to avoid deficiency or toxicity. For the researchers and scientists, it provides the gaps in the research, so it aims to provide insights that could advance diagnostic and therapeutic strategies across various medical disciplines.

Lava flow field development and lava tube formation during the 1858–1861 eruption of Vesuvius (Italy), unravelled by historical documentation, lidar data and 3D mapping

Somma-Vesuvius is well known for its powerful Plinian explosive eruptions, however during the last eruptive cycle (1631–1944), persistent activity took place on the stratovolcano as mild and violent Strombolian, and effusive eruptions, forming more than one hundred lava flow fields. An important mechanism of lava transport within lava flow fields is the formation and development of lava tubes. The presence of lava tubes in a flow field can greatly increase their distance of emplacement. Observations of lava tubes at Vesuvius have been documented in historical records and speleological reports but no modern scientific studies are available. This work focuses on lava tubes formed in the compound lava flow field of the long-lived 1858 eruption (from 27 May 1858 to 12 April 1861) that was fed by seven eruptive fissures. The temporal and spatial evolution of the 1858 lava flow field was reconstructed using historical documentation. The exposed lava flow field surface was analysed using a 1-m resolution lidar Digital Surface Model (DSM). Surveys to fully digitize the interior and the overlying surface of the largest lava tube found in the 1858 lava flow field were conducted using a terrestrial laser scanner, optical cameras, and an Unmanned Aerial Vehicle (UAV). The accurate 3D model obtained was used to precisely quantify the inner dimensions and to better constrain the morphologies of the lava tube. Observed internal features were described and used to gain information on the formation and activity of the lava tube. Our data allowed us to understand that the described lava tube formed as an inflated lava flow inside which lava flowed through during an extended period ultimately draining out completely at the end of the eruption. Understanding how lava flow fields develop and how lava tubes form on Vesuvius is crucial to re-evaluate the last effusive activity of the volcano and its impact on hazard assessment.

Dark Current Transport and Junction Capacitance Mechanism in InP One-Side Junction Photodiodes

Dark Current Transport and Junction Capacitance Mechanism in InP One-Side Junction Photodiodes

The CaABCG14 transporter gene regulates the capsaicin accumulation in Pepper septum

Capsaicin (CAP), a crucial compound found in chili peppers, not only contributes to their spicy flavor but also possesses several industrial applications. CAP biosynthetic pathway is well known, while its transport mechanism remains elusive. Herein, we performed a comparative transcriptome analysis conducted on pepper fruit tissues at three different stages of development. Four important CAP transporter genes, including one MATE and three ABCs, were identified by differential expression and WGCNA analysis. Specifically, the expression patterns of three ABC genes were assessed in the septum of fruits from nine distinct genotypes of peppers with high capsaicin levels. Interestingly, CaABCG14 was associated with variations in CAP concentration and co-expressed with genes involved in CAP biosynthesis. Transient expression assay revealed that CaABCG14 is localized to the membrane and nucleus. Silencing of CaABCG14 resulted in a notable reduction in the levels of CAP contents and the expression of its biosynthetic genes in the septum of pepper. The overexpression of CaABCG14 greatly intensified the cytotoxic effects of CAP on the yeast cells. Taken together, we for the first time identified a new transporter gene CaABCG14, regulating the CAP accumulation in pepper septum. These findings offer a fresh molecular theoretical framework for CAP transport and accumulation.

Motorless transport of microtubules along tubulin, RanGTP, and salt gradients

Microtubules are dynamic filaments that assemble spindles for eukaryotic cell division. As the concentration profiles of soluble tubulin and regulatory proteins are non-uniform during spindle assembly, we asked if diffusiophoresis - motion of particles under solute gradients - can act as a motorless transport mechanism for microtubules. We identify the migration of stable microtubules along cytoplasmic and higher concentration gradients of soluble tubulin, MgCl2, Mg-ATP, Mg-GTP, and RanGTP at speeds O(100) nm/s, validating the diffusiophoresis hypothesis. Using two buffers (BRB80 and CSF-XB), microtubule behavior under MgCl2 gradients is compared with negatively charged particles and analyzed with a multi-ion diffusiophoresis and diffusioosmosis model. Microtubule diffusiophoresis under gradients of tubulin and RanGTP is also compared with the charged particles and analyzed with a non-electrolyte diffusiophoresis model. Further, we find that tubulin and RanGTP display concentration dependent cross-diffusion that influences microtubule diffusiophoresis. Finally, using Xenopus laevis egg extract, we show that diffusiophoretic transport occurs in an active cytoplasmic environment.

Effects of microplastics on the rheological properties of sediment slurries in aquatic environments

Sediment slurries, characterized by their high concentrations of fine-grained cohesive sediment, are prevalent in various aquatic environments, including fluid mud, sediment gravity flows, and dredging slurries. Abundant microplastics have been detected in sediment slurries, which indicates that these slurries function as carriers for the transport of microplastics. However, there is a dearth of understanding on how sediment slurries transport microplastics. To ascertain the transport mechanisms, elucidating the effects of microplastics on the rheological properties of sediment slurries is a prerequisite because these properties govern the flow dynamics and mobility of such slurries. This study conducts experimental and theoretical investigations to examine, interpret, and quantify the effects of microplastics on the rheological properties of sediment slurries. Microplastics are shown to increase the yield stress and viscosity of sediment slurries via enhancing sediment aggregation. A new descriptor, specifically, the effective volume fraction, is proposed to characterize the effects of microplastics on sediment aggregation. Based on the newly-proposed descriptor, a new analytical model is proposed to predict the yield stress and viscosity of sediment slurries with microplastics. This study lays a foundation for further interpretating the flow dynamics and thus the transport processes of sediment slurries laden with microplastics.

Towards the CdS/SnSe solar cell optimization: Understanding the transport mechanisms

Towards the CdS/SnSe solar cell optimization: Understanding the transport mechanisms

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.

A comparative study of Schottky barrier heights and charge transport mechanisms in 3C, 4H, and 6H silicon carbide polytypes

A comparative study of Schottky barrier heights and charge transport mechanisms in 3C, 4H, and 6H silicon carbide polytypes

Large magnetoresistance and spin negative differential resistance in photoisomers-based molecular spin valves

By using non-equilibrium Green's functions in combination with density functional theory, the spin transport properties of photoisomers-based molecular spin valves constructed by salicylidene methylamine connected with two cobalt- dibenzotetraaza[14]annulene (Co-DBTAA) complex molecules via acetylene linkers are explored. A large magnetoresistance (MR) effect with a MR ratio larger than 104 can be observed in the molecular spin valves whether salicylidene methylamine is in the cis-enol form or the trans-keto form. Moreover, spin negative differential resistance (NDR) effects are also observed in the photoisomers-based molecular spin valves. The spin transport mechanisms are explored for MR and spin NDR effects observed in the molecular spin valves.

Enhanced anammox-mediated nitrogen removal in bioelectrochemical systems at prolonged negative electrode potentials.

Bioelectrochemical anaerobic ammonium oxidation (anammox) systems allow eco-friendly removal of nitrogen from reject wastewater coming from biogas processing as the anammox bacteria have previously shown to have c-type cytochromes acting in the extracellular electron transport (EET) mechanism between the bacteria and electrode. The anammoxosome compartment present in anammox bacteria features a highly curved membrane and contains tubular structures along with electron-dense particles that contain iron, which could enhance the process of EET and enhance nitrogen removal by properly applied potentials. In this study, nitrogen removal was investigated in the electrostimulated anammox nitrogen removal (EANR) cells operated comparatively at open circuit and at applied potentials of - 300mV, - 500mV, and - 700mV vs. Ag/AgCl. At peak performance (at - 700mV vs. Ag/AgCl), the EANR showed up to 140% higher specific nitrogen removal rate (11.2 ± 0.3g N/m2/day) compared to the control reactors without applied potential (8.3 ± 0.2g N/m2/day). The microbial community on the cathode with the applied potential had a higher relative proportion of unclassified Candidatus Brocadia (7.5%) compared to inoculum (> 0.01%), in contrast to cathode without potential (0.74%) and control (0.2%). The EANR system demonstrated to achieve ammonium and nitrite removal efficiencies of 91% and 53%, respectively, during a 24-h test cycle from an initial TN concentration of ~ 100mg N/L. After 150h, it achieved complete removal of all nitrogen compounds, reaching a 100% removal efficiency. The EANR would be very useful in the establishment of field-scale bilateral anammox-bioelectrochemical technology combining microbial fuel cell bioanodes and EANR biocathodes for wastewater treatment.