Transport Mechanism Research Articles

On the Charge Transport Mechanism and the Dielectric Behavior of Fe-doped SnO2/rGO heterostructure

On the Charge Transport Mechanism and the Dielectric Behavior of Fe-doped SnO2/rGO heterostructure

Mucin incorporated electrospun fibrous matrix of zein and PVP: Towards transmucosal propranolol hydrochloride delivery

Mucoadhesive drug delivery systems are being widely explored as a substitute for conventional drug delivery devices. Several polymers and their functional modifications are under investigations. In that scenario, the cohesive influence of mucin in the polymer system itself to the biologically available mucin in the mucosa is a novel approach. The added advantage of mucin in augmenting mucoadhesion was explored. A two-fold increase in the force of adhesion and an eight-fold increase in the work of adhesion were intriguing observations to be noted. Mucin incorporation in the matrix was done via EDC crosslinker. The results of the TNBS assay confirmed 39 % of mucin binding. A three-fold decrease of elongation at break (%) after mucin binding is a piece of quantitative information to corroborate the same. This work also investigates the efficiency of the mucoadhesive matrix towards the release of Propranolol Hydrochloride (PL). Low oral bioavailability of PL demands its administration via mucosal route to avoid hepatic first-pass metabolism. The release study of PL in PBS and permeation through RPMI 2650 cells revealed a burst release followed by a sustained release profile and best fitted with Korsmeyer Peppas model. PL permeation through the cell monolayer without a cell junction opening pursued a transcellular transport mechanism. Drug permeation through porcine buccal mucosa also assured adequate permeation in ex-vivo conditions. The sustained release of PL from MUZPVP and prolonged residence time of the matrix over mucosa due to increased mucoadhesion guarantees an optimistic drug delivery device to the biomedical discipline.

Averaged flow in a rotating flat layer at librations

Abstract One of the important areas in fluid mechanics is thermal convection; its study is an urgent task from the point of view of effective control of heat and mass transfer. With increasing energy consumption worldwide, improved energy transfer methods are required. Various complicating factors can either strengthen or weaken energy transport mechanisms. In the current work, attention is paid to the libration effect as one of the effective ways to control heat transfer in a rotating cavity. The experiments are aimed at a study of convective flows generated in a flat layer unevenly rotating around a horizontal axis. The flat boundaries are kept at different temperatures. It is found that the cavity librations noticeably intensify the heat transfer in a layer. The flow structure obtained using the PIV method for the cases of uniform and non-uniform rotation of the cavity is presented for the first time. The effectiveness of librations for the intensifying heat and mass transfer in a rotating hydrodynamic system is shown.

Determination of metal ion transport rate of human ZIP4 using stable zinc isotopes

The essential microelement zinc is absorbed in the small intestine mainly by the zinc transporter ZIP4, a representative member of the Zrt/Irt-like protein (ZIP) family. ZIP4 is reportedly upregulated in many cancers, making it a promising oncology drug target. To date, there have been no reports on the turnover number of ZIP4, which is a crucial missing piece of information needed to better understand the transport mechanism. In this work, we used a non-radioactive zinc isotope, 70Zn, and inductively coupled plasma mass spectrometry (ICP-MS) to study human ZIP4 (hZIP4) expressed in HEK293 cells. Our data showed that 70Zn can replace the radioactive 65Zn as a tracer in kinetic evaluation of hZIP4 activity. This approach, combined with the quantification of the cell surface expression of hZIP4 using biotinylation or surface-bound antibody, allowed us to estimate the apparent turnover number of hZIP4 to be in the range of 0.08-0.2 s-1. The turnover numbers of the truncated hZIP4 variants are significantly smaller than that of the full-length hZIP4, confirming a crucial role for the extracellular domain in zinc transport. Using 64Zn and 70Zn, we measured zinc efflux during the cell-based transport assay and found that it has little effect on the zinc import analysis under these conditions. Finally, we demonstrated that use of laser ablation (LA) ICP-TOF-MS on samples applied to a solid substrate significantly increased the throughput of the transport assay. We envision that the approach reported here can be applied to the studies of metal transporters beyond the ZIP family.

Membrane transport of rare earth metal ions N,N’-bisdioctylphosphorylmethyl-1,4-diaminobutane by the active transport mechanism

Membrane transport of rare earth metal ions N,N’-bisdioctylphosphorylmethyl-1,4-diaminobutane by the active transport mechanism

Deep insights into the sodium transport mechanism and phase evolution in Na4VP2O9 cathode/anode material

For the entire intercalation/deintercalation range of Na4VP2O9, quantum mechanics is applied to investigate sodium transport mechanism and a machine learning force field is used instead of ab initio method to offers an applicable method for the full understanding of the complicated Na + movements dynamically. It shows chain of '8′ shaped units horizontally and repeated alternating round aggregate and '8′ shaped long chain vertically. For primitive Na4VP2O9, facile Na+ transportation along a-axis is observed with an energy barrier of 0.16 V. As a cathode material, Na3VP2O9 also shows fast Na + diffusion with a minimal diffusion energy barrier 0.27 eV along a-axis. However, for the fully sodiated state of Na4VP2O9, Na+ diffusion in the lattice is significantly restricted with an energy barrier of 0.92 eV along b-axis. Accordingly, the sodium ion diffusion coefficients at room temperature for Na3VP2O9, Na4VP2O9 and Na5VP2O9 are 1.2 × 10−9 cm2 s−1, 5.9 × 10−9 cm2 s−1 and 8.2 × 10−11 cm2 s−1, respectively. The formation energy convex hull originated from the removal of Na1 sites and the occupation of E8cO8 cavities reveals an intermediate phase, Na3.5VP2O9, for the NaxVP2O9 (3 ≤ x ≤ 4) and three intermediate phases, Na4.5VP2O9, Na4.625VP2O9 and Na4.75VP2O9, for the NaxVP2O9 (4 ≤ x ≤ 5).

Investigation on radon levels in soil and water associated with Mount Tampomas geothermal activity in Indonesia

ObjectiveTo investigate radon emanation in geothermal manifestations around Mount Tampomas, West Java, Indonesia, and assess radon concentrations in soil and water samples. MethodsRadon measurements were conducted using the Durridge Rad7 instrument, supplemented with a soil gas probe for in-situ soil radon measurements at a depth of 80 cm. In-situ water radon measurements were performed using the Rad Aqua instrument, while radon measurements for hot water samples were conducted separately. Radon measurements for hot water samples were corrected for decay using a radon decay correction factor. ResultsThe analysis of radon measurements revealed a wide range of concentrations in soil and water samples. Soil radon concentrations ranged from 15 Bq/m³ to 4660 Bq/m³, with localized hotspots exhibiting exceptionally high concentrations. Water radon measurements showed elevated levels, ranging from 0.2 Bq/L to 13.4 Bq/L in-situ, particularly in hot springs. In collected water samples, radon concentrations ranged from 1 Bq/L to 6 Bq/L. These combined results highlight significant variability in radon levels across different water sources influenced by geothermal activity. ConclusionsThese findings indicate active emanation processes influenced by geological factors and underscore the role of subsurface geology and aquifer characteristics in radon transport mechanisms. The presence of localized radon hotspots suggests the need for comprehensive monitoring and proactive management strategies to mitigate environmental and public health risks associated with radon exposure.

Advancements in CIGS/ZnS Heterojunction Solar Cells: Experimental and Numerical Analysis

This study presents a comprehensive experimental investigation conducted on a CIGS-based solar cell incorporating a ZnS buffer layer. The primary objective was to determine key parameters of the CIGS/ZnS heterojunction, including parasitic resistances (Rs and Rsh), ideality factor (n), and barrier height (ϕB), using experimental current-voltage (I-V) characteristics over a temperature range of 150K to 300K under dark conditions. The heterojunction was modelled using a single-diode electrical circuit that accounted for parasitic resistances. Two methods were employed for parameter determination: direct analysis of the (I-V) curves and Cheung's method. Additionally, the charge transport mechanism within the heterojunction is investigated and discussed. Furthermore, the performance of the Al:ZnO/i:ZnO/ZnS/CIGS/Mo solar cell was assessed using the SCAPS-1D simulator, demonstrating an initial solar energy conversion efficiency of 15.01%. To enhance this efficiency, a hole transport layer (HTL) was integrated between the back electrode and the absorber layer. Extensive studies were conducted to optimize the thickness and doping density of the HTL, including a comparative analysis of different materials used as HTLs. These optimizations resulted in a significant increase in conversion efficiency, reaching up to 28.68%.

Unusual Vibrational Coupling of the Schiff Base in the Retinal Chromophore of Sodium Ion-Pumping Rhodopsins.

A Schiff base in the retinal chromophore of microbial rhodopsin is crucial to its ion transport mechanism. Here, we discovered an unprecedented isotope effect on the C═N stretching frequency of the Schiff base in sodium ion-pumping rhodopsins, showing an unusual interaction of the Schiff base. No amino acid residue attributable to the unprecedented isotope effect was identified, suggesting that the H-O-H bending vibration of a water molecule near the Schiff base was coupled with the C═N stretching vibration. A twist in the polyene chain in the chromophore for the sodium ion-pumping rhodopsins enabled this unusual interaction of the Schiff base. The present discovery provides new insights into the interaction network of the retinal chromophore in microbial rhodopsins.

Deciphering the Isotopic Imprint of Nitrate to Reveal Nitrogen Source and Transport Mechanisms in a Tile‐Drained Agroecosystem

Deciphering the Isotopic Imprint of Nitrate to Reveal Nitrogen Source and Transport Mechanisms in a Tile‐Drained Agroecosystem

Transport and inhibition mechanisms of the human noradrenaline transporter.

The noradrenaline transporter (also known as norepinephrine transporter) (NET) has a critical role in terminating noradrenergic transmission by utilizing sodium and chloride gradients to drive the reuptake of noradrenaline (also known as norepinephrine) into presynaptic neurons1-3. It is a pharmacological target for various antidepressants and analgesic drugs4,5. Despite decades of research, its structure and the molecular mechanisms underpinning noradrenaline transport, coupling to ion gradients and non-competitive inhibition remain unknown. Here we present high-resolution complex structures of NET in two fundamental conformations: in the apo state, and bound to the substrate noradrenaline, an analogue of the χ-conotoxin MrlA (χ-MrlAEM), bupropion or ziprasidone. The noradrenaline-bound structure clearly demonstrates the binding modes of noradrenaline. The coordination of Na+ and Cl- undergoes notable alterations during conformational changes. Analysis of the structure of NET bound to χ-MrlAEM provides insight into how conotoxin binds allosterically and inhibits NET. Additionally, bupropion and ziprasidone stabilize NET in its inward-facing state, but they have distinct binding pockets. These structures define the mechanisms governing neurotransmitter transport and non-competitive inhibition in NET, providing a blueprint for future drug design.

Mechanisms of influence of confluence containing spur-dike on microplastic transport and fate

The issue of microplastic pollution is an urgent and undeniable global ecological concern. Due to the intricate three-dimensional (3D) hydrodynamic properties, the confluence is highly susceptible to microplastic contamination, particularly in the presence of spur dike disturbance. The present research goal is to elucidate the underlying mechanism governing the impact of the spur dike on transport and retention fate of microplastic at the confluence. A 3D hydrodynamic-microplastic transport model was developed at the confluence, and the Computational Fluid Dynamics (CFD) coupled with Discrete Element Method (DEM) method was employed to conduct the simulation. The concentration distribution, residence time, and trajectory of microplastics with different sizes and materials, as well as the effect of various angles of the spur dike on them were explored. The results indicate that (i) Large quantities of polyamide and polystyrene microplastics (less than 1 mm in diameter) with a residence time greater than 70 s are present in the flow stagnation zone, flow separation zone, the vicinity of spur dike, and downstream of the flow separation. (ii) The layout of the spur dike will lead to an increase in microplastic concentrations upstream of the spur dike and downstream of the flow separation. (iii) Vorticity and mixing layer thickness play crucial roles in the retention of microplastics within the flow separation and spur dike field. (iv) The dimensionless angles of the spur dike (αN) exhibit a linear and inverse relationship with the dimensionless standard deviations (σN) within the spur dike field. This study will expand our understanding of the transport and retention mechanisms of microplastics, and provide valuable insights for accurately identifying pollution hotspots of microplastic pollution at confluences with spur dikes.

Organic solar cells: Exploring the future and sustainability of clean energy

As a critical technology in renewable energy, organic solar cells play an important role in energy transition and sustainable development. This paper examines the development and significance of organic solar cells in terms of energy demand, environmental requirements, and industrial growth. With the development of China's energy structure adjustment and carbon peak carbon neutral targets, interest in novel energy technologies is growing. The paper then describes the interaction between photons and materials and the electron-hole separation and charge transport mechanism of organic solar cells. In addition, the characteristics and potential applications of organic solar cells with various structures, such as bilayer heterojunction devices, intrinsic heterojunction devices, molecular DA junction devices, and stacked devices, are described in depth. In the outlook section, the paper emphasizes the future potential of organic solar cells, including efficiency enhancements, cost reductions, and integration with energy storage technologies. In conclusion, organic solar cells have tremendous potential in the field of renewable energy, and they are anticipated to lead the energy transition and contribute to sustainable development.

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.

Tailoring Interfacial Structures to Regulate Carrier Transport in Solid-State Batteries.

Solid-state lithium-ion batteries (SSLIBs) have been considered as the priority candidate for next-generation energy storage system, due to their advantages in safety and energy density compare with conventional liquid electrolyte systems. However, the introduction of numerous solid-solid interfaces results in a series of issues, hindering the further development of SSLIBs. Therefore, a thorough understanding on the interfacial issues is essential to promote the practical applications for SSLIBs. In this review, the interface issues are discussed from the perspective of transportation mechanism of electrons and lithium ions, including internal interfaces within cathode/anode composites and solid electrolytes (SEs), as well as the apparent electrode/SEs interfaces. The corresponding interface modification strategies, such as passivation layer design, conductive binders, and thermal sintering methods, are comprehensively summarized. Through establishing the correlation between carrier transport network and corresponding battery electrochemical performance, the design principles for achieving a selective carrier transport network are systematically elucidated. Additionally, the future challenges are speculated and research directions in tailoring interfacial structure for SSLIBs. By providing the insightful review and outlook on interfacial charge transfer, the industrialization of SSLIBs are aimed to promoted.

Substitution of an isovalent Te-ion in SnSe thin films for tuning optoelectrical properties

In present work, SnSe1-xTex thin films with varying Te concentrations were deposited on glass substrate through thermal evaporation technique. SnSe1-xTex thin films were characterized using X-ray diffraction (XRD), atomic force microcopy (AFM), X-ray photoelectron spectroscopy (XPS), UV–Vis NIR spectroscopy and room-temperature hall measurements technique. XRD patterns revealed that all the samples had a polycrystalline orthorhombic structure. Additionally, a low level of Te impurity improved the crystalline quality of the SnSe thin films. AFM images showed a noticeable alteration in the surface structure of the SnSe thin films caused by Te doping. UV–Vis NIR spectroscopy was employed to assess the optical characteristics of SnSe1-xTex thin films, revealing a variation in the optical band gap energy (Eg) between 1.75 and 1.89 eV, attributed to Te doping. The Hall effect measurement revealed n-type conductivity, and the carrier concentration decreased as the Te dopant concentration increased, corresponding to a decrease in antisite SnSe defects. The experimental findings suggest that adding a moderate amount of Te is a beneficial method for enhancing the optical and electrical properties of SnSe films. Furthermore, the Schottky device parameters of the Ag/SnSe1-xTex/Al:ZnO structure were established by analyzing the temperature-dependent Current-Voltage (I–V-T) characteristics through the thermionic emission current transport mechanism.

Xenolith Petrochronology (San Luis Potosi, Mexico) Constrains Heat Sources for Cenozoic Ultrahigh‐Temperature Metamorphism in the Lower Crust

AbstractUltrahigh‐temperature (UHT; >900°C) metamorphism drives crustal differentiation and is widely recognized in the rock record, but its geodynamic causes are debated. Previous work on granulite‐facies metapelite xenoliths from San Luis Potosí, Mexico suggests the lower crust experienced a protracted UHT metamorphic event that coincided with the onset of regional extension. To determine the duration, conditions, and heat sources of UHT metamorphism recorded by these xenoliths, this study characterizes the major‐element, trace‐element, and U‐Pb isotopic systematics of quartz, rutile, feldspar, garnet, and zircon by in situ electron microprobe (EPMA) and laser‐ablation inductively coupled‐plasma mass spectrometry (LA‐ICP‐MS), and augments these data with detailed petrography, thermobarometry, phase equilibria modeling, and diffusion modeling. Thermobarometry and phase equilibria modeling suggest peak metamorphic conditions exceeded 0.7 GPa and 900°C. Zircon petrochronology confirms >15 Myr of UHT conditions since its onset at ∼30 Ma. A small population of zircon record elevated temperatures following transition from backarc compression to extension during the waning stages of orogenesis (60–37 Ma). Garnet preserves trace‐element zoning and mineral inclusions consistent with suprasolidus garnet growth and subsequent compositional modification by intracrystalline rare‐earth element diffusion during protracted heating, with diffusion chronometry timescales in agreement with zircon data, followed by fluid‐driven remobilization of trace elements along now‐healed fractures within ∼1 Myr of eruption. In sum, these data are most compatible with lithospheric mantle attenuation or removal as the dominant heat transport mechanism driving synextensional UHT metamorphism and crustal melting, which has bearing on models for crustal differentiation and formation of modern and ancient granulite terranes globally.

Direct observation of the electronic structure and many-body interactions of low-mobility carriers in perylene diimide derivative

Despite the rapid progresses in the field of organic semiconductors, aided by the development of high-mobility organic materials, their high carrier mobilities are often unipolar, being sufficiently high only for either electrons or holes. Yet, the basic mechanisms underlying such significant mobility asymmetry largely remains elusive. We perform angle-resolved photoelectron spectroscopy to reveal the occupied band structures and the many-body interactions for low-mobility hole carriers in a typical n-type semiconductor perylene diimide derivative. The band dispersion exhibits strong renormalization to the calculated non-interacting electronic structure. The analysis including many-body interactions elucidate that the significant mass enhancement can be understood in terms of strong charge–phonon coupling, leading to an important mechanism of polaron band transport of low intrinsic carrier mobility in organic semiconductors.

Maximizing Potential Applications of MAX Phases: Sustainable Synthesis of Multielement Ti3AlC2.

This study employs the molten-salt-shielded method to dope the Ti3AlC2 MAX phase with Nb and Mo, aiming to expand the intrinsic potential of the material. X-ray diffraction confirms the preservation of the hexagonal lattice structure of Ti3AlC2, while Raman and X-ray photoelectron spectroscopic analyses reveal the successful incorporation of dopants with subtle yet significant alterations in the vibrational modes and chemical environment. Scanning electron microscopy with energy-dispersive X-ray spectroscopy characterizations illustrate the characteristic layered morphology and uniform dopant distribution. Density functional theory simulations provide insights into the modified electronic structure, displaying changes in carrier transport mechanisms and potential increases in metallic conductivity, particularly when doping occurs at both the M and A sites. The computational findings are corroborated by the experimental results, suggesting that the enhanced material may possess improved properties for electronic applications. This comprehensive approach not only expands the MAX phase family but also tailors its functionality, which could allow for the production of hybrid materials with novel functionalities not present in the pristine form.

Quantitative PET imaging and modeling of molecular blood-brain barrier permeability.

Blood-brain barrier (BBB) disruption is involved in the pathogenesis and progression of many neurological and systemic diseases. Non-invasive assessment of BBB permeability in humans has mainly been performed with dynamic contrast-enhanced magnetic resonance imaging, evaluating the BBB as a structural barrier. Here, we developed a novel non-invasive positron emission tomography (PET) method in humans to measure the BBB permeability of molecular radiotracers that cross the BBB through different transport mechanisms. Our method uses high-temporal resolution dynamic imaging and kinetic modeling to jointly estimate cerebral blood flow and tracer-specific BBB transport rate from a single dynamic PET scan and measure the molecular permeability-surface area (PS) product of the radiotracer. We show our method can resolve BBB PS across three PET radiotracers with greatly differing permeabilities, measure reductions in BBB PS of 18 F-fluorodeoxyglucose (FDG) in healthy aging, and demonstrate a possible brain-body association between decreased FDG BBB PS in patients with metabolic dysfunction-associated steatotic liver inflammation. Our method opens new directions to efficiently study the molecular permeability of the human BBB in vivo using the large catalogue of available molecular PET tracers.