Transport Mechanism Research Articles

From mixed to hybrid facies volcanic debris avalanche at Colima Volcano: sedimentology and numerical modeling as evidence of transport and emplacement mechanisms

From mixed to hybrid facies volcanic debris avalanche at Colima Volcano: sedimentology and numerical modeling as evidence of transport and emplacement mechanisms

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

The method of membrane extraction for rare earth elements (REE) using the carrier N, N’-bisdioctylphosphorylmethyl-1,4-diaminobutane (DPDA-8) ions, leveraging an active transport mechanism, has been optimized. The distribution of DPDA-8 within the membrane pores was confirmed using scanning electron microscopy (SEM). Both light and heavy REE extractions from a simulated solution using DPDA-8 and trioctylphosphine oxide (TOPO) in 1,2-dichlorobenzene were explored. The influence of feed solution pH, carrier and anion concentration, supported liquid membrane (SLM) type and stability, and cell temperature, among other parameters, were meticulously examined. The results indicate a decrease in permeability with a decrease in feed solution pH attributed to competitive acid transport through the membrane. Additionally, the formation of H-complexes between carriers and perchloric or phosphoric acids was investigated using Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. Changes in the stretching bands of amino and phosphine oxide groups in DPDA-8 were monitored and characterized. XRD analysis of the crystal structures of salts DPDA-6·ClO4 and DPDA-12·H2PO4 revealed a two-dimensional layered supramolecular organization with varying anion positions relative to hydrophobic fragments. The DPDA-8 carrier demonstrated significantly higher permeability values compared to TOPO, with differences in permeability exceeding twofold for certain metals. FTIR spectroscopy identified the main coordination centers of DPDA-8 during the liquid–liquid extraction of specific REEs.

Theoretical perspectives on CO2 separation by ionic liquids: Addressing crucial questions

The global population explosion necessitates more natural resources for energy, making it a major factor in climate change. CO2 is a leading actor in the greenhouse gas effect, and advancements in CO2 capture processes have attracted researchers in recent years. Numerous technologies are practiced for CO2 separation. Nevertheless, due to the intricate nature of gases and different process conditions, most of them continue to face challenges. To overcome these challenges, researchers focus on finding or designing innovative materials compatible with various processes. From the discovery of high CO2 solubility of ionic liquids (ILs), these unique compounds have rapidly gained popularity for different applications like gas separation. Molecular simulations play a crucial role in supporting researchers in understanding the connection between the properties and chemical structure of newly developed materials as ILs in a time-efficient manner. Despite the growing number of molecular simulation studies, there is a gap in the review papers that effectively highlight the benefits and feasibility of the theoretical approach. Up to date, mostly experimental studies mainly focusing on gas transport mechanisms and the relationship between chemical composition and properties were summarized. Herein, we concentrated on molecular simulation studies investigating the adsorption- and membrane-based CO2 separation performance of confined ILs. We systematically addressed prominent questions posed by researchers in each simulation study, demonstrating how to examine confined ILs and interpret the resulting data in relation to gas separation performance. The most pertinent inquiries encompass the influence of ion type (cation or anion) on gas adsorption at the gas–liquid interface and through the confined IL phase, the significance of the confined form of cation or anion in gas transport, the impact of IL thickness on gas separation, and the discernible effects of the material in which ILs are confined. Therefore, we hope to guide researchers in developing innovative membranes or adsorbents by leveraging insights obtained from the answers to these questions derived from molecular simulations of confined ILs.

Exchange bias and topological Hall effect of Fe and Co intercalated NbS2 single crystals

In recent years, the topological Hall effect generated by noncoplanar magnetic structures has been studied extensively. Some two-dimensional chalcogenides with 3d transition metal intercalations also exhibit similar properties. In this study, we investigated the crystalline structure and the magnetic and transport properties of Fe and Co codoped NbS2 single crystals. The structural results indicate disorder between the Fe and Co atoms within the interlayers of NbS2. Magnetic measurements showed that the vertical exchange bias effect appeared below the Néel temperature (TN), with a maximum value of approximately 2.5 mμB/f.u. at 2 K, which can be ascribed to the appearance of a spin-glass state. Additionally, accompanying the antiferromagnetic phase transition, nontrivial electrical transport properties were observed. Below TN, the magnetoresistance became positive and exhibited an initial increase, followed by a decrease with decreasing temperature. The Hall resistivity shows a hump-like curve near TN, indicating a topological Hall effect. This behavior is related to fluctuations in the spin chirality, which affects the scattering of charge carriers. Based on the correlation between the magnetoresistance and Hall resistivity responses, it is believed that the magnetic moments of the doped Fe and Co atoms in a single crystal compete with each other near the Néel temperature, resulting in complex magnetic structures such as noncoplanar and noncollinear arrangements. Such a two-dimensional antiferromagnetic material system provides an ideal platform for studying unconventional transport mechanisms.

Paracellular Transport and Renal Tubule Calcium Handling: Emerging Roles in Kidney Stone Disease.

The kidney plays a major role in maintenance of serum calcium concentration, which must be kept within a narrow range to avoid disruption of numerous physiologic processes that depend critically on the level of extracellular calcium, including cell signaling, bone structure, and muscle and nerve function. This defense of systemic calcium homeostasis comes, however, at the expense of the dumping of calcium into the kidney tissue and urine. Because of the large size and multivalency of the calcium ion, its salts are the least soluble among all the major cations in the body. The potential pathologic consequences of this are nephrocalcinosis and kidney stone disease. In this review, we discuss recent advances that have highlighted critical roles for the proximal tubule and thick ascending limb in renal calcium reabsorption, elucidated the molecular mechanisms for paracellular transport in these segments, and implicated disturbances in these processes in human disease.

Characterization of radon gas transmission rate in pore structures of different rock layers by radon daughters inversion calculation

Determining the transmission rate of radon gas in overburden strata is crucial for conducting a comprehensive study of radon gas's longitudinal and long-distance migration mechanisms. This study investigates the mineral components of rocks in the underground strata of the mining area using the X-ray diffraction method. Additionally, it examines the pore structure parameters of the rocks at different depths using the low-temperature nitrogen adsorption method. This research introduces an approach to inversion calculate the radon gas transmission rate through the activity ratio of radon's characteristic daughters based on the decay law and activity balance of 210Po and 210Pb daughters. In addition, it determines the transmission rates of radon gas in overlying strata at various depths through this method. The relationship between the rock's mineral composition and pore structure is investigated, and the effects of pore structure and mineral composition on the radon gas transmission rate are analyzed. The findings indicated that the pore structure exerts a dual impact on radon gas transport: macropores serve as channels for upward radon gas transport, while micropores offer most of the adsorption area. In contrast, the radon gas transmission rate is indirectly influenced by the mineral composition content associated with the medium's adsorption capacity and pore structure. In the studied lithologies, an increase in quartz content promotes radon gas transmission, while an increase in clay mineral content impedes it. Finally, the mechanisms of radon gas transport, daughter adsorption, and the impacts of rock pore structure and mineral composition on the radon transmission rate are discussed.

Few-layer Bi2O2Se: a promising candidate for high-performance near-room-temperature thermoelectric applications

Advancements in high-temperature thermoelectric (TE) materials have been substantial, yet identifying promising near-room-temperature candidates for efficient power generation from low-grade waste heat or TE cooling applications has become critical but proven exceedingly challenging. Bismuth oxyselenide (Bi2O2Se) emerges as an ideal candidate for near-room-temperature energy harvesting due to its low thermal conductivity, high carrier mobility and remarkable air-stability. In this study, the TE properties of few-layer Bi2O2Se over a wide temperature range (20-380 K) are investigated, where a charge transport mechanism transitioning from polar optical phonon to piezoelectric scattering at 140 K is observed. Moreover, the Seebeck coefficient (S) increases with temperature up to 280 K then stabilizes at∼-200μV K-1through 380 K. Bi2O2Se demonstrates high mobility (450 cm2V-1s-1) within the optimum power factor (PF) window, despite itsT-1.25dependence. The high mobility compensates the minor reduction in carrier densityn2Dhence contributes to maintain a robust electrical conductivity∼3 × 104S m-1. This results in a remarkable PF of 860μW m-1K-2at 280 K without the necessity for gating (Vg= 0 V), reflecting the innate performance of the as-grown material. These results underscore the considerable promise of Bi2O2Se for room temperature TE applications.

Rambutan‐Like Mg−Bi−O : Fe Assemblies Loaded with Fomesafen Herbicide to Induce the Fast Germination of Pinto Bean Plants

AbstractAssemblies of magnesium and bismuth oxides (Mg−Bi−O) were synthesized with (MBO : Fe) and without iron (MBO) by using a hydrothermal method. Such assemblies were utilized to promote the germination and growth of pinto bean seedlings. The MBO : Fe assemblies had rambutan‐like morphology, which is composed by nanohairs/flagella. The MBO : Fe assemblies were loaded with fomesafen herbicide and the release kinetics of such herbicide was explained by using the Korsmeyer‐Peppas model and the non‐Fickian transport mechanism. The cumulative fomesafen release at pH 7.5 reached percentages of 4.38 %, 71.02 %, 75.04 %, and 100 % for the MBO, MBO‐1 % Fe, MBO‐3 % Fe, and MBO‐5 % Fe, respectively. Also, the MBO and MBO : Fe assemblies were utilized to promote the growth of pinto bean plants. The germination percentages for the MBO, MBO‐1 % Fe, MBO‐3 % Fe, and MBO‐5 % Fe samples were 83.33, 100, 91.67 and 100 %, respectively. Such percentages are higher than that for the control plants grown without MBO : Fe (66.67 %). The longest root/shoot lengths (20.62/48 cm) were obtained for the plant grown with the MBO‐3 % Fe assembly. In contrast, lower root/shoot lengths (14.7/30.66 cm) were obtained for the control plants. Thus, MBO : Fe assemblies loaded with fomesafen improved the physical characteristics of the bean plants, which is of interest for the sustainable agriculture.

Thermal Energy Transport through Nonbonded Native Contacts in Protein.

Within the protein interior, where we observe various types of interactions, nonuniform flow of thermal energy occurs along the polypeptide chain and through nonbonded native contacts, leading to inhomogeneous transport efficiencies from one site to another. The folded native protein serves not merely as thermal transfer medium but, more importantly, as sophisticated molecular nanomachines in cells. Therefore, we are particularly interested in what sort of "communication" is mediated through native contacts in the folded proteins and how such features are quantitatively depicted in terms of local transport coefficients of heat currents. To address the issue, we introduced a concept of inter-residue thermal conductivity and characterized the nonuniform thermal transport properties of a small globular protein, HP36, using equilibrium molecular dynamics simulation and the Green-Kubo formula. We observed that the thermal transport of the protein was dominated by that along the polypeptide chain, while the local thermal conductivity of nonbonded native contacts decreased in the order of H-bonding > π-stacking > electrostatic > hydrophobic contacts. Furthermore, we applied machine learning techniques to analyze the molecular mechanism of protein thermal transport. As a result, the contact distance, variance in contact distance, and H-bonding occurrence probability during MD simulations are found to be the top three important determinants for predicting local thermal transport coefficients.

Transfer Efficiency and Organization in Turbulent Transport over Alpine Tundra

The exchange of momentum, heat and trace gases between atmosphere and surface is mainly controlled by turbulent fluxes. Turbulent mixing is usually parametrized using Monin–Obukhov similarity theory (MOST), which was derived for steady turbulence over homogeneous and flat surfaces, but is nevertheless routinely applied to unsteady turbulence over non-homogeneous surfaces. We study four years of eddy-covariance measurements at a highly heterogeneous alpine valley site in Finse, Norway, to gain insights into the validity of MOST, the turbulent transport mechanisms and the contributing coherent structures. The site exhibits a bimodal topography-following flux footprint, with the two dominant wind sectors characterized by organized and strongly negative momentum flux, but different anisotropy and contributions of submeso-scale motions, leading to a failure of eddy-diffusivity closures and different transfer efficiencies for different scalars. The quadrant analysis of the momentum flux reveals that under stable conditions sweeps transport more momentum than the more frequently occurring ejections, while the opposite is observed under unstable stratification. From quadrant analysis, we derive the ratio of the amount of disorganized to organized structures, that we refer to as organization ratio (OR). We find an invertible relation between transfer efficiency and corresponding organization ratio with an algebraic sigmoid function. The organization ratio further explains the scatter around scaling functions used in MOST and thus indicates that coherent structures modify MOST. Our results highlight the critical role of coherent structures in turbulent transport in heterogeneous tundra environments and may help to find new parametrizations for numerical weather prediction or climate models.

Probabilistic modeling of energy transfer in disordered organic semiconductors

The non-radiative energy transfer process governs the transport of excitons in organic semiconductors, directly affecting the performance of organic optoelectronic devices. Successful models describe this transfer in terms of energy donor–acceptor pair sites, in contrast to experimental photophysical properties, which reflect the average behavior of the molecular ensemble. In this study, an energetic and spatial probability density function is proposed to determine the average non-radiative energy rate for homotransfer processes. This approach considers the energetic-spatial distribution typical of disordered semiconducting polymers. The average homotransfer rate is significantly dependent on the energy of the donor site, allowing the identification of the photophysical process most likely to occur. Values of the order of 1011 s−1 were predicted and are consistent with experimental results. This approach was used to evaluate how the energy transfer efficiency in heterostructures is affected by the energy and position of the energy donor site. The model presented in this study can be explored in other organic systems to investigate exciton transport mechanisms in new organic optoelectronic device architectures.

Variations in plume activity reveal the dynamics of water-filled faults on Enceladus

After discovering a jet activity near the south pole of Saturn’s moon Enceladus, the Cassini mission demonstrated the existence of a subsurface water ocean with a unique sampling opportunity through flybys. Diurnal variations in the observed brightness of the plume suggest a tidal control, although the existence and timing of two activity maxima seem to contradict stress analysis predictions. Here, we re-interpret the observed plume variability by combining a 3D global model of tidal deformation of the fractured ice shell with a 1D local model of transport processes within south-polar faults. Our model successfully predicts the observed plume’s temporal variability by combining two independent vapour transport mechanisms: slip-controlled jet flow and normal-stress-controlled ambient flow. Moreover, it provides a possible explanation for the differences between the vapour and solid emission rates during the diurnal cycle and the observed fractionation of the various icy particle families. Our model prediction could be tested by future JWST observations targeted when Enceladus is at different positions on its orbit and could be used to determine the optimal strategy for plume material sampling by future space missions.

JWST MIRI and NIRCam observations of NGC 891 and its circumgalactic medium

We present new JWST observations of the nearby, prototypical edge-on, spiral galaxy NGC 891. The northern half of the disk was observed with NIRCam in its F150W and F277W filters. Absorption is clearly visible in the mid-plane of the F150W image, along with vertical dusty plumes that closely resemble the ones seen in the optical. A $ kpc ^2$ area of the lower circumgalactic medium (CGM) was mapped with MIRI F770W at 12 pc scales. Thanks to the sensitivity and resolution of JWST, we detect dust emission out to $ 4$ kpc from the disk, in the form of filaments, arcs, and super-bubbles. Some of these filaments can be traced back to regions with recent star formation activity, suggesting that feedback-driven galactic winds play an important role in regulating baryonic cycling. The presence of dust at these altitudes raises questions about the transport mechanisms at play and suggests that small dust grains are able to survive for several tens of million years after having been ejected by galactic winds in the disk-halo interface. We lay out several scenarios that could explain this emission: dust grains may be shielded in the outer layers of cool dense clouds expelled from the galaxy disk, and/or the emission comes from the mixing layers around these cool clumps where material from the hot gas is able to cool down and mix with these cool cloudlets. This first set of data and upcoming spectroscopy will be very helpful to understand the survival of dust grains in energetic environments, and their contribution to recycling baryonic material in the mid-plane of galaxies.

Surface Passivation of the Cu2–xSe Electrode During the Chemical Bath Deposition

Herein, p‐type flexible and transparent electrodes of Cu2–xSe are produced at different conversion times at 20, 25, and 30 s of polyester/Cu thin films via chemical bath deposition. To study the charge transport properties across the Cu2–xSe layer, the organic light‐emitting diodes (OLEDs) are produced according to the following configuration: polyester/Cu2–xSe/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate)/poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene]/aluminum (polyester/Cu2–xSe/PEDOT:PSS/MEH‐PPV/Al), resulting in a direct tunneling in the transport of holes. The control of the barrier's energy between the Cu2–xSe electrode and the MEH‐PPV polymer allows it to tune selectively of the OLED’ charge transport mechanism. The morphological analysis of the Cu2–xSe electrode, carried out using atomic force microscopy, as well as the temperature dependence of the current–voltage measurements in the OLED (50–300 K) shows the ideal deposition time in the chemical bath. In contrast, impedance spectroscopy results confirm the inexistence of the Cu2–xSe/PEDOT:PSS interface using 30 s to Cu2–xSe synthesis. As a result, the control of the injection mechanism of charges can be obtained by reducing the barrier energy to hole transport during the synthesis process of the Cu2–xSe layer via chemical bath deposition, thus simplifying and reducing the costs of the device's processing.

Interface Collaborative Strategy for High Mobility Organic Single‐Crystal Field‐Effect Transistors with Ideal Current–Voltage Curves

AbstractThe key roles of electrode/semiconductor and semiconductor/dielectric interfaces play in the ideality of organic field‐effect transistors (OFETs) by traditional device preparation technologies are not yet fully understood, which severely limits progress in the design of molecules, the understanding of transport mechanisms, and the circuit applications of OFETs. Herein, at a quantitative level, the origin of nonideal current–voltage (I–V) curves and possibly overestimated mobility in single‐crystal OFETs is revealed, including contact resistance (Rc), charge trapping, and scattering at interfaces of devices. Impressively, an efficient interface collaborative strategy, which consists of transferred “doped” electrodes with tunable contact “doping” localized regions at the source‐drain contacts and polymer‐modified SiO2 with suitable surface polarity (γsp) is further demonstrated that have great advantages in the construction of ideal high mobility devices. Also, an interesting double‐edged sword effect of γsp of dielectric on the ideality of OFETs is observed. The dielectric with a lower γsp can result in higher mobility, while too low γsp would degrade the device ideality due to significant effect of charge scattering. The findings not only provide new perspectives and strategies to construct ideal OFETs but also offer useful guidance to correctly evaluate organic semiconductor materials.

Evidence of a Large Debris Avalanche Event (22.0 Ma) from the Comondú Group on the Baja California Sur Peninsula, Mexico

The morphological, sedimentological, and microtextural characteristics of Miocene debris avalanche deposits which extend from the Punta Coyote to the vicinity of the city of La Paz, were studied along the eastern of the Baja California Peninsula. The debris avalanche deposits studied include a mixture of angular mega blocks whose composition comes from the deposits that make up the Comondú Group: pre-Comondú (red sandstones and conglomerates with intercalated ignimbrites), the Upper Unit (brownish sandstones, shales, and conglomerate), and breccia, with a predominance of jigsaw cracks, injection structures, and fault structures. These deposits were studied and analyzed considering the stratigraphic relationships between the rock formations present in the mega-blocks. Six stratigraphic sections were measured to describe the composition and morphology of the clastic components present in the mega-blocks of the debris avalanche. Two different units (m1 and m2), were identified in the debris avalanche deposits. Unit m1 is the oldest, with a thickness of 100m, and consists of a chaotic set of mega-blocks up to 100 m in diameter derived from the pre-Comondú Group, and Upper Unit. The deposits are highly heterolithic, with angular and highly fractured clasts at different scales. While the unit m2 consists principally of 20-100 m thick volcaniclastic layers dominated by poorly sorted, breccias and minor epiclastic deposits. According to stratigraphic relationships, the collapse occurred at 22.0 Ma. The debris deposit covers an area of 150 km2 and has an estimated volume of 1.3 km3. The characteristic suggests a transport mechanism with a disintegration of the mega-blocks and a contact/collision interaction. Where mega-blocks moved within a dense flow in a buffered manner, remaining consistent over long distances. The observed structures and textures suggest that the mega-blocks were mainly produced by the alteration and ingestion of older substrates by the avalanche of moving debris. The avalanche flowed over pre-existing topography excavated in the Comondú Group sequence, and flow indicators reveal a west-southwest direction, exhibiting a typical mountainous avalanche topography. The study of ancient debris avalanche events not only provides a deeper understanding of these natural phenomena but also contributes to the development of tools to predict, mitigate, and manage risk areas.

Mechanism of proton transport in SLC25 family proteins

Mechanism of proton transport in SLC25 family proteins

Anomalous Electrical Behavior of 4H-SiC Schottky Diodes in Presence of Stacking Faults

In this work, we investigated the impact of crystallographic defects (specifically stacking faults, SFs) on the mechanisms of the current transport in 4H-SiC Schottky contacts. The electrical characteristics were studied under both forward and reverse bias. In particular, while the presence of SFs under the contact did not show a significant impact on the forward characteristics of the Schottky diode, a significant increase in the leakage current occurred under reverse bias in defective diodes. This anomalous behavior can be explained by a space-charge limited current model, consistent with the presence of a trapping state distribution in the 4H-SiC gap. An increase of the reverse bias above 30 V leads to a complete trap filling. The weak temperature-dependence of the leakage current observed at highest voltage suggests that a tunneling of the carriers through the barrier can be also present.

Uncoupling Protein 1: biochemical and biophysical studies of the proton transport mechanism

Uncoupling Protein 1: biochemical and biophysical studies of the proton transport mechanism

Caveolin Regulates the Transport Mechanism of the Walnut-Derived Peptide EVSGPGYSPN to Penetrate the Blood-Brain Barrier.

Bioactive peptides, derived from short protein fragments, are recognized for their neuroprotective properties and potential therapeutic applications in treating central nervous system (CNS) diseases. However, a significant challenge for these peptides is their ability to penetrate the blood-brain barrier (BBB). EVSGPGYSPN (EV-10) peptide, a walnut-derived peptide, has demonstrated promising neuroprotective effects in vivo. This study aimed to investigate the transportability of EV-10 across the BBB, explore its capacity to penetrate this barrier, and elucidate the regulatory mechanisms underlying peptide-induced cellular internalization and transport pathways within the BBB. The results indicated that at a concentration of 100 μM and osmotic time of 4 h, the apparent permeability coefficient of EV-10 was Papp = 8.52166 ± 0.58 × 10-6 cm/s. The penetration efficiency of EV-10 was influenced by time, concentration, and temperature. Utilizing Western blot analysis, immunofluorescence, and flow cytometry, in conjunction with the caveolin (Cav)-specific inhibitor M-β-CD, we confirmed that EV-10 undergoes transcellular transport through a Cav-dependent endocytosis pathway. Notably, the tight junction proteins ZO-1, occludin, and claudin-5 were not disrupted by EV-10. Throughout its transport, EV-10 was localized within the mitochondria, Golgi apparatus, endoplasmic reticulum, lysosomes, endosomes, and cell membranes. Moreover, Cav-1 overexpression facilitated the release of EV-10 from lysosomes. Evidence of EV-10 accumulation was observed in mouse brains using brain slice scans. This study is the first to demonstrate that Cav-1 can facilitate the targeted delivery of walnut-derived peptide to the brain, laying a foundation for the development of functional foods aimed at CNS disease intervention.