Machine learning reveals key ion selectivity mechanisms in polymeric membranes with subnanometer pores

Machine learning unveils molecular transport mechanisms obscured by entropy-enthalpy compensation in polymeric membranes.

Correlation between diffusion coefficient values of chloride ions obtained through column and ion migration tests in cementitious matrices with varying contents of silica fume and mortar

Corrosion is one of the main phenomena that lead to pathological manifestations in reinforced concrete structures under aggressive environments. with the chloride ion being the most responsible for its occurrence. In this way, understanding the transport mechanisms of this ion through the microstructure of the concrete is of fundamental importance to prevent or delay the penetration of these aggressive agents to guarantee a durable structure. In the literature, there are extensive studies concerning the diffusion of chlorides in concrete and the influence of pozzolanic additions in this mechanism. However, only a few correlate the different methods of analysis. This work aims to determine the chloride ion diffusion coefficients in concrete containing various levels of silica fume (5%, 10%, and 15%) or varying the mortar content (54%, 80%, and 100%), and compares the results obtained through column tests and chloride migration tests. It was observed that, although the techniques used were quite distinct, the diffusion values obtained were similar, contributing to the validation of both techniques. Furthermore, the variation in the mortar ratio causes a reduction in the interfacial transition zone of coarse aggregate/mortars and an increase in the content of aluminates, which promotes a similar effect to the use of silica fume.

Investigation of transport mechanisms induced by filament-coupling bridges- network in Bi-2212 wires

One of the features unique in Bi-2212/Ag wires is the network of bridges between the filaments formed by grains grown through the Ag matrix during the partial-melt heat treatment process. Although these interconnections favor a redistribution of the current among the filaments allowing high critical current density, they represent a strong electrical coupling between the filaments themself. Such a coupling increases the AC losses, present also in case of charge and discharge of DC magnets, principal applications of this kind of superconductor. In this work, through transport and magnetic measurements and their comparison, we study the behavior of these bridges as a function of applied magnetic field and temperature and the implications they have on the electrical coupling. The experiment has been performed on two multifilamentary wires prepared by GDG-PIT process starting from two commercial Bi-2212 precursor powders: Nexans and Engi-Mat. The reported results provide information on the effective length scale on which the filaments are coupled as a function of the field and temperature and we believe that such findings can be useful in magnet design.

Peptide-Mucin Binding and Biosimilar Mucus-Permeating Properties

This study aimed to understand the role of the mucus layer (a biological hydrogel) in the transport mechanisms of peptides. Using established in vitro models, the mucin-binding activity and mucus-permeating property of peptides were determined. Uncharged peptides with relatively high hydrophilicity, including MANT, TNGQ, and PASL, as well as cationic peptides, including KIPAVF and KMPV, possessed strong mucin-binding activity. Contrarily, uncharged peptides with high hydrophobicity index, including YMSV and QIGLF, exhibited weak mucin-binding activity. Only TNGQ, which has high Boman index and hydrophilicity, showed a high biosimilar mucus-permeating property with a permeability of 96 ± 30% after 60 min. TNGQ showed the potential for high bioavailability due to the high mucin-binding and biosimilar mucus-permeating activities.

Structural basis for the assembly and electron transport mechanisms of the dimeric photosynthetic RC-LH1 supercomplex

The reaction center (RC) and light-harvesting complex 1 (LH1) form a RC-LH1 core supercomplex that is vital for the primary reactions of photosynthesis in purple photosynthetic bacteria. Some species possess the dimeric RC-LH1 complex with an additional polypeptide PufX, representing the largest photosynthetic complex in anoxygenic phototrophs. However, the details of the architecture and assembly mechanism of the RC-LH1 dimer are unclear. Here we report seven cryo-electron microscopy (cryo-EM) structures of RC-LH1 supercomplexes from Rhodobacter sphaeroides. Our structures reveal that two PufX polypeptides are positioned in the center of the S-shaped RC-LH1 dimer, interlocking association between the components and mediating RC-LH1 dimerization. Moreover, we identify a new transmembrane peptide, designated PufY, which is located between the RC and LH1 subunits near the LH1 opening. PufY binds a quinone molecule and prevents LH1 subunits from completely encircling the RC, creating a channel for quinone/quinol exchange. Genetic mutagenesis, cryo-EM structures, and computational simulations enable a mechanistic understanding of the assembly and electron transport pathways of the RC-LH1 dimer and elucidate the roles of individual components in ensuring the structural and functional integrity of the photosynthetic supercomplex.

Control and understanding of metal contacts to β-Ga2O3 single crystals: a review

Gallium oxide (Ga2O3) is a promising semiconductor for high power devices and solar blind ultraviolet photodetectors due to its large bandgap, a high breakdown field, and high thermal stability. Recently, a considerable achievement has been obtained for the growth of high-quality β-Ga2O3 and high performance β-Ga2O3 based devices. However, rapid advance in device performance can be limited by the critical issues of metal contacts to β-Ga2O3 such as barrier height, leakage current, ohmic contact, and surface, interfacial and deep states. This article aims to provide a review on the recent studies in the control and understanding of metal contacts to β-Ga2O3, particularly in terms of the barrier formation. This review suggests that understanding the current transport mechanisms of metal contacts to β-Ga2O3 more thoroughly is necessary to enhance the performance, stability and reliability of β-Ga2O3 based devices.

Relationship between Structure and Biological Activity of Various Vitamin K Forms

Vitamin K is involved many biological processes, such as the regulation of blood coagulation, prevention of vascular calcification, bone metabolism and modulation of cell proliferation. Menaquinones (MK) and phylloquinone vary in biological activity, showing different bioavailability, half-life and transport mechanisms. Vitamin K1 and MK-4 remain present in the plasma for 8–24 h, whereas long-chain menaquinones can be detected up to 96 h after administration. Geometric structure is also an important factor that conditions their properties. Cis-phylloquinone shows nearly no biological activity. An equivalent study for menaquinone is not available. The effective dose to decrease uncarboxylated osteocalcin was six times lower for MK-7 than for MK-4. Similarly, MK-7 affected blood coagulation system at dose three to four times lower than vitamin K1. Both vitamin K1 and MK-7 inhibited the decline in bone mineral density, however benefits for the occurrence of cardiovascular diseases have been observed only for long-chain menaquinones. There are currently no guidelines for the recommended doses and forms of vitamin K in the prevention of osteoporosis, atherosclerosis and other cardiovascular disorders. Due to the presence of isomers with unknown biological properties in some dietary supplements, quality and safety of that products may be questioned.

Free Energy Analyses of Cell-Penetrating Peptides Using the Weighted Ensemble Method

Cell-penetrating peptides (CPPs) have been widely used for drug-delivery agents; however, it has not been fully understood how they translocate across cell membranes. The Weighted Ensemble (WE) method, one of the most powerful and flexible path sampling techniques, can be helpful to reveal translocation paths and free energy barriers along those paths. Within the WE approach we show how Arg9 (nona-arginine) and Tat interact with a DOPC/DOPG(4:1) model membrane, and we present free energy (or potential mean of forces, PMFs) profiles of penetration, although a translocation across the membrane has not been observed in the current simulations. Two different compositions of lipid molecules were also tried and compared. Our approach can be applied to any CPPs interacting with various model membranes, and it will provide useful information regarding the transport mechanisms of CPPs.

Analysis of the problems of mechanical gearboxes of transport systems and their solution using a magnetic sensor

Objective: Increasing reliability of mechanical gearboxes using a magnetic sensor, which will sig nifi cantly increase the reliability of transport mechanisms and systems in general. Methods: An analysis of incidents covered in the media was carried out. Results: Conclusions are drawn about the consequences of failure of mechanical gearboxes. To prevent emergency situations caused by a breakdown of a mechanical gearbox, it is proposed to use a magnetic sensor, which allows carrying out analysis and diagnostics of the gearbox and its components during operation. A mathematical model of a magnetic sensor is compiled and a block diagram of a device for processing the output signal of the sensor modulator is presented. Practical importance: Failure of a mechanical gearbox is a common problem that leads to a stop of transport mechanisms and systems. Detection of a mechanical gearbox malfunction can signifi cantly reduce the cost of repairs, as well as prevent unexpected damage to the mechanism, which can lead to a complete stop of the transport system. The use of a magnetic sensor in the traction gearbox of an electric train will reduce the likelihood of a traction gearbox breakdown during operation and reduce the cost of repairs, increase the reliability of the traction drive, and also simplify the commissioning of new electric trains and traction gearboxes.