Loss Of Polarity Research Articles

Heterointerface between Carbon Nano-Onions and Fluorinated Boron Nitride Nanostructures for Improved Microwave Absorption Properties.

Carbon-based materials are considered to be promising candidates for lightweight microwave absorption materials (MAMs). However, single carbon-based materials cannot meet the requirements of wide effective absorption bandwidth (EAB) and strong microwave absorption due to the missing magnetic loss. Combining with lightweight magnetic materials via rational design of microstructures attends to be an effective way to achieve high-performance microwave absorption. In this study, core-shell carbon nano-onions@fluorinated boron nitrides (CNOs@F-BNNOs) nanocomposites with N-C and F-B bridging were obtained by a simple in situ pyrolytic polymerization as well as a hydrothermal fluorination strategy and exhibited excellent microwave absorption properties. Furthermore, the results indicate that the addition of F-BNNOs not only improves polarization loss and optimizes impedance matching but also enhances the magnetic loss effect, thereby improving the electromagnetic wave absorption performance (EWAP). Among these compositions, CNOs@F-BNNOs achieve an excellent minimum reflection loss (RLmin) value of -43.23 dB at 17.23 GHz, with an EAB of 10.54 GHz at a thickness of 2.80 mm. Additionally, CNOs@F-BNNOs have excellent thermal conductivity. Therefore, this work presents a novel approach to constructing lightweight, efficient, and promising core-shell microwave absorption materials (MAMs).

Enhanced dielectric losses in α-MnO2via protonation modulation.

MnO6 octahedra without distortions in α-MnO2 have a low dipole content, which limits their dielectric loss capabilities. Herein, we develop protonated MnO2 with distorted MnO6 octahedra for increased dipole numbers via a two-step hydrothermal method. In comparison with α-MnO2, this protonated MnO2 provides greatly improved dipole polarization loss capabilities, resulting in a reflection loss value of -19.1 dB with an effective absorption bandwidth of 3.3 GHz at a low thickness of 2 mm.

Multifunctional Carbon Foam with Nanoscale Chiral Magnetic Heterostructures for Broadband Microwave Absorption in Low Frequency

The construction of carbon nanocoil (CNC)-based chiral-dielectric-magnetic trinity composites is considered as a promising approach to achieve excellent low-frequency microwave absorption. However, it is still challenging to further enhance the low frequency microwave absorption and elucidate the related loss mechanisms. Herein, the chiral CNCs are first synthesized on a three-dimensional (3D) carbon foam and then combined with the FeNi/NiFe2O4 nanoparticles to form a novel chiral-dielectric-magnetic trinity foam. The 3D porous CNC-carbon foam network provides excellent impedance matching and strong conduction loss. The formation of the FeNi-carbon interfaces induces interfacial polarization loss, which is confirmed by the density functional theory calculations. Further permeability analysis and the micromagnetic simulation indicate that the nanoscale chiral magnetic heterostructures achieve magnetic pinning and coupling effects, which enhance the magnetic anisotropy and magnetic loss capability. Owing to the synergistic effect between dielectricity, chirality, and magnetism, the trinity composite foam exhibits excellent microwave absorption performance with an ultrabroad effective absorption bandwidth (EAB) of 14GHz and a minimum reflection of loss less than - 50dB. More importantly, the C-band EAB of the foam is extended to 4GHz, achieving the full C-band coverage. This study provides further guidelines for the microstructure design of the chiral-dielectric-magnetic trinity composites to achieve broadband microwave absorption.

Lamp2 Deficiency Enhances Susceptibility to Oxidative Stress-Induced RPE Degeneration.

Autophagy and lysosomal degradation are vital processes that protect cells from oxidative stress. This study investigated the role of lysosome-associated membrane protein 2 (Lamp2), a lysosomal protein essential for autophagosome maturation and lysosome biogenesis, in maintaining retinal health under oxidative stress. To induce oxidative stress, young Lamp2 knockout (KO) and wild-type mice received an intravenous injection of a low dose (10mg/kg) of sodium iodate (NaIO3). We examined retinal histopathology and morphological changes in the RPE. The involvement of resident microglia or infiltrating macrophages was assessed using immunostaining, flow cytometry, and real-time PCR for chemokines and cytokines. After administering a low-dose NaIO3, Lamp2 KO mice showed significant RPE degeneration, whereas wild-type mice had minimal damage. Histological analysis and electron microscopy revealed significant thinning of the outer nuclear layer and loss of RPE epithelial polarity in Lamp2 KO mice. Additionally, there was a significant increase in ionized calcium-binding adaptor molecule 1-positive microglia and macrophages in the outer retina. Early proliferation of CD45lowMHC-IIlow resident microglia was followed by the infiltration of CD45highLy6Chigh monocytes and the engraftment of CD11b+CD45high monocyte-derived macrophages. Transcript levels of monocyte chemoattractant protein 1, macrophage inflammatory protein 1β, Il- 1β, and Il-6 also increased in the retinas of Lamp2 KO mice. Furthermore, pretreatment with the macrophage-depleting agent clodronate prevented NaIO3-induced RPE degeneration and macrophage infiltration in Lamp2 KO mice. Lamp2 deficiency, when combined with oxidative stress, leads to RPE degeneration in vivo. Lysosomal dysfunction also promotes macrophage engraftment and triggers neurotoxic inflammation.

Effectiveness-MTU modeling approach for hydrogen separation with dense metallic membranes

Effectiveness-MTU modeling approach for hydrogen separation with dense metallic membranes

Multiple synergistic effects of structural coupling and dielectric-magnetic loss in promoting microwave absorption of bark-derived absorbers

The explode development of global automation and digitization brings increasing electromagnetic radiation, threatening information security and health. Biomass wave-absorbing materials stand out among massive absorbers due to their green and environmentally friendly features, yet remains severe challenge in equilibration between impedance matching and efficient loss ability. Herein, this work innovatively used waste bark which amounts up to 400 million cubic meters generated from forest as carbon precursor. The FeCo@C nanocomposites derived from FeCo-MOF precursor are introduced on the surface of bark-derived carbon pore using vacuum impregnation and carbonization methods, and tree bark-derived porous carbon (TPC)/FeCo@C composites are successfully fabricated. The unique hierarchical structure composed of three-dimensional (3D) parallel pore structure of bark-derived carbon and yolk-shell structure of FeCo@C favors to optimizing impedance matching and prolonging attenuation paths of microwaves. Additionally, the introduction of FeCo@C can promote interface polarization loss, as well as enhance synergistic effects of dielectric-magnetic losses. Multiple synergistic effects of structural coupling and dielectric-magnetic loss endow TPC/FeCo@C composite attractive absorbing ability. The optimized TPC/FeCo@C-5 exhibits a minimum reflection loss (RLmin) of − 61.04 dB and the effective bandwidth (EAB) of 7.25 GHz at a matching thickness of 2.64 mm, which is superior to most biomass-based absorbers. Apparently, this work presents a valuable concept for the secondary utilization of discarded bark in the domain of microwave absorption, which is significant for achieving energy saving and environmental protection and addressing electromagnetic pollution.

Modelling hydrogen deblending from natural gas using Pd-based dense metallic membranes with an empirical polarization model

Modelling hydrogen deblending from natural gas using Pd-based dense metallic membranes with an empirical polarization model

Sandwich‐Like CNTs/Carbon@Si3N4 Porous Foam for Temperature‐Insensitive Electromagnetic Wave Absorption

AbstractDespite considerable efforts to tune the morphology and composition from the macroscopic level to the nanoscale level of electromagnetic wave‐absorbing materials (EWMs), achieving strong and wide‐bandwidth absorption under a temperature‐variant environment remains extremely difficult due to the temperature‐sensitive electromagnetic‐absorbing mechanisms that involve dipole polarization and conductive loss. Here, by integrating the highly conductive carbon nanotubes (CNTs) networks and the temperature‐stable silicon nitride (Si3N4) protective layer, a CNTs/amorphous carbon@Si3N4 (C‐CNT‐Si3N4) porous foam composed of sandwich‐like Si3N4/C‐CNT/Si3N4 strut, which exhibits excellent temperature‐insensitive electromagnetic‐absorbing properties from room temperature to 600 °C, is demonstrated. To be specific, the value of the minimum reflection loss is always lower than −50 dB, and a temperature‐insensitive effective absorbing bandwidth covering the whole X band throughout a thickness range of 4.8–6.1 mm is achieved. The superior temperature‐insensitive electromagnetic‐absorbing property is due to the synergistic effects of irregular polarization loss derived from lattice vacancies and heterogeneous interface, slightly increased conductive loss derived from decreasing carrier mobility, and increasing carrier concentration under a rising temperature environment.

CSE-8, a filamentous fungus-specific Shr3-like chaperone, facilitates endoplasmic reticulum exit of chitin synthase CHS-3 (class I) in Neurospora crassa

Chitin is a crucial structural polysaccharide in fungal cell walls, essential for maintaining cellular plasticity and integrity. Its synthesis is orchestrated by chitin synthases (CHS), a major family of transmembrane proteins. In Saccharomyces cerevisiae, the cargo receptor Chs7, belonging to the Shr3-like chaperone family, plays a pivotal role in the exit of Chs3 from the endoplasmic reticulum (ER) and its subsequent activity in the plasma membrane (PM). However, the auxiliary machinery responsible for CHS trafficking in filamentous fungi remains poorly understood. The Neurospora crassa genome encodes two orthologues of Chs7: chitin synthase export (CSE) proteins CSE-7 (NCU05720) and CSE-8 (NCU01814), both of which are highly conserved among filamentous fungi. In contrast, yeast forms only possess a single copy CHS export receptor. Previous research highlighted the crucial role of CSE-7 in the localization of CHS-4 at sites of cell wall synthesis, including the Spitzenkörper (SPK) and septa. In this study, CSE-8 was identified as an export protein for CHS-3 (class I). In the Δcse-8 knockout strain of N. crassa, CHS-3-GFP fluorescence was absent from the SPK or septa, indicating that CSE-8 is required for the exit of CHS-3 from the ER. Additionally, sexual development was disrupted in the Δcse-8 strain, with 20% of perithecia from homozygous crosses exhibiting two ostioles. A Δcse-7;Δcse-8 double mutant strain showed reduced N-acetylglucosamine (GlcNAc) content and decreased radial growth. Furthermore, the loss of cell polarity and the changes in subcellular distribution of CSE-8-GFP and CHS-3-GFP observed in hyphae under ER stress induced by the addition of tunicamycin and dithiothreitol reinforce the hypothesis that CSE-8 functions as an ER protein. The current evidence suggests that the biogenesis of CHS exclusive to filamentous fungi may involve pathways independent of CSE-mediated receptors.

Linear Dielectric Polymers with Ferroelectric-Like Crystals for High-Temperature Capacitive Energy Storage.

Achieving optimal capacitive energy storage performance necessitates the integration of high energy storage density, typical of ferroelectric dielectrics, with the low polarization loss associated with linear dielectrics. However, combining these characteristics in a single dielectric material is challenging due to the inherent contradictions between the spontaneous polarization of ferroelectric dielectrics and the adaptability of linear dielectrics to changes in the electric field. To address this issue, a linear isotactic sulfonylated polynorbornene dielectric characterized by ferroelectric-like crystals has been developed. The sulfonyl dipoles in the ferroelectric-like crystals are oriented in the same direction, thereby enabling this polymer to exhibit a considerable dielectric constant (7.5) at room temperature. Notably, when the operating temperature surpasses the polymer's glass transition temperature (Tg ≈ 140 °C), its dielectric constant rises to 12 with just minor changes in the dissipation factor. At 150 °C, 90% efficiency of the discharge energy density reaches as high as 6.76 Jcm-1 under a low electric field of 320 MV m-1, which is ten times that of the state-of-the-art, high-temperature, capacitor-grade polyetherimide. The enhancement of high-temperature capacitive performance, achieved by utilizing the crystallinity of isotactic polymers to form a polar structure, presents a new perspective for the design of high-temperature dielectric polymers.

Activated Graphite with Richly Oxygenated Surface from Spent Lithium-Ion Batteries for Microwave Absorption.

Designing spent graphite anodes from lithium-ion batteries (LIBs) for applications beyond regenerated batteries offers significant potential for promoting the recycling of spent LIBs. The battery-grade graphite, characterized by a highly graphitized structure, demonstrates excellent conductive loss capabilities, making it suitable for microwave absorption. During the Li-ion intercalation and deintercalation processes in battery operation, the surface layer of spent graphite (SG) becomes activated, forming oxygen-rich functional groups that enhance the polarization loss mechanism. To further control the polarization loss and achieve optimized impedance matching, reduced graphene oxide (rGO) is employed as a modifier. Herein, rGO serves as a binder, effectively combining individual SG particles. The matched Fermi levels of SG and rGO reduce the interfacial barrier, facilitating rapid electron transfer. Simultaneously, their combination forms a 3D conduction network, which not only enhances multiple scattering, reflection, and attenuation of electromagnetic waves but also provides abundant polarization centers for increased microwave absorption. As a result, the optimized SG/rGO aerogel achieves an impressive effective absorption bandwidth of 7.04GHz and accompanied by a minimum reflection loss of -51.1dB. This study broadens the scope of spent LIBs utilization and provides insights for wilder and more functional applications.

Polar mesospheric ozone loss initiates downward coupling of solar signal in the Northern Hemisphere

Solar driven energetic particle precipitation (EPP) is an important factor in polar atmospheric ozone balance and has been linked to ground-level regional climate variability. However, the linking mechanism has remained ambiguous. The observed and simulated ground-level changes start well before the processes from the main candidate, the so-called EPP-indirect effect, would start. Here we show that initial reduction of polar mesospheric ozone and the resulting change in atmospheric heating rapidly couples to dynamics, transferring the signal downwards, shifting the tropospheric jet polewards. This pathway is not constrained to the polar vortex. Rather, a subtropical route initiated by a changing wind shear plays a key role. Our results show that the signal propagates downwards in timescales consistent with observed tropospheric level climatic changes linked to EPP. This pathway, from mesospheric ozone to regional climate, is independent of the EPP-indirect effect, and solves the long-standing mechanism problem for EPP effects on climate.

Broadband polarization-maintaining anti-resonant fiber design via swarm intelligence.

In this study, we utilized a discrete point configuration method in conjunction with genetic algorithm (GA) and particle swarm optimization (PSO) to design broadband polarization-maintaining anti-resonant fibers (PM-ARFs). The resulting structure features a confinement loss (CL) below 0.17 dB/m, birefringence of approximately 8.2 × 10-5, and a polarization loss ratio (PLR) close to 297 at 1550 nm, providing a usable bandwidth of 340 nm across a range from 1.27 μm to 1.61 μm. This design approach provides additional design freedom beyond parameter optimization and component stacking typical of intelligent design methods. Our study offers a robust design methodology for broadband PM-ARFs, with significant implications for the design of other non-uniform optical waveguides.

Intercalation-Induced Interlayer and Defect Engineering in Ti3C2Tx MXene for Ultralow-Reflection Electromagnetic Interference Shielding.

Interlayer and defect engineering significantly affects the electrical conductivity and electromagnetic interference (EMI) shielding of Ti3C2Tx MXene. Previous studies have prioritized the size of the intercalant over its synergy with chemical affinity, limiting the elucidation of the intercalation mechanism and the precise control of the interlayer spacing (d-spacing). Herein, we synthesize MXene aerogels with a tunable d-spacing and defect density using a series of amine molecules of different sizes and chemical affinities as intercalants and cross-linkers. Particularly, the intercalation of p-phenylenediamine (PPD) increases the d-spacing of MXene from 0.960 to 1.642 nm. Simultaneously, the increased d-spacing contributes to an increased defect density within the Ti-Ti layer. Hence, the PPD@MXene aerogel exhibits reduced surface electric field intensity and increased internal polarization loss, resulting in absorption-dominated EMI shielding. The absorptivity reaches 0.92, far exceeding the reported shielding materials, with a shielding effectiveness of 50.4 dB. This study provides a theoretical foundation and preliminary guidance for the development of interlayer-engineered MXene shielding materials.

Multiple Schottky Contacts Motivated via Defects to Tune the Response Ability of Electromagnetic Waves

AbstractMetal‐organic framework (MOF) derivatives employed as novel microwave‐absorbing materials (MAMs) have garnered significant attention due to their diverse in situ or ex situ coordinated components and the flexibility in nano‐microstructure fabrication. A well‐designed heterointerface can provide an optimal balance between impedance and high‐loss capability. However, precisely tuning semiconductor‐metal‐carbon heterostructures remains a huge challenge. Herein, a multi‐component NiS/Co3S4/NiCo@CNTs/NC nanohybrid with hollow structure is elaborately fabricated using a convenient solvothermal method followed by high‐temperature pyrolysis, forming a unique heterostructure with multiple Schottky contacts. This nanohybrid demonstrates a remarkable reflection loss value of −75.9 dB at thickness of 2.6 mm. The transcendent microwave absorption (MA) capacity is primarily attributed to the intense polarization relaxation process and superb impedance‐matching properties of the semiconductor/metal/carbon hybrid structure with Schottky barriers. In addition, the built‐in electric field established at the Schottky heterointerfaces increases the electron transport capabilities. Notably, the controllable introduction of numerous defects into the carbon layer intensifies the interfacial polarization effect at the Schottky heterointerfaces of the nanohybrid. This study offers innovative insights into the mechanisms of polarization loss and the development of high‐performance MAMs.

A novel cellulose-derived graphite carbon/ZnO composite by atomic layer deposition as an over-wideband microwave absorbent.

It is a major challenge to obtain broadband microwave absorption (MA) properties using low dielectric or magnetic nanoparticle-decorated carbon composites due to the limited single conductive loss or polarization loss of the carbon materials used as substrates. Novel pure cellulose-derived graphite carbon (CGC) materials can be used as an exceptional substrate option due to their special defective graphitic carbon structure, which provides both conduction and polarization loss. Herein, CGC@ZnO composites were first synthesized by atomic layer deposition (ALD) for use as microwave absorbents. Thanks to the multiple interfaces composed of graphitic carbon, defective carbon, and polar ZnO molecules, the CGC@ZnO composites exhibited superior MA properties. Specifically, the CZ-3 achieved a minimum reflection loss (RLmin) of -50.5 dB (over 99.999% MA) at 6.16 GHz in 2.98 mm. Amazingly, the maximum effective absorption bandwidth (RL < 10 dB, EABmax) could reach up to 6.48 GHz at only 1.59 mm. The ultra-broadband absorption property is mainly attributed to its strong electromagnetic attenuation capability and excellent impedance matching, making it one of the most promising materials for MA applications.

Emodin Enhanced Microwave-Responsive Heterojunction with Powerful Bactericidal Capacity and Immunoregulation for Curing Bacteria-Infected Osteomyelitis.

Eradication of osteomyelitis caused by bacterial infections is still a major challenge. Microwave therapy has the inherent advantage of deep penetration in curing deep tissue infections. However, the antibacterial efficiency of sensitizers is limited by the weak energy of microwaves. Here, a hybrid heterojunction system (Fe3O4/CuS/Emo) is designed for curing bacterially infected osteomyelitis. As an enhanced microwave sensitizer, it shows supernormal microwave response ability. Specifically, Fe3O4 acts as a matrix to mediate magnetic loss. After CuS loading, the heterogeneous interface forms induce significant interfacial polarization, which increasing dielectric loss. On the basis of the heterojunction formed by the two semiconductors, emodin is innovatively introduced to modify it. This integration not only accelerates the movement of charge carriers but also enhances polarization loss due to the numerous functional groups present on the surface. This further optimizes the microwave thermal and catalytic response. In addition, the unique anti-inflammatory properties of emodin confer the ability of hybrid heterojunction to regulate the immune microenvironment. In vivo studies reveal that heterojunction modified by emodin programmed elimination of bacteria and regulation of the immune microenvironment. It offers a revolutionary approach to the treatment of bacterial osteomyelitis.

Transmission electron microscopy analysis of Co3O4 degradation induced by electron irradiation.

This study presents an investigation into the electron beam damage phenomenon of Co3O4 under transmission electron microscopy (TEM). It was found that after irradiation at a dose rate of 6.78 × 106 e/nm2s, Co3O4 crystals exhibited surface reconstruction and faceting features. Electron energy loss spectroscopy (EELS) analysis indicates that the damage process initiates with the desorption of oxygen anions, which subsequently leads to a reduction in the valence state of cobalt cations and corresponding atomic rearrangement. High resolution TEM (HRTEM) reveals that surface faceting, which has an epitaxial relationship with the bulk, could help maintain the crystal lattice of face-centered cubic (fcc) Co3O4 despite Co-O bond breakage upon beam exposure. With a finely focused electron beam, the hole drilling effect was observed. The structural degradation is proposed to arise from inelastic damage that induced partial desorption of oxygen anions and rearrangement of valence-reduced cobalt cations to epitaxially grow on the surface, suggesting an interplay between irradiation damage and material restructuring. The relative phase stability of Co3O4, combined with its interfacial structure developed upon irradiation, are beneficial to magnetic loss and interfacial polarization loss, thereby rendering Co3O4 a promising candidate as an effective EMW absorber.

Largely enhanced electromagnetic wave absorption via surface coating of carbonyl iron particles with liquid metal

CIP@LM heterointerfaces can efficiently control polarization losses, balance impedance matching in magnetic materials, and boost electromagnetic wave absorption.

MEOP based 3He polarization and injection system for experiments below 1 K

Metastability exchange optical pumping (MEOP) is a widely used technique for producing polarized 3He. In connection with an experiment to search for the electric dipole moment of the neutron (nEDM) we have built a MEOP based 3He polarization and injection system to prepare 80 % polarized 3He at room temperature which will be injected into a ∼ 400 mK measurement cell filled with superfluid 4He. We describe the polarization and injection system, which is designed to allow for final concentrations of 10-8–10-10 of 80% polarized 3He in the superfluid filled measurement cell. Only ≈ 0.72% polarization loss due to gradients is expected during injection