Active Barrier Research Articles

Sulfur-vacancy induced asymmetric active site for Bi19S27Br3 nanorods photocatalyzes CO2 conversion to ethylene

The photocatalytic conversion of CO2 into high value-added C2 products remains a significant challenge due to the limited active sites and high energy barrier of C-C coupling process. Herein, the sulfur-vacancy was established on the surface of Bi19S27Br3 nanorods, leading to the electron on residual S atoms become unstable and active. Under the light irradiation, the photoexcited electron transfer from S atoms to neighboring Bi atoms to generate in-situ charge-polarized Bi(3-x)+ asymmetric active sites, which can enhance CO2 adsorption-activation capacity and regulate C-C coupling process for the C1 intermediate. The experimental results and theoretical calculation confirm that more charges aggregate around the induced Bi atoms, reducing the energy barrier of the C-C coupling reaction and improving C2H4 formation. Consequently, the sulfur-vacancy Bi19S27Br3 nanorods achieve efficient C2H4 generation through photocatalytic CO2 reduction, which C2H4 formation rate is 17.80 µmol g−1 after 5-hour photocatalytic reaction, with the product selectivity and electron selectivity of 49 % and 85 %, respectively, outperforming the low sulfur-vacancy Bi19S27Br3 nanorods by four-folds. This research provides new insights into the design of photocatalysts.

Extracellular purines in lung endothelial permeability and pulmonary diseases.

The purinergic signaling system is an evolutionarily conserved and critical regulatory circuit that maintains homeostatic balance across various organ systems and cell types by providing compensatory responses to diverse pathologies. Despite cardiovascular diseases taking a leading position in human morbidity and mortality worldwide, pulmonary diseases represent significant health concerns as well. The endothelium of both pulmonary and systemic circulation (bronchial vessels) plays a pivotal role in maintaining lung tissue homeostasis by providing an active barrier and modulating adhesion and infiltration of inflammatory cells. However, investigations into purinergic regulation of lung endothelium have remained limited, despite widespread recognition of the role of extracellular nucleotides and adenosine in hypoxic, inflammatory, and immune responses within the pulmonary microenvironment. In this review, we provide an overview of the basic aspects of purinergic signaling in vascular endothelium and highlight recent studies focusing on pulmonary microvascular endothelial cells and endothelial cells from the pulmonary artery vasa vasorum. Through this compilation of research findings, we aim to shed light on the emerging insights into the purinergic modulation of pulmonary endothelial function and its implications for lung health and disease.

Combined measures in lake restoration – A powerful approach as exemplified from Lake Groote Melanen (the Netherlands)

Controlling lake eutrophication is a challenge. A case-specific diagnostics driven approach is recommended that will guide to a suite of measures most promising in restoration of eutrophic lakes as exemplified by the case of the shallow lake Groote Melanen, The Netherlands. A lake system analysis identified external and internal nutrient load as main reasons for poor water quality and reoccurring cyanobacterial blooms in the lake. Based on this analysis, a package of restoration measures was implemented between January 2015 and May 2016. These measures included fish removal, dredging, capping of peat rich sediment with sand and an active barrier (lanthanum-modified bentonite), diversion of two inlet streams, reconstruction of banks, and planting macrophytes. Dredging and sand capping caused temporarily elevated turbidity and suspended solids concentrations, while addition of the lanthanum-modified clay caused a temporary exceedance of the Dutch La standard for freshwaters. Diversion of inflow streams caused 35 % less water inflow and larger water level fluctuations, but the lake remained water transporting with strongly improved water quality as was revealed by comparing five years pre-intervention water quality data with five years’ post-intervention data. Total phosphorus concentration in the water column was reduced by 93 % from 0.47 mg P l-1 before the intervention to 0.03 mg P l-1 after the intervention, total nitrogen by 66 % from 1.27 to 0.21 mg N l-1, total chlorophyll-a by 75 % from 68 to 16 µg l-1, cyanobacteria chlorophyll-a by 88 % from 32 to 4 µg l-1. Turbidity had declined by 58 % from 23.5 FTU to on average 9.9 FTU. No cyanobacteria blooms were recorded over the entire post-intervention monitoring period (2016–2021). Submerged macrophytes increased from complete absence before intervention to around 10 %–15 % coverage after intervention. Repeated fish removal lowered the fish stock to below 100 kg ha-1 with 12 % of bream and carp remaining. Hence, the package of cohesive measures that was based on a thorough diagnosis resulted in rapidly, strongly and enduringly improved water quality. This case provides evidence for the power of combining measures in restoring eutrophic lakes.

Theoretical Investigations of Hydrolysis Mechanisms of N(SiMe3)3.

Tris(trimethylsilyl)amine (N(SiMe3)3) is one of the most important intermediate products in the indirect synthesis of ammonia (NH3) from nitrogen (N2), which could be hydrolyzed to NH3 under mild conditions. Herein, the hydrolysis mechanism of N(SiMe3)3 has been systematically investigated using density functional theory (DFT) with explicit combined implicit water models. Under neutral conditions, the active barrier of the hydrolysis of N(SiMe3)3 is 17.6 kcal mol-1 in water solvent. The attacking of proton to N center and OH group to the Si atom from water is decoupled for the stabilization of OH group by solvent water molecules, which lower the hydrolysis energy barriers. Furthermore, under acid conditions, N(SiMe3)3 is easily coordinated with proton to form [NH(SiMe3)3]+, and the energy barrier of the hydrolysis reaction could be reduced to 11.5 kcal mol-1 of the first stage, making it being promoted according to the chemical equilibrium. Thus, the results provide an explanation for the possible mechanism of the quantitative conversion of N(SiMe3)3 to NH3 under mild conditions. The decoupled hydrolysis mechanism may play important role in other hydrolysis processes.

The neurodevelopmental genes alan shepard and Neuroglian contribute to female mate preference in African Drosophila melanogaster.

Mate choice is a key trait that determines fitness for most sexually reproducing organisms, with females often being the choosy sex. Female preference often results in strong selection on male traits that can drive rapid divergence of traits and preferences between lineages, leading to reproductive isolation. Despite this fundamental property of female mate choice, very few loci have been identified that contribute to mate choice and reproductive isolation. We used a combination of population genetics, quantitative complementation tests, and behavioural assays to demonstrate that alan shepard and Neuroglian contribute to female mate choice, and could contribute to partial reproductive isolation between populations of Drosophila melanogaster. Our study is among the first to identify genes that contribute to female mate preference in this historically important system, where female preference is an active premating barrier to reproduction. The identification of loci that are primarily known for their roles in neurodevelopment provides intriguing questions of how female mate preference evolves in populations via changes in sensory system and higher learning brain centres.

Development of a biofabricated 3D in vitro vessel model for investigating transendothelial migration in stem cell therapy

Systemic stem cell therapies hold promise for treating severe diseases, but their efficiency is hampered by limited migration of injected stem cells across vascular endothelium towards diseased tissues. Understanding transendothelial migration is crucial for improving therapy outcomes. We propose a novel 3D in vitro vessel model that aids to unravel these mechanisms and thereby facilitates stem cell therapy development. Our model simulates inflammation through cytokine diffusion from the tissue site into the vessel. It consists of a biofabricated vessel embedded in a fibrin hydrogel, mimicking arterial wall composition with smooth muscle cells and fibroblasts. The perfusable channel is lined with a functional endothelium which expresses vascular endothelial cadherin, provides an active barrier function, aligns with flow direction and is reconstructed by in situ two-photon-microscopy. Inflammatory cytokine release (tumor necrosis factor α, stromal-derived factor (1) is demonstrated in both a transwell assay and the 3D model. In proof-of-principle experiments, mesoangioblasts, known as a promising candidate for a stem cell therapy against muscular dystrophies, are injected into the vessel model, showing shear-resistant endothelial adhesion under capillary-like flow conditions. Our 3D in vitro model offers significant potential to study transendothelial migration mechanisms of stem cells, facilitating the development of improved stem cell therapies.

Petal-by-petal tree-blossoming shaped bimetallic MOF-based material over SBA-15: Diverse designability, synergistic catalysis, and thermodynamics/kinetic analysis

Transition metal-based bimetallic MOF (CoMo-ZIF) with two different metal ions (Co/Mo) possess specific synergistic catalytic effect in olefins oxidation, but poor diffusion efficiency and less active areas limit its application. Herein, a novel CoMo-ZIF-based nanocomposite is fabricated via an in-situ solvothermal approach to break down active area or diffusion efficiency barrier of CoMo-ZIF via employing SBA-15 as the matrix and nanosacle polyoxometalate (POM) as external active species. Characterizations reveal that pristine rose-type CoMo-ZIF (∼350 nm diameter) alters to rambutan-like hollow sphere and eventually self-assembles into hierarchical petal-by-petal nanoflakes (ca. 20∼50 nm in thickness) after SBA-15 and POM introduction, respectively. POM@CoMo-ZIF@SBA-15 with super large pore size (10.44 nm) and increased active (Co2+ + Co3+)/satellite (1.92) exhibits excellent catalytic activity in cyclopentene (CPE) oxidation to glutaric acid (GAC) with 57.1 % CCPE, 61.6 % SGAC, and good reusability with 54.3∼57.1 % CCPE and 58.4∼63.2 % SGAC during 6 cycles. What's more, thermodynamic analysis indicates that CPE oxidation to GAC is a spontaneous reaction at 273.15∼373.15 K, and kinetic study shows that the key to develop CPE to GAC is to reduce activation energies of cyclopentene oxide ring-opening to 1,2-cyclopentanediol (73.8298 kJ⋅mol−1) and glutaradehyde (118.4571 kJ⋅mol−1). This study not only pioneers a promising strategy for oriented design of MOF-based materials, but also serves as a valuable reference for the computation of various chemical reactions.

Active Thermochemical Barrier Coatings Using Metal Oxides: First Experimental Results.

A new concept of active thermal coating based on the use of reversible thermochemical reactions is presented in this paper. The new active thermal barrier coating uses redox reactions to buffer the temperature changes that a metallic component may suffer at high temperatures. The heat is stored when the temperature is equal/above the reduction temperature of the active coating (endothermic reaction) and the heat is released when the temperature is equal/below the oxidation temperature (exothermic reaction). The paper describes the development and testing of a reactive thermal barrier coating based on the redox reaction of Co3O4 and its cyclability. Co3O4 was chosen as a reference material due to the high enthalpy of reaction (844 kJ/kg) and redox reversibility. The activity of coatings with 1, 2, and 3 Co3O4 layers was demonstrated by simultaneous thermal analysis, showing good stability for 5 five cycles.

Leuco Ethyl Violet as Self-Activating Prodrug Photocatalyst for In Vivo Amyloid-Selective Oxygenation.

Aberrant aggregates of amyloid-β (Aβ) and tau protein (tau), called amyloid, are related to the etiology of Alzheimer disease (AD). Reducing amyloid levels in AD patients is a potentially effective approach to the treatment of AD. The selective degradation of amyloids via small molecule-catalyzed photooxygenation in vivo is a leading approach; however, moderate catalyst activity and the side effects of scalp injury are problematic in prior studies using AD model mice. Here, leuco ethyl violet (LEV) is identified as a highly active, amyloid-selective, and blood-brain barrier (BBB)-permeable photooxygenation catalyst that circumvents all of these problems. LEV is a redox-sensitive, self-activating prodrug catalyst; self-oxidation of LEV through a hydrogen atom transfer process under photoirradiation produces catalytically active ethyl violet (EV) in the presence of amyloid. LEV effectively oxygenates human Aβ and tau, suggesting the feasibility for applications in humans. Furthermore, a concept of using a hydrogen atom as a caging group of a reactive catalyst functional in vivo is postulated. The minimal size of the hydrogen caging group is especially useful for catalyst delivery to the brain through BBB.

Active trench barrier RC-IGBT with pinch-off and carrier accumulation effects

Active trench barrier RC-IGBT with pinch-off and carrier accumulation effects

The bouncing barrier revisited: Impact on key planet formation processes and observational signatures

Context. A leading paradigm in planet formation is currently the streaming instability and pebble accretion scenario. Notably, dust must grow into sizes in a specific regime of Stokes numbers in order to make the processes in the scenario viable and sufficiently effective. The dust growth models currently in use do not implement some of the growth barriers suggested to be relevant in the literature. Aims. We investigate if the bouncing barrier, when effective, has an impact on the timescales and efficiencies of processes such as the streaming instability and pebble accretion as well as on the observational appearance of planet-forming disks. Methods. We implemented a formalism for the bouncing barrier into the publicly available dust growth model DustPy and ran a series of models to understand the impact. Results. We found that the bouncing barrier has a significant effect on the dust evolution in planet-forming disks. In many cases, it reduces the size of the typical or largest particles available in the disk; it produces a very narrow, almost monodisperse, size distribution; and it removes most μm-sized grains in the process, with an impact on scattered light images. It modifies the settling and therefore the effectiveness of and timescales for the streaming instability and for pebble accretion. An active bouncing barrier may well have observational consequences: It may reduce the strength of the signatures of small particles (e.g., the 10 μm silicate feature), and it may create additional shadowed regions visible in scattered light images. Conclusions. Modeling of planet formation that leans heavily on the streaming instability and on pebble accretion should take the bouncing barrier into account. The complete removal of small grains in our model is not consistent with observations. However, this could be resolved by incomplete vertical mixing or some level of erosion in collisions.

Research on the Arrangement of Additional Source for Large Space Protection of an Active Noise Barrier

When active noise control technology is applied to traffic noise control, additional sources are often added to the facade of the barrier, and error sensors are placed in the protected area. The noise reduction effect in the area without error sensors is often ignored. In this paper, the effect of the additional source configuration on the sound field in the space without error sensors is researched. By analyzing the directivity and distribution of the sound field at the top of the barrier under various conditions, it is believed that the optimal location of the additional source is related to the height of the primary source and the barrier. An approximate model is established to evaluate the optimal location of the additional source for achieving a good noise reduction effect in a large space. Experiments are also carried out to verify the model. The conclusions are beneficial for improving the noise reduction effect in the area higher than the barrier and without error microphones.

Nonreciprocal Intelligent Soundproof Barrier with Active Nonlocal Acoustic Metastructure

Sound insulation is an important issue in daily life and has applications in various scenarios. Conventional acoustic passive metamaterial barriers are designed as a reciprocal sound insulation. However, for some specific application scenarios, unidirectional acoustic insulation is required, which is an enormous challenge for breaking the reciprocity of sound transport with conventional passive metamaterials. Here, a soundproof barrier with nonlocal acoustic metastructure is proposed, which consists of a microcontroller to connect a pair of spatially separated microphones and speakers, to tailoring the acoustic wave transmission for realizing nonreciprocal acoustic insulation. The theoretical calculation and experiment measurement indicated that the active acoustic barrier with a selectable working frequency can realize the suppressive effect in one direction and the enhancive effect in the other direction for an incident acoustic signal. Particularly, the function of an active soundproof barrier can be freely switched to forward, backward, and bidirectional sound insulation by tailoring the nonlocal distance of the digital meta‐atom. Furthermore, this acoustic metastructure is extended from a one‐dimentional waveguide to a two‐dimentional plane to illustrate that it is still valid in an open‐field environment. The proposed customizable nonreciprocal soundproof barriers provide an avenue for many applications in the specific scenarios that require unidirectional sound insulation and high air permeability.

Hypoxia-induced ZEB1 promotes cervical cancer immune evasion by strengthening the CD47-SIRPα axis

BackgroundThe dynamic interaction between cancer cells and tumour-associated macrophages (TAMs) in the hypoxic tumour microenvironment (TME) is an active barrier to the effector arm of the antitumour immune response. Cancer-secreted exosomes are emerging mediators of this cancer-stromal cross-talk in the TME; however, the mechanisms underlying this interaction remain unclear.MethodsExosomes were isolated with ExoQuick exosome precipitation solution. The polarizing effect of TAMs was evaluated by flow cytometry, western blot analysis, immunofluorescence staining and in vitro phagocytosis assays. Clinical cervical cancer specimens and an in vivo xenograft model were also employed.ResultsOur previous study showed that hypoxia increased the expression of ZEB1 in cervical squamous cell carcinoma (CSCC) cells, which resulted in increased infiltration of TAMs. Here, we found that hypoxia-induced ZEB1 expression is closely correlated with CD47-SIRPα axis activity in CSCC, which enables cancer cells to evade phagocytosis by macrophages and promotes tumour progression. ZEB1 was found to directly activate the transcription of the CD47 gene in hypoxic CSCC cells. We further showed that endogenous ZEB1 was characteristically enriched in hypoxic CSCC cell-derived exosomes and transferred into macrophages via these exosomes to promote SIRPα+ TAM polarization. Intriguingly, exosomal ZEB1 retained transcriptional activity and reprogrammed SIRPα+ TAMs via activation of the STAT3 signalling pathway in vitro and in vivo. STAT3 inhibition reduced the polarizing effect induced by exosomal ZEB1. Knockdown of ZEB1 increased the phagocytosis of CSCC cells by macrophages via decreasing CD47 and SIRPα expression.ConclusionsOur results suggest that hypoxia-induced ZEB1 promotes immune evasion in CSCC by strengthening the CD47-SIRPα axis. ZEB1-targeted therapy in combination with CD47-SIRPα checkpoint immunotherapy may improve the outcomes of CSCC patients in part by disinhibiting innate immunity.

Improving Insertion Loss of Sonic Crystal Active Noise Barrier by Reinforcement Learning and Finite Difference Time Domain Simulations

Improving Insertion Loss of Sonic Crystal Active Noise Barrier by Reinforcement Learning and Finite Difference Time Domain Simulations

Near Infrared-Activatable Biomimetic Nanoplatform for Tumor-Specific Drug Release, Penetration and Chemo-Photothermal Synergistic Therapy of Orthotopic Glioblastoma.

Glioblastoma multiforme (GBM), a highly invasive and prognostically challenging brain cancer, poses a significant hurdle for current treatments due to the existence of the blood-brain barrier (BBB) and the difficulty to maintain an effective drug accumulation in deep GBM lesions. We present a biomimetic nanoplatform with angiopep-2-modified macrophage membrane, loaded with indocyanine green (ICG) templated self-assembly of SN38 (AM-NP), facilitating active tumor targeting and effective blood-brain barrier penetration through specific ligand-receptor interaction. Upon accumulation at tumor sites, these nanoparticles achieved high drug concentrations. Subsequent combination of laser irradiation and release of chemotherapy agent SN38 induced a synergistic chemo-photothermal therapy. Compared to bare nanoparticles (NPs) lacking cell membrane encapsulation, AM-NPs significantly suppressed tumor growth, markedly enhanced survival rates, and exhibited excellent biocompatibility with minimal side effects. This NIR-activatable biomimetic camouflaging macrophage membrane-based nanoparticles enhanced drug delivery targeting ability through modifications of macrophage membranes and specific ligands. It simultaneously achieved synergistic chemo-photothermal therapy, enhancing treatment effectiveness. Compared to traditional treatment modalities, it provided a precise, efficient, and synergistic method that might have contributed to advancements in glioblastoma therapy.

Study on the role of oxygen vacancy in the catalytic dissociation of H2 on MoO3 and the formation mechanism of HxMoO3

This study focuses on the effect of oxygen vacancies on the dissociation of H2 from MoO3 and the consequent formation of HxMoO3. Furthermore, a comparison of the properties of three distinct MoO3 (bulk-MoO3, Pd/MoO3 and mesoporous MoO3) after hydrogenation is conducted in order to develop a deeper understanding of the intrinsic activity of MoO3. Both the experimental and DFT findings demonstrate that the breaking rate of an HH bond extremely restrained the hydrogen spillover on bulk-MoO3, while the Mo acid site caused by the abundant O defects on mesoporous MoO3 greatly enhanced its inherent catalytic activity, leading to its remarkable ability to dissociate H2. The active barrier energy of H2 dissociation on MoO3 decreased significantly from 3.82 eV (perfect MoO3 surface) to 0.52 eV (Mo acid site), which is comparable to that of noble metals. Our results may provide useful insights into the mechanism by which H2 dissociates from MoO3 to form HxMoO3.

Microstructure evolution and cyclic oxidation performance of Cr2AlC as active diffusion barrier for NiCrAlY coating on TiAl alloy

Cr2AlC diffusion barrier was prepared between NiCrAlY coating and TiAl alloy. Long-term cyclic oxidation was conducted at 900 °C in air for 1000 cycles(h). Cr2AlC and transformed Cr7C3, α-Cr and TiC had significant blocking effects on Ti diffusion. So, the Al-rich phase in the NiCrAlY coatings was NiAl rather than Ni2TiAl, which inhibited the generation of TiO2 and avoided the presence of α-Cr in the Al2O3 scales. As a result, the stability and spalling resistance of the Al2O3 scales were enhanced.

Construction of a Test Facility and the Test of an Active Tritium Permeation Barrier

In future fusion or fission reactors, tritium permeation may present a serious challenge. In order to separate the water steam cycle from gas streams containing significant amounts of tritium, a permeation barrier is necessary. Tritium permeation into the environment through steam generators and heat exchangers can be a significant hazard regarding radiation and environmental safety. In the scope of the project TRANSversal Actions for Tritium (TRANSAT), a facility has been set up to perform tests on various scaled and functioning permeation barrier mock-ups at the Tritium Laboratory Karlsruhe (TLK). The facility was built in a standard glove-box unit in accordance to the technical terms and requirements of tritium handling at TLK. The behavior of an active permeation barrier was investigated. Within the first series of TRANSAT experiments, four different mock-ups have been tested for tritium permeation. Migrated tritium is oxidized to tritiated water (HTO) using Carulite reactors and molecular sieves for HTO trapping. This paper will present the construction, setup, and commissioning of the facility as well as the first series of TRANSAT experiments including their evaluation.

The Dual Role of the Airway Epithelium in Asthma: Active Barrier and Regulator of Inflammation.

Chronic airway inflammation is the cornerstone on which bronchial asthma arises, and in turn, chronic inflammation arises from a complex interplay between environmental factors such as allergens and pathogens and immune cells as well as structural cells constituting the airway mucosa. Airway epithelial cells (AECs) are at the center of these processes. On the one hand, they represent the borderline separating the body from its environment in order to keep inner homeostasis. The airway epithelium forms a multi-tiered, self-cleaning barrier that involves an unstirred, discontinuous mucous layer, the dense and rigid mesh of the glycocalyx, and the cellular layer itself, consisting of multiple, densely interconnected cell types. On the other hand, the airway epithelium represents an immunologically highly active tissue once its barrier has been penetrated: AECs play a pivotal role in releasing protective immunoglobulin A. They express a broad spectrum of pattern recognition receptors, enabling them to react to environmental stressors that overcome the mucosal barrier. By releasing alarmins-proinflammatory and regulatory cytokines-AECs play an active role in the formation, strategic orientation, and control of the subsequent defense reaction. Consequently, the airway epithelium is of vital importance to chronic inflammatory diseases, such as asthma.