Channel Structure Research Articles

Context-enhanced YOLOv5s for accurate apple detection in complex natural environments

Abstract Object detection in natural environments is a critical challenge for agricultural automation, particularly for small and occluded targets such as apples among foliage. We propose an innovative detection framework CSFN-YOLOv5s. Firstly, the context augmentation module-spatial pyramid pooling faster cross stage partial channel structure is constructed to introduce additional background and context information, so that the model can understand the image data more deeply and improve its robustness and generalization ability. Secondly, four detection layers are applied to obtain finer-grained feature expression and smaller receptive field, which improves the precision of small target detection by finely capturing the details. Thirdly, normalized wasserstein distance is used to mitigate the sensitivity for small object localization errors, showing a significant improvement. The experimental results and analysis show that the mAP of the final model reaches 98.5%, which is significantly better than other mainstream target detection models. Especially for the small target detection task in the natural complex environment, the proposed CSFN-YOLOv5s model shows higher detection precision and verifies its target detection effect.

Fundamentals of Viscoelastic Particle Focusing in Suddenly Expanded Microfluidic Channels.

Particles focusing in suddenly expanded microfluidic channels with viscoelastic biofluids have attracted increased interests due to the potential biomedical applications. In this work, three types of suddenly expanded channels were designed and employed for experiments. These suddenly expanded channels contained a certain number of triangular expansion structures on the sides of the straight channel to investigate the effect of secondary flow on particle viscoelastic focusing and we investigated particle focusing behavior in those three channels with 0.1% hyaluronic acid (HA) solution. The effects of various suddenly expanded channel structures on particle focusing were discussed. The results indicated that the viscoelastic focusing effect was enhanced by using the sudden expansion structures. Consequently, particles with multi-peak distributions were successfully focused into a focusing stream by using the secondary flow induced by the suddenly expanded structure. Finally, the viscoelastic focusing of leukocytes was explored using suddenly expanded channels. This work offers a deep understanding on the fundamentals of particle focusing in suddenly expanded channels and the results will enable the design of particles focusing microfluidic devices with suddenly expanded channels for critical applications in biomedicine.

Inositol 1,4,5-Trisphosphate Receptor 1 Gain-of-Function Increases the Risk for Cardiac Arrhythmias in Mice and Humans.

Ca2+ mishandling in cardiac Purkinje cells is a well-known cause of cardiac arrhythmias. The Purkinje cell resident inositol 1,4,5-trisphosphate receptor 1 (ITPR1) is believed to play an important role in Ca2+ handling, and ITPR1 gain-of-function (GOF) has been implicated in cardiac arrhythmias. However, nearly all known disease-associated ITPR1 variants are loss-of-function and are primarily linked to neurological disorders. Whether ITPR1 GOF has pathological consequences, such as cardiac arrhythmias, is unclear. This study aimed to identify human ITPR1 GOF variants and determine the impact of ITPR1 GOF on Ca2+ handling and arrhythmia susceptibility. There are a large number of rare ITPR1 missense variants reported in open data repositories. Based on their locations in the ITPR1 channel structure, we selected and characterized 33 human ITPR1 missense variants from open databases and identified 21 human ITPR1 GOF variants. We generated a mouse model carrying a human ITPR1 GOF variant, ITPR1-W1457G (W1447G in mice). We showed that the ITPR1-W1447G± and recently reported ITPR1-D2594K± GOF mutant mice were susceptible to stress-induced ventricular arrhythmias. Confocal Ca2+ and voltage imaging in situ in heart slices and Ca2+ imaging and patch-clamp recordings of isolated Purkinje cells showed that ITPR1-W1447G± and ITPR1-D2594K± variants increased the occurrence of stress-induced spontaneous Ca2+ release, delayed afterdepolarization, and triggered activity in Purkinje cells. To assess the potential role of ITPR1 variants in arrhythmia susceptibility in humans, we looked up a gene-based association study in the UK Biobank data set and identified 7 rare ITPR1 missense variants showing potential association with cardiac arrhythmias. Remarkably, in vitro functional characterization revealed that all these 7 ITPR1 variants resulted in GOF. Our studies in mice and humans reveal that enhanced function of ITPR1, a well-known movement disorder gene, increases the risk for cardiac arrhythmias.

Hydrothermal Stability of Active Sites in Cu-Exchanged Small-Pore Zeolites for the Selective Catalytic Reduction of NOx.

Combining operando X-ray absorption spectroscopy (XAS) and computational modelling shows unequivocally the distribution of active species in fresh and hydrothermally aged Cu-CHA and Cu-AEI zeolites during NH3-assisted selective catalytic reduction of NOx. Four principal species co-exist: (i) CuI cations coordinated to NH3, (ii) CuI cations coordinated to the zeolite framework, (iii) solvated CuII cations, and (iv) framework-coordinated CuII species (CuII st) formed upon hydrothermal ageing of the zeolite sample. The CuII st species were only observed in the hydrothermally aged zeolite samples and are formed upon the interaction of hydrated CuII cations with extra-framework Al (EFAl) generated during the hydrothermal treatment. These sites are inactive for NOx reduction, leading to a decrease in the catalytic performance of the hydrothermally aged zeolites. CuII st formation was higher in Cu-CHA (~46 %) than in Cu-AEI (~28 %). The better hydrothermal stability of Cu in the AEI framework is attributed to the tortuous channel structure of AEI that hinders the migration of hydrated CuII cations during hydrothermal ageing.

Analysis of cell characteristics using back oxide trap charge effect in various channel structures of 3D-NAND flash

Abstract This study investigates how trap charges in the back oxide layer affect the memory performance of 3D NAND flash memory. We used TCAD to simulate the effect on cell reliability, focusing on retention and interference characteristics, based on changes in current paths and program speed as initial cell characteristics. Additionally, we applied these findings to various channel structures — planar, concave, and convex — that can occur in 3D NAND. Our results indicate that the optimal trap charge for enhancing cell performance lies between -10¹¹ and -10¹⁰ /cm³ and should not exceed -1011 /cm3. Through this research, we can expect the potential for effectively inserting trap charges in actual manufacturing processes to improve the performance characteristics of 3D NAND cells.

Estimating the Electric Fields Driving Lightning Dart Leader Development With BIMAP‐3D Observations

AbstractIn this paper, a numerical dart leader model has been implemented to understand the leader's development and the corresponding electric field changes observed by the 3D broadband mapping and polarization (BIMAP‐3D) system. The model assumes the extending leader channel is equipotential and has a linear charge distribution induced by an ambient electric field. The charge distribution induced by the ambient field can be used to model the electric field change at the ground. We then find the ambient electric field which best fits the field change measurements at the two BIMAP stations. The estimated ambient electric field decreases in the direction of dart leader propagation. Our observations and modeling results are consistent with our earlier hypothesis that dart leader speed is proportional to the electric field at the leader tip. The model also supports our earlier analysis that leader speed variations near branch junctions were due to previous charge deposits near the junctions. The modeled tip electric field is generally lower than the breakdown field unless the pre‐dart‐leader channel has a significant temperature of 3,000 K. This is consistent with the fact that dart leaders typically do not form new branches into the virgin air. Furthermore, the tip field is generally close to the negative streamer stability field at ambient temperatures, explaining the nature of the narrow and well‐defined channel structure. In addition to the charge distribution and the ambient and tip electric field, the development of the channel potential and current distribution are also presented.

3D Aligned Tetrameric Ion Channels with Universal Residue Labels for Comparative Structural Analysis.

Despite their large functional diversity and poor sequence similarity, tetrameric and pseudo-tetrameric potassium, sodium, calcium and cyclic-nucleotide gated channels, as well as two-pore channels, transient receptor potential channels and ionotropic glutamate receptors share a common folding pattern of the transmembrane (TM) helices in the pore-forming domain. In each subunit or repeat, the pore domain has two TM helices connected by a membrane-reentering P-loop. The P-loop includes a membrane-descending helix, P1, which is structurally the most conserved element of these channels, and residues that contribute to the selectivity-filter region at the constriction of the ion-permeating pathway. In 24-TM channels, the pore domain is surrounded by four voltage-sensing domains, each with conserved folding of four TM helices. Hundreds of atomic-scale structures of these channels, referred to as "P-loop channels", have been obtained through X-ray crystallography or cryogenic electron microscopy. The number of experimental structures of P-loop channels deposited in the Protein Data Bank is rapidly increasing. AlphaFold3, RoseTTAFold and other computational tools can be used to generate 3D models of P-loop channels that lack experimental structures. While comparative structural analysis of P-loop channels is desirable, it is hindered by variations in residue numbers and 3D orientations of the channels. To address this problem, we have developed a universal residue-labeling scheme for TM helices and P-loops. We further created a database of P-Loop Ion Channels (PLIC; www.plic3da.com), which currently includes over four hundreds 3D-aligned structures with relabeled residues. We use this database to compare multiple 3D structures of channels from different subfamilies. The comparison, which for the first time employs statistical methods, highlights conserved and variable elements in the channels' folding, reveals irregularities, and identifies outliers that warrant further analysis.

Bone replacement material with optimized structure, manufactured using additive printing technology

Abstract Additive manufacturing with Arburg Plastic Freeforming (APF), an extrusion-based additive manufacturing process, was used to produce biomimetic bone scaffolds for assistance of osteosynthesis made of poly-caprolactone (PCL) with channel structures for the ingrowth of blood vessels. The specific creation of defined channel structures is very important to support the ingrowth of blood vessels, which significantly supports the regeneration of natural tissue. The tibia model used was divided into the corticalis and the spongiosa to be able to compare the realization of the different requirements of the two natural structures with the printed structures separately. Microtome cuts of the manufactured bone scaffolds with channels were prepared for characterization with light microscopy. Compression tests were carried out on a tensile testing machine. It was found that the channels in the tibial cortex led to a slightly higher stiffness compared to those without channels due to the frame outlines. Overall, however, the stiffness of the Polycaprolactone (PCL) scaffolds was significantly lower than that of natural bone. In the spongiosa scaffolds, the stiffness with channels was lower than that without channels, but still within the physiological range, as was the model without channels. The porosity was within the required range for both scaffold types.

Structures of TASK-1 and TASK-3 K2P channels provide insight into their gating and dysfunction in disease.

TASK-1 and TASK-3 are pH-sensitive two-pore domain (K2P/KCNK) K+ channels. Their functional roles make them promising targets for treatment of multiple disorders including sleep apnea, pain, and atrial fibrillation. Mutations in these channels are also associated with neurodevelopmental and hypertensive disorders. A previous crystal structure of TASK-1 revealed a lower "X-gate" as a hotspot for missense gain-of-function (GoF) mutations associated with DDSA (developmental delay with sleep apnea). However, the mechanisms of gating in TASK channels are still not fully understood. Here, we resolve structures for both human TASK-1 and TASK-3 by cryoelectron microscopy (cryo-EM), as well as a recurrent TASK-3 variant (G236R) associated with KCNK9 imprinting syndrome (KIS) (formerly known as Birk-Barel syndrome). Combined with functional studies of the X-gating mechanism, we provide evidence for how a highly conserved gating mechanism becomes defective in disease, and also provide further insight into the pathway of conformational changes that underlie the pH-dependent inhibition of TASK channel activity.

Conversion of Isolated Voids into Channel Spaces by Modulating the Stacking Manner of Hydrogen-Bonded Ladders.

1,2,3,4-Tetrakis(carboxyphenyl)benzene (CPB) forms a predictable ladder-shaped porous motif through intermolecular hydrogen-bonding of the carboxy groups. The stacking manner of the ladder motif, on the other hand, cannot be controlled, yielding a crystal structure with discrete inclusion spaces. To modulate the stacking manner, its derivative CPB(OMe) with methoxy substituent groups at 5,6-positions was synthesized and crystallized to yield a crystalline hydrogen-bonded organic framework (HOF), in which the ladder motifs are stacking with a different manner to form 1D inclusion channels, instead of discrete voids. Because of the channel structure, removal of the included solvent molecules can be easily conducted, and the resultant activated HOF CPB(OMe)-a exhibited micropores with BET surface area of 199 m2 g-1, which is larger than that of the other HOF CPB-a.

Impacts of Post‐Fire Debris Flows on Fluvial Morphology and Sediment Transport in a California Central Coast Stream

AbstractPost‐fire debris flows alter impacted fluvial systems, but few studies quantify the magnitude and timing of reach‐scale channel response to these events. In August 2020, the Big Creek watershed along California's central coast burned in the Dolan Fire; in January 2021, an atmospheric river event triggered post‐fire debris flows in steep tributaries to the Big Creek. Here, we characterize the evolution of fluvial morphology and grain size in Big Creek, a cascade and step‐pool channel downstream of tributaries in which post‐fire debris flows initiated, using pre‐ and post‐fire structure from motion (SfM) and airborne lidar surveys. We also make comparisons to Devil's Creek, an adjacent basin which burned but did not experience post‐fire debris flows. We observe grain size fining following debris flows in Big Creek, but the coarsest 40% of the grain size distribution remained essentially unchanged despite reorganization of channel structure. Changes in grain size and elevated post‐fire peak flows account for approximately equal portions of a substantial increase in modeled bedload transport capacity one year post‐fire. In Big Creek, geomorphic recovery is well underway just two years post‐fire. A valley‐spanning log jam, which formed during debris flows, acts as a sediment trap upstream of our Big Creek study reach, and is partially responsible for accelerating recovery processes. In contrast, Devil's Creek exhibited little change in morphology or grain size despite elevated post‐fire peak flows. This period of geomorphic dynamism following the Dolan Fire has complex ecological impacts, notably for the threatened anadromous salmonid spawning habitat in Big Creek.

Adaptation of an additively manufactured reactor concept for catalytic methanation with in-situ tar co-reforming of biogenic syngas

The methanation of biogenic syngas for GreenLNG production is a promising alternative for fossil gas. The market price of renewable methane is currently still too high to compete with fossil LNG. One of the reasons for that is the extensive gas cleaning that is necessary for the methanation of syngas from the thermochemical gasification of biomass. A main cost factor is the removal of tar components. As part of the Horizon Europe project CarbonNeutralLNG, we propose a 3D-printed methanation reactor, which makes use of the freedom in design gained by the additive manufacturing process in order to adapt the reactor design for the in-situ co-reforming of tars. The reactor uses heat pipes and a conically widened reaction channel to effectively control local temperatures, suiting the needs of the methanation reaction. A temperature hot spot near the inlet provides the necessary conditions (high temperature, a suitable catalyst and sufficient residence time) for the reforming of tar species, that are present in the syngas. Two reactor concepts are proposed. ADDmeth3.1 uses a dedicated internal channel structure that serves as a counter-current heat exchanger for the feed gas, whereas ADDmeth3.2 is optimized to fill the triangular footprint of a scalable reactor module as best as possible. Both designs were subject to a preliminary feasibility study, to ensure sufficient heat removal and a finite element analysis regarding structural stability was performed. Minimum safety factors against yielding of 3.53 and higher were achieved even without the internal diamond lattice support structure. The triangular modular reactor cell can easily be scaled up by connecting multiple cells in parallel, since the triangular shape can be extended efficiently into a honeycomb pattern.

Structure and function of the human mitochondrial MRS2 channel.

The human mitochondrial RNA splicing 2 protein (MRS2) has been implicated in Mg2+ transport across mitochondrial inner membranes, thus having an important role in Mg2+ homeostasis critical for mitochondrial integrity and function. However, the molecular mechanisms underlying its fundamental channel properties such as ion selectivity and regulation remain unclear. Here we present a structural and functional investigation of MRS2. Cryo-electron microscopy structures in various ionic conditions reveal a pentameric channel architecture and the molecular basis of ion permeation and potential regulation mechanisms. Electrophysiological analyses demonstrate that MRS2 is a Ca2+-regulated, nonselective channel permeable to Mg2+, Ca2+, Na+ and K+, which contrasts with its prokaryotic ortholog, CorA, operating as a Mg2+-gated Mg2+ channel. Moreover, a conserved arginine ring within the pore of MRS2 functions to restrict cation movements, thus preventing the channel from collapsing the proton motive force that drives mitochondrial adenosine triphosphate synthesis. Together, our results provide a molecular framework for further understanding MRS2 in mitochondrial function and disease.

Threading MOF membranes with polymer chains for superior benzene/cyclohexane separation

High performance membranes for benzene/cyclohexane separation are crucial. Metal–organic frameworks (MOFs), given by their high structural designability, are expected to provide satisfying membrane performance for this separation. In this study, polymer chains were threaded into the pores of MOF UiO-66, to reconstruct the structures of the membrane channels. The permeance of benzene and selectivity of benzene/cyclohexane were boosted simultaneously, compared with the bare UiO-66 membranes. The performance enhancement was rationalized since the solubility of benzene was improved meanwhile the diffusivity of cyclohexane dropped by virtue of the new adsorption sites of benzene and narrower membrane channels created by threading polymers. The as-synthesized polyvinyl alcohol (PVA)-threaded UiO-66 membranes exhibited a benzene permeance around 110 GPU and a benzene/cyclohexane selectivity around 30.

Freeze–Thaw Response of Permeability and Absorption Channel Structure and Moisture Distribution in Different Coal Ranks

Freeze–Thaw Response of Permeability and Absorption Channel Structure and Moisture Distribution in Different Coal Ranks

Jaringan Sekresi Pada Tanaman Dysoxylum parasiticum Osbeck (Meliaceae) di Mataram, Lombok

Dysoxylum parasiticum is a flowering plant from the Meliaceae family. This plant has a number of secondary metabolite compounds that have not been specifically identified at the anatomical and tissue level. The presence of secondary metabolite compounds can be identified through the presence of secretory tissue in plants. The aim of this research is to determine the structure, type and location of the secretory tissue in the stem and leaf organs. Preparations were made using the fresh preparation method, and slicing using the free-hand section method, with Tuloidine blue O 0.025% staining. The results show that the secretory tissue has an elongated channel structure like a lumen surrounded by epithelial cells. The location of the secretory tissue in the stem is evenly distributed in the cortex and pith, in the petiole of the leaf it is only found in the cotex, and in the leaf blade, the secretion ducts are found in the cortex of the midrib and the mesophyll of the leaf blade.

Energetic Characteristics of Hydrophobic Porous Materials as Candidates for Manufacturing of Nanorockets.

A new propulsion mechanism for nano- and microrocket engines is hypothesized. It is based on the instantaneous expulsion from hydrophobic nanopores triggered by irradiation from electromagnetic microwaves, ultrasound, or sudden pressure release. A large energy output is needed for the propulsion of a nanoparticle, and the value can be determined experimentally and by means of atomistic simulations. As such, we measured the heat of intrusion of water into ITQ-29 (LTA) pure silica zeolite with cage structure of pores. The heat effect is exothermic and equal to -7.3 ± 0.8 J/g of zeolite. Similar values were reported for chabazite, ZIF-8, and grafted mesoporous silica EVA. All these materials have cage structures of pores. In contrast, silicalite-1 (MFI) zeolite with a channel structure of pores exhibits endothermic intrusion. Molecular dynamics simulations of pure silica zeolites with LTA, CHA, and MFI topologies at a broad range of water loadings show that water becomes thermodynamically stable in cage-shaped pores while it is unstable in channel-shaped pores. A large energy release is expected during water expulsion from channel-type pores.

Turing-type nanochannel membranes with extrinsic ion transport pathways for high-efficiency osmotic energy harvesting.

Two-dimensional (2D) nanofluidic channels with confined transport pathways and abundant surface functional groups have been extensively investigated to achieve osmotic energy harvesting. However, solely relying on intrinsic interlayer channels results in insufficient permeability, thereby limiting the output power densities, which poses a significant challenge to the widespread application of these materials. Herein, we present a nanoconfined sacrificial template (NST) strategy to create a crafted channel structure, termed as Turing-type nanochannels, within the membrane. Extrinsic interlaced channels are formed between the lamellae using copper hydroxide nanowires as sacrificial templates. These Turing-type nanochannels significantly increase transport pathways and functional areas, resulting in a 23% enhancement in ionic current while maintaining a cation selectivity of 0.91. The output power density of the Turing-type nanochannel membrane increases from 3.9 to 5.9 W m-2 and remains stable for at least 120 hours. This membrane exhibits enhanced applicability in real saltwater environments across China, achieving output power densities of 7.7 W m-2 in natural seawater and 9.8 W m-2 in salt-lake brine. This work demonstrates the promising potential of the Turing-channel design for nanoconfined ionic transport in the energy conversion field.

Tailored Metal–Organic Framework‐Based Nanozymes for Enhanced Enzyme‐Like Catalysis

AbstractThe global crisis of bacterial infections is exacerbated by the escalating threat of microbial antibiotic resistance. Nanozymes promise to provide ingenious solutions. Here, we reported a homogeneous catalytic structure of Pt nanoclusters with finely tuned metal–organic framework (ZIF‐8) channel structures for the treatment of infected wounds. Catalytic site normalization showed that the active site of the Pt aggregates structure with fine‐tuned pore modifications structure had a catalytic capacity of 14.903×105 min−1, which was 18.7 times higher than that of the Pt particles in monodisperse state in ZIF‐8 (0.793×105 min−1). In situ tests revealed that the change from homocleavage to heterocleavage of hydrogen peroxide at the interface of the nanozyme was one of the key reasons for the improvement of nanozyme activity. Density‐functional theory and kinetic simulations of the reaction interface jointly determine the role of the catalytic center and the substrate channel together. Metabolomics analysis showed that the developed nanozyme, working in conjunction with reactive oxygen species, could effectively block energy metabolic pathways within bacteria, leading to spontaneous apoptosis and bacterial rupture. This pioneering study elucidates new ideas for the regulation of artificial enzyme activity and provides new perspectives for the development of efficient antibiotic substitutes.

Influence of MIL-53 on the catalytic performance of metallocene in propylene polymerization

In this study, we investigate the application of metal-organic frameworks (MOFs) as a support for metallocene catalysts in the polymerization of propylene. MOFs such as MIL-53 and other conventional supports, SBA-15 and SiO2, were employed to immobilize the Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst activated with methylaluminoxane (MAO). The effects of the physicochemical properties of these supports on catalytic performance and polymer properties were investigated. MIL-53, characterized by its channel structure, facilitated higher molecular weight polypropylene production and exhibited double the catalytic activity of SBA-15 and SiO2 supports. The MIL-53/MAO/Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst also demonstrated higher comonomer incorporation and lower polymer melting points. The higher activity, elevated molecular weight, and increased reactivity towards 1-hexene of the MIL-53/MAO/Me2Si(2-Me-4-PhInd)2ZrCl2 catalyst are attributed to the electronic and steric effects of MIL-53. This study underscores the significant role of MOF structure in influencing polymerization behavior and highlights the potential of MOF-supported catalysts for tailored polymer properties.