Search Results (58)

Accurate seamount identification is important for understanding submarine tectonic and magmatic processes and for supporting deep-sea geomorphological analysis. However, seamount recognition faces a severe class imbalance as abyssal plains constitute the majority of deep-sea topography while seamounts occupy only a minimal portion, which makes accurate segmentation difficult. To address this issue, this study proposes an improved U-Net architecture, termed Spatial–Channel Reconstruction U-Net (RSCU-Net), built upon a Residual Spatial–Channel Reconstruction Convolution (Res-SCConv) module. The Res-SCConv module is embedded into each skip connection of the U-Net architecture. The model combines a Spatial Reconstruction Unit (SRU) and a Channel Reconstruction Unit (CRU) to suppress dominant background interference and reduce channel redundancy, and further introduces a Selective Kernel-based Multi-scale Gradient Module (SK-MGM) to improve boundary refinement. Experiments on the GEBCO 2023 bathymetric dataset, including 696 training samples and 88 independent test samples, show that RSCU-Net achieves an Accuracy of 0.938, Recall of 0.833, F1-score of 0.720, and IoU of 0.563. Compared with the baseline U-Net, Recall improves from 0.741 to 0.833 and IoU from 0.405 to 0.563. Additional validation on the Suda Seamount dataset yields an Accuracy of 0.987, F1-score of 0.958, and IoU of 0.920, demonstrating the robustness and generalization capability of the proposed method. Full article

Skeletal muscle differentiation is tightly regulated by membrane potential dynamics and voltage-dependent ion channel activity. Potassium (K⁺) and calcium (Ca²⁺) currents cooperate to orchestrate the transition of myoblasts into fusion-competent myotubes, and alterations in this process are associated with dystrophic phenotypes. Here, we investigated the electrophysiological remodeling accompanying C2C12 myogenesis and the modulatory effects of the polyphenol resveratrol (RES) on calcium voltage-gated channel subunit alpha 1 S (CACNA1S, Cav1.1, L-type) currents. Whole-cell patch-clamp recordings were performed in proliferating and differentiating C2C12 cells to characterize the temporal expression of K⁺ currents and voltage-dependent Ca²⁺ channels (VDCCs). During differentiation, three electrophysiological subpopulations were identified according to K⁺ current profiles: SK4+/EAG−/Kir−, SK4−/EAG+/Kir−, and SK4−/EAG+/Kir+. This sequence paralleled a progressive membrane hyperpolarization from −20 mV to −70 mV, consistent with the physiological maturation of myogenic cells. In C2C12 myocytes, nimodipine-sensitive L-type currents were the only Ca²⁺ conductance observed. Their activation threshold (~−30 mV) and half-activation voltage (V/2 ≈ −12 mV) indicated the co-expression of embryonic and adult Cav1.1 isoforms. Exposure to RES (30 µM, 48 h) produced a depolarizing shift in activation (ΔV/2 ≈ +9 mV) and a reduction in current amplitude across all voltages, consistent with a transition toward the adult splice variant of Cav1.1. These findings suggest that RES promotes electrophysiological maturation of skeletal muscle cells by modulating calcium channel expression and gating behavior. Given its known ability to correct splicing abnormalities in CACNA1S and related genes, resveratrol emerges as a promising pharmacological agent for restoring calcium homeostasis in neuromuscular disorders such as myotonic dystrophy type 1 (DM1). Full article

Magnesium ions regulate synaptic and nonsynaptic neuronal excitability from intracellular (Mg²⁺_i) and extracellular (Mg²⁺_o) domains, modulating voltage- and ligand-gated ion channels. K+ inward rectifier (Kir) channel inward rectification arises from Mg²⁺_i blocking the pore and outward K⁺ current, while Mg²⁺_o targets external sites. Mg²⁺_i causes voltage-dependent Ca²⁺ voltage-gated (Ca_V) and Na⁺ voltage-gated (Na_V) channel block while phosphorylation modulates channel activity. Mg²⁺_o elicits direct voltage-dependent Ca_V channel block, and screens surface charge, and in Na_V channels reduces conduction and may cause depolarization by quantum tunneling across closed channels. Mg²⁺_i is an allosteric large conductance Ca²⁺-activated K⁺ (BK) channel activator, binding to low-affinity sites to alter Ca²⁺ and voltage sensitivity but reduces small conductance Ca²⁺-activated K⁺ (SK) channels’ outward K⁺ current and induces inward rectification. N-Methyl-D-aspartate receptor (NMDAR) channels are inhibited by Mg²⁺_i binding within the pore, while Mg²⁺_o stabilizes excitability through voltage-dependent block, Mg²⁺_o forms Mg-ATP complex modifying purinergic P2X receptor (P2XR) channel affinity and gating and directly blocks the pore. Mg²⁺_o reduces gamma-aminobutyric acid type A receptor (GABA_AR) channel Cl⁻ current amplitude and augments susceptibility to blockers. Mg²⁺_o and Mg²⁺_i block nicotinic acetylcholine receptor (nAChR) channels through voltage-dependent pore binding and surface charge screening, impeding current flow and altering gating. Full article

Drug-resistant epilepsy remains a therapeutic challenge, requiring new molecular targets beyond conventional antiepileptic drugs. Small-conductance calcium-activated potassium (SK) channels and Na/K-ATPase (NKA) contribute to afterhyperpolarization via distinct mechanisms, offering complementary ways to suppress hyperexcitability. We examined SK activation and NKA modulation in synchronized epileptiform activity in a primary culture of cortical neurons obtained from rat embryos. Epileptiform discharges were induced by magnesium-free solution and assessed by patch-clamp and calcium imaging. The SK2/3 activator CyPPA (10 µM) reduced epileptiform current (EC) amplitude and integral and decreased synchronized calcium transient (CT) frequency but gradually elevated basal calcium. In contrast, ouabain (1 nM), a selective modulator of high-affinity NKA isoforms, attenuated EC amplitude, strongly suppressed CTs, and showed persistent effects after washout, accompanied by asynchronous glial calcium activity. Co-application of CyPPA with ouabain abolished CyPPA-induced calcium elevation while maintaining suppression of neuronal synchrony. The broader SK/IK activator NS309 (10 µM) reduced CT frequency and basal calcium without affecting glia. Thus, SK activation and NKA signaling suppress epileptiform synchronization through distinct yet convergent pathways: SK channels via afterhyperpolarization and NKA via afterhyperpolarization and calcium-dependent signaling. Their combination enhances efficacy and prevents adverse calcium buildup, supporting SK–NKA co-targeting as a strategy against drug-resistant epilepsy. Full article

B-raf (rapidly accelerated fibrosarcoma) is a crucial player within the ERK/MAPK signaling pathway. In the CNS, B-raf has been implicated in neuronal differentiation, long-term memory, and major depression. Mice with forebrain neuron-specific B-raf knockout show behavioral deficits in spatial learning tasks and impaired hippocampal long-term potentiation (LTP). To elucidate the mechanism(s) underlying diminished synaptic plasticity in B-raf-deficient mice, we performed whole-cell recordings from CA1 pyramidal cells in hippocampal slices of control and B-raf mutant mice. We found that the NMDA/AMPA ratio of excitatory postsynaptic currents (EPSCs) at the Schaffer collateral—CA1 pyramidal cell synapses was significantly reduced in B-raf mutants, which would at least partially account for their impaired LTP. Interestingly, the reduced NMDA component of field postsynaptic potentials in mutant preparations was partially reinstated by blocking the apamin-sensitive small-conductance Ca²⁺-activated K⁺ (SK) channels, which have also been reported to modulate hippocampal LTP and learning tasks. To determine the impact of B-raf-dependent signaling on SK current, we isolated the apamin-sensitive tail current after a strong depolarizing event and found indeed a significantly bigger SK current in B-raf-deficient cells compared to controls, which is consistent with the reduced action potential firing and the stronger facilitating effect of apamin on CA1 somatic excitability in B-raf-mutant hippocampus. Our data suggest that B-raf signaling readjusts the delicate balance between NMDA receptors and SK channels to promote synaptic plasticity and facilitate hippocampal learning and memory. Full article

An analog joint source-channel coding (AJSCC) based on Shannon–Kotel’nikov (S-K) mapping transmitting discrete-time encoded samples in orthogonal frequency division multiplexing (OFDM) systems over wireless channel has exhibited excellent performance. However, the phenomenon of carrier frequency offset (CFO) caused by the frequency mismatch between the transmitter’s and receiver’s local oscillators often exists in actual scenarios; thus, in this paper the performance of AJSCC-OFDM with CFO is analyzed and the S-K mapping is optimized. A joint optimization strategy is developed to maximize the signal-to-distortion ratio (SDR) subject to CFO constraints. Considering that the optimized AJSCC-OFDM strategies will change the amplitude distribution of encoded symbol, the peak-to-average power ratio (PAPR) characteristics under different AJSCC parameters are also analyzed. Full article

Fibrosis represents a pivotal pathological process in numerous diseases, characterized by excessive deposition of extracellular matrix (ECM) that disrupts normal tissue architecture and function. In the heart, cardiac fibrosis significantly impairs both structural integrity and functional capacity, contributing to the progression of heart failure. Central to this process are cardiac fibroblasts (CFs), which, upon activation, differentiate into contractile myofibroblasts, driving pathological ECM accumulation. Transforming growth factor-beta (TGFβ) is a well-established regulator of fibroblast activation; however, the precise molecular mechanisms, particularly the involvement of ion channels, remain poorly understood. Emerging evidence highlights the regulatory role of ion channels, including calcium-activated potassium (K_Ca) channels, in fibroblast activation. This study elucidates the role of ion channels and investigates the mechanism by which Yoda1, an agonist of the mechanosensitive ion channel Piezo1, modulates TGFβ-induced fibroblast activation. Using NIH/3T3 fibroblasts, we demonstrated that TGFβ-induced activation is regulated by tetraethylammonium (TEA)-sensitive potassium channels, but not by specific K⁺ channel subtypes such as BK, SK, or IK channels. Intriguingly, Yoda1 was found to inhibit TGFβ-induced fibroblast activation through a Piezo1-independent mechanism. Transcriptomic analysis revealed that Yoda1 modulates fibroblast activation by altering gene expression pathways associated with fibrotic processes. Bromodomain-containing protein 4 (BRD4) was identified as a critical mediator of Yoda1’s effects, as pharmacological inhibition of BRD4 with JQ1 or ZL0454 suppressed TGFβ-induced expression of the fibroblast activation marker Periostin (Postn). Conversely, BRD4 overexpression attenuated the inhibitory effects of Yoda1 in both mouse and rat CFs. These results provide novel insights into the pharmacological modulation of TGFβ-induced cardiac fibroblast activation and highlight promising therapeutic targets for the treatment of fibrosis-related cardiac pathologies. Full article

Zoharite (IMA 2017-049), (Ba,K)₆ (Fe,Cu,Ni)₂₅S₂₇, and gmalimite (IMA 2019-007), ideally K₆□Fe²⁺₂₄S₂₇, are two new sulfides of the djerfisherite group. They were discovered in an unusual gehlenite–wollastonite paralava with pyrrhotite nodules located in the Hatrurim pyrometamorphic complex, Negev Desert, Israel. Zoharite and gmalimite build grained aggregates confined to the peripheric parts of pyrrhotite nodules, where they associate with pentlandite, chalcopyrite, chalcocite, digenite, covellite, millerite, heazlewoodite, pyrite and rudashevskyite. The occurrence and associated minerals indicate that zoharite and gmalimite were formed at temperatures below 800 °C, when sulfides formed on external zones of the nodules have been reacting with residual silicate melt (paralava) locally enriched in Ba and K. Macroscopically, both minerals are bronze in color and have a dark-gray streak and metallic luster. They are brittle and have a conchoidal fracture. In reflected light, both minerals are optically isotropic and exhibit gray color with an olive tinge. The reflectance values for zoharite and gmalimite, respectively, at the standard COM wavelengths are: 22.2% and 21.5% at 470 nm, 25.1% and 24.6% at 546 nm, 26.3% and 25.9% at 589 nm, as well as 27.7% and 26.3% at 650 nm. The average hardness for zoharite and for gmalimite is approximately 3.5 of the Mohs hardness. Both minerals are isostructural with owensite, (Ba,Pb)₆(Cu,Fe,Ni)₂₅S₂₇. They crystallize in cubic space group Pm$\overline{3}$m with the unit-cell parameters a = 10.3137(1) Å for zoharite and a = 10.3486(1) Å for gmalimite. The calculated densities are 4.49 g·cm⁻³ for the zoharite and 3.79 g·cm⁻³ for the gmalimite. The primary structural units of these minerals are M₈S₁₄ clusters, composed of MS₄ tetrahedra surrounding a central MS₆ octahedron. The M site is occupied by transition metals such as Fe, Cu, and Ni. These clusters are further connected via the edges of the MS₄ tetrahedra, forming a close-packed cubic framework. The channels within this framework are filled by anion-centered polyhedra: SBa₉ in zoharite and SK₉ in gmalimite, respectively. In the M₈S₁₄ clusters, the M atoms are positioned so closely that their d orbitals can overlap, allowing the formation of metal–metal bonds. As a result, the transition metals in these clusters often adopt electron configurations that reflect additional electron density from their local bonding environment, similar to what is observed in pentlandite. Due to the presence of shared electrons in these metal–metal bonds, assigning fixed oxidation states—such as Fe²⁺/Fe³⁺ or Cu⁺/Cu²⁺—becomes challenging. Moreover, modeling the distribution of mixed-valence cations (Fe²⁺/³⁺, Cu⁺/²⁺, and Ni²⁺) across the two distinct M sites—one located in the MS₆ octahedron and the other in the MS₄ tetrahedra—often results in ambiguous outcomes. Consequently, it is difficult to define an idealized end-member formula for these minerals. Full article

Small conductance Ca²⁺-activated K⁺ (SK) channels are expressed in atria and ventricles. However, the data on the contribution of SK channels to atrial action potential (AP) repolarization are inconsistent. We investigated the effect of SK channel modulators on AP morphology in rabbit atrial myocytes and tested the hypothesis that pharmacological activation of SK channels suppresses pacing-induced Ca²⁺ transient (CaT) and AP duration (APD) alternans. At the cellular level, alternans are observed as beat-to-beat alternations in contraction, APD, and CaT amplitude, representing a risk factor for arrhythmias, including atrial fibrillation. Our results show that SK channel inhibition by apamin did not affect atrial APD under basal conditions. However, SK channel activation by NS309 significantly shortened APD, indicating the expression of functional SK channels. Moreover, the activation of SK channels reduced CaT amplitude and sarcoplasmic reticulum Ca²⁺ load. Activation of SK channels also suppressed pacing-induced CaT and APD alternans. K_V7.1 potassium channel inhibition, simulating long QT syndrome type-1 conditions, increased the risk of atrial CaT alternans, which was abolished by the activation of SK channels. In summary, our data suggest that pharmacological modulation of SK channels can potentially reduce atrial arrhythmia risk arising from pathological APD prolongation. Full article

(1) Objective: As light propagates through water, it undergoes significant attenuation and scattering, causing underwater images to experience color distortion and exhibit a bluish or greenish tint. Additionally, suspended particles in the water further degrade image quality. This paper proposes an improved U-Net network model for underwater image enhancement to generate high-quality images. (2) Method: Instead of incorporating additional complex modules into enhancement networks, we opted to simplify the classic U-Net architecture. Specifically, we replaced the standard convolutions in U-Net with our self-designed efficient basic block, which integrates a simplified channel attention mechanism. Moreover, we employed Layer Normalization to enhance the capability of training with a small number of samples and used the GELU activation function to achieve additional benefits in image denoising. Furthermore, we introduced the SK fusion module into the network to aggregate feature information, replacing traditional concatenation operations. In the experimental section, we used the “Underwater ImageNet” dataset from “Enhancing Underwater Visual Perception (EUVP)” for training and testing. EUVP, established by Islam et al., is a large-scale dataset comprising paired images (high-quality clear images and low-quality blurry images) as well as unpaired underwater images. (3) Results: We compared our proposed method with several high-performing traditional algorithms and deep learning-based methods. The traditional algorithms include He, UDCP, ICM, and ULAP, while the deep learning-based methods include CycleGAN, UGAN, UGAN-P, and FUnIEGAN. The results demonstrate that our algorithm exhibits outstanding competitiveness on the underwater imagenet-dataset. Compared to the currently optimal lightweight model, FUnIE-GAN, our method reduces the number of parameters by 0.969 times and decreases Floating-Point Operations Per Second (FLOPS) by more than half. In terms of image quality, our approach achieves a minimal UCIQE reduction of only 0.008 while improving the NIQE by 0.019 compared to state-of-the-art (SOTA) methods. Finally, extensive ablation experiments validate the feasibility of our designed network. (4) Conclusions: The underwater image enhancement algorithm proposed in this paper significantly reduces model size and accelerates inference speed while maintaining high processing performance, demonstrating strong potential for practical applications. Full article

The assessment of grain size and sediment output is crucial for analyzing the pace of sediment erosion, engineering dams and reservoirs, anticipating the impact of climate change and human activities on river systems, and comprehending the presence of trace and heavy metal pathogens and micropollutants. In July 2024, 16 samples of bed sediments were collected from the mainstream of Wadi Fatima and its tributaries in the Makkah region of Saudi Arabia to identify the depositional environments and the hydrodynamic conditions using Passega diagram, Linear Discriminate Function (LDF) and bivariate plots. The results indicate that the sediments being studied exhibit polymodal properties in both the upstream and midstream regions of the main channel of Wadi Fatima. However, in the downstream region, the samples show trimodal properties. Regarding tributaries, the WFT1, WFT2, and WFT4 sediments exhibit polymodal properties, except for WFT3, which is bimodal. Folk’s classification system categorizes the samples into four distinct classes/facies: gravel, sandy gravel, gravely sand, and sand, with respective proportions of 13%, 62%, 6%, and 19%. The sediments found in Wadi Fatima contain a range of graphic mean (M_Z) values, from −3.34 (indicating medium gravel) to 2.48 (indicating fine sand). On average, the M_Z value is −0.79, which shows extremely fine gravel. The standard deviation (sorting (σi)) values of the samples analyzed from Wadi Fatima vary between 0.71 (moderately sorted) and 3.44 (very poorly sorted), with an average of 2.00 (very poorly sorted). The data exhibits a range of skewness (Sk) values, ranging from −0.41 (showing a very coarse Sk) to 0.82 (representing a indicating a very fine Sk). On average, the data shows a Sk value of −0.02, indicating a symmetrical distribution. The kurtosis (K) values span from 0.51 (indicating a very platykurtic distribution) to 2.65 (indicating a very leptokurtic distribution), with an average of 0.95 (indicating a mesokurtic distribution). Full article

This paper explores physical layer group key generation in wireless relay networks with a star topology. In this setup, the relay node plays the role of either a trusted or untrusted central node, while one legitimate node (Alice) acts as the reference node. The channel between the relay and Alice serves as the reference channel. To enhance security during the channel measurement stage, a cooperative jamming-based scheme is proposed in this paper. This scheme allows the relay to obtain superimposed channel observations from both the reference channel and other relay channels. Then, a public discussion is utilized to enable all nodes to obtain estimates of the reference channel. Subsequently, the legitimate nodes can agree on a secret key (SK) that remains secret from the eavesdropper (Eve), or a private key (PK) that needs to be secret from both the relay and Eve. This paper also derives the lower and upper bounds of the SK/PK capacity. Notably, it demonstrates that there exists only a small constant difference between the SK/PK upper and lower bounds in the high signal-to-noise ratio (SNR) regime. Simulation results confirm the effectiveness of the proposed scheme for ensuring security and efficiency of group key generation. Full article

Neuroplasticity in the amygdala and its central nucleus (CeA) is linked to pain modulation and pain behaviors, but cellular mechanisms are not well understood. Here, we addressed the role of small-conductance Ca²⁺-activated potassium (SK) channels in pain-related amygdala plasticity. The facilitatory effects of the intra-CeA application of an SK channel blocker (apamin) on the pain behaviors of control rats were lost in a neuropathic pain model, whereas an SK channel activator (NS309) inhibited pain behaviors in neuropathic rats but not in sham controls, suggesting the loss of the inhibitory behavioral effects of amygdala SK channels. Brain slice electrophysiology found hyperexcitability of CeA neurons in the neuropathic pain condition due to the loss of SK channel-mediated medium afterhyperpolarization (mAHP), which was accompanied by decreased SK2 channel protein and mRNA expression, consistent with a pretranscriptional mechanisms. The underlying mechanisms involved the epigenetic silencing of the SK2 gene due to the increased DNA methylation of the CpG island of the SK2 promoter region and the change in methylated CpG sites in the CeA in neuropathic pain. This study identified the epigenetic dysregulation of SK channels in the amygdala (CeA) as a novel mechanism of neuropathic pain-related plasticity and behavior that could be targeted to control abnormally enhanced amygdala activity and chronic neuropathic pain. Full article

Pacemaking activity in substantia nigra dopaminergic neurons is generated by the coordinated activity of a variety of distinct somatodendritic voltage- and calcium-gated ion channels. We investigated whether these functional interactions could arise from a common localization in macromolecular complexes where physical proximity would allow for efficient interaction and co-regulations. For that purpose, we immunopurified six ion channel proteins involved in substantia nigra neuron autonomous firing to identify their molecular interactions. The ion channels chosen as bait were Cav1.2, Cav1.3, HCN2, HCN4, Kv4.3, and SK3 channel proteins, and the methods chosen to determine interactions were co-immunoprecipitation analyzed through immunoblot and mass spectrometry as well as proximity ligation assay. A macromolecular complex composed of Cav1.3, HCN, and SK3 channels was unraveled. In addition, novel potential interactions between SK3 channels and sclerosis tuberous complex (Tsc) proteins, inhibitors of mTOR, and between HCN4 channels and the pro-degenerative protein Sarm1 were uncovered. In order to demonstrate the presence of these molecular interactions in situ, we used proximity ligation assay (PLA) imaging on midbrain slices containing the substantia nigra, and we could ascertain the presence of these protein complexes specifically in substantia nigra dopaminergic neurons. Based on the complementary functional role of the ion channels in the macromolecular complex identified, these results suggest that such tight interactions could partly underly the robustness of pacemaking in dopaminergic neurons. Full article

Image dehazing aims to reconstruct potentially clear images from corresponding images corrupted by haze. With the rapid development of deep learning-related technologies, dehazing methods based on deep convolutional neural networks have gradually become mainstream. We note that existing dehazing methods often accompany an increase in computational overhead while improving the performance of dehazing. We propose a novel lightweight dehazing neural network to balance performance and efficiency: the g2D-Net. The g2D-Net borrows the design ideas of input-adaptive and long-range information interaction from Vision Transformers and introduces two kinds of convolutional blocks, i.e., the g2D Block and the FFT-g2D Block. Specifically, the g2D Block is a residual block with second-order gated units, which inherit the input-adaptive property of a gated unit and can realize the second-order interaction of spatial information. The FFT-g2D Block is a variant of the g2D Block, which efficiently extracts the global features of the feature maps through fast Fourier convolution and fuses them with local features. In addition, we employ the SK Fusion layer to improve the cascade fusion layer in a traditional U-Net, thus introducing the channel attention mechanism and dynamically fusing information from different paths. We conducted comparative experiments on five benchmark datasets, and the results demonstrate that the g2D-Net achieves impressive dehazing performance with relatively low complexity. Full article