•Equivalent circuit models for three typical EEG electrodes were proposed.•Area-normalized impedance was used throughout the whole analysis.•Impedance fitting with mild pressure and skin abrasion ...conditions were investigated.•Inspiration for development of novel conductive-gel-free electrodes was discussed.
The electrode-scalp impedance of six subjects is studied by electrochemical impedance spectroscopy using three representative electrodes, namely wet electrodes, semi-dry electrodes, and dry electrodes. With the analysis of proposed equivalent models and area-normalized impedance (kΩ cm2), the specific electrode double layer resistances are 530 Ω cm2 for all electrodes, their specific contact resistances Res are 80 Ω cm2, 114 Ω cm2 and 20,077 Ω cm2, and their specific skin resistances Rs are 867 Ω cm2, 1730 Ω cm2 and 46,145 Ω cm2 for these three representative electrodes respectively. When pressure was applied on dry electrodes, Res reduced by 47% and Rs reduced by 81%. When pressure was applied on semi-dry electrodes, Rs reduced by 50% (Res is not applicable for semi-dry electrodes). After application of scalp abrasion for dry electrodes, Res reduced by 36% and Rs reduced by 82%. After application of scalp abrasion for semi-dry electrodes, Rs reduced by 64%. Seeking novel interface materials may break through the bottleneck for dry electrodes development in terms of integrated materials, mechanical support and electronic circuitry, while semi-dry electrodes have much development space to meet a balance of quick setup, comfortable wear, and satisfactory signal quality in many medical and out-clinic applications.
Emerging real-world EEG applications require gel-free electrodes, which have to break through technical bottlenecks and achieve satisfactory electrode-skin impedance. It is crucial to understand the ...electrical properties of the electrode-skin interface. In this work, the electrode-skin impedance of bioelectrodes (wet, semi-dry, and dry) has been studied systemically, concerning not only magnitude but stability. Various factors have been investigated including types of electrodes, skin locations, pressure, skin abrasion, and electrode contact area. The electrode-skin impedance always decreases in the following order: forearm, scalp and forehead for all electrodes. Compared with the impedances of wet electrodes and semi-dry electrodes, the dry electrode impedances are significantly higher (58.50±64.16kΩcm2) and unstable (impedance variation 31.2±31.3kΩ/10min). Even worse, the dry electrode impedance variation between six subjects is considerably large (57.5–540.0kΩ). As a result, no satisfactory EEG signals could be obtained. Moreover, the dry electrode impedances are lowered significantly under pressure or after skin abrasion. Accordingly, alpha rhythms from the dry electrodes appeared with the assistance of pressure or skin abrasion. These findings provide insights for the development of new gel-free electrodes to complement the emerging new EEG applications, such as brain-computer interfaces and wearable EEGs.
Lacking the structural information of crystalline solids, the origin of the relaxation dynamics of metallic glasses is unclear. Here, we report the evolution of stress relaxation of high-entropy ...metallic glasses with distinct β relaxation behavior. The fraction of liquidlike zones, determined at each temperature by the intensity of stress decay, is shown to be directly related to both the aging process and the spectrum of relaxation modes obtained by mechanical spectroscopy. The results shed light on the intrinsic correlation between the static and dynamic mechanical response in high-entropy and conventional metallic glasses, pointing toward a sluggish diffusion high-entropy effect in the liquid dynamics.
A novel polyacrylamide/polyvinyl alcohol superporous hydrogel (PAAm/PVA SPH)-based semi-dry electrode was constructed for capturing electroencephalogram (EEG) signals at the hairy scalp, showing ...automatically 'charge-discharge' electrolyte concept in EEG electrode development.
In this regard, PAAm/PVA SPH was polymerized
in the hollow electrode cavity by freezing polymerization, which acted as a dynamic reservoir of electrolyte fluid. The SPH can be completely 'charged' with electrolyte fluid, such as saline, in just a few seconds and can be 'discharged' through a few tiny pillars into the scalp at a desirable rate. In this way, an ideal local skin hydration effect was achieved at electrode-skin contact sites, facilitating the bioelectrical signal pathway and significantly reducing electrode-skin impedance. Moreover, the electrode interface effectively avoids short circuit and inconvenient issues.
The results show that the semi-dry electrode displayed low and stable contact impedance, showing non-polarization properties with low off-set potential and negligible potential drift. The average temporal cross-correlation coefficient between the semi-dry and conventional wet electrodes was 0.941. Frequency spectra also showed almost identical responses with anticipated neural electrophysiology responses.
Considering prominent advantages such as a rapid setup, robust signal, and user-friendliness, the new concept of semi-dry electrodes shows excellent potential in emerging real-life EEG applications.
Display omitted
•The Ca–Pb compounds are mechanically stable.•Ca3Pb has the largest hardness, while CaPb3 possesses the smallest hardness.•The elastic anisotropy follows the order ...Ca2Pb>Ca5Pb3>CaPb>Ca3Pb>CaPb3.•The order of ΘD is: Ca3Pb>Ca5Pb3>CaPb>Ca2Pb>CaPb3.
To better clarify and understand the anisotropic elastic properties of Ca–Pb intermetallic compounds, the structural and elastic properties of the Ca–Pb compounds (Ca3Pb, Ca2Pb, Ca5Pb3, CaPb and CaPb3) have been investigated by using the first-principles calculations based on density functional theory. The calculated equilibrium structural parameters are in good agreement with the available experimental data. Elastic properties including bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio, are obtained by Voigt–Reuss–Hill approximation. All Ca–Pb compounds are mechanically stable. The brittle and ductile properties are discussed by using B/G and Poisson’s ratio. The elastic anisotropies of Ca–Pb compounds are investigated via the anisotropic index and the 3D figures of directional dependences of reciprocals of elastic moduli. Finally, the anisotropic sound velocities and Debye temperatures of the Ca–Pb compounds are predicted.
Rare diseases affect > 400 million people globally with a disproportionate burden falling on children, resulting in high morbidity and mortality rates. Affected individuals in some under-resourced ...countries have limited access to expert care or treatments; moreover, they suffer long diagnostic journeys during which debilitating and life-threatening complications occur. Lysosomal storage disorders (LSD) are prototype rare diseases due, in the main, to inherited deficiencies of lysosomal enzymes/transporters that affect up to 1 in 5000 newborns. Recognizing the need to provide treatment access to people with LSDs everywhere, a collaborative partnership was pioneered and set up 30 years ago. Partnering with local authorities, non-government organizations across six continents, local as well as international experts, a robust, sustainable Humanitarian Program emerged that now represents the most enduring charitable access program for LSD treatment. Here we present the history, process, lasting beneficial effect of the program to develop healthcare systems and infrastructures, and the lessons learned from addressing major unmet needs for LSDs.
The plant‐pathogenic fungus Sclerotinia sclerotiorum has a broad host range and a worldwide distribution. Boscalid, an inhibitor of succinate dehydrogenase in the electron transport chain of fungi, ...is highly effective in controlling sclerotinia stem rot caused by S. sclerotiorum. The current study characterized the S. sclerotiorum boscalid‐resistant (BR) mutants obtained by fungicide induction. Among the bioactive fungicides against S. sclerotiorum, cross‐resistance was not detected between boscalid and dimethachlon, fluazinam or carbendazim; positive cross‐resistance was detected between boscalid and carboxin; and negative cross‐resistance was detected between boscalid and kresoxim‐methyl. Compared to their parental isolates, BR mutants had slower radial growth, no ability to produce sclerotia, lower virulence and oxalic acid content but higher mycelial respiration and succinate dehydrogenase (SDH) activity. Moreover, BR mutants had decreased sensitivity to salicylhydroxamic acid (SHAM) but not to oxidative stress. All the results indicated that the risk of resistance to boscalid in S. sclerotiorum is low to moderate. DNA sequence analysis showed that all of the BR mutants had the same point mutation A11V (GCA to GTA) in the iron sulphur protein subunit (SDHB). Interestingly, expression of the cytochrome b (cytb) gene was reduced to different degrees in the BR mutants, and this might be correlated with the negative cross‐resistance between boscalid and kresoxim‐methyl. Such information is vital in the design of resistance management strategies.
Geological disasters such as landslides and debris flows pose a serious threat to human life and property. To mitigate this risk, monitoring and early warning systems are essential. However, ...monitoring high-angle landslide areas can be challenging due to the steep and complex terrain, making it difficult to carry out large-scale and refined deformation measurements using existing methods. This paper proposes a method to measure the large-scale deformation of landslide bodies based on nap-of-the-object photogrammetry. The method uses UAVs to acquire high-resolution 3D models of steep and high landslide areas at multiple time periods. Then, 3D model matching is employed to obtain accurate variation information for terrain deformation measurement. To obtain fine 3D models, a terrain-adaptive nap-of-the-object photogrammetric flight planning is applied to design the optimal photographic positions and directions for capturing ultra-high-resolution images. The images are processed using photogrammetric principles and technologies to produce fine 3D models. For terrain deformation measurement, an algorithm is proposed to obtain 3D correspondences by fusing DEM differential and 3D model texture matching. The 3D points variation vectors are then calculated, and the large-scale deformation measurement results of the landslide body can be derived after the vectors are aggregated. Experiments were conducted on the Lijiebeishan landslide in Gansu Province, western China. The results showed that the proposed deformation measurement method was highly effective in accurately detecting areas with displacement greater than 5 cm, and the large-scale deformation trend is consistent with GNSS predictions. In conclusion, the proposed method is an effective way to measure the large-scale deformation of landslide bodies in high-angle landslide areas, providing a valuable tool for monitoring and early warning systems.
PDF
