Stratified Strata Research Articles

Airborne transient electromagnetic imaging method based on wavelet neural network

The airborne transient electromagnetic method is a crucial technique for near-surface exploration in rugged terrains. In this study, we introduce a multi-input, single-output double-hidden wavelet neural network design for airborne transient electromagnetic pseudo-resistivity imaging. We construct uniform half-space, stratified stratum, and three-dimensional geoelectric models. By evaluating various performance indicators of neural networks that employ different wavelet basis functions as activation functions, we identify the most suitable wavelet basis functions. The quasi-resistivity is computed using both the wavelet neural network and the backpropagation neural network and then juxtaposed with traditional apparent resistivity. Our findings indicate that the wavelet neural network's quasi-resistivity aligns more closely with the resistivity of the real model. It is also more responsive to low resistivity anomalies than the conventional apparent resistivity translation algorithm. The wavelet approach moderates the undershoot or overshoot occurrences during abrupt stratum changes, offering a more accurate representation of subterranean electrical properties. When compared to the backpropagation neural network, the wavelet neural network provides a superior fit for the model, rendering a smoother quasi-resistivity depth curve. Therefore, it stands out as an improved method for pseudo-resistivity imaging. By processing survey data via the trained wavelet neural network, we find that the all-time apparent resistivity and quasi-resistivity align well with real-world situations. The wavelet neural network prominently showcases the low-resistance calculation results, offering a broader resistivity range. This clarity enhances anomaly detection, confirming the wavelet neural network's applicability and practicality for airborne transient electromagnetic imaging.

Stability analysis for excavation in frictional soils based on upper bound method

This paper adopted both the numerical and analytical methods to investigate the excavation stability against base heave failure. The finite element limit analysis method (OPTUM) was firstly employed to calculate the safety factor of the excavation stability against base heave failure, and the failure mechanism of the excavation was obtained. Based on the analysis and observation of the numerical results, a rigid block rotational failure mechanism was proposed, and the analytical formula of the safety factor of the excavation was developed through the upper bound method of limit analysis. In order to verify the rationality of the proposed failure mechanism, the analytical formula of the safety factor and the failure pattern of excavation were compared with the numerical results and the existing classical failure mechanism. Furthermore, the influences of soil and excavation conditions on the excavation stability were analyzed and discussed. Finally, a rigid block rotational failure mechanism under stratified stratum conditions was also proposed to consider effects of the complex soil conditions on the excavation stability. The results show that the proposed rigid block rotational failure mechanism provides a more critical safety factor calculation result for actual engineering examples and obtains a more continuous and smooth failure surface, which can serve as an alternative for the analytical method of excavation stability.

The inter-laboratory validation study of EpiSensA for predicting skin sensitization potential.

The Epidermal Sensitization Assay (EpiSensA) is a reconstructed human epidermis (RhE)-based gene expression assay for predicting the skin sensitization potential of chemicals. Since the RhE model is covered by a stratified stratum corneum, various kinds of test chemicals, including lipophilic ones and pre-/pro-haptens, can be tested with a route of exposure akin to an in vivo assay and human exposure. This article presents the results of a formally managed validation study of the EpiSensA that was carried out by three participating laboratories. The purpose of this validation study was to assess transferability of the EpiSensA to new laboratories along with its within- (WLR) and between-laboratory reproducibility (BLR). The validation study was organized into two independent stages. As demonstrated during the first stage, where three sensitizers and one non-sensitizer were correctly predicted by all participating laboratories, the EpiSensA was successfully transferred to all three participating laboratories. For Phase I of the second stage, each participating laboratory performed three experiments with an identical set of 15 coded test chemicals resulting in WLR of 93.3%, 93.3%, and 86.7%, respectively. Furthermore, when the results from the 15 test chemicals were combined with those of the additional 12 chemicals tested in Phase II of the second stage, the BLR for 27 test chemicals was 88.9%. Moreover, the predictive capacity among the three laboratories showed 92.6% sensitivity, 63.0% specificity, 82.7% accuracy, and 77.8% balanced accuracy based on murine local lymph node assay (LLNA) results. Overall, this validation study concluded that EpiSensA is easily transferable and sufficiently robust for assessing the skin sensitization potential of chemicals.

Keratin Promotes Differentiation of Keratinocytes Seeded on Collagen/Keratin Hydrogels.

Keratinocytes undergo a complex process of differentiation to form the stratified stratum corneum layer of the skin. In most biomimetic skin models, a 3D hydrogel fabricated out of collagen type I is used to mimic human skin. However, native skin also contains keratin, which makes up 90% of the epidermis and is produced by the keratinocytes present. We hypothesized that the addition of keratin (KTN) in our collagen hydrogel may aid in the process of keratinocyte differentiation compared to a pure collagen hydrogel. Keratinocytes were seeded on top of a 100% collagen or 50/50 C/KTN hydrogel cultured in either calcium-free (Ca-free) or calcium+ (Ca+) media. Our study demonstrates that the addition of keratin and calcium in the media increased lysosomal activity by measuring the glucocerebrosidase (GBA) activity and lysosomal distribution length, an indication of greater keratinocyte differentiation. We also found that the presence of KTN in the hydrogel also increased the expression of involucrin, a differentiation marker, compared to a pure collagen hydrogel. We demonstrate that a combination (i.e., containing both collagen and kerateine or “C/KTN”) hydrogel was able to increase keratinocyte differentiation compared to a pure collagen hydrogel, and the addition of calcium further increased the differentiation of keratinocytes. This multi-protein hydrogel shows promise in future models or treatments to increase keratinocyte differentiation into the stratum corneum.

Eastern Lomonosov Ridge: Constraints for a variable ice mass thickness during former glaciations

Here we present dense acoustic and swath bathymetry data sets as well as geological age constraints that allow a new view on past glacial processes at the Siberian termination of Lomonosov Ridge in the Arctic Ocean between 81° and 84° 20′ N. Here, the seabed is marked by three sets of streamlined glacial lineations observed at present water depths of ~760 m to 1250 m. The shallower streamlined glacial lineations were likely formed during MIS 6 and the deeper ones during MIS 12. Other observations include recessional moraines and pockmarks on a flattened ridge crest. In the subsurface, an acoustically transparent unit above well stratified strata is interpreted as subglacial diamicton overlying pre-glacial sediments at an erosional contact. Furthermore, the diamicton is interpreted to have been deposited as lenses in glacially-eroded proximal settings. In contrast, some parts of the seafloor and subsurface show no glacial overprint in water depths as shallow as 819 m. To explain these findings, we propose that the Siberian termination of Lomonosov Ridge was covered by an ice mass of spatial and temporal variable thickness between ~780 to ~1250 m, that was likely composed of sea ice and thick icebergs calved from ice shelves.

Cause investigation of ground sliding during tunneling in sloping and stratified stratum

Cause investigation of ground sliding during tunneling in sloping and stratified stratum

Incorporating electromagnetic measurements into drilling systems with a relay station

Electromagnetic measurement while drilling (EM-MWD) systems transmit downhole data by emitting electromagnetic waves into the formation, thereby carrying the emitted data to a surface antenna; however, these electromagnetic waves are attenuated when transmitted into the formation. To further extend depth capabilities, Extended-Range EM-MWD systems have been developed. Expanding on this approach, this paper introduces an EM-MWD system that incorporates a relay station within ultra-deep wells; our proposed system consists of a downhole instrument assembly, a relay station and a ground receiver assembly. After decoding a received signal, the relay station amplifies, filters and recodes the signal; then, the relay station emits the augmented signal. Through numerical simulations, as presented in this paper, propagation characteristics of electromagnetic waves in heterogeneous and stratified strata show that when the resistivity of the upper formation and the lower formation is kept constant, the voltage of the ground receiving signal first increases and then decreases with the increased resistivity of the interlayer. Similarly, when the resistivity of the upper stratum and interlayer is kept constant, the voltage of the ground receiving signal first increases and then decreases with the increased resistivity of the lower stratum. This paper also presents the design schemes, the technology used to process the insulation gap, and the power-saving technology to increase the lifetime of the downhole instruments. Furthermore, the working principle of the relay station is described. Moreover, by analysing the electric and magnetic excitation methods, under the same conditions, signal attenuation is fast and the signal strength obtained on the ground is low when magnetic excitation is used. Therefore, an electric excitation method is adopted for implementing the relay station. To conclude, suggestions as to reasonable locations of the relay station and reception and decoding of the ground signal are provided.

Serial decoupling of bolts in coal mine roadway supports

Bolt supports within stratified strata in coal mines contribute to the unique characteristics of low-buried engineering structures such as tunnels or subways. Failure at the bolt interface is the main trigger of support failure in such settings. This paper comprehensively investigates the serial decoupling mechanism at a resin–rock interface, which is a process that occurs frequently in stratified strata. There are, however, different evolutionary processes that exist at the interface, from a total bonding stage to a plastic bonding stage, a slippage plastic bonding stage, a slippage plastic stage and a total slippage stage, sequentially. These processes accelerate the shortening speed of anchor life, whereupon axial force will fluctuate at each stage and corresponding equations can be derived successfully. Finally, a long-term field monitoring test which verifies the theoretical results and effective measures, such as pregrouting, can be used to prevent serial decoupling. The service life of the bolt system also can be prolonged.

Assessment of physical environment of primary schools in Mosul city

Background: Physical school environment considered one of the critical points for children growth and development. Schools are large places that present significant opportunities for getting an accident or infection. Objective: To assess the physical environmental health criteria of primary schools in Mosul city. Methods: A descriptive cross sectional study design has been adopted. A sample of 25 schools has been taken using multi-stage stratified stratum sampling technique. A special questionnaire form has been prepared depending on WHO criteria for schools environment. A separate questionnaire form has been filled by the investigator herself for each school. Results: Study results revealed that 52% of the schools are near a main street, 80%of schools are close to sources of pollution specially garbages, 20% of schools have maintained gardens, 72% of schools have inadequate faucets, 92% of schools have inadequate toilets. Whereas only 24% of toilets founds have good sanitary conditions. On the other hand only 20% of classrooms were found to be appropriate, 48% of schools were having inadequate lighting and 28% have inadequate ventilation. Keywords: School environment, primary school, physical.

Response of Human Skin Equivalents to <I>Sarcoptes scabiei</I>

Studies have shown that molecules in an extract made from bodies of the ectoparasitic mite, Sarcoptes scabiei De Geer, modulate cytokine secretion from cultured human keratinocytes and fibroblasts. In vivo, in the parasitized skin, these cells interact with each other by contact and cytokine mediators and with the matrix in which they reside. Therefore, these cell types may function differently together than they do separately. In this study, we used a human skin equivalent (HSE) model to investigate the influence of cellular interactions between keratinocytes and fibroblasts when the cells were exposed to active/burrowing scabies mites, mite products, and mite extracts. The HSE consisted of an epidermis of stratified stratum corneum, living keratinocytes, and basal cells above a dermis of fibroblasts in a collagen matrix. HSEs were inoculated on the surface or in the culture medium, and their cytokine secretions on the skin surface and into the culture medium were determined by enzyme-linked immunosorbent assay. Active mites on the surface of the HSE induced secretion of cutaneous T cell-attracting chemokine, thymic stromal lymphopoietin, interleukin (IL)-1alpha, IL-1beta, IL-1 receptor antagonist (IL-1ra), IL-6, IL-8, monocyte chemoattractant protein-1, granulocyte/macrophage colony-stimulating factor, and macrophage colony-stimulating factor. The main difference between HSEs and monocultured cells was that the HSEs produced the proinflammatory cytokines IL-1alpha and IL-1beta and their competitive inhibitor IL-1ra, whereas very little of these mediators was previously found for cultured keratinocytes and fibroblasts. It is not clear how the balance between these cytokines influences the overall host response. However, IL-1ra may contribute to the depression of an early cutaneous inflammatory response to scabies in humans. These contrasting results illustrate that cell interactions are important in the host's response to burrowing scabies mites.

Gas hydrate and chemosynthetic biota in mounded bathymetry at mid-slope hydrocarbon seeps: Northern Gulf of Mexico

We present nested surveys of four hydrocarbon seeps that contain abundant, shallow deposits of gas hydrate. The two sites mapped in greatest detail were at ∼550 m depths, the others at ∼1050 and ∼1900 m, respectively. Formation and dissociation of shallow deposits generated variability in seafloor geology and ecology that appeared to decrease at greater depths. The deposits typically formed mounds in a size range from a few meters to hundreds of meters in diameter and centimeters to tens of meters in height. These high-flux regions are also colonized by chemosynthetic species. At the two shallower seeps, data comprised laser line-scan mosaics, analog side-scan sonar mosaics, dense bathymetric grids, quantitative video records, 2–12 kHz chirp sub-bottom profiles and surface reflectance, 3D seismic data. Additional ground-truth data were obtained from piston cores and numerous animal and sediment collections. Datasets were assembled as GIS layers and geographically co-registered. In the shallower sites, gas hydrate deposits and extensive chemosynthetic communities were concentrated adjacent to lithified fault scarps where surface reflectance data from 3D seismic records showed the lowest amplitudes. Sub-bottom profiles revealed complex and abrupt transitions from regions in which surface strata appear as distinct, closely spaced layers to areas in which the strata were blanked by continuous, moderate-intensity returns. Within the blanked zone and adjacent to the normally stratified strata, the seafloor had a distinctively undulating profile caused by irregular hydrate deposits. Hydrate occurred as layers, which were ∼10 cm to >1 m thick, and generally buried under tens of centimeters of sediment, but occasionally exposed as outcrops on slopes. Sediments over hydrate deposits were covered with bacterial mats. Larger mounds were colonized by continuous aggregations of vestimentiferans tube worms. Outcropping hydrate deposits were colonized by the polychaete Hesiocaeca methanicola and by the seep mussel Bathymodiolus childressi. Streams of oil and gas escape from vents in the seafloor or from patches of exposed gas hydrate. The tube worms were most abundant in regions that reflected less seismic energy than the surrounding seafloor. At the deeper sites, preliminary survey results found similar topography, and biological colonies that included bacterial mats and mussels, but no active gas venting and very few colonies of tube worms. Negative surface reflectance amplitudes were also absent on these mounds. This suggests that development of chemosynthetic communities changes substantially with increasing depth.

Study of the Tensile Properties of Living Skin Equivalents

The living skin equivalent is one of the more advanced clinical applications in the field of tissue engineering. It is a promising therapeutic option for burn victims and a strong potential for manifold in vitro experiments. However, researchers have encountered major drawbacks in the reconstruction of the dermal layer. Peripheral anchorage of the dermal equivalent component has been a valuable solution to many of these problems. In this work, we have carried out the mechanical analysis of skin equivalent models, based on this dermal anchoring technique, with a study of their biaxial tensile properties. Differences between models were related to the origin of collagen, either bovine or human, and on the culture techniques: immersion or at the air-liquid interface. The study was accomplished in vitro using 25.4-mm-diameter disk-shaped specimens with an indentation test. In appropriate wet condition, the specimens were punctured with a spherical tip at a quasi-static rate. We measured the load applied against the tip vs deflection up to the breaking point. Our results show that skin equivalents presented a typical exponential load-deflection relationship. All skin equivalents presented large extensibility up to 1.41 expressed in a ratio of deflection vs specimen's radius. The maximum tensile strength (0.871-1.169 Newton) and energy calculations (3.75-6.432 N.mm) was offered by living skin equivalent, made with human types I and III collagens, cultured at the air-liquid interface. In these conditions, our results suggest the tensile properties of living skin equivalents were enhanced due to the development of well stratified stratum corneum.

Pathways of ionic flow through human skin in vivo

The pathways of electric current have been examined with special electrodes and methods. The results indicate that the flow through ordinary stratified stratum corneum is negligible, and that the dominant ionic path is through the sweat duct units. Here the cells of interest may be oriented perpendicular to the main stratified orientation of the skin, and this may affect the methods and interpretations of absorption/permeability studies.

Filtration problems with a piecewise-linear resistance law

The article discusses elementary solutions of problems of nonlinear filtration with a piece-wise-linear resistance law, and analyzes their behavior with a relative increase in the resistance in the region of small velocities, and a transition to the law of filtration with a limiting gradient. The results obtained are applied to a determination of the dimensions of the stagnant zones in stratified strata. The law of filtration with a limiting gradient $$\begin{gathered} w = - \frac{k}{\mu }\left( {grad p - G\frac{{grad p}}{{|grad p|}}} \right),|grad p| > G \hfill \\ w = 0,|grad p|< G \hfill \\ \end{gathered}$$ (0.1) describes motion in some intermediate range of velocities w, but its satisfaction in the region of the smallest velocities, as a rule, remains unverified. It is natural to pose the problem of the degree to which a divergence between the true filtration law and its approximation (0.1) affects the accuracy of calculation of the flow fields, and the significance of a determination of the dimensions of the stagnant zones under such conditions. To answer this problem to some measure, there are considered below several simple exact (elementary) solutions obtained for a more general nonlinear filtration law $$\begin{gathered} grad p = - (\mu /k) (w + \lambda )w/w,\lambda = kG/\mu ,w \geqslant w_0 \hfill \\ grad p = - \mu w/k\varepsilon ), w \leqslant w_0 ,\varepsilon = w_0 /w_0 + \lambda \hfill \\ \end{gathered}$$ (0.2) going over into (0.1) with w0→ 0. The solutions obtained are applied also to an evaluation of the dimensions of stagnant zones, forming in stratified strata when the effects of the limiting gradient in one of the intercalations are considerable.

Nonlinear fully established filtration of a liquid in a stratified stratum

Nonlinear fully established filtration of a liquid in a stratified stratum