Thin-layer Method Research Articles

The Essential Oil of Rocket Seeds Maintains Its Antibacterial Effects After Encapsulation in Nanoliposomes

IntroductionIt has been demonstrated that the essential oil (EO) of Eruca sativa seeds could be potentially used as an antiseptic agent. However, the application of EOs is restricted because of their chemical instability and volatility. Encapsulation in liposomes is an efficient technique for the protection of the oils. MethodsThe EO of the seeds was obtained using the hydro-distillation method. Liposomal formulation of the oil was prepared using thin layer method. ResultsGC/MS analysis indicated that erucin (1-isothiocyanato-4-methylsulfanylbutane) was the main compound of the oil, accounting for 88.86%. The prepared oil-loaded liposomes had more negative zeta potential (−17.13 mV) compared with the empty liposomes (−9.26 mV), indicating the higher stability of the liposomal oil. SEM imaging confirmed that the encapsulation of the oil does not cause any distortion in the structure of the liposomes, in comparison to the oil-free liposomes. The seed oil showed antimicrobial activities at 20 μg/ml (against Staphylococcus aureus, Enterobacter aerogenes, and Escherichia coli) and 80 μg/ml (against Enterococcus faecalis, Pseudomonas aeruginosa, and Klebsiella pneumonia), while the minimum inhibitory concentration values of the liposomal EO were 160 μg/ml against E faecalis, 80 μg/ml against P aeruginosa and K pneumonia, and 20 μg/ml against S aureus, E aerogenes, and E coli. ConclusionsAntibacterial experiments revealed that the EO of Eruca sativa seeds maintained its antibacterial effect after loading into the liposomes. Moreover, encapsulation in liposomes could improve the sustainability of the oil and increased the bioavailability of its active chemical compounds.

Physicochemical Characteristics of Porous Starch Obtained by Combined Physical and Enzymatic Methods-Part 2: Potential Application as a Carrier of Gallic Acid.

Wettability measurements were performed for aqueous dispersions of native and modified corn, potato, and pea starch granules deposited on glass plates by the thin layer method using test liquids of a different chemical nature (polar water and formamide or non-polar diiodomethane). High values of the determination coefficient R2 confirm that the linear regression model describes the relationship between the wetting time and the square of the penetration distance very well, indicating the linear nature of the Washburn relationship. A change in free energy (enthalpy) during the movement of the liquid in the porous layer was determined for all starches before and after modification in contact with test liquids. Wetting times for polar liquids increased significantly (from 3 to 4 fold), especially for corn starch. The lower the value of the adhesive tension, the easier the wetting process takes place, and consequently, the adsorption process is facilitated. Adhesive tension for polar substances applies to the adsorption of hydrophilic substances, while in the case of apolar substances, adhesive tension applies to the adsorption of hydrophobic substances. For the adsorption of gallic acid on starch, the relationships obtained for polar substances are crucial. The adsorption of gallic acid by forming hydrogen bonds or, more generally, donor-acceptor (acid-base) bonds is definitely higher for corn starch than other starches. Therefore, this starch has the most significant potential for use as a carrier of gallic acid or, more broadly, compounds from the polyphenol group.

Assessment of Antimicrobial and Cytotoxic Activities of Liposomes Loaded with Curcumin and Lippia origanoides Essential Oil.

(1) Introduction: Curcumin and Lippia origanoides essential oils have a broad spectrum of biological activities; however, their physicochemical instability, low solubility, and high volatility limit their therapeutic use. Encapsulation in liposomes has been reported as a feasible approach to increase the physicochemical stability of active substances, protect them from interactions with the environment, modulate their release, reduce their volatility, improve their bioactivity, and reduce their toxicity. To date, there are no reports on the co-encapsulation of curcumin and Lippia origanoides essential oils in liposomes. Therefore, the objective of this work is to prepare and physiochemical characterize liposomes loaded with the mixture of these compounds and to evaluate different in vitro biological activities. (2) Methods: Liposomes were produced using the thin-layer method and physiochemical characteristics were calculated. The antimicrobial and cytotoxic activities of both encapsulated and non-encapsulated compounds were evaluated. (3) Results: Empty and loaded nanometric-sized liposomes were obtained that are monodisperse and have a negative zeta potential. They inhibited the growth of Staphylococcus aureus and did not exhibit cytotoxic activity against mammalian cells. (4) Conclusions: Encapsulation in liposomes was demonstrated to be a promising strategy for natural compounds possessing antimicrobial activity.

Effect of ultrasound exposure time in the size distribution of lecithin liposomes in the nanoscale

Abstract The characteristics of liposome suspensions subjected to ultrasound were studied using the Nanoparticle Trajectory Analysis (NTA) technique. These were prepared with either DPPC or soy lecithin using the thin layer method. For each preparation protocol, the size and ζ potential probability densities were determined by averaging the densities obtained in several measurements. Ultrasound exposure changed the characteristics of the size and ζ potential distributions. For the size distribution, the exposure resulted in an increment of the number of liposomes with diameters in the range of ∼ 100 nm, the corresponding size distributions became slimmer, with mean diameters smaller than the ones without exposure. This is reflected in the reduction of the polydispersity index experienced by the liposome suspensions after sonication. For DPPC liposomes, it changed from ≈ 0.26 without exposure to ≈ 0.19 after 10 min sonication whereas for soy lecithin liposomes it changed from ≈ 0.30 without exposure to ≈ 0.21 after 10 min sonication. For the ζ potential, after 10 min exposure, the distributions became wider, with mean values more negative than the ones without exposure. The mean ζ potential, for DPPC liposomes, changed from ≈ −35 mV without exposure to ≈ −39 mV after 10 min sonication whereas for soy lecithin liposomes it changed from ≈ −38 mV without exposure to ≈ −42 mV after 10 min sonication. Therefore, our results show that exposure to ultrasound reduced the polydispersity and increased the stability of the liposome suspensions.

Simplified Tunnel–Soil Model Based on Thin-Layer Method–Volume Method–Perfectly Matched Layer Method

In order to analyze the ground vibration responses induced by the dynamic loads in a tunnel, this paper proposes a new simplified tunnel–soil model. Specifically, based on the basic theory of the thin-layer method (TLM), the basic solution of three-dimensional layered foundation soil displacement was derived in the cylindrical coordinate system. The perfectly matched layer (PML) boundary condition was applied to the TLM. Subsequently, a tunnel–soil dynamic interaction analysis model was established using the volume method (VM) in conjunction with the TLM-PML method. The displacement frequency response function of the foundation soil around the tunnel foundation was derived. Finally, a ground vibration test under an impact load in a tunnel was carried out. The test and calculated results were compared. The comparison results show that the ground vibration acceleration response values within 25 m from the load are similar. Compared with the test results, the theoretical calculation results exhibit a decreasing trend in the range of 40–80 Hz between 25 and 60 m, with the maximum reduction being approximately one order of magnitude. In addition, the experimental comparison demonstrates that the model can be used to analyze the ground vibrations caused by underground loads.

Response surface methodology mediated optimization of phytosulfokine and plant growth regulators for enhanced protoplast division, callus induction, and somatic embryogenesis in Angelica Gigas Nakai

BackgroundAngelica Gigas (Purple parsnip) is an important medicinal plant that is cultivated and utilized in Korea, Japan, and China. It contains bioactive substances especially coumarins with anti-inflammatory, anti-platelet aggregation, anti-cancer, anti-diabetic, antimicrobial, anti-obesity, anti-oxidant, immunomodulatory, and neuroprotective properties. This medicinal crop can be genetically improved, and the metabolites can be obtained by embryonic stem cells. In this context, we established the protoplast-to-plant regeneration methodology in Angelica gigas.ResultsIn the present investigation, we isolated the protoplast from the embryogenic callus by applying methods that we have developed earlier and established protoplast cultures using Murashige and Skoog (MS) liquid medium and by embedding the protoplast in thin alginate layer (TAL) methods. We supplemented the culture medium with growth regulators namely 2,4-dichlorophenoxyaceticacid (2,4-D, 0, 0.75, 1.5 mg L− 1), kinetin (KN, 0, 0.5, and 1.0 mg L− 1) and phytosulfokine (PSK, 0, 50, 100 nM) to induce protoplast division, microcolony formation, and embryogenic callus regeneration. We applied central composite design (CCD) and response surface methodology (RSM) for the optimization of 2,4-D, KN, and PSK levels during protoplast division, micro-callus formation, and induction of embryogenic callus stages. The results revealed that 0.04 mg L− 1 2,4-D + 0.5 mg L− 1 KN + 2 nM PSK, 0.5 mg L− 1 2,4-D + 0.9 mg L− 1 KN and 90 nM PSK, and 1.5 mg L− 1 2,4-D and 1 mg L− 1 KN were optimum for protoplast division, micro-callus formation and induction embryogenic callus. MS basal semi-solid medium without growth regulators was good for the development of embryos and plant regeneration.ConclusionsThis study demonstrated successful protoplast culture, protoplast division, micro-callus formation, induction embryogenic callus, somatic embryogenesis, and plant regeneration in A. gigas. The methodologies developed here are quite useful for the genetic improvement of this important medicinal plant.

Migration and Transformation of Taxane Allelochemicals in Soil.

The migration and transformation of allelochemicals are important topics in the exploration of allelopathy. Current research on the migration of allelochemicals mostly uses soil column and thin layer methods and verifies it by sowing plant seeds. However, traditional methods inevitably ignore the flux caused by the movement of allelochemicals carried by water. In fact, the flux determines the amount of allelochemicals that directly affect plants. In this work, a method of microdialysis combined with a soil column and UPLC-MS/MS to detect the flux of allelochemicals was developed for the first time and successfully applied to the detection of five taxane allelochemicals in soil. Meanwhile, by adding taxane allelochemicals to the soil and detecting their transformation products using UPLC-MS/MS, the half-life of taxane in the soil was determined, and the transformation pathway of taxane allelochemicals in the soil was further speculated.

Higher-order thin layer method as an efficient forward model for calculating dispersion curves of surface and Lamb waves in layered media

The thin layer method (TLM) is an effective semi-discrete numerical tool for analyzing wave motion in stratified media. The TLM can calculate the eigenvalues and eigenvectors for both propagating and decaying waves, which is essential to simulate waves near the source. The eigenvectors are particularly useful in various applications, such as estimating modal contributions, calculating synthetic seismograms, determining Green’s function, analyzing site response, and solving wave amplification problems in earthquake engineering, to name a few. In practice, most engineering applications use linear element-based TLM. However, the overall performance of TLM depends upon the type of element and the number of thin layers. The linear element TLM requires relatively thin sub-layers to obtain an accurate solution, making it computationally expensive and time-consuming. This study explores the potential of using non-linear higher-order TLM (HTLM) for forward modeling. The mathematical framework of TLM is used to formulate the generalized HTLM in determining the multimodal dispersion curve of Rayleigh, Love, and Lamb waves. The convergence and computational efficiency of different orders of HTLM have been investigated on a diverse set of published soil profiles and plate-like structures. Since non-linear interpolation functions better capture the change in displacement and stress between the layers, the findings reveal that the HTLM consistently outperforms the linear element TLM in terms of accuracy. Furthermore, the computational efficiency of different order HTLM is analyzed by comparing the total degrees of freedom and CPU time. Remarkably, higher-order HTLMs exhibit improved accuracy without increasing the computational burden, making them an attractive option for practical applications such as global search-based inversion and full spectrum inversions where fast and economical forward modeling is essential. Therefore, the HTLM will become helpful in seismic wavefield modeling, dynamic soil characterization, non-destructive evaluation methods, wave propagation analysis through waveguides, seismic site response analysis, etc.

EFFECT OF SKIN FAT ON CAPSAICIN TRANSFERSOME GEL: IN VITRO PENETRATION STUDIES USING FRANZ DIFFUSION CELLS

Objective: Capsaicin is a highly lipophilic substance that generally uses an organic cosolvent added to diffusion medium in penetration tests to increase penetration by fluidizing fat. This study aims to determine the effect of subcutaneous fat on the penetration of capsaicin as lipophilic substances formulated into transfersome and compare it to hydrophilic substances, namely vitamin C. Methods: The thin layer method was used to develop the transfersome formulation using Phospholipon 90G and Tween 80. Vesicle size, zeta potential, deformability index, morphology, and entrapment efficiency were all characterized. The transfersome suspension was then developed into a gel formulation using 1% carbomer. The in vitro penetration test was performed using a Franz diffusion cell of rat skin with and without subcutaneous fat. Results: The cumulative amount of penetration on fat-free membranes compared to membranes with fat for capsaicin transfersome gel 920.28±3.42 μg/cm2 and 762.22±1.73 μg/cm2, respectively, then for non-transfersome capsaicin gel was 833.33±0.84 μg/cm2 and 595.80±0.32 μg/cm2 respectively, and for vitamin C non-transfer some gel 776.45±1.19 μg/cm2 and 654.69±3.36 μg/cm2 respectively. Conclusion: According to these results, it can be concluded that the presence of subcutaneous fat affects inhibiting the penetration of lipophilic substances.

The mechanics of the Gentle Driving of Piles

Gentle Driving of Piles (GDP) is a new vibratory installation technology for tubular (mono)piles. It is characterized by the simultaneous application of low-frequency axial and high-frequency torsional vibrations, envisaged to achieve both high installation performance and reduced underwater noise emissions. The concept of GDP has been demonstrated experimentally in a medium-scale onshore field campaign, showcasing the potential of the method in terms of installation and post-installation performances. To further comprehend the mechanics of the GDP method, the driving process is studied by means of a novel pile–soil model; this framework has been recently developed and successfully applied to the problem of axial vibratory driving. In particular, the pile is treated as a thin cylindrical shell via a Semi-analytical Finite Element (SAFE) approach and a linear elastic layered soil half-space is considered via the Thin-Layer Method (TLM) coupled with Perfectly Matched Layers (PMLs). The pile–soil coupling is realized through a hereditary frictional interface and an elasto-plastic tip formulation, both characterized by standard geotechnical in-situ measurements. The comparison of numerical results with field data is favourable for drivability purposes, showcasing the potential of the numerical framework for the analysis of GDP. Conclusively, the mechanics of the installation process are deciphered and the redirection of the friction force vector – induced by high-frequency torsion – is identified as the main driving mechanism of GDP.

Higher-order thin layer method (HTLM) based wavefield modeling approach

Traditional free vibration-based forward modeling approaches provide only the theoretical modal solution that lacks information regarding modal amplitudes. Moreover, they ignore the influence of source-receiver layout on the wavefield. Numerical wavefield modeling approaches can generate a dispersion spectrum mimicking the actual field test; however, numerical methods are not efficient in terms of computational time and produce numerical artifacts. Furthermore, they can be contaminated with leaky waves for soil strata with a high Poisson's ratio. This study presents a new wavefield modeling approach for developing full dispersion spectra of stratified media incorporating source-receiver configuration. The proposed method calculates the theoretical modal amplitude using the higher-order thin layer method and determines the vertical displacement responses at specified virtual receiver positions in the frequency-space domain. Afterward, it searches for spectral values at each frequency over a broad range of trial phase velocities to create a full dispersion spectrum. The accuracy and computational efficacy of the present method are demonstrated on different soil profiles adopted from literature, including normally dispersive media, irregularly dispersive media with high-velocity contrast, and a crustal level model. Results indicate the proposed approach can clearly distinguish the relative spectral amplitude of each mode and dominant dispersion trend. Calculated seismograms and dispersion images are compared with the existing 2D staggered grid finite difference method. Although both methods yield similar results, the current method is at least two orders (x102) faster than the staggered grid finite difference method. Unlike numerical approaches, the proposed method does not require additional computational resources to model materials with a high Poisson's ratio. Furthermore, it minimizes the contamination of leaky waves in the dispersion spectrum when modeling a high Poisson's ratio. The proposed method does not produce any numerical artifacts and can be used to generate accurate synthetic seismograms as well as dispersion spectra. In addition, the proposed wavefield modeling approach can be effectively used to develop an accurate and faster inversion scheme by including the entire dispersion spectrum.

Lumped parameter model for vertical vibrations of surface circular foundations on nonhomogeneous soil

PurposeA newly developed frequency-independent lumped parameter model (LPM) is the purpose of the present paper. This new model’s direct outcome ensures high efficiency and a straightforward calculation of foundations’ vertical vibrations. A rigid circular foundation shape resting on a nonhomogeneous half-space subjected to a vertical time-harmonic excitation is considered.Design/methodology/approachA simple model representing the soil–foundation system consists of a single degree of freedom (SDOF) system incorporating a lumped mass linked to a frequency-independent spring and dashpot. Besides that, an additional fictitious mass is incorporated into the SDOF system. Several numerical methods and mathematical techniques are used to identify each SDOF’s parameter: (1) the vertical component of the static and dynamic foundation impedance function is calculated. This dynamic interaction problem is solved by using a formulation combining the boundary element method and the thin layer method, which allows the simulation of any complex nonhomogeneous half-space configuration. After, one determines the static stiffness’s expression of the circular foundation resting on a nonhomogeneous half-space. (2) The system’s parameters (dashpot coefficient and fictitious mass) are calculated at the resonance frequency; and (3) using a curve fitting technique, the general formulas of the frequency-independent dashpot coefficients and additional fictitious mass are established.FindingsComparisons with other results from a rigorous formulation were made to verify the developed model’s accuracy; these are exceptional cases of the more general problems that can be addressed (problems like shallow or embedded foundations of arbitrary shape, other vibration modes, etc.).Originality/valueIn this new LPM, the impedance functions will no longer be needed. The engineer only needs a limited number of input parameters (geometrical and mechanical characteristics of the foundation and the soil). Moreover, a simple calculator is required (i.e. we do not need any sophisticated software).

A non-linear three-dimensional pile–soil model for vibratory pile installation in layered media

This paper presents a computationally efficient model for vibratory pile installation. A semi-analytical finite element (SAFE) model for thin cylindrical shells is derived to represent the pile. The linear dynamic response of the soil medium is described by means of Green’s functions via the Thin-Layer Method (TLM) coupled with Perfectly Matched Layers (PMLs) to account for the underlying elastic half-space. Furthermore, the non-linear pile–soil interaction is addressed through a history-dependent frictional interface and a visco-elasto-plastic tip reaction model that can be characterized on the basis of standard geotechnical in-situ measurements. The solution to the non-linear dynamic pile–soil interaction problem is based on the sequential application of the Harmonic Balance Method (HBM). The constituent components of the model are first benchmarked against established numerical schemes. Subsequently, model predictions are compared with experimental data collected from field tests. It is demonstrated that the proposed model amalgamates rigorous theoretical elements and promising prediction capabilities in a computationally efficient framework, applicable to engineering practice.

A Thin Layer Method for the LA-ICP-MS Analysis of Trace Element Concentrates

A method is proposed for the analysis of trace element concentrates by a thin layer method in combination with inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation (LA). Trace elements concentrates were evaporated on preliminarily prepared areas of a high-purity silicon substrate, after which an LA-ICP-MS analysis was performed. The influence of the LA parameters and the conditions for recording the spectra on the signal of the analytes and the substrate material was studied. The analytical capabilities of the thin layer method in combination with LA-ICP-MS for the analysis of high-purity substances with the preconcentration of trace elements were evaluated. Using an analysis of high-purity nitric acid as an example, it was shown that the limits of detection for analytes in the LA-ICP-MS analysis of trace element concentrates using the thin layer method are in the range from n × 10–11 to n × 10–8 wt %. Thus, the development of combined procedures of analysis, including the preconcentration of trace elements and an analysis of concentrates by LA-ICP-MS, makes it possible to reduce the limits of detection for most analytes by one order of magnitude compared to instrumental ICP-MS analysis.

Carbon dioxide partial pressures and emissions of the Yarlung Tsangpo River on the Tibetan Plateau

Rivers are important routes for material and energy transport between terrestrial and marine ecosystems. Recent global-scale assessments of carbon (C) have suggested that C emission fluxes to the atmosphere are comparable to the fluvial C fluxes to the ocean. However, many previous studies only collected data from inland rivers in low altitude regions. Therefore, it remains unclear how plateau rivers affect C flux. In this study, 20 monitoring sites were set up along the Yarlung Tsangpo (YT) River on the Tibetan Plateau and detailed observations were carried out in the wet and dry seasons. The riverine CO2 fluxes exhibited significant seasonal patterns which ranged from 597.12 ± 292.63 μatm in the wet season to 368.72 ± 123.50 μatm in the dry season. The CO2 emission flux (FCO2) obtained from floating chamber method, ranging from 8.44 ± 6.94 mmol m−2 d−1 in sunmmer to 3.62 ± 6.32 mmol m−2 d−1 in winter, with an average value of 6.03 mmol m−2 d−1. Generally, the river was a weak carbon source with respect to the atmosphere. However, the pCO2 and FCO2 were much lower than that for other large rivers around the globe, which were obviously restrained by the weak microbial activities due to the low primary productivity and carbonate buffer activities in the carbonate background. Carbon loss via atmosphere exchange in the YT River on the plateau accounted for 2.2% and 10.6% of the riverine dissolved carbon fluxes (67.77 × 109 mol a−1) according to the floating chamber and thin boundary layer methods, respectively. The YT River probably acts as a “pipeline” to transport weathered nutrients from the plateau to downstream areas. Our results demonstrated the characteristics of a “weak outgassing effect and a high transport flux of carbon” for the plateau river, which is different from rivers on plains. Considering the global relevance of Tibetan Plateau, further studies with enhanced spatiotemporal resolution are needed to better understand the important role of plateau rivers on carbon budgets and climate change over both regional and global cycles.

Application of the Unscented Kalman Filter to Estimate the Material Properties of a Layered Half-Space

Full waveform inversion (FWI) to estimate physical properties of a system is one of the major research topics in science and engineering. This study proposes a probabilistic approach toward these solutions by applying the unscented Kalman filter (UKF). The responses of the vertical displacements of a layered half-space subjected to a harmonic vertical disk load on the surface are calculated from an estimated profile of shear-wave velocities and compared with measurements or observations. In the calculation of the dynamic responses, the thin-layer method (TLM), which is efficient for layered media, is employed. In order to improve the solutions to the considered inverse problem, regularization terms are included in the observations so that the differences in the material properties between two consecutive layers vanish. The proposed UKF method is demonstrated with a variety of FWI problems in a layered half-space. The results show that the proposed method can estimate the material properties of a layered half-space accurately.

Study on the Influence of Origin and Vinegar Roasting Process on the Chemical Composition of Nutgrass Galingale Rhizome

To provide a basis for the development of quality standards by studying the changes in the chemical composition of nutgrass galingale rhizome of different origins, before and after its vinegar roasting and to provide a basis for the correct evaluation of the quality changes of nutgrass galingale rhizome of different origins, before and after its vinegar roasting. A thin-layer method was developed to identify the water-soluble components of aconite. The volatile oil content of nutgrass galingale rhizome was determined according to the volatile oil determination method in Appendix XVI, Part I of the 2010 Chinese Pharmacopoeia. The volatile oil content of nutgrass galingale rhizome from Shandong and Anhui was higher (1.59 % and 1.61 %), while the volatile oil content of nutgrass galingale rhizome from Guangdong was the lowest (1.14 %). The highest content of beta-sitosterol was found in Anhui (0.017923 %) and the lowest in Guangdong (0.010893 %). The total flavonoid content of nutgrass galingale rhizome from Henan was the highest (0.95381 %) and the total flavonoid content of nutgrass galingale rhizome from Shandong was the lowest (0.63565 %). The volatile oil content and beta-sitosterol content decreased and the total flavonoid content increased in all three groups after vinegar roasting. Shandong and Anhui Nutgrass Galingale Rhizome have better medicinal efficacy and the use of vinegar roasting method for the concoction of nutgrass galingale rhizome is reasonable.

THIN NICKEL LAYER BEHAVIOUR IN NATURAL SEA WATER

Various methods were used, in order to protect the material base; the study subject has been put under various conditions and were thus implemented in an attempt to prolong the operating life and to require less maintenance and replacement of parts. Pulsed laser deposition method was used to cover a S 235 carbon steel sample with a thin nickel film, using laser ablation and thus obtaining a protective layer, offering increased corrosion resistance. S 235 carbon steel samples were covered on a single face with thin films. The material used for laser ablation is nickel. The samples were immersed for 126 days in static seawater at ambient temperature and were individually weighted on the analytic balance at different time intervals, in order to determine the corrosion process speed. The study was performed by employing the gravimetric method. Through the corrosion research process using the gravimetric method, the parallelepiped samples covered with Ni using pulsed laser deposition were immersed 126 days in static sea water at environment temperature. The corroded surfaces, after being submerged in seawater, were investigated using optical microscopy and atomic force microscopy. Atomic force microscopy investigations performed on long-term corrosion-tested samples highlight areas with compact and homogeneous surfaces that did not allow the corrosive agent to interact with the base material, a fact confirmed by optical metallographic analysis. Wave mode images show discontinuities of surface-deposited incipient corrosion points that are possible pathways of the corrosive agent to the sample material. The analysis made on one side thin film covered sample, after a long term corrosion test, using atomic force microscopy investigation and gravimetric test, shows the rate of corrosion, the discontinuities of the surface and the corrosion pitting in the material. Evaluating the method of thin film deposition layer leads to the obtainment of high reliability and low cost material parts using this method. The corrosion rate is established, remains constant and protection of the material base is achieved.

Forest trees as a natural metamaterial for surface wave attenuation in stratified soils

Forest trees have been shown to act as a natural metamaterial to attenuate elastic waves. However, the existing studies assumed that forest trees are located on homogeneous soils and did not consider the soil stratification that widely exists in natural strata. This study investigates the forest trees as a natural metamaterial to manipulate the propagation of elastic waves in stratified soils. A semi-analytical method is proposed to calculate the dynamic responses of a layered half-space coupled with arbitrary number of trees. A close-form Green’s function for a harmonic line load on a layered half-space is derived by the thin layer method, and subsequently used to determine the multiple scattered wavefield induced by forest trees as surface oscillators. The attenuation performance of forest trees on stratified soils is systematically investigated. Trees with a graded array of heights can provide a wide attenuation zone at frequencies below 80 Hz. Since the higher surface wave modes in a layered half-space can propagate forward without being affected by trees, the attenuation efficiency of trees on stratified soils is significantly lower than that of trees on corresponding homogeneous soils. The performance uncertainty induced by the randomness of the height, sizes, and spacing of trees is subsequently investigated through a Monte Carlo simulation. The forest trees can still obtain a significant attenuation efficiency at frequencies below 80 Hz even the randomness of tree properties being considered. The randomness in height and radius leads to significant uncertainty in attenuation performance, while the randomness in spacing results in reasonable uncertainty.

Probabilistic Full-Waveform Inversion Considering the Discontinuities of the Material Properties of a Layered Half-Space

The goal of full-waveform inversion (FWI) is to extract quantitative information pertaining to the material and geometrical properties from measured wave fields with their full contents considered. As an inverse problem, FWI itself is associated with ill-posedness, which means instability and nonuniqueness of the solution, because the fields are measured only at some locations. Owing to these unfavorable conditions, several regularization techniques have been utilized for stable estimations, but it is difficult when using a regularization technique to select a regularization factor, which has no physical meaning. In this paper, the FWI approach is applied to estimate the material properties of a layered half-space. The thin-layered method, an efficient analysis method for wave propagation in a layered medium, is employed for this purpose. It is formulated in the maximum a posteriori (MAP) form, and Tikhonov regularization is expressed as a prior distribution, whose standard deviation replaces the role of the regularization factor to ensure an intuitive meaning. Additionally, a technique to remove outliers is newly introduced for the regularization technique; it captures discontinuities accurately in the material properties of a layered half-space. Through this additional technique, the limitation of the smoothness effect in existing regularization techniques is alleviated. The proposed MAP approach including the regularization-based prior and outlier-removal technique is applied to several numerical examples to estimate the profiles of the shear velocities of a layered half-space. The numerical investigations conducted here confirm the validity of the proposed approach with satisfactory accuracy.