Thin-layer Method Research Articles

Three-dimensional transient half-space dynamics using the dual reciprocity boundary element method

The dual reciprocity boundary element method (DRBEM) is studied thoroughly in the present paper. To the best knowledge of the authors, the DRBEM has never been applied to 3D half-space dynamics previously. In the present paper, the mathematical derivation of the method is presented, with stress placed on peculiarities of the method when applied to transient half-space dynamics. It has been found that semi-infinite domains (half-space) are more difficult to simulate, since the truncation of the discretization of the half-space surface by boundary elements results in excessive spurious wave reflection on the border of the discretized region. Mathematical derivation of the method is followed by its numerical implementation. Wave propagation due to various kinds of loading in the time-domain is studied afterward, aimed at the validation of the method. The main advantage of the DRBEM over its counterparts, used to model infinite and semi-infinite domains (such as classical BEM formulation, integral transformations, thin layer method), is that it produces time- and frequency-independent matrices (mass and stiffness matrix), by preserving a boundary-only discretization (no internal nodes necessary). This makes the method very attractive, since this feature is very close to the common engineering understanding and the final equation of motion has a similar form like the one known from the finite element method. Moreover, the formulation allows for seamless incorporation of non-homogeneous initial conditions, i.e. non-zero initial displacements and velocities and surface tractions can be prescribed.

Analyses of wave field from high-speed train on viaduct at shallow/deep soft grounds

In this paper, based on field measurements for the passage of the Shinkansen high speed trains on viaducts, the author reports the induced ground vibration features at distinctly different sites: one site is characterized by a deep soft soil and the other by a shallow soft soil both of which lie on stiff bottom. The conventional vibration assessment is normally addressed to the vibration levels based on acceleration maxima. However, in view of the vibration reception by nearby residents, firstly, a detailed investigation is attempted on the recorded time histories and on their Fourier spectra, locating the so-called low frequency vibration generation at the former site and such vibration impediment at the latter site. Then, theoretical consideration is to clarify the Shinkansen-train induced ground vibrations from a viaduct. The characterization based on the wave theory using the thin layer method reveals that, depending on the depth of surface layer, the ground-borne vibration is of significantly low frequency wave modes of dispersive propagation when it is deep or it makes the wave modes shifted towards higher frequency range when it is shallow. This finding makes an important element to better predict and assess vibration level and to develop barriers against it for mitigation.

Development and Validation of a TLC-Densitometric Method for the Simultaneous Quantitation of Strychnine and Brucine from Strychnos spp. and its Formulations

A simple, sensitive, and specific thin-layer chromatography densitometric method has been developed for the simultaneous quantitation of strychnine and brucine. These two marker compounds are quantitated in the seeds of Strychnos nux-vomica, Strychnos ignatii, and its formulations. The method involves densitometric evaluation of strychnine and brucine after resolving it by high-performance TLC on silica gel plate with toluene-ethyl acetate-diethyl amine-methanol (7:2:1:0.3 v/v) as the mobile phase. The method is validated for precision (interday and intraday), repeatability, and accuracy. The relationship between the concentration of standard solutions and the peak response is linear within the concentration range of 160 to 480 ng/spot for strychnine and 80 to 480 ng/spot for brucine. Instrumental precision is found to be 0.54 and 0.78 (% CV), and repeatability of the method is 1.01 and 1.06 (% CV) for strychnine and brucine, respectively. Accuracy of the method is checked by recovery study conducted at three different levels and the average percentage recovery is found to be 99.13% for strychnine and 100.16% for brucine. The proposed HPTLC method for the simultaneous quantitation of strychnine and brucine is found to be simple, precise, specific, sensitive, and accurate, and it can be used for routine quality control of raw material of Strychnos spp. It also can be applied in quantitating any of these marker compounds in other formulations.

Three-dimensional absorbing boundary for analysis of fluid-saturated porous media

Saturated porous media shows a complicated interaction behaviour of solid and fluid. The new formulation, called thin layer method, is able to absorb all kind of energies. It computes the associated mode shapes for both Rayleigh and Love surface waves in saturated soil. In this method, effect of pore water pressure generation is considered in three-dimensional condition. In the soil-structure interaction analysis the submerged condition affects significantly the characteristics of the waves generated by the dynamic excitations and increases the soil stiffness when loading rate is fast relative to the pore fluid diffusions rate. The present method can take into account the effects of pore fluid motions relative to the soil skeleton and thus the effects of submerged soil. Good results with compare to analytical solution in spite of zero distance between structure and boundary shows that this absorbing boundary can greatly suppress spuriously reflected waves and efficiently model the far field of the system with sufficient accuracy.

Development and Evaluation of Thin-Layer Chromatography-Digital Image-Based Analysis for the Quantitation of the Botanical Pesticide Azadirachtin in Agricultural Matrixes and Commercial Formulations: Comparison with ELISA

A simple thin-layer chromatography-digital image-based analytical method has been developed for the quantitation of the botanical pesticide, azadirachtin. The method was validated by analyzing azadirachtin in the spiked food matrixes and processed commercial pesticide formulations, using acidified vanillin reagent as a postchromatographic derivatizing agent. The separated azadirachtin was clearly identified as a green spot. The Rf value was found to be 0.55, which was similar to that of a reference standard. A standard calibration plot was established using a reference standard, based on the linear regression analysis [r2 = 0.996; y = 371.43 + (634.82)x]. The sensitivity of the method was found to be 0.875 microg azadirachtin. Spiking studies conducted at the 1 ppm (microg/g) level in various agricultural matrixes, such as brinjal, tomato, coffee, and cotton seeds, revealed the recoveries of azadirachtin in the range of 67-92%. Azadirachtin content of commercial neem formulations analyzed by the method was in the range of 190-1825 ppm (microg/mL). Further, the present method was compared with an immunoanalytical method enzyme-linked immonosorbent assay developed earlier in our laboratory. Statistical comparison of the 2 methods, using Fischer's F-test, indicated no significant difference in variance, suggesting that both methods are comparable.

Contribution of Humidity to the Lethality of Surface-Attached Heat-Resistant Salmonella during the Thermal Processing of Cooked Ready-to-Eat Roast Beef

To provide meat processors with data to assess the safety of cooked ready-to-eat roast beef production parameters, a study was conducted to determine the contribution of humidity to the lethality of salmonellae during thermal processing. Destruction of Salmonella during thermal processing at different levels of humidity and a constant cooking temperature of 82.2°C was examined. Raw beef top round roasts purchased from a commercial supplier were inoculated with a seven-strain cocktail of heat-shocked Salmonella. Inoculated roasts were thermally processed to an internal temperature of 62.8°C at0to 90% humidity. Salmonella counts were determined utilizing the thin agar layer method on xylose-lysine-desoxychlolate agar to facilitate the enumeration of injured cells. Significant differences (P < 0.05) in Salmonella counts were observed between roasts processed at 30% humidity and those processed at 15% humidity or lower. Salmonella reductions were less than the regulatory performance standard of 6.5 log units at a humidity of <30%. These results indicate that cooked ready-to-eat roast beef can be safely processed under conditions outside of the U.S. Department of Agriculture (USDA) Food Safety and Inspection Service “safe harbor” guidelines. However, the results also indicate that one of these current safe harbor guidelines for the production of cooked ready-to-eat roast beef ≥62.8°C product internal temperature with humidity introduced for ≥50% of the cooking cycle) could result in a finished product that does not meet USDA performance standards. This specific guideline should be clarified with a minimum relative humidity requirement to ensure the production of a safe product.

Influence of the soil profile randomness on the seismic response of multilayered soils with a rigid inclusion

AbstractThe paper deals with the seismic response of a multilayered soil. It focuses on the influence of the uncertainty that may affect the soil height (SH). The soil under study is considered as a superposition of layers that extend horizontally to infinity. A tunnel, located inside this soil, is supposed to behave as a rigid inclusion; it represents a part of the Algiers subway. Its dynamical response is investigated under Boumerdes earthquake effect, 21 May 2003 (MW =6.5). The soil accelerations are collected at Keddara station (12 from the epicentre) as it corresponds to bedrock. As the study is devoted herein to SH wave propagation, the accelerations under study correspond to the EW horizontal direction.The SH below the tunnel is assumed to be a random variable. For this purpose, a log‐normal distribution is adopted. The probabilistic seismic response of the soil is thus investigated. The mean and standard deviation of the tunnel displacement as well as of both the extreme ground acceleration and the transfer function are analysed. The present analysis is based on the boundary element method, which is adequate for the case of systems with infinite boundaries, while Green's functions are calculated using the thin layer method. Copyright © 2007 John Wiley &amp; Sons, Ltd.

薄層法を用いた理論地震動の計算精度向上とその検証

Thin layer method is numerically effective tool to evaluate theoretical ground motions due to large-scale seismic fault, especially when fault parmeters have large complexity or soil property gradually varies in depth direction. In spite of those advantages, there remain several problems in connection with its formulation, e.g., discretization artifacts, artifical reflection of waves impinging at the bottom, and numerical instability when epicentral distance is extremely small. This paper describes some modeling techniques to improve these numerical problems and shows its validation. This method is also applied to ground motion evaluation at near-fault, surface faulting and the 2007 Noto Hanto earthquake.

ON QUANTIZATION OF SYSTEMS WITH SECOND CLASS CONSTRAINTS

It is shown that quantization of the dynamical systems with second class constraints actually can be reduced to quantization of the systems with first class constraints. The motion of the non-relativistic particle along the plane curve and on a surface is considered. The results coincide with those of the "thin layer method". Influence of the non-physical variables on the physical sector is demonstrated.

Fate of Escherichia coli Strains Inoculated in Model Cheese Elaborated with or without Starter and Treated by High Hydrostatic Pressure

The aim of this research was to study high hydrostatic pressure inactivation of two strains of Escherichia coli (E. coli O59:H21 [CECT 405] and E. coli O157:H7 [CECT 5947]) inoculated in washed-curd model cheese elaborated with and without starter and the ability of these strains for survival, recovery, and growth. Samples were treated at 300, 400, and 500 MPa for 10 min at 20°C and analyzed after the treatment and after 1, 7, and 15 days of storage at 8°C to study the behavior of Escherichia populations. Cheeses elaborated with starter showed the maximum lethality at 400 and 500 MPa, and no significant differences in the baroresistant behavior of either strains were detected, except for E. coli O157:H7 at 400 MPa in cell counts obtained with thin agar layer method medium, where the decrease value was significantly lower. In cheese elaborated without starter, the highest decrease value was observed at 500 MPa, except for E. coli O59:H21 in cell counts obtained with selective culture medium, where the highest decrease value was also found at 400 MPa. The ability to repair and grow was not observed in model cheese elaborated with starter, as cell counts of treated samples decreased after 15 days of storage at 8°C. By contrast, in cheese elaborated without starter, all pressurized samples showed the trend to repair and grow during the storage period in both strains. These results suggest that the presence of starter and low pH values are the main factors that control the ability of Escherichia strains inoculated in this type of cheese and treated by high hydrostatic pressure to recover and grow.

Consolidation Statistics Investigation via Thin Layer Method Analysis

In this paper, the Thin Layer Method (TLM) is adapted for solving one-dimensional primary consolidation problems. It is also combined with a stochastic formulation integrating Monte Carlo simulations to investigate primary consolidation of a random heterogeneous soil profile. This latter is modeled as a set of superposed layers extending horizontally to infinity, and having random properties. Spatial variability of soil properties is considered in the vertical direction only. Soil properties of interest are elastic modulus and soil permeability, modeled herein as spatially random fields. Lognormal distribution is chosen because it is suitable for strictly non-negative random variables, and enables analyzing the large variability of such properties. The statistics regarding final settlement and its corresponding time are investigated by performing a parametric study, which integrates the influence of variation coefficient of both elastic modulus and soil permeability, and vertical correlation length. Obtained results indicate that heterogeneity significantly influences primary consolidation of the soil profile, generating a quite different way of soil grain rearrangement and water pressure dissipation in comparison to the homogeneous case, and causing a delay in the consolidation process.

An explicit time domain solution for ground stratum response to harmonic moving load

Based on the thin layer method originally proposed in frequency domain, an explicit time domain semi–analytical solution has been developed for simulating three-dimensional layered ground responses to harmonic moving loads. The Fourier–Laplace transforms were applied to derive the transformed solution that satisfied the boundary conditions of horizontal infinities. The eigenvalue decomposition was performed with respect to Laplace parameter to express the ground motion corresponding to the eigenmodes. The formulation for each eigenmode incorporating the moving load expression was transformed back into time domain analytically, and the global system responses were given by means of the general mode superposition method. The proposed explicit time domain solution is suitable for studying various types of moving load acting on or inside the ground. In this paper a moving harmonic load with rectangular distribution was adopted to demonstrate the ground response simulation. Two illustrative examples for moving load with speeds below or above the ground Rayleigh wave velocity were presented to test the computational accuracy and efficiency of the proposed approach. A parametric study was also performed to investigate the influences of soil properties on the ground responses.

An attempt to use LA-ICP-SMS to quantify enrichment of trace elements on pyrite surfaces in oxidizing mine tailings

Metals released from oxidation and weathering of sulphide minerals in mine tailings are to a high degree retained at deeper levels within the tailings themselves. To be able to predict what could happen in the future with these secondarily retained metals, it is important to understand the retention mechanisms. In this study an attempt to use laser ablation high-resolution ICP-MS (LA-ICP-SMS) to quantify enrichment of trace elements on pyrite surfaces in mine tailings was performed. Pyrite grains were collected from a profile through the pyrite-rich tailings at the Kristineberg mine in northern Sweden. At each spot hit by the laser, the surface layer was analyzed in the first shot, and a second shot on the same spot gave the chemical composition of the pyrite immediately below. The crater diameter for a laser shot was known, and by estimating the crater depth and total pyrite surface, the total enrichment on pyrite grains was calculated. Results are presented for As, Cd, Co, Cu, Ni and Zn. The results clearly show that there was an enrichment of As, Cd, Cu and Zn on the pyrite surfaces below the oxidation front in the tailings, but not of Co and Ni. Arsenic was also enriched on the pyrite grains that survived in the oxidized zone. Copper has been enriched on pyrite surfaces in unoxidized tailings in the largest amount, followed by Zn and As. However, only 1.4 to 3.1% of the Cd and Zn released by sulphide oxidation in the oxidized zone have been enriched on the pyrite surfaces in the unoxidized tailings, but for As and Cu corresponding figures are about 64 and 43%, respectively. There were many uncertainties in these calculations, and the results shall not be taken too literally but allowed the conclusion that enrichment on pyrite surfaces is an important process for retention of As and Cu below the oxidation front in pyrite rich tailings. Laser ablation is not a surface analysis technique, but more of a thin layer method, and gives no information on the type of processes resulting in enrichment on the pyrite surfaces. Although only pyrite grains that appeared to be fresh and without surface coatings were used in this study, the possibility that a thin layer of Fe-hydroxides occurred must be considered. Both adsorption to the pyrite directly or to Fe-oxyhydroxides may explain the enrichment of As, Cd, Cu and Zn on the pyrite surfaces, and, in the case of Cu, also the replacement of Fe(II) by Cu(II) in pyrite.

Analysis of moving load induced ground vibrations based on thin-layer method

A time-domain solution of layered ground vibration due to moving load has been developed based on the thin layer method. Fourier-Laplace transforms are applied to derive the transformed domain solution that satisfies the boundary conditions of horizontal infinities. The eigen-decomposition approach is used with respect to the Laplace parameter, and the final ground response solution is constructed with the mode superposition method. The reliability and computation accuracy of the solution are proved by comparison with a closed-form solution. A single soil stratum on rigid bedrock is used to reveal the vibration features induced by a rectangular load moving at speeds below or above ground Rayleigh wave velocity.

THIN LAYER METHOD ANALYSIS OF SPOUTED BED DRIED MALAYSIAN PADDY – CHARACTERISTIC DRYING CURVES

ABSTRACT A lab‐scale spouted bed dryer was used for the drying of paddy. The Malaysian grown paddy is a sample of Geldart's Group D particle. Drying was carried out in the dryer at two different internal configurations, namely with or without the installation of a draft tube, and at several drying temperatures (60–90C), air flow rates (1.14–1.45 m/s) and bed heights (30–45 cm). Drying kinetics of paddy in spouted bed showed only induction and falling rate periods, without constant drying rate period. Thin layer method analysis shows characteristic drying rate curves of linear and exponential functions for the first and second falling rate period, respectively, in conventional spouted bed drying. A single power function was observed in spouted bed drying with a draft tube, mainly as a result of a better tempering effect that gave a lower drying rate gradient.

Equimolar Production of Amyloid β-Protein and Amyloid Precursor Protein Intracellular Domain from β-Carboxyl-terminal Fragment by γ-Secretase

We showed previously that cells expressing wild-type (WT) beta-amyloid precursor protein (APP) or coexpressing WTAPP and WT presenilin (PS) 1/2 produced APP intracellular domains (AICD) 49-99 and 50-99, with the latter predominating. On the other hand, the cells expressing mutant (MT) APP or coexpressing WTAPP and MTPS1/2 produced a greater proportion of AICD-(49-99) than AICD-(50-99). In addition, the expression of amyloid beta-protein (Abeta) 49 in cells resulted in predominant production of Abeta40 and that of Abeta48 leads to preferential production of Abeta42. These observations suggest that epsilon-cleavage and gamma-cleavage are interrelated. To determine the stoichiometry between Abeta and AICD, we have established a 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonic acid-solubilized gamma-secretase assay system that exhibits high specific activity. By using this assay system, we have shown that equal amounts of Abeta and AICD are produced from beta-carboxyl-terminal fragment (C99) by gamma-secretase, irrespective of WT or MTAPP and PS1/2. Although various Abeta species, including Abeta40, Abeta42, Abeta43, Abeta45, Abeta48, and Abeta49, are generated, only two species of AICD, AICD-(49-99) and AICD-(50-99), are detected. We also have found that M233T MTPS1 produced only one species of AICD, AICD-(49-99), and only one for its counterpart, Abeta48, in contrast to WT and other MTPS1s. These strongly suggest that epsilon-cleavage is the primary event, and the produced Abeta48 and Abeta49 rapidly undergo gamma-cleavage, resulting in generation of various Abeta species.

Determination of trace elements in suspensions and filtrates of drinking and surface water by wavelength-dispersive X-ray fluorescence spectrometry

An X-ray fluorescence method (XRF) is presented that allowed low detection limits (at the 0.1-23 ng mL(-1) level) to be obtained for Cr, Mn, Fe, Ni, Zn, Sr, Pb, Bi and Br in water. The samples were prepared using a thin layer method. Trace elements were determined via the calibration curve and standard addition. Absorption effects and inhomogenities in prepared samples were checked for using the emission-transmission method and internal standards, respectively. The results from the XRF method were compared with the results from the inductively coupled plasma atomic emission spectrometry method.

Evaluation of a Double Layer Agar Plate For Direct Enumeration of Vibrio parahaemolyticus

ABSTRACTA double layer agar plate (DLAP) was developed according to the thin agar layer (TAL) method as a 1‐step procedure for direct enumeration of injured Vibrio parahaemolyticus cells based on the formation of unique purple colonies by V. parahaemolyticus. The DLAP was prepared by overlaying an equal volume (10 mL) of a nonselective medium (tryptic soy agar supplemented with 1.5% NaCl) onto a selective medium (Bio‐Chrome Vibrio medium). The DLAP was capable of detecting V. parahaemolyticus in mixed cultures containing non‐Vibrio bacteria. Production of purple colonies by V. parahaemolyticus on DLAP was not affected by the growth of other bacteria, even when V. parahaemolyticus was only a small fraction (5%) of the entire bacterial population. Direct plating on DLAP was found as effective as the most probable number (MPN) method for recovering heat‐and cold‐injured V. parahaemolyticus cells, which could not be detected by direct plating on Bio‐Chrome Vibrio medium or thiosulfate‐citrate‐bile salts‐sucrose agar. The DLAP offers an alternative to the MPN method for detecting injured V. parahaemolyticus cells and can be used as a simple 1‐step procedure for quick screening of V. parahaemolyticus in foods.

A Solid Agar Overlay Method for Recovery of Heat-Injured Listeria monocytogenes

A solid agar overlay method was developed for recovery of heat-injured Listeria monocytogenes. Presolidified nonselective tryptic soy agar with 0.6% yeast extract (TSAYE, 2% agar) was overlaid on top of solidified modified Oxford agar (MOX). Heat injury of L. monocytogenes was conducted at 58°C for 6 min in a jacketed flask filled with tryptic soy broth. Both noninjured and heat-treated L. monocytogenes cells were plated onto TSAYE, MOX, and TSAYE-MOX plates. No significant differences (P > 0.05) in recovery were found among the three media for noninjured bacterial cells. Recovery of heat-injured L. monocytogenes cells on TSAYE-MOX overlay plates was equivalent to that on the nonselective TSAYE medium, whereas recovery on the selective MOX medium was significantly lower (P < 0.05) compared with both TSAYE and the overlay plates. There were no significant differences (P > 0.05) among the overlay plates prepared 0, 2, 4, 6, 8, 16, and 24 h prior to plating heat-injured bacterial cells. The TSAYE-MOX overlay also allowed differentiation of L. monocytogenes from a mixture of four other types of foodborne pathogens. This solid agar overlay method for recovery of heat-injured L. monocytogenes cells is less time-consuming and less complicated than the conventional overlay-underlay technique and the double overlay modification of the thin agar layer method and may allow for greater laboratory plating efficiencies.

Electroplating of titanium on iron by galvanic contact deposition in NaCl–TiCl2 molten salt

A commercial titanium coating method is not available with the exception of physical vapor deposition or titanium cladding which are a very expensive processes. However, it is very attractive to coat the surface of steel with a thin titaniumlayer for improving its corrosion resistance against salt water or acids. This paper describes a method for electroplatinga thin titanium layer on an iron surface by galvanic contact deposition in which pure titanium and an iron electrode areimmersed into a molten salt (NaCl–TiCl2) at high temperature; both electrodes are connected through an external circuit. By immersing iron in the molten salt for 10 h at 1200 K, we obtained a flat and thin layer of titanium–iron alloy on iron. The thickness and composition of this layer were 50710 mm and Ti—15–16 mol% Fe, respectively. The corrosion resistance of this titanium-rich alloy layer is expected to be greater than that of steel. Galvanic contact deposition is a very simple method in which iron and titanium electrodes are just immersed into molten salts without the use of an external power source. Thus, the capability of the method presently proposed could be suggested so as to improve the corrosion resistance of steel, particularly from the practical process point of view.