Differential Permeability Research Articles

Analysis of Electromagnetic Inspection Method of Opposite Side Carburization Depth in Steel Plate Taking Account of Minor Loop

There is a need to inspect the opposite side of carburized layer in a heating furnace steel tube in an oil-refining plant. The conductivity of the layer with carburization is larger than the layer without carburization in the steel, and its permeability is smaller than the layer without carburization. Then, the estimation of the opposite side carburized depth in the steel is possible by using the differences of these electromagnetic properties. In this paper, the electromagnetic inspection method using a dc magnetic field and a minute ac magnetic field is proposed. The behavior of flux in steel is examined using 3-D nonlinear FEM taking account of minor loops and eddy current. It is shown that the inspection of opposite side of carburized depth in the steel is possible using the differential permeability of minor loop of which the position on the hysteresis loop is affected by the depth of carburized layer.

A Differential Permeability 3-D Formulation for Anisotropic Vector Hysteresis Analysis

In the previous work, we introduced a formulation joining two concepts: 1) the source-field technique and 2) the differential permeability method. It was shown that the resulting procedure produces accurate results for non-linear cases and it was favorably compared with the more classical approach considering the actual permeability. Here, we extend this formulation for vector hysteresis cases that are modeled by the Jiles-Atherton approach. It considers the magnetic anisotropy of the ferromagnetic sheets.

Applications of Impedance Plane and Magnetic Differential Permeability in Microstructural Characterization of AISI D2 Tool Steel

Two nondestructive electromagnetic/magnetic techniques including hysteresis loop and eddy current methodologies have been used to characterize microstructural changes of AISI D2 cold work tool steel as a result of quench and tempering treatments. To measure the fraction retained austenite in quenched microstructure, six specimens were austenitized in the range of 1000-1130 °C. Samples austenitized at 1080 °C were also tempered in the range of 200-650 °C for characterization by eddy current and magnetic hysteresis loop outputs, nondestructively. Impedance point movement and maximum differential permeability were measured as a function of austenitizing/tempering temperature to characterize the microstructural features. The study shows that there are good correlations between microstructural variations detected by destructive methods (hardness, XRD and microscopic observation) and outputs of the nondestructive techniques.

Funcionalización de polietileno de baja densidad con anhídrido maleico en estado fundido

In this study, low density polyethylene (LDPE) was modified with maleic anhydride (AM) in the molten state by using different concentrations of dycumil peroxide (DCP) (0.25, 0.50, 0.75 and 1.0 %). The materials obtained were characterized by gel content, acid-base titrations, infrared spectroscopy (IR), differential scanning calorimetry (DSC), thermogravimetry (TGA), rheological analysis, mechanical properties, hardness and oxygen permeability. Rheometric analysis indicated that the optimum time to obtain the mixtures is ca.7.5 minutes. IR analyses showed that the AM was grafted into the LDPE backbone. The grafting degree increased with the content of DCP and the highest grafting degree (1.12 ± 0.015 %), was exhibited by the sample obtained employing the highest amount of DCP. Thermal stability of the functionalized samples was slightly higher than LDPE. The crystallinity of the functionalized samples was different, when compared to LDPE. The rheological behavior presented by the samples was pseudoplastic. The mechanical properties, hardness and the oxygen permeability were dependent of the amount of DCP and AM grafted into LDPE.

Simultaneous multiagent hyperpolarized 13C perfusion imaging

To demonstrate simultaneous hyperpolarization and imaging of three (13)C-labeled perfusion MRI contrast agents with dissimilar molecular structures ([(13)C]urea, [(13)C]hydroxymethyl cyclopropane, and [(13)C]t-butanol) and correspondingly variable chemical shifts and physiological characteristics, and to exploit their varying diffusibility for simultaneous measurement of vascular permeability and perfusion in initial preclinical studies. Rapid and efficient dynamic multislice imaging was enabled by a novel pulse sequence incorporating balanced steady state free precession excitation and spectral-spatial readout by multiband frequency encoding, designed for the wide, regular spectral separation of these compounds. We exploited the varying bilayer permeability of these tracers to quantify vascular permeability and perfusion parameters simultaneously, using perfusion modeling methods that were investigated in simulations. "Tripolarized" perfusion MRI methods were applied to initial preclinical studies with differential conditions of vascular permeability, in normal mouse tissues and advanced transgenic mouse prostate tumors. Dynamic imaging revealed clear differences among the individual tracer distributions. Computed permeability maps demonstrated differential permeability of brain tissue among the tracers, and tumor perfusion and permeability were both elevated over values expected for normal tissues. Tripolarized perfusion MRI provides new molecular imaging measures for specifically monitoring permeability, perfusion, and transport simultaneously in vivo.

Ion permeability of artificial membranes evaluated by diffusion potential and electrical resistance measurements

In the present article, a novel model of artificial membranes that provides efficient assistance in teaching the origins of diffusion potentials is proposed. These membranes are made of polycarbonate filters fixed to 12-mm plastic rings and then saturated with a mixture of creosol and n-decane. The electrical resistance and potential difference across these membranes can be easily measured using a low-cost volt-ohm meter and home-made Ag/AgCl electrodes. The advantage of the model is the lack of ionic selectivity of the membrane, which can be modified by the introduction of different ionophores to the organic liquid mixture. A membrane treated with the mixture containing valinomycin generates voltages from -53 to -25 mV in the presence of a 10-fold KCl gradient (in to out) and from -79 to -53 mV in the presence of a bi-ionic KCl/NaCl gradient (in to out). This latter bi-ionic gradient potential reverses to a value from +9 to +20 mV when monensin is present in the organic liquid mixture. Thus, the model can be build stepwise, i.e., all factors leading to the development of diffusion potentials can be introduced sequentially, helping students to understand the quantitative relationships of ionic gradients and differential membrane permeability in the generation of cell electrical signals.

Neural-FEM approach for the analysis of hysteretic materials in unbounded domain

Purpose – This paper aims the application of a novel synergy between a neural network (NN) and the finite element method (FEM) in the solution of electromagnetic problem involving hysteretic material in unbounded domain. Design/methodology/approach – The hysteretic nature of the material is taken into account by an original NN able to perform the modelling of any kind of quasi-static loop (saturated and non-saturated, symmetric or asymmetric). An appositely developed iterative FEM procedure is presented for the solution of this kind of problems in unbounded domains. Findings – By starting from a small set of measured loops, the NN manages the values of the magnetic field, H, and the flux density, B, as inputs while the differential permeability is the output. In particular, the proposed NN is capable to perform the modelling of saturated and non-saturated, symmetric or asymmetric hysteresis loops. Practical implications – The development of an efficient method for the solution of a complicated electromagnetic problem in unbounded domain by using an iterative approach and NNs, which can be implemented also in existing FEM code. Originality/value – The paper shows that the combination of FEM, iterative procedure and NNs allows us to produce effective solutions of electromagnetic problems in unbounded domains involving also nonlinear hysteretic magnetic materials with an acceptable computational cost.

Differential permeability behaviour of P9 and T22 power station Steels

Analysis of the electromagnetic (EM) properties of power station steels, measured using a non-contact magnetic sensor, is of significance as such properties are indicative of the microstructure of the material and can be potentially exploited for non-destructive testing. In this paper, we present EM measurements of cylindrical power station steel samples (P9 and T22 grades) with different microstructures: normalised and tempered (representative of the initial condition), as normalised and after service exposure. In order to obtain the magnetic properties the B–H curves of these samples were measured. Cylindrical air-cored and printed circuit board (PCB) coil integrated sensors were used to measure the incremental permeability. Analytical and numerical methods (Finite Elements Methods) were employed to calculate the sensor response of these samples. The electromagnetic properties of the different steels were inferred by fitting the finite element models to the measured results. In addition, sensitivity and error analysis were carried out to evaluate the accuracy of the method.

Certification of hardened surface layers by magnetic and electromagnetic methods

The possibilities of certification of hardened surface layers by measurement of coercive force, eddy current inspection and analysis of the field dependence of differential magnetic permeability μ d (H) are considered. The advantages of analysis of the pattern of peaks on the μ d (H) dependence for estimating the state of surface-hardened steels subjected to subsequent force loading are shown.

Giant Barkhausen Jumps in Exchange Biased Bulk Nanocomposites Sintered from Core-Shell $\hbox{Fe}_{3}\hbox{O}_{4}{-}\hbox{CoO}$ Nanoparticles

The magnetic behavior of spark plasma sintered Fe3O4-CoO nanoparticles is studied. The samples sintered at 500 exhibit density over 90% and average magnetite grain size about 100 nm. When the nanocomposite is field cooled below the Neel temperature of CoO, hysteresis loops shows an exchange field of 80 mT at 100 K together with a coercivity of 0.4 T, ten times larger than nanostructured magnetite prepared in the same conditions. When the sample is zero field cooled, the hysteresis loops exhibits giant Barkhausen jumps. The density of jumps gradually decrease on heating and disappear between 150 and 170 K. The stochastic character of the jumps is visible in the plot of the differential permeability. This phenomenon is thought to be due to self-field cooling.

Magnetic sensing for microstructural assessment of power station steels: Differential permeability and magnetic hysteresis

Failure of power station steel components can have severe economic impacts and also present significant risks to life and the environment. Currently components are inspected during costly shut-downs as no in-situ technique exists to monitor changes in microstructure of in-service steel components. Electromagnetic inspection has the potential to provide information on microstructure changes in power station steels in-situ. In this paper, tests have been carried out on pipe and tube samples in different microstructural conditions, using a lab-based closed magnetic circuit and impedance measurement systems. EM properties have been identified with correlations to material properties, which can quantify degradation in-situ and at elevated temperatures.

Preparation and characterization of micro and nanocomposites based on poly(vinyl alcohol) for packaging applications

In the present work, micro and nano composites based on poly(vinyl alcohol) matrix reinforced with cellulose (micro) and bentonite (nano) were obtained by film casting. The resulting composite materials were characterized by means of differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, FTIR spectroscopy, water absorption, permeability, and mechanical tests. The effect of the micro and nano fillers on the thermal, mechanical, and water absorption properties of the matrix was determined. The effects of polymer molecular weight and processing steps were also studied. Based on the results of the work, the potential biodegradability and the low cost of the starting materials, it can be concluded that the produced materials may be promising for packaging applications.

Evaluation of case depth in induction-hardened steels: Magnetic hysteresis measurements and hardness-depth profiling by differential permeability analysis

We have studied case depth of induction-hardened steel rods using magnetic hysteresis technique. A step-like behavior of magnetization curve, a decrease of maximum flux density, and an increase of coercivity with case depth, typical for surface-hardened steels, were observed, reflecting a mixture of magnetically hard hardened layer and soft core. Differential permeability exhibited a double peak structure with high- and low-field peaks due to hardened layer and core, respectively. Analysis for the area and position of the permeability peaks, based on a simple model, demonstrated that the volume fraction of hardened layer can be quantitatively and directly inferred from the permeability data alone. Although this method is generally restricted to the case in which a double peak structure in differential permeability is observed, this analysis method can be a possible technique to non-destructively construct depth profile of Vickers hardness from magnetic measurements.

Outlook of Preisach Modeling and Magnetic Non Destructive Testing

The Preisach formalism is used as a basis for a vector model of magnetic hysteresis in soft magnetic materials subject to tensile stress. The model uses as vector elementary hysteresis operator the Stoner-Wohlfarth mechanism of coherent rotation while the Preisach density is constructed as the weighed sum of probability density functions corresponding to the high and low induction regions. The model reproduces the basic phenomenology of stress-dependent hysteresis: the double peak in differential permeability modeled as the effect of internal demagnetizing fields emerging from residual stresses; the increase in coercivity due to increased pinning; the decrease in magnetic induction as the result of non-180o domain rotation. The role of the negative differential permeability near remanence and its derivative is discussed with respect to residual stresses and magnetic NDT.

Population genetic structure of Picea engelmannii, P. glauca and their previously unrecognized hybrids in the central Rocky Mountains

Areas of geographic overlap between potentially hybridizing species provide the opportunity to study interspecific gene flow and reproductive barriers. Here we identified hybrids between Picea engelmannii and P. glauca by their genetic composition at 17 microsatellite markers, and determined the broad-scale geographic distribution of hybrids in the central Rocky Mountains of North America, a geographic region where hybrids and isolation between species had not previously been studied. Parameter estimates from admixture models revealed considerable variation in ancestry within and among collection sites, suggesting that within this area of geographic overlap, the interaction of the two species varies extensively. The results document a previously unrecognized patchy distribution of hybrids between P. engelmannii and P. glauca, including locations where hybrids were not known or expected to exist. Further, the ancestry of many hybrids was consistent with multiple generations of hybridization, with probable directional backcrossing to P. engelmannii, suggesting a relatively porous species boundary. The identification and characterization of hybridization between these spruce in this region raises the question of what factors maintain barriers to gene flow in these long-lived forest trees. The current research lays the groundwork for future study of the ecological and evolutionary contexts of their hybridization, as well as of differential introgression and permeability of species boundaries.

Various Coiled Magnetoimpedance Based on Differential Magnetic Permeability Variation

The present work is focused on high sensitivity (5000 V/T) transverse coiled GMI transducers manufactured with various magnetic materials, magnetically excited at low frequencies (f < 50 kHz) by an insulated coil which is also used for the measurement of the DC and low frequency magnetic field. The impedance and the sensitivity of different types of ferromagnetic material as nanocrystalline ribbons (Finemet) annealed under longitudinal and transverse magnetic fields, as mumetal ribbons and Mn–Zn thin ferrite core are investigated with respect to the static magnetic field. From these results, the differential magnetic permeability is approximated in order to predict sensitivity behavior in relation to the anisotropy magnetic field and the magnitude and the frequency of current excitation.

Changing Trends of Commonly Used Intensive Care Unit Antibiotics Due to Differential Membrane Permeability in Resistant Escherichia coli Collected in EASE Programme

In order to understand resistance pattern of Escherichia coli clinical isolates, the outer membrane permeability trend of different antibiotics was studied. The outer membrane permeability of Elores was compared with other commonly used intensive care unit (ICU) drugs being used in the treatment of various infections caused by resistant E. coli. A total of fifty three isolates collected under EASE programme from North Indian hospitals, fifteen extended spectrum β-lactamases (ESBL) positive clinical isolates of E. coli were included in the study. Michaelis constants (Km) and maximal rates of substrate hydrolysis (Vmax) were determined from Lineweaver-Burk plot. Permeability coefficient was determined using the method described by Zimmermann and Rosslet. Elores demonstrated the lowest Vmax/Km ratio further indicating its lower affinity (high Km 209.9 ± 17.4 μM) towards β-lactamase or more stability against β-lactamase enzyme. The other comparator drugs including penems, colistin, β-lactam and β-lactamase inhibitor combinations exhibited three to ten folds higher Vmax/Km ratio compared to Elores indicating very high affinity for β-lactamase induced degradation. Elores penetrated the outer membrane of ESBL producing resistant E. coli with permeability coefficient approximately 1.8, 2.2, 6.9, 2.5 and 2.3 times higher than imipenem plus cilastatin, meropenem, colistin, cefoperazone plus sulbactam, piperacillin plus tazobactam, respectively. The increased penetration of the Elores leads to higher periplasmic concentration of the drug resulting in reduced MIC. Our results clearly demonstrated that Elores exhibited the highest permeability coefficient, enhanced penetration, greater stability and periplasmic concentration leading to higher susceptibility towards resistant E. coli compared to other drugs. Therefore, Elores can be considered as an empiric drug of choice for the treatment of infections caused by E. coli positive with ESBL.

Absorption and Metabolism Characteristics of Rutin in Caco‐2 Cells

The intestinal absorption and metabolism characteristics of the potentially beneficial polyphenol rutin were studied by measuring the intracellular accumulation and transport of rutin into Caco-2 cells with the sensitive and reliable analytical method of HPLC-coupled tandem mass spectrometry. Rutin and glucuronidated rutin were absorbed differently by the basolateral and apical membranes, and rutin showed differential permeability through the apical and basolateral sides. Approximately 33% of the rutin was metabolized to glucuronidated rutin, and the intracellular concentration of glucuronidated rutin was much lower than that of parent rutin. P-glycoprotein and multidrug-resistant proteins 2 and 3 were involved in the transmembrane transport and intracellular accumulation of rutin by Caco-2 cells. These results suggest that a specific transport system mediates rutin movement across the apical membrane in Caco-2 cells and that metabolic enzymes are important for this process.

Differential Permeability of the Blood-Testis Barrier During Reinitiation of Spermatogenesis in Adult Male Rats

The blood-testis barrier (BTB) sequesters meiotic spermatocytes and differentiating spermatids away from the vascular environment. We aimed to assess whether meiosis and postmeiotic differentiation could occur when the BTB is permeable. Using a model of meiotic suppression and reinitiation, BTB function was assessed using permeability tracers of small, medium, and large (0.6-, 70-, and 150-kDa) sizes to emulate blood- and lymphatic-borne factors that could cross the BTB. Adult rats (n = 9/group) received the GnRH antagonist acyline (10 wk) to suppress gonadotropins, followed by testosterone (24cm Silastic implant), for 2, 4, 7, 10, 15, and 35 days. In acyline-suppressed testes, all tracers permeated the seminiferous epithelium. As spermatocytes up to diplotene stage XIII reappeared, both the 0.6- and 70-kDa tracers, but not 150 kDa, permeated around these cells. Intriguingly, the 0.6- and 70-kDa tracers were excluded from pachytene spermatocytes at stages VII and VIII but not in subsequent stages. The BTB became progressively impermeable to the 0.6- and 70-kDa tracers as stages IV-VII round spermatids reappeared in the epithelium. This coincided with the appearance of the tight junction protein, claudin-12, in Sertoli cells and at the BTB. We conclude that meiosis can occur when the BTB is permeable to factors up to 70 kDa during the reinitiation of spermatogenesis. Moreover, BTB closure corresponds with the presence of particular pachytene spermatocytes and round spermatids. This research has implications for understanding the effects of BTB dynamics in normal spermatogenesis and also potentially in states where spermatogenesis is suppressed, such as male hormonal contraception or infertility.

Experiments on ferrimagnetism

Ferrimagnetism undoubtedly deserves a proper place in the undergraduate laboratory on electricity and magnetism. Four student experiments on ferrimagnetism are considered: (i) the hysteresis loops and permeability of a ‘soft’ ferrite; (ii) the differential permeability versus a dc bias; (iii) the frequency dependence of the complex permeability and (iv) the electromagnetic interference suppression by ferrite chokes and beads. Two ferrite cores taken off a low-frequency choke and a power cord are used. The measurements are simple and straightforward and show the important properties of ferrites and their applications. The values of the permeability of the ferrite core determined in experiments (i)–(iii) are in reasonable agreement. The frequency dependence of the complex permeability of the ferrites is similar to that given by the manufacturers. The capability of absorbing electromagnetic waves in a definite frequency range shown in experiment (iv) demonstrates one of the principles of Stealth technology. The equipment necessary for the experiments can be found in many student laboratories.