Hysteresis Parameters Research Articles

Characterization of Nd(Tb)–Fe–B-based exchange-spring nanocomposite magnets

The authors attempt to optimize for performance the composition of R 2Fe14B/Fe3B-based hard nanocomposite alloys with R = neodymium (Nd) and terbium (Tb) by optimizing phases in order to develop hysteresis parameters such as maximum magnetization, coercivity and maximum energy product through variation in composition and heat treatment. The samples were prepared from arc-melted ingots of different compositions. The crystallization temperatures were obtained from the differential scanning calorimeter traces of the samples with the composition Nd4−x Tb x Fe71Co5Cu0·5Nb1B18·5 (x = 0·0, 0·2, 0·4, 0·6, 0·8 and 1·0). Depending on their crystallization temperatures, the samples were annealed at 600, 625, 650, 675 and 700°C for 10 min. Amorphosity and crystallization behavior were studied by X-ray diffraction using copper (Cu) Kα radiation (1·5418 Å). The Mössbauer spectra of all the samples were recorded at room temperature by using iron-57 (57Fe) Mössbauer spectrometry in transmission geometry with a constant-acceleration spectrometer. Magnetic properties were determined by a vibrating-sample magnetometer in the as-cast and annealed conditions. Although the highest values of coercivity and remanent ratio were found to be 4·18 kOe and 0·72, respectively, for the sample of composition Nd3Tb1Fe71Co5Cu0·5Nb1B18·5 annealed at 650°C with a higher concentration of terbium, the highest maximum energy product was determined to be 12·67 MGOe for the sample of Nd3·8Tb0·2Fe71Co5Cu0·5Nb1B18·5.

Magnetic biomonitoring with moss bags to assess stop-and-go traffic induced particulate matter and heavy metal concentrations

Urban air quality is strongly affected by the surrounding local traffic and emission compounds such as particulate matter (PM) and heavy metals, which pose a serious health risk globally. These compounds are known to be traffic related, but fairly few studies have focused on point source emissions of traffic flow. In this study we applied magnetic biomonitoring using moss bags (Sphagnum papillosum) to study the point source emissions caused by stop-and-go traffic. Moss bags were placed alternately at traffic light crossings (n = 19) and midway areas between the crossings (n = 29) along four street transects and one separate traffic light crossing in the city of Turku, Finland. Samples were analysed for mass-specific magnetic susceptibility (χ), hysteresis parameters and elemental components. The PM was composed of fine-grained pseudo-single-domain (PSD) magnetite and the concentrations of χ, Cu, Mo and Sb significantly differed between traffic light crossing areas compared to midway areas. The elements Ba, Cu, Fe, Mo, Ni, Pb, Sb and Ti showed moderate to high levels of accumulation and correlated strongly with χ and saturation magnetisation (MS). Our results show that a high volume of stop-and-go traffic is a major source of harmful PM pollution especially along busy main roads. To improve urban air quality and public health we strongly advice the municipal administrations to pay more attention to urban planning and traffic management to reduce stop-and-go traffic and decrease the levels of urban PM pollution.

Effects of CoFe2O4 substitution on magnetic properties of NiFe2O4 spinel ferrite

Functional magnetic materials of composition Ni1 − xCoxFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were prepared using NiFe2O4 (soft) and CoFe2O4 (semi-hard) nanomaterials following solid state synthesis technique. Magnetic properties of synthesized samples were studied employing XRD, FESEM, VSM and DSC techniques. Curie temperature, Tc of all the samples were determined from the temperature dependence of permeability and compared with the peak temperature of DSC thermograph. Tc is found to decrease with increasing CoFe2O4 substitution which has been ascribed due to weakening of JAB super-exchange interaction between tetrahedral and octahedral sites. The detail hysteresis parameters such as Ms, Mr, Hc have been determined from M-H loop measured at 80, 200 and 300K. Saturation magnetization, Ms measured at 80K was found much higher compared with data at 300K. Ms is found to increase with decreasing temperature and attained a maximum value corresponding to CoFe2O4 at any measurement temperature which may be attributed to higher magnetic moment of CoFe2O4 compared with NiFe2O4. A gradual magnetic hardening was observed to increase with increasing CoFe2O4 content with a maximum value of Hc at x = 0.8. Initial permeability as a function of frequency has been measured by an impedance analyzer. Phase transition temperature determined from DSC measurements and temperature dependence of initial permeability was found to display a good correlation. In addition, magnetic hardening of soft NiFe2O4 with increasing amount of CoFe2O4 substitution is also explained based on the existing theories of magnetism.

Experimental study on constitutive relation of the high performance marine structural steel under extreme cyclic loads

Jacket offshore platform serving in the marine environment is often subjected to severe dynamic loads such as winds, waves, currents and earthquakes. The alternating stress state of jacket offshore platform will lead to the degradation of mechanical properties of the structural steel, which results in the decline of the overall bearing capacity. In this paper, eighteen types of cyclic loading program designed according to the characteristics of the steel and extreme cyclic loads are presented for the first time. The hysteresis behavior of structural steel NV-D36 under various cyclic loading program is studied. The changing process of energy dissipation capacity of the steel under different loading program is compared. The hysteresis skeleton curve of steel under variable amplitude cyclic loading is fitted based on the basis of the classical Ramberg-Osgood model. The parameters of combined hardening of the steel based on Chaboche constitutive model are calibrated. The results of the cyclic loading are numerically simulated with the obtained hysteresis skeleton curves and parameters. The combined hardening criterion can be used to analyze the responses of the steel under cyclic loading, and the parameters can be applied to study the dynamic properties of the jacket offshore platform of structural steel NV-D36.

Ferroelectric behavior in nanocrystalline KNbO3 synthesized by a modified polymerized complex method

Effect of nanocrystalline size of the particles on ferroelectric properties of KNbO3 is studied. Properties like hysteresis parameters, phase transition temperatures and domain morphology in nanocrystallites were studied by using P-E hysteresis, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) techniques, respectively. Nanocrystalline KNbO3 compound was synthesized by a modified polymerized complex method and room-temperature structural phase was characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Field emission gun-scanning electron microscopy (FEG-SEM) was used to reveal the size and morphology of the particles. It was found that the present nanoparticles of sizes ranging from 50 to 250 nm bears polarization values <1 μC/cm2, and undergo cubic-tetragonal and tetragonal-orthorhombic phase transitions at 312 and 87 °C respectively. Although the value of polarization is small as compared to the bulk reported in the literature, the nature of P-E loops along with phase transitions and presence of 60, 90 and 180° domain structures indicates retention of ferroelectric nature in KNbO3 even at the nanolevel.

Elucidation of microwave absorption mechanisms in Co–Ga substituted Ba–Sr hexaferrites in X-band

The tunable microwave absorbers are used to combat the electromagnetic pollution created by the development of high speed electronic devices. In the present paper, we report microwave absorption characteristics of M-type Ba0.5Sr0.5CoxGaxFe12−2xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) hexagonal ferrite compositions prepared by using double sintering ceramic method. X-ray diffraction analysis of the prepared compositions revealed the formation of M-phase along with the minor traces of hematite in substituted compositions. The microwave absorption has been elucidated substantially through various mechanisms in the test frequency range from 8.2 to 12.4 GHz, which is still partially explored in literature. The substitution of Co2+ and Ga3+ ions enhances microwave absorption, bandwidth, decreases thickness and improves impedance matching. The hysteresis parameters also comply with the microwave absorption. The optimal reflection loss of − 29.74 dB is observed in the composition x = 0.2 at 8.28 GHz with 2.0 mm thickness. The investigated mechanisms of microwave absorption can be incorporated to optimize the absorption and design of the microwave absorbers.

Electrochemical Evaluation of Nanostructured Thin Films Formed By Polycaprolactone-Fe2O3-Al2O3 Composites in Hank Solution

Magnetic iron nanoparticles have been studied for the last years due to their properties and it potential application in biomedical topics; as hyperthermia, magnetic resonance imaging (MRI) agents, biosensors, magnetic carriers and targeted drug delivery. In this context, the aim of this study was to study the electrochemical behavior of a nanostructured magnetic polycaprolactone/hematite-alumina composite in order to identify the corrosion mechanisms of coating immersed in an artificial body solution at 37 °C. The composite material was developed during the synthesis of the polycaprolactone (PCL) matrix with simultaneous additions of alumina (Al2O3) and hematite (Fe2O3) nanoparticles in a 1.5 % of weight ratio. Hematite fraction was the magnetic factor of composite coating. The particles were synthesized by sol-gel technique, using stoichiometric aluminum isopropoxide Al(OC3H7)3 and ferric chloride (FeCl3) as precursors maintained at 85 °C during 72 hours of reaction in propanol as solvent and 6 M nitric acid as catalyst under continuous stirring. The synthesis was realized at vacuum of -300 mercury millimeters (Hg mm) condition with an injection of 1.39 g of helium flux as inert gas. The resulting sols were dried to 60 °C during 48 hours. Obtained powders were characterized by DSC/TGA, Fourier transform infrared spectroscopy (FTIR) and X-Ray Diffraction analysis (XRD), Morphological characterization of powders and composite coatings were done by scanning electron microscopy (SEM), and hysteresis parameters showed the formation of magnetic hematite and alumina nanoparticles. In accord with DSC/TGA analysis, each sample were heat treated at 1100 °C. Coatings were obtained by immersion technique using foils of 316L stainless steel as substrate and composite mixture in liquid condition, and then were dried in oven at 60 °C. Corrosion behavior were evaluated by the three electrochemical techniques. Potentiodinamic test applying a -500 to 1500 mV vs open corrosion potential (OCP) with a 1 mV/s scan rate. Linear polarization resistance (LPR) realized within a ± 15 mV vs OCP at 1 mV/s scan rate each 15 minutes during 48 h. Impedance spectroscopy (EIS) was realized in the frequency of 30 kHz to 0.01 Hz with a potential signal amplitude of 30 mV vs OCP. Hank's saline solution at 37 °C was the used electrolyte. Three electrodes cell arrangement was used with an Ag/AgCl saturated reference electrode, platinum wire as auxiliary electrode and the coating samples. Results showed an average thickness of the coating of 1.43 μm. Electrochemical results showed the coating sample behavior with two potential range windows associated to the effect of PCL/Al2O3-Fe2O3 nanoparticles composite and the substrate reaction interface respectively, since PCL and 316L substrate showed wide resistive potential window and moderated window respectively with a difference of 3 order of magnitude between both. The EIS results presented a high resistive mechanism by the PCL coating, but decreased by the oxides particles additions, showing a mechanism governed by diffusion of species through polymeric matrix paths promoted by the oxide nanoparticles. The SEM characterization of samples after immersion was realized in order to complement the discussions of results. Keywords: polycaprolactone/hematite-alumina composite; Electrochemical techniques; Hank’s solution. Acknowledgements The present research was supported by CONACYT for the project financing number: CB-2014-01-243236, I0017 Fund.

Identification of Linear and Nonlinear Parameters for Systems with Local Non-Linearity

A new method based on dynamic response sensitivity is proposed for the identification of local nonlinear system. The unknown local nonlinear hysteresis parameters are identified together with linear structural parameters. The sensitivities of structural dynamic response with respect to unknown parameters are derived. The identification equation is set up based on Taylor’s first order approximation, and is solved with the damped least-squares method. A four-story shearing system with rubber isolation bearing of nonlinear hysteresis model is studied to validate the proposed method. Numerical simulation with noisy measured accelerations shows that the proposed method can accurately identify both linear and nonlinear parameters of the system. This method provides a new approach for detecting local nonlinear structures with incomplete measured output information.

Theoretical and Experimental Study of the Magnetic Properties and Size of Distribution of PVDF + Fe Based Nanocomposites

It was found that the coagulation of the Fe nanoparticles takes place when they are introduced into the polymer matrix. The increase in particle size depends on their concentration in the polymer matrix, the type and properties of polymer (polar, non-polar, viscosity, etc.), reaction mode, etc. Fe particles, coagulate when they are introduced into the polymer matrix, the oxidation of their surface layer not occur, and the magnetic size does not change, hence, does not change the magnetic characteristics. The magnetic hysteresis parameters depend on the size and concentration of the Fe particles. At the same time, have been shown that at low fields the theoretical and experimental dependence of M(H) correlate to each other very well. The hysteresis has been observed at the polarization of the nanoparticles. The increasing of nanoparticles size led to difference in theoretical and experimental values, that in the theory can be explained by acceptance of nanocluster as single domain particle and their interphase interactions are not taken into account.

Forward Modeling of Thermally Activated Single‐Domain Magnetic Particles Applied to First‐Order Reversal Curves

AbstractTheoretical first‐order reversal curves (FORCs) were generated by numerically solving a thermally activated Stoner‐Wohlfarth model for assemblages of randomly oriented magnetic particles. The thermally activated Stoner‐Wohlfarth model extends previous models based on Preisach theory. The new numerical simulations show that the shapes of reversal curves and the FORC distributions are significantly modified by the effect of the thermal energy only if superparamagnetic particles are predominant. However, most assemblages containing moderate amounts of superparamagnetic particles are hardly distinguishable from stable single‐domain assemblages. The most relevant thermal effect is a reduction of coercivity that translates in a shift of the FORC distribution toward the origin. Not all of the distinctive characteristics previously predicted for superparamagnetic grain assemblages were confirmed by our calculations, and most of the observed modifications due to thermal effects can be considered minor. A direct comparison with hysteresis parameters shows that these simpler experiments can be equally effective in characterizing viscous and superparamagnetic particles.

A Critical Appraisal of the “Day” Diagram

AbstractThe “Day” diagram (Day et al., 1977,https://doi.org/10.1016/0031-9201(77)90108-X) is used widely to make inferences about the domain state of magnetic mineral assemblages. Based on theoretical and empirical arguments, the Day diagram is demarcated into stable “single domain” (SD), “pseudo single domain” (“PSD”), and “multidomain” (MD) zones. It is straightforward to make the necessary measurements for a sample and to plot results within the “domain state” framework based on the boundaries defined by Day et al. (1977,https://doi.org/10.1016/0031-9201(77)90108-X). We discuss 10 issues that limit Day diagram interpretation, including (1) magnetic mineralogy, (2) the associated magnetocrystalline anisotropy type, (3) mineral stoichiometry, (4) stress state, (5) surface oxidation, (6) magnetostatic interactions, (7) particle shape, (8) thermal relaxation, (9) magnetic particle mixtures, and (10) definitional/measurement issues. In most studies, these variables are unknowns and cannot be controlled for, so that hysteresis parameters for single bulk samples are nonunique and any data point in a Day diagram could result from infinite combinations of relevant variables. From this critical appraisal, we argue that the Day diagram is fundamentally ambiguous for domain state diagnosis. Widespread use of the Day diagram has also contributed significantly to prevalent but questionable views, including underrecognition of the importance of stable SD particles in the geological record and reinforcement of the unhelpful PSD concept and of its geological importance. Adoption of approaches that enable correct domain state diagnosis should be an urgent priority for component‐specific understanding of magnetic mineral assemblages and for quantitative rock magnetic interpretation.

Dependence of magnetic and microwave loss on evolving microstructure in yttrium iron garnet

The parallel magnetic and microwave loss dependence on microstructural evolutions in several polycrystalline yttrium iron garnet samples were studied in detail, focusing on the attendant occurrence of their relationships. In this study, polycrystalline YIG samples were synthesized by employing the mechanical alloying technique and sintering toroidal compacts at temperatures from 600 to 1400 °C. The samples were characterized for their evolution in crystalline phases, structure, microstructure, magnetic hysteresis parameters, microwave losses and electrical resistivity. The results showed an increasing tendency of the saturation magnetization with grain size, which is attributed to crystallinity increase in the grains. The M–H hysteresis loop results showed a transition from disordered-to-ordered magnetism which belongs to different magnetically dominant stages of formation. The starting appearance of room temperature ferromagnetic order suggested by the sigmoid-shaped loops seems to be dependent on crystallinity, phase purity and a sufficient number of large enough magnetic domain-containing grains having been formed in the microstructure. An increasing trend of transmission loss with grain size may be attributed to increment of loss contribution from hysteresis and domain wall resonance of the samples. The changes in crystallinity and microstructure, and the associated processes of microwave resonance and relaxation due to domain wall movements and damping of spin rotation contributes to the variations in transmission loss and ferromagnetic linewidth of the samples. The increased electrical resistivity while the microstructure was evolving is believed to strongly indicates improved phase purity and compositional stoichiometry.

In-phase thermomechanical fatigue damage evolution of long fiber-reinforced ceramic-matrix composites using fatigue hysteresis-based damage parameters

Under in-phase (IP) thermomechanical fatigue (TMF) loading, the thermal cyclic temperature changes with decreasing or increasing applied stress upon unloading or loading, and the fiber/matrix interface shear stress in the long fiber-reinforced ceramic-matrix composites (CMCs) changes with applied cycles. In this paper, the in-phase TMF damage evolution of CMCs has been investigated, considering the coupling effects of TMF loading stress level, thermal cyclic temperature and applied cycles. The interface debonding and sliding lengths are determined based the thermomechanical micromechanical stress field and the fracture mechanics approach. The relationships between the TMF hysteresis parameters, interface damage, thermal cyclic temperature and applied cycles have been developed. The damage accumulation processes subjected to in-phase TMF for different fibers volume fraction, peak stress, matrix crack spacing, interface properties and thermal cyclic temperature range have been analyzed. The distinction of the damage evolution between the in-phase TMF and isothermal fatigue (IF) loading at the same applied stress has been analyzed. The damage evolution of cross-ply CMCs subjected to the in-phase TMF and IF loading have been predicted.

Structural and Magnetic Рroperties of Copper Substituted Mg-Ferrites

Polycrystalline ferrite powders of Mg1-xCuxFe2O4 (x = 0.2, 0.4, 0.6, 0.8, 1) system synthesized by ceramic technology have been investigated. Samples showed the non-monotonic dependency of heat generation effect in AC magnetic field with increasing concentration of copper. To reveal peculiarities of the structural and magnetic state of the samples and their influence on the heat generation ability we performed a complex study, including X-ray diffractometry, Mössbauer spectroscopy, Scanning electron microscopy, measurements of temperature dependencies of susceptibility and saturation magnetization, hysteresis parameters and FORC. Typical ferrimagnetic character with small coercivity and saturation magnetization was found. We carried out that anomalous influence of Cu2+ ion substitution respectively to the Mg1-xCuxFe2O4 ferrite powder manifested in heat generation ability rise up to x=0.6. The subsequent sharp reducing of this characteristic were accompanied by the main phase crystal structure distortion followed by phase separation to cubic and tetragonal structure. This was matched by in an increase of ferrite particles crystallite size and size distribution appearance. The saturation magnetization and Curie temperature dependencies observed for powders via Cu substitution was explained by phase composition, the cations distributions between ferrite sublattices, modulation of exchange interaction.

The magnetic method as a tool to investigate the Werenskioldbreen environment (south-west Spitsbergen, Arctic Norway)

We used a novel approach of applying magnetic analyses to investigate the material released from the receding glacier Werenskioldbreen on Spitsbergen, Svalbard, Arctic Norway. Surface sediments were taken from the bay Nottinghambukta and the Werenskioldbreen foreland, along two main proglacial streams. Magnetic analyses, namely the low-field mass magnetic susceptibility, anhysteretic susceptibility mass normalized and hysteresis parameters, served to determine magnetic properties and identify the magnetic composition of the study material. We selected two distinct types of sediments. The first group, consisting of magnetite and pyrrhotite, has more single-domain grains in comparison to the second one, containing only magnetite. In the second group, multi-domain particles dominate. Deposits from the north stream, glacier river and an area close to the estuary of Nottinghambukta include magnetite and pyrrhotite. Magnetite was found in the south stream and in the outside part of the bay. Magnetic composition reflects different source rocks of sediments. This study demonstrates the utility of the magnetic method in analysing the current state of glacier environments.

Estimation of Flow and Hysteresis Parameters Applicable to WAG Experiments

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 183321, “An Improved Approach for Estimation of Flow and Hysteresis Parameters Applicable to WAG Experiments,” by Pedram Mahzari and Mehran Sohrabi, Heriot-Watt University, prepared for the 2016 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 7–10 November. The paper has not been peer reviewed. Water-alternating-gas (WAG) injection has demonstrated encouraging results for improving oil recovery. However, numerical simulation of three-phase flow and the associated hysteresis effects are not well-understood. In the complete paper, a new assessment of the WAG-hysteresis model, which was developed originally for water-wet conditions, was carried out by automatic history matching of two coreflood experiments in water-wet and mixed-wet conditions. The results indicate that history matching the entire WAG experiment would lead to a significantly improved simulation outcome. Introduction Using an optimization software, the authors have carried out a series of history-matching exercises on coreflood experiments to evaluate the performance of the WAG-hysteresis model and to simulate WAG experiments conducted on mixed-wet and water-wet cores at near-miscible conditions. The main difference here compared with previous work is the tuning of the parameters relevant to the WAG-hysteresis model on entire WAG experiments (rather than on individual cycles of one experiment) with a new methodology to estimate more-representative two-phase relative permeability curves from the WAG experiments. Coreflood Experiments and History-Matching Method There are numerous coreflood experiments in the literature that can be used for studying pure WAG-related interactions at near-miscible conditions. The unique advantages of this data set are gravity-segregation effect has been excluded by rotating the core while the fluids were being injected and all the fluids (water/oil/gas) were thermodynamically pre-equilibrated to minimize the effect of mass transfers at near-miscible conditions. Therefore, the processes taking place in the coreflood experiments can be attributed solely to multiphase flow and hysteresis effects. The following coreflood tests were selected from the data set to investigate the behavior of flow functions with respect to fluid saturation, injection scenario, and initial wettability: Continuous gas injection in the water-wet core saturated with oil at irreducible water saturation, used to estimate two-phase gas/oil relative permeabilities Continuous gas injection in the mixed-wet core saturated with oil at irreducible water saturation, used to estimate two-phase gas/oil relative permeabilities WAG experiment performed at low-gas/oil-interfacial-tension (near-miscible) conditions in a mixed-wet core, with the starting water-injection displacement used to obtain water/oil-flow functions WAG experiment performed at near-miscible conditions in a water-wet core, with the starting water-injection displacement used to obtain water/oil-flow functions

Random mixed-metal Co1-xNix single-chain magnets with simultaneous azide, carboxylate and tetrazolate bridges.

This paper reports the magnetic properties of a series of isomorphous metal-organic frameworks based on random heterometallic Co1-xNix chains with simultaneous azide, carboxylate and tetrazolate bridges. All the mixed-metal compounds show intrachain FM interactions, field-induced metamagnetism, and SCM-like slow magnetic relaxation. These behaviors are quite different from the parent Co(ii) and Ni(ii) materials, and even a small amount of metal replacement can cause significant magnetic changes. The static properties such as AF ordering, metamagnetic critical field and the hysteresis parameters show complicated composition dependence. Most interestingly, the mixed-metal systems can show a higher blocking temperature than the Co(ii) compound, suggesting that the randomly distributed metal ions have synergistic effects on slow relaxation of magnetization. This is phenomenologically associated with the competitive effects of Δτ and τo.

Electrocaloric behavior and temperature dependent scaling of dynamic hysteresis of BaxSr1-xTiO3 (x = 0.7, 0.8 and 0.9) bulk ceramics

This article presents electrocaloric effect in BaxSr1-xTiO3 ferroelectric ceramics using an indirect approach based on Maxwell’s relations. The peak electrocaloric performance is found to be an adiabatic temperature change of 0.67, 0.83, and 0.61 K and isothermal entropy change of 0.9, 1, and 0.7 J/kg.K for x = 0.7, 0.8, and 0.9, respectively, under an electric field of 33 kV/cm. The electrocaloric coefficient of performance (COP) of materials were also estimated as 17, 5.47, and 5.68 when x = 0.7, 0.8, and 0.9, respectively, in BaxSr1-xTiO3 at 33 kV/cm (303 K). Further, the ferroelectric hysteresis parameters scaling relations of coercive field (E c) and remnant polarization (P r) as a function of temperature have been estimated. The back switching polarization (P bc) as a function of temperature (T) was estimated by the Arrhenius law in order to understand the domain dynamics, and the average activation energy was evaluated.

Impact of an iron mine and a nickel smelter at the Norwegian/Russian border close to the Barents Sea on surface soil magnetic susceptibility and content of potentially toxic elements

An important problem in soil magnetometry is unraveling the soil contamination signal in areas with multiple emitters. Here, geophysical and geochemical measurements were performed at four sites on a north - south transect along the Pasvik River in the Barents Region (northern Norway). These sites are influenced by depositions from the Bjørnevatn iron mine and a Ni-Cu smelter in Nikel, Russia. To relate the degree and type of pollution from these sources to the corresponding magnetic signal, the topsoil concentrations of 12 Potentially Toxic Elements (PTEs) (As, Cd, Co, Cr, Cu, Fe, Mo, Ni, Pb, Se, Ti, Zn), were determined, magnetic hysteresis parameters and thermomagnetic properties were measured. In situ magnetic low-field susceptibility decreases from north to south with increasing distance from the iron mine. Relatively large magnetic multidomain grains of magnetite and/or titanomagnetite are responsible for the strong magnetic signal from the topsoil close to Bjørnevatn. These particles are related to increased enrichment factors of As, Mo and Cu, yielding high positive correlation coefficients with susceptibility values. At a site furthest away from the iron mine and located 7 km from the Ni-Cu smelter magnetic susceptibility values are much lower but significant positive correlations on the level of p < .1 with 8 PTEs (Ni, Cu, Co, Se, As, Zn, Cd, Cr) have been observed. The magnetic signal in this area is due to fine-grained primary sulphides and secondary fine-grained magnetite and/or maghemite.

Relationship of corneal hysteresis and optic nerve parameters in healthy myopic subjects

The association between corneal biomechanical properties and glaucoma is an area of much interest. We determined the relationship between corneal hysteresis (CH) and optic nerve parameters in healthy myopic subjects in the current study. CH was measured with Reichert Ocular Response Analyzer in 108 eyes from 108 healthy myopic subjects. All subjects received retinal nerve fiber layer and optic disc imaging Cirrus HD-OCT, GDx ECC, and Heidelberg Retina Tomograph II. None of the tested optic nerve parameters showed statistical significance with CH by using correlation analysis. For RNFL parameters, there was a negative but not statistically significant correlation between CH and average RNFL thickness obtained with OCT (r = −0.15, p = 0.13). For optic disc parameters, there was a negative but not statistically significant correlation between CH and rim area measured with OCT (r = −0.10, p = 0.29). The current study did not find any statistically significant relationship between CH and optic nerve parameters as measured by all three imaging modalities in healthy myopic eyes. Therefore, the relationship observed previously in glaucoma subjects is likely coming to fruition as optic nerve damage is caused by the disease.