Evolution Of Magnetic Susceptibility Research Articles

Sub-voxel quantitative susceptibility mapping for assessing whole-brain magnetic susceptibility from ages 4 to 80.

The evolution of magnetic susceptibility of the brain is mainly determined by myelin in white matter (WM) and iron deposition in deep gray matter (DGM). However, existing imaging techniques have limited abilities to simultaneously quantify the myelination and iron deposition within a voxel throughout brain development and aging. For instance, the temporal trajectories of iron in the brain WM and myelination in DGM have not been investigated during the aging process. This study aimed to map the age-related iron and myelin changes in the whole brain, encompassing myelin in DGM and iron deposition in WM, using a novel sub-voxel quantitative susceptibility mapping (QSM) method. To achieve this, a cohort of 494 healthy adults (18-80 years old) was studied. The sub-voxel QSM method was employed to obtain the paramagnetic and diamagnetic susceptibility based on the approximated map from acquired map. The linear relationship between and maps was established from the regression coefficients on a small cohort data acquired with both 3D gradient recalled echo data and mapping. Large cohort sub-voxel susceptibility maps were used to create longitudinal and age-specific atlases via group-wise registration. To explore the differential developmental trajectories in the DGM and WM, we employed nonlinear models including exponential and Poisson functions, along with generalized additive models. The constructed atlases reveal the iron accumulation in the posterior part of the putamen and the gradual myelination process in the globus pallidus with aging. Interestingly, the developmental trajectories show that the rate of myelination differs among various DGM regions. Furthermore, the process of myelin synthesis is paralleled by an associated pattern of iron accumulation in the primary WM fiber bundles. In summary, our study offers significant insights into the distinctive developmental trajectories of iron in the brain's WM and myelination/demyelination in the DGM in vivo. These findings highlight the potential of using sub-voxel QSM to uncover new perspectives in neuroscience and improve our understanding of whole-brain myelination and iron deposit processes across the lifespan.

Modeling and Mapping of Soil Water Erosion Risks in the Srou Basin (Middle Atlas, Morocco) Using the EPM Model, GIS and Magnetic Susceptibility

Abstract The Oued Srou watershed located in the Middle Atlas Mountain of Morocco has been a subject of serious soil erosion problems due to the combination of natural factors and anthropic activities. Therefore, soil erosion hazard assessment and mapping can be handy to initiate remedial measures in the area. In this study, the improved Erosion Potential Model (EPM) integrated with GIS and remote sensing techniques is employed to map and assess the vulnerability of the Oued Srou watershed to the water erosion phenomenon and its impact on the silting of the Ahmed El Hansali dam. The results of the EPM model showed that the maximum annual soil loss rates were in the range of 5-652 m3/km2/year, with an average of 49 m3/km2/year. The delivery coefficient ratio showed that about 34433 t/year of the sediments reach the outlet of the watershed. The correlation analysis between all erosion factors revealed the following order of their importance in the water erosion control: soil sensitivity to erosion, soil protection, slope, erosive state, temperature, and rainfall. The magnetic susceptibility provided results on the evolution of soils; it showed that the most degraded soils had a high erosion rate. Generally, the stable soils not eroded showed an upward increase of magnetic susceptibility values in soil profiles; the evolution of magnetic susceptibility of degraded soils is disturbed. The magnetic susceptibility has also made it possible to highlight the source zones of sediments that reach the outlet of the watershed.

Temporal changes in magnetic signal of burnt soils – A compelling three years pilot study

Wildfires strongly affect soils, including iron biogeochemical cycling and carbon storage. Thus, it is important to reveal the dynamics of iron oxide synthesis and transformations during and after a wildfire. This study investigates the temporal stability of strongly magnetic minerals appearing after a wildfire. Following a designed experimental fire, samples from vegetation ash and mineral soil were taken immediately after and at progressively longer time intervals. The magnetic susceptibility monitoring of samples during three years period demonstrates an initial increase in magnetic signal of ash-rich material taken immediately after the fire followed by a gradual decrease over time. The behavior of samples collected later after the fire showed only a moderate decrease. It is suggested that the magnetic susceptibility rise during the laboratory storage could be due to the increased availability of nutrients and microbial activity immediately after the fire and related intense redox reactions involving iron oxide particles. The decreasing trend in magnetic susceptibility is ascribed to the oxidation of ultrafine magnetite particles with time. All mineral soil samples from the deeper level showed an initial susceptibility increase, assigned to a similar process. Magnetic susceptibility monitoring was also carried out on samples gathered shortly after natural wildfires. The soil samples affected by strong and long wildfires show a decrease in magnetic susceptibility with time. This effect is more pronounced in the surface black-colored ash layer. The ash material from a site disturbed by a strong short wildfire demonstrates behavior similar to the ash from the experimental fire. It is supposed that the temporal evolution of magnetic susceptibility of the mineral alteration products of wildfires is influenced by the grain size of the produced iron oxide particles, their redox reactions mediated by the heterotrophic bacteria, as well as the amplifying role of pyrogenic carbon for intensification of the redox reactions.

Magnetic susceptibility and facies relationship in Bajocian–Bathonian carbonates from the Azé caves, southeastern Paris Basin, France

Abstract This study focuses on three Bajocian and Bathonian carbonate sections from the southeastern part of the Paris Basin (Mâconnais area, in the east of France). The main goals of the study are to propose a palaeoenvironmental model, to get insight into vertical and lateral facies evolution, to improve correlations and to better understand the origin of the magnetic susceptibility (MS) signal in these deposits. The sedimentological setting corresponds to a ramp, with two types of geometries: (1) a homoclinal carbonate ramp with oolitic shoals; and (2) a multiple-slopes carbonate ramp with reef complexes. The MS signal appears to be influenced by facies and ramp geometry. The evolution of MS seems to be mainly related to changes in carbonate productivity and water agitation: oolitic facies and reef complexes, with high carbonate production show the lowest signal, while storm deposits are characterized by higher values. In addition, the MS signal from proximal tempestites have higher values than distal ones. MS appears to be a useful complementary proxy for palaeoenvironmental interpretations, correlations and sequential stratigraphy. The facies evolution, supported by MS curves, shows at least nine successive depositional sequences, which were inserted into the regional sequential canvas.

Sedimentary development and magnetic susceptibility evolution of the Frasnian in Western Belgium (Dinant Synclinorium, La Thure section)

Abstract Recent opening of the La Thure quarry in Western Belgium allowed the collection of new data from a poorly outcropping area of the Belgian Frasnian platform. The studied section covers an interval extending from the falsiovalis to hassi s.l. Zones. Sedimentological analyses allowed the reconstruction of depositional settings in the northwestern part of the Dinant Synclinorium after the demise of the extended Givetian carbonate platform. Two depositional models are distinguished: (a) siliciclastic drowned platform during the Early Frasnian; and (b) a fore-reef depositional setting belonging to a rimmed shelf during the Middle Frasnian. Moreover, interpreted depositional settings in the northwestern part of the Dinant Synclinorium allowed to constraint the direction of the main facies belts for the Belgian Frasnian platform. Combination of MS and geochemistry demonstrates the inherent-parallel link existing between variation in MS values and proxy for terrestrial input (such as Si and Al). This observation means that, despite the remagnetization occurring within the Belgian Frasnian lithologies, the main trends in the MS signal from the La Thure section still reflect some syn-sedimentary conditions. The increase in MS and clastic input proxies recorded in distal fore-reef deposit within the punctata Zone are likely to be considered as enhanced by rapid and strong shallowing events recognized in the ‘ puncata Event’ interval.

Crossover in the magnetic response of single-crystallineBa1−xKxFe2As2and Lifshitz critical point evidenced by Hall effect measurements

We report the doping evolution of magnetic susceptibility $\chi (T)$ and Hall coefficient $R_H$ in high quality Ba$_{1-x}$K$_x$Fe$_2$As$_2$ ($0.13 \leq x \leq 1$) single crystals. It is found that the normal-state magnetic susceptibility of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ compounds undergoes a crossover from linear-$T$ dependence in the undoped and underdoped samples into KFe$_2$As$_2$-type magnetic response in the overdoped samples with increasing K content. Hall coefficient $R_H$ of underdoped sample $x$=0.22 shows a rapid increase above spin-density-wave transition temperature $T_{SDW}$. Below $T_{SDW}$, it increases slowly. $R_H$ of optimally doped and slightly overdoped samples ($0.34 \leq x \leq 0.65$) shows relative weak temperature dependence and saturation tendency below 150 K. However, $R_H$ of K heavily overdoped samples ($0.80 \leq x \leq 1$) increases rapidly below 150 K. Meanwhile, Hall angle $cot \theta _H$ displays a concave temperature dependence within the doping range $0.22 \leq x \leq 0.55$, whereas it changes to a convex temperature dependence within the doping range $0.65 \leq x \leq 1$. The dramatic change coincides with Lifshitz transition occurred around the critical doping $x$=0.80, where ARPES measurements had confirmed that electron pocket disappears with excess hole doping in Ba$_{1-x}$K$_x$Fe$_2$As$_2$ system. It is suggested that the characteristic temperature $T$* at around $120 \sim 150$ K observed in susceptibility and Hall coefficient, as well as previously reported resistivity data, may indicate an incoherence-coherence crossover in Ba$_{1-x}$K$_x$Fe$_2$As$_2$ system.

Differential developmental trajectories of magnetic susceptibility in human brain gray and white matter over the lifespan

As indicated by several recent studies, magnetic susceptibility of the brain is influenced mainly by myelin in the white matter and by iron deposits in the deep nuclei. Myelination and iron deposition in the brain evolve both spatially and temporally. This evolution reflects an important characteristic of normal brain development and ageing. In this study, we assessed the changes of regional susceptibility in the human brain in vivo by examining the developmental and ageing process from 1 to 83 years of age. The evolution of magnetic susceptibility over this lifespan was found to display differential trajectories between the gray and the white matter. In both cortical and subcortical white matter, an initial decrease followed by a subsequent increase in magnetic susceptibility was observed, which could be fitted by a Poisson curve. In the gray matter, including the cortical gray matter and the iron-rich deep nuclei, magnetic susceptibility displayed a monotonic increase that can be described by an exponential growth. The rate of change varied according to functional and anatomical regions of the brain. For the brain nuclei, the age-related changes of susceptibility were in good agreement with the findings from R2* measurement. Our results suggest that magnetic susceptibility may provide valuable information regarding the spatial and temporal patterns of brain myelination and iron deposition during brain maturation and ageing.

Electrodeposition of thin films and nanowires Ni–Fe alloys, study of their magnetic susceptibility

Electrodeposition of thin films and nanowires Ni–Fe alloys is presented. For the thin films, we have studied the impact of various electrolytic conditions (magnetic induction, pH, and substrate) on the composition and magnetic susceptibility. Whatever the electrolytic conditions, the evolution of the composition versus the polarization exhibited first a decrease of the Ni content within the deposit followed by an increase. However, at constant polarization, the obtained values were different. Concerning the evolution of the magnetic susceptibility versus the composition, it is known that it decreases with the enhancement of the Ni percentage. The reason is that the susceptibility of iron is higher than that of Ni. It can also observe a sharp rupture in the evolution of magnetic susceptibility, which appeared near the Invar composition (Ni36Fe64). Our results show that the electrolytic conditions do not affect the position of the rupture point for the thin films but modify the susceptibility values. For the nanowires, a polycarbonate membrane has been used as a template. The structural characteristics of wires were examined using X-ray diffraction. According to the composition and as described in the literature for the electrodeposited thin films, a change between the body-centered cubic structure and face-centered cubic structure was obtained for the nanowires. However, for the nanowires this modification appeared for a lower Ni content than for this in thin films. Finally, a comparison of their magnetic susceptibility with thin films exhibited a shift toward the lower Ni contents for the rupture point.

Temperature evolution of magnetic susceptibility during devitrification of Cu-free HITPERM alloy

Development of structural and magnetic properties of the Fe 44.5Co 44.5Zr 7B 4 alloy during its successive devitrification from amorphous to nanocrystalline state was investigated. Temperature independence of the initial susceptibility in a wide temperature range (20–600 °C) was observed. The origin of such susceptibility behavior was described through the compensation of lowering exchange interaction between nanocrystalline grains and their magnetization at increased temperatures. The stabilization of the domain structure, due to atom pair directional ordering, was confirmed by measurements of the amplitude dependence of susceptibility in a wide field range, where the initial susceptibility remains constant (Perminvar effect).

Diagenetic versus detrital origin of the magnetic susceptibility variations in some carbonate Frasnian–Famennian boundary sections from Northern Africa and Western Europe: implications for paleoenvironmental reconstructions

To provide a new insight into the diagenetic versus detrital origin of the magnetic susceptibility variations in ancient carbonate sequences, a study was conducted within four Frasnian–Famennian platform carbonate sections from Germany, France and Morocco. The study includes along-section magnetic susceptibility and carbonate content measurements complemented by analyses of magnetic hysteresis parameters, inorganic geochemistry and clay mineralogy. Our results show that the magnetic susceptibility evolution is dominantly controlled by the variations in the concentration of low-coercivity ferromagnetic magnetite grains and, to a lesser extent, of paramagnetic clays. In more detail, hysteresis ratios suggest the coexistence of two magnetite populations with significantly different grain size: (1) a dominantly coarse-grained detrital fraction including a mixture of multi-domain and single-domain particles (2) an authigenic fine-grained fraction composed of a mixture of single-domain and superparamagnetic particles. Despite a diagenetic imprint on the clay assemblages, no relationship is established between magnetic susceptibility and illite crystallinity, therefore discarding a noticeable distortion of primary within-section magnetic susceptibility evolution. The overall inherited character of the magnetic susceptibility fluctuations is corroborated by a significant correlation of magnetic susceptibility with terrigenous proxies (Zr, Th). The poorer correlation of magnetic susceptibility with the Fe content is consistent with the existence of a very fine-grained authigenic magnetite component that possibly induces a global magnetic susceptibility increase at the section scale, but no distortion of the within-section evolution. The magnetic susceptibility curves presented here provide a general record of climate-driven detrital influx and carbonate productivity through Frasnian–Lower Famennian times.

Paleointensity data from Early Cretaceous Ponta Grossa dikes (Brazil) using a multisample method

Abstract Definition of the long-term variation of the geomagnetic virtual dipole moment requires more reliable paleointensity results. Here, we applied a multisample protocol to the study of the 130.5 Ma Ponta Grossa basaltic dikes (southern Brazil) that carry a very stable dual-polarity magnetic component. The magnetic stability of the samples was checked using thermomagnetic curves and by monitoring the magnetic susceptibility evolution through the paleointensity experiments. Twelve sites containing the least alterable samples were chosen for the paleointensity measurements. Although these rocks failed stepwise double-heating experiments, they yielded coherent results in the multisample method for all sites but one. The coherent sites show low to moderate field intensities between 5.7±0.2 and 26.4±0.7 μT (average 13.4±1.9 μT). Virtual dipole moments for these sites range from 1.3±0.04 to 6.0±0.2 × 1022 A m2 (average 2.9±0.5 × 1022 A m2). Our results agree with the tendency for low dipole moments during the Early Cretaceous, immediately prior to the Cretaceous Normal Superchron (CNS). The available paleointensity database shows a strong variability of the field between 80 and 160 Ma. There seems to be no firm evidence for a Mesozoic Dipole Low, but a long-term tendency does emerge from the data with the highest dipole moments occurring at the middle of the CNS.

Magnetic susceptibility evolution and sedimentary environments on carbonate platform sediments and atolls, comparison of the Frasnian from Belgium and Alberta, Canada

Magnetic susceptibility (MS) measurements on carbonate rocks are considered as a proxy for impurities delivered to the carbonate environments. In the absence of strong climatic or tectonic variations, bulk MS values have been linked to sea level variations, because sea-level fall increases clastic supply and therefore increases in magnetic mineral deposition. In this paper we explore the relationship between the average magnitude of bulk MS, with shallowing-up sequences and facies evolution in different Devonian carbonate complexes. Similarities and differences between these parameters have been scrutinized in carbonate attached platform and detached platforms (mounds and/or atolls) from Belgium and Canada. In the carbonate attached platforms from Belgium and Canada, the MS patterns are directly related to depositional environment. Mean MS values increase from the most distal towards the most proximal facies and towards the top of the majority of fourth-order shallowing-up sequences. These trends are in agreement with theoretical background (MS increases with regression). In the Belgian detached platform, the average MS pattern generally shows an opposite behaviour to that observed in the attached carbonate platforms. Average MS decreases towards the most proximal facies and towards the top of a majority of the fourth-order shallowing-up sequences. This behaviour can be explained by the influence of sedimentary rate and water agitation during deposition. A high sedimentary rate will dilute the magnetic minerals in the atoll facies and the high water agitation during deposition may be expected to have prevented the deposition of the magnetic grains. So, the combination of these two effects will result in the observed low values in the atoll crown and lagoonal facies. In the Canadian detached platform, MS is mainly negative. This means that the limestones are very pure. The technique does not appear to be appropriate in these rocks. The variations of average MS behaviour by platform type can imply difficulties in correlating carbonates from different settings. A comparison of time equivalent mound and platform deposits shows that after an important regressive surface, the MS values are increasing for the platform deposits and decreasing for the mound. So MS evolution can be in complete opposition (caused by highly different sedimentary rates) in different depositional settings. The MS signal preserved in carbonate rocks is probably mainly related to 1) varying clastic supplies; 2) varying carbonate accumulation rates (dilution of the magnetic minerals by high carbonate production) and 3) potentially diagenesis.

Growth, structural, IR and magnetic studies of a new gadolinium metaphosphate, Gd(PO 3) 3

The crystal structure of gadolinium metaphosphate Gd(PO 3) 3 has been established by X-ray diffraction. This compound crystallizes in the orthorhombic system (space group C222 1, Z = 4) with cell parameters: a = 8.4530 (3), b = 11.0576 (4) and c = 7.1952 (2) Å. The structure was refined to R 1 = 0.0234 and w R 2 = 0.0502 using 2180 independent reflections ( I > 2 σ( I)). Phosphorus atoms are in slightly irregular tetrahedral oxygen coordination, gadolinium atoms are in considerably distorted dodecahedral oxygen coordination. Formally, the 3D framework in the structure can be described by the PO 4 tetrahedra sharing corners to form helical chains and the GdO 8 polyhedra sharing edges in a zigzag fashion. The shortest Gd–Gd distance is 4.174 (2) Å. The infrared spectrum of the title compound recorded at room temperature in the frequency range of 400–4000 cm −1, confirm the atomic arrangement within the structure. Below T C = 25 K, the magnetic susceptibility evolution is characteristic of a ferromagnetic order. In the high-temperature region above 100 K, the susceptibility follows a Curie–Weiss law with C = 7.91 cm 3 K mol −1 and θ = 9.96 K.

Crystal Structure and Magnetic Properties of Li2Mn2(SO4)3

The crystal structure of dilithium dimanganese trisulfate Li2Mn2(SO4)3 has been established by single-crystal X-ray diffraction. This compound crystallizes in the orthorhombic system (space group Pbca, Z=8) with cell parameters a=8.686(2) Å, b=8.792(2) Å, and c=24.146(4) Å. The structure was refined to R=0.035 and Rw=0.037 using 2622 independent reflections. Lithium and sulfur atoms are in most regular tetrahedral oxygen coordination, manganese atoms are in slightly distorted octahedral oxygen coordination. Formally, the 3-D framework can be described, starting from the Li2Mg2(SO4)3 structure, by condensation of Sc2(WO4)3-type slabs. As a result, half of the LiO4 and MnO6 polyhedra share an edge, forming Li2O6 and Mn2O10 dimeric entities. Below TN=10 K, the magnetic susceptibility evolution is characteristic of a long-range antiferromagnetic order. In the high-temperature region, the susceptibility follows a Curie–Weiss law with C=8.51 cm3 K mol−1 and θ=−19 K. In a Mn2O10 bioctahedron the Mn2+ cations are indeed antiferromagnetically coupled with an interaction parameter J=−6.5 cm−1.

Magnetostratigraphy of Pliocene Sediments From the Stirone River (Po Valley)

The Miocene-Pliocene and Pliocene-Pleistocene boundaries bracket a Pliocene section, approximately 800 m thick, along the Stirone river near Parma (Northern Italy). From the base to the top, the sequence consists mainly of blue clays (Zanclean in age), whitish laminates, silty clays and sandstones of Piacenzian age. A debris flow, which is the sedimentary expression of a hiatus, separates the Zanclean from the Piacenzian sediments. Thermomagnetic analysis, thermal evolution of magnetic susceptibility, acquisition and removal of anhysteretic and isothermal remanent magnetization (ARM and IRM) by alternating field and thermal methods, X-ray diffraction and scanning electron-microscopy (SEM) have been used in conjunction to try and unravel the complex magnetic mineralogy of the Stirone samples. Two major carriers of the magnetic remanence appear to be pseudo-single domain (PSD) magnetite and high-coercivity pyrrhotite in varying amounts and grain sizes. Five different magnetic indicators yield roughly consistent logs, with magnetite being important in the lower part of the section and pyrrhotite becoming dominant upsection. Six zones with more or less uniform properties have been outlined. Except in the lowermost zone where magnetite is also an important carrier, pyrrhotite in the 150-350°C range is taken to be the main carrier of the characteristic and, we believe, primary magnetization. The overall mean direction for about 200 samples is D = 0, I = 52 (ag5 = 3), corresponding to a lack of local rotation about a vertical axis but implying some 10 of inclination shallowing. The magnetostratigraphy encompasses ten successive polarity zones. Correlation of magnetic and biostratigraphic results to the geomagnetic polarity time scale and to the biozonation of the Mediterranean area leads to the proposal that the Thvera subchron and part of the above reversed polarity zone are missing, as revealed by the absence of the Sphaeroidinellopsis seminulina s.1. Zone and by the occurence of Globorotalia margaritae from the very base of the section. The Sidufjall and Nunivak subchrons are recognized and the first occurrence of Globorotalia puncticulata occurs just above Nunivak subchron. The Cochiti subchron is observed next. A remarkable hiatus involves the upper part of the Gilbert chron up to the lower part of the Kaena subchron based on the record of the last occurrence of G. margaritae and G. puncticulata and the first occurence of G. aemiliana and G. bononiemis. Another hiatus involving the Reunion and Olduvai subchrons is suggested to occur in the upper part of the Pliocene sequence based on the absence of the G. inflata Zone and on the first occurrence of'Artica islandica, which marks the Pliocene/Pleistocene boundary, towards the top of the section. The average sedimentation rate is estimated to be 450-500 m Ma-' for the early Pliocene and 200-300 m Ma-1 for the late Pliocene. Despite highly non-uniform sedimentation, both reflecting the episodic nature of coupled tectonic and sedimentary processes on 359 Downloaded from https