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Sample records for generalised magnetic susceptibility

  1. Generalised relativistic Ohm's laws, extended gauge transformations, and magnetic linking

    SciTech Connect

    Pegoraro, F.

    2015-11-15

    Generalisations of the relativistic ideal Ohm's law are presented that include specific dynamical features of the current carrying particles in a plasma. Cases of interest for space and laboratory plasmas are identified where these generalisations allow for the definition of generalised electromagnetic fields that transform under a Lorentz boost in the same way as the real electromagnetic fields and that obey the same set of homogeneous Maxwell's equations.

  2. Generalised relativistic Ohm's laws, extended gauge transformations, and magnetic linking

    NASA Astrophysics Data System (ADS)

    Pegoraro, F.

    2015-11-01

    Generalisations of the relativistic ideal Ohm's law are presented that include specific dynamical features of the current carrying particles in a plasma. Cases of interest for space and laboratory plasmas are identified where these generalisations allow for the definition of generalised electromagnetic fields that transform under a Lorentz boost in the same way as the real electromagnetic fields and that obey the same set of homogeneous Maxwell's equations.

  3. Magnetic susceptibilities of minerals

    USGS Publications Warehouse

    Rosenblum, Sam; Brownfield, I.K.

    2000-01-01

    Magnetic separation of minerals is a topic that is seldom reported in the literature for two reasons. First, separation data generally are byproducts of other projects; and second, this study requires a large amount of patience and is unusually tedious. Indeed, we suspect that most minerals probably are never investigated for this property. These data are timesaving for mineralogists who concentrate mono-mineralic fractions for chemical analysis, age dating, and for other purposes. The data can certainly be used in the ore-beneficiation industries. In some instances, magnetic-susceptibility data may help in mineral identification, where other information is insufficient. In past studies of magnetic separation of minerals, (Gaudin and Spedden, 1943; Tille and Kirkpatrick, 1956; Rosenblum, 1958; Rubinstein and others, 1958; Flinter, 1959; Hess, 1959; Baker, 1962; Meric and Peyre, 1963; Rojas and others, 1965; and Duchesne, 1966), the emphasis has been on the ferromagnetic and paramagnetic ranges of extraction. For readers interested in the history of magnetic separation of minerals, Krumbein and Pettijohn (1938, p. 344-346) indicated nine references back to 1848. The primary purpose of this paper is to report the magnetic-susceptibility data on as many minerals as possible, similar to tables of hardness, specific gravity, refractive indices, and other basic physical properties of minerals. A secondary purpose is to demonstrate that the total and best extraction ranges are influenced by the chemistry of the minerals. The following notes are offered to help avoid problems in separating a desired mineral concentrate from mixtures of mineral grains.

  4. Magnetic susceptibility, petrofabrics and strain

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham John

    1988-12-01

    Magnetic susceptibility is a non-destructive technique for quantifying the average fabric of a small sample of rock. The interpretation of the magnetic fabric is not always straightforward. However, the principal directions of the magnitude ellipsoid of susceptibility commonly show orientations consistent with the kinematic interpretations of folds, shear zones and other structural features. The directions may correspond with the orientations of strained objects or with the planar-linear mineral orientations. There will usually be multiple mineralogical sources of susceptibility, often involving silicates. If the sources are known, or if the susceptibility can be attributed to a single mineral species, it may be possible to establish a correlation between the strain ellipsoid and the susceptibility ellipsoid. This correlation will be of principal directions in many instances and occasionally there may be a weak correlation of strain magnitudes as well. In other circumstances it may be possible to establish a correlation between changes in susceptibility and the strain. Nevertheless magnetic fabric studies are not routine substitutes for strain analysis. Even where information on strain is not provided, the magnetic fabrics (and subfabrics) yield a measure of the preferred crystallographic orientation or preferred dimensional orientation of the minerals that may be integrated profitably with other petrofabric data. Experimental deformation of certain synthetic aggregates indicates that directions of magnetic susceptibility spin rapidly with advancing strain, especially where the matrix grains undergo crystal-plastic deformation. In certain experiments, simple shear appears to change the intensity of magnetic fabric more effectively than pure shear. Experiments indicate also that the initial anisotropy of a rock-like material is not easily overprinted by deformation whereas field studies are equivocal.

  5. Magnetic susceptibility of topological nodal semimetals

    NASA Astrophysics Data System (ADS)

    Mikitik, G. P.; Sharlai, Yu. V.

    2016-11-01

    Magnetic susceptibility of the topological Weyl, type-II Weyl, Dirac, and line node semimetals is theoretically investigated. Dependences of this susceptibility on the chemical potential, temperature, direction, and magnitude of the magnetic field are found. The obtained results show that magnetic measurements can be very useful in investigating these semimetals. As an example, we calculate magnetic susceptibility of Cd3As2 ,Na3Bi , and Ca3P2 .

  6. Accuracy of magnetic resonance based susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Erdevig, Hannah E.; Russek, Stephen E.; Carnicka, Slavka; Stupic, Karl F.; Keenan, Kathryn E.

    2017-05-01

    Magnetic Resonance Imaging (MRI) is increasingly used to map the magnetic susceptibility of tissue to identify cerebral microbleeds associated with traumatic brain injury and pathological iron deposits associated with neurodegenerative diseases such as Parkinson's and Alzheimer's disease. Accurate measurements of susceptibility are important for determining oxygen and iron content in blood vessels and brain tissue for use in noninvasive clinical diagnosis and treatment assessments. Induced magnetic fields with amplitude on the order of 100 nT, can be detected using MRI phase images. The induced field distributions can then be inverted to obtain quantitative susceptibility maps. The focus of this research was to determine the accuracy of MRI-based susceptibility measurements using simple phantom geometries and to compare the susceptibility measurements with magnetometry measurements where SI-traceable standards are available. The susceptibilities of paramagnetic salt solutions in cylindrical containers were measured as a function of orientation relative to the static MRI field. The observed induced fields as a function of orientation of the cylinder were in good agreement with simple models. The MRI susceptibility measurements were compared with SQUID magnetometry using NIST-traceable standards. MRI can accurately measure relative magnetic susceptibilities while SQUID magnetometry measures absolute magnetic susceptibility. Given the accuracy of moment measurements of tissue mimicking samples, and the need to look at small differences in tissue properties, the use of existing NIST standard reference materials to calibrate MRI reference structures is problematic and better reference materials are required.

  7. Magnetization and magnetic susceptibility of DyH3

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1975-01-01

    The magnetization and differential magnetic susceptibility of powdered DyH3 samples are measured at a temperature of 4.2 K in applied magnetic fields ranging up to 9 Teslas. The differential magnetic susceptibility is also investigated in the zero applied field. Magnetization is plotted as a function of field strength, and differential susceptibility is described as a function of both field strength and temperature. A saturation magnetic moment of 5.12 Bohr magnetons per ion is derived from the magnetization data, and the zero-field susceptibility measurements are found to indicate antiferromagnetic ordering below 3.45 K. The susceptibility at 4.2 K is shown to have an inverse-square dependence on field strength for values of not less than 0.3 Tesla.

  8. Magnetic susceptibility of tetragonal titanium dioxide

    USGS Publications Warehouse

    Senftle, F.E.; Pankey, T.; Grant, F.A.

    1960-01-01

    Careful measurements have been made of the magnetic susceptibility of the rutile and anatase crystalline forms of titanium dioxide. The magnetic susceptibility of a single crystal of high-purity rutile was found to be (0.067??0.0015)??10-6 emu per gram, and was temperature-independent from 55??to 372??K. Difficulty was encountered in obtaining a good value of the magnetic susceptibility of anatase because of impurities. However, a value of 0.02??10-6 emu per gram was obtained as a maximum value for anatase powder. A discussion is given for the different values obtained for anatase and rutile. ?? 1960 The American Physical Society.

  9. Static spin susceptibility in magnetically ordered states

    NASA Astrophysics Data System (ADS)

    Kuboki, Kazuhiro; Yamase, Hiroyuki

    2017-08-01

    We report that special care is needed when longitudinal magnetic susceptibility is computed in a magnetically ordered phase, especially in metals. We demonstrate this by studying static susceptibility in both a ferromagnetic and an antiferromagnetic state in the random phase approximation to the two-dimensional Hubbard model on a square lattice. In contrast to the case in the disordered phase, a first derivative of the chemical potential (or the density) with respect to a magnetic field does not vanish in a magnetically ordered phase when the field is applied parallel to the magnetic moment. This effect is crucial and should be included when computing magnetic susceptibility in the ordered phase, otherwise an unphysical result would be obtained. In addition, consequently the magnetic susceptibility becomes different when computed at a fixed density and a fixed chemical potential in the ordered phase. In particular, we cannot employ magnetic susceptibility at a fixed chemical potential to describe a system with a fixed density even if the chemical potential is tuned to reproduce the correct density.

  10. Magnetization and magnetic susceptibility of DyH3

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1974-01-01

    The magnetization and differential magnetic susceptibility of powdered samples of DyH3 have been measured at 4.2 K in applied magnetic fields ranging to 9 Teslas. The differential magnetic susceptibility has also been studied in zero applied field as a function of temperature. The magnetization data are described by an equation of the form M = aB/(1 + bB + cB. The ratio a/b is a measure of the saturation magnetization and gives an effective moment of 5.12 Bohr magnetons per ion. The zero field susceptibility exhibits a maximum at T = 3.45 K, and an inflection point near 2.85 K. The susceptibility at 4.2 K has a 1/B squared dependence on the applied magnetic field for B approximately greater than 0.3 Teslas.

  11. Materials with low DC magnetic susceptibility for sensitive magnetic measurements

    NASA Astrophysics Data System (ADS)

    Khatiwada, R.; Dennis, L.; Kendrick, R.; Khosravi, M.; Peters, M.; Smith, E.; Snow, W. M.

    2016-02-01

    Materials with very low DC magnetic susceptibility have many scientific applications. To our knowledge however, relatively little research has been conducted with the goal to produce a totally nonmagnetic material. This phrase in our case means after spatially averaging over macroscopic volumes, it possesses an average zero DC magnetic susceptibility. We report measurements of the DC magnetic susceptibility of three different types of nonmagnetic materials at room temperature: (I) solutions of paramagnetic salts and diamagnetic liquids, (II) liquid gallium-indium alloys and (III) pressed powder mixtures of tungsten and bismuth. The lowest measured magnetic susceptibility among these candidate materials is in the order of 10-9 cgs volume susceptibility units, about two orders of magnitude smaller than distilled water. In all cases, the measured concentration dependence of the magnetic susceptibility is consistent with that expected for the weighted sum of the susceptibilities of the separate components within experimental error. These results verify the well-known Wiedemann additivity law for the magnetic susceptibility of inert mixtures of materials and thereby realize the ability to produce materials with small but tunable magnetic susceptibility. For our particular scientific application, we are also looking for materials with the largest possible number of neutrons and protons per unit volume. The gallium-indium alloys fabricated and measured in this work possess to our knowledge the smallest ratio of volume magnetic susceptibility to nucleon number density per unit volume for a room temperature liquid, and the tungsten-bismuth pressed powder mixtures possess to our knowledge the smallest ratio of volume magnetic susceptibility to nucleon number density per unit volume for a room temperature solid. This ratio is a figure of merit for a certain class of precision experiments that search for possible exotic spin-dependent forces of Nature.

  12. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    Thorpe, A.; Senftle, F.E.

    1959-01-01

    An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

  13. Sources of magnetic susceptibility in a slate

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham; Mothersill, John; Tarling, Don; Alford, Craig

    1986-01-01

    Magnetic susceptibility and its anisotropy in the Borrowdale Volcanic slates at Kentmere in the English Lake District are attributed largely to preferred orientation of a paramagnetic chlorite of diabantite-ripidolite composition. In units of 10 -6 cgs/g, the principal susceptibilities for the slates are 9.61; 9.42; 8.69 and for the chlorite grains the minimum anisotropy is represented by principal susceptibilities of 11.57; 11.22 and 9.15. Because the magnetic susceptibility is carried by a tightly packed, matrix-forming mineral that has recrystallised during the deformation it is not possible to imagine simple grain rotation as being responsible for the anisotropy of susceptibility.

  14. Magnetic Susceptibility of Collapsed Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ando, Tsuneya

    2017-02-01

    The orbital magnetic susceptibility is calculated in collapsed carbon nanotubes within an effective-mass scheme for two magnetic-field configurations, perpendicular and parallel to the flattened plane. The response is diamagnetic in both directions and is much larger for the perpendicular configuration, with some rare exceptions. In chiral nanotubes, calculated results show small and almost negligible effects of collapsing except for some modification due to change in the effective magnetic field. In nonchiral zigzag and armchair nanotubes, the susceptibility is strongly modified, depending on relative displacement of two layers in the flattened region.

  15. Magnetic Susceptibility of Wet vs. Dry Sediment and Mass Normalized vs. Volume Normalized Magnetic Susceptibility

    NASA Astrophysics Data System (ADS)

    Kletetschka, G.; Hruba, J.; Nabelek, L.

    2015-12-01

    The measurement of magnetic susceptibility in sediments represents a fast and non-destructive technique that can be used to deduce the concentration of magnetic minerals [1, 2]. Magnetic minerals change their magnetic properties with temperature [3]. Heating (during a fire, laboratory, with the purpose of manufacturing a product, etc.) can modify a number of sediment properties [4, 5]. Heat-induced sediment mineralogical changes may cause irreversible changes in the sediment mineral structure and composition, and they occur at a wide range of temperature [6]. We provided measurements of magnetic susceptibility on samples from the Stara Jimka (SJ) paleo lacustrine site in the Bohemian Forest using magnetic susceptibility meter MS-30. Sediment samples of approximately 0.2 cm thickness were weighed and put into plastic containers. First, measurements of magnetic susceptibility were taken on wet samples. Then the containers were put into the oven and sediment was dried at temperature of 110°C. After drying and cooling to room temperature, measurements of magnetic susceptibility were repeated. Dry samples were also weighed. Comparison of magnetic susceptibility of dry versus wet samples showed higher values of magnetic susceptibility of dry samples. This enhancement was probably caused during oven-drying, when constituents of sediment (mainly clays) underwent heat-induced changes. We also compared volume normalized values of magnetic susceptibility with mass normalized values. Mass normalized magnetic susceptibility was burdened by greater noise. References: [1] QUIJANO, L. et al. 2001. Magnetic Susceptibilty in Topsoils and Bulk Cores of Cultivated Calcisols. [2] DEARING, J. A. 1994. Environmental Magnetic Susceptibility. [3] HANESCH, M. and SCHOLGER, R. 2005. The Influence of Soil Type on the Magnetic Susceptibility Measured throughout Soil Profiles. [4] FARWIG, V. J. et al. 2004. The Effects of Heating on Mineral Magnetic Enhancement of Soils. [5] KLETETSCHKA, G

  16. Magnetic susceptibility of petroleum reservoir fluids

    NASA Astrophysics Data System (ADS)

    Ivakhnenko, Oleksandr P.; Potter, David K.

    A knowledge of the magnetic properties of petroleum reservoir fluids may provide new techniques for improved reservoir characterisation, petroleum exploration and production. However, magnetic information is currently scarce for the vast majority of reservoir fluids. For instance, there is little in the literature concerning basic magnetic susceptibility values of crude oils or formation waters. We have therefore measured the mass magnetic susceptibility ( χm) of several crude oils, refined oil fractions, and formation waters from local and world-wide sites. All the fluids measured were diamagnetic, however there were distinct differences in magnitude between the different fluid types. In particular, χm for the crude oils was more negative than for the formation waters of the same locality. The magnetic susceptibility of the oils appears to be related to their main physical and chemical properties. The results correlated with the density, residue content, API (American Petroleum Institute) gravity, viscosity, sulphur content and metal concentration of the fluids. Light fractions of crude oil were the most diamagnetic. The magnetic measurements potentially allow physical and chemical differences between the fluids to be rapidly characterised. The results suggest other possible applications, such as passive in situ magnetic susceptibility sensors for fluid monitoring (for example, the onset of water breakthrough, or the detection of migrating fines) in reservoirs, which would provide an environmentally friendly alternative to radioactive tracers. The mass magnetic susceptibilities of the fluids in relation to typical reservoir minerals may also play a role in fluid-rock interactions, such as studies of wettability. The χm of crude oil from the various world-wide oil provinces that were tested also showed some differences, possibly reflecting broad physical and chemical features of the geological history of each province.

  17. Separation of magnetic susceptibility components from magnetization curves

    NASA Astrophysics Data System (ADS)

    Kosareva, L.; Nourgaliev, D.; Kuzina, D.; Spassov, S.; Fattakhov, A.

    2014-12-01

    Modern lake sediments are a unique source of information for climate changes, regionally and globally, because all environmental variations are recorded by these sediments with high resolution. The magnetic properties of Chernyshov Bay (Aral Sea) sediments we investigated from core number 4 (N45o57'04.2''; E59o17'14.3'') are taken at far water depth of 9.5 m. The length of the core is 4.16 m. Samples for measurements were taken to plastic sample boxes with internal dimensions 2x2x2 cm. Remanent magnetization curves were measured by coercivity spectrometer for the separate determination of the different contributions to the total bulk magnetic susceptibility. There was measured also magnetic susceptibility using MS2 susceptibility meter. Those operations were done for data comparison between 2 susceptibilities obtained from different equipment. Our goal is to decipher the magnetic susceptibility signal in lake sediments by decomposing the bulk susceptibility signal of a lake sediment sequence into ferromagnetic (χf), dia-/paramagnetic (χp) and superparamagnetic (χsp) components using data from remanent and indused magnetization curves Each of these component has a different origin: paramagnetic minerals are usually attributed to terrigenous sediment input, ferromagnetics are of biogenic origin, and superparamagnetic minerals may be of either biogenic or terrigenous origin. Comparison between susceptibility measurements of MS2-Bartington susceptometer and of the coercivity spectrometer has shown good correlation. The susceptibility values measured in two different equipment are fairly close and indicate thus the reliability the proposed method. In research also has shown water level changes in Aral Sea based on magnetic susceptibility. The work is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University also by RFBR research projects No. 14-05-31376 - а, 14-05-00785- а.

  18. Anisotropy of the magnetic susceptibility of gallium

    USGS Publications Warehouse

    Pankey, T.

    1960-01-01

    The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25??C. The following anisotropic diamagnetic susceptibilities were found: a axis (-0.119??0. 001)??10-6 emu/g, b axis (-0.416??0.002)??10 -6 emu/g, and c axis (-0.229??0.001) emu/g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (-0.257??0.003)??10-6 emu/g at 25??C, and (-0.299??0.003)??10-6 emu/g at -196??C. The susceptibility of liquid gallium was (0.0031??0.001) ??10-6 emu/g at 30??C and 100??C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi-energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state. ?? 1960 The American Institute of Physics.

  19. Magnetic susceptibilities of cluster-hierarchical models

    NASA Astrophysics Data System (ADS)

    McKay, Susan R.; Berker, A. Nihat

    1984-02-01

    The exact magnetic susceptibilities of hierarchical models are calculated near and away from criticality, in both the ordered and disordered phases. The mechanism and phenomenology are discussed for models with susceptibilities that are physically sensible, e.g., nondivergent away from criticality. Such models are found based upon the Niemeijer-van Leeuwen cluster renormalization. A recursion-matrix method is presented for the renormalization-group evaluation of response functions. Diagonalization of this matrix at fixed points provides simple criteria for well-behaved densities and response functions.

  20. New Magnetic Susceptibility and Magnetic Field Tools for Wireline Logging

    NASA Astrophysics Data System (ADS)

    Williams, T.; Evans, H.; Robinson, S.; Goldberg, D.; Tool Design Team

    2008-12-01

    Two new tools are being developed to provide downhole magnetic measurements for the Integrated Ocean Drilling Program (IODP) and other scientific drilling programs. The Magnetic Susceptibility Sonde (MSS) is built and has been run successfully in land boreholes, and the Multi-sensor Magnetometer Module (MMM) is at the design stage. Magnetic susceptibility is one of the best measurements for investigating stratigraphic changes in marine sediments, because the measurement is quick, repeatable, and non-destructive, and because different lithologies often have strongly contrasting susceptibilities. The MSS includes a Bartington sensor with a 12-cm vertical resolution, sufficient to resolve thin beds and track astronomical cyclicity for paleoceanographic studies, together with a deep-reading sensor that is minimally affected by tool standoff from the borehole wall. These downhole susceptibility measurements will complement the susceptibility measured on core and be invaluable for core-log integration. We have proposed to build a new magnetometer tool, the MMM, to measure the magnetic field in the borehole, from which we can calculate the magnetization and polarity of the rocks surrounding the borehole. The combination of a three-axis fluxgate magnetometer, an accurate Overhauser effect total-field magnetometer, and optical gyroscope orientation in a single tool will provide the capability to measure a wide range of rock types, from highly magnetic basalts to more weakly magnetized unlithified sediments. The magnetization of the igneous ocean crust is a fundamental subject in marine geophysics, and downhole measurements offer the advantages of oriented paleomagnetic data and continuous coverage in these difficult-to-recover rocks. The tool will also be able to provide downhole magnetostratigraphy in marine sediment sequences, as demonstrated with the previous generation of IODP downhole magnetometer (a commercial tool, no longer available). Both these new tools will run

  1. Magnetic susceptibility of oxy- and carbonmonoxyhemoglobins.

    PubMed Central

    Savicki, J P; Lang, G; Ikeda-Saito, M

    1984-01-01

    The room temperature magnetic susceptibilities of human and carp oxy- and carbonmonoxyhemoglobin solutions were measured in a 30-gauss (1 G = 10(-4) T) field with a superconducting magnetometer. To within experimental uncertainty, the susceptibility was the same for both the oxy and carbonmonoxy forms, and salt concentration did not effect it. A variety of sample preparations were used; the iron chemical state was verified by Mössbauer spectroscopy. A value of -0.580 +/- 0.010 X 10(-6) centimeter-gram-second (cgs) system was obtained for the mass susceptibility of the protein. We attribute the paramagnetism sometimes observed in oxyhemoglobin solutions to the presence of a small amount of the deoxy form. PMID:6591198

  2. Magnetic Susceptibility in the Vertebral Column

    NASA Astrophysics Data System (ADS)

    Schick, F.; Nagele, T.; Lutz, O.; Pfeffer, K.; Giehl, J.

    1994-01-01

    A magnetic resonance method is described which provides good-quality field-mapping images of the spine, although the in vivo signals from red bone marrow of the vertebral bodies exhibit similar fractions of lipid and water protons with their chemical-shift difference of 3.4 ppm. The susceptibilities of bone marrow and intervertebral disks were examined in 20 cadaveric human spines, 9 healthy volunteers, and 9 patients with degenerative disk alterations. The influence of geometrical properties was studied in cylindrical spine phantoms of different size and contents with different susceptibility. The measurements reveal interindividual differences of the susceptibility of the intervertebral disks in healthy subjects. Three out of nine degenerated disks with low signal in T2-weighted spin-echo images showed irregularities of the field distribution within the nucleus pulposus.

  3. Magnetic susceptibility as a biosignature in stromatolites

    NASA Astrophysics Data System (ADS)

    Petryshyn, Victoria A.; Corsetti, Frank A.; Frantz, Carie M.; Lund, Steve P.; Berelson, William M.

    2016-03-01

    Microbialites have long been a focus of study in geobiology because they are macroscopic sedimentary records of the activities of microscopic organisms. However, abiotic processes can result in microbialite-like morphologies. Developing robust tools for substantiating the biogenicity of putative microbialites remains an important challenge. Here, we report a new potential biosignature based on the detrital magnetic mineral component present in nearly all sedimentary rocks. Detrital grains falling onto a hard, abiogenic, chemically precipitated structure would be expected to roll off surfaces at high incline angles. Thus, the distribution of grains in an abiogenic microbialite should exhibit a dependence on the dip angle along laminae. In contrast, a microbialite formed by the active trapping and binding of detrital grains by microorganisms could exhibit a distribution of detrital grains significantly less dependent on the dip angle of the laminae. However, given that most ancient stromatolites are micritic (composed of carbonate mud), tracking detrital grains vs. precipitated carbonate is not straightforward. Recent advances in our ability to measure miniscule magnetic fields open up the possibility to map magnetic susceptibility as a tracer of detrital grains in stromatolites. In abiogenic carbonate precipitation experiments, magnetic susceptibility fell to zero when the growth surface was inclined above 30° (the angle at which grains rolled off). In cyanobacterial mat experiments, even vertically inclined mats held magnetic material. The results indicate that cyanobacterial mats trap and bind small grains more readily than abiogenic carbonate precipitates alone. A variety of stromatolites of known and unknown biogenicity were then analyzed. Tested stromatolites span many different ages (Eocene to Holocene) and depositional environments (hot springs, lakes), and compositional forms (micritic, sparry crusts, etc.). The results were consistent with the laboratory

  4. Giant Magnetic Susceptibility of Gold Nanorods Detected by Magnetic Alignment

    NASA Astrophysics Data System (ADS)

    van Rhee, P. G.; Zijlstra, P.; Verhagen, T. G. A.; Aarts, J.; Katsnelson, M. I.; Maan, J. C.; Orrit, M.; Christianen, P. C. M.

    2013-09-01

    We have determined the magnetic properties of single-crystalline Au nanorods in solution using an optically detected magnetic alignment technique. The rods exhibit a large anisotropy in the magnetic volume susceptibility (ΔχV). ΔχV increases with decreasing rod size and increasing aspect ratio and corresponds to an average volume susceptibility (χV), which is drastically enhanced relative to bulk Au. This high value of χV is confirmed by SQUID magnetometry and is temperature independent (between 5 and 300 K). Given this peculiar size, shape, and temperature dependence, we speculate that the enhanced χV is the result of orbital magnetism due to mesoscopic electron trajectories within the nanorods.

  5. Magnetic Susceptibility Measurement System for Small and Weak Magnetic Substances

    NASA Astrophysics Data System (ADS)

    Grant, Julius Reynard

    In this study a system is constructed which uses a force method for taking magnetic susceptibility measurements of small (< 100 mg) and weak (< 100x 10-6 emu/g) magnetic substances. The system is constructed with several pieces of readily available hardware. Some of the hardware includes a stable frame structure, a CAHN electrobalance, electromagnet, a thermocouple, a power supply, interfaces, and a personal computer. Each of these components is tested individually as well as together with other devices. Since the electrobalance is extremely sensitive the balance must be placed on a stable frame. The completed system is capable of studying the magnetic properties from room temperature to 77 K of a variety of samples. In addition, a novel method is developed to produce hysteresis loops for especially small and weak magnetic samples. Extensive testing is done to ensure the magnetization results obtained on known samples compare with what has been reported. Some of the samples that have been measured are MnO (TN was 122 K), CdSe (magnetic susceptibility was -0.3 x 10-6 emu/g) with iron attached ligands, FexTeyOz type samples with and without nickel, a YBaCuO superconductor, and cells doped with magnetite nanoparticles. The results are compared to measurements made with SQUID magnetometers.

  6. Nonlinear Susceptibility Magnitude Imaging of Magnetic Nanoparticles.

    PubMed

    Ficko, Bradley W; Giacometti, Paolo; Diamond, Solomon G

    2015-03-15

    This study demonstrates a method for improving the resolution of susceptibility magnitude imaging (SMI) using spatial information that arises from the nonlinear magnetization characteristics of magnetic nanoparticles (mNPs). In this proof-of-concept study of nonlinear SMI, a pair of drive coils and several permanent magnets generate applied magnetic fields and a coil is used as a magnetic field sensor. Sinusoidal alternating current (AC) in the drive coils results in linear mNP magnetization responses at primary frequencies, and nonlinear responses at harmonic frequencies and intermodulation frequencies. The spatial information content of the nonlinear responses is evaluated by reconstructing tomographic images with sequentially increasing voxel counts using the combined linear and nonlinear data. Using the linear data alone it is not possible to accurately reconstruct more than 2 voxels with a pair of drive coils and a single sensor. However, nonlinear SMI is found to accurately reconstruct 12 voxels (R(2) = 0.99, CNR = 84.9) using the same physical configuration. Several time-multiplexing methods are then explored to determine if additional spatial information can be obtained by varying the amplitude, phase and frequency of the applied magnetic fields from the two drive coils. Asynchronous phase modulation, amplitude modulation, intermodulation phase modulation, and frequency modulation all resulted in accurate reconstruction of 6 voxels (R(2) > 0.9) indicating that time multiplexing is a valid approach to further increase the resolution of nonlinear SMI. The spatial information content of nonlinear mNP responses and the potential for resolution enhancement with time multiplexing demonstrate the concept and advantages of nonlinear SMI.

  7. Magnetic susceptibilities of antiferromagnetic Re4+ compounds

    NASA Astrophysics Data System (ADS)

    Chatterjee, Ibha; Desai, V. P.

    1981-11-01

    The low-temperature (0-30 K) antiferromagnetic susceptibilites of hexachloro- and hexabromorhenates (K2ReCl6 and K2ReBr6) are explained by using correlated effective-field theory and considering XY symmetry of the exchange Hamiltonian. The theory gives a good account of the observed magnetic susceptibilities of these compounds and the sublattice magnetization of the K2ReCl6 compound. The nearest- and next-nearest-neighbor exchange integrals for these compounds are J1=-1.32 cm-1, J2=0.20 cm-1 for K2ReCl6 and J1=-1.82 cm-1, J2=0.15 cm-1 for K2ReBr6.

  8. Properties of atoms in molecules: Magnetic susceptibilities

    NASA Astrophysics Data System (ADS)

    Bader, Richard F. W.; Keith, Todd A.

    1993-09-01

    The molecular magnetic susceptibility tensor χ is expressible as a sum of atomic or group contributions. An atomic contribution consists of a basin and a surface component; the former is given by the integral of a magnetization density over the basin of the atom, and the latter, by the integral of the flux in the position weighted current density through the interatomic surfaces that the atom shares with its bonded neighbors. The surface component is obtained as a consequence of the atomic hypervirial theorem defining the average of the velocity operator. Magnetic properties are determined by the observable electron current density, and the atomic behavior of this field has been correlated with corresponding behavior of the electron density. Thus the importance of the magnetization within an atomic basin relative to the flux in current through its interatomic surfaces parallels the extent to which the electron density is localized within the individual atomic basins. For example, 77% of the pronounced anisotropy in benzene arises from the flux in current through the interatomic surfaces of the ring atoms induced by a field applied perpendicular to the ring surface. The methyl and methylene group contributions to χ¯ are found to be transferable in the homologous series of hydrocarbons and to equal Pascal's group increments within experimental error.

  9. Generalised lipodystrophy.

    PubMed

    Choo, K E; Sharifah, A; Ariffin, W A; Mafauzy, M

    1990-06-01

    We report a Malay girl suffering from generalised lipodystrophy, with clinical features of absence of body adipose tissue, hepatomegaly, hyperpigmentation and muscular hypertrophy. She also had hyperlipaemia, hypercholesterolemia and non-ketotic insulin-resistant diabetes mellitus. The possibility of malnutrition-related diabetes mellitus was excluded because of (a) no personal or family history of malnutrition (b) no pancreatic calcification (c) total loss of subcutaneous fat and (d) her requirement for insulin was more than 21.2 units/kg body weight which would be too high even for malnutrition-related diabetes mellitus. Attempts were made to control her diabetes initially with subcutaneous boluses insulin, then continuous intravenous insulin infusion (CIVII) and finally orally with fenfluramine and chlorpropamide.

  10. Structural and magnetic properties of multi-core nanoparticles analysed using a generalised numerical inversion method

    NASA Astrophysics Data System (ADS)

    Bender, P.; Bogart, L. K.; Posth, O.; Szczerba, W.; Rogers, S. E.; Castro, A.; Nilsson, L.; Zeng, L. J.; Sugunan, A.; Sommertune, J.; Fornara, A.; González-Alonso, D.; Barquín, L. Fernández; Johansson, C.

    2017-04-01

    The structural and magnetic properties of magnetic multi-core particles were determined by numerical inversion of small angle scattering and isothermal magnetisation data. The investigated particles consist of iron oxide nanoparticle cores (9 nm) embedded in poly(styrene) spheres (160 nm). A thorough physical characterisation of the particles included transmission electron microscopy, X-ray diffraction and asymmetrical flow field-flow fractionation. Their structure was ultimately disclosed by an indirect Fourier transform of static light scattering, small angle X-ray scattering and small angle neutron scattering data of the colloidal dispersion. The extracted pair distance distribution functions clearly indicated that the cores were mostly accumulated in the outer surface layers of the poly(styrene) spheres. To investigate the magnetic properties, the isothermal magnetisation curves of the multi-core particles (immobilised and dispersed in water) were analysed. The study stands out by applying the same numerical approach to extract the apparent moment distributions of the particles as for the indirect Fourier transform. It could be shown that the main peak of the apparent moment distributions correlated to the expected intrinsic moment distribution of the cores. Additional peaks were observed which signaled deviations of the isothermal magnetisation behavior from the non-interacting case, indicating weak dipolar interactions.

  11. Structural and magnetic properties of multi-core nanoparticles analysed using a generalised numerical inversion method

    PubMed Central

    Bender, P.; Bogart, L. K.; Posth, O.; Szczerba, W.; Rogers, S. E.; Castro, A.; Nilsson, L.; Zeng, L. J.; Sugunan, A.; Sommertune, J.; Fornara, A.; González-Alonso, D.; Barquín, L. Fernández; Johansson, C.

    2017-01-01

    The structural and magnetic properties of magnetic multi-core particles were determined by numerical inversion of small angle scattering and isothermal magnetisation data. The investigated particles consist of iron oxide nanoparticle cores (9 nm) embedded in poly(styrene) spheres (160 nm). A thorough physical characterisation of the particles included transmission electron microscopy, X-ray diffraction and asymmetrical flow field-flow fractionation. Their structure was ultimately disclosed by an indirect Fourier transform of static light scattering, small angle X-ray scattering and small angle neutron scattering data of the colloidal dispersion. The extracted pair distance distribution functions clearly indicated that the cores were mostly accumulated in the outer surface layers of the poly(styrene) spheres. To investigate the magnetic properties, the isothermal magnetisation curves of the multi-core particles (immobilised and dispersed in water) were analysed. The study stands out by applying the same numerical approach to extract the apparent moment distributions of the particles as for the indirect Fourier transform. It could be shown that the main peak of the apparent moment distributions correlated to the expected intrinsic moment distribution of the cores. Additional peaks were observed which signaled deviations of the isothermal magnetisation behavior from the non-interacting case, indicating weak dipolar interactions. PMID:28397851

  12. Repetitive transcranial magnetic stimulation for generalised anxiety disorder: a pilot randomised, double-blind, sham-controlled trial.

    PubMed

    Diefenbach, Gretchen J; Bragdon, Laura B; Zertuche, Luis; Hyatt, Christopher J; Hallion, Lauren S; Tolin, David F; Goethe, John W; Assaf, Michal

    2016-09-01

    Repetitive transcranial magnetic stimulation (rTMS) holds promise for treating generalised anxiety disorder (GAD) but has only been studied in uncontrolled research. This is the first randomised controlled trial (clinicaltrials.gov: NCT01659736) to investigate the efficacy and neural correlates of rTMS in GAD. Twenty five participants (active n = 13; sham, n = 12) enrolled. rTMS was targeted at the right dorsolateral prefrontal cortex (DLPFC, 1 Hz, 90% resting motor threshold). Response and remission rates were higher in the active v. sham groups and there were significant group × time interactions for anxiety, worry and depressive symptoms, favouring active v. sham. In addition, right DLPFC activation during a decision-making gambling task increased at post-treatment for active rTMS only, and changes in neuroactivation correlated significantly with changes in worry symptoms. Findings provide preliminary evidence that rTMS may improve GAD symptoms in association with modifying neural activity in the stimulation site. © The Royal College of Psychiatrists 2016.

  13. Magnetic Susceptibility Measurements for in Situ Characterization of Lunar Soil

    NASA Technical Reports Server (NTRS)

    Oder, R. R.

    1992-01-01

    Magnetic separation is a viable method for concentration of components of lunar soils and rocks for use as feedstocks for manufacture of metals, oxygen, and for recovery of volatiles such as He-3. Work with lunar materials indicates that immature soils are the best candidates for magnetic beneficiation. The magnetic susceptibility at which selected soil components such as anorthite, ilmenite, or metallic iron are separated is not affected by soil maturity, but the recovery of the concentrated components is. Increasing soil maturity lowers recovery. Mature soils contain significant amounts of glass-encased metallic iron. Magnetic susceptibility, which is sensitive to metallic iron content, can be used to measure soil maturity. The relationship between the ratio of magnetic susceptibility and iron oxide and the conventional maturity parameter, I(sub s)/FeO, ferromagnetic resonant intensity divided by iron oxide content is given. The magnetic susceptibilities were determined using apparatus designed for magnetic separation of the lunar soils.

  14. A note on the electric and magnetic susceptibilities

    NASA Astrophysics Data System (ADS)

    Heras, José A.

    2017-01-01

    The linear electric and magnetic susceptibilities exhibit different values in Gaussian and SI units even when these constants are dimensionless. In this note we fix this practical inconvenience by redefining the permittivity and permeability of a linear medium in Gaussian units in such a way that their associated electric and magnetic susceptibilities have the same numerical values as those of the SI units.

  15. Magnetic Susceptibility and Morphology of Natural Magnetic Mineral Deposit in Vicinity of Human’s Living

    NASA Astrophysics Data System (ADS)

    Zulaikah, S.; Azzahro, R.; Pranita, S. B.; Mu'alimah, E. S.; Munfarikha, N.; Dewiningsih; Fitria, W. L.; Niarta, H. A.

    2017-05-01

    Magnetic susceptibility and morphology of magnetic minerals have been explored to some samples from the different environment near the vicinity of human’s living, such as hot spring, apple plantation, paddy plantation, and reservoir. Magnetic susceptibility ranged from - 0.0009 × 10-6 m3/kg (Peat in central Borneo) to 98.27 × 10-6 m3/kg (Polluted Soil in Jalan Sukarno Hatta Malang). The grain size of magnetic mineral not more than that of 300 μm. Data analysis informs us that each environment where the magnetic minerals were deposited, influenced the two physical properties both of magnetic susceptibility and morphology of magnetic minerals. Regarding the environment process, magnetic susceptibility depends upon the grain size beside the kinds of magnetic minerals. So, it can be concluded that in every environment, the magnetic minerals have specific properties including magnetic susceptibility and the morphology of magnetic minerals.

  16. The magnetic susceptibility of soils in Krakow, southern Poland

    NASA Astrophysics Data System (ADS)

    Wojas, Anna

    2017-06-01

    Studies into the magnetic susceptibility have been used to assess the soils contamination in the Krakow area. The results of topsoil (over a 2 × 2 km grid), subsoil (37 shallow holes) and soil samples (112) measurements were presented as maps of soil magnetic susceptibility (both volume and mass) illustrating the distribution of parameters in topsoil horizon (0-10 cm) and differential magnetic susceptibility maps between topsoil horizon and subsoil (40-60 cm). All evidence leads to the finding that the highest values of magnetic susceptibility of soil are found exclusively in industrial areas. Taking into consideration the type of land use, the high median value (89.8 × 10-8 m3kg-1) was obtained for samples of cultivated soils and is likely to be connected with occurrence of fertile soil (chernozem). Moreover, enrichment of soils with Pb and Zn accompanies magnetic susceptibility anomalies in the vicinity of the high roads and in the steelworks area, respectively.

  17. MR measurement of alloy magnetic susceptibility: towards developing tissue-susceptibility matched metals.

    PubMed

    Astary, Garrett W; Peprah, Marcus K; Fisher, Charles R; Stewart, Rachel L; Carney, Paul R; Sarntinoranont, Malisa; Meisel, Mark W; Manuel, Michele V; Mareci, Thomas H

    2013-08-01

    Magnetic resonance imaging (MRI) can be used to relate structure to function mapped with high-temporal resolution electrophysiological recordings using metal electrodes. Additionally, MRI may be used to guide the placement of electrodes or conductive cannula in the brain. However, the magnetic susceptibility mismatch between implanted metals and surrounding brain tissue can severely distort MR images and spectra, particularly in high magnetic fields. In this study, we present a modified MR method of characterizing the magnetic susceptibility of materials that can be used to develop biocompatible, metal alloys that match the susceptibility of host tissue in order to eliminate MR distortions proximal to the implant. This method was applied at 4.7T and 11.1T to measure the susceptibility of a model solid-solution alloy of Cu and Sn, which is inexpensive but not biocompatible. MR-derived relative susceptibility values of four different compositions of Cu-Sn alloy deviated by less than 3.1% from SQUID magnetometry absolute susceptibility measurements performed up to 7T. These results demonstrate that the magnetic susceptibility varies linearly with atomic percentage in these solid-solution alloys, but are not simply the weighted average of Cu and Sn magnetic susceptibilities. Therefore susceptibility measurements are necessary when developing susceptibility-matched, solid-solution alloys for the elimination of susceptibility artifacts in MR. This MR method does not require any specialized equipment and is free of geometrical constraints, such as sample shape requirements associated with SQUID magnetometry, so the method can be used at all stages of fabrication to guide the development of a susceptibility matched, biocompatible device.

  18. MR Measurement of Alloy Magnetic Susceptibility: Towards Developing Tissue-Susceptibility Matched Metals

    PubMed Central

    Astary, Garrett W.; Peprah, Marcus K.; Fisher, Charles R.; Stewart, Rachel L.; Carney, Paul R.; Sarntinoranont, Malisa; Meisel, Mark W.; Manuel, Michele V.; Mareci, Thomas H.

    2013-01-01

    Magnetic resonance imaging (MRI) can be used to relate structure to function mapped with high-temporal resolution electrophysiological recordings using metal electrodes. Additionally, MRI may be used to guide the placement of electrodes or conductive cannula in the brain. However, the magnetic susceptibility mismatch between implanted metals and surrounding brain tissue can severely distort MR images and spectra, particularly in high magnetic fields. In this study, we present a modified MR method of characterizing the magnetic susceptibility of materials that can be used to develop biocompatible, metal alloys that match the susceptibility of host tissue in order to eliminate MR distortions proximal to the implant. This method was applied at 4.7 T and 11.1 T to measure the susceptibility of a model solid-solution alloy of Cu and Sn, which is inexpensive but not biocompatible. MR-derived relative susceptibility values of four different compositions of Cu-Sn alloy deviated by less than 3.1% from SQUID magnetometry absolute susceptibility measurements performed up to 7 T. These results demonstrate that the magnetic susceptibility varies linearly with atomic percentage in these solid-solution alloys, but are not simply the weighted average of Cu and Sn magnetic susceptibilities. Therefore susceptibility measurements are necessary when developing susceptibility-matched, solid-solution alloys for the elimination of susceptibility artifacts in MR. This MR method does not require any specialized equipment and is free of geometrical constraints, such as sample shape requirements associated with SQUID magnetometry, so the method can be used at all stages of fabrication to guide the development of a susceptibility matched, biocompatible device. PMID:23727587

  19. The influence of soil moisture on magnetic susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Maier, G.; Scholger, R.; Schön, J.

    2006-06-01

    An important methodological question for magnetic susceptibility measurements is if a variation of the soil conductivity, as a result of a change in soil moisture, influences the measured susceptibility values. An answer to this question is essential because an accurate magnetic susceptibility mapping requires a grid of comparable magnetic susceptibility values, which indicate the magnetic iron-mineral contents of the soils. Therefore, in the framework of the MAGPROX project (EU-Project EVK2-CT-1999-00019), the study aims at investigating the influence of soil moisture and the possible correlation between magnetic susceptibility and electric conductivity. This approach was realised by model experiments in the laboratory and a field monitoring experiment, which was performed in an analogical manner as the model. For the laboratory experiment, a plastic tub with a water in- and outflow system and installed lines of electrodes was used. The measurements were carried out with layers of different magnetic material within the experimental sand formation under varying water saturation conditions. For the field experiment, which was carried out from July to December 2003, two test sites were selected. The magnetic susceptibility was measured by means of the recently developed vertical soil profile kappa meter SM400 and a commonly used Bartington MS2D probe. The electric resistivity was recorded using a 4-point light system (laboratory) and a ground conductivity meter EM38 (field). The knowledge of the resistivity of the sand formation enabled an estimation of porosity and water saturation in consideration of the Archie equations. The laboratory experiment results showed a very slight variation of measured magnetic susceptibility under different degrees of moisture, indicating mainly the influence from the diamagnetic contribution of the water volume. A measurement error in connection with the measurement method, for example caused by an interfering effect of soil

  20. Dynamic magnetic susceptibility and electrical detection of ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Zhang, Yin; Wang, X. S.; Yuan, H. Y.; Kang, S. S.; Zhang, H. W.; Wang, X. R.

    2017-03-01

    The dynamic magnetic susceptibility of magnetic materials near ferromagnetic resonance (FMR) is very important in interpreting the dc voltage obtained in its electrical detection. Based on the causality principle and the assumption that the usual microwave absorption lineshape of a homogeneous magnetic material around FMR is Lorentzian, the general forms of the dynamic magnetic susceptibility of an arbitrary sample and the corresponding dc voltage lineshapes of its electrical detection were obtained. Our main findings are as follows. (1) The dynamic magnetic susceptibility is not a Polder tensor for a material with an arbitrary magnetic anisotropy. The two off-diagonal matrix elements of the tensor near FMR are not, in general, opposite to each other. However, the linear response coefficient of the magnetization to the total radio frequency (rf) field (the sum of the external and internal rf fields due to precessing magnetization is a quantity which cannot be measured directly) is a Polder tensor. This may explain why the two off-diagonal susceptibility matrix elements were always wrongly assumed to be opposite to each other in almost all analyses. (2) The frequency dependence of dynamic magnetic susceptibility near FMR is fully characterized by six real numbers, while its field dependence is fully characterized by seven real numbers. (3) A recipe of how to determine these numbers by standard microwave absorption measurements for a sample with an arbitrary magnetic anisotropy is proposed. Our results allow one to unambiguously separate the contribution of the anisotropic magnetoresistance to the dc voltage signals from the anomalous Hall effect. With these results, one can reliably extract the information of spin pumping and the inverse spin-Hall effect, and determine the spin-Hall angle. (4) In the case that resonance frequency is not sensitive to the applied static magnetic field, the field dependence of the matrix elements of dynamic magnetic susceptibility, as

  1. Magnetic susceptibility anisotropy outside the central nervous system.

    PubMed

    Dibb, Russell; Xie, Luke; Wei, Hongjiang; Liu, Chunlei

    2017-04-01

    Magnetic-susceptibility-based MRI has made important contributions to the characterization of tissue microstructure, chemical composition, and organ function. This has motivated a number of studies to explore the link between microstructure and susceptibility in organs and tissues throughout the body, including the kidney, heart, and connective tissue. These organs and tissues have anisotropic magnetic susceptibility properties and cellular organizations that are distinct from the lipid organization of myelin in the brain. For instance, anisotropy is traced to the epithelial lipid orientation in the kidney, the myofilament proteins in the heart, and the collagen fibrils in the knee cartilage. The magnetic susceptibility properties of these and other tissues are quantified using specific MRI tools: susceptibility tensor imaging (STI), quantitative susceptibility mapping (QSM), and individual QSM measurements with respect to tubular and filament directions determined from diffusion tensor imaging. These techniques provide complementary and supplementary information to that produced by traditional MRI methods. In the kidney, STI can track tubules in all layers including the cortex, outer medulla, and inner medulla. In the heart, STI detected myofibers throughout the myocardium. QSM in the knee revealed three unique layers in articular cartilage by exploiting the anisotropic susceptibility features of collagen. While QSM and STI are promising tools to study tissue susceptibility, certain technical challenges must be overcome in order to realize routine clinical use. This paper reviews essential experimental findings of susceptibility anisotropy in the body, the underlying mechanisms, and the associated MRI methodologies. Copyright © 2016 John Wiley & Sons, Ltd.

  2. Computed inverse MRI for magnetic susceptibility map reconstruction

    PubMed Central

    Chen, Zikuan; Calhoun, Vince

    2015-01-01

    Objective This paper reports on a computed inverse magnetic resonance imaging (CIMRI) model for reconstructing the magnetic susceptibility source from MRI data using a two-step computational approach. Methods The forward T2*-weighted MRI (T2*MRI) process is decomposed into two steps: 1) from magnetic susceptibility source to fieldmap establishment via magnetization in a main field, and 2) from fieldmap to MR image formation by intravoxel dephasing average. The proposed CIMRI model includes two inverse steps to reverse the T2*MRI procedure: fieldmap calculation from MR phase image and susceptibility source calculation from the fieldmap. The inverse step from fieldmap to susceptibility map is a 3D ill-posed deconvolution problem, which can be solved by three kinds of approaches: Tikhonov-regularized matrix inverse, inverse filtering with a truncated filter, and total variation (TV) iteration. By numerical simulation, we validate the CIMRI model by comparing the reconstructed susceptibility maps for a predefined susceptibility source. Results Numerical simulations of CIMRI show that the split Bregman TV iteration solver can reconstruct the susceptibility map from a MR phase image with high fidelity (spatial correlation≈0.99). The split Bregman TV iteration solver includes noise reduction, edge preservation, and image energy conservation. For applications to brain susceptibility reconstruction, it is important to calibrate the TV iteration program by selecting suitable values of the regularization parameter. Conclusions The proposed CIMRI model can reconstruct the magnetic susceptibility source of T2*MRI by two computational steps: calculating the fieldmap from the phase image and reconstructing the susceptibility map from the fieldmap. The crux of CIMRI lies in an ill-posed 3D deconvolution problem, which can be effectively solved by the split Bregman TV iteration algorithm. PMID:22446372

  3. Anisotropy of magnetic susceptibility: Measurement schemes

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham John; Stupavsky, Mike

    The precision of AMS determination is enhanced by measuring susceptibility in directions with a uniform orientation distribution that include the four body diagonals. Some standard 10.5 cm³ samples with mean susceptibility < 100µSI possess too few “magnetic” grains for reliable petrofabric interpretation whatever the measurement strategy. We should only interpret their AMS if they pass fabric homogeneity tests.

  4. Pyrolytic Graphite Foam: A Passive Magnetic Susceptibility Matching Material

    PubMed Central

    Lee, Gary C.; Goodwill, Patrick W.; Phuong, Kevin; Inglis, Ben A.; Scott, Greig C.; Hargreaves, Brian A.; Li, Lizabeth; Chen, Alex C.; Shah, Rachana N.; Conolly, Steven M.

    2012-01-01

    Purpose To evaluate a novel soft, lightweight cushion that can match the magnetic susceptibility of human tissue. The magnetic susceptibility difference between air and tissue produces field inhomogeneities in the B0 field, which leads to susceptibility artifacts in MR studies. Materials and Methods Pyrolytic graphite (PG) microparticles are uniformly embedded into a foam cushion to reduce or eliminate field inhomogeneities at accessible air and tissue interfaces. 3T MR images and field maps of an air/water/PG foam phantom were acquired. Q measurements on a 4T tuned head coil and pulse sequence heating tests at 3T were also performed. Results The PG foam improved susceptibility matching, reduced the field perturbations in phantoms, does not heat, and is non-conductive. Conclusion The susceptibility matched PG foam is lightweight, safe for patient use, adds no noise or MRI artifacts, is compatible with RF coil arrays, and improves B0 homogeneity, which enables more robust MR studies. PMID:20815067

  5. Relationship between magnetic susceptibility and strain in laboratory experiments

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham; Alford, Craig

    1987-02-01

    Under experimental conditions of 1.5 kbar confining pressure and at a strain-rate of 5 × 10 -6 sec -1 at room temperature the principal directions of magnetic susceptibility of a dry, synthetic, magnetite-bearing sandstone rotate toward principal strain directions. The rotation is faster than that expected from rotation of a line in homogeneous strain. Fluid pressures of 200 or 700 bars do not appear to affect the development of anisotropy of susceptibility. The change in bulk anisotropy shows a power law correlation with strain ratio where the initial susceptibility ellipsoid was nearly coaxial with the bulk strain axes during the experiment. More generally, in those situations, as well as ones in which the initial susceptibility ellipsoid was strongly inclined to the bulk strain axes there exists a common matrix M which relates the initial susceptibility tensor kij, the final susceptibility tensor k' ij and the strain tensor eij: eijk' ij = Mk' ij

  6. MAGNETIC SUSCEPTIBILITIES OF SOME RARE EARTH OXIDES.

    DTIC Science & Technology

    MAGNETIC PROPERTIES), SODIUM COMPOUNDS, MOLYBDATES, GADOLINIUM COMPOUNDS, TERBIUM COMPOUNDS, DYSPROSIUM COMPOUNDS, HOLMIUM COMPOUNDS, EUROPIUM COMPOUNDS...THULIUM COMPOUNDS, YTTERBIUM COMPOUNDS, SAMARIUM COMPOUNDS, GALLIUM COMPOUNDS, OXIDES, SINGLE CRYSTALS, ANISOTROPY, FERROMAGNETISM, ANTIFERROMAGNETISM, NUCLEAR SPINS

  7. Ac magnetic susceptibility study of in vivo nanoparticle biodistribution

    NASA Astrophysics Data System (ADS)

    Gutiérrez, L.; Mejías, R.; Barber, D. F.; Veintemillas-Verdaguer, S.; Serna, C. J.; Lázaro, F. J.; Morales, M. P.

    2011-06-01

    We analysed magnetic nanoparticle biodistribution, before and after cytokine conjugation, in a mouse model by ac susceptibility measurements of the corresponding resected tissues. Mice received repeated intravenous injections of nanoparticle suspension for two weeks and they were euthanized 1 h after the last injection. In general, only 10% of the total injected nanoparticles after multiple exposures were found in tissues. The rest of the particles may probably be metabolized or excreted by the organism. Our findings indicate that the adsorption of interferon to DMSA-coated magnetic nanoparticles changes their biodistribution, reducing the presence of nanoparticles in lungs and therefore their possible toxicity. The specific targeting of the particles to tumour tissues by the use of an external magnetic field has also been studied. Magnetic nanoparticles were observed by transmission electron microscopy in the targeted tissue and quantified by ac magnetic susceptibility.

  8. Core loss and magnetic susceptibility of superparamagnetic Fe nanoparticle assembly

    NASA Astrophysics Data System (ADS)

    Kin, Masane; Kura, Hiroaki; Ogawa, Tomoyuki

    2016-12-01

    Toroidal-shaped high-density Fe nanoparticle assemblies (FNAs) were fabricated by molding different sized Fe nanoparticles (NPs), and the effect of the magnetic behavior of the FNAs on the core loss and the magnetic susceptibility was investigated. An FNA with 4.3 nm diameter Fe NPs exhibits superparamagnetism at room temperature while an FNA with 6.4 nm diameter Fe NPs doesn't exhibit superparamagnetism at room temperature. AC magnetization curves at 1, 10 and 100 kHz were measured to evaluate the core loss of the toroidal-shaped FNAs. Both FNAs exhibited no significant eddy current loss, which suggests that surfactants on the NP surface effectively act to electrically insulate the NPs, and the NPs are not sintered together when the FNAs are molded. The AC magnetization curves had no hysteresis for the FNA with 4.3 nm diameter Fe NPs, i.e., the core loss was minimal for the superparamagnetic FNA. The magnetic susceptibility of the superparamagnetic FNA with 4.3 nm Fe NPs was 12 times higher than that estimated from Langevin theory due to the effect of strong magnetic dipole interaction. These results suggest that the superparamagnetic FNA has potential as a magnetic core material that exhibits low core loss and high magnetic susceptibility, even at high frequency.

  9. Magnetic susceptibility of tektites and some other glasses

    USGS Publications Warehouse

    Senftle, F.E.; Thorpe, A.

    1959-01-01

    The magnetic susceptibility at several magnetic field strengths of about thirty tektites from various localities have been measured. The susceptibility ranges from 2 ?? 10-6 to about 7.9 ?? 10-6 e.m.u./g. Tektites from a given locality have similar susceptibilities. The intensity of magnetization of all the tektites measured is zero or very small. For comparison, the same measurements have been made on about thirty obsidians. The magnetic susceptibilities cover approximately the same range, but the intensity of magnetization of the impurity was found to be much higher. By heating the obsidians to 1450??C the intensity of magnetization was reduced to zero. From the above data, it is shown that the tektites must have been heated well above 1400??C, and that essentially all the iron is in solution. On the other hand, the evidence shows that obsidians have not been heated much above this temperature, and that there is a significant amount of undissolved iron in the glass, probably as magnetite. Further, if tektites are extraterrestrial, they probably entered the earth's atmosphere as a glass. ?? 1959.

  10. Anisotropy of magnetic susceptibility: rock composition versus strain

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham

    1987-07-01

    The shape of the susceptibility ellipsoid for a metamorphic tectonite with a strong crystallographic preferred orientation of silicates is strongly influenced by the anisotropy of the most abundant magnetic silicate in the absence of magnetite. Where traces (< 1%) of magnetite are present, inter-specimen variation in the amount of magnetite can override the effects of strain in controlling the shape of the susceptibility ellipsoid.

  11. Magnetic susceptibility and exchange coupling in the mineral ardennite

    USGS Publications Warehouse

    Thorpe, A.N.; Senftle, F.E.; Donnay, G.

    1969-01-01

    Ardennite, a rare silicate mineral, contains about 19 wt.% manganese. Some of the manganese atoms are in positions which are close enough to allow negative exchange and hence a reduction of the total magnetic susceptibility. It is shown that the susceptibility can be accounted for approximately by the treatment of Earnshaw and Lewis (1958) for S = 5 2 and a Hamiltonian H = -2g??Hb-2JS1??S2. ?? 1969.

  12. Magnetic susceptibility fabrics in slates: Structural, mineralogical and lithological influences

    NASA Astrophysics Data System (ADS)

    Borradaile, G.; Sarvas, P.

    1990-02-01

    A single, penetrative tectonic deformation of Archean greywackes, accompanied by low grade metamorphism, generated low-field magnetic susceptibility fabrics that are coaxial with the rock's schistosity although there are multiple sources of magnetic susceptibility. Pre-metamorphic magnetite and the metamorphic minerals pyrrhotite, biotite and chlorite (variety thuringite: daphnite-aphrosiderite) are responsible for the anisotropy of susceptibility. These minerals grew with preferred crystallographic orientations influenced by the prevailing stress regime. On its own, rotation cannot be invoked to explain the alignment of the metamorphic minerals. There are varying proportions of at least two of these minerals in most specimens. For 153 specimens the degree of anisotropy increases as the mean susceptibility increases over the range from 100 to 700 (in units of 10 -6 S.I.)- Theory shows that this is to be expected either due to increasing the traces of strongly oriented ferrimagnetics or due to increasing the proportion of chlorite. In the latter case this simultaneously increased its preferred orientation by closer packing. Stress-influenced crystallization of chlorite rapidly achieves saturation alignment and a limiting magnetic anisotropy although strain may continue to increase. Samples taken through individual graded beds show that the susceptibility ellipsoid varies from oblate in slaty rocks to a neutral shape in sandier rocks. However, its orientation is always structurally controlled, with the minimum susceptibility axis perpendicular to schistosity.

  13. Magnetic susceptibility and isothermal remanent magnetization in human tissues: a study case.

    PubMed

    Sant'Ovaia, H; Marques, G; Santos, A; Gomes, C; Rocha, A

    2015-12-01

    This study evaluated the magnetic properties, magnetic susceptibility and isothermal remanent magnetization (IRM) of tissue samples from the brain, liver, spleen, pancreas, heart and lungs, resected from human corpses, with the aim of identifying the magnetic mineral structures and understanding their possible connection to diseases, professional activity, age and gender of the individual, smoking habits and the environment. The heart was the organ with the highest values of magnetic susceptibility and the pancreas showed the lowest values. No relationship was found between magnetic susceptibility, IRM values and ages of the individuals. However the samples obtained in females showed lower values of magnetic susceptibility than those resected from males. The samples collected from the lungs of smokers have higher values of magnetic susceptibility and IRM indicating the presence of magnetic particles with an anthropic origin. Moreover, the complexity of the magnetic behaviour of these tissues may suggest a contribution of both biogenic and anthropogenic magnetic particles also due to some professional activities. In the brain a heterogeneous distribution of the magnetic susceptibility values was found, which might be related mainly to the diamagnetic behaviour of myelin-rich structures. This study suggests that although the diamagnetic and paramagnetic behaviour is common to all structures, magnetite-type structures are always present in the tissues and hematite-type structures may also contribute to the magnetic signal of the sample. IRM values are only dependent on the presence of magnetite or hematite-type magnetic structures and so this technique seems more suitable to achieve the characterization of biomagnetic structures than magnetic susceptibility.

  14. Correlation of strain with anisotropy of magnetic susceptibility (AMS)

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham J.

    1991-01-01

    Existing correlations between strain and anisotropy of low-field magnetic susceptibility (AMS) have been re-assessed using a single parameter to express both anisotropies. The P' parameter ( Hrouda, 1982) shows potential as a powerful single expression of the intensity of strain and of AMS. Previous correlations are improved by use of this parameter. Cautious optimism is justified for correlations between strain and susceptibility in a certain strain window between a lower limit (excluding the incomplete overprint of predeformation anisotropy) and an upper limit (excluding the effects of saturation anisotropy). For successful correlations the influence of stress-controlled recrystallisation should be minimal and the mineralogical sources of susceptibility must predate deformation.

  15. Measurements of thermal magnetic susceptibility of hematite and goethite

    NASA Astrophysics Data System (ADS)

    Minyuk, P. S.; Subbotnikova, T. V.; Plyashkevich, A. A.

    2011-09-01

    Magnetic susceptibility (MS) of natural specimens of hematite and goethite is studied under continuous heating with various additives: with carbon (sugar), nitrogen (carbamide), and elemental sulfur. It is found that heating of hematite with carbon above 450°C results in the formation of single-domain magnetite, while the magnetic susceptibility rises by a factor of 165. The increase in magnetic susceptibility on heating of hematite with nitrogen above 540°C reflects the generation of a single-domain maghemite with the Curie point of about 650°C, which is stable to heating. After the first heating, the magnetic susceptibility increases by 415 times. The subsequent cycle of thermal treatment results in the transition of maghemite to hematite, a decrease of MS, and an increase of coercivity. Heating with sulfur produces a stable single-domain magnetite at a temperature above the Curie point, which is manifested in the cooling curves. Here, the MS increases by a factor of 400. The heating curves for goethite exhibit a sharp drop in susceptibility to a temperature of 350-360°C, which reflects the transition of hematite to goethite. Heating of hematite with carbon produces stable maghemite at above 530°C, and with sulphur and nitrogen, it produces magnetite. When heated with pyrite, hematite reduces to magnetite under the action of sulfur released from pyrite.

  16. Effect of centrifugation on dynamic susceptibility of magnetic fluids

    NASA Astrophysics Data System (ADS)

    Pshenichnikov, Alexander; Lebedev, Alexander; Lakhtina, Ekaterina; Kuznetsov, Andrey

    2017-06-01

    The dispersive composition, dynamic susceptibility and spectrum of times of magnetization relaxation for six samples of magnetic fluid obtained by centrifuging two base colloidal solutions of the magnetite in kerosene was investigated experimentally. The base solutions differed by the concentration of the magnetic phase and the width of the particle size distribution. The procedure of cluster analysis allowing one to estimate the characteristic sizes of aggregates with uncompensated magnetic moments was described. The results of the magnetogranulometric and cluster analyses were discussed. It was shown that centrifugation has a strong effect on the physical properties of the separated fractions, which is related to the spatial redistribution of particles and multi-particle aggregates. The presence of aggregates in magnetic fluids is interpreted as the main reason of low-frequency (0.1-10 kHz) dispersion of the dynamic susceptibility. The obtained results count in favor of using centrifugation as an effective means of changing the dynamic susceptibility over wide limits and obtaining fluids with the specified type of susceptibility dispersion.

  17. Using triaxial magnetic fields to create high susceptibility particle composites.

    PubMed

    Martin, James E; Venturini, Eugene; Gulley, Gerald L; Williamson, Jonathan

    2004-02-01

    We report on the use of triaxial magnetic fields to create a variety of isotropic and anisotropic magnetic particle/polymer composites with significantly enhanced magnetic susceptibilities. A triaxial field is a superposition of three orthogonal ac magnetic fields, each generated by a Helmholtz coil in series resonance with a tunable capacitor bank. Field frequencies are in the range of 150-400 Hz. Because both the field amplitudes and frequencies can be varied, a rich variety of structures can be created. Perhaps the most unusual effects occur when either two or three of the field components are heterodyned to give beat frequencies on the order of 1 Hz. This leads to a striking particle dynamics that evolves into surprising structures during resin gelation. These structures are found to have perhaps the highest susceptibility that a particle composite can have. The susceptibility anisotropy of these composites can be controlled over a wide range by judicious adjustment of the relative field amplitudes. These experimental data are supported by large-scale Brownian dynamics simulations of the complex many-body interactions that occur in triaxial magnetic fields. These simulations show that athermal three-dimensional field heterodyning leads to structures with a susceptibility that is as high as that achieved with thermal annealing. Thus with coherent particle motions we can achieve magnetostatic energies that are quite close to the ground state.

  18. Geostatistical Microscale Study of Magnetic Susceptibility in Soil Profile and Magnetic Indicators of Potential Soil Pollution.

    PubMed

    Zawadzki, Jarosław; Fabijańczyk, Piotr; Magiera, Tadeusz; Rachwał, Marzena

    Directional variograms, along the soil profile, can be useful and precise tool that can be used to increase the precision of the assessment of soil pollution. The detail analysis of spatial variability in the soil profile can be also an important part of the standardization of soil magnetometry as a screening method for an assessment of soil pollution related to the dust deposition. The goal of this study was to investigate the correlation between basic parameters of spatial correlations of magnetic susceptibility in the soil profile, such as a range of correlation and a sill, and selected magnetometric indicators of soil pollution. Magnetic indicators were an area under the curve of magnetic susceptibility versus a depth in the soil profile, values of magnetic susceptibility at depths ranging from 1 to 10 cm, and maximum and background values of magnetic susceptibility in the soil profile. These indicators were previously analyzed in the literature. The results showed that a range of correlation of magnetic susceptibility was significantly correlated with magnetic susceptibility measured at depths 1, 2, and 3 cm. It suggests that a range of correlation is a good measure of pollutants' dispersion in the soil profile. The sill of the variogram of magnetic susceptibility was found to be significantly correlated with the area under the curve of plot of magnetic susceptibility that is related to the soil pollution. In consequence, the parameters of microscale spatial variability of magnetic susceptibility in s soil profile are important measures that take into consideration the spatial aspect of s soil pollution.

  19. Multifractal model of magnetic susceptibility distributions in some igneous rocks

    USGS Publications Warehouse

    Gettings, Mark E.

    2012-01-01

    Measurements of in-situ magnetic susceptibility were compiled from mainly Precambrian crystalline basement rocks beneath the Colorado Plateau and ranges in Arizona, Colorado, and New Mexico. The susceptibility meter used measures about 30 cm3 of rock and measures variations in the modal distribution of magnetic minerals that form a minor component volumetrically in these coarsely crystalline granitic to granodioritic rocks. Recent measurements include 50–150 measurements on each outcrop, and show that the distribution of magnetic susceptibilities is highly variable, multimodal and strongly non-Gaussian. Although the distribution of magnetic susceptibility is well known to be multifractal, the small number of data points at an outcrop precludes calculation of the multifractal spectrum by conventional methods. Instead, a brute force approach was adopted using multiplicative cascade models to fit the outcrop scale variability of magnetic minerals. Model segment proportion and length parameters resulted in 26 676 models to span parameter space. Distributions at each outcrop were normalized to unity magnetic susceptibility and added to compare all data for a rock body accounting for variations in petrology and alteration. Once the best-fitting model was found, the equation relating the segment proportion and length parameters was solved numerically to yield the multifractal spectrum estimate. For the best fits, the relative density (the proportion divided by the segment length) of one segment tends to be dominant and the other two densities are smaller and nearly equal. No other consistent relationships between the best fit parameters were identified. The multifractal spectrum estimates appear to distinguish between metamorphic gneiss sites and sites on plutons, even if the plutons have been metamorphosed. In particular, rocks that have undergone multiple tectonic events tend to have a larger range of scaling exponents.

  20. Understanding the Magnetic Susceptibility Measurements by Using an Analytical Scale

    ERIC Educational Resources Information Center

    Cano, M. E.; Cordova-Fraga, T.; Sosa, M.; Bernal-Alvarado, J.; Baffa, O.

    2008-01-01

    A description of the measurement procedure, related theory and experimental data analysis of the magnetic susceptibility of materials is given. A short review of previous papers in the line of this subject is presented. This work covers the whole experimental process, in detail, and presents a pragmatic approach for pedagogical sake. (Contains 2…

  1. Variable Temperature Equipment for a Commercial Magnetic Susceptibility Balance

    ERIC Educational Resources Information Center

    Lotz, Albert

    2008-01-01

    Variable temperature equipment for the magnetic susceptibility balance MSB-MK1 of Sherwood Scientific, Ltd., is described. The sample temperature is controlled with streaming air heated by water in a heat exchanger. Whereas the balance as sold commercially can be used only for room temperature measurements, the setup we designed extends the…

  2. Variable Temperature Equipment for a Commercial Magnetic Susceptibility Balance

    ERIC Educational Resources Information Center

    Lotz, Albert

    2008-01-01

    Variable temperature equipment for the magnetic susceptibility balance MSB-MK1 of Sherwood Scientific, Ltd., is described. The sample temperature is controlled with streaming air heated by water in a heat exchanger. Whereas the balance as sold commercially can be used only for room temperature measurements, the setup we designed extends the…

  3. Calculation of nonlinear magnetic susceptibility tensors for a uniaxial antiferromagnet

    NASA Astrophysics Data System (ADS)

    Lim, Siew-Choo; Osman, Junaidah; Tilley, D. R.

    2000-11-01

    In this paper, we present a derivation of the nonlinear susceptibility tensors for a two-sublattice uniaxial antiferromagnet up to the third-order effects within the standard definition by which the rf magnetization m is defined as a power series expansion in the rf fields h with the susceptibility tensors χ(q) as the coefficients. The starting point is the standard set of torque equations of motion for this problem. A complete set of tensor elements is derived for the case of a single-frequency input wave. Within a circular polarization frame (pnz) expressions are given for the first-order susceptibility, second-harmonic generation, optical rectification, third-harmonic generation and intensity-dependent susceptibility. Some of the coefficients with representative resonance features in the far infrared are illustrated graphically and we conclude with a brief discussion of the implications of the resonance features arising from the calculations and their potential applications.

  4. Accuracy of MRI-based Magnetic Susceptibility Measurements

    NASA Astrophysics Data System (ADS)

    Russek, Stephen; Erdevig, Hannah; Keenan, Kathryn; Stupic, Karl

    Magnetic Resonance Imaging (MRI) is increasingly used to map tissue susceptibility to identify microbleeds associated with brain injury and pathologic iron deposits associated with neurologic diseases such as Parkinson's and Alzheimer's disease. Field distortions with a resolution of a few parts per billion can be measured using MRI phase maps. The field distortion map can be inverted to obtain a quantitative susceptibility map. To determine the accuracy of MRI-based susceptibility measurements, a set of phantoms with paramagnetic salts and nano-iron gels were fabricated. The shapes and orientations of features were varied. Measured susceptibility of 1.0 mM GdCl3 solution in water as a function of temperature agreed well with the theoretical predictions, assuming Gd+3 is spin 7/2. The MRI susceptibility measurements were compared with SQUID magnetometry. The paramagnetic susceptibility sits on top of the much larger diamagnetic susceptibility of water (-9.04 x 10-6), which leads to errors in the SQUID measurements. To extract out the paramagnetic contribution using standard magnetometry, measurements must be made down to low temperature (2K). MRI-based susceptometry is shown to be as or more accurate than standard magnetometry and susceptometry techniques.

  5. Anisotropy of magnetic susceptibility of some metamorphic minerals

    NASA Astrophysics Data System (ADS)

    Borradaile, G.; Keeler, W.; Alford, C.; Sarvas, P.

    1987-09-01

    The anisotropy of susceptibility of metamorphic rocks can be due to paramagnetic rock-forming silicates such as amphiboles, chlorites and micas. It is not always necessary to invoke fabrics of separate grains of iron oxide to explain the anisotropy. Minimum estimates of lattice anisotropies of typical samples of silicates have maximum-to-minimum ratios of 1.1-1.7. Since the magnetic anisotropies of most metamorphic rocks are less than this, these minerals can control the anisotropy of susceptibility because their preferred crystallographic orientations are usually very strong in comparison with the preferred dimensional orientation of magnetite and because they are more abundant than magnetite.

  6. Magnetic susceptibility in three-dimensional nodal semimetals

    NASA Astrophysics Data System (ADS)

    Koshino, Mikito; Hizbullah, Intan Fatimah

    2016-01-01

    We study the magnetic susceptibility in various three-dimensional gapless systems, including Dirac and Weyl semimetals, and a line-node semimetal. The susceptibility is decomposed into the orbital term, the spin term and also the spin-orbit cross term, which is caused by the spin-orbit interaction. We show that the orbital susceptibility logarithmically diverges at the band touching energy in the point-node case, while it exhibits a stronger δ -function singularity in the line node case. The spin-orbit cross term is shown to be paramagnetic in the electron side while diamagnetic in the hole side, in contrast with other two terms which are both even functions in Fermi energy. The spin-orbit cross term in the nodal semimetal is found to be directly related to the chiral surface current induced by the topological surface modes.

  7. Susceptibility measurements of impurity-helium condensates containing magnetic impurities

    NASA Astrophysics Data System (ADS)

    Paulsen, C.; Järvinen, J.; Bernard, E. P.; Khmelenko, V. V.; Lee, D. M.

    2009-02-01

    The magnetic susceptibilities of impurity-helium condensates (IHCs), containing nanocrystals of molecular oxygen and atomic nitrogen free radicals embedded in molecular N2 have been measured via a SQUID magnetometer in the temperature range between 1.1 and 2.1 K. The susceptibilities of the samples containing nitrogen atoms followed Curie-Weiss behavior with very small Weiss temperatures ranging from 0 to -0.4 K. The behavior of samples composed of O2 nanocrystals deviated sharply from results for bulk solid. The susceptibilities of the samples were 102 larger than for bulk solid O2 and showed Curie-Weiss behavior with a Weiss temperature in the range from -4.5 K to -5 K. This result is qualitatively consistent with results obtained in other laboratories for O2 confined in restricted geometries.

  8. Determining magnetic susceptibilities of everyday materials using an electronic balance

    NASA Astrophysics Data System (ADS)

    Laumann, Daniel; Heusler, Stefan

    2017-05-01

    The magnetic properties of an object and its interaction with an external magnetic field can be described through the magnetic (volume) susceptibility χV, which divides nearly all kinds of matter into diamagnetic, paramagnetic, and ferromagnetic substances. Quantitative measurements of χV are usually technically sophisticated or require the investigation of substances with high values of χV to reveal meaningful results. Here, we show that both diamagnetic and paramagnetic effects in everyday materials can be measured using only an electronic balance and a neodymium magnet, both of which are within the reach of typical introductory college and high school physics classrooms. The experimental results match related literature values remarkably well.

  9. The use of magnetic susceptibility as a forensic search tool.

    PubMed

    Pringle, Jamie K; Giubertoni, Matteo; Cassidy, Nigel J; Wisniewski, Kristopher D; Hansen, James D; Linford, Neil T; Daniels, Rebecca M

    2015-01-01

    There are various techniques available for forensic search teams to employ to successfully detect a buried object. Near-surface geophysical search methods have been dominated by ground penetrating radar but recently other techniques, such as electrical resistivity, have become more common. This paper discusses magnetic susceptibility as a simple surface search tool illustrated by various research studies. These suggest magnetic susceptibility to be a relatively low cost, quick and effective tool, compared to other geophysical methods, to determine disturbed ground above buried objects and burnt surface remains in a variety of soil types. Further research should collect datasets over objects of known burial ages for comparison purposes and used in forensic search cases to validate the technique. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  10. Magnetic susceptibility properties of pesticide contaminated volcanic soil

    NASA Astrophysics Data System (ADS)

    Agustine, Eleonora; Fitriani, Dini; Safiuddin, La Ode; Tamuntuan, Gerald; Bijaksana, Satria

    2013-09-01

    Pesticides, unfortunately, are still widely used in many countries as way to eradicate agricultural pests. As they are being used continuously over a long period of time, they accumulate as residues in soils posing serious threats to the environment. In this study, we study the changes in magnetite-rich volcanic soils that were deliberately contaminated by pesticide. Such changes, in any, would be useful in the detection of pesticide residue in contaminated soils. Two different types of magnetically strong volcanic soil from the area near Lembang, West Java, Indonesia were used in this study where they were contaminated with varying concentrations of pesticide. The samples were then measured for magnetic susceptibility at two different frequencies. The measurements were then repeated after a period of three months. We found a reduction of magnetic susceptibility as well as a reduction in SP (superparamagnetic) grains proportion in contaminated soil. These might be caused by pesticide-induced magnetic dissolution as supported by SEM analyses. However the impact of pesticide concentration as well as exposure time on magnetic dissolution is still inconclusive.

  11. Detecting compaction disequilibrium with anisotropy of magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Schwehr, Kurt; Tauxe, Lisa; Driscoll, Neal; Lee, Homa

    2006-11-01

    In clay-rich sediment, microstructures and macrostructures influence how sediments deform when under stress. When lithology is fairly constant, anisotropy of magnetic susceptibility (AMS) can be a simple technique for measuring the relative consolidation state of sediment, which reflects the sediment burial history. AMS can reveal areas of high water content and apparent overconsolidation associated with unconformities where sediment overburden has been removed. Many other methods for testing consolidation and water content are destructive and invasive, whereas AMS provides a nondestructive means to focus on areas for additional geotechnical study. In zones where the magnetic minerals are undergoing diagenesis, AMS should not be used for detecting compaction state. By utilizing AMS in the Santa Barbara Basin, we were able to identify one clear unconformity and eight zones of high water content in three cores. With the addition of susceptibility, anhysteretic remanent magnetization, and isothermal remanent magnetization rock magnetic techniques, we excluded 3 out of 11 zones from being compaction disequilibria. The AMS signals for these three zones are the result of diagenesis, coring deformation, and burrows. In addition, using AMS eigenvectors, we are able to accurately show the direction of maximum compression for the accumulation zone of the Gaviota Slide.

  12. ac susceptibility study of a magnetite magnetic fluid

    NASA Astrophysics Data System (ADS)

    Ayala-Valenzuela, O. E.; Matutes-Aquino, J. A.; Galindo, J. T. Elizalde; Botez, C. E.

    2009-04-01

    Magnetite nanometric powder was synthesized from metal salts using a coprecipitation technique. The powders were used to produce magnetic fluid via a peptization method, with hydrocarbon Isopar M as liquid carrier and oleic acid as surfactant. The complex magnetic susceptibility χ =χ'+iχ″ was measured as a function of temperature T in steps of 2.5 K from 3 to 298 K for frequencies ranging from f =10 to 10 000 Hz. The magnetic fluid real and imaginary components of the ac susceptibility show a prominent maximum at temperatures that increase with the measuring frequency, which is attributed to a spin-glass-like behavior. The peak temperature Tp1 of χ″ depends on f following the Vogel-Fulcher law f =f0 exp[E /kB(Tp1-T0)], where f0 and E are positive constants and T0 is a parameter related to particle interactions. There is another kind of peak temperature, Tp2, in the loss factor tan δ =χ″/χ' which is related to a magnetic aftereffect. The peak temperature Tp2 is far less than Tp1 and shows an Arrhenius-type dependence on f.

  13. Lithological and pedological influences on the magnetic susceptibility of soil: their consideration in magnetic pollution mapping.

    PubMed

    Hanesch, Monika; Rantitsch, Gerd; Hemetsberger, Sigrid; Scholger, Robert

    2007-09-01

    Magnetic susceptibility measurements are widely used to map and monitor the heavy metal pollution of soils. However, the magnetic properties of soils are influenced significantly by the bedrock lithology and soil-forming processes. Therefore, a main challenge in the data interpretation is to filter out the anthropogenic pollution signal. In this study we address this problem by analysing susceptibility values, heavy metal concentrations, as well as pedological parameters in a large soil data set from the eastern segment of Austria, covering a wide range of different lithologies and soil types. The statistic assessment demonstrates an influence of lithology and soil type on the magnetic susceptibility signal. Therefore anomalies are defined in sub sets of different soil types separately. Three different methods were applied to detect susceptibility anomalies: the median absolute deviation method, the boxplot method, and the population modelling method. These methods evaluate topsoil data only and can therefore also be applied to field measurements of magnetic susceptibility. The results were compared to the conventional method of calculating the difference of topsoil and subsoil susceptibility. All three approaches identify the main anomalies in the study area and are successful in circumventing the problem of erroneous anomaly definition due to pedological processes. However, knowledge of the lithological background is still necessary for a meaningful interpretation and can only be substituted by a large amount of data. The tested methods lead to thresholds of different height and therefore act as filters of different strength for the definition of anomalies.

  14. Orbital magnetic susceptibility of graphene and MoS2

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Rubio, A.; Stauber, T.; Gómez-Santos, G.; Asgari, R.; Guinea, F.

    2016-02-01

    We calculate the orbital magnetic susceptibility χorb for an 8-band tight-binding model of gapless and gapped graphene using Green's functions. Analogously, we study χorb for a MoS2 12-band model. For both materials, we unravel the character of the processes involved in the magnetic response by looking at the contribution at each point of the Brillouin zone. By this, a clear distinction between intra- and interband excitations is generally possible and we are able to predict qualitative features of χorb only through the knowledge of the band structure. The study is complemented by comparing the magnetic response with that of 2-band lattice Hamiltonians which reduce to the Dirac and Bernevig-Hughes-Zhang models in the continuum limit.

  15. Temperature dependence of magnetic susceptibility in the vicinity of martensitic transformation in ferromagnetic shape memory alloys.

    PubMed

    Zablotskii, V; Pérez-Landazábal, J I; Recarte, V; Gómez-Polo, C

    2010-08-11

    Temperature dependences of low-field quasistatic magnetic susceptibility in the vicinity of martensitic transitions in an NiFeGa alloy are studied both by experiment and analytically. Pronounced reversible jumps of the magnetic susceptibility were observed near the martensitic transition temperature. A general description of the temperature dependences of the susceptibility in ferromagnetic austenite and martensite phases and the susceptibility jump at the transition is suggested. As a result, the main factors governing the temperature dependences of the magnetic susceptibility in the magnetic shape memory alloys are revealed. The magnetic susceptibility jump value is found to be related to changes of: (i) magnetic anisotropy; (ii) magnetic domain wall geometrical constraints (those determined by the alignment and size of twin variants) and (iii) mean magnetic domain spacing.

  16. Magnetic resonance and magnetic susceptibility study of vanadium oxide—decylamine nanotubes

    NASA Astrophysics Data System (ADS)

    Panich, Alexander M.; Felner, Israel; Shames, Alexander I.; Lee, Cheol Eui

    2016-11-01

    We report on magnetic susceptibility, 51V NMR and EPR study of multiwall vanadium oxide—decylamine nanotubes. Our measurements reveal the presence of a diamagnetic V5+ and two paramagnetic V4+ ions, respectively. NMR spectra and magnetic susceptibility data estimate the V4+ ions as ˜31%-35% of the entire vanadium ions content. EPR evidences that the paramagnetic V4+ subsystem consists of ˜10% of individual ions (hyperfine structured polycrystalline pattern) and ˜90% of exchange coupled entities (Lorentzian line).

  17. Quantification of magnetic susceptibility in several strains of Bacillus spores: implications for separation and detection.

    PubMed

    Melnik, Kristie; Sun, Jianxin; Fleischman, Aaron; Roy, Shuvo; Zborowski, Maciej; Chalmers, Jeffrey J

    2007-09-01

    Three strains of Bacillus: Bacillus atrophaeus (formally Bacillus globigii), Bacillus thuringiensis, and Bacillus cereus were tested for their intrinsic magnetic susceptibility. All three strains when sporulated demonstrated significant magnetic susceptibility using an instrument referred to as Cell Tracking Velocimetry. Energy dispersive spectroscopy also confirmed the presence of paramagnetic elements, Fe and Mn, in the spore form of the bacteria. It was demonstrated that this magnetic susceptibility is sufficient to separate and deposit these spores on glass slides in a magnetic deposition system. These results indicate the potential to separate spores with intrinsic magnetic susceptibility directly out of water or air samples.

  18. Mapping soil magnetic susceptibility and mineralogy in Ukraine

    NASA Astrophysics Data System (ADS)

    Menshov, Oleksandr; Pereira, Paulo; Kruglov, Oleksandr; Sukhorada, Anatoliy

    2017-04-01

    Soil suatainable planning is fundamental for agricultural areas. Soil mapping and modeling are increasingly used in agricultural areas in the entire world (Brevik et al., 2016). They are beneficial to land managers, to reduce soil degradation, increase soil productivity and their restoration. Magnetic susceptibility (MS) methods are low cost and accurate for the developing maps of agricultural areas.. The objective of this work is to identify the minerals responsible for MS increase in soils from the two study areas in Poltava and Kharkiv region. The thermomagnetic analyses were conducted using the KLY-4 with an oven apparatus. The hysteresis parameters were measured with the Rotating Magnetometer at the Geophysical Centre Dourbes, Belgium. The results showed that all of samples from Kharkiv area and the majortity of the samples collected in Poltava area represent the pseudo single domain (PSD) zone particles in Day plot. According to Hanesch et al. (2006), the transformation of goethite, ferrihydrite or hematite to a stronger ferrimagnetic phase like magnetite or maghemite is common in strongly magnetic soils with high values of organic carbon content. In our case of thermomagnetic study, the first peak on the heating curve near 260 ˚C indicates the presence of ferrihydrite which gradually transforms into maghemite (Jordanova et al., 2013). A further decrease in the MS identified on the heating curve may be related to the transformation of the maghemite to hematite. A second MS peak on the heating curve near 530 ˚C and the ultimate loss of magnetic susceptibility near 580 ˚C were caused by the reduction of hematite to magnetite. The shape of the thermomagnetic curves suggests the presence of single domain (SD) particles at room temperature and their transformation to a superparamagnetic (SP) state under heating. Magnetic mineralogical analyses suggest the presence of highly magnetic minerals like magnetite and maghemite as well as slightly magnetic goethite

  19. Generalized longitudinal susceptibility for magnetic monopoles in spin ice

    PubMed Central

    Bramwell, Steven T.

    2012-01-01

    The generalized longitudinal susceptibility χ(q,ω) affords a sensitive measure of the spatial and temporal correlations of magnetic monopoles in spin ice. Starting with the monopole model, a mean field expression for χ(q,ω) is derived as well as expressions for the mean square longitudinal field and induction at a point. Monopole motion is shown to be strongly correlated, and both spatial and temporal correlations are controlled by the dimensionless monopole density x which defines the ratio of the magnetization relaxation rate and the monopole hop rate. Thermal effects and spin-lattice relaxation are also considered. The derived equations are applicable in the temperature range where the Wien effect for magnetic monopoles is negligible. They are discussed in the context of existing theories of spin ice and the following experimental techniques: DC and AC magnetization, neutron scattering, neutron spin echo and longitudinal and transverse field μSR. The monopole theory is found to unify diverse experimental results, but several discrepancies between theory and experiment are identified. One of these, concerning the neutron scattering line shape, is explained by means of a phenomenological modification to the theory. PMID:23166378

  20. Spectroscopic AC Susceptibility Imaging (sASI) of Magnetic Nanoparticles.

    PubMed

    Ficko, Bradley W; Nadar, Priyanka M; Diamond, Solomon G

    2015-02-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurement to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R(2) = 0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R(2) = 0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R(2) = 0.97, p <0.001). These results demonstrate the concept of ASI and advantages of sASI.

  1. Spectroscopic AC susceptibility imaging (sASI) of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Ficko, Bradley W.; Nadar, Priyanka M.; Diamond, Solomon G.

    2015-02-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurements to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement set and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R2=0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R2=0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R2=0.97, p<0.001). These results demonstrate the concept of ASI and advantages of sASI.

  2. Idiopathic generalised tremor syndrome in two cats.

    PubMed

    Mauler, Daniela A; Van Soens, Iris; Bhatti, Sofie F; Cornelis, Ine; Martlé, Valentine A; Van Ham, Luc M

    2014-04-01

    Two male neutered domestic shorthair cats were evaluated for generalised tremors. On neurological examination both cats showed whole-body tremors, worsening with stress. A mainly cerebellar disorder was suspected. Blood examination, cerebrospinal fluid analysis and electrophysiological examination of both cats and magnetic resonance imaging of the brain in one cat were normal. Idiopathic generalised tremor syndrome (IGTS) was suspected owing to the exclusion of underlying causes and the clinical similarities with the syndrome in dogs. Treatment as recommended for dogs was initiated and resulted in improvement. This report describes the first cases of IGTS in cats.

  3. Effect of Anti-dots on the Magnetic Susceptibility in a Superconducting Long Prism

    NASA Astrophysics Data System (ADS)

    Aguirre, C. A.; Joya, Miryam R.; Barba-Ortega, J.

    2017-02-01

    The magnetic susceptibility of a long mesoscopic superconducting square prism containing one/two (dot) anti-dots is calculated in the framework of the Ginzburg-Landau theoretical model. This magnetic susceptibility shows jumps at each of the vortex transition fields. We studied the influence of the number, size and geometry of the anti-dots on the magnetic susceptibility in a superconducting sample. We found interesting physical behavior when several kinds of materials filled into the anti-dot are considered.

  4. Measurement of magnetic susceptibility in pulsed magnetic fields using a proximity detector oscillator.

    PubMed

    Ghannadzadeh, S; Coak, M; Franke, I; Goddard, P A; Singleton, J; Manson, J L

    2011-11-01

    We present a novel susceptometer with a particularly small spatial footprint and no moving parts. The susceptometer is suitable for use in systems with limited space where magnetic measurements may not have been previously possible, such as in pressure cells and rotators, as well as in extremely high pulsed fields. The susceptometer is based on the proximity detector oscillator, which has a broad dynamic resonant frequency range and has so far been used predominantly for transport measurements. We show that for insulating samples, the resonance frequency behavior as a function of field consists of a magnetoresistive and an inductive component, originating, respectively, from the sensor coil and the sample. The response of the coil is modeled, and upon subtraction of the magnetoresistive component the dynamic magnetic susceptibility and magnetization can be extracted. We successfully measure the magnetization of the organic molecular magnets Cu(H(2)O)(5)(VOF(4))(H(2)O) and [Cu(HF(2))(pyz)(2)]BF(4) in pulsed magnetic fields and by comparing the results to that from a traditional extraction susceptometer confirm that the new system can be used to measure and observe magnetic susceptibilities and phase transitions.

  5. Magnetic Susceptibility Effects and Lorentz Damping in Diamagnetic Fluids

    NASA Technical Reports Server (NTRS)

    Ramachandran, Narayanan; Leslie, Fred W.

    2000-01-01

    A great number of crystals (semi-conductor and protein) grown in space are plagued by convective motions which contribute to structural flaws. The character of these instabilities is not well understood but is associated with density variations in the presence of residual gravity and g-jitter. Both static and dynamic (rotating or travelling wave) magnetic fields can be used to reduce the effects of convection in materials processing. In semi-conductor melts, due to their relatively high electrical conductivity, the induced Lorentz force can be effectively used to curtail convective effects. In melts/solutions with reduced electrical conductivity, such as aqueous solutions used in solution crystal growth, protein crystal growth and/or model fluid experiments for simulating melt growth, however, the variation of the magnetic susceptibility with temperature and/or concentration can be utilized to better damp fluid convection than the Lorentz force method. This paper presents a comprehensive, comparative numerical study of the relative damping effects using static magnetic fields and gradients in a simple geometry subjected to a thermal gradient. The governing equations are formulated in general terms and then simplified for the numerical calculations. Operational regimes, based on the best damping technique for different melts/solutions are identified based on fluid properties. Comparisons are provided between the numerical results and available results from experiments in surveyed literature.

  6. Magnetic Susceptibility Effects and Lorentz Damping in Diamagnetic Fluids

    NASA Technical Reports Server (NTRS)

    Ramachandran, Narayanan; Leslie, Fred W.

    2000-01-01

    A great number of crystals (semi-conductor and protein) grown in space are plagued by convective motions which contribute to structural flaws. The character of these instabilities is not well understood but is associated with density variations in the presence of residual gravity and g-jitter. Both static and dynamic (rotating or travelling wave) magnetic fields can be used to reduce the effects of convection in materials processing. In semi-conductor melts, due to their relatively high electrical conductivity, the induced Lorentz force can be effectively used to curtail convective effects. In melts/solutions with reduced electrical conductivity, such as aqueous solutions used in solution crystal growth, protein crystal growth and/or model fluid experiments for simulating melt growth, however, the variation of the magnetic susceptibility with temperature and/or concentration can be utilized to better damp fluid convection than the Lorentz force method. This paper presents a comprehensive, comparative numerical study of the relative damping effects using static magnetic fields and gradients in a simple geometry subjected to a thermal gradient. The governing equations are formulated in general terms and then simplified for the numerical calculations. Operational regimes, based on the best damping technique for different melts/solutions are identified based on fluid properties. Comparisons are provided between the numerical results and available results from experiments in surveyed literature.

  7. Promoting and Assessing Mathematical Generalising

    ERIC Educational Resources Information Center

    Hill, Tiffany; Lannin, John; van Garderen, Delinda

    2015-01-01

    Helping students generalise mathematical ideas is an essential component of teaching and learning of mathematics (Lannin, Ellis, Elliott & Zbiek, 2011). However, it can be challenging for primary teachers to assess and promote generalisation. Because generalisation is an essential part of mathematics instruction, the authors highlight the…

  8. Promoting and Assessing Mathematical Generalising

    ERIC Educational Resources Information Center

    Hill, Tiffany; Lannin, John; van Garderen, Delinda

    2015-01-01

    Helping students generalise mathematical ideas is an essential component of teaching and learning of mathematics (Lannin, Ellis, Elliott & Zbiek, 2011). However, it can be challenging for primary teachers to assess and promote generalisation. Because generalisation is an essential part of mathematics instruction, the authors highlight the…

  9. Magnetic susceptibility and magnetic resonance measurements of the moisture content and hydration condition of a magnetic mixture material

    SciTech Connect

    Tsukada, K. Kusaka, T.; Saari, M. M.; Takagi, R.; Sakai, K.; Kiwa, T.; Bito, Y.

    2014-05-07

    We developed a magnetic measurement method to measure the moisture content and hydration condition of mortar as a magnetic mixture material. Mortar is a mixture of Portland cement, sand, and water, and these materials exhibit different magnetic properties. The magnetization–magnetic field curves of these components and of mortars with different moisture contents were measured, using a specially developed high-temperature-superconductor superconducting quantum interference device. Using the differences in magnetic characteristics, the moisture content of mortar was measured at the ferromagnetic saturation region over 250 mT. A correlation between magnetic susceptibility and moisture content was successfully established. After Portland cement and water are mixed, hydration begins. At the early stage of the hydration/gel, magnetization strength increased over time. To investigate the magnetization change, we measured the distribution between bound and free water in the mortar in the early stage by magnetic resonance imaging (MRI). The MRI results suggest that the amount of free water in mortar correlates with the change in magnetic susceptibility.

  10. Power-law resistivity, magnetic relaxation and ac susceptibility

    SciTech Connect

    Gilchrist, J.; van der Beek, C.J.

    1994-07-01

    The nonlinear diffusion of magnetic flux into a superconducting sample can be studied by measuring the relaxation of the magnetisation after application of a step field or by measuring the ac susceptibility, {chi}{sub 1} and its third harmonic, {chi}{sub 3}, or preferably both methods covering different time scales. Each has been analysed recently for a field-cooled sample of a material whose creep activation energy depends logarithmically on current density, J corresponding to a power-law relation between electric field, E and J. Here, results are compared, using a universal scaling depth. Maximum {chi}{sub 1}{double_prime} {vert_bar}{chi}{sub 3}{vert_bar} and values occur, and also the magnetisation has relaxed to half its initial value when the scaling depth is comparable to the sample half-thickness.

  11. Anisotropy of magnetic susceptibility parameters: Guidelines for their rational selection

    NASA Astrophysics Data System (ADS)

    Cañón-Tapia, Edgardo

    1994-06-01

    Twenty-eight parameters used to characterize measurements of the anisotropy of magnetic susceptibility are compared theoretically in this work by introducing the concept of the field of susceptibility tensors, which allows the representation of parameters as families of lines in a plane. It is demonstrated that the foliation and lineation parameters are but a special case of the shape parameters, implying that the resolution of these two rock fabric elements using AMS measurements alone is more an artifact of the numerical range of definition of some parameters than a quantification of two physically independent features. Also, it is shown that parameters presumably of the same type do not necessarily yield equivalent interpretation of results in a qualitative sense, and therefore, caution should be strongly exercised when parameters are to be selected. Paramters quantifying the degree of anisotropy are, in general, equivalent to each other because of the very small departure observed in natural rocks from the isotropic case. However, a final consideration of the possible ability to differentiate rock types and a convenient range of values allowing expression of the degree of anisotropy in a well-defined percentage are pointed out as the main factors to be considered before selecting one parameter within this class.

  12. Controlling the magnetic susceptibility in an artificial elliptical quantum ring by magnetic flux and external Rashba effect

    SciTech Connect

    Omidi, Mahboubeh Faizabadi, Edris

    2015-03-21

    Magnetic susceptibility is investigated in a man-made elliptical quantum ring in the presence of Rashba spin-orbit interactions and the magnetic flux. It is shown that magnetic susceptibility as a function of magnetic flux changes between negative and positive signs periodically. The periodicity of the Aharonov-Bohm oscillations depends on the geometry of the region where magnetic field is applied, the eccentricity, and number of sites in each chain ring (the elliptical ring is composed of chain rings). The magnetic susceptibility sign can be reversed by tuning the Rashba spin-orbit strength as well. Both the magnetic susceptibility strength and sign can be controlled via external spin-orbit interactions, which can be exploited in spintronics and nanoelectronics.

  13. Magnetic Susceptibility Measurements as a Proxy for Hydrocarbon Biodegradation

    NASA Astrophysics Data System (ADS)

    Mewafy, F.; Atekwana, E. A.; Slater, L. D.; Werkema, D.; Revil, A.; Ntarlagiannis, D.; Skold, M.

    2011-12-01

    Magnetic susceptibility (MS) measurements have been commonly used in paleoclimate studies, as a proxy for environmental pollution such as heavy metal contamination, and for delineating zones of oil seeps related to hydrocarbon exploration. Few studies have assessed the use of MS measurements for mapping zones of oil pollution. In this study, we investigated the variation in magnetic susceptibility across a hydrocarbon contaminated site undergoing biodegradation. Our objective was to investigate if MS measurements could be used as a proxy indicator of intrinsic bioremediation linked to the activity of iron reducing bacteria. An improved understanding of the mechanisms generating geophysical signatures associated with microbial enzymatic activity could permit the development of geophysical imaging technologies for long-term, minimally invasive and sustainable monitoring of natural biodegradation at oil spill sites. We used a Bartington MS probe to measure MS data along fifteen boreholes within contaminated (both free phase and dissolved phase hydrocarbon plumes) and clean areas. Our results show the following: (1) an enhanced zone of MS straddling the water table at the contaminated locations, not observed at the clean locations; (2) MS values within the free product plume are higher compared to values within the dissolved product plume; (3) the MS values within the vadoze zone above the free product plume are higher compared to values within the dissolved product plume; 4) the zone of high MS is thicker within the free product plume compared to the dissolved product plume. We suggest that the zone of enhanced MS results from the precipitation of magnetite related to the oxidation of the hydrocarbons coupled to iron reduction. Our data documents a strong correlation between MS and hydrocarbon concentration. We conclude that recognition of these zones of enhanced magnetite formation allows for the application of MS measurements as a: (1) low cost, rapid monitoring

  14. Impact of wastewater application on magnetic susceptibility in Terric Histosol soil

    NASA Astrophysics Data System (ADS)

    Sokołowska, Zofia; Alekseev, Andrey; Skic, Kamil; Brzezińska, Małgorzata

    2016-01-01

    In this work, we attempted to analyse the changes in magnetic susceptibility in Terric Histosol soil irrigated with municipal wastewater in a period of four years. Effects of different plants (poplar and willow), wastewater doses, depths, as well as the concentration of the elements and the total carbon content were tested. The study showed that systematic wastewater irrigation diminished magnetic susceptibility values in the top layer of soil. However, statistical analysis revealed that both doses of wastewater and growing plants did not have a significant impact on the magnetic susceptibility of obtained results. Magnetic susceptibility decreased significantly with the depth, in accordance with higher total carbon and lower content of magnetic particles. High correlation coefficients were found between magnetic susceptibility and Zn, Al2O3, Fe2O3, MnO content, whereas no correlation was observed for Cr, as well as for Pb.

  15. Magnetic Susceptibility Cyclostratigraphy of the Ediacaran Wonoka Formation, South Australia, from a Portable Susceptibility Meter

    NASA Astrophysics Data System (ADS)

    Minguez, D. A.; Kodama, K. P.

    2014-12-01

    We present the results of a rock magnetic cyclostratigraphy of the Ediacaran Wonoka Fm., from the Flinders Ranges, South Australia. The Wonoka Fm. records the Shuram C-isotope excursion, and the results of this study provide an estimate of its duration. Measurements of magnetic susceptibility (MS) were made in the field with a portable susceptibility meter (GF Instruments SM-20) every 0.4 m over 600 m of dominantly carbonate stratigraphic section, with a 100 meter interval of fine sand turbidites. We filter the data series to pass wavelengths shorter than 300 meters (the Rayleigh frequency for our data series) and use Multi Taper Method (MTM) time series analysis to estimate the power spectrum of the series. We fit a red noise model to the MTM spectrum and calculate 99% chi squared confidence limits to identify cycles with statistical significance. Unambiguous spectral peaks rise above the 99% confidence level with wavelengths of 116.9 m, 45.5 m, 23.1 m, 7.0 m, 2.5 m, 1.7 m, 1.3 m, 1.2 m, 0.9 m, and 0.8 m. Haines (1988, Sed. Geo. V 58) recognizes cycles in clastic sediment delivery to the carbonate portions of the Wonoka with an average wavelength of 8 m and hypothesizes a climate driver related to Milankovitch cycles. The 7 m cycle in MS is likely a more precise measure of the same phenomenon. Furthermore, cycles with wavelengths of 24.1 m, 7.0 m, 1.7m, 1.26 m, and 0.9 m exhibit ratios matching modeled durations of long eccentricity (405 kyr), short eccentricity (123 kyr), obliquity (29 kyr), and the 2 periods of precession (19 and 14 kyr) for the late Neoproterozoic. This interpretation yields a duration of 10 Myr for the 600 m we sampled. Assuming a constant sedimentation rate yields an 11.3 Myr estimate for the ~675 m thick Shuram C-isotope excursion. However, uncertainty lies in applying the MTM-based estimate to the turbidite section. Our estimate will be refined and compared with laboratory rock magnetic measurements in an ongoing study of the Wonoka Fm.

  16. Tectonic applications of magnetic susceptibility and its anisotropy

    NASA Astrophysics Data System (ADS)

    Borradaile, G. J.; Henry, B.

    1997-03-01

    Anisotropy of low field magnetic susceptibility (AMS) is a versatile petrofabric tool. For magnetite, AMS primarily defines grain-shape anisotropy; for other minerals, AMS expresses crystallographic control on magnetic properties. Thus, we may infer the orientation-distribution of a dominant mineral from the AMS of a rock. AMS principal directions can record current directions from sediment, flow-directions from magma, finite-strain directions from tectonized rocks and stress-directions from low-strain, low-temperature, neotectonic environments. AMS measurements may reveal some aspects of the strain-path, where carefully selected. For example, we may compare different parts of a heterogeneously strained domain, different minerals in a homogeneously strained site, AMS with schistosity/mineral lineation, and AMS with remanence-anisotropy. Such measurements isolate the orientation-distributions of different minerals, adding a temporal scale to the kinematic sequence. Normally, we can interpret the principal directions of AMS distributions as a physically significant direction, such as a current direction, magmatic flow or finite-strain axis. However, calibrating the AMS ellipsoid shape against the magnitude of the controlling physical process is very difficult. Primarily, this is because the shape of the AMS ellipsoid combines contributions from several minerals whose individual AMS ellipsoids are of different shape. Thus, small variations in the proportions of minerals change the shape of the rock's AMS ellipsoid, even if the alignment process were of constant intensity. In deformed rocks, AMS is more strain-sensitive than calcite twinning or the alignment of calcite or quartz c-axes. Not all AMS fabrics relate to crystallographic or grain alignment. First, displacement fabrics generate AMS where an isotropic matrix of high susceptibility displaces unevenly spaced objects of low susceptibility and suitable scales. Second, AMS location fabrics occur where sub

  17. Approximate relationship of coal bed methane and magnetic characteristics of rock via magnetic susceptibility logging

    NASA Astrophysics Data System (ADS)

    Zhao, Yonghui; Wu, Jiansheng; Zhang, Pingsong; Xiao, Pengfei

    2012-02-01

    In coal bed methane (CBM) exploration, how to improve the accuracy for locating and evaluating the CBM deposits is still a problem due to the rarity of occurrence of CBM. Combined with the distribution of the CBM content in the Huainan coalfield, the approximate relationship between the occurrence of CBM and the magnetic properties of the coal bed and adjacent mudstone have been widely discussed by magnetic logging. Experimental results show that magnetic susceptibility of the coal bed and adjacent mudstone would clearly increase with the CBM content in a coal bed. According to the results of the experiment, the prediction of the CBM content has been accomplished for different coal beds, and the results are consistent with the distribution of the CBM content throughout the whole coalfield. Preliminary data analysis reveals that there is indeed a correlation between the changes of magnetic rock characteristics and the occurrence of the CBM, and this finding may shed some light on the evaluation of CBM.

  18. Oxygen adsorption and the magnetic susceptibility of ice at low temperatures

    USGS Publications Warehouse

    Senftle, F.E.; Thorpe, A.

    1962-01-01

    WHEN dealing with the magnetic susceptibility of tumour tissue1, we reported the magnetic susceptibility of ice at various temperatures from 273??K. down to 77??K. Since this publication, the authors have made many susceptibility measurements of ice, using the same equipment, and have obtained similar results, that is, a relatively large increase in diamagnetism below 150??K. Normal diamagnetism is not dependent on temperature, and hence further experiments were made of the magnetic susceptibility of ice at low temperatures in an attempt to determine some extraneous cause of the increased diamagnetism. ?? 1962 Nature Publishing Group.

  19. Unusual hysteresis in the magnetic susceptibility of cubic hexaboride KB6.

    PubMed

    Etourneau, J; Ammar, A; Villesuzanne, A; Villeneuve, G; Chevalier, B; Whangbo, M-H

    2003-07-14

    Electrical resistivity, magnetic susceptibility, and electron paramagnetic resonance measurements were carried out for cubic hexaboride KB(6), which is one electron short of completely filling its conduction band. It is found that KB(6) is not metallic and has localized spins. KB(6) exhibits a highly unusual hysteresis in the magnetic susceptibility below 100 K, which suggests that it undergoes a slow relaxation process.

  20. Magnetic properties of nested carbon nanostructures studied by electron spin resonance and magnetic susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Bandow, Shunji

    1996-07-01

    Nested carbon nanostructures, e.g., nanotubes and nanoballs, are separated from the coexisting materials of carbon flakes and needle-like fragments by sonication, centrifugalization and low-temperature combustion. Content of nanotubes at the final stage separation is in excess of 85% by weight. The nested carbon nanostructures (≳85 wt % tubules) are studied by electron spin resonance (ESR) and magnetic susceptibility measurements. The temperature dependence of the conduction-ESR intensity for the nested carbons is similar to that for graphite. On the other hand, the g value is almost constant (g=2.0096±0.0004 at room temperature) between 40 and 300 K, in contrast to that of graphite. These ESR features are discussed in terms of the electronic structure of carbon nanotubes predicted by theoretical calculation. The magnetic field dependence of differential magnetic susceptibility (χdiff) indicates a logarithmic divergence in the magnetic field H≤2 kG and the χdiff is a positive value at H≊0.8 kG, which is qualitatively consistent with the magnetic properties of metallic carbon nanotube enunciated by Ajiki and Ando.

  1. The influence of radioactive decay on actinide magnetic susceptibility measurements obtained using the Evans method.

    PubMed

    Autillo, Matthieu; Kaden, Peter; Geist, Andreas; Guerin, Laetitia; Moisy, Philippe; Berthon, Claude

    2014-05-14

    In order to explain the higher magnetic susceptibility of some aquo actinide ions than predicted by Hund's rules, the molar magnetic susceptibilities of two americium isotopes ((241)Am and (243)Am) were measured using the Evans method. The results obtained show a growing change in the magnetic susceptibility with α and also a β(-) activity increase in solution. β(-) particle effects appear to be stronger than radicals formed by α particles on the experimental values. The temperature dependence of Am(iii) magnetic susceptibility has been observed but from experiments carried out here, it appears to be difficult to prove whether this effect arises from radicals or β(-). Finally, magnetic susceptibilities of americium recorded in different media (HClO4, HCl, and HNO3) have been compared to alpha and beta emissions' impact.

  2. Some factors affecting an increase in magnetic susceptibility of cement dusts

    NASA Astrophysics Data System (ADS)

    Gołuchowska, Beata J.

    2001-09-01

    The aim of the research was to explain reasons of fluctuation in magnetic susceptibility of cement dusts and the consequences for the environment. The research comprised measurements of magnetic susceptibility and Fe content in dusts, and also in raw materials, additives, fuels, mixtures and clinkers used for cement production. The samples were taken in four cement plants located in Opole Province (southern Poland). In addition to this, the influence of two production methods (dry and wet) on magnetic susceptibility of dusts and some aspects of ferrimagnetic minerals formation in the process of clinker burning were considered. It was proven that magnetic susceptibility of dusts depends on raw materials and fuels but especially on additives used for cement production, method of production and the carbon monoxide content in gases from clinker rotary kilns. Statistically important linear correlations between magnetic susceptibility and Fe suggest that during clinker burning, ferrimagnetic minerals may be formed.

  3. Application of broadband alternating current magnetic susceptibility to the characterization of magnetic nanoparticles in natural materials

    NASA Astrophysics Data System (ADS)

    Kodama, Kazuto

    2013-01-01

    A new method is proposed for characterizing magnetic particles by measuring low-field alternating current magnetic susceptibility at a number of frequency steps spanning four orders of magnitude, from 125 Hz to 512 kHz. This method was tested using natural samples with various grain size distributions, including basalt (Kilauea, Hawaii), loess and paleosol (Luochuan, China), tuff (Yucca Mountain, Nevada), granite (Minnesota Valley, Minnesota), and andesite (Sakurajima, Japan). The resulting frequency spectrum of magnetic susceptibility (FSMS) of the basalt, loess/paleosol, and tuff decreases with increasing frequency, but at different rates of decrease. The FSMS of the basalt is characterized by a monotonic decrease with increasing frequency over the entire range. The FSMS of the loess/paleosol and the tuff decreases more markedly than that of the basalt, which agrees with previous results showing that superparamagnetic particles are dominant in such material. Quantitative estimates using FSMSs allow reconstruction of characteristic grain size distributions and clearly identify differences in the distribution of superparamagnetic particles. The multidomain granite sample has no distinct frequency dependence, which is probably due to the smooth displacement of domain walls in the presence of the external field. In contrast, the FSMSs of the andesite samples exhibit maxima over a limited frequency range, between 16 and 128 kHz. This behavior, together with low-temperature measurements, can be accounted for by magnetic resonance of domain walls in the multidomain phenocrysts.

  4. Three-dimensional quantification of susceptibility artifacts from various metals in magnetic resonance images.

    PubMed

    Imai, Haruki; Tanaka, Yoji; Nomura, Naoyuki; Tsutsumi, Yusuke; Doi, Hisashi; Kanno, Zuisei; Ohno, Kikuo; Ono, Takashi; Hanawa, Takao

    2013-09-01

    Susceptibility artifacts generated in magnetic resonance (MR) images were quantitatively evaluated for various metals using a three-dimensional (3-D) artifact rendering to demonstrate the correlation between magnetic susceptibility and artifact volume. Ten metals (stainless steel, Co-Cr alloy, Nb, Ti, Zr, Mo, Al, Sn, Cu and Ag) were prepared, and their magnetic susceptibilities measured using a magnetic balance. Each metal was embedded in a Ni-doped agarose gel phantom and the MR images of the metal-containing phantoms were taken using 1.5 and 3.0 T MR scanners under both fast spin echo and gradient echo conditions. 3-D renderings of the artifacts were constructed from the images and the artifact volumes were calculated for each metal. The artifact volumes of metals decreased with decreasing magnetic susceptibility, with the exception of Ag. Although Sn possesses the lowest absolute magnetic susceptibility (1.8×10(-6)), the artifact volume from Cu (-7.8×10(-6)) was smaller than that of Sn. This is because the magnetic susceptibility of Cu was close to that of the agarose gel phantom (-7.3×10(-6)). Since the difference in magnetic susceptibility between the agarose and Sn is close to that between the agarose and Ag (-17.5×10(-6)), their artifact volumes were almost the same, although they formed artifacts that were reversed in all three dimensions.

  5. Magnetic susceptibility for a two-channel Anderson model

    NASA Astrophysics Data System (ADS)

    Líbero, Valter L.; Ferreira, João V. B.; Oliveira, Luiz N.; Cox, Daniel L.

    2001-03-01

    Non-Fermi-liquid magnetic properties are studied using a generalized two-channel Anderson model suitable for compounds like U_xTh_1-xRu_2Si2 or La_1-xCe_xCu_2.2Si2 in the low concentration regime, for which single-site characteristics of the f-electrons are experimentally evident^1. The model encompasses a spin doublet and two (degenerate) channel doublets as impurity levels, opening two channels in the conduction band, with hybridization strength V1 and V_2. The interleaving Numerical Renormalization Group procedure^2,3 determines the temperature-dependent susceptibility \\chi. For the isotropic case V_1=V2 non-Fermi liquid behavior, \\chi ≈ -ln T, is obtained. This non-trivial fixed-point, however, is unstable against channel anisotropy: for V1 ne V2 normal-Fermi liquid behavior is recovered. 1- Tae-Suk Kim and D. L. Cox, Phys. Rev. Lett. 75, 1622 (1995). 2- S. C. Costa, C. A. Paula, V. L. Líbero and L. N. Oliveira, Phys. Rev. B 55, 30 (1997). 3- J. V. B. Ferreira and V. L. Líbero, Phys. Rev. B 61, 10615 (2000).

  6. Magnetic susceptibility for use in delineating hydric soils

    USGS Publications Warehouse

    Grimley, D.A.; Vepraskas, M.J.

    2000-01-01

    Field indicators are used to identify hydric soil boundaries and to delineate wetlands. The most common field indicators may not be seen in some soils with thick, dark, mollic epipedons, and do not form in Fe-poor soils. This study evaluated magnetic susceptibility (MS) meter as a field tool to determine hydric soil boundaries. Five Mollisoldominated sites formed in glacial deposits in Illinois were evaluated along with one Ultisol-dominated site formed in Coastal Plain sediments of North Carolina. Measurements of volumetric MS were made along transects at each site that extended from wetland into upland areas. One created wetland was evaluated. Field indicators were used to identify the hydric soils. Results showed that volumetric MS values were significantly (P 0.15) differences in MS were found for Coastal Plain hydric and nonhydric soils where MS values were low (<10 ?? 10-5 SI). Critical MS values that separated hydric and nonhydric soils varied between 20 ?? 10-5 and 30 ?? 10-5 SI for the loessal soils evaluated in Illinois. Such critical values will have to be determined on site using field indicators until specific values can be defined for hydric soils within a given parent material. With a critical MS value in hand, a wetland delineator can make MS measurements along transects perpendicular to the envisioned hydric soil boundary to quickly and quantitatively identify it.

  7. Analogue sandbox experiments, anisotropy of magnetic susceptibility (AMS) and paleomagnetism

    NASA Astrophysics Data System (ADS)

    Almqvist, Bjarne; Koyi, Hemin

    2017-04-01

    In this contribution we present results from AMS measurements on samples from analogue models simulating fold-thrust belts. The models are made of 99 % well sorted beach sand, consisting of quartz and feldspar and 1 % magnetite, by volume. The sand is contained within a model space with initial size of 30 cm width, 60 cm length and 2 cm height. Four models with identical setup were deformed by bulk shortening (compression) ranging from 8 % to 33 %. In each model, three different tectonic domains were studied, representing the state of deformation, analogous to the compression experienced by a mountain belt. The hinterland, closest to the "pushing" side of the model (backstop) accommodate the largest deformation where thrust wedges develop. The foreland, being farthest away from the backstop, remains weakly affected by the compression. A transition zone separates these two end-member domains, where deformation is apparent by layer-parallel shortening and thickening, but thrusting is absent (deformation is accommodated by penetrative strain). With progressive shortening (compression), more of the model is deformed and the hinterland gradually expands. The analyzed AMS closely reflects the deformation in the models, and can be quantitatively used to study the development of model deformation. The initial undeformed fabric is oblate (depositional) and uniform throughout the model, where the k3 axes tightly group as a pole to the bedding/foliation plane. During shortening, the original magnetic fabric becomes gradually overprinted, with a reduction in the degree of anisotropy in the transition zone and development of a triaxial susceptibility ellipsoid. Principal susceptibility axes become more scattered. The degree of anisotropy increases in the hinterland, and the fabric consist of a mix of prolate and oblate susceptibility ellipsoids. The k1 axes obtain a grouping that is parallel to the backstop (i.e., parallel to the strike of the "orogenic wedge"). AMS analysis

  8. Quantum renormalizations in anisotropic multisublattice magnets and the modification of magnetic susceptibility under irradiation

    NASA Astrophysics Data System (ADS)

    Val'kov, V. V.; Shustin, M. S.

    2015-11-01

    The dispersion equation of a strongly anisotropic one-dimensional magnet catena-[FeII(ClO4)2{FeIII(bpca)2}]ClO4 containing alternating high-spin (HS) ( S = 2) and low-spin (LS) ( S = 1/2) iron ions is obtained by the diagram technique for Hubbard operators. The analysis of this equation yields six branches in the excitation spectrum of this magnet. It is important that the crystal field for ions with spin S = 2 is described by the Hamiltonian of single-ion easy-plane anisotropy, whose orientation is changed by 90° when passing from one HS iron ion to another. The U( N) transformation technique in the atomic representation is applied to diagonalize a single-ion Hamiltonian with a large number of levels. It is shown that the modulation of the orientation of easy magnetization planes leads to a model of a ferrimagnet with easy-axis anisotropy and to the formation of energy spectrum with a large gap. For HS iron ions, a decrease in the mean value of the spin projection due to quantum fluctuations is calculated. The analysis of the specific features of the spectrum of elementary excitations allows one to establish a correspondence to a generalized Ising model for which the magnetic susceptibility is calculated in a wide range of temperatures by the transfer-matrix method. The introduction of a statistical ensemble that takes into account the presence of chains of different lengths and the presence of iron ions with different spins allows one to describe the experimentally observed modification of the magnetic susceptibility of the magnet under optical irradiation.

  9. Quantum renormalizations in anisotropic multisublattice magnets and the modification of magnetic susceptibility under irradiation

    SciTech Connect

    Val’kov, V. V. Shustin, M. S.

    2015-11-15

    The dispersion equation of a strongly anisotropic one-dimensional magnet catena-[Fe{sup II}(ClO{sub 4}){sub 2}(Fe{sup III}(bpca){sub 2})]ClO{sub 4} containing alternating high-spin (HS) (S = 2) and low-spin (LS) (S = 1/2) iron ions is obtained by the diagram technique for Hubbard operators. The analysis of this equation yields six branches in the excitation spectrum of this magnet. It is important that the crystal field for ions with spin S = 2 is described by the Hamiltonian of single-ion easy-plane anisotropy, whose orientation is changed by 90° when passing from one HS iron ion to another. The U(N) transformation technique in the atomic representation is applied to diagonalize a single-ion Hamiltonian with a large number of levels. It is shown that the modulation of the orientation of easy magnetization planes leads to a model of a ferrimagnet with easy-axis anisotropy and to the formation of energy spectrum with a large gap. For HS iron ions, a decrease in the mean value of the spin projection due to quantum fluctuations is calculated. The analysis of the specific features of the spectrum of elementary excitations allows one to establish a correspondence to a generalized Ising model for which the magnetic susceptibility is calculated in a wide range of temperatures by the transfer-matrix method. The introduction of a statistical ensemble that takes into account the presence of chains of different lengths and the presence of iron ions with different spins allows one to describe the experimentally observed modification of the magnetic susceptibility of the magnet under optical irradiation.

  10. AC Magnetic Properties of Large Volume of Water — Susceptibility Measurement in Unshielded Environment

    NASA Astrophysics Data System (ADS)

    Tsukada, Keiji; Kiwa, Toshihiko; Masuda, Yuuki

    2006-10-01

    To investigate the effect of low-frequency magnetic-field exposure of a human body, the low-frequency AC magnetic property of a large volume of water was measured by low-frequency magnetic field exposure (from 50 Hz to 1.2 kHz). The results indicate that the AC magnetic property of water is due to diamagnetism in the low-frequency range. The phase between the main magnetic field and the generated magnetic field remained constant at about 180°. Results were not affected by conductivity or pH. Moreover, the magnetic-field strength from water showed a susceptibility frequency dependence proportional to the frequency above approximately 400 Hz. Because of the incremental effects of susceptibility, the magnetic field from water was measured using a conventional magnetic sensor (magnetic resistive; MR) in an unshielded environment.

  11. Three-dimensional magnetization vector inversion for high-susceptibility magnetic anomaly

    NASA Astrophysics Data System (ADS)

    Liu, Shuang; Hu, Xiangyun

    2016-04-01

    It was meaningful to recover the distributions of total magnetization vector (TMV) since of which the intensity and direction are distorted by the self-demagnetization. We evaluated and compared three approaches of three-dimensional magnetization vector inversion (MVI): (1) simultaneously inverting the TMV's three orthogonal components (MMM); (2) the magnitude, inclination and declination (MID); (3) orderly inverting the magnetization intensity, inclination and declination based on the transformed magnitude magnetic anomaly (M-ID). The primary implementation of MVI was to establish the symmetric positive definite matrix equations on the corrections of the model parameters and observed data sets. Then the optimal solutions were iteratively computed by use of the preconditioned conjugate gradient algorithm. We used the synthetic and real data sets to test these methods and the tests revealed that the isochronous MMM inversion aggravated the geophysical non-uniqueness problem and MID performed low stability of convergence due to the strong dependence on the starting models. While the sequential M-ID showed superior stability and precision of inverting the magnetization intensity and direction by making successive use of the amplitude and phase information of the magnetic anomaly. Finally, the achieved TMV distributions were used to investigate the influence of self-demagnetization and to recover the high susceptibility distributions when the self-demagnetization effect was not negligible.

  12. Non-Magnetic Factors Affecting Magnetic Susceptibility of the Loess-Paleosol Sequences in the Chinese Loess Plateau

    NASA Astrophysics Data System (ADS)

    Wang, H.; Feng, Z.

    2009-12-01

    Several different proposals have been adopted to explain the linkage between the magnetic susceptibility of loess-paleosol sequences and the associated past climate. First, the intensity of dustfall controlled the variation in the susceptibility. Second, the degree of pedogenesis controlled the variation. A third proposal states that the susceptibility signal is a result of the competing processes between pedogenic enhancement and detrital inheritance. This paper examines the acceptability as the summer monsoon proxy from nonmagnetic perspectives. Several conclusions can be drawn from our data. First, clay translocation within the Last Interglacial paleosol S1 profiles must have moved some of the magnetic minerals downward so that the susceptibility reflects only the post-translocation distribution of the magnetic susceptibility-producing minerals. Second, the best-developed paleosol S1S3 (equivalent to MIS 5e) at most of the sections studied is not well expressed by the magnetic susceptibility because this paleosol developed in underlying coarse loess (L2) and coarse textures tend to lower the susceptibility. Third, carbonate concentration is negatively correlated with the magnetic susceptibility or suppresses the magnetic susceptibility peak when the susceptibility enhancement exceeds the carbonate dilution effect. It should be stressed that the susceptibility signal and its contributors in eolian sequences can be site- and time-dependent within the Chinese Loess Plateau. A stronger eolian component northwestward and a stronger pedogenic component southeastward are the general trends, but the trends can be complicated by those site- and time-dependent factors. Therefore, a more comprehensive model is needed to more precisely address the relationship between the paleoclimate and the proxy.

  13. Support Vector Machines and Generalisation in HEP

    NASA Astrophysics Data System (ADS)

    Bethani, A.; Bevan, A. J.; Hays, J.; Stevenson, T. J.

    2016-10-01

    We review the concept of support vector machines (SVMs) and discuss examples of their use. One of the benefits of SVM algorithms, compared with neural networks and decision trees is that they can be less susceptible to over fitting than those other algorithms are to over training. This issue is related to the generalisation of a multivariate algorithm (MVA); a problem that has often been overlooked in particle physics. We discuss cross validation and how this can be used to improve the generalisation of a MVA in the context of High Energy Physics analyses. The examples presented use the Toolkit for Multivariate Analysis (TMVA) based on ROOT and describe our improvements to the SVM functionality and new tools introduced for cross validation within this framework.

  14. Collaborative Generalisation: Formalisation of Generalisation Knowledge to Orchestrate Different Cartographic Generalisation Processes

    NASA Astrophysics Data System (ADS)

    Touya, Guillaume; Duchêne, Cécile; Ruas, Anne

    Cartographic generalisation seeks to summarise geographical information from a geographic database to produce a less detailed and readable map. This paper deals with the problem of making different automatic generalisation processes collaborate to generalise a complete map. A model to orchestrate the generalisation of different areas (cities, countryside, mountains) by different adapted processes is proposed. It is based on the formalisation of cartographic knowledge and specifications into constraints and rules sets while processes are described to formalise their capabilities. The formalised knowledge relies on generalisation domain ontology. For each available generalisation process, the formalised knowledge is then translated into process parameters by an adapted translator component. The translators allow interoperable triggers and allow the choice of the proper process to apply on each part of the space. Applications with real processes illustrate the usability of the proposed model.

  15. Establishment and implications of a characterization method for magnetic nanoparticle using cell tracking velocimetry and magnetic susceptibility modified solutions.

    PubMed

    Zhang, Huading; Moore, Lee R; Zborowski, Maciej; Williams, P Stephen; Margel, Shlomo; Chalmers, Jeffrey J

    2005-04-01

    Magnetic micro and nanoparticles conjugated to affinity labels have become a significant, commercial reagent. It has been demonstrated that the performance of cell separation systems using magnetic labels is a function of the magnitude of the magnetic force that can be generated through labeling. This magnetic force is proportional to the number of magnetic particles bound to the cell, the magnetic energy gradient, and the particle-field interaction parameter. This particle-field interaction parameter, which is the product of the relative volumetric, magnetic susceptibility and the volume of the micro or nanoparticle, is a fundamental parameter which can be used to characterize the magnetic particles. An experimental technique is presented which measures the volumetric magnetic susceptibility of particles through the use of susceptibility modified solutions and an experimental instrument, Cell Tracking Velocimetry, CTV. Experimental studies were conducted on polystyrene microspheres alone and those bound to four different magnetic nanoparticles. The experimentally determined values of the magnetic susceptibility of the polystyrene microspheres are consistent with values found from literature. Consequently, magnetic susceptibility measurements of these polystyrene microspheres bound with the magnetic nanoparticles combined with particle size measurements using commercial dynamic light scattering instrument allowed estimates of the particle-field interaction parameter to be made for four commercial, magnetic nanoparticles. The value found for MACS beads is close to what is reported from an independent study. The values for MACS beads and Imag beads are found to agree with what is observed from experiments. Finally, an experimental demonstration of the impact that differences in this field interaction parameter has on the labeling of human lymphocytes is presented.

  16. Isochronal Annealing Studies in Pu and Pu Alloys Using Magnetic Susceptibility

    SciTech Connect

    McCall, S. K.; Fluss, M. J.; Chung, B. W.; McElfresh, M. W.; Chapline, G.F.; Jackson, D. D.; Haire, Richard {Dick} G

    2007-01-01

    The isochronal annealing of the low temperature accumulated damage from the radioactive decay of plutonium in {alpha}-Pu, {delta}-Pu{sub 1-x}Ga{sub x} (x = 0.043) and {delta}-Pu{sub 1-x}Am{sub x} (x = 0.224) was characterized using magnetic susceptibility. In each specimen, thermal annealing, as tracked by magnetic susceptibility, only commenced when T > 33 K and the magnetic susceptibility changes due to defects were fully annealed at T not, vert, similar 300 K. The {alpha}-Pu magnetic susceptibility isochronal annealing data is similar to earlier measurements of resistivity characterized isochronal annealing. However, the {delta}-Pu{sub 1-x}Ga{sub x} (x = 0.043) magnetic susceptibility isochronal annealing data, when compared with similar resistivity data, indicates that for this alloy magnetic susceptibility studies are more sensitive to vacancies than to the interstitials accumulated at low temperatures. The Pu{sub 1-x}Am{sub x} (x = 0.224) alloy shows a remarkable change in properties, over a limited temperature range beginning where interstitial defects are first mobile, and characterized by an induced effective moment of order 1.1 {mu}{sub B}/Pu. This transient behavior may be evidence for a disorder driven low temperature phase transition, perhaps indicative of a compositional and structural proximity to a state possessing significant magnetic moments.

  17. Classification of soil magnetic susceptibility and prediction of metal detector performance: case study of Angola

    NASA Astrophysics Data System (ADS)

    Preetz, Holger; Altfelder, Sven; Hennings, Volker; Igel, Jan

    2009-05-01

    Soil magnetic properties can seriously impede the performance of metal detectors used in landmine clearance operations. For a proper planning of clearance operations pre-existing information on soil magnetic susceptibility can be helpful. In this study we briefly introduce a classification system to assess soil magnetic susceptibilities from geoscientific maps. The classification system is based on susceptibility measurements conducted on archived lateritic soil samples from 15 tropical countries. The system is applied to a soil map of Angola, resulting in a map that depicts soil magnetic susceptibilities as a worst case scenario. An additional layer depicting the surveyed mine affected communities in Angola is added to the map, which demonstrates that a large number of those are located in areas where soil is expected to impede metal detector performance severely.

  18. Nonlinear Regularization for Per Voxel Estimation of Magnetic Susceptibility Distributions from MRI Field Maps

    PubMed Central

    Kressler, Bryan; de Rochefort, Ludovic; Liu, Tian; Spincemaille, Pascal; Jiang, Quan; Wang, Yi

    2010-01-01

    Magnetic susceptibility is an important physical property of tissues, and can be used as a contrast mechanism in magnetic resonance imaging. Recently, targeting contrast agents by conjugation with signaling molecules and labeling stem cells with contrast agents have become feasible. These contrast agents are strongly paramagnetic, and the ability to quantify magnetic susceptibility could allow accurate measurement of signaling and cell localization. Presented here is a technique to estimate arbitrary magnetic susceptibility distributions by solving an ill-posed inversion problem from field maps obtained in an MRI scanner. Two regularization strategies are considered, conventional Tikhonov regularization, and a sparsity promoting nonlinear regularization using the ℓ1 norm. Proof of concept is demonstrated using numerical simulations, phantoms, and in a stroke model mouse. Initial experience indicates that the nonlinear regularization better suppresses noise and streaking artifacts common in susceptibility estimation. PMID:19502123

  19. Nonmonotonic magnetic susceptibility of dipolar hard-spheres at low temperature and density.

    PubMed

    Kantorovich, Sofia; Ivanov, Alexey O; Rovigatti, Lorenzo; Tavares, José Maria; Sciortino, Francesco

    2013-04-05

    We investigate, via numerical simulations, mean field, and density functional theories, the magnetic response of a dipolar hard sphere fluid at low temperatures and densities, in the region of strong association. The proposed parameter-free theory is able to capture both the density and temperature dependence of the ring-chain equilibrium and the contribution to the susceptibility of a chain of generic length. The theory predicts a nonmonotonic temperature dependence of the initial (zero field) magnetic susceptibility, arising from the competition between magnetically inert particle rings and magnetically active chains. Monte Carlo simulation results closely agree with the theoretical findings.

  20. Magnetic susceptibility variations in Loess sequences and their relationship to astronomical forcing

    NASA Technical Reports Server (NTRS)

    Verosub, Kenneth L.; Singer, Michael J.

    1992-01-01

    The long, well-exposed and often continuous sequences of loess found throughout the world are generally thought to provide an excellent opportunity for studying long-term, large-scale environmental change during the last few million years. In recent years, the most fruitful loess studies have been those involving the deposits of the loess in China. One of the most intriguing results of that work has been the discovery of an apparent correlation between variations in the magnetic susceptibility of the loess sequence and the oxygen isotope record of the deep sea. This correlation implies that magnetic susceptibility variations are being driven by astronomical parameters. However, the basic data have been interpreted in various ways by different authors, most of whom assumed that the magnetic minerals in the loess have not been affected by post-depositional processes. Using a chemical extraction procedure that allows us to separate the contribution of secondary pedogenic magnetic minerals from primary inherited magnetic minerals, we have found that the magnetic susceptibility of the Chinese paleosols is largely due to a pedogenic component which is present to a lesser degree in the loess. We have also found that the smaller inherited component of the magnetic susceptibility is about the same in the paleosols and the loess. These results demonstrate the need for additional study of the processes that create magnetic susceptibility variations in order to interpret properly the role of astronomical forcing in producing these variations.

  1. Microstructure and magnetic susceptibility of as-cast Zr-Mo alloys.

    PubMed

    Suyalatu; Nomura, Naoyuki; Oya, Kei; Tanaka, Yuko; Kondo, Ryota; Doi, Hisashi; Tsutsumi, Yusuke; Hanawa, Takao

    2010-03-01

    The microstructures and magnetic susceptibilities of Zr-Mo alloys were investigated to develop a Zr alloy with a low magnetic susceptibility for magnetic resonance imaging (MRI). The microstructure was evaluated with an X-ray diffractometer (XRD), an optical microscope (OM) and a transmission electron microscope (TEM), and the magnetic susceptibility was measured with a magnetic susceptibility balance. The alpha' phase with acicular structure was dominant in Zr-1Mo alloys, while the omega and beta phases with the equiaxed and relatively flat (no acicular) microstructure was dominant in Zr-3Mo. The mixed microstructural features of Zr-1Mo and Zr-3Mo were observed in Zr-2Mo, which consists of the alpha', omega and beta phases. The beta phase is stabilized when the Mo content exceeds over 3 mass% Mo. As-cast Zr-Mo alloys showed a minimum value of magnetic susceptibility at 3 mass% Mo, and the value abruptly increased up to 10% Mo before remaining stable up to 15 mass% Mo. XRD, OM and TEM revealed that the minimum value of the susceptibility was closely related to the appearance of the athermal omega phase in the beta phase. As the Mo content decreases from 3 mass%, the alpha' phase appears with the omega and beta phases. On the other hand, as the Mo content increases from 3 mass%, the beta phase increases and the omega phase decreases. Thus the appearance of the alpha' and beta phase leads to an increase in magnetic susceptibility. The magnetic susceptibility of as-cast Zr-3Mo alloy was almost one-third that of Ti-6Al-4V, which is commonly used for medical implant devices. Zr-Mo alloys are useful for medical devices used under MRI.

  2. The magnetic susceptibility on the transverse antiferromagnetic Ising model: Analysis of the reentrant behavior

    NASA Astrophysics Data System (ADS)

    Neto, Minos A.; de Sousa, J. Ricardo; Padilha, Igor T.; Rodriguez Salmon, Octavio D.; Roberto Viana, J.; Dinóla Neto, F.

    2016-06-01

    We study the three-dimensional antiferromagnetic Ising model in both uniform longitudinal (H) and transverse (Ω) magnetic fields by using the effective-field theory (EFT) with finite cluster N = 1 spin (EFT-1). We analyzed the behavior of the magnetic susceptibility to investigate the reentrant phenomena that we have seen in the same phase diagram previously obtained in other papers. Our results shows the presence of two divergences in the susceptibility that indicates the existence of a reentrant behavior.

  3. Correlation of AC Loss Data from Magnetic Susceptibility Measurements with YBCO Film Quality (Postprint)

    DTIC Science & Technology

    2012-02-01

    excimer laser operating at the KrF, 248 nm , wavelength. Substrates included LaAlO3 ( 100 ) and SrTiO3 ( 100 ) single crystal substrates as well as buffered...AFRL-RZ-WP-TP-2012-0100 CORRELATION OF AC LOSS DATA FROM MAGNETIC SUSCEPTIBILITY MEASUREMENTS WITH YBCO FILM QUALITY (POSTPRINT) Paul N...CORRELATION OF AC LOSS DATA FROM MAGNETIC SUSCEPTIBILITY MEASUREMENTS WITH YBCO FILM QUALITY (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT

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

    PubMed

    Li, Wei; Wu, Bing; Batrachenko, Anastasia; Bancroft-Wu, Vivian; Morey, Rajendra A; Shashi, Vandana; Langkammer, Christian; De Bellis, Michael D; Ropele, Stefan; Song, Allen W; Liu, Chunlei

    2014-06-01

    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. Copyright © 2013 Wiley Periodicals, Inc.

  5. Prediction of Stroke Subtype and Recanalization Using Susceptibility Vessel Sign on Susceptibility-Weighted Magnetic Resonance Imaging.

    PubMed

    Kang, Dong-Wan; Jeong, Han-Gil; Kim, Do Yeon; Yang, Wookjin; Lee, Seung-Hoon

    2017-06-01

    The susceptibility vessel sign (SVS) is a hypointense signal visualized because of the susceptibility effect of thrombi, sensitively detected on susceptibility-weighted magnetic resonance imaging. The relationship of SVS parameters with the stroke subtype and recanalization status after endovascular treatment remains uncertain. The data from 89 patients with acute stroke caused by anterior circulation infarcts who underwent susceptibility-weighted magnetic resonance imaging before endovascular treatment were examined. Independent reviewers, blinded to the stroke subtype and recanalization status, measured the SVS diameter, length, and estimated volume. The intra- and interrater agreements of the SVS parameters were assessed. The SVS was identified in 78% of the patients. SVS was more commonly associated with cardioembolism than with noncardioembolism (P=0.01). The SVS diameter (P<0.01) and length (P=0.01) were larger in the cardioembolism group. The SVS diameter was larger in the recanalization group (thrombolysis in cerebral infarction ≥2b) than in the nonrecanalization group (P=0.04). Multivariable analysis revealed that the SVS diameter was an independent predictor of cardioembolism (adjusted odds ratio, 1.97; 95% confidence interval, 1.34-2.90; P<0.01). There was no significant association between the SVS volume and the recanalization status (adjusted odds ratio, 1.003; 95% confidence interval, 0.999-1.006; P=0.12). The optimal cutoff value of the SVS diameter for the cardioembolism was 5.5 mm (sensitivity, 45.6%; specificity, 93.8%). Increased SVS diameter on susceptibility-weighted magnetic resonance imaging may predict cardioembolism. No clear association was found between SVS volume and endovascular recanalization. © 2017 The Authors.

  6. Effect of Object Orientation Angle on T2* Image and Reconstructed Magnetic Susceptibility: Numerical Simulations

    PubMed Central

    Chen, Zikuan; Calhoun, Vince

    2013-01-01

    The magnetic field resulting from material magnetization in magnetic resonance imaging (MRI) has an object orientation effect, which produces an orientation dependence for acquired T2* images. On one hand, the orientation effect can be exploited for object anisotropy investigation (via multi-angle imaging); on the other hand, it is desirable to remove the orientation dependence using magnetic susceptibility reconstruction. In this report, we design a stick-star digital phantom to simulate multiple orientations of a stick-like object and use it to conduct various numerical simulations. Our simulations show that the object orientation effect is not propagated to the reconstructed magnetic susceptibility distribution. This suggests that accurate susceptibility reconstruction methods should be largely orientation independent. PMID:25114542

  7. Magnetic field dependent polarizability and electric field dependent diamagnetic susceptibility of a donor in Si

    NASA Astrophysics Data System (ADS)

    Muthukrishnaveni, M.; Srinivasan, N.

    2016-09-01

    The polarizability and diamagnetic susceptibility values of a shallow donor in Si are computed. These values are obtained for the cases bar{E}allel bar{B} and bar{E} bot bar{B}. The anisotropy introduced by these perturbations are properly taken care of in the expressions derived for polarizability and magnetic susceptibility. Our results show that the numerical value of the contribution from electric field to diamagnetic susceptibility is several orders smaller than that of the magnetic field effect. Polarizability values are obtained in a magnetic field by two different methods. The polarizability values decrease as the intensity of magnetic field increases. Using the Clausius-Mossotti relation, the anisotropic values of the refractive indices for different magnetic fields are estimated.

  8. Acute generalised exanthematous pustulosis.

    PubMed

    Fernando, Suran L

    2012-05-01

    Acute generalised exanthematous pustulosis (AGEP) is a severe cutaneous adverse reaction and is caused by drugs in >90% of cases. It is rare, with an incidence of 1-5 patients per million per year. The clinical manifestations are characterised by fever and the rapid appearance of disseminated sterile pustules 3-5 days after the commencement of treatment. It is accompanied by marked neutrophilia. Mucous membranes are not typically involved. The drugs conferring the highest risk of AGEP according to the EuroSCAR study are aminopenicillins, pristinamycin, hydroxychloroquine, antibacterial sulphonamides, terbinafine and diltiazem. The pathogenesis of AGEP involves the initial influx of CD8 cytotoxic T-cells resulting in the apoptosis of keratinocytes and formation of vesicles. Then CXCL-8-producing and granulocyte macrophage-colony stimulating factor-producing CD4 cells enter the epidermis, resulting in neutrophil mediated inflammation and the formation of pustules. As a result, the histology reveals intraepidermal, usually subcorneal, pustules and an accompanying neutrophilic and lymphocytic infiltrate. Epicutaneous patch testing may also support the diagnosis by causing a localised pustular reaction 48-96 h after the offending drug is applied. The condition usually resolves by 15 days after the causative drug is withdrawn but oral corticosteroid therapy may be necessary in some individuals. The mortality rate is up to 5% and mostly occurs in elderly people who have significant comorbidities.

  9. Epilepsy (generalised seizures).

    PubMed

    Cross, J Helen

    2015-04-17

    About 3% of people will be diagnosed with epilepsy during their lifetime, but about 70% of people with epilepsy eventually go into remission. We conducted a systematic review and aimed to answer the following clinical question: What are the effects of additional treatments in people with drug-resistant epilepsy characterised by generalised seizures? We searched: Medline, Embase, The Cochrane Library, and other important databases up to April 2014 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). We found four studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. In this systematic review we present information relating to the effectiveness and safety on the addition of the following interventions: lacosamide, lamotrigine, levetiracetam, perampanel, and zonisamide versus the addition of placebo.

  10. Paleoclimatic forcing of magnetic susceptibility variations in Alaskan loess during the late Quaternary

    SciTech Connect

    Beget, J.E.; Stone, D.B.; Hawkins, D.B. )

    1990-01-01

    Visual matches and statistical tests suggest correlations between marine isotope curves, retrodictive solar insolation at lat 65{degree}N, and magnetic susceptibility profiles through late Quaternary age Alaskan loess sections. The susceptibility changes largely appear to reflect variability in magnetite content due to climatically controlled changes in wind intensity and competence. Magnetic susceptibility profiles through massive loess can provide stratigraphic context for intercalated paleosols and tephras. A prominent paleosol correlated with marine isotope stage 5 occurs several metres above the Old Crow ash in loess sections, indicating that this important tephra is older than suggested by thermoluminescence dates, and may have been deposited ca. 215 {plus minus}25 ka.

  11. Quantitative susceptibility mapping (QSM): Decoding MRI data for a tissue magnetic biomarker.

    PubMed

    Wang, Yi; Liu, Tian

    2015-01-01

    In MRI, the main magnetic field polarizes the electron cloud of a molecule, generating a chemical shift for observer protons within the molecule and a magnetic susceptibility inhomogeneity field for observer protons outside the molecule. The number of water protons surrounding a molecule for detecting its magnetic susceptibility is vastly greater than the number of protons within the molecule for detecting its chemical shift. However, the study of tissue magnetic susceptibility has been hindered by poor molecular specificities of hitherto used methods based on MRI signal phase and T2* contrast, which depend convolutedly on surrounding susceptibility sources. Deconvolution of the MRI signal phase can determine tissue susceptibility but is challenged by the lack of MRI signal in the background and by the zeroes in the dipole kernel. Recently, physically meaningful regularizations, including the Bayesian approach, have been developed to enable accurate quantitative susceptibility mapping (QSM) for studying iron distribution, metabolic oxygen consumption, blood degradation, calcification, demyelination, and other pathophysiological susceptibility changes, as well as contrast agent biodistribution in MRI. This paper attempts to summarize the basic physical concepts and essential algorithmic steps in QSM, to describe clinical and technical issues under active development, and to provide references, codes, and testing data for readers interested in QSM.

  12. Dynamic magnetic susceptibility of systems with long-range magnetic order

    SciTech Connect

    Vannette, Matthew Dano

    2009-01-01

    The utility of the TDR as an instrument in the study of magnetically ordered materials has been expanded beyond the simple demonstration purposes. Results of static applied magnetic field dependent measurements of the dynamic magnetic susceptibility, χ, of various ferromagnetic (FM) and antiferromagnetic (AFM) materials showing a range of transition temperatures (1-800 K) are presented. Data was collected primarily with a tunnel diode resonator (TDR) at different radio-frequencies (~10-30 MHz). In the vicinity of TC local moment ferromagnets show a very sharp, narrow peak in χ which is suppressed in amplitude and shifted to higher temperatures as the static bias field is increased. Unexpectedly, critical scaling analysis fails for these data. It is seen that these data are frequency dependent, however there is no simple method whereby measurement frequency can be changed in a controllable fashion. In contrast, itinerant ferromagnets show a broad maximum in χ well below TC which is suppressed and shifts to lower temperatures as the dc bias field is increased. The data on itinerant ferromagnets is fitted to a semi-phenomenological model that suggests the sample response is dominated by the uncompensated minority spins in the conduction band. Concluding remarks suggest possible scenarios to achieve frequency resolved data using the TDR as well as other fields in which the apparatus may be exploited.

  13. Dynamic magnetic susceptibility of systems with long-range magnetic order

    NASA Astrophysics Data System (ADS)

    Vannette, Matthew Dano

    The utility of the TDR as an instrument in the study of magnetically ordered materials has been expanded beyond the simple demonstration purposes. Results of static applied magnetic field dependent measurements of the dynamic magnetic susceptibility, chi, of various ferromagnetic (FM) and antiferromagnetic (AFM) materials showing a range of transition temperatures (1-800 K) are presented. Data was collected primarily with a tunnel diode resonator (TDR) at different radio-frequencies (~10-30 MHz). In the vicinity of TC local moment ferromagnets show a very sharp, narrow peak in chi which is suppressed in amplitude and shifted to higher temperatures as the static bias field is increased. Unexpectedly, critical scaling analysis fails for these data. It is seen that these data are frequency dependent, however there is no simple method whereby measurement frequency can be changed in a controllable fashion. In contrast, itinerant ferromagnets show a broad maximum in chi well below TC which is suppressed and shifts to lower temperatures as the dc bias field is increased. The data on itinerant ferromagnets is fitted to a semi-phenomenological model that suggests the sample response is dominated by the uncompensated minority spins in the conduction band. Concluding remarks suggest possible scenarios to achieve frequency resolved data using the TDR as well as other fields in which the apparatus may be exploited.

  14. Magnetic susceptibilities measured on rocks of the upper Cook Inlet, Alaska

    USGS Publications Warehouse

    Alstatt, A.A.; Saltus, R.W.; Bruhn, R.L.; Haeussler, P.J.

    2002-01-01

    We have measured magnetic susceptibility in the field on most of the geologic rock formations exposed in the upper Cook Inlet near Anchorage and Kenai, Alaska. Measured susceptibilities range from less than our detection limit of 0.01 x 10-3 (SI) to greater than 100 x 10-3 (SI). As expected, mafic igneous rocks have the highest susceptibilities and some sedimentary rocks the lowest. Rocks of the Tertiary Sterling Formation yielded some moderate to high susceptibility values. Although we do not have detailed information on the magnetic mineralogy of the rocks measured here, the higher susceptibilities are sufficient to explain the magnitudes of some short-wavelength aeromagnetic anomalies observed on recent surveys of the upper Cook Inlet.

  15. Magnetic susceptibility and dielectric properties of peat in Central Kalimantan, Indonesia

    NASA Astrophysics Data System (ADS)

    Budi, Pranitha Septiana; Zulaikah, Siti; Hidayat, Arif; Azzahro, Rosyida

    2017-07-01

    Peatlands dominate almost all regions of Borneo, yet its utilization has not been developed optimally. Any information in this field could be obtained using soil magnetization methods by determining the magnetic succeptibility in terms of magnetic susceptibility value that could describe the source and type of magnetic minerals which could describe the source and type of magnetic minerals. Moreover, the dielectric properties of peat soil were also investigated to determine the level of water content by using the dielectric constant value. Samples was taken at six different locations along Pulang pisau to Berengbengkel. Magnetic susceptibility mass value at these locations ranged between -0.0009 - 0.712 (×10-6 m3/kg). Based on the average magnetic susceptibility value, samples that were taken from T1, T3 and T5 belonged to the type of paramagnetic mineral, while samples which were taken from T2, T4 and T6 belonged to the group of diamagnetic mineral. The low value of magnetic susceptibility of peat was probably derived from the pedogenic process. The average value of peat soil in six locations has a large dielectric constant value that is 28.2 which indicated that there was considerable moisture content due to the hydrophilic nature of peatland which means that the ability of peat in water binding is considerably high.

  16. Analysis of Concentration Dependences of Magnetic Susceptibilities of Disperse Magnetite-Containing Media

    NASA Astrophysics Data System (ADS)

    Sandulyak, A. S.; Sandulyak, D. A.; Polismakova, M. N.; Sandulyak, A. V.; Kiselev, D. O.; Ershova, V. A.

    2017-07-01

    Analysis has been made of the dependences of magnetic susceptibilities of powders and colloids with a dispersed phase of magnetite particles depending on their concentration for volume fractions of ferroparticles of 0.1-0.85 at a magnetic field strength from 25 to 520 kA/m.

  17. Heterogeneous anisotropic magnetic susceptibility of the myelin-water layers causes local magnetic field perturbations in axons.

    PubMed

    Puwal, Steffan; Roth, Bradley J; Basser, Peter J

    2017-04-01

    One goal of MRI is to determine the myelin water fraction in neural tissue. One approach is to measure the reduction in T2 * arising from microscopic perturbations in the magnetic field caused by heterogeneities in the magnetic susceptibility of myelin. In this paper, analytic expressions for the induced magnetic field distribution are derived within and around an axon, assuming that the myelin susceptibility is anisotropic. Previous models considered the susceptibility to be piecewise continuous, whereas this model considers a sinusoidally varying susceptibility. Many conclusions are common in both models. When the magnetic field is applied perpendicular to the axon, the magnetic field in the intraaxonal space is uniformly perturbed, the magnetic field in the myelin sheath oscillates between the lipid and water layers, and the magnetic field in the extracellular space just outside the myelin sheath is heterogeneous. These field heterogeneities cause the spins to dephase, shortening T2 *. When the magnetic field is applied along the axon, the field is homogeneous within water-filled regions, including between lipid layers. Therefore the spins do not dephase and the magnetic susceptibility has no effect on T2 *. Generally, the response of an axon is given as the superposition of these two contributions. The sinusoidal model uses a different set of approximations compared with the piecewise model, so their common predictions indicate that the models are not too sensitive to the details of the myelin-water distribution. Other predictions, such as the sensitivity to water diffusion between myelin and water layers, may highlight differences between the two approaches. Copyright © 2016 John Wiley & Sons, Ltd.

  18. 3D and 4D magnetic susceptibility tomography based on complex MR images

    DOEpatents

    Chen, Zikuan; Calhoun, Vince D

    2014-11-11

    Magnetic susceptibility is the physical property for T2*-weighted magnetic resonance imaging (T2*MRI). The invention relates to methods for reconstructing an internal distribution (3D map) of magnetic susceptibility values, .chi. (x,y,z), of an object, from 3D T2*MRI phase images, by using Computed Inverse Magnetic Resonance Imaging (CIMRI) tomography. The CIMRI technique solves the inverse problem of the 3D convolution by executing a 3D Total Variation (TV) regularized iterative convolution scheme, using a split Bregman iteration algorithm. The reconstruction of .chi. (x,y,z) can be designed for low-pass, band-pass, and high-pass features by using a convolution kernel that is modified from the standard dipole kernel. Multiple reconstructions can be implemented in parallel, and averaging the reconstructions can suppress noise. 4D dynamic magnetic susceptibility tomography can be implemented by reconstructing a 3D susceptibility volume from a 3D phase volume by performing 3D CIMRI magnetic susceptibility tomography at each snapshot time.

  19. Magnetic susceptibility measurement of solid oxygen at pressures up to 3.3 GPa

    SciTech Connect

    Mito, M. Yamaguchi, S.; Tsuruda, H.; Deguchi, H.; Ishizuka, M.

    2014-01-07

    The magnetic susceptibility of solid oxygen had long been observed only in the restricted pressure region below 0.8 GPa. We succeeded in extending the pressure region up to 3.3 GPa by clamping condensed oxygen in the sample chamber of a miniature diamond anvil cell and measuring the dc magnetic susceptibility using a superconducting quantum interference device magnetometer. In this experiment, the well-known α–β and β–γ transitions are observed in the phase diagram, suggesting consistency with the previous results of X-ray and Raman studies. In addition, a new magnetic anomaly is observed in the β phase.

  20. Magnetic susceptibility measurement of solid oxygen at pressures up to 3.3 GPa

    NASA Astrophysics Data System (ADS)

    Mito, M.; Yamaguchi, S.; Tsuruda, H.; Deguchi, H.; Ishizuka, M.

    2014-01-01

    The magnetic susceptibility of solid oxygen had long been observed only in the restricted pressure region below 0.8 GPa. We succeeded in extending the pressure region up to 3.3 GPa by clamping condensed oxygen in the sample chamber of a miniature diamond anvil cell and measuring the dc magnetic susceptibility using a superconducting quantum interference device magnetometer. In this experiment, the well-known α-β and β-γ transitions are observed in the phase diagram, suggesting consistency with the previous results of X-ray and Raman studies. In addition, a new magnetic anomaly is observed in the β phase.

  1. Quantification of magnetic nanoparticles with broadband measurements of magnetic susceptibility in the frequency domain

    NASA Astrophysics Data System (ADS)

    Kodama, Kazuto; An, Zhisheng; Chang, Hong; Qiang, Xiaoke

    2015-04-01

    Measurement of low-field magnetic susceptibility over a wide band of frequencies spanning four orders of magnitude is a useful method for the assessment of the grain size distribution of ultrafine magnetic particles smaller than the SP/SSD boundary. This method has been applied to a loess/paleosol sequence at Luochuan in the Chinese Loess Plateau. The studied succession consists of sequences from the latest paleosol unit to the upper part of the loess unit, spanning the last glacial-interglacial cycle. Reconstructed grain size distributions (GSDs) consist of volume fractions on the order of 10-24 m3, and the mean GSDs are modal but with distinctive skewness among the loess, the weakly developed paleosol (weak paleosol), and the mature paleosol. This indicates that the mean volume of SP particles in this sequence tends to increase during the transition from the loess to the paleosol. An index, defined as the difference between χ130 at the lowest (130 Hz) and χ500k at the highest (500 kHz) frequencies normalized to χ130, is judged to be a more suitable index than previous frequency dependence parameters for the concentration of SP particles. This index has a strong correlation with χ130, showing a continuous 'growth curve' with the rate of increase being highest for the loess, moderate for the weak paleosol, and saturated for the paleosol. The characteristic curve suggests that smaller SP particles are preferentially formed in the earlier stage of pedogenesis rather than the later phase when even larger particles are formed in the mature paleosol. These results demonstrate that the broad-band-frequency susceptibility measurement will be useful for the quantitative assessment of magnetic nanoparticles in soils and sediments. Additionally, we point out that the measurement in the frequency domain generally requires time and may not be most suitable to routine measurements. We thus propose an alternative manner, the measurement in the time domain that can be

  2. Magnetic Susceptibility of Fe-Doped YBa2Cu3O7-δ

    NASA Astrophysics Data System (ADS)

    Noguchi, Satoru; Inoue, Jun; Okuda, Kiichi; Maeno, Yoshiteru; Fujita, Toshizo

    1988-03-01

    Magnetic properties of YBa2(Cu1-xFex)3O7-δ with 0≤q}x{≤q}0.085 were investigated by dc- and ac-magnetic susceptibility in a temperature range from 4.2 to 300 K. The susceptibility in the normal state follows the Curie-Weiss law χ{=}C/(T-\\varTheta)+χ0 with constant paramagnetism χ0. The effective magnetic moments estimated from the Curie constant are 3.4{˜4.0 μB/Fe, which are consistent with the magnetic moment obtained in the Mössbauer experiments. From the ac susceptibility in the superconducting state, a decrease of volume fraction of superconductivity was observed with increasing Fe-concentration.

  3. Quartz helix magnetic susceptibility balance using the Curie-Cheneveau principle

    USGS Publications Warehouse

    Senftle, F.E.; Lee, M.D.; Monkewicz, A.A.; Mayo, J.W.; Pankey, T.

    1958-01-01

    A quartz spring balance is described which can be used to measure the magnetic susceptibility of submilligram amounts of sample. The magnetic field is supplied by a moving permanent magnet, and the susceptibility is determined by the deflection of the spring observed in a measuring microscope. The apparatus is calibrated by a comparison standard (platinum) and results are shown for platinum, nickel aluminate, lead, manganese, and sucrose. A precision of better than 2% can be obtained on submilligram amounts of paramagnetic substances having a magnetic susceptibility of from 1 to 50??10-6 emu/g. On weakly paramagnetic or diamagnetic substances comparable precision can be obtained on less than 10 mg amounts of sample. ?? 1958 The American Institute of Physics.

  4. Transverse complex magnetic susceptibility of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a longitudinal uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Kalmykov, Yu. P.; Coffey, W. T.

    1997-08-01

    The infinite hierarchy of differential-recurrence relations for the equilibrium transverse correlation functions appropriate to magnetic relaxation of single-domain ferromagnetic particles with uniaxial anisotropy subjected to a uniform external magnetic field H0 is derived by averaging Gilbert's equation. Exact expressions in terms of matrix continued fractions for the transverse complex magnetic susceptibility are obtained with the aid of linear-response theory by solving the infinite hierarchy. The principal features of the spectra are emphasized in figures showing the real and imaginary parts of the complex magnetic susceptibility. The accuracy and the range of the applicability of analytical results based on the effective eigenvalue method is established. It is shown that this method provides in general a good approximation to the exact solution with the exception of the range of low-to-intermediate barrier heights of the anisotropy potential where at small H0 there exists essentially a spread of the precession frequencies of the magnetization.

  5. Probe imaging studies of magnetic susceptibility and permeability for sensitive characterisation of carbonate reservoir rocks

    NASA Astrophysics Data System (ADS)

    Ivakhnenko, Aleksandr; Bigaliyeva, Akmaral; Dubinin, Vladislav

    2016-04-01

    In this study were disclosed the main principals of identifying petrophysical properties of carbonate reservoirs such as porosity, permeability and magnetic susceptibility. While exploring and developing reservoir there are significant diversity of tasks that can be solved by appropriate knowledge of properties which are listed above. Behavior of fluid flow, distribution of hydrocarbons and other various industrial applications can be solved by measuring areal distribution of these petrophysical parameters. The results demonstrate how magnetic probe and hysteresis measurements correlate with petrophysical parameters in carbonate reservoirs. We made experimental measurements and theoretical calculations of how much magnetic susceptibility depends on the porosity of the rocks and analyzed data with graphics. In theoretical model of the carbonate rocks we considered calcite, dolomite, quartz and combinations of calcite and dolomite, calcite and Fe-dolomite, calcite and quartz, calcite and aragonite with increasing concentrations of the dolomite, Fe-dolomite, quartz and aragonite up to 50% with step of 5%. Here we defined dependence of magnetic susceptibility from the porosity: the higher porosity measurements, the less slope of magnetic susceptibility, consequently mass magnetization is higher for diamagnetic and lower for paramagnetic carbonate rocks, but in the both cases magnetic susceptibility tries to reach zero with increasing of the total porosity. Rock measurements demonstrate that reservoir zones of the low diamagnetic magnetic susceptibility are generally correlated with higher permeability and also porosity distribution. However for different carbonate reservoirs we establish different relationships depending on the complexity of their mineralogy and texture. Application of integral understanding in distribution of permeability, porosity and mineral content in heterogeneous carbonates represented by this approach can be useful tool for carbonate reservoir

  6. Calculation of susceptibility through multiple orientation sampling (COSMOS): a method for conditioning the inverse problem from measured magnetic field map to susceptibility source image in MRI.

    PubMed

    Liu, Tian; Spincemaille, Pascal; de Rochefort, Ludovic; Kressler, Bryan; Wang, Yi

    2009-01-01

    Magnetic susceptibility differs among tissues based on their contents of iron, calcium, contrast agent, and other molecular compositions. Susceptibility modifies the magnetic field detected in the MR signal phase. The determination of an arbitrary susceptibility distribution from the induced field shifts is a challenging, ill-posed inverse problem. A method called "calculation of susceptibility through multiple orientation sampling" (COSMOS) is proposed to stabilize this inverse problem. The field created by the susceptibility distribution is sampled at multiple orientations with respect to the polarization field, B(0), and the susceptibility map is reconstructed by weighted linear least squares to account for field noise and the signal void region. Numerical simulations and phantom and in vitro imaging validations demonstrated that COSMOS is a stable and precise approach to quantify a susceptibility distribution using MRI.

  7. Magnetic susceptibility of Inconel alloys 718, 625, and 600 at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Goldberg, Ira B.; Mitchell, Michael R.; Murphy, Allan R.; Goldfarb, Ronald B.; Loughran, Robert J.

    1990-01-01

    After a hydrogen fuel bleed valve problem on the Discovery Space Shuttle was traced to the strong magnetization of Inconel 718 in the armature of the linear variable differential transformer near liquid hydrogen temperatures, the ac magnetic susceptibility of three samples of Inconel 718 of slightly different compositions, one sample of Inconel 625, and on sample of Inconel 600 were measured as a function of temperature. Inconel 718 alloys are found to exhibit a spin glass state below 16 K. Inconel 600 exhibits three different magnetic phases, the lowest-temperature state (below 6 K) being somewhat similar to that of Inconel 718. The magnetic states of the Inconel alloys and their magnetic susceptibilities appear to be strongly dependent on the exact composition of the alloy.

  8. Homogeneous magnetic susceptibilities of tektites: Implications for extreme homogenization of source material

    NASA Astrophysics Data System (ADS)

    Werner, Tomasz; Borradaile, Graham John

    Low field magnetic susceptibility of 151 tektites from the Australasian strewn field is dominated by paramagnetism of the silicate glass. Ferromagnetic contributions are negligible because the formation of oxides was suppressed during rapid quenching. A few samples from the Central European strewn field show similar properties. Also, susceptibilities calculated from the large number of published geochemical analyses yield similar low susceptibilities. To produce low mass susceptibilities in such a narrow range of 50-100×10 -9 m 3 kg -1, paramagnetic behaviour and negligible remanence, a target source that is both appropriate and widespread over the Earth's surface is required. Modern marine sediments would appear to fill these requirements. The uniformity of the material, and hence its magnetic properties would be enhanced by the thorough mixing of molten terrestrial sedimentary during vaporization and ejection and its subsequent rapid quenching.

  9. Magnetic Susceptibility Analysis of Soil Affected by Hydrocarbon in Wonocolo Traditional Oil Field, Indonesia

    NASA Astrophysics Data System (ADS)

    Ulfah, Melianna; Wijatmoko, Bambang; Fitriani, Dini

    2017-04-01

    Magnetic susceptibility of soil affected by hydrocarbon was studied through cored soil samples in two zones (Zone One and Zone Two) of an oil field in Wonocolo Village, East Java. We also collected soil samples as the background from a residential area near the oil field (Zone Three). The Zone One, consisted two cores near producing well; the Zone Two consisted two cores obtained from near a dry hole well and a discontinued well; and the Zone Three consisted two cores to validate the initial soil magnetic susceptibility value in this area. The hydrocarbon content measurement was also done for the upper part of each cores using distillation method to identify the correlation between magnetic susceptibility and hydrocarbon content. From magnetic susceptibility measurement in dual frequency, samples from the Zone One and Zone Two have magnetic susceptibility range from 6,1 × 10-8 m3kg-1 - 160 × 10-8 m3kg-1 and 15,7 × 10-8 m3kg-1 - 417,9 × 10-8 m3kg-1, respectively. Whereas background samples from Zone Three have magnetic susceptibility range from 4,8 × 10-8 m3kg-1 to 81,1 × 10-8 m3kg-1. We found low χfd (%) in samples with high magnetic susceptibility values, shown that there was no indication of superparamagnetic minerals in the samples. The hydrocarbon content measurement shows the value range of 8% - 14% only exists in the upper part of all cores in Zone One and one core in Zone Two. From this analysis, we assume that other than the volume of the hydrocarbon content in soil, the period of petroleum hydrocarbon deposition in soil and the fossil fuel combustion generated in the study site could differently increase the soil magnetic susceptibility value in this area. Positive correlation between the two parameters hopefully could contribute to develop environmental magnetic methods for detecting oil spills in soil, especially to remediate former hydrocarbon exploration and production area.

  10. Design of Low Temperature AC Susceptibility Measurement Scheme for Molecular Magnets

    NASA Astrophysics Data System (ADS)

    Korenblit, Simcha; Moon, Byoung; Lee, Yoonseok; Sultan, Reza

    2006-03-01

    AC susceptibility is one of the most important physical properties in many materials such as magnetic materials and superconductors. Although there are many commercial AC susceptibility measurement systems which cover a broad range of temperatures, it is still a daunting task to extend their measurement range into the low millikelvins. We are currently developing a low temperature AC susceptometer for the mK range. As a part of this effort, we have developed a versatile low-cost computer controlled coil-winder to make various types of coils. We have designed primary and secondary coils and wound them using the machine, and performed characterization of the AC susceptometer. In this presentation, I will explain the basics of magnetic susceptibility, its measurement, design considerations for building an AC magnetic susceptometer, and discuss the details of an actual apparatus designed and realized by the authors.

  11. Quantitative susceptibility mapping (QSM): Decoding MRI data for a tissue magnetic biomarker

    PubMed Central

    Wang, Yi; Liu, Tian

    2015-01-01

    In MRI, the main magnetic field polarizes the electron cloud of a molecule, generating a chemical shift for observer protons within the molecule and a magnetic susceptibility inhomogeneity field for observer protons outside the molecule. The number of water protons surrounding a molecule for detecting its magnetic susceptibility is vastly greater than the number of protons within the molecule for detecting its chemical shift. However, the study of tissue magnetic susceptibility has been hindered by poor molecular specificities of hitherto used methods based on MRI signal phase and T2* contrast, which depend convolutedly on surrounding susceptibility sources. Deconvolution of the MRI signal phase can determine tissue susceptibility but is challenged by the lack of MRI signal in the background and by the zeroes in the dipole kernel. Recently, physically meaningful regularizations, including the Bayesian approach, have been developed to enable accurate quantitative susceptibility mapping (QSM) for studying iron distribution, metabolic oxygen consumption, blood degradation, calcification, demyelination, and other pathophysiological susceptibility changes, as well as contrast agent biodistribution in MRI. This paper attempts to summarize the basic physical concepts and essential algorithmic steps in QSM, to describe clinical and technical issues under active development, and to provide references, codes, and testing data for readers interested in QSM. Magn Reson Med 73:82–101, 2015. © 2014 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance. This is an open access article under the terms of the Creative commons Attribution License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited. PMID:25044035

  12. Mapping Magnetic Susceptibility Anisotropies of White Matter in vivo in the Human Brain at 7 Tesla

    PubMed Central

    Li, Xu; Vikram, Deepti S; Lim, Issel Anne L; Jones, Craig K; Farrell, Jonathan A.D.; van Zijl, Peter C. M.

    2012-01-01

    High-resolution magnetic resonance phase- or frequency- shift images acquired at high field show contrast related to magnetic susceptibility differences between tissues. Such contrast varies with the orientation of the organ in the field, but the development of quantitative susceptibility mapping (QSM) has made it possible to reproducibly image the intrinsic tissue susceptibility contrast. However, recent studies indicate that magnetic susceptibility is anisotropic in brain white matter and, as such, needs to be described by a symmetric second-rank tensor (χ¯¯). To fully determine the elements of this tensor, it would be necessary to acquire frequency data at six or more orientations. Assuming cylindrical symmetry of the susceptibility tensor in myelinated white matter fibers, we propose a simplified method to reconstruct the susceptibility tensor in terms of a mean magnetic susceptibility, MMS = (χ∥ + 2χ⊥)/3 and a magnetic susceptibility anisotropy, MSA = χ∥ − χ⊥, where χ∥ and χ⊥ are susceptibility parallel and perpendicular to the white matter fiber direction, respectively. Computer simulations show that with a practical head rotation angle of around 20°–30°, four head orientations suffice to reproducibly reconstruct the tensor with good accuracy. We tested this approach on whole brain 1×1×1 mm3 frequency data acquired from five healthy subjects at 7 T. The frequency information from phase images collected at four head orientations was combined with the fiber direction information extracted from diffusion tensor imaging (DTI) to map the white matter susceptibility tensor. The MMS and MSA were quantified for regions in several large white matter fiber structures, including the corona radiata, posterior thalamic radiation and corpus callosum. MMS ranged from −0.037 to −0.053 ppm (referenced to CSF being about zero). MSA values could be quantified without the need for a reference and ranged between 0.004 and 0.029 ppm, in line with

  13. Quantification of cellular properties from external fields and resulting induced velocity: magnetic susceptibility.

    PubMed

    Chalmers, J J; Haam, S; Zhao, Y; McCloskey, K; Moore, L; Zborowski, M; Williams, P S

    1999-09-05

    An experimental technique is discussed in which the magnetic susceptibility of immunomagnetically labeled cells can be determined on a cell-by-cell basis. This technique is based on determining the magnetically induced velocity that an immunomagnetically labeled cell has in a well-defined magnetic energy gradient. This velocity is determined through the use of video recordings of microscopic images of cells moving in the magnetic energy gradient. These video images are then computer digitized and processed using a computer algorithm, cell tracking velocimetry, which allows larger numbers (>10(3)) of cells to be analyzed.

  14. Comparison between theory and simulations for the magnetization and the susceptibility of polydisperse ferrofluids.

    PubMed

    Szalai, I; Nagy, S; Dietrich, S

    2013-11-20

    The influence of polydispersity on the magnetization of ferrofluids is studied based on a previously published magnetization equation of state (Szalai and Dietrich, 2011 J. Phys.: Condens. Matter 23 326004) and computer simulations. The polydispersity of the particle diameter is described by the gamma distribution function. Canonical ensemble Monte Carlo simulations have been performed in order to test these theoretical results for the initial susceptibility and the magnetization. The results for the magnetic properties of the polydisperse systems turn out to be in quantitative agreement with our present simulation data. In addition, we find good agreement between our theory and experimental data for magnetite-based ferrofluids.

  15. Sub-micron mapping of GHz magnetic susceptibility using scanning transmission x-ray microscopy

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng; Bailey, William E.

    2012-10-01

    We report submicron imaging (˜0.75 μm resolution) of complex magnetic susceptibility in a micron-size ferromagnetic heterostructure using time-resolved scanning transmission x-ray microscopy. The real and imaginary parts of the susceptibility are extracted from the phase and amplitude of the small-angle (<20°) rotational response of the local magnetization under microwave excitation. Frequency-dependent response patterns were observed in an incompletely saturated bilayer element. The technique is extensible to higher frequencies (to ˜10 GHz), better spatial resolution, and layer-specific measurement.

  16. Effect of copper addition on density and magnetic susceptibility of lithium borate glasses

    NASA Astrophysics Data System (ADS)

    Kashif, I.; Soliman, A. A.; Farouk, H.; El-Shorpagy, M.; Sanad, A. M.

    2008-11-01

    Glasses of the (100- x) (Li 2O·2B 2O 3)· x CuO system, where x=0, 5, 10, 15, 20, 25 mol%, were prepared by melt quench technique. The glass samples were studied by magnetic susceptibility, density and infrared (IR) spectroscopic measurements. Molar volumes were estimated from density data. IR spectroscopic and density data show that the copper ions play a network modifier role and some ions as a network former by increasing the copper content in the studied glasses. The magnetic susceptibility data show a variable behavior due to the presence of two types of copper ions, cuprous (Cu +) and cupric (Cu 2+), in all samples.

  17. Magnetic susceptibilities of rectangular Heisenberg S=1/2 antiferromagnets

    NASA Astrophysics Data System (ADS)

    Valleau, Tom; Butcher, Rob; Keith, Brian; Landee, Christopher; Turnbull, Mark; Sandvik, Anders

    2008-03-01

    Rectangular antiferromagnets are two-dimensional systems with inequivalent exchange strengths (J', J) along the two principle axes with J' ≡ αJ, α <1. They have an intermediate dimensionality that can vary continuously from 1D (α = 0 ) to square 2D (α = 1). There exist a number of physical realizations of rectangular antiferromagnets (CuPzBr2, CuPzCl2, CuPz(N3)2 where Pz = pyrazine) but there has been no previous mechanism for interpreting their susceptibilities in terms of two exchange parameters. We have simulated the susceptibility of the rectangular S=1/2 Heisenberg antiferromagnet using the stochastic series expansion quantum Monte Carlo method [1] and used the results to interpret our experimental data. For example, copper pyrazine diazide, CuPz(N3)2, has a primary exchange of 15.5 K and an anisotropy parameter α = 0.4. The stronger exchange is due to the superexchange pathway through the pyrazine molecule and the weaker corresponds to the azide bridges. [1] A. Sandvik, PRB 59, R14157 (1999).

  18. Magnetic fabric (anisotropy of magnetic susceptibility) constraints on emplacement mechanism of clastic dikes

    NASA Astrophysics Data System (ADS)

    Cho, Hyeongseong; Son, Moon; Sohn, Young Kwan; Park, Mi Eun

    2017-05-01

    Clastic dikes are generally classified into neptunian and injected dikes. Using the magnetic fabrics (AMS: anisotropy of magnetic susceptibility), we attempt to classify the clastic dikes in the Late Cretaceous Dadaepo Basin, SE Korea, and interpret their emplacement mechanisms. The neptunian dikes exhibit a typical oblate sedimentary fabric which makes a sharp contrast with the injected dikes. The fabrics of the injected dikes are greatly influenced by current conditions and transportation types of filling materials. Based on the AMS fabrics, they are classified into four types. (1) VP (vertical flow-parallel) type is formed by imbrication of long axis of grains in low- to moderate-energy vertical flow of a Newtonian fluid and characterized by a bilateral symmetry of fabrics across the dike. (2) VT (vertical flow-transverse fabric) type results from grain rolling in vertical high-energy flow and is characterized by subvertical k2 and subhorizontal k1 axes on the dike plane. (3) HP (horizontal flow-parallel) type is formed by imbrication of long axis of grains in horizontal low- to moderate-energy flow, resulting in subvertical k3 and subhorizontal k1 and k2 axes. (4) HT (horizontal flow-transverse) type is formed by grain rolling in horizontal high-energy flow, resulting in streaked k2-k3 on the dike plane and horizontally clustered k1 axes. The AMS fabrics of each type can be a significant indicator for flow direction. Based on abundant AMS fabrics formed by high-energy current, coexistence of paleoseismic structures, and tectonic setting of the basin, earthquake-induced liquefaction is the most plausible trigger for the dike formation.

  19. Effects of Size, deGennes and Ginzburg-Landau Parameters on the Magnetic Susceptibility of an Isotropic Superconductor

    NASA Astrophysics Data System (ADS)

    Aguirre, C. A.; González, J. D.; Barba-Ortega, J.

    2016-01-01

    The magnetic signature of a nanoscopic superconductor immersed in a magnetic applied field H_e is calculated numerically. The calculated magnetic susceptibility partial M / partial H_e of a superconducting nanoprism shows discontinuities and a quasiperiodic modulation at the vortex transition fields H_T (fields for which one or several vortices enter/leave the sample). In this contribution, we studied the influence of the sample size, the Ginzburg-Landau parameter κ and the deGennes parameter b on the magnetic susceptibility in a type-II isotropic superconductor. We found distinct signatures of the magnetic susceptibility when superconducting samples of two and three dimensions are considered.

  20. Preliminary comparisons between mutagenicity and magnetic susceptibility of respirable airborne particulate

    NASA Astrophysics Data System (ADS)

    Morris, W. A.; Versteeg, J. K.; Bryant, D. W.; Legzdins, A. E.; McCarry, B. E.; Marvin, C. H.

    The magnetic susceptibility of respirable urban airborne particulate and the mutagenic potency and organic content of extracts prepared from these particles are both related to mobile and stationary combustion processes. Analyses of the organic extracts prepared from these particulate samples showed the presence of certain polycyclic aromatic hydrocarbons (PAH), certain keto-PAH and thia-PAH. The enhanced magnetic signatures of air particulate material collected in an urban environment are directly related to the presence of magnetite-rich spherules which are likely to have been produced by the oxidation of pyrite to magnetite during the combustion process. A total of 62 filters collected between May 1990 and June 1991 at an air quality monitoring station in Hamilton, Ontario were examined. A plot of magnetic susceptibility of these filters and the mutagenic potencies of the organic extracts prepared from these filters in the Salmonella/microsome assay show a significant correlation. Neither magnetic susceptibility nor mutagenicity show a similar simple direct relationship to particulate loading. Plots of wind direction vs wind speed indicate that the highest mutagenicity and susceptibility levels are predominantly associated with (a) easterly derived winds, (b) low to moderate wind velocities, and (c) enhanced levels of SO 2 and NO 2. In contrast, low mutagenicity and susceptibility levels are intimately associated with (a) southwesterly derived winds, (b) moderate to high wind velocities, and (c) the presence of high ozone levels which accompany higher summer temperatures. These observations suggest that rapid magnetic susceptibility measurements could be used to pre-select filters for more extensive evaluations such as organic compound analyses or biological assays.

  1. Impact of Long-Term Irrigation with Treated Sewage on Soil Magnetic Susceptibility and Organic Matter Content in North China.

    PubMed

    Yang, P G; Yang, M; Mao, R Z; Byrne, J M

    2015-07-01

    This study assessed the effect on magnetic susceptibility and organic matter content of arable soil by irrigation with either treated sewage or groundwater. Results indicated that organic matter and magnetic susceptibility values in the soil irrigated with sewage were increased by 7.1 % and 13.5 %, respectively, compared to agricultural soil that irrigated with groundwater. Both the sewage and groundwater irrigated soils contained a significant fraction of ultrafine superpara magnetic grains, as indicated by high frequency dependent susceptibility (χfd > 6 %). The enhancement of soil magnetic properties was determined to be caused by anthropogenic sewage irrigation and agrochemical use by investigation of vertical soil profiles. Magnetic susceptibility parameters were shown to be significantly correlated with organic matter content (y = 0.0057x + 1.3439, R(2) = 0.09, p < 0.05). This work indicates that measurements of magnetic susceptibility may offer a rapid first step for identifying the potential pollution in arable soils.

  2. EPR and magnetic susceptibility measurements on CeB{sub 6}

    SciTech Connect

    Terzioglu, Cabir; Browne, D. A.; Goodrich, R. G.; Hassan, A.; Fisk, Z.

    2001-06-15

    We report measurements of temperature and magnetic field dependent magnetic susceptibility and electron paramagnetic resonance in the paramagnetic phase of CeB{sub 6}. From calculations of the possible ground state level structure of the interacting 4f electrons it is found that the fourfold degenerate {Gamma}{sub 8} is split into two doublets with equal g factors and an energy separation of the order of 30 K.

  3. Magnetic susceptibility study of the heavy rare-earth stannate pyrochlores

    NASA Astrophysics Data System (ADS)

    Bondah-Jagalu, V.; Bramwell, S. T.

    2001-11-01

    The series of magnetic rare earth pyrochlore stannates R2Sn2O7 (R = rare earth, except Ce and Pm) have been investigated by powder susceptibility measurements down to T =1.8 K. The results are compared to results for the analogous titanate series, which are well-known frustrated magnets. Unlike the titanates, the whole series can be formed in the cubic pyrochlore structure. Possible experimental advantages of studying the stannates are discussed.

  4. Observation of a Strongly Enhanced Magnetic Susceptibility of Pd in Au-Pd-Au Sandwiches

    NASA Astrophysics Data System (ADS)

    Brodsky, M. B.; Freeman, A. J.

    1980-07-01

    Exceptionally large increases in the magnetic susceptibility (indicating nearly magnetic ordering) of thin films of Pd sandwiched between thicker Au films have been observed at low temperatures-presumably due to the expansion of the Pd average lattice constant by the Au. The large resultant Stoner factors and the modified paramagnon model of Levin and Valls indicate the possibility of observing p-wave superconductivity in Pd structures with reduced proximity effects.

  5. A Torque Balance Measurement of Anisotropy of the Magnetic Susceptibility in White Matter

    PubMed Central

    van Gelderen, Peter; Mandelkow, Hendrik; de Zwart, Jacco A.; Duyn, Jeff H.

    2014-01-01

    Purpose Recent MRI studies have suggested that the magnetic susceptibility of white matter (WM) in the human brain is anisotropic, providing a new contrast mechanism for the visualization of fiber bundles and allowing the extraction of cellular compartment-specific information. This study provides an independent confirmation and quantification of this anisotropy. Methods Anisotropic magnetic susceptibility results in a torque exerted on WM when placed in a uniform magnetic field, tending to align the WM fibers with the field. To quantify the effect, excised spinal cord samples were placed in a torque balance inside the magnet of a 7 T MRI system and the magnetic torque was measured as function of orientation. Results All tissue samples (n=5) showed orienting effects, confirming the presence of anisotropic susceptibility. Analysis of the magnetic torque resulted in reproducible values for the WM volume anisotropy that ranged from 13.6 to 19.2 ppb. Conclusion The independently determined anisotropy values confirm estimates inferred from MRI experiments and validate the use of anisotropy to extract novel information about brain fiber structure and myelination. PMID:25399830

  6. Obtaining the magnetic susceptibility of the heme complex from DFT calculations

    NASA Astrophysics Data System (ADS)

    Pereira, L. M. O.; Resende, S. M.; Leite Alves, H. W.

    2016-09-01

    Magnetic field interactions with particles, as observed in magnetophoresis, are becoming important tool to understand the nature of the iron role in heme molecular complex, besides other useful applications. Accurate estimations of some macroscopic magnetic properties from quantum mechanical calculations, such as the magnetic susceptibility, can also check the reliability of the heme microscopic models. In this work we report, by using the Stoner criterion, a simple way to obtain the magnetic susceptibility of the heme complex from Density Functional Theory calculations. Some of our calculated structural properties and electronic structure show good agreement with both the available experimental and theoretical data, and the results show that its groundstate is a triplet 3A state. From the obtained results, we have evaluated the exchange interaction energy, J = 0.98 eV, the associated magnetic energy gain, Δ EM =-0.68 eV, and the magnetic susceptibility, χ0=1.73 ×10-6 cm3/mol for the heme alone (with uncompleted Fe ligands). If we consider the heme complex with the two histidine residues (completing the Fe ligands), we have then obtained χ0=5.27 ×10-12 cm3/g, which is in good agreement with experimental magnetophoresis data.

  7. Multifractal magnetic susceptibility distribution models of hydrothermally altered rocks in the Needle Creek Igneous Center of the Absaroka Mountains, Wyoming

    USGS Publications Warehouse

    Gettings, M.E.

    2005-01-01

    Magnetic susceptibility was measured for 700 samples of drill core from thirteen drill holes in the porphyry copper-molybdenum deposit of the Stinkingwater mining district in the Absaroka Mountains, Wyoming. The magnetic susceptibility measurements, chemical analyses, and alteration class provided a database for study of magnetic susceptibility in these altered rocks. The distribution of the magnetic susceptibilities for all samples is multi-modal, with overlapping peaked distributions for samples in the propylitic and phyllic alteration class, a tail of higher susceptibilities for potassic alteration, and an approximately uniform distribution over a narrow range at the highest susceptibilities for unaltered rocks. Samples from all alteration and mineralization classes show susceptibilities across a wide range of values. Samples with secondary (supergene) alteration due to oxidation or enrichment show lower susceptibilities than primary (hypogene) alteration rock. Observed magnetic susceptibility variations and the monolithological character of the host rock suggest that the variations are due to varying degrees of alteration of blocks of rock between fractures that conducted hydrothermal fluids. Alteration of rock from the fractures inward progressively reduces the bulk magnetic susceptibility of the rock. The model introduced in this paper consists of a simulation of the fracture pattern and a simulation of the alteration of the rock between fractures. A multifractal model generated from multiplicative cascades with unequal ratios produces distributions statistically similar to the observed distributions. The reduction in susceptibility in the altered rocks was modelled as a diffusion process operating on the fracture distribution support. The average magnetic susceptibility was then computed for each block. For the purpose of comparing the model results with observation, the simulated magnetic susceptibilities were then averaged over the same interval as the

  8. Magnetic Susceptibility: Correlations with Clay Content and Apparent Diffusion Coefficients Controlling Electrical Double Layer Polarization

    NASA Astrophysics Data System (ADS)

    Robinson, T.; Keating, K.; Robinson, J.; Slater, L. D.; Parker, B. L.

    2016-12-01

    Clay content and mineralogy play a critical role in determining the spectral induced polarization (SIP) response in soils and rocks. Clay minerals enhance the induced polarization response of soils due to an increase in the mineral surface area. Traditionally, x-ray diffraction (XRD) techniques are used to determine clay content, requiring intact samples to be ground into powder. Magnetic susceptibility (MS) measurements have previously been used to estimate clay content of samples when paramagnetic clays (e.g. illite and chlorite) dominate the response. Building on this work, this study assumes that sandstone samples from two lithologic formations could be approximated as a simple mixture of diamagnetic quartz and a paramagnetic component. Paramagnetic susceptibility is assumed proportional to iron content and thus to the iron bearing clays that control the susceptibility response. Fractions of iron rich clay components were determined with XRD and the volume magnetic susceptibility values of these clays were used to estimate clay content. We evaluated these clay content estimates with SIP measurements (imaginary conductivity magnitude and characteristic time constant (tau)) and properties related to fluid flow, including permeability and pore normalized surface area (Spor). A recently proposed SIP permeability model that uses a single value of the diffusion coefficient for clays and sands was evaluated to see whether apparent diffusion coefficients are correlated with magnetic susceptibility. Our findings show that MS can be helpful in rapidly determining clay content and also brings insight into the effect of paramagnetic clays on SIP measurements.

  9. Single crystal magnetic structure and susceptibility of CoSe2O5

    DOE PAGES

    Rodriguez, Efrain E.; Cao, Huibo; Haiges, Ralf; ...

    2015-09-08

    The structure of CoSe2O5 consists of one-dimensional ribbons of edge-sharing CoO6 octahedra bound together by polyanionic subunits of Se2O5. Previous work on polycrystalline samples reported a canted antiferromagnetic arrangement of the magnetic moments below the ordering temperature of 8.5 K. Here, we report a single crystal investigation using variable temperature and field magnetic susceptibility and low-temperature neutron diffraction to more precisely characterize the nature of the magnetic ground state of CoSe2O5. Contrary to previous reports, we find that the single crystal magnetic structure shows no canting of the antiferromagnetic ground state, and in the process have identified several field-induced changesmore » to the magnetization. Lastly, we discuss these results in the context of the revised magnetic structure and highlight the importance of crystal growth for the accurate characterization of these properties.« less

  10. 3D linear inversion of magnetic susceptibility data acquired by frequency domain EMI

    NASA Astrophysics Data System (ADS)

    Thiesson, J.; Tabbagh, A.; Simon, F.-X.; Dabas, M.

    2017-01-01

    Low induction number EMI instruments are able to simultaneously measure a soil's apparent magnetic susceptibility and electrical conductivity. This family of dual measurement instruments is highly useful for the analysis of soils and archeological sites. However, the electromagnetic properties of soils are found to vary over considerably different ranges: whereas their electrical conductivity varies from ≤ 0.1 to ≥ 100 mS/m, their relative magnetic permeability remains within a very small range, between 1.0001 and 1.01 SI. Consequently, although apparent conductivity measurements need to be inverted using non-linear processes, the variations of the apparent magnetic susceptibility can be approximated through the use of linear processes, as in the case of the magnetic prospection technique. Our proposed 3D inversion algorithm starts from apparent susceptibility data sets, acquired using different instruments over a given area. A reference vertical profile is defined by considering the mode of the vertical distributions of both the electrical resistivity and of the magnetic susceptibility. At each point of the mapped area, the reference vertical profile response is subtracted to obtain the apparent susceptibility variation dataset. A 2D horizontal Fourier transform is applied to these variation datasets and to the dipole (impulse) response of each instrument, a (vertical) 1D inversion is performed at each point in the spectral domain, and finally the resulting dataset is inverse transformed to restore the apparent 3D susceptibility variations. It has been shown that when applied to synthetic results, this method is able to correct the apparent deformations of a buried object resulting from the geometry of the instrument, and to restore reliable quantitative susceptibility contrasts. It also allows the thin layer solution, similar to that used in magnetic prospection, to be implemented. When applied to field data it initially delivers a level of contrast

  11. Magnetic Susceptibility as a Proxy for Investigating Microbial Mediated Iron Reduction

    EPA Science Inventory

    We investigated magnetic susceptibility (MS) variations in hydrocarbon contaminated sediments. Our objective was to determine if MS can be used as an intrinsic bioremediation indicator due to the activity of iron-reducing bacteria. A contaminated and an uncontaminated core were r...

  12. Magnetic susceptibility in the deep layers of the primary motor cortex in Amyotrophic Lateral Sclerosis.

    PubMed

    Costagli, M; Donatelli, G; Biagi, L; Caldarazzo Ienco, E; Siciliano, G; Tosetti, M; Cosottini, M

    2016-01-01

    Amyotrophic Lateral Sclerosis (ALS) is a progressive neurological disorder that entails degeneration of both upper and lower motor neurons. The primary motor cortex (M1) in patients with upper motor neuron (UMN) impairment is pronouncedly hypointense in Magnetic Resonance (MR) T2* contrast. In the present study, 3D gradient-recalled multi-echo sequences were used on a 7 Tesla MR system to acquire T2*-weighted images targeting M1 at high spatial resolution. MR raw data were used for Quantitative Susceptibility Mapping (QSM). Measures of magnetic susceptibility correlated with the expected concentration of non-heme iron in different regions of the cerebral cortex in healthy subjects. In ALS patients, significant increases in magnetic susceptibility co-localized with the T2* hypointensity observed in the middle and deep layers of M1. The magnetic susceptibility, hence iron concentration, of the deep cortical layers of patients' M1 subregions corresponding to Penfield's areas of the hand and foot in both hemispheres significantly correlated with the clinical scores of UMN impairment of the corresponding limbs. QSM therefore reflects the presence of iron deposits related to neuroinflammatory reaction and cortical microgliosis, and might prove useful in estimating M1 iron concentration, as a possible radiological sign of severe UMN burden in ALS patients.

  13. Magnetic Susceptibility as a Proxy for Investigating Microbial Mediated Iron Reduction

    EPA Science Inventory

    We investigated magnetic susceptibility (MS) variations in hydrocarbon contaminated sediments. Our objective was to determine if MS can be used as an intrinsic bioremediation indicator due to the activity of iron-reducing bacteria. A contaminated and an uncontaminated core were r...

  14. Analysis of the susceptibility of condensed oxygen under high pressures and in strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Kilit Doğan, E.; Yurtseven, H.

    2017-03-01

    The temperature dependence of the magnetic susceptibility is analyzed at some constant pressures by a power-law formula using the experimental data from the literature for the α - β and β - γ transitions in oxygen. A weak discontinuous (nearly continuous) transition occurring from the α to the β phase, becomes more discontinuous (weakly first order) for the β - γ transition as observed experimentally, which can be explained in terms of the critical exponents deduced from our analysis. The magnetic field dependence of the differential susceptibility is also analyzed in this study for the α -O2 at 4.2 K by a power-law formula using the experimental data. λ-type of observed behaviour of the differential susceptibility is discussed in terms of our analysis for the α -O2 .

  15. Anisotropic magnetic susceptibility of erbium and ytterbium in zircon, ZrSiO4

    USGS Publications Warehouse

    Thorpe, A.N.; Briggs, Charles; Tsang, T.; Senftle, F.; Alexander, Corrine

    1977-01-01

    Magnetic susceptibility measurements have been made for both Er- and Yb-doped (1̃03ppm) zircon single crystals with the magnetic field perpendicular and parallel to the [001] axis. Large susceptibility anisotropies were found in both cases. Our observed anisotropies of ZrSiO4: Yb indicate small populations (1̃9%) of Yb ions at the axial (tetragonal) sites, as the susceptibility of ZrSiO4: Yb would be nearly isotropic if the Yb ions only occupied the orthorhombic sites. For Er3+ in orthorhombic sites of zircon, our data indicate that the first excited state is paramagnetic with gx = 9 and gy 5̃ at 20 cm-1 above the ground state (gx 0̃, gy 1̃5). The first excited state is quite similar to the ground states observed for Er3+ in many host lattices. ?? 1977.

  16. Estimating the contribution of Brownian and Néel relaxation in a magnetic fluid through dynamic magnetic susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Maldonado-Camargo, L.; Torres-Díaz, I.; Chiu-Lam, A.; Hernández, M.; Rinaldi, C.

    2016-08-01

    We demonstrate how dynamic magnetic susceptibility measurements (DMS) can be used to estimate the relative contributions of Brownian and Néel relaxation to the dynamic magnetic response of a magnetic fluid, a suspension of magnetic nanoparticles. The method applies to suspensions with particles that respond through Brownian or Néel relaxation and for which the characteristic Brownian and Néel relaxation times are widely separated. First, we illustrate this using magnetic fluids consisting of mixtures of particles that relax solely by the Brownian or Néel mechanisms. Then, it is shown how the same approach can be applied to estimate the relative contributions of Brownian and Néel relaxation in a suspension consisting of particles obtained from a single synthesis and whose size distribution straddles the transition from Néel to Brownian relaxation.

  17. Improvement of immunoassay detection system by using alternating current magnetic susceptibility.

    PubMed

    Kawabata, R; Mizoguchi, T; Kandori, A

    2016-03-01

    A major goal with this research was to develop a low-cost and highly sensitive immunoassay detection system by using alternating current (AC) magnetic susceptibility. We fabricated an improved prototype of our previously developed immunoassay detection system and evaluated its performance. The prototype continuously moved sample containers by using a magnetically shielded brushless motor, which passes between two anisotropic magneto resistance (AMR) sensors. These sensors detected the magnetic signal in the direction where each sample container passed them. We used the differential signal obtained from each AMR sensor's output to improve the signal-to-noise ratio (SNR) of the magnetic signal measurement. Biotin-conjugated polymer beads with avidin-coated magnetic particles were prepared to examine the calibration curve, which represents the relation between AC magnetic susceptibility change and polymer-bead concentration. For the calibration curve measurement, we, respectively, measured the magnetic signal caused by the magnetic particles by using each AMR sensor installed near the upper or lower part in the lateral position of the passing sample containers. As a result, the SNR of the prototype was 4.5 times better than that of our previous system. Moreover, the data obtained from each AMR sensor installed near the upper part in the lateral position of the passing sample containers exhibited an accurate calibration curve that represented good correlation between AC magnetic susceptibility change and polymer-bead concentration. The conclusion drawn from these findings is that our improved immunoassay detection system will enable a low-cost and highly sensitive immunoassay.

  18. Improvement of immunoassay detection system by using alternating current magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Kawabata, R.; Mizoguchi, T.; Kandori, A.

    2016-03-01

    A major goal with this research was to develop a low-cost and highly sensitive immunoassay detection system by using alternating current (AC) magnetic susceptibility. We fabricated an improved prototype of our previously developed immunoassay detection system and evaluated its performance. The prototype continuously moved sample containers by using a magnetically shielded brushless motor, which passes between two anisotropic magneto resistance (AMR) sensors. These sensors detected the magnetic signal in the direction where each sample container passed them. We used the differential signal obtained from each AMR sensor's output to improve the signal-to-noise ratio (SNR) of the magnetic signal measurement. Biotin-conjugated polymer beads with avidin-coated magnetic particles were prepared to examine the calibration curve, which represents the relation between AC magnetic susceptibility change and polymer-bead concentration. For the calibration curve measurement, we, respectively, measured the magnetic signal caused by the magnetic particles by using each AMR sensor installed near the upper or lower part in the lateral position of the passing sample containers. As a result, the SNR of the prototype was 4.5 times better than that of our previous system. Moreover, the data obtained from each AMR sensor installed near the upper part in the lateral position of the passing sample containers exhibited an accurate calibration curve that represented good correlation between AC magnetic susceptibility change and polymer-bead concentration. The conclusion drawn from these findings is that our improved immunoassay detection system will enable a low-cost and highly sensitive immunoassay.

  19. Magnetoresistance, susceptibility and magnetization measurements on RNiBC compounds (R = Er, Ho, Dy, Tb, and Gd)

    NASA Astrophysics Data System (ADS)

    Tróchez, J. C.; Sánchez, D. R.; Giordanengo, B.; Fontes, M. B.; Continentino, Múcio; Baggio-Saitovitch, E. M.

    1997-08-01

    We studied magnetic behavior of the RNiBC compounds by magnetic and transport measurements. At low temperatures, each compound has different magnetic structure. Magnetoresistivity data are in good accordance with theory of magnetic elementary interactions, susceptibility reveals the magnetic transition and Curie Weiss behavior and magnetization shows low value of the saturation compared with the free R+3 ion that confirm that crystalline electric field is strong as in the RNi2B2C series.

  20. Impact of grass cover on the magnetic susceptibility measurements for assessing metal contamination in urban topsoil.

    PubMed

    Golden, Nessa; Zhang, Chaosheng; Potito, Aaron P; Gibson, Paul J; Bargary, Norma; Morrison, Liam

    2017-03-02

    In recent decades, magnetic susceptibility monitoring has developed as a useful technique in environmental pollution studies, particularly metal contamination of soil. This study provides the first ever examination of the effects of grass cover on magnetic susceptibility (MS) measurements of underlying urban soils. Magnetic measurements were taken in situ to determine the effects on κ (volume magnetic susceptibility) when the grass layer was present (κ(grass)) and after the grass layer was trimmed down to the root (κ(no grass)). Height of grass was recorded in situ at each grid point. Soil samples (n=185) were collected and measurements of mass specific magnetic susceptibility (χ) were performed in the laboratory and frequency dependence (χfd%) calculated. Metal concentrations (Pb, Cu, Zn and Fe) in the soil samples were determined and a gradiometry survey carried out in situ on a section of the study area. Significant correlations were found between each of the MS measurements and the metal content of the soil at the p<0.01 level. Spatial distribution maps were created using Inverse Distance Weighting (IDW) and Local Indicators of Spatial Association (LISA) to identify common patterns. κ(grass) (ranged from 1.67 to 301.00×10(-5) SI) and κ(no grass) (ranged from 2.08 to 530.67×10(-5) SI) measured in situ are highly correlated [r=0.966, n=194, p<0.01]. The volume susceptibility datasets in the presence and absence of grass coverage share a similar spatial distribution pattern. This study re-evaluates in situ κ monitoring techniques and the results suggest that the removal of grass coverage prior to obtaining in situ κ measurements of urban soil is unnecessary. This layer does not impede the MS sensor from accurately measuring elevated κ in soils, and therefore κ measurements recorded with grass coverage present can be reliably used to identify areas of urban soil metal contamination.

  1. Global Lithospheric Apparent Susceptibility Distribution Converted from Geomagnetic Models by CHAMP and Swarm Satellite Magnetic Measurements

    NASA Astrophysics Data System (ADS)

    Du, Jinsong; Chen, Chao; Xiong, Xiong; Li, Yongdong; Liang, Qing

    2016-04-01

    Recently, because of continually accumulated magnetic measurements by CHAMP satellite and Swarm constellation of three satellites and well developed methodologies and techniques of data processing and geomagnetic field modeling etc., global lithospheric magnetic anomaly field models become more and more reliable. This makes the quantitative interpretation of lithospheric magnetic anomaly field possible for having an insight into large-scale magnetic structures in the crust and uppermost mantle. Many different approaches have been utilized to understand the magnetized sources, such as forward, inversion, statistics, correlation analysis, Euler deconvolution, signal transformations etc. Among all quantitative interpretation methods, the directly converting a magnetic anomaly map into a magnetic susceptibility anomaly map proposed by Arkani-Hamed & Strangway (1985) is, we think, the most fast quantitative interpretation tool for global studies. We just call this method AS85 hereinafter for short. Although Gubbins et al. (2011) provided a formula to directly calculate the apparent magnetic vector distribution, the AS85 method introduced constraints of magnetized direction and thus corresponding results are expected to be more robust especially in world-wide continents. Therefore, in this study, we first improved the AS85 method further considering non-axial dipolar inducing field using formulae by Nolte & Siebert (1987), initial model or priori information for starting coefficients in the apparent susceptibility conversion, hidden longest-wavelength components of lithospheric magnetic field and field contaminations from global oceanic remanent magnetization. Then, we used the vertically integrated susceptibility model by Hemant & Maus (2005) and vertically integrated remanent magnetization model by Masterton et al. (2013) to test the validity of our improved method. Subsequently, we applied the conversion method to geomagnetic field models by CHAMP and Swarm satellite

  2. Alternating current magnetic susceptibility of a molecular magnet submonolayer directly patterned onto a micro superconducting quantum interference device

    SciTech Connect

    Martínez-Pérez, M. J.; Luis, F.; Bellido, E.; Ruiz-Molina, D.; Miguel, R. de; Sesé, J.; Lostao, A.; and others

    2011-07-18

    We report the controlled integration, via dip pen nanolithography, of monolayer dots of ferritin-based CoO nanoparticles (12 μ{sub B}) into the most sensitive areas of a microSQUID sensor. The nearly optimum flux coupling between these nanomagnets and the microSQUID improves the achievable sensitivity by a factor 10{sup 2}, enabling us to measure the linear susceptibility of the molecular array down to very low temperatures (13 mK). This method opens the possibility of applying ac susceptibility experiments to characterize two-dimensional arrays of single molecule magnets within a wide range of temperatures and frequencies.

  3. In situ measurement of alternating current magnetic susceptibility of Pd-hydrogen system for determination of hydrogen concentration in bulk.

    PubMed

    Akamaru, Satoshi; Hara, Masanori; Matsuyama, Masao

    2012-07-01

    An alternating current magnetic susceptometer for use as a hydrogen gauge for hydrogen-storage materials was designed and developed. The experimental system can simultaneously measure the hydrogen equilibrium pressure and the magnetic susceptibility of metal hydrides. The background voltage of the susceptometer was stabilized for a long period of time, without any adjustments, by attaching an efficient compensation circuit. The performance of the susceptometer at a static hydrogen concentration was demonstrated by measuring the magnetic susceptibility of a Pd-hydrogen system under equilibrium conditions. The in situ measurement of the magnetic susceptibility of Pd during hydrogen absorption was carried out using the susceptometer. Since the in situ magnetic susceptibility obtained at a lower initial hydrogen pressure agreed with the magnetic susceptibility measured at a static hydrogen concentration, the susceptometer could be used to determine the hydrogen concentration in Pd in situ. At a higher initial hydrogen pressure, enhancement of the magnetic susceptibility was observed at the beginning of hydrogen absorption because the magnetic moments induced by the large temporary strain generated in the Pd affected the magnetic susceptibility.

  4. Can the magnetic susceptibility record of Chinese Red Clay sequence be used for palaeomonsoon reconstructions?

    NASA Astrophysics Data System (ADS)

    Zhao, Guoyong; Han, Yan; Liu, Xiuming; Chang, Liao; Lü, Bin; Chen, Qu; Guo, Xuelian; Yan, Junhui; Yan, Jun

    2016-03-01

    Red Clay underlying the loess-palaeosol sequences on the Chinese Loess Plateau is an eolian deposit. There is a controversy over whether magnetic susceptibility (χ) variations in Red Clay sequence can be used as an indicator of summer palaeomonsoon intensity. This study investigates the magnetic mineralogy, magnetic concentration and magnetic grain size distribution of Jiaxian Red Clay with multimagnetic methods. Our results indicate that the magnetic properties of Jiaxian Red Clay are similar to those of the Quaternary loess-palaeosol sequences, and ultrafine ferrimagnetic grains produced during pedogenesis are responsible for an increase in susceptibility, therefore the χ enhancement mechanism of Red Clay is similar to that of the overlying loess-palaeosol sequences. This paper explores χ variations in the Red Clay sequence through spatial and temporal analysis. The susceptibility variation of six sites along a NNE to SSW transect correlate to palaeoclimatic cycles, so χ can be used to trace the summer palaeomonsoon intensity from a spatial perspective. However, a simple loess-derived calibration function cannot be used to quantitative reconstruct the palaeomonsoon intensity variations thought time. An adjusted calibration function for palaeosols from Red Clay sequence needs to be developed, so that χ can be used to quantitative reconstruct palaeomonsoon intensity. Further study is necessary to develop such a transfer function.

  5. Magnetization, magnetic susceptibility, effective magnetic moment of Fe{sup 3+} ions in Bi{sub 25}FeO{sub 39} ferrite

    SciTech Connect

    Zatsiupa, A.A.; Bashkirov, L.A.; Troyanchuk, I.O.; Petrov, G.S.; Galyas, A.I.; Lobanovsky, L.S.; Truhanov, S.V.

    2014-04-01

    Magnetic susceptibility for ferrite Bi{sub 25}FeO{sub 39} is measured at 5–950 K in the magnetic field of 0.86 T. It is shown that Bi{sub 25}FeO{sub 39} is paramagnetic in the temperature range 5−950 K. The saturation magnetization is equal to 5.04μ{sub B} per formula unit at 5 K in a magnetic field of 10 T. It is found that at 5−300 K the effective magnetic moment of Fe{sup 3+} ions in Bi{sub 25}FeO{sub 39} is equal to 5.82μ{sub B}. - Graphical abstract: The dependence of the magnetization (n, μ{sub B}) on the magnetic field for one formula unit of Bi{sub 25}FeO{sub 39} at 5 K. - Highlights: • Magnetic susceptibility for Bi{sub 25}FeO{sub 39} is measured at 5–950 K in the magnetic field of 0.86 T. • It is shown that Bi{sub 25}FeO{sub 39} is paramagnetic in the temperature range 5−950 K. • The saturation magnetization is equal to 5.04μ{sub B} per formula unit at 5 K in a magnetic field of 10 T.

  6. Magnetic susceptibility effects on 13C MAS NMR spectra of carbon materials and graphite.

    PubMed

    Freita, J C; Emmerich, F G; Cernicchiaro, G R; Sampaio, L C; Bonagamba, T J

    2001-01-01

    13C high-resolution solid-state nuclear magnetic resonance (NMR) was employed to study carbon materials prepared through the thermal decomposition of four different organic precursors (rice hulls, endocarp of babassu coconut, peat, and PVC). For heat treatment temperatures (HTTs) above about 600 C, all materials presented 13C NMR spectra composed of a unique resonance line associated with carbon atoms in aromatic planes. With increasing HTT a continuous broadening of this resonance and a diamagnetic shift in its central frequency were verified for all samples. The evolution of the magnitude and anisotropy of the magnetic susceptibility of the heat-treated carbon samples with HTT explains well these findings. It is shown that these results are better understood when a comparison is made with the features of the 13C NMR spectrum of polycrystalline graphite, for which the magnetic susceptibility effect is also present and is much more pronounced.

  7. Synthesis, spectral and magnetic susceptibility studies on tetrachloro metal(II)phthalocyanines

    NASA Astrophysics Data System (ADS)

    Somashekarappa, M. P.; Venugopala Reddy, K. R.; Harish, M. N. K.; Keshavayya, J.

    2005-10-01

    The present paper describes a simple method for the synthesis of symmetrically substituted 1,8,15,22-tetrachloro phthalocyanines of copper, cobalt, nickel and zinc. The title complexes are synthesized from the corresponding tetraamino metal phthalocyanines by modified Sandmeyers method and in turn the tetraamino metal phthalocyanines are prepared from 3-nitrophthalic acid. The bluish-green coloured tetrachloro metal phthalocyanine complexes are characterized by elemental, electronic, IR, magnetic susceptibility and X-ray powder diffraction studies to check the purity and the structural integrity. The magnetic susceptibility studies revealed that, the experimental values are higher than that of the spin only value magnetic moment, and the presence of intermolecular co-operative effects.

  8. The complex initial reluctivity, permeability and susceptibility spectra of magnetic materials

    NASA Astrophysics Data System (ADS)

    Hamilton, N. C.

    2015-03-01

    The HF complex permeability spectrum of a magnetic material is deduced from the measured impedance spectrum, which is then normalized to a series permeability spectrum. However, this series permeability spectrum has previously been shown to correspond to a parallel magnetic circuit, which is not appropriate. Some of the implications of this truth are examined. This electric/magnetic duality has frustrated efforts to interpret the shape of the complex magnetic permeability spectra of materials, and has hindered the application of impedance spectroscopy to magnetic materials. In the presence of magnetic loss, the relationship between the relative magnetic permeability and the magnetic susceptibility is called into question. The use of reluctivity spectra for expressing magnetic material properties is advocated. The relative loss factor, tanδm/μi is shown to be an approximation for the imaginary part of the reluctivity. A single relaxation model for the initial reluctivity spectra of magnetic materials is presented, and its principles are applied to measurements of a high permeability ferrite. The results are presented as contour plots of the spectra as a function of temperature.

  9. Eddy currents in the anisotropy of out-of-phase magnetic susceptibility measurement - A model study

    NASA Astrophysics Data System (ADS)

    Jezek, Josef; Hrouda, Frantisek

    2016-04-01

    Analytical solutions of Maxwell equations for eddy currents caused by AC field in a conductive sphere, known from 1950s, provide a general formula for magnetic susceptibility. It contains the parameters describing the sphere (its size, conductivity and permeability), surrounding medium (permeability) and the applied field (frequency). The formula is complex and without numerical evaluation it is difficult to distinguish the real (in-phase) and imaginary (out-of-phase) part of susceptibility. Representing all the parameters by only two, relative permeability (sphere vs. medium) and skin ratio (summarizing the effect of sphere size, conductivity and permeability, and frequency of the field), we derive approximate formulas for both phases and the phase angle. These are valid for a reasonable range of parameters (from rock magnetism point of view) and enable us to study their influence. The in-phase susceptibility depends very weakly on the fourth power of the skin ratio while the out-of-phase susceptibility depends more strongly on its second power. The coefficients of the dependence are expressed by means of relative permeability. The approximations of in-phase and out-of-phase susceptibilities provide a possibility to assess possible effects of eddy currents in rocks in case of low content of conductive minerals and solve problems of the type by which size one piece of a mineral in the measured sample can produce a phase shift that is observed by measurement. Examples of magnetite and pyrrhotite are given.

  10. Time-domain Response of a Metal Detector to a Target Buried in Soil with Frequency-dependent Magnetic Susceptibility

    DTIC Science & Technology

    2016-07-06

    metallic sphere buried in a non-conducting soil half-space with frequency-dependent complex magnetic susceptibility. The sphere is chosen as a simple...prototype for the small metal parts in low-metal landmines, while soil with dispersive magnetic susceptibility is a good model for some soils that are...the frequency domain. Approximate theoretical expressions for weakly magnetic soils are found to fit the experimental data very well, which allowed the

  11. Origin of magnetic susceptibility variations in early Paleogene BBCP cores (Wyoming)

    NASA Astrophysics Data System (ADS)

    Clyde, W. C.; Welter, G. W.; Roehl, U.; Westerhold, T.

    2012-12-01

    Magnetic susceptibility logs from late Paleocene-early Eocene cores taken during the Bighorn Basin Coring Project (BBCP) show significant variability that, in some cases (e.g. Polecat Bench), looks periodic in nature. In order to better understand the underlying mineralogical factors that cause this variability, we analyzed a suite of discrete samples from the cores using step-wise thermal demagnetization of a 3-axis orthogonal isothermal remananent magnetization (IRM) and back field (DC) demagnetization. Representative samples were collected from core depths that showed low, medium, or high susceptibilities based on the multi-sensor core logs. Bulk mass normalized susceptibility was measured for each of these discrete samples and compared to the corresponding core log measurement. Only those samples that showed good agreement between measured susceptibility and core log data were analyzed further. A hard (1.1 T) IRM was acquired and measured in a step-wise fashion along the z-axis of each sample with subsequent back-field IRMs of -100 and -300mT applied to further constrain the proportions of different magnetic minerals. After reacquiring a 1.1 T IRM along the z-axis, medium coercivity (0.4 mT) and low coercivity (.12 mT) IRMs were acquired along the y and x-axes of the samples and thermally demagnetized in a step-wise fashion. Results show that various mechanisms are responsible for elevated bulk susceptibility signals in these cores. At Polecat Bench, the highest susceptibility values are associated with coarser grained units (sandstones and siltstones) with high concentrations of detrital magnetite. At Gilmore Hill, higher susceptibilities are associated with higher concentrations of pedogenic hematite. Susceptibility values at Basin Substation are generally low and show mixed assemblages of hematite and magnetite. To assess whether hyperthermal events are associated with significant changes to magnetic mineralogy in these settings, we compared results from

  12. Magnetic susceptibility of surface soils in the Mu Us Desert and its environmental significance

    NASA Astrophysics Data System (ADS)

    Liu, Xiaokang; Lu, Ruijie; Lü, Zhiqiang; Du, Jing; Jia, Feifei; Li, Tengfei; Chen, Lu; Wu, Yongqiu

    2017-04-01

    Magnetic susceptibility has been widely used as a climatic proxy in paleoclimatic research. In arid and semi-arid regions, the magnetic properties of modern surface soil are significantly influenced by precipitation. This is demonstrated by observed positive correlations between percentage frequency-dependent magnetic susceptibility (χfd%), which reflects the presence of fine-grained (superparamagnetic, SP) grains produced during weathering and pedogenesis, and regional mean annual precipitation (MAP). To further investigate this relationship, we measured the magnetic properties of 104 surface soil samples collected along two transects (AA and BB) spanning a rainfall gradient across the Mu Us Desert in northern China. There were no systematic trends in magnetic properties along transect BB; the χfd% values remained relatively low and stable, probably reflecting weak pedogenesis and the domination of the magnetic properties by lithology. In contrast, along transect AA there was a significant positive correlation (p < 0.01) between χfd% and regional MAP. From this relationship, we developed a transfer function (P = 274.1 + 1424.4 × χfd%) and used it to produce quantitative estimates of paleo-precipitation within three Holocene aeolian sections located in the southern the modern Mu Us Desert. The results show that the variations of reconstructed precipitation are consistent with those of lithological properties, and they also confirm previous conclusions that paleosol development in the study area is dominated by precipitation. Overall the results further demonstrate the feasibility of using frequency-dependent magnetic susceptibility to quantitatively reconstruct regional paleo-precipitation, including within a geographically diverse desert area. In addition, they provide an improved understanding of the main sand provenance in Mu Us Desert.

  13. Effect of molecule-particle binding on the reduction in the mixed-frequency alternating current magnetic susceptibility of magnetic bio-reagents

    NASA Astrophysics Data System (ADS)

    Yang, C. C.; Yang, S. Y.; Chen, H. H.; Weng, W. L.; Horng, H. E.; Chieh, J. J.; Hong, C. Y.; Yang, H. C.

    2012-07-01

    By specifically bio-functionalizing magnetic nanoparticles, magnetic nanoparticles are able to label target bio-molecules. This property can be applied to quantitatively detect molecules invitro by measuring the related magnetic signals of nanoparticles bound with target molecules. One of the magnetic signals is the reduction in the mixed-frequency ac magnetic susceptibility of suspended magnetic nanoparticles due to the molecule-particle association. Many experimental results show empirically that the molecular-concentration dependent reduction in ac magnetic susceptibility follows the logistic function. In this study, it has been demonstrated that the logistic behavior is originated from the growth of particle sizes due to the molecule-particle association. The analytic relationship between the growth of particle sizes and the reduction in ac magnetic susceptibility is developed.

  14. Non-perturbative treatment of molecules in linear magnetic fields: calculation of anapole susceptibilities.

    PubMed

    Tellgren, Erik I; Fliegl, Heike

    2013-10-28

    In the present study a non-perturbative approach to ab initio calculations of molecules in strong, linearly varying, magnetic fields is developed. The use of London atomic orbitals (LAOs) for non-uniform magnetic fields is discussed and the standard rationale of gauge-origin invariance is generalized to invariance under arbitrary constant shifts of the magnetic vector potential. Our approach is applied to study magnetically induced anapole moments (or toroidal moments) and the related anapole susceptibilities for a test set of chiral and nonchiral molecules. For the first time numerical anapole moments are accessible on an ab initio level of theory. Our results show that the use of London atomic orbitals dramatically improves the basis set convergence also for magnetic properties related to non-uniform magnetic fields, at the cost that the Hellmann-Feynman theorem does not apply for a finite LAO basis set. It is shown that the mixed anapole susceptibility can be related to chirality, since its trace vanishes for an achiral molecule.

  15. Frequency-dependent magnetic susceptibility of magnetite and cobalt ferrite nanoparticles embedded in PAA hydrogel.

    PubMed

    van Berkum, Susanne; Dee, Joris T; Philipse, Albert P; Erné, Ben H

    2013-05-14

    Chemically responsive hydrogels with embedded magnetic nanoparticles are of interest for biosensors that magnetically detect chemical changes. A crucial point is the irreversible linkage of nanoparticles to the hydrogel network, preventing loss of nanoparticles upon repeated swelling and shrinking of the gel. Here, acrylic acid monomers are adsorbed onto ferrite nanoparticles, which subsequently participate in polymerization during synthesis of poly(acrylic acid)-based hydrogels (PAA). To demonstrate the fixation of the nanoparticles to the polymer, our original approach is to measure low-field AC magnetic susceptibility spectra in the 0.1 Hz to 1 MHz range. In the hydrogel, the magnetization dynamics of small iron oxide nanoparticles are comparable to those of the particles dispersed in a liquid, due to fast Néel relaxation inside the particles; this renders the ferrogel useful for chemical sensing at frequencies of several kHz. However, ferrogels holding thermally blocked iron oxide or cobalt ferrite nanoparticles show significant decrease of the magnetic susceptibility resulting from a frozen magnetic structure. This confirms that the nanoparticles are unable to rotate thermally inside the hydrogel, in agreement with their irreversible fixation to the polymer network.

  16. Frequency-Dependent Magnetic Susceptibility of Magnetite and Cobalt Ferrite Nanoparticles Embedded in PAA Hydrogel

    PubMed Central

    van Berkum, Susanne; Dee, Joris T.; Philipse, Albert P.; Erné, Ben H.

    2013-01-01

    Chemically responsive hydrogels with embedded magnetic nanoparticles are of interest for biosensors that magnetically detect chemical changes. A crucial point is the irreversible linkage of nanoparticles to the hydrogel network, preventing loss of nanoparticles upon repeated swelling and shrinking of the gel. Here, acrylic acid monomers are adsorbed onto ferrite nanoparticles, which subsequently participate in polymerization during synthesis of poly(acrylic acid)-based hydrogels (PAA). To demonstrate the fixation of the nanoparticles to the polymer, our original approach is to measure low-field AC magnetic susceptibility spectra in the 0.1 Hz to 1 MHz range. In the hydrogel, the magnetization dynamics of small iron oxide nanoparticles are comparable to those of the particles dispersed in a liquid, due to fast Néel relaxation inside the particles; this renders the ferrogel useful for chemical sensing at frequencies of several kHz. However, ferrogels holding thermally blocked iron oxide or cobalt ferrite nanoparticles show significant decrease of the magnetic susceptibility resulting from a frozen magnetic structure. This confirms that the nanoparticles are unable to rotate thermally inside the hydrogel, in agreement with their irreversible fixation to the polymer network. PMID:23673482

  17. Identification of Heavy Metal Pollution Derived From Traffic in Roadside Soil Using Magnetic Susceptibility.

    PubMed

    Yang, Pingguo; Ge, Jing; Yang, Miao

    2017-06-01

    The study integrates surface and vertical distribution of magnetic susceptibility and heavy metal contents (Pb, Cu, Zn and Fe) to characterize the signature of vehicle pollutants in roadside soils at Linfen city, China. Sites with reforestation and without vegetation cover were investigated. The results showed that magnetic susceptibility and heavy metal contents were higher at the roadside without trees than in the reforest belt. The variations of magnetic susceptibility and heavy metal contents decreased both with distance and with depth. The maximum value was observed at 5-10 m away from the roadside edge. The vertical distribution in soil revealed accumulation of pollutants in 0-5 cm topsoils. The average contents were higher than the background values and in the order Fe (107.21 g kg(-1)), Zn (99.72 mg kg(-1)), Pb (90.99 mg kg(-1)), Cu (36.14 mg kg(-1)). Coarse multi domain grains were identified as the dominating magnetic particles. Multivariate statistical and SEM/EDX analyses suggested that the heavy metals derived from traffic sources. Trees act as efficient receptors and green barrier, which can reduce vehicle derived pollution.

  18. Cross-language treatment generalisation

    PubMed Central

    Goral, Mira; Levy, Erika S.; Kastl, Rebecca

    2009-01-01

    Background Recent investigations of language gains following treatment in bilingual individuals with chronic aphasia appear to confirm early reports that not only the treated language but also the non-treated language(s) benefit from treatment. The evidence, however, is still suggestive, and the variables that may mitigate generalisation across languages warrant further investigation. Aims We set out to examine cross-language generalisation of language treatment in a trilingual speaker with mild chronic aphasia. Methods & Procedures Language treatment was administered in English, the participant’s second language (L2). The first treatment block focused on morphosyntactic skills and the second on language production rate. Measurements were collected in the treated language (English, L2) as well as the two non-treated languages: Hebrew (the participant’s first language, L1) and French (the participant’s third language, L3). Outcomes & Results The participant showed improvement in his production of selected morphosyntactic elements, such as pronoun gender agreement, in the treated language (L2) as well as in the non-treated French (L3) following the treatment block that focused on morphosyntactic skills. Speech rate also improved in English (L2) and French (L3) following that treatment block. No changes were observed in Hebrew, the participant’s L1. Conclusions Selective cross-language generalisation of treatment benefit was found for morphosyntactic abilities from the participant’s second language to his third language. PMID:20221311

  19. Testing the indicative value of magnetic susceptibility measurements for concluding on site potentials and risks provoked by fly ash deposition.

    PubMed

    Fürst, C; Lorz, C; Zirlewagen, D; Makeschin, F

    2010-12-01

    The article presents results of testing the indicative value of magnetic susceptibility for fly ash deposition and its effects on forest site properties. Base saturation and concentrations of Ca and Mg were used as indicators for nutrient pools resulting from fly ash deposition. Concentrations of Fe, Al, Mn, Cd and Black Carbon were used as indicators for risks of leaching. The correlation of magnetic susceptibility with concentrations of nutrient, acidic cations, heavy metals, base saturation and Black Carbon was calculated. Additionally, we tested the suitability of magnetic susceptibility as a parameter in a linear regression based model to predict the concentrations of Ca, Mg, Fe, Al, Mn, Cd and Black Carbon. We were able to show a positive correlation between magnetic susceptibility and the selected indicators. In contrast to previous studies, we were also able to demonstrate the suitability of magnetic susceptibility to predict the size of fly ash deposition influenced nutrient pools mainly for humus layers, especially for Oa horizons. The spatial distribution of magnetic susceptibility showed also a positive correlation with regionalized base saturation. However, because of the data base and other factors impacting the measurement and modeling results, some shortcomings of using a linear regression model must be noted. From these results, we concluded that magnetic susceptibility might be a valuable parameter in a multiple regression based approach, but should not be used alone for predicting effects of fly ash deposition.

  20. Demonstrating and Measuring Relative Molar Magnetic Susceptibility Using a Neodymium Magnet

    ERIC Educational Resources Information Center

    Malerich, Charles; Ruff, Patricia K.; Bird, Aubrey

    2004-01-01

    An easy-to-see method for demonstrating and measuring the magnetic force between paramagnetic substance and a rare earth magnet is presented. The readily available trapezoid-shaped neodymium magnet and a low cost, easy-to-set-up, portable apparatus are used in the experiments.

  1. Demonstrating and Measuring Relative Molar Magnetic Susceptibility Using a Neodymium Magnet

    ERIC Educational Resources Information Center

    Malerich, Charles; Ruff, Patricia K.; Bird, Aubrey

    2004-01-01

    An easy-to-see method for demonstrating and measuring the magnetic force between paramagnetic substance and a rare earth magnet is presented. The readily available trapezoid-shaped neodymium magnet and a low cost, easy-to-set-up, portable apparatus are used in the experiments.

  2. Anisotropy of the Magnetic Susceptibility of the Alnö alkaline and carbonatite igneous complex

    NASA Astrophysics Data System (ADS)

    Andersson, M.; Almqvist, B.; Malehmir, A.; Troll, V. R.; Snowball, I.; Lougheed, B.

    2013-12-01

    The Alnö igneous complex in central Sweden is one of the largest (radius ~2.5 km) of the few well-known alkaline and carbonatite ring-intrusions in the world. The lithologies span from alkaline silicate rocks (nepheline syenite, ijolite, and pyroxenite) to a range of carbonatite dykes (e.g. sövite) with variable composition. The depth extent, dip, and dip direction of the alkaline and carbonatite rocks have been inferred from surface geological mapping, and a dome-shaped magma chamber with the roof at ~2 km below the palaeosurface was inferred to have supplied steeply dipping radial dykes and (shallowly dipping) cone sheets. Recent high-resolution reflection seismic profiles and gravity and ground magnetic measurements suggest, in turn, a saucer-shaped magma chamber at ~3 km depth below present day land surface. To provide further insight into the internal flow mechanics of these dykes and into their emplacement mechanisms, we have measured the anisotropy of magnetic susceptibility (AMS). About 250 samples from 119 oriented cores were collected with a handheld drilling machine from 26 localities within the Alnö complex. Prior to preparation of discrete samples for AMS, the cores were measured for their density and for ultrasonic P- and S-wave velocities. Most of the sampling locations lie on a transect through the intrusion. Three locations have been sampled in detail, to determine the variation of AMS within individual carbonatite dykes. The AMS of samples were measured in low-field, using a KLY-2 Kappabridge. Bulk magnetic susceptibility ranges from 3.01e-5 to 2.50e-1 SI, and correlates with lithology. The sövites have the widest range of susceptibility (average 4.32e-2, with a range from 3.01e-5 to 2.50e-1 SI), whereas fenites have the lowest average susceptibility (average 2.06e-3, with a range from 9.86e-5 to 1.47e-2 SI); nepheline-syenite, ijolite and pyroxenite have susceptibilities between these two end member lithologies. Sövite consists mainly of

  3. Investigation of roadside pollution in Aliaga Industrial Zone (Izmir/Turkey) by using magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Timur, Emre

    2014-05-01

    Pollution of soils is significantly reducing environmental quality and affecting human health. As a condition for effective protection and remediation actions, the screening and detection of soil and sediment pollution has become increasingly important. The pollutants of most cases are usually heavy metals, organic contaminants and agricultural applications such as chemical fertilizers, pestisides and hormones. The aim of this study is to trace the distribution and concentration of contaminants in soils along roads carrying both appreciably high and low traffic along three roads around Aliaga industrial zone. Magnetic susceptibility (Bartington MS2E) is used for pollution mapping in the field. The distribution of the susceptibility values represents contaminated areas strongly influenced by traffic frequency, roadside topography, vegetation and meteorological conditions. It was determined that approximately 5 m along both sides of Canakkale-Izmir highway, which has a very high traffic density (250 car/min), shows very high susceptibility values in comparison with the rest of the profile. This value reduced to 2.4 m and 0.7 m along two side roads, which are 300 and 1100 m away from the highway. Also these roads were having traffic densities of 47 cars/min and 3 cars/min respectively. The measurements were repeated in summer and winter seasons in order to observe possible climate effects. Also soil samples were collected at 2 stations in both sides of the roads to compare the heavy metal content with the background values. According to geochemical data Fe-oxides are found to be responsible for the high values of magnetic susceptibility. It was determined that magnetic susceptibility is a rapid and cheap method for investigating potentially contaminated areas.

  4. Anisotropy of complex magnetic susceptibility as an indicator of strain and petrofabric in rocks bearing sulphides

    NASA Astrophysics Data System (ADS)

    Borradaile, G. J.; Puumala, M.; Stupavsky, M.

    1992-02-01

    A new method, anisotropy of complex magnetic susceptibility (ACMS), for determining the petrofabric of specimens with conductive minerals is developed. The method uses the same induction coil equipment and techniques that can be used for the measurement of the anisotropy of magnetic susceptibility (AMS). However, a higher (100 kHz) operating frequency emphasizes the electrical conductivity response and thus yields a measure of the anisotropy of electrical conductivity of the specimen. The method was tested on variably deformed plasticine samples containing aluminium fabric markers and on synthetic aggregates of pyrrhotite and talc-pyrrhotite mixtures deformed triaxially at a confining pressure of 200 MPa (2 kbar) by up to 35% homogeneous shortening. ACMS successfully defines the petrofabric and permits prediction of the principal directions of finite strain. The intensity of AMS and, to a lesser extent, of ACMS correlate with the strain ratio in these simple, coaxial, flattening plane strain experimental deformations on selected materials.

  5. Metal-insulator transitions and magnetic susceptibility in doped cuprate compounds

    NASA Astrophysics Data System (ADS)

    Dzhumanov, S.; Kurbanov, U. T.; Khudayberdiev, Z. S.; Hafizov, A. R.

    2016-11-01

    Results are presented from a theoretical study of the possibility of hole carrier localization and metal-insulator transitions which show up in the temperature dependences of the magnetic susceptibility χ(T) of doped copper-oxide (cuprate) compounds. The criteria for metal-insulator transitions owing to strong hole-lattice interactions and the formation of very narrow polaron bands in these materials with reduced doping level x are analyzed. It is shown that these kinds of metal-insulator transitions occur in underdoped La2-xSrxCuO4 and YBa2Cu3O6+x cuprates (i.e., for x ranging from 0.04 to 0.12). The characteristic temperature dependences χ(T) of the HTSC cuprates are found for different doping levels. These results are in good agreement with experimental data on metal-insulator transitions and the magnetic susceptibility of the HTSC cuprates.

  6. Magnetic susceptibility measurements as proxy method to monitor soil pollution: development of experimental protocols for field surveys.

    PubMed

    D'Emilio, Mariagrazia; Chianese, Domenico; Coppola, Rosa; Macchiato, Maria; Ragosta, Maria

    2007-02-01

    In the framework of the development of new methods for measuring and monitoring soil pollution, this paper deals with the use of magnetic methodologies to monitor the heavy metals presence in soils. In particular it shows a procedure for collecting magnetic susceptibility measurements in order to interpret them as proxy variable for monitoring heavy metals in soils. Magnetic measurements are carried out using a magnetic susceptibility meter with two different probes for in situ field surveys. The experimental procedure is divided in two parts. In the first part we carry out laboratory tests aimed to evaluate, for both the probes, the effective investigation depth for soil, the measurement reproducibility under different conditions, and the influence of water content. We complete this part comparing in situ measurements obtained by means of two probes with different characteristics. In the second part we carry out tests to evaluate the relationships between heavy metal levels and magnetic susceptibility values of soil samples. We investigate the variability of the magnetic susceptibility measurements contaminating different soil samples with well known concentration of heavy metals. Moreover we study the correlation between magnetic susceptibility values and metal concentrations, determined by means of AAS, in soil samples collected during a field survey. Results suggest that a careful check of the experimental procedure play a crucial role for using magnetic susceptibility measurements for heavy metals in situ monitoring. This is very helpful both for improving the quality of data and for making simpler data interpretation.

  7. Magnetic susceptibility oscillation in neutron stars with the hadron-quark transition

    SciTech Connect

    Jiang, W. Z.; Van Giai, N.

    2006-11-02

    We analyze the de Hass-van Alphen (HVA) oscillation of magnetic susceptibility in the nuetron star matter using an analytic relativistic expression obtained before, showing that the oscillation frequency is proportional to the squared chemical potential and the reciprocal of the field, and is independent of the temperature. The numerical results for the HVA oscillation are also shown. A superposition of the HVA oscillations changes the oscillation properties drastically if the color deconfinement occurs at high densities.

  8. On the origin of magnetic a.c. susceptibility non-SRT anomalies in intermetallic compounds

    SciTech Connect

    Bartolome, J.; Garcia, L.M.; Lazaro, F.J.; Grincourt, Y.; Fuente, L.G. de la; Francisco, C. de; Munoz, J.M.; Fruchart, D.

    1994-03-01

    The anomaly detected in the magnetic a.c. susceptibility of many intermetallic compounds between 100 and 300 K, and in particular in Nd{sub 2}Fe{sub 14}B at 220 K, has been induced in a controlled manner by thermal annealing. The anomaly has been interpreted in terms of thermal activated processes of defects imposing their dynamical behavior on the domain walls coupled to them, thus solving the controversy on its origin.

  9. Magnetic susceptibility as a simple tracer for fluvial sediment source ascription during storm events.

    PubMed

    Rowntree, Kate M; van der Waal, Bennie W; Pulley, Simon

    2016-12-07

    Sediment tracing using a single tracer, low frequency magnetic susceptibility (Xlf), was used to apportion suspended sediment to geologically defined source areas and to interpret sediment source changes during flood events in the degraded catchment of the Vuvu River, a headwater tributary of the Mzimbubu River, South Africa. The method was tested as a simple tool for use by catchment managers concerned with controlling erosion. The geology of the 58 km(2) catchment comprises two distinct formations: basalt in the upper catchment with a characteristically high magnetic susceptibility and shales with a low magnetic susceptibility in the lower catchment. Application of an unmixing model incorporating a Monte Carlo uncertainty analysis showed that Xlf provided a means to assign the proportion of each geological province contributing to the river's sediment load. Grab water samples were collected at ten-minute intervals during flood events for subsequent analysis of suspended sediment concentration and the magnetic susceptibility of the filtered sediment. Two floods are presented in detail, the first represents a significant event at the start of the wet season (max. discharge 32 m(3) s(-1)); the second was a smaller flood (max discharge 14 m(3) s(-1)) that occurred a month later. Suspended sediment concentrations during the twelve monitored events showed a characteristic decline over the wet season. The main source of suspended sediment was shown to be from the mudstones in the lower catchment, which contributed 86% of the total measured load. The sediment dynamics during the two floods monitored in detail were quite different from each other. In the first the sediment concentration was high (11 g L(-1)), peaking after the flood peak. The Xlf value increased during the event, indicating that contribution to the sediment load from basalt in the upper catchment increased during the recession limb. In the second, smaller flood the sediment peak (6 g L(-1

  10. [Study of relation between crushed lava spectrum and magnetic susceptibility in Xiangshan uranium orefield].

    PubMed

    Wu, Zhi-Chun; Guo, Fu-Sheng; Liu, Lin-Qing; Jiang, Yong-Biao

    2013-12-01

    Rock spectrum research is the base of the remote sensing geology. It's of great significance of exploring the relations between rock spectrum and other rock natures. In the present study, 36 fine crushed lava samples each measuring 5 cmX5 cmX 5 cm were tested for its spectrums by SVC HR-768 portable spectrometer. But before measuring each sample, white boards should be calibrated and after measuring the curves of spectrum of each sample should make a 5 nm smooth resample so that meteoric water and noise caused by external environment can be eliminated. After such smooth resample, at the spectrum scope of 1 112-1322 nm, taking band value as horizontal axis and reflectivity as vertical axis, linear equations of rock samples can be obtained. Taking the slopes as the horizontal axis and volume magnetic susceptibility as vertical axis, y= -0. 256 31n(x) + 0. 913 7 was thus obtained and its equation correlation coefficient is up to 0. 78. The result shows that volume magnetic susceptibility is mainly caused by Fe2+ , and that the amount of Fe2+ can be almost measured in the spectrum scope of 1112 approximately 1322 nm that has a good correlation with volume magnetic susceptibility.

  11. Magnetism of a sigma-phase Fe60V40 alloy: Magnetic susceptibilities and magnetocaloric effect studies

    NASA Astrophysics Data System (ADS)

    Bałanda, Maria; Dubiel, Stanisław M.; Pełka, Robert

    2017-06-01

    Magnetic properties of a sigma-phase Fe60V40 intermetallic compound were studied by means of ac and dc magnetic susceptibility and magnetocaloric effect measurements. The compound is a soft magnet yet it was found to behave like a re-entrant spin-glass system. The magnetic ordering temperature was found to be TC ≈ 170 K, while the spin-freezing temperature was ∼164 K. Its relative shift per decade of ac frequency was 0.002, a value smaller than that typical of canonical spin-glasses. Magnetic entropy change, ΔS, in the vicinity of TC was determined for magnetic field, H, ranging between 5 and 50 kOe. Analysis of ΔS in terms of the power law yielded the critical exponent, n, vs. temperature with the minimum value of 0.75 at TC, while from the analysis of a relative shift of the maximum value of ΔS with the field a critical exponent Δ = 1.7 was obtained. Based on scaling laws relationships values of other two exponents viz. β = 0.6 and γ = 1 were determined.

  12. Magnetic susceptibility, specific heat and magnetic structure of CuNi{sub 2}(PO{sub 4}){sub 2}

    SciTech Connect

    Escobal, Jaione; Pizarro, Jose L.; Mesa, Jose L. . E-mail: joseluis.mesa@ehu.es; Larranaga, Aitor; Fernandez, Jesus Rodriguez; Arriortua, Maria I.; Rojo, Teofilo

    2006-10-15

    CuNi{sub 2}(PO{sub 4}){sub 2} phosphate has been synthesized by the ceramic method at 800 deg. C in air. The crystal structure consists of a three-dimensional skeleton constructed from MO{sub 4} (M{sup II} =Cu and Ni) planar squares and M{sub 2}O{sub 8} dimers with square pyramidal geometry, which are interconnected by (PO{sub 4}){sup 3-} oxoanions with tetrahedral geometry. The magnetic behavior has been studied on powdered sample by using susceptibility, specific heat and neutron diffraction data. The bimetallic copper(II)-nickel(II) orthophosphate exhibits a three-dimensional magnetic ordering at, approximately, 29.8 K. However, its complex crystal structure hampers any parametrization of the J-exchange parameter. The specific heat measurements exhibit a three-dimensional magnetic ordering ({lambda}-type) peak at 29.5 K. The magnetic structure of this phosphate shows ferromagnetic interactions inside the Ni{sub 2}O{sub 8} dimers, whereas the sublattice of Cu(II) ions presents antiferromagnetic couplings along the y-axis. The change of the sign in the magnetic unit-cell, due to the [1/2, 0, 1/2] propagation vector determines a purely antiferromagnetic structure. - Graphical abstract: Magnetic structure of CuNi2(PO4)2.

  13. Ferromagnetic ordering in NpAl2: Magnetic susceptibility and 27Al nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Martel, L.; Griveau, J.-C.; Eloirdi, R.; Selfslag, C.; Colineau, E.; Caciuffo, R.

    2015-08-01

    We report on the magnetic properties of the neptunium based ferromagnetic compound NpAl2. We used magnetization measurements and 27Al NMR spectroscopy to access magnetic features related to the paramagnetic and ordered states (TC=56 K). While very precise DC SQUID magnetization measurements confirm ferromagnetic ordering, they show a relatively small hysteresis loop at 5 K reduced with a coercive field HCo~3000 Oe. The variable offset cumulative spectra (VOCS) acquired in the paramagnetic state show a high sensitivity of the 27Al nuclei spectral parameters (Knight shifts and line broadening) to the ferromagnetic ordering, even at room temperature.

  14. Strain analysis in quartzites with negative magnetic susceptibility using AMS and EBSD data

    NASA Astrophysics Data System (ADS)

    Rajendraprasad Renjith, A.; Mamtani, Manish A.

    2016-04-01

    This study is being done with the objective of trying to understand whether the anisotropy of magnetic susceptibility (AMS) data can provide information about strain in quartzites with negative magnetic susceptibility. For this, nine quartzite samples have been collected from Rengali Province (located in the eastern part of India) with bulk magnetic susceptibility between -13.6 x 10-6 SI units and -3.06 x 10-6 SI units. Since these rocks did not show any visible foliation or lineation, AMS analysis was performed using KLY-4S Kappabridge and the orientation of three principal axes of the AMS ellipsoid (K1>K2>K3) were determined. Thin sections were prepared parallel to the K1K3 plane of the AMS ellipsoid (plane parallel to lineation and perpendicular to foliation), which is equivalent to the XZ plane of the strain ellipsoid. SEM based electron backscatter diffraction (EBSD) analysis, shape preferred orientation (SPO) analysis and strain analysis were carried out in these sections. Recently, Renjith et al. (2016) used the same samples to establish that the AMS in quartzites gives information about the SPO and not the CPO. To further evaluate the robustness of AMS in strain analysis, the authors have integrated the degree of magnetic anisotropy (Pj - a measure of the eccentricity of AMS ellipsoid; Tarling and Hrouda, 1993) with the intensity of SPO (κ ; Piazolo and Passchier, 2002), and the strain (E - calculated using AMOCADO; Gerik and Kruhl, 2009) from the same samples from Rengali. EBSD data were used as the basis for the above calculations. Whilst the orientation of long axis of quartz grains from EBSD statistical data was used to calculate κ , the grain boundary map generated from EBSD analysis was used as the basis to determine strain (E). It is found that the sample with minimum Pj also has a minimum κ and E, and vice-versa. Hence it is concluded that one-to-one correlation exists between the degree of magnetic anisotropy, strain and intensity of SPO in

  15. Low-frequency low-field magnetic susceptibility of ferritin and hemosiderin.

    PubMed

    Allen, P D; St Pierre, T G; Chua-anusorn, W; Ström, V; Rao, K V

    2000-02-21

    Low-frequency low-field magnetic susceptibility measurements were made on four samples of mammalian tissue iron oxide deposits. The samples comprised: (1) horse spleen ferritin; (2) dugong liver hemosiderin; (3) thalassemic human spleen ferritin; and (4) crude thalassemic human spleen hemosiderin. These samples were chosen because Mössbauer spectroscopic measurements on the samples indicated that they exemplified the variation in magnetic and mineral structure found in mammalian tissue iron oxide deposits. The AC-magnetic susceptometry yielded information on the magnetization kinetics of the four samples indicating samples 1, 2, and 3 to be superparamagnetic with values of around 10(11) s(-1) for the pre-exponential frequency factor in the Néel-Arrhenius equation and values for characteristic magnetic anisotropy energy barriers in the range 250-400 K. Sample 4 was indicated to be paramagnetic at all temperatures above 1.3 K. The AC-magnetic susceptometry data also indicated a larger magnetic anisotropy energy distribution in the dugong liver sample compared with samples 1 and 3 in agreement with previous Mössbauer spectroscopic data on these samples. At temperatures below 200 K, samples 1-3 exhibited Curie-Weiss law behavior, indicating weak particle-particle interactions tending to favor antiparallel alignment of the particle magnetic moments. These interactions were strongest for the dugong liver hemosiderin, possibly reflecting the smaller separation between mineral particles in this sample. This is the first magnetic susceptometry study of hemosiderin iron deposits and demonstrates that the AC-magnetic susceptometry technique is a fast and informative method of studying such tissue iron oxide deposits.

  16. Molar Cotton-Mouton constants and anisotropy of magnetic susceptibility of benzyl chlorides and benzyl bromides

    SciTech Connect

    Vul'fson, S.G.; Dianova, O.M.; Vereshchagin, A.N.

    1987-01-10

    Based on an analysis of electrical and optical data, they previously established the steric structure of a series of benzyl halides and found that the polarizability ellipsoid of the aromatic nucleus undergoes significant rearrangement of its semiaxes in comparison to the semiaxes in toluene (I). In all of the systems examined the mobility of the electron cloud in the plane of the ring increases and decreases in the perpendicular direction. A conformation is realized in which the benzene ring is close to shielding of the C-H bond. Hyperconjugation of the ..pi..arom-sigmaC-Hal* type, particularly manifested in the nuclear quadrupole resonance spectra, is apparently responsible for the observed effects. The effect of similar interactions on the magnetic properties has not been studied either experimentally or theoretically. The anisotropies of magnetic susceptibility of molecules or groups of atoms can be calculated from the known optical polarizabilities using data on the magnetic birefringence constant (the Cotton-Mouton effect) of compounds in the form of vapors or solutions. The molar Cotton-Mouton constants of the title compounds were measured and the magnetic susceptibility ellipsoids (MSE) of the C/sub 6/H/sub 5/-C fragment in benzyl halides and (I), whose MSe is known, were comparatively estimated in the present study.

  17. Magnetic susceptibility of hcp iron and the seismic anisotropy of Earth's inner core

    NASA Astrophysics Data System (ADS)

    Grechnev, G. E.; Ahuja, R.; Eriksson, O.

    2003-08-01

    The seismic anisotropy of the Earth’s core is believed to be due to a preferred orientation of hexagonal close packed (hcp) iron crystals that constitute the dominating element in the inner core. In this connection, the magnetic properties of the hcp iron in an external magnetic field are very interesting and are studied here by employing an ab initio full-potential linear muffin tin orbital method. By this means the magnetic susceptibility χ of hcp iron and its anisotropy energy for pressures and temperatures corresponding to the Earth’s inner core conditions have been evaluated in the framework of the local spin density approximation. The accuracy of this method has been validated by calculating the anisotropic susceptibility of paramagnetic transition metals that form in the hcp crystal structure at ambient conditions. Our calculations demonstrate that for hcp iron the anisotropy of χ is dependent on the c/a ratio. In conjunction with recent data on the c/a ratio and elastic constants of hcp iron, the magnetic anisotropy can explain the seismic anisotropy of the Earth’s inner core.

  18. Field and temperature dependences of anisotropic magnetic susceptibility of CaNdAlO{sub 4} crystal

    SciTech Connect

    Fink-Finowicki, J.; Puzniak, R.; Baran, M.; Byszewski, P.; Gutowski, M.; Szymczak, H.; Pajaczkowska, A. |

    1994-03-01

    The measurements of temperature dependences of magnetic susceptibility both in (a-b) plane, and along c-axis of CaNdAlO{sub 4} single crystal have been performed. The strong uniaxial anisotropy of magnetic properties has been found. The low field susceptibility along c-axis is well described by the Curie law, while the susceptibility in (a-b) plane can be described by Curie-Weiss law suggesting the presence of antiferromagnetic interactions between neodymium ions. However, the anisotropy of magnetic susceptibility can also appear to be due to crystal field acting on magnetic ions in a system without any exchange interaction. The successful description of experimental data was done in frames of the crystal field approximation.

  19. Magnetic susceptibility and the spatial variability of heavy metals in soils developed on basalt

    NASA Astrophysics Data System (ADS)

    Cervi, Eduardo Cimino; da Costa, Antonio Carlos Saraiva; de Souza Junior, Ivan Granemann

    2014-12-01

    Topsoil magnetic susceptibility (κ) is a fast and convenient method used to detect potentially polluted areas by heavy metals. Topsoil measurements are carried out in situ with Bartington MS2D loop sensor, designed to measure the magnetic susceptibility of top 10 cm of soil and detect 90% of the total signal from a depth of 6 cm. However, soils developed on basalt are difficult to assess due to their large amounts of ferrimagnetic minerals. The aim of this study was evaluate the applicability of κ to discriminate anthropogenic/lithogenic environments characterized by different parent materials in the city of Maringá/Brazil. In this paper, topsoil susceptibility (κ) was measured in 66 urban soils using a Bartington MS2D loop sensor. To investigate the magnetic background levels, samples of a Rhodic Ferralsol profile were measured using a laboratory MS2B sensor. X-ray diffractometry (XRD) analysis was carried out to verify the mineralogical composition of the different lithology. Cu, Fe, Ni, Mn, Pb and Zn concentrations were measured in 29 topsoil samples. The κ values ranged from 316 × 10- 5 SI in a sandstone region to 6,945 × 10- 5 SI in soils developed on basalt. The χfd values of urban topsoil varied from 2% to 11.3%. Lower values of κ and χfd in the sandstone region indicated that the lithogenic contribution is of primary significance. Significant positive correlations between κ and Cu, Fe and Mn are related to the parent material, enriched in iron oxides, as verified by XRD. The background values (mean of 4,235 × 10- 8 m3 kg- 1) were higher in subsoil, suggesting the inexistence of anthropogenic pollution. The topsoil susceptibility was efficient for distinguish different lithogenic environments. Although anthropogenic pollution in soils developed on basalt is difficult to assess due to the high natural background, our results suggest that heavy metal contents are not related to the human activity.

  20. Fabrics revealed in basal glacier ice through anisotropy of magnetic susceptibility data

    NASA Astrophysics Data System (ADS)

    Fleming, E.; Lovell, H.; Benn, D.; Stevenson, C.; Hambrey, M.; Petronis, M. S.; Fairchild, I. J.

    2012-12-01

    The properties of basal ice are important for understanding interactions between glaciers and their substrates and is therefore of significant importance for understanding glacier motion and the processes operating at the glacier bed. Anisotropy of magnetic susceptibility (AMS) uses the magnetic properties of minerals to reveal subtle fabrics. AMS can provide considerable information regarding the kinematics of deformation within rocks and sediment and has recently been applied to glacial geology to investigate subglacially deformed sediments. In this study, we present, as far as we are aware, the first AMS study from basal ice to investigate deformation within a glacier. Basal ice samples, field descriptions and structural measurements were collected from north-eastern and south-western exposures at the tidewater margin of Tunabreen, a surging glacier in Svalbard. AMS data indicate that the magnetic lineations (k1) are aligned parallel or sub-parallel to glacier flow direction from aerial photographs and parallel to the direction of extension and shear revealed from structural observations at the ice outcrop (folds, lineations, macrofabric). The magnetic foliation, given by the K1/K2 plane, dips gently up glacier, generally parallel to visible foliations within the ice. The magnetic fabric is interpreted as being formed by a preferred alignment of paramagnetic and ferromagnetic grains within detrital debris located at ice crystal boundaries. We hypothesise that as the glacier flowed, simple shear affected the basal ice causing stretching and extension. As such, detrital minerals in the spaces between ice crystals rotated into a preferred orientation reflecting the strain. On the north-western section, the imbrications of magnetic lineations away from the glacier margins suggest that, as well as longitudinal extension, there is a component of lateral shear. In contrast, at the south-eastern margin, the divergence of magnetic lineation away from flow reveals lateral

  1. Magnetic Susceptibility of liquid Gd-NM (NM = Cu, Ga, Ge) alloys

    NASA Astrophysics Data System (ADS)

    Shimakura, Hironori; Tahara, Shuta; Okada, Tatsuya; Ohno, Satoru

    2017-08-01

    For rare earth alloys, the indirect interaction of RKKY is at work between rare-earth atoms. Therefore, the magnetism of them depends on the number of conduction electrons and the distance between rare-earth metals. In this work, to reveal the relationship between the number of conduction electrons and magnetic property of rare earth metal alloys, magnetic susceptibility measurements for liquid Gd-NM (NM = Cu, Ga, Ge) was performed by Faraday method. As the results, it was observed that the sign of paramagnetic Curie temperature of Cu-Gd alloys are positive at all composition, while Ga-Gd and Ge-Gd alloys show negative paramagnetic Curie temperature at certain composition. Moreover, it was indicated when the alloy at certain composition shows highest melting temperature, it has the lowest paramagnetic Curie temperature.

  2. Characterization of tissue magnetic susceptibility-induced distortions for MRIgRT

    SciTech Connect

    Stanescu, T.; Wachowicz, K.; Jaffray, D. A.

    2012-12-15

    Purpose: MR image geometric integrity is one of the building blocks of MRI-guided radiotherapy. In particular, tissue magnetic susceptibility-induced effects are patient-dependent and their behavior is difficult to assess and predict. In this study, the authors investigated in detail the characteristics of susceptibility ({chi}) distortions in the context of MRIgRT, including the case of two common MR-linac system configurations. Methods: The magnetic field distortions were numerically simulated for several imaging parameters and anatomical sites, i.e., brain, lung, pelvis (with air pockets), and prostate. The simulation process consisted of (a) segmentation of patient CT data into susceptibility relevant anatomical volumes (i.e., soft-tissue, bone and air/lung), (b) conversion of CT data into susceptibility masks by assigning bulk {chi} values to the structures defined at (a), (c) numerical computations of the local magnetic fields by using a finite difference algorithm, and (d) generation of the geometric distortion maps from the magnetic field distributions. For each patient anatomy, the distortions were quantified at the interfaces of anatomical structures with significantly different {chi} values. The analysis was performed for two specific orientations of the external main magnetic field (B{sub 0}) characteristic to the MR-linac systems, specifically along the z-axis for a bore MR scanner and in the (x,y)-plane for a biplanner magnet. The magnetic field local perturbations were reported in ppm. The metrics used to quantify the geometric distortions were the maximum, mean, and range of distortions. The numerical simulation algorithm was validated using phantom data measurements. Results: Susceptibility-induced distortions were determined for both quadratic and patient specific geometries. The numerical simulations showed a good agreement with the experimental data. The measurements were acquired at 1.5 and 3 T and with an encoding gradient varying between 3

  3. Single crystal magnetic structure and susceptibility of CoSe{sub 2}O{sub 5}

    SciTech Connect

    Rodriguez, Efrain E.; Cao, Huibo; Haiges, Ralf; Melot, Brent C.

    2016-04-15

    The structure of CoSe{sub 2}O{sub 5} consists of one-dimensional ribbons of edge-sharing CoO{sub 6} octahedra bound together by polyanionic subunits of Se{sub 2}O{sub 5}. Previous work on polycrystalline samples reported a canted antiferromagnetic arrangement of the magnetic moments below the ordering temperature of 8.5 K. Here, we report a single crystal investigation using variable temperature and field magnetic susceptibility and low-temperature neutron diffraction to more precisely characterize the nature of the magnetic ground state of CoSe{sub 2}O{sub 5}. Contrary to previous reports, we find that the single crystal magnetic structure shows no canting of the antiferromagnetic ground state, and in the process have identified several field-induced changes to the magnetization. We discuss these results in the context of the revised magnetic structure and highlight the importance of crystal growth for the accurate characterization of these properties.

  4. An adapted Coffey model for studying susceptibility losses in interacting magnetic nanoparticles

    PubMed Central

    Osaci, Mihaela

    2015-01-01

    Summary Background: Nanoparticles can be used in biomedical applications, such as contrast agents for magnetic resonance imaging, in tumor therapy or against cardiovascular diseases. Single-domain nanoparticles dissipate heat through susceptibility losses in two modes: Néel relaxation and Brownian relaxation. Results: Since a consistent theory for the Néel relaxation time that is applicable to systems of interacting nanoparticles has not yet been developed, we adapted the Coffey theoretical model for the Néel relaxation time in external magnetic fields in order to consider local dipolar magnetic fields. Then, we obtained the effective relaxation time. The effective relaxation time is further used for obtaining values of specific loss power (SLP) through linear response theory (LRT). A comparative analysis between our model and the discrete orientation model, more often used in literature, and a comparison with experimental data from literature have been carried out, in order to choose the optimal magnetic parameters of a nanoparticle system. Conclusion: In this way, we can study effects of the nanoparticle concentration on SLP in an acceptable range of frequencies and amplitudes of external magnetic fields for biomedical applications, especially for tumor therapy by magnetic hyperthermia. PMID:26665090

  5. Magnetic susceptibility and relation to initial 87Sr/86Sr for granitoids of the central Sierra Nevada, California

    USGS Publications Warehouse

    Bateman, P.C.; Dodge, F.C.W.; Kistler, R.W.

    1991-01-01

    Measurement of the magnetic susceptibility of more than 6000 samples of granitic rock from the Mariposa 1?? by 2?? quadrangle, which crosses the central part of the Sierra Nevada batholith between 37?? and 38??N latitude, shows that magnetic susceptibility values are above 10-2 SI units in the east and central parts of the batholith and drop abruptly to less than 10-3 SI units in the western foothills. In a narrow transitional zone, intermediate values (10-3 to 10-2) prevail. Magnetic susceptibility appears to decrease slightly westward within the zones of both high and low values. Magnetic susceptibility in plutonic rocks is chiefly a function of the abundance of magnetite, which depends, in turn, on the total iron content of the rocks and their oxidation ratio. Correlations of magnetic susceptibility with initial 87Sr/86Sr suggest that oxidation ratios have been inherited from the source regions for the magmas from which the rocks crystallized. Reduction of Fe3+ to Fe2+ by organic carbon or other reducing substances may also have affected magnetic susceptibility. -from Authors

  6. 150 000 Years of Loess Deposition in Interior Alaska as Told by Magnetic Susceptibility

    NASA Astrophysics Data System (ADS)

    Jensen, B. J. L.; Evans, M. E.; Froese, D. G.; Kravchinsky, V. A.

    2015-12-01

    The Halfway House loess deposit in interior Alaska contains a well-studied and complex paleomagnetic and paleoenvironmental record. Unfortunately, a lack of chronologic control has made it difficult to interpret the results of these studies. Detailed reexamination of stratigraphy, paleomagnetics and tephrostratigraphy reveals a relatively complete marine isotope stage (MIS) 6 to Holocene record constrained by the Old Crow (124 ± 10 ka), VT (106 ± 10 ka), Sheep Creek-Klondike (ca. 80 ka), Dominion Creek (77 ± 8 ka) and Dawson (ca. 30.2 cal ka BP) tephras. Two well-developed paleosols are shown to have formed during Marine Isotope Stages (MIS) 5e and 5a, while MIS 5c and 5b are either poorly represented or absent. A magnetic excursion is identified as the post-Blake excursion (94.1 ± 7.8 ka) and provides independent age control while adding to an increasing body of evidence that Alaskan loess is a detailed recorder of variations of the Earth's magnetic field over time. High-resolution magnetic susceptibility profiles placed into this new chronostratigraphic framework help refine loess deposition models for the interior of Alaska, while providing a means to correlate to previous magnetic studies at this site. The profiles support the hypothesis that wind-intensity is the main variable controlling fluctuations in susceptibility, with the highest susceptibility during peak glacial times and the lowest values in paleosols representing interglacials. However, the correlation of the susceptibility record to global marine d18O records is complicated by highly variable accumulation rates. We find the lowest rates of accumulation during peak warm and cold stages, while abrupt increases are associated with periods of transition between marine isotope stages, represented by intermediate susceptibility values. Previous accumulation models for Alaska have emphasized the role of surface roughness as an important variable controlling loess accumulation. However our results

  7. AC susceptibility as a tool to probe the dipolar interaction in magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Landi, Gabriel T.; Arantes, Fabiana R.; Cornejo, Daniel R.; Bakuzis, Andris F.; Andreu, Irene; Natividad, Eva

    2017-01-01

    The dipolar interaction is known to substantially affect the properties of magnetic nanoparticles. This is particularly important when the particles are kept in a fluid suspension or packed within nano-carriers. In addition to its usual long-range nature, in these cases the dipolar interaction may also induce the formation of clusters of particles, thereby strongly modifying their magnetic anisotropies. In this paper we show how AC susceptibility may be used to obtain information regarding the influence of the dipolar interaction in a sample. We develop a model which includes both aspects of the dipolar interaction and may be fitted directly to the susceptibility data. The usual long-range nature of the interaction is implemented using a mean-field approximation, whereas the particle-particle aggregation is modeled using a distribution of anisotropy constants. The model is then applied to two samples studied at different concentrations. One consists of spherical magnetite nanoparticles dispersed in oil and the other of cubic magnetite nanoparticles embedded on polymeric nanospheres. We also introduce a simple technique to address the presence of the dipolar interaction in a given sample, based on the height of the AC susceptibility peaks for different driving frequencies.

  8. Frequency dependence of the absorption component of the magnetic susceptibility in superconducting Y1Ba2Cu3O7

    NASA Astrophysics Data System (ADS)

    Ducharme, S.; Durny, R.; Hautala, J.; Symko, O. G.; Taylor, P. C.

    Measurements of an apparent magnetic-field-dependent absorption (imaginary part of the a.c. magnetic susceptibility) in superconducting Y1Ba2Cu3O7 ceramics and crystals are reported. The absorption, which is observed over a wide range of frequencies but only when the material is below the superconducting transition temperature, is characterized by a narrow (about 30 Gauss FWHM at 6 MHz) peak and a wide (greater than 10 kG) feature, both of which are maximum at zero magnetic field. The absorption strength varies approximately as one over the square root of the frequency. The unusual magnetic-field-dependent peaks in the magnetic susceptibility are inherent in single grains and therefore do not originate from intergrain Josephson currents or multigrain (i.e., percolative) loops. The susceptibility peaks must be due to bulk behavior, interactions at grain surfaces, intragrain current loops, or intragrain Josephson junctions.

  9. The utilisation of magnetic susceptibility as a vector toward mineralisation in common rock and ore forming minerals.

    NASA Astrophysics Data System (ADS)

    English, Matthew; Raub, Tim

    2015-04-01

    Aeromagnetic and ground magnetic surveys of mineral deposits and prospective terrain are a fundamental technique used in mining and economic geology. Inversion of survey data to source parameters (i.e., identification of ore zones) is often simplified by assuming a single, canonical or 'average' value for the magnetic susceptibility of each mappable unit. In some mineral deposits, canonical magnetic susceptibility values for several dominant ore and accessory minerals will be used to calculate mineral concentrations, 3-D distributions, etc. In general, magnetic susceptibility is widely recognised by economic geologists as a fundamental, easily-measured tool used to better understand the prospectivity of ore deposits. Despite this, the quantitative application of magnetic susceptibility, in context of detailed ore petrology, is still a developing field yet one with great potential. In order to assess to what extent, and in which systems, magnetic susceptibility is a vector toward mineralisation, we present aspects of an extensive database of single crystal and ore mineral aggregate samples. This reveals trends and magnitudes for several important rock-forming and ore-associated minerals during alteration, paragenesis, and enrichment. For example, current literature canonical values show that the magnetic susceptibility for pure quartz is strongly diamagnetic but ranges between -1.78x10-5 and -1.00x10-5 (k, vol. SI). However, metamorphic bull quartz and chrysoprase are commonly paramagnetic, with common values for chrysoprase as high as 2.11x10-3. In contrast, measurements from rose quartz samples are lower than those described for pure quartz with modal measurements as low as -2.08x10-5. Measurements for rock crystal quartz form a distribution best described by the canonical diamagnetic value of -1.40x10-5. Modelling should take into account that rock crystal quartz is rarely the best petrological analogue at deposit-scale or in a quartzose terrain. The difference

  10. Magnetic resonance characteristics and susceptibility weighted imaging of the brain in gadolinium encephalopathy.

    PubMed

    Samardzic, Dejan; Thamburaj, Krishnamoorthy

    2015-01-01

    To report the brain imaging features on magnetic resonance imaging (MRI) in inadvertent intrathecal gadolinium administration. A 67-year-old female with gadolinium encephalopathy from inadvertent high dose intrathecal gadolinium administration during an epidural steroid injection was studied with multisequence 3T MRI. T1-weighted imaging shows pseudo-T2 appearance with diffusion of gadolinium into the brain parenchyma, olivary bodies, and membranous labyrinth. Nulling of cerebrospinal fluid (CSF) signal is absent on fluid attenuation recovery (FLAIR). Susceptibility-weighted imaging (SWI) demonstrates features similar to subarachnoid hemorrhage. CT may demonstrate a pseudo-cerebral edema pattern given the high attenuation characteristics of gadolinium. Intrathecal gadolinium demonstrates characteristic imaging features on MRI of the brain and may mimic subarachnoid hemorrhage on susceptibility-weighted imaging. Identifying high dose gadolinium within the CSF spaces on MRI is essential to avoid diagnostic and therapeutic errors. Copyright © 2013 by the American Society of Neuroimaging.

  11. EPR and magnetic susceptibility investigation of iron-zinc-phosphate glass ceramics

    SciTech Connect

    Popa, A.; Stefan, R.; Bosca, M.; Dan, V.; Pop, V.; Pascuta, P.

    2013-11-13

    (Fe{sub 2}O{sub 3}){sub x}⋅(P{sub 2}O{sub 5}){sub 40}⋅(ZnO){sub 60−x} glass ceramics containing different concentrations of Fe{sub 2}O{sub 3} ranging from 1 to 20 mol% were obtained by heat treatment of glass samples at 650 °C for 2 h. The structural and magnetic properties of these glass ceramics were investigated by means of electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The EPR spectra of the studied samples revealed absorptions centered at g ≈ 2.0 and 4.3. The compositional variations of the intensity and line width of these absorption lines was interpreted in terms of the variation in Fe{sup 3+} and Fe{sup 2+} ions concentration in the glass ceramics as well as the interaction between the iron ions. The magnetic susceptibility data evidenced the presence of both Fe{sup 3+} and Fe{sup 2+} ions, with their relative content depending on the Fe{sub 2}O{sub 3} concentration. Dipolar and superexchange interactions involving iron ions were revealed depending on the iron content of the sample.

  12. Temporal Changes in Magnetic Susceptibility Induced by Microbial Manipulation of Iron Minerals

    NASA Astrophysics Data System (ADS)

    Enright, A. M.; Price, A.; Rosier, C. L.; Beaver, C. L.; Rossbach, S.; Ntarlagiannis, D.; Slater, L. D.; Lund, A.; Atekwana, E. A.

    2016-12-01

    Sequential iron extractions were used to determine the mineral and oxidation state speciation of iron in a series of cores from an oil spill site in Bemidji, Minnesota. Cores were collected over five years, from a location where a magnetic susceptibility (MS) anomaly was initially observed in 2011. Further field and laboratory MS measurements confirmed the magnetic anomaly, yet revealed a trend to lower MS values over the measured time frame. Conventional interpretation typically dictates that MS peaks are indicative of mixed-valence oxide mineral phases (i.e. magnetite or greigite) here the diminished, but persistent MS anomaly is most closely coupled with high concentrations of the fully-oxidized iron oxides, such as hematite. Microbiological community fingerprinting analysis (PCR-DGGE) of core samples suggest that the anomaly could result from methanogenically-derived magnetite occurring during water table high stand, which was then oxidized as water levels seasonally decreased. The diminished, but persistent presence of magnetic susceptibility anomaly appears to indicate the transformation of magnetite to iron oxides mediated by microbial metabolic processes (i.e. methanogenesis). We hypothesize that the MS response is related to the biological transformations of iron in the groundwater table fluctuation zone, and that the magnitude of the anomaly evolves along with oxidation state of iron in the sediments, and may serve as a record of the microbial manipulation of iron.

  13. Young Australian Indigenous Students' Growing Pattern Generalisations: The Role of Gesture When Generalising

    ERIC Educational Resources Information Center

    Miller, Jodie

    2014-01-01

    This paper explores how young Indigenous students' (Year 2 and 3) generalise growing patterns. Piagetian clinical interviews were conducted to determine how students articulated growing pattern generalisations. Two case studies are presented displaying how students used gesture to support and articulate their generalisations of growing patterns.…

  14. Design and development of novel MRI compatible zirconium- ruthenium alloys with ultralow magnetic susceptibility

    PubMed Central

    Li, H.F.; Zhou, F.Y.; Li, L.; Zheng, Y.F.

    2016-01-01

    In the present study, novel MRI compatible zirconium-ruthenium alloys with ultralow magnetic susceptibility were developed for biomedical and therapeutic devices under MRI diagnostics environments. The results demonstrated that alloying with ruthenium into pure zirconium would significantly increase the strength and hardness properties. The corrosion resistance of zirconium-ruthenium alloys increased significantly. High cell viability could be found and healthy cell morphology observed when culturing MG 63 osteoblast-like cells and L-929 fibroblast cells with zirconium-ruthenium alloys, whereas the hemolysis rates of zirconium-ruthenium alloys are <1%, much lower than 5%, the safe value for biomaterials according to ISO 10993-4 standard. Compared with conventional biomedical 316L stainless steel, Co–Cr alloys and Ti-based alloys, the magnetic susceptibilities of the zirconium-ruthenium alloys (1.25 × 10−6 cm3·g−1–1.29 × 10−6 cm3·g−1 for zirconium-ruthenium alloys) are ultralow, about one-third that of Ti-based alloys (Ti–6Al–4V, ~3.5 × 10−6 cm3·g−1, CP Ti and Ti–6Al–7Nb, ~3.0 × 10−6 cm3·g−1), and one-sixth that of Co–Cr alloys (Co–Cr–Mo, ~7.7 × 10−6 cm3·g−1). Among the Zr–Ru alloy series, Zr–1Ru demonstrates enhanced mechanical properties, excellent corrosion resistance and cell viability with lowest magnetic susceptibility, and thus is the optimal Zr–Ru alloy system as therapeutic devices under MRI diagnostics environments. PMID:27090955

  15. Design and development of novel MRI compatible zirconium- ruthenium alloys with ultralow magnetic susceptibility.

    PubMed

    Li, H F; Zhou, F Y; Li, L; Zheng, Y F

    2016-04-19

    In the present study, novel MRI compatible zirconium-ruthenium alloys with ultralow magnetic susceptibility were developed for biomedical and therapeutic devices under MRI diagnostics environments. The results demonstrated that alloying with ruthenium into pure zirconium would significantly increase the strength and hardness properties. The corrosion resistance of zirconium-ruthenium alloys increased significantly. High cell viability could be found and healthy cell morphology observed when culturing MG 63 osteoblast-like cells and L-929 fibroblast cells with zirconium-ruthenium alloys, whereas the hemolysis rates of zirconium-ruthenium alloys are <1%, much lower than 5%, the safe value for biomaterials according to ISO 10993-4 standard. Compared with conventional biomedical 316L stainless steel, Co-Cr alloys and Ti-based alloys, the magnetic susceptibilities of the zirconium-ruthenium alloys (1.25 × 10(-6) cm(3)·g(-1)-1.29 × 10(-6) cm(3)·g(-1) for zirconium-ruthenium alloys) are ultralow, about one-third that of Ti-based alloys (Ti-6Al-4V, ~3.5 × 10(-6) cm(3)·g(-1), CP Ti and Ti-6Al-7Nb, ~3.0 × 10(-6) cm(3)·g(-1)), and one-sixth that of Co-Cr alloys (Co-Cr-Mo, ~7.7 × 10(-6) cm(3)·g(-1)). Among the Zr-Ru alloy series, Zr-1Ru demonstrates enhanced mechanical properties, excellent corrosion resistance and cell viability with lowest magnetic susceptibility, and thus is the optimal Zr-Ru alloy system as therapeutic devices under MRI diagnostics environments.

  16. Design and development of novel MRI compatible zirconium- ruthenium alloys with ultralow magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Li, H. F.; Zhou, F. Y.; Li, L.; Zheng, Y. F.

    2016-04-01

    In the present study, novel MRI compatible zirconium-ruthenium alloys with ultralow magnetic susceptibility were developed for biomedical and therapeutic devices under MRI diagnostics environments. The results demonstrated that alloying with ruthenium into pure zirconium would significantly increase the strength and hardness properties. The corrosion resistance of zirconium-ruthenium alloys increased significantly. High cell viability could be found and healthy cell morphology observed when culturing MG 63 osteoblast-like cells and L-929 fibroblast cells with zirconium-ruthenium alloys, whereas the hemolysis rates of zirconium-ruthenium alloys are <1%, much lower than 5%, the safe value for biomaterials according to ISO 10993-4 standard. Compared with conventional biomedical 316L stainless steel, Co–Cr alloys and Ti-based alloys, the magnetic susceptibilities of the zirconium-ruthenium alloys (1.25 × 10‑6 cm3·g‑1–1.29 × 10‑6 cm3·g‑1 for zirconium-ruthenium alloys) are ultralow, about one-third that of Ti-based alloys (Ti–6Al–4V, ~3.5 × 10‑6 cm3·g‑1, CP Ti and Ti–6Al–7Nb, ~3.0 × 10‑6 cm3·g‑1), and one-sixth that of Co–Cr alloys (Co–Cr–Mo, ~7.7 × 10‑6 cm3·g‑1). Among the Zr–Ru alloy series, Zr–1Ru demonstrates enhanced mechanical properties, excellent corrosion resistance and cell viability with lowest magnetic susceptibility, and thus is the optimal Zr–Ru alloy system as therapeutic devices under MRI diagnostics environments.

  17. Momentum-dependent susceptibilities and magnetic exchange in bcc iron from supercell dynamical mean-field theory calculations

    NASA Astrophysics Data System (ADS)

    Belozerov, A. S.; Katanin, A. A.; Anisimov, V. I.

    2017-08-01

    We analyze the momentum and temperature dependences of the magnetic susceptibilities and magnetic exchange interaction in paramagnetic bcc iron by a combination of density functional theory and dynamical mean-field theory (DFT+DMFT). By considering a general derivation of the orbital-resolved effective model for spin degrees of freedom for Hund's metals, we relate momentum-dependent susceptibilities in the paramagnetic phase to the magnetic exchange. We then calculate nonuniform orbital-resolved susceptibilities at high-symmetry wave vectors by constructing appropriate supercells in the DMFT approach. Extracting the irreducible parts of susceptibilities with respect to Hund's exchange interaction, we determine the corresponding orbital-resolved exchange interactions, which are then interpolated to the whole Brillouin zone. Using the spherical model we estimate the temperature dependence of the resulting exchange between local moments.

  18. Self-assembled magnetic bead biosensor for measuring bacterial growth and antimicrobial susceptibility testing.

    PubMed

    Kinnunen, Paivo; McNaughton, Brandon H; Albertson, Theodore; Sinn, Irene; Mofakham, Sima; Elbez, Remy; Newton, Duane W; Hunt, Alan; Kopelman, Raoul

    2012-08-20

    Bacterial antibiotic resistance is one of the major concerns of modern healthcare worldwide, and the development of rapid, growth-based, antimicrobial susceptibility tests is key for addressing it. The cover image shows a self-assembled asynchronous magnetic bead rotation (AMBR) biosensor developed for rapid detection of bacterial growth. Using the biosensors, the minimum inhibitory concentration of a clinical E. coli isolate can be measured within two hours, where currently tests take 6-24 hours. A 16-well prototype is also constructed for simple and robust observation of the self-assembled AMBR biosensors.

  19. Magnetic susceptibility and neutron diffraction experiments on nuclear ordering in copper

    NASA Astrophysics Data System (ADS)

    Jyrkkio, Teppo

    Experimental curves of entropy and susceptibility versus temperature for copper nuclear spins down to the ordered state were obtained. Impurities and anomalous spin-lattice relaxation in copper at submilli-Kelvin temperatures were observed. Phase diagrams for spontaneous nuclear ordering in copper were derived. Nuclear antiferromagnetic ordering in copper was investigated. The feasibility of neutron diffraction experiments on ordered copper nuclei at nano-Kelvin temperature was studied. Neutron scattering experiments on nuclear magnets were carried out. Calibration and applications of polarized neutron thermometry at milli- and micro-Kelvin temperatures is described.Observation of nuclear antiferromagnetic order in copper by neutron diffraction at nano-Kelvin temparatures is reported.

  20. Technique for magnetic susceptibility determination in the highly doped semiconductors by electron spin resonance

    SciTech Connect

    Veinger, A. I.; Zabrodskii, A. G.; Tisnek, T. V.; Goloshchapov, S. I.; Semenikhin, P. V.

    2014-08-20

    A method for determining the magnetic susceptibility in the highly doped semiconductors is considered. It is suitable for the semiconductors near the metal - insulator transition when the conductivity changes very quickly with the temperature and the resonance line form distorts. A procedure that is based on double integration of the positive part of the derivative of the absorption line having a Dyson shape and takes into account the depth of the skin layer is described. Analysis is made for the example of arsenic-doped germanium samples at a rather high concentration corresponding to the insulator-metal phase transition.

  1. Magnetic susceptibility variation of MSW compost-amended soils: in-situ method for monitoring heavy metal contamination.

    PubMed

    Yoshida, Mitsuo; Jedidi, Naceur; Hamdi, Helmi; Ayari, Fethia; Hassen, Abdennaceur; M'Hiri, Ali

    2003-04-01

    Magnetic susceptibility was measured for agricultural soils in Mornag area, Tunisia, where the soils were partly amended by manure or compost obtained from municipal solid waste stabilisation ('MSW compost'). Our study indicates that natural non-treated soils and manure-amended soils are always low in magnetic susceptibility, but MSW compost-amended soils show higher values of this parameter. Actually, the increase of magnetic susceptibility shows a direct correspondence with the increasing of the amount of MSW compost added to the soil. According to the magnetic mineralogical investigation carried out by isothermal remanent magnetisation acquisition technique, higher magnetic susceptibility values are depending on an increase in ferromagnetic components such as either magnetite (beta-Fe3O4) or maghemite (gamma-Fe2O3) particles. The growth in content of these ferromagnetic components corresponds to an increase of the concentration of heavy metals in soils, which means that magnetic susceptibility indirectly indicates the concentration of heavy metals in MSW compost-amended soils.

  2. Magnetic susceptibility, artifact volume in MRI, and tensile properties of swaged Zr-Ag composites for biomedical applications.

    PubMed

    Imai, Haruki; Tanaka, Yoji; Nomura, Naoyuki; Doi, Hisashi; Tsutsumi, Yusuke; Ono, Takashi; Hanawa, Takao

    2017-02-01

    Zr-Ag composites were fabricated to decrease the magnetic susceptibility by compensating for the magnetic susceptibility of their components. The Zr-Ag composites with a different Zr-Ag ratio were swaged, and their magnetic susceptibility, artifact volume, and mechanical properties were evaluated by magnetic balance, three-dimensional (3-D) artifact rendering, and a tensile test, respectively. These properties were correlated with the volume fraction of Ag using the linear rule of mixture. We successfully obtained the swaged Zr-Ag composites up to the reduction ratio of 96% for Zr-4, 16, 36, 64Ag and 86% for Zr-81Ag. However, the volume fraction of Ag after swaging tended to be lower than that before swaging, especially for Ag-rich Zr-Ag composites. The magnetic susceptibility of the composites linearly decreased with the increasing volume fraction of Ag. No artifact could be estimated with the Ag volume fraction in the range from 93.7% to 95.4% in three conditions. Young's modulus, ultimate tensile strength (UTS), and 0.2% yield strength of Zr-Ag composites showed slightly lower values compared to the estimated values using a linear rule of mixture. The decrease in magnetic susceptibility of Zr and Ag by alloying or combining would contribute to the decrease of the Ag fraction, leading to the improvement of mechanical properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Effects of phase constitution on magnetic susceptibility and mechanical properties of Zr-rich Zr-Mo alloys.

    PubMed

    Suyalatu; Kondo, Ryota; Tsutsumi, Yusuke; Doi, Hisashi; Nomura, Naoyuki; Hanawa, Takao

    2011-12-01

    The effects of the microstructures and phases of Zr-rich Mo alloys on their magnetic susceptibilities and mechanical properties were investigated in order to develop a Zr alloy with low magnetic susceptibility for use in magnetic resonance imaging (MRI). The magnetic susceptibility was measured with a magnetic susceptibility balance, while mechanical properties were evaluated by a tensile test. The microstructure was evaluated with an X-ray diffractometer, an optical microscope, and a transmission electron microscope. Evaluation of the microstructures revealed that the α' phase was the dominant form at less than 2% Mo content in the as-cast alloy. The ω phase was formed in as-cast Zr-3Mo but disappeared with aging at 973 K. Magnetic susceptibility was reflected in the phase constitution: the susceptibility showed a local minimum at Zr-(0.5-1)Mo with mostly α' phase and a minimum at Zr-3Mo with mostly β and ω phases. The magnetic susceptibility of as-cast Zr-3Mo increased at 973 K due to disappearance of the ω phase. However, the susceptibility was still as low as that of as-cast Zr-1Mo. The ultimate tensile strength of α'-based Zr-Mo alloys was tailored from 674 to 970 MPa, and the corresponding elongation varied from 11.1% to 2.9%. Because Zr-Mo alloys containing ω phase were found, through tensile tests, to be brittle this phase should be avoided, irrespective of the low magnetic susceptibility, in order to maintain mechanical reliability. Elongation of the Zr-3Mo alloy was dramatically improved when the phase constitution was changed to α and β phases by aging at 973 K for 86.4 ks. The magnetic susceptibilities of the α'-based Zr-Mo alloys are one-third those of Ti-6Al-4V and Ti-6Al-7Nb, and thus these Zr alloys are useful for medical devices under MRI. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  4. Supersymmetric backgrounds and generalised special holonomy

    NASA Astrophysics Data System (ADS)

    Coimbra, André; Strickland-Constable, Charles; Waldram, Daniel

    2016-06-01

    We define intrinsic torsion in generalised geometry and use it to introduce a new notion of generalised special holonomy. We then consider generic warped supersymmetric flux compactifications of M theory and Type II of the form {{{R}}}D-{1,1}× M. Using the language of {E}d(d)× {{{R}}}+ generalised geometry, we show that, for D≥slant 4, preserving minimal supersymmetry is equivalent to the manifold M having generalised special holonomy and list the relevant holonomy groups. We conjecture that this result extends to backgrounds preserving any number of supersymmetries. As a prime example, we consider { N }=1 in D = 4. The corresponding generalised special holonomy group is {SU}(7), giving the natural M theory extension to the notion of a G 2 manifold, and, for Type II backgrounds, reformulating the pure spinor {SU}(3)× {SU}(3) conditions as an integrable structure.

  5. RECONSTRUCTING PALEO-SMT POSITIONS ON THE CASCADIA MARGIN USING MAGNETIC SUSCEPTIBILITY

    SciTech Connect

    Johnson, Joel; Phillips, Stephen

    2014-09-30

    Magnetic susceptibility (κ) is a mixed signal in marine sediments, representing primary depositional and secondary diagenetic processes. Production of hydrogen sulfide via anaerobic oxidation of methane (AOM) at the sulfate-methane transition (SMT) and organoclastic sulfate reduction above the SMT can result in the dissolution of iron oxides, altering κ in sediments in methane gas and gas hydrate bearing regions. We investigated records of κ on the Cascadia margin (ODP Sites 1249 and 1252; IODP Site 1325) using a Zr/Rb heavy mineral proxy from XRF core scanning to identify intervals of primary detrital magnetic susceptibility and intervals and predict intervals affected by magnetite dissolutions. We also measured total sulfur content, grain size distributions, total organic carbon (TOC) content, and magnetic mineral assemblage. The upper 100 m of Site 1252 contains a short interval of κ driven by primary magnetite, with multiple intervals (> 90 m total) of decreased κ correlated with elevated sulfur content, consistent with dissolution of magnetite and re-precipitation of pyrite. In the upper 90 m of Site 1249, κ is almost entirely altered by diagenetic processes, with much of the low κ explained by a high degree of pyritization, and some intervals affected by the precipitation of magnetic iron sulfides. At Site 1325, κ between 0-20 and 51-73 mbsf represents primary mineralogy, and in the interval 24-51 mbsf, κ may be reduced due to pyritization. This integrated approach allows for a prediction of primary κ and the amount of κ loss at each site when compared to actual κ measurements. In the case of magnetite dissolution and full pyritization, these drawdowns in κ are supported by sulfur measurements, and the exposure times of magnetite to hydrogen sulfide can be modeled. The presence of methane and methane hydrates at these sites, as well as large variations in TOC content, suggest that the past migration rates of the SMT and variation in sulfate

  6. [Heavy Metals Accmultio in the Caofeidian Reclamation Soils: Indicated by Soil Magnetic Susceptibility].

    PubMed

    Xue, Yong; Zhou, Qian; Li, Yuan; Zhang, Hai-bo; Hu, Xue-feng; Luo, Yong-ming

    2016-04-15

    The environmental magnetism method has been widely applied to identify soil heavy metal pollution, which is characterized by simplicity, efficiency, non-destructivity and sensitivity. The present study used magnetic susceptibility to assess the accumulation of heavy metals in soils of the Caofeidian industrial zone which is a typical reclamation area in northern China. The study area was divided into three sub-zones based on the function, including industrial zone, living zone, natural tidal flat and wetland. A total of 35 topsoil samples (0-10 cm) and 3 soil profiles were collected from the three sub-zones. Magnetic susceptibility (X(lf)), iron oxide (Fe2O3) contents and heavy metals contents (Cr, Ni, Cu, Zn, As, Pb, Mn and V) of the samples were analyzed. The results showed that X(lf) values and heavy metals contents exhibited higher spatial variability in the top soil of the industrial zone, indicating the severe impacts of industrial activities. In the soil profiles of the industrial and living zones, all heavy metals were enriched to different degrees in the upper layer (0-20 cm). However, there was no significant change of heavy metal contents in the soil profiles of tidal flat which was far from the industrial area. The X(lf) value was significantly (P < 0.01) positively correlated with the contents of Fe2O3, Ni, Cu, As and V in the industrial top soil. This indicated that X(lf) could be used as an indicator for heavy metal accumulation in the industrial zone. However, the X(lf) value was not suitable to be an indicator to show the heavy metal accumulation in the soils of living zone and natural tidal flat. This might be associated with the different sources of magnetic materials among the different sub-zones and the special characteristics of the soils in the tidal flat and wetland.

  7. Exploiting the Temperature Dependence of Magnetic Susceptibility to Control Convection in Fundamental Studies of Solidification Phenomena

    NASA Technical Reports Server (NTRS)

    Seybert, C. D.; Evans, J. W.; Leslie, Fred; Jones, W. K., Jr.

    2000-01-01

    It is well known that convection is a dominant mass transport mechanism when materials are solidified on Earth's surface. This convection is caused by gradients in density (and therefore gravitational force) that are brought about by gradients in temperature, composition or both. Diffusion of solute is therefore dwarfed by convection and the study of fundamental parameters, such as dendrite tip shape and growth velocity in the absence of convection is nearly impossible. Significant experimental work has therefore been carried out in orbiting laboratories with the intent of minimizing convection by minimizing gravity. One of the best known experiments of this kind is the Isothermal Dendritic Growth Experiment (IDGE), supported by NASA. Naturally such experiments are costly and one objective of the present investigation is to develop an experimental method whereby convection can be- halted, in solidification and other experiments, on the surface. A second objective is to use the method to minimize convection resulting from the residual accelerations suffered by experiments in microgravity. The method to be used to minimize convection relies on the dependence of the magnetic susceptibility of a fluid on temperature or composition (whichever is driving convection). All materials experience a force when placed in a magnetic field gradient. The direction and magnitude of that force depend on the magnetic susceptibility of the material. Consequently the force will vary if the susceptibility varies with temperature or composition. With a magnetic field gradient in the right direction (typically upward) and of the right magnitude, this variation in the magnetic force can be made to exactly cancel the variation in the gravitational force. Expressed another way, normal buoyancy is exactly countered by a "magnetic buoyancy". To demonstrate the principle, a solution of MnC12 in water has been used. First the variation of the susceptibility of this paramagnetic solution with

  8. Exploiting the Temperature Dependence of Magnetic Susceptibility to Control Convection in Fundamental Studies of Solidification Phenomena

    NASA Technical Reports Server (NTRS)

    Seybert, C. D.; Evans, J. W.; Leslie, Fred; Jones, W. K., Jr.

    2000-01-01

    It is well known that convection is a dominant mass transport mechanism when materials are solidified on Earth's surface. This convection is caused by gradients in density (and therefore gravitational force) that are brought about by gradients in temperature, composition or both. Diffusion of solute is therefore dwarfed by convection and the study of fundamental parameters, such as dendrite tip shape and growth velocity in the absence of convection is nearly impossible. Significant experimental work has therefore been carried out in orbiting laboratories with the intent of minimizing convection by minimizing gravity. One of the best known experiments of this kind is the Isothermal Dendritic Growth Experiment (IDGE), supported by NASA. Naturally such experiments are costly and one objective of the present investigation is to develop an experimental method whereby convection can be- halted, in solidification and other experiments, on the surface. A second objective is to use the method to minimize convection resulting from the residual accelerations suffered by experiments in microgravity. The method to be used to minimize convection relies on the dependence of the magnetic susceptibility of a fluid on temperature or composition (whichever is driving convection). All materials experience a force when placed in a magnetic field gradient. The direction and magnitude of that force depend on the magnetic susceptibility of the material. Consequently the force will vary if the susceptibility varies with temperature or composition. With a magnetic field gradient in the right direction (typically upward) and of the right magnitude, this variation in the magnetic force can be made to exactly cancel the variation in the gravitational force. Expressed another way, normal buoyancy is exactly countered by a "magnetic buoyancy". To demonstrate the principle, a solution of MnC12 in water has been used. First the variation of the susceptibility of this paramagnetic solution with

  9. Influence of the angle between cleavage and bedding on the anisotropy of magnetic susceptibility and the degree of phyllosilicate preferred orientation

    NASA Astrophysics Data System (ADS)

    Debacker, T. N.; Sintubin, M.

    2003-04-01

    Due to the common scarcity of strain markers and the often fine-grained lithologies, performing strain analyses in slate belts may be difficult. As an alternative, one may use methods such as phyllosilicate preferred orientation (X-ray pole figure goniometry) and anisotropy of magnetic susceptibility (AMS). However, a large number of factors influence the results of these analytical methods. One of the factors is the angle between cleavage and bedding. The study area is the Brabant Massif, a single-phase deformed, low-grade slate belt in N-Belgium consisting of a steep Cambrian core surrounded by Ordovician-Silurian sequences. In the southern part of the Cambrian core, the transition between steeply plunging folds, considered typical for the steep core, and gently plunging folds, considered characteristic for the peripheral Ordovician-Silurian sequences, occurs in homogeneous mudstones of the Lower Cambrian Oisquercq Formation. In these deposits mica and chlorite show a similar degree of preferred orientation. Mica is always aligned along the cleavage, whereas chlorite is aligned along the bedding. Clear intersection pole figure patterns characterise samples with large cleavage/bedding angles, whereas flattening fabrics only become apparent for samples with small cleavage/bedding angles. For both mica and chlorite, the degree of preferred orientation is higher for samples with small cleavage/bedding angles. The magnetic fabric shows prolate susceptibility ellipsoids for samples with large cleavage/bedding angles and oblate susceptibility ellipsoids for samples with small cleavage/bedding angles (cf. Housen et al., 1993). The short axis of the susceptibility ellipsoid is generally oriented perpendicular to bedding, occasionally perpendicular to cleavage or with an intermediate orientation. The long axis of the susceptibility ellipsoid is always parallel to the cleavage/bedding intersection. The shape parameter T shows an almost linear relationship with respect to

  10. Magnetic resonance susceptibility weighted imaging in neurosurgery: current applications and future perspectives.

    PubMed

    Di Ieva, Antonio; Lam, Timothy; Alcaide-Leon, Paula; Bharatha, Aditya; Montanera, Walter; Cusimano, Michael D

    2015-12-01

    Susceptibility weighted imaging (SWI) is a relatively new imaging technique. Its high sensitivity to hemorrhagic components and ability to depict microvasculature by means of susceptibility effects within the veins allow for the accurate detection, grading, and monitoring of brain tumors. This imaging modality can also detect changes in blood flow to monitor stroke recovery and reveal specific subtypes of vascular malformations. In addition, small punctate lesions can be demonstrated with SWI, suggesting diffuse axonal injury, and the location of these lesions can help predict neurological outcome in patients. This imaging technique is also beneficial for applications in functional neurosurgery given its ability to clearly depict and differentiate deep midbrain nuclei and close submillimeter veins, both of which are necessary for presurgical planning of deep brain stimulation. By exploiting the magnetic susceptibilities of substances within the body, such as deoxyhemoglobin, calcium, and iron, SWI can clearly visualize the vasculature and hemorrhagic components even without the use of contrast agents. The high sensitivity of SWI relative to other imaging techniques in showing tumor vasculature and microhemorrhages suggests that it is an effective imaging modality that provides additional information not shown using conventional MRI. Despite SWI's clinical advantages, its implementation in MRI protocols is still far from consistent in clinical usage. To develop a deeper appreciation for SWI, the authors here review the clinical applications in 4 major fields of neurosurgery: neurooncology, vascular neurosurgery, neurotraumatology, and functional neurosurgery. Finally, they address the limitations of and future perspectives on SWI in neurosurgery.

  11. Magnetic susceptibility and element composition mangrove sediments in Malang, East Java

    NASA Astrophysics Data System (ADS)

    Azzahro, Rosyida; Zulaikah, Siti; Diantoro, Markus; Budi, Pranitha Septiana

    2017-07-01

    Mangrove sediment has a unique environmental absorption characteristics, as it has two sources of sediment which are from allocthonous sediment and authochtonous sediment. In this research, the mangrove sediment samples are taken from Clungup Mangrove Conservation in Malang, East Java, Indonesia. The samples are taken from four spots around the mouth of the river, and four spots around mangrove conservation. Those samples are analyzed based on the magnetic characteristics and the element composition to reveal the magnetic properties and element composition so in the future they can be used as indicators to trace the source of magnetic minerals that are precipitated in the mangrove ecosystem. The magnetic susceptibility value based on mass for mangrove sediment around the river area h as the range of (38,8-2130)×10-8m3kg-1, while for the conservation area has the range of (0,97-122,5)×10-8m3kg-1. Based on XRF analysis, the mangrove sediment both from the river area and mangrove conservation area has a non-metallic element S, Br, metallic element Ca, Si, Al, K, Ti, Sr, and heavy metallic element Fe, Ni, Cu, Cr, Zn, Zr, Mn, and V, with the highest concentration of Fe element followed by Ca, Al, Si, and Ti.

  12. Thermomagnetic behavior of magnetic susceptibility - heating rate and sample size effects

    NASA Astrophysics Data System (ADS)

    Jordanova, Diana; Jordanova, Neli

    2015-12-01

    Thermomagnetic analysis of magnetic susceptibility k(T) was carried out for a number of natural powder materials from soils, baked clay and anthropogenic dust samples using fast (11oC/min) and slow (6.5oC/min) heating rates available in the furnace of Kappabridge KLY2 (Agico). Based on the additional data for mineralogy, grain size and magnetic properties of the studied samples, behaviour of k(T) cycles and the observed differences in the curves for fast and slow heating rate are interpreted in terms of mineralogical transformations and Curie temperatures (Tc). The effect of different sample size is also explored, using large volume and small volume of powder material. It is found that soil samples show enhanced information on mineralogical transformations and appearance of new strongly magnetic phases when using fast heating rate and large sample size. This approach moves the transformation at higher temperature, but enhances the amplitude of the signal of newly created phase. Large sample size gives prevalence of the local micro- environment, created by evolving gases, released during transformations. The example from archeological brick reveals the effect of different sample sizes on the observed Curie temperatures on heating and cooling curves, when the magnetic carrier is substituted magnetite (Mn0.2Fe2.70O4). Large sample size leads to bigger differences in Tcs on heating and cooling, while small sample size results in similar Tcs for both heating rates.

  13. Strain, anisotropy of anhysteretic remanence, and anisotropy of magnetic susceptibility in a slaty tuff

    NASA Astrophysics Data System (ADS)

    Nakamura, Norihiro; Borradaile, Graham J.

    2001-10-01

    Finite strain data for the Borrowdale slaty tuffs compare variably with the anisotropy of magnetic susceptibility (AMS) and anisotropy of anhysteretic remanent magnetization (AARM). Finite strain, determined from lapilli-rims, shows that slaty cleavage was formed by coaxial flattening with X: Y: Z in the ratio 1.74:1.21 and 0.48. AARM was measured in different coercivity windows to isolate contributions from magnetite of different grain sizes: (a) 0-3 mT for multi-domain (MD), (b) 3-15 mT for pseudo-single-domain (PSD) and (c) 15-60 mT for single-domain (SD). AMS combines petrofabric contributions from silicates as well as magnetite. Magnetite grains may grow, recrystalize or rearrange domains after or during metamorphism and postdate or overlap with the silicate's fabric evolution. AMS foliation, defined by paramagnetic chlorites, is parallel to slaty cleavage. AARM foliation for SD magnetites is offset clockwise from AMS foliation, which may reflect late crystallization or domain-rearrangement of magnetites in response to a latter noncoaxial increment. AMS fabric-shape consistently corresponds to strain ellipsoids and indicates that the strain-induced AMS fabric is susceptible to the change of oblateness rather than strain intensity. Furthermore, investigation of the different AARM subfabrics and finite strain shows that only SD magnetite's AARM correlates with finite strain, and weakly at that.

  14. Lake Michigan's late Quaternary limnological and climate history from ostracode, oxygen isotope, and magnetic susceptibility

    USGS Publications Warehouse

    Forester, Richard M.; Colman, Steven M.; Reynolds, Richard L.; Keigwin, Loyd D.

    1994-01-01

    The limnology of Lake Michigan has changed dramatically since the late Pleistocene in response to the expansion and contraction of continental glaciers, to differential isostatic rebound, and to climate change. The lake sediment's stratigraphic trends, magnetic susceptibility, δ18O, and ostracode species abundance ratios provide criteria to identify the lake's response to glacial ice and to differential isostatic rebound. The latter phenomena dominate the lake's late Pleistocene and early Holocene history. The lake's hydrological budget provides the primary linkage between the lake and climate, particularly effective moisture. Dissolved salts were stored in the lake's water column when the lake's output shifted toward evaporation, but were flushed when output shifted toward outflow. The lake's salt storage history may be interpreted from some ostracode, δ18O, and magnetic susceptibility records found in sediment cores. Climate change influenced the entire lake's limnological history, but became the primary limnological driver from about the middle-Holocene to the present. The complex limnological history of Lake Michigan resulted in substantial changes in the ostracode species assemblages; from about 12,000 ka to about 5,500 ka, five ostracode intervals can be identified. These ostracode intervals provide a within-lake biostratigraphy and a stratigraphic reference for reconstruction of the paleoenvironmental dynamics of the lake.

  15. Geophysical monitoring of simulated graves with resistivity, magnetic susceptibility, conductivity and GPR in Colombia, South America.

    PubMed

    Molina, Carlos Martin; Pringle, Jamie K; Saumett, Miguel; Evans, Gethin T

    2016-04-01

    In most Latin American countries there are significant numbers of both missing people and forced disappearances, ∼71,000 Colombia alone. Successful detection of buried human remains by forensic search teams can be difficult in varying terrain and climates. Three clandestine burials were simulated at two different depths commonly encountered in Latin America. In order to gain critical knowledge of optimum geophysical detection techniques, burials were monitored using: ground penetrating radar, magnetic susceptibility, bulk ground conductivity and electrical resistivity up to twenty-two months post-burial. Radar survey results showed good detection of modern 1/2 clothed pig cadavers throughout the survey period on 2D profiles, with the 250MHz antennae judged optimal. Both skeletonised and decapitated and burnt human remains were poorly imaged on 2D profiles with loss in signal continuity observed throughout the survey period. Horizontal radar time slices showed good anomalies observed over targets, but these decreased in amplitude over the post-burial time. These were judged due to detecting disturbed grave soil rather than just the buried targets. Magnetic susceptibility and electrical resistivity were successful at target detection in contrast to bulk ground conductivity surveys which were unsuccessful. Deeper burials were all harder to image than shallower ones. Forensic geophysical surveys should be undertaken at suspected burial sites. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  16. Anisotropy of Magnetic Susceptibility Studies in Lava Flows of the Eastern Anatolia Region, Turkey

    NASA Astrophysics Data System (ADS)

    Ucar, Hakan; Cengiz Cinku, Mualla

    2017-04-01

    Eastern Anatolia comprises one of the high plateaus of the Alpine-Himalaya mountain belt with an average elevation of 2 km above the sea level. Available geochronologic data indicate that the volcanism started in the south of the region around the north of Lake Van and continued towards the norths in a age interval of 15.0 Ma to 0.4 Ma. The products are exposed as stratovolcanoes like Agri, Tendurek, Suphan and Girekol with the eruption of andesitic to rhyolitic lavas, ignimbrites and basaltic lava flows. In this study, anisotropy of magnetic susceptibility measurements were carried out on different lava flows (Tendurek, Girekol and Suphan) to determine the flow direction of lavas. It has been shown that the direction of maximum susceptibility is associated with magma flow direction in the vertical direction, while a horizontal flow direction is predicted for the volcano structure of Suphan. Anisotropy of magnetic measurements show a trend of lineation towards the center of the projection and shallow-dipping foliations which are largely scattered.

  17. Noncontact technique for measuring the electrical resistivity and magnetic susceptibility of electrostatically levitated materials.

    PubMed

    Rustan, G E; Spyrison, N S; Kreyssig, A; Prozorov, R; Goldman, A I

    2012-10-01

    We describe the development of a new method for measuring the electrical resistivity and magnetic susceptibility of high temperature liquids and solids. The technique combines a tunnel diode oscillator with an electrostatic levitation furnace to perform noncontact measurements on spherical samples 2-3 mm in diameter. The tank circuit of the oscillator is inductively coupled to the sample, and measurements of the oscillator frequency as a function of sample temperature can be translated into changes in the sample's electrical resistivity and magnetic susceptibility. Particular emphasis is given on the need to improve the positional stability of the levitated samples, as well as the need to stabilize the temperature of the measurement coil. To demonstrate the validity of the technique, measurements have been performed on solid spheres of pure zirconium and low-carbon steel. In the case of zirconium, while absolute values of the resistivity were not determined, the temperature dependence of the resistivity was measured over the range of 640-1770 K and found to be in good agreement with literature data. In the case of low-carbon steel, the ferromagnetic-paramagnetic transition was clearly observable and, when combined with thermal data, appears to occur simultaneously with the solid-solid structural transition.

  18. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    SciTech Connect

    Ohno, S.; Shimakura, H.; Tahara, S.; Okada, T.

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  19. Magnetic Susceptibility of Ancient and Modern Potsherds Using a Fast, Cheap and Portable Probe

    NASA Astrophysics Data System (ADS)

    Glover, P. W.

    2009-05-01

    It has been estimated that there exist over 100 million ancient potsherds in various collections worldwide, many of which have never been studied and for which the provenance is ambiguous or unknown. Indeed, many collections are extremely badly catalogued or completely mixed-up. We have been using a novel portable probe to measure the magnetic susceptibility and electrical conductivity of potsherds in the hope that this fast, cheap and portable measurement can provide data that will help to sort similar looking potsherds into sets in a manner which may help to define their provenance. The probe, which resembles a firearm, uses the Hall effect to make a non-destructive measurement on the potsherd. The probe is attached to an Dell Axim X51 PDA, which runs software that allows the measurement to be carried out and logged. Each measurement, which is made by pressing a button on the gun, takes only a few seconds. We have made measurements on three suites of ancient potsherds as well as a suite of modern potsherds that were created by using a garden centre and a hammer! In each case a set of 5 stacked measurements were taken on the inside and outside faces of the potsherd in two perpendicular directions. Potsherds which were either (i) so flat that the inside and outside could not be distinguished, (ii) so curved (radius of curvature less than 5 cm) that the probe tip could not approach the surface sufficiently closely, or (iii) smaller than the probe tip, were excluded from the suite of measurements. Each suite contained over 50 measureable potsherds. All measurements were completed within one day. In this pilot study we found that (1) each suite was represented by a normal distribution of magnetic susceptibility values, (2) the four different suites could be distinguished statistically on the basis of their magnetic susceptibility measurements, but (3) the distinction was not sufficiently powerful to separate all potsherds (i.e., there was a significant overlap of the

  20. Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids

    NASA Astrophysics Data System (ADS)

    Sindt, Julien O.; Camp, Philip J.; Kantorovich, Sofia S.; Elfimova, Ekaterina A.; Ivanov, Alexey O.

    2016-06-01

    The frequency-dependent magnetic susceptibility of a ferrofluid is calculated under the assumption that the constituent particles undergo Brownian relaxation only. Brownian-dynamics simulations are carried out in order to test the predictions of a recent theory [A. O. Ivanov, V. S. Zverev, and S. S. Kantorovich, Soft Matter 12, 3507 (2016), 10.1039/C5SM02679B] that includes the effects of interparticle dipole-dipole interactions. The theory is based on the so-called modified mean-field approach and possesses the following important characteristics: in the low-concentration, noninteracting regime, it gives the correct single-particle Debye-theory results; it yields the exact leading-order results in the zero-frequency limit; it includes particle polydispersity correctly from the outset; and it is based on firm theoretical foundations allowing, in principle, systematic extensions to treat stronger interactions and/or higher concentrations. The theory and simulations are compared in the case of a model monodisperse ferrofluid, where the effects of interactions are predicted to be more pronounced than in a polydisperse ferrofluid. The susceptibility spectra are analyzed in detail in terms of the low-frequency behavior, the position of the peak in the imaginary (out-of-phase) part, and the characteristic decay time of the magnetization autocorrelation function. It is demonstrated that the theory correctly predicts the trends in all of these properties with increasing concentration and dipolar coupling constant, the product of which is proportional to the Langevin susceptibility χL. The theory is in quantitative agreement with the simulation results as long as χL≲1 .

  1. Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids.

    PubMed

    Sindt, Julien O; Camp, Philip J; Kantorovich, Sofia S; Elfimova, Ekaterina A; Ivanov, Alexey O

    2016-06-01

    The frequency-dependent magnetic susceptibility of a ferrofluid is calculated under the assumption that the constituent particles undergo Brownian relaxation only. Brownian-dynamics simulations are carried out in order to test the predictions of a recent theory [A. O. Ivanov, V. S. Zverev, and S. S. Kantorovich, Soft Matter 12, 3507 (2016)1744-683X10.1039/C5SM02679B] that includes the effects of interparticle dipole-dipole interactions. The theory is based on the so-called modified mean-field approach and possesses the following important characteristics: in the low-concentration, noninteracting regime, it gives the correct single-particle Debye-theory results; it yields the exact leading-order results in the zero-frequency limit; it includes particle polydispersity correctly from the outset; and it is based on firm theoretical foundations allowing, in principle, systematic extensions to treat stronger interactions and/or higher concentrations. The theory and simulations are compared in the case of a model monodisperse ferrofluid, where the effects of interactions are predicted to be more pronounced than in a polydisperse ferrofluid. The susceptibility spectra are analyzed in detail in terms of the low-frequency behavior, the position of the peak in the imaginary (out-of-phase) part, and the characteristic decay time of the magnetization autocorrelation function. It is demonstrated that the theory correctly predicts the trends in all of these properties with increasing concentration and dipolar coupling constant, the product of which is proportional to the Langevin susceptibility χ_{L}. The theory is in quantitative agreement with the simulation results as long as χ_{L}≲1.

  2. Magnetic susceptibility induced white matter MR signal frequency shifts--experimental comparison between Lorentzian sphere and generalized Lorentzian approaches.

    PubMed

    Luo, J; He, X; Yablonskiy, D A

    2014-03-01

    The nature of the remarkable phase contrast in high-field gradient echo MRI studies of human brain is a subject of intense debates. The generalized Lorentzian approach (He and Yablonskiy, Proc Natl Acad Sci USA 2009;106:13558-13563) provides an explanation for the anisotropy of phase contrast, the near absence of phase contrast between white matter and cerebrospinal fluid, and changes of phase contrast in multiple sclerosis. In this study, we experimentally validate the generalized Lorentzian approach. The Generalized Lorentzian Approach suggests that the local contribution to frequency shifts in white matter does not depend on the average tissue magnetic susceptibility (as suggested by Lorentzian sphere approximation), but on the distribution and symmetry of magnetic susceptibility inclusions at the cellular level. We use ex vivo rat optic nerve as a model system of highly organized cellular structure containing longitudinally arranged myelin and neurofilaments. The nerve's cylindrical shape allowed accurate measurement of its magnetic susceptibility and local frequency shifts. We found that the volume magnetic susceptibility difference between nerve and water is -0.116 ppm, and the magnetic susceptibilities of longitudinal components are -0.043 ppm in fresh nerve, and -0.020 ppm in fixed nerve. The frequency shift observed in the optic nerve as a representative of white matter is consistent with generalized Lorentzian approach but inconsistent with Lorentzian sphere approximation. Copyright © 2013 Wiley Periodicals, Inc.

  3. Magnetic Susceptibility Induced White Matter MR Signal Frequency Shifts - Experimental Comparison between Lorentzian Sphere and Generalized Lorentzian Approaches

    PubMed Central

    Luo, J.; He, X.; Yablonskiy, D.A.

    2013-01-01

    Purpose The nature of the remarkable phase contrast in high field gradient echo MRI studies of human brain is a subject of intense debates. The Generalized Lorentzian Approach (GLA) (He & Yablonskiy, PNAS 2009;106:13558) provides an explanation for the anisotropy of phase contrast, the near absence of phase contrast between WM and CSF, and changes of phase contrast in multiple sclerosis. In this study we experimentally validate the GLA. Theory and Methods The GLA suggests that the local contribution to frequency shifts in WM does not depend on the average tissue magnetic susceptibility (as suggested by Lorentzian sphere approximation), but on the distribution and symmetry of magnetic susceptibility inclusions at the cellular level. We use ex vivo rat optic nerve as a model system of highly organized cellular structure containing longitudinally arranged myelin and neurofilaments. The nerve's cylindrical shape allowed accurate measurement of its magnetic susceptibility and local frequency shifts. Results We found that the volume magnetic susceptibility difference between nerve and water is −0.116ppm, and the magnetic susceptibilities of longitudinal components are −0.043ppm in fresh nerve, and −0.020ppm in fixed nerve. Conclusion The frequency shift observed in the optic nerve as a representative of WM is consistent with GLA but inconsistent with Lorentzian sphere approximation. PMID:23637001

  4. Uncertainty of spatial distributions of soil magnetic susceptibility in areas of different type of land cover and anthropogenic pressure

    NASA Astrophysics Data System (ADS)

    Zawadzki, Jaroslaw; Fabijańczyk, Piotr

    2016-04-01

    There is still a high interest in the improvement of soil magnetometry procedures that would increase its accuracy. Soil magnetometry is usually used as a fast screening method that is used to assess the degree of soil pollution. As the magnetometric measurements do not provide the exact information about the concentration of elements in soil, it is very important to determine the uncertainty of the spatial distributions of soil magnetic susceptibility. The goal of this study was to analyze and present geostatistical methods of assessing the uncertainty of spatial distribution of soil magnetic susceptibility in areas of different land cover and anthropogenic pressure. In particular, spatial distributions of magnetic susceptibility measured on the soil surface using a MS2D Bartington device were calculated using indicator methods that make it possible to calculate the probability of exceeding the critical levels of soil magnetic susceptibility. Measurements were performed in areas located in the Upper Silesian Industrial Area in Poland, and in Norway. In these areas soil magnetic susceptibility was measured on the soil surface using a MS2D Bartington device. Additionally, soil samples were taken in order to perform chemical measurements that included the determination of a concentration of selected elements. Acknowledgment The research leading to these results has received funding from the Polish-Norwegian Research Programme operated by the National Centre for Research and Development underthe Norwegian Financial Mechanism 2009-2014 in the frame of Project IMPACT - Contract No Pol-Nor/199338/45/2013.

  5. Magnetic fabric of selected loess/paleosol sections as studied by AMS, anisotropy of frequency-dependent susceptibility and anisotropy of out-of-phase susceptibility

    NASA Astrophysics Data System (ADS)

    Chadima, M.; Hrouda, F.; Jezek, J.

    2015-12-01

    The preferred orientation of magnetic minerals in loess/paleosol sequencies can be studied through the anisotropy of magnetic susceptibility (AMS), which can be above all employed in the investigation of the dynamics of the eolian deposition including the changes in paleowind directions. In addition, it can be used in the indication of the post-depositional magnetic fabric re-working, or in tracing the magnetic fabric changes during pedogenesis. Recently developed techniques using anisotropy of frequency-dependent susceptibility (fdAMS) and anisotropy of out-of-phase susceptibility (opAMS) can assess the magnetic sub-fabrics of viscous particles on transition between SP and SSD. The width of the particle size interval investigated by the fdAMS is controlled by the operating frequencies used and their differences. In case of opAMS, the interval is always narrower than that in fdAMS and depends also on the operating frequency used. In three loess/paleosol sequences investigated in the Czech Republic, the degrees of AMS, fdAMS, and opAMS are significantly lower in paleosols than in loess horizons. This indicates that the preferred orientation of magnetic particles created during pedogenesis is much weaker than that of the particles deposited during loess formation. In addition, the degrees of fdAMS and opAMS are much higher than that of AMS. This may indicate strong anisotropy of viscous magnetic particles, because the fdAMS and opAMS are primarily controlled by them. The degree of AMS of the whole rock is low due to compensation effects of SP and SSD particles, whose grain anisotropies are anti-coaxial. The principal directions of AMS, fdAMS, and opAMS are mostly roughly co-axial suggesting more or less identical origins of magnetic sub-fabrics according to grain size. Less frequently, the principal directions of fdAMS or opAMS differ from those of AMS probably indicating post-depositional effects on particular grain-size classes. The fdAMS and opAMS show as powerful

  6. SU-F-I-24: Feasibility of Magnetic Susceptibility to Relative Electron Density Conversion Method for Radiation Therapy

    SciTech Connect

    Ito, K; Kadoya, N; Chiba, M; Matsushita, H; Jingu, K; Sato, K; Nagasaka, T; Yamanaka, K; Dobashi, S; Takeda, K

    2016-06-15

    Purpose: The aim of this study is to develop radiation treatment planning using magnetic susceptibility obtained from quantitative susceptibility mapping (QSM) via MR imaging. This study demonstrates the feasibility of a method for generating a substitute for a CT image from an MRI. Methods: The head of a healthy volunteer was scanned using a CT scanner and a 3.0 T MRI scanner. The CT imaging was performed with a slice thickness of 2.5 mm at 80 and 120 kV (dual-energy scan). These CT images were converted to relative electron density (rED) using the CT-rED conversion table generated by a previous dual-energy CT scan. The CT-rED conversion table was generated using the conversion of the energy-subtracted CT number to rED via a single linear relationship. One T2 star-weighted 3D gradient echo-based sequence with four different echo times images was acquired using the MRI scanner. These T2 star-weighted images were used to estimate the phase data. To estimate the local field map, a Laplacian unwrapping of the phase and background field removal algorithm were implemented to process phase data. To generate a magnetic susceptibility map from the local field map, we used morphology enabled dipole inversion method. The rED map was resampled to the same resolution as magnetic susceptibility, and the magnetic susceptibility-rED conversion table was obtained via voxel-by-voxel mapping between the magnetic susceptibility and rED maps. Results: A correlation between magnetic susceptibility and rED is not observed through our method. Conclusion: Our results show that the correlation between magnetic susceptibility and rED is not observed. As the next step, we assume that the voxel of the magnetic susceptibility map comprises two materials, such as water (0 ppm) and bone (-2.2 ppm) or water and marrow (0.81ppm). The elements of each voxel were estimated from the ratio of the two materials.

  7. Magnetic AC susceptibility study of the cobalt segregation process in melt-spun Cu-Co alloys

    NASA Astrophysics Data System (ADS)

    López, A.; Lázaro, F. J.; von Helmolt, R.; García-Palacios, J. L.; Wecker, J.; Cerva, H.

    1998-08-01

    Temperature and frequency-dependent AC susceptibility has been used to characterize Cu 90Co 10 melt-spun ribbons, about 15 μm thick, in order to see to what extent this technique yields information about the segregation of cobalt in this alloy. The interpretation of the results includes, as a prerequisite, a transmission electron microscopy (TEM) characterization and makes use of previous field-dependent magnetization data on the same samples. Due to their different dynamical magnetic properties, the large intergrain precipitates, the small intragrain aggregates and the remaining Cu-Co solid solution, previously detected in these alloys, are independently observed by AC susceptibility as ferromagnetic, superparamagnetic and spin-glass species. Contrary to other, mostly local, microstructural characterization techniques of use with nanostructured materials, the AC susceptibility yields information about the whole sample. Furthermore, unlike the measurement of the temperature-dependent magnetization which is the magnetic technique mostly used until now, the results are basically independent of the thermal history. The correlation between microstructure and magnetic properties is illustrated by a scheme which includes magnetization, AC susceptibility and TEM data.

  8. Anisotropy of magnetic susceptibility (AMS) in the Siilinjärvi carbonatite complex, eastern Finland

    NASA Astrophysics Data System (ADS)

    Almqvist, Bjarne; Karell, Fredrik; Högdahl, Karin; Malehmir, Alireza; Heino, Pasi; Salo, Aleksi

    2017-04-01

    We present a set of AMS measurements on samples from the Siilinjärvi alkaline-carbonatite complex in eastern Finland. The complex has a tabular shape (ca. 16 km long, 1.5 km wide) that strikes north-south and is constrained within a steeply dipping N-S oriented deformation zone. It consists of a mixture of lithologies, including carbonatite, fenite and glimmerite (mica-rich rocks), which is hosted within a Precambrian granite and gneiss. After emplacement of the carbonatite, the complex was subsequently intruded by diabase dykes. Deformation has occurred in several episodes after dyke intrusions, and strain is heterogeneously distributed among the different lithologies. Strain localizes mainly within glimmerite and carbonatite, and at the contacts between dykes and glimmerite/carbonatite where shear zones develop locally. Structures provide indications for both simple (strike-slip) and pure shear components in the deformation history of the complex, although the former may dominate. Thirty-six localities were sampled, providing 272 specimens for AMS measurements, within the southern and eastern parts of the Siilinjärvi open-pit mine (within the complex), mainly from diabase dykes, glimmerite and carbonatites; a smaller number of samples were collected from fenite. Sampling was carried out in order to investigate magnetic fabrics in relation to the emplacement of the dykes and their structural relationship to the glimmerite/carbonatite. Structural measurements were made to accompany the magnetic fabric study. The magnetic fabric shows a magnetic foliation plane that is oriented north-south, with sub-horizontal k3-axes oriented nearly east-west. Magnetic lineation (k1) clusters sub-vertically, but does show a tendency to spread along the north-south magnetic foliation great circle. The dataset can be further divided into two sub-sets based on the bulk susceptibility (km) and degree of anisotropy (P). The bulk of the data set ( 70 %), belonging to samples of diabase

  9. Temperature-dependency of Magnetic Susceptibility U Advantages and Limits For Magneto-mineralogical Studies

    NASA Astrophysics Data System (ADS)

    Kontny, A.

    Low-field magnetic susceptibility measurements in the temperature range U192 to 700 C (k(T)) are a widely applied method used for the identification of magnetic phases and characteristic magnetic phase transitions. One of the advantages of this method is the precise determination of titanomagnetite composition independently from grain size. However, the interpretations of k(T)-curves often are discussed controversially because other effects like grain size or the occurrence of more than one magnetic phase complicate the courses. Case studies from the titanomagnetite and titanohe- matite solid solution series including pure magnetite and hematite will be presented and variations in chemical composition, alteration and grain size will be discussed in relation to their geological significance. (1) In subaerially extruded basaltic lava differences in the low-temperature legs of the k(T) curves indicate variations in the degree of high-temperature (deuteric) oxidation of titanomagnetite. This alteration to magnetite-rich titanomagnetite is accompanied by a grain size reduction, which can be correlated with the development of a susceptibility peak at about U160 C. Fur- ther oxidation transforms the titanomagnetite into titanohematite which again results in a characteristic k(T) behavior at low temperatures with a decrease in k with in- creasing temperature (2) Hydrothermal alteration from magnetite to hematite creates a hematite phase that cannot be seen in k(T)-curves. However, hematite that is grown in sediments, can be identified by its Tc. Therefore it is assumed that crystallinity of magnetic phases seems to play a significant role to explain a different behaviour. (3) Submarine basalts rapidly quenched from high temperatures often show wide anti- clines in the k(T)-curves which can be correlated with a range of chemical composition and grain sizes, including small amounts of pure magnetite. This feature is commonly attributed to low-temperature alteration of single

  10. Three-dimensional analysis of magnetic susceptibility in areas with different type of land use

    NASA Astrophysics Data System (ADS)

    Zawadzki, Jarosław; Fabijańczyk, Piotr

    2015-04-01

    The knowledge of the type of semivariance and its parameters such as nugget-effect, range of correlation and sill, that quantitatively characterize spatial variability of a studied environmental phenomenon, can be essential for both measurements planning and analysis of results. In particular this is the truth in the case of magnetometric measurements of soil pollution. Field magnetometry is internationally recognized as valuable, convenient and affordable tool for soil pollution screening and assessment. However, this geophysical method usually requires support of detailed statistical and geostatistical analyses. The goal of this study was to evaluate the parameters of spatial variability of soil magnetic susceptibility depending on the terrain usage. To do so, several types of study area were specially selected: forest, arable field and urban park. Some of the study areas were neighboring to each other, in order to ensure that the anthropogenic pressure was the same at each site. In order to analyze soil magnetic susceptibility in 3-dimensional space, measurements were performed on the soil surface and in soil profile, using the MS2D and MS2C Bartington instruments, respectively. MS2D measurements were performed using quasi-regular grids, and at each sample point 10 single MS2D readings were carried out in the circle with the diameter of about 2 meters. MS2C measurements were performed using soil cores collected in the field, down to the depth of about 30cm. Such approach combines the advantages of both types of measurements and allows to get deeper insight into the distribution of soil pollution. As the first step of the analysis, the semivariances of magnetic susceptibility were calculated and thoroughly modeled for all different forms of land use, on the basis of only the MS2D measurements. Then, the MS2D and MS2C measurements were jointed into one three-dimensional data set, and were used together to calculate and model the semivariances. Finally, the

  11. Magnetic susceptibility and hardness of Au-xPt-yNb alloys for biomedical applications.

    PubMed

    Uyama, Emi; Inui, Shihoko; Hamada, Kenichi; Honda, Eiichi; Asaoka, Kenzo

    2013-09-01

    Metal devices in the human body induce serious metal artifacts in magnetic resonance imaging (MRI). Metals artifacts are mainly caused by a volume magnetic susceptibility (χv) mismatch between a metal device and human tissue. In this research, Au-xPt-yNb alloys were developed for fabricating MRI artifact-free biomedical metal devices. The magnetic properties, hardness and phase constitutions of these alloys were investigated. The Au-xPt-8Nb alloys showed satisfactory χv values. Heat treatments did not clearly change the χv values for Au-xPt-8Nb alloys. The Vickers hardness (HV) of these two alloys was much higher than that of high-Pt alloys; moreover, aging at 700°C increased the HV values of these two alloys. A dual phase structure consisting of face-centered cubic α1 and α2 phases was observed and aging at 700°C promoted phase separation. The Au-5Pt-8Nb and Au-10Pt-8Nb alloys showed satisfactory χv values and high hardness and are thus suggested as candidates for MRI artifact-free alloys for biomedical applications. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  12. A Method for Whole Brain Ex Vivo Magnetic Resonance Imaging with Minimal Susceptibility Artifacts

    PubMed Central

    Shatil, Anwar S.; Matsuda, Kant M.; Figley, Chase R.

    2016-01-01

    Magnetic resonance imaging (MRI) is a non-destructive technique that is capable of localizing pathologies and assessing other anatomical features (e.g., tissue volume, microstructure, and white matter connectivity) in postmortem, ex vivo human brains. However, when brains are removed from the skull and cerebrospinal fluid (i.e., their normal in vivo magnetic environment), air bubbles and air–tissue interfaces typically cause magnetic susceptibility artifacts that severely degrade the quality of ex vivo MRI data. In this report, we describe a relatively simple and cost-effective experimental setup for acquiring artifact-free ex vivo brain images using a clinical MRI system with standard hardware. In particular, we outline the necessary steps, from collecting an ex vivo human brain to the MRI scanner setup, and have also described changing the formalin (as might be necessary in longitudinal postmortem studies). Finally, we share some representative ex vivo MRI images that have been acquired using the proposed setup in order to demonstrate the efficacy of this approach. We hope that this protocol will provide both clinicians and researchers with a straight-forward and cost-effective solution for acquiring ex vivo MRI data from whole postmortem human brains. PMID:27965620

  13. Ac-susceptibility investigations of superspin blocking and freezing in interacting magnetic nanoparticle ensembles

    NASA Astrophysics Data System (ADS)

    Botez, Cristian E.; Morris, Joshua L.

    2016-03-01

    We have investigated the effect of dipolar interactions on the superspin blocking and freezing of 9 nm average size Fe3O4 magnetic nanoparticle ensembles. Our dynamic susceptibility data reveals a two-regime behavior of the blocking temperature, T B, upon diluting a Fe3O4/hexane magnetic fluid. As the nanoparticle volume ratio, Φ, is reduced from an as-prepared reference Φ = 1 to Φ = 1/96, the blocking temperature decreases from 46.1 K to 34.2 K, but higher values reenter upon further diluting the magnetic fluid to Φ = 1/384 (where T B = 42.5 K). We found evidence that cooling below T B within the higher concentration range (Φ > 1/48) leads to the collective freezing of the superspins, whereas individual superspin blocking occurs in the presence of weaker interactions (Φ < 1/96). The unexpected increase of the blocking temperature with the decrease of the inter-particle interactions observed at low nanoparticle concentrations is well described by the Mørup-Tronc model.

  14. Low temperature magnetic susceptibility behavior of the Neuschwanstein EL6 meteorite and mineral daubreelite (FeCr2S4)

    NASA Astrophysics Data System (ADS)

    Kohout, T.; Kletetschka, G.; Lehtinen, M.; Pesonen, L. J.; Wasilewski, P. J.

    2006-12-01

    Neuschwanstein meteorite (enstatite chondrite EL-6) fall occurred on April 6, 2002 close to Neuschwanstein castle in Bavaria, Germany. Total three meteorite bodies were found on the fall site. Two fragments coming from a 1750g body found on July 14, 2002 were obtained to the Division of Geophysics, University of Helsinki. The low temperature magnetic properties were investigated using KLY-3 and KLY-4 kappabridges equipped with low temperature control unit. During the low-temperature susceptibility measurements an unknown kink feature was observed at ~150 K on all measured samples. The closest known magnetic transition is the curie temperature Tc ~170 K of synthetic FeCr2S4 mentioned in Müller et al., 2006. FeCr2S4 is naturally present in enstatite chondrites and iron meteorites in the form of mineral daubreelite and was reported to be present in the Neuschwanstein meteorite in Zipfel and Dreibus, 2003. The extensive study of magnetic susceptibility of Neuschwanstein meteorite and daubreelite extract form Coahuila iron meteorite (hexahedrite, II A) was conducted in order to investigate the low temperature magnetic susceptibility of those materials and its field and frequency dependence. The results indicate Tc of natural daubreelite extract from Coahuila meteorite to be ~160 K what is slightly lower than the Tc of synthetic FeCr2S4 reported in Müller et al., 2006. The magnetic susceptibility of natural daubreelite from Coahuila meteorite and of ~150 K feature in Neuschwanstein meteorite show no field dependence of magnetic susceptibility. Due to the similarity in the low temperature magnetic susceptibility behaviour of Neuschwanstein meteorite and daubreelite extract from Coahuila meteorite we link the Neuschwanstein ~150 K feature to the Tc of daubreelite present in this meteorite. The 10 K difference of the Tc of daubreelite in Neuschwanstein and Coahuila meteorites can be attributed to the presence of impurities or structural deformations in the daubreelite

  15. Effect of electron-electron interaction on the magnetic moment and susceptibility of a parabolic GaAs quantum dot

    NASA Astrophysics Data System (ADS)

    Boda, Aalu; Kumar, D. Sanjeev; Sankar, I. V.; Chatterjee, Ashok

    2016-11-01

    The problem of a parabolically confined two-dimensional semiconductor GaAs quantum dot with two interacting electrons in the presence of an external magnetic field and the spin-Zeeman interaction is studied using a method of numerical diagonalization. The energy spectrum is calculated as a function of the magnetic field. The magnetic moment (M) and the magnetic susceptibility (χ) show zero temperature diamagnetic peaks due to the exchange induced singlet-triplet transitions. The position and the number of these peaks depend both on the confinement strength of the quantum dot and the strength of the electron-electron interaction (β) .

  16. Magnetism in Complex Oxides Probed by Magnetocaloric Effect and Transverse Susceptibility

    NASA Astrophysics Data System (ADS)

    Bingham, Nicholas S.

    Magnetic oxides exhibit rich complexity in their fundamental physical properties determined by the intricate interplay between structural, electronic and magnetic degrees of freedom. The common themes that are often present in these systems are the phase coexistence, strong magnetostructural coupling, and possible spin frustration induced by lattice geometry. While a complete understanding of the ground state magnetic properties and cooperative phenomena in this class of compounds is key to manipulating their functionality for applications, it remains among the most challenging problems facing condensed-matter physics today. To address these outstanding issues, it is essential to employ experimental methods that allow for detailed investigations of the temperature and magnetic field response of the different phases. In this PhD dissertation, I will demonstrate the relatively unconventional experimental methods of magnetocaloric effect (MCE) and radio-frequency transverse susceptibility (TS) as powerful probes of multiple magnetic transitions, glassy phenomena, and ground state magnetic properties in a large class of complex magnetic oxides, including La0.7Ca0.3- xSrxMnO3 (x = 0, 0.05, 0.1, 0.2 and 0.25), Pr0.5Sr0.5MnO3, Pr1-xSrxCoO 3 (x = 0.3, 0.35, 0.4 and 0.5), La5/8- xPrxCa3/8MnO3 (x = 0.275 and 0.375), and Ca3Co2O 6. First, the influences of strain and grain boundaries, via chemical substitution and reduced dimensionality, were studied via MCE in La0.7Ca 0.3-xSrxMnO 3. Polycrystalline, single crystalline, and thin-film La0.7Ca 0.3-xSrxMnO 3 samples show a paramagnetic to ferromagnetic transition at a wide variety of temperatures as well as an observed change in the fundamental nature of the transition (i.e. first-order magnetic transition to second order magnetic transition) that is dependent on the chemical concentration and dimensionality. Systematic TS and MCE experiments on Pr0.5Sr0.5MnO 3 and Pr0.5Sr0.5CoO3 have uncovered the different nature of low

  17. Generalised Eisenhart lift of the Toda chain

    SciTech Connect

    Cariglia, Marco; Gibbons, Gary

    2014-02-15

    The Toda chain of nearest neighbour interacting particles on a line can be described both in terms of geodesic motion on a manifold with one extra dimension, the Eisenhart lift, or in terms of geodesic motion in a symmetric space with several extra dimensions. We examine the relationship between these two realisations and discover that the symmetric space is a generalised, multi-particle Eisenhart lift of the original problem that reduces to the standard Eisenhart lift. Such generalised Eisenhart lift acts as an inverse Kaluza-Klein reduction, promoting coupling constants to momenta in higher dimension. In particular, isometries of the generalised lift metric correspond to energy preserving transformations that mix coordinates and coupling constants. A by-product of the analysis is that the lift of the Toda Lax pair can be used to construct higher rank Killing tensors for both the standard and generalised lift metrics.

  18. Subsectors, Dynkin diagrams and new generalised geometries

    NASA Astrophysics Data System (ADS)

    Strickland-Constable, Charles

    2017-08-01

    We examine how generalised geometries can be associated with a labelled Dynkin diagram built around a gravity line. We present a series of new generalised geometries based on the groups Spin( d, d) × ℝ + for which the generalised tangent space transforms in a spinor representation of the group. In low dimensions these all appear in subsectors of maximal supergravity theories. The case d = 8 provides a geometry for eight-dimensional backgrounds of M theory with only seven-form flux, which have not been included in any previous geometric construction. This geometry is also one of a series of "half-exceptional" geometries, which "geometrise" a six-form gauge field. In the appendix, we consider exam-ples of other algebras appearing in gravitational theories and give a method to derive the Dynkin labels for the "section condition" in general. We argue that generalised geometry can describe restrictions and subsectors of many gravitational theories.

  19. Magnetic susceptibility measurements on ancient and modern potsherds using a fast, cheap and portable probe

    NASA Astrophysics Data System (ADS)

    Glover, P. W. J.

    2009-04-01

    It has been estimated that there exist over 100 million ancient potsherds in various collections worldwide, many of which have never been studied and for which the provenance is ambiguous or unknown. Indeed, many collections are extremely badly catalogued or completely mixed-up. We have been using a novel portable probe to measure the magnetic susceptibility and electrical conductivity of potsherds in the hope that this fast, cheap and portable measurement can provide data that will help to sort similar looking potsherds into sets in a manner which may help to define their provenance. The probe, which resembles a firearm, uses the Hall effect to make a non-destructive measurement on the potsherd. The probe is attached to an Dell Axim X51 PDA, which runs software that allows the measurement to be carried out and logged. Each measurement, which is made by pressing a button on the gun, takes only a few seconds. We have made measurements on three suites of ancient potsherds as well as a suite of modern potsherds that were created by using a garden centre and a hammer! In each case a set of 5 stacked measurements were taken on the inside and outside faces of the potsherd in two perpendicular directions. Potsherds which were either (i) so flat that the inside and outside could not be distinguished, (ii) so curved (radius of curvature less than 5 cm) that the probe tip could not approach the surface sufficiently closely, or (iii) smaller than the probe tip, were excluded from the suite of measurements. Each suite contained over 50 measureable potsherds. All measurements were completed within one day. In this pilot study we found that (1) each suite was represented by a normal distribution of magnestic susceptibility values, (2) the four different suites could be distinguished statistically on the basis of their magnetic susceptibilty measurements, but (3) the distinction was not sufficiently powerful to separate all potsherds (i.e., there was a significant overlap of the

  20. Magnetic susceptibility data for some exposed bedrock in the western conterminous United States

    USGS Publications Warehouse

    Gettings, Mark E.; Bultman, Mark W.

    2014-01-01

    In-place rock magnetic susceptibility measurements for 746 sites in the western conterminous United States are reported in a database. Of these 746 sites, 408 sites are in the Silverton Caldera area of the San Juan Mountains of southwestern Colorado. Of the 408 sites in the Silverton Caldera area, 106 sites are underground. The remaining 338 sites outside the Silverton Caldera area were on outcropping rock, are distributed from southern Arizona to northwestern Wyoming, and include data from California, Nevada, Utah, Colorado, and New Mexico. Rock-density measurements are included for some sites. These data have been collected by various U.S. Geological Survey studies from 1991 through 2012 and are intended to help improve geophysical modeling of the Earth’s crust in the Western United States. A map-based graphical user interface is included to facilitate use of the data.

  1. Noncontact technique for measuring the electrical resistivity and magnetic susceptibility of electrostatically levitated melts

    NASA Astrophysics Data System (ADS)

    Rustan, G. E.; Spyrison, N. S.; Kreyssig, A.; Prozorov, R.; Goldman, A. I.

    2012-02-01

    Over the last two decades the popularity of levitation methods for studying equilibrium and supercooled melts has increased steadily. Measurements of density, viscosity, surface tension, and atomic structure have become well established. In contrast, measurements of electrical resistivity and magnetic susceptibility of levitated melts have been very limited. To fill this void, we have combined the tunnel diode oscillator (TDO) technique with electrostatic levitation (ESL) to perform inductively coupled measurements on levitated melts. A description of the basic operating principles of the TDO and ESL will be given, as well as a description of the implementation and performance characteristics of this technique. Preliminary measurements of electrical resistivity in the solid and liquid state will be presented for samples of Zr, Si, and Ge, as well as the measurements of ferromagnetic transitions in Fe and Co based alloys.

  2. Magnetic susceptibility and heat capacity of graphene in two-band Harrison model

    NASA Astrophysics Data System (ADS)

    Mousavi, Hamze; Bagheri, Mehran; Khodadadi, Jabbar

    2015-11-01

    Using a two-band tight-binding Harrison model and Green's function technique, the influences of both localized σ and delocalized π electrons on the density of states, the Pauli paramagnetic susceptibility, and the heat capacity of a graphene sheet are investigated. We witness an extension in the bandwidth and an increase in the number of Van-Hove singularities as well. As a notable point, besides the magnetic nature which includes diamagnetism in graphene-based nanosystems, a paramagnetic behavior associated with the itinerant π electrons could be occurred. Further, we report a Schottky anomaly in the heat capacity. This study asserts that the contribution of both σ and π electrons play dominant roles in the mentioned physical quantities.

  3. Magnetic susceptibility as a proxy for investigating microbially mediated iron reduction

    NASA Astrophysics Data System (ADS)

    Mewafy, Farag M.; Atekwana, Estella A.; Werkema, D. Dale, Jr.; Slater, Lee D.; Ntarlagiannis, Dimitrios; Revil, André; Skold, Magnus; Delin, Geoffrey N.

    2011-11-01

    We investigated magnetic susceptibility (MS) variations in hydrocarbon contaminated sediments. Our objective was to determine if MS can be used as an intrinsic bioremediation indicator due to the activity of iron-reducing bacteria. A contaminated and an uncontaminated core were retrieved from a site contaminated with crude oil near Bemidji, Minnesota and subsampled for MS measurements. The contaminated core revealed enriched MS zones within the hydrocarbon smear zone, which is related to iron-reduction coupled to oxidation of hydrocarbon compounds and the vadose zone, which is coincident with a zone of methane depletion suggesting aerobic or anaerobic oxidation of methane is coupled to iron-reduction. The latter has significant implications for methane cycling. We conclude that MS can serve as a proxy for intrinsic bioremediation due to the activity of iron-reducing bacteria iron-reducing bacteria and for the application of geophysics to iron cycling studies.

  4. Magnetic susceptibility as a proxy for investigating microbially mediated iron reduction

    USGS Publications Warehouse

    Mewafy, F.M.; Atekwana, E.A.; Werkema, D.D.; Slater, L.D.; Ntarlagiannis, D.; Revil, A.; Skold, M.; Delin, G.N.

    2011-01-01

    We investigated magnetic susceptibility (MS) variations in hydrocarbon contaminated sediments. Our objective was to determine if MS can be used as an intrinsic bioremediation indicator due to the activity of iron-reducing bacteria. A contaminated and an uncontaminated core were retrieved from a site contaminated with crude oil near Bemidji, Minnesota and subsampled for MS measurements. The contaminated core revealed enriched MS zones within the hydrocarbon smear zone, which is related to iron-reduction coupled to oxidation of hydrocarbon compounds and the vadose zone, which is coincident with a zone of methane depletion suggesting aerobic or anaerobic oxidation of methane is coupled to iron-reduction. The latter has significant implications for methane cycling. We conclude that MS can serve as a proxy for intrinsic bioremediation due to the activity of iron-reducing bacteria iron-reducing bacteria and for the application of geophysics to iron cycling studies. ?? 2011 by the American Geophysical Union.

  5. Fahr disease: use of susceptibility-weighted imaging for diagnostic dilemma with magnetic resonance imaging

    PubMed Central

    Solak, Aynur; Genc, Berhan; Kulu, Ugur

    2015-01-01

    Fahr disease (FD) is a well-defined rare neurodegenerative disease that is characterized by idiopathic bilateral symmetric extensive striopallidodentate calcifications. The patients may present with diverse manifestations, most commonly movement disorder, cognitive impairment, and ataxia. Computed tomography (CT) is considered to be critical for accurate diagnosis because it is difficult to reliably identify calcifications by routine magnetic resonance imaging (MRI). Susceptibility-weighted imaging (SWI) is a relatively new 3D gradient-echo (GE) MR sequence with special phase and magnitude processing. SWI phase images can recognize calcifications definitively with higher sensitivity compared to other MRI sequences. In this article, we present two cases of FD with different manifestations and neuroimaging in different age groups and genders, which were diagnosed by SWI and confirmed with CT, and we discuss the contribution of SWI in the diagnosis of FD. In conclusion, we suggest integrating SWI with MRI protocol to identify calcifications in suspicion of neurodegenerative disorders. PMID:26435928

  6. Fahr disease: use of susceptibility-weighted imaging for diagnostic dilemma with magnetic resonance imaging.

    PubMed

    Sahin, Neslin; Solak, Aynur; Genc, Berhan; Kulu, Ugur

    2015-08-01

    Fahr disease (FD) is a well-defined rare neurodegenerative disease that is characterized by idiopathic bilateral symmetric extensive striopallidodentate calcifications. The patients may present with diverse manifestations, most commonly movement disorder, cognitive impairment, and ataxia. Computed tomography (CT) is considered to be critical for accurate diagnosis because it is difficult to reliably identify calcifications by routine magnetic resonance imaging (MRI). Susceptibility-weighted imaging (SWI) is a relatively new 3D gradient-echo (GE) MR sequence with special phase and magnitude processing. SWI phase images can recognize calcifications definitively with higher sensitivity compared to other MRI sequences. In this article, we present two cases of FD with different manifestations and neuroimaging in different age groups and genders, which were diagnosed by SWI and confirmed with CT, and we discuss the contribution of SWI in the diagnosis of FD. In conclusion, we suggest integrating SWI with MRI protocol to identify calcifications in suspicion of neurodegenerative disorders.

  7. Electronic heat capacity and magnetic susceptibility of ferromagnetic silicene sheet under strain

    NASA Astrophysics Data System (ADS)

    Yarmohammadi, Mohsen

    2017-01-01

    The electronic heat capacity (EHC) and magnetic susceptibility (MS) of the two-dimensional material ferromagnetic graphene's silicon analog, silicene, are investigated by the strain-induced and the applied electric field within the Green's function technique and the Kane-Mele Hamiltonian. Dirac cone approximation has been performed to investigate the system under strain along the zigzag (ZZ) direction. The main attention is focused on the effects of external static electric field in the presence of strain on EHC and MS of a ferromagnetic silicene sheet. In the presence of strain, carriers have a larger effective mass and transport decreases. As a result, the temperature dependence of EHC and MS gives a critical strain around 10%. Furthermore, electric field breaks the reflection symmetry of the structure and a transition to the topological insulator for strained ferromagnetic silicene has occurred when the electric field is increased. In this phase, EHC and MS have weird behaviors with temperature.

  8. Hadronic vacuum polarization and muon g -2 from magnetic susceptibilities on the lattice

    NASA Astrophysics Data System (ADS)

    Bali, Gunnar S.; Endrődi, Gergely

    2015-09-01

    We present and test a new method to compute the hadronic vacuum polarization function in lattice simulations. This can then be used, e.g., to determine the leading hadronic contribution to the anomalous magnetic moment of the muon. The method is based on computing susceptibilities with respect to external electromagnetic plane wave fields and allows for a precision determination of both the connected and the disconnected contributions to the vacuum polarization. We demonstrate that the statistical errors obtained with our method are much smaller than those quoted in previous lattice studies, primarily due to a very effective suppression of the errors of the disconnected terms. These turn out to vanish within small errors, enabling us to quote an upper limit. We also comment on the accuracy of the vacuum polarization function determined from present experimental R -ratio data.

  9. Generalised tetanus in an unvaccinated adult.

    PubMed

    Muldoon, E G; Cavanagh, S; Fleming, C

    2010-03-01

    A 76-year-old previously well farmer presented having caught his left index finger in a gate. He gave no history of prior tetanus vaccination. The patient was treated in the emergency department; the wound cleaned, sutured and he was given tetanus toxoid prior to discharge. Eleven days later he represented unable to open his mouth. On examination he was noted to have trismus, generalised muscle spasms, diaphoresis and emotional lability and he was diagnosed with generalised tetanus.

  10. Magnetic Susceptibility of Brain Iron is Associated with Childhood Spatial IQ

    PubMed Central

    Carpenter, Kimberly L.H.; Li, Wei; Wei, Hongjiang; Wu, Bing; Xiao, Xue; Liu, Chunlei; Worley, Gordon; Egger, Helen Link

    2016-01-01

    Iron is an essential micronutrient for healthy brain function and development. Because of the importance of iron in the brain, iron deficiency results in widespread and lasting effects on behavior and cognition. We measured iron in the basal ganglia of young children using a novel MRI method, quantitative susceptibility mapping, and examined the association of brain iron with age and cognitive performance. Participants were a community sample of 39 young children recruited from pediatric primary care who were participating in a five-year longitudinal study of child brain development and anxiety disorders. The children were ages 7 to 11 years old (mean age: 9.5 years old) at the time of the quantitative susceptibility mapping scan. The Differential Abilities Scale was administered when the children were 6 years old to provide a measure of general intelligence and verbal (receptive and expressive), non-verbal, and spatial performance. Magnetic susceptibility values, which are linearly related to iron concentration in iron-rich areas, were extracted from regions of interest within iron-rich deep gray matter nuclei from the basal ganglia, including the caudate, putamen, substantia nigra, globus pallidus, and thalamus. Controlling for scan age, there was a significant positive association between iron in the basal ganglia and spatial IQ, with this effect being driven by iron in the right caudate We also replicated previous findings of a significant positive association between iron in the bilateral basal ganglia and age. Our finding of a positive association between spatial IQ and mean iron in the basal ganglia, and in the caudate specifically, suggests that iron content in specific regions of the iron-rich deep nuclei of the basal ganglia influences spatial intelligence. This provides a potential neurobiological mechanism linking deficits in spatial abilities reported in children who were severely iron deficient as infants to decreased iron within the caudate. PMID

  11. Magnetic Susceptibility Analyses of Nanophase Iron Particle Diameters and Volumes Produced through Laser Irradiation.

    NASA Astrophysics Data System (ADS)

    Markley, M. M.; Kletetschka, G.

    2015-12-01

    Micrometeorite impacts greatly modify surfaces exposed to the space environment. This interaction vaporizes the surficial material and allows for the re-precipitation of minerals and iron. Characterizing the recondensed iron or nanophase metallic iron (npFe0) improves our interpretations in remote sensing of planetary surfaces. We irradiated olivine samples with energies simulating micrometeorite impact energies from around the inner Solar System. They revealed npFe0 as single domain (SD) and superparamagnetic (SPM) iron grains varying in size. Spectrally they changed the spectral reflectance of silicate minerals and contribute to "space weathering": (1) darkens the overall reflectance, (2) steepens (or reddens) the spectral slope, and (3) decreases the contrast in the silicate 1 µm band. Using frequency dependent magnetic susceptibility (MS), we revealed patterns of npFe0 sizes. Fresh samples contained some nanophase magnetic sources due to decreasing magnetic susceptibility, when changing frequency from 4 kHz to 16 kHz. Using the fresh olivine as a standard, the lunar analog displayed increased MS at the lower 4 kHz indicating that more iron was transformed into magnetic sources. At 16 kHz, the MS decreased due to SPM particles that were being formed with sizes <10 nm. With the Mercury analog, at higher 16 kHz frequencies the MS increased rather than decreased. We can infer that the excess energy from our laser converted the amount of smaller <10 nm SPM particles by growth into an increasing volume of >10 nm particles. With the asteroid analog, we found a lower MS at 16 kHz, but nothing less MS than the Lunar analog. The 4 kHz MS was similar to the fresh olivine. At the lowest irradiation energy for the asteroid sample we have evidence that we are producing npFe0 particles. Our data compares well with traditional methods of forming npFe0, such as thermal processing of olivine, suggesting that with laser irradiation there is a linear increase of nanoparticles

  12. Effect of Low-Frequency AC Magnetic Susceptibility and Magnetic Properties of CoFeB/MgO/CoFeB Magnetic Tunnel Junctions

    PubMed Central

    Chen, Yuan-Tsung; Lin, Sung-Hao; Sheu, Tzer-Shin

    2014-01-01

    In this investigation, the low-frequency alternate-current (AC) magnetic susceptibility (χac) and hysteresis loop of various MgO thickness in CoFeB/MgO/CoFeB magnetic tunneling junction (MTJ) determined coercivity (Hc) and magnetization (Ms) and correlated that with χac maxima. The multilayer films were sputtered onto glass substrates and the thickness of intermediate barrier MgO layer was varied from 6 to 15 Å. An experiment was also performed to examine the variation of the highest χac and maximum phase angle (θmax) at the optimal resonance frequency (fres), at which the spin sensitivity is maximal. The results reveal that χac falls as the frequency increases due to the relationship between magnetization and thickness of the barrier layer. The maximum χac is at 10 Hz that is related to the maximal spin sensitivity and that this corresponds to a MgO layer of 11 Å. This result also suggests that the spin sensitivity is related to both highest χac and maximum phase angle. The corresponding maximum of χac is related to high exchange coupling. High coercivity and saturation magnetization contribute to high exchange-coupling χac strength.

  13. Diffeomorphic susceptibility artifact correction of diffusion-weighted magnetic resonance images.

    PubMed

    Ruthotto, L; Kugel, H; Olesch, J; Fischer, B; Modersitzki, J; Burger, M; Wolters, C H

    2012-09-21

    Diffusion-weighted magnetic resonance imaging is a key investigation technique in modern neuroscience. In clinical settings, diffusion-weighted imaging and its extension to diffusion tensor imaging (DTI) are usually performed applying the technique of echo-planar imaging (EPI). EPI is the commonly available ultrafast acquisition technique for single-shot acquisition with spatial encoding in a Cartesian system. A drawback of these sequences is their high sensitivity against small perturbations of the magnetic field, caused, e.g., by differences in magnetic susceptibility of soft tissue, bone and air. The resulting magnetic field inhomogeneities thus cause geometrical distortions and intensity modulations in diffusion-weighted images. This complicates the fusion with anatomical T1- or T2-weighted MR images obtained with conventional spin- or gradient-echo images and negligible distortion. In order to limit the degradation of diffusion-weighted MR data, we present here a variational approach based on a reference scan pair with reversed polarity of the phase- and frequency-encoding gradients and hence reversed distortion. The key novelty is a tailored nonlinear regularization functional to obtain smooth and diffeomorphic transformations. We incorporate the physical distortion model into a variational image registration framework and derive an accurate and fast correction algorithm. We evaluate the applicability of our approach to distorted DTI brain scans of six healthy volunteers. For all datasets, the automatic correction algorithm considerably reduced the image degradation. We show that, after correction, fusion with T1- or T2-weighted images can be obtained by a simple rigid registration. Furthermore, we demonstrate the improvement due to the novel regularization scheme. Most importantly, we show that it provides meaningful, i.e. diffeomorphic, geometric transformations, independent of the actual choice of the regularization parameters.

  14. Diffeomorphic susceptibility artifact correction of diffusion-weighted magnetic resonance images

    NASA Astrophysics Data System (ADS)

    Ruthotto, L.; Kugel, H.; Olesch, J.; Fischer, B.; Modersitzki, J.; Burger, M.; Wolters, C. H.

    2012-09-01

    Diffusion-weighted magnetic resonance imaging is a key investigation technique in modern neuroscience. In clinical settings, diffusion-weighted imaging and its extension to diffusion tensor imaging (DTI) are usually performed applying the technique of echo-planar imaging (EPI). EPI is the commonly available ultrafast acquisition technique for single-shot acquisition with spatial encoding in a Cartesian system. A drawback of these sequences is their high sensitivity against small perturbations of the magnetic field, caused, e.g., by differences in magnetic susceptibility of soft tissue, bone and air. The resulting magnetic field inhomogeneities thus cause geometrical distortions and intensity modulations in diffusion-weighted images. This complicates the fusion with anatomical T1- or T2-weighted MR images obtained with conventional spin- or gradient-echo images and negligible distortion. In order to limit the degradation of diffusion-weighted MR data, we present here a variational approach based on a reference scan pair with reversed polarity of the phase- and frequency-encoding gradients and hence reversed distortion. The key novelty is a tailored nonlinear regularization functional to obtain smooth and diffeomorphic transformations. We incorporate the physical distortion model into a variational image registration framework and derive an accurate and fast correction algorithm. We evaluate the applicability of our approach to distorted DTI brain scans of six healthy volunteers. For all datasets, the automatic correction algorithm considerably reduced the image degradation. We show that, after correction, fusion with T1- or T2-weighted images can be obtained by a simple rigid registration. Furthermore, we demonstrate the improvement due to the novel regularization scheme. Most importantly, we show that it provides meaningful, i.e. diffeomorphic, geometric transformations, independent of the actual choice of the regularization parameters.

  15. Preparation, Magnetic Susceptibility, and Specific Heat on Interlanthanide Perovskites {ital AB}O

    SciTech Connect

    Ito, Kentaro; Tezuka, Keitaro; Hinatsu, Yukio

    2001-02-15

    The interlanthanide perovskites LaHoO{sub 3}, LaErO{sub 3}, LaTmO{sub 3}, LaYbO{sub 3}, LaLuO{sub 3}, CeTmO{sub 3}, CeYbO{sub 3}, CeLuO{sub 3}, PrYbO{sub 3}, and PrLuO{sub 3} were prepared by the coprecipitation method. Their magnetic susceptibility measurements were carried out in the temperature range between 1.8 and 300 K, and it was found that LaYbO{sub 3}, CeYbO{sub 3}, and PrYbO{sub 3} had antiferromagnetic ordering with a weak ferromagnetism at 2.7 K. LaErO{sub 3} also showed antiferromagnetic ordering at 2.4 K. Specific heat measurements for LaErO{sub 3} and LaYbO{sub 3} showed the {lambda}-type anomaly at 2.4 and 2.7 K, respectively, which is in good agreement with the susceptibility measurements.

  16. Mechanism of Formation of Volcanic Bombs and Achneliths: Insights From Anisotropy of Magnetic Susceptibility Measurements.

    NASA Astrophysics Data System (ADS)

    Canon-Tapia, E.

    2016-12-01

    Volcanic bombs and achneliths are a special type of pyroclastic fragments formed by mildly explosive volcanic eruptions. The common explanation for the general shapes of these types of particles is that they are the result of the rush of air acting on a fluid clot during flight. A competing, less commonly quoted model, envisages the shapes of volcanic bombs as the result of forces acting at the moment of ejection of liquid from the magma pool in the conduit, experiencing an almost negligible modification through its travel on the air. Quantitative evidence supporting either of those two models is limited, or might not be directly applicable to all morphological types. In this work, anisotropy of magnetic susceptibility (AMS) is used as a source of information that provides clues concerning the mechanism of formation of volcanic bombs and achneliths in general. AMS results indicate a fundamental difference between two of the most common morphological bomb types, and are used to constraint mechanisms of formation. It is shown that neither of the two most common mechanisms of formation of volcanic bombs seems acceptable on its current form. An alternative, two-step process is therefore outlined. The first step involves ejection of a small volume of magma dragged on top of large bubbles of gas that reach the surface of a magma pool. The second stage involves the disruption of the ejected magma either as the result of the bursting of the gas bubble, or as a consequence of currents of air that further destabilize already formed jets of liquid. This destabilization is not equivalent to the aerodynamic deformation invoked in current models. Finally, the evidence presented by the anisotropy of magnetic susceptibility indicates that some types of volcanic bombs are likely to preserve the initial deformation, whereas some others might loose it completely.

  17. Prediction of Ba, Mn and Zn for tropical soils using iron oxides and magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Marques Júnior, José; Arantes Camargo, Livia; Reynaldo Ferracciú Alleoni, Luís; Tadeu Pereira, Gener; De Bortoli Teixeira, Daniel; Santos Rabelo de Souza Bahia, Angelica

    2017-04-01

    Agricultural activity is an important source of potentially toxic elements (PTEs) in soil worldwide but particularly in heavily farmed areas. Spatial distribution characterization of PTE contents in farming areas is crucial to assess further environmental impacts caused by soil contamination. Designing prediction models become quite useful to characterize the spatial variability of continuous variables, as it allows prediction of soil attributes that might be difficult to attain in a large number of samples through conventional methods. This study aimed to evaluate, in three geomorphic surfaces of Oxisols, the capacity for predicting PTEs (Ba, Mn, Zn) and their spatial variability using iron oxides and magnetic susceptibility (MS). Soil samples were collected from three geomorphic surfaces and analyzed for chemical, physical, mineralogical properties, as well as magnetic susceptibility (MS). PTE prediction models were calibrated by multiple linear regression (MLR). MLR calibration accuracy was evaluated using the coefficient of determination (R2). PTE spatial distribution maps were built using the values calculated by the calibrated models that reached the best accuracy by means of geostatistics. The high correlations between the attributes clay, MS, hematite (Hm), iron oxides extracted by sodium dithionite-citrate-bicarbonate (Fed), and iron oxides extracted using acid ammonium oxalate (Feo) with the elements Ba, Mn, and Zn enabled them to be selected as predictors for PTEs. Stepwise multiple linear regression showed that MS and Fed were the best PTE predictors individually, as they promoted no significant increase in R2 when two or more attributes were considered together. The MS-calibrated models for Ba, Mn, and Zn prediction exhibited R2 values of 0.88, 0.66, and 0.55, respectively. These are promising results since MS is a fast, cheap, and non-destructive tool, allowing the prediction of a large number of samples, which in turn enables detailed mapping of

  18. Iron core formation in horse spleen ferritin: magnetic susceptibility, pH, and compositional studies.

    PubMed

    Hilty, S; Webb, B; Frankel, R B; Watt, G D

    1994-11-15

    Horse spleen ferritin (HoSF) reconstituted with small iron cores ranging in size from 8 to 500 iron atoms was studied by magnetic susceptibility and pH measurements to determine when the added Fe3+ begins to aggregate and form antiferromagnetically coupled clusters and also to determine the hydrolytic state of the iron at low iron loading. The Evans NMR magnetic susceptibility measurements showed that at iron loadings as low as 8 Fe3+/HoSF, at least half of the added iron atoms were involved in antiferromagnetic exchange interactions and the other half were present as isolated iron atoms with S = 5/2. As the core size increased to about 24 iron atoms, the antiferromagnetic exchange interactions among the iron atoms increased until reaching the limiting value of 3.8 Bohr magnetons per iron atom, the value present in holo HoSF. HoSF containing eight or more Fe3+ to which eight Fe2+ were added showed that the Fe2+ ions were at sites remote from the Fe3+ and that the resulting HoSF consisted of individual, noninteracting Fe2+ and the partially aggregated Fe3+. pH measurements for core reduction showed that Fe(OH)3 was initially present at all iron loadings but that in the absence of iron chelators the reduced iron core is partially hydrolyzed. Proton induced x-ray emission spectroscopy showed that Cl- is transported into the iron core during reduction, forming a stable chlorohydroxy Fe(II) mineral phase.

  19. Automated Generalisation Within NMAs in 2016

    NASA Astrophysics Data System (ADS)

    Stoter, Jantien; van Altena, Vincent; Post, Marc; Burghardt, Dirk; Duchêne, Cecile

    2016-06-01

    Producing maps and geo-data at different scales is traditionally one of the main tasks of National (and regional) Mapping Agencies (NMAs). The derivation of low-scale maps (i.e. with less detail) from large-scale maps (with more detail), i.e. generalisation, used to be a manual task of cartographers. With the need for more up-to-date data as well as the development of automated generalisation solutions in both research and industry, NMAs are implementing automated generalisation production lines. To exchange experiences and identify remaining issues, a workshop was organised end 2015 by the Commission on Generalisation and Multirepresentation of the International Cartographic Association and the Commission on Modelling and Processing of the European Spatial Data Research. This paper reports about the workshop outcomes. It shows that, most NMAs have implemented a certain form of automation in their workflows, varying from generalisation of certain features while still maintaining a manual workflow; semiautomated editing and generalisation to a fully automated procedure.

  20. Magnetic susceptibility, chemical element content and morphology of magnetic mineral in surface sediment of Kamp Walker and Hubay rivers as an inlet of Sentani lake, Papua-Indonesia

    NASA Astrophysics Data System (ADS)

    Zulaikah, Siti; Sisinggih, Dian; Bungkang, Yusuf; Dani, Zem; Ong, Mahfud David

    2017-07-01

    As an inlet of Sentani lake, Kamp Walker and Hubay rivers have a different environment characteristic, i.e. Kamp Walker has a proximate inhabitant, while Hubay has a relatively more natural environment. In this study, we conduct measurement of magnetic susceptibility, Fe content and morphology of magnetic mineral extracted from the two rivers surface sediment. The magnetic susceptibility of low frequency (χlf) of sediment samples from the two rivers are varies from 11.11 × 10-6 kg/m3 to 24.96 10-6 kg/m3 for Kamp Walker with dependence frequency susceptibility (χfd) from 0.031% to 0.367%. Meanwhile, for HubayRivers we find the χlf varies from 4.56 × 10-6 kg/m3 to 16.93 × 10-6 kg/m3 and χfd from 0.104% to 1.033%. Fe content of the sample from the two river are also has a different average i.e around 60% for Hubay and 50% for Kamp Walker, that may because of the source of magnetic minerals on sediment are mainly a lithogenic magnetic mineral in Hubay, and anthropogenic magnetic mineral in Kamp Walker. The morphology of magnetic mineral, based on the SEM image shows a rounded and crystalline shape.

  1. Nonlinear susceptibility of a quantum spin glass under uniform transverse and random longitudinal magnetic fields

    NASA Astrophysics Data System (ADS)

    Magalhaes, S. G.; Morais, C. V.; Zimmer, F. M.; Lazo, M. J.; Nobre, F. D.

    2017-02-01

    The interplay between quantum fluctuations and disorder is investigated in a quantum spin-glass model, in the presence of a uniform transverse field Γ , as well as of a longitudinal random field hi, which follows a Gaussian distribution characterized by a width proportional to Δ . The interactions are infinite-ranged, and the model is studied through the replica formalism, within a one-step replica-symmetry-breaking procedure; in addition, the dependence of the Almeida-Thouless eigenvalue λAT (replicon) on the applied fields is analyzed. This study is motivated by experimental investigations on the LiHoxY1 -xF4 compound, where the application of a transverse magnetic field yields rather intriguing effects, particularly related to the behavior of the nonlinear magnetic susceptibility χ3, which have led to a considerable experimental and theoretical debate. We have analyzed two physically distinct situations, namely, Δ and Γ considered as independent, as well as these two quantities related, as proposed recently by some authors. In both cases, a spin-glass phase transition is found at a temperature Tf, with such phase being characterized by a nontrivial ergodicity breaking; moreover, Tf decreases by increasing Γ towards a quantum critical point at zero temperature. The situation where Δ and Γ are related [Δ ≡Δ (Γ )] appears to reproduce better the experimental observations on the LiHoxY1 -xF4 compound, with the theoretical results coinciding qualitatively with measurements of the nonlinear susceptibility χ3. In this later case, by increasing Γ gradually, χ3 becomes progressively rounded, presenting a maximum at a temperature T* (T*>Tf ), with both the amplitude of the maximum and the value of T* decreasing gradually. Moreover, we also show that the random field is the main responsible for the smearing of the nonlinear susceptibility, acting significantly inside the paramagnetic phase, leading to two regimes delimited by the temperature T*, one for Tf

  2. The initial magnetic susceptibility of polydisperse ferrofluids: A comparison between experiment and theory over a wide range of concentration

    NASA Astrophysics Data System (ADS)

    Solovyova, Anna Y.; Goldina, Olga A.; Ivanov, Alexey O.; Lebedev, Aleksandr V.; Elfimova, Ekaterina A.

    2016-08-01

    Temperature dependencies of the static initial magnetic susceptibility for ferrofluids at various concentrations are studied using experiment and statistical-mechanical theories. Magnetic susceptibility measurements are carried out for twelve samples of magnetite-based fluids stabilized with oleic acid over a wide range of temperatures (210 K ≲T ≲ 390 K); all samples have the same granulometric composition but different volume ferroparticle concentrations (0.2 ≲ φ ≲ 0.5). Experimental results are analyzed using three theories: the second-order modified mean-field theory (MMF2) [A. O. Ivanov and O. B. Kuznetsova, Phys. Rev. E 64, 41405 (2001)]; its correction for polydisperse ferrofluids arising from Mayer-type cluster expansion and taking into account the first terms of the polydisperse second virial coefficient [A. O. Ivanov and E. A. Elfimova, J. Magn. Magn. Mater 374, 327 (2015)]; and a new theory based on MMF2 combined with the first terms of the polydisperse second and third virial contributions to susceptibility. It turns out that the applicability of each theory depends on the experimental sample density. If twelve ferrofluid samples are split into three groups of strong, moderate, and low concentrated fluids, the temperature dependences of the initial magnetic susceptibility in each group are very precisely described by one of the three theories mentioned above. The determination of a universal formula predicting a ferrofluid susceptibility over a broad range of concentrations and temperatures remains as a challenge.

  3. The initial magnetic susceptibility of polydisperse ferrofluids: A comparison between experiment and theory over a wide range of concentration.

    PubMed

    Solovyova, Anna Y; Goldina, Olga A; Ivanov, Alexey O; Lebedev, Aleksandr V; Elfimova, Ekaterina A

    2016-08-28

    Temperature dependencies of the static initial magnetic susceptibility for ferrofluids at various concentrations are studied using experiment and statistical-mechanical theories. Magnetic susceptibility measurements are carried out for twelve samples of magnetite-based fluids stabilized with oleic acid over a wide range of temperatures (210 K ≲T ≲ 390 K); all samples have the same granulometric composition but different volume ferroparticle concentrations (0.2 ≲ φ ≲ 0.5). Experimental results are analyzed using three theories: the second-order modified mean-field theory (MMF2) [A. O. Ivanov and O. B. Kuznetsova, Phys. Rev. E 64, 41405 (2001)]; its correction for polydisperse ferrofluids arising from Mayer-type cluster expansion and taking into account the first terms of the polydisperse second virial coefficient [A. O. Ivanov and E. A. Elfimova, J. Magn. Magn. Mater 374, 327 (2015)]; and a new theory based on MMF2 combined with the first terms of the polydisperse second and third virial contributions to susceptibility. It turns out that the applicability of each theory depends on the experimental sample density. If twelve ferrofluid samples are split into three groups of strong, moderate, and low concentrated fluids, the temperature dependences of the initial magnetic susceptibility in each group are very precisely described by one of the three theories mentioned above. The determination of a universal formula predicting a ferrofluid susceptibility over a broad range of concentrations and temperatures remains as a challenge.

  4. Skill Generalisation in Teaching Spelling to Children with Learning Difficulties

    ERIC Educational Resources Information Center

    Kohnen, Saskia; Nickels, Lyndsey; Coltheart, Max

    2010-01-01

    A central focus in remedial teaching is the generalisation of responses to contexts in which a student has never been explicitly instructed. Remarkably little is known about how and when generalisation occurs. In this article we examine generalisation effects in the context of spelling. Three areas are discussed: generalisation between spelling…

  5. Petrophysical Characterization of Stony Meteorites Using Low Field Magnetic Susceptibility: Initial Results From Anisotropy Measurements

    NASA Astrophysics Data System (ADS)

    Smith, D. L.; Ernst, R. E.; Herd, R. K.; Claire, S.

    2004-05-01

    Low field magnetic susceptibility represents a fast, systematic and non-destructive technique of meteorite classification [1-4]. We previously reported measurements of bulk susceptibility, and its frequency dependence, along with a `proxy' measure of anisotropy, on 204 specimens from 108 different meteorites in the National Meteorite Collection of Canada [5,6]. Measurements were performed on a Sapphire Instruments Model 2B. Bulk susceptibility values followed expected trends, governed by metal content, with values increasing from LL, to L, to H, to E chondrites. Frequency dependence (19000 vs 825 Hz) was greatest in H and C chondrites. Aubrites (AUB) and Howardites (HOW) had the lowest. Anisotropy of magnetic susceptibility (AMS) was measured using a `proxy' approach: the mean value determined from a series of random sample orientations was compared with repeated measurements in one orientation. AUB, E chondrites and Martian SNCs had the largest inferred anisotropies, while LL and C chondrites had the lowest. Here we report initial results from a follow-up study. Quantitative measurements of the AMS were made on 67 stony meteorite specimens. AMS measurements [3,5,6,7,8,9] can provide information on the physical fabric of the meteorite, and may relate to its deformational history. Samples measured show significant degrees of anisotropy ranging from 1-50 % for an individual specimen (in parentheses is the number of specimens used in the class mean): AUB (5), Acapulcoites (1) and E chondrites (10) display the largest degrees of anisotropy, 40±11 (1 standard deviation), 34, and 24±10, respectively. These classes are followed by Diogenite (1) 20, H (13) 14±7 and L (10) 13±6 chondrites, Brachinite (1) 11, Ureilite (2) 8, Eucrite (4) 7±4, C chondrites (14) 6±3, and Rumurutiite (1) 4. These results match a similar trend based on the `proxy' method [5,6]: AUB and E chondrites were found to have the highest inferred anisotropies followed by tightly grouped H and L

  6. Angular Dependent Magnetic Susceptibility with Photoexcitation Studies on Prussian Blue Analog Thin Films

    NASA Astrophysics Data System (ADS)

    Pajerowski, D. M.; Park, J.-H.; Meisel, M. W.; Frye, F. A.; Talham, D. R.

    2008-03-01

    Prussian blue analog systems are the topic of ongoing research because of their novel physical effects. One such effect is persistent photoinduced magnetism, found in CoFe analogs. For such an optical system, in an attempt to maximize the material's interaction with incident photons, a thin film geometry is often utilized; this geometry can produce new effects [1]. Samples of different starting materials have been characterized with respect to photoinduced states, angular dependent susceptibility, film thickness, and chemical formula. Notably, magnetic anisotropies present in the systems show a dependence on the studied factors. One class of interesting starting materials are RbjNik[Cr(CN)6]l.nH2O and RbjCok[Fe(CN)6]l.nH2O heterostructures, generated by sequential adsorption on a Melinex substrate, that display behavior different than a noninteracting admixture of the two materials by themselves. [1] J.-H. Park, E. Cizmar, M. W. Meisel, Y. D. Huh, F. Frye, S. Lane, and D. R. Talham, Appl. Phys. Lett. 85, 3797 (2004).

  7. Prenatal alcohol exposure reduces magnetic susceptibility contrast and anisotropy in the white matter of mouse brains.

    PubMed

    Cao, Wei; Li, Wei; Han, Hui; O'Leary-Moore, Shonagh K; Sulik, Kathleen K; Allan Johnson, G; Liu, Chunlei

    2014-11-15

    Prenatal alcohol exposure can result in long-term cognitive and behavioral deficits. Fetal alcohol spectrum disorder (FASD) refers to a range of permanent birth defects caused by prenatal alcohol exposure, and is the most common neurodevelopmental disorder in the US. Studies by autopsy and conventional structural MRI indicate that the midline structures of the brain are particularly vulnerable to prenatal alcohol exposure. Diffusion tensor imaging (DTI) has shown that abnormalities in brain white matter especially the corpus callosum are very common in FASD. Quantitative susceptibility mapping (QSM) is a novel technique that measures tissue's magnetic property. Such magnetic property is affected by tissue microstructure and molecular composition including that of myelin in the white matter. In this work, we studied three major white matter fiber bundles of a mouse model of FASD and compared it to control mice using both QSM and DTI. QSM revealed clear and significant abnormalities in anterior commissure, corpus callosum, and hippocampal commissure, which were likely due to reduced myelination. Our data also suggested that QSM may be even more sensitive than DTI for examining changes due to prenatal alcohol exposure. Although this is a preclinical study, the technique of QSM is readily translatable to human brain. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. In-situ magnetic susceptibility measurements as a tool to follow geomicrobiological transformation of Fe minerals.

    PubMed

    Porsch, Katharina; Dippon, Urs; Rijal, Moti Lal; Appel, Erwin; Kappler, Andreas

    2010-05-15

    Fe minerals sorb nutrients and pollutants and participate in microbial and abiotic redox reactions. Formation and transformation of Fe minerals is typically followed by mineral analysis at different time points. However, in lab studies the available sample amount is often limited and sampling may even influence the experimental conditions. We therefore evaluated the suitability of in situ magnetic susceptibility (MS) measurements, which do not require sampling, as an alternative tool to follow ferro(i)magnetic mineral (trans-)formation during ferrihydrite reduction by Shewanella oneidensis MR-1, and in soil microcosms. In our experiments with MR-1, a large initial increase in volume specific MS (kappa) followed by a slight decrease correlated well with the initial formation of magnetite and further reduction of magnetite to siderite as also identified by micro-XRD. The presence of humic acids retarded magnetite formation, and even inhibited magnetite formation completely, depending on their concentration. In soil microcosms, an increase in kappa accompanied by increasing concentrations of HCl-extractable Fe occurred only in microbially active set-ups, indicating a microbially induced change in soil Fe mineralogy. Based on our results, we conclude that MS measurements are suitable to follow microbial Fe mineral transformation in pure cultures as well as in complex soil samples.

  9. Basaltic lava characterization using magnetic susceptibility identification and presence of opaque minerals in Ijen volcanic complex, Banyuwangi, East Java

    NASA Astrophysics Data System (ADS)

    Pratama, Aditya; Hafidz, Abd.; Bijaksana, Satria; Abdurrachman, Mirzam

    2017-07-01

    Reliable volcanic map and deep understanding of magmatic processes are very important in exploration of natural resources and mitigation of volcanic hazards. The conservative method in volcanic mapping still depends on qualitative approach thus it often failed to characterize volcanic products properly. Rock magnetic methods are quantitative approaches that classify rocks based on their magnetic properties. In this study, magmatic processes in basaltic lavas from Ijen volcanic complex in Banyuwangi, East Java were studied using combined rock magnetic and petrogenesis approaches. Samples of basaltic lavas from 13 localities, taken from three eruption sources were measuredfor their mass-specific magnetic susceptibility. The samples were then also subjected to petrographic and X-ray Fluorescence Spectrometry (XRF) analyses for their minerals composition and petrogenesis. Preliminary results show that the distinction in magnetic characters might be due to the quantity of magnetic minerals contained in rocks.

  10. Using magnetic susceptibility to discriminate between soil moisture regimes in selected loess and loess-like soils in northern Iran

    NASA Astrophysics Data System (ADS)

    Valaee, Morteza; Ayoubi, Shamsollah; Khormali, Farhad; Lu, Sheng Gao; Karimzadeh, Hamid Reza

    2016-04-01

    This study used discriminant analysis to determine the efficacy of magnetic measures for discriminating between four soil moisture regimes in northern Iran. The study area was located on loess deposits and loess-like soils containing similar parent material. Four soil moisture regimes including aridic, xeric, udic, and aquic were selected. A total of 25 soil profiles were drug from each regime and composite soil samples were collected within the moisture control section. A set of magnetic measures including magnetic susceptibility at low (χlf) and high (χhf) frequencies, frequency-dependent magnetic susceptibility (χfd), saturation isothermal remnant magnetization (SIRM), and isothermal remnant magnetization (IRM100 mT, IRM 20 mT) were measured in the laboratory. Dithionite citrate bicarbonate (Fed) and acid oxalate (Feo) contents of all soil samples were also determined. The lowest and highest χlf and χhf were observed in aquic and udic moisture regimes, respectively. A similar trend was obtained for Fed and Fed-Feo. The significant positive correlation between Fed and SIRM (r = 0.60; P < 0.01) suggested the formation of stable single domains (SSD) due to pedogenic processes. The results of discriminant analysis indicated that a combination of magnetic measures could successfully discriminate between the selected moisture regimes in the study area (average accuracy = 80%). It can thus be concluded that magnetic measures could be applied as a powerful indicator for differentiation of soil moisture regimes in the study area.

  11. Anisotropy of magnetic susceptibility of Eolian sediments in Altun Shan: implications for Altyn Tagh Fault tectonics since Pleistocene

    NASA Astrophysics Data System (ADS)

    Zhang, R.

    2015-12-01

    Ancient windblown (eolian) dust, such as in Chinese Loess Plateau (CLP), are treasured for understanding the evolution of aridity and influence by Plateau(mountain)uplift on climate change. Anisotropy of magnetic susceptibility (AMS) is an effective tool in tracking atmospheric direction under weak to moderate speed currents to reconstruct the paleomonsoon model was studied in recent years. Whilst it is sometimes directly or indirectly associated with the effects of tectonic process and developed as a results of burial diagenesis process for these eolian sediments. Here we firstly investigated AMS in a Red clay sequence (eolian deposits during Miocene to Pliocene) accumulated in the margin of Altun Mountains, which has the similar mineral content as that in CLP. The average north-west orientations of minimum magnetic susceptibility (Kmin) axes is tilting towards the active Althy Tagh Fault direction and the average direction of intermediate magnetic susceptibility (Kint) axes is close to be vertical and compacted by the gravity as a second force. The average maximum magnetic susceptibility (Kmax) is perpendicular to either tectonic or gravity directions. Considering there is no obvious metamorphic effects and plastic deformation of particles, we attribute these two stresses determined the transition of petrofabrics from the deposition to tectonics, by the intensified Pleistocene activity of Altyn Tagh Fault.

  12. A comparative quantitative analysis of magnetic susceptibility artifacts in echo planar and PROPELLER diffusion-weighted images

    NASA Astrophysics Data System (ADS)

    Cho, Jae-Hwan; Lee, Hae-Kag; Yang, Han-Joon; Lee, Gui-Won; Park, Yong-Soon; Chung, Woon-Kwan

    2013-01-01

    In this study, the authors investigated whether periodically-rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion-weighted imaging (DWI) can remove magnetic susceptibility artifacts and compared apparent diffusion coefficient (ADC) values for PROPELLER DWI and the common echo planar (EP) DWI. Twenty patients that underwent brain MRI with a metal dental implant were selected. A 3.0T MR scanner was then used to obtain EP DWI, PROPELLER DWI, and corresponding apparent diffusion coefficient (ADC) maps for a b-value of 0 and 1,000 s/mm2. The frequencies of magnetic susceptibility artifacts in four parts of the brain (bilateral temporal lobes, pons, and orbit) were selected. In the ADC maps, we measured the ADC values of both sides of the temporal lobe and the pons. According to the study results, the frequency of magnetic susceptibility artifacts in PROPELLER DW images was lower than it was in EP DW images. In ADC maps, the ADC values of the bilateral temporal lobes and the pons were all higher in PROPELLER ADC maps than in EP ADC maps. Our findings show that when a high-field MRI machine is used, magnetic susceptibility artifacts can distort anatomical structures and produce high-intensity signals. Furthermore, our findings suggest that in many cases, PROPELLER DWI would be helpful in terms of achieving a correct diagnosis.

  13. Magnetic susceptibility of Dirac electrons in single-component molecular conductor [Pd(dddt)2] under pressure

    NASA Astrophysics Data System (ADS)

    Suzumura, Yoshikazu; Kato, Reizo

    2017-05-01

    Using a tight-binding model with four lattice sites per unit cell, we examine a three-dimensional Dirac electron in a single-component molecular conductor [Pd(dddt)2], which consists of HOMO and LUMO orbitals. The Dirac cone, which originates from the interplay of the intralayer and interlayer transfer energies, gives a semimetallic state owing to a slight variation in energy along the line of the Dirac point. Electronic states of the Dirac electron are examined by calculating the temperature (T) dependence of magnetic (spin) susceptibility. It is shown that magnetic susceptibility remains finite at zero temperature and the variation with increasing temperature exhibits a T-linear dependence. The role of the HOMO and LUMO orbitals is discussed in terms of local susceptibility.

  14. 1D magnetic interactions in Cu(II) oxovanadium phosphates (VPO), magnetic susceptibility, DFT, and single-crystal EPR.

    PubMed

    Venegas-Yazigi, Diego; Spodine, Evgenia; Saldias, Marianela; Vega, Andrés; Paredes-García, Verónica; Calvo, Rafael; de Santana, Ricardo Costa

    2015-04-20

    We report the crystal face indexing and molecular spatial orientation, magnetic properties, electron paramagnetic resonance (EPR) spectra, and density functional theory (DFT) calculations of two previously reported oxovanadium phosphates functionalized with Cu(II) complexes, namely, [Cu(bipy)(VO2)(PO4)]n (1) and [{Cu(phen)}2(VO2(H2O)2)(H2PO4)2 (PO4)]n (2), where bipy = 2,2'-bipyridine and phen = 1,10-phenanthroline, obtained by a new synthetic route allowing the growth of single crystals appropriate for the EPR measurements. Compounds 1 and 2 crystallize in the triclinic group P1̅ and in the orthorhombic Pccn group, respectively, containing dinuclear copper units connected by two -O-P-O- bridges in 1 and by a single -O-P-O- bridge in 2, further connected through -O-P-O-V-O- bridges. We emphasize in our work the structural aspects related to the chemical paths that determine the magnetic properties. Magnetic susceptibility data indicate bulk antiferromagnetism for both compounds, allowing to calculate J = -43.0 cm(-1) (dCu-Cu = 5.07 Å; J defined as Hex(i,j) = -J Si·Sj), considering dinuclear units for 1, and J = -1.44 cm(-1) (dCu-Cu = 3.47 Å) using the molecular field approximation for 2. The single-crystal EPR study allows evaluation of the g matrices, which provide a better understanding of the electronic structure. The absence of structure of the EPR spectra arising from the dinuclear character of the compounds allows estimation of weak additional exchange couplings |J'| > 0.3 cm(-1) for 1 (dCu-Cu = 5.54 Å) and a smaller value of |J'| ≥ 0.15 cm(-1) for 2 (dCu-Cu = 6.59 Å). DFT calculations allow evaluating two different exchange couplings for each compound, specifically, J = -36.60 cm(-1) (dCu-Cu = 5.07 Å) and J' = 0.20 cm(-1) (dCu-Cu =5.54 Å) for 1 and J = -1.10 cm(-1) (dCu-Cu =3.47 Å) and J' = 0.01 cm(-1) (dCu-Cu = 6.59 Å) for 2, this last value being in the range of the uncertainties of the calculations. Thus, these values are in good agreement

  15. Rock magnetic properties, magnetic susceptibility, and organic geochemistry comparison in core LZ1029-7 Lake El'gygytgyn, Russia Far East

    NASA Astrophysics Data System (ADS)

    Murdock, K. J.; Wilkie, K.; Brown, L. L.

    2013-02-01

    Susceptibility measurements performed on initial short (~ 16 m) cores PG1351 taken from Lake El'gygytgyn exhibited a large range in values. This observation led to the suggestion of widespread magnetite dissolution within the sediments due to anoxic conditions within the lake. Rock magnetic properties and their comparison with magnetic susceptibility, total organic carbon (TOC), and bulk δ13Corg proxies in core LZ1029-7, taken from the same site as the previously drilled PG1351, provide an insight into the character of the magnetic minerals present within the lake and can further the understanding of processes that may be present in the newer long core sediments. Susceptibility measurements (χ) of discrete samples corroborate the two order of magnitude difference seen in previous continuous susceptibility measurements (κ), correlating high values with interglacial periods and low values with glacial intervals. Hysteresis parameters indicate that the majority of the magnetic material to be magnetite of PSD size. TOC values increase while δ13Corg values decrease in one section of LZ1029-7, which is defined as the Last Glacial Maximum (LGM), and help confine the age of the core to approximately 62 ka. Increases in TOC during the most recent glacial interval suggest increased preservation of organic carbon during this period. High TOC and low magnetic susceptibility during the LGM support the theory of perennial ice cover during glacial periods, which would lead to lake stratification and therefore anoxic bottom water conditions. Low temperature magnetic measurements confirmed the presence of magnetite, but also indicated titanomagnetite and possibly siderite, rhodochrosite, and/or vivianite were present. The latter three minerals are found only in anoxic environments, and further support the notion of magnetite dissolution.

  16. Rock magnetic properties, magnetic susceptibility, and organic geochemistry comparison in core LZ1029-7 Lake El'gygytgyn, Far Eastern Russia

    NASA Astrophysics Data System (ADS)

    Murdock, K. J.; Wilkie, K. M.; Brown, L. L.

    2012-09-01

    Susceptibility measurements performed on initial short (3-16 m) cores taken from Lake El'gygytgyn exhibited a large range in values. This observation led to the suggestion of widespread magnetite dissolution within the sediments due to anoxic conditions within the lake. Rock magnetic properties and their comparison with magnetic susceptibility, Total Organic Carbon (TOC), and bulk δ13Corg proxies in core LZ1029-7 provide an insight into the character of the magnetic minerals present within the lake and can further the understanding of processes that may be present in the newer long core sediments Susceptibility measurements (χ) of discrete samples corroborate the two order of magnitude difference seen in previous continuous susceptibility measurements (κ), correlating high values with interglacial periods and low values with glacial intervals. Hysteresis parameters defined the majority of the magnetic material to be magnetite of PSD size. TOC values increase while δ13Corg values decrease in one section of LZ1029-7, which is defined as the Last Glacial Maximum (LGM), and help confine the age of the core to approximately 62 kyr. Increases in TOC during the most recent glacial interval suggest increased preservation of organic carbon during these times High TOC and low magnetic susceptibility during the LGM support the theory of perennial ice cover during glacial periods, which would lead to lake stratification and therefore anoxic bottom water conditions. Low temperature magnetic measurements also confirmed the presence of magnetite, but also indicated titanomagnetite, siderite and/or rhodochrosite, and vivianite were present. The latter three minerals are found only in anoxic environments, and further support the notion of magnetite dissolution.

  17. Measuring the magnetic-field-dependent chemical potential of a low-density three-dimensional electron gas in n -GaAs and extracting its magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Roy Choudhury, Aditya N.; Venkataraman, V.

    2016-01-01

    We report the magnetic-field-dependent shift of the electron chemical potential in bulk, n -type GaAs at room temperature. A transient voltage of ˜100 μ V was measured across a Au-Al2O3 -GaAs metal-oxide-semiconductor capacitor in a pulsed magnetic field of ˜6 T . Several spurious voltages larger than the signal that had plagued earlier researchers performing similar experiments were carefully eliminated. The itinerant magnetic susceptibility of GaAs is extracted from the experimentally measured data for four different doping densities, including one as low as 5 ×1015cm-3 . Though the susceptibility in GaAs is dominated by Landau-Peierls diamagnetism, the experimental technique demonstrated can be a powerful tool for extracting the total free carrier magnetization of any electron system. The method is also virtually independent of the carrier concentration and is expected to work better in the nondegenerate limit. Such experiments had been successfully performed in two-dimensional electron gases at cryogenic temperatures. However, an unambiguous report on having observed this effect in any three-dimensional electron gas has been lacking. We highlight the 50 year old literature of various trials and discuss the key details of our experiment that were essential for its success. The technique can be used to unambiguously yield only the itinerant part of the magnetic susceptibility of complex materials such as magnetic semiconductors and hexaborides, and thus shed light on the origin of ferromagnetism in such systems.

  18. Understanding the morphological mismatch between magnetic susceptibility source and t2* image.

    PubMed

    Chen, Zikuan; Calhoun, Vince

    2013-01-01

    Recent research has shown that a T2* image (either magnitude or phase) is not identical to the internal spatial distribution of a magnetic susceptibility (χ) source. In this paper, we examine the reasons behind these differences by looking into the insights of T2*-weighted magnetic resonance imaging (T2*MRI) and provide numerical characterizations of the source/image mismatches by numerical simulations. For numerical simulations of T2*MRI, we predefine a 3D χ source and calculate the complex-valued T2* image by intravoxel dephasing in presence and absence of diffusion. We propose an empirical α-power model to describe the overall source/image transformation. For a Gaussian-shaped χ source, we numerically characterize the source/image morphological mismatch in terms of spatial correlation and FWHM (full width at half maximum). In theory, we show that the χ-induced fieldmap is morphologically different from the χ source due to dipole effect, and the T2* magnitude image is related to the fieldmap by a quadratic transformation in the small phase angle regime, which imposes an additional morphological change. The numerical simulations with a Gaussian-shaped χ source show that a T2* magnitude image may suffer an overall source/image morphological shrinkage of 20% to 25% and that the T2* phase image is almost identical to the fieldmap thus maintaining a morphological mismatch from the χ source due to dipole effect. The morphological mismatch between a bulk χ source and its T2* image is caused by the 3D convolution during tissue magnetization (dipole effect), the nonlinearity of the T2* magnitude and phase calculation, and the spin diffusion effect. In the small phase angle regime, the T2* magnitude exhibits an overall morphological shrinkage, and the T2* phase image suffers a dipole effect but maintains the χ-induced fieldmap morphology.

  19. Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Maffione, Marco; Hernandez-Moreno, Catalina; Ghiglione, Matias C.; Speranza, Fabio; van Hinsbergen, Douwe J. J.; Lodolo, Emanuele

    2015-12-01

    The southernmost segment of the Andean Cordillera underwent a complex deformation history characterized by alternation of contractional, extensional, and strike-slip tectonics. Key elements of southern Andean deformation that remain poorly constrained, include the origin of the orogenic bend known as the Patagonian Orocline (here renamed as Patagonian Arc), and the exhumation mechanism of an upper amphibolite facies metamorphic complex currently exposed in Cordillera Darwin. Here, we present results of anisotropy of magnetic susceptibility (AMS) from 22 sites in Upper Cretaceous to upper Eocene sedimentary rocks within the internal structural domain of the Magallanes fold-and-thrust belt in Tierra del Fuego (Argentina). AMS parameters from most sites reveal a weak tectonic overprint of the original magnetic fabric, which was likely acquired upon layer-parallel shortening soon after sedimentation. Magnetic lineation from 17 sites is interpreted to have formed during compressive tectonic phases associated to a continuous N-S contraction. Our data, combined with the existing AMS database from adjacent areas, show that the Early Cretaceous-late Oligocene tectonic phases in the Southern Andes yielded continuous contraction, variable from E-W in the Patagonian Andes to N-S in the Fuegian Andes, which defined a radial strain field. A direct implication is that the exhumation of the Cordillera Darwin metamorphic complex occurred under compressive, rather than extensional or strike-slip tectonics, as alternatively proposed. If we agree with recent works considering the curved Magallanes fold-and-thrust belt as a primary arc (i.e., no relative vertical-axis rotation of the limbs occurs during its formation), then other mechanisms different from oroclinal bending should be invoked to explain the documented radial strain field. We tentatively propose a kinematic model in which reactivation of variably oriented Jurassic faults at the South American continental margin controlled

  20. Soil magnetic susceptibility reflects soil moisture regimes and the adaptability of tree species to these regimes

    USGS Publications Warehouse

    Wang, J.-S.; Grimley, D.A.; Xu, C.; Dawson, J.O.

    2008-01-01

    Flooded, saturated or poorly drained soils are frequently anaerobic, leading to dissolution of the strongly magnetic minerals, magnetite and maghemite, and a corresponding decrease in soil magnetic susceptibility (MS). In this study of five temperate deciduous forests in east-central Illinois, USA, mean surface soil MS was significantly higher adjacent to upland tree species (31 ?? 10-5 SI) than adjacent to floodplain or lowland tree species (17 ?? 10-5 SI), when comparing regional soils with similar parent material of loessal silt. Although the sites differ in average soil MS for each tree species, the relative order of soil MS means for associated tree species at different locations is similar. Lowland tree species, Celtis occidentalis L., Ulmus americana L., Acer saccharinum L., Carya laciniosa (Michx. f.) Loud., and Fraxinus pennsylvanica Marsh. were associated with the lowest measured soil MS mean values overall and at each site. Tree species' flood tolerance rankings increased significantly, as soil MS values declined, the published rankings having significant correlations with soil MS values for the same species groups. The three published classifications of tree species' flood tolerance were significantly correlated with associated soil MS values at all sites, but most strongly at Allerton Park, the site with the widest range of soil drainage classes and MS values. Using soil MS measurements in forests with soil parent material containing similar initial levels of strongly magnetic minerals can provide a simple, rapid and quantitative method to classify soils according to hydric regimes, including dry conditions, and associated plant composition. Soil MS values thus have the capacity to quantify the continuum of hydric tolerances of tree species and guide tree species selection for reforestation. ?? 2007 Elsevier B.V. All rights reserved.

  1. Asteroid impact vs. Deccan eruptions: The origin of low magnetic susceptibility beds below the Cretaceous-Paleogene boundary revisited

    NASA Astrophysics Data System (ADS)

    Abrajevitch, Alexandra; Font, Eric; Florindo, Fabio; Roberts, Andrew P.

    2015-11-01

    The respective roles of an asteroid impact and Deccan Traps eruptions in biotic changes at the Cretaceous-Paleogene (K-Pg) boundary are still debated. In many shallow marine sediments from around the world, the K-Pg boundary is marked by a distinct clay layer that is often underlain by a several decimeter-thick low susceptibility zone. A previous study of the Gubbio section, Italy (Lowrie et al., 1990), attributed low magnetization intensity in this interval to post-depositional dissolution of ferrimagnetic minerals. Dissolution was thought to be a consequence of downward infiltration of reducing waters that resulted from rapid accumulation of organic matter produced by mass extinctions after the K-Pg event. We compare the magnetic properties of sediments from the Gubbio section with those of the Bidart section in southern France. The two sections are similar in their carbonate lithology and the presence of a boundary clay and low susceptibility zone. When compared to background Cretaceous sediments, the low susceptibility zone in both sections is marked by an absence of biogenic magnetite, a decrease in total ferrimagnetic mineral content, and a preferential loss of magnetite with respect to hematite - features that are consistent with reductive dissolution. However, unlike the Gubbio section, where the low susceptibility zone starts immediately below the boundary clay, the low susceptibility zone and the clay layer at Bidart are separated by a ∼4-cm carbonate interval that contains abundant biogenic magnetite. Such separation casts doubt on a causal link between the impact and sediment bleaching. More likely, the low susceptibility layer marks a different environmental event that preceded the impact. An episode of increased atmospheric and oceanic acidity associated with Deccan Traps volcanism that occurred well before the K-Pg impact is argued here to account for the distinct magnetic properties of the low susceptibility intervals.

  2. Motion robust magnetic susceptibility and field inhomogeneity estimation using regularized image restoration techniques for fMRI.

    PubMed

    Yeo, Desmond Teck Beng; Fessler, Jeffrey A; Kim, Boklye

    2008-01-01

    In functional MRI, head motion may cause dynamic nonlinear field-inhomogeneity changes, especially with large out-of-plane rotations. This may lead to dynamic geometric distortion or blurring in the time series, which may reduce activation detection accuracy. The use of image registration to estimate dynamic field inhomogeneity maps from a static field map is not sufficient in the presence of such rotations. This paper introduces a retrospective approach to estimate magnetic susceptibility induced field maps of an object in motion, given a static susceptibility induced field map and the associated object motion parameters. It estimates a susceptibility map from a static field map using regularized image restoration techniques, and applies rigid body motion to the former. The dynamic field map is then computed using susceptibility voxel convolution. The method addresses field map changes due to out-of-plane rotations during time series acquisition and does not involve real time field map acquisitions.

  3. Rock magnetic and anisotropy of magnetic susceptibility(AMS) of earthquake affected soft sediments: Examples from Shillong and Latur (Deccan Trap), India.

    NASA Astrophysics Data System (ADS)

    Lakshmi, B. V., ,, Dr.; Gawali, Mr. Praveen B.; Deenadayalan, K., ,, Dr.; Ramesh, D. S., ,, Prof.

    2017-04-01

    Rock magnetic and anisotropy of magnetic susceptibility (AMS) of earthquake affected soft sediments: Examples from Shillong and Latur (Deccan Trap), India. B.V.Lakshmi, Praveen B.Gawali, K.Deenadayalan and D.S.Ramesh Indian Institute of Geomagnetism, plot 5, sector 18, Near Kalamboli Highway, New Panvel(W), Navi Mumbai 410218 Combined rock magnetism and anisotropy of magnetic susceptibility (AMS) studies on earthquake induced soft and non-soft sediments from Shillong and Latur, India have thrown up interesting results. The morphology of hysteresis loops, the pattern of isothermal remanent magnetization (IRM) acquisition, and temperature dependence of susceptibility indicate that titano-magnetite/magnetite is the main magnetic carrier in these sediments. We also analyzed the anisotropy of magnetic susceptibility (AMS) of liquefaction features within the seismically active Dauki fault, Shillong Plateau. We discovered that host sediments (non-liquefied), are characterized by an oblate AMS ellipsoid and liquefied sediment are characterized by a triaxial AMS ellipsoid, well grouped maximum susceptibility axis K1 (NNW-SSE trend). Field evidence and AMS analysis indicate that most of these features were emplaced by injection inferred to be due to seismically triggered fluidization. Anisotropy of magnetic susceptibility (AMS) of deformed and undeformed unconsolidated clay samples of Deccan Trap terrain from the 2000-year-old paleoearthquake site of Ther village, Maharashtra, India, was also studied. Such deposits are rare in the compact basaltic terrain because of which the results acquired are very important. The undeformed clay samples exhibit typical sedimentary fabric with an oblate AMS ellipsoid, whereas the deformed samples are tightly grouped in the inferred compression direction, probably effected by an earthquake, exhibiting prolate as well as oblate AMS ellipsoids. Rock magnetic and AMS methodology can help understand the behavior of different sediments to the

  4. Determination of Magnetic Parameters of Maghemite (γ-Fe2O3) Core-Shell Nanoparticles from Nonlinear Magnetic Susceptibility Measurements

    NASA Astrophysics Data System (ADS)

    Syvorotka, Ihor I.; Pavlyk, Lyubomyr P.; Ubizskii, Sergii B.; Buryy, Oleg A.; Savytskyy, Hrygoriy V.; Mitina, Nataliya Y.; Zaichenko, Oleksandr S.

    2017-04-01

    Method of determining of magnetic moment and size from measurements of dependence of the nonlinear magnetic susceptibility upon magnetic field is proposed, substantiated and tested for superparamagnetic nanoparticles (SPNP) of the "magnetic core-polymer shell" type which are widely used in biomedical technologies. The model of the induction response of the SPNP ensemble on the combined action of the magnetic harmonic excitation field and permanent bias field is built, and the analysis of possible ways to determine the magnetic moment and size of the nanoparticles as well as the parameters of the distribution of these variables is performed. Experimental verification of the proposed method was implemented on samples of SPNP with maghemite core in dry form as well as in colloidal systems. The results have been compared with the data obtained by other methods. Advantages of the proposed method are analyzed and discussed, particularly in terms of its suitability for routine express testing of SPNP for biomedical technology.

  5. Relaxation dynamics of modulated magnetic phases in the skyrmion host GaV4S8 : An ac magnetic susceptibility study

    NASA Astrophysics Data System (ADS)

    Butykai, Ádám; Bordács, Sándor; Kiss, László F.; Szigeti, Bertalan György; Tsurkan, Vladimir; Loidl, Alois; Kézsmárki, István

    2017-09-01

    We report on the slow magnetization dynamics observed upon the magnetic phase transitions of GaV4S8 , a multiferroic compound featuring a long-ranged cycloidal magnetic order and a Néel-type skyrmion lattice in a relatively broad temperature range below its Curie temperature. The fundamental difference between GaV4S8 and the chiral helimagnets, the prototypical skyrmion host compounds, lies within the polar symmetry of GaV4S8 , promoting a cycloidal instead of a helical magnetic order and rendering the magnetic phase diagram essentially different from that in the cubic helimagnets. Our ac magnetic susceptibility study reveals slow relaxation dynamics at the field-driven phase transitions between the cycloidal, skyrmion lattice and field-polarized states. At each phase boundary, the characteristic relaxation times were found to exhibit a strong temperature dependence, starting from the minute range at low temperatures, decreasing to the micro- to millisecond range at higher temperatures.

  6. Determination of Magnetic Parameters of Maghemite (γ-Fe2O3) Core-Shell Nanoparticles from Nonlinear Magnetic Susceptibility Measurements.

    PubMed

    Syvorotka, Ihor I; Pavlyk, Lyubomyr P; Ubizskii, Sergii B; Buryy, Oleg A; Savytskyy, Hrygoriy V; Mitina, Nataliya Y; Zaichenko, Oleksandr S

    2017-12-01

    Method of determining of magnetic moment and size from measurements of dependence of the nonlinear magnetic susceptibility upon magnetic field is proposed, substantiated and tested for superparamagnetic nanoparticles (SPNP) of the "magnetic core-polymer shell" type which are widely used in biomedical technologies. The model of the induction response of the SPNP ensemble on the combined action of the magnetic harmonic excitation field and permanent bias field is built, and the analysis of possible ways to determine the magnetic moment and size of the nanoparticles as well as the parameters of the distribution of these variables is performed. Experimental verification of the proposed method was implemented on samples of SPNP with maghemite core in dry form as well as in colloidal systems. The results have been compared with the data obtained by other methods. Advantages of the proposed method are analyzed and discussed, particularly in terms of its suitability for routine express testing of SPNP for biomedical technology.

  7. Mössbauer spectroscopy, magnetization, magnetic susceptibility, and low temperature heat capacity of α-Na2NpO4

    NASA Astrophysics Data System (ADS)

    Smith, Anna L.; Hen, Amir; Magnani, Nicola; Sanchez, Jean-Pierre; Colineau, Eric; Griveau, Jean-Christophe; Raison, Philippe E.; Caciuffo, Roberto; Konings, Rudy J. M.; Cheetham, Anthony K.

    2016-03-01

    The physical and chemical properties at low temperatures of hexavalent disodium neptunate α-Na2NpO4 are investigated for the first time in this work using Mössbauer spectroscopy, magnetization, magnetic susceptibility, and heat capacity measurements. The Np(VI) valence state is confirmed by the isomer shift value of the Mössbauer spectra, and the local structural environment around the neptunium cation is related to the fitted quadrupole coupling constant and asymmetry parameters. Moreover, magnetic hyperfine splitting is reported below 12.5 K, which could indicate magnetic ordering at this temperature. This interpretation is further substantiated by the existence of a λ-peak at 12.5 K in the heat capacity curve, which is shifted to lower temperatures with the application of a magnetic field, suggesting antiferromagnetic ordering. However, the absence of any anomaly in the magnetization and magnetic susceptibility data shows that the observed transition is more intricate. In addition, the heat capacity measurements suggest the existence of a Schottky-type anomaly above 15 K associated with a low-lying electronic doublet found about 60 cm-1 above the ground state doublet. The possibility of a quadrupolar transition associated with a ground state pseudoquartet is thereafter discussed. The present results finally bring new insights into the complex magnetic and electronic peculiarities of α-Na2NpO4.

  8. The generalised Sylvester matrix equations over the generalised bisymmetric and skew-symmetric matrices

    NASA Astrophysics Data System (ADS)

    Dehghan, Mehdi; Hajarian, Masoud

    2012-08-01

    A matrix P is called a symmetric orthogonal if P = P T = P -1. A matrix X is said to be a generalised bisymmetric with respect to P if X = X T = PXP. It is obvious that any symmetric matrix is also a generalised bisymmetric matrix with respect to I (identity matrix). By extending the idea of the Jacobi and the Gauss-Seidel iterations, this article proposes two new iterative methods, respectively, for computing the generalised bisymmetric (containing symmetric solution as a special case) and skew-symmetric solutions of the generalised Sylvester matrix equation ? (including Sylvester and Lyapunov matrix equations as special cases) which is encountered in many systems and control applications. When the generalised Sylvester matrix equation has a unique generalised bisymmetric (skew-symmetric) solution, the first (second) iterative method converges to the generalised bisymmetric (skew-symmetric) solution of this matrix equation for any initial generalised bisymmetric (skew-symmetric) matrix. Finally, some numerical results are given to illustrate the effect of the theoretical results.

  9. Metastable Zr-Nb alloys for spinal fixation rods with tunable Young's modulus and low magnetic resonance susceptibility.

    PubMed

    Zhao, X L; Li, L; Niinomi, M; Nakai, M; Zhang, D L; Suryanarayana, C

    2017-10-15

    Good ductility, low magnetic susceptibility, and tunable Young's modulus are highly desirable properties for materials usage as spinal fixation rods. In this study, the effects of niobium content on the microstructure, magnetic susceptibility, and mechanical properties of Zr-xNb (13≤x≤23wt%) alloys were investigated. For the Zr-15Nb and Zr-17Nb alloys, a remarkable increase in Young's modulus was achieved due to the occurrence of deformation-induced ω phase transformation. This was the result of the competition of two factors associated with the Nb content: an increase of the stability of β phase and a decrease of the amount of athermal ω phase with increasing Nb content. When the Nb content was 15% or 17%, the amount of deformation-induced ω phase was maximum. Moreover, the magnetic susceptibility decreased with the deformation-induced β→ω phase transformation, and the Zr-17Nb alloy with apparent kink bands exhibited a smaller amount of springback than the Zr-15Nb alloy with {332} 〈113〉 mechanical twins. Furthermore, the ions released from the Zr-xNb alloys in accelerated immersion tests were at a very low level. The combination of low initial Young's modulus, and its remarkable variation induced by deformation, low magnetic susceptibility, good ductility, and smaller springback make the Zr-17Nb alloy a potential candidate for spinal fixation rods. For the rods of spinal fixation devices, it is important but difficult to lower the springback for bending formativeness while keeping the low initial Young's modulus for biocompatibility and lower the magnetic susceptibility for postoperative examination simultaneously. In this study, Zr-17Nb alloy was successfully developed via deformation-induced ω phase transformation during loading, simultaneously meeting the abovementioned properties for spinal fixation rods. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  10. Magnetic susceptibility of Dirac fermions, Bi-Sb alloys, interacting Bloch fermions, dilute nonmagnetic alloys, and Kondo alloys

    NASA Astrophysics Data System (ADS)

    Buot, Felix A.; Otadoy, Roland E. S.; Rivero, Karla B.

    2017-03-01

    Wide ranging interest in Dirac Hamiltonian is due to the emergence of novel materials, namely, graphene, topological insulators and superconductors, the newly-discovered Weyl semimetals, and still actively-sought after Majorana fermions in real materials. We give a brief review of the relativistic Dirac quantum mechanics and its impact in the developments of modern physics. The quantum band dynamics of Dirac Hamiltonian is crucial in resolving the giant diamagnetism of bismuth and Bi-Sb alloys. Quantitative agreement of the theory with the experiments on Bi-Sb alloys has been achieved, and physically meaningful contributions to the diamagnetism has been identified. We also treat relativistic Dirac fermion as an interband dynamics in uniform magnetic fields. For the interacting Bloch electrons, the role of translation symmetry for calculating the magnetic susceptibility avoids any approximation to second order in the field. The expressions for magnetic susceptibility of dilute nonmagnetic alloys give a firm theoretical foundation of the empirical formulas used in fitting experimental results. The unified treatment of all the above calculations is based on the lattice Weyl-Wigner formulation of discrete phase-space quantum mechanics. For completeness, the magnetic susceptibility of Kondo alloys is also given since Dirac fermions in conduction band and magnetic impurities exhibit Kondo effect.

  11. Magnetic susceptibility of the South African Agouron scientific drillcores quantifies iron and sulfur alteration relevant to geochemical oxygenation proxies

    NASA Astrophysics Data System (ADS)

    Raub, T. D.; Nayak, P. M.; Tikoo, S. M.; Johnson, J. E.; Peek, S.; Fischer, W. W.; Kirschvink, J. L.

    2010-12-01

    Various geochemical characteristics of sedimentary iron- and sulfur-bearing minerals motivate early- to late-oxygenation hypotheses from South African and Australian scientific drillcores. Most intervals of these drillcores appear to be remagnetized (in some cases multiple times); and ~2.0 Ga magnetic sulfide crystallization is particularly pervasive in carbonaceous siltstones of the ca. 2.7-2.2 Ga Griqualand margin of Kaapvaal craton. Robust interpretation of trace element abundances suggesting “whiffs” to “pervasive” levels of late Archean oxygen depends upon systematics of presumed depositional iron speciation; so multiple iron- and sulfur-mineral-altering events affecting existing drillcore records call straightforward interpretations into question. We report ca. 10,000 magnetic susceptibility measurements and associated detailed rock-magnetic results from all lithologies of Archean basinal and slope facies in drillcores GKP and GKF and relatively younger and shallower facies in Paleoproterozoic drillcores GEC and GTF. Specific carbonaceous siltstone and carbonate intervals are less-altered as revealed by coherent and relatively low magnetic susceptibilities: geochemical and biomarker interpretations based upon data from these intervals should be preferred to those from others. Magnetic susceptibility tracks subtle facies variation in drillcore GTF diamictite and suggests highly-structured Paleoproterozoic glacioeustatic sequence architecture consistent with assignment of Makganyene glaciation and its associated geochemical signature to a ca. 2.2 Ga “Snowball Earth” ice age.

  12. Anisotropy of out-of-phase magnetic susceptibility of rocks as a tool for direct determination of magnetic sub-fabrics of some minerals: An introductory study

    NASA Astrophysics Data System (ADS)

    Hrouda, František; Chadima, Martin; Ježek, Josef; Pokorný, Jiří

    2016-10-01

    The magnetic susceptibility measured in alternating field can in general be resolved into a component that is in-phase with the applied field and a component that is out-of-phase. While in non-conductive diamagnetic, paramagnetic and many ferromagnetic materials the phase is effectively zero, in some ferromagnetic minerals, such as pyrrhotite, hematite, titanomagnetite or small magnetically viscous grains of magnetite, it is clearly non-zero. The anisotropy of out-of-phase susceptibility (opAMS) can then be used as a tool for the direct determination of the magnetic sub-fabrics of the minerals with non-zero phase. The error in determination of out-of-phase susceptibility non-linearly increases with decreasing phase angle. This may result in imprecise determination of the opAMS in specimens with very low phase angle. The degree of opAMS is higher than that of ipAMS, which may in contrast result in slightly increasing precision n the opAMS determination. It is highly recommended to inspect the results of the statistical tests of each specimen and to exclude the specimens whose opAMS is determined with insufficient precision from further processing. In rocks, whose magnetism is dominated by the mineral with non-zero out-of-phase susceptibility, the principal directions of the opAMS and ipAMS are virtually coaxial, while the degree of opAMS is higher than that of ipAMS. In some specific cases, the opAMS provides us with similar data to those provided by anisotropies of low-field dependent susceptibility and frequency-dependent susceptibility. The advantage of the opAMS compared to the other two anisotropies is its simultaneous measurement with the ipAMS during one measuring process, while the other two anisotropies require the AMS measurements in several fields or at least at two operating frequencies.

  13. Anisotropy of out-of-phase magnetic susceptibility of rocks as a tool for direct determination of magnetic subfabrics of some minerals: an introductory study

    NASA Astrophysics Data System (ADS)

    Hrouda, František; Chadima, Martin; Ježek, Josef; Pokorný, Jiří

    2017-01-01

    The magnetic susceptibility measured in alternating field can in general be resolved into a component that is in-phase with the applied field and a component that is out-of-phase. While in non-conductive diamagnetic, paramagnetic and many ferromagnetic materials the phase is effectively zero, in some ferromagnetic minerals, such as pyrrhotite, hematite, titanomagnetite or small magnetically viscous grains of magnetite, it is clearly non-zero. The anisotropy of out-of-phase susceptibility (opAMS) can then be used as a tool for the direct determination of the magnetic subfabrics of the minerals with non-zero phase. The error in determination of out-of-phase susceptibility non-linearly increases with decreasing phase angle. This may result in imprecise determination of the opAMS in specimens with very low phase angle. The degree of opAMS is higher than that of ipAMS, which may in contrast result in slightly increasing precision n the opAMS determination. It is highly recommended to inspect the results of the statistical tests of each specimen and to exclude the specimens whose opAMS is determined with insufficient precision from further processing. In rocks, whose magnetism is dominated by the mineral with non-zero out-of-phase susceptibility, the principal directions of the opAMS and ipAMS are virtually coaxial, while the degree of opAMS is higher than that of ipAMS. In some specific cases, the opAMS provides us with similar data to those provided by anisotropies of low-field dependent susceptibility and frequency-dependent susceptibility. The advantage of the opAMS compared to the other two anisotropies is its simultaneous measurement with the ipAMS during one measuring process, while the other two anisotropies require the AMS measurements in several fields or at least at two operating frequencies.

  14. A method for the integration of satellite vegetation activities observations and magnetic susceptibility measurements for monitoring heavy metals in soil.

    PubMed

    D'Emilio, Mariagrazia; Macchiato, Maria; Ragosta, Maria; Simoniello, Tiziana

    2012-11-30

    We present a procedure for monitoring heavy metals in soil based on the integration of satellite and ground-based techniques, tested in an area affected by high anthropogenic pressure. High resolution multispectral satellite data were elaborated to obtain information on vegetation status. Magnetic susceptibility measurements of soils were collected as proxy variable for monitoring heavy metal presence. Chemical analyses of heavy metals were used for supporting and validating the integrated monitoring procedure. Magnetic and chemical measurements were organized in a GIS environment to be overlapped to satellite-based elaborations and to analyze the pattern distribution. Results show the presence of correlation between anomalies in vegetation activity and soil characteristics. The relationship between the distribution of normalized difference vegetation index anomalies and magnetic susceptibility values provides hints for adopting the integrated procedure as preliminary screening to minimize monitoring efforts and costs by supporting the planning activities of field campaigns.

  15. Comparison of optomagnetic and AC susceptibility readouts in a magnetic nanoparticle agglutination assay for detection of C-reactive protein.

    PubMed

    Fock, Jeppe; Parmvi, Mattias; Strömberg, Mattias; Svedlindh, Peter; Donolato, Marco; Hansen, Mikkel Fougt

    2017-02-15

    There is an increasing need to develop biosensor methods that are highly sensitive and that can be combined with low-cost consumables. The use of magnetic nanoparticles (MNPs) is attractive because their detection is compatible with low-cost disposables and because application of a magnetic field can be used to accelerate assay kinetics. We present the first study and comparison of the performance of magnetic susceptibility measurements and a newly proposed optomagnetic method. For the comparison we use the C-reactive protein (CRP) induced agglutination of identical samples of 100nm MNPs conjugated with CRP antibodies. Both methods detect agglutination as a shift to lower frequencies in measurements of the dynamics in response to an applied oscillating magnetic field. The magnetic susceptibility method probes the magnetic response whereas the optomagnetic technique probes the modulation of laser light transmitted through the sample. The two techniques provided highly correlated results upon agglutination when they measure the decrease of the signal from the individual MNPs (turn-off detection strategy), whereas the techniques provided different results, strongly depending on the read-out frequency, when detecting the signal due to MNP agglomerates (turn-on detection strategy). These observations are considered to be caused by differences in the volume-dependence of the magnetic and optical signals from agglomerates. The highest signal from agglomerates was found in the optomagnetic signal at low frequencies. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Spatial variability of soil magnetic susceptibility in an agricultural field located in Eastern Ukraine

    NASA Astrophysics Data System (ADS)

    Menshov, Oleksandr; Pereira, Paulo; Kruglov, Oleksandr

    2015-04-01

    Magnetic susceptibility (MS) have been used to characterize soil properties. It gives an indirect information about heavy metals content and degree of human impacts on soil contamination derived from atmospheric pollution (Girault et al., 2011). This method is inexpensive in relation to chemical analysis and very useful to track soil pollution, since several toxic components deposited on soil surface are rich in particulates produced by oxidation processes (Boyko et al., 2004; Morton-Bernea et al., 2009). Thus, identify the spatial distribution of MS is of major importance, since can give an indirect information of high metals content (Dankoub et al., 2012). This allows also to distinguish the pedogenic and technogenic origin magnetic signal. For example Ukraine chernozems contain fine-grained oxidized magnetite and maghemite of pedogenic origin formed by weathering of the parent material (Jeleńska et al., 2004). However, to a correct understanding of variables distribution, the identification of the most accurate interpolation method is fundamental for a better interpretation of map information (Pereira et al., 2013). The objective of this work is to study the spatial variability of soil MS in an agricultural fields located in the Tcherkascy Tishki area (50.11°N, 36.43 °E, 162 m a.s.l), Ukraine. Soil MS was measured in 77 sampling points in a north facing slope. To estimate the best interpolation method, several interpolation methods were tested, as inverse distance to a weight (IDW) with the power of 1,2,3,4 and 5, Local Polynomial (LP) with the power of 1 and 2, Global Polynomial (GP), radial basis functions - spline with tension (SPT), completely regularized spline (CRS), multiquatratic (MTQ), inverse multiquatratic (IMTQ), and thin plate spline (TPS) - and some geostatistical methods as, ordinary kriging (OK), Simple Kriging (SK) and Universal Kriging (UK), used in previous works (Pereira et al., 2014). On average, the soil MS of the studied plot had 686

  17. Linking Anisotropy of Magnetic Susceptibility (AMS) to transport direction: The Gavarnie Thrust, Axial Zone, Pyrenees

    NASA Astrophysics Data System (ADS)

    Marcén, Marcos; Casas-Sainz, Antonio; Román-Berdiel, Teresa; Soto, Ruth; Oliva-Urcía, Belén

    2017-04-01

    This work deals with the application of the anisotropy of magnetic susceptibility (AMS), structural analysis and microstructural analysis to the study of shear zones. Mylonitized fault rocks have been sampled in the Gavarnie Trust, one of the main structures of the Pyrenean Axial Zone, which was structured as a south-verging antiformal stack during the Alpine Orogeny. In the studied area, the Gavarnie Unit (Silurian-Carboniferous, low grade metasedimentary rocks) overthrust the Millares and Bielsa Units (Permian and Cretaceous cover, Cambro-Ordovician medium grade metamorphic rocks and granitoids), with a minimum horizontal displacement of 12km. Three profiles of the shear zone were studied with the goal of observing changes in the transport direction, the strain distribution and the orientation of the magnetic ellipsoid., One profile is parallel to the basal thrust plane, where the core zone has been identified, and the other two are vertical transects (profiles 1 and 2), perpendicular to the thrust plane. The shear zone, developed into the hangingwall phyllitic Silurian and Devonian units, is at least 30 m wide. The structural analysis reveals that the Silurian rocks are the local detachment level, which becomes thinner and pinchs out completely towards the South, where the detachment level is within the Devonian units (Fourche de la Sede Fm.). In both vertical profiles, the shear zone shows a decrease in the strain from the contact with the Cretaceous limestones at the footwall, towards the upper limit of the shear zone. This is evidenced by the lower development of mylonitic foliations and SCC' structures and the upwards increase of brittle deformation. The transport direction inferred from SC structures (stretching lineations in S and C planes) is constant in all sites, with an average of N190E. AMS data are in perfect agreement with the structural analysis, being the magnetic foliation parallel to the S or C planes of the SC structures. The magnetic

  18. Diagenetic Control Of The Magnetic Susceptibility Variations In Core MD98-2172 In The Eastern Timor Sea

    NASA Astrophysics Data System (ADS)

    Li, H.; Zhang, S.; Bai, L.; Fang, N.

    2008-12-01

    Detailed mineral magnetic measurements, integrated with grain-size distribution and X-ray diffraction (XRD) analyses, were made on the marine sediments of Core MD98-2172, retrieved from the Eastern Timor Sea. Values of magnetic susceptibility of this core drop sharply down-core since the depth of ~3.85 m and get to very low at ~5.35 m. But both results of XRD and grain-size distribution show no sudden change of the terrigenous input through the whole core. Mineral magnetic results indicate that the depth of ~3.85 m below the sediment/water interface may be an oxic/anoxic boundary and the sediments below ~3.85 m have been greatly subjected to the reductive diagenesis, while the sediments of the top ~3.85 m are seldom affected. The magnetic properties of the top 3.85-m sediments are dominated by pseudo-single domain (PSD) magnetite, and its content and grain size show little down-core variations. While the magnetic mineral assemblages that have survived in the sediments below ~3.85 m may record different stages of the reductive diagenesis: (1) the sediments from the 3.85-5.35 m interval are at the stage of iron oxide reduction; PSD magnetite is the major magnetic contributor, but it becomes less abundant and coarser down-core; (2) the sediments below ~5.35 m are at the stage of sulphate reduction; ferrimagnetic minerals almost vanish and paramagnetic minerals contribute to the susceptibility down-core variations, including pyrite as evidenced by high-temperature magnetic susceptibility measurements. However, the susceptibility variations below ~5.35 m of Core MD98-2172 show obvious periodicity, despite the intense effect of reductive diagenesis. Furthermore, the susceptibility down-core variations are coincident with the fluctuations of the amounts of fine detrital particles (<8 μm), which may mainly come from the advection of the Indonesia Throughflow and/or the river input from the Timor Island. Therefore, for Core MD98-2172, the susceptibility variations below ~5

  19. Diagenetic control of magnetic susceptibility variation in Core MD98-2172 from the Eastern Timor Sea

    NASA Astrophysics Data System (ADS)

    Li, Haiyan; Zhang, Shihong; Bai, Lingyan; Fang, Nianqiao

    2010-11-01

    Detailed mineral magnetic measurements, integrated with grain-size distribution and X-ray diffraction (XRD) analyses, were made on the marine sediments of Core MD98-2172, retrieved from the Eastern Timor Sea. Values of magnetic susceptibility in this core drop sharply down-core from ˜3.85 m deep below sediment/water interface and are very low at ˜5.35 m. However, both XRD and grain-size distribution results show no sudden change in terrigenous input during sedimentation. Mineral magnetic results indicate that the depth of ˜3.85 m may be an oxic/anoxic boundary. Therefore, the sediments below ˜3.85 m have been subjected to intense reductive diagenesis, whereas the sediments above ˜3.85 m are seldom affected. The magnetic properties of the sediments shallower than 3.85 m are dominated by pseudo-single domain (PSD) magnetite, with little down-core variation in its content and grain size. Below ˜3.85 m, the magnetic mineral assemblages that have survived in the sediments may record different stages of the reductive diagenesis: (1) the sediments from the 3.85-5.35 m interval are at the stage of iron oxide reduction; PSD magnetite is the major magnetic contributor, but it becomes less abundant and coarser down-core; (2) the sediments below ˜5.35 m are at the stage of sulphate reduction; ferrimagnetic minerals almost vanish and paramagnetic minerals contribute to down-core susceptibility variations, including pyrite as evidenced by high-temperature magnetic susceptibility measurements. However, the susceptibility variations below ˜5.35 m of Core MD98-2172 show obvious periodicity, despite the intense effect of reductive diagenesis. Furthermore, the down-core susceptibility variations are coincident with fluctuations in the quantity of fine detrital particles (<8 μm), which may come mainly from the advection of the Indonesia Throughflow (ITF) and/or river input from Timor. Therefore, for Core MD98-2172, susceptibility variation below ˜5.35 m, which potentially

  20. The use of the anisotropy of magnetic remanence in the resolution of the anisotropy of magnetic susceptibility into its ferromagnetic and paramagnetic components

    NASA Astrophysics Data System (ADS)

    Hrouda, František

    2002-04-01

    The anisotropy of magnetic susceptibility (AMS) is often controlled by both ferromagnetic (sensu lato) and paramagnetic minerals. The anisotropy of magnetic remanence (AMR) is solely controlled by ferromagnetic minerals. Jelı´nek (Trav. Geophys. 37 (1993)) introduced a tensor derived from the isothermal AMR whose normalized form equals the normalized susceptibility tensor provided that the ferromagnetic fraction is represented by multi-domain magnetite. The present paper shows the close correlation between these tensors for a collection of strongly magnetic specimens containing multi-domain magnetite. In addition, acceptable correlation between the tensors was also found for a collection of specimens containing single-domain magnetite. A new method is developed for the AMS resolution into ferromagnetic and paramagnetic components using the AMR. Some examples are presented of this resolution in mafic microgranular enclaves in granodiorite and in gneisses of the KTB borehole.

  1. The anisotropy of magnetic susceptibility of uniaxial superparamagnetic particles: Consequences for its interpretation in magnetite and maghemite bearing rocks

    NASA Astrophysics Data System (ADS)

    Lanci, Luca; Zanella, Elena

    2016-01-01

    A simple model that provides a quantitative description of the magnetic susceptibility of superparamagnetic to stable single-domain uniaxial magnetic particles can be built in the framework of the theory of stochastic resonance. This model expands that of Mullins and Tile (1973) for superparamagnetic grains by considering the dependence of superparamagnetic susceptibility on the particle orientation and thus describes the anisotropy of magnetic susceptibility (AMS) of ensembles of superparamagnetic as well as single-domain particles. The theory predicts that on the contrary of stable single domain, the maximum anisotropy of superparamagnetic particles is parallel to their easy axis and shows that the AMS of ensembles of uniaxial particle is strongly dependent on the distribution of particle grain size, coercivity, measurement temperature, and frequency. It also explains why the inverse AMS pattern expected for stable single-domain particles is rarely observed in natural samples. We use examples of well-characterized obsidian specimens to show that, as predicted by the theory, in the presence of significant superparamagnetic contributions, the maximum susceptibility axis of AMS is directed along the preferential direction of particles easy axis.

  2. Intrinsic functional brain mapping in reconstructed 4D magnetic susceptibility (χ) data space.

    PubMed

    Chen, Zikuan; Calhoun, Vince

    2015-02-15

    By solving an inverse problem of T2*-weighted magnetic resonance imaging for a dynamic fMRI study, we reconstruct a 4D magnetic susceptibility source (χ) data space for intrinsic functional mapping. A 4D phase dataset is calculated from a 4D complex fMRI dataset. The background field and phase wrapping effect are removed by a Laplacian technique. A 3D χ source map is reconstructed from a 3D phase image by a computed inverse MRI (CIMRI) scheme. A 4D χ data space is reconstructed by repeating the 3D χ source reconstruction for each time point. A functional map is calculated by a temporal correlation between voxel signals in the 4D χ space and the timecourse of the task paradigm. With a finger-tapping experiment, we obtain two 3D functional mappings in the 4D magnitude data space and in the reconstructed 4D χ data space. We find that the χ-based functional mapping reveals co-occurrence of bidirectional responses in a 3D activation map that is different from the conventional magnitude-based mapping. The χ-based functional mapping can also be achieved by a 3D deconvolution of a phase activation map. Based on a subject experimental comparison, we show that the 4D χ tomography method could produce a similar χ activation map as obtained by the 3D deconvolution method. By removing the dipole effect and other fMRI technological contaminations, 4D χ tomography provides a 4D χ data space that allows a more direct and truthful functional mapping of a brain activity. Published by Elsevier B.V.

  3. Diagnostic accuracy of susceptibility-weighted magnetic resonance imaging for the evaluation of pineal gland calcification

    PubMed Central

    Böker, Sarah M.; Bender, Yvonne Y.; Diederichs, Gerd; Fallenberg, Eva M.; Wagner, Moritz; Hamm, Bernd; Makowski, Marcus R.

    2017-01-01

    Objectives To determine the diagnostic performance of susceptibility-weighted magnetic resonance imaging (SWMR) for the detection of pineal gland calcifications (PGC) compared to conventional magnetic resonance imaging (MRI) sequences, using computed tomography (CT) as a reference standard. Methods 384 patients who received a 1.5 Tesla MRI scan including SWMR sequences and a CT scan of the brain between January 2014 and October 2016 were retrospectively evaluated. 346 patients were included in the analysis, of which 214 showed PGC on CT scans. To assess correlation between imaging modalities, the maximum calcification diameter was used. Sensitivity and specificity and intra- and interobserver reliability were calculated for SWMR and conventional MRI sequences. Results SWMR reached a sensitivity of 95% (95% CI: 91%-97%) and a specificity of 96% (95% CI: 91%-99%) for the detection of PGC, whereas conventional MRI achieved a sensitivity of 43% (95% CI: 36%-50%) and a specificity of 96% (95% CI: 91%-99%). Detection rates for calcifications in SWMR and conventional MRI differed significantly (95% versus 43%, p<0.001). Diameter measurements between SWMR and CT showed a close correlation (R2 = 0.85, p<0.001) with a slight but not significant overestimation of size (SWMR: 6.5 mm ± 2.5; CT: 5.9 mm ± 2.4, p = 0.02). Interobserver-agreement for diameter measurements was excellent on SWMR (ICC = 0.984, p < 0.0001). Conclusions Combining SWMR magnitude and phase information enables the accurate detection of PGC and offers a better diagnostic performance than conventional MRI with CT as a reference standard. PMID:28278291

  4. Diagnostic accuracy of susceptibility-weighted magnetic resonance imaging for the evaluation of pineal gland calcification.

    PubMed

    Adams, Lisa C; Böker, Sarah M; Bender, Yvonne Y; Diederichs, Gerd; Fallenberg, Eva M; Wagner, Moritz; Hamm, Bernd; Makowski, Marcus R

    2017-01-01

    To determine the diagnostic performance of susceptibility-weighted magnetic resonance imaging (SWMR) for the detection of pineal gland calcifications (PGC) compared to conventional magnetic resonance imaging (MRI) sequences, using computed tomography (CT) as a reference standard. 384 patients who received a 1.5 Tesla MRI scan including SWMR sequences and a CT scan of the brain between January 2014 and October 2016 were retrospectively evaluated. 346 patients were included in the analysis, of which 214 showed PGC on CT scans. To assess correlation between imaging modalities, the maximum calcification diameter was used. Sensitivity and specificity and intra- and interobserver reliability were calculated for SWMR and conventional MRI sequences. SWMR reached a sensitivity of 95% (95% CI: 91%-97%) and a specificity of 96% (95% CI: 91%-99%) for the detection of PGC, whereas conventional MRI achieved a sensitivity of 43% (95% CI: 36%-50%) and a specificity of 96% (95% CI: 91%-99%). Detection rates for calcifications in SWMR and conventional MRI differed significantly (95% versus 43%, p<0.001). Diameter measurements between SWMR and CT showed a close correlation (R2 = 0.85, p<0.001) with a slight but not significant overestimation of size (SWMR: 6.5 mm ± 2.5; CT: 5.9 mm ± 2.4, p = 0.02). Interobserver-agreement for diameter measurements was excellent on SWMR (ICC = 0.984, p < 0.0001). Combining SWMR magnitude and phase information enables the accurate detection of PGC and offers a better diagnostic performance than conventional MRI with CT as a reference standard.

  5. Precision magnetization and susceptibility measurements on ErRh/sub 4/B/sub 4/ in the ferromagnetic and superconducting phases

    SciTech Connect

    Behroozi, F.; Crabtree, G.W.; Campbell, S.A.; Levy, M.; Snider, D.; Johnston, D.C.; Matthias, B.T.

    1980-01-01

    Preliminary data giving the first continuous d.c. magnetization and suceptibility results for ErRh/sub 4/B/sub 4/ in the superconducting and magnetic states are presented. The susceptibility was obtained directly from the d.c. voltage induced in a pair of balanced coils, one of which contained the sample, by the linear sweep of an external field. The magnetization was obtained simultaneously by analog integration of the susceptibility signal.

  6. Impacts of geology and land use on magnetic susceptibility and selected heavy metals in surface soils of Mashhad plain, northeastern Iran

    NASA Astrophysics Data System (ADS)

    Karimi, Alireza; Haghnia, Gholam Hosain; Ayoubi, Shamsollah; Safari, Tayebeh

    2017-03-01

    Magnetic susceptibility is a fast, inexpensive and reliable technique for estimating and monitoring the anthropogenic contamination of soil with heavy metals. However, it is essential to determine the factors affecting magnetic susceptibility before applying this technique to environmental studies. The objectives of this study were to investigate i) the effect of parent materials and land use on the magnetic susceptibility and concentrations of Fe, Ni, Pb and Zn, and ii) capability of magnetic susceptibility as an indicator of anthropogenic heavy metals contamination of soil in Mashhad plain, northeastern Iran. One hundred seventy-eight composite surface soil samples (0-10 cm) were taken. The aqua-regia extractable concentrations of Fe, Ni, Zn and Pb were determined by atomic absorption spectroscopy. Magnetic susceptibility at low and high frequency (χlf and χhf) were measured and frequency dependent susceptibility (χfd) was calculated. The average concentrations of Fe, Ni, Pb and Zn were 22,812, 61.4, 74.1 and 31.6 mg kg- 1, respectively. The highest contents of Pb (69.1 mg kg- 1) and Zn (149 mg kg- 1) were observed in urban area. The highest concentration of Ni was 41,538 mg kg- 1 observed in the soils developed from ultramafic rocks. Magnetic susceptibility varied from 20.3 on marly sediments to 311.8 × 10- 8 m3 kg- 1 on ultramafic rocks. A positive strong correlation (Pvalue < 0.01, r = 0.88) was obtained between Ni and χlf. There were no significant relationships between Zn and Pb with χlf, therefore it seems that magnetic susceptibility has not been affected significantly by anthropogenic activities which enhanced Pb and Zn concentrations in urban soils. The results indicated that magnetic susceptibility was mainly controlled by Ni containing minerals with lithogenic origin. Therefore, in the soils studied, magnetic susceptibility could not be employed as indicator of anthropogenic contamination of soil with heavy metals.

  7. Susceptibility investigation of the nanoparticle coating-layer effect on the particle interaction in biocompatible magnetic fluids

    NASA Astrophysics Data System (ADS)

    Morais, P. C.; Santos, J. G.; Silveira, L. B.; Gansau, C.; Buske, N.; Nunes, W. C.; Sinnecker, J. P.

    2004-05-01

    AC susceptibility was used to investigate the effect of the surface-coating layer in two biocompatible, magnetite-based, magnetic fluid samples. Dextran and dimercaptosuccinic acid (DMSA) were the surface coating species. The temperature and frequency dependence of the peak susceptibility was discussed using the Vogel-Fulcher relation, from which the typical energy barrier (temperature correction) values of 1340±20 K (70±3 K) and 1230±30 K (86±5 K) were obtained for the dextran- and DMSA-coated nanoparticles, respectively.

  8. Magnetic susceptibility as an indicator to paleo-environmental pollution in an urban lagoon near Istanbul city

    NASA Astrophysics Data System (ADS)

    Alpar, Bedri; Unlu, Selma; Altinok, Yildiz; Ongen, Sinan

    2014-05-01

    For assessing anthropogenic pollution, magnetic susceptibility profiles and accompanying data were measured along three short cores recovered at the southern part of an urban lagoon; Kucukcekmece, Istanbul, Turkey. This marine inlet, connected to the Sea of Marmara by a very narrow channel, was used as a drinking water reservoir 40-50 years ago before it was contaminated by municipal, agricultural and industrial activities, mainly carried by three streams feeding the lagoon. The magnetic signals decrease gradually from the lake bottom towards the core base showing some characteristic anomalies. These signatures were tested as an environmental magnetic parameter against the lithological diversity (silici-clastic, total organic matter and carbonate), metal enrichments with larger variations (Pb, Mn, Zn, Ni, Co, Cr, U and Al) and probable hydrocarbon contamination. Mineral assemblage was determined by a computer driven X-ray diffractometer. The heavy metal concentrations and total petroleum hydrocarbons (TPH) were measured by ICP-MS and UVF spectrometry, respectively. Magnetic susceptibility shows slightly higher values in interlayers containing higher silici-clastic material and organic content which may suggest first-order changes in the relative supplies of terrigenous and biogenic materials. On the basis of cluster analyses, enhanced magnetic signals could be correlated with the elevated concentrations of Co, Zn, U, Pb and TPH along the cores. The Pb concentrations at the upper parts of the cores were higher than the "Severe Effect Level" and could pose a potential risk for living organisms. Greater amounts of organic carbon tend to accumulate in muddy sediments. In fact, there are a few studies reporting some relationship between enhanced magnetic signals and organic contamination mainly due to petroleum aromatic hydrocarbons. In conclusion, the magnetic susceptibility changes in sedimentary depositional environments could be used as a rapid and cost

  9. Application of Anisotropy of Magnetic Susceptibility to large-scale fault kinematics: an evaluation

    NASA Astrophysics Data System (ADS)

    Casas, Antonio M.; Roman-Berdiel, Teresa; Marcén, Marcos; Oliva-Urcia, Belen; Soto, Ruth; Garcia-Lasanta, Cristina; Calvin, Pablo; Pocovi, Andres; Gil-Imaz, Andres; Pueyo-Anchuela, Oscar; Izquierdo-Llavall, Esther; Vernet, Eva; Santolaria, Pablo; Osacar, Cinta; Santanach, Pere; Corrado, Sveva; Invernizzi, Chiara; Aldega, Luca; Caricchi, Chiara; Villalain, Juan Jose

    2017-04-01

    Major discontinuities in the Earth's crust are expressed by faults that often cut across its whole thickness favoring, for example, the emplacement of magmas of mantelic origin. These long-lived faults are common in intra-plate environments and show multi-episodic activity that spans for hundred of million years and constitute first-order controls on plate evolution, favoring basin formation and inversion, rotations and the accommodation of deformation in large segments of plates. Since the post-Paleozoic evolution of these large-scale faults has taken place (and can only be observed) at shallow crustal levels, the accurate determination of fault kinematics is hampered by scarcely developed fault rocks, lack of classical structural indicators and the brittle deformation accompanying fault zones. These drawbacks are also found when thick clayey or evaporite levels, with or without diapiric movements, are the main detachment levels that facilitate large displacements in the upper crust. Anisotropy of Magnetic Susceptibility (AMS) provides a useful tool for the analysis of fault zones lacking fully developed kinematic indicators. However, its meaning in terms of deformational fabrics must be carefully checked by means of outcrop and thin section analysis in order to establish the relationship between the orientation of magnetic ellipsoid axes and the transport directions, as well as the representativity of scalar parameters regarding deformation mechanisms. Timing of faulting, P-T conditions and magnetic mineralogy are also major constraints for the interpretation of magnetic fabrics and therefore, separating ferro- and para-magnetic fabric components may be necessary in complex cases. AMS results indicate that the magnetic lineation can be parallel (when projected onto the shear plane) or perpendicular (i.e. parallel to the intersection lineation) to the transport direction depending mainly on the degree of shear deformation. Changes between the two end-members can

  10. Magnetothermal Convection of Water with the Presence or Absence of a Magnetic Force Acting on the Susceptibility Gradient

    PubMed Central

    Maki, Syou

    2016-01-01

    Heat transfer of magnetothermal convection with the presence or absence of the magnetic force acting on the susceptibility gradient (fsc) was examined by three-dimensional numerical computations. Thermal convection of water enclosed in a shallow cylindrical vessel (diameter over vessel height = 6.0) with the Rayleigh-Benard model was adopted as the model, under the conditions of Prandtl number 6.0 and Ra number 7000, respectively. The momentum equations of convection were nondimensionalized, which involved the term of fsc and the term of magnetic force acting on the magnetic field gradient (fb). All the computations resulted in axisymmetric steady rolls. The values of the averaged Nu, the averaged velocity components U, V, and W, and the isothermal distributions and flow patterns were almost completely the same, regardless of the presence or absence of the term of fsc. As a result, we found that the effect of fsc was extremely small, although much previous research emphasized the effect with paramagnetic solutions under an unsteady state. The magnitude of fsc depends not only on magnetic conditions (magnitudes of magnetic susceptibility and magnetic flux density), but also on the thermal properties of the solution (thermal conductivity, thermal diffusivity, and viscosity). Therefore the effect of fb becomes dominant on the magnetothermal convection. Active control over the density gradient with temperature will be required to advance heat transfer with the effect of fsc. PMID:27606823

  11. Pauli magnetic susceptibility of bilayer graphene and hexagonal boron-nitride

    NASA Astrophysics Data System (ADS)

    Mousavi, Hamze; Jalilvand, Samira; Kurdestany, Jamshid Moradi

    2016-12-01

    We study the contribution of s and p orbitals on the Pauli magnetic susceptibility (PMS) and density of state (DOS) of the following three structures (1) bilayer graphene (2) bilayer boron-nitride (BN) and (3) bilayer graphene-BN within a two-band tight-binding Harrison Hamiltonian and the Green's function technique. It is shown that in all three cases, the contribution of s and px or py orbitals have no states around the Fermi level, while for bilayer graphene and graphene-BN the total DOS and DOS of pz orbital appear to be a linear function around this level. We show explicitly that for bilayer BN the contribution of pz orbital does not have states around the Fermi level, because of ionization energy difference between the boron (B) and nitrogen (N) atoms. We find that the bandwidth of s, px or py is more extension than case of pz orbital as a result of the Van-Hove singularities in the DOS. This leads to consideration of the PMS in two, low and high temperature, regions.

  12. Spin magnetic susceptibility of ferromagnetic silicene in the presence of Rashba spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Mirabbaszadeh, Kavoos; Yarmohammadi, Mohsen; Khodadadi, Jabbar

    2017-03-01

    In the current work, the effect of extrinsic Rashba spin-orbit coupling (RSOC) on the electronic band structure (BS) and magnetic susceptibility (MS) of ferromagnetic silicene is investigated in the presence of external perpendicular electric field. The Kane-Mele Hamiltonian and Dirac cone approximation besides the Green's functions approach have been used to study the MS of the spin-up and spin-down bands. By changing the electric field, energy of the inter-band transitions and MS are tuned. Our findings show that MS could be easily controlled by an external electric field and RSOC. The system shows three phases: Topological insulator (TI), valley-spin polarized metal (VSPM) and band insulator (BI) for various RSOC and electric field strengths. The maximum and minimum value of MS appears in the VSPM and BI regimes, respectively. RSOC leads to the distortion of BS and reduction of the effective mass which in combination with SOC provides some changes like phase transition of VSPM from antiferromagnetic to the paramagnetic phase. Strong RSOC results to the drastic reduction of MS and double peak of the spin-up or spin-down curves at low temperatures.

  13. Magnetic susceptibility measurements as proxy method to monitor soil pollution: the case study of S. Nicola di Melfi.

    PubMed

    D'Emilio, Mariagrazia; Caggiano, Rosa; Coppola, Rosa; Macchiato, Maria; Ragosta, Maria

    2010-10-01

    The development of in situ, cheep, noninvasive, and fast strategies for soil monitoring is a crucial task for environmental research. In this paper, we present the results of three field surveys carried out in an industrial area of Southern Italy: S. Nicola di Melfi. The monitoring procedure is based on soil magnetic susceptibility measurements carried out by means of experimental protocols that our research group developed during the last years. This field surveys is supported by both geological characterization of the area and analytical determinations of metal concentrations in soils. Magnetic studies were carried out not only in situ but also in laboratory. Results show that, taking into account the influence due to the geomorphologic difference, soil magnetic susceptibility is an optimal indicator of the anthropogenic impact. So, our monitoring strategy discloses that the combined use of magnetic susceptibility measurements and soil geomorphology information may be used as a useful tool for the temporal monitoring of pollution evolution and for a fast screening of polluted zones.

  14. Anisotropic Change in the Magnetic Susceptibility of a Dynamic Single Crystal of a Cobalt(II) Complex.

    PubMed

    Yao, Zi-Shuo; Wu, Shu-Qi; Kitagawa, Yasutaka; Su, Sheng-Qun; Huang, You-Gui; Li, Guo-Ling; Ni, Zhong-Hai; Nojiri, Hiroyuki; Shiota, Yoshihito; Yoshizawa, Kazunari; Kang, Soonchul; Kanegawa, Shinji; Sato, Osamu

    2017-01-16

    Atypically anisotropic and large changes in magnetic susceptibility, along with a change in crystalline shape, were observed in a Co(II) complex at near room temperature. This was achieved by combining oxalate molecules, acting as rotor, and a Co(II) ion with unquenched orbital angular momentum. A thermally controlled 90° rotation of the oxalate counter anion triggered a symmetry-breaking ferroelastic phase transition, accompanied by contraction-expansion behavior (ca. 4.5 %) along the long axis of a rod-like single crystal. The molecular rotation induced a minute variation in the coordination geometry around the Co(II) ion, resulting in an abrupt decrease and a remarkable increase in magnetic susceptibility along the direction perpendicular and parallel to the long axis of the crystal, respectively. Theoretical calculations suggested that such an unusual anisotropic change in magnetic susceptibility was due to a substantial reorientation of magnetic anisotropy induced by slight disruption in the ideal D3 coordination environment of the complex cation.

  15. Identifying Successive Eruption of Guntur Volcanic Complex Using Magnetic Susceptibility and Polarimetric Synthetic Aperture Radar (PolSAR) Data

    NASA Astrophysics Data System (ADS)

    Saepuloh, Asep; Bakker, Erwin

    2017-06-01

    Identifying distribution and stratigraphic of volcanic products are important not only for mitigating volcanic hazards, but also to know the characteristics of the successive eruptions. Guntur volcanic complex located in Garut, West Java, Indonesia was selected as study area because of the last eruption took place in 1847 and the volcanic activity has been dormant since then, however its seismicity is still active. During the period of July to October 2009, the hypocentre distribution of volcano tectonic earthquakes is mostly located at western flank of the volcano, beneath Guntur - Gandapura craters at the depth of less than 5 km. This study is aimed to identify distribution and succession of volcanic products based on their magnetic properties and backscattering signal of Polarimetric Synthetic Aperture Radar (PolSAR) data. The polarimetric decomposition method was used to identify the distribution of the volcanic products based on their scattering characteristics. Then, the field measurement using SM-30 magnetic susceptibility meter was performed to confirm the units of volcanic products and interpret their successions. According to the polarimetric decomposition method, we could identify fifteen successive eruptions formed Guntur Volcano Complex and termed as Khuluk and Gumuk in Indonesian standard. The successions were produced Gumuk Windu, Gumuk Malang, Gumuk Pulus, Gumuk Putrri, Khuluk Meungpeuk, Gumuk Cakra, Gumuk Gandapura, Gumuk Putri, Gumuk Gajah, Gumuk Batususun, Khuluk Pasirlaku, Gumuk Agung, Gumuk Picung, Gumuk Pasirmalang, Gumuk Masigit, Khuluk Kabuyutan and Khuluk Guntur. The magnetic susceptibility confirmed that the variations of magnetic susceptibility of rocks at each gumuk agreed with their stratigraphy.

  16. Susceptibility of CoFeB/AlOx/Co Magnetic Tunnel Junctions to Low-Frequency Alternating Current

    PubMed Central

    Chen, Yuan-Tsung; Chang, Zu-Gao

    2013-01-01

    This investigation studies CoFeB/AlOx/Co magnetic tunneling junction (MTJ) in the magnetic field of a low-frequency alternating current, for various thicknesses of the barrier layer AlOx. The low-frequency alternate-current magnetic susceptibility (χac) and phase angle (θ) of the CoFeB/AlOx/Co MTJ are determined using an χac analyzer. The driving frequency ranges from 10 to 25,000 Hz. These multilayered MTJs are deposited on a silicon substrate using a DC and RF magnetron sputtering system. Barrier layer thicknesses are 22, 26, and 30 Å. The X-ray diffraction patterns (XRD) include a main peak at 2θ = 44.7° from hexagonal close-packed (HCP) Co with a highly (0002) textured structure, with AlOx and CoFeB as amorphous phases. The full width at half maximum (FWHM) of the Co(0002) peak, decreases as the AlOx thickness increases; revealing that the Co layer becomes more crystalline with increasing thickness. χac result demonstrates that the optimal resonance frequency (fres) that maximizes the χac value is 500 Hz. As the frequency increases to 1000 Hz, the susceptibility decreases rapidly. However, when the frequency increases over 1000 Hz, the susceptibility sharply declines, and almost closes to zero. The experimental results reveal that the mean optimal susceptibility is 1.87 at an AlOx barrier layer thickness of 30 Å because the Co(0002) texture induces magneto-anisotropy, which improves the indirect CoFeB and Co spin exchange-coupling strength and the χac value. The results concerning magnetism indicate that the magnetic characteristics are related to the crystallinity of Co.

  17. Detection of the pedogenic magnetic fraction in volcanic soils developed on basalts using frequency-dependent magnetic susceptibility: comparison of two instruments

    NASA Astrophysics Data System (ADS)

    Grison, Hana; Petrovsky, Eduard; Kapicka, Ales; Hanzlikova, Hana

    2017-01-01

    SUMMARYIn studies of the <span class="hlt">magnetic</span> properties of soils, the frequency-dependent <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> percentage (χFD%) is often used for the identification of ultrafine <span class="hlt">magnetically</span> superparamagnetic/stable single-domain (SP/SSD) particles. This parameter is commonly used as an indicator for increased pedogenesis. In strongly <span class="hlt">magnetic</span> soils, the SP/SSD <span class="hlt">magnetic</span> signal (mostly bio-pedogenic) may be masked by lithological signals; making pedogenesis hard to detect. In this study we compare results for the detection of ultrafine SP/SSD <span class="hlt">magnetic</span> particles in andic soils using two instruments: a Bartington MS2B dual-frequency meter and an AGICO Kappabridge MFK1-FA. In particular, the study focuses on the effect of pedogenesis by investigating the relationship between specific soil <span class="hlt">magnetic</span> and chemical properties (soil organic carbon and pHH2O). The values of χFD% obtained with the MS2B varied from 2.4 to 5.9%, and mass-specific <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (χLF) from 283 to 1688 × 10-8 m3 kg-1, while values of χFD% and χLF obtained with the MFK1-FA varied from 2.7 to 8.2% and from 299 to 1859 × 10-8 m3 kg-1, respectively. Our results suggest that the detection of the SP/SSD <span class="hlt">magnetic</span> fraction can be accomplished by comparing relative trends of χFD% along the soil profile. Moreover, the discrimination between bio-pedogenic and lithogenic <span class="hlt">magnetic</span> contributions in the SP/SSD fraction is possible by comparing the χFD% and χLF data determined in the fine earth (<2 mm) and the coarse fraction (4-10 mm) samples down the soil profile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoJI.209..654G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoJI.209..654G"><span>Detection of the pedogenic <span class="hlt">magnetic</span> fraction in volcanic soils developed on basalts using frequency-dependent <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>: comparison of two instruments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grison, Hana; Petrovsky, Eduard; Kapicka, Ales; Hanzlikova, Hana</p> <p>2017-05-01</p> <p>In studies of the <span class="hlt">magnetic</span> properties of soils, the frequency-dependent <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> percentage (χFD%) is often used for the identification of ultrafine <span class="hlt">magnetically</span> superparamagnetic/stable single-domain (SP/SSD) particles. This parameter is commonly used as an indicator for increased pedogenesis. In strongly <span class="hlt">magnetic</span> soils, the SP/SSD <span class="hlt">magnetic</span> signal (mostly bio-pedogenic) may be masked by lithological signals; making pedogenesis hard to detect. In this study, we compare results for the detection of ultrafine SP/SSD <span class="hlt">magnetic</span> particles in andic soils using two instruments: a Bartington MS2B dual-frequency meter and an AGICO Kappabridge MFK1-FA. In particular, the study focuses on the effect of pedogenesis by investigating the relationship between specific soil <span class="hlt">magnetic</span> and chemical properties (soil organic carbon and pHH2O). The values of χFD% obtained with the MS2B varied from 2.4 to 5.9 per cent, and mass-specific <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (χLF) from 283 to 1688 × 10-8 m3 kg-1, while values of χFD% and χLF obtained with the MFK1-FA varied from 2.7 to 8.2 per cent and from 299 to 1859 × 10-8 m3 kg-1, respectively. Our results suggest that the detection of the SP/SSD <span class="hlt">magnetic</span> fraction can be accomplished by comparing relative trends of χFD% along the soil profile. Moreover, the discrimination between bio-pedogenic and lithogenic <span class="hlt">magnetic</span> contributions in the SP/SSD fraction is possible by comparing the χFD% and χLF data determined in the fine earth (<2 mm) and the coarse fraction (4-10 mm) samples down the soil profile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JPhy1...1..765H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JPhy1...1..765H"><span>Model calculation of the static <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> in light rare earth metallic systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hammoud, Y.; Parlebas, J. C.</p> <p>1991-05-01</p> <p>Using the impurity Anderson model in the large N_f approximation, where N_f is the orbital and spin degeneracy of the f level, we calculate the zero temperature static paramagnetic <span class="hlt">susceptibility</span> of light rare earth metallic systems. The calculation is performed for large values of the Coulomb U_ff electron-electron interactions with respect of the V hybridization of f1 and f2 configurations with the conduction states (i.e. f0 configuration) : we only keep the leading terms in a development in successive powers of 1/U_ff and V. Our numerical results on the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> start from a simple analytic expression and are discussed in terms of the f level position, the hybridization V, the shape and filling of the conduction band and also the finite U_ff effects. Finally we present calculated curves for the <span class="hlt">susceptibility</span> versus V in connection with the αγ transition of cerium and utilizing the same parameters as those used previously to obtain core level LIII absorption spectra : also in the case of the <span class="hlt">susceptibility</span>, the hybridization appears to be an important parameter to describe the phase change from γ to α cerium. Nous utilisons le modèle d'Anderson à une impureté dans l'approximation des grands N_f où N_f est la dégénérescence d'orbitale et de spin du niveau f et nous calculons alors la susceptibilité paramagnétique statique (à température nulle) dans les systèmes métalliques de terres rares légères. Nous effectuons notre calcul pour des valeurs de l'interaction de Coulomb U_ff grandes par rapport à l'hybridation V des configurations f1 et f2 avec les états de conduction (c.-à-d. la configuration f0): nous ne retenons que les termes les plus imporatnts dans un développement en puissances successives de 1/U_ff et V. Ensuite nous discutons nos résultats numériques à partir d'une forme analytique simple obtenue pour la susceptibilité magnétique en fonction de la position du niveau f, de l'hybridation V, de la forme et du</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985PhRvB..32.5966B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985PhRvB..32.5966B"><span>Spin <span class="hlt">susceptibility</span> in three-dimensional nearly <span class="hlt">magnetic</span> disordered fermion systems in the weakly localized regime</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Béal-Monod, M. T.</p> <p>1985-11-01</p> <p>The temperature dependence of the spin <span class="hlt">susceptibility</span> χ(T) is studied in a weakly disordered itinerant-fermion system close to a <span class="hlt">magnetic</span> instability. The paramagnon model is used with a Hubbard-type contact repulsion among opposite spins, with the Stoner enhancement of the pure system (1-I¯)-1>>1. The result is shown to be different from the usual one obtained in the case of a screened Coulomb interaction: The 2-phDP (two-particle-hole-diffusion-propagator) diagrams, which cancel altogether in the Coulomb interaction case, are shown to give, here, for the contact interaction, a finite contribution which is of the same order in (ɛFτ)-1 as the 3-phDP and 4-phDP diagrams where τ is the lifetime due to disorder, and ɛF the Fermi energy. Instead of a unique temperature range Tτ<<1 in the Coulomb case, here one has to distinguish two ranges: When Tτ<<(1-I¯), the usual 3- and 4-phDP diagrams dominate and one recovers χ(T)~= √Tτ /(1-I¯)2 as was first announced by Al'tshuler and Aronov; but when (1-I¯)<Tτ<<1, the 2-phDP diagrams dominate, yielding χ(T)~(Tτ)3/2/(1-I¯)5/2, which is non-negligible near the <span class="hlt">magnetic</span> instability. At T=0, the 2-phDP diagrams definitely dominate as they enhance the effective interaction (I¯eff-I¯)~=(ɛFτ)-2(1 -I¯)-1/2 and let the system be closer to <span class="hlt">magnetism</span>, while the 3- and 4-phDP diagrams play a minor role at 0 K. The present study accounts only for phDP processes. Effects due to ppDP's (particle-particle diffusion propagators) should also be studied within the same framework to incorporate the contributions of the 2-ppDP diagrams. Finally, the latest developments using renormalization-group analysis of Finkel'stein and of Castellani et al. with a screened Coulomb interaction ought to be modified to account for the contact-interaction case where spin constraints yield the noncancellation of the 2-phDP-and also most likely of the 2-ppDP-diagrams.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMMM..418..169K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMMM..418..169K"><span><span class="hlt">Magnetization</span> and <span class="hlt">susceptibility</span> of a parabolic InAs quantum dot with electron-electron and spin-orbit interactions in the presence of a <span class="hlt">magnetic</span> field at finite temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumar, D. Sanjeev; Mukhopadhyay, Soma; Chatterjee, Ashok</p> <p>2016-11-01</p> <p>The <span class="hlt">magnetization</span> and <span class="hlt">susceptibility</span> of a two-electron parabolic quantum dot are studied in the presence of electron-electron and spin-orbit interactions as a function of <span class="hlt">magnetic</span> field and temperature. The spin-orbit interactions are treated by a unitary transformation and an exactly soluble parabolic interaction model is considered to mimic the electron-electron interaction. The theory is finally applied to an InAs quantum dot. <span class="hlt">Magnetization</span> and <span class="hlt">susceptibility</span> are calculated using canonical ensemble approach. Our results show that Temperature has no effect on <span class="hlt">magnetization</span> and <span class="hlt">susceptibility</span> in the diamagnetic regime whereas electron-electron interaction reduces them. The temperature however reduces the height of the paramagnetic peak. The Rashba spin-orbit interaction is shown to shift the paramagnetic peak towards higher <span class="hlt">magnetic</span> fields whereas the Dresselhaus spin-orbit interaction shifts it to the lower <span class="hlt">magnetic</span> field side. Spin-orbit interaction has no effect on <span class="hlt">magnetization</span> and <span class="hlt">susceptibility</span> at larger temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JHEP...01..124A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JHEP...01..124A"><span>Exactly marginal deformations from exceptional <span class="hlt">generalised</span> geometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ashmore, Anthony; Gabella, Maxime; Graña, Mariana; Petrini, Michela; Waldram, Daniel</p> <p>2017-01-01</p> <p>We apply exceptional <span class="hlt">generalised</span> geometry to the study of exactly marginal deformations of N = 1 SCFTs that are dual to generic AdS5 flux backgrounds in type IIB or eleven-dimensional supergravity. In the gauge theory, marginal deformations are parametrised by the space of chiral primary operators of conformal dimension three, while exactly marginal deformations correspond to quotienting this space by the complexified global symmetry group. We show how the supergravity analysis gives a geometric interpretation of the gauge theory results. The marginal deformations arise from deformations of <span class="hlt">generalised</span> structures that solve moment maps for the <span class="hlt">generalised</span> diffeomorphism group and have the correct charge under the <span class="hlt">generalised</span> Reeb vector, generating the R-symmetry. If this is the only symmetry of the background, all marginal deformations are exactly marginal. If the background possesses extra isometries, there are obstructions that come from fixed points of the moment maps. The exactly marginal deformations are then given by a further quotient by these extra isometries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhLB..767..278L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhLB..767..278L"><span>Hyperscaling violating solutions in <span class="hlt">generalised</span> EMD theory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Li</p> <p>2017-04-01</p> <p>This short note is devoted to deriving scaling but hyperscaling violating solutions in a <span class="hlt">generalised</span> Einstein-Maxwell-Dilaton theory with an arbitrary number of scalars and vectors. We obtain analytic solutions in some special case and discuss the physical constraints on the allowed parameter range in order to have a well-defined holographic ground-state solution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20215620','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20215620"><span><span class="hlt">Magnetic</span> and structural properties of an octanuclear Cu(II) S=1/2 mesoscopic ring: <span class="hlt">Susceptibility</span> and NMR measurements</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lascialfari, A.; Jang, Z. H.; Borsa, F.; Gatteschi, D.; Cornia, A.; Rovai, D.; Caneschi, A.; Carretta, P.</p> <p>2000-03-01</p> <p><span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span>, {sup 1}H NMR and {sup 63}Cu NMR-NQR experiments on two slightly different species of the molecular S=1/2 antiferromagnetic (AF) ring Cu8, [Cu{sub 8}(dmpz){sub 8}(OH){sub 8}]{center_dot}2C{sub 5}H{sub 5}N (Cu8P) and [Cu{sub 8}(dmpz){sub 8}(OH){sub 8}]{center_dot}2C{sub 5}H{sub 5}NO{sub 2} (Cu8N), are presented. The <span class="hlt">magnetic</span> energy levels are calculated exactly for an isotropic Heisenberg model Hamiltonian in zero <span class="hlt">magnetic</span> field. From the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements we estimate the AF exchange coupling constant J{approx}1000 K and the resulting gap {delta}{approx}500 K between the S{sub T}=0 ground state and the S{sub T}=1 first excited state. The {sup 63,65}Cu NQR spectra indicate the presence of four crystallographically inequivalent copper nuclei in each ring. From the combination of the {sup 63}Cu NQR spectra and of the {sup 63}Cu NMR spectra at high <span class="hlt">magnetic</span> field, we estimate the quadrupole coupling constant v{sub Q} of each site and the average asymmetry parameter {eta} of the electric-field gradient tensor. The nuclear spin-lattice relaxation rate (NSLR) decreases exponentially on decreasing temperature for all nuclei investigated. The gap parameter extracted from {sup 63}Cu NQR-NSLR is the same as for the <span class="hlt">susceptibility</span> while a smaller value is obtained from the {sup 63}Cu NMR-NSLR in an external <span class="hlt">magnetic</span> field of 8.2 T. (c) 2000 The American Physical Society.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22027919','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22027919"><span>High-temperature studies of the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of samarium and the Al{sub 2}Sm compound</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Uporova, N. S.; Uporov, S. A.; Sidorov, V. E.</p> <p>2012-02-15</p> <p>The <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of metallic samarium and the Al{sub 2}Sm intermetallic compound has been experimentally studied by the Faraday method in the temperature range of 300-1800 K. It has been shown that the temperature dependences of the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of Sm and Al{sub 2}Sm in a crystalline state can be described in the framework of Van Vleck paramagnetism theory taking into account variable valence and the contribution from the conduction electrons. Using this theoretical interpretation of the data, the effective valence of samarium in the metallic state and in the Al{sub 2}Sm intermetallic compound has been estimated as a function of the temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSMGP11A..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSMGP11A..04B"><span>Preliminary AMS Study in Cretaceous Igneous Rocks of Valle Chico Complex, Uruguay: Statistical Determination of <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barcelona, H.; Mena, M.; Sanchez-Bettucci, L.</p> <p>2009-05-01</p> <p>The Valle Chico Complex, at southeast Uruguay, is related Paraná-Etendeka Province. The study involved basaltic lavas, quarz-syenites, and rhyolitic and trachytic dikes. Samples were taken from 18 sites and the AMS of 250 specimens was analyzed. The AMS is modeled by a second order tensor K and it graphical representation is a symmetric ellipsoid. The axes relations determine parameters which describe different properties like shape, lineation, and foliation, degree of anisotropy and bulk <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>. Under this perspective, one lava, dike, or igneous body can be considered a mosaic of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> domains (MSD). The DSM is an area with specific degree of homogeneity in the distribution of parameters values and cinematic conditions. An average tensor would weigh only one MSD, but if the site is a mosaic, subsets of specimens with similar parameters can be created. Hypothesis tests can be used to establish parameter similarities. It would be suitable considered as a MSD the subsets with statistically significant differences in at least one of its means parameters, and therefore, be treated independently. Once defined the MSDs the tensor analysis continues. The basalt-andesitic lavas present MSD with an NNW <span class="hlt">magnetic</span> foliation, dipping 10. The K1 are sub-horizontal, oriented E-W and reprsent the magmatic flow direction. The quartz-syenites show a variable <span class="hlt">magnetic</span> fabric or prolate ellipsoids mayor axes dispose parallel to the flow direction (10 to the SSE). Deformed syenites show N300/11 <span class="hlt">magnetic</span> foliation, consistent with the trend of fractures. The K1 is subvertical. The MSD defined in rhyolitic dikes have <span class="hlt">magnetic</span> foliations consistent with the structural trend. The trachytic dikes show an important indetermination in the <span class="hlt">magnetic</span> response. However, a 62/N90 <span class="hlt">magnetic</span> lineation was defined. The MSDs obtained are consistent with the geological structures and contribute to the knowledge of the tectonic, magmatic and kinematic events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SedG..351...80D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SedG..351...80D"><span>Stratigraphic correlations in mid- to late-Proterozoic carbonates of the Democratic Republic of Congo using <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delpomdor, Franck R. A.; Devleeschouwer, Xavier; Spassov, Simo; Préat, Alain R.</p> <p>2017-04-01</p> <p>In this paper, we have tested the application of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements in Cu-Ag-Zn-Pb-(Fe)-mineralized carbonates of the BIe subgroup (Democratic Republic of Congo) as an efficient tool for regional and global high-resolution stratigraphic correlations in the Neoproterozoic marine carbonates. To achieve this goal, we integrate the low-field <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (XLF) data with facies analyses, geochemistry and isotope stratigraphy. The microfacies analyses of two cores, Tshinyama#S70 and Kafuku#15, drilled in the early Neoproterozoic carbonates of the Mbuji-Mayi Supergroup reveal a deep carbonate ramp setting associated with a microbial/stromatolitic mid-ramp environment. High-resolution stratigraphic correlations using <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> and C-isotope curves established for both cores, 190 km apart, suggest a sedimentary hiatus at the base of the Tshinyama#S70 succession. C-O and Sr isotopes and Sr/Ca and Fe abundances show that a diagenetic meteoric overprint affected the series of the Tshinyama#S70 core and a thermal effect related to mineralizing fluids affected the Kafuku#15 core carbonates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22413482','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22413482"><span>Detection of microcalcifications by characteristic <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> effects using MR phase image cross-correlation analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Baheza, Richard A.; Welch, E. Brian; Gochberg, Daniel F.; Sanders, Melinda; Harvey, Sara; Gore, John C.; Yankeelov, Thomas E.</p> <p>2015-03-15</p> <p>Purpose: To develop and evaluate a new method for detecting calcium deposits using their characteristic <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> effects on <span class="hlt">magnetic</span> resonance (MR) images at high fields and demonstrate its potential in practice for detecting breast microcalcifications. Methods: Characteristic dipole signatures of calcium deposits were detected in <span class="hlt">magnetic</span> resonance phase images by computing the cross-correlation between the acquired data and a library of templates containing simulated phase patterns of spherical deposits. The influence of signal-to-noise ratio and various other MR parameters on the results were assessed using simulations and validated experimentally. The method was tested experimentally for detection of calcium fragments within gel phantoms and calcium-like inhomogeneities within chicken tissue at 7 T with optimized MR acquisition parameters. The method was also evaluated for detection of simulated microcalcifications, modeled from biopsy samples of malignant breast cancer, inserted in silico into breast <span class="hlt">magnetic</span> resonance imaging (MRIs) of healthy subjects at 7 T. For both assessments of calcium fragments in phantoms and biopsy-based simulated microcalcifications in breast MRIs, receiver operator characteristic curve analyses were performed to determine the cross-correlation index cutoff, for achieving optimal sensitivity and specificity, and the area under the curve (AUC), for measuring the method’s performance. Results: The method detected calcium fragments with sizes of 0.14–0.79 mm, 1 mm calcium-like deposits, and simulated microcalcifications with sizes of 0.4–1.0 mm in images with voxel sizes between (0.2 mm){sup 3} and (0.6 mm){sup 3}. In images acquired at 7 T with voxel sizes of (0.2 mm){sup 3}–(0.4 mm){sup 3}, calcium fragments (size 0.3–0.4 mm) were detected with a sensitivity, specificity, and AUC of 78%–90%, 51%–68%, and 0.77%–0.88%, respectively. In images acquired with a human 7 T scanner, acquisition times below 12</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4344475','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4344475"><span>Detection of microcalcifications by characteristic <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> effects using MR phase image cross-correlation analysis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Baheza, Richard A.; Welch, E. Brian; Gochberg, Daniel F.; Sanders, Melinda; Harvey, Sara; Gore, John C.; Yankeelov, Thomas E.</p> <p>2015-01-01</p> <p>Purpose: To develop and evaluate a new method for detecting calcium deposits using their characteristic <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> effects on <span class="hlt">magnetic</span> resonance (MR) images at high fields and demonstrate its potential in practice for detecting breast microcalcifications. Methods: Characteristic dipole signatures of calcium deposits were detected in <span class="hlt">magnetic</span> resonance phase images by computing the cross-correlation between the acquired data and a library of templates containing simulated phase patterns of spherical deposits. The influence of signal-to-noise ratio and various other MR parameters on the results were assessed using simulations and validated experimentally. The method was tested experimentally for detection of calcium fragments within gel phantoms and calcium-like inhomogeneities within chicken tissue at 7 T with optimized MR acquisition parameters. The method was also evaluated for detection of simulated microcalcifications, modeled from biopsy samples of malignant breast cancer, inserted in silico into breast <span class="hlt">magnetic</span> resonance imaging (MRIs) of healthy subjects at 7 T. For both assessments of calcium fragments in phantoms and biopsy-based simulated microcalcifications in breast MRIs, receiver operator characteristic curve analyses were performed to determine the cross-correlation index cutoff, for achieving optimal sensitivity and specificity, and the area under the curve (AUC), for measuring the method’s performance. Results: The method detected calcium fragments with sizes of 0.14–0.79 mm, 1 mm calcium-like deposits, and simulated microcalcifications with sizes of 0.4–1.0 mm in images with voxel sizes between (0.2 mm)3 and (0.6 mm)3. In images acquired at 7 T with voxel sizes of (0.2 mm)3–(0.4 mm)3, calcium fragments (size 0.3–0.4 mm) were detected with a sensitivity, specificity, and AUC of 78%–90%, 51%–68%, and 0.77%–0.88%, respectively. In images acquired with a human 7 T scanner, acquisition times below 12 min, and voxel sizes of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGP21A3645S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGP21A3645S"><span>Paleomagnetism and Anisotropy of <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> study of the Miocene Jack Springs Tuff (Nevada, USA)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shields, S.; Petronis, M. S.; Pluhar, C. J.; Gordon, L.</p> <p>2014-12-01</p> <p>The mid-Miocene Jack Springs Tuff (JST) outcrops across the western Mina Deflection accommodation zone, west-central Nevada and into eastern California. Previously, the source location for the JST was unknown, yet recent studies northwest of Mono Lake, CA have identified a relatively un-rotated structural block in which to reference the paleomagnetic data. Although new studies have indicated that this block may be rotated up to 13º, we argue that the probable source area is located near the Bodie Hills, CA. At this site, the paleomagnetic reference direction is D = 353°, I = 43°, α95 = 7.7° (Carlson et al, 2013). Based on these data, the JST can be used to measure absolute vertical-axis rotation as well as enable reconstruction of the paleo-topography using the corrected anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) data. A total of 19 sites were sampled to constrain Cenozoic to recent vertical axis rotation within the region and AMS experiments were conducted to determine the flow direction of the JST. Curie point estimates indicate that the JST ranges in titanium concentration from 0.042 to 1.10, indicating a low to moderate titanomagnetite phase (Akimoto, 1962). Demagnetization experiments reveal mean destructive fields of the NRM ranging between 15mT and 40mT suggesting that both multi-domain to pseudo-single domain grains are the dominant ferromagnetic phases that carry the remanence and AMS fabric. Preliminary paleomagnetic data yield stable single component demagnetization behavior for most sites that, after structural correction, indicate clockwise vertical axis rotation ranging from +20°± 10° to +60°± 11° between multiple fault blocks. The uncorrected AMS data yield oblate <span class="hlt">magnetic</span> fabrics that can be used to infer the transport direction, source region, and paleovalley geometry of the JST. These data are tentatively interpreted to indicate west to east transport of the JST across the Mono Basin region into the Mina Deflection that was erupted and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23429012','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23429012"><span><span class="hlt">Generalised</span> insulin oedema after intensification of treatment with insulin analogues.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Adamo, Luigi; Thoelke, Mark</p> <p>2013-02-20</p> <p>We report a case of <span class="hlt">generalised</span> insulin oedema after intensification of treatment with genetically modified insulin. This is the first case of <span class="hlt">generalised</span> oedema in response to treatment with insulin analogues in a patient not insulin naive.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70033068','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70033068"><span>Soil <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>: A quantitative proxy of soil drainage for use in ecological restoration</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Grimley, D.A.; Wang, J.-S.; Liebert, D.A.; Dawson, J.O.</p> <p>2008-01-01</p> <p>Flooded, saturated, or poorly drained soils are commonly anaerobic, leading to microbially induced magnetite/maghemite dissolution and decreased soil <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (MS). Thus, MS is considerably higher in well-drained soils (MS typically 40-80 ?? 10-5 standard international [SI]) compared to poorly drained soils (MS typically 10-25 ?? 10-5 SI) in Illinois, other soil-forming factors being equal. Following calibration to standard soil probings, MS values can be used to rapidly and precisely delineate hydric from nonhydric soils in areas with relatively uniform parent material. Furthermore, soil MS has a moderate to strong association with individual tree species' distribution across soil moisture regimes, correlating inversely with independently reported rankings of a tree species' flood tolerance. Soil MS mapping can thus provide a simple, rapid, and quantitative means for precisely guiding reforestation with respect to plant species' adaptations to soil drainage classes. For instance, in native woodlands of east-central Illinois, Quercus alba , Prunus serotina, and Liriodendron tulipifera predominantly occur in moderately well-drained soils (MS 40-60 ?? 10-5 SI), whereas Acer saccharinum, Carya laciniosa, and Fraxinus pennsylvanica predominantly occur in poorly drained soils (MS <20 ?? 10-5 SI). Using a similar method, an MS contour map was used to guide restoration of mesic, wet mesic, and wet prairie species to pre-settlement distributions at Meadowbrook Park (Urbana, IL, U.S.A.). Through use of soil MS maps calibrated to soil drainage class and native vegetation occurrence, restoration efforts can be conducted more successfully and species distributions more accurately reconstructed at the microecosystem level. ?? 2008 Society for Ecological Restoration International.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SedG..230...77L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SedG..230...77L"><span><span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> variations and provenance of surface sediments in the South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Jianguo; Chen, Zhong; Chen, Muhong; Yan, Wen; Xiang, Rong; Tang, Xianzan</p> <p>2010-10-01</p> <p><span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> (MS) and grain sizes of surface sediments are measured to characterize sediment sources and their distribution in the South China Sea (SCS). Distribution characteristics of MS of bulk samples (MSB), fine-grained fraction (MSF) and coarse-grained fraction (MSC) are examined to explore the factors affecting MS values in sediment transport and deposition processes. Affected by dilution of quartz and carbonate abundance, MSC is not suitable for tracing sediment sources in the region. Instead, MSF provides a good parameter for tracking transport and deposition of complex and coarse-grained sediments such as those from Luzon Island volcanics and from the Pearl and Mekong Rivers, which often have high MSF values showing a decreasing trend with water depth on the continental shelf (water depth < 200 m). To the west of Luzon Island, Kuroshio intrusion into the SCS is the predominant factor for sediment transport after high MSF volcanic materials from the Luzon Island are discharged into the sea. Sediments from the Pearl River are transported southwestward under the China coastal current and then deposited between the Pearl River mouth and Hainan Island. To the southwest of Taiwan Island in the northeastern SCS, where sediments are mainly derived from Taiwan Island and/or the Yangtze River, both the Kuroshio intrusion and the China coastal current are significant in determining sediment transport and deposition. In the south, most of high MSF sediments from the Mekong River are transported eastward under the influence of northeastward currents in summer after entering the sea and then deposited on the northern Sunda Shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26778607','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26778607"><span>Task-evoked brain functional <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> mapping by independent component analysis (χICA).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Zikuan; Calhoun, Vince D</p> <p>2016-03-01</p> <p>Conventionally, independent component analysis (ICA) is performed on an fMRI magnitude dataset to analyze brain functional mapping (AICA). By solving the inverse problem of fMRI, we can reconstruct the brain <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (χ) functional states. Upon the reconstructed χ dataspace, we propose an ICA-based brain functional χ mapping method (χICA) to extract task-evoked brain functional map. A complex division algorithm is applied to a timeseries of fMRI phase images to extract temporal phase changes (relative to an OFF-state snapshot). A computed inverse MRI (CIMRI) model is used to reconstruct a 4D brain χ response dataset. χICA is implemented by applying a spatial InfoMax ICA algorithm to the reconstructed 4D χ dataspace. With finger-tapping experiments on a 7T system, the χICA-extracted χ-depicted functional map is similar to the SPM-inferred functional χ map by a spatial correlation of 0.67 ± 0.05. In comparison, the AICA-extracted magnitude-depicted map is correlated with the SPM magnitude map by 0.81 ± 0.05. The understanding of the inferiority of χICA to AICA for task-evoked functional map is an ongoing research topic. For task-evoked brain functional mapping, we compare the data-driven ICA method with the task-correlated SPM method. In particular, we compare χICA with AICA for extracting task-correlated timecourses and functional maps. χICA can extract a χ-depicted task-evoked brain functional map from a reconstructed χ dataspace without the knowledge about brain hemodynamic responses. The χICA-extracted brain functional χ map reveals a bidirectional BOLD response pattern that is unavailable (or different) from AICA. Copyright © 2016 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18984068','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18984068"><span><span class="hlt">Magnetic</span> resonance imaging method based on <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> effects to estimate bubble size in alveolar products: application to bread dough during proving.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>De Guio, François; Musse, Maja; Benoit-Cattin, Hugues; Lucas, Tiphaine; Davenel, Armel</p> <p>2009-05-01</p> <p><span class="hlt">Magnetic</span> resonance imaging has proven its potential application in bread dough and gas cell monitoring studies, and dynamic processes such as dough proving and baking can be monitored. However, undesirable <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> effects often affect quantification studies, especially at high fields. A new low-field method is presented based on local assessment of porosity in spin-echo imaging, local characterization of signal loss in gradient-echo imaging and prediction of relaxation times by simulation to estimate bubble radii in bread dough during proving. Maps of radii showed different regions of dough constituting networks which evolved during proving. Mean radius and bubble distribution were assessed during proving.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JSG....27.1750E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JSG....27.1750E"><span>Deformation regime variations in an arcuate transpressional orogen (Ribeira belt, SE Brazil) imaged by anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> in granulites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Egydio-Silva, Marcos; Vauchez, Alain; Raposo, Maria Irene B.; Bascou, Jérôme; Uhlein, Alexandre</p> <p>2005-10-01</p> <p>The Ribeira belt of southeastern Brazil displays an arcuate shape, with a structural trend that varies from ˜NS in the northern domain to ENE-WSW in the southern domain. This curvature is accompanied by a transition from contraction-dominated to transcurrent-dominated tectonics. The transition in deformation regime is accommodated in the central domain of the belt where granulitic rocks dominate and mineral-stretching lineations are commonly concealed by metamorphic recrystallization. We present anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) data from 664 samples from 62 sites in high-temperature gneisses, granulites and migmatites of the transitional, central domain of the belt, with the aim of investigating: (1) how well AMS allows one to map the mineral-stretching lineation and foliations in domains displaying a complex kinematic framework and (2) to investigate the kinematic pattern at the transition between the thrusting dominated and a wrench-faulting dominated orogenic segments. The mean <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> is 7.54×10 -3 SI. The degree of anisotropy varies from 1.32 up to 4.31, with an average value of 1.53. The shape parameter T is generally >0 meaning that the AMS ellipsoid is dominantly oblate. <span class="hlt">Magnetic</span> lineations and foliations form a consistent pattern correlated with the modification of the structural characteristics observed along the Ribeira belt. In the southern wrench-fault-dominated domain, the <span class="hlt">magnetic</span> lineation is subhorizontal, parallel to the trend of the steeply dipping <span class="hlt">magnetic</span> foliation. This correlation with the fabric observed in mylonites suggests that the <span class="hlt">magnetic</span> fabric is a valid proxy of the tectonic fabric in granulites. Results from the northern domain show that it comprises two sub-domains both displaying a ˜NS-trending <span class="hlt">magnetic</span> foliation. Eastward, over a broad area, the <span class="hlt">magnetic</span> foliation is consistently steeply dipping and bears a shallowly to moderately plunging <span class="hlt">magnetic</span> lineation. Westward, the dip of the foliation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15968677','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15968677"><span><span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> matching at the air-tissue interface in rat lung by using a superparamagnetic intravascular contrast agent: influence on transverse relaxation time of hyperpolarized helium-3.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vignaud, Alexandre; Maître, Xavier; Guillot, Geneviève; Durand, Emmanuel; de Rochefort, Ludovic; Robert, Philippe; Vivès, Véronique; Santus, Robin; Darrasse, Luc</p> <p>2005-07-01</p> <p>Transverse relaxation of hyperpolarized helium-3 <span class="hlt">magnetization</span> in respiratory airways highly depends on local <span class="hlt">magnetic</span> field gradients induced by the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> difference between gas and pulmonary tissue. Fast transverse relaxation is known to be an important feature that yields information about lung microstructure and function, but it is also an essential limitation in designing efficient strategies for lung imaging. Using intravascular injections of a superparamagnetic contrast agent in rats, it was possible to increase the overall <span class="hlt">susceptibility</span> of the perfused lung tissues and hence to match it with the gas <span class="hlt">susceptibility</span>. The transverse decay time constant of inhaled hyperpolarized helium-3 was measured in multiple-spin-echo experiments at 1.5 T as a function of the superparamagnetic contrast agent concentration in the animal blood. The time constant was increased by a factor of 3 when an optimal concentration was reached as predicted for <span class="hlt">susceptibility</span> matching by combining intrinsic <span class="hlt">susceptibilities</span> of tissue, blood, and gas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=phronesis&pg=4&id=EJ915392','ERIC'); return false;" href="https://eric.ed.gov/?q=phronesis&pg=4&id=EJ915392"><span>The Case: <span class="hlt">Generalisation</span>, Theory and Phronesis in Case Study</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Thomas, Gary</p> <p>2011-01-01</p> <p>Arguments for the value of case study are vitiated by assumptions about the need for <span class="hlt">generalisation</span> in the warrant of social scientific inquiry--and little <span class="hlt">generalisation</span> is legitimate from case study, although an argument exists for the role of the case in the establishment of a form of <span class="hlt">generalisation</span> in a certain kind of theory, a line of…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006SPIE.6217E..01D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006SPIE.6217E..01D"><span>Time-domain response of a metal detector to a target buried in soil with frequency-dependent <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Das, Y.</p> <p>2006-05-01</p> <p>The work reported in this paper is a part of on-going studies to clarify how and to what extent soil electromagnetic properties affect the performance of induction metal detectors widely used in humanitarian demining. This paper studies the specific case of the time-domain response of a small metallic sphere buried in a non-conducting soil half-space with frequency-dependent complex <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>. The sphere is chosen as a simple prototype for the small metal parts in low-metal landmines, while soil with dispersive <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> is a good model for some soils that are known to adversely affect the performance of metal detectors. The included analysis and computations extend previous work which has been done mostly in the frequency domain. Approximate theoretical expressions for weakly <span class="hlt">magnetic</span> soils are found to fit the experimental data very well, which allowed the estimation of soil model parameters, albeit in an ad hoc manner. Soil signal is found to exceed target signal (due to an aluminum sphere of radius 0.0127 m) in many cases, even for the weakly <span class="hlt">magnetic</span> Cambodian laterite used in the experiments. How deep a buried target is detected depends on many other factors in addition to the relative strength of soil and target signals. A general statement cannot thus be made regarding detectability of a target in soil based on the presented results. However, computational results complemented with experimental data extend the understanding of the effect that soil has on metal detectors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JETP..124..957A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JETP..124..957A"><span>Effect of defects in the rare-earth sublattice of the Kondo insulator YbB12 on its spectral characteristics and <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alekseev, P. A.; Kuznetsov, A. V.; Savchenkov, P. S.; Menushenkov, A. P.; Shitsevalova, N. Yu.</p> <p>2017-06-01</p> <p>The results of measuring the static and dynamic <span class="hlt">magnetic</span> <span class="hlt">susceptibilities</span> of several series of samples, which are based on the YbB12 Kondo insulator and are substituted in the rare-earth sublattice, are analyzed. Substitution is performed by nonmagnetic isoelectronic Lu ions; <span class="hlt">magnetic</span> isoelectronic Tm ions; and nonisoelectronic nonmagnetic Y, Sc, and Zr ions. The static <span class="hlt">susceptibility</span> is measured by a SQUID magnetometer in weak fields, and the dynamic <span class="hlt">susceptibility</span> is determined from inelastic neutron scattering data. The <span class="hlt">magnetic</span> properties are simulated using the spectral function found from neutron experimental data. A one-to-one correspondence is established between the influence of an impurity on the initial neutron spectrum and the temperature dependence of the static <span class="hlt">susceptibility</span>. The results obtained allow one to analyze the relation between the <span class="hlt">magnetic</span> properties and the electronic structure of the compounds of the given class.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/960232','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/960232"><span>Response to "Comment on ' A New Derivation of the Plasma <span class="hlt">Susceptibility</span> Tensor for a Hot <span class="hlt">Magnetized</span> Plasma Without Infinite Sums of Products of Bessel Functions'</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Qin, Hong; Phillips, Cynthia K.; Davidson, Ronald C.</p> <p>2008-02-20</p> <p>We welcome the Comment by Lerche et al on our recent paper titled "A new derivation of the plasma <span class="hlt">susceptibility</span> tensor for a hot <span class="hlt">magnetized</span> plasma without infinite sums of products of Bessel functions." The Comment brings up additional historical facts about previous research on the infinite sums of products of Bessel functions appearing in the plasma <span class="hlt">susceptibility</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhA...49s5201G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhA...49s5201G"><span>Quantum mechanics of a <span class="hlt">generalised</span> rigid body</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gripaios, Ben; Sutherland, Dave</p> <p>2016-05-01</p> <p>We consider the quantum version of Arnold’s <span class="hlt">generalisation</span> of a rigid body in classical mechanics. Thus, we quantise the motion on an arbitrary Lie group manifold of a particle whose classical trajectories correspond to the geodesics of any one-sided-invariant metric. We show how the derivation of the spectrum of energy eigenstates can be simplified by making use of automorphisms of the Lie algebra and (for groups of type I) by methods of harmonic analysis. We show how the method can be extended to cosets, <span class="hlt">generalising</span> the linear rigid rotor. As examples, we consider all connected and simply connected Lie groups up to dimension 3. This includes the universal cover of the archetypical rigid body, along with a number of new exactly solvable models. We also discuss a possible application to the topical problem of quantising a perfect fluid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22572334','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22572334"><span>Sequential experimental design based <span class="hlt">generalised</span> ANOVA</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chakraborty, Souvik Chowdhury, Rajib</p> <p>2016-07-15</p> <p>Over the last decade, surrogate modelling technique has gained wide popularity in the field of uncertainty quantification, optimization, model exploration and sensitivity analysis. This approach relies on experimental design to generate training points and regression/interpolation for generating the surrogate. In this work, it is argued that conventional experimental design may render a surrogate model inefficient. In order to address this issue, this paper presents a novel distribution adaptive sequential experimental design (DA-SED). The proposed DA-SED has been coupled with a variant of <span class="hlt">generalised</span> analysis of variance (G-ANOVA), developed by representing the component function using the <span class="hlt">generalised</span> polynomial chaos expansion. Moreover, <span class="hlt">generalised</span> analytical expressions for calculating the first two statistical moments of the response, which are utilized in predicting the probability of failure, have also been developed. The proposed approach has been utilized in predicting probability of failure of three structural mechanics problems. It is observed that the proposed approach yields accurate and computationally efficient estimate of the failure probability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JCoPh.317...15C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JCoPh.317...15C"><span>Sequential experimental design based <span class="hlt">generalised</span> ANOVA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chakraborty, Souvik; Chowdhury, Rajib</p> <p>2016-07-01</p> <p>Over the last decade, surrogate modelling technique has gained wide popularity in the field of uncertainty quantification, optimization, model exploration and sensitivity analysis. This approach relies on experimental design to generate training points and regression/interpolation for generating the surrogate. In this work, it is argued that conventional experimental design may render a surrogate model inefficient. In order to address this issue, this paper presents a novel distribution adaptive sequential experimental design (DA-SED). The proposed DA-SED has been coupled with a variant of <span class="hlt">generalised</span> analysis of variance (G-ANOVA), developed by representing the component function using the <span class="hlt">generalised</span> polynomial chaos expansion. Moreover, <span class="hlt">generalised</span> analytical expressions for calculating the first two statistical moments of the response, which are utilized in predicting the probability of failure, have also been developed. The proposed approach has been utilized in predicting probability of failure of three structural mechanics problems. It is observed that the proposed approach yields accurate and computationally efficient estimate of the failure probability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1335307','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1335307"><span>Single crystal <span class="hlt">magnetic</span> structure and <span class="hlt">susceptibility</span> of CoSe<sub>2</sub>O<sub>5</sub></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rodriguez, Efrain E.; Cao, Huibo; Haiges, Ralf; Melot, Brent C.</p> <p>2015-09-08</p> <p>The structure of CoSe<sub>2</sub>O<sub>5</sub> consists of one-dimensional ribbons of edge-sharing CoO<sub>6</sub> octahedra bound together by polyanionic subunits of Se<sub>2</sub>O<sub>5</sub>. Previous work on polycrystalline samples reported a canted antiferromagnetic arrangement of the <span class="hlt">magnetic</span> moments below the ordering temperature of 8.5 K. Here, we report a single crystal investigation using variable temperature and field <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> and low-temperature neutron diffraction to more precisely characterize the nature of the <span class="hlt">magnetic</span> ground state of CoSe<sub>2</sub>O<sub>5</sub>. Contrary to previous reports, we find that the single crystal <span class="hlt">magnetic</span> structure shows no canting of the antiferromagnetic ground state, and in the process have identified several field-induced changes to the <span class="hlt">magnetization</span>. Lastly, we discuss these results in the context of the revised <span class="hlt">magnetic</span> structure and highlight the importance of crystal growth for the accurate characterization of these properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5359224','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5359224"><span>Dynamic <span class="hlt">Susceptibility</span> Contrast <span class="hlt">Magnetic</span> Resonance Imaging Protocol of the Normal Canine Brain</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stadler, Krystina L.; Pease, Anthony P.; Ballegeer, Elizabeth A.</p> <p>2017-01-01</p> <p>Perfusion <span class="hlt">magnetic</span> resonance imaging (MRI), specifically dynamic <span class="hlt">susceptibility</span> MRI (DSC-MRI) is routinely performed as a supplement to conventional MRI in human medicine for patients with intracranial neoplasia and cerebrovascular events. There is minimal data on the use of DSC-MRI in veterinary patients and a DSC-MRI protocol in the veterinary patient has not been described. Sixteen normal dogs, 6 years or older were recruited for this study. The sample population included 11 large dogs (>11 kg) and 5 small dogs (<11 kg). DSC-MRI was performed on a 1.5-T MRI using an adjusted protocol inherent to the MRI. Contrast media was injected using an automatic power injector. Injections were made after five MR measurements were obtained. Following image acquisition, an arterial input function (AIF) graph mapping the transit time of contrast within the cerebral arteries was generated. The manually selected time points along this graph were used to compute perfusion maps. A dose and rate of 0.1 mmol/kg gadolinium-based contrast media at 3 ml/s followed by 10 ml saline flush at 3 ml/s was used in all dogs greater than 11 kg. In all dogs >11 kg, a useable AIF and perfusion map was generated. One dog less than 11 kg received the same contrast dose and rate. In this patient, the protocol did not generate a useable AIF. The remainder of the dogs less than 11 kg followed a protocol of 0.2 mmol/kg gadolinium-based contrast media at 1.5 ml/s with a 10 ml saline flush at 1.5 ml/s. A useable AIF and perfusion map was generated in the remaining dogs <11 kg using the higher contrast dose and slower rate protocol. This study establishes a contrast dose and administration rate for canine DSC-MRI imaging that is different in dogs greater than 11 kg compared to dogs less than 11 kg. These protocols may be used for future applications to evaluate hemodynamic disturbances in canine intracranial pathology. PMID:28377923</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMGP23A..05W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMGP23A..05W"><span>The Latitudinal Gradient of Rainfall, Mineralogy, Albedo and <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> in West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williams, E. R.; Balsam, W.; Schaaf, C.; Yang, X.; Zhang, Q.; Ji, J.; Rossman, G.; Garimella, S.; Oldfield, F.; Lyons, J. R.; Ellwood, B.; Hartman, H.; Hicks, E.; Mansot, J. L.; Cesaire, T.; Thomas, P.</p> <p>2008-12-01</p> <p>In order to investigate the effect of climate on soil and surface sediment properties we examined four transects around the Sahara Desert. The transects were located in Mali, Niger, Benin, Togo, Egypt and Morocco and, with the exception of Egypt, each crossed a significant climatological rainfall gradient. The Egyptian transect was designed to characterize one of the driest portions of the Sahara Desert. Our study included laboratory measurements of mineralogy (XRD), elemental composition (XRF), grain size, optical reflectance (lab), <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (MS)and remanences. In addition, albedo was determined from the MODIS satellite imagery from space. Many of our laboratory measurements exhibited variations with the rainfall gradient. Iron oxides (hematite and goethite), kaolinite, Al2O3, and TiO2 increased with increasing rainfall whereas SiO2, illite, and grain size decreased with increasing rainfall. Both laboratory-determined reflectivity and satellite-determine albedo decreased as rainfall increased. In part, this decrease in reflectivity/albedo with increasing rainfall appears to be the result of hematite, the dominant coloring agent for the soil in this region and the origin of the 'red' Sahel. The physical interpretation of these results centers on rainfall as a long-term leaching agent of surface material, and the control of physical properties by specific mineralogy. SiO2 is highly reflective and iron oxides are strongly absorptive in the visible range. The solubility of SiO2 in rainwater is orders of magnitude larger than all the iron oxides, with hematite the least soluble. It has long been recognized that leaching by rainfall produces dark red laterite in the near-surface oxidizing environment, a prominent geological feature throughout the high rainfall belt of West Africa. Laterite beds represent simultaneous enrichments of all iron oxides and a reduction in SiO2 by leaching. In the Sahara desert where rainfall is minimal (<10 mm/yr), SiO2 is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28377923','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28377923"><span>Dynamic <span class="hlt">Susceptibility</span> Contrast <span class="hlt">Magnetic</span> Resonance Imaging Protocol of the Normal Canine Brain.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stadler, Krystina L; Pease, Anthony P; Ballegeer, Elizabeth A</p> <p>2017-01-01</p> <p>Perfusion <span class="hlt">magnetic</span> resonance imaging (MRI), specifically dynamic <span class="hlt">susceptibility</span> MRI (DSC-MRI) is routinely performed as a supplement to conventional MRI in human medicine for patients with intracranial neoplasia and cerebrovascular events. There is minimal data on the use of DSC-MRI in veterinary patients and a DSC-MRI protocol in the veterinary patient has not been described. Sixteen normal dogs, 6 years or older were recruited for this study. The sample population included 11 large dogs (>11 kg) and 5 small dogs (<11 kg). DSC-MRI was performed on a 1.5-T MRI using an adjusted protocol inherent to the MRI. Contrast media was injected using an automatic power injector. Injections were made after five MR measurements were obtained. Following image acquisition, an arterial input function (AIF) graph mapping the transit time of contrast within the cerebral arteries was generated. The manually selected time points along this graph were used to compute perfusion maps. A dose and rate of 0.1 mmol/kg gadolinium-based contrast media at 3 ml/s followed by 10 ml saline flush at 3 ml/s was used in all dogs greater than 11 kg. In all dogs >11 kg, a useable AIF and perfusion map was generated. One dog less than 11 kg received the same contrast dose and rate. In this patient, the protocol did not generate a useable AIF. The remainder of the dogs less than 11 kg followed a protocol of 0.2 mmol/kg gadolinium-based contrast media at 1.5 ml/s with a 10 ml saline flush at 1.5 ml/s. A useable AIF and perfusion map was generated in the remaining dogs <11 kg using the higher contrast dose and slower rate protocol. This study establishes a contrast dose and administration rate for canine DSC-MRI imaging that is different in dogs greater than 11 kg compared to dogs less than 11 kg. These protocols may be used for future applications to evaluate hemodynamic disturbances in canine intracranial pathology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhA.122..754S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhA.122..754S"><span><span class="hlt">Magnetic</span> order and electronic properties of Li2Mn2(MoO4)3 material for lithium-ion batteries: ESR and <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suleimanov, N. M.; Prabaharan, S. R. S.; Khantimerov, S. M.; Nizamov, F. A.; Michael, M. S.; Drulis, H.; Wisniewski, P.</p> <p>2016-08-01</p> <p>We describe the application of electron spin resonance (ESR) and <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> methods to study the <span class="hlt">magnetic</span> properties and valence state of transition metal ions in Li2Mn2(MoO4)3 polyanion compound previously studied for its cathode-active properties in lithium containing batteries. ESR measurements of Li2Mn2(MoO4)3 have shown the presence of Mn2+ ions in the octahedral environment of oxygen ions. It is found that the part of manganese ions occupy the anti-site positions in lithium sublattice. The absence of the ESR signal from molybdenum ions indicates that they are non-<span class="hlt">magnetic</span> and adopt the 6+ valence state. Considerable overlapping between 3d orbitals of transition metal and 2p oxygen orbitals has been experimentally established. This leads to the indirect exchange interaction and antiferromagnetic ordering of manganese ions at 1.4 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JSG....34...54B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JSG....34...54B"><span>Anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) and diamagnetic fabrics in the Durness Limestone, NW Scotland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borradaile, G. J.; Almqvist, B. S. G.; Geneviciene, I.</p> <p>2012-01-01</p> <p>AMS fabrics in the Durness limestone show principal axes with orientations that are counterintuitive to, but symmetrical, with the regional tectonic axes ( X, Y, Z) where X is the stretching axis and Z is the shortening axis. In the field, cleavage ( XY) is nearly NS and nearly vertical. Low-field <span class="hlt">susceptibility</span> measurements of 57 cores with positive bulk <span class="hlt">susceptibility</span> (κ > 0) have a nearly vertical maximum <span class="hlt">susceptibility</span> (κ MAx) that is similarly oriented to the regional extension axis ( X) but with intermediate <span class="hlt">susceptibility</span> approximately parallel to the regional EW shortening axis. We explain this fabric as the blending of an oblate subhorizontal bedding with a north-south feeble tectonic AMS fabric, parallel to the regional N-S vertical cleavage. The 79 diamagnetic ( κ < 0) cores reveal a similar AMS fabric when the orientations of the maximum and minimum axes are exchanged to produce a paramagnetic-compatible fabric.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22342939','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22342939"><span>[<span class="hlt">Susceptibility</span> weighted <span class="hlt">magnetic</span> resonance sequences "SWAN, SWI and VenoBOLD": technical aspects and clinical applications].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hodel, J; Rodallec, M; Gerber, S; Blanc, R; Maraval, A; Caron, S; Tyvaert, L; Zuber, M; Zins, M</p> <p>2012-05-01</p> <p><span class="hlt">Susceptibility</span>-weighted MR sequences, T2 star weighted angiography (SWAN, General Electric), <span class="hlt">Susceptibility</span> weighted imaging (SWI, Siemens) and venous blood oxygen level dependant (VenoBOLD, Philips) are 3D spoiled gradient-echo sequence that provide a high sensitivity for the detection of blood degradation products, calcifications, and iron deposits. For all these sequences, an appropriate echo time allows for the visualization of <span class="hlt">susceptibility</span> differences between adjacent tissues. However, each of these sequences presents a specific technical background. The purpose of this review was to describe 1/the technical aspects of SWAN, VenoBOLD and SWI sequences, 2/the differences observed in term of contrast within the images, 3/the key imaging findings in neuroimaging using <span class="hlt">susceptibility</span>-weighted MR sequences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.4657B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.4657B"><span>Case Study Of Spatial <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> Screening Within The Urban Area Of Tuebingen, SW Germany, As A Proxy For Poly-cyclic Aromatic Hydrocarbon Contamination</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blaha, U.; Steidle, D. K.; Hoffmann, V.; Appel, E.; Grathwohl, P.</p> <p></p> <p>In situ <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> screening was performed in the southern part of Tübin- gen city, SW Germany. The main purpose of this case study was to prove the applica- bility of in situ <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements on soils in a variably polluted and densely populated urban environment. Road and rail traffic, house heating and small-scale industry are regarded as the sources of air-borne pollutants in Tübingen city. The impact of any kind of anthropogenic input on soils was studied taking into account specific areas in the city and the topography. A topographical dependence of in situ <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> as well as Shot spotsT of strongly increased values & cedil;were observed. More detailed investigation on selected spots, measuring the suscepti- bility on vertical soil profiles in the laboratory, provided information about the origin of the recorded <span class="hlt">magnetic</span> signal. Rock <span class="hlt">magnetic</span> measurements provided additional in- formation about the origin of mineral phases in the soils. PAH (Poly-cyclic Aromatic Hydrocarbon) analyses on selected soil samples revealed a direct link to the observed <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> indicating that <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> might be a proxy for PAH contamination in soils.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760014990','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760014990"><span><span class="hlt">Magnetization</span> and <span class="hlt">magnetic</span> <span class="hlt">susceptibilities</span> of GdH3, HoH3, ErH3 and YbH3</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Flood, D. J.</p> <p>1976-01-01</p> <p>The <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of powdered samples of HoH3, ErH3, GdH3 and YbH3 have been measured in the temperature range from 4.2 to 1.2 K. Two broad, local maxima are observed in the variation of chi versus T for GdH3, with maxima in (delta chi delta T) versus T at 1.8 K and 3.3 K. The inverse <span class="hlt">susceptibilities</span> for HoH3 and ErH3 both obey a Curies-Weiss law over a limited range (4.2 to 2.6K and 4.2 to 2 K respectively) with values for the Weiss constant of -4.25 K and -1.11 K, and effective moments of 8.6 and 7.7 Bohr magnetons respectively. The <span class="hlt">susceptibility</span> of YbH3 is independent of temperature over the range investigated. High-field <span class="hlt">magnetization</span> measurements yield extrapolated saturation moments of 7.0 + or - 0.25 Bohr magnetons/ion for GdH3, 6.1 + or - 0.2 Bohr magnetons/ion for HoH3 and 3.74 + or - 0.11 Bohr magnetons/ion for ErH3. In addition, ErH3 exhibits a van Vleck paramagnetism in the high field region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..MARA32012Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..MARA32012Q"><span>Nonlinear and ac <span class="hlt">Susceptibility</span> of the Dilute Ising <span class="hlt">Magnet</span> LiHoxY1-xF4</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Quilliam, Jeffrey; Meng, Shuchao; Mugford, Chas; Kycia, Jan</p> <p>2008-03-01</p> <p>Recent work has called into question the existence of a spin glass transition in the dilute dipolar Ising <span class="hlt">magnet</span> LiHoxY1-xF4 [1]. Other work has suggested that there is an exotic spin liquid phase found at a Ho concentration of x = 0.045 [2]. In order to carefully study the dynamics of this system, we have put together a SQUID magnetometer which allows for measurements of ac <span class="hlt">susceptibility</span> and nonlinear <span class="hlt">susceptibility</span> over a large frequency range. We present results from measurements on single crystals of LiHoxY1-xF4, particularly on an x = 0.045 sample, in an attempt to either reproduce the exotic ``anti-glass'' physics that was previously observed or to detect a spin glass transition. [1] P. E. Jonnson et al. PRL 98, 256403 (2007) [2] S. Ghosh et al. Science 296, 2195 (2002)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JMMM..431..141I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JMMM..431..141I"><span>The influence of interparticle correlations and self-assembly on the dynamic initial <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> spectra of ferrofluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivanov, A. O.; Kantorovich, S. S.; Elfimova, E. A.; Zverev, V. S.; Sindt, J. O.; Camp, P. J.</p> <p>2017-06-01</p> <p>Using computer simulations and a mean-field theoretical approach, we study how the growth in dipolar interparticle correlations manifests itself in the frequency-dependent initial <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of a ferrofluid. Our recently developed theory gives the correct single-particle Debye-theory results in the low-concentration, non-interacting regime; and it yields the exact leading-order contributions from interparticle correlations. The <span class="hlt">susceptibility</span> spectra are analysed in terms of the low-frequency behaviours of the real and imaginary parts, and the position of the peak in the imaginary part. By comparing the theoretical predictions to the results from Brownian dynamics simulations, it is possible to identify the conditions where correlations are important, but where self-assembly has not developed. We also provide a qualitative explanation for the behaviour of spectra beyond the mean-field limit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18181645','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18181645"><span>Preparation of bovine serum albumin surface-imprinted submicrometer particles with <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> through core-shell miniemulsion polymerization.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tan, Chau Jin; Chua, Hong Gap; Ker, Kwee Hong; Tong, Yen Wah</p> <p>2008-02-01</p> <p>Molecular imprinting is a state-of-the-art technique for preparing mimics of natural, biological receptors. Nevertheless, the imprinting of macromolecules like proteins remains a challenge due to their bulkiness and sensitivity to denaturation. In this work, a surface imprinting strategy based on covalently immobilized template molecules was adopted for protein imprinting. Bovine serum albumin (BSA) surface-imprinted submicrometer particles (500-600 nm) with <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> were prepared through a two-stage core-shell miniemulsion polymerization system using methyl methacrylate and ethylene glycol dimethacrylate as functional and cross-linking monomers, respectively. The particles possessed a novel red blood cell-like structure and exhibited a very favorable recognition property toward the template BSA molecules in aqueous medium. In a two-protein system, the particles had shown a very high specific recognition of the template proteins over the nontemplate proteins. The <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> was imparted through the successful encapsulation of Fe3O4 nanoparticles. Their superparamagnetic nature increases their potential applications in the fields such as <span class="hlt">magnetic</span> bioseparation, cell labeling, and bioimaging. In addition, the importance of template immobilization for successful protein imprinting had also been illustrated to demonstrate the potential of this approach as a general methodology for protein imprinting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930022691&hterms=Wais&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DWais','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930022691&hterms=Wais&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DWais"><span>Lithology and chronology of ice-sheet fluctuations (<span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of cores from the western Ross Sea)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jennings, Anne E.</p> <p>1993-01-01</p> <p>The goals of the marine geology part of WAIS include reconstructing the chronology and areal extent of ice-sheet fluctuations and understanding the climatic and oceanographic influences on ice-sheet history. As an initial step toward attaining these goals, down-core volume <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (MS) logs of piston cores from three N-S transects in the western Ross Sea are compared. The core transects are within separate petrographic provinces based on analyses of till composition. The provinces are thought to reflect the previous locations of ice streams on the shelf during the last glaciation. <span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> is a function of <span class="hlt">magnetic</span> mineral composition, sediment texture, and sediment density. It is applied in the western Ross Sea for two purposes: (1) to determine whether MS data differentiates the three transects (i.e., flow lines), and thus can be used to make paleodrainage reconstructions of the late Wisconsinan ice sheet; and (2) to determine whether the MS data can aid in distinguishing basal till diamictons from diamictons of glacial-marine origin and thus, aid paleoenvironmental interpretations. A comparison of the combined data of cores in each transect is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930022691&hterms=Ross&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DRoss%2BP.%252C','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930022691&hterms=Ross&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DRoss%2BP.%252C"><span>Lithology and chronology of ice-sheet fluctuations (<span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of cores from the western Ross Sea)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jennings, Anne E.</p> <p>1993-01-01</p> <p>The goals of the marine geology part of WAIS include reconstructing the chronology and areal extent of ice-sheet fluctuations and understanding the climatic and oceanographic influences on ice-sheet history. As an initial step toward attaining these goals, down-core volume <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (MS) logs of piston cores from three N-S transects in the western Ross Sea are compared. The core transects are within separate petrographic provinces based on analyses of till composition. The provinces are thought to reflect the previous locations of ice streams on the shelf during the last glaciation. <span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> is a function of <span class="hlt">magnetic</span> mineral composition, sediment texture, and sediment density. It is applied in the western Ross Sea for two purposes: (1) to determine whether MS data differentiates the three transects (i.e., flow lines), and thus can be used to make paleodrainage reconstructions of the late Wisconsinan ice sheet; and (2) to determine whether the MS data can aid in distinguishing basal till diamictons from diamictons of glacial-marine origin and thus, aid paleoenvironmental interpretations. A comparison of the combined data of cores in each transect is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Tectp.656..175I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Tectp.656..175I"><span>Anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> in diamagnetic limestones reveals deflection of the strain field near the Dead Sea Fault, northern Israel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Issachar, R.; Levi, T.; Marco, S.; Weinberger, R.</p> <p>2015-08-01</p> <p>To exploit the potential of anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) as a tool to estimate the strain field around major faults, we measured the AMS of calcite-bearing diamagnetic rocks that crop out next to the Dead Sea Fault (DSF) in northern Israel. Through integrated <span class="hlt">magnetic</span> and geochemical methods we found that the rocks are almost pure calcite rocks and therefore the <span class="hlt">magnetic</span> fabric is primarily controlled by preferred crystallographic orientation (PCO) with the minimum principal AMS axes (k3) parallel to calcite c-axes. We applied a separation procedure in several samples with high Fe content in order to calculate the AMS anisotropy parameters and compare them to pure diamagnetic rocks. AARM, thermo-<span class="hlt">susceptibility</span> curves and IRM were used to characterize the <span class="hlt">magnetic</span> phases. We found that for Fe content below 500 ppm the AMS is mostly controlled by the diamagnetic phase and showed that differences in the degree of anisotropy P' up to 3% (P' = 1.005 to 1.023) and in anisotropy difference Δk (up to ~ 0.25 × 10- 6 SI) in diamagnetic rocks are related to differences of strain magnitudes. The spatial distribution of the <span class="hlt">magnetic</span> fabrics indicates ~ N-S maximum shortening parallel to the strike of the Hula Western Border fault (HWBF), one of the main strands of the DSF in northern Israel. The anisotropy parameters suggest that the strain magnitudes increase eastward with the proximity to the HWBF. These results suggest that the strain field near the HWBF is locally deflected as a consequence of the DSF activity. In light of the "fault weakness" model and geological setting of the study area, we suggest that the area accommodates dominant transtension during the Pleistocene. The present study demonstrates the useful application of AMS measurements in "iron-free" limestones as recorders of the strain field near plate boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8106R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8106R"><span>Correlations between soil <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> and the content of particular elements as a reflection of pollution level, land use and parent rocks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rachwał, Marzena; Magiera, Tadeusz; Bens, Oliver; Kardel, Kati</p> <p>2015-04-01</p> <p><span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> is a worldwide used measure of (ferri)<span class="hlt">magnetic</span> minerals occurring in soils, sediments and dusts. In soils, these minerals are of various origin: air-derived particulate pollutions, parent rocks or pedogenesis. Human activity causes different changes in the content of <span class="hlt">magnetic</span> minerals as well as their spatial and vertical distribution in soil profiles. <span class="hlt">Magnetic</span> minerals are characterized by an affinity for other elements occurring in the soil, so positive correlations between <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> and particular elements like macrocomponents or heavy metals often occurs. The archival soil samples collected from different soil horizons in the territory of the Free State of Saxony (Germany) were subjected to the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements using Bartington MS2B. Additionally, samples were chemically analyzed by the S Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences in Potsdam. Values of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> varied from 9.3 to 1382 ×10-8 m3/kg in organic soil horizon and from 0.1 to 2105 ×10-8 m3/kg in dipper layers. Calculated correlation coefficients between <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> and some elements indicate significant relationships characteristic for different factors influenced soil properties (pollution level, land use and parent rocks). The northern part of Saxony is divided by the Elbe into two parts: east part with loose sedimentary rocks and the west one with more solid loess bedrock enriched by spectrum of elements from the Ore Mountains. Correlations between <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> and Ca, Fe, Mn, and Zn were stated in the eastern, while soil <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of the western part revealed a correlation with Fe, P, Cd, Cu, Pb, Zn, Mo, U, V, and W. Taking into account influences of industry and urbanization, soil <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> is enhanced in the areas with higher population density comparing with rural sites. In the area of Hoyerswerda and Weisswasser with low <span class="hlt">magnetic</span> natural</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSMMA11B..03M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSMMA11B..03M"><span>Measurement of Meteorite Density, Porosity and <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span>: Fast, Non- destructive, Non-contaminating and Very Informative</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Macke, R. J.; Britt, D. T.; Consolmagno, G. J.</p> <p>2009-05-01</p> <p>The development of the "glass bead" method [1] for measuring bulk density, coupled with other fast, non- destructive and non-contaminating methods for measuring grain density and <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>, has enabled broad surveys of large meteorite collections. We have employed these methods extensively on meteorites in numerous collections, including those at the Vatican, the American Museum of Natural History (New York), the National Museum of Natural History (Washington, DC), Texas Christian University, University of New Mexico, and Arizona State University. We present here a summary of some of the findings to date. Using the glass bead method, the meteorite is placed into a container which is then filled entirely with small (sub- millimeter) glass beads. The beads behave collectively as an Archimedean fluid, flowing around the sample to fill the empty space in the container. Through mass measurement, the volume displaced by the sample can be determined. Grain density is determined via helium ideal-gas pycnometry. <span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> is determined using a commercially available hand-held device [2]. Among notable findings to date, grain density and <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> together can distinguish H, L and LL ordinary chondrite falls into clearly distinct groupings [3]. On the other hand, enstatite chondrites of EH and EL subgroups are indistinguishable in these properties, indicating that EH and EL do not differ significantly in iron content [4]. Carbonaceous chondrites can have porosities that are significantly higher than ordinary chondrites and (especially for aqueously altered meteorites) lower density, though these also vary according to subgroups [5]. References: [1] Consolmagno and Britt, 1998. M&PS 33, 1231-1240. [2] Gattacceca et al., 2004. GJI 158, 42-49. [3] Consolmagno et al., 2006. M&PS 41, 331-342. [4] Macke et al., 2009. LPSC 40, 1598. [5] Consolmagno et al., 2008. MetSoc 71, 5038.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMoSt1123..394W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMoSt1123..394W"><span>Two novel CPs with double helical chains based rigid tripodal ligands: Syntheses, crystal structures, <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> and fluorescence properties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Xiao; Hou, Xiang-Yang; Zhai, Quan-Guo; Hu, Man-Cheng</p> <p>2016-11-01</p> <p>Two three-dimensional coordination polymers (CPs), namely [Cd(bpydb)- (H2bpydb)]n·0.5nH2O (1), and [Cu2(bpydb)2]n (2) (2,6-di-p-carboxyphenyl-4,4'- bipyridine1 = H2bpydb), containing a novel double-helical chains, which have been solvothermal synthesized, characterized, and structure determination. CPs 1-2 reveal the new (3,5)-net and (3,6)-net alb topology, respectively. The fluorescence properties of CPs 1-2 were investigated, and <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements indicate that compound 1 has dominating antiferromagnetic couplings between metal ions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22269321','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22269321"><span><span class="hlt">Magnetic</span> field induced third order <span class="hlt">susceptibility</span> of third order harmonic generation in a ZnMgSe strained quantum well</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mark, J. Abraham Hudson Peter, A. John</p> <p>2014-04-24</p> <p>Third order <span class="hlt">susceptibility</span> of third order harmonic generation is investigated in a Zn{sub 0.1}Mg{sub 0.9}Se/Zn{sub 0.8}Mg{sub 0.2}Se/Zn{sub 0.1}Mg{sub 0.9}Se quantum well in the presence of <span class="hlt">magnetic</span> field strength. The confinement potential is considered as the addition of energy offsets of the conduction band (or valence band) and the strain-induced potential in our calculations. The material dependent effective mass is followed throughout the computation because it has a high influence on the electron energy levels in low dimensional semiconductor systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1591.1410M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1591.1410M"><span><span class="hlt">Magnetic</span> field induced third order <span class="hlt">susceptibility</span> of third order harmonic generation in a ZnMgSe strained quantum well</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mark, J. Abraham Hudson; Peter, A. John</p> <p>2014-04-01</p> <p>Third order <span class="hlt">susceptibility</span> of third order harmonic generation is investigated in a Zn0.1Mg0.9Se/Zn0.8Mg0.2Se/Zn0.1Mg0.9Se quantum well in the presence of <span class="hlt">magnetic</span> field strength. The confinement potential is considered as the addition of energy offsets of the conduction band (or valence band) and the strain-induced potential in our calculations. The material dependent effective mass is followed throughout the computation because it has a high influence on the electron energy levels in low dimensional semiconductor systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JChPh.120.2382D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JChPh.120.2382D"><span>On the variation of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of a molecular crystal with temperature: The 2,4,6-triphenylverdazyl system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Datta, Sambhu N.; Navada, Geetha K.</p> <p>2004-02-01</p> <p><span class="hlt">Magnetic</span> <span class="hlt">susceptibilities</span> of spin-1/2 systems of orthorhombic and higher crystal symmetries have been numerically investigated while taking possible anisotropy in the coupling constants along different crystal axes into account. The work relies on the magnon-based theory of ferromagnetic (FM) and antiferromagnetic (AFM) crystal systems of types FFF, AFF, AAF, and AAA [J. Chem. Phys. 111, 9009 (1999)]. The AAF crystal, in particular, shows interesting changes in the temperature dependence of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> when the ferromagnetic exchange coupling constant is varied. We especially show that the <span class="hlt">susceptibility</span> anomalies of molecular crystals fit naturally within the framework of the extended magnon-theoretical formalism, and do not necessarily imply a FM→AFM or a reverse phase transition. A real system, molecular crystal of 2,4,6-triphenylverdazyl (2,4,6-TPV), has been investigated here. It was previously interpreted as an AAF system from observed <span class="hlt">susceptibility</span> data [Tomiyoshi et al., Phys. Rev. B 49, 16031 (1994)]. The trend of the temperature dependence of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> studied in the present work also indicates that the crystal belongs to the AAF category with a less prominent FM exchange coupling constant. To reinforce our conclusions, we have adopted a two-pronged strategy. First, the geometry of the 2,4,6-TPV monomer has been optimized here by ab initio unrestricted Hartree-Fock (UHF) calculations using the STO-3G basis set. The optimized geometry is almost planar. A subsequent calculation has been carried out with the phenyl rings twisted out of the plane of the nitrogen atoms. The STO-3G optimized geometry, and the same geometry except for the twisted phenyl rings, have been used to perform ab initio coupled-cluster (UCCSD-T) calculations with the same basis, and UHF as well as density-functional (UB3LYP) calculations using the 6-31G basis set. The calculated data can easily rationalize the twists while the species remains in crystal. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP21C2262M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP21C2262M"><span><span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> and Geochemistry Records in the Yax-1 Borehole in the Chicxulub Impact Crater: A paleoclimatic approach in the K/Pg and P/E Boundaries.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marca-Castillo, M.; Perez-Cruz, L. L.; Fucugauchi, J. U.; Buitrón Sánchez, B. E.</p> <p>2015-12-01</p> <p>Chicxulub impact crater is located in the northwestern sector of Yucatan Peninsula, Mexico. It is the best-preserved multi-ring impact crater on Earth. Several studies have been focused in this crater structure due its association with the Cretaceous/Paleogenous boundary events. The aim of this study is document the abrupt climate changes during the K/Pg and P/E boundaries based on the stratigraphy, <span class="hlt">magnetic</span> properties (<span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>) and geochemical (major elements) records in the Yaxcopoil-1 (Yax-1) borehole in the Chicxulub impact crater. The Yax 1 was drilled at 20° 44' 38.45'' N, 89° 43' 6.70'' W. Two intervals from 830 to 750 and between 750 and 700 m depth were selected for this study. <span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> logs and X-Ray Fluorescence (XRF) measures were taken every 10 cm using a Bartington <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> meter and a Thermo Scientific Niton XL3tGOLDD XRF analyzer. Results show variations in <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> logs and major elements (Ca, Si, Fe, Ti and Si) content in the K/Pg boundary at ca. 794 m depth. <span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> decrease abruptly, Ca values increase, and the other elements show low values. Geochemical results, manly the Ca-record, suggest that the P/E boundary might have happened around 745 m depth. These values are compared with 13C isotopes and they coincide with the Carbon Isotope Excursion (CIE), suggesting their relationship with the abrupt climate change and with the ocean acidification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9783E..57S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9783E..57S"><span>Quantitative evaluation of <span class="hlt">susceptibility</span> effects caused by dental materials in head <span class="hlt">magnetic</span> resonance imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Strocchi, S.; Ghielmi, M.; Basilico, F.; Macchi, A.; Novario, R.; Ferretti, R.; Binaghi, E.</p> <p>2016-03-01</p> <p>This work quantitatively evaluates the effects induced by <span class="hlt">susceptibility</span> characteristics of materials commonly used in dental practice on the quality of head MR images in a clinical 1.5T device. The proposed evaluation procedure measures the image artifacts induced by <span class="hlt">susceptibility</span> in MR images by providing an index consistent with the global degradation as perceived by the experts. <span class="hlt">Susceptibility</span> artifacts were evaluated in a near-clinical setup, using a phantom with <span class="hlt">susceptibility</span> and geometric characteristics similar to that of a human head. We tested different dentist materials, called PAL Keramit, Ti6Al4V-ELI, Keramit NP, ILOR F, Zirconia and used different clinical MR acquisition sequences, such as "classical" SE and fast, gradient, and diffusion sequences. The evaluation is designed as a matching process between reference and artifacts affected images recording the same scene. The extent of the degradation induced by <span class="hlt">susceptibility</span> is then measured in terms of similarity with the corresponding reference image. The matching process involves a multimodal registration task and the use an adequate similarity index psychophysically validated, based on correlation coefficient. The proposed analyses are integrated within a computer-supported procedure that interactively guides the users in the different phases of the evaluation method. 2-Dimensional and 3-dimensional indexes are used for each material and each acquisition sequence. From these, we drew a ranking of the materials, averaging the results obtained. Zirconia and ILOR F appear to be the best choice from the <span class="hlt">susceptibility</span> artefacts point of view, followed, in order, by PAL Keramit, Ti6Al4V-ELI and Keramit NP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21399269','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21399269"><span>Static <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>, crystal field and exchange interactions in rare earth titanate pyrochlores.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Malkin, B Z; Lummen, T T A; van Loosdrecht, P H M; Dhalenne, G; Zakirov, A R</p> <p>2010-07-14</p> <p>The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site <span class="hlt">susceptibilities</span> of rare earth titanate pyrochlores R(2)Ti(2)O(7) (R = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) is analyzed in the framework of crystal field theory and a mean field approximation. Analytical expressions for the site and bulk <span class="hlt">susceptibilities</span> of the pyrochlore lattice are derived taking into account long range dipole-dipole interactions and anisotropic exchange interactions between the nearest neighbor rare earth ions. The sets of crystal field parameters and anisotropic exchange coupling constants have been determined and their variations along the lanthanide series are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EPJC...76..693M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EPJC...76..693M"><span><span class="hlt">Generalised</span> model for anisotropic compact stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maurya, S. K.; Gupta, Y. K.; Ray, Saibal; Deb, Debabrata</p> <p>2016-12-01</p> <p>In the present investigation an exact <span class="hlt">generalised</span> model for anisotropic compact stars of embedding class 1 is sought with a general relativistic background. The generic solutions are verified by exploring different physical aspects, viz. energy conditions, mass-radius relation, stability of the models, in connection to their validity. It is observed that the model presented here for compact stars is compatible with all these physical tests and thus physically acceptable as far as the compact star candidates RXJ 1856-37, SAX J 1808.4-3658 ( SS1) and SAX J 1808.4-3658 ( SS2) are concerned.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhLB..766...55C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhLB..766...55C"><span><span class="hlt">Generalising</span> the coupling between spacetime and matter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carloni, Sante</p> <p>2017-03-01</p> <p>We explore the idea that the coupling between matter and spacetime is more complex than the one originally envisioned by Einstein. We propose that such coupling takes the form of a new fundamental tensor in the Einstein field equations. We then show that the introduction of this tensor can account for dark phenomenology in General Relativity, maintaining a weak field limit compatible with standard Newtonian gravitation. The same paradigm can be applied any other theory of gravitation. We show, as an example, that in the context of conformal gravity a <span class="hlt">generalised</span> coupling is able to solve compatibility issues between the matter and the gravitational sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1299497','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1299497"><span>The <span class="hlt">susceptibility</span> of pure tubulin to high <span class="hlt">magnetic</span> fields: a <span class="hlt">magnetic</span> birefringence and x-ray fiber diffraction study.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bras, W; Diakun, G P; Díaz, J F; Maret, G; Kramer, H; Bordas, J; Medrano, F J</p> <p>1998-01-01</p> <p>The orientational behavior of microtubules assembled in strong <span class="hlt">magnetic</span> fields has been studied. It is shown that when microtubules are assembled in a <span class="hlt">magnetic</span> field, they align with their long axis parallel to the <span class="hlt">magnetic</span> field. The effect of several parameters known to affect the microtubule assembly are investigated with respect to their effect on the final degree of alignment. Aligned samples of hydrated microtubules suitable for low-resolution x-ray fiber diffraction experiments have been produced, and the results obtained from the fiber diffraction experiments have been compared with the <span class="hlt">magnetic</span> birefringence experiments. Comparisons with earlier fiber diffraction work and small-angle x-ray solution scattering experiments have been made. PMID:9512047</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Tecto..33.2526P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Tecto..33.2526P"><span>The curved Magallanes fold and thrust belt: Tectonic insights from a paleomagnetic and anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Poblete, F.; Roperch, P.; Hervé, F.; Diraison, M.; Espinoza, M.; Arriagada, C.</p> <p>2014-12-01</p> <p>The Magallanes fold and thrust belt (FTB) presents a large-scale curvature from N-S oriented structures north of 52°S to nearly E-W in Tierra del Fuego Island. We present a paleomagnetic and anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) study from 85 sites sampled in Cretaceous to Miocene marine sediments. <span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> is lower than 0.0005 SI for 76 sites and mainly controlled by paramagnetic minerals. AMS results indicate that the sedimentary fabric is preserved in the undeformed areas of Tierra del Fuego and the more external thrust sheets units, where an incipient lineation due to layer parallel shortening is recorded. Prolate AMS ellipsoids, indicating a significant tectonic imprint in the AMS fabric, are observed in the internal units of the belt. AMS results show a good correlation between the orientation of the <span class="hlt">magnetic</span> lineation and the fold axes. However, in Península Brunswick, the AMS lineations are at ~20° counterclockwise to the strike of the fold axes. Pretectonic stable characteristic remanent <span class="hlt">magnetizations</span> (ChRM) were determined in seven sites. A counterclockwise rotation (21.2° ± 9.2°) is documented by ChRM data from four sites near the hinge of the belt in Península Brunswick and near Canal Whiteside while there is no evidence of rotation near the nearly E-W oriented Vicuña thrust within Tierra del Fuego. The curved shape of the Cenozoic Magallanes FTB is not related to vertical axis rotation, and thus, the Magallanes FTB can be considered as a primary arc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3428333','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3428333"><span>Erythrocyte Enrichment in Hematopoietic Progenitor Cell Cultures Based on <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> of the Hemoglobin</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jin, Xiaoxia; Abbot, Stewart; Zhang, Xiaokui; Kang, Lin; Voskinarian-Berse, Vanessa; Zhao, Rui; Kameneva, Marina V.; Moore, Lee R.; Chalmers, Jeffrey J.; Zborowski, Maciej</p> <p>2012-01-01</p> <p>Using novel media formulations, it has been demonstrated that human placenta and umbilical cord blood-derived CD34+ cells can be expanded and differentiated into erythroid cells with high efficiency. However, obtaining mature and functional erythrocytes from the immature cell cultures with high purity and in an efficient manner remains a significant challenge. A distinguishing feature of a reticulocyte and maturing erythrocyte is the increasing concentration of hemoglobin and decreasing cell volume that results in increased cell magnetophoretic mobility (MM) when exposed to high <span class="hlt">magnetic</span> fields and gradients, under anoxic conditions. Taking advantage of these initial observations, we studied a noninvasive (label-free) <span class="hlt">magnetic</span> separation and analysis process to enrich and identify cultured functional erythrocytes. In addition to the <span class="hlt">magnetic</span> cell separation and cell motion analysis in the <span class="hlt">magnetic</span> field, the cell cultures were characterized for cell sedimentation rate, cell volume distributions using differential interference microscopy, immunophenotyping (glycophorin A), hemoglobin concentration and shear-induced deformability (elongation index, EI, by ektacytometry) to test for mature erythrocyte attributes. A commercial, packed column high-gradient <span class="hlt">magnetic</span> separator (HGMS) was used for <span class="hlt">magnetic</span> separation. The <span class="hlt">magnetically</span> enriched fraction comprised 80% of the maturing cells (predominantly reticulocytes) that showed near 70% overlap of EI with the reference cord blood-derived RBC and over 50% overlap with the adult donor RBCs. The results demonstrate feasibility of label-free <span class="hlt">magnetic</span> enrichment of erythrocyte fraction of CD34+ progenitor-derived cultures based on the presence of paramagnetic hemoglobin in the maturing erythrocytes. PMID:22952572</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22952572','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22952572"><span>Erythrocyte enrichment in hematopoietic progenitor cell cultures based on <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of the hemoglobin.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jin, Xiaoxia; Abbot, Stewart; Zhang, Xiaokui; Kang, Lin; Voskinarian-Berse, Vanessa; Zhao, Rui; Kameneva, Marina V; Moore, Lee R; Chalmers, Jeffrey J; Zborowski, Maciej</p> <p>2012-01-01</p> <p>Using novel media formulations, it has been demonstrated that human placenta and umbilical cord blood-derived CD34+ cells can be expanded and differentiated into erythroid cells with high efficiency. However, obtaining mature and functional erythrocytes from the immature cell cultures with high purity and in an efficient manner remains a significant challenge. A distinguishing feature of a reticulocyte and maturing erythrocyte is the increasing concentration of hemoglobin and decreasing cell volume that results in increased cell magnetophoretic mobility (MM) when exposed to high <span class="hlt">magnetic</span> fields and gradients, under anoxic conditions. Taking advantage of these initial observations, we studied a noninvasive (label-free) <span class="hlt">magnetic</span> separation and analysis process to enrich and identify cultured functional erythrocytes. In addition to the <span class="hlt">magnetic</span> cell separation and cell motion analysis in the <span class="hlt">magnetic</span> field, the cell cultures were characterized for cell sedimentation rate, cell volume distributions using differential interference microscopy, immunophenotyping (glycophorin A), hemoglobin concentration and shear-induced deformability (elongation index, EI, by ektacytometry) to test for mature erythrocyte attributes. A commercial, packed column high-gradient <span class="hlt">magnetic</span> separator (HGMS) was used for <span class="hlt">magnetic</span> separation. The <span class="hlt">magnetically</span> enriched fraction comprised 80% of the maturing cells (predominantly reticulocytes) that showed near 70% overlap of EI with the reference cord blood-derived RBC and over 50% overlap with the adult donor RBCs. The results demonstrate feasibility of label-free <span class="hlt">magnetic</span> enrichment of erythrocyte fraction of CD34+ progenitor-derived cultures based on the presence of paramagnetic hemoglobin in the maturing erythrocytes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GGG....17.2940I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GGG....17.2940I"><span>Improving the method of low-temperature anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (LT-AMS) measurements in air</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Issachar, R.; Levi, T.; Lyakhovsky, V.; Marco, S.; Weinberger, R.</p> <p>2016-07-01</p> <p>This study examines the limitations of the method of low-temperature anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (LT-AMS) measurements in air and presents technical improvements that significantly reduce the instrumental drift and measurement errors. We analyzed the temperature profile of porous chalk core after cooling in liquid nitrogen and found that the average temperature of the sample during the LT-AMS measurement in air is higher than 77K and close to 92K. This analysis indicates that the <span class="hlt">susceptibility</span> of the paramagnetic minerals are amplified by a factor ˜3.2 relative to that of room temperature AMS (RT-AMS). In addition, it was found that liquid nitrogen was absorbed in the samples during immersing and contributed diamagnetic component of ˜-9 × 10-6 SI to the total mean <span class="hlt">susceptibility</span>. We showed that silicone sheet placed around and at the bottom of the measuring coil is an effective thermal protection, preventing instrument drift by the cold sample. In this way, the measuring errors of LT-AMS reduced to the level of RT-AMS, allowing accurate comparison with standard AMS measurements. We examined the applicability of the LT-AMS measurements on chalk samples that consist <5% (weight) of paramagnetic minerals and showed that it helps to efficiently enhance the paramagnetic fabric. The present study offers a practical approach, which can be applied to various types of rocks to better delineate the paramagnetic phase using conventional equipment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4508405','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4508405"><span>Proton Nuclear <span class="hlt">Magnetic</span> Resonance Spectroscopy as a Technique for Gentamicin Drug <span class="hlt">Susceptibility</span> Studies with Escherichia coli ATCC 25922</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>García-Álvarez, Lara; Busto, Jesús H.; Avenoza, Alberto; Sáenz, Yolanda; Peregrina, Jesús Manuel</p> <p>2015-01-01</p> <p>Antimicrobial drug <span class="hlt">susceptibility</span> tests involving multiple time-consuming steps are still used as reference methods. Today, there is a need for the development of new automated instruments that can provide faster results and reduce operating time, reagent costs, and labor requirements. Nuclear <span class="hlt">magnetic</span> resonance (NMR) spectroscopy meets those requirements. The metabolism and antimicrobial <span class="hlt">susceptibility</span> of Escherichia coli ATCC 25922 in the presence of gentamicin have been analyzed using NMR and compared with a reference method. Direct incubation of the bacteria (with and without gentamicin) into the NMR tube has also been performed, and differences in the NMR spectra were obtained. The MIC, determined by the reference method found in this study, would correspond with the termination of the bacterial metabolism observed with NMR. Experiments carried out directly into the NMR tube enabled the development of antimicrobial drug <span class="hlt">susceptibility</span> tests to assess the effectiveness of the antibiotic. NMR is an objective and reproducible method for showing the effects of a drug on the subject bacterium and can emerge as an excellent tool for studying bacterial activity in the presence of different antibiotic concentrations. PMID:25972417</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25972417','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25972417"><span>Proton Nuclear <span class="hlt">Magnetic</span> Resonance Spectroscopy as a Technique for Gentamicin Drug <span class="hlt">Susceptibility</span> Studies with Escherichia coli ATCC 25922.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>García-Álvarez, Lara; Busto, Jesús H; Avenoza, Alberto; Sáenz, Yolanda; Peregrina, Jesús Manuel; Oteo, José A</p> <p>2015-08-01</p> <p>Antimicrobial drug <span class="hlt">susceptibility</span> tests involving multiple time-consuming steps are still used as reference methods. Today, there is a need for the development of new automated instruments that can provide faster results and reduce operating time, reagent costs, and labor requirements. Nuclear <span class="hlt">magnetic</span> resonance (NMR) spectroscopy meets those requirements. The metabolism and antimicrobial <span class="hlt">susceptibility</span> of Escherichia coli ATCC 25922 in the presence of gentamicin have been analyzed using NMR and compared with a reference method. Direct incubation of the bacteria (with and without gentamicin) into the NMR tube has also been performed, and differences in the NMR spectra were obtained. The MIC, determined by the reference method found in this study, would correspond with the termination of the bacterial metabolism observed with NMR. Experiments carried out directly into the NMR tube enabled the development of antimicrobial drug <span class="hlt">susceptibility</span> tests to assess the effectiveness of the antibiotic. NMR is an objective and reproducible method for showing the effects of a drug on the subject bacterium and can emerge as an excellent tool for studying bacterial activity in the presence of different antibiotic concentrations. Copyright © 2015, American Society for Microbiology. All Rights Reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhRvB..75r4536S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhRvB..75r4536S"><span>Successive superconducting transitions in Ta2S2C studied by electrical resistivity and nonlinear ac <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suzuki, Masatsugu; Suzuki, Itsuko S.; Noji, Takashi; Koike, Yoji; Walter, Jürgen</p> <p>2007-05-01</p> <p>Ta2S2C compound undergoes superconducting transitions at Tcl=3.60±0.02K and Tcu=9.0±0.2K . The nature of successive superconducting transitions has been studied from electrical resistivity and linear and nonlinear ac <span class="hlt">magnetic</span> <span class="hlt">susceptibilities</span>. The resistivity ρ at H=0 shows a local maximum near Tcu , a kinklike behavior around Tcl , and reduces to zero at below T0=2.1K . The lnT dependence of ρ is observed at H=50kOe at low temperatures, which is due to a two-dimensional weak-localization effect. Below Tcu , a two-dimensional superconducting phase occurs in each TaC layer. The linear and nonlinear <span class="hlt">susceptibilities</span> χ1″ , χ3' , χ5' , and χ7' as well as the difference δχ (=χFC-χZFC) between the field-cooled (FC) and zero-field-cooled (ZFC) <span class="hlt">susceptibilities</span> start to appear below 6.0K , the onset temperature of irreversibility. A drastic growth of the in-plane superconducting coherence length below 6.0K gives rise to a three-dimensional superconducting phase below Tcl through interplanar Josephson couplings between adjacent TaC layers. The oscillatory behavior of χ3″ , χ5″ , and χ7″ below Tcl is related to the nonlinear behavior arising from the thermally activated flux flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25992509','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25992509"><span>Measurement of <span class="hlt">susceptibility</span> artifacts with histogram-based reference value on <span class="hlt">magnetic</span> resonance images according to standard ASTM F2119.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heinrich, Andreas; Teichgräber, Ulf K; Güttler, Felix V</p> <p>2015-12-01</p> <p>The standard ASTM F2119 describes a test method for measuring the size of a <span class="hlt">susceptibility</span> artifact based on the example of a passive implant. A pixel in an image is considered to be a part of an image artifact if the intensity is changed by at least 30% in the presence of a test object, compared to a reference image in which the test object is absent (reference value). The aim of this paper is to simplify and accelerate the test method using a histogram-based reference value. Four test objects were scanned parallel and perpendicular to the main <span class="hlt">magnetic</span> field, and the largest <span class="hlt">susceptibility</span> artifacts were measured using two methods of reference value determination (reference image-based and histogram-based reference value). The results between both methods were compared using the Mann-Whitney U-test. The difference between both reference values was 42.35 ± 23.66. The difference of artifact size was 0.64 ± 0.69 mm. The artifact sizes of both methods did not show significant differences; the p-value of the Mann-Whitney U-test was between 0.710 and 0.521. A standard-conform method for a rapid, objective, and reproducible evaluation of <span class="hlt">susceptibility</span> artifacts could be implemented. The result of the histogram-based method does not significantly differ from the ASTM-conform method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGP23A1038T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGP23A1038T"><span>Preliminary Anisotropy of <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> and Paleomagnetic Data from Mafic Dikes in the Chili Quadrangle, Rio Arriba County, New Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trujillo, R. V.; Petronis, M. S.; Lineline, J.</p> <p>2011-12-01</p> <p>Migration of magma at shallow levels of the crust is a fundamental process that has bearing on the construction of volcanoes, associated hazards in active volcanic terranes, and igneous mass redistribution in near surface environments. This study examines a suite of Miocene mafic dikes in the Española Basin, north-central NM. The problems addressed by this research involves: 1) collect paleomagnetic data from the dikes to discern components of vertical-axis rotation across structural blocks, between separate dikes, and along strike within individual dikes, and 2) obtain anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) data, thin section, and field observations, to infer magma flow within each dike and document any variation in magma flow patterns within the swarm. We plan to test the following hypotheses: 1) the mafic dikes experienced some degree of vertical axis rotation associated with rifting and/or intrusion of younger dikes 2) the magma flow pattern within the dikes reflects lateral emplacement with flow directed away from the magma ascent location. Low-field <span class="hlt">susceptibility</span> versus temperature experiments yield a spectrum of results reflecting thermomagnetic behavior typical of intermediate composition titanomagnetite while others exhibit a more complex behavior with the presence of two or more <span class="hlt">magnetic</span> phases. Curie point estimates range from ~ 100°C to 575°C indicating a range of moderate to low Ti- titanomagnetite compositions as well as some evidence of a Fe-sulfide phase, possibly pyrrhotite. AMS fabric data reveal a combination of both prolate and oblate <span class="hlt">susceptibility</span> ellipsoids. At several sites, the fabrics are oblate from the paired dike margins and reveal a unique magma flow direction. <span class="hlt">Susceptibility</span> values are high and consistent with a ferromagnetic phase providing encouraging evidence that the remanence is likely a primary thermoremanent <span class="hlt">magnetization</span> and geologically stable. Paleomagnetic analysis is underway and should help further constrain the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5230783','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5230783"><span>Simultaneous Quantitative MRI Mapping of T1, T2* and <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> with Multi-Echo MP2RAGE</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kober, Tobias; Möller, Harald E.; Schäfer, Andreas</p> <p>2017-01-01</p> <p>The knowledge of relaxation times is essential for understanding the biophysical mechanisms underlying contrast in <span class="hlt">magnetic</span> resonance imaging. Quantitative experiments, while offering major advantages in terms of reproducibility, may benefit from simultaneous acquisitions. In this work, we demonstrate the possibility of simultaneously recording relaxation-time and <span class="hlt">susceptibility</span> maps with a prototype Multi-Echo (ME) <span class="hlt">Magnetization</span>-Prepared 2 RApid Gradient Echoes (MP2RAGE) sequence. T1 maps can be obtained using the MP2RAGE sequence, which is relatively insensitive to inhomogeneities of the radio-frequency transmit field, B1+. As an extension, multiple gradient echoes can be acquired in each of the MP2RAGE readout blocks, which permits the calculation of T2* and <span class="hlt">susceptibility</span> maps. We used computer simulations to explore the effects of the parameters on the precision and accuracy of the mapping. In vivo parameter maps up to 0.6 mm nominal resolution were acquired at 7 T in 19 healthy volunteers. Voxel-by-voxel correlations and the test-retest reproducibility were used to assess the reliability of the results. When using optimized paramenters, T1 maps obtained with ME-MP2RAGE and standard MP2RAGE showed excellent agreement for the whole range of values found in brain tissues. Simultaneously obtained T2* and <span class="hlt">susceptibility</span> maps were of comparable quality as Fast Low-Angle SHot (FLASH) results. The acquisition times were more favorable for the ME-MP2RAGE (≈ 19 min) sequence as opposed to the sum of MP2RAGE (≈ 12 min) and FLASH (≈ 10 min) acquisitions. Without relevant sacrifice in accuracy, precision or flexibility, the multi-echo version may yield advantages in terms of reduced acquisition time and intrinsic co-registration, provided that an appropriate optimization of the acquisition parameters is performed. PMID:28081157</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28263417','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28263417"><span>Methods for the computation of templates from quantitative <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> maps (QSM): Toward improved atlas- and voxel-based analyses (VBA).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hanspach, Jannis; Dwyer, Michael G; Bergsland, Niels P; Feng, Xiang; Hagemeier, Jesper; Bertolino, Nicola; Polak, Paul; Reichenbach, Jürgen R; Zivadinov, Robert; Schweser, Ferdinand</p> <p>2017-03-06</p> <p>To develop and assess a method for the creation of templates for voxel-based analysis (VBA) and atlas-based approaches using quantitative <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> mapping (QSM). We studied four strategies for the creation of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> brain templates, derived as successive extensions of the conventional template generation (CONV) based on only T1 -weighted (T1 w) images. One method that used only T1 w images involved a minor improvement of CONV (U-CONV). One method used only <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> maps as input for template generation (DIRECT), and the other two used a linear combination of <span class="hlt">susceptibility</span> and T1 w images (HYBRID) and an algorithm that directly used both image modalities (MULTI), respectively. The strategies were evaluated in a group of N = 10 healthy human subjects and semiquantitatively assessed by three experienced raters. Template quality was compared statistically via worth estimates (WEs) obtained with a log-linear Bradley-Terry model. The overall quality of the templates was better for strategies including both <span class="hlt">susceptibility</span> and T1 w contrast (MULTI: WE = 0.62; HYBRID: WE = 0.21), but the best method depended on the anatomical region of interest. While methods using only one modality resulted in lower WEs, lowest overall WEs were obtained when only T1 w images were used (DIRECT: WE = 0.12; U-CONV: WE = 0.05). Template generation strategies that employ only <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> contrast or both <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> and T1 w contrast produce templates with the highest quality. The optimal approach depends on the anatomical structures of interest. The established approach of using only T1 w images (CONV) results in reduced image quality compared to all other approaches studied. 2 J. Magn. Reson. Imaging 2017. © 2017 International Society for <span class="hlt">Magnetic</span> Resonance in Medicine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JHEP...11..092C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JHEP...11..092C"><span><span class="hlt">Generalised</span> structures for N=1 AdS backgrounds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coimbra, André; Strickland-Constable, Charles</p> <p>2016-11-01</p> <p>We expand upon a claim made in a recent paper [arXiv:1411.5721] that generic minimally supersymmetric AdS backgrounds of warped flux compactifications of Type II and M theory can be understood as satisfying a straightforward weak integrability condition in the language of {E}_{d(d)}× {R}+ <span class="hlt">generalised</span> geometry. Namely, they are spaces admitting a <span class="hlt">generalised</span> G-structure set by the Killing spinor and with constant singlet <span class="hlt">generalised</span> intrinsic torsion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......277B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......277B"><span>Determining the Efficacy of <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> as an Analytical Tool in the Middle Devonian Gas Bearing Shale of Taylor County, West Virginia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baird, John</p> <p></p> <p>The <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of two Middle Devonian shale units, the Mahantango Formation and Marcellus Shale, was recorded in order to determine if <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> could be used to predict (1) transgressive and regressive cycles, (2) brittleness, and (3) total organic content (TOC). A core from Taylor County, West Virginia was selected for this purpose. Transgressive and regressive cycles were detected through variations of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> values with maximum flooding surfaces indicated by troughs in the data and maximum regressive surfaces indicated by peaks. A sequence stratigraphic framework based upon variations in gamma ray and density measurements was used to establish a standard to gauge the accuracy of predictions made through <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>. It was found that the accuracy of the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> method was similar to the gamma-density method in detecting a large 2nd order cycle, when both shale units were evaluated together. When the units were evaluated separately, it was found that both methods detected the same 3rd order cycles. However, within the Mahantango Formation the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> method was more accurate recording 4th order cycles that the gamma-density method did not. Conversely, within the Marcellus Shale, the gamma-density method was more accurate recording 4th order cycles that the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> method did not. It was concluded that the increased accuracy of the gamma-density method in the Marcellus shale was due to an increased sensitivity in the gamma ray and density logs as a response to the large amounts of TOC in the formation This increased sensitivity allowed for smaller variations to be more easily detected. The Mahantango Formation does not have large quantities of TOC. This diminished the sensitivity of the gamma and density logs allowing for the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> method to be more accurate. It was assumed that variations in brittleness are driven by transgressive and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28075328','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28075328"><span><span class="hlt">Magnetization</span> at the interface of Cr2O3 and paramagnets with large stoner <span class="hlt">susceptibility</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cao, Shi; Street, M; Wang, Junlei; Wang, Jian; Zhang, Xiaozhe; Binek, Ch; Dowben, P A</p> <p>2017-03-15</p> <p>From the Cr 2p3/2 x-ray <span class="hlt">magnetic</span> circular dichroism signal, there is clear evidence of interface polarization with overlayers of both Pd and Pt on chromia (Cr2O3). The residual boundary polarization of chomia is stronger for a Pt overlayer than in the case of a Pd overlayer. The reduction of chromia boundary <span class="hlt">magnetization</span> with a paramagnetic metal overlayer, compared to the free surface, is interpreted as a response to the induced spin polarization in Pt and Pd. <span class="hlt">Magnetization</span> induced in a Pt overlayer, via proximity to the chromia boundary <span class="hlt">magnetization</span>, is evident in the polar magneto-optical Kerr measurements. These results are essential to explainations why Pt and Pd are excellent spacer layers for voltage controlled exchange bias, in the [Pd/Co] n /Pd/Cr2O3 and [Pt/Co] n /Pt/Cr2O3 perpendicular magneto-electric exchange bias systems. The findings pave the way to realize ultra-fast reversal of induced <span class="hlt">magnetization</span> in a free moment paramagnetic layer, with possible application in voltage-controlled <span class="hlt">magnetic</span> random access memory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JPCM...29jLT01C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JPCM...29jLT01C"><span><span class="hlt">Magnetization</span> at the interface of Cr2O3 and paramagnets with large stoner <span class="hlt">susceptibility</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cao, Shi; Street, M.; Wang, Junlei; Wang, Jian; Zhang, Xiaozhe; Binek, Ch; Dowben, P. A.</p> <p>2017-03-01</p> <p>From the Cr 2p3/2 x-ray <span class="hlt">magnetic</span> circular dichroism signal, there is clear evidence of interface polarization with overlayers of both Pd and Pt on chromia (Cr2O3). The residual boundary polarization of chomia is stronger for a Pt overlayer than in the case of a Pd overlayer. The reduction of chromia boundary <span class="hlt">magnetization</span> with a paramagnetic metal overlayer, compared to the free surface, is interpreted as a response to the induced spin polarization in Pt and Pd. <span class="hlt">Magnetization</span> induced in a Pt overlayer, via proximity to the chromia boundary <span class="hlt">magnetization</span>, is evident in the polar magneto-optical Kerr measurements. These results are essential to explainations why Pt and Pd are excellent spacer layers for voltage controlled exchange bias, in the [Pd/Co] n /Pd/Cr2O3 and [Pt/Co] n /Pt/Cr2O3 perpendicular magneto-electric exchange bias systems. The findings pave the way to realize ultra-fast reversal of induced <span class="hlt">magnetization</span> in a free moment paramagnetic layer, with possible application in voltage-controlled <span class="hlt">magnetic</span> random access memory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhRvB..69i4436P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhRvB..69i4436P"><span><span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> and spin dynamics of a polyoxovanadate cluster: A proton NMR study of a model spin tetramer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Procissi, D.; Shastri, A.; Rousochatzakis, I.; Al Rifai, M.; Kögerler, P.; Luban, M.; Suh, B. J.; Borsa, F.</p> <p>2004-03-01</p> <p>We report <span class="hlt">susceptibility</span> and nuclear <span class="hlt">magnetic</span> resonance (NMR) measurements in a polyoxovanadate compound with formula (NHEt)3[VIV8VV4As8O40(H2O)]ṡH2O≡{V12}. The <span class="hlt">magnetic</span> properties can be described by considering only the central square of localized V4+ ions and treated by an isotropic Heisenberg Hamiltonian of four intrinsic spins 1/2 coupled by nearest-neighbor antiferromagnetic interaction with J˜17.6 K. In this simplified description the ground state is nonmagnetic with ST=0. The 1H NMR linewidth (full width at half maximum) data depend on both the <span class="hlt">magnetic</span> field and temperature, and are explained by the dipolar interaction between proton nuclei and V4+ ion spins. The behavior of the nuclear spin-lattice relaxation rate T-11 in the temperature range (4.2 300 K) is similar to that of χT vs T and it does not show any peak at low temperatures contrary to previous observations in antiferromagnetic rings with larger intrinsic spins. The results are explained by using the general features of the Moriya formula and by introducing a single T-independent broadening parameter for the electronic spin system. From the exponential T dependence of T-11 at low T (2.5 K<T<4.2 K) we have obtained a field dependent gap following the linear relation ΔNMR=Δ0-gμBH, with the gap Δ0˜17.6 K in agreement with the <span class="hlt">susceptibility</span> data. Below 2.5 K the proton T-11 deviates from the exponential decrease indicating the presence of a small, almost temperature independent, but strongly field dependent, nuclear relaxation contribution, which we will investigate in detail in the near future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28324122','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28324122"><span>MR imaging differentiation of Fe(2+) and Fe(3+) based on relaxation and <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> properties.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dietrich, Olaf; Levin, Johannes; Ahmadi, Seyed-Ahmad; Plate, Annika; Reiser, Maximilian F; Bötzel, Kai; Giese, Armin; Ertl-Wagner, Birgit</p> <p>2017-04-01</p> <p>The aim of this study is to evaluate the MR imaging behavior of ferrous (Fe(2+)) and ferric (Fe(3+)) iron ions in order to develop a noninvasive technique to quantitatively differentiate between both forms of iron. MRI was performed at 3 T in a phantom consisting of 21 samples with different concentrations of ferrous and ferric chloride solutions (between 0 and 10 mmol/L). A multi-echo spoiled gradient-echo pulse sequence with eight echoes was used for both T 2* and quantitative <span class="hlt">susceptibility</span> measurements. The transverse relaxation rate, R 2* = 1/T 2*, was determined by nonlinear exponential fitting based on the mean signals in each sample. The <span class="hlt">susceptibilities</span>, χ, of the samples were calculated after phase unwrapping and background field removal by fitting the spatial convolution of a unit dipole response to the measured internal field map. Relaxation rate changes, ΔR 2*(c Fe), and <span class="hlt">susceptibility</span> changes, Δχ(c Fe), their linear slopes, as well as the ratios ΔR 2*(c Fe) / Δχ(c Fe) were determined for all concentrations. The linear slopes of the relaxation rate were (12.5 ± 0.4) s(-1)/(mmol/L) for Fe(3+) and (0.77 ± 0.09) s(-1)/(mmol/L) for Fe(2+) (significantly different, z test P < 0.0001). The linear slopes of the <span class="hlt">susceptibility</span> were (0.088 ± 0.003) ppm/(mmol/L) for Fe(3+) and (0.079 ± 0.006) ppm/(mmol/L) for Fe(2+). The individual ratios ΔR 2*/Δχ were greater than 40 s(-1)/ppm for all samples with ferric solution and lower than 20 s(-1)/ppm for all but one of the samples with ferrous solution. Ferrous and ferric iron ions show significantly different relaxation behaviors in MRI but similar <span class="hlt">susceptibility</span> patterns. These properties can be used to differentiate ferrous and ferric samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5700433','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5700433"><span>Synthesis and <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of M /SUB x/ V/sub 2/O/sub 3//sup +/y solid solutions (M = Ca, Sr, Ba)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Volkov, V.L.; Milova, G.D.; Perelyaev, V.A.</p> <p>1985-12-01</p> <p>The authors synthesize and study the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of solid solutions of alkaline-earth metal oxides in V/sub 2/O/sub 3/. As the initial substances ultrapure V/sub 2/O/sub 5/, CaCo/sub 3/, BaCO/sub 3/, and SrCO/sub 3/ and chemically pure metavanadates and orthovanadates of alkaline-earth metals were used. The x-ray analysis was carried out on a DRON-2.5 diffractometer with ionization detection of Cu Ka radiation. The <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> was measured by the Faraday method. The authors establish the existence of solid solutions of composition MxV/sub 2/O/sub 3//sup +/y, determine their crystallographic parameters, and study the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>. The transition temperature of the specimens decreases as the radius of the M/sup 2 +/ ions and the unit-cell parameter c of the crystal decrease.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNS52A..05K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNS52A..05K"><span>A Laboratory Study to Determine the Effect of Field Strength and <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> on the NMR Estimated Water Content in Unconsolidated Sediments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keating, K.; Grunewald, E. D.; Walsh, D. O.</p> <p>2015-12-01</p> <p>Geophysical nuclear <span class="hlt">magnetic</span> resonance (NMR) well logging data can provide direct information about subsurface water content. While NMR water content estimates are known to be accurate in low <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> materials, it has often been assumed that NMR measurements cannot be used in high <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> materials due to internal <span class="hlt">magnetic</span> field inhomogeneities that arise due to <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> contrasts in the material. In this study we compare the NMR estimated water content using laboratory measurements made at two low <span class="hlt">magnetic</span> field strengths (with Larmor frequencies of 275 kHz and 2 MHz) on both synthetic and natural unconsolidated sediments with a range of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> values. NMR measurements were collected on seven water-saturated materials with <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> values spanning three orders of magnitude (3.6x10-6 SI to 7.0 x10-3 SI). T2 relaxation time data was collected with echo times, tE, ranging from 200 to 3000 μs. The results show that for the materials with low <span class="hlt">magnetic</span> <span class="hlt">susceptibilities</span> (< 5x10-4 SI), the total water content was accurately estimated at both field strengths. For the materials with high <span class="hlt">magnetic</span> <span class="hlt">susceptibilities</span> (> 5x10-4 SI) the water content was more accurately estimated using the data collected at 275 kHz (> 80% detected at tE = 400 μs) than the data collected at 2 MHz (< 40% detected at tE = 400 μs). Furthermore, the 275 kHz data showed water content underestimation errors increased only slightly with increased tE, compared to substantial increases in errors for the 2 MHz data as tE was increased. This finding suggests that there is an advantage for collecting measurements at lower field strengths even for long tE. We explain the differences in the water content estimates at the two field strengths by considering the shape of the echoes and the coil and pulse bandwidths, and find excellent agreement with the range of collected NMR data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014RuMaS..69..957B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014RuMaS..69..957B"><span>Turbulence for the <span class="hlt">generalised</span> Burgers equation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boritchev, A. A.</p> <p>2014-12-01</p> <p>This survey reviews rigorous results obtained by A. Biryuk and the author on turbulence for the <span class="hlt">generalised</span> space-periodic Burgers equation \\displaystyle u_t+f'(u)u_x=ν uxx+η,\\qquad x \\in S^1={R}/{Z}, where f is smooth and strongly convex, and the constant 0<ν\\ll 1 corresponds to the viscosity coefficient. Both the unforced case ( η=0) and the case when η is a random force which is smooth with respect to x and irregular (kick or white noise) with respect to t are considered. In both cases sharp bounds of the form Cν-δ, δ≥slant 0, are obtained for the Sobolev norms of u averaged over time and over the ensemble, with the same value of δ for upper and lower bounds. These results yield sharp bounds for small-scale quantities characterising turbulence, confirming the physical predictions. Bibliography: 56 titles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMMM..385...65A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMMM..385...65A"><span>AC-<span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of Dy doped ZnO compounds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akyol, Mustafa; Ekicibil, Ahmet; Kiymaç, Kerim</p> <p>2015-07-01</p> <p>Dy doped ZnO polycrystalline diluted <span class="hlt">magnetic</span> semiconductor compounds have been prepared by the so called solid state reaction method. We have studied the M-H and AC <span class="hlt">magnetic</span> properties of the compounds by using a PPMS magnetometer, and explored the phases and crystal structure by using a X-ray powder diffractometer. The XRD spectra of the compounds show that the substitution of Dy3+ for Zn2+ causes almost no change in the hexagonal wurtzite structure of ZnO, and the Dy3+ ions are successfully substituted into the Zn2+ site of the ZnO matrix. The <span class="hlt">magnetic</span> measurements, M-H and χ-T, for T in the range from 10 to 300 K, show a paramagnetic behavior, including indirect antiferromagnetic couplings between some Dy3+ <span class="hlt">magnetic</span> moments. Since the Curie-Weiss temperatures, θ, are all negative but decrease in magnitude with increasing Dy concentration. On the other hand, the calculated effective <span class="hlt">magnetic</span> moments, μeff, per Dy3+ ion slowly increase with increasing Dy concentration, but are all very close to the free ion value of μeff, ~11.0 μB. Therefore, the trends of the magnitudes of θs and μeff s indicate that the samples are not only paramagnetic but also have antiferromagnetic couplings due to the complex nature of the compounds. In addition, the thermal variation of average <span class="hlt">magnetic</span> moment, Peff(T), per Dy3+ ion have been calculated, and have been found to be gradually increasing with increasing temperature and Dy concentration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6264G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6264G"><span>The relation between anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) and mineral filling of foraminifers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guzhikova, Anastasia; Grishchenko, Vladimir; Surinsky, Arseny; Tselmovich, Vladimir</p> <p>2017-04-01</p> <p>The comparison of bio- and magnetostratigraphic data in four sections of Jurassic-Cretaceous sediments of Mountain Crimea and Saratov region (Russia) detected the presence of correlation between the AMS parameter T and the amount of foraminifers in rock sample: disk-shaped <span class="hlt">magnetic</span> particles dominance is connected with high quantity of foraminifers and therefore, cigar-shaped particles signify low foraminifer content. Parameter T (shape parameter) representing the <span class="hlt">magnetic</span> particle form: T values close to 1 indicate the plain (disc-shaped) form of <span class="hlt">magnetic</span> particles, T values close to (-1) highlight the prolate (cigar-shaped) form. To understand the nature of this interrelation a few disc-shaped foraminifers were studied using microprobe analysis. The results of this study have shown that inner spaces of foraminifers are completely filled by pyrite, which grains are covered with thin magnetite tape (the thickness of the tape is less than 200 nanometers). We suppose that this magnetite tape provides the main influence to anisotropy's character. In the Maastrichtian of Mountain Crimea the relation between AMS and amount of foraminifers appears to be more significant after the heating of samples in the muffle furnace till 500°C during 1 hour. Primary <span class="hlt">magnetic</span> texture was nearly chaotic, but after the heating it acquired the view peculiar to rocks containing plain ferromagnetic particles, formed in calm hydrodynamic environment. This event may be explained by transition (at the temperature of 450°C) of non-<span class="hlt">magnetic</span> pyrite, fulfilling the inner structure of foraminifers, to the high-<span class="hlt">magnetic</span> magnetite. The relations between petromagnetic parameters and special aspects of micropaleontological complexes involve studies that are more special because they gain much interest and perspectives in the area of sedimentological and paleoecological reconstructions. The finance part of the study was supported by RFBR: Russian Foundation for Basic Research (projects №№ 16</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2646180','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2646180"><span>Identification of Calcification with <span class="hlt">Magnetic</span> Resonance Imaging Using <span class="hlt">Susceptibility</span>-Weighted Imaging: A Case Study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wu, Zhen; Mittal, Sandeep; Kish, Karl; Yu, Yingjian; Hu, J.; Haacke, E. Mark</p> <p>2008-01-01</p> <p><span class="hlt">Susceptibility</span> weighted imaging (SWI) is a new MRI technique that can identify calcification by using phase images. We present a single case with a partially calcified oligodendroglioma, multiple calcified cysticercosis lesions, and multiple physiologic calcifications in the same patient. SWI phase images and computed tomography (CT) images are compared. SWI phase images showed the same calcified lesions as shown on CT and sometimes some new calcifications. Our conclusion is that SWI filtered phase images can identify calcifications as well as CT in this case. PMID:19097156</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/942979','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/942979"><span>Long-range <span class="hlt">magnetic</span> order in Mn[N(CN)2]2(pyz) {pyz = pyrazine}. <span class="hlt">susceptibility</span>, <span class="hlt">magnetization</span>, specific heat and neutron diffraction measurements and electronic structure calculations.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Manson, J. L.; Huang, Q.-Z.; Lynn, J. W.; Koo, H.-J.; Whangbo, M.-H.; Bateman, R.; Wada, N.; Awaga, K.; Argyriou, D. N.; Miller, J. S.; Univ. of Maryland; National Inst. of Standards & Technology; North Carolina State Univ.; Oxford Research Instruments; Univ. of Tokyo; Univ. of Utah</p> <p>2001-01-10</p> <p>Using dc <span class="hlt">magnetization</span>, ac <span class="hlt">susceptibility</span>, specific heat, and neutron diffraction, we have studied the <span class="hlt">magnetic</span> properties of Mn[N(CN){sub 2}]{sub 2}(pyz) (pyz = pyrazine) in detail. The material crystallizes in the monoclinic space group P2{sub 1}/n with a = 7.3248(2), b = 16.7369(4), and c = 8.7905(2) {angstrom}, {beta} = 89.596(2){sup o}, V = 1077.65(7) {angstrom}{sup 3}, and Z = 4, as determined by Rietveld refinement of neutron powder diffraction data at 1.35 K. The 5 K neutron powder diffraction data reflect very little variation in the crystal structure. Interpenetrating ReO{sub 3}-like networks are formed from axially elongated Mn{sup 2+} octahedra and edges made up of {mu}-bonded [N(CN){sub 2}]{sup -} anions and neutral pyz ligands. A three-dimensional antiferromagnetic ordering occurs below T{sub N} = 2.53(2) k. The <span class="hlt">magnetic</span> unit cell is double the nuclear one along the a- and c-axes, giving the (1/2, 0, 1/2) superstructure. The crystallographic and antiferromagnetic structures are commensurate and consist of collinear Mn{sup 2+} moments, each with a magnitude of 4.15(6) {mu}{sub B} aligned parallel to the a-direction (Mn-pyz-Mn chains). Electronic structure calculations indicate that the exchange interaction is much stronger along the Mn-pyz-Mn chain axis than along the Mn-NCNCN-Mn axes by a factor of approximately 40, giving rise to a predominantly one-dimensional <span class="hlt">magnetic</span> system. Thus, the variable-temperature <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> data are well described by a Heisenberg antiferromagnetic chain model, giving g = 2.01(1) and J/k{sub B} = -0.27(1) K. Owing to single-ion anisotropy of the Mn{sup 2+} ion, field-induced phenomena ascribed to spin-flop and paramagnetic transitions are observed at 0.43 and 2.83 T, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Scientific+AND+claims+AND+issue&id=EJ1054046','ERIC'); return false;" href="http://eric.ed.gov/?q=Scientific+AND+claims+AND+issue&id=EJ1054046"><span>Supporting Teachers to Attend to <span class="hlt">Generalisation</span> in Science Classroom Argumentation</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Shemwell, Jonathan T.; Gwarjanski, Kalee R.; Capps, Daniel K.; Avargil, Shirly; Meyer, Joanna L.</p> <p>2015-01-01</p> <p>In scientific arguments, claims must have meaning that extends beyond the immediate circumstances of an investigation. That is, claims must be <span class="hlt">generalised</span> in some way. Therefore, teachers facilitating classroom argumentation must be prepared to support students' efforts to construct or criticise <span class="hlt">generalised</span> claims. However, widely used…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11114062','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11114062"><span><span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> shift selected imaging (MESSI) and localized (1)H(2)O spectroscopy in living plant tissues.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhong, K; Li, X; Shachar-Hill, Y; Picart, F; Wishnia, A; Springer, C S</p> <p>2000-11-01</p> <p>Maize root segments permeated with aqueous solutions of the paramagnetic agents GdDTPA(2-) or DyDTPA-BMA display two well-resolved NMR peaks corresponding to the signals from intracellular and extracellular (1)H(2)O, which arise from well-understood bulk <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> effects. This allows each component to be studied separately. Images obtained at each frequency with MESSI editing, and single- and multiple-voxel ('spectroscopic imaging') localized spectra, clearly indicate that the agents permeate into the interstitial spaces, and into the longitudinal (xylem/phloem) channels in the stele (core) of the root, confirming earlier assessments. We believe these are the first images of a multicellular tissue acquired in vivo exclusively from the intracellular water proton resonance. This method can be further exploited to study water transport in similar systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005NIMPB.239..281L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005NIMPB.239..281L"><span>The effects of 137Cs and 60Co γ radiation on the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of BSCCO textured thin rods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leyva, A.; Cruz, C. M.; Mora, M.; Shtejer, K.; Diez, J. C.; Angurel, L. A.; Piñera, I.; Abreu, Y.</p> <p>2005-09-01</p> <p>Bi 2Sr 2CaCu 2O x superconducting thin rods textured by the laser floating zone melting method were irradiated with 1250 and 662 keV γ rays. The behavior of some of its superconducting properties with the exposure dose was studied by the measurement of dynamic <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span>. It was observed that, for different dose levels according to the energy of the incident radiation, the rods preserve their superconducting intragrain properties, evidencing the high resistance of the material to the γ radiation damage. In all the cases it was verified that, with increasing exposure dose, the onset temperature of the superconducting transition increases. The possible mechanisms that should take place are analyzed in the text. The χac measurements also show the increasing behavior of the superconducting volume fraction in the sample with the exposure dose.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005E%26PSL.238..110V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005E%26PSL.238..110V"><span>The use of field dependence of AC <span class="hlt">susceptibility</span> for the interpretation of <span class="hlt">magnetic</span> mineralogy and <span class="hlt">magnetic</span> fabrics in the HSDP-2 basalts, Hawaii [rapid communication</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vahle, Carsten; Kontny, Agnes</p> <p>2005-09-01</p> <p> anisotropy exhibit differences of the field dependence parameter if measured parallel to kmax or kmin axis. Therefore, in addition to compositional effects and the temperature dependence, the <span class="hlt">magnetic</span> fabric has to be considered for the interpretation of field dependent <span class="hlt">susceptibility</span> measurements. The influence of intrinsic (Ti-content, magnetocrystalline anisotropy), and extrinsic (shape and alignment of grains) factors for the interpretation of the degree of anisotropy has to be kept in mind when interpreting AMS data in terms of strain rates experienced by moving lava during emplacement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990040275','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990040275"><span>Exploiting the Temperature/Concentration Dependence of <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> to Control Convection in Fundamental Studies of Solidification Phenomena</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Evans, J. W.; Xu, Dong; Jones, W. Kinzy, Jr.; Szofran, Frank R.</p> <p>1999-01-01</p> <p>The objective of this new research project is to demonstrate by experiment, supplemented by mathematical modeling and physical property measurement, that the effects of buoyancy driven convection can be largely eliminated in ground-based experiments, and further reduced in flight, by applying a new technique. That technique exploits the dependence of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> on composition or temperature. It is emphasized at the outset that the phenomenon to be exploited is fundamentally and practically different from the <span class="hlt">magnetic</span> damping of convection in conducting liquids that has been the subject of much prior research. The concept suggesting this research is that all materials, even non-conductors, when placed in a <span class="hlt">magnetic</span> field gradient, experience a force. Of particular interest here are paramagnetic and diamagnetic materials, classes which embrace the "model alloys", such as succinonitrile-acetone, that have been used by others investigating the fundamentals of solidification. Such alloys will exhibit a dependence of <span class="hlt">susceptibility</span> on composition. The consequence is that, with a properly oriented field (gradient) a force will arise that can be made to be equal to, but opposite, the buoyancy force arising from concentration (or temperature) gradients. In this way convection can be stilled. The role of convection in determining the microstructure, and thereby properties, of materials is well known. Elimination of that convection has both scientific and technological consequences. Our knowledge of diffusive phenomena in solidification, phenomena normally hidden by the dominance of convection, is enhanced if we can study solidification of quiescent liquids. Furthermore, the microstructure, microchemistry and properties of materials (thereby practical value) are affected by the convection occurring during their solidification. Hitherto the method of choice for elimination of convection has been experimentation in microgravity. However, even in low Earth orbit</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP31A1096H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP31A1096H"><span>Implications of Late Pliocene-Pleistocene Humidity Fluctuations in the Qaidam Paleolake (NE Tibetan Plateau) Deduced from <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> Measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herb, C.; Appel, E.; Koutsodendris, A.; Zhang, W.; Pross, J.; Fang, X.</p> <p>2014-12-01</p> <p>The Qaidam Basin (NE Tibetan Plateau) contains a near-continuous, up to 12 km thick sequence of Cenozoic strata that offers a unique opportunity for studying long-term climate change. We investigate the 940-m-long drill core SG-1 from the western Qaidam Basin, which is characterized by a long-term transition from a semi-deep freshwater lake to nearly complete exsiccation of the water body, detected by several studies including geochemical and lithological observations. Based on magnetostratigraphy and optically stimulated luminescence dating, and refined by orbital tuning, the SG-1 core spans the interval from 2.69 to 0.1 Ma. Moisture availability in the western Qaidam Basin deduced from the pollen ratio Artemisia/Chenopodiaceae (A/C), suggests desert to steppe vegetation along core SG-1 as a long-term feature. <span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> (χ) is well suited for the high-resolution investigation of paleohumidity. The meaning of χ as a paleohydrology proxy is shown by comparing χ to other <span class="hlt">magnetic</span> proxies for checking its relation to <span class="hlt">magnetic</span> grain sizes and <span class="hlt">magnetic</span> mineralogy as well as to pollen results. χ variations are analyzed to obtain regional information on the factors leading to the drying process of the Qaidam paleolake as well as potential driving factors for humidity fluctuations (e.g., insolation). An important topic that needs further investigation is the influence of monsoon in the Qaidam Basin. While the southern part of the Tibetan Plateau is directly affected by monsoon precipitation through the topographic barrier, its influence in the past is questionable in the hyper-arid Qaidam Basin. We check a potential coupling to the monsoon system in the western Qaidam Basin by comparing our χ record to reconstructions of the Asian monsoon system from other archives as well as searching evidence from orbital cyclicities found in the χ time series.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23266939','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23266939"><span><span class="hlt">Magnetic</span> <span class="hlt">susceptibility</span> measurements to detect coal fly ash from the Kingston Tennessee spill in Watts Bar Reservoir.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cowan, Ellen A; Seramur, Keith C; Hageman, Steven J</p> <p>2013-03-01</p> <p>An estimated 229,000 m(3) of coal fly ash remains in the river system after dredging to clean-up the 2008 Tennessee Valley Authority (TVA) spill in Kingston, Tennessee. The ash is heterogeneous with clear, orange and black spheres and non-spherical amorphous particles. Combustion produces iron oxides that allow low field <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (χ(LF)) and percent frequency dependent <span class="hlt">susceptibility</span> (χ(FD)%) to be used to discriminate between coal fly ash and sediments native to the watershed. Riverbed samples with χ(LF) greater than 3.0 × 10(-6) m(3)/kg, have greater than 15% ash measured by optical point counting. χ(LF) is positively correlated with total ash, allowing ash detection in riverbed sediments and at depth in cores. The ratio of ash sphere composition is altered by river transport introducing variability in χ(LF). Measurement of χ(LF) is inexpensive, non-destructive, and a reliable analytical tool for monitoring the fate of coal ash in this fluvial environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JPCM...11.4381S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JPCM...11.4381S"><span>The effect of pressure on the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of RInCu4 (R = Gd, Er and Yb)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Svechkarev, I. V.; Panfilov, A. S.; Dolja, S. N.; Nakamura, H.; Shiga, M.</p> <p>1999-06-01</p> <p>The <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of the intermetallic compounds RInCu4 (R = Gd, Er and Yb) was measured under helium gas pressure up to 2 kbar at the fixed temperatures 78, 150 and 300 K. For YbInCu4, which exhibits a first-order valence phase transition at TVicons/Journals/Common/simeq" ALT="simeq" ALIGN="TOP"/>40 K, the Grüneisen parameter for the Kondo energy, icons/Journals/Common/Omega" ALT="Omega" ALIGN="TOP"/>Kicons/Journals/Common/equiv" ALT="equiv" ALIGN="TOP"/>-dlnTK/dlnV = -32, is large and typical for Ce-based heavy-fermion systems in magnitude but opposite in sign. The effect of atomic disorder is discussed on the basis of the data for a chemically disordered sample; the pressure effect at T = 78 K is strongly enhanced due to the spatial dispersion of pressure-sensitive TV, and hence dTV/dP = -2.0 K kbar-1 is obtained by assuming a Gaussian distribution of TV. On the basis of an extrapolation of the experimental pressure dependence, a (P,T) phase diagram is proposed for YbInCu4. Reference compounds with stable f moments, GdInCu4 and ErInCu4, show negligible pressure dependences of the <span class="hlt">susceptibility</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EP%26S...61..173C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EP%26S...61..173C"><span>Anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> analysis of the Cantera Ignimbrite, San Luis Potosi, México: flow source recognition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caballero-Miranda, C. I.; Torres-Hernández, J. R.; Alva-Valdivia, L. M.</p> <p>2009-01-01</p> <p>Anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) was selected as the key technique to find the source of the widespread Cantera Ignimbrite and to seek its possible relationship with the San Luis Potosí Caldera. Eighteen sites (372 specimens from 155 cores) from the Oligocene Cantera Ignimbrite were sampled. AMS was measured on a KLY2 Kappabridge. AMS data were processed with Anisoft 3 software using Jelinek statistics as well as `SpheriStat' principal components and density distribution. Mean <span class="hlt">susceptibilities</span> range from 290 to 5026 × 10-6 SI (average = 2526 × 10-6 SI). The anisotropy degree ( P j) ranges from 1.005 to 1.055, with only one site displaying a value of 1.134 ( P j average = 1.031). AMS ellipsoid shapes are mostly oblate, with the T-factor ranging from 0.843 to 0.144 ( T average = 0.529), although one site is mainly prolate ( T = -0.005), and three additional sites have an important proportion of prolate specimens. <span class="hlt">Magnetic</span> fabrics of most sites shows k3 axes around nearly circular distributions and k 1- k 2 axes around elongated-girdle distributions defining sub-horizontal foliation planes; exceptions to this are related to sites with a significant percentage of prolate specimens. Flow directions inferred from AMS analysis indicate several ignimbrite sources located along selected NW-SE linear features (faults and fractures such as El Potosino Fault) as well as along the rim of the caldera structure. The geometry of volcanic outcrops, the NW-SE faulting-fracture system, as well as the AMS results suggest that this is a caldera structure resembling the trapdoor-type (Lipman, 1997).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28112941','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28112941"><span>Puzzling Lack of Temperature Dependence of the PuO2 <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> Explained According to Ab Initio Wave Function Calculations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gendron, Frédéric; Autschbach, Jochen</p> <p>2017-02-02</p> <p>The electronic structure and the <span class="hlt">magnetic</span> properties of solid PuO2 are investigated by wave function theory calculations, using a relativistic complete active space (CAS) approach including spin-orbit coupling. The experimental <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> is well reproduced by calculations for an embedded PuO8(12-) cluster model. The calculations indicate that the surprising lack of temperature dependence of the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> χ of solid PuO2 can be rationalized based on the properties of a single Pu(4+) ion in the cubic ligand field of the surrounding oxygen ions. Below ∼300 K, the only populated state is the nonmagnetic ground state, leading to standard temperature-independent paramagnetism (TIP). Above 300 K, there is an almost perfect cancellation of temperature-dependent contributions to χ that depends delicately on the mixing of ion levels in the electronic states, their relative energies, and the <span class="hlt">magnetic</span> coupling between them.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SSCom.153...60P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SSCom.153...60P"><span>Low temperature <span class="hlt">magnetic</span> ground state in bulk Co0.3Zn0.7Fe2O4 spinel ferrite system: Neutron diffraction, <span class="hlt">magnetization</span> and ac-<span class="hlt">susceptibility</span> studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parmar, Harshida; Acharya, Prashant; Upadhyay, R. V.; Siruguri, V.; Rayaprol, Sudhindra</p> <p>2013-01-01</p> <p>The system under study is a bulk Co0.3Zn0.7Fe2O4 ferrite, synthesized by wet chemical route technique and having <span class="hlt">magnetic</span> in-homogeneity at the microscopic scale, due to the concentration of <span class="hlt">magnetic</span> ion at a tetrahedral site below the site percolation threshold for the ferrimagnetic ordering. To unravel the <span class="hlt">magnetic</span> ground state of this system, low temperature neutron diffraction, <span class="hlt">magnetization</span> and ac-<span class="hlt">susceptibility</span> measurements were carried out. In the temperature-dependent neutron diffraction analysis, a diffused scattering signal appears at the low Q region below (1 1 1) <span class="hlt">magnetic</span> Bragg peak at all temperature, indicating the presence of a finite <span class="hlt">magnetic</span> cluster with infinite <span class="hlt">magnetic</span> network. The diffused scattering signal intensity decreases with increases in <span class="hlt">magnetic</span> field at T=10 K. The ac-<span class="hlt">susceptibility</span> measurement exhibits three peak behavior in χ' and χ″ indicating the presence of finite <span class="hlt">magnetic</span> clusters and cluster-cluster interaction in the system. The absence of <span class="hlt">magnetic</span> (2 0 0) peak in neutron diffraction at 2 K and bifurcation of zero field and field cooled <span class="hlt">magnetization</span> indicate the phase transition from uniaxial random ferromagnetic (URF) phase to semi spin glass or canted random ferromagnetic (CRF) phase in the system with temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1861c0039P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1861c0039P"><span>Pollution detected innovation of hazardous and toxic substance disposal by <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> method in Cikijing River, Rancaekek for testing water quality standards</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prananda, Yovan; Taufik, Febri; Alief, R.; Fikrianti, S.; M. Hardian, T.; Widodo</p> <p>2017-07-01</p> <p>Water pollution can defect surround the source of pollution. An example is Cikijing River, located in Rancaekek, Bandung which has expected contaminated by water disposal. Total loss approach by Total Economic Valuation is Rp 11.385.847.532.188 (± 11.4 trillion). One of the dangerous effect is the water quality in there. The aim of this research is to know and prove water disposal contaminated in that river. This research was conducted by mapping the <span class="hlt">magnetic</span> anomaly which obtained from the surrounding river. Afterward, modeling the research is conducted to get the <span class="hlt">susceptibility</span> value. In the previous research, the geological condition of our research field is Kosambi Formation (clay, sandstone, shale). The Kosambi Formation <span class="hlt">susceptibility</span> value estimated 0.017cgs unit there after it used to be background <span class="hlt">susceptibility</span>. As the result of modeling <span class="hlt">magnetic</span> anomaly from the anomaly map, the <span class="hlt">susceptibility</span> contrast shows negative value. The relation between <span class="hlt">magnetic</span> anomaly and <span class="hlt">susceptibility</span> indicated the hazardous and toxic substance pollution, which affected Cikijing River and around there.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JMagR.127...17S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JMagR.127...17S"><span>Using Bulk <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> to Resolve Internal and External Signals in the NMR Spectra of Plant Tissues</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shachar-Hill, Yair; Befroy, Douglas E.; Pfeffer, Philip E.; Ratcliffe, R. George</p> <p>1997-07-01</p> <p>Internal and external NMR signals from a variety of plant cells and plant tissues can be resolved by changing the bulk <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (BMS) of the perfusing medium with [Gd (EDTA)]-or Dy(DTPA-BMA). This separation is observed in samples consisting of cylindrical cells oriented along theB0field, and is consistent with established theoretical predictions about BMS effects. Evidence is presented that the shifted signals represent material outside the tissue as well as some contribution from intercellular spaces and cell walls, while intracellular signals are unshifted. The paramagnetic complexes used to separate the signals are shown to be nontoxic and to have no effect on a number of transport processes. The method has been applied to roots, shoots, and giant algal cells, facilitating the interpretation of thein vivospectra from a range of biologically important <span class="hlt">magnetic</span> isotopes. The potential of the method for studies of transport is illustrated with experiments showing: (i)14N/15N isotopic exchange of nitrate in roots; (ii) the influx of HDO into root and shoot segments; and (iii) the use of saturation transfer to follow water movement into and out of plant cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2008/1352/','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2008/1352/"><span>Mineralogic Causes of Variations in <span class="hlt">Magnetic</span> <span class="hlt">Susceptibility</span> of Late Pleistocene and Holocene Sediment from Great Salt Lake, Utah</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Reynolds, Richard L.; Rosenbaum, Joseph G.; Thompson, Robert S.</p> <p>2008-01-01</p> <p>We describe here results of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (MS) measurements and <span class="hlt">magnetic</span> mineralogy of sediments sampled in three cores from the south basin of Great Salt Lake. The cores were obtained in 1996 with a Kullenburg-type piston corer at sites in close proximity: core 96-4 at 41 deg 01.00' N, 112 deg 28.00' W and cores 96-5 and 96-6 at 41 deg 00.09' N, 112 deg 23.05' W. Cores 96-5 (2.16 m long) and -6 combine to make a composite 11.31-m sediment record. Sediments in core 96-4 (5.54 m long) correspond to the approximate depth interval of 3.9-9.6 m in the composite core of 96-5 and -6 based on similarities in the MS records as described below. The central goal of the research was to provide a sediment record of paleoenvironmental change in the northeastern Basin and Range Province over the past 40,000 years. Specific targets included a sedimentologic record of lake-level change combined with a pollen record of climatic change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995PEPI...87..183R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995PEPI...87..183R"><span>Anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> in the Ponta Grossa dyke swarm (Brazil) and its relationship with magma flow direction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Raposo, Maria Irene Bartolomeu; Ernesto, Marcia</p> <p>1995-01-01</p> <p>Measurements of anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> (AMS) in 95 mafic dykes (mainly tholeiites 10-200 m in width) from the Mesozoic Ponta Grossa swarm, Southern Brazil, revealed two main types of <span class="hlt">magnetic</span> fabric. Type I fabric (plane K1- K2 parallel to the dyke plane) represents magma flow within the dykes, whereas Type II (plane K1- K3 parallel to the dyke plane) is compatible with a fabric pattern reflecting vertical compaction of the magma column. Fabric Type I dominates (51% of the dykes) within the swarm, whereas Type II (38% of the dykes) concentrates mainly in the western region where the dykes intrude sediments. Considering the dykes with Type I fabrics, it is concluded that 58% of the dykes were fed by horizontal or sub-horizontal ( K1 inclinations less than 30°) magmatic flow, and 42% were fed by inclined to vertical ( K1 inclinations more than 30°) magma flow. The latter are more frequent in the southeastern part of the swarm, suggesting a magma source close to this area, although there may have been other sources in other regions where dykes with inclined flow and distinct chemical characteristics are also found.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JMagR.160...47D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JMagR.160...47D"><span>The elimination of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> artifacts in the micro-image of liquid-solid interfaces: internal gradient modulation by the CPMG RF train</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duh, Andrej; Mohorič, Aleš; Stepišnik, Janez; Serša, Igor</p> <p>2003-01-01</p> <p>Distortions of <span class="hlt">magnetic</span> resonance images near solid-liquid interface appear as the result of the restriction to spin self-diffusion in the proximity of impermeable boundary as well as of a <span class="hlt">susceptibility</span> difference. The spectral analysis of spin echo enables to resolve, in a simple way, how various RF-gradient pulse sequences reduce the effect of the internal <span class="hlt">magnetic</span> field induced by the <span class="hlt">susceptibility</span> difference at interfaces. The 1D diffusion-weighted imaging of water in the narrow notch tested efficiency of some sequence. The notch was milled in a piece of Plexiglas. The method can be used to distinguish the <span class="hlt">susceptibility</span> effect from the effects of applied gradients when investigating the transport of fluid through a porous structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JMMM...86...78K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JMMM...86...78K"><span>A study on the <span class="hlt">magnetic</span> <span class="hlt">susceptibilities</span> and optical absorption spectra on single crystals of Gd(III) pyrogermanate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kundu, T.; Ghosh, D.; Wanklyn, B. M.</p> <p>1990-04-01</p> <p>The paper reports for the first time the experimental results of the measurements of <span class="hlt">magnetic</span> <span class="hlt">susceptibilities</span> ( K⊥ and K|) and their anisotropy (Δ K) between 300 and 21.8 K and the optical absorption spectra (UV region) at 12.5 K on single crystals of gadolinium pyrogermanate (GdPG). The anisotropy, which is only 211×10 -6 emu/mol at room temperature and increases by two orders of magnitude at 21 K, is predominantly a crystal field (CF) effect on the 8S {7}/{2} ground term, through higher order perturbations. Interpretation of the observed <span class="hlt">magnetic</span> data was carried out by considering a conventional spin Hamiltonian ( Hs) to derive expressions for K⊥ and K| in terms of four effective crystal field parameters (ECFP). The value s of ECFP were varied to obtain a very close fitting between the theoretical and experimental values of K⊥, K|, δ K and K¯ The splitting of the 8S {7}/{2} term corresponding to these values of ECFP was found to be large, which suggests a strong CF effect in GdPG, as also observed in other RPG crystal studied earlier. The thermal characteristics of the <span class="hlt">magnetic</span> anisotropy below 30 K deviate by about 5% which could not be explained by CF effects alone. A series expansion method was adopted to analyse the results of K⊥ and K| below 30 K, however the corresponding coefficient B2α and B3α were observed t o be unusually high indicating the presence of CF effect even in this temperature region. The Schottky specific heat, Csch, between 300 and 21 K for GdPG has been calculated and this shows a maximum at Tmax=17 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhyS...73..519M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhyS...73..519M"><span>Persistent current and low-field <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> in one channel mesoscopic loops and Möbius strips</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maiti, Santanu K.</p> <p>2006-06-01</p> <p>I study persistent current and low-field <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of one-dimensional normal metal mesoscopic rings and Möbius strips threaded by slowly varying <span class="hlt">magnetic</span> flux phi. In strictly one-channel perfect rings, current shows saw-tooth-like variation with phi for the cases where the rings contain odd and even number of electrons Ne respectively. But in disordered rings, current shows a continuous variation with phi. In these systems current has only phi0 flux-quantum periodicity. Now in Möbius strips, the motion of the electrons in the transverse direction has an important factor on persistent current and also on low-field <span class="hlt">magnetic</span> response. If the electrons are unable to hop in the transverse direction then an electron encircles the system twice before returning to its initial position and current obtains phi0/2 flux-quantum periodicity unlike phi0 flux-quantum periodicity in strictly one-channel rings or multi-channel cylinders. The sign of the low-field currents in one-channel mesoscopic rings can be predicted exactly, even in the presence of impurity in these systems. For perfect rings current has only diamagnetic behaviour in the limit of zero field irrespective of the total number of electrons Ne. On the other hand, in dirty rings, current shows paramagnetic and diamagnetic signs respectively for the rings with even and odd Ne. In Möbius strips for zero hopping strength of the electrons in the transverse direction we get exactly the same behaviour as in strictly one-channel rings, but for nonzero transverse hopping strength the sign of the low-field currents cannot be predicted since it strongly depends on Ne and the specific realization of disorder configuration of the systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JAP...105gB518S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JAP...105gB518S"><span>ac <span class="hlt">susceptibility</span> studies of <span class="hlt">magnetic</span> relaxation in nanoparticles of Ni dispersed in silica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, V.; Seehra, M. S.; Bonevich, J.</p> <p>2009-04-01</p> <p>Temperature dependence of ac <span class="hlt">susceptibilities</span> χ' and χ″ are reported using frequencies fm=0.1, 1, 99, 499, and 997 Hz for nanoparticles of Ni dispersed in silica (Ni/SiO2:15/85) with the mean sizes D =3.8, 11.7, 15, and 21 nm (σ ≃0.2 nm), as determined by transmission electron microscopy. The blocking temperatures TB, as determined by peaks in χ″ versus T data, are fit to the Vogel-Fulcher law based on the following equation: TB=To+Ta/ln(fo/fm). Using the attempt frequency fo=1.82×1010 Hz, Ta (K)=310 (21), 954(17), 1334(14), and 1405(47) are determined for D =3.8, 11.7, 15, and 21 nm, respectively, along with To (representing the interparticle interaction)=0, 0, 6.6(0.7), and 12.5(2.5) K respectively. The magnitudes of Ta=KaV/k yield the anisotropy constant Ka increasing with decreasing D (or volume V) due to contributions from surface anisotropy. The validity of the theoretical result χ″=C∂(χ'T)/∂T with C ≃π/[2 ln(fo/2πfm)] is checked and the calculated values of fo are consistent with experimental value of fo=1.82×1010 Hz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21913790','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21913790"><span>Review of the theory of <span class="hlt">generalised</span> dielectrophoresis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lei, U; Lo, Y J</p> <p>2011-09-01</p> <p><span class="hlt">Generalised</span> dielectrophoresis (gDEP), including conventional dielectrophoresis (cDEP), electrorotation (ER) and travelling wave dielectrophoresis (twDEP), is an effective tool for particle (cell) manipulation and characterisation, even down to the level of nano-sized objects such as DNA, proteins and viruses. All the disciplines of gDEP are originated from the interaction of an applied electric field with its polarisation effect on the particle and can be studied systematically in a unified approach under electrostatics. In this review, the authors discuss both the quasi-static and transient theory of gDEP in an unbounded medium for both spherical and ellipsoidal particles. Then the quasi-static theory of wall effect is discussed on gDEP for a spherical particle. The wall effect is minor for ER, twDEP and cDEP parallel to wall(s), but could be significant for cDEP normal to wall(s). Force and torque expressions in terms of electric potential and its derivatives are provided and suggested for a robust calculation of the twDEP force and DEP torque. Discussions are provided for the application of the theory to nano-sized particles. The authors also illustrate some features of the Clausius-Mossotti factor using erythrocyte as an example, including both the crossover (DEP) and peak frequencies (ER) at low and high-frequency limits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NuPhB.897..781A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NuPhB.897..781A"><span>Threshold corrections, <span class="hlt">generalised</span> prepotentials and Eichler integrals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Angelantonj, Carlo; Florakis, Ioannis; Pioline, Boris</p> <p>2015-08-01</p> <p>We continue our study of one-loop integrals associated to BPS-saturated amplitudes in N = 2 heterotic vacua. We compute their large-volume behaviour, and express them as Fourier series in the complexified volume, with Fourier coefficients given in terms of Niebur-Poincaré series in the complex structure modulus. The closure of Niebur-Poincaré series under modular derivatives implies that such integrals derive from holomorphic prepotentials fn, <span class="hlt">generalising</span> the familiar prepotential of N = 2 supergravity. These holomorphic prepotentials transform anomalously under T-duality, in a way characteristic of Eichler integrals. We use this observation to compute their quantum monodromies under the duality group. We extend the analysis to modular integrals with respect to Hecke congruence subgroups, which naturally arise in compactifications on non-factorisable tori and freely-acting orbifolds. In this case, we derive new explicit results including closed-form expressions for integrals involving the Γ0 (N) Hauptmodul, a full characterisation of holomorphic prepotentials including their quantum monodromies, as well as concrete formulæ for holomorphic Yukawa couplings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24405325','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24405325"><span>Partial spin ordering and complex <span class="hlt">magnetic</span> structure in BaYFeO4: a neutron diffraction and high temperature <span class="hlt">susceptibility</span> study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thompson, Corey M; Greedan, John E; Garlea, V Ovidiu; Flacau, Roxana; Tan, Malinda; Nguyen, Phuong-Hieu T; Wrobel, Friederike; Derakhshan, Shahab</p> <p>2014-01-21</p> <p>The novel iron-based compound, BaYFeO4, crystallizes in the Pnma space group with two distinct Fe(3+) sites, that are alternately corner-shared [FeO5](7-) square pyramids and [FeO6](9-) octahedra, forming into [Fe4O18](24-) rings, which propagate as columns along the b-axis. A recent report shows two discernible antiferromagnetic (AFM) transitions at 36 and 48 K in the <span class="hlt">susceptibility</span>, yet heat capacity measurements reveal no <span class="hlt">magnetic</span> phase transitions at these temperatures. An upturn in the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements up to 400 K suggests the presence of short-range <span class="hlt">magnetic</span> behavior at higher temperatures. In this Article, variable-temperature neutron powder diffraction and high-temperature <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements were performed to clarify the <span class="hlt">magnetic</span> behavior. Neutron powder diffraction confirmed that the two <span class="hlt">magnetic</span> transitions observed at 36 and 48 K are due to long-range <span class="hlt">magnetic</span> order. Below 48 K, the <span class="hlt">magnetic</span> structure was determined as a spin-density wave (SDW) with a propagation vector, k = (0, 0, (1)/3), and the moments along the b-axis, whereas the structure becomes an incommensurate cycloid [k = (0, 0, ∼0.35)] below 36 K with the moments within the bc-plane. However, for both cases the ordered moments on Fe(3+) are only of the order ∼3.0 μB, smaller than the expected values near 4.5 μB, indicating that significant components of the Fe moments remain paramagnetic to the lowest temperature studied, 6 K. Moreover, new high-temperature <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements revealed a peak maximum at ∼550 K indicative of short-range spin correlations. It is postulated that most of the <span class="hlt">magnetic</span> entropy is thus removed at high temperatures which could explain the absence of heat capacity anomalies at the long-range ordering temperatures. Published spin dimer calculations, which appear to suggest a k = (0, 0, 0) <span class="hlt">magnetic</span> structure, and allow for neither low dimensionality nor geometric frustration, are inadequate to explain the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1123583','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1123583"><span>Partial Spin Ordering and Complex <span class="hlt">Magnetic</span> Structure in BaYFeO4: A Neutron Diffraction and High Temperature <span class="hlt">Susceptibility</span> Study</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Thompson, Corey; Greedan, John; Garlea, Vasile O; Flacau, Roxana; Tan, Malinda; Derakhshan, Shahab</p> <p>2014-01-01</p> <p>The novel iron-based compound, BaYFeO4, crystallizes in the Pnma space group with two distinct Fe3+ sites, that are alternately corner-shared [FeO5]7 square pyramids and [FeO6]9 octahedra, forming into [Fe4O18]24 rings, which propagate as columns along the b-axis. A recent report shows two discernible antiferromagnetic (AFM) transitions at 36 and 48 K in the <span class="hlt">susceptibility</span>, yet heat capacity measurements reveal no <span class="hlt">magnetic</span> phase transitions at these temperatures. An upturn in the <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements up to 400 K suggests the presence of shortrange <span class="hlt">magnetic</span> behavior at higher temperatures. In this Article, variable-temperature neutron powder diffraction and hightemperature <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements were performed to clarify the <span class="hlt">magnetic</span> behavior. Neutron powder diffraction confirmed that the two <span class="hlt">magnetic</span> transitions observed at 36 and 48 K are due to long-range <span class="hlt">magnetic</span> order. Below 48 K, the <span class="hlt">magnetic</span> structure was determined as a spin-density wave (SDW) with a propagation vector, k = (0, 0, 1/3), and the moments along the b-axis, whereas the structure becomes an incommensurate cycloid [k = (0, 0, 0.35)] below 36 K with the moments within the bc-plane. However, for both cases the ordered moments on Fe3+ are only of the order 3.0 B, smaller than the expected values near 4.5 B, indicating that significant components of the Fe moments remain paramagnetic to the lowest temperature studied, 6 K. Moreover, new high-temperature <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> measurements revealed a peak maximum at 550 K indicative of short-range spin correlations. It is postulated that most of the <span class="hlt">magnetic</span> entropy is thus removed at high temperatures which could explain the absence of heat capacity anomalies at the long-range ordering temperatures. Published spin dimer calculations, which appear to suggest a k = (0, 0, 0) <span class="hlt">magnetic</span> structure, and allow for neither low dimensionality nor geometric frustration, are inadequate to explain the observed complex <span class="hlt">magnetic</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8779282','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8779282"><span>[The <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> of the melanin in the eyes of representatives of different vertebrate classes].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zagal'skaia, E O</p> <p>1995-01-01</p> <p>The magnetoperceptivity (Chi) and element composition of eye pigment epitelium (EPE) melanin in vertebrate animals were measured. The minimal values of EPE Chi were found in winter-sleeping and anabiotic animals (Ursus arctos, Rana temporaria). The magnetoperception was high in migrating animals (Oncorhynchus keta, 0. gorbuscha, Anas crecca) and in wild gray rats as well, EPE magnetoperceptivity in albino rats wasn't practicaly established. In the majority of cases the quantity of magnetoperceptivity correlates with per-cent content of iron. The evident correlation between melanin <span class="hlt">magnet</span> properties and the life strategy of the investigated animals allows to propose the participance of eye pigment epithelium in orientation and navigation of the animals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRB..120..662M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRB..120..662M"><span>Magma flow pattern in dykes of the Azores revealed by anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moreira, M. A.; Geoffroy, L.; Pozzi, J. P.</p> <p>2015-02-01</p> <p>The localization of magma melting areas at the lithosphere bottom in extensional volcanic domains is poorly understood. Large polygenetic volcanoes of long duration and their associated magma chambers suggest that melting at depth may be focused at specific points within the mantle. To validate the hypothesis that the magma feeding a mafic crust, comes from permanent localized crustal reservoirs, it is necessary to map the fossilized magma flow within the crustal planar intrusions. Using the AMS, we obtain magmatic flow vectors from 34 alkaline basaltic dykes from São Jorge, São Miguel and Santa Maria islands in the Azores Archipelago, a hot-spot related triple junction. The dykes contain titanomagnetite showing a wide spectrum of solid solution ranging from Ti-rich to Ti-poor compositions with vestiges of maghemitization. Most of the dykes exhibit a normal <span class="hlt">magnetic</span> fabric. The orientation of the <span class="hlt">magnetic</span> lineation k1 axis is more variable than that of the k3 axis, which is generally well grouped. The dykes of São Jorge and São Miguel show a predominance of subhorizontal magmatic flows. In Santa Maria the deduced flow pattern is less systematic changing from subhorizontal in the southern part of the island to oblique in north. These results suggest that the ascent of magma beneath the islands of Azores is predominantly over localized melting sources and then collected within shallow magma chambers. According to this concept, dykes in the upper levels of the crust propagate laterally away from these magma chambers thus feeding the lava flows observed at the surface.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26068945','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26068945"><span>Evaluating the <span class="hlt">Generalisability</span> of Trial Results: Introducing a Centre- and Trial-Level <span class="hlt">Generalisability</span> Index.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gheorghe, Adrian; Roberts, Tracy; Hemming, Karla; Calvert, Melanie</p> <p>2015-11-01</p> <p>Few randomised controlled trials (RCTs) recruit centres representatively, which may limit the external validity of trial results. The aim of this study was to propose a proof-of-concept method of assessing the <span class="hlt">generalisability</span> of the clinical and cost-effectiveness findings of a given RCT. We developed a <span class="hlt">generalisability</span> index (Gix), informed by centre-level characteristics, as a measure of centre and trial representativeness. The centre-level Gix quantifies how representative a centre is in relation to its jurisdiction, e.g. a country or health authority. The trial-level Gix quantifies how representative trial recruitment is in relation to clinical practice in the jurisdiction. Taking a real-world RCT as a case study and assuming trial-wide results to represent 'true jurisdiction values', we used simulation methods to recreate 5000 RCTs and investigate the relationship between trial representativeness, reflected by the standardised trial-Gix, and the deviation of simulated trial results from the 'true values'. The simulation study provides evidence that trial results (odds ratio for the primary outcome and incremental quality-adjusted life-years) were influenced by the representativeness of the sample of recruiting centres. Simulated RCTs with the closest results to the 'true values' were those whose recruitment closely mirrored the jurisdiction-wide context. Results appeared robust to six alternative specifications of the Gix. Our findings suggest that an unrepresentative selection of centres limits the external validity of trial results. The Gix may be a valuable tool to help facilitate rational selection of trial centres and ensure the <span class="hlt">generalisability</span> of results at the jurisdiction level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JVGR...91..167O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JVGR...91..167O"><span>Correlation of deposits and vent locations of the proximal Campanian Ignimbrite deposits, Campi Flegrei, Italy, based on natural remanent <span class="hlt">magnetization</span> and anisotropy of <span class="hlt">magnetic</span> <span class="hlt">susceptibility</span> characteristics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ort, Michael H.; Rosi, Mauro; Anderson, Charles D.</p> <p>1999-08-01</p> <p>Correlation of the distal deposits of the Campanian Ignimbrite with their proximal equivalents in the Campi Flegrei caldera is complicated by a lack of medial exposures, complex and limited proximal stratigraphic sections, and large lateral facies changes. Paleomagnetic data from 10 sites in and near the Campi Flegrei yield natural remanent <span class="hlt">magnetizations</span> (NRM) that are statistically indistinguishable from the distal Campanian Ignimbrite. In addition, their virtual geomagnetic pole (VGP) yields a possible correlatio