共查询到20条相似文献,搜索用时 31 毫秒
1.
Makoto Suto Hiroaki Mamiya Ryo Kasuya Balachandran Jeyadevan 《Journal of magnetism and magnetic materials》2009,321(10):1493-1496
The relative contributions of Néel and Brownian relaxations on magnetic heat dissipation were studied by investigating the physical, magnetic and heating characteristics of magnetite nanoparticle suspensions with average diameters of 12.5 and 15.7 nm. Heating characteristics depended on the dispersion states of particles. The specific absorption rates (SAR) dropped by 27% for the 12.5 nm particles to 16.8×10−9 W g−1 Oe−2 Hz−1 and by 67% for the 15.7 nm particles to 9.69×10−9 W g−1 Oe−2 Hz−1, when the particle rotation was suppressed by dispersing magnetite nanoparticles in hydro-gel. 相似文献
2.
Investigation of magneto-anisotropy field for system of particles with near superparamagnetic volume
L.P. Ol’khovik A.S. Kamzin E.L. Karyakina Z.I. Sizova E.V. Shurinova 《Journal of magnetism and magnetic materials》2008
We obtained the temperature dependence for low-field boundary of the anisotropy field distribution in a system of barium hexaferrite nanocrystals in the temperature range from 300 to 700 K. We treated the experimental data taking into account the influence of thermal fluctuations on the anisotropy field and the transition of particles into the paramagnetic state, stimulated by external magnetic field. We showed that the dependence under consideration is formed by particles of different volume, which increased from 3.5×10−18 to 40×10−18 cm3 while the particles lost their magnetic stability with the temperature growth. 相似文献
3.
Shahriar KhushrushahiMarkus Zahn 《Journal of magnetism and magnetic materials》2011,323(10):1302-1308
Ferrofluid spin-up flow is studied within a sphere subjected to a uniform rotating magnetic field from two surrounding spherical coils carrying sinusoidally varying currents at right angles and 90° phase difference. Ultrasound velocimetry measurements in a full sphere of ferrofluid shows no measureable flow. There is significant bulk flow in a partially filled sphere (1-14 mm/s) of ferrofluid or a finite height cylinder of ferrofluid with no cover (1-4 mm/s) placed in the spherical coil apparatus. The flow is due to free surface effects and the non-uniform magnetic field associated with the shape demagnetizing effects. Flow is also observed in the fully filled ferrofluid sphere (1-20 mm/s) when the field is made non-uniform by adding a permanent magnet or a DC or AC excited small solenoidal coil. This confirms that a non-uniform magnetic field or a non-uniform distribution of magnetization due to a non-uniform magnetic field are causes of spin-up flow in ferrofluids with no free surface, while tangential magnetic surface stress contributes to flow in the presence of a free surface.Recent work has fitted velocity flow measurements of ferrofluid filled finite height cylinders with no free surface, subjected to uniform rotating magnetic fields, neglecting the container shape effects which cause non-uniform demagnetizing fields, and resulting in much larger non-physical effective values of spin viscosity η′∼10−8−10−12 N s than those obtained from theoretical spin diffusion analysis where η′≤10−18 N s. COMSOL Multiphysics finite element computer simulations of spherical geometry in a uniform rotating magnetic field using non-physically large experimental fit values of spin viscosity η′∼10−8−10−12 N s with a zero spin-velocity boundary condition at the outer wall predicts measureable flow, while simulations setting spin viscosity to zero (η′=0) results in negligible flow, in agreement with the ultrasound velocimetry measurements. COMSOL simulations also confirm that a non-uniform rotating magnetic field or a uniform rotating magnetic field with a non-uniform distribution of magnetization due to an external magnet or a current carrying coil can drive a measureable flow in an infinitely long ferrofluid cylinder with zero spin viscosity (η′=0). 相似文献
4.
Mg-based films have been prepared by pulsed laser deposition technique for photocathode applications. We have investigated the influence of pulse laser duration on morphology and photoemissive properties. Two laser sources have been used, generating pulses of 30 ns at 308 nm (XeCl excimer laser), 5 ps and 500 fs at 248 nm (KrF excimer laser) to grow Mg films onto Si and Cu substrates in high vacuum (∼10−7 Pa) and at room temperature. Morphological investigations carried out by scanning electron microscopy (SEM) have revealed that, in our experimental conditions, the number and the mean size of the droplets on the films surfaces decreases as the pulse laser duration shortens. The contamination level of Mg film surfaces have been studied by energy dispersive X-ray spectroscopy (EDX). The photoelectron performances in terms of quantum efficiency (QE) and emission stability have been tested in a UHV DC photodiode cell (10−7 Pa). Measures of the QE of the samples surfaces have revealed a decrease on the initial value for Mg-based photocathodes prepared by fs laser (from 7.8 × 10−4 to 6.6 × 10−4) PLD with respect to ps (from 6.2 × 10−4 to 7.4 × 10−4) and ns lasers (from 5.0 × 10−4 to 1.6 × 10−3). A comparison among Mg-based photocathodes prepared by ns, ps and fs PLD for the production of high brightness electron beams has been presented and discussed. 相似文献
5.
J.K. Tripathi 《Applied Surface Science》2007,253(21):8689-8694
Fe film (∼50 nm) have been deposited on pSi substrate by electron beam evaporation technique. The bilayers have been irradiated by 100 MeV Fe7+ ions having fluences of 1 × 1013, 1 × 1014 and 5 × 1014 ions cm−2. SEM study of the unirradiated devices show surface modifications having a annular structures. From XRD study of the bilayer, it is observed that grain size has reduced from 70 to 25 nm after the irradiation for a fluence of 1 × 1014 ions cm−2. Moreover electronic transport data of the bilayer show practically no effect on the current flow for a fluence of 1 × 1013 ions cm−2 irradiation whereas for 1 × 1014 ions cm−2 fluence, there is very significant change in current flow (by two orders in magnitude) across the bilayer. However, for a higher fluence of irradiation 5 × 1014 ions cm−2, the bilayer becomes highly resistive. It has been found from the above observations that the fluence of 1 × 1014 ions cm−2 of swift heavy ion irradiation is a optimum fluence. 相似文献
6.
Dye-sensitized phototransformation of chlorophenols and their subsequent chemiluminescence reactions
A novel chemiluminescence (CL) reaction of chlorophenols (CPs), including 2-chlorophenol (2-CP), 4-CP, 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP) was reported, which was based on the oxidation of the phototransformed CPs by N-bromosuccinimide (NBS). It was found that the dye-sensitized phototransformation is a prerequisite for the subsequent CL reaction, and the presence of 1.9×10-2 mol L−1 Triton X-100 or 3.7×10-3 mol L−1 CTAB can greatly enhance the CL intensity. A neutral sample solution with the presence of 2×10-5 mol L−1 fluorescein (FL) was found to be optimum for the phototransformation of 2-CP, 4-CP, 2,4-DCP and PCP, but a lower pH of 5.3 was more suitable for 2,4,6-TCP. Based on the CL reaction, detection limits of 8.6×10−8, 1.1×10−7, 1.5×10-7, 4.6×10-8 and 3.0×10−5 mol L−1 were achieved, respectively, for 2-CP, 4-CP, 2,4-DCP, 2,4,6-TCP and PCP with the optimized conditions in the flow system. The mechanism of the phototransformation and the subsequent CL reaction were preliminarily studied and it was suggested that the singlet oxygen formed in the dye-sensitization process was responsible for the conversion of CPs into light-emitting precursors. These intermediate products were suggested to be peroxide compounds after testing by a luminal-based post-column CL detection experiment. 相似文献
7.
In this paper we present a study of the magnetic anisotropy constant of nanocrystalline magnetic particles of CoxFe(3−x)O4, with x ranging from 0.05 to 1.6, synthesized by a combustion reaction. The magnetic anisotropy constants were obtained by fitting the high-field part of the major hysteresis loops with the law of approach equation down to temperatures of 4 K and up to fields of 60 kOe. The anisotropy constant depends strongly on both temperature and cobalt content x, exhibiting a nonmonotic dome-shaped dependence on x with a maximum at x=1.0. We found that fits at lower temperatures, i.e., 4 and 72 K, give values of K1 that are approximately one order of magnitude higher than those at higher temperatures, i.e., 272 and 340 K. For example, K1 for specimens with x=0.8 and 1.0 are 4.21×107 and 4.22×107 ergs/cm3 at 4 K, and 7.64×106 and 7.51×106 ergs/cm3 at 340 K, respectively. Thus, our determination of temperature-dependence of the anisotropy constant represents an improvement over existing works. 相似文献
8.
New types of hybrid material have been synthesized by using four different methods of immobilization of humic acid (HA) on chitin. The most stable hybrid material toward the change of medium acidity was then utilized as sorbent for Cr(III).The HA was extracted from peat soil of Gambut District, South Kalimantan, Indonesia, using the recommended procedure of International Humic Substances Society (IHSS), while the chitin was isolated from crab shell waste through deproteination using 3.5% (w/v) NaOH and followed by removal of inorganic impurities using 1 M HCl. The four methods of immobilization of HA on chitin were (i) Method A: chitin powder (4 g) was gently poured into the stirred solution of 0.4 g HA in 40 mL of 0.01 M NaOH. After overnight stirring, the solid was separated, washed with water, and dried in oven at 70 °C. (ii) Method B: gelatinous chitin (40 g) in 250 mL of 0.5 M HCl was reacted with HA (4 g) in 500 mL of 0.5 M NaOH and aged for 24 h. The product was washed with water and dried. (iii) Method C: HA powder (0.5 g) was mixed with the stirred gel of chitin (2.5 g) in 60 mL of CaCl2 saturated methanol and the mixture was then washed with the mixed solution of 25 mL of 2 M sodium citrate and ethylene glycol 1:1. The solid was separated, washed with water, and dried. (iv) Method D: the solution of HA (0.056 g) in 10 mL of 0.01 M NaOH was reacted with the gel of chitin (0.2 g) in 10 mL of CaCl2 saturated methanol. After 24 h stirring, the solid was separated from the reaction medium, washed with the mixed solution of 2 M sodium citrate and ethylene glycol 1:1, and followed by washing with water and drying. Parameters investigated in this study consisted of the stability test of the immobilized HA, as well as the rate constant (k1), capacity (b), and energy (E) of sorption as well as the rate constant of desorption (k−1). The k1 and k−1 were determined according to a kinetic model of first order sorption reaching equilibrium, while the b and E were determined according to the Langmuir isotherm model.Compared to HA, Methods, A, C, and D; Method B produced the most stable immobilization of HA on chitin. The hybrid material (Chitin-HA) synthesized through Method B was stable in the acidity range that equivalent to pH 2.0-11.0. At the acidity giving maximum sorption, i.e. pH 5, the presence of immobilized HA on the Chitin-HA enhanced more than three times the k1 and k−1, i.e. from 0.057 min−1 and 8.51 × 10−4 (min−1) (mol/L) for chitin to 0.183 min−1 and 3.27 × 10−3 (min−1) (mol/L) for the Chitin-HA. On the contrary, the presence of HA on Chitin-HA only gave small increase on b and small decrease on E. The values of b and E for Cr(III) on chitin were 1.45 × 10−2 mol/g and 23.12 kJ/mol, respectively, while those on Chitin-HA were 1.78 × 10−2 mol/g and 19.95 kJ/mol, respectively. 相似文献
9.
Magnetic measurements have been performed on 40-nm sphere-like Fe3 − δO4 (δ=0.043) nanoparticles using a Quantum Design vibrating sample magnetometer. Coating Fe3 − δO4 nanoparticles with SiO2 effectively eliminates magnetic interparticle interactions so that the coercive field HC in the high-temperature range between 300 K and the Curie temperature (855 K) can be well fitted by an expression for noninteracting randomly oriented single-domain particles. From the fitting parameters, the effective anisotropy constant K is found to be (1.38±0.11)×105 erg/cm3, which is very close to the bulk magnetocrystalline anisotropy constant of 1.35×105 erg/cm3. Moreover, the inferred mean particle diameter from the fitting parameters is in quantitative agreement with that determined from transmission electron microscope. Such a quantitative agreement between data and theory suggests that the ensemble of our SiO2-coated sphere-like Fe3 − δO4 nanoparticles represents a good system of noninteracting randomly-oriented single-domain particles. 相似文献
10.
G. BalakrishnanT.N. Sairam P. Kuppusami R. ThiumurugesanE. Mohandas V. GanesanD. Sastikumar 《Applied Surface Science》2011,257(20):8506-8510
ZrO2 thin films were deposited at various oxygen partial pressures (2.0 × 10−5-3.5 × 10−1 mbar) at 973 K on (1 0 0) silicon and quartz substrates by pulsed laser deposition. The influence of oxygen partial pressure on structure, surface morphology and optical properties of the films were investigated. X-ray diffraction results indicated that the films are polycrystalline containing both monoclinic and tetragonal phases. The films prepared in the oxygen partial pressures range 2.0 × 10−5-3.5 × 10−1 mbar contain nanocrystals of sizes in the range 54-31 nm for tetragonal phase. The peak intensity of the tetragonal phase decreases with the increase of oxygen partial pressures. Surface morphology of the films examined by AFM shows the formation of nanostructures. The RMS surface roughness of the film prepared at 2.0 × 10−5 mbar is 1.3 nm while it is 3.2 nm at 3.5 × 10−1 mbar. The optical properties of the films were investigated using UV-visible spectroscopy technique in the wavelength range of 200-800 nm. The refractive index is found to decrease from 2.26 to 1.87 as the oxygen partial pressure increases from 2.0 × 10−5 to 3.5 × 10−1 mbar. The optical studies show two different absorption edges corresponding to monoclinic and tetragonal phases. 相似文献
11.
The hydrothermal synthesis and magnetic entropy change for the perovskite manganite La0.5Ca0.3Sr0.2MnO3 have been studied. The La0.5Ca0.3Sr0.2MnO3 can be produced as phase-pure, crystalline powders in one step from solutions of metal salts in aqueous potassium hydroxide solution at a temperature of 513 K in 72 h. Scanning electron microscopy shows that the materials are made up of cuboid-shaped particles in typical dimension of 4.0×2.5×1.6 μm. Heat treatment can improve the magnetocaloric effect for the hydrothermal sample. The maximum magnetic entropy change ΔSM for the as-prepared sample is 0.88 J kg−1 K−1 at 315 K for a magnetic field change of 2.0 T. It increases to 1.52 J kg−1 K−1, near its Curie temperature (317 K) by annealing the sample at 1473 K for 6 h. The hydrothermal synthesis method is a feasible route to prepare high-quality perovskite material for magnetic refrigeration application. 相似文献
12.
Charles E. Miller Matthew A. Montgomery Christopher Johnstone Brian Kovaric 《Journal of Molecular Spectroscopy》2004,228(2):355-374
High-resolution near-infrared (4000-8500 cm−1) spectra of 13C-enriched carbon dioxide have been recorded using the McMath-Pierce Fourier transform spectrometer at the Kitt Peak National Solar Observatory. We observed over 1000 line positions for the 16O13C16O isotopologue, the majority of which have previously been observed only in spectra of the Venusian atmosphere [J. Mol. Spectrosc. 67 (1977) 304]. These have been analyzed to determine spectroscopic constants for 28 different vibrational states. The analysis yielded RMS fitting residuals <1.5 × 10−4 cm−1 for the strongest bands and RMS residuals <5 × 10−4 cm−1 for most other fitted bands. A 5% 18O-enrichment in the sample enabled us to observe 410 line positions from 5 near-infrared vibrational bands of the 16O13C18O isotopologue. Analysis of the 16O13C18O bands yielded RMS fitting residuals <2 × 10−4 cm−1. Additionally, the first fits for the 16O13C18O 11101 ← 01101 and 11102 ← 01101 hot bands yielded RMS residuals of 2.3 × 10−4 and 2.2 × 10−4 cm−1, respectively. Critical reevaluations of the spectroscopic constants for the low lying vibrational states for both isotopologues have been performed as part of the analysis. 相似文献
13.
In this study, the influence of oxygen on high rate (up to 110 nm m/min) sputtered aluminum doped zinc oxide films (ZnO:Al) was systematically investigated. Different oxygen gas flows from 0 sccm to 8 sccm were inputted into the chamber during the preparation of ZnO:Al films from dual rotatable ceramic targets under high discharge power (14 kW). The resistivity increases from 4.2 × 10−4 Ω cm to 4.3 × 10−2 Ω cm with the rising oxygen gas flow. While both the carrier concentration and mobility drop by one order of magnitude from 3.4 × 1020 cm−3 to 2.5 × 1019 cm−3 and from 43.5 cm2/V s to 5.6 cm2/V s, respectively. The as-grown ZnO:Al films and after-etched ZnO:Al films after a chemical wet etching step in diluted HCl solution (0.5%) exhibit different surface structures. All films show high light transmission and low light absorption but different light scattering properties (diffusion and haze) because of different surface structures. Moreover, ZnO:Al films display different optical bandgaps between 3.51 eV and 3.27 eV, which are corresponding to different carrier concentrations. The variation of mobility and morphology is related with chemisorption of oxygen in the grain boundaries as well as high energetic oxygen ions bombardment. 相似文献
14.
Based on ambient atmosphere scanning tunneling microscope (STM) technique, scanning tunneling spectroscopy (STS) combined with statistics analysis was developed to investigate the single-molecule conductance of various kinds of molecules which were self-assembled on the Au (1 1 1). Conductance histograms obtained from current-voltage curves revealed well-defined peaks at integer multiples of a fundamental conductance and were used to identify the conductance of a single molecule. The conductances of saturated molecules like 1,8-octanedithol and hexanethiocyanate were found to be 0.072 × 10−4G0 and 0.06 × 10−4G0 respectively and 0.23 × 10−4G0 and 0.13 × 10−4G0 for unsaturated molecules like 5,5′-dithiol- 2,2′,5′,2″-terthiophene and 4,4′-dithio-tert(phenylene ethylene). 相似文献
15.
A.V. Moholkar K.Y. Rajpure C.H. Bhosale 《Journal of Physics and Chemistry of Solids》2007,68(10):1981-1988
Transparent conducting thin films of fluorine-doped tin oxide (FTO) have been deposited onto the preheated glass substrates of different thickness by spray pyrolysis process using SnCl4·5H2O and NH4F precursors. Substrate thickness is varied from 1 to 6 mm. The films are grown using mixed solvent with propane-2-ol as organic solvent and distilled water at optimized substrate temperature of 475 °C. Films of thickness up to 1525 nm are grown by a fine spray of the source solution using compressed air as a carrier gas. The films have been characterized by the techniques such as X-ray diffraction, optical absorption, van der Pauw technique, and Hall effect. The as-deposited films are preferentially oriented along the (2 0 0) plane and are of polycrystalline SnO2 with a tetragonal crystal structure having the texture coefficient of 6.19 for the films deposited on 4 mm thick substrate. The lattice parameter values remain unchanged with the substrate thickness. The grain size varies between 38 and 48 nm. The films exhibit moderate optical transmission up to 70% at 550 nm. The figure of merit (φ) varies from 1.36×10−4 to 1.93×10−3 Ω−1. The films are heavily doped, therefore degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance (Rs) of 7.5 Ω is obtained for a typical sample deposited on 4 mm thick substrate. The resistivity (ρ) and carrier concentration (nD) vary over 8.38×10−4 to 2.95×10−3 Ω cm and 4.03×1020 to 2.69×1021 cm−3, respectively. 相似文献
16.
The temporal variation in electron and ion concentrations have been measured in shock-heated mixtures of Ar + (0-2)% C3O2 in the 2000-3600 K temperature and 15-30 bar pressure range. Experiments in pure argon proved that the observed free electrons and ions originate from inherent impurities of sodium. The equilibrium concentrations of free charges in argon were established during (1-3) × 10−5 s and varied from 4 × 1011 cm−3 at T5 = 2500 K to 5 × 1012 cm−3 at 3500 K. In the reactive mixtures, containing C3O2, the time profiles of electron and ion concentrations showed a more complicate behavior—a fast rise to a maximum followed by a gradual decay. The maximum ion concentrations were much higher and electron concentrations were much lower than in similar conditions in argon. The extent of the subsequent decay of electron concentration increased proportionally to the square of the C3O2 concentration. In the mixture with 2% C3O2 the final electron concentration was about 100 times less than in pure argon. The characteristic decay time of free charges varied from 400 to 40 μs and decreased proportionally to the square root of the charge concentration. The data analysis is based on the assumption that the observed redistribution of electron and ion concentrations is caused by charging of the carbon particles formed during pyrolysis of C3O2. The kinetics of particle charging and the final distribution of charges were evaluated by the analysis of electron and ion fluxes to the particles in accordance with the electric potentials of charged particles and corresponding sodium ionization. A predominance of negatively charged particles, caused by the high electron mobility, resulted in their much higher concentration than the concentration of free electrons. 相似文献
17.
M.M. Socías-Viciana J. Tévar de Fez M.D. Ureña-Amate E. González-Pradas M. Fernández-Pérez F. Flores-Céspedes 《Applied Surface Science》2006,252(17):6053-6057
The adsorption of chloridazon (5-amino-4-chloro-2-phenylpyridazin-3(2H)-one) on natural and ammonium kerolite samples from aqueous solution at 10, 25 and 40 °C has been studied by using batch experiments. The experimental data points were fitted to the Langmuir equation in order to calculate the adsorption capacities (Xm) of the samples; two straight lines were obtained, which indicates that the adsorption process takes place in two different stages. Values for Xm1 (first stage) ranged from 1.1 × 10−2 mol kg−1 for natural kerolite at 40 °C up to 5.1 × 10−2 mol kg−1 for ammonium kerolite at 10 °C and the values for Xm2 (second stage) ranged from 9.1 × 10−2 mol kg−1 for natural kerolite at 40 °C up to 14 × 10−2 mol kg−1 for natural kerolite at 10 °C. The adsorption experiments showed on the one hand, that the ammonium kerolite is more effective than natural kerolite to adsorb chloridazon in the range of temperature studied and on the other hand, that the lower temperature, the more effective the adsorption of chloridazon on the adsorbents studied. 相似文献
18.
S.Y. Li B.W. Wang L. Weng Y. Zhou Y. Sun W.M. Huang 《Journal of magnetism and magnetic materials》2008
Based on the analysis of the magnetostriction for Terfenol-D composites, Terfenol-D 2-2 magnetostrictive composites have been prepared with laminations perpendicular to [1 1 2] axes. Then one of the samples was annealed in the vacuum at 423 K for 15 min at the magnetic field of 240 kA/m, which is along the direction of laminations and vertical to the [1 1 2] axes of the specimen. The static magnetostriction λ and dynamic magnetostrictive coefficient d33 of samples were measured under the compressive stress of 0, 2, 4, 6 and 8 MPa. Effects of the compressive stress and the magnetic field heat treatment on the magnetostriction λ have been investigated. It is found that the magnetostriction of 2-2 composites can be improved under the compressive stress when the magnetic field is larger than 20 kA/m. The magnetostriction of 2-2 composites with the magnetic field heat treatment increases under compressive stress, and it can reach 1390×10−6 at the magnetic field of 200 kA/m and under the compressive stress of 4 MPa, much larger than the value of 860×10−6 without the magnetic field heat treatment. The highest magnetostriction of the 2-2 composite with the magnetic field heat treatment can reach 1530×10−6. The dynamic magnetostrictive coefficient d33 of 2-2 composites with the magnetic field heat treatment have been improved, compared with that without magnetic field heat treatment. The maximum value of d33 of the sample with magnetic field heat treatment is 71% larger than that without magnetic field heat treatment. 相似文献
19.
V. Vasanthi A. Shanmugavani C. Sanjeeviraja R. Kalai Selvan 《Journal of magnetism and magnetic materials》2012
CdFe2O4 particles were synthesized by the microwave assisted combustion method using two different fuels—glycine and urea. Microwave heating provides higher chemical yield within a minute. The synthesized particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), ac impedance spectroscopy, vibrating sample magnetometry (VSM) and electron spin resonance (ESR) methods. XRD analysis shows the cubic structure of CdFe2O4. The high and low frequency absorption bands of CdFe2O4 were found using FTIR analysis. Spherical morphology was revealed from the SEM images. ESR and VSM measurements reveal the antiferromagnetic behavior of CdFe2O4. The electrical conductivities of CdFe2O4 synthesized using glycine and urea are 6.5×10−7 S cm−1 and 4.7×10−8 S cm−1 respectively at 240 oC. At elevated temperatures an occurrence of increase in conductivity was observed, which indicates the semiconducting behavior of CdFe2O4. The dielectric spectral analysis reveals that dielectric constant of CdFe2O4 decreases with frequency and increases with temperature. 相似文献
20.
Joy Liau Masoud Shiehmorteza Olivier M. Girard Claude B. Sirlin Mark Bydder 《Magnetic resonance imaging》2013
This study evaluates the robustness of a magnetic resonance (MR) fat quantification method to changes in R2* caused by an intravenous infusion of superparamagnetic iron oxide (SPIO) contrast agent. The R2* and proton density fat fraction (PDFF) were measured in liver and spine in 14 subjects using an investigational sequence (IDEAL IQ) provided by the MR scanner vendor. Measurements were made before and after SPIO infusion. Results showed SPIO significantly increased R2* in both liver (p = 8.8 × 10− 8) and spine (p =1.3 × 10− 2) but PDFFs were not significantly different in either the liver (p = 5.5 × 10− 1) or the spine (p = 5.6 × 10− 1). These results confirm that the IDEAL IQ method of fat quantification is robust to changes in R2*. 相似文献