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230 results on '"Pankhurst, Q. A."'

85. Increased levels of magnetic iron compounds in Alzheimer's disease.

Author

Pankhurst Q, Hautot D, Khan N, Dobson J, Pankhurst, Quentin, Hautot, Dimitri, Khan, Nadeem, and Dobson, Jon

Abstract

A study of the magnetic properties of superior temporal gyrus brain tissue from 11 Alzheimer's disease (AD) and 11 age-matched control subjects demonstrates an exponential correlation between the concentrations of the Fe;{2+}-ion-containing iron oxide, magnetite (Fe{3}O{4}), and the fraction of those particles that are smaller than 20 nm in diameter. These data provide circumstantial evidence in favor of their genesis within the 8 nm diameter cores of the iron storage protein ferritin. We also show, for the first time, that the total concentration of biogenic magnetite is generally higher in the AD brain (in some cases as much as 15 times greater than controls) and that there are gender-based differences, with AD female subjects having significantly higher concentrations than all other groups. These results provide insights which may guide current efforts to develop iron-based MRI diagnosis of AD. [ABSTRACT FROM AUTHOR]

Published
2008
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93. Mössbauer study of NH4FeCl3: A quasi one-dimensional magnet

Author

Sheen, N. I., McCann, V. H., and Pankhurst, Q. A.

Abstract

NH4FeCl3 is a quasi one-dimensional magnet. Mössbauer spectra of powder samples of NH4FeCl3 have been recorded in the temperature range 1.3 to 250 K. The structural phase change between 10 and 30 K was not accompanied by changes in the Mössbauer spectra. Apparently, the changes in the local environment of the Fe2+ ions are not sufficient to affect the quadrupole splitting. The Mössbauer spectrum at 1.3 K, belowTN=1.7(2) K, is magnetically split, but cannot be fitted to just one iron site. It appears to be a superposition of at least two broadened spectra, one with an internal fieldB=4.7(1) T perpendicular to the principalz-axis of the electric field gradient, the other with zero field. The intensity for these sites was found to be 3.3∶1. The fit is improved if slow relaxation is allowed between the two sites. Broadening of the lines starts to occur at 6 K, well aboveTN. This has not been reported for the other members of the AFeX3 group.

Published
1994
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96. The effect of misalignment on the spin-flop transition in K2FeF5

Author

Pankhurst, Q., Johnson, C., Jones, D., and Thomas, M.

Abstract

Abstract: Spin-flop transitions in K2FeF5 subject to an applied field (i) parallel to the easy axis, and (ii) directed at 33 to the easy axis are found to be (i) abrupt and (ii) smooth, in accordance with theoretical predictions.

Published
1988
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97. Magnetic ordering below 10K in the high-Tc superconductor YBa2(Cu0.985Fe0.015)3O7−σ

Author

Pankhurst, Q., Morrish, AH., Zhou, X., and Maartense, I.

Abstract

Abstract: The high-temperature superconductor with the nominal composition YBa2Cu3O7−σ has been doped with iron 93% enriched in57Fe. When 1.5 at % Fe substitutes for Cu, the transition temperature is reduced by about 30 K with full ac shielding (X′=−1/4π) achieved by ≈40 K. At room temperature the Mssbauer spectrum consists of three overlapping doublets. Below 10 K, hyperfine-field splitting is observed; relaxation still takes place at T=1.8 K.

Published
1988
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99. Challenges and recommendations for magnetic hyperthermia characterization measurements

Author

Wells, J., Ortega, D., Steinhoff, U., Dutz, S., Garaio, E., Sandre, O., Natividad, E., Cruz, M. M., Brero, F., Southern, P., Pankhurst, Q. A., and Spassov, S.

Subjects
3. Good health
Abstract

The localized heating of magnetic nanoparticles (MNPs) via the application of time-varying magnetic fields – a process known as magnetic field hyperthermia (MFH) – can greatly enhance existing options for cancer treatment; but for broad clinical uptake its optimization, reproducibility and safety must be comprehensively proven. As part of this effort, the quantification of MNP heating – characterized by the specific loss power (SLP), measured in W/g, or by the intrinsic loss power (ILP), in Hm2/kg – is frequently reported. However, in SLP/ILP measurements to date, the apparatus, the analysis techniques and the field conditions used by different researchers have varied greatly, leading to questions as to the reproducibility of the measurements. An interlaboratory study (across N = 21 European sites) of calorimetry measurements that constitutes a snapshot of the current state-of-the-art within the MFH community has been undertaken. Identical samples of two stable nanoparticle systems were distributed to all participating laboratories. Raw measurement data as well as the results of in-house analysis techniques were collected along with details of the measurement apparatus used. Raw measurement data was further reanalyzed by universal application of the corrected-slope method to examine relative influences of apparatus and results processing. The data show that although there is very good intralaboratory repeatability, the overall interlaboratory measurement accuracy is poor, with the consolidated ILP data having standard deviations on the mean of ca. ± 30% to ± 40%. There is a strong systematic component to the uncertainties, and a clear rank correlation between the measuring laboratory and the ILP. Both of these are indications of a current lack of normalization in this field. A number of possible sources of systematic uncertainties are identified, and means determined to alleviate or minimize them. However, no single dominant factor was identified, and significant work remains to ascertain and remove the remaining uncertainty sources. We conclude that the study reveals a current lack of harmonization in MFH characterization of MNPs, and highlights the growing need for standardized, quantitative characterization techniques for this emerging medical technology.

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