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The chance of life-threatening complications occurring late after brain irradiation limits the efficacy of this form of cancer therapy. The molecular and cellular events that trigger radiation-induced brain damage are still unknown, but since they have the potential to serve as valuable targets for therapeutic intervention they are worth delineating. In this murine study, the effect of irradiation on the expression of molecules which are known to contribute to brain damage in other model systems was examined. Expression of genes encoding cytokines (TNF-alpha/beta, IL-1 alpha/beta, IL-2, IL-3, IL-4, IL-5, IL-6 and IFN-gamma), cytokine receptors (TNF-Rp55 and p75, IL-1R- p60 and p80, IFN-gamma R, and IL-6R), the cell adhesion molecule (ICAM-1), inducible nitric oxide synthetase (iNOS), anti-chymotrypsin (EB22/5.3), and the gliotic marker (GFAP) was evaluated over a 6-month period using a sensitive RNase protection assay (RPA). We had previously demonstrated that within 24 h of brain irradiation there is an acute transitory molecular response involving TNF-alpha, IL-1, ICAM-1, EB22/5.3 and GFAP. This study shows re-elevation of TNF-alpha, EB22/5.3 and GFAP mRNA levels at 2-3 months, but only TNF-alpha mRNA was overexpressed at 6 months. These time points are when neurological abnormalities are seen after higher doses. The data suggest that TNF-alpha may be involved in late brain responses to irradiation and could contribute to clinical symptoms.

Based on the Bean–Rodbell model, which assumes a linear variation of exchange coupling with atom spacing, the magnetovolume effects in LaFe13−xSix (x = 1.2–2.0) have been systematically studied. A relation between phase volume and magnetization is first obtained by comparing the structural and magnetic data collected at various temperatures. The maximum spontaneous magnetostriction thus derived is dependent on the content of Si, linearly decreasing from ∼2.15% for x = 1.2 to ∼1.12% for x = 2. Based on these results and limited experimental data, the parameters involved in the Bean–Rodbell model are determined for the LaFe13−xSix compounds. Further analysis indicates that the Bean–Rodbell model equipped with these parameters gives a satisfactory description of the magnetovolume effects produced by interstitial hydrogen for the LaFe11.44Si1.56 hydride. To explain the pressure effects, in contrast, changes of the parameters under pressure, which are a result of the enhancement of the first-order character of the phase transition, have to be taken into account. These results indicate that either the increase or the decrease of the Curie temperature is simply a consequence of the variation of the phase volume due to the introduction of interstitial atoms or the application of a high pressure, and can be described well by the Bean–Rodbell model.

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Our recent progress on magnetic entropy change (∆S) involving martensitic transition in both conventional and metamagnetic NiMn-based Heusler alloys is reviewed. For the conventional alloys, where both martensite and austenite exhibit ferromagnetic (FM) behavior but show different magnetic anisotropies, a positive ∆S as large as 4.1 J·kg −1 ·K −1 under a field change of 0-0.9 T was first observed at martensitic transition temperature T M ∼ 197 K. Through adjusting the Ni:Mn:Ga ratio to affect valence electron concentration e/a, T M was successfully tuned to room temperature, and a large negative ∆S was observed in a single crystal. The −∆S attained 18.0 J·kg −1 ·K −1 under a field change of 0-5 T. We also focused on the metamagnetic alloys that show mechanisms different from the conventional ones. It was found that post-annealing in suitable conditions or introducing interstitial H atoms can shift the T M across a wide temperature range while retaining the strong metamagnetic behavior, and hence, retaining large magnetocaloric effect (MCE) and magnetoresistance (MR). The melt-spun technique can disorder atoms and make the ribbons display a B2 structure, but the metamagnetic behavior, as well as the MCE, becomes weak due to the enhanced saturated magnetization of martensites. We also studied the effect of Fe/Co co-doping in Ni 45 (Co 1−x Fe x ) 5 Mn 36.6 In 13.4 metamagnetic alloys. Introduction of Fe atoms can assist the conversion of the Mn-Mn coupling from antiferromagnetic to ferromagnetic, thus maintaining the strong metamagnetic behavior and large MCE and MR. Furthermore, a small thermal hysteresis but significant magnetic hysteresis was observed around T M in Ni 51 Mn 49−x In x metamagnetic systems, which must be related to different nucleation mechanisms of structural transition under different external perturbations.

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