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An increase in hyperpolarized (HP) [1‐13C]lactate production has been suggested as a biomarker for cancer occurrence as well as for response monitoring of cancer treatment. Recently, the use of metformin has been suggested as an anticancer or adjuvant treatment. By regulating the cytosolic NAD+/NADH redox state, metformin stimulates lactate production and increases the HP [1‐13C]lactate conversion rate in the kidney, liver, and heart. In general, increased HP [1‐13C]lactate is regarded as a sign of cancer occurrence or tumor growth. Thus, the relationship between the tumor suppression effect of metformin and the change in metabolism monitored by HP [1‐13C]pyruvate MRS in cancer treatment needs to be investigated. The present study was performed using a brain metastasis animal model with MDA‐MB‐231(BR)‐Luc breast cancer cells. HP [1‐13C]pyruvate MRS, T2‐weighted MRI, and bioluminescence imaging were performed in groups treated with metformin or adjuvant metformin and radiation therapy. Metformin treatment alone did not display a tumor suppression effect, and the HP [1‐13C]lactate conversion rate increased. In radiation therapy, the HP [1‐13C]lactate conversion rate decreased with tumor suppression, with a p‐value of 0.028. In the adjuvant metformin and radiation treatment, the tumor suppression effect increased, with a p‐value of 0.001. However, the apparent HP [1‐13C]lactate conversion rate (Kpl) was observed to be offset by two opposite effects: a decrease on radiation therapy and an increase caused by metformin treatment. Although HP [1‐13C]pyruvate MRS could not evaluate the tumor suppression effect of adjuvant metformin and radiation therapy due to the offset phenomenon, metabolic changes following only metformin pre‐treatment could be monitored. Therefore, our results indicate that the interpretation of HP [1‐13C]pyruvate MRS for response monitoring of cancer treatment should be carried out with caution when metformin is used as an adjuvant cancer therapy. [ABSTRACT FROM AUTHOR]

Structural and magnetic characterizations have been performed on NiFe-FeMn exchange-biased bilayers grown by molecular beam epitaxy. The growth of the films showed high-quality epitaxy with well-defined flat interface between the layers. Magnetic measurements confirmed that the films showed not only a comparable exchange anisotropy field ([H.sub.ex]) to that of sputtered films but also a lowered threshold thickness of 2 nm at which [H.sub.ex] vanishes for the FeMn. Index Terms--Exchange anisotropy, magnetic characterization, molecular beam epitaxy, structural characterization.

Three-dimensional atom-probe tomography and transmission electron microscopy have been utilized to study the effects of Ta getter presputtering and either a Mg or Ru free-layer cap on the elemental distributions and properties of MgO-based magnetic tunnel junctions after annealing. Annealing the samples resulted in crystallization of the amorphous CoFeB layer and diffusion of the majority of the boron away from the crystallized CoFeB layers. The Ta getter presputter is found to reduce the segregation of boron at the MgO/CoFeB interface after annealing, improving the tunneling magnetoresistance of the tunnel junction. This effect is observed for samples with either a Ru free-layer cap or a Mg free-layer cap and is thought to be a result of a reduced oxygen concentration within the MgO due to the effect of Ta getter presputtering. A Ru free-layer cap provides superior magnetic and magnetotransport properties compared to a Mg free-layer cap. Mg from the Mg free-layer cap is observed to diffuse toward the MgO tunnel barrier upon annealing, degrading both the crystalline quality of the CoFeB and magnetic isolation of the CoFeB free-layer from the CoFeB reference-layer. Lateral variations in the B distribution within the CoFeB free-layer are observed in the samples with a Ru free-layer cap, which are associated with crystalline and amorphous grains. The B-rich, amorphous grains are found to be depleted in Fe, while the B-poor crystalline grains are slightly enriched in Fe. [ABSTRACT FROM AUTHOR]

The magnetic properties and the microstructures of the Mn-Ir/Ni-Fe multilayers with various stacking structures and buffer layer materials have been investigated. The (111) texture of Mn-Ir/Ni-Fe is obtained in the top structures with Ta or Zr buffer. However, all multilayers which contain Mn-Ir films deposited on Ni-Fe films exhibit high [H.sub.ex], regardless of the (111) preferred orientation of Mn-Ir film. The TS multilayers which show high [H.sub.ex] have large Mn-Ir grains at the interface, compared with BS multilayers without exchange anisotropy. The multilayers which reveal the exchange anisotropy also have the groin-to-grain epitaxial tendency at interface of Mn-Ir/Ni-Fe. It is concluded that the [H.sub.ex] is not related to the (111) texture of the Mn-Ir film, but related to the grain size of the Mn-Ir film and the morphology at the interface between the Mn-Ir and the Ni-Fe grains. Key word--Mn-Ir/Ni-Fe, stacking structure, buffer layer, (111) texture, [H.sub.ex], epitaxial tendency, the grain size of Mn-Ir