Monte carlo simulation study on the dose and dose-averaged linear energy transfer distributions in carbon ion radiotherapy.

Dose-averaged linear energy transfer (LETd) is conventionally evaluated from the relative biological effectiveness (RBE)-LETd fitted function used in the treatment planning system. In this study, we calculated the physical doses and their linear energy transfer (LET) distributions for patterns of typical CIRT beams using Monte Carlo (MC) simulation. The LETd was then deduced from the MC simulation and compared with that obtained from the conventional method. The two types of LETd agreed well with each other, except around the distal end of the spread-out Bragg peak. Furthermore, an MC simulation was conducted with the material composition of water and realistic materials. The profiles of physical dose and LETd were in good agreement for both techniques. These results indicate that the previous studies to analyze the minimum LETd in CIRT cases are valid for practical situations, and the material composition conversion to water little affects the dose distribution in the irradiation field.

3D molecular network and magnetic ordering, formed by multi-dentate magnetic couplers, bis(benzene)chromium(i) and [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl.

The reaction between bis(benzene)chromium(0), Cr0(C6H6)2, and [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (abbreviated as TDTD) formed single crystals of the 1 : 1 salt, [CrI(C6H6)2]+[TDTD]-. The crystal structure of [Cr(C6H6)2][TDTD] belongs to the monoclinic P21/c space group, and involves a CdSO4-type network (or quartz dual net), which is formed by CHN hydrogen bonds between [Cr(C6H6)2]+ (S = 1/2) and [TDTD]- (S = 1/2). In addition to this network, the two components form an alternating chain crystal with a π-π overlap along the [110] and [11[combining macron]0] directions. The theoretical calculations for the pairwise intermolecular magnetic exchange interactions in [Cr(C6H6)2][TDTD] reveal the presence of 3D interactions, ranging from an antiferromagnetic interaction of -8.96 cm-1 to a ferromagnetic one of 1.70 cm-1. The temperature dependence of the paramagnetic susceptibility χp indicates the dominance of an antiferromagnetic interaction with a negative Weiss constant of -4.8 K and a magnetic ordering at 8 K, which can be characterized in terms of weak ferromagnetism.