Reductive Activation of N2 using a Calcium/Potassium Bimetallic System Supported by an Extremely Bulky Diamide Ligand

An extremely bulky xanthene bridged diamide ligand (TCHPNON = 4,5-bis(2,4,6-tricyclohexylanilido)-2,7-diethyl-9,9-dimethyl-xanthene) has been developed and used to prepare two monomeric diamido-calcium complexes [(TCHPNON)Ca(D)n] (D = THF, n = 2, 3; D = toluene, n = 1, 4). Reduction of 4 with 5% w/w K/KI under an N2 atmosphere gave the first well-defined, anionic s-block complex of activated dinitrogen, [{K(TCHPNON)Ca}2(-2:2-N2)] 5, presumably via a transient calcium(I) intermediate

Direct and Bystander Effect on Cervix Cancer Cells (SiHa) Exposed to High Dose-Rate Gamma Radiation Sourced from Ir 192 Used in Brachytherapy

Introduction: Brachytherapy is a preferred choice of radiotherapy in the treatment of sensitive tissues&nbsp; cancer&nbsp; like&nbsp; intestine&nbsp; and&nbsp; gonad.&nbsp; The&nbsp; treatment&nbsp; is&nbsp; expensive&nbsp; because&nbsp; of&nbsp; the&nbsp; frequent replacement of radionuclide sources. A better understanding of cell killing and the cellular responses at&nbsp; different&nbsp; dose&nbsp; rates,&nbsp; might&nbsp; aid&nbsp; in tumor&nbsp; cell&nbsp; killing&nbsp; with&nbsp; fewer&nbsp; doses&nbsp; thereby&nbsp; enhancing&nbsp; a&nbsp; better prognosis. Methods: The cervix cancer cell line was irradiated with doses ranging from 2Gy-10 Gy at three different dose-rates as used in brachytherapy along with unexposed sample as control. The biological effects&nbsp; of&nbsp; different&nbsp; doses&nbsp; and&nbsp; dose&nbsp; rate&nbsp; of&nbsp; the&nbsp; cells&nbsp; was&nbsp; assessed&nbsp; by&nbsp; measuring&nbsp; its&nbsp; cytotoxicity,genotoxicity&nbsp; and&nbsp; clonogenic&nbsp; ability&nbsp; of&nbsp; exposed&nbsp; cells.&nbsp; The&nbsp; bystander&nbsp; effect&nbsp; was&nbsp; examined&nbsp; by&nbsp; co-culturing the exposed tumor cells with the unexposed normal blood lymphocyte and vice-versa.&nbsp;Results: A significant and dose dependent changes in cell viability (trypan blue exclusion), genotoxicity (Micronucleus assay) and colony forming ability (Clonogenic assay) was observed in the cells exposed to different doses of radiation (p&lt;0.0001); however, the changes were dose-rate independent.urthermore,&nbsp; the&nbsp; bystander&nbsp; study&nbsp; results&nbsp; show&nbsp; an&nbsp; enhanced&nbsp; cell&nbsp; killing&nbsp; in&nbsp; the&nbsp; tumor cells which suggest a beneficial bystander effects.Conclusion: The observed elevated bystander response in the tumour cells compared to that of normal blood lymphocytes suggest that if it happens under in-vivo situation, could results in has a therapeutic gain.</p

Dosimetric evaluation of a three-dimensional treatment planning system

The computerized treatment planning system plays a major role in radiation therapy in delivering correct radiation dose to the patients within ±5% as recommended by the ICRU. To evaluate the dosimetric performance of the Treatment Planning system (TPS) with three-dimensional dose calculation algorithm using the basic beam data measured for 6 MV X-rays. Eleven numbers of test cases were created according to the Technical Report Series-430 (TRS 430) and are used to evaluate the TPS in a homogeneous water phantom. These cases involve simple field arrangements as well as the presence of a low-density material in the beam to resemble an air in-homogeneity. Absolute dose measurements were performed for the each case with the MU calculation given by the TPS, and the measured dose is compared with the corresponding TPS calculated dose values. The result yields a percentage difference maximum of 2.38% for all simple test cases. For complex test cases in the presence of in-homogeneity, beam modifiers or beam modifiers with asymmetric fields a maximum percentage difference of 5.94% was observed. This study ensures that the dosimetric calculations performed by the TPS are within the accuracy of ±5% which is very much warranted in patient dose delivery. The test procedures are simple, not only during the installation of TPS, but also repeated at periodic intervals