Irradiated targets, treatment

Weik and Rademann have described the use of phosphoranes as polymer-bound acylation equivalents [65]. The authors chose a norstatine isostere as a synthetic target and employed classical polymer-bound triphenylphosphine in their studies (Scheme 7.54). Initial alkylation of the polymer-supported reagent was achieved with bromoacetonitrile under microwave irradiation. Simple treatment with triethyl-amine transformed the polymer-bound phosphonium salt into the corresponding stable phosphorane, which could be efficiently coupled with various protected amino acids. In this acylation step, the exclusion of water was crucial. 

Treatment of irradiated targets. The chemical operations relative to the production of transplutonium elements (americium 243, curium 244) are all performed using a nitric acid medium. The highly corrosive nature of the solutions concentrated with Cl" ions, which were used in the USA for the development of the Tramex process (JO, and the instability of SCN" ions to radiation (12), led us to select nitric acid solution to perform the chemical separations. Once the medium was selected, it was necessary to find an adequate additive which, in combination with a suitable extractant, would allow solution of the main problem namely separation of the trivalent actinides from triva-lent lanthanides. 

The treatment scheme for the first irradiated targets (8) was based on the TLAHNO-/DTPA system implemented by liquid-liquid extraction. After dissolution of the Pu/Al targets by nitric acid, the solution was adjusted to low acidity by addition of Al(NO-)-. (OH) and then countercurrently contacted with an organic isoiution of the composition 0.64 M TLA.HNO- in dodecane containing 3 vol % 2-octanol. The co-extracted elements are then separated by selective stripping as follows ... 

All the separation methods mentioned in this article, and, in general, the. chemical treatment, can be equally well applied to targets which have been irradiated with other particles, for example in a linear accelerator or cyclotron. 

Members of the phosphoinositide (PI)-3 kinase family appear to be involved in the phosphorylation of H2A.X. The SQ motif matches a common target site for these kinases and the formation of y-H2A.X in response to double stranded breaks is inhibited by wortmannin, an inhibitor of PI-3 kinases [63]. Examination of cell lines deficient in the PI-3 kinase ATM indicated that it has a major role in phosphorylating H2A.X in response to double strand breaks [64]. ATM can phosphorylate H2A.X in vitro suggesting that it may directly phosphorylate H2A.X in vivo [64]. Another PI-3 kinase ATR appears to be involved in phosphorylating H2A.X in response to replicational stress induced by treatment of dividing cells with hydroxyurea or by irradiating them with ultraviolet light [65]. It has been hypothesized that PI-3 kinases such as ATM are recruited to, or activated at, the site of the double stranded break and then phosphorylate H2A.X molecules around the break point [40,64,66]. 

The first cyclotron was built by Ernest O. Lawrence in 1932, and since 1938, cyclotrons have been used for patient treatment. In Berkeley, in 1954, the first human target irradiated with protons was the pituitary gland with the aim to suppress its function for slowing down the metastatic development of breast cancer. 

This paper describes a new reaction which may yield useful amounts of the product isotope following neutron capture by lanthanide or actinide elements. The trivalent target ion is exchanged into Linde X or Y zeolite, fixed in the structure by appropriate heat treatment, and irradiated in a nuclear realtor. The (n, y) product isotope, one mass unit heavier than the target, is ejected from its exchange site location by y recoil. It may then be selectively eluted from the zeolite. The reaction has been demonstrated with several rare earths, and with americium and curium. Products typically contain about 50% of the neutron capture isotope, accompanied by about 1% of the target isotope. The effect of experimental variables on enrichment is discussed. 

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