End of bombardment

For comparison, all the radiochemical yields (RCY) of labelled compounds are expressed in percentages from the cyclotron-produced labelled precursor. They are decay corrected from the end of bombardment (BOB) except when stated. 

Please notice Footnote 3 of Table 1 regarding the stereochemistry. BOB, end of bombardment EOS, end of synthesis. 

I. The yields and purity were determined by gamma spectroscopy. Iron-52 from the nickel target contains a trace of 44.6-d Fe-59 impurity (average 0.33% at end of bombardment). The 2.7-y Fe-55 impurity, which emits 5.9-keV (24.3%) and 6.5-keV (3.3%) x-rays and no gamma rays, is determined by means of a high-resolution Si(Li) x-ray detector or thin window Ge detector. It amounts to... 

No iron breakthrough was observed from these elutions. Utilizing the Fe-59 impurity, breakthrough was checked up to five days after end of bombardment, long past the useful life of the generator. There was still no detectable iron breakthrough. 

Listed in Table I are the results of nine production runs for strontium. Targets ranging in mass from 64 to 457 grams have been irradiated with production as high as 28 Ci at end-of-bombardment... 

Table IV is a similar compilation of the parameters in an Fe-52 production run. Five nickel disks, weighing 34.7 grams were irradiated for 17.2 hours using aluminum spacers. A total of 1102 mCi of Fe-52 was produced, corrected to end of bombardment (EOB), with 1067 mCi (EOB) recovered for an overall yield of 97%. Also recovered in this procedure was 5.6 mCi of Fe-59.

Consider the reaction 29Si(180, p2n) which populates the metastable and ground states of 44Sc. Using the decay scheme shown below, and the fact that at end of bombardment (EOB) one observed 1000 photons/second of energy 271.2 keV and 1000 photons/second of energy 1157.0 keV, calculate the ratio of the cross... 

To monitor tumor response to capecitabine therapy noninvasively, Zheng and co-workers, from the Indiana University School of Medicine, developed the synthesis of the fluorine- 18-labeled capecitabine as a potential radiotracer for positron emission tomography (PET) imaging of tumors.28 Cytosine (20) was nitrated at the C-5 position with nitric acid in concentrated sulfuric acid at 85°C, followed by neutralization to provide 5-nitrocytosine (27) in moderate yield. This nitro pyrimidine was then carried through the glycosylation and carbamate formation steps, as shown in the Scheme below, to provide the 6/s-protected 5-nitro cytidine 28 in 47% for the three-step process. Precursor 28 was then labeled by nucleophilic substitution with a complex of 18F-labeled potassium fluoride with cryptand Kryptofix 222 in DMSO at 150 °C to provide the fluorine-18-labe led adduct. This intermediate was not isolated, but semi-purified and deprotected with aqueous NaOH in methanol to provide [l8F]-capecitabine in 20-30% radiochemical yield for the 3-mg-scale process. The synthesis time for fluorine-18 labeled capecitabine (including HPLC purification) from end of bombardment to produce KI8F to the final formulation of [18F]-1 for in vivo studies was 60-70 min. 

The sample being analyzed in this experiment contains fissionable material that had been sealed in a quartz tube and irradiated with neutrons. The material was dissolved in strong mineral acid to prepare it for radiochemical analysis of fission products. You will be informed of the date and time of the end of bombardment (EOB), the type of material, the amount of fissionable material in your sample, and the acid type and strength. You can assume that the person who prepared the sample based the amount of fissile material to be irradiated and the period of irradiation on the available neutron flux and the desired amounts of fission product radionuclides. You should estimate the activities of the major fission products that remain after the time interval between formation and analysis. 

Determine the number of atoms at the end of bombardment for any given radionuclide, i, from its gamma rays observed corrected for branching ratio values and the counting efficiency of that gamma ray by Eq. 18.1. 

At the end of bombardment, the Faraday cup rod was removed and the catcher foil torn off. The foil was dissolved in a few drops of 8 M hydrochloric acid containing a little nitric... 

The gas Inlet and outlet were so arranged that the gas could leave only by passing through the absorbing material. By this technique, nitrogen and neon activities were easily separated from the carbon activities by pumping off. Measurements for the carbon activities could be started within a fraction of a second after the end of bombardment. 

To remove Ra from Th targets, the usual method of co-pptn. with BaCla Is used. The target Is dissolved In HC1 (with ammonium fluoelllcate catalyst added), the soln. Is saturated with HC1 gas and cooled In Ice, and the BaCls ppt. Is brought down within -10 min after the end of bombardment. The pptn. Is made from about 10 ml of HC1 using about 1 mg of Ba carrier. 

This potent acetylcholineesterase inhibitor261 274 has been obtained262 by methyla-tion of tetrahydroacridine with [nC]methyl iodide after deprotonation by sodium hydride in DMSO at 100 °C in 45 min total synthesis time from end of bombardment (EOB) (equation 109). 

The fact that mica (and fused silica) can serve as solid state track detector (SSTD) of fission fragments was reported shortly before the final stage of development of the method for element 104 [12-14], In the dielectric solids, fission fragments produce tiny tracks visible by electron microscopy. Mica and silica are very resistant to active chemical reagents and elevated temperatures. The tracks proved to stay in hostile conditions of real experiments for a reasonably long time. Thanks to this, after the end of bombardment (EOB), the mica sheets could be etched with hydrofluoric acid to enlarge the tracks to micrometer size they were distinct in appearance and were searched out by scanning the surface of the detectors with an... 

What are the chemical forms of 18F that are obtained at the end of bombardment to be used for further chemical synthesis ... 

We assume that irradiation is carried out by a homogeneous particle flux in a neutron reactor. The minimum amount of an element which can be detected increases with the efficiency of the measuring apparatus the bombarding flux the reaction cross-section ff, the irradiation time (up to saturation activity), the decay constant, X, of the radioactive nuclide formed, and the time from end of bombardment to start of counting, fcooi- y proper selection of t- and the sensitivity for any element can be changed and... 

Figure 6 a Chemical composition of raw source, as determined by HPLC separation the count rate corrected for decay to the end of bombardment b Chemical composition of purined source, as determined by HPLC separation the count rate corrected for decay to the end of bombardment,... 

The mathematical relationship expressed in (8) shows that the amount of induced radioactivity, and therefore the sensitivity of measurement, is influenced by factors that are constant for a particular isotope (i.e., its activation cross section and the decay constant of the induced radionuclide species). Likewise, variable factors that are controlled by the experimenter—that is, length of bombardment time the elapsed time from end of bombardment to the time of radioactivity measurement (the decay period) sample weight and the method of measuring the radioactivity—also influence the sensitivity of the activation analysis method for a given element. 

Berkeley cyclotron for several months prior to shipping the plate to Segre s group in Italy in late December, 1936. Perrier and Segre began their radiochemical studies in late January, more than 6 weeks after the end of bombardment. On the surface exposed to the deuterons, they found strong activity, chiefly due to very slow electrons ascribed to more than one substance of a half-value period of some months in addition to (which they could not explain, but did not attribute to reactions with molybdenum). 

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