The cross sections of the reactions 14 N(n, α) 11 B and 14 N(n, t) 12 C have been measured for neutron energies 5. 46-7.2 MeV. The neutrons are generated in the reaction D(d, n) on a solid titanium target. The work employs digital spectrometry. The charged-particle detector is a pulsed ionization chamber with a Frisch grid, filled with a kyrpton-nitrogen mixture. The cross sections are measured for four groups of α particles α 0 , α 1 , α 2 , and α 3 from the reaction 14 N(n, α) 11 B and for tritium from the reaction 14 N(n, t) 12 C. The energy resolution of the spectrometer was 60 keV. The errors in determining the cross sections for the reactions (n, α) and (n, t) are 10-15%. The measurement results are compared with the ENDF/V VI evaluation. Good agreement is obtained in the neutron energy range 5.45-6.5 MeV. At higher energies, the discrepancy reaches 30%.One variant of nuclear fuel for advanced reactors is nitride fuel. Considering the high nitrogen content in a reactor core, it is useful to analyze nuclear data for the reactions where neutrons interact with 14 N nuclei.The analysis showed that there is a large spread in the experimental data for the cross sections of the reactions which are the main sources of helium and tritium production, respectively: 14 N(n, α) 11 B and 14 N(n, t) 12 C. In turn, information about the helium content of materials is necessary to estimate their radiation resistance. Data on tritium are important for radiation predictions.The reaction where nitrogen is split by fast neutrons 14 N(n, α) 11 B can proceed via several channels with conversion of the residual nucleus 11 B into the ground state (α 0 ) or excited states (α i ) (see Table 1). Both reactions are endothermal.The latest investigations of these reactions were performed in the 1980s. In [1], an ionization chamber with a Frisch grid was used to detect charged particles. The chamber was filled with nitrogen or a mixture of nitrogen and argon. The investigations were performed in the neutron energy range 1.3-8.2 MeV. The neutron flux was monitored with an omniwave counter, and its absolute value was determined using the standard Ra-Be neutron source. The cross sections for all channels of the reaction were obtained in the work: α 0 , α 1 , α 2 , α 3 , and t. The authors estimated the error of the total cross section measurements to be 30% for the reaction 14 N(n, α) 11 B and 40% for the channels α 2 , α 3 , and t. The weak aspect of the experiment is the fact that the neutron flux was not determined with adequate accuracy.The measurement method used in [2] differed by the calibration of the neutron flux. The monitor consisted of an omniwave counter and two organic scintillators. The neutron detector was calibrated using the well-known cross section of the reaction 6 Li(n, α) 3 H with neutron energy 2.48 MeV. The energy range of the investigations was 4-6.4 MeV. The cross section of the reaction channels α 0 , α 1 , and t was measured with error 15-20% for channel α 0 and 30% for the channels α 1 and t. A drawback of th...
The alternating cyclocopolymer of maleic anhydride with divinyl ether (MADVE) hydrolyzate, as mimicker of furan related and anionic residues alternation in nucleic acids (NA) backbone, is immune stimulating agonist and competitive antagonist for viral genome NA interventions. The targeted pre‐modification of MADVE by antiviral vectors via grafting to the MA anhydride residues before hydrolysis led to more potent and promising antiviral inhibitors. To develop the MADVE capacity for novel modifications we applied the reversible addition – fragmentation chain transfer (RAFT) technique using dibenzyl trithiocarbonate as a RAFT agent. The insertion of trithiocarbonate unit in polymeric chain provided a pseudo living RAFT‐polymerization, resulting in: 1) the effective control of polymerization degree (increased with time and conversion), and 2) the narrow dispersive (PDI = 1.1–1.2) products MADVE‐S‐CS‐S‐MADVE yield. These products can be used as novel polymeric RAFT‐agents for synthesis of new block‐copolymers MADVE‐(block)‐CS3‐(block)‐MADVE, for instance with polystyrene blocks. Combined together the RAFT‐ and graft‐ reactivity allows both modify the polymer backbone (RAFT‐synthesis) and regulate the side groups or branches (grafted to MADVE moieties) with final hydrolysis of unused anhydride units to acidic polyelectrolyte derivatives. This plural reactive capacity of the obtained macro reagents essentially enhances their potential as platform for purposed synthesis of novel (bio‐) functional polymeric compounds.
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