Utilization of thermal neutron induced in-situ chain reactions and the (n,p) reaction with fast neutrons for compositional characterization of lithium titanate

A methodology has been developed for the complete compositional characterization of lithium titanate (LTO) using neutron activation, which is quite challenging and no literature report is available so far. The concept of thermal neutron induced in-situ chain reactions ⁶Li(n,α)³H and ¹⁶O(³H,n)¹⁸F has been used for the determination of Li and O through the measurement of ¹⁸F activity. The method is capable of analyzing Li and O in percentage level as reported in the present analysis of two types of lithium titanate samples. Spectroscopic interference of the elements which can directly or indirectly affect the outcome, were evaluated meticulously. Determination of Ti was carried out using fast neutron activation through the product isotopes like ⁴⁷Sc, ⁴⁸Sc, generated via (n,p) nuclear reactions. Fast neutron activation methodology seems to be advantageous for Ti determination over thermal neutron activation, as it offers self validation through different isotopes and multiple gamma lines.

Evaluating the dependency of neutron spectra and absorbed dose rates on the collimation field size in fast neutron therapy

The aim of this research was to investigate the relationship between the collimator aperture and fast-neutron flux, neutron-energy spectrum and absorbed dose rate. For remote therapy, rather large fluxes of fast neutrons are needed which can create dose levels in the tissues of at least 0.1 Gy/min with a source-patient distance of 1 m. Advantageously for these purposes, the ⁹Be(d, n) reaction was investigated with deuteron energy of 13.6 MeV. The mean energy of the outgoing neutrons was obtained using the code PACE 4 (LISE++) which gave the value of about 5.2 MeV. The maximum neutron flux was at an energy of about 2.5 MeV. Samples activation analysis was deployed to measure the neutron flux in the energy-region [0–14 MeV]. The experimental works were carried out using Al, Fe, Cu and Cd foils which installed on the collimator apertures. To investigate the neutron spectrum, fluxes, and dose rates absorbed at the position of patients, experiments were conducted for four different neutron irradiation-field sizes, which can be modified by the removable-polyethylene parts. Simulation results obtained by the code MCNP-4C and PACE4 (LISE++) were comparable with the experimental data to some extent with consideration of some uncertainties of PACE4 results. It can be concluded that the neutron flux is depended on the irradiation-field size where the neutron flux output for bigger aperture size was about +25% comparing with the smaller ones. These results could play a significant role in improving the neutron flux and optimizing the collimation system utilized in fast neutron therapy. In addition, this can lead to optimization of irradiation canals installed in the nuclear reactors which employed for production of medical isotopes, material testing and many other applications.

[Results of surgical and radiotherapeutic treatment of adenoid cystic carcinoma of the salivary glands]

Surgical treatment in patients with rare adenoid cystic carcinoma (ACC) of the salivary glands is considered to be the state of the art. With respect to an additional radiotherapy there are different approaches regarding the type of radiotherapy and timing. In this study the overall survival and recurrence-free survival in 52 individuals with salivary gland ACC who were treated at the University Hospital in Essen and received irradiation with fast neutrons and photons (mixed beam technique) either A) immediately following surgical treatment or B) only after the appearance of local recurrence were compared. Group A (n = 28, first diagnosis, FD September 1991-September 2009) received adjuvant radiotherapy immediately postoperative, group B (n = 24, FD June 1979-November 2001) underwent primarily surgical tumor resection according to the treatment regimen at that time and were irradiated only on the appearance of a local recurrence. In comparison to group B, patients in group A showed a lower recurrence rate and a significantly longer local relapse-free survival. Group B, however, showed a significantly higher overall survival. The frequency of distant metastasis occurred equally in both groups but the onset of distant metastasis was significantly earlier in group A. In general, overall survival was negatively influenced by distant metastasis. The local recurrence rate was very high after primary surgical treatment only. The immediate adjuvant high-linear energy transfer (LET) radiotherapy reduced the local recurrence rates. Irradiation after the appearance of a recurrence had a positive influence on overall survival. Overall, definitive high-LET radiotherapy in the mixed beam technique enabled high local control rates both primarily postoperative and also locoregional recurrences.

Identification and characterization of a fast-neutron-induced mutant with elevated seed protein content in soybean

KEY MESSAGE

Protein content of soybean is critical for utility of soybean meal. A fast-neutron-induced deletion on chromosome 12 was found to be associated with increased protein content. Soybean seed composition affects the utility of soybean, and improving seed composition is an essential breeding goal. Fast neutron radiation introduces genomic mutations resulting in novel variation for traits of interest. Two elite soybean lines were irradiated with fast neutrons and screened for altered seed composition. Twenty-three lines with altered protein, oil, or sucrose content were selected based on near-infrared spectroscopy data from five environments and yield tested at five locations. Mutants with significantly increased protein averaged 19.1-36.8 g kg-1 more protein than the parents across 10 environments. Comparative genomic hybridization (CGH) identified putative mutations in a mutant, G15FN-12, that has 36.8 g kg-1 higher protein than the parent genotype, and whole genome sequencing (WGS) of the mutant has confirmed these mutations. An F2:3 population was developed from G15FN-12 to determine association between genomic changes and increased protein content. Bulked segregant analysis of the population using the SoySNP50K BeadChip identified a CGH- and WGS-confirmed deletion on chromosome 12 to be responsible for elevated protein content. The population was genotyped using a KASP marker designed at the mutation region, and significant association (P < 0.0001) between the deletion on chromosome 12 and elevated protein content was observed and confirmed in the F3:4 generation. The F2 segregants homozygous for the deletion averaged 27 g kg-1 higher seed protein and 8 g kg-1 lower oil than homozygous wild-type segregants. Mutants with altered seed composition are a new resource for gene function studies and provide elite materials for genetic improvement of seed composition.

Tagging fast neutrons from a 252Cf fission-fragment source

Coincidence and time-of-flight measurement techniques are employed to tag fission neutrons emitted from a ²⁵²Cf source sealed on one side with a very thin layer of Au. The source is positioned within a gaseous ⁴He scintillator detector. Together with α particles, both light and heavy fission fragments pass through the thin layer of Au and are detected. The fragments enable the corresponding fission neutrons, which are detected in a NE-213 liquid-scintillator detector, to be tagged. The resulting continuous polychromatic beam of tagged neutrons has an energy dependence that agrees qualitatively with expectations. We anticipate that this technique will provide a cost-effective means for the characterization of neutron-detector efficiency in the energy range 1-6MeV.

Effect of irradiation of wheat grains with fast neutrons on the grain yield and other characteristics of the plants

The effects of fast neutrons from a (252)Cf source in the fluence range 10(5)-10(8)n/cm(2) on the Egyptian wheat cultivar (Sakha 92) were studied. The experiment was conducted for three successive seasons (2008/2009, 2009/2010, and 2010/2011) to study the effect of the irradiation on the plant growth, grain yield, and physiological changes of three generations of plants produced by irradiated moisturized grains. A low fast-neutron fluence 2 × 10(6)n/cm(2) increased the yield throughout the three mutagenic generations considerably. It also increased concentrations of the total chlorophyll, sugars, and crude protein. These changes improve the quantity and quality of the grain. Also, a study of the effect of salinity of the irrigation water on the characteristics of the third-generation grains produced by neutron-irradiated grains was performed. With increasing concentration of sodium chloride in the irrigation water in the range 0.5-1.5%, concentrations of osmoprotectants, namely, reducing sugars and proline amino acids, increased. The concentration of Na(+) in the grains increased in parallel with the salinity of the irrigation water regardless of irradiation, while the concentrations of Ca(2+) and K(+) decreased.