Russellhaas5125

A compact D-D fast neutron generator system was developed with an emphasis on imaging applications. It is equipped with an electron cyclotron resonance microwave ion source, an electric field method electron suppression electrode, and a rotating beam target. The design, mechanical assembling, and initial performance of the system is presented in this work. Electrostatics and charged particle tracing simulations were employed to dimension components in the vacuum system and estimate the size of the ion beam spot on the target surface. Stable operation of the neutron generator was possible with accelerating potentials of up to -120 kV and an estimated averaged ion beam current of around 0.5 mA. At these conditions, the neutron yield was estimated to 6 ⋅ 107 s-1 based on a combination of detailed Monte Carlo MCNP6 models and the ambient dose rate reading of an LB6411 neutron probe. The neutron emitting spot size was compared to the ion beam spot size and experimentally determined with an attenuating edge technique to be between 1.7 and 2.6 mm. With these neutron yield and emitting spot size values, the system compares favorably with commercially available neutron generators, and this context is also presented.Neutron capture therapy (NCT) is a radiotherapeutic technique that is designed to utilize the neutron capture reaction and damage the tumor cells through the energy release from the reaction. Nuclear reactors are typically utilized in this therapy because of the high neutron fluence rate that can be achieved. There has been minimal work to evaluate the effectiveness of neutron generators in NCT. check details This work presents the preliminary simulation results of utilizing of a deuterium-deuterium generator in boron neutron capture therapy. MCNP 6.1 was used to model the detailed geometry of the neutron generator and the phantom. Neutron moderators and photon shielding were used to optimize the neutron fluence rate in the tumor and decrease the photon dose in the phantom respectively. The study showed that a good localization of the neutron dose can be achieved in the tumor area with a reduction of the photon dose in the surrounding areas.To address the issue of eye lens dosimetry in nuclear industry, we initiated the project to quantify the beta and gamma-ray source term in CANDU power plants and to convert this source term into dosimetric quantities of interest, such as eye lens dose and personal dose equivalents Hp(10), Hp(0.07). This way, the eye lens dose can be compared with dosimetric operational quantities to evaluate whether independent dosimetry is required for eye lens protection, or present dosimetry is adequate.The measurement of material level change in uranium fluorination has an essential influence on uranium production quality. In this study, a method to determine the level change of uranium fluorination mixture in the hopper by online radiation meter outside hopper is established. We have designed an experiment to study the change of radiation field outside the hopper with a known height of radioactive material to discover its regular pattern. The experimental results show that when the probe is placed 50 mm away from the cylinder wall, the average radiation dose is more significant, and the change of radiation dose measured by the instrument at this position is more evident than that at other positions. Then through the measurement of the external radiation field of the hopper with unknown material level to estimate the material level, and by opening the cover of hopper to verify the accuracy of the material level measurement method. Based on the experimental results and theoretical analysis, a method and formula for judging the mixture material are proposed. This method can quickly determine the level of uranium fluoride mixture in the hopper online, realize the accurate control of material parameters in the process of uranium conversion, and improve the quality of uranium conversion products.For the hafnium element, the cross sections of 179Hf(γ,γ')179mHf and natHf(γ,x)179mHf reactions were measured at 8 MeV and 15 MeV bremsstrahlung end point energies respectively using activation method and off-line gamma-ray spectroscopy. The bremsstrahlung radiation spectra were generated by bombarding a 0.1 mm tungsten target with 8 MeV and 15 MeV electrons at 5 μA beam current and also theoretically simulated by GEANT4 computer code. The flux weighted average cross sections of 179Hf (γ,γ')179mHf and natHf(γ,x)179mHf reactions were measured by using 115In(γ,γ')115mIn and 197Au(γ,n)196Au as flux monitor reactions at 8 MeV and 15 MeV bremsstrahlung radiation respectively. The measured cross sections are found close to the corresponding theoretical cross sections estimated by TALYS 1.95 and TENDL 2019 computer codes. These hafnium cross sections at 8 MeV and 15 MeV bremsstrahlung radiation will be new additions to the EXFOR library, as so far not reported in literature.

We investigated whether nanopore amplicon sequencing of aqueous humor was capable of rapid pathogen identification in infectious endophthalmitis.

5 cases of culture-positive bacterial endophthalmitis and 3 cases of fungal endophthalmitis (1 culture-positive and 2 presumed) were included. DNA was extracted from the aqueous humor and vitreous specimen, and PCR of bacterial rDNA (16S) and fungal rDNA (ITS1 and D1/2/3) was performed. Then, nanopore amplicon sequencing was performed for 2 h. The results of amplicon sequencing were compared to those of conventional culture studies.

In all cases, pathogens were identified by amplicon sequencing of aqueous humor specimens. In 3 cases of bacterial endophthalmitis, the identified microbes were confirmed by culture studies of both aqueous humor and vitreous specimens. In 2 cases of bacterial and 1 case of fungal endophthalmitis, the identified pathogens were confirmed only by culture studies of vitreous specimens. In all cases, amplicon sequencing identified pathogen in a shorter turnaround time than culture studies. In 2 cases with negative culture results, amplicon sequencing of aqueous humor identified fungal pathogens.

Our data demonstrates the potential of amplicon nanopore sequencing using aqueous humor to enable rapid, sensitive and less invasive microbial diagnosis of endophthalmitis.

Our data demonstrates the potential of amplicon nanopore sequencing using aqueous humor to enable rapid, sensitive and less invasive microbial diagnosis of endophthalmitis.