Assessment of organ and effective doses received by adult patients undergoing computed tomography in three hospitals in Brazzaville, Congo Republic.

The present study aimed to evaluate adult patient data collected from three hospitals in Brazzaville, Congo Republic, for the purpose of estimating organ and effective doses for each included examination type. A total of 1277 adult patients (aged 16-97 years) who underwent head, chest, abdominopelvic (AP), chest-abdomen-pelvis (CAP), and lumbar spine computed tomography scans were considered. The organ and effective doses were estimated using a Monte Carlo-based method. The effective doses were also determined using k-factors. In general, the organ and effective doses estimated in this study were higher than those reported in the literature. The k-factor method underestimated the effective dose by up to 65.9%. This study demonstrates that urgent steps should be taken to reduce doses administered to patients to optimal levels. Such optimal levels may be achieved by adopting local diagnostic reference levels, together with the implementation of dose reduction strategies.

ASSESSMENT OF MEASUREMENT UNCERTAINTY FOR THE MEASUREMENT OF THE QUANTITY PERSONAL DOSE EQUIVALENT HP (10) IN PHOTON FIELDS USING THE GUM FRAMEWORK AND THE MONTE CARLO METHODS: APPLICATION TO GABON RESULTS OBTAINED DURING THE 2018 IAEA REGIONAL INTERCOMPARISON EXERCISE.

This paper describes the essential of the "Guide to the expression of Uncertainty in Measurement" Framework (GUMF) Method and Monte Carlo Method (MCM) for propagating uncertainties, with an application to Gabon results obtained during the 2018 International Atomic Energy Agency (IAEA) regional intercomparison exercise. The work has shown that the output quantity Hp (10) follows a lognormal distribution. The study has also shown that although the normal distribution does not best approximate the distribution of the output quantity Hp (10), it has been observed that its estimate, the associated standard uncertainty and the coverage interval determined by GUMF and MCM were close, meaning that the application of the GUMF could still be seen as valid. Finally, the results obtained by the two methods are in agreement with International Commission on Radiological Protection and IAEA requirements for overall accuracy.

Charge transport in a DNA model with solvent interaction.

The charge transport in the modified DNA model is studied by taking into account the factor of solvent and the effect of coupling motions of nucleotides. We report on the presence of the modulational instability (MI) of a plane wave for charge migration in DNA and the generation of soliton-like excitations in DNA nucleotides. By applying the continuum approximation, we show that the original differential-difference equation for the DNA dynamics can be reduced to a set of three coupled nonlinear equations. The linear stability analysis of wave solutions of the coupled systems is performed and the growth rate of instability is found numerically. We also investigate the impact of solvent interaction. The solvent factor introduces a new behavior to the wave patterns, modifying also the intrinsic properties of localized structures. In the numerical simulations, we show that the solitons exists when taking into account the effect of solvent and confirms an highest propagation of localized structures in the systems. The effect of solvent forces introduces a robustness behavior to the formed patterns, reinforcing the idea that the information in the DNA model is confined and concentrated to specific regions for efficiency. We also show that the localized structures can be disappeared with the highest value of solvent factor and thereafter the information within the molecule is not perceptible or not transmitted to another sites.

Study of soil-fern transfer of naturally occurring alpha emitting radionuclides in the Southern Region of Cameroon.

This study was carried out in the localities Melondo and Ngombas located in the Southern Region of Cameroon where there are known to be uranium-bearing and high background radiation areas. Activity concentrations of naturally occurring radionuclides 210Po, 238U, 235U, 234U, 232Th, 230Th, 228Th and 226Ra were determined in soil and fern (filicophyta) samples collected at 10 points in both localities. In soil, the average values of these activity concentrations (in Bq.kg-1 d.w.) were 210Po(130 ± 10), 238U(126 ± 11.6), 235U(5 ± 1), 234U(131 ± 10), 232Th(400 ± 22), 230Th(145 ± 11), 228Th(381 ± 21) and 226Ra(154 ± 28) at Melondo; and 210Po(228 ± 1), 238U(170 ± 11), 235U(9 ± 2), 234U(179 ± 12), 232Th(200 ± 18), 230Th(184 ± 18), 228Th(228 ± 22) and 226Ra(416 ± 7) at Ngomba. In fern the average activity concentrations were: 210Po(35 ± 3), 238U(0.68 ± 0.05), 235U(0.042 ± 0.01), 234U(0.90 ± 0.05), 232Th(1.2 ± 0.2), 230Th(0.7 ± 0.1), 228Th(39 ± 3) and 226Ra(14 ± 3) at Melondo and 210Po(24 ± 2), 238U(0.82 ± 0.06), 235U(0.046 ± 0.01), 234U(0.92 ± 0.06), 232Th(0.8 ± 0.2), 230Th(0.9 ± 0.2), 228Th(15 ± 5) and 226Ra(14 ± 3) at Ngomba. The soil-fern transfer factors (TF) (in kg.kg-1) were respectively 210Po(1.64 × 10-1), 238U (5 × 10-3), 235U(7 × 10-3), 234U(6 × 10-3), 232Th(3 × 10-3), 230Th(5 × 10-3), 228Th(7.9 × 10-2), and 226Ra(5.1 × 10-2). The highest TF for fern was for 210Po, probably because of atmospheric deposition. The TFs of uranium and thorium were comparable to those given in the IAEA handbook for grass.

Charge transport in DNA model with vibrational and rotational coupling motions.

The dynamics of the Peyrard-Bishop model for vibrational motion of DNA dynamics, which has been extended by taking into account the rotational motion for the nucleotides (Silva et al., J. Biol. Phys. 34, 511-519, 2018) is studied. We report on the presence of the modulational instability (MI) of a plane wave for charge migration in DNA and the generation of soliton-like excitations in DNA nucleotides. We show that the original differential-difference equation for the DNA dynamics can be reduced in the continuum approximation to a set of three coupled nonlinear equations. The linear stability analysis of continuous wave solutions of the coupled systems is performed and the growth rate of instability is found numerically. Numerical simulations show the validity of the analytical approach with the generation of wave packets provided that the wave numbers fall in the instability domain.

Energy transport in the three coupled α-polypeptide chains of collagen molecule with long-range interactions effect.

The dynamics of three coupled α-polypeptide chains of a collagen molecule is investigated with the influence of power-law long-range exciton-exciton interactions. The continuum limit of the discrete equations reveal that the collagen dynamics is governed by a set of three coupled nonlinear Schrödinger equations, whose dispersive coefficient depends on the LRI parameter r. We construct the analytic symmetric and asymmetric (antisymmetric) soliton solutions, which match with the structural features of collagen related with the acupuncture channels. These solutions are used as initial conditions for the numerical simulations of the discrete equations, which reveal a coherent transport of energy in the molecule for r > 3. The results also indicate that the width of the solitons is a decreasing function of r, which help to stabilize the solitons propagating in the molecule. To confirm further the efficiency of energy transport in the molecule, the modulational instability of the system is performed and the numerical simulations show that the energy can flow from one polypeptide chain to another in the form of nonlinear waves.

Dynamics of kink, antikink, bright, generalized Jacobi elliptic function solutions of matter-wave condensates with time-dependent two- and three-body interactions.

By using the F-expansion method associated with four auxiliary equations, i.e., the Bernoulli equation, the Riccati equation, the Lenard equation, and the hyperbolic equation, we present exact explicit solutions describing the dynamics of matter-wave condensates with time-varying two- and three-body nonlinearities. Condensates are trapped in a harmonic potential and they exchange atoms with the thermal cloud. These solutions include the generalized Jacobi elliptic function solutions, hyperbolic function solutions, and trigonometric function solutions. In addition, we have also found rational function solutions. Solutions constructed here have many free parameters that can be used to manipulate and control some important features of the condensate, such as the position, width, velocity, acceleration, and homogeneous phase. The stability of the solutions is confirmed by their long-time numerical behavior.

Dynamics of matter-wave condensates with time-dependent two- and three-body interactions trapped by a linear potential in the presence of atom gain or loss.

Bose-Einstein condensates with time varying two- and three-body interatomic interactions, confined in a linear potential and exchanging atoms with the thermal cloud are investigated. Using the extended tanh-function method with an auxiliary equation, i.e., the Lenard equation, many exact solutions describing the dynamics of matter-wave condensates are derived. An important issue is the time management of the cubic and the quintic nonlinearities by tuning the rate of exchange of atoms between the condensate and the thermal background. In addition, adjusting the strength of the linear potential, the rate of exchange of atoms, and many other free parameters allow one to control many features of the condensate such as its height, width, position, velocity, acceleration, and its direction, respectively. Full numerical solutions corroborate the analytical predictions.

Transfer of ²³8U and ²³²Th from soil to plant in a high background radiation area of the southwestern region of Cameroon.

In order to estimate the soil-to-plant transfer factors (TFs) of some natural radionuclides, the activity of ²³8U and ²³²Th was measured in the soil and in agricultural crop samples collected from identified high background radiation areas in the southwestern region of Cameroon. The results showed that the ²³8U and ²³²Th TFs values were in the ranges 1.0×10⁻²-12.2×10⁻¹ kg kg⁻¹ and 5.0×10⁻²-9.7×10⁻¹ kg kg⁻¹, respectively. These computed TFs values were found to be globally higher than those proposed by the International Atomic Energy Agency.

Annual intakes of (226)Ra, (228)Ra and (40)K in staple foodstuffs from a high background radiation area in the southwest region of Cameroon.

Concentrations of naturally occurring radionuclides (226)Ra, (228)Ra and (40)K were determined in five most consumed vegetables in a high-level background radiation area (HLBRA) in the southwest region of Cameroon. A total of 25 foodstuff samples collected from Akongo, Ngombas, Awanda, Bikoué and Lolodorf rural districts were analyzed by gamma spectrometry. The average activity concentration values of (226)Ra, (228)Ra and (40)K were respectively 2.30, 1.50 and 140.40 Bq kg(-1) fresh-weights. The effective dose for individual consumption of the investigated foodstuff types was calculated on an estimated annual intake of such diets in the study area. The estimated total daily effective doses from the ingestion of the investigated foodstuffs for each studied long-life natural radionuclide were respectively 0.41 µSv for (226)Ra, 0.84 µSv for (228)Ra and 0.71 µSv for (40)K. The total annual effective dose was estimated at 0.70 mSv y(-1). (228)Ra (44%) and (40)K (36%) were found to be the main sources for internal irradiation which is very likely due to the specific uptake of these radionuclides by the studied plants.

High background radiation investigated by gamma spectrometry of the soil in the southwestern region of Cameroon.

The aim of this work is to determine the radioactivity concentration of (226)Ra, (232)Th and (40)K in sub-surface (0-5 cm) soil samples collected from Awanda, Bikoué, Ngombas in the southwestern region of Cameroon, to assess their contribution to the external dose exposure relative to the United Nation Scientific Committee on Effects of Atomic Radiation (UNSCEAR) data. An HPGe p-type detector coupled to a multichannel analyzer was used to perform measurements and data processing. The activity concentrations of (226)Ra varied from 0.06+/-0.01 to 0.27+/-0.02 kBq kg(-1) with a mean value of 0.13+/-0.01 kBq kg(-1) wet weight. The activity concentrations of (232)Th varied from 0.10+/-0.01 to 0.70+/-0.05 kBq kg(-1) with a mean value of 0.39+/-0.03 kBq kg(-1) wet weight, and (40)K concentrations varied from 0.37+/-0.02 to 1.53+/-0.11 kBq kg(-1) with a mean value of 0.85+/-0.07 kBq kg(-1) wet weight, respectively. The mean value of outdoor annual effective doses were estimated to be 0.48 mSv y(-1), 0.39 mSv y(-1) and 0.38 mSv y(-1) from Ngombas, Awanda and Bikoué, respectively. The studied areas can be said to have a high background radiation level.

Natural background dose measurements in south Cameroon.

The natural background doses due to (40)K, (226)Ra and (232)Th have been measured in soil samples collected from various sampling sites in the locality of Lolodorf, Cameroon. For data acquisition and analysis, a high-purity germanium detector and a PC-based MCA were used. The mean activity concentrations of (40)K, (226)Ra and (232)Th were measured to be 2001 +/- 521, 329 +/- 491 and 414 +/- 309 Bq kg(-1), respectively, in rock samples, while in soil samples the activity concentrations were found to be 1482 +/- 280 Bq kg(-1) for (40)K, 134 +/- 64 Bq kg(-1) for (226)Ra and 177 +/- 102 Bq kg(-1) for (232)Th. The average outdoor absorbed dose rates in air, 1 m above the ground surface due to soil samples, were estimated to be 218 +/- 61 and 250 +/- 97 nGy h(-1) in the locations of Ngombas and Bikoue, respectively. The corresponding annual effective dose rates in air were determined to be 0.267 mSv y(-1) in Ngombas and 0.307 mSv y(-1) in Bikoue. The level of radioactivity in the studied area is relatively high.