Hasil untuk "Radioactivity and radioactive substances"

Watila Lins Silva, Max Santos Ramos, Regio Santos Gomes et al.

This study presents a comparative analysis between Monte Carlo simulations (MCNP-5) and experimental measurements of thermal neutron fluence using gold foil activation at the TNF2 irradiation facility of the Neutron Metrology Laboratory (LNMRI/IRD). The MCNP-5 model was constructed to replicate the irradiator geometry and source configuration. Gold foils, both bare and cadmium-covered, were irradiated and analyzed via gamma spectrometry to determine the induced activity of 198Au. The results of the calculated nuclear reaction rates were compared to the measured activities through C/E (Calculated/Experimental) analysis. The findings show consistent agreement within experimental uncertainty, supporting the accuracy of the MCNP model and reinforcing the role of TNF2 in the national and international metrological infrastructure for neutron dosimetry. Future developments will include improvements in flux mapping and personal dosimetry applications.

Atsushi Hirano, Hidenori Kagamifuchi, Ken Koyabu et al.

Thomas C. L. Truemam, Andrés Yagüe López, Maria Lugaro et al.

Several short-lived radionuclides (SLRs) are know to have existed in the early Solar System (ESS). These species, which typically decay with half-lives of the order of a few million years, can be used to probe the timescale of events preceding the birth of the Sun. We investigate the ESS origin of $^{53}$Mn, produced by core-collapse (CCSNe) and Type Ia supernovae (SNe Ia), and $^{60}$Fe, produced exclusively by CCSNe. We model the evolution of the radioactive-to-stable abundance ratios of these SLRs with a galactic chemical evolution (GCE) framework accounting for different supernova yields, SN Ia delay times, and other galactic features $(K)$. A further set of models are calculated assuming that SN Ia did not contribute any $^{53}$Mn to the ESS. The predicted ratios are compared to meteoritic ratios to derive a distribution of solar isolation times that includes uncertainties due to stochastic chemical enrichment and precision of the ESS values. The isolation times are then compared to those of $^{107}$Pd and $^{182}$Hf calculated in previous work. A self-consistent solution can be found within the current uncertainties, especially when using the GCE setups with $K = 1.6$ and 2.3, although the maximum likelihood for the \iso{60}Fe distribution is typically $\sim 4-5$ Myr shorter than for \iso{53}Mn. The predicted \iso{60}Fe/\iso{53}Mn ratio, instead, is completely inconsistent with the ESS value; this could be resolved using a larger fraction of faint CCSNe than usually considered in GCE models.

V. Yu. Golikov, A. V. Vodovatov, D. D. Lavreshov

Based on the information regarding the parameters of routine radiographic procedures the values of the conversion coefficients to the effective dose in patients of different weights were calculated. The numerical values of the conversion coefficients correspond to the effective dose values during a given radiographic examination, which is completely determined by a set of technical, geometric, and dosimetric parameters normalized to the absorbed dose value in the air at a distance of 1 m from the tube focus (Ke, μSv/mGy)), or to the dose-area product value measured during the examination (Kd, μSv/(cGy cm2)). t is shown that the Ke factors have a greater relative spread of their values than the Kd factors. Within each weight group of patients, the Kd factor value for a patient of standard weight can be converted to the value for a patient of different weight. Furthermore, extrapolation of the calculated Kd values to infant weights well below 2.6 kg (down to 0.6 kg), i.e. for premature infants, yields satisfactory estimates of the Kd value.

Camila Sampaio Nogueira, Rodrigo Sanas Zamboni, Sergei Anatolyevich Paschuk et al.

Facial foundations play a significant role in beauty routines. However, the presence of heavy metals and toxic elements in cosmetics is a concern due to potential health risks. This study investigated the chemical composition of 52 facial foundation samples obtained in Curitiba and São Paulo, Brazil, using X-ray fluorescence for elemental identification. Quantification was performed using the standard addition method and calibration curves. The results indicated the presence of Cu, Zn, Br, Zr, and Ba in concentrations exceeding the limits established by the Brazilian Health Regulatory Agency (ANVISA). Cd and Ni, elements prohibited in cosmetic formulations, exhibited maximum concentrations of 277 ± 51 µg/g and 130 ± 10 µg/g, respectively. The highest concentration of Zr reached 589 ± 57 µg/g, approximately six times the regulatory limit. In contrast, Ba concentrations exceeded 14,000 µg/g, approximately 60 times the limit, with the highest concentration recorded at 30,867 ± 1,500 µg/g. These findings underscore the need for rigorous monitoring of cosmetic products in Brazil and highlight discrepancies between the marketed cosmetics and ANVISA regulations. Additionally, this study contributes to the growing knowledge regarding potentially harmful elements in facial foundations.

Tuğba Hacıosmanoğlu

Radiopharmaceuticals are used in nuclear medicine diagnosis and treatment ptotochols. The radiopharmaceutical activity given to the patient should be determined by dose calibrator before administration. The activity given to the patient is very important to know how the radiation affect the patient.It is not possible to understand the presence of radiation with the sense organs.   The contact with the substance is essential for radiation to be detected. While doing any practices involving the nuclear medicine  administration of a radiopharmaceutical, it is essential to use sensitive instrumentation for the detection and measurement of radioactive emissions. This is also especially important for experimental work contributing to scientific knowledge relating radiation doses to biological effects and it is importatnt to use an accurate measure of therapeutic levels of radioactivity. Dose calibrators, unlike other ion chamber detectors, are closed and pressurized rooms filled with argon gas. Ionization chamber radionuclide calibrators analyze the total amount of activity present by measuring the total amount of ionization produced by the sample. Therefore, for both application accuracy and radiation safety, it is very important that the dose calibrator accurately determines the activity to be delivered to the patient.

Qian Wu, Zhen Liu, Liqiong He et al.

Samuel N. Paul, Chiara Frazzoli, Francis D. Sikoki et al.

Alvaro E. Chavarria

Highly pixelated solid-state detectors offer outstanding capabilities in the identification and suppression of backgrounds from natural radioactivity. We present the background-identification strategies developed for the DAMIC experiment, which employs silicon charge-coupled devices to search for dark matter. DAMIC has demonstrated the capability to disentangle and measure the activities of every $β$ emitter from the $^{32}$Si, $^{238}$U and $^{232}$Th decay chains in the silicon target. Similar strategies will be adopted by the Selena Neutrino Experiment, which will employ hybrid amorphous $^{82}$Se/CMOS imagers to perform spectroscopy of $ββ$ decay and solar neutrinos. We present the proposed experimental strategy for Selena to achieve zero-background in a 100-ton-year exposure.

E. Yu. Nikolskii, S. A. Krupko, I. A. Muzalevskii et al.

The proton and deuteron pickup reactions 2H(10Be,3He)9Li and 2H(10Be,4He)8Li radioactive beam produced by the new fragment separator ACCULINNA-2 at FLNR, JINR\@. These measurements were initially motivated as test reactions intended for the elucidation of results obtained in the study of the extremely neutron-rich 7H and 6H systems created in the 2H(10Be,3He)9Li and 2H(10Be,4He)8Li reactions using the same setup. In the 2H(10Be,3He)9Li reaction the 9Li ground-state ($3/2^-$) and its first excited state (2.69MeV, $1/2^-$) were identified in the low-energy region of its excitation spectrum. The differential cross sections for the 9Li g.~s.) population were extracted at forward center-of-mass angles ($3^\circ-13^\circ$) and compared with the FRESCO calculations. Spectroscopic factor of $\sim 1.7$, derived by a model for the 10Be$ = p +$9Li(g.s.) clustering was found in accord with the experimental data. The energy spectrum of 8Li populated in the 2H(10Be,4He)8Li reaction shows the strong peak which corresponds to excitation of the second excited state of 8Li (2.25 MeV, $3^+$). The fact that the ground and the first excited states of 8Li were not observed is fully consistent with Shell-Model calculations carried out for the 10Be g.\,s. and 8Li level structure applying momentum selection rules.

Bruno Takara, Felipe Freitas, Alexandre Bacelar et al.

We present a Machine Learning algorithm based on Python which can be used to aid COVID-19 diagnosis. This algorithm employs Convolutional Neural Networks (CNN) of ResNet-18 architecture from thoracic X-ray images to build a trained dataset that enables further comparisons between common pulmonary diseases and COVID-19 diagnosed patients to classify the radiological findings as being due the COVID-19 or other pathologies. We discuss the importance of setting the right parameters related to training and what they might represent in clinical procedures. We used a dataset containing 942 COVID-19 labeled radiographs from HCPA - Hospital das Clínicas de Porto Alegre and compared it to a public dataset from NIH Clinical Center containing images of pulmonary diseases. Lastly, our trained model had an accuracy of 81.76% for the imbalanced classes and an accuracy of 46.94% for the balanced classes, when compared to other pulmonary diseases such as pneumonia, edema, mass, consolidation, and fibrosis. These results disclose the difficulty of diagnosing COVID-19 from a chest radiograph as it resembles other pulmonary illnesses and makes room for further research in this matter.

Marcus Oliveira, Matheus Savi, Marco Andrade et al.

The aim of this study was to evaluate the feasibility of using acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) 3D printing filaments as materials for mammography phantom construction, comparing their attenuation properties at two different set-ups: at a Calibration Laboratory and directly to a mammography unit. The attenuation of 3D printed test phantoms of two types of common 3D printing Fused Filament Fabrication (FFF) filaments (ABS and PLA) were characterized in comparison with polymethylmethacrylate (PMMA). The measurements were carried out with standard IEC 61267 X-rays, using RQR 2-M and RQR 4-M beam qualities at the Instruments Calibration Laboratory, and then applied to a mammography unit, with measurements with 28 kVp and 35 kVp. Attenuation characteristics evaluated indicates the suitable equivalence of PLA to PMMA for 3D printing breast tissue equivalent complex phantoms. The plastic materials used in this study suggest that the FFF technique may be suitable for mammography phantom development.

Aline Fabiane Gonçalves de Oliveira

Nos estudos de qualidade do ar, os modelos atmosféricos são amplamente utilizados para estimar e concentrar o comportamento da distribuição espacial de poluentes liberados na atmosfera, origens de fontes pontuais. Os dados coletados das Normas Climatológicas determinam uma referência importante para esses estudos, os dados exportados para eventos e eventos climáticos e climáticos, como variabilidade de luvas, desvios e anomalias de temperatura, dispersão de poluentes ou ar, etc. é válido para os dados da estação meteorológica do Centro de Desenvolvimento de Tecnologia Nuclear (CDTN) para o período 1997-2017, comparando com uma climatologia normal do Instituto Nacional de Meteorologia do INMET para o período 1981-2010. Com base nos resultados,

Ana Paula Gimenes Tessaro, Roberto Vicente, Júlio Takehiro Marumo et al.

Radiation-induced advanced oxidation processes have been proposed for the treatment of various types of wastes. However, electron beam technologies for the removal of recalcitrant compounds in petroleum wastes are still poorly understood. This work aims at evaluating the effects on the degradation of organic matter from oil sludge by electron beam irradiation. Characterization methods were employed to identify the chemical elements present in the waste. Radiometric analysis was performed to identify radionuclides and measure dose rates. Preliminary immobilization of the untreated waste with cement indicated resistance values very close to the minimum established in national regulation. To treat the waste, an electron beam accelerator, model Dynamitron II, with variable current up to 25 mA was employed and the irradiation doses ranged from 20 to 200 kGy. Solutions were prepared with an initial H2O2 concentration of 1.34 mol·L-1. The effects on the removal of total organic carbon are discussed.

J. Ryu, C. Park, J. Park et al.

Jong Hyeok Park, Jae Kwon, Min Young Lee et al.

M.A. Hernández-Ceballos, M. Sangiorgi, B. García-Puerta et al.

Olga Tchaikovskaya, E. Bocharnikova

Humic substances or natural organic materials recently have they attracted steady attention as promising biologically active substances. These compounds are widely distributed in natural waters and soils, and have a wide range of chemical and physical properties. Their structure includes a large number of diverse functional groups, which determines their complex-forming, surface-active and redox properties, as well as contributes to their biological activity and possess detoxifying properties. Using humic substances, it is possible to reduce the toxicity of an important class of toxicants - radionuclides. Technogenic pollution by radioactive elements is a consequence of the extraction and processing of radioactive materials, the operation of nuclear power stations, the placement of radioactive waste, accidents at nuclear enterprises, etc. In most cases, technogenic radioactive contamination is caused by isotopes of uranium, thorium, etc., as well as tritium, which is one of the most common decay products of radioisotopes used in the nuclear industry. As a rule, enterprises control discharges, conduct wastewater treatment, reducing the content of radionuclides to an acceptable limit. Moreover, even residual radioactivity can lead to disruption of the physiological functions of aquatic microorganisms, which are the initial link in the food chain for all organisms. The influence of biologically active nanostructures is able to correct the state of aquatic microorganisms. In the presence of humic substances under the influence of radiation, organic molecules are transformed by the mechanisms of direct and indirect photolysis. However, experiments show that the addition of a humic fraction containing both humic and fulvic acids to an aqueous solution of phenol leads to a decrease in the efficiency of phenol decomposition. We managed to find the conditions and fix the effective decomposition of phenol in an aqueous solution when exposed to radiation with a wavelength of 222 nm from an excilamp in the presence of fulvic acid.

Mahbubunnabi Tamal

To accurately quantify in vivo radiotracer uptake using Positron Emission Tomography (PET) is a challenging task due to low signal-to-noise ratio (SNR) and poor spatial resolution of PET camera along with the finite image sampling constraint. Furthermore, inter lesion variations of the SNR and contrast along with the variations in size of the lesion make the quantitation even more difficult. One of the ways to improve the quantitation is via post reconstruction filtering with Gaussian Filter (GF). Edge preserving Bilateral Filter (BF) and Nonlinear Diffusion Filter (NDF) are the alternatives to GF that can improve the SNR without degrading the image resolution. However, the performance of these edge preserving methods are only optimum for high count and low noise cases. A novel parameter free gradient vector orientation based nonlinear diffusion filter (GVOF) is proposed in this paper that is insensitive to statistical fluctuations (e. g., SNR, contrast, size etc.). GVOF method applied on the PET images collected with the NEMA phantom with varying levels of contrast and noise reveals that the GVOF method provides the highest SNR, CNR (contrast-to-noise ratio) and resolution compared to the original and other filtered images. The percentage bias in estimating the maximum activity representing SUVmax (Maximum Standardized Uptake Value) for the spheres with diameter > 2cm where the partial volume effects (PVE) is negligible is the lowest for the GVOF method. The GVOF method also improves the maximum intensity reproducibility. Robustness of the GVOF against variation in sizes, contrast levels and SNR makes it a suitable post filtering method for both accurate diagnosis and response assessment. Furthermore, its capability to provide accurate quantitative measurements irrespective of the SNR, it can also be effective in reduction of radioactivity dose.

Rodrigo Modesto Gadelha, Andréa Vidal Ferreira, Guilherme Albuquerque Cavalcante Souza et al.

Positron emission tomography (PET) is widely used in preclinical trials, generating molecular images applied to biochemical, metabolic and functional investigation of organs and tissues. The positron emitters 11C and 18F radionuclides are relevant for different diseases studies. However, they have different positron energies, ranges, and branching ratio. This could result in a distinct quality between the acquired PET images. Thus, the aim of this study is to evaluate the image quality performance of the PET scanner (LabPET 4, GE) at CDTN/CNEN using the NEMA NU 4-2008 standards and specific phantom for these two different positron emitters. The NEMA image-quality (IQ) phantom consists of 3 different regions to analyze distinct characteristics: uniformity, recovery coefficients (RCs) and spill-over rations (SOR) in air and water. The IQ phantom was filled with two different aqueous solutions (18F-FDG and 11C-PK11195), both activities calibrated at the beginning of acquisition (3.7MBq). The IQ phantom was placed in the center of the field-of-view (FOV) and measured with the typical whole body imaging protocol. The images were reconstructed following the Molecular Imaging Laboratory (LIM/CDTN) standard protocol: MLEM-3D algorithm, 20 iterations, no high-resolution mode, no attenuation or scatter corrections, no post-filtering. PMOD® software was used to perform images post-processing following NEMA analyses standard. The %SD of medium concentration activity for 18F and 11C was 7.7 and 14.5, respectively. The RCs for 18F and 11C were 0.11 and 0.12 respectively for the 1-mm-diameter rod and 0.88 and 0.77 for the 5-mm-diameter rod. SORs in air were 0.19 and 0.22, respectively, and in water 0.29 and 0.33. Experimental results demonstrates that when 18F radionuclide is used, PET images presents a better performance in the image quality tests compared to 11C PET images.