Efficient computational modeling of electronic stopping power of organic polymers for proton therapy optimization.

This comprehensive study delves into the intricate interplay between protons and organic polymers, offering insights into proton therapy in cancer treatment. Focusing on the influence of the spatial electron density distribution on stopping power estimates, we employed real-time time-dependent density functional theory coupled with the Penn method. Surprisingly, the assumption of electron density homogeneity in polymers is fundamentally flawed, resulting in an overestimation of stopping power values at energies below 2 MeV. Moreover, the Bragg rule application in specific compounds exhibited significant deviations from experimental data around the stopping maximum, challenging established norms.

SAFIIRA: A heavy-ion multi-purpose irradiation facility in Brazil.

This work describes the new facility for applied nuclear physics at the University of Sao Paulo, mainly for irradiation of electronic devices. It is a setup composed of a quadrupole doublet for beam focusing/defocusing plus multiple scattering through gold foils to produce low intensity, large-area, and high-uniformity heavy-ion beams from 1H to 107Ag. Beam intensities can be easily adjusted from 102 particles cm2/s to hundreds of nA for an area as large as 2.0 cm2 and uniformity better than 90%. Its irradiation chamber has a high-precision motorized stage, and the system is controlled by a LabViewTM environment, allowing measurement automation. Design considerations and examples of use are presented.

A low-cost portable system for elemental mapping by XRF aiming in situ analyses.

This work presents the development of a portable system that allows 2D elemental mapping of large areas (maximum of 35.0 × 35.0 cm2) by XRF. A measuring head, composed of an x-ray source and a detector, is mounted on a 3-axis stage with movement reproducibility better that 0.03 mm. The final elemental map resolution of 1.4 mm was experimentally determined in the best condition of collimation, and the same experiments indicate that the resolution is fully dominated by the x-ray beam spot size. The main goal of this new setup is to perform analyses of historical, archaeological and geological objects. Because it's lightweight, our setup has the potential to be of great utility for in situ analyses, given the great difficulty and high costs transporting the artifacts from the museum to a laboratory. The importance of this instrumentation is related to the need to identify the distribution of the chemical elements in large surface areas of cultural heritage objects by a nondestructive method.

External PIGE-PIXE measurements at the São Paulo 8UD tandem accelerator / Medidas externas do PIGE-PIXE em São Paulo 8UD acelerador tandem

An external PIGE-PIXE setup was installed on a beam line of the 8 MV tandem Pelletron accelerator of the Open Nuclear Physics Laboratory (LAFN). Proton beam energy was chosen in the 8-12 MeV range, sufficient to get an acceptable gamma ray yield but not so high as to prevent us from measuring X-rays. This also allowed the use of a thick aluminum exit window (0.5 mm) instead of the usual thin and sometimes fragile plastic windows. This external PIXE-PIGE system was used to analyze trace element concentrations in the enamel of human and animal teeth. The main interest was to find compatible human teeth substitutes for dentistry laboratory practice and chemical tests. In spite of their morpho-histological similarity, trace element concentrations in human and animal teeth have not yet been compared. Teeth from humans, cattle and swine collected primary at São Paulo region were analyzed. The elements Cu, K, Zn, Fe, Ti, Sr, V, Mn and Zr were detected by high energy external beam PIXE technique. Though preliminary, the results showed that the trace element concentrations observed in the enamel of human and swine are more similar to each other than to cattle teeth

Radioaerosol 99mTc-DTPA characterization produced by some nebulizers.

1. The radioaerosol 99mTc-DTPA produced by jet and ultrasonic nebulizers was characterized by measuring the median mass diameter (MMD) and geometric standard deviation (sigma g) and these characteristics were interpreted in terms of the aerodynamic principles of inertial impactation. 2. Jet nebulizers of the same model, with different outflows (NSA = 0.14 ml/min; NSB = 0.24 ml/min and NSC = 0.40 ml/min) showed different radioaerosol mass distribution, with MMD (NSC) > MMD (NSA). The ultrasonic nebulizer US-1000 from Narcosul, which is operated with an air flow of 2 l/min and frequency of 1.6 MHz, generated radioaerosol with MMD = 2.40 microns, higher than that obtained with most of the jet nebulizers evaluated (NSA = 1.50 microns; NSB1V = 1.40 microns; NSB2V = 1.20 microns and PITT#1 - 0.80 microns), and the ultrasonic nebulizer presented the highest outflow of the nebulized solution (1.15 ml/min). 3. Connecting one or two impactation reservoirs to the NSB jet nebulizer modified the mass distribution, which became significantly narrower for NSB2V when compared to the other two nebulizers. NSB2V presented a mass percentage with a diameter of 3 microns or less and a sufficient outflow for use in ventilation and pulmonary permeability studies. 4. Comparison of the mass collected in the cascade impactor and the total mass generated by the NSB, NSB1V and NSB2V nebulizers showed, on average, 4.5% efficiency in radioaerosol generation with a diameter of less than 16 microns and 3.2% efficiency for a diameter of 3 microns or less.

Radioaerosol 99mTc-DTPA characterization produced by some nebulizers

1. The radioaerosol 99mTc-DTPA produced by jet and ultrasonic nebulizers was characterized by measuring the median mass diameter (MMD) and geometric standard deviation (sigma g) and these characteristics were interpreted in terms of the aerodynamic principles of inertial impactation. 2. Jet nebulizers of the same model, with different outflows (NSA = 0.14 ml/min; NSB = 0.24 ml/min and NSC = 0.40 ml/min) showed different radioaerosol mass distribution, with MMD (NSC) > MMD (NSA). The ultrasonic nebulizer US-1000 from Narcosul, which is operated with an air flow of 2 l/min and frequency of 1.6 MHz, generated radioaerosol with MMD = 2.40 microns, higher than that obtained with most of the jet nebulizers evaluated (NSA = 1.50 microns; NSB1V = 1.40 microns; NSB2V = 1.20 microns and PITT#1 - 0.80 microns), and the ultrasonic nebulizer presented the highest outflow of the nebulized solution (1.15 ml/min). 3. Connecting one or two impactation reservoirs to the NSB jet nebulizer modified the mass distribution, which became significantly narrower for NSB2V when compared to the other two nebulizers. NSB2V presented a mass percentage with a diameter of 3 microns or less and a sufficient outflow for use in ventilation and pulmonary permeability studies. 4. Comparison of the mass collected in the cascade impactor and the total mass generated by the NSB, NSB1V and NSB2V nebulizers showed, on average, 4.5 efficiency in radioaerosol generation with a diameter of less than 16 microns and 3.2 efficiency for a diameter of 3 microns or less.