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Cosmic rays have the potential to induce significant changes in atmospheric chemical reactions by generating ions, thereby influencing the atmosphere's chemical composition. The use of particle–molecule interaction models that account for the molecular structure of the atmospheric medium can advance our understanding on the role of ions, and enables a quantitative analysis of the impact of ion-molecule reactions on atmospheric modifications. This study marks the initial effort to expand the Geant-DNA toolkit for atmospheric applications. Building on our previous work, we extended the validation of new electron impact interaction models with the nitrogen and oxygen molecules up to 10 MeV. Additionally, we introduce electron cross sections for the carbon dioxide molecule, due to its crucial role as a major greenhouse gas. We present the implementation of the cross section models in Geant4-DNA, along with their validation through simulations of stopping power and range. The differential cross sections have been verified against analytical calculations, demonstrating good agreement with existing literature data for all three molecules. The implementation has been validated through simulations of stopping power and range in N 2 , O 2 , CO 2 , and a i r. Results demonstrate agreement within 6% compared to reference data from the ESTAR database. The cross section models for the N 2 , O 2 , and CO 2 atmospheric molecules have been implemented in the Geant4-DNA toolkit. This evolution is crucial for studying ionic reactive chemical networks in a quantitative manner, assessing the impact of ionization on chemical reactions occurring in the atmosphere and their implications for climate. • Cosmic rays ionization impacts atmospheric chemical reactions significantly. • Current atmospheric models inadequately explain the role of ions. • We present new electron impact cross section models (10 eV–10 MeV) for N 2 , O 2 , CO 2. • Their validation in the three molecules and in the air material was successful. • They were implemented in Geant4-DNA in three new classes, and will be released soon. [ABSTRACT FROM AUTHOR]

• We assessed the patient and staff exposures in cardiac procedures using the voxellized phantoms. • We determined the HT/KAP and E/KAP coefficients considering several dose-dependent parameters. • We evaluated the effectiveness of the mobile radiation protection cabin against routine equipment. • We demonstrated the efficiency of GEANT4 to estimate the effective and organ doses in IC procedure. The aim of this study is to assess the radiation exposure of the patient and the medical staff during interventional cardiology procedures. Realistic exposure scenarios were developed using the adult reference anthropomorphic phantoms adopted by the International Commission on Radiological Protection (ICRP 110 Male and ICRP 110 Female ), and the radiation transport code G eant 4 (version 10.3). The calculated equivalent and effective doses were normalised by the simulated Kerma-Area Product (KAP), resulting in two conversion coefficients H T / KAP and E / KAP. To properly evaluate the risk of exposure, several dose-dependent parameters have been investigated, namely: radiological parameters (tube kilovoltage peak (kVp), type of projection, field size (FOV)), and operator positions. Four projections (AP , PA , LAO 25 ° and RAO 25 °) were simulated for three X-ray energy spectra (80 , 100 and 120 kVp) with four different values of FOV (15 × 15 cm 2 , 20 × 20 cm 2 , 25 × 25 cm 2 and 30 × 30 cm 2 ). The results showed that the conversion coefficients values increase with increasing tube voltage as well as the FOV size. Recommended projection during the interventional cardiology procedures, whenever possible, should be the PA projection rather than AP projection. The most critical projection for the patient and the main operator is the RAO 25 ° projection and the LAO 25 ° projection respectively. The comparison of our results with the literature data showed good agreement allowing their use in the dosimetric characterization of interventional cardiology procedures. [ABSTRACT FROM AUTHOR]

• Clustered distributions of gold nanoparticles in a cell induce higher radiation effect than uniform distributions. • The distance between nanoparticles clusters and cellular substructures affects the enhancement ratio. • The radiation enhancement ratio depends on distant interactions like chemical species diffusion. This paper presents a Monte-Carlo study focusing on the effects of gold nanoparticles on the energy deposition patterns produced by incident photons in the close vicinity of the mitochondrial network modeled as a tube. Spherical shaped gold nanoparticles of 30 nm diameter were placed in a micrometric (10 × 10 × 10 μ m3) water phantom containing a tube of 300 nm diameter and 5 μ m length. The tube represented a mitochondrial fragment and nanoparticles were distributed in the water phantom outside the tube. Photons of 120 keV were simulated using the Geant4 Livermore processes and the Geant4-DNA electron processes to account for secondary electrons collisions. The Livermore processes took into account the Auger cascade inside the gold material. A data mining algorithm was then used to analyze the energy deposition clusters inside the water phantom and the tube. A comparison was made between the results obtained for a uniform distribution of nanoparticles and a vesicle distribution model. The results including energy deposition clusters are also compared to dose enhancement ratios. [ABSTRACT FROM AUTHOR]

Highlights • The electromagnetic physics models of Geant4 v10.4 have been compared for nanoscale electron transport. • Livermore offers the best performance among the condensed-history models. • Livermore is the least sensitive to variation of stepsize limit but the most sensitive to the tracking cut. • Differences between condensed-history and discrete models is significant for sub-keV electrons and/or nanometer targets. Abstract The Geant4 toolkit offers a range of electromagnetic (EM) models for simulating the transport of charged particles down to sub-keV energies. They can be divided to condensed-history (CH) models (like the Livermore and Penelope models) and the track-structure (TS) models included in the Geant4-DNA low-energy extension of Geant4. Although TS models are considered the state-of-the-art for nanoscale electron transport, they are difficult to develop, computationally intensive, and commonly tailored to a single medium (e.g., water) which prohibits their use in a wide range of applications. Thus, the use of CH models down to sub-keV energies is particularly intriguing in the context of general-purpose Monte Carlo codes. The aim of the present work is to compare the performance of the CH models of Geant4 against the recently implemented TS models of Geant4-DNA for nanoscale electron transport. Calculations are presented for two fundamental quantities, the dose-point-kernel and the microdosimetric lineal energy. The influence of user-defined simulation parameters (tracking and production cuts, and maximum step size) on the above calculations is also examined. It is shown that Livermore offers the best performance among the CH models of Geant4 for nanoscale electron transport. However, even under optimally-chosen simulation parameters, the differences between the CH and TS models examined may be sizeable for low energy electrons (<1 keV) and/or nanometer size targets (<100 nm). [ABSTRACT FROM AUTHOR]

Cosmic rays have the potential to significantly affect the atmospheric composition by increasing the rate and changing the types of chemical reactions through ion production. The amount and states of ionization, and the spatial distribution of ions produced are still open questions for atmospheric models. To precisely estimate these quantities, it is necessary to simulate particle–molecule interactions, down to very low energies. Models enabling such simulations require interaction probabilities over a broad energy range and for all energetically allowed scattering processes. In this paper, we focus on electron interaction with the two most abundant molecules in the atmosphere, i.e., N 2 and O 2 , as an initial step. A set of elastic and inelastic cross section models for electron transportation in oxygen and nitrogen molecules valid in the energy range 10 eV – 1 MeV, is presented. Comparison is made with available theoretical and experimental data and a reasonable good agreement is observed. Stopping power is calculated and compared with published data to assess the general consistency and reliability of our results. Good overall agreement is observed, with relative differences lower than 6% with the ESTAR database. • Cosmic rays ionization can significantly affect chemical reactions in the atmosphere. • The role of ions is still poorly explained by current atmospheric models. • We propose accurate physical models for electron impact interaction with N 2 and O 2. • We reimplemented these models in C++, and we obtained promising preliminary results. • These models will be included in Geant4-DNA in the near future. [ABSTRACT FROM AUTHOR]

A new alternative set of elastic and inelastic cross sections has been added to the very low energy extension of the Geant4 Monte Carlo simulation toolkit, Geant4-DNA, for the simulation of electron interactions in liquid water. These cross sections have been obtained from the CPA100 Monte Carlo track structure code, which has been a reference in the microdosimetry community for many years. They are compared to the default Geant4-DNA cross sections and show better agreement with published data. In order to verify the correct implementation of the CPA100 cross section models in Geant4-DNA, simulations of the number of interactions and ranges were performed using Geant4-DNA with this new set of models, and the results were compared with corresponding results from the original CPA100 code. Good agreement is observed between the implementations, with relative differences lower than 1% regardless of the incident electron energy. Useful quantities related to the deposited energy at the scale of the cell or the organ of interest for internal dosimetry, like dose point kernels, are also calculated using these new physics models. They are compared with results obtained using the well-known Penelope Monte Carlo code. [ABSTRACT FROM AUTHOR]

Emerging radiotherapy treatments including targeted particle therapy, hadron therapy or radiosensitisation of cells by high-Z nanoparticles demand the theoretical determination of radiation track structure at the nanoscale. This is essential in order to evaluate radiation damage at the cellular and DNA level. Since 2007, Geant4 offers physics models to describe particle interactions in liquid water at the nanometre level through the Geant4-DNA Package. This package currently provides a complete set of models describing the event-by-event electromagnetic interactions of particles with liquid water, as well as developments for the modelling of water radiolysis. Since its release, Geant4-DNA has been adopted as an investigational tool in kV and MV external beam radiotherapy, hadron therapies using protons and heavy ions, targeted therapies and radiobiology studies. It has been benchmarked with respect to other track structure Monte Carlo codes and, where available, against reference experimental measurements. While Geant4-DNA physics models and radiolysis modelling functionalities have already been described in detail in the literature, this review paper summarises and discusses a selection of representative papers with the aim of providing an overview of a) geometrical descriptions of biological targets down to the DNA size, and b) the full spectrum of current micro- and nano-scale applications of Geant4-DNA. [ABSTRACT FROM AUTHOR]

Modeling the radio-induced effects in biological medium still requires accurate physics models to describe the interactions induced by all the charged particles present in the irradiated medium in detail. These interactions include inelastic as well as elastic processes. To check the accuracy of the very low energy models recently implemented into the GEANT4 toolkit for modeling the electron slowing-down in liquid water, the simulation of electron dose point kernels remains the preferential test. In this context, we here report normalized radial dose profiles, for mono-energetic point sources, computed in liquid water by using the very low energy “GEANT4-DNA” physics processes available in the GEANT4 toolkit. In the present study, we report an extensive intra-comparison of profiles obtained by a large selection of existing and well-documented Monte-Carlo codes, namely, EGSnrc, PENELOPE, CPA100, FLUKA and MCNPX. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents stopping power and ranges of electrons, protons, and alpha particles in liquid water, calculated using the latest Geant4-DNA processes implemented in the Geant4 Monte Carlo simulation toolkit. Inelastic cross sections are obtained using the first Born approximation and semi-empirical formulas like Rudd’s model for ionisation and the Miller and Green formula for excitation. Elastic collisions and vibrational excitations are considered for tracking electrons until complete thermalisation (0.025eV). A speed scaling procedure with an effective charge screening term was used to compute alpha particle and heavy ion cross sections. Geant4-DNA simulations were carried out using thin liquid water volumes to determine the linear energy loss (dE/dX), while larger volumes were used to obtain the particle range. While results converge for highly energetic particles, differences are observed for low energies when the applied theoretical models begin to diverge from each other. Results show a good agreement between the analytical calculations obtained from the models, the Geant4-DNA Monte Carlo simulation predictions and the data published in the ICRU reports. Geant4-DNA processes apply to the following energy ranges: 0.025eV–1MeV for electrons, 100eV–100MeV for protons and 1keV–400MeV for alpha particles in liquid water, however since experimental data for very low energies is scarce and very difficult to obtain these processes could not be thoroughly validated so they are recommended for energies above 1eV for electrons, 1keV for protons and 10keV for alpha particles. Relativistic, highly charged ions were implemented in our own “house” version of the code and will be available in future releases of Geant4. [Copyright &y& Elsevier]

Abstract: This paper presents a study of energy deposits induced by ionising particles in liquid water at the molecular scale. Particles track structures were generated using the Geant4-DNA processes of the Geant4 Monte-Carlo toolkit. These processes cover electrons (0.025eV–1MeV), protons (1keV–100MeV), hydrogen atoms (1keV–100MeV) and alpha particles (10keV–40MeV) including their different charge states. Electron ranges and lineal energies for protons were calculated in nanometric and micrometric volumes. [Copyright &y& Elsevier]

Abstract: The present work provides an accurate description of the elastic scattering process for low-energy electrons (10eV–10keV) in liquid water by means of a free-parameter quantum-mechanical treatment. The calculations are performed in the partial-wave formalism by means of a total interaction potential taking into account a static contribution as well as fine effects like exchange and polarization contributions. The obtained results in terms of singly differential and total cross sections exhibit relatively good agreement with available experimental data (in gaseous water). They have been incorporated into the Geant4 toolkit, which has been recently extended with physics processes for microdosimetry applications in liquid water down to the electronvolt scale. They offer an improved alternative to the semi-empirical and to the screened Rutherford models already available in this very low-energy extension. [Copyright &y& Elsevier]