Search Results (32)

Single-electron emission from the coronene (C₂₄H₁₂) molecule induced by the impact of 100 keV H⁺ projectiles is investigated using the continuum distorted wave–eikonal initial state approximation within a semi-classical impact-parameter framework. Multi-center orbitals in the initial channel are derived using the Gaussian quantum chemistry software package, while wave functions of the emitted electron in the exit channel are evaluated using a spherically averaged static potential of the molecular core. The evaluated total ionization cross sections and probabilities are compared and discussed with results obtained from a simplified description of the molecule in which the molecular geometry is ignored. The ionization cross sections of the molecular orbitals generally increase monotonically with decreasing binding energy; however, several deviations from this overall trend are observed. Both the overall trend and the deviations are interpreted in terms of information-theoretical quantities. Full article

Bisphenol A type epoxy resin has the problem of relatively high brittleness after curing. Although traditional polysiloxane toughening methods can improve toughness, they often come at the expense of strength. In this paper, methylphenyl dimethoxysilane (MPS) was used as a monomer to synthesize end-hydroxyl poly(methylphenyl)siloxane (PMPS), which was then used to modify E51 epoxy resin. The structure and reaction degree were characterized by infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry and viscosity tests. The mechanical test results show that when the PMPS content is 20 wt%, the tensile, flexural, compressive and impact strengths of the modified resin increase by 31.26%, 26.16%, 18.53% and 98.66%, respectively, compared with the unmodified resin, and the tensile and flexural elastic moduli increase by 38.36% and 32.25%, respectively. The fracture toughness increases by 60.29%, indicating that the strength, stiffness and toughness of the material have all been improved. Dynamic mechanical analysis shows that the glass transition temperature and crosslinking density of the system gradually decrease with increasing PMPS content. Thermogravimetric analysis shows that the introduction of PMPS increases the char yield and decreases the maximum thermal decomposition rate, thereby enhancing the thermal stability of the system. Microscopic morphology analysis by optical microscopy, scanning electron microscopy and atomic force microscopy shows that the system has good compatibility, and the internal different modulus phases are distributed in a network-like manner, forming a uniform co-continuous or bicontinuous phase structure. This structure effectively promotes stress transfer and energy dissipation, alleviates local stress concentration, and thus comprehensively improves the mechanical properties of the resin system. Full article

The chemical evolution of simple molecules into higher-order structures, such as amino acids, is a fundamental process occurring throughout the cosmos. Methane (CH₄) serves as a key precursor in this evolutionary sequence and is prevalent on planetary bodies like Mars and Saturn. In these environments, CH₄ is frequently ionized by cosmic radiation, forming the methane radical cation (CH₄⁺). In this study, the ion-molecule reactions between CH₄⁺ and neutral CH₄ (CH₄⁺ + CH₄ → products) were investigated using direct ab initio molecular dynamics (AIMD) simulations to elucidate the underlying reaction mechanisms. Our calculations demonstrate that proton transfer (PT) occurs efficiently, yielding the methanium ion (CH₅⁺) and the highly reactive methyl radical (CH₃): CH₄⁺ + CH₄ → CH₅⁺ + CH₃. Furthermore, the reaction outcomes exhibit a strong dependence on the impact parameter (b). Collisions at very low impact parameters (b = 0–0.2 Å) resulted in non-reactive, billiard-ball-like scattering. Within the range of b = 0.2–3.0 Å, the formation of a long-lived complex, [CH₅-CH₃]⁺, was observed. In the intermediate range of b = 3.0–5.0 Å, a proton-stripping mechanism predominated in PT channel, while collisions at b > 5.0 Å were exclusively non-reactive. The reaction mechanism was qualitatively discussed. These findings provide a detailed atomistic picture of the collision dynamics governing methane-derived molecular evolution in celestial environments. Full article

We investigate the 75 keV proton impact ionization of helium. The convoluted quasi-Sturmian approach is extended to treat both the direct ionization and the electron capture to the continuum by proposing an ansatz for the Coulomb three-body Green’s function operator, for the kernel of which the leading asymptotic form contains the wave function of the 3C model. The resulting 3C-like model is tested numerically. Fully differential cross-sections are calculated for different energy-loss regimes and compared with recent experimental data. Full article

We investigate theoretically the 75 keV proton-impact ionization of atomic helium. The convoluted quasi-Sturmian approach is extended to treat, on an equal footing, both the direct mechanism and the electron capture to the continuum. This is achieved by proposing an ansatz of the Green’s function of the three-body Coulomb system $(e^{-},{\mathrm{He}}^{+},p^{+})$ that is compatible with the well-known 3C correlated continuum wave function. The model that stems from this approximation, named $3\tilde{C}$, is tested numerically using parabolic Sturmian expansions. Calculations of fully differential cross sections are presented for different regimes of energy losses, namely for ejected electron energies below, nearly equal to, and above the cusp energy. Our results are compared with recent experimental measurements and other theoretical calculations. The proposed $3\tilde{C}$ model yields very encouraging results and paves the way towards a more advanced Lippmann–Schwinger approach based on the 3C model. Full article

The X1.59 solar flare on 3 July 2021, was the first X-class flare of Solar Cycle 25 and the first since the X-class flare on 10 September 2017. This event was notable for producing a rare geomagnetic crochet, a temporary and localized perturbation in Earth’s magnetic field during the flare’s peak. To the best of our knowledge, this study represents the first VLF-based analysis of this event, as well as the first comprehensive multi-instrument investigation of it. VLF observations from the NAA and DHO transmitters were used to investigate the ionospheric response via amplitude and phase variations. Key low ionosphere parameters, including the effective reflection height, sharpness factor, time delay and electron density profiles were derived. The results reveal rapid ionospheric responses closely correlated with X-ray flux peaks, including sudden phase and amplitude perturbations indicative of increased low ionosphere ionization and the geomagnetic crochet effect. Simultaneously, cosmic-ray measurements from ground detectors showed negligible modulation and no significant Forbush decrease, consistent with the flare’s weak and partially Earth-directed CME. Also, the spectrum of energetic protons measured in-situ in near-Earth space shows little disturbance. This integrated study demonstrates the sensitivity of the lower ionosphere to intense solar radiation and highlights the limited short-term impact on cosmic-ray and solar energetic proton flux, providing a comprehensive assessment of flare-driven space-weather effects during the early phase of Solar Cycle 25. Full article

The High-Energy Ray Observatory (HERO) is a space-based experiment designed to measure the spectrum and composition of cosmic rays using an ionization calorimeter. The instrument’s effective geometric factor is at least 12 m²·sr for protons and 16 m²·sr or more for nuclei and electrons. Over an exposure period of approximately 5 to 7 years, the mission will enable high-resolution, element-by-element measurements of cosmic ray spectra in the energy range of 10¹² to 10¹⁶ eV per particle. A Monte Carlo simulation of the calorimeter—based on a scintillation detector with and without boron additives—was carried out using the GEANT4 software package. In this study, we examine the impact of boron additives in scintillator materials on energy resolution and their potential for discriminating between electromagnetic and hadronic components of cosmic rays. The primary objectives are to demonstrate that boron does not degrade detector characteristics and that it enables an additional timing-based method for cosmic-ray component rejection. The planned launch of the orbital experiment is scheduled for no earlier than 2029. Full article

Ionizing radiation (IR) as a stress inducer has a significant impact on various normal stem cells differentiation through activation of various signaling pathways. Low levels of oxidative stress of IR may preserve or even enhance cell differentiation. In response to IR, reactive oxygen species (ROS) can activate various signaling pathways that promote cell differentiation, notably through the involvement of nuclear factor erythroid 2–related factor 2 (NRF2). NRF2 interacts with multiple pathways, including Wnt/β-catenin (osteogenesis), PPARγ (adipogenesis), and BDNF/TrkB (neurogenesis). This response is dose-dependent: low doses of IR activate NRF2 and support differentiation, while high doses can overwhelm the antioxidant system, resulting in cell death. However, the quality of various types of IR, such as proton and carbon ion radiation, may have a varied impact on stem cells (SCs) differentiation compared to X-rays. Hence, activation of the NRF2 signaling pathway in SCs and cell differentiation depends on the level of stress and the quality and quantity of IR. This review is an update to explore how IR modulates SCs fate toward osteogenic, adipogenic, and neurogenic lineages through the NRF2 signaling pathway. We highlight mechanistic insights, dose-dependent effects, and therapeutic implications, bridging gaps between experimental models and clinical translation. Full article

(1) Background: Ionizing radiation in the Earth’s atmosphere drives key chemical transformations affecting atmospheric composition. Despite their environmental relevance, experimental data on proton collisions with hydrofluorocarbons remain limited, and theoretical models for total cross-sections and stopping power are still underdeveloped. (2) Methods: This study applies Rudd’s semiempirical model to calculate proton impact ionization cross-sections for the CF₃CH₂F molecule, considering contributions from both outer and inner electron shells. The model enables the estimation of differential cross-sections and the average energy of secondary electrons. In addition, we calculate the photoionization cross-sections using a discretized representation of the continuum—the so-called pseudo-spectrum—obtained through TDDFT with PBE0 as an exchange–correlation functional and compare it with the cross-section obtained for proton impact in the high-energy limit. (3) Results: The Rudd model proves highly adaptable and suitable for numerical applications. However, its validation is hindered by the scarcity of experimental data. Existing models, such as SRIM and Bethe–Bloch, show significant discrepancies due to their limited applicability at intermediate energies and lack of molecular structure consideration. (4) Conclusions: A comparison between the Rudd and BEB models reveals strong agreement in the analyzed energy range. This consistency stems from both models accounting for the molecular structure of the target, as well as from the fact that protons and electrons possess charges of the same magnitude, supporting a coherent description of ionization processes at these energies. Full article

Radiation impacts on space-based systems operating on various orbits are evaluated in this paper. Specifically, satellite operations in Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geosynchronous Orbit (GEO) are analyzed. Special focus is given on quantifying the effect of high-energy particle space radiation on materials used for critical power components, where component fault can lead to total mission failure. Methods, using multiple computational platforms for the quantification of non-ionizing energy loss (NIEL) and displacement damage dose (DDD), are used to assess semiconductor damage at specific orbital altitudes. Detailed simulations were conducted for Gallium Arsenide Indium Phosphide (GaInP/GaAs/Ge) solar cells with various cover glass thicknesses, and the survivability of GaInP/GaAs/Ge cells was compared with that of Si cells. It was assessed that radiation exposure due to high-energy protons at 10,000 km is more prevalent than 20,000 km orbits and that electron bombardment is a major electronic damage culprit. For MEO at 10,000 km, MEO at 20,000 km, and GEO at 36,000 km, we determined the 1-year maximum power (Pmax) losses due to protons to be 23%, 8%, and 1% and losses due to electrons to be 11%, 14%, and 10%. Total integrated spectra Pmax losses for those altitudes are 25%, 16%, and 10%, respectively. Full article

This study investigates how the presence of quantum vortices affects the ionization cross-section of helium atoms by 75 keV proton impact, with special attention to the region near the electron capture to the continuum (ECC) cusp. It has been found that these vortices cause a significant reduction in the intensity of the ${\left|T\right|}^2$ distribution in the low-energy region of the ECC cusp, leading to a considerable distortion that facilitates its experimental determination. Furthermore, the analysis shows that one of the vortices coincides with the Thomas angle (a parameter coming from the classical ion-electron Thomas mechanism). Full article

Solar proton events (SPEs) affect the Earth’s atmosphere, causing additional ionization in the high-latitude mesosphere and stratosphere. Ionization rates from such solar proton events maximize in the stratosphere, but the formation of ozone-depleting nitrogen and hydrogen oxides begins at mesospheric altitudes. The destruction of mesospheric ozone is associated with protons with energies of about 10 MeV and higher and will strongly depend on the intensity of the flux of these particles. Most studies investigating the impact of SPEs on the characteristics of the middle atmosphere have been based on either simulations or reanalysis datasets, and some studies have used satellite observations to validate model results. We study the impact of SPEs on cold-season ozone loss in both the northern and southern hemispheres using Aura MLS mesospheric ozone measurements over the 2004 to 2024 period. Here, we show how strongly SPEs can deplete polar mesospheric ozone in different hemispheres and attempt to evaluate this dependence on the intensity of solar proton events. We found that moderate SPEs consisting of protons with an energy of more than 10 MeV and a flux intensity of more than 100 pfu destroy mesospheric ozone in the northern hemisphere up to 47% and in the southern hemisphere up to 33%. For both hemispheres, the peak of winter ozone loss was observed at about 76 km. In the northern hemisphere, maximum winter ozone loss was observed on the second day after a solar proton event, but in the southern hemisphere, winter ozone depletion was already detected on the first day. In the southern hemisphere, mesospheric ozone concentrations return to pre-event levels on the ninth day after a solar proton event, but in the northern hemisphere, even on the tenth day after a solar proton event, the mesospheric ozone layer may not be fully recovered. The strong SPEs with a proton flux intensity of more than 1000 pfu lead to a maximum winter ozone loss of up to 85% in the northern hemisphere, and in the southern hemisphere winter, ozone loss reaches 73%. Full article

We present a classical treatment of the ionization and electron-capture processes in the interaction of protons with neutral noble-gas atoms, namely, Ne, Ar, Kr, and Xe. We used a three-body classical-trajectory Monte Carlo (CTMC) method to calculate the total (TCS) and differential (DCS) cross sections of single-electron processes. The Garvey-type model potential was employed in the CTMC model to describe the collision between the projectile and the target, accounting for the screening effect of the inactive electrons. The TCSs are evaluated for impact energies in the energy range between 0.2 keV and 50 MeV for a number of sub-shells of the targets. The ionization DCS are evaluated for an impact energy of 35 keV, focusing on the outer sub-shells only. We found that our ionization and electron-capture TCSs are in very good agreement with the previous theoretical and experimental data for all targets. Moreover, we presented single (SDCS)- and double (DDCS)-differential cross sections as a function of the energy and ejection angle of the ionized electron for all collision systems. Full article

Many liqueurs, including spirits infused with botanicals, are crafted not only for their taste and flavor but also for potential medicinal benefits. However, the scientific evidence supporting their medicinal effects remains limited. This study aims to verify in vitro anticancer activity and bioactive compounds in shochu spirits infused with Cordyceps militaris, a Chinese medicine. The results revealed that a bioactive fraction was eluted from the spirit extract with 40% ethanol. The infusion time impacted the inhibitory effect of the spirit extract on the proliferation of colon cancer-derived cell line HCT-116 cells, and a 21-day infusion showed the strongest inhibitory effect. Furthermore, the spirit extract was separated into four fractions, A-D, by high-performance liquid chromatography (HPLC), and Fractions B, C, and D, but not A, exerted the effects of proliferation inhibition and apoptotic induction of HCT-116 cells and HL-60 cells. Furthermore, Fractions B, C, and D were, respectively, identified as adenosine, cordycepin, and N⁶-(2-hydroxyethyl)-adenosine (HEA) by comprehensive chemical analyses, including proton nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FT-IR), and electrospray ionization mass spectrometry (ESI-MS). To better understand the bioactivity mechanisms of cordycepin and HEA, the agonist and antagonist tests of the A3 adenosine receptor (A3AR) were performed. Cell viability was suppressed by cordycepin, and HEA was restored by the A3AR antagonist MR1523, suggesting that cordycepin and HEA possibly acted as agonists to activate A3ARs to inhibit cell proliferation. Molecular docking simulations revealed that both adenosine and cordycepin bound to the same pocket site of A3ARs, while HEA exhibited a different binding pattern, supporting a possible explanation for the difference in their bioactivity. Taken together, the present study demonstrated that cordycepin and HEA were major bioactive ingredients in Cordyceps militaries-infused sweet potato shochu spirits, which contributed to the in vitro anticancer activity. Full article

Phytophthora parasitica is an oomycete pathogen that infects a broad range of crops of worldwide economic interest; among them are citrus species. In general, some Citrus and the rootstocks of related genera offer considerable resistance against P. parasitica; therefore, understanding the mechanisms involved in the virulence of this pathogen is crucial. In this work, P. parasitica secondary metabolite production was studied using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) and ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/ESI-Q-TOF-MS) combined with chemometric tools, and its metabolic profile was evaluated under the influence of Citrus sunki (a highly susceptible host) and Poncirus trifoliata (a resistant genotype) extracts. The root extracts of Citrus sunki had an influence on the growth and hyphae morphology, and the root extracts of P. trifoliata had an influence on the zoospore behavior. In parallel, the spatial distribution of several metabolites was revealed in P. parasitica colonies using MALDI-MSI, and the metabolite ion of m/z 246 was identified as the protonated molecule of Arg-Ala. The MALDI-MSI showed variations in the surface metabolite profile of P. parasitica under the influence of the P. trifoliata extract. The P. parasitica metabolome analysis using UHPLC-ESI-Q-TOF-MS resulted in the detection of Arg-Gln (m/z 303.1775), as well as L-arginine (m/z 175.1191) and other unidentified metabolites. Significant variations in this metabolome were detected under the influence of the plant extracts when evaluated using UHPLC-ESI-Q-TOF-MS. Both techniques proved to be complementary, offering valuable insights at the molecular level when used to assess the impact of the plant extracts on microbial physiology in vitro. The metabolites identified in this study may play significant roles in the interaction or virulence of P. parasitica, but their functional characterization remains to be analyzed. Overall, these data confirm our initial hypotheses, demonstrating that P. parasitica has the capabilities of (i) recognizing host signals and altering its reproductive programing and (ii) distinguishing between hosts with varying responses in terms of reproduction and the production of secondary metabolites. Full article