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Recent Submissions

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    Few Body Effects in the Electron and Positron Impact Ionization of Atoms
    (MDPI, 2021-06-09) Campeanu, Radu I.; Parkin, D. T.
    Triple differential cross sections (TDCS) are presented for the electron and positron impact ionization of inert gas atoms in a range of energy sharing geometries where a number of significant few body effects compete to define the shape of the TDCS. Using both positrons and electrons as projectiles has opened up the possibility of performing complementary studies which could effectively isolate competing interactions that cannot be separately detected in an experiment with a single projectile. Results will be presented in kinematics where the electron impact ionization appears to be well understood and using the same kinematics positron cross sections will be presented. The kinematics are then varied in order to focus on the role of distortion, post collision interaction (pci), and interference effects.
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    Electron and Positron Impact Ionization of Molecules
    (MDPI, 2024-07-23) Nagy, Ladislau; Tóth, István; Campeanu, Radu I.
    We review our group’s most significant results concerning the collision of positrons and electrons with small molecules. Total and triple differential cross sections for the ionization of these targets were calculated in the distorted wave Born approximation using Gaussian molecular orbitals. Different models were tested. The obtained theoretical results reproduced, in most cases, the features observed in the experimental data.
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    Triple-Differential Cross-Section Calculations for Positron Impact Ionization of Argon
    (MDPI, 2025-05-04) Campeanu, Radu I.; Bálint, Zsuzsánna; Nagy, Ladislau
    Triple-differential cross-sections for the positron impact ionization of argon were calculated using a distorted-wave Born approximation (DWBA) convoluted to the experimental uncertainties. In almost all of the cases studied, our results agree well with the positions and heights of the experimental peaks.
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    Electron Impact Ionization of Krypton at Intermediate Energies
    (MDPI, 2026-07-17) Campeanu, Radu I.; Nagy, Ladislau
    The distorted-wave approach is applied to electron impact single ionization of krypton. We find that our models CPE4 and DW2 give results which are in fair agreement with the experiments. Both models contain a final state representation which includes the electrostatic repulsion between the ejected electron and the scattered electron.
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    Evidence of an upper entrainment limit for walking with fractal auditory stimuli
    (PeerJ, 2025-10-27) Power, Cecilia Rose; Sorensen, Kristen L.; Drake, Janessa D. M.; Gage, William H.
    Background: Variability exists in all biological signals, and in human gait research it has been found to be an indicator of neuromuscular system functioning. Detrended fluctuation analysis (DFA), a nonlinear method used to quantify the strength of long-range correlations in the temporal structure of stride-to-stride gait variability, has revealed gait differences in certain populations that are not observed with traditional linear measures like standard deviation. Previous research suggests that humans can adapt gait patterns to match different variability structures through sensory cues, such as auditory metronomes. However, the upper limits of adaptability and the strength of long-term correlations in gait variability remain unclear. Exploring these limits not only deepens our understanding of neuromuscular control mechanisms but could also inform the design of targeted interventions, such as rehabilitation strategies, to enhance motor control in clinical populations. The aim of this study was to investigate the possible upper limits of long-term correlations in stride-to-stride gait variability, characterized by the fractal scaling index (FSI) using DFA. Methods: Fourteen healthy young adults (age 25 ± 3 years; seven females) completed seven treadmill walking trials at a fixed, self-selected speed. The first trial was uncued, and during the remaining six trials participants timed their steps to an auditory metronome with FSI ranging between 1.00 and 1.25. Gait FSI, velocity, stride time, cadence, and the time difference between heel contact and the associated metronome "tones" were calculated. Results: Uncued gait FSI averaged 0.76 (±0.1). As the metronome FSI increased from 1.00 to 1.15, gait FSI approximated 1.00. Beyond 1.15 (metronome FSI values of 1.20 and 1.25), gait FSI dropped below 0.70, resembling uncued walking. Other gait measures remained unchanged. These findings suggest an upper gait FSI limit of approximately 1.00 during entrainment to metronome FSI values <1.20, beyond which adaptability diminishes. Conclusions: This study establishes the upper entrainment limit for gait FSI during synchronization with fractal auditory stimuli, with implications for designing effective gait rehabilitation interventions targeting specific variability patterns.