Sultan B. Dabagov

The demand for lightweight, flexible, and lead-free radiation shielding for next-generation extravehicular activity suits and aerospace habitat liners is rapidly intensifying. This study investigates the structural organization and X-ray attenuation performance (10–60 keV) of polyethylenimine/graphene oxide (PEI/GO) composites with GO loadings up to 50 wt%. Microstructural evolution was systematically tracked via optical image quantification (dispersion, connectivity, and local mixing indices) correlated with micro-Raman spectral mapping. Raman analysis confirmed a structural transition at 40 wt% GO, driven by a dynamic competition between covalent amine–epoxide/carboxyl functionalization and localized π–π stacking of sp² domains. X-ray transmission and linear attenuation coefficients were evaluated using a dual approach, coupling experimental X-ray exposures with deterministic NIST XCOM calculations and stochastic Monte Carlo simulations. The results demonstrate that GO significantly amplifies low-energy photoelectric absorption due to its oxygen-rich functionalities. An anomalous thickness-dependent attenuation paradox, which can be explained by accounting for forward-scattered Compton buildup in thick blocks and spatial edge refraction along non-percolating cluster interfaces in thin films, was observed experimentally. These findings provide critical material design rules for advanced, flexible, and wearable photon shields operating without mass penalties.

In this study, the influence of the in-plane electric field and dielectric confinement on impurity states in C d S e nanoplatelets was investigated theoretically and numerically using the Finite Element Method. The photoionization of a hydrogen-like donor impurity was studied for various orientations of the electric field in the plane of the nanoplatelet (NPL), accounting for polarization along the axial direction within the Takagahara model. We demonstrate that an increase in NPL thickness enhances the spatial overlap between bound and excited states through axial delocalization, while the dielectric constant of the surrounding medium primarily modulates transition energies. Analysis of electric-field dynamics reveals that in-plane fields induce significant spectral shifts and peak damping. Furthermore, we establish the profound role of spatial anisotropy, observing a strong dependence of the binding energy and oscillator strength on the field angle. This behavior is shown to be highly sensitive to different impurity positions within the NPL. Notably, positioning the impurity at the NPL corner breaks spatial inversion symmetry, resulting in increased photoionization intensity and the emergence of a second transition peak. These findings demonstrate that CdSe NPLs are promising candidates for tunable optoelectronic devices and field-sensitive nanosensors through the precise modification of field magnitude, direction, and dielectric mismatch.

A new measurement of the magnetic anomaly a μ of the positive muon is presented based on data taken from 2020 to 2023 by the Muon g − 2 Experiment at Fermi National Accelerator Laboratory (FNAL). This dataset contains over 2.5 times the total statistics of our previous results. From the ratio of the precession frequencies for muons and protons in our storage ring magnetic field, together with precisely known ratios of fundamental constants, we determine a μ = 1 165 920 710 ( 162 ) × 10 − 12 (139 ppb) for the new datasets, and a μ = 1 165 920 705 ( 148 ) × 10 − 12 (127 ppb) when combined with our previous results. The new experimental world average, dominated by the measurements at FNAL, is a μ ( exp ) = 1 165 920 715 ( 145 ) × 10 − 12 (124 ppb). The measurements at FNAL have improved the precision on the world average by over a factor of 4.