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The nature of cosmological dark matter finds its explanation in physics beyond the Standard Model of elementary particles. The landscape of dark matter candidates contains a wide variety of species, either elusive or hardly detectable in direct experimental searches. Even in case, when such searches are possible the interpretation of their results implies additional sources of information, which provide indirect effects of dark matter. Some nontrivial probes for the nature of the dark matter are presented in the present issue.

In this article, the authors carry out a pioneering study of monocrystalline TlInS${}_2〈5\%\mathrm{\text{C}}〉$ at higher than room-temperatures using impedance spectroscopy. It is shown that in TlInS${}_2〈5\%\mathrm{\text{C}}〉$ crystals at temperatures higher than 400 K, the nature of conductivity is predominantly ionic. Moreover, characteristics of impedance spectra behavior of TlInS${}_2〈5\%\mathrm{\text{C}}〉$ monocrystal samples were studied using the measurement frequency range of 25–10⁶ Hz. For the measured frequency range, it is shown that curves of active and reactive impedance components undergo a dispersion characterized by decreasing values of $Z^{\prime }$ and $Z^{\prime \prime }$, as the frequency of the electric field and radiation dose increases.

The measurement of patients’ dosages of radiation caused by medical diagnostics continues to be challenging. A Cantor sequence photonic crystal structure using porous silicon doped with a polymer of polyvinyl alcohol, carbol fuchsin and crystal violet (DPV) is proposed. The influence rules of geometrical and optical parameters such as the radiation doses, number of periods, porosity of porous layers, incident angle and thickness of layers are investigated using MATLAB based on the transfer matrix method. The transmittance of the Cantor sequence of a defective photonic crystal sensor under different conditions is investigated to select the optimum conditions. The proposed system recorded the accepted sensitivity of 0.265nm/Gy, FoM of 6.5Gy${}^{-1}$, Q of 12,701, RS of $6\times 10^{-3}$ and LoD of $8\times 10^{-3}$ for gamma radiation. The suggested detector has simple design, accurate monitoring efficiency and immense potential for gamma radiation sensing.

Two-photon excited fluorescence (TPEF) spectroscopy and imaging were used to investigate the effects of gamma-irradiation on neural stem and precursor cells (NSPCs). While the observed signal from reduced nicotinamide adenine dinucleotide (NADH) was localized to the mitochondria, the signal typically associated with oxidized flavoproteins (Fp) was distributed diffusely throughout the cell. The measured TPEF emission and excitation spectra were similar to the established spectra of NAD(P)H and Fp. Fp fluorescence intensity was markedly increased by addition of the electron transport chain (ETC) modulator menadione to the medium, along with a concomitant decrease in the NAD(P)H signal. Three-dimensional (3D) neurospheres were imaged to obtain the cellular metabolic index (CMI), calculated as the ratio of Fp to NAD(P)H fluorescence intensity. Radiation effects were found to differ between low-dose (≤ 50 cGy) and high-dose (≥ 50 cGy) exposures. Low-dose irradiation caused a marked drop in CMI values accompanied by increased cellular proliferation. At higher doses, both NAD(P)H and Fp signals increased, leading to an overall elevation in CMI values. These findings underscore the complex relationship between radiation dose, metabolic state, and proliferation status in NSPCs and highlight the ability of TPEF spectroscopy and imaging to characterize metabolism in 3D spheroids.

Potassium iron hexacyanoferrate/polyacrylamide nanohybrid hydrogel (PB/PAM-gel) was successfully synthesized via a convenient one-pot gamma radiation route. The as-prepared PB/PAM-gel has compact internal three-dimensional porous structures with well-dispersed PB nanowires, which exhibit good elasticity and excellent swelling performance. The adsorption experiments reveal that the PB/PAM-gel can rapidly and selectively adsorb Cs${}^{+}$ from the solution in a wide range of pH. The maximum adsorption capacity reaches 131mgg${}^{-1}$. This nanohybrid hydrogel is very stable and can be easily separated from the solution after adsorption. It can be applied as a potential adsorbent for Cs${}^{+}$ removal from radioactive wastewater.

Intentionally doped LiCaAlF₆ (LiCAF) single crystals are prospective scintillators, especially for thermal neutron detection through the ⁶Li(n,t)⁴He nuclear reaction. Four different LiCAF scintillator samples were tested in various neutron and gamma fields. Two of the tested samples were LiCAF:Eu and LiCAF:Eu,Na single crystals, and another two samples were made of LiCAF:Eu micro crystals dispersed in transparent rubber, with different rubber dimensions. All LiCAF samples contain lithium enriched to${}^6$Li. A plutonium–beryllium source was used as a neutron source. The neutron spectrum was modified by moderator and filter to get different ratios between thermal, epithermal and fast neutron fluence rates. The MCNP code was used for calculations of the fluence rates for different configurations. Radionuclides ${}^{137}$Cs and ${}^{60}$Co were applied as gamma radiation sources. The light signal from the scintillator was evaluated with a photomultiplier and a multichannel analyzer. The purpose of this work was to study the characteristics of LiCAF scintillators, especially the ability to discriminate signals from neutron and gamma radiation, which is the basic scintillator condition for neutron detection in mixed neutron-gamma radiation fields. Generally, the discrimination can be done by the pulse height and/or the pulse shape of the evaluated signals. Both methods can be used for a LiCAF scintillator. However, only the pulse height discrimination method is discussed in this paper. The possibility of fast neutron detection with LiCAF scintillators was also tested.