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The spectacular properties of liquid helium at low temperature are generally accepted as the signature of the bosonic nature of this system. Particularly the superfluid phase is identified with a Bose–Einstein condensed fluid. However, the relationship between the superfluidity and the Bose–Einstein condensation is still largely unknown. Studying a perturbed liquid ⁴He system would provide information on the relationship between the two phenomena. Liquid ⁴He confined in porous media provides an excellent example of a boson system submitted to disorder and finite-size effects.

Much care should be paid to the sample preparation, particularly the confining condition should be defined quantitatively. To achieve homogeneous confinement conditions, firstly a suitable porous sample should be selected, the experiments should then be conducted at a lower pressure than the saturated vapor pressure of bulk helium.

Several interesting effects have been shown in confined ⁴He samples prepared as described above. Particularly we report the observation of the separation of the superfluid-normal fluid transition temperature, T_c, from the temperature at which the Bose–Einstein condensation is believed to start, T_BEC, the existence of metastable densities for the confined liquid accessible to the bulk system as a short-lived metastable state only and strong clues for a finite lifetime of the elementary excitations at temperatures as low as 0.4 K.

Hydrogen adsorption isotherms for (8, 0) platinum-decorated single-walled carbon nanotube were studied using molecular dynamics simulation. Adsorption isotherms were obtained for both internal and external surfaces of nanotube at several temperatures from 77 K up to 400 K. The results were compared with the bare nanotube at the same conditions. Adsorption coverage, isosteric heat, binding energy, hydrogen desorption, and readsorption were calculated for both internal and external surfaces of nanotube. At low temperatures, hydrogen molecules were adsorbed significantly, but at higher temperatures, thermal energies reduced this capacity. Under the same conditions, the platinum-decorated single-walled carbon nanotube hydrogen adsorption is significantly higher than the bare one.

The environmental impact of untreated dye effluent is a concern due to potential mutagenic and allergic effects. This study aims to develop a cost-effective selenium-doped biochar as an adsorbent material to remove acid red (AR) and crystal violet (CV) dyes from water. Selenium nanoparticles (SeNPs) were produced using chemical and biological synthesis methods. The SEM, EDX, XRD, FTIR, and BET surface analysis methods were used to characterize the biochar and selenium-doped biochar (Se-AC and BSe-AC) samples. Surface modification with SeNPs resulted in an increase in surface area to 14.560m²/g for Se-AC and 85.456m²/g for BSe-AC. Different adsorption isotherms (Langmuir, Freundlich, and Temkin) and adsorption kinetic models (pseudo-firstorder, pseudo-secondorder, and intra-particle diffusion kinetics) were investigated to understand the adsorption patterns of biochar, Se-AC, and BSe-AC. The maximum adsorption capacities of biochar, Se-AC, and BSe-AC for AR and CV dye were found to be between 0.48mgg${}^{-1}$ and 7.51mgg${}^{-1}$, 2.31mgg${}^{-1}$ and 7.86mgg${}^{-1}$, and 6.88mgg${}^{-1}$ and 9.09mgg${}^{-1}$, respectively, at 313K. The obtained negative $\mathrm{\Delta }{G}^{\circ }$ indicates effective adsorption, while a positive $\mathrm{\Delta }{H}^{\circ }$ suggests an endothermic reaction for both dyes. BSe-AC is an eco-friendly alternative to biochar for removing AR and CV.