We report the discovery of two consecutive, pressure driven magnetic instabilities in ${\mathrm{Yb}}_2{\mathrm{Pd}}_2\mathrm{Sn}$. They emerge in a non-Fermi liquid environment at the initial and the final point of a dome-like, single magnetic phase at pressures ${\mathrm{p}}_{\mathrm{c}1}\approx 1$ GPa and ${\mathrm{p}}_{\mathrm{c}2}\approx 4$ GPa. This singular behavior of Yb compounds is supposed to result from mutually competing, pressure modified energy scales, which in case of ${\mathrm{Yb}}_2{\mathrm{Pd}}_2\mathrm{Sn}$ cause a sign change of the pressure dependence of the Kondo temperature $T_K$ and magnetic ordering temperature $T_N$.

In this study we investigated how two different approaches to drawing free body diagrams influence the development of students’ understanding of Newton’s laws, including their ability to identify real forces. For this purpose we developed a 12-item two-tier multiple choice survey and conducted a quasiexperiment. This experiment included two groups of first-year physics students from Rijeka (RG) ($n_e=27$) and Split (SG) ($n_c=25$) Universities. Students from both groups solved mechanics problems for a period of two class hours. The only difference was that RG students used the superposition of forces approach to solving mechanics problems and in SG the decomposition of forces approach has been used. The ANCOVA ($n_c=17$, $n_e=17$) showed a statistically significant difference in favor of RG, whereby the effect sizes were moderate to large, and the largest differences have been observed in the ability of identifying real forces. Students from the control group (SG) more often exhibited the misconception that forces and their components act on a body independently and simultaneously. Our results support the idea that the practice of resolving forces into the components may not be the most effective way to develop understanding of Newton’s laws and the concept of force.

The nature of the magnetically ordered state in calcium cuprate ${\mathrm{Ca}}_{0.85}{\mathrm{CuO}}_2$ has been studied by electron-spin resonance and magnetic-susceptibility measurements. A gap of 83 K in the spin excitation spectrum has been detected arising from the ordering of ${\mathrm{Cu}}^{2+}$ spins in the ${\mathrm{CuO}}_2$ chains. The magnetic structure can be considered as one dimensional and consists of short even-number spin segments with an antiferromagnetic coupling. The segments are separated by nonmagnetic ${\mathrm{Cu}}^{3+}$ ions that make the intersegment superexchange coupling constant vanishingly small. The observed magnetic structure can be explained by a simple geometrical model of a distribution of ${\mathrm{Cu}}^{2+}$ and ${\mathrm{Cu}}^{3+}$ ions that is determined by the ${\mathrm{Ca}}_{0.85}{\mathrm{CuO}}_2$ specific structure. For a stoichiometric approximant ${\mathrm{Ca}}_{0.833}{\mathrm{CuO}}_2$ the magnetic chains consist of regularly spaced noninteracting quartets of spins whereas the incommensurability of Ca and Cu lattices in ${\mathrm{Ca}}_{0.85}{\mathrm{CuO}}_2$ implies that in addition to the quartets there exist also segments with larger but still relatively small number of spins. The observed structure closely resembles the spin-Peierls dimerization where the insertion of the ${\mathrm{Cu}}^{3+}$ ions into the ${\mathrm{Cu}}^{2+}$ linear chain plays the role of a lattice distortion.

We aim to elucidate the mode of antibacterial action of the laser-synthesized silver colloid against Escherichia coli. Membrane integrity was studied by flow cytometry, while the strain viability of the treated culture was determined by plating. The spectrofluorometry was used to obtain the time development of the reactive oxygen species (ROS) inside the nanoparticle-treated bacterial cells. An integrated atomic force and bright-field/fluorescence microscopy system enabled the study of the cell morphology, Young modulus, viability, and integrity before and during the treatment. Upon lethal treatment, not all bacterial cells were shown to be permeabilized and have mostly kept their morphology with an indication of cell lysis. Young modulus of untreated cells was shown to be distinctly bimodal, with randomly distributed softer parts, while treated cells exhibited exponential softening of the stiffer parts in time. Silver nanoparticles and bacteria have shown a masking effect on the raw fluorescence signal through absorbance and scattering. The contribution of cellular ROS in the total fluorescence signal was resolved and it was proven that the ROS level inside the lethally treated cells is not significant. It was found that the laser-synthesized silver nanoparticles mode of antibacterial action includes reduction of the cell’s Young modulus in time and subsequently the cell leakage.