Preparation and dielectric properties of the lead-free BaFe<Subscript>1/2</Subscript>Nb<Subscript>1/2</Subscript>O<Subscript>3</Subscript> ceramics obtained from mechanically triggered powder

In the paper the influence of mechanical activation of the powder on the final dielectric properties lead-free Ba(Fe_1/2Nb_1/2)O₃ (BFN) ceramic was examined. The BFN ceramics were obtained by 3-steps route. Firstly, the substrates were pre-homogenized in a planetary ball mill. Than, the powder was activated in vibratory mill (the shaker type SPEX 8000 Mixer Mill) for different duration between 25 h and 100 h. The influence of the milling time on the BFN powder was monitored by X-ray diffraction. The diffraction data confirmed that the milling process of the starting components is accompanied by partial synthesis of the BFN materials. The longer of the high-energy milling duration the powders results in increasing the amount of amorphous/nanocrystalline content. The mechanically activated materials were sintered in order to obtain the ceramic samples. During this temperature treatment the final crystallisation of the powder appeared what was confirmed by XRD studies. The performed dielectric measurements have revealed the reduction of the dielectric loss of the BFN ceramics compared to materials obtained by classic methods.     

Correlation between Ferromagnetic Layer Easy Axis and the Tilt Angle of Self Assembled Chiral Molecules

The spin–spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates.     

Effects of Different Drying Methods on the Retention of Bioactive Compounds,On-Line Antioxidant Capacity and Color of the Novel Snack from Red-Fleshed Apples

The aim of this study was to determine the effect of different drying methods: convective (at 50, 60, 70 °C), vacuum-microwave (at 120, 240, 360, 480 W and 360 W with reduction to 120 W) and hybrid (convective pre-drying at 50, 60, 70 °C followed by vacuum-microwave drying at 120 W) on the quality parameters of novel red-fleshed apple fruit snacks (RFAs), such as phenolics, on-line antioxidant capacity, water activity and color. Drying kinetics, including a temperature profile of dried material, and modified Page model were determined. Freeze-drying was used as a control method. The highest content of bioactive compounds in the samples was retained following freeze-drying, then hybrid, vacuum-microwave and finally convection drying. The antioxidant capacity measured by on-line 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), identified anthocyanins, flavan-3-ols and phenolic acid as the main compounds responsible for this activity. Unfavorable changes in color, formation of hydroxymethylfurfural (HMF) and degradation of polyphenolics were noted along with increasing drying temperature and magnetron power. The red-fleshed apple snacks are a promising high-quality dehydrated food product belonging to functional foods category.     

Blue-Shift Hydrogen Bonds in Silyltriptycene Derivatives: Antibonding σ* Orbitals of the Si−C Bond as Effective Acceptors of Electron Density

Triptycene derivatives are widely utilized in different fields of chemistry and materials sciences. Their physicochemical properties, often of pivotal importance for the rational design of triptycene-based functional materials, are influenced by noncovalent interactions between substituents mounted on the triptycene skeleton. Herein, a unique interaction between electron-rich substituents in the peri position and the silyl group located on the bridgehead sp³-carbon is discussed on the example of 1,4-dichloro-9-(p-methoxyphenyl)-silyltriptycene (TRPCl) which exists in solution in the form of two rotamers differing by dispositions, syn or anti, of the Si−C_Ph (the C_Ph atom is from the p-methoxyphenyl group) bond against the peri-Cl atom. For the first time, substantial differences between the Si−C_Ph bonds in these two dispositions are identified, based on indirect experimental and direct theoretical evidence. For these two orientations, the experimental ¹J(Si,C_Ph) values differ by as much as 10 percent. The differences are explained in terms of effective electron density transfer from the peri-Cl atom to the antibonding σ* orbitals of the Si−X bonds (X=H, C_Ph) oriented anti to that atom. The electronic effects are revealed by an NBO analysis. Connections of these observations with the notion of blue-shifting hydrogen bonds are discussed.     

On the symmetry of the seminal Horodecki state

It is shown that the seminal Horodecki 2-qutrit state belongs to the class of states displaying symmetry governed by a commutative subgroup of the unitary group U(3). Taking a conjugate subgroup one obtains another classes of symmetric states and one finds equivalent representations of the Horodecki state. These results are generalized to d⊗d systems.     

A New Route to 3-Phosphonylpyrazoles

The regioselective synthesis of 3-diethoxyphosphonopyrazoles has been accomplished through the addition of aryl or alkyl hydrazines to (3-ethoxyacryloyl)phosphonic acid diethyl ester. An example of hydrolysis of the pyrazolephosphonic ester to the corresponding acid is described.     

SO(2) Symmetry of a Maxwell p-Form Theory

We find a universal SO(2) symmetry of a p-form Maxwell theory for both odd and even p. For odd p, it corresponds to the duality rotations but for even p, it defines a new set of transformations which is not related to duality rotations. In both cases, a symmetry group defines a subgroup of the O(2,1) group of R-linear canonical transformations which has also a natural representation on the level of quantization condition for p-brane dyons.