Unconventional order/disorder behaviour in Al–Co–Cu–Fe–Ni multi-principal element alloys after casting and annealing

The effect of Cu concentration on the order/disorder behaviour of the AlCoCuxFeNi (x = 0.6 to 3.0) multi-principal element alloys was investigated. BCC and/or FCC phases were observed in the microstructures of the alloys after casting and annealing at 1050 ◦C followed by slow cooling. Interesting is that the alloys form ordered structures after casting and disordered structures after annealing and slow cooling, while the opposite would be expected. The ordering in the as-cast state is explained by the strong affinity of Al to transition metals, which results in the formation of supercell structures having sublattices occupied by certain elements only. Disordering after annealing has two reasons. Either the phase is composed of nearly pure element (Cu) and is disordered by default or it is composed of randomly distributed nano-segregated regions within a single phase resulting in a uniform distribution of all elements in the sublattices and therefore appearing to be macroscopically disordered. The reason for the formation of such nano-segregated areas might reside in the reduction of Gibbs free energy due to the annealing by the interplay between enthalpy and entropy

Synthesis and properties of open fullerenes encapsulating ammonia and methane

We describe the synthesis and characterisation of open fullerene (1) and its reduced form (2) in which CH₄ and NH₃ are encapsulated, respectively. The ¹H NMR resonance of endohedral NH₃ is broadened by scalar coupling to the quadrupolar ¹⁴N nucleus, which relaxes rapidly. This broadening is absent for small satellite peaks, which are attributed to natural abundance ¹⁵N. The influence of the scalar relaxation mechanism on the linewidth of the ¹H ammonia resonance is probed by variable temperature NMR. A rotational correlation time of τc= 1.5 ps. is determined for endohedral NH₃, and of τc=57±5 ps. for the open fullerene, indicating free rotation of the encapsulated molecule. IR spectroscopy of NH3@2 at 5 K identifies three vibrations of NH₃ (ν₁, ν₃ and ν₄) redshifted in comparison with free NH₃, and temperature dependence of the IR peak intensity indicates the presence of a large number of excited translational/ rotational states. Variable temperature ¹H NMR spectra indicate that endohedral CH4 is also able to rotate freely at 223 K, on the NMR timescale. Inelastic neutron scattering (INS) spectra of CH₄@1 show both rotational and translational modes of CH₄. Energy of the first excited rotational state (J=1) of CH₄@1 is significantly lower than that of free CH₄

The crisis of family in the end of 20th century and beginning of 21th century

Tato bakalářská práce je úvahou o rodině (označované jako nukleární), jejím počátku a vývoji v čase. Důraz je kladen na přelom moderní a postmoderní doby. Rodina je zkoumána jak z pohledu státu, tak i z pohledu jednotlivce. Pozornost je zaměřena na příčiny, které způsobily vlastní rozpad a nestabilitu rodiny. Dále na důsledky, které z toho plynou a lze je považovat za vlastní počátek krize rodiny. Rozvodovost, klesající sňatečnost a (ne)přirozený úbytek obyvatelstva je důkazem toho, že lidé už nežijí v širokém ochranném pásmu své rodiny jako před desítkami let, ale naopak se stále častěji ocitají na pokraji příbuzenské samoty.The bachelor thesis is a consideration about family (described as nuclear), in its beginning and developing during the time period. Emphasis is focused directly to break of postmodern and modern period. The family is studied from the state aspect and from individual aspect too. Observance is focused to reasons, which are responsible for destroying and instability of the family. Results coming from this family posture are start of family crisis. Evidence of human disunion from wide protected zone of family are divorce rate, marriage rate and unnatural decreasing our population.Katedra sociálních vědDokončená práce s úspěšnou obhajobo

NMR absolute shielding scale and nuclear magnetic dipole moment of 207 Pb

An absolute shielding scale is proposed for 207Pb nuclear magnetic resonance (NMR) spectroscopy. It is based on ab initio calculations performed on an isolated tetramethyllead Pb(CH3)4 molecule and the assignment of the experimental resonance frequency from the gas-phase NMR spectra of Pb(CH3)4, extrapolated to zero density of the buffer gas to obtain the result for an isolated molecule. The computed207Pb shielding constant is 10 790 ppm for the isolated molecule, leading to a shielding of 10799.7 ppm for liquid Pb(CH3)4 which is the accepted reference standard for 207Pb NMR spectra. The new experimental and theoretical data are used to determine μ(207Pb), the nuclear magnetic dipole moment of 207Pb, by applying the standard relationship between NMR frequencies, shielding constants and nuclear moments of two nuclei in the same external magnetic field. Using the gas-phase 207Pb and (reference) proton results and the theoretical value of the Pb shielding in Pb(CH3)4, we find μ(207Pb) = 0.59064 μN. The analysis of new experimental and theoretical data obtained for the Pb2+ ion in water solutions provides similar values of μ(207Pb), in the range of 0.59000–0.59131 μN