Synthesis and cytotoxic activity of substituted hexahydro-2H-4,6-(epoxymethano)chromen-8(5H)-ones obtained from (–)-verbenone

Russian Chemical Bulletin - A number of compounds with a substituted hexahydro-2H-4,6-(epoxymethano)chromen8(5H)-one framework was synthesized starting from monoterpenoid (–)-verbenone and...     

Effects of process parameters on the optical constants of highly textured V2O5 thin films

The optical properties of the highly-textured V₂O₅ thin-films grown on Si(100) by sputter-deposition at various oxygen reactive-pressures were investigated in detail. The profiles of the optical constants, namely the refractive index and extinction coefficient, of V₂O₅ films were evaluated in the photon-energy range of 1–5 eV. At photon-energy above 2.5 eV, the dispersion behavior in optical constants is explained based on Lorentz-Drude model. The refractive index dispersion fits to a Cauchy’s relation at photon-energy below 2.5 eV, where the V₂O₅-film is mostly transparent. The optical transitions across the bandgap occur at energy ～2.5–3.2 eV depending on the V₂O₅ growth conditions and film-microstructure. The highly-textured and c-axis oriented V₂O₅-films, fabricated under optimum conditions of temperature and oxygen partial pressure, exhibit excellent optical characteristics similar to V₂O₅ single crystals.     

Fusion-fission of heavy and superheavy nuclei

The process of fusion-fission of heavy and superheavy nuclei (SHE) with Z=82–122 formed in the reactions with ⁴⁸Ca and ⁵⁸Fe ions at energies near and below the Coulomb barrier has been studied. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR) and at the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL) using the time-of-flight spectrometer of fission fragments CORSET and the neutron multidetector DEMON. As a result of the experiments, mass and energy distributions (MED) of fission fragments; fission, quasifission, and evaporation residue cross sections; and multiplicities of neutrons and γ-quanta and their dependences on the mechanism of formation and decay of compound systems have been studied.     

Tracking dissipation in capture reactions

Nuclear dissipation in capture reactions is investigated using backtracing, a new analysis protocol. Combining analysis procedure with dynamical models, the difficult and long-standing problem of competition and mixing between quasifission and fusion-fission is solved for the first time. The nature of the relevant dissipation is determined as one-body dissipation. At low excitation energy where shell effects are strongly effective, the shape of the mass distribution could be a powerful check of the nature and the magnitude of the dissipation.     

Non-linear conductivity of one-dimensional charge density wave

A pure system with one-dimensional CDW placed in a homogeneous electric field is considered. Non-linear effects are found to appear due to motion of a soliton superstructure. The dependence of the differential conductivity on the electric field is calculated.     

Investigation of the reaction <Superscript>208</Superscript>Pb(<Superscript>18</Superscript>O, <Emphasis Type="Italic">f</Emphasis>): Folding angular distributions of fission fragments and gamma-ray multiplicity

Correlations between folding angular distributions of fission fragments and the gamma-ray multiplicity are studied for ¹⁸O + ²⁰⁸Pb interactions at energies of the beam of ¹⁸O ions in the range E _lab = 78–198.5 MeV. The probabilities are determined for complete-and incomplete-fusion processes inevitably followed by the fission of nuclei formed in these processes. It is found that the probability of incomplete fusion followed by fission increases with increasing energy of bombarding ions. It is shown that, for the incomplete-fusion process, folding angular distributions of fission fragments have a two-component structure. The width of folding angular distributions (FWHM) for complete fusion grows linearly with increasing energy of ¹⁸O ions. The multiplicity of gamma rays from fission fragments as a function of the linear-momentum transfer behaves differently for different energies of projectile ions. This circumstance is explained here by the distinction between the average angular momenta of participant nuclei in the fusion and fission channels, which is due to the difference in the probabilities of fission in the cases where different numbers of nucleons are captured by the target nucleus.     

Ferromagnet–superconductor hybrids

The new class of phenomena described in this review is based on the interaction between spatially separated, but closely located ferromagnets and superconductors, the so-called ferromagnet–superconductor hybrids (FSH). Typical FSH are: coupled uniform and textured ferromagnetic and superconducting films, magnetic dots over a superconducting film, magnetic nanowires in a superconducting matrix, etc. The interaction is provided by the magnetic field generated by magnetic textures and supercurrents. The magnetic flux from magnetic structures or topological defects can pin vortices or create them, changing the transport properties and transition temperature of the superconductor. On the other hand, the magnetic field from supercurrents (vortices) strongly interacts with the magnetic subsystem, leading to formation of coupled magnetic–superconducting topological defects.

The proximity of ferromagnetic layer dramatically changes the properties of the superconducting film. The exchange field in ferromagnets not only suppresses the Cooper-pair wavefunction, but also leads to its oscillations, which in turn leads to oscillations of observable values: the transition temperature and Josephson current. In particular, in the ground state of the Josephson junction the relative phase of two superconductors separated by a layer of ferromagnetic metal is equal to?π?instead of the usual zero (the so-called π-junction). Such a junction carries a spontaneous supercurrent and possesses other unusual properties. Theory predicts that rotation of magnetization transforms s-pairing into p-pairing. The latter is not suppressed by the exchange field and serves as a carrier of long-range interaction between superconductors.     

Vortex domain walls in helical magnets

We show that helical magnets exhibit a nontrivial type of domain wall consisting of a regular array of vortex lines, except for a few distinguished orientations. This result follows from topological consideration and is independent of the microscopic models. We used simple models to calculate the shape and energetics of vortex walls in centrosymmetric and noncentrosymmetric crystals. Vortices are strongly anisotropic, deviating from the conventional Berezinskii-Kosterlitz-Thouless form. The width of the domain walls depend only weakly on the magnetic anisotropy, in contrast to ferromagnets and antiferromagnets. We show that vortex walls can be driven by external currents and in multiferroics also by electric fields.     

Principles of demineralization: modern strategies for the isolation of organic frameworks. Part I. Common definitions and history

In contrast to biomineralization phenomena, that are among the most widely studied topics in modern material and earth science and biomedicine, much less is systematized on modern view of demineralization. Biomineralized structures and tissues are composites, containing a biologically produced organic matrix and nano- or microscale amorphous or crystalline minerals. Demineralization is the process of removing the inorganic part, or the biominerals, that takes place in nature via either physiological or pathological pathways in organisms. In vitro demineralization processes, used to obtain mechanistic information, consist in the isolation of the mineral phase of the composite biomaterials from the organic matrix. Physiological and pathological demineralization include, for example, bone resorption mediated by osteoclasts. Bioerosion, a more general term for the process of deterioration of the composite biomaterials represents chemical deterioration of the organic and mineral phase followed by biological attack of the composite by microorganisms and enzymes. Bioerosional organisms are represented by endolithic cyanobacteria, fungi, algae, plants, sponges, phoronids and polychaetes, mollusks, fish and echinoids.In the history of demineralization studies, the driving force was based on problems of human health, mostly dental caries. In this paper we summarize and integrate a number of events, discoveries, milestone papers and books on different aspect of demineralization during the last 400 years. Overall, demineralization is a rapidly growing and challenging aspect of various scientific disciplines such as astrobiology, paleoclimatology, geomedicine, archaeology, geobiology, dentistry, histology, biotechnology, and others to mention just a few.