Superconductivity emerging from an electronic phase separation in the charge ordered phase of RbFe2_2As2_2

$^{75}$As, $^{87}$Rb and $^{85}$Rb nuclear quadrupole resonance (NQR) and $^{87}$Rb nuclear magnetic resonance (NMR) measurements in RbFe$_2$As$_2$ iron-based superconductor are presented. We observe a marked broadening of $^{75}$As NQR spectrum below $T_0\simeq 140$ K which is associated with the onset of a charge order in the FeAs planes. Below $T_0$ we observe a power-law decrease in $^{75}$As nuclear spin-lattice relaxation rate down to $T^*\simeq 20$ K. Below that temperature the nuclei start to probe different dynamics owing to the different local electronic configurations induced by the charge order. A fraction of the nuclei probes spin dynamics associated with electrons approaching a localization while another fraction probes activated dynamics possibly associated with a pseudogap. These different trends are discussed in the light of an orbital selective behaviour expected for the electronic correlations.Comment: 5 pages, 3 figures and 4 pages of supplemental materia

Magnetic phase diagram of Ca-substituted EuFe2_2As2_2

The simultaneous presence of a Fe-related spin-density wave and antiferromagnetic order of Eu$^{2+}$ moments ranks EuFe$_2$As$_2$ among the most interesting parent compounds of iron-based pnictide superconductors. Here we explore the consequences of the dilution of Eu$^{2+}$ magnetic lattice through on-site Ca substitution. By employing macro- and microscopic techniques, including electrical transport and magnetometry, as well as muon-spin spectroscopy, we study the evolution of Eu magnetic order in both the weak and strong dilution regimes, achieved for Ca concentration $x(\mathrm{Ca}) = 0.12$ and 0.43, respectively. We demonstrate the localized character of the Eu antiferromagnetism mediated via RKKY interactions, in contrast with the largely itinerant nature of Fe magnetic interactions. Our results suggest a weak coupling between the Fe and Eu magnetic sublattices and a rapid decrease of the Eu magnetic interaction strength upon Ca substitution. The latter is confirmed both by the depression of the ordering temperature of the Eu$^{2+}$ moments, $T_\mathrm{N}$, and the decrease of magnetic volume fraction with increasing $x(\mathrm{Ca})$. We establish that, similarly to the EuFe$_2$As$_2$ parent compound, the investigated Ca-doped compounds have a twinned structure and undergo a permanent detwinning upon applying an external magnetic field

Ablation of smooth muscle myosin heavy chain SM2 increases smooth muscle contractility and results in postnatal death in mice

The smooth muscle myosin heavy chains (SMHC) are motor proteins powering smooth muscle contraction. Alternate splicing of SHMC gene at the C-terminus produces SM1, and SM2 myosin isoforms; SM2 (200 kDa) contains a unique 9-amino-acid sequence at the carboxyl terminus, whereas SM1 (204 kDa) has a 43 amino acid non-helical tail region. To date the functional difference between C-terminal isoforms has not been established; therefore, we used an exon-specific gene targeting strategy and generated a mouse model specifically deficient in SM2. Deletion of exon-41 of the SMHC gene resulted in a complete loss of SM2 in homozygous (_SM2^-/-^_) mice, accompanied by a concomitant down-regulation of SM1 in bladders. While heterozygous (_SM2^+/-^_) mice appeared normal and fertile, _SM2^-/-^_ mice died within 30 days after birth. The peri-mortal _SM2^-/-^_ mice showed reduced body weight, distention of the bladder and alimentary tract, and end-stage hydronephrosis. Interestingly, strips from _SM2^-/-^_ bladders showed increased contraction to K^+^ depolarization or M3 receptor activation. These results suggest that SM2 myosin has a distinct functional role in smooth muscle, and the deficiency of SM2 increases smooth muscle contractility, and causes dysfunctions of smooth muscle organs, including the bladder that leads to the end-stage hydronephrosis and postnatal death

Mathematical modeling of dynamic processes of diffusion masstransfer in heterogeneous halflimited flat magnetic mediums

Методом інтеґральних перетворень Фур’є з n-точками спряження побудовано математичну модель процесів дифузійного переносу в багатошарових магнітних напівобмежених середовищах. Знайдено точний розв`язок такої задачі шляхом побудови головних розв`язків – фундаментальних функцій Коші і Гріна. Досліджено умови їх збіжності. Здійснено моделювання дифузійного пeреносу та проведено адекватність моделі за результатами натуpних експериментів.Mathematical model of diffusion mathtransfer in multilayer magnetic halflimited medium with use of n-conjuction points Fouirer transformation has been built. The analitycal olution of such problem according to Couchy and Green function has been found for the first time. The conditions of convergence. Mathematical modeling of diffusion masstransfer and adequacy check has been done

Detection of low-energy charged particles by channel electron multipliers

Experimental determinations of the detection efficiency for positrons impacting a channel electron multiplier with incident energies between 0–1400 eV are presented. A log-normal dependence with energy is established and used to compute the positron-to-positronium detection efficiency ratio as a function of positronium energy, as required for determining quantities involving the ratio of positron and positronium rates. A log-normal energy-dependence is also observed in results of previous work with electrons, protons and ions

Modeling of chrome diffusion transfer processes in multicomposite oxide nanofilms

Побудовано математичну модель дифузійного переносу в багатокомпозитних оксидних наноплівках. За результатами експериментальних досліджень вмісту хрому в зразках, створених за технологією виробництва супертонкого волокна, отримано розподіли коефіцієнтів дифузії хрому. Змодельовано кінетику процесу дифузії у вигляді розподілів вмісту хрому в зразку для різних технологічних зрізів та часових тривалостей формування мультишару наноплівки.This paper deals with a problem of mathematical modeling of diffusive transport in multilayer mediums. The aim is to analyze and to model the diffusion transfer of chromium (Cr) in the mineral fibers on the basis of the proposed mathematical model of multicomposite medium. Multycomposite medium with established uniform layers n and n +1- th layer, whose thickness is much greater than the previous ones is analysed. The proposed mathematical model is based on the account of component interdiffusion between adjacent layers of n-layer medium. To find a solution of the problem Fourier integral transformations were consistently applied. For numerical simulation results of experimental studies on chromium distribution in feeders operated for 20 and 30 days in the production of super-thin basalt fibers (STBF) were used. Having applied the approaches of optimal control theory of distributed systems for analysis of experimental distributions, the diffusion coefficients of chromium (Cr) in a medium layers were obtained. Examples of numerical modeling of the distribution of chromium in production of STBF are provided. These concentration distributions are constructed for different time points of forming process of multicomposite nanofilms. For ease of analysis of diffusion transfer kinetics, distributions are given for the five time points, that correspond to conditionally stages of protective layer formation from the beginning (0.25T) to the end (1T). While analyzing the results it is worth stressing the almost complete coincidence of model chromium distribution curve with corresponding experimental distributions. The maximum deviation between these two concentrations for the period of multycomposite completion are less than 3%, which tesifies the reliability of the proposed model. These spatially distributed chromium concentration distributions for various technological sections of oxide nanofilms and time durations of multiconposite nanofils formation process allow to analyse of the kinetics of multilayer formation, that can be applied for the process operations improvement and new nanomaterials properties study