Giant phonon anomalies in the pseudo-gap phase of TiOCl

We report infrared and Raman spectroscopy results of the spin-1/2 quantum magnet TiOCl. Giant anomalies are found in the temperature dependence of the phonon spectrum, which hint to unusual coupling of the electronic degrees of freedom to the lattice. These anomalies develop over a broad temperature interval, suggesting the presence of an extended fluctuation regime. This defines a pseudo-gap phase, characterized by a local spin-gap. Below 100 K a dimensionality cross-over leads to a dimerized ground state with a global spin-gap of about 2$\Delta_{spin}\approx$~430 K.Comment: 4 pages, 3 figures, for further information see http://www.peter-lemmens.d

Infrared optical properties of the spin-1/2 quantum magnet TiOClTiOCl

We report results on the electrodynamic response of $TiOCl$, a low-dimensional spin-1/2 quantum magnet that shows a spin gap formation for T$<T_{c1}$= 67 $K$. The Fano-like shape of a few selected infrared active phonons suggests an interaction between lattice vibrations and a continuum of low frequency (spin) excitations. The temperature dependence of the phonon mode parameters extends over a broad temperature range well above $T_{c1}$, indicating the presence of an extended fluctuation regime. In the temperature interval between 200 $K$ and $T_{c1}$ there is a progressive dimensionality crossover (from two to one), as well as a spectral weight shift from low towards high frequencies. This allows us to identify a characteristic energy scale of about 430 $K$, ascribed to a pseudo spin-gap

Lattice Relaxation and Charge-Transfer Optical Transitions Due to Self-Trapped Holes in Non-Stoichiometric LaMnO3_3 Crystal

We use the Mott-Littleton approach to evaluate polarisation energies in LaMnO$_3$ lattice associated with holes localized on both Mn$^{3+}$ cation and O$^{2-}$ anion. The full (electronic and ionic) lattice relaxation energy for a hole localized at the O-site is estimated as 2.4 eV which is appreciably greater than that of 0.8 eV for a hole localized at the Mn-site, indicating on the strong electron-phonon interaction in the former case. Using a Born-Haber cycle we examine thermal and optical energies of the hole formation associated with electron ionization from Mn$^{3+}$, O$^{2-}$ and La$^{3+}$ ions in LaMnO$_3$ lattice. For these calculations we derive a phenomenological value for the second electron affinity of oxygen in LaMnO$_3$ lattice by matching the optical energies of La$^{4+}$ and O$^-$ hole formation with maxima of binding energies in the experimental photoemission spectra. The calculated thermal energies predict that the electronic hole is marginally more stable in the Mn$^{4+}$ state in LaMnO$_3$ host lattice, but the energy of a hole in the O$^-$ state is only higher by a small amount, 0.75 eV, rather suggesting that both possibilities should be treated seriously. We examine the energies of a number of fundamental optical transitions, as well as those involving self-trapped holes of Mn$^{4+}$ and O$^-$ in LaMnO$_3$ lattice. The reasonable agreement with experiment of our predicted energies, linewidths and oscillator strengths leads us to plausible assignments of the optical bands observed. We deduce that the optical band near 5 eV is associated with O(2p) - Mn(3d) transition of charge-transfer character, whereas the band near 2.3 eV is rather associated with the presence of Mn$^{4+}$ and/or O$^-$ self-trapped holes in non-stoichiometric LaMnO$_3$ compound.Comment: 18 pages, 6 figures, it was presented partially at SCES-2001 conference in Ann Arbor, Michiga

The Infestation of Fleas of the Long-Tailed Souslik with Entomoparasitic Nematodes in Tuva Mountain Natural Plague Focus

Entomoparasitic nematodes are supposed to be a link between parts of Yersinia pestis population in the environment and the flea vector. The aim of the study was to assess the prevalence and intensity of infestation in the fleas of the long-tailed souslik with entomoparasitic nematodes on the territory of Mongun-Taiginsky station in the Tuva natural plague focus. Materials and methods. Fleas were collected during the scheduled epizootiological surveys in 2019–2021. In the course of taxonomic identification the presence of parasitic nematodes was registered. In order to evaluate the intensity of nematode invasion, a total of 190 fleas were dissected. The number of adult parasitizing females and presence of larvae was recorded. Statistical processing of the data was performed with the help of conventional methods using the Excel software. The criterion χ2 was applied; the influence of various factors (species, gender of fleas) on the studied parameters was assessed through single- and two-factor analysis of variance. Results and discussion. During three years of observations, entomoparasitic nematodes were found in six species of fleas: Citellophilus tesquorum, Frontopsylla elatoides, Rhadinopsylla li transbaikalica, Frontopsylla hetera, Oropsylla alaskensis, and Neopsylla mana. The differences in infestation with nematodes between the species are presented. The highest invasion rate – 25.1–25.6 % – is observed in Rh. li transbaikalica. The gender of leas does not influence their infestation. It is established that invaded fleas are more often found in the nest than in the fur of animals, they are less actively migrate to the burrow entrance compared to not invaded ones. Evaluation of infestation prevalence has revealed that fleas Rh. li transbaikalica are the hosts for nematodes of mono- or oligoxenic species, which do not occur in other fleas

Control of Mooij correlations at the nanoscale in the disordered metallic Ta - nanoisland FeNi multilayers

Localisation phenomena in highly disordered metals close to the extreme conditions determined by the Mott-Ioffe-Regel (MIR) limit when the electron mean free path is approximately equal to the interatomic distance is a challenging problem. Here, to shed light on these localisation phenomena, we studied the dc transport and optical conductivity properties of nanoscaled multilayered films composed of disordered metallic Ta and magnetic FeNi nanoisland layers, where ferromagnetic FeNi nanoislands have giant magnetic moments of 10^3-10^5 Bohr magnetons (\mu_B). In these multilayered structures, FeNi nanoisland giant magnetic moments are interacting due to the indirect exchange forces acting via the Ta electron subsystem. We discovered that the localisation phenomena in the disordered Ta layer lead to a decrease in the Drude contribution of free charge carriers and the appearance of the low-energy electronic excitations in the 1-2 eV spectral range characteristic of electronic correlations, which may accompany the formation of electronic inhomogeneities. From the consistent results of the dc transport and optical studies we found that with an increase in the FeNi layer thickness across the percolation threshold evolution from the superferromagnetic to ferromagnetic behaviour within the FeNi layer leads to the delocalisation of Ta electrons from the associated localised electronic states. On the contrary, we discovered that when the FeNi layer is discontinuous and represented by randomly distributed superparamagnetic FeNi nanoislands, the Ta layer normalized dc conductivity falls down below the MIR limit by about 60%. The discovered effect leading to the dc conductivity fall below the MIR limit can be associated with non-ergodicity and purely quantum (many-body) localisation phenomena, which need to be challenged further.Comment: 29 pages, 8 figures. This is a post-peer-review, precopyedit version of an article published in Scientific Reports. The final authenticated version is available online at http://dx.doi.org/10.1038/s41598-020-78185-

Errors in chromosome segregation during oogenesis and early embryogenesis

Errors in chromosome segregation occurring during human oogenesis and early embryogenesis are very common. Meiotic chromosome development during oogenesis is subdivided into three distinct phases. The crucial events, including meiotic chromosome pairing and recombination, take place from around 11 weeks until birth. Oogenesis is then arrested until ovulation, when the first meiotic division takes place, with the second meiotic division not completed until after fertilization. It is generally accepted that most aneuploid fetal conditions, such as trisomy 21 Down syndrome, are due to maternal chromosome segregation errors. The underlying reasons are not yet fully understood. It is also clear that superimposed on the maternal meiotic chromosome segregation errors, there are a large number of mitotic errors taking place post-zygotically during the first few cell divisions in the embryo. In this chapter, we summarise current knowledge of errors in chromosome segregation during oogenesis and early embryogenesis, with special reference to the clinical implications for successful assisted reproduction

Особенности организации помощи и диспансерное наблюдение взрослых, больных муковисцидозом

Based on the long-term surveillance of 127 patients older than 15 yrs and 173 children aged 3 months to 15 yrs we concluded of the survival age of cystic fibrosis patients in Russia (16.9 ±1.1 yrs). Patients older than 15 yrs take 30.1 % of all the investigated patients. Under the adequate surveillance and treatment conditions 82.4 % of adult patients keep their social activity and only 17.6 % of the patients do not work and do not study.На основании многолетнего наблюдения за 127 пациентами старше 15 лет и 173 детьми в возрасте от 3 мес. до 15 лет делаются выводы о возрасте выживаемости больных муковисцидозом в России (16,9 ± 1,1 год), лица старше 15 лет среди всех обследованных составляют 30,1 % . При правильно организованном диспансерном наблюдении и лечении 82,4 % взрослых сохраняют социальную активность и только 17,6 % не работают и не учатся