Sigma Oscillations Protect or Reinstate Motor Memory Depending on their Temporal Coordination with Slow Waves

Targeted memory reactivation (TMR) during post-learning sleep is known to enhance motor memory consolidation but the underlying neurophysiological processes remain unclear. Here, we confirm the beneficial effect of auditory TMR on motor performance. At the neural level, TMR enhanced slow waves (SW) characteristics. Additionally, greater TMR-related phase-amplitude coupling between slow (0.3-2 Hz) and sigma (12-16 Hz) oscillations after the SW peak was related to higher TMR effect on performance. Importantly, sounds that were not associated to learning strengthened SW-sigma coupling at the SW trough and the increase in sigma power nested in the trough of the potential evoked by these unassociated sounds was related to the TMR benefit. Altogether, our data suggest that, depending on their precise temporal coordination during post learning sleep, slow and sigma oscillations play a crucial role in either memory reinstatement or protection against irrelevant information; two processes that critically contribute to motor memory consolidation.

Formation of modified whitlockite-related calcium phosphates under conditions of coprecipitation from aqueous solutions

The features of phase formation during wet coprecipitation from aqueous system Сa2+–NO3––Х (Х – NaH2PO4, Na2HPO4, Na3PO4) at the molar ratio Са2+/РО43–=1.6 and room temperature have been investigated. It was found formation of whitlockite-related calcium phosphates (trigonal system, space group R-3c). The results of elemental analysis indicated the chemical modification of calcium phosphates by sodium cations (samples contained 0.3–0.6 wt.% Na+). According to the resulta of thermogravimetry, the synthesized samples contained up to 6 wt.% of sorption water. Heating of samples to the temperature of 6000C is accompanied by water removal and an increase in particle size from 20–50 nm to 500 nm. It was shown that the use of sodium nitrate as a source of sodium cations in the formation of sodium-containing calcium phosphates allows obtaining compositions of whitlockite- and apatite-related phases. The mass ratio of phases can be adjusted by changing the content of sodium cations in the initial solution. The synthesized samples were characterized by X-ray powder diffraction, thermogravimetry, scanning electron microscopy and FTIR spectroscopy methods. Optimized conditions for preparation of whitlockite-related sodium-containing calcium phosphates as well as composites based on them with apatite-related phase can be further used in the development of materials with the required resorption rate for orthopedics.

Assignment of enantiomorphs for the chiral allotrope β-Mn by diffraction methods

The assignment of enantiomorphs by diffraction methods shows fundamental differences for x-rays and electrons. This is particularly evident for the chiral allotrope of β-Mn. While it is not possible to determine the sense of chirality of β-Mn with established x-ray diffraction methods, Kikuchi pattern simulation of the enantiomorphs reveals differences, if dynamical electron diffraction is considered. Quantitative comparison between experimental and simulated Kikuchi patterns allows the spatially resolved assignment of the enantiomorph in polycrystalline materials of β-Mn, as well as the structurally strongly related phase Pt2Cu3B. On the basis of enantiomorph distribution maps, crystals were extracted from enantiopure domains by micropreparation techniques. The x-ray diffraction analyses confirm the assignment of the Kikuchi pattern evaluations for Pt2Cu3B and do not allow to distinguish between the enantiomorphs of β-Mn.

A partly disordered 2 × 2 × 2 – superstructure of γ-brass related phase in Mn–Ni–Zn system

The T phase in the Mn–Ni–Zn system was obtained as a product of high-temperature solid-state syntheses from the loaded composition of MnxNi2−xZn11 (x = 0.2–1.5)/MnxNi15.38−xZn84.62 (x = 1.54–11.54). The crystal structure of the T phase has been explored by means of X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The structures were solved in the face-centered cubic space group F 4 ‾ 3 m $F‾{4}3m$ (216) and contain 409–410 atoms/unit cell. The lattice constants were found to be a = 18.1727(2) and 18.1954(1) Å for crystals C1 and C2, respectively. The crystal structure denoted the T phase is a (2aγ)3-superstructure of the ordinary cubic γ-brass-type phase. The phase is isostructural to (Fe, Ni)Zn6.5. A “cluster” description has been used to visualize the crystal structure of the title phase. The structures have been constructed by the five distinct clusters and they are situated about the high symmetry sites of the face-centered cubic lattice. The T phase is stabilized at a valance electron concentration of 1.78, which is slightly higher than those expected for typical γ-brass Hume‐Rothery compounds.

Li vs. Zn substitution in Li17Si4 – Li17–ε–δZnεSi4 connecting the structures of Li21Si5 and Li17Si4

Binary lithium silicides play a crucial role in high energy density anode materials for rechargeable batteries. During charging processes of Si anodes Li15Si4 is formed as a metastable phase which has been stabilized through Li by Mg, Zn and Al substitution. Here we investigate Li by Zn substitution in the lithium-richest phase Li17Si4 and report on the particular site preference of Zn atoms since Zn is substituting Li atoms only on one out of 13 possible lithium sites. This site preference shows an interesting relation to the closely related phase Li21Si5 and thus Li17−ε−δZnεSi4 with ε = 0.025(1) and δ = 0.033(1) can be considered as the missing link between the structures of Li21Si5 (= Li4.20Si) and Li17Si4 (= Li4.25Si).

A new computational method for molecular design of a liquid–liquid extractant and related phase equilibrium based on group contribution

A new selection method is developed for group contribution combined with molecular design for an extractant in liquid–liquid extraction.