Application of Vacuum Infiltration in Cryopreservation of Isolated Grape Buds

Preserving the gene pool of grapes, referred to the vegetatively propagated plants is a complicated task, which can be also solved by cryopreservation of the buds. To saturate such bulk and heterogeneous samples with cryoprotectants the novel methods are required. The effectiveness of vacuum infiltration and 60 min standard passive saturation (soaking) of isolated grape buds of the Russian Concord variety with a cryoprotective solution PVS 2 were compared in this research. To saturate by vacuum infiltration the buds were incubated in cryoprotective solution for 15 min at 40 kPa, afterwards, the pressure was gradually increased to atmospheric level. The efficiency of bud saturation was evaluated with low-temperature differential scanning calorimetry by changing the enthalpies and temperatures of phase transitions as well as the intensity of heat capacity jump at glass transition. The use of vacuum in the saturation of isolated grape buds were found to lead to a strong rise in cryoprotectant concentration in them and a significant decrease in the amount of free water crystallized during cooling compared to passive soaking in a PVS 2 vitrification solution.

Superconductivity in K- and Na-doped BaFe2As2: What can we learn from heat capacity and pressure dependence of Tc

A brief overview of changes in the superconducting transition temperature under pressure and evolution of specific heat capacity jump at Tc for two related families of iron-based superconductors, Ba 1-x K x Fe 2 As 2 (0.2 ≤ x ≤ 1.0) and Ba 1-x Na x Fe 2 As 2 (0.2 ≤ x ≤ 0.9) will be given. For Ba 1-x K x Fe 2 As 2 the specific heat capacity jump at Tc measured over the whole extent of the superconducting dome shows clear deviation from the empirical, [Formula: see text], scaling (known as the BNC scaling) for x > 0.7. At the same concentrations range apparent equivalence of effects of pressure and K -substitution on Tc fails. These observations suggests a significant change of the superconducting state for x > 0.7. In contrast, the data for the large portion of Ba 1-x Na x Fe 2 As 2 (0.2 ≤ x ≤ 0.9) series follow the BNC scaling. However, the pressure dependence of Tc (measured up to ~12 kbar) have clear nonlinearities for Na concentration in 0.2–0.25 region, that may be consistent with Tc crossing the phase boundaries of the emergent, narrow, antiferromagnetic/tetragonal phase. Results will be discussed in context other studies of these two related families of iron-based superconductors.

Nanocomposites Based on Hyperbranched Polymers and Montmorillonite

Nanocomposites based on hyperbranched polymers and sodium montmorillonite were prepared over the full range of compositions. The XRD analysis showed the full exfoliation of silicate layers at lower silicate content (up to 9.1 wt%). With the further increase of silicate loading, an intercalated structure was developed with a constant d-spacing due to the unique structure of hyperbranched polymers. The heat capacity jump at the glass transition of the nanocomposites was found to deviate from the two-phase model prediction, indicating the formation of a rigid amorphous fraction. The glass transition temperature and heat capacity jump behaviors suggested that the molecular mobility of hyperbranched polymers were restricted by the introduction of silicate layers. The mechanical properties of the nanocomposites were also investigated.