**Preface to "Signal Analysis in Power Systems"**

This issue is devoted to reviews and applications of modern methods of signal processing used to analyze the operation of a power system and evaluate the performance of the system in all aspects. Monitoring capability with data integration, advanced analysis of support system control, and enhanced power security are the key issues discussed in the paper "Analysis of the Power Supply Restoration Time after Failures in Power Transmission Lines". Advanced statistical analysis of the power system is presented in papers "Combined Cluster Analysis and Global Power Quality Indices for the Qualitative Assessment of the Time-Varying Condition of Power Quality in an Electrical Power Network with Distributed Generation" and "The Application of Hierarchical Clustering to Power Quality Measurements in an Electrical Power Network with Distributed Generation", demonstrating the cutting-edge developments in this emerging area. The relatively new concept of virtual power plants, related to ongoing research in cooperation with industrial partners from the energy sector is presented in the paper "A Case Study on Distributed Energy Resources and Energy-Storage Systems in a Virtual Power Plant Concept: Technical Aspects". New concepts of photovoltaic energy forecasting complete the issue with the paper "Forecasting Solar PV Output Using Convolutional Neural Networks with a Sliding Window Algorithm".

> **Zbigniew Leonowicz** *Editor*


**2. Materials and Methods**

#### *2.1. Isolation of Actinobacterial Strain*

Strain NEAU-H2T was isolated from the rhizosphere soil of wheat (*Triticum aestivum* L.) collected from Zhumadian, Henan Province, Central China (32◦98 N, 114◦02 E). The root sample was air-dried for 24 h at room temperature, and then the surface soil was shaken off gently. After, the sample was shaken at 250 rpm in 100 mL of sterile water with glass beads for 30 min at 20 ◦C and then filtered with a single layer of gauze to obtain the rhizosphere soil suspension. The suspension was serially diluted and spread on cellulose-proline agar (CPA) [12] supplemented with cycloheximide (50 mg·L−1) and nalidixic acid (20 mg·L−1), and cultured at 28 ◦C for 3 weeks. Strain NEAU-H2T was isolated and purified on the International *Streptomyces* Project (ISP) medium 3 [13], and maintained as glycerol suspensions (20%, *v*/*v*) at −80 ◦C.


**2. Materials and Methods**

#### *2.1. Blastocystis Culture*

*Blastocystis* ST7 cultures were grown axenically in 8 mL of Iscove's Modified Dulbecco's Medium (IMDM) (Gibco-Catalogue no 12,200,069 Thermo Fisher scientific) with 10% heat-inactivated horse serum (HIHS) (Gibco-Catalogue no 26,050,088 Thermo Fisher scientific). All cultures were passaged every 3–4 days depending on their growth rate and were subsequently expanded. All cultures were incubated at 37 ◦C in 95% CO2 and 5% O2. The gas concentration was maintained by a gas pack (BD-Catalogue no 261205) in an anaerobic chamber (Oxoid-Product code 10,107,992 Fisher scientific). Cell counts were achieved manually using a Neubauer haemocytometer (Brand-Catalogue no 717810).

#### *2.2. Cell lysis and Metabolite Extraction*

*Blastocystis* cultures intended for metabolite extraction were pooled in a 50 mL tube and centrifuged at 1000× *g* for 5 min at 4 ◦C and the supernatant was discarded. Resulting pellets were re-suspended in 5 mL of Locke's solution and given 2× washes with Stone's modification of Locke's solution (ATCC medium 1671), which was removed by a subsequent centrifugation at 1000× *g* for 5 min at 4 ◦C. The washed pellets were snap frozen in liquid nitrogen and stored at −80 ◦C.

Three steps were implemented for each experiment to determine the optimum extraction protocol and were each repeated four times. The conditions of each of the 4 experiments are shown in Table 1.

**Table 1.** Conditions of each experiment used to determine the best lysis method, incubation temperature and extraction solvent.

Step 1: Three cell cultures were thawed, resuspended in 5 mL of Lockes' solution and then homogenised by vortexing for 30 s. These were then divided into two equal weight batches for parallel analysis. Each batch was centrifuged at 1000× *g* for 5 min at 4 ◦C, after which the supernatant was removed.

Step 2: The two batches were added to one of two different solvents: either 4 mL of ethanol:water (3:1) or 4 mL of methanol:water (1:1). The two different solvent batches were further processed at either −20 ◦C, room temperature (RT) or 60 ◦C (with samples for each solvent at each of the three temperatures). Each batch was then disrupted using one of two methods; either sonication in 3 × 30 s bursts or bead bashing by vortexing with 200 mg of 0.4 mm glass beads for 30 s followed by a 3-min incubation at either −20 ◦C, RT or 60 ◦C, then followed by vortexing for a further 30 s.

Step 3: Resulting solutions were then divided into 4 × 1 mL aliquots and centrifuged for 15 min at 4 ◦C at 10,000× *g*. The supernatants were decanted into fresh tubes and lyophilised.


**1. Introduction**

Magnetic nanofilms have attracted increasing attention in recent years, especially in the CoFeB system. CoFeB is a soft ferromagnetic material, which has been extensively applied in spintronic devices. When a CoFeB film is thinner than 1.7 nm, it shows a perpendicular magnetic anisotropy (PMA), implying its easy axis is obviously out-ofplane [1,2]. The PMA in Ta/CoFeB/MgO stack, first identified by Ikeda et al., has promising applications in spin-transfer torque devices [3]. Moreover, magnetic tunnel junctions

**Citation:** Liu, W.-J.; Chang, Y.-H.; Fern, C.-L.; Chen, Y.-T.; Jhou, T.-Y.; Chiu, P.-C.; Lin, S.-H.; Lin, K.-W.; Wu, T.-H. Annealing Effect on the Contact Angle, Surface Energy, Electric Property, and Nanomechanical Characteristics of Co40Fe40W20 Thin Films. *Coatings* **2021**, *11*, 1268. https://doi.org/10.3390/ coatings11111268

Academic Editor: Angela De Bonis

Received: 7 October 2021 Accepted: 18 October 2021 Published: 20 October 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

(MTJs) have been widely investigated because of their wide applications in spintronic magnetic devices, such as reading heads of hard disks and magnetoresistance random access memories (MRAM) [4–7]. The CoFeB film was combined with the MgO layer to form MTJs. A PMA in magnetic films is an essential characteristic for MTJs [8,9]. On the other hand, CoFeB magnetic film has been extensively used as a free or pinned layer in MTJs. CoFeB and MgO layers via post-annealing result in a high spin polarization and high tunneling magnetoresistance (TMR) [10–15]. Meng et al. reported that post-annealing at 250 ◦C could effectively increase TMR about nine times [16]. The CoFeB-MgO-based MTJs are considered as a potential candidate for MRAM with high PMA, lower critical switching current density (Jc), and high TMR [17,18]. Researchers have paid great attention to increasing the PMA and the thermal stability of MTJs structure. Inserting other metal spacer layers in the MTJs system was common and effective in improving its various properties [19–21]. Tungsten (W) has a high melting point, high mechanical strength, and high-temperature thermal conductivity. In recent years, people have paid more and more attention to adding new elements to material in magnetic fields. Especially, the study of adding other elements to the CoFe matrix has also increased. However, few researchers have paid attention to adding W to CoFe alloy. The research on the efficacy of CoFeW is noteworthy because it is a promising material. It is usually inserted into MTJ as a free layer or pinned layer or is combined with other layers in a multilayer structure. It can be widely used in magnetic and semiconductor applications. In our previous studies, the relationship between magnetism and structure of CoFeW films, as deposited and annealed, has been studied [22]. This study is an extension of our previous research to investigate contact angle and surface energy. However, few research studies have focused on the adhesive properties of CoFeW films. In addition, the effectiveness of CoFeW-based multilayer structure is sensitive to the temperature environment. It is of great significance to study the characteristics of CoFeW films deposited by direct-current (DC) magnetron sputtering in as-deposited and annealing conditions. The strong adhesion is a critical property for MTJ. Strong adhesion is a critical property for MTJs. Therefore, this study measured the contact angle of Co40Fe40W20 thin films with different thicknesses and heat treatment conditions by a measuring analyzer via deionized (DI) water and glycerol. The Young equation was used to calculate the surface energy. Finally, this study discussed the correlation between grain size, contact angle, surface energy, and adhesion. The findings can provide a reference to future research on MTJs.