**6. Conclusion**

Koren et al. observed the local superconductivity in Bi2Te2Se and Bi2Se3 films below 2–3 K, which was naturally induced by small amounts of superconducting Bi inclusions or precipitations on the surface [78]. Moreover, Le et al. reported superconductivity at an onset critical temperature of approximately 3.1 K in a topological insulator 200-nm-thick Bi2Te3 thin film grown by pulsed laser deposition [53]. Indeed, **Figure 12a** shows the normalized resistivity *ρ/ ρ*300 K of a 46-nm-thick Bi2Te3 film (S1) and a 200-nm-thick Bi2Te3 film (S2) as functions of temperatures (*T*) from 1.8 to 300 K. Both films show a decrease in resistivity (*ρ*) with decreasing *T* in the range of 20–300 K, implying that the films exhibit weak metallic properties commonly seen in narrow band-gap semiconductors with high carrier concentrations [53]. Below 20 K (**Figure 12a**, the lower inset), the *ρ/ρ*300 K of S1 shows a gentle upturn because of the weak localization of electrons [7], whereas the *ρ/ρ*300 K of S2 reaches a plateau before dropping slightly at *Tc1* ≈ 5.8 K and then sharply at *Tc2* ≈ 3.1 K. **Figure 12b** further shows the *H*||c-dependent *ρ*(*T*) of S2 in the low *T* regime, where *H*||c is the applied magnetic field along the *c*-axis of the

76 Applications of Laser Ablation - Thin Film Deposition, Nanomaterial Synthesis and Surface Modification

*T* = 1.8 K. This nonzero *ρ* at low *T* indicates that the superconducting volume ratio is not 100%.

(1

with increasing *H||c* from 0 to 0.2 T, strongly indicating that both transitions are supercon-

The detailed investigations of S2 strongly suggest the existence of superconducting Bi nanoclusters on the surface that induce the *Tc1* ~ 5.8 K. EDS lateral elemental mapping revealed that the distributions of Te and Bi were not uniform, and many Bi-rich (47–54 at.%) clusters were visible (green color), as shown in the upper inset in **Figure 12a**, differing substantially from the uniform distribution and cluster-free surface observed in film S1. The size distribution and the most probable size of Bi-rich clusters are in the range of 400–2400 nm and 560–772 nm, respectively. Intriguingly, a closer inspection reveals that Bi-rich clusters are composed by some

The Bi-rich environment on the film surface is confirmed by AES analysis (**Figure 12c**) [53]. This is because the vapor pressure of Te (at *T*S = 300°C) is approximately 105 times higher than that of Bi, and therefore, more Te atoms are re-evaporated from the 300°C substrates [79]. The loss of Te is more severe in film S2 than in film S1 (14.3% in S2 and 4.5% in S1 at depth *Z* = 0, **Figure 12c**) because of the six times longer deposition time of S2 (60 min) compared to S1 (10 min). In addition, the nonstoichiometric effect is strongly depth-dependent (**Figure 12c**). The Te/Bi ratio gradually increases toward the stoichiometric ratio of 3/2 in 200-nm-thick films or slightly exceeds it (Te-rich) in 46-nm-thick films when the depth (*Z*) of the films increases. Under such a sufficiently high surface concentration of Bi atoms, the Bi clusters precipitate and segregate readily on the S2 surface to minimize overall free energy, as long as the substrate temperature of 300°C is higher than the 271°C melting point of Bi, as demonstrated in **Figure 12f**. Notably, the Bi clusters can only be observed in highly Bi-rich (14.3% at *Z* = 0) films (S2) and not in low Bi-rich (4.5% at *Z* = 0) films (S1), suggesting a critical Bi-rich concentration for Bi precipitation (separating a Bi phase) in a Bi2Te3 film [53]. The *Tc1* at ~5.8 K found in our samples should be induced by the superconducting transition of the Bi nanoclusters, which is

but does not go down to zero, even at

) decreases from 3.1 (5.8) to 1.8 (5.4) K

film. At *H*||c = 0, *ρ* drops abruptly by 8% below 2

Bi nanoclusters (or nanograins) with a size of 20–62 nm.

The inset in **Figure 12b** shows that the 2

ducting in nature.

This chapter provides the effects of ambient pressures and substrate temperatures in PLD growths on the structural-morphology, thermoelectric, nanomechanical, and magnetoresistance properties of bismuth chalcogenide thin films. The thermoelectric power factor of the stoichiometric Bi2Te3films grown in the range of 220–340°C and *PAr* of 80 Pa reached remarkably high values, ranging between 18.2 ± 0.25 and 24.3 ± 0.44 μW cm−1 K−2. The optimal *PF* values were 5.54 ± 0.34 μW cm−1 K−2 for the layered hexagonal platelet Bi2Se3 films deposited at 300°C and *P*He of 40 Pa and 8.3 μW cm−1 K−2 for the nanocrystalline Bi3Se2Te films deposited at 250°C and *P*He of 40 Pa. We also reported the effects of *P*He in PLD on nanomechanical properties (i.e., hardness and Young's modulus) of Bi2Te3 and Bi3Se2Te thin films. It was observed that the hardness and Young's modulus increased with increasing *P*He, depending on the grain sizes following the inverse Hall-Petch effect for Bi2Te3 films grown at *P*He ≤ 2.0 × 10−3 Torr and following the Hall-Petch relationship for Bi3Se2Te grown at *P*He of 2.0 × 10−5 to 6.5 × 10−1 Torr. PLD has been successfully employed to grow epitaxially bismuth chalcogenide thin films on large-misfit substrates, for example, Bi2Te3/SrTiO3 (1 0 0), Bi2Se3/Al2O3 (0 0 0 1), and Bi3Se2Te/ Al2O3 (0 0 0 1). The magnetotransport studies show that the bismuth chalcogenide thin films such as Bi2Te3, Bi2Se3, and Bi3Se2Te films present a two-dimensional weak antilocalization effect in a low magnetic field (*B*) regime and linear magnetoresistance in a high *B* regime, which could be attributed to the topological insulator surface states. Furthermore, proximity-induced superconductivities in Bi2Te3 thin films have an onset *Tc* of approximately 3.1 K, evidently induced by Bi inclusions (nanoclusters with onset *Tc* at 5.8 K) segregated on the surface of films.


*2.8. Vaccination of Cats*

The vaccine Fel-CuMV and the vaccine production was described previously [36]. A vaccine dose contained 100 μg Fel-CuMV (HypoCatTM) formulated in 1 mL aqueous buffer solution. Subcutaneous injections were applied in study weeks 4, 7 and 10 (main study) and 56 (extension study). The vaccine used in this study was produced by Benchmark Vaccines Limited, UK using a GMP-like production process. Prior to each vaccination, the cats were thoroughly examined by one of the participating veterinarians for their general health status, including a routine physical exam with measurement of the body weight and temperature, checking the site of injection, pulse and breathing rate, abdomen palpation and general appearance. During the course of the study, the owners regularly checked the health of their animal. Twenty-four hours after every injection the owners were called by the study personnel to enquire after the well-being of the cat.

## *2.9. Antibody Responses in Cats*

Blood for serum antibody measurements was collected from the vena jugularis or cephalica using serum tubes (Sarstedt, Germany). Sampling was done in the study weeks 4, 7, 10, 27, 56, 62, and 78. After clotting (30 min) and centrifugation (1000 ×*g*, 5 min) of blood samples, sera were transferred to labeled polypropylene tubes (Eppendorf tubes, 1.5 mL, Germany) and stored at ≤ −15 ◦C until thawed for antibody analyses.

A validated ELISA (developed by HypoPet AG) was performed to determine anti-Fel d 1 IgG in cat sera previously described [36]. ELISA titers are given as the reciprocals of the dilutions needed to achieve 50% of the optical density of the maximal signal measured at saturation (OD50). The geometric mean titers were calculated from the individual titers of the cats from each group.

## *2.10. Data and Statistical Analyses*

The analysis for the human part included data from 9 out of 10 participants and was performed according to the "per protocol" (PP) analysis. Analyses were conducted in this way because one participant had urticaria, accompanied by pruritus and wheal formation, on two occasions during the study. The participant was unable to distinguish urticaria symptoms from the symptoms of cat allergy and was thus excluded from analysis. The analyses of cat data included all 13 cats, whereas the correlation of antibody responses in cats with measurements of human allergic symptoms included data from 9 out of 10 participants with their respective study cats (*n* = 9).

Statistical analyses were performed with Excel, Graph Pad Prism and R. Data were summarized by descriptive statistics: mean, standard deviation, median, first and third quartile, minimum, and maximum. This study was classified as a pilot study because there was no pre-existing information available concerning the expected change in symptoms of allergic cat owners before and after immunization of their cats (the effect size). The changes in the symptoms of the main study were evaluated using an exact Wilcoxon matched-paired signed rank test. Hypotheses were tested at a two-sided significance level of α = 0.05. For comparison between baseline and course of study, the mean of all values was computed.


Scope, Nutritional Importance and Value Addition in Palmyrah (*Borassus flabellifer L.*): An Under Exploited Crop

*Merugu Chandra Surya Rao, Dokka Venkata Swami, P. Ashok, Satya Prakash Nanda and Banavath Babu Rao*


**4. Conclusions**

In this work, the failure mechanism of symmetrical grain boundaries (GB) under external strain effects in body-centered cubic (bcc) iron are investigated via the molecular dynamics (MD) method. The local atomic structure evolution, energy state change, atomic displacements and free volumes were calculated for the above purpose. The following conclusions have been made:

(1) Full MD relaxations at high temperatures are necessary to obtain the lower energy states of GBs for further simulations under external strain.

(2) Two mechanisms are explored for the failure of symmetrical GBs under the external strain effect, including slip system activation, dislocation nucleation and dislocation network formation initially from the GB plane region induced by the external strain field or from the bcc-fcc phase interface induced by phase transformation under external strain effects.

(3) The change in free volume near the GB plane or bcc-fcc interface is not only related to the local structure change in the above two mechanisms, but can also lead to increases in the local stress concentration, providing a new explanation for the failure of GBs in BCC iron system.

**Supplementary Materials:** The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/met12091448/s1, Figure S1: Schematic of grain boundary simulation model used in the present work. For stress-strain simulations, the external tensile strain field is applied on top and bottom surface of box, Figure S2: Atomic potential energy (**a**) and displacement distribution (**b**) of ∑3(112) GB at state with peak stress, Figure S3: Example of FCC lattice structure in fcc phase after phase transition, Figure S4: Snapshots (y-z plane) shows ∑ = 5(013) undergoes phase transition and green atom is fcc struc-ture blue atom is bcc. Then the GB happens to crack at 31 ps, region a, b and c are most obvious, Figure S5: Atomic potential energy (**a**) and displacement distribution (**b**) of ∑5(013) GB at state with peak stress, Figure S6: (**a**) The structure of ∑5(012) when slip system is activated with strain around 8%. The potential energy(b), stress(c) and atomic displacement distribution(d) at this state are shown respectively. Figure S7: (**a**) The structure of ∑3(111) when slip system is activated with strain around 14%. The potential energy, stress and atomic displacement distribution at this state are shown in (**b**), (**c**) and (**d**) respectively, Figure S8: Distribution of free volume near ∑3(111) GB region at (**a**) 0 ps and (**b**) at 28 ps (strain around 14%), Table S1: The peak tensile stresses of all cases studied in this work are listed in table.

**Author Contributions:** Conceptualization, N.G.; methodology, W.M. and N.G.; software, W.M.; validation, W.M.; formal analysis, W.M.; investigation, W.M.; resources, N.G.; data curation, W.M.; writing—original draft preparation, W.M.; writing—review and editing, Y.D., M.Y., Z.W., Y.L., N.G., L.D. and X.W.; visualization, W.M.; supervision, N.G.; project administration, N.G.; funding acquisition, N.G., X.W. and Y.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Natural Science Foundation of China, grant number (Project Nos. 12075141, 12175125 and 12105159).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are contained within the article.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**