The effects of uniaxial compressive stress on the normal state 17 O nuclear magnetic resonance properties of the unconventional superconductor Sr2RuO4 are reported. The paramagnetic shifts of both planar and apical oxygen sites show pronounced anomalies near the nominal a-axis strain εaa ≡ εv, that maximizes the superconducting transition temperature, Tc. The spin susceptibility weakly increases on lowering the temperature below T 10 K, consistent with an enhanced density of states associated with passing the Fermi energy through a van Hove singularity. Although such a Lifshitz transition occurs in the γ band, formed by the Ru dxy states hybridized with in-plane O pπ orbitals, the large Hund's coupling renormalizes the uniform spin susceptibilty, which, in turn, affects the hyperfine fields of all nuclei. We estimate this "Stoner" renormalization, S, by combining the data with first-principles calculations and conclude that this is an important part of the strain effect, with implications for superconductivity.
In this study, different geographical populations of Rhipicephalus sanguineus sensu lato were compared by molecular, biological, and morphometric methods. Phylogenetic trees were constructed using 12S and 16S rDNA sequences and showed two distinct clades: one composed of ticks from Brazil (Jaboticabal, SP), Cuba (Havana) Thailand (Bangkok) and the so-called "tropical strain" ticks. The second clade was composed of ticks from Spain (Zaragoza), Argentina (Rafaela, Santa Fe) and the so-called "temperate strain" ticks. Morphometric analysis showed good separation between females of the two clades and within the temperate clade. Males also exhibited separation between the two clades, but with some overlap. Multiple biological parameters revealed differences between the two clades, especially the weight of the engorged female. These results confirm the existence of at least two species under the name "R. sanguineus".
A synthetic 20 amino acid peptide of the ribosomal protein P0 from ticks, when conjugated to keyhole limpet hemocyanin from Megathura crenulata and used as an immunogen against Rhipicephalus microplus and Rhipicephalus sanguineus s.l. species, has shown efficacies of around 90%. There is also experimental evidence of a high efficacy of this conjugate against Amblyomma mixtum and Ixodes ricinus species, which suggest that this antigen could be a good broad-spectrum anti-tick vaccine candidate. In this study, the P0 peptide (pP0) was chemically conjugated to Bm86 as a carrier protein. SDS-PAGE analysis of this conjugate demonstrated that it is highly heterogeneous in size, carrying from 1 to 18 molecules of pP0 per molecule of Bm86. Forty-nine out of the 54 lysine residues and the N-terminal end of Bm86 were found partially linked to pP0 by using LC-MS/MS analysis and the combination of four different softwares. Several post-translational modifications of Bm86 protein were also identified by mass spectrometry. High immunogenicity and efficacy were achieved when dogs and cattle were vaccinated with the pP0–Bm86 conjugate and challenged with R. sanguineus s.l. and R. microplus, respectively. These results encourage the development of this antigen with promising possibilities as an anti-tick vaccine.
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