Competition of perpendicular magnetic anisotropy and exchange magnetic anisotropy in a Pt/Co/α-Cr₂O₃(0001) thin film

We investigated perpendicular magnetic anisotropy and exchange magnetic anisotropy in a Pt/Co/α-Cr₂O₃(0001) thin film grown on an α-Al₂O₃(0001) substrate. The film exhibits perpendicular magnetic anisotropy below a Co thickness of 1.2 nm at room temperature. Independent of the magnetic easy direction of the Co layer, the perpendicular exchange bias (PEB) appears in a direction perpendicular to the film below 80 K. The maximum unidirectional magnetic anisotropy energy estimated from the exchange bias field is 0.33 erg/cm², which is higher than the reported PEB strength. The perpendicular exchange bias is accompanied by the in-plane remanent magnetization and an increase in the in-plane coercivity. We speculate that the increases in the in-plane remanent magnetization and the in-plane coercivity are caused by the spin canting of Cr³⁺ in the α-Cr₂O₃(0001) layer.Yu Shiratsuchia, Hayato Noutomi, Hiroto Oikawa, Toshiaki Fujita, and Ryoichi Nakatani, Journal of Applied Physics 109, 07C101 (2011); https://doi.org/10.1063/1.3535555

Detection and in situ switching of unreversed interfacial antiferromagnetic spins in a perpendicular-exchange-biased system

By using the perpendicular-exchange-biased Pt/Co/α-Cr₂O₃ system, we provide experimental evidence that the unreversed uncompensated Cr spins exist at the Co/α-Cr₂O₃ interface. The unreversed uncompensated Cr spin manifests itself in both the vertical shift of an element-specific magnetization curve and the relative peak intensity of soft-x-ray magnetic circular dichroism spectrum. We also demonstrate an in situ switching of the interfacial Cr spins and correspondingly a reversal of the exchange bias without interfacial atomic diffusion. Such switching shows the direct relationship between the interfacial antiferromagnetic spins and origin of the exchange bias. The demonstrated switching of exchange bias would likely offer a new design of advanced spintronics devices, using the perpendicular-exchange-biased system, with low power consumption and ultrafast operation.Y.Shiratsuchi, H.Noutomi, H.Oikawa, et al. Detection and in situ switching of unreversed interfacial antiferromagnetic spins in a perpendicular-exchange-biased system. Physical Review Letters 109, 077202 (2012); https://doi.org/10.1103/PhysRevLett.109.077202

Consequences of Lineage-Specific Gene Loss on Functional Evolution of Surviving Paralogs: ALDH1A and Retinoic Acid Signaling in Vertebrate Genomes

Genome duplications increase genetic diversity and may facilitate the evolution of gene subfunctions. Little attention, however, has focused on the evolutionary impact of lineage-specific gene loss. Here, we show that identifying lineage-specific gene loss after genome duplication is important for understanding the evolution of gene subfunctions in surviving paralogs and for improving functional connectivity among human and model organism genomes. We examine the general principles of gene loss following duplication, coupled with expression analysis of the retinaldehyde dehydrogenase Aldh1a gene family during retinoic acid signaling in eye development as a case study. Humans have three ALDH1A genes, but teleosts have just one or two. We used comparative genomics and conserved syntenies to identify loss of ohnologs (paralogs derived from genome duplication) and to clarify uncertain phylogenies. Analysis showed that Aldh1a1 and Aldh1a2 form a clade that is sister to Aldh1a3-related genes. Genome comparisons showed secondarily loss of aldh1a1 in teleosts, revealing that Aldh1a1 is not a tetrapod innovation and that aldh1a3 was recently lost in medaka, making it the first known vertebrate with a single aldh1a gene. Interestingly, results revealed asymmetric distribution of surviving ohnologs between co-orthologous teleost chromosome segments, suggesting that local genome architecture can influence ohnolog survival. We propose a model that reconstructs the chromosomal history of the Aldh1a family in the ancestral vertebrate genome, coupled with the evolution of gene functions in surviving Aldh1a ohnologs after R1, R2, and R3 genome duplications. Results provide evidence for early subfunctionalization and late subfunction-partitioning and suggest a mechanistic model based on altered regulation leading to heterochronic gene expression to explain the acquisition or modification of subfunctions by surviving ohnologs that preserve unaltered ancestral developmental programs in the face of gene loss

Process-induced damage and its effect on strength of composite - aluminum alloy joint by FDS technique

Flow drilling screw (FDS) is a novel joining technique that enables high-speed joining of dissimilar metals with one-shot process of hole machining, female thread forming and fastening from one side. The damage after FDS process and its effect on joint strength and fracture behaviour near the screw by load-bearing tests for FDS joints between aluminum alloy and carbon fibre reinforced thermoplastics (CFRTP) are evaluated. Cross-sectional observation after joining process reveals that delamination in CFRTP is clearly suppressed and matrix resin is filled in the screw thread compared to the case with CFRP using thermosetting resin. In the joint strength test with shear loading and the cross-shaped tensile tests where the screw is pulled out in its axial direction, only the fibre micro-buckling is observed until fracture. These experimental results recommend that CFRTP laminates should be applied as composite side since this technique utilizes frictional heat by the screw that can contribute to plastic flow or deformation of the thermoplastic resin with high fracture toughness. It is also clarified that damage growth is further suppressed by using CFRTP/Al hybrid laminates where aluminum alloy sheets are inserted between CFRTP plies, which leads to improve the joint strength

Detection of Debonding Area in Aluminium-GFRP Laminates by Electromagnetic Transducer

Electromagnetic Acoustic Transducer (EMAT) is applied to nondestructive testing of aluminum-GFRP laminates. Because of its high specific strength, laminated FRP came to be used in place of metal materials. However, once delamination is introduced by the impact force in the out-of-plane direction, the compressive strength in the in-plane direction is greatly reduced. To improve the tolerance for impact force, fiber metal laminates (FML) have been developed. Since debonding may occur at the interface of FRP and metal sheet, nondestructive detection of the debonding is required as health monitoring of the FML. In this study, GFRP laminates were molded on aluminum sheets, and we measured the distribution of standing wave amplitude in the aluminum sheets using EMAT for shear wave. In the bonded area, the shear wave is partially transmitted to the FRP on reflection at the boundary, which makes the attenuation coefficient larger than that in the debonded area. It was found that in scanning the EMAT, the standing wave amplitude starts to change when the center of the EMAT passes the boundary between bonding and debonding areas. It was also revealed that minimum size of the debonding area that EMAT can detect is comparable to its effective area. For accurate evaluation of the debonding area, resonant frequency measurement is recommended at each point

Exploring the relationship between plasma substance P and glottal incompetence in the elderly

We speculated that increased blood-plasma levels of Substance P may serve as an indicator of glottal incompetence, which is usually indicated by reduced maximum phonation time. We performed an initial study to test the plausibility of this hypothesis. Patients with dysphonia caused by glottal incompetence were asked to perform vocal exercises for six months to reduce glottal incompetence and we compared the plasma concentration of Substance P before and after the vocal exercise to detect correlation between maximum phonation time and plasma concentration of Substance P. Based on the results, we further hypothesized that patients exhibiting dysphonia with maximum phonation time less than 14 s, in particular less than 10 sec, caused by glottal incompetence may have increased plasma concentration of Substance P with the results of elevated thresholds of cough reflex associated with subclinical aspiration in airways. Further study is needed on patients with decreased Substance P levels, with low scores on Activities of Daily Living and who are hospitalized with aspiration pneumonia

Endogenous CCL21-Ser deficiency reduces B16–F10 melanoma growth by enhanced antitumor immunity

The chemokine CCL21 regulates immune and cancer cell migration through its receptor CCR7. The Ccl21a gene encodes the isoform CCL21-Ser, predominantly expressed in the thymic medulla and the secondary lymphoid tissues. This study examined the roles of CCL21-Ser in the antitumor immune response in Ccl21a-knockout (KO) mice. The Ccl21a-KO mice showed significantly decreased growth of B16–F10 and YUMM1.7 melanomas and increased growth of MC38 colon cancer, despite no significant difference in LLC lung cancer and EO771 breast cancer. The B16–F10 tumor in Ccl21a-KO mice showed melanoma-specific activated CD8+ T cell and NK cell infiltration and higher Treg counts than wild-type mice. B16–F10 tumors in Ccl21a-KO mice showed a reduction in the positive correlation between the ratio of regulatory T cells (Tregs) to activated CD8+ T cells and tumor weight. In Ccl21a-KO tumor, the intratumoral Tregs showed lower co-inhibitory receptors TIM-3 and TIGIT. Taken together, these results suggest that endogenous CCL21-Ser supports melanoma growth in vivo by maintaining Treg function and suppressing antitumor immunity by CD8+ T cells