An Aminopeptidase Acting as a Potential Factor in Host Adaptation of Mycoplasma Gallinarum

Unlike most other host-specific mycoplasmas, Mycoplasma gallinarum exists as a commensal with a host range including most poultry as well as some mammals. This property of M. gallinarum may reflect unique mechanisms for its colonization and persistence in hosts. Whereas M. gallinarum shows leucine and arginine aminopeptidase activity, the genes encoding the enzymes had not been cloned and characterized. We identified an aminopeptidase gene (APN) by oligonucleotide hybridization to a genomic library of M. gallinarum in lambda ZAPII bacteriophage. Nucleotide sequence analysis of overlapping phage clones identified a 1,362 bp open reading frame (ORF) encoding a putative leucine aminopeptidase gene. Database searches indicate that this ORF has 68% nucleotide identity and 51% amino acid identity with the M. salivarium leucine aminopeptidase gene. The active sites of the leucine aminopeptidases in other eukaryotes and prokaryotes were conserved in the cloned aminopeptidase gene. Northern-blot hybridization analysis showed that this ORF is expressed as a 1.5 kb transcript. Southern-blot hybridization analysis demonstrated this gene was present as a single copy in M. gallinarum. Characterization of the leucine aminopeptidase demonstrated that it is a metallo-aminopeptidase (EC 3.4.11.1) and is located in the cytoplasm with a weak interaction with the cell membrane. The subcellular location was further confirmed by immunoblotting with polyclonal anti-recombinant APN serum and M. gallinarum Triton-114 partitions. Immunoblotting results with sera from three chickens experimentally infected with M. gallinarum showed that there were very few proteins in M. gallinarum exposed to the host immune responses and that leucine aminopeptidase was not able to stimulate production of specific humoral antibody. Our results suggest that this leucine aminopeptidase play a role in nutrition supply for the host adaptation of M. gallinarum and that the enzyme was not strongly immunogenic

Threshold current of field-free perpendicular magnetization switching using anomalous spin-orbit torque

Spin-orbit torque (SOT) is a candidate technique in next generation magnetic random-access memory (MRAM). Recently, experiments show that some material with low-symmetric crystalline or magnetic structures can generate anomalous SOT that has an out-of-plane component, which is crucial in switching perpendicular magnetization of adjacent ferromagnetic (FM) layer in the field-free condition. In this work, we analytically derive the threshold current of field-free perpendicular magnetization switching using the anomalous SOT. And we numerically calculate the track of the magnetic moment in a FM free layer when an applied current is smaller and greater than the threshold current. After that, we study the applied current dependence of the switching time and the switching energy consumption, which shows the minimum energy consumption decreases as out-of-plane torque proportion increases. Then we study the dependences of the threshold current on anisotropy strength, out-of-plane torque proportion, FM free layer thickness and Gilbert damping constant, and the threshold current shows negative correlation with the out-of-plane torque proportion and positive correlation with the other three parameters. Finally, we demonstrate that when the applied current is smaller than the threshold current, although it cannot switch the magnetization of FM free layer, it can still equivalently add an effective exchange bias field H_{bias} on the FM free layer. The H_{bias} is proportional to the applied current J_{SOT}, which facilitates the determination of the anomalous SOT efficiency. This work helps us to design new spintronic devices that favor field-free switching perpendicular magnetization using the anomalous SOT, and provides a way to adjust the exchange bias field, which is helpful in controlling FM layer magnetization depinning

Perinatal COVID vaccination and breastfeeding during a pandemic : influences on decision making

"When the COVID-19 vaccine was first offered to pregnant individuals, little research was available on the effects of the vaccine on mom and baby (Sutton et. al, 2020; Fisher et. Al, 2021). Due to misinformation and other factors, low vaccine confidence (and vaccine hesitancy/skepticism) has been observed in Missouri and throughout the Midwest Ecological characteristics of a community, such as higher income and perceived community support, can have a significant impact on local breastfeeding practices. (Isherwood et. al, 2019). The purpose of this study was to examine how habitus influenced women’s health behavior regarding breastfeeding and COVID-19 vaccination. Habitus = The reflection of deeply ingrained habits, skills, and beliefs that shape an individual's perception of the world (Power, 1999)"--Background

Magnon-mediated interlayer coupling in an all-antiferromagnetic junction

The interlayer coupling mediated by fermions in ferromagnets brings about parallel and anti-parallel magnetization orientations of two magnetic layers, resulting in the giant magnetoresistance, which forms the foundation in spintronics and accelerates the development of information technology. However, the interlayer coupling mediated by another kind of quasi-particle, boson, is still lacking. Here we demonstrate such a static interlayer coupling at room temperature in an antiferromagnetic junction Fe2O3/Cr2O3/Fe2O3, where the two antiferromagnetic Fe2O3 layers are functional materials and the antiferromagnetic Cr2O3 layer serves as a spacer. The N\'eel vectors in the top and bottom Fe2O3 are strongly orthogonally coupled, which is bridged by a typical bosonic excitation (magnon) in the Cr2O3 spacer. Such an orthogonally coupling exceeds the category of traditional collinear interlayer coupling via fermions in ground state, reflecting the fluctuating nature of the magnons, as supported by our magnon quantum well model. Besides the fundamental significance on the quasi-particle-mediated interaction, the strong coupling in an antiferromagnetic magnon junction makes it a realistic candidate for practical antiferromagnetic spintronics and magnonics with ultrahigh-density integration.Comment: 19 pages, 4 figure

Field-free spin-orbit torque switching enabled by interlayer Dzyaloshinskii-Moriya interaction

Perpendicularly magnetized structures that are switchable using a spin current under field-free conditions can potentially be applied in spin-orbit torque magnetic random-access memory(SOT-MRAM).Several structures have been developed;however,new structures with a simple stack structure and MRAM compatibility are urgently needed.Herein,a typical structure in a perpendicular spin-transfer torque MRAM,the Pt/Co multilayer and its synthetic antiferromagnetic counterpart with perpendicular magnetic anisotropy, was observed to possess an intrinsic interlayer chiral interaction between neighboring magnetic layers,namely the interlayer Dzyaloshinskii-Moriya interaction (DMI) effect. Furthermore, using a current parallel to the eigenvector of the interlayer DMI, we switched the perpendicular magnetization of both structures without a magnetic field, owing to the additional symmetry-breaking introduced by the interlayer DMI. This SOT switching scheme realized in the Pt/Co multilayer and its synthetic antiferromagnet structure may open a new avenue toward practical perpendicular SOT-MRAM and other SOT devices

Observation of Fluctuation Spin Hall Effect in Antiferromagnet

The spin Hall effect (SHE) can generate a pure spin current by an electric current, which is promisingly used to electrically control magnetization. To reduce power consumption of this control, a giant spin Hall angle (SHA) in the SHE is desired in low-resistivity systems for practical applications. Here, critical spin fluctuation near the antiferromagnetic (AFM) phase-transition is proved as an effective mechanism to create an additional part of SHE, named as fluctuation spin Hall effect (FSHE). This FSHE enhances the SHA due to the AFM spin fluctuation between conduction electrons and local spins. We detect the FSHE with the inverse and direct spin Hall effect (ISHE and DSHE) set-up and their temperature (T) dependences in the Cr/MgO/Fe magnetic tunnel junctions (MTJs). The SHA is significantly enhanced when temperature is approached to the N\'eel temperature (T_N) and has a peak value of -0.34 at 200 K near T_N. This value is higher than the room-temperature value by 240% and comparable to that of heavy metals Ta and W. Furthermore, the spin Hall resistivity of Cr well fits the modeled T-dependence when T approaches T_N from low temperatures, implying the AFM spin fluctuation nature of strong SHA enhancement. Thus, this study demonstrates the critical spin fluctuation as a prospective way of increasing SHA and enriches the AFM material candidates for spin-orbitronic devices.Comment: 27 pages, 9 figure

Record thermopower found in an IrMn-based spintronic stack

The Seebeck effect converts thermal gradients into electricity. As an approach to power technologies in the current Internet-of-Things era, on-chip energy harvesting is highly attractive, and to be effective, demands thin film materials with large Seebeck coefficients. In spintronics, the antiferromagnetic metal IrMn has been used as the pinning layer in magnetic tunnel junctions that form building blocks for magnetic random access memories and magnetic sensors. Spin pumping experiments revealed that IrMn Néel temperature is thickness-dependent and approaches room temperature when the layer is thin. Here, we report that the Seebeck coefficient is maximum at the Néel temperature of IrMn of 0.6 to 4.0 nm in thickness in IrMn-based half magnetic tunnel junctions. We obtain a record Seebeck coefficient 390 (±10) μV K-1 at room temperature. Our results demonstrate that IrMn-based magnetic devices could harvest the heat dissipation for magnetic sensors, thus contributing to the Power-of-Things paradigm

Current-driven magnetization switching in a van der Waals ferromagnet Fe3GeTe2

The recent discovery of ferromagnetism in two-dimensional (2D) van der Waals (vdW) materials holds promises for novel spintronic devices with exceptional performances. However, in order to utilize 2D vdW magnets for building spintronic nanodevices such as magnetic memories, key challenges remain in terms of effectively switching the magnetization from one state to the other electrically. Here, we devise a bilayer structure of Fe3GeTe2/Pt, in which the magnetization of few-layered Fe3GeTe2 can be effectively switched by the spin-orbit torques (SOTs) originated from the current flowing in the Pt layer. The effective magnetic fields corresponding to the SOTs are further quantitatively characterized using harmonic measurements. Our demonstration of the SOT-driven magnetization switching in a 2D vdW magnet could pave the way for implementing low-dimensional materials in the next-generation spintronic applications