165 research outputs found
Unconventional magnetic order on the hyperhoneycomb Kitaev lattice in -Li2IrO3: full solution via magnetic resonant x-ray diffraction
The recently-synthesized iridate -LiIrO has been proposed as a
candidate to display novel magnetic behavior stabilized by frustration effects
from bond-dependent, anisotropic interactions (Kitaev model) on a
three-dimensional "hyperhoneycomb" lattice. Here we report a combined study
using neutron powder diffraction and magnetic resonant x-ray diffraction to
solve the complete magnetic structure. We find a complex, incommensurate
magnetic order with non-coplanar and counter-rotating Ir moments, which
surprisingly shares many of its features with the related structural polytype
"stripyhoneycomb" -LiIrO, where dominant Kitaev interactions
have been invoked to explain the stability of the observed magnetic structure.
The similarities of behavior between those two structural polytypes, which have
different global lattice topologies but the same local connectivity, is
strongly suggestive that the same magnetic interactions and the same underlying
mechanism governs the stability of the magnetic order in both materials,
indicating that both - and -LiIrO are strong candidates
to realize dominant Kitaev interactions in a solid state material.Comment: 14 pages, 9 figure
Electrical switching of magnetic polarity in a multiferroic BiFeO3 device at room temperature
We have directly imaged reversible electrical switching of the cycloidal
rotation direction (magnetic polarity) in a (111)-BiFeO3 epitaxial-film device
at room temperature by non-resonant x-ray magnetic scattering. Consistent with
previous reports, fully relaxed (111)-BiFeO3 epitaxial films consisting of a
single ferroelectric domain were found to comprise a sub-micron-scale mosaic of
magneto-elastic domains, all sharing a common direction of the magnetic
polarity, which was found to switch reversibly upon reversal of the
ferroelectric polarization without any measurable change of the magneto-elastic
domain population. A real-space polarimetry map of our device clearly
distinguished between regions of the sample electrically addressed into the two
magnetic states with a resolution of a few tens of micron. Contrary to the
general belief that the magneto-electric coupling in BiFeO3 is weak, we find
that electrical switching has a dramatic effect on the magnetic structure, with
the magnetic moments rotating on average by 90 degrees at every cycle.Comment: 6 pages, 5 figures; corrected figure
Direct observation of charge order in triangular metallic AgNiO2 by single-crystal resonant X-ray scattering
We report resonant X-ray scattering measurements on the orbitally-degenerate
triangular metallic antiferromagnet 2H-AgNiO2 to probe the spontaneous
transition to a triple-cell superstructure at temperatures below 365 K. We
observe a strong resonant enhancement of the supercell reflections through the
Ni K-edge. The empirically extracted K-edge shift between the
crystallographically-distinct Ni sites of 2.5(3) eV is much larger than the
value expected from the shift in final states, and implies a core-level shift
of ~1 eV, thus providing direct evidence for the onset of spontaneous honeycomb
charge order in the triangular Ni layers. We also provide band-structure
calculations that explain quantitatively the observed edge shifts in terms of
changes in the Ni electronic energy levels due to charge order and
hybridization with the surrounding oxygens.Comment: 5 pages, 4 figure
Non-coplanar and counter-rotating incommensurate magnetic order stabilized by Kitaev interactions in -Li2IrO3
Materials that realize Kitaev spin models with bond-dependent anisotropic
interactions have long been searched for, as the resulting frustration effects
are predicted to stabilize novel forms of magnetic order or quantum spin
liquids. Here we explore the magnetism of -LiIrO, which has the
topology of a 3D Kitaev lattice of inter-connected Ir honeycombs. Using
resonant magnetic x-ray diffraction we find a complex, yet highly-symmetric
incommensurate magnetic structure with non-coplanar and counter-rotating Ir
moments. We propose a minimal Kitaev-Heisenberg Hamiltonian that naturally
accounts for all key features of the observed magnetic structure. Our results
provide strong evidence that -LiIrO realizes a spin Hamiltonian
with dominant Kitaev interactions.Comment: 10 pages, 7 figure
Proteinase Activated Receptor 4 in the Jejunum of Healthy Horses and of Horses With Epiploic Hernia
Proteinase activated receptor 4 (PAR4) in the gastrointestinal tract is involved in the regulation of inflammation and pain pathways. The aim of the present study was to evaluate the distribution and expression of PAR4 in the jejunum of healthy horses and in the pathologic tracts from horses undergoing surgery for herniation of the small intestine through the epiploic foramen. Eight healthy horses (Group H) and eight horses with epiploic hernia (Group EH) were included; the jejunum samples were collected at the slaughter or intraoperatively after enterectomy, respectively. To evaluate PAR4 expression in sections of the jejunum, immunofluorescence, western blot and quantitative polymerase chain reaction (qRT-PCR) were performed. Immunohistochemistry of PAR4 in the jejunum of the healthy horses showed that receptors are predominantly expressed in the immune cell population scattered throughout the lamina propria of the mucosa and in the submucosa. Quantitative PCR data demonstrated that PAR4 mRNA was detectable in all of the samples analyzed without any difference between the H and the EH groups, however the PAR4 protein level was significantly lower in the jejunums of the EH horses. In the Group EH horses, PAR4 immunoreactivity was mainly expressed in the mast cells and was extensively distributed in the sierosa. In the lamina propria of mucosa of Group EH, leukocytes were less abundant than in Group H. In this study, the distribution and expression of PAR4 in the jejunums of the healthy horses and in those with spontaneous occurring epiploic hernia was demonstrated
Expression of Proteinase-Activated Receptor 2 During Colon Volvulus in the Horse
Large colon volvulus in horses is associated with a poor prognosis, especially when ischemic-reperfusion injury of the affected intestinal tract develops. Proteinase-activated receptor 2 (PAR2) plays an important role in the pathogenesis of inflammation in the gastrointestinal tract. The aim of this study was to evaluate the distribution and expression of PAR2 in colonic pelvic flexure of horses spontaneously affected by large colon volvulus (CVH group). Eight horses admitted for severe abdominal colon volvolus and which underwent surgery were included. Colon samples were collected after enterotomy. Data previously obtained from healthy horses were used as a control group. Histologic evaluation was carried out to grade the severity of the colon lesions. Immunofluorescence, western blot and quantitative polymerase chain reaction (RT-qPCR) were carried out on colon samples to evaluate PAR2 expression. In addition, the transcriptional profile of cytokines and chemokines was evaluated using RT2 Profiler™ PCR Array Horse Cytokines & Chemokines. Three out of the eight patients were euthanised due to clinical deterioration. Immunostaining for PAR2 was observed in the enterocytes, intestinal glands and neurons of the submucosal and myenteric plexi. In the CVH horses, the expression of PAR2 mesenger RNA (mRNA) did not differ significantly from that of the healthy animals; western blots of the mucosa of the colon tracts showed a clear band of the expected molecular weight for PAR2 (~44 kDa) and a band smaller than the expected molecular weight for PAR2 (25kDa), suggesting its activation. The gene expressions for C-X-C motif ligand 1 (CXCL1); interleukin 8 (IL8), macrophage inflammatory protein 2 beta (MIP-2BETA) were upregulated in the colic horses as compared with the colons of the healthy horses. Therefore, in the present study, the expression and activation of PAR2 in the colons of horses in the presence of an inflammatory reaction like that occurring in those with spontaneous colon volvulus was confirmed
studies on tursiops truncatus and stenella coeruleoalba dolphin species from retinal cell morphological comparisons towards its surrounding environment
AbstractIn this current study, the retinal cell morphology of two dolphin species, Tursiops truncatus and Stenella coeruleoalba was compared, and supplemented with a miniature review of how it relates to surrounding environment. Retinal cell morphology involved sectioning and retino-separation of eyes, morphometric analysis of retinal cell layers and its corresponding neurons, followed by stratigraphy of both retina and area/density of ganglion neuron cell bodies. A qualification criteria was developed to describe both thickness and visibility. To relate with surrounding environment of studied species, we searched relevant synthesized literature combining such key words as 'dolphin', 'Tursiops truncatus', 'Stenella coeruleoalba', 'eye', 'vision', 'ecology' and 'environment'. Retinal cell morphology comparisons showed that the thickness of outer nuclear layer had upper (37.8 – 38.5 μm) whereas outer plexiform layer had lower (7.8 – 8.7 μm) range values, with some differences between individual retinal layers (p<0.05) but specific to some cases. Area of ganglion cell layer of multipolar neurons of retina of both studied species could surpass the 800 μm2 mark, which suggests the presence of 'giant' size cell types. Plausibly, the retino-morphological comparisons of studied dolphin species depict the context of micro-view, and able to relate with a macro-view with respect to its surrounding environment
Multi-Donor longitudinal antibody repertoire sequencing reveals the existence of public antibody clonotypes in HIV-1 infection
Characterization of single antibody lineages within infected individuals has provided insights into the development of Env-specific antibodies. However, a systems-level understanding of the humoral response against HIV-1 is limited. Here, we interrogated the antibody repertoires of multiple HIV-infected donors from an infection-naive state through acute and chronic infection using next-generation sequencing. This analysis revealed the existence of “public” antibody clonotypes that were shared among multiple HIV-infected individuals. The HIV-1 reactivity for representative antibodies from an identified public clonotype shared by three donors was confirmed. Furthermore, a meta-analysis of publicly available antibody repertoire sequencing datasets revealed antibodies with high sequence identity to known HIV-reactive antibodies, even in repertoires that were reported to be HIV naive. The discovery of public antibody clonotypes in HIV-infected individuals represents an avenue of significant potential for better understanding antibody responses to HIV-1 infection, as well as for clonotype-specific vaccine development
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