87 research outputs found
Chalcogen-height dependent magnetic interactions and magnetic order switching in FeSeTe
Magnetic properties of iron chalcogenide superconducting materials are
investigated using density functional calculations. We find the stability of
magnetic phases is very sensitive to the height of chalcogen species from the
Fe plane: while FeTe with optimized Te height has the double-stripe-type
magnetic ordering, the single-stripe-type ordering
becomes the ground state phase when Te height is lowered below a critical value
by, e.g., Se doping. This behavior is understood by opposite Te-height
dependences of the superexchange interaction and a longer-range magnetic
interaction mediated by itinerant electrons. We also demonstrate a linear
temperature dependence of the macroscopic magnetic susceptibility in the
single-stripe phase in contrast to a constant behavior in the double-stripe
phase. Our findings provide a comprehensive and unified view to understand the
magnetism in FeSeTe and iron pnictide superconductors.Comment: 4 pages, 4 figure
Enhanced spin density wave in LaOFeSb
We predict atomic, electronic, and magnetic structures of a hypothetical
compound LaOFeSb by first-principles density-functional calculations. It is
shown that LaOFeSb prefers a stripe-type antiferromagnetic phase (i.e., spin
density wave (SDW) phase) to the non-magnetic (NM) phase, with a larger Fe spin
moment and greater SDW-NM energy difference than those of LaOFeAs. The SDW
phase is found to favor the orthorhombic structure while the tetragonal
structure is more stable in the NM phase. In the NM-phase LaOFeSb, the
electronic bandwidth near the Fermi energy is reduced compared with LaOFeAs,
indicating smaller orbital overlap between Fe states and subsequently
enhanced intra-atomic exchange coupling. The calculated Fermi surface in the NM
phase consists of three hole and two electron sheets, and shows increased
nesting between two hole and two electron sheets compared with LaOFeAs.
Monotonous changes found in our calculated material properties of LaOFePn
(Pn=P, As, and Sb), along with reported superconducting properties of doped
LaOFeP and LaOFeAs, suggest that doped LaOFeSb may have a higher
superconducting transition temperature.Comment: 5 pages with 3 figures and 1 table, double colum
Low-velocity anisotropic Dirac fermions on the side surface of topological insulators
We report anisotropic Dirac-cone surface bands on a side-surface geometry of
the topological insulator BiSe revealed by first-principles
density-functional calculations. We find that the electron velocity in the
side-surface Dirac cone is anisotropically reduced from that in the
(111)-surface Dirac cone, and the velocity is not in parallel with the wave
vector {\bf k} except for {\bf k} in high-symmetry directions. The size of the
electron spin depends on the direction of {\bf k} due to anisotropic variation
of the noncollinearity of the electron state. Low-energy effective Hamiltonian
is proposed for side-surface Dirac fermions, and its implications are presented
including refractive transport phenomena occurring at the edges of tological
insulators where different surfaces meet.Comment: 4 pages, 2 columns, 4 figure
Simultaneous detection and subtyping of porcine endogenous retroviruses proviral DNA using the dual priming oligonucleotide system
The purpose of this study was to develop a multiplex PCR that can detect porcine endogenous retrovirus (PERV) proviral genes (pol, envA, envB, envC) and porcine mitochondrial DNA, using a dual priming oligonucleotide (DPO) system. The primer specifically detected the PERV proviral genes pol, envA, envB, envC, and porcine mitochondrial DNA only in samples of pig origin. The sensitivity of the primer was demonstrated by simultaneous amplification of all 5 target genes in as little as 10 pg of pig DNA containing PERV proviral genes and mitochondrial DNA. The multiplex PCR, when applied to field samples, simultaneously and successfully amplified PERV proviral genes from liver, blood and hair root samples. Thus, the multiplex PCR developed in the current study using DPO-based primers is a rapid, sensitive and specific assay for the detection and subtyping of PERV proviral genes
Experimental infection of a newly emerging Korean type I porcine reproductive and respiratory syndrome virus isolate in colostrum-deprived pigs
Dichotomizing Level of Pial Collaterals on Multiphase CT Angiography for Endovascular Treatment in Acute Ischemic Stroke: Should It Be Refined for 6-Hour Time Window?
Purpose Although endovascular treatment is currently thought to only be suitable for patients who have pial arterial filling scores >3 as determined by multiphase computed tomography angiography (mpCTA), a cut-off score of 3 was determined by a study, including patients within 12 hours after symptom onset. We aimed to investigate whether a cut-off score of 3 for endovascular treatment within 6 hours of symptom onset is an appropriate predictor of good functional outcome at 3 months. Materials and Methods From April 2015 to January 2016, acute ischemic stroke patients treated with mechanical thrombectomy within 6 hours of symptom onset were enrolled into this study. Pial arterial filling scores were semi-quantitatively assessed using mpCTA, and clinical and radiological parameters were compared between patients with favorable and unfavorable outcomes. Multivariate logistic regression analysis was then performed to investigate the independent association between clinical outcome and pial collateral score, with the predictive power of the latter assessed using C-statistics. Results Of the 38 patients enrolled, 20 (52.6%) had a favorable outcome and 18 had an unfavorable outcome, with the latter group showing a lower mean pial arterial filling score (3.6±0.8 vs. 2.4±1.2, P=0.002). After adjusting for variables with a P-value of 2 vs. ≤2. Conclusion A pial arterial filling cut-off score of 2 as determined by mpCTA appears to be more suitable for predicting clinical outcomes following endovascular treatment within 6 hours of symptom onset than the cut-off of 3 that had been previously suggested
The assessment of efficacy of porcine reproductive respiratory syndrome virus inactivated vaccine based on the viral quantity and inactivation methods
<p>Abstract</p> <p>Background</p> <p>There have been many efforts to develop efficient vaccines for the control of porcine reproductive and respiratory syndrome virus (PRRSV). Although inactivated PRRSV vaccines are preferred for their safety, they are weak at inducing humoral immune responses and controlling field PRRSV infection, especially when heterologous viruses are involved.</p> <p>Results</p> <p>In all groups, the sample to positive (S/P) ratio of IDEXX ELISA and the virus neutralization (VN) titer remained negative until challenge. While viremia did not reduce in the vaccinated groups, the IDEXX-ELISA-specific immunoglobulin G increased more rapidly and to significantly greater levels 7 days after the challenge in all the vaccinated groups compared to the non-vaccinated groups (<it>p </it>< 0.05). VN titer was significantly different in the 10<sup>6 </sup>PFU/mL PRRSV vaccine-inoculated and binary ethylenimine (BEI)-inactivated groups 22 days after challenge (<it>p </it>< 0.05). Consequently, the inactivated vaccines tested in this study provided weak memory responses with sequential challenge without any obvious active immune responses in the vaccinated pigs.</p> <p>Conclusions</p> <p>The inactivated vaccine failed to show the humoral immunity, but it showed different immune response after the challenge compared to mock group. Although the 10<sup>6 </sup>PFU/mL-vaccinated and BEI-inactivated groups showed significantly greater VN titers 22 days after challenge, all the groups were already negative for viremia.</p
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