113 research outputs found
Magnetic Fluctuations and Correlations in MnSi - Evidence for a Skyrmion Spin Liquid Phase
We present a comprehensive analysis of high resolution neutron scattering
data involving Neutron Spin Echo spectroscopy and Spherical Polarimetry which
confirm the first order nature of the helical transition and reveal the
existence of a new spin liquid skyrmion phase. Similar to the blue phases of
liquid crystals this phase appears in a very narrow temperature range between
the low temperature helical and the high temperature paramagnetic phases.Comment: 11 pages, 16 figure
Spin correlations and exchange in square lattice frustrated ferromagnets
The J1-J2 model on a square lattice exhibits a rich variety of different
forms of magnetic order that depend sensitively on the ratio of exchange
constants J2/J1. We use bulk magnetometry and polarized neutron scattering to
determine J1 and J2 unambiguously for two materials in a new family of vanadium
phosphates, Pb2VO(PO4)2 and SrZnVO(PO4)2, and we find that they have
ferromagnetic J1. The ordered moment in the collinear antiferromagnetic ground
state is reduced, and the diffuse magnetic scattering is enhanced, as the
predicted bond-nematic region of the phase diagram is approached.Comment: 4 pages, 4 figure
MicroRNA expression profiling of porcine mammary epithelial cells after challenge with Escherichia coli in vitro
Background Coliform mastitis is a symptom of postpartum dysgalactia syndrome
(PDS), a multifactorial infectious disease of sows. Our previous study showed
gene expression profile change after bacterial challenge of porcine mammary
epithelial cells (PMECs). These mRNA expression changes may be regulated
through microRNAs (miRNAs) which play critical roles in biological processes.
Therefore, miRNA expression profile was investigated in PMECs. Results PMECs
were isolated from three lactating sows and challenged with heat-inactivated
potential mastitis-causing pathogen Escherichia coli (E. coli) for 3 h and 24
h, in vitro. At 3 h post-challenge with E. coli, target gene prediction
identified a critical role of miRNAs in regulation of host immune responses
and homeostasis of PMECs mediated by affecting pathways including cytokine
binding (miR-202, miR-3277, miR-4903); IL-10/PPAR signaling (miR-3277,
miR-4317, miR-548); and NF-ĸB/TNFR2 signaling (miR-202, miR-2262, miR-885-3p).
Target genes of miRNAs in PMECs at 24 h were significantly enriched in
pathways associated with interferon signaling (miR-210, miR-23a, miR-1736) and
protein ubiquitination (miR-125, miR-128, miR-1280). Conclusions This study
provides first large-scale miRNA expression profiles and their predicted
target genes in PMECs after contact with a potential mastitis-causing E. coli
strain. Both, highly conserved miRNAs known from other species as well as
novel miRNAs were identified in PMECs, representing candidate predictive
biomarkers for PDS. Time-dependent pathogen clearance suggests an important
role of PMECs in inflammatory response of the first cellular barrier of the
porcine mammary gland
Static critical exponents of the ferromagnetic transition in spin glass re-entrant systems
The static critical phenomenology near the Curie temperature of the
re-entrant metallic alloys Au_0.81Fe_0.19, Ni_0.78Mn_0.22, Ni_0.79Mn_0.21 and
amorphous a-Fe_0.98Zr_0.08 is studied using a variety of experimental
techniques and methods of analysis. We have generally found that the values for
the exponents alpha, beta, gamma and delta depart significantly from the
predictions for the 3D Heisenberg model and are intermediate between these
expectations and the values characterizing a typical spin glass transition.
Comparing the exponents obtained in our work with indices for other re-entrant
systems reported in the literature, a weak universality class may be defined
where the exponents distribute within a certain range around average values.Comment: 17 pages, 11 figure
Parâmetros genéticos de características de carcaça, reprodução e crescimento na raça Canchim.
O objetivou deste trabalho foi estimar parâmetros genéticos, utilizando inferência bayesiana sob o modelo animal, para as características peso ao sobreano (PES), circunferência escrotal ao sobreano (CE), idade ao primeiro parto (IPP), área de olho de lombo (AOL) e espessura de gordura (EG), visando fornecer subsídios para o programa de melhoramento genético da raça Canchim. Os dados utilizados neste estudo foram cedidos pela Associação Brasileira de Criadores de Canchim e contaram com 5.935 animais nascidos entre os anos de 1993 e 2011. As estimativas de herdabilidade foram 0,25; 0,43; 0,39; 0,19; e 0,11 para PES, CE, AOL, EG e IPP, respectivamente. As estimativas de herdabilidade sugerem que as características de carcaça, peso e circunferência escrotal ao sobreano devam responder à seleção direta, enquanto que para a idade ao primeiro parto espera-se que poucos ganhos sejam obtidos por meio da seleção. As correlações genéticas apontam para importantes respostas correlacionadas que favoreceriam na redução na idade ao primeiro parto, aumento de peso corporal e melhoria na qualidade da carcaça em animais da raça Canchim
Yb-Yb correlations and crystal-field effects in the Kondo insulator YbB12 and its solid solutions
We have studied the effect of Lu substitution on the spin dynamics of the
Kondo insulator YbB12 to clarify the origin of the spin-gap response previously
observed at low temperature in this material. Inelastic neutron spectra have
been measured in Yb1-xLuxB12 compounds for four Lu concentrations x = 0, 0.25,
0.90 and 1.0. The data indicate that the disruption of coherence on the Yb
sublattice primarily affects the narrow peak structure occurring near 15-20 meV
in pure YbB12, whereas the spin gap and the broad magnetic signal around 38 meV
remain almost unaffected. It is inferred that the latter features reflect
mainly local, single-site processes, and may be reminiscent of the inelastic
magnetic response reported for mixed-valence intermetallic compounds. On the
other hand, the lower component at 15 meV is most likely due to dynamic
short-range magnetic correlations. The crystal-field splitting in YbB12
estimated from the Er3+ transitions measured in a Yb0.9Er0.1B12 sample, has the
same order of magnitude as other relevant energy scales of the system and is
thus likely to play a role in the form of the magnetic spectral response.Comment: 16 pages in pdf format, 9 figures. v. 2: coauthor list updated; extra
details given in section 3.2 (pp. 6-7); one reference added; fig. 5 axis
label change
Muon spin rotation and neutron scattering study of the non-centrosymmetric tetragonal compound CeAuAl3
We have investigated the non-centrosymmetric tetragonal heavy-fermion
compound CeAuAl3 using muon spin rotation (muSR), neutron diffraction (ND) and
inelastic neutron scattering (INS) measurements. We have also revisited the
magnetic, transport and thermal properties. The magnetic susceptibility reveals
an antiferromagnetic transition at 1.1 K with a possibility of another magnetic
transition near 0.18 K. The heat capacity shows a sharp lambda-type anomaly at
1.1 K in zero-filed, which broadens and moves to higher temperature in applied
magnetic field. Our zero-field muSR and ND measurements confirm the existence
of a long-range magnetic ground state below 1.2 K. Further the ND study reveals
an incommensurate magnetic ordering with a magnetic propagation vector k = (0,
0, 0.52) and a spiral structure of Ce moments coupled ferromagnetically within
the ab-plane. Our INS study reveals the presence of two well-defined crystal
electric field (CEF) excitations at 5.1 meV and 24.6 meV in the paramagnetic
phase of CeAuAl3 which can be explained on the basis of the CEF theory.
Furthermore, low energy quasi-elastic excitations show a Gaussian line shape
below 30 K compared to a Lorentzian line shape above 30 K, indicating a
slowdown of spin fluctuation below 30 K. We have estimated a Kondo temperature
of TK=3.5 K from the quasi-elastic linewidth, which is in good agreement with
that estimated from the heat capacity. This study also indicates the absence of
any CEF-phonon coupling unlike that observed in isostructural CeCuAl3. The CEF
parameters, energy level scheme and their wave functions obtained from the
analysis of INS data explain satisfactorily the single crystal susceptibility
in the presence of two-ion anisotropic exchange interaction in CeAuAl3.Comment: 28 pages and 17 figure
Magnetic fluctuations in frustrated Laves hydrides R(Mn_{1-x}Al_{x})_{2}H_{y}
By neutron scattering, we have studied the spin correlations and spin
fluctuations in frustrated Laves hydrides, where magnetic disorder sets in the
topologically frustrated Mn lattice. Below the transition towards short range
magnetic order, static spin clusters coexist with fluctuating and alsmost
uncorrelated spins. The magnetic response shows a complexe lineshape, connected
with the presence of the magnetic inhomogeneities. Its analysis shows the
existence of two different processes, relaxation and local excitations, for the
spin fluctuations below the transition. The paramagnetic fluctuations are
discussed in comparison with classical spin glasses, cluster glasses, and non
Fermi liquid itinerant magnets
Band Calculations for Ce Compounds with AuCu-type Crystal Structure on the basis of Dynamical Mean Field Theory I. CePd and CeRh
Band calculations for Ce compounds with the AuCu-type crystal structure
were carried out on the basis of dynamical mean field theory (DMFT). The
auxiliary impurity problem was solved by a method named NCAvc
(noncrossing approximation including the state as a vertex correction).
The calculations take into account the crystal-field splitting, the spin-orbit
interaction, and the correct exchange process of the virtual excitation. These are necessary features in the
quantitative band theory for Ce compounds and in the calculation of their
excitation spectra. The results of applying the calculation to CePd and
CeRh are presented as the first in a series of papers. The experimental
results of the photoemission spectrum (PES), the inverse PES, the
angle-resolved PES, and the magnetic excitation spectra were reasonably
reproduced by the first-principles DMFT band calculation. At low temperatures,
the Fermi surface (FS) structure of CePd is similar to that of the band
obtained by the local density approximation. It gradually changes into a form
that is similar to the FS of LaPd as the temperature increases, since the
band shifts to the high-energy side and the lifetime broadening becomes
large.}Comment: 12 pasges, 13 figure
Strong Longitudinal Magnetic Fluctuations near Critical End Point in UCoAl: A ^59Co-NMR Study
We report ^59Co-NMR measurements in UCoAl where a metamagnetism occurs due to
enhancement of ferromagnetism by magnetic field. The metamagnetic transition
from a paramagnetic (PM) state to a ferromagnetic state is a first order
transition at low temperatures, but it changes to a crossover at high
temperatures on crossing the critical end pint (CEP) at T_CEP ~ 12 K. The
contrasting behavior between the relaxation rates 1/T_1 and 1/T_2 suggests that
the longitudinal magnetic fluctuation of U moment is strongly enhanced
especially near the CEP. A wide diffusion of the fluctuation from the CEP can
be confirmed even in the PM state where the magnetic transition does not occur.Comment: 5pages, 6 figures, to be published in J. Phys. Soc. Jp
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