705 research outputs found
IL17A (interleukin 17A)
Interleukin-17A (IL17A), a characteristic cytokine produced by the T helper 17 cells (Th17 cells), can form either a homodimer or a heterodimer with IL17F.It is produced not only by Th17 cells, but also by cytotoxic CD8+ T cells (Tc17 cells), ?d T cells, invariant natural killer T cells (iNKT cells), lymphoid tissue inducer cells (LTi cells), and other hematopoietic and non-hematopoietic cells. During development, these cells exhibit flexible or plastic features distinct from those of Th1 and Th2 cells. IL17A plays important roles in the pathogenesis of autoimmune diseases and in the host defenses against bacterial and fungal infections.Expression of IL17A and its related factors, as well as the infiltration of IL17A-producing cells into the tumor microenvironment, has been implicated in anti-tumor or pro-tumor effects in various cancers
Thermodynamic Studies on Non Centrosymmetric Superconductors by AC Calorimetry under High Pressures
We investigated the non centrosymmetric superconductors CePtSi and UIr by
the ac heat capacity measurement under pressures. We determined the pressure
phase diagrams of these compounds. In CePtSi, the N\'{e}el temperature
= 2.2 K decreases with increasing pressure and becomes zero at the
critical pressure 0.6 GPa. On the other hand, the
superconducting phase exists in a wider pressure region from ambient pressure
to 1.5 GPa. The phase diagram of CePtSi is very
unique and has never been reported before for other heavy fermion
superconductors. In UIr, the heat capacity shows an anomaly at the Curie
temperature = 46 K at ambient pressure, and the heat capacity
anomaly shifts to lower temperatures with increasing pressure. The present
pressure dependence of was consistent with the previous studies by
the resistivity and magnetization measurements. Previous ac magnetic
susceptibility and resistivity measurements suggested the existence of three
ferromagnetic phases, FM1-3. shows a bending structure at 1.98,
2.21, and 2.40 GPa .The temperatures where these anomalies are observed are
close to the phase boundary of the FM3 phase.Comment: This paper was presented at the international workshop ``Novel
Pressure-induced Phenomena in Condensed Matter Systems(NP2CMS)" August 26-29
2006, Fukuoka Japa
Coexistence of Ferromagnetism and Superconductivity in Noncentrosymmetric Materials with Cubic Symmetry
This is a model study for the emergence of superconductivity in
ferromagnetically ordered phases of cubic materials whose crystal structure
lacks inversion symmetry. A Ginzburg-Landau-type theory is used to find the
ferromagnetic state and to determine the coupling of magnetic order to
superconductivity. It is found that noncentrosymmetricity evokes a helical
magnetic phase. If the wavelength of the magnetic order is long enough, it
gives rise to modulations of the order parameter of superconductivity, both in
modulus and complex phase. At magnetic domain walls the nucleation of
superconductivity is found to be suppressed as compared to the interior of
ferromagnetic domains.Comment: 5 pages, 2 figure
Strong-Coupling Superconductivity of CeIrSi with the Non-centrosymmetric Crystal Structure
We studied the pressure-induced superconductor CeIrSi with the
non-centrosymmetric tetragonal structure under high pressure. The electrical
resistivity and ac heat capacity were measured in the same run for the same
sample. The critical pressure was determined to be = 2.25 GPa,
where the antiferromagnetic state disappears. The heat capacity
shows both antiferromagnetic and superconducting transitions at pressures close
to . On the other hand, the superconducting region is extended to
high pressures of up to about 3.5 GPa, with the maximum transition temperature
= 1.6 K around GPa. At 2.58 GPa, a large heat capacity
anomaly was observed at = 1.59 K. The jump of the heat capacity in
the form of is 5.7 0.1.
This is the largest observed value among previously reported superconductors,
indicating the strong-coupling superconductivity. The electronic specific heat
coefficient at is, however, approximately unchanged as a function
of pressure, even at .Comment: This paper will be published in J. Phys. Soc. Jpn. on the August
issue of 200
Pressure Evolution of the Ferromagnetic and Field Re-entrant Superconductivity in URhGe
Fine pressure () and magnetic field () tuning on the ferromagnetic
superconductor URhGe are reported in order to clarify the interplay between the
mass enhancement, low field superconductivity (SC) and field reentrant
superconductivity (RSC) by electrical resistivity measurements. With increasing
, the transition temperature and the upper critical field of the low field
SC decrease slightly, while the RSC dome drastically shifts to higher fields
and shrinks. The spin reorientation field also increases. At a
pressure GPa, the RSC has collapsed while the low field SC persists
and may disappear only above 4 GPa. Via careful studies of the
inelastic resistivity term, it is demonstrated that this drastic change
is directly related with the dependence of the effective mass which
determines the critical field of the low field SC and RSC on the basis of
triplet SC without Pauli limiting field.Comment: 5 pages, 6 figures, to appear in Journal of the Physical Society of
Japa
Ferromagnetic Quantum Critical Fluctuations and Anomalous Coexistence of Ferromagnetism and Superconductivity in UCoGe Revealed by Co-NMR and NQR Studies
Co nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR)
studies were performed in the recently discovered UCoGe, in which the
ferromagnetic and superconducting (SC) transitions were reported to occur at
K and K (N. T. Huy {\it et al.}, Phys.
Rev. Lett. {\bf 99} (2007) 067006), in order to investigate the coexistence of
ferromagnetism and superconductivity as well as the normal-state and SC
properties from a microscopic point of view. From the nuclear spin-lattice
relaxation rate and Knight-shift measurements, we confirmed that
ferromagnetic fluctuations which possess a quantum critical character are
present above and the occurrence of ferromagnetic transition at
2.5 K in our polycrystalline sample. The magnetic fluctuations in the normal
state show that UCoGe is an itinerant ferromagnet similar to ZrZn and
YCo. The onset SC transition was identified at K, below
which of 30 % of the volume fraction starts to decrease due to the
opening of the SC gap. This component of , which follows a
dependence in the temperature range of K, coexists with the
magnetic components of showing a dependence below .
From the NQR measurements in the SC state, we suggest that the self-induced
vortex state is realized in UCoGe.Comment: 5 pages, 7 figures. submitted to J. Phys. Soc. Jpn. To appear in J.
Phys. Soc. Jp
Nonuniform Spin Triplet Superconductivity due to Antisymmetric Spin-Orbit Coupling in Noncentrosymmetric Superconductor CePtSi
We show that the nonuniform state (Fulde-Ferrel-Larkin-Ovchinnikov (FFLO)
state) of the spin triplet superconductivity in noncentrosymmetric systems is
stabilized by antisymmetric spin-orbit coupling even if the magnetic field is
absent. The transition temperature of the spin triplet superconductivity is
reduced by the antisymmetric spin-orbit coupling in general. This pair breaking
effect is shown to be similar to the Pauli pair breaking effect due to magnetic
field for the spin singlet superconductivity, in which FFLO state is stabilized
near the Pauli limit (or Chandrasekhar-Clogston limit) of external magnetic
field. Since there are gapless excitations in nonuniform superconducting state,
some physical quantities such as specific heat and penetration depth should
obey the power low temperature-dependences. We discuss the possibility of the
realization of nonuniform state in CePtSi.Comment: 8 pages, 6 figure
Microscopic Coexistence of Ferromagnetism and Superconductivity in Single-Crystal UCoGe
Unambiguous evidence for the microscopic coexistence of ferromagnetism and
superconductivity in UCoGe ( K and
0.6 K) is reported from Co nuclear quadrupole resonance (NQR). The
Co-NQR signal below 1 K indicates ferromagnetism throughout the sample
volume, while nuclear spin-lattice relaxation rate in the ferromagnetic
(FM) phase decreases below due to the opening of the
superconducting(SC) gap. The SC state was found to be inhomogeneous, suggestive
of a self-induced vortex state, potentially realizable in a FM superconductor.
In addition, the Co-NQR spectrum around show that the FM
transition in UCoGe possesses a first-order character, which is consistent with
the theoretical prediction that the low-temperature FM transition in itinerant
magnets is generically of first-order.Comment: 5 pages, 5 figure
Microscopic Mechanism and Pairing Symmetry of Superconductivity in the Noncentrosymmetric Heavy Fermion Systems CeRhSI and CeIrSi
We study the pairing symmetry of the noncentrosymmetric heavy fermion
superconductors CeRhSi and CeIrSi under pressures, which are both
antiferromagnets at ambient pressure. We solve the Eliashberg equation by means
of the random phase approximation and find that the mixed state of extended
s-wave and p-wave rather than the wave state could be realized by
enhanced antiferromagnetic spin fluctuations. It is elucidated that the gap
function has line nodes on the Fermi surface and the resulting density of state
in the superconducting state shows a similar character to that of usual d-wave
superconductors, resulting in the NMR relaxation rate that exhibits
no coherence peak and behaves like at low temperatures
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