37 research outputs found
Ferromagnetic Quantum Criticality in the Quasi-One-Dimensional Heavy Fermion Metal YbNi4P2
We present a new Kondo-lattice system, YbNi4P2, which is a clean
heavy-fermion metal with a severely reduced ferromagnetic ordering temperature
at T_C=0.17K, evidenced by distinct anomalies in susceptibility, specific-heat,
and resistivity measurements. The ferromagnetic nature of the transition, with
only a small ordered moment of ~0.05mu_B, is established by a diverging
susceptibility at T_C with huge absolute values in the ferromagnetically
ordered state, severely reduced by small magnetic fields. Furthermore, YbNi4P2
is a stoichiometric system with a quasi-one-dimensional crystal and electronic
structure and strong correlation effects which dominate the low temperature
properties. This is reflected by a stronger-than-logarithmically diverging
Sommerfeld coefficient and a linear-in-T resistivity above T_C which cannot be
explained by any current theoretical predictions. These exciting
characteristics are unique among all correlated electron systems and make this
an interesting material for further in-depth investigations.Comment: 14 pages, 6 figure
Magnetic and structural properties of the iron silicide superconductor LaFeSiH
The magnetic and structural properties of the recently discovered
pnictogen/chalcogen-free superconductor LaFeSiH (~K) have been
investigated by Fe synchrotron M{\"o}ssbauer source (SMS) spectroscopy,
x-ray and neutron powder diffraction and Si nuclear magnetic resonance
spectroscopy (NMR). No sign of long range magnetic order or local moments has
been detected in any of the measurements and LaFeSiH remains tetragonal down to
2 K. The activated temperature dependence of both the NMR Knight shift and the
relaxation rate is analogous to that observed in strongly overdoped
Fe-based superconductors. These results, together with the
temperature-independent NMR linewidth, show that LaFeSiH is an homogeneous
metal, far from any magnetic or nematic instability, and with similar Fermi
surface properties as strongly overdoped iron pnictides. This raises the
prospect of enhancing the of LaFeSiH by reducing its carrier
concentration through appropriate chemical substitutions. Additional SMS
spectroscopy measurements under hydrostatic pressure up to 18.8~GPa found no
measurable hyperfine field
A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)
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Unveiling Nanometer Scale Extinction and Scattering Phenomena through Combined Electron Energy Loss Spectroscopy and Cathodoluminescence Measurements
Strain-induced crystallization in sustainably crosslinked epoxidized natural rubber
International audienc
Structure of Fluorinated Side-Chain Smectic Copolymers:Â Role of the Copolymerization Statistics
Interleukin-1 enhances the ATP-evoked release of arachidonic acid from mouse astrocytes.
During neuropathological states associated with inflammation, the levels of cytokines such as interleukin-1beta (IL-1beta) are increased. Several studies have suggested that the neuronal damage observed in pathogenesis implicating IL-1beta are caused by an alteration in the neurochemical interactions between neurons and astrocytes. We report here that treating striatal astrocytes in primary culture with IL-1beta for 22-24 hr enhances the ATP-evoked release of arachidonic acid (AA) with no effect on the ATP-induced accumulation of inositol phosphates. The molecular mechanism responsible for this effect involves the expression of P2Y2 receptors (a subtype of purinoceptor activated by ATP) and cytosolic phospholipase A2 (cPLA2, an enzyme that mediates AA release). Indeed, P2Y2 antisense oligonucleotides reduce the ATP-evoked release of AA only from IL-1beta-treated astrocytes. Further, both the amount of cPLA2 (as assessed by Western blotting) and the release of AA resulting from direct activation of cPLA2 increased fourfold in cells treated with IL-1beta. We also report evidence indicating that the coupling of newly expressed P2Y2 receptors to cPLA2 is dependent on PKC activity. These results suggest that during inflammatory conditions, IL-1beta reveals a functional P2Y2 signaling pathway in astrocytes that results in a dramatic increase in the levels of free AA. This pathway may thus contribute to the neuronal loss associated with cerebral ischemia or traumatic brain injury
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Interleukin-1 enhances the ATP-evoked release of arachidonic acid from mouse astrocytes.
During neuropathological states associated with inflammation, the levels of cytokines such as interleukin-1beta (IL-1beta) are increased. Several studies have suggested that the neuronal damage observed in pathogenesis implicating IL-1beta are caused by an alteration in the neurochemical interactions between neurons and astrocytes. We report here that treating striatal astrocytes in primary culture with IL-1beta for 22-24 hr enhances the ATP-evoked release of arachidonic acid (AA) with no effect on the ATP-induced accumulation of inositol phosphates. The molecular mechanism responsible for this effect involves the expression of P2Y2 receptors (a subtype of purinoceptor activated by ATP) and cytosolic phospholipase A2 (cPLA2, an enzyme that mediates AA release). Indeed, P2Y2 antisense oligonucleotides reduce the ATP-evoked release of AA only from IL-1beta-treated astrocytes. Further, both the amount of cPLA2 (as assessed by Western blotting) and the release of AA resulting from direct activation of cPLA2 increased fourfold in cells treated with IL-1beta. We also report evidence indicating that the coupling of newly expressed P2Y2 receptors to cPLA2 is dependent on PKC activity. These results suggest that during inflammatory conditions, IL-1beta reveals a functional P2Y2 signaling pathway in astrocytes that results in a dramatic increase in the levels of free AA. This pathway may thus contribute to the neuronal loss associated with cerebral ischemia or traumatic brain injury
Magnetic structures of the ternary silicide Nd6Ni1.67Si3
The ternary silicides RE6T1:67Si3 (RE = Ce, Pr, Nd, Gd, Tb and T = Co, Ni) crystallizing with the hexagonal Ce6Ni1:67Si3-type structure has been recently extensively studied. It has been shown that some of these compounds exhibit interesting magnetocaloric properties. In this work, the magnetic structures of the Nd6Ni1:67Si3 compound were determined by means of neutron powder diÂźraction. According to previous magnetization and speciÂŻc heat measurements, this compound exhibits two successive magnetic transitions at 84K and 38K. The ÂŻrst transition corresponds to a ferromagnetic arrangement of the Nd-moments along the c-axis and the second one to a non-collinear ferromagnetic arrangement yielding a conical structure. The magnetic structures of Nd6Ni1:67Si3 are compared to those of the Nd6Co1:67Si3 homologous ternary silicide