892 research outputs found
Unconventional magnetism in multivalent charge-ordered YbPtGe probed by Pt- and Yb-NMR
Detailed Pt- and Yb nuclear magnetic resonance (NMR) studies
on the heterogeneous mixed valence system YbPtGe are reported. The
temperature dependence of the Pt-NMR shift indicates the
opening of an unusual magnetic gap below 200\,K. was analyzed by a
thermal activation model which yields an isotropic gap \,K. In contrast, the spin-lattice relaxation rate () does
not provide evidence for the gap. Therefore, an intermediate-valence picture is
proposed while a Kondo-insulator scenario can be excluded. Moreover,
() follows a simple metallic behavior, similar to the reference
compound YPtGe. A well resolved NMR line with small shift is assigned to
divalent Yb. This finding supports the proposed model with two sub-sets
of Yb species (di- and trivalent) located on the Yb2 and Yb1 site of the
YbPtGe lattice.Comment: Submitted in Physical Review B (Rapid Communication
Superconductivity in the New Platinum Germanides MPt4Ge12 (M = Rare-earth and Alkaline-earth Metals) with Filled Skutterudite Structure
New germanium-platinum compounds with the filled-skutterudite crystal
structure were synthesized. The structure and composition were investigated by
X-ray diffraction and microprobe analysis. Magnetic susceptibility, specific
heat, and electrical resistivity measurements evidence superconductivity in
LaPt4Ge12 and PrPt4Ge12 below 8.3K. The parameters of the normal and
superconducting states were established. Strong coupling and a crystal electric
field singlet groundstate is found for the Pr compound. Electronic structure
calculations show a large density of states at the Fermi level. Similar
behavior with lower T_c was observed for SrPt4Ge12 and BaPt4Ge12.Comment: RevTeX, 4 figures, submitted to Physical Review Letters July 12, 200
Evidence for time-reversal symmetry breaking in superconducting PrPt4Ge12
Zero and longitudinal field muon spin rotation (muSR) experiments were
performed on the superconductors PrPt4Ge12 and LaPt4Ge12. In PrPt4Ge12 below Tc
a spontaneous magnetization with a temperature variation resembling that of the
superfluid density appears. This observation implies time-reversal symmetry
(TRS) breaking in PrPt4Ge12 below Tc = 7.9 K. This remarkably high Tc for an
anomalous superconductor and the weak and gradual change of Tc and of the
related specific heat anomaly upon La substitution in La_(1-x)Pr_xPt_4Ge_(12)
suggests that the TRS breaking is due to orbital degrees of freedom of the
Cooper pairs.Comment: To appear in Phys. Rev. B. 5 pages, 3 figure
Field-induced magnetic transitions in the quasi-two-dimensional heavy-fermion antiferromagnets Ce_{n}RhIn_{3n+2} (n=1 or 2)
We have measured the field-dependent heat capacity in the tetragonal
antiferromagnets CeRhIn and CeRhIn, both of which have an
enhanced value of the electronic specific heat coefficient
mJ/mol-Ce K above . For the specific heat data at zero
applied magnetic field are consistent with the existence of an anisotropic
spin-density wave opening a gap in the Fermi surface for CeRhIn while
CeRhIn shows behavior consistent with a simple antiferromagnetic
magnon. From these results, the magnetic structure, in a manner similar to the
crystal structure, appears more two-dimensional in CeRhIn than in
CeRhIn where only about 12% of the Fermi surface remains ungapped
relative to 92% for CeRhIn. When both compounds behave in a
manner expected for heavy fermion systems as both and the electronic
heat capacity decrease as field is applied. When the field is applied in the
tetragonal basal plane (), CeRhIn and CeRhIn have very
similar phase diagrams which contain both first- and second-order field-induced
magnetic transitions .Comment: 15 pages, 4 figure
The acceleration of transitions to urban sustainability: a case study of Brighton and Hove
Cities raise major challenges and opportunities for achieving sustainability. Much literature on urban sustainability focuses on specific aspects such as planning practices, urban policy or the diffusion of more sustainable technologies or practices. However, attempts at understanding the mechanisms of structural change towards sustainability have resulted in the emergence of an interdisciplinary field of sustainability transitions research. Transitions research has developed a phase model of transitions in which predevelopment, take-off, acceleration and stabilization phases are distinguished. However, the acceleration phase has received limited attention so far. This is a crucial gap as policy makers are keen to accelerate transitions. This paper aims to enhance our understanding of how local actions contribute towards accelerating urban sustainability transitions. It does so by testing an acceleration mechanisms framework through exploring the collective agency of local initiatives in urban sustainability transitions. Drawing on a case study of the city of Brighton & Hove (UK), the paper finds that despite favourable local political conditions, there is a lack of evidence of acceleration apart from in individual domains such as food or mobility. Progress is found to depend on the agency of initiatives to both scale up sustainable practices and embed these practices into local governance arrangements
Charge-Doping driven Evolution of Magnetism and non-Fermi-Liquid Behavior in the Filled Skutterudite CePt4Ge12-xSbx
The filled-skutterudite compound CePt4Ge12 is situated close to the border
between intermediate-valence of Ce and heavy-fermion behavior. Substitution of
Ge by Sb drives the system into a strongly correlated and ultimately upon
further increasing the Sb concentration into an antiferromagnetically ordered
state. Our experiments evidence a delicate interplay of emerging Kondo physics
and the formation of a local 4f moment. An extended non-Fermi-liquid region,
which can be understood in the framework of a Kondo-disorder model, is
observed. Band-structure calculations support the conclusion that the physical
properties are governed by the interplay of electron supply via Sb substitution
and the concomitant volume effects.Comment: 5 pages, 3 Figur
Management performance assessment of higher vocational education institutions based on the competitive advantage Growth analysis
Inertial parameters and superfluid-to-normal phase transition in superdeformed bands
The quasiclassically exact solution for the second inertial parameter is found in self-consistent way. It is shown that superdeformation and
nonuniform pairing arising from the rotation induced pair density significantly
reduce this inertial parameter. The different limiting cases for ,
which allow to study an interplay between rapid rotation, pairing correlations,
and mean field deformation, are considered. The new signature for the
transition from pairing to normal phase is suggested in terms of the variation
of versus spin. Experimental data indicate the existence of
such transition in the three superdeformed mass regions.Comment: 8 pages, LaTeX, 3 figure
Upper Cervical Spine Trauma: WFNS Spine Committee Recommendations
Craniovertebral junction (CVJ) trauma is a challenging clinical condition. Being a highly mobile functional unit at the junction of the skull and the vertebral column, traumatic events in this area may produce devastating neurological complications and death. Additionally, many of the CVJ traumatic injuries can be left undiagnosed or even raise difficult treatment dilemmas. We present a literature review in the format of recommendations on the diagnosis and management of different scenarios for upper cervical trauma and produce recommendations, which can be applicable to various areas of the globe.info:eu-repo/semantics/publishedVersio
Pinning the catalytic centre: A new concept for catalysts development
A new concept for the development of catalysts is introduced. Utilizing ordered Pd-Ga intermetallic compounds high selectivity and long-term stability in the acetylene hydrogenation can be achieved. The high selectivity observed for all compounds (Pd3Ga7, PdGa, Pd2Ga) indicates that not only the surface geometric site isolation but also the suppression of hydride formation through a covalent bonding interaction absent in conventional Pd alloys are important for achieving superior catalytic properties. Our results demonstrate that structurally well-defined intermetallic compounds exhibit a high potential in heterogeneous catalysis and are promising candidates for industrial applications
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