3,153 research outputs found
Comparing Leadership Practices in Internationally Focused Non-Profit Organizations
This study examines the effective leadership practices in non-profit international organizations. A review of the literature identifies common leadership practices. An in-depth case study examines effective leadership practices in one successful non-profit organization. This will show consistency between the review of the literature and the in-depth case studies. Effective leadership practices have been identified as: systems for engaging others, long term leadership practices, and creative collaboration
Quasiquartet CEF ground state with possible quadrupolar ordering in the tetragonal compound YbRuGe
e have investigated the magnetic properties of YbRuGe by means of
magnetic susceptibility (T), specific heat C(T) and electrical
resistivity (T) measurements performed on flux grown single crystals. The
Curie-Weiss behavior of (T) along the easy plane, the large magnetic
entropy at low temperatures and the weak Kondo like increase in (T)
proves a stable trivalent Yb state. Anomalies in C(T), (T) and (T)
at T = 10.2 K, T = 6.5 K and T = 5.7 K evidence complex
ordering phenomena, T being larger than the highest Yb magnetic ordering
temperature found up to now. The magnetic entropy just above T amounts to
almost Rln4, indicating that the crystal electric field (CEF) ground state is a
quasiquartet instead of the expected doublet. The behavior at T is rather
unusual and suggest that this transition is related to quadrupolar ordering,
being a consequence of the CEF quasiquartet ground state. The combination of a
quasiquartet CEF ground state, a high ordering temperature, and the relevance
of quadrupolar interactions makes YbRuGe a rather unique system
among Yb based compounds.Comment: 11 pages, 5 figure, submitted to PRB rapi
Non-Fermi-liquid behavior in Ce(RuFe)Ge: cause and effect
We present inelastic neutron scattering measurements on the intermetallic
compounds Ce(RuFe)Ge (=0.65, 0.76 and 0.87). These
compounds represent samples in a magnetically ordered phase, at a quantum
critical point and in the heavy-fermion phase, respectively. We show that at
high temperatures the three compositions have the identical response of a local
moment system. However, at low temperatures the spin fluctuations in the
critical composition are given by non-Fermi-liquid dynamics, while the spin
fluctuations in the heavy fermion system show a simple exponential decay in
time. In both compositions, the lifetime of the fluctuations is determined
solely by the distance to the quantum critical point. We discuss the
implications of these observations regarding the possible origins of
non-Fermi-liquid behavior in this system.Comment: 4 figures, submitted to PR
A Subset of the CERN Virtual Machine File System: Fast Delivering of Complex Software Stacks for Supercomputing Resources
Delivering a reproducible environment along with complex and up-to-date
software stacks on thousands of distributed and heterogeneous worker nodes is a
critical task. The CernVM-File System (CVMFS) has been designed to help various
communities to deploy software on worldwide distributed computing
infrastructures by decoupling the software from the Operating System. However,
the installation of this file system depends on a collaboration with system
administrators of the remote resources and an HTTP connectivity to fetch
dependencies from external sources. Supercomputers, which offer tremendous
computing power, generally have more restrictive policies than grid sites and
do not easily provide the mandatory conditions to exploit CVMFS. Different
solutions have been developed to tackle the issue, but they are often specific
to a scientific community and do not deal with the problem in its globality. In
this paper, we provide a generic utility to assist any community in the
installation of complex software dependencies on supercomputers with no
external connectivity. The approach consists in capturing dependencies of
applications of interests, building a subset of dependencies, testing it in a
given environment, and deploying it to a remote computing resource. We
experiment this proposal with a real use case by exporting Gauss-a Monte-Carlo
simulation program from the LHCb experiment-on Mare Nostrum, one of the top
supercomputers of the world. We provide steps to encapsulate the minimum
required files and deliver a light and easy-to-update subset of CVMFS: 12.4
Gigabytes instead of 5.2 Terabytes for the whole LHCb repository
Re-entrant hidden order at a metamagnetic quantum critical end point
Magnetization measurements of URu2Si2 in pulsed magnetic fields of 44 T
reveal that the hidden order phase is destroyed before appearing in the form of
a re-entrant phase between ~ 36 and 39 T. Evidence for conventional itinerant
electron metamagnetism at higher temperatures suggests that the re-entrant
phase is created in the vicinity of a quantum critical end point.Comment: 8 pages, including 3 figures (Physical Review Letters, in press) a
systematic error in the field calibration has been fixed since the original
submission of this manuscrip
Magnetic properites of the Heavy Fermion Antiferromagnets YbNiAl and YbPtAl
Measurements of electrical resistivity and Hall effect as a function of
magnetic field on the Heavy Fermion Systems YbNiAl and YbPtAl are presented.
Both compounds order antiferro magnetically and show metamagnetic behavior in a
magnetic field. Scaling behavior of the magnetoresistance above TN suggests
that the paramagnetic regime for YbNiAl can be described in terms of a single
ion Kondo effect.Comment: 12 pages including 5 figures (submitted to the SCES 94 Conference,
Ansterdam
Theory for Magnetic Anisotropy of Field-Induced Insulator-to-Metal Transition in Cubic Kondo Insulator YbB_{12}
Magnetization and energy gap of Kondo insulator YbB_{12} are calculated
theoretically based on the previously proposed tight-binding model composed of
Yb 5d and 4f orbitals. It is found that magnetization
curves are almost isotropic, naturally expected from the cubic symmetry, but
that the gap-closing field has an anisotropy: the gap closes faster for the
field in (100) direction than in (110) and (111) directions, in accord with the
experiments. This is qualitatively understood by considering the maximal
eigenvalues of the total angular momentum operators projected on each direction
of the magnetic field. But the numerical calculation based on the band model
yields better agreement with the experiment.Comment: 4 pages, 4 figures, to appear in J. Phys. Soc. Jp
Non-Fermi Liquid Behavior In Quantum Critical Systems
The problem of an electron gas interacting via exchanging transverse gauge
bosons is studied using the renormalization group method. The long wavelength
behavior of the gauge field is shown to be in the Gaussian universality class
with a dynamical exponent in dimensions .
This implies that the gauge coupling constant is exactly marginal. Scattering
of the electrons by the gauge mode leads to non-Fermi liquid behavior in . The asymptotic electron and gauge Green's functions, interaction
vertex, specific heat and resistivity are presented.Comment: 9 pages in REVTEX 2.0. Submitted to Phys. Rev. Lett. 3 figures in
postscript files can be obtained at [email protected]. The filename is
gan.figures.tar.z and it's compressed. You can uncompress it by using
commands: "uncompress gan.figures.tar.z" and "tar xvf gan.figures.tar
Decoupling between Field-instabilities of Antiferromagnetism and Pseudo-metamagnetism in Rh-doped CeRu2Si2 Kondo Lattice
Doping Kondo lattice system CeRu2Si2 with Rh-8% (Ce(Ru0.92Rh0.08)2Si2) leads
to drastic consequences due to the mismatch of the lattice parameters between
CeRu2Si2 and CeRh2Si2. A large variety of experiments clarifies the unusual
properties of the ground state induced by the magnetic field from longitudinal
antiferromagnetic (AF) mode at H = 0 to polarized paramagnetic phase in very
high magnetic field. The separation between AF phase, paramagnetic phase and
polarized paramagnetic phase varying with temperature, magnetic field and
pressure is discussed on the basis of the experiments down to very low
temperature. Similarities and differences between Rh and La substituted alloys
are discussed with emphasis on the competition between transverse and
longitudinal AF modes, and ferromagnetic fluctuations.Comment: 10 pages, 21 figures, accepted for publication in J. Phys. Soc. Jp
Intermediate Valence Model for the Colossal Magnetoresistance in Tl_{2}Mn_{2}O_{7}
The colossal magnetoresistance exhibited by Tl_{2}Mn_{2}O_{7} is an
interesting phenomenon, as it is very similar to that found in perovskite
manganese oxides although the compound differs both in its crystalline
structure and electronic properties from the manganites. At the same time,
other pyrochlore compounds, though sharing the same structure with
Tl_{2}Mn_{2}O_{7}, do not exhibit the strong coupling between magnetism and
transport properties found in this material. Mostly due to the absence of
evidence for significant doping into the Mn-O sublattice, and the tendency of
Tl to form conduction bands, the traditional double exchange mechanism
mentioned in connection with manganites does not seem suitable to explain the
experimental results in this case. We propose a model for Tl_{2}Mn_{2}O_{7}
consisting of a lattice of intermediate valence ions fluctuating between two
magnetic configurations, representing Mn-3d orbitals, hybridized with a
conduction band, which we associate with Tl. This model had been proposed
originally for the analysis of intermediate valence Tm compounds. With a
simplified treatment of the model we obtain the electronic structure and
transport properties of Tl_{2}Mn_{2}O_{7}, with good qualitative agreement to
experiments. The presence of a hybridization gap in the density of states seems
important to understand the reported Hall data.Comment: 8 pages + 5 postscript fig
- …