935 research outputs found
Guns and butter? Military expenditure and health spending on the eve of the Arab Spring
We examine the validity of the guns-versus-butter hypothesis in the pre-Arab Spring era. Using panel data from 1995 to 2011–the eve of the Arab uprisings–we find no evidence that increased security needs as measured by the number of domestic terrorist attacks are complemented by increased military spending or more importantly ‘crowd out’ government expenditure on key public goods such as health care. This suggests that both expenditure decisions were determined by other considerations at the government level
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
A long survival of a patient with brain metastasis of unknown site of the primary tumor
Eighty percent of brain metastases (BM) are diagnosed in patients with known primary site of cancer. BM of unknown primary represents a difficult diagnosis. In up to 15% of patients with BM, the site of the primary tumor will not be detected despite investigations. The prognosis of this entity is very poor. We report here a case of a long survival of a patient with brain metastasis of unknown primary. The conclusion that can be drawn is that within BM of unknown primary exist patients with a very good prognosis that must be collected and published in order to base recommendations
Influence of long-range correlated quenched disorder on the adsorption of long flexible polymer chains on a wall
The process of adsorption on a planar wall of long-flexible polymer chains in
the medium with quenched long-range correlated disorder is investigated. We
focus on the case of correlations between defects or impurities that decay
according to the power-low for large distances , where . Field theoretical approach in and directly in
dimensions up to one-loop order for the semi-infinite m-vector
model (in the limit ) with a planar boundary is used. The whole set of
surface critical exponents at the adsorption threshold , which separates
the nonadsorbed region from the adsorbed one is obtained. Moreover, we
calculate the crossover critical exponent and the set of exponents
associated with them. We perform calculations in a double and
expansion and also for a fixed dimension , up to one-loop
order for different values of the correlation parameter .
The obtained results indicate that for the systems with long-range correlated
quenched disorder the new set of surface critical exponents arises. All the
surface critical exponents depend on . Hence, the presence of long-range
correlated disorder influences the process of adsorption of long-flexible
polymer chains on a wall in a significant way.Comment: 4 figures, 2 table
Star polymers: A study of the structural arrest in presence of attractive interactions
Simulations and Mode-Coupling Theory calculations, for a large range of the
arm number and packing fraction have shown that the structural
arrest and the dynamics of star polymers in a good solvent are extremely rich:
the systems show a reentrant melting of the disordered glass nested between two
stable fluid phases that strongly resemble the equilibrium phase diagram.
Starting from a simple model potential we investigate the effect of the
interplay between attractive interactions of different range and ultrasoft core
repulsion, on the dynamics and on the occurrence of the ideal glass transition
line. In the two cases considered so far, we observed some significant
differences with respect to the purely repulsive pair interaction. We also
discuss the interplay between equilibrium and non equilibrium phase behavior.
The accuracy of the theoretical tools we utilized in our investigation has been
checked by comparing the results with molecular dynamics simulations.Comment: 24 pages, 14 figures, accepted for publication in Physical Review
Incommensurate magnetism in the coupled spin tetrahedra system Cu2Te2O5Cl2
Neutron scattering studies on powder and single crystals have provided new
evidences for unconventional magnetism in Cu2Te2O5Cl2. The compound is built
from tetrahedral clusters of S=1/2 Cu2+ spins located on a tetragonal lattice.
Magnetic ordering, emerging at TN=18.2 K, leads to a very complex multi-domain,
most likely degenerate, ground state, which is characterized by an
incommensurate (ICM) wave vector k ~ [0.15, 0.42,1/2]. The Cu2+ ions carry a
magnetic moment of 0.67(1) mB/ Cu2+ at 1.5 K and form a four helices spin
arrangement with two canted pairs within the tetrahedra. A domain
redistribution is observed when a magnetic field is applied in the tetragonal
plane (Hc≈0.5 T), but not for H||c up to 4 T. The excitation spectrum is
characterized by two well-defined modes, one completely dispersionless at 6.0
meV, the other strongly dispersing to a gap of 2 meV. The reason for such
complex ground state and spin excitations may be geometrical frustration of the
Cu2+ spins within the tetrahedra, intra- and inter-tetrahedral couplings having
similar strengths and strong Dzyaloshinski-Moriya anisotropy. Candidates for
the dominant intra- and inter-tetrahedral interactions are proposed
Micellization of Sliding Polymer Surfactants
Following up a recent paper on grafted sliding polymer layers (Macromolecules
2005, 38, 1434-1441), we investigated the influence of the sliding degree of
freedom on the self-assembly of sliding polymeric surfactants that can be
obtained by complexation of polymers with cyclodextrins. In contrast to the
micelles of quenched block copolymer surfactants, the free energy of micelles
of sliding surfactants can have two minima: the first corresponding to small
micelles with symmetric arm lengths, and the second corresponding to large
micelles with asymmetric arm lengths. The relative sizes and concentrations of
small and large micelles in the solution depend on the molecular parameters of
the system. The appearance of small micelles drastically reduces the kinetic
barrier signifying the fast formation of equilibrium micelles.Comment: Submitted to Macromolecule
Exotic fluids and crystals of soft polymeric colloids
We discuss recent developments and present new findings in the colloidal
description of soft polymeric macromolecular aggregates. For various
macromolecular architectures, such as linear chains, star polymers, dendrimers
and polyelectrolyte stars, the effective interactions between suitably chosen
coordinates are shown to be ultrasoft, i.e., they either remain finite or
diverge very slowly at zero separation. As a consequence, the fluid phases have
unusual characteristics, including anomalous pair correlations and mean-field
like thermodynamic behaviour. The solid phases can exhibit exotic, strongly
anisotropic as well as open crystal structures. For example, the diamond and
the A15-phase are shown to be stable at sufficiently high concentrations.
Reentrant melting and clustering transitions are additional features displayed
by such systems, resulting in phase diagrams with a very rich topology. We
emphasise that many of these effects are fundamentally different from the usual
archetypal hard sphere paradigm. Instead, we propose that these fluids fall
into the class of mean-field fluids.Comment: 22 pages, uses iopart.cls and iopart10.clo; submitted to Journal of
Physics Condensed Matter, special issue in honour of professor Peter Puse
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