1,086 research outputs found
Czech Social Reform/Non-reform: Routes, Actors and Problems
In this contribution, the author first considers the characteristics of the Czechoslovak communist welfare state and its theoretical alternatives. Throughout the reform process, dependency on both corporatist and socialist regimes won out, while residualist efforts were promoted in the beginning, but were later held back. The author then considers the possible actors involved in social reforms. In this respect, when proceeding from a general to a more concrete level, thought should first be devoted to the social classes and their ideologies, and second to political parties and their leaders. The author goes on to summarise the particular problems and traps in individual sections of the Czech social system. While no objection to decent standards of social protection and health care could be raised, the poor efficiency of their achievement should evoke concern. The author concludes by reflecting on the possible specificities of Czech social reform in comparison with the other countries undergoing reform and the EU. The current lethargy of the Czech welfare system corresponds to a “frozen edifice”, just as in most Western countries. However, such stagnation is apparently acceptable to both the politicians (who mask it in reformist rhetoric) and the population (which learned to master taking advantage of the generous welfare state) and thus is basically sustainable in the long run.http://deepblue.lib.umich.edu/bitstream/2027.42/40037/3/wp651.pd
Human Carrying Capacity and Human Health
The issue of overpopulation has fallen out of favor among most contemporary demographers, economists, and epidemiologists. Discussing population control has become taboo. This taboo could be hazardous to public healt
Temperature dependence of the spectral weight in p- and n-type cuprates: a study of normal state partial gaps and electronic kinetic energy
The optical conductivity of CuO2 (copper-oxygen) planes in p- and n-type
cuprates thin films at various doping levels is deduced from highly accurate
reflectivity data. The temperature dependence of the real part sigma1(omega) of
this optical conductivity and the corresponding spectral weight allow to track
the opening of a partial gap in the normal state of n-type Pr{2-x}Ce(x)CuO4
(PCCO), but not of p-type Bi2Sr2CaCu2O(8+delta} (BSCCO) cuprates. This is a
clear difference between these two families of cuprates, which we briefly
discuss. In BSCCO, the change of the electronic kinetic energy Ekin - deduced
from the spectral weight- at the superconducting transition is found to cross
over from a conventional BCS behavior (increase of Ekin below Tc to an
unconventional behavior (decrease of Ekin below Tc) as the free carrier density
decreases. This behavior appears to be linked to the energy scale over which
spectral weight is lost and goes into the superfluid condensate, hence may be
related to Mott physics
The low-energy phase-only action in a superconductor: a comparison with the XY model
The derivation of the effective theory for the phase degrees of freedom in a
superconductor is still, to some extent, an open issue. It is commonly assumed
that the classical XY model and its quantum generalizations can be exploited as
effective phase-only models. In the quantum regime, however, this assumption
leads to spurious results, such as the violation of the Galilean invariance in
the continuum model. Starting from a general microscopic model, in this paper
we explicitly derive the effective low-energy theory for the phase, up to
fourth-order terms. This expansion allows us to properly take into account
dynamic effects beyond the Gaussian level, both in the continuum and in the
lattice model. After evaluating the one-loop correction to the superfluid
density we critically discuss the qualitative and quantitative differences
between the results obtained within the quantum XY model and within the correct
low-energy theory, both in the case of s-wave and d-wave symmetry of the
superconducting order parameter. Specifically, we find dynamic anharmonic
vertices, which are absent in the quantum XY model, and are crucial to restore
Galilean invariance in the continuum model. As far as the more realistic
lattice model is concerned, in the weak-to-intermediate-coupling regime we find
that the phase-fluctuation effects are quantitatively reduced with respect to
the XY model. On the other hand, in the strong-coupling regime we show that the
correspondence between the microscopically derived action and the quantum XY
model is recovered, except for the low-density regime.Comment: 29 pages, 11 figures. Slightly revised presentation, accepted for
publication in Phys. Rev.
Nanoscale Phase Separation in Colossal Magnetoresistance Materials: A Lesson for the Cuprates?
A recent vast experimental and theoretical effort in manganites has shown
that the colossal magnetoresistance effect can be understood based on the
competition of charge-ordered and ferromagnetic phases. The general aspects of
the theoretical description appear to be valid for any compound with intrinsic
phase competition. In high temperature superconductors, recent experiments have
shown the existence of intrinsic inhomogeneities in many materials, revealing a
phenomenology quite similar to that of manganese oxides. Here, the results for
manganites are briefly reviewed with emphasis on the general aspects. In
addition, theoretical speculations are formulated in the context of Cu-oxides
by mere analogy with manganites. This includes a tentative explanation of the
spin-glass regime as a mixture of antiferromagnetic and superconducting
islands, the rationalization of the pseudogap temperature T* as a Griffiths
temperature where clusters start forming upon cooling, the prediction of
"colossal" effects in cuprates, and the observation that quenched disorder may
be far more relevant in Cu-oxides than previously anticipated.Comment: 25 pages, 14 figures, post-muSR2002 Superconductivity Worksho
Doping dependence of the resonance peak and incommensuration in high- superconductors
The doping and frequency evolutions of the incommensurate spin response and
the resonance mode are studied based on the scenario of the Fermi surface
topology. We use the slave-boson mean-field approach to the
model and including the antiferromagnetic fluctuation correction in the
random-phase approximation. We find that the equality between the
incommensurability and the hole concentration is reproduced at low frequencies
in the underdoped regime. This equality observed in experiments was explained
{\it only} based on the stripe model before. We also obtain the downward
dispersion for the spin response and predict its doping dependence for further
experimental testing, as well as a proportionality between the low-energy
incommensurability and the resonance energy. Our results suggest a common
origin for the incommensuration and the resonance peak based on the Fermi
surface topology and the d-wave symmetry.Comment: 5 pages, 4 PS figure
Non-Fermi liquid behavior of SrRuO_3 -- evidence from infrared conductivity
The reflectivity of the itinerant ferromagnet SrRuO_3 has been measured
between 50 and 25,000 cm-1 at temperatures ranging from 40 to 300 K, and used
to obtain conductivity, scattering rate, and effective mass as a function of
frequency and temperature. We find that at low temperatures the conductivity
falls unusually slowly as a function of frequency (proportional to
\omega^{-1/2}), and at high temperatures it even appears to increase as a
function of frequency in the far-infrared limit. The data suggest that the
charge dynamics of SrRuO_3 are substantially different from those of
Fermi-liquid metals.Comment: 4 pages, 3 postscript figure
A long-lasting measles epidemic in Maroua, Cameroon 2008-2009: mass vaccination as response to the epidemic.
A measles outbreak occurred in Maroua, Cameroon, from January 2008 to April 2009. In accordance with recent World Health Organization guidelines, an outbreak-response immunization (ORI) was conducted in January 2009. The aim of this study was to investigate the causes of the epidemic in order to guide vaccination strategies
Powerlaw optical conductivity with a constant phase angle in high Tc superconductors
In certain materials with strong electron correlations a quantum phase
transition (QPT) at zero temperature can occur, in the proximity of which a
quantum critical state of matter has been anticipated. This possibility has
recently attracted much attention because the response of such a state of
matter is expected to follow universal patterns defined by the quantum
mechanical nature of the fluctuations. Forementioned universality manifests
itself through power-law behaviours of the response functions. Candidates are
found both in heavy fermion systems and in the cuprate high Tc superconductors.
Although there are indications for quantum criticality in the cuprate
superconductors, the reality and the physical nature of such a QPT are still
under debate. Here we identify a universal behaviour of the phase angle of the
frequency dependent conductivity that is characteristic of the quantum critical
region. We demonstrate that the experimentally measured phase angle agrees
precisely with the exponent of the optical conductivity. This points towards a
QPT in the cuprates close to optimal doping, although of an unconventional
kind.Comment: pdf format, 9 pages, 4 color figures include
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