1,736 research outputs found
Polls and the political process: the use of opinion polls by political parties and mass media organizations in European postâcommunist societies (1990â95)
Opinion polling occupies a significant role within the political process of most liberal-capitalist societies, where it is used by governments, parties and the mass media alike. This paper examines the extent to which polls are used for the same purposes in the post-communist countries of Central and Eastern Europe, and in particular, for bringing political elites and citizens together. It argues that these political elites are more concerned with using opinion polls for gaining competitive advantage over their rivals and for reaffirming their political power, than for devolving political power to citizens and improving the general processes of democratization
CenĂĄrios futuros da infraestrutura de transporte e seus impactos na competitividade das exportaçÔes de carne suĂna e nas suas emissĂ”es de gases de efeito estufa.
bitstream/item/78909/1/Comunicado-505.pdfProjeto/Plano de Ação: 04.08.08.017
Collective excitation of a Bose-Einstein condensate by modulation of the atomic scattering length
We excite the lowest-lying quadrupole mode of a Bose-Einstein condensate by
modulating the atomic scattering length via a Feshbach resonance. Excitation
occurs at various modulation frequencies, and resonances located at the natural
quadrupole frequency of the condensate and at the first harmonic are observed.
We also investigate the amplitude of the excited mode as a function of
modulation depth. Numerical simulations based on a variational calculation
agree with our experimental results and provide insight into the observed
behavior.Comment: Submitted to PR
EmissĂŁo de diĂłxido de carbono na cama de primeiro lote de duas linhagens de frangos de corte.
Increased metabolic activity in the septum and habenula during stress is linked to subsequent expression of learned helplessness behavior
Uncontrollable stress can have a profound effect on an organism's ability to respond effectively to future stressful situations. Behavior subsequent to uncontrollable stress can vary greatly between individuals, falling on a spectrum between healthy resilience and maladaptive learned helplessness. It is unclear whether dysfunctional brain activity during uncontrollable stress is associated with vulnerability to learned helplessness; therefore, we measured metabolic activity during uncontrollable stress that correlated with ensuing inability to escape future stressors. We took advantage of small animal positron emission tomography (PET) and 2-deoxy-2[(18)F]fluoro-D-glucose ((18)FDG) to probe in vivo metabolic activity in wild type Sprague Dawley rats during uncontrollable, inescapable, unpredictable foot-shock stress, and subsequently tested the animals response to controllable, escapable, predictable foot-shock stress. When we correlated metabolic activity during the uncontrollable stress with consequent behavioral outcomes, we found that the degree to which animals failed to escape the foot-shock correlated with increased metabolic activity in the lateral septum and habenula. When used a seed region, metabolic activity in the habenula correlated with activity in the lateral septum, hypothalamus, medial thalamus, mammillary nuclei, ventral tegmental area, central gray, interpeduncular nuclei, periaqueductal gray, dorsal raphe, and rostromedial tegmental nucleus, caudal linear raphe, and subiculum transition area. Furthermore, the lateral septum correlated with metabolic activity in the preoptic area, medial thalamus, habenula, interpeduncular nuclei, periaqueductal gray, dorsal raphe, and caudal linear raphe. Together, our data suggest a group of brain regions involved in sensitivity to uncontrollable stress involving the lateral septum and habenula
Anomalous dimensions of leading twist conformal operators
We extend and develop a method for perturbative calculations of anomalous
dimensions and mixing matrices of leading twist conformal primary operators in
conformal field theories. Such operators lie on the unitarity bound and hence
are conserved (irreducible) in the free theory. The technique relies on the
known pattern of breaking of the irreducibility conditions in the interacting
theory. We relate the divergence of the conformal operators via the field
equations to their descendants involving an extra field and accompanied by an
extra power of the coupling constant. The ratio of the two-point functions of
descendants and of their primaries determines the anomalous dimension, allowing
us to gain an order of perturbation theory. We demonstrate the efficiency of
the formalism on the lowest-order analysis of anomalous dimensions and mixing
matrices which is required for two-loop calculations of the former. We compare
these results to another method based on anomalous conformal Ward identities
and constraints from the conformal algebra. It also permits to gain a
perturbative order in computations of mixing matrices. We show the complete
equivalence of both approaches.Comment: 21 pages, 4 figures; references adde
The anomaly of the oxygen bond-bending mode at 320 cm and the additional absorption peak in the c-axis infrared conductivity of underdoped YBaCuO single crystals revisited by ellipsometricmeasurements
We have performed ellipsometric measurements of the far-infrared c-axis
dielectric response of underdoped YBaCuO single
crystals. Here we report a detailed analysis of the temperature-dependent
renormalization of the oxygen bending phonon mode at 320 cm and the
formation of the additional absorption peak around 400-500 cm. For a
strongly underdoped YBaCuO crystal with T=52 K we
find that, in agreement with previous reports based on conventional reflection
measurements, the gradual onset of both features occurs well above T at
T*150 K. Contrary to some of these reports, however, our data establish
that the phonon anomaly and the formation of the additional peak exhibit very
pronounced and steep changes right at T. For a less underdoped
YBaCuO crystal with T=80 K, the onset temperature of
the phonon anomaly almost coincides with T. Also in contrast to some
previous reports, we find for both crystals that a sizeable fraction of the
spectral weight of the additional absorption peak cannot be accounted for by
the spectral-weight loss of the phonon modes but instead arises from a
redistribution of the electronic continuum. Our ellipsometric data are
consistent with a model where the bilayer cuprate compounds are treated as a
superlattice of intra- and inter-bilayer Josephson-junctions
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