368 research outputs found
Economia verde e sustentabilidade
(Primeiro Parágrafo do Artigo)A idéia de economia verde surgiu recentemente e ganha projeção cada vez mais acentuada por meio da conferência conhecida como Rio+20. Para entendê-la um pouco melhor, precisamos buscar a gênese do conceito, que se encontra na idéia de deenvolvimento econômico sustentável, também conhecido como desenvolvimento sustentável
Anomalous expansion and phonon damping due to the Co spin-state transition in RCoO_3 with R = La, Pr, Nd and Eu
We present a combined study of the thermal expansion and the thermal
conductivity of the perovskite series RCoO_3 with R = La, Nd, Pr and Eu. The
well-known spin-state transition in LaCoO_3 is strongly affected by the
exchange of the R ions due to their different ionic radii, i.e. chemical
pressure. This can be monitored in detail by measurements of the thermal
expansion, which is a highly sensitive probe for detecting spin-state
transitions. The Co ions in the higher spin state act as additional scattering
centers for phonons, therefore suppressing the phonon thermal conductivity.
Based on the analysis of the interplay between spin-state transition and heat
transport, we present a quantitative model of the thermal conductivity for the
entire series. In PrCoO_3, an additional scattering effect is active at low
temperatures. This effect arises from the crystal field splitting of the 4f
multiplet, which allows for resonant scattering of phonons between the various
4f levels.Comment: 15 pages including 5 figure
Intervention for Children Exposed to Interparental Violence (IPV): Assessment of Needs and Research Priorities
In this paper we review the development of interventions for children who have been exposed to interparental violence (IPV), assess current needs in the evaluation of interventions, and provide suggestions for research priorities in this area. Interventions for negative outcomes associated with exposure to IPV only recently have been carefully designed and evaluated, thus knowledge regarding program effectiveness is minimal. Three of the most comprehensive interventions that have been evaluated are presented. Each has demonstrated effectiveness, and focuses on children with different levels of symptoms and distress. However, many questions remain regarding which interventions are beneficial for diverse children with different kinds and intensities of problems. A number of research priorities and suggestions for further improvements in the evaluation of effectiveness of interventions are identified.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44276/1/10567_2004_Article_469659.pd
Anomalous thermal expansion and strong damping of the thermal conductivity of NdMnO and TbMnO due to 4f crystal-field excitations
We present measurements of the thermal conductivity and the thermal
expansion of NdMnO and TbMnO. In both compounds a splitting of
the multiplet of the ion causes Schottky contributions to
. In TbMnO this contribution arises from a crystal-field splitting,
while in NdMnO it is due to the Nd-Mn exchange coupling. Another
consequence of this coupling is a strongly enhanced canting of the Mn moments.
The thermal conductivity is greatly suppressed in both compounds. The main
scattering process at low temperatures is resonant scattering of phonons
between different energy levels of the multiplets, whereas the complex 3d
magnetism of the Mn ions is of minor importance.Comment: 9 pages including 6 figure
Path integral quantization of electrodynamics in dielectric media
In the present paper we study the Faddeev-Popov path integral quantization of
electrodynamics in an inhomogenious dielectric medium. We quantize all
polarizations of the photons and introduce the corresponding ghost fields.
Using the heat kernel technique, we express the heat kernel coefficients in
terms of the dielectricity and calculate the ultra violet
divergent terms in the effective action. No cancellation between ghosts and
"non-physical" degrees of freedom of the photon is observed.Comment: 10 pages, Latex, submitted to J.Phys.A, revised (a misprint in the
bibliography
Intrinsic decoherence and classical-quantum correspondence in two coupled delta-kicked rotors
We show that classical-quantum correspondence of center of mass motion in two
coupled delta-kicked rotors can be obtained from intrinsic decoherence of the
system itself which occurs due to the entanglement of the center of mass motion
to the internal degree of freedom without coupling to external environment
Scheme for generating entangled states of two field modes in a cavity
This paper considers a two-level atom interacting with two cavity modes with
equal frequencies. Applying a unitary transformation, the system reduces to the
analytically solvable Jaynes-Cummings model. For some particular field states,
coherent and squeezed states, the transformation between the two bare basis's,
related by the unitary transformation, becomes particularly simple. It is shown
how to generate, the highly non-classical, entangled coherent states of the two
modes, both in the zero and large detuning cases. An advantage with the zero
detuning case is that the preparation is deterministic and no atomic
measurement is needed. For the large detuning situation a measurement is
required, leaving the field in either of two orthogonal entangled coherent
states.Comment: Accepted in J. Mod. Opt.; 12 pages; Replaced with revised version.
Extended discussion of experimental realizations, earlier studies in the
field and on the frequency dependence in the adiabatic eliminatio
Strong damping of phononic heat current by magnetic excitations in SrCu_2(BO_3)_2
Measurements of the thermal conductivity as a function of temperature and
magnetic field in the 2D dimer spin system SrCu(BO) are presented.
In zero magnetic field the thermal conductivity along and perpendicular to the
magnetic planes shows a pronounced double-peak structure as a function of
temperature. The low-temperature maximum is drastically suppressed with
increasing magnetic field. Our quantitative analysis reveals that the heat
current is due to phonons and that the double-peak structure arises from
pronounced resonant scattering of phonons by magnetic excitations.Comment: a bit more than 4 pages, 2 figures included; minor changes to improve
the clarity of the presentatio
International Commercial Arbitration: Fifty Years After the New York Convention
a one-day conference held at the Dean Rusk Center on January 30, 2009. The event, co-sponsored by the Georgia Journal of International and Comparative Law, featured Gary Born as keynote speaker and other leaders in the field of international commercial arbitration including Robert Davidson, Executive Director of JAMS Arbitration Practice; William K. Slate, II, President, American Arbitration Association; and Anne Marie Whitesell, Former Secretary General of the ICC International Court of Arbitration
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