393 research outputs found
Manual sobre criação de galinha caipira na agricultura familiar: noçÔes båsicas.
bitstream/item/61192/1/CPATU-Doc114.pd
Manual sobre criação de suĂnos na agricultura familiar: noçÔes bĂĄsicas.
bitstream/item/61199/1/CPATU-Doc115.pd
Evidence for the immobile bipolaron formation in the paramagnetic state of the magnetoresistive manganites
Recent research suggests that the charge carriers in the paramagnetic state
of the magnetoresistive manganites are small polarons. Here we report studies
of the oxygen-isotope effects on the intrinsic resistivity and thermoelectric
power in several ferromagnetic manganites. The precise measurements of these
isotope effects allow us to make a quantitative data analysis. Our results do
not support a simple small-polaron model, but rather provide compelling
evidence for the presence of small immobile bipolarons, i.e., pairs of small
polarons. Since the bipolarons in the manganites are immobile, the present
result alone appears not to give a positive support to the bipolaronic
superconductivity theory for the copper-based perovskites.Comment: 6 pages, 5 figures, monor correction
Prognostic and therapeutic significance of carbohydrate antigen 19-9 as tumor marker in patients with pancreatic cancer
In pancreatic cancer ( PC) accurate determination of treatment response by imaging often remains difficult. Various efforts have been undertaken to investigate new factors which may serve as more appropriate surrogate parameters of treatment efficacy. This review focuses on the role of carbohydrate antigen 19- 9 ( CA 19- 9) as a prognostic tumor marker in PC and summarizes its contribution to monitoring treatment efficacy. We undertook a Medline/ PubMed literature search to identify relevant trials that had analyzed the prognostic impact of CA 19- 9 in patients treated with surgery, chemoradiotherapy and chemotherapy for PC. Additionally, relevant abstract publications from scientific meetings were included. In advanced PC, pretreatment CA 19- 9 levels have a prognostic impact regarding overall survival. Also a CA 19- 9 decline under chemotherapy can provide prognostic information for median survival. A 20% reduction of CA 19- 9 baseline levels within the first 8 weeks of chemotherapy appears to be sufficient to define a prognostic relevant subgroup of patients ('CA 19- 9 responder'). It still remains to be defined whether the CA 19- 9 response is a more reliable method for evaluating treatment efficacy compared to conventional imaging. Copyright (c) 2006 S. Karger AG, Basel
Multi-phonon Raman scattering in semiconductor nanocrystals: importance of non-adiabatic transitions
Multi-phonon Raman scattering in semiconductor nanocrystals is treated taking
into account both adiabatic and non-adiabatic phonon-assisted optical
transitions. Because phonons of various symmetries are involved in scattering
processes, there is a considerable enhancement of intensities of multi-phonon
peaks in nanocrystal Raman spectra. Cases of strong and weak band mixing are
considered in detail. In the first case, fundamental scattering takes place via
internal electron-hole states and is participated by s- and d-phonons, while in
the second case, when the intensity of the one-phonon Raman peak is strongly
influenced by the interaction of an electron and of a hole with interface
imperfections (e. g., with trapped charge), p-phonons are most active.
Calculations of Raman scattering spectra for CdSe and PbS nanocrystals give a
good quantitative agreement with recent experimental results.Comment: 16 pages, 2 figures, E-mail addresses: [email protected],
[email protected], [email protected], accepted for publication in
Physical Review
From thermal rectifiers to thermoelectric devices
We discuss thermal rectification and thermoelectric energy conversion from
the perspective of nonequilibrium statistical mechanics and dynamical systems
theory. After preliminary considerations on the dynamical foundations of the
phenomenological Fourier law in classical and quantum mechanics, we illustrate
ways to control the phononic heat flow and design thermal diodes. Finally, we
consider the coupled transport of heat and charge and discuss several general
mechanisms for optimizing the figure of merit of thermoelectric efficiency.Comment: 42 pages, 22 figures, review paper, to appear in the Springer Lecture
Notes in Physics volume "Thermal transport in low dimensions: from
statistical physics to nanoscale heat transfer" (S. Lepri ed.
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