Indução de perfilhos em mudas de pupunheira.

A pupunheira é uma palmeira produtora de palmito com capacidade de perfilhamento, o que torna a cultura perene, sendo uma alternativa ao extrativismo ilegal de palmito nativo. Tendo em vista a importância e escassez de estudos sobre a propagação vegetativa dessa espécie e que o aumento do número de perfilhos é pré-requisito chave nessa metodologia, o presente trabalho teve por objetivo estudar diferentes métodos para indução de perfilhos em mudas de pupunheira em quatro épocas diferentes. Os tratamentos constituíram-se de: 1) arqueamento do caule; 2) arqueamento do caule com aplicação de 150 mg kg -1 de benzilaminopurina; 3) arqueamento do caule com aplicação de 150 mg kg-1 de ácido giberélico e; 4) anelamento do caule. O delineamento estatístico foi inteiramente casualizado, com 4 repetições de 20 plantas por tratamento. Estudos anatômicos dos caules foram realizados e a formação de perfilhos e mortalidade das plantas submetidas aos diferentes tratamentos avaliados. As análises anatômicas possibilitaram caracterizar os tecidos do caule e localizar o meristema apical. O arqueamento do caule não foi eficiente, enquanto o anelamento apresenta potencial para a indução de perfilhos

Systematic tight-binding analysis of ARPES spectra of transition-metal oxides

We have performed systematic tight-binding (TB) analyses of the angle-resolved photoemission spectroscopy (ARPES) spectra of transition-metal (TM) oxides A$M$O$_3$ ($M=$ Ti, V, Mn, and Fe) with the perovskite-type structure and compared the obtained parameters with those obtained from configuration-interaction (CI) cluster-model analyses of photoemission spectra. The values of $\epsilon_d-\epsilon_p$ from ARPES are found to be similar to the charge-transfer energy $\Delta$ from O $2p$ orbitals to empty TM 3d orbitals and much larger than $\Delta-U/2$ ($U$: on-site Coulomb energy) expected for Mott-Hubbard-type compounds including SrVO$_3$. $\epsilon_d-\epsilon_p$ values from {\it ab initio} band-structure calculations show similar behaviors to those from ARPES. The values of the $p-d$ transfer integrals to describe the global electronic structure are found to be similar in all the estimates, whereas additional narrowing beyond the TB description occurs in the ARPES spectra of the $d$ band.Comment: 5 pages, 3 figure

Materials Design using Correlated Oxides: Optical Properties of Vanadium Dioxide

Materials with strong electronic Coulomb interactions play an increasing role in modern materials applications. "Thermochromic" systems, which exhibit thermally induced changes in their optical response, provide a particularly interesting case. The optical switching associated with the metal-insulator transition of vanadium dioxide (VO2), for example, has been proposed for use in "intelligent" windows, which selectively filter radiative heat in hot weather conditions. In this work, we develop the theoretical tools for describing such a behavior. Using a novel scheme for the calculation of the optical conductivity of correlated materials, we obtain quantitative agreement with experiments for both phases of VO2. On the example of an optimized energy-saving window setup, we further demonstrate that theoretical materials design has now come into reach, even for the particularly challenging class of correlated electron systems.Comment: 4+x pages, 2 figure

Indução de perfilhos em mudas de pupunheira.

<p align="JUSTIFY"><em>Bactris</em> <em>gasipaes</em> produces heart-of-palm. Peach palm is a perennial crop that has a tillering capacity, being an alternative to illegal extraction. There is a lack of studies about vegetative propagation technics for this species. The present study aimed to analyze different tillering induction methods in Bactris gasipaes var. gasipaes seedlings in four different seasons. The treatments were: 1) stem bending; 2) stem bending and application of 150 mg kg^-1 of benzylaminopurine; 3) stem bending and application of 150 mg kg^-1 of gibberellic acid and; 4) stem girdling. The experimental design was random with 4 replicates of 20 plants per treatment. Anatomical analyses were conducted at the stem, and the tillering and mortality of the treated plants were evaluated. It was possible to identify the stem tissues and the meristematic apex site by anatomical analysis. The stem bending treatments were inefficient; but girdling presented potential as tillers inducer.</p

Probing the Redox States at the Surface of Electroactive Nanoporous NiO Thin Films

Nanoporous NiO thin film electrodes were obtained via plasma-assisted microwave sintering and characterized by means of a combination of electrochemical techniques and X-ray photoelectron spectroscopy (XPS). The aim of this study is the elucidation of the nature of the surface changes introduced by the redox processes of this nanostructured material. NiO undergoes two distinct electrochemical processes of oxidation in aqueous electrolyte with the progress of NiO anodic polarization. These findings are consistent with the sequential formation of oxyhydroxide species at the surface, the chemical nature of which was assessed by XPS. Electronic relaxation effects in the Ni 2p spectra clearly indicated that the superficial oxyhydroxide species resulted to be beta-NiOOH and gamma-NiOOH. We also show for the first time spectral evidence of an electrochemically generated Ni(IV) species. This study has direct relevance for those applications in which NiO electrodes are utilized in aqueous electrolyte, namely catalytic water splitting or electrochromism, and may constitute a starting point for the comprehension of electronic phenomena at the NiO/organic electrolyte interface of cathodic dye-sensitized solar cells (p-DSCs)