1,048 research outputs found
Classical and quantum-linearized descriptions of degenerate optomechanical parametric oscillators
Recent advances in the development of modern quantum technologies have opened
the possibility of studying the interplay between spontaneous parametric
down-conversion and optomechanics, two of the most fundamental nonlinear
optical processes. Apart from practical reasons, such scenario is very
interesting from a fundamental point of view, because it allows exploring the
optomechanical interaction in the presence of a strongly quantum-correlated
field, the spontaneously down-converted mode. In this work we analyze such
problem from two approximate but valuable perspectives: the classical limit and
the limit of small quantum fluctuations. We show that, in the presence of
optomechanical coupling, the well-known classical phase diagram of the optical
problem gets modified by the appearance of new dynamical instabilities. As for
the quantum-mechanical description, we prove the ability of the squeezed
down-converted field to cool down the mechanical motion not only to thermal but
also to squeezed thermal mechanical states, and in a way that can be much less
sensitive to parameters (e.g., detuning of the driving laser) than standard
sideband cooling.Comment: New version including the quantum linearized description of the
system and appendices. Accepted in Physical Review
Circular dichroism of anthocyanidin 3-glucoside self-aggregates
“NOTICE: this is the author’s version of a work that was accepted for publication in Phytochemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Phytochemistry Volume 88, April 2013, Pages 92–98. DOI 10.1016/j.phytochem.2012.12.011 ."“NOTICE: this is the author’s version of a work that was accepted for publication in Phytochemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Phytochemistry Volume 88, April 2013, Pages 92–98. DOI 10.1016/j.phytochem.2012.12.011 .""Self-association constants for the flavylium cations of the six most common anthocyanidin 3-glucosides were determined by circular dichroism (CD) and UV–Vis spectroscopy. Along with previous 1H NMR results, all measurements were consistent with a monomer–dimer model. The CD spectra of the antho-cyanidin 3-glucosides were similar to the analogues 3,5-diglucosides. All dimers of the anthocyanidin 3-glucosides exhibited left-handed CD signals, with petunidin-3-glucoside and myrtillin having the most intense signals. In addition, the magnitude of the molar ellipticity, [h], was generally higher for the 3-glucosides than for the 3,5-diglucosides. For all six anthocyanins studied, the CD absorption spectra of their dimers showed evidence of the splitting of the monomer absorption into lower (J) and higher (H) energy bands. The angle and the distance between the dipolar moments of the two monomers comprising the dimer were obtained from the lower energy absorption band. While the angle was more or less similar in all six dimers, the separation distance between the monomer dipole moments differed dramatically. The intensity of the CD signal displayed a linear dependence with the inverse square of the dipole moment distances.
Chemical evolution of the colour systems generated by riccionidin A, 3-deoxyanthocyanidins and anthocyanins
UIDB/50006/2020
MEX/Ref. 288188The kinetics and thermodynamics (in acidic solutions) of the five chemical species reversibly interconnected by external stimuli (a multistate), such as pH and light, generated by the liverworts colorant riccionidin A were investigated. The degradation products of the multistate formed after 10 days at neutral pH were identified. The behaviour of riccionidin A multistate was compared with previous results reported for the equivalent systems based on 3-deoxyanthocyanidins (found in mosses and ferns) and anthocyanins (ubiquitous in angiosperms). The five chemical species have mutatis mutandis similar structures in the three multistates. The most dramatic difference is the extremely slow interconversion rate between flavylium cation and trans-chalcone in riccionidin A and related compounds multistates (tens of days) when compared with deoxyanthocyanins (a few days) and anthocyanins (several hours), at room temperature. The mole fraction distribution of the five species that constitute the multistate as a function of pH is also different in the three families of compounds. Some considerations regarding the chemical evolution of the three systems are given.authorsversionpublishe
Anatase as an alternative application for preventing biodeterioration of mortars: evaluation and comparison with other biocides
International Biodeterioration & Biodegradation 64(2010)388 e 396The aim of this study is the comparison between different treatments(anatase and two conventional biocides:Biotin T and Anios)for preventing biodeterioration of mortars.The treatments were applied both in the laboratory on mortar slabs and in situ on walls of Palácio Nacional da Pena(Sintra,Portugal).
Mortar slabs treated with anatase (pure and Fe3þ doped)applied as acoating or by mixing within the mortar were prepared,and their surfaces characterized by different methodologies.The mortars were
inoculated with cyanobacteria and chlorophyta species,incubated for a period of 4 months and the
chlorophyll content quantified by extraction method and fluorescence emission.For comparison purposes untreated mortar slabs were inoculated,incubated and finally treated with the biocides.After two weeks the respective chlorophyll contents was quantified.
In situ studies in two external walls of Palácio Nacional da Pena covered by organisms were also performed by direct application of aqueous solutions of the three products,and the efficiency of the
treatment monitored by spectrophotometry using the CIELAB method.Lichens and other phototrophic microorganisms were identified by direct observation with a microscope and cyanobacteria,green microalgae, bacteria and fungi by DNA-based molecular analysis targeting the 16S and 18S ribosomal RNAgenes.
The results show that anatase is a better agent for preventing biodeterioration than the two tested conventional biocides,both in mortars slabsand in situ studies.In fact,photographic and colorimetric
records made in two external walls of Palácio Nacional da Pena after two weeks of treatments application showed that lichens and other phototrophic microorganisms disappear from the places where anatase
was applied
Dynamic Elastic Modulus Variability in Anisotropic and Isotropic Materials: Comparison by Acoustic Emission
This study compared the variation of the dynamic elastic modulus (E) of three types of composite pipes made by the filament winding process and a steel alloy specimen, according to signal source changes. The specimens were produced with three different winding angles, i.e., ±50°, ±52.5°, and ±55°. The moduli were obtained through a known signal source and the angular variation, according to two sensors positioned over the specimen's surface. In a previous article, the variation in the velocity of acoustic emission (AE) signals, performed in the same type of pipes, was discussed based on the standards for glass fiber-reinforced epoxy (GFRE) filament wound specimens. This work took these preliminary findings to compare with the results found for steel alloy pipes (SAE 1020). This data was used with appropriate equations to determine the dynamic elastic moduli of each material. It was found that, even for small angular differences, the modulus changes position concerning the lamination angle. Thus, the lower the quality control, the lower the final product with composite materials. As expected, for isotropic materials such as steel alloys, the modulus remains constant along the angles, while for anisotropic ones, it is dependent on the principal directions of stress and strain, or on the other hand, dependent on the correlation between the angular wave velocity of the AE signals
Teoria da imputação objetiva.
Orientador: Juarez Cirino dos SantosMonografia (especialização) - Universidade Federal do Paraná, Setor de Ciências JurÃdicas, Curso de Especialização em Direito Penal e CriminologiaBusca-se com o presente trabalho monográfico fazer um exposição acerca da moderna teoria da imputação objetiva, traçando seu histórico desde o platonismo até a atualidade. Delineia-se, ainda, um paralelo entre essa teoria e as mais importantes teorias causais, através de um aprofundado estudo doutrinário, onde demonstra-se a vantagem da sua utilização. Conclui-se que o impendente amadurecimento doutrinário e jurisprudencial trará importante avanço em busca de respostas mais justas ao jurisdicionado e à coletividade em geral
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