Uma metodologia para o projeto teórico de conversores moleculares de luz

Recentlly, we have proposed the representation of lanthanides within AM1 as sparkles for the purpose of obtaing ground state geometries of their complexes. We tested our quantum chemical sparkle model (SMLC/AM1) for the prediction of the crystallographic structure of complexes with coordination number nine, eight and seven. A technique is introduced for the theoretical prediction of eletronic spectra of the organic part of lanthanide complexes by replacing the metal ion by a point charge with the ligands held in their positions as determined by the SMLC/AM1, and by computing the theoretical spectra via the intermediate neglect of differential overlap/spectroscopic-configuration interaction (INDO/S-CI).

Geração e controle das cores luz primárias em vidros para dispositivos "full color"

We are working in a new multi-doped glassy material to generate simultaneously the three primary light color (by addition) of the visible spectrum, with the control of the intensity of each one, allowing the simulation of any color: a full-color generator device. Tm+3, Tb+3 and Eu+3 ions were used (0.01 to 5,0 mol%) as blue, green and red narrow line emitters. A wide color gamut was obtained under ultraviolet excitation by varying the material composition. The chromaticity diagram is covered, including the white simulation.

Fotodegradação de polímeros clorados irradiados com a luz síncrotron - I. Emissão de gases

Chlorinated polymers (PVC, PVDC and E-CTFE) were irradiated with white light produced at the Brazilian Synchrotron Light Source (LNLS). The emitted gases were analyzed by mass spectrometry. The spectra were dominated by peaks related to hydrochloric acid, HCl, and chlorine (35Cl). The measured HCl intensity is used to evaluate the sensitivity of the polymers over a broad energy range. PVDC showed the greatest light sensitivity as compared to PVC and E-CTFE.

Fragmentação de moléculas pela luz síncrotron e por elétrons rápidos. I. O caso do halotano, C2F3HClBr

The photofragmentation of a core-excited halogenated compound, Halotane (C2F3HClBr), generally used as anesthetic by inhalation, has been studied using high energy photons and electrons near C 1s ionization edge (~ 300 eV), using time-of-flight mass spectrometry in multicoincidence mode. We observe strong differences between the molecular fragmentation induced by photons and electron impact.

Coordenação local do Eu(III) em híbridos orgânicos/inorgânicos emissores de luz branca

Eu3+ luminescence and EXAFS (Extended X-ray Absorption Fine Structure) results are presented for organic-inorganic hybrid gel hosts composed of a siliceous network to which small chains of oxyethylene units are covalently grafted by means of urea bridges. Coordination numbers for Eu3+ ions range from 12.8 to 9.7 with increasing Eu3+ concentration while the Eu3+-first neighbours mean distance is found to be constant at 2.48-2.49 Å in the same concentration range. Emission spectra display a broad band in the green/blue spectral region superposed to narrow lines appearing in the yellow/red region in such a way that for the eyes emission appears white. The broad band is assigned to intrinsic NH groups emission and also to electron-hole recombination in the nanosised siliceous domains. The narrow lines are assigned to intra-4f6, 5D0->7F0-4 Eu3+ transitions and from the energy position of the 7F0-4 levels a mean distance could be calculated for the Eu3+-first neighbours. The calculated results are in good agreement with the experimental ones obtained from EXAFS analysis.

Sideróforos: uma resposta dos microorganismos

Siderophores (from the Greek: "iron carriers") are defined as relatively low molecular weight, ferric ion specific chelating agents elaborated by microorganisms growing under low iron stress. The role of these compounds is to scavenge iron from the environment and to make this essential chemical element available to the microbial cell. The present paper is a brief presentation of siderophore coordination chemistry with emphasis on those aspects relevant to the transportation of iron (III) complexes across biological membranes. Finally, the role of siderophores in infection and their clinical potential as iron scavenging molecules are reviewed.

Cálculo ab initio de intensidades Raman dinâmicas utilizando a teoria da resposta linear

In this paper a methodology for the computation of Raman scattering cross-sections and depolarization ratios within the Placzek Polarizability Theory is described. The polarizability gradients are derived from the values of the dynamic polarizabilities computed at the excitation frequencies using ab initio Linear Response Theory. A sample application of the computational program, at the HF, MP2 and CCSD levels of theory, is presented for H2O and NH3. The results show that high correlated levels of theory are needed to achieve good agreement with experimental data.

Degradação do pesticida Padron® por processos fotoquímicos utilizando luz artificial e solar

Destruction of Padron® (dye and picloram) was evaluated using a photoreactor and a solar reactor. Photolysis was observed using only a germicide lamp (GL). Black light (BL) and H2O2 (172 mmol L-1) promoted a conversion of 49% and 6% of dye and picloram, respectively. Photocatalytic processes were more efficient using TiO2/GL (96%-dye; 60%-picloram) than TiO2/BL (44%-dye; 40%-picloram). Photolysis using sunlight was not observed during PadronÒ recirculation in the reactor constructed with four borosilicate tubes. Meanwhile, adding H2O2 resulted in 12% conversion of dissolved organic compounds. Finally, the most efficient mineralization (60%) was obtained using the Fenton reaction ( H2O2-176 mmol L-1; FeSO4x6H2O-90 mmol L-1) and sunlight.

Efeito do triacilglicerídeo de cadeia média, da fibra e do cálcio na disponibilidade de magnésio e de zinco pelo método in vitro e metodologia de superfície de resposta

Nutritional therapy with enteral diets became highly specialized in the last years. This work aims to study the effect of the components of a formulation, namely fiber, calcium and medium-chain triglycerides, for dialysability of minerals. Analysis of multiple variables was done using response surface methodology. The level curve showed that the tertiary interaction MCT-fiber-calcium was the one that presented the highest synergism in the formulation. The proportion of 33% MCT, 25% fiber and 42% calcium, gave the best formulation for availability of magnesium.

Efeito antagônico do ferro e do zinco em uma formulação de alimentação enteral utilizando planejamento de misturas da metodologia de superfície de resposta

Nutritional therapy with enteral diets became substantially specialized over the last years. This work's aim was to study the effect of the components of a formulation: fiber, calcium and medium-chain triglycerides for dialysability of minerals. Analysis of multiple variables was carried out using response surface methodology. The level curve showed an antagonic effect of interaction between iron and zinc. TCM was the variable responsible for characterizing competition between the two minerals in the formulation. More studies on foods are needed for knowing the effecs of minerals in formulations.

Aplicação da metodologia de planejamento fatorial e análise de superfícies de resposta para otimização da fermentação alcoólica

In the present work, the influence of the amount of nitrogen and phosphorus and degrees Brix on the yield and productivity of alcoholic fermentation has been evaluated. The methodology used was factorial design and response surface analysis. Within the range studied only for phosphorus a statistically significant effect was observed. The broth of sugar cane of the CB 453 variety already possessed enough nitrogen for the fermentation. The mathematical and empirical model was validated for productivity and not for yield. The concentration of alcohol produced in the fermentation was not enough to cause cellular growth inhibition.

Otimização de método para determinação de flavonóis e flavonas em frutas por cromatografia líquida de alta eficiência utilizando delineamento estatístico e análise de superfície de resposta

This work optimized the HPLC conditions for the simultaneous determination of luteolin, apigenin, myricetin, quercetin and kaempferol in aglycone form, as well defined the best conditions for hydrolysis/extraction of these flavonoids in fruits, using the statistical central composite design and response surface analysis. A reverse phase method was developed using a gradient of methanol/water acidified with 0.3% formic acid as mobile phase and a photodiode array detector. The samples were extracted with methanol/water (50:50 v/v) at 90 ºC. The optimum time and HCl concentration varied for the different fruits investigated, demonstrating the necessity of optimizing these conditions for each fruit analyzed. Good recovery (87.1 to 96.3%), repeatability and linearity were obtained.

Influência da luz e da temperatura sobre a oxidação do óleo essencial de capim-limão (Cymbopogon citratus (D.C.) Stapf)

The identification of the chemical compounds of the essential oil was performed with a gas chromatograph coupled to a mass spectrometer. The oil was left in the presence and absence of light and submitted to different temperatures to evaluate its stability. The yields of the major compounds were evaluated every fifteen days. Citral and myrcene, the major compounds of the essential oil, were degraded over time in both the presence and absence of light, but temperature only influenced the degradation of myrcene.

Aplicação da metodologia de superfície de resposta no estudo da produção e extração da poligalacturonase

The aim of this work was to verify the effects of initial medium moisture content (U), addition of ammonium sulphate (N) and of potassium phosphate (P) in the production of the polygalacturonase through the solid-state fermentation, using cashew apple husk as substrate and Aspergillus niger CCT0916 as transformation agent. We also studied the best extraction conditions of the produced enzyme. The best condition of production was with U of 40%, 1% of N and 0% of P being reached an activity of the poligalacturonase of 10.1 U/g. The best extraction condition is an agitation system with a time of 100 min and a solvent-fermented medium volume ratio of 5 mL/g.

Construção de câmara de luz ultravioleta para fotopolimerização de fases estacionárias monolíticas

The assembly of a photochemical reactor with six fluorescent lamps, used for photopolymerizations is described. This chamber presents a mobile support, allowing the placement of samples at different heights and a safety lock that interrupts the radiation, if it is opened during operation. The mirrored internal walls avoid the dispersion and non-uniform distribution of light. There is no high heating because the own character of the used lamps. All parts could be purchased in commerce with less than U$ 150,00. This reactor was successfully used for monolithic stationary phase photopolymerization.