Síntese e atividade anti-HCV, anti-candida e antibacteriana de nitrochalconas

Pós-graduação em Química - IBILCE

Avaliação do Clinpro XT® na redução da permeabilidade da dentina radicular e resistência a desafios ácidos, na obliteração de túbulos dentinários e rugosidade superficial da dentina

Pós-graduação em Odontologia - FOAR

Obtenção e caracterização de nanocelulose a partir de fibras de Chorisia speciosa St. Hil

Natural fibers have been highlighted as a renewable material that can replace materials from oil and its derivatives. In this context, Brazil becomes the perfect setting because of the diversity of fibers found in its territory, such as sugarcane, sisal, rice, cotton, coconut, pineapple, among others. The paineiras (Chorisia speciosa St. Hil) are typically Brazilian trees, which produce paina as fruit. These fruits are still little studied as a source of lignocellulose by research groups. This project aimed obtaining and characterization of cellulose nanofibers from the fibers from the paina fibers. Obtaining nanocellulose is practically made through simplified chemical processes. First, was performed out pre-treatments to removal of waxes, lignin and hemicellulose. The first stage of pre-treatment was carried out by alkaline aqueous solution of sodium hydroxide (NaOH) at 5wt%, where the fibers were under constant agitation for 1h at 70°C. Through alkali treatment it was possible to remove most of the lignin, hemicellulose, waxes and extractives. After the alkaline treatment was done bleaching with an aqueous solution of sodium hydroxide (NaOH) to 4wt% and hydrogen peroxide (H2O2) to 24wt% 1:1 during 2h with constant stirring to 50 °C. Through bleaching was possibe to remove residual lignin, and got cellulose with 72% of crystallinity. Nanocellulose of paina fibers was extracted using different conditions of acid hydrolysis with sulfuric acid (H2SO4) to 50wt%. After acid hydrolysis, the suspensions were centrifuged during 30 min and dialyzed in water to remove excess acid until neutral pH (6-7). Then the suspensions were passed by ultrasonification in an ultrasound 20 kHz during 1h in an ice bath. Untreated, alkalinized and bleached fibers as well as cellulose nanoparticles were characterized by the techniques of thermogravimetry ... (Complete abastract click electronic access below)

RB30-246 Testing Ice Cream for Butterfat

Butterfat is usually the most expensive ingredient of ice cream; hence, great care is necessary in controllng its use. The manufacturer of ice cream, whether doing a large or a small volume of business, must manufacture a product that will comply with the established fat standard. Some means of determining the percentage of butterfat in the product must be available in order to establish this control. This 1930 research bulletin discusses the different testing equipment used to test butterfat in ice cream.

Phytoplankton Dynamics in Three Rocky Mountain Lakes, Colorado, U.S.A.

In 1984 and 1985 seasonal changes in phytoplankton were studied in a system of three lakes in Loch Vale, Rocky Mountain National Park, Colorado. Three periods were evident: (1) A spring bloom, during snowmelt, of the planktonic diatom Asterionella Formosa, (2) a mid- summer period of minimal algal abundance, and (3) a fall bloom of the blue-green alga Oscillatoria limnetica. Seasonal phytoplankton dynamics in these lakes are controlled partially by the rapid flushing rate during snowmelt and the transport of phytoplankton from the highest lake to the lower lakes by the stream, Icy Brook. During snowmelt, the A. formosa population in the most downstream lake has a net rate of increase of 0.34 d-1, which is calculated from the flushing rate and from the A. formosa abundance in the inflow from the upstream lake and in the downstream lake. Measurement of photosynthetic rates at different depths during the three periods confirmed the rapid growth of A. formosa during the spring. The decline in A. formosa after snowmelt may be related to grazing by developing zooplankton populations. The possible importance of the seasonal variations in nitrate concentrations were evaluated in situ enrichment experiments. For A. formosa and O. limnetica populations, growth stimulation resulted from 8- or 16-micromolar amendments of calcium nitrate and sulfuric acid, but the reason for this stimulation could not be determined from these experiments.

Obtenção e caracterização de nanocelulose a partir de fibras de Chorisia speciosa St. Hil

Natural fibers have been highlighted as a renewable material that can replace materials from oil and its derivatives. In this context, Brazil becomes the perfect setting because of the diversity of fibers found in its territory, such as sugarcane, sisal, rice, cotton, coconut, pineapple, among others. The paineiras (Chorisia speciosa St. Hil) are typically Brazilian trees, which produce paina as fruit. These fruits are still little studied as a source of lignocellulose by research groups. This project aimed obtaining and characterization of cellulose nanofibers from the fibers from the paina fibers. Obtaining nanocellulose is practically made through simplified chemical processes. First, was performed out pre-treatments to removal of waxes, lignin and hemicellulose. The first stage of pre-treatment was carried out by alkaline aqueous solution of sodium hydroxide (NaOH) at 5wt%, where the fibers were under constant agitation for 1h at 70°C. Through alkali treatment it was possible to remove most of the lignin, hemicellulose, waxes and extractives. After the alkaline treatment was done bleaching with an aqueous solution of sodium hydroxide (NaOH) to 4wt% and hydrogen peroxide (H2O2) to 24wt% 1:1 during 2h with constant stirring to 50 °C. Through bleaching was possibe to remove residual lignin, and got cellulose with 72% of crystallinity. Nanocellulose of paina fibers was extracted using different conditions of acid hydrolysis with sulfuric acid (H2SO4) to 50wt%. After acid hydrolysis, the suspensions were centrifuged during 30 min and dialyzed in water to remove excess acid until neutral pH (6-7). Then the suspensions were passed by ultrasonification in an ultrasound 20 kHz during 1h in an ice bath. Untreated, alkalinized and bleached fibers as well as cellulose nanoparticles were characterized by the techniques of thermogravimetry ... (Complete abastract click electronic access below)

Saccharification of Brazilian sisal pulp: evaluating the impact of mercerization on non-hydrolyzed pulp and hydrolysis products

Cultivation of sisal, a plant with a short growth cycle, is highly productive in Brazil. This work is part of extensive research in which sisal is valued. In these studies, sisal fibers are used in the preparation of bio-based composites and in the derivatization of the pulp, including posterior preparation of films. This study aimed to examine the use of sisal pulp in the production of bioethanol, which can potentially be a high efficiency process because of the cellulose content of this fiber. A previous paper addressed the hydrolysis of sisal pulp using sulfuric acid as a catalyst. In the present study, the influence of the mercerization process on the acid hydrolysis of sisal pulp was evaluated. Mercerization was achieved in a 20% wt NaOH solution, and the cellulosic pulp was suspended and vigorously mixed for 1, 2 and 3 h, at 50 A degrees C. The previously characterized mercerized pulps were hydrolyzed (100 A degrees C, 30% H2SO4, v/v), and the results are compared with those obtained for unmercerized pulp (described in a companion paper). The starting sample was characterized by viscometry, alpha-cellulose content, crystallinity index and scanning electron microscopy. During the reactions, aliquots were withdrawn, and the liquor was analyzed by HPLC. The residual pulps (non-hydrolyzed) were also characterized by the techniques described for the initial sample. The results revealed that pretreatment decreases the polyoses content as well as causes a decrease of up to 23% in the crystallinity and up to 21% in the average molar mass of cellulose after 3 h of mercerization. The mercerization process proved to be very important to achieve the final target. Under the same reaction conditions (30% and 100 A degrees C, 6 h), the hydrolysis of mercerized pulp generated yields of up to 50% more glucose. The results of this paper will be compared with the results of subsequent studies obtained using other acids, and enzymes, as catalysts.

Oxygen reduction reaction on a Pt/carbon fuel cell catalyst in the presence of trace quantities of ammonium ions: An RRDE study

The effect of trace quantities of ammonia on oxygen reduction reaction (ORR) on carbon-supported platinum catalysts in perchloric acid solutions is assessed using rotating ring disk electrode (RRDE) technique. The study demonstrates that ammonia has detrimental effects on ORR. The most significant effect takes place in the potential region above 0.7 V vs RHE. The effect is explained by the electrochemical oxidation of ammonia, which blocks Pt active sites and increases the formation of H2O2. This leads to losses in the disk currents and increments in the ring currents. The apparent losses in ORR currents may occur in two ways, namely, through the blocking of the active sites for ORR as well as by generating a small anodic current, which is believed to have a lower contribution. In addition, a detrimental effect of sodium cations in the potential range below 0.75 V vs RHE was demonstrated. This effect is most likely due to the co-adsorption of sodium cations and perchlorate anions on the Pt surface. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Influence of Modifications to the Pechini Method on the Electroactivity and Stability of Pt-RuOx/C Catalysts

Since electrode electroactivity and stability depend directly on the nature, morphology, and structure of the material, we have investigated how modifications to the Pechini method during the synthesis of Pt-RuOx/C electrocatalysts affected catalyst activity. The structure and stability of the resulting materials were investigated after their submission to a large number of potential scans and to constant potential for a prolonged time period in sulfuric acid 0.5 mol L-1 and methanol 0.1 mol L-1 solution. DMFC tests were accomplished using membrane electrode assemblies (MEAs) prepared by hot-pressing a pretreated Nafion 117 membrane together with the prepared Pt-RuOx anodes and a Pt cathode (from E-TEK), in order to compare the catalytic activity of the materials prepared by different methods. The stability studies demonstrated that the catalyst whose resin/carbon support mixture was agitated in a balls mill before undergoing heat-treatment was more stable than the other prepared catalysts. The catalysts synthesized with the single resin consisting of Pt and Ru and subjected to ultrasound before heat-treatment furnished the highest power density in the single fuel cell. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.011208jes]

Mechanistic changes observed in heavy water for nitrate reduction reaction on palladium-modified Pt(hkl) electrodes

Reduction of nitrate on palladium-modified platinum single-crystal electrodes has been investigated both voltammetrically and spectroscopically in acidic media (pH = 1). Results obtained in H2O and D2O solvents are compared for the three crystallographic orientations. FTIR and differential electrochemical mass spectrometry (DEMS) results clearly indicate that the isotopic substitution of the solvent has a large effect in the mechanism of the reaction, changing the nature of the detected products. For Pt(111)/Pd and Pt(100)/Pd, N2O is detected as the main product of nitrate reduction when D2O is used as solvent, while no N2O is detected when the reaction is performed in H2O. For Pt(110)/Pd, N2O is detected in both solvents, although the use of D2O clearly favours the preferential formation of this product. The magnitude of voltammetric currents is also affected by the nature of the solvent. This has been analysed considering, in addition to the different product distribution, the existence of different transport numbers and optical constants of the solvent.

On the diurnal cycle of urban aerosols, black carbon and the occurrence of new particle formation events in springtime Sao Paulo, Brazil

Large conurbations are a significant source of the anthropogenic pollution and demographic differences between cities that result in a different pollution burden. The metropolitan area of Sao Paulo (MASP, population 20 million) accounts for one fifth of the Brazilian vehicular fleet. A feature of MASP is the amount of ethanol used by the vehicular fleet, known to exacerbate air quality. The study describes the diurnal behaviour of the submicron aerosol and relies on total particle number concentration, particle number size distribution, light scattering and light absorption measurements. Modelled planetary boundary layer (PBL) depth and air mass movement data were used to aid the interpretation. During morning rush-hour, stagnant air and a shallow PBL height favour the accumulation of aerosol pollution. During clear-sky conditions, there was a wind shift towards the edge of the city indicating a heat island effect with implications on particulate pollution levels at the site. The median total particle number concentration for the submicron aerosol typically varied in the range 1.6 x 10(4)-3.2 x 10(4) cm(-3) frequently exceeding 4 x 10(4) cm-3 during the day. During weekdays, nucleation-mode particles are responsible for most of the particles by numbers. The highest concentrations of total particle number concentrations and black carbon (BC) were observed on Fridays. Median diurnal values for light absorption and light scattering (at 637 nm wavelength) varied in the range 12-33 Mm(-1) and 21-64 Mm(-1), respectively. The former one is equal to 1.8-5.0 mu g m(-3) of BC. The growth of the PBL, from the morning rush-hour until noon, is consistent with the diurnal cycle of BC mass concentrations. Weekday hourly median single-scattering albedo (omega(0)) varied in the range 0.59-0.76. Overall, this suggests a top of atmosphere (TOA) warming effect. However, considering the low surface reflectance of urban areas, for the given range of omega(0), the TOA radiative forcing can be either positive or negative for the sources within the MASP. On the average, weekend omega(0) values were 0.074 higher than during weekdays. During 11% of the days, new particle formation (NPF) events occurred. The analysed events growth rates ranged between 9 and 25 nm h(-1). Sulphuric acid proxy concentrations calculated for the site were less than 5% of the concentration needed to explain the observed growth. Thus, other vapours are likely contributors to the observed growth.

Synthesis of high-surface-area gamma-Al2O3 from aluminum scrap and its use for the adsorption of metals: Pb(II), Cd(II) and Zn(II)

Several types of alumina were synthesized from sodium aluminate (NaAlO2) by precipitation with sulfuric acid (H2SO4) and subsequently calcination at 500 degrees C to obtain gamma-Al2O3. The precursor aluminate was derived from aluminum scrap. The various gamma-Al2O3 synthesized were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), adsorption-desorption of N-2 (S-BET) and scanning electron microscopy (SEM). XRD revealed that distinct phases of Al2O3 were formed during thermal treatment. Moreover, it was observed that conditions of synthesis (pH, aging time and temperature) strongly affect the physicochemical properties of the alumina. A high-surface-area alumina (371 m(2) g(-1)) was synthesized under mild conditions, from inexpensive raw materials. These aluminas were tested for the adsorption of Cd(II), Zn(II) and Pb(II) from aqueous solution at toxic metal concentrations, and isotherms were determined. (C) 2012 Elsevier B.V. All rights reserved.

Sequential extraction of phosphorus in an Oxisol amended with biosolids in a long-term field experiment in Brazil

The continued growth of large cities is producing increasing volumes of urban sewage sludge. Disposing of this waste without damaging the environment requires careful management. The application of large quantities of biosolids (treated sewage sludge) to agricultural lands for many years may result in the excessive accumulation of nutrients like phosphorus (P) and thereby raise risks of eutrophication in nearby water bodies. We evaluated the fractionation of P in samples of an Oxisol collected as part of a field experiment in which biosolids were added at three rates to a maize (Zea mays L) plantation over four consecutive years. The biosolids treatments were equivalent to one, two and four times the recommended N rate for maize crops. In a fourth treatment, mineral fertilizer was applied at the rate recommended for maize. Inorganic P forms were extracted with ammonium chloride to remove soluble and loosely bound P; P bound to aluminum oxide (P-Al) was extracted with ammonium fluoride; P bound to iron oxide (P-Fe) was extracted with sodium hydroxide; and P bound to calcium (P-Ca) was extracted with sulfuric acid. Organic P was calculated as the difference between total P and inorganic P. The predominant fraction of P was P-Fe, followed by P-Al and P-Ca. P fractions were positively correlated to the amounts of P applied, except for P-Ca. The low values of P-Ca were due to the advanced weathering processes to which the Oxisol have been subjected, under which forms of P-Ca are converted to P-Fe and P-Al. The fertilization with P via biosolids increased P availability for maize plants even when a large portion of P was converted to more stable forms. Phosphorus content in maize leaves and grains was positively correlated with P fractions in soils. From these results it can be concluded that the application of biosolids in highly weathered tropical clayey soils for many years, even above the recommended rate based on N requirements for maize, tend to be less potentially hazardous to the environment than in less weathered sandy soils because the non-readily P fractions are predominant after the addition of biosolids. (C) 2012 Elsevier B.V. All rights reserved.

SUPERAÇÃO DE DORMÊNCIA DAS SEMENTES E CONTROLE QUÍMICO DE Momordicacharantia L.

Objetivou-se com este estudo avaliar diferentes métodos para a superação da dormência das sementes e a eficiência de herbicidas no controle químico de plantas de Momordicacharantia L. no estádio reprodutivo. O primeiro experimento constituiu-seem esquema fatorial 2 x 8 (duas épocas de coleta das sementes (2006 e 2007) e oito métodos de quebra de dormência: escarificação mecânica; imersão em ácido sulfúrico concentrado e a 50%; imersão em nitrato de potássio a 2%por três e seis horas; calor seco a 60°C; água quente a 60°C e uma testemunha sem tratamento). No segundo ensaio avaliou-se o controle da Momordicacharantia L. por meio de seis herbicidas distintos: Imazapic, Metsulfuron-methyl, Metribuzin, 2,4-D, Amicarbazone, Paraquat e uma testemunha sem aplicação de herbicidas. Em ambos os ensaios, o delineamento experimental utilizado foi o inteiramente casualizados, com quatro repetições. Após a aplicação dos tratamentos,pode-se concluir que a imersão das sementes em ácido sulfúrico concentrado por 3 minutos proporcionou uma maior porcentagem e velocidade de germinação e que o herbicida Metribuzin alcançou, embora tardiamente, um controle total das plantas de melão de São-Caetano.

Local Structure of Hydrogen-Bonded Liquids

Ordinary yet unique, water is the substance on which life is based. Water seems, at first sight, to be a very simple molecule, consisting of two hydrogen atoms attached to one oxygen. Its small size belies the complexity of its action and its numerous anomalies, central to a broad class of important phenomena, ranging from global current circulation, terrestrial water and CO2 cycles to corrosion and wetting. The explanation of this complex behavior comes from water's unique ability to form extensive three-dimensional networks of hydrogen-bonds, whose nature and structures, in spite of a great deal of efforts involving a plethora of experimental and theoretical techniques, still lacks a complete scientific understanding. This thesis is devoted to the study of the local structure of hydrogen-bonded liquids, with a particular emphasis on water, taking advantage of a combination of core-level spectroscopies and density functional theory spectra calculations. X-ray absorption, in particular, is found to be sensitive to the local hydrogen-bond environment, thus offering a very promising tool for spectroscopic identification of specific structural configurations in water, alcohols and aqueous solutions. More specifically, the characteristic spectroscopic signature of the broken hydrogen-bond at the hydrogen side is used to analyze the structure of bulk water, leading to the finding that most molecules are arranged in two hydrogen-bond configurations, in contrast to the picture provided by molecular dynamics simulations. At the liquid-vapor interface, an interplay of surface sensitive measurements and theoretical calculations enables us to distinguish a new interfacial species in equilibrium with the gas. In a similar approach the cluster form of the excess proton in highly concentrated acid solutions and the different coordination of methanol at the vacuum interface and in the bulk can also be clearly identified. Finally the ability of core-level spectroscopies, aided by sophisticated density functional theory calculations, to directly probe the valence electronic structure of a system is used to observe the nature of the interaction between water molecules and solvated ions in solution. Water around transition metal ions is found to interact with the solute via orbital mixing with the metal d-orbitals. The hydrogen-bond between water molecules is explained in terms of electrostatic interactions enhanced by charge rehybridization in which charge transfer between connecting molecules is shown to be fundamental.