Spectrophotometric flow-injection determination of sulphite in white wines involving gas diffusion through a concentric tubular membrane

A flow-injection system is proposed for the spectrophotometric determination of sulphite in white wines. The method involves analyte conversion to SO2, gas diffusion through a Teflon® semi-permeable membrane, collection into an alkaline stream (pH 8), reaction with Malachite green (MG) and monitoring at 620 nm. With a concentric tubular membrane, the system design was simplified. Influence of reagent concentrations, pH of donor and acceptor streams, temperature, timing, surfactant addition and presence of potential interfering species of the wine matrix were investigated. A pronounced (ca. 100%) enhancement in sensitivity was noted by adding cetylpyridinium chloride (CPC). The proposed system is robust and baseline drift is not observed during 4 h operating periods. Only 400 μL of sample and 0.32 mg MG are required per determination. The system handles 30 samples per hour, yielding precise results (r.s.d. < 0.015 for 1.0 - 20.0 mg L-1 SO2) in agreement with those obtained by an alternative procedure.

Degradation of dipyrone by electrogenerated H2O2 combined with Fe2+ using a modified gas diffusion electrode

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Desenvolvimento e avaliação de eletrodos de difusão gasosa (EDG) para geração de H2O2 in situ e sua aplicação na degradação do corante reativo azul 19

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A Semi-Continuous Analyzer for the Fluorimetric Determination of Atmospheric Formaldehyde

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

NOISE GENERATED BY CAVITATION IN ORIFICE-PLATES WITH SOME GASEOUS EFFECTS.

An experimental investigation of the noise generated by cavitation in turbulent shear flows produced by confined sharp-edge orifice-plates is reported. The acoustic source strength of cavitation was determined by means of reciprocity type measurements. Experimentally determined scaling parameters are applied to a model to prototype scaling formula derived from dimensional analysis. The proposed formula is checked experimentally. Comparative photographic observations of the cavitation patterns for two different values of gas content are presented. The observed sound reduction, that occurs when supersaturated conditions exist downstream the orifice-plates, is explained by the effects of gas diffusion into the cavitation bubbles, and by simple acoustic attenuation.

Degradation of dipyrone via advanced oxidation processes using a cerium nanostructured electrocatalyst material

This work studied the degradation of dipyrone, via electrochemical processes and via electro-Fenton reaction using a 4% CeO2/C gas diffusion electrode (GDE) prepared via modified polymeric precursor method. This material was used to electrochemically generate H2O2 through oxygen reduction. The mean crystallite sizes estimated by the Scherrer equation for 4% CeO2/C were 4 nm for CeO2-x (0 4 4) and 5 nm for CeO2 (1 1 1) while using transmission electron microscopy (TEM) the mean nanoparticle size was 5.4 nm. X-ray photoelectron spectroscopy (XPS) measurements revealed nearly equal concentrations of Ce(III) and Ce(IV) species on carbon, which contained high oxygenated acid species like CO and OCO. Electrochemical degradation using Vulcan XC 72R carbon showed that the dipyrone was not removed during the two hour electrolysis in all applied potentials by electro-degradation. Besides, when the Fenton process was employed the degradation was much similar when using cerium catalysts but the mineralization reaches just to 50% at -1.1 V. However, using the CeO2/C GDE, in 20 min all of the dipyrone was degraded with 26% mineralization at -1.3 V and when the Fenton process was employed, all of the dipyrone was removed after 5 min with 57% mineralization at -1.1 V. Relative to Vulcan XC72R, ceria acts as an oxygen buffer leading to an increase in the local oxygen concentration, facilitating H2O2 formation and consequently improving the dipyrone degradation © 2013 Elsevier B.V. All rights reserved.

Low tungsten content of nanostructured material supported on carbon for the degradation of phenol

A comparative study using different mass proportions of WO3/C (1%, 5%, 10% and 15%) for H2O2 electrogeneration and subsequent phenol degradation was performed. To include the influence of the carbon substrate and the preparation methods, all synthesis parameters were evaluated. The WO3/C materials were prepared by a modified polymeric precursor method (PPM) and the sol-gel method (SGM) on Vulcan XC 72R and Printex L6 carbon supports, verifying the most efficient metal/carbon proportion. The materials were physically characterized by X-ray diffraction (XRD) and by X-ray photoelectron spectroscopy (XPS) techniques. The XRD and the XPS techniques identified just one phase containing WO3 and elevated oxygen concentration on carbon with the presence of WO3. The oxygen reduction reaction (ORR), studied by the rotating ring-disk electrode technique, showed that WO3/C material with the lowest tungsten content (1% WO3/C), supported on Vulcan XC 72R and prepared by SGM, was the most promising electrocatalyst for H2O2 electrogeneration. This material was then analyzed using a gas diffusion electrode (GDE) and 585mgL-1 of H2O2 was produced in acid media. This GDE was employed as a working electrode in an electrochemical cell to promote phenol degradation by an advanced oxidative process. The most efficient method applied was the photo-electro-Fenton; this method allowed for 65% degradation and 11% mineralization of phenol during a 2-h period. Following 12h of exhaustive electrolysis using the photo-electro-Fenton method, the total degradation of phenol was observed after 4h and the mineralization of phenol approached 75% after 12h. © 2013 Elsevier B.V.

Efeito de hipercabia no desenvolvimento de ovos de Trachemys scripta

Females of the painted turtle, Trachemys scripta, have an annual reproductive cycle. Their nest periods in Brazil starts around September and they lay about 7 - 10 eggs in nests dug in the soil. The eggs hatch in December. It is possible that the nest cover cause problems for the gas diffusion, also, the rain can wet or compact the soil covering the nest, or even soaked the whole area. Those problems may change the nests intern atmosphere decreasing O2 partial pressure (hypoxia) and increasing CO2 partial pressure (hypercarbia). The main objective of this study was to determine if and how hypercarbia (3% and 6%CO2), could influence the eggs and early posthatching development of the Trachemys scripta. We used three experimental groups of eggs incubated in: normal atmosphere (Control group CG, n = 14), hypercarbia with 3% of CO2 (G3%, n = 16) and with 6% of CO2 (G6%, n = 15). The profile of the mass increment during the egg development were not different among the groups, GC = 9.89±0.81g; G3% = 10.11±0.60g and G6% = 10.58±0.36g. In addition, the mass of the post-hatching turtles were the not different. There were not differences between the duration of the incubation period among the experimental groups, GC = 60.12±0.97days, G3% = 59.00±0.98days and G6% = 60.80±1.14days. The mortality rates were not affected by the hypercarbia, GC = 0.43 (43%), G3% = 0.27 (27%) and G6% = 0.37 (37%). Furthermore, the mass increment and the metabolic rate were the same among the early development of the turtles until 3 month after hatching. We conclude that hypercarbia (up to 6% of CO2) does not cause any alteration on the eggs or post-hatching normal development. It is possible that the combination of hypercarbia and hypoxia change those results

CH and C2 radicals characterization in natural gas turbulent diffusion flames

This paper reports the construction of an axisymmetric nonpremixed piloted jet burner, with well-defined initial and boundary conditions, known as the Delft burner, to assess turbulence-chemistry interaction in non-premixed turbulent flames. Detailed experimental information is described, involving hot-wire anemometry, thin-wire thermocouples and chemiluminescence visualization measurements. Radial profile of the axial mean velocity indicates excellent agreement between flow patterns developed within Delft installation and the one described herein. Chemiluminescence emissions from CH and C2 free-radicals were acquired with a CCD camera. Tomography reconstruction analysis was utilised to compare radical emissions and temperature spatial distributions. There was a strong dependence between temperature and CH/C 2 emissions. This is an indication that these radicals can be used in flame front studies.

Assessment of a high-order finite difference upwind scheme for the simulation of convection-diffusion problems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

An investigation on parallel, divergent and convergent acetylene dual jet diffusion flames

Results are presented and discussed of an experimental investigation on acetylene turbulent dual jet diffusion flames. The study includes parameters of flames in parallel, divergent and convergent configurations. Tests with two parallel jets with addition of helium in the fuel stream were also performed and analysed. The variation of overall flame length and of other name physical characteristics, such as width, volume and conditions for lifting, are presented as functions of burner tip Reynolds number, jet distance from each other and inclination angle. The effects of diluent concentration in the fuel gas stream are presented for single and two parallel jets. (C) 1999 Elsevier B.V. Ltd.

Nebular gas drag and co-orbital system dynamics

Aims. We study trajectories of planetesimals whose orbits decay due to gas drag in a primordial solar nebula and are perturbed by the gravity of the secondary body on an eccentric orbit whose mass ratio takes values from mu(2) = 10(-7) to mu(2) = 10(-3) increasing ten times at each step. Each planetesimal ultimately suffers one of the three possible fates: (1) trapping in a mean motion resonance with the secondary body; (2) collision with the secondary body and consequent increase of its mass; or (3) diffusion after crossing the orbit of the secondary body.Methods. We take the Burlirsh-Stoer numerical algorithm in order to integrate the Newtonian equations of the planar, elliptical restricted three-body problem with the secondary body and the planetesimal orbiting the primary. It is assumed that there is no interaction among planetesimals, and also that the gas does not affect the orbit of the secondary body.Results. The results show that the optimal value of the gas drag constant k for the 1: 1 resonance is between 0.9 and 1.25, representing a meter size planetesimal for each AU of orbital radius. In this study, the conditions of the gas drag are such that in theory, L4 no longer exists in the circular case for a critical value of k that defines a limit size of the planetesimal, but for a secondary body with an eccentricity larger than 0.05 when mu(2) = 10(-6), it reappears. The decrease of the cutoff collision radius increase the difusions but does not affect the distribution of trapping. The contribution to the mass accretion of the secondary body is over 40% with a collision radius 0.05R(Hill) and less than 15% with 0.005R(Hill) for mu(2) = 10(-7). The trappings no longer occur when the drag constant k reachs 30. That means that the size limit of planetesimal trapping is 0.2 m per AU of orbital radius. In most cases, this accretion occurs for a weak gas drag and small secondary eccentricity. The diffusions represent most of the simulations showing that gas drag is an efficient process in scattering planetesimals and that the trapping of planetesimals in the 1: 1 resonance is a less probable fate. These results depend on the specific drag force chosen.

Anomalous diffusion of pions at RHIC

After pointing out the difference between normal and anomalous diffusion, we consider a hadron resonance cascade (HRC) model simulation for particle emission at RHIC and point out that rescattering in an expanding hadron resonance gas leads to a heavy tail in the source distribution. The results are compared to recent PHENIX measurements of the tail of the particle emitting source in Au+Au collisions at RHIC. In this context, we show how can one distinguish experimentally the anomalous diffusion of hadrons from a second order QCD phase transition.

The effects of ice-water storage on blood gas and acid-base measurements

Objective: To determine the effects of storage of arterial and venous blood samples in ice water on blood gas and acid-base measurements.Design: Prospective, in vitro, laboratory study.Setting: School of veterinary medicine.Subjects: Six healthy dogs.Measurements and main results: Baseline measurements of partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), pH, hemoglobin concentration (tHb), oxyhemoglobin saturation, and oxygen content (ContO(2)) were made. Bicarbonate (HCO3) and standard base excess (SBE) were calculated. Arterial and venous blood samples were separated into 1 and 3 mL samples, anaerobically transferred into 3 mL plastic syringes, and stored in ice water for 6 hours. Measurements were repeated at 15, 30 minutes, and 1, 2, 4, and 6 hours after baseline measurements. Arterial (a) PO2 increased significantly from baseline after 30 minutes of storage in the 1 mL samples and after 2 hours in the 3 mL samples. Venous (v) PO2 was significantly increased from baseline after 4 hours in the 1 mL samples and after 6 hours in the 3 mL samples. The pHa significantly decreased after 2 hours of storage in the 1 mL samples and after 4 hours in the 3 mL samples. In both the 1 and 3 mL samples, pHv decreased significantly only after 6 hours. Neither the arterial nor the venous PCO2 values changed significantly in the 1 mL samples and increased only after 6 hours in the 3 mL samples. No significant changes in tHb, ContO(2), SBE, or HCO3 were detected.Conclusions: the PO2 of arterial and venous blood increased significantly when samples were stored in plastic syringes in ice water. These increases are attributable to the diffusion of oxygen from and through the plastic of the syringe into the blood, which occurred at a rate that exceeded metabolic consumption of oxygen by the nucleated cells.

Gas concentration and temperature excited Delft turbulent jet in acoustically flames

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)