Increased carbon dioxide concentration in the air reduces the severity of Ceratocystis wilt in Eucalyptus clonal plantlets

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Colorimetric determination of formaldehyde in air using a hanging drop of chromotropic acid

A simple and sensitive method to determine parts per billion (ppb) of atmospheric formaldehyde in situ, using chromotropic acid, is described. A colorimetric sensor, coupled to a droplet of 15.5 muL chromotropic acid, was constructed and used to sample and quantify formaldehyde. The sensor was set up with two optical fibers, a right emitting diode (LED) and two photodiodes. The reference and transmitted light were measured by a photodetection arrangement that converts the signals into units of absorbance. Air was sampled around the chromotropic acid droplet. A purple product was formed and measured after the sampling terminated (typically 7 min). The response is proportional to the sampling period, analyte concentration and sample flow rate. The detection limit is similar to2 ppb and can be improved by using longer sampling times and/or a sampling flow rate higher than that used in this work, 200 mL min(-1). The present technique affords a simple, inexpensive near real-time measurement with very little reagent consumption. The method is selective and highly sensitive. This sensor could be used either for outdoor or indoor atmospheres.

Colorimetric determination of ammonia in air using a hanging drop

A simple and sensitive method for determining atmospheric ammonia (NH3), using a hanging drop, is described. A colorimetric sensor is composed of two optical fibers and the source of monochromatic light implemented was a red light emitting diode (LED) (635 nm). Preliminary experiments were carried out in order to optimize the geometry of the sensor. These tests showed that the best signal absorbance was obtained using a 22 muL deionized water drop for sampling the gas and as addition of 4 muL of each of the reactants to form the blue dye (indophenol). Some important analytical parameters were also studied, including sampling time and flow rate. The analytical curve was constructed with a concentration range of 3-20 ppbv of gaseous NH3 standard. The detection limit reached was of ca 0.5 ppbv. It was observed that formaldehyde and diethylamine did not interfere. However, studies showed that hydrogen sulfide caused a negative interference of 20%, when present in the atmosphere in a concentration equal to that of NE3. The method considered here was shown to be easy to apply, making it possible to make a determination every 17 min.

Colorimetric determination of sulfur dioxide in air using a droplet collector of malachite green solution

The measurement of sulfur dioxide in air at the parts-per-billion level is described. The experimental arrangement consists of two optical fibers placed on opposite sides of a liquid droplet of malachite green solution. After light has been passed through the droplet, the transmitted light is measured by a referenced photodetection arrangement. The light used in this absorption process is from a monochromatic source (lambda(max) 625 nm). This arrangement permits the variation of color in the droplet to be measured. The sulfur dioxide in the sample is collected by the droplet; it reacts with malachite green resulting in a colorless dye. The decoloration of the solution is proportional to the concentration of sulfur dioxide sampled. The signal depends on the sample flow rate. The present technique is simple, inexpensive, and permits a fast and near real time measurement while consuming very little reagent, (C) 1999 Academic Press.

SOLIDS COATED WITH SODIUM TETRACHLOROPALLADATE - SORBENTS FOR REDUCED SULFUR-COMPOUNDS IN AIR

A study of the preconcentration of tioethers in air by means of the passage of gas flow on solid sorbents coated with sodium tetrachloropalladate was undertaken with the aim of achieving chemical fixation. This fixation presented high specificity and blocked the migration of the sorbed compound through the other active sites. The species obtained were selectively dissolved in organic solvents, resulting in the sulfur reduced compound concentration in the organic phase, which could be determined spectrophotometrically.

Determination of BTEX by GC-MS in air of offset printing plants: Comparison between conventional and ecological inks

The use of inks containing organic solvents by the offset printing process implies in the release of volatile organic compounds to the work environment. Many of these compounds such as benzene, toluene, ethylbenzene, and the xylene isomers (well known by the acronym BTEX) are extremely toxic. In this study, the BTEX concentrations were determined in two different printing plants that use distinct types of inks: the conventional and the so-called ecological, which is manufactured based on vegetal oil. Concentration ranges were 43-84, 15-3,480, 2-133, 5-459, and 2-236 μg m-3 for benzene, toluene, ethylbenzene, m + p-xylene, and o-xylene, respectively, for the conventional printing plant. At the ecological printing plant, concentration ranges were below limit of detection (concentrations are lower at the ecological printing environment than in the conventional, where mineral oil-based inks are used. However, the worker who cleans the printing matrices is exposed to high concentrations of ethylbenzene and xylenes, due probably to the cleaning product's composition (containing high amounts of BTEX). Although the BTEX concentrations found in both printing work environments were below the limits considered by the Brazilian Law for Activities and Unhealthy Operations (NR-15), the exposure to such vapors characterizes risk to the workers' health for some of the evaluated samples, mainly the personal ones. © Springer Science+Business Media B.V. 2009.

Real-time monitoring of ozone in air using substrate-integrated hollow waveguide mid-infrared sensors

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Development of a simple method for determination of NO2 in air using digital scanner images

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mapping of adhesion forces on soil minerals in air and water by atomic force spectroscopy (AFS)

The adhesion force between an atomic force microscope (AFM) tip and sample surfaces, mica and quartz substrates, was measured in air and water. The force curves show that the adhesion has a strong dependence on both the surface roughness and the environmental conditions surrounding the sample. The variability of the adhesion force was examined in a series of measurements taken at the same point, as well as at different places on the sample surface. The adhesion maps obtained from the distribution of the measured forces indicated regions contaminated by either organic compounds or adsorbed water. Using simple mathematical expressions we could quantitatively predict the adhesion force behavior in both air and water. The experimental results are in good agreement with theoretical calculations, where the adhesion forces in air and water were mostly associated with capillary and van der Waals forces, respectively. A small long-range repulsive force is also observed in water due to the overlapping electrical double-layers formed on both the tip and sample surfaces.

Treatment of PET and PU polymers by atmospheric pressure plasma generated in dielectric barrier discharge in air

Plasma treatments are frequently employed to modify surface properties of materials such as adhesivity, hydrophobicity, oleophobicity etc. Present work deals with surface modification of common commercial polymers such as polyethylene terephthalate (PET) and polyurethane (PU) by an air dielectric barrier discharge (DBD) at atmospheric pressure. The DBD treatment was performed in a plain reactor in wire-duct geometry (non-uniform field reactor), which was driven by a 60 Hz power supply. Material characterization was carried out by water contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The plasma-induced modifications are associated with incorporation of polar oxygen and nitrogen containing groups on the polymer surface. The AFM analysis reveals that the plasma treatment roughens the material surface. Due to these structural and morphological changes the surface of DBD-treated polymers becomes more hydrophilic resulting in enhanced adhesion properties. (C) 2010 Elsevier B.V. All rights reserved.

Bacterial sterilization by a dielectric barrier discharge (DBD) in air

Cold atmospheric plasma treatment of microorganisms and living tissues has become a popular topic in modern plasma physics and in medical science. The plasma is capable of bacterial inactivation and noninflammatory tissue modification, which makes it an attractive tool for treatment of skin diseases, open injuries and dental caries. Because of their enhanced plasma chemistry, Dielectric Barrier Discharges (DBDs) have been widely investigated for some emerging applications such as biological and chemical decontamination of media at ambient conditions. Despite the high breakdown voltage in air at atmospheric pressure, the average current of DBD discharges is low. Therefore, a DBD can be applied in direct contact with biological objects without causing any damage. In this work a 60 Hz DBD reactor, which generates cold atmospheric plasma inside Petri dishes with bacterial culture, is investigated. Samples of Staphylococcus aureus, a Gram-positive bacterium and Escherichia coil a Gram-negative bacterium were selected for this study. The bacterial suspensions were evenly spread on agar media planted in Petri dishes. The reactor electrodes were placed outside the Petri dish, thus eliminating the risk of samples microbial contamination. The covered Petri dish with agar medium in it serves as dielectric barrier during the treatment. The plasma processing was conducted at same discharge power (similar to 1.0 W) with different exposure time. Sterilization of E. coil and S. aureus was achieved for less than 20 min. Plasma induced structural damages of bacteria were investigated by Scanning Electron Microscopy. (C) 2010 Elsevier B.V. All rights reserved.

Relation among optical, thermal and thermo-optical properties and niobium concentration in tellurite glasses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Plasma progesterone concentration in beef heifers receiving exogenous glucose, insulin, or bovine somatotropin

Three experiments were conducted to evaluate plasma concentrations of glucose, insulin, IGF-I, and progesterone (P4) in pubertal beef heifers receiving exogenous glucose, insulin, or sometribove zinc. All heifers used had no luteal P4 synthesis but received a controlled internal drug-releasing device containing 1.38 g of P4 to estimate treatment effects on hepatic P4 degradation. In Exp. 1, 8 pubertal, nulliparous Angus x Hereford heifers (initial BW = 442 +/- 14 kg; initial age = 656 +/- 7 d) were randomly assigned to receive, in a crossover design containing 2 periods of 10 h, intravenous (i.v.) infusions (10 mL) of insulin (1 mu g/kg of BW; INS) or saline (0.9%; SAL). Treatments were administered via jugular venipuncture in 7 applications (0.15 mu g insulin/kg BW per application) 45 min apart (from 0 to 270 min). Blood samples were collected immediately before each infusion as well as at -120, -60, 330, 390, and 450 min relative to the first infusion. Heifers receiving INS had greater (P < 0.01) plasma insulin, reduced (P <= 0.04) plasma glucose and IGF-I, and similar (P = 0.62) plasma P4 concentrations compared with SAL heifers. In Exp. 2, the same heifers were assigned to receive, in a similar experimental design as Exp. 1, i.v. infusions (10 mL) of 1) insulin (1 mu g/kg BW) and glucose (0.5 g/kg BW; INS+G) or 2) SAL. Heifers receiving INS+G had greater (P <= 0.02) plasma insulin, glucose, and P4 but reduced (P = 0.01) plasma IGF-I concentrations compared with SAL heifers. In Exp. 3, the same heifers were assigned to receive, in a crossover design containing 2 periods of 14 d, subcutaneous (s.c.) injections of 1) 250 mg of sometribove zinc (BST) or 2) SAL. Blood samples were collected 3 h apart (0900, 1200, 1500, and 1800 h) from heifers on d 6, 8, and 10 relative to treatment administration (d 1). Heifers receiving BST had greater (P < 0.01) plasma glucose and IGF-I and similar (P >= 0.67) plasma insulin and P4 concentrations compared with SAL heifers. Results from this series of experiments suggested that concurrent increases in glucose and insulin are required to reduce hepatic catabolism and increase plasma concentrations of P4 in bovine females.