Simultaneous determination of BTX and total hydrocarbons in water employing near infrared spectroscopy and multivariate calibration

A method for the simultaneous determination of benzene, toluene and xylenes (BTX) in water based on the use of a silicone sensing phase, detection by near infrared spectroscopy and multivariate calibration is described. A Doehlert design was employed to define the calibration and external validation sets, which were prepared in the concentration ranges of 2.0–30 mg L⁻¹ for benzene, 4.0–40 mg L⁻¹ for toluene and 1.0–15 mg L⁻¹ for xylenes; these ranges were selected after evaluation of the concentration of these compounds in a water sample contaminated by gasoline. The determinations were performed by inserting a polydimethylsiloxane (PDMS) rod (3.2 mm diameter and 5.0 mm long) into a flask containing the aqueous BTX solution (without headspace), made 3.0 mol L⁻¹ with sodium chloride in order to improve the extraction of the hydrocarbons by the polymer. After extraction, the cylinder was placed in a home-made cell for absorbance measurements from 800 to 2500 nm. The calibration models were constructed using Partial Least Square (PLS) regression and Multiple Linear Regression (MLR), with variables selected by the Successive Projection Algorithm (SPA). PLS models provided relative errors of prediction of 10.9%, 13.3%, 21.9% and 9.6% for benzene, toluene, xylenes and total hydrocarbons, respectively. These values can be considered acceptable for the concentration range studied, indicating that the proposed method can be useful for simultaneous determination of aromatic compounds in water employing NIR.     

The effect of side chains on the partial specific volumes of poly(o-alkylphenyl methacrylate)s and polydiitaconates

Partial specific volumes ν of a series of poly(o-alkyl phenyl methacrylate)s and polydiitaconates were determined by density measurements, in toluene and tetrahydrofuran solutions, respectively. The effect of the size and nature of the side groups on partial specific volume is analyzed. Good agreement is found between the experimental ν values and those obtained theoretically from the group contribution method.     

Are Nanosilica,Potassium Silicate and New Soluble Sources of Silicon Effective for Silicon Foliar Application to Soybean and Rice Plants?

Silicon - Foliar application of silicon (Si) is an effective way of supplying this beneficial element to plants. The emergence of new potential liquid sources for foliar application requires...     

Dynamic framework with adaptive contention window and multipath routing for video-streaming services over mobile ad hoc networks

The number of portable electronic devices capable of maintaining wireless communications increases day by day. Such mobile nodes may easily self-configure to form a Mobile Ad Hoc Network (MANET) without the help of any established infrastructure. As the number of mobile devices grows, the demand of multimedia services such as video-streaming from these networks is foreseen to increase as well. This paper presents a proposal which seeks to improve the experience of the end users in such environment. The proposal is called dCW-MMDSR (dynamic Contention Window-Multipath Multimedia Dynamic Source Routing), a cross-layer multipath routing protocol which includes techniques to achieve a dynamic assignment of the Contention Window of the IEEE 802.11e MAC level. In addition, it includes multipath routing suitable for layered coded video to improve the performance of the service. The operation is simple and suitable for low capacity wireless devices. Simulations show the benefits under different scenarios.     

Effect of the reaction field electrostatic term on the molecular dynamics simulation of the activation domain of procarboxypeptidase B

Molecular dynamics simulations of the activation domain of porcineprocarboxypeptidase B (ADBp) were performed in order to examinethe effects of the inclusion of a reaction field (RF) term intothe calculation of electrostatics forces for highly chargedproteins. Two simulations were performed with the GROMOS96 package,studying the influence of counterions on the final results.Comparison with previous results without the inclusion of theRF term (Martí-Renom,M.A., Mas,J.M., Oliva,B., Querol,E.and Avilés,F.X., Protein Engng, 1998, 11, 101–110)shows that the structure is well maintained when the RF termis included. Moreover, the analysis of the trajectories showsthat simulations of solvated highly-charged proteins are sensitiveto the presence of counterions, the secondary structures beingmore stable when their charges are neutralized.     

Impact of avoidance angle mitigation techniques on the interference produced by non‐GSO systems in a multiple non‐GSO interference environment

This paper adresses the impact of avoidance angle mitigation techniques on the interference produced by non‐GSO systems in a multiple non‐GSO interference environment. It considers a situation involving a victim LEO system and two other non‐GSO interfering systems (one MEO and another LEO) that mitigate around (and only around) the victim LEO system. Interference statistics are obtained using the so called Analytical Method for non‐GSO interference computations. The methodology described, including the interference model adopted, and the type of result obtained in Section 3, that shows the variation of the percentage of the total time allowance used by the interference as a function of the Earth station‐based and the satellite‐based avoidance angles, are very helpful in the process of selecting adequate values for these angles. The burden imposed on the mitigating systems by the use of avoidance angle strategies was evaluated through its impact on the coverage capability of the mitigating systems. Copyright © 2003 John Wiley & Sons, Ltd.     

Mega capture of the Rio Negro and formation of the Anavilhanas Archipelago, Central Amazônia, Brazil: Evidences in an SRTM digital elevation model

In the Central Amazônia (Brazil), the Solimões River and the Negro River (“Rio Negro”) merge to form the Amazonas, the largest river in the world. Analysis of a digital elevation model produced by the Shuttle Radar Topographic Mission (SRTM) in that region reveals the relicts of a large ancient drainage system hidden by the tropical rain forest. Interpretation of this unreported terrain feature in the context of the regional geological framework indicates that the present lower course of the Rio Negro results from a mega fluvial capture driven by an active tectonic regime prevailing in the Amazonian basin. The diversion of the Rio Negro was controlled by pre-existing NW-SE structural features, in which the arrangement of fault blocks compelled the river to funnel down into a strait. Partially blocked by this natural barrier, the Rio Negro widens upstream, assuming a lake-like appearance (up to 20 km-wide). Free space availability and low energy favored the deposition of sediments to form the Anavilhanas Archipelago, the largest group of freshwater islands on the world, refuge of a diversified fauna and flora.     

Spread SCPC/FDMA,spread TDMA/FDMA and SSMA/FDMA transmission through A non-linear satellite channel with an earth-station off-axis emission constraint

This paper analyses and compares possible access schemes to be used in satellite networks with a large number of small earth-stations. Basically, frequency division (FDMA), time division (TDMA), and spread spectrum multiple access (SSMA) are considered. For TDMA, one single carrier originated in one particular earth-station is transmitted in each sub-band and therefore a single-channel-per-carrier system results (SCPC/FDMA). For TDMA and SSMA, it is assumed that groups of earth-stations using either of these access schemes share the full available band in FDMA. The corresponding systems are thus TDMA/FDMA and SSMA/FDMA. Moreover, for SCPC/FDMA and TDMA/FDMA individual carriers may be spread to the extent that the available bandwidth is always fully occupied. Spectral efficiencies for these three access modes (Spread SCPC/FDMA, Spread TDMA/FDMA and SSMA/FDMA) are computed and compared for transmission through a non-linear satellite channel and optimum operating points for the non-linear amplifier are also determined. Comparisons are also performed for the situation in which transmitting earth-stations are bounded to obey an off-axis emission constraint.     

Development of mixed beverages made of caja (Spondias mombin L.) and cashew apple (Anacardium occidentale) added of fructooligosaccharides and inulin

The purpose of this work was to develop three mixed drinks based on caja (Spondias mombin L.) and cashew apple (Anacardium occidentale) pulps, added prebiotic ingredients and to evaluate their chemical, physicochemical and sensory properties. Four formulations with combinations of two pulp fruit, sucrose and prebiotic ingredients (Standard inulin, inulin high performance-HP-and fructooligosaccharides FOS) were developed. The mixed drinks were submitted the following analysis pH, acidity, soluble solids, sugars, ascorbic acid, total carotenoids, total polyphenols and acceptance ratings of the sensory attributes such as: consistency, sweetness and overall impression, attitude and consumers purchase preference. The pH, total soluble solids and polyphenol results showed difference (p < or = 0.01) significant, while for the analysis of total acidity, sugars, ascorbic acid and carotenoids, it was not observed significant difference. The sensory attributes evaluates showed results ranging in scale between "I did not like or disliked "and" liked "(average 5.80 to 7.06). The attributes sweetness, consistency and attitude of buying showed no difference (p > 0.05) between drinks, however, differed significantly (p < or = 0.05) for the attribute of overall impression. The drink with FOS showed a similar acceptance when compared to traditional (sucrose) drink, showing an option of meeting the functional food expectations of consumers, who seek healthy, nutritious and tasty foods.