Discrepancies over the onset of surfactant monomer aggregation interpreted by fluorescence, conductivity and surface tension methods

Molecular probe techniques have made important contributions to the determination of microstructure of surfactant assemblies such as size, stability, micropolarity and conformation. Conductivity and surface tension were used to determine the critical aggregation concentration (cac) of polymer-surfactant complexes and the critical micellar concentration (cmc) of aqueous micellar aggregates. The results are compared with those of fluorescent techniques. Several surfactant systems were examined, 1-butanol-sodium dodecylsulfate (SDS) mixtures, solutions containing poly(ethylene oxide)-SDS, poly(vinylpyrrolidone)-SDS and poly(acrylic acid)-alkyltrimethylammonium bromide complexes. We found differences between the cac and cmc values obtained by conductivity or surface tension and those obtained by techniques which use hydrophobic probe.

Electrical characteristics of eddy current position sensor

In the thesis the principle of work of eddy current position sensors and the main cautions that must be taken into account while sensor design process are explained. A way of automated eddy current position sensor electrical characteristics measurement is suggested. A prototype of the eddy current position sensor and its electrical characteristics are investigated. The results obtained by means of the automated measuring system are explained.

DFM(A)- aspects for a fixed electrical attenuator design

The goal of this paper is to describe a complete and extensive prototype design of a fixed electrical attenuator. The paper starts by describing the function and by giving some basic information about the attenuators. After a comprehensive description of the component, the facts of reverse engineering are discussed. The method itself is applied to ease manufacturing and design stages of this component. Information about materials and applied manufacturing technologies are also included in this report. By applying some specified DFMA-aspects the final design turned out to be a potential prototype device to be manufactured and for further analyse.

Medidas de resistividade elétrica DC em sólidos: como efetuálas corretamente

This paper deals with the most common methods for determining the dc electrical resistivity in solid materials. A brief overview of the fundamental concepts related to the electrical resistivity on materials is introduced. Undoubtedly, the most common and useful procedure to determine the electrical resistivity (rho) is the fourpoint probe method. Some crucial mistakes regarding the experimental procedure and the appropriated correction factors are found in the literature. Thus, the correction factor for the most common sample geometries were gathered and revised in order to provide an easy way to use and apply them.

Electrical machine in a Hybrid Electrical Vehicle

Hybrid electric vehicles (HEV) have attracted very much attention during the latest years. Increasing environmental concern and an increase in fuel prices are key factors for the growing interest towards the HEV. In a hybrid electric vehicle the power train consists of both a mechanical power system and an electric power transmission system. The major subsystems in the mechanical power system are the internal combustion engine which powers the vehicle; electric power transmission including an energy storage, power electronic inverter, hybrid control system; the electric motor drive that runs either in the generating mode or in the motoring mode to process the power flow between the energy storage and the electrical machine. This research includes two advanced electric motors for a parallel hybrid: induction machine and permanent magnets synchronous machine. In the thesis an induction motor and a permanent magnet motor are compared as propulsion motors. Electric energy storages are also studied.

Determinação de bromato em melhoradores de farinha por cromatografia de troca iônica com detecção espectrofotométrica

KBrO3 is registered by the FAO/OMS as a genotoxic and carcinogenic compound. In spite of this, KBrO3 is still employed by Brazilian bakeries. Nowadays ion exchange chromatography (IEC) is the most rapid and trustful method for BrO3- analysis. When at high concentrations, chloride ions can interfere in the BrO3- analysis, if the detection is performed by electrical conductivity. On the other hand, spectrophotometric detection, presented here is based on the absorption of BrO3- in the ultraviolet region (210 - 230 nm) where the absortion of chloride ions is very low, thus making possible the qualitative and quantitative analysis of BrO3- in flour improver samples.

Aplicació de tècniques geofísiques electromagnètiques a la localització de zones afectades per abocaments incontrolats de residus

Increase of the metropolitan area of cities provoking a progressive settlement of zones that previously had a different territorial use. These zones are usually located within city houndaries and for many years have been affected hy the waste of many kinds of residues. Qualitative analysis of the electrical behaviour of soil, based on maps and cross sections of apparent conductivity, allows us to locate anomalies generated by the wastes. Moreover, the electrornagnetic techniques (EM-31 and EM-34 Geonics devices) are cheaper than other survey methods. Two examples in the campus of the University of Girona, in the southern area of Girona city, illustrate the environmental problem and the applicability of the geophysical method

Explosion-proof requirements for Electrical Machines in Chemical, Oil and Gas Industry in Russia and CIS Countries

One of the main industries which form the basis of Russian Economical structure is oil and gas. This industry is also playing a significant role for CIS countries. Oil and gas industry is developing intensively attracting foreign investments. This situation is providing sustainable development of machinery production for hazardous areas. Operating in oil and gas areas is always related with occurrence of explosion gas atmospheres. Machines for hazardous areas must be furnished with additional protection of different types. Explosion protection is regulated with standards according to which equipment must be manufactured. In Russia and CIS countries explosion-proof equipment must be constructed in compliance with GOST standards. To confirm that equipment is manufactured according to standards’ requirements and is safe and reliable it must undergo the approval procedure. Certification in Russia is governed by Federal Laws and legislation. Each CIS country has its own approval certificates and permissions for operating in hazardous areas.

Multichannel distribution strategy for electrical equipment marketing

The thesis examines System Integration and original equipment manufacturer (OEM) channel in the St. Petersburg drives market. The aim of the study was to increase understanding the relationship between OEM and SI and producers, problems and ongoing trends. The collected data was analyzed in order to find out which features of a power electronic drive product exercise a significant influence for the Russian companies decision. An essential part of this study was interviews as primary information sources, organized with SI and OEM companies which represented the basic SPb industry segments. The wholesalers and end users are left out from the analysis. The collected data was analyzed in order to find out which features of a power electronic drive product exercise a significant influence for the Russian companies decision.

Electrical and magnetic properties of new compounds of the conductor anion [Ni(dmit)2]- and nitronyl nitroxide magnetic radicals

Three compounds have been synthesized with formulae [3-MeRad][Ni(dmit)2] (1), [4-MeRad][Ni(dmit)2] (2) and [4-PrRad][Ni(dmit)2] (3) where [Ni(dmit)2]- is an anionic pi-radical (dmit = 1,3-dithiol-2-thione-4,5-dithiolate) and [3-MeRad]+ is 3-N-methylpyridinium alpha-nitronyl nitroxide, [4-MeRad]+ is 4-N-methylpyridinium alpha-nitronyl nitroxide and [4-PrRad]+ is 4-N-propylpyridinium alpha-nitronyl nitroxide. The temperature-dependent magnetic susceptibility of 1 revealed that an antiferromagnetic interaction operates between the 3-MeRad+ radical cations with exchange coupling constants of J1 = - 1.72 cm-1 and antiferromagnetism assigned to the spin ladder chains of the Ni(dmit)2 radical anions. Compound 1 exhibits semiconducting behavior and 3 presents capacitor behavior in the temperature range studied (4 - 300 K).

Combined dielectrophoretic and impedance system for on-chip controlled bacteria concentration: Application to Escherichia coli

The present paper reports a bacteria autonomous controlled concentrator prototype with a user-friendly interface for bench-top applications. It is based on a micro-fluidic lab-on-a-chip and its associated custom instrumentation, which consists in a dielectrophoretic actuator, to pre-concentrate the sample, and an impedance analyser, to measure concentrated bacteria levels. The system is composed by a single micro-fluidic chamber with interdigitated electrodes and a instrumentation with custom electronics. The prototype is supported by a real-time platform connected to a remote computer, which automatically controls the system and displays impedance data used to monitor the status of bacteria accumulation on-chip. The system automates the whole concentrating operation. Performance has been studied for controlled volumes of Escherichia coli (E. coli) samples injected into the micro-fluidic chip at constant flow rate of 10 μL/min. A media conductivity correcting protocol has been developed, as the preliminary results showed distortion of the impedance analyser measurement produced by bacterial media conductivity variations through time. With the correcting protocol, the measured impedance values were related to the quantity of bacteria concentrated with a correlation of 0.988 and a coefficient of variation of 3.1%. Feasibility of E. coli on-chip automated concentration, using the miniaturized system, has been demonstrated. Furthermore, the impedance monitoring protocol had been adjusted and optimized, to handle changes in the electrical properties of the bacteria media over time.

Formação de micelas mistas entre o sal biliar colato de sódio e o surfactante aniônico dodecanoato de sódio

Mixed-micelle formation between sodium chlolate (NaC) and the anionic surfactant sodium dodecanoate (SDoD) in Tris-HCl buffer solutions, pH 9.00, varying the molar fraction of the surfactants, was investigated by means of electrical conductivity and steady-state fluorescence of pyrene. The critical micelar concentration (cmc) was measured from the equivalent conductance versus the square root of the molar surfactant concentration plots and the regular solution theory (RST) was used to predict the mixing behavior. The I1/I3 pyrene ratio-surfactant concentration plots were used as an additional technique to follow the behavior and the changes in the micropolarity of the mixed micelles.

Nanocompósitos de poliuretana termoplástica e nanotubos de carbono de paredes múltiplas para dissipação eletrostática

Polyurethane/multi-walled carbon nanotube (MWCNT) nanocomposites have been prepared with nanotube concentrations between 0.01 wt% and 1 wt%. MWCNT as-synthesized samples with ~74 nm diameter and ~7 μm length were introduced by solution processing in the polyurethane matrix. Scanning electron microscopy (SEM) images demonstrated good dispersion and adhesion of the CNTs to the polymeric matrix. The C=O stretching band showed evidence of perturbation of the hydrogen interaction between urethanic moieties in the nanocomposites as compared to pure TPU. Differential scanning calorimetry and positron anihilation lifetime spectroscopy measurements allowed the detection of glass transition displacement with carbon nanotube addition. Furthermore, the electrical conductivity of the nanocomposites was significantly increased with the addition of CNT.

Efecto del catión, del anión y del co-ión sobre la agregación de líquidos iónicos en solución acuosa

The aggregation behavior of thirteen 1-alkyl-3-methylimidazolium based ionic liquids in aqueous solution is presented, considering variations of the alkyl side chain length as well as the anionic moiety. Cation and anion molecular volumes are selected as appropriate molecular descriptors. Additionally, the existing relationship between critical micelle concentration (CMC) and electrolyte concentration in solution is established, aiming to clarify ion effects. CMC values were obtained by measuring electrical conductivity and surface tension. It was confirmed that aggregation of ionic liquids in aqueous solution and in presence of inorganic salts is affected by the factors developed in this study.