Utilização de eletrodos sólidos de amálgama para a determinação analítica de compostos orgânicos e inorgânicos

This review reports the use of solid amalgam electrodes in the electroanalytical determination of organic and inorganic compounds. The different types of amalgam electrodes are presented, and attention is paid to solid amalgam electrode, and here is presented details about the pre-treatment for activation and renovation and also possible modifications in its surface. The wide potential range, higher signal-to-noise ratio, mechanical stability enabling their application in flowing systems, and principally their resistance toward passivation, indicate that the solid amalgam electrodes are environmentally friendly alternatives to mercury electrodes, without loss in the sensitivity and reproducibility in voltammetric responses.

Surface Modification of Ceramics

Ceramics are widely used in industrial applications due to their advantageous thermal and mechanical stability. Corrosion of ceramics is a great problem resulting in significant costs. Coating is one method of reducing adversities of corrosion. There are several different thin film deposition processes available such as sol-gel, Physical and Chemical Vapour Deposition (PVD and CVD). One of the CVD processes, called Atomic Layer Deposition (ALD) stands out for its excellent controllability, accuracy and wide process capability. The most commonly mentioned disadvantage of this method is its slowness which is partly compensated by its capability of processing large areas at once. Several factors affect the ALD process. Such factors include temperature, the grade of precursors, pulse-purge times and flux of precursors as well as the substrate used. Wrongly chosen process factors may cause loss of self-limiting growth and thus, non-uniformities in the deposited film. Porous substrates require longer pulse times than flat surfaces. The goal of this thesis was to examine the effects of ALD films on surface properties of a porous ceramic material. The analyses applied were for permeability, bubble point pressure and isoelectric point. In addition, effects of the films on corrosion resistance of the substrate in aqueous environment were investigated. After being exposured to different corrosive media the ceramics and liquid samples collected were analysed both mechanically and chemically. Visual and contentual differences between the exposed and coated ceramics versus the untreated and uncoated ones were analysed by scanning electron microscope. Two ALD film materials, dialuminium trioxide and titanium dioxide were deposited on the ceramic substrate using different pulse times. The results of both film materials indicated that surface properties of the ceramic material can be modified to some extent by the ALD method. The effect of the titanium oxide film on the corrosion resistance of the ceramic samples was observed to be fairly small regardless of the pulse time.

Suurnopeus-turbokoneroottoreiden termodynaaminen ja mekaaninen mallinnus sekä rakenneanalyysi

Tässä väitöskirjassa tarkastellaan suurnopeustekniikan eri sovelluksissa ilmeneviä roottoreihin liittyviä rakenteellisia vaatimuksia ja haasteita. Tässä yhteydessä suurnopeustekniikalla tarkoitetaan järjestelyä, jossa sähkökone (moottori, generaattori) ja toimilaite (turbiini, kompressori, puhallin) on kytketty ilman vaihdetta suoraan mekaanisesti yhteen ja jossa yhteisen roottorin pyörimisnopeus on selvästi suurempi kuin 50/60 hertsin verkosta syötetyn kaksinapaisen vaihtovirtasähkökoneen tahtinopeus. Tyypillistä suurnopeuskoneen roottorille on suuri tehotiheys ja suuri mekaaninen kuormitus. Siksi esimerkiksi sähkökoneen jäähdytys on entistä haasteellisempaa kasvavien rautahäviöiden ja pienempien lämmönsiirtopinta-alojen vuoksi. Tämän työn tavoitteet voidaan jakaa kolmeen osaan:  Yhdistetyn sähkö- ja turbokoneen roottorin mekaanisen rakenteen tarkastelu, jonka tavoitteena on pienentää lämmönkehitystä ja tehostaa kriittisten kohtien jäähdytystä. Tähän liittyy sähkömagneettisten häviöiden keskittäminen jäähdytyksen kannalta edullisiin kohtiin  Yhdistetyn sähkö- ja turbokoneen roottorin mekaanisen rakenteen tarkastelu kriittisten ominaistaajuuksien kannalta  Yhdistetyn sähkö- ja turbokoneen roottorin mekaanisen rakenteen analysointi lujuustekniseltä kannalta. Tähän liittyvät mm. erilaiset ahdistussovitteet ja niiden säilyminen korkeilla pyörimisnopeuksilla sekä niiden roottoria jäykistävä vaikutus ja lämmön johtuminen kyseisissä liitospinnoissa. Tämän työn tieteellinen uutuusarvo on nimenomaan yhdistetyn sähkö- ja turbokoneen roottorin rakenteen analysointi ottamalla samanaikaisesti huomioon kaikki edellä mainitut näkökohdat: jäähtyminen erityisen kuumissa kohdissa, sähköisten häviöiden alentaminen ja niiden jakautuman huomioon ottaminen, roottorin jäykkyyden maksimointi, lujuusrasitusten hallinta ja rakenteen mekaaninen stabiliteetti sekä lämpöteknisten ylimenovastusten tarkastelu.

Bearing-spesific complications of total hip arthroplasty: characterization and treatment

Hip resurfacing arthroplasty (HRA) and large head metal-on-metal total arthroplasty (LDH MoM THA) gained popularity during the last decade. Adverse reaction to metal debris (ARMD) is a unique complication of metal bearings. ARMD is a complex reaction caused by metal debris from metal-on- metal bearing surfaces and from trunnion corrosion of modular junctions. We analyzed survivorship of 8059 LDH MoM THAs based on data of the Finnish Arthroplasty Register. We found relatively high short-term survivorship for some LDH MoM THAs, but there were remarkable differences between the devices studied. After some alarming reports of failing MoM THAs, we studied the first 80 patients who had received a ReCap-M2a-Magnum implant at our institution and evaluated the prevalence of ARMD. We found a high prevalence of pseudotumors, and, because of this, we discontinued the use of MoM bearings and followed up all patients with a MoM THA. Bone loss due infection, osteolysis or fracture poses a great challenge for reconstructive and fracture surgery. Onlay allografting for both revision and fracture surgery provides mechanical stability and increases bone stock. Bone loss and implant stability must be assessed preoperatively and adequately classified; this provides guidelines for the operative treatment of periprosthetic fractures and revision THA. In our studies on structural allografts union rates were high, although the rates of infections and dislocations were marked. In summary, early results of the use of LDH MoM devices were encouraging. However, the survival of the LDH MoMs varied. The prevalence of adverse reaction to metal debris was high after application of the ReCap-Magnum THA. New implants should be introduced carefully and under close surveillance by University clinics and arthroplasty registers.

Copper(II) complexes of embelin and 2-aminobenzimidazole encapsulated in zeolite Y-potential as catalysts

Copper(II) complexes of two biologically important ligands, viz., embelin (2,5-dihydroxy-3-undecyl-2,5-cyclohexadien 1,4-dione) and 2-aminobenzimidazole were entrapped in the cages of zeolite Y by the flexible ligand method. The capability of these compounds in catalyzing the reduction of oxygen (industrially known as deoxo reaction) was explored and the results indicate an enhancement of the catalytic properties from that of the simple copper ion exchanged zeolite. These point to the ability of the ligands in enhancing the oxygen binding capability of the metal ion. Elemental analyses, Fourier transform infrared (FTIR), diffuse reflectance and EPR spectral studies, magnetic susceptibility measurements, TG, surface area analyses and powder X-ray diffraction studies were used in understanding the presence, composition and structure of the complexes inside the cages. The study also reveals the increased thermal and mechanical stability of the complexes as a result of encapsulation.

GaInAsP-basierende Resonatorstrukturen

Physikalische Grundlagenforschung und anwendungsorientierte physikalische Forschung auf den Gebieten nanoskaliger kristalliner und amorpher fester Körper haben in vielfacher Weise eine große Bedeutung. Neben dem Verständnis für die Struktur der Materie und die Wechselwirkung von Objekten von der Größe einiger Atome ist die Erkenntnis über die physikalischen Eigenschaften nanostrukturierter Systeme von hohem Interesse. Diese Forschung eröffnet die Möglichkeit, die mit der Mikroelektronik begonnene Miniaturisierung fortzusetzen und wird darüber hinaus neue Anwendungsfelder eröffnen. Das Erarbeiten der physikalischen Grundlagen der Methoden zur Herstellung und Strukturierung ist dabei zwingend notwendig, da hier Wirkungsprinzipien dominieren, die erst bei Strukturgrößen im Nanometerbereich auftreten oder hinreichend stark ausgeprägt sind. Insbesondere Halbleitermaterialien sind hier von großem Interesse. Die in dieser Arbeit untersuchten Resonatorstrukturen, die auf dem kristallinen Verbindungshalbleitermaterial GaInAsP/InP basieren, erschließen wichtige Anwendungsfelder im Bereich der optischen Datenübertragung sowie der optischen Sensorik. Hergestellt wird das Halbleitermaterial mit der Metallorganischen Gasphasenepitaxie. Die experimentell besimmten Kenngrößen lassen Rückschlüsse auf die Güte der Materialien, die quantenmechanischen Wirkungsprinzipien und die Bauelementcharakteristik zu und führen zu optimal angepassten Kristallstrukturen. Auf Basis dieser optimierten Materialien wurde ein durchstimmbarer Fabry-Perot-Filter hergestellt, der aus einer Kombination aus InP-Membranen und Luftspalten besteht und elektromechanisch aktuiert werden kann. Das GaInAsP dient hierbei als wenige hundert nm dicke Opferschicht, die ätztechnisch hochselektiv beseitigt wird. Die Qualität der Grenzflächen zum InP ist entscheidend für die Qualität der freigeätzten Kavitäten und damit für die mechanische Gesamtstabilität der Struktur. Der in dieser Arbeit beschriebene Filter hat eine Zentralwellenlänge im Bereich von 1550 nm und weist einen Durchstimmbereich von 221 nm auf. Erzielt wurde dieser Wert durch ein konsistentes Modell der wirkenden Verspannungskomponenten und einer optimierten epitaktischen Kontrolle der Verspannungsparameter. Das realisierte Filterbauelement ist vielversprechend für den Einsatz in der optischen Kommunikation im Bereich von WDM (wavelength division multiplexing) Anwendungen. Als weitere Resonatorstrukur wurde ein Asymmetrisch gekoppelter Quantenfilm als optisch aktives Medium, bestehend aus GaInAsP mit variierender Materialkomposition und Verspannung, untersucht, um sein Potential für eine breitbandige Emission zu untersuchen und mit bekannten Modellen zu vergleichen. Als Bauelementdesign wurde eine kantenemittierende Superlumineszenzleuchtdiode gewählt. Das Ergebnis ist eine Emissionskurve von 100 nm, die eine höhere Unabhängigkeit vom Injektionsstrom aufweist als andere bekannte Konzepte. Die quantenmechanischen Wirkungsprinzipien - im wesentlichen die Kopplung der beiden asymmetrischen Potentialtöpfe und die damit verbundene Kopplung der Wellenfunktionen - werden qualitativ diskutiert. Insgesamt bestätigt sich die Eignung des Materials GaInAsP auch für neuartige, qualitativ höchst anspruchsvolle Resonatorstrukturen und die Bedeutung der vorgestellten und untersuchten Resonatorkonzepte. Die vorgestellten Methoden, Materialien und Bauelemente liefern aufgrund ihrer Konzeption und der eingehenden experimentellen Untersuchungen einen Beitrag sowohl zu den zugrunde liegenden mechanischen, optoelektronischen und quantenmechanischen Wirkungsprinzipien der Strukturen, als auch zur Realisierung neuer optoelektronischer Bauelemente.

Influence of encapsulation and coating materials on the survival of Lactobacillus plantarum and Bifidobacterium longum in fruit juices

The aim of this work was to compare alginate and pectin beads for improving the survival of Lactobacillus plantarum and Bifidobacterium longum during storage in pomegranate and cranberry juice, and to evaluate the influence of various coating materials, including chitosan, gelatin and glucomannan on cell survival and on the size and hardness of the beads. In pomegranate juice, free cells of L. plantarum died within 4 weeks of storage and those of B. longum within 1 week; in cranberry juice both types of cells died within one week. Encapsulation within either alginate or pectin beads improved cell survival considerably, but coating of the beads with chitosan or gelatin improved it even further; coating with glucomannan did not have any positive effect. The double gelatin coated pectin beads gave the highest protection among all types of beads, as a final concentration of approximately 108 CFU/mL and 106 CFU/mL for both L. plantarum and B. longum was obtained after 6 weeks of storage in pomegranate and cranberry juice, respectively. The good protection could be attributed to the very strong interaction between the two polymers, as measured by turbidity experiments, leading to the formation of a polyelectrolyte complex. It was also shown that the coating was able to inhibit the penetration of gallic acid within the beads, which was used in this study as a model phenolic compound with antimicrobial activity; this is a likely mechanism through which the beads were able to protect the cells from the antimicrobial activity of phenolic compounds present in both types of juices. Despite their good protective effect, the pectin beads were considerably softer than the alginate beads, an issue that should be addressed in order to increase their mechanical stability.

Avaliação da influência do nacl em pastas de cimento portland para cimentação de poços de petróleo em zonas evaporíticas

One of the major current challenges for oilwell companies is the extraction of oil from evaporitic zones, also known as pre-salt basins. Deep reservoirs are found under thick salt layers formed from the evaporation of sea water. Salt layers seal the flow of oil from underneath rock formations, which store hydrocarbons and increase the probability of success in oil and gas exploration. Oilwells are cemented using Portland-based slurries to promote mechanical stability and zonal isolation. For pre-salt oilwells, NaCl must be added to saturate the cement slurries, however, the presence of salt in the composition of slurries affects their overall behavior. Therefore, the objective of the present study was to evaluate the effect of the addition of 5 to 25% NaCl on selected properties of Portland-based slurries. A series of tests were carried out to assess the rheological behavior, thickening time, free water and ultrassonic compressive strength. In addition, the slurries were also characterized by thermal analysis, X ray diffraction and scanning electron microscopy. The results showed that the addition of NaCl affected the thickening time of the slurries. NaCl contents up to 10% shortened the thickening time of the slurries. On the other hand, concentrations in excess of 20% not only extended the thickening time, but also reduced the strength of hardened slurries. The addition of NaCl resulted in the formation of a different crystalline phase called Friedel´s salt, where free chlorine is bonded to tricalcium aluminate

Formulação de pastas cimentícias com adição de suspensões de quitosana para cimentação de poços de petróleo

Primary cementing is one of the main operations in well drilling responsible for the mechanical stability and zonal isolation during the production of oil. However, the cement sheath is constantly under mechanical stresses and temperature variations caused by the recovery of heavy oil. In order to minimize fracture and wear of the cement sheath, new admixtures are developed to improve the properties of Portland cement slurries and avoid environmental contamination caused by leaking gas and oil. Polymers with the ability to form polymeric films are candidates to improve the properties of hardened cement slurries, especially their fracture energy. The present study aimed at evaluating the effect of the addition of a chitosan suspension on cement slurries in order to improve the properties of the cement and increase its performance on heavy oil recovery. Chitosan was dissolved in acetic ac id (0.25 M and 2 M) and added to the formulation of the slurries in different concentrations. SEM analyses confirmed the formation of polymeric films in the cementitious matrix. Strength tests showed higher fracture energy compared to slurries without the addition of chitosan. The formation of the polymeric films also reduced the permeability of the slurry. Therefore, chitosan suspensions can be potentially used as cementing admixtures for heavy oil well applications

Utilização de nanosílica como aditivo estendedor para pastas cimentantes de baixa densidade destinadas à cimentação de poços petrolíferos

Cementing operations are conducted at different times of the well s life and they have high importance, because the functions are fundamental to keep good properties during a long life of the well, such as, maintain the mechanical stability of the well, to promote the isolation hydraulic and support the tubing. In some situations, the rocky zones have low fractures pressures and require the use of lightweight slurries to prevent the hydrostatic pressure in the formation is greater than the pressure of fracture. There are three ways to reduce the density of cement slurries: exterders water additives, microspheres and foamed slurries. The most used extender water additive is sodium bentonite, which is a clay with a good capacity of water absorption and expansion of its volume, the main disadvantage of this additive is the reduction of the strength. Currently, the use of nanoscale particles has received special attention, mainly because they get new functionalities. Following this trend, this paper aims to use a colloidal solution of nano-silica as an exterders water additives for use in oil wells. Slurries were designed with fixed 13lb/gal density and concentration of nano silica 0.1 gpc; 0.4 gpc; 0.7 and 1gpc, the influence of nano-silica was studied at these levels in isolation and combined varying concentrations of CaCl2,. Tests including rheology, stability, strength, thickening time, porosity and permeability. Besides the API tests, microstructural characterizations were performed after 28 days of the slurries, X-ray diffraction (XRD) and scanning electron microscopy (SEM)

Influência da adição do NaCl e KCl em sistemas de pastas contendo sílica para poços de petróleo em zonas evaporíticas e carbonáticas

One of the major challenges faced nowadays by oil companies is the exploration of pre-salt basins. Thick salt layers were formed in remote ages as a consequence of the evaporation of sea water containing high concentrations of NaCl and KCl. Deep reservoirs can be found below salt formations that prevent the outflow of oil, thus improving the success in oil prospection. The slurries used in the cement operations of salt layers must be adequate to the properties of those specific formations. At the same time, their resulting properties are highly affected by the contamination of salt in the fresh state. It is t herefore important to address the effects of the presence of salt in the cement slurries in order to assure that the well sheath is able to fulfill its main role to provide zonal isolation and mechanical stability. In this scenario, the objective of the present thesis work was to evaluate the effect of the presence of NaCl and KCl premixed with cement and 40% silica flour on the behavior of cement slurries. Their effect in the presence of CO2 was also investigated. The rheological behavior of slurries containing NaCl and KCl was evaluated along with their mechanical strength. Thermal and microstructural tests were also carried out. The results revealed that the presence of NaCl and KCl affected the pozzolanic activity of silica flour, reducing the strength of the hardened slurries containing salt. Friedel´s salt was formed as a result of the bonding between free Cl- and tricalcium aluminate. The presence of CO2 also contributed to the degradation of the slurries as a result of a process of carbonation/bicarbonataion

Compósitos Portland-biopolímeros para cimentação de poços de petróleo

The oil production in mature areas can be improved by advanced recovery techniques. In special, steam injection reduces the viscosity of heavy oils, thus improving its flow to surrounding wells. On the other hand, the usually high temperatures and pressures involved in the process may lead to cement cracking, negatively affecting both the mechanical stability and zonal isolation provided by the cement sheath of the well. The addition of plastic materials to the cement is an alternative to prevent this scenario. Composite slurries consisting of Portland cement and a natural biopolymer were studied. Samples containing different contents of biopolymer dispersed in a Portland cement matrix were prepared and evaluated by mechanical and rheological tests in order to assess their behavior according to API (American Petroleum Institute) guidelines. FEM was also applied to map the stress distribution encountered by the cement at bottom bole. The slurries were prepared according to a factorial experiment plan by varying three parameters, i.e., cement age, contents of biopolymer and water-to-cement ratio. The results revealed that the addition of the biopolymer reduced the volume of free water and the setting time of the slurry. In addition, tensile strength, compressive strength and toughness improved by 30% comparing hardened composites to plain Portland slurries. FEM results suggested that the stresses developed at bottomhole may be 10 to 100 times higher than the strength of the cement as evaluated in the lab by unconfined mechanical testing. An alternative approach is proposed to adapt the testing methodology used to evaluate the mechanical behavior of oilwell cement slurries by simulating the confined conditions encountered at bottornhole

Desenvolvimento de sistemas de aditivos químicos para aplicação em cimentações de poços de petróleo

The primary cementing is an important step in the oilwell drilling process, ensuring the mechanical stability of the well and the hydraulic isolation between casing and formation. For slurries to meet the requirements for application in a certain well, some care in the project should be taken into account to obtain a cement paste with the proper composition. In most cases, it is necessary to add chemicals to the cement to modify its properties, according to the operation conditions and thus obtain slurries that can move inside the jacket providing a good displacement to the interest area. New technologies of preparation and use of chemicals and modernization of technological standards in the construction industry have resulted in the development of new chemical additives for optimizing the properties of building materials. Products such as polycarboxylate superplasticizers provide improved fluidity and cohesion of the cement grains, in addition to improving the dispersion with respect to slurries without additives. This study aimed at adapting chemical additives used in civil construction to be used use in oilwell cement slurries systems, using Portland cement CPP-Special Class as the hydraulic binder. The chemical additives classified as defoamer, dispersant, fluid loss controller and retarder were characterized by infrared absorption spectroscopy, thermogravimetric analyses and technological tests set by the API (American Petroleum Institute). These additives showed satisfactory results for its application in cement slurries systems for oil wells. The silicone-based defoamer promoted the reduction of air bubbles incorporated during the stirring of the slurries. The dispersant significantly reduced the rheological parameters of the systems studied. The tests performed with the fluid loss controller and the retarder also resulted in suitable properties for application as chemical additives in cement slurries

Chlorhexidine increases the longevity of in vivo resin-dentin bonds

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Myotoxic effects of mastoparan from Polybia paulista (Hymenoptera, Epiponini) wasp venom in mice skeletal muscle

In a previous study, we showed that the Polybia paulista wasp venom causes strong myonecrosis. This study was undertaken to characterize the myotoxic potency of mastoparan (Polybia-MPII) isolated from venom (0.25 mu g/mu l) and injected in the tibial anterior (TA) muscle (i.m.) of Balb/c mice. The time course of the changes was followed at muscle degenerative (3 and 24 h) and regenerative (3, 7, and 21 days) periods (n = 6) after injection and compared to matched controls by calculation of the percentage of cross-sectional area affected and determination of creatine kinase (CK) activity (n = 10). The results showed that although NIP was strongly myotoxic, its capacity for regeneration was maintained high. Since the extent of tissue damage was not correlated with the CK serum levels, which remained very low, we raised the hypothesis that the enzyme underwent denaturation by the peptide. Evidence suggested that MP induced the death of TA fibers by necrosis and apoptosis and had the sarcolemma as its primordial target. Given its amphiphilic polycationic nature and based on the vast spectrum of functions attributed to the peptide, we suggest that MP interaction with cell membrane impaired the phosphorylation of dystrophin essential for sarcolemma mechanical stability, and disturbed Ca2+ mobilization with obvious implications on sarcoplasmic reticulum and mitochondrial functioning. (c) 2007 Elsevier Ltd. All rights reserved.