Sulphate-reducing bacteria associated with biocorrosion: a review

Biocorrosion means any process of corrosion in wich microorganisms are somehow involved. As far as the petroleum industry is concerned, the anaerobic type is the more important, with Sulphate-Reducing Bacteria (SRB) accouting for half of the described processes. SRB are obligate anaerobs that use sulphur, sulphate or other oxidized sulphur compounds as oxidizing agents when decomposing organic material. A typical product of SRB metabolism, hydrogen sulphide -H2S-, is extremely toxic. In the present work we review the literature on mechanisms underlying biocorrosive process in wich SRB are involved and summarize some of the ultrastructural and eletrochemical work developed using SRB obtained from water injection flow in wells located on PETROBRAS offshore marine plataforms, sampled directly in the field over metallic probes, or cultured under laboratory conditions. Biofilms develop when SRB adhere to inert surfaces. A high diversity of morphological types is found inside these biofilms. Their extracellular matrix is highly hydrated and mainly anionic, as shown by its avid reaction with cationic compounds like ruthenium red. We have noted that variations in iron contet lead to interesting changes in the ultrastructure of the bacterial cell coat and also in the rate of corrosion induced in metallic test cupons. Since routine methods to prevent and treat SRB contamination and biodeterioration involve the use of biocides that are toxic and always have some environmental impact, an accurate diagnosis of biocorrosion is always required prior to a treatment decision. We developed a method that detects and semi-quantifies the presence of living or dead SRB by using free silver potentials as an indicator of corrosive action by SRB-associated sulphides. We found a correlation between sulphide levels (determined either by spectrophotometry, or using a silver electrode -E(Ag)- that measured changes in free potentials induced by the presence of exogeneously added sulphide) and SRB concentration (enumerated by a culturing method). E (Ag) was characterized under a variety of conditions andwas found to be relatively immune to possible interference resulting from aeration of media or from the psence of iron corrosion products. The method offers a simple, rapid, and effective means of diagnosing biocorrosive processes prior to their control.

Behavior study of pipes after forming, coating and bending

A study of the main types of coatings and its processes that modern industry commonly apply to prevent to the corrosion due to the environmental effects to energetic market pipelines have been done. Extracting main time and temperature range values, coating heat treatment recreation have been applied to x65 pipelines steel grade samples obtained from a pipe which was formed using UOE forming process. Experimental tensile tests and Charpy V‐Notch Impact test have been carried out for a deeply knowledge of the influence on the steel once this recreations are applied. The Yield Strength and toughness have been improved despite lower values in rupture strain and ductile‐brittle temperature transition have been obtained. Finite Element Method have been applied to simulate the entirely pipe cold bending process to predict the mechanical properties and behaviour of the pipe made from x65 steel grade under different conditions.

Repair of schistosomal intestinal vascular lesions after curative treatment

The process of repairing intestinal vascular lesions induced by schistosomiasis in mice was studied before and after curative chemotherapy, by means of histopathology coupled with injections of the mesenteric veins with India ink or plastic, in this case followed by corrosion in strong acid. The granulomas were avascular, mainly formed while within blood vessels, and were associated with distortion of the intestinal vasculature in their proximity, represented by tortuosities, focal dilatation, narrowing, and anastomosis of the mucosal and submucosal veins. Two to four months after cure of schistosomiasis involuting granulomas were seen to be slowly vascularized, a process going from the periphery toward the center of the granulomas. No intravascular granulomas were seen four months after treatment. The previously distorted mucosal and submucosal veins gradually regained their normal appearance, only a slight tortuosity remaining.

Early Carboniferous age of the Versoyen ophiolites and consequences: non-existence of a "Valais ocean'' (Lower Penninic, western Alps)

Ophiolites occur at several places in the Lower Penninic of the W and Central Alps. They are generally ascribed to oceanic crust of a so-called ``Valais ocean'' of Cretaceous age which plays a fundamental role in many models of Alpine paleogeography and geodynamics. The type locality and only observational base for the definition of a ``Valais ocean'' in the W Alps is the Versoyen ophiolitic complex, on the French-Italian boundary W of the Petit St-Bernard col. The idea of a "Valais ocean'' is based on two propositions that are since 40 years the basis for most reconstructions of the Lower Penninic: (1) The Versoyen forms the (overturned) stratigraphic base of the Cretaceous-Tertiary Valais-Tarentaise series; and (2) it has a Cretaceous age. We present new field and isotopic data that severely challenge both propositions. (1) The base of the Versoyen ophiolite is a thrust. It overlies a wildflysch with blocks of Versoyen rocks, named the Mechandeur Formation. This ``supra-Tarentaise'' wildflysch has been confused with an (overturned) stratigraphic transition from the Versoyen to the Valais-Tarentaise series. Thus the contact Versoyen/Tarentaise is not stratigraphic but tectonic, and the Versoyen ophiolite has no link with the Valais basin. This thrust corresponds to an inverse metamorphic discontinuity and to an abrupt change in tectonic style. (2) The contact of the Versoyen complex with the overlying Triassic-Jurassic Petit St-Bernard (PSB) series is stratigraphic (and not tectonic as admitted by all authors since 50 years). Several types of sedimentary structures polarize it and show that the PSB series is younger than the Versoyen. Consequently the Versoyen ophiolitic complex is Paleozoic and forms the basement of the PSB Mesozoic sediments. They both belong to a single tectonic unit, named the Versoyen-Petit St-Bernard nappe. (3) Ion microprobe U-Pb isotopic data on zircons from the main gabbroic intrusion in the Versoyen complex give a crystallization age of 337.0 +/- 4.1 Ma (Visean, Early Carboniferous). These zircons show typical oscillatory zoning and no overgrowth or corrosion. and are interpreted to date the Versoyen magmatism. These U-Pb data are in excellent agreement with our field observations and confirm the Paleozoic age of the Versoyen ophiolite. The existence of a ``Valais ocean'' of Cretaceous age in the W Alps becomes very improbable. The eclogite facies metamorphism of the Versoyen-Petit St-Bernard nappe results from an Alpine intra-continental subduction, guided by a Paleozoic oceanic suture. This is an example of the lone term influence of inherited deep-seated structures on a Much younger orogeny. This might well be a major cause of of the inherent complexity of the Alps.

Remodeling of hepatic vascular changes after specific chemotherapy of schistosomal periportal fibrosis

Hepatosplenic schistosomiasis was the first human disease in which the possibility of extensive long standing hepatic fibrosis being degraded and removed has been demonstrated. When such changes occurred, the main signs of portal hypertension (splenomegaly, esophageal varices) progressively disappeared, implying that a profound vascular remodeling was concomitantly occurring. Hepatic vascular alterations associated with advanced schistosomiasis have already been investigated. Obstruction of the intrahepatic portal vein branches, plus marked angiogenesis and compensatory hyperplasia and hypertrophy of the arterial tree are the main changes present. However, there are no data revealing how these vascular changes behave during the process of fibrosis regression. Here the mouse model of pipestem fibrosis was used in an investigation about these vascular alterations during the course of the infection, and also after treatment and cure of the disease. Animals representing the two polar hepatic forms of the infection were included: (1) "isolated granulomas" characterized by isolated periovular granulomas sparsely distributed throughout the hepatica parenchyma; and (2) 'pipestem fibrosis' with periovular granulomas and fibrosis being concentrated within portal spaces, before and after treatment, were studied by means of histological and vascular injection-corrosion techniques. Instances of widespread portal vein obstruction of several types were commonly found in the livers of the untreated animals. These obstructive lesions were soon repaired, and completely disappeared four months following specific treatment of schistosomiasis. Treatment was accomplished by the simultaneous administration of praziquantel and oxamniquine. The most impressive results were revealed by the technique of injection of colored masses into the portal system, followed by corrosion in strong acid. The vascular lesions of non-treated pipestem fibrosis were represented in the plastic casts by considerable diminution of the fine peripheral portal vein radicles, plus dilatation of periportal collaterals. Four months after treatment, this last picture appeared replaced by tufts of newly interwoven vessels formed along the main portal vein branches, disclosing a strong angiomatoid reparative change. Understanding about the cellular elements at play during fibro-vascular repairing changes of hepatic schistosomiais represents a matter of considerable scientific and conceptual importance. At present time one may only speculate about the participation of some type of natural stem-cell capable of restoring the diseased liver back to normal once the cause of the disorder has been eliminated.

Angiogenesis in Wounds Treated by Microdeformational Wound Therapy.

BACKGROUND:: Mechanical forces play an important role in tissue neovascularization and are a constituent part of modern wound therapies. The mechanisms by which vacuum assisted closure (VAC) modulates wound angiogenesis are still largely unknown. OBJECTIVE:: To investigate how VAC treatment affects wound hypoxia and related profiles of angiogenic factors as well as to identify the anatomical characteristics of the resultant, newly formed vessels. METHODS:: Wound neovascularization was evaluated by morphometric analysis of CD31-stained wound cross-sections as well as by corrosion casting analysis. Wound hypoxia and mRNA expression of HIF-1α and associated angiogenic factors were evaluated by pimonidazole hydrochloride staining and quantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Vascular endothelial growth factor (VEGF) protein levels were determined by western blot analysis. RESULTS:: VAC-treated wounds were characterized by the formation of elongated vessels aligned in parallel and consistent with physiologically function, compared to occlusive dressing control wounds that showed formation of tortuous, disoriented vessels. Moreover, VAC-treated wounds displayed a well-oxygenated wound bed, with hypoxia limited to the direct proximity of the VAC-foam interface, where higher VEGF levels were found. By contrast, occlusive dressing control wounds showed generalized hypoxia, with associated accumulation of HIF-1α and related angiogenic factors. CONCLUSIONS:: The combination of established gradients of hypoxia and VEGF expression along with mechanical forces exerted by VAC therapy was associated with the formation of more physiological blood vessels compared to occlusive dressing control wounds. These morphological changes are likely a necessary condition for better wound healing.

CD36 deficiency leads to choroidal involution via COX2 down-regulation in rodents.

BACKGROUND: In the Western world, a major cause of blindness is age-related macular degeneration (AMD). Recent research in angiogenesis has furthered the understanding of choroidal neovascularization, which occurs in the "wet" form of AMD. In contrast, very little is known about the mechanisms of the predominant, "dry" form of AMD, which is characterized by retinal atrophy and choroidal involution. The aim of this study is to elucidate the possible implication of the scavenger receptor CD36 in retinal degeneration and choroidal involution, the cardinal features of the dry form of AMD. METHODS AND FINDINGS: We here show that deficiency of CD36, which participates in outer segment (OS) phagocytosis by the retinal pigment epithelium (RPE) in vitro, leads to significant progressive age-related photoreceptor degeneration evaluated histologically at different ages in two rodent models of CD36 invalidation in vivo (Spontaneous hypertensive rats (SHR) and CD36-/- mice). Furthermore, these animals developed significant age related choroidal involution reflected in a 100%-300% increase in the avascular area of the choriocapillaries measured on vascular corrosion casts of aged animals. We also show that proangiogenic COX2 expression in RPE is stimulated by CD36 activating antibody and that CD36-deficient RPE cells from SHR rats fail to induce COX2 and subsequent vascular endothelial growth factor (VEGF) expression upon OS or antibody stimulation in vitro. CD36-/- mice express reduced levels of COX2 and VEGF in vivo, and COX2-/- mice develop progressive choroidal degeneration similar to what is seen in CD36 deficiency. CONCLUSIONS: CD36 deficiency leads to choroidal involution via COX2 down-regulation in the RPE. These results show a novel molecular mechanism of choroidal degeneration, a key feature of dry AMD. These findings unveil a pathogenic process, to our knowledge previously undescribed, with important implications for the development of new therapies.

Effects of triamcinolone acetonide on vessels of the posterior segment of the eye.

PURPOSE: This study investigates the effects of triamcinolone acetonide (TA) on retinal endothelial cells in vitro and explores the potential vascular toxic effect of TA injected into the vitreous cavity of rats in vivo. METHODS: Subconfluent endothelial cells were treated with either 0.1 mg/ml or 1 mg/ml TA in 1% ethanol. Control cells were either untreated or exposed to 1% ethanol. Cell viability was evaluated at 24 h, 72 h, and five days using the tetrazolium 3-(4,5-dimethylthiazol-2-yl)-2,5 phenyltetrazolium bromide test (MTT) and lactate dehydrogenase (LDH) assays. Cell proliferation was evaluated by 5-bromo-2-deoxyuridine (BrdU) test. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling assay (TUNEL assay), annexin-binding, and caspase 3 activation. Caspase-independent cell deaths were investigated by immunohistochemistry using antibodies against apoptosis inducing factor (AIF), cytochrome C, microtubule-associated protein (MAP)-light chain 3 (MAP-LC3), and Leukocyte Elastase Inhibitor/Leukocyte Elastase Inhibitor-derived DNase II (LEI/L-DNase II). In vivo, semithin and ultrathin structure analysis and vascular casts were performed to examine TA-induced changes of the choroidal vasculature. In addition, outer segments phagocytosis assay on primary retinal pigment epithelium (RPE) cells was performed to assess cyclooxygenase (COX-2) and vascular endothelial growth factor (VEGF) mRNAs upregulation with or without TA. RESULTS: The inhibitory effect of TA on cell proliferation could not explain the significant reduction in cell viability. Indeed, TA induced a time-dependent reduction of bovine retinal endothelial cells viability. Annexin-binding positive cells were observed. Cytochrome C was not released from mitochondria. L-DNase II was found translocated to the nucleus, meaning that LEI was changed into L-DNase II. AIF was found nuclearized in some cells. LC3 labeling showed the absence of autophagic vesicles. No autophagy or caspase dependent apoptosis was identified. At 1 mg/ml TA induced necrosis while exposure to lower concentrations for 3 to 5 days induced caspase independent apoptosis involving AIF and LEI/L-DNase II. In vivo, semithin and ultrathin structure analysis and vascular casts revealed that TA mostly affected the choroidal vasculature with a reduction of choroidal thickness and increased the avascular areas of the choriocapillaries. Experiments performed on primary RPE cells showed that TA downregulates the basal expression of COX-2 and VEGF and inhibits the outer segments (OS)-dependent COX-2 induction but not the OS-dependent VEGF induction. CONCLUSIONS: This study demonstrates for the first time that glucocorticoids exert direct toxic effect on endothelial cells through caspase-independent cell death mechanisms. The choroidal changes observed after TA intravitreous injection may have important implications regarding the safety profile of TA use in human eyes.

Field Evaluation of Elliptical Fiber Reinforced Polymer Dowel Performance, June 2005

Fiber reinforced polymer (FRP) composite materials are making an entry into the construction market in both buildings and pavements. The application to pavements so far has come in the form of joint reinforcement (dowels and tie bars). FRP resistance to salt corrosion in dowels has made it an alternative to standard epoxy-coated steel dowels for pavements. Iowa State University has completed a large amount of laboratory research to determine the diameter, spacing, and durability of FRP dowels. This report documents the performance of elliptical FRP dowels installed in a field situation. Ten joints were monitored in three consecutive test sections, for each of three dowel spacings (10, 12, and 15 inches) including one instrumented dowel in each test section. The modulus of dowel bar support was determined using falling weight deflectometer (FWD) testing and a loaded crawl truck. FWD testing was also used to determine load transfer efficiency across the joint. The long-term performance and durability of the concrete was also evaluated by monitoring faulting and joint opening measurements and performing visual distress surveys at each joint. This report also contains similar information for standard round, medium elliptical, and heavy elliptical steel dowels in a portion of the same highway. In addition, this report provides a summary of theoretical analysis used to evaluate joint differential deflection for the dowels.

Sustainable Development and Concrete Technology, May 2004

For a variety of reasons, the concrete construction industry is not sustainable. First, it consumes huge quantities of virgin materials. Second, the principal binder in concrete is portland cement, the production of which is a major contributor to greenhouse gas emissions that are implicated in global warming and climate change. Third, many concrete structures suffer from lack of durability which has an adverse effect on the resource productivity of the industry. Because the high-volume fly ash concrete system addresses all three sustainability issues, its adoption will enable the concrete construction industry to become more sustainable. In this paper, a brief review is presented of the theory and construction practice with concrete mixtures containing more than 50% fly ash by mass of the cementitious material. Mechanisms are discussed by which the incorporation of high volume of fly ash in concrete reduces the water demand, improves the workability, minimizes cracking due to thermal and drying shrinkage, and enhances durability to reinforcement corrosion, sulfate attack, and alkali-silica expansion. For countries like China and India, this technology can play an important role in meeting the huge demand for infrastructure in a sustainable manner.

Field Evaluation of Elliptical Fiber Reinforced Polymer Dowel Performance, June 2003

Fiber composite materials (FRP) are making an entry into the construction market in both buildings and pavements. The application to pavements comes in the form of joint reinforcement (dowels and tie bars) to date. FRP resistance to salt corrosion in dowels has made it an alternative to standard epoxy coated dowels for pavements. Iowa State University has completed a large amount of laboratory research into the determination of diameter, spacing, and durability of FRP dowels. This report documents the installation of a series of FRP elliptical-shaped dowel joints (including instrumented units) in a field situation and the beginning of a two-year study to compare laboratory results to in-service pavements. Ten joints were constructed for each of three dowel spacings of 10, 12, and 15 inches ( 254, 305, and 381 mm) with one instrumented joint in each test section. The instrumented bars will be load tested with a loaded truck and FWD testing.

Laboratory Study of Structural Behavior of Alternative Dowel Bars, April 2006

Load transfer across transverse joints has always been a factor contributing to the useful life of concrete pavements. For many years, round steel dowels have been the conventional load transfer mechanism. Many problems have been associated with the round steel dowels. The most detrimental effect of the steel dowel is corrosion. Repeated loading over time also damages joints. When a dowel is repeatedly loaded over a long period of time, the high bearing stresses found at the top and bottom edge of a bar erode the surrounding concrete. This oblonging creates multiple problems in the joint. Over the past decade, Iowa State University has performed extensive research on new dowel shapes and materials to mitigate the effects of oblonging and corrosion. This report evaluates the bearing stress performance of six different dowel bar types subjected to two different shear load laboratory test methods. The first load test is the AASHTO T253 method. The second procedure is an experimental cantilevered dowel test. The major objective was to investigate and improve the current AASHTO T253 test method for determining the modulus of dowel support, k0. The modified AASHTO test procedure was examined alongside an experimental cantilever dowel test. The modified AASHTO specimens were also subjected to a small-scale fatigue test in order to simulate long-term dowel behavior with respect to concrete joint damage. Loss on ignition tests were also performed on the GFRP dowel specimens to determine the resin content percentage. The study concluded that all of the tested dowel bar shapes and materials were adequate with respect to performance under shear loading. The modified AASHTO method yielded more desirable results than the ones obtained from the cantilever test. The investigators determined that the experimental cantilever test was not a satisfactory test method to replace or verify the AASHTO T253 method.

A morphometric study of mechanotransductively induced dermal neovascularization.

BACKGROUND:: Mechanical stretch has been shown to induce vascular remodeling and increase vessel density, but the pathophysiologic mechanisms and the morphologic changes induced by tensile forces to dermal vessels are poorly understood. METHODS:: A custom computer-controlled stretch device was designed and applied to the backs of C57BL/6 mice (n = 38). Dermal and vascular remodeling was studied over a 7-day period. Corrosion casting and three-dimensional scanning electron microscopy and CD31 staining were performed to analyze microvessel morphology. Hypoxia was assessed by immunohistochemistry. Western blot analysis of vascular endothelial growth factor (VEGF) and mRNA expression of VEGF receptors was performed. RESULTS:: Skin stretching was associated with increased angiogenesis as demonstrated by CD31 staining and vessel corrosion casting where intervascular distance and vessel diameter were decreased (p < 0.01). Immediately after stretching, VEGF dimers were increased. Messenger RNA expression of VEGF receptor 1, VEGF receptor 2, neuropilin 1, and neuropilin 2 was increased starting as early as 2 hours after stretching. Highly proliferating epidermal cells induced epidermal hypoxia starting at day 3 (p < 0.01). CONCLUSIONS:: Identification of significant hypoxic cells occurred after identification of neovessels, suggesting an alternative mechanism. Increased expression of angiogenic receptors and stabilization of VEGF dimers may be involved in a mechanotransductive, prehypoxic induction of neovascularization.

Estudio sobre la resistencia quimica de baldosas ceramicas no-esmaltadas para pavimentos industriales

The chemical resistance of ceramic tiles is the subject of the European Standard UNE-EN ISO 10545-13. In order to evaluate the effect of aqueous solutions of several chemicals agents on the aspect of the tile surface, this standard establishes a series of tests at room temperature followed by visual inspection. According to this standard the tiles of this study are classified as being of maximum resistance (UHA). However operating conditions can be more aggressive than those detailed in the standard. So, a systematic study has been undertaken. In the present work, the effect of aqueous solutions of several organic and inorganic acids on the tile surface is evaluated. Samples immersed in different solutions are subjected to the following conditions: T= 60º C; pH=2 and to agitation processes. Visual analysis, as well as optical microscopy and scanning electron microscopy (SEM) were performed in order to determine the possible variation of the superficial aspect of tiles. Moreover, atomic absorption spectrophotometry has been used in order to obtain quantitative information concerning the solubility of system M (III)-L (M= Fe; L= H2O or L= ligand). The results obtained show, in all cases, a progressive dissolution of iron oxide precipitates presents in the ceramic body

Structural characterization of laser-treated Cr3C2-NiCr coatings

The interconnected porosity of the Cr3C2-NiCr coatings obtained by high-velocity oxy fuel spraying is detrimental in corrosion and wear resistance applications. Laser treatments allow sealing of their surfaces through melting and resolidification of a thin superficial layer. A Nd:YAG laser beam was used to irradiate Cr3C2-NiCr coatings either in the continuous wave mode or at different repetition rates in the pulsed one. Results indicated that high peak and low mean laser irradiances are not good, since samples presented deep grooves and an extensive crack network. At low peak and higher mean laser irradiances the surface was molten, and only a few shallow cracks were observed. The interconnected porosity was completely eliminated in a layer up to 80 m thick, formed by large Cr7C3 grains imbedded in a NiCr matrix.