The angioarchitecture of estrous, pseudopregnant and pregnant rabbit ovary as seen by scanning electron microscopy of vascular corrosion casts

Ovarian angioarchitecture was studied by scanning electron microscopy of vascular corrosion casts in estrous, pseudopregnant (stimulated with human chorionic gonadotropin) and pregnant rabbits. In all samples, the proper ovarian branch of the ovarian artery (ramus ovaricus) entered the ovarian hilus near the caudal pole of the organ and ran parallel to the major axis of the hilus. The extraovarian venous drainage was formed by several vessels emptying into a distal large vein. The ramus ovaricus exhibited various degrees of coiling and branched in the medulla. The coiling of the ramus ovaricus and its ramifications were maintained in all samples. A venous meshwork and/or flat vein branches closely enveloped the arterial coils found in the hilus and outer medulla. At this level numerous arteriovenous contacts were demonstrated in all samples. The coiled arteries, prior to entering the ovarian cortex, supplied several small peripheral follicles which were drained by the hilar veins. In the cortex the coiled arteries branched in numerous thin, straight or slightly undulated arterioles which supplied developing estrous follicles and pseudopregnant corpora lutea. The arterioles supplying the pregnant corpora lutea were long, large and tightly spiraled. The venous drainage followed the modifications of the arterial supply. These data demonstrate that ovarian cycle and pregnancy induced significant changes in the cortical vessels, which adapted their structure to the temporary functional needs of the recruited follicles or corpora lutea. Hilar and medullary vessels have permanent structures that may represent morphological devices for (a) a continuous control of the blood flow (spiral arteries) and (b) a local recirculation of endocrine products (arteriovenous contacts) comparable to the ”countercurrent mechanism” previously shown to operate in ovaries of other species, but not yet found in rabbits. Received: 19 June 1996 / Accepted: 7 October 1996     

Influence of Cr3+ on microbial cluster formation in biofilm and on steel corrosion

Pit corrosion of mild steel in seawater increased with Cr³⁺ concentration. SEM observations showed that increasing Cr³⁺ concentration caused microbes in biofilm on the steel surface to aggregate forming clusters. AFM images suggested that pit corrosion occurred largely on the mild steel surface between clusters, and only little corrosion on the surface covered by microbes.     

Toward an Active and Stable Catalyst for Oxygen Evolution in Acidic Media: Ti‐Stabilized MnO2

Catalysts are required for the oxygen evolution reaction, which are abundant, active, and stable in acid. MnO₂ is a promising candidate material for this purpose. However, it dissolves at high overpotentials. Using first‐principles calculations, a strategy to mitigate this problem by decorating undercoordinated surface sites of MnO₂ with a stable oxide is developed here. TiO₂ stands out as the most promising of the different oxides in the simulations. This prediction is experimentally verified by testing sputter‐deposited thin films of MnO₂ and Ti–MnO₂. A combination of electrochemical measurements, quartz crystal microbalance, inductively coupled plasma mass spectrometry measurements, and X‐ray photoelectron spectroscopy is performed. Small amounts of TiO₂ incorporated into MnO₂ lead to a moderate improvement in stability, with only a small decrease in activity. This study opens up the possibility of engineering surface properties of catalysts so that active and abundant nonprecious metal oxides can be used in acid electrolytes.     

Morphological and quantitative changes in paternal brood‐pouch vasculature during embryonic development in two Syngnathus pipefishes

Vascular corrosion casts of Syngnathus floridae and Syngnathus fuscus brood pouches were examined by scanning electron microscopy. Morphological and quantitative data on the vasculature of the paternal brood pouch during each stage of embryonic development were investigated to explore potential changes during brooding, to consider interspecific differences and to provide structural evidence for previously reported functional roles of the brood pouch. The brood pouches of both species are highly vascularized structures with cup‐like arrangements of brood‐pouch vasculature developing around each embryo shortly after fertilization and breaking down before fry release. The density and size of paternally derived blood vessels in contact with the embryos were found to be consistent for S. fuscus once this structure was established early in development. On the contrary, these vasculature measurements varied with early S. floridae brood stages when the embryo still relied heavily on the yolk sac. Diameter measurements of S. fuscus brood‐pouch blood vessels were also comparatively smaller during these early developmental stages, suggesting that the structural stability and opportunity for greater transport via slower blood flow may contribute to greater paternal allocation. This is the first study to document changes in brood‐pouch vasculature during specific stages of embryonic development, to show regression of this vasculature before fry release and to provide morphological data for two syngnathid species for which information on brood‐pouch physiology is available.     

Evaluation of water corrosion,scaling extent and heterotrophic plate count bacteria in asbestos and polyethylene pipes in drinking water distribution system

Corrosion and scaling is one of the most important factors influencing drinking water quality that cause health disorders and economic problems. The aim of this study was to evaluate these phenomena in two sources of surface (Makou city) and ground water (Khoy city) in water networks. Corrosion and scaling potential was surveyed by Langelier, Ryzener, aggressiveness, Larson and Puckorius Indices and with measuring water physical, chemical, and microbial parameters. Statistical paired samples t-test displayed significant difference in means value of Langelier, Ryzener, Puckorius indices between cold and warm seasons of the year in Khoy samples and significant difference in means value of Ryzener, Puckorius and aggressiveness indices between cold and warm seasons of the year in Makou samples (p-value <0.001). Heterotrophic plate count water samples investigated in two cold and hot seasons in Khoy were respectively 14 ± 16 cfu ml^?1 and 41 ± 26 cfu ml^?1 and in the town of Makou were 11 ± 7 cfu ml^?1 and 61 ± 29 cfu ml^?1, respectively. In terms of health impacts, corrosion in different mains is important, then providing proper measures for balancing water quality before entering to the network and substituting of mains to prevent economic and health problems are necessary.     

An assessment of the early stages of microfouling and corrosion of 70:30 copper nickel alloy in the presence of two marine bacteria

The early stages of bacterial settlement on 70:30 copper nickel alloy was followed by scanning electron microsocopy. Two strains of marine bacteria (Pseudomonas sp and Vibrio alginolyticus) isolated from polluted harbour sea water were used. The corrosion behaviour of the alloy was studied through corrosion potential measurements made in sterile and contaminated sea water. According to our results microbial colonisation of the metal surface occurs within the first 24 h for the two bacteria used. Well defined microbial colonies with localised corrosion underneath were seen by SEM after short periods of exposure. Corrosion attack seems to be closely related to passive film modification by the bacterial settlement.     

Anaerobic microbial activities including hydrogen mediated acetogenesis within natural gas transmission lines

Microbially influenced corrosion (MIC) is being increasingly recognised as a serious problem. To investigate the role of MIC, radiotracer activity and lipid biomass measurements were performed on samples from offshore and on‐shore natural gas transmission systems. These measurements evaluated the biomass and metabolism of microbial communities residing inside transmission pipelines. Aqueous and nonaqueous hydrocarbon samples from liquid separators, sludge catchers and nodules attached to pipe walls were aseptically recovered and inoculated into anaerobic tubes for radiotracer time course experiments or preserved with chloroform‐methanol for total lipid analyses. MPN enrichments and phospholipid biomass determinations estimated microbial populations of 10⁴—10⁷ cells per gram in several samples. General microbial metabolism was demonstrated by [l‐¹⁴C]acetate incorporation into lipids and by [¹⁴C]CO₂ production from [U‐¹⁴C]glucose. [¹⁴C]Acetate was slowly mineralised to ¹⁴CO₂ without significant methane production. [¹⁴C]Acetate was produced by fermentation of [¹⁴C]glucose, [¹⁴C]palmitate and by hydrogen mediated acetogenesis in the presence of [^I4C]CO₂. In one location acetogenesis from hydrogen and carbon dioxide accounted for 0–7 mmol.l^‐1 of acetate production per week. These results demonstrated that microorganisms could utilise natural gas impurities to produce organic acids. This activity could adversely affect the structural integrity (MIC) of high pressure natural gas pipelines.     

Microbiological influences in 'blue water' copper corrosion

AIMS: To investigate the influence of micro-organisms associated with copper corrosion on 'blue water' corrosion in drinking water. METHODS AND RESULTS: Laboratory rigs comprising of polycarbonate containers attached to annealed copper plumbing tubes were filled with Melbourne drinking water and sterilized by autoclaving. The copper tubes were inoculated with sterile or nonsterile extracts obtained from corroding copper and allowed to stand for 7 days. The extracts were drained and the tubes flushed and filled with sterile water from the rig. The water within the tubes was removed weekly for analysis and the tubes were refilled with freshly aerated water. The tube water sampled was analysed for pH, total copper and the presence of micro-organisms. Sterile rigs and rigs containing nonsterile water, both without tube inoculums, were used as controls. The results demonstrated that tubes inoculated with nonsterile corrosion extracts showed statistically higher copper release compared with the other rigs. Copper release as blue water was only observed after a lag period of 9 weeks. The internal surfaces of tubes releasing copper showed significant amounts of corrosion products and the presence of biofilm. Bacteria isolated from the corroding tubes included Acidovorax spp. and Sphingomonas sp. CONCLUSIONS: The results demonstrate a microbial role in blue water, as corrosion was induced in new copper tubes by exposure to nonsterile copper corrosion products. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential for micro-organisms present in corrosion products to initiate blue water corrosion presents significant implications for the management of corrosion in distribution systems.