Mechanistic Leak-Detection Modeling for Single Gas-Phase Pipelines: Lessons Learned from Fit to Field-Scale Experimental Data

The use of pipelines is one of the most popular ways of delivering gas phases as shown by numerous examples in hydrocarbon transportation systems in Arctic regions, oil and gas production facilities in onshore and offshore wells, and municipal gas distribution systems in urban areas. A gas leak from pipelines can cause serious problems not only because of the financial losses associated but also its social and environmental impacts. Therefore, establishing an early leak detection model is vital to safe and secure operations of such pipeline systems.A leak detection model for a single gas phase is presented in this study by using material balance and pressure traverse calculations. The comparison between two steady states, with and without leak, makes it possible to quantify the magnitude of disturbance in two leak detection indicators such as the change in inlet pressure (ΔPin) and the change in outlet flow rate (Δqout) in a broad range of leak locations (xleak) and leak opening sizes (dleak). The results from the fit to large-scale experimental data of Scott and Yi (1998) show that the value of leak coefficient (CD), which is shown to be the single-most important but largely unknown parameter, ranges from 0.55 to 4.11, and should be a function of Reynolds number (NRe) which is related to leak characteristics such as leak location (xleak), leak opening size (dleak), leak rate (qleak) and system pressure. Further investigations show that between the two leak detection indicators, the change in outlet flow rate (Δqout) is superior to the change in inlet pressure (ΔPin) because of larger disturbance, if the pressure drop along the pipeline is relatively small compared to the outlet pressure; otherwise, the change in inlet pressure (ΔPin) is superior to the change in outlet flow rate (Δqout).Key words: Leak; Leak detection modeling; Pipeline; Leak coefficient; Gas flow in pip

Canine liver transplantation under nva cyclosporine versus cyclosporine

The immunosuppressive qualities and other features of a new cyclosporine (CsA) analogue, Nva 2-cyclosporine (Nva 2-CsA) were examined using canine orthotopic liver allografts. The mean survival time was 11.8±9.6 (SD) days in dogs without treatment, 60.8±34.4 days with Nva 2-CsA and 65.1±33.0 days with CsA. Functional abnormalities indicating toxic side effects were not noted either with Nva 2-CsA or with CsA. Using the same oral dose, the rate of blood level rise and the amount of the rise were greater with Nva2-CsA. Histopathologically, Nva2-CsA the treatment was associated with the same degree of hydropic vocuolation in the pars recta of the proximal tubules as CsA treatment. Thus, in the dog, Nva2-CsA had identical immunosuppressive properties as CsA, with no functionally detectable toxicity affecting the liver and kidney. © 1986 by The Williams & Wilkins Co

Low flow venovenous bypasses in small dogs and pediatric patients undergoing replacement of the liver

A venovenous bypass for transplantation of the liver was developed and evaluated in dogs and applied clinically, with flows that averaged less than 500 milliliters per minute. Fatal pulmonary emboli were seen in two of 40 experiments. The venovenous flow in the four pediatric recipients was 200 to 1,200 milliliters per minute, and there were no complications

Different response to epidermal growth factor of hepatocytes in cultures isolated from male or female rat liver. Inhibitor effect of estrogen on binding and mitogenic effect of epidermal growth factor

Deoxyribonucleic acid (DNA) synthesis in hepatocytes isolated from the livers of male and female rats has been compared in monolayer culture. Plating efficiency, DNA and protein content, viability, and morphologic appearance were the same in cultures prepared with hepatocytes isolated from male or female rats. Epidermal growth factor (EGF)-induced DNA synthesis was significantly higher in hepatocytes from male rats than in hepatocytes from female rats. This was the case whether hepatocytes were isolated from normal or partially hepatectomized male or female rats. Hepatocytes isolated from regenerating liver synthesize more DNA than those isolated from normal liver in response to EGF. This increased response to EGF in hepatocytes derived from regenerating liver was relatively the same for male- and female-derived hepatocytes, but the magnitude of the response was considerably higher in male-derived hepatocytes. In contrast, in vivo DNA synthesis in the liver remnant after partial hepatectomy was similar in male and female rats if measured 24 h after the operation. A comparison of EGF binding to male- and female-derived hepatocytes maintained in primary culture indicated a lower number of high-affinity receptors for EGF in the female hepatocytes. The addition of estrogen to primary cultures of hepatocytes isolated from male rats inhibited EGF binding as well as EGF-induced DNA synthesis. Our studies show significant differences in DNA synthesis in response to EGF when male and female hepatocytes are compared in primary culture. The regenerative response after partial hepatectomy, on the other hand, was the same in male and female rats. Thus, our studies indicate that the sex of the donor rat is important when hepatocytes in culture are used for a variety of studies, such as hepatocyte metabolism, induction and control of DNA synthesis, and hepatocarcinogenesis. In addition, our results indicate that caution is advised when inferences are made from in vitro findings for in vivo conditions. © 1987

Heavy metal removal from aqueous solutions by sorption using natural clays from Burkina Faso

The acid-base properties of two raw and purified mixed clays from Burkina Faso were studied, as well as their potential to remove copper(II), lead(II) and chromium(III), and thereby their ability to be used to purify water from heavy metals. The purification procedure of the clays involved removal of carbonates, iron oxides and organic matter. A determination of the elemental composition of the mixed clays revealed the presence of aluminum, iron and silicon as main constituents. The high alkaline pH in one of the samples is attributable to the presence of carbonate in the raw clay. The point of zero charge (pHpzc) values of the clays, as determined by potentiometric titrations, were 6.79 and 9.52 for the raw clays, while after purification they were 6.87 and 6.76, respectively. Metal adsorption to the clay surfaces started at pH values below pHpzc, strongly indicating formation of inner-sphere complexes. With contact time of 48 h, complete removal of copper(II) was achieved at pH 8 for all samples. More than 90% of the lead(II) removal was attributed to adsorption while for chromium(III), it was 85%. Adsorption to organic matter and iron oxides, and precipitation of metal hydroxides gave significant contributions to the removal of metal ions in aqueous systems.Key words: Mixed clays, potentiometric titration, heavy metals, pHpzc

Reversible Metal-Semiconductor Transition of ssDNA-Decorated Single-Walled Carbon Nanotubes

A field effect transistor (FET) measurement of a SWNT shows a transition from a metallic one to a p-type semiconductor after helical wrapping of DNA. Water is found to be critical to activate this metal-semiconductor transition in the SWNT-ssDNA hybrid. Raman spectroscopy confirms the same change in electrical behavior. According to our ab initio calculations, a band gap can open up in a metallic SWNT with wrapped ssDNA in the presence of water molecules due to charge transfer.Comment: 13 pages, 6 figure