Corrosion inhibition by fatty acid triazoles for mild steel in formic acid

5-Heptadec-8-enyl-4-phenyl-4H–[1,2,4] triazole-3-thiol (HPTT), 4-phenyl-5-undecyl-4H–[1,2,4] triazole-3-thiol (PUTT), and 5-dec-9-enyl-4-phenyl-4H–[1,2,4] triazole-3-thiol (DPTT) were synthesized and their influence on the inhibition of corrosion of mild steel in 20% formic acid was investigated by weight loss and potentiodynamic polarization techniques. The inhibition efficiency of these compounds was found to vary with their nature and concentration, temperature and immersion time. The values of activation energy and free energy of adsorption of the triazoles were calculated to investigate the mechanism of corrosion inhibition. Good inhibition efficiency (>90%) was found even at lower concentration (i.e., 25 ppm) in acid solution. The adsorption on mild steel surfaces was found to obey Temkin's adsorption isotherm. Potentiodynamic polarization results revealed that the compounds studied are mixed type inhibitors. Electrochemical impedance spectroscopy was also used to investigate the mechanism of the corrosion inhibition.     

In situ nucleic acid hybridization of cytokines in primary biliary cirrhosis: predominance of the Th1 subset

Primary biliary cirrhosis (PBC) is an autoimmune liver disease characterized by destruction of the intrahepatic bile ducts. It is generally believed that cellular immune mechanisms, particularly involving T cells, result in this bile duct damage. The relative strength of Th1 and Th2 responses has recently been proposed to be an important factor in the pathophysiology of various autoimmune diseases. In this study, we have attempted to identify the Th subset balance in PBC, by detection of cytokines specific to the two T-cell subsets, i.e., interferon gamma (IFN-gamma) for Th1 cells and interleukin-4 (IL-4) for Th2 cells. We analyzed IFN-gamma and IL-4 messenger RNA (mRNA) positive cells in liver sections from 18 patients with PBC and 35 disease controls including chronic active hepatitis C, extrahepatic biliary obstruction (EBO), and normal liver, using nonisotopic in situ hybridization and immunohistochemistry. Mononuclear cells expressing IFN-gamma and IL-4 mRNA were aggregated in inflamed portal tracts in PBC livers, but were rarely present in extrahepatic biliary obstruction, alcoholic fibrosis, or normal liver sections. The IFN-gamma and IL-4 mRNA positive cells in PBC livers were detected in significantly higher numbers than in control livers (P < .01). Moreover, IFN-gamma mRNA expression was more commonly detected than IL-4 expression in PBC livers, and the levels of IFN-gamma mRNA expression were highly correlated with the degree of portal inflammatory activity. IFN-gamma mRNA-positive cells were detected primarily around damaged bile ducts that were surrounded by lymphoid aggregates. The data indicate that Th1 cells are the more prominent T-cell subset in the lymphoid infiltrates in PBC.     

The free radicals--the hidden culprits--an update

Free radicals are normally produced as a by-product of cellular metabolism. Free radicals are capable of killing bacteria, damage biomolecules, provoke immune response, activate oncogens, cause atherogenesis and enhance ageing process. However, in healthy conditions nature has endowed human body with enormous antioxidant potential. Subtle balance exists between free radical generation and antioxidant defence system to cope with oxidative stress by various enzymes and vitamins at cellular level which prevent the occurrence of disease. However, factors tilting the balance in favour of excess free radicals generation lead to widespread oxidative tissue damage and diseases. Therefore, trouble starts when there is an excess of free radicals and the defence mechanism lags behind. Overwhelming production of free radicals in response to exposure to toxic chemicals and ageing may necessitate judicious antioxidant supplement to help alleviate free radical mediated damage.     

Surface modification of calcium carbonates studied by inverse gas chromatography and the effect on mechanical properties of filled polypropylene

Inverse gas chromatography (IGC) has been used to characterize the surfaces of a pure calcitic calcium carbonate as well as samples that had been treated with sodium polyacrylate and/or stearic acid. The dispersive components of the surface free energy for the pure material agreed well with related literature data. Polar contributions to the surface interactions with a range of probes were determined. The results show that the surface treatments reduced the polarities of the surfaces and that modification with stearic acid produced a non-polar, low-energy surface. Some mechanical properties of the polypropylene composites containing the modified calcium carbonates were found to correlate well with the filler surface energies. Copyright © 2004 Society of Chemical Industry     

Electrical conductivity,thermoelectric power and dielectric constant of a Gd2Ti2O7 single crystal

Electrical conductivity, thermoelectric power and dielectric constant of a Gd₂Ti₂O₇ single crystal have been studied in the temperature range 300–1000 K. Gd₂Ti₂O₇ is found to be an-type semiconductor with energy band gap 1.5 eV. It exhibits an extrinsic nature up to 675 K and an intrinsic nature above 675 K. The thermoelectric power increases with temperature in the region 300–675 K whereas it decreases with temperature in the region 675–1000 K. The dielectric constant increases slowly in the temperature range 300–675 K but this increase becomes fast in the temperature range 675–1000 K.     

Tunnel diode-loaded rectangular microstrip antenna for millimeter range

Theoretical investigations conducted for Ge tunnel diode-integrated rectangular patch antenna reveals that such an antenna exhibits frequency tunability with the bias voltage. The Ge tunnel diode-loaded patch can be operated in the millimeter range (51.042-54.013 GHz). The range of frequency obtainable for operation is 2971 MHz. The radiation pattern shows variation with the bias voltage and the radiated power, the beamwidth and the directivity vary inversely with the bias voltage. Thus, the Ge tunnel diode-loaded patch can be used to achieve electronic tuning (BW=5.66%) with the bias voltage.     

Nonlinear stress analysis of offshore pipelines during pickup operations

This paper presents a method of analyzing the stresses in a submarine pipeline as it is picked up off the sea floor by barge davits. A nonlinear large-deflection analysis is used and the pipeline is modeled as a series of finite beam segments from the ocean bottom on up. The governing equations are derived and the pipeline configuration satisfying known boundary conditions is determined by an initial-value approach using an iterativetype technique. Boundary conditions at the mudline are identified by modeling the pipeline resting on the ocean bed as a semi-infinite tensioned beam on an elastic foundation. The effects of a nonlinear stress-strain curve for the pipe material are included and both Ramberg-Osgood and Hutchinson formulations are considered. With the technique suggested, any given pickup procedure can be analyzed or a reliable procedure can be developed based on a given allowable pipe stress level and any desired improvement in the final configuration and/or stress levels may be achieved by a variation of the parameters involved. A practical example is examined to demonstrate the applicability of the analysis presented, which should provide a useful tool in either judging or developing a pickup procedure.