Inhibition of Aluminum Alloy Corrosion in 0.5 M Nitric Acid Solution by 4-4-Dimethyloxazolidine-2-thione

The corrosion inhibition of Al-Alloy (Al2024) in 0.5 M nitric acid solution at 30 °C was achieved using 4-4-dimethyloxazolidine-2-thione (DMT) as a corrosion inhibitor. The electrochemical performance of the DMT was studied by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization measurements, and scanning electron microscopic study (SEM). The results indicated that DMT acts as an inhibitor for Al2024 in 0.5 M nitric acid. Polarization curves indicated that DMT was a mixed-type inhibitor. Inhibition efficiencies were observed to be increased with an increase in DMT concentration and attains approximately to 93.4% at 2 mM of DMT in 0.5 M nitric acid. The adsorption of DMT model on Al2024 surface obeyed in accordance with Langmuir adsorption isotherm model. The value of the free energy of adsorption ΔG _ads indicated that the adsorption of DMT molecule was a spontaneous process and was typical of physical and chemical adsorption.     

Feasibility of using various photovoltaic systems for window-type air-conditioning units under hot-arid climates

This paper reports on the feasibility of using various Photovoltaic (PV) systems namely; Grid PV (GPV), Stand-Alone PV (SAPV), Grid PV Wind (GPVW) and PV Wind (PVW) for supplying the power requirements of a window-type air-conditioning system or other small loads. It was found that the GPVW system is the best system to meet the load requirement of a window-type air-conditioning system under the climatic conditions of Oman with values ranging from $39,500 to $56,500 for the capital cost and $9,000 to $33,000 for the total net capital cost depending on the wind speed. These values are attractive for remote off grid applications.     

Estimating the uncertainty in the estimated mean area under the ROC curve of a classifier

This article considers the problem of binary classification and its assessment in a distribution-free approach. We estimate the area under the ROC curve (a more general performance metric than the error rate) of a classifier using a bootstrap-based estimator. We then use the method of the influence function to estimate the uncertainty of that estimate from the very same bootstrap samples. Monte Carlo trials show that small-sample estimates can be obtained with little bias.     

Robust wireless location over fading channels

This paper develops an estimation algorithm for the time and amplitude of arrival of a known transmitted sequence over a single-path fading channel. The algorithm is optimized to enhance robustness to fast channel fading and low signal-to-noise ratio (SNR) conditions, which are common in wireless location applications. The paper also presents a noise and fading bias correction technique for amplitude of arrival estimation that improves the estimation accuracy significantly. The proposed algorithm is then applied to the case of code-division multiple-access (CDMA) wireless location finding for which the paper gives simulation results that demonstrate significant estimation accuracy improvement over known algorithms.     

An implementation of distributed shared memory

Shared memory is a simple yet powerful paradigm for structuring systems. Recently, there has been an interest in extending this paradigm to non-shared memory architectures as well. For example, the virtual address spaces for all objects in a distributed object-based system could be viewed as constituting a global distributed shared memory. We propose a set of primitives for managing distributed shared memory. We present an implementation of these primitives in the context of an object-based operating system as well as on top of Unix.     

Diurnal changes in radionuclides uptake by phytoplankton in small scale ecosystems

A continuous release of cesium-134 and strontium-85 into a simulated river system was maintained for more than 3 weeks for the purpose of evaluating the influence of photosynthetic oxygen production on cesium and strontium uptake. The flow rates and radioisotope concentration were maintained at a constant input throughout the experiment.The flow through time in the model river system was 6 h. Samples were taken from various stations every 4 h over a 36 h time interval. Temperature, dissolved oxygen, as well as other routine measurements were made. Samples were processed for plankton count and radioactivity in both the suspended phytoplankton and the water.The uptake of ¹³⁴Cs by phytoplankton was related to diurnal photosynthetic production of oxygen and a linear relationship exists between rate of change in ¹³⁴Cs concentration and the rate of net photosynthetic oxygen production.     

Needle track seeding following percutaneous ethanol injection for treatment of hepatocellular carcinoma

We report two cases of needle track seeding in the subcutaneous tissue and intercostal muscles following percutaneous ethanol injection for the treatment of hepatocellular carcinoma. In one patient, tumor seeding was observed 11 months after a total of 12 alcohol injections, and in the other patient, tumor seeding was observed 30 months after a total of 18 alcohol injections. The cases reported in the literature are discussed.     

Soot formation in gas turbines using heavy fuels. 1

The aim of this study was to determine the impact of the broadening of fuel specifications on the performance of a gas turbine combustor, particularly on soot formation and oxidation, and flame tube durability. Tests were conducted with a fully-developed combustor system, the main measurements comprising total radiation, exhaust smoke and temperatures at different locations. Five fuels were used: kerosine, as aviation fuel; gas oil, as the current industrial gas turbine fuel and possible future aviation fuel; R25 (where 25 is the volume percentage of residual fuel oil in the blend with gas oil), as equivalent to crude oil now in use in many utility gas turbines; and also R50 and R70 to represent future heavier fuels. Combustor pressures were 0.3, 0.7 and 1.0 MPa. Inlet air temperatures were 313, 390 and 460 K. Primary zone air/fuel mass ratios were 12, 15 and 25. Total air/fuel ratios were 60 and 120. Attempts were made to develop a mathematical model of the soot formation-oxidation processes that occur in the system, and to include in the model some parameters to represent the change in fuel properties. In this paper, comparison of the soot formation predictions of the model with the experimental data is seen to be favourable, particularly at full power conditions.     

Purification of mitomycins produced by Streptomyces caespitosus

Mitomycins were fermentatively produced using certain agricultural raw by-products by Streptomyces caespitosus NRRL 2564. The excreted antibiotics were thoroughly extracted with ethyl acetate at pH 6.0–8.0. The ethyl acetate extract was extensively purified by paper and thin-layer chromatographic techniques. The most efficient solvent systems in the complete separation of mitomycins were water-benzene-methanol (2:1:1 by vol.) in the case of paper chromatography, while acetone-ligroin-n-octanol (5:5:2 by vol.) was suitable for silical gel and alumina thin-layer plates. Pure samples of mitomycins A, B and C were obtained by preparative thin-layer chromatography using the solvent system composed of acetone-ligroin-n-octanol (5:5:2 by vol.). The active principles of mitomycins A, B and C, when biologically assayed on Bacillus subtilis ATCC 6622, were 980, 955 and 1000 μg/mg respectively. Mitomycin A can be converted into mitomycin C by exposing thin-layer chromatograms to concentrated ammonia vapour for 20 min.     

New polyisobutylene-based model ionomers

Mechanical properties of tri-arm polyisobutylene based ionomers have been investigated. Number average molecular weights (¯M_n's) of the polymers were varied from 8,300 to 34,000. The ionomer of lowest ¯M_n (8,300) exhibits very low extension at break (～ 150%) while the others with ¯M_n's of 11,000, 14,000 and 34,000 show very high extensions, often exceeding 1,000%, and display relatively low permanent set and low hysteresis behavior. Since the ionic bonding is located exclusively at the chain ends, end-linked pseudo networks are formed due to coulombic attractions.At higher temperatures the coulombic interactions are weakened and the networks can be compression molded (～150°C).