Polarography of eosin and erythrosin in solutions of varying pH at the DME

The polarographic behaviour of eosin and erythrosin in buffer solutions of pH 4–11 is discussed. The observed waves are assigned to the reduction of furan and pyrone rings of the molecule of erythrosin at pH 4–11 and for eosin at pH ?7. The nature of the waves is also investigated. In alkaline media the electrode reaction is essentially diffusion controlled whereas at pH < 8 adsorption of the reduction products contributes in the electrodes process.     

Stability of spontaneous passive films on high strength Mo-containing stainless steels in aqueous solutions

The stability of naturally grown passive films on some Mo-containing stainless steel specimens was examined in aerated and deaerated universal buffer solutions with different pH (2–12) as well as in sulphate and chloride solutions. Open circuit potential (E _oc) and electrochemical impedance spectroscopy (EIS) were used as measuring techniques. In all cases, E _oc shifts towards less negative values with time until the potential reaches its steady-state (E _ss) value. The E _ss value is found to be more positive with decrease in solution pH or increase in Mo content in the alloy and becomes less positive in deaerated buffer solutions. Also, the thickening rate of the outer layer for the duplex passive film increases with increasing extent of Mo in the steel substrate or pH of the test solution. For a given alloy, E _ss decreases linearly with the anion concentration (C), and is always more positive in Cl⁻ than in SO₄²⁻ media for C ≥ 0.05 M. Analysis of the EIS data showed that the total resistance (R _T) of the passive film has higher values in aerated solutions, and is generally lower in basic solutions. This indicates that lower solution pH favours the formation of oxide films offering better protection. Furthermore, the higher values of R _T in Na₂SO₄ solutions suggest the formation of more stable passive films in sulphate than in chloride solutions. This is discussed on the basis of the relative degree of anion incorporation into the passive films.     

Radar topography data reveal drainage relics in the eastern Sahara

The Shuttle Radar Topographic Mission (SRTM) elevation data reveal segments of inactive drainage channel systems in the eastern Sahara. Four sites are investigated and their drainage networks are delineated and compared with processed Synthetic Aperture Radar (SAR) and Enhanced Thematic Mapper Plus (ETM+) images. These include parts of the drainage lines that lead to the Kufra Oasis in Libya; the eastern Gilf Kebir drainage system that straddles the border region between Egypt and Sudan; the lower reach of Wadi Howar, the extinct western Nile tributary in Sudan; and a reversed flow channel of Wadi Kubbaniya northwest of Aswan in Egypt. These features are delineated using SRTM data and a Geographic Information System (GIS) hydrologic routine. The results show that the SRTM signals penetrate the desert‐sandy surfaces and map ancient drainage systems in the same way as SAR. The study also demonstrates that SRTM data can be used to confirm or modify pathways of channel courses mapped from radar images alone. Because of this capability, it is also recommended that SRTM data be used in place of GTOPO30 elevation data in hydrologic modelling of sand‐covered deserts.     

Effect of tempering on the toughness of a Cr- Mo bainitic steel

The effect of tempering on impact and fracture toughness properties of a Cr-Mo bainitic steel was studied in the quenched and stress relieved (Q & SR) condition. The lowest tempering parameter used resulted in considerable improvement in impact properties. Further tempering increased the upper shelf energy, had a minor effect on the transition temperature, and increased both the initiation fracture toughness (J_IC) and the tearing modulus(T). However, the effect on J_IC andT was much greater than the effect on the impact upper shelf energy. The results were discussed in light of the changes in microstructure and flow properties due to tempering.     

Mechanism of the polarographic reduction of some sulphonphthaleins in aqueous and alcoholic buffers

The polarographic reduction of cresol red, thymol blue, bromo-cresol purple, bromophenol blue and bromocresol green are studied in buffered aqueous solutions and alcohol—water mixtures of pH 2–11.5. It was found that in solutions of pH values ? 10 the five depolarizers are reduced along two one-electron waves of equal heights. In solutions of pH values <7, bromo-cresol purple and bromophenol blue are reduced through a single two-electron wave. Whereas cresol red, thymol blue and bromo-cresol green are reduced in two one-electron steps. Medium and substituent effects on i₁ and E_{$\text{1}\text{2}$} are discussed.     

The electrochemical behavior of Sn–Ag binary alloys in sulfate solutions

The corrosion and passivation behavior of four binary xSn–Ag (x = 26, 50, 70, and 96.5 wt%) alloys and their pure metal components was investigated in sodium sulfate solutions using electrochemical techniques. The influence of two different electrolytic parameters, namely, concentration (0.01–1.0 M ) and pH (3.0–11.0) were studied while the specimens were potentiodynamically polarized between ?1000 and 500 mV versus saturated calomel electrode (SCE). The results showed that the corrosion current density (i_corr) increases with increasing either the tin content in the alloy or the ions concentration in the electrolyte. Increasing the pH value of a constant composition sulfate solution was found to improve the corrosion resistance of the tin‐richer alloys (x = 50–96.5 wt%), and decreases a little the stability of the silver‐rich one (74 wt% Ag). Impedance measurements at the free corrosion potential (E_corr) give good support for these results, where a small addition of tin to silver up to the intermetallic ratio (x = 26 wt%) gives an alloy with better corrosion resistance to the aggressive sulfate medium. In terms of the tin ratio, the order of surface film stability on the tested samples, generally follows the ranking: 26 > 96.5 > 50 > Ag > 70 > Sn. The good corrosion resistance of the tin‐rich alloy (x = 96.5 wt%), surpassing those for the pure constituents tin and silver can be attributed to the homogenous phase structure of this eutectic mixture.     

Optic disc detection from normalized digital fundus images by means of a vessels' direction matched filter

Optic disc (OD) detection is a main step while developing automated screening systems for diabetic retinopathy. We present in this paper a method to automatically detect the position of the OD in digital retinal fundus images. The method starts by normalizing luminosity and contrast through out the image using illumination equalization and adaptive histogram equalization methods respectively. The OD detection algorithm is based on matching the expected directional pattern of the retinal blood vessels. Hence, a simple matched filter is proposed to roughly match the direction of the vessels at the OD vicinity. The retinal vessels are segmented using a simple and standard 2-D Gaussian matched filter. Consequently, a vessels direction map of the segmented retinal vessels is obtained using the same segmentation algorithm. The segmented vessels are then thinned, and filtered using local intensity, to represent finally the OD-center candidates. The difference between the proposed matched filter resized into four different sizes, and the vessels' directions at the surrounding area of each of the OD-center candidates is measured. The minimum difference provides an estimate of the OD-center coordinates. The proposed method was evaluated using a subset of the STARE project's dataset, containing 81 fundus images of both normal and diseased retinas, and initially used by literature OD detection methods. The OD-center was detected correctly in 80 out of the 81 images (98.77%). In addition, the OD-center was detected correctly in all of the 40 images (100%) using the publicly available DRIVE dataset.     

Drivers and barriers to adopting EDI: a sector analysis of UK industry

This paper presents the results of research comparing the effects of Electronic Data Interchange (EDI) on seven UK industry sectors. The sectors investigated were retail, manufacturing, distribution, utilities, pharmaceutical, government and services. The analysis focuses in particular on similarities and differences in the implementation process and examines the difficulties experienced and benefits achieved by the various industry sectors. Further, the level of EDI integration with internal business processes is investigated. A framework is described which is based on a survey, a case study of successful EDI implementation and interviews with both service providers and users. It provides a potential tool for practitioners covering important aspects of EDI implementation and integration.