New phenothiazine dyes and pigments

The synthesis of three new azaphenothiazine ring systems and an evaluation of their use as intermediates for new dyes and pigments is described. 2-Amino-5-bromopyrazine-3[4H]-thione (11) was prepared and converted to the novel 1,4,6,9-tetraazaphenothiazine ring system. The reaction of 4,5-diaminopyrimidine-6[1H]-thione (15) with 2,3-dichloropyrazines gave the isomeric 1,4,6,8-tetraazaphenothiazine ring system, another new heterocycle in this series. With 2,3-dichloroquinoxaline a previously unknown tetracyclic tetraazaphenothiazine ring system was isolated in satisfactory yields. The properties and reactions of these new heterocyclic systems are presented. Mixed nitric and sulphuric acids convert them to their 5-sulphoxides. Structural assignments were based on chemical evidence and their UV, IR, NMR and mass spectra. Mechanistic pathways to these compounds are also proposed.     

Palm kernel shell as a lightweight aggregate for concrete

These concrete mixes of widely differing water/cement ratios were made using palm kernel shell as course aggregate. The properties tested include the physical properties of the shell, the compressive, flexural and tensile splitting strengths of the concrete. These properties were compared with those of similar concrete specimens made with crushed granite as course aggregate. Results of the tests suggest that palm kernel shell cannot produce concrete with compressive strength above 30 MPa. However, for concrete grade 25 and below, the material was found to compare favourably with other conventional aggregate such as crushed granite.     

Evaluation of the Effects of Corrosion on Fatigue Life of Clad Aluminum Alloy 2024-T3-Riveted Lap Joints with Acoustic Emission Monitoring

Corrosion affects the fatigue life of clad aluminum alloy-riveted lap joints, such as those found on an aircraft fuselage structure. Single-, double-, and triple-column-riveted lap joint specimens were fabricated and corroded in a Q-Fog accelerated corrosion chamber for five months using an ASTM G85-A5 prohesion test. Specimens were taken out of the chamber every 4?weeks, and the corrosion products which had been deposited on them were removed by immersion in concentrated nitric acid. For each corroded specimen, the mass loss with corresponding corrosion rate was determined. The specimens were fatigue loaded to failure on an MTS Universal Testing Machine with acoustic emission monitoring. Results indicate that exposure of lap joint specimens to this corrosive environment increased corrosion (mass loss), corrosion rate, and significantly reduced fatigue life. For a prolonged exposure in the corrosive environment, the fatigue life was reduced to zero, which has significant implication for aging aircraft. Acoustic emission monitoring successfully detected fatigue failure. Two failure modes, multisite crack damage and shear of the rivets, were observed.     

Electrochemical behavior of multifunctional graphene–polyimide nanocomposite film in two different electrolyte solutions

The effect of solvent on specific capacitance, bulk resistance, and charge/discharge capacity of graphene/polyimide composite films is studied by electrochemical methods. Composite films are synthesized by in situ condensation polymerization of poly (amic acid) in the presence of 50 wt % partly exfoliated graphene sheets followed by thermal curing at 250°C. Raman spectrum of the exfoliated graphene sheets show an increase in the ratio of I_D to I_G peak intensities from 0.167 to 0.222, suggesting increased defects in graphene basal planes. Electrochemical measurements carried out by using 0.4M potassium hexafluorophosphate (KPF₆) dissolved in propylene carbonate and N‐methylpyrrolidone at 25°C show that the composite system exhibits both pseudocapacitance and supercapacitance behaviors, with an average capacitance of 40 and 36.5 F g^?1, respectively. Bulk resistance of the composite obtained by using KPF₆–propylene carbonate electrolyte solution is 300% lower than that obtained in KPF₆–N‐methylpyrrolidone solution, with a fairly stable specific capacity of 85 μAhr g^?1, with 80% retention observed after 30 charge–discharge cycles. Fourier transform infrared spectroscopy measurements show shifts in the cyclic imide carbonyl peak from 1778 to 1774 cm^?1, which suggests that some form of interaction exists between the graphene and polyimide. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42673.     

Inhibition of CO2 corrosion of N80 carbon steel by carboxylic quaternary imidazoline and halide ions additives

The inhibition of the corrosion of N80 mild steel by 2-undecyl-1-1-ethylamino-1-ethylcarboxyl quaternary imidazoline (CQI) in CO₂-saturated 3% NaCl and 3% Na₂SO₄ solutions was studied using electrochemical methods. Inhibition efficiency increased with increase in CQI concentration and synergistically increased in the presence of halide ions. CQI inhibited the corrosion reaction by chemical adsorption on the metal/solution interface in halide free solutions and by a combination of chemical and coulombic attraction in the presence of halide ions. The adsorption characteristics of the inhibitor were approximated by Frumkin isotherm and El-Awady et al. kinetic–thermodynamic model.     

Carbon dioxide corrosion inhibition of N80 carbon steel in single liquid phase and liquid/particle two‐phase flow by hydroxyethyl imidazoline derivatives

CO₂ corrosion inhibition of N80 steel in liquid single‐phase and liquid/particle two‐phase flow by 2‐undecyl‐1‐hydroxyethyl imidazoline (HEI‐11) and 2‐undecyl‐1‐hydroxyethyl‐1‐hydroxyethyl quaternary imidazoline (HQI‐11) was investigated using weight loss, potentiodynamic polarization, EIS, and scanning electron microscope (SEM) techniques. The results show that the corrosion rate in the absence and presence of the imidazolines is strongly dependent on the flow condition and presence of entrained sand particles. The imidazolines function via a mixed‐type corrosion inhibition mechanism. The inhibition efficiencies of the imidazolines followed the trend HQI‐11 > HEI‐11 in all the systems studied. Inhibition mechanism has been discussed in relation to the polycentric adsorption sites on the imidazoline molecules.     

Lead and cadmium levels of commonly administered pediatric syrups in Nigeria: A public health concern?

Fifty different pediatric syrups were randomly sampled from patent medicine stores and pharmaceutical shops within Awka, in Anambra State between November 2007 and May 2008. Syrups were ashed before digestion using conc. aqua regia, HCl:HNO₃ (3:1) and lead and cadmium were assayed with AAS 205A. Results revealed that 60 and 98% of the sample size had lead and cadmium respectively. The lead levels ranged from 0.01 in chloroquine to 1.08 mg/l in magcid suspension. The highest level of cadmium was seen in magcid suspension with concentration of 2.45 mg/l while lowest concentration of 0.01 in emzolyn and colipan. About 41.2% of the locally made syrup had none detectable levels of lead while all the syrup had detectable levels of cadmium.Lead levels ranged from 0.01 mg/l in cadiphen manufactured in Dholka, India to 0.09 in maxiquine made in England. About 68.8% of the imported syrups of the imported syrups had non detectable levels of lead. Chloramphenicol and zentel albendazole syrups had 0.60 and 0.88 mg/l of cadmium respectively. Bellis cough syrup showed the lowest level (0.01 mg/l) of cadmium. Only erythromycin suspension representing 6.3% had non detectable level of cadmium of the imported syrups. Due to the Cd and Pb levels found, we suggest that the behaviour scenario (here, self administration without medical assistance) should be properly taken under control. Along with this, contamination sources or vulnerable practices during syrups preparation should be also assessed in a tiered approach, towards the minimization of noxious presence in syrups and the promotion of quality of Nigerian-made products.     

Nephrotic syndrome in Nigerian children with homozygous sickle cell disease

Two hundred and seventy two children with the nephrotic syndrome were seen and followed up at the Paediatric Renal Unit of the University of Nigeria Teaching Hospital, Enugu over 12 1/2 year period, between June 1983 and December 1995. Of these, there were nine (3.3%) children with homozygous sickle cell disease (SS). This latter group had a mean age of 9.6 +/- 3.2 years, male to female ratio of 1:2 and serum cholesterol of 3.13 +/- 1.48 mmol/l at the time of diagnosis. The mortality rate was 55.6% in these sicklers, death occurring within one and a half to five years of diagnosis. Causes of death were attributable to sickle cell disease in 60%, renal diseases in 20%, and other causes in 20%. Renal biopsy in two of the sicklers showed membrano-proliferative glomerulonephritis (MPGN) and focal glomerulosclerosis (FGS) respectively. Homozygous sickle cell disease does seem to predispose to the development of the nephrotic syndrome and those that do develop nephrotic syndrome exhibit some special characteristics, when compared to non-sicklers with nephrotic syndrome. These include older age of onset of the nephrotic syndrome, reverse sex ratios, lower serum cholesterol, higher mortality rate and sickle cell complications rather than chronic renal failure as the major cause of death.