Microbial quality of hemodialysis water,a survey of six centers in Lagos,Nigeria

Patients with end‐stage kidney disease (ESRD) on maintenance hemodialysis (HD) are usually exposed to large volumes of dialysate, which is separated from patients' blood only by thin membrane of dialyzer. It is therefore essential to frequently monitor the quality of HD water to ensure that it meets the recommended standards. The objective of this study was to evaluate the microbial quality of HD water in Lagos, Nigeria. Four sets of pre‐ and post‐treatment water samples, 20 mL each, were collected from six HD centers in Lagos and tested for microbial contamination using the molten Tryptic soy agar in accordance with Association for Advancement of Medical Instrumentation (AAMI) and European Best Practice Guidelines (EBPG). Pyrogen tests were also conducted on pre‐ and post‐treatment samples using standard technique. Information on water treatment modalities, maintenance practices and quality control measures in each center were obtained using a questionnaire. All centers use treated water for HD purpose. None of the HD centers met EBPG/AAMI guidelines for microbial contaminants as the mean levels of Escherichia coli in both feed and treated water were 441.7 ± 87.90 and 168.5 ± 64.03, respectively. E. coli was the commonest organism isolated in both feed and treated water in all the centers. HD water quality is still a neglected problem in our environment and more efforts are required to ensure good water quality for HD purpose.     

Exploring biomass based carbon black as filler in epoxy composites: Flexural and thermal properties

Carbon blacks (CB), derived from bamboo stem (BS-CB), coconut shells (CNS-CB) and oil palm empty fiber bunch (EFB-CB), were obtained by pyrolysis of fibers at 700 °C, characterized and used as filler in epoxy composites. The results obtained showed that the prepared carbon black possessed well-developed porosities and are predominantly made up of micropores. The BS-CB, CNS-CB and EFB-CB filled composites were prepared and characterized using scanning electron microscope (SEM) and thermogravimetric analyzer (TGA). The SEM showed that the fractured surface of the composite indicates its high resistance to fracture. The CBs–epoxy composites exhibited better flexural properties than the neat epoxy, which was attributed to better adhesion between the CBs and the epoxy resin. TGA showed that there was improvement in thermal stability of the carbon black filled composites compared to the neat epoxy resin.     

Effects of pigeon pea and plantain starches on the compressional, mechanical, and disintegration properties of paracetamol tablets

A study has been made of the effects of pigeon pea starch obtained from the plant Cajanus cajan (L) Millisp. (family Fabaceae) and plantain starch obtained from the unripe fruit of Musa paradisiaca L. (family Musaceae) on the compressional, mechanical, and disintegration properties of paracetamol tablets in comparison with official corn starch BP. Analysis of compressional properties was done by using density measurements, and the Heckel and Kawakita equations, whereas the mechanical properties of the tablets were evaluated by using tensile strength (T--a measure of bond strength) and brittle fracture index (BFI--a measure of lamination tendency). The ranking for the mean yield pressure, P(y), for the formulations containing the different starches was generally corn < pigeon pea < plantain starch while the ranking for P(k), an inverse measure of the amount of plasticity, was pigeon pea < plantain < corn starch, which indicated that formulations containing corn starch generally exhibited the fastest onset of plastic deformation, whereas those formulations containing pigeon pea starch exhibited the highest amount of plastic deformation during tableting. The tensile strength of the tablets increased with increase in concentration of the starches while the Brittle Fracture Index decreased. The ranking for T was pigeon pea > plantain > corn starch while the ranking for BFI was corn > plantain > pigeon pea starch. The bonding capacity of the formulations was in general agreement with the tensile strength results. The disintegration time (DT) of the formulation increased with concentration of plantain and corn starches but decreased with concentration of pigeon pea starch. The general ranking of DT values was plantain < pigeon pea < corn starch. Notably, formulations containing pigeon pea starch exhibited the highest bond strength and lowest brittleness, suggesting the usefulness of pigeon pea starch in producing strong tablets with minimal lamination tendency. Plantain starch, on the other hand, would be more useful where faster disintegration of tablet is desired. The results show that the starches could be useful in various formulations depending on the intended use of the tablets with the implication that the experimental starches can be developed for commercial purposes.     

Rubber seed oil modified with maleic anhydride and fumaric acid and their alkyd resins as binders in water‐reducible coatings

Rubber seed oil (RSO) was modified with different amounts of maleic anhydride, and RSO alkyds (50% oil length) were modified to various extents by the incorporation of different amounts of maleic anhydride and fumaric acid. All the resins were evaluated as water‐reducible binders. Modification with maleic anhydride increased the acid and saponification values of RSO but reduced the iodine value. RSO modified with maleic anhydride exhibited lower amounts of volatile organic compounds (<20 g/L) than the corresponding RSO alkyds (34–87 g/L). The alkyd samples were superior to the modified RSO in chemical resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3256–3259, 2003     

Epoxidation and hydroxlation of rubber seed oil: one‐pot multi‐step reactions

Epoxidized and hydroxylated rubber seed oils were prepared by peroxyformic acid generated in situ by reacting formic acid and hydrogen peroxide with RSO, a renewable resource. The structural and physico‐chemical properties of RSO have been determined. The fatty acid composition showed a high content of polyunsaturated fatty acids. The modified products were characterized with regard to their structure and properties. The findings of this study revealed that both hydroxylated and epoxidized RSO can be prepared by one‐pot multi‐step reactions.     

Interface electrochemical corrosion behaviour of alclad Al–Zn–Mg–Cu–Cr Al alloy adhesively bonded with carbon fibre reinforced plastic stiffener

Abstract

Stiffening of Al alloy aircraft structures with carbon fibre reinforced plastic laminate called ‘patches’ is considered as a viable option to enhance fatigue life. Interface so created between the reinforcement and Al alloy structure is potential site for crevice corrosion attack. Therefore, studies were conducted to investigate the interface corrosion behaviour of peak and two-step aged Al–Zn–Mg–Cu–Cr alclad alloy with and without the patch and examine the possibility to control the interfacial attack with the addition of cerium chloride inhibitor exposed to 3·5 wt-% NaCl solution for the durations of 2 and 168 h. Electrochemical impedance spectroscopy revealed that the interface attack was significantly reduced by the addition of 1000 ppm cerium chloride. The response of the peak and two-step aged alloy for such an addition was further investigated and found that the alloy under step aged condition behaves better than that of the peak aged condition.     

Crack Propagation Behaviour in Thin Aluminium Alloy Sheet Repaired with Adhesively Bonded CFRP Patch

For reducing the crack tip stress intensity factor, adhesively bonded composite patches are employed for crack repair in thin structure. Experimental work was carried out to study environmental assisted cracking behaviour of crack repaired with single-sided bonded patch in aluminium alloy of 7xxx series in peak-aged condition. The observations were also made on crack in this alloy without any patch repair. The specimen developed for conducting the experiments simulated plane stress condition of thin structure. The patched and un-patched tensile test specimens were loaded simultaneously at constant load in the presence of 3.5% weight NaCl solution. The experimental set-up simulated the saline or corrosive environment. Aggressive effect of corrosion attack on crack due to anodic dissolution along with hydrogen embrittlement leading to faster crack growth in patched specimen was revealed compared to un-patched specimen. The present study is the improvement over similar researches carried out earlier in terms of design of test specimen under plane stress condition so as to obtain all the three regions of crack growth.     

Enhancing the Environmentally Assisted Cracking Resistance of Aircraft Quality Al Alloy of Type AA7075 Stiffened with Polymer Matrix Composite Using Cerium Chloride Inhibitor

This study explores a methodology to raise environmentally assisted cracking resistance of alclad Al–Zn–Mg–Cu (AA7075) alloy, used in aircraft structures, stiffened with polymer matrix composite asymmetric patch in order to suppress growth of fatigue cracks. Fracture mechanics studies of adhesively bonded center-pre-cracked Al alloy specimens having stiffeners were carried out in 3.5 wt% sodium chloride environment to understand the effect of cerium chloride inhibitor on the threshold stress intensity for stress corrosion cracking as well as the second-stage (steady-state) crack growth rate. It was observed that in the peak- and the two-step-aged tempers, the crack growth rate of the alloy reduced by two and a half, and four times, respectively, while the threshold stress intensity increased by 14–15% due to the addition of 1000 ppm of this inhibitor. The study offers a method to enhance significantly life of aging aircrafts stiffened with polymer matrix composite.     

Exploring isolated lignin material from oil palm biomass waste in green composites

Lignin obtained from oil palm biomass empty fruit bunches (EFB) fibers, has been used as curing agent in green epoxy composites. Epoxy–lignin composites, with varying lignin content (15%, 20%, 25% and 30%), reinforced with EFB fiber were prepared. The effect of EFB-based lignin on the mechanical, thermal and morphology properties of the composites were investigated and compared with the composites cured with isophorone diamine curing agent. The improved thermal stability and the observed microstructure of the fractured surface of the composites were attributed to good fiber–matrix interaction, induced by the curing agent. The epoxy composites cured with 25% lignin content proved to be a better matrix and gave optimum value compared with other formulations which was confirmed by its mechanical, thermal and morphological properties.