ENERGY HARVESTING MICROGENERATORS FOR BODY SENSOR NETWORKS

Body sensor networks have the potential to become an asset for personalizing healthcare delivery to patients in need. A key limitation for a successful implementation of body sensor networks comes from the lack of a continuous, reliable power source for the body-mounted sensors. The aim of this thesis is to model and optimize a micro-energy harvesting generator that prolongs the operational lifetime of body sensors and make them more appealing, especially for personalized healthcare purposes. It explores a model that is suitable for harvesting mechanical power generated from human body motions. Adaptive optimization algorithms are used to maximize the amount of power harvested from this model. Practicality considerations discuss the feasibility of optimization and overall effectiveness of implementing the energy harvester model with respect to body sensor power requirements and its operational lifetime

Extraction-spectrophotometric determination of nickel at microgram level in water and wastewater using 2-[(2-mercaptophenylimino)methyl]phenol

An extraction-spectrophotometric method for determination of nickel at sub ppm level using 2-[(2-mercaptophenylimino)methyl]phenol (MPMP) as the new extractant is described. The reagent reacts with nickel(II) at pH > 10 and form a 1:2 brown complex, which is extracted into chloroform. The complex has a maximum absorption at 421 nm with the molar absorptivity of 2.41 × 105 M-1 cm-1. Beer’s law is obeyed over the range of 0.011-0.30 µg mL-1. The Sandell’s sensitivity for 0.001 absorbance unit is 5.34 × 10-4 µg cm-2. The relative standard deviation at 0.018 µg mL-1 is 1.1 % (n = 8). The procedure was successfully applied to determination of nickel in wastewater and standard alloy and the accuracy was determined by recovery experiment, independent analysis by furnace-AAS, and analysis of a certified reference martial. KEY WORDS: Ni determination, Liquid-liquid extraction, Schiff bases, Spectrophotometry Bull. Chem. Soc. Ethiop. 2008, 22(3), 323-329

Determination of Lead and Cadmium in Different Samples by Flow Injection Atomic Absorption Spectrometry Incorporating a Microcolumn of Immobilized Ammonium Pyrrolidine Dithiocarbamate on Microcrystalline Naphthalene

A new flow injection on-line preconcentration system adapted to flame atomic absorption spectrometry (FAAS) for lead and cadmium determination at the µg L–1 level was developed. Ammonium pyrrolidine dithiocarbamate was immobilized on microcrystalline naphthalene and was used as sorbent material in microcolumn preparation. Deposition of lead and cadmium was effected by processing a standard or solution of analytes at pH = 2–9 on the column. Injection of 500 µL of ethanolic solution of acetic acid (0.5 mol L–1) and hydrochloric acid (0.25 mol L–1) served to elute the retained species to atomic absorption spectrometry (AAS). A sample volume of 25 mL resulted in preconcentration factors of 65 and 53 for lead and cadmium, respectively, and precision at 60 µg L–1 was 2.7 % and 3.6 % (RSD) for lead and cadmium, respectively. The procedure was applied to tap water, river water, sea water, pine leaf and human blood samples. The accuracy was assessed through recovery experiments and independent analyses by furnace AAS

Determination of Lead and Cadmium in Different Samples by Flow Injection Atomic Absorption Spectrometry Incorporating a Microcolumn of Immobilized Ammonium Pyrrolidine Dithiocarbamate on Microcrystalline Naphthalene

A new flow injection on-line preconcentration system adapted to flame atomic absorption spectrometry (FAAS) for lead and cadmium determination at the µg L–1 level was developed. Ammonium pyrrolidine dithiocarbamate was immobilized on microcrystalline naphthalene and was used as sorbent material in microcolumn preparation. Deposition of lead and cadmium was effected by processing a standard or solution of analytes at pH = 2–9 on the column. Injection of 500 µL of ethanolic solution of acetic acid (0.5 mol L–1) and hydrochloric acid (0.25 mol L–1) served to elute the retained species to atomic absorption spectrometry (AAS). A sample volume of 25 mL resulted in preconcentration factors of 65 and 53 for lead and cadmium, respectively, and precision at 60 µg L–1 was 2.7 % and 3.6 % (RSD) for lead and cadmium, respectively. The procedure was applied to tap water, river water, sea water, pine leaf and human blood samples. The accuracy was assessed through recovery experiments and independent analyses by furnace AAS

Effect of hydrogen on creep properties of SUS304 austenitic stainless steel

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A combined micromechanics/materials science approach to understanding high temperature hydrogen attack

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Mechanistic model for hydrogen accelerated fatigue crack growth in a low carbon steel

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Synthesis of a chitosan-based chelating resin and its application to the selective concentration and ultratrace determination of silver in environmental water samples

A novel chelating resin using chitosan as a base material, ethylenediamine-type chitosan, has been synthesized for the first time in the present study, and applied to the collection/concentration of ultratrace amounts of silver in environmental water samples. In the present study, ultratrace amounts of silver collected on the resin were eluted and determined by ICP-MS. The resin packed in a 1 mL mini column could adsorb silver selectively and quantitatively at a flow rate of 2 mL min(-1) in the wide pH range from 1 to 8, and silver adsorbed on the resin could be easily recovered by passing 1 M nitric acid as an eluent into the column. High adsorption capacity for silver at pH 5, 0.37 mmol mL(-1) of the resin, was achieved, and t(1/2) of the adsorption is less than 5 min. The effect of chloride on the collection of silver was examined by varying chloride concentrations from 10(-4) to 0.75 M; the results showed that the present resin can be used for the collection/concentration of ultratrace amounts of silver in natural waters, as well as seawater. To ensure the accuracy and the precision of the method, CASS-4 near shore seawater reference material from the NRCC has been analyzed. This is not a certified SRM for silver, but has been used for comparative silver analysis by several groups, who report very similar results to those that are reported here. The developed method using ethylenediamine-type chitosan resin gives 0.7 pg mL(-1) of the detection limit when 50-fold enrichment was used. The proposed method was successfully applied to the determination of silver in tap, river, and seawater samples

Salicylic acid functionalized silica-coated magnetite nanoparticles for solid phase extraction and preconcentration of some heavy metal ions from various real samples

A method for the preconcentration of trace heavy metal ions in environmental samples has been reported. The presented method is based on the sorption of Cu(II), Cd(II), Ni(II) and Cr(III) ions with salicylic acid as respective chelate on silica-coated magnetite nanoparticles. Prepared adsorbent was characterized by XRD, SEM, BET and FT-IR measurements. The metals content of the sorbed complexes are eluted using 4.0 mL of 1.0 mol L-1 nitric acid. The influences of the analytical parameters including pH, amount of solid phase and condition of eluting solution, the effects of matrix ions on the retention of the analytes were examined. The accuracy and precision of suggested method were tested by analyzing of certified reference materials. The detection limits (3Sb/m, N = 8) for Cu(II), Cd(II), Ni(II) and Cr(III) ions are 0.22, 0.11, 0.27 and 0.15 μg L-1, respectively, and the maximum preconcentration factor is 200. The method was successfully applied to the evaluation of these trace and toxic metals in various waters, foods and other samples