| 1. |
- Asrat, Daniel, et al.
(författare)
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Prevalence of Helicobacter pylori vacA and cagA genotypes in Ethiopian dyspeptic patients
- 2004
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Ingår i: Journal of Clinical Microbiology. - 1098-660X. ; 42:6, s. 2682-2684
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Tidskriftsartikel (refereegranskat)abstract
- A total of 300 gastric biopsy samples and 50 Helicobacter pylori isolates were collected from Ethiopian adult dyspeptic patients. The vacA and cagA genes were detected in 90 and 79% of biopsy specimens, respectively, and in 100 and 87% of clinical isolates, respectively. Both genes were detected in 84% of the gastric biopsy samples and in 87% of the clinical isolates. Among vacA genotypes, the s1/m1 genotype was the most common in gastric biopsy samples (48%). The vacA and cagA positive H. pylori strains were detected to a higher degree in patients with chronic active gastritis (71%) than patients with other histopathological findings (29%) (P < 0.05).
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| 2. |
- Burks, Terrance, 1969-
(författare)
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Application of Nanomaterials for the Removal of Hexavalent Chromium and their Biological Implications
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The International Agency for Research on Cancer (IARC) stated that chromium in the form of Cr(VI) has been deemed to be a class-A human carcinogen. It has been a major contaminant associated with wastewater. Moreover, the existence of heavy metals in aquatic systems is a critical concern for the environment as well as industries that manufacture or consume these particular elements. In order to remove these particular toxic metals, several well-known conventional methods including ion-exchange, filtration and adsorption are used. Amongst these methods, adsorption offers significant advantages such as the low-cost materials, ease of operation and efficiency in comparison to the other conventional methods.The aim of this work was to develop nanomaterials (particles and fibers) to address some critical issues for the treatment of heavy metals, especially chromium in aqueous systems. Furthermore, the use of nanomaterials and how they relate to nanoscale operations at the biological level has generated considerable concerns in spite of their novel properties.The first part of this thesis deals with the synthesis and characterizations of Fe3O4, magnetite, as nanoparticles which were further coated with surfactants bis(2,4,4-trimethylpentyl)dithiophosphinic acid, Cyanex-301, and 3-Mercaptopropionic acid with the active compound being the thiol (SH) groups, that will suffice as a viable material for Cr(VI) removal from aqueous solutions. The proposed mechanism was the complexation between the thiol group on Cyanex-301 and 3-Mercaptopropionic acid, respectively. The effect of different parameters on the adsorption including contact time, initial and final Cr(VI) ion concentration and solution pH was investigated.The second part of this thesis encompassed the fabrication of flexible nanocomposite materials, with a large surface area and architecture for the removal of Cr(VI) in batch and continuous flow mode. A technique known as electrospinning was used to produce the nanofibers. The flexible yet functional materials architecture has been achieved by growing ZnO nanorod arrays through chemical bath deposition on synthesized electrospun poly-L-lactide nanofibers. Moreover, polyacrylonitrile nanofibers (PAN) were synthesized and adapted by the addition of hydroxylamine hydrochloride to produce amidoxime polyacrylonitrile nanofibers (A-PAN). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to identify the morphologies and particle sizes whereas Fourier-Transform Infrared spectroscopy (FT-IR) was used to identify either the presence or absence of functional groups for the formation of PAN and A-PAN nanofibers. The optimization of functionalized nanoadsorbents to adsorb Cr(VI) was also carried out to investigate the effect of experimental parameters: contact time, solution pH, initial, final and other metal ion concentration. Commercially manufactured pristine engineered (TiO2, ZnO and SiO2) nanoparticles and lab-made functionalized (Fe3O4 and CeO2) nanoparticles were studied while the powders were suspended in appropriate media by Dynamic Light Scattering (DLS) to identify their cytotoxicity effects.
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| 3. |
- Burks, Terrance, et al.
(författare)
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ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI)
- 2015
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Ingår i: Journal of Environmental and Public health. - : Hindawi Publishing Corporation. - 1687-9805 .- 1687-9813. ; 2015
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Tidskriftsartikel (refereegranskat)abstract
- Nanomaterials of ZnO-PLLA nanofibers have been used for the adsorption of Cr(VI) as a prime step for the purification of water.The fabrication and application of the flexible ZnO-PLLA nanofiber nanocomposite as functional materials in this well-developedarchitecture have been achieved by growing ZnO nanorod arrays by chemical bath deposition on synthesized electrospun poly-Llactidenanofibers. The nanocomposite material has been tested for the removal and regeneration of Cr(IV) in aqueous solutionunder a “continuous flow mode” by studying the effects of pH, contact time, and desorption steps.Theadsorption of Cr(VI) speciesin solution was greatly dependent upon pH. SEM micrographs confirmed the successful fabrication of the ZnO-PLLA nanofibernanocomposite.Theadsorption and desorption of Cr(VI) species were more likely due to the electrostatic interaction between ZnOand Cr(VI) ions as a function of pH.The adsorption and desorption experiments utilizing the ZnO-PLLAnanofiber nanocompositehave appeared to be an effective nanocomposite in the removal and regeneration of Cr(VI) species.
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| 4. |
- Bursell, Martin, et al.
(författare)
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La0.6Ca0.4CoO3, La0.1Ca0.9MnO3 and LaNiO3 as bifunctional oxygen electrodes
- 2002
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Ingår i: Electrochimica Acta. - 0013-4686 .- 1873-3859. ; 47:10, s. 1651-1660
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Tidskriftsartikel (refereegranskat)abstract
- A series of perovskite catalysts was investigated for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte and at room temperature, supplied by oxygen or air. A meniscus cell was used to screen-test candidate catalysts for their bifunctionality and assess their activity for ORR at 3 mm depth of immersion (DOI) in the electrolyte. Based on the meniscus data LaNiO3, La0.1Ca0.9MnO3 and La0.6Ca0.4CoO3 were selected for further assessment in microelectrode and half-cell studies. Activity tests for the ORR and OER, Tafel slopes at high current densities and apparent activation energies for the ORR were determined using a microelectrode technique on samples of the selected perovskites, La0.1Ca0.9MnO3, La0.6Ca0.4CoO3 and LaNiO3 with and without graphite support. Tafel slopes of ca. 120 mV per decade and apparent activation energies of approximately 18 kcal mol(-1) were measured at high cathodic current densities. Cycle-life and performance of La0.1Ca0.9MnO3, La0.6Ca0.4CoO3 and LaNiO3-based gas-diffusion electrodes in half-cell configurations were tested at a constant current density of 25 mA cm(-2) With subsequent and intermittent polarizations. Similar activities resulted in the ORR, while increased numbers of cycles were observed for the La0.1Ca0.9MnO3-based electrode. Furthermore, electrode material compositions, especially PTFE contents were optimized to conform to the establishment of the three phase interactions of the electrode structure, Transmission Electron microscopy (TEM) and BET-surface area analyses were carried out in order to find out the morphological and surface properties of the perovskite materials.
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| 5. |
- Caetano de Souza, Antonio Carlos, et al.
(författare)
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A low cost & safe system of hydrogen production utilizing NaBH4 and CoO catalysis
- 2007
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Ingår i: 2nd International Congress University-Industry Cooperation (UNIDU07).
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Konferensbidrag (refereegranskat)abstract
- The objective of this study was to evaluate the hydrogen production through hydrolysisof sodium borohydride (NaBH4) utilizing catalysts containing CoO. The reactant is safe and stable(when dry) at room temperature. Few works and studies have presented results of investigationsutilizing catalysts containing cobalt; however utilizing catalysts containing CoO were not found yet.In this work simple and cheap hydrogen generation system was developed having reactions atnormal conditions of temperature and pressure. A solution containing a gravimetric composition of10% wt. NaOH, 10% wt. NaBH4 and 80% wt. H2O was utilized. The reaction was carried out atvarious times using the same catalyst to evaluate its performance. This catalyst presented highrates of hydrogen production, especially at its start-up (about 99% of the theoretical hydrogenvolume was produced) at room temperature. After start-up, e.g., when more solution was put, rateof hydrogen production decreased having its production performance also decreased. Probablythis fact occurred due to the formation of the solid phase products such as NaBO2 which might fillthe porous catalyst structure; decreasing the catalytic area. This catalyst is suggested in situationswhere high production rates are necessary such as start-up of fuel cells.
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| 6. |
- Caetano de Souza, Antonio Carlos, et al.
(författare)
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Hydrogen production through hydrolysis of NaBH4: The use of catalysts containing Pt and Pt-Ru
- 2007
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Ingår i: 2nd International Congress University-Industry Cooperation (UNIDU07).
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Konferensbidrag (refereegranskat)abstract
- Several works about hydrolysis of NaBH4 utilizing various catalysts (such as catalysts containing Pt or Ru) are available in the literature. Investigations involving NaBH4 has increased due to the possibility to produce hydrogen using simple and safe systems, even at room temperatures with very high efficiencies. A solution containing a gravimetric composition of 10%wt. NaOH, 10%wt. NaBH4 and 80%wt. H2O was utilized and the reaction was initiated immediately as soon as this solution was put in the chosen catalysts, in this case, catalysts containing Pt and mixtures of Pt-Ru. Catalysts containing Pt and Pt-Ru presented high yields of hydrogen after the solution being inserted in the reaction vessel several times. In this study it was found out that the rates of hydrogen production were increased with catalysts containing Pt and Pt-Ru (99 and 96% of theoretical hydrogen production respectively). The catalysts containing Pt presented higher production rate, while the catalysts containing the mixed Pt-Ru presented a quasi-linear production, e.g., stable production rate.
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| 7. |
- Chamoun, Mylad, et al.
(författare)
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Bifunctional Performance of Flow Assisted Rechargeable Iron-Air Alkaline Batteries
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Low cost rechargeable iron-air alkaline batteries have all essential attributes to adapt for large scale energy storage applications. To actualize this implementation needs to overcome the challenges including poor efficiency and short cycle lifetime. Herein, suitable synthesized catalysts for the air electrode were investigated prior to iron-air cell testing. NiCo2O4 as sole catalyst proved exceptional bifunctional OER/ORR activity and stability over 440 h operation in air. This catalyst fitted into an electrolyte and oxygen flow assisted rechargeable iron-air prototype and performed stable over 588 h and had an energy density of 377 Wh kg-1 Fe. Inadequate coulombic efficiencies of 75 – 85% and energy efficiencies around 50% hurt the performance of the cell though and needed further development. Nevertheless, the findings in this work reports the opportunities and obstacles of the rechargeable iron-air battery.
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| 8. |
- Chamoun, Mylad, et al.
(författare)
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Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.
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| 9. |
- Dong, Hanwu, et al.
(författare)
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An air-metal hydride battery using MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) in the anode and a perovskite in the cathode
- 2010
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 35:9, s. 4336-4341
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen storage alloy MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) (MH) was tested as anode material in a metal hydride-air cell. The cathode was a non-noble metal air electrode based on a mixture of perovskite and pyrolyzed macrocycles on carbon. Polarization and discharge capacities of the electrodes were measured and compared at 22 degrees C and 40 degrees C using air or oxygen at the cathode. Discharge capacity reaching 330 mAh/g MH with pure oxygen at 40 degrees C and 305 mAh/g MH with air at 22 degrees C were obtained. Power densities and/or energy densities were found to significantly depend on the increase of the electrode kinetics on both the ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction). However, for air electrode, an increase of oxygen concentration by using pure oxygen gas plays a more important role than an 18 degrees C temperature increase. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
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| 10. |
- Endalew, Abebe K., et al.
(författare)
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Heterogeneous catalysis for biodiesel production from Jatropha curcas oil (JCO)
- 2011
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 36:5, s. 2693-2700
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Tidskriftsartikel (refereegranskat)abstract
- This work focuses on the development of heterogeneous catalysts for biodiesel production from high free fatty acid (FFA) containing Jatropha curcas oil (KO). Solid base and acid catalysts were prepared and tested for transesterification in a batch reactor under mild reaction conditions. Mixtures of solid base and acid catalysts were also tested for single-step simultaneous esterification and transesterification. More soap formation was found to be the main problem for calcium oxide (CaO) and lithium doped calcium oxide (Li-CaO) catalysts during the reaction of jatropha oil and methanol than for the rapeseed oil (RSO). CaO with Li doping showed increased conversion to biodiesel than bare CaO as a catalyst. La(2)O(3)/ZnO, La(2)O(3)/Al(2)O(3) and La(0.1)Ca(0.9)MnO(3) catalysts were also tested and among them La(2)O(3)-ZnO showed higher activity. Mixture of solid base catalysts (CaO and Li-CaO)and solid acid catalyst (Fe(2)(SO(4))(3)) were found to give complete conversion to biodiesel in a single-step simultaneous esterification and transesterification process. (C) 2011 Elsevier Ltd. All rights reserved.
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