Infrared and photocatalytic studies of model bacterial species for water treatment

The use of a CO2 infrared (IR) laser and photocatalysis for water treatment microorganism disinfection purposes was investigated. During CO2 infrared (IR) laser treatment E. cloacae inactivation was comparable to inactivation via ultraviolet (UV) treatment; however no inactivation of the more resistant B. subtilis endospores occurred. Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy of the bacterial cells displayed increased polysaccharide contents after IR treatment. FTIR and Raman spectroscopy of simple carbohydrates before and after IR laser treatment displayed no spectral changes, with the exception of N-acetyl-D-glucosamine (NAG), which was partially attributed to sampling techniques. E. cloacae inactivation during IR treatment was attributed to localised and overall temperature increases within the water. Due to the inability to inactivate B. subtilis endospores this technique is not suitable for water treatment purposes. Photocatalytic water treatment using novel TiO2 colloids prepared via a postsynthetic microwave-modification process (MW-treated) was also examined. These colloids were characterised using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses and compared to Degussa P25 and convection hydrothermally-treated (HT-treated) TiO2. Slurry suspensions displayed comparable E. coli inactivation rates, so the colloids were examined in immobilised form using both a model organic degradant, oxalic acid, and E. coli. Oxalic acid degradation studies showed that the MW-treated colloids displayed similar inactivation rates to the HT-treated TiO2, due to their pure anatase composition, while Degussa P25 displayed higher inactivation rates. Investigations into the effect of shortening UV wavelength were also performed. Degussa P25 was the only catalyst which displayed higher apparent quantum yields upon shortening the UV wavelength, which was attributed to its mixed-phase anatase-rutile composition. As E. coli inactivation was observed using distilled water, photocatalysis in natural river water was trailed. It was discovered that the pH had to be lowered from 7.5 to 5.0 and the initial cell concentration must be approximately 1 x 103 colony forming units (CFU) per cm3 or less for inactivation to be observed during a 5 hour treatment period. At a catalyst loading of 1.0 mg per cm2, Degussa P25 absorbed all the applied UVA irradiation; however the MW- and HT-treated TiO2 colloids did not due to their smaller particle size. Therefore sandwich experiments were devised to evaluate the effect of unabsorbed UV irradiation within the system. Small colony variants were identified after photocatalytic and UV treatment, which pose a potential threat to public health. Further investigation of the different TiO2 colloids was performed using in situ FTIR, both with and without an applied potential and compared to a thermally prepared TiO2 catalyst. The latter displayed potential dependent photocatalysis, while the mesoporous TiO2 catalysts displayed potential independent photocatalysis. All catalyst types displayed increased degradation rates upon the application of a positive bias, which was followed in situ via the production of CO2. Sodium oxalate and NAG was examined for photocatalytic degradation, both of which were degraded to CO2, with proposed break-down products identified when using NAG

MEASURES TO REDUCE THE HIGH INCIDENCE OF STRUCTURAL FAILURES IN NIGERIA

Within the last few decades, Nigeria has been experiencing a great transformation in terms of population growth and the provisions of developmental facilities for the wellbeing of the masses. The built environmental sector was not left out in the process. This is because the construction of houses and infrastructures are essential to man next as air, water, and food (Salau, 1996). These structures served as residences, places of work, worship, entertainment, as means of transportation, etc. As the population and economic activities continued to explode, the demand became more pressing. This justified the massive housing and infrastructural development that has been going on in the urban and rural areas of the country in the recent times. But an embarrassing feature of our building and infrastructural developmental strive is the failure rate verified among the existing structures and those under construction. The cost of these collapses, in terms of human life and economic waste, cannot be over emphasized. As the effect of the global warming began to take its toll in many parts of the world, including Nigeria, the need to arrest this ugly situation in our built environment becomes very expedient (Ede, 2010). In light of these issues, this paper analyses the problems of structural integrity in Nigeria as the environmental setup worsens and proffers measures bordering on the improved professionalism and craftsmanship that will reduce the menace drastically

Building Collapse in Nigeria: the Trend of Casualties the Last Decade (2000 -2010)

Over the last 10 years, the incidence of building collapse in Nigeria has become so alarming and does not show any sign of abating. Each collapse carries along with it tremendous effects that cannot be easily forgotten by any of its victim. These include loss of human lives, economic wastage in terms of loss of properties, jobs, incomes, loss of trust, dignity and exasperation of crises among the stake holders and environmental disaster. It can be rightly said that any pursuit of human endeavor has its cost, but the cost being paid in the Nigerian building industry cannot be justified. The fact that Nigeria is undergoing a tremendous transformation in the built environment cannot be over emphasized. This is in line with the growth that is being experience in the infrastructural and building industries all over the world for the effects of technological breakthroughs and consequently the ICT flattened world. But experiencing negative trends in the Nigerian building industries while other parts of the world are experiencing total improvements brings to fore the need to come out boldly and confront this ugly situation. The world today is facing a lot of other more serious man-made and natural crises such as global climate change which requires greater preparedness than the level on which we are standing today. For these facts, this paper addresses the impacts of building collapse on Nigerian strive for sustainable developmental. Probabilistic model of the linear regression analysis was used to establish the trend of heights and casualties. The results of this research will go a long way in reducing the building collapse phenomenon and the implications on the efforts of the nation to achieve the Millennium Developmental Goals (MDGs) and the Vision 20-2020

Rotor resonances of high-speed permanent-magnet brushless machines

For high-speed machines, in particular, it is very important to accurately predict natural frequencies of the rotor at the design stage so as to minimize the likelihood of failure. Finite-element analysis and experimental measurements are used to establish the natural frequencies and modes of the rotor of a high-speed permanent-magnet brushless motor, and to assess the influence of leading design parameters, such as the active length, the shaft diameter and extension, the bearings, and the material properties

Effect of optimal torque control on rotor loss of fault-tolerant permanent-magnet brushless machines

A faulted phase in a fault-tolerant permanent-magnet brushless machine can result in significant torque ripple. However, this can be minimized by using an appropriate optimal torque control strategy. Inevitably, however, this results in significant time harmonics in the phase current waveforms, which when combined with inherently large space harmonics, can result in a significant eddy-current loss in the permanent magnets on the rotor. This paper describes the optimal torque control strategy which has been adopted, and discusses its effect on the eddy-current loss in the permanent magnets of four-, five-, and six-phase fault-tolerant machines