Adsorption of the nitrification inhibitors dicyandiamide (DCD) and nitrapyrin (2-chloro-6(trichloromethyl)-pyridine) on humic acid (HA) and fulvic acid (FA) extracted from five Indiana soils was studied. Ten mg of HA or FA were suspended in aqueous solutions (10 ml) of either DCD (5,10, 20, 40 and 80 ug ml-1) or nitrapyrin (2,4,6,8,12 ug ml-1). The amount of nitrification inhibitor absorbed was evaluated after shaking the suspension of DCD for 48 h or nitrapyrin for 24 h. Infrared spectra of the nitrification inhibitor-humic material complexes were recorded. The results indicated that FA adsorbed more DCD than HA, and HA was a better adsorbent for nitrapyrin. Correlation between Freundlich K values and organic carbon content of HA and FA was not statistically significant, indicating a slight contribution of hydrophobic forces in the adsorption of DCD and nitrapyrin. The infrared spectra provided evidence that adsorption occurred predominantly through an ionic bonding mechanism involving the protonated amino group of DCD or the nitrogen of the pyridine ring of nitrapyrin and the negative functional groups of the humic materials. / Department of Natural Resources

One of the most valuable assets in any organisation is the employees, although a small percent of employees in organisations are truly motivated and energised. It is essential for organisations to look into the engagement of its employees. This mini-dissertation focuses on a comparative study of the occupational wellness between lecturers and the technical IT support staff of an academic institution of the North West province in South Africa. The objectives were to determine and compare the engagement of employees in the categories mentioned above. Thereafter a comparison was made with specific aspects of the work and work environment. Literary research was done in order to discuss and conceptualise terms such as wellness and health, occupational stress and occupational wellness. Thereafter the burnout and engagement concepts were discussed. Empirical research was done by using questionnaires that were disseminated among the two different employee groups identified for the study. Firstly, the Work and Well-being questionnaire was used to determine the work engagement levels of the different groups. This questionnaire focussed on the vigour, absorption and dedication dimensions of the study sample. In this survey the reliability indicated that all the dimensions of engagement were accepted and that employees of the IT support staff group have an overall higher level of work engagement than the lecturer group. Secondly, the Job Resources questionnaire was used to evaluate how specific aspects of the work and work environment are experienced by both IT personnel and lecturing personnel. Results gained from the Cronbach‟s alpha coefficient method indicated that the questionnaire regarding factors like emotional overload, achievement, collegiality, supervision, information regarding performance and satisfaction with pay were indicated as reliable and accurate. The results from the Job Resources questionnaire indicated that emotional overload and feelings of achievement in the work environment is higher in the IT group than for lecturers. The rest of the factors tested were significantly equal for both groups. The final chapter takes the information from the previous chapters to reach a conclusion. The key finding was that the IT sample has a higher level of absorption and dedication of engagement than the lecturer sample. Secondly, the findings were that the emotional overload and achievement for the sample population is higher for the IT staff than the lecturing staff. The collegiality, supervision, information regarding performance and satisfaction with pay were at the same level for both the IT group and lecturer group. Limitations were identified along with recommendations to the organisation and future research possibilities. / Thesis (M.B.A.)--North-West University, Potchefstroom Campus, 2010

This thesis describes the photochemical synthesis of silver nano particles, several ways to make these particles as well as control the size and shape of the colloidal particles. Understanding the primary reactions in photochemical nanoparticle formation has lead to important contributions to the overall mechanism of metal nanoparticle synthesis. The size and shape control of the particles is shown to have important implications for the Raman spectrum of surface bound molecules. The particles have also been used in antibacterial properties where it was shown that silver nanoparticles are more antibacterial than the corresponding silver cation, while remaining non-toxic to several common cell lines. The particles were also shown to have some interesting properties that can be exploited in lithography and optoelectronics.

No description available.

Sensitive and selective absorption spectroscopy techniques are applied to the detection of the excited species present in a range of low pressure inductively coupled plasmas (ICPs). The state densities and temperatures of various species are investigated across the parameter space accessible (plasma power and pressure) to aid in the understanding of the kinetic processes occurring. The experimental methods are based upon various forms of absorption spectroscopy, incorporating wavelength modulation and/or an optical enhancement cavity. The probing radiation is generated either directly using a CW diode laser or indirectly through the use of frequency conversion techniques. The absolute number densities of all four levels (1s₂, 1s₃, 1s₄ and 1s₅) present in the first excited manifold of atomic argon and neon are determined as a function of plasma operating conditions. A kinetic model is constructed to simulate these populations using cross-sections taken from the literature together with further measurements on the electron density and temperature obtained with a Langmuir probe. The model elucidates the importance of populational redistribution within the 1s manifold via excitation to the 2p_n levels, and highlights the mechanism of radiative decay (with radiative trapping taken into account) as the ultimate loss route for the 1s manifold. Measurements are made using cavity enhanced absorption spectroscopy (CEAS) on the 2p₅ and 2p₆ state densities in argon in order to draw additional conclusions about the nature of the discharge and to verify the kinetic model. The populations of the 1s₃ and 1s₄ states are probed in a neon plasma with helium, argon and nitrogen as a dopant gas, with the aim of manipulating the EEDFs. The addition of N₂ and Ar to the neon discharge resulted in a reduction in the 1s₃ and 1s₄ populations, while the addition of He resulted in an increase. These observations are consistent with a decrease and an increase, respectively, in the electron temperatures. The populations of the vibrational levels v = 0, 1, 3, and 6 of the A(³Σ_u⁺) state of molecular nitrogen are determined as a function of plasma operating conditions in a N₂ discharge using CEAS. A selection of vibrational bands within the B(³Π_g)←A(³Σ_u⁺) system are probed, with calibration achieved using cavity ring-down spectroscopy. At 25 mTorr and 200 W power the populations of the v = 0, 1,3, and 6 levels are (1.31 ± 0.16) × 10¹¹ cm^-3, (8.44 ± 1.01) × 10¹⁰ cm^-3, (2.83 ± 0.34) × 10¹⁰ cm^-3 and (5.27 ± 0.63) × 10⁹ cm^-3, respectively, corresponding to a vibrational temperature of 3600 ± 150 K. In addition, the observation of the N₂⁺(X²Σ_g⁺) molecular ion in v = 0 using both CEAS and CEAS in combination with wavelength modulation spectroscopy is presented (which is found to improve the sensitivity for this measurement by approximately an order of magnitude). At 10 mTorr and 400 W the total population in N₂⁺(X²Σg⁺, v = 0) is (1.26 ± 0.15) × 10⁹ molecules cm^-3, consistent with data obtained using a Langmuir probe. The density of oxygen atoms present in their ground state (³P₂) is investigated using the technique of CEAS, and at 500 W and 100 mTorr the concentration is estimated to be (2.2 ± 0.3) × 10¹⁴ cm^-3. This corresponds to a dissociation efficiency, δ, of O₂ of 0.06. Furthermore, a difference frequency generation (DFG) system is constructed to generate radiation at 1.9 μm in order to probe the (0,0) band of the O₂(b¹Σ_g⁺←a¹Δ_g) quadrupolar system. A minimum detectable absorbance of 1.3 × 10^-5 over a 10 cm cell is determined by calibrating the system on an ammonia absorption, placing a limit of 1.8 × 10¹⁶ cm^-3 on the total v = 0 population of O₂(a¹Δ_g) in a microwave discharge operating with 5 Torr pure O₂.

No description available.

No description available.

No description available.

No description available.

No description available.