L'objectif de cette thèse a été d'évaluer l'effet biogéochimique de deux forçages : l'acidification de l'océan et les dépôts de poussières sahariennes. Dans un premier temps, nous avons montré que dans une région dite Low Nutrient Low Chlorophyll (LNLC) l'effet de l'acidification de l'océan sur les cycles marins de l'azote (N), du phosphore (P) et du fer (Fe) sera surement négligeable. L'acidification des eaux de surface appauvries en N et P n'affecterait pas la spéciation de ces éléments, et la composition de la communauté planctonique, n'étant pas significativement modifiée, n'induirait pas de changement dans la dynamique des nutriments inorganiques. Dans un deuxième temps, les expériences menées pendant cette thèse nous ont permis de mieux paramétriser les processus post-dépôts des nutriments atmosphériques à la surface de l'eau de mer lors d'un évènement saharien. Les échanges dissous/particulaire ont lieu sur une courte échelle de temps. Ils sont à la fois contrôlés par la dynamique verticale des particules et la nature de la matière organique dissoute (DOM) pouvant s'agréger sur les particules lithogéniques. Dans des conditions d'acidification de l'océan, alors que la dissolution des éléments anthropiques adsorbés sur les poussières sahariennes, tels que l'azote inorganique, ne sera pas affectée, celle des éléments d'origine crustale (P et Fe) pourrait être accrue ou accélérée selon les agrégats organique-minéral formés. Le rôle majeur du processus d'agrégation dans la mise à disposition des nutriments atmosphériques a été mis en évidence par une rapide et importante formation abiotique de particules exopolymériques transparentes juste après le dépôt de poussières. / The objective of this thesis was to assess the biogeochemical effect of two forcings: the ocean acidification and the dust deposition. Firstly, we showed that in the Low Nutrient Low Chlorophyll (LNLC) area the effect of the ocean acidification on the marine cycle of nitrogen (N), phosphorus (P) and iron (Fe) will be likely negligible. The pH decrease of the surface waters depleted in N and P would not affect the speciation of these elements, and the absence of effect on the composition of the plankton community would not lead to a shift in the dynamic of inorganic nutrients. Secondly, the experiments performed during this thesis allowed a better parametrization of the post-depositional processes of atmospheric nutrients in the surface seawater after a Saharan event. The exchanges dissolved/particulate occurred in the short timescale. They were controlled by both the particles dynamic and the nature of the dissolved organic matter (DOM) that can aggregate with the lithogenic particles. Under ocean acidification conditions, while the dissolution of anthropogenic elements adsorbed onto dust, such as the inorganic nitrogen, will not be affected, the dissolution of the crustal elements (P and Fe) could be higher and faster according the formation of organic-dust aggregates. The major role of the aggregation process on the availability of atmospheric nutrients was highlighted by the rapid and large abiotic formation of transparent exopolymeric particles (TEP) following the dust deposition to the surface waters.

Magister Legum - LLM / The monitoring and supervision of local government is usually done by central governments. However in some countries like South Africa where there three spheres of government the provincial executive is charged with the supervision of the local sphere of government. In Zimbabwe the monitoring and supervision of local government is done by the central government through the relevant Minister. This study will look at the appointment of a caretaker to act as council in terms of section 80 of the UCA. Although a similar provision exists in section 158 of the RDCA, it is section 80 that has been vigorously applied by the Minister in recent times and which has caused an outcry from urban local authorities. / South Africa

This thesis deals with the dissolution (liquidation) of business companies in the Czech Republic. Besides the general characteristics of winding-up process the issue is further analyzed from the point of view of business law and accounting. The thesis is also supplemented with tax aspects of the dissolution of companies. Bankruptcy and insolvency proceedings are also mentioned marginally.

Organic ligand complexation reactions at the mineral-water interface play an important role in several environmental and geochemical processes such as adsorption, dissolution, precipitation, pollutant transport, nutrient cycling, and colloidal stability. Although organic ligand surface complexation reactions have been extensively studied, a molecular level understanding regarding the mechanisms underlying the adsorption of such compounds is still limited. The purpose of the current study was to investigate the interactions between some common naturally occurring organic ligands and a common aluminosilicate clay mineral, kaolinite, using a combination of macroscopic and microscopic experimental methods. Molecular level information regarding the structure and binding mode of adsorbed species was obtained using in situ MIR-FTIR spectroscopy. Other experimental techniques including adsorption experiments, surface titrations, and surface complexation modelling were also employed in order to quantify and describe the macroscopic adsorption properties of the organic ligands examined. Three low molecular weight organic acids (oxalic, salicylic, and phthalic acid) and humic acid were chosen as representative organic ligands. Spectroscopic evidence revealed that low molecular weight organic acids are able to form both inner and outer sphere complexes on kaolinite, and the relative concentrations of these surface complexes varies with solution chemistry. Inner sphere coordination modes inferred are a mononuclear bidentate for oxalate (five-membered chelate ring) and phthalate (seven-membered chelate ring); and a mononuclear monodenate (six-membered pseudochelate ring) for salicylic acid. Similar coordination modes were shown to form on simpler mineral (hyrd)oxides. Elucidation of the coordination chemistry of these ligands can provide insights into the dissolution mechanisms of silicate minerals In contrast to low molecular weight organic acids, there was no evidence of inner sphere complexation by humic acid acids on kaolinite or gibbsite. The combined spectroscopic and macroscopic adsorption results suggest that cation bridging and van der Waals interactions are the two most probable mechanisms for the adsorption of humic acid by these mineral substrates. This finding casts doubts over the use of low molecular weight organic acids as humic acid analogs.

The several million years preceding the Cretaceous/Paleogene (K/Pg) boundary has been the focus of many studies. Changes in ocean circulation and sea level, extinctions, and major volcanic events have all been documented for this interval. Important research questions these changes raise include the climate dynamics during the warm, but not hot, time after the decay of the Late Cretaceous greenhouse interval and the stability of ecosystems prior to the mass extinctions at the end-Cretaceous. I document several biotic perturbations as well as changes in ocean circulation during the Maastrichtian stage of the latest Cretaceous that question whether the biosphere was being preconditioned for the end-Cretaceous extinction. The first event at Shatsky Rise in the tropical North Pacific was the brief acme of inoceramid clams at ~71 Ma, followed by their abrupt extinction during the “mid-Maastrichtian event” at 70.1 Ma. The second is an intriguing dissolution event that began ~67.8 Ma at Ocean Drilling Program Site 1209 (2387 m). The dissolution event is marked by very poor planktic foraminiferal preservation and sharply reduced calcareous plankton diversity. The shift into the dissolution interval was initially gradual, then rapid. Within the late Maastrichtian dissolution interval, the planktic/benthic (P/B) ratio is low, planktic foraminifera are highly fragmented, larger taxa are mostly absent, small taxa are relatively abundant, and planktic foraminifera and nannofossil species richness are low. The event is followed by an abrupt recovery in carbonate preservation ~300 kyr prior to the K/Pg boundary. Was the dissolution event caused by a change in deep water circulation, migration of the site out of the high productivity tropical belt, or ocean acidification associated with Deccan Traps volcanism? Our data show that changing deep water masses, coupled with reduced productivity and associated decrease in pelagic carbonate flux was responsible for the dissolution interval, while Deccan Traps volcanism may have caused surface ocean acidification ~200-kyr prior to the K/Pg mass extinction event.

>Magister Scientiae - MSc / Fly ash is the most abundant of the waste materials generated from coal combustion in coal-fired power stations. South Africa uses more than 100 million tonnes of low grade bituminous coal annually to produce cheap electricity thereby generating huge amounts of fly ash each year. The disposal of fly ash has been a major concern to the world because of its potential environmental impact due to the possible leaching of the toxic elements contained in fly ash. This study centres on the chemical characterization and leaching behaviour of the fly ashes generated from SASOL Synfuels and ESKOM power station at Secunda and Tutuka in South Africa respectively. The aim is to understand the composition of the fly ashes and to determine the leachability of species from the ashes in order to predict the environmental effect of the different ash handling system of the coalfired stations (wet disposal system in Secunda and dry disposal system in Tutuka). Several leaching methods were employed in this study in order to develop a methodology for evaluating and modelling ash system and were able to discriminate between ash types and model ash handling system. Fly ashes from the two South African coal-fired stations were subjected to total acid-digestion and XRF analyses in order to determine the total amounts of major and minor species contained in the fly ashes. The total acid-digestion test and the XRF analysis revealed that the major species such as Al, Si, Ca, Na, Mg, K, Sr, Ba and S04, and minor species such as Fe, Ti, V, Mn, Cr, Ni and Cu were present in both fly ashes in fairly similar concentrations. The mineralogical characterization by XRD of Secunda and Tutuka fly ashes revealed mullite and quartz as the major mineral phases with minor peaks of CaO and calcite. Several leaching tests and different leaching conditions were employed in this study in order to develop a standardized replicable methodology for environmental impact assessment and for modelling the impact of different ash handling scenarios. The fly ashes were exposed to these different leaf leachant of different pHs on the leachability of species from the fly ashes. To achieve this, DIN-S4, TCLP and ANC tests were employed. The natural pH of the fly ash leachates were very high ranging between 12.56 and 13.08. The DIN-S4 leaching test revealed that the easily soluble species of the fly ashes include Ca, Mg, Na, K and S04 and various toxic elements. The leachates from the TCLP test recorded higher concentrations of Ca, Mg, Na, K and S04 which was attributed to the slight decrease in the pH due to the addition of a acidic leachant with a pH of 2.88. Comparison of the amount leached (DIN-S4) from the fly ashes with the total concentrations of each of the components of the fly ashes (determined by the total acid-digestion), the percentage of each of the readily soluble species ranged from 15-24.23% for Ca, 0.23-0.45% for K, 0.58-0.82% for Na, 0.0047-0.007% for Mg, 0.96-3.33% for Ba and 0.012-1.51 % for S04 per dry mass of each component in the fly ash. The ANC test revealed the effect of a leachant of specified pH on the release of species from the fly ashes with concentrations of the major and minor species leached out of the fly ashes found to be higher than the concentrations released into the leachates when DIN-S4 and TCLP test were considered at specific pH and showed the pH dependence of the solubility and release of species. These tests also showed the effect of the liquid to solid ratio upon leachability of species. In addition to the batch leaching tests mentioned above, dissolution kinetics and up-flow percolation tests were carried out on the fly ashes to determine the leaching behaviours of the fly ashes over time and the factors controlling the release of species from the fly ashes in the long term. The dissolution kinetics test was done for an extended period of 60 days with recycle of the leachant and the up-flow percolation test was carried out with constant leachant renewal until a liquid/solid ratio of 20 was attained (:::::;9d0ays). The geochemical computer code PHREEQC and MINTEQ database was used for geochemical modelling of the leachates at various reaction times and LIS ratios. The geochemical modelling results revealed that the release of the species from the fly ashes is controlled by the solubility of mineral phases in many case except for Na. The release of Ca, S04, Mg, Ba and Sr in the leachates of the fly ashes were predicted to be controlled by portlandite, gypsum, brucite, barite and celestite respectively while birnessite, magnetite, BaCr04, CaMo04 and Ba(As04h were predicted to be the mineral phases controlling the release of Mn, Fe, Cr, Mo and As respectively. The pH of the leachates plays a significant role in the leaching of both major and minor species from the fly ashes. The concentrations of species leached into solution at low pH (ANC and TCLP) were higher than the concentrations released at high pH (DIN-S4, dissolution kinetics and up-flow percolation tests). The amounts of the toxic elements such as As, Se, Cd, Cr and Pb that leached out of the fly ashes when in contact with demineralized water (DIN-S4) were very low and below the target water quality range (TWQR) of South African Department of Water Affairs and Forestry (DWAF), but the amounts of As and Se leached out by acidic leachant applied in the TCLP test and at lower pH ranging between 8 and 10 the case of the ANC test were slightly higher than the TWQR, which is an indication that the pH of the leaching solution and the contact time playa significant role on the leaching of species out of the fly ashes. This study revealed that the leaching of species from the fly ashes depends on various factors which include: physical and chemical characteristics and mineralogical composition of the fly ashes, the total concentrations of species in the ash, the rate of flow through the ash system and more importantly the pH of the leachant to which the ash system is exposed to. The results of different experiments and analysis carried out on the two South African fly ashes (Secunda and Tutuka fly ashes) showed that, despite the high concentrations of soluble species or leachable elements in the fly ashes, the leaching of major, minor and trace elements into the soils and the groundwater could be minimized if certain conditions such as avoiding acidic precipitation that could reduce the pH of the ash system are adhered to. The leaching trends of the species and the geochemical modelling data also showed that the formation of secondary mineral phases could reduce the release of toxic elements, the release of which would require aggressive low pH leachants, high flow rate, high recharge and long-term leaching for the dissolution of the formed mineral phases. In conclusion, the combination of the leaching tests employed in this study gives information on the leaching behaviour of the Secunda and Tutuka fly ashes and the factors controlling the leaching of the elements from the fly ashes. This study has been able to show that elements are leached out of the fly ashes at both alkaline and acidic pH. It is also revealed in the study that the disposal techniques employed by the coal-fired stations which were simulated by using the dissolution kinetics and up-flow percolation tests are adequate methods for modelling of the ash disposal scenario. These two methods show that the dry disposal system at Tutuka will encourage equilibration of the ash/water system thereby facilitating the precipitation of mineral phases that could control the release of both major and minor species from the fly ash, whereas the wet ashing system at Secunda may expose the ash to sufficient flow to rapidly leach species out into the environment.

The aim of this report is company liquidation and her possible risks.The theoretical part of this dissertation deal with the general law business liquidation of the company, primarily focused on the legal status of the liquidator and his individual acts within the liquidation process.The analytical part analyse the course of liquidation of a particular company from the perspective of liquidator. The target is carry out problem-free liquidation with the greatest possible benefit for shareholders.

The unique symmetry requirements of second harmonic generation (SHG) provide exquisite selectivity to chiral crystals, enabling independent quantitative modeling of the nucleation and crystal growth of active pharmaceutical ingredients (APIs) within amorphous solid dispersions (ASDs) during accelerated in situ stability testing, and in vitro dissolution testing. ASDs, in which an API is maintained in an amorphous state within a polymer matrix, are finding increasing use to address solubility limitations of small-molecule APIs. SHG microscopy yielded limits of detection for ritonavir crystals as low as 10 ppm, which is about two orders of magnitude lower than other methods currently available for crystallinity detection in ASDs. The quantitative capabilities of SHG analysis were substantially improved further while simultaneously dramatically reducing the total sample volume and storage burden through in situ analysis. Single particle tracking of crystal growth performed in situ enabled substantial improvements in the signal to noise ratio (SNR) for recovered crystal nucleation and growth rates by nonlinear optical microscopy. Upon dissolution, the presence of solubilizing additives in biorelevant media greatly affected the generation and stabilization of supersaturated solutions. SHG microscopy was found to enable the detection of crystals even in the highly turbid Ensure Plus® system. Analysis of the SHG micrographs clearly indicated that differences in the nucleation kinetics rather than growth rates dominated the overall trends in crystallinity. For weakly basic drugs, the fate of dissolution in fasted-state simulated intestinal fluid (FaSSIF, pH 6.5) varied with the ASDs drug loading, and was highly affected by the pre-exposure to the fasted-state simulated gastric fluid (FaSSGF, pH 1.6) medium, versus the dissolution in FaSSIF medium alone. The presence of crystals during the first stage of posaconazole ASDs dissolution in FaSSGF acted as nuclei for further crystallization in the later dissolution stage in FaSSIF. The results provide insights of better formulation prediction of poorly soluble drugs, as well as understanding origins of intraluminal absorption variability for such systems

The erosion or dissolution of stainless steel grade 304 as base metal by molten brazing fillermetal was investigated using one nickel and two iron based filler metals. The difference betweentwo iron filler metal is 5 % Manganese content in one of the filler metal. The Wettability of fillermetal is effected by oxidation of base or filler metal for which high vacuum or non reacting gasis used as a furnace atmosphere to reduce the partial pressure of oxygen. The furnace parameterseffecting erosion of base metal was observed e.g. peak temperature and brazing time. The effectof filler mass was also observed. The erosion depth was measured by light optical microscope.All the three filler metal shows different erosion behavior in nitrogen atmosphere compare tohigh vacuum. In high vacuum some of the elements evaporates at brazing temperature whichchanges the properties of filler metal. This change of composition in filler metal was observed byEDX analysis. SEM analysis was used to identify different element rich phases.

One main reason for the use of Fe-Cu-C system in PM industry is the presence of liquid phase (copper) at the start of sintering (1120oC). The diffusion of liquid copper into iron causes swelling in the structure. This in turn can cause high dimensional change and, if not controlled properly, may cause distortion. So it is of paramount importance to control the copper diffusion. Carbon, added as graphite, reduces the swelling of copper by changing the dihedral angle. The affect of graphite on copper diffusion depends on the graphite type, particle size of graphite and heating rate. The aim of this work was to find the influence of graphite type and particle size of graphite on copper diffusion. Water Atomized iron (ASC100.29) produced in Höganäs AB was taken as the base powder.  Two types of graphite were used each with two different particle sizes. Two different graphite quantities (0.2% & 0.8%) for each type was taken. Natural fine graphite (UF4), Natural coarse graphite (PG44), Synthetic fine graphite (F10) and  Synthetic coarse graphite (KS44) were the graphites used in this work. Powders were compacted at 600 Mpa and the sintering was done at 1120oC for 30 minutes in 90/10 N2/H2. Dilatometry and metallographic investigation of the samples sintered in the production furnace were used to understand the graphite influence.   The investigation showed that at low graphite levels (0.2%), the affect of graphite type or graphite size was not significant on copper diffusion. At high graphite levels (0.8%),  synthetic graphites were more effective in reducing the swelling of copper. Influence of  particle size of synthetic graphites on Cu diffusion was not significant compared to the influence of particle size of natural graphite. There was also a considerable affect of heating rate on graphite dissolution and copper swelling.