Requirement for the growth and maintenance of Alphanizomenon flos-aquae in culture

Aphanizomenon flos-aquae from Upper Klamath Lake, Oregon was introduced into culture in a precipitate -free medium developed by modification of McLachlan's ASM medium. This medium ASMT No. 8 contained no organic substances other than ethylendiaminetetraacetate (EDTA) and Trishydroxymethylamino methane (Tris), and was developed by modifying the concentrations of certain elements, by adding sodium bicarbonate and a 1/25 dilution of Arnon's trace element solutions B and C. Cultures of Aphanizomenon in this medium have been maintained in combined daylight and supplemental fluorescent illumination at 15° C. The alga has shown good growth, and has retained the morphological integrity of the colonial flake for more than 14 months. The results of experiments to obtain a medium further improved for the culture of Aphanizomenon, by additional variation of the concentration of elements in ASMT No. 8 are also reported. Preliminary experiments utilizing ultra-violet irradiation and chlorine treatment for elimination of bacteria indicate that bacteria possibly may be removed from cultures of Aphanizomenon. These experiments have determined that exposures can be used that materially reduce bacterial numbers without apparent change in the morphology of the alga. Earlier experiments were made with the alga assumed to be in a unialgal condition as no other alga was demonstrated to be present in the stock cultures. Problems with a contaminating alga, Oscillatoria sp., have since appeared and have not been entirely solved. The complete elimination of Oscillatoria has not been achieved as filaments of this alga were found to grow between filaments of Aphanizomenon, both in the lake and in cultures. Attempts at removal by repeated washing were found to be ineffective. The suggested solution by re-isolation from stock cultures exhibiting, both microscopically and macroscopically, no contamination, has not yet been employed

Gigue

This music score was submitted for the Kaleidoscope 2020 Call for Scores, an open access collaboration with the UCLA Music Library

Sonatine for String Quartet

This music score was submitted for the Kaleidoscope 2020 Call for Scores, an open access collaboration with the UCLA Music Library

Sonatine for String Quartet

This music score was submitted for the Kaleidoscope 2020 Call for Scores, an open access collaboration with the UCLA Music Library

A critical investigation into missing persons in underground mines and related tracking technology

Even though mining has always been at the heart of the economy, it is also regarded as one of the most hazardous industries. Miners and any other persons who work underground can, not only be fatally injured during mining accidents, but also from being trapped underground. This study shows that there is a significant number of fatalities caused by miners going missing underground. These miners are deceased due to being trapped underground for an extended period of time without any help. These fatalities are often incorrectly reported, attributing the fatalities to the initial event. This study shows that the miners can survive the initial event, but become trapped in unknown, life threatening locations. Several accidents that led to miners going missing were investigated. It was found that the lack of positioning information regarding the missing miners causes search-and-rescue operations to either fail or last longer. This study shows that the miners who were deceased from being trapped/lost underground could have been saved by such a system that can urgently provide their locations. A slow implementation of these systems in mines could suggest a failure to learn by the industry; in realising the need and value of these systems. The aim of this study was to firstly emphasize the need and value of these systems in underground mines. Secondly, to make the industry aware of the availability of different systems in the market. Lastly, to define and recommend a suitable and fit for purpose system. The identified systems are mainly classified into Through-the-Wire (TTW), Through-the-Air (TTA) and Through-the-Earth (TTE) systems according to their signal transmission techniques and frequency spectrum. TTW systems transmit signals through cable connections. The TTW systems are used as phones or network infrastructure. TTA systems enable the exchange of signals wirelessly in the air as a medium of signal transmission. TTE systems propagate seismic or electromagnetic signals through rock. The functions, capabilities and limitations of these systems were investigated. Furthermore, devices used for similar purposes in related industries with the potential to be adopted in the mining industry were studied. Several factors that can affect the suitability and applicability of these systems in underground mining environments were investigated. With a wide variety of systems commercially available, there was a need to determine the most suitable and fit for purpose system. This was done by, firstly developing user requirements that resemble an ideal system. Secondly, the underground areas in which miners are expected to work and travel were identified. Lastly, from the investigated accidents, scenarios in which miners can go missing were derived. These parameters were used to evaluate the suitability of the systems. Therefore, the most suitable and fit for purpose system can thus be selected based on the evaluation outcomes. Even though all these systems worked well, it was found that no single system could satisfy all the user requirements, no single system was suitable in all the underground areas and no single system was suitable for all the going missing scenarios. This necessitated the need to assess the possibility of integrating different systems to improve suitability and effectiveness. It was recommended that mining operations identify further scenarios in which persons can go missing, especially those that are more relevant to their underground areas. The user requirements and underground areas should be considered and used for selecting a suitable system. The mining industry needs to learn and realise the need and value of these systems to save lives.Dissertation (MEng)--University of Pretoria, 2018.Mining EngineeringMEngUnrestricte

New directions for higher education

Publ. comme no 138, summer 2007 de la revue New directions for higher educationIndexBibliogr. à la fin des texte

Growth of Aphanizomenon flos-aquae in defined media

A strain of Aphanizomenon flos-aquae Born. et Flah. has been introduced into culture and maintained since August of 1964 in completely defined media. It exhibits the planktonic, colonial flake form found in nature, and both heterocysts and akinetes are present. The color and size of the flake and general appearance of the cells is substantially improved over that found at the time of collection in Upper Klamath Lake, Klamath County, Oregon. Initially, A. flos-aquae was isolated and cultured in a medium designated ASMT No, 8, a modification of the ASM of McLachlan and Gorham. ASMT No. 8 contained no organic substances other than disodium ethylenedinitrilotetra-acetate (Na₂EDTA) and Tris(hydroxymethyl) aminomethane (Tris). Experiments demonstrated that Tris was not essential for the growth of Aphanizomenon and the medium minus Tris was designated ASM No. 8. Factorial experiments indicated that better growth and morphological condition of the alga were obtained in media containing combinations of ferric chloride, Na₂EDTA and a new iron source, hydrogen ferric ethylenediamine di-o-hydroxyphenylacetate (EDDHA) than that obtained in ASMT No. 8. Best growth and condition of the alga was obtained in a medium designated ASM No. 8a which contained 0. 54 mg of ferric chloride, 3. 0 mg Na₂EDTA and 0, 07 mg of iron as EDDHA per liter. A. flos-aquae has been grown in ASM No. 8a for a year and a half. Factorial experiments gave evidence that there were significant interactions between the various mineral ions of ASM No. 8a, between the mineral ions and light intensity, light intensity and temperature, between different media, temperature and culture location, between culture location, temperature and light intensity and between different media, temperature and the quality of light used for the culture of the alga, Growth rate experiments and an analysis of covariance demonstrated that there was no significant difference between the growth rates of A. flos-aquae at different pH, temperatures or light intensities. The alga exhibited the same growth and morphological condition at pH from 6. 9 to 9. 2, and there was no significant difference in the growth rate or condition of Aphanizomenon cultured at temperatures of approximately 15 C and 20 C. The alga also exhibited the same response to culture under light from artificial sources at illumination intensities of 40, and approximately 70 or 110 ft-c. At light intensities above 140 ft-c, the alga exhibited chlorosis, loss of the colonial flake form or lysis. The alga showed both growth and good maintenance of condition in a north facing window at light intensities up to 300 ft-c supplied by natural daylight supplemented with light from fluorescent tubes. These light intensities were of variable magnitude and duration resulting from changes in cloud cover and day length. Preliminary experiments have shown that A. flos-aquae reduces acetylene and that the contaminant bacteria apparently do not. In addition, there was an indication that the rate of acetylene reduction was increased in relation to increasing concentrations of Vitamin B₁₂ (cobalamin). Further experiments need to be conducted using both acetylene reduction and N¹⁵ enriched nitrogen before a definitestatement can be made that Aphanizomenon does fix nitrogen. The growth of A. flos-aquae was definitely related to the concentration of nitrate nitrogen. There was a significant reduction in the mean yield of the alga when nitrate was omitted from ASM No. 8a, but the condition and morphology of the alga was unchanged. Nitrite nitrogen was not a suitable substitute for nitrate in the metabolism of the alga and higher concentrations of nitrite were toxic to Aphanizomenon. Bacteria-free cultures of Aphanizomenon were not obtained despite attempts at purification using pasteurization of akinetes contained in bottom sediments, ultraviolet irradiation and chlorine treatment of culture material. A screening test using antibiotics on both the alga and contaminant bacteria exhibited some promise that treatment with one or two antibiotics inhibited the bacteria without apparently killing the alga