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Highly concentrated ammonium nitrate emulsions are extensively used as an explosive in the mining industry. The emulsion is made from a supercooled aqueous salt solution with various stabilisers and an organic hydrocarbon phase under vigorous stirring to room temperature. The resulting emulsion is thermodynamically unstable and tends to crystallise over time. This is not suitable for the transportation or pumping of the emulsion in its application. This study showed that the crystallisation process of highly concentrated ammonium nitrate emulsions can be influenced by varying the emulsion droplet size as well as the types and ratios of surfactants used during the preparation stage. The results showed that there were significant differences in the rheological properties of the freshly-prepared emulsion, based on both the emulsion droplet size, and the type of surfactant and ratio of surfactants used. A decrease of the emulsion droplet size resulted in the increase of the elastic character, which can be explained by more compact network organisation of droplets. In terms of the different surfactants, it was shown that the Pibsa-Imide stabilised emulsions resulted in an emulsion with the highest storage modulus over the entire strain amplitude regions as well as the highest shear stresses over the whole shear rate region. The study showed that the relatively slow emulsion crystallisation process can be studied by using powder X-ray diffraction (PXRD). The amount of amorphous and crystalline phases present in the sample can be effectively quantified by using the Partial Or No Known Crystal Structural (PONKCS) method which can model accurately the contributions of the amorphous halo. An external standard calibration method, which used a different amorphous material with the crystalline material to obtain a suitable calibration constant, was employed. The results showed that the method would quantify the amount of the fully crystallised emulsion to be between 80 and 90 percent, which was in agreement with the solid content added during sample preparation and confirmed by Thermal Gravimetric Analysis (TGA). The simultaneous TGA / DSC results were able to show the number of solid/solid peak transitions as well as the total moisture content to be around 20 percent by mass in various emulsion samples studied. The study was able to model the crystallisation by using the Avrami and Tobin kinetic relationships which are commonly used for the crystallisation processes of polymers. The Avrami relationship proved to be useful in describing the type of crystallisation that occurred. This was based on literature where the exponent parameter (n) which was between 1 and 4 would relate to different types of crystallisation models. The results of this study showed that the crystallisation process would change for the samples that had shown a longer crystallisation process. The results indicated that the samples prepared with the lower Pibsa-Urea ratio showed a more sporadic crystallisation process, whereas the samples with the higher ratio of Pibsa-Urea showed a more controlled crystallisation process. The study also considered the rheological properties of the fresh emulsion, which showed that droplet size also had an influence on the stress strain relationship of the emulsion droplets.

The objectives of this study were: 1) To evaluate short-term composting of hardwood bark with combinations of poultry litter and ammonium nitrate and 2) To determine the suitability of composted material for ornamental plant media. In a 3-month accelerated composting study, hardwood bark was amended with (20% & 40%) poultry litter, (1% & 2%) ammonium nitrate, or unamended. Composting was run in fifteen 35- gallon containers and samples were collected at day 0, 45, and 90 for pH, moisture content, carbon-to-nitrogen ratio, compost maturity, toxicity, and green house evaluations. The amendment containing 40% poultry litter showed significantly higher weight reduction than others at days 45 and 90. Also, this treatment showed significantly higher mass weight in transplanted zinnia and gardenia than other treatments and was comparable to commercial media. Overall, results indicated that the amendment of hardwood bark with poultry litter could produce comparable product to currently used commercial container media.

Thesis (M. Sc.)--Carleton University, 2001. / Includes bibliographical references (p. 84-90). Also available in electronic format on the Internet.

Increased development in Canadas northern environments has increased the need for accurate methods to detect adverse impacts on tundra ecosystems. Ammonium nitrate is a common water pollutant associated with many industrial and municipal activities, including diamond mining, and is of special concern due to the toxicity of ammonia in aquatic systems. One solution to reduce exposure of sensitive aquatic systems to nitrogenous compounds is to atomize (atmospherically disperse in fine particles) contaminated water over the arctic tundra which will reduce N loading to surface water. However, the toxicity of ammonium nitrate to arctic soils is poorly understood. In this study I investigate the potential toxicity of ammonium nitrate solutions to arctic soil functions such as carbon mineralization, nitrification and plant growth, to determine concentrations that can be applied without causing significant inhibition to these processes. <p>Arctic ecosystems are based on a soil type termed a cryosol that has an underlying permafrost layer. Often these soils are subject to cryoturbation, a process which heaves and mixes the soil, bringing the mineral horizons to the surface. I hypothesized that phytotoxicity test results in arctic soils would be highly variable compared to other terrestrial ecosystems due to the cryoturbation process and subsequent range of soil characteristics. The variability associated with phytotoxicity tests was evaluated using Environment Canadas standardized plant toxicity test in three cryoturbated soils from Canadas arctic exposed to a reference toxicant, boric acid. The phytotoxicity of boric acid to northern wheatgrass (<i>Elymus lanceolatus </i>) in cryosols was much greater than commonly reported in other soils, with less than 150 ug boric acid g-1 soil needed to inhibit root and shoot growth by 20%. There was also large variability in the phytotoxicity test results, with coefficients of variation for 10 samples ranging from 160 to 79%. Due to this variability in cryoturbated arctic soils, more than 30 samples should be collected from each control and potentially impacted area to accurately assess contaminant effects, and ensure that false negatives of toxicant impacts in arctic soils are minimized. <p>To characterize the toxicity of ammonium nitrate I exposed a variety of arctic soils and a temperate soil to different concentrations of ammonium nitrate solution over a 90 day time period. Dose responses of carbon mineralization, nitrification and phytotoxicity test parameters were estimated for ammonium nitrate applications. In addition to direct toxicity, the effect of ammonium nitrate on ecosystem resistance was investigated by dosing nitrogen impacted soils with boric acid. Ammonium nitrate solutions had no effect on carbon mineralization activity, and affected nitrification rates in only one soil, a polar desert soil from Cornwallis Island. In contrast, ammonium nitrate applications (43 mmol N L-1 soil water) significantly impaired seedling emergence, root length and shoot length of northern wheatgrass. Concentrations of ammonium nitrate in soil water that inhibited plant parameters by 20% varied between 43 to 280 mmol N L-1 soil water, which corresponds with 2,100 to 15,801 mg L-1 in the application water. Arctic soils were more resistant to ammonium nitrate toxicity than the temperate soil under these study conditions. However, it is not clear if this represents a general trend for all polar soils, and because nitrogen is an essential macro-nutrient, nitrogenous toxicity should likely be considered a special case for soil toxicity. As soil concentrations could be maintained under inhibitory levels with continual application of low concentrations of ammonium nitrate over the growing season, atomization of wastewater contaminated with ammonium nitrate is a promising technology for mitigation of nitrogen pollution in polar environments. <p>Increased development in Canadas northern environments has increased the need for accurate methods to detect adverse impacts on tundra ecosystems. Ammonium nitrate is a common water pollutant associated with many industrial and municipal activities, including diamond mining, and is of special concern due to the toxicity of ammonia in aquatic systems. One solution to reduce exposure of sensitive aquatic systems to nitrogenous compounds is to atomize (atmospherically disperse in fine particles) contaminated water over the arctic tundra which will reduce N loading to surface water. However, the toxicity of ammonium nitrate to arctic soils is poorly understood. In this study I investigate the potential toxicity of ammonium nitrate solutions to arctic soil functions such as carbon mineralization, nitrification and plant growth, to determine concentrations that can be applied without causing significant inhibition to these processes. <p>Arctic ecosystems are based on a soil type termed a cryosol that has an underlying permafrost layer. Often these soils are subject to cryoturbation, a process which heaves and mixes the soil, bringing the mineral horizons to the surface. I hypothesized that phytotoxicity test results in arctic soils would be highly variable compared to other terrestrial ecosystems due to the cryoturbation process and subsequent range of soil characteristics. The variability associated with phytotoxicity tests was evaluated using Environment Canadas standardized plant toxicity test in three cryoturbated soils from Canadas arctic exposed to a reference toxicant, boric acid. The phytotoxicity of boric acid to northern wheatgrass (<i>Elymus lanceolatus </i>) in cryosols was much greater than commonly reported in other soils, with less than 150 ug boric acid g-1 soil needed to inhibit root and shoot growth by 20%. There was also large variability in the phytotoxicity test results, with coefficients of variation for 10 samples ranging from 160 to 79%. Due to this variability in cryoturbated arctic soils, more than 30 samples should be collected from each control and potentially impacted area to accurately assess contaminant effects, and ensure that false negatives of toxicant impacts in arctic soils are minimized. <p>To characterize the toxicity of ammonium nitrate I exposed a variety of arctic soils and a temperate soil to different concentrations of ammonium nitrate solution over a 90 day time period. Dose responses of carbon mineralization, nitrification and phytotoxicity test parameters were estimated for ammonium nitrate applications. In addition to direct toxicity, the effect of ammonium nitrate on ecosystem resistance was investigated by dosing nitrogen impacted soils with boric acid. Ammonium nitrate solutions had no effect on carbon mineralization activity, and affected nitrification rates in only one soil, a polar desert soil from Cornwallis Island. In contrast, ammonium nitrate applications (43 mmol N L-1 soil water) significantly impaired seedling emergence, root length and shoot length of northern wheatgrass. Concentrations of ammonium nitrate in soil water that inhibited plant parameters by 20% varied between 43 to 280 mmol N L-1 soil water, which corresponds with 2,100 to 15,801 mg L-1 in the application water. Arctic soils were more resistant to ammonium nitrate toxicity than the temperate soil under these study conditions. However, it is not clear if this represents a general trend for all polar soils, and because nitrogen is an essential macro-nutrient, nitrogenous toxicity should likely be considered a special case for soil toxicity. As soil concentrations could be maintained under inhibitory levels with continual application of low concentrations of ammonium nitrate over the growing season, atomization of wastewater contaminated with ammonium nitrate is a promising technology for mitigation of nitrogen pollution in polar environments.

Increased development in Canadas northern environments has increased the need for accurate methods to detect adverse impacts on tundra ecosystems. Ammonium nitrate is a common water pollutant associated with many industrial and municipal activities, including diamond mining, and is of special concern due to the toxicity of ammonia in aquatic systems. One solution to reduce exposure of sensitive aquatic systems to nitrogenous compounds is to atomize (atmospherically disperse in fine particles) contaminated water over the arctic tundra which will reduce N loading to surface water. However, the toxicity of ammonium nitrate to arctic soils is poorly understood. In this study I investigate the potential toxicity of ammonium nitrate solutions to arctic soil functions such as carbon mineralization, nitrification and plant growth, to determine concentrations that can be applied without causing significant inhibition to these processes. <p>Arctic ecosystems are based on a soil type termed a cryosol that has an underlying permafrost layer. Often these soils are subject to cryoturbation, a process which heaves and mixes the soil, bringing the mineral horizons to the surface. I hypothesized that phytotoxicity test results in arctic soils would be highly variable compared to other terrestrial ecosystems due to the cryoturbation process and subsequent range of soil characteristics. The variability associated with phytotoxicity tests was evaluated using Environment Canadas standardized plant toxicity test in three cryoturbated soils from Canadas arctic exposed to a reference toxicant, boric acid. The phytotoxicity of boric acid to northern wheatgrass (<i>Elymus lanceolatus </i>) in cryosols was much greater than commonly reported in other soils, with less than 150 ug boric acid g-1 soil needed to inhibit root and shoot growth by 20%. There was also large variability in the phytotoxicity test results, with coefficients of variation for 10 samples ranging from 160 to 79%. Due to this variability in cryoturbated arctic soils, more than 30 samples should be collected from each control and potentially impacted area to accurately assess contaminant effects, and ensure that false negatives of toxicant impacts in arctic soils are minimized. <p>To characterize the toxicity of ammonium nitrate I exposed a variety of arctic soils and a temperate soil to different concentrations of ammonium nitrate solution over a 90 day time period. Dose responses of carbon mineralization, nitrification and phytotoxicity test parameters were estimated for ammonium nitrate applications. In addition to direct toxicity, the effect of ammonium nitrate on ecosystem resistance was investigated by dosing nitrogen impacted soils with boric acid. Ammonium nitrate solutions had no effect on carbon mineralization activity, and affected nitrification rates in only one soil, a polar desert soil from Cornwallis Island. In contrast, ammonium nitrate applications (43 mmol N L-1 soil water) significantly impaired seedling emergence, root length and shoot length of northern wheatgrass. Concentrations of ammonium nitrate in soil water that inhibited plant parameters by 20% varied between 43 to 280 mmol N L-1 soil water, which corresponds with 2,100 to 15,801 mg L-1 in the application water. Arctic soils were more resistant to ammonium nitrate toxicity than the temperate soil under these study conditions. However, it is not clear if this represents a general trend for all polar soils, and because nitrogen is an essential macro-nutrient, nitrogenous toxicity should likely be considered a special case for soil toxicity. As soil concentrations could be maintained under inhibitory levels with continual application of low concentrations of ammonium nitrate over the growing season, atomization of wastewater contaminated with ammonium nitrate is a promising technology for mitigation of nitrogen pollution in polar environments. <p>Increased development in Canadas northern environments has increased the need for accurate methods to detect adverse impacts on tundra ecosystems. Ammonium nitrate is a common water pollutant associated with many industrial and municipal activities, including diamond mining, and is of special concern due to the toxicity of ammonia in aquatic systems. One solution to reduce exposure of sensitive aquatic systems to nitrogenous compounds is to atomize (atmospherically disperse in fine particles) contaminated water over the arctic tundra which will reduce N loading to surface water. However, the toxicity of ammonium nitrate to arctic soils is poorly understood. In this study I investigate the potential toxicity of ammonium nitrate solutions to arctic soil functions such as carbon mineralization, nitrification and plant growth, to determine concentrations that can be applied without causing significant inhibition to these processes. <p>Arctic ecosystems are based on a soil type termed a cryosol that has an underlying permafrost layer. Often these soils are subject to cryoturbation, a process which heaves and mixes the soil, bringing the mineral horizons to the surface. I hypothesized that phytotoxicity test results in arctic soils would be highly variable compared to other terrestrial ecosystems due to the cryoturbation process and subsequent range of soil characteristics. The variability associated with phytotoxicity tests was evaluated using Environment Canadas standardized plant toxicity test in three cryoturbated soils from Canadas arctic exposed to a reference toxicant, boric acid. The phytotoxicity of boric acid to northern wheatgrass (<i>Elymus lanceolatus </i>) in cryosols was much greater than commonly reported in other soils, with less than 150 ug boric acid g-1 soil needed to inhibit root and shoot growth by 20%. There was also large variability in the phytotoxicity test results, with coefficients of variation for 10 samples ranging from 160 to 79%. Due to this variability in cryoturbated arctic soils, more than 30 samples should be collected from each control and potentially impacted area to accurately assess contaminant effects, and ensure that false negatives of toxicant impacts in arctic soils are minimized. <p>To characterize the toxicity of ammonium nitrate I exposed a variety of arctic soils and a temperate soil to different concentrations of ammonium nitrate solution over a 90 day time period. Dose responses of carbon mineralization, nitrification and phytotoxicity test parameters were estimated for ammonium nitrate applications. In addition to direct toxicity, the effect of ammonium nitrate on ecosystem resistance was investigated by dosing nitrogen impacted soils with boric acid. Ammonium nitrate solutions had no effect on carbon mineralization activity, and affected nitrification rates in only one soil, a polar desert soil from Cornwallis Island. In contrast, ammonium nitrate applications (43 mmol N L-1 soil water) significantly impaired seedling emergence, root length and shoot length of northern wheatgrass. Concentrations of ammonium nitrate in soil water that inhibited plant parameters by 20% varied between 43 to 280 mmol N L-1 soil water, which corresponds with 2,100 to 15,801 mg L-1 in the application water. Arctic soils were more resistant to ammonium nitrate toxicity than the temperate soil under these study conditions. However, it is not clear if this represents a general trend for all polar soils, and because nitrogen is an essential macro-nutrient, nitrogenous toxicity should likely be considered a special case for soil toxicity. As soil concentrations could be maintained under inhibitory levels with continual application of low concentrations of ammonium nitrate over the growing season, atomization of wastewater contaminated with ammonium nitrate is a promising technology for mitigation of nitrogen pollution in polar environments.

Triticum aestivum is of major importance both nutritionally and economically globally. Traditional breeding mechanisms have been unsuccessful at keeping pace with the increasing demand for better yielding and more resilient wheat varieties. The introduction of foreign genes into systems has provided a new tool for crop improvement, but has been difficult to apply to elite wheat varieties mainly as result of their recalcitrance to prerequisite tissue culture. Investigations here demonstrate that modification of the ammonium nitrate content in direct somatic embryogenesis induction medium can increase the number of primary embryos produced by over two fold in the elite hard red wheat cultivar Superb. The number of primary embryos which were capable of transitioning into shoot development also increased by two fold. Biolistic transformation efficiency was also improved when targeted scutellar tissue was exposed to elevated ammonium nitrate levels. / x, 81 leaves : ill. ; 29 cm.

Submitted by Mirella Dos Santos Pereira (mirella.pereira03@yahoo.com.br) on 2018-04-25T01:21:25Z No. of bitstreams: 1 SANTOS ME LIXIVIAÇÃO DE AMÔNIO E NITRATO EM UM LATOSSOLO VERMELHO DISTRÓFICO CULTIVADO COM ALGODOEIRO (Gossypium hirsutum L. var. latifolium Hutch) EM FUNÇÃO DE DOSES E FONTES DE NITROGENIO EM SISTEMA.pdf: 1257009 bytes, checksum: 385811a0387d0bad8e49328df2332608 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-04-25T17:36:55Z (GMT) No. of bitstreams: 1 pereira_ms_me_ilha.pdf: 1120515 bytes, checksum: 1e52b35de3dead43b0a5a28321210e3b (MD5) / Made available in DSpace on 2018-04-25T17:36:55Z (GMT). No. of bitstreams: 1 pereira_ms_me_ilha.pdf: 1120515 bytes, checksum: 1e52b35de3dead43b0a5a28321210e3b (MD5) Previous issue date: 2018-03-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O N é um dos elementos mais dinâmicos no solo, conforme sua transformação no meio. A lixiviação de nitrato e do amônio no solo é considerada a principal perda do N disponível às plantas, quanto maior for à aplicação deste elemento no solo, maior será o potencial de poluição do solo e da água. Objetivou-se, neste trabalho, avaliar a lixiviação de amônio e nitrato em um Latossolo Vermelho em diferentes profundidas do solo, em função de doses e fontes de N distintas, em sistemas irrigado e não irrigado nas condições de campo. O experimento foi conduzido no ano agrícola 2014/15, na área experimental da fazenda de ensino, pesquisa e extensão, localizada no município de Selvíria-MS. Utilizou-se o delineamento em blocos casualizados, com 20 tratamentos dispostos em fatorial 5x2x2, com 4 repetições. Aplicou-se 5 doses de nitrogênio (0 (testemunha); 25; 50; 100 e 150 kg de N ha-1), as fontes de N utilizadas foram: nitrato de amônio e a ureia, aplicados em uma única adubação de cobertura via solo aos 45 após a emergência. As amostras de solo colhidas foram analisadas em laboratório, para a determinação da concentração da lixiviação do NO3- e do NH4+ no solo. Avaliou – se os parâmetros de crescimento, estado nutricional e da produtividade do algodoeiro durante seu ciclo. Os resultados permitiram concluir que o sistema irrigado foi o que propiciou maior lixiviação dos teores de nitrato e amônio nas profundidades de 0 a 0,8 m do solo e o sistema não irrigado foi o que apresentou maior concentração. A profundidade de 0,4 – 0,6 m foi a que constatou a maior acúmulo desses nutrientes no solo. / The N is one of the most dynamic elements in the soil, according to its transformation in the environment. The leaching of nitrate and ammonium in the soil is considered the main loss of the N available to the plants, the greater the application of this element in the soil, the greater the pollution potential of soil and water. The objective of this work was to evaluate the leaching of ammonium and nitrate in a Red Latosol in different depths of the soil, as a function of different N sources and sources, in irrigated and non-irrigated systems under field conditions. The experiment was conducted in the agricultural year 2014/15, in the experimental area of the teaching, research and extension farm, located in the municipality of Selvíria, Brasil state of mato grosso do sul. A randomized complete block design was used, with 20 treatments arranged in 5x2x2 factorial, with 4 replications. Five nitrogen doses (0 (control), 25, 50, 100 and 150 kg of N ha-1) were applied, the N sources used were: ammonium nitrate and urea, applied in a single cover fertilization only at 45 after the emergency. The soil samples collected were analyzed in the laboratory for the determination of the leaching concentration of NO3- and NH4+ in the soil. The parameters of growth, nutritional status and yield of cotton during its cycle were evaluated. The results allowed to conclude that the irrigated system provided the highest leaching of the nitrate and ammonium contents in the 0 to 0,8 m depths of the soil and the non irrigated system presented the higher concentration. The depth of 0,4 – 0,6 m showed the greatest accumulation of these nutrients in the soil.

Ammonium nitrate (AN) is commonly used as an explosive and as a fertilizer. In both roles it is provided as prills or pellets, approximately spherical and a few millimetres in diameter. The microstructures of several commercially-available AN compositions were investigated usingenvironmental scanning electron microscopy (ESEM) and X-ray microtomography. Those intended for explosive use were found to bemore porous than those intended for fertilizer use. The pores in explosiveprills were also found to form a connected network. The elemental composition of pellets of mixed AN and dolomite was investigated using energy-dispersive X-ray spectroscopy (EDX); the dolomite additivewas found to take the form of grains roughly 50 μm in size. The compaction behaviour of confined cylindrical beds of these prillsand pellets was studied at strain rates between 4 x 10-4 s-1 and 200 s-1. Quasi-static experiments were performed using a screw-driven instrumented press, while higher-rate experiments used a drop weight,instrumented with a line laser and load cell. The resistance of a bed to compaction was found to depend on the microstructure of its prills in most cases. Denser prills offered greater resistance to compaction. The exception to this rule was a pellet, rather than prill, formulation. Beds were also found to offer more resistance to compaction at higher strain rates. The Kawakita compaction model was found to agree well with the experimental data. A commercial fertilizer, not containing any AN, was assessed for use as an inert mock for AN prills and pellets. Prills of a suitable size for this purpose were found using EDX to consist of P2O5, with a coatingof unknown composition. They were supplied mixed with smaller K2CO3 and urea prills. The mixture was found to have comparablecompaction behaviour to AN compositions, indicating that it was useful as a mock for those compositions. In a plate impact experiment on a single layer of P2O5 prills, very little light was observed. Thisindicated that these prills were sufficiently inert for these purposes. The light produced by shocked granular ammonium nitrate beds and single prill layers was investigated using high-speed framing photography, photodiodes and gated visible-light spectroscopy. Framing photography of prill layers suggested that reaction in prill beds was dominatedby effects internal to prills. This was further supported by the similarity between photodiode recordings of prill beds and beds of inert prills containing a single reactive prills. Framing photography of drop weight experiments searching for a mechanism for initiation of reaction by interaction between prills found nothing. Decay of the light output of the beds suggested that in both granularand prill beds this light output was due to small regions heated to thousands of kelvin, which then cooled. Spectroscopic study confirmed this. These regions were found to reach a peak temperature of 6660 ± 20 K, well in excess of the approximately 2000 K predicted by a simple chemical model. Investigation of spectral lines observedduring this study indicated that the exothermic reaction that led to heating of these emitting regions involved NO.

Increased nitrogen (N) costs and environmental concerns have created a need to reevaluate current sidedress N application recommendations for corn. Injection of Urea Ammonium-Nitrate (UAN) may reduce N-loss via ammonia (NH?) volatilization compared to current surface application methods. This study evaluated injection and surface-banding application techniques of UAN in two ways: (1) by conducting a laboratory experiment where NH?-N loss was measured from UAN applied by both techniques across varying residue covers; and (2) by performing a field study where the application methods were compared by their effect on corn grain yield, ear leaf tissue N content, and stalk nitrate (NO3). The laboratory system used to compare the NH?-N loss from the UAN application methods was evaluated and found to be capable of providing rapid, accurate, and precise measurements of N loss throughout a range of N rates and conditions. In the laboratory study, injection of UAN reduced NH?-N losses to <1% of applied N. Surface-banding of UAN resulted in NH?-N losses between 15.3 and 32.5% of applied N. Results from the field study suggest that differences between application methods were commonly seen in ear leaf tissue N, where injection of UAN was often found to increase tissue N compared to surface-banding. Also, injection of UAN reduced the optimal N rate by 25 kg N ha?? compared to surface-banding. The results suggest that injection of UAN reduces the potential of NH?-N losses and is a practice worth considering in developing an efficient N fertilizer program. / Master of Science