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Campbell, Duncan J. "The chemical composition of soil solutions extracted from top soils in the Oxford area : the magnitude and range of variability". Thesis, University of Oxford, 1985. http://ora.ox.ac.uk/objects/uuid:e70e0323-8383-45f2-91f5-9cb2c26b5008.
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Although the soil solution lies at the centre of many of the processes which occur in soils, little information is available on the chemical composition of the soil solutions of field soils, or on the temporal and spatial variability of such solutions. The suitability of an immiscible fluid centrifugation method for obtaining samples of the soil solution was evaluated. The method was found to be substantially free from interferences and well suited to routine use. It was adapted for use with soils of low bulk density. Yields of soil solution from soils at or near field capacity ranged from 20 to 50% of the total water present. However little or no soil solution could be extracted from dry soils. Displaced solutions were analysed for about 20 solutes principally by inductively coupled plasma spectroscopy. Typical solute concentrations in soil solutons from six neutral and calcareous soil series in the Oxford area were in the range 10-2.4 to 10-3.4 M for Na, K, Ca, S, Cl, N03, alkalinity and dissolved organic carbon (DOC); 10-3.4 to 10-4.4 M for Mg, Si and P and <10-5.33 M for B, Li r Y, Ba, Mn, Cu, Fe, V, Zn, Al, Pb f Ni, Cd, Co, Sr and Mo. Short-range (5-10 m) variability was significantly less, and between-soil series variability significantly more, than the variability found between grass fields on the same soil series for most solutes. The main exception to this was N03 which exhibited a large between-field variability. In general, soil solutions from arable soils were more dilute than those from nearby pasture soils. Solutions from poorly drained sites on a heavy clay soil were more concentrated than those from freely draining sites on the same soil series. A year-long sampling programme showed that with the exception of P and alkalinity the concentrations of solutes in the soil solution changed significantly with time. The temporal range in the concentrations of solutes was found to increase in the order Si-Pandlt;alkalinity-Feandlt;Naandlt;Ca-Sr-Mg-Cuandlt;S-DOCandlt;K-Znandlt;Cl-pHandlt;Mn.
2
Saito, Hiroshi Harlan. "Effects of temperature and heating rate on off-gas composition and pyrene removal from an artifically-contaminated soil". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11060.
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Munzur, Basak. "Chemical Composition Of Atmospheric Particles In The Aegean Region". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609373/index.pdf.
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Daily aerosol samples were collected at the Çandarli which is located on Aegean coast of Turkey. A rural site was selected to monitor atmospheric pollution by long range transport. Sampling was performed in both summer and winter seasons, and in total 151 samples were obtained. Concentrations of elements in the samples were measured in order to identify sources and possible source locations of pollutants. Measured concentrations of trace elements at the Ç
andarli station were compared with those measured at various sites around the world and, also in Turkey. As a result of comparison, level of pollution at the Aegean Region was found to be lower than the Mediterranean Region and Black Sea Region. Air flow climatology at Ç
andarli was investigated in order to determine potential source regions for pollutants. Frequency of air flows from Russia and Western Europe are higher suggesting that emissions from these industrial regions affect the chemical composition of particulate matter. Besides these, it was concluded that contributions from Central and Eastern European countries are significantly high because of frequent air mass transport. Concentrations of elements measured at Ç
andarli station were found to show short and seasonal variations. Such variations in concentrations are explained by variations in the source strengths and transport patterns. Positive matrix factorization (PMF) was applied to determine sources of elements and contribution of sources to each element. This analysis revealed 5 sources, two local anthropogenic emissions factor, one soil factor, one sea salt factor and one long range transport factor. Distribution of Potential Source Contribution Function (PSCF) values showed that main sources of SO42- are observed in Bulgaria, Romania, Poland, Ukraine and central part of Aegean region.
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Furtado, Francisca Mirlanda Vasconcelos. "Feature soil, growth and chemical composition of grass in tifton fertilization and irrigation of aquaculture with wastewater". Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15397.
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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorThis work was carried out to evaluate the effects of nitrogen fertilization in areas of irrigated pastures with biofertilizados effluents from fish farming. Four doses of nitrogen fertilizer were used for 3 cycles of Tifton-85 grass cut every 28 days and irrigated with wastewater from fish farming. After each cutting the grass was fertilized with the respective doses of fertilizer. The design was completely randomized in a factorial 2 x 4 with four replicates. Four doses of nitrogen fertilizer dose corresponded to 0 to N; 198 kg N ha-1 yr-1 33% of the dose of N; 396 kg N ha-1 yr-1 66% of the dose of N; and 600 kg N ha-1 yr-1 corresponding to 100% of the dose of growth assessment the design was completely randomized using the nitrogen dosages described and four replications. The area per plot was used to harvest the fresh biomass to be analyzed, which was immediately measured on a digital scale pendulum for its determination. After all installments have their biomass values known and properly stored, they were sent to the laboratory of plant analysis Embrapa Mid-North. The collected biomass is fractionated into categories: whole plant (pseudo stem and leaf without senescent material), only pseudoculm, only leaf and senescent material. The stored material was taken for laboratory analysis of animal- nutrition LANA, Federal University Of CearÃ. Analyzes to determine the levels of dry matter were held (MS), mineral matter (MM), ether extract (EE), crude protein (% N x 6.25 = PB). The cellular content of the contents (CC) and hemicellulose (HEM) were obtained following the post- analysis equations. The fiber values of neutral detergent fiber (NDF) and acid detergent fiber (ADF) were measured after preparation of the material to be analyzed in bags of TNT (100 g / m2) with dimensions of 4 x 5cm and engagement in analysis instrument fibers (Ankom220Â). Nitrogen fertilization influenced the soil chemical characteristics as the base saturation and potential soil acidity in Tifton 85 irrigated pasture with fish farm effluents, where nitrogen (N) influenced positively to the growth of Tifton 85 irrigated with wastewater fish farming. Nitrogen fertilization in conjunction with wastewater from fish farming. The absence of nitrogen fertilization promoted increase in dry matter content in Tifton-85 grass, as well as high levels of ADF and NDF. Leaf fraction of Tifton 85 has a higher amount of organic compounds in relation to pseudoculm fraction, and this can change the true values of ether extract and crude protein. The wastewater fish farming along with the application of ammonium sulfate positive effect on the chemical composition of Tifton 85 grass.
Este trabalho foi conduzido com o objetivo de avaliar os efeitos da adubaÃÃo nitrogenada em Ãreas de pastagens irrigadas com efluentes biofertilizados oriundos da piscicultura. Quatro doses de adubo nitrogenado foram utilizados durante 3 ciclos do capim Tifton-85, cortado a cada 28 dias e irrigado com Ãgua residuÃria de piscicultura. ApÃs cada corte o capim era adubado com as respectivas doses de adubo. O delineamento utilizado foi inteiramente casualizado em esquema fatorial 2 x 4 com quatro repetiÃÃes. As quatro doses de adubo nitrogenado correspondiam a dose 0 de N; 198 kg de N ha-1 ano-1 33 % da dose de N; 396 kg de N ha-1 ano-1 66% da dose de N; e 600 kg de N ha-1 ano-1 que correspondeu a 100% da dose de N. Para avaliaÃÃo do crescimento o delineamento utilizado foi inteiramente casualizado utilizando as dosagens de nitrogÃnio descritas e quatro repetiÃÃes. A Ãrea da parcela Ãtil foi utilizada para a colheita da biomassa fresca a ser analisada, que foi imediatamente medida em uma balanÃa digital de pendulo para sua determinaÃÃo. ApÃs todas as parcelas terem seus valores de biomassa conhecidos e devidamente armazenados, estes eram encaminhados ao laboratÃrio de analises vegetais da Embrapa Meio-Norte. A biomassa coletada foi fracionada em categorias: planta inteira (pseudocolmo e folha sem o material senescente), somente pseudocolmo , somente folha e material senescente. O material armazenado foi levado para o laboratÃrio de analise de nutriÃÃo animal- LANA, da Universidade Federal Do CearÃ. Foram realizadas anÃlises para determinaÃÃo dos teores de matÃria seca (MS), matÃria mineral (MM), extrato etÃreo (EE), proteÃna bruta (% de N x 6,25 = PB). Os teores do conteÃdo celular (CC) e hemicelulose (HEM) foram obtidos seguindo-se as equaÃÃes pÃs analises. Os valores de fibra em detergente neutro (FDN) e fibra em detergente Ãcido ( FDA), foram mensurados apÃs o acondicionamento do material a ser analisado em saquinhos de TNT (100 g/m2) com dimensÃes de 4 x 5cm e acoplamento em aparelho analisador de fibras (Ankom220Â). A adubaÃÃo nitrogenada influenciou caracterÃsticas quÃmicas do solo como a saturaÃÃo por base e acidez potencial do solo em pastagem de capim- tifton 85 irrigada com efluentes de piscicultura, onde o nitrogÃnio (N) influenciou positivamente para o crescimento do capim-tifton 85 irrigado com efluentes de piscicultura. A adubaÃÃo nitrogenada em conjunto com a Ãgua residuÃria de piscicultura. A ausÃncia de adubaÃÃo nitrogenada promoveu aumento nos teores de matÃria seca no capim tifton-85, assim como elevados teores de FDA e FDN. A fraÃÃo folha do capim tifton 85 possui maior quantidade de compostos orgÃnicos em relaÃÃo a fraÃÃo pseudocolmo, e isso pode alterar os valores verdadeiros de extrato etÃreo e proteÃna bruta. A Ãgua residuÃria de piscicultura junto com a adubaÃÃo nitrogenada proporcionou efeito positivo na composiÃÃo bromatologica do capim Tifton 85.
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Mofokeng, Motiki Meshack. "Growth, yield and chemical composition of Pelargonium sidoides DC. in response to nitrogen and soil water management". Diss., University of Pretoria, 2015. http://hdl.handle.net/2263/50704.
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Pelargonium sidoides DC. is one of many medicinal plant species that are harvested in the wild. The current trade in these medicinal plants has negatively affected their distribution in the wild due to unsustainable harvesting. The demand for medicinal plants is unlikely to decrease, but sustainability of the supply is questionable. This is because commercial exploitation threatens to deplete their populations, resulting in many species being considered vulnerable to extinction and being lost from their natural habitat. Increased demand, which is already too high to be met by sustainable harvesting, and price increases presents potential opportunities for cultivating indigenous medicinal plants at a commercial scale. A need for basic information on how to grow the plants and other related matters necessitates that field trials be conducted, before farmers could be expected to venture into cultivating medicinal plants and this study aimed at developing such information.
The specific objectives of the study were to investigate 1) the physiological and morphological, 2) the yield components and 3) chemical composition of P. sidoides in response to soil water and nitrogen levels. The study was conducted under a rainshelter as a randomized complete block design with three irrigation levels, four nitrogen levels and three replicates. The irrigation treatments were 30% allowable depletion level (ADL) (well watered treatment), 50% ADL (moderately stressed treatment) and 70% ADL (severely stressed treatment), while the nitrogen levels were 0, 50, 100 and 150 kg · N · ha-1. Dried root samples were analyzed for the presence of two standard compounds, scopoletin and esculin, using thin layer chromatography (TLC) and for metabolite profiling using the nuclear magnetic resonance technique (NMR).
Nitrogen and water level had no significant interaction effect on all measured parameters. Water stress significantly reduced stomatal conductance, while nitrogen had no significant effect on it. The well watered control had a significantly higher leaf area index, plant height and leaf area compared to the water stressed treatments. Nitrogen had a significant effect on the number of leaves, where 100 kg · N · ha-1 had a significantly higher number of leaves compared to other nitrogen treatments. The well watered treatment again had a significantly higher total biomass, fresh and dry root yield; and nitrogen use efficiency compared to the water stressed treatments. The water use efficiency was significantly decreased in the well watered treatment. Water stress significantly increased nitrogen content and chlorophyll content of P. sidoides plants and leaves, respectively. Nitrogen levels of 50 and 100 kg · N · ha-1 resulted in a significantly higher total biomass compared to the control. TLC analysis showed the presence of the two standard compounds in all treatment samples analyzed. The orthogonal partial least square discriminatory analysis (OPLS-DA), which was performed on the NMR spectral data, showed separation between the irrigation treatments, resulting in two clusters representing the well watered treatment and the water stressed treatments. Asparagine, arginine, sucrose, xylose, glucose and citric acid were found to be the compounds associated with the separation. There was no separation of the samples regarding the nitrogen treatments which is indicative of the small effect of nitrogen on the metabolite content of the treatments. The results from this study showed a relationship between physiological, morphological and yield response as well as chemical composition of P. sidoides. The observed stomatal closure under water stress conditions, due to low turgor pressure in the guard cells, had a significant negative effect on leaf area, leaf area index, total biomass and root yield. Also the increases in total biomass and root yield under well watered conditions could be attributed to the increased primary metabolite content, under such conditions. The recommendation from the study is that P. sidoides plants should be grown under well watered conditions for a year or two to increase growth and root yield. Thereafter plants can be exposed to water stress in the second season, which is expected to increase the concentration of important secondary metabolites.Dissertation (MInst Agrar)--University of Pretoria, 2015.
tm2015
Plant Production and Soil Science
MInst Agrar
Unrestricted
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Nchabeleng, Lehlohonolo. "Effects of different climatic and soil factors at different locations on chemical composition of bush tea (Athrixia phylicoides DC.)". Thesis, University of Limpopo (Turfloop Campus), 2012. http://hdl.handle.net/10386/740.
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Soltani, Dashtbozorg Soroosh. "Microbial Rhamnolipids as Environmentally Friendly Biopesticides: Congener Composition Produced, Adsorption in Soil, and Effects on Phytophthora sojae". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1438175115.
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Terrill, Thomas Howard. "Effects of soil moisture and al-nitrilotriacetate on yeild chemical composition and digestibility of ryegrass (Lolium multiflorum, L.) by meadow voles". Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/53088.
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Flooding effects mineral composition of pasture grasses, but little is known concerning effects on mineral metabolism and fiber digestibility in animals. Experiments were conducted to investigate effects of flooding and Al-nitrilo-triacetate (Al-NTA) on growth, chemical composition and digestibility of annual ryegrass (Lolium multiflorum, L.). Ryegrass was grown in a greenhouse experiment on Bucks silt loam soil with two soil moisture levels (flooding and 80% field capacity) and two Al rates (0 and 135 mg/kg) as Al-NTA.
Flooding increased Al, Fe, Cu, Ca and fiber and decreased dry matter yield, Mg, K and Zn concentrations. Treatment with 135 mg/kg Al had no effect on Al in plants, but decreased Ca and P concentrations.
Two digestion trials were conducted with meadow voles (Microtus pennsylvanicus) fed forage harvested from the greenhouse experiment. Voles were housed in stainless steel metabolism cages for total collections of feed and feces. A 2-day preliminary, during which voles were fed 100% ryegrass, preceded a 3-day collection period. At the end of the collection period, a blood sample was taken from the animals.
Forage grown under flooding increased apparent absorption of Al, and Ca concentration in urine samples. Apparent absorption of Mg and serum Mg were decreased, and dry matter digestibility tended to decrease.
Grazing forages produced under flooded conditions would increase potential for outbreaks of grass tetany in animals due to reduced Mg intake and absorption. Altered Mg and Ca metabolism appeared related to Al ingestion. Lowered animal performance could result from reduced DM digestibility.Master of Science
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Bergknut, Magnus. "Characterization of PAH-contaminated soils focusing on availability, chemical composition and biological effects". Doctoral thesis, Umeå : Umeå University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-789.
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Joseph, Gilbert. "A comparative study of the chemical composition of soils from aquaculture systems in the Cochin estuarine area". Thesis, Central Marine Fisheries Research Institute, 1985. http://eprints.cmfri.org.in/11071/1/Joseph%20Gilbert%20P.%20G..pdf.
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In recent years there has been an increasing awareness
of the role and benefits of scientific fish farming in coastal
waters for augmenting fish production of India, although a
traditional practice of aquaculture has been prevailing in these waters for a long time. A comprehensive knowledge of the ecology of the different culture systems forms an integral part of the scientific farming because it directly influences the rate of production. The growth and survival of the organisms used for culture depend largely on the overall productivity of the pond, which in turn, is influenced by the various environmental characteristics of the water and the fertility of the pond soil. In short, the water and soil conditions to a great extent determine the success or failure of the culture operation. Further, the information on the various environmental characteristics of the pond water and soil, availability of essential elements and the rate of organic productivity, would not only help to adopt successful management principles and culture techniques but also to manipulate the ecosystem providing the necessary inputs for obtaining better production. Besides providing an overall picture of the productivity of the ponds, studies on soils furnish information on the inputs to enhance the fertility of soils and also help in selection of suitable sites for construction of farms.
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Dejene, Mashilla. "Grain storage methods and their effects on Sorghum grain quality in Hararghe, Ethiopia /". Uppsala : Dept. of Ecology and Crop Production Science, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/a454.pdf.
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Whatmuff, Mark. "The effect of applied 'high magnesium' bitterns upon the physical and chemical properties of soils from Wakool-Tullakool Irrigation District, New South Wales, Australia". Thesis, The University of Sydney, 1991. https://hdl.handle.net/2123/26371.
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This study was concerned with determining the effect upon soil structure when the drainage scheme evaporation pond product "high magnesium bitterns" was applied to soils from the Wakool-Tullakool irrigation district, N.S.W, Australia.
Two soils were chosen covering the extremes of soil types found in the district.
They were;
1. Burraboi Sandy Loam (Gn 2.63) a Calcic Aqiuc Haplustult and,
2. Moulmein Clay (Ug5.24) a Typic Chromoxerert.
Laboratory tests were carried out to determine the basic physical and chemical properties of the two soils. Clay mineralogy for the two soils was determined using X- ray diffractometry.
Both Na/Ca and Na/Mg cation exchange isotherms were constructed from data obtained using a sequential dialysis equilibration on the clay fraction of both soils. The final solution concentration was set at 0.006 mmol(+)L-1 thus approximating the actual soil solution at field capacity.
Both soil clays showed exchange preference for the divalent cations over the monovalent cation Na. The values of K(VAN) show that Na selectivity at very low values of ENa decreases rapidly with increasing ENa to a minimum value after which Na selectivity increases. The values of Kex, the thermodynamic exchange constant, for Burraboi Sandy Loam were 0.746 for the Na/Ca system and 1.193 for the Na/Mg system. Thus the Ca system shows a decrease in Na selectivity relative to the Mg system. There was no significant difference in between the values of Kex for the Na/Ca and Na/Mg systems in Moulmein Clay. The calculated values of the rational activity coefficients /Na and /M2+ were not equal to unity over the range of Na saturation, and Kex did not remain constant, Thus non-ideal exchange occurred. It was also evident that some heterogeneity of exchange sites existed.
An infiltration trial using diluted bitterns was carried out on Moulmein clay to assess its effect on the infiltration characteristic of the soil. No significant difference between treatments could be detected and it is thought that soil variability masked any treatment effect. A separate experiment on the same site where the infiltered soil was sampled for moisture content in a vertical grid pattern, showed that the downward movement of infiltering solute, when the soil is at the peak of its drying cycle, is governed by vertical movement through conducting macropores. Little lateral movement was seen and the solute did not penetrate the soil matrix to any great extent until redistribution occurred. Upon wetting soil swelling occurred and infiltration effectively ceased.
Laboratory examination of samples taken from the infiltration trial also showed no detectable treatment differences. The total concentration of the immiscibly displaced soil solution increased with depth in all treatments as inferred by electrical conductivity measurements. It is thought that the infiltering solution moved rapidly down the profile carrying salts dissolved from the macropore periphery stopping when the pores became constricted in a region of increased soil moisture and subsequent soil swelling.
Emerson structural stability tests carried out on the infiltration samples showed that the soils treated with the diluted bitterns (0.1 M and 0.01M) had slightly improved structural stability moving from class 1 and 2 to class 3, as defined by Emerson. This could be due to displacement of the Na by Mg or due to an increase in ionic strength in the soil solution.
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Bopape-Mabapa, Moshidi Paulina. "Yield characteristics, carbon capture and chemical composition of moringa oleifera under diverse planting population and agro-ecological conditions of the Limpopo Province". Thesis, University of Limpopo, 2019. http://hdl.handle.net/10386/2860.
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Thesis (Ph. D. Agric. (Plant Production)) --University of Limpopo, 2019Moringa oleifera is a multipurpose fast growing tree which is widely cultivated in tropical and subtropical regions of the world due to its numerous benefits. The benefits include medicinal use, industrial use, soil fertility, water purification, climate change mitigation as well as of nutritional value for humans and livestock. Recently, many areas globally have been rendered vulnerable to climate change as well as food insecurity. Climate change increases irregularities of rainfall and temperature patterns in semi-arid conditions. One practical way to address this challenge in the agricultural sector is to introduce more trees crop species which are found to be more tolerant than annual crops under harsh growing conditions. Moringa is one species that could be considered under variable climatic conditions for positive outcomes through climate change adaptation and mitigation as well as life sustenance against food insecurity threats. Production of moringa in South Africa is exclusively for leaf processing and consumption. To date, there is no documented information available about seed and oil yield production of moringa mainly in the Limpopo Province of South Africa. The aim of the study was to generate knowledge on moringa growth, nutritional composition, seed and oil yield production as well as its response to drought through gaseous exchange parameters, as influenced by plant density under diverse agro-ecological locations in Limpopo Province. The study was conducted in the Limpopo Province, South Africa, from November 2013 to January 2016. The study area falls within the semi-region which is characterized by low and erratic rainfall which predominately falls in summer as well as extremely low or high temperatures. A survey was conducted from November 2013 to September 2014 in five districts of the Limpopo Province. Focus group discussion, questionnaires and field observations were used for data collection. A total of 150 moringa growers formed part of the focus group and a questionnaire was administered to only thirty-one farmers, who constitute the population of farmers producing moringa within an area of 0.25 ha or more. A second study was conducted at two experimental sites in the Limpopo Province of northern part of South Africa to evaluate for the first time, the effect of plant density and cutting interval on biomass production and chemical composition of moringa grown under two diverse climatic conditions. Four different planting densities (435 000, 300 000, 200 000 and 100 000 plants/ha) were arranged in a randomized complete block design and experimental samples were replicated four times. A third study was conducted over two years to achieve additional objectives which included evaluation of gaseous exchange, biomass, seed, and oil yield. Untreated seeds of Moringa oleifera were used for establishing the trial at densities of 5 000, 2 500, 1 667 and 1 250 plants ha-1, with eight replicates. The same study was used to achieve the objective on gaseous exchange in comparison with other two naturally growing tree species of mopane (Colophospermum mopane) and marula (Sclerocarya birrea) trees growing within the moringa trial vicinity. The study was further used to evaluate the effect of planting density on biomass, grain, oil yield production and nutritional composition of Moringa oleifera trees. The last part of the study was carried out in the five districts of the Limpopo Province to determine the influence of soil physical and chemical properties on the nutritional composition of moringa leaves. The farms that were identified during the survey were also used to achieve other objectives of the study. In order to determine soil and leaf nutritional composition, soil samples were collected and analyzed for physical and chemical properties. The harvested leaves were dried at room temperature and their nutritional compositions were determined using standard methods. Findings from the studies revealed the following: The survey indicated that there are potential moringa farmers in all the districts of the province, with the intention to commercialize the tree. Majority of farmers grow moringa on 0.251.0 ha and have been producing the crop for the past 2 years. The study on planting density and cutting frequency revealed satisfactory nutritional composition in the leaves across the cutting frequencies and that, an increase in the plant density led to enhanced biomass production. The study on the monthly and seasonal gaseous exchange revealed significant differences in net photosynthetic rate, transpiration, sub-stomatal CO2 and stomatal conductance. However, planting densities of Moringa oleifera had no significant effect on all the gaseous exchange parameters measured. In a comparison of moringa with other tree species growing in the vicinity of moringa, the results differed significantly in gaseous exchange. The highest activity in photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E) and sub-stomatal CO2 (Ci), as well as higher stomatal density, was found in moringa. The findings from the biomass, seed yield and oil yield study showed that the increase in measured biomass, seed and oil yield increased with increasing planting density. However, seed oil concentration was non-significant. Findings from the ecology study revealed that moringa improved soil nutritional composition; mainly in areas where the trees were more than three years old as compared to control soils where moringa had not been planted. The soil nutritional composition differed with soil textural classes with the clay soils recording higher nutrient ion values. The study revealed that moringa can be produced in many locations of the Limpopo Province without negatively affecting leaf nutritional composition. Moringa leaves contain high level of nutrients even under marginal production areas irrespective of the planting density. A population of 5000 plants ha-1 can be used for seed and oil yield production where temperatures are favourable for improved farmers’ livelihoods. The results strongly showed with no doubt, the superiority of moringa in capturing more carbon among the three species. Moringa maintained good leaf yield even under drought condition, which is an indication of its potential to act as a good sink for carbon dioxide absorption. It can, therefore, be recommended for many parts of Limpopo Province for climate change mitigation and adaptation strategies and food security. KEY CONCEPTS: agro-ecology, biomass, climate change, commercialization, drought, food security, gas exchange, leaf chemical composition, location, Moringa oleifera, oil, seed, soil textural class, survey, trees, weather, yield
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Gregorauskienė, Virgilija. "Cheminių elementų kiekių kaitos dėsningumai Lietuvos dirvožemio profilyje". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121227_090556-03063.
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Disertaciniame darbe analizuojama Lietuvos dirvožemio cheminės sudėties vertikali kaita, paremta akredituotose laboratorijose nustatytais Lietuvos teritorijoje gautais duomenimis, analizuotais taikant standartizuotus matematinius–statistinius metodus. Tai leido objektyviai pagrįsti vertikalaus cheminių elementų pasiskirstymo dirvožemyje bendrus dėsningumus ir išryškinti Lietuvos dirvožemio vertikalios geocheminės sudėties specifiką tarptautiniame kontekste. Dirvožemio granuliometrinės sudėties ir išskirtų frakcijų cheminės sudėties analizė išryškino sąsajas tarp dirvožemio granuliometrinės ir cheminės sudėties. Disertacijoje apibendrintos dirvodarinių uolienų bei atskirų jų litologinių tipų pirminės cheminės sudėties savybės ir šių savybių vaidmuo dirvožemio profilio formavimesi. Apžvelgiant geocheminės sudėties kaitą atskiruose dirvožemio profiliuose, atskleista įvairių dirvodaros procesų bei žmogaus veiklos įtaka vertikaliam elementų persiskirstymui dirvožemyje. Lietuvos teritorijoje tolygiai išdėstytų dirvožemio kasinių geocheminių tyrimų duomenys leido korektiškai suformuoti tipinius smėlio–priesmėlio ir molio–priemolio dirvožemio geocheminius profilius ir atskleisti jų būdingąsias savybes. Realių duomenų pagrindu sudarytas tipinio Lietuvos dirvožemio geocheminio profilio modelis ir išryškintos esminės dirvožemio vertikalios geocheminės sudėties kaičiosios savybės – Lietuvos dirvožemyje vyrauja daugumos elementų išplovimas ir išnešimas už profilio ribų.Vertical alternation of chemical composition in Lithuanian soil profile has been investigated in the study. Investigations are based on the certified analytical data, by applying standard mathematical–statistical data processing that enables to justify the vertical distribution patterns of trace and major elements and obtain internationally comparable concluding results on the national soil geochemistry. Soil grain size analysis and chemical analysis of separated sand, silt and clay particles revealed the relation between the soil grain size and chemical composition. Investigation of chemical composition of the soil parent material reflected its dominance as soil forming factor. Geochemical survey of the 74 individual soil profiles, representing all soil regions and main soil types, allowed to expose various soil forming processes and on its background to generalize geochemical features and ascertain the dominant ones in the sand–loamy sand and the loam–clay soil of Lithuania. On the base of original geochemical data the model geochemical soil profile was created and the dominant geochemical process was determined – element depletion and removal out of soil profile prevails in Lithuania.
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Angst, Gerrit [Verfasser], Carsten W. [Akademischer Betreuer] [Gutachter] Mueller i Karsten [Gutachter] Kalbitz. "Disentangling the sources, chemical composition, and spatial distribution of soil organic matter in topsoil and subsoil under European beech / Gerrit Angst ; Gutachter: Carsten W. Mueller, Karsten Kalbitz ; Betreuer: Carsten W. Mueller". München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/111779668X/34.
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El, Make Mahmoud. "Base-cations in relation to weathering of phyllosilicates and forest management in Swedish forest ecosystems /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-5899-4.pdf.
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Rothpfeffer, Caroline. "From wood to waste and waste to wood : aspects on recycling waste products from the pulp mill to the forest soil /". Uppsala : Dept. of Forest Soils, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200783.pdf.
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Kouakoua, Ernest. "La matière organique et la stabilité structurale d'horizons de surface de sols ferrallitiques argileux : effet du mode de gestion des terres". Nancy 1, 1998. http://www.theses.fr/1998NAN10016.
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Cette étude concerne essentiellement des sols ferrallitiques argileux (du Congo, du Brésil et de la Martinique). Les formes de matière organique (MO) susceptibles de variations importantes avec le mode de gestion de terres et la stabilité de l'agrégation ont été étudiées par différentes approches : par fractionnement granulométrique du sol et par extraction du sol à l'eau chaude. La stabilité structurale est estimée par le taux de macroagregats stables à l'eau (AS) avant et après traitement à l'eau chaude (ASE). La diminution importante des teneurs en C total dans les horizons de surface des sols cultivés après défrichement de la végétation naturelle a été généralement confirmée. Le fractionnement granulométrique de la MO montre que : (I) tous échantillons confondus, les contenus en C augmentent des fractions sableuses aux fractions argileuses, (II) toutes les fractions sont concernées par les variations des contenus en C, mais avec des amplitudes variables selon la fraction, le type de sol et le mode de gestion. Toutefois, les variations de la fraction sableuse sont les plus importantes. La mise en culture intensive induit aussi une diminution des teneurs en C soluble à l'eau chaude (CS) et en sucres totaux (CST) des sols. Les relations entre MO des sols et AS ont été étudiées pour les MO solubles à l'eau chaude et pourles fractions granulométriques de la MO. On a pu montrer, comme d'autres auteurs, l'existence de relations hautement significatives entre teneur en CS et AS. Pourtant l'étude de l'effet direct de ces MO solubles ne met pas en évidence un effet agrégeant de ces MO. Quant au contenu en C des fractions granulométriques des sols, seules les MO associées aux fractions sableuses (débris végétaux) montrent une corrélation significative avec AS. Compte-tenu des observations ci-dessus, on ne peut toutefois conclure à un effet réel et direct de cette fraction sur l'agrégation. En conclusion, ce travail n'aura pas permis d'identifier avec certitude une fraction organique agrégeante dans ces sols. Il aura toutefois conduit à montrer que les MO solubles à l'eau chaude ne le sont probablement pas, et que, dans ces sols A argile 1 : 1 ou le processus de désagrégation est dominé par le phénomène d'éclatement, les MO associées aux fractions sableuses pourraient éventuellement jouer un rôle important dans la stabilité structurale.
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Souto, Patrícia Carneiro. "Acumulação e decomposição da serapilheira e distribuição de organismos edáficos em área de caatinga na Paraíba, Brasil". Universidade Federal da Paraíba, 2006. http://tede.biblioteca.ufpb.br:8080/handle/tede/8199.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Nutrient cycling is fundamental to forest maintenance, and involves the deposition of organic material, its decomposition and nutrient release for reabsorption by superior plants. These processes are regulated by biotic and abiotic factors that determine the environmental sustainability. This study had the objectives to determine the monthly litter production and the time necessary to the accumulated litter to disappear, characterize the process of decomposition, evaluate the microbial activity and the effect of climatic and soil conditions on it, determine the fluctuations of the microorganisms and mesofauna communities in a Caatinga forest site, and, finally, analyze liter quality in order to identify the different phases of the process of organic matter decomposition and nutrient enrichment. Field work was carried out at the RPPN of the Fazenda Tamanduá, located in Santa Terezinha (PB), from October 2003 to September 2004 (period 1 = P1) and from October 2004 to September 2005 (period 2 = P2) in seven transects systematically located in the RPPN area. Litter production were estimated from monthly litter collection from 20 1mx1m collector boxes randomly distributes in the transects. The collected litter was fractioned into leaves, stems, reproductive structures and miscellany, and then dried and weighed. Every three months the deposited litter on the soil was collected from 0,5mx0,5m frames, dried and weighed, to calculate the decomposition factor (K) and the time required to 50 and 95% of litter decomposition. The rate of litter decomposition was estimated in nylon bags with 30g of dried litter. These 480 nylon bags were divided equitably and placed around the 20 collector boxes. Every month, one nylon bag from each collector bag was recovered from the field and the litter inside was taken out, cleaned and weighed to determine its weight loss. Diurnal and nocturnal microbial activity was measured by means of soil respiration. Macronutrients composition of the deposited litter and in the litter inside the nylon bag was determined. Litter production during P1 and P2 was 1290.9 kg ha-1 and 1947.5 kg ha-1, respectively, totaling 3238.5 kg ha-1. Leaf, stem, reproductive structure and miscellany fractions corresponded to 64.14, 23.48, 10.9 and 1.46% of total litter production, respectively. More litter deposition was observed in the beginning of the dry season. The values of the coefficient of litter decomposition were 1.1 and 1.4 for P1 and P2, respectively, and mean a fast nutrient transfer from litter to soil. The time required to 50 and 95% litter decomposition was 229.9 and 996.4 days, respectively, in P1, and 178.8 and 770.1 days, respectively, in P2. Initial litter weight loss in nylon bags was fast due to the degradation of labile composts by microorganisms, and decreased afterward due to the more resistant and more lignified materials of the remaining litter. Fungi population was larger than the bacteria population, favored by soil water availability. Mesofauna was mainly represented by Diptera’s 67.24% of the total number of counted mesofauna individuals or of the total biomass of mesofauna individuals and Acarine’s (53.49%), in P1 and P2, respectively. The low values of Shannon (0.38) and Pielou (0.15) indexes denoted the distribution heterogeneity of the mesofauna representatives. The order of macronutrient concentrations in the accumulated litter was as follow: N > Ca > S > K > Mg > P. Litter P content was higher than the expected for dry tropical forests.
A ciclagem de nutrientes, fundamental para a manutenção das florestas, envolve desde a deposição de material orgânico, sua decomposição e disponibilidade de nutrientes para os vegetais superiores. Todos esse processos são regulados por fatores bióticos e abióticos que determinam a sustentabilidade do ambiente. Este trabalho teve como objetivos determinar a produção mensal de serapilheira e o tempo necessário para o desaparecimento da serapilheira acumulada; caracterizar o processo de decomposição; avaliar a atividade microbiana e a influência das condições edafoclimáticas durante esse processo; conhecer as flutuações das comunidades de microrganismos e da mesofauna do solo em área de caatinga e, por último, analisar a qualidade da serapilheira a fim de identificar as diferentes fases do processo de decomposição e concentração de nutrientes. O trabalho foi desenvolvido na RPPN pertencente à Fazenda Tamanduá, localizada no município de Santa Terezinha (PB), durante dois anos, sendo o período 1 compreendido de outubro/2003 a setembro/2004 e o período 2 compreendido de outubro/2004 a setembro/2005. Foram demarcados sete transectos, onde foram realizadas todas as avaliações. Para a produção da serapilheira, foram distribuídas 20 caixas coletoras de 1m x 1m, sendo mensalmente coletado todo o material precipitado, que foi separado nas seguintes frações: folhas, galhos, estruturas reprodutivas e miscelânea; depois foi seco em estufa e pesado. A cada três meses foi coletada a serapilheira acumulada no solo, utilizando-se uma moldura metálica de 0,50 m x 0,50 m. Todo o material acumulado na moldura foi retirado, seco em estufa e pesado, calculando-se assim o fator de decomposição K e o tempo necessário para decompor 50% e 95% da serapilheira. Na avaliação da taxa de decomposição da serapilheira, utilizou-se sacola de náilon contendo cada uma 30g de serapilheira previamente seca. Próximo de cada caixa coletora foram distribuídas 24 sacolas de náilon contendo serapilheira, totalizando 480 sacolas. Mensalmente foram coletadas 20 sacolas, sendo o material retirado, limpo e pesado para avaliar a perda de peso em relação ao inicial. Paralelamente, avaliou-se no campo, a atividade microbiana, medida pela respiração edáfica, nos turnos diurno e noturno. Determinou-se também a qualidade química da serapilheira depositada e a que foi decomposta nas sacolas de náilon, quanto à concentração dos macronutrientes. A produção de serapilheira durante o período 1 de estudo foi de 1290,95 kg ha-1 e 1947,56 kg ha-1 no período 2, totalizando 3.238,51 kg ha-1, sendo a fração folhas predominante na serapilheira devolvida ao solo com 64,14%, seguida da fração galhos (23,48%), estruturas reprodutivas (10,92%) e miscelânea (1,46%). A maior deposição ocorreu no início da estação seca, caracterizando a sazonalidade. Os coeficientes de decomposição (K) de 1,1 para o período 1 e, 1,4 para o período 2, indicam uma transferência mais rápida dos nutrientes contidos na serapilheira para o solo. O tempo necessário para decompor 50% e 95% da serapilheira foi de 229,9 dias e 996,4 dias, respectivamente, período 1. No período 2, o tempo de meia vida foi de 178,8 e 770,15 dias para decompor 95%.A maior perda de peso da serapilheira acondicionada nas sacolas de náilon ocorreram no início do período de exposição, resultado da degradação dos compostos lábeis pelos microrganismos, sendo a velocidade do processo diminuída ao longo do tempo, devido a permanência das partes mais resistentes e lignificadas da serapilheira. Quanto a microbiota, a maior população foi de fungos, em relação à de bactérias, estimulado, principalmente, pelas condições favoráveis na disponibilidade hídrica do solo. Os grupos predominantes da mesofauna foram Díptera com 67,24% no período 1 e Acarine com 53,49% no período 2. Os baixos valores nos índices de Shannon (0,38) e de Pielou (0,15), indicaram uma baixa uniformidade na distribuição dos indivíduos. Quanto à composição química da serapilheira, a serapilheira depositada apresentou concentração de nutrientes na seguinte ordem: N > Ca > > S > K > Mg > P, sendo os teores de P encontrados na serapilheira considerados elevados para florestas tropicais secas.
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HAMA, PATRICIA. "Estudo da influencia da chuva acida na concentracao de aluminio em solos proximos a uma termoeletrica a carvao". reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10951.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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BONA, IRENE A. T. "Estudo de assinaturas químicas em cerâmica da tradição tupiguarani da região central do estado do Rio Grande do Sul, Brasil". reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11433.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Ouhdouch, Yedir. "Bacteries actinomycetales rares productrices d'antifongiques : criblage, selection et etude taxonomique d'une souche active ; purification de l'antifongique elabore". Nancy 1, 1989. http://www.theses.fr/1989NAN10077.
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Chateau, Denis. "Etude de l'influence de la structure et de la composition de matériaux hybrides monolithiques sur les propriétés optiques (luminescence et absorption non-linéaire)". Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2013. http://tel.archives-ouvertes.fr/tel-00863807.
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Le procédé sol-gel permet la réalisation de matériaux optiquement performants et la possibilité d'intégrer diverses molécules dans ces systèmes ouvre les portes à des applications dans de nombreux domaines. Nous nous sommes intéressés en particulier à la réalisation de matériaux sol-gel monolithiques, fortement dopés avec des molécules actives, dans le cadre de la réalisation de limiteurs optiques performants dans le visible et dans l'infrarouge.La mise au point de procédés et de matrices sol-gel compatibles avec divers types de chromophores a tout d'abord été effectuée. Une investigation des paramètres expérimentaux et de la nature des précurseurs influençant la microstructure des matériaux a été réalisée, ainsi que la mise au point de méthodes de gélification accélérée capables de piéger efficacement les chromophores dans les matrices sol-gel même à de très hautes concentrations.Le dopage des matrices obtenues avec différents chromophores pour la limitation optique dans le visible et dans l'infrarouge s'en est suivi, avec une étude de l'impact des matrices sur les propriétés optiques des dopants. L'évaluation des performances en limitation a révélé les performances exceptionnelles des systèmes étudiés dans le visible, et des résultats prometteurs pour l'infrarouge.Enfin, la synthèse de nanoparticules d'or isotropes et anisotropes et leur incorporation dans les matériaux préparés a permis de mettre en évidence des effets d'exaltation importants sur les propriétés non-linéaires des chromophores au sein des matrices sol-gel et permettent d'améliorer les performances en limitation de manière considérable.
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Orwin, K. H. "Soil microbial stability and function : the role of diversity, composition and soil resources". Thesis, University of Canterbury. Biological Sciences, 2004. http://hdl.handle.net/10092/6810.
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Soil microbial function and stability may affect many other ecosystem functions, including soil carbon storage, nutrient cycling and plant productivity. However, the drivers of soil microbial stability itself are little understood. This thesis therefore aimed to develop a method and indices capable of quantifying soil microbial stability in terms of the resistance (amount of change caused by a disturbance), and resilience (rate of recovery) of the soil microbial community to a model disturbance, and to determine the role of three potential drivers of soil microbial function arid stability: diversity, composition and soil resources. Initially, soil microbial stability and soil resources were measured during three chronosequences to assess whether stability changes in a natural environment and whether resources are an important driver of these changes. Although soil resources were frequently related to resistance and resilience, the direction and strength of correlations depended on the response variable and chronosequence considered. This suggested a factor related to soil resources, which varied across chronosequences, was a stronger driver of soil microbial stability than resources themselves. Two potential factors were plant species composition and diversity. A glasshouse experiment that tested these factors was harvested at 4 times throughout a 16-month period. Plant species composition, but not diversity, proved to be a strong driver of soil microbial function and stability. As different plant species may alter soil microbial function and stability by depositing different carbon substrates, a further experiment manipulated the composition and diversity of carbon substrates added to a base soil. The composition, and sometimes the diversity, of added substrates affected the soil microbial community, its function and stability. Diversity effects saturated at low levels and depended on which substrates were added. The overall conclusion from this set of experiments was that the strongest drivers of soil microbial function and stability seemed to be the composition of plant and soil microbial communities as well as soil resources.
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Azevedo, Luiz Otavio Roffee. "Infra-Red Spectrophotometry and X-Ray Diffractometry as Tools in the Study of Nickel Laterites". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/231213.
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Nickel silicate laterite deposits developed on ultra-mafic rocks are similar in many general respects but they vary considerably in detail. The mineralogy of these surficial deposits is very complex and difficult to determine because of the fine grained nature and solid solution characteristics of the hydrous secondary minerals and because many of the phases are actually mineraloids that are poorly ordered or amorphous. To try some new approaches toward clarification of these phases, 24 samples from New Caledonia and Puerto Rico ranging from the ophiolite-ultramafic olivine-pyroxene-chromite-serpentine substrate rocks upward through intermediate phases of weathering to the final oxide -hydroxide iron cap phase were analyzed with the infrared spectrophotometer (IR -10) and with the automated X –ray diffractometer. Four limonite samples were also mineralogically analyzed. Goethite, secondary quartz, cryptomelane, hematite, chromite, talc, thuringite, and garnierite have been identified in various samples as weathering profile products.
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Chung, Meng-Chen. "Chemical composition and transport of ambient aerosols". Thesis, University of Essex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298838.
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Siegel, Karolina. "Chemical composition of summertime High Arctic aerosols". Licentiate thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-184291.
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This thesis presents new insights into the chemical composition of semi-volatile compounds in aerosol samples collected in the central Arctic Ocean close to the North Pole in September 2018. The central Arctic Ocean is an inaccessible location due to the lack of land areas along with heavy pack ice conditions. Therefore, large knowledge gaps remain to understand the Arctic climate system, and in particular the role of aerosol particles in its pristine atmosphere. The chemical composition of the aerosol samples was analysed on a molecular level using High Resolution Time-of-Flight Chemical Ionization Mass Spectrometry coupled to a Filter Inlet for Gases and AEROsols (FIGAERO-HRToF-CIMS). The analysis revealed a significant signal from compounds that are likely from marine sources. One important precursor for marine aerosols is dimethyl sulfide (DMS), a gas released by phytoplankton and ice algae in the Arctic Ocean. DMS oxidises in the atmosphere to produce oxidation products that can contribute to aerosol growth. Analysis of air mass origin with backward trajectories showed that the highest ambient DMS concentrations originated from marine areas around the pack ice. However, no correlation could be shown within the pack ice between ambient DMS and its oxidation product methanesulfonic acid (MSA) in the particle phase. As FIGAERO-HRToF-CIMS is commonly used in areas with higher particle concentrations and has never been used in the central Arctic before, this thesis further demonstrates its suitability for measurements of aerosol chemical composition in this remote region.Denna avhandling ämnar att presentera nya kunskaper om den kemiska sammansättningen av halvflyktiga föreningar i aerosolprover som samlades in i Norra ishavet nära Nordpolen i september 2018. Den innersta delen av Norra ishavet är svårtillgängligt på grund av bristen på fasta landområden ihop med kompakt packis. Därför kvarstår stora kunskapsluckor i förståelsen av klimatsystemet i Arktis, och i synnerhet aerosolpartiklars roll i dess orörda atmosfär. Den kemiska sammansättningen av aerosolproverna analyserades på molekylnivå med högupplöst kemisk joniseringsmasspektrometri kopplad till ett filterinsläpp för gaser och aerosoler (FIGAERO-HRToF-CIMS). Analysen visade på en tydlig signal från föreningar som sannolikt har marina källor. En viktig kemisk föregångare till marina aerosoler är dimetylsulfid (DMS), en gas som frigörs av fytoplankton och isalger i Ishavet. DMS oxiderar i atmosfären till oxidationsprodukter som kan bidra till en storleksökning av aerosoler. Genom analys av provluftens ursprung med trajektorieanalys visades att de högsta DMS-koncentrationerna kom från havsområdena runt packisen. Ingen korrelation kunde emellertid visas inom packisområdet mellan DMS i gasfas och dess oxidationsprodukt metansulfonsyra (MSA) i partikelfas. Eftersom FIGAERO-HRToF-CIMS ofta används i områden med högre partikelkoncentrationer och aldrig har använts i de inre delarna av Arktis tidigare, visar denna avhandling även att tekniken är lämplig för att mäta den kemiska sammansättningen av aerosoler i detta avlägsna polarområde.
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Keeling, William G. "Effects of soil texture, soil depth, and treatment on septic tank effluent renovation". Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06082009-171000/.
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Gangloff, Sophie. "Evaluation of the mechanisms of trace elements transport (Pb, Rare Earth Elements,... ) and the elemental and isotopic fractionation (Ca and Sr) at the interface water-soil-plant". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAH002/document.
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Ce travail est axé sur l’étude d’un profil de sol et des solutions de sol prélevés sur une parcelle expérimentale couvertes d’épicéas. Tous ces échantillons proviennent du Bassin Versant du Strengbach (Observatoire HydroGéochimique de l’Environnement – OHGE), ont été échantillonnés à différentes profondeurs (5, 10, 30 et 60 cm) et durant la période comprise entre 2009 et 2013.Les caractérisations des extraits des sols par spectroscopie Infra-Rouge ont permis de mettre en évidence les modifications des groupements fonctionnels organiques avec la profondeur et que ces modifications ont une forte incidence sur le comportement des cations (majeurs et traces) dans le sol. Des expérimentations d’ultra-filtration ont permis d’identifier les flux colloïdaux et dissous du carbone organique ainsi que ceux des éléments majeurs et traces présents dans les solutions de sol. L’utilisation conjointe des traceurs isotopiques (87Sr/86Sr et δ44/40Ca) et chimiques (Terres Rares) ont mis en évidence des processus ayant lieu aux interfaces eau-sol-plante, comme le prélèvement racinaire ou l’altération des solsThis work is focused on the study of a profile of soil and soil solutions collected on an experimental plot covered with spruce. All these samples come from the watershed of the Strengbach (environment - OHGE Hydrogeochimique Observatory), were sampled at different depths (5, 10, 30 and 60 cm) and during the period between 2009 and 2013. Characterizations of soil extracts by infrared spectroscopy allowed to highlight changes in the organic functional groups with depth and that these changes have a significant impact on the behaviour of the cations (major and trace) in the soil. Ultrafiltration experiments helped to identify flows of colloidal and dissolved organic carbon as well as those of the major and trace-element present in soil solutions. The joint use of isotope tracers (87Sr / 86Sr and δ44 / 40 Ca) and chemical (Rare Earth Elements) have highlighted processes taking place at the water-soil-plant interface, as the uptake by root or soil alteration
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Troton, Didier. "Modifications de la composition lipidique des thylakoides intervenant au cours de l'adaptation d'euglena gracilis au diuron". Paris 7, 1987. http://www.theses.fr/1987PA077169.
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Hamuda, Salah Saed. "The relation between soil composition and its thermal characteristics". Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.514996.
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Nel, Jacques A. "Vegetation and microbial determinants of soil carbon isotopic composition". Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28072.
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Typically, soil δ¹³C and δ¹⁵N values tend to increase with depth across a wide range of ecosystems. Changes in δ¹³C with depth have been attributed to vegetation changes (i.e. C₃/C₄ shifts), but the similarity in δ¹³C and δ¹⁵N profiles suggest that microbial decomposition may play an important role. The determinants of soil δ¹³C and δ¹⁵N, however, are complex and microbial decomposition and vegetation shifts are not the only mechanisms that drive the fractionation of the isotopes with depth. We explored the utility of using δ¹³C as a proxy for vegetation change by considering alternative mechanisms for the changes in soil δ¹³C with depth. These alternate mechanisms may weaken the interpretation of soil δ¹³C as an indicator of vegetation change if the measured δ¹³C changes are small. We hypothesized that: (1) if soil-related processes such as mineralization and dark CO₂-fixation by microbes and roots contribute significantly to the δ¹³C signature of bulk soil at depth, one cannot simply determine whether the δ¹³C value of the soil at depth is indicative of a past vegetation assemblies (i.e. C₃/C₄ transitions); (2) changes in soil δ¹³C and δ¹⁵N values are linked through common microbially mediated decomposition-related processes; (3) anaplerotic CO₂ fixation by microbes and roots may contribute significantly to soil δ¹³C values, while N₂-fixation may contribute to soil δ¹⁵N values with depth. Microbial processing of SOM during decomposition leads to ¹³C-enrichement of SOM with depth and has been modelled using a Rayleigh distillation process. Anaplerotic fixation of soil CO₂ is, however, known to occur in microbes and roots and we suggest that this has a role in determining soil SOM δ¹³C values through cumulative incorporation of bulk atmosphere CO₂ into SOM. These processes vary greatly between soils and environments. The correspondence between soil δ¹³C and δ¹⁵N was assessed by compiling data from soil depth profiles from widely distributed sites and conducting an analysis of global δ¹³C and δ¹⁵N variations in surface soils in order to determine relationships between soil isotopes and with climate and soil properties. Strong positive correlations between δ¹³C and δ¹⁵N values through soil profiles were found at a number of sites and were found to be independent of vegetation type. Globally, soil δ¹³C and δ¹⁵N values were also found to be significantly positively correlated across a wide range of climates and biomes. The global correspondences between δ¹³C and δ¹⁵N values may suggest a mechanistic link between δ¹³C and δ¹⁵N through the process of SOM decomposition and microbial processing. Anaplerotic CO₂ fixation by soil microbes and roots was assessed using soils from 10 sites across South Africa differing in soil properties and incubated in the dark for 3 d under continuous exposure to ¹³CO₂- and ¹⁵N₂-enriched atmospheres with varying soil moisture (10, 50 and 100% of field capacity) and temperature (4, 25, 40°C). There was no evidence of significant N₂ fixation in any treatment. Significant soil anaplerotic CO₂ fixation, however, occurred in all soils. Highest rates of anaplerotic CO₂ fixation occurred in soils at 50% field capacity and 25°C, suggesting a link with microbial biotic activity. Soils with low C and N concentrations and low C:N ratios exhibited the highest rates of CO₂ fixation in soils, indicating a link between anaplerotic CO₂ fixation rates and soil nutrient status. The higher rates of CO₂ fixation in soils with low nutrients may indicate that soil microbes rely increasingly on anaplerotic fixation as SOM-N declines, forcing greater reliance on de novo amino acid synthesis, and thus anaplerotic CO₂ fixation. The ubiquitous occurrence of anaplerotic ¹³CO₂ fixation in these soils indicates that anaplerotic fixation is likely important in contributing to determining soil δ¹³C values. Diffusion of low δ¹³C bulk atmospheric CO₂ (ca. -10‰) into the soil atmosphere (<< -10‰) will drive soil CO₂ δ¹³C towards ca. -10‰, and constant anaplerotic CO₂ fixation will result in SOM δ¹³C also tending towards 10‰ in more highly processed SOM deeper in the soil. The consequences of decomposition and the linked anaplerotic activity for soil δ¹³C values may be erroneously interpreted as evidence for C₄ vegetation being invaded by C₃ vegetation, potentially leading to incorrect conservation decisions. We argue that δ¹³C should only be used as a proxy for vegetation change where decomposition rates and anaplerotic CO₂ fixation are low and/or their effect on soil δ¹³C values can be accounted for.
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Fang, Xingxiao. "Chemical Composition of Soybean Root Epidermal Cell Walls". Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/1281.
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The root epidermis, being the outermost cell layer of the organ, is in contact with the soil environment. The position of the epidermis determines its important roles, such as taking up water and ions from the surrounding soil, and defending against harmful microorganisms. What is the chemical composition of the walls in this layer? The chemical nature of the soybean epidermal wall modifying substance was investigated in this study with the use of histochemical tests coupled with electron microscopy, and chemical depolymerizations in combination with chromatography. Soybean (Glycine max) was used as a test species in the present studay. Results of histochemical and electron microscopical studies indicated that the epidermal walls are modified with suberin. The suberized epidermal walls were permeable to apoplastic tracers, differing from those of cells with suberized Casparian bands, possibly due to the spatial distribution or chemical components of the suberin. Suberin may occur in a diffuse form linked with other wall components in the epidermis. What is the chemical nature of this modification, and does it play a role in pathogen resistance? The root epidermal wall compositions of two soybean cultivars were compared; one (cv. Conrad) is resistant to Phytophthora sojae and the other (cv. OX 760-6) is susceptible to this root-rot oomycete. Their epidermal walls were isolated enzymatically and subjected to two different degradation methods, i. e. BF3-MeOH transesterification and nitrobenzene oxidation. The compositions of depolymerisates of the cell walls determined by GC-MS indicated four dominant suberin monomers varying in chain length from C16 to C24. In all epidermal cell walls, ω-hydroxycarboxylic acids were more abundant than diacids, carboxylic acids and alcohols. Two of the monomers detected (hydroxycarboxylic acid and a,ω-dicarboxylic acid) are known to be characteristic suberin markers. The quantitative chemical compositions significantly differed in the epidermal cell walls of the two soybean varieties. Walls of the resistant cultivar (Conrad) had a greater quantity of both the aliphatic and aromatic components of the polymer than the susceptible cultivar (OX760-6), providing evidence to support the hypothesis that preformed suberin plays a role in plant defense.
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Mao, Yasin Sufi. "Effect of chemical composition on saline water evaporation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0027/MQ50827.pdf.
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Stonkutė, Edita. "Chemical composition of kinematically identified galactic stellar group". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130925_093107-33619.
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A number of stellar streams, moving and kinematic groups were identified in the Milky Way galaxy. Some of them are suspected to originate from accreted satellites. Can we also find such traces of ancient merger events in the solar neighbourhood? Helmi et al. (2006) identified three new coherent groups of stars in the Geneva-Copenhagen survey (Nordström et al. 2004) and suggested that those might correspond to remains of disrupted satellites.
With the detailed chemical composition analysis of the newly identified kinematic group we aim to contribute to the Galactic substructure studies. The main aim of the study is to perform a high-resolution spectroscopic elemental abundance analysis in stars belonging to one of the newly identified kinematic groups and to compare the results with other stars in the Galactic disc.
We performed the detailed chemical analysis of 21 stars attributed to Group 3 of the Geneva-Copenhagen survey and six comparison Galactic thin disc stars. The main atmospheric parameters and abundances of 22 chemical elements were determined. All programme stars are overabundant in oxygen and α-elements compared with the Galactic thin-disc. This abundance pattern has similar characteristics to those of the Galactic thick disc. The abundances of chemical elements produced predominantly by the r-process are overabundant in comparison with Galactic thin-disc dwarfs of the same metallicity. The abundances of iron-group elements and chemical elements produced mainly... [to full text]Paukščių Tako galaktikoje yra identifikuota žvaigždžių srautų, judančių bei kinematinių grupių, kurių kilmė siejama su įkritusiomis galaktikomis. Aktualu ištirti, ar yra tokių senųjų substruktūrų pėdsakų mūsų Saulės aplinkoje? Helmi ir kt. (2006), panaudoję Nordström ir kt. (2004) Ženevos–Kopenhagos apžvalgos (ŽKA) katalogą, identifikavo tris naujas koherentines žvaigždžių grupes, kurios pasižymi išskirtiniais kinematiniais parametrais ir gali būti užgalaktinės kilmės. Šiuo disertacijos darbu siekiama prisidėti prie Galaktikos substruktūrų tyrimų, nustatant detalią cheminę vienos iš Helmi ir kt. identifikuotų žvaigždžių grupių sudėtį. Svarbu išsiaiškinant, ar ŽKA kinematinės grupės žvaigždžių atmosferų cheminė sudėtis skiriasi nuo Galaktikos disko žvaigždžių. Nustatėme 21 3–osios ŽKA kinematinės grupės bei 6 palyginamųjų plonojo disko žvaigždžių atmosferų pagrindinius parametrus bei 22 cheminių elementų gausas. Kinematinės žvaigždžių grupės deguonies ir α–elementų gausos yra padidėjusios lyginant su plonuoju disku ir yra panašios į storojo disko. Cheminių elementų, daugiausia pagaminamų s–procese, gausos ir geležies grupės elementų gausos yra panašios į to paties metalingumo plonojo disko nykštukių cheminių elementų gausas, o cheminių elementų, daugiausia pagaminamų r–procese, gausos yra padidėjusios lyginant su plonuoju disku. Panaši cheminė tirtos kinematinės grupės bei storojo Galaktikos disko sudėtis rodo, kad kinematinės žvaigždžių grupės ir storojo disko žvaigždžių... [toliau žr. visą tekstą]
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Anantawaraskul, Siripon. "Chemical composition distribution of binary and multicomponent copolymers". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84462.
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Chemical composition distribution (CCD) of copolymers describes the distribution of average comonomer content among copolymer chains. This information is very important as CCD can significantly influence physical properties of copolymers. The main goal of this study is to further our understanding of the CCD of copolymers.The present understanding of CCD of multicomponent copolymers is very limited and there are no analytical equations capable of describing this distribution. In the present study, analytical expressions for describing the CCDs of random multicomponent copolymers are developed using a statistical approach. The results from this theoretical expression are validated with the results from Stockmayer's distribution and Monte Carlo simulations for limiting cases.
In the case of semi-crystalline binary copolymers, temperature rising elution fractionation (Tref) and crystallization analysis fractionation (Crystat) can be used for the estimation of CCD. The effects of chain microstructure and operating conditions on these techniques are investigated using a series of ethylene/alpha-olefin copolymers with well-defined microstructures. Both molecular weight and comonomer content are shown to significantly affect the shape of Crystaf profiles. Fortunately, comonomer content is the main determining factor for Crystaf peak temperature, permitting the use reliable calibration curves for this technique. A Crystaf model based on the average ethylene sequence distribution in the chains is proposed and the results from this model show very good agreement with the present and previously reported experimental data.
The typical operating conditions used in Tref and Crystaf analyses are found to lead to fractionation conditions that are far from the thermodynamic equilibrium. Consequently, crystallization kinetics can strongly influence the CCD estimated with Tref and Crystaf. Sample cocrystallization during analysis is also considered as it may interfere with the fractionation processes of both techniques. The similarity of chain crystallizabilities and fast cooling rates are found to promote cocrystallization. Cocrystallization under a certain conditions can be so strong that it can seriously affect the interpretation of the CCD measured with Crystaf and Tref.
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Mao, Yasin Sufi 1963. "Effect of chemical composition on saline water evaporation". Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21600.
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The purpose of this work was to investigate the evaporation rates of various brines and to compare them to the evaporation rates of pure water under the same environmental conditions in the laboratory. NaCl, MgCl 2 and KCl were the salts used in the experiments, at three densities. Mixtures of the salts were also used. One set of experiments was conducted under free convection while the other was conducted under forced convection, both over pans. Temperature was relatively constant for the experiments but relative humidity was not controlled. Wind profiles were measured during the forced convection experiments and an aerodynamic equation used to calculate evaporation for comparison with the observed evaporation rates. Surface temperatures were also measured. Water activities of all the brine and brine mixtures were also measured and compared to predictions by Raoult's law. In general, it was found the evaporation rate of brines was lower than that of pure water and that the water activities and evaporation rates were density-dependent to a certain extent. More precisely, they were dependent on the actual constituents in the brine due to the different molecular weights, and the number of ions dissolving from a given weight of salt or salt mixture. Evaporation rates can better be estimated on this basis than on the basis of density alone, as one would expect from Raoult's Law.
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Gott, Paige. "Variation in the chemical composition of crude glycerin". Connect to resource, 2009. http://hdl.handle.net/1811/37082.
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Tkacz, Andrzej. "Plant genotype, immunity and soil composition control the rhizosphere microbiome". Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/48113/.
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Three model plant and three crop plant species were grown for three generations in sand and compost. Pots were inoculated with 10 % soil initially, and with 10% of growth medium from the previous generation in generations 2 and 3, keeping replicates separate for all three generations. The microbiome community structure of the plant rhizosphere in each generation was characterised using ARISA DNA fingerprinting and 454 sequencing. Rhizosphere bacterial and fungal communities are different from those in bulk soil and there are also differences in the microbial community between different plant species. Plants both select and suppress specific bacteria and fungi in the rhizosphere microbiome, presumably via composition of their root exudates. Two out of three most abundant bacteria selected in the rhizosphere were isolated. These isolates proved to possess plant growth promotion properties. Plants are able to “farm” the soil in order to enrich it with plant growth promoting rhizobacteria (PGPR) species. However, in some plant species rhizospheres, invasions of opportunists and pathogens take place, mimicking events in plant monocultures. Other experiments using this multi-replicate system allowed for statistical analysis of the influence of Arabidopsis and Medicago mutants on the rhizosphere microbiome. Three groups of Arabidopsis mutants were tested: plants unable to produce aliphatic glucosinolates, plants impaired in the PAMP-triggered immune response and plants unable and over-expressed in methyl halides production and one group of Medicago mutants which are impaired in the mycorrhization ability. All these plant genotypes, except those for methyl-halide production and one genotype involved in PAMP response, significantly altered the rhizosphere microbiome.
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Jensen, Soren Ross. "Composition and biodegradation potential of polychlorinated alkane mixtures". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82604.
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A Monte Carlo Model was developed to simulate the free-radical chlorination of n-alkanes by which polychlorinated alkane mixtures are produced. The model parameters were the relative reactivity of the hydrogen atoms on the alkane chain to chlorine free-radical substitution. The values of the parameters were determined by free-radical chlorination experiments; by interpolation of data from these experiments or from data in the literature. The result of the model is a complete characterization of the molecular composition of PCA mixtures of any carbon chain length and degree of chlorination. Properties of modeled PCA mixtures were in good agreement with properties of real PCA mixtures. This model represents the first published attempt to characterize polychlorinated alkane mixtures.The substrate specificity of oxygenolytic dehalogenase enzymes was determined. Biodegradation experiments were performed to determine what specific arrangements of chlorine atoms on n-alkane carbon chains could be acted upon by the enzymes. Terminally substituted chlorinated n-alkanes were readily dehalogenated by Pseudomonas sp.273, which expresses the enzymes. Vicinal chlorine atoms on the carbon chain could not be removed by oxygenolytic dehalogenases. By combining the results from the Monte Carlo model and the biodegradation experiments, it was possible to generate an estimate for the upper limit to aerobic biodegradation.
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Jackson, Andrew William. "Analysis of soil chemical residues and other soil factors associated with past human activity". Thesis, University of Bristol, 2001. http://hdl.handle.net/1983/2f03f40f-c71c-46bd-9078-05fd07efd027.
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Nielsen, Uffe Nygaard. "Influences on species richness and composition of belowground communities at multiple spatial scales". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=24811.
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Herich, Hanna. "The relationship between aerosol chemical composition and hygroscopic growth /". Zürich : ETH, 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18239.
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Fokine, Michael. "Photosensitivity, chemical composition gratings and optical fiber based components". Doctoral thesis, KTH, Mikroelektronik och informationsteknik, IMIT, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3436.
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The different topics of this thesis include high-temperaturestable fiber Bragg gratings, photosensitivity and fiber basedcomponents. Fiber Bragg gratings (FBG) are wavelength dispersiverefractive index structures manufactured through UV exposure ofoptical fibers. Their applications range from WDM filters,dispersion compensators and fiber laser resonators fortelecommunication applications to different types of point ordistributed sensors for a variety of applications. One aim of this thesis has been to study a new type of FBGreferred to as chemical composition grating. These gratingsdiffer from other types of FBG in that their refractive indexstructure is attributed to a change in the chemicalcomposition. Chemical composition gratings have shown to beextremely temperature stable surviving temperatures in excessof 1000 oC. Photosensitivity of pure silica and germanium-dopedcore fibers in the presence of hydroxyl groups has also beenstudied and different types of fiber based components have beendeveloped. The main result of the thesis is a better understanding ofthe underlying mechanism of the formation of chemicalcomposition gratings and their decay behavior at elevatedtemperatures. The refractive index modulation is caused by aperiodic change in the fluorine concentration, which has beenverified through time-of-flight secondary-ion-mass spectrometryand through studies of the decay behavior of chemicalcomposition gratings. A model based on diffusion of dopants hasbeen developed, which successfully predicts the thermal decayat elevated temperatures. Studies of the dynamics of chemicalcomposition grating formation have resulted in a manufacturingtechnique that allows for reproducible gratingfabrication. The main results regarding photosensitivity is a method tosignificantly increase the effect of UV radiation on standardtelecommunications fiber. The method, referred to asOH-flooding, has also been applied to pure-silica core fibersresulting in the first report of strong grating formation insuch fibers. Finally, research into different schemes for developingfiber-based components has resulted in two types of singlefiber integrated Mach-Zehnder interferometers; one passiveinterferometer that can be used as an optical filter and oneactive interferometer controlled with internal metalelectrodes. Keywords:optical fibers, fiber Bragg gratings,photosensitivity, thermal stability, fiber sensors, chemicalcomposition gratings, fiber components, Mach-Zehnderinterferometer, optical switch, optical modulator.QC 20100607
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Aziz, Haji Muhammad Majdi Pehin Dato Haji Abdul. "Baseline study on chemical composition of Brunei Darussalam rivers". Thesis, Brunel University, 2005. http://bura.brunel.ac.uk/handle/2438/4820.
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The research provides data of pH and conductivity, some anions (e. g. fluoride, chloride, bromide, nitrate, phosphate and sulphate), monovalent cations (e. g sodium, ammonium and potassium), divalent cations (e. g calcium and magnesium) heavy metals (e. g. iron, copper, zinc, nickel, cobalt, cadmium and manganese) and organic compounds – from water samples of rivers of Brunei Darussalam, namely, Brunei River, Belait River, Tutong River and Temburong River. The higher values of certain parameters with respect to the acceptable standard limits for river water indicate the pollution in river water samples of the study area, make the waters unsuitable for various applications and do pose a human health hazard. The pH levels in Brunei Darussalam is quite reassuring and mostly safe. Although there are some stretches of rivers that show slightly lower levels of pH, there is no cause for any alarm as these waterways are not sources of drinking water. As for anions and cations, the only anion of significant levels detected in Brunei Rivers is chloride whereas only monovalent cation detected in significant levels, is sodium. The concentrations of chloride and sodium ions are below the standard concentrations. Brunei Rivers are still free from chloride and sodium pollution. For heavy metals, only iron is detected in Brunei Rivers. Brunei being a oil based country experiments were done to identify levels of a numbers of significant toxic organic compounds, including, toluene and benzene which have been detected in the waters of the oil mining district of Belait District but are within normal limits. The use of a photolytic cell system to achieve the photodegradation of benzene, toluene, ethylenediaminetetra-acetic acid (EDTA) and the surfactant – hexadecyltrimethyl-ammonium bromide (C19H42NBr) is reported. The system has been optimised by investigating the effects of the addition of hydrogen peroxide (H202) as an oxidant and the addition of titanium dioxide (TiO2) as a catalyst. The results show that the photolytic system can be used to achieve >99% degradation of organic contaminants. The research also includes a final chapter on management system which covers water protection, pollution control and solid waste management in Brunei. In addition to investigating various factors of the solid waste management in Brunei, the researcher has also exposed some of the weaknesses that need immediate addressing. Various measures have been suggested to make Brunei's water more efficient. Moreover, ways of preserving the high quality of Brunei's water figures in this chapter.
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Kariptas, Ergin. "Chemical composition of Rhodococcus ruber with different growth conditions". Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340719.
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Siddiqui, Mohammad Nahid. "Studies on structure and chemical composition of Arabian asphalt". Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/671.
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Hort, Joanne. "Cheddar cheese : its texture, chemical composition and rheological properties". Thesis, Sheffield Hallam University, 1997. http://shura.shu.ac.uk/19833/.
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Procedures associated with Quantitative Descriptive Analysis were used to identify and subsequently train a panel to quantify the perceived textural attributes of Cheddar cheese. Seventeen types of Cheddar were assessed by the panel for creaminess, crumbliness (fingers), crumbliness (chewing), firmness, graininess, hardness (first bite), hardness (cutting), and springiness. Cluster and Principal Component analyses of the sensory data revealed that the cheese samples could be subdivided into young, mature and extra mature Cheddars in terms of the textural attributes measured. The panel was also able to distinguish between the low fat and genuine Cheddars. The percentage fat, moisture and salt contents and the pH level of the seventeen Cheddar samples were established. An inverse correlation between fat and moisture content and a positive correlation between pH level and salt content were observed. The rheological properties were measured using three tests performed on an Instron Universal Testing Machine - a compression test, a cutting test and a stress relaxation test - and, where appropriate, were reported in terms of true stress and true (Hencky) strain curves. The viscoelastic properties of Cheddar observed during stress relaxation tests were modeled using a Generalised Maxwellian model consisting of two exponential elements and a residual term. Considerable variation in all the rheological properties was observed amongst the Cheddar samples. The rheological parameters did not distinguish between the samples to the same extent as the sensory assessment. However, Cluster Analysis of the rheological data did differentiate between the rheological profiles of the young (mild & medium) and the remaining mature/extra mature samples. The relationships between the textural attributes and the chemical and rheological parameters were investigated. No relationship between chemical composition and texture was identified, but correlations between the rheological parameters and the textural attributes were not uncommon. Multiple regression techniques were employed to construct mathematical models to predict the textural attributes from the rheological data. Successful models were constructed utilising parameters from the compression and cutting tests for all the attributes apart from creaminess. More precise models were constructed for firmness, springiness and crumbliness (fingers) where the action of the instrumental test from which the rheological parameters were obtained resembled the test method used by the panel. The chemical, textural and rheological properties of an English Cheddar were determined at various stages during its ripening period to investigate any changes that occurred. A slight increase in pH was the only chemical change recorded. Progressive changes in the majority of the textural attributes were observed. The most dramatic changes included a decrease in springiness and an increase in creaminess. A changing rheological profile was also observed during maturation, a decreasing strain at fracture being the most notable development. The sequence of changes in both the textural and rheological properties was divided into three fairly distinct phases, the initial stage reflecting the developments necessary before the cheese would be suitable for retail sale and the final stage including the development of the necessary textural attributes characteristic of a Mature English Cheddar. It was evident that the timing of the maturation period was pertinent to the development of textural attributes characteristic of particular maturities of Cheddar cheese. The textural attributes of the maturing Cheddar were also predicted at each stage of maturation using the mathematical models constructed in the initial study. Accurate predictions were made for all the attributes except crumbliness (chewing) and graininess.
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Kameel, Fathima R. "Optical Properties and Chemical Composition of Secondary Organic Aerosol". Kent State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1240332384.
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Clark, Lauren Lisa. "Composition and cycling of marine organic phosphorus /". Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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