Дисертації з теми "Carbon and nitrogen stocks"
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Silva, Jéssica Caroline dos Santos. "Estoques e fluxos de carbono e nitrogênio acima e abaixo do solo em fragmentos de Floresta Atlântica no sul do Brasil." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/64/64135/tde-30112017-101614/.
Повний текст джерелаTropical evergreen forests have a key role in the global carbon and nitrogen cycles. The Atlantic Forest is a vanishing South American tropical biome of immense structural complexity. The structure and functioning of these forests are relatively unknown. In this context, the main objective of this study was to investigate the forest structure by estimating aboveground live biomass (AGLB), belowground biomass (BGB) and litterfall. The determination of carbon and nitrogen concentrations in soils and vegetation allowed to quantify stocks and fluxes of these two elements. Four 0.25 ha-plots were established in two elevations (200 m asl and 800 m asl) in forests located on the slopes of the Serra do Mar, on the northeast coast of the State of Santa Catarina, southern Brazil. The sampling areas are located in the municipality of Joinville. The historical average annual temperature is 20°C and rainfall is approximately 2200 mm. The AGLB varied along the sites from approximately 300 Mg.ha-1 (submontane) to 380 Mgoha-1 (montane), AGDB varied from 6.8 to 6.6 Mgoha-1 and BGB (roots) varied from 54 to 66 Mg.ha -1, respectively. . The average litterfall production of 6.4 Mg.ha-1 ano-1 and 6.9 Mg.ha-1 ano-1 were found in the submontante and montane study sites, respectively. Leaves were the major component of litterfall contributing ~68% in both sites. Total carbon and nitrogen stocks were higher in the montane site. Total carbon stock (AGLB + BGB) increased from 208 Mg.ha-1 in the submontane site to 390 Mg.ha-1 in the montane. While, total nitrogen stock increased from 7 Mg.ha-1 to 16 Mg.ha-1, respectively. Fluxes of carbon and nitrogen via litterfall in the submontane and montane site varied from 3.0 to 3.2 Mg.ha-1 and from 0.12 to 0.14 Mg.ha-1, respectively. ?13C values in each compartment were similar between the two sites, and representative of C3 plants. As expected, there was an enrichment of ?13C and ?15N values in depth in each studied site. ?15N values where higher in leaves, litter and soil of the submontane site, possibly due higher nitrogen availability in this site; or low residence time of soil and depleted 15N in litterfall of the montane site. Overall, latitutinal (in terms of light availability) and altitudinal (in tems of precipitation and temperature) position were determinant in the nitrogen and carbon composition, allocation and dynamics in these ecosystems
Kyulavski, Vladislav Dimitrov. "Greenhouse gas emissions and soil carbon stocks associated with crop residues and organic fertilizers mixtures in sugar cane cropping systems." Thesis, La Réunion, 2019. https://elgebar.univ-reunion.fr/login?url=http://thesesenligne.univ.run/19_27_VDKyulav.pdf.
Повний текст джерелаIn the current environmental context, it is crucial to optimize the use of resources to reduce waste and greenhouse gas (GHG) emissions. Renewable resources use and recycling lies at the heart of the circular economy model, in which a waste is a mobilizable, transformable, reusable and therefore renewable resource. In agriculture, the “virtuous circle” of circular economy can be achieved through the recycling of organic wastes as fertilizer and the adoption of an agroecological approach that favors ecosystem services for pest control, soil protection and carbon stocks increase, one of the examples of which is mulching. In sugarcane cropping systems straw left on the soil surface is also increasingly coveted by industrial sector to produce second-generation agrofuels. The emerging competition for biomass use and the underlying environmental issues make it necessary to assess both, the agronomic and the environmental advantages and disadvantages of joint recycling of sugarcane mulch and organic fertilizers. Therefore, the objectives of this work are i) to compare the effect of fertilizers of contrasting physicochemical quality, on the decomposition of a sugarcane mulch, and ii) to evaluate the potential of GHG emissions from mulch-fertilizer mixtures, according to the quantity of straw left and the quality of the fertilizers applied. The research strategy adopted in a first step aimed to detect carbon/nitrogen interactions during the combined recycling of straw and organic fertilizers. We have thus tested the predictability of the mineralization dynamics of C and N of the organic materials alone, or in mixture (straw/fertilizer) in the laboratory, by a simple additive model, and a mechanistic model of carbon and nitrogen transformation in the soil - CANTIS. Our results showed that both models overestimated the C mineralization and did not correctly predict the N mineralization of the mixtures. This antagonistic interaction for the mixtures was corrected by the application of a contact factor in CANTIS, which reflects the bioavailability decrease of C and N, due to distribution heterogeneities at a fine scale within the soil. In a second step, we conducted field trials (under real conditions) to measure both the decomposition of sugarcane straw mixed with organic fertilizers and GHG emissions. The amount of straw decomposed was proportional to the initial amount left and was affected neither by the amount of straw nor the type of fertilizer provided. This proportionality is transposable to the potential for carbon sequestration in the soil and should be considered when setting up carbon sequestration or when exporting the straw for alternative use. The type of fertilizer plays a key role in GHG emissions in the short term after fertilization. The highest average CO2 and N2O emission fluxes were obtained by applying pig slurry, which has a high water content and is rich in mineral N. Conversely, the kinetics of GHG emissions from solid fertilizers have been governed by environmental factors, some of which could be controlled, such as water intake or fertilizer quantity application. The use of organic fertilizers is beneficial when they are rich in organic N and poor in water content, such as dry sewage sludge, but the mineralization of nitrogen in this case is gradual and requires elaboration of a specific application strategies to meet crop needs. A better integration of the interactions between the different N and C sources should be considered, in order to develop modeling as a precise tool for the management of an agroecosystem
Langenbruch, Christina. "Effects of nutrient cycling through litter of different broadleaved deciduous tree species on soil biochemical properties and the dynamics of carbon and nitrogen in soil." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-F1C2-F.
Повний текст джерелаFerreira, Ademir de Oliveira. "COMPARTIMENTOS DA MATÉRIA ORGÂNICA DO SOLO COMO INDICADORES DO SEQÜESTRO DE CARBONO EM SISTEMA PLANTIO DIRETO DE LONGA DURAÇÃO." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2009. http://tede2.uepg.br/jspui/handle/prefix/2199.
Повний текст джерелаDecrease in soil organic carbon (SOC) content of the surface layer into deeper layers indicates the occurrence of the stratification in the profile due to continuous C addition of crop residues enriching the soil surface layer. The objective of this study was: in Chapter 3 the relationship of stratification (RE) of C of the soil organic matter (SOM) pools can be an indicator of C sequestration in no-tillage soils? In the chapter 4 the tensile strength of aggregates is affected by the C content of Pedosequence of Latosol with medium and clay texture? in Chapter 5 which is the C balance and the amount of crop residue needed to maintain a stable C balance in a Latosol with a medium and clay texture? The experimental design was a completely randomized 2x2x2 factorial with 12 treatments. Treatments consisted of: a) an Oxisol (Red Latosol) with medium and clayey texture, b) two soil sampling periods (T1 and T2) with one year interval between them, and c) two soil sampling depths (0-5 and 5-20 cm). The soil attributes assessed were: the separation of water stable aggregates classes (19-8, 8-4, 4-2, 2-1, 1-0,5 and 05-0,25 mm), particulate organic carbon (POC), total particulate nitrogen (TPN) in the aggregate classes. Also was determined total organic carbon (TOC) and total nitrogen (NT) in the whole sample and in the aggregates sizes classes and tensile strength of aggregates. The relationship of stratification was calculated by dividing the TOC and TN values of 0-5 cm layer by the values of the same attributes of 5-20 cm layer. The C sequestration rate and the stratification ratio changes were calculated by the difference between the T2 values minus T1. The tensile strength was measured in soil aggregates and assessed in 1920 aggregates for each sampling time. Also TOC and NT content were measured in aggregates. The aggregates greater than 8 mm represented more than 70 of the total mass in both the clay and in sandy soil. The relationship of stratification ratio (0-5:5-20 cm) of SOC, TN, POC and TPN soil indicated the improvement of the surface layer. A significant linear relationship between the SR and C sequestration rate in both textural classes showed an increase in C sequestration and was more evident in LV with medium texture. The increase in TOC content resulted in decreased tensile strength (TS) of the aggregates and was more evident in the 0-5 cm layer. The TS showed inverse relationship with the soil density and was higher in the LV medium texture. The rate of sequestration of C was 0.86 for the LV with medium texture and 0.76 Mg ha-1 for the clay texture and to maintain the stable balance of C is required an input of 8.6 Mg ha-1 of crop residues. The results presented confirm the hypothesis of SR to be a sensitive indicator for the rate of carbon sequestration in no-tillage soil. Key-words: Carbon stock, Carbon balance, Carbon sequestration, Soil management systems, particulate organic carbon, particulate nitrogen.
A redução no conteúdo de carbono (C) da camada superficial em direção as camadas mais profundas do solo indica a formação da estratificação no perfil devido à adição contínua de C pelos resíduos orgânicos resultando no enriquecendo a camada superficial do solo. O objetivo deste trabalho foi avaliar os seguintes assuntos: a) a relação de estratificação (RE) de C dos compartimentos da matéria orgânica do solo (MOS) pode ser um indicador do seqüestro de C no sistema plantio direto. b) a resistência tênsil dos gregados pode ser afetada pelo conteúdo de C em Pedossequencia de Latossolo com textura média e argilosa. c) o balanço de C e a quantidade de resíduos culturais necessária para manter o equilíbrio estável de C em um Latossolo com textura média e argilosa. O delineamento experimental foi um fatorial 2x2x2 inteiramente casualizado com 12 tratamentos. Os tratamentos constituíram-se de: a) um Latossolo Vermelho com textura média e argilosa, duas épocas de amostragem do solo (E1 e E2) com um ano de intervalo entre si e duas profundidades de amostragem (0-5 e 5-20 cm). Os atributos avaliados foram: a separação das classes de agregados do tamisamento úmido (19-8, 8-4, 4-2, 2-1, 1-0,5 e 05-0,25 mm), o carbono orgânico particulado (COP), o nitrogênio total particulado (NTP) nas classes de agregado, o C orgânico total (COT) e o nitrogênio total (NT) na amostra integral e nas classes de agregados e a resistência tênsil dos agregados. A relação de estratificação (RE) foi calculada dividindo-se o valor de COT e NT da camada de 0-5 cm pelo valor na camada 5-20 cm. A taxa de seqüestro de C e a variação da relação de estratificação foram calculadas através da diferença (D) entre os valores da E2 menos o da E1. A resistência tênsil (RT) do solo foi avaliada em 1920 agregados de cada época de coleta, determinando-se, também o conteúdo de COT e NT. A classe de agregado > 8 mm representou mais de 70% da massa dos agregados tanto na textura argilosa como na arenosa. Da mesma forma, o conteúdo de COT e NT foram maiores na classe de agregado > do que 4 mm comparado as demais classes nas duas classes texturais. A relação de estratificação 5:5-20 cm) de COT, NT, COP e NTP do solo indicou a melhoria da qualidade do solo da camada superficial. A relação linear e significativa entre o DRE com a taxa de seqüestro de carbono nas duas classes texturais mostrou o aumento no seqüestro de C e foi mais evidente no LV com textura média. O incremento do conteúdo de COT resultou na diminuição da resistência tênsil (RT) dos agregados e foi mais evidente na camada de 0-5 cm. A RT apresentou relação inversa com a densidade do solo e foi superior no LV textura média. A taxa de seqüestro de C foi de 0,86 para o LV textura média e 0,76 Mg ha-1 para o textura argilosa e para manter o equilíbrio estável de C é necessário o aporte de 8,6 Mg ha-1 de resíduos culturais. Os resultados apresentados confirmaram a hipótese da RE ser um indicador sensível para a taxa de seqüestro de carbono no solo em um sistema sob plantio direto consolidado.
Juice, Stephanie. "The Environmental Microbiome In A Changing World: Microbial Processes And Biogeochemistry." ScholarWorks @ UVM, 2020. https://scholarworks.uvm.edu/graddis/1181.
Повний текст джерелаManlay, Raphael. "Organic matter dynamics in mixed-farming systems of the West African savanna: a village case study from south Senegal." Diss., Institute of Forestry, Agricultural and Environmental Engineering (ENGREF), 2000. http://hdl.handle.net/10919/71623.
Повний текст джерелаDurigan, Mariana Regina. "Mudanças nos estoques de carbono e nitrogênio do solo em função da conversão do uso da terra no Pará." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-03062013-093119/.
Повний текст джерелаThe land use change in the Brazilian Amazon has been identified as the main source of CO2 to the atmosphere due to emissions of soil carbon and nitrogenl. The management practice adopted can strongly influence the soil C and N stocks and may works like a sink or source of C and N to the atmosphere. Furthermore, can be changed: the soil fertility and bulk density as well as the SOM fractions and C source of the SOM. With the objective of evaluate the impact of the land use change in eastern Amazonia soil samples were collected in the main land uses in Santarém region, Para State of Brazil, at three depths: 0-10, 10-20 and 20-30 cm. Through the samples was performed the physicochemical characterization of the areas and were determined the soil C and N contents as well the isotopes ? 13C and ? 15N in order to quantify the soil C and N stocks and understand the SOM dynamics and evaluate the SOM origin. For a subset of samples were performed the physical fractionation of SOM and the determination of microbial biomass C to understand how the land use change may interfere in these fractions. Added to these determinations were estimated the emission factors based on the methodology described by the IPCC. Through the physicochemical characterization study areas can be characterized as a clayey loamy soils. The highest values of pH, macronutrients, CEC , sum of bases and base saturation were observed in croplands (CP), suggesting that the use of practices such as fertilization and liming are able to change the soil fertility patterns in the Amazon, increasing their fertility. For C and N stocks can be said that the land use change in the study area is contributing to the loss of soil C and N, especially when the conversion is done for croplands (CP) and grasslands (GS) areas and the value observed for soil C stocks in the 0-30 cm layer in these areas were 49.21 Mg C ha-1 (GS) and 48.60 Mg C ha-1 (CP). The highest ? 13C value was found in GS, -25.08 ?, suggesting that for these areas is occurring an isotope dilution and that part of the soil C is still remaining from forest. The SOM fractions showed changes in the amount of C and in the proportion of light and occluded fractions, especially in the uses CP and GS. The labile SOM fractions (microbial biomass) also showed a large difference between the UF and CP uses (526.21 and 296.78 mg g-1 of dry soil), indicating that CP affects the soil C and N stocks and also the SOM fractions. The emission factors calculated confirm all results observed for the conversion of UF for CP, and for this use the emission factor was 0.93 ± 0.033, and then this was the use that emitted more C. Based on the results we conclude that the introduction of croplands in Santarem region is the main cause of soil C and N loss and consequently contributes more to the greenhouse gases emission.
Truong, Van Vinh. "Carbon stocks and fluxes in tropical mangrove (Southern Vietnam)." Thesis, Nouvelle Calédonie, 2018. http://www.theses.fr/2018NCAL0002.
Повний текст джерелаMangrove forests significantly contribute to energy flow, nutrient and carbon cycling in the coastal ocean, being a sink for atmospheric CO2. Mangroves forests are highly productive and store high amount of carbon both in their soils and in their biomass. During leaf litter decomposition, nutrients and carbon can be recycled or exported to adjacent ecosystems by the tidal action. Can Gio mangrove, degraded by the spraying of defoliants during the Vietnam War, successfully recovered through replantation and natural regeneration after 40 years. To date, the Can Gio mangrove forest is the largest contiguous mangrove forest in Vietnam, and became the first Mangrove Biosphere Reserve in this country. The main objective of this PhD thesis was to characterize carbon cycling within the Can Gio mangrove forest, which is a tropical one.The results of this PhD thesis allowed to: - Develop allometric equations and to estimate the aboveground biomass of Rhizophora apiculata Blume planted mangroves forest in Southern Vietnam; - Calculate the total carbon stocks in different mangrove stands developing under the tropical climate of Southern Vietnam; - Characterize the leaf litter decomposition rates, and assess nutrients and trace metals dynamics during litter decay processes, as well as the evolution of δ13C during decay; - Determine the seasonal variability CO2 fluxes at different interfaces: soil-air, water-air and trunk-air, and to characterize CO2 concentrations profiles in the canopy
Wang, Eugenia. "Growth of nitrogen-containing carbon nanofibers." Connect to resource, 2006. http://hdl.handle.net/1811/6446.
Повний текст джерелаTitle from first page of PDF file. Document formatted into pages: contains 55 p.; also includes graphics. Includes bibliographical references (p. 51). Available online via Ohio State University's Knowledge Bank.
Burch, Hilary Jane. "Bioapplications of nitrogen-doped carbon nanotubes." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437176.
Повний текст джерелаLiang, Jianglin, and 梁江林. "Ruthenium-catalyzed carbon-nitrogen bond formations." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31245729.
Повний текст джерелаShiao, Jeansong. "Properties of diamondlike carbon and nitrogen containing diamondlike carbon films." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1056992626.
Повний текст джерелаZhang, Min. "Study on selective carbon-carbon, carbon-nitrogen, and carbon-oxygen bonds formation starting from alkynes." Rennes 1, 2009. http://www.theses.fr/2009REN1S036.
Повний текст джерелаLa thèse est composée de deux parties. La partie I présente la formation catalytique de liaisons C-C, C-N et C-O : une série d’ethers, de diényle, furanes 2,5-disubstitués, cétones allyliques et γ-fonctionalisées et quinolines polysubstituées ont été préparées à partir d’alcynes avec l’aide initiale d’un catalyseur de ruthenium. La partie II présente la formation de liaisons C-C, C-N, C-O: une variété de tetrahydropyridines, et de 1,3-oxazines ont été synthétisées à partir d’alcynes electrophiles via des réactions à composants multiples
Ye, Yuxuan Ph D. Massachusetts Institute of Technology. "Development of new transition metal-catalyzed carbon-fluorine, carbon-nitrogen, and carbon-carbon bond forming processes." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118281.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references.
Chapter 1. Palladium-Catalyzed Fluorination of Cyclic Vinyl Triflates: Dramatic Effect of TESCF₃ as an Additive A method for the synthesis of cyclic vinyl fluorides with high levels of regiochemical fidelity has been achieved by Pd-catalysis employing a new biarylphosphine ligand and TESCF₃ as a crucial additive. Five, six, and seven-membered vinyl triflate substrates, as well as a few acyclic substrates undergo the transformation successfully. The intriguing "TESCF₃ effect" provided a new tool for addressing the problem of the formation of regioisomers in Pd-catalyzed fluorination reactions. Chapter 2. Mechanistic Studies on Pd-Catalyzed Fluorination of Cyclic Vinyl Triflates: Evidence for in situ Ligand Modification by TESC₃ as an additive. A detailed mechanistic hypothesis for the Pd-catalyzed fluorination of cyclic vinyl triflates, and the unusual effect of TESCF₃ as an additive has been developed by combined experimental and computational studies. The preference of conducting [beta]-hydrogen elimination rather than reductive elimination from the trans-LPd(vinyl)F complex, which is generated predominantly due to the trans-effect, caused the poor regioselectivity of the fluorination reaction under TESCF₃-free conditions. An in situ ligand modification by trifluoromethyl anion, leading to the generation of the cis-LPd(vinyl)F complex which prefers reductive elimination rather than Phydrogen elimination, is proposed to be responsible for the improved regioselectivity of the fluorination reaction when TESCF₃ was used as an additive. Chapter 3. CuH-Catalyzed Enantioselective Alkylation of Indoles with Ligand-Controlled Regiodivergence A method for the enantioselective synthesis of either NI- and C3-chiral indoles by CuH-catalysis, depending on the choice of ligand, was developed. In contrast to conventional indole functionalization in which indoles are used as nucleophiles, hydroxyindole derivatives are employed as electrophiles in this method. DFT calculations indicated that the extent to which the Cu-P bonds of the alkylcopper intermediate distort, determines the regioselectivity of the reaction.
by Yuxuan Ye.
Ph. D. in Organic Chemistry
Schubert, Maria. "Carbon partitioning in nitrogen fixing root nodules." Doctoral thesis, [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=96736597X.
Повний текст джерелаPozo, Alejandro del. "Carbon/nitrogen relations in cereals and legumes." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317269.
Повний текст джерелаTASAYCO, CARLOS MANUEL SANCHEZ. "NITROGEN INCORPORATION INTO AMORPHOUS FLUORINATED CARBON FILMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3698@1.
Повний текст джерелаAs propriedades tribológicas de revestimentos de carbono usados em discos rígidos magnéticos foram de enorme importância para o contínuo aumento da densidade de informação armazenada nos mesmos. As características mecânicas e estruturais de filmes de carbono amorfo também foram indispensáveis para o desenvolvimento de revestimentos que atendessem às especificações do desenvolvimento destes dispositivos: alta dureza e densidade, além de baixo coeficiente de atrito e alta resistência ao desgaste. Neste trabalho são apresentados os efeitos da incorporação de nitrogênio em filmes de carbono fluorado (a-C:H:F) depositados pela técnica de deposição por vapor químico assistido por plasma. As propriedades mecânicas e estruturais foram investigadas com o uso das técnicas nucleares (retroespalhamento Rutherford, detecção de recuo elástico, reação nuclear), espectroscopia de fotoelétrons induzidos por raios-X, medidas de tensão interna (por perfilometria), espectroscopia de absorção no infravermelho, espectroscopia Raman, microscopia de força atômica e medidas de ângulo de contato. Foi depositada uma série de filmes onde foi variada a pressão de N2 em uma atmosfera precursora de CH4-CF4 (1:2) (PN2 = 0% até 60%). A tensão de autopolarização foi fixada em - 350V. Os resultados obtidos mostram que as propriedades dos filmes são controladas pela incorporação de nitrogênio que chega a 20 at.%. Identificou-se um decaimento na taxa de deposição com o incremento da pressão parcial de N2, e um sensível decaimento na concentração de flúor. O filme fica menos tensionado, o que pode resultar em uma melhoria na adesão. Entretanto, o ângulo de contato diminui, resultando em um aumento no coeficiente de atrito. Novos estudos procurando aumentar simultaneamente as concentrações de F e N são sugeridos.
The tribological properties of carbon coatings of hard magnetic disks played an important role for the continuous increase of their storage capacity. The mechanical and structural properties were also important: high density, hardness and wear resistance, and low friction coefficient. In this work, we study the effects of the nitrogen incorporation into fluorinated carbon films (a-C:H:F) deposited by plasma enhanced chemical vapor deposition. The film properties were investigated by using a multitechnique approach: nuclear techniques (Rutherford backscattering, elastic recoil and nuclear reaction analyses), x-ray photoelectron spectroscopy, internal stress measurements by perfilometry, Raman and Infrared spectroscopies, atomic force microscopy and contact angle measurements. Films were deposited changing the N2 partial pressure in a precursor atmosphere also composed by a fixed CH4-CF4 mixture (1:2) (PN2: 0 - 60%), with the self-bias voltage of -350V. The results show that the film properties are controlled by the nitrogen incorporation, with an important fluorine content reduction. The internal stress reduction may result in an increase of the film adhesion. However, the contact angle decreases upon nitrogen incorporation, resulting in an increase of the friction coefficient. New studies with the goal of obtain a simultaneous increase of both fluorine and nitrogen content are suggested.
Kivimäki, Sanna Katariina. "Changes in carbon and nitrogen dynamics in Sphagnum capillifolium under enhanced nitrogen deposition." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5728.
Повний текст джерелаMohammed, Askia Musah. "Biomass, carbon, nutrient stocks and litter decomposition in Ghanain cocoa ecosystems." Thesis, University of Reading, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625496.
Повний текст джерелаKingham, Rachel. "The broad-scale impacts of livestock grazing on saltmarsh carbon stocks." Thesis, Bangor University, 2013. https://research.bangor.ac.uk/portal/en/theses/the-broadscale-impacts-of-livestock-grazing-on-saltmarsh-carbon-stocks(a81ba92d-ac40-49c4-ba93-982bffb077d9).html.
Повний текст джерелаHeidorn, Christina Melanie. "Soil carbon dynamics in a nitrogen-enriched grassland." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0028/MQ50343.pdf.
Повний текст джерелаInce, Christopher Paul. "Investigations into palladium-catalysed carbon-nitrogen bond formation." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392496.
Повний текст джерелаAbualghaith, Abdulaziz. "Carbon and nitrogen metabolisn in orchid-mycorrhiza associations." Thesis, University of Sheffield, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604555.
Повний текст джерелаAlvarado, Adriana Delgado. "Interactions between carbon and nitrogen metabolism in legumes." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274992.
Повний текст джерелаLewis, Jason Douglas. "Carbon, nitrogen, and water fluxes from turfgrass ecosystems." Diss., Kansas State University, 2010. http://hdl.handle.net/2097/4376.
Повний текст джерелаDepartment of Horticulture, Forestry, and Recreation Resources
Dale J. Bremer
Turfgrass covers 1.9% of the nation’s surface area and is the largest irrigated crop in the USA. Developed urbanized land is projected to double by 2025, which will increase turf’s environmental impact. Studies were conducted to evaluate environmental impacts by characterizing nitrogen, carbon, and water fluxes in turfgrass ecosystems. Emissions of nitrous oxide (N[subscript]2O), a major greenhouse gas and ozone depleter were measured from bermudagrass (Cynodon dactylon L. Pers. x C. transvaalensis Burtt-Davy) (bermuda), perennial ryegrass, (Lolium perenne L.) (rye), and zoysiagrass, (Zoysia japonica Steud.) (zoysia) under regional N management. In a separate study, N2O fluxes were measured from bermuda fertilized with controlled-release N fertilizers including polymer-coated and organic-N, and quick release urea. Emissions of N2O were measured using static surface chambers and gas chromatography. Zoysia, with less N requirements, had lower emissions than bermuda. Cumulative N[subscript]2O emissions were similar among N types. To measure water and carbon fluxes, a portable non-steady state chamber was designed and tested. The chamber had minimal affects to the canopy during field measurements: leak values averaged <1.5 micromol CO[subscript]2 m[superscript]-2 s[superscript]-1; average chamber pressure was 0.09 Pa ±0.01 Pa; temperature rise inside the chamber averaged 0.74C; and the chamber had 90% photosynthetically active radiation transmittance. Using the chamber, differences were detected in net photosynthesis (Pnet), gross photosynthesis (Pg), evapotranspiration (ET), canopy stomatal conductance (gc), and water use efficiency (WUE) in well-watered tall fescue (Festuca arundinacea Schreb.), Kentucky bluegrass (Poa pratensis L.) (KBG), zoysia, and bermuda. Irrigation requirements, visual quality ratings, and genetic rooting potential of 28 KBG cultivars and 2 Texas bluegrass hybrids (P. pratensis x P. arachnifera Torr.) were quantified in greenhouse and rainout facility studies. Average water applied ranged from 23.4 to 40.0 cm among cultivars. Bedazzled, Preakness, and Bartitia required less water and had higher average quality than other cultivars. Compact America and Mid-Atlantic phenotypes exhibited greatest potential for success in integrating reduced water inputs with maintenance of acceptable visual quality. Results indicated that turfgrass management could mitigate N[subscript]2O emissions and conserve water while maintaining healthy turfgrass, and the new chamber will enhance turfgrass studies by providing rapid measurements of photosynthesis.
Chaichana, Saisiri. "Dissolved organic carbon and nitrogen in coastal waters." Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/62312/.
Повний текст джерелаMori-Quiroz, Luis Martin. "Transition metal catalyzed Carbon-nitrogen bond forming reactions." Revista de Química, 2015. http://repositorio.pucp.edu.pe/index/handle/123456789/101381.
Повний текст джерелаCarbon-nitrogen (C–N) bond forming reactions are fundamental transformations in nature and also basic processes for the preparation of molecules and materials relevant to human activities. The development of new and efficient reactions for the formation of C–N bonds are therefore of great interest in academic and industrial settings. Progress in the last 20 years has focused mainly in Csp2–N bond forming processes; however, there is growing range of transition metal catalyzed reactions for the introduction of nitrogen in alkyl frameworks (Csp3–N bond formation). This article describes a selection of modern catalytic methods for the formation of C–N bonds.
Curtis-Summers, Shirley. "Stable Isotopes of Carbon and Nitrogen and Diet." Society of Antiquaries of Scotland, 2016. http://hdl.handle.net/10454/17856.
Повний текст джерелаChizari, Kambiz. "Synthesis of nitrogen-doped carbon nanotubes : catalytic applications." Strasbourg, 2011. http://www.theses.fr/2011STRA6047.
Повний текст джерелаSince the discovery of carbon nanotubes (CNT) in 1991, a lot of efforts have been done in order to find out their intrinsic properties and their possible applications. One of the most efficient methods used for tuning its physical and chemical properties is doping CNTs by nitrogen or boron. The aim of this work deals with the synthesis of nitrogen-doped carbon nanotubes (N-CNTs) and with the study of the catalytic performance of this material either as catalyst support or as a metal-free catalyst. The influence of the different synthesis parameters on the physical and chemical properties of the N-CNTs was investigated. Afterwards, the N-CNTs were used as catalyst support for the hydrogenation of cinnamaldehyde and its catalytic performance was compared to that obtained on the undoped CNTs. It was shown that N-CNTs synthesized in different conditions lead to different catalytic performances which was mainly linked with the nature of the incorporated nitrogen species. The N-CNTs were also employed as a metal-free catalyst for the selective oxidation of H2S into elemental sulfur and the results are discussed within this thesis. Recently 2D carbon material, namely graphene, has received a great interest due to its special physical properties. The previous investigations on the other graphitic material such as carbon nanotubes facilitate the understanding of the properties and behavior of this material. In this thesis we also worked on the synthesis of the few-layer graphene (FLG), using microwave irradiations. A preliminary study has also done on the nitrogen-doping of this material by microwave treatment on the expanded graphite dispersed in ammonium hydroxide. The FLGs were used as a catalyst support for the hydrogenation of cinnamaldehyde and its catalytic performance is compared to other graphitic materials such as natural graphite, expanded graphite and carbon nanotubes
Ning, Xue. "Carbon molecular sieve membranes for nitrogen/methane separation." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53986.
Повний текст джерелаNeary, Erika L., Daniel G. Neary, Steven T. Overby, and Sally M. Haase. "Prescribed Fire Impacts on Soil Carbon and Nitrogen." Arizona-Nevada Academy of Science, 2002. http://hdl.handle.net/10150/296593.
Повний текст джерелаKrause, Caitlin Joy. "Evaluating the toxicity of nitrogen-functionalized carbon nanotubes." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4667.
Повний текст джерелаPatenauden, Geneviève. "Quantifying forest carbon stocks and changes in support of the Kyoto Protocol." Thesis, University of Oxford, 2006. https://ora.ox.ac.uk/objects/uuid:0d69355d-db71-45a6-b0e7-7f9673f1118b.
Повний текст джерелаTavallali, Leila. "Spatial and temporal variability of carbon stocks within the River Colne Estuary." Thesis, University of Essex, 2018. http://repository.essex.ac.uk/21405/.
Повний текст джерелаDou, Fugen. "Long-term tillage, cropping sequence, and nitrogen fertilization effects on soil carbon and nitrogen dynamics." Texas A&M University, 2006. http://hdl.handle.net/1969.1/3831.
Повний текст джерелаCrook, Hannah D. "Carbon and nitrogen cycling in upland wetlands : impacts of changing climate and atmospheric nitrogen deposition." Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412169.
Повний текст джерелаSandoval, Rojano Stefania. "Functionalization of carbon nanomaterials with nitrogen, halides and oxides." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/394000.
Повний текст джерелаGraphene and carbon nanotubes (CNTs) are of wide interest in materials science due to their outstanding properties. Several approaches allow modulating their properties further expanding their potential applications in many fields. This thesis reports on the functionalization of carbon nanomaterials with nitrogen, halides and oxides. The modification of the structure of multiwalled carbon nanotubes (MWCNTs) and graphene derivatives has been carried out through solid-gas and solid-liquid reactions. Different methods of functionalization, which include oxidation, nitrogen functionalization and doping, as well as endohedral and exohedral modifications have been employed for tuning the properties of the prepared nanostructures. A systematic study of the conditions of treatment and an extensive characterization has allowed the determination of the structural characteristics of the samples and the evaluation of some of their physical and chemical properties. In this thesis we propose a simple, efficient and reproducible method for the synthesis of nitrogen-containing reduced graphene oxide (RGO). The nature of the nitrogen atoms within the RGO lattice has been tuned by ammonolysis treatments of graphene oxide (GO) in the range of 25 ˚C-800 ˚C. The reported protocol allows the introduction of aliphatic moieties (N-functionalization) and structural nitrogen (N-doping). Additionally, the structural composition of the N-containing RGO has been modified by post-annealing the material under non-oxidizing atmospheres. High temperature treatments induce internal rearrangements, leading to samples with an enhanced thermal stability. On the other hand, endohedral and exohedral functionalization of MWCNTs with inorganic materials have been carried out. We report on the formation of single-layered inorganic nanotubes within the cavities of MWCNTs through a molten phase capillary wetting technique. We have optimized the conditions of the synthesis to enhance the growth of the single-layered nanotubes, while decreasing the formation of other nanostructures (nanoparticles, nanorods and nanosnakes). A new technique for the confinement and/or release of the filled substances within the hollow cavity of the CNTs has also been developed. We have explored the potential of fullerenes as corking agents and as promoting species for the release of guest structures. Finally, we have prepared MWCNTs decorated with reduced titanium oxides employing high temperature treatments. By oxidation of MWCNTs self-standing titania “nano-necklaces” are formed. The photocatalytic performance of the carbon supported materials overpasses that of the reference material titania P25.
Rajab, T. M. A. "Studies on carbon metabolism and nitrogen fixation by Gloeothece." Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638610.
Повний текст джерелаTan, M. Md. "Aspects of carbon, nitrogen and sulphur diagenesis in sediments." Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353295.
Повний текст джерелаLodwig, Emma Mary. "Regulation of carbon and nitrogen metabolism in Rhizobium leguminosarum." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368874.
Повний текст джерелаNewton, Jason. "A carbon and nitrogen isotope study of CO3 chondrites." Thesis, Open University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259887.
Повний текст джерелаCavan, Graeme Patrick. "Interaction of carbon and nitrogen metabolism in Schizosaccharomyces pombe." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259573.
Повний текст джерелаTundel, Rachel E. (Rachel Elizabeth). "Advances in palladium-catalyzed carbon-nitrogen bond forming processes." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36283.
Повний текст джерелаVita. Leaf 68 blank.
Includes bibliographical references.
Chapter 1. Microwave-assisted, palladium-catalyzed C-N bond-forming reactions with aryl/heteroaryl nonaflates/halides and amines using the soluble amine bases DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) and a catalyst system consisting of Pd2dba3 and ligands (XantPhos, 2-dicylcohexylphosphino-2',4',6'-triisopropyl-1,1 '-biphenyl (XPhos) and 2-di-tert-butylphosphino-2',4',6'-triisopropyl-1, '-biphenyl) resulted in good to excellent yields of arylamines in short reaction times. Chapter 2. Using a catalyst comprised of the bulky, electron-rich monophosphine ligand di-tert-Butyl XPhos (2-di-tert-butylphosphino-2',4',6'-triisopropyl-1,1'-biphenyl) and Pd2dba3 with sodium tert-butoxide as the base, amino heterocycles were coupled successfully with aryl/heteroaryl halides in moderate to excellent yields.
by Rachel E. Tundel.
S.B.
Clark, D. R. "Carbon-nitrogen stress, and the growth of marine phytoplankton." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636260.
Повний текст джерелаRennie, Anthony. "Nitrogen-enriched carbon materials for high-power electrochemical capacitors." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16769.
Повний текст джерелаMarsay, Christopher Matthew. "Particulate trace metals, carbon and nitrogen in the Mesopelagic." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/351794/.
Повний текст джерелаLi, Jinling. "Effects of Biosolids on Carbon Sequestration and Nitrogen Cycling." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/49585.
Повний текст джерелаPh. D.
Ogbu, Chidiebere, and Gregory Dr Bishop. "Peroxide Sensing Using Nitrogen-Doped Screen-Printed Carbon Electrodes." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/93.
Повний текст джерелаDezi, Silvia <1974>. "Modelling the effects of nitrogen deposition and carbon dioxide enrichment on forest carbon balance." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3362/.
Повний текст джерелаHarris, Wylie Neal. "Grassland carbon and nitrogen dynamics: effects of seasonal fire and clipping in a mixed-grass prairie of the southern great plains." Texas A&M University, 2003. http://hdl.handle.net/1969.1/3911.
Повний текст джерела