994 resultados para Nitrogen Doping
Resumo:
Inland waters are of global biogeochemical importance receiving carbon inputs of ~ 4.8 Pg C y-1. Of this 12 % is buried, 18 % transported to the oceans, and 70 % supports aquatic secondary production. However, the mechanisms that determine the fate of organic matter (OM) in these systems are poorly defined. One important aspect is the formation of organo-mineral complexes in aquatic systems and their potential as a route for OM transport and burial vs. their use potential as organic carbon (C) and nitrogen (N) sources. Organo-mineral particles form by sorption of dissolved OM to freshly eroded mineral surfaces and may contribute to ecosystem-scale particulate OM fluxes. We tested the availability of mineral-sorbed OM as a C & N source for streamwater microbial assemblages and streambed biofilms. Organo-mineral particles were constructed in vitro by sorption of 13C:15N-labelled amino acids to hydrated kaolin particles, and microbial degradation of these particles compared with equivalent doses of 13C:15N-labelled free amino acids. Experiments were conducted in 120 ml mesocosms over 7 days using biofilms and streamwater sampled from the Oberer Seebach stream (Austria), tracing assimilation and mineralization of 13C and 15N labels from mineral-sorbed and dissolved amino acids.Here we present data on the effects of organo-mineral sorption upon amino acid mineralization and its C:N stoichiometry. Organo-mineral sorption had a significant effect upon microbial activity, restricting C and N mineralization by both the biofilm and streamwater treatments. Distinct differences in community response were observed, with both dissolved and mineral-stabilized amino acids playing an enhanced role in the metabolism of the streamwater microbial community. Mineral-sorption of amino acids differentially affected C & N mineralization and reduced the C:N ratio of the dissolved amino acid pool. The present study demonstrates that organo-mineral complexes restrict microbial degradation of OM and may, consequently, alter the carbon and nitrogen cycling dynamics within aquatic ecosystems.
Resumo:
Foraminifera are an important faunal element of the benthos in oxygen-depleted settings such as Oxygen Minimum Zones (OMZs) where they can play a relevant role in the processing of phytodetritus. We investigated the uptake of phytodetritus (labeled with 13C and 15N) by cal-careous foraminifera in the 0-1 cm sediment horizon under different oxygen concentrations within the OMZ in the eastern Arabian Sea. The in situ tracer experiments were carried out along a depth transect on the Indian margin over a period of 4 to 10 days. The uptake of phy-todetrital carbon within 4 days by all investigated species shows that phytodetritus is a rele-vant food source for foraminifera in OMZ sediments. The decrease of total carbon uptake from 540 to 1100 m suggests a higher demand for carbon by species in the low-oxygen core region of the OMZ or less food competition with macrofauna. Especially Uvigerinids showed high uptake of phytodetrital carbon at the lowest oxygenated site. Variation in the ratio of phytodetrital carbon to nitrogen between species and sites indicates that foraminiferal carbon and nitrogen use can be decoupled and different nutritional demands are found between spe-cies. Lower ratio of phytodetrital carbon and nitrogen at 540 m could hint for greater demand or storage of food-based nitrogen, ingestion or hosting of bacteria under almost anoxic condi-tions. Shifts in the foraminiferal assemblage structure (controlled by oxygen or food availabil-ity) and in the presence of other benthic organisms account for observed changes in the pro-cessing of phytodetritus in the different OMZ habitats. Foraminifera dominate the short-term processing of phytodetritus in the OMZ core but are less important in the lower OMZ bounda-ry region of the Indian margin as biological interactions and species distribution of foraminifera change with depth and oxygen levels.
Resumo:
The relatively high elastic modulus coupled with the presence of toxic vanadium (V) in Ti6Al4 V alloy has long been a concern in orthopaedic applications. To solve the problem, a variety of non-toxic and low modulus beta-titanium (beta-Ti) alloys have been developed. Among the beta-Ti alloy family, the quaternary Ti-Nb-Zr-Ta (TNZT) alloys have received the highest attention as a promising replacement for Ti6Al4 V due to their lower elastic modulus and outstanding long term stability against corrosion in biological environments. However, the inferior wear resistance of TNZT is still a problem that must be resolved before commercialising in the orthopaedic market. In this work, a newly-developed laser surface treatment technique was employed to improve the surface properties of Ti-35.3Nb-7.3Zr-5.7Ta alloy. The surface structure and composition of the laser-treated TNZT surface were examined by grazing incidence x-ray diffraction (GI-XRD) and x-ray photoelectron spectroscopy (XPS). The wear and corrosion resistance were evaluated by pin-on-plate sliding test and anodic polarisation test in Hanks’ solution. The experimental results were compared with the untreated (or base) TNZT material. The research findings showed that the laser surface treatment technique reported in this work can effectively improve the wear and corrosion resistance of TNZT.
Resumo:
This work aimed to assess how potassium (K) and nitrogen (N) fertilisation may affect the use of precipitation in terms of vegetative and flowering response of 15-year-old carob trees during a 3-year experiment. A field trial was conducted in 1997, 1998 and 1999 in Algarve (Southern Portugal) in a calcareous soil. Four fertilisation treatments were tested: no fertiliser (control); 0.8 kg N/tree (N treatment); 1 kg K 2 O/tree (K treatment) and 0.8 kg N/tree plus 1 kg K 2 O/tree (NK treatment). No irrigation was applied during the experimental period. Branch length increments were measured every month throughout the growing season and inflorescence number was registered once per year. There was a strong seasonal effect on vegetative growth, since low levels of precipitation (115 mm) during October 1998–March 1999 suppressed the increment in branch length. N supplied to the trees (N and NK treatments) tended to increase water use indices in terms of vegetative growth. No response to K alone was observed in trees fertilised only with K. The number of inflorescences increased throughout the experimental period, particularly for N and NK treatments, and a reduction of the precipitation amount during April, May and June, may also enhance flowering. This knowledge could be important when making decisions concerning fertilisation under dry conditions. The results reported here indicate that tree growth (expressed as the branch growth) and flower production under dry-farming conditions, may be achieved by applying 0.8 kg of N (as ammonium nitrate) per tree during the growing season. However, N uptake and use depends on soil water availability.
Resumo:
O Azoto (N): da ciência para a sociedade é um projecto de comunicação de ciência que tem por objecNvo consciencializar os jovens para as ameaças que o azoto (N) em excesso traz para a humanidade. Pode ser dividido em duas partes. Uma, de invesNgação, sobre a análise de resultados de uma consulta pública realizada entre professores, usando o método qualitaNvo do focus group, para compreender a sua sensibilidade e propostas de solução para minimizar o excesso de N no ambiente. Os resultados obNdos foram instrumentais para o desenvolvimento da segunda parte. Esta segunda parte é uma proposta de projecto a submeter ao Horizon 2020, no âm-‐ bito da “Science with and for Society “. Nela se propõe uma abordagem educaNva trans-‐disciplinar, conseguida através da interacção entre docentes do secundário, e do ensino superior, associação de pais e organizações cívicas não governamentais, com vista à consciencialização dos jovens para as ameaças do N em excesso no meio ambiente, fazendo o enquadramento cien@fico e fornecendo abordagens tecnológi-‐ cas. A inovação desta proposta baseia-‐se: (i) no acompanhamento e desenvolvimen-‐ to profissional dos docentes do secundário, (ii) na moNvação dos estudantes a de-‐ senvolver o seu próprio estudo e pesquisa com a tutoria dos docentes, da escola e do ensino superior, e (iii) no desenvolvimento de capacidades de comunicação dos jo-‐ vens para exercer uma cidadania acNva em prol da minimização das ameaças do N.
Resumo:
Polyhydroxyalkanoates (PHA) production using mixed microbial cultures (MMC) requires a multi-stage process involving the microbial selection of PHA-storing microorganisms, typically operated in sequencing batch reactors (SBR), and an accumulation reactor. Since low-cost renewable feedstocks used as process feedstock are often nitrogen-deficient, nutrient supply in the selection stage is required to allow for microbial growth. In this context, the possibility to uncouple nitrogen supply from carbon feeding within the SBR cycle has been investigated in this study. Moreover, three different COD:N ratios (100:3.79, 100:3.03 and 100:2.43) were tested in three different runs which also allowed the study of COD:N ratio on the SBR performance. For each run, a synthetic mixture of acetic and propionic acids at an overall organic load rate of 8.5 gCOD L-1 d-1 was used as carbon feedstock, whereas ammonium sulfate was the nitrogen source in a lab-scale sequence batch reactor (SBR) with 1 L of working volume. Besides, a sludge retention time (SRT) of 1 d was used as well as a 6 h cycle length. The uncoupled feeding strategy significantly enhanced the selective pressure towards PHA-storing microorganisms, resulting in a two-fold increase in the PHA production (up to about 1.3 gCOD L-1). A high storage response was observed for the two runs with the COD:N ratios (gCOD:gN) of 100:3.79 and 100:3.03, whereas the lowest investigated nitrogen load resulted in very poor performance in terms of polymer production. In fact, strong nitrogen limitation caused fungi to grow and a very poor storage ability by microorganisms that thrived in those conditions. The COD:N ratio also affected the polymer composition, indeed the produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) showed a variable HV content (1-20 %, w/w) among the three runs, lessening as the COD:N increased. This clearly suggests the possibility to use the COD:N ratio as a tool for tuning polymer properties regardless the composition of the feedstock.
Resumo:
The potential and applicability of UHPSFC-MS/MS for anti-doping screening in urine samples were tested for the first time. For this purpose, a group of 110 doping agents with diverse physicochemical properties was analyzed using two separation techniques, namely UHPLC-MS/MS and UHPSFC-MS/MS in both ESI+ and ESI- modes. The two approaches were compared in terms of selectivity, sensitivity, linearity and matrix effects. As expected, very diverse retentions and selectivities were obtained in UHPLC and UHPSFC, proving a good complementarity of these analytical strategies. In both conditions, acceptable peak shapes and MS detection capabilities were obtained within 7min analysis time, enabling the application of these two methods for screening purposes. Method sensitivity was found comparable for 46% of tested compounds, while higher sensitivity was observed for 21% of tested compounds in UHPLC-MS/MS and for 32% in UHPSFC-MS/MS. The latter demonstrated a lower susceptibility to matrix effects, which were mostly observed as signal suppression. In the case of UHPLC-MS/MS, more serious matrix effects were observed, leading typically to signal enhancement and the matrix effect was also concentration dependent, i.e., more significant matrix effects occurred at the lowest concentrations.
Resumo:
Big sports events like the 2008 European Football Championship are a challenge for anti-doping activities, particularly when the sports event is hosted by two different countries and there are two laboratories accredited by the World Anti-Doping Agency. This challenges the logistics of sample collection as well as the chemical analyses, which must be carried out timeously. The following paper discusses the handling of whereabouts information for each athlete and the therapeutic use exemption system, experiences in sample collection and transportation of blood and urine samples, and the results of the chemical analysis in two different accredited laboratories. An overview of the analytical results of blood profiling and growth hormone testing in comparison with the distribution of the normal population is also presented.
Resumo:
The use of certain perfonnance enhancing substances and methods has been defined as a major ethical breach by parties involved in the governance of highperfonnance sport. As a result, elite athletes worldwide are subject to rules and regulations set out in international and national anti-doping policies. Existing literature on the development of policies such as the World Anti-Doping Code and The Canadian antiDoping Program suggests a sport system in which athletes are rarely meaningfully involved in policy development (Houlihan, 2004a). Additionally, it is suggested that this lack of involvement is reflective of a similar lack of involvement in other areas of governance concerning athletes' lives. The purpose ofthis thesis is to examine the history and current state of athletes' involvement in the anti-doping policy process in Canada's high-perfonnance sport system. It includes discussion and analysis of recently conducted interviews with those involved in the policy process as well as an analysis of relevant documents, including anti-doping policies. The findings demonstrate that Canadian athletes have not been significantly involved in the creation of recently developed antidoping policies and that a re-evaluation of current policies is necessary to more fully recognize the reality of athletes' lives in Canada's high-perfonnance sport system and their rights within that system.
Resumo:
The maximum amount of ethyl carbamate (EC), a known animal carcinogen produced by the reaction of urea and ethanol, allowed in alcoholic beverages is regulated by legislation in many countries. Wine yeast produce urea by the metabolism of arginine, the predominant assimilable amino acid in must. This action is due to arginase (encoded by CARl). Regulation of CARl, and other genes in this pathway, is often attributed to a well-documented phenomenon known as nitrogen catabolite repression. The effect of the timing of di-ammonium phosphate (DAP) additions on the nitrogen utilization, regulation of CARl, and EC production was investigated. A correlation was found between the timing of DAP addition and the utilization of nitrogen. When DAP was added earlier in the fermentations, less amino nitrogen and more ammonia nitrogen was sequestered from the media by the cells. It was also seen that early DAP addition led to more total nitrogen being used, with a maximal difference of ~25% between fermentations where no DAP was added versus addition at the start of the fermentation. The effect of the timing ofDAP addition on the expression of CARJ during fermentation was analyzed via northern transfer and the relative levels of CARl expression were determined. The trends in expression can be correlated to the nitrogen data and be used to partially explain differences in EC formation between the treatments. EC was quantified at the end of fermentation by GC/MS. In Montrachet yeast, a significant positive correlation was found between the timing of DAP addition, from early to late, and the final EC concentration m the wine (r = 0.9226). In one of the fermentations, EC levels of 30.5 ppb was foimd when DAP was added at the onset of fermentation. A twofold increase (69.5 ppb) was observed when DAP was added after 75% of the sugars were metabolized. When no DAP was added, the ethyl carbamate levels are comparable at a value of 38 ppb. In contrast, the timing of DAP additions do not affect the level EC produced by the yeast ECU 18 in this manner. The study of additional yeast strains shows that the effect of DAP addition to fermentations is strain dependent. Our results reveal the potential importance of the timing of DAP addition to grape must with respect to EC production, and the regulatory effect of DAP additions on the expression of genes in the pathway for arginine metabolism in certain wine yeast strains.
Resumo:
Gene doping is the most recent addition to the list of banned practices formulated by the World Anti-doping Agency. It is a subset of doping that utilizes the technology involved in gene therapy. The latter is still in the experimental phase but has the potential to be used as a type of medical treatment involving alterations of a patient‘s genes. I apply a pragmatic form of ethical inquiry to evaluate the application of this medical innovation in the context of sport for performance-enhancement purposes and how it will affect sport, the individual, society and humanity at large. I analyze the probable ethical implications that will emerge from such procedures in terms of values that lie at the heart of the major arguments offered by scholars on both affirmative and opposing sides of the debate on gene doping, namely fairness, autonomy and the conception of what it means to be human.