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1
Layton, Raymond J. "Macroinvertebrate colonization and production in new experimental ponds." Diss., This resource online, 1989. http://scholar.lib.vt.edu/theses/available/etd-03042009-040552/.
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Christman, Van D. "Ecology of benthic macroinvertebrates in experimental ponds." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-07282008-134927/.
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Rosenzweig, Michael S. "Phytoplankton colonization and seasonal succession in new experimental ponds." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/31916.
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Jenkins, David G. "Structure and function of zooplankton colonization in twelve new experimental ponds /." This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-08252008-162217/.
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Lee, Byung Joon. "Experimental and modeling studies for optimizing flocculant-aided sediment retention ponds." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1239895729/.
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Jenkins, David Glenn. "Structure and function of zooplankton colonization in twelve new experimental ponds." Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/39237.
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This study examined the structural and functional development of zooplankton communities in 12 new experimental ponds for one year and tested four predictions derived from the Random Placement Hypothesis (Coleman 1981). Physico-chemistry, zooplankton colonization dynamics, zooplankton community structure and function were analyzed every two weeks from 5 February 1988 to 10 February 1989. Ponds varied in physico-chemistry at points in time but followed similar patterns during the study year.
Ponds were not colonized by zooplankton similarly. Some species occurred in all ponds with about the same timing, but many species exhibited variable timing among ponds or never occurred in more than a few ponds. Colonization curves varied among ponds and through time, and species accrual curves differed in both accrual rates and the numbers of species accrued. Observed colonization curves did not closely match the curve expected according to the Random Placement Hypothesis.
Zooplankton community structure also varied among ponds. Multivariate analyses could not discern similar trends in zooplankton community structure among ponds due to the disparity of species trends among ponds. species data were pooled into taxa (Copepoda, Cladocera, Rotifera, ostracoda and Chaoborus) and analyzed. Rotifers dominated zooplankton communities in densities and biomass, and ponds differed in taxa densities and biomasses.
Zooplankton community function was more similar among ponds than community structure. Multivariate analyses indicated ponds generally followed similar trajectories in zooplankton community function through the year.
Zooplankton did not colonize experimental ponds equally and did not develop similar zooplankton community structure among ponds. Dispersal processes probably limited colonization and development of zooplankton community structure. Zooplankton community function was generally more similar among ponds than community structure, probably due to the functional redundancy of zooplankton species. Implications of these results for experimental pond studies are discussed.Ph. D.
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Tsavdaris, Alexandros. "An evaluation of vegetated SuDS ponds using experimental and numerical methods." Thesis, University of Portsmouth, 2015. https://researchportal.port.ac.uk/portal/en/theses/an-evaluation-of-vegetated-suds-ponds-using-experimental-and-numerical-methods(11e1eaa0-9dea-4693-a4f2-899cf0a75911).html.
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Aquatic ecosystems are threatened by a variety of contaminants contained in road runoff. Pollutant mitigation is therefore an important function of sustainable drainage systems such as vegetated ponds. However, design is predominantly based on “black box” approaches. In addition, most studies do not evaluate alternative design layouts for a given location and hydrological regime. This research project evaluates a small vegetated pond, by means of experimental and numerical methods. The vegetated wet detention pond (two flow balancing basins separated by a berm) had 1.6m maximum depth, 304m³ storage capacity, a hydro-brake controlling the outflow, and was equipped with sediment traps and stage loggers (at the inlet/outlet) for monitoring purposes. It received road runoff after a bio-retention area and a swale (L=80m) adjacent to an urban road. Experimental methods included the collection of water/sediment from strategic parts of the system and subsequent analysis. Water quality investigation included BOD5, COD, TSS, VSS, pH, heavy metals and other elements. Sediment quality analysis included particle size distribution, accumulation rates, volatile substance content and heavy metal/elements concentrations in different size fractions. Numerical methods included the evaluation of the current design under extreme flow conditions, in terms of flow distributions, followed by investigating alternative geometries for the same footprint in the interest of promoting sustainable flow regimes and sedimentation potential. The storm events exhibited first flush patterns in the inflow, but linear associations between many pollutants in the inlet and the outlet, suggested short-circuiting was affecting effluent quality during storm events. The pond system showed variability and complexity in the behaviour of pollutants with influences due to spatial, seasonal, and site-specific effects. The pollution levels in the pond (water, sediments) were low compared to standards and the pond seemed to have relieved the River Wallington (receiving water-body) from a great amount of pollution. However, increased salinity and low biodegradability of material found in the pond could be of concern in the long-term. The system promoted sedimentation although there was indication of post-depositional re-suspension especially under high flows. Vegetation probably encouraged buffering while increasing the levels of biogenic debris in the pond water. The main factors contributing to the water and sediment quality fluctuations were identified during this study. These factors were of a broad-spectrum of variables related to environmental stressors and design properties. The modelling of the vegetation was very intricate although the CFD code modelled relatively accurately the flow distributions within the vegetated domain. The simulations suggest that the excessive vegetation diverged the flow from the basins to the un-vegetated banks and therefore, increased the re-suspension potential of settled material. The response of this particular vegetated pond in terms of sedimentation potential and velocity distributions (during the design flow) was highly influenced by the geometry and the vegetation cover of the pond system. In addition, simulations indicated that the most appropriate design layout for the given flow regime was an elliptical pond with a submerged/emergent island placed at a central location. The response of this pond layout, in respect of velocity distributions, could be up to 30% more efficient than the existing configuration. The research findings of this study contributed to greater knowledge of the dynamic nature of treatment mechanisms in vegetated SuDS and offered innovative information on how to simulate (vegetated) SuDS ponds using CFD codes.
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Madon, Sharook P. "Bioenergetics of young-of-year walleye and trophic interactions in experimental ponds /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu148784368895977.
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Swirepik, Jody, and n/a. "Physical disturbance of Potamogeton tricarinatus and sediment by carp (Cyprinus carpio) in experimental ponds." University of Canberra. Resource, Environmental & Heritage Sciences, 1999. http://erl.canberra.edu.au./public/adt-AUC20061113.155736.
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The impact of carp on a rhizomatous macrophyte was examined in two consecutive years
using three outdoor aquaculture ponds with naturally established beds of Potamogeton
tricarinatus. Each pond was divided with wire fencing to form a carp (500 kg ha-1) and
control treatment. After 6 weeks, plant biomass had declined to the same extent in the
carp and control treatments, indicating that direct physical disturbance by carp was not
reducing the biomass of P. tricarinatus. In a second experiment, carp were added to two
of the same ponds when plants were regenerating after a 9-11 month drying period. After
8 weeks, P. tricarinatus biomass in the carp treatments was between one half and one
tenth of the biomass in the control treatments and one control treatment supported more
Najas tenuifolia than the paired carp treatment. The lower biomass of Potamogeton in
the carp treatments was a result of fewer shoots and less growth per shoot. Rhizomes
had been undermined in the carp treatment with less than 1% of plants growing from
rhizome compared to 36% in the control treatment. Accumulation of sediment into traps
was significantly higher in the carp treatments (2.5 to 77.5 times more than the control).
On average, carp resuspended 662 kg dry sediment ha-1 for each 100 kg ha-1 of carp or
6.6 times their wet weight biomass in dry sediments each day. Some implications of high
sediment resuspension are discussed. The research demonstrates that well anchored
macrophyte species can show tolerance to the physical disturbance associated with carp
benthic feeding, however, these same species are vulnerable during regenerating and
recruitment stages. It is suggested that anchorage is the most important factor for
determining plant tolerance to carp. The implications for aquatic plant and riverine
management are discussed, including the importance of excluding carp from newly
flooded wetlands and the role of carp in determining alternative stable states.
10
Taylor, Scott. "Exploring factors driving organic carbon burial and storage in small constructed ponds : an experimental approach." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/36143/.
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The significance of ponds in the terrestrial carbon cycle has received increasing attention in recent years. Evidence suggests that ponds exhibit rates of biogeochemical cycling orders of magnitude greater than larger water bodies and, cumulatively, the storage of organic carbon (OC) in small ponds may equal or possibly surpass that of large water bodies. This project furthers our understanding of OC storage within ponds, combining survey and experimental approaches to accurately quantify sediment carbon stocks and accumulation rates. It incorporates four distinct, yet complimentary components aiming to: i) Evaluate the accuracy of estimating OC storage in entire ponds from sediment cores; ii) Monitor physicochemical dynamics and quantify OC storage across newly constructed ponds; iii) Quantify OC storage across a suite of mature ponds and assess the impact of vegetation community development; iv) Identify variations in microbial communities between different ponds in relation to sediment physicochemistry and vegetation coverage, exploring the implications for OC storage and burial. Carbon stocks were surveyed in 12 mature ponds across an experimental field site at Druridge Bay, Northumberland. Comprehensive historical ecological data was used to separate these ponds into three distinct groups based on hydrology and vegetation. One pond was selected from each of the resulting three groups and exhumed in its entirety to accurately quantify OC storage. Three sediment cores were taken beforehand in a novel attempt to evaluate the percentage difference between sediment core estimates and whole pond sediment OC storage. Whole pond exhumation suggests that the three ponds stored between 1565 – 2288 g OC m2, whilst results from the cores alone gave estimates within a 10-15% range. A further three ponds from each group were selected to quantify burial rates using sediment cores. Results suggest the ponds have stored between 1413 – 4459 g OC m2 over 20 yrs, equating to around 67 – 212 g OC m2 yr-1. OC storage was greater in ponds that had undergone the fastest establishment of vascular plant communities. Three new ponds were constructed at the Druridge site. Physicochemical parameters were monitored at approximately fortnightly intervals across a period of three years. All three ponds were hyper-eutrophic, dominated by algae. However, OC storage was negligible, further suggesting that OC burial is only significant upon the establishment of vascular plant communities. Sediment samples were subject to 16s rRNA analysis to identify microbial communities involved in carbon cycling. Variations in microbial community composition between ponds were observed and showed complex relationships with sediment physicochemistry and vegetation coverage. Microbial diversity was significantly higher in ponds storing more OC. Ponds dominated by Juncus vegetation, had lower diversity and a greater abundance of facultative anaerobic bacteria, and stored less OC. The intense rates of OC burial observed in this study demonstrate the functional capacity of constructed ponds to operate as significant sinks of OC. High rates of OC accumulation compared to the surrounding terrestrial landscape highlights the potential for their construction across landscapes to act as versatile, yet effective carbon mitigation features.
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Sayer, Asaad Hameed. "An experimental and theoretical investigation of novel configurations of solar ponds for use in Iraq." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/841722/.
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Solar energy is likely to be the energy of the future; solar ponds, especially salinity gradient solar ponds (SGSPs), facilitate simple and cost-effective thermal energy storage. Research on maximising their potential is of particular relevance to developing countries, which often have an abundance of solar energy and a critical need for increased power supplies. For this research, a theoretical model for heat transfer in a SGSP was developed to study the energy balance in the three separate zones: the upper convective zone (UCZ), lower convective zone or storage zone (LCZ) and non-convective zone (NCZ). The model showed that the LCZ temperature could reach more than 90 °C in summer and more than 50 °C in winter, in a pond in the Middle East. It was also concluded that surface heat loss occurred mainly by evaporation. The new model was also used to examine the feasibility of a second type of solar pond, the gel pond; this offers solutions to some of the SGSP’s challenges, but presents other difficulties relating to cost and labour. To verify the theoretical results of the SGSP, a small experimental pond was constructed and operated for 71 days in Nasiriyah, Iraq. It was observed that adding a thin surface layer (0.5 cm) of paraffin eliminated the significant evaporation seen in the uncovered pond. Further analysis of the evaporation rate showed a significant correlation with temperature, solar radiation and humidity. Crucially, it was also noted that while the salinity gradient in the NCZ remained substantially intact, the temperature profile became approximately uniform throughout the pond after about 50 days. Analytical formulae to describe the concentrations and temperatures of the UCZ and LCZ were derived. The results achieved and comparisons with the experimental data showed that these equations can be used to compute both concentrations and temperatures.
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Arumugam, Phillip T. "An experimental approach to golden perch (Macquaria ambigua) fry-zooplankton interactions in fry rearing ponds, south-eastern Australia /." Title page, contents and introduction only, 1986. http://web4.library.adelaide.edu.au/theses/09PH/09pha793.pdf.
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Giménez, Grau Pau. "Nutrients and algal growth in the oligotrophy: a field experimental approach in mountain lakes = Nutrients i creixement algal en la oligotròfia: una aproximació experimental de camp en estanys de muntanya." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/402582.
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The main objectives of this dissertation were (a) to determine the effects of nitrogen (N) and phosphorus (P) fertilization on the growth of microalgal groups of periphyton and phytoplankton, and (b) to evaluate some indicators of the regulatory processes (e.g. N:P content, chlorophyll content per biovolume) involved in such growth responses. To do so, we followed a field experimental approach of short-term nutrient enrichments (21-25 days), using nutrient-diffusing substrates in the case of epilithic periphyton (Chapter 1), and mesocosms in the case of phytoplankton (Chapter 2 and 3). These experiments were performed in lakes of the Pyrenees, a region of particular interest because the average conditions are just on the threshold between the N and P limitation of algal growth. Moreover, most of these lakes are oligotrophic, and the nutrient availability is highly conditioned by N and P inputs of atmospheric origin, which appears to be changing due to human activities and global change.
In the first chapter, we evaluated the influence of the main factors controlling the algal colonization of epilithic periphyton, and compared the differences between the two major algal groups (i.e. diatoms and chlorophytes). We selected nine lakes and two streams to account for environmental gradients of trophic status and water renewal, while the influence of N and P availability was evaluated in each location using nutrient-diffusing substrata. Water renewal had a significant positive effect on the algal colonization of epilithic periphyton, although this influence was only significant for diatoms. Lake trophic status (i.e. dissolved organic carbon) was the second most influential factor in the algal colonization, and similarly affected diatoms and chlorophytes. High N:P availability tended to favour chlorophytes over diatoms. The nutrient enrichments inhibited the growth of diatoms -particularly the N enrichments-, but this adverse effects were mitigated by high water currents. Chlorophytes better tolerated high nutrient levels than diatoms.
The second chapter aimed to assess the influence of nutrient availability on the productivity, the composition of major phytoplankton groups, and the C:N:P proportions in seston, and evaluate the interrelationships among them. We noticed that the response of productivity, community structure, and seston C:N:P to increasing P availability was not strictly coherent. Productivity was especially sensitive to low and intermediate P additions, while seston C:N:P was only markedly changed under high P supply. The highest P-enrichment lead the seston C:N:P toward Redfield proportions in a non-linear way. N excess conditions reduced the growth of phytoplankton and enhanced the differentiation of autotrophic community, but did not affect seston C:N:P. High ammonium availability tended to increase seston C:P and N:P ratios, as well as to stimulate productivity and alter phytoplankton structure when P stress diminished.
Finally, we evaluated the relationships among nutrient availability, growth, and chlorophyll content per biovolume in phytoplankton. Specifically, we evaluated to what extent intense growth is associated with high chlorophyll content or with a major plasticity of that content. Pigments content and their plasticity were determined for all algal groups estimating power-law based models. We observed that diatoms and chlorophytes were the two groups that showed the highest growth capacity, what could be associated with their ability to increase the chlorophyll content per biovolume when nutrient supply increases. Chrysophyceans and dinoflagellates achieved their maximum growth rates at relatively low P supply, and may be better adapted to cope with low P availability.Els principals objectius d’aquesta tesi han estat els de (a) determinar els efectes de la fertilització de nitrogen (N) i fòsfor (P) sobre el creixement dels grups algals del perífiton i del fitoplàncton, i (b) avaluar la influència d’alguns processos reguladors (p.ex. contingut de N:P, contingut de clorofil·la per biovolum) involucrats en les respostes del creixement. S’ha seguit una aproximació experimental de camp basada en la utilització de substrats difusors de nutrients en el cas del perífiton (Capítol 1), i en l’addició de nutrients a mesocosms en el cas del fitoplàncton (Capítol 2 i 3). En el primer capítol es va avaluar la influència dels factors que controlen la colonització del perífiton per part de les diatomees i dels cloròfits. La renovació de l’aigua i l’estat tròfic (DOC) van tenir un efecte positiu en la colonització algal. L’alta disponibilitat de N en relació a P va tendir a afavorir els cloròfits per sobre de les diatomees. Les addicions de nutrients (sobretot de N) van resultar perjudicials pel creixement de les diatomees en molts casos, mentre que els cloròfits van tolerar millor aquestes altes concentracions. En el segon capítol es van observar diferents pautes de resposta de la producció, l’estructura de la comunitat i la composició C:N:P del seston a diferents enriquiments amb P. La producció primària va augmentar considerablement a addicions baixes i mitjanes de P, mentre que les proporcions C:N:P del seston només van canviar de forma marcada -dirigint-se cap a “Redfield”- a altes addicions de P. Les condicions d’excés de N van reduir el creixement del fitoplàncton però no van afectar les proporcions C:N:P. Finalment es van avaluar les relacions entre disponibilitat de nutrients, creixement i contingut de clorofil·la per biovolum en el fitoplàncton. Les diatomees i els cloròfits van demostrar tenir les capacitats de creixement més altes, i això podria estar associat amb la seva habilitat d’incrementar el contingut de clorofil·la quan la disponibilitat de nutrients augmenta. Les crisofícies i les dinofícies van assolir les màximes taxes de creixement a concentracions de P comparativament baixes, indicant que estarien més ben adaptades a baixes disponibilitats de nutrients.
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Balci, Pinar. "Ecology of Chironomids Associated with Myriophyllum Spicatum L. and Heteranthera Dubia Macm." Thesis, University of North Texas, 2002. https://digital.library.unt.edu/ark:/67531/metadc5803/.
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Macroinvertebrate communities inhabiting an exotic, Myriophyllum spicatum, and a native, Heteranthera dubia macrophyte were studied from March 1999 to June 2000 in experimental ponds. Although macrophyte architecture explained some variation in macroinvertebrate abundance between the two macrophytes, most variation was explained by the sampling months. Total number of macroinvertebrates was found to be positively correlated with epiphyton biomass which differed significantly between the two plant types and among sampling months. Taxa richness did not vary between the two plant types. Chironomid larvae were the most abundant organisms and dominated by Apedilum elachistus on both plant communities. Annual production of five chironomid species was estimated by the size-frequency method. Production estimates (P) in g dry wt m-2 yr-1 of plant surface area for the predator Tanypodinae larvae were: Larsia decolarata, P= 0.77 and 0.67, Labrundinia virescens, P= 0.59 and 0.35 on M. spicatum and H. dubia, respectively. Larvae of Cricotopus sylvestris and Psectrocladius vernalis were collected from M. spicatum from March to mid-June. Production of C. sylvestris was found to be 0.46 g dry wt m-2, whereas it was 0.07 g dry wt m-2 for P. vernalis for this period. Apedilum elachistus exhibited the highest productivity: 9.9 g dry wt m-2 yr-1 of plant surface area on M. spicatum, and 8.5 g dry wt m-2 yr-1 on H. dubia. These production estimates are among the highest production values reported for a single species. Additionally, post-ovipositing development times for five chironomid species collected from Myriophyllum and Heteranthera were determined. Three different temperatures (15°, 20° and 25°C) were chosen to rear eggs under 12L: 12D photoperiod. Egg development times ranged between 1-4 days. Larval development times ranged from 44 days at 20°C for Tanypus neopunctipennis to as few as 9 days at 20°C for Larsia decolorata.
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Bronsoms, i. Fabrellas Sílvia. "Proteïnes petites i riques en ponts disulfur com a models de producció recombinant i plegament." Doctoral thesis, Universitat Autònoma de Barcelona, 2002. http://hdl.handle.net/10803/3481.
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El PCI, la hirudina i el LCI formen part de la família de proteïnes petites i riques en ponts disulfur, que conté un gran nombre de biopèptids amb potencials aplicacions biotecnològiques, com són els factors de creixement, les toxines, els inhibidors de proteases o desintegrines.A causa de la presència dels ponts disulfur l'expressió recombinant d'aquestes proteïnes és complexa. En el primer treball de la tesi s'estudien tres sistemes de producció recombinant: un sistema eucariota (Pichia pastoris) i dos sistemes procariotes (Escherichia coli). S'optimitzen diversos paràmetres per tal de millorar el seu nivell de producció i es busquen sistemes que permetin simplificar el seu procés de purificació. S'aconsegueix desenvolupar un sistema en E.coli amb una producció final de proteïna que és 10 cops superior al sistema de partida.
En el segon treball s'analitza el paper de les regions precursores del PCI en el plegament de la forma madura. S'analitza el procés de replegament oxidatiu in vitro de les diverses pro-formes del PCI per tal de caracteritzar la seva influència sobre la velocitat o la eficiència del plegament de la forma madura. També s'estudia la influència de la pro-regió N-terminal sobre el procés de plegament in vivo en E.coli del PCI madur i d'una sèrie de mutants que presenten un mal plegament o un baix nivell d'expressió recombinant. Finalment es duu a terme una caracterització estructural de la forma corresponent al PCI amb la pro-regió N-terminal a través d'estudis de bescanvi protó/deuteri, exoproteòlisi limitada, espectroscopia de dicroïsme circular i ressonància magnètica nuclear.
En l'últim treball s'analitza el procés de plegament proteic de la hirudina i del LCI a través de l'estudi de les reaccions de bescanvi protó/deuteri seguides per espectrometria de masses MALDI-TOF. Es caracteritza l'adquisició d'estabilitat conformacional al llarg del procés de plegament de les dues proteïnes. S'aïllen una sèrie d'intermediaris de plegament i es determina la seva estabilitat; la qual cosa ens permet estudiar les diferències existents entre les vies de plegament de les dues proteïnes. Finalment s'estima la contribució de les interaccions covalents i no-covalents en l'estabilitat final de la proteïna nativa.
PCI, hirudin and LCI belong to the familly of small disulfide-rich proteins, which also contains other biologically important biopeptides like growth factors, desintegrins, toxins or protease inhibitors.
These proteins cannot be usually produced at high levels by recombinant DNA approaches due to the presence of the disulfide bridges. To deal with this, we selected three different systems for heterologous expression: one based in external secretion by the yeast Pichia pastoris and two others based in the periplasmic secretion in Escherichia coli, using powerful promoters in all cases. Several parameters were optimized to improve PCI production and to simplify the purification protocol. Finally, a new method was developed, which lead to a final PCI production 10-fold higher than the previously described system.
In the second work of the thesis, the role of the PCI pro-regions on the mature peptide folding was analyzed. The in vitro oxidative refolding of mature PCI was compared with that of the pro-forms to characterize their influence on mature PCI folding rates and folding efficiency, using RP-HPLC to analyze the acid-trapped disulfide intermediates collected during the refolding process. The influence of the N-terminal pro-region on the expression or folding of several PCI variants reported to give a low expression yield or a low folding efficiency in vivo in E.coli was also studied. In addition, the presence of ordered structural elements in the N-terminal extension of PCI was investigated by deuteron to proton exchange, limited exoproteolysis, circular dicroism spectroscopy and nuclear magnetic ressonance.
In the last work, the folding process of hirudin and LCI was analyzed by deuteron to proton exchange monitored by MALDI-TOF mass spectrometry. The comparison of the number of slow exchanging protons of different samples along the folding pathway provided an easy and fast way to follow the protein folding process. Additionally, the deuteron to proton exchange experiments on purified folding intermediates allowed us to characterize the differences between the two folding pathways and to measure the contribution of the disulfide bonds versus the non-covalent forces to the stability of the native protein.
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Kheder, Noha. "Experimental demonstration of OCDMA and OTDMA PONs with FEC and burst-mode reception." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19245.
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Passive optical networks (PONs) are a promising economic solution in delivering data to the end-user. We demonstrate experimentally the uplink of a spectral-amplitude-coded optical code division multiple access (SAC-OCDMA) and an optical time division multiple access (OTDMA) PON, with burst-mode reception. The receiver performs clock and data recovery (CDR), phase acquisition and forward-error-correction (FEC). Using FEC we demonstrate an error-free 7x622 Mbps uplink of an incoherent SAC-OCDMA PON, while operating at a relatively low power of around -24 dBm. In going to from a back-to-back architecture to a local sources PON configuration the penalty introduced is less than 1 dB. We show that the burst-mode functionality of the receiver enables instantaneous phase acquisition and zero packet loss. However, it introduces a power penalty of around 1dB, which is the price to pay to accommodate bursty traffic and achieve instantaneous phase acquisition using zero bits of preamble.Les réseaux optiques passifs (PONs - "passive optical networks”) sont une solution économique pour la livraison de données à l'utilisateur final. Nous démontrons expérimentalement l'uplink d'un lien CDMA (accès multiples à répartition des codes) et TDMA (accès multiples à répartition dans le temps) PON, avec réception qui supporte un trafic de paquets en rafale ("burst-mode traffic"). Le récepteur peut rétablir rapidement les impulsions d'horloge et les données (CDR "clock-and-data recovery") et effectuer la correction d'erreurs sans voie de retour (FEC - "forward error correction"). En utilisant un FEC, nous démontrons une transmission 'uplink' sans-erreur à 7x622 Mbps d'un lien SAC-OCDMA incohérent PON, opérant à une puissance relativement basse d'environ -24 dBm. D'une configuration jumelée à une configuration de PON, la pénalité de puissance est de moins de 1 décibel. Nous montrons que le récepteur permet l'acquisition de phase de façon instantanée sans perte de paquets donnant une pénalité de puissance d'environ 1 décibel, le prix à payer pour supporter le trafic de paquets en rafale.
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Puig, Serrano Jordi. "Transferència electrònica i mecanisme associat a l'oxidació de composts homo-bimetàl·lics (M= Rh(I), Ir(I)) amb ponts alquiltiolat. Efectes de solvatació." Doctoral thesis, Universitat Autònoma de Barcelona, 2001. http://hdl.handle.net/10803/3124.
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Les reaccions de transferència electrònica engloben bona part dels processos químics i, en conseqüència, presenten un gran interès pel químic molecular. En l'estudi de sistemes bimetàl·lics, especialment en aquells sistemes on els dos centres metàl·lics es troben a distàncies properes però lleugerament majors a la d'enllaç, bona part d'aquest interès es centra en la reactivitat en assistència bimetàl·lica. Donada la naturalesa, fonamentalment electrònica, de la interacció bimetàl·lica, les metodologies de l'electroquímica molecular (Voltametria Cíclica, Coulombimetria i tècniques derivades) són adequades per a realitzar l'estudi químico-físic del procés de transferència electrònica i, en conseqüència, permeten aportar una valuosa informació, tant a nivell cinètic com termodinàmic. L'oxidació monoelectrònica del sistema bimetàl·lic de partida (oxidació centrada fonamentalment en els metalls, inicialment amb estructura electrònica formal d8d8) genera un complex de valència mixta, formalment d8d7. L'estudi electroquímic indica una important deslocalització de valència entre ambdós centres metàl·lics (d7.5d7.5) consistent amb l'anàlisi espectroscòpica. En base a aspectes cinètics i termodinàmics de la transferència electrònica en diferents medis, s'estableix que aquesta manifesta clars efectes de solvatació, ambdós, a nivell estàtic i dinàmic (fricció dielèctrica).
Els efectes de solvatació resulten inductors de la reactivitat del compost de valència mixta electrogenerat envers un procés de reestructuració (isomerització redox intramolecular) resultat de la reducció formal dels centres metàl·lics (recuperant-se l'estructura electrònica formal d8d8 pels centres metàl·lics) i l'oxidació dels lligands ponts connectors. L'estudi estableix que aquesta isomerització redox té lloc en resposta a la solvatació d'una única molècula d'agent solvantant, probablement mitjançant la localització de l'espin en un dels dos centres metàl·lics.
El treball aporta l'estudi cinètic de la dependència de l'equilibri entre els confòrmers syn-endo vs syn-exo amb la solvatació.
Finalment, la detecció d'intermedis (electroquímica i espectroscòpica) i la caracterització estructural del producte final d'evolució permet proposar un mecanisme global i definir així la tendència intrínsica del sistema davant l'oxidació.
Electron transfer reactions play a key rol in many chemical processes and, consequently, are subject of great interest for molecular chemists. In the case of bimetallic systems, specially those contain at short (but higher than the bond) metal-metal distance, the main interest is focused on the so called bimetallic assisted reactivity. Due to the intrinsic nature - mainly electronic - of bimetallic interaction, molecular electrochemistry methodologies (e.g. Cyclic Voltammetry, Coulometry and related) allows to achieve suitable kinetic and thermodynamic data, even to describe the electron transfer particularities .
The initial one-electron oxidation occurs formally centered on the metal atoms. It implies the generation of a mixed valence cation complex, formally d7d8. The electrochemical description indicates an important spin delocalization (d7.5d7.5) among the two centers. Spectroscopical data agree with this interpretation. On the basis of kinetics and thermodynamical data for the electron transfer reaction in different media, solvation effects are described as static. At least in a case an important dynamic (dielectric friction) contribution was also observed.
Solvation effects are inductors on the reactivity of the electrogenerated mixed-valence cation upon an internal estructuration process (intramolecular redox isomerization), yielding to the formal reduction of the metal centers (the formal d8d8 electronic situation is recovered) accompained by the bridging ligands oxidation. Only a molecule of solvating agent causes the redox isomerization, probably by means of the spin localization on mainly one of the metal centers.
This work also include an approach to the solvation dependence on syn-endo vs syn-exo conformational equilibrium, previous to the anodic charge transfer process.
Finally, the intermediates detection (by electrochemical and spectroscopical methods) has been available, in almost the critical cases. Also the fully structure characterization of the final evolution product has been achieved. Thus, the experimental data allows us to propose a detailed mechanism, moreover, to define the general treats of the intrinsic system tende.
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Doutremepuich, Christian. "Etude des heparines de bas poids moleculaire dans un modele de thrombose veineuse experimentale." Paris 7, 1992. http://www.theses.fr/1992PA077052.
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Obtenues par gel-filtration a partir de l'heparine commerciale, les fractions de bas poids moleculaire possedent une activite antithrombotique lorsqu'elles sont administrees dans un modele de thrombose veineuse experimentale. Les fractions de bas poids moleculaire administrees a faible posologie dans ce modele experimental, possedent une activite antithrombotique superieure a celle de l'heparine non fractionnee. Ces fractions amenent un risque hemorragique plus reduit que l'heparine. Le mecanisme de l'activite antithrombotique de ces fractions d'heparine n'est qu'imparfaitement connu: action sur les activites anti-thrombine et anti-facteur dix active via l'anti-thrombine trois, ainsi que sur la fibrinolyse dont elle renforce l'activite; et sur les cellules sanguines. Toutefois, cette activite antithrombotique peut varier selon la methode de preparation utilisee. En conclusion, les fractions d'heparine de bas poids moleculaire possedent une activite experimentale antithrombotique importante et une activite hemorragique reduite que les essais cliniques vont confirmer
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Chen, Qingyuan. "An experimental study of air entrainment in a blade coating system with a pressurised pond applicator." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/5807.
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Pérez-Herreros, Jesús. "Dynamic soil-structure interaction of pile foundations : experimental and numerical study." Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0002.
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La réponse dynamique d’une structure supportée par des fondations profondes constitue un problème complexe d’Interaction Sol-Structure (ISS). Sous chargement sismique, les pieux sont soumis à la sollicitation imposée par le sol (interaction cinématique) et aux forces d’inertie transmises par la superstructure (interaction inertielle). Le dimensionnement des fondations profondes soumises à des sollicitations sismiques est souvent réalisé au moyen de méthodes conservatrices visant à assurer que les fondations ne soient pas endommagées. La plupart de ces méthodes considèrent le comportement de la fondation élastique linéaire et par conséquent la capacité de la fondation à dissiper de l’énergie du fait des mécanismes non-linéaires est négligée. Cette approche était justifiée dans le passé en raison du manque d’informations sur le comportement non-linéaire des fondations et de l’absence d’outils numériques adaptés. De telles limitations deviennent de plus en plus obsolètes, puisqu’un nombre pertinent de résultats expérimentaux et numériques sont maintenant disponibles, ainsi que de nouvelles méthodes de conception (Pecker et al. 2012). Dans cette thèse, le comportement des pieux isolés et des groupes de pieux sous chargement sismique est étudié avec une approche couplant l’expérimental et le numérique. Des essais dynamiques en centrifugeuse sont effectués avec un sol stratifié, plusieurs configurations de fondations et une série de séismes et sollicitations sinusoïdales. Des calculs non-linéaires aux éléments finis sont également effectués et comparés aux résultats expérimentaux afin d’étudier la capacité des modèles numériques à reproduire de manière satisfaisante la réponse non-linéaire des fondations. Un nouveau macroélément pour les groupes de pieux sous chargement sismique est proposé et validé numériquement. Le macroélément permet de prendre en compte les effets de groupe et leur variation avec la fréquence de sollicitation (interaction pieu-sol-pieu) ainsi que la non-linéarité développée dans le système. Le nouveau macroélément est enfin utilisé pour effectuer une analyse dynamique incrémentale (IDA) du pylône centrale d’un pont à haubansThe dynamic response of a structure supported by pile foundations is a complex Soil-Structure Interaction (SSI) problem. Under earthquake loading, the piles are subjected to loadings due to the deformation imposed by the soil (kinematic interaction) and to the inertial forces transmitted by the superstructure (inertial interaction). The design of deep foundations under seismic loadings is often carried out by means of conservative methods that aim to assure zero damage of the foundation. Most of these methods consider the behavior of the foundation as linear elastic. As a result, the capability of the foundation to dissipate energy during seismic loading due to nonlinear mechanisms is neglected. This approach was justified in the past due to the lack of information about the nonlinear behavior of foundations and the absence of adapted numerical tools. Such limitations are becoming more and more obsolete, as a relevant number of experimental and numerical results are now available as well as new design methods (Pecker et al. 2012). In this Ph.D, the behavior of single piles and pile groups under seismic loading is studied using both experiments and finite element calculations. Dynamic centrifuge tests are carried out with a multilayered soil profile, several foundation configurations and a series of earthquakes and sinusoidal base shakings. Nonlinear finite element calculations are also performed and compared to experimental results to investigate the ability of current computational models to satisfactorily reproduce the nonlinear response of foundations. A novel macroelement for pile group foundations under seismic loading is developed and numerically validated. It allows taking into account the group effects and their variation with the loading frequency (pile-soil-pile interaction) as well as the nonlinearity developed in the system. Finally, the macroelement model for pile groups is used to perform an Incremental Dynamic Analysis (IDA) of the main pylon of a cable-stayed bridge
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Olives, Pons Juana Maria [Verfasser], Assumpció [Gutachter] Vila-Mitjà, Raquel [Gutachter] Piqué, Blanco Vigil Pablo Cayetano Gutachter] Noriega, Jordi [Gutachter] Sabater-Mir, and François [Gutachter] [Bertemes. "Social norms as strategy of regulation of reproduction among hunting-fishing-gathering societies : an experimental approach using a multi-agent based simulation system / Juana Maria Olives Pons ; Gutachter: Assumpció Vila-Mitjà, Raquel Piqué, Pablo Cayetano Noriega Blanco Vigil, Jordi Sabater-Mir, François Bertemes." Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2019. http://d-nb.info/1212434838/34.
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Faghiri, Pegah. "La variation de l'ordre des constituants dans le domaine préverbal en persan : approche empirique." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCA161.
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Cette thèse propose une étude quantitative de la variation de l'ordre des constituants en persan avec un intérêt particulier pour l'ordre relatif entre le COD et le COI étant donné son rôle crucial dans les analyses de la structure du SV. Afin de remédier à une lacune empirique dont souffre l’étude de la syntaxe du persan, notre premier objectif est d’évaluer, à partir de données empiriques robustes, l’hypothèse largement admise selon laquelle il existe un ordre relatif canonique dichotomique entre les compléments verbaux, dépendant du marquage différentiel de l'objet (MDO). Notre second objectif, relatif à la linguistique générale et à la typologie, est de contribuer aux débats controversés sur les préférences translinguistiques de l'ordre des mots en étudiant, dans une langue SOV à structure mixte, les effets des facteurs tels que le poids (ou la longueur relative). Les résultats de nos études de corpus et de nos expériences montrent l’inadéquation du critère MDO pour expliquer l’ordre relatif entre le COD et le COI. Cette conclusion nous conduit à réfuter également l’hypothèse de la position syntaxique double de l’objet au profit d’une structure plate pour le SV. De plus, nos données révèlent une préférence « long-avant-court » subordonnée aux facteurs contribuant à la saillance, tels que la définitude, l'animéité et le rôle grammatical. Nous arguons que cette préférence échappe, en partie ou totalement, aux modèles du traitement se fondant sur la distance entre la tête et ses dépendants, alors qu’elle est compatible avec l'hypothèse selon laquelle dans les langues SOV l'accessibilité conceptuelle des constituants longs favorise leur production plus en amont dans la phraseThis thesis proposes a quantitative study of word order variations in Persian, focusing on the relative order between the direct object (DO) and the indirect object (IO). The latter plays a crucial role in the theoretical analyses of the VP, which in the absence of quantitative studies lack solid empirical underpinning. My first goal is to contribute to the study of Persian syntax by providing reliable data in order to evaluate the prevailing hypothesis according to which there exists a dual canonical relative order between the two objects triggered by the Differential Object marking (DOM). My second goal is to contribute to the ongoing debates on word order preferences in general linguistics and typology by bringing in data on an SOV language with mixed head-direction. To this end, I study the effect of factors such as grammatical weight (or relative length), which are claimed to influence the linear order across languages. First, the results of our corpus and experimental studies show that the DOM account of the relative order between the DO and the IO is flawed. Based on this conclusion, I also reject the two object positions hypothesis and plead for a flat structure view of the VP. Second, our data reveal a “long-before-short” preference, which is shown to depend on the effect of salience-enhancing factors such as definiteness, animacy and the grammatical role. I argue that while this preference is, either totally or partially, incompatible with the predictions of processing-oriented dependency-based models, it can be accounted for by production models assuming that the greater conceptual accessibility of longer constituents favors their early position in SOV languages
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Tran, Khanh Le. "Étude de la résistance et de la stabilité des tôles courbes cylindriques en acier : applications aux ouvrages d'art." Phd thesis, Université Paris-Est, 2012. http://pastel.archives-ouvertes.fr/pastel-00808411.
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Les tôles courbes sont de plus en plus fréquemment utilisées dans le domaine des ouvrages d'art à la fois pour raisons esthétiques et pour leurs performances mécaniques. Leur dimensionnement est cependant difficile du fait de l'absence de méthode dédiée dans les normes européennes, en particulier en ce qui concerne le voilement de l'Eurocode 3. Le recours à la modélisation par éléments finis est donc nécessaire mais bien souvent coûteux. La présente étude vise ainsi à développer une méthode simplifiée pour le dimensionnement des panneaux cylindriques soumis à une compression uniaxiale. La méthodologie utilisée est basée sur la démarche générale de l'Eurocode 3 pour tous les types de vérifications de stabilité. L'expression analytique obtenue est en bon accord avec les standards des recommandations de l'Eurocode. Cependant, cette démarche peut être difficile à reproduire dans la pratique quotidienne des ingénieurs face à un nouveau problème tel qu'une combinaison de chargements par exemple. Une méthode alternative basée sur la méthode des plans d'expérience numérique a donc été développée. Basée sur des outils statistiques, l'application de cette méthode permet facilement d'obtenir un résultat avec une bonne précision tout en nécessitant que peu simulations
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Boutoux, Guillaume. "Sections efficaces neutroniques via la méthode de substitution." Phd thesis, Bordeaux 1, 2011. http://tel.archives-ouvertes.fr/tel-00654677.
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Les sections efficaces neutroniques des noyaux de courte durée de vie sont des données cruciales pour la physique fondamentale et appliquée dans des domaines tels que la physique des réacteurs ou l'astrophysique nucléaire. En général, l'extrême radioactivité de ces noyaux ne nous permet pas de procéder à des mesures induites par neutrons. Cependant, il existe une méthode de substitution (" surrogate " dans la littérature) qui permet de déterminer ces sections efficaces neutroniques par l'intermédiaire de réactions de transfert ou de réactions de diffusion inélastique. Son intérêt principal est de pouvoir utiliser des cibles moins radioactives et ainsi d'accéder à des sections efficaces neutroniques qui ne pourraient pas être mesurées directement. La méthode est basée sur l'hypothèse de formation d'un noyau composé et sur le fait que la désexcitation ne dépend essentiellement que de l'énergie d'excitation et du spin et parité de l'état composé peuplé. Toutefois, les distributions de moments angulaires et parités peuplés dans des réactions de transfert et celles induites par neutrons sont susceptibles d'être différentes. Ce travail fait l'état de l'art sur la méthode substitution et sa validité. En général, la méthode de substitution fonctionne très bien pour extraire des sections efficaces de fission. Par contre, la méthode de substitution dédiée à la capture radiative est mise à mal par la comparaison aux réactions induites par neutrons. Nous avons réalisé une expérience afin de déterminer les probabilités de désexcitation gamma du 176Lu et du 173Yb à partir des réactions de substitution 174Yb(3He,p)176Lu* et 174Yb(3He,alpha)173Yb*, respectivement, et nous les avons comparées avec les probabilités de capture radiative correspondantes aux réactions 175Lu(n,gamma) et 172Yb(n,gamma) qui sont bien connues. Cette expérience a permis de comprendre pourquoi, dans le cas de la désexcitation gamma, la méthode de substitution donne des écarts importants par rapport à la réaction neutronique correspondante. Ce travail dans la région de terres rares a permis d'évaluer dans quelle mesure la méthode de substitution peut s'appliquer pour extraire des probabilités de capture dans la région des actinides. Des expériences précédentes sur la fission ont aussi pu être réinterprétées. Ce travail apporte donc un éclairage nouveau sur la méthode de substitution.
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Magnusson, Katarina Anna. "A quantitative and experimental investigation of foodweb dynamics in intermittent freshwater ponds." 2006. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=449856&T=F.
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Hrušková, Lenka. "Fytoplankton experimentálních tůní: kolonizace a sezónní vývoj." Master's thesis, 2010. http://www.nusl.cz/ntk/nusl-296202.
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Artificial ponds are excellent for the study of phytoplankton ecology. They permit repeatable initial conditions and sufficient replication of independent experimental units in complex experiments to test hypotheses about the control of structure and function in natural communities. There were 20 experimental ponds constructed in Kokoř nsko Protected Landscape Area, from which samples were taken and analyzed. This study was part of the EU BIOPOOL. During the first two years after the filling of the ponds the colonization and the seasonal development of phytoplankton communities in the ponds were examined. The phytoplankton species composition was determined, then species richness and relative abundance of individual taxa were quantified. Species composition data were compared with the environmental parameters measured (temperature, oxygen concentration, pH, transparency, conductivity, depth, chlorophyll-a concentration, and zooplankton). In the spring 2007, the ponds were periodic, and followed a similar trend over time (February- April). There were dominated by the following taxonomic groups: Dinophyta, Chrysophyta, Cryptophyta, and Euglenophyta. After installing foil on the bottom of the ponds, the ponds were of permanent character. In terms of environmental parameters, the individual ponds...
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Hnatiuk, Stacy Dawn. "Experimental manipulation of ponds to determine the impact of common carp (Cyprinus carpio L.) in Delta Marsh, Manitoba : effects on water quality, algae, and submersed vegetation." 2006. http://hdl.handle.net/1993/7963.
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Since their introduction to Canada in the late 1800s, common carp (Cyprinus cnlyio L.) have lead to declines in the habitat quality of many aquatic systems. Carp re-suspend sediments, which leads to decreased water clarity, altered water chemistry, and shifts the ecosystem to a phytoplankton-dominated state. I monitored changes in water quality, and abundance of algae and submersed vegetation in Delta Marsh over two years. Ten ponds (1-13 ha) that had varying degrees of exposure to carp were used. Following one year of background characterization in 2001, manipulations were carried out prior to the second year of monitoring in 2002. New channels were created into two previously isolated ponds, while carp were excluded from four others ponds by screens or dikes. Four others remained unmanipulated. The results indicate that carp are contributing to the habitat degradation of Delta Marsh. Phytoplankton abundance, suspended solids, nutrients (P and Si), and turbidity increased with greater densities of young-of-the-year carp and the occurrence of large carp. Excluding large carp lead to a switch from a turbid, phytoplankton-dominated state to a clear, macrophyte-dominated state in peripheral ponds. Recommendations are made for further research and management of carp in Manitoba waters.
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Wu, Chuan-Wei, and 吳傳偉. "Numerical Routing and Experimental Verification of Detention Pond for Different Rainfall Durations." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/57889984810673837742.
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碩士國立中興大學
土木工程學系
90
Abstract Land development is known to cause a large coefficient of surface runoff. When rainfall happens, more floods occur downstream than upstream. A detention pond must be constructed to reduce the peak time and peak discharge by making use of storage volume. This study utilizes detention pond experiments to verify that the numerical routing of continuity equation, and discusses the hydrology characteristics of detention with triangle or trapezoid inflow hydrograph by using a rectangular spillway and an orifice outlet. The results of this study are outlined as follows: 1.The foundation of numerical routing is the hydrology continuity equation (3-3). By using the Runge-Kutta method, we can calculate the governing equations (3-19) ~ (3-22) of triangle and trapezoid inflow hydrology. The verification of detention experiments shows us that the outflow hydrology is close to numerical result no matter what kind of outlet is used. It shows that the continuity equation can accurately simulate the characteristics of a detention pond. 2.In this research, the experience formulas for peak reduction κ are (5-5) and (5-6) with triangle hydrology and formulas (5-8) and (5-9) representing trapezoid hydrograph. In addition, figs.5-16 and 5-30 show the relationship between dimensionless peak lag time Ts and peak outflow Qop/Qip. The value of Ts is less when Qop/Qip is larger under the triangle inflow hydrograph. Under the trapezoid inflow hydrograph, Ts is larger than 0 when the value of Qop/Qip is equal to 1. It means although peak discharge can’t be reduced, peak time can lag. 3.Figures 5-17, 5-20, 5-31, 5-34 show the differences of storage volume between triangle inflow hydrographs and trapezoid inflow hydrographs. The detention of trapezoid hydrograph needs larger storage volumes and less size of an outlet than the triangle hydrograph. In addition, the storage volume for the orifice is less than the spillway; this means the outlet for the rectangular orifice has a better detention effect.