Tesi: "Diel cycle"

1

Currie, Rebecca J. (Rebecca Jean). "Upper and Lower Temperature Tolerances of Three Freshwater Game-Fish Species Exposed to Cycling Temperatures". Thesis, University of North Texas, 1995. https://digital.library.unt.edu/ark:/67531/metadc279105/.

Testo completo

Abstract (sommario):

A total of 670 critical thermal maxima (CTMax) and minima (CTMin) were determined for three freshwater fishes acclimated to three constant temperatures and a diel regimen cycling between the lowest and highest acclimation temperatures. In all species temperature tolerance was directly related to acclimation temperature and slopes relating these variables indicate that acclimation temperature has a greater influence on tolerance of low rather than high temperatures. CTMax and CTMin values generated following exposure to 32 days of oscillating temperatures indicate that in general, fishes had temperature tolerance acclimation states consistent with the average temperature and not either the highest or lowest temperature of the diel cycle.

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Papadopoulou, Sofia. "The influence of diel cycles on the bacterial community composition of two boreal lakes : A case study in Jämtland". Thesis, Uppsala universitet, Limnologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-447209.

Testo completo

Abstract (sommario):

In the Boreal region, the length of day and night varies extremely over the year and organisms are exposed to different diel (24 h) fluctuations of light and temperature. Among them are pelagic populations of bacteria that are ubiquitous in freshwater ecosystems. The structure of prokaryotic assemblages in lakes is regulated by both abiotic and biotic parameters known to have diel patterns; yet, knowledge on changes of the active bacterial community composition (aBCC) over diel cycles is limited, especially at short temporal scales. Here, measurements of physicochemical parameters, nutrient levels and chlorophyll a concentrations, characterization of the carbon pool and 16S rRNA sequencing were used to elucidate the aBCC in a peat bog and the oligotrophic lake Klocka in Jämtland county, Sweden. I show that the activity of bacterioplankton communities remained relatively stable at 6-h intervals and did not follow any diel patterns during an uneven light regime period in June. However, the activity of peat bog communities changed in a cyclic pattern over three diel cycles during an even light period in September, whereas diel changes did not substantially differentiate between sampling periods and among depths in Klocka. The results of the thesis provide valuable insights into the importance of diel cycles in bacterial diversity and community dynamics in lentic habitats.

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Barkdull, Natalie Shepherd. "Impacts of Glacial Meltwater on Geochemistry and Discharge of Alpine Proglacial Streams in the Wind River Range, Wyoming, USA". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8590.

Testo completo

Abstract (sommario):

Shrinking alpine glaciers alter the geochemistry of sensitive mountain streams by exposing reactive freshly-weathered bedrock and releasing decades of atmospherically-deposited trace elements from glacier ice. Changes in the timing and quantity of glacial melt also affect discharge and temperature of alpine streams. To investigate the effects of glacier ice melt on the geochemistry and hydrology of proglacial streams in the arid Intermountain West, we sampled supraglacial meltwaters and proglacial streams in the Dinwoody Creek watershed in the Wind River Range, Wyoming during late summer 2015, when the contributions of glacier meltwater were highest. Supraglacial meltwater was enriched in 8 trace elements (Cd, Co, Cu, MeHg, Mn, Pb, THg, Zn) relative to proglacial meltwaters. Concentrations of major ions (Mg2+, K+, Na+, Ca2+, SO42-) and the remaining 30+ analyzed trace elements were enriched in proglacial streams relative to supraglacial meltwater. To evaluate the diurnal effects of glacial meltwater on the chemistry and hydrology of proglacial streams, we collected hourly water samples of Dinwoody Creek and deployed loggers to monitor water depth, temperature, and specific conductance (SPC) at 15-min intervals over a 1-week period. The influx of glacial meltwater between 10:00 and 20:00 diluted solute concentrations and affected the relative enrichment/depletion of highly soluble elements (major ions, alkaline earth elements), less than REEs. Stable isotopes of H and O (δD, δ18O) in Dinwoody Creek were more depleted during peak runoff (10:00 – 20:00) than base flow, reflecting contributions from isotopically depleted glacial meltwaters. Looping hysteresis patterns were observed between water depth versus DO, pH, temperature and SPC in glaciated streams. Hysteresis patterns were affected by changes in weather and varied depending on the type of stream (glaciated versus non-glaciated) and the distance to glacier toe. Combination of multiple hydrologic tracers (solute concentrations, high frequency logger data, stable isotopes) shows strong potential to improve estimates of glacial meltwater contributions to Dinwoody Creek. Our results suggest that elevated concentrations of heavy metals in glacier ice melt across the Intermountain West may negatively impact sensitive alpine streams.

Gli stili APA, Harvard, Vancouver, ISO e altri

4

Grácio, Ana Rita Pereira. "Diel variation in movement patterns and habitat use by the near-threatened cabrera vole in mediterranean farmland". Master's thesis, Universidade de Évora, 2016. http://hdl.handle.net/10174/18612.

Testo completo

Abstract (sommario):

As variações circadianas no comportamento animal e o seu impacto nas populações constituem desafios importantes em ecologia e conservação. Nesta tese documentam-se as variações circadianas no uso do habitat e padrões de movimento pelo rato de Cabrera, em habitats Mediterrânicos fragmentados. O estudo baseou-se no radio-seguimento de indivíduos em habitats dominados por herbáceas e arbustos. Os resultados indicaram que a proporção de tempo despendido em deslocações, a distância percorrida, e a selecção do tipo de vegetação, estão fortemente interrelacionados, variando consideravelmente ao longo de diferentes períodos do dia. Os ratos movimentaram-se mais frequentemente e maiores distâncias nos períodos diurnos, durante os quais as áreas dominadas por herbáceas foram usadas mais intensivamente. Durante a estação seca houve alguma tendência para a diminuição dos movimentos durante as horas mais quentes. Estes resultados são discutidos no sentido de mostrar como indicadores comportamentais podem contribuir para melhorar a gestão e conservação da espécie; ABSTRACT: Understanding the circadian variations in species behaviour and its impacts on population is a challenging topic in ecology and conservation. This thesis documents the circadian variations in habitat use and movement patterns by Cabrera voles in fragmented Mediterranean farmland. The study was based on radiotracking data of individuals living in habitat patches dominated by wet grasses and shrubs. Results indicated that the proportion of time animals spent moving, the distance moved and the selection strength of vegetation were closely linked behavioural traits, which varied considerably across the 24 hour cycle. Voles moved more frequently and over larger distances during daytime, which was when wet grasses were used more intensively. During the dry season there was some tendency for a decrease in movement activity during the hottest hours of the day. These results are used to discuss how behavioural indicators may be useful to improve conservation management of the species.

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Neves, Leonardo Mitrano. "Estrutura e diversidade das assembleias de peixes recifais na Ba?a da Ilha Grande: import?ncia de vari?veis f?sicas, da estrutura do habitat e varia??es temporais de curto prazo". Universidade Federal Rural do Rio de Janeiro, 2013. https://tede.ufrrj.br/jspui/handle/jspui/2485.

Testo completo

Abstract (sommario):

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2018-10-02T13:28:26Z No. of bitstreams: 1 2013 - Leonardo Mitrano Neves.pdf: 2710150 bytes, checksum: e76a622435676fcc3b2281358ce93865 (MD5)
Made available in DSpace on 2018-10-02T13:28:27Z (GMT). No. of bitstreams: 1 2013 - Leonardo Mitrano Neves.pdf: 2710150 bytes, checksum: e76a622435676fcc3b2281358ce93865 (MD5) Previous issue date: 2013-04-30
Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPQ
Rocky reef fish assemblages change along extreme environmental conditions gradients; both spatial (across gradients of distance from the river mouths) and short term temporal (diel cycle of light intensity). Moreover, changes in connection to habitat heterogeneity can occur, even for tropical rocky reefs with a more homogenous habitat structure. Knowledge of the way that fish assemblages respond to these changes is fundamental to identify the variables that determine spatial patterns and to predict how impacts in great or low intensity can affect diversity. The main aims of this study were: (1) to determine influence of physical (distance from river mouth and wave exposure), biological (benthic cover) and structural (substratum height and number of shelters) variables in structuring fish assemblages, species richness, abundance, biomass and trophic groups diversity; (2) to assess diel changes in composition and structure of fish assemblages; (3) to relate changes in species composition (beta diversity) with habitat heterogeneity for a small scale (among transects in a given area), and the relationship between beta and alfa diversity (species richness, richness estimation and Shannon diversity). Subaquatic visual census were carried out in Ilha Grande coastal reefs, encompassing (1) islands distributed along a spatial gradient of distance from river mouth; (2) six different time periods, i.e., sunrise (06:00h), morning (08:30h), afternoon (14:00h), sunset (17:30h), early night (19:30h) and night (21:00h) in two shallow coastal reef; and (3) in transect in four areas to assess beta biodiversity. Habitat structure (benthic cover and topographic complexity) assessment was performed (objectives 1 and 3). The distance from river mouth explained from 12.4% to 38.2% of the estimated components of variation (ECV) of PERMANOVA for all analyzed response variables, playing a major role in determining spatial patterns of fish assemblages. Differences between reefs close and far from river mouth reached a maximum of 4.5x for richness, 11x for biomass and 10x for abundance. The substrate height was positively related to fish abundance, species richness and trophic groups diversity (ECV between 7.3 % and 17.4%), whereas the number of shelters was positively associated to small-sized species abundance such as Stegastes fuscus, Emblemariopsis signifer and Scartella cristata. Benthic cover had significant influence to determine spatial pattern in fish assemblage structure and diversity of trophic groups (ECV = 8% and 10%, respectively), but not in species richness, biomass and fish abundance. Wave exposure had significant influence on fish assemblage structure only (ECV = 10%). The fish assemblage changes drastically along diel cycle. Species richness and fish abundance were at the highest during the period of the day with intermediary values at twilight periods, and at the lowest during the night. The highest difference in assemblage structure was found between the periods of the day and the night. The families Sciaenidae, mainly represented by Pareques acuminatus, and Pempheridae represented by Pempheris schomburgkii were more abundant during the night, whereas Haemulidae Haemulon steindachneri, Pomacentridae Abudefduf saxatilis, Chaetodondidae Chaetodon striatus, and Labrisomidae Malacoctenus delalandii were more abundant during the day. The twilight periods were similar in assemblage structure, and had as characteristics species of the day (H. steindachneri, M. acutirostris) and the night (P. acuminatus), reflecting a transitional period. Significant positive relationship was detected between habitat heterogeneity and beta diversity. The area with more ix homogeneous habitat and low variation in fish assemblage was dominated by little threedimensionally complex organisms (zoanthids), while areas that had fleshy algae, turf and zoanthids with a more even percentage cover had higher heterogeneity and beta diversity. For all measures of examined alfa diversity, the area with more heterogeneous habitat and with the highest beta diversity had the highest alfa diversity compared with areas with more homogenous habitat e lowest beta diversity. However, positive relationship between alfa and beta diversity was significant for species richness, but not for estimate of richness and Shannon index. This study demonstrated that changes in assemblages in spatial and short term (from transects to 10 km, and diel cycle) scales may be attributed to changes in local habitat structure, both composition of dominant benthic organisms and habitat heterogeneity and can be associated to behavioral characteristics mainly related to strategies of food acquirement and protection against predation
As assembleias de peixes recifais variam atrav?s de gradientes de mudan?as extremas nas condi??es ambientais, tanto espaciais (ao longo de gradientes de dist?ncia da foz de rios) quanto em escalas temporais curtas (ao longo do ciclo di?rio de intensidade luminosa). Al?m disto, varia??es em resposta ao n?vel de heterogeneidade do habitat tamb?m podem ocorrer, mesmo entre recifes rochosos situados fora de intensos gradientes ambientais. Entender como as assembleias de peixes respondem a tais mudan?as ? fundamental para identificar vari?veis determinantes dos padr?es espaciais e predizer como impactos de grande e pequena intensidade podem afetar os padr?es de diversidade. Os principais objetivos deste estudo foram: (1) determinar a influ?ncia de vari?veis f?sicas (dist?ncia da foz do rio e exposi??o a ondas), biol?gicas (cobertura b?ntica) e estruturais (altura do substrato e n?mero de ref?gios) na estrutura??o das assembleias de peixes, riqueza de esp?cies, abund?ncia, biomassa e diversidade dos grupos tr?ficos; (2) avaliar as mudan?as ao longo do ciclo di?rio na composi??o e estrutura da assembleia de peixes recifais; (3) relacionar a varia??o na composi??o de esp?cies (beta diversidade) com a heterogeneidade do habitat, para uma pequena escala (entre transectos de uma mesma ?rea), e as rela??es entre a beta diversidade e medidas de diversidade alfa (riqueza de esp?cies, estimativa da riqueza e diversidade de Shannon). Para tal, censos visuais subaqu?ticos foram realizados (1) em cost?es rochosos da ba?a da Ilha Grande, em ilhas localizadas atrav?s de um gradiente de dist?ncia da foz de rios; (2) em seis diferentes hor?rios, compreendendo o amanhecer (06:00h), manh? (08:30h), tarde (14:00h), anoitecer (17:30h) e in?cio da noite (19:30h) e noite (21:00h) em dois recifes rochosos rasos; e (3) em transectos de quatro ?reas para avaliar diversidade beta. Avalia??es da estrutura do habitat (cobertura b?ntica e complexidade topogr?fica) foram realizadas (para objetivos 1 e 3). A dist?ncia da foz do rio explicou entre 12,4% a 38,2% da estimativa dos componentes de varia??o (ECV) da PERMANOVA de todas as vari?veis respostas analisadas, desempenhando um papel principal nos padr?es espaciais da assembleia de peixes. Diferen?as entre recifes pr?ximos e distantes da foz atingiram um m?ximo de at? 4,5x para a riqueza, 11x para a biomassa e 10x para a abund?ncia. A altura do substrato foi positivamente relacionada com a abund?ncia de peixes, riqueza de esp?cies e diversidade dos grupos tr?ficos (ECV entre 7,3% a 17,4%), enquanto o n?mero de ref?gios foi associado positivamente com a abund?ncia de esp?cies de pequeno porte, como Stegastes fuscus, Emblemariopsis signifer e Scartella cristata. O efeito da cobertura b?ntica foi significativo em determinar os padr?es espaciais da estrutura da assembleia de peixes e da diversidade dos grupos tr?ficos (ECV = 8% e 10%, respectivamente), por?m n?o foram observadas influ?ncias significativas da cobertura b?ntica na riqueza de esp?cies, biomassa e abund?ncia. A exposi??o ?s ondas teve um efeito significativo apenas para a estrutura da assembleia de peixes (ECV = 10%). As assembleias de peixes variaram drasticamente ao longo do ciclo di?rio. A riqueza de esp?cies e a abund?ncia de peixes foram maiores durante os hor?rios do dia, com valores intermedi?rios nos hor?rios crepusculares e atingiram os menores valores durante a noite. Maiores diferen?as na estrutura da assembleia foram observadas entre o per?odo diurno e noturno. Durante a noite, as fam?lias Sciaenidae, representado por Pareques acuminatus, e Pempheridae vii representado por Pempheris schomburgkii foram mais abundantes, enquanto Haemulidae Haemulon steindachneri, Pomacentridae Abudefduf saxatilis, Chaetodondidae Chaetodon striatus, e Labrisomidae Malacoctenus delalandii foram abundantes durante o dia. Os hor?rios crepusculares foram semelhantes entre si, sendo caracterizados por esp?cies tanto dos hor?rios do dia (H. steindachneri, M. acutirostris) quanto da noite (P. acuminatus), refletindo esse per?odo de transi??o. Rela??es positivas significativas foram detectadas entre a heterogeneidade do habitat e a beta diversidade. A ?rea com habitat mais homog?neo e de menor varia??o na composi??o da assembleia foi dominada por organismos tridimensionalmente pouco complexos (zoant?deos), enquanto a ?reas que apresentaram algas frondosas, matriz de algas epil?ticas (MAE) e zoant?deos com uma percentagem de cobertura mais equitativa, tiveram a maior heterogeneidade do habitat e beta diversidade. Para todas as medidas de diversidade alfa utilizadas, a ?rea com habitat mais heterog?neo e com maior beta diversidade, apresentou uma diversidade alfa maior do que a ?rea com habitat mais homog?neo e de menor beta diversidade. Entretanto, as rela??es positivas entre a beta diversidade e a diversidade alfa foram significativas apenas para a riqueza de esp?cies, e n?o para a estimativa da riqueza e a diversidade de Shannon. Este estudo demonstrou que varia??es nas assembleias em escalas espaciais e temporais curtas (desde entre transectos at? 10 km, e ao longo do ciclo di?rio) podem ser atribu?das a mudan?as na estrutura dos habitats locais, tanto na composi??o dos organismos bent?nicos dominantes quanto na heterogeneidade do habitat e podem ser associadas a caracter?sticas comportamentais principalmente associadas a estrat?gias de obten??o de alimento e prote??o contra preda??o

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Giron, Aline Karen Santana. "Variaçãos sazonal e migração vertical da comunidade zooplanctônica (exceto Rotifera) do reservatório de Itupararanga, Votorantim, SP". Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/1528.

Testo completo

Abstract (sommario):

Made available in DSpace on 2016-06-02T19:26:22Z (GMT). No. of bitstreams: 1 GIRON_Aline_Karen_Santana_2013.pdf: 2858732 bytes, checksum: 4ad23866f7e01480263dd620fcc75074 (MD5) Previous issue date: 2013-07-24
The present study aimed to analyse the Itupararanga reservoir zooplankton community in relation to diel and seasonal variation and vertical migration of the organisms in the water column and verify if there are patterns of variation. For this two samples were performed in the reservoir in 2011: in February, rainy period and in july, dry period. The collections were performed in diel cycle (every four hours), in three different layers of the water column (surface, middle and bottom) and in two environments of the reservoir (dam and central body). Stratification in the water column was observed for both environments and both periods. 25 species of the mesozooplankton were identified. Chaoborus larvae were more abundant in February in relation to july and the opposite was observed for cladocerans and copepods. Among the copepods, dominance of juvenile stages (nauplii and copepodites) was observed in both environments and periods. Among the adults of copepods the specie more abundant was Notodiaptomus deitersi (1.298 org.m3) and among the cladocerans was Bosmina freyi (32.282 org.m3). The peak of the total density of the zooplankton community occurred during the dry period in the dam environment with 81.211 org.m3. Chaoborus exercised predation pressure on microcrustaceans during the rainy period. During the dry period, in the absence of Chaoborus in the water column, cladocerans and copepods were more ecologically successful. For all of the groups was observed the usual pattern of vertical migration; reverse migration was not observed. Despite predation pressure, the microcrustaceans not altered their vertical distribution for decrease special overlap with Chaoborus. For all of the groups the migration pattern adopted seems a result of escape from predators and search for good food resources.
O presente estudo teve como objetivo analisar a comunidade zooplanctônica do reservatório de Itupararanga com relação à variação nictemeral, sazonal e migração vertical dos organismos na coluna de água e verificar a existência de padrões de variação. Para isto foram realizadas duas coletas no reservatório no ano de 2011: em fevereiro, período chuvoso e em julho, período seco. As coletas foram realizadas no ciclo nictemeral (de 4 em 4 horas), em três diferentes estratos da coluna de água (superfície, meio e fundo) e em dois pontos do reservatório (barragem e corpo central). Foi observada estratificação na coluna de água para ambos os pontos e em ambos os meses. Foram identificadas 25 espécies do mesozooplâncton. Larvas de Chaoborus spp. foram mais abundantes em fevereiro com relação a julho sendo o contrário observado para Cladocera e Copepoda. Entre os Copepoda observou-se dominância dos estágios juvenis (náuplios e copepoditos) para ambos os pontos e em ambos os períodos. Entre os adultos a espécie de Copepoda mais abundante foi Notodiaptomus deitersi (1.298 org.m3) e entre os Cladocera a espécie mais abundante foi Bosmina freyi (32.282 org.m3). O pico de densidade total da comunidade zooplanctônica ocorreu durante o período seco no ponto da barragem com 81.211 org.m3. Chaoborus exerceu pressão de predação sobre os microcrustáceos durante o período chuvoso. Durante o seco, na ausência de Chaoborus na coluna de água, foi observado maior sucesso ecológico para Cladocera e Copepoda. Para todos os grupos foi observado o padrão comum de migração vertical; migração reversa não foi observada. Apesar da pressão de predação, os microcrustáceos não ajustaram sua distribuição vertical de forma a diminuir a sobreposição espacial com Chaoborus. Para todos os grupos considerados o padrão de migração adotado parece ter sido resultado da fuga de predadores e busca por boas condições alimentares.

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Verspecht, Florence. "Temporal dynamics of the coastal water column". University of Western Australia. School of Environmental Systems Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0097.

Testo completo

Abstract (sommario):

Field measurements and numerical modelling of the shallow coastal waters offshore in south-western Australia were used to describe changes in the water column's vertical structure and the biological response on temporal scales of the order of hours and days. A cycle of chlorophyll a concentration, primary production, and photosystem II function on a diel timescale, which was related to changes in the solar irradiance and thermal structure, was identified. The diel cycle included (1) vertically well-mixed (or weakly linear) conditions in density and chlorophyll a early in the morning, resulting from vertical mixing through penetrative overnight convection; (2) depleted chlorophyll a concentration in the surface layer during the middle of the day due to photoinhibition; (3) an increased chlorophyll a concentration in the bottom layer by late afternoon due to optimum light conditions; and (4) the formation of a chlorophyll a break point (CBP) at the thermocline, which migrated downwards with the deepening surface mixed layer. On a longer timescale (days), moored acoustic instruments were used to derive echo level (EL), which approximated suspended particulate matter (SPM). Wind events ultimately controlled SPM, a conclusion based on (1) elevated EL during high windgenerated turbulence and bed shear stress, (2) positive time-lagged correlations between wind speed and EL at three field sites with different exposures to wave action, and (3) significant negative correlations between wind speed and depth-differentiated echo level (d(EL)/dz) at all sites. Sea breezes produced a similar response in EL through the water column to a small storm event, and wind-driven SPM resuspension resulted in a reduction in the sub-surface light climate (kd). Near-bed dissolved oxygen concentrations varied in accord with elevated wind speeds, EL and kd, highlighting a possible suppression of photosynthesis. One-dimensional modelling revealed that wind stirring was most often the dominant process in these waters. It was found that for a brief period during thermal stratification there was shear production of turbulent instabilities that migrated from the thermocline to the surface and the seabed. Convective cooling was not able to mix the water column entirely overnight without the addition of wind, and minimum wind speeds were determined for this complete vertical mixing. Bottom-generated turbulence was limited to a small region above the bed, and was deemed insignificant compared with mixing generated at the surface. Minimum wind speeds required for de-stratification and prevention of stratification were determined for summer, autumn and winter. A hypothetical desalination outfall was simulated for all seasons and it was concluded that positioning of the discharge at middepth was preferable compared to at the seabed. The results of this thesis advance the current knowledge of coastal biophysical oceanography and provide new insights into the temporal dynamics of the coastal water column of south-western Australia.

Gli stili APA, Harvard, Vancouver, ISO e altri

8

Goebel, Patrick C. "Distribution, Abundance and Movement of Fish among Seagrass and Mangrove Habitats in Biscayne Bay". NSUWorks, 2016. http://nsuworks.nova.edu/occ_stuetd/403.

Testo completo

Abstract (sommario):

Inshore tropical and subtropical estuaries harbor a relatively high abundance and diversity of organisms. Specifically within estuaries, mangrove and seagrass habitats provide shelter and food for a plethora of organisms, through some or all their life histories. Given the biological connection between offshore coral reefs and coastal estuaries, there is a critical need to understand the underlying processes that determine distribution and abundance patterns within mangrove-seagrass habitats. The predatory fish assemblage within the mangrove and seagrass beds of Biscayne Bay, Florida (USA), was examined over 24-hr. time periods along a distance and habitat gradient from the mangrove edge and nearshore environment (0–300 m) to farshore (301–700 m) seagrass beds. This thesis also investigated the occurrence, distribution and timing of reef fish movement between offshore coral reef habitat and inshore seagrass beds over 24-hr periods. Results indicate that fish predators differed over both the sampling period and with distance from mangrove edge. The results also demonstrated reef fishes move into Biscayne Bay at dusk and exit at dawn by utilizing Broad Creek Channel as a passageway. This work supports the idea of diel migration of selected reef fishes to inshore seagrass beds and highlights the importance of connective channels between habitats. The results suggest that the degradation or loss of seagrass habitat could differentially impact the life-history stages of reef fish species.

Gli stili APA, Harvard, Vancouver, ISO e altri

9

Vaughan, Chester Dewey. "Cycle-to-cycle control of reconfigurable die sheet metal forming". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17953.

Testo completo

Abstract (sommario):

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references (leaves 85-86).
This research addresses cycle to cycle control as applied to a sheet metal stretch forming process. More specifically, it attempts to validate the use of cycle to cycle (CtC) control for a multiple input-multiple output process. The work presented in this thesis attempts to answer some basic manufacturing questions. The first is, "Can a multivariable discrete system control theory be used to model a sheet metal shape control process?" The second question is, "Does such a "cycle to cycle control system provide a significant improvement over the present industry standard control methods". To address these questions, CtC control methods are applied to a reconfigurable die stretch forming process. The theoretical foundation of the stretch forming process is presented. Several open and closed loop control methods are discussed. A methodology for evaluating the part quality is defined in terms of the process mean shift and variance. The system dynamics are presented in terms of unwanted process disturbances. In-depth experiments are then performed to quantify the process performance under CtC control. The CtC process yield is compared the process yield of an identical process under open loop control using the Expected Quality Loss Function. It is shown that implementation of the reconfigurable die under CtC control eliminates the process mean shift but increases the part variation. It is also shown that CtC control produces the highest yield of acceptable parts.
by Chester Dewey Vaughan, IV.
S.M.

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Meier, Fabian. "Solar thermochemical cycle for ammonia production based on aluminium-based redox reactions". Zürich : Eidgenössische Technische Hochschule, 2007. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=310.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Zimmerli, Urs. "Limit cycles in homogeneous azeotropic distillation". Zürich : ETH, Eidgenössische Technische Hochschule Zürich, 2001. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=15.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

12

Roberts, Michael John, e edu au jillj@deakin edu au mikewood@deakin edu au wildol@deakin edu au kimg@deakin. "A Modified Life Cycle Inventory of Aluminium Die Casting". Deakin University. School of Engineering and Technology, 2003. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20040825.110759.

Testo completo

Abstract (sommario):

Aluminium die casting is a process used to transform molten aluminium material into automotive gearbox housings, wheels and electronic components, among many other uses. It is used because it is a very efficient method of achieving near net shape with the required mechanical properties. Life Cycle Assessment (LCA) is a technique used to determine the environmental impacts of a product or process. The Life Cycle Inventory (LCI) is the initial phase of an LCA and describes which emissions will occur and which raw materials are used during the life of a product or during a process. This study has improved the LCI technique by adding in manufacturing and other costs to the ISO standardised methods. Although this is not new, the novel application and allocation methods have been developed independently. The improved technique has then been applied to Aluminium High Pressure Die Casting. In applying the improved LCI to this process, the cost in monetary terms and environmental emissions have been determined for a particular component manufactured by this process. A model has been developed in association with an industry partner so this technique can be repeatedly applied and used in the prediction of costs and emissions. This has been tested with two different products. Following this, specialised LCA software modelling of the aluminium high pressure die casting process was conducted. The variations in the process have shown that each particular component will have different costs and emissions and it is not possible to generalise the process by modelling only one component. This study has concentrated on one process within die casting but the techniques developed can be used across any variations in the die casting process.

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Ikeme, Patience Obianuju. "Human ecological stress and menstrual function". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360734.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

14

Adams, Barbara Ann Nieland. "The effect of the human menstrual cycle on kilocalorie and nutrient intake". Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45580.

Testo completo

Abstract (sommario):

Kilocalorie, protein, fat and carbohydrate intakes of five women were examined during the period of at least one menstrual cycle. Kilocalorie intake was significantly lower in the periovulatory phase of the cycle compared to the midluteal phase (t=2.10, p <.05). Carbohydrate and fat intakes were higher, although not significantly, during the midluteal phase compared to the periovulatory phase. Mean intake was 85 kilocalories higher in the postovulatory phase compared to preovulatory, but the difference was not significant. Mean carbohydrate and fat intakes were also increased, but not significantly, in the postovulatory phase. Protein intakes remained relatively stable when phases of the cycle were compared. A spectral analysis of variance produced two cycles showing monophasic sine component variations. Protein intake had a significant monophasic variation in two cycles; fat and carbohydrate had significant monophasic variation in one cycle each. The period of two to four days contained the most often significant sine components (10) and the period of five to seven days was next with five significant values.

Master of Science

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Hischier, Illias. "CO₂ splitting via a solar thermochemical cycle based on Zn/ZnO redox reactions: thermodynamic and kinetic analysis". Zürich : ETH, Swiss Federal Institute of Technology Zurich, Institute of Energy Technology, 2008. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=360.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Sieti, Natalia. "Life cycle environmental and economic sustainability in the baby food sector". Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/life-cycle-environmental-and-economic-sustainability-in-the-baby-food-sector(f098fc2e-6148-443c-b374-16fb506730d3).html.

Testo completo

Abstract (sommario):

This research addresses life cycle environmental and economic sustainability in the baby food sector. In the UK, this sector has been growing rapidly, expanding by around 30% between 2009 and 2014, by which time it was worth an estimated Â£181 million per year. This growth sits within a context of high emissions from the food sector: in 2015, UK net GHG emissions were estimated to be 496 million tonnes (Mt) and the domestic food chain was responsible for 115 Mt CO2 eq. emissions. However, within this overall food chain, very little is known about the sustainability of the baby food sector, with almost no prior literature in the area. The research presented here begins with market research to identify the characteristics of products available in the ready-made food market, in which wet and dry products in jars and pouches dominate sales. Subsequently, 12 representative products are selected from those available on the market and each is assessed in detail to establish its environmental and economic impacts using life cycle assessment (LCA), life cycle costing (LCC) and value added (VA) assessment. The findings of these product-level assessments are then compared to home-made equivalents and finally scaled up according to sales volumes to provide an overall view of the baby food sector as a whole. Wet and dry variants of ready-made porridge products are assessed first as the most commonly consumed breakfast option. The dry product is shown to have 5%-70% the impacts of the wet, on average, and the importance of product formulation is clear: for dry porridge, reformulation could reduce impacts by up to 67%. For the wet porridge, switching from glass jars to plastic pouches is also shown to decrease impacts by up to 89%. Assessment of 11 wet ready-made products demonstrates that the highest impacts are found in spaghetti Bolognese and salmon risotto, and that raw materials are the major hotspot of the life cycle, contributing 12-69%, followed by manufacturing at 2-49%. When combined into a range of weekly diets limited differences are observed between diets, except in cases where dairy-free diets result in compensatory increases in meat consumption. When the aforementioned selection of ready-made products is compared to its home-made equivalent, the home-made options are shown to have lower impacts by 50% to 17 times. This is due to the avoidance of manufacturing and extra packaging stages, as well as shorter supply chains resulting in less waste overall. At the product level, the LCC of ready-made meals ranges from Â£0.08 to Â£0.26 per 125 g product, compared to Â£0.02-Â£0.20 for the home-made equivalents. Value added is, on average, approximately four times higher for ready-made meals than homemade, illustrating the potential profit of the sector. Annually, the ready-made baby food sector has an LCC of Â£40m and carbon footprint of 109 kt CO2 eq. This carbon footprint represents only 0.1% of the UK food and drinks sector. The results of this research show that considerable improvements can be made to the environmental and economic sustainability of baby foods, both ready- and homemade, while home-made options tend to have lower costs and environmental impacts. The outputs provide benchmarking and improvement opportunities for industry and government, as well as insight for consumers.

Gli stili APA, Harvard, Vancouver, ISO e altri

17

McGinnis, Amanda Anne. "Effects of menstrual cycle phases and dietary behavior on threshold and preference for sucrose". Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54379.

Testo completo

Abstract (sommario):

The effects of menstrual cycle (MC) phases (post-menses, premenses, and menses) and dietary behavior (Normal (N), Restrainer (R), and Restrainer/Disinhibitor (RD)) on women's thresholds and preferences for sucrose solutions was investigated. MC phase was determined using both daily temperature readings and days of menses. Dietary group was assigned on the basis of women's responses to the Three Factor Eating Questionnaire (Stunkard and Messick, 1985). Women reported for sensory testing every third day for five weeks following a two-week training phase. Each evening subjects filled out a questionnaire to assess their overall daily fluctuations in total consumption; cravings for sweets; mood (feeling good, happy, and tired); pain (menstrual and other discomfort); metabolic need for energy (hunger, and fatigue); and stress. The results indicated that threshold did not vary due to MC phase (p = 0.9118), dietary behavior (p = 0.4037), or the interaction of these two variables (p = 0.2940). Preference for sucrose fluctuated as a result of MC phase only (p = 0.0441). Of the variables assessed daily, only "other discomfort" (p = 0.0486), "feeling good" (p = 0.0091), and "feeling hungry" (p = 0.0944) correlated with preference for sucrose. However, these correlations did not relate with MC phase clearly, indicating preference is not the manifestation of these theorized causes of MC distress. In general this study does not support the negative mood, or increased metabolic need for energy theory of MC distress. The theory of a decreased pain threshold found some support. The theory implicating dietary behavior in the development of MC distress symptoms was significantly supported. The fact MC phases have been implicated in the perpetuation of eating disorders implies the need for a counseling approach for the women most significantly affected, i.e. the R/D group.
Master of Science

Gli stili APA, Harvard, Vancouver, ISO e altri

18

Tavakoli, Shahab. "Modélisation du cycle thermique des moules de fonderie sous pression". Thesis, Paris 10, 2014. http://www.theses.fr/2014PA100095.

Testo completo

Abstract (sommario):

La réduction de la masse des véhicules, notamment des Groupes Motopropulseurs contribue à la réduction des émissions polluantes. Aujourd’hui afin d’aboutir à cet objectif, la conception de pièces automobiles (Carter Mécanisme, Carter Cylindre) en matériau allégé tel que l’aluminium et ses alliages est en plein essor. Pour la production de grande série, ces alliages sont mis en œuvre par le procédé de fonderie ‘’Aluminium sous pression’’.Ce procédé utilise des moules métalliques. La maîtrise du comportement thermique du moule : chauffage, refroidissement interne (par circuit) et externe, est un point clef pour la qualité et la cadence de production.Dans ce mémoire, le processus industriel est détaillé depuis la fermeture du moule et l’injection du métal liquide jusqu’à l’ouverture du moule et l’extraction de la pièce (carter mécanisme RENAULT). Ensuite, le design détaillé du moule, les différentes générations de circuit de refroidissement et les paramètres de chaque étape de la fabrication utilisés compte tenu du système de refroidissement actuel sont présentés. Le circuit de refroidissement du moule est aujourd’hui positionné dans le moule de façon empirique. Le but ultime de cette thèse est de donner les éléments clés de la conception du circuit de refroidissement d’un point vue thermique. Pour cela, une modélisation complète du phénomène a été réalisée et validée par 8 thermocouples et la position du system de refroidissement a été définie a partir des équations thermiques. Le cycle thermique du moule a été donc optimisé et nous a permis d’abaisser et d’homogénéiser les champs de température à la surface du moule pendant la production en vue d’une augmentation de la productivité, la santé des pièces et la durée de vie du moule
Reducing the weight of vehicles, specially the powertrain Group, contributes to the reduction of the emissions. Today, in order to achieve this objective, the automobile parts conception (Housing gear box, Cylinder block) in lightweight materials such as aluminum and its alloys is increasing. For the mass production, aluminum alloys are formed by a foundry process called ‘’High Pressure Die Casting’’.This process uses the metal molds. Control the thermal behavior of the mold : Heating, intern cooling (by circuit) and extern cooling, is a key point to ensure castings quality and rate of production.In this thesis, the industrial process has been detailed since the mold closing and aluminum melting injection in the die, to the mold opening time and the part (Gearbox RENAULT) ejection. Then, the mold design details, different generation of the cooling systems and the parameters of each step of the manufacturing process taking into account the actual cooling system are presented. The actual cooling systems in the dies are positioned today in empirical way. The ultimate goal of this thesis is to provide the key elements for the cooling system conception from the thermal behavior point of view. For this one, a complete modeling of the phenomena has been realized and validated by 8 thermocouples and the cooling system position has been defined from the thermal equations. The thermal cycle of the die has been optimized and allowed us to reduce and homogenize the temperature fields on the die surface during the production. The rate of production, the castings quality and the lifetime of the die have been consequently increased

Gli stili APA, Harvard, Vancouver, ISO e altri

19

Haussener, Sophia. "Efficiency calculations and optimization analysis of a solar reactor for the high temperature step of the zinc/zinc-oxide thermochemical redox cycle". Zürich : ETH, Eidgenössische Technische Hochschule Zürich, Departement Maschinenbau und Verfahrenstechnik, 2007. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=331.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Matasci, Cecilia. "Life cycle assessment of 21 buildings: analysis of the different life phases and highlighting of the main causes of their impact on the environment". Zürich : ETH, Eidgenössische Technische Hochschule Zürich, 2008. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=381.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Powell, Thomas William Robert. "Closing loops to rebalance the global carbon cycle : biomass flows modelling of global agricultural carbon fluxes". Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/18699.

Testo completo

Abstract (sommario):

Since the beginning of farming, and even before, humans have been actively modifying our environment in order to harvest biomass. With the ‘Great Acceleration’ of the industrial age, the global system of biomass harvest for food production has become a major driver of Earth system processes, and caused multi-dimensional sustainability issues which must be addressed in order to meet continued increases in demand for food and other biomass. In addition, bioenergy generation, with the subsequent storage of some or all of the carbon content of the feedstock (known as bioenergy with carbon storage or BECS), is now seen as an important tool for rebalancing the carbon cycle. This thesis has used a biomass flows modelling approach to examine possible trajectories for the socio-ecological metabolism of humanity, with a focus on fluxes of carbon contained in biomass. This approach connects social and economic drivers of biomass harvest with physical Earth systems processes such as the global carbon cycle. Meeting growing food demand in the years 2000-2050 is likely to be a significant challenge in its own right, necessitating the harvest of over 30% of terrestrial biomass. This can only be done without significant damage to natural ecosystems if large increases in efficiency and intensity of food production are achieved, or diets are altered. The production of livestock products is shown to be a major cause of inefficiency in biomass harvest, and changes to livestock demand or production are particularly powerful in ensuring a less damaging relationship with Earth system processes. If increases in efficiency are achieved, it may be possible to grow dedicated bioenergy crops, which, combined with the biomass available in waste and residue streams can be used to generate significant carbon dioxide removal (CDR) fluxes via BECS. Following this strategy it is possible to have a non-trivial effect on atmospheric CO2 concentration by 2050. Increasing the intensity of biomass harvest, particularly when low intensity pasture is replaced with intense bioenergy cropping, also has significant implications for ecological energy flows, and the potential trade-off between protecting biodiversity and growing bioenergy crops to mitigate climate change is also discussed. This body of work presents several interesting areas of potential conflict in different drivers of biomass harvest, and suggestions are made for ways in which to develop the approach in order to explore them.

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Hock, Florian. "Point-in-time vs. through-the-cycle : Berücksichtigung zyklischer Effekte in der Kreditrisikosteuerung". Hamburg Diplomica Verlag, 2008. http://www.wiso-net.de/r%5Febook/webcgi?START=A60&DOKV%5FDB=DIPL,ADIP&DOKV%5FNO=978383660749068&DOKV%5FHS=0&PP=1.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Jarvis, Toby. "The vertical export of carbon and nitrogen caused by zooplankton diel vertical migration". Thesis, Open University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272958.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Wang, Bin. "The prediction of low cycle fatigue for die casting with FEM". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57753.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Mallek, Hichem. "Les réseaux biodégradables autocicatrisants utilisant des monomères biosourcés par réactions de Diels-Alder". Thesis, Saint-Etienne, 2013. http://www.theses.fr/2013STET4019.

Testo completo

Abstract (sommario):

Ce mémoire de thèse a pour objectif l'élaboration de réseaux élastomères thermoreversibles. Ces réseaux à base de polycaprolactone (PCL), dont la plupart des constituants sont issus de la biomasse, auront la particularité d'être recyclables et biodégradables
The aim of this thesis is to elaboration of the thermoreversible elastomers networks. These polycaprolactone-based networks (PCL-based networks), most of which of the constituents from biomass, will have the particularity of being recyclable and biodegradable

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Gostner, Walter. "Integrale Analyse eines murfähigen Wildbaches anhand einer Fallstudie Integral analysis of a debris flow in an alpine torrent based on a case study : Schlussbericht, Cycle d'études postgrade en aménagements hydrauliques 1999 - 2002 /". Zürich : ETH, Eidgenössische Technische Hochschule Zürich, Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie (VAW), 2002. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=78.

Testo completo

Abstract (sommario):

Nachdiplomarbeit École polytechnique fédérale de Lausanne, 2002.
Text dt., ital. und engl. Zus.fassung. Abschlussarbeit zum Nachdiplomstudium in hydraulischen Anlagen an der EPFL (École polytechnique fédérale de Lausanne). Die Betreuung der Arbeit ist an der Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie (VAW) der ETH Zürich erfolgt.

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Krause, Marcus. "Environmental Life Cycle Costing (ELCC) für Produkte der Solarenergie: Die Verbindung von Life Cycle Assessment (LCA) und Life Cycle Costing (LCC) - from Cradle to Grave - angewandt auf die Photovoltaik. Anforderungen bei der Durchführung und aktueller Stand in der Praxis". Technische Universität Dresden, 2011. https://tud.qucosa.de/id/qucosa%3A26141.

Testo completo

Abstract (sommario):

Vor dem Hintergrund der zukünftigen Notwendigkeit einer nachhaltigen Energieversorgung beschäftigt sich die vorliegende Arbeit mit Technologien der regenerativen Energiequelle Solarenergie, insbesondere Photovoltaik (PV). Systeme zur Nutzung der unerschöpflich verfügbaren, sauberen und im Prinzip “frei Haus” gelieferten Energie der Sonne können eine bedeutsame Rolle in einer umweltverträglicheren Zukunft spielen. Allerdings ist die Herstellung der erforderlichen Komponenten heute i.d.R. noch energie- und kostenintensiv, weshalb für eine korrekte Bewertung dieser Technologien der gesamte Lebenszyklus betrachtet werden muss. Zur tieferen Analyse der PV wird die Methodik des Environmental Life Cycle Costing (ELCC) auf der Grundlage von drei Grundideen eingeführt. Konkret sind dies die Ausgangspunkte: Nachhaltigkeit, Lebenszyklusdenken und die Drei-Dimensionalität dieses Instrumentes durch die gemeinsame Betrachtung ökologischer, ökonomischer und technischer Aspekte in ihrem Zusammenspiel. Ausgehend von theoretischen Elementen der Ökobilanzierung (Life Cycle Assessment) und des Life Cycle Costings, verbunden mit den technischen Eigenschaften der Photovoltaik werden wichtigste Anforderungen und Schritte für die Durchführung eines ELCC für PV beschrieben. Mittels einer softwaregestützten Inhaltsanalyse wird im Anschluss der definierte Rahmen für ein ELCC für PV getestet (und modifiziert) gegen eine Auswahl von 135 bereits existierender Studien, die sich mit dem Lebenszyklus von PV-Technologien aus ökologischer und ökonomischer Sicht beschäftigen. Im Ergebnis hieraus können die wichtigsten Elemente eines ELCC für PV, wie beispielsweise ökologische Wirkungskategorien oder ökonomische Indikatoren, identifiziert werden (methodisches Feedback). In einem nächsten Schritt werden die Studien hinsichtlich ihrer “Qualität” bezogen auf ökologische, ökonomische und übergreifende Inhalte eines ELCC für PV bewertet. Auf diese Weise kann ein Inventar von Lebenszyklusanalysen für PV erstellt werden, das nach den Technologien und der inhaltlichen Qualität bezüglich eines ELCC strukturiert ist und für weitere Analysen als Grundlage dienen kann. Aus den bisherigen Ergebissen kann eine erste Einschätzung zum aktuellen Stand des ELCC für PV in der Literatur vorgenommen werden: Es existiert bereits ein großer Pool von Studien, die sich mit dem Lebenszyklus der PV beschäftigen. Mit Blick auf die Anforderungen eines ELCC für PV besteht jedoch Nachholbedarf in der Verbindung und gemeinsamen Betrachtung von hot spots und trade offs aus ökologischer und ökonomischer Perspektive. Der definierte theoretische Rahmen für ein ELCC für PV, die kodierten Studien sowie das erstellte Inventar von Lebenszyklusanalysen der PV können nun als Grundlage für weitere Analysen dienen. Insbesondere eine inhaltliche Auswertung der konkreten Ergebnisse von Studien kann so einen Benchmark und Orientierung für neue Lebenszyklusanalysen für PV-Technologien liefern.
The special need of a sustainable energy supply in mind the technologies of the renewable source solar energy, especially photovoltaics (PV) is main subject of the present thesis. Using the inexhaustible, clean and “freely delievered” power from the sun solar devices may play a major role in a cleaner future, but, on the other hand, they are still energy consuming and expensive in their production which consequently demands a whole life cycle perspective when assessing this technology. For a closer look at PV the methodology of Environmental Life Cycle Costing (ELCC) is introduced by following three theoretical points of view. Namely these are sustainability, life cycle thinking and the three dimensional nature of this tool by regarding environmental, economic and technical aspects in their interaction. Based on theoretical elements of Life Cycle Assessment and Life Cycle Costing in combination with the technical background of photovoltaics main requirements and steps for performing an ELCC for PV are described. By executing software based content analysis the defined framework is checked (and modified) against a choice of 135 existing studies analyzing the life cycle of PV technologies from an environmental or economic perspective. As a result the main elements of an ELCC for PV, e.g. environmental impact categories and economic indicators, are identified (methodological feedback). Within the next step the existing studies are rated by their “quality” regarding the environmental, economic and more general parts of an ELCC for PV in order to create an inventory of life cycle studies for PV. This inventory is structured by technologies as well as quality of content respecting ELCC and might be used for further analyses. At this stage the results propose the possibility of a first estimate of the present status of ELCC for PV: until now there is a good pool of existing analyses of the life cycle of PV systems. But from an ELCC perspective the examination of common hot spots and trade offs between economic and environmental aspects should be expanded. The theoretical framework of ELCC for PV, the encoded studies and the inventory of life cycle analyses for PV are now the starting point for further analyses, especially of the individual outcome within studies, which will then pose a benchmark for new life cycle studies of PV technology.

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Michel, Servane. "Fortune, Providence et liberté : une lecture augustinienne du cycle arthurien en prose". Thesis, Paris 4, 2014. http://www.theses.fr/2014PA040026.

Testo completo

Abstract (sommario):

L'histoire arthurienne, dans le cycle en prose, s'étend de manière linéaire et eschatologique depuis les temps évangéliques jusqu'à la fin du royaume d'Arthur. En reliant ainsi les temps contemporains à ceux de l'Histoire sainte – notamment grâce au motif du Graal – le roman revendique une autorité prophétique qui peut être interprétée à la lumière de La Cité de Dieu : Augustin y mène une lecture exégétique tant des Écritures saintes que de l'histoire profane, cherchant à manifester le dessein salvifique de la Providence. Et c'est bien sur la question du salut que se clôt le cycle puisque, après la chute d'Arthur et la destruction de la chevalerie, le dernier mot du roman revient à la conversion : le salut final de Lancelot fait suite à celui de Gauvain. Le sort ultime des deux plus grands héros de la chevalerie invite à lire La Mort Artu comme une apocalypse non seulement au sens de châtiment – celui du monde arthurien, condamné dans La Queste comme trop terrien – mais aussi comme une révélation : l'héroïsme profane rejoint l'objet ultime du désir chrétien. La présence de Fortune peut être considérée en ce sens : le dernier roman du cycle lui confie le soin d'exprimer le scandale du malheur et en fait un autre relais, avec l'aventure ou la mescheance, du langage de la foi. C'est certes trahir l'héritage d'Augustin, qui bannissait de toute bouche chrétienne Fortune et ses avatars, pour incompatibilité avec la foi dans la Providence. Mais cette même foi est en réalité affirmée dans un langage proprement romanesque, qui assume ainsi le tragique de l'existence humaine – pour le transformer dans le sursaut ultime de la foi ou le laisser au seul horizon de la cité terrestre
Arthurian history is eschatological : the prose cycle drive it from evangelical times to the end of king Arthur's reign. With the Grail theme, narratives links their contemporary world straight to Sacred History and claims for a kind of prophetical authority. This scheme may be interpreted according to The City of God, where Augustine reads both Scripture and profane history. Through his exegesis he intends to show the action of providence and the process of salvation in human history. The prose romances themselves end in salvation : after King Arthur's fall and the destruction of chivalry, the last word is given to conversion – Lancelot's soul is taken to Paradise, after Gawain's one. For those excellent knights La Mort Artu should be read as an apocalypse, not only in the sense of punishment – La Queste had condemned the Arthurian world as « terrien » – but also as a "revelation" : profane heroism is identified to the highest Christian desire. The well-known presence of Fortune in La Mort Artu takes another sense : in personal or collective calamities, this character points out either the moral scandal or the irrational aspect of their causes. With Fortune, aventure and mescheance also relay Christian language to narrate the unexplainable. Prose romances betray Augustine's precepts : The City of God forbade the use of Fortune or similar terms that contradict the Christian faith. But in Arthurian romances providentialism is nonetheless present and proclaimed. In that "Age of Faith", the proper language of romance expresses the tragical aspects of human existence, and either lead to an eternal destiny, in the act of faith, or stay in the horizon of the terrestrial city

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Janoco, Martin. "Evaluating the sustainability of vegetarian, vegan, and New Nordic diets in Sweden : Combining environmental and nutritional aspects". Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-260278.

Testo completo

Abstract (sommario):

Changing the western dietary pattern toward a healthier diet with reduced intake of animal foods is a commonly recognized strategy in the ongoing effort for global sustainability. Since animal foods tend to have a high environmental impact, vegetarian diets are often suggested as an ecological alternative to the typical Western diet. The low sum of environmental impacts, however, does not on its own necessarily translate to a sustainable diet. Sustainability encompasses many other aspects, such as nutritional adequacy, affordability, and cultural acceptability. As regards the elimination of animal foods in particular, health-related aspects ought to be considered since some nutrients are supplied primarily via animal products which may lead to nutritional deficiencies and potential negative health effects in the long term. Furthermore, since the main function of diets is the supply of (adequate) nutrition, the environmental impacts of diets ought to be compared in light of their nutritional quality. In this project the environmental impact on climate change, land use, blue water footprint, and biodiversity damage potential of four diets is assessed, along with their nutritional adequacy and financial cost. The four assessed diets are: an average Swedish diet, New Nordic diet, vegetarian diet, and vegan diet. The environmental impacts are normalized with a nutritient-rich diet score (NRD) to compare the impacts of diets in relation to their nutritional quality. The vegan diet, followed by the vegetarian diet, resulted in the lowest overall impact with the exception of blue water footprint, however, the normalization with NRD score lessened the relative differences between the New Nordic, vegetarian, and vegan diet. Furthermore, the nutritional assessment showed a potentially unsustainable intake of vitamin D in vegetarians and vit. D and B12 in vegans, which is not properly reflected in the nutritional quality score. Nevertheless, the use of the nutritional score is fairly simple and provides opportunity for linking the health-related aspect of diets to their environmental impact. Joined with indicators on other sustainability aspects, such as the economic, this method can offer a more holistic picture of the sustainability of diets.
Att ändra det västerländska kostmönstret mot en hälsosammare diet med minskat intag av animaliska livsmedel är en allmänt erkänd strategi i den pågående ansträngningen för global hållbarhet. Eftersom djurfoder tenderar att ha stor miljöpåverkan, är vegetariska dieter ofta föreslagna som ett ekologiskt alternativ till den typiska västerländska kosten. Den låga summan av miljöpåverkan innebär emellertid inte nödvändigtvis att det är en hållbar diet. Hållbarhet omfattar många andra aspekter, såsom näringskrav, överkomlighet och kulturell acceptans. När det gäller avskaffandet av animaliska livsmedel bör i synnerhet hälsorelaterade aspekter beaktas eftersom vissa näringsämnen levereras primärt via animaliska produkter vilket kan leda till näringsbrist och potentiellt negativa hälsoeffekter på lång sikt. Eftersom dietens huvudsakliga funktion är tillförseln av (tillräcklig) näring, borde miljöpåverkan av dieter jämföras med hänsyn till deras näringskvalitet. I detta projekt bedöms miljöpåverkan med avseende på klimatförändringar, markanvändning, blått blåvattenavtryck och biologisk mångfaldskador för fyra dieter tillsammans med deras näringsbehov och ekonomiska kostnader. De fyra bedömda kostvanorna är: en genomsnittlig svensk diet, ny nordisk kost, vegetarisk kost och vegansk kost. Miljöpåverkan normaliseras med ett näringsrikt diettvärde (NRD) för att jämföra effekterna av dieter i förhållande till deras näringskvalitet. Vegansk diet, följt av vegetarisk kost, resulterade i den lägsta övergripande effekten, med undantag för blå vattenavtryck, men normaliseringen med NRD-poäng minskade de relativa skillnaderna mellan den nya nordiska, vegetariska och veganska dieterna. Vidare visade näringsvärderingen ett potentiellt ohållbart intag av vitamin D för vegetarianer och vit. D och B12 för veganer, vilket inte korrekt återspeglas I det näringsmässiga kvalitetsresultatet. Ändå är användningen av näringsvärdet ganska enkelt och ger möjlighet att koppla den hälsorelaterade aspekten av dieter till deras miljöpåverkan. Genom att kombinera indikatorer för andra hållbarhetsaspekter, såsom den ekonomiska, kan denna metod erbjuda en mer holistisk bild av dieters hållbarhet.

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Brisse, Julien. "Valorisation de la lignine par incorporation dans les polyesters aliphatiques". Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS504.pdf.

Testo completo

Abstract (sommario):

Ce travail a été consacré à la synthèse et à la caractérisation de copolyesters dérivés d’une lignine organosolve. Après purification, la lignine a été modifiée chimiquement par estérification ou éthérification de ses fonctions réactives. Les échantillons résultants présentent des fonctions réactives plus homogènes, majoritairement constituées d’alcools aliphatiques, et une solubilité dans les solvants organiques usuels améliorée. Leurs fonctions hydroxy aliphatiques ont ensuite été utilisées pour amorcer la polymérisation par ouverture de cycle de l’ε-caprolactone conduisant à des systèmes partiellement gélifiés suite à des réactions secondaires d’estérification, de transestérification et d’éthérification. Pour contourner ce problème, les fonctions hydroxy de la lignine ont été utilisées comme points de greffage d’oligomères de poly(ε-caprolactone) (PCL) monofonctionnels à extrémité chlorure d’acide (COCl) à partir d’un rapport COCl/OH variant de 0,25 à 0,70. Les synthèses ont abouti à des copolyesters thermoplastiques (Mn = 7000 à 12300 g/mol) incorporant jusqu’à 60% de lignine dans leur structure. Ceux-ci sont solubles dans les solvants courants et leur stabilité thermique est améliorée comparée à celle des réactifs initiaux. En s’inspirant de cette méthode de greffage, un oligomère de PCL difonctionnel à extrémités COCl incorporant deux adduits de Diels-Alder de type maléimide/furane par macromolécule a été greffé à la lignine. Le matériau résultant est réticulé et devient soluble dans le DMSO à 120°C suite à la dissociation des adduits par réaction de rétro Diels-Alder. L’ensemble des produits synthétisés a été caractérisé par des techniques analytiques adaptées (RMN, SEC, TGA, DSC, FTIR)
This work was devoted to the synthesis and the characterization of copolyesters derived from an organosolv wheat straw lignin extracted using the CIMV pulping process. A basic hydrolysis step followed by organic washes yielded a purified lignin that was then chemically modified by esterification or etherification of its reactive functions using triethylene glycol, chlorinated methoxyalkanes, haloalcohols or 1-bromotetradecane. The resulting samples exhibit homogeneous reactive functions, mainly composed with aliphatic alcohols. Their solubility within usual organic solvents is improved, especially using bromoalcane. Their aliphatic hydroxy functions were then used to initiate the ring opening polymerization of ε-caprolactone, in bulk or in solution, between 25 et 150°C, using stannous(II) ethylhexanoate or 1,5,7-triazabicyclo[4.4.0]dec-5-ene as a catalyst. This led to partially cross-linked systems due to side reactions of esterification, transesterification and etherification. To get around this problem, monofunctional poly(ε-caprolactone) (PCL) oligomers bearing an acyl chloride (COCl) end group was grafted onto triethylene glycol-modified lignin (Lp-TEG) with a COCl/OH ratio from 0.25 to 0.70. This led to thermoplastic copolyesters (Mn = 7000 to 12300 g/mol) incorporating up to 60% of lignin in their structure. Those ones are soluble within common solvents and show upgraded thermal stability compared to the starting materials. Adapted from this method, a difonctional PCL oligomer bearing COCl end groups and two Diels-Alder adducts per macromolecule was then grafted onto Lp-TEG. This led to a lignin based innovative 3D PCL network which is soluble in DMSO at 120°C after retro Diels-Alder reaction. All of the synthesized products were characterized by suitable analytical techniques (NMR, SEC, TGA, DSC, FTIR)

Gli stili APA, Harvard, Vancouver, ISO e altri

31

Miles, Lana. "Die toepassing van projekbestuursbeginsels in die proses van plaasarbeiderbemagtiging / L. Miles". Thesis, North-West University, 2004. http://hdl.handle.net/10394/482.

Testo completo

Abstract (sommario):

There are more or less 900 000 farm workers in South Africa. Among these approximately 600 000 are permanently employed, while the rest are seasonal workers. It is estimated that six to seven million people are currently living on farms, which implies that up to seven people are dependent on the wages of a single farm worker. In order to improve the situation of farm workers, the Department of Labour implemented the minimum wage system for farm workers on 1 March 2003. The argument is posed, however, that many farm workers would lose their jobs because of the sectoral stipulations. Unemployment has far-reaching consequences. Farm workers who have lived on farms before, have to resettle and adapt to new social structures, such as community structures and new codes of conduct. In order to adapt to social change, it is argued that training agencies could use project management as a suitable management tool to launch empowering interventions. The analysis of the social conditions in which farm workers find themselves ought to be undertaken on the basis of a specific theory on changes. From this perspective certain theories of social change have been identified. Empowerment is discussed as a process of change. This means an increase in influence and control by acquiring knowledge and skills by means of the necessary training. While theorists on conflict view conflict as the main driving force in change, empowerment is considered to be the process by means of which change can be managed effectively. For the rest the principles of project management are discussed to show that the project cycle is based on project management principles. If project management principles and the project cycle are applied as yardsticks during an empowerment project, the chances of being successful will be much better than when launching an unstructured and unplanned project. The most important conclusion to be made from this research is that the management of change by means of empowerment projects is of decisive importance to unemployed farm workers. Empowerment projects for unemployed farm workers are the first steps in the direction of effective management of social change and sustainable development in South Africa.
Thesis (M. Ontwikkeling en Bestuur)--North-West University, Potchefstroom Campus, 2005.

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Dudic, Dalibor [Verfasser]. "Modell für die Fabrik-Life-Cycle-orientierte Produktplanung und -entwicklung / vorgelegt von Dalibor Dudic". Heimsheim : Jost-Jetter, 2010. http://d-nb.info/1010696564/34.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Stinson-Bagby, Kelly Lucile. "Microstructural Evolution in Thermally Cycled Large-Area Lead and Lead-Free Solder Joints". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34573.

Testo completo

Abstract (sommario):

Currently, there are two major driving forces for considering alternative materials to lead- based products, specifically interconnections, in electronics applications, including the impending legislation or regulations which may tax, restrict, or eliminate the use of lead and the trend toward advanced interconnection technology, which may challenge the limits of present soldering technology. The reliability of solder joints is a concern because fracture failures in solder joints accounts for 70% of failures in electronic components. Lead-free solders are being investigated as replacements for lead solders currently used in electronics. Thermo-mechanical properties describe the stresses accumulated due to thermal fatigue as a result of CTE mismatch within the system. By understanding the failure mechanisms related to lead-free solders, the application of lead- free solders could be more strategically designed for specific applications. The objective of this thesis is to observe microstructural change in large-area solder joints caused by thermal cycling and relate these changes to reliability issues in large-area lead and lead-free solder constructed semiconductor power devices. This study focused on the microstructural changes within the solder alloy of a large-area solder joint under thermal cycling conditions. Two major primary observations were made from this research, they are: 1) due to a combination of testing conditions and material properties, the lead-free solders, Sn/3.5Ag and Sn/Ag/0.7Cu, sustained the most severe damage as compared to Sn/37Pb, and 2) due to elevated stresses at the solder/substrate interface in a simulated power semiconductor device sample damage was found to be most severe.
Master of Science

Gli stili APA, Harvard, Vancouver, ISO e altri

34

Schneider, Arne. "Die strategische Planung des Produktportfolios bei Automobilherstellern : Konzeption eines Instruments zur Bewertung des Cycle-Plans /". Baden-Baden : Nomos, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015410314&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Trautheim, Andreas. "Digitale Transformation zurück in die Zukunft [Präsentationsfolien]". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-214129.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

36

Leite, Pedro Terra. "História natural de Mastigodryas bifossatus (Serpentes, Colubridae) em domínio subtropical no Brasil". Universidade Federal de Santa Maria, 2006. http://repositorio.ufsm.br/handle/1/5249.

Testo completo

Abstract (sommario):

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Mastigodryas bifossatus is a large snake in the Colubrinae subfamily. It s widely distributed in open areas over the entire South America. The dissection of 224 especimens of this snake, proceeding from the southern states of Rio Grande do Sul, Santa Catarina and Paraná, stored in herpetological colections in Brazil, provides information on dietary habits, habitat use, daily and seazonal activities, sexual dimorphism and reproductive cycles of this snake in subtropical domains in Brazil. This snake eats mainly amphibians of the Leptodactylidae´s family (80%), mammals (10%) and lizards (2%). Eight percent of the items found could not be identified. There is no ontogenetic diet shift in M. bifossatus, but as the snake grows larger, the range of preys grow as well. Most specimens inhabit open areas during the day. The activity patterns are seazonal and unimodal. Adult specimens of M. bifossatus can reach average of 1115 mm in snout-vent-lenght, and female snakes are slightly bigger than male snakes. The reproductive cycle of females is seazonal, with vittelogenesis occuring from july on. Egg laying has been recorded from november to january. The average number of offsprings per clutch is 14 and there is positive correlation between clutch size and female lenght.
Mastigodryas bifossatus é uma serpente de grande porte pertencente à subfamília Colubrinae, família Colubridae. É distribuída ao longo de grande parte da América do Sul, onde vive em áreas abertas. A dissecação de 224 espécimes desta serpente provenientes dos estados do Rio Grande do Sul, Santa Cataria e Paraná, depositados em coleções herpetológicas no Brasil, proveram dados sobre hábitos alimentares, uso do substrato, atividade diária e sazonal, dimorfismo sexual, comprimento corporal e ciclo reprodutivo desta serpente em domínio subtropical no Brasil. Esta espécie alimenta-se preferencialmente de anfíbios da família Leptodactylidae (80%), seguido de mamíferos (10%) e lagartos (2%). Não há mudança ontogenética na dieta de M. bifossatus, mas há um aumento na gama de presas à medida que esta serpente atinge comprimentos corporais maiores. É uma serpente diurna que habita áreas abertas. A atividade é sazonal, com padrão unimodal. Os exemplares adultos de M. bifossatus atingem em média 1115 mm de comprimento rostro - cloacal, sendo as fêmeas um pouco maiores que os machos. O ciclo reprodutivo das fêmeas é sazonal, com vitelogênese ocorrendo a partir do mês de julho. Oviposições foram registradas de novembro a janeiro. O número médio de filhotes por ninhada é 14 e há correlação positiva entre o tamanho da ninhada e o comprimento das fêmeas.

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Xu, Zhanjie. "Nouvelle synthèse de dérivés hétérocycliques thiazoliques, sélénazoliques, coumariniques, thiocoumariniques et quinolonéiques. Étude et évaluation de leur activité potentielle anticancéreuse". Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0079/document.

Testo completo

Abstract (sommario):

Nous avons réalisé la synthèse de thiazoles, sélénazoles, thiéno[2,3-d]thiazoles et thiéno[2,3-d][1,3]sélénazoles, ce dernier étant préparé facilement à partir de cyanamide et de sulfure de carbone. Nous avons de cette manière pu synthétiser des 4-amino-1,3-thiazoles et 1,3-sélénazoles substitués en position 2 et 5 en deux étapes. Appliqué ces hétérocycles, les 4-halogéno-1,3-thiazoles et 1,3-sélénazoles ont été synthétisés par la méthode de Doyle. La labilité des halogènes dans les dérivés précédents a permis de préparer de nouveaux thiéno[2,3-d]thiazoles et [1,3]sélénazoles. La détermination du potentiel antiprolifératif de ces composés a permis de mettre en évidence deux composés, présentant des IC50 de l’ordre du micromolaire sur les lignées cellulaires cancéreuses : MCF-7, PC-3, Hs683, U373, SKMEL-28 et A549. Un composé surtout a montré une activité d’inhibition de Na+/K+-ATPase et de l'oncogène Ras. Par ailleurs dans un second sujet, nous nous sommes intéressés à la mise au point d’une synthèse des deux isomères (alpha et bêta) de 4-butoxylvinyl-coumarines, -thiocoumarine et -2-quinolones par couplage de Heck. Nous avons ainsi pu montrer que suivant le substituant présent en position 4 des hétérocycles le couplage était régiosélectif. Ces dérivés butoxyvinyliques se caractérisaient par leur caractère diénique et nous avons étudié leur réactivité, stéréoséléctivité et régiosélectivité avec différents diénophiles dans des réactions de cycloaddition de Diels-Alder. Parmi tous les composés polyhétérocycliques ainsi préparés, nous avons identifié des composés tétracycliques à noyau quinonique qui présentent un potentiel anticancéreux par des valeurs d’IC50 sur l’inhibition des phosphatases CDC25 et sur plusieurs lignées de cellules tumorales
We performed the synthesis of thiazoles, selenazoles, thieno[2,3-d]thiazoles and thieno[2,3-d][1,3] selenazoles which are easily prepared from cyanamide and carbon disulfide. By this way, we have synthesized 4-amino-1,3-thiazoles et 1,3-selenazoles substituted in position 2 and 5 in two steps. Used these heterocycles, 4-halogeno-1,3-thiazoles et 1,3-selenazoles were synthesized by Doyle’s method. Lability of halogens in previous derivatives allowed to prepare new thieno[2,3-d]thiazoles and [1,3]selenazoles. Determination of the antiproliferative activity of these compounds has brought out two compounds, showing IC50 values in micromolar range on investigated cancer cell lines: MCF-7, PC-3, Hs683, U373, SKMEL-28, and A549. One particular compound showed a high activity of anti-Na+/K+-ATPase and anti-ROS. In addition in the second subject, we were interested in the development of the synthesis of two isomers (alpha and beta) of 4-butoxylvinyl-coumarins, -thiocoumarin and -2-quinolones by Heck coupling. We showed that, depending on the substituent in the position 4 of the heterocycle, the coupling was regioselective. These butoxyvinylic derivatives, characterized by dienic character, were studied for their reactivity, stereoselectivity and regioselectivity with several dienophiles in Diels-Alder cycloaddition. Among all the polyheterocyclic compounds prepared, we have identified the tetracyclic compounds with quinonic ring which have potential anticancer activity by inhibition of CDC25 phosphatase and on several tumor cell lines

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Matthee, Suzette. "The development of two-week menu cycles for households with children allergic to wheat, soy, cow's milk and egg respectively". Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/53102.

Testo completo

Abstract (sommario):

Thesis (MSc Consumer Sc)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Food allergies in children are a growing problem and have various effects on these children, their households, the community and the economy. No medication or cure is currently available to consumers suffering from food-allergies. Medical teams are aware of the patients' need for support, but information is lacking and understanding of their basic needs and problems neglected. Two qualitative research methods, namely the focus group technique and case studies were used to investigate the emotional and physical environment of children allergic to wheat, soy, cow's milk and egg respectively. Five focus group meetings were conducted with the caregivers of food-allergic children. Two during the pilot study and three in the main study. A total of twenty three participants attended the three meetings of the main study. A meeting schedule was developed and the meetings carefully moderated. After the data had been obtained from the focus group meetings, there was a need for more in-depth information and understanding. Seven of the participants of the focus groups were identified, through developed criteria, to be further investigated as case studies. Five units of investigation were identified for the case studies. It was the (i) caregiver, (ii) allergic child, (iii) other children, (iv) "non-caregiver parent" and (v) household. Some of the matters that were investigated in both the focus groups and case studies were health consciousness, menu planning, recipe needs and use, reading of food labels, hidden allergens and the social and emotional effects of having and being a food-allergic child. A great need for better support and educational programs to assist these households were identified. Very few of the households were health conscious, while they all experienced problems with menu planning, identifying hidden allergens and suffered from social and or emotional problems. Very few participants made use of recipes or identified a need for allergen-free recipes. After having gained insight in the daily lives of these households, four - virtually identical, two-week menu cycles were developed to suit the life style requirements and restrictions of these children. The same recipes were used, but allergens omitted, replacements made and the recipes adapted as necessary. Product scouting was done for hidden allergens in selected popular convenience foods, especially those from the lowest level of the USDA Food Guide Pyramid. Hidden allergens appeared to be a problem when food is prepared and bought for the food allergic child. It should be taken into account that despite the information stated on the food label undeclared allergens might still be present in food. The two-week menu cycle for the child allergic to cow's milk was then quantitatively evaluated for nutritional adequacy by FoodFinder ™ 2 - a software program, for children aged between seven and ten years. All the macronutrients and micronutrients identified by the National Survey in 1999 as insufficient «67% of the RDA) among South African children aged between one and nine years, were evaluated as well as those mentioned in the WHO Dietary and Health Goals. All the nutrients were sufficient, except for calcium and Vitamin D. Supplementation is advised. The sensory acceptability of the menu-items in the two-week menu cycles were not evaluated. A vast number of issues pertaining to the food-allergic child require further research. A great need exists for the development of educational programs to support the households with food-allergic children. The identification of hidden allergens and the development of reliable sensory testing models for food-allergic children are all areas that should urgently be researched further.
AFRIKAANSE OPSOMMING: Voedsel-allergieë by kinders is 'n groeiende probleem met 'n verskeidenheid effekte op dié kinders, hulle huishoudings, die gemeenskap en die ekonomie. Tans is geen medikasie of kuur teen voedsel-allergieë beskikbaar nie. Mediese spanne is bewus van die behoefte aan sorg en leiding wat deur dié spesifieke groep verbruikers benodig word, maar inligting oor hulle behoeftes en probleme is ontoereikend. Twee kwalitatiewe navorsingsmetodes, naamlik die fokusgroeptegniek en gevallestudies, is gebruik om die emosionele en fisiese omgewing van kinders allergies vir onderskeidelik grane, soja, melk en eiers te ondersoek. Tydens 'n voorloperstudie is twee fokusgroepvergaderings gehou. Vir die hoofstudie is drie fokusgroepvergaderings met versorgers van kinders met 'n voedsel-allergie gehou met 'n totaal van drie en twintig deelnemers. 'n Vergaderingskedule is ontwikkel en die vergaderings is sorgvuldig gemodereer. Nadat die data van die fokusgroepe ingesamel is, was daar behoefte aan meer in diepte inligting en begrip. Aan die hand van ontwikkelde kriteria is sewe van die deelnemers aan die fokus groepe as gevallestudies geselekteer. Vyf eenhede van ondersoek is geïdentifiseer vir die gevallestudies. Dit is: (i) die allergiese kind, (ii) versorger, (iii) ander kinders, (iv) die "nie-versorgende" ouer en (v) die huishouding. Sommige van die aspekte wat in beide die fokusgroepe en gevallestudies ondersoek is, was gesondheidsbewustheid, spyskaartbeplanning, die gebruik en behoefte aan resepte, lees van voedseletikette, verskuilde allergene en die sosiale en emosionele effek van 'n voedsel-allergie op die kind sowel as die ouers. 'n Groot behoefte aan beter ondersteuning en opvoedkundige programme, om hierdie huishoudings te help, is geïdentifiseer. Baie min van die huishoudings was werkilk gesondheidsbewus, terwyl hulle almal probleme met spyskaartbeplanning, identifisering van verborge allergene en sosioemosionele probleme ondervind het. Weinig van die deelnemers het gebruik gemaak van resepte of het 'n behoefte aan allergeen-vrye resepte ondervind. Nadat insig in die daaglikse lewenstyl van hierdie huishouding verkry is, is vier amper-identiese twee-weekse siklusspyskaarte ontwikkel wat die lewenstyl en behoeftes van hierdie huishoudings aanspreek. Dieselfde resepte was gebruik vir al vier twee-weeksiklusspyskaarte, met die verskil dat verskillende allergene vervang is, na gelang van die allergie verskillende behoefte. Marknavorsing is gedoen op alledaagse produkte en is hoofsaaklik gefokus op die produkte wat die basis van die voedselpiramide uitmaak. Daar is bevind dat verskeulde allergene voorkom in produkte waar dit nie verwag word nie, en soms selfs nie op die voedseletikette verklaar word nie. Die twee-weeksiklusspyskaart van die melk-allergiese kind is kwantitatief ge-evalueer vir toereikendheid van die dieet vir kinders tussen die ouderdomme sewe tot tien jaar op die Foodfinder TM 2 - sagteware program. Die makro- en mikronutriente wat volgens 'n nasionale opname in 1999 as problematiese «67% van die RDA) vir kinders in die ouderdomsgroep een tot nege, uitgewys is, is geneem en die voedingstowwe is ook teen die Werêld Gesondheidsorganisasie (WHO) se dieetdoelwitte getoets. AI die nutriënte was voldoende volgens die analise, behalwe kalsium en Vitamen D. Supplementasie word aanbeveel vir dié twee nutriënte. Die sensoriese aanvaarbaarheid van die spyskaartitems in die siklusspyskaart is nie getoets nie. Verskeie aspekte wat vorendag gekom het, benodig verdere navorsing. 'n Groot behoefte aan die ontwikkeling van opvoedkundige programme, wat die huishoudings met voedsel-allergiese kinders ondersteun, bestaan. Die identifikasie van verskuilde allergene en die ontwikkeling van 'n beproefte sensoriese toetsmodel vir voedsel-allergiese kinders is potensiële gebiede wat dringend verder nagevors behoort te word.

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Tsang, Bo-yee, e 曾寶怡. "Food intake, resting metabolic rate and diet-induced thermogenesis of young Chinese females in the luteal and follicular phases of themenstrual cycle". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31219998.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

40

Rothe, Hannes [Verfasser]. "Educational Service Improvement Cycle : Ein Vorgehen zur Analyse von Nutzungsdaten für die kontinuierliche Weiterentwicklung webbasierter Lernservices / Hannes Rothe". Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1081077816/34.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Meinel, Dominik [Verfasser]. "Die Kraft-Wärme-Kopplung auf Basis von zweistufigen Organic Rankine Cycles / Dominik Meinel". München : Verlag Dr. Hut, 2020. http://d-nb.info/1219476668/34.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

42

Gibert, Fabien. "Télédétection du CO2 atmosphérique par Lidar DIAL Doppler Hétérodyne à 2 microns". Phd thesis, Ecole Polytechnique X, 2005. http://pastel.archives-ouvertes.fr/pastel-00001903.

Testo completo

Abstract (sommario):

Le travail de thèse s'organise en plusieurs parties. Le premier chapitre décrit le cadre scientifique dans lequel s'inscrit la thèse : branche atmosphérique du cycle du carbone, changement climatique et protocole de Kyoto, réseau de mesures actuel et principales missions spatiales. Ce chapitre montre notamment comment s'insèrent les différents aspects que j'ai traité pendant la thèse: modélisation, expérimentation et études théoriques dans le cadre plus général de la restitution des flux de surface et de la mesure du C02 atmosphérique. Au final, je m'intéresse plus particulièrement à l'apport scientifique et aux objectifs d'une mesure de C02 atmosphérique par Lidar DIAL à partir de l'espace. Dans le chapitre II, on s'intéresse au domaine d'étude et plus particulièrement à l'évolution du C02 atmosphérique à la méso-échelle. La représentativité temporelle horizontale et verticale d'une mesure de C02 est évaluée dans le but de cadrer l'étude expérimentale. Par ailleurs on y étudie les processus à l'origine de la variabilité du rapport de mélange dans les différentes parties de 1'atmosphère pour mettre au point une méthode de mesure efficace permettant de rendre compte des phénomènes observés. Nous verrons comment cc travail d'étude du C02 atmosphérique à la moyenne échelle a permis, entre autre, de mettre au point une méthode originale de restitution et de caractérisation des flux de surface naturels dans la région du Sud-Ouest parisien. Fort de cette étude et des objectifs de mesure décrits dans le chapitre I, le chapitre III discute la mesure DIAL avant d'en rechercher une optimisation pour obtenir le maximum de précision sur la mesure de concentration. Un soin tout particulier est porté à la spectroscopie, à l'optimisation de paramètre tels que l'épaisseur optique de la colonne d'air sondée et l'énergie des impulsions lasers émises dans l'atmosphère, et à l'analyse des erreurs statistiques et systématiques. Le chapitre IV décrit le système expérimental réalisé au Laboratoire de Météorologie dynamique pendant ces trois années: LIDIA. " Lidar pour la mesure du Dioxyde de carbone Atmosphérique ". Le Lidar DIAL Doppler a été conçu à partir d'un Lidar Doppler déjà existant au Service d'Aéronomie [Bruneau-00, Le Rille-02]. Le chapitre décrit le Lidar, les différentes transformations, les éléments ajoutés et les performances du système global dans le cadre des mesures DIAL. Un intérêt particulier est donné au traitement de signal. Suit alors la partie principale du travail de recherche avec la présentation et la discussion des résultats expérimentaux. Des mesures réalisées de jour et de nuit en fin d'année 2004 et pendant l'année 2005 y sont décrites pour illustrer les différentes possibilités d'une mesure DIAL pour répondre aux objectifs scientifiques décrits dans le chapitre I : mesures intégrées au niveau du sol et validation avec des mesures in-situ, mesures verticales dans la couche limite atmosphérique (CLA), utilisation des cibles nuageuses, mesures dans la troposphère libre et mesures résolues dans la CLA. Nous voyons notamment l'apport de mesures de vent et de vitesses verticales simultanées avec des mesures de concentration pour expliquer les processus naturels ou anthropiques à l'origine de la variation temporelle du rapport de mélange en CO2. Le dernier chapitre s'appuie sur le travail expérimental précédent pour prévoir les performances de futurs systèmes de mesure DIAL aéroporté ou spatial capable de répondre aux objectifs scientifiques à moyen et long terme. Différentes perspectives de travail pour l'amélioration du système expérimental et pour la conception d'un nouveau système y sont abordées. Enfin une conclusion permet de souligner et de rassembler les principaux résultats du travail de thèse.

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Claasen, Clinton Jared. "Die stil avontuur an evaluation of Hendrik Hofmeyr's song-cycle with an emphasis on the poetry of Elisabeth Eybers". Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10233.

Testo completo

Abstract (sommario):

Includes bibliographical references.
Forty-six opuses in Hofmeyr's oeuvre are either inspired by or set to Afrikaans texts. This is indicative of his love for the language and of the culture in which he feels most comfortable. Of these works, the Afrikaans song is the most predominant genre which spans his entire compositional career. However, only one cycle, Alleenstryd, has been the subject of extensive academic evaluation (Roos, 2000; May, 2003; Cupido, 2010). For the purposes of this dissertation, I have decided to investigate Die stil avontuur, a cycle based on seven poems by Elisabeth Eybers. Die stil avontuur, commissioned by Lina Spies in celebration of Eybers' ninetieth birthday traces, like Robert Schumann's Frauenlieben und -leben, the life of a woman from the first meeting of her beloved to his death. My motivation for selecting this cycle as the subject for my study, besides considering it a high-point in both Hofmeyr's oeuvre and South African song, is one of identifying a number of correlations between Eybers and Hofmeyr. Both being recipients of international awards for their respective arts, they also both left their birth country in self-imposed exile. Another aspect common to both artists is their struggle to reconcile aspects of their upbringing with their arts.

Gli stili APA, Harvard, Vancouver, ISO e altri

44

Tsang, Bo-yee. "Food intake, resting metabolic rate and diet-induced thermogenesis of young Chinese females in the luteal and follicular phases of the menstrual cycle /". Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19324224.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

45

Smati, Hossem Edine. "Physical forcing of zooplankton in the upper oligotrophic ocean off Bermuda (northwestern Atlantic) and New Caledonia (southwestern Pacific) from acoustics and net measurements". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4073.

Testo completo

Abstract (sommario):

Les forçages physiques conditionnent la discontinuité dans l'espace et le temps (patchiness) du plancton dans l'océan. La thèse s'est basée sur deux exemples. Le premier concerne le nord-ouest des Sargasses où une série temporelle à du macrozooplankton a été analysée à partir du rétro signal acoustique (Sv) mesuré avec un ADCP 153-KHz. Trois types de tourbillons ont été identifiés: un tourbillon cyclonique productif, la périphérie d'un tourbillon "mode-water", et la périphérie d'un tourbillon anticyclonique. Les valeurs de Sv ont augmenté au cours du passage des tourbillons, avec une hausse plus marquée associée au bord des tourbillons cyclonique et anticyclonique, ce qui suggère une réponse biologique significative aux upwelling localisées dans la zone frontale de ces tourbillons. Dans le deuxième exemple, la distribution spatiale et temporelle du zooplancton a été étudiée au large de la Nouvelle-Calédonie au cours de deux campagnes multidisciplinaires en 2011. La variabilité du zooplancton a été évaluée à l'aide d'échantillonnage au filet ainsi qu'à partir de mesures acoustiques (ADCP embarqué, échosondeur scientifique et TAPS). Des amplitudes plus élevées de la migration verticale nycthémérale (DVM) du zooplancton étaient associées à une plus grande abondance de petit zooplancton et aux eaux froides du sud de la zone d'étude, tandis que des amplitudes de DVM plus faibles dans le nord étaient associés à des eaux plus chaudes et à de plus grande abondance des grands organismes. Ces mesures acoustique ont clairement mis en évidence le rôle des forçage physique, notamment des structures à méso-échelle, sur la répartition spatiale et temporelle du zooplancton
Physical forcing drives the space and time discontinuity (patchiness) of plankton in the ocean. The thesis was focused on the role of these forcing on the zooplankton, studied using both acoustic and traditional methods with net sampling. The study was based on two examples. The first one concerns the northwestern Sargasso Sea where high resolution time-series data on 0-200m macrozooplankton abundance and distribution off Bermuda was estimated from volume backscattering strength (Sv) measured with a 153-Khz ADCP. Three types of eddies were identified: a productive cyclonic eddy, the periphery of a mode water eddy, and the periphery of an anticyclonic eddy. Sv values increased during passage of theses eddies, with a more pronounced increase associated with the edge of the cyclonic and the anticyclonic eddies, suggesting a significant biological response to localized upwelling in the high velocity boundary of these eddies. In the second example, spatial and temporal distribution of zooplankton off New Caledonia was studied during two multidisciplinary cruises in 2011. Zooplankton variability was assessed using net sampling together with acoustic measurements (shipborne ADCP, scientific echosounder and TAPS). Higher amplitudes of diel vertical migration (DVM) of zooplankton were associated with higher abundance of large zooplankton and cold waters to the south of the study area, while lower DVM amplitudes in the north were associated with warmer waters and higher abundance of small organisms. These acoustic measurements clearly evidenced the role of physical forcing, particularly mesoscale features, in shaping zooplankton space and time distribution

Gli stili APA, Harvard, Vancouver, ISO e altri

46

Deleens, Raynald. "Contribution au développement de nouvelles carbofonctionnalisations d'alcènes, préparation de polycycles aminofonctionnalisés en jonction de cycles et synthèse d'un disélénure chiral de symétrie C2". Rouen, 2002. http://www.theses.fr/2002ROUES062.

Testo completo

Abstract (sommario):

Ce travail focalise sur la mise au point de nouvelles réactions de carbofonctionnalisation et de nouvelles stratégies destinées à la synthèse de cycles et de polycycles fonctionnalisés. Dans une première partie, l'étude d'une nouvelle méthodologie de carbofonctionnalisation d'alcènes, reposant sur l'interaction entre un ion épisélénonium et un silane non activé, a été abordée. Deux processus, intermoléculaire et intramoléculaire, sont considérés. Plusieurs voies de synthèse des différents précurseurs sont décrites. Les conditions opératoires permettant la formation de l'ion épisélénonium, ainsi que la rupture de la liaison carbone-silicium, ont été définies. Les essais ne permettent cependant pas d'observer la cyclisation attendue. Une stratégie de synthèse de bicycles comportant un atome d'azote en jonction de cycle est présentée ensuite. Le processus repose sur l'utilisation d'équivalents synthétiques du nitroacétylène dans une double réaction séquentielle de cycloaddition. En particulier les β-phénylthionitroéthylène et β-phénylsélénonitroéthylène ont été utilisés comme diénophile. Les conditions hyperbare permettent la préparation des cycles attendus avec de bons rendements, et de bonnes régiosélectivité et stéréosélectivité. La mise au point d'une nouvelle méthode d'insaturation du cycloadduit primaire, faisant intervenir un carbénoi͏̈de, permet de générer les nitroalcènes cycliques nécessaires pour la seconde réaction de Diels-Alder. Les conditions sont douces et fournissent les produits attendus avec des rendements bons à excellents. L'activation thermique et hyperbare permet la production des cycloadduits finaux avec de bons rendements. Une version asymétrique des réactions impliquées dans ces deux premières parties est possible. A cette fin, la conception et la synthèse d'un nouvel inducteur chiral, de symétrie C2, à partir de proline, sont décrites. L'évaluation du pouvoir d'induction de ce disélénure et de ses dérivés est en cours
This work deals with the optimisation of new strategies for the synthesis of functionalised polycycles. In the first part, the study of a new methodology of alkenes carbofunctionalisation, based on the interaction between an episelenonium ion and a non activated silane, was examined. A strategy for the synthesis of bicyclic skeleton with a nitrogen atom at the junction is then described. It is based on the utilisation of nitroacetylene synthetic equivalents in a sequential double cycloaddition reaction. Hyperbaric conditions give access to expected adducts in good yields, and good regio and stereoselectivity. The optimisation of a new method to introduce a double bond in the cycloadduct, using carbenoid, yields cyclic nitroalkenes that could be involved in a second Diels-Alder reaction. An asymmetric version of the reactions described in these two parts is possible. Thus, the conception and the synthesis of a new chiral inductor, parenting a C2 symmetry, from proline, are described

Gli stili APA, Harvard, Vancouver, ISO e altri

47

Laquièvre, Aurélie. "Mécanismes élémentaires de plasticité des systèmes polymères amorphes : influence de la modification de la structure macromoléculaire par la chimie « Click »". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10124/document.

Testo completo

Abstract (sommario):

Les objectifs de cette thèse portent sur l’élaboration de nouveaux matériaux réticulés réversibles et sur la compréhension de leurs propriétés mécaniques. Pour atteindre ces objectifs, nous avons exploité deux stratégies : la réaction de Diels-Alder (DA) à partir de copolymères parfaitement définis dotés de motifs furanes et la remarquable réactivité des azlactones vis-à-vis des amines. Les copolymères ont été synthétisés par polymérisation radicalaire contrôlée afin d’obtenir des copolymères parfaitement définis fonctionnalisés en chaine latérale. Différents copolymères réticulés ont été préparés via la réaction de DA et caractérisés en termes de température de transition vitreuse et de taux de gonflement. L’étude de leurs propriétés thermiques et viscoélastiques a mis en évidence une influence de la réticulation. Dans un second temps, les propriétés telles que leur réversibilité et leur comportement mécanique ont été étudiées. Nous avons défini l’existence d’une relation entre les mécanismes de plasticité et l’évolution structurale induite. Concernant les copolymères à base d’azlactones, nous avons montré que la nouvelle plateforme polymère était facilement modifiable par une grande variété d’amines primaires permettant d’élaborer de nouveaux matériaux avec des propriétés intéressantes (fluorescent, électroactif…). Les polymères fonctionnalisés ainsi obtenus ont été caractérisés par diverses techniques d’analyses qui ont permis de traduire le caractère quantitatif de la réaction. Enfin, des matériaux réticulés ont également été élaborés par la réaction des motifs azlactones avec un composé diamine
The main objectives of this work were the elaborate new reversible crosslinked materials and to get a better understanding of their physical and mechanical properties. Two strategies have been investigated to prepare such materials. The first one consisted in applying to well-defined furan functionalized side-chain copolymers the Diels-Alder (DA) / retroDiels-Alder reactions. The second approach was based on the high reactivity of azlactone units embedding in well-defined copolymer chains toward primary amines. The controlled radical polymerization has been exploited in order to provide an effective way for the control synthesis of the well-defined side-chain functionalized copolymers. Then, various crosslinked materials have been prepared using the DA reaction and characterized to determine their glass transition temperature and their swelling ratio. The study of their thermal and viscoelastic properties highlighted the deep impact of the crosslinking. Then, their reversible and mechanical behaviors were investigated and we observed a correlation between the plastic deformation mechanisms and the induced structural evolution. Concerning the azlactone based copolymer, we have shown that this new polymeric platform could be efficiently modified by various primary amines, affording new materials with interesting properties (fluorescence, electroactive,…). The ring-opening reactions of azlactone functionalized copolymers were fully characterized proving the quantitative character of this reaction. Endly, crosslinked materials have been also elaborated by treating the azlactone copolymer with a diamino component

Gli stili APA, Harvard, Vancouver, ISO e altri

48

Espinosa, Rodriguez Edgar. "Préparation de polyéthylènes portant des fonctions réactives en extrémité de chaînes et leur utilisation en tant qu’agents de couplage pour la conception de matériaux originaux à base de polyéthylène". Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10292/document.

Testo completo

Abstract (sommario):

Le polyéthylène (PE) est omniprésent dans notre vie de tous les jours et ce principalement car il présente des propriétés thermiques et mécaniques qu’on ne retrouve pas d’autres polymères. Cependant, sa très faible réactivité chimique fait qu’il est difficile de l’incorporer dans des architectures macromoléculaires plus complexes qui pourraient profiter de ses propriétés uniques. La modification de polymères fonctionnels en extrémité de chaîne par des réactions de couplage efficaces est un outil très utilisé pour la conception d’architectures macromoléculaires. Parmi les différentes réactions envisageables, la réaction de cyclo-addition 1,3 dipolaire de Huisgen entre un azoture et un alcyne est très utilisée dans le domaine de la science des polymères pour lier des polymères entre eux. Une autre méthode performante est le couplage par une réaction d’addition de type hétéro Diels-Alder (HDA) entre un diène et un dithioformate. L’objectif de ce travail de thèse est dans un premier temps d’identifier un système de polymérisation catalytique de l’éthylène qui permette de synthétiser du polyéthylène de masse molaire variable et comportant à une extrémité une fonction réactive. Puis cette extrémité réactive est mise à profit dans des réactions de couplage efficaces comme celles mentionnées plus haut pour la synthèse d’architectures macromoléculaires incorporant des segments de PE
Polyethylene (PE) is a polymer of great importance in our everyday life due to its unique thermal and mechanical properties. However, it suffers from lack of reactivity that prevents to introduce it into more complexed architectures the final properties of which would benefit from these unique features. The modification of end-functionalized polymers through orthogonal and efficient coupling reactions is a powerful and widely used tool for the design of various macromolecular architectures. In today’s polymer science the copper catalyzed azide-alkyne cycloaddition (CuAAC) is the most frequently used « click » reaction. Another efficient coupling method is the hetero Diels-Alder (HDA) reaction between a diene end-functionalized polymer and the electron deficient dithioester end-group of a polymer synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. Our first aim was to fin and optimize the best ethylene catalytic polymerization system that would allow to produce PE with different molar masses and end functional groups. In a second step, we tried to introduce polyethylene segments in macromolecular architectures by taking advantage of the best attributes of the aforementioned coupling reactions

Gli stili APA, Harvard, Vancouver, ISO e altri

49

Vergnerie, Cédric. "La théorie des caractéristiques dans les Vorlesungen über die Theorie der algebraischen Gleichungen de Kronecker : la fin du cycle d’idées sturmiennes ?" Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC238/document.

Testo completo

Abstract (sommario):

Hourya Sinaceur présente dans son ouvrage Corps et Modèles la théorie des caractéristiques de Kronecker comme la ﬁn d’« un cycle d’idées sturmiennes », la situant ainsi dans une histoire de l’algébrisation du théorème de Sturm. Pourtant, cette théorie est souvent aussi présentée comme le point de départ de certains des premiers travaux de topologie de la toute ﬁn du dix-neuvième siècle. Nous souhaitons dans cette thèse rendre compte de la façon dont ces deux histoires se rencontrent au sein de la théorie de Kronecker. Pour cela, nous disposons d’un matériel particulièrement éclairant et jusqu’alors très peu exploité : les manuscrits des cours que Kronecker a donnés à l’Université de Berlin entre 1872 et 1891 sur la Théorie des équations algébriques. Nous commencerons par présenter ces manuscrits, leur contenu et leur contexte de rédaction. Nous nous intéresserons ensuite plus précisément à la reprise du théorème de Sturm par Kronecker, et nous montrerons que la théorie des caractéristiques n’est pas seulement un prolongement algébrique de ce théorème, mais qu’elle se transforme pour fournir certains des outils analytiques que Poincaré utilisera lors de la construction de son Analysis Situs. L’exposition de la théorie des caractéristiques dans ses cours est l’occasion pour Kronecker de reprendre trois des quatre démonstrations que Gauss a données du théorème fondamental de l’algèbre, et nous montrerons comment, dans la pratique de Kronecker, la notion même de racine est interrogée
In her book Corps et Modèles, Hourya Sinaceur presented Kronecker’s theory of characteristics as the end of a “cycle of Sturmian ideas”, making it a step in history of the algebraization of Sturm’s theorem. However, this theory is often also introduced as the starting point of some of the early works of topology of the very end of the nineteenth century. In this PhD thesis, I will describe how these two stories are connected in Kronecker’s theory. To achieve this, I used material which has seldom been discussed before : the manuscripts of the courses that Kronecker gave at the University of Berlin between 1872 and 1891 on the Theory of algebraic equations. I begin with the presentation of these manuscripts, their contents and their writing contexts. I then look more closely at Kronecker’s rework of the theorem of Sturm and show that the theory of characteristics is not only an algebraic extension of this theorem but also that it is transformed in order to provide some of the analytic tools that Poincaré will use for the construction of his Analysis Situs. The exposition of the theory of characteristics in his courses is an opportunity for Kronecker to take up three of the four demonstrations from Gauss of the fundamental theorem of algebra, and I will show how, in Kronecker’s practice, the very notion of root is questioned

Gli stili APA, Harvard, Vancouver, ISO e altri

50

Ouellet, Luc. "Synthèse rapide de 14ß-hydroxystéroïdes via la réaction de Diels-Alder transannulaire ayant le cycle à aromatique et fonctionnalise en C17 et C18". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq21808.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Tesi sul tema "Diel cycle"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili