• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 199
  • 60
  • 45
  • 32
  • 29
  • 17
  • 7
  • 7
  • 7
  • 5
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 455
  • 99
  • 66
  • 52
  • 51
  • 50
  • 49
  • 47
  • 46
  • 41
  • 36
  • 35
  • 35
  • 33
  • 33
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

Poluentes Orgânicos Persistentes em sangue de aves marinhas no Arquipélago de São Pedro e São Paulo e na Ilha da Trindade / Persistent Organic Pollutants in blood of seabirds in the São Pedro and São Paulo Archipelago and Trindade Island

Silva, Daniela Alves Maia da 08 March 2019 (has links)
As aves marinhas são sensíveis às alterações em todos os níveis tróficos, decorrentes de variações na disponibilidade de presas e contaminação por alguns compostos, capazes de se acumular nos tecidos dos organismos e magnificar-se através da cadeia trófica. As ilhas oceânicas brasileiras abrigam importantes colônias reprodutivas de aves marinhas e, apesar de serem consideradas locais remotos, estão sujeitas à contaminação decorrente de atividades humanas. Este trabalho avaliou a presença de poluentes orgânicos persistentes (POPs) em sangue, uma matriz não-destrutiva, de seis espécies de aves marinhas no Arquipélago de São Pedro e São Paulo e na Ilha da Trindade, que possibilita o monitoramento destes indivíduos ao longo dos anos. Os resultados indicaram que os principais POPs detectados no sangue (em ng g-1 de massa úmida) foram PCBs (0,05 a 55,09), DDTs (0,01 a 17,36) e Mirex (0,01 a 5,53). A migração influenciou nos altos níveis de POPs encontrados em Pterodroma arminjoniana e a massa (g) média dos indivíduos apresentou uma forte correlação negativa com as concentrações dos compostos predominantes no sangue. O sexo das aves não contribuiu significativamente nas concentrações de POPs em espécies monotípicas, exceto para a espécie Sula leucogaster que apresenta dimorfismo sexual acentuado. O comportamento alimentar, avaliado através da análise de isótopos estáveis de carbono e de nitrogênio (δ13C e δ15N), bem como as condições biológicas de cada animal contribuíram para explicar as variações nos perfis de contaminação entre as diferentes espécies. No geral, observou-se que as concentrações de POPS nos dois locais apresentaram valores baixos e similares sugerindo a via atmosférica como principal mecanismo de entrada desses contaminantes para estas regiões. Os resultados inéditos de POPs em sangue das aves marinhas nas duas mais recentes unidades de conservação marinhas criadas no Brasil, podem contribuir como referência para o monitoramento desses compostos em longo-prazo nessas regiões. / Seabirds are sensitive to changes at all trophic levels, due to variations in prey availability and contamination by some compounds, which can be accumulated in the tissues of organisms and to be magnified through the trophic chain. The Brazilian oceanic islands harbor important seabird breeding colonies and, although they are considered remote sites, they are subject to contamination from human activities. This work evaluated the presence of Persistent Organic Pollutants (POPs) in blood, a non-destructive matrix, of six species of seabirds in the São Pedro and São Paulo Archipelago (SPSPA) and Trindade Island (TI), that allows the monitoring of these individuals over the years. The results indicated that the major POPs detected in blood (ng g-1 in wet weight) were PCBs (0.05 to 55.09), DDTs (0.01 to 17.36) and Mirex (0.01 to 5,53). Migration influenced the high levels of POPs found in Pterodroma arminjoniana and the mean mass (g) of the individuals drove a strong negative correlation with the concentrations of the predominant compounds in the blood. The gender of the individuals did not contribute significantly to the concentrations of POPs in monotypic species, except for the species Sula leucogaster that presents marked sexual dimorphism. The feeding behavior was evaluated through the analysis of stable isotopes of carbon and nitrogen (δ13C and δ15N) as well as the biological conditions of each animal contributed to explain the variations in the contamination profiles between the different species. In general, we observed that POPS concentrations at both sites presented low and similar values suggesting the atmospheric transport as the main input mechanism of these compounds for these regions. The unpublished results of POPs, in blood of seabirds from the two most recent marine conservation units created in Brazil, can contribute as reference values for their long-term monitoring in those regions.
382

Comparing locomotor behaviour of the fish species Danio rerio and Leucaspius delineatus under the influence of chemical stressors

Baganz, Daniela 22 May 2006 (has links)
Diese Dissertation ist ein Beitrag zum Forschungsfeld der Stressökologie, im Spe-ziellen der Verhaltensökotoxikologie. Das spontane lokomotorische Verhalten der Fischarten Danio rerio und Leucaspius delineatus wurde unter sublethaler Expo-sition mit dem Cyanobakterientoxin Microcystin-LR (MC-LR) und dem Xenobio-tikums 2.4.4`-Trichlorobiphenyl (PCB 28) quantifiziert. Die Schwimmgeschwin-digkeit und Anzahl der Wendungen wurden kontinuierlich mit einem automati-schen Video-Monitoringsystem unter Laborbedingungen aufgezeichnet. In Hin-blick auf zyklische Aspekte wurden die Verhaltensanalysen mit chronobiologi-schen Methoden kombiniert. Hiermit wurde gezeigt, dass MC-LR und PCB 28 zu signifikanten Effekten in Verhalten und Aktivitätsrhythmik beider Fischarten führten. Höhere Konzentrati-onen beider Untersuchungssubstanzen verursachten eine deutliche Aktivitätsredu-zierung bei Danio rerio und Leucaspius delineatus. Einige der festgestellten Do-sis-Wirkungsbeziehungen entsprechen der Hormesistheorie, z. B. war bei geringe-ren MC-LR Konzentrationen ein Aktivitätsanstieg und bei höheren ein Aktivitäts-abfall beider Fischarten zu verzeichnen. Die Exposition mit MC-LR und PCB 28 verringerte bei beiden Testfischarten die Synchronisation der Aktivität mit dem Zeitgeber Licht. Dies führte bei beiden Fischarten zu einer Phasenverschiebung. Bei Leucaspius delineatus war unter dem Einfluss von MC-LR eine Phasenumkehr zu verzeichnen, die Fische wechselten von Tag- zu Nachtaktivität. Die Cosinor Analyse zeigte Dosis abhängige Veränderungen der circadianen Rhythmen der Schwimmaktivität (z.B. MESOR, Akrophase) unter Einfluss von MC-LR und PCB 28 an. Die Power Spektral Analyse indizierte für beide Fischar-ten unter Einwirkung von MC-LR and PCB 28 eine reduzierte Dominanz des cir-cadianen Rhythmuspeaks. Da die registrierten Unterschiede in der Reaktion beider Fischarten auf MC-LR und PCB 28 eher gering waren, sind Ergebnisse der Art Danio rerio, die häufig in Toxizitätstests verwendet wird, mit denen der einheimischen Art Leucaspius deli-neatus vergleichbar. Die Ergebnisse belegen, dass Verhaltensuntersuchungen in Kombination mit chronobiologischen Auswertemethoden eine sensitive und zuverlässige Abschät-zung des Gefährdungspotentials von Substanzen sowohl auf dem Gebiet der Öko-toxikologie als auch für Biomonitoring ermöglichen. / This thesis contributes to the field of stress ecology specifically behavioural ecotoxicology. The spontaneous locomotor behavior of two fish species Danio re-rio and Leucaspius delineatus was recorded and quantified continuously under sublethal exposure to the cyanotoxin microcystin-LR (MC-LR) and the xenobioti-cum 2.4.4`-trichlorobiphenyl (PCB 28). By using an automated video-monitoring system, the swimming velocity and the number of turns were assessed under labo-ratory conditions. For analysing cyclic aspects basic behavioural analyses were combined with chronobiological procedures as cosinor analysis and power spec-tral analysis. Both MC-LR and PCB 28 acted as stressors and caused significant changes in the behaviour and circadian activity rhythms of Danio rerio as well as Leucaspius de-lineatus. So for both species elevated concentrations of the stressors led to a re-duction of their activity. Some dose-responses correspond to the hormesis theory, e.g., there was an increase of daytime activity at lower MC-LR concentrations and a decrease at elevated concentrations of MC-LR for both species. A degree of desynchronisation of activity to the zeitgeber light, which led to a phase shift was caused by the chemicals in both fish species. In Leucaspius de-lineatus this shift was so drastic that this species reversed their significant diurnal activity and became nocturnal under the influence of MC-LR. The Cosinor analysis revealed MC-LR- and PCB 28-induced, dose-dependent al-terations of the circadian rhythms of activity (e.g., MESOR, acrophase). The power spectral analysis showed that the dominance of the circadian rhythmic peak (of 24 h) was reduced under MC-LR and PCB 28 for both species. Since the observed differences in the reactions of both species to MC-LR and PCB 28 were rather small, the results of the species Danio rerio which is widely used for environmental risk assessment tests, are comparable to those of the native European species Leucaspius delineatus. The findings of this study proved that the basic behavioural analyses combined with chronobiological procedures could be valuable tools for the study of stressful or even harmful environmental factors in the field of ecotoxicology as well as for biomonitoring.
383

Dioxin emissions from small-scale combustion of bio-fuel and household waste

Hedman, Björn January 2005 (has links)
<p>Denna avhandling behandlar rökgasutsläpp av persistenta organiska föroreningar, framförallt dioxiner, vid förbränning av fasta biobränslen och torrt hushållsavfall i relativt små anläggningar (5-600 kW) utan avancerad rökgasreningsteknik.</p><p>Samförbränning av avfall och biobränsle i effektiva mindre biobränslepannor testades som en alternativ strategi till den vanligen förekommande storskaliga hanteringen och förbränningen fast hushållsavfall. Medan storskalig förbränning av avfall ger investeringsmässiga fördelar med rökgasreningsteknik etc. kan små lokala anläggningar ha transportmässiga fördelar och möjligheter till utnyttjande av lokala biobränsletillgångar. Källsorterat, torrt, brännbart hushållsavfall insamlades från hushåll i glesbygd och samförbrändes i brikettform med energigräset rörflen i 150-600 kW biobränslepannor. Endast undantagsvis understeg dioxinemissionerna gällande gränsvärden för avfallsförbränning och nivåerna av väteklorid i rökgas översteg gränsvärdena flerfaldigt. Det bedömdes att någon form av extra rökgasrening är nödvändig för att säkerställa nivågränserna. Dioxiner hittades också i det eldade avfallet, framförallt i textilfraktionen. Dioxinmängderna i rökgaserna var oftast lägre än i det ingående bränslet.</p><p>Intermittent pelletseldning gav oväntat höga utsläpp av dioxiner med en emissionsfaktor på 28 ng(WHO-TEQ)/kg. Vedeldning i en modern miljömärkt villapanna gav betydligt lägre utsläpp av dioxiner än eldning i en gammal kombipanna och eldning med full lufttillförsel, som kan jämföras med användning av ackumulatortank, resulterade i upp till 90% minskning av utsläpp av dioxiner jämfört med eldning med reducerat lufttillskott (’pyreldning’). Eldning av plastavfall i en vedpanna gav höga utsläpp av dioxiner.</p><p>Okontrollerad förbränning av trädgårdsavfall och hushålls avfall i tunna eller som öppen eld ’bakgårdsbränning’, gav stora variationer i utsläppsnivåer som bara delvis kunde kopplas till avfallsinnehåll. Resultaten visar att denna typ av förbränning kan vara en betydande källa till dioxiner i miljön, och ett emissionsfaktorintervall på 4-72 ng (WHO-TEQ)/kg föreslås för bedömningar av utsläpp från backgårdsbränning av avfall med låga eller måttliga klorhalter.</p><p>En sammanfattande slutsats av alla försök är att dioxin utsläpp beror på komplicerade samband mellan bränsleinnehåll och förbränningsbetingelser. Bränslen med mycket höga klorhalter av ger oftast högre utsläpp av dioxiner än bränslen med låga klorhalter medan små skillnader döljs av variationer i förbränningsbetingelser.</p> / <p>This thesis deals with emissions of persistent organic pollutants, primarily dioxins, from the combustion of solid biofuels and dry combustible household waste in relatively small facilities, 5-600 kW, without advanced air pollution controls.</p><p>Co-combustion of waste and biofuel in effective small boilers was tested as an alternative to prevailing large-scale management and combustion strategies for handling municipal solid waste. This approach includes no advanced air pollution control systems, but offers two advantages: limiting transport and providing scope to use local biofuel resources. Source-sorted, dry, combustible household waste was collected from households in a sparsely populated area and co-combusted as briquettes together with reed canary-grass in 150-600 kW biofuel boilers. Most trials showed difficulties to meet regulative limits for the emissions of dioxins valid for incineration of MSW and the regulated limits for emissions of hydrochloric acid were exceeded manifold. It was concluded that additional flue-gas cleaning will be needed to ensure that emissions are sufficiently low. Dioxins were also found in the waste, especially in the textile fraction. The mass of dioxins in the flue-gas emissions was generally lower than the mass in the fuel input.</p><p>Intermittent combustion of wood pellets in a residential boiler resulted in an unexpectedly high dioxin emissions factor of 28 ng (WHO-TEQ)/kg fuel. Combustion of wood in a modern environmentally certified boiler yielded considerably lower dioxin emissions than combustion in an old boiler, and combustion with a full air supply, i.e. with use of heat storage tank, resulted in up to 90% reductions in dioxin emission factors compared to combustion with reduced air supply. Combustion of plastic waste in a residential wood boiler resulted in high emissions of dioxins.</p><p>Tests of uncontrolled combustion of garden and household waste in barrels or open fires, ‘backyard burnings’, resulted in emissions with large variations that could only be partly correlated to the waste constituents. The results imply that this may be an important source of dioxins in the environment and an emission factor range of 4-72 ng (WHO-TEQ)/kg is suggested for estimating emissions from backyard burnings of lightly and moderately chlorine-contaminated waste.</p><p>A summarized conclusion from all of the experiments is that predicting emission levels from waste contents is not straightforward (except that fuels with very high chlorine levels will usually result in high levels of dioxins in flue-gas emissions). Moderate differences in chlorine levels will usually be masked by the effect of variations in combustion conditions.</p>
384

Dioxin emissions from small-scale combustion of bio-fuel and household waste

Hedman, Björn January 2005 (has links)
Denna avhandling behandlar rökgasutsläpp av persistenta organiska föroreningar, framförallt dioxiner, vid förbränning av fasta biobränslen och torrt hushållsavfall i relativt små anläggningar (5-600 kW) utan avancerad rökgasreningsteknik. Samförbränning av avfall och biobränsle i effektiva mindre biobränslepannor testades som en alternativ strategi till den vanligen förekommande storskaliga hanteringen och förbränningen fast hushållsavfall. Medan storskalig förbränning av avfall ger investeringsmässiga fördelar med rökgasreningsteknik etc. kan små lokala anläggningar ha transportmässiga fördelar och möjligheter till utnyttjande av lokala biobränsletillgångar. Källsorterat, torrt, brännbart hushållsavfall insamlades från hushåll i glesbygd och samförbrändes i brikettform med energigräset rörflen i 150-600 kW biobränslepannor. Endast undantagsvis understeg dioxinemissionerna gällande gränsvärden för avfallsförbränning och nivåerna av väteklorid i rökgas översteg gränsvärdena flerfaldigt. Det bedömdes att någon form av extra rökgasrening är nödvändig för att säkerställa nivågränserna. Dioxiner hittades också i det eldade avfallet, framförallt i textilfraktionen. Dioxinmängderna i rökgaserna var oftast lägre än i det ingående bränslet. Intermittent pelletseldning gav oväntat höga utsläpp av dioxiner med en emissionsfaktor på 28 ng(WHO-TEQ)/kg. Vedeldning i en modern miljömärkt villapanna gav betydligt lägre utsläpp av dioxiner än eldning i en gammal kombipanna och eldning med full lufttillförsel, som kan jämföras med användning av ackumulatortank, resulterade i upp till 90% minskning av utsläpp av dioxiner jämfört med eldning med reducerat lufttillskott (’pyreldning’). Eldning av plastavfall i en vedpanna gav höga utsläpp av dioxiner. Okontrollerad förbränning av trädgårdsavfall och hushålls avfall i tunna eller som öppen eld ’bakgårdsbränning’, gav stora variationer i utsläppsnivåer som bara delvis kunde kopplas till avfallsinnehåll. Resultaten visar att denna typ av förbränning kan vara en betydande källa till dioxiner i miljön, och ett emissionsfaktorintervall på 4-72 ng (WHO-TEQ)/kg föreslås för bedömningar av utsläpp från backgårdsbränning av avfall med låga eller måttliga klorhalter. En sammanfattande slutsats av alla försök är att dioxin utsläpp beror på komplicerade samband mellan bränsleinnehåll och förbränningsbetingelser. Bränslen med mycket höga klorhalter av ger oftast högre utsläpp av dioxiner än bränslen med låga klorhalter medan små skillnader döljs av variationer i förbränningsbetingelser. / This thesis deals with emissions of persistent organic pollutants, primarily dioxins, from the combustion of solid biofuels and dry combustible household waste in relatively small facilities, 5-600 kW, without advanced air pollution controls. Co-combustion of waste and biofuel in effective small boilers was tested as an alternative to prevailing large-scale management and combustion strategies for handling municipal solid waste. This approach includes no advanced air pollution control systems, but offers two advantages: limiting transport and providing scope to use local biofuel resources. Source-sorted, dry, combustible household waste was collected from households in a sparsely populated area and co-combusted as briquettes together with reed canary-grass in 150-600 kW biofuel boilers. Most trials showed difficulties to meet regulative limits for the emissions of dioxins valid for incineration of MSW and the regulated limits for emissions of hydrochloric acid were exceeded manifold. It was concluded that additional flue-gas cleaning will be needed to ensure that emissions are sufficiently low. Dioxins were also found in the waste, especially in the textile fraction. The mass of dioxins in the flue-gas emissions was generally lower than the mass in the fuel input. Intermittent combustion of wood pellets in a residential boiler resulted in an unexpectedly high dioxin emissions factor of 28 ng (WHO-TEQ)/kg fuel. Combustion of wood in a modern environmentally certified boiler yielded considerably lower dioxin emissions than combustion in an old boiler, and combustion with a full air supply, i.e. with use of heat storage tank, resulted in up to 90% reductions in dioxin emission factors compared to combustion with reduced air supply. Combustion of plastic waste in a residential wood boiler resulted in high emissions of dioxins. Tests of uncontrolled combustion of garden and household waste in barrels or open fires, ‘backyard burnings’, resulted in emissions with large variations that could only be partly correlated to the waste constituents. The results imply that this may be an important source of dioxins in the environment and an emission factor range of 4-72 ng (WHO-TEQ)/kg is suggested for estimating emissions from backyard burnings of lightly and moderately chlorine-contaminated waste. A summarized conclusion from all of the experiments is that predicting emission levels from waste contents is not straightforward (except that fuels with very high chlorine levels will usually result in high levels of dioxins in flue-gas emissions). Moderate differences in chlorine levels will usually be masked by the effect of variations in combustion conditions.
385

Impacts des oxystérols par le biais des LXRs et du AhR dans la myélinisation / Impact of oxysterols on myelination processes through LXRs and AhR

Shackleford, Ghjuvan'Ghjacumu 17 June 2014 (has links)
La formation de la gaine de myéline est un processus complexe et finement régulé. Une altération de l’expression des gènes codant pour les protéines structurales de cette gaine entraine de graves neuropathies démyélinisantes. Notre objectif est d’identifier de nouvelles voies de signalisation capables de moduler l’expression de ces gènes. Les cellules de Schwann et les oligodendrocytes contiennent et synthétisent de grande quantité de dérivés oxydés du cholestérol : les oxystérols. Ces molécules sont connues pour leurs rôles dans le maintien de l’homéostasie du cholestérol et dans la progression des maladies neurodégénératives. Les oxystérols peuvent être classés en deux groupes : ceux dont l’oxydation a lieu sur la chaine carbonée latérale (25OH) et ceux qui portent une oxydation sur l’un des cycles du cholestérol (7KC). Nous nous sommes tout d’abord intéressés à la première catégorie d’oxystérols. Nous avons montré que le 25OH, réprimait l’expression des gènes de la myéline périphérique P0 et PMP22. Cette activité répressive était le fruit d’un mécanisme direct conduisant à une augmentation de la quantité des LXRs liés à leurs éléments de réponse sur les promoteurs des gènes de la myéline, et d’un mécanisme indirect provoquant une diminution de l’activité de la voie Wnt/β-caténine. En revanche, dans le SNC, nos résultats indiquent que le 25OH active l’expression des gènes de la myéline PLP et MBP. Le traitement, par ces oxystérols, de cultures organotypiques de cervelet démyélinisées par la lysolécithine permet une remyélinisation des axones des cellules de Purkinje. Nous nous sommes ensuite penchés sur le rôle du corégulateur transcriptionnel RIP140. Ce dernier peut soit agir comme un corépresseur soit comme un coactivateur. Il peut interagir avec le LXR. L’invalidation de RIP140 dans le poisson zèbre altère les gaines de myéline. Nous avons montré que RIP140 possédait des rôles bivalents dans la régulation de la myélinisation. En effet, il est capable d’activer mais aussi de réprimer l’activité transcriptionnelle de P0 et de PMP22. Enfin, nous nous sommes intéressés à la seconde catégorie d’oxystérols. Le 7KC est l’oxystérol majoritairement présent dans le SNP et la CS. Il est connu pour moduler l’action du récepteur aux dioxines : le AhR. Ce récepteur a été très largement étudié dans un cadre toxicologique. Cependant ses rôles et ses ligands endogènes restent à ce jour encore assez méconnus. Nos résultats indiquent que le AhR est impliqué dans le contrôle de l’expression des gènes de la myéline périphérique. L’invalidation du AhR, chez la souris, provoque des anomalies structurales de la gaine de myéline conduisant à des déficits moteurs. Cette étude a permis de mieux comprendre les dialogues entre les voies de signalisation gouvernant le processus de myélinisation. Ce travail apporte également de nouvelles perspectives thérapeutiques des maladies neurodégénératives comme la CMT1A ou la sclérose en plaques. / The myelination of axons is a complex process performed by Schwann cells (SC) and by oligodendrocytes (OL) respectively in the peripheral nervous system (PNS) and in the central nervous system (CNS). A slight change in expression of myelin structural proteins has a deep impact on the development and preservation of nerve fibers and their myelin sheaths, as observed for example in Charcot-Marie-Tooth disease or in Pelizaeus-Merzbacher disease. Our aim is to identify new signaling pathways able to control the expression of these structural proteins. SC and OL contain and synthesize high amount of reactive molecules generated from the oxidation of cholesterol: the oxysterols. Their implication in cholesterol homeostasis and in the progression of neurodegenerative disorders is well known but few data are available for their functions in myelination of PNS and CNS. Firstly, we demonstrate that oxysterols inhibit peripheral myelin gene expression: MPZ and PMP22. This downregulation is mediated by two mechanisms: by increasing the binding of LXRs to myelin genes promoters and by inhibiting the Wnt/β-catenin pathway leading to a decrease of b-catenin recruitment at the levels of the MPZ and PMP22 promoters. However, in the CNS, our data demonstrate that activation of LXRS by oxysterols stimulate myelin genes expression (PLP and MBP). Interestingly, by using demyelinated organotipc culture of cerebellum, we show that oxysterols enhance OL differentiation and promote remyelination, via LXRs. Then, we studied the role of the transcriptional coregulatory, RIP140, in myelination. RIP140 is able to act as a corepressor or as a coactivator and can interact with LXRs. In Zebrafish, the knocked down of the orthologue of RIP140 led to a decrease of peripheral and central myelin gene expression and to a defect in myelin sheath ultrastructure. Finally, we focused on impact of AhR in myelination process. AhR is a ligand activated transcription factor mostly known to interact with environmental pollutant like dioxins to mediate their toxic and carcinogenic effect. However, its detoxifying activity is posterior to the apparition of the gene and its physiological roles and endogenous ligands remain elusive. We show that the main oxysterol in the nervous system is 7-ketocholesterol which is an endogenous modulator of AhR. We report that the constitutive absence of AhR in mice leads to defects in locomotion behaviors. We studied the impact of this invalidation on the myelin of sciatic nerve. We observed a severe demyelinating phenotype and deregulation of myelin genes expression. Moreover, we demonstrated a cross-talk between AhR and Wnt/β-catenin pathways. Our data reveal a new endogenous role of AhR in myelination process.
386

Detection and Quantification of PCB insoil using GC/MS : - method development and education for users

Saba, Elias January 2013 (has links)
The aim of this paper is to document the development of a method for detectionand quantification of Polychlorinated biphenyls (PCB) in soil using GasChromatography (GC) connected to a Quadrupole Mass Spectrometer (MS) via aninternal standard (CB189). The method developed is performed in conjunction withthe information provided by the Swedish environmental agency (Svenskanaturvårdsverket, SNV) in regards to PCB limits for sensitive land usage. The steps ofthe method and maintenance of the GC/MS are used to create a user manual andan attempt at transformative learning is done in an effort to teach the staff atLjungaLab AB so that at the very least, independent analysis can be run and at best,new methods and application are independently developed for the GC/MS. Anevaluation of the teaching efforts is also done to assess what grade of learning isachieved. / Syftet med denna uppsats är att dokumentera utvecklingen av en metod fördetektion och kvantifiering av polyklorerade bifenyler (PCB) i jord med hjälp avgaskromatografi (GC) ansluten till en masspektrometer (MS) och med användningav en intern standard (CB189). Metoden som utvecklats skapades med hjälp avuppgifter från det svenska naturvårdsverket (SNV) angående PCB-gränser för känsligmarkanvändning. Därefter skapades en användarmanual som beskriver stegen imetoden och även underhåll av GC/MS. Personalen på LjungaLab AB undervisadesi hur man använder och underhåller instrumenten för att, åtminstone, kunna köraoberoende analyser, och i bästa fall, utveckla nya metoder och tillämpningarsjälvständigt. Det sistnämda är ett försök till transformativ lärande. En utvärdering avlärarinsatser sker också för att bedöma vilken grad av lärande som uppnås.
387

Design and implementation of an SPB converter for fault tolerant PMSynRel motor control

Apostolopoulos, Nikolaos January 2015 (has links)
The stacked polyphase bridges (SPB) converter topology is investigated in the presentthesis as a fault-tolerant choice for permanent-magnet synchronous reluctance (PMSyn-Rel) motor control. Integrated motor drive systems are studied as they offer great benefitsfor propulsion applications. Moreover, the importance of a modular topology, like theSPB, for an electric powertrain is discussed. The latter consists of a number of seriesconnected, 3-phase 2-level inverter submodules that supply separate sets of windings ina multi-star motor. The specifications of building a four-board SPB setup are examined,while the challenges of an active voltage balancing controller are analyzed. The designprocess is explained step-by-step and the final printed circuit boards (PCBs) are presented.Furthermore, the significance of low electromagnetic interference design for a converterthat requires high speed communication is highlighted. Finally, the prototype is testedthoroughly and the expected fault-tolerant capabilities are validated on a PMSynRel motor. / I detta examensarbete unders¨ok SPB-omriktartopologin (stacked polyphase bridges converter)i termer av ett feltolerant elektriskt drivsystem f¨or en permamentmagnetassisteradsynkron reluktansmaskin (PMSynRel). SPB-omriktaren best°ar av ett antal seriekoppladetrefasomriktare av tv°aniv°atyp som, var och en, f¨orser effekt till en trefaslindningtillh¨orande en modul¨ar elmaskin av multifastyp. Specifikation, design och konstruktion aven SPB-omriktare med fyra seriekopplade moduler studeras. Designproceduren presenterasi en steg-f¨or-steg-process och de tillverkade kretskorten presenteras utf¨orligt. Kommunikationenmellan de olika kretskorten unders¨oks med s¨arskild tonvikt p°a l°ag elektromagnetiskinterferens vilket ¨ar n¨odv¨andigt om h¨og kommunikationshastighet skall kunnauppn°as. Den f¨ardigst¨allda prototypen har utv¨arderats experimentellt och kapaciteten f¨orfeltolerans har demonstrerats vid drift av en PMSynRel-maskin utrustad med en multifaslindning.
388

Architectures d'intégration mixte monolithique-hybride de cellules de commutation de puissance sur puces multi-pôles silicium et assemblages optimisés / Mixed monolithic-hybrid integration of power switching cells on multi-terminal silicon chips and optimized assemblies

Lale, Adem 07 December 2017 (has links)
Actuellement, le module de puissance (convertisseur de puissance) standard hybride 2D est la technologie de référence qui domine le marché de la moyenne et de la forte puissance. Ce dernier se présente sous la forme d'un boitier à multi-puces discrètes. Les puces à semi-conducteur sont reliées entre elles par des faisceaux de wire-bonding (câblage par fils) pour former des cellules de commutation. La technologie d'interconnexion wire-bonding présente une grande maturité technologique, et ses modes de défaillance sont bien connus aujourd'hui. Toutefois, cette technologie est un facteur limitant en termes de performances électrique et thermomécanique, d'intégrabilité tridimensionnelle et de productivité. Ces travaux de thèse ont pour objectif de proposer et d'étudier de nouvelles architectures de convertisseurs de puissance très intégrés. Comparée à la technologie hybride, dite de référence, les architectures proposées visent à un degré d'intégration plus poussé, avec un effort d'intégration partagé et conjoint au niveau semi-conducteur (intégration monolithique) et au niveau assemblage (intégration hybride). L'intégration monolithique consiste à intégrer les interrupteurs formant les cellules de commutation dans de nouvelles architectures de puces, passant ainsi de la notion de puce dipôle à celle de macro-puce multi-pôle. L'intégration hybride repose sur le développement de nouvelles technologies de report et d'assemblage de ces macro-puces. Pour valider les trois nouvelles architectures d'intégrations proposées, la démarche a consisté dans un premier temps à étudier et valider le fonctionnement des nouvelles puces par des simulations SentaurusTM TCAD. Ensuite, les puces multi-pôles ont été réalisées en s'appuyant sur la filière IGBT disponible dans la plateforme de micro-fabrication du LAAS-CNRS. Pour finir, les puces ont été reportées sur des cartes PCB, afin de réaliser des circuits de conversions prototypes. La maille de commutation très intégrée proposée présente une inductance parasite inférieure au nanohenry, ce qui est remarquable comparée à ce qui est présenté dans l'état de l'art (env. 20 nH). / Currently, the standard 2D hybrid power module (power converter) is the reference technology for the medium and high power market. This hybrid power module is a discrete multi-chip case. The semi-conductor chips are interconnected by wire-bonding to form switching cells. The wire-bonding interconnection technology is a limiting factor in terms of electrical and thermomechanical performances, three-dimensional integrability and productivity. The aim of this thesis is to study new architectures of very integrated power converters. Compared to the so-called hybrid reference technology, the proposed architectures aim at a greater degree of integration, with an integration at both the semi-conductor level (monolithic integration) and the packaging level (hybrid integration). Monolithic integration consists in integrating switching cells into new multi-terminal macro-chip architectures. Hybrid integration consists in developing of new technologies to assemble these macro-chips. To validate the different proposed integration architectures, the first step was to study and validate the operating modes of the new chips by SentaurusTM TCAD simulations. Then, the multi-terminal chips were realized in the micro and nanotechnology platform of LAAS-CNRS laboratory. Finally, the chips were bonded on PCB substrates to realize power converter circuit prototypes. The highly integrated switching loop presents a stray inductance loop lower than one nanohenry, wich is an important improvement as compared to the values reported in literature (about 20 nH).
389

Design of a grating lobe mitigated antenna array architecture integrated with low loss PCB filtering structures / Design av en sidloblindrande gruppantenn integrerad med låg förlust PCBfilterstrukturer

Salvador Lopez, Eduardo January 2023 (has links)
Massive multiple input multiple output - MIMO systems are a reality and modern communication systems rely upon this technology to cope with the increasing need for capacity and network usage. Antenna arrays are at the heart of the of the massive-MIMO system and are the enabling technology. The defining cost of such a system is the number of transmit receive ports TRx as they dictate the number of control points and the associated digital control computational capacity. Typically users are spread along the azimuth and there is limited angular user spread along elevation. This enables us to group the elements in elevation which of course limits the elevation scanning performance. The element grouping result in grating lobes when we do elevation scanning. In the newly introduced frequency range 3 - FR3 in the envisioned 6G communication systems that is from 6-20 GHz it will not be allowed to transmit power above the horizon and the resulting grating lobes from the standard grouping should be mitigated. This project is structured into two parts. In the first part a grating lobe mitigation technique based on irregular subarray grouping utilizing the wellknown Penrose irregular tessellation is developed. This tessellation is based into two geometrical shapes where when put together they can fully tile the space aperiodically. Introducing this apperiodicity the grating or quantization lobes of the array are mitigated. In addition, in the first part a beam forming algorithm is developed based on particle swarm optimization that is able to produce the optimal weights for the array steering as well as optimize some of the embedded patterns of the irregular grouping. The last optimization step of the irregular subarray patterns is utilized only when the grouping results in a narrow pattern in azimuth and as a result we have static single port beamforming networks. This of course is a trade off between the broadside gain and the azimuth steerability of the array. In the second part of this thesis two low loss band pass filters have been developed with a PCB integrated suspended stripline techology. The filters were optimised for the frequencies within FR3. The resulted filtering structures can further be integrated at the input port of the proposed feeding network with the same technology. The two parts of this thesis target to introduce on one hand a antenna array architecture with subarray groupings that produce no grating lobes and on the other hand the proposed filtering structures have small enough dimensions to fit within the subarray footprint. / Dagens moderna kommunikationssystem använder sig av Massive multiple input multiple output (m-MIMO) för att kunna möta det allt större kraven på kapacitet och nätverksanvändning. Gruppantenner är den mest fundamentala delen av massive-MIMO system och möjliggör dess funktion. För ett sådant system (m-MIMO-system), så kommer den största kostnaden från antalet sändare/mottagare (TRx) -portar som används. Antalet portar i ett massiveMIMO system bestämmer vilken kapacitet systemet har till hands när det gäller lobformning. Vanligtvis är användare utspridda i det horisontella planet, samtidigt som de är begränsade i sin spridning i höjdled. Detta möjliggör användandet av en gruppantenn som grupperar sina antennelement i höjdled, vilket såklart begränsar gruppantennens lobformning i höjdled. Grupperandet av antennelement skapar sidlober när gruppantennen lobformar i höjdled. I det nya frekvensbandet, 3 - FR3 i det föreställda 6G kommunikationssystemet som opererar mellan 6-20 GHz, så kommer det inte att vara tillåtet att sända ut effekt över horisonten, samtidigt som de sidlober som kommer från standardgruppering måste begränsas. Detta projekt är strukturerat i två delar. I första delen så presenteras ett sätt att lindra sidlober, som baseras på irreguljära gruppantenner via Penrose tessellation. Denna tessellation är indelad i två geometriska former sådan att när vi sätter ihop dem så kan de framgångsrikt täcka vår geometri icke-periodvist. Genom att introducera denna icke-periodicitet så kan sidloberna från gruppanetnnen lindras. Utöver detta så är också så är en lobformningsalgoritm skapad som baseras på particle swarm optimization (PSO), som kan skapa de optimala vikterna för lobformning och lobstyrning. Det sista optimiseringssteget av de irreguljära gruppantennmönstret används bara när gruppering av antennelement resulterar i ett snävt mönster i azimut-riktning. Därför använder vi ett statiskt enportsmatningsnätverk. Detta är såklart en vägning mellan bredsideförstärkning och förmågan att kunna lobforma i det horisontella planet. I den andra delen så har två låg förlust bandpassfilter utvecklats med en PCB-integrerad suspended sripline teknik. Filtrerna optimerades för frekvenser inom FR3. De resulterande filterstrukturerna kan integreras längs input-porten av det föreslagna matningsnätverket som använder sig av den samma teknik. De två delarna i denna uppsats presenterar dels en gruppantenn med irreguljär antennelementsindelning som lindrar sidlober, samt dels filterstrukturer som kan användas tillsammans med gruppantennen.
390

Integrated silicon technology and hardware design techniques for ultra-wideband and next generation wireless systems

Huo, Yiming 18 May 2017 (has links)
The last two decades have witnessed the CMOS processes and design techniques develop and prosper with unprecedented speed. They have been widely employed in contemporary integrated circuit (IC) commercial products resulting in highly added value. Tremendous e orts have been devoted to extend and optimize the CMOS process and its application for future wireless communication systems. Meanwhile, the last twenty years have also seen the fast booming of the wireless communication technology typically characterized by the mobile communication technology, WLAN technology, WPAN technology, etc. Nowadays, the spectral resource is getting increasingly scarce, particularly over the frequency from 0.7 to 6 GHz, whether the employed frequency band is licensed or not. To combat this dilemma, the ultra wideband (UWB) technology emerges to provide a promising solution for short-range wireless communication while using an unlicensed wide band in an overlay manner. Another trend of obtaining more spectrum is moving upwards to higher frequency bands. The WiFi-Alliance has already developed a certi cation program of the 60-GHz band. On the other side, millimeterwave (mmWave) frequency bands such as 28-GHz, 38-GHz, and 71-GHz are likely to be licensed for next generation wireless communication networks. This new trend poses both a challenge and opportunity for the mmWave integrated circuits design. This thesis combines the state-of-the-art IC and hardware technologies and design techniques to implement and propose UWB and 5G prototyping systems. First of all, by giving a thorough analysis of a transmitted reference pulse cluster (TRPC) scheme and mathematical modeling, a TRPC-UWB transceiver structure is proposed and its features and speci cations are derived. Following that, the detailed design, fabrication and veri cation of the TRPC-UWB transmitter front end and wideband voltage-controlled oscillators (VCOs) in CMOS process is presented. The TRPCUWB transmitter demonstrates a state-of-the-art energy e ciency of 38.4 pJ/pulse. Secondly, a novel system architecture named distributed phased array based MIMO (DPA-MIMO) is proposed as a solution to overcome design challenges for the future 5G cellular user equipment (UE) design. In addition, a prototyping design of on-chip mmWave antenna with radiation e ciency enhancement is presented for the IEEE 802.11ad application. Furthermore, two wideband K-band VCO prototypes based on two di erent topologies are designed and fabricated in a standard CMOS process. They both show good performance at center frequencies of 22.3 and 26.1 GHz. Finally, two CMOS mmWave VCO prototypes working at the potential future 5G frequency bands are presented with measurement results. / Graduate / 2018-04-30 / amenghym@gmail.com

Page generated in 0.0205 seconds