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1
Lavigne, Hélène. "Hémodialyse : contamination microbiologique et pyrogénique du dialysat." Bordeaux 2, 1992. http://www.theses.fr/1992BOR2P088.
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KORB, EVELYNE. "Le test limulus applique a la recherche qualitative des endotoxines bacteriennes dans des produits injectables prepares industriellement." Strasbourg 1, 1995. http://www.theses.fr/1995STR15014.
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Kätzel, Uwe. "Dynamic Light Scattering for the Characterization of Polydisperse Fractal Systems by the Example of Pyrogenic Silica." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1197634640783-66357.
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Dynamic light scattering (DLS) is a method to size submicron particles by measuring their thermal motion (diffusion) in suspensions and emulsions. However, the validity of the Stokes-Einstein equation that relates the diffusion coefficient and the particle size is limited to spherical particles and very low concentrations. Within this thesis, DLS is used for the characterization of suspensions of pyrogenic silica which consists of fractal-like aggregates composed of sintered spherical primary particles. These structural features clearly complicate the understanding of DLS experiments and have been a severe obstacle to employing DLS as routine standard tool for the characterization of pyrogenic silica. The main objective of this thesis is therefore to evaluate the application of DLS in product development and quality assurance of pyrogenic silica industry, what essentially means to identify those structural properties of fractal aggregates which are measurable with DLS and to quantify the method’s sensitivity to changes in these properties. The investigations presented here are split up into four parts, simulations that establish a relation between structural and hydrodynamic properties, experiments validating the simulation results, the characterization of concentrated suspensions and the application-oriented analysis of DLS data for specific industrially relevant measurement tasksDie Dynamische Lichtstreuung (DLS) ist eine Messmethode zur Größenbestimmung submikroner Partikel. Dabei wird primär die stochastische Bewegung der Teilchen (Diffusion) in Suspensionen und Emulsionen bewertet. Die Stokes-Einstein Gleichung, die das Verhältnis zwischen gemessenem Diffusionskoeffizienten und Partikelgröße wiedergibt, ist jedoch nur für kugelförmige Teilchen, die in sehr niedriger Konzentration vorliegen, gültig. In der vorliegenden Arbeit wird die dynamische Lichtstreuung zur Charakterisierung von Suspensionen pyrogener Kieselsäure eingesetzt. Diese besteht aus fraktalen Aggregaten, die wiederum aus versinterten aber meist kugelförmigen Primärpartikeln zusammengesetzt sind. Diese strukturellen Eigenschaften erschweren die Anwendbarkeit der DLS bzw. die Interpretation der Messergebnisse und verhinderten bisher den Einsatz der DLS als Routinemethode zur Charakterisierung pyrogener Kieselsäuren. Das Hauptziel dieser Arbeit ist daher eine Bewertung der Möglichkeiten der DLS für die Produktentwicklung und Qualitätssicherung in der Herstellung pyrogener Kieselsäuren. Das bedeutet im Besonderen, dass sowohl die messbaren granulometrischen Eigenschaften als auch die Sensitivität der Methode bei Eigenschaftsänderungen ermittelt werden müssen. Die hier durchgeführten Arbeiten sind in vier Teile gegliedert: Simulationen, die eine Beziehung zwischen strukturellen und hydrodynamischen Eigenschaften herstellen, Experimente zur Validierung der Simulationsergebnisse, die Charakterisierung konzentrierter Suspensionen und die anwendungsorientierte Auswertung von DLS-Daten für spezifische industrierelevante Messaufgaben
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Welsch, Janina. "Pyrogene Wirkung von mycoplasmalen Lipopeptiden und bakteriellem Endotoxin bei Toll like Rezeptor-2-defizienten Mäusen und bei CD36-defizienten spontan hypertensiven Ratten." Giessen VVB Laufersweiler, 2010. http://geb.uni-giessen.de/geb/volltexte/2010/7430/index.html.
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Sandin, Emma. "Optimization of the In vitro Pyrogen Test (IPT) Regarding Detection of Pyrogens in Air Samples." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54297.
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Pyrogens are substances that may induce fever in the human body. They can be parts of bacteria, virus or fungi and due to the reaction they may cause in the body, they are routinely looked for in the medical technology industries. A method called in vitro pyrogen test (IPT) has been developed to detect these pyrogens. It is based on the fever reaction in the human body and only requires blood in combination with a solution believed to contain pyrogens. If the result is positive, the production of cytokines is started. The cytokines of interest in the IPT method are those involved in the fever process and two of them are IL-1β and TNF-α, which are the cytokines used as markers of infection in this study. Since the production of cytokines is in proportion to the amount of pyrogens, the inflammation-inducing potential of the sample can be decided. Due to problems in standardizing the method, mainly because it handles with living blood cells, focus is still pointed at improving it. The aim of this study was to optimize parameters within the IPT method by analysing air samples taken in indoor surroundings believed to contain pyrogens. The different parameters included extraction of the filter from the air sampling, incubation of whole blood and sample extract and analysis of the incubation with ELISA (enzyme linked immunosorbent assay). More specific, some of the issues concerned extraction media, time and shaking intensity for the extraction, blood ratio for the whole blood incubation and cytokines suitable for the method. A possible approach for the IPT method, when analysing air samples containing pyrogens, was reached.Pyrogener kallas ämnen som framkallar feber och de kan exempelvis bestå av hela eller delar av bakterier, virus eller svamp (fungi). En metod som kallas för in vitro pyrogen test (IPT) har utvecklats för att detektera dessa pyrogener. Metoden bygger på att en lösning som misstänks innehålla pyrogener får komma i kontakt med blod från en människa. Efter en inkubering på mellan 4-24 timmar har blodet reagerat på eventuella pyrogener och bildat cytokiner, där mängden cytokiner är proportionell mot mängden pyrogener. De intressanta cytokinerna i den här studien var IL-1β och TNF-α, som båda är involverade i feberprocessen. Det har varit svårigheter med att standardisera metoden, mycket beroende på att det är levande celler som hela metoden bygger på, så syftet med den här studien var att förbättra in vitro pyrogen test. Luftprover tagna i inomhusmiljöer som misstänks innehålla pyrogener har använts i försöken att optimera varje steg i processen. De olika stegen inkluderade extraktion av filter som använts vid luftprovtagningen, inkubering med helblod och provextrakt och analys av inkuberingen med ELISA (enzyme linked immunosorbent assay). Några av de parametrar som undersöktes gällde extraktionsmedium, skaktid och skakintensitet under extraktionen, blodförhållande under helblodsinkuberingen och lämpliga cytokiner för metoden. Studien resulterade i att en metodik, för att analysera luftprov innehållande pyrogener med in vitro pyrogen test, kunde tas fram.
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Welsch, Janina [Verfasser]. "Pyrogene Wirkung von mycoplasmalen Lipopeptiden und bakteriellem Endotoxin bei Toll-like-Rezeptor-2-defizienten Mäusen und bei CD36-defizienten spontan hypertensiven Ratten / eingereicht von Janina Welsch." Giessen : VVB Laufersweiler, 2010. http://d-nb.info/100187997X/34.
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FUKUMORI, NEUZA T. O. "Determinação de endotoxina bacteriana (pirogênio) em radiofármacos pelo método de formação de gel. Validação." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11606.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Bowen, Jenna Louise. "Detection of lipopolysaccharide pyrogens by molecularly imprinted polymers." Thesis, Cardiff University, 2011. http://orca.cf.ac.uk/54444/.
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Lipopolysaccharide (LPS) is commonly implicated in the development and rapid progression of sepsis however no efficient diagnostic assay currently exists. The over-arching aim of this project was therefore to develop a novel biomimetic peptide-polymer hybrid system capable of recognising and binding LPS in a variety of biologically relevant environments. Target selective peptides (both commercially available and synthesised) have been used as high affinity 'functional monomers' in a molecular imprinting approach. To reduce the concept to practice, a bi-functionalised resin was prepared so as to allow the use of two independent surface attachment strategies. Controlled polymer growth was initiated from surface bound iniferter groups whilst the attachment of the peptide was achieved through amme-amine imidoester linkages or via azide-alkyne "click" chemistry. Polymyxin, a small, conformationally constrained cyclic peptide that possesses high affinity for lipopolysaccharide (LPS) was used to provide proof-of-principle. Polymyxin resins, produced via the immobilisation of alkyne derivitised polymyxin B on the surface of azidomethyl polystyrene via "click" chemistry, were able to efficiently bind LPS from aqueous solutions with an apparent Ka of 0.2 μM. Although the development of the peptide-polymer hybrid system using these resins appeared somewhat unsuccessful, whether the observed reduction in binding is due to changes in the Bmax or the Kd of the resin remains to be elucidated. The assay performed with the polymerisation samples produced using resin displaying polymyxin immobilised via a dimethyl adipimidate linker, suggest that the hypothesised approach is feasible but that optimisation of a number of variables is needed before definitive results can be obtained.
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Oyewo, E. A. "A study of exogenous and endogenous pyrogens in malaria fever." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377667.
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Sagay, B. O. "Some biological effects and pharmacology of Interleukin-1/endogenous pyrogen." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233196.
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Fukumori, Neuza Taeko Okasaki. "Determinação de endotoxina bacteriana (pirogênio) em radiofármacos pelo método de formação de gel. Validação." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-13102011-144714/.
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Antes do Ensaio do Lisado de Amebócitos do Limulus (LAL), a única forma de se avaliar a pirogenicidade em drogas parenterais e dispositivos médicos era o ensaio de pirogênio em coelhos da Farmacopéia Americana (USP). Especialmente para radiofármacos, o ensaio LAL é a escolha para a determinação de endotoxina bacteriana (pirogênio). O objetivo deste trabalho foi validar o método de formação de gel para alguns radiofármacos sem uma interferência mensurável. O guia do método LAL do Food and Drug Administration (FDA) define interferência como uma condição que causa uma diferença significativa entre os pontos finais de gelificação das séries de controle positivo da água e controle positivo do produto utilizando-se um endotoxina padrão. Os experimentos foram realizados de acordo com o teste de endotoxinas bacterianas da USP na m-iodobenzilguanidina-131I, nos radioisótopos Gálio-67 e Tálio-201, nos reagentes liofilizados DTPA, Fitato, GHA, SAH e Sn Coloidal. A Máxima Diluição Válida (MDV) foi calculada para cada produto com base na sua dose clínica e diluições seriadas abaixo da MDV foram avaliadas em duplicata para a detecção de interferências. A sensibilidade declarada do reagente de LAL foi de 0,125 UE mL-1 (Unidades de Endotoxina por mililitro). Para a validação, uma série de diluições foi feita utilizando-se padrão de endotoxina (PE) nas concentrações de 0,5 a 0,03 UE mL-1 para a confirmação da sensibilidade do reagente de LAL, em quadruplicata. A mesma série de diluições foi feita com o PE e o produto diluído 100 vezes em três lotes consecutivos de cada radiofármaco. Os produtos m-iodobenzilguanidina-131I, Gálio-67, Tálio-201, DTPA, SAH e Sn Coloidal foram compatíveis com o método no fator de diluição 1:100. Fitato e GHA apresentaram interferência no ensaio de formação de gel. Outras técnicas para determinar endotoxinas como o ensaio cromogênico (desenvolvimento de cor) e o turbidimétrico (desenvolvimento de turbidez) foram avaliadas para obter informações qualitativas e quantitativas sobre as concentrações de endotoxinas nas amostras.Before the Limulus amebocyte lysate (LAL) test, the only available means of pirogenicity testing for parenteral drugs and medical devices was the United States Pharmacopoeia (USP) rabbit pyrogen test. Especially for radiopharmaceuticals, the LAL assay is the elective way to determine bacterial endotoxin. The aim of this work was to validate the gel clot method for some radiopharmaceuticals without measurable interference. The FDAs LALTest guideline defines interference as a condition that causes a significant difference between the endpoints of a positive water control and positive product control series using a standard endotoxin. Experiments were performed in accordance to the USP bacterial endotoxins test in the 131I- m-iodobenzylguanidine; the radioisotopes Gallium-67 and Thallium-201; the liophylized reagents DTPA, Phytate, GHA, HSA and Colloidal Tin. The Maximum Valid Dilution (MVD) was calculated for each product based upon the clinical dose of the material and a twofold serial dilution below the MVD was performed in duplicate to detect interferences. The labeled sensitivity of the used LAL reagent was 0.125 EU mL-1 (Endotoxin Units per milliliter). For validation, a dilution series was performed, a twofold dilution of control standard endotoxin (CSE) from 0.5 to 0.03 EU mL-1, to confirm the labeled sensitivity of the LAL reagent being tested in sterile and non pyrogenic water, in quadruplicate. The same dilution series was performed with the CSE and the product in the 1:100 dilution factor, in three consecutive batches of each radiopharmaceutical. The products 131I-m-iodobenzylguanidine, Gallium-67, Thallium-201, DTPA, HSA and Colloidal Tin were found compatible with the LAL test at a 1:100 dilution factor. Phytate and GHA showed some interference in the gel clot test. Other techniques to determine endotoxins as the chromogenic (color development) and the turbidimetric test (turbidity development), were also assessed to get valuable quantitative and qualitative information about the endotoxin concentration in samples.
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Smith, Jennifer Ann. "The fibrinogen-binding site on streptococcus pyrogenes type 5 M protein." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389577.
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Christ-Kohlrausch, Friederike. "Unterschiede im Transfer von Zytokininduzierenden Substanzen (CIS) über High-Flux Dialyse Membranen /." Berlin : Grauer Verl, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014908426&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Daneshian, Mardas. "Detection and characterization of the detection and characterization of the immunostimulatory properties of airborne pyrogens." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-23677.
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Eliason, Heather L. "The influence of pregnancy on the febrile response to pyrogens in rats." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ34671.pdf.
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Charlton, Fraser Graham. "Structure-function relationships of streptococcal pyrogenic exotoxin A." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285321.
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Greis, Andrea. "Charakterisierung der pyrogenen Eigenschaften des Fibroblasten-stimulierenden Lipopeptids-1 (FSL-1) beim Meerschweinchen." Giessen : VVB Laufersweiler, 2007. http://geb.uni-giessen.de/geb/volltexte/2007/4756/index.html.
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Greis, Andrea [Verfasser]. "Charakterisierung der pyrogenen Eigenschaften des Fibroblasten-stimulierenden Lipopeptids-1 (FSL-1) beim Meerschweinchen / eingereicht von Andrea Greis." Giessen : VVB Laufersweiler, 2007. http://d-nb.info/988716267/34.
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Flesch, Jürgen [Verfasser]. "Untersuchungen zu den Gleichgewichten und zur Reaktionskinetik bei der Entsäuerung pyrogener Kieselsäuren in der Wirbelschicht / Jürgen Flesch." Aachen : Shaker, 2005. http://d-nb.info/1186587989/34.
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Abul, Habib T. "Interaction of steroidal and non-steroidal anti-inflammatory agents with pyrogenic immunomodulators." Thesis, University of Aberdeen, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305321.
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The objective of the study was to investigate the possibility that the synthetic glucocorticoid analogue, dexamethasone was antipyretic. In addition, the possible involvement of peripheral PGE2 during fever and the mechanism by which ketoprofen, dexamethasone and the neuropeptide ACTH1-24 interact with fever in response to pyrogenic immunomodulators such as Poly I:C, LPS and IL-1/EP and their effect on PGE2 biosynthesis both in vivo and in vitro in the rabbit was also investigated. The febrile response was measured as changes in rectal temperatures and CSF levels of PGE2 were estimated by collecting samples from the third cerebral ventricle by using a push-pull perfusion system. PGE2 release was also measured in vitro from rabbit monocytes prepared by Percoll density gradient centrifugation. PGE2 was estimated by RIA. Ketoprofen (3 mg/Kg s.c.) administered prior to or after the onset of fever completely inhibited the febrile response to all pyrogens. Dexamethasone (1 mg/kg i.v.) attenuated the febrile response to Poly I:C (5 μ g/Kg i.v.) but only if administered between 0.5 - 2 hours before Poly I:C and a maximum effect was observed with 3 mg/Kg. Fever in response to LPS (50 - 200 ng/Kg i.v.), IL-1/EP (50 μl/animal = 5 x 108 cell equivalents i.v.), TNF (15 μg/animal i.v.) or Poly I:C (5 μg i.c.v.) was also attenuated by pretreatment for 1 hour with dexamethasone. ACTH1-24 (1 - 10 μg/Kg i.v.) produced a dose-related hypothermia at an ambient temperature of 22 ± 2oC. A non-hypothermic dose of ACTH1-24 (5 μg/Kg i.v.) significantly reduced the febrile response to Poly I:C (5 μg/Kg i.v.) or IL-1/EP (50 μl/animal i.v.). Poly I:C, LPS and IL-1/EP administered i.v. were found to produce a significant increase in the plasma PGE_2 level (in order of 6 - 8 fold) which occurred simultaneously with the rise in body temperature. Ketoprofen (3 mg/Kg s.c.) abolished both the rise in body temperature and the increase in plasma PGE_2 level. Dexamethasone (3 mg/Kg i.v.) pretreatment (1 hour) attenuated the pyrogen-stimulated increase in both parameters. If dexamethasone was administered after the onset of fever in response to Poly I:C, it potentiated both the increase in body temperature and plasma PGE_2. ACTH_1-24 (5 μg/Kg i.v.) significantly reduced the febrile response to Poly I:C and IL-1/EP but had no effect on plasma PGE2 levels. Poly I:C and IL-1/EP increased the amount of PGE2 detected in the perfusate collected from the third cerebral ventricle. The increase was in the order of 2 - 4 fold compared with control levels which parallelled the increase in body temperature. Ketoprofen abolished the fever and the increase in CSF PGE2 level. Dexamethasone also significantly attenuated the febrile response and reduced the amount of PGE2 in the CSF perfusate. Experiments were also carried out on rabbit monocytes in vitro. Poly I:C, LPS and IL-1/EP all increased the concentration of PGE2 in culture supernatants. Ketoprofen and dexamethasone significantly reduced pyrogen-stimulated release of PGE2, but ACTH1-24 had no effect. The protein synthesis inhibitor anisomycin reduced Poly I:C and LPS-stimulated release of PGE2 but had no effect on IL-1/EP-stimulated release of PGE2. In addition, anisomycin antagonised the inhibitory effect of dexamethasone on the PGE2 released from monocytes in the presence of IL-1/EP. These results suggest that the increase in plasma PGE2 levels in response to the pyrogenic agents may contribute to their pyrogenicity. In addition, the antipyretic actions of dexamethasone and ketoprofen may involve a reduction in circulating levels of PGE2 and this action of dexamethasone may occur via the induction of a protein intermediate possibly the PLA2 inhibitory protein, lipocortin.
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Gatley, Joan Marguerite. "The prevalence of Leptospira serovars causing infection in dogs in South Africa." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/27119.
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Leptospirosis is a disease of global importance with a changing epidemiology in both humans and animals. It is also a significant zoonosis particularly in the developing world. To date there is limited knowledge of the incidence of leptospirosis in dogs in South Africa. This study was undertaken on a subset of dogs in South Africa to determine the presence of leptospiral antibodies to serovars known to infect dogs. Serum samples from both stray and owned dogs from various parts of South Africa were collected and tested against fifteen serovars of Leptospira. Five hundred and thirty samples were tested and twenty-five tested positive to seven different serovars. Nine of the 25 samples tested positive to more than one serovar. The two serovars that were most frequently represented were L. Canicola, which reacted to seventeen sera, and L. Pyrogenes, which reacted to nine sera in all. Currently the only vaccines available in South Africa in different combinations contain either L. Canicola, L. Icterohaemorrhagiae, L. Pomona or L. Grippotyphosa. The results show that the use of vaccines containing L. Canicola is still justifiable in certain regions of the country. However, the presence of antibodies to L. Pyrogenes in several dogs indicates that there is a need to investigate for the presence of antibodies in a larger group of dogs. This would allow vaccine manufacturers to tailor the Leptospira antigens present in vaccines to include those that are prevalent in a particular region or country. CopyrightDissertation (MSc)--University of Pretoria, 2009.
Veterinary Tropical Diseases
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Bugnicourt, Elodie Gérard Jean-François Galy Jocelyne. "Development of sub-micro structured composites based on an epoxy matrix and pyrogenic silica." Villeurbanne : Doc'INSA, 2006. http://docinsa.insa-lyon.fr/these/pont.php?id=bugnicourt.
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Essery, Stephen D. "Studies on the role of the pyrogenic staphylococcal toxins in sudden infant death syndrome." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/21229.
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The aim of this study was to examine how infection might play a role in SIDS in relation to developmental and environmental risk factors identified in epidemiological studies by examining the binding of bacterial toxins to human cells and their effects, singly and in combination on induction of inflammatory mediators. There is a correlation between the incidence of SIDS, isolation of Staphylococcus aureus and expression of the Lewisa blood group antigen in the 2 to 4 month age range. Lewisa has previously been shown to act as a surface receptor for certain bacteria on human epithelial cells, the first stage of this study was to develop a screening method to detect adhesions that bind Lewisa on toxigenic strains of S. aureus and other bacteria isolated from SIDS infants. Additional experiments indicated that some of the superantigenic toxins of S. aureus utilise this antigen as a receptor on monocytes and are capable of stimulating the production of inflammatory mediators from these cells. The pertussis toxin of B. pertussis is capable of binding to Lewisa and Lewisx and it has been suggested that asymptomatic whooping is one cause of SIDS. Changes in the age range of SIDS infants were observed between 1988 and 1994, after the DPT immunisation schedule was changed from 3 months to 2 months of age in October 1990. The protective effect of DPT immunisation suggested in several large epidemiological studies was examined with reference to antigenic cross reactivity between the DPT vaccine and the staphylococcal toxins. Results obtained in enzyme linked immunosorbent assays (ELISA) indicated that antibodies cross-reactive with the staphylococcal toxins were produced by rabbits in response to DPT immunisation. Assays for nitric oxide production by human monocytes in response to the toxins indicated that the antibodies were able to neutralise partially some of the inflammatory activities of the toxins.
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Nakamura, Yoshiko. "Direct pyrogenic input from prostaglandin EP3 receptor-expressing preoptic neurons to the dorsomedial hypothalamus." Kyoto University, 2007. http://hdl.handle.net/2433/135896.
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Hayes, Katherine. "Fire History and Soil Carbon in Old Growth Coast Redwood Forests across the Late Holocene." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23746.
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Fire is an important ecological feature across temperate forests, yet characteristics of the coast redwood fire regime remain uncertain due to generally few fire histories. This study examines legacies of fire in redwood forests in northern California through radiocarbon dating and quantification of soil macro-charcoal, soil carbon and pyrogenic carbon in old growth redwood stands. We sampled soils in the Headwaters Forest Reserve, a protected fragment of old growth redwood in Humboldt County, California. Radiocarbon dates from macro-charcoal indicate fire events occurring a maximum of 6,840 calibrated years BP, predating existing records. Composite 14C dates show increased fire activity within the last 1,000 years in synchrony with existing dendrochronological records. Soil C averaged 928 g/m2, of which a high proportion was pyrogenic C (15-30%). Information from this multi-proxy reconstruction clarifies our understanding of the nature of coast redwood fires, contributing to ongoing discussions of coast redwood fire management.
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Sriskandan, Shiranee. "A study of the superantigen streptococcal pyrogenic exotoxin A in invasive group A streptococcal disease." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266009.
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Fourmentin, Aymeric. "Revêtements polyuréthane-acrylate organiques/inorganiques superhydrophobes." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI096/document.
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Ce travail de thèse a porté sur le développement de revêtements organiques/inorganiques photopolymérisables superhydrophobes à partir de procédés d’élaboration simples associés à des produits commerciaux largement diffusés. Pour cela, des revêtements à matrice polyuréthane acrylate (PUA), intrinsèquement hydrophiles, incluant différents composés à base de silicium ont été élaborés par enduction ou pulvérisation. L’objectif a été d’apporter en surface des revêtements une structuration multi-échelle et une chimie à caractère hydrophobe nécessaires pour atteindre la superhydrophobie, c’est-à-dire un angle de contact avec l’eau supérieur à 150° et une hystérésis de mouillage inférieure à 10°. L’introduction de molécules de polysilsesquioxane polyédrique (POSS), présentant un ligand acrylate et sept ligands isobutyle, a apporté une nanostructuration et un comportement hydrophobe aux revêtements PUA à des concentrations très faibles (≤ 1% en masse.). Cependant, la rugosité apportée se révèle trop faible et cette stratégie ne peut aboutir à la superhydrophobie des revêtements. L’introduction de particules de silice pyrogénée, modifiées en surface par des chaînes polydiméthylsiloxane, a permis d’établir une structuration multi-échelle et une chimie à caractère hydrophobe à la surface des revêtements PUA, leur conférant ainsi la superhydrophobie. De plus, le procédé d’élaboration a joué un rôle majeur sur les modifications physico-chimiques de surface des revêtements : la superhydrophobie est obtenue à une concentration relativement élevée de 30 et 60% en masse de silice pyrogénée respectivement par pulvérisation et enduction. Afin de diminuer ces concentrations, la combinaison des deux stratégies précédentes, c’est-à-dire l’introduction simultanée de POSS et de silice pyrogénée, a été considérée. Ceci a permis d’exacerber le caractère hydrophobe des revêtements tout en préservant la rugosité établie par la silice pyrogénée. Cette approche a conduit à la diminution de la concentration de silice nécessaire pour obtenir la superhydrophobie dans le cas des revêtements élaborés par pulvérisationThis work deals with the development of organic/inorganic superhydrophobic UV-curable coatings manufactured through simple processes and from commercially available products. To achieve this goal, a hydrophilic polyurethane acrylate matrix (PUA) was used, in which several silicon-based compounds were introduced. The coatings were deposited using either bar- or spray-coating. The main objective was to structure the surface thanks to a multiscale roughness, while bringing a hydrophobic character, two properties needed to obtain a superhydrophobic coating (defined by a water contact angle superior to 150° and a water contact angle hysteresis inferior to 10°). The introduction of polyhedral oligomeric silsesquioxane molecules (POSS), presenting one acrylate and seven isobutyl ligands, brought a nanostructuration and a hydrophobic behavior to PUA coatings, even at low concentrations (≤ 1%wt.). However, the roughness obtained was not sufficient to bring the superhydrophobicity to the coatings.The introduction of fumed silica particles, functionalized by PDMS chains, established multiscale roughness and hydrophobic behavior at the surface, leading to superhydrophobic coatings. Moreover, the process had a high influence on physico-chemical modifications at the coatings’surface: superhydrophobicity is obtained for a relatively high concentration of fumed silica, 30%wt. and 60%wt. respectively for spray and bar-coating. In order to decrease these concentrations, we tried the combination of the two previous strategies: introduction of POSS molecules and fumed silica particles. This path raised the hydrophobic behavior of the coatings while keeping intact the roughness brought by fumed silica particles. This approach allowed to decrease the silica concentration needed to obtain superhydrophobicity for spray-coated coatings
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Kätzel, Uwe. "Dynamic Light Scattering for the Characterization of Polydisperse Fractal Systems by the Example of Pyrogenic Silica." [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1197634640783-66357.
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Wilkinson, Marshall Frederick. "A vasopressinergic pathway within the brain and its role in drug-induced antipyresis and pyrogenic tolerance." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31414.
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There is strong evidence which supports a physiological role for arginine vasopressin (AVP) in the negative modulation of the febrile process within the central nervous system (CNS). This evidence arises from a variety of experimental techniques employed in a number of different animal models. The CNS locus of action for AVP-mediated antipyresis is within a rostral diencephalic site called the ventral septal area (VSA). It has become evident that the mechanism by which AVP and aspirin-like drugs transduce changes in febrile body temperature are similar. Moreover, antipyretic drugs and AVP may share a common CNS locus of action. Therefore, investigations were conducted to determine whether antipyretic drugs are functionally linked to the endogenous antipyretic system of the brain. In addition, an examination of the role for centrally acting AVP and the natural suppression of fever during pyrogenic tolerance to endotoxin was conducted.
AVP receptor antagonists of the peripheral V₁ and V₂ sub-type or saline control were microinjected into the VSA of rats rendered febrile by an intracerebroventricular (icv) injection of E. coli endotoxin, to assess the effects on the antipyresis elicited by indomethacin. Blockade of central V₁ but not V₂ receptors significantly attenuated the antipyretic effects of indomethacin given intraperitoneally. This effect was even more pronounced when the V₁ antagonist was infused for 30 min before and for 60 min after indomethacin administration. The V₁ analogue alone was without thermoregulatory effects.
In order to determine whether the above effects were applicable to antipyretic drugs in general, central V₁ blockade was performed in the febrile rat subsequently treated with intraperitoneal sodium salicylate or acetaminophen. Salicylate-induced antipyresis was blocked, in a dose related manner, by VSA administration of the AVP V₁ antagonist. The fever reducing capacity of acetaminophen was unaffected by central V₁ blockade. Collectively these antipyretic drug studies, suggest that some but not all antipyretic drugs activate the endogenous AVP antipyretic pathway within the brain. Moreover, these data suggest that the mechanism of action of antipyretic drugs can no longer be simply explained as an action on prostaglandin biosynthesis.
Endogenous release of AVP from VSA nerve terminals during endotoxin fever and drug-induced antipyresis was examined using the technique of push-pull perfusion. The release of AVP into the perfusion fluid remained unaltered by indomethacin injected into the non-febrile rat. However, during fever indomethacin prompted both an antipyresis as well as a significant increase in AVP release. Acetaminophen injected intraperitoneally also evoked an antipyresis but with no concomitant release of AVP within the VSA. These results are consistent with the antagonist studies.
The effects on central AVP release by indomethacin appear to be related to the pyrogen employed because the drug did not evoke the release of AVP when administered prior to the hyperthermia produced by icv PGE₂. Indeed, PGE₂ itself stimulated AVP release which was inhibited by indomethacin treatment. These results are not consistent with an antipyretic role for AVP and await further clarification.
Analysis of the release of AVP into the plasma and cerebrospinal fluid (CSF) were conducted during the fever evoked by intravenous endotoxin and subsequent to antipyretic intervention. Intravenous endotoxin was a provocative stimulus for plasma AVP release. Endotoxin-stimulated plasma AVP levels were unaffected by intraperitoneal injections of indomethacin, sodium salicylate or acetaminophen. In non-febrile controls, indomethacin, and to some extent acetaminophen, prompted increases in plasma AVP; although the temporal course of this release was different between the two drugs. Within the CSF, endotoxin treatment did not alter the normal diurnal rhythm of AVP release. Indomethacin treatment significantly suppressed CSF AVP release in non-febrile animals. A similar but non-significant trend was observed in febrile rats. Collectively, these studies demonstrate the independent regulation of AVP release within three separate biological compartments in response to febrogenic and antipyretic stimuli.
The suppression of fever after repeated daily intravenous injections of bacterial endotoxins was thought to be exclusively a hepatic phenomenon. Experiments were conducted to determine whether a central mechanism involving AVP may also contribute to the antipyretic state observed during pyrogenic tolerance. In endotoxin tolerant animals, administration of a V₁ but not V₂ AVP receptor antagonist within the VSA, resulted in a significant reversal of the tolerant pyrogenic response. These data support the hypothesis that the central endogenous antipyretic system, involving AVP, plays a role in the mechanism of endotoxin tolerance.
Tolerance does not develop following repeated central injections of pyrogens. Further experiments were performed to determine whether tolerance-induced activation of the antipyretic pathway would render an animal hyporesponsive to centrally administered pyrogens. When injected icv, during active endotoxin tolerance, the thermoregulatory responses to PGE₂ or endotoxin were not significantly suppressed from non-tolerant controls. However, analysis of VSA push-pull perfusates performed during a tolerant reaction to intravenous endotoxin revealed that increased AVP activity occurs within the first 30 min after the intravenous injection, well before the time PGE₂ or endotoxin were injected into the cerebral ventricles. This suggests that the antipyretic system is only activated briefly and may explain why centrally evoked fevers were unaffected during active endotoxin tolerance.
In summary, this thesis research has demonstrated a direct functional link between the mechanism of action of antipyretic drugs and the endogenous antipyretic system within the brain. These results call into question the hypothesis whereby the fever reducing properties of antipyretic drugs can be explained exclusively as a result of the inhibition of prostaglandin biosynthesis. In addition, the differential effects on AVP release by antipyretic drugs suggests a number of biological pathways that can be activated by these drugs. Finally, a role for the AVP endogenous antiypretic system in the suppression of fever during endotoxin tolerance was established.Medicine, Faculty of
Cellular and Physiological Sciences, Department of
Graduate
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Schindler, Stefanie [Verfasser]. "The use of species specific ELISAs and bioassays for the purpose of detecting pyrogenic contaminations / vorgelegt von Stefanie Schindler." Berlin : Mensch-und-Buch-Verl, 2006. http://d-nb.info/97923509X/34.
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McClean, Gary James. "Impact of land-use change for lignocellulosic biomass crop production on soil organic carbon stocks in Britain." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/19568.
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The contribution of energy from biomass sources is projected to increase in Britain to assist in meeting renewable energy targets and reducing anthropogenic CO2 emissions. With increasing concerns over the sustainability of food crop-based biofuels, purpose-grown lignocellulosic biomass crops such as Miscanthus and short rotation coppice (SRC) willow have been promoted as more sustainable feedstocks for the production of heat and electricity as well as for the future production of liquid biofuels. With the introduction of the Energy Crops Scheme, land-use change (LUC) for lignocellulosic biomass crop production has become increasingly common in Britain in recent decades. However, there is limited understanding of the impact this has on soil organic carbon (SOC) stocks and limited predictability concerning the overall trajectory, magnitude and rate of SOC changes under a range of different conditions. Using a chronosequence of 93 biomass crop plantations in England and Wales, mainly of 1 to 14 years age, empirical models were developed to determine the short term trajectory of SOC stocks following LUC from arable and grassland to SRC willow and Miscanthus production. SOC stocks were calculated for each site using a fixed sampling depth of 30 cm and estimated changes were inferred by comparing with typical pre-change SOC stocks. These results indicate that only LUC from arable crops to SRC willow demonstrated an overall increase in SOC stocks, by an estimated 15.3 ± 2.2 t C ha-1 (± 95% confidence intervals) after 14 years and 68.8 ± 49.4 t C ha-1 after 22 years. LUC from arable crops to Miscanthus and from both arable crops and grassland to SRC willow and Miscanthus demonstrated no overall net effect on SOC stocks. Soil texture and climate data were measured for each site and multivariable models were created to assess the influence of different environmental conditions on SOC trajectory. In most cases the addition of these explanatory variables improved the model fit, and the models provide some preliminary estimates of more region-specific changes in SOC following LUC. Since LUC to biomass crops often causes a loss of SOC, at least in the short term, the potential for pyrogenic carbon (PyC) to ameliorate this effect was investigated. Studies indicate that PyC can interact with and stabilise native SOC, a process termed negative priming, although the potential for PyC to reduce LUC-induced losses of SOC by negative priming has not yet been assessed. Although negative priming has been observed in many studies, most of these are long term incubation experiments which do not account for the impact of environmental weathering of PyC on interactions with native SOC. Here the aim was to assess the impact of environmentally weathered PyC on native SOC mineralisation at different points in LUC from arable crops to SRC willow. Soil was sampled to a 5 cm depth from multiple recently established SRC willow plantations approximately 2 years after amendment with PyC. Cumulative CO2 flux was measured weekly from incubated soil and soil-surface CO2 flux was also measured in the field. The results demonstrate a PyC-induced increase in CO2 flux for the surface 5 cm of soil. However, no net effect on soil-surface CO2 flux was observed in the field. Although the mechanisms for these contrasting effects remain unclear, they do not suggest that PyC can reduce LUC-induced SOC losses through negative priming.
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Gauduchon, Françoise. "Production in situ de liquide pour le traitement de l'insuffisance rénale chronique : application à la préparation de poches de D.P.C.A." Compiègne, 1987. http://www.theses.fr/1987COMPI254.
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Les critères requis pour les bains d'hémodialyse, liquides d'hémofiltration et de dialyse péritonéale sont recensées dans une étude bibliographique détaillée. Le problème des pyrogènes est plus particulièrement approfondi. Les divers modes de purification de l'eau pour dialyse sont présentés. La partie expérimentale porte sur la mise au point et l'évaluation d'un procédé de préparation extemporanée in situ de poches de D. P. C. A. (Dialyse Péritonéale Continue Ambulatoire). Des poches de liquide stérile et apyrogène ont été produites et stockées. La conformité aux normes a été vérifiée dans l'ensemble sur le pan de la formation et des éléménts indésirables. Mais il subsiste quelques questions au niveau de la stabilité du pH et de la présence de nitrates et de sous-produits de glucose. Les résultats obtenus démontrent la faisabilité d'un tel procédé et la conception d'une machine spéciale fonctionnant sur cette base peut-être à présent envisagée avec succès sur le plan technologique.
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Bobak, Deanna M. "Polycyclic Aromatic Hydrocarbon Characterization in Otter Creek, Northwest Ohio." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271441527.
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Hilscher, André [Verfasser], Heike E. [Akademischer Betreuer] Knicker, Jörg [Akademischer Betreuer] Völkel, and Christian [Akademischer Betreuer] Siewert. "Degradation, chemical alteration and stabilisation of pyrogenic plant residues in soil / André Hilscher. Gutachter: Heike E. Knicker ; Jörg Völkel ; Christian Siewert. Betreuer: Heike E. Knicker." München : Universitätsbibliothek der TU München, 2011. http://d-nb.info/1014329604/34.
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Gandhi, Kamal Jit Kaur. "The importance of fire-skips as biotic refugia and the influence of forest heterogeneity on epigaeic beetles in pyrogenic stands of the northern Rocky Mountains." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ47034.pdf.
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Bugnicourt, Elodie. "Development of sub-micro structured composites based on an epoxy matrix and pyrogenic silica : mechanical behavior related to the interactions and morphology at multi-scale." Lyon, INSA, 2005. http://theses.insa-lyon.fr/publication/2005ISAL0113/these.pdf.
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Epoxy networks are known to present insufficient mechanical properties for certain applications, especially due to their brittleness. This work was aimed at developing novel composites based on an epoxy matrix and pyrogenic silica in order to enhance mechanical properties of epoxys for applications such as coatings, adhesives or structural materials. Pyrogenic silica has been extensively used in order to reinforce rubbers and for rheological modifications, but only few studies deal with the addition of fumed silica into thermosetting polymers. Unlike conventional additives (organic modifiers or micro-fillers), sub-micronic fillers generally allow increasing both the toughness and the stiffness of polymeric materials, trend also checked in this work in case of fumed silica. In this study, the natures of epoxy-amine comonomers generating the matrix, as well as those of silica surface modification were varied in order to design finely the interactions developed in the system (covalent bonding vs. Physical interactions) and investigate the influence of silica on networks both in the rubbery and glassy states at room temperature. One of the main challenges consisted in controlling silica dispersion state thanks to the optimization of the different steps of the processing. The morphology was characterized at multi-scale at various stages of the processing by complementary techniques. A particular attention was paid to the interactions effectively developed at the interface between the filler and the matrix. The mechanical behavior of the materials was investigated using mechanical dynamic analysis, tensile test and fracture measurements. The relationships between the structure and mechanical behavior of epoxy / pyrogenic silica composites were finally discussed in order to understand the reinforcement mechanisms involved. The effect of silica on the thermal behavior and fire resistance of epoxy networks was also characterizedLes réseaux époxys présentent des propriétés insuffisantes pour certaines applications, en particulier à cause de leur fragilité. L'objectif de ce travail était de développer des composites à matrice époxy-amine et charges de silice pyrogénée afin d'améliorer les propriétés mécaniques des époxys pour des utilisations comme revêtements, adhésifs ou matériaux de structure. La silice pyrogénée a été fréquemment employée pour renforcer des élastomères ou dans un but de modification rhéologique, mais peu d'études traitent de l'addition de silice pyrogénée dans des réseaux thermodurcissables. Contrairement aux additifs conventionnels (organiques ou micro-charges), les charges sub-microniques permettent généralement d'augmenter à la fois la rigidité et la ténacité des matériaux polymères, tendance qui a été vérifiée dans ce travail pour la silice pyrogénée. En faisant varier la nature des comonomères époxy-amine et de la modification chimique de la surface de la silice, la nature des interactions développées au sein du système a pu être modulée (liaisons covalentes vs. Interactions physiques) et l'influence de la silice pyrogénée a pu être étudiée à la fois sur des réseaux dans l'état caoutchoutique et vitreux à température ambiante. Un des principaux défis de cette étude était le contrôle de l'état de dispersion de la silice grâce à l'optimisation de chaque étape du procédé. Les morphologies ont été caractérisées à de multiples échelles tout au long de la mise en œuvre par diverses techniques complémentaires. Une attention particulière a été portée aux interactions effectivement développées entre les charges et la matrice. Le comportement mécanique des matériaux a été caractérisé par analyse mécanique dynamique, test de traction et mécanique de la rupture. Les relations entre la structure et le comportement mécanique des composites époxy / silice pyrogénée ont enfin été discutées afin de comprendre les mécanismes de renforcement impliqués. L'effet de la silice a également été investigué sur les propriétés thermiques et la résistance au feu des réseaux époxys
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Cannavan, Fabiana de Souza. "A estrutura e composição de comunidades microbianas (Bacteria e Archaea) em fragmentos de carvão pirogênico de Terra Preta de Índio da Amazônia Central." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/64/64133/tde-20092012-102334/.
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As Terras Pretas de Índio (TPI), também conhecida por Amazonian Dark Earth, apresentam horizonte A antrópico, elevado pH, nutrientes importantes para o crescimento das plantas, elevado teor de carvão pirogênico e intensa atividade biológica quando comparadas aos seus solos de origem. A comunidade microbiana do solo é essencial para o funcionamento dos ecossistemas, sendo fundamentais em processos de decomposição da matéria orgânica, na disponibilização de nutrientes para as plantas e na ciclagem de nutrientes. Este estudo teve como objetivo acessar as estruturas e composição das comunidades de Bacteria e Archaea em fragmentos de carvão pirogênico (provenientes de TPI), TPI e solo adjacente (ADJ) utilizando as técnicas moleculares. Os solos foram coletados em quatro sítios arqueológicos (Balbina, Barro Branco, Costa do Açutuba e Hatahara), localizados na Amazônia Central. Em geral, as TPIs apresentaram elevados valores de pH, P e Ca corroborando com resultados anteriores em TPIs. As amostras de TPI dos sítios Balbina, Barro Branco e Hatahara apresentaram maior número de cópias do gene 16S rRNA de Bacteria quando comparadas com as amostras de solo ADJ. Os resultados obtidos pelas técnicas de fingerprinting (Terminal Restriction Fragment Length Polymorphism - T-RFLP e Denaturing Gradient Gel Electrophoresis - DGGE) utilizando o gene 16S rRNA de Bacteria e Archaea revelaram que as estruturas das comunidades bacterianas em fragmentos de carvão apresentaram diferenças significativas quando comparados com os solos ADJ. A partir da técnica de pirosequenciamento, os filos Proteobacteria, Actinobacteria e Crenarchaeota apresentaram predominância nos fragmentos de carvão. Observou-se também que em fragmentos de carvão, os microorganismos encontrados podem estar diretamente relacionados aos ciclos do N e C. Além disso, a presença desses micro-organismos em fragmentos de carvão pode favorecer a microbiota do solo e, consequentemente, sua qualidade. Neste sentido, o carvão pode também servir como elemento de recuperação em ambientes degradados, agindo como condicionador do solo sendo esta uma alternativa promissora no manejo de solos agrícolas.Amazonian Dark Earth (ADE), also known as Terra Preta de Índio, present tropical A horizon, high pH, important nutrients for plant growth, high pyrogenic charcoal levels and intense biological activity when compared to its soil of origin. Soil microbial community is essential for ecosystem function, which is involved in fundamental processes such as the decomposition of organic matter, availability of nutrients to plants and the nutrient cycling. The objective of this study was to assess the structure and composition of bacterial and archaeal communities in fragments of pyrogenic charcoal (from ADE), ADE and adjacent soil (ADJ) using molecular techniques. The soils were collected in four archaeological sites (Balbina, Barro Branco, Costa do Açutuba and Hatahara), located in the central Amazon. In general, ADE presented high values of pH, P and Ca agreeing with previous results in ADE. ADE samples in Balbina, Barro Branco and Hatahara sites presented higher bacterial 16S rRNA gene copy number in comparison with ADJ soil samples. The results obtained with the fingerprinting techniques (Terminal Restriction Length Polymorphism, T-RFLP and Denaturing Gradient Gel Electrophoresis, DGGE) using the bacterial and archaeal 16S rRNA genes revealed that bacterial community structure in charcoal fragments differed significantly when compared to the ADJ soils. Using the pyrosequencing technique, the phyla Proteobacteria, Actinobacteria and Crenarchaeota were predominant in charcoal fragments. It was also observed that microorganisms from charcoal fragments may be directly related to the N and C cycles. Furthermore, the presence of these microorganisms in charcoal fragments may favor the soil microbiota and, consequently, its quality. In this context, pyrogenic charcoal can serve as an element to recover degraded areas acting as soil conditioner and a promising alternative to the management of agricultural soils.
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Crandall, Trevor William. "Wildfire in the West: How Megafires and Storm Events Affect Stream Chemistry and Nutrient Dynamics in Semi-Arid Watersheds." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8886.
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Climate change is causing larger wildfires and more extreme precipitation events throughout the world. As these ecological disturbances increasingly coincide, they are altering lateral fluxes of sediment, organic matter, and nutrients. Increased lateral flux of nutrients could exacerbate eutrophication and associated harmful algal blooms, and increased sediment and organic matter flux could degrade the water supply. Here, we report the immediate stream chemistry response of watersheds in central Utah (USA) that were affected by a megafire followed by an extreme precipitation event in 2018. The wildfires burned throughout the summer of 2018 until the remnants of Hurricane Rosa released torrential rain on the still smoldering, 610-km2 burn scar. To assess how these multiple stressors affected lateral material fluxes, we collected daily to hourly water samples at 10 stream locations starting immediately before the storm event until three weeks after it finished. We quantified suspended sediment, solute and nutrient concentrations, water isotopes, and the concentration, optical properties, and reactivity of dissolved organic matter. For all land-use types, the wildfire caused substantial increases in sediment concentration and flux, increasing total suspended sediment by over 20-fold, attributable to the loss of stabilizing vegetation and increased runoff. Unexpectedly, dissolved organic carbon (DOC) was 2.1-fold higher in burned watersheds, despite the decrease in plant and soil organic matter, and this DOC was 1.3-fold more biodegradable and 2.0-fold more photodegradable than in unburned watersheds based on 28-day light and dark incubations. However, nitrogen and phosphorus concentrations were higher in watersheds with high anthropogenic influences, regardless of burn status. Likewise, direct human land use had a greater effect than wildfire on runoff response, with rapid storm water signals in urban and agricultural areas and a slow arrival of storm water in unburned areas without direct human influence. These findings indicate how megafires and intense rainfall fundamentally increase short-term sediment flux and alter organic matter concentration and characteristics, confirming previous research. These fluxes of degradable dissolved and particulate organic matter could exert short-term pressure on ecosystems already fragmented by human infrastructure. However, in contrast with previous research, which overwhelming focuses on burned-unburned comparisons in pristine watersheds, we found that the presence of urban and agricultural activity exerted a much greater influence on nutrient status than the wildfire. This novel finding suggests that reducing nutrient fluxes from urban and agricultural areas could make ecosystems more resilient to megafire and extreme precipitation events. Together with reducing anthropogenic climate change to reduce the frequency and extent of large wildfires, improving nutrient management should be a priority in semi-arid regions such as Utah.
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Nedjari, Nabila. "Etude du vieillissement de silices pyrogéniques à taux d’humidité relative variables." Thesis, Mulhouse, 2012. http://www.theses.fr/2012MULH5111/document.
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Les silices pyrogéniques sont très utilisées comme charge pour les polysiloxanes mais elles sont l’un des principaux constituants des superisolants thermiques. Cependant, l’échelle nanométrique de ces silices et leur chimie de surface (groupes silanol) est également responsable de leur aptitude à adsorber la vapeur d’eau, ce qui a pour conséquence d’altérer leurs propriétés d’isolant thermique au cours du temps, notamment lors de leur stockage dans des conditions non contrôlées. Malgré son importance industrielle ce phénomène n’a fait l’objet dans la littérature que d’une seule étude assez limitée.En effet, initialement la surface de ces silices ne sont que partiellement hydroxylées et la présence de ponts siloxanes tendus, susceptibles de réagir avec l’eau va mener à une évolution de leurs propriétés de surface en présence d’humidité.Une première étude a porté sur les silices N20, T30 et T40 (Wacker Chemie AG) sont obtenues par combustion de SiCl4 dans un mélange air/H2, de surfaces spécifiques égales respectivement à 200, 300 et 400 m2/g. Elles ont été vieillies à température constante 22,5 ± 0,1 °C, dans une enceinte fermée, sous humidité relative (HR) contrôlée : 62, 75, 84, 92 et 100%.L'adsorption d'eau a été suivie par gravimétrie. La masse d’eau adsorbée, par unité de surface augmente à la fois avec HR et la surface spécifique. Cette augmentation qui peut atteindre près de 60% de la masse initiale pour une HR de 100%, est liée à l’augmentation de l’hydrophilie de la surface de la silice liée à la formation de nouveaux groupes silanol. Nous avons démontré que cette augmentation suit une cinétique du 1er ordre et que la constante cinétique passe par un maximum pour une RH égale à 84%.L’augmentation du nombre de silanol superficiels a été confirmée par leur dosage chimique. Leur densité superficielle augmente d’environ 50%, passant de 2,4 SiOH/nm2 à 3,6 SiOH/nm2 pour l’HR égale à 100%.La spectroscopie IR atteste clairement d’une diminution nette des silanol isolés au profit de silanol fortement liés par pont hydrogène. Les spectroscopies RMN du proton et du silicium confirment l’augmentation de la densité locale en groupes silanols.L’évolution des propriétés superficielles des silices vieillies environ 1000 h a été suivie par chromatographie inverse à dilution infinie (CGI-DI) et concentration finie (CGI-CF).La CGI-DI pratiquée avec des sondes alcanes linéaires et cycliques démontre que le vieillissement n’affecte que très faiblement tant la composante dispersive de l’énergie de surface que leur rugosité à l’échelle moléculaire, autrement dit qu’il ne modifie pas la morphologie de la surface. Notamment la rugosité superficielle des silices T30 et T40 n’est pas affectée.La variation de l’hétérogénéité superficielle avec le vieillissement a été déterminée, en termes de fonctions de distribution des énergies d’adsorption de l’isopropanol, par CGI-CF.Le processus de vieillissement conduit, comme attendu, à une augmentation de la composante de haute énergie liée à l'apparition de nouveaux groupes silanol par ouverture nucléophile des ponts siloxane. Le glissement du maximum de cette composante vers les hautes énergies montre la formation d’un nouveau type de silanol plus interactif par liaison hydrogène.Ces résultats confirment la réactivité des silices de combustion vis-à-vis de l'eau lorsqu’elles sont exposées à une humidité relative élevée. L'eau est chimisorbée sur la surface de la silice par une réaction d'ouverture des ponts siloxane. L'étude de l'influence de la variation de l'humidité relative, montre qu’il existe un seuil (HR50%) au-dessous duquel ces silices restent stables par rapport à la vapeur d'eau. [...]Pyrogenic silicas , produced by combustion of SiCl4 into a mixture hydrogene/air, are widely used as filler for polysiloxanes, but also as one of the main components of super-thermal insulating. However, the nanoscale of these silicas and surface chemistry (silanol groups) is also responsible for their ability to adsorb water vapour, which alters their insulation and reinforcement properties, especially when stored in uncontrolled conditions. Initially the surface of pyrogenic silicas is partially hydroxylated, silanol groups, but presents also strained siloxane bridges, which can react with adsorbed water, leading to a change in their surface properties when exposed to the atmospheric moisture. Despite its industrial importance, this phenomenon has been rarely studied in the literature, except a single study, which was rather limited.Our study was focused on a set of six pyrogenic silicas, having specific surface areas comprised between 150 to 400 m2 / g. They were aged at constant temperature 22.5 ± 0.1 ° C in a closed chamber under controlled relative humidity (RH): 62, 75, 84, 92 and 100%.The water adsorption was followed gravimetrically. The mass of water adsorbed per unit area increases with both HR and the specific surface area. This increase, which can reach nearly 60% of the initial mass at 100% RH, is induced by the increase of their surface hydrophilicity due to the formation of new silanol groups. But, the study of the influence of the variation in RH, indicates that a threshold exists around HR50%, below which these silicas are stable.Finally, fitting the gravimetric curves, it was evidenced that the water sorption follows a first order kinetics and that the kinetic constant goes through a maximum for an HR equal to 84%. This increase of silanol density was testified by chemical titration. It increases by about 50%, from 2.4 to 3.6 SiOH/nm2 for ageing under 100% RH, but is dependent of the specific surface area and surface roughness. IR spectroscopy clearly indicates a net decrease of isolated silanol band correlated with an increase of H-bounded silanol. Proton and silicon NMR spectroscopies confirm the increase of the local density silanol groups on the aged silca surface.Finally, the evolution of the surface properties of these silica samples, aged during about 1000 h, was followed by inverse gas chromatography in infinite dilution (IGC-ID) and at finite concentration (CGI-FC) conditions.The CGI-ID was performed using linear and cyclic alkane probes. It shows that the ageing process affects only very slightly both the dispersive component of surface energy and the nano-roughness at the molecular level of all studied, indicating that the surface morphology is quite unchanged. Then; the variation of their surface heterogeneities with ageing time, in terms of the distribution functions of the probe adsorption energies, was assessed by CGI-CF, using isopropanol as probe.The aging process leads, as expected, to an increase of the high energy component related to the appearance of new silanol groups by nucleophilic opening of siloxane bridges by water confirming the reactivity of fumed silicas toward water when exposed to a high RH. All our observations, existence of a threshold, maximum for the kinetic constant and decrease of the chemisorbed of water amount with both specific surface area and surface roughness is supported by a model for the ageing process. [...]
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Yin, Quanyi. "Thiol-para-fluoro modified PPFS as building blocks for the design of silica-based nanocomposite and layer by layer self-assembled thin films." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI025/document.
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Ce travail de thèse décrit la préparation de deux types de films de polymères : i) des films nanocomposites à base de silice pyrogénée aux propriétés superhydrophobes et ii) des films LbL auto-assemblés, incluant tous deux des dérivés de poly(2,3,4,5,6-pentaflurostyrene) (PPFS), utilisés comme briques élémentaires. La stratégie utilisée ici consiste à exploiter les nombreux avantages que présente la réaction de substitution du fluor en position para du PPFS avec un thiol, pour générer de nouveaux dérivés aux propriétés ajustables. Ainsi, le premier volet de la thèse a consisté à introduire des chaînes de PPFS de façon covalente à la surface de silice pyrogénée par une stratégie dite de «grafting through» en utilisant la polymérisation radicalaire contrôlée par le voir nitroxydes, en présence de PS-DEPN comme macroamorceur. La cinétique de polymérisation du PFS avec et sans particules silice a été étudiée dans divers solvants, différentes particules hybrides de silices modifiées en surface par une couronne de PPFS ont été préparé. Ensuite, un thiol perfluoré (perfluorodecanethiol:PFDT) a été utilisé pour modifier le PPFS, considéré dans ce cadre comme matrice hôte pour la préparation des nanocomposites et pour modifier le PPFS présent à la surface des particules de silice. A partir de là, un large panel de films nanocomposite a été préparé à partir des différentes combinaisons possibles de polymère hôte (PPFS ou PPFS-PFDT) et de charges inorganiques de silice (modifiées par le PPFS ou par le PPFS-PFDT). Les propriétés de mouillabilité ainsi que la morphologie de surface de chaque film ont été analysées et il en résulte que certains films présentent un caractère superhydrophobe. Le deuxième volet de la thèse a porté sur la modification du PPFS par des thiols porteurs de fonctions acide carboxylique, toujours par la réaction de substitution décrite précédemment. Différents dérivés de PPFS carboxylés de DS variés ont été synthétisés. Leur habilité à développer des liaisons hydrogène avec un polymère modèle accepteur de liaison H (la poly(4-vinyl pyridine) (P4VP)) a été étudiée. Il en ressort que dépendamment de la nature du solvant, des mélanges miscibles ou des complexes interpolymères ont ensuite été formés. Des solutions de complexes préformés ont été successivement déposées par spin-coating pour construire des films. De plus, des films multicouches LbL stabilisés par des liaisons H entre le PPFS carboxylé et la P4VP ont été élaborés and il a été démontré que la nature du solvant de dépôt, ainsi que le taux de modification du PPFS, impactent fortement le mécanisme de croissance, l’épaisseur du film et les caractéristiques de surface, en termes de topologie et de mouillabilitéThis work describes the preparation of two kinds of thin polymer films : i) self-cleaning silica-based (nano)composites films and ii) LbL self-assembling films, both including poly(2,3,4,5,6-pentaflurostyrene) (PPFS) derivatives, as building blocks. The cornerstone of the approach is to exploit the thiol-para fluoro substitution reaction to PPFS chains in order to generate derivatives with tailored properties. In this frame, PPFS chains were anchored onto the surface of vinyl-functionalized fumed silica nanoparticles by nitroxide-mediated polymerization (NMP) in presence of PS-DEPN as macro-initiator via a “grafting through” strategy. The kinetics of NMP of PFS were investigated in presence and without silica in various solvents and well-characterized hybrid silica particles containing different polymer grafting weight were declined. Then, perfluorodecanethiol (PFDT) was employed to modify PPFS, considered as the host polymer matrix, and to functionalize PPFS chains tethered to silica particles. A large panel of (nano)composite films from the different possible host matrix/silica particles combinations was prepared. The wettability and the surface morphology of each film were discussed, as a function of the host structure (PPFS or PPFS-PFDT with different DS) and silica (modified with PPFS or PPFS-PFDT), as well as the silica content. It results that superhydrophobic features can be reached. Subsequently, PPFS was modified by using carboxylic acid mercapto modifier via the thiol-para fluoro coupling. Various carboxylated PPFS derivatives differing in the degree of substitution (DS) were prepared and their ability to develop H-bonds in solution with a model strong H-bond acceptor partner (poly(4-vinyl pyridine) (P4VP)) was investigated. Dependently on the nature of the solvent, a miscible blend or interpolymer complexes (IPC) were achieved. IPC-containing solutions were used to successfully fabricate spin-assisted films. Furthermore, H-bonds mediated LbL self-assembly multilayer films involving carboxylated PPFS and P4VP were prepared and it was evidenced that the nature of the deposition solvent as well as the extent of the modification (quantified by the DS), impact the growth mechanism, the thickness and the surface features, in terms of topology and wettability
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Lopes, Izabela Gimenes. "Avaliação do Teste de Ativação de Monócitos na determinação da contaminação pirogênica com ácido lipoteicóico em produtos injetáveis." reponame:Repositório Institucional da FIOCRUZ, 2014. https://www.arca.fiocruz.br/handle/icict/8111.
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Fundação Oswaldo Cruz. Instituto Nacional de Controle de Qualidade em Saúde
O teste de detecção de pirogênio é preconizado nas farmacopeias como teste de segurança imprescindível para a avaliação da qualidade de produtos injetáveis. Os métodos alternativos ao teste de pirogênio em coelhos são o Teste de Lisado de Amebócitos de Limulus (LAL) e o Teste de Ativação de Monócitos (MAT). Esses métodos ainda não podem substituir o teste em coelhos por completo, pois no caso do LAL os resultados podem não ser confiáveis quando a análise é realizada na presença de algumas substâncias interferentes com alto teor de lipídios e proteínas (encontrados nos medicamentos biológicos) e glucanas, além disso, o teste só detecta endotoxinas. Em relação ao MAT, já que o teste é sensível para todos os tipos de pirogênios e tem o mesmo mecanismo biológico responsável pela reação de febre em humanos, o Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) recomendou sua utilização desde que fique demonstrada a equivalência de seus resultados ao teste em coelhos, em conformidade com a regulamentação aplicável. Verifica-se assim, que a literatura carece de dados que envolvam a comparação entre a dose limite que causa febre em coelhos e a correspondência para o MAT relacionado ao ácido lipoteicóico (ALT), sendo assim, esse estudo tem como objetivo principal avaliar a utilização do MAT na detecção da contaminação de ALT de S. aureus em Cloreto de Sódio 0,9 % apirogênico artificialmente contaminado, através do estabelecimento de curva dose-resposta de ALT em coelhos; curva concentração-resposta de ALT para o MAT e avaliação em paralelo dos resultados obtidos utilizando ALT no teste em coelhos, LAL cromogênico e MAT. A resposta de febre foi observada a partir de 75.000 ng de ALT/Kg nos coelhos e no MAT para sangue criopreservado/IL-1β foi estabelecida em 50.000 ng/mL de ALT, ou 5,41 UEE/mL. O teste de LAL apresentou resultado falso-reativo a partir de 10.000 ng/mL de ALT. Os resultados apresentados neste estudo fornecem informações importantes sobre a comparação entre o teste de pirogênio em coelhos, MAT e LAL, contribuindo com dados para a validação do MAT, envolvendo outros pirogênios que não a endotoxina, e também para a aceitação deste teste pelos órgãos regulatórios no Brasil visando uma possível substituição do uso de animais, garantindo, assim, a segurança da saúde da população.
The pyrogenic test is preconized in the Pharmacopeias as a safety test indispensable for the quality of evaluation of injectable products. The alternative methods to the rabbit pyrogen test are the Limulus Amebocite Lysate (LAL) Test and the Monocyte Activation Test (MAT). These methods cannot replace the rabbit test completely yet, for in the case of LAL the results may not be reliable when the analysis is carried out in the presence of some interfering substances with high content of lipids and proteins (found in biological medicines) and glucans, moreover, the test only detects endotoxins. Concerning the MAT, since the test is sensitive to all types of pyrogens and has the same biological mechanism responsible for the fever reaction in humans, the Interagency Coordinating Committee on the Validation of Alternative Methods (Comitê de Coordenação Interagências sobre Validação de Métodos Alternativos - ICCVAM) have recommended its utilization provided that the equivalence of its results from the rabbit test, in conformity with the applicable regulation. It can be verified, then, that the literature lacks the data which involves the comparison between the limit dose that causes fever in rabbits and the consequence for the MAT related to the lipoteichoic acid (LTA), that being so, the aim of this study is mainly the utilization of MAT in the detection of the contamination of LTA of S. aureus in apyrogenic 0.9 % Sodium Chloride artificially contaminated, through the establishment of the dose-response curve of LTA in rabbits; concentration-response curve of LTA for the MAT and parallel evaluation of the results obtained by utilizing LTA in the test in rabbits, chromogenic LAL and MAT. The fever response was observed from 75.000 ng of LTA/Kg in rabbits and in MAT and for cryopreserved blood/IL-1β was established in 50.000 ng/mL of LTA, or 5,41 UEE/mL. The LAL test presented a false-positive result from 10.000 ng/mL of ALT. The results presented in this study provide important information on the comparison between the rabbit pyrogen test, MAT and LAL, contributing with data to the evaluation of MAT, involving pyrogens other than endotoxin, and also to the acceptance of this test by the regulatory organs in Brazil aiming at a possible animal substitution, and guaranteeing, then, the health security of the population.
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Chess, Jacob Dillon. "Effect of Aerogel on the Thermal Performance of Corrugated Composite Sandwich Structures." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1962.
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Current insulation solutions across multiple industries, especially the commercial sector, can be bulky and ineffective when considering their volume. Aerogels are excellent insulators, exhibiting low thermal conductivities and low densities with a porosity of around 95%. Such characteristics make aerogels effective in decreasing conductive heat transfer within a solid. These requirements are crucial for aerospace and spaceflight applications, where sensitive components exist among extreme temperature environments. When implemented into insulation applications, aerogel can perform better than existing technology while using less material, which limits the amount of volume allocated for insulation. The application of these materials into composites can result in enhancing a material's thermal and mechanical properties when exposed to mechanical testing.
The main objective of this study was to perform theoretical and experimental analysis on a corrugated composite sandwich structure integrated with aerogel insulation by studying its effective thermal conductivity. The aerogel material used was Pyrogel XT-E, a silica aerogel-based fiberglass insulation manufactured by Aspen Aerogels. Theoretical models of the corrugated composite sandwich structure were constructed in ANSYS Workbench based on geometry from a previous study. The main goal of the theoretical models was to analytically and computationally study the effective thermal conductivity of this sample; the conditions of these simulations were modeled after the experimental setup. Additionally, two insulation studies were performed using the thermal models. The first study was performed on a flat plate structure to determine the optimal thickness of Pyrogel XT-E in a flat plate orientation. The second study compared multiple types of common insulation materials to Pyrogel XT-E when integrated into the corrugated composite sandwich structure model. As expected, aerogel particles and Pyrogel XT-E outperformed all insulation materials and had the lowest effective thermal conductivity. Experimental data was obtained using a test enclosure and a heating element source with an integrated temperature control circuit that was designed and built for this study. This experimental data was compared to the theoretical data obtained from the thermal model simulations. The corrugated composite sandwich structure did not perform as well as expected due to thermal bridging along the composite corrugation. Its effective thermal conductivity was much higher than that of the flat plate structure, even though the effective Pyrogel XT-E layer in the corrugated composite sandwich structure was more than twice as thick as the layer in the flat plate structure. Despite thermal bridging, the corrugated composite sandwich structure exhibits superb thermal resistance, which adds to its impressive strength. Thermal conductivity results from this study can be used to design efficient materials for high structural and thermal stress applications.
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Terceti, Mateus de Souza. "Diversidade bacteriana do gene 16S rRNA em carvão pirogênico de Terra Preta Antropogênica da Amazônia Central e Oriental." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/64/64133/tde-18122009-143646/.
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A Terra Preta Antropogênica (TPA) tem essa denominação porque é encontrada em sítios arqueológicos, onde viveram grupos pré-históricos e é considerada um dos solos mais férteis do mundo. Nela é encontrada grande quantidade de material deixado por grupos indígenas como fragmentos cerâmicos, artefatos líticos, e especialmente carvão pirogênico. Estudos realizados com o carvão pirogênico verificaram que ele aumenta a capacidade de trocas catiônicas nesses solos. Por meio de microscopia de fluorencência, foi observada a presença de microrganismos habitando esse carvão, no entanto, não se sabe quais seriam. Devido à falta de informações sobre a diversidade bacteriana nessas estruturas, este trabalho estudou a diversidade bacteriana em amostras de carvão pirogênico de solos TPA coletadas nos sítios Lagoa Balbina (Amazônia Central- Amazonas) e Mina I (Amazônia Oriental - Pará), através de técnicas moleculares independentes de cultivo. O estudo visou também comparar essa diversidade com a encontrada no solo de onde carvão foi isolado. As estruturas de carvão foram separadas fisicamente dos solos e seu DNA genômico total extraído e usado como molde em reação de PCR utilizando oligonucleotídeos do gene 16S rRNA para o Domínio Bacteria. O produto da PCR foi clonado em vetor e os clones foram sequenciados e comparados com o banco de dados de 16S rRNA do RDPX. Com a construção das bibliotecas de clones do gene 16S rRNA a partir das amostras de carvão pirogênico observou-se que existe maior número de bactérias desconhecidas no carvão pirogênico do que no solo onde ele foi isolado. Acidobacteria foi o filo predominante nas bibliotecas de carvão pirogênico das duas localidades de estudo, assim como na biblioteca do solo do sítio Mina I. Já na biblioteca do solo do sítio Lagoa Balbina houve predominância do filo Firmicutes. Por meio do método de rarefação foi possível constatar uma menor riqueza de UTOs nas comunidades bacterianas presentes nas estruturas de carvão pirogênico quando comparado à riqueza de UTOs das comunidades bacterianas cujo habitat é o solo. Mas quando se compara a riqueza de UTOs entre as estruturas de carvão isoladas das duas localidades, observa-se que a riqueza é maior no sítio Mina I. Os valores obtidos com os índices de diversidade revelaram menor diversidade de UTOs nas bibliotecas obtidas para o carvão pirogênico das duas regiões estudadas se comparado dos valores para as bibliotecas obtidas do solo da mesma região. Os valores obtidos com os métodos não paramétricos revelaram maior riqueza de UTOs para as bibliotecas do carvão do sítio Mina I e solo TPA do sítio Balbina. A análise da PCA revelou que as bibliotecas do sítio Balbina mostraram-se altamente similares. Em adição, a análise com S-Libshuff, verificou que todas as bibliotecas comparadas são significativamente diferentes quanto à composição das comunidades bacterianas. O carvão pirogênico não é uma estrutura inerte, pois é capaz de ser habitado por diferentes bactérias e a sua estrutura da comunidade bacteriana é diferente daquela de onde ele foi segregadoAnthropogenic Dark Earth (ADE) has this denomination because it is found at archeological sites, where prehistoric groups lived, and it is considered one of the most fertile soils of the world. In this soil a great amount of material left by indigenous groups was found as ceramic fragments, lithic workmanships, and especially pyrogenic black carbon. Studies accomplished with the pyrogenic black carbon verified that it increases the capacity of cationic changes in soils. Through fluorescence microscopy, the presence of microorganisms was observed inhabiting that black carbon, however, this community is still unknown,due to the lack of information about the bacterial diversity in those structures.This work studied the bacterial diversity in samples of pyrogenic black carbon of ADE soils, collected at the sites Lagoa Balbina (Central Amazon) and Mina I (Oriental Amazon), through molecular techniques independent of cultivation. The study also sought to compare that diversity with the one of the soil where black carbon was isolated. The structures of black carbon were separate physically from the soils and total genomic DNA was extracted and used as template in a PCR reaction, using primers of the 16S rRNA gene for the Bacteria Domain. The PCR product was used for construction of clone libraries and the clones were sequenced and compared with the 16S rRNA of RDPX database. The 16S rRNA gene clone libraries from the samples of pyrogenic black carbon, it shown that is a larger number of unknown bacteria in the black carbon than in the soil where it was isolated. Acidobacteria was the predominant phylum in the pyrogenic black carbon libraries from the both studied places, as well as in the soil library from Mina I site. However in the library Lagoa Balbina site there was predominance of the phylum Firmicutes. Through the rarefaction method it was possible to verify a smaller richness of OTUs in the bacterial communities presents in the pyrogenic black carbon structures when compared to the OTUs richness of the bacterial soil communities.But, when the OTUs richness is compared among the isolated structures of pyrogenic black carbon of the two places, it is observed that the richness is higher in the Mina I site. The values from diversity indexes revealed smaller diversity of OTUs in the pyrogenic black carbon libraries when compared with the soil libraries for the two studied areas. The obtained values with the nonparametric methods revealed larger OTUs richness in the black carbon library of Mina I site and in the ADE soil library of the Balbina site. The PCA analysis showed that the libraries of the site Balbina site were highly similar. In addition, the analysis with S-Libshuff verified that all of the compared libraries were significantly different in bacterial communities composition. The pyrogenic black carbon is not an inert structure, once it is capable of being inhabited by different bacteria, and its bacterial community structure is different from that one where is was segregated
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Roucher, Clémentine. "Evolution de l'épidémiologie et des critères diagnostiques du paludisme clinique à Dielmo de 1990 à 2010." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM5062.
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En Afrique tropicale, là où le paludisme est fortement endémique, la plupart des individus sont semi-immuns et les infections asymptomatiques sont très répandues. Ainsi la détection de parasites dans le sang de malades fébriles n'est pas un critère suffisant pour distinguer le paludisme des autres causes de fièvre. A Dielmo, un village du Sénégal d'environ 500 habitants en 2010, un suivi épidémiologique continu très étroit du paludisme a débuté en 1990. Dans ce village où la transmission est pérenne, la mise en place de moyens de lutte et de prévention contre le paludisme de plus en plus efficaces a profondément transformé l'épidémiologie du paludisme. Dans ce travail, nous analysons l'impact de ces interventions sur les prévalences parasitaires, les densités parasitaires et les critères diagnostiques du paludisme et nous mesurons l'évolution du paludisme clinique à Plasmodium falciparum, P. malariae et P. ovale de juin 1990 à décembre 2010. Les données parasitologiques et cliniques ont été analysées par régression logistique à effet aléatoire pour étudier la relation entre les densités parasitaires et le risque de fièvre. Les prévalences parasitaires des trois espèces plasmodiales ont considérablement diminué lors de l'abandon de la chloroquine en traitement de première ligne et de son remplacement par des combinaisons thérapeutiques, puis sont devenues presque nulles après la mise en place de moustiquaires imprégnées d'insecticides à longue durée d'action. Les seuils pyrogéniques calculés nous ont permis de mesurer la densité d'incidence des accès palustres et d'étudier l'impact des mesures de lutte sur la morbidité palustre dans la populationIn tropical Africa, where malaria is highly endemic, most people are semi-immune and asymptomatic infections are widespread. Thus, the detection of malaria parasites in the blood of febrile patients is not a sufficient criterion for distinguishing malaria from other causes of fever. In Dielmo, a Senegalese village of about 500 inhabitants in 2010, a very closely continuous epidemiological monitoring of malaria began in 1990. In this village where the transmission is perennial, the establishment of more effective means of control and prevention against malaria have profoundly changed the epidemiology of malaria. In this work, we analyze the impact of these interventions on the parasite prevalences, the parasite densities and the malaria diagnostic criteria and we measure the evolution of Plasmodium falciparum, P. malariae and P. ovale clinical malaria from June 1990 to December 2010 in Dielmo. Parasitological and clinical data are analyzed in a random effect logistic regression to investigate the relationship between parasite density and fever risk. The prevalence of the three Plasmodium species decreased dramatically with the abandonment of chloroquine as first line treatment and his replacing with the combination therapies and became almost zero after the introduction of long lasting insecticidal nets. Pyrogenic thresholds calculated enabled us to measure the incidence density of malaria and to study the impact of intervention methods on malaria morbidity in the population
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Silva, Sâmala Glícia Carneiro. "Caracterização físico-hídrica e fracionamento físico da matéria orgânica em solo com horizonte antrópico." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-28092016-155747/.
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Nos últimos anos o interesse pelo estudo da Terra Preta de Índio (TPI) tem aumentado em razão das suas características únicas em relação aos solos normalmente encontrados na região, como sua maior fertilidade natural. Diversos estudos relatam que a presença do chamado carbono pirogênico na composição das TPIs é a responsável por esta superioridade, entretanto ainda não se sabe se este afeta as propriedades físicas dos solos de TPI. Esta pesquisa tem como objetivo comparar o comportamento de propriedades físico-hídricas de solos antrópicos (Terra Preta de Índio) com um solo adjacente por meio da determinação de suas propriedades físicas, e verificar a distribuição do carbono pirogênico entre os diferentes compartimentos da matéria orgânica em solos de TPI e adjacentes. Para este estudo foram coletadas amostras indeformadas em anéis volumétricos e blocos em uma área de TPI e adjacente. As áreas estão localizadas na Floresta Nacional de Caxiuanã, estado do Pará. As propriedades físicas analisadas foram textura, porosidade total, macro e microporosidade, curva de retenção da água no solo, condutividade hidráulica saturada, permeabilidade do solo ao ar e estabilidade de agregados. Para verificar o comportamento da matéria orgânica foi realizado o fracionamento físico, onde foram analisados a distribuição do carbono total e pirogênico nas diferentes frações da matéria orgânica. Verificou-se diferença nas duas áreas quanto às propriedades físicas porosidade total, macro e microporosidade, condutividade hidráulica do solo (Ksat), permeabilidade do solo ao ar (Ka), e retenção de água no solo, entretanto não foi possível verificar diferenças na estabilidade de agregados entre as duas áreas. A distribuição da matéria orgânica nas diferentes frações do solo foi distinta nas duas áreas, onde verificou-se que na área de TPI o C no solo foi predominante na fração macroagregados, enquanto que na área adjacente o carbono se localizou em maior quantidade na fração microagregados. Os valores de carbono pirogênico foram maiores na área de TPI do que na área adjacente, demostrando que a matéria orgânica das TPIs apresenta uma composição diferenciada, modificando o comportamento das propriedades físicas dos solos.In recent years the interest in the study of Terra Preta de Indio or Amazonian Dark Earths (TPI) has increased, especially because of its unique characteristics when related to typical soils of the region, as its higher natural fertility. Several studies have reported that the presence of so-called pyrogenic carbon in its composition is responsible for this superiority, however it is not known if it affects the physical properties of TPI soils. This research aims to compare the behavior of physical and hydraulic properties of anthropic soils (Terra Preta de Indio) to an adjacent soil by determining its physical properties, and evaluating the distribution of the pyrogenic carbon between the different compartments of organic matter for both soils. For this study, undisturbed soil samples were collected in volumetric cylinders and blocks from a TPI and adjacent area. The areas are located in Caxiuanã National Forest, state of Pará, Brazil. The analyzed physical properties were texture, porosity, macro and microporosity, soil water retention curve, soil saturated hydraulic conductivity, soil permeability to air and aggregate stability. A physical fractionation was performed to verify the behavior of organic matter, which analyzed the distribution of the total and pyrogenic carbon in the different fractions of organic matter. There were difference in the two areas regarding the physical properties as total porosity, macro and microporosity, soil hydraulic conductivity (Ksat), air permeability to soil (Ka), and soil water retention, however it was not possible to see differences in stability aggregates between the two areas. The distribution of organic matter in different soil fractions was different in the two areas, where it was found that in the TPI area, soil carbon was prevalent in the macroaggregates fraction, while the adjacent area had larger amounts in the microaggregates fraction. The values for pyrogenic carbon were higher in the TPI area, showing that the organic matter of TPIs has a different composition which modifies the behavior of physical properties in the soil.
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Lutfalla, Suzanne. "Persistance à long terme des matières organiques dans les sols : caractérisation chimique et contrôle minéralogique." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLA008/document.
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Les sols stockent trois fois plus de carbone que l'atmosphère sous la forme d'un mélange de molécules, la matière organique des sols (MOS). Certaines de ces molécules sont présentes dans le sol depuis des centaines voire des milliers d'années. Trois mécanismes de protection sont utilisés pour expliquer cette persistance à long terme des matières organiques dans les sols : (i) la récalcitrance chimique, (ii) la protection physique dans les agrégats et (iii) la protection physicochimique par adsorption sur les surfaces minérales. Le but de ce projet de thèse est d’améliorer la compréhension de ces processus de protection et de leur importance relative. Mon projet de thèse utilise des échantillons permettant l'accès au carbone persistant : les jachères nues de longue durée (5 sites en Europe). Il s'agit de parcelles maintenues vierges de toute végétation dans lesquelles, au fur et à mesure de la biodégradation, la quantité totale de carbone diminue, entraînant un enrichissement relatif en carbone persistant. La première étude expérimentale de ce travail de thèse vise à tester l'efficacité des méthodes d'oxydation chimique. Les deux réactifs les plus couramment utilisés -l'hypochlorite de sodium NaOCl et le peroxyde d'hydrogène H2O2- ont été testés sur des échantillons de la plus longue jachère nue (Versailles). Il est conclu que les méthodes d'oxydation chimique n'arrivent pas à isoler efficacement un réservoir de carbone persistant à l'échelle du siècle.En termes de mécanismes de persistance, les résultats obtenus montrent que la récalcitrance chimique n'est pas le principal mécanisme de protection. En effet, sur la durée de la jachère nue, la composition chimique de la MOS, caractérisée par spectroscopie NEXAFS, ne présente que peu de changements. Un enrichissement en composés présentant des groupements acides carboxyliques est détecté pour tous les sites testés. Une étude poussée de la persistance spécifique du carbone pyrogénique des sols a aussi été réalisée, ces composés sont actuellement considérés cinq fois plus persistants que le carbone total. Les résultats montrent que le carbone pyrogénique est moins persistant que prévu. En effet, le temps de résidence moyen du carbone pyrogénique obtenu par la méthode BPCA (116 ans) est seulement 1,6 fois supérieur à celui de la MOS (73 ans). L'étude du contrôle minéralogique de la persistance des MOS montre que les argiles contenant du potassium (illite) protègent moins de carbone que les argiles smectitiques. Le rapport C/N décroit avec le temps dans toutes les fractions argiles, ce qui prouve que les composés riches en azote sont préférentiellement préservés. Enfin, la présence de microagrégats dans la fraction grossière des argiles implique la coexistence de deux mécanismes de protection : la protection physique et la protection par adsorption sur les minérauxSoils store three times more carbon than the atmosphere, under the form of a complex mixture of molecules called soil organic matter (SOM). Some of these molecules have been standing in the soil for hundreds to thousands of years. Three main mechanisms are invoked to explain this long term carbon persistence in soils, (i) chemical recalcitrance, (ii) physical protection in aggregates and (iii) protection by adsorption on mineral surfaces. One of the major challenges in SOM science is to better understand the relative importance of each mechanism, that is the aim of this PhD project. Here, we use samples from by long term bare fallows (5 sites across Europe). These experimental plots have been kept free of vegetation by manual or chemical weeding for several decades and have been regularly sampled and stored. As the duration of the bare fallow increases, biodegradation occurs and samples get enriched in persistent carbon.First experiments consisted in testing the efficiency of chemical oxidations (two reagent were tested, sodium hypochlorite –NaOCl- and hydrogen peroxide –H2O2) on the longest bare fallow. We concluded that oxidation methods were not able to efficiently isolate a pool of persistent carbon at the centennial timescale. In terms of mechanisms of persistence, the obtained results show that chemical recalcitrance does not seem to be the major mechanism. Indeed, over the duration of the bare fallow, the chemical composition of SOM, as seen by synchrotron based NEXAFS spectroscopy, shows little changes. There is a consistent increase in carboxylics for all sites (12% increase on average) though it is significant for 2 out of the 4 selected sites. We also studied the particular persistence of soil pyrogenic carbon, which is thought to be at least five times more persistent than bulk SOM. Results show that pyrogenic carbon lacks long term persistence. Indeed the BPCA-estimated mean residence time of pyrogenic carbon (116 years) is on average 1.6 times longer than MRT for bulk SOM (73 years). Finally, the study of mineralogical control of the persistence of SOC showed that clay minerals containing potassium (illite) seemed to protect less carbon. As seen by NEXAFS-STXM, more mineral surfaces with very little SOM appear with the duration of bare fallow. C:N ratio decreased in all clay fractions, suggesting a preferential persistence of N-rich compounds. Presence of microaggregates in the coarser clay fraction led to the coexistence of two protection mechanisms: adsorption and physical protection
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Grard, Anthony. "Etude de primaires pour l'adhésion d'assemblages métal-élastomère silicone." Electronic Thesis or Diss., Toulon, 2019. http://www.theses.fr/2019TOUL0021.
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L’usage d’élastomères silicones (HCRs) en tant qu’amortisseurs ou joints est croissant dans les domaines de l’aéronautique et du spatial en raison de leur stabilité aux facteurs environnementaux (UV, température, ozone). Les HCRs sont souvent assemblés à une partie métallique via l’emploi de primaires à base d’organosilanes et/ou d’additifs polysiloxanes. Néanmoins, le rôle des composés des primaires n’est pas totalement compris. Ce travail vise à améliorer la compréhension des mécanismes d’adhérisation d’un HCR sur un substrat d’alliage métallique via l’utilisation de primairesThe use of silicone rubbers (HCRs) as dampers or seals is growing in aeronautic and space fields because of their stability to environmental parameters (UV, temperature, ozone). Usually, HCRs are assembled to a metal part via the use of organosilanes based primers and/or polysiloxane additives. However, the role of primer compounds is not well understood. This work aims to improve the understanding of adhesion mechanisms between a HCR and a metal via the use of primers
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Abbruzzini, Thalita Fernanda. "The role of biochar on greenhouse gas offsets, improvement of soil attributes and nutrient use efficiency in tropical soils." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-30092015-115437/.
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The solid product of pyrolysis, called \"biochar\" (BC) in the context of improving soil properties as part of agronomic or environmental management, also got into focus as a climate mitigation strategy. The researcher investigated the effects of BC on soil attributes, nitrogen (N) use and GHG emissions. In Chapter 1 the origin of BC was commented. In Chapter 2, BC from sugarcane straw was characterized, and its priming on native SC was evaluated with the treatments: (T1) Soil; (T2) BC; (T3) Soil + BC 10 Mg ha-1; (T4) Soil + BC 20 Mg ha-1; and (T5) Soil + BC 50 Mg ha-1. In Chapter 3, it was evaluated the combination of BC, filter cake (F) and vinasse (V), in relation to soil attributes and carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions. The treatments were: (T1) Soil + FC + V; (T2) Soil + FC + V + BC 10 Mg ha-1; (T3) Soil + FC + V + BC 20 Mg ha-1; and (T4) Soil + FC + V + BC 50 Mg ha-1. In Chapter 4, the nitrogen (N) use efficiency was investigated in a pot trial under wheat using NH4[15N]O3 and rates of BC, with the treatments: (T1) Soil, with N, no BC; (T2) Soil, with N, BC 10 Mg ha-1; (T3) Soil, with N, BC 20 Mg ha-1; and (T4) Soil, with N, BC 50 Mg ha-1. BC had C and N contents higher compared to the feedstock. Total K, Mg and P also increased. The lowest CO2 fluxes were for BC, and CO2 from soil and soil + BC did not differ. The highest CO2 - C4 was in the first day, and there were no differences in the CO2 - C3. The BC presents characteristics to improve soil attributes. BC stability is an opportunity to reduce CO2 emissions. In Chapter 3, soil pH, P and base contents increased and Al3+ decreased with BC to sandy soil. Impacts of BC on the CEC were higher in sandy soil. Mineral N decreased with BC. Cumulative CO2 in T1 were higher in sandy and clayey soils than the control. T2 and T3 in sandy soil increased CO2 emissions, but T4 did not differ from T1. BC reduced N2O emissions from sandy and clayey soils relative to T1. BC with FC and V affected pH, CEC, P and base contents. However, those effects were higher in sandy soil. The BC supressed N2O from V and FC. In Chapter 4, BC decreased N2O from N fertilization compared to only N fertilizer. T4 had higher tillering and grain yield. Also, T2 to T4 had higher 100-grain weight and shoot. T3 and T4 had the highest N in grains. The application of BC to soil improves N availability and use efficiency, enhances grain yields and reduces N2O from N fertilization. This study opened encouraging perspectives to the evaluation of sugarcane straw BC to improve soil quality and mitigate GHG emissions.O produto sólido da pirólise, denominado \"biochar\" (BC) no contexto da melhoria nos atributos do solo como parte do manejo agrícola e ambiental, também tem se destacado na mitigação das mudanças climáticas. O pesquisador investigou os efeitos do BC nos atributos do solo, uso do nitrogênio (N) e emissões de GEE. No Cap. 1 comentou-se a origem do BC. No Cap. 2, caracterizou-se o BC de palha de cana-de-açúcar e avaliou-se o potencial de decomposição do C do solo, com os tratamentos: (T1) Solo; (T2) BC; (T3) Solo + BC 10 Mg ha-1; (T4) Solo + BC 20 Mg ha-1 (T4); e (T5) Solo + BC 50 Mg ha-1. No Cap. 3, avaliou-se a combinação BC, torta de filtro (TF) e vinhaça (V) em atributos do solo e fluxos de dióxido de carbono (CO2), metano (CH4) e óxido nitroso (N2O) nos tratamentos: (T1) Solo + TF + V; (T2) Solo + TF + V + BC 10 Mg ha-1; (T3) Solo + TF + V + BC 20 Mg ha-1; e (T4) Solo + TF + V + BC 50 Mg ha-1. No Cap. 4 investigou-se a eficiência de uso do N num experimento em vasos com trigo usando NH4 [15N]O3 e doses de BC, com os tratamentos: (T1) Solo, com N, sem BC; (T2) Solo, com N, BC 10 Mg ha-1; (T3) Solo, com N, BC 20 Mg ha-1; e (T4) Solo, com N, BC 50 Mg ha-1. Os teores de C e N do BC foram maiores comparado à biomassa. K, Mg e P totais também aumentaram. Os menores fluxos de CO2 foram do BC. O CO2 do solo e solo + BC não diferiram. Observou-se maior CO2 - C4 no primeiro dia de incubação, porém sem diferenças no CO2 - C3. O BC apresenta características para melhorar atributos do solo e reduzir as emissões de CO2. No Cap. 3, pH, P e bases aumentaram e o Al3+ diminuíu com o BC. Os impactos do BC na CTC foram maiores em solo arenoso. O N mineral diminuíu com o BC. O CO2 acumulado no T1 foi maior nos solos arenoso e argiloso comparado ao controle. O T2 e T3 aumentaram o CO2 acumulado do arenoso relativo ao T1, enquanto T4 e T1 não diferiram. O BC reduziu as emissões de N2O pelos solos arenoso e argiloso comparado ao T1. O BC combinado à TF e V afetaram pH, CTC, P e bases do solo arenoso. O BC suprimiu o N2O de solos com V e TF. No Cap. 4, o BC diminuíu as emissões de N2O comparado ao fertilizante N apenas. T4 teve rendimento de grãos superior ao T1. T2 a T4 apresentaram maior peso de 100 grãos e biomassa aérea. T3 e T4 tiveram maior N em grãos. O BC melhora o uso do N, a produção de grãos e reduz o N2O de fertilizante N, abrindo perspectivas para a avaliação do BC de palha de cana-de-açúcar na melhoria da qualidade do solo e mitigar das emissões de GEE.
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Forny, Laurent. "L'eau en poudre." Compiègne, 2007. http://www.theses.fr/2007COMP1701.
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Cette étude a pour objet l'élaboration de poudres sèches en apparence mais qui contiennent une quantité importante de matière active sous forme liquide. Ainsi, l'eau en poudre (à base de silice pyrogénique hydrophobe) peut incorporer jusqu'à 98% d'eau en masse. Les particules ont une taille moyenne d'environ 150 μm et présentent une bonne coulabilité. La libération de l'eau s'effectue par évaporation ou par pression mécanique. La structure des particules a été étudiée par microscopie électronique après cryofracture ou sublimation de l'eau. Les particules individuelles se composent d'une gouttelette d'eau enrobée par une coquille de silice. Il existe deux modes de fabrication: les procédés à fort taux de cisaillement de type mixeur et les procédés de pulvérisation de type granulateur. La qualité du produit dépend de la contribution énergétique du procédé et de l'angle de contact liquide/particule (évalué par intrusion d'eau). Les perspectives d'applications sont nombreusesWater-rich powders, also called "dry water", containing up to 98% (by weight) of water and still maintaining the same flow properties as a dry powder were prepared by a simple mixing process. Dry water particles are a very convenient carrier system that can be easily produced at industrial scale. Water can be released by evaporation or under mechanical stress. The structure of individual particles bas been studied by electronic microscopy after freeze fracture or water sublimation. Each particle consist in a micrometric water droplet (average diameter of 150 μm) surrounded by a network build up by association of hydrophobic fumed silica particles. Two types of mixing processes were used: high shear processes and atomization processes such as granulators. The quality of the final product depends on the energetic contribution of the process and on the solid/liquid contact angle (evaluated by water intrusion). Potential applications are numerous in the food, pharmaceutical, and cosmetics industry
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Landmann, Tobias. "A case study for Skukuza estimating biophysical properties of fires using EOS-MODIS satellite data /." Doctoral thesis, [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970359403.
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