8,525 research outputs found
Mechanisms for accumulation and migration of technetium-99 in saltmarsh sediments
No full textThis thesis describes the development of analytical methods for both the bulk determination of 99Tc, and determination of 99Tc in sequential extracts from sediments. These methods have been used to collect data, which, along with trace and major element data have been used to interpret the mechanisms for 99Tc input, migration and accumulation in saltmarshes. The inventory of 99Tc stored in the Thornflatt Saltmarsh, Esk Estuary has also been determined. The routine determination of 99Tc in bulk samples uses 99mTc as a yield monitor. Samples are ignited stepwise to 550°C and the 99Tc is extracted using 8M nitric acid. Many contaminants are precipitated with Fe(OH)3 and the Tc in the supernant is pre-concentrated and further purified using anion-exchange chromatography. Final separation of Tc from Ru is achieved by extraction of Tc into 5% TnOA in xylene from 2M sulphuric acid. The yield is determined by γ-spectrometric analysis of 99mTc. Determination of 99Tc is made by liquid scintillation counting. Typical recoveries are in the order of 70-95% and the method has a detection limit of 1.7 Bq/kg for a sample size of 10g. Determination of Tc in sequential extracts uses operationally defined procedures to extract: exchangeable Tc, reducible Tc and oxidisable Tc. An initial water wash is used to extract any occluded Tc and a final leach in 8 M nitric acid is used to dissolve any residual Tc. The isolation of 99Tc uses TEVA resin for Extracts 1-4 and the decontamination procedure developed for bulk analysis for Extract 5. 99mTc was used as a yield monitor, and determination of 99Tc is by liquid scintillation counting. Limits of detection were dependent on the amount of 99mTc tracer used but were found to be as low as 2.4 Bq/kg for a sample size of 2g. A study was made of the mechanisms responsible for the accumulation and migration of Tc in estuarine sediments using sediments collected from saltmarshes at Thornflatt, Carlaverock and the Ribble Estuary. 99Tc was present at determinable activities in all the sediment cores taken from these sites. Good correlations between Tc and CaO as well as CO3 concentrations and poor correlation between Tc and radionuclides adsorbed to inorganic detritus infer a direct input of 99Tc to marsh sediments. Determination of 99Tc in biota living on the marsh also showed that this was not a significant pathway for input of Tc to the sediments. Sequential extraction data imply sorption to an organic fraction of the sediment. Stable element and sequential extraction data indicates that Tc is readily oxidised and remobilised before reprecipitation where redox conditions are favourable. Data indicate a reduction potential between those of the MnIV to MnII reaction and the FeIII to FeII reaction is necessary for re-accumulation to occur, as suggested by published thermodynamic data. Data collected from reducing sediments imply that similar mechanisms are responsible for the accumulation of Mn (e.g. reduction by sulphate reducing bacteria) and the accumulation of Tc. The inventory of 99Tc held within the Thornflatt saltmarsh is proportionally less than that of 137Cs or 241Am when compared to discharges from Sellafield. However a higher proportion of 99Tc is transferred from Seliafield and incorporated into saltmarsh sediments than is suggested by previously published standard distribution coefficient data. Saltmarsh sediments are therefore a more important sink of 99Tc than extrapolations made from inventories of other radionuclides would suggest
Service-oriented models for audiovisual content storage
No full textWhat are the important topics to understand if involved with storage services to hold digital audiovisual content? This report takes a look at how content is created and moves into and out of storage; the storage service value networks and architectures found now and expected in the future; what sort of data transfer is expected to and from an audiovisual archive; what transfer protocols to use; and a summary of security and interface issues
T0-Berekening: Status Quo van UNIBEST-TC
No full textDit rapport gaat in op de ontwikkelingen bij het UNIBETS-TC model. Met dit model wordt het cross-shore en longshore sediment transport berekend. Om inzicht te krijgen in de verbeteringen in het model wordt er in dit rapport een T0-berekening (een berekening op tijdstip T=0) gemaakt. Dit maakt het mogelijk de ontwikkelingen te evalueren door het te vergelijken met een dergelijke exercitie op het moment T1. Met de berekening wordt er antwoord gegeven op de vragen of het UNIBEST-TC model één heel jaar de ontwikkeling van het kustprofiel kan doorrekenen en in hoeverre het model de werkelijkheid beschrijft. Geconcludeerd wordt dat het (nieuwe) UNIBEST-TC model het dwarstransport in de goede orde van grootte bepaald, maar dat het model geen rekening houdt met het ontstaan van banken. Verder onderzoek is nodig. Het model houdt verder goed rekening met de interactie tussen langs- en dwarstransport en biedt daarnaast een goede mogelijkheid om het lot van een zandsuppletie te bestuderen
Gut microbiota-derived butyrate inhibits hepatic cholesterol synthesis via a PPARγ/SREBP2 signaling pathway in high-fat diet (HFD)-fed mice
No full textDysregulated lipid and cholesterol metabolism is associated with various metabolic diseases and even cancers. The liver is a critical organ for lipid and cholesterol metabolism. Previous evidence suggests that gut microbiota is associated with lipid and cholesterol metabolism, but little is known about the specific effects of gut microbiota on hepatic lipid and cholesterol biosynthesis. This dissertation investigated the comprehensive influence of gut microbiota on hepatic lipid metabolism and also explored the mechanism by which the gut microbiota modulates hepatic cholesterol biosynthesis.
The first study was aimed to comprehensively evaluate the effects of gut microbiota on hepatic lipid metabolism. Using a pseudo-germ-free mouse model constructed by an antibiotics cocktail (Abx), we found that Abx treatment for 5 weeks successfully decreased the gut microbiota, accompanied by a reduced amount of microbial synthesized components (Lipopolysaccharides (LPS)) and metabolites (butyrate and isovalerate) in mice fed a high fat diet (HFD). This depletion of microbiota decreased their body weight. Meanwhile, gut microbiota depletion lowered the serum levels of glucose, total cholesterol (TC), low-density lipoproteins (LDL), insulin, and leptin. Moreover, microbiota depletion inhibited the fat deposition in both white adipose tissue and liver. As for the mechanism, RNA-seq results showed that gut microbiota depletion altered the expression of hepatic genes involved in fatty acid and cholesterol metabolism such as fatty acid translocase (Cd36), monoacylglycerol o-acyltransferase 1 (Mogat1), cytochrome P450 family 39 subfamilies A polypeptide 1 (Cyp39a1), ATP-binding cassette subfamily C member 3 (Abcc3), and Acyl-CoA:glycerol-3-phosphate acyltransferase (Gpat3). In addition, mice with microbial depletion exhibited lower relative abundance of bacteria related to abnormal metabolism and inflammation, including Lachnospiraceae, Coriobacteriaceae_UCG-002, Enterorhabdus, Faecalibaculum, and Desulfovibrio. Furthermore, a correlation analysis revealed strong associations between the altered gut microbiota and serum cholesterol level. These findings suggest that the gut microbiota plays an important role in the lipid and cholesterol metabolism.
The second study further investigated the underlying mechanism by which the gut microbiota influences cholesterol metabolism. In line with our previous study, we found that Abx-depleted gut microbiota for 10 weeks decreased the serum TC and LDL-c levels, confirming the role of gut microbiota in modulating cholesterol metabolism. However, the hepatic TC level was increased by gut microbiota depletion. Furthermore, RNA-seq analysis results showed that the hepatic genes involved in cholesterol synthesis were up-regulated by gut microbiota depletion, which might be the reason for increased hepatic TC level. Through correlation analysis, we observed strong negative associations between butyrate-producing bacteria and hepatic cholesterol level. Additionally, specific elimination of butyrate-producers via metronidazole decreased the colonic butyrate level to an undetectable level and up-regulated the expression of sterol regulatory element-binding protein (Srebp2) and its downstream genes involved in cholesterol biosynthesis in the liver. However, butyrate treatment increased colonic butyrate level and down-regulated the expression of genes associated with cholesterol biosynthesis. Furthermore, a treatment with an antagonist of PPARγ, GW9662, successfully neutralized the suppressed effects of butyrate on the expression of genes involved in cholesterol biosynthesis. Our findings offer insight into how butyrate-producing bacteria play a pivotal role in hepatic cholesterol biosynthesis, supporting the potential of microbiota-based interventions in maintaining cholesterol homeostasis.
Overall, these data suggest that gut microbiota depletion influences hepatic fatty acid and cholesterol metabolism. Moreover, gut microbiota-derived butyrate acts as a molecule that mediates hepatic cholesterol synthesis. Furthermore, PPARγ/SREBP2 signaling was hypothesized to be a mediator between gut microbiota-derived butyrate and hepatic cholesterol synthesis in mice fed an HFD
Anomaly of thermal expansion close to Tc in Bi1.7Pb0.3Sr2Ca2Cu3O10+y
No full textAn anomalously big jump of thermal expansion in the c direction of the Bi1.7Pb0.3Sr2Ca2Cu3O10+y has been observed at a temperature slightly above the superconductivity transition temperature, Tc. The jump is one order of magnitude bigger than the estimated value with the classical theory of superconductivity. This anomalously big jump vanishes after the samples were annealed in O2 for a long time and became nonsuperconducting. The correlation between the anomaly and the Tc support the view that electron–phonon interaction as well as superconductivity is enhanced by anharmonicity of phonons in high-Tc cuprates
TC Insight
No full textIn dit project is er een product geïmplementeerd voor Priva. Priva is een bedrijf dat gespecialiseerd is in klimaatbeheersing in de tuinbouw en kantoorgebouwen. Priva levert regeltechnische software en hardware waarop verschillende componenten zoals CV-ketels, radiatoren en klimaatplafonds kunnen worden aangesloten. De software van Priva regelt vervolgens dat de componenten in deze zogeheten klimaatbeheersingsinstallaties met elkaar kunnen samenwerken en een bepaald binnenklimaat bewerkstelligen. In grote klimaatbeheersingsinstallaties zijn veel componenten van elkaar afhankelijk. Als er in één component een storing optreedt, dan kan deze storing effect hebben op de werking van andere componenten. Deze componenten kunnen als gevolg daarvan weer afwijkend gedrag gaan vertonen. Een uitdaging die vaak voorkomt is dat er afwijkend gedrag wordt vastgesteld in een component, maar dat de daadwerkelijke oorzaak van een probleem in een ander deel van de installatie ligt. Als de afhankelijkheden tussen verschillende componenten inzichtelijk in kaart zouden kunnen worden gebracht, dan zou het makkelijker worden om te achterhalen waar precies de oorzaak ligt als er afwijkend gedrag wordt geconstateerd. Deze gedachte vormt het uitgangspunt voor onze opdracht. In ons uiteindelijke product is het mogelijk om van een klimaatbeheersingsinstallatie de afhankelijkheden tussen verschillende componenten weer te geven. Deze informatie is zowel in een voor computers makkelijk verwerkbaar formaat alsook visueel exporteerbaar. Omdat deze software meer inzicht geeft in de werking van klimaatbeheersingsinstallaties is deze gedoopt tot TC Insight. Er is in het ontwikkelproces gebruikt gemaakt van Test Driven Development, een methode die goede designkeuzes afdwingt en testbare code oplevert. Verder is de software iteratief ontwikkeld volgens de Scrum ontwikkelmethode. Deze methode gaf de opdrachtgever een goed beeld van de bezigheden van het ontwikkelteam en gaf de mogelijkheid om vroeg in het proces feedback te geven zodat deze snel verwerkt kon worden.Software TechnologyElectrical Engineering, Mathematics and Computer Scienc
Model TC-497 Overland Train MkII
No full textPhotograph of the Model TC-497 Overland Train Mkii, the largest and most powerful of all the "land trains" produced by LeTourneau. The TC-497 was built for the U.S. Army to transport cargo in the Arctic under a wide variety of road conditions, according to author Eric Orlemann. It contained nine cargo trailers, a control car and two trailing power units. The TC-497 weighed 135 tons. Its overall length was about 527 feet
Vergelijking UNIBEST-TC en DUROSTA: Twee tijdsafhankelijke dwarstransportmodellen
No full textVoor de berekening van de grootte van het dwarstransport zijn momenteel in Nederland twee computermodellen in gebruik, te weten UNISEST-TC en DUROSTA. UNISEST-TC is ontwikkeld voor 'algemeen' gebruik, met gemiddelde condities. DUROSTA is ontwikkeld voor gebruik voor zware condities, waarbij hoge waterstanden kunnen optreden en een zware golfaanval. Hierbij treedt aileen zeewaarts transport op. Wanneer met beide modellen zware condities worden doorgerekend, waarbij veeI duinafslag of duinerosie plaatsvindt, vertonen beide modellen in onder andere het afslagprofiel verschillen. Dit onderzoek had tot doel meer inzicht te krijgen in deze verschillen en het bepalen van de gevoeligheid van beide modellen voor verschillende duinafslag bepalende factoren.Hydraulic EngineeringCivil Engineering and Geoscience
RILEM TC 243-SGM report: grouting for historic architectural surfaces
No full textHistoric Structures are commonly coated with mortar layers (plasters, renders, flooring) for protection and decoration. These well finished architectural stratigraphic surfaces often suffer from deterioration, such as lack of adhesion or detachment between support and mortar layers and even between mortar layers. Grouting and filling voids between delaminated layers can be an effective intervention if the layers are compact. This paper deals with aspects pertinent to the selection, design and implementation of a grout for the in situ stabilization and preservation of historic architectural surfaces. It presents the methodological approach, in accordance with the conservation principles, including sections on diagnosis, study and assessment of the deterioration phenomena, definition of grout requirements, selection of proper ingredients for custom-made or commercial grouts, as well as making and testing trial mixes, field testing and Assessment of the effectiveness of grouting. The aim of this paper, that is elaborated in the frame of RILEM TC 243 SGM, is to serve as a guide for users of lime-based grouts for the reattachment and reinstatement of historical architectural surfaces.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied MechanicsHeritage & Technolog
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