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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
431

Needle Trap Device and Solid Phase Microextraction Combined with Portable GC-MS for On-Site Applications

Warren, Jamie January 2011 (has links)
Needle trap device (NTD) is a technique that is useful for a wide variety of applications involving the sample preparation of compounds with a wide range of chemico-physico properties, and varying volatilities. A newly designed NTD that improves the performance relative to previous NTD designs is simple to produce is developed. The NTD utilizes a side-hole needle with a modified tip to improve the sealing between the NTD and narrow neck liner of the GC injector, thereby increasing the desorption efficiency. The slurry packing method was applied, evaluated, and NTDs prepared by this method were compared to NTDs prepared using the vacuum aspiration method. NTD geometries including blunt tip with a side-hole needle, tapered tip with side-hole needle, dome tapered tip with side-hole, sliding tip with side-hole and blunt tip with no side-hole needle (expanded desorptive flow) were prepared and evaluated. Sampling performance and desorption efficiency were investigated using automated headspace extraction of benzene, toluene, ethylbenzene, p¬-xylene (BTEX), anthracene and pyrene. The tapered tip and sliding tip NTDs were found to have increased desorption efficiency. SPME and NTDs are valuable sample preparation tools for on-site analysis. Combining both extraction techniques allows for the differentiation of free and particle-bound compounds in a sample matrix. Portable GC/MS instrumentation can achieve fast separation, identification, and quantitation of samples prepared by the above techniques on-site without the need for transport to the laboratory. This minimizes the effects of volatiles lost and sample degradation during storage time. Here, SPME and tapered tip NTDs combined with portable GC/MS are used to investigate free and total emissions of BTEX and select PAHs from gasoline and diesel exhaust. Using the above optimized technologies, cigarette smoke in a smoking area where people were actively smoking and inside a smoker’s car were also investigated. Target contaminants were found in the investigated matrices at ng/mL levels.
432

Jämförelse av metoder för peroxidbestämningar i bränslen : A comparison of methods for determination of peroxide content in fuel

Ly, Becky January 2010 (has links)
New energy resources that can replace petroleum diesel are needed and biodiesel may be an excellent substitute. During storage and use, biodiesel can oxidize and form peroxides, leading to degradation of the fuel. It is therefore important to determine the peroxide content of the fuel. In this thesis the triphenylphosphine method, which involves GC-MS analysis has been compared to the standard iodometric method which involves titration with sodium thiosulfate. Working standards were made to see how well the iodometric method worked and also in order to make a calibration curve in GC-MS. Aged samples were then analyzed. The results showed that both methods gave good linearity and repeatability with limits of detection (LOD) and quantification (LOQ) of 0,06 mM and 0 17-0,65 mM respectively. However, the iodometric method seemed more circumstantial since it needed a lot of solvents and different reagents. The triphenylphosphine method was on contrary very simple to use and did not require too much preparation work. The latter also showed better reproducibility. In conclusions, both methods can be used in evaluating the peroxide content of biodiesel, but the triphenylphosphine method has the advantages of higher simplicity and better reproducibility.
433

Fused-Droplet Electrospray Ionization Mass Spectrometry Combined with Pyrolysis for Polarity and Organic Composition of Soil, Tobacco,and Humic Acid

Li, Kuang-Feng 09 August 2004 (has links)
none
434

PEG含浸木材のGC/MSによる残存PEG測定

NAKAMURA, Toshio, NAKAMURA, Shinya, NISHIMOTO, Hiroshi, 中村, 俊夫, 中村, 晋也, 西本, 寛 03 1900 (has links)
第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告
435

Porting of £gC/OS-II Embedded Operating System on a Reconfigurable Platform

Lin, Yu-en 16 February 2008 (has links)
£gC/OS-II is a portable, scalable and preemptive real time kernel. In this paper, we describe the work of porting £gC/OS-II to the Xilinx ML310 platform, which is equipped with a Virtex-II Pro FPGA. Moreover, we also present the accomplishment of an OS4RS (Operating System for Reconfigurable System) prototype by integrating £gC/OS-II with the partial reconfiguration capability of the Virtex-II Pro FPGA. For the porting of the £gC/OS-II, we mainly port the code related to context switch, interrupt, and timer. Moreover, for the OS4RS prototype, we partition the FPGA into four regions and allow different circuits (i.e. hardware tasks) to be dynamically reconfigured (i.e. downloaded) into the regions under the control of £gC/OS-II. Finally, we propose an algorithm to predict and pre-configure the hardware tasks so as to reduce the waiting time of task reconfiguration. According to the simulation results, the proposed algorithm can reduce the waiting time effectively.
436

Jämförelse av produktionsmetoder vid byggande av gång- och cykeltunnel. / Productions of a pedestrian and cyclist tunnel. Comparison between productions methods.

Aronsson, Mattias, Karlsson, Jimmy January 2003 (has links)
<p>Vi har i denna rapport jämfört produktionsmetoder vid byggande av gång- och cykeltunnel under järnväg. de metoder vi har jämfört är lansering och platsgjutning. Projektet som vi har studerat är byggandet av en gong- och cykeltunnel under järnväg vid Mjölby station. Vid detta projekt lanseras halva tunneln in och halva platsgjuts. </p><p>Det vi har jämfört är dels de geotekniska aspekterna, där vi främst har tittat på vikten av förundersökningar, jordegenskapens inverkan, spontning och grundvattnets inverkan. Vi har också tittat på produktionstekniska aspekter, då främst storleken av arbetsområdet och arbetsmiljön. Vi har även betraktat ekonomi och produktionstid i de båda metoderna. </p><p>Vi har i denna rapport främst använt oss av muntliga källor som gett sina synpunkter på hur tunneln ska eller bör utformas. Vi har sedan sammanställt alla synpunkter och åsikter och skaffat oss en egen uppfattning om de båda metoderna och när de bör användas. </p><p>Det vi kommit fram till när vi har jämfört dessa båda metoder är att lansering har många fördelar vad gäller arbetsmiljö, tid och ekonomi. vid enklare tunnelprojekt är denna metod att föredra om förutsättningar finns. platsgjutning har dock de fördelar att den kan användas vid de flesta tunnelbyggnationer och att tågtrafiken kan flyta på utan längre störningar. </p><p>Vid stora projekt som det i Mjölby anser vi att en kombination av metoderna är den allra bästa lösningen.</p>
437

Identification of Chlorinated Fatty Acids in Standard Samples and Fish Lipids : Verification and Validation of Extraction, Transesterification and GC-MS/XSD

Brown, Philip, Järlskog, Ida January 2015 (has links)
Chlorine gas bleaching was a common method used in pulp industries. As a consequence, significant amounts of chlorine were discharged into surrounding aquatic ecosystems, affecting the biota. Chlorinated organic pollutants are formed when chlorine react with organic material. Octadecanoic acid (stearic acid) is one of the most common saturated fatty acids in aquatic biota. In a naturally occurring process two and four chlorine atoms, respectively, are added over the unsaturated bonds, forming 9,10-dichloro octadecanoic acid and 9,10,12,13-tetrachloro octadecanoic acid. These are the chlorinated fatty acids (ClFA) under investigation in this Bachelor’s Thesis. The methodological framework for measuring ClFA is investigated in this essay. The scope is to evaluate the method of isolating and quantifying the compounds as described in Åkesson-Nilsson’s (2004) dissertation. The method includes: extraction of the lipid, transesterification (where the fatty acids, including the ClFAs, are separated from the lipids and transformed into their respective methyl esters through two methods, acidic catalysis with BF3 or H2SO4), separation (by solid phase extraction) and determination of ClFA concentration with a halogen specific detector (GC-XSD/MS). Furthermore, the scope is to investigate collected fish samples (from Norrsundet) with the abovementioned method. By making a dilution series with known concentrations it was possible to establish calibration curves, to give in an indication of the effectiveness of the method. BF3 is in need of updating due to being experienced as slower and less stable than the H2SO4-method. However, it was concluded that the H2SO4-method was more effective on the standard samples and that the BF3-method was more effective on the fish lipid samples. In one of the lipid samples (lavaret transesterified with BF3) a detectable concentration of 9,10,12,13-tetrachloro octadecanoic acid was discovered. Therefore, we question SEPAs decision to cancel investigations in Norrsundet. Our results could indicate that ClFAs are still an issue that could affect the ecosystem’s biota.
438

Extraktion av opolära narkotikaklassade substanser ur fettinnehållande matriser

Gustafsson, Heidi January 2015 (has links)
En metod som kan användas för att extrahera opolära narkotika- och läkemedelssubstanser ur matriser med ett högt fettinnehåll har tagits fram. Metoden är baserad på ett extraktionsprotokoll från Livsmedelsverket (SLV K1-f4-m018.3) som används för analys av bekämpningsmedel i animaliska livsmedel. Metoden har sedan optimerats för forensiska applikationer genom att ändra olika variabler. Två av variablerna som testades var olika typer av extraktionsmedel och mängden tillsatt C18 (oktadekylsilyl)-sorbent. Experimenten visade att acetonitril som extraktionsmedel och en ökad tillsats av C18 eliminerade den största andelen av fettmolekylerna i matrisen utan att kompromissa med utbytet av den undersökta analyten. Analyterna som undersöktes var 5F-AKB48, tetrahydrocannabinol (THC) och alprazolam och den fettinnehållande matrisen utgjordes av smör. Metoden lyckades minska fetthalten i smörproverna från ca 80- till 3-5 % fett samtidigt som ett utbyte av analyterna erhölls på 70-90 %. Analyten med högst utbyte efter extraktionen var 5F- AKB48 med ett utbyte på cirka 90 %. Utbytet för alprazolam och THC blev 72- respektive 75 %. Vid extraktion med etylacetat, som var det extraktionsmedel som användes i den ursprungliga metoden (SLV K1-f4-m018.3), erhölls inga minskningar av fetthalten överhuvudtaget utan hamnade runt 80 % i samtliga analyser. När metodens kapacitet testades med ökade fetthalter visade det sig att fetthalten efter extraktionen blev lägre i de prover som hade en högre fetthalt från början. Utbytet av analyten (5F-AKB48 i detta fall) påverkades däremot inte nämnvärt av de ökade fetthalterna utan höll sig stabilt runt 85 %.
439

Tracing late Holocene changes in lake-water total organic carbon : A multi-proxy approach based on sediment bio-geochemistry and a faecal biomarker

Jonsson, Sofia January 2015 (has links)
Long-term dynamics of lake-water total organic carbon (LW-TOC) concentrations in freshwater lakes provide an important perspective on the recent increases in LW-TOC observed in many of these systems and may assist with the identification of natural and anthropogenic drivers of change. This study examines how LW-TOC in Dragsjön, a lake situated in an area with a long history of anthropogenic land use, has changed in response to natural and anthropogenic perturbations throughout the Holocene. To provide a better understanding of the processes involved, a multi-proxy study was conducted and included multi-element geochemistry (17 major and trace elements), biogenic silica, organic matter (OM) content and composition, and the faecal biomarker “coprostanol”. The direct biomarker for anthropogenic presence, “coprostanol”, and a detailed characterisation of OM composition are for the first time applied for tracing changes in LW-TOC. Natural processes contributed to stable LW-TOC concentrations in Dragsjön for most part of the Holocene. Humans were present in the catchment from AD 100 as indicated by coprostanol, but did not begin to affect LW-TOC until c. AD 1500. In the last 500 years LW-TOC steadily declined from 17 to 10 mg L-1 in response to anthropogenic alterations to the terrestrial biomass balance. The increase in LW-TOC during the last 70 years likely represents a recovery from anthropogenic disturbance rather than a baseline shift in response to any of the number of proposed recent stressors. The faecal biomarker coprostanol and OM composition provided information essential for identifying and characterising the effects of anthropogenic disturbance.
440

Leaching of Residual Monomers, Oligomers and Additives from Polyethylene, Polypropylene, Polyvinyl Chloride, High-density Polyethylene and Polystyrene Virgin Plastics

Björnsdotter, Maria January 2015 (has links)
Plastic debris are accumulating in our oceans and are degraded into smaller pieces which eventually becomes small enough to be available to lower thropic level organisms. Microplastics, commonly defined as plastic particles &lt;5 mm, are globally distributed and found at remote locations far away from industrialized and populated areas. The effects of macro sized plastics is well understood whilst the effects of microplastics is hard to predict. It is known that microplastics act as transfer vectors for a wide range of toxic chemicals into organisms, and it is also known that the particle itself can cause toxic responses such as increased immune response and endocrine disruption. Researchers utilize virgin plastic pellets in order to determine the toxicological effect of the plastic particle itself, but resent research suggest that these virgin plastics may release chemicals that contribute to the toxic response and thus complicates the interpretation of the results. In present study, five different virgin plastics were allowed to leach in artificial seawater under conditions that mimic those used in particle toxicity studies. Plastics included were polyethylene, polypropylene, polyvinyl chloride, high-density polyethylene and polystyrene. Leachable monomers and oligomers were found in three of the five plastics tested: polyvinyl chloride, high-density polyethylene and polystyrene. Leached compounds from polyvinyl chloride were not identified due to time limitations. Aliphatic hydrocarbons in the size C14-C22 were leached out from high-density polyethylene in the concentration range 0.47 × 10-3 – 1.13 × 10-3 μg ml-1 within 24 hours. Polystyrene was found to leach styrene monomer which reached a concentration of 0.17 μg ml-1 within 24 hours.

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