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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.
561

Pyrolytic Esterification Derivatization Chemistry for the Qualitative Determination of Sulfonate Surfactants and Indirect Detection of Sulfate Surfactants through On-Line Degradation Products for Gas Chromatography-Mass Spectrometry

Igwebuike, Alexander 11 July 2023 (has links)
No description available.
562

Polycyclic Aromatic Hydrocarbons In Urban Soils From West Yorkshire, UK. Investigation into Abundances, Sources and Determining Factors

Hamed, Heiam A.M. January 2018 (has links)
This study aims to determine the concentration of 16 Polycyclic Aromatic Hydrocarbons (PAHs) in urban soils from West Yorkshire in order to determine what the factors are controlling their distribution and abundances. Although PAHs have been reported before from soils and sediments, the majority of these studies have come from China, sometimes with contrasting results, which emphasises the need to obtain equivalent data from other areas. Therefore this work provides the first measurements of their type from the area studied. Soil samples were collected from one hundred sites across an area from Bradford to Leeds on two occasions, one in autumn and one in the following summer. The soil samples were analyzed by X-ray diffraction and all found to have similar mineralogical composition, which was mainly silica and calcite. Trials using iodine as a marker for PAHs showed there were notable interactions between the minerals and PAHs, with calcium carbonate absorbing PAHs much more than silica. There is a negative correlation between the soil organic content (determined by loss on ignition) and PAHs, which confirms the PAH-mineral interaction. Gas chromatography with mass spectrometry (GC-MS) using targeted selected ion monitoring was used to determine and quantify PAHs in the one hundred soil samples with the aid of PAH external standards. The results showed highest concentrations of total PAHs in the same sample from Leeds from the autumn (1,525 ng/g) and in the summer (1,768 ng/g). In Bradford there was only moderate pollution of PAHs, the maximum being 122 ng/g. However the majority of data from Bradford showed lower levels of pollution in both summer and autumn. On the basis of prior published information, the ratio of these compounds has been used to help in identifying sources. In the samples collected from Bradford in both seasons and Leeds in autumn the PAH pollution originated from pyrogenic, biomass and petroleum combustion, however in the summer the source appeared more to be from a petrogenic source. These ratios in the samples which were collected from the area between Bradford and Leeds implied pyrogenic, biomass source of pollution in the autumn, but in the summer another source of organic compounds was indicated namely petroleum combustion. When the locations were resampled nine months later, after taking into account within-site variability, there was a strong indication that the PAH concentrations were higher. This might have been due to a seasonal effect, but when a further (third) subsample was taken at a later date it showed a further increase in PAH level which suggests the effect is accumulative rather than seasonal. The results were analysed using Principal Component Analysis (PCA) to determine whether the type of road had an effect on the concentration of the 16 PAHs compounds, but it was concluded that there was no such effect. However, the distance from the soil sample to the nearest road did have an effect on the concentration of the 16 PAH compounds, especially in soil samples having the shortest distance to the road. Traffic volume was also tested and found to influence the PAH concentrations. It is notable that, comparing the groupings from autumn with those from summer by cluster analyses, they largely had the same compounds grouping together in both cases; only two compounds differed at all in where they occurred in the clusters, with consistent patterns of grouping found for the other compounds. These analyses indicate that PAH compounds behave in a consistent way amongst groups of PAH compounds. The grouping of PAHs appears linked to their sources rather than number of rings or molecular weight. / Libyan Government and Embassy
563

Industrial Applications of Plant Secondary Metabolites

Lin, Yun 03 August 2017 (has links)
No description available.
564

Prediction and Classification of Physical Properties by Near-Infrared Spectroscopy and Baseline Correction of Gas Chromatography Mass Spectrometry Data of Jet Fuels by Using Chemometric Algorithms

Xu, Zhanfeng 26 July 2012 (has links)
No description available.
565

Impact of cocoa (Theobroma cacao L.) fermentation on composition and concentration of polyphenols: Development of fermentation model system and utilization of yeast starter cultures

Lee, Andrew H. 28 September 2017 (has links)
Consumption of cocoa and dark chocolate products has been associated with positive health outcomes including reduced onset of cardiovascular disease, inflammation, diabetes, obesity, and platelet disorders. Cocoa polyphenols, putatively responsible for these beneficial activities, are highly impacted by cocoa variety, agronomic effects and processing history. However, the difference in polyphenol concentration and composition between cocoa products originating from different hybrid clones (selected for high yield) or from different fermentation conditions is not fully understood. Detailed polyphenol characterization including determination of total polyphenol and total procyanidin concentrations, and qualitative and quantitative analysis of (mean) degree of polymerization was conducted. Significant differences in total polyphenol and procyanidin concentrations were observed between five genetic clones grown by the USDA-ARS Cocoa Germplasm Repository located in Mayagüez, Puerto Rico. To facilitate cocoa fermentation research in laboratories distant from cocoa harvesting sites, a laboratory-scale cocoa fermentation model system was developed in this study. This model system used dried, unfermented, cocoa beans and simulated pulp medium as the starting material. The model system supported growth of the essential succession of cocoa fermenting microorganisms and generated similar chemical changes to those observed in on-farm cocoa fermentation. Using this model system, the impact of inoculation with proprietary yeast strains Saccharomyces cerevisiae Lev F and Saccharomyces cerevisiae Lev B on cocoa polyphenol concentration and composition was evaluated. Inoculation with both yeast strains resulted in increased fermentation rate and Lev B inoculation resulted in higher total polyphenol and procyandin contents at the end of fermentation. Overall, the present work addressed the influence of cocoa variety selection and fermentation process conditions on the composition and concentration of polyphenols. These findings will contribute to continued efforts to develop cocoa products with optimized bioactivity and maximum disease preventative effects. / PHD
566

Ancient lipids reveal continuity in culinary practices across the transition to agriculture in Northern Europe

Craig, O.E., Steele, Valerie J., Fischer, Anders, Hartz, S., Andersen, S.H., Donohoe, P., Glykou, A., Saul, H., Jones, D.M., Koch, E., Heron, Carl P. January 2011 (has links)
No / Farming transformed societies globally. Yet, despite more than a century of research, there is little consensus on the speed or completeness of this fundamental change and, consequently, on its principal drivers. For Northern Europe, the debate has often centered on the rich archaeological record of the Western Baltic, but even here it is unclear how quickly or completely people abandoned wild terrestrial and marine resources after the introduction of domesticated plants and animals at approximately 4000 calibrated years B.C. Ceramic containers are found ubiquitously on these sites and contain remarkably well-preserved lipids derived from the original use of the vessel. Reconstructing culinary practices from this ceramic record can contribute to longstanding debates concerning the origins of farming. Here we present data on the molecular and isotopic characteristics of lipids extracted from 133 ceramic vessels and 100 carbonized surface residues dating to immediately before and after the first evidence of domesticated animals and plants in the Western Baltic. The presence of specific lipid biomarkers, notably omega-(o-alkylphenyl)alkanoic acids, and the isotopic composition of individual n-alkanoic acids clearly show that a significant proportion ( approximately 20%) of ceramic vessels with lipids preserved continued to be used for processing marine and freshwater resources across the transition to agriculture in this region. Although changes in pottery use are immediately evident, our data challenge the popular notions that economies were completely transformed with the arrival of farming and that Neolithic pottery was exclusively associated with produce from domesticated animals and plants.
567

New investigations into the Uluburun resin cargo

Stern, Ben, Heron, Carl P., Tellefsen, T., Serpico, M. January 2008 (has links)
No / Resin found within Canaanite amphorae from the Late Bronze Age shipwreck discovered off the coast of southwest Turkey at Uluburun has previously been identified as Pistacia sp. Although evidence from Egypt suggests that this resin was in high demand and typically transported in such amphorae, it has also been proposed that the amphorae contained wine, with the resin used to seal the interior surfaces and to flavour and/or preserve the wine. To attempt to resolve this question, we have analysed five samples of pistacia resin found in amphorae from the shipwreck using a range of analytical techniques which have used in the past for the analysis of wine residues: spot tests, FT-IR, and HPLC-MS-MS. As well as the archaeological samples, we have analysed modern samples of pistacia resin, leaves and fruit to determine the effectiveness of each technique and to exclude the possibility of false positive results. In addition to the analyses for wine we also detail analysis (GC-MS) of the terpenoids for the purpose of further molecular characterisation of the resin. Bulk stable isotope analysis was used in comparison with similar resins to attempt to identify the geographical origin of the resin.
568

The circulation and consumption of Red Lustrous Wheelmade Ware: petrographic, chemical and residue analysis

Knappett, C., Kilikoglou, V., Steele, Valerie J., Stern, Ben January 2005 (has links)
Yes / Red Lustrous Wheelmade ware is one of the most recognisable classes of pottery from the Late Bronze Age of the east Mediterranean. Yet both its production source and the nature of its contents and use remain a source of some debate. These questions are tackled here through an intensive programme of scientific analysis involving 95 samples of Red Lustrous Wheelmade ware and related wares from seven sites in Turkey, Cyprus and Egypt. Petrography and instrumental neutron activation analysis are combined in the study of the ceramic fabrics, with a view to specifying the source of this ware; while gas chromatography and gas chromatography-mass spectrometry are used to analyse absorbed and visible residues in and on the sherd samples, in the hope of shedding light on vessel contents and possible use. The results of the fabric analysis show the ware to be extremely homogeneous, indicative of a single source: northern Cyprus is at present the most likely candidate, although further analysis, particularly of clay samples from the region in question, would certainly be desirable. The residue analysis suggests that Red Lustrous Wheelmade ware might have been used to carry some kind of plant oils, possibly perfumed, and that in some instances the vessel interior was coated with beeswax as a sealant. / AHRC
569

Analysis of partially carbonised residues from the Chiseldon Cauldrons by gas chromatography-mass spectrometry and gas chromatography-combustion-isotope ratio mass spectrometry

Steele, Valerie J. January 2017 (has links)
No / During the micro-excavation of the cauldrons, residues were identified which appeared different from the surrounding soil and metal corrosion products. Thirty-seven of these residues from nine cauldrons and two significant fragments of incomplete cauldrons were analysed by gas chromatography-mass spectrometry (GC-MS) along with two samples of soil from the micro-excavation for comparison. The aim of the analysis was to determine whether these residues contained any organic material related to the use of the cauldrons, specifically lipids (fats, waxes, resins etc.) from the preparation of food or drink. Two of the samples from the cauldrons were also sent for compound specific carbon stable isotope analysis by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) to give a more precise identification of the residues.
570

浮遊藻類から細菌類への有機物の流れ : 新手法による微生物ル-プの検証

浜, 健夫 03 1900 (has links)
科学研究費補助金 研究種目:一般研究(C) 課題番号:03640552 研究代表者:浜 健夫 研究期間:1991-1992年度

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