Several heterogeneously catalysed reactions have been studied at pressures above and below the critical pressure of carbon dioxide in both carbon dioxide and nitrogen. The purpose of this study was to ascertain if carbon dioxide above its critical pressure and temperature would have a beneficial effect on the active life time of the catalysts When the Beckmann rearrangement of cyclohexanone oxime was studied it was discovered that using carbon dioxide above its critical pressure and temperature was beneficial to catalyst lifetime at both 250°C and 300°C, however the beneficial effect was also observed in nitrogen under the same conditions. It is proposed that the benefits at higher pressures are due to an increased residence time in the reactor or increased competition for active sites. When the process was performed at 380°C, a previously unreported impurity was observed in the collected samples. This was shown to be N-ethyl caprolactam, it is proposed that this is formed by a Ritter style reaction with 5-cyanopent-1-ene known to be formed during the reaction When the Fries rearrangement of phenyl acetate was studied it was discovered that increasing reactor pressure appeared to have little or no effect on the catalyst; it is thought this is because the reaction temperature of 150°C is below the boiling point of phenyl acetate, and that the reaction being observed occurs purely in the liquid phase. When the Diels-Alder addition of isoprene to methyl acrylate was studied, it was discovered that using carbon dioxide above its critical pressure had the effect of improving catalyst lifetime and conversion to desired product, with the greatest effect being at 50 bar. It was discovered that using nitrogen under the same conditions led to a greater improvement in conversion and catalyst lifetime. It is thought that the reactions in carbon dioxide are in a near critical state at 50 bar leading to the maximum effect at this pressure, and at higher pressures the reactions are bi- or multi-phasic, leading to the decrease in the effect. In the process of studying the above reactions an effective rig for the study of high pressure heterogeneously catalysed reactions was built.

Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 187-192).

Yes / Objectives Isotope ratio analyses of dentine collagen were used to characterize short-term changes in physiological status (both dietary status and biological stress) across the life course of children afforded special funerary treatment. Materials and Methods Temporal sequences of δ15N and δ13C isotope profiles for incrementally-forming dentine collagen were obtained from deciduous teeth of 86 children from four early-medieval English cemeteries. Thirty-one were interred in child-specific burial clusters, and the remainder alongside adults in other areas of the cemetery. Isotope profiles were categorized into four distinct patterns of dietary and health status between the final prenatal months and death. Results Isotope profiles from individuals from the burial clusters were significantly less likely to reflect weaning curves, suggesting distinctive breastfeeding and weaning experiences. This relationship was not simply a factor of differential age at death between cohorts. There was no association of burial location with stage of weaning at death, nor with isotopic evidence of physiological stress at the end of life. Discussion This study is the first to identify a relationship between the extent of breastfeeding and the provision of child-specific funerary rites. Limited breastfeeding may indicate the mother had died during or soon after birth, or that either mother or child was unable to feed due to illness. Children who were not breastfed will have experienced a significantly higher risk of malnutrition, undernutrition and infection. These sickly and perhaps motherless children received care to nourish them during early life, and were similarly provided with special treatment in death. / University of Sheffield Early Career Researcher Scheme by a grant awarded to ECA in 2014-15.

Cellulose-inferred lake water oxygen-isotope records were obtained from five throughflow lakes situated along a north-south transect across Fennoscandia to help develop a better picture of Holocene changes in atmospheric circulation in the region. This research addresses prior evidence for the existence of non-temperature-dependent shifts in d18O of precipitation in the early Holocene attributed to changes in atmospheric circulation. The validity of this hypothesis is tested through the development of oxygen-isotope records from lake sediments and their interpretation in the context of independent reconstructions of temperature and precipitation from pollen and chironomid head-capsules collected from the same or nearby sites, and well-documented changes in vegetation composition. Records of carbon and nitrogen elemental content and isotopic composition and magnetic susceptibility are included in this multi-proxy investigation. Extensive modern isotope hydrology datasets spanning several years at four of the five sites also help to inform interpretations of the cellulose d18O records. Key results from this research are: 1) Elevated d18O in relation to prevailing temperature occurred during the early Holocene (c. 10,000-6000 cal. BP) for sites in northern Fennoscandia (Lake Tibetanus, Lake Spåime), in harmony with previous interpretations suggesting that strong zonal atmospheric circulation led to deepening of the precipitation and isotope shadows in the lee of the Scandes Mountains. 2) Evidence from a southern site (Arbovatten) reveals a previously unrecognized negative offset in the d18O-temperature relation during the early Holocene, apparently transferred directly from the North Atlantic without the orographic effects associated with a topographic barrier. 3) The modern d18O-temperature relation appears to have been established throughout Fennoscandia by c. 6000-4000 cal. BP, probably due to generally weaker circumpolar atmospheric circulation in response to lower summer insolation. 4) Comparison of two sites (Lake Spåime, Svartkälstjärn) in a west-east transect across central Fennoscandia reveals higher-frequency variability in atmospheric circulation at submillennial scales throughout the Holocene, which appears to be analogous to contemporary variability in the North Atlantic Oscillation (NAO) at seasonal-to-decadal time-scales. Evidence of such NAO-like variability also exists at two northern sites (Lake Keitjoru, Oikojärvi) during the Holocene, likely reflecting variations in summer and winter atmospheric circulation. 5) Complex lake-specific changes in productivity occurred in response to Holocene climate change, as revealed by carbon and nitrogen elemental and isotopic data in lake sediments. A major shift in atmospheric circulation pattern occurring at c. 4000 cal. BP probably led to a reduction in soil-derived 13C-depleted nutrients in five lakes (Lake Keitjoru, Oikojärvi, Lake Spåime, Svartkälstjärn, Arbovatten) associated with changes in terrestrial vegetation. Changes in sediment nitrogen isotope composition also occurred in these lakes at c. 4000 cal. BP, possibly reflecting changing nutrient supply dynamics because of enhanced nitrogen losses during spring snowmelt.

Cellulose-inferred lake water oxygen-isotope records were obtained from five throughflow lakes situated along a north-south transect across Fennoscandia to help develop a better picture of Holocene changes in atmospheric circulation in the region. This research addresses prior evidence for the existence of non-temperature-dependent shifts in d18O of precipitation in the early Holocene attributed to changes in atmospheric circulation. The validity of this hypothesis is tested through the development of oxygen-isotope records from lake sediments and their interpretation in the context of independent reconstructions of temperature and precipitation from pollen and chironomid head-capsules collected from the same or nearby sites, and well-documented changes in vegetation composition. Records of carbon and nitrogen elemental content and isotopic composition and magnetic susceptibility are included in this multi-proxy investigation. Extensive modern isotope hydrology datasets spanning several years at four of the five sites also help to inform interpretations of the cellulose d18O records. Key results from this research are: 1) Elevated d18O in relation to prevailing temperature occurred during the early Holocene (c. 10,000-6000 cal. BP) for sites in northern Fennoscandia (Lake Tibetanus, Lake Spåime), in harmony with previous interpretations suggesting that strong zonal atmospheric circulation led to deepening of the precipitation and isotope shadows in the lee of the Scandes Mountains. 2) Evidence from a southern site (Arbovatten) reveals a previously unrecognized negative offset in the d18O-temperature relation during the early Holocene, apparently transferred directly from the North Atlantic without the orographic effects associated with a topographic barrier. 3) The modern d18O-temperature relation appears to have been established throughout Fennoscandia by c. 6000-4000 cal. BP, probably due to generally weaker circumpolar atmospheric circulation in response to lower summer insolation. 4) Comparison of two sites (Lake Spåime, Svartkälstjärn) in a west-east transect across central Fennoscandia reveals higher-frequency variability in atmospheric circulation at submillennial scales throughout the Holocene, which appears to be analogous to contemporary variability in the North Atlantic Oscillation (NAO) at seasonal-to-decadal time-scales. Evidence of such NAO-like variability also exists at two northern sites (Lake Keitjoru, Oikojärvi) during the Holocene, likely reflecting variations in summer and winter atmospheric circulation. 5) Complex lake-specific changes in productivity occurred in response to Holocene climate change, as revealed by carbon and nitrogen elemental and isotopic data in lake sediments. A major shift in atmospheric circulation pattern occurring at c. 4000 cal. BP probably led to a reduction in soil-derived 13C-depleted nutrients in five lakes (Lake Keitjoru, Oikojärvi, Lake Spåime, Svartkälstjärn, Arbovatten) associated with changes in terrestrial vegetation. Changes in sediment nitrogen isotope composition also occurred in these lakes at c. 4000 cal. BP, possibly reflecting changing nutrient supply dynamics because of enhanced nitrogen losses during spring snowmelt.

タンデトロン加速器質量分析計業績報告 Summaries of Researches Using AMS 2002 (平成14)年度

The evaluation of the soil spatial variability using a fast, robust and cheap tool is one of the key steps towards the implementation of Precision Agriculture (PA) successfully. Soil organic carbon (OC), soil total nitrogen (TN) and soil moisture content (MC) are needed to be monitored for both agriculture and environmental applications. The literature has proven that visible and near infrared (vis-NIR) spectroscopy to be a quick, cheap and robust tool to acquire information about key soil properties simultaneously with relatively high accuracy. The on-line vis-NIR measurement accuracy depends largely on the quality of calibration models. In order to establish robust calibration models for OC, TN and MC valid for few selected European farms, several factors affecting model accuracy have been studied. Nonlinear calibration techniques, e.g. artificial neural network (ANN) combined with partial least squares regression (PLSR) has provided better calibration accuracy than the linear PLSR or principal component regression analysis (PCR) alone. It was also found that effects of sample concentration statistics, including the range or standard derivation and the number of samples used for model calibration are substantial, which should be taking into account carefully. Soil MC, texture and their interaction effects are other principle factors affecting the in situ and on-line vis-NIR measurement accuracy. This study confirmed that MC is the main negative effect, whereas soil clay content plays a positive role. The general calibration models developed for soil OC, TN and MC for farms in European were validated using a previously developed vis-NIR on-line measurement system equipped with a wider vis-NIR spectrophotometer (305 – 2200 nm) than the previous version. The validation results showed this wider range on-line vis-NIR system can acquire larger than 1500 data point per ha with a very good measurement accuracy for TN and OC and excellent accuracy for MC. The validation also showed that spiking few target field samples into the general calibration models is an effective and efficient approach for upgrading the implementation of the on-line vis-NIR sensor for measurement in new fields in the selected European farms.

Tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) is a cool-season perennial grass used in pastures throughout the Southeastern United States. The grass can harbor a fungal endophyte (Epichloë coenophiala) thought to provide the plant with enhanced resistance to biotic and abiotic stress. However, the alkaloids produced by the common variety of the endophyte cause severe animal health issues resulting in a considerable amount of research focused on eliminating the toxic class of alkaloids while retaining the positive abiotic and biotic stress tolerance attributes of the other alkaloids. In doing so, very little attention has been paid to the direct influence the fungal-plant symbiosis has on rhizosphere processes. Therefore, my objectives were to study the influence of this relationship on plant biomass production, root exudate composition, and soil biogeochemical processes using tall fescue cultivars PDF and 97TF1 without an endophyte (E-), or infected with the common toxic endophyte (CTE+), or with two novel endophytes (AR542E+, AR584E+). I found that root exudate composition and plant biomass production were influenced by endophyte status, tall fescue cultivar, and the interaction of cultivar and endophyte. Cluster analysis showed that the interaction between endophyte and cultivar results in a unique exudate profile. These interactions had a small but perceptible impact on soil microbial community structure and function with an equally small and perceptible impact on carbon and nitrogen cycling in soils from rhizobox and field sites. These studies represent the first comprehensive analysis of root exudate chemistry from common toxic and novel endophyte infected tall fescue cultivars and can be used to help explain in part the observed changes in C and N cycling and storage in pastures throughout the Southeast U.S..

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2002. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.