• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 326
  • 249
  • 158
  • 12
  • 8
  • 6
  • 4
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 876
  • 201
  • 163
  • 143
  • 88
  • 50
  • 48
  • 48
  • 46
  • 44
  • 43
  • 42
  • 41
  • 40
  • 40
  • 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.
1

The biochemical toxicology of serum carboxylesterase in pigeons (Columba livia)

Jackson, John B. 1994 (has links)
No description available.
2

An investigation of potential immunological and metabolic indices of environmental water quality in the shore crab, Carcinus maenas

Hauton, Christopher 1995 (has links)
No description available.
3

Studies on the preparation of pentacyclic triterpenoids

Perkins, Gemma 1995 (has links)
No description available.
4

Biodegradation of algal lipids and significance for sediment studies

Teece, Mark A. 1994 (has links)
No description available.
5

Lipids in recent sediments of the eastern North Atlantic

Madureira, Luiz Augusto dos Santos 1994 (has links)
No description available.
6

Biomarkers of exposure to complex environmental mixtures

Naufal, Ziad Sami 2008 (has links)
Maternal exposure to genotoxic chemicals may produce a variety of adverse birth outcomes. Depending on the dose and duration of exposure, adverse birth outcomes can range from premature or low-birth weight, to congenital abnormalities including neural tube defects (NTDs). The research described in this dissertation focused on several rural counties in Shanxi province, China. Shanxi has one of the highest rates of NTDs in the world. In 2005, the incidence of NTDs in the study counties ranged from 8 to 24 cases per 1,000 births. While some of these birth defects are likely to be related to nutrition, it is also suggested that environmental factors play a significant role. One such factor includes polycyclic aromatic hydrocarbon (PAH) exposure as a result of combustion of coal for indoor heating and cooking. Human populations in Shanxi depend heavily on coal as their main source of energy. This study determined the concentrations of PAHs in house dust, venous blood and placenta of study participants. Dust was collected from homes in the study site. Carcinogenic PAH levels in dust collected from kitchen floors ranged from 12 to 2,000 µg/m2. The genotoxic potential of dust was confirmed by shortterm bioassays. Median concentrations of total PAHs in placenta from children born with NTDs were elevated compared to matched controls and appeared to be associated with the risk of having a child with a NTD. Tobacco smoking was not associated with elevated levels of PAH biomarkers in this study population. Levels of bulky DNA adducts in placenta have also been quantified using 32P-postlabeling. Adduct levels do not appear to be significantly different between cases and controls and were not associated with deletions in enzymes GSTM1 or GSTT1. These data suggest that children born with NTDs may be at increased risk due to exposure to genotoxic PAHs. Studies with a larger number of subjects are needed to further elucidate the relationship between PAH exposure and adverse birth outcomes.
7

Physiological and cellular level responses of Enteromorpha spp. to chemical and thermal stress

Lewis, Stella Anne 1998 (has links)
The aims of this project were to investigate the cellular stress response (CSR) in Enteromorpha spp. and assess the potential of the Stress-70 protein (an indicator of the CSR) as a biomarker of pollutant exposure and acquired tolerance in Enteromorpha spp., compared with conventional physiological endpoints of toxicity. Cross-reactivity of a commercial Stress-70 antibody with E. intestinalis proteins was determined and used to develop an assay for Stress-70. Using this assay E. intestinalis was found to exhibit a typical heat shock response. Stress-70 proved to be a relatively insensitive biomarker of copper exposure and did not appear to be involved in copper tolerance, the genetic basis of which was investigated by growing E. intestinalis using a novel culturing technique. Although growth was variable, it provided a simple, consistent and sensitive measure of copper toxicity. The chlorophyll fluorescence parameter Fv/Fm was insensitive to copper exposure. Nutrient limitation enhanced copper toxicity and significantly impaired growth, Fv/Fm and Stress-70 production in E. intestinalis. In both copper ‘sensitive’ and ‘tolerant’ E. intestinalis, copper exposure did not affect the ability to raise a heat shock response. In ‘sensitive’ algae, copper and heat shock were additive stressors, with heat shock acting as a stronger inducer of Stress-70. Only heat shock affected 'tolerant' algae. Zinc was less toxic than copper but in contrast to copper studies, Stress-70 was a relatively sensitive indicator of zinc exposure, compared to Fv/Fm and growth. Studies of triazine herbicides revealed that on a molarity basis, Irgarol 1051 was more toxic to E. intestinalis than atrazine. Fv/Fm and growth were strongly affected by Irgarol exposure, but Stress-70 levels were unaltered by exposure to the herbicide. Fv/Fm and Stress-70 were poor in situ biomarkers of pollution, but another chlorophyll fluorescence parameter - complementary area - appeared to correlate with levels of organic pollution. Overall, Stress-70 was found not to be a useful biomarker of exposure to copper or triazines in E. intestinalis, or in situ pollution. However, the Stress-70 assay developed has a number of alternative applications and Enteromorpha spp. were deemed to be potentially useful in pollution monitoring with the selection of suitable biomarker responses.
8

The sulphur geochemistry of Jurassic source rocks

Hill, Alan Frederick Mark 1995 (has links)
In immature Jurassic shales of differing depositional environment from Great Britain (Ro<0.5) the C32 hopane and C29 sterane isomerisation provide an accurate indication of relative maturities. For mature Viking Graben samples (Ro>0.7) a reliable indication of relative maturity is gained if Tmax, Ts(Ts+Tm), C29ββ/(ββ+αα) steranes and the Triaromatic Index are considered together. The most reliable parameters for the determination of depositional redox are pristane/phytane and the C35/C34 homohopane ratio, together with the concentrations of V, Cu, Ni and Mo. In the brackish lagoon of the Brora Coal Formation (BCF) low sulphate availability does not appear to have limited the pyritisation of iron relative to the open marine facies of the Brora Argillaceous Formation (BAF). Despite this δ34Spyrite for BCF samples indicates that sulphate reduction took place in a closed system due to the rapid depletion of available sulphate. Only low concentrations of excess H2S were available for incorporation within the organic matter, organic sulphur abundances in the BCF being much lower than for the BAF. In open-marine sequences an increase in TOC is associated with an increase in anoxia, the preservation of hydrogen-rich organic matter and the abundance of organic sulphur. A generally correlated increase in pyrite sulphur suggests both these modes of sulphur are associated with increasing concentrations of diagenetic sulphides (H2S and its partial oxidation products) generated through bacterial sulphate reduction. The greatest abundances of organic sulphur are formed when sulphide concentrations are high whilst sub-oxic surficial sediments are maintained so that polysulphides are generated within the sediment (by partial oxidation of H2S) for rapid sulphur incorporation. Improved preservation of labile organic matter leads to a increase in the abundance of organic compounds (e.g. sterenes and phytol derivatives) in which suitable functionalities exist for sulphur incorporation.
9

Global and local controls upon the deposition of organic-rich Cretaceous sequences of western Venezuela : a geochemical study

Perez-Infante, Julio Vicente 1996 (has links)
No description available.
10

An evaluation of biochemical and molecular techniques for monitoring microbial survival and persistence in soils

Macnaughton, Sarah 1992 (has links)
No description available.

Page generated in 0.0524 seconds