Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 334 for “"biogenic"”.
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Biogenic silica dynamics of Arctic marine ecosystems
… silicon (Si) cycle through the formation of biogenic silica (bSiO2). Continental shelves account for half of the total marine area in the Arctic, yet our knowledge of the cycling of Si for this critically climate-impacted region is limited. The overall objective of this thesis was to improve …
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Hydrothermal processing of biogenic residues in Germany
… field of action is the more efficient use of biogenic residues as secondary raw materials. However, high water containing biomasses are still a problem since they need an energy- and cost-intensive pre-treatment for many conversion processes, which can make their use uneconomical. Hydrothermal …
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Mechanisms of biogenic formaldehyde generation in wood
This work addresses biogenic formaldehyde (CH₂O) generated by wood during the manufacture of non-structural wood-based composites, from which CH₂O emissions are regulated. The target for regulation has been anthropogenic CH₂O released from hydrolytically unstable amino resins like …
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Trace element geochemistry of marine biogenic particulate matter
… of trace element/major element ratios in the biogenic materials. The majority of the trace elements in the samples were directly associated with the non-skeletal organic phases of the plankton. These associations included a very labile fraction which was rapidly released into seawater and a …
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INFLUENCE OF BIOGENIC AMINES ON BOVINE LUTEAL STEROIDOGENESIS
<p>To investigate the role of catecholamines and biogenic amines in the control of bovine luteal steroidogenesis, studies were conducted utilizing collagenase-dispersed luteal cells in a short-term incubation system. Studies designed to assess the role of catecholamines showed that the stimulatory …
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Modeling secondary organic aerosol formation from biogenic hydrocarbons
<p>Secondary organic aerosol (SOA) is formed generally by the oxidation of gas-phase volatile organic compounds (VOCs) to form semi- or non-volatile products that then undergo gas to particle partitioning. In this work, the Caltech Atmospheric Chemistry Mechanism (CACM) and the Model to Predict the …
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Trace element geochemistry of marine biogenic particulate matter
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1981.
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The production of biogenic gases in the marine environment
The biogenic trace gases dimethylsulphide (DMS) and methane play a major role in the Earth’s climate and atmospheric chemistry. DMS makes a significant negative contribution to radiative forcing and methane is an important greenhouse gas. The marine environment is an important source of both DMS …
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Effective management solutions for biogenic odour in drinking water
Biogenic taste and odour in drinking water has become a global concern for water utilities, as eutrophication and climate change are increasing the likelihood of algal blooms and other microbial events in waterbodies. Unpleasant taste and odour perceived by consumers may result in complaints and …
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High Resolution Paleothermometry Using Biogenic Silica: A Feasibility Study
<p> Biogenic silica is produced by numerous organisms that include grasses, protozoa, and Chrysophyceae, as well as marine and freshwater diatoms and sponges (Simpson and Volcani, 1981). It is therefore not uncommon for biogenic silica to be found in environments subject to wildfires. Experimental …
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Biogenic Tracers Through the Holocene on the Alaskan Shelf
… (1) develop an analytical method for determining biogenic calcite, (2) identify the major sources of biogenic matter into the system over the Holocene, and (3) assemble the history of depositional events that have occurred in the Alaskan shelf over the Holocene.</p> <p>The C/N and δ<sup>13</sup>C …
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The Search For Volatile Biogenic Emissions In Geothermal Areas
A primary discipline of astrobiology is the search for life outside of the earth’s ecosystem. Detecting biosignatures in outer space is one way this search is conducted. To understand the biosignatures to look for and study in space, it is useful to gain a better understanding of life in diverse …
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The Search For Volatile Biogenic Emissions In Geothermal Areas
A primary discipline of astrobiology is the search for life outside of the earth’s ecosystem. Detecting biosignatures in outer space is one way this search is conducted. To understand the biosignatures to look for and study in space, it is useful to gain a better understanding of life in diverse …
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Mechanistic understanding of biogenic Mn-oxide mediated bisphenol A degradation
Bisphenol A (BPA) is a monomer of polycarbonate plastic which is produced in a large volume. The environmental fate of BPA has been of great concern due to its estrogenic properties. BPA had been considered recalcitrant under anoxic conditions, but recent studies showed that BPA is degraded by …
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Emission of biogenic halocarbons in temperate and tropical coastal zones
Biogenically-produced halocarbons play an important role in regional and global biogeochemical processes. These compounds are short-lived (lifetimes <6 months) and so have temporal and spatial variability in their atmospheric distributions. Marine regions, in particular coastlines, have been …
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Biogenic buildups and carbonate sedimentation, Dry Tortugas Reef Complex, Florida
… a general depth of 17-21 m.</p> <p>Three basic biogenic buildups (facies) comprise the reef complex: 1) detrital lagoonal bank, 2) Montastrea reef bank and 3) <i>Acropora palmata</i> reef. These facies lie adjacent to one another and are also present in vertical succession as individual growth …
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Analysis of Biogenic Amines by GC/FID and GC/MS
Low levels of biogenic amines occur naturally, but high levels (FDA sets 50 ppm of histamine in fish as the maximum allowable level) can lead to scombroid poisoning. Amines in general are difficult to analyze by Gas Chromatography (GC) due to their lack of volatility and their interaction with the …
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3D printing of bone scaffolds using powders derived from biogenic sources
… used in the present work are three types of biogenic calcium carbonate, i.e. calcium carbonate that is produced by living organisms in the form of aragonite or calcite. Among the different sources, three biogenic calcium carbonates were chosen: cuttlefish (Sepia Officinalis) bones, mussel …
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