A phytoplankton bloom dominated by the pennate diatom Nitzschia
curta (Van Heurck) Hasle was observed during January-February 1983 at
a receding ice-edge in the Western Ross Sea, Antarctica. The core of
the bloom was found between 100-150 Km from the ice-edge. Nitzschia
curta cell densities up to 22 x 10⁶...
Dissolved silicic acid (Si(OH)4) and biogenic silica (BSiO2) concentrations were measured on four different cruises in the Southern Ocean along 1700 W from late October 1997 to mid-March 1998. These data were used to construct a vertically integrated Si budget in the surface layer from 58° to 68° S. Throughout...
Diatoms are a ubiquitous group of plankton responsible for 20-40% of oceanic
primary production, and a higher fraction of organic matter export to the ocean
interior. Diatoms actively transport dissolved inorganic silicon into their cells, and
through the process of silicification (i.e. biogenic silica production) they build tough
and intricate...
As the frequency and intensity of wildfires continue to occur in the West, so does the need for measures intended to improve firefighter safety; public safety; and the protection of property, resources, and wildlife. Furthermore, as human activity in the expanding Wildland Urban Interface increases, so does the need for...
The focus of this thesis is to design, characterize, and apply novel computational methods and molecular systems to interrogate heterogeneous human gut microbiome-related phenomena. In Chapter 2, I design, implement, and characterize a method for embedding co-occurrence patterns derived from massive 16s amplicon datasets. I use this method to 1....
Boreal and temperate biomes host nearly half of the earth’s forested ecosystems. The temperate rainforests of the Pacific coast of North America constitute nearly half of all temperate rainforests on earth. Along the northern extent of this region, the perhumid and sub-polar rainforests of southeast and southcentral Alaska are among...
There is a growing body of research that describes the benefits of place-based environmental education (EE) within the schools, including improved competencies, better interpersonal skills, decreased gaps in social divides, increased pupil engagement in learning, increased community awareness, and increased environmental stewardship. Though the benefits are many, few schools utilize...
Gut-brain communication consists of bidirectional routes between cognitive centers of the brain and peripheral intestines. This bidirectional communication is the result of the interplay between enteroendocrine cells (EECs), enteric nervous system, central nervous system, the vagus nerve, and our microbiota. Multiple studies have associated gut microbial dysbiosis with neurological disorders...
New delivery methods for radiotracers are constantly being proposed. Two key properties of the delivery method must be analyzed: dose to patient and effectiveness of delivery. In this work, the localized skin dose for intranasal administration of 18F was determined utilizing MCNP code. An anatomically accurate nasal cavity was constructed...
Natural landscapes around the world have experienced serious loss and degradation, which negatively impacts ecosystem service provision by these landscapes. As a result, there have been serious investments to restore natural capital. However, restoration faces complex trade-offs, such as that between restoration quality, or how closely the restored landscapes resembles...
Current neutron dosimetry methods rely on the assumption that charged particle equilibrium (CPE) is established within the tissue medium. This maintains that the kinetic energy transferred to the medium (KERMA) is equivalent to absorbed dose. However, this assumption is only valid for large volumes such as the whole body. For...
Over the last ten years, clinical, pre-clinical and animal studies have shown associations between the microbiota and neurological functions. Recent work by the scientific community on the gut-microbiome-brain axis have revealed that gut dysbiosis and specific microbial taxa are associated with a myriad of neurological conditions, such as autism spectrum...
The lens dose equivalent (LDE) is a regulatory limit set to protect radiation workers. Current methods for estimating the LDE are specific to beam sources in a vacuum and require interpolating data from tables. A new set of deterministic equations for photon and electron point sources has been developed. These...
A long running problem in mathematical biology is the prediction of extinction events, a specialized case of the larger global stability problem found in differential equations and dynamical systems theory. A central technical question is how to introduce the randomness observed in real ecological systems not accounted for in deterministic...
Microbial ecology has been transformed by metagenomics, the study of the genetic in-formation in entire communities of organisms. In the following we develop metagenomic tools arising from the classic Wasserstein metric as applied to questions regarding the diversity between microbial communities. We provide a novel proof of the characteriza-tion of...
Since the International Commission on Radiation Protection (ICRP) recommended a revision to the eye lens dose limits in ICRP Publication 118 (Stewart, 2012) the radiation protection community has conducted many new studies related to eye dosimetry. The recommended reduction of eye lens dose limits may result in the reduction of...
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DavidM. Hamby
Abstract:
Since the International Commission on Radiation Protection (ICRP
When the ICRP updated their recommended limits for eye dose, they ignited a renewed interest in eye dosimetry. Especially, how the updated eye dose estimates affect current regulations and what that would mean to a radiation worker. Radiation workers are commonly required to wear leaded eyeglasses to reduce their dose...
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DavidM. Hamby
Abstract:
When the ICRP updated their recommended limits for eye dose, they
Internal dosimetry models show a representation of how radionuclides move through the body. This study takes a look at radiation wounds by modelling a puncture wound to the hand using Microshield software. An analysis of these models provides a triangulation method that could be used to investigate wound characteristics, as...
In 1965 Malcolm X said that we are living in a time of extremism. People in power have misused it now there has to be a change, and a better world has to be built, and the only way it's going to be built is with extreme methods. And I,...
Cancer risk at low-dose ionizing radiation has been the subject of great scientific controversy in the past century. The clear majority of national and international radiation protection regulators adopt the linear no-threshold (LNT) model based on the atomic-bomb survivors Life Span Study (LSS) for solid cancer risk assessment. The LNT...
Nuclear energy is very efficient and cost-effective, but the stigma attached to it hinders its expansion around the world. However, with rising concerns over climate change and the fact that nuclear energy effectively has zero greenhouse gas emissions, there is an opportunity for nuclear to be more acceptable as a...
CR-39 foils were irradiated as part of nuclear accident dosimetry experiments using the Godiva reactor at the Nevada National Security Site and the Caliban and Prospero reactors at the Valduc Centre for Nuclear Studies in France. The irradiated foils were chemically etched using the standard Lawrence Livermore National Laboratory process...
Forest harvest persists as one of the most globally important industries, and crucially provides raw wood products for both building and fuel materials. Mechanistically complex abiotic and biotic processes curb ecosystem recovery following timber harvest and it is of great importance to understand the effects of this practice on biogeochemical...
My thesis explores the later work of author J.D. Salinger, including two narratives featured in Nine Stories, "A Perfect Day for Bananafish," and "Teddy," and Franny and Zooey, "Raise High the Roof Beam, Carpenters," and "Seymour: an Introduction." Through my analysis I argue that the religious nature of Salinger's fiction...
To quantify the relative activity contributions of beta emitters in mixed emission source spectra, the triple-layer phoswich detector was modeled to generate beta energy absorption spectra from mixed beta sources. These mixed sources include four pure beta emitters (C-14, Tc-99, Sr-90, and Y-90). Monte Carlo N-Particle (MCNP) computer code was...
The Code of Federal Regulations (10CFR20.1201) mandates occupational dose limits to the shallow, lens and deep tissue layers. The NRC-accepted procedure of estimating dose to these layers from contamination events is laborious. The current work aims to further the development of a portable phoswich-style skin dosimeter that will operate in...
The recent reductions to the international dose limit recommendations for the lens
of the eye have renewed interest in radiation protection strategies in interventional
fluoroscopy, where eye-lens radiation exposure occurs frequently. Radiationshielding
eyewear can significantly reduce lens dose in these scenarios, but accurate
protection factors are elusive because they depend...
The human health and environmental effects following a postulated accidental release of radioactive material to the environment has been a public and regulatory concern since the early development of nuclear technology and researched extensively to better understand the potential risks for accident mitigation and emergency planning purposes. The objective of...
'Hot particle' skin dosimetry calculations are commonly performed using homogeneous dose-point kernels (DPK) in conjunction with scaling and backscatter models to account for non-homogeneous geometries. A new scaling model for determining the actual DPK for beta-particles transmitted by a high-Z source material has been developed. The model is based on...
Recent changes in the historiography of American Transcendentalism
have inspired a reappraisal of the relationship between the Transcendentalist
movement in New England and the pietistic wing of the Unitarian church. This
thesis explores this reappraisal through a close reading of selected writings by
Henry Ware Jr. in juxtaposition to the...
Nathaniel Hawthorne lived and wrote in an age of reform efforts, and the progressive movement with which he was most familiar was Transcendentalism. However, he was not sympathetic with Emerson's idealism, a sentiment which comes out in his fiction in way of critique. Throughout Hawthorne's work there is an emphasis...
Bildungsroman in Contemporary Black Women's Fiction is a study of Toni
Morrison's The Bluest Eye and Alice Walker's The Color Purple. Both of these writers
implement a newer version of the genre of Bildungsroman to reveal the complexities
involved in coming of age for a young woman of color. Both...
The purpose of this research was to develop and test a radiation detector to perform beta dosimetry and spectroscopy. The detector utilizes plastic scintillator volumes to produce scintillation light in proportion to the amount of energy deposited in them, and a large-area avalanche photodiode to convert the light to electrical...
The National Council of Radiation Protection and Measurements
Report No. 49, originally issued on September 15, 1976, has been the
primary design guide for diagnostic x-ray structural shielding in the
United States. To further protect the public from various areas of
medical radiation exposure, NCRP issued Report 116 in 1987...
As human exploration of space continues, eventually sights will be set on establishing a permanent manned habitat on the surface of Mars. The success of such a base will depend on many new and developing technologies. Low mass and high energy density power production units will be of paramount importance....
As mandated by the Comprehensive Nuclear Test Ban Treaty (CTBT), the United States (US) is involved in the development and deployment of an International Monitoring System (IMS) for monitoring nuclear explosions. The US system, developed at Pacific Northwest National Laboratory, is known as the Automated Radioxenon Sampler/Analyzer (ARSA). The US...
The Department of Nuclear Engineering at Oregon State University has recently introduced a neutron radiography facility (OSNRF). The facility is dependent on a neutron source established by the OSU TRIGA® Reactor (OSTR). It was unknown how accurately a computerized model of the OSTR in conjunction with the OSNRF could represent...
This paper explores the language theories of Gary Snyder, an important modern environmental author whose early work was associated with the Beat movement of the early 1950's. I am particularly interested in Snyder's thoughts on how language relates to nature. I focus primarily on Snyder's prose in attempts to understand...
Fortuitous dosimeters are radiosensitive objects carried by an individual who was exposed to radiation. These objects can be analyzed some time after exposure and the results can be used to aid in calculating radiation fields and doses received by individuals. Items that make good fortuitous dosimeters are those that are...
Multi-layer optically coupled scintillation based radiation detectors, known as phoswich detectors, have rapidly evolved in recent years. During the same time, digital signal processing has improved radiation discrimination accuracy and enhanced reliability, while reducing complexity and size of traditional analog signal processing methods. A new generation of high-speed radiation detectors...
Digital Instrumentation and Detection is becoming the future of radiation detection and measurement. Computers are able to perform digitally what before would have taken an extensive array of analog equipment. The art of teaching radiation detection and measurement is following this same pattern of a shift from purely analog to...
International recommendations provided by the International Commission on Radiation Protection (ICRP), as well as national regulations, set by the U.S. Nuclear Regulatory Commission (NRC), state that the exposure of skin to highly concentrated radioactive sources should be monitored at specified depths in skin and kept below specific dose equivalence levels....
Tissue weighting factors, w[subscript T], used to convert equivalent dose to effective dose, account for differences in radiosensitivity of various organs in the human body and allow users to compare individual organ detriment to whole body risk. They are explicitly calculated in ICRP 26, 60, and 103, although the methods...
This work focuses on the generation and collection of four specific
radioxenon isotopes; xenon-131m, xenon-133m, xenon-133 and xenon-135. These
nuclides are created by fissioning a highly enriched uranium sample using a
thermal neutron source from a university research reactor. The three main aspects
of this work include:
(1) Conducting preliminary...
This thesis is a study of Herman Melville’s symbolism. I have chosen to investigate the elemental images of water, fire, and stone in Moby-Dick (1851), Pierre; Or, The Ambiguities (1852), and Clarel; A Poem and Pilgrimage in the Holy Land (1876). This work is a semiotic study, insofar as the...
In This Side of Paradise, The Great Gatsby, and several of his short stories, F. Scott Fitzgerald questions the importance of wealth as a factor in supporting happiness and fostering the American Dream on an individual basis. With these texts, Fitzgerald acknowledges that wealth is a factor and, simultaneously, a...
A lack of data concerning tungsten-based medical shields, specifically unit dose transport pigs, may lead to unnecessary exposure to medical personnel. Available research comparing lead to sintered tungsten shows that tungsten is approximately 1.5 - 10.0 times more effective as a radiation shield. However, this research lacks high-energy vs. low-energy...
In 2004 the National Toxicology Program published an article describing their intent to pursue toxicology testing and risk assessment practices solely reliant on high throughput in vitro datasets and in silico modeling for dose-response assessments. Support and contributions form regulatory agencies and a significant portion of the life sciences community...
Following European-American colonization of North America and associated landscape changes, barred owls (Strix varia) underwent a dramatic expansion of their historical range. The barred owl expanded across the previously tree-less Great Plains that had limited their distribution, and into the forests along the west coast. In these western forests they...
Metal organic frameworks(MOFs) are a class of crystalline materials utilized in gas storage, chemicalsensing, and other engineering applications. Recently chemists have begun synthesizing MOFs withmoving parts in order to further these applications. A wide array of dynamic MOFs have been created andtheorized. Among them is the interlocking of a ring...
The thesis analyzes the demographic, attitudinal and
behavioral characteristics of animal rights activists,
placing them in the context of resource policy. It is
argued that the animal rights movement combined the
Victorian critique of empiricism with a reaction to
modernity that was characteristic of other contemporary mass
movements. Animal rights...
The two most economically important plant pathogens in the Pseudoperonospora (Peronosporaceae) genus are P. cubensis, causal agent of cucurbit downy mildew, and P. humuli, causal agent of hop downy mildew. These organisms have been shown to be very closely related phylogenetically and morphologically. In 2005, researchers in Korea proposed that...
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David. H. Gent Cynthia M. Ocamb
The two most economically important plant pathogens in