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A Compton-Suppressed Phoswich Detector for Gamma Spectroscopy
Get PDFA phoswich detector with two scintillation layers has been designed and assembled at Oregon State University. This detector is able to identify and reject Compton events and ultimately reduce the Compton continuum in gamma energy spectra. In this detector, CsI(Tl) crystal is used to primarily detect photoelectric events. The CsI(Tl) crystal is partially surrounded by a BGO crystal layer to capture and identify Compton-scattered photons. Both crystals are optically coupled to a single photomultiplier tube. A real-time, FPGA-based digital pulse shape analysis was developed to discriminate and reject Compton-induced pulses from the CsI(Tl) crystal. All the digital pulse processing functions including pulse shape discrimination analysis, pile-up rejection and energy measurement were implemented in an on-board FPGA device. In this paper, the results of recent measurements using radioactive lab sources will be presented and discussed.Keywords: Phoswich Detectors, Digital Pulse-Shape Discrimination, Compton Suppression, Gamma Spectroscopy, Scintillator
Agronomic guidelines for flexible cropping systems in dryland areas of Oregon
Get PDFFlexible cropping systems allow for an opportunistic change in an established rotation. Plant-available soil water is the most reliable indicator of potential yield.Keywords: plant-available soil water, dryland farming, flexible cropping systemsPublished November 2009. Reviewed December 2013. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalo
Solid-State Dynamics of Uranyl Polyoxometalates
Get PDFUnderstanding fundamental uranyl polyoxometalate
(POM) chemistry in solution and the solid state is
the first step to defining its future role in the development
of new actinide materials and separation processes
that are vital to every step of the nuclear fuel cycle. Many
solid-state geometries of uranyl POMs have been described,
but we are only beginning to understand their
chemical behavior, which thus far includes the role of templates
in their self-assembly, and the dynamics of encapsulated
species in solution. This study provides unprecedented
detail into the exchange dynamics of the encapsulated
species in the solid state through Magic Angle Spinning
Nuclear Magnetic Resonance (MAS NMR) spectroscopy. Although
it was previously recognized that capsule-like molybdate
and uranyl POMs exchange encapsulated species
when dissolved in water, analogous exchange in the solid
state has not been documented, or even considered.
Here, we observe the extremely high rate of transport of
Li⁺ and aqua species across the uranyl shell in the solid
state, a process that is affected by both temperature and
pore blocking by larger species. These results highlight
the untapped potential of emergent f-block element materials
and vesicle-like POMs.Keywords: polyoxometalate, solid-state NMR, uranyl, proton MAS NMR, ion-exchang
Teton Russet: An Early-Maturing, Dual-Purpose Potato Cultivar Having Higher Protein and Vitamin C Content, Low Asparagine, and Resistances to Common Scab and Fusarium Dry Rot
Get PDFTeton Russet is an early-maturing, medium-russeted, potato cultivar with high merit for both fresh-pack and processing. In early harvest trials in the Pacific Northwest, Teton Russet had total yields similar to Russet Norkotah, and higher than Ranger Russet and Russet Burbank. Marketable yield of Teton Russet in the early harvest trials was also comparable to or higher than Russet Norkotah in Washington and Oregon, and higher than Ranger Russet and Russet Burbank at these sites, as well as in Idaho. In full-season trials, while total yield of the earlier-maturing Teton Russet tended to be lower than Ranger Russet and Russet Burbank, marketable yield was generally higher than Russet Burbank across the majority of sites due to its higher percentage of U.S. No. 1 tubers. Teton Russet is suitable for processing, with acceptable fry color following up to 8 months of storage at 8.9°C. Uniformity of fry color was also very consistent. Teton Russet has shown lower levels of the amino acid asparagine relative to Ranger Russet and Russet Burbank which may contribute to lower acrylamide levels in French fries and other processed potato products. Teton Russet is notable for having resistance to common scab (Streptomyces spp.) and Fusarium dry rot, and is moderately resistant to tuber net necrosis. Analyses have also shown Teton Russet to have significantly higher protein levels than Russet Norkotah, Ranger Russet, and Russet Burbank, as well as higher vitamin C content than Russet Norkotah and Russet Burbank. Teton Russet was released in 2011 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Pacific Northwest Potato Variety (Tri-State) Development Program.Keywords: Processing, Solanum tuberosum, Variety, Asparagine, Breeding, Common scab resistance, Acrylamide, Fusarium dry rot resistance, Fresh pac
Energy Flux and Dissipation in Luzon Strait: Two Tales of Two Ridges
Get PDFInternal tide generation, propagation, and dissipation are investigated in Luzon Strait, a system of two quasi-parallel ridges situated between Taiwan and the Philippines. Two profiling moorings deployed for about 20 days and a set of nineteen 36-h lowered ADCP-CTD time series stations allowed separate measurement of diurnal and semidiurnal internal tide signals. Measurements were concentrated on a northern line, where the ridge spacing was approximately equal to the mode-1 wavelength for semidiurnal motions, and a southern line, where the spacing was approximately two-thirds that. The authors contrast the two sites to emphasize the potential importance of resonance between generation sites. Throughout Luzon Strait, baroclinic energy, energy fluxes, and turbulent dissipation were some of the strongest ever measured. Peak-to-peak baroclinic velocity and vertical displacements often exceeded 2 m s⁻¹ and 300 m, respectively. Energy fluxes exceeding 60 kW m⁻¹ were measured at spring tide at the western end of the southern line. On the northern line, where the western ridge generates appreciable eastward-moving signals, net energy flux between the ridges was much smaller, exhibiting a nearly standing wave pattern. Overturns tens to hundreds of meters high were observed at almost all stations. Associated dissipation was elevated in the bottom 500-1000 m but was strongest by far atop the western ridge on the northern line, where >500-m overturns resulted in dissipation exceeding 2 x 10⁻⁶ W kg⁻¹ (implying diapycnal diffusivity K[subscript p] > 0.2 m² s⁻¹). Integrated dissipation at this location is comparable to conversion and flux divergence terms in the energy budget. The authors speculate that resonance between the two ridges may partly explain the energetic motions and heightened dissipation.Keywords: Propagation, South China sea, Generation, Hawaiian ridge, Turbulence, Topography, Model, Internal tide, Ocea
Global assessment of ocean carbon export by combining satellite observations and food-web models
Get PDFThe export of organic carbon from the surface ocean by sinking particles is an important, yet
highly uncertain, component of the global carbon cycle. Here we introduce a mechanistic assessment of the
global ocean carbon export using satellite observations, including determinations of net primary production
and the slope of the particle size spectrum, to drive a food-web model that estimates the production of sinking
zooplankton feces and algal aggregates comprising the sinking particle flux at the base of the euphotic
zone. The synthesis of observations and models reveals fundamentally different and ecologically consistent
regional-scale patterns in export and export efficiency not found in previous global carbon export assessments.
The model reproduces regional-scale particle export field observations and predicts a climatological mean
global carbon export from the euphotic zone of ~6 Pg C yr⁻¹. Global export estimates show small variation
(typically <10%) to factor of 2 changes in model parameter values. The model is also robust to the choices of
the satellite data products used and enables interannual changes to be quantified. The present synthesis of
observations and models provides a path for quantifying the ocean’s biological pump.Keywords: remote sensing, biological pump, food webs, carbon cycle, carbon expor
Wildfire exposure and fuel management on western US national forests
Get PDFSubstantial investments in fuel management activities on national forests in the western US are part of a national strategy to reduce human and ecological losses from catastrophic wildfire and create fire resilient landscapes. Prioritizing these investments within and among national forests remains a challenge, partly because a comprehensive assessment that establishes the current wildfire risk and exposure does not exist, making it difficult to identify national priorities and target specific areas for fuel management. To gain a broader understanding of wildfire exposure in the national forest system, we analyzed an array of simulated and empirical data on wildfire activity and fuel treatment investments on the 82 western US national forests. We first summarized recent fire data to examine variation among the Forests in ignition frequency and burned area in relation to investments in fuel reduction treatments. We then used simulation modeling to analyze fine-scale spatial variation in burn probability and intensity. We also estimated the probability of a mega-fire event on each of the Forests, and the transmission of fires ignited on national forests to the surrounding urban interface. The analysis showed a good correspondence between recent area burned and predictions from the simulation models. The modeling also illustrated the magnitude of the variation in both burn probability and intensity among and within Forests. Simulated burn probabilities in most instances were lower than historical, reflecting fire exclusion on many national forests. Simulated wildfire transmission from national forests to the urban interface was highly variable among the Forests. We discuss how the results of the study can be used to prioritize investments in hazardous fuel reduction within a comprehensive multi-scale risk management framework.Keywords: Risk assessment, Wildfire exposure, Wildfire risk, Burn probability, National fores
Sea-surface aerodynamic roughness
Get PDFThis study surveys and evaluates similarity theory for estimating the sea-surface drag coefficient with the bulk aerodynamic method. The most commonly used formulations of the aerodynamic roughness length, required by similarity theory, are examined using data sets from four different field programs. These relationships include the Charnock formulation and the wave age modified Charnock relationship. The goal is to assess the overall performance of simple formulations of the roughness length including cases where the Charnock formulation is not expected to apply, and to assess the errors resulting from application of the Charnock formulation to all conditions, as is done in many numerical models where an explicit wave model cannot be accommodated. This examination indicates that spurious self-correlation explains more variance than actual physical relationships, even after eliminating weak wind cases. Frequent cases of anomalously low stress and very small values of the Charnock coefficient further reduce the usefulness of this formulation for the present data sets. Causes of the frequent very small values of the Charnock coefficient are briefly investigated.Keywords: Roughness length, Aerodynamic roughness length, Wave state, Charnock formulation, Monin-Obukhov similarity, Sea-surface stres
Sequestrate fungi from Patagonian Nothofagus forests: Cystangium (Russulaceae, Basidiomycota)
Get PDFSix species of Cystangium, a genus of
sequestrate taxa related to Russula, were collected
in Patagonia (Argentina and Chile) during autumn
2001. Two species, C. depauperatum Singer & A.H.
Sm. and C. nothofagi (E. Horak) Trappe, Castellano &
T. Lebel, were already known from this region, while
four new species, C. domingueziae, C. gamundiae, C.
grandihyphatum and C. longisterigmatum, are described,
illustrated and a key to the species is
provided. In addition, sequences of the ITS (rDNA)
region were obtained to explore the phylogenetic
relationships of our South American Cystangium
species.This is the publisher’s final pdf. The article is copyrighted by the Mycological Society of America and published by Allen Press Inc. It can be found at: http://www.mycologia.org/.Keywords: Russulales, Mycorrhiza, Truffle-like fungi, Hypogeous fung
Pinniped and seabird predation: implications for recovery of threatened stocks of salmonids in Oregon under the Oregon Plan for Salmon and Watersheds
Get PDFThe Independent Multidisciplinary Science Team (IMST) was directed to evaluate the extent of predatory impacts of marine mammals and seabirds on salmonids and to recommend actions to mitigate impacts. IMST focused on the Oregon Department of Fisheries and Wildlife Action Plans because they provide the programmatic direction for the State of Oregon in the context of the Oregon Plan for Salmon and Watersheds (Oregon Plan). Marine mammals and seabirds have been considered detrimental to salmon production for a long time, and extensive control programs are part of the history of salmon management. Unfortunately Oregon have not invested in enough research to accurately define the dimensions of the problem. Uncertainty regarding predators of salmonids by pinnipeds and birds is expressed in five science questions addressed in the report. IMST concludes that California sea lion, Pacific harbor seal, Caspian tern and cormorant populations along the Oregon coast have all increased in recent years, coinciding with historical lows in salmonid abundance. Predation by these species may be a factor in the lack of recoveries of some depressed salmonid stocks but there is no compelling scientific evidence that predation has been a primary cause for recent decline of salmonids. No comprehensive studies have been conducted to evaluate the importance of predation on escapement of wild stocks relative to other factors.This report was written by the Independent Multidisciplinary Science Team of the Oregon Plan for Salmon and Watersheds.Keywords: salmon, Oregon Plan for Salmon and Watershed, California sea lion, Caspian tern, cormorant, salmonids, pinnipeds, predation, seabirds, Pacific harbor sea