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No full textPrevious studies have shown that both younger and older adults exhibit similar brain activity while anticipating monetary gain but older adults exhibit less brain activity comparing to younger adults while anticipating monetary loss. In Anderson et al.’s (2011) study, they found that visual search was slower with a salient, task-irrelevant distractor previously associated with high reward than with an equally salient distractor previously associated with a smaller reward. We aim to determine if this modulation also occurs in a spatial cuing paradigm. In addition to this, we will examine effects of loss (low and high) between younger and older adults.Keywords: capture, reward, attentionKeywords: capture, reward, attentio
Influence of forest age on forms of carbon in Douglas-fir soils in the Oregon Coast Range
Full text linkThe amount and type of carbon (C) in a forest soil reflects the past balance between C accumulation and loss. In an old-growth forest soil, C is thought to be in dynamic equilibrium between accumulations and losses. Disturbance upsets this equilibrium by altering the microclimate, the amount and type of vegetation growing on a site, and properties that affect organic matter decomposition. We measured total C and forms of soil C in the L, F, and H layers and in the light fraction of soil organic matter in the 0- 10 cm of mineral soil in old-, second-, and young-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) soils in the Oregon Coast Range. Total C in L, F, and H layers and in organic material in the top 10 cm of mineral soil in old-growth forests was higher than in young- or second-growth forests. Old-growth forests had a higher lignin concentration and lower concentrations of sugar, hemicellulose, and cellulose in the L, F, and H layers and in the light fraction of organic material than second- or young-growth forests. Old-growth forests had greater amounts of fats, waxes, and oils, sugar, cellulose, and lignin, in the L, F, and H layers per square hectare and greater amounts of hemicellulose, cellulose, and lignin in the light fraction of organic matter in the 0-10 cm of mineral soil per square hectare than young- and second-growth forests. Concentrations of fats, waxes, and oils, sugar, and tannin in the light fraction of organic matter in the 0-10 cm of mineral soil did not differ with forest age.Keywords: stand age, soil carbon, density fractionation, carbon pool, forest soilsKeywords: stand age, soil carbon, density fractionation, carbon pool, forest soil
Quasi-three-dimensional modeling of rip current systems
Full text linkThe focus of the paper is the analysis of the flow in rip current systems generated by
channels in longshore bars on a beach. The horizontal variations of rip current systems are
described through the use of the quasi-three-dimensional nearshore circulation model
SHORECIRC. Model predictions are compared to laboratory measurements of waves and
current velocities throughout the entire rip current system and show reasonable
agreement. The rips in the two channels are found to behave differently because of the
depth variation across the basin. It is found that higher bottom stress leads to more stable
flow where the rip current meanders less and fewer eddies are generated. The wave
current interaction creates forcing which reduces the distance rip currents flow offshore
and can lead to a slow pulsation of the rip current. This pulsation is in addition to the
instabilities of a jet which can also be present in rip currents. The three dimensionality of
the rip current system is found to have a significant effect on the overall circulation
patterns.Keywords: numerical modeling, rip currents, nearshore circulation, wave
Fast walking tree method via recurrence reduction for biological string alignment
Full text linkThe meaning of biological sequences is a central problem
of modern biology. Although string matching is well understood
in the edit-distance model, biological strings
with transpositions and inversions violate this model's
assumptions. To align biologically reasonable strings, we
proposed the Walking Tree Method [4,5,6,7,8], an
approximate string alignment method that can handle
insertion, deletions, substitutions, translocations, and
more than one level of inversions. Our earlier versions
were able to align whole bacterial genomes (~1 Mbps)
and discover and verify genes. As extremely long
sequences can now be deciphered rapidly and accurately
without amplification [2,3,15], speeding up the method
becomes necessary. Via a technique that we call it
"recurrence reduction" in which same computations can
be looked up rather than recomputed, we are able to
significantly improve the performance, e.g., 400% for 1-
million base pair alignments.Keywords: Walking tree method, Biological string alignment, Recurrence reductionKeywords: Walking tree method, Biological string alignment, Recurrence reductio
Projected wave conditions in the Eastern North Pacific under the influence of two CMIP5 climate scenarios
Full text linkHindcast and 21st century winds, simulated by General Circulation Models (GCMs), were used to drive global- and regional-scale spectral wind-wave generation models in the Pacific Ocean Basin to assess future wave conditions along the margins of the North American west coast and Hawaiian Islands. Three-hourly winds simulated by four separate GCMs were used to generate an ensemble of wave conditions for a recent historical time-period (1976–2005) and projections for the mid and latter parts of the 21st century under two radiative forcing scenarios (RCP 4.5 and RCP 8.5), as defined by the fifth phase of the Coupled Model Inter-comparison Project (CMIP5) experiments. Comparisons of results from historical simulations with wave buoy and ERA-Interim wave reanalysis data indicate acceptable model performance of wave heights, periods, and directions, giving credence to generating projections. Mean and extreme wave heights are projected to decrease along much of the North American west coast. Extreme wave heights are projected to decrease south of ∼50°N and increase to the north, whereas extreme wave periods are projected to mostly increase. Incident wave directions associated with extreme wave heights are projected to rotate clockwise at the eastern end of the Aleutian Islands and counterclockwise offshore of Southern California. Local spatial patterns of the changing wave climate are similar under the RCP 4.5 and RCP 8.5 scenarios, but stronger magnitudes of change are projected under RCP 8.5. Findings of this study are similar to previous work using CMIP3 GCMs that indicates decreasing mean and extreme wave conditions in the Eastern North Pacific, but differ from other studies with respect to magnitude and local patterns of change. This study contributes toward a larger ensemble of global and regional climate projections needed to better assess uncertainty of potential future wave climate change, and provides model boundary conditions for assessing the impacts of climate change on coastal systems.Keywords: Wave climate, Eastern North Pacific, Climate change, GCM
Power Efficient Architectures for High Accuracy Analog-to-Digital Converters
Full text linkIncremental ADCs (IADCs) have found wide applications in sensor interface circuitry since, compared to ∆Σ ADCs, they provide low-latency high-accuracy conversion and easy multiplexing among multiple channels. On the other hand, continuous-time ∆Σ ADCs (CTDSM) have been receiving more and more attention as a power-efficient solution in targeting medium to high accuracy over wider range of signal bandwidth (tens of MHz). In this dissertation, novel configurations have been explored in both architectures for power-efficient and high-accuracy data conversion.
First, a multi-step incremental ADC (IADC) using multi-slope extended counting technique is described. Only one active integrator is used in the three-step conversion cycle. The accuracy of the IADC is extended by having it configured as multi-slope ADCs in two additional steps. The proposed IADC uses the same circuitry as a first-order IADC (IADC1), but it exhibits as good efficiency as its second-order ∆Σ ADC counterpart. For the same accuracy, the conversion cycle is shortened by a factor of more than 2⁹ compared to the IADC1. Fabricated in 0.18-μm CMOS process, the prototype ADC occupies 0.5 mm². With a 642 kHz clock, it achieves SNDR of 52.2 dB in the first step. The SNDR is boosted to 79.8 dB in the second step, and to 96.8 dB in the third step, over a 1 kHz signal band. The power consumption is 35 µW from a 1.5 V power supply. This gives an excellent Schreier FoM of 174.6 dB.
Secondly, a multi-step incremental ADC with extended binary counting is proposed. It achieves high accuracy by splitting one conversion cycle into two serial steps. During the first step, the ADC works as a first-order incremental ADC (IADC1). The second step reuses the single integrator and extends the accuracy to 16 bits by a two-capacitor SAR-assisted binary counting technique. For the same accuracy, the conversion cycle is shortened by a factor of more than 2⁸ as compared to the single-step IADC. Fabricated in 0.18-μm CMOS process, the SAR-assisted IADC achieves a peak SNR/SNDR/DR of 97.1/96.6/100.2 dB over a 1.2 kHz bandwidth, while dissipating 33.2 μW from a 1.5 V supply. This gives a Schreier FoM of 175.8 dB and Walden FoM of 0.25 pJ/conv.-step.
Finally, the design of a continuous-time ∆Σ modulator (CTDSM) to be used in an ultrasound beamformer for biomedical imaging is described. To achieve better resolution, the prototype modulator operates at 1.2 GHz. It incorporates a digital excess loop delay (ELD) compensation to replace the active adder in front of the internal quantizer. A digitally controlled reference-switching matrix, combined with the data-weighted averaging (DWA) technique, results in a delay-free feedback path. A multi-bit FIR feedback DAC, along with its compensation path, is used to achieve lower clock jitter sensitivity and better loop filter linearity. The modulator achieves 79.4 dB dynamic range, 77.3 dB SNR and 74.3 dB SNDR over a 15 MHz signal bandwidth. Fabricated in a 65 nm CMOS process, the core modulator occupies an area of only 0.16 mm² and dissipates 6.96 mW from a 1 V supply. A 58.6 fJ/conversion-step figure of merit was achieved.Keywords: Incremental ADC, multi-step operation, instrumentation and measurement, sensor interface, analog-to-digital converter, extended counting, chopper stabilization, delta-sigma ADC, multi-slope ADCsKeywords: Incremental ADC, multi-step operation, instrumentation and measurement, sensor interface, analog-to-digital converter, extended counting, chopper stabilization, delta-sigma ADC, multi-slope ADC
Continuous precipitation of ceria nanoparticles from a continuous flow micromixer
Full text linkCerium oxide nanoparticles were continuously
precipitated from a solution of cerium(III) nitrate and ammonium
hydroxide using a static microchannel T-mixer. Tmixer
synthesis results were compared with synthesis results
from batch precipitation. Findings show that the method of
mixing is important in the ceria precipitation process. Uniform
porous film structures and nanorods were produced
when the particle chemistry was synthesized using T-mixing
followed by spin coating. Batch mixing, when using higher
NH₄OH feed concentrations followed by spin coating, was
characterized by the heavy agglomeration of nanoparticles.
Similar, high aspect ratio nanorods were produced when
feed conditions in both batch mixing and T-mixing were
identical demonstrating that the momentum effects of continuous
microchannel T-mixing did not impact the synthesis
process. In addition, it was found that the micromixing
approach reduced the exposure of the Ce(OH)₃ precipitates
to oxygen, yielding hydroxide precipitates in place of CeO₂
precipitates. The key advantage of the micro-scale T-mixing
approach is higher throughput which is important for the
scaling of ceria nanoparticle production.Keywords: Ceria, Nanoparticles, Continuous flow synthesis, Microreactor, MicromixerKeywords: Ceria, Nanoparticles, Continuous flow synthesis, Microreactor, Micromixe
Knapweed hay as a nutritional supplement for beef cows fed low-quality forage
Full text linkAdvancing our ability to use invasive plants for producing commodities is central to the agricultural industry. Our objective was to evaluate Russian knapweed (Acroptilon repens [L.] DC.) as a winter feed supplement for ruminant livestock. In Experiment 1, we utilized three ruminally cannulated steers in a completely randomized design to compare the ruminal degradation characteristics of alfalfa and Russian knapweed. In the second experiment, Russian knapweed and alfalfa were compared as protein supplements using 48 midgestation, beef cows (530 ± 5 kg) offered ad libitum hard fescue (Festuca brevipila Tracey) straw in an 84-d study. Treatments included an unsupplemented control and alfalfa or Russian knapweed provided on an iso-nitrogenous basis. In Experiment 1, the rate and effective degradability of neutral detergent fiber was greater for alfalfa compared with Russian knapweed (P ≤ 0.02). Ruminal lag time for NDF (period before measurable disappearance began) was greater for knapweed (P = 0.03). Soluble nitrogen, rate of N degradation, rumen degradable N, and effective degradability of N were all greater for alfalfa compared with Russian knapweed (P &spilt; 0.01). In Experiment 2, supplementation increased (P &spilt; 0.01) cow weight gain and BCS compared to the unsupplemented control with no difference between alfalfa and Russian knapweed (P = 0.47). There was no difference (P = 0.60) in the quantity of straw offered between the unsupplemented cows and supplemented groups, but alfalfa fed cows were offered approximately 11% more (P = 0.03) than Russian knapweed-fed cows. Total DM offered to cows was greater (P &spilt; 0.01) for supplemented compared with unsupplemented cows with no difference noted between alfalfa and Russian knapweed (P = 0.79). Russian knapweed is comparable to alfalfa as a protein supplement for beef cows consuming low-quality forage. Using Russian knapweed as a nutritional supplement can help solve two major production problems; managing an invasive weed, and providing a feedstuff that reduces an impediment in livestock production systems.Keywords: Russian knapweed, Invasive weeds, Digestible protein, Livestock fee
The effect of low dose ionizing radiation on homeostasis and functional integrity in an organotypic human skin model
Full text linkOutside the protection of Earth’s atmosphere, astronauts are exposed to low doses of high linear energy transfer (LET) radiation. Future NASA plans for deep space missions or a permanent settlement on the moon are limited by the health risks associated with space radiation exposures. There is a paucity of direct epidemiological data for low dose exposures to space radiation-relevant high LET ions. Health risk models are used to estimate the risk for such exposures, though these models are based on high dose experiments. There is increasing evidence, however, that low and high dose exposures result in different signaling events at the molecular level, and may involve different response mechanisms. Further, despite their low abundance, high LET particles have been identified as the major contributor to health risk during manned space flight. The human skin is exposed in every external radiation scenario, making it an ideal epithelial tissue model in which to study radiation induced effects. Here, we exposed an in vitro three dimensional (3-D) human organotypic skin tissue model to low doses of high LET oxygen (O), silicon (Si) and iron (Fe) ions. We measured proliferation and differentiation profiles in the skin tissue and examined the integrity of the skin’s barrier function. We discuss the role of secondary particles in changing the proportion of cells receiving a radiation dose, emphasizing the possible impact on radiation-induced health issues in astronauts.Keywords: Differentiation profile, 3D skin equivalent, Heavy ion, Ionizing radiation, Radiation qualityKeywords: Differentiation profile, 3D skin equivalent, Heavy ion, Ionizing radiation, Radiation qualit