8,990 research outputs found
Unravelling collembolan life belowground: Stoichiometry, metabolism and release of carbon and nitrogen
This thesis investigated carbon and nitrogen dynamics of soil dwelling Collembola by using direct measurements and stable isotope additions. In an isotope change experiment, collembolans exchanged between 6 and 10% of carbon and nitrogen in their body tissue per day to metabolism and between 0.5 and 2% to reproduction. When collembolans on low and high protein diets were compared, animals on the low protein quality depleted their tissue 15N values relative to those on high quality diet indicating that the nitrogen turnover decreased on the low protein quality diet. In a wheat microcosm investigating
source contributions from soil, roots and isotope labelled green manure the mixing model analysis indicated that photosynthate (root derived C) was the main carbon source for collembolans (54–79% of total C) indicating that the rhizosphere channel is very important for collembolans in addition to the detritus based channel
Compressed Sensing Based Direct Conversion Receiver With Interference Reducing Sampling
This paper describes a direct conversion receiver applying compressed sensing
with the objective to relax the analog filtering requirements seen in the
traditional architecture. The analog filter is cumbersome in an \gls{IC} design
and relaxing its requirements is an advantage in terms of die area, performance
and robustness of the receiver. The objective is met by a selection of sampling
pattern matched to the prior knowledge of the frequency placement of the
desired and interfering signals. A simple numerical example demonstrates the
principle. The work is part of an ongoing research effort and the different
project phases are explained.Comment: 3 pages, 5 figures, submitted to IEEE International Conference On
Sensing Communication and Networking 2014 (poster
Charting the Midwest: An Inventory and Analysis of Greenhouse Gas Emissions in America's Heartland
Presents a comprehensive overview of the Midwest's role in global climate change as a major emitter of greenhouse gases in both national and international terms. Analyzes emissions data, trends, and drivers by region, state, economic sector, and gas
Model-Based Calibration of Filter Imperfections in the Random Demodulator for Compressive Sensing
The random demodulator is a recent compressive sensing architecture providing
efficient sub-Nyquist sampling of sparse band-limited signals. The compressive
sensing paradigm requires an accurate model of the analog front-end to enable
correct signal reconstruction in the digital domain. In practice, hardware
devices such as filters deviate from their desired design behavior due to
component variations. Existing reconstruction algorithms are sensitive to such
deviations, which fall into the more general category of measurement matrix
perturbations. This paper proposes a model-based technique that aims to
calibrate filter model mismatches to facilitate improved signal reconstruction
quality. The mismatch is considered to be an additive error in the discretized
impulse response. We identify the error by sampling a known calibrating signal,
enabling least-squares estimation of the impulse response error. The error
estimate and the known system model are used to calibrate the measurement
matrix. Numerical analysis demonstrates the effectiveness of the calibration
method even for highly deviating low-pass filter responses. The proposed method
performance is also compared to a state of the art method based on discrete
Fourier transform trigonometric interpolation.Comment: 10 pages, 8 figures, submitted to IEEE Transactions on Signal
Processin
Contracts in the Salmon Aquaculture Industry: An Analysis of Norwegian Salmon Exports
Sales and distribution innovations have increased productivity in the salmon aquaculture industry. In this article, we investigate the use of fixed price contracts for Norwegian salmon exports to France based on all export transactions between the two countries. Our analysis shows that almost 25% of these exports were traded using fixed price contracts and contract prices were renegotiated at different intervals, including as infrequently as once a year. Some contracts allow the contracting parties to adjust contract prices when the export price moves significantly. Benchmark analysis, which shows a marginal 0.5% difference between average unit revenue for the year from spot sales relative to contract sales, indicates that contracts primarily change revenue time profiles. The use of contracts creates a wedge between salmon export prices and spot prices in periods of price volatility, which in turn reduces price transmission.Contracts, salmon aquaculture, International Relations/Trade, Productivity Analysis, Research Methods/ Statistical Methods, L14, Q22,
Old Metal-rich Globular Cluster Populations: Peak Color and Peak Metallicity Trends with Mass of Host Spheroids
We address the problem of the factors contributing to a peak color trend of
old metal-rich globular cluster (MRGC) populations with mass of their hosts,
early-type galaxies and spheroidal subsystems of spiral ones (spheroids). The
color-mass trend is often converted to a metallicity-mass trend under the
assumption that age effects are small or negligible. While direct estimates of
the ages of MRGC populations neither can rule out nor reliably support the
populations' age trend, key data on timing of the formation of spheroids and
other indirect evidence imply it in the sense: the more massive spheroid the
older on average its MRGC population. We show that the contribution of an
allowable age trend of the MRGC populations to their peak color trend can
achieve up to ~50 % or so. In this event the comparable value of the color
trend, ~30 %, is due to alpha-element ratio systematic variations of the order
of Delta[alpha/Fe] ~ 0.1 to 0.2 dex because of a correlation between the
[alpha/Fe] ratios and age. Hence a systematic variation of exactly [Fe/H]
ratios may turn out to be less significant among the contributors, and its
range many times lower, i.e. of the order of Delta[Fe/H] ~ 0.1 or even none,
than the corresponding range deduced by assuming no age trend.Comment: 5 pages, 1 figure, accepted for publication in Astronomische
Nachrichte
Exploratory modeling: Extracting causality from complexity
On 22 May 2011 a massive tornado tore through Joplin, Mo., killing 158 people. With winds blowing faster than 200 miles per hour, the tornado was the most deadly in the United States since modern record keeping began in the 1950s. ©2014. American Geophysical Union. All Rights Reserved
Dual-labelled (13C/15N) green manure to differentiate between plant uptake of organic and inorganic N
Experimental data is still lacking for determining whether plant uptake of organic nitrogen in agricultural soils contributes substantially to the total N uptake. Pulseinjection studies with dual-labelled amino acids have confirmed that non-mycorrhizal crops possess the capacity to take up organic N but failed to quantify the uptake relative to total N uptake
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