Evaluation of the CENTURY model with laboratory measured soil respiration

Non-Peer ReviewedThe CENTURY model is widely used in assessing the effect of management on soil C dynamics. However, recent testing of the model revealed that it performed unsatisfactorily in simulating soil C changes in southwestern Saskatchewan, suggesting that the model may need further testings and modifications. Evaluations of the model were made with measurements conducted in an laboratory experiment which included different straw placements (incorporated in the soil and applied on the soil surface) and soil water regimes (continuously moist and moist-dry). Results from model testing revealed some weaknesses of the model and modifications were made to improve model performance. The temperature function was modified to slightly increase the relative decomposition rate when temperatures were below the reference temperature. The moisture function was modified to reduce the relative decomposition rate when the soil moisture was very low. The modified model also assumed that soil mineral N is readily available for the use of decomposition of soil C pools, but only about 6.6 mg m-2 d-1 of soil N is available for C pools on the soil surface. When N availability is less than that required for maximum decomposition rates of soil or surface pools, decomposition rates of these pools were reduced until supply met demand. The modified model improved simulations of daily C fluxes, cumulative CO2 emissions and soil mineral N. To use this modified model for estimating soil respiration in the field, further studies on the N availability for soil surface C pools and the dryness of surface-placed residue are needed. The concentration of CO2 in the atmosphere has increased by about 25% since the beginning of the industrial revolution. There are concerns that continuing increases in levels of CO2 and other greenhouse gases will contribute to global warming. Soils contains about three times as much C as the atmosphere, and they have the potential to store additional C (Campbell and Zentner, 1993). Agricultural soils on the Canadian prairies contain about 3 Pg soil organic carbon (SOC) in the top 30 cm layer, which is about 20 times the amount of CO2-C emitted annually by fossil fuel combustion in Canada. Research shows that if properly managed agricultural lands could be an important sink for C. Management options to enhance C storage in Canadian prairie soils include: decreasing summer fallow frequency, reducing tillage, including legumes in crop rotations, proper fertilization, and growing forage and trees on marginal lands (Campbell and Zentner, 1993; Campbell et al., 1995). For example, reduction in tillage intensity, especially no-tillage (NT) cropping, has been shown to increase SOC at various locations (Janzen, et al. 1998). Although changes in SOC occur when soil management practices are altered (Mann, 1986), it is common for these changes to remain undetectable for 10 or 20 years. The reason is that because of the inherent spatial variability of SOC in the field, too many samples are required to be taken to ensure that small differences can be statistically separated (Campbell et al., 1976; Campbell et al., 2000). Thus, we often use a process-based simulation model that describes soil organic matter turnover and nitrogen cycling dynamics in soils to estimate management induced SOC changes. The CENTURY model (Parton et al., 1987) is one of such models that is the most widely used and has been extensively evaluated in various ecosystems (Scholes et al., 1997). However, the recent testing of the CENTURY model revealed that it performed unsatisfactorily in simulating soil C changes in a 30-yr crop rotation experiment in southwestern Saskatchewan (Campbell et al., 1999), suggesting that the model may need further testings and modifications for use on the Canadian prairies. Because of the problems associated with SOC measurement and the variability of environmental conditions in the field, it is difficult to rigorously test the mechanism of a process-based soil organic matter model. Alternatively, the model can be readily tested against measurements of CO2 emissions from a controlled laboratory experiment. The objectives of this study were thus: (1) to test the validity of the CENTURY model with the soil respiration measured from laboratory experiments and (2) to address the weaknesses revealed during the model testings by modifying the model

Generalized Buneman pruning for inferring the most parsimonious multi-state phylogeny

Accurate reconstruction of phylogenies remains a key challenge in evolutionary biology. Most biologically plausible formulations of the problem are formally NP-hard, with no known efficient solution. The standard in practice are fast heuristic methods that are empirically known to work very well in general, but can yield results arbitrarily far from optimal. Practical exact methods, which yield exponential worst-case running times but generally much better times in practice, provide an important alternative. We report progress in this direction by introducing a provably optimal method for the weighted multi-state maximum parsimony phylogeny problem. The method is based on generalizing the notion of the Buneman graph, a construction key to efficient exact methods for binary sequences, so as to apply to sequences with arbitrary finite numbers of states with arbitrary state transition weights. We implement an integer linear programming (ILP) method for the multi-state problem using this generalized Buneman graph and demonstrate that the resulting method is able to solve data sets that are intractable by prior exact methods in run times comparable with popular heuristics. Our work provides the first method for provably optimal maximum parsimony phylogeny inference that is practical for multi-state data sets of more than a few characters.Comment: 15 page

InPBi Single Crystals Grown by Molecular Beam Epitaxy

InPBi was predicted to be the most robust infrared optoelectronic material but also the most difficult to synthesize within In-VBi (V = P, As and Sb) 25 years ago. We report the first successful growth of InPBi single crystals with Bi concentration far beyond the doping level by gas source molecular beam epitaxy. The InPBi thin films reveal excellent surface, structural and optical qualities making it a promising new III–V compound family member for heterostructures. The Bi concentration is found to be 2.4 ± 0.4% with 94 ± 5% Bi atoms at substitutional sites. Optical absorption indicates a band gap of 1.23 eV at room temperature while photoluminescence shows unexpectedly strong and broad light emission at 1.4–2.7 μm which can't be explained by the existing theory

Non-Markovian dynamics in a spin star system: The failure of thermalization

In most cases, a small system weakly interacting with a thermal bath will finally reach the thermal state with the temperature of the bath. We show that this intuitive picture is not always true by a spin star model where non-Markov effect predominates in the whole dynamical process. The spin star system consists a central spin homogeneously interacting with an ensemble of identical noninteracting spins. We find that the correlation time of the bath is infinite, which implies that the bath has a perfect memory, and that the dynamical evolution of the central spin must be non- Markovian. A direct consequence is that the final state of the central spin is not the thermal state equilibrium with the bath, but a steady state which depends on its initial state.Comment: 8 page

Mass measurements of neutron-deficient Y, Zr, and Nb isotopes and their impact on rp and νp nucleosynthesis processes

© 2018 The Authors. Published by Elsevier B.V. This manuscript is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence (CC BY-NC-ND 4.0). For further details please see: https://creativecommons.org/licenses/by-nc-nd/4.0/Using isochronous mass spectrometry at the experimental storage ring CSRe in Lanzhou, the masses of 82Zr and 84Nb were measured for the first time with an uncertainty of ∼10 keV, and the masses of 79Y, 81Zr, and 83Nb were re-determined with a higher precision. The latter are significantly less bound than their literature values. Our new and accurate masses remove the irregularities of the mass surface in this region of the nuclear chart. Our results do not support the predicted island of pronounced low α separation energies for neutron-deficient Mo and Tc isotopes, making the formation of Zr–Nb cycle in the rp-process unlikely. The new proton separation energy of 83Nb was determined to be 490(400) keV smaller than that in the Atomic Mass Evaluation 2012. This partly removes the overproduction of the p-nucleus 84Sr relative to the neutron-deficient molybdenum isotopes in the previous νp-process simulations.Peer reviewe

Quantum spin pumping with adiabatically modulated magnetic barrier's

A quantum pump device involving magnetic barriers produced by the deposition of ferro magnetic stripes on hetero-structure's is investigated. The device for dc- transport does not provide spin-polarized currents, but in the adiabatic regime, when one modulates two independent parameters of this device, spin-up and spin-down electrons are driven in opposite directions, with the net result being that a finite net spin current is transported with negligible charge current. We also analyze our proposed device for inelastic-scattering and spin-orbit scattering. Strong spin-orbit scattering and more so inelastic scattering have a somewhat detrimental effect on spin/charge ratio especially in the strong pumping regime. Further we show our pump to be almost noiseless, implying an optimal quantum spin pump.Comment: 14 pages, 9 figures. Manuscript revised with additional new material on spin-orbit scattering and inelastic scattering. Further new additions on noiseless pumping and analytical results with distinction between weak and strong pumping regimes. Accepted for publication in Physical Review

MIP-based protein profiling: A method for interspecies discrimination

Due to recent public concern and interest in the authenticity and origin of meat, for example, the 2013 “horsemeat scandal” in the human food chain, novel sensor strategies for the discrimination between protein species are highly sought after. In this work, molecularly imprinted polymers (MIPs) are utilised for protein discrimination using electrochemical sensor and spectrophotometric techniques. MIP selectivity between two proteins of similar molecular weight (haemoglobin and serum albumin) were compared across three different species, namely pork, beef and human. Bulk MIPs resulted in Kd and Bmax values of 184±23 µM, and 582 µmol g-1 for BHb, 246.3±26 µM, and 673 µmol g-1 for HHb; 276±31 µM, and 467 µmol g-1 for PHb. With the aid of chemometrics, i.e. multivariate analysis and pattern recognition, distinctive protein profiles have been achieved for species discrimination in both spectrophotometric and electrochemical analysis experiments. MIP suitability and selectivity within complex matrices was also assessed using urine, human plasma and human serum. Pattern recognition MIP-based protein profiling demonstrated positive outputs yielding either a ‘bovine’ or ‘not-bovine’ outcome (p = 0.0005) for biological samples spiked with/without bovine using respective bovine haemoglobin MIPs

A hyperchaotic system without equilibrium

Abstract: This article introduces a new chaotic system of 4-D autonomous ordinary differential equations, which has no equilibrium. This system shows a hyper-chaotic attractor. There is no sink in this system as there is no equilibrium. The proposed system is investigated through numerical simulations and analyses including time phase portraits, Lyapunov exponents, and Poincaré maps. There is little difference between this chaotic system and other chaotic systems with one or several equilibria shown by phase portraits, Lyapunov exponents and time series methods, but the Poincaré maps show this system is a chaotic system with more complicated dynamics. Moreover, the circuit realization is also presented

Direct Measurements of the Branching Fractions for D0→K−e+νeD^0 \to K^-e^+\nu_e and D0→π−e+νeD^0 \to \pi^-e^+\nu_e and Determinations of the Form Factors f+K(0)f_{+}^{K}(0) and f+π(0)f^{\pi}_{+}(0)

The absolute branching fractions for the decays $D^0 \to K^-e ^+\nu_e$ and $D^0 \to \pi^-e^+\nu_e$ are determined using $7584\pm 198 \pm 341$ singly tagged $\bar D^0$ sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC. In the system recoiling against the singly tagged $\bar D^0$ meson, $104.0\pm 10.9$ events for $D^0 \to K^-e ^+\nu_e$ and $9.0 \pm 3.6$ events for $D^0 \to \pi^-e^+\nu_e$ decays are observed. Those yield the absolute branching fractions to be $BF(D^0 \to K^-e^+\nu_e)=(3.82 \pm 0.40\pm 0.27)$ and $BF(D^0 \to \pi^-e^+\nu_e)=(0.33 \pm 0.13\pm 0.03)$. The vector form factors are determined to be $|f^K_+(0)| = 0.78 \pm 0.04 \pm 0.03$ and $|f^{\pi}_+(0)| = 0.73 \pm 0.14 \pm 0.06$. The ratio of the two form factors is measured to be $|f^{\pi}_+(0)/f^K_+(0)|= 0.93 \pm 0.19 \pm 0.07$.Comment: 6 pages, 5 figure