Modelling diverse root density dynamics and deep nitrogen uptake — a simple approach

We present a 2-D model for simulation of root density and plant nitrogen (N) uptake for crops grown in agricultural systems, based on a modification of the root density equation originally proposed by Gerwitz and Page in J Appl Ecol 11:773–781, (1974). A root system form parameter was introduced to describe the distribution of root length vertically and horizontally in the soil profile. The form parameter can vary from 0 where root density is evenly distributed through the soil profile, to 8 where practically all roots are found near the surface. The root model has other components describing root features, such as specific root length and plant N uptake kinetics. The same approach is used to distribute root length horizontally, allowing simulation of root growth and plant N uptake in row crops. The rooting depth penetration rate and depth distribution of root density were found to be the most important parameters controlling crop N uptake from deeper soil layers. The validity of the root distribution model was tested with field data for white cabbage, red beet, and leek. The model was able to simulate very different root distributions, but it was not able to simulate increasing root density with depth as seen in the experimental results for white cabbage. The model was able to simulate N depletion in different soil layers in two field studies. One included vegetable crops with very different rooting depths and the other compared effects of spring wheat and winter wheat. In both experiments variation in spring soil N availability and depth distribution was varied by the use of cover crops. This shows the model sensitivity to the form parameter value and the ability of the model to reproduce N depletion in soil layers. This work shows that the relatively simple root model developed, driven by degree days and simulated crop growth, can be used to simulate crop soil N uptake and depletion appropriately in low N input crop production systems, with a requirement of few measured parameters

CPT Violation Implies Violation of Lorentz Invariance

An interacting theory that violates CPT invariance necessarily violates Lorentz invariance. On the other hand, CPT invariance is not sufficient for out-of-cone Lorentz invariance. Theories that violate CPT by having different particle and antiparticle masses must be nonlocal.Comment: Minor changes in the published versio

An Internet-Based Tool for Use in Assessing the Likely Effect of Intensification on Losses of Nitrogen to the Environment

The EU Nitrates, Habitat and National Emissions Ceilings directives and the Kyoto Agreement mean that agricultural losses of NO3, NH3 and N2O are under scrutiny by national and international environmental authorities. When farmers wish to intensify their operations, the authorities must then assess the likely environmental impact of the change in operation. The FARM-N internet tool was developed to help farmers and authorities agree how the farm will be structured and managed in the future, and to provide an objective assessment of the environmental losses that will result

Temperature and volatile organic compound concentrations as controlling factors for chemical composition of alpha-pinene-derived secondary organic aerosol

This work investigates the individual and combined effects of temperature and volatile organic compound precursor concentrations on the chemical composition of particles formed in the dark ozonolysis of alpha-pinene. All experiments were conducted in a 5m(3) Teflon chamber at an initial ozone concentration of 100 ppb and initial alpha-pinene concentrations of 10 and 50 ppb, respectively; at constant temperatures of 20, 0, or -15 degrees C; and at changing temperatures (ramps) from -15 to 20 and from 20 to -15 degrees C. The chemical composition of the particles was probed using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). A four-factor solution of a positive matrix factorization (PMF) analysis of the combined HR-ToF-AMS data is presented. The PMF analysis and the elemental composition analysis of individual experiments show that secondary organic aerosol particles with the highest oxidation level are formed from the lowest initial alpha-pinene concentration (10 ppb) and at the highest temperature (20 degrees C). A higher initial alpha-pinene concentration (50 ppb) and/or lower temperature (0 or -15 degrees C) results in a lower oxidation level of the molecules contained in the particles. With respect to the carbon oxidation state, particles formed at 0 degrees C are more comparable to particles formed at 15 degrees C than to those formed at 20 degrees C. A remarkable observation is that changes in temperature during particle formation result in only minor changes in the elemental composition of the particles. Thus, the temperature at which aerosol particle formation is induced seems to be a critical parameter for the particle elemental composition. Comparison of the HR-ToF-AMS-derived estimates of the content of organic acids in the particles based on m/z 44 in the mass spectra show good agreement with results from off-line molecular analysis of particle filter samples collected from the same experiments. Higher temperatures are associated with a decrease in the absolute mass concentrations of organic acids (R-COOH) and organic acid functionalities (-COOH), while the organic acid functionalities account for an increasing fraction of the measured particle mass.Peer reviewe

Perturbative Hamiltonian constraints for higher order theories

We present a method for constructing a consistent low energy canonical formalism for higher order time-derivative theories, extending the Dirac method to include perturbative Hamiltonian constraints. We apply it to two paradigmatic examples: the Pais-Uhlenbeck oscillator and the Bernard-Duncan scalar field. We also compare the results, both at the classical and quantum level, with the ones corresponding to a direct perturbative construction applied to the exact higher order theory. This comparison highligths the soundness of the present formalism.Comment: 26 pages, 4 figures; review section shortened and appendices change

Shockingly low water abundances in Herschel / PACS observations of low-mass protostars in Perseus

Protostars interact with their surroundings through jets and winds impacting on the envelope and creating shocks, but the nature of these shocks is still poorly understood. Our aim is to survey far-infrared molecular line emission from a uniform and significant sample of deeply-embedded low-mass young stellar objects in order to characterize shocks and the possible role of ultraviolet radiation in the immediate protostellar environment. Herschel/PACS spectral maps of 22 objects in the Perseus molecular cloud were obtained as part of the `William Herschel Line Legacy' survey. Line emission from H$_\mathrm{2}$O, CO, and OH is tested against shock models from the literature. Observed line ratios are remarkably similar and do not show variations with source physical parameters. Observations show good agreement with the shock models when line ratios of the same species are compared. Ratios of various H$_\mathrm{2}$O lines provide a particularly good diagnostic of pre-shock gas densities, $n_\mathrm{H}\sim10^{5}$ cm$^{-3}$, in agreement with typical densities obtained from observations of the post-shock gas. The corresponding shock velocities, obtained from comparison with CO line ratios, are above 20 km\,s$^{-1}$. However, the observations consistently show one-to-two orders of magnitude lower H$_\mathrm{2}$O-to-CO and H$_\mathrm{2}$O-to-OH line ratios than predicted by the existing shock models. The overestimated model H$_\mathrm{2}$O fluxes are most likely caused by an overabundance of H$_\mathrm{2}$O in the models since the excitation is well-reproduced. Illumination of the shocked material by ultraviolet photons produced either in the star-disk system or, more locally, in the shock, would decrease the H$_\mathrm{2}$O abundances and reconcile the models with observations. Detections of hot H$_\mathrm{2}$O and strong OH lines support this scenario.Comment: 28 pages, 12 figures, accepted to Astronomy & Astrophysic

Effects of post-mortem storage conditions of bovine epididymides on sperm characteristics:investigating a tool for preservation of sperm from endangered species

The aim of this study was to establish and validate a reliable and efficient protocol for the recovery and cryopreservation of epididymal spermatozoa used for in vitro fertilization, using bulls of two different age classes. Testicles from 26 (37–51 weeks old, group 1) and 19 (52–115 weeks old, group 2) Danish Holstein bulls were collected after slaughter and stored at 5°C. After 0, 24 or 48 h, epididymides were isolated and spermatozoa collected. Assessments included spermatozoal motility, viability and morphology before and after cryopreservation and in vitro embryo production. Results showed that live spermatozoa can be collected from epididymides of bulls after their death. Storage of the testicles at 5°C for 24 h followed by cryopreservation of recovered epididymal spermatozoa resulted in 21% (group 1) and 31% (group 2) blastocysts produced in vitro. These results illustrate that epididymal spermatozoa recovered from testicles kept in specific conditions can be used to preserve genetic material from endangered and threatened species or populations in nature as well as in domestic and zoo animals

Modeling of mouse experiments suggests that optimal anti-hormonal treatment for breast cancer is diet-dependent

Estrogen receptor positive breast cancer is frequently treated with anti-hormonal treatment such as aromatase inhibitors (AI). Interestingly, a high body mass index has been shown to have a negative impact on AI efficacy, most likely due to disturbances in steroid metabolism and adipokine production. Here, we propose a mathematical model based on a system of ordinary differential equations to investigate the effect of high-fat diet on tumor growth. We inform the model with data from mouse experiments, where the animals are fed with high-fat or control (normal) diet. By incorporating AI treatment with drug resistance into the model and by solving optimal control problems we found differential responses for control and high-fat diet. To the best of our knowledge, this is the first attempt to model optimal anti-hormonal treatment for breast cancer in the presence of drug resistance. Our results underline the importance of considering high-fat diet and obesity as factors influencing clinical outcomes during anti-hormonal therapies in breast cancer patients.Comment: 44 pages, 21 figure