Effects of cropping practice dynamics on permanent grassland vegetation during the conversion to organic farming

The aim of this work was to identify the impact of farming practices on permanent grassland vegetation during the conversion from conventional to organic farming. We considered functional and species diversities in order to compare the different grassland categories based on the farming practices used over a period of six years - five years before conversion and one year after. We identified three categories of grasslands: those generally cut twice a year, those intensely grazed, and those that were used under diversified practices. We showed that grasslands characterised by cutting and low fertilization level have the highest species richness compared to the other two categories (23.2, 16.9 and 17 species, respectively), and the lowest pastoral index (45.9, 66.8 and 68.6, respectively). These cut paddocks also presented the highest functional diversity (i.e., richness of functional property attributes) for two of the properties studied: means of dispersal and establishment strategy as defined by Grime. Grasslands with diversified practices (grazing, cutting and nitrogen supply) were not characterised by any single or combined functional property attribute, to the contrary of the two other categories. Finally, farming practices alone do not explain all of the differences in vegetation. We therefore hypothesize that, first, the dynamics of permanent grassland vegetation following conversion to organic farming is only initiated by agricultural practices and, second, other key factors such as landscape characteristics affect these dynamics

Sub-femtosecond stark control of molecular photoexcitation with near single-cycle pulses.

Electric fields can tailor molecular potential energy surfaces by interaction with the electronic state-dependent molecular dipole moment. Recent developments in optics have enabled the creation of ultra-short few-cycle optical pulses with precise control of the carrier envelope phase (CEP) that determines the offset of the maxima in the field and the pulse envelope. This opens news ways of controlling ultrafast molecular dynamics by exploiting the CEP. In this work, we show that the photoabsorption efficiency of oriented H2CSO (sulfine) can be controlled by tuning the CEP. We further show that this control emanates from a resonance condition related to Stark shifting of the electronic energy levels

Net Charge on a Noble Gas Atom Adsorbed on a Metallic Surface

Adsorbed noble gas atoms donate (on the average) a fraction of an electronic charge to the substrate metal. The effect has been experimentally observed as an adsorptive change in the electronic work function. The connection between the effective net atomic charge and the binding energy of the atom to the metal is theoretically explored.Comment: ReVvTeX 3.1 format, Two Figures, Three Table

Assessing the agro-environmental sustainability of organic mixed-crop dairy systems on the basis of a multivariate approach

Sustainable development calls upon the farming sector to commit itself to the transmission of natural resources to future generations. The INRA research team of Mirecourt studies the design of environmentally-friendly farming systems. The design of these systems is based on a multitude of objectives, and their evaluation is determined by a wide range of criteria. This work aims at determining the practical conditions for implementing agricultural systems considered to be sustainable from an environmental point of view. Two organic dairy systems considered to be environmentally friendly ex ante have been designed in partnership with the staff of the INRA research team of Mirecourt. A grazing dairy system and a mixed-crop dairy system are being experimentally tested at the system scale. The two systems have environmental and agricultural objectives. They are managed using multi-objective decision rules and are assessed on their biotechnical and practical properties, using a structured multiyear experimental design, completed by a model-based assessment. Assessment is oriented towards progressive and permanent re-designing of the systems in order to increase their environmental sustainability and feasibility at the practical level. Knowledge acquired from the two prototypes will then have to be validated on commercial farms

Strongly Temperature Dependent Sliding Friction for a Superconducting Interface

A sudden drop in mechanical friction, between an adsorbed nitrogen monolayer and a lead substrate, occurs when the lead passes through the superconducting transition temperature. We attribute this effect to a sudden drop at the superconducting transition temperature of the substrate Ohmic heating. The Ohmic heating is due to the electronic screening current that results from the sliding adsorbed film.Comment: Revte

Low-lying, Rydberg states of polycyclic aromatic hydrocarbons (PAHs) and cyclic alkanes

TD-DFT calculations of low-lying, Rydberg states of a series of polycyclic hydrocarbons and cyclic alkanes are presented. Systematic variations in binding energies and photoelectron angular distributions for the first members of the s, p and d Rydberg series are predicted for increasing molecular complexity. Calculated binding energies are found to be in very good agreement with literature values where they exist for comparison. Experimental angle-resolved photoelectron spectroscopy results are presented for coronene, again showing very good agreement with theoretical predictions of binding energies and also for photoelectron angular distributions. The Dyson orbitals for the small "hollow" carbon structures, cubane, adamantane and dodecahedrane, are shown to have close similarities to atomic s, p and d orbitals, similar to the superatom molecular orbitals (SAMOs) reported for fullerenes, indicating that these low-lying, diffuse states are not restricted to π-conjugated molecules. © 2017 the Owner Societies

Model reduction in the back step fluid–thermal problem with variable geometry

A methodology is presented to undertake the development of reduced-order models (ROMs) in variable geometry fluid–thermal problems using the method of snapshots. First, some snapshots are calculated in computational domains that vary in both shape and number of grid points. These snapshots are projected onto a so-called virtual grid (defined in a virtual geometry) using a smooth transformation. Proper orthogonal decomposition (POD) modes are obtained from the associated virtual snapshots and projected back onto the original grids, where they are used to define expansions of the flow variables. The associated POD mode amplitudes are obtained minimizing a residual, which is calculated in terms of the reconstructed solution. POD modes are calculated using only a part of the computational domain, which will be called the projection window, and the residual is defined using only a limited number of points of the computational domain. This methodology is illustrated addressing the problem of heat transfer downstream of a backward facing step in the 2-D steady, laminar regime, with three free parameters, namely the Reynolds number, the wall temperature, and the step height

Angle-Resolved Photoelectron Spectroscopy and Scanning Tunnelling Spectroscopy Studies of the Endohedral Fullerene Li@C60

M. S., E. B., J. O. F. T. and E. E. B. C. gratefully acknowledge financial support from the Leverhulme Foundation (RPF-298 “PES of hollow nanomaterials”). M. S. and H. J. C. acknowledge the financial support of EPSRC DTP studentships (EP/M508214/1 and EP/N509644/1). R. S. acknowledges financial support from the Scottish Funding Council through SRD-Grant (HRO7003). The work of FR and BM is supported by the Fonds de la Recherche Fondamentale Collective (#T.0132.16 and J.0012.18) and by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award # DE-SC0012628. BM and FR thank the Fonds National de la Recherche (FRS.FNRS, Belgium) for its support. Computational resources were provided by Consortium des équipements de calcul intensif (CECI, FNRS 2.5020.11).Gas phase photoelectron spectroscopy (Rydberg Fingerprint Spectroscopy), TDDFT calculations and low temperature STM studies are combined to provide detailed information on the properties of the diffuse, low-lying Rydberg-like SAMO states of isolated Li@C60 endohedral fullerenes. The presence of the encapsulated Li is shown by the calculations to produce a significant distortion of the lowest-lying S- and P-SAMOs that is dependent on the position of the Li inside the fullerene cage. Under the high temperature conditions of the gas phase experiments, the Li is mobile and able to access different positions within the cage. This is accounted for in the comparison with theory that shows a very good agreement of the photoelectron angular distributions, allowing the symmetry of the observed SAMO states to be identified. When adsorbed on a metal substrate at low temperature, a strong interaction between the low-lying SAMOs and the metal substrate moves these states to energies much closer to the Fermi energy compared to the situation for empty C60 while the Li remains frozen in an off-centre position.Publisher PDFPeer reviewe

Photo-ionization and fragmentation of Sc3N@C80 following excitation above the Sc K-edge

We have investigated the ionization and fragmentation of a metallo-endohedral fullerene, Sc3N@C80, using ultrashort (10 fs) x-ray pulses. Following selective ionization of a Sc (1s) electron (hν = 4.55 keV), an Auger cascade leads predominantly to either a vibrationally cold multiply charged parent molecule or multifragmentation of the carbon cage following a phase transition. In contrast to previous studies, no intermediate regime of C2 evaporation from the carbon cage is observed. A time-delayed, hard x-ray pulse (hν = 5.0 keV) was used to attempt to probe the electron transfer dynamics between the encapsulated Sc species and the carbon cage. A small but significant change in the intensity of Sc-containing fragment ions and coincidence counts for a delay of 100 fs compared to 0 fs, as well as an increase in the yield of small carbon fragment ions, may be indicative of incomplete charge transfer from the carbon cage on the sub-100 fs time scale