Charge localization in multiply charged clusters and their electrical properties: Some insights into electrospray droplets

The surface composition of charged Lennard-Jones clusters A$_N^{n+}$, composed of N particles (55 \leq N \leq 1169) among which n are positively charged with charge q, thus having a net total charge Q = nq, is investigated by Monte Carlo with Parallel Tempering simulations. At finite temperature, the surface sites of these charged clusters are found to be preferentially occupied by charged particles carrying large charges, due to Coulombic repulsions, but the full occupancy of surface sites is rarely achieved for clusters below the stability limit defined in this work. Large clusters (N = 1169) follow the same trends, with a smaller propensity for positive particles to occupy the cluster surface at non-zero temperature. We show that these charged clusters rather behave as electrical spherical conductors for the smaller sizes (N \leq 147) but as spheres uniformly charged in their volume for the larger sizes (N = 1169).Comment: 10 pages and 4 figure

an iron L-edge X-ray absorption study of the active centre

Iron L-edge X-ray absorption spectra of the active centre of myoglobin in the met-form, in the reduced form and upon ligation to O2, CO, NO and CN are presented. The strength of ligation with the iron centre is finger-printed through the variation of the L3 : L2 intensity ratio. Charge Transfer Multiplet calculations are performed and give qualitative information about oxidation states as well as charge transfer

Desorption of alkali atoms from 4He nanodroplets

The dynamics following the photoexcitation of Na and Li atoms located on the surface of helium nanodroplets has been investigated in a joint experimental and theoretical study. Photoelectron spectroscopy has revealed that excitation of the alkali atoms via the (n+1) -> ns transition leads to the desorption of these atoms. The mean kinetic energy of the desorbed atoms, as determined by ion imaging, shows a linear dependence on excitation frequency. These experimental findings are analyzed within a three-dimensional, time-dependent density functional approach for the helium droplet combined with a Bohmian dynamics description of the desorbing atom. This hybrid method reproduces well the key experimental observables. The dependence of the observables on the impurity mass is discussed by comparing the results obtained for the 6Li and 7Li isotopes. The calculations show that the desorption of the excited alkali atom is accompanied by the creation of highly non-linear density waves in the helium droplet that propagate at supersonic velocities

La fiscalité du bénéfice réel agricole doit-elle continuer de subventionner l’accumulation des moyens de production ?

En matière de fiscalité sur le revenu, l’activité agricole fait l’objet de deux régimes spéciaux : le régime du bénéfice forfaitaire réputé en voie de régression et le régime du bénéfice réel appelé à concerner la grande majorité des exploitations agricoles. Comme tout régime spécial d’imposition au bénéfice réel, le régime du réel agricole reprend des dispositions générales applicables à l’ensemble des activités économiques (le BIC ou régime du bénéfice industriel et commercial) auxquelles s..

Defining Mediterranean and Black Sea biogeochemical Subprovinces and Synthetic ocean indicators using mesoscale oceanographic features

The Mediterranean and Black Seas are semi-enclosed basins characterized by high environmental variability and growing anthropogenic pressure, which has led to increasing need for a bioregionalization of the oceanic environment at local and regional scales that can be used as a geographical reference with managerial applications. We aim to develop synthetic indices of the key oceanographic dynamics of each region to quantify baselines from which to assess variability and change. To do this, we compile a data set of 101 months (2002-2010) of a variety of both “classical” (i.e., sea surface temperature, surface chlorophyll a, and bathymetry) and “mesoscale” (i.e., eddy kinetic energy, finite-size Lyapunov exponents, and surface frontal gradients) ocean features that we use to characterize the surface ocean variability. We employ a k-means clustering algorithm to objectively define biogeochemical regions based on classical features, and for the first time, on mesoscale features and a combination of both classical and mesoscale features. Principal components analysis is then performed on the oceanographic variables to define integrative indices to monitor at monthly resolutions the environmental changes within each resultant region. Using both the classical and mesoscale features, we find five biogeochemical regions for the Mediterranean and Black Seas. Interestingly, the use of mesoscale variables contributes highly in the delineation of the open ocean. The first axis of the principal component analysis is explained primarily by classical ocean features and the second axis is explained by mesoscale features. Biogeochemical regions identified by the present study can be useful within the European management framework as an objective geographical framework of the Mediterranean and Black Seas, and the integrative environmental indices developed here can be used to monitor variability and long-term change.JRC.H.1-Water Resource

SEMICLASSICAL STUDY OF THE PHOTODISSOCIATION DYNAMICS OF VIBRATIONALLY EXCITED NH3_3(\ A) MOLECULES

A. W. Jasper, S. Nangia, C. Zhu and D. G. Truhlar, Acc. Chem. Res. 39D. A. McCormack and K. F. Lim, Phys. Chem. Chem. Phys. 1Author Institution: Department of Chemistry, University of Minnesota, 207 Pleasant Street S.E., Minneapolis, MN 55455-0431, USAThe photodissociation dynamics of ammonia upon excitation of the out-of-plane bending mode (mode $\nu_2$ with $n_2$=0,..,6 quanta of vibration) on its \~A electronic state is investigated by means of several semiclassical methods and compared to experiments. Five semiclassical methods are tested: one mean-field approach (the CSDM method), two surface-hopping methods (the FSTU and FSTU/SD methods) and two surface-hopping methods with zero-point energy preservation (the FSTU/SD/TRAPZ and FSTU/SD/mTRAPZ methods).}, 101 (2006); A. W. Jasper and D. G. Truhlar, J. Chem. Phys. \textbf{127}, 194306 (2007); D. Bonhommeau and D. G. Truhlar (in preparation)} We found a qualitative difference between distributions obtained for $n_2 = 0$ and $n_2 > 1$ which is experimentally observed. Distributions obtained for $n_2 = 1$ present an intermediate behavior between distributions obtained for smaller and larger n$_2$ values. The dynamics is also found to be highly electronically nonadiabatic with all these methods. NH$_2$ internal energy distributions may have a negative energy tail when the zero-point energy (ZPE) conservation is not ensured throughout the dynamics. Unlike the original TRAPZ (TRAjectory Projection onto Zero-point energy orbits) method,}, 1 (1999)} the mTRAPZ (modified TRAPZ) method does not lead to unphysical results and is much less time consuming. The effect of including ZPE corrections in semiclassical dynamics is also discussed in terms of agreement with experimental findings

Couplage AFM/Raman et spectroscopie Raman exaltée par effet de pointe de nanostructures

Pour mieux comprendre leurs propriétés, diverses nanostructures individuelles ont été étudiées à l aide d une technique couplant microscopie à force atomique et spectroscopie Raman confocale. Sous excitation lumineuse polarisée, la composition chimique, la structure et la présence de défauts a pu être précisée dans des nanobâtonnets d oxydes métalliques (ZnO et a-Fe2O3). Sous irradiation laser résonnante, les spectres de nanotubes de carbone monoparoi enrobés de polymères ont révélé notamment l absence de transfert de charge polymère-nanotube et un effet de désolvatation. Finalement, des feuillets de graphène oxydé et des ADNs double-brin peignés ont pu être préparés et caractérisés par spectroscopie Raman exaltée par effet de pointe en atteignant une résolution spatiale latérale voisine du rayon de courbure de l apex de la pointe utilisée ( 12 nm), bien plus faible que la limite de diffraction, ce qui ouvre la voie à de nouveaux travaux spectroscopiques à l échelle nanométrique.To better understand their properties, various nanostructures have been studied using a technique combining atomic force microscopy and confocal Raman spectroscopy. Under polarized light excitation, the chemical composition, the structure and the presence of defects has been described in metal oxides nanorods (ZnO et a-Fe2O3). Under resonant laser excitation, Raman spectra of polymer-wrapped single-walled carbon nanotubes have revealed the absence of polymer-nanotube charge transfer and an effect due to desolvation. Finally, graphene oxide sheets and combed double-stranded DNAs have been prepared and characterized using tip-enhanced Raman spectroscopy with a lateral spatial resolution down to the curvature radius of the apex of the used tip ( 12 nm), well below the diffraction limit, which opens new opportunities for spectroscopic works at the nanometer scale.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

When High Market Prices Sustain the Pressure on Fish Stocks: Ups and Downs of the European Eel Fishery Between 1961 and 2005

European eel (Anguilla anguilla) is one of the most important commercial species in France (eel larvae (glass eel) exports to Asia valuing more than 60 million euros in 2005) but also an endangered species with regard to the dropping recruitment. This species is particularly sensitive to oceanographic and climatic factors but also to anthropogenic factors. Prices of the European glass eel have tremendously increased for the past 40 years from a few euros per kilo to more than 1000 euros per kilo in 2005. The eel market offers a particular field of interest for research because of the mixed ecological and economic factors affecting the price equilibrium. An important set of market data between 1961 and 2005 has been collected from one of the most important glass eel traders in France. These data seem to be more reliable than the official statistics because the industry has a strong incentive to shadow their prices due to the high value of information on this market. We first examined the relationship between environmental factors and market data. Our results show the strong influence of oceanic environmental features on recruitment of European eel. These environmental factors might explain the production decrease in the early 1980s. We also demonstrate that this lower recruitment has led to an increase in price which has attracted other fishermen. When modelling prices like financial time series, we observed two structural breaks on the glass eel market. The emergence of new markets (Japan and then China) where the price elasticity is rather low has significantly enhanced the profitability of the fishery. It is commonly admitted that the low level of landings should hinder the economic returns of the fishery and hence keep the fishermen away from it. In the present case study, the reduction of landings has been compensated by higher market prices to such an extent that the licensed fishermen have kept on harvesting, thus increasing the pressure on stocks

Dynamics and thermodynamics of decay in charged clusters

We propose a method for quantifying charge-driven instabilities in clusters, based on equilibrium simulations under confinement at constant external pressure. This approach makes no assumptions about the mode of decay and allows different clusters to be compared on an equal footing. A comprehensive survey of stability in model clusters of 309 Lennard-Jones particles augmented with Coulomb interactions is presented. We proceed to examine dynamic signatures of instability, finding that rate constants for ejection of charged particles increase smoothly as a function of total charge with no sudden changes. For clusters where many particles carry charge, ejection of individual charges competes with a fission process that leads to more symmetric division of the cluster into large fragments. The rate constants for fission depend much more sensitively on total charge than those for ejection of individual particles

COASTAL MAPPING AND KITESURFING

Collecting data on aquatic biodiversity is very challenging because of the difficulty to access underwater ecosystems. Over the years, field surveys have become easier and cheaper with the development of low cost electronics. Commercial and recreational vessels, including sailboats, can now substantially complement expensive scientific surveys and arrays of observation buoys deployed across the world oceans (Pesant et al., 2015, Karsenti et al., 2011). Meanwhile, a large variety of marine animals such as birds, mammals, and fish have become data collection platforms for both biological and environmental parameters through the advent of archival tags. It becomes obvious that data collection in coastal and high seas will become more popular and that citizen will play a growing role in acquiring information on ocean dynamics (physical, chemical and biological parameters). However, currently, very few attempts have been made to use Human beings as observation platforms. In this paper we describe large datasets (more than 200,000 pictures) that have been recently collected along the coast of Mauritius by using popular and cheap platforms such as kite surf and Stand Up Paddle. We describe the characteristics of the data collected and showcase how they can be geolocated and used to complement remote sensing and mapping in order to drastically extend the current scope of “old school” fieldwork. We point out some of the main limitations encountered which need to be addressed to foster this citizen science approach such as data storage and transmission, deep learning to automate image recognition. The methods are all based on open source softwares