Adsorption of imidazole on Au(111) surface: Dispersion corrected density functional study

We use density functional theory in the generalized gradient approximation to study the adsorption of imidazole on the Au(111) surface and account for dispersion effect using Grimme's empirical dispersion correction technique. Our results show that the adsorption energy of imidazole depends on the slab size and on the adsorption site. In agreement with other studies, we find the largest adsorption energy for imidazole on a top site of Au(111). However, we also note that the adsorption energy at other sites is substantial

Understanding of matrix embedding: a theoretical spectroscopic study of CO interacting with Ar clusters, surfaces and matrices

Through benchmark studies, we explore the performance of PBE density functional theory, with and without Grimme's dispersion correction (DFT-D3), in predicting spectroscopic properties for molecules interacting with rare gas matrices. Here, a periodic-dispersion corrected model of matrix embedding is used for the first time. We use PBE-D3 to determine the equilibrium structures and harmonic vibrational frequencies of carbon monoxide in interaction with small Ar clusters (CO–Arn, n = 1, 2, 3), with an Ar surface and embedded in an Ar matrix. Our results show a converging trend for both the vibrational frequencies and binding energies when going from the gas-phase to a fully periodic approach describing CO embedding in Ar. This trend is explained in terms of solvation effects, as CO is expected to alter the structure of the Ar matrix. Due to a competition between CO–Ar interactions and Ar–Ar interactions, perturbations caused by the presence of CO are found to extend over several Å in the matrix. Accordingly, it is mandatory to fully relax rare gas matrices when studying their interaction with embedded molecules. Moreover, we show that the binding energy per Ar is almost constant (∼−130 cm−1 atom−1) regardless of the environment of the CO molecule. Finally, we show that the concentration of the solute into the cold matrix influences the spectroscopic parameters of molecules embedded into cold matrices. We suggest hence that several cautions should be taken before comparing these parameters to gas phase measurements and to theoretical data of isolated species

NECC : un jeu de simulation pour l'aide à la décision collective. Application à une région méditerranéenne “virtuelle”

International audienceBeaucoup d'instruments d'aide à la décision sont maintenant accessibles et utilisés par les agriculteurs et les conseillers agricoles. Les simulations de budget sont les plus fréquemment utilis ées et les techniques d'optimisation sont très utilisées dans la recherche. Mais ces instruments ont des limites. De très nombreuses questions (marché, utilisation de ressources naturelles limitées) ne peuvent être prises en considération uniquement au niveau d'une exploitation agricole mais requièrent une approche globale. Le point central de cette communication est le jeu de rˆole développé pour tester différentes politiques de l'eau. Le jeu (NECC, négociation et évaluation des choix collectifs) se déroule en deux phases. Chaque joueur gère une exploitation ou un groupe d'exploitations. Chaque année, il doit décider son assolement, mais dans une première phase, il est en situation de décision individuelle, sans concertation, sans connaître la disponibilité en eau et le prix des produits qui dépendent des choix des autres joueurs. Dans une seconde étape, chacun des décideurs peut négocier avec les autres décideurs afin d'améliorer son système d'exploitation, le modèle utilisé calcule la rentabilité, en fonction du déficit hydrique et des prix en relation avec la production globale. Les décisions qui en découlent peuvent être très variées, de la simple information à une coopération, jusqu'à des stratégies de concurrence ou d'opposition. Les acteurs peuvent négocier et décider différentes formules pour ajuster la demande et la disponibilité en eau. Nous utilisons ce jeu avec de vrais acteurs et cela permet d'identifier la nécessité de coordination entre les différents acteurs qui prennent des décisions et la valeur de la négociation pour établir un ensemble de règles applicables collectivement. Ce jeu est un excellent outil d'apprentissage de la négociation et un support de test pour de nouvelles règles de gestion collective. MEDTER constitue une application dans une petite région méditerranéenne comprenant différents systèmes de production agricole

A supplement containing multiple types of gluconeogenic substrates alters intake but not productivity of heat-stressed Afshari lambs

Citation: Mahjoubi, E., Amanlou, H., Yazdi, M. H., Aghaziarati, N., Noori, G. R., Vahl, C. I., . . . Baumgard, L. H. (2016). A supplement containing multiple types of gluconeogenic substrates alters intake but not productivity of heat-stressed Afshari lambs. Journal of Animal Science, 94(6), 2497-2505. doi:10.2527/jas2015-9697Thirty-two Afshari lambs were used in a completely randomized design with a 2 x 2 factorial arrangement of treatments to evaluate a nutritional supplement designed to provide multiple gluconeogenic precursors during heat stress (HS). Lambs were housed in thermal neutral (TN) conditions and fed ad libitum for 8 d to obtain covariate data (period 1 [P1]) for the subsequent experimental period (period 2 [P2]). During P2, which lasted 9 d, half of the lambs were subjected to HS and the other 16 lambs were maintained in TN conditions but pair fed (PFTN) to the HS lambs. Half of the lambs in each thermal regime were fed (top-dressed) 100 g/d of a feed supplement designed to provide gluconeogenic precursors (8 lambs in HS [heat stress with Glukosa {HSG}] and 8 lambs in PFTN [pair-fed thermal neutral with Glukosa]) and the other lambs in both thermal regimes were fed only the basal control diet (HS without Glukosa [HSC] and pair-fed thermal neutral without Glukosa). Heat stress decreased DMI (14%) and by design there were no differences between the thermal treatments, but HSG lambs had increased DMI (7.5%; P < 0.05) compared with the HSC lambs. Compared with PFTN lambs, rectal temperature and skin temperature at the rump, shoulder, and legs of HS lambs were increased (P < 0.05) at 0700 and 1400 h. Rectal temperature at 1400 h decreased for HSG lambs (0.15 +/- 0.03 degrees C; P < 0.05) compared with HSC lambs. Despite similar DMI between thermal treatments, ADG for HS and PFTN lambs in P2 was decreased 55 and 85%, respectively, compared with lambs in P1 (P < 0.01). Although the prefeeding glucose concentration was not affected by thermal treatment or diet, HSG lambs had increased postfeeding glucose concentration compared with HSC lambs (P < 0.05). In contrast to the glucose responses, circulating insulin was influenced only by thermal treatment; HS lambs had increased insulin concentration (P < 0.01) before feeding and decreased concentration (P < 0.05) after feeding compared with PFTN lambs. Heat-stressed lambs had decreased NEFA concentration before feeding (P < 0.01) but not after feeding relative to PFTN lambs. Although this nutritional strategy did not affect ADG, the lower rectal temperature in HSG lambs indicates that dietary inclusion of a mixture of glucogenic precursors can potentially benefit animal health during HS

Using web and mobile phone technologies to collect food market prices in Africa. Approaching real-time data and use of crowdsourcing, 2013 - 2016

Large agricultural commodity price swings observed in recent years have made the importance of accessible, timely, accurate and frequently updated price data more obvious. This study investigates the potential of innovative web and mobile phone technologies and alternative data collection methods such as crowdsourcing in order to collect food price data in Africa. The report summarises these experiences through the lessons learned and provides a detailed overview and assessment of different aspects of the collected data that can be of help for the success of future food price collection exercises.JRC.D.4-Economics of Agricultur

Study of critical properties in B-spinel ZnxCd1-xCr2Se4 (0.35 ≤ x ≤ 0.58)

The critical behaviour of the B-spinel ZnxCd1-xCr2Se4 systems is studied in the concentration range 0.35≤x≤0.58. The mean field theory and the ferromagnetic spin-wave theory at low temperatures are combined to calculate the exchange integrals up to the third nearest neighbours. The ferromagnetic critical region is studied by the high-temperature series expansion (H.T.S.) extrapolated with the Padé (P.A) approximants method. The critical temperatures T c and the critical exponents associated with the magnetic susceptibility (γ) and the correlation length (ν) are estimated. The obtained values of T c are in good agreement with those obtained by magnetic measurements. The values of γ and ν are sensitive to the dilution ratio x. For the compounds situated in the ferromagnetic region ( 0.35≤x≤0.41), they are close to those of 3D Heisenberg model. For the compounds presenting re-entrant behaviour ( 0.41≤x≤0.58 ), γ and ν deviate slowly from those of this model and approach the values found in re-entrant systems.The critical behaviour of the B-spinel ZnxCd1-xCr2Se4 systems is studied in the concentration range 0.35≤x≤0.58. The mean field theory and the ferromagnetic spin-wave theory at low temperatures are combined to calculate the exchange integrals up to the third nearest neighbours. The ferromagnetic critical region is studied by the high-temperature series expansion (H.T.S.) extrapolated with the Padé (P.A) approximants method. The critical temperatures T c and the critical exponents associated with the magnetic susceptibility (γ) and the correlation length (ν) are estimated. The obtained values of T c are in good agreement with those obtained by magnetic measurements. The values of γ and ν are sensitive to the dilution ratio x. For the compounds situated in the ferromagnetic region ( 0.35≤x≤0.41), they are close to those of 3D Heisenberg model. For the compounds presenting re-entrant behaviour ( 0.41≤x≤0.58 ), γ and ν deviate slowly from those of this model and approach the values found in re-entrant systems

Study of Magnetic Superexchange in diluted Systems Znx Cd1-xCr2Se4 ( 0.35 ≤ x ≤ 0.58 )

The effects of cationic substitutions at different concentrations within the lattice Znx Cd1-xCr2Se4 (0.35≤x≤0.58) on the electronic transfer in chromium ions are investigated. For this propose, after taking into account the exchange integrals, we use the Anderson’s-Kanamori theory of superexchange to determine the transfer integrals bσσ and bπσ . With the use of the conventional molecular orbital model the covalency-mixing parameters, λσ and λπ, the electron spin transfer coefficients, ƒ i (i=σ, π, s ), and the total charge, C, transferred from ligand to the chromium ions, are evaluated. The variation of bσσ and bσπ with x agree with the passage of the system from ferromagnetic to antiferromagnetic order. For the compound presenting re-entrant behaviour (0.45≤x≤0.58), f s exhibits anomalous. The increasing in C with x is consistent with the expected decrease in covalency of the non magnetic cation in tetrahedral site.The effects of cationic substitutions at different concentrations within the lattice Znx Cd1-xCr2Se4 (0.35≤x≤0.58) on the electronic transfer in chromium ions are investigated. For this propose, after taking into account the exchange integrals, we use the Anderson’s-Kanamori theory of superexchange to determine the transfer integrals bσσ and bπσ . With the use of the conventional molecular orbital model the covalency-mixing parameters, λσ and λπ, the electron spin transfer coefficients, ƒ i (i=σ, π, s ), and the total charge, C, transferred from ligand to the chromium ions, are evaluated. The variation of bσσ and bσπ with x agree with the passage of the system from ferromagnetic to antiferromagnetic order. For the compound presenting re-entrant behaviour (0.45≤x≤0.58), f s exhibits anomalous. The increasing in C with x is consistent with the expected decrease in covalency of the non magnetic cation in tetrahedral site

Periodic dispersion-corrected approach for isolation spectroscopy of N2 in an argon environment: Clusters, surfaces, and matrices

© 2017 American Chemical Society. Ab initio and Perdew, Burke, and Ernzerhof (PBE) density functional theory with dispersion correction (PBE-D3) calculations are performed to study N 2 -Ar n (n ≤ 3) complexes and N 2 trapped in Ar matrix (i.e., N 2 @Ar). For cluster computations, we used both Møller-Plesset (MP2) and PBE-D3 methods. For N 2 @Ar, we used a periodic-dispersion corrected model for Ar matrix, which consists on a slab of four layers of Ar atoms. We determined the equilibrium structures and binding energies of N 2 interacting with these entities. We also deduced the N 2 vibrational frequency shifts caused by clustering or embedding compared to an isolated N 2 molecule. Upon complexation or embedding, the vibrational frequency of N 2 is slightly shifted, while its equilibrium distance remains unchanged. This is due to the weak interactions between N 2 and Ar within these compounds. Our calculations show the importance of inclusion of dispersion effects for the accurate description of geometrical and spectroscopic parameters of N 2 isolated, in interaction with Ar surfaces, or trapped in Ar matrices

Phenolic characterization and antioxidant activity of two endemic wormwood species of Morocco: Artemisia ifranensis J. Didier and Artemisia mesatlantica

Artemisia ifranensis and Artemisia mesatlantica are two endemic species in Morocco belonging to the Asteraceae family. Located in the region of Moroccan Atlas, they are very much sought after by the local population for their therapeutic properties.However, given the limited studies conducted on these species and in order to contribute to their valorization, we selected them in full bloom in the region of Timahdite for a phytochemical study and an evaluation of their antioxidant properties. The results of phytochemical screening revealed their richness in polyphenols, sterols, triterpenes and mucilages. The extraction yields of the total polyphenols by maceration in a methanol-water mixture (80/20) were 10.10% for A. mesatlantica and 16.66% for A. ifranensis. The determination of the total phenols by the Folin-Ciocalteu method after fractionation of the polyphenolic extracts showed the abundance of these compounds in the butanolic fraction of A. Mesatlantica and the methanolic extract of A. Ifranensis. For the total flavonoids dosed with aluminum trichloride, the ethyl acetate fractions of A. Mesatlantica and butanolic acid. Ifranensis were the richest. In addition, the crude extract of A. Mesatlantica was particularly rich in condensed tannins.Evaluation of the antioxidant activity by reduction of iron (FRAP) and trapping of the free radical DPPH * showed that all the extracts have a moderate antioxidant power.These early studies on A. mesatlantica and A. ifranensis of Timahdite reveal their abundance of important chemical compounds. Also, due to the ability of these plants to trap radicals, they can be considered as sources of natural antioxidants