Growth kinetics of the compound layers: Effect of the nitriding potential

AbstractThe aim of this work is to study the effect of the nitriding potential on development of the compound layers during the gas nitriding of Armco Fe and XC38 carbon steel. The gas nitriding experiments were realized in an atmosphere of partially dissociated gas ammonia (NH3) at 520∘C under a variable nitriding potential (from 0.25 to 3.5atm−0.5) for 2 h.Using XRD analysis and SEM observations of the cross-sections of the treated samples, it was shown that the compound layer was composed of γ′ iron nitride after exceeding a critical value of the nitriding potential that depends on the substrate’s nature. A linear semi-logarithmic relationship relating the nitriding potential to the experimentally measured layer thickness for the γ′ phase was used to evaluate the critical nitriding potential giving rise to its formation on the material substrate. It was found that the required value of the critical nitriding potential for XC steel is greater than that of Armco iron

Force calculation and atomic-structure optimization for the full-potential linearized augmented plane-wave code WIEN

Following the approach of Yu, Singh, and Krakauer [Phys. Rev. B 43 (1991) 6411] we extended the linearized augmented plane wave code WIEN of Blaha, Schwarz, and coworkers by the evaluation of forces. In this paper we describe the approach, demonstrate the high accuracy of the force calculation, and use them for an efficient geometry optimization of poly-atomic systems.Comment: submitted to Comp. Phys. Commun., 27 pages, 3 figure

Investigation of A1g phonons in YBa2Cu3O7 by means of LAPW atomic-force calculations

We report first-principles frozen-phonon calculations for the determination of the force-free geometry and the dynamical matrix of the five Raman-active A1g modes in YBa2Cu3O7. To establish the shape of the phonon potentials atomic forces are calculated within the LAPW method. Two different schemes - the local density approximation (LDA) and a generalized gradient approximation (GGA) - are employed for the treatment of electronic exchange and correlation effects. We find that in the case of LDA the resulting phonon frequencies show a deviation from experimental values of approximately -10%. Invoking GGA the frequency values are significantly improved and also the eigenvectors are in very good agreement with experimental findings.Comment: 15 page

Phonon dispersion and electron-phonon interaction for YBa_2Cu_3O_7 from first-principles calculations

We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the high-T_c superconductor YBa_2Cu_3O_7 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. The calculated phonon dispersion curves are in excellent agreement with Raman, infrared and neutron data. Calculation of the Eliashberg function alpha^2F leads to a small electron-phonon coupling lambda=0.27 in disagreement with earlier approximate treatments. Our calculations strongly support the view that conventional electron-phonon coupling is not an important contribution to superconductivity in high-T_c materials.Comment: 4 pages, 4 figure

Structure optimization effects on the electronic properties of Bi2_2Sr2_2CaCu2_2O8_8

We present detailed first-principles calculations for the normal state electronic properties of the high T$_C$ superconductor Bi$_2$Sr$_2$CaCu$_2$O$_8$, by means of the linearized augmented plane wave (LAPW) method within the framework of density functional theory (DFT). As a first step, the body centered tetragonal (BCT) cell has been adopted, and optimized regarding its volume, $c/a$ ratio and internal atomic positions by total energy and force minimizations. The full optimization of the BCT cell leads to small but visible changes in the topology of the Fermi surface, rounding the shape of CuO$_2$ barrels, and causing both the BiO bands, responsible for the pockets near the \textit{\=M} 2D symmetry point, to dip below the Fermi level. We have then studied the influence of the distortions in the BiO plane observed in nature by means of a $\sqrt{2}\times\sqrt{2}$ orthorhombic cell (AD-ORTH) with $Bbmb$ space group. Contrary to what has been observed for the Bi-2201 compound, we find that for Bi-2212 the distortion does not sensibly shift the BiO bands which retain their metallic character. As a severe test for the considered structures we present Raman-active phonon frequencies ($q = 0$) and eigenvectors calculated within the frozen-phonon approximation. Focussing on the totally symmetric A$_{g}$ modes, we observe that for a reliable attribution of the peaks observed in Raman experiments, both $c$- and a-axis vibrations must be taken into account, the latter being activated by the in-plane orthorhombic distortion.Comment: 22 pages, 4 figure

Assessment of the application for renewal of authorisation of GalliPro ® (Bacillus subtilis DSM 17299) for chickens for fattening

GalliPro \uae is the trade name for a feed additive based on viable cells of a strain of Bacillus subtilis intended for use as a zootechnical additive (gut flora stabiliser) in feed for chickens for fattening. The product is currently authorised for use in chickens for fattening. This opinion concerns the renewal of this authorisation. Bacillus subtilis is considered by EFSA to be suitable for the qualified presumption of safety (QPS) approach to establish the safety for the target species, consumers and the environment. The identity of the strain present in the additive was established and evidence was provided on the lack of toxigenic potential as well as acquired antibiotic resistance determinants to antibiotics of human and veterinary importance. Accordingly, this strain is presumed safe for the target species, consumers of products derived from animals fed the additive and the environment. Since no concerns are expected from other components of the additive, GalliPro \uae is considered safe for the target species, consumers and the environment. The applicant has provided evidence that the additive currently in the market complies with the existing conditions of authorisation. The FEEDAP Panel confirms its previous conclusions that GalliPro \uae is safe for the target species; consumers of products from animals fed the additive and the environment. GalliPro \uae should be considered a potential respiratory sensitiser. In the absence of data, the FEEDAP Panel cannot conclude on the potential of GalliPro \uae for skin and eyes irritancy and dermal sensitisation

Safety and efficacy of Bonvital® (Enterococcus faeciumDSM 7134) as a feed additive for laying hens

open23siFollowing a request from the European Commission, EFSA Panel on Additives and Products or Substances used in Animal Feed was asked to deliver a scientific opinion on the safety and efficacy of Bonvital® for laying hens. Bonvital® is an additive containing viable cells of Enterococcus faeciumDSM 7134 marketed in two forms, a granular and a powder form, both with a guaranteed minimum concentration of E. faeciumDSM 7134 of 1.0 × 1010 colony forming units (CFU)/g additive. Bonvital® in either form is intended for use in feed for laying hens at the minimum concentration of 1.0 × 109 CFU/kg complete feed and at the maximum concentration of 1.0 × 1010 CFU/kg feedingstuffs. Bonvital powder® is also proposed for use in water for drinking at the minimum concentration of 5.0 × 108 CFU/L. The use of Bonvital® in animal nutrition is considered safe for the target animals. The results of a tolerance trial in which hens were fed the additive at 10-fold the maximum recommended dose support this conclusion. Delivery of comparable doses of the additive via water for drinking is considered as safe for laying hens. Bonvital® at the proposed conditions of use is safe for consumers of products derived from animals fed the additive and for the environment. Bonvital® is not a dermal or ocular irritant but a potential dermal and respiratory sensitiser. Bonvital® has the potential to be efficacious in improving the hen's performance when supplemented at 1.0 × 109 CFU/kg feed or 5.0 × 108 CFU/L water for drinking.openBampidis V.; Azimonti G.; Bastos M.; Christensen H.; Dusemund B.; Kouba M.; Fasmon Durjava M.; Lopez-Alonso M.; Lopez Puente S.; Marcon F.; Mayo B.; Pechova A.; Petkova M.; Ramos F.; Sanz Y.; Villa R.; Woutersen R.; Dierick N.; Martelli G.; Anguita M.; Galobart J.; Revez J.; Brozzi R.Bampidis V.; Azimonti G.; Bastos M.; Christensen H.; Dusemund B.; Kouba M.; Fasmon Durjava M.; Lopez-Alonso M.; Lopez Puente S.; Marcon F.; Mayo B.; Pechova A.; Petkova M.; Ramos F.; Sanz Y.; Villa R.; Woutersen R.; Dierick N.; Martelli G.; Anguita M.; Galobart J.; Revez J.; Brozzi R

Efficacy of the feed additive containing Companilactobacillus farciminis (formerly Lactobacillus farciminis) CNCM I-3740 (Biacton\uae) for chickens for fattening, turkeys for fattening and laying hens (ChemVet dk A/S)

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the efficacy of the additive consisting of Companilactobacillus farciminis (formerly Lactobacillus farciminis) CNCM I-3740 (tradename: Biacton\uae) for chickens for fattening, turkeys for fattening and laying hens. The additive is a preparation containing viable cells of C. farciminis CNCM I-3740 at the minimum concentration of 1  7 109 CFU/g additive. In a previous opinion, the FEEDAP Panel assessed the safety and the efficacy of the product when used in these target species. The Panel concluded that based on the qualified presumption of safety of the active agent, and the lack of concerns deriving from other components of the additive, Biacton\uae was presumed safe for the target animals, consumers and the environment. Regarding the safety for the user, the FEEDAP Panel could not conclude on the potential of the additive to be irritant to skin and eyes or its dermal sensitisation due to the lack of data. However, it concluded that the additive should be considered a respiratory sensitiser. The data provided in the previous assessment to support the efficacy of the additive did not allow drawing conclusions on the efficacy of the additive in any of the target species. The additional information submitted with chickens for fattening and laying hens did not provide sufficient evidence to conclude on the efficacy of Biacton\uae for these target species. No new information was provided that would lead the Panel to reconsider the conclusions already reached on the use of the additive with turkeys for fattening. The FEEDAP Panel, based on the available data, cannot conclude on the efficacy of Biacton\uae in chickens for fattening, turkeys for fattening and laying hens

Safety of the feed additive consisting of manganese chelates of lysine and glutamic acid for all animal species (Zinpro Animal Nutrition)

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety for target animals of manganese chelates of lysine and glutamic acid (Manganese-LG) as a nutritional feed additive for all animal species. The European Commission request followed an opinion of the FEEDAP Panel published in 2020; in that opinion, the FEEDAP Panel could conclude on the safety of the additive for chickens for fattening, but not for the rest of the target animals. The applicant submitted additional information to allow the FEEDAP Panel to complete its assessment; these additional data, comprising two tolerance studies (one with chickens for fattening and one with laying hens), were the subject of this opinion. The tolerance study in laying hens was not considered for the assessment since the housing conditions of the animals were not appropriate according to the relevant EU provisions. The results of the tolerance study in chickens for fattening showed that Manganese-LG at the highest level tested – 800 mg Mn/kg feed – is safe for these target animals. The FEEDAP Panel also considered a previous tolerance study in chickens for fattening. Taking all the evidence together the Panel concluded that Manganese-LG is safe for chickens for fattening at 150 mg Mn/kg feed, with a margin of safety of 5.5. This conclusion can be extrapolated to all animal species and categories provided that the maximum authorised levels in the EU for total manganese in feed are not exceeded