Van der Waals effects on grazing incidence fast atom diffraction for H/LiF(001)

We theoretically address grazing incidence fast atom diffraction (GIFAD) for H atoms impinging on a LiF(001) surface. Our model combines a description of the H-LiF(001) interaction obtained from Density Functional Theory calculations with a semi-quantum treatment of the dynamics. We analyze simulated diffraction patterns in terms of the incidence channel, the impact energy associated with the motion normal to the surface, and the relevance of Van der Waals (VdW) interactions. We then contrast our simulations with experimental patterns for different incidence conditions. Our most important finding is that, for normal energies lower than 0.5 eV and incidence along the channel, the inclusion of Van der Waals interactions in our potential energy surface yields a greatly improved accord between simulations and experiments. This agreement strongly suggests a non-negligible role of Van der Waals interactions in H/LiF(001) GIFAD in the low-to-intermediate normal energy regime

Trajectory-dependent energy loss for swift He atoms axially scattered off a silver surface

Angle- and energy-loss- resolved distributions of helium atoms grazingly scattered from a Ag(110) surface along low indexed crystallographic directions are investigated considering impact energies in the few keV range. Final projectile distributions are evaluated within a semi-classical formalism that includes dissipative effects due to electron-hole excitations through a friction force. For mono-energetic beams impinging along the $[1\bar{1}0]$, $[1\bar{1}2]$ and $[1\bar{1}0]$ directions, the model predicts the presence of multiple peak structures in energy-loss spectra. Such structures provide detailed information about the trajectory-dependent energy loss. However, when the experimental dispersion of the incident beam is taken into account, these energy-loss peaks are completely washed out, giving rise to a smooth energy-loss distribution, in fairly good agreement with available experimental data

Thermodynamic study of metal sulphides conversion to oxides in hydrometallurgy

This paper presents thermodynamic study of the conversion of metal sulphides to oxides of the CuAg sulphide concentrate as a final product after mechano-chemical leaching of tetrahedrite. The conversion of sulphides to oxides is carried out by oxidation leaching in NaOH solution. The thermodynamic calculation was performed for the sulphide concentrate containing the following sulphides: CuS, CuFeS2, FeS, Sb2S3, As2S3, Bi2S3 and HgS. Based on the change of Gibbs free energy (ΔG°) and the equilibrium constant (K), conversion of metal sulphides to oxides from the qualitative assessment of the chemical reaction can occur as the result of the thermodynamic reaction abilities

Competition between electron and phonon excitations in the scattering of nitrogen atoms and molecules off tungsten and silver surfaces

We investigate the role played by electron-hole pair and phonon excitations in the interaction of reactive gas molecules and atoms with metal surfaces. We present a theoretical framework that allows us to evaluate within a full-dimensional dynamics the combined contribution of both excitation mechanisms while the gas particle-surface interaction is described by an ab-initio potential energy surface. The model is applied to study energy dissipation in the scattering of N$_2$ on W(110) and N on Ag(111). Our results show that phonon excitation is the dominant energy loss channel whereas electron-hole pair excitations represent a minor contribution. We substantiate that, even when the energy dissipated is quantitatively significant, important aspects of the scattering dynamics are well captured by the adiabatic approximation.Comment: 4pages and 3 figure

Diffraction of swift atoms after grazing scattering from metal surfaces: N/Ag(111) system

6 páginas, 6 figuras.-- PACS number(s): 79.20.Rf, 79.60.Bm, 34.20.Cf, 61.85.+pDiffraction patterns produced by grazing scattering of fast N atoms from a Ag(111) surface are investigated by employing the surface eikonal approximation. This method is a distorted-wave theory that takes into account the coherent addition of contributions coming from different projectile paths. In the model the projectile-surface potential is obtained from an accurate density-functional theory calculation. The dependence of the scattered projectile spectra on impact energy and incidence channel is analyzed, and possible incident direction and energy range for the observation of the interference patterns are predicted. In addition, it is found that as a result of the high reactivity of N atoms, asymmetries of the surface potential might be detected through their effects on diffraction patterns.M.S.G. acknowledges financial support from CONICET, UBA, and ANPCyT of Argentina.Peer reviewe

Příspěvek k hodnotám dnešních dětí

Studium hodnotových orientací člověka, jeho životních postojů a preferencí je jednou z nejsložitějších a nejkomplexnějších oblastí, na kterou se lze ve společenskovědním výzkumu zaměřit. Situace je ještě komplikovanější v případě, kdy se cílovou skupinou stávají právě děti a mladí lidé, jejichž osobnost se stále dynamicky vyvíjí a podléhá mnoha vnějším tlakům a vlivům a zároveň také vnitřním biologickým zákonitostem. Studium této problematiky také ztěžuje nejednotné vymezení základních pojmů a velké množství definic a teorií, které jsou s touto oblastí spojeny. Ve výzkumu Hodnotové orientace dětí ve věku 6 – 15 let jsme se zaměřili na hlavní socializační činitele v životě dětí, které ve výzkumu nazýváme „klíčoví hráči“. Zařadili jsme mezi ně rodinu, školu, způsoby trávení volného času a zaměřili jsme se na to, jaký vztah děti k nim mají, jaké preference jim přidělují a jak který z nich život dětí ovlivňuje. V příspěvku jsou prezentována vybraná dílčí zjištění týkající se priorit a hodnotových orientací dnešních dětí v souvislosti se způsoby trávení volného času a socioekonomickými ukazateli

Assess and Address: Screening and Management for Depression in Patients with Chronic Heart Failure

Background: Depression is two to three times more likely in patients with heart failure (HF) than in the general population. Comorbid HF and depression are associated with poor outcomes and increased healthcare burden. Clinical guidelines from professional organizations recommend routine depression screening in patients with HF. However, screening is not systematically implemented in outpatient cardiology settings. Objective: The objective of this process improvement project was to create a sustainable process for an outpatient cardiology clinic to screen adults with chronic HF for depression, to identify patients who have an elevated depression screening score, and to initiate an evidence-based treatment algorithm for patients evaluated as having elevated screening scores due to depression. Methods: A nurse practitioner-led process improvement project, set in an outpatient cardiology clinic, administered the Patient Health Questionnaire (PHQ-9) tool to patients who presented to the clinic for HF care. The score was reviewed by the provider and, if elevated, addressed with assessment and plan. Compliance was measured by the percentage of patients screened. Clinical impact was measured by percentage of patients with an elevated PHQ-9 score addressed with a documented treatment plan by the provider.Results: Post-implementation results for four Plan-Do-Study-Act cycles were 38%, 68%, 72%, and 66%, for an overall of 61.9% of patients screened during the project. Twenty-one unique patients (13.17%) had elevated PHQ-9 scores; all of whom had a documented assessment and treatment plan. Conclusions: We demonstrated how a screening protocol and an accompanying treatment algorithm can be successfully implemented in an outpatient cardiology clinic. Elements of success included a standardized screening protocol, a clinical support algorithm for treatment/referral, an optimized electronic medical record that supported the screening tool used, and a follow-up system for patients with significant depressive symptoms. Stakeholder engagement throughout the project informed iterative changes and provided direction for sustainability.Doctor of Nursing Practic

Příspěvek k hodnotám dnešních dětí

Studium hodnotových orientací člověka, jeho životních postojů a preferencí je jednou z nejsložitějších a nejkomplexnějších oblastí, na kterou se lze ve společenskovědním výzkumu zaměřit. Situace je ještě komplikovanější v případě, kdy se cílovou skupinou stávají právě děti a mladí lidé, jejichž osobnost se stále dynamicky vyvíjí a podléhá mnoha vnějším tlakům a vlivům a zároveň také vnitřním biologickým zákonitostem. Studium této problematiky také ztěžuje nejednotné vymezení základních pojmů a velké množství definic a teorií, které jsou s touto oblastí spojeny. Ve výzkumu Hodnotové orientace dětí ve věku 6 – 15 let jsme se zaměřili na hlavní socializační činitele v životě dětí, které ve výzkumu nazýváme „klíčoví hráči“. Zařadili jsme mezi ně rodinu, školu, způsoby trávení volného času a zaměřili jsme se na to, jaký vztah děti k nim mají, jaké preference jim přidělují a jak který z nich život dětí ovlivňuje. V příspěvku jsou prezentována vybraná dílčí zjištění týkající se priorit a hodnotových orientací dnešních dětí v souvislosti se způsoby trávení volného času a socioekonomickými ukazateli

Density functional theory calculations of nitrogen adsorption features on Fe(111) surfaces

Trabajo presentado al Workshop on Controlled Atomic Dynamics on Solid Surfaces: Atom an Molecular Manipulation, celebrado en Donostia-San sebastián (España) del 13 al 16 de Mayo de 2013.The interaction of nitrogen with metal surfaces has been one of the most popular topics of research in surface science for the last decades. This is due in part to the industrial importance of ammonia synthesis, typically obtained from nitrogen and hydrogen catalyzed over iron-based compounds. The rate limiting step in ammonia synthesis is the adsorption and dissociation of nitrogen on the catalyst surface. In Fe surfaces, the reactivity of the process depends on the face, the Fe(111) and Fe(211) surfaces being the most reactive ones. Although Fe(111) is the most reactive iron face for N2 dissociation, the dynamics of such process has not been analyzed in detail. In this work we present exhaustive calculations of the interaction of nitrogen atoms and molecules with the Fe(111) surface. These calculations set the basis for subsequent analysis of the N2 dissociation dynamics. We perform Density functional Theory spin-polarized calculations using VASP code. We first study the relaxation of the Fe(111) surface, which was a matter of controversy in the past. From here, we calculate the interaction energy of nitrogen atoms and molecules when approaching the Fe(111) surface. Our results show the preferred adsorption paths and sites for nitrogen adsorption, as well as the adsorption energies. We finally discuss the dynamics of the dissociation process and make the link with the high reactivity properties of the surface.Peer reviewe