30 év az öngyilkosság ellen: Munkacsoportunk depresszió- és szuicidprevenciós kutatásainak összefoglalása – 1985–2015

In this paper we gather and discuss the results of our workgroup on depression and suicide prevention published between 1985 and 2015. We hope that this summary will focus the interest of the scientific community on suicidology and turn the attention of decision-makers on the fact that despite of its marked decrease in the past three decades, the suicide rate in Hungary is still the second highest in the EU. So, based on expert opinion, joint action is needed in order to achieve a further decrease of suicide rate in Hungary. © 2015, Hungarian Association of Psychopharmacology. All rights reserved

Depression in Parkinson's disease

The prevalence of major and minor depression in Parkinson’s disease is around 30–40% but, unfortunately, depression remains frequently underrecognized and often undertreated. However, recognition and appropriate treatment of depression in patients with Parkinson’s disease is essential for improving the cross-sectional picture and longitudinal course. This review focuses on the epidemiology, pathophysiology and different treatment modalities of depression in Parkinson’s disease. | A major és minor depresszió prevalenciája Parkinson-kórban szenvedôk között körülbelül 30-40%, ugyanakkor a depresszió ebben a betegcsoportban aluldiagnosztizált és alulkezelt kórkép. A depresszió diagnózisának és az adekvát kezelésének elmaradása nemcsak a depressziós tünetek perzisztálásához, de csökkent életminôséghez, az alapbetegség súlyosabb tüneti képéhez és kedvezôtlenebb prognózisához is vezetnek. Összefoglaló tanulmányunkban a Parkinson-kórban megjelenô depresszió epidemiológiai, patofiziológiai és terápiás vonatkozásait tárgyaljuk

Stability of vacancy-hydrogen clusters in nickel from first-principles calculations

The interactions of hydrogen (H) atoms with vacancies are investigated by means of ab initio calculations. The lowest segregation energies are -0.27 and -0.41 eV at single vacancies and divacancies, respectively. These values are in excellent agreement with those corresponding to the two characteristic peaks of the thermal desorption spectra. The microscopic interpretation of the experimental data is therefore clarified. An energetic model is built from the ab initio data and used to study the influence of H bulk concentration and temperature on the concentration of vacancy-H clusters. Analytical expressions, validated by Monte Carlo simulations, are given. The mean vacancy occupation and the H-induced vacancy enrichment are calculated at two temperatures representative of H embrittlement experiments and stress corrosion cracking at high temperatures. The stability domain of VH6 clusters is found to significantly overlap with the experimental conditions for embrittlement. Therefore, vacancy clustering at high concentrations can be qualitatively discussed based on VH6–VH6 interactions that are found weakly repulsive. Consequences on H damage in Ni are discussed. The effect of metal vibrations on segregation and local hydride stability is qualitatively evaluated by off-lattice Monte Carlo simulations using a semi-empirical Ni–H potential. They are shown to shift local hydride stability towards higher H concentrations

Hydrogen influence on diffusion in nickel from first-principles calculations

We propose a method to evaluate the diffusion coefficient of vacancy-hydrogen clusters (VHn) in metals. The key is a good separation of time scales between H diffusion and the metal-vacancy exchange. The Ni-H system is investigated in details, using ab initio calculations, but the arguments can be transposed to other systems. It is shown that cluster diffusion can be treated as an uncorrelated random walk and that H is always in equilibrium before the vacancy-metal exchange. Then, the diffusion coefficient is a sum over jump paths of the equilibrium probability of being in a specific VHn configuration times the corresponding activation terms. The influence of H on the energy barrier is well reproduced by effective pair interactions between the jumping Ni and the H atoms inside the vacancy. This model is motivated by an analysis of the electronic charge redistribution in key saddle configurations. The interaction is repulsive and decreases with distance. The model is used to find easy jump path, reduce the number of saddle searches, and provide an estimate of the error expected from this reduction. The application to the Ni-H system shows that vacancies are drastically slowed down by H. The effects of temperature and bulk H concentration are explored and the origin of the non-Arrhenius behavior is explained. At equilibrium, VHn clusters always induce a speedup of metal diffusion. The implications concerning H induced damage, in particular in regards to Ni-Cr oxidation, are discussed

Site stability and pipe diffusion of hydrogen under localised shear in aluminium

International audienceThis paper studies the effect of a plastic shear on the tetrahedral vs. octahedral site stability for hydrogen, in aluminium. Based on Density Functional Theory calculations, it is shown that the tetrahedral site remains the most stable site. It transforms into the octahedral site of the local hexagonal compact structure of the intrinsic stacking fault. The imperfect stacking is slightly attractive with respect to a regular lattice site. It is also shown that the shearing process involves a significant decrease of the energetic barrier for hydrogen jumps, at half the value of the Shockley partial Burgers vector, but not in the intrinsic stacking fault. These jumps involve a displacement component perpendicular to the shearing direction which favours an enhancement of hydrogen diffusion along edge dislocation cores (pipe diffusion). The magnitude of the boost in the jump rate in the direction of the dislocation line, according to Transition State Theory and taking into account the zero point energy correction, is of the order of a factor 50, at room temperature. First Passage Time Analysis is used to evaluate the effect on diffusion which is significant, by only at the nanoscale. Indeed, the common dislocation densities are too small for these effects (trapping, or pipe diffusion) to have a signature at the macroscopic level. The observed drop of the effective diffusion coefficient could therefore be attributed to the production of debris during plastic straining, as proposed in the literature